Salting-in electrolyte enables reversible heavy p-block electrochemistry in water

Salting-in electrolyte enables reversible heavy p-block electrochemistry in water | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Salting-in electrolyte enables reversible heavy p-block electrochemistry in water Hui Ying Yang, Yang-Feng Cui, Ming Zhang, Yunhai Zhu, Haobin Song, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8632446/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Heavy p-block elements (HPEs; Sn, Pb, Sb, Bi, Se and Te)1,2, with flexible electronic structures and rich multielectron redox chemistry, hold promise for electrochemically driven technologies in functional coatings, electronics, and energy conversion and storage3–15. However, their aqueous electrochemistry remains challenging because direct exposure of HPE cations to water readily triggers parasitic reactions, including hydrolysis, corrosion, precipitation, gas evolution, and passivation16–21. Here we challenge the prevailing assumption in electrolyte design that dissolving HPE cations necessitates hydration, and propose a counterintuitive principle of “dissolved but not hydrated” to unlock aqueous HPE electrochemistry. We implement this concept through a dual-salt salting-in electrolyte strategy, distilled into a two-parameter design principle. The auxiliary cation should be strongly hydrated yet weakly ion-pairing to suppress water activity, while the auxiliary anion should preferentially coordinate HPE cations to expel water from their solvation shells. First-principles descriptor screening, corroborated by spectroscopic analyses, interrogates a curated library of hundreds of cation–anion combinations and identifies Ca2+–Cl– as the uniquely optimal auxiliary-ion pair that most effectively suppresses water activity and drives anion coordination to HPE cations, thereby forming water-shielded chlorocomplexes that stabilize HPE cations in water. This electrolyte design enables reversible plating and stripping across the HPE family (Sn, Pb, Sb, Bi, Se and Te), yielding uniform electrodeposits and rendering HPEs viable multielectron electrodes in aqueous batteries. The proposed HPE-based aqueous batteries enabled by this salting-in electrolyte exhibit stable rechargeability with high capacity retention. By rendering an intrinsically unstable class of elements redox-active in water, this work overcomes long-standing barriers to heavy p-block electrochemistry and establishes a general framework for multielectron aqueous electrochemical systems. Physical sciences/Materials science/Materials for energy and catalysis Physical sciences/Energy science and technology/Energy storage/Batteries Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Heavy p-block elements (HPEs), commonly defined as p-block congeners from groups 13 to 17 in periods 4 to 6 (Fig. 1a), encompass a key subset comprising Pb, Sn, Sb, Bi, Se and Te that is central to modern technologies 1,2 , with applications spanning conventional packaging, advanced electronics and emerging electrochemical energy-storage systems driven by rapid electrification. Their technological value is most often realized as coatings and deposited layers on diverse substrates, tailored to the application, including Pb for radiation shielding, corrosion protection, solar cells and lead–acid batteries 3–5 ; Sn for tinplate packaging, electronic solders, Sn-metal batteries, and Sn-based Na-ion and Li-ion batteries 6–8 ; Sb and Bi as essential components in thermoelectrics, alloy-type negative electrodes of Na-ion batteries and electrocatalysts for CO 2 reduction 8–11 ; and Se and Te as semiconducting chalcogenides for optoelectronic and thermoelectric devices, as well as high-capacity electrodes increasingly explored in alkali-metal batteries 9,12–15 . However, how to translate the materials promise of HPEs into manufacturable coatings and layers on target substrates that deliver conformal growth and precise compositional control, while remaining low cost, environmentally benign and practical, remains challenging. Established physical vapor deposition (PVD) relies on vacuum-assisted vaporization of solid precursors followed by gas-phase transport and condensation 22 , whereas chemical vapor deposition (CVD) employs volatile species and thermally activated surface reactions but remains dependent on tailored precursors, elevated temperatures and vacuum infrastructure 23 . By contrast, electrochemical deposition provides a solution-based, low-temperature, and inherently scalable route for fabricating metallic and semiconducting layers 24 . It proceeds through mass transport, interfacial desolvation, electron transfer, and surface nucleation and growth, enabling the direct cathodic reduction of dissolved ions on conductive substrates 25 . In contrast to vapor-phase routes (PVD and CVD), electrochemical methods offer precise control over composition, morphology, and thickness without requiring vacuum infrastructure or high-temperature processing. Collectively, these attributes position electrochemical deposition as a compelling platform for scalable and sustainable manufacturing of HPE materials. Realizing such electrochemistry requires the corresponding HPE cations to be both chemically stable and sufficiently soluble in solvent (Fig. 1b, left). However, aqueous HPE electrochemistry remains fundamentally constrained (Fig. 1b, right), because multivalent HPE cations are intrinsically incompatible with water. These cations typically suffer from low solubility (e.g., Pb 2+ , Te 4+ , and Se 4+ ), pronounced hydrolytic instability (e.g., Sn 2+ , Sb 3+ , Bi 3+ , Se 4+ , and Te 4+ ), and complicated parasitic side reactions (e.g., Sn 2+ , Se 4+ and Te 4+ ), which collectively undermine electrochemical reversibility and impede controlled deposition 16–21 . Previous attempts to overcome these challenges have typically resorted to toxic acids such as fluoroboric acid (HBF 4 ) and hexafluorosilicic acid (H 2 SiF 4 ) in aqueous solutions, or to expensive high-concentration salt electrolytes, high-temperature molten salts, ionic liquids, and organic solvents 26–31 . Beyond the significant increases in cost and safety risks, these approaches often suffer from poor electrochemical reversibility and sluggish kinetics. 21,26,28,32–38 . These long-standing limitations have fundamentally impeded the development and broader application of aqueous electrochemical deposition of HPEs. In this work, we recast the fundamental solvation-design problem, recognizing that reversible aqueous HPE electrochemistry is unattainable within current electrolyte-design principles. First-principles descriptor-guided auxiliary ion screening The instability of HPE cations in water stems primarily from the strong electrostatic attraction between the highly positive electrostatic potential (ESP) of HPE cations and the electron-rich O atoms of H 2 O (Fig. 1c, left). Although anions with highly negative ESP could, in principle, outcompete H 2 O for coordination at HPE cation centers through electrostatic attraction (Fig. 1c and Supplementary Fig. 1), current aqueous electrolyte design assumes that dissolving HPE cations necessitates hydration, leading to predominantly H 2 O-rich solvation shells in which ion pairing occurs mainly in solvent-separated or contact forms. Within this framework, dissolution becomes effectively inseparable from hydration, and hydration in turn initiates the failure pathways of aqueous HPE electrochemistry. Here we challenge this hydration-based assumption and propose a counterintuitive electrolyte-design principle of “dissolved but not hydrated” HPE cations to unlock aqueous HPE electrochemistry. To implement this principle, we devised a salting-in electrolyte strategy based on a dual-salt design comprising an HPE salt and an auxiliary salt, in which the auxiliary salt is selected to suppress H 2 O activity and drive HPE cation coordination from hydration to anion coordination. Guided by first-principles interaction descriptors that quantify cation hydration and cation–anion pairing, we screened a curated library of hundreds of cation–anion combinations to pinpoint auxiliary ions that satisfy these coupled requirements (Supplementary Note 1). Accordingly, the auxiliary cation should be strongly hydrated to most effectively suppress bulk water activity, thereby minimizing direct H 2 O coordination to HPE cations. On this basis, we evaluated a library of monovalent (Li + , Na + and K + ), divalent (Be 2+ , Mg 2+ and Ca 2+ ), trivalent (Al 3+ ), and first-row transition-metal (TM) ions (Cr 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ ) using ab initio molecular dynamics (AIMD) to resolve their hydration structures and density functional theory (DFT) to quantify hydration strength (Fig. 1d,e and Supplementary Figs. 2–5). Higher coordination numbers (CNs) and more negative binding energies correspond to stronger hydration. Among these candidates in their hydrated forms (Fig. 1d,e), Li + and Na + combine weak binding with low CNs; Be 2+ and Al 3+ show distinctly strong binding yet low CNs, whereas K + reaches higher CNs but with much weaker binding; and TM ions and Mg 2+ display strong binding but only modest CNs. By contrast, Ca 2+ stands out by stabilizing seven- and eight-coordinate hydration shells with substantial binding energies, matching our hydration-driven design goal. We next screened auxiliary anions using a single design rule: they should preferentially coordinate to HPE cations over auxiliary cations to form anion-protective HPE complexes. We evaluated a panel of anions, including Cl – , Br – , I – , perchlorate (ClO 4 – ), nitrate (NO 3 – ), acetate (OAc – ), tetrafluoroborate (BF 4 – ), methanesulfonate (MSA – ), hexafluorophosphate (PF 6 – ), triflate (OTf – ), and bis(trifluoromethanesulfonyl)imide (TFSI – ). To quantify this preference, we used Pb 2+ as the benchmark HPE cation, as it has the lowest positive ESP among the HPE cations and thus the weakest electrostatic interaction with the negatively charged anions (Fig. 1c and Supplementary Fig. 1). Mapping ESP distributions on anion surfaces clearly differentiates these candidates (Fig. 1f). Smaller anions with more concentrated negative charge, such as Cl – , exhibit more negative ESP values than larger, charge-delocalized species, such as TFSI – , whereas OAc – is strongly anisotropic, with very negative carboxylate oxygen sites and a much less negative methyl group. We then used the lowest-ESP site on each anion as the coordination locus to construct Ca 2+ and Pb 2+ complexes with one to four ligands. Across the anion coordination series, three-coordinate complexes consistently exhibit the most negative binding energies and are therefore the most stable species (Supplementary Figs. 6–8). For Ca 2+ within these three-coordinate series, binding strength increases nearly linearly as the anionic ESP minimum becomes more negative, from weak TFSI – to strong OAc – binding (Fig. 1g). However, this trend becomes less definitive for Pb 2+ : [Pb(TFSI) 3 ] – remains weakly bound, whereas [PbCl 3 ] – and [Pb(OAc) 3 ] – display nearly identical binding energies (Fig. 1h). Moreover, Pb 2 + –Cl – and Pb 2+ –OAc – interactions are substantially stronger than Pb 2+ –H 2 O coordination, indicating that both anions act as plausible ligands in water (Supplementary Figs. 6a,b and 8a). A closer comparison reveals that [Ca(OAc) 3 ] – binds more strongly than [Pb(OAc) 3 ] – , whereas [CaCl 3 ] – is less strongly bound than [PbCl 3 ] – (Fig. 1g,h). Thus, when Ca 2+ and Pb 2+ coexist in aqueous solutions, the relative binding strengths dictate that OAc – is driven to associate with Ca 2+ , whereas Cl – is preferentially bound to Pb 2+ . Electron localization function (ELF) mapping of three-coordinate Pb 2+ complexes reveals a stereochemically active lone pair (6s 2 ) occupying a basin opposite the ligands, which drives pyramidalization into trigonal-pyramidal geometries (Fig. 1h, insets; Supplementary Figs. 9–11). In contrast, Ca 2+ lacks a lone pair and adopts more open trigonal-planar configurations (Fig. 1g, insets). Independent gradient model based on Hirshfeld (IGMH) analysis shows how the lone-pair-induced steric field alters anion binding (Fig. 1i; Supplementary Figs. 12–14). In trigonal-planar [Ca(OAc) 3 ] – , each OAc – binds Ca 2+ strongly in a bidentate fashion through both carboxylate oxygens, whereas in trigonal-pyramidal [Pb(OAc) 3 ] – the lone pair occupies one coordination site, forcing OAc – to bind mainly through a single oxygen and weakening its overall interaction (Fig. 1i, top). By comparison, compact Cl⁻ ligands in [PbCl 3 ] – are barely affected by this steric crowding and retain Pb–Cl bonds stronger than those in planar [CaCl 3 ] – (Fig. 1i, bottom). Supplementary binding-energy analyses confirm that Cl – –H 2 O interactions are much weaker than Pb 2+ –Cl – bonding and only slightly stronger than H 2 O–H 2 O hydrogen bonding (Supplementary Figs. 15 and 16), thereby excluding hydrated Cl – as the limiting factor for HPE cation–Cl – coordination. Among the auxiliary cations examined, Ca 2+ , aside from weakly hydrated monovalent ions, displays the weakest binding for Cl – (Supplementary Figs. 17 and 18), whereas higher-ESP HPE cations (Sn 2+ , Sb 3+ , Bi 3+ , Se 4+ , and Te 4+ ) bind Cl⁻ more strongly than H 2 O (Supplementary Figs. 19–23). First-principles screening thus establishes Ca 2+ as the optimal auxiliary cation, strongly hydrated yet only weakly binding to anions, and identifies Cl – as the preferred auxiliary anion, binding strongly to HPE cations but only weakly to Ca 2+ within the dual-salt design framework. A general salting-in strategy for HPE cations To map the solvation landscape of candidate auxiliary chlorides that suppress H 2 O activity while maintaining readily releasable Cl – , we used DFT to enumerate all plausible Cl – -bearing solvation structures, assessed their stability from binding energies, and quantified cation–Cl – interactions using IGMH analysis (Supplementary Note 2). Each structure is placed on a two-dimensional map of binding energy vs. an IGMH-derived interaction index (Fig. 2a, constructed from Supplementary Figs. 24–34), where more negative sign ( λ 2 ) ρ values indicate stronger cation–Cl – attraction. On this IGMH–energy map, Li + , Na + , and K + form loosely bound Cl – -bearing hydrated structures with low overall binding energies and only weakly vdW-level cation–Cl – binding. Ca 2+ , in contrast, maintains strong overall hydration yet still exhibits a predominantly vdW-level Ca 2+ –Cl – binding. Mg 2+ strengthens into a weakly attractive regime, whereas first-row transition-metal ions together with Be 2+ and Al 3+ show pronounced direct cation–Cl⁻ attraction. Notably, among the representative complexes, [CaCl(H 2 O) 7 ] + exemplifies the desired balance. It couples extensive hydration with a weak Ca 2+ –Cl – association (insets of Fig. 2a), placing aqueous CaCl 2 in an optimal regime that suppresses H 2 O activity while preserving high availability of free Cl – . To translate the descriptor-guided conclusions into practice, we implemented a salting-in strategy using representative auxiliary chlorides (NaCl, KCl, MgCl 2 , CaCl 2 , MnCl 2 , and ZnCl 2 ). Taking Pb 2+ as a model HPE cation, we examined whether these salts could release enough coordinatively available Cl – to convert sparingly soluble PbCl 2 into soluble chlorocomplexes. PbCl 2 solubility was quantified by increasing the chloride concentration from 1 m to the highest practical integer molalities for each salt, namely 6 m NaCl, 4 m KCl, 5 m MgCl 2 , 6 m CaCl 2 , 6 m MnCl 2 , and, for comparison, 6 m ZnCl 2 . As shown in Fig. 2b, NaCl and KCl, despite weak cation–Cl – interactions, afford only modest salting-in effect because each contributes a single Cl – and weakly suppresses H 2 O activity. Among the divalent chlorides, MnCl 2 gives limited gains (~0.07 m PbCl 2 at 5 m MnCl 2 ) and ZnCl 2 gives none; both fall in the strong cation–Cl – attraction regime of Fig. 2a ( sign ( λ 2 ) ρ < −0.05 a.u.), with Zn 2+ in particular favoring first-shell Cl – over H 2 O and thus retaining chloride (Supplementary Fig. 29a). By contrast, MgCl 2 produces a measurable but smaller salting-in effect than CaCl 2 , consistent with Mg 2+ –Cl – interactions in the attractive-weak regime, whereas Ca 2+ combines strong hydration with a weak vdW-level Ca 2+ –Cl – contact. Consequently, CaCl 2 furnishes the largest pool of coordinatively available Cl – and yields the highest PbCl 2 solubility (~0.40 m) via formation of soluble chlorocomplexes (Fig. 2b), in agreement with the two-parameter map (Fig. 2a). Pb L 3 -edge X-ray absorption fine structure (EXAFS) analysis identifies the soluble Pb 2+ species in 6 m CaCl 2 containing 0.4 m PbCl 2 (Fig. 2c, Supplementary Fig 35, and Supplementary Tables 1 and 2). The Fourier-transformed spectrum exhibits a dominant first-shell peak at ~2.4 Å (uncorrected for phase shift), which fits Pb–Cl scattering with an optimal fitted coordination number of three and shows no detectable Pb–O contribution from H 2 O (Supplementary Note 3), supporting its assignment to [PbCl 3 ] – (Fig. 2c). This assignment is consistent with the DFT-optimized structure of a trigonal-pyramidal geometry (Fig. 1h, inset). In CaCl 2 solutions up to 6 m, Raman spectra reveal a strongly disrupted hydrogen-bond network of bulk water (Fig. 2d; Supplementary Figs. 36 and 37) and 17 O NMR spectra exhibit pronounced upfield shifts (Fig. 2e; Supplementary Fig. 38), together confirming that Ca 2+ most effectively lowers H 2 O activity through strong hydration (Supplementary Note 4). Ca K-edge EXAFS analysis further elucidates the high-coordination hydration structure of Ca 2+ (Fig. 2f, Supplementary Fig. 39, Supplementary Tables 3 and 4, and Supplementary Note 5). In the dilute 1 m CaCl 2 solution, Fourier-transformed EXAFS and first-shell fitting suggest that Ca 2+ is reasonably modeled as being coordinated by eight H 2 O molecules to form [Ca(H 2 O) 8 ] 2+ (Fig. 2f, top). In 6 m CaCl 2 solution, one H 2 O molecule is readily replaced by Cl ‒ , yielding a stable [CaCl(H 2 O) 7 ] + configuration (Fig. 2f, middle), which remains essentially unchanged upon addition of 0.4 m PbCl 2 (Fig. 2f, bottom). Consistently, 35 Cl NMR spectra exhibit progressive upfield shifts from 1 m to 6 m CaCl 2 solutions (Supplementary Fig. 40), tracking the transformation from [Ca(H 2 O) 8 ] 2+ to [CaCl(H 2 O) 7 ] + . IGMH analysis further reveals that [PbCl 3 ] – exhibits a pronounced blue attractive region along the Pb–Cl contacts ( sign ( λ 2 ) ρ = ‒0.057 a.u.), consistent with strong halogen-bond-like binding, in sharp contrast to the weak, vdW-level Ca 2+ –Cl – contact in [CaCl(H 2 O) 7 ] + (Fig. 2g). Overall, CaCl 2 -based SICEs solubilize Pb 2+ as [PbCl 3 ] – , consistent with strong Ca 2+ hydration and weak Ca 2+ –Cl – pairing (Fig. 2h). Building on these insights, we extended the CaCl 2 -based SICE to a broader family of hydrolysis-prone HPE cations, including Sn 2+ , Sb 3+ , Bi 3+ , Te 4+ , and Se 4+ (Supplementary Note 6). Notably, 6 m CaCl 2 effectively suppresses hydrolysis and stabilizes these HPE cations in water as dissolved but not hydrated chlorocomplexes, in sharp contrast to CaCl 2 -free solutions (Supplementary Figs. 41–46). Raman bands attributable to HPE–Cl stretching, together with DFT-optimized structures, confirm that HPE cations remain as trigonal-pyramidal [SnCl 3 ]⁻, tetrahedral [SbCl 4 ]⁻, and octahedral [BiCl 6 ] 3 ⁻ and [TeCl 6 ] 2 ⁻ chlorocomplexes 39 – 44 , even when solubilized to high concentrations of up to 6 m SnCl 2 , 4 m SbCl 3 , 2.5 m BiCl 3 , and 3 m TeCl 4 in 6 m CaCl 2 (Fig. 2i–l). IGMH analyses place these HPE–Cl interactions within the stable, halogen-bond-like regime (insets of Fig. 2 i–l; Supplementary Fig. 47). Together with binding-energy analyses (Supplementary Figs. 19–22), these results show that in CaCl 2 -based SICEs, Cl – outcompetes H 2 O in the first coordination shell of HPE cations, thereby suppressing their intrinsic tendency toward hydrolysis by stabilizing them as Cl – -protected soluble chlorocomplexes. However, Se 4+ represents an exception. Despite its appreciable Se 4+ –Cl⁻ affinity (Supplementary Fig. 23), no fully Cl⁻-coordinate complex is detected. Instead, CaCl 2 diverts the hydrolysis pathway. In 1 m SeCl 4 , the dominant product is trigonal-pyramidal H 2 SeO 3 (3H 2 O + Se 4+ → H 2 SeO 3 + 4H + ), whereas in 6 m CaCl 2 + 1 m SeCl 4 the product shifts to trigonal-pyramidal SeOCl 2 (H 2 O + 2Cl – + Se 4+ → SeOCl 2 + 2H + ), as confirmed by Raman spectra and DFT-optimized structures (Fig. 2m and Supplementary Fig. 48) 45,46 . IGMH analyses reveal strong Se–O (aqua/hydroxo/oxo) interactions together with appreciable Se–Cl attraction (insets of Fig. 2m; Supplementary Fig. 49), rationalizing the coexistence and persistence of H 2 SeO 3 and SeOCl 2 . This behavior reflects an intrinsic Se 4+ preference for O donors: Cl – cannot fully displace aqua/hydroxo/oxo ligands, thereby stabilizing the mixed oxo–chloride SeOCl 2 in the CaCl 2 -based SICE. Reversible heavy p-block electrochemistry in SICEs Having established that CaCl 2 -based SICEs stabilize HPE cations as dissolved chlorocomplexes in water, we next evaluated their redox reversibility against the corresponding HPEs. Electrochemical tests were carried out in a three-electrode configuration using 6 m CaCl 2 containing 1 m of the target chlorides, except PbCl 2 , which was limited to 0.4 m by solubility (Fig. 3a–c, Supplementary Figs. 50 and 51, and Supplementary Note 7). Cyclic voltammetry (CV) reveals well-defined and reversible redox couples for [PbCl 3 ] – /Pb, [SnCl 3 ] – /Sn, [SbCl 4 ] – /Sb, [BiCl 6 ] 3– /Bi, and [TeCl 6 ] 2– /Te at –0.32 V, –0.30 V, 0.05 V, 0.06 V, and 0.57 V vs. SHE, respectively (Fig. 3a). The low-polarization responses reflect fast charge-transfer kinetics enabled by soluble chlorocomplexes. In parallel, the SeOCl 2 /Se couple delivers highly reversible redox peaks at 0.90 V vs. SHE in CaCl 2 -based SICE, in stark contrast to the sluggish kinetics and cathodic shift to 0.63 V observed in 1 m SeCl 4 electrolyte, where hydrolyzed oxyanions prevail (Fig. 3b). SeOCl 2 reduces markedly faster than H 2 SeO 3 owing to the facile cleavage of relatively weak, halogen-bond-like Se-Cl bonds, whereas H 2 SeO 3 and its derivatives (HSeO 3 – and SeO 3 2– ) undergo slow, multistep proton-coupled electron-transfer pathways that require breaking stronger Se–O/Se–OH linkages (Supplementary Fig. 49). Galvanostatic electrochemical deposition further confirms the high electrochemical stability of all chlorocomplexes studied, yielding flat potential plateaus and consistent deposition of the target HPEs without discernible polarization buildup over time (Fig. 3c). To assess structural and morphological features, the galvanostatic electrodeposits were systematically examined by scanning electron microscopy (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray diffraction (XRD), as detailed in Supplementary Note 8.1 (Supplementary Figs. 52–58). SEM images show that electrochemical reduction of soluble chlorocomplexes—[PbCl 3 ] – , [SnCl 3 ] – , [SbCl 4 ] – , [BiCl 6 ] 3– , [TeCl 6 ] 2– , and SeOCl 2 —yields compact deposits with distinct morphologies and compositions, demonstrating the broad applicability of SICEs for HPE electrodeposition (Fig. 3d–i and Supplementary Fig. 52). Pb deposits form large, faceted grains with uniform spatial distribution (Fig. 3d); Sn deposits yield well-defined faceted grains of uniform size (Fig. 3e); Sb deposits form densely packed spherical grains (Fig. 3f); Bi deposits exhibit a lamellar morphology composed of micron-sized stacked plates (Fig. 3g); and Te deposits develop smooth hemispherical grains with a broad size distribution (Fig. 3h). In contrast, Se deposits as a continuous amorphous-like film lacking discernible crystalline features (Fig. 3i). HAADF-STEM imaging resolves clear lattice fringes for Pb, Sn, Sb, Bi, and Te, with interplanar spacings of ~0.29 nm for Pb (111) plane, ~0.29 nm for Sn (200) plane, ~0.31 nm for Sb (012) plane, ~0.23 nm for Bi (110) plane, and ~0.22 nm for Te (110) plane (Fig. 3j–n and Supplementary Figs. 53–57), in agreement with XRD patterns (Fig. 3p). By contrast, Se shows neither lattice fringes in HAADF-STEM nor Bragg peaks in XRD, confirming its amorphous nature (Fig. 3o,p and Supplementary Fig. 58). Energy-dispersive spectroscopy (EDS) elemental mapping reveals that Se accounts for 99.1 at% among Se, O, and Cl, verifying the high purity and compositional uniformity of the deposited film (inset of Fig. 3i). The CaCl 2 -based SICEs further enable one-step electrodeposition of representative heavy p-block alloys (e.g. PbSn and BiSb) through controlled tuning of chlorocomplex precursor ratios (Supplementary Figs. 59–61 and Supplementary Note 8.2). Collectively, these results show that SICEs overcome the intrinsic instabilities of aqueous heavy p-block electrochemistry, establishing a generalizable platform for reliable electrodeposition of high-quality HPEs and their alloys. We further confirmed the high reversibility of heavy p-block electrochemistry through repeated HPE plating and stripping behaviors in symmetric and asymmetric cells. Using Pb as a representative case, the PbǀǀPb symmetric cell maintains low polarization (<20 mV) for nearly 3,000 h (Fig. 3q), while the PbǀǀCu asymmetric cell delivers stable plating/stripping behavior with a high average CE of 99.9% over 500 cycles (Fig. 3r,s). More importantly, the electrochemical reversibility enabled by CaCl 2 -based SICEs is universally applicable across a wide spectrum of HPEs. Symmetric cells employing Sn, Sb, Bi, Se, and Te electrodes all exhibit low polarization (typically <80 mV) and long-term stability with cycling lifetimes from 1,000 to 3,600 h (Fig. 3t). Corresponding asymmetric cells achieve high average CEs (99.6–100.0%; Fig. 3u), further confirming the universality of the salting-in chlorocomplex strategy across diverse heavy p-block systems. Detailed electrochemical data are provided in Supplementary Figs. 62–66. Post-cycling morphological and structural analyses of both HPE electrodes and their electrodeposits on current collectors reveal dense, dendrite-free morphologies without detectable byproducts (Supplementary Figs. 67–75), underscoring the highly reversible HPE plating/stripping behavior and rationalizing the durable cycling lifetimes (Supplementary Note 9). This high electrochemical reversibility persists in concentrated chlorocomplex electrolytes based on SICEs with 6 m SnCl 2 , 4 m SbCl 3 , 2.5 m BiCl 3 , or 3 m TeCl 4 (Supplementary Fig. 76). Rechargeable aqueous HPE-electrode batteries Here we focus on aqueous batteries as a representative system, given their inherently high-power density, safety, and low-cost characteristics. We recognize that technology-ready aqueous electrode chemistries with stable multielectron redox pathways remain scarce. However, when HPE cations are stabilized as chlorocomplexes in SICEs, these elements can operate as either negative or positive electrodes via reversible plating and stripping, enabling rational full-cell pairing with suitable counter electrodes and greatly expanding the design space of aqueous batteries. Enabled by reversible plating and stripping in CaCl 2 -based SICEs (Fig. 3t,u), HPEs as electrodes fulfill the essential criterion for stable and reversible multielectron redox in water. They span a wide redox window from –0.32 V vs. SHE for [PbCl 3 ] – /Pb to 0.90 V vs. SHE for SeOCl 2 /Se, and deliver high theoretical specific capacities (258.7–1358.2 mAh g –1 ), along with long-term reversibility, dendrite-free deposition, corrosion resistance, and tunable redox potentials (Fig. 4a and Supplementary Fig. 77a) 7,14,15,21,31,47,48 . Within this landscape, Sn and Pb, with low redox potentials and moderate specific capacities, are ideal negative electrode candidates; Sb and Bi, with intermediate potentials and higher specific capacities, can function as either negative or positive electrodes; and Se and Te electrodes, featuring high redox potentials and four-electron pathways, emerge as promising high-energy positive electrodes. To exemplify this concept, we first constructed aqueous Pb-metal batteries using metallic Pb foil as the negative electrode, paired with conventional I – /I 2 , Br – /Br 2 , and Cl – /Cl 2 conversion positive electrodes (Supplementary Fig. 77b). These configurations deliver theoretical specific energies of 100, 182, and 278 Wh kg –1 for PbǀǀPbI 2 , PbǀǀPbBr 2 , and PbǀǀPbCl 2 full batteries, respectively. Unlike century-old lead–acid batteries that rely on concentrated, corrosive H 2 SO 4 electrolyte and suffer from limited rechargeability and low specific energy (~40 Wh kg –1 ) 3 , the proposed architecture exploits the soluble [PbCl 3 ] – chlorocomplex to establish a distinct aqueous chemistry where Pb 2+ shuttles reversibly between the negative and positive electrodes. As shown in Fig. 4b, the PbǀǀPbI 2 full battery delivers a discharge capacity of 110 mAh g –1 at 0.5 C (1 C = 116 mA g –1 ) and retains 94 mAh g –1 at 10 C, demonstrating rapid charge-transfer kinetics and excellent rate capability. The discharge capacity fully recovers to 110 mAh g –1 after rate cycling and remains at 92 mAh g –1 after 500 cycles at 0.5 C (Fig. 4c), effectively suppressing the capacity degradation typically observed for iodide-based positive electrodes. Long-term cycling confirms excellent durability, with >90% capacity retention over 800 and 1,000 cycles at 1 C and 5 C, respectively, corresponding to discharge capacities of 100 and 90 mAh g –1 (Supplementary Fig. 78). Furthermore, the PbǀǀPbBr 2 full battery exhibits higher discharge capacities (>125 mAh g –1 ) and elevated operating voltages (>1.2 V) at 2 C and 5 C (1 C = 146 mA g –1 ), retaining ~80% of its initial discharge capacity after 1,000 cycles (Fig. 4d–f). Notably, the more energetic PbǀǀPbCl 2 full battery delivers a discharge capacity of 165 mAh g –1 (theoretical capacity of 192 mAh g –1 for PbCl 2 ) and maintains a stable output voltage above 1.4 V for over 200 cycles (Supplementary Fig. 79). We further expanded the design space of HPE-based batteries by constructing a new class of aqueous Sn-metal batteries, in which the [SnCl 3 ] – /Sn couple features a favorable redox potential of –0.30 V vs. SHE and a high specific capacity of 451.7 mAh g –1 , establishing Sn as a promising high-energy negative electrode. However, as in lead–acid systems, most reported aqueous Sn-metal batteries employ strongly acidic electrolytes, where the intrinsic challenges of Sn 2+ —including limited solubility, oxidative instability, hydrolysis, and acid-induced corrosion—remain unresolved 7,49 . In contrast, SICEs address these issues by stabilizing Sn 2+ as highly soluble [SnCl 3 ] – chlorocomplexes, thereby eliminating solubility and stability constraints and suppressing corrosive degradation of the metallic negative electrode. This stabilization allows the Sn negative electrode to be paired flexibly with both I 2 and KBr positive electrodes (Supplementary Fig. 77c). The SnǀǀI 2 full battery, employing a four-electron 2I – /I 2 /2I + conversion positive electrodes with two discharge plateaus, delivers a high discharge capacity of 380 mAh g –1 at 2 C (1 C = 400 mA g –1 ) and maintains stable cycling for over 500 cycles (Fig. 4g,h). In parallel, the SnǀǀKBr full battery operates at an average voltage above 1.2 V and retains a capacity of ~150 mAh g –1 after 200 cycles (Supplementary Fig. 80a,b). To extend this HPE-based design paradigm, we investigated four-electron Te and Se positive electrodes, which offer high theoretical specific capacities (840.2 and 1358.2 mAh g –1 ) and favorable redox potentials of 0.57 V and 0.90 V vs. SHE, respectively. Motivated by these properties, we constructed high-energy aqueous hybrid batteries by pairing the two-electron [SnCl 3 ] – /Sn negative electrode with either the [TeCl 6 ] 2– /Te or SeOCl 2 /Se positive electrode, employing decoupled SICEs to ensure electrochemical compatibility between the anodic and cathodic species (Supplementary Fig. 77d). Both SnǀǀTe and SnǀǀSe full batteries exhibit stable four-electron conversion reactions sustained for over 100 h of continuous cycling (Fig. 4i). The SnǀǀTe full battery displays highly overlapping charge/discharge curves, indicative of efficient redox reversibility (Fig. 4j), while the SnǀǀSe full battery operates at a higher voltage of ~1.1 V (Fig. 4k), consistent with the intrinsically higher redox potential of the SeOCl 2 /Se couple relative to [TeCl 6 ] 2– /Te. This proof-of-concept demonstrates the electrochemical compatibility of soluble HPE cations and establishes a battery architecture that enables dual reversible plating/stripping behavior within a single device. Together with additional rechargeable Sb- and Bi-based batteries (Supplementary Figs. 77e,f and 80c–f, and Supplementary Note 10), these results confirm the generality of SICE-enabled HPE-based electrochemical systems. To underscore their translational potential, we assembled a larger-format PbǀǀPbBr 2 full battery that delivers performance comparable to its small-scale counterpart and successfully powers a commercial LED (Fig. 4l,m). This demonstration highlights the practical viability, versatility, and scalability of the SICE strategy for next-generation aqueous energy storage. Conclusion In summary, heavy p-block electrochemistry in water, long regarded as intrinsically unstable under conventional electrolyte design, is reframed here as a problem of solvation design, motivating a counterintuitive “dissolved but not hydrated” concept to overcome this instability. Rather than tolerating direct HPE cation–H 2 O contact, we re-engineer the solvation shells of HPE cations into anion-coordination-dominated environments that shield them from hydrolysis and other parasitic reactions. Building on this principle, first-principles-based descriptors of cation hydration and cation–anion binding, corroborated by spectroscopic analyses, enabled the screening of hundreds of cation–anion pairs, pinpointing auxiliary salts that pair a strongly hydrated yet weakly coordinating cation with an anion that preferentially coordinates HPE cations. The resulting CaCl 2 -based SICE establishes a chlorocomplex-dominated solvation regime in which anion-protective HPE cations, rather than hydrated species, govern multielectron redox and render an otherwise unstable family of elements reversibly redox-active in water. From a technological standpoint, CaCl 2 -based SICEs shift heavy p-block electrochemistry from toxic, corrosive, high-temperature, or nonaqueous baths to benign aqueous electrolytes that support compositionally precise HPE electrodeposition and rechargeable multielectron aqueous batteries with HPE electrodes. These demonstrations likely represent only a small subset of what is possible: by making heavy p-block electrochemistry viable in water, the same solvation-design framework could unlock aqueous routes to thermoelectric and optoelectronic devices, electrocatalysis, electronic metallization and protective coatings, and electrochemical recycling of heavy p-block materials. Methods Materials and electrolytes Sodium chloride (NaCl, 99%), potassium chloride (KCl, 99%), magnesium chloride (MgCl 2 , 99%), calcium chloride (CaCl 2 , 99%), manganese chloride (MnCl 2 , 99%), zinc chloride (ZnCl 2 , 98%), lead chloride (PbCl 2 , 99%), tin (Ⅱ) chloride dihydrate (SnCl 2 ∙2H 2 O, 99%), antimony chloride (SbCl 3 , 99%), bismuth chloride (BiCl 3 , 98%), selenium chloride (SeCl 4 , 98%) and tellurium chloride (TeCl 4 , 99%) were purchased from Sigma-Aldrich. The electrolytes were prepared by dissolving the calculated amounts of chlorides in deionized water according to the molality (m, mol kg – 1 ). Unless otherwise specified, electrochemical investigations of Pb, Sn, Sb, Bi, Te, and Se systems were conducted in aqueous electrolytes of 0.4 m PbCl 2 , 1 m SnCl 2 , 1 m SbCl 3 , 1 m BiCl 3 , 1 m TeCl 4 , and 1 m SeCl 4 , each dissolved in 6 m CaCl 2 . For Sn-based electrolytes, 1 vol% Polyethylene glycol (PEG 400) was additionally added during electrochemical measurements. Preparation of current collectors Copper (Cu) foil (~9 μm thickness), titanium (Ti) foil (~20 μm thickness), Ti mesh with 100 mesh, polytetrafluoroethylene (PTFE) aqueous dispersion solution, and conductive carbon (Ketjen black; KB) were purchased from Crand New Energy Technology. Cu and Ti foils were directly used as the current collectors for PbǀǀCu and SnǀǀCu cells, and SbǀǀTi and BiǀǀTi cells, respectively, without additional treatments. KB electrode was prepared by thoroughly grinding KB and PTFE in a mass ratio of 9:1 in isopropanol (99%, Sigma-Aldrich) until forming a homogeneous and dough-like mass. The resulting mixture was then pressed onto Ti mesh and dried in a vacuum oven at 80 °C overnight, yielding a KB loading of ~3 mg cm –2 . The KB electrode was used as current collectors for SeǀǀKB and TeǀǀKB cells and three-electrode measurements. The current collectors of Cu foil, Ti foil and KB-coated electrode were cut into 12 mm diameter discs. Preparation of HPE electrodes Lead (Pb, >99%), tin (Sn, >99%), and bismuth (Bi, >99%) foils (purchased from SCI Materials Hub) were rolled using a roll press (MSK-2150-H5) to a final thickness of 100 μm for use as electrode materials. Antimony (Sb, >99.99%) beads with (≤5 mm), tellurium (Te, >99.99%) powder of ~30 mesh, and selenium (Se, >99.99%) powder (~50 mesh) were purchased from Sigma-Aldrich. Prior to electrode fabrication, they were ball-milled at 500 rpm for 24 h under a 50-min milling 10-min resting condition, yielding uniformly dispersed powders with average sizes in the micrometer range. Sb or Se electrodes were fabricated by thoroughly grinding Sb or Se powder, KB, and PTFE in a mass ratio of 8:1:1 in isopropanol. Te electrode was similarly prepared by grinding Te powder, graphite (purchased from Crand New Energy Technology), KB, and PTFE in a mass ratio of 6:2:1:1 in isopropanol. The mixtures were ground until forming plasticine-like masses, which were then pressed onto Ti mesh and dried in a vacuum oven at 80 °C overnight, yielding active material loadings of ~20 mg cm –2 . The electrodes, including Sn, Pb, Sb, Bi, Se, and Te, were cut into circular discs with a diameter of 10 mm. Preparation of haloid electrodes Lead iodide (PbI 2 , 99%), lead bromide (PbBr 2 , 98%), iodine (I 2 , 99%), potassium bromine (KBr, 99%), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI], 98%) and tetrapropylammonium bromide (TPABr, 98%) were purchased from Sigma-Aldrich. Active carbon (AC, YP80F) was purchased from Crand New Energy Technology. PbI 2 , PbBr 2 , PbCl 2 , BiCl 3 , SbCl 3 , I 2 , and KBr electrodes were prepared by mixing the active materials with additives in specific mass ratios. The detailed compositions and mass ratios were as follows: PbI 2 (6:2:1:1 for PbI 2 : AC: KB: PTFE), PbBr 2 (6:1: 2:0.5:0.5 for PbBr 2 : TPABr: AC: KB: PTFE), PbCl 2 (6: 3: 2: 1: 0.5 for PbCl 2 : [BMIM][TFSI]: AC: KB: PTFE), BiCl 3 (6:3.5:2:1:0.5 for BiCl 3 : [BMIM][TFSI]: AC: KB: PTFE), SbCl 3 (5:3:2:0.5:0.5 for SbCl 3 : [BMIM][TFSI]: AC: KB: PTFE), I 2 (4:4:1:1 for I 2 : AC: KB: PTFE), and KBr (6:1:2:0.5:0.5 for KBr: TPABr: AC: KB: PTFE). All materials were ground thoroughly in isopropanol until forming a uniform and dough-like paste. The resulting slurries were then pressed onto Ti mesh and dried at 70 °C in an oven for 8 h. The active material loadings were ~3.0 mg cm –2 for PbI 2 , ~4.5 mg cm –2 for PbBr 2 , ~3.1 mg cm –2 for PbCl 2 , ~3.3 mg cm –2 for BiCl 3 , ~3.8 mg cm –2 for SbCl 3 , ~2.5 mg cm –2 for I 2 , and ~3.5 mg cm –2 for KBr. The electrodes, including PbI 2 , PbBr 2 , PbCl 2 , BiCl 3 and SbCl 3 , I 2 and KBr, were cut into circular discs with a diameter of 10 mm. Swagelok cell assembly The custom-made Swagelok-type cell was used for cell cycling. Two-electrode configurations, including symmetric (PbǀǀPb, SnǀǀSn, SbǀǀSb, BiǀǀBi, SeǀǀSe and TeǀǀTe), asymmetric (PbǀǀCu, SnǀǀCu, SbǀǀTi, BiǀǀTi, SeǀǀKB and TeǀǀKB), and full (PbǀǀPbI 2 , PbǀǀPbBr 2 , PbǀǀPbCl 2 , BiǀǀBiCl 3 , and SbǀǀSbCl 3 ) cells, were assembled with electrodes placed face-to-face in Swagelok-type cells. The electrodes were separated by a glass fiber separator (GF/A, Whatman) soaked with ~100 μL of electrolyte. Unless otherwise specified, the electrolytes used for electrochemical tests were 0.4 m PbCl 2 + 6 m CaCl 2 for Pb-based systems, 1 m SnCl 2 + 6 m CaCl 2 for Sn-based systems, 1 m SbCl 3 + 6 m CaCl 2 for Sb-based systems, 1 m BiCl 3 + 6 m CaCl 2 for Bi-based systems, 1 m SeCl 4 + 6 m CaCl 2 for Se-based systems, and 1 m TeCl 4 + 6 m CaCl 2 for Te-based systems. Membrane-separated dual-chamber cell assembly The home-built two-electrode membrane-separated dual-chamber cell was used for hybrid cell cycling.The hybrid SnǀǀI 2 battery was assembled using a Sn anode, a glass fiber separator soaked with ~100 μL of 1 m SnCl 2 + 5 m CaCl 2 electrolyte (anolyte side), a Nafion 117 ion-exchange membrane, a second separator soaked with ~100 μL of 5 m CaCl 2 electrolyte (catholyte side), and an I 2 cathode. The SnǀǀKBr cell followed the same configuration, using 6 m CaCl 2 electrolyte as the catholyte and a KBr cathode. For SnǀǀSe and SnǀǀTe cells, the catholyte comprised 1 m SeCl 4 or TeCl 4 in 6 m CaCl 2 , with Se or Te as the cathode, respectively. The Nafion membrane enabled Ca 2+ conduction to balance charge between compartments and was pretreated by soaking in 1 m CaCl 2 for 24 h and rinsing thoroughly with deionized water before use. Electrochemical measurements Three-electrode cyclic voltammetry (CV) and galvanostatic electrodeposition experiments were carried out in beaker cells containing 10 mL of electrolyte per test, using a Biologic VMP3 workstation. The three-electrode setup consisted of a KB-coated working electrode, a KCl-saturated Ag/AgCl reference electrode, and a Pb, Sn, Sb, Bi, Se, or Te counter electrode. Two-electrode galvanostatic cycling tests were conducted using a multichannel Neware battery testing system. All electrochemical measurements were carried out at room temperature. Materials characterizations 17 O and 35 Cl nuclear magnetic resonance (NMR) spectra were collected using a Bruker ( AVANCE III, HD 500 MHz) NMR spectrometer. Chemical shifts for 17 O NMR were referenced to an internal capillary tube containing D 2 O, while 35 Cl NMR was referenced to a saturated NaCl in D 2 O sealed within a capillary tube placed inside the NMR tube. Scanning electron microscopy (SEM) was performed using a JEOL JSM-7600F microscope to examine surface morphologies. X-ray diffraction (XRD) patterns were collected on a Bruker D8 Advance diffractometer with Cu Kα radiation (λ = 1.5406 Å). Raman spectra, including both high- and low-frequency regions, were obtained using a Horiba LabRAM HR Evolution spectrometer equipped with a 532 nm laser. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was carried out on a JEOL JEM-ARM200F NeoARM microscope operating at 200 kV with a spherical aberration corrector. HAADF-STEM samples were prepared using a focused ion beam (FIB) system (ZEISS Crossbeam 540). X-ray absorption spectroscopy was used to characterize the coordination of Ca 2+ and Pb 2+ in aqueous medium. The measurements were conducted at the XAFCA beamline of the Singapore Synchrotron Light Source (SSLS). All data acquisition was performed in transmission mode employing a Si(111) double-crystal monochromator except for sample of 1 m CaCl 2 solution at Ca K-edge which is performed in SDD mode. Data are collected at Ca K-edge and Pb L 3 -edge. All data were processed with Athena and Artemis (version 0.9.26) 50 . The value of E 0 was determined by the first peak position of the first derivative of the XANES curve. WT-EXAFS analysis was conducted using HAMA Fortran software 51 , employing the Morlet wavelet as the mother wavelet function. The kappaMorlet and sigmaMorlet parameters were adjusted to optimize k-resolution for different R regions. Geometric structure optimization prior to AIMD Simulation All simulations were carried out using spin-polarized methods as implemented in the QUICKSTEP code of the CP2K 2025 package 52,53 based on DFT. The general gradient approximation (GGA) parametrized by Perdew, Burke, and Ernzerhof (PBE) 54 was used as the exchange-correlation functional. The Kohn-Sham (KS) equations were solved according to the Gaussian and plane wave (GPW) formalism. Grimme’s DFT-D3 correction 55 was adopted to describe the weak van der Waals interaction. The GPW used Goedecker-Teter-Hutter pseudo potentials 56 to describe the interactions between core and valence electrons, while the valence electron density was represented in terms of Gaussian type orbital (GTO) basis set functions. In particular, we used DZVP-MOLOPT-SR-GTH basis sets for geometry optimization and TZVP-MOLOPT-SR-GTH basis sets for static calculations, and the Brillouin zone integration was sampled using a Monkhorst-Pack 57 special k-point mesh with a resolution of 2π*0.04 was applied. The convergence criterion for the maximum force was set as 5 × 10 −4 atomic units. The auxiliary PW basis set, which is needed for the efficient solution of the Poisson's equation in reciprocal space, was truncated at 500 Ry. All Electronic structure and wave function analysis were conducted using Multiwfn software 58 . AIMD simulations All AIMD simulations reported here were performed using DFT with the Gaussian and Plane Wave combined approach as implemented in CP2K/Quickstep. The electrons were treated using the exchange correlation PBE functional with a Grimme D3 correction. Core electrons were described using the Goedecker-Teter-Hutter (GTH) pseudo-potentials, and the valence density was developed on a double-zeta DZVP basis set along with an auxiliary plane wave basis set with cutoff energy of 500 Ry. The temperature of the simulation was maintained at 300 K using the Canonical sampling through velocity rescaling (CSVR) thermostat coupled to the system. The AIMD simulations were performed with a time step of 1 fs to investigate the hydration structures of auxiliary cations in water. Each system contained one cation and 60 H 2 O molecules, with additional Cl ‒ placed in a distant corner of the simulation box to maintain charge neutrality without perturbing hydrated interactions. For all the MD trajectories, the initial ~3 ps was regarded as the equilibration period, and then followed by production periods of 10 ps. Note that due to the large size of the supercells, only Γ point was used in all calculations. For AIMD simulations involving transition metal cations, we considered spin polarization, while other cations were not considered. Geometric optimization and property analysis of solvation structures All the structures used in density functional theory calculation were optimized by Gaussian 16 at B3LYP hybrid function with def2-TZVP basis. Then a single point calculation was carried at same level. DFT-D3(BJ) method was used to describe weak interaction between molecules. The electrostatic potential, IGMH 59 , molecular vdW volume 60 and ELF 61 were analyzed by Multiwfn and was drawn by VMD package 62 . The total binding energy (D E ) was calculated using the [Ca(H 2 O) n ] 2+ ( n = 1‒8) complex as an example, according to D E = E Ca(H2O)n ‒ E Ca ‒ n E H2O , where E Ca(H2O)n , E Ca , and E H2O are the energies of [Ca(H 2 O) n ] 2+ , Ca 2+ , and H 2 O, respectively. Declarations Data Availability All data needed to evaluate the conclusions in the paper are present in the paper and/or Supplementary Information Acknowledgements This work was financially supported by A*STAR RIE2025 Manufacturing, Trade and Connectivity (MTC) Programmatic Fund grant M24N6b0043. We gratefully acknowledge Dr. Shibo Xi for assistance with the X-ray absorption measurements performed at the XAFCA beamline of the Singapore Synchrotron Light Source (SSLS). Also, we gratefully acknowledge Dr. Haozhe Zhang for independent external validation of the salting-in strategy-enabled reversible heavy p-block electrochemistry performed at Argonne National Laboratory. Author contributions All authors approved the final version of the manuscript. Y.S.M. and H.Y.Y supervised the project. Y.-F.C. proposed the research direction and conceived the idea of the work. Y.-F.C. designed and performed the experiments. 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Phys. Chem. Chem. Phys. 23 , 20323–20328 (2021). Humphrey, W., Dalke, A. & Schulten, K. VMD: Visual molecular dynamics. J. Mol. Graphics 14 , 33–38 (1996). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformationNature.pdf Supporting Information for Paper Submission Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8632446","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":594639355,"identity":"bf25346c-f55b-4823-811d-fff916e9039e","order_by":0,"name":"Hui Ying Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIiWNgGAWjYJACZgYGCQY2BgbGBxB+AvFamA1I0QIGbBJEaTE4fvbw68I2i8Q+6fZr1YVtdQz87DkGjD9+4dFyJi/NemabRGKbzJmy2zPbDjNI9rwxYObtw6PlQI6ZMS9Ii0RO2m3etgMMBjdyDJgZe/BoOf8GoaWYF+gwe6AWxp/4tNzIMX4M0ZJ+jJm3jZnBQCLHgIHnB24tkjfemDHznJMwBtrCLM1z7jCPxJlnBYd5G3Br4TufY/yZp6xOdv6M9Icghhx/e/LGhz/+4NaicAASHY4NDDzgmOQBEQcY23BrkW9gYP4ApO0ZGNgfIInjsWUUjIJRMApGHAAA59FQHQL53VwAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-2244-8231","institution":"National University of Singapore","correspondingAuthor":true,"prefix":"","firstName":"Hui","middleName":"Ying","lastName":"Yang","suffix":""},{"id":594639356,"identity":"0838c074-dac1-4411-bfaa-298c301af435","order_by":1,"name":"Yang-Feng Cui","email":"","orcid":"https://orcid.org/0000-0003-4060-7627","institution":"NUS","correspondingAuthor":false,"prefix":"","firstName":"Yang-Feng","middleName":"","lastName":"Cui","suffix":""},{"id":594639357,"identity":"71bef294-4c87-4138-96b8-610c3e39a574","order_by":2,"name":"Ming Zhang","email":"","orcid":"","institution":"NUS","correspondingAuthor":false,"prefix":"","firstName":"Ming","middleName":"","lastName":"Zhang","suffix":""},{"id":594639358,"identity":"7fd569c1-06ab-4f30-8909-aeeab0afa91f","order_by":3,"name":"Yunhai Zhu","email":"","orcid":"https://orcid.org/0000-0002-2333-2740","institution":"Wuhan Textile University","correspondingAuthor":false,"prefix":"","firstName":"Yunhai","middleName":"","lastName":"Zhu","suffix":""},{"id":594639359,"identity":"0b928847-8631-4679-a141-5cb04582bce2","order_by":4,"name":"Haobin Song","email":"","orcid":"","institution":"Singapore University of Technology and Design","correspondingAuthor":false,"prefix":"","firstName":"Haobin","middleName":"","lastName":"Song","suffix":""},{"id":594639360,"identity":"4e167cf7-7060-4085-962a-58c7d1020eb7","order_by":5,"name":"Yifan Li","email":"","orcid":"","institution":"NUS","correspondingAuthor":false,"prefix":"","firstName":"Yifan","middleName":"","lastName":"Li","suffix":""},{"id":594639361,"identity":"8f41438e-e93b-4013-92f9-9464f2e64e71","order_by":6,"name":"Nan Zhao","email":"","orcid":"","institution":"NUS","correspondingAuthor":false,"prefix":"","firstName":"Nan","middleName":"","lastName":"Zhao","suffix":""},{"id":594639362,"identity":"3df98377-74c2-4c34-b05c-03b1472a7815","order_by":7,"name":"Wenjing Li","email":"","orcid":"","institution":"NUS","correspondingAuthor":false,"prefix":"","firstName":"Wenjing","middleName":"","lastName":"Li","suffix":""},{"id":594639363,"identity":"fa4fd653-7492-433f-b599-87046ce0a871","order_by":8,"name":"Ying Shirley Meng","email":"","orcid":"https://orcid.org/0000-0001-8936-8845","institution":"The University of Chicago","correspondingAuthor":false,"prefix":"","firstName":"Ying","middleName":"Shirley","lastName":"Meng","suffix":""}],"badges":[],"createdAt":"2026-01-18 16:05:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8632446/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8632446/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104385025,"identity":"de334ea6-8fe5-440e-9d59-3158479315d1","added_by":"auto","created_at":"2026-03-11 08:37:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1721569,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign principles for stabilizing HPE cations in water.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Position of representative HPEs in the periodic table. \u003cstrong\u003eb\u003c/strong\u003e, Schematic illustration of heavy p-block electrochemistry, showing soluble HPE cations formed through anion-coordinate solvation with strongly hydrated auxiliary cations, in contrast to insoluble HPE cations in water. \u003cstrong\u003ec\u003c/strong\u003e, Surface ESP distributions of HPE cations, H\u003csub\u003e2\u003c/sub\u003eO, and anions. \u003cstrong\u003ed\u003c/strong\u003e, CNs of auxiliary cations in water obtained from AIMD simulations (derived from Supplementary Figs. 2, 3). \u003cstrong\u003ee\u003c/strong\u003e, Binding energies of hydrated auxiliary cations with varying CNs of H\u003csub\u003e2\u003c/sub\u003eO molecules.\u003cstrong\u003e f\u003c/strong\u003e, Surface ESP distributions of various anions mapped as a function of their molecular van der Waals (vdW) volumes. \u003cstrong\u003eg\u003c/strong\u003e, Correlation between Ca\u003csup\u003e2+\u003c/sup\u003e–anion binding energy for trianionic coordination structures and the anionic ESP minima. Insets: ELF maps (isosurface = 0.5) of DFT-optimized [CaCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e and [Ca(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e structures. \u003cstrong\u003eh\u003c/strong\u003e, Correlation between Pb\u003csup\u003e2+\u003c/sup\u003e–anion binding energy for trianionic coordination structures and the\u003cem\u003e \u003c/em\u003eanionic ESP minima. Insets: ELF maps (isosurface = 0.5) of DFT-optimized [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e and [Pb(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e structures. \u003cstrong\u003ei\u003c/strong\u003e,\u003cem\u003e Sign\u003c/em\u003e(\u003cem\u003eλ\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003eρ\u003c/em\u003e colored isosurfaces of \u003cem\u003eδg\u003c/em\u003e\u003csub\u003einter\u003c/sub\u003e\u003csup\u003e \u003c/sup\u003e= 0.01 a.u. from IGMH analyses of DFT-optimized [Ca(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e, [Pb(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e, [CaCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e, and [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e–\u003c/sup\u003e structures.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/8e787bc5e0a949a8c3a6cb86.png"},{"id":104406278,"identity":"fbe1cabc-af09-4657-8b83-e65b10c9427f","added_by":"auto","created_at":"2026-03-11 12:25:11","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1112766,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProposed\u003c/strong\u003e \u003cstrong\u003eSICEs. a\u003c/strong\u003e, Relationship between binding energy and \u003cem\u003esign\u003c/em\u003e(\u003cem\u003eλ\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003eρ\u003c/em\u003e value at the attractive cation–Cl\u003csup\u003e–\u003c/sup\u003e interaction where \u003cem\u003eδg\u003c/em\u003e\u003csub\u003einter\u003c/sub\u003e reaches its maximum. Insets: \u003cem\u003esign\u003c/em\u003e(\u003cem\u003eλ\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003eρ\u003c/em\u003e-colored isosurfaces at \u003cem\u003eδg\u003c/em\u003e\u003csub\u003einter\u003c/sub\u003e = 0.01 a.u. from IGMH analyses of representative solvation structures. \u003cstrong\u003eb\u003c/strong\u003e, Solubility of PbCl\u003csub\u003e2\u003c/sub\u003e in various chloride-based solutions. \u003cstrong\u003ec\u003c/strong\u003e, Fourier transform magnitudes of Pb L\u003csub\u003e3\u003c/sub\u003e-edge EXAFS spectrum (solid line) and fit (hollow circles) for 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solution. \u003cstrong\u003ed\u003c/strong\u003e, \u003cstrong\u003ee\u003c/strong\u003e, Percentage of strong hydrogen-bonds obtained from Raman spectra (\u003cstrong\u003ed\u003c/strong\u003e) and \u003csup\u003e17\u003c/sup\u003eO NMR chemical shifts (\u003cstrong\u003ee\u003c/strong\u003e) in aqueous NaCl, KCl, MgCl\u003csub\u003e2\u003c/sub\u003e, CaCl\u003csub\u003e2\u003c/sub\u003e, MnCl\u003csub\u003e2\u003c/sub\u003e and ZnCl\u003csub\u003e2\u003c/sub\u003e solutions with increasing concentrations. \u003cstrong\u003ef\u003c/strong\u003e, Fourier transform magnitudes of the Ca K-edge EXAFS spectra (solid line) and fits (hollow circles) for 1 m CaCl\u003csub\u003e2\u003c/sub\u003e, 6 m CaCl\u003csub\u003e2\u003c/sub\u003e and 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solutions. \u003cstrong\u003eg\u003c/strong\u003e, Scatter plots of \u003cem\u003eδg\u003c/em\u003e\u003csub\u003einter \u003c/sub\u003eagainst \u003cem\u003esign\u003c/em\u003e(\u003cem\u003eλ\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003eρ\u003c/em\u003e for Ca\u003csup\u003e2+\u003c/sup\u003e–Cl\u003csup\u003e‒\u003c/sup\u003e interactions in [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e–Cl\u003csup\u003e‒\u003c/sup\u003e interactions in [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e. \u003cstrong\u003eh\u003c/strong\u003e, Schematic of soluble Pb\u003csup\u003e2+\u003c/sup\u003e formation in water via strongly hydrated [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e‒\u003c/sup\u003e-coordinated [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e. \u003cstrong\u003ei–l,\u003c/strong\u003e Raman spectra of SnCl\u003csub\u003e2 \u003c/sub\u003e(\u003cstrong\u003ei\u003c/strong\u003e), SbCl\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003ej\u003c/strong\u003e), BiCl\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003ek\u003c/strong\u003e) and TeCl\u003csub\u003e4\u003c/sub\u003e (\u003cstrong\u003el\u003c/strong\u003e) in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solutions with increasing concentrations. \u003cstrong\u003em\u003c/strong\u003e, Raman spectra of 1 m SeCl\u003csub\u003e4\u003c/sub\u003e and 1 m SeCl\u003csub\u003e4\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solutions. Insets: \u003cem\u003esign\u003c/em\u003e(\u003cem\u003eλ\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003eρ\u003c/em\u003e-colored isosurfaces at \u003cem\u003eδg\u003c/em\u003e\u003csub\u003einter\u003c/sub\u003e\u003csup\u003e \u003c/sup\u003e= 0.01 a.u. from IGMH analysis of DFT-optimized [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e (\u003cstrong\u003ei\u003c/strong\u003e), [SbCl\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e (\u003cstrong\u003ej\u003c/strong\u003e), [BiCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3‒\u003c/sup\u003e (\u003cstrong\u003ek\u003c/strong\u003e), [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2‒\u003c/sup\u003e (\u003cstrong\u003el\u003c/strong\u003e), and H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e and SeOCl\u003csub\u003e2\u003c/sub\u003e (\u003cstrong\u003em\u003c/strong\u003e) structures.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/9cb6ad565283707e28eb4895.png"},{"id":104385027,"identity":"d2d659da-d505-43ac-b2a0-46bcb503daca","added_by":"auto","created_at":"2026-03-11 08:37:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1905113,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eReversible heavy p-block electrochemistry. a\u003c/strong\u003e, \u003cstrong\u003eb\u003c/strong\u003e, CV curves of [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e/Pb, [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e/Sn, [SbCl\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e‒\u003c/sup\u003e/Sb, and [BiCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3‒\u003c/sup\u003e/Bi (\u003cstrong\u003ea\u003c/strong\u003e), and H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e/Se and SeOCl\u003csub\u003e2\u003c/sub\u003e/Se (\u003cstrong\u003eb\u003c/strong\u003e) in SICEs at a scan rate of 1 mV s\u003csup\u003e‒1\u003c/sup\u003e. \u003cstrong\u003ec\u003c/strong\u003e, Galvanostatic electrodeposition of HPEs in SICEs at 10 mA cm\u003csup\u003e‒2\u003c/sup\u003e for 1 h. \u003cstrong\u003ed–i\u003c/strong\u003e, SEM images of Pb (\u003cstrong\u003ed\u003c/strong\u003e), Sn (\u003cstrong\u003ee\u003c/strong\u003e), Sb (\u003cstrong\u003ef\u003c/strong\u003e), Bi (\u003cstrong\u003eg\u003c/strong\u003e), Te (\u003cstrong\u003eh\u003c/strong\u003e), and Se (\u003cstrong\u003ei\u003c/strong\u003e) electrodeposits. Scale bars: 20 μm. Inset in (\u003cstrong\u003ei\u003c/strong\u003e): EDS mapping of Se electrodeposits. \u003cstrong\u003ej–o\u003c/strong\u003e, Atomic-resolution HAADF-STEM images of Pb (\u003cstrong\u003ej\u003c/strong\u003e), Sn (\u003cstrong\u003ek\u003c/strong\u003e), Sb (\u003cstrong\u003el)\u003c/strong\u003e, Bi (\u003cstrong\u003em\u003c/strong\u003e), Te (\u003cstrong\u003en\u003c/strong\u003e), and Se (\u003cstrong\u003eo\u003c/strong\u003e) electrodeposits. Scale bars: 2 nm. \u003cstrong\u003ep\u003c/strong\u003e, Corresponding XRD patterns of HPE electrodeposits with standard reference codes. \u003cstrong\u003eq\u003c/strong\u003e, Cycling performance of PbǀǀPb symmetric cell at 1 mA cm\u003csup\u003e‒2 \u003c/sup\u003eand 1 mAh cm\u003csup\u003e‒2\u003c/sup\u003e. \u003cstrong\u003er\u003c/strong\u003e, \u003cstrong\u003es\u003c/strong\u003e, Voltage profiles (\u003cstrong\u003er\u003c/strong\u003e) and CE (\u003cstrong\u003es\u003c/strong\u003e) of PbǀǀCu asymmetric cell at 1 mA cm\u003csup\u003e‒2 \u003c/sup\u003ewith a fixed plated capacity of 1 mAh cm\u003csup\u003e‒2\u003c/sup\u003e. \u003cstrong\u003et\u003c/strong\u003e,\u003cstrong\u003e u\u003c/strong\u003e, Summary of cycle life (\u003cstrong\u003et\u003c/strong\u003e) and average CEs (\u003cstrong\u003eu\u003c/strong\u003e) of symmetric and asymmetric HPE cells during repeated plating/stripping behaviors.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/bbf11e0c3531218413df1fe0.png"},{"id":104780048,"identity":"93f3224f-12ab-4ddd-81f7-efdfb668331e","added_by":"auto","created_at":"2026-03-17 07:49:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":900462,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProposed aqueous HPE-based batteries. a\u003c/strong\u003e, Redox potentials and theoretical specific capacities of HPE electrodes. \u003cstrong\u003eb\u003c/strong\u003e, \u003cstrong\u003ec\u003c/strong\u003e, Rate-dependent charge/discharge profiles (\u003cstrong\u003eb\u003c/strong\u003e) and cycling performance (\u003cstrong\u003ec\u003c/strong\u003e) of PbǀǀPbI\u003csub\u003e2\u003c/sub\u003e full battery at different rates.\u003cstrong\u003e d–f\u003c/strong\u003e, Charge/discharge profiles of PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e full batteries at 2 C (\u003cstrong\u003ed\u003c/strong\u003e) and 5 C (\u003cstrong\u003ee\u003c/strong\u003e), and corresponding cycling performance (\u003cstrong\u003ef\u003c/strong\u003e). \u003cstrong\u003eg\u003c/strong\u003e, \u003cstrong\u003eh\u003c/strong\u003e, Charge/discharge profiles (\u003cstrong\u003eg\u003c/strong\u003e) and cycling performance (\u003cstrong\u003eh\u003c/strong\u003e) of SnǀǀI\u003csub\u003e2\u003c/sub\u003e full battery at 2 C. \u003cstrong\u003ei–k\u003c/strong\u003e, Voltage polarization curves of SnǀǀSe and SnǀǀTe full batteries at 2 mA cm\u003csup\u003e‒2 \u003c/sup\u003eand 1 mAh cm\u003csup\u003e‒2 \u003c/sup\u003e(\u003cstrong\u003ei\u003c/strong\u003e), and corresponding charge/discharge profiles of SnǀǀTe (\u003cstrong\u003ej\u003c/strong\u003e) and SnǀǀSe (\u003cstrong\u003ek\u003c/strong\u003e) full batteries. \u003cstrong\u003el\u003c/strong\u003e,\u003cstrong\u003e M\u003c/strong\u003e, Charge/discharge profiles of scaled-up PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e full battery at 40 mA (\u003cstrong\u003el\u003c/strong\u003e), and its photograph powering an LED display (\u003cstrong\u003em\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/4c4625df23c49b98a14b217a.png"},{"id":104784202,"identity":"2bd1d41a-e215-425c-bc28-cb740e8186eb","added_by":"auto","created_at":"2026-03-17 08:05:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7765992,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/fee00a6e-e785-4aa3-9c3d-8838d6bb9a66.pdf"},{"id":104385029,"identity":"40773c88-7023-4212-ba77-63ff1a34ac48","added_by":"auto","created_at":"2026-03-11 08:37:13","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":13674450,"visible":true,"origin":"","legend":"Supporting Information for Paper Submission","description":"","filename":"SupplementaryInformationNature.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8632446/v1/eecc2f5c96ec4667eacbc841.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Salting-in electrolyte enables reversible heavy p-block electrochemistry in water","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHeavy p-block elements (HPEs), commonly defined as p-block congeners from groups 13 to 17 in periods 4 to 6 (Fig. 1a), encompass a key subset comprising Pb, Sn, Sb, Bi, Se and Te that is central to modern technologies\u003csup\u003e1,2\u003c/sup\u003e, with applications spanning conventional packaging, advanced electronics and emerging electrochemical energy-storage systems driven by rapid electrification. Their technological value is most often realized as coatings and deposited layers on diverse substrates, tailored to the application, including Pb for radiation shielding, corrosion protection, solar cells and lead\u0026ndash;acid batteries\u003csup\u003e3\u0026ndash;5\u003c/sup\u003e; Sn for tinplate packaging, electronic solders, Sn-metal batteries, and Sn-based Na-ion and Li-ion batteries\u003csup\u003e6\u0026ndash;8\u003c/sup\u003e; Sb and Bi as essential components in thermoelectrics, alloy-type negative electrodes of Na-ion batteries and electrocatalysts for CO\u003csub\u003e2\u003c/sub\u003e reduction\u003csup\u003e8\u0026ndash;11\u003c/sup\u003e; and Se and Te as semiconducting chalcogenides for optoelectronic and thermoelectric devices, as well as high-capacity electrodes increasingly explored in alkali-metal batteries\u003csup\u003e9,12\u0026ndash;15\u003c/sup\u003e. However, how to translate the materials promise of HPEs into manufacturable coatings and layers on target substrates that deliver conformal growth and precise compositional control, while remaining low cost, environmentally benign and practical, remains challenging. Established physical vapor deposition (PVD) relies on vacuum-assisted vaporization of solid precursors followed by gas-phase transport and condensation\u003csup\u003e22\u003c/sup\u003e, whereas chemical vapor deposition (CVD) employs volatile species and thermally activated surface reactions but remains dependent on tailored precursors, elevated temperatures and vacuum infrastructure\u003csup\u003e23\u003c/sup\u003e. By contrast, electrochemical deposition provides a solution-based, low-temperature, and inherently scalable route for fabricating metallic and semiconducting layers\u003csup\u003e24\u003c/sup\u003e. It proceeds through mass transport, interfacial desolvation, electron transfer, and surface nucleation and growth, enabling the direct cathodic reduction of dissolved ions on conductive substrates\u003csup\u003e25\u003c/sup\u003e. In contrast to vapor-phase routes (PVD and CVD), electrochemical methods offer precise control over composition, morphology, and thickness without requiring vacuum infrastructure or high-temperature processing. Collectively, these attributes position electrochemical deposition as a compelling platform for scalable and sustainable manufacturing of HPE materials.\u003c/p\u003e\n\u003cp\u003eRealizing such electrochemistry requires the corresponding HPE cations to be both chemically stable and sufficiently soluble in solvent (Fig. 1b, left). However, aqueous HPE electrochemistry remains fundamentally constrained (Fig. 1b, right), because multivalent HPE cations are intrinsically incompatible with water. These cations typically suffer from low solubility (e.g., Pb\u003csup\u003e2+\u003c/sup\u003e, Te\u003csup\u003e4+\u003c/sup\u003e, and Se\u003csup\u003e4+\u003c/sup\u003e), pronounced hydrolytic instability (e.g., Sn\u003csup\u003e2+\u003c/sup\u003e, Sb\u003csup\u003e3+\u003c/sup\u003e, Bi\u003csup\u003e3+\u003c/sup\u003e, Se\u003csup\u003e4+\u003c/sup\u003e, and Te\u003csup\u003e4+\u003c/sup\u003e), and complicated parasitic side reactions (e.g., Sn\u003csup\u003e2+\u003c/sup\u003e, Se\u003csup\u003e4+\u003c/sup\u003e and Te\u003csup\u003e4+\u003c/sup\u003e), which collectively undermine electrochemical reversibility and impede controlled deposition\u003csup\u003e16\u0026ndash;21\u003c/sup\u003e. Previous attempts to overcome these challenges have typically resorted to toxic acids such as fluoroboric acid (HBF\u003csub\u003e4\u003c/sub\u003e) and hexafluorosilicic acid (H\u003csub\u003e2\u003c/sub\u003eSiF\u003csub\u003e4\u003c/sub\u003e) in aqueous solutions, or to expensive high-concentration salt electrolytes, high-temperature molten salts, ionic liquids, and organic solvents\u003csup\u003e26\u0026ndash;31\u003c/sup\u003e. Beyond the significant increases in cost and safety risks, these approaches often suffer from poor electrochemical reversibility and sluggish kinetics.\u003csup\u003e21,26,28,32\u0026ndash;38\u003c/sup\u003e. These long-standing limitations have fundamentally impeded the development and broader application of aqueous electrochemical deposition of HPEs. In this work, we recast the fundamental solvation-design problem, recognizing that reversible aqueous HPE electrochemistry is unattainable within current electrolyte-design principles.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFirst-principles descriptor-guided auxiliary ion screening\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe instability of HPE cations in water stems primarily from the strong electrostatic attraction between the highly positive electrostatic potential (ESP) of HPE cations and the electron-rich O atoms of H\u003csub\u003e2\u003c/sub\u003eO (Fig. 1c, left).\u0026nbsp;Although anions with highly negative ESP could, in principle, outcompete H\u003csub\u003e2\u003c/sub\u003eO for coordination at HPE cation centers through electrostatic attraction (Fig. 1c and Supplementary Fig. 1), current aqueous electrolyte design assumes that dissolving HPE cations necessitates hydration, leading to predominantly H\u003csub\u003e2\u003c/sub\u003eO-rich solvation shells in which ion pairing occurs mainly in solvent-separated or contact forms. Within this framework, dissolution becomes effectively inseparable from hydration, and hydration in turn initiates the failure pathways of aqueous HPE electrochemistry. Here we challenge this hydration-based assumption and propose a counterintuitive electrolyte-design principle of \u0026ldquo;dissolved but not hydrated\u0026rdquo; HPE cations to unlock aqueous HPE electrochemistry. To implement this principle, we devised a salting-in electrolyte strategy based on a dual-salt design comprising an HPE salt and an auxiliary salt, in which the auxiliary salt is selected to suppress H\u003csub\u003e2\u003c/sub\u003eO activity and drive HPE cation coordination from hydration to anion coordination.\u0026nbsp;Guided by first-principles interaction descriptors that quantify cation hydration and cation\u0026ndash;anion pairing, we screened a curated library of hundreds of cation\u0026ndash;anion combinations to pinpoint auxiliary ions that satisfy these coupled requirements (Supplementary Note 1).\u003c/p\u003e\n\u003cp\u003eAccordingly, the auxiliary cation should be strongly hydrated to most effectively suppress bulk water activity, thereby minimizing direct H\u003csub\u003e2\u003c/sub\u003eO coordination to HPE cations. On this basis, we evaluated a library of monovalent (Li\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e and K\u003csup\u003e+\u003c/sup\u003e), divalent (Be\u003csup\u003e2+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e), trivalent (Al\u003csup\u003e3+\u003c/sup\u003e), and first-row transition-metal (TM) ions (Cr\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Co\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e) using ab initio molecular dynamics (AIMD) to resolve their hydration structures and density functional theory (DFT) to quantify hydration strength (Fig. 1d,e and Supplementary Figs. 2\u0026ndash;5). Higher coordination numbers (CNs) and more negative binding energies correspond to stronger hydration. Among these candidates in their hydrated forms (Fig. 1d,e), Li\u003csup\u003e+\u003c/sup\u003e and Na\u003csup\u003e+\u003c/sup\u003e combine weak binding with low CNs; Be\u003csup\u003e2+\u003c/sup\u003e and Al\u003csup\u003e3+\u003c/sup\u003e show distinctly strong binding yet low CNs, whereas K\u003csup\u003e+\u003c/sup\u003e reaches higher CNs but with much weaker binding; and TM ions and Mg\u003csup\u003e2+\u003c/sup\u003e display strong binding but only modest CNs. By contrast, Ca\u003csup\u003e2+\u003c/sup\u003e stands out by stabilizing seven- and eight-coordinate hydration shells with substantial binding energies, matching our hydration-driven design goal. We next screened auxiliary anions using a single design rule: they should preferentially coordinate to HPE cations over auxiliary cations to form anion-protective HPE complexes. We evaluated a panel of anions, including Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e, Br\u003csup\u003e\u0026ndash;\u003c/sup\u003e, I\u003csup\u003e\u0026ndash;\u003c/sup\u003e, perchlorate (ClO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e), nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e), acetate (OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e), tetrafluoroborate (BF\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e), methanesulfonate (MSA\u003csup\u003e\u0026ndash;\u003c/sup\u003e), hexafluorophosphate (PF\u003csub\u003e6\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e), triflate (OTf\u003csup\u003e\u0026ndash;\u003c/sup\u003e), and bis(trifluoromethanesulfonyl)imide (TFSI\u003csup\u003e\u0026ndash;\u003c/sup\u003e). To quantify this preference, we used Pb\u003csup\u003e2+\u003c/sup\u003e as the benchmark HPE cation, as it has the lowest positive ESP among the HPE cations and thus the weakest electrostatic interaction with the negatively charged anions (Fig. 1c and Supplementary Fig. 1). Mapping ESP distributions on anion surfaces clearly differentiates these candidates (Fig. 1f). Smaller anions with more concentrated negative charge, such as Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e, exhibit more negative ESP values than larger, charge-delocalized species, such as TFSI\u003csup\u003e\u0026ndash;\u003c/sup\u003e, whereas OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e is strongly anisotropic, with very negative carboxylate oxygen sites and a much less negative methyl group. We then used the lowest-ESP site on each anion as the coordination locus to construct Ca\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e complexes with one to four ligands.\u003c/p\u003e\n\u003cp\u003eAcross the anion coordination series, three-coordinate complexes consistently exhibit the most negative binding energies and are therefore the most stable species (Supplementary Figs. 6\u0026ndash;8). For Ca\u003csup\u003e2+\u003c/sup\u003e within these three-coordinate series, binding strength increases nearly linearly as the anionic ESP minimum becomes more negative, from weak TFSI\u003csup\u003e\u0026ndash;\u003c/sup\u003e to strong OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e binding (Fig. 1g). However, this trend becomes less definitive for Pb\u003csup\u003e2+\u003c/sup\u003e: [Pb(TFSI)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e remains weakly bound, whereas [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e and [Pb(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e display nearly identical binding energies (Fig. 1h). Moreover, Pb\u003csup\u003e2\u003c/sup\u003e\u003csup\u003e+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e interactions are substantially stronger than Pb\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO coordination, indicating that both anions act as plausible ligands in water (Supplementary Figs. 6a,b and 8a). A closer comparison reveals that [Ca(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e binds more strongly than [Pb(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, whereas [CaCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e is less strongly bound than [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u0026nbsp;\u003c/sup\u003e(Fig. 1g,h). Thus, when Ca\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e coexist in aqueous solutions, the relative binding strengths dictate that OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e is driven to associate with Ca\u003csup\u003e2+\u003c/sup\u003e, whereas Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e is preferentially bound to Pb\u003csup\u003e2+\u003c/sup\u003e. Electron localization function (ELF) mapping of three-coordinate Pb\u003csup\u003e2+\u003c/sup\u003e complexes reveals a stereochemically active lone pair (6s\u003csup\u003e2\u003c/sup\u003e) occupying a basin opposite the ligands, which drives pyramidalization into trigonal-pyramidal geometries (Fig. 1h, insets; Supplementary Figs. 9\u0026ndash;11). In contrast, Ca\u003csup\u003e2+\u003c/sup\u003e lacks a lone pair and adopts more open trigonal-planar configurations (Fig. 1g, insets). Independent gradient model based on Hirshfeld (IGMH) analysis shows how the lone-pair-induced steric field alters anion binding (Fig. 1i; Supplementary Figs. 12\u0026ndash;14). In trigonal-planar [Ca(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, each OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e binds Ca\u003csup\u003e2+\u003c/sup\u003e strongly in a bidentate fashion through both carboxylate oxygens, whereas in trigonal-pyramidal [Pb(OAc)\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e the lone pair occupies one coordination site, forcing OAc\u003csup\u003e\u0026ndash;\u003c/sup\u003e to bind mainly through a single oxygen and weakening its overall interaction (Fig. 1i, top). By comparison, compact Cl⁻ ligands in [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e are barely affected by this steric crowding and retain Pb\u0026ndash;Cl bonds stronger than those in planar [CaCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e (Fig. 1i, bottom). Supplementary binding-energy analyses confirm that Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO interactions are much weaker than Pb\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e bonding and only slightly stronger than H\u003csub\u003e2\u003c/sub\u003eO\u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO hydrogen bonding (Supplementary Figs. 15 and 16), thereby excluding hydrated Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e as the limiting factor for HPE cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e coordination. Among the auxiliary cations examined, Ca\u003csup\u003e2+\u003c/sup\u003e, aside from weakly hydrated monovalent ions, displays the weakest binding for Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e (Supplementary Figs. 17 and 18), whereas higher-ESP HPE cations (Sn\u003csup\u003e2+\u003c/sup\u003e, Sb\u003csup\u003e3+\u003c/sup\u003e, Bi\u003csup\u003e3+\u003c/sup\u003e, Se\u003csup\u003e4+\u003c/sup\u003e, and Te\u003csup\u003e4+\u003c/sup\u003e) bind Cl⁻ more strongly than H\u003csub\u003e2\u003c/sub\u003eO (Supplementary Figs. 19\u0026ndash;23). First-principles screening thus establishes Ca\u003csup\u003e2+\u003c/sup\u003e as the optimal auxiliary cation, strongly hydrated yet only weakly binding to anions, and identifies Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e as the preferred auxiliary anion, binding strongly to HPE cations but only weakly to Ca\u003csup\u003e2+\u003c/sup\u003e within the dual-salt design framework.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA general salting-in strategy for HPE cations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo map the solvation landscape of candidate auxiliary chlorides that suppress H\u003csub\u003e2\u003c/sub\u003eO activity while maintaining readily releasable Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e, we used DFT to enumerate all plausible Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e-bearing solvation structures, assessed their stability from binding energies, and quantified cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e interactions using IGMH analysis (Supplementary Note 2). Each structure is placed on a two-dimensional map of binding energy vs. an IGMH-derived interaction index (Fig. 2a, constructed from Supplementary Figs. 24\u0026ndash;34), where more negative \u003cem\u003esign\u003c/em\u003e(\u003cem\u003e\u0026lambda;\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003e\u0026rho;\u003c/em\u003e values indicate stronger cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e attraction. On this IGMH\u0026ndash;energy map, Li\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, and K\u003csup\u003e+\u003c/sup\u003e form loosely bound Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e-bearing hydrated structures with low overall binding energies and only weakly vdW-level cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e binding. Ca\u003csup\u003e2+\u003c/sup\u003e, in contrast, maintains strong overall hydration yet still exhibits a predominantly vdW-level Ca\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e binding. Mg\u003csup\u003e2+\u003c/sup\u003e strengthens into a weakly attractive regime, whereas first-row transition-metal ions together with Be\u003csup\u003e2+\u003c/sup\u003e and Al\u003csup\u003e3+\u003c/sup\u003e show pronounced direct cation\u0026ndash;Cl⁻ attraction. Notably, among the representative complexes, [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e exemplifies the desired balance. It couples extensive hydration with a weak Ca\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e association (insets of Fig. 2a), placing aqueous CaCl\u003csub\u003e2\u003c/sub\u003e in an optimal regime that suppresses H\u003csub\u003e2\u003c/sub\u003eO activity while preserving high availability of free Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e. To translate the descriptor-guided conclusions into practice, we implemented a salting-in strategy using representative auxiliary chlorides (NaCl, KCl, MgCl\u003csub\u003e2\u003c/sub\u003e, CaCl\u003csub\u003e2\u003c/sub\u003e, MnCl\u003csub\u003e2\u003c/sub\u003e, and ZnCl\u003csub\u003e2\u003c/sub\u003e). Taking Pb\u003csup\u003e2+\u003c/sup\u003e as a model HPE cation, we examined whether these salts could release enough coordinatively available Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e to convert sparingly soluble PbCl\u003csub\u003e2\u003c/sub\u003e into soluble chlorocomplexes. PbCl\u003csub\u003e2\u003c/sub\u003e solubility was quantified by increasing the chloride concentration from 1 m to the highest practical integer molalities for each salt, namely 6 m NaCl, 4 m KCl, 5 m MgCl\u003csub\u003e2\u003c/sub\u003e, 6 m CaCl\u003csub\u003e2\u003c/sub\u003e, 6 m MnCl\u003csub\u003e2\u003c/sub\u003e, and, for comparison, 6 m ZnCl\u003csub\u003e2\u003c/sub\u003e. As shown in Fig. 2b, NaCl and KCl, despite weak cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e interactions, afford only modest salting-in effect because each contributes a single Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e and weakly suppresses H\u003csub\u003e2\u003c/sub\u003eO activity. Among the divalent chlorides, MnCl\u003csub\u003e2\u003c/sub\u003e gives limited gains (~0.07 m PbCl\u003csub\u003e2\u003c/sub\u003e at 5 m MnCl\u003csub\u003e2\u003c/sub\u003e) and ZnCl\u003csub\u003e2\u003c/sub\u003e gives none; both fall in the strong cation\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e attraction regime of Fig. 2a (\u003cem\u003esign\u003c/em\u003e(\u003cem\u003e\u0026lambda;\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003e\u0026rho;\u003c/em\u003e \u0026lt; \u0026minus;0.05 a.u.), with Zn\u003csup\u003e2+\u003c/sup\u003e in particular favoring first-shell Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e over H\u003csub\u003e2\u003c/sub\u003eO and thus retaining chloride (Supplementary Fig. 29a). By contrast, MgCl\u003csub\u003e2\u003c/sub\u003e produces a measurable but smaller salting-in effect than CaCl\u003csub\u003e2\u003c/sub\u003e, consistent with Mg\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e interactions in the attractive-weak regime, whereas Ca\u003csup\u003e2+\u003c/sup\u003e combines strong hydration with a weak vdW-level Ca\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e contact. Consequently, CaCl\u003csub\u003e2\u003c/sub\u003e furnishes the largest pool of coordinatively available Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e and yields the highest PbCl\u003csub\u003e2\u003c/sub\u003e solubility (~0.40 m) via formation of soluble chlorocomplexes (Fig. 2b), in agreement with the two-parameter map (Fig. 2a).\u003c/p\u003e\n\u003cp\u003ePb L\u003csub\u003e3\u003c/sub\u003e-edge X-ray absorption fine structure (EXAFS) analysis identifies the soluble Pb\u003csup\u003e2+\u003c/sup\u003e species in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e containing 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e (Fig. 2c, Supplementary Fig 35, and Supplementary Tables 1 and 2). The Fourier-transformed spectrum exhibits a dominant first-shell peak at ~2.4 \u0026Aring; (uncorrected for phase shift), which fits Pb\u0026ndash;Cl scattering with an optimal fitted coordination number of three and shows no detectable Pb\u0026ndash;O contribution from H\u003csub\u003e2\u003c/sub\u003eO (Supplementary Note 3), supporting its assignment to [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e (Fig. 2c). This assignment is consistent with the DFT-optimized structure of a trigonal-pyramidal geometry (Fig. 1h, inset). In CaCl\u003csub\u003e2\u003c/sub\u003e solutions up to 6 m, Raman spectra reveal a strongly disrupted hydrogen-bond network of bulk water (Fig. 2d; Supplementary Figs. 36 and 37) and \u003csup\u003e17\u003c/sup\u003eO NMR spectra exhibit pronounced upfield shifts (Fig. 2e; Supplementary Fig. 38), together confirming that Ca\u003csup\u003e2+\u003c/sup\u003e most effectively lowers H\u003csub\u003e2\u003c/sub\u003eO activity through strong hydration (Supplementary Note 4). Ca K-edge EXAFS analysis further elucidates the high-coordination hydration structure of Ca\u003csup\u003e2+\u003c/sup\u003e (Fig. 2f, Supplementary Fig. 39, Supplementary Tables 3 and 4, and Supplementary Note 5). In the dilute 1 m CaCl\u003csub\u003e2\u003c/sub\u003e solution, Fourier-transformed EXAFS and first-shell fitting suggest that Ca\u003csup\u003e2+\u003c/sup\u003e is reasonably modeled as being coordinated by eight H\u003csub\u003e2\u003c/sub\u003eO molecules to form [Ca(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e8\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e (Fig. 2f, top). In 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solution, one H\u003csub\u003e2\u003c/sub\u003eO molecule is readily replaced by Cl\u003csup\u003e‒\u003c/sup\u003e, yielding a stable [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e configuration (Fig. 2f, middle), which remains essentially unchanged upon addition of 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e (Fig. 2f, bottom). Consistently, \u003csup\u003e35\u003c/sup\u003eCl NMR spectra exhibit progressive upfield shifts from 1 m to 6 m CaCl\u003csub\u003e2\u003c/sub\u003e solutions (Supplementary Fig. 40), tracking the transformation from [Ca(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e8\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e to [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e. IGMH analysis further reveals that [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e exhibits a pronounced blue attractive region along the Pb\u0026ndash;Cl contacts (\u003cem\u003esign\u003c/em\u003e(\u003cem\u003e\u0026lambda;\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003e\u0026rho;\u003c/em\u003e = ‒0.057 a.u.), consistent with strong halogen-bond-like binding, in sharp contrast to the weak, vdW-level Ca\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e contact in [CaCl(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e7\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e (Fig. 2g). Overall, CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs solubilize Pb\u003csup\u003e2+\u003c/sup\u003e as [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, consistent with strong Ca\u003csup\u003e2+\u003c/sup\u003e hydration and weak Ca\u003csup\u003e2+\u003c/sup\u003e\u0026ndash;Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e pairing (Fig. 2h).\u003c/p\u003e\n\u003cp\u003eBuilding on these insights, we extended the CaCl\u003csub\u003e2\u003c/sub\u003e-based SICE to a broader family of hydrolysis-prone HPE cations, including Sn\u003csup\u003e2+\u003c/sup\u003e, Sb\u003csup\u003e3+\u003c/sup\u003e, Bi\u003csup\u003e3+\u003c/sup\u003e, Te\u003csup\u003e4+\u003c/sup\u003e, and Se\u003csup\u003e4+\u003c/sup\u003e (Supplementary Note 6). Notably, 6 m CaCl\u003csub\u003e2\u003c/sub\u003e effectively suppresses hydrolysis and stabilizes these HPE cations in water as dissolved but not hydrated chlorocomplexes, in sharp contrast to CaCl\u003csub\u003e2\u003c/sub\u003e-free solutions (Supplementary Figs. 41\u0026ndash;46). Raman bands attributable to HPE\u0026ndash;Cl stretching, together with DFT-optimized structures, confirm that HPE cations remain as trigonal-pyramidal [SnCl\u003csub\u003e3\u003c/sub\u003e]⁻, tetrahedral [SbCl\u003csub\u003e4\u003c/sub\u003e]⁻, and octahedral [BiCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u003c/sup\u003e⁻ and [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2\u003c/sup\u003e⁻ chlorocomplexes\u003csup\u003e39\u003c/sup\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003csup\u003e44\u003c/sup\u003e, even when solubilized to high concentrations of up to 6 m SnCl\u003csub\u003e2\u003c/sub\u003e, 4 m SbCl\u003csub\u003e3\u003c/sub\u003e, 2.5 m BiCl\u003csub\u003e3\u003c/sub\u003e, and 3 m TeCl\u003csub\u003e4\u003c/sub\u003e in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e (Fig. 2i\u0026ndash;l). IGMH analyses place these HPE\u0026ndash;Cl interactions within the stable, halogen-bond-like regime (insets of Fig. 2 i\u0026ndash;l; Supplementary Fig. 47). Together with binding-energy analyses (Supplementary Figs. 19\u0026ndash;22), these results show that in CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs, Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e outcompetes H\u003csub\u003e2\u003c/sub\u003eO in the first coordination shell of HPE cations, thereby suppressing their intrinsic tendency toward hydrolysis by stabilizing them as Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e-protected soluble chlorocomplexes. However, Se\u003csup\u003e4+\u003c/sup\u003e represents an exception. Despite its appreciable Se\u003csup\u003e4+\u003c/sup\u003e\u0026ndash;Cl⁻ affinity (Supplementary Fig. 23), no fully Cl⁻-coordinate complex is detected. Instead, CaCl\u003csub\u003e2\u003c/sub\u003e diverts the hydrolysis pathway. In 1 m SeCl\u003csub\u003e4\u003c/sub\u003e, the dominant product is trigonal-pyramidal H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e (3H\u003csub\u003e2\u003c/sub\u003eO + Se\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e + 4H\u003csup\u003e+\u003c/sup\u003e), whereas in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e + 1 m SeCl\u003csub\u003e4\u003c/sub\u003e the product shifts to trigonal-pyramidal SeOCl\u003csub\u003e2\u003c/sub\u003e (H\u003csub\u003e2\u003c/sub\u003eO + 2Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e + Se\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; SeOCl\u003csub\u003e2\u003c/sub\u003e + 2H\u003csup\u003e+\u003c/sup\u003e), as confirmed by Raman spectra and DFT-optimized structures (Fig. 2m and Supplementary Fig. 48)\u003csup\u003e45,46\u003c/sup\u003e. IGMH analyses reveal strong Se\u0026ndash;O (aqua/hydroxo/oxo) interactions together with appreciable Se\u0026ndash;Cl attraction (insets of Fig. 2m; Supplementary Fig. 49), rationalizing the coexistence and persistence of H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e and SeOCl\u003csub\u003e2\u003c/sub\u003e. This behavior reflects an intrinsic Se\u003csup\u003e4+\u003c/sup\u003e preference for O donors: Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e cannot fully displace aqua/hydroxo/oxo ligands, thereby stabilizing the mixed oxo\u0026ndash;chloride SeOCl\u003csub\u003e2\u003c/sub\u003e in the CaCl\u003csub\u003e2\u003c/sub\u003e-based SICE.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReversible heavy p-block electrochemistry\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;in SICEs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHaving established that CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs stabilize HPE cations as dissolved chlorocomplexes in water, we next evaluated their redox reversibility against the corresponding HPEs. Electrochemical tests were carried out in a three-electrode configuration using 6 m CaCl\u003csub\u003e2\u003c/sub\u003e containing 1 m of the target chlorides, except PbCl\u003csub\u003e2\u003c/sub\u003e, which was limited to 0.4 m by solubility (Fig. 3a\u0026ndash;c, Supplementary Figs. 50 and 51, and Supplementary Note 7). Cyclic voltammetry (CV) reveals well-defined and reversible redox couples for [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Pb, [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Sn, [SbCl\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Sb, [BiCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026ndash;\u003c/sup\u003e/Bi, and [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2\u0026ndash;\u003c/sup\u003e/Te at \u0026ndash;0.32 V, \u0026ndash;0.30 V, 0.05 V, 0.06 V, and 0.57 V vs. SHE, respectively (Fig. 3a). The low-polarization responses reflect fast charge-transfer kinetics enabled by soluble chlorocomplexes. In parallel, the SeOCl\u003csub\u003e2\u003c/sub\u003e/Se couple delivers highly reversible redox peaks at 0.90 V vs. SHE in CaCl\u003csub\u003e2\u003c/sub\u003e-based SICE, in stark contrast to the sluggish kinetics and cathodic shift to 0.63 V observed in 1 m SeCl\u003csub\u003e4\u003c/sub\u003e electrolyte, where hydrolyzed oxyanions prevail (Fig. 3b). SeOCl\u003csub\u003e2\u003c/sub\u003e reduces markedly faster than H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e owing to the facile cleavage of relatively weak, halogen-bond-like Se-Cl bonds, whereas H\u003csub\u003e2\u003c/sub\u003eSeO\u003csub\u003e3\u003c/sub\u003e and its derivatives (HSeO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e and SeO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026ndash;\u003c/sup\u003e) undergo slow, multistep proton-coupled electron-transfer pathways that require breaking stronger Se\u0026ndash;O/Se\u0026ndash;OH linkages (Supplementary Fig. 49). Galvanostatic electrochemical deposition further confirms the high electrochemical stability of all chlorocomplexes studied, yielding flat potential plateaus and consistent deposition of the target HPEs without discernible polarization buildup over time (Fig. 3c).\u003c/p\u003e\n\u003cp\u003eTo assess structural and morphological features, the galvanostatic electrodeposits were systematically examined by scanning electron microscopy (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray diffraction (XRD), as detailed in Supplementary Note 8.1 (Supplementary Figs. 52\u0026ndash;58). SEM images show that electrochemical reduction of soluble chlorocomplexes\u0026mdash;[PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, [SbCl\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e, [BiCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026ndash;\u003c/sup\u003e, [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2\u0026ndash;\u003c/sup\u003e, and SeOCl\u003csub\u003e2\u003c/sub\u003e\u0026mdash;yields compact deposits with distinct morphologies and compositions, demonstrating the broad applicability of SICEs for HPE electrodeposition (Fig. 3d\u0026ndash;i and Supplementary Fig. 52). Pb deposits form large, faceted grains with uniform spatial distribution (Fig. 3d); Sn deposits yield well-defined faceted grains of uniform size (Fig. 3e); Sb deposits form densely packed spherical grains (Fig. 3f); Bi deposits exhibit a lamellar morphology composed of micron-sized stacked plates (Fig. 3g); and Te deposits develop smooth hemispherical grains with a broad size distribution (Fig. 3h). In contrast, Se deposits as a continuous amorphous-like film lacking discernible crystalline features (Fig. 3i). HAADF-STEM imaging resolves clear lattice fringes for Pb, Sn, Sb, Bi, and Te, with interplanar spacings of ~0.29 nm for Pb (111) plane, ~0.29 nm for Sn (200) plane, ~0.31 nm for Sb (012) plane, ~0.23 nm for Bi (110) plane, and ~0.22 nm for Te (110) plane (Fig. 3j\u0026ndash;n and Supplementary Figs. 53\u0026ndash;57), in agreement with XRD patterns (Fig. 3p). By contrast, Se shows neither lattice fringes in HAADF-STEM nor Bragg peaks in XRD, confirming its amorphous nature (Fig. 3o,p and Supplementary Fig. 58). Energy-dispersive spectroscopy (EDS) elemental mapping reveals that Se accounts for 99.1 at% among Se, O, and Cl, verifying the high purity and compositional uniformity of the deposited film (inset of Fig. 3i). The CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs further enable one-step electrodeposition of representative heavy p-block alloys (e.g. PbSn and BiSb) through controlled tuning of chlorocomplex precursor ratios (Supplementary Figs. 59\u0026ndash;61 and Supplementary Note 8.2). Collectively, these results show that SICEs overcome the intrinsic instabilities of aqueous heavy p-block electrochemistry, establishing a generalizable platform for reliable electrodeposition of high-quality HPEs and their alloys.\u003c/p\u003e\n\u003cp\u003eWe further confirmed the high reversibility of heavy p-block electrochemistry through repeated HPE plating and stripping behaviors in symmetric and asymmetric cells. Using Pb as a representative case, the PbǀǀPb symmetric cell maintains low polarization (\u0026lt;20 mV) for nearly 3,000 h (Fig. 3q), while the PbǀǀCu asymmetric cell delivers stable plating/stripping behavior with a high average CE of 99.9% over 500 cycles (Fig. 3r,s). More importantly, the electrochemical reversibility enabled by CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs is universally applicable across a wide spectrum of HPEs. Symmetric cells employing Sn, Sb, Bi, Se, and Te electrodes all exhibit low polarization (typically \u0026lt;80 mV) and long-term stability with cycling lifetimes from 1,000 to 3,600 h (Fig. 3t). Corresponding asymmetric cells achieve high average CEs (99.6\u0026ndash;100.0%; Fig. 3u), further confirming the universality of the salting-in chlorocomplex strategy across diverse heavy p-block systems. Detailed electrochemical data are provided in Supplementary Figs. 62\u0026ndash;66. Post-cycling morphological and structural analyses of both HPE electrodes and their electrodeposits on current collectors reveal dense, dendrite-free morphologies without detectable byproducts (Supplementary Figs. 67\u0026ndash;75), underscoring the highly reversible HPE plating/stripping behavior and rationalizing the durable cycling lifetimes (Supplementary Note 9). This high electrochemical reversibility persists in concentrated chlorocomplex electrolytes based on SICEs with 6 m SnCl\u003csub\u003e2\u003c/sub\u003e, 4 m SbCl\u003csub\u003e3\u003c/sub\u003e, 2.5 m BiCl\u003csub\u003e3\u003c/sub\u003e, or 3 m TeCl\u003csub\u003e4\u003c/sub\u003e (Supplementary Fig. 76).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRechargeable aqueous HPE-electrode batteries\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHere we focus on aqueous batteries as a representative system, given their inherently high-power density, safety, and low-cost characteristics. We recognize that technology-ready aqueous electrode chemistries with stable multielectron redox pathways remain scarce. However, when HPE cations are stabilized as chlorocomplexes in SICEs, these elements can operate as either negative or positive electrodes via reversible plating and stripping, enabling rational full-cell pairing with suitable counter electrodes and greatly expanding the design space of aqueous batteries. Enabled by reversible plating and stripping in CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs (Fig. 3t,u), HPEs as electrodes fulfill the essential criterion for stable and reversible multielectron redox in water. They span a wide redox window from \u0026ndash;0.32 V vs. SHE for [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Pb to 0.90 V vs. SHE for SeOCl\u003csub\u003e2\u003c/sub\u003e/Se, and deliver high theoretical specific capacities (258.7\u0026ndash;1358.2 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), along with long-term reversibility, dendrite-free deposition, corrosion resistance, and tunable redox potentials (Fig. 4a and Supplementary Fig. 77a)\u003csup\u003e7,14,15,21,31,47,48\u003c/sup\u003e. Within this landscape, Sn and Pb, with low redox potentials and moderate specific capacities, are ideal negative electrode candidates; Sb and Bi, with intermediate potentials and higher specific capacities, can function as either negative or positive electrodes; and Se and Te electrodes, featuring high redox potentials and four-electron pathways, emerge as promising high-energy positive electrodes.\u003c/p\u003e\n\u003cp\u003eTo exemplify this concept, we first constructed aqueous Pb-metal batteries using metallic Pb foil as the negative electrode, paired with conventional I\u003csup\u003e\u0026ndash;\u003c/sup\u003e/I\u003csub\u003e2\u003c/sub\u003e, Br\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Br\u003csub\u003e2\u003c/sub\u003e, and Cl\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Cl\u003csub\u003e2\u003c/sub\u003e conversion positive electrodes (Supplementary Fig. 77b). These configurations deliver theoretical specific energies of 100, 182, and 278 Wh kg\u003csup\u003e\u0026ndash;1\u003c/sup\u003e for PbǀǀPbI\u003csub\u003e2\u003c/sub\u003e, PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e, and PbǀǀPbCl\u003csub\u003e2\u0026nbsp;\u003c/sub\u003efull batteries, respectively. Unlike century-old lead\u0026ndash;acid batteries that rely on concentrated, corrosive H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte and suffer from limited rechargeability and low specific energy (~40 Wh kg\u003csup\u003e\u0026ndash;1\u003c/sup\u003e)\u003csup\u003e3\u003c/sup\u003e, the proposed architecture exploits the soluble [PbCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e chlorocomplex to establish a distinct aqueous chemistry where Pb\u003csup\u003e2+\u003c/sup\u003e shuttles reversibly between the negative and positive electrodes. As shown in Fig. 4b, the PbǀǀPbI\u003csub\u003e2\u003c/sub\u003e full battery delivers a discharge capacity of 110 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e at 0.5 C (1 C = 116 mA g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) and retains 94 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e at 10 C, demonstrating rapid charge-transfer kinetics and excellent rate capability. The discharge capacity fully recovers to 110 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e after rate cycling and remains at 92 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e after 500 cycles at 0.5 C (Fig. 4c), effectively suppressing the capacity degradation typically observed for iodide-based positive electrodes. Long-term cycling confirms excellent durability, with \u0026gt;90% capacity retention over 800 and 1,000 cycles at 1 C and 5 C, respectively, corresponding to discharge capacities of 100 and 90 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (Supplementary Fig. 78). Furthermore, the PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e full battery exhibits higher discharge capacities (\u0026gt;125 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) and elevated operating voltages (\u0026gt;1.2 V) at 2 C and 5 C (1 C = 146 mA g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), retaining ~80% of its initial discharge capacity after 1,000 cycles (Fig. 4d\u0026ndash;f). Notably, the more energetic PbǀǀPbCl\u003csub\u003e2\u003c/sub\u003e full battery delivers a discharge capacity of 165 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (theoretical capacity of 192 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e for PbCl\u003csub\u003e2\u003c/sub\u003e) and maintains a stable output voltage above 1.4 V for over 200 cycles (Supplementary Fig. 79).\u003c/p\u003e\n\u003cp\u003eWe further expanded the design space of HPE-based batteries by constructing a new class of aqueous Sn-metal batteries, in which the [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Sn couple features a favorable redox potential of \u0026ndash;0.30 V vs. SHE and a high specific capacity of 451.7 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, establishing Sn as a promising high-energy negative electrode. However, as in lead\u0026ndash;acid systems, most reported aqueous Sn-metal batteries employ strongly acidic electrolytes, where the intrinsic challenges of Sn\u003csup\u003e2+\u003c/sup\u003e\u0026mdash;including limited solubility, oxidative instability, hydrolysis, and acid-induced corrosion\u0026mdash;remain unresolved\u003csup\u003e7,49\u003c/sup\u003e. In contrast, SICEs address these issues by stabilizing Sn\u003csup\u003e2+\u003c/sup\u003e as highly soluble [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e chlorocomplexes, thereby eliminating solubility and stability constraints and suppressing corrosive degradation of the metallic negative electrode. This stabilization allows the Sn negative electrode to be paired flexibly with both I\u003csub\u003e2\u003c/sub\u003e and KBr positive electrodes (Supplementary Fig. 77c). The SnǀǀI\u003csub\u003e2\u003c/sub\u003e full battery, employing a four-electron 2I\u003csup\u003e\u0026ndash;\u003c/sup\u003e/I\u003csub\u003e2\u003c/sub\u003e/2I\u003csup\u003e+\u003c/sup\u003e conversion positive electrodes with two discharge plateaus, delivers a high discharge capacity of 380 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e at 2 C (1 C = 400 mA g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) and maintains stable cycling for over 500 cycles (Fig. 4g,h). In parallel, the SnǀǀKBr full battery operates at an average voltage above 1.2 V and retains a capacity of ~150 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e after 200 cycles (Supplementary Fig. 80a,b). To extend this HPE-based design paradigm, we investigated four-electron Te and Se positive electrodes, which offer high theoretical specific capacities (840.2 and 1358.2 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) and favorable redox potentials of 0.57 V and 0.90 V vs. SHE, respectively. Motivated by these properties, we constructed high-energy aqueous hybrid batteries by pairing the two-electron [SnCl\u003csub\u003e3\u003c/sub\u003e]\u003csup\u003e\u0026ndash;\u003c/sup\u003e/Sn negative electrode with either the [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2\u0026ndash;\u003c/sup\u003e/Te or SeOCl\u003csub\u003e2\u003c/sub\u003e/Se positive electrode, employing decoupled SICEs to ensure electrochemical compatibility between the anodic and cathodic species (Supplementary Fig. 77d). Both SnǀǀTe and SnǀǀSe full batteries exhibit stable four-electron conversion reactions sustained for over 100 h of continuous cycling (Fig. 4i). The SnǀǀTe full battery displays highly overlapping charge/discharge curves, indicative of efficient redox reversibility (Fig. 4j), while the SnǀǀSe full battery operates at a higher voltage of ~1.1 V (Fig. 4k), consistent with the intrinsically higher redox potential of the SeOCl\u003csub\u003e2\u003c/sub\u003e/Se couple relative to [TeCl\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2\u0026ndash;\u003c/sup\u003e/Te. This proof-of-concept demonstrates the electrochemical compatibility of soluble HPE cations and establishes a battery architecture that enables dual reversible plating/stripping behavior within a single device. Together with additional rechargeable Sb- and Bi-based batteries (Supplementary Figs. 77e,f and 80c\u0026ndash;f, and Supplementary Note 10), these results confirm the generality of SICE-enabled HPE-based electrochemical systems. To underscore their translational potential, we assembled a larger-format PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e full battery that delivers performance comparable to its small-scale counterpart and successfully powers a commercial LED (Fig. 4l,m). This demonstration highlights the practical viability, versatility, and scalability of the SICE strategy for next-generation aqueous energy storage.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, heavy p-block electrochemistry in water, long regarded as intrinsically unstable under conventional electrolyte design, is reframed here as a problem of solvation design, motivating a counterintuitive \u0026ldquo;dissolved but not hydrated\u0026rdquo; concept to overcome this instability. Rather than tolerating direct HPE cation\u0026ndash;H\u003csub\u003e2\u003c/sub\u003eO contact, we re-engineer the solvation shells of HPE cations into anion-coordination-dominated environments that shield them from hydrolysis and other parasitic reactions. Building on this principle, first-principles-based descriptors of cation hydration and cation\u0026ndash;anion binding, corroborated by spectroscopic analyses, enabled the screening of hundreds of cation\u0026ndash;anion pairs, pinpointing auxiliary salts that pair a strongly hydrated yet weakly coordinating cation with an anion that preferentially coordinates HPE cations. The resulting CaCl\u003csub\u003e2\u003c/sub\u003e-based SICE establishes a chlorocomplex-dominated solvation regime in which anion-protective HPE cations, rather than hydrated species, govern multielectron redox and render an otherwise unstable family of elements reversibly redox-active in water. From a technological standpoint, CaCl\u003csub\u003e2\u003c/sub\u003e-based SICEs shift heavy p-block electrochemistry from toxic, corrosive, high-temperature, or nonaqueous baths to benign aqueous electrolytes that support compositionally precise HPE electrodeposition and rechargeable multielectron aqueous batteries with HPE electrodes. These demonstrations likely represent only a small subset of what is possible: by making heavy p-block electrochemistry viable in water, the same solvation-design framework could unlock aqueous routes to thermoelectric and optoelectronic devices, electrocatalysis, electronic metallization and protective coatings, and electrochemical recycling of heavy p-block materials.\u003c/p\u003e\n"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials and electrolytes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSodium chloride (NaCl, 99%), potassium chloride (KCl, 99%), magnesium chloride (MgCl\u003csub\u003e2\u003c/sub\u003e, 99%), calcium chloride (CaCl\u003csub\u003e2\u003c/sub\u003e, 99%), manganese chloride (MnCl\u003csub\u003e2\u003c/sub\u003e, 99%), zinc chloride (ZnCl\u003csub\u003e2\u003c/sub\u003e, 98%), lead chloride (PbCl\u003csub\u003e2\u003c/sub\u003e, 99%), tin (Ⅱ) chloride dihydrate (SnCl\u003csub\u003e2\u003c/sub\u003e∙2H\u003csub\u003e2\u003c/sub\u003eO, 99%), antimony chloride (SbCl\u003csub\u003e3\u003c/sub\u003e, 99%), bismuth chloride (BiCl\u003csub\u003e3\u003c/sub\u003e, 98%), selenium chloride (SeCl\u003csub\u003e4\u003c/sub\u003e, 98%) and tellurium chloride (TeCl\u003csub\u003e4\u003c/sub\u003e, 99%) were purchased from Sigma-Aldrich. The electrolytes were prepared by dissolving the calculated amounts of chlorides in deionized water according to the molality (m, mol kg\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e). Unless otherwise specified, electrochemical investigations of Pb, Sn, Sb, Bi, Te, and Se systems were conducted in aqueous electrolytes of 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e, 1 m SnCl\u003csub\u003e2\u003c/sub\u003e, 1 m SbCl\u003csub\u003e3\u003c/sub\u003e, 1 m BiCl\u003csub\u003e3\u003c/sub\u003e, 1 m TeCl\u003csub\u003e4\u003c/sub\u003e, and 1 m SeCl\u003csub\u003e4\u003c/sub\u003e, each dissolved in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e. For Sn-based electrolytes, 1 vol% Polyethylene glycol (PEG 400) was additionally added during electrochemical measurements.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePreparation of current collectors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCopper (Cu) foil (~9 \u0026mu;m thickness), titanium (Ti) foil (~20 \u0026mu;m thickness), Ti mesh with 100 mesh, polytetrafluoroethylene (PTFE) aqueous dispersion solution, and conductive carbon (Ketjen black; KB) were purchased from Crand New Energy Technology. Cu and Ti foils were directly used as the current collectors for PbǀǀCu and SnǀǀCu cells, and SbǀǀTi and BiǀǀTi cells, respectively, without additional treatments. KB electrode was prepared by thoroughly grinding KB and PTFE in a mass ratio of 9:1 in isopropanol (99%, Sigma-Aldrich) until forming a homogeneous and dough-like mass. The resulting mixture was then pressed onto Ti mesh and dried in a vacuum oven at 80 \u0026deg;C overnight, yielding a KB loading of ~3 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e. The KB electrode was used as current collectors for SeǀǀKB and TeǀǀKB cells and three-electrode measurements. The current collectors of Cu foil, Ti foil and KB-coated electrode were cut into 12 mm diameter discs.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePreparation of HPE electrodes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLead (Pb, \u0026gt;99%), tin (Sn, \u0026gt;99%), and bismuth (Bi, \u0026gt;99%) foils (purchased from SCI Materials Hub) were rolled using a roll press (MSK-2150-H5) to a final thickness of 100 \u0026mu;m for use as electrode materials. Antimony (Sb, \u0026gt;99.99%) beads with (\u0026le;5 mm), tellurium (Te, \u0026gt;99.99%) powder of ~30 mesh, and selenium (Se, \u0026gt;99.99%) powder (~50 mesh) were purchased from Sigma-Aldrich. Prior to electrode fabrication, they were ball-milled at 500 rpm for 24 h under a 50-min milling 10-min resting condition, yielding uniformly dispersed powders with average sizes in the micrometer range. Sb or Se electrodes were fabricated by thoroughly grinding Sb or Se powder, KB, and PTFE in a mass ratio of 8:1:1 in isopropanol. Te electrode was similarly prepared by grinding Te powder, graphite (purchased from Crand New Energy Technology), KB, and PTFE in a mass ratio of 6:2:1:1 in isopropanol. The mixtures were ground until forming plasticine-like masses, which were then pressed onto Ti mesh and dried in a vacuum oven at 80 \u0026deg;C overnight, yielding active material loadings of ~20 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e. The electrodes, including Sn, Pb, Sb, Bi, Se, and Te, were cut into circular discs with a diameter of 10 mm.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePreparation of haloid electrodes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLead iodide (PbI\u003csub\u003e2\u003c/sub\u003e, 99%), lead bromide (PbBr\u003csub\u003e2\u003c/sub\u003e, 98%), iodine (I\u003csub\u003e2\u003c/sub\u003e, 99%), potassium bromine (KBr, 99%), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI], 98%) and tetrapropylammonium bromide (TPABr, 98%) were purchased from Sigma-Aldrich. Active carbon (AC, YP80F) was purchased from Crand New Energy Technology. PbI\u003csub\u003e2\u003c/sub\u003e, PbBr\u003csub\u003e2\u003c/sub\u003e, PbCl\u003csub\u003e2\u003c/sub\u003e, BiCl\u003csub\u003e3\u003c/sub\u003e, SbCl\u003csub\u003e3\u003c/sub\u003e, I\u003csub\u003e2\u003c/sub\u003e, and KBr electrodes were prepared by mixing the active materials with additives in specific mass ratios. The detailed compositions and mass ratios were as follows: PbI\u003csub\u003e2\u003c/sub\u003e (6:2:1:1 for PbI\u003csub\u003e2\u003c/sub\u003e: AC: KB: PTFE), PbBr\u003csub\u003e2\u003c/sub\u003e (6:1: 2:0.5:0.5 for PbBr\u003csub\u003e2\u003c/sub\u003e: TPABr: AC: KB: PTFE), PbCl\u003csub\u003e2\u003c/sub\u003e (6: 3: 2: 1: 0.5 for PbCl\u003csub\u003e2\u003c/sub\u003e: [BMIM][TFSI]: AC: KB: PTFE), BiCl\u003csub\u003e3\u003c/sub\u003e (6:3.5:2:1:0.5 for BiCl\u003csub\u003e3\u003c/sub\u003e: [BMIM][TFSI]: AC: KB: PTFE), SbCl\u003csub\u003e3\u003c/sub\u003e (5:3:2:0.5:0.5 for SbCl\u003csub\u003e3\u003c/sub\u003e: [BMIM][TFSI]: AC: KB: PTFE), I\u003csub\u003e2\u003c/sub\u003e (4:4:1:1 for I\u003csub\u003e2\u003c/sub\u003e: AC: KB: PTFE), and KBr (6:1:2:0.5:0.5 for KBr: TPABr: AC: KB: PTFE). All materials were ground thoroughly in isopropanol until forming a uniform and dough-like paste. The resulting slurries were then pressed onto Ti mesh and dried at 70 \u0026deg;C in an oven for 8 h. The active material loadings were ~3.0 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for PbI\u003csub\u003e2\u003c/sub\u003e, ~4.5 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for PbBr\u003csub\u003e2\u003c/sub\u003e, ~3.1 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for PbCl\u003csub\u003e2\u003c/sub\u003e, ~3.3 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for BiCl\u003csub\u003e3\u003c/sub\u003e, ~3.8 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for SbCl\u003csub\u003e3\u003c/sub\u003e, ~2.5 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for I\u003csub\u003e2\u003c/sub\u003e, and ~3.5 mg cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e for KBr. The electrodes, including PbI\u003csub\u003e2\u003c/sub\u003e, PbBr\u003csub\u003e2\u003c/sub\u003e, PbCl\u003csub\u003e2\u003c/sub\u003e, BiCl\u003csub\u003e3\u003c/sub\u003e and SbCl\u003csub\u003e3\u003c/sub\u003e, I\u003csub\u003e2\u003c/sub\u003e and KBr, were cut into circular discs with a diameter of 10 mm.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSwagelok cell assembly\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe custom-made Swagelok-type cell was used for cell cycling. Two-electrode configurations, including symmetric (PbǀǀPb, SnǀǀSn, SbǀǀSb, BiǀǀBi, SeǀǀSe and TeǀǀTe), asymmetric (PbǀǀCu, SnǀǀCu, SbǀǀTi, BiǀǀTi, SeǀǀKB and TeǀǀKB), and full (PbǀǀPbI\u003csub\u003e2\u003c/sub\u003e, PbǀǀPbBr\u003csub\u003e2\u003c/sub\u003e, PbǀǀPbCl\u003csub\u003e2\u003c/sub\u003e, BiǀǀBiCl\u003csub\u003e3\u003c/sub\u003e, and SbǀǀSbCl\u003csub\u003e3\u003c/sub\u003e) cells, were assembled with electrodes placed face-to-face in Swagelok-type cells. The electrodes were separated by a glass fiber separator (GF/A, Whatman) soaked with ~100 \u0026mu;L of electrolyte. Unless otherwise specified, the electrolytes used for electrochemical tests were 0.4 m PbCl\u003csub\u003e2\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Pb-based systems, 1 m SnCl\u003csub\u003e2\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Sn-based systems, 1 m SbCl\u003csub\u003e3\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Sb-based systems, 1 m BiCl\u003csub\u003e3\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Bi-based systems, 1 m SeCl\u003csub\u003e4\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Se-based systems, and 1 m TeCl\u003csub\u003e4\u003c/sub\u003e + 6 m CaCl\u003csub\u003e2\u003c/sub\u003e for Te-based systems. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMembrane-separated dual-chamber cell assembly\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe home-built two-electrode membrane-separated dual-chamber cell was used for hybrid cell cycling.The hybrid SnǀǀI\u003csub\u003e2\u003c/sub\u003e battery was assembled using a Sn anode, a glass fiber separator soaked with ~100 \u0026mu;L of 1 m SnCl\u003csub\u003e2\u003c/sub\u003e + 5 m CaCl\u003csub\u003e2\u003c/sub\u003e electrolyte (anolyte side), a Nafion 117 ion-exchange membrane, a second separator soaked with ~100 \u0026mu;L of 5 m CaCl\u003csub\u003e2\u003c/sub\u003e electrolyte (catholyte side), and an I\u003csub\u003e2\u003c/sub\u003e cathode. The SnǀǀKBr cell followed the same configuration, using 6 m CaCl\u003csub\u003e2\u003c/sub\u003e electrolyte as the catholyte and a KBr cathode. For SnǀǀSe and SnǀǀTe cells, the catholyte comprised 1 m SeCl\u003csub\u003e4\u003c/sub\u003e or TeCl\u003csub\u003e4\u003c/sub\u003e in 6 m CaCl\u003csub\u003e2\u003c/sub\u003e, with Se or Te as the cathode, respectively. The Nafion membrane enabled Ca\u003csup\u003e2+\u003c/sup\u003e conduction to balance charge between compartments and was pretreated by soaking in 1 m CaCl\u003csub\u003e2\u003c/sub\u003e for 24 h and rinsing thoroughly with deionized water before use.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectrochemical measurements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree-electrode cyclic voltammetry (CV) and galvanostatic electrodeposition experiments were carried out in beaker cells containing 10 mL of electrolyte per test, using a Biologic VMP3 workstation. The three-electrode setup consisted of a KB-coated working electrode, a KCl-saturated Ag/AgCl reference electrode, and a Pb, Sn, Sb, Bi, Se, or Te counter electrode. Two-electrode galvanostatic cycling tests were conducted using a multichannel Neware battery testing system. All electrochemical measurements were carried out at room temperature.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials characterizations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e17\u003c/sup\u003eO and \u003csup\u003e35\u003c/sup\u003eCl nuclear magnetic resonance (NMR) spectra were collected using a Bruker (\u003cem\u003eAVANCE\u003c/em\u003e \u003cem\u003eIII,\u003c/em\u003e \u003cem\u003eHD\u003c/em\u003e 500 MHz) NMR spectrometer. Chemical shifts for \u003csup\u003e17\u003c/sup\u003eO NMR were referenced to an internal capillary tube containing D\u003csub\u003e2\u003c/sub\u003eO, while \u003csup\u003e35\u003c/sup\u003eCl NMR was referenced to a saturated NaCl in D\u003csub\u003e2\u003c/sub\u003eO sealed within a capillary tube placed inside the NMR tube. Scanning electron microscopy (SEM) was performed using a JEOL JSM-7600F microscope to examine surface morphologies. X-ray diffraction (XRD) patterns were collected on a Bruker D8 Advance diffractometer with Cu K\u0026alpha; radiation (\u0026lambda; = 1.5406 \u0026Aring;). Raman spectra, including both high- and low-frequency regions, were obtained using a Horiba LabRAM HR Evolution spectrometer equipped with a 532 nm laser. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was carried out on a JEOL JEM-ARM200F NeoARM microscope operating at 200 kV with a spherical aberration corrector. HAADF-STEM samples were prepared using a focused ion beam (FIB) system (ZEISS Crossbeam 540). X-ray absorption spectroscopy was used to characterize the coordination of Ca\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e in aqueous medium. The measurements were conducted at the XAFCA beamline of the Singapore Synchrotron Light Source (SSLS). All data acquisition was performed in transmission mode employing a Si(111) double-crystal monochromator except for sample of 1 m CaCl\u003csub\u003e2\u003c/sub\u003e solution at Ca K-edge which is performed in SDD mode. Data are collected at Ca K-edge and Pb L\u003csub\u003e3\u003c/sub\u003e-edge. All data were processed with Athena and Artemis (version 0.9.26)\u003csup\u003e50\u003c/sup\u003e. The value of\u003cem\u003e E\u003csub\u003e0\u003c/sub\u003e\u003c/em\u003e was determined by the first peak position of the first derivative of the XANES curve. WT-EXAFS analysis was conducted using HAMA Fortran software\u003csup\u003e51\u003c/sup\u003e, employing the Morlet wavelet as the mother wavelet function. The kappaMorlet and sigmaMorlet parameters were adjusted to optimize k-resolution for different R regions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGeometric structure optimization prior to AIMD Simulation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll simulations were carried out using spin-polarized methods as implemented in the QUICKSTEP code of the CP2K 2025 package\u003csup\u003e52,53\u003c/sup\u003e based on DFT. The general gradient approximation (GGA) parametrized by Perdew, Burke, and Ernzerhof (PBE)\u003csup\u003e54\u003c/sup\u003e was used as the exchange-correlation functional. The Kohn-Sham (KS) equations were solved according to the Gaussian and plane wave (GPW) formalism. Grimme\u0026rsquo;s DFT-D3 correction\u003csup\u003e55\u003c/sup\u003e was adopted to describe the weak van der Waals interaction. The GPW used Goedecker-Teter-Hutter pseudo potentials\u003csup\u003e56\u003c/sup\u003e to describe the interactions between core and valence electrons, while the valence electron density was represented in terms of Gaussian type orbital (GTO) basis set functions. In particular, we used DZVP-MOLOPT-SR-GTH basis sets for geometry optimization and TZVP-MOLOPT-SR-GTH basis sets for static calculations, and the Brillouin zone integration was sampled using a Monkhorst-Pack\u003csup\u003e57\u003c/sup\u003e special k-point mesh with a resolution of 2\u0026pi;*0.04 was applied. The convergence criterion for the maximum force was set as 5 \u0026times; 10\u003csup\u003e\u0026minus;4\u003c/sup\u003e atomic units. The auxiliary PW basis set, which is needed for the efficient solution of the Poisson\u0026apos;s equation in reciprocal space, was truncated at 500 Ry. All Electronic structure and wave function analysis were conducted using Multiwfn software\u003csup\u003e58\u003c/sup\u003e. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAIMD simulations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll AIMD simulations reported here were performed using DFT with the Gaussian and Plane Wave combined approach as implemented in CP2K/Quickstep. The electrons were treated using the exchange correlation PBE functional with a Grimme D3 correction. Core electrons were described using the Goedecker-Teter-Hutter (GTH) pseudo-potentials, and the valence density was developed on a double-zeta DZVP basis set along with an auxiliary plane wave basis set with cutoff energy of 500\u0026thinsp;Ry. The temperature of the simulation was maintained at 300\u0026thinsp;K using the Canonical sampling through velocity rescaling (CSVR) thermostat coupled to the system. The AIMD simulations were performed with a time step of 1 fs to investigate the hydration structures of auxiliary cations in water. Each system contained one cation and 60 H\u003csub\u003e2\u003c/sub\u003eO molecules, with additional Cl\u003csup\u003e‒\u003c/sup\u003e placed in a distant corner of the simulation box to maintain charge neutrality without perturbing hydrated interactions. For all the MD trajectories, the initial ~3 ps was regarded as the equilibration period, and then followed by production periods of 10 ps. Note that due to the large size of the supercells, only \u0026Gamma; point was used in all calculations. For AIMD simulations involving transition metal cations, we considered spin polarization, while other cations were not considered.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGeometric optimization and property analysis of solvation structures\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the structures used in density functional theory calculation were optimized by Gaussian 16 at B3LYP hybrid function with def2-TZVP basis. Then a single point calculation was carried at same level. DFT-D3(BJ) method was used to describe weak interaction between molecules. The electrostatic potential, IGMH\u003csup\u003e59\u003c/sup\u003e, molecular vdW volume\u003csup\u003e60\u003c/sup\u003e and ELF\u003csup\u003e61\u003c/sup\u003e were analyzed by Multiwfn and was drawn by VMD package\u003csup\u003e62\u003c/sup\u003e. The total binding energy (D\u003cem\u003eE\u003c/em\u003e) was calculated using the [Ca(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003en\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e (\u003cem\u003en\u003c/em\u003e = 1‒8) complex as an example, according to D\u003cem\u003eE \u003c/em\u003e= \u003cem\u003eE\u003c/em\u003e\u003csub\u003eCa(H2O)n \u003c/sub\u003e‒ \u003cem\u003eE\u003c/em\u003e\u003csub\u003eCa \u003c/sub\u003e‒ n\u003cem\u003eE\u003c/em\u003e\u003csub\u003eH2O\u003c/sub\u003e,\u003csub\u003e \u003c/sub\u003ewhere\u003csub\u003e \u003c/sub\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003eCa(H2O)n\u003c/sub\u003e, \u003cem\u003eE\u003c/em\u003e\u003csub\u003eCa\u003c/sub\u003e,\u003csub\u003e \u003c/sub\u003eand \u003cem\u003eE\u003c/em\u003e\u003csub\u003eH2O \u003c/sub\u003eare the energies of [Ca(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003en\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e,\u003csup\u003e \u003c/sup\u003eCa\u003csup\u003e2+\u003c/sup\u003e, and H\u003csub\u003e2\u003c/sub\u003eO, respectively.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data needed to evaluate the conclusions in the paper are present in the paper and/or Supplementary Information\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by A*STAR RIE2025 Manufacturing, Trade and Connectivity (MTC) Programmatic Fund grant M24N6b0043. We gratefully acknowledge Dr. Shibo Xi for assistance with the X-ray absorption measurements performed at the XAFCA beamline of the Singapore Synchrotron Light Source (SSLS). Also, we gratefully acknowledge Dr. Haozhe Zhang for independent external validation of the salting-in strategy-enabled reversible heavy p-block electrochemistry performed at\u0026nbsp;Argonne National Laboratory.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors approved the final version of the manuscript. Y.S.M. and H.Y.Y supervised the project. Y.-F.C. proposed the research direction and conceived the idea of the work. Y.-F.C. designed and performed the experiments. Y.-F.C., M.Z., H.S., Y.L., N.Z. and W.L. performed the materials characterizations and data analysis. Y.-F.C. and M.Z. performed the theoretical studies. Y.-F.C., Y.H.Z., Y.S.M. and H.Y.Y wrote the manuscript. All authors contributed to the discussion and the manuscript preparation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMelen, R. L. Frontiers in molecular p-block chemistry: From structure to reactivity. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e363\u003c/strong\u003e, 479\u0026ndash;484 (2019).\u003c/li\u003e\n\u003cli\u003eFinney, B. A., Peterson, K. A. Beyond chemical accuracy in the heavy p-block: The first ionization potentials and electron affinities of Ga\u0026ndash;Kr, In\u0026ndash;Xe, and Tl\u0026ndash;Rn. \u003cem\u003eJ\u003c/em\u003e\u003cem\u003e. Chem. Phys\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e 151, 024303 (2019). \u003c/li\u003e\n\u003cli\u003eLopes, P. P. \u0026amp; Stamenkovic, V. R. 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Graphics\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, 33\u0026ndash;38 (1996). \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8632446/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8632446/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Heavy p-block elements (HPEs; Sn, Pb, Sb, Bi, Se and Te)1,2, with flexible electronic structures and rich multielectron redox chemistry, hold promise for electrochemically driven technologies in functional coatings, electronics, and energy conversion and storage3–15. However, their aqueous electrochemistry remains challenging because direct exposure of HPE cations to water readily triggers parasitic reactions, including hydrolysis, corrosion, precipitation, gas evolution, and passivation16–21. Here we challenge the prevailing assumption in electrolyte design that dissolving HPE cations necessitates hydration, and propose a counterintuitive principle of “dissolved but not hydrated” to unlock aqueous HPE electrochemistry. We implement this concept through a dual-salt salting-in electrolyte strategy, distilled into a two-parameter design principle. The auxiliary cation should be strongly hydrated yet weakly ion-pairing to suppress water activity, while the auxiliary anion should preferentially coordinate HPE cations to expel water from their solvation shells. First-principles descriptor screening, corroborated by spectroscopic analyses, interrogates a curated library of hundreds of cation–anion combinations and identifies Ca2+–Cl– as the uniquely optimal auxiliary-ion pair that most effectively suppresses water activity and drives anion coordination to HPE cations, thereby forming water-shielded chlorocomplexes that stabilize HPE cations in water. This electrolyte design enables reversible plating and stripping across the HPE family (Sn, Pb, Sb, Bi, Se and Te), yielding uniform electrodeposits and rendering HPEs viable multielectron electrodes in aqueous batteries. The proposed HPE-based aqueous batteries enabled by this salting-in electrolyte exhibit stable rechargeability with high capacity retention. By rendering an intrinsically unstable class of elements redox-active in water, this work overcomes long-standing barriers to heavy p-block electrochemistry and establishes a general framework for multielectron aqueous electrochemical systems.","manuscriptTitle":"Salting-in electrolyte enables reversible heavy p-block electrochemistry in water","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-11 08:37:08","doi":"10.21203/rs.3.rs-8632446/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-chemistry","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"nchem","sideBox":"Learn more about [Nature Chemistry](http://www.nature.com/nchem/)","snPcode":"","submissionUrl":"","title":"Nature Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f0549115-cdbb-462e-b3b1-3afb45731e3e","owner":[],"postedDate":"March 11th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":63283400,"name":"Physical sciences/Materials science/Materials for energy and catalysis"},{"id":63283401,"name":"Physical sciences/Energy science and technology/Energy storage/Batteries"}],"tags":[],"updatedAt":"2026-03-11T08:37:08+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-11 08:37:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8632446","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8632446","identity":"rs-8632446","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}