Interfacial Manipulation via In-Situ Grown ZnSe Overlayer toward Highly Reversible Zn Metal Anodes

Interfacial Manipulation via In-Situ Grown ZnSe Overlayer toward Highly Reversible Zn Metal Anodes | 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 Article Interfacial Manipulation via In-Situ Grown ZnSe Overlayer toward Highly Reversible Zn Metal Anodes Xianzhong Yang, Chao Li, Zhongti Sun, Shuai Yang, Zixiong Shi, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-400312/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Zn metal anode has garnered growing scientific and industrial interest owing to its appropriate redox potential, low cost and good safety. Nevertheless, the instability of Zn metal, caused by dendrite formation, hydrogen evolution and side reactions, gives rise to poor electrochemical stability and unsatisfactory cycling life, greatly hampering large-scale utilization. Herein, an in-situ grown ZnSe layer with controllable thickness is crafted over one side of commercial Zn foil via chemical vapor deposition, aiming to achieve optimized interfacial manipulation between aqueous electrolyte/Zn anode. Thus-derived ZnSe overlayer not only prevents water penetration and restricts Zn 2+ two-dimensional diffusion, but also homogenizes the electric field at the interface and facilitates favorable (002) plane growth of Zn. As a result, dendrite-free and homogeneous Zn deposition is obtained; side reactions are concurrently inhibited. In consequence, a high Coulombic efficiency of 99.2% and high cyclic stability for 860 cycles at 1.0 mA cm –2 in symmetrical cells is harvested. Meanwhile, when paired with V 2 O 5 cathode, assembled full cell achieves an outstanding initial capacity (200 mAh g –1 ) and elongated lifespan (a capacity retention of 84% after 1000 cycles) at 5.0 A g –1 . Our highly reversible Zn anode enabled by the interfacial manipulation strategy is anticipated to satisfy the demand of industrial and commercial use. Energy Engineering Materials Engineering Electronic Materials and Devices Zn metal anode Energy storage Batteries energy and catalysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Recent years have witnessed a burgeoning development of advanced energy storage systems to meet the urgent energy demand in individual and industrial applications. In this sense, aqueous rechargeable batteries have stimulated increased attentions due to their intrinsic safety and environmental benignity, as compared to their counterparts with flammable organic electrolytes 1 – 4 . The high ionic conductivity of aqueous electrolyte in addition endows the corresponding devices with excellent rate performance and fast reaction kinetics. To capitalize on these merits, aqueous Zn-ion batteries (AZIBs) coupled with affordable and nontoxic features are worthy of in-depth investigation. More encouragingly, Zn metal is an appealing anode candidate on the ground of outstanding volumetric specific capacity (5855 mAh cm − 3 ) and appropriate redox potential (− 0.76 V vs . standard hydrogen electrode) 5 , 6 . Nevertheless, the commercial Zn foil anode is far from ideal to realize reversible dissolution/deposition during electrochemical cycling (Scheme 1a ). This is primarily owing to the fact that the surface protuberance is highly likely to trigger an intense cusp effect, in turn resulting in the uneven deposition of Zn and radical formation of dendrites 7 , 8 . Thus-grown dendrites could ultimately pierce the separator and induce short-circuit failure of the battery 9 . Meanwhile, problematic issues including hydrogen evolution 10 and side reactions 11 remain urgent to be solved since they are main origins of catastrophic volume expansion, electrode corrosion and surface passivation. Therefore, it is of vital importance to develop effective avenues to protect Zn anode from these caveats toward the realization of high-performance AZIB devices. In response, strategic efforts have been devoted to tackle aforementioned bottlenecks in pursuit of achieving highly reversible Zn anodes 2 , which mainly encompass electrolyte modulation 12 – 14 , host design 15 and interface engineering 16 . Firstly, the composition and concentration of electrolytes exert a significant impact on the Zn stripping/plating behaviors. For instance, the innovative “water in salt” electrolyte (1 M Zn(TFSI) 2 and 20 M LiTFSI) can effectively restrain Zn dendrite and suppress hydrogen evolution throughout forming a new solvation sheath 13 . Secondly, zincophilic host design allows the dictation of the Zn/host interface to harvest a low Zn nucleation barrier 15 or facilitate a heteroepitaxial Zn nucleation 17 , accordingly enabling the inhibition of the dendrite growth. Last but not the least, Zn/electrolyte interface engineering has been extensively explored due to its direct influence over Zn nucleation and growth. This can be implemented by introducing artificial protective layer comprising conductive or non-conductive coatings 11 . The conductive coatings, such as graphene 4 , MXene 16 , In 18 , Au 19 and Cu 20 , are beneficial to guiding a homogeneous Zn deposition to eliminate the dendrite. In parallel, the non-conductive shields, including TiO 2 21, 22 , CaCO 3 23 , ZnO 24 , ZrO 2 25 , ZnS 26 and kaolin 27 , would deactivate the dendritic formation via decreasing the nucleation energy barrier and inhibit hydrogen evolution by protecting the active Zn from the direct attack of the bulk electrolyte. Despite promising protection effects achieved on the anode side, it is worth noting that these prevailing strategies rely heavily upon ex-situ coating of foreign layers over Zn foils, which normally leads to non-uniform films with uncontrolled thickness uniformity and limited production scalability. In turn, the high-rate cyclability could be disabled and the energy density of entire device might be undermined. This would ultimately spur us to develop a simple yet effective method to precisely regulate the anode/electrolyte interface toward stabilized Zn anode. Herein, we devise a highly reversible Zn anode realized by in-situ grown Zn selenide (ZnSe) overlayer via chemical vapor deposition (CVD) (Scheme 1b ), accomplishing efficient interface manipulation in a manner analogous to the artificial solid electrolyte interphase (SEI) for alkali metal anode protection 28 . Our designing strategy harnessing sufficient scalability and intrinsic simplicity holds the potential to adequately meet practical demands. The initially disordered Zn protuberances are converted to ZnSe nanoparticles upon selenization, where ultrathin ZnSe layer is accordingly produced and uniformly bound to Zn metal to form a vertically aligned heterostructure (ZnSe@Zn). Such an interface engineering can simultaneously lower the Zn nucleation overpotential and homogenize the local current density to a great extent. The favorable zincophilicity of ZnSe would help restrict the two-dimensional diffusion of Zn ions along the interface. As a result, the growth of Zn dendrite is effectively inhibited. In addition, the in-situ formed ZnSe overlayer enables to decline the de-solvation energy barrier of hydrated-Zn, thereby boosting Zn 2+ transfer kinetics and deactivating hydrogen evolution. Benefiting from our interfacial manipulation, thus-derived ZnSe@Zn anode features an elongated lifespan of 860 h at a current density of 1.0 mA cm − 2 . It can even sustain a stable stripping/plating operation at 10 mA cm − 2 for as long as 260 h. More impressively, the full cell based on ZnSe@Zn anode harvests a capacity retention of 84% after 1000 cycles at 5.0 A g − 1 . Our highly reversible Zn anode enabled by the interfacial manipulation strategy is anticipated to satisfy the demand of industrial and commercial use. Results Synthesis and characterization of ZnSe overlayer . Fig. 1a schematically depicts the synthetic set-up for the in-situ growth of ZnSe overlayer on commercial Zn foil by CVD. The Zn foil serving as the growth substrate is placed at the downstream of the Ar/H 2 gas flow, which assists to carry the sublimed Se powders coming from the upstream (See Methods). This ambient-pressure process is facile, simple, economical and potentially scalable. It also bypasses the lengthy high-temperature annealing and tedious vacuum operations. The size of the product, ZnSe@Zn, is merely limited by the furnace dimension. Fig. 1b presents a digital photograph of a 20 cm × 10 cm sized ZnSe@Zn foil with perfect film homogeneity produced in a 4-inch tube furnace, demonstrating the viability of large-scale synthesis toward practical applications. The surface morphology of ZnSe overlayer was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As shown in Fig. 1c, the full coverage of ZnSe layer upon CVD reaction is helpful to even out a plethora of sharp protuberances on bare Zn surface (Supplementary Fig. 1). Close-up view further suggests that thus-grown ZnSe exists in the form of nanoparticles with diameters of 30-50 nm (Fig. 1c inset; Supplementary Fig. 2). Such a three-dimensional porous texture would be beneficial to Zn 2+ transport. Notably, the thickness of ZnSe overlayer can be simply dictated by controlling the CVD synthetic parameters, i.e. , altering the temperature ramping rate and dwelling duration (Fig. 1d; Supplementary Fig. 3). Fig. 1e presents a side-view SEM image of ZnSe overlayer (affording a thickness of 0.75 μm), where corresponding elemental maps manifest uniform distribution of detected elements. The wettability to electrolyte is one of the key factors for reversible Zn stripping/plating as it exerts influence upon interfacial ion-transfer resistance 8 . In this respect, bare Zn foil possesses a fairly poor wettability by 2 M ZnSO 4 electrolyte, displaying a contact angle of 82° based on static contact angle measurement (Fig. 1f). In contrast, the contact angle sharply declines to 14° on ZnSe@Zn foil (ZnSe thickness: 0.75 μm), implying markedly enhanced wettability (Fig. 1g). The contact angle values in the case of ZnSe@Zn foil with different ZnSe thickness are further compared (Supplementary Fig. 4), amongst which the 0.75 μm-thick ZnSe harvests the smallest contact angle. Collected XRD patterns of ZnSe@Zn and bare Zn indicate that the ZnSe grows primarily along (111) direction (Fig. 1h; Supplementary Fig. 5) 29 . Recognizable Raman signals further verify the successful preparation of ZnSe overlayer (Supplementary Fig. 6). Elec trochemical performance of ZnSe@Zn To evaluate the plating/stripping reversibility and Zn utilization of Zn anode with/without ZnSe protection, Coulombic efficiency (CE) measurements were carried out in two-electrode cells (ZnSe@Ti–Zn and Ti–Zn) with a fixed capacity of 0.5 mAh cm −2 at a current density of 2.0 mA cm − 2 . The ZnSe coating on Ti foil was obtained by CVD to derive the ZnSe@Ti electrode (Supplementary Fig. 7). In terms of the galvanostatic cycling performance, ZnSe@Ti–Zn cell presents an initial plating-stripping voltage hysteresis of 87 mV, which is obviously lower than that (133 mV) of bare Ti–Zn cell (Fig. 2a inset; Supplementary Fig. 8). Encouragingly, ZnSe@Ti–Zn cell could maintain 400 cycles with an average CE of 99.2%, indicating favorable reversibility and excellent durability (Fig. 2a). In stark contrast, bare Ti–Zn cell merely sustains for 50 cycles with drastic fluctuations of CE values, suggesting the presence of side reactions and dendrite growth. It is safe to conclude that the ZnSe overlayer would well manipulate the nucleation and growth of Zn toward a highly reversible anode. To verify the advanced effect of anode protection via in-situ formed ZnSe overlayer, galvanostatic cyclic stability of symmetric cells was evaluated under various current densities and areal capacities. Fig. 2b shows the long-term cycling performance of bare Zn and ZnSe@Zn symmetric cells at 1.0 mA cm −2 with a capacity of 1.0 mAh cm −2 . Upon cycling for ~80 h, a sudden and irreversible voltage rise occurs for bare Zn cell, which could be attributed to the accumulation of adverse “dead Zn” and by-products. The presence of these species is detrimental throughout occluding ion transport pathways, resulting in a large voltage hysteresis of 128 mV. In contrast, ZnSe@Zn symmetric cell readily displays a far more stable voltage profile with much declined voltage hysteresis of 30 mV that sustains more than 860 h, approximately 10 times longer in comparison with bare Zn cell. Note that our CVD route is versatile enough to enable the delicate control over the thickness of ZnSe layer, where an optimized thickness at 0.75 μm could be gained in response to generating the smallest polarization (Supplementary Fig. 9). This result echoes well with the observation from electrolyte wettability tests. The refinement of electrolyte/ZnSe@Zn interface, which expedites the electrokinetics of Zn deposition, can further be confirmed throughout electrochemical impedance spectroscopy (EIS) analysis. As disclosed in the Nyquist plots in Fig. 2c, the impedance of the bare Zn cell manifests a remarkable increase (from 0.7 to 7.7 kΩ) after 10 cycles, whereas the impedance of the ZnSe@Zn cell shows a slight decrease from 0.4 to 0.25 kΩ, revealing that the ZnSe overlayer is competent in declining charge transfer resistance in aqueous ZnSO 4 electrolyte. According to Sand’s model 30 , the formation time of dendrite is inversely proportional to current density. In addition, the interfacial electric field becomes rather uneven under elevated current densities, inducing less yet adverse nucleation sites. Areal specific capacity is also a nontrivial factor, where a higher one would augment the dendrite size. Therefore, Zn plating/stripping behavior quickly deteriorates under high current densities/capacities due to rampant dendrite formation 7 . Impressively, the ZnSe@Zn cell still remains highly stable for more than 250 h even under the high current density/capacity at 10.0 mA cm −2 /10.0 mAh cm −2 (Fig. 2d; Supplementary Fig. 10), representing one of the best performances achieved by far in such stringent conditions (Supplementary Table 1). Fig. 2e displays the rate performances of symmetric cells with a fixed capacity of 1.0 mAh cm −2 under varied current densities from 1.0 to 10.0 mA cm −2 . Apparently, ZnSe@Zn cell harvests a much lower voltage hysteresis at all current densities in comparison with bare Zn counterpart, demonstrating superior stability and high reversibility. In addition, dramatic reduction of nucleation overpotential tested under various conditions was witnessed upon the introduction of ZnSe overlayer (Supplementary Fig. 11), which is conducive to uniform deposition of Zn. Mechanism analysis on ZnSe protection effect To probe the electrochemical protection mechanism of ZnSe overlayer in ZnSO 4 electrolyte system, in-situ / ex-situ scrutinization in combination with electroanalytic characterization were carried out. First of all, real-time Zn plating/stripping process in transparent cell configuration was visualized with the aid of operando optical microscopy. A current density of 5.0 mA cm −2 was employed for the electrodeposition. As depicted in Fig. 3a, a number of randomly distributed protrusions commence to appear on the surface of bare Zn anode after 30 min deposition. When the deposition time reaches 60 min, the growth of dendrites is evident. In comparison, ZnSe@Zn anode retains a smooth surface texture during the entire plating process with no discernible dendritic formation (Fig. 3b), intuitively reflecting the capability of ZnSe overlayer in restraining the dendrite growth. Post-mortem SEM characterization of bare Zn and ZnSe@Zn anodes in transparent cells was conducted after 40-cycled plating/stripping process at 1.0 mA cm –2 (Fig. 3c-f; Supplementary Fig. 12). As for the bare Zn anode, along with the mossy Zn generated on the surface, noticeable pits (marked by dotted cycle in Fig. 3c) are also produced owing to the uneven plating/stripping and severe side reactions 31, 32 . By contrast, the ZnSe@Zn anode affords a compact, uniform and dendrite-free morphology with no observed protuberances and/or pits (Fig. 3e). Moreover, the thickness of deposited Zn on ZnSe@Zn anode (15 μm) stays much smaller as compared to that on bare Zn (136 μm), indicative of effective mitigation of dendrite formation with the ZnSe overlayer. Supplementary results for electrodes cycled at 5.0 mA cm –2 in transparent cells and at 1.0 mA cm –2 in coin cells further corroborate the positive impact of ZnSe protection (Supplementary Fig. 13 and 14). Post-mortem XRD was performed to identify the composition change of cycled electrodes. As shown in Fig. 3g, Zn 4 SO 4 (OH) 6• 4H 2 O by-product is proven to be generated on bare Zn upon cycling. This insoluble species would inevitably induce high overpotential of Zn symmetric cell due to its impenetrable nature for Zn ion. In contrast, there is no trace of by-product diffraction peak for ZnSe@Zn electrode, implying high reversibility of Zn dissolution/deposition reaction by virtue of ZnSe overlayer. Note further that the peak intensity ratio of Zn (002) to Zn (101) plane for ZnSe@Zn after cycling significantly augments about 12 times as compared to that for bare Zn. The existing similarity of lattice structure between ZnSe (111) and Zn (002) plane possibly guide an oriented Zn formation (Supplementary Fig. 15 and 16), where ZnSe layer can act as a template to induce (002) monocrystal Zn. Such a Zn growth behavior is desirable for anode protection 17, 33 . More intriguingly, there is no sign of ZnSe signals whatsoever for the ZnSe@Zn electrode after cycling, indicating the fall-off of ZnSe coating from the Zn foil, in good agreement with visualized characterizations (Supplementary Fig. 16; Supplementary Video 1). This phenomenon stems primarily from the fact that Zn is deposited at the interface between ZnSe overlayer and underlying Zn foil, where a flat and oriented Zn film is readily formed prior to the ZnSe detachment. Thus-produced Zn film enables to continuously guide a uniform Zn deposition even in the absence of ZnSe coating. Collectively, our results demonstrate that ZnSe overlayer is crucial to achieve optimized interfacial manipulation targeting highly reversible Zn anode. The suppression effect on Zn corrosion via ZnSe overlayer was analyzed by linear polarization tests in 2 M ZnSO 4 electrolyte (Fig. 3h). In comparison with bare Zn, the corrosion potential of the ZnSe@Zn reaches −1.013 V (−1.017 V for bare Zn), suggesting that it is less prone to corrosion. Meanwhile, the declined corrosion current by ca. 300 μA cm –2 again represents a retarded corrosion rate 34 . It is well received that the corrosion mainly originates from hydrogen evolution reaction (HER) accompanied by Zn dissolution/deposition reaction in weakly acidic ZnSO 4 electrolyte 11 . Along this line, HER activity was additionally evaluated by linear sweep voltammetry (LSV) measurements 24 . As displayed in Fig. 3i, it is striking to find that ZnSe@Zn electrode harvests a depressed HER capability as compared to that of bare Zn electrode. The solvation of Zn 2+ is a major obstacle for circumventing rapid transport of Zn ions throughout the interface between electrolyte and Zn anode 24, 35 . The activation energy ( E a ), which represents the energy required for de-solvation 36 , can be quantitatively derived using the Arrhenius equation: 1/ R ct = A exp (− E a / RT ), where R ct is the charge transfer resistance and R is the ideal gas constant. Herein, R ct (Supplementary Table 2) was fitted based on the variable-temperature EIS curves of Zn-Zn and ZnSe@Zn-ZnSe@Zn symmetric cells from 15 to 60 ℃ (Fig. 3j-k). It is evident that all R ct values of ZnSe@Zn cell (Fig. 3k) are much lower than those of bare Zn cell (Fig. 3j). Accordingly, E a of ZnSe@Zn can be calculated to be ~44.0 kJ mol −1 (Fig. 3l), in contrast to that of bare Zn cell (~67.5 kJ mol −1 ). This result implies the superior kinetics of Zn 2+ transfer throughout the interface between electrolyte and anode. The nucleation and deposition of Zn relies heavily upon the electric field distributions at the anode/electrolyte interface 7, 16 . To investigate the role of in-situ grown ZnSe overlayer played in regulating interfacial electric field, finite element method carried out by COMSOL Multiphysics was employed. As depicted in Fig. 4a, the electric field distribution is homogeneous on bare Zn anode harnessing an ideally smooth surface. Nevertheless, the presence of micro-protrusions would strengthen the surrounding field intensity, which is expected to guide uneven deposition of Zn and lead to the dendrite formation (Fig. 4b). Encouragingly, these protuberances could be well eliminated by in-situ selenation process. In response, the peak value of field intensity sharply decreases from 2.2×10 5 to 1.6×10 4 V m −1 with the aid of ZnSe overlayer (Fig. 4c). Such a textured ZnSe coating further helps homogenize the electric field on Zn surface, followed by building up uniform charge flux. Theoretical simulation based on density functional theory (DFT) route was performed to gain insight into the interaction between Zn and ZnSe. The calculated adsorption energy of a Zn atom on ZnSe support is apparently higher than that on bare Zn support (Fig. 4d; Supplementary Fig. 17). The strong affinity of Zn with ZnSe would be of benefit to suppressing two-dimensional (2D) diffusion of Zn ions. Chronoamperometry was accordingly employed to probe the Zn 2+ diffusion dynamics at the anode/electrolyte interface (Supplementary Fig. 18). The current density of bare Zn symmetric cell continues to increase beyond 140 s under 150 mV, implying a violent 2D diffusion process. In turn, Zn 2+ and hydrated Zn 2+ ions tend to aggregate and grow into dendrites to minimize the surface energy (Fig. 4e). As for the ZnSe@Zn electrode, the 2D diffusion only occurs within the initial 20 s, after which a stable three-dimensional (3D) diffusion pattern becomes predominant. As illustrated in Fig. 4f, a desolvation process proceeds rapidly for hydrated Zn 2+ ions upon their arrival at the ZnSe layer owing to low activation energy. Benefiting from a favorable 3D diffusion, Zn 2+ could then pass through the ZnSe layer rapidly under the potential gradient resulting from the high electron resistance of ZnSe 37 (Supplementary Fig. 19). This fast 3D diffusion process was confirmed by the high ionic conductivity of ZnSe layer reaching ~1.7 × 10 –5 S cm –1 (Supplementary Fig. 20). Finally, these Zn ions are reduced to Zn 0 and start to grow along (002) plane on Zn metallic surface. E lectrochemical performance of AZIB full cells To demonstrate the feasibility of thus-designed ZnSe@Zn anode in practical devices, AZIB full cells comprising KV 12 O 30-y ·nH 2 O (KVOH) 38 cathode (see methods) and ZnSe@Zn anode were assembled employing 2 M ZnSO 4 electrolyte (Supplementary Fig. 21). Fig. 5a records the CV profiles of ZnSe@Zn−KVOH and bare Zn−KVOH cells at a scan rate of 0.1 mV s –1 in a voltage window between 0.2 and 1.6 V. Both cells manifest two main pairs of redox signals corresponding to two-step redox reactions of V 3+ /V 4+ and V 4+ /V 5+ . The higher current response of full cell with ZnSe@Zn anode as compared to bare Zn anode implies a higher capacity value, which can be confirmed by galvanostatic charge/discharge (GCD) curves in Fig. 5b. Fig. 5c draws a comparison of rate performances of both cells. As expected, ZnSe@Zn−KVOH harvests a capacity of 294.2, 259.2, 232.9, 193.4 and 155.1 mAh g −1 at 0.5, 1.0, 2.0, 5.0 and 10.0 A g −1 , respectively. When the current density returns to 0.5 A g –1 , the device still retains a capacity of 253.1 mAh g –1 . This readily outperforms the bare Zn−KVOH cell under identical conditions. Such outstanding reversibility and rate capability could be attributed to the inhibition of dendrite formation/side reactions and the maintenance of a homogeneous interface via the versatile ZnSe coating, which functions as a high-performance artificial SEI layer. Nyquist plots before and after cycling also reveal that the ZnSe@Zn−KVOH cell exhibits lower charge-transfer resistance and promoted ion diffusion kinetics in comparison with the Zn−KVOH counterpart (Fig. 5d). The long-term cyclic stability of both cells was further evaluated (Fig. 5e). As for ZnSe@Zn−KVOH full cell, it manages to deliver an initial capacity of 194.5 mAh g −1 and stabilizes at 163.9 mAh g −1 after 1000 cycles with a retention rate of 84% at 5.0 A g −1 . In contrast, the capacity of bare Zn−KVOH cell sharply drops to 47.2 mAh g −1 after 1000 cycles. More impressively, ZnSe@Zn anode harnessing mechanical robustness and large-scale availability enlists the construction of flexible AZIB full cells (see methods) toward practical applications (Supplementary Fig. 22). Fig. 5f presents the GCD profiles of assembled flexible AZIB at 2.0 mA cm −2 under various bending angles of 0°, 90°, 135°, and 180°. Notably, 97.8% of the initial capacity could be retained upon bending at 180°, showing excellent mechanical flexibility. As a proof-of-concept demonstration, Fig. 5g displays digital photos of the working states of two flexible AZIBs in tandem configuration, enabling to continuously powering a light emitting diode (LED) indicator under different bending angles, showing its application prospect in wearable electronics. Taken together, these results corroborate that the ZnSe overlayers can effectively inhibit the parasitic reactions at the anode/electrolyte interface and guide uniform Zn deposition in favor of advanced stability of AZIB. Discussion In summary, we have developed a high-performance Zn anode via in-situ CVD coating of ZnSe overlayer harnessing high uniformity, thickness tailorability and scalability. Thus-designed ZnSe@Zn anode demonstrates a high Zn utilization of 99.2% and an elongated cycle life of 860 h during repetitive Zn plating/stripping. Even experiencing harsh conditions (10.0 mA cm − 2 /10.0 mAh cm − 2 ), it can still sustain to operate as long as 260 h, outperforming the state-of-the-art anode counterparts. The protection mechanism of ZnSe overlayer has been systematically explored by a suite of experimental characterizations in harmonization with theoretical simulations. The optimized interfacial manipulation throughout such a ZnSe layer can help accelerate the kinetics of Zn 2+ deposition by reducing de-solvation energy and restrict the 2D diffusion of Zn 2+ via strong Zn affinity. Meanwhile, HER and other side reactions can be effectively handicapped. As a result, the ZnSe@Zn anode exhibits stable cycling capability, low voltage hysteresis as well as smooth dendrite-free surface. Encouragingly, assembled ZnSe@Zn − KVOH full cell delivers a remarkable cycling stability with a capacity retention of 84% after 1000 cycles. Our ZnSe@Zn anodes affording versatility and simplicity may greatly promote the industrialization of Zn-based energy storage systems. Methods Preparation of ZnSe-coated Zn foil (ZnSe@Zn) The ZnSe overlayer was realized via an ambient pressure chemical vapor deposition process using tube furnace (Thermo Fisher Scientific). In brief, Zn foil (thickness: ~0.1 mm; length: ~20 cm; 99.99% purity; Alfa Aesar) and Se powders (~100 mg, 99.99%, Aladdin) were placed at the downstream and upstream position, respectively. The quartz tube was purged for 30 min using 540 sccm (standard cubic centimeters per minute) Ar gas. Afterwards, 50 sccm H 2 /Ar mixture (10% H 2 ) was used as the carrier gas during growth and cooling. The quartz tube was heated to 300 ℃ in 15 min, and then cooled to room temperature under preset dwelling time. The surface of Zn foil turned into faint yellow due to the formation of ZnSe. Then the ZnSe coated Zn foil (ZnSe@Zn) was annealed at 325 ℃ for 30 min with 10 sccm H 2 /Ar. Note that the ZnSe coated Ti foil was fabricated by a similar process as compared to that of ZnSe@Zn foil except that the Ti foil was placed on top of Zn foil and the tube furnace was kept at 320 ℃ for 1 h. Preparation of KVOH KVOH nanostructure was prepared by a modified hydrothermal method 38 . Typically, 0.364 g V 2 O 5 (Energy Chemical, 99%) and 0.087 g K 2 SO 4 (Macklin, 99.99%) were dissolved into 80 mL of DI water, followed by slow dripping of 2.0 mL 30% H 2 O 2 into the solution under magnetic stirring. After continuous stirring for 30 min, the orange mixture was gradually transformed into a transparent red solution, which was then transferred into 100 mL Teflon autoclave under 120 ℃ for 6 h. Upon centrifugation, the precipitates were dried by a cryodesiccation process for 30 h to preserve the urchin-shaped morphology. Finally, light green colored KV 12 O 30-y ·nH 2 O (KVOH) powders can be obtained. The KVOH electrode was prepared by casting slurry onto a Ti mesh. The slurry was composed of active material KVOH, conductive carbon (Super P) and binder (PVDF) with a mass ratio of 7:2:1. The electrode was then dried in a vacuum oven under 80 ℃ for 12 h. The mass loading was adjusted to ~1.0 mg cm −2 . Electrochemical tests The Zn-Zn symmetric cell, Ti-Zn asymmetric cell and KVOH-Zn full-cell were fabricated based on CR2032 coin cell configuration. Prior to assembly, all the foils were cut into circle discs with a diameter of 13 mm. The cells were assembled at ambient conditions at room temperature. The electrodes were separated by glass fiber separators (Φ = 19 mm, Whatman). 2 M ZnSO 4 aqueous solution was used as the electrolyte. The GCD cycling tests were carried out on the Neware battery-testing system. EIS, linear polarization, chronoamperogram and CV measurements of the batteries were recorded on electrochemical workstation (CHI660E, China). The linear polarization measurements were recorded in a three-electrode configuration, where bare Zn or ZnSe@Zn plate were used as the working electrode, Zn foil as the counter electrode, and saturated calomel (SCE) as the reference electrode, respectively. Moreover, the ZnSe@Zn and bare Zn electrodes were also assembled into transparent symmetric cells 34 , followed by an in-situ optical observation to detect electrode evolution during continuous Zn plating/stripping process at a current density of 5.0 mA cm –2 . HER tests were carried out using a three-electrode system controlled by an electrochemical workstation (CHI 760E, China). Graphite carbon and Ag/AgCl electrode (filled with saturated KCl) were used as counter electrode and reference electrode, respectively. The reference electrode (Ag/AgCl) calibration was performed in 0.1 M H 2 SO 4 electrolyte with a Zn plate (1×1 cm –2 ) serving as the working electrode. Prior to the test, the solution was bubbled with N 2 gas for 30 min to establish a N 2 saturation conditions. Linear sweep voltammetry (LSV) was conducted at a scan rate of 2 mV s –1 . All potentials measured were calibrated to reversible hydrogen electrode (RHE) using the following equation: E ( vs. RHE) = E ( vs. Ag/AgCl) + 0.059 pH + 0.198. Theoretical calculations All computations were performed by spin-unrestricted density functional theory, carried out by Vienna Ab-initio Simulation Package 39 with projector augmented wave pseudopotential 40 . Electronic exchange-correlation interactions were described by GGA-PBE 41 functional with the Grimme’s D3 dispersion correction 42 . The kinetic energy cutoff with plane wave was set to be 400 eV. First Brillouin zone integrations were sampled by the mesh size 5×5×1 for Zn (001) slab and 4×4×1 for ZnSe (111) slab. Zn (001) and ZnSe (111) slab with periodically repeating (3×3) and (2×2) unit cell by 4 layers was constructed for the Zn atom adsorption, respectively. The thickness of vacuum layer was set to 15 Å. The bottom layer was fixed to the bulk position. The other layers and adsorbed Zn atom were relaxed fully until the total energy was less than 10 –5 eV and residual force per atom was lower than 0.02 eV/Å. The adsorption energy was calculated by the formula: E ads = E total – E slab – E zn , where E total , E slab and E Zn are the total energy with/without the adsorption of Zn atom and atomic energy of Zn, respectively. Electric field simulation A parallel plate capacitor model was used to simulate the electric field distribution at the interface between anode and electrolyte based on COMSOL Multiphysics software. In this simplified model, the length of two electrodes was 2 μm and the distance between them was 1 μm. The protuberances of bare Zn surface were represented by two cones. Hemisphere arrays were used to represent ZnSe nanoparticles. The sizes of Zn protuberances and ZnSe nanoparticles in simulations were based on the results of SEM characterizations. The ionic conductivity of ZnSO 4 was 5 S m –1 . 43 The experimental observed voltage hysteresis (with/without ZnSe overlayer) was set as cathodic potential, while the anodic potential is a constant of zero. Declarations Data availability The data supporting the findings of this work are available within the article and its Supplementary Information files. All other relevant data supporting the findings of this study are available from the corresponding author on request. Acknowledgment This work was financially supported by the National Natural Science Foundation of China (51702225), the Natural Science Foundation of Jiangsu Province (BK20170336), Suzhou Science and Technology Project-Prospective Application Research Program (SYG202038) and the China Post-doctoral Foundation (Grant No. 7131705619). The authors also acknowledge support from the Suzhou Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Suzhou, China. Author contributions J.Y.S. designed the concept. X.Z.Y., C.L., R.H., B.Z.L. and M.L.W. prepared and characterized the ZnSe@Zn anode and KVOH cathode. X.Z.Y., C.L., Z.X.S., Y.H.W., S.L. and Y.W.S. performed the electrochemical test and explored the protective mechanism using in-situ and ex-situ characterization tools. Z.T.S. conducted the DFT calculation. S.Y. performed the COMSOL simulations. X.Z.Y., S.X.D. and J.Y.S. wrote the manuscript. All authors discussed the experimental and theoretical results and commented on the manuscript. All authors have approved to the final version of the manuscript. Competing interests The authors declare no competing interests. References Chao D, et al. Roadmap for advanced aqueous batteries: from design of materials to applications. Sci. Adv. 6 , eaba4098 (2020). Zhang Q, Luan J, Tang Y, Ji X, Wang H. Interfacial Design of Dendrite-Free Zinc Anodes for Aqueous Zinc-Ion Batteries. Angew. Chem. Int. Ed. 59 , 13180–13191 (2020). Tang B, Shan L, Liang S, Zhou J. Issues and opportunities facing aqueous zinc-ion batteries. Energy Environ. Sci. 12 , 3288–3304 (2019). Li C, et al. Directly grown vertical graphene carpets as janus separators toward stabilized Zn metal anodes. Adv. Mater. 32 , 2003425 (2020). Li H, et al. Advanced rechargeable zinc-based batteries: Recent progress and future perspectives. Nano Energy 62 , 550–587 (2019). Blanc LE, Kundu D, Nazar LF. Scientific challenges for the implementation of Zn-ion batteries. Joule 4 , 771–799 (2020). Yang Q, et al. Do zinc dendrites exist in neutral zinc batteries: a developed electrohealing strategy to in situ rescue in-service batteries. Adv. Mater. 31 , 1903778 (2019). Yang Q, et al. Dendrites in Zn-based batteries. Adv. Mater. 32 , 2001854 (2020). Cao Z, Zhuang P, Zhang X, Ye M, Shen J, Ajayan PM. Strategies for Dendrite-Free Anode in Aqueous Rechargeable Zinc Ion Batteries. Adv. Energy Mater. 10 , 2001599 (2020). Ma L, et al. Toward practical high-areal-capacity aqueous zinc-metal batteries: quantifying hydrogen evolution and a solid-ion conductor for stable zinc anodes. Adv. Mater. , DOI: 10.1002/adma.202007406 , (2021). Yi Z, Chen G, Hou F, Wang L, Liang J. Strategies for the stabilization of Zn metal anodes for Zn-ion batteries. Adv. Energy Mater. 11 , 2003065 (2020). Cao L, et al. Solvation structure design for aqueous Zn metal batteries. J. Am. Chem. Soc. 142 , 21404–21409 (2020). Wang F, et al. Highly reversible zinc metal anode for aqueous batteries. Nat. Mater. 17 , 543–549 (2018). Zhang N, et al. Cation-deficient spinel ZnMn 2 O 4 cathode in Zn(CF 3 SO 3 ) 2 electrolyte for rechargeable aqueous Zn-ion battery. J. Am. Chem. Soc. 138 , 12894–12901 (2016). Zhang Q, et al. The three-dimensional dendrite-free zinc anode on a copper mesh with a zinc-oriented polyacrylamide electrolyte additive. Angew. Chem. Int. Ed. 58 , 15841–15847 (2019). Zhang N, Huang S, Yuan Z, Zhu J, Zhao Z, Niu Z. Direct self-assembly of MXene on Zn anodes for dendrite-free aqueous zinc-ion batteries. Angew. Chem. Int. Ed. 60 , 2861–2865 (2020). Zheng J, et al. Reversible epitaxial electrodeposition of metals in battery anodes. Science 366 , 645–648 (2019). Han D, et al. A corrosion-resistant and dendrite-free zinc metal anode in aqueous systems. Small 16 , 2001736 (2020). Cui M, et al. 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Highly reversible Zn anode enabled by controllable formation of nucleation sites for Zn-based batteries. Adv. Funct. Mater. 30 , 1908528 (2020). Hao J, et al. An in-depth study of Zn metal surface chemistry for advanced aqueous Zn-ion batteries. Adv. Mater. 32 , 2003021 (2020). Deng C, et al. A sieve-functional and uniform‐porous kaolin layer toward stable zinc metal anode. Adv. Funct. Mater. 30 , 2000599 (2020). Cha E, et al. 2D MoS 2 as an efficient protective layer for lithium metal anodes in high-performance Li-S batteries. Nat. Nanotechnol. 13 , 337–344 (2018). Xiang B, et al. Green-light-emitting ZnSe nanowires fabricated via vapor phase growth. Appl. Phys. Lett. 82 , 3330–3332 (2003). Bai P, Li J, Brushett FR, Bazant MZ. Transition of lithium growth mechanisms in liquid electrolytes. Energy Environ. Sci. 9 , 3221–3229 (2016). Guo W, et al. Dendrite-free Zn anode with dual channel 3D porous frameworks for rechargeable Zn batteries. Energy Storage Mater. 30 , 104–112 (2020). Wood KN, et al. Dendrites and pits: untangling the complex behavior of lithium metal anodes through operando video microscopy. ACS Cent. Sci. 2 , 790–801 (2016). Zhang K, Yan Z, Chen J. Electrodeposition accelerates metal-based batteries. Joule 4 , 10–11 (2020). Zhao Z, et al. Long-life and deeply rechargeable aqueous Zn anodes enabled by a multifunctional brightener-inspired interphase. Energy Environ. Sci. 12 , 1938–1949 (2019). Kundu D, Vajargah SH, Wan L, Adams B, Prendergast D, Nazar LF. Aqueous vs. nonaqueous Zn-ion batteries: consequences of the desolvation penalty at the interface. Energy Environ. Sci. 11 , 881–892 (2018). Yan C, et al. Regulating the inner helmholtz plane for stable solid electrolyte interphase on lithium metal anodes. J. Am. Chem. Soc. 141 , 9422–9429 (2019). Liang X, et al. A facile surface chemistry route to a stabilized lithium metal anode. Nat. Energy 2 , 17119 (2017). Tian M, et al. Structural engineering of hydrated vanadium oxide cathode by K + incorporation for high-capacity and long-cycling aqueous zinc ion batteries. Energy Storage Mater. 29 , 9–16 (2020). Kresse G, Furthmuller J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comp. Mater. Sci. 6 , 15–50 (1996). Blochl PE. Projector augmented-wave method. Phys. Rev. B 50 , 17953–17979 (1994). Perdew JP, Burke K, Ernzerhof M. Generalized gradient approximation made simple Phys. Rev. Lett. 78 , 1396–1396 (1997). Grimme S, Antony J, Ehrlich S, Krieg H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132 , 154104 (2010). Rogac MB, Babic V, Perger TM, Neueder R, Barthel J. Conductometric study of ion association of divalent symmetric electrolytes: I. CoSO 4 , NiSO 4 ,CoSO 4 and ZnSO 4 in water. J. Mol. Liq. 118 , 111–118 (2005). Additional Declarations There is NO Competing Interest. Supplementary Files ZnSeprotectedZnanodeSI2021.04.06.docx Supplementary Information SupplementaryVideo1.mp4 Supplementary Video 1 Cite Share Download PDF Status: Posted 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-400312","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":22083965,"identity":"a26a8175-2eae-427e-b498-230adcb5bb3a","order_by":0,"name":"Xianzhong Yang","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xianzhong","middleName":"","lastName":"Yang","suffix":""},{"id":22083966,"identity":"ed896390-d736-49ee-98c9-e8636ed186b9","order_by":1,"name":"Chao Li","email":"","orcid":"","institution":"Shandong University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Chao","middleName":"","lastName":"Li","suffix":""},{"id":22083967,"identity":"6a2d6e79-c3fe-4e62-a83f-bc841e9420c5","order_by":2,"name":"Zhongti Sun","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhongti","middleName":"","lastName":"Sun","suffix":""},{"id":22083968,"identity":"d4d6a509-185f-44d6-9536-03b054f01730","order_by":3,"name":"Shuai Yang","email":"","orcid":"","institution":"State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Shuai","middleName":"","lastName":"Yang","suffix":""},{"id":22083969,"identity":"c003750a-f147-4c6e-81f1-a7700c79ad1f","order_by":4,"name":"Zixiong Shi","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zixiong","middleName":"","lastName":"Shi","suffix":""},{"id":22083970,"identity":"1927144c-f380-4d79-a229-1138f8898a19","order_by":5,"name":"Rong Huang","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Rong","middleName":"","lastName":"Huang","suffix":""},{"id":22083971,"identity":"7d7debe3-47f1-4442-b747-7b02df2026f9","order_by":6,"name":"Bingzhi Liu","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Bingzhi","middleName":"","lastName":"Liu","suffix":""},{"id":22083972,"identity":"83303f22-f17a-4563-9b5d-462010db1acc","order_by":7,"name":"Shuo Li","email":"","orcid":"","institution":"Soochow 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Sun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYJACA4YKGzkwzcDATKyWM2nGpGlhYGw7lNhAtBb5GbkHinnOHEifPyN54weGCuvEBvazB/A76kZegjFPxZ3cDTfSiiUYzqQnNvDkJeDXIpFjYMxz5lnuBiBDgrHtcGKDBI8BAYcBtfC2HU4HMox/MP4jQgvDDYiWBCDDTIKxgQgtBmfeGBjOOZNmuOHMszKLhGPpxm08OQQc1p5jZvCmwkZevj15840PNday/exnCDiMgYHNiAfGTABxCakHAuaHP4hQNQpGwSgYBSMYAAD0QEZrjqylPgAAAABJRU5ErkJggg==","orcid":"","institution":"Soochow University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Jingyu","middleName":"","lastName":"Sun","suffix":""}],"badges":[],"createdAt":"2021-04-07 06:40:53","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-400312/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-400312/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":8237533,"identity":"072f3513-edb1-4fde-bcd8-09ae704493a5","added_by":"auto","created_at":"2021-04-20 18:09:08","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1401038,"visible":true,"origin":"","legend":"Synthesis and characterization of ZnSe@Zn. (a) Schematic illustration of CVD growth of uniform ZnSe overlayer on Zn foil. (b) Photograph showing a large-scale ZnSe@Zn product. (c) Top-view SEM image of ZnSe@Zn foil. Inset: High magnification SEM and AFM images of ZnSe@Zn. (d) Thickness histogram of ZnSe layer grown under different heating/dwelling time conditions. In this regard, “10-0” denotes that a heating time is 10 min and a dwelling time is 0 min. (e) Side-view SEM and elemental maps of ZnSe@Zn. Digital photo showing the contact angle values of ZnSO4 electrolyte on (f) bare Zn and (g) 0.75 μm-thick ZnSe@Zn. (h) XRD patterns of bare Zn and thus-prepared ZnSe@Zn.","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/0be34e346456c2fffae5eec5.jpeg"},{"id":8237534,"identity":"67d5b879-79ad-42ff-957c-86d381d4acda","added_by":"auto","created_at":"2021-04-20 18:09:08","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":761640,"visible":true,"origin":"","legend":"Electrochemical performances of the symmetric cells employing ZnSe@Zn and bare Zn electrodes. (a) Coulombic efficiencies of Zn plating/stripping process in ZnSe@Ti–Zn and bare Ti–Zn cells with a current density of 2.0 mA cm−2 and a capacity of 0.5 mAh cm−2. Inset: Corresponding voltage profiles at the first cycle. (b) Long-term galvanostatic cycling of ZnSe@Zn and bare Zn symmetric cells at a current density of 1.0 mA cm−2 and a capacity of 1.0 mAh cm−2. Inset: Detailed voltage profiles of ZnSe@Zn and bare Zn symmetric cells at specific cycling time. (c) Nyquist plots of symmetric cells using ZnSe@Zn and bare Zn before cycling and after 10 cycles. (d) Cycling performance of ZnSe@Zn and bare Zn symmetric cells at an elevated current density of 10.0 mA cm−2 and a capacity of 10.0 mAh cm−2. (e) Rate performances for ZnSe@Zn and bare Zn symmetric cells at various current densities with a capacity of 1.0 mAh cm−2.","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/36f77182f22be0058246faa8.jpeg"},{"id":8236789,"identity":"6f19e4ee-9eeb-4406-a361-536233d439b6","added_by":"auto","created_at":"2021-04-20 18:06:08","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":831158,"visible":true,"origin":"","legend":"Instrumental insights into the protective effects of ZnSe overlayer on Zn anodes. In-situ optical microscopy visualization of Zn plating on (a) bare Zn and (b) ZnSe@Zn electrode at 5.0 mA cm−2. Scale bars: 200 μm. Top-view SEM images of (c) bare Zn and (d) ZnSe@Zn electrodes after 40 cycles. Cross-sectional SEM image of (e) bare Zn and (f) ZnSe@Zn electrodes after 40 cycles. (g) XRD patterns of bare Zn and ZnSe@Zn electrodes after 40 cycles. (h) Linear polarization curves presenting the corrosion on bare Zn and ZnSe@Zn. (i) Linear sweep voltammetry profiles of bare Zn and ZnSe@Zn. Inset: Tafel plots. Nyquist plots at different temperatures for (j) bare Zn and (k) ZnSe@Zn. (l) Corresponding Arrhenius curves and comparison of activation energies of bare Zn and ZnSe@Zn. ","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/d928c1fb21ab35a00916c2ba.jpeg"},{"id":8237537,"identity":"2b0c9066-a9a2-4a6d-9c08-861280df5b90","added_by":"auto","created_at":"2021-04-20 18:09:08","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":795862,"visible":true,"origin":"","legend":"Theoretical simulation and analysis. Simulated electric field distributions on bare Zn electrode (a) without and (b) with protuberances. (c) Simulated electric field distributions on ZnSe@Zn electrode. (d) Adsorption energy of Zn atom on Zn and ZnSe substrates. The inset in (d) shows the corresponding computational models. The green, gray and orange ball represents the Zn adatom, Zn and Se atoms, respectively. Schematics of Zn2+ diffusion and reduction processes on (e) bare Zn and (f) ZnSe@Zn electrodes, respectively.","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/2d93a504299a6e216fc1123d.jpeg"},{"id":8236786,"identity":"b9b19728-f957-461e-9d3d-ec657bdc417e","added_by":"auto","created_at":"2021-04-20 18:06:08","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":481778,"visible":true,"origin":"","legend":"Electrochemical performances of Zn-KVOH full cells affording bare Zn or ZnSe@Zn anode. (a) CV curves at a scan rate of 0.1 mV s–1. (b) GCD profiles at 0.2 A g–1. (c) Rate performances. (d) Nyquist plots before and after cycling. (e) Long-term cycling performances at 5.0 A g–1 for 1000 cycles. (f) GCD profiles of a flexible ZnSe@Zn-KVOH cell tested at 2.0 mA cm−2 under different bending angles. (g) Digital photos showing the working states of flexible ZnSe@Zn-KVOH cells in series to power a LED indicator under different bending angles.","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/c0eecf0792fa75fed4a5a759.jpeg"},{"id":8237536,"identity":"ecc10c98-6872-4d89-a83c-931c002bc2d1","added_by":"auto","created_at":"2021-04-20 18:09:08","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":276154,"visible":true,"origin":"","legend":"Scheme 1 Schematic diagram showing Zn deposition on bare Zn anode and ZnSe@Zn anode. (a) Severe corrosion, dendritic formation and hydrogen evolution occur on bare Zn anode upon electrochemical cycling. (b) Inhibited corrosion/hydrogen evolution and dendrite-free Zn deposition occur on ZnSe@Zn anode with in-situ grown ZnSe overlayer functioning as artificial SEI.","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/d6659a2b5fb8d1b739708ac1.jpeg"},{"id":13687470,"identity":"ed1dd45a-5723-40a1-925c-7e7dde544c54","added_by":"auto","created_at":"2021-09-17 12:20:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1303548,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/a61084a7-1cdf-4e02-bb2a-2f861fc4f231.pdf"},{"id":8237948,"identity":"b429646c-c53d-45c5-a700-b4b1913c8493","added_by":"auto","created_at":"2021-04-20 18:12:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":5573655,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"ZnSeprotectedZnanodeSI2021.04.06.docx","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/4b1ee9c0a75a4fc167687dac.docx"},{"id":8237532,"identity":"6814f9c9-91b2-4629-965e-2a5b948ee6ef","added_by":"auto","created_at":"2021-04-20 18:09:08","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":195430,"visible":true,"origin":"","legend":"Supplementary Video 1","description":"","filename":"SupplementaryVideo1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-400312/v1/cbf114b062645d98ee9111db.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Interfacial Manipulation via In-Situ Grown ZnSe Overlayer toward Highly Reversible Zn Metal Anodes","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRecent years have witnessed a burgeoning development of advanced energy storage systems to meet the urgent energy demand in individual and industrial applications. In this sense, aqueous rechargeable batteries have stimulated increased attentions due to their intrinsic safety and environmental benignity, as compared to their counterparts with flammable organic electrolytes\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. The high ionic conductivity of aqueous electrolyte in addition endows the corresponding devices with excellent rate performance and fast reaction kinetics. To capitalize on these merits, aqueous Zn-ion batteries (AZIBs) coupled with affordable and nontoxic features are worthy of in-depth investigation. More encouragingly, Zn metal is an appealing anode candidate on the ground of outstanding volumetric specific capacity (5855 mAh cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e) and appropriate redox potential (\u0026minus;\u0026thinsp;0.76 V \u003cem\u003evs\u003c/em\u003e. standard hydrogen electrode)\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Nevertheless, the commercial Zn foil anode is far from ideal to realize reversible dissolution/deposition during electrochemical cycling (Scheme \u003cspan class=\"InternalRef\"\u003e1a\u003c/span\u003e). This is primarily owing to the fact that the surface protuberance is highly likely to trigger an intense cusp effect, in turn resulting in the uneven deposition of Zn and radical formation of dendrites\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Thus-grown dendrites could ultimately pierce the separator and induce short-circuit failure of the battery\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Meanwhile, problematic issues including hydrogen evolution\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e and side reactions\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e remain urgent to be solved since they are main origins of catastrophic volume expansion, electrode corrosion and surface passivation. Therefore, it is of vital importance to develop effective avenues to protect Zn anode from these caveats toward the realization of high-performance AZIB devices.\u003c/p\u003e\n\u003cp\u003eIn response, strategic efforts have been devoted to tackle aforementioned bottlenecks in pursuit of achieving highly reversible Zn anodes\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, which mainly encompass electrolyte modulation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, host design\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e and interface engineering\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Firstly, the composition and concentration of electrolytes exert a significant impact on the Zn stripping/plating behaviors. For instance, the innovative \u0026ldquo;water in salt\u0026rdquo; electrolyte (1 M Zn(TFSI)\u003csub\u003e2\u003c/sub\u003e and 20 M LiTFSI) can effectively restrain Zn dendrite and suppress hydrogen evolution throughout forming a new solvation sheath\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Secondly, zincophilic host design allows the dictation of the Zn/host interface to harvest a low Zn nucleation barrier\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e or facilitate a heteroepitaxial Zn nucleation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, accordingly enabling the inhibition of the dendrite growth. Last but not the least, Zn/electrolyte interface engineering has been extensively explored due to its direct influence over Zn nucleation and growth. This can be implemented by introducing artificial protective layer comprising conductive or non-conductive coatings\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. The conductive coatings, such as graphene\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, MXene\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, In\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, Au\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e and Cu\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e, are beneficial to guiding a homogeneous Zn deposition to eliminate the dendrite. In parallel, the non-conductive shields, including TiO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e21, 22\u003c/sup\u003e, CaCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e23\u003c/sup\u003e, ZnO\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e25\u003c/sup\u003e, ZnS\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e and kaolin\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, would deactivate the dendritic formation \u003cem\u003evia\u003c/em\u003e decreasing the nucleation energy barrier and inhibit hydrogen evolution by protecting the active Zn from the direct attack of the bulk electrolyte. Despite promising protection effects achieved on the anode side, it is worth noting that these prevailing strategies rely heavily upon \u003cem\u003eex-situ\u003c/em\u003e coating of foreign layers over Zn foils, which normally leads to non-uniform films with uncontrolled thickness uniformity and limited production scalability. In turn, the high-rate cyclability could be disabled and the energy density of entire device might be undermined. This would ultimately spur us to develop a simple yet effective method to precisely regulate the anode/electrolyte interface toward stabilized Zn anode.\u003c/p\u003e\n\u003cp\u003eHerein, we devise a highly reversible Zn anode realized by \u003cem\u003ein-situ\u003c/em\u003e grown Zn selenide (ZnSe) overlayer \u003cem\u003evia\u003c/em\u003e chemical vapor deposition (CVD) (Scheme \u003cspan class=\"InternalRef\"\u003e1b\u003c/span\u003e), accomplishing efficient interface manipulation in a manner analogous to the artificial solid electrolyte interphase (SEI) for alkali metal anode protection\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Our designing strategy harnessing sufficient scalability and intrinsic simplicity holds the potential to adequately meet practical demands. The initially disordered Zn protuberances are converted to ZnSe nanoparticles upon selenization, where ultrathin ZnSe layer is accordingly produced and uniformly bound to Zn metal to form a vertically aligned heterostructure (ZnSe@Zn). Such an interface engineering can simultaneously lower the Zn nucleation overpotential and homogenize the local current density to a great extent. The favorable zincophilicity of ZnSe would help restrict the two-dimensional diffusion of Zn ions along the interface. As a result, the growth of Zn dendrite is effectively inhibited. In addition, the \u003cem\u003ein-situ\u003c/em\u003e formed ZnSe overlayer enables to decline the de-solvation energy barrier of hydrated-Zn, thereby boosting Zn\u003csup\u003e2+\u003c/sup\u003e transfer kinetics and deactivating hydrogen evolution. Benefiting from our interfacial manipulation, thus-derived ZnSe@Zn anode features an elongated lifespan of 860 h at a current density of 1.0 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. It can even sustain a stable stripping/plating operation at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e for as long as 260 h. More impressively, the full cell based on ZnSe@Zn anode harvests a capacity retention of 84% after 1000 cycles at 5.0 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Our highly reversible Zn anode enabled by the interfacial manipulation strategy is anticipated to satisfy the demand of industrial and commercial use.\u003c/p\u003e\n"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eSynthesis and characterization of ZnSe overlayer\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eFig. 1a schematically depicts the synthetic set-up for the \u003cem\u003ein-situ\u003c/em\u003e growth of ZnSe overlayer on commercial Zn foil by CVD. The Zn foil serving as the growth substrate is placed at the downstream of the Ar/H\u003csub\u003e2\u003c/sub\u003e gas flow, which assists to carry the sublimed Se powders coming from the upstream (See Methods). This ambient-pressure process is facile, simple, economical and potentially scalable. It also bypasses the lengthy high-temperature annealing and tedious vacuum operations. The size of the product, ZnSe@Zn, is merely limited by the furnace dimension. Fig. 1b presents a digital photograph of a 20 cm \u0026times; 10 cm sized ZnSe@Zn foil with perfect film homogeneity produced in a 4-inch tube furnace, demonstrating the viability of large-scale synthesis toward practical applications. The surface morphology of ZnSe overlayer was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As shown in Fig. 1c, the full coverage of ZnSe layer upon CVD reaction is helpful to even out a plethora of sharp protuberances on bare Zn surface (Supplementary Fig. 1). Close-up view further suggests that thus-grown ZnSe exists in the form of nanoparticles with diameters of 30-50 nm (Fig. 1c inset; Supplementary Fig. 2). Such a three-dimensional porous texture would be beneficial to Zn\u003csup\u003e2+\u003c/sup\u003e transport. Notably, the thickness of ZnSe overlayer can be simply dictated by controlling the CVD synthetic parameters, \u003cem\u003ei.e.\u003c/em\u003e, altering the temperature ramping rate and dwelling duration (Fig. 1d; Supplementary Fig. 3). Fig. 1e presents a side-view SEM image of ZnSe overlayer (affording a thickness of 0.75 \u0026mu;m), where corresponding elemental maps manifest uniform distribution of detected elements.\u003c/p\u003e\n\u003cp\u003eThe wettability to electrolyte is one of the key factors for reversible Zn stripping/plating as it exerts influence upon interfacial ion-transfer resistance\u003csup\u003e8\u003c/sup\u003e. In this respect, bare Zn foil possesses a fairly poor wettability by 2 M ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte, displaying a contact angle of 82\u0026deg; based on static contact angle measurement (Fig. 1f). In contrast, the contact angle sharply declines to 14\u0026deg; on ZnSe@Zn foil (ZnSe thickness: 0.75 \u0026mu;m), implying markedly enhanced wettability (Fig. 1g). The contact angle values in the case of ZnSe@Zn foil with different ZnSe thickness are further compared (Supplementary Fig. 4), amongst which the 0.75 \u0026mu;m-thick ZnSe harvests the smallest contact angle. Collected XRD patterns of ZnSe@Zn and bare Zn indicate that the ZnSe grows primarily along (111) direction (Fig. 1h; Supplementary Fig. 5)\u003csup\u003e29\u003c/sup\u003e. Recognizable Raman signals further verify the successful preparation of ZnSe overlayer (Supplementary Fig. 6).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElec\u003c/strong\u003e\u003cstrong\u003etrochemical performance of ZnSe@Zn\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo evaluate the plating/stripping reversibility and Zn utilization of Zn anode with/without ZnSe protection, Coulombic efficiency (CE) measurements were carried out in two-electrode cells (ZnSe@Ti\u0026ndash;Zn and Ti\u0026ndash;Zn) with a fixed capacity of 0.5 mAh cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e at a current density of 2.0 mA cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003csup\u003e2\u003c/sup\u003e. The ZnSe coating on Ti foil was obtained by CVD to derive the ZnSe@Ti electrode (Supplementary Fig. 7). In terms of the galvanostatic cycling performance, ZnSe@Ti\u0026ndash;Zn cell presents an initial plating-stripping voltage hysteresis of 87 mV, which is obviously lower than that (133 mV) of bare Ti\u0026ndash;Zn cell (Fig. 2a inset; Supplementary Fig. 8). Encouragingly, ZnSe@Ti\u0026ndash;Zn cell could maintain 400 cycles with an average CE of 99.2%, indicating favorable reversibility and excellent durability (Fig. 2a). In stark contrast, bare Ti\u0026ndash;Zn cell merely sustains for 50 cycles with drastic fluctuations of CE values, suggesting the presence of side reactions and dendrite growth. It is safe to conclude that the ZnSe overlayer would well manipulate the nucleation and growth of Zn toward a highly reversible anode.\u003c/p\u003e\n\u003cp\u003eTo verify the advanced effect of anode protection \u003cem\u003evia in-situ \u003c/em\u003eformed ZnSe overlayer, galvanostatic cyclic stability of symmetric cells was evaluated under various current densities and areal capacities. Fig. 2b shows the long-term cycling performance of bare Zn and ZnSe@Zn symmetric cells at 1.0 mA cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e with a capacity of 1.0 mAh cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e. Upon cycling for ~80 h, a sudden and irreversible voltage rise occurs for bare Zn cell, which could be attributed to the accumulation of adverse \u0026ldquo;dead Zn\u0026rdquo; and by-products. The presence of these species is detrimental throughout occluding ion transport pathways, resulting in a large voltage hysteresis of 128 mV. In contrast, ZnSe@Zn symmetric cell readily displays a far more stable voltage profile with much declined voltage hysteresis of 30 mV that sustains more than 860 h, approximately 10 times longer in comparison with bare Zn cell. Note that our CVD route is versatile enough to enable the delicate control over the thickness of ZnSe layer, where an optimized thickness at 0.75 \u0026mu;m could be gained in response to generating the smallest polarization (Supplementary Fig. 9). This result echoes well with the observation from electrolyte wettability tests. The refinement of electrolyte/ZnSe@Zn interface, which expedites the electrokinetics of Zn deposition, can further be confirmed throughout electrochemical impedance spectroscopy (EIS) analysis. As disclosed in the Nyquist plots in Fig. 2c, the impedance of the bare Zn cell manifests a remarkable increase (from 0.7 to 7.7 k\u0026Omega;) after 10 cycles, whereas the impedance of the ZnSe@Zn cell shows a slight decrease from 0.4 to 0.25 k\u0026Omega;, revealing that the ZnSe overlayer is competent in declining charge transfer resistance in aqueous ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte. According to Sand\u0026rsquo;s model\u003csup\u003e30\u003c/sup\u003e, the formation time of dendrite is inversely proportional to current density. In addition, the interfacial electric field becomes rather uneven under elevated current densities, inducing less yet adverse nucleation sites. Areal specific capacity is also a nontrivial factor, where a higher one would augment the dendrite size. Therefore, Zn plating/stripping behavior quickly deteriorates under high current densities/capacities due to rampant dendrite formation\u003csup\u003e7\u003c/sup\u003e. Impressively, the ZnSe@Zn cell still remains highly stable for more than 250 h even under the high current density/capacity at 10.0 mA cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e/10.0 mAh cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e (Fig. 2d; Supplementary Fig. 10), representing one of the best performances achieved by far in such stringent conditions (Supplementary Table 1). Fig. 2e displays the rate performances of symmetric cells with a fixed capacity of 1.0 mAh cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e under varied current densities from 1.0 to 10.0 mA cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e. Apparently, ZnSe@Zn cell harvests a much lower voltage hysteresis at all current densities in comparison with bare Zn counterpart, demonstrating superior stability and high reversibility. In addition, dramatic reduction of nucleation overpotential tested under various conditions was witnessed upon the introduction of ZnSe overlayer (Supplementary Fig. 11), which is conducive to uniform deposition of Zn.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMechanism analysis on ZnSe protection \u003c/strong\u003e\u003cstrong\u003eeffect\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo probe the electrochemical protection mechanism of ZnSe overlayer in ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte system, \u003cem\u003ein-situ\u003c/em\u003e/\u003cem\u003eex-situ\u003c/em\u003e scrutinization in combination with electroanalytic characterization were carried out. First of all, real-time Zn plating/stripping process in transparent cell configuration was visualized with the aid of \u003cem\u003eoperando\u003c/em\u003e optical microscopy. A current density of 5.0 mA cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e was employed for the electrodeposition. As depicted in Fig. 3a, a number of randomly distributed protrusions commence to appear on the surface of bare Zn anode after 30 min deposition. When the deposition time reaches 60 min, the growth of dendrites is evident. In comparison, ZnSe@Zn anode retains a smooth surface texture during the entire plating process with no discernible dendritic formation (Fig. 3b), intuitively reflecting the capability of ZnSe overlayer in restraining the dendrite growth. Post-mortem SEM characterization of bare Zn and ZnSe@Zn anodes in transparent cells was conducted after 40-cycled plating/stripping process at 1.0 mA cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e (Fig. 3c-f; Supplementary Fig. 12). As for the bare Zn anode, along with the mossy Zn generated on the surface, noticeable pits (marked by dotted cycle in Fig. 3c) are also produced owing to the uneven plating/stripping and severe side reactions\u003csup\u003e31, 32\u003c/sup\u003e. By contrast, the ZnSe@Zn anode affords a compact, uniform and dendrite-free morphology with no observed protuberances and/or pits (Fig. 3e). Moreover, the thickness of deposited Zn on ZnSe@Zn anode (15 \u0026mu;m) stays much smaller as compared to that on bare Zn (136 \u0026mu;m), indicative of effective mitigation of dendrite formation with the ZnSe overlayer. Supplementary results for electrodes cycled at 5.0 mA cm\u003csup\u003e\u0026ndash;2 \u003c/sup\u003ein transparent cells and at 1.0 mA cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e in coin cells further corroborate the positive impact of ZnSe protection (Supplementary Fig. 13 and 14).\u003c/p\u003e\n\u003cp\u003ePost-mortem XRD was performed to identify the composition change of cycled electrodes. As shown in Fig. 3g, Zn\u003csub\u003e4\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e(OH)\u003csub\u003e6\u0026bull;\u003c/sub\u003e4H\u003csub\u003e2\u003c/sub\u003eO by-product is proven to be generated on bare Zn upon cycling. This insoluble species would inevitably induce high overpotential of Zn symmetric cell due to its impenetrable nature for Zn ion. In contrast, there is no trace of by-product diffraction peak for ZnSe@Zn electrode, implying high reversibility of Zn dissolution/deposition reaction by virtue of ZnSe overlayer. Note further that the peak intensity ratio of Zn (002) to Zn (101) plane for ZnSe@Zn after cycling significantly augments about 12 times as compared to that for bare Zn. The existing similarity of lattice structure between ZnSe (111) and Zn (002) plane possibly guide an oriented Zn formation (Supplementary Fig. 15 and 16), where ZnSe layer can act as a template to induce (002) monocrystal Zn. Such a Zn growth behavior is desirable for anode protection\u003csup\u003e17, 33\u003c/sup\u003e. More intriguingly, there is no sign of ZnSe signals whatsoever for the ZnSe@Zn electrode after cycling, indicating the fall-off of ZnSe coating from the Zn foil, in good agreement with visualized characterizations (Supplementary Fig. 16; Supplementary Video 1). This phenomenon stems primarily from the fact that Zn is deposited at the interface between ZnSe overlayer and underlying Zn foil, where a flat and oriented Zn film is readily formed prior to the ZnSe detachment. Thus-produced Zn film enables to continuously guide a uniform Zn deposition even in the absence of ZnSe coating. Collectively, our results demonstrate that ZnSe overlayer is crucial to achieve optimized interfacial manipulation targeting highly reversible Zn anode.\u003c/p\u003e\n\u003cp\u003eThe suppression effect on Zn corrosion \u003cem\u003evia \u003c/em\u003eZnSe overlayer was analyzed by linear polarization tests in 2 M ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte (Fig. 3h). In comparison with bare Zn, the corrosion potential of the ZnSe@Zn reaches \u0026minus;1.013 V (\u0026minus;1.017 V for bare Zn), suggesting that it is less prone to corrosion. Meanwhile, the declined corrosion current by \u003cem\u003eca.\u003c/em\u003e 300 \u0026mu;A cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e again represents a retarded corrosion rate\u003csup\u003e34\u003c/sup\u003e. It is well received that the corrosion mainly originates from hydrogen evolution reaction (HER) accompanied by Zn dissolution/deposition reaction in weakly acidic ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte\u003csup\u003e11\u003c/sup\u003e. Along this line, HER activity was additionally evaluated by linear sweep voltammetry (LSV) measurements\u003csup\u003e24\u003c/sup\u003e. As displayed in Fig. 3i, it is striking to find that ZnSe@Zn electrode harvests a depressed HER capability as compared to that of bare Zn electrode.\u003c/p\u003e\n\u003cp\u003eThe solvation of Zn\u003csup\u003e2+\u003c/sup\u003e is a major obstacle for circumventing rapid transport of Zn ions throughout the interface between electrolyte and Zn anode\u003csup\u003e24, 35\u003c/sup\u003e. The activation energy (\u003cem\u003eE\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e), which represents the energy required for de-solvation\u003csup\u003e36\u003c/sup\u003e, can be quantitatively derived using the Arrhenius equation: 1/\u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e =\u003cem\u003eA\u003c/em\u003eexp (\u0026minus;\u003cem\u003eE\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e/\u003cem\u003eRT\u003c/em\u003e), where \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e is the charge transfer resistance and \u003cem\u003eR\u003c/em\u003e is the ideal gas constant. Herein, \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e (Supplementary Table 2) was fitted based on the variable-temperature EIS curves of Zn-Zn and ZnSe@Zn-ZnSe@Zn symmetric cells from 15 to 60 ℃ (Fig. 3j-k). It is evident that all \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e values of ZnSe@Zn cell (Fig. 3k) are much lower than those of bare Zn cell (Fig. 3j). Accordingly, \u003cem\u003eE\u003c/em\u003e\u003csub\u003ea\u003c/sub\u003e of ZnSe@Zn can be calculated to be ~44.0 kJ mol\u003csup\u003e\u0026minus;1\u003c/sup\u003e (Fig. 3l), in contrast to that of bare Zn cell (~67.5 kJ mol\u003csup\u003e\u0026minus;1\u003c/sup\u003e). This result implies the superior kinetics of Zn\u003csup\u003e2+\u003c/sup\u003e transfer throughout the interface between electrolyte and anode.\u003c/p\u003e\n\u003cp\u003eThe nucleation and deposition of Zn relies heavily upon the electric field distributions at the anode/electrolyte interface\u003csup\u003e7, 16\u003c/sup\u003e. To investigate the role of \u003cem\u003ein-situ\u003c/em\u003e grown ZnSe overlayer played in regulating interfacial electric field, finite element method carried out by COMSOL Multiphysics was employed. As depicted in Fig. 4a, the electric field distribution is homogeneous on bare Zn anode harnessing an ideally smooth surface. Nevertheless, the presence of micro-protrusions would strengthen the surrounding field intensity, which is expected to guide uneven deposition of Zn and lead to the dendrite formation (Fig. 4b). Encouragingly, these protuberances could be well eliminated by \u003cem\u003ein-situ\u003c/em\u003e selenation process. In response, the peak value of field intensity sharply decreases from 2.2\u0026times;10\u003csup\u003e5\u003c/sup\u003e to 1.6\u0026times;10\u003csup\u003e4 \u003c/sup\u003eV m\u003csup\u003e\u0026minus;1\u003c/sup\u003e with the aid of ZnSe overlayer (Fig. 4c). Such a textured ZnSe coating further helps homogenize the electric field on Zn surface, followed by building up uniform charge flux.\u003c/p\u003e\n\u003cp\u003eTheoretical simulation based on density functional theory (DFT) route was performed to gain insight into the interaction between Zn and ZnSe. The calculated adsorption energy of a Zn atom on ZnSe support is apparently higher than that on bare Zn support (Fig. 4d; Supplementary Fig. 17). The strong affinity of Zn with ZnSe would be of benefit to suppressing two-dimensional (2D) diffusion of Zn ions. Chronoamperometry was accordingly employed to probe the Zn\u003csup\u003e2+\u003c/sup\u003e diffusion dynamics at the anode/electrolyte interface (Supplementary Fig. 18). The current density of bare Zn symmetric cell continues to increase beyond 140 s under 150 mV, implying a violent 2D diffusion process. In turn, Zn\u003csup\u003e2+\u003c/sup\u003e and hydrated Zn\u003csup\u003e2+\u003c/sup\u003e ions tend to aggregate and grow into dendrites to minimize the surface energy (Fig. 4e). As for the ZnSe@Zn electrode, the 2D diffusion only occurs within the initial 20 s, after which a stable three-dimensional (3D) diffusion pattern becomes predominant. As illustrated in Fig. 4f, a desolvation process proceeds rapidly for hydrated Zn\u003csup\u003e2+\u003c/sup\u003e ions upon their arrival at the ZnSe layer owing to low activation energy. Benefiting from a favorable 3D diffusion, Zn\u003csup\u003e2+\u003c/sup\u003e could then pass through the ZnSe layer rapidly under the potential gradient resulting from the high electron resistance of ZnSe\u003csup\u003e37\u003c/sup\u003e (Supplementary Fig. 19). This fast 3D diffusion process was confirmed by the high ionic conductivity of ZnSe layer reaching ~1.7 \u0026times; 10\u003csup\u003e\u0026ndash;5\u003c/sup\u003e S cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (Supplementary Fig. 20). Finally, these Zn ions are reduced to Zn\u003csup\u003e0\u003c/sup\u003e and start to grow along (002) plane on Zn metallic surface.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eE\u003c/strong\u003e\u003cstrong\u003electrochemical performance\u003c/strong\u003e\u003cstrong\u003e of AZIB full cells \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo demonstrate the feasibility of thus-designed ZnSe@Zn anode in practical devices, AZIB full cells comprising KV\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e30-y\u003c/sub\u003e\u0026middot;nH\u003csub\u003e2\u003c/sub\u003eO (KVOH)\u003csup\u003e38\u003c/sup\u003e cathode (see methods) and ZnSe@Zn anode were assembled employing 2 M ZnSO\u003csub\u003e4\u003c/sub\u003e electrolyte (Supplementary Fig. 21). Fig. 5a records the CV profiles of ZnSe@Zn\u0026minus;KVOH and bare Zn\u0026minus;KVOH cells at a scan rate of 0.1 mV s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e in a voltage window between 0.2 and 1.6 V. Both cells manifest two main pairs of redox signals corresponding to two-step redox reactions of V\u003csup\u003e3+\u003c/sup\u003e/V\u003csup\u003e4+\u003c/sup\u003e and V\u003csup\u003e4+\u003c/sup\u003e/V\u003csup\u003e5+\u003c/sup\u003e. The higher current response of full cell with ZnSe@Zn anode as compared to bare Zn anode implies a higher capacity value, which can be confirmed by galvanostatic charge/discharge (GCD) curves in Fig. 5b. Fig. 5c draws a comparison of rate performances of both cells. As expected, ZnSe@Zn\u0026minus;KVOH harvests a capacity of 294.2, 259.2, 232.9, 193.4 and 155.1 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e at 0.5, 1.0, 2.0, 5.0 and 10.0 A g\u003csup\u003e\u0026minus;1\u003c/sup\u003e, respectively. When the current density returns to 0.5 A g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, the device still retains a capacity of 253.1 mAh g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. This readily outperforms the bare Zn\u0026minus;KVOH cell under identical conditions. Such outstanding reversibility and rate capability could be attributed to the inhibition of dendrite formation/side reactions and the maintenance of a homogeneous interface \u003cem\u003evia\u003c/em\u003e the versatile ZnSe coating, which functions as a high-performance artificial SEI layer. Nyquist plots before and after cycling also reveal that the ZnSe@Zn\u0026minus;KVOH cell exhibits lower charge-transfer resistance and promoted ion diffusion kinetics in comparison with the Zn\u0026minus;KVOH counterpart (Fig. 5d). The long-term cyclic stability of both cells was further evaluated (Fig. 5e). As for ZnSe@Zn\u0026minus;KVOH full cell, it manages to deliver an initial capacity of 194.5 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e and stabilizes at 163.9 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e after 1000 cycles with a retention rate of 84% at 5.0 A g\u003csup\u003e\u0026minus;1\u003c/sup\u003e. In contrast, the capacity of bare Zn\u0026minus;KVOH cell sharply drops to 47.2 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e after 1000 cycles.\u003c/p\u003e\n\u003cp\u003eMore impressively, ZnSe@Zn anode harnessing mechanical robustness and large-scale availability enlists the construction of flexible AZIB full cells (see methods) toward practical applications (Supplementary Fig. 22). Fig. 5f presents the GCD profiles of assembled flexible AZIB at 2.0 mA cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e under various bending angles of 0\u0026deg;, 90\u0026deg;, 135\u0026deg;, and 180\u0026deg;. Notably, 97.8% of the initial capacity could be retained upon bending at 180\u0026deg;, showing excellent mechanical flexibility. As a proof-of-concept demonstration, Fig. 5g displays digital photos of the working states of two flexible AZIBs in tandem configuration, enabling to continuously powering a light emitting diode (LED) indicator under different bending angles, showing its application prospect in wearable electronics. Taken together, these results corroborate that the ZnSe overlayers can effectively inhibit the parasitic reactions at the anode/electrolyte interface and guide uniform Zn deposition in favor of advanced stability of AZIB.\u003c/p\u003e"},{"header":"Discussion","content":" \u003cp\u003eIn summary, we have developed a high-performance Zn anode \u003cem\u003evia in-situ\u003c/em\u003e CVD coating of ZnSe overlayer harnessing high uniformity, thickness tailorability and scalability. Thus-designed ZnSe@Zn anode demonstrates a high Zn utilization of 99.2% and an elongated cycle life of 860 h during repetitive Zn plating/stripping. Even experiencing harsh conditions (10.0 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e/10.0 mAh cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), it can still sustain to operate as long as 260 h, outperforming the state-of-the-art anode counterparts. The protection mechanism of ZnSe overlayer has been systematically explored by a suite of experimental characterizations in harmonization with theoretical simulations. The optimized interfacial manipulation throughout such a ZnSe layer can help accelerate the kinetics of Zn\u003csup\u003e2+\u003c/sup\u003e deposition by reducing de-solvation energy and restrict the 2D diffusion of Zn\u003csup\u003e2+\u003c/sup\u003e \u003cem\u003evia\u003c/em\u003e strong Zn affinity. Meanwhile, HER and other side reactions can be effectively handicapped. As a result, the ZnSe@Zn anode exhibits stable cycling capability, low voltage hysteresis as well as smooth dendrite-free surface. Encouragingly, assembled ZnSe@Zn\u0026thinsp;\u0026minus;\u0026thinsp;KVOH full cell delivers a remarkable cycling stability with a capacity retention of 84% after 1000 cycles. Our ZnSe@Zn anodes affording versatility and simplicity may greatly promote the industrialization of Zn-based energy storage systems.\u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003ePreparation of ZnSe-coated Zn \u003c/strong\u003e\u003cstrong\u003efoil\u003c/strong\u003e\u003cstrong\u003e (ZnSe@Zn)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe ZnSe overlayer was realized \u003cem\u003evia\u003c/em\u003e an ambient pressure chemical vapor deposition process using tube furnace (Thermo Fisher Scientific). In brief, Zn foil (thickness: ~0.1 mm; length: ~20 cm; 99.99% purity; Alfa Aesar) and Se powders (~100 mg, 99.99%, Aladdin) were placed at the downstream and upstream position, respectively. The quartz tube was purged for 30 min using 540 sccm (standard cubic centimeters per minute) Ar gas. Afterwards, 50 sccm H\u003csub\u003e2\u003c/sub\u003e/Ar mixture (10% H\u003csub\u003e2\u003c/sub\u003e) was used as the carrier gas during growth and cooling. The quartz tube was heated to 300 ℃ in 15 min, and then cooled to room temperature under preset dwelling time. The surface of Zn foil turned into faint yellow due to the formation of ZnSe. Then the ZnSe coated Zn foil (ZnSe@Zn) was annealed at 325 ℃ for 30 min with 10 sccm H\u003csub\u003e2\u003c/sub\u003e/Ar. Note that the ZnSe coated Ti foil was fabricated by a similar process as compared to that of ZnSe@Zn foil except that the Ti foil was placed on top of Zn foil and the tube furnace was kept at 320 ℃ for 1 h. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePreparation of KVOH \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eKVOH nanostructure was prepared by a modified hydrothermal method\u003csup\u003e38\u003c/sup\u003e. Typically, 0.364 g V\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e (Energy Chemical, 99%) and 0.087 g K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (Macklin, 99.99%) were dissolved into 80 mL of DI water, followed by slow dripping of 2.0 mL 30% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e into the solution under magnetic stirring. After continuous stirring for 30 min, the orange mixture was gradually transformed into a transparent red solution, which was then transferred into 100 mL Teflon autoclave under 120 ℃ for 6 h. Upon centrifugation, the precipitates were dried by a cryodesiccation process for 30 h to preserve the urchin-shaped morphology. Finally, light green colored KV\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e30-y\u003c/sub\u003e\u0026middot;nH\u003csub\u003e2\u003c/sub\u003eO (KVOH) powders can be obtained.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe KVOH electrode was prepared by casting slurry onto a Ti mesh. The slurry was composed of active material KVOH, conductive carbon (Super P) and binder (PVDF) with a mass ratio of 7:2:1. The electrode was then dried in a vacuum oven under 80 ℃ for 12 h. The mass loading was adjusted to ~1.0 mg cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectrochemical tests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Zn-Zn symmetric cell, Ti-Zn asymmetric cell and KVOH-Zn full-cell were fabricated based on CR2032 coin cell configuration. Prior to assembly, all the foils were cut into circle discs with a diameter of 13 mm. The cells were assembled at ambient conditions at room temperature. The electrodes were separated by glass fiber separators (\u0026Phi; = 19 mm, Whatman). 2 M ZnSO\u003csub\u003e4\u003c/sub\u003e aqueous solution was used as the electrolyte.\u003c/p\u003e\n\u003cp\u003eThe GCD cycling tests were carried out on the Neware battery-testing system. EIS, linear polarization, chronoamperogram and CV measurements of the batteries were recorded on electrochemical workstation (CHI660E, China). The linear polarization measurements were recorded in a three-electrode configuration, where bare Zn or ZnSe@Zn plate were used as the working electrode, Zn foil as the counter electrode, and saturated calomel (SCE) as the reference electrode, respectively. Moreover, the ZnSe@Zn and bare Zn electrodes were also assembled into transparent symmetric cells\u003csup\u003e34\u003c/sup\u003e, followed by an \u003cem\u003ein-situ\u003c/em\u003e optical observation to detect electrode evolution during continuous Zn plating/stripping process at a current density of 5.0 mA cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eHER tests were carried out using a three-electrode system controlled by an electrochemical workstation (CHI 760E, China). Graphite carbon and Ag/AgCl electrode (filled with saturated KCl) were used as counter electrode and reference electrode, respectively. The reference electrode (Ag/AgCl) calibration was performed in 0.1 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte with a Zn plate (1\u0026times;1 cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e) serving as the working electrode. Prior to the test, the solution was bubbled with N\u003csub\u003e2\u003c/sub\u003e gas for 30 min to establish a N\u003csub\u003e2\u003c/sub\u003e saturation conditions. Linear sweep voltammetry (LSV) was conducted at a scan rate of 2 mV s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. All potentials measured were calibrated to reversible hydrogen electrode (RHE) using the following equation:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eE\u003c/em\u003e (\u003cem\u003evs.\u003c/em\u003e RHE) = \u003cem\u003eE\u003c/em\u003e (\u003cem\u003evs.\u003c/em\u003e Ag/AgCl) + 0.059 pH + 0.198.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTheoretical calculations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll computations were performed by spin-unrestricted density functional theory, carried out by Vienna \u003cem\u003eAb-initio \u003c/em\u003eSimulation Package\u003csup\u003e39\u003c/sup\u003e with projector augmented wave pseudopotential\u003csup\u003e40\u003c/sup\u003e. Electronic exchange-correlation interactions were described by GGA-PBE\u003csup\u003e41\u003c/sup\u003e functional with the Grimme\u0026rsquo;s D3 dispersion correction\u003csup\u003e42\u003c/sup\u003e. The kinetic energy cutoff with plane wave was set to be 400 eV. First Brillouin zone integrations were sampled by the mesh size 5\u0026times;5\u0026times;1 for Zn (001) slab and 4\u0026times;4\u0026times;1 for ZnSe (111) slab. Zn (001) and ZnSe (111) slab with periodically repeating (3\u0026times;3) and (2\u0026times;2) unit cell by 4 layers was constructed for the Zn atom adsorption, respectively. The thickness of vacuum layer was set to 15 \u0026Aring;. The bottom layer was fixed to the bulk position. The other layers and adsorbed Zn atom were relaxed fully until the total energy was less than 10\u003csup\u003e\u0026ndash;5\u003c/sup\u003e eV and residual force per atom was lower than 0.02 eV/\u0026Aring;. The adsorption energy was calculated by the formula: \u003cem\u003eE\u003c/em\u003e\u003csub\u003eads\u003c/sub\u003e = \u003cem\u003eE\u003c/em\u003e\u003csub\u003etotal\u003c/sub\u003e \u0026ndash; \u003cem\u003eE\u003c/em\u003e\u003csub\u003eslab\u003c/sub\u003e \u0026ndash; \u003cem\u003eE\u003c/em\u003e\u003csub\u003ezn\u003c/sub\u003e, where \u003cem\u003eE\u003c/em\u003e\u003csub\u003etotal\u003c/sub\u003e, \u003cem\u003eE\u003c/em\u003e\u003csub\u003eslab\u003c/sub\u003e and \u003cem\u003eE\u003c/em\u003e\u003csub\u003eZn\u003c/sub\u003e are the total energy with/without the adsorption of Zn atom and atomic energy of Zn, respectively.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectric field simulation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA parallel plate capacitor model was used to simulate the electric field distribution at the interface between anode and electrolyte based on COMSOL Multiphysics software. In this simplified model, the length of two electrodes was 2 \u0026mu;m and the distance between them was 1 \u0026mu;m. The protuberances of bare Zn surface were represented by two cones. Hemisphere arrays were used to represent ZnSe nanoparticles. The sizes of Zn protuberances and ZnSe nanoparticles in simulations were based on the results of SEM characterizations. The ionic conductivity of ZnSO\u003csub\u003e4\u003c/sub\u003e was 5 S m\u003csup\u003e\u0026ndash;1\u003c/sup\u003e.\u003csup\u003e43\u003c/sup\u003e The experimental observed voltage hysteresis (with/without ZnSe overlayer) was set as cathodic potential, while the anodic potential is a constant of zero.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data supporting the findings of this work are available within the article and its Supplementary Information files. All other relevant data supporting the findings of this study are available from the corresponding author on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (51702225), the Natural Science Foundation of Jiangsu Province (BK20170336), Suzhou Science and Technology Project-Prospective Application Research Program (SYG202038) and the China Post-doctoral Foundation (Grant No. 7131705619). The authors also acknowledge support from the Suzhou Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Suzhou, China.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.Y.S. designed the concept. X.Z.Y., C.L., R.H., B.Z.L. and M.L.W. prepared and characterized the ZnSe@Zn anode and KVOH cathode. X.Z.Y., C.L., Z.X.S., Y.H.W., S.L. and Y.W.S. performed the electrochemical test and explored the protective mechanism using \u003cem\u003ein-situ\u003c/em\u003e and \u003cem\u003eex-situ\u003c/em\u003e characterization tools. Z.T.S. conducted the DFT calculation. S.Y. performed the COMSOL simulations. X.Z.Y., S.X.D. and J.Y.S. wrote the manuscript. All authors discussed the experimental and theoretical results and commented on the manuscript. All authors have approved to the final version of the manuscript.\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\u003cli\u003e\u003cspan\u003eChao D, \u003cem\u003eet al.\u003c/em\u003e Roadmap for advanced aqueous batteries: from design of materials to applications. \u003cem\u003eSci. 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Nevertheless, the instability of Zn metal, caused by dendrite formation, hydrogen evolution and side reactions, gives rise to poor electrochemical stability and unsatisfactory cycling life, greatly hampering large-scale utilization. Herein, an\u003cem\u003e in-situ \u003c/em\u003egrown ZnSe layer with controllable thickness is crafted over one side of commercial Zn foil \u003cem\u003evia\u003c/em\u003e chemical vapor deposition, aiming to achieve optimized interfacial manipulation between aqueous electrolyte/Zn anode. Thus-derived ZnSe overlayer not only prevents water penetration and restricts Zn\u003csup\u003e2+\u003c/sup\u003e two-dimensional diffusion, but also homogenizes the electric field at the interface and facilitates favorable (002) plane growth of Zn. As a result, dendrite-free and homogeneous Zn deposition is obtained; side reactions are concurrently inhibited. In consequence, a high Coulombic efficiency of 99.2% and high cyclic stability for 860 cycles at 1.0 mA cm\u003csup\u003e–2 \u003c/sup\u003ein symmetrical cells is harvested. Meanwhile, when paired with V\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e cathode, assembled full cell achieves an outstanding initial capacity (200 mAh g\u003csup\u003e–1\u003c/sup\u003e) and elongated lifespan (a capacity retention of 84% after 1000 cycles) at 5.0 A g\u003csup\u003e–1\u003c/sup\u003e. Our highly reversible Zn anode enabled by the interfacial manipulation strategy is anticipated to satisfy the demand of industrial and commercial use.\u003c/p\u003e","manuscriptTitle":"Interfacial Manipulation via In-Situ Grown ZnSe Overlayer toward Highly Reversible Zn Metal Anodes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-04-20 18:06:05","doi":"10.21203/rs.3.rs-400312/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5c523f1e-04b8-4b25-ba22-470899824fd2","owner":[],"postedDate":"April 20th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":3779852,"name":"Energy Engineering"},{"id":3779853,"name":"Materials Engineering"},{"id":3779854,"name":"Electronic Materials and Devices"}],"tags":[],"updatedAt":"2021-07-30T09:50:44+00:00","versionOfRecord":[],"versionCreatedAt":"2021-04-20 18:06:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-400312","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-400312","identity":"rs-400312","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}