Iron-Doped Nickel Disulfide as an Efficient Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries

Iron-Doped Nickel Disulfide as an Efficient Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries | 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 Research Article Iron-Doped Nickel Disulfide as an Efficient Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries Liming Song, Feiyu Wang, Qiang Liu, Xianwu Li, Yong Xiang, Jie Tan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8972766/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 18 You are reading this latest preprint version Abstract Severe polysulfide shuttle effect and sluggish redox kinetics remain primary impediments to the practical application of high-energy-density lithium-sulfur (Li-S) batteries. Herein, a metal-organic framework (MOF)-assisted strategy was employed to fabricate a bimetallic Fe-doped NiS 2 catalyst. The incorporation of Fe via in situ synthesis effectively modulates the electronic structure of NiS 2 , constructing synergistic bimetallic active sites. Comprehensive experimental analyses and density functional theory (DFT) calculations verify that these sites not only significantly enhance the chemisorption of lithium polysulfides (LiPSs) but also lower the energy barrier for their catalytic conversion, achieving a balance between adsorption and kinetics. Furthermore, the catalyst inherits the porous and layered architecture from its MOF precursor, which prevents structural collapse and provides ample space for physical LiPSs confinement. Benefiting from this dual-confinement and accelerated redox kinetics, the Li-S battery equipped with the Fe-NiS 2 /PP separator delivers superior electrochemical performance: a high initial discharge capacity of 1395 mAh g⁻¹ at 0.1 C and remarkable long-term cycling stability with a capacity decay rate as low as 0.07% per cycle over 500 cycles at 1 C. This work demonstrates the effectiveness of bimetallic modulation, offering a feasible strategy for designing functional interlayers to advance the practical application of Li-S batteries. Lithium-sulfur battery Metal-organic frameworks Synergistic catalysis Bimetallic sites Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Lithium-sulfur (Li-S) batteries represent a promising energy storage system with high theoretical specific capacity (1675 mAh g − 1 ) and strong commercial potential. Sulfur is an ideal electrode candidate owing to its Earth abundance, low cost, and environmentally benign reaction products [ 1 – 4 ]. However, the commercialization of Li-S batteries is hindered by several critical challenges, primarily the severe capacity fading caused by the polysulfide shuttle effect, as well as the low utilization of active materials and sluggish kinetics arising from the insulating nature of sulfur and its discharge products (Li 2 S and Li 2 S 2 ) [ 5 – 9 ]. In conventional Li-S cells employing commercial separators, soluble polysulfide intermediates migrate through the separator and deposit on the lithium anode, leading to active material loss and performance degradation. To mitigate these challenges, the introduction of an interlayer between the separator and the sulfur cathode has been widely investigated as an effective strategy to inhibit polysulfide diffusion [ 10 – 14 ]. Among various candidates, metal-organic frameworks (MOFs) [ 15 , 16 ], stand out due to their highly ordered porosity and tunable metal nodes. These features offer a dual-protection mechanism: the nanochannels provide physical spatial confinement as a molecular sieving [ 17 , 18 ], while the unsaturated metal sites offer chemical anchoring for sulfur species [ 19 ]. However, pristine MOFs typically suffer from poor electrical conductivity and limited intrinsic catalytic activity, which hampers the rapid conversion of intercepted polysulfides. While single-metal active sites can adsorb polysulfides, they are often constrained by the linear scaling relationship, unable to simultaneously satisfy the requirements for strong adsorption and fast desorption/conversion. To break this limitation, constructing bimetallic active centers via heteroatom doping has emerged as a robust solution. The introduction of a second metal atom induces lattice distortion and modulates the electronic band structure of the host material. This orbital-level engineering creates synergistic "sulfiphilic-lithiophilic" bifunctional sites, which not only dramatically enhance electrical conductivity but also lower the energy barriers for redox reactions [ 20 , 21 ]. By leveraging the synergy between the MOF-derived porous architecture and bimetallic catalytic sites, it is possible to achieve high-efficiency sulfur immobilization and conversion. For instance, in the Fe, N-co-doped porous graphene designed reported by Hou et al. [ 22 ], Fe atoms are anchored at the edges of graphene pores through Fe-N 4 or Fe-N 2 coordination configurations. The strong coupling between the 3d orbitals of Fe and the p orbitals of LiPSs strengthens the trapping of LiPSs, while N atoms further immobilize Li⁺ via Li-N bonding, synergistically suppressing LiPSs diffusion and accelerating their conversion. In the Co, N-co-doped graphene@carbon nanotube composite prepared by Zhou’s group through reductive pyrolysis of a bimetallic MOF [ 23 ], Co atoms serve as catalytic centers to lower the nucleation barrier of Li 2 S, and N-doped carbon constructs an efficient electron transport network. Moreover, the Co-N 4 active sites enable bidirectional catalysis of LiPSs reduction and Li 2 S oxidation, achieving synergistic optimization of catalytic function and conductive performance. In this work, we report the rational design of an Fe-doped NiS 2 catalyst via a MOF-assisted route. This catalyst is integrated onto a commercial separator to construct a robust Fe-NiS 2 /PP interlayer. Distinct from single-component counterparts, the Fe doping creates synergistic bimetallic active sites that optimize the adsorption-catalysis balance for polysulfides, while the MOF-derived porous architecture ensures efficient ion transport and physical confinement. Combined experimental characterizations and density functional theory (DFT) calculations are employed to elucidate the mechanism: Fe doping constructs highly active bimetallic sites that simultaneously strengthen the chemisorption of polysulfides and lower the activation energy barriers for their subsequent conversion. The impact of this Fe-NiS 2 /PP separator on the electrochemical performance, specifically in terms of enhancing redox kinetics, improving rate capability, and suppressing polysulfide shuttling—is systematically investigated. This work demonstrates the effectiveness of bimetallic modulation, offering a feasible strategy for designing functional interlayers to advance the practical application of Li-S batteries. Experimental section Materials and preparation Fe-Ni MOF Layered Fe-NiS 2 was prepared by a two-step hydrothermal reaction method. Specifically, 0.425 g of NiCl 2 ·6H 2 O and 0.83 g of terephthalic acid (PTA) were dissolved into 90 mL of N, N-dimethylformamide (DMF) and stirred for 30 min. Subsequently, 10 mL of NaOH aqueous solution (0.4 M) was added dropwise to the mixture. After the addition of FeCl 3 ·6H 2 O, the obtained mixture solution was kept at 100°C for 8 h. The precipitate was centrifuged, washed, and dried in vacuum at 60°C overnight to obtain the product Fe-Ni MOF. Fe-NiS 2 The precursor, together with 50 mL of thioacetamide, was dispersed into 75 mL of ethanol by stirring. After being placed into an autoclave and kept at 120°C for 4 h, the resulting black product was washed with deionized water followed by drying in vacuum to obtain layered Fe-NiS 2 [ 24 ]. Fe-NiS 2 /PP modified separator : The Fe-NiS 2 powder, Super P, and PVDF were mixed uniformly in an agate mortar at a mass ratio of 8:1:1. N-methyl pyrrolidone (NMP) was added and stirred for 12 h. After that, the slurry was evenly coated on the Celgard 2500 separator and dried at 60°C overnight under vacuum. The treated separator was subsequently cut into circular pieces with a diameter of 16.5 mm, yielding the desired Fe-NiS 2 /PP modified separator. C/S composites : The Ketjen Black was mixed with sulfur powder at the mass ratio of 2:8, after holding at 155°C for 12 h with a heating rate of 5°C min − 1 . A mixture of sulfur composites and PVDF with the mass ratio of 9:1 were dispersed in an appropriate amount of NMP to give a slurry, which was then coated on aluminum foil and vacuum dried at 60°C overnight. The circular sulfur cathodes (12 mm in diameter) were obtained with sulfur content of 1 mg cm − 2 . Material characterization X-ray diffraction (XRD) was performed on a Rigaku D/max2500PC instrument (Japan) with CuKα radiation (40 kV, 20 mA) at a scan rate of 10° min − 1 over 20–60°. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) elemental analysis were obtained using a FEI450 SEM instrument. Transmission electron microscopy (TEM) for morphology and elemental analysis was conducted using a FEI Titan G260-300 high-resolution instrument (USA). X-ray photoelectron spectroscopy (XPS) was carried out on a Kratos AXIS ULTRA DLD instrument (Japan) with Al Kα radiation (1486.7 eV), and all peaks were calibrated using the C 1s peak at 284.8 eV. Density functional theory (DFT) calculations were employed to analyze the energy optimization pathway of the materials. Contact angle measurement was performed via a Dataphysics-OCA20 tester (Germany), using Fe-NiS 2 /PP modified separator as the sample, Celgard 2500 PP separator as the control, and Li-S electrolyte as the liquid. Cyclic voltammetry (CV) (potential range: 1.6–2.8 V, scan rate of 0.1–0.5 mVs − 1 ) and electrochemical impedance spectroscopy (EIS) (frequency range: 0.01–100 kHz) were conducted on a CHI660E electrochemical workstation. Electrochemical tests 2032 coin cells were assembled in a glove box filled with Ar, using C/S as the cathode, lithium sheets as the anode, Fe-NiS 2 /PP or Celgard 2500 as separator, and 1.0 M lithium ditrifluoromethane sulfonimide (LITFSI) dissolved in DOL/DME (1:1 v/v) containing 1 wt % LiNO 3 as the electrolyte. Li 2 S 6 solution was prepared by dissolving sulfur powder and Li 2 S in a molar ratio of 5:1 in DOL and DME solutions (1:1 v/v) at 50°C with vigorous stirring for 24 h. Results and discussion Figure 1 Schematic illustration of the MOF-assisted synthetic route for Fe-NiS 2 and the corresponding bimetallic synergistic mechanism that promotes the fast conversion of polysulfides Li 2 S n to Li 2 S. As presented in Fig. 2 a-c, SEM and TEM images reveal that the obtained Fe-NiS 2 successfully retains the characteristic lamellar architecture of its MOF precursor (Fig. S1 ) without obvious structural collapse. TEM observations further confirm this well-preserved multilayered sheet-like structure. Inheriting this porous and ordered architecture is critical, as it not only prevents structural collapse but also ensures the maximal exposure of active sites. This stable layered nanostructure offers a high specific surface area and abundant interfacial active sites, which are crucial for Li-S battery separator modifications to facilitate electrolyte wetting, efficient polysulfide adsorption, and catalytic conversion. Moreover, EDS mapping results (Fig. 2 d) demonstrate a homogeneous distribution of Fe, Ni, and S elements throughout the material. Such uniform elemental dispersion promotes consistent electrochemical reactions, thereby laying a structural foundation for enhanced overall battery performance. The prepared Fe-NiS 2 powder was first characterized by XRD to determine its phase composition (Fig. 3 a). The XRD pattern of Fe-NiS 2 exhibits well-defined diffraction peaks at 31.30°, 35.16°, 38.80°, 45.14°, 53.60°, and 53.68°, corresponding to the (200), (210), (211), (220), (311), and (230) planes of cubic pyrite NiS 2 (PDF#11–0099), respectively, confirming its isostructural nature. No distinct peaks related to Fe-doped NiS 2 were observed, which can be attributed to the low Fe doping content in the system. However, compared with NiS 2 , the diffraction peaks of Fe-NiS 2 shift slightly to higher angles, consistent with a reduction in lattice parameters due to Fe doping (Fig. S2). XPS further confirmed the presence of Ni, S and Fe elements in the heterostructure (Fig. 3 b-c and S2), providing experimental evidence for the successful incorporation of Fe into the NiS 2 lattice to achieve bimetallic modulation. a XRD pattern of Fe-NiS 2 . b XPS spectrum of Ni 2p for Fe-NiS 2 . c XPS spectrum of S 2p for Fe-NiS 2 . d UV-vis absorption spectra of Fe-NiS 2 /Li 2 S 6 and Li 2 S 6 solutions; and the photographs of the corresponding solutions. e Top-view crystal structure of NiS 2 (Ni site is labeled). f Top-view crystal structure of Fe-NiS 2 (Fe site is labeled). g Calculated binding energies of LiPSs intermediates on Fe-NiS 2 and NiS 2 . h Gibbs free energy profiles for SRR on Fe-NiS 2 and NiS 2 surfaces at equilibrium potential. To investigate the interaction between Fe-NiS 2 and polysulfides, adsorption experiments were conducted by adding Fe-NiS 2 powder to a Li 2 S 6 solution. Significant decolorization of the solution was observed, indicating strong adsorption of LiPSs by the powder. This was further supported by ultraviolet-visible (UV-Vis) absorption spectroscopy, where the characteristic peak intensity in the range of 350–400 nm was significantly lower for the solution containing Fe-NiS 2 , consistent with the adsorption results (Fig. 3 d). While physical adsorption is evident, the fundamental origin of this enhanced performance lies in the electronic structure modulation induced by Fe incorporation. To elucidate how this bimetallic synergy intrinsically promotes the reaction kinetics, density functional theory (DFT) calculations were performed. Through modeling, the original (210) crystal planes of NiS 2 and Fe-NiS 2 were obtained (Fig. S4). Figure 3 e and 3 f show the crystal structures of pristine NiS 2 and Fe-doped NiS 2 , respectively, where Fe atoms partially substitute Ni atoms. The adsorption energies of polysulfides and the mechanism of the stepwise sulfur reduction reaction (SRR) were calculated (Fig. S5). As shown in Fig. 3 g, Fe-NiS 2 exhibits stronger adsorption energy for polysulfides compared to pristine NiS 2 , which may be attributed to the synergistic effect of bimetallic atoms. Figure 3 h shows the Gibbs free energy profiles for the conversion of S 8 to Li 2 S. It has been established in previous studies that the solid-phase reduction of Li 2 S 2 to Li 2 S is the rate-determining step in SRR. A similar rate-determining behavior was observed in this study. For this step, Fe-NiS 2 shows a significantly lower energy barrier compared to NiS 2 . This significantly reduced energy barrier confirms that the Fe-Ni bimetallic centers effectively accelerate the rate-determining step, thereby promoting the rapid conversion of polysulfides and mitigating their accumulation. After coating Fe-NiS 2 onto the commercial separator, the physical structure and physicochemical properties of the composite were first evaluated. Cross-sectional SEM images (Fig. 4 a-c) reveal that the functional Fe-NiS 2 coating layer has a uniform thickness of approximately 10 µm. Beyond thickness, the interaction between the separator and the electrolyte is critical. Dynamic contact angle measurements (Fig. 4 d) demonstrate that the Fe-NiS 2 /PP separator achieves complete wetting within 0.5 s, significantly faster than the bare PP separator. This reduced contact angle highlights the superior oleophilicity of the modified surface. Such thorough wetting ensures rapid electrolyte infiltration, which is conducive to facilitating efficient electron/ion transfer, particularly under high-sulfur-loading conditions where rapid ion supply is pivotal. Complement this superior wettability, the mechanical robustness of the separator is equally vital for practical handling and operation. As shown in Fig. 4 e, even after repeated folding, the Fe-NiS 2 layer remained fully intact with no signs of peeling or cracking. This indicates that the modifying layer is firmly adhered to the PP substrate, possessing sufficient flexibility and mechanical strength to withstand the stress of battery assembly and volume expansion. Ultimately, these physicochemical and mechanical advantages translate into enhanced electrochemical stability. Conventional PP separators typically suffer from poor wettability and low ionic conductivity, resulting in an uneven electric field distribution that promotes irregular lithium dendrite growth. In contrast, the Fe-NiS 2 coating, which characterized by high electrical conductivity and excellent electrolyte wettability, homogenizes the lithium-ion flux. This promotes uniform lithium deposition (Fig. 4 f), effectively suppressing dendrite growth. To empirically validate this, Li||Li symmetric cells were assembled. In comparison to the bare PP cell, the Li||Fe-NiS 2 /PP||Li cell maintained a stable overpotential, confirming that the modified separator effectively optimizes ion transport and extends battery cycle life. To further investigate the electrocatalytic activity of the Fe-NiS 2 /PP separator, CV profiles were recorded. As shown in Fig. 5 , both cells exhibit two typical cathodic peaks (corresponding to the reduction of S 8 to soluble Li 2 S n and then to insoluble Li 2 S 2 and Li 2 S) and one anodic peak (oxidation of Li 2 S to S 8 ). The Fe-NiS 2 /PP cell exhibits a noticeably narrower potential separation between the oxidation and reduction peaks shown in Fig. 5 a. This reduced polarization signifies faster charge transfer kinetics and a lower energy barrier for the polysulfide redox conversion. More crucially, as shown in Fig. 5 b-c, compared to the cell with the pristine PP separator, the Fe-NiS 2 /PP cell displays significantly sharper redox peaks with higher current densities, indicating improved sulfur utilization and accelerated reaction rates enabled by the abundant bimetallic active sites. Based on these data, the linear relationship between the peak current and the square root of the scan rate is plotted in Fig. 5 d. According to the Randles-Sevcik equation, the distinctively steeper slopes observed for the Fe-NiS 2 /PP cell correspond to higher lithium-ion diffusion coefficients across all redox stages, confirming that the porous MOF-derived framework effectively expedites ion transport. These results provide compelling electrochemical evidence that the orbital-engineered Fe-NiS 2 catalyst effectively facilitates the rapid "solid-liquid-solid" phase transformation, thereby boosting the overall rate capability and energy efficiency. a EIS Nyquist plots comparing the Fe-NiS 2 /PP composite separator cell with the pure PP separator cell. b Initial GCD profiles of the Fe-NiS 2 /PP and pure PP separator cells, measured at 0.1C. c Rate performance of the Fe-NiS 2 /PP and PP separator cells tested at various current densities (0.1C to 3C). d GCD profiles of the Fe-NiS 2 /PP separator cell recorded at different current rates. e Long-term cycling performance and corresponding Coulombic efficiency of the Fe-NiS 2 /PP and PP separator cells at 1C. Figure 6 a shows the Nyquist plots of the assembled batteries. The curves exhibit a semicircular feature in the high- and medium-frequency regions, corresponding to the charge-transfer resistance (R ct ), and a linear trend in the low-frequency region, indicating the diffusion impedance of lithium ions within the solid electrode (Z w ). Among all tested cells, the battery with the Fe-NiS 2 /PP separator demonstrates the lowest impedance, suggesting efficient charge transport and rapid redox reaction kinetics within the electrode. Benefiting from the robust MOF-derived framework and the efficient polysulfide conversion catalyzed by the bimetallic active sites, the Fe-NiS 2 /PP separator is expected to significantly enhance battery performance. To investigate this, CR2032 coin cells were assembled and tested. As shown in Fig. 6 b, during the initial discharge at 0.1 C, the battery with the Fe-NiS 2 /PP separator delivers a specific discharge capacity of 1395 mAh g − 1 , significantly higher than that of the cell with a conventional PP separator (1235 mAh g − 1 ), along with lower polarization. In rate performance tests (Fig. 6 c-d), the Fe-NiS 2 /PP cell maintains well-defined charge/discharge voltage plateaus and higher specific discharge capacities at various current densities. In contrast, the PP-based cell exhibits notable capacity loss and increased polarization at higher rates, highlighting the superior rate capability and catalytic efficiency of the Fe-NiS 2 /PP separator (Fig. S6). Long-term cycling stability tests (Fig. 6 e) reveal that after 500 cycles at 1 C, the Fe-NiS 2 /PP cell retains about 65% of its initial capacity, with an average capacity decay rate of only 0.07% per cycle, which is much lower than the 0.15% per cycle observed for the PP-based cell. These results demonstrate the significantly improved electrochemical cycling stability of the battery employing the Fe-NiS 2 /PP separator. Conclusion In summary, an Fe-doped NiS 2 -modified polypropylene Fe-NiS 2 /PP separator was fabricated via a MOF-assisted route and applied in Li-S batteries. The introduction of Fe into the NiS 2 structure enhances polysulfide adsorption through bimetallic synergy and improves the catalytic conversion of sulfur species. Combined with the conductive framework provided by the PP substrate, the composite separator facilitates efficient electron/ion transport and suppresses the polysulfide shuttle effect. As a result, the battery equipped with the Fe-NiS 2 /PP separator demonstrates significantly improved electrochemical performance: an initial discharge capacity of 1395 mAh g − 1 at 0.1 C, remarkable rate capability with stable voltage profiles under varied currents, and enhanced long-term cyclability with a capacity retention of 65% after 500 cycles at 1 C and an average decay rate of only 0.07% per cycle. DFT calculations further substantiated the strengthened polysulfide adsorption and reduced energy barrier for sulfur reduction on Fe-NiS 2 surfaces. This work highlights the effectiveness of transition-metal doping in designing multifunctional interlayers for Li-S batteries, offering a feasible strategy to advance high-energy-density storage systems toward practical application. Declarations Author Contribution All authors contributed to the study conception and design. Material synthesis and characterization were performed by Liming Song, Feiyu Wang. Electrochemical measurements were conducted by Xianwu Li. Data analysis was performed by Yong Xiang. The first draft of the manuscript was written by Jie Tan and Liming Song. The work was supervised by Qiang Liu. All authors read and approved the final manuscript. Funding The Inner Mongolia Autonomous Region Science and Technology Program (Grant Nos. 2025YFHH0167 and 2023YFKL0019) and the Key-Area Research and Development Program of Dongguan (Grant No. 20241201300022). Conflicts of Interest The authors declare that they have no conflict of interest. Data availability All relevant data are within the manuscript and its supplementary materials. Supplementary Information The following is the supplementary data to this article. Acknowledgments This work was supported by the Inner Mongolia Autonomous Region Science and Technology Program (Grant Nos. 2025YFHH0167 and 2023YFKL0019) and the Key-Area Research and Development Program of Dongguan (Grant No. 20241201300022). 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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-8972766","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":599732462,"identity":"f52ae428-2b45-42b9-af8a-4af3c3bb7a3f","order_by":0,"name":"Liming Song","email":"","orcid":"","institution":"Inner Mongolia North Hauler Joint Stock Co.,Ltd","correspondingAuthor":false,"prefix":"","firstName":"Liming","middleName":"","lastName":"Song","suffix":""},{"id":599732463,"identity":"58f8fe8b-a93a-4f05-acdd-1657bd1dbf15","order_by":1,"name":"Feiyu Wang","email":"","orcid":"","institution":"Inner Mongolia North Hauler Joint Stock Co.,Ltd","correspondingAuthor":false,"prefix":"","firstName":"Feiyu","middleName":"","lastName":"Wang","suffix":""},{"id":599732464,"identity":"2ebf5934-acb7-405a-848f-dd60a1344f6b","order_by":2,"name":"Qiang Liu","email":"","orcid":"","institution":"University of Science and Technology Beijing","correspondingAuthor":false,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Liu","suffix":""},{"id":599732465,"identity":"1df0eb9b-bbc2-4b0d-8d21-820ebcbd3521","order_by":3,"name":"Xianwu Li","email":"","orcid":"","institution":"Inner Mongolia North Hauler Joint Stock Co.,Ltd","correspondingAuthor":false,"prefix":"","firstName":"Xianwu","middleName":"","lastName":"Li","suffix":""},{"id":599732468,"identity":"304813a9-9422-4488-b9ca-eb99e5ce735d","order_by":4,"name":"Yong Xiang","email":"","orcid":"","institution":"Institute of Electronic and Information Engineering of UESTC in Guangdong","correspondingAuthor":false,"prefix":"","firstName":"Yong","middleName":"","lastName":"Xiang","suffix":""},{"id":599732469,"identity":"f0960ce2-38a8-415f-817f-4b23d2e4d06b","order_by":5,"name":"Jie Tan","email":"data:image/png;base64,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","orcid":"","institution":"University of Electronic Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Jie","middleName":"","lastName":"Tan","suffix":""}],"badges":[],"createdAt":"2026-02-26 03:23:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8972766/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8972766/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104401464,"identity":"d733b346-c084-462d-9b2b-592053daed38","added_by":"auto","created_at":"2026-03-11 12:12:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":886101,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the preparation process of Fe-NiS\u003csub\u003e2\u003c/sub\u003e.\u003csub\u003e\u0026nbsp;\u0026nbsp;\u0026nbsp;\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/2ee185e1a62c0de77a8b412c.png"},{"id":103939407,"identity":"94623af6-da28-4ad5-b6de-de4d182b1662","added_by":"auto","created_at":"2026-03-04 18:49:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":751742,"visible":true,"origin":"","legend":"\u003cp\u003eCharacterization of Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003ea\u003c/strong\u003e SEM image of Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003eb\u003c/strong\u003e-\u003cstrong\u003ec\u003c/strong\u003e TEM images of Fe-NiS\u003csub\u003e2 \u003c/sub\u003ewith different magnifications. \u003cstrong\u003ed\u003c/strong\u003e EDS elemental mapping images corresponding to Ni, S, and Fe elements in Fe-NiS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/1ee6c605ea7c469930add99b.png"},{"id":103939409,"identity":"ff3a2f85-568f-4647-a1de-1a2a146e525e","added_by":"auto","created_at":"2026-03-04 18:49:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":699131,"visible":true,"origin":"","legend":"\u003cp\u003eStructural, spectral, and adsorption property characterizations of NiS\u003csub\u003e2\u003c/sub\u003e and Fe-NiS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e XRD pattern of Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003eb \u003c/strong\u003eXPS spectrum of Ni 2p for Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003ec\u003c/strong\u003e XPS spectrum of S 2p for Fe-NiS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ed\u003c/strong\u003e UV-vis absorption spectra of Fe-NiS\u003csub\u003e2\u003c/sub\u003e/Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e and Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e solutions; and the photographs of the corresponding solutions. \u003cstrong\u003ee\u003c/strong\u003e Top-view crystal structure of NiS\u003csub\u003e2\u003c/sub\u003e (Ni site is labeled). \u003cstrong\u003ef \u003c/strong\u003eTop-view crystal structure of Fe-NiS\u003csub\u003e2\u003c/sub\u003e (Fe site is labeled). \u003cstrong\u003eg\u003c/strong\u003e Calculated binding energies of LiPSs intermediates on Fe-NiS\u003csub\u003e2\u003c/sub\u003e and NiS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003eh\u003c/strong\u003e Gibbs free energy profiles for SRR on Fe-NiS\u003csub\u003e2\u003c/sub\u003e and NiS\u003csub\u003e2\u003c/sub\u003e surfaces at equilibrium potential.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/fb993ae30cea60b3dc7ef401.png"},{"id":103939412,"identity":"78153c65-5137-473c-ac9a-0d33ce0c84a6","added_by":"auto","created_at":"2026-03-04 18:49:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1071521,"visible":true,"origin":"","legend":"\u003cp\u003eMorphology and Physicochemical Characterization of Pristine PP and Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP Modified Separators. \u003cstrong\u003ea\u003c/strong\u003e-\u003cstrong\u003ec\u003c/strong\u003e SEM image of the pristine PP separator and the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP modified separator. \u003cstrong\u003ed\u003c/strong\u003e Contact angle test of the PP separator and the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP modified separator. \u003cstrong\u003ee\u003c/strong\u003e Digital photographs of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator before and after coiling, and wrinkling. \u003cstrong\u003ef\u003c/strong\u003e Voltage profiles of Li||Li cells at various current densities.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/ad0555071cca13df06116ce2.png"},{"id":103939410,"identity":"07905d7c-24c5-40e4-b7a3-286b900a7010","added_by":"auto","created_at":"2026-03-04 18:49:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":520647,"visible":true,"origin":"","legend":"\u003cp\u003eCV characterization of Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP. \u003cstrong\u003ea\u003c/strong\u003e CV curves of Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP at a scan rate of 0.2 mV/s. \u003cstrong\u003eb\u003c/strong\u003e-\u003cstrong\u003ec\u003c/strong\u003e CV curves of PP and Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP at scan rates of 0.2-0.5 mV/s; \u003cstrong\u003ed\u003c/strong\u003e Linear fitting plot of Peak 1 current versus square root of scan rate.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/3aec208309430c9cdbbf8625.png"},{"id":104401515,"identity":"17166052-48ff-444c-845c-594f98746c1a","added_by":"auto","created_at":"2026-03-11 12:12:53","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1083198,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical Performance of Li-S Batteries with Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP Composite Separator.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea \u003c/strong\u003eEIS Nyquist plots comparing the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP composite separator cell with the pure PP separator cell.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb \u003c/strong\u003eInitial GCD profiles of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and pure PP separator cells, measured at 0.1C. \u003cstrong\u003ec\u003c/strong\u003e Rate performance of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP separator cells tested at various current densities (0.1C to 3C).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ed \u003c/strong\u003eGCD profiles of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator cell recorded at different current rates. \u003cstrong\u003ee\u003c/strong\u003e Long-term cycling performance and corresponding Coulombic efficiency of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP separator cells at 1C.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/2ad83aa699b46c32c5e44593.png"},{"id":104407958,"identity":"a3d0d96b-113f-4cb5-b9f6-4cb17e250bc9","added_by":"auto","created_at":"2026-03-11 12:41:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5871671,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/97aaf290-4638-4baf-b95b-0705aa43290d.pdf"},{"id":103939414,"identity":"2a17e536-e50c-4db9-92f4-ddecb9171cb1","added_by":"auto","created_at":"2026-03-04 18:49:07","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1689657,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8972766/v1/19cd82fac7c2e8a6a6bdf46a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eIron-Doped Nickel Disulfide as an Efficient Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLithium-sulfur (Li-S) batteries represent a promising energy storage system with high theoretical specific capacity (1675 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and strong commercial potential. Sulfur is an ideal electrode candidate owing to its Earth abundance, low cost, and environmentally benign reaction products [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, the commercialization of Li-S batteries is hindered by several critical challenges, primarily the severe capacity fading caused by the polysulfide shuttle effect, as well as the low utilization of active materials and sluggish kinetics arising from the insulating nature of sulfur and its discharge products (Li\u003csub\u003e2\u003c/sub\u003eS and Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003e) [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In conventional Li-S cells employing commercial separators, soluble polysulfide intermediates migrate through the separator and deposit on the lithium anode, leading to active material loss and performance degradation.\u003c/p\u003e \u003cp\u003eTo mitigate these challenges, the introduction of an interlayer between the separator and the sulfur cathode has been widely investigated as an effective strategy to inhibit polysulfide diffusion [\u003cspan additionalcitationids=\"CR11 CR12 CR13\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Among various candidates, metal-organic frameworks (MOFs) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], stand out due to their highly ordered porosity and tunable metal nodes. These features offer a dual-protection mechanism: the nanochannels provide physical spatial confinement as a molecular sieving [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], while the unsaturated metal sites offer chemical anchoring for sulfur species [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, pristine MOFs typically suffer from poor electrical conductivity and limited intrinsic catalytic activity, which hampers the rapid conversion of intercepted polysulfides. While single-metal active sites can adsorb polysulfides, they are often constrained by the linear scaling relationship, unable to simultaneously satisfy the requirements for strong adsorption and fast desorption/conversion.\u003c/p\u003e \u003cp\u003eTo break this limitation, constructing bimetallic active centers via heteroatom doping has emerged as a robust solution. The introduction of a second metal atom induces lattice distortion and modulates the electronic band structure of the host material. This orbital-level engineering creates synergistic \"sulfiphilic-lithiophilic\" bifunctional sites, which not only dramatically enhance electrical conductivity but also lower the energy barriers for redox reactions [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. By leveraging the synergy between the MOF-derived porous architecture and bimetallic catalytic sites, it is possible to achieve high-efficiency sulfur immobilization and conversion.\u003c/p\u003e \u003cp\u003eFor instance, in the Fe, N-co-doped porous graphene designed reported by Hou et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], Fe atoms are anchored at the edges of graphene pores through Fe-N\u003csub\u003e4\u003c/sub\u003e or Fe-N\u003csub\u003e2\u003c/sub\u003e coordination configurations. The strong coupling between the 3d orbitals of Fe and the p orbitals of LiPSs strengthens the trapping of LiPSs, while N atoms further immobilize Li⁺ via Li-N bonding, synergistically suppressing LiPSs diffusion and accelerating their conversion. In the Co, N-co-doped graphene@carbon nanotube composite prepared by Zhou\u0026rsquo;s group through reductive pyrolysis of a bimetallic MOF [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], Co atoms serve as catalytic centers to lower the nucleation barrier of Li\u003csub\u003e2\u003c/sub\u003eS, and N-doped carbon constructs an efficient electron transport network. Moreover, the Co-N\u003csub\u003e4\u003c/sub\u003e active sites enable bidirectional catalysis of LiPSs reduction and Li\u003csub\u003e2\u003c/sub\u003eS oxidation, achieving synergistic optimization of catalytic function and conductive performance.\u003c/p\u003e \u003cp\u003eIn this work, we report the rational design of an Fe-doped NiS\u003csub\u003e2\u003c/sub\u003e catalyst via a MOF-assisted route. This catalyst is integrated onto a commercial separator to construct a robust Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP interlayer. Distinct from single-component counterparts, the Fe doping creates synergistic bimetallic active sites that optimize the adsorption-catalysis balance for polysulfides, while the MOF-derived porous architecture ensures efficient ion transport and physical confinement. Combined experimental characterizations and density functional theory (DFT) calculations are employed to elucidate the mechanism: Fe doping constructs highly active bimetallic sites that simultaneously strengthen the chemisorption of polysulfides and lower the activation energy barriers for their subsequent conversion. The impact of this Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator on the electrochemical performance, specifically in terms of enhancing redox kinetics, improving rate capability, and suppressing polysulfide shuttling\u0026mdash;is systematically investigated. This work demonstrates the effectiveness of bimetallic modulation, offering a feasible strategy for designing functional interlayers to advance the practical application of Li-S batteries.\u003c/p\u003e"},{"header":"Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterials and preparation\u003c/h2\u003e \u003cp\u003e \u003cstrong\u003eFe-Ni MOF\u003c/strong\u003e \u003cp\u003eLayered Fe-NiS\u003csub\u003e2\u003c/sub\u003e was prepared by a two-step hydrothermal reaction method. Specifically, 0.425 g of NiCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO and 0.83 g of terephthalic acid (PTA) were dissolved into 90 mL of N, N-dimethylformamide (DMF) and stirred for 30 min. Subsequently, 10 mL of NaOH aqueous solution (0.4 M) was added dropwise to the mixture. After the addition of FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, the obtained mixture solution was kept at 100\u0026deg;C for 8 h. The precipitate was centrifuged, washed, and dried in vacuum at 60\u0026deg;C overnight to obtain the product Fe-Ni MOF.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFe-NiS\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e \u003cp\u003eThe precursor, together with 50 mL of thioacetamide, was dispersed into 75 mL of ethanol by stirring. After being placed into an autoclave and kept at 120\u0026deg;C for 4 h, the resulting black product was washed with deionized water followed by drying in vacuum to obtain layered Fe-NiS\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eFe-NiS\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003e/PP modified separator\u003c/b\u003e: The Fe-NiS\u003csub\u003e2\u003c/sub\u003e powder, Super P, and PVDF were mixed uniformly in an agate mortar at a mass ratio of 8:1:1. N-methyl pyrrolidone (NMP) was added and stirred for 12 h. After that, the slurry was evenly coated on the Celgard 2500 separator and dried at 60\u0026deg;C overnight under vacuum. The treated separator was subsequently cut into circular pieces with a diameter of 16.5 mm, yielding the desired Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP modified separator.\u003c/p\u003e \u003cp\u003e \u003cb\u003eC/S composites\u003c/b\u003e: The Ketjen Black was mixed with sulfur powder at the mass ratio of 2:8, after holding at 155\u0026deg;C for 12 h with a heating rate of 5\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A mixture of sulfur composites and PVDF with the mass ratio of 9:1 were dispersed in an appropriate amount of NMP to give a slurry, which was then coated on aluminum foil and vacuum dried at 60\u0026deg;C overnight. The circular sulfur cathodes (12 mm in diameter) were obtained with sulfur content of 1 mg cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMaterial characterization\u003c/h3\u003e\n\u003cp\u003eX-ray diffraction (XRD) was performed on a Rigaku D/max2500PC instrument (Japan) with CuKα radiation (40 kV, 20 mA) at a scan rate of 10\u0026deg; min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e over 20\u0026ndash;60\u0026deg;. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) elemental analysis were obtained using a FEI450 SEM instrument. Transmission electron microscopy (TEM) for morphology and elemental analysis was conducted using a FEI Titan G260-300 high-resolution instrument (USA). X-ray photoelectron spectroscopy (XPS) was carried out on a Kratos AXIS ULTRA DLD instrument (Japan) with Al Kα radiation (1486.7 eV), and all peaks were calibrated using the C 1s peak at 284.8 eV. Density functional theory (DFT) calculations were employed to analyze the energy optimization pathway of the materials. Contact angle measurement was performed via a Dataphysics-OCA20 tester (Germany), using Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP modified separator as the sample, Celgard 2500 PP separator as the control, and Li-S electrolyte as the liquid. Cyclic voltammetry (CV) (potential range: 1.6\u0026ndash;2.8 V, scan rate of 0.1\u0026ndash;0.5 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and electrochemical impedance spectroscopy (EIS) (frequency range: 0.01\u0026ndash;100 kHz) were conducted on a CHI660E electrochemical workstation.\u003c/p\u003e\n\u003ch3\u003eElectrochemical tests\u003c/h3\u003e\n\u003cp\u003e2032 coin cells were assembled in a glove box filled with Ar, using C/S as the cathode, lithium sheets as the anode, Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP or Celgard 2500 as separator, and 1.0 M lithium ditrifluoromethane sulfonimide (LITFSI) dissolved in DOL/DME (1:1 v/v) containing 1 wt % LiNO\u003csub\u003e3\u003c/sub\u003e as the electrolyte.\u003c/p\u003e \u003cp\u003eLi\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e solution was prepared by dissolving sulfur powder and Li\u003csub\u003e2\u003c/sub\u003eS in a molar ratio of 5:1 in DOL and DME solutions (1:1 v/v) at 50\u0026deg;C with vigorous stirring for 24 h.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e Schematic illustration of the MOF-assisted synthetic route for Fe-NiS\u003csub\u003e2\u003c/sub\u003e and the corresponding bimetallic synergistic mechanism that promotes the fast conversion of polysulfides Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003en\u003c/sub\u003e to Li\u003csub\u003e2\u003c/sub\u003eS.\u003c/p\u003e \u003cp\u003eAs presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-c, SEM and TEM images reveal that the obtained Fe-NiS\u003csub\u003e2\u003c/sub\u003e successfully retains the characteristic lamellar architecture of its MOF precursor (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e) without obvious structural collapse. TEM observations further confirm this well-preserved multilayered sheet-like structure. Inheriting this porous and ordered architecture is critical, as it not only prevents structural collapse but also ensures the maximal exposure of active sites. This stable layered nanostructure offers a high specific surface area and abundant interfacial active sites, which are crucial for Li-S battery separator modifications to facilitate electrolyte wetting, efficient polysulfide adsorption, and catalytic conversion. Moreover, EDS mapping results (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed) demonstrate a homogeneous distribution of Fe, Ni, and S elements throughout the material. Such uniform elemental dispersion promotes consistent electrochemical reactions, thereby laying a structural foundation for enhanced overall battery performance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe prepared Fe-NiS\u003csub\u003e2\u003c/sub\u003e powder was first characterized by XRD to determine its phase composition (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The XRD pattern of Fe-NiS\u003csub\u003e2\u003c/sub\u003e exhibits well-defined diffraction peaks at 31.30\u0026deg;, 35.16\u0026deg;, 38.80\u0026deg;, 45.14\u0026deg;, 53.60\u0026deg;, and 53.68\u0026deg;, corresponding to the (200), (210), (211), (220), (311), and (230) planes of cubic pyrite NiS\u003csub\u003e2\u003c/sub\u003e (PDF#11\u0026ndash;0099), respectively, confirming its isostructural nature. No distinct peaks related to Fe-doped NiS\u003csub\u003e2\u003c/sub\u003e were observed, which can be attributed to the low Fe doping content in the system. However, compared with NiS\u003csub\u003e2\u003c/sub\u003e, the diffraction peaks of Fe-NiS\u003csub\u003e2\u003c/sub\u003e shift slightly to higher angles, consistent with a reduction in lattice parameters due to Fe doping (Fig. S2). XPS further confirmed the presence of Ni, S and Fe elements in the heterostructure (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb-c and S2), providing experimental evidence for the successful incorporation of Fe into the NiS\u003csub\u003e2\u003c/sub\u003e lattice to achieve bimetallic modulation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003ea\u003c/b\u003e XRD pattern of Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cb\u003eb\u003c/b\u003e XPS spectrum of Ni 2p for Fe-NiS\u003csub\u003e2\u003c/sub\u003e. \u003cb\u003ec\u003c/b\u003e XPS spectrum of S 2p for Fe-NiS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003ed\u003c/b\u003e UV-vis absorption spectra of Fe-NiS\u003csub\u003e2\u003c/sub\u003e/Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e and Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e solutions; and the photographs of the corresponding solutions. \u003cb\u003ee\u003c/b\u003e Top-view crystal structure of NiS\u003csub\u003e2\u003c/sub\u003e (Ni site is labeled). \u003cb\u003ef\u003c/b\u003e Top-view crystal structure of Fe-NiS\u003csub\u003e2\u003c/sub\u003e (Fe site is labeled). \u003cb\u003eg\u003c/b\u003e Calculated binding energies of LiPSs intermediates on Fe-NiS\u003csub\u003e2\u003c/sub\u003e and NiS\u003csub\u003e2\u003c/sub\u003e. \u003cb\u003eh\u003c/b\u003e Gibbs free energy profiles for SRR on Fe-NiS\u003csub\u003e2\u003c/sub\u003e and NiS\u003csub\u003e2\u003c/sub\u003e surfaces at equilibrium potential.\u003c/p\u003e \u003cp\u003eTo investigate the interaction between Fe-NiS\u003csub\u003e2\u003c/sub\u003e and polysulfides, adsorption experiments were conducted by adding Fe-NiS\u003csub\u003e2\u003c/sub\u003e powder to a Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e6\u003c/sub\u003e solution. Significant decolorization of the solution was observed, indicating strong adsorption of LiPSs by the powder. This was further supported by ultraviolet-visible (UV-Vis) absorption spectroscopy, where the characteristic peak intensity in the range of 350\u0026ndash;400 nm was significantly lower for the solution containing Fe-NiS\u003csub\u003e2\u003c/sub\u003e, consistent with the adsorption results (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003eWhile physical adsorption is evident, the fundamental origin of this enhanced performance lies in the electronic structure modulation induced by Fe incorporation. To elucidate how this bimetallic synergy intrinsically promotes the reaction kinetics, density functional theory (DFT) calculations were performed. Through modeling, the original (210) crystal planes of NiS\u003csub\u003e2\u003c/sub\u003e and Fe-NiS\u003csub\u003e2\u003c/sub\u003e were obtained (Fig. S4). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef show the crystal structures of pristine NiS\u003csub\u003e2\u003c/sub\u003e and Fe-doped NiS\u003csub\u003e2\u003c/sub\u003e, respectively, where Fe atoms partially substitute Ni atoms. The adsorption energies of polysulfides and the mechanism of the stepwise sulfur reduction reaction (SRR) were calculated (Fig. S5). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg, Fe-NiS\u003csub\u003e2\u003c/sub\u003e exhibits stronger adsorption energy for polysulfides compared to pristine NiS\u003csub\u003e2\u003c/sub\u003e, which may be attributed to the synergistic effect of bimetallic atoms. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh shows the Gibbs free energy profiles for the conversion of S\u003csub\u003e8\u003c/sub\u003e to Li\u003csub\u003e2\u003c/sub\u003eS. It has been established in previous studies that the solid-phase reduction of Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003e to Li\u003csub\u003e2\u003c/sub\u003eS is the rate-determining step in SRR. A similar rate-determining behavior was observed in this study. For this step, Fe-NiS\u003csub\u003e2\u003c/sub\u003e shows a significantly lower energy barrier compared to NiS\u003csub\u003e2\u003c/sub\u003e. This significantly reduced energy barrier confirms that the Fe-Ni bimetallic centers effectively accelerate the rate-determining step, thereby promoting the rapid conversion of polysulfides and mitigating their accumulation.\u003c/p\u003e \u003cp\u003eAfter coating Fe-NiS\u003csub\u003e2\u003c/sub\u003e onto the commercial separator, the physical structure and physicochemical properties of the composite were first evaluated. Cross-sectional SEM images (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-c) reveal that the functional Fe-NiS\u003csub\u003e2\u003c/sub\u003e coating layer has a uniform thickness of approximately 10 \u0026micro;m. Beyond thickness, the interaction between the separator and the electrolyte is critical. Dynamic contact angle measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed) demonstrate that the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator achieves complete wetting within 0.5 s, significantly faster than the bare PP separator. This reduced contact angle highlights the superior oleophilicity of the modified surface. Such thorough wetting ensures rapid electrolyte infiltration, which is conducive to facilitating efficient electron/ion transfer, particularly under high-sulfur-loading conditions where rapid ion supply is pivotal. Complement this superior wettability, the mechanical robustness of the separator is equally vital for practical handling and operation. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee, even after repeated folding, the Fe-NiS\u003csub\u003e2\u003c/sub\u003e layer remained fully intact with no signs of peeling or cracking. This indicates that the modifying layer is firmly adhered to the PP substrate, possessing sufficient flexibility and mechanical strength to withstand the stress of battery assembly and volume expansion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUltimately, these physicochemical and mechanical advantages translate into enhanced electrochemical stability. Conventional PP separators typically suffer from poor wettability and low ionic conductivity, resulting in an uneven electric field distribution that promotes irregular lithium dendrite growth. In contrast, the Fe-NiS\u003csub\u003e2\u003c/sub\u003e coating, which characterized by high electrical conductivity and excellent electrolyte wettability, homogenizes the lithium-ion flux. This promotes uniform lithium deposition (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef), effectively suppressing dendrite growth. To empirically validate this, Li||Li symmetric cells were assembled. In comparison to the bare PP cell, the Li||Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP||Li cell maintained a stable overpotential, confirming that the modified separator effectively optimizes ion transport and extends battery cycle life.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further investigate the electrocatalytic activity of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator, CV profiles were recorded. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, both cells exhibit two typical cathodic peaks (corresponding to the reduction of S\u003csub\u003e8\u003c/sub\u003e to soluble Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003en\u003c/sub\u003e and then to insoluble Li\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003e and Li\u003csub\u003e2\u003c/sub\u003eS) and one anodic peak (oxidation of Li\u003csub\u003e2\u003c/sub\u003eS to S\u003csub\u003e8\u003c/sub\u003e). The Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP cell exhibits a noticeably narrower potential separation between the oxidation and reduction peaks shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea. This reduced polarization signifies faster charge transfer kinetics and a lower energy barrier for the polysulfide redox conversion. More crucially, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb-c, compared to the cell with the pristine PP separator, the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP cell displays significantly sharper redox peaks with higher current densities, indicating improved sulfur utilization and accelerated reaction rates enabled by the abundant bimetallic active sites. Based on these data, the linear relationship between the peak current and the square root of the scan rate is plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. According to the Randles-Sevcik equation, the distinctively steeper slopes observed for the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP cell correspond to higher lithium-ion diffusion coefficients across all redox stages, confirming that the porous MOF-derived framework effectively expedites ion transport. These results provide compelling electrochemical evidence that the orbital-engineered Fe-NiS\u003csub\u003e2\u003c/sub\u003e catalyst effectively facilitates the rapid \"solid-liquid-solid\" phase transformation, thereby boosting the overall rate capability and energy efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003ea\u003c/b\u003e EIS Nyquist plots comparing the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP composite separator cell with the pure PP separator cell.\u003c/p\u003e \u003cp\u003e \u003cb\u003eb\u003c/b\u003e Initial GCD profiles of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and pure PP separator cells, measured at 0.1C. \u003cb\u003ec\u003c/b\u003e Rate performance of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP separator cells tested at various current densities (0.1C to 3C).\u003c/p\u003e \u003cp\u003e \u003cb\u003ed\u003c/b\u003e GCD profiles of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator cell recorded at different current rates. \u003cb\u003ee\u003c/b\u003e Long-term cycling performance and corresponding Coulombic efficiency of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP and PP separator cells at 1C.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea shows the Nyquist plots of the assembled batteries. The curves exhibit a semicircular feature in the high- and medium-frequency regions, corresponding to the charge-transfer resistance (R\u003csub\u003ect\u003c/sub\u003e), and a linear trend in the low-frequency region, indicating the diffusion impedance of lithium ions within the solid electrode (Z\u003csub\u003ew\u003c/sub\u003e). Among all tested cells, the battery with the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator demonstrates the lowest impedance, suggesting efficient charge transport and rapid redox reaction kinetics within the electrode.\u003c/p\u003e \u003cp\u003eBenefiting from the robust MOF-derived framework and the efficient polysulfide conversion catalyzed by the bimetallic active sites, the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator is expected to significantly enhance battery performance. To investigate this, CR2032 coin cells were assembled and tested. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, during the initial discharge at 0.1 C, the battery with the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator delivers a specific discharge capacity of 1395 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, significantly higher than that of the cell with a conventional PP separator (1235 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), along with lower polarization. In rate performance tests (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-d), the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP cell maintains well-defined charge/discharge voltage plateaus and higher specific discharge capacities at various current densities. In contrast, the PP-based cell exhibits notable capacity loss and increased polarization at higher rates, highlighting the superior rate capability and catalytic efficiency of the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator (Fig. S6).\u003c/p\u003e \u003cp\u003eLong-term cycling stability tests (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee) reveal that after 500 cycles at 1 C, the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP cell retains about 65% of its initial capacity, with an average capacity decay rate of only 0.07% per cycle, which is much lower than the 0.15% per cycle observed for the PP-based cell. These results demonstrate the significantly improved electrochemical cycling stability of the battery employing the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, an Fe-doped NiS\u003csub\u003e2\u003c/sub\u003e-modified polypropylene Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator was fabricated via a MOF-assisted route and applied in Li-S batteries. The introduction of Fe into the NiS\u003csub\u003e2\u003c/sub\u003e structure enhances polysulfide adsorption through bimetallic synergy and improves the catalytic conversion of sulfur species. Combined with the conductive framework provided by the PP substrate, the composite separator facilitates efficient electron/ion transport and suppresses the polysulfide shuttle effect. As a result, the battery equipped with the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator demonstrates significantly improved electrochemical performance: an initial discharge capacity of 1395 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 0.1 C, remarkable rate capability with stable voltage profiles under varied currents, and enhanced long-term cyclability with a capacity retention of 65% after 500 cycles at 1 C and an average decay rate of only 0.07% per cycle. DFT calculations further substantiated the strengthened polysulfide adsorption and reduced energy barrier for sulfur reduction on Fe-NiS\u003csub\u003e2\u003c/sub\u003e surfaces. This work highlights the effectiveness of transition-metal doping in designing multifunctional interlayers for Li-S batteries, offering a feasible strategy to advance high-energy-density storage systems toward practical application.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material synthesis and characterization were performed by Liming Song, Feiyu Wang. Electrochemical measurements were conducted by Xianwu Li. Data analysis was performed by Yong Xiang. The first draft of the manuscript was written by Jie Tan and Liming Song. The work was supervised by Qiang Liu. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Inner Mongolia Autonomous Region Science and Technology Program (Grant Nos. 2025YFHH0167 and 2023YFKL0019) and the Key-Area Research and Development Program of Dongguan (Grant No. 20241201300022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll relevant data are within the manuscript and its supplementary materials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe following is the supplementary data to this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Inner Mongolia Autonomous Region Science and Technology Program (Grant Nos. 2025YFHH0167 and 2023YFKL0019) and the Key-Area Research and Development Program of Dongguan (Grant No. 20241201300022).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZhou G, Li L, Wang D-W et al (2015) A Flexible Sulfur-Graphene-Polypropylene Separator Integrated Electrode for Advanced Li\u0026ndash;S Batteries. 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Chem Eng J 470:144148. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cej.2023.144148.p\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2023.144148.p\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Lithium-sulfur battery, Metal-organic frameworks, Synergistic catalysis, Bimetallic sites","lastPublishedDoi":"10.21203/rs.3.rs-8972766/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8972766/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSevere polysulfide shuttle effect and sluggish redox kinetics remain primary impediments to the practical application of high-energy-density lithium-sulfur (Li-S) batteries. Herein, a metal-organic framework (MOF)-assisted strategy was employed to fabricate a bimetallic Fe-doped NiS\u003csub\u003e2\u003c/sub\u003e catalyst. The incorporation of Fe via in situ synthesis effectively modulates the electronic structure of NiS\u003csub\u003e2\u003c/sub\u003e, constructing synergistic bimetallic active sites. Comprehensive experimental analyses and density functional theory (DFT) calculations verify that these sites not only significantly enhance the chemisorption of lithium polysulfides (LiPSs) but also lower the energy barrier for their catalytic conversion, achieving a balance between adsorption and kinetics. Furthermore, the catalyst inherits the porous and layered architecture from its MOF precursor, which prevents structural collapse and provides ample space for physical LiPSs confinement. Benefiting from this dual-confinement and accelerated redox kinetics, the Li-S battery equipped with the Fe-NiS\u003csub\u003e2\u003c/sub\u003e/PP separator delivers superior electrochemical performance: a high initial discharge capacity of 1395 mAh g⁻\u0026sup1; at 0.1 C and remarkable long-term cycling stability with a capacity decay rate as low as 0.07% per cycle over 500 cycles at 1 C. This work demonstrates the effectiveness of bimetallic modulation, offering a feasible strategy for designing functional interlayers to advance the practical application of Li-S batteries.\u003c/p\u003e","manuscriptTitle":"Iron-Doped Nickel Disulfide as an Efficient Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-04 18:49:01","doi":"10.21203/rs.3.rs-8972766/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-22T08:49:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-12T08:00:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-10T07:39:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-10T05:06:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-08T12:44:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-03T05:44:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"5329565785998988605974082397551923385","date":"2026-03-02T03:22:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"323083055129613559753378470862774508062","date":"2026-03-02T00:53:29+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-01T06:53:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"151129650441360662986517016249835651777","date":"2026-03-01T06:23:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"99158020260122819972332987998141756066","date":"2026-03-01T02:10:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"301693367422426720602222818364204636063","date":"2026-02-28T13:26:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"16185370546800052449046874284153372849","date":"2026-02-28T02:32:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"322795181454858732701600828800015689218","date":"2026-02-27T14:45:56+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-27T14:31:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-27T10:58:51+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-27T10:54:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2026-02-26T03:15:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e538804b-ba1c-41ac-b5d8-c9da3390eb68","owner":[],"postedDate":"March 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-16T09:09:21+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-04 18:49:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8972766","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8972766","identity":"rs-8972766","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}