Rechargeable Aqueous Zinc-ion Batteries Research Articles

Building Ion-Conductive Supramolecular Elastomeric Protective Layer via Dynamic Hard Domain Design for Stable Zinc Metal Anodes.

The instability of zinc metal anode caused by zinc dendrite growth and severe parasitic reactions has significantly restricted the extensive application of rechargeable aqueous zinc-ion batteries (RAZBs). Herein, based on the strategy of dynamic hard domains, we develop an ion-conductive supramolecular elastomer consisting of Zn salts and the polyurethane-urea-polypropylene glycol polymer skeleton. This elastomer combines high mechanical strength, high ionic conductivity, decent hydrophobicity, and high adhesion to stabilize the electrode-electrolyte interface. In the elastomer system, this elastomer can dynamically adapt to the volume changes of Zn anodes during repeated zinc plating/stripping processes through the reversible dissociation/reassociation of hierarchical hydrogen bonds (H-bonds) formed by the polar groups of urea and urethane moieties. Meanwhile, the coordination of Zn2+ with soft polypropylene glycol (PPG) segments contributes to fast ion transport. This hydrophobic elastomer can also effectively inhibit water-induced corrosion by shielding the active Zn metal from the aqueous electrolyte. Based on the above synergies, the surface-modified anode shows excellent cycling stability above 550 h at a high current density of 5 mA cm-2 and a capacity of 2.5 mAh cm-2. Moreover, the assembled Zn//MnO2 full cell also displayed an enhanced electrochemical performance. This work provides inspiration for the design of solid electrolyte interphase (SEI) layers in aqueous battery chemistry to accelerate the application of RAZBs.

Synergistic Modulation of Mass Transfer and Parasitic Reactions of Zn Metal Anode via Bioinspired Artificial Protection Layer.

Rechargeable aqueous zinc-ion batteries are regarded as promising energy storage devices due to their attractive economic benefits and extraordinary electrochemical performance. However, the sluggish Zn2+ mass transfer behavior and water-induced parasitic reactions that occurred on the anode-electrode interface inevitably restrain their applications. Herein, inspired by the selective permeability and superior stability of plasma membrane, a thin UiO-66 metal-organicframework layer with smart aperture size is ex-situ decorated onto the Zn anode. Experimental characterizations in conjunction with theoretical calculations demonstrate that this bio-inspired layer promotes the de-solvation process of hydrated Zn2+ and reduces the effective contact between the anode and H2 O molecules, thereby boosting Zn2+ deposition kinetics and restraining interfacial parasitic reactions. Hence, the Zn||Zn cells could sustain a long lifespan of 1680h and the Zn||Cu cells yielded a stable coulombic efficiency of over 99.3% throughout 600 cycles under the assistance of the bio-inspired layer. Moreover, pairing with δ-MnO2 cathode, the full cells also demonstrate prominent cycling stability and rate performance. From the bio-inspired design philosophy, this work provides a novel insight into the development of aqueous batteries.

Inhibiting zinc dendrites and side reactions enabled by solvation structure regulation and facile de-solvation process

Rechargeable aqueous zinc-ion batteries show great promise as next-generation energy storage devices given their advantages of low cost and high safety. However, dendrite growth and detrimental side reactions result in poor reversibility of Zn anodes. Here, TEG molecules were introduced as additives to regulate the solvation structure through occupying the position of water molecules in the solvation shell, which also further decreasing the de-solvation energy barrier. The lower de-solvation energy barrier is beneficial for the dissociation of solvation water molecules and help to restrain the water decomposition and the related by-products. Theoretical studies also reveal that TEG is more easily adsorbed on the surface of zinc than water molecules, electrons are more easily transferred from the TEG molecule to the zinc foil, thus promoting the uniform deposition of zinc atoms. Benefiting from the solvation structure regulation and facile de-solvation process of Zn2+, Zn/Zn symmetric cell achieve a long cycling life of 2000 h at the current density and capacity of 1 mA cm−2 and 1mAh cm−2, and a MnO2-Zn full cell reach a superior stability of 3000 cycles at the current density of 1000 mA g−1.

Activating Selenium Cathode Chemistry for Aqueous Zinc-Ion Batteries.

Aqueous rechargeable zinc-ion batteries (ARZIBs) are a promising next-generation energy storage device by virtue of the superior safety and low cost of both the aqueous electrolyte and zinc metal anode. However, their development has been hindered by the lack of suitable cathodes with high volumetric capacity that can provide both lightweight and compact size. Herein we report a novel cathode chemistry based on amorphous Se doped with transition metal Ru that mitigates the resistive surface layer produced by the side reactions between the Se cathode and aqueous electrolyte. This improvement can permit high volumetric capacity in this system. Distinct from conventional conversion mechanisms between Se and ZnSe in Se||Zn cells, this strategy realizes synchronous proton and Zn2+ intercalation/deintercalation in the Ru-doped amorphous Se||Zn half cells. Moreover, an unanticipated Zn2+ deposition/stripping process in this system further contributes to the superior electrochemical performance of this new cathode chemistry. Consequently, the Ru-doped amorphous Se||Zn half cells are found to deliver a record-high capacity of 721 mAh g-1 /3472 mAh cm-3 , and superior cycling stability of over 800 cycles with only 0.015% capacity decay per cycle. This reported work opens the door for new chemistries that can further improve the gravimetric and volumetric capacity of ARZIBs. This article is protected by copyright. All rights reserved.

Successive Gradient Internal Electric Field Strategy Toward Dendrite‐Free Zinc Metal Anode

AbstractWith the rapidly increasing demand for grid‐scale energy storage systems, rechargeable aqueous zinc ion batteries (ZIBs) are capturing attention as a highly promising technology with low cost and high safety. Nevertheless, rampant dendrite growth, hydrogen evolution reaction (HER), and corrosion of the zinc anode have dramatically impacted their practical application. Here, a self‐supported modified layer with ultrafine high‐entropy nanoparticles (2 nm) as the zincophilic sites is realized to modify the Zn anode for the first time. High‐entropy materials with unique continuously distributed potential gaps significantly reduce the activation energy of multi‐electron reactions and modulate ion transport during zinc deposition. Moreover, thanks to the hydrophobic properties and effective desolventizing ability of the ultrafine high‐entropy nanomaterial, the unfavorable side reactions of the zinc anode are prevented to promote the zinc deposition process. As a result, stable cycling of 3500 h at 1 mA cm−2 and 600 h at a high current density of 10 mA cm−2 is achieved. Coin cells and flexible pouch cells assembled with KMO and NH4V4O10 cathodes also demonstrate promoted electrochemical performance. The dual effects of accelerating and homogenizing mechanisms in high‐entropy materials provide a new strategy for stabilizing zinc metal anodes.

Highly conductive manganese sesquioxide/Nitrogen-doped reduced graphene oxide composite for aqueous rechargeable zinc-ion batteries cathode

Highly conductive manganese sesquioxide/Nitrogen-doped reduced graphene oxide composite for aqueous rechargeable zinc-ion batteries cathode

Carbon nanofiber-coated MnO composite as high-performance cathode material for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) are a promising next-generation energy storage technology owing to their intrinsic safety, low cost, and sustainability. However, typical AZIB cathode materials, such as manganese oxides, have poor conductivity and structural stability, leading to low energy storage capacity and poor cycle life, thus, limiting practical applications. In this work, manganese oxide coated with carbon nanofibers (MnO@CNFs) was developed as an AZIB cathode. A facile synthetic strategy based on electrospinning was employed to obtain these composites, which showed dramatically improved electrochemical activity and structural stability. The MnO@CNFs cathode, exhibited a high specific capacity (430 mAh g−1 at 0.1 A g−1), excellent rate capability, and long cycling durability (81% retained after 2500 cycles at 1.0 A g−1). The electrochemical reaction mechanism with complex phase evolution was explored by ex-situ characterization after charging/discharging, indicating the high reversibility and good cycling stability of the co-insertion process of H+/Zn2+ in the MnO@CNFs electrode. This study provides a facile and versatile strategy for fabricating high-performance Mn-based cathode materials and offers a deeper understanding of the energy storage mechanism in AZIBs.

Construction of Cation-Sieving Function Layers Enabling Dendrite-Free Zinc Metal Anodes for Durable Aqueous Systems.

Rechargeable aqueous zinc-ion batteries are considered as promising candidates for safe and green energy storage. Yet, Zn anodes still suffer from serious challenges. Herein, an effective cation-sieve of polyethersulfone-modified sulfonated polyether ether ketone is developed as protective coating layer of the Zn anodes. Cation-only transmission and dense property of the layer can protect the Zn from active water and anions, inhibiting corrosion, hydrogen evolution reaction (HER), and passivation. Zincophilic property of the layer can homogenize Zn2+ flow, and promote uniform plating of Zn. Therefore, protected symmetric Zn||Zn cell can maintain as long as 5600h with a low polarization at 1.0mA cm-2 and 0.5 mAh cm-2, and still long as 800h at 5.0mA cm-2 and 5.0 mAh cm-2. It is found that not only the dendrites but also the popular existed passivation product of Zn4SO4(OH)6·5H2O can be inhibited effectively. In asymmetric Zn||Ti cells, average Coulombic efficiency can reach 98.2%, suggesting corrosion and HER are restrained effectively. Matched with MnO2 cathode, full cells using coated Zn exhibit much better cycling performance than that using bare Zn. Moreover, Zn4O3(SO4)·7H2O (ZSH)-assisted reversible conversion mechanism between the ZSH and ZnxHyMnO2 is revealed through operando Raman.

Anchoring Polar Organic Molecules in Defective Ammonium Vanadate for High-Performance Flexible Aqueous Zinc-Ion Battery.

Ammonium vanadate (NVO) often has unsatisfactory electrochemical performance due to the irreversible removal of NH4 + during the reaction. Herein, layered DMF-NVO nanoflake arrays (NFAs) grown on highly conductive carbon cloth (CC) are employed as the binder-free cathode (DMF-NVO NFAs/CC), which produces an enlarged interlayer spacing of 12.6Å (against 9.5 Å for NH4 V4 O10 ) by effective N, N-dimethylformamide (DMF) intercalation. Furthermore, the strong attraction of highly polar carbonyl and ammonium ions in DMF can stabilize the lattice structure, and low-polar alkyl groups can interact with the weak electrostatic generated by Zn2+ , which allows Zn2+ to be freely intercalated. The DMF-NVO NFAs/CC//Zn battery exhibits an impressive high capacity of 536 mAh g-1 at 0.5Ag-1 , excellent rate capability, and cycling performance. The results of density functional theory simulation demonstrate that the intercalation of DMF can significantly reduce the band gap and the diffusion barrier of Zn2+ , and can also accommodate more Zn2+ . The assembled flexible aqueous rechargeable zinc ion batteries (FARZIBs) exhibit outstanding energy density and power density, up to 436Wh kg-1 at 400W kg-1 , and still remains 180Wh kg-1 at 4000W kg-1 . This work can provide a reference for the design of cathode materials for high-performance FARZIBs.

(Digital Presentation) Understanding the Electrochemical Stability of Potential Current Collectors in Zinc Sulfate Electrolyte for Rechargeable Aqueous Zinc Ion Battery Application

The need for clean and sustainable energy sources has witnessed a sudden upsurge in recent years owing to rising environmental degradation and climate disruption brought on by an overdependence on fossil fuels [1-3]. Electrochemical energy conversion technology is a crucial complement to the storage and on-demand utilization of renewable energy resources [4-6]. Rechargeable aqueous zinc ion batteries (AZIBs) have gained a significant research upsurge in recent times owing to their attractive potential for large-scale energy storage applications. In addition to low cost and naturally abundant raw materials, AZIBs technology offers competitive electrochemical performance and compatibility with water-based electrolyte systems, thereby eliminating the safety concerns associated with prevalent lithium-based battery technology. Moreover, multivalent AZIBs offer the opportunity to attain high energy and power density by permitting multiple electron transfers during reversible electrochemical operations [7]. In the context of AZIBs, significant research efforts are being actively pursued to develop high energy density cathode materials and to address the issue of Zn dendrite formation [8]. However, the selection of stable and low-cost current collectors is equally important as it serves as a bridge between the battery components and the external circuit, thereby influencing the battery capacity and its rate capability [9-10]. In this work, we have analyzed the electrochemical behavior of potential current collectors that are used globally in battery applications, namely Ni, Al, carbon paper, Cu mesh, graphite, and stainless steel in near-neutral aqueous ZnSO4 electrolyte (pH value = 5-6). The electrochemical stability of different current collectors has been investigated using linear sweep voltammetry and chronoamperometry techniques for their application as anode and cathode collectors. Scanning electron microscopy analysis has also been performed to understand the sign of corrosion post-electrochemical study. With stability up to 2.3 V w.r.t. Zn/Zn2+, Ni has proved to be the most corrosion-resistant current collector among the tested collectors on the cathode side. Although Zn itself is sufficiently stable at the anode side than any other current collector under the ZnSO4 electrolyte environment, Ni has shown considerable stability. Nonetheless, understanding the electrochemical stability of current collectors for AZIBs is a vital step in their design and future practical applications.

Synergistic "Anchor-Capture" Enabled by Amino and Carboxyl for Constructing Robust Interface of Zn Anode.

While the rechargeable aqueous zinc-ion batteries (AZIBs) have been recognized as one of the most viable batteries for scale-up application, the instability on Zn anode-electrolyte interface bottleneck the further development dramatically. Herein, we utilize the amino acid glycine (Gly) as an electrolyte additive to stabilize the Zn anode-electrolyte interface. The unique interfacial chemistry is facilitated by the synergistic "anchor-capture" effect of polar groups in Gly molecule, manifested by simultaneously coupling the amino to anchor on the surface of Zn anode and the carboxyl to capture Zn2+ in the local region. As such, this robust anode-electrolyte interface inhibits the disordered migration of Zn2+, and effectively suppresses both side reactions and dendrite growth. The reversibility of Zn anode achieves a significant improvement with an average Coulombic efficiency of 99.22% at 1mAcm-2 and 0.5mAhcm-2 over 500 cycles. Even at a high Zn utilization rate (depth of discharge, DODZn) of 68%, a steady cycle life up to 200h is obtained for ultrathin Zn foils (20μm). The superior rate capability and long-term cycle stability of Zn-MnO2 full cells further prove the effectiveness of Gly in stabilizing Zn anode. This work sheds light on additive designing from the specific roles of polar groups for AZIBs.

Role of Conducting Polymer in Aqueous Zinc Ion Batteries

Owing to high safety and low cost, aqueous rechargeable zinc-ion batteries (ZIBs) is currently a major research topic. In this study, we propose the microwave-assisted hydrothermal synthesis of polypyrrole (PPy)-coated Na1.1V3O7.9 (P-NVO) nanorods for the first time as a highenergy and high-power cathode material for ZIBs. The highly conductive PPy surface-coating layer is significant to enhance the electronic conductivity and Zn2+ diffusion kinetics, leading to utilize the V3+/V4+/V5+ multiple redox reactions of the NVO cathode in ZIBs. Compared to the NVO cathode, therefore, the P-NVO cathode offers higher discharge capacity, power capability and cycling stability; in particular, PPy coating triggers the full theoretical capacity of the NVO cathode (527 mAh g- 1 with ~ 3 mol Zn insertion per formula unit) and directly reflects a superior energy density of 408 Wh kg-1. Even at a high current density of 6000 mA g- 1, the P-NVO cathode sustains 1000 cycles with almost 100% capacity retention. Galvanostatic intermittent titration technique, cyclic voltammetry, in situ X-ray diffraction, and ex situ X-ray absorption near edge structure analyses are combined to verify the superior Zn2+ storage mechanism of the P-NVO cathode.

In Situ Mechanical Measurements in Vanadium Pentoxide Cathodes for Aqueous Zinc-Ion Batteries during Battery Cycling

Aqueous rechargeable zinc-ion batteries (AZIBs) are currently gaining traction as a potential successor to lithium-ion batteries for use in large-scale, stationary energy storage applications due to their inherent safety, low environmental impact, and low-cost. Recent advances have made breakthroughs in these anode and electrolyte stability; however, cathode development still lags preventing the commercial use of AZIBs. Vanadium pentoxide (V2O5) shows promise as a cathode material due to its low cost, environmental friendliness, and high specific capacity versus zinc (in excess of 400 mAh/g)1. V2O5 exhibits a single layer crystal structure which provides a large number of theoretical storage sites2. However, charge storage mechanisms and driving force behind the capacity fade in V2O5 are not well known yet. The lack of understanding surrounding insertion and storage mechanisms of zinc ions into V2O5 cathodes must be addressed to progress toward commercial viability.In this study, we aim to conduct in-operando stress and stress measurements in V2O5 during battery cycling. Curvature interferometry and digital image correlation techniques will be employed for in operando stress and strain measurements, respectively the composite V2O5 cathode will consist of a 7:2:1 ratio of active material, super P, and PVDF binder. By combining stress and strain measurements, coupled with spectroscopy studies, our goal is to identify the how interfacial stress and structural strains play a role on the charge storage mechanisms in V2O5.

Massive anionic fluorine substitution two-dimensional δ-MnO2 nanosheets for high-performance aqueous zinc-ion battery

As one of the most promising materials for rechargeable aqueous zinc ion batteries (AZIBs), manganese oxide (δ-MnO2) need overcome the fatal limitations of structural instability and manganese dissolution for future practical application. Crystal high-orientated two-dimensional δ-MnO2 nanosheets with massive anionic fluorine were synthesized by a lava method with quenching treatment. When employed as a cathode material for zinc ion batteries, it exhibits a long cycling lifespan and high multiplicity performance. The fluorine atoms substitution can not only stabilize the manganese‑oxygen octahedron [MnO6] structure by introducing fluorine‑manganese chemical bonding, but also regulate the Mn3+/Mn4+ ratio by increasing the Mn3+ concentration content. Meanwhile, the obtained high-orientated 2D nanosheets structure can accelerate the ions kinetic behaviors for high rate electrochemical performance by shortening the ion translation and increasing the electronic conductivity. The optimized δ-MnO2 nanosheets exhibit a superior electrochemical performance of 288 mAh g−1 at current densities of 100 mA g−1. An excellent cycling lifespan up to 96 % capacity retention is indicated as well after 200 cycles at a current density of 200 mA g−1. This element doping strategy by molten salt quenching method has the benefits of simple synthesis steps and high yield with high economic efficiency.

Triple-function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries.

Aqueous rechargeable zinc-ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple-functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H2O is inhabited by reconstructing hydrogen bonds due to the strong interaction of TMS and H2O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn2+-6H2O ultimately to achieve a novel solvent co-intercalation ((Zn-TMS)2+) mechanism, and the intercalated TMS works as a "pillar" that provides more zincophilic sites and stabilize the structure of cathode (NH4V4O10, (NVO)). Consequently, the Zn||NVO battery exhibits a remarkable high specific capacity of 515.6 mAh g-1 at a low current density of 0.2 A g-1 for over 40 days. This multi-functional electrolytes and solvent co-intercalation mechanism will significantly propel the practical development of aqueous batteries.

Triple‐function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries

AbstractAqueous rechargeable zinc‐ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple‐functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H2O is inhibited by reconstructing hydrogen bonds due to the strong interaction between TMS and H2O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn2+ ultimately to achieve a novel solvent co‐intercalation ((Zn‐TMS)2+) mechanism, and the intercalated TMS works as a “pillar” that provides more zincophilic sites and stabilizes the structure of cathode (NH4V4O10, (NVO)). Consequently, the Zn||NVO battery exhibits a remarkably high specific capacity of 515.6 mAh g−1 at a low current density of 0.2 A g−1 for over 40 days. This multi‐functional electrolytes and solvent co‐intercalation mechanism will significantly propel the practical development of aqueous batteries.

Building block effect induces horizontally oriented bottom Zn(002) deposition for a highly stable zinc anode

The practical application of zinc anodes for rechargeable aqueous zinc-ion batteries is hindered to uncontrollable dendritic zinc deposition and side reactions. And the deposition of zinc is like building blocks layer by layer, typically considered as nucleation, growth and evolution driven by electric field. Yet the important role of the bottommost deposits is generally ignored. Here, we developed a highly self-adaptable polydimethylsiloxane (PDMS)/montmorillonite (MMT) film to regulate the process of zinc deposition sustainably. In the nucleation and growth stages of zinc, the two-step regulation of the building block effect benefits from the adsorption of oxygen-containing sites on PDMS and fast zinc ion nanochannels in the negatively charged interlayer of MMT to achieve targeted-capture of zinc ions and ordered-deposition, thus inducing horizontally oriented Zn(002) deposition in the initial nucleation layer and providing a flat deposition site for the subsequently deposited metal. In the evolutionary stage of Zn, the PDMS/MMT (PMZn) interfacial layer can achieve a conformal contact with the anode due to the high dynamic adaptability and self-healing of the micro-crosslinking of Si-O-Si and B-O bonds. Consequently, PMZn@Cu||Zn offers higher coulombic efficiency(CE) (99.77%) and the PMZn@Zn anodes exhibit an ultra-long cycle life of 2000 h, more than 10 times that of bare zinc anodes. The stability of the high capacity of PMZn@Zn||MnO2 full cells far exceeds that of Zn||MnO2. This strategy provides an effective approach to develop a stable Zn metal anode for aqueous rechargeable Zn batteries.

Regulating zinc deposition for dendrite-free aqueous zinc-ion batteries: A zincophilic chitosan polyelectrolyte hydrogel modified glass fiber separator

Rechargeable aqueous zinc-ion batteries (AZIBs) are a promising low-cost, safe, and eco-friendly alternative to lithium-ion batteries. However, the inhomogeneous deposition of metallic zinc on the anode and severe side reactions have hindered their large-scale application. In this study, we developed a zincophilic separator by coating and gelating natural chitosan (CS) onto one side of conventional glass fiber (GF) separators (named CS-GF separator), which regulates zinc anode performance. The uniformly distributed CS hydrogel layer on GF anchors numerous water molecules and H+ in the electrolyte, inhibiting their activity and restraining side reactions. The functional groups of the CS-GF separator interact with zinc ions, promoting their diffusion and transfer kinetics and alleviating dendritic growth during zinc plating/stripping. Furthermore, the CS hydrogel layer improves the flatness of the GF separator and homogenizes its pore size distribution, guiding the uniform transport and deposition of zinc ions. The Zn||Zn symmetrical cells using CS-GF separators possess superior long-life stability (1000 h at 2 mA cm−2/1 mA h cm−2), and high Coulombic efficiency of 99.6 %. Additionally, the rate capacity and cyclability of the Zn||NaV3O8 full cells with CS-GF separators are significantly improved. Therefore, the low-cost and scalable CS-GF separator holds tremendous great potential for practical application in AZIBs.

Porous flower-like Zn0.18V2O5·0.84 H2O as cathode for ultralong lifespan aqueous zinc-ion batteries

Vanadium-based oxides have attracted extensive attention in the study of cathode materials for aqueous rechargeable zinc-ion batteries (ZIBs) due to multivalent state, high capacity and inexpensive cost. Nevertheless, the disadvantages with vanadium dissolution and poor cycle stability in the cathode limit its application. To cope with these problems, we design a novel porous zinc vanadium oxide (Zn0.18V2O5·0.84 H2O) with enhanced transport kinetics and structural stability during cycling due to the action of interlayer doping of Zn2+. Specially, the Zn0.18V2O5·0.84 H2O as the cathode of ZIBs manifests an excellent specific capacity of 416 mAh g−1 at 1 A g−1 and the retention capacity is 189 mAh g−1 after 10,000 cycles at 10 A g−1. It also offers a significant rate performance and attaches an energy density of up to 279.5 wh kg−1. Moreover, the electrode was placed in 3 M Zn(CF3SO3)2 electrolyte for 4500 h without obvious change, indicating that the porous structure is not liable to collapse, and the electrode is rich in contact with the electrolyte, which shortens the diffusion path of Zn2+.

Gradient fluorinated and hierarchical selective adsorption coating for Zn-Based aqueous battery

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered as one of the most promising large-scale energy storage system due to their high energy density, low cost and inherent safety. However, the notorious dendrite growth and severe side reactions, impede their practical application. Herein, we constructed a multifunctional gradient composite fluorinated coating with insulating ZnF2 outside and Zn/Sn alloy inside. ZnF2 outside and Zn/Sn alloy inside perform their own functions and solve the dendrites and side reactions jointly. Density functional theory (DFT) calculations and Molecular dynamics (MD) simulations demonstrate that the electronically insulating ZnF2 layer on the surface can regulate the transport of Zn2+ cations, limit the free H2O molecules and improve the dissolution of Zn2+, at the same time, the zincophilicity Zn/Sn alloy inside work as the favorable nucleation sites for Zn atoms and lowers the Zn2+ diffusion energy barrier. As a result, the ZnF2-Sn@Zn electrode in a symmetrical cell exhibits a long cycle life of about 1400 h, as well as 91 % capacity retention after 1400 cycles at 1 A/g in the ZnF2-Sn@Zn//MnO2@CNT full batteries. This work provides a practically promising strategy and new insights for the electrolyte and anode interface design.