Towards advanced zinc anodes by interfacial modification strategies for efficient aqueous zinc metal batteries

Developing sustainable and clean energy sources(e.g.,solar,wind,and tide energy)is essential to achieve the goal of carbon neutrality.Due to the discontinuous and inco nsistent nature of common clean energy sources,high-performance energy storage technologies are a critical part of achieving this target.Aqueous zinc metal batteries(AZMBs)with inherent safety,low cost,and competitive performance are regarded as one of the promising candidates for grid-scale energy storage.However,zinc metal anodes(ZMAs)with irreversible problems of dendrite growth,hydrogen evolution reaction,self-corrosio n,and other side reactions have seriously hindered the development and commercialization of AZMBs.An increasing number of researchers are focusing on the stability of ZMAs,so assessing the effectiveness of existing research strategies is critical to the development of AZMBs.This review aims to provide a comprehensive overview of the fundamentals and challenges of AZMBs.Resea rch strategies for interfacial modification of ZMAs are systematically presented.The features of artificial interfacial coating and in-situ interfacial coating of ZMAs are compared and discussed in detail,as well as the effect of modified interfacial ZMA on the full-battery performance.Finally,perspectives are provided on the problems and challenges of ZMAs.This review is expected to offer a constructive reference for the further development and commercialization of AZMBs.

Engineering hydrophobic protective layers on zinc anodes for enhanced performance in aqueous zinc-ion batteries

Aqueous zinc-ion batteries possess substantial potential for energy storage applications;however,they are hampered by challenges such as dendrite formation and uncontrolled side reactions occurring at the zinc anode.In our investigation,we sought to mitigate these issues through the utilization of in situ zinc complex formation reactions to engineer hydrophobic protective layers on the zinc anode surface.These robust interfacial layers serve as effective barriers,isolating the zinc anode from the electrolyte and active water molecules and thereby preventing hydrogen evolution and the generation of undesirable byproducts.Additionally,the presence of numerous zincophilic sites within these protective layers facilitates uniform zinc deposition while concurrently inhibiting dendrite growth.Through comprehensive evaluation of functional anodes featuring diverse functional groups and alkyl chain lengths,we meticulously scrutinized the underlying mechanisms influencing performance variations.This analysis involved precise modulation of interfacial hydrophobicity,rapid Zn^(2+)ion transport,and ordered deposition of Zn^(2+)ions.Notably,the optimized anode,fabricated with octadecylphosphate(OPA),demonstrated exceptional performance characteristics.The Zn//Zn symmetric cell exhibited remarkable longevity,exceeding 4000 h under a current density of 2 mA cm^(-2)and a capacity density of 2 mA h cm^(-2),Furthermore,when integrated with a VOH cathode,the complete cell exhibited superior capacity retention compared to anodes modified with alternative organic molecules.

In Situ Growth of 2D Metal–Organic Framework Ion Sieve Interphase for Reversible Zinc Anodes

Zinc metal anodes are gaining popularity in aqueous electrochemical energy storage systems for their high safety,cost-effectiveness,and high capacity.However,the service life of zinc metal anodes is severely constrained by critical challenges,including dendrites,water-induced hydrogen evolution,and passivation.In this study,a protective two-dimensional metal–organic framework interphase is in situ constructed on the zinc anode surface with a novel gel vapor deposition method.The ultrathin interphase layer(~1μm)is made of layer-stacking 2D nanosheets with angstrom-level pores of around 2.1Å,which serves as an ion sieve to reject large solvent–ion pairs while homogenizes the transport of partially desolvated zinc ions,contributing to a uniform and highly reversible zinc deposition.With the shielding of the interphase layer,an ultra-stable zinc plating/stripping is achieved in symmetric cells with cycling over 1000 h at 0.5 mA cm−2 and~700 h at 1 mA cm^(−2),far exceeding that of the bare zinc anodes(250 and 70 h).Furthermore,as a proof-of-concept demonstration,the full cell paired with MnO_(2) cathode demonstrates improved rate performances and stable cycling(1200 cycles at 1 A g−1).This work provides fresh insights into interphase design to promote the performance of zinc metal anodes.

Challenges and opportunities facing zinc anodes for aqueous zinc-ion battery

Rechargeable aqueous zinc-ion batteries(ZIBs)have gained attention as promising candidates for nextgeneration large-scale energy storage systems due to their advantages of improved safety,environmental sustainability,and low cost.However,the zinc metal anode in aqueous ZIBs faces critical challenges,including dendrite growth,hydrogen evolution reactions,and corrosion,which severely compromise Coulombic efficiency and cycling stability,hindering their broader adoption.This review first explores the fundamental mechanisms underlying these challenges and then examines current strategies to address them,focusing on structural design,surface modifications,electrolyte optimization,and alloying treatments.Finally,potential future directions are discussed,outlining a pathway toward achieving high-performance aqueous ZIBs.

Interfacial parasitic reactions of zinc anodes in zinc ion batteries:Underestimated corrosion and hydrogen evolution reactions and their suppression strategies

Featured with high power density,improved safety and low-cost,rechargeable aqueous zinc-ion batteries(ZIBs) have been revived as possible candidates for sustainable energy storage systems in recent years.However,the challenges inherent in zinc(Zn) anode,namely dendrite formation and interfacial parasitic reactions,have greatly impeded their practical application.Whereas the critical issue of dendrite formation has attracted widespread concern,the parasitic reactions of Zn anodes with mildly acidic electrolytes have received very little attentions.Considering that the low Zn reversibility that stems from interfacial parasitic reactions is the major obstacle to the commercialization of ZIBs,thorough understanding of these side reactions and the development of correlative inhibition strategies are significant.Therefore,in this review,the brief fundamentals of corrosion and hydrogen evolution reactions at Zn surface is presented.In addition,recent advances and research efforts addressing detrimental side reactions are reviewed from the perspective of electrode design,electrode-electrolyte interfacial engineering and electrolyte modification.To facilitate the future researches on this aspect,perspectives and suggestions for relevant investigations are provided lastly.

Stable Zinc Anodes Enabled by Zincophilic Cu Nanowire Networks

Zn-based electrochemical energy storage(EES)systems have received tremendous attention in recent years,but their zinc anodes are seriously plagued by the issues of zinc dendrite and side reactions(e.g.,corrosion and hydrogen evolution).Herein,we report a novel strategy of employing zincophilic Cu nanowire networks to stabilize zinc anodes from multiple aspects.According to experimental results,COMSOL simulation and density functional theory calculations,the Cu nanowire networks covering on zinc anode surface not only homogenize the surface electric field and Zn^(2+)concentration field,but also inhibit side reactions through their hydrophobic feature.Meanwhile,facets and edge sites of the Cu nanowires,especially the latter ones,are revealed to be highly zincophilic to induce uniform zinc nucleation/deposition.Consequently,the Cu nanowire networks-protected zinc anodes exhibit an ultralong cycle life of over 2800 h and also can continuously operate for hundreds of hours even at very large charge/discharge currents and areal capacities(e.g.,10 mA cm^(-2)and 5 mAh cm^(-2)),remarkably superior to bare zinc anodes and most of currently reported zinc anodes,thereby enabling Zn-based EES devices to possess high capacity,16,000-cycle lifespan and rapid charge/discharge ability.This work provides new thoughts to realize long-life and high-rate zinc anodes.

MXene-assisted polymer coating from aqueous monomer solution towards dendrite-free zinc anodes

Coating polymer on the surface is an effective way to realize functional modification of the materials for diverse applications,which has been proved to enhance the stability of metal anodes in batteries.However,given the limited operability of coating from polymer dispersions,it is imperative to develop simple aqueous-based strategies from monomers for versatile polymer coating.Herein,a Ti_(3)C_(2)Tx MXene-assisted approach is proposed to construct polymer coating on zinc metal surfaces directly from the aqueous solution of monomers in an ice bath.By combining a doctor-blading method with spontaneous polymerization of monomers on the substrates at room temperature,a uniform,adhesive,and versatile coating layer assisted by a small amount of MXene is produced in one step.Additionally,MXene nanosheets serve as nanofillers to further enhance the mechanical strength and ionic conductivity of the polymer coating.Benefiting from good film formation and improved interfacial contact,the coated zinc anode exhibits a long cycling lifespan of over 1900 h.The assembled full cells show excellent cycling stability with a high capacity retention of 85.0%at 16 A g^(-1)over 2600 cycles.This work provides a simple and efficient way to produce polymer coatings directly from monomers,which may give new insights into design multifunctional polymer coatings for various applications.

Toward stable and highly reversible zinc anodes for aqueous batteries via electrolyte engineering

Featuring low cost, high abundance, low electrochemical potential, and large specific capacity, zinc(Zn)metal holds great potential as an anode material for next-generation rechargeable aqueous batteries.However, the poor reversibility resulting from dendrite formation and side reactions poses a major obstacle for its practical application. Electrolyte, which is regarded as the “blood” of batteries, has a direct impact on reaction kinetics, mass transport, and side reactions and thus plays a key role in determining the electrochemical performance of Zn electrodes. Therefore, considerable efforts have been devoted to modulating the electrolytes to improve the performance of Zn electrodes. Although significant progress has been made, achieving stable and highly reversible Zn electrodes remains a critical challenge. This review aims to provide a systematic summary and discussion on electrolyte strategies for highperformance aqueous Zn batteries. The(electro)-chemical behavior and fundamental challenges of Zn electrodes in aqueous electrolytes are first discussed. Electrolyte modulation strategies developed to address these issues are then classified and elaborated according to the underlying mechanisms.Finally, remaining challenges and promising future research directions on aqueous electrolyte engineering are highlighted. This review offers insights into the design of highly efficient electrolytes for new generation of rechargeable Zn batteries.

Design Strategies for Aqueous Zinc Metal Batteries with High Zinc Utilization: From Metal Anodes to Anode-Free Structures

Aqueous zinc metal batteries(AZMBs)are promising candidates for next-generation energy storage due to the excellent safety, environmental friendliness, natural abundance, high theoretical specific capacity, and low redox potential of zinc(Zn) metal. However,several issues such as dendrite formation, hydrogen evolution, corrosion, and passivation of Zn metal anodes cause irreversible loss of the active materials. To solve these issues, researchers often use large amounts of excess Zn to ensure a continuous supply of active materials for Zn anodes. This leads to the ultralow utilization of Zn anodes and squanders the high energy density of AZMBs. Herein, the design strategies for AZMBs with high Zn utilization are discussed in depth, from utilizing thinner Zn foils to constructing anode-free structures with theoretical Zn utilization of 100%, which provides comprehensive guidelines for further research. Representative methods for calculating the depth of discharge of Zn anodes with different structures are first summarized. The reasonable modification strategies of Zn foil anodes, current collectors with pre-deposited Zn, and anode-free aqueous Zn metal batteries(AF-AZMBs) to improve Zn utilization are then detailed. In particular, the working mechanism of AF-AZMBs is systematically introduced. Finally, the challenges and perspectives for constructing high-utilization Zn anodes are presented.

Carbon enhanced nucleophilicity of Na_(3)V_(2)(PO_(4))_(3):A general approach for dendrite-free zinc metal anodes

Zincophilic property and high electrical conductivity are both very important parameters to design novel Zn anode for aqueous Zn-ion batteries(AZIBs).However,single material is difficult to exhibit zincophilic property and high electrical conductivity at the same time.Herein,originating from theoretical calculation,a zincophilic particle regulation strategy is proposed to address these limitations and carbon coated Na_(3)V_(2)(PO_(4))_(3)is taken as an example to be a protective layer on zinc metal(NVPC@Zn).Na_(3)V_(2)(PO_(4))_(3)(NVP)is a common cathode material for Zn-ion batteries,which is zincophilic.Carbon materials not only offer an electron pathway to help Zn deposition onto NVPC surface,but also enhance the zinc nucleophilicity of Na_(3)V_(2)(PO_(4))_(3).Hence,this hybrid coating layer can tune zinc deposition and resist side reactions such as hydrogen generation and Zn metal corrosion.Experimentally,a symmetrical battery with NVPC@Zn electrode displays highly reversible plating/stripping behavior with a long cycle lifespan over 1800 h at2 mA cm^(-2),much better than carbon and Na_(3)V_(2)(PO_(4))_(3)solely modified Zn electrodes.When the Na_(3)V_(2)(PO_(4))_(3)is replaced with zincophobic Al2O3or zincophilic V2O3,the stability of the modified zinc anodes is also prolonged.This strategy expands the option of zincophilic materials and provides a general and effective way to stabilize the Zn electrode.

Recent advances and perspectives of zinc metal-free anodes for zinc ion batteries

Zinc-ion batteries(ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides,transition metal sulfides, MXene(two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.

Achieving an ion-homogenizing and corrosion-resisting interface through nitro-coordination chemistry for stable zinc metal anodes

Suppression of uncontrollable dendrite growth and water-induced side reactions of Zn metal anodes is crucial for achieving long-lasting cycling stability and facilitating the practical implementations of aqueous Zn-metal batteries.To address these challenges,we report in this study a functional nitro-cellulose interfacial layer(NCIL)on the surface of Zn anodes enlightened by a nitro-coordination chemistry strategy.The NCIL exhibits strong zincophilicity and superior coordination capability with Zn^(2+)due to the highly electronegative and highly nucleophilic nature of the nitro functional group.This characteristic facilitates a rapid Zn-ion desolvation process and homogeneous Zn plating,effectively preventing H_(2) evolution and dendrite formation.Additionally,the negatively charged surface of NCIL acts as a shield,repelling SO_(4)^(2-)anions and inhibiting corrosive reactions on the Zn surface.Remarkably,reversible and stable Zn plating/stripping is achieved for over 5100 h at a current density of 1 mA cm^(-2),which is nearly 30 times longer than that of bare Zn anodes.Furthermore,the Zn/V_(2)O_(5) full cells with the functional interface layer deliver a high-capacity retention of 80.3%for over 10,000 cycles at 5 A g^(-1).This research offers valuable insights for the rational development of advanced protective interface layers in order to achieve ultra-long-lifeZnmetal batteries.

Imide-pillared covalent organic framework protective films as stable zinc ion-conducting interphases for dendrite-free Zn metal anodes

The notorious growth of zinc dendrite and the water-induced corrosion of zinc metal anodes(ZMAs)restrict the practical development of aqueous zinc ion batteries(AZIBs).In this work,a zinc metallized,imide-pillared covalent organic framework(ZPC)protective film has been engineered as a stable Zn^(2+)ion-conducting interphase to modulate interfacial kinetics and suppress side reactions for ZMAs.Compared to bare Zn,ZPC@Zn exhibits a higher Zn^(2+)ionic conductivity,a larger Zn^(2+)transference number,a lower electronic conductivity,a smaller desolvation activation energy and correspondingly a significant suppression of corrosion,hydrogen evolution and Zn dendrites.Impressively,the ZPC@Zn||ZPC@Zn symmetric cell obtains a cycling lifespan over 3000 h under 5 mA cm^(-2)for 1 mA h cm^(-2).The ZPC@Zn||NH_(4)V_(4)O_(10)coin-type full battery delivers a specific capacity of 195.8 mA h g^(-1)with a retention rate of78.5%at 2 A g^(-1)after 1100 cycles,and the ZPC@Zn||NH_(4)V_(4)O_(10) pouch full cell shows a retention of70.1%in reversible capacity at 3 A g^(-1)after 1100 cycles.The present incorporation of imide-linked covalent organic frameworks in the surface modification of ZMAs will offer fresh perspectives in the search for ideal protective films for the practicality of AZIBs.

Porous zinc metal anodes for aqueous zinc-ion batteries:Advances and prospectives

The intensifying challenges posed by climate change and the depletion of fossil fuels have spurred concerted global efforts to develop alternative energy storage solutions.Aqueous zinc-ion batteries(AZIBs)have emerged as promising candidates for large-scale electrochemical energy storage systems because of their intrinsic safety,cost-effectiveness,and environmental sustainability.However,Zn dendrite growth consis-tently poses a remarkable challenge to the performance improvement and commercial viability of AZIBs.The use of three-dimensional porous Zn anodes instead of planar Zn plates has been demonstrated as an effec-tive strategy to regulate the deposition/stripping behavior of Zn2+ions,thereby inhibiting the dendrite growth.Here,the merits of porous Zn anodes were summarized,and a comprehensive overview of the recent advancements in the engineering of porous Zn metal anodes was provided,with a particular emphasis on the structural orderliness and critical role of porous structure modulation in enhancing battery performance.Furthermore,strategic insights into the design of porous Zn anodes were presented to facilitate the practical implementation of AZIBs for grid-scale energy storage applications.

Surface coatings of two-dimensional metal-organic framework nanosheets enable stable zinc anodes

Aqueous zinc-ion batteries (ZIBs) have been considered as safe and scalable energy storage solutions,but the dendrite and corrosion issues of Zn anodes have hindered their further application.Herein,we demonstrate that two-dimensional metalorganic framework (MOF) nanosheets can act as protective coatings to prevent dendrite formation and hydrogen evolution of Zn anodes.The morphology of MOFs was tuned from octahedral nanoparticles (UiO-67-3D) to nanosheets (UiO-67-2D),leading to significantly enhanced protective performance.UiO-67-2D nanosheets-coated Zn anodes displayed smaller polarization,longer cycling lifetime and lower H_(2) evolution than those of UiO-67-3D nanoparticles in symmetrical cells,which has been attributed to the higher concentration of surface Zr-OH/H_(2)O to induce uniform Zn deposition and one-dimensional (1D) channels perpendicular to the Zn surface to regulate Zn^(2+) diffusion.The assembled UiO-67-2D@Zn||Mn_(2)O_(3)/C full cell shows a high capacity of240 m Ah g^(-1)at 1 A g^(-1) and excellent cycling stability.

In-situ chemical conversion film for stabilizing zinc metal anodes

Zinc metal anodes face several challenges,including the uncontrolled formation of dendrites,hydrogen evolution,and corrosion,which seriously hinder their application in practice.To address the above problems such as dendrite formation and corrosion,we present a simple and applicable immersion method that enables in situ formation of a zinc phytate(PAZ)coating on the surface of commercial Zn flakes via a substitution reaction.This protective coating mitigates corrosion of zinc flakes by the electrolyte,reduces the interfacial impedance,and accelerates the migration kinetics of zinc ions.Besides,this method can preferentially expose the(002)crystal plane with strong atomic bonding,which not only improves the corrosion resistance of the zinc flake,but can also guide the parallel deposition of zinc ions along the(002)crystal plane and reduce the formation of dendrites.Benefiting from the above advantages,the PAZ@Zn‖Cu half-cell has shown over 900 cycles with average coulombic efficiency(CE)of99.81%at 4 mA cm^(-2).Besides,the PAZ@Zn‖PAZ@Zn symmetric cell operate stably for>1000 h at5 mA cm^(-2)and>340 h at 10 mA cm^(-2).Furthermore,we demonstrated that this in situ chemical treatment enables the formation of a robust,well-bound protective coating.This method provides insights for advancing the commercialization of zinc anodes and other metal anodes.

Recent progress of dendrite-free stable zinc anodes for advanced zinc-based rechargeable batteries:Fundamentals,challenges,and perspectives

Zinc-based batteries are a very promising class of next-generation electrochemical energy storage systems,with high safety,eco-friendliness,abundant resources,and the absence of rigorous manufacturing conditions.However,practical applications of zinc-based rechargeable batteries are impeded by the low Coulombic efficiency,inferior cyclability,and poor rate capability,due to the instability of zinc anode.Herein,effective strategies for dendritefree zinc anode are symmetrically reviewed,especially highlighting specific mechanisms,delicate design of electrode and current collectors,controlled electrode|electrolyte interface,ameliorative electrolytes,and advanced separators design.First,the particular mechanisms of dendrites formation and the associated fundamentals of the stable Zn metal anodes are presented elaborately.Then,recent key strategies for dendrites prevention and hydrogen evolution reaction suppression are categorized,discussed,and analyzed in detail in view of the electrodes,electrolytes,and separators.Finally,the challenging perspectives and major directions of stable zinc anodes are briefly discussed for further industrialization and commercialization of zinc-based rechargeable batteries.

Critical factors to inhibit water-splitting side reaction in carbon-based electrode materials for zinc metal anodes

Zinc metal anodes(ZMA)have high theoretical capacities(820 mAh g−1 and 5855 mAh cm−3)and redox potential(−0.76 V vs.standard hydrogen electrode),similar to the electrochemical voltage window of the hydrogen evolution reaction(HER)in a mild acidic electrolyte system,facilitating aqueous zinc batteries competitive in next-generation energy storage devices.However,the HER and byproduct formation effectuated by water-splitting deteriorate the electrochemical performance of ZMA,limiting their application.In this study,a key factor in promoting the HER in carbon-based electrode materials(CEMs),which can provide a larger active surface area and guide uniform zinc metal deposition,was investigated using a series of threedimensional structured templating carbon electrodes(3D-TCEs)with different local graphitic orderings,pore structures,and surface properties.The ultramicropores of CEMs are the determining critical factors in initiating HER and clogging active surfaces by Zn(OH)2 byproduct formation,through a systematic comparative study based on the 3D-TCE series samples.When the 3D-TCEs had a proper graphitic structure with few ultramicropores,they showed highly stable cycling performances over 2000 cycles with average Coulombic efficiencies of≥99%.These results suggest that a well-designed CEM can lead to high-performance ZMA in aqueous zinc batteries.

The Trade‑Offs in the Design of Reversible Zinc Anodes for Secondary Alkaline Batteries

Zinc-based batteries have long occupied the largest share of the primary battery market,but this advantage has not continued in the secondary battery market.This is mainly because the cycling performance of secondary zinc-based batteries is significantly limited by the poor reversibility of zinc electrodes,including the formation of zinc dendrites,electrode deformation,corrosion,and hydrogen evolution.To solve the above problems,researchers have developed many novel strategies,such as surface coating,use of electrode additives,use of electrolyte additives,and electrode structure design.However,the implementation of these strategies inevitably requires consideration of trade-offs because the core factors that limit the reversibility of zinc electrodes are not isolated but intertwined.Therefore,fully understanding the trade-offs in the zinc electrode design process is necessary to fundamentally improve the cycling performance of the zinc electrode and construct a practical secondary zinc-based battery.This perspective gives an introduction to various problems that limit the cycling of zinc electrodes and discusses the theoretical causes of these problems.The trade-offs in various typical strategies are systematically analyzed,and their positive and negative effects on performance are discussed.This work aims to provide insights for the development of highly reversible zinc anodes for practical secondary zinc-based batteries.

Recent Progress and Prospects on Dendrite-free Engineerings for Aqueous Zinc Metal Anodes

Rechargeable zinc-ion batteries with mild aqueous electrolytes are one of the most promising systems for large-scale energy storage as a result of their inherent safety,low cost,environmental-friendliness,and acceptable energy density.However,zinc metal anodes always suffer from unwanted dendrite growth,leading to low Coulombic efficiency and poor cycle stability and during the repeated plating/stripping processes,which substantially restrict their further development and application.To solve these critical issues,a lot of research works have been dedicated to overcoming the drawbacks associated with zinc metal anodes.In this overview,the working mechanisms and existing issues of the zinc metal anodes are first briefly outlined.Moreover,we look into the ongoing processes of the different strategies for achieving highly stable and dendrite-free zinc metal anodes,including crystal engineering,structural engineering,coating engineering,electrolyte engineering,and separator engineering.Finally,some challenges being faced and prospects in this field are provided,together with guiding significant research directions in the future.