Growth and inhibition of zinc anode dendrites in Zn-air batteries:Model and experiment

Zinc(Zn)-air batteries are widely used in secondary battery research owing to their high theoretical energy density,good electrochemical reversibility,stable discharge performance,and low cost of the anode active material Zn.However,the Zn anode also leads to many challenges,including dendrite growth,deformation,and hydrogen precipitation self-corrosion.In this context,Zn dendrite growth has a greater impact on the cycle lives.In this dissertation,a dendrite growth model for a Zn-air battery was established based on electrochemical phase field theory,and the effects of the charging time,anisotropy strength,and electrolyte temperature on the morphology and growth height of Zn dendrites were studied.A series of experiments was designed with different gradient influencing factors in subsequent experiments to verify the theoretical simulations,including elevated electrolyte temperatures,flowing electrolytes,and pulsed charging.The simulation results show that the growth of Zn dendrites is controlled mainly by diffusion and mass transfer processes,whereas the electrolyte temperature,flow rate,and interfacial energy anisotropy intensity are the main factors.The experimental results show that an optimal electrolyte temperature of 343.15 K,an optimal electrolyte flow rate of 40 ml·min^(-1),and an effective pulse charging mode.

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.

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.

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.

Hetero Nucleus Growth Stabilizing Zinc Anode for High‑Biosecurity Zinc‑Ion Batteries

Biocompatible devices are widely employed in modernized lives and medical fields in the forms of wearable and implantable devices,raising higher requirements on the battery biocompatibility,high safety,low cost,and excellent electrochemical performance,which become the evaluation criteria toward developing feasible biocompatible batteries.Herein,through conducting the battery implantation tests and leakage scene simulations on New Zealand rabbits,zinc sulfate electrolyte is proved to exhibit higher biosecurity and turns out to be one of the ideal zinc salts for biocompatible zinc-ion batteries(ZIBs).Furthermore,in order to mitigate the notorious dendrite growth and hydrogen evolution in mildly acidic electrolyte as well as improve their operating stability,Sn hetero nucleus is introduced to stabilize the zinc anode,which not only facilitates the planar zinc deposition,but also contributes to higher hydrogen evolution overpotential.Finally,a long lifetime of 1500 h for the symmetrical cell,the specific capacity of 150 mAh g^(-1)under 0.5 A g^(-1)for the Zn-MnO_(2)battery and 212 mAh g^(-1)under 5 A g^(-1)for the Zn—NH4V4O10 battery are obtained.This work may provide unique perspectives on biocompatible ZIBs toward the biosecurity of their cell components.

Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High‑Performance Zinc Anode:Principles,Strategies,and Challenges

The last several years have witnessed the prosperous development of zinc-ion batteries(ZIBs),which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety.However,the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth,hydrogen evolution,and corrosion passivation on anode side.A functionally and structurally well-designed anode current collectors(CCs)is believed as a viable solution for those problems,with a lack of summarization according to its working mechanisms.Herein,this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs,which can be divided into zincophilic modification,structural design,and steering the preferred crystal facet orientation.The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

Recent advances in interfacial modification of zinc anode for aqueous rechargeable zinc ion batteries

To tackle energy crisis and achieve sustainable development, aqueous rechargeable zinc ion batteries have gained widespread attention in large-scale energy storage for their low cost, high safety, high theoretical capacity, and environmental compatibility in recent years. However, zinc anode in aqueous zinc ion batteries is still facing several challenges such as dendrite growth and side reactions(e.g., hydrogen evolution), which cause poor reversibility and the failure of batteries. To address these issues, interfacial modification of Zn anodes has received great attention by tuning the interaction between the anode and the electrolyte. Herein, we present recent advances in the interfacial modification of zinc anode in this review. Besides, the challenges of reported approaches of interfacial modification are also discussed.Finally, we provide an outlook for the exploration of novel zinc anode for aqueous zinc ion batteries.We hope that this review will be helpful in designing and fabricating dendrite-free and hydrogenevolution-free Zn anodes and promoting the practical application of aqueous rechargeable zinc ion batteries.

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.

Realizing Highly Reversible Zinc Anode via Controlled-current Pre-deposition

Aqueous zinc ion batteries have been considered as the prominent candidate in the next-generation batteries for its low cost,safety and high theoretical capacity.Nonetheless,formation of zinc dendrites and side reactions at the electrode/electrolyte interface during the zinc plating/stripping process affect the cycling reversibility of the zinc anode.Regulation of the zinc plating/stripping process and realizing a highly reversible zinc anode is a great challenge.Herein,we applied a simple and effective approach of controlled-current zinc pre-deposition at copper mesh.At the current density of 40 mA cm^(-2),where the electron/ion transfers are both continuous and balanced,the Zn@CM-40 electrode with the(002)crystal plane orientation and the compactly aligned platelet morphology was successfully obtained.Compared with the zinc foil,the Zn@CM-40 exhibits greatly enhanced reversibility in the repeated plating/stripping(850 h at 1 mA cm^(-2))for the symmetric battery test.A series of characterization techniques including electrochemical analyses,XRD,SEM and optical microscopy observation,were used to demonstrate the correlation between the structure of pre-deposited zinc layer and the cycling stability.The COSMOL Multiphysics modeling demonstrates a more uniform electric field distribution in the Zn@CM than the zinc foil due to the aligned platelet morphology.Furthermore,the significant improvement is also achieved in a Zn||MnO_(2)full battery with a high capacity-retention(87%vs 47.8%).This study demonstrates that controlled-current electrodeposition represents an important strategy to regulate the crystal plane orientation and the morphology of the pre-deposited zinc layer,hence leading to the highly reversible and dendrite-free zinc anode for high-performance zinc ion batteries.

MXene ink hosting zinc anode for high performance aqueous zinc metal batteries

Despite the safety,low cost,and high theoretical capacity(820 mA h g^(-1))of Zn metal anodes,the practical application of aqueous Zn metal batteries remains a critical challenge due to the Zn dendrite growth,corrosion,and hydrogen evolution reaction.Herein,we demonstrate the MXene ink hosting Zn metal anodes(MX@Zn)for high-performance and patternable Zn metal full batteries.The as-designed MX@Zn electrode is more facile and reversible than bare Zn and CC@Zn,as verified by better cyclic stability and lower overpotentials of symmetric cells with the plating capacity of 0.05 mA h cm^(-2)at 0.1 m A cm^(-2)and of 1 m A h cm^(-2)at 1 m A cm^(-2).The MX@Zn|MnO_(2)full cells deliver a high specific capacity of 281.9 m A h g^(-1),91.5%of the theoretical capacity,achieving 50%capacity retention from 60 mA g^(-1)to 300 mA g^(-1)and 79.7%of initial capacity after 200 cycles.Moreover,the patterned devices based on the MX@Zn electrode achieve high energy and power densities of 348.57 Wh kg^(-1)and 1556 W kg^(-1),respectively,along with a capacity retention of 64%and Coulombic efficiency of 99%over 500 cycles.The high performance of MX@Zn is attributed to the high electrical conductivity and hydrophilicity of MXene and rapid ion diffusion through the 3D interconnected porous channels.

In situ polymerization of poly(3,4-ethylenedioxythiophene)protective layer towards stable zinc anode

Aqueous zinc-ion devices are considered promising candidates for energy storage due to their high safety,low cost and relatively high energy density.However,the dendrite growth,hydrogen evolution reaction(HER)and corrosion of the zinc anode significantly limit the development of Zn-ion devices.Here,an inexpensive poly(3,4-ethylenedioxythiophene)(PEDOT)protective layer was constructed in situ on the Zn surface using electropolymerization to suppress dendrite growth and side reactions,thereby enhancing the reversibility of Zn.Experimental and theoretical calculations revealed that this hydrophilic protective layer promotes the desolvation process of hydrated Zn^(2+)and facilitates the transport of zinc ions,thus improving the thermodynamic and kinetic properties of Zn^(2+)deposition and inhibiting interfacial side reactions.Consequently,the optimized PEDOT@Zn symmetric battery exhibited a cycling stability exceeding 1250 h at 0.5 mA·cm^(-2)and 0.25 mAh·cm^(-2),with a significantly reduced overpotential(from 91.8 to 35 mV).With the assistance of the PEDOT protective layer,the PEDOT@Zn//Cu battery maintained approximately 99.5%Coulombic efficiency after 450 cycles.Ex-situ scanning electron microscopy(SEM)and in situ optical microscopy characterizations further confirmed that the PEDOT protective layer can effectively suppress the growth of zinc dendrites.Additionally,the Zn-ion capacitors assembled by the PEDOT@Zn and activated carbon also demonstrated outstanding cycling stability.

Stabilizing zinc anode via a chelation and desolvation electrolyte additive

The uncontrollable dendrites growth and intricately water-induced side reactions occurred on zinc anode leads to safety issues and poor electrochemical kinetics,which largely limit the widespread application of zinc-ion batteries(ZIBs).Herein,ethylenediaminetetraacetic acid disodium salt(EDTA-2Na)is utilized as an electrolyte additive to strengthen the reversibility and cycling stability of zinc anode.Experimental results and theoretical calculation demonstrate that the EDTA-2Na presents a much stronger coordination with Zn^(2+)when comparing with H_(2)O molecular,implying the EDTA-2Na is capable to enter the solvation shell of[Zn(OH_(2))_(6)]^(2+)and coordinate with Zn^(2+)ions,thus achieving a flat and smooth zinc deposition with less by-products(Zn_(4)SO_(4)(OH)6·xH_(2)O and H_(2)).Consequently,the zinc symmetric battery with EDTA-2Na additive delivers an excellent cycling stability up to 1800 h under current density of 1 mA cm^(-2),and the hydrogen evolution reaction(HER),corrosion,by-product issues are significantly inhibited.Moreover,the rate performance and stability of coin-type and pouch-type Zn||MnO2/graphite batteries are significantly boosted via EDTA-2Na additive(248 mAh g^(-1)at 0.1 A g^(-1),81.3%after 1000 cycles at a A g^(-1)).This kind of electrolyte additive with chelation and desolvation functions shed lights on strategies of improving zinc anode stability for further application of ZIBs.

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.

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.

An Electrochemical Perspective of Aqueous Zinc Metal Anode

Based on the attributes of nonflammability,environmental benignity,and cost-effectiveness of aqueous electrolytes,as well as the favorable compatibility of zinc metal with them,aqueous zinc ions batteries(AZIBs)become the leading energy storage candidate to meet the requirements of safety and low cost.Yet,aqueous electrolytes,acting as a double-edged sword,also play a negative role by directly or indirectly causing various parasitic reactions at the zinc anode side.These reactions include hydrogen evolution reaction,passivation,and dendrites,resulting in poor Coulombic efficiency and short lifespan of AZIBs.A comprehensive review of aqueous electrolytes chemistry,zinc chemistry,mechanism and chemistry of parasitic reactions,and their relationship is lacking.Moreover,the understanding of strategies for suppressing parasitic reactions from an electrochemical perspective is not profound enough.In this review,firstly,the chemistry of electrolytes,zinc anodes,and parasitic reactions and their relationship in AZIBs are deeply disclosed.Subsequently,the strategies for suppressing parasitic reactions from the perspective of enhancing the inherent thermodynamic stability of electrolytes and anodes,and lowering the dynamics of parasitic reactions at Zn/electrolyte interfaces are reviewed.Lastly,the perspectives on the future development direction of aqueous electrolytes,zinc anodes,and Zn/electrolyte interfaces are presented.

Electrolyte engineering for optimizing anode/electrolyte interface towards superior aqueous zinc-ion batteries:A review

Aqueous zinc-ion batteries(AZIBs) are promising candidates for the large-scale energy storage systems due to their high intrinsic safety,cost-effectiveness and environmental friendliness.However,issues such as dendrite growth,hydrogen evolution reaction,and interfacial passivation occurring at the anode/electrolyte interface(AEI) have hindered their practical application.Constructing a stable AEI plays a key role in regulating zinc deposition and improving the cycle life of AZIBs.The fundamentals of AEI and the challenges faced by the Zn anode due to unstable interfaces are discussed.A comprehensive summary of electrolyte regulation strategies by electrolyte engineering to achieve a stable Zn anode is provided.The effectiveness evaluation techniques for stable AEI are also analyzed,including the interfacial chemistry and surface morphology evolution of the Zn anode.Finally,suggestions and perspectives for future research are offered about enabling a durable and stable AEI via electrolyte engineering,which may pave the way for developing high-performance AZIBs.

High donor-number and low content electrolyte additive for stabilizing zinc metal anode

The aqueous zinc ion batteries(AZIBs)are thought as promising competitors for electrochemical energy storage,though their wide application is curbed by the uncontrollable dendrite growth and gas evolution side reactions.Herein,to stabilize both zinc anodes and water molecules,we developed a modified electrolyte by adding a trace amount of N,N-diethylformanmide(DEF)into the ZnSO_(4)electrolyte for the first time in zinc ion batteries.The effectiveness of DEF is predicted by the comparison of donor number and its preferential adsorption behavior on the zinc anode is further demonstrated by several spectroscopy characterizations,electrochemical methods,and molecular dynamics simulation.The modified electrolyte with 5%v.t.DEF content can ensure a stable cycling life longer than 3400 h of Zn‖Zn symmetric cells and an ultra-reversible Zn stripping/plating process with a high coulombic efficiency of 99.7%.The Zn‖VO_(2)full cell maintains a capacity retention of 83.5%and a 104 mA h g^(-1)mass capacity after 1000cycles.This work provides insights into the role of interfacial adsorption behavior and the donor number of additive molecules in designing low-content and effective aqueous electrolytes.