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.

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.

Solvation strategies in various electrolytes for advanced zinc metal anode

Aqueous zinc-ion batteries(AZIBs),known for their high safety,low cost,and environmental friendliness,have a wide range of potential applications in large-scale energy storage systems.However,the notorious dendrite growth and severe side reactions on the anode have significantly hindered their further practical development.Recent studies have shown that the solvation chemistry in the electrolyte is not only closely related to the barriers to the commercialization of AZIBs,but have also sparked a number of valuable ideas to address the challenges of AZIBs.Therefore,we systematically summarize and discuss the regulatory mechanisms of solvation chemistry in various types of electrolytes and the influence of the solvation environment on battery performance.The challenges and future directions for solvation strategies based on the electrolyte environment are proposed to improve their performance and expand their application in AZIBs.

Double-Doped Carbon-Based Electrodes with Nitrogen and Oxygen to Boost the Areal Capacity of Zinc-Bromine Flow Batteries

Ensuring a stable power output from renewable energy sources,such as wind and solar energy,depends on the development of large-scale and long-duration energy storage devices.Zinc–bromine fl ow batteries(ZBFBs)have emerged as cost-eff ective and high-energy-density solutions,replacing expensive all-vanadium fl ow batteries.However,uneven Zn deposition during charging results in the formation of problematic Zn dendrites,leading to mass transport polarization and self-discharge.Stable Zn plating and stripping are essential for the successful operation of high-areal-capacity ZBFBs.In this study,we successfully synthesized nitrogen and oxygen co-doped functional carbon felt(NOCF4)electrode through the oxidative polymerization of dopamine,followed by calcination under ambient conditions.The NOCF4 electrode eff ectively facilitates effi cient“shuttle deposition”of Zn during charging,signifi cantly enhancing the areal capacity of the electrode.Remarkably,ZBFBs utilizing NOCF4 as the anode material exhibited stable cycling performance for 40 cycles(approximately 240 h)at an areal capacity of 60 mA h/cm^(2).Even at a high areal capacity of 130 mA h/cm^(2),an impressive energy effi ciency of 76.98%was achieved.These fi ndings provide a promising pathway for the development of high-areal-capacity ZBFBs for advanced energy storage systems.

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.

Research status and perspectives of MXene-based materials for aqueous zinc-ion batteries

Aqueous zinc-ion batteries(AZIBs)as green battery systems have attracted widespread attention in large-scale electrochemical energy storage devices,owing to their high safety,abundant Zn materials,high theoretica specific capacity and low redox potential.Nevertheless there are some thorny issues in AZIBs that hinder their practical application,such as low intrinsic electron conductivity,slow ion migration kinetics,zinc dendrites and side reactions.MXene-based materials with superior conductivity,large polar surface and abundant active sites can simultaneously serve as cathode materials,electrolyte additive and protection layer of anode to regulate redox reactions of AZIBs.Although various materials have been used to improve electrochemical performances of AZIBs there is a lack of in-depth discussion on the regulation mechanism of MXene-based materials for AZIBs.In this review,we elaborate the research progress of MXenebased materials in AZIBs,including their application in cathode materials and inhibition of zinc dendrites.Finally the future prospects and development directions of MXenebased materials that may improve performance of AZIBs are prospected.

A review on covalent organic frameworks for rechargeable zinc-ion batteries

In recent years,rechargeable zinc-ion batteries(ZIBs)are considered to be a promising alternative to lithium-ion batteries owing to their high safety and theoretical capacity with low cost.Nevertheless,the in-depth development of rechargeable zinc-ion batteries is restricted by a sequence of issues,such as the dissolution and structure collapse of cathode materials,the formation of by-products,severe anode corrosion,passivation,and the growth of zinc dendrites.The covalent organic frameworks(COFs)can solve the above problems to a certain extent owing to their ideal characteristics,such as rigid structure,insolubility,high porosity,and abundant active sites.COFs,as advanced materials for ZIBs,have attracted researchers'attention.In this review,we systematically summarized the synthesis methods of COFs and discussed the application of several advanced characterization technologies in COFs,which would provide a reference for the in-depth research of COFs.In addition,we elucidated the use of COFs as cathode materials and anode protective layers in rechargeable ZIBs.Finally,we discussed the challenges and solutions in the development of COF materials,which would provide constructive insights into the future direction of COFs.

Functionalizing the interfacial double layer to enable uniform zinc deposition

Due to the unsatisfactory electrode/electrolyte interface,the metallic Zn dendrites and corrosion are easily induced,severely hindering the applications of zinc-ion batteries(ZIBs).Herein,a strategy that engineers the interfacial double layer by an extremely low concentration of sulfolane is proposed to tune the Zn stripping/plating behavior.It is revealed that the highly-polar sulfolane can predominately occupy the inner Helmholtz layer over water,and then regulate the upcoming Zn2+to directly deposit downward.Simultaneously,the widened Helmholtz layer can weaken the electric field intensity,which will generate more nucleation sites and reduce the nuclei radius,thereby promoting uniform zinc deposition as well.Moreover,corrosion byproducts can be inhibited since fewer water molecules can contact the Zn electrodes.Consequently,the battery performance can be naturally optimized.With an optimum amount of sulfolane,the Zn||Zn battery can operate for more than 1,100 h under1 m A cm^(-2)and 1 m Ah cm^(-2).And the as-constructed Zn||NaV_(3)O_(8)·1.5H_(2)O battery demonstrates considerably higher cycling stability than that without sulfolane.Overall,this work has provided a deep insight into constructing a functional interfacial double layer to regulate zinc deposition,which can also act as a reference for other metal-based batteries.

Review of regulating Zn^(2+) solvation structures in aqueous zinc-ion batteries

Aqueous zinc-ion batteries,due to their high power density,intrinsic safety,low cost,and environmental benign,have attracted tremendous attentions recently.However,their application is severely plagued by the inferior energy density and short cycling life,which was mainly ascribed to zinc dendrites,and interfacial side reactions,narrow potential window induced by water decomposition,all of which are highly related with the Zn^(2+)solvation structures in the aqueous electrolytes.Therefore,in this review,we comprehensively summarized the recent development of strategies of regulating Zn^(2+)solvation structures,specially,the effect of zinc salts,nonaqueous co-solvents,and functional additives on the Zn^(2+)solvation structures and the corresponding electrochemical performance of aqueous zinc-ion batteries.Moreover,future perspectives focused on the challenges and possible solutions for design and commercialization of aqueous electrolytes with unique solvation structures are provided.

Host-guest supramolecular interaction behavior at the interface between anode and electrolyte for long life Zn anode

The hydrogen evolution reaction (HER) and dendrite growth associated with Zn anode have become the main bottlenecks for the further development of zinc ion batteries (ZIBs).In this work,the electrochemical activity of H_(3)O^(+) is inhibited by the supramolecular host–guest complex composed of H_(3)O^(+) as guest and 18-crown-6 as host.The even Zn plating is induced by the host–guest complex electrostatic shielding layer on Zn anode,as detected by in-situ optical microscopy.The lamellar Zn is plated which profits from the improved Zn plating behavior.Density functional theory (DFT) calculation presents the stable structure of complex.The less produced H_(2) content is monitored online by a mass spectrometer during Zn plating/stripping,which indicates HER can be hampered by the host–guest behavior.Thus,the ZIBs with long life and high Coulombic efficiency are achieved via introducing 18-crown-6.The proposed host–guest supramolecular interaction is expected to facilitate the furthermore development of Zn batteries.

Ti_(3)C_(2)T_(x)-TiSe_(2) analogous heterostructure for flexible zinc ion battery

Exploring zinc-free anode materials is one of the effective strategies to get the zinc dendrites problem of flexible zinc ion battery(ZIB)solved.In this work,an analogous heterostructure(AHS)is constructed from the excellent MXene(Ti_(3)C_(2)T_(x))and TiSe_(2) nanosheets.The AHS not only possesses numerous diffu-sion paths and Zn^(2+)storage sites but also possesses a stable conductive network to accelerate charge transfer in the electrode.As a collaborative advantage,electrochemical measurement results show that MXene/TiSe_(2) electrodes display an excellent specific capacity of 177.9 mAh g^(-1) at 0.10 A g^(-1) and a long-term cycling stability of 77.4%capacity retention after 400 cycles.DFT computations further demon-strate the excellent performance of MXene/TiSe_(2) electrodes including desirable electronic conductivity and low Zn^(2+)migration barriers.The assembled flexible ZIB not only delivers a good specific capacity of 42.2μAh cm^(-2) at 0.20 mA cm^(-2) and a competitive energy density of 37.4μWh cm^(-2) but also exhibits excellent flexibility and thermostability.Furthermore,after 400 cycles at 0.60 A g^(-1),flexible ZIB shows a capacity retention of 73.8%.This work gives a successful attempt to design 2D layered materials as Zn metal-free anode for flexible ZIB.

TEGDME Electrolyte Additive for High-performance Zinc Anodes

Aqueous zinc ion batteries(AZIBs)are expected to have a wide range of applications for large-scale electrochemical energy storage systems,but their practical application is severely limited by the presence of zinc dendrites,hydrogen evolution reactions(HER),corrosion reactions,and other problems.Electrolyte optimization is considered to be one of the most effective methods for improving zinc anodes due to its simplicity,low production cost and remarkable effectiveness in suppressing zinc dendrite growth.In this paper,a tetra(ethylene glycol)dimethyl ether(TEGDME)electrolyte additive was used to improve the stability of the zinc anode by adding 0.1 g/L TEGDME to the conventional ZnSO_(4) electrolyte to prepare a mixed electrolyte.The effect of TEGDME on the side reactions of zinc anode was first assessed by linear sweep voltammetry(LSV)and potentiodynamic polarization.The effect of TEGDME on the structure and morphology of zinc surfaces was observed using an X-ray diffractometer(XRD)and a scanning electron microscope(SEM).And finally,the electrochemical performance of Zn|Zn symmetric cells,Zn||Ti asymmetric cells and Zn-MnO_(2) full cells with ZnSO_(4)+TEGDME electrolyte was tested by cyclic voltammetry(CV)and galvanostatic cycling.The results show that the addition of TEGDME improves the surface wettability of the Zn anode and reduces the growth of dendrites through solvation structure modulation to suppress HER and zinc corrosion.Thus,TEGDME keeps the Zn anode to maintain a flat surface during charging and discharging,improving the reversibility of plating/stripping.The cycle life of the Zn||Ti asymmetric cell was improved and the Coulombic efficiency was 100%after 100 cycles.The Zn||Zn symmetric cells can be cycled stably for 1800 h at a current density of 1 mA/cm^(2) and a fixed capacity of 1 mA·h/cm^(2),while the capacity retention of the Zn-MnO_(2) full cell can be effectively improved from 51.46%to 68.29%at 100 cycles.By using TEGDME electrolyte additives,the cycle life of aqueous zinc ion batteries can be effectively improved,providing a new idea for the development of highly reversible zinc anodes.

High-surface-area titanium nitride nanosheets as zinc anode coating for dendrite-free rechargeable aqueous batteries

Aqueous zinc-ion batteries(AZIBs)have become attractive energy storage devices,owing to their high energy density,low cost,and environmental friendliness.However,the stability of the zinc-metal anode has been retarded by dendrites and side reactions during the cycling process,limiting its practical application in secondary batteries.In this work,porous titanium nitride(TiN)nanosheets with a high surface area are demonstrated as a multiplefunction anode coating to realize long-term dendrite-free AZIBs.The TiN nanosheets with the features of high specific surface area and metallic properties optimize electron conduction and zinc-ion flux,lowering the polarization on the electrode surface.In this way,the TiN-coated zinc electrodes exhibit a long cycle performance for more than 600 h without any dendrite formation.In addition,the full AZIB assembly based on the TiN-coated zinc electrode has a stable cycling performance for over 600 cycles with 97.04%capacity retention.This work expands applications of the inorganic porous materials as protective layers in high-energy battery systems.

Intrinsically zincophobic protective layer for dendrite-free zinc metal anode

Aqueous zinc anodes have attracted the attention of many researchers owing to their high safety,low cost,and high theoretical specific capacity.However,its practical application is severely limited by the dendrite growth on zinc anode.Herein,we develop an intrinsically zincophobic barium-titanate protective layer with a porous structure to suppress the zinc dendrite formation by homogenizing the ion distribution on the anode surface,increasing the nucleation sites,and limiting the irregular zinc growth.Based on these synergistic effects,the coated zinc anode can exhibit long cycle life(840 h at 0.5 mA/cm^(2) for 0.5 mAh/cm^(2))and low voltage hysteresis(36 mV).This work can provide a feasible direction for the design of intrinsically zincophobic coating materials to uniformize the zinc stripping and plating.

Application of in-situ characterization techniques in modern aqueous batteries

The development of high-performance aqueous batteries calls for an in-depth knowledge of their chargedischarge redox and failure mechanism,as well as a systematic understanding of the dynamic evolution of microstructure,phase composition,chemical composition,and local chemical environment of the materials for battery.In-situ characterization technology is expected to understand and reveal the problems faced by aqueous rechargeable batteries,such as the dissolution of electrode materials,the growth of metal negative electrode dendrites,passivation,corrosion,side reactions and a series of problems.Based on this,typical in-situ characterization techniques and their basic mechanisms are summarized,including in-situ optical visualization,in-situ microscopy techniques(in-situ scanning electron microscopy(SEM),in-situ transmission electron microscopy(TEM)),in-situ X-ray techniques(in-situ X-ray diffraction(XRD),in-situ X-ray photoelectron spectroscopy(XPS),in-situ near-edge structural X-ray absorption spectroscopy(XANES)),and in-situ spectroscopy techniques(in-situ Raman spectroscopy,in-situ Fourier transform infrared(FTIR)).Moreover,some emerging techniques concerning aqueous battery research,especially gas evolution and materials dissolution issues,such as in-situ electrochemical quartz crystal microbalance(EQCM).in-situ fiber-optic sensing,in-situ gas chromatography(GC) are introduced.At last,the applications of advanced in-situ characterizations in future research of aqueous batteries are emphasized and discussed,along with some of the remaining challenges and possible solutions.

Rational design of nitrogen doped hierarchical porous carbon for optimized zinc-ion hybrid supercapacitors

Aqueous rechargeable zinc-ion hybrid supercapacitors are considered to be a promising candidate for large-scale energy storage devices owing to their high safety,long life,and low price.In this paper,a nitrogen doped hierarchical porous carbon is evaluated as the cathode for aqueous rechargeable zinc-ion hybrid supercapacitors.Benefiting from the synergistic merits of excellent structural features of N-HPC and tiny zinc dendrite of Zn anode in ZnSO4 electrolyte,the zinc-ion hybrid supercapacitor exhibits excellent energy storage performance including high capacity of 136.8 mAh·g^−1 at 0.1·Ag^−1,high energy density of 191 Wh·kg^−1,large power density of 3,633.4 W·kg^−1,and satisfactory cycling stability of up to 5,000 cycles with a capacity retention of 90.9%.This work presents a new prospect of developing high-performance aqueous rechargeable zinc ion energy storage devices.

Aqueous Zn^(2+)/Na^(+) dual-salt batteries with stable discharge voltage and high Coulombic efficiency by systematic electrolyte regulation

While aqueous Zn-Na hybrid batteries have garnered widespread attention because of their low cost and high safety,it is still challenging to achieve long cycle-life and stable discharge-voltage due to sluggish reaction kinetics,zinc dendrite formation,and side reactions.Herein,we design a Zn^(2+)/Na^(+) dual-salt battery,in which sodiation of the NVP cathode favors zinc intercalation under an energy threshold,leading to decoupled redox reactions on the cathode and anode.Systematic investigations of the electrolyte effects show that the ion intercalation mechanism and the kinetics in the mixture of triflate-and acetate-based electrolytes are superior to those in the common acetate-only electrolytes.As a result,we have achieved fast discharging capability,suppressed zinc dendrites,a stable discharge voltage at 1.45 V with small polarization,and nearly 100%Coulombic efficiency in the dual-salt mixture electrolyte with optimized concentration of 1 M Zn(OAc)_(2)+1 M NaCF_(3)SO_(3).This work demonstrates the importance of electrolyte regulation in aqueous dual-salt hybrid batteries for the energy storage.