Application Of Modified Zinc Oxide In High Rate Zinc-nickel Battery

Zinc-nickel secondary batteries have the advantages of high operating voltage and energy density,wide working temperature range,abundant raw materials and environmental friendliness,suggesting great potential for energy conversion and storage.The poor conductivity and serious dissolubility in alkaline electrolyte of zinc oxide cause various problems such as deformation of zinc anode,zinc dendrite,passivation,self-corrosion,etc,so that its inherent high rate charge-discharge performance has not been brought into full play.Considering the inherent advantages and existing problems of zinc-nickel batteries,combined with the application prospects of marketization,this paper focuses on modified zinc oxide based on the idea of composite synergy fort high rates charge-discharge performance of zinc-nickel batteries:（1）Spherical Zn O was synthesized by a simple water bath method,and a layer of ZIF-8 was grown in situ in dimethylimidazole in ethanol solution,forming Zn O@ZIF-8.For the inherent insulating properties of ZIF-8,the corrosion potential can be increased,achieving high Coulombic efficiency.In addition,the ordered nanochannels increase the specific surface area of the materials,reduce the current density,inhibiting the deformation of the zinc anode.The higher binding energy and lower diffusion barrier of nitrogen atoms and zinc atoms on ZIF-8facilitate the uniform deposition of zinc,thereby inhibiting the formation and growth of dendrites.Therefore,the construction of Zn O@ZIF-8 as anode for Zn-Ni batteries can effectively improve the cycling stability of the system at high rates.Zn O@ZIF-8 still maintains a capacity of 536m A h g^-1 after 1150 cycles at 5 C,which is 90%of the initial capacity(596 m A h g^-1).（2）The Zn O@MXene composite was synthesized on a novel two-dimensional material MXene（Ti₃C₂T_x）matrix by a simple water-bath co-precipitation method.Through a series of characterizations,it is confirmed that the Zn O nanosheets are vertically distributed on the MXene surface.Compared with pure Zn O,Zn O@MXene,as an anode material for Zn-Ni batteries,exhibits excellent discharge specific capacity,rate performance and cycle life.After 1500 cycles at 10 C,Zn O@MXene still maintains a capacity of 594 m A h g^-1,which is very close to the original capacity(596 m A h g^-1).The average discharge specific capacity can reach 625 m A h g^-1,which is 96%of the theoretical capacity(650m A h g^-1).The excellent electrochemical performance can be attributed to three aspects:firstly,the ultra-high conductivity of MXene accelerates electron transport and suppresses electrochemical polarization;secondly,MXene has a low ion diffusion barrier and excellent ion diffusion mobility,which accelerates the diffusion of zincate at the electrode-electrolyte interface,and the concentration difference at the solid-liquid interface can be effectively alleviated.In addition,the abundant oxygen atoms on the surface of the MXene layer act as"seed points"favorable for uniform nucleation,and these nucleation sites are accompanied by rapid electron transfer,which further induces uniform zinc deposition,thereby inhibiting the growth of zinc dendrites.The synergistic effect enables the rate performance of the zinc-nickel battery to be fully utilized,achieving a stable 1500 cycles at 10 C.（3）Herarchical Zn O@Sn O₂ was synthesized by calcination after hydrothermal method with urea as alkali source,stannous chloride as the source of tin.On the one hand,hierarchical flower morphology has increased ion interface reaction,reduce the concentration polarization,on the other hand,the introduction of Sn O₂ improves the formation of hydrogen corrosion,reduced the precipitation of hydrogen.In addition,Sn doping can form a conductive network,which improves the conductivity of zinc electrode,accelerates the conduction process of electrons between active substances and between active substances and fluid collector,and facilitates charge transfer during electrochemical reactions,so that reduces the electrochemical polarization of the electrode,and achieves excellent charge-discharge performance under the condition of high rate.During 1000 charge-discharge cycles,the coulombic efficiency of the herarchical Zn O@Sn O₂ remains above 80%.Considering the simplicity and economy of the preparation process,the commercialization of herarchical Zn O@Sn O₂ is more feasible.