Structural Design And Performance Study Of Anode For Aqueous Zinc-ion Battery

The development and utilization of renewable and clean energy are of strategic importance to reduce the consumption of traditional fossil energy,alleviate environmental problems and create a sustainable ecological environment.Electrochemical energy storage devices can store renewable energy sources,such as wind and solar energy,which is essential to building an efficient and reliable power system.Lithium-ion batteries dominate the portable electronic device market and are gradually penetrating the powered vehicle market due to their high energy density and long cycle life.However,on the one hand,the global shortage of lithium resources has led to the inability of lithium-ion batteries to meet the growing demand.On the other hand,lithium-ion batteries’safety problems have seriously affected their large-scale application development.As the anode of an Aqueous zinc ion battery,metallic zinc is one of the ideal anode materials because of its abundant reserves,non-toxicity,high safety,high theoretical volume-specific capacity(5855 m Ah cm^-3),and low electrode potential（-0.762 V vs.standard hydrogen electrode potential（SHE））.Although aqueous zinc ion batteries have attracted increased attention and extensive research as an ideal candidate anode material for large-scale energy storage device systems.However,several significant scientific problems of zinc metal anode still need to be solved in commercial application in aqueous zinc-ion batterie.（1）the growth of zinc dendrites during battery cycling can puncture the separator,leading to a short circuit and reducing the battery’s cycle life.（2）the thermodynamic instability of zinc metal in water can lead to corrosion and passivation,which seriously hinders the diffusion of zinc ions.（3）zinc metal will undergo a hydrogen evolution reaction during the battery charge and discharge process,which may cause the battery to expand or even crack.Therefore,achieving a stable and efficient reversible zinc metal anode is crucial to solving the problem.This thesis is based on the structural design of the zinc metal anode.First,the structure-performance relationship between the structural design of the zinc metal anode and the inhibition of zinc dendrite growth is studied.Second,the synergistic effect of structural design and interface modification can inhibit the growth of zinc dendrites,avoid the occurrence of side reactions,and improve the electrochemical performance of aqueous zinc-ion batteries.The main findings of the thesis are as follows.1.Vertically aligned pore structure of zinc metal anode（LVP-Zn）was prepared by laser etching method.The zinc deposition behavior was investigated by regulating the size of the pore diameter and pore spacing of the LVP-Zn anode.The uniform vertically aligned pore structure can effectively reduce the current density on the electrode surface and lead to the metallic zinc uniformly deposited in the pore structure.The polyimide tape（PI）coated on the surface can effectively inhibit the occurrence of side reactions.The assembled symmetric cell can be cycled stably at a current density of 0.2-5 m A cm^-2 after zinc deposition at the LVP-Zn electrode.The full cell assembled with the cathode material Mn O₂ can achieve a high specific capacity of 270 m Ah g^-1 and high-capacity retention at a current density of 1 A g^-1,exhibiting excellent electrochemical performance.2.Nafion-modified patterned zinc anode（N@P-Zn）was prepared by a metal mesh-assisted calendering method combined with Nafion coating.The relationship between stress generation and zinc dendrite growth during Zn metal deposition was investigated by theoretical calculations and in situ observations.The prepared patterned zinc anode can effectively release the stress changes induced during zinc deposition and inhibit the growth of dendrites.On this basis,the N@P-Zn composite anode was obtained by combining the patterned zinc anode with the Nafion layer.The effect of the Nafion coating on inhibiting the side reactions was investigated.The symmetric cell assembled with the N@P-Zn electrode can stably run for 1200 h at a high current density of 10 m A cm^-2 with low voltage polarization.The assembled flexible full cell delivered a high capacity of about186 m Ah g^-1.It can be stably run for over 150 cycles and still operate in different bending states with good mechanical stability.