Fabrication And Mechanism Study Of Highly-reversible Zinc Anode Via Controlled-current Electrodeposition

Aqueous zinc ion batteries are widely regarded as outstanding candidates for next-generation batteries because of their low cost,high safety,and high theoretical capacity.However,the zinc dendrites formed on the surface of the zinc anode during the plating/stripping process can seriously affect its cycling stability and may even pierce the separator,which may cause a short-circuit of the battery.Regulating the plating/stripping process of zinc anodes and suppressing the growth of zinc dendrites are necessary conditions for realizing highly reversible zinc anodes.On this basis,in this thesis,the anode material（Zn@CM）with a certain crystal plane orientation and ordered platelet morphology is prepared by the controlled-current electrodeposition method to pre-deposit zinc on the copper mesh.By adjusting the current density during the pre-deposition process,the crystal plane orientation and morphology of the zinc deposition were optimized.As the zinc anode,the effect of the pre-deposited crystal plane orientation and morphology on the zinc plating/stripping process during the charge-discharge process was explored.This study shows that the controlled-current electrodeposition method is an important strategy to control the orientation of crystal planes and the morphology during the pre-deposition of zinc,so that it can be used as an anode material for aqueous zinc-ion batteries to achieve highly reversible,dendrite-free zinc plating/stripping.The following are the main findings:1.Using commercial copper mesh as the base material,zinc was pre-deposited on the surface of the copper mesh by the controlled-current electrodeposition method to prepare the electrode material（Zn@CM）of aqueous zinc ion batteries.The crystal orientation and morphology of the pre-deposited zinc can be effectively controlled by regulating the current density during the pre-deposition process.The experimental results show that the pre-deposited zinc anode Zn@CM-40 shows obvious（002）crystal plane orientation and ordered platelet array morphology at a current density of 40 m A cm^-2.After being assembled into symmetric batteries,galvanostatic charge-discharge cycling tests show that Zn@CM-40 exhibits excellent cycle reversibility in repeated plating/stripping processes.At the current density of 1 m A cm^-2,Zn@CM-40||Zn@CM-40 can cycle stably for 850 h,and its overpotential is only 40 m V.The symmetric battery assembled with zinc foil exhibited a polarization voltage as high as80 m V during cycling.The short-circuit of the symmetric battery occurred after 90 h of cycling.In addition,Zn@CM-40 as Zn anode also performed significantly better electrochemical performance in Zn|Mn O₂ full batteries than zinc foil.Zn@CM-40||Mn O₂ still showed a high capacity retention rate after 500 cycles.2.COSMOL Multiphysics modeling demonstrates a more uniform electric field distribution in Zn@CM-40 than the zinc foil due to the aligned platelet morphology,which is beneficial to the uniform deposition of zinc.The deposition process of the electrode was observed by optical microscopy.Compared with the zinc foil,zinc was uniformly deposited on the surface of the Zn@CM-40 electrode.This indicates that Zn@CM-40 can effectively inhibit the growth of zinc dendrites.3.The electrodeposition of zinc on Cu foil,Cu foam,Al mesh and Ni mesh was used to study the effect of different substrate materials on the electrochemical performance.Based on the electrodeposition morphology and the electrochemical properties of the electrodes,the influence mechanism of the substrate materials on the electrodes was analyzed.The higher specific surface area and zincphilic of the substrate material can provide more nucleation sites for zinc deposition and promote the uniform deposition of zinc ions.