Preparation And Electrochemical Properties Of Zinc-friendly Modified Carbon Cloth For Zinc Metal Anode

The rapid progress of renewable energy technologies and the increasing energy demand for automobiles and portable electronic devices have increased the demand for energy storage systems with high performance and sustainability.Lithium-ion batteries,which currently dominate the market,are difficult to develop further due to the lack of lithium metal resources in the earth’s crust,while zinc-based energy storage devices have become a promising new energy storage device due to the abundant zinc metal resources,high theoretical capacity and low cost.However,the problem of growing zinc dendrites during the cyclic charging and discharging process is the most important problem that hinders its large-scale application.Carbon cloth is a typical three-dimensional collector electrode material with high specific surface area and excellent electrical conductivity,which can homogenize the electric field on the electrode surface to suppress the generation of zinc dendrites and is an ideal material for zinc metal anode.However,the high formation barrier of zinc metal on the surface of carbon cloth can adversely affect the uniform deposition of zinc metal,so it needs to be studied for modification.Based on this,this thesis selects commercial carbon cloth as the conductive body and designs a variety of three-dimensional zinc metal anode electrodes by subsequent surface modification methods,aiming to fundamentally inhibit the growth of zinc dendrites,promote the uniform nucleation and subsequent deposition of zinc,and ultimately improve the electrochemical properties such as cycle stability and cycle life of zinc metal anodes.The main contents of the study are as follows:Oxygen-doped carbon cloth（OCC）was prepared by a simple hydrothermal method.The results showed that the O/C on the carbon cloth surface increased from the original 1.9%to9.2%,and OCC had a higher average Coulomb efficiency（CE）（97.07%）and lower nucleation overpotential（36.9 mV）compared to CC.the OCC@Zn electrode could be stably cycled for 250 h at 1 mA cm^-2and 1 mAh cm^-2,which was better than CC@Zn at the same conditions cycle time（200h）.The higher electrochemical performance was also observed in the full cell test with CaV₈O₂₀（CVO）cathode material,where the OCC@Zn||CVO full cell has a high specific capacity of 158.9 mAh g^-1at a current density of 1A g^-1and still has a capacity retention of 81%after 400 cycles.This is due to the fact that the oxygen element in OCC provides abundant active sites on the carbon cloth surface with stronger binding energy to zinc ions,which reduces the two-dimensional diffusion of zinc ions on the surface.ZIF-8/OCC was firstly prepared by in situ growth of zeolite imidazole ester skeleton material（ZIF-8）on the surface of OCC using a simple in situ growth and high-temperature pyrolysis method,and the oxygen-doped carbon cloth（ZNC/OCC）modified by Zn O particle-nitrogen-doped carbon nanosheet arrays was fabricated after subsequent heat treatment.The results showed that the ZNC/OCC surface was successfully loaded with uniformly distributed nanosheet structures and had zinc oxide（Zn O）particles mosaic with doping of nitrogen-containing functional groups compared to OCC.In the half-cell test,ZNC/OCC has a very low nucleation overpotential of 30.6 mV at a current density of 1 mA cm^-2and still has a very high Coulomb efficiency of 98.21%after 550 cycles of stabilization.In further symmetric cell tests,the ZNC/OCC@Zn electrode can be stably cycled for 500 h at a low polarization potential of 10.5 mV at a current density of 1 mAh cm^-2.This is due to the fact that the nanosheet arrays on the OCC surface not only provide more active sites,but also the uniformly distributed Zn O particles and nitrogen-containing functional groups in them have higher binding energy to zinc metal,which can further promote the uniform deposition of zinc metal.can further promote the uniform deposition of zinc metal.Surface-grown Cu-doped ZIF-8-derived multistage skeletons of oxygen-doped carbon cloth（Cu_xZNC/OCC）were prepared by doping different molar ratios of copper elements during the in situ growth of ZIF-8 by in situ growth and high-temperature pyrolysis.The results showed that carbon nanotubes were successfully generated on the surface of the nanosheet arrays by suitable Cu doping ratios,and Cu₁ZNC/OCC had a very low nucleation overpotential of 24.6mV at a current density of 1 mA cm^-2and could still have a stable high Coulomb efficiency after 600 cycles.In the symmetric cell test at the same current density,the Cu₁ZNC/OCC electrode can be stably cycled for 800 h at a low polarization potential of 17.4 mV.This is due to the formation of carbon nanotubes on the ZIF-8 surface by pyrolytic reduction of Cu metal as catalytic C and N element sites during the preparation process to further increase the pro-Zn active sites on the material surface,while accommodating the Zn volume changes during the deposition/exfoliation process.