Preparation And Electrochemical Performance Of Micro-arc Oxidation Composite Film Anode On Titanium Surface

As a secondary battery,lithium-ion battery has been widely used in smart phones,notebook computers and other portable electronic devices since the 20th century because of its advantages such as high energy density,long cycle life,high operating voltage,no memory effect,low self-discharge and environmental friendliness.At present,in the field of electric vehicles,lithium-ion batteries also serve as the main power source.Si,Si O₂ and transition metal dihalide MoS₂ have attracted extensive attention due to their high theoretical specific capacity,but they have common shortcomings.The volume expansion is a serious problem in the process of lithium/delithium.Such volume change makes them powdery and then flake off from the collector fluid in the charging and discharging process,resulting in deterioration of electrochemical properties,which seriously limits their commercial development.The transition metal oxide TiO₂ becomes a potential anode material for lithium-ion batteries due to its low volume change(only about 3%)and high discharge platform(about 1.7V)in the process of Li⁺embedding and de-embedding.In this paper,porous TiO₂ was prepared on the surface of titanium foil by plasma electrolytic oxidation technology,and the TiO₂/Si O₂/Si and TiO₂/MoS₂ composite films were synthesized by adjusting the electrolyte parameters and introducing magnetron sputtering technology to obtain the anode materials with high specific capacity,good cycle stability and rate performance.The main research contents of this paper are as follows:(1)The plasma electrolytic oxidation technology was employed to prepare a TiO₂ film on the Ti foil,and then Si O₂/Si was deposited on the TiO₂ film by magnetron sputtering technology to prepare a silicon-containing plasma electrolytic oxidation composite film.This composite film was used as the anode of the lithium-ion battery and a Li foil was used as the counter electrode.The capacity,cycling stability,cyclic voltammetry curves and electrochemical impedance spectra were measured by the battery test system and electrochemical workstation.The experimental results showed that the composite film was composed of TiO₂/Si O₂/Si with a porous morphology.TiO₂,Si O₂ and Si all participated in the redox reactions with Li⁺.After 100 cycles under a current density of 100?A cm^-2,the capacity remained at about 530 m Ah g^-1.Moreover,after cycling under a high current density of 1000?A cm^-2,the capacity can come back to 95%of the initial capacity.This suggests that the prepared TiO₂/Si O₂/Si composite film has an excellent rate capability with stable structural retention,and its electrochemical performance is much better than that of the pure TiO₂ anode.Therefore,the plasma electrolytic oxidation technology can produce porous and binder-free TiO₂ anode materials on the surface of titanium foil with high efficiency.It can also combine with the magnetron sputtering technology to prepare high capacity composite film anodes,which has a bright prospect of industrial application.(2)A sphere-like MoS₂ and porous TiO₂ composite film was prepared on Ti foil by plasma electrolytic oxidation and magnetron sputtering methods.The prepared film was assembled as a binder-free anode in the lithium-ion battery and a Li foil served as the counter electrode.The specific capacity and cycling stability of the electrode were evaluated,together with the cyclic voltammograms and electrochemical impedance spectra.The TiO₂/MoS₂ composite film anode combined the advantages of TiO₂ with high structural stability and MoS₂ with high theoretical capacity.The electrochemical performance exhibited a specific capacity above 400 m Ah g^-1 at the current density of 100?A cm^-2,which was much higher than that of the TiO₂ anode.Besides,after cycling under a high current density of 1000?A cm^-2,the capacity came back to 91%of the initial capacity,showing a good rate capability.The porous TiO₂ prepared by plasma electrolytic oxidation can provide a significant number of internal channels for the Li⁺diffusion,resulting in a high porosity of 33.5%?41.6%,and a high Li⁺diffusion coefficient of 3.12×10^-14?6.67×10^-14cm~2 s^-1.The structural characteristics of the composite films were beneficial for the enhanced electrochemical performance.