Controllable Preparation And Electrochemical Properties Of Si Based Thin Film Materials

With the rapid development of lithium-ion battery and its wide application in many fields,the traditional commercial carbon anode materials can not meet the needs of people for high-capacity lithium-ion battery.Among them,silicon-based anode materials for lithium-ion batteries have attracted much attention due to their high specific capacity,low self discharge rate and high charge-discharge efficiency.However,the volume change of silicon-based materials in the charge discharge process is huge(more than 300%),resulting in the collapse of the structure of the materials,resulting in poor cycle performance of silicon electrode materials.However,silicon-based thin film materials not only have high specific capacity and good stability,so it has attracted more attention and research.In this paper,the negative electrode materials of pure Si film,Si-Ti composite film,Si-Ti@Si and Si@Si-Ti composite film were prepared by magnetron sputtering,and the structural characteristics and electrochemical properties of the film materials were studied.At the same time,the application of silicon-based film materials in solid electrolyte was preliminarily explored.The main conclusions are as follows:(1)It is found that when the sputtering power of Si target is 120 W and the pure Si film is used as the anode material of Li-ion battery,the negative material of Si film not only has excellent compactness and uniformity,but also shows good cycle stability and high reversible specific capacity.At the current density of 0.2 C,the charge specific capacity of the first cycle is 3595 mAh/g.After 150 cycles,the charge specific capacity is still as high as 2768 mAh/g,and the capacity retention rate is over76%.At the same time,the high capacity Si thin film negative electrode material prepared under 120 W sputtering power also has good rate performance.(2)When Si-Ti composite materials are used as anode materials of lithium-ion batteries,120-1 W,120-5 W and 120-10 W are three groups of Si-Ti composite film materials.Compared with pure Si-120 W film anode materials,the charge specific capacity is low and the cycle effect is not improved significantly.In general,the electrochemical performance of 120-1 W is better than that of 120-5 W and 120-10 W.(3)The electrochemical performance of Si@Si-Ti composite film is better than that of Si-Ti and Si-Ti@Si composite film,which not only improves the cycling performance of pure Si film,but also improves the specific capacity of charge compared with Si-Ti composite film.The initial specific capacity of Si@Si-Ti composite film reaches 2230 mAh/g,after 400 cycles,the capacity retention rate is still reached 79%.(4)The negative electrode materials of Si thin film prepared by RF magnetron sputtering were initially applied to solid electrolyte,and the influence of solid electrolyte on the electrochemical performance of the negative electrode materials of Si based thin film was analyzed.The specific capacity of charge in the first cycle can reach 3373 mAh/g,and it increases gradually in the first 10 weeks.The specific capacity of charge in the ninth cycle is 3491 mAh/g.In addition,we can not find the reduction peak of SEI film formation in the cyclic voltammetry curve,and also found that the polarization of SEI film in solid electrolyte is small.