Preparation And Performance Of Silicon Thin Film Anode For Li-Ion Batteries

With the development of multi-functional electronic devices and the maturing of the electric vehicle market,the research community and the business community are particularly concerned about the development of high-performance lithium-ion battery electrode materials.Silicon material has a high discharge specific capacity,low discharge platform,rich crustal reserves and friendly environmental protection characteristics,which makes it a potential electrode material to replace the existing commercial graphite anode.However,silicon materials also have many obvious disadvantages as lithium ion anode materials.First,the large volume change?more than 300%?during the cycle causes cracking,pulverization and peeling of the electrode,resulting in a continuous decay or even complete failure of the lithium ion battery capacity.Second,low conductivity limits the release of silicon material capacity,resulting in poor rate performance of silicon materials.In response to the above problems,many researchers have improved the cycling performance of silicon materials by constructing nanostructures and compounding other materials.Compared to other nanostructures,two-dimensional nanofilms grow directly on the current collector,avoiding the loss of capacity caused by the addition of conductive agents and binders.Compared with some new nanostructures,the preparation process of two-dimensional films is more mature and has the potential for large-scale production.This paper mainly focuses on pure Si film and Si-Zr composite film as anode materials for lithium ion batteries.Si films with different crystallinity were prepared by microwave plasma vapor deposition.Amorphous silicon films with different film thickness and Si-Zr composite films with different compositions were prepared by RF magnetron sputtering.The composition,structure and electrochemical performance of the film anodes were analyzed..In this paper,the effects of crystallinity and film thickness on the cycle performance of pure Si films were investigated.The effects of film composition on the cycle performance and interface contact resistance of Si-Zr composite films were investigated.The capability performance of pure Si and Si-Zr composite films were compared.The results show that with the increase of crystallinity,the cycling stability of Si thin film anode materials is getting worse and the capacity decays rapidly.The amorphous Si film has the best cycling performance.As the thickness of the film increases,the stress released during the cycling of the Si film increases,and the Si electrode material exhibits more severe cracking and pulverization,resulting in poor cycle stability of the electrode.The study of Si-Zr composite film shows that the addition of Zr inhibits the cracking and pulverization of the film electrode during the cycle,and improves the cycling stability of the film electrode.As the Zr content increases,the cycling stability of the Si-Zr composite film anode increases continuously.Among them,Si_71.3Zr_28.7 performs the best cycling stability,and the capacity retention rate after 300 cycles is as high as 72%.Electrochemical impedance spectroscopy results show that the interface contact resistance of Si-Zr composite film decreases first and then increases with the increase of Zr content.Si_86.3Zr_13.7 has the lowest interface contact resistance,and its corresponding rate performance is better than that of pure Si film,indicating that Si-Zr composite film has good rate performance.