Preparation And Investigation Of Sn-based Films Anode Materials For Lithium Ion Batteries

In this paper,we use physical vapor deposition(PVD)to produce tin-based film anode.Comparing to powder materials,tin nano film relieve absolute volume expansion during discharge/charge process.The carbon layer not only suppresses tin's allotropy transformation,but also improves the diffusion ability of lithium ions,which improves the cycling performance observably.In this paper,we produce three structures: pure Sn film,two layers film(Sn/C and C/Sn)and Sn/C/Sn three layers film.We want to know how different structures affect electrochemical properties.By comparing Sn with Sn/C,we find that when carbon layer was deposited on tin layer,the cycling performance is promising.After cycling 70 cycles at 0.5 C current density,the specific capacity remains 597.8 mAhg-1,after 100 cycles the specific capacity remains 479.6 mAhg-1,which is more larger than graphite(372 mAhg-1).The capacity retention is superior during 70 cycles and efficiency remains about 98%.By ex-situ XRD and electrochemical measurement methods,comparing to Sn ample,we find that carbon layer not only suppresses tin's allotropy transformation and decomposition of electrolyte,but also improves the diffusion ability of lithium ions and electrical conductivity,which improves the cycling performance observably.Under the experimental results of ex-situ XRD,we try to research reversibility of phase transition through experiment and theoretical calculation.Finally,the result shows that heat treatment can't cause phase transition reversibly.