Enhanced cycling stability of SiO_x/Si/nickel foam thin film anodes for lithium ion batteries

摘要

Silicon has been known as the next generation anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity (4200 mA h g~(-1)). However silicon anodes face the challenge of large volume change over 400 % during lithiation/delithiation cycles, leading to the pulverization of the silicon based electrodes. In this study, radio frequency (RF) magnetron sputtering is used to deposit amorphous silicon thin films on nickel foam current collectors. This flexible three-dimensional structure is found to relieve stress caused by the volume expansion. Furthermore, SiO_x is coated on the previously fabricated silicon anodes as a buffer layer. The oxygen contents and the thickness of the SiO_x are controlled by depositing under different Ar/O_2 ratios, and depositing times. The electrochemical behaviors of the SiO_x/Si/nickel foam electrodes toward lithium are studied. It is found that the SiO_x/Si/nickel foam electrodes with optimized oxygen contents and thickness of SiO_x films exhibit high cycling stability and coulombic efficiency. The results are attributed to the stress relaxation effect provided by the flexible nickel foams and the SiO_x buffer layers.