Influences of oxygen content on the electrochemical performance of a-SiOx thin-film anodes

Silicon suboxide (SiOx) is a promising anode material for lithium ion batteries (LIBs), due to its high specific capacity, small volume variation and superior cycle performance. Herein, we demonstrated the determining roles of oxygen contents on the behavior of SiOx upon lithium by means of thin-film type electrodes. The SiOx thin-film anodes with different oxygen contents were prepared by sputtering with Cu foil as substrates. XRD and Raman investigations reveal that these SiOx films are amorphous. As anodes, it is found that increasing oxygen contents in SiOx endows an enhanced cycle stability, but does harm to their initial Coulombic efficiency and capacity. Among all the a-SiOx film anodes (x = 0.4, 0.7, 1.1 and 1.5), the SiO0.7 electrode with a thickness of 450 nm exhibits excellent cycle performance and rate capability, with a high initial discharge capacity of 463 μAh cm−2 μm−1 at the current density of 64 μA cm−2 and a high capacity retention of 90% after 300 cycles. This superior performance is ascribed to that the in-situ formed lithium oxide/silicates compounds during discharge effectively alleviates the large volume change of Si components, but also suppresses the electron leakage from the surface of active particles, shutting down the further decomposition of electrolytes and then the formation of thick solid interphase layer. These results will provide inspirations for designing high-performance Si based anodes for lithium ion batteries. [Display omitted]