Electrochemical Performance of Si/Graphite/Carbon Composite Electrode in Mixed Electrolytes Containing LiBOB and LiPF6

The influences of lithium bis(oxalato) borate (LiBOB), vinylene carbonate (VC)-containing LiPF6, and the mixed electrolytes with their different ratios on the electrochemical properties of Si/graphite/disordered carbon (Si/G/DC) composite electrode were investigated. Si/G/DC in mixed electrolytes presented better cyclability than in LiPF6 with VC and a higher specific capacity than in LiBOB. Si/G/DC in 0.5 M LiBOB+0.38 M LiPF6 electrolytes exhibited a high reversible capacity of 512 mAh g(-1) and a high and stable coulombic efficiency after the first cycle when cycled at a rate of 168 mA g(-1). Even after 220 cycles, the reversible capacity was still as high as 432 mAh g(-1), with a capacity fading of less than 0.08% per cycle. The analysis of scanning electron microscopy, electrochemical impedance spectra, and X-ray photoelectron spectroscopy indicated that the improvement of Si/G/DC composite electrode in cyclability resulted from the formation of impact and stable solid electrolyte interphase layers.