Double-shell interphase design enabling suppressed side reactions for stable Si battery anode

Silicon (Si)-based anode is promising for the next-generation high-energy lithium-ion batteries due to the high capacity. However, it suffers parasitic side reactions between electrode and electrolyte in the initial cycle, which consumes abundant active lithium and makes it one of the limiting factors for the implementation of Si-based anodes. It is of vital importance to suppress the side reactions at the electrode interphase and improve the electrochemical/chemical stability. Here, we designed an ultrathin double-shell interphase structure (∼15 nm), consisting of an inner VO2 nanoshell and an outer C nanoshell. The inner VO2 nanolayer avoided the direct contact between active Si and electrolyte, and, thus, hindered the side reactions between them. The carbon nanolayer stabilized the VO2 layer mechanically and improved the electronic conductivity of the anode materials. Thus, a thin solid electrolyte interphase was formed on the as-designed Si@VO2@C surface, and high initial Coulombic efficiency (ICE) was realized. Notably, the Si@VO2@C electrode exhibited a high reversible capacity of 2300 mAh g−1 at 0.1 C and high ICE of 90.2%, which was about 18% higher than that of a pristine Si electrode. Also, the electrode displayed stable electrochemical cycling with high capacity retention of 84.8% for 100 cycles at 0.4 C. With 15 wt. % addition into the graphite, the hybrid electrode Si@VO2@C/graphite exhibited a high reversible charge capacity of 596 mAh g−1 and satisfactory cycling performance with high capacity retention of 83.8% at 100 mA g−1 under a high area capacity of 3.46 mAh cm−2, showing promise for the practical application.