Nitrogen Plasma-Treated Core–Bishell Si@SiO_x@TiO_2−δ: Nanoparticles with Significantly Improved Lithium Storage Performance

Si-based anode materials have attracted considerable attention because of their ultrahigh reversible capacity. However, poor cycling stability caused by the large volume change during cycling prevented the commercial application of Si anodes for lithium-ion batteries (LIBs). To overcome these challenges, in the present study, we designed a nitrogen plasma-treated core–bishell nanostructure where the Si nanoparticle was encapsulated into a SiOx shell and N-doped TiO2−δ shell. Here, the SiOx inside the shell and the TiO2 outside the shell act as binary buffer matrices to accommodate the large volume change and also help to stabilize the solid electrolyte interphase films on the shell surface. More importantly, the plasma-induced N-doped TiO2−δ shell with many Ti3+ species and oxygen vacancies plays a key role in improving the electrical conductivity of Si anodes. Owing to the synergistic effects of SiOx and N-doped TiO2−δ bishells, the cycling stability and rate performance of Si anodes are significantly enhanced. The as-obtained sample exhibits superior cycling stability with a capacity retention of 650 mA h g–1 at 200 mA g–1 after 300 cycles. This strategy is favorable for improving the electrochemical performances of Si-based anodes to employ in practical LIBs.