Regulation of Si nanodomain size and its effect on electrochemical performance in prelithiated SiO anode

Silicon monoxide (SiO) is a promising anode material for lithium-ion batteries (LIBs) due to its relatively low volume change and superior cycling performance compared to silicon (Si). However, its low initial Coulombic efficiency (ICE) should be improved when the addition of SiO is higher than 5 wt% in graphite. Many prelithiation attempts have been made to improve its ICE, among which chemical prelithiation is widely used. However, the complex microstructures of prelithiated SiO (pre-SiO) hinder exploring the interconnection between microstructure and composition changes with its electrochemical performance. The size of Si nanodomains embedded in pre-SiO plays a crucial role in electrochemical performance. Herein, samples with different sizes of Si nanodomains are prepared via regulating the degree of prelithiation. Then the structure, composition evolutions and the size effect of Si nanodomains on the electrochemical performance are well investigated. The Si nanodomain size grows with the incremental prelithiation degree, leading to more capacity degradation. It is indicated that prelithiation promotes the growth of Si nanodomains and an appropriate Si nanodomain size of ∼10 nm is essential to retard volume expansion thus improving the cyclability. These results give fundamental insight into the pre-SiO for its future applications as the next-generation LIBs anodes.