Surface nitridation of Si enabled gradient artificial solid electrolyte interface and self-optimized structural evolution

Silicon (Si), a promising high-capacity anode material for lithium-ion batteries, suffers from severe volume changes upon cycling, leading to rapid capacity fading. This study mitigates the capacity fading issue by introducing a surface SiN x layer on micron Si, which is in-situ converted into a Li x SiN y -based artificial solid electrolyte interphase (SEI). This artificial SEI not only effectively restricts SEI growth to the outmost surface, but also induces a self-optimized structural evolution of the inner Si from micron particles to nanoporous network within 20 cycles. This self-optimized nanoprous Si network exhibits low volume expansion and enhanced reaction kinetics. Consequently, the Si@SiN x /TiN demonstrates a high capacity, stable cycling, and good fast-charging capability.