High Cycle Stability of Nanoporous Si Composites in All-solid-state Lithium-ion Batteries

Stress relaxation of Si with large structural fluctuations is a critical challenge for its practical application in lithium-ion batteries (LIBs). In this study, nanoporous Si particles, which are prepared by Mg2Si reduction of mesoporous SiO2 spheres, are applied as an anode active material for all-solid-state LIBs (ASSLIBs) with a Li3PS4 solid electrolyte. Nanoporous Si half-cells exhibit an excellent cyclability with a high-capacity retention of about 90% at 50 cycles compared to non-porous Si half-cells below 20%. The cross-sectional characteristics of nanoporous and non-porous Si composite anodes are accurately compared using electrochemical impedance spectroscopy and field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. Based on these results, we conclude that the expansion/contraction of nanosized Si pores and the elastic deformation of Li3PS4 effectively relieve the structural stress derived from the volume change of Si particles/aggregates during lithiation and delithiation, resulting in high cycle stability. These findings provide valuable information for the rational design of Si-based anodes for high-performance ASSLIBs.