Microscopic observation of nanoporous Si-Li3PS4 interface in composite anodes with stable cyclability

Nanoporous Si particles, which are prepared from Mg2Si reduction of SiO2 fumes, and Li3PS4 solid electrolyte are composited to accommodate the volume expansion of Si. Cross-sectional FE-SEM and EDX measurements after charging/discharging show that nanoporous Si particles/aggregates entangle the surrounding electrolyte to make close contact, resulting in the preservation of low interfacial resistance and high cycle stability. While, in non-porous Si composite anodes, large cracks are formed at the Si-Li3PS4 interface, causing low capacity retention. To the best of our knowledge, this is the first microscopic study to demonstrate that nanoporous structure relieves the volume change of Si.