Hybrid oxide solid electrolyte of crystalline garnet and highly deformable glass for all-solid-state lithium-ion batteries

Oxide solid electrolytes (SEs) are promising materials for all-solid-state lithium-ion batteries because of their superior safety and stability. However, crystalline oxide SEs with relatively high ionic conductivity show low deformability and limited contact between SE particles, which hinders the formation of lithium-ion transport pathways. Meanwhile, highly deformable oxide glass SEs exhibit good contact between particles but low ionic conductivity. This study seeks to combine the advantages of both types of SEs in a hybrid oxide SE comprising a crystalline garnet-type oxide of Li6.5La3Zr1.5Ta0.5O12 (LLZT) and a deformable oxide glass 45Li2SO4–30Li2CO3–25LiBr. The controlled synthesis of LLZT via a flux method affords particles with suitable shape and size to allow the deformable SE to fill the interparticle spaces. The hybrid SE pellets prepared by cold pressing show a relative density of 96% and higher ionic conductivity than the original crystalline and glass SEs as a result of the good interparticle contact. Furthermore, oxide-type all-solid-state LiNi1/3Co1/3Mn1/3O2–Si and Li2S–Si full battery cells fabricated using the garnet–glass hybrid SE as a separator layer show relatively high area capacity and specific energy density compared with other oxide-type all-solid-state lithium-ion batteries.