Quantitative Evaluation and Improvement of Interfacial Li + Transfer Between SiO x Electrode and Garnet‐Type Ta‐Doped Li 7 La 3 Zr 2 O 12 Electrolyte

Abstract A flat and smooth Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 (LLZT) pellet was used as a model solid electrolyte to evaluate Li + transfer resistivity (Ω cm 2 ) at an interface between an LLZT electrolyte and a silicon suboxide (SiO x ) electrode. Two types of interfaces were employed; one was a “joint interface” that was formed by depositing a SiO x thin film directly on the LLZT pellet. The other was a “contact interface” that was formed by compressing a SiO x thin film on a Cu foil to the LLZT pellet, which is a more realistic and practicable interface in all‐solid‐state batteries. The quantitative evaluation of interfacial resistances revealed that Li + transfer at the solid/solid interfaces was intrinsically more sluggish than that for a solid/liquid one using an electrolyte solution. The interfacial resistivity could be reduced by introducing an artificial solid electrolyte interphase (SEI) to the contact SiO x /LLZT interface.