An appropriate reference and counter electrode in an all-solid-state battery using NASICON-structured solid electrolyte

Anti-NASICON-structured Fe₂(MoO₄)₃ (FMO) thin films are formed on NASICON-structured LATP solid-state electrolyte by pulsed laser deposition, and their electrochemical properties are investigated. The FMO thin films operate at 3.0 V flat voltage vs. Li/Li⁺ within the potential window of LATP. The apparent diffusion coefficient of the FMO thin film on LATP is almost consistent with that measured in a conventional organic liquid electrolyte (0.5–1.2 × 10^-12 cm² s⁻¹) and stable and fast charge–discharge reactions are realized. These results indicate that FMO/LATP is appropriate as a reference and counter electrode for all-solid-state batteries using NASICON-structured LATP. Combining crystalline electrode-solid electrolytes with a similar framework structure at relatively low temperatures will play an important role in realizing reversible electrode reactions. An all-solid-state battery, FMO/LATP/LiCoO₂, is developed to apply the FMO as a reference and counter electrode, and the SSB operates at 1.0 V without visible capacity fading.