Solid Solvent in Salt: All-Solid-State Batteries Based on High LiTFSI Composition

Abstract A solid solvent in salt concept is applied to all-solid-state batteries (ASSBs) using a soft solid electrolyte (SE) composed of lithium bis(trifluoromethanesulfonyl)imide, succinonitrile, and ethylene carbonate with a weight ratio of 85/11/4. The developed SE exhibits an ionic conductivity of ∼10−4 S/cm at room temperature and an electrochemical stability window of approximately 5 V. Electrochemical performance was evaluated using lithium, graphite, and SiOX anodes paired with a LiFePO4 (LFP) cathode. The ASSBs, including LFP/SE/SiOX and LFP/SE/graphite configurations, demonstrates reversible cycling at room temperature without the application of external pressure, highlighting the potential of the soft SE for practical ASSB applications.