A "rigid and flexible" multi-functional structure for solid-state Li-metal batteries

Solid state batteries (SSBs) represent a next -generation electrochemical device for safe and high-energy-density energy storage. Solid state electrolyte (SSE) is a key component in SSBs. Among all types of SSEs (sulfides, halides, oxides, and polymers), oxide -based SSEs exhibit a good balance between conductivity and stability. However, one critical issue is the high interfacial resistance with solid electrodes. For perovskite SSEs, an additional issue is the reducibility upon contact with Li metal, lowering Faradaic efficiency. Here in this study, we explore a multi-functional structure with a flexible solid polymer electrolyte (SPE) as an interlayer between electrodes and a ceramic perovskite electrolyte Li6/16Sr7/16Ta3/4Hf1/4O3 (LSTH). The polymethylmethacrylate (PMMA)-polyethylene glycol diacrylate (PEGDA) SPE with a room-temperature ionic conductivity of 2.20 x 10-3 S cm -1 minimizes the interfacial resistance while protecting LSTH from catastrophic Li-reduction, preventing concentration polarization and suppressing Li dendrite attack. We show that application of this structure enables the cyclability of Li/Li half -cells, which is otherwise unattainable with pure LSTH, and achievement of 129.8 mAh g-1 specific discharge capacity at 0.1C of a full cell with LiFePO4 cathode and Li anode.