Flexible, Synergistic Ceramic–Polymer Hybrid Solid-State Electrolyte for Secondary Lithium Metal Batteries

A novel hybrid solid-state electrolyte (HSSE) comprising a layered stack of a flexible single-particle-thick membrane (SPTM) and ion-conducting polymeric interposers is demonstrated. The flexible SPTM, made of a monolayer of ion-conducting ceramic particles laterally interconnected by a soft insulating polymer, renders controlled lithium-ion transfer through hard ceramic particles enabling efficient dendrite suppression. The thin-, pressure-deformable ion-conducting polymer interposer improves interfacial contact with electrodes and accommodates volume change during battery operation while protecting Li-sensitive ceramic particles. The synergistic effect of the components in the HSSE facilitated a stable cycling behavior of the Li//Li cell for more than 1000 h at 0.2 mA cm–2, and the system could withstand even higher current densities (∼0.7 mA cm–2) at room temperature where polymer electrolytes are often subjected to a short-circuit. An all-solid-state battery configured with Li/HSSE/LiFePO4 delivered high capacity close to its theoretical value (170 mAh g–1) and high Coulombic efficiency (>99%) at room temperature.