Ceramic-Based Flexible Sheet Electrolyte for Li Batteries

The increasing demand for high-energy-density batteries stimulated the revival of research interest in Li-metal batteries. The garnet-type ceramic Li₇La₃Zr₂O₁₂ (LLZO) is one of the few solid-state fast-ion conductors that are stable against Li metal. However, the densification of LLZO powders usually requires high sintering temperatures (e.g., 1200 °C), which likely result in Li loss and various side reactions. From an engineering point of view, high-temperature sintering of thin LLZO electrolytes (brittle) at a large scale is difficult. Moreover, the high interfacial resistance between the solid LLZO electrolytes and electrodes is a notorious problem. Here, we report a practical synthesis of a flexible composite Al-doped LLZO (Al-LLZO) sheet electrolyte (75 μm in thickness), which can be mass-produced at room temperature. This ceramic-based flexible sheet electrolyte enables Li-metal batteries to operate at both 60 and 30 °C, demonstrating its potential application for developing practical Li-metal batteries.