Thin laminar inorganic solid electrolyte with high ionic conductance towards high-performance all-solid-state lithium battery

The development of thin solid-state electrolytes with high ionic conductivity and mechanical strength is essential for high-performance all-solid-state lithium batteries. Although Inorganic solid electrolytes (ISEs) possess high ionic conductivity, fabricating thin and mechanically stable ISEs is still challenging. Herein, Li7La3Zr2O12 (LLZO) nanosheets with lateral size of 3–5 μm and thickness of ~4.5 nm were prepared, and then self-assembled into thin, defect-free, and freestanding LLZO laminar ISE (LLISE). Compared to LLZO pellet (>200 μm) obtained by cold-pressing method, LLISE with a thickness of 12 μm attains an almost 10-times higher ionic conductivity of 1.30 × 10−4 S cm−1 at 30 °C because of the short Li-ion diffusion distance. Importantly, this thin thickness gives high ionic conductance (0.17 S at 30 °C) and energy density of 340 Wh kg−1, ranking one of the highest values among reported solid-state electrolytes. Meanwhile, the compressive strength of LLISE with a thickness of 20 μm (LLISE-20) reaches 3.2 Gpa. The Li symmetrical cell assembled with LLISE-20 can work over 1500 h without obvious polarization under a current density of 0.2 mA cm−2 at 60 °C. The LFP/Li cell exhibits superior cycling stability of 143.2 mAh g−1 at 0.5C and 60 °C after 200 cycles with low capacity decay of 0.05% per cycle.