A nanocrystal garnet skeleton-derived high-performance composite solid-state electrolyte membrane

Composite solid-state electrolytes (SSEs) can improve the flexibility of the oxide SSEs to decrease the interfacial resistance between the electrolytes and the electrodes. However, the ceramic nanofillers within the composite SSEs suffer from the agglomeration at high concentrations, decreasing the ion conductivities. In this study, a continuous nanocrystal Li6.5La3Zr1.5Ta0.5O12 (LLZTO) skeleton is prepared by the ultrafast high-temperature sintering (UHS) together with tape-casting. Due to the short sintering time of ∼5 s from precursors, the LLZTO grains are restrained to ∼300 nm with limited Li loss. Even with trace solvent (3 wt%), the composite SSE membrane exhibits an ion conductivity of 5 × 10−4 S⋅cm−1, ∼50 times higher than the DOL electrolyte (1 × 10−5 S⋅cm−1, 8 wt% solvent), which further proves the high Li-ion conductivity of the nanocrystal LLZTO skeleton. The composite SSE membrane exhibits a critical current density of 3.4 mA⋅cm−2, among the highest reported values for ceramic-polymer SSEs. The Li/composite SSEs/Li symmetric cells can cycle ∼ 120 h at the current density from 0.2 to 0.4 mA⋅cm−2. The LiFePO4/LLZTO-PEGDA composite SSEs/Li full cell exhibits a high specific discharge capacity of ∼150 mAh⋅g−1 for 50 cycles with a Coulombic efficiency of ∼ 97%. To explore the processability of the membrane with large size, we also demonstrate a pouch cell (2 cm × 5 cm) with a high specific capacity of ∼150 mAh⋅g−1 for ∼25 cycles and a capacity retention of ∼ 94.5%. This work paves a new way to manufacture the nanocrystal ceramic SSE skeleton for high energy density all-solid-state batteries.