Preparation of high-density garnet thin sheet electrolytes for all-solid-state Li-Metal batteries by tape-casting technique

Garnet electrolyte is a promising candidate for the development of all-solid-state Li-metal batteries, because of its safety and stability against Li metal. However, its practical application is limited by the difficulty in production of its high-density thin sheet. In this work, we have fabricated garnet thin sheet electrolytes (Li6.4La3Zr1.4Ta0.6O12, LLZTO) by tape-casting technique. By using Li2O as a liquid-phase sintering additive, a high relative density up to 99% was achieved. Electrochemical results show the LLZTO sheets have an ionic conductivity of 5.2 × 10−4 S cm−1 at 30 °C and good cycling stability against Li metal. Based on the sheets, all-solid-state Li/LLZTO/LiFePO4 batteries exhibit excellent reversible cycles at 60 °C and 0.1C with an initial discharge specific capacity of 125.8 mA h g−1 and a retention of 92.3% after 50 cycles. These results indicate that the tape-casting process demonstrated here provides an effective method of producing high-density garnet thin sheet electrolytes for high-performance all-solid-state Li-metal batteries.