High-performance solid-state lithium metal batteries achieved by interface modification

Garnet-structured ceramic electrolyte Li6.75La3Zr1.75Ta0.25O12 (LLZTO) attracts significant consideration in solid-state Li metal batteries due to its wide electrochemical window and favorable compatibility with Li metal. However, the deployment of LLZTO is severely hampered by poor contact between LLZTO and Li metal anode. In this paper, an ultra-thin Al-Si interface buffer layer (10 nm) is constructed on LLZTO by a magnetron sputtering method, which allows superior wetting of Li onto the LLZTO surface due to the alloying reaction between the Al-Si layer and Li metal. The resulting Li/Al-Si coated LLZTO (ASL)/Li symmetrical cell delivers an interfacial resistance of 15.0 Ω cm−2, which is much lower than that of 1140.3 Ω cm−2 for the bare LLZTO symmetrical cell. Moreover, the Li/ASL/Li symmetrical cells exhibit stable plating/striping performance (800 h) with small voltage hysteresis at 1.0 mA cm−2. Besides, the full cell with LiFePO4 cathode reveals a high capacity of 124.1 mA h g−1 after 600 cycles at 0.5C with a low-capacity decay of 0.032% per cycle. We believe this work will facilitate the development of solid-state rechargeable batteries.