Nanosecond Laser Cleaning Method to Reduce the Surface Inert Layer and Activate the Garnet Electrolyte for a Solid-State Li Metal Battery

The garnet-type electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) has been widely researched for its high ionic conductivity and excellent stability against the Li anode. However, the garnet electrolyte is susceptible to CO2 and H2O in air to form a Li2CO3 insulating layer leading to poor wettability with the Li anode, which hinders its practical application. Herein, we introduced a simple method to effectively reduce the Li2CO3 layer on the garnet electrolyte surface by laser cleaning and made the garnet surface back with lithiophilicity. The resulting Li/garnet interfacial resistance decreased to 76.4 Ω·cm2 at 30 °C and 3.1 Ω·cm2 at 80 °C. The assembled Li symmetric cell with the as-laser-treated electrolyte steadily cycled for 300 h under 0.1 and 0.2 mA·cm–2 at 80 °C. The solid-state battery coupled with the composite LiFePO4 cathode and the Li anode exhibited stable long-term cycling performance for over 100 cycles with a capacity retention of 84.8%. This work provided a novel method to reduce the surface inert layer and make the garnet electrolyte reveal the intrinsic lithiophilicity by laser cleaning process with high efficiency, which helped address the challenges for the application of garnet-based solid-state batteries.