A Simple and Efficient Strategy for Ameliorating Li/LLZO Interfacial Contact

Li₇La₃Zr₂O₁₂(LLZO) is considered as one of the most promising solid-state electrolytes for lithium (Li) metal batteries due to its wide electrochemical window and good electrochemical stability against Li metal. However, undesired lithium carbonate (Li₂CO₃) contamination cannot be avoided and it turns the LLZO surface to a lithophobic surface. The consequent large interfacial resistance limits its electrochemical performances. Herein, a drop-casting method using metal oxides is introduced to remove Li₂CO₃and improve the interfacial contact between Li metal and Li_6.4La₃Zr_1.4Ta_0.6O₁₂(LLZTO). For example, due to the reduction and alloying reactions between gallium oxide (Ga₂O₃) and molten Li, a Li-Ga-O layer is formed, which exhibits an excellent wetting property on the LLZTO surface. During the alloying process of the lithiophilic Li-Ga-O interlayer, it breaks the Li₂CO₃contamination layer into fragments by alloying expansion force, allowing the Li-Ga-O interlayer to spread to the LLZTO surface. Benefiting from the improved interfacial contact, the interfacial resistance decreases from 1789 to 4.35 ω/cm². The Li symmetric cell cycles over 2000 hs under 0.235 mA/cm²and the Li|Ga₂O₃@LLZTO|LiCoO₂full cell works for 100 cycles at room temperature.