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 Li2CO3 and improve the interfacial contact between Li metal and Li6.4La3Zr1.4Ta0.6O12 (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 Li2CO3 contamination 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/cm2 and the Li|Ga2O3@LLZTO|LiCoO2 full cell works for 100 cycles at room temperature.