Improved Performance of All-Solid-State Lithium Metal Batteries via Physical and Chemical Interfacial Control

Lithium metal batteries (LMBs) show several limitations, such as high flammability and Li dendrite growth. All-solid-state LMBs (ASSLMBs) are promising alternatives to conventional liquid electrolyte (LE)-based LMBs. However, it is challenging to prepare a solid electrolyte with both high ionic conductivity and low electrode–electrolyte interfacial resistance. In this study, to overcome these problems, a solid composite electrolyte (SCE) consisting of Li_6.25La₃Zr₂Al_0.25O₁₂ and polyvinylidene fluoride-co-hexafluoropropylene is used, which has attracted considerable attention in recent years as a solid-state electrolyte. To operate LMBs without an LE, optimization of the electrode–solid-electrolyte interface is crucial. To achieve this, physical and chemical treatments are performed, i.e., direct growth of each layer by drop casting and thermal evaporation, and plasma treatment before the Li evaporation process, respectively. The optimized ASSLMB (amorphous V₂O_5−x (1 µm)/SCE (30 µm)/Li film (10 µm)) has a high discharge capacity of 136.13 mAh g⁻¹ (at 50 °C and 5 C), which is 90% of that of an LMB with an LE. It also shows good cycling performance (>99%) over 1000 cycles. Thus, the proposed design minimizes the electrode–solid-electrolyte interfacial resistance, and is expected to be suitable for integration with existing commercial processes.