Enhanced Bulk and Interfacial Conductivity in All-Solid-State Lithium Metal Batteries via Garnet Surface Phosphorylation
Lin Yang, Yongbiao Mu, Lingfeng Zou, Chao Li, Xin Wang, Yitian Feng, Youqi Chu, Chaozhu Huang, Qing Zhang, Lin Zeng
Abstract
The composite electrolyte of polyvinylidene fluoride (PVDF) and Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO) is considered one of the most promising electrolytes for next-generation lithium batteries. However, the presence of Li 2 CO 3 on the LLZO surface reduces conductivity and leads to PVDF chain cross-linking. In this study, H 3 PO 4 is used to remove the alkaline Li 2 CO 3 layer, and the effect of residual Li 3 PO 4 on bulk conductivity and lithium metal interface conduction is investigated. The phosphorylation of the LLZO surface enhances ion transport channels, increasing ionic conductivity to 5.06 × 10 –4 S cm –1 . Notably, Li 3 PO 4 catalyzes the decomposition of LiFSI, facilitating the formation of abundant inorganic compounds with rapid lithium-ion diffusion capability such as Li 3 N, LiF and Li 2 S 2 O 7, which increases the interfacial exchange current density of lithium symmetric batteries by approximately 3.5 times. Additionally, a Li||LFP battery achieved 89% capacity retention after 400 cycles at 1C. These results demonstrate a promising strategy for developing commercial solid-state electrolytes for all-solid-state lithium metal batteries.