Enhanced Bulk and Interfacial Conductivity in All-Solid-State Lithium Metal Batteries via Garnet Surface Phosphorylation.

Yang, Lin; Mu, Yongbiao; Zou, Lingfeng; Li, Chao; Wang, Xin; Feng, Yitian; Chu, Youqi; Huang, Chaozhu et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

The composite electrolyte of polyvinylidene fluoride (PVDF) and Li<sub>6.5</sub>La<sub>3</sub>Zr<sub>1.5</sub>Ta<sub>0.5</sub>O<sub>12</sub> (LLZO) is considered one of the most promising electrolytes for next-generation lithium batteries. However, the presence of Li<sub>2</sub>CO<sub>3</sub> on the LLZO surface reduces conductivity and leads to PVDF chain cross-linking. In this study, H<sub>3</sub>PO<sub>4</sub> is used to remove the alkaline Li<sub>2</sub>CO<sub>3</sub> layer, and the effect of residual Li<sub>3</sub>PO<sub>4</sub> 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<sup>-4</sup> S cm<sup>-1</sup>. Notably, Li<sub>3</sub>PO<sub>4</sub> catalyzes the decomposition of LiFSI, facilitating the formation of abundant inorganic compounds with rapid lithium-ion diffusion capability such as Li<sub>3</sub>N, LiF and Li<sub>2</sub>S<sub>2</sub>O<sub>7</sub>, 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.