Chemically Lithiated Poly(vinylidene difluoride) with In Situ Generated LiF Nanofiller as Hybrid Artificial Layer for Stable Lithium Metal Anodes

Hybrid artificial layer based on inorganic/polymer composite endows superior toughness and mechanical strength, which can achieve high stability of lithium metal anode. However, the large particle size and uneven distribution of inorganic fillers hinder the uniform flow of lithium ions across the membrane, making it difficult to achieve smooth lithium metal deposition/stripping. In this work, a chemical lithiation-induced defluorination strategy is proposed to engineer poly(vinylidene difluoride) (PVDF)-based artificial layers, enabling in situ incorporation of highly dispersed LiF nanofiller within the polymer matrix and precise control over the LiF content. This approach significantly improves the uniformity of the hybrid artificial layer, provides abundant conduction pathways for lithium-ion transport, reduces the migration energy barrier, and enhances the ionic conductivity and electrochemical kinetics. With the modified PVDF artifical layer, Li||Cu cells can stably cycle for more than 1000 h at 1 mA cm^-2 and 1 mAh cm^-2, while lithium metal cells Li||LFP with a N/P ratio of 1.5 and anode-free cells Cu||NCM811 assembled with commercial cathodes can maintain 89% and 57% capacity after 100 cycles, respectively. This work provides new insights into the polymer materials modification represented by PVDF and demonstrates its potential application in lithium metal batteries.