Efficient Ion Migration and Stable Interface Chemistry of PVDF‐Based Electrolytes for Solid‐State Lithium Metal Batteries

Poly(vinylidene fluoride) (PVDF)-based electrolytes with "Li salt-polymer-trace residual solvent" configuration have shown great potential in solid-state lithium metal batteries (SSLMBs). However, the interface failure initiated by the residual solvent and the sluggish Li⁺ migration kinetics caused by the intricacy of the Li⁺-interaction environment severely precludes the large-scale commercial application of PVDF-based electrolytes in SSLMBs. Herein, the PVDF-based electrolytes are fabricated by compositing the PVDF matrix and sand-ground silicon monoxide (SiO-a) fillers with silicon monoxide/silicon-suboxide/silicon-dioxide (Si/SiO_x(0<x<2)/SiO₂)heterostructure. Results show that SiO-a not only forcefully anchors the highly reactive N, N-dimethylformamide (DMF) molecules, significantly alleviating the side reactions at the electrode-electrolyte interface, but also the anchored DMF molecule dipole exhibits stronger bond dipole moment (C═ O; 7.1 × 10^-30 C m) than PVDF (C─F; 3.6 × 10^-30 C m), thus weakens the ion-dipole interaction of Li⁺···F, making Li⁺-hopping easily along polymer chains. Consequently, the obtained electrolyte exhibits dramatic electrochemical properties, including a superior ionic conductivity (0.39 mS cm^-1) and sufficient Li⁺ transference number (0.54). Additionally, the LFP||Li battery presents an outstanding performance at the wide temperature range of -10-60 °C. Even at a high mass loading of ≈11 mg cm^-2, the LFP||Li battery also delivers an impressive specific capacity (156.9 mAh g^-1) along with average coulombic efficiency (99.8%).