Phase Structure Regulation of PVDF-based Polymers Toward Fast Ion-Transport Kinetics and Stable Interface

Poly(vinylidene fluoride) (PVDF) has emerged as a promising polymer matrix for gel polymer electrolytes (GPEs), owing to its low cost, robust chemical stability, and high density of polar fluorine-containing functional groups. However, its practical implementation is still limited by the insufficient ionic conductivity and poor interfacial stability with lithium metal anodes. A synergistic strategy is proposed to address both limitations simultaneously. By using a water-soluble ionic salt- lithium bis(fluorosulfonyl)imide (LiFSI) as an additive during the phase inversion preparation process, β-phase-rich PVDF-based polymer can be achieved. Theoretical calculations and experimental results all demonstrate that the high-dielectric β-PVDF facilitates Li salt dissociation and guides uniform Li⁺ flux distribution, leading to a significantly enhanced kinetic of ion-transport and improved interfacial stability of the GPEs. Furthermore, LiFSI also effectively inhibits interfacial dehydrofluorination, stabilizing the slurry at a molecular level. These synergistic enhancements accelerate ion-transport kinetics (σ: 1.94 × 10^-3 S cm^-1, t₊: 0.61), and reinforce interfacial compatibility, which collectively endow the integrated electrode fabricated with superior structural and electrochemical stability, demonstrating its great potential for the application of flexible batteries. This work not only establishes a scalable solution-processable route for β-phase-rich PVDF-based polymer manufacturing but also enriches fundamental insights into interface stabilization strategies for flexible solid-state battery systems.