A robust plasma-assisted strategy for constructing continuous ion-transport pathways in poly(vinylidene fluoride)-based composite solid electrolytes toward dendrite-free lithium metal batteries

Poly(vinylidene fluoride) (PVDF)-based solid electrolytes can improve the safety of solid-state lithium metal batteries (SSLMBs), but poor polymer-ceramic contact, filler agglomeration, discontinuous ion-transport pathways, and low ionic conductivity remain major limitations. Here, we fabricate a three-dimensional electrospun composite electrolyte containing radio-frequency (RF) plasma-treated yttria-stabilized zirconia (p-YSZ) and the fast-ion conductor Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO). RF plasma treatment creates an oxygen-deficient p-YSZ surface that promotes salt dissociation and improves adhesion to the polymer matrix, while LLZTO contributes fast Li-ion-conduction domains. The optimized active-inert dual-filler electrolyte reaches an ionic conductivity of 6.1 × 10⁻⁴ S cm⁻¹ at room temperature, a Li⁺ transference number of 0.67, and an electrochemical stability window of 5.2 V. Li||p-Y/L-PVDF||Li symmetric cells cycle for more than 3000 h at 0.2 mA cm⁻², and Li||p-Y/L-PVDF||LiFePO₄ cells retain 86% of their capacity after 500 cycles at 1C. Density functional theory calculations show that the oxygen-deficient dual-filler interface redistributes charge and modifies the adsorption of Li-containing species, providing an atomistic basis for the experimentally observed improvement in ion transport. These results establish RF plasma activation of an inert filler as a practical route to improving the interfaces and transport network in PVDF-based composite electrolytes.