Synergistic modification of PVDF-based electrolyte with HfO₂ and ionic liquid for lithium metal battery exhibiting enhanced cycle stability and kinetics

Poly(vinylidene fluoride) (PVDF) based electrolytes are promising for lithium metal batteries, yet they suffer from low ionic conductivity, severe Li-metal side reactions, and poor dendrite suppression. This study presents a synergistic modification strategy integrating HfO₂ nanoparticles with ionic liquid to develop a high-performance composite electrolyte (PVHE). The incorporated HfO₂ nanoparticles adsorb residual dimethylformamide (DMF) solvent to suppress interfacial side reactions, while simultaneously facilitating the in-situ formation of a Hf-containing stable solid electrolyte interphase (SEI) that improves interfacial stability and inhibits lithium dendrite growth. The ionic liquid enhances the ionic conductivity by reducing the crystallinity of PVDF and regulating the solvation structure, synergistically achieving multiple performance breakthroughs with HfO₂. The PVHE composite electrolyte exhibits an ionic conductivity of 5.75 × 10⁻⁴ S cm⁻¹ at 30 °C and a critical current density of 2.4 mA cm⁻². The Li|PVHE|Li cell cycles stably for over 1500 h at 0.1 mA cm⁻², and the Li|PVHE|NCM811 cell shows a capacity retention of 80.7% after 500 cycles at 1C. The multicomponent synergistic modification strategy offers a viable pathway toward the practical application of PVDF-based electrolytes and advances the understanding of the interactions among components in composite electrolyte systems.