Hybridizing poly(vinylidene fluoride-co-hexafluoropropylene) with Li_6.5La₃Zr_1.5Ta_0.5O₁₂ as a lithium-ion electrolyte for solid state lithium metal batteries

Polymer/ceramic composite solid electrolyte is an appealing solution for the exploitation of flexible solid-state lithium-metal batteries. Here we report a solid-state Li-ion electrolyte composing of poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) polymer, ceramic powder Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) and lithium salt LiTFSI. The composite electrolyte exhibits a high ionic conductivity of 8.80 × 10⁻⁵ S·cm⁻¹ at room temperature. A coin battery with LiFePO₄ cathode is cycled under 0.5 C at room temperature for long cycles, achieving a Coulombic efficiency of 99.6% without virtually capacity loss (1st: 101.4 mAh·g⁻¹ and 500th: 110.9 mAh·g⁻¹). Such excellent performance can be ascribed to the formation of high ionic conductivity by LLZTO active garnet reducing polymer crystallinity. These results show that the developed polymer/ceramic composite has potential to be a high-performance electrolyte for solid-state lithium-metal batteries.