Competitive Li-ion coordination for constructing a three-dimensional transport network to achieve ultra-high ionic conductivity of a composite solid-state electrolyte†

Abstract

The porous structure of poly(vinylidene fluoride) (PVDF)-based polymer electrolytes and their disordered ion transport properties restrict the continuous and highly efficient transport of lithium ions (Li⁺), which is a major challenge in further improving ionic conductivity. Herein, we constructed a compact composite solid-state electrolyte with a three-dimensional continuous Li⁺ transport network by coupling a heat-treated polyacrylonitrile fiber network with an interconnected metal organic framework coating layer (h-PAN@MOF). The MOF crystal surface exhibits strong interactions with CO of N,N-dimethylformamide (DMF), effectively weakening the Li⁺–O binding strength of DMF in the Li⁺ solvation structure. Highly-efficient Li⁺ transport channels and networks were constructed to achieve a high ionic conductivity of 1.03 × 10⁻³ S cm⁻¹. The MOF-dependent Li⁺ coordination environment prompts the formation of a stable interphase. The h-PAN@MOF network also contributes to the high tensile strength (20.84 MPa) of the compact electrolyte. The Li||LiNi_0.8Mn_0.1Co_0.1O₂ full cells with the h-PAN@MOF network realize robust cycling for 1000 cycles at 5C. This work provides a facile strategy for regulating the Li⁺ coordination state and its spatial distribution in solid-state electrolytes for fast-charging solid-state Li metal batteries.