Realization of Enhanced Interfacial Lithium-Ion Transfer in Composite Polymer Electrolytes via Grafting Oligo-PEG Molecular Brushes on Silica-Coated Nanofibers for All-Solid-State Lithium Metal Batteries

Polyether-based polymer electrolytes are attractive but still challenging for high-energy-density solid-state lithium metal batteries due to their limited Li-ion conductivity at room temperature. Herein, an oligomeric polyethylene glycol methyl ether methacrylate (PEGMEM)-modified silica-coated polyimide fibrous scaffold (PINF@PEGMEM-SiO₂) was introduced in polyethylene glycol dimethyl ether (PEGDME) to enhance the Li-ion transportation at room temperature. PINF@PEGMEM-SiO₂ was developed to build a continuous and interconnected interface for continuous Li-ion transportation in bulk. The carbonyl groups (C═O) of PEGMEM on SiO₂ can promote the dissociation of lithium salts and enhance the migration of free Li ions at the interface. The same -C-C-O- unit contained in both PEGMEM and PEGDME ensures the compatibility of PEGMEM at the interface and PEGDME in the bulk. The prepared PEGDME-based polymer electrolyte exhibits a high ionic conductivity of 1.14 × 10^-4 S cm^-1 at 25 °C and an improved Li-ion transference number of 0.41. Furthermore, LiFePO₄/Li and LiNi_0.8Co_0.1Mn_0.1O₂/Li cells with excellent cyclability and rate capability at ambient temperature are obtained.