A lithiated organic nanofiber-reinforced composite polymer electrolyte enabling Li-ion conduction highways for solid-state lithium metal batteries

Abstract

Solid polymer electrolytes (SPEs) with good flexibility and low cost are very promising for all-solid-state lithium metal batteries, but they suffer from the trade-off between ionic conductivity at room temperature and mechanical stability. Herein, a robust composite polymer electrolyte is prepared by thermal lamination of PEO polymer electrolyte films onto a lithiated organic nanofiber membrane (LOF), which could combine the merits of 3D Li-ion conduction highways for high ionic conductivity and nanofiber-reinforced networks for good mechanical properties. The intimate combination between the nanofibers and the PEO matrix endows the LOF-reinforced PEO composite (LOF-CPE) with homogeneous structure, leading to an enhanced ultimate tensile stress of 8.9 MPa. Furthermore, the introduction of the LOF significantly decreases the crystallinity of the polymer matrix, which accelerates polymer segmental motion. The well-designed LOF also constructs an interfacial percolation network with additional active Li⁺, resulting in the formation of high-speed Li-ion conduction pathways. Therefore, the as-prepared LOF-CPE delivers an excellent ionic conductivity of 7.41 × 10⁻⁵ S cm⁻¹ at 30 °C. While used as a SPE in LiFePO₄|Li solid-state batteries, the batteries exhibit good cyclability with a capacity retention of 82% after 500 cycles under 0.5C. This work provides a very promising strategy for solid polymer electrolytes to simultaneously achieve high ionic conductivity and excellent mechanical properties towards high-performance solid-state lithium metal batteries.