Ivy-like electrospun block copolymer fibers supported polymer solid electrolytes with wide electrochemical stability window for all-solid-state Li-metal battery

Abstract

All-solid-state lithium metal batteries (ASSLMBs) are considered as next-generation energy storage devices due to their high specific energy density and safety, and solid polymer electrolytes (SPEs) are an important component of ASSLMBs. Poly(ethylene oxide) (PEO) is the most prevalent matrix of SPE but is criticized for its poor mechanical properties and a narrow electrochemical stability window. To address this issue, poly(vinylidene fluoride)-b-poly(poly(ethylene glycol) methyl ether methacrylate (PVDF-b-PPEGMA) copolymer fibers with an ivy-like morphology were prepared by electrospinning and used to support PEO/lithium salt electrolytes. The electrospun PVDF-b-PPEGMA copolymer fiber membrane provides an uncial hierarchical structure with large pore size, good compatibility and adhesion with PEO due to side ethylene oxide units in the PPEGMA segment. The ivy-like fibers supported SPE exhibited good thermal stability and high mechanical strength. Furthermore, ASSLMBs assembled using the above SPE, LiFePO₄ cathode, and lithium metal anode possessed a wide electrochemical stable window (5.58 V vs. Li/Li⁺) and good initial discharge capabilities at 60 °C.