Synergistic Effects of Plasticizer and 3D Framework toward High-Performance Solid Polymer Electrolyte for Room-Temperature Solid-State Lithium Batteries

TLDR

Solid polymer electrolytes can alleviate safety issues in commercial lithium ion batteries, but their low room‑temperature ionic conductivity and poor mechanical properties limit practical use. The study proposes a composite solid polymer electrolyte comprising PEO, the plasticizer succinonitrile, and a 3D glass fiber framework to enhance conductivity and mechanical strength. The composite, PEO–SN25–LiTFSI10–GF, is fabricated by integrating 25 wt % succinonitrile and a glass fiber network into the PEO matrix, yielding high ionic conductivity and mechanical robustness. The optimized electrolyte achieves 2.85 × 10⁻⁴ S cm⁻¹ conductivity, a 5.5 V electrochemical window, >8 MPa tensile strength, and delivers a LiFePO₄ cell with 98.5 % capacity retention after 100 cycles at 0.2 C at room temperature.

Abstract

Solid polymer electrolytes (SPEs) can alleviate the safety issues existing in commercialized lithium ion batteries with liquid electrolyte. However, the low room-temperature ionic conductivity and poor mechanical properties of current polymer electrolyte hinder its practical applications. Herein, a composite solid polymer electrolyte consisting of poly(ethylene oxide) (PEO), the solid plasticizer succinonitrile (SN), and a 3D framework glass fiber (GF) with high ionic conductivity and good mechanical property is proposed. The optimized composite electrolyte PEO–SN25–LiTFSI10–GF has a room-temperature ionic conductivity of 2.85 × 10–4 S cm–1, which is 100 times higher than that of pristine PEO. An electrochemical window up to 5.5 V and a tensile strength of over 8 MPa are also exhibited by the optimized composite electrolyte. The solid-state LiFePO4/PEO–SN25–LiTFSI10–GF/Li battery shows good cyclic performance with a capacity retention of 98.5% after 100 cycles at 0.2 C under room temperature, demonstrating a promising polymer composite electrolyte for the next-generation solid-state lithium batteries with high energy density and high safety.