In-situ curing poly(N,N'-Methylenebisacrylamide)-based composite electrolyte reinforced with high-strength glass fiber skeleton for solid state lithium ion batteries

Polymer solid-state electrolytes have been extensively studied for their favorable flexibility, ease of processing, and good interfacial contact. However, the low ionic conductivity, narrow electrochemical window and poor mechanical properties restrict their practical application. Here, a novel poly(N,N'-Methylenebisacrylamide) (PMBA)-based composite electrolyte reinforced with high-strength glass fiber (GF) skeleton is fabricated via in-situ polymerization. Due to the high electrolyte uptake of PMBA network and the strong interaction between the amide units and other components in the electrolyte, it displays high ionic conductivity (1.53 mS cm⁻¹) and lithium-ion transference number (0.74) at ambient temperature, respectively. The synergistic effect of the polymer network and GF skeleton endows the electrolyte with excellent mechanical properties (2.05 GPa), thermal stability, and flame-retardant characteristics. Furthermore, the electrolyte exhibits favorable interface compatibility with the anode and cathode. The Li||Li symmetrical cell exhibits excellent Li plating/stripping reversibility for over 1200 h at 0.1 mA cm⁻². The LFP||Li exhibit high discharge capacity of 138.5 mAh/g at 1C. Noteworthy, the LFP|DEE@PMBA-GF|Li cell demonstrates outstanding cycling stability with 83.7 % capacity retention after 600 cycles at 1C and 99.89 % average Coulombic efficiency. Additionally, the LFP|DEE@PMBA-GF|graphite pouch cell with high cathode mass loading (∼12 mg cm⁻²) demonstrates satisfactory safety and electrochemical performance.