Flame-retardant reinforced halloysite nanotubes as multi-functional fillers for PEO-based polymer electrolytes

High ionic conductivity, fire safety, and broad electrochemical windows are crucial considerations for the next generation of solid polymer electrolytes (SPEs) employed in solid-state lithium-ion batteries. Based on these factors, we design a novel nanohybrid filler by loading a phosphazene-based flame retardant into halloysite nanotubes (HNT@FPPN). A 36 % reduction in the peak heat release rate (pHRR) confirms the enhanced fire safety of poly(ethylene oxide) (PEO)-based PEO-5HNT@FPPN SPE. Besides, the PEO-5HNT@FPPN electrolyte exhibits an enhanced ionic conductivity of 1.82 × 10-4 S cm−1 at 45 °C. The improved ionic conductivity is attributed to the plasticization effect of nanohybrids, which reduces the crystallinity and aids the motion of PEO chains. After 100 cycles, the as-fabricated Li/PEO-5HNT@FPPN/LiFePO4 cell shows stable cycling at 0.1C with a specific discharge capacity of 145 mAh/g. These findings demonstrate the unique properties of modified PEO SPEs, which may open new pathways for designing safer electrolytes.