3D hierarchical fireproof gel polymer electrolyte towards high-performance and comprehensive safety lithium-ion batteries

Abstract

Gel polymer electrolyte (GPE) stands as an extensively investigated solid-state electrolytes for next-generation lithium-ion batteries (LIBs). Nonetheless, their inherent flammability necessitates the addition of flame retardants, which adversely impact LIBs’ electrochemical performance. Herein, we propose a groundbreaking conceive of a fireproof cross-linking composite GPE that united phosphene and a P-N synergistic flame retardant (DPM), equipping a dual-enhanced conduction effect on Li+ ions and a cooperative P-N flame-retardant effect. By strategically manipulating the polymer segments hierarchy and incorporating efficient function groups from DPM, freely Li+ mobility has been propelled, thereby delivering satisfactory ionic conductivity (1.263 mS cm−1, 20 ℃), elevated oxidative stability (5.42 V vs. Li+/Li) and improved Li+ transference number (0.53). The composite GPE-based batteries (LFP||Li, NCM523||Li and LFP||Graphite) indicate acceptable specific capacities at 1 C, together with good reversible capacity retention rate and stable coulombic efficiency after 200 cycles. Noticeably, the pouch cells (LFP||Graphite) assembled with composite GPE demonstrate superior safety robustness and fire-resistance under mechanical mishandling and ignition situations. Finally, the elucidation of Li+ ions interaction mechanism with polymer matrix is unraveled through molecular orbital energy levels and density function theory (DFT) calculation. This study offers valuable insights for harnessing novel electrolyte materials in high-safety LIBs.