Flame-retardant polybenzimidazole-based composite separator for enhanced high-temperature performance and fire safety of lithium-ion batteries

Abstract

The non-uniform pore size distribution and high flammability of commercial separators pose significant challenges to the safe application of high-energy-density lithium-ion batteries. In this study, a flame-retardant composite separator (P@HLi) with high thermal stability was successfully developed, which not only suppressed lithium dendrite growth but also improved high-temperature cycling performance of batteries and significantly enhanced their thermal safety. Li//Li symmetric batteries equipped with P@HLi-20 separators demonstrated stable cycling for over 600 h at a low polarization potential (approximately 50 mV), effectively reducing the formation of “dead lithium” and lithium dendrites. The LFP//Li and NCM811//Li cells with P@HLi-20 separators delivered initial discharge specific capacities of 142.0 and 167.9 mAh/g, respectively. Notably, the LFP//Li battery with P@HLi-20 separator showed excellent high-temperature cycling performance, maintaining 98.0% capacity retention and a discharge capacity of 131.1 mAh/g after 100 cycles at 1 C at 90 °C. Furthermore, pouch cells assembled with P@HLi-20 separators exhibited reductions of 52.67% in peak heat release rate (PHRR) and 68.42% in total heat release (THR) compared to those using Celgard separators, demonstrating superior thermal safety. These results confirm that the P@HLi separator offers comprehensive improvements in both electrochemical performance and safety characteristics.

Graphical abstract

Keywords

poly(arylene ether benzimidazole) / fire safety / flame retardant / lithium-ion batteries / high-temperature performance

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