Flame-retardant ethylene carbonate-less electrolytes for mitigating combustible gas evolution in LiFePO4 pouch cells

Safety concerns of lithium iron phosphate (LiFePO₄) batteries primarily stem from flammable gas generation, posing explosion risks in energy storage applications. Distinct from layered oxide cathodes, the olivine-structured LiFePO₄ exhibits minimal electrolyte oxidation. The dominant thermal reactions occur at the lithiated anode, where conventional ethylene carbonate (EC)-based electrolytes undergo reductive decomposition, generating substantial combustible gases while contributing to thermal accumulation. Herein, we developed a flame-retardant EC-less electrolyte (FR-EC-less) with a dual-salt formulation, designed to mitigate exothermic reactions and gas generation at the anode-electrolyte interface, thus significantly enhancing the thermal stability of LiFePO 4 batteries. This FR-EC-less electrolyte, formulated with 10 wt% EC and 0.8 M lithium hexafluorophosphate (LiPF 6 ) and 0.4 M lithium bis(fluorosulfonyl)imide (LiFSI). The FR-EC-less exhibits an initial capacity of 5.453 Ah, retaining 89.7 % capacity after 2300 cycles, significantly outperforming conventional electrolytes (86.4 %). Material-level thermal analysis indicates that FR-EC-less markedly reduces heat generation to −126.2 J/g, with conventional sample exhibiting −200.5 J/g. Further validation in a 10 Ah LiFePO 4 pouch cell demonstrated a 38.5 % reduction in total gas generation relative to the conventional electrolyte, alongside a 41.0 % decrease in combustible gas evolution. This study identifies a promising electrolyte design that balances thermal stability and cycle durability, enhancing the safety performance of LiFePO 4 batteries.