Salt Anion Chemistry Enables High Performance LiFePO 4 /Graphite Batteries Under Extremely Elevated Temperatures

ABSTRACT LiFePO 4 /Graphite (LFP/Gr) batteries have been dominantly used in electric vehicles and stationary energy storage systems. However, they suffer from significant performance degradation under elevated temperatures, primarily due to the use of the dominant salt, LiPF 6 , which is prone to thermal decomposition or hydrolysis to form acidic species (e.g., HF), thereby inducing iron dissolution and accelerating lithium inventory loss and capacity decay. Here, we report a thermally and hydrolytically stable lithium borate salt, namely lithium difluoro(1,2‐dihydroxyethane‐1,1,2,2‐tetracarbonitrile) borate (LiDFTCB), to address above issues. The DFTCB − anion features cyano groups with lone‐pair electrons that coordinate with H + and Fe 3+ /Fe 2+ , effectively mitigating HF‐induced damage to LFP cathode and suppressing Fe 3+ /Fe 2+ dissolution. Additionally, LiDFTCB forms compact and conductive interphases enriched with LiF and Li 3 N, synergistically stabilizing electrode/electrolyte interphases and enhancing Li + transport kinetics. Furthermore, the LiDFTCB‐based cell exhibits improved thermal stability with lower heat release and temperature increase rate. Consequently, the 1.7 Ah pouch cells with LiDFTCB show superior cycling performance, achieving 1643 cycles (vs. 669 cycles for LiPF 6 ) with 80% capacity retention at 55°C, and 100 cycles with 89% capacity retention at 100°C. This work highlights the pivotal role of anion chemistry in improving cycling performance under elevated temperatures.