Using green deep eutectic solvents for targeted regeneration to improve the cycle life of spent lithium iron phosphate batteries

Abstract

The rapid growth of lithium iron phosphate (LFP) batteries in electric vehicles and energy storage systems necessitates the development of sustainable and efficient recycling strategies to address impending end-of-life management challenges. Conventional pyrometallurgical and hydrometallurgical methods are often suffered from high energy consumption, environmental pollution, and economic inefficiency. In this study, a green deep eutectic solvent (DES) system, which was composed of lithium chloride, urea, and ascorbic acid, was developed for the direct regeneration of degraded LFP cathodes. Through integrated experimental and theoretical approaches, the regeneration mechanism was elucidated, wherein a reductive environment was provided for the conversion of Fe3+ to Fe2+, and highly efficient Li+ replenishment into vacant sites was achieved. The regenerated cathode material was shown to exhibit a high specific capacity of 163.5 mA h/g at 0.1C and excellent cycling stability, with 92.6% capacity retention after 300 cycles at 1C. With significantly reduced energy consumption and economic cost compared to conventional hydrometallurgical and pyrometallurgical routes, this DES-based regeneration method represented a highly promising and sustainable pathway for the resource recovery from spent lithium-ion batteries.