Multi-stage closed-loop regeneration of spent lithium iron phosphate cathodes via high-pressure oxidative leaching

Abstract

Due to their high safety and long cycle life, lithium iron phosphate (LFP) batteries are widely adopted in electric vehicles and energy storage systems. As the first generation of power batteries reaches their end-of-life, the development of efficient and environmentally friendly recycling technologies has become an imminent need. A method of green leaching and regeneration of spent lithium iron phosphate is proposed. In this work, the high-pressure oxidation leaching of iron phosphate residue, acid solubilization, synthesis, aging, and calcination were conducted to regenerate iron phosphate. Simultaneously, the pure lithium solution obtained in the preceding step was precipitated to obtain high-purity lithium carbonate. Subsequently, the recovered iron phosphate was synthesised with lithium carbonate to obtain regenerated lithium iron phosphate, whose physical and chemical properties comply with the Chinese standard (YS/T 582–2013). The initial specific capacity of the coin cell assembled with recycled lithium iron phosphate was 132.2 mAh/g at 1C, and the specific capacity remaine 53.0 mAh/g after 1000 cycles, corresponding to a capacity retention rate of 40.0 %, which is consistent with the performance of commercial lithium iron phosphate. When assembling soft pack batteries with recycled lithium iron phosphate as the cathode, the batteries have passed safety performance tests such as nail penetration, extrusion, and short circuit, demonstrating good safety performance. The corresponding all-solid-state battery performance is also comparable to that of commercial lithium iron phosphate. This approach will be conducive to arge-scale recycling of spent batteries in the future.