Failure characteristics and efficient binder removal from spent LiFePO₄ cathodes for recycling

With the rapid development of new energy vehicles and energy storage industry, lithium iron phosphate (LiFePO₄) batteries are widely used due to their advantages of low cost, high safety, and long cycle life, and their failure analysis and recycling after decommissioning have significant economic and environmental benefits. This paper systematically analyzes the failure characteristics of three different failure types of lithium iron phosphate battery cathode (normal aging, N-LFP; performance diving, D-LFP; and swelling, S-LFP), and compares the effects of two pretreatment methods, argon-air thermal processing and N-methylpyrrolidone (NMP) soaking, on the spent cathodes. The results show that all three kinds of LFP electrodes have irreversible phase transitions (LiFePO₄ →Li 1-x FePO₄) caused by active lithium deficiency, with the most serious lithium deficiency in the D-LFP material, and severe destruction of the carbon coating in the S-LFP material, which is covered with more electrolyte decomposition products. The NMP immersion treatment effectively removes the binder, maintains the structural integrity of the material, providing a better basis for significantly improving the electrochemical properties and subsequent solid-phase repair processes.