Direct regeneration of spent LiFePO4 cathode material via a simple solid-phase method

Abstract

For realizing the goals of “carbon peak” and “carbon neutrality”, lithium-ion batteries (LIB) with LiFePO₄ as the cathode material have been widely applied. However, this has also led to a large number of spent lithium-ion batteries, and the safe disposal of spent lithium-ion batteries is an urgent issue. Currently, the main reason for the capacity decay of LiFePO₄ materials is the Li deficiency and the formation of the Fe³⁺ phase. In order to address this issue, we performed high-temperature calcination of the discarded lithium iron phosphate cathode material in a carbon dioxide environment to reduce or partially remove the carbon coating on its surface. Subsequently, mechanical grinding was conducted to ensure thorough mixing of the lithium source with the discarded lithium iron phosphate. The reaction between CO₂ and the carbon coating produced a reducing atmosphere, reducing Fe³⁺ to Fe²⁺ and thereby reducing the content of Fe³⁺. The Fe³⁺ content in the repaired LiFePO₄ material is reduced. The crystal structure of spent LiFePO₄ cathode materials was repaired more completely compare with the traditional pretreatment method, and the repaired LiFePO₄ material shows good electrochemical performance and cycling stability. Under 0.1 C conditions, the initial capacity can reach 149.1 mAh/g. It can be reintroduced for commercial use.