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

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. In this paper, starting from the failure mechanism of discarded lithium iron phosphate cathode materials, the repair mechanism of lithium iron phosphate cathode materials is explained by using the principle that CO2 can thin or partially remove the carbon coating, and according to the comparison of electrochemical performance, it can be seen that the discarded lithium iron phosphate cathode materials are successfully repaired. This provides an effective low-energy pathway for the recycling of lithium iron phosphate cathode materials. [Display omitted]