Effect of Cu impurity on the electrochemical performance of regenerated LiFePO4/C electrode materials

The electrochemical property of lithium-ion batteries (LIBs) is partly determined by the electrode materials. Although enormous researches focus on improving conductivity and structural stability of materials, less attention has been paid to the effect of the impurities in materials such as Copper in LiFePO4/C. In this work, the effect of Copper impurities in regenerated LiFePO4/C on the performance of batteries is studied. Batteries with mixture of materials such as Copper impurity and commercial LiFePO4/C (Cu-LFP) are used in this study. Results indicate that the mixture of materials showed worse electrochemical properties such as lower specific capacity and cyclic stability (especially for 0.68%Cu-LFP, discharge specific capacity was 8.94 mAh g(-1) at 0.1C after 5th cycle), higher median voltage (MV), and DC internal resistance (DCIR) during discharging. Then, Recycled Cu-LFP from spent Cu-LFP batteries were regenerated. It is found that regenerated Cu-LFP has a better electrochemical property apart from self-discharge. Regenerated 0.3%Cu-LFP delivered a capacity of 148.33 mAh g(-1) at rate of 0.1C and maintains 131.33 mAh g(-1) with a high-capacity retention rate of 94.43% at 1C after 150 cycles. Even as cathode materials of 18,650 batteries, the specific capacity was 124.25 mAh g(-1), and 85.99% of its initial capacity was retained over 2000 cycles, which is considered as electrode material of the energy storage devices. This study can provide new guidelines for recycled and reused spent cathode materials containing impurities.