Trifunctional Copper-Substitution in LiMn<sub>0.6</sub>Fe<sub>0.4</sub>PO<sub>4</sub> Nanocrystal for Enhanced Lithium Storage
Junjie Han, Jianhui Zhu, Xuanlong He, Ming Yang, Chenxi Yan, Dingtao Ma, Lipeng Zhang, Peixin Zhang
Abstract
LiMn 0.6 Fe 0.4 PO 4 is limited in practical applications due to its low electronic conductivity and slow Li + diffusion rate. Therefore, Cu doping was applied to modify LiMn 0.6 Fe 0.4 PO 4, and the mechanism of Cu 2+ “three-function” synergistic enhancement of the cathode material performance was explored. Compared to the undoped sample (LMFP), the Cu-doped sample (LMFP-Cu 1%) exhibited significantly improved electronic conductivity and Li + diffusion coefficient. First-principles calculations also confirmed the high electronic conductivity and low Li + diffusion barrier of LiMn 0.6 Fe 0.4 PO 4 @C. Additionally, LiMn 0.6 Fe 0.39 Cu 0.01 PO 4 @C demonstrated excellent rate performance and cycling stability, with discharge capacities of 160.3 mA h g –1 and 121.2 mA h g –1 at 0.1 and 2C rates, respectively. After 200 cycles at 1C rate, the capacity retention was 92.5%. The first principle calculation of DFT can help to show that the introduction of Cu can effectively reduce the diffusion barrier and intrinsic conductivity of Li +, in situ XRD analysis revealed that LiMn 0.6 Fe 0.39 Cu 0.01 PO 4 @C exhibited good structural stability and reversibility. The incorporation of Cu 2+ represents a promising approach to improving the lithium storage capabilities of LiMn 0.6 Fe 0.4 PO 4 cathode materials.