Trifunctional Copper-Substitution in LiMn_0.6Fe_0.4PO₄ Nanocrystal for Enhanced Lithium Storage

LiMn_0.6Fe_0.4PO₄ is limited in practical applications due to its low electronic conductivity and slow Li⁺ diffusion rate. Therefore, Cu doping was applied to modify LiMn_0.6Fe_0.4PO₄, and the mechanism of Cu²⁺ "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_0.6Fe_0.4PO₄@C. Additionally, LiMn_0.6Fe_0.39Cu_0.01PO₄@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_0.6Fe_0.39Cu_0.01PO₄@C exhibited good structural stability and reversibility. The incorporation of Cu²⁺ represents a promising approach to improving the lithium storage capabilities of LiMn_0.6Fe_0.4PO₄ cathode materials.