Abstract
An olivine-structured solid solution, LiFe0.4Mn0.4Co0.2PO4/C nanocomposite, was synthesized as cathode materials for Li-ion batteries by the coprecipitation-and-milling method using stearic acid as the carbon source. Thus-formed LiFe0.4Mn0.4Co0.2PO4/C solid solution was well confirmed and characterized by various techniques such as SEM, TEM and XRD. The LiFe0.4Mn0.4Co0.2PO4/C-based cathode delivered an initial discharge capacity of 163.3 mAh g−1 at 0.1 C, together with a capacity retention rate of 86.6% after 50 cycles in the potential range of 2.5–5 V. Even at 1 C, a discharge capacity of 104.7 mAh g−1 was maintained after 100 cycles. The good electrochemical performance of the LiFe0.4Mn0.4Co0.2PO4/C could be attributed to the homogeneous mixing of Fe, Mn and Co elements in relevant precursor solid solution Fe0.4Mn0.4Co0.2C2O4·2H2O. Its characteristic CV profiles reveal three pairs of anodic/cathode peaks which could be assigned to the redox reactions of Co3+/Co2+, Mn3+/Mn2+ and Fe3+/Fe2+ with potential plateaus at about 4.7 V, 4.1 V and 3.5 V in the charge/discharge curves, respectively. Our study demonstrates that the LiFe0.4Mn0.4Co0.2PO4/C is a promising cathode material of Li-ion battery and the coprecipitation-and-milling method represents a workable strategy towards the synthesis of high-performance phosphate-type composite cathode.