Preparation and electrochemical properties of LiMn1−xFexPO4/C composite cathode materials for lithium ion batteries

Carbon-coated LiMn1−xFexPO4/C (x=0, 0.1, 0.3, 0.5) nanoparticles have been synthesized by a two-step sol–gel method. The materials show good crystallinity and a uniform grain size of about 100 nm. The LiMn1−xFexPO4/C composites deliver the best initial specific discharge capacities of 160 mA h g−1 at 0.05 C for x=0.3, LiMn0.7Fe0.3PO4/C retained 157 mA h g−1 (97.8%) after 40 cycles, demonstrating excellent cyclability. Results suggest that the improved cycling stability of the doped composites results from mitigated Mn2+ dissolution due to Fe2+ substitution. Impedance measurements reveal the Rct and Ws impedance of the doped composites to be much lower than the non-doped samples.