Enhanced carbon-coating performance of LiMn0.8Fe0.2PO4/C via solvothermal method by adding of graphene

The high energy density graphene-LiMn0.8Fe0.2PO4/C(graphene-LMFP/C) composite material with ordered olivine structure was synthesized in 5:3(v/v) ethylene glycol-water mixed solvent in the presence of ascorbic acid/glucose as the reducing agent at 240 °C for 4 h. The crystalline structure, morphology, micro-structure and particle size were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Its electrochemical properties were also studied. Because of the addition of graphene, the material exhibits high discharge capacity, good rate performance and high cycling stability. It delivers an initial discharge capacity of 160 mAh g−1 at 0.05C, which is 94.2% of the theoretical value of 170 mAh g−1. It also delivers excellent rate property, achieving a discharge capacity of 156, 123 and 106 mAh g−1 at 0.1C, 5C and 10C at 25 °C. Moreover, it has good cycling stability, it retains 92.9% of the initial capacity over 80 cycles at 1C, which are comparable to carbon-coated LiMn0.8Fe0.2PO4/C (LMFP/C). The better cycling stability of graphene-LMFP/C is believed to be associated with the using of graphene.