LiMn0.5Fe0.5PO4 solid solution materials synthesized by rheological phase reaction and their excellent electrochemical performances as cathode of lithium ion battery

Carbon coated LiMn0.5Fe0.5PO4 solid solution materials (LiMn0.5Fe0.5PO4/C) are synthesized by rheological phase reaction with stearic acid as carbon source, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET and TG/DTG. The results show that well-crystallized olivine structure LiMn0.5Fe0.5PO4 nanoplatelets with no obvious impurity phase are obtained. The as-synthesized materials are served as cathode of lithium ion battery and investigated by galvanostatic charge/discharge tests. The results demonstrate that, in comparison with the LMFP materials of different Mn:Fe ratio (LiMn0.2Fe0.8PO4/C and LiMn0.8Fe0.2PO4/C) synthesized by the same route of rheological phase reaction, the LiMn0.5Fe0.5PO4/C exhibit excellent rate specific capability, and can deliver discharge capacity of 138, 99, 80, 72, 67 and 55 mAh g(-1) at respectively 0.1, 1, 5, 10, 15 and 20C rates. Moreover, the electrode possesses good cycle stability. A specific capacity of 100 mAh g(-1) at 1C after 300 cycles of charge-discharge at room temperature is reached, which represents 95% of capacity retention. The significantly improved electrochemical performances of the LiMn0.5Fe0.5PO4/C cathode are attributed to the uniformly distributed particles and the enhancement of conductivity that is originated from the surface coating of carbon on primary particles. (c) 2013 Elsevier B.V. All rights reserved.