Preparation and Electrochemical Properties of Homogeneous Carbon-Coated LiFe0.9Mn0.1PO4 as Cathode Material for Lithium-Ion Batteries

Homogeneous carbon-coated LiFe0.9Mn0.1PO4 cathode material was synthesized by one-step solid-state reaction using glucose as carbon source. Powder X-ray diffractometry (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic measurements were employed to characterize the samples. Mn-doping and carbon co-modification did not affect the olivine structure of LiFePO4, but improved its kinetics in terms of capacity delivery, polarization and rate capability. When compared with the undoped LiFePO4/C, the LiFe0.9Mn0.1PO4/C sample presented good size distribution - around 100-200 nm - and better electrochemical performance. At current rates of 0.1, 1.0, 3.0 and 10.0C (C = 170 mA g(-1)), the LiFe0.9Mn0.1PO4/C electrode delivered discharge capacities of 154.1, 138.8, 120.0 and 94.0 mA h g(-1), respectively. Results obtained by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated that the polarization and charge transfer resistance of the sample were greatly decreased by Mn-doping.