Solvothermal synthesis of LiCo_(1-x)Mn_xPO4/C cathode materials for lithium-ion batteries

摘要

LiCo_(1-x)Mn_xPO4/C cathode materials are selectively synthesized by a solvothermal method in ethylene glycol solvent using glucose, LiCl, H3PO4, MnCl2·4H2O, and Co(NO3)2·6H2O as precursors. The obtained samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) and the electrochemical performances are also evaluated using a LAND CT2001A battery test system at room temperature. XRD result demonstrates the formation of LiCo_(1-x)Mn_xPO4 solid solution and the enlarged channels are benefit for Li~+ migration. SEM graph indicates that the particle size of LiCo_(0.5)Mn_(0.5)PO4/C is about several hundred nanometers and aggregates to large particles located in the range of 2-3 μm. TEM image illustrates that the core/ shell-structured LiCo_(0.5)Mn_(0.5)PO4/C solid solution is indeed obtained by this method. The high specific surface area (35 m~2/g) of LiCo_(0.5)Mn_(0.5)PO4/C could make this solid solution contact with the electrolyte more sufficiently and benefit for Li~+ transportation. The capacity, flat voltage, and cyclical stability of LiCo_(1-x)Mn_xPO4/C are improved compared to LiMnPO4 and LiCoPO4 due to the improved electronic conductivity and lithium-ion conductivity which resulted from carbon coating and foreign element incorporation.