Solution combustion synthesis and electrochemical properties of yttrium-doped LiMnPO4/C cathode materials for lithium ion batteries

Phospho-olivine pristine LiMnPO4/C and yttrium-substituted LiMn1–xYxPO4/C (x = 0, 0.01, 0.03, 0.05) were synthesized by a solution combustion method. The effects of Y-doped on structure, morphology and electrochemical performances were investigated. From powder X-ray diffraction pattern, all substituted materials adopt an identical structure to that of the LiMnPO4 olivine structure, suggesting that the yttrium ion was well incorporated into the crystal lattice, without any changes in the host crystal structure. The electrochemical impedance spectroscopy provides clearly that yttrium-substituting reduces the charge transfer impedance and improves the lithium ion diffusion through the structure. When x = 0.01, the material shows an excellent capacity and stability during charge/discharge process. The initial specific discharge capacity can reach up to 156.84 mAh/g at C/20, with a coulombic efficiency of about 96.11%, which is 14% higher than that of the pristine material. The results confirm that the cyclic stability and the electrochemical performances of LiMnPO4/C are highly improved by Y-doping.