Effect of Nb⁵⁺ Doping on the Structure and Electrochemical Performances of LiFePO₄

Nb-doped Li_xNb_0.005Fe_yPO₄/C cathode material for lithium-ion batteries were prepared by two-fluid spray-drying using FePO₄·2H₂O, LiOH·H₂O, C₆H₁₂O₆(glucose) as raw materials under N₂ atmosphere. The effects of doping Nb⁵⁺ on the structure, morphology and electrochemical performances of LiFePO₄ were investigated. The results show that Li_xNb^0.005Fe_yPO₄/C has Olivine Structure and pure phase. The Li_xNb_0.005Fe_yPO₄/C had an initial discharge specific capacity of 158.5mAh/g at 0.1C and its specific capacities were 109mAh/g at 5C. The initial charge/discharge efficiency reached 93.9%. The discharge specific capacity of the Li_xNb_0.005Fe_yPO₄/C at 253K is 82.2mAh/g. This investigation suggests that the Nb⁵⁺ doped material possess high rate capability and excellent low temperature electrochemical performance. (paper)