Electrochemical behavior of Mg-doped 7LiFePO4–Li3V2(PO4)3 composite cathode material for lithium-ion batteries

Mg-doping effects on the electrochemical property of LiFePO 4 –Li 3 V 2 (PO 4 ) 3 composite materials, a mutual-doping system, are investigated. X-ray diffraction study indicates that Mg doping decreases the cell volume of LiFePO 4 in the composite. The cyclic voltammograms reveal that the reversibility of the electrode reaction and the diffusion of lithium ion is enhanced by Mg doping. Mg doping also improves the conductivity and rate capacity of 7LiFePO 4 –Li 3 V 2 (PO 4 ) 3 composite material and decreases the polarization of the electrode reaction. The discharge capacity of the Mg-doped composite was 93 mAh g −1 at the current density of 1,500 mA g −1 , and Mg-doped composite has better discharge performance than the original 7LiFePO 4 –Li 3 V 2 (PO 4 ) 3 composite at low temperature, too. At −30 °C, the discharge capacity of Mg-doped LFVP is 89 mAh g −1 , higher than that of the original composite. Electrochemical impedance spectroscopy study shows that Mg 2+ doping could enhance the electrochemical activity of 7LiFePO 4 –Li 3 V 2 (PO 4 ) 3 composite. Mg doping has a positive influence on the electrochemical performance of the LiFePO 4 –Li 3 V 2 (PO 4 ) 3 composite material.