Mechano-chemical Synthesis Of LiFePO₄/C Cathode Material And Its Modification

Itensive research and development work is being conducted to further improve the performance of lithum ion batteries and reduce the cost of electrode material.The synthesis and modification of LiFePO₄/C were studied by mechanical alloying (MA) process in details.The effects of synthetic parameters of ball-milling time, ball-to-powder ratio, calcining temperature, calcining time and the carborn content on the electrochemical properties of LiFePO₄/C were studied. when the ball-milling time, ball-to-powder ratio, calcining temperature, calcining time and the carborn content were 6h, 7:1, 700℃, 8h and 8%, respectively, LiFePO₄/C showed the best properties. At 0.1C rate, its discharge capacity was 113mAh g?1 and maintained about 96% capacity after cycled 10 times. The effects of fluorine substitution together with manganese doping on the structural and electrochemical properties of LiFe0.8Mn0.2PO4/C cathode materials were studied. XRD analyses indicate that F-substitution did not alter the crystal structure of LiMn0.2Fe0.8PO4 phase. Rietveld refinement of XRD patterns of the synthesized materials showed that lattice parameters decreased with increasing fluorine content. The results of electrochemical measurement show that F-substitution can improve the electrochemical properties of LiFePO₄/C and Mn-doping can improve the average working voltage. LiFe0.8Mn0.2(PO4)0.9F0.3/C exhibited the best electrochemical properties. At 0.1C rate, its discharge capacity was 128.3mAh g^-1. The LiFe_0.8Mn_0.2(PO₄)_0.9F_0.3/C sample also showed the minimum polarization.