Synthesis Of LiFePO₄Cathode Material By A Rotor-Stator Reacotor And Ni²⁺、Mn²⁺ Doping Modification

In order to improve the charge/discharge, cycling performance and high temperature behaviour of LiFePO4material, precursors of LiFePO4material were prepared by co-precipitation in a rotor-stator reactor, and carbon coating followed by calcining at700℃for8h, the LiFePO4/C material was synthesised. Different process conditions were studied and the optium condition was finally determined. The Mn2+, Ni2+doping modification of LiFePO4material were also studied, LiFe1-xMnxPO4/C(x=0.0,0.1,0.2,0.3) and LiFe1-xNixPO4/C(x=0.00,0.03,0.05,0.07) materials were prepared, too. Compare two series of materials on the electrochemical performance, it could be discovered that LiFe0.95Ni0.05P04/C material owns the best electrochemical performance and high temperature behaviour at0.1C under50℃, the first discharge capacity was158.2mAh·g-1, after100cycles, the capacity retention was94.2%. Even at5C under25℃, it still has good electrochemical performance, the first discharge capacity was116.2mAh·g-1, after100cycles, the capacity retention was82.3%.1. The effects of reaction temperature, flow rate of LiOH, pH of solution, rotation speed of the rotor-stator and reaction time on the phase of LiFePO4/C material were investigated. At last, the optium reaction condition were confirmed:reaction temperature was50℃, flow rate of LiOH was8mL·min-1, pH of the solution was9, rotation speed of the rotor-stator was2000r·min-and reaction time was2h.2. The electrochemical performance of LiFe0.8Mn0.2P04/C and LiFe0.95Ni0.05PO4/C materials were tested by Land CT2001A at25℃,50℃respectively. It shows that two materials both have good charge/discharge and cycle performance under25℃at0.1C and5C, the first discharge capacity of LiFe0.8Mn0.2PO4/C material were153.2and115.3mAh·g-1, respectively, after100cycles, the capacity retention was95.4%and80.4%. The first discharge capacity of LiFe0.95Ni0.05PO4/C material at0.1C and5C were155.7,116.2mAh·g-1, respectively. After100cycles, the capacity retention was96.5%and82.3%. Two materials also have good electrochemical performance and high temperature behaviour under50℃at0.1C, the first discharge capacity of two materials were156.4,158.2mAh·g-1, respectively. After100cycles, the capacity retention was93.8%and94.2%. It also shows that LiFe0.8Mn0.2PO4/C and LiFe0.95Ni0.05PO4/C materials could have good high temperature behaviour.