The effects of carbon nanotubes on the electrochemical performance of LiFePO4 composite cathode materials for Li-ion batteries

The multi-walled carbon nanotubes (MWNTs) have been added into LiFePO₄ as composite electrodes of lithium battery by ball milling. The charge-discharge capacity, cyclic voltammetry, cycle life, alternating current impedance and discharge temperatures characteristic are investigated. It´s found that adding carbon nanotubes is advantageous to enhance the electrochemical performance of the LiFePO₄ electrodes as a whole. The composite electrode with 10% MWNTs adding quality exhibites a superior charge-discharge performance, and has initial charge capacities of 148 mAhg^-1 and discharge capacities of 145 mAhg^-1 respectively in the initial cycle at 0.1C charge-discharge rate. And the discharge capacity is 135 mAhg^-1 at 0.5C rate and 124 mAhg^-1 at 1.5C rate. The resistance values of LiFePO₄/MWNTs composite electrode adding MWNTs quantity from 0% to 20% have a significant decrease when adding appropriate MWNTs. After 80 cycles, it has still 131mAh/g and the capacity holding is 90% after 80 cycles. The discharge capacity of composite electrode increases with increasing environment temperatures from 0 to 60°C, and maximal value is 153 mAhg^-1 in the temperature of 60°Cand has better performance of high temperature.