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 degrees C, and maximal value is 153 mAhg(-1) in the temperature of 60 degrees C and has better performance of high temperature.