Improving the cycling performance of LiFePO4 cathode material by poly(3,4-ethylenedioxythiopene) coating

LiFePO4 composite cathode materials with PEDOT [poly(3,4-ethylenedioxythiopene)] were prepared by electropolymerization or by blending methods. The cycling performance of these composites in lithium test cells were then evaluated and compared with bare and carbon-coated LiFePO4. The electrodes were further fine tuned by optimizing the materials and different preparative methods adopted. It was found that the LiFePO4/PEDOT composite obtained by direct electropolymerization over the cathode shows better cycling performance in terms of capacity (110 mA h g(LFP)(-1) at 2C) and capacity retention (125 mA h g(LFP)(-1) after 50 cycles at C/2). We attribute the improved performance to an enhanced conductivity, as evidenced by the initial impedance of the cathodes and low charge-discharge polarization during cycling.