Abstract
Polypyrrole-film was coated directly onto LiMn2O4 electrode by electrochemical polymerization. Both of bare electrode and modified electrode were characterized by X-ray diffraction and electrochemical techniques. The XRD patterns demonstrated that polypyrrole was deposited onto the LiMn2O4 electrode. The charge-discharge tests revealed that modified electrode by polypyrrole-film has an excellent rechargeability, 98.2% of the initial discharge capacity and 90.1% of the maximal discharge capacity after 150 cycles, but for bare electrode, only 53.4% of the initial discharge capacity. The CV curves showed that the new method is very efficient for restraining capacity fade of LiMn2O4, in fair agreement with the charge-discharge test. The EIS measurements in a frequency range from 100kHz to 1mHz were conducted on the electrodes. It was exhibited that the existence of polypyrrole-film decreases the charge transfer resistance and facilitates the charge-transfer reaction in the LiMn2O4 material, which is favorable for improving performance of LiMn2O4 cathode.