Electrochemical Impedance Analysis of C/LiFePO4 Batteries in Cycling Process

In this paper, the cycle performance and capacity fading of commercial C/LiFePO4 batteries were studied at different rate. The electrochemical impedance spectroscopy (EIS) of the battery was tested and analyzed in different charge-discharge cycles. The morphologies of anode and cathode at different cycle numbers were also characterized by scanning electron microscope (SEM). The experimental results show that the capacity fading of the batteries become faster at higher rate cycling. The SEM images of the cycled electrodes exhibit that capacity fading of the batteries is possibly attributed to the degradation of the anode structure. When the performance of the battery deteriorates sharply, there is a new semicircular arc appearing in the low-mid frequency region in the relative EIS, indicats that the change of EIS can correlate with the state of the battery performance degradation. Therefore, the performance characteristics of battery can be evaluated according to electrochemical impedance spectroscopy. It could also provide scientific and technical support for the fast evaluation system of battery on the cycling performance.