Lithium-ion batteries: Evaluation study of different charging methodologies based on aging process

In this paper, high power 7 A h LiFePO4-based cells (LFP) have been used to investigate the impact of the charging methodology on the battery's lifetime. Three charging techniques have been used: Constant Current (CC), Constant Current-Constant Voltage (CC-CV) and Constant Current-Constant Voltage with Negative Pulse (CC-CVNP). A comparative study between these techniques is presented in this research. For this purpose, a characterization of the batteries has been performed using capacity test and electrochemical impedance spectroscopy (EIS). As expected the obtained results showed that the battery's aging rate depends on the charging methodology. Indeed, it has been shown that a combination of low amplitude and fewest number of negative pulses has a positive effect on battery's capacity fading. From the impedance measurements, the results have demonstrated that the CC-CVNP technique with low amplitude and fewest number of negative pulses is more effective than the other techniques in reducing the concentration polarization resistance and the diffusion time constant. This research has provided an extended analysis to select the proper charging methodology that can be used to design an enhanced charging system.