Study on the Charging Behaviors of Lithium-Ion Batteries by Analysis of Li Distribution in the Electrode Particles

The charging behaviors of lithium-ion batteries are closely related with the charging current and temperature. Generally, the constant current-constant voltage (CC-CV) mode is the most widely applied charging protocol for lithium-ion batteries. This paper establishes a multi-scale thermal-electrochemical model with considering the Li diffusion process in the electrode particles to investigate the battery charging performances. The change rules of the charging capacity and charging time are separately discussed based on the analysis of the transient characteristics of Li concentration inside the electrode particles when charging with the CC-CV mode.

It is known that the charged capacity is determined by the amount of the transferred Li between the negative and positive electrodes [1, 2]. The experimental and numerical results are compared in Fig.1. Fig.2 shows the distributions of Li concentration inside a carbon particle when battery is in charging with the CC-CV mode (4C→3.6V→0.02C) at 25°C. As the charging time increases, the gradient of Li concentration during the CC charging stage slightly decreases, while it decreases markedly during the CV stage.

The results show that the charged capacity in the CC stage decreases with the increase of the charging current when the current is lower than 4C, whereas it changes slightly in case of the charging current is higher than 4C; the CC charging time decreases with the increase of the charge current, while the change of the CV charging time is slight. For EVs application, the battery is recommended to only charge 90% of the total capacity, which can shorten the charging time significantly.

References

1. L.-x. Li, X.-c. Tang, Y. Qu and H.-t. Liu, Journal of Central South University of Technology, 18, 319 (2011).

2. N. Yang, X. Zhang and G. Li, Journal of Power Sources, 272, 68 (2014).