Abstract
The charging and discharging processes of Lithium-ion battery are bothelectrochemical and physical processes. During the reaction, there are extremely complex mechanisms of stress changes. At present, the research at the micro level is negligible. In this paper, a new method combining experimental verification and theoretical reasoning is used to study the mechanics of lithium-ion batteries in the charging process. The effects of different charge rates to the battery stresses are also researched. The results show that: the lithium-ion battery internal stresses in the process of charging caused by the stacking forces and insertionforcestogether, and the stacking forces are greater than insertion forces with the same concentration of lithium ions. As the lithium ions are inserted into the particles, those two forces are in continual changing. The phase transition of electrode particles also has an impact on the inner stresses synchronously, resulting in a stress curve platform. Finally, the mechanism of stress attenuation when the current is cut off was discussed and demonstrated. In this paper, the study of the stress mechanism of lithium-ion batteries can provide ideas for stress modeling.
Keywords: lithium-ion battery; stress mechanism; Li-intercalation; stack; charge rate