Abstract:

According to the current industry research on the cycle characteristics of lithium battery modules, it has been determined that the main factor affecting the cycle performance of energy storage modules is the module expansion force. Through this study, the failure mechanism of the cycle attenuation characteristic of the energy storage module is identified. By improving the optimal design of the module structure, the increase in module expansion force can be greatly reduced, and the cycle life of the modules can be extended. Firstly, the causal and correlational relationships are accurately identified from the failure mechanism. Subsequently, a method is proposed to determine the foam size and bonding position between cells, enabling the optimization of the structural design of energy storage modules. Finally, a 1P8S energy storage module that uses a lithium iron phosphate 280 Ah cell was selected as the research object. A conventional energy storage module 1-1 was compared with an optimized energy storage module 2-1, both using the same 1P8S stack. The module cycle test was conducted under ambient temperature conditions of 25 ℃, employing a step charge of 0.5 C (140 A) discharge. The results show that the optimized energy storage module 2-1 exhibits improved performance in pressure and temperature differences at the end of charge and discharge compared to the conventional energy storage module 1-1. Specifically, the average pressure difference at the charging and discharging ends of the optimized energy storage module 2-1 is reduced by 24% and 37.7%, respectively. The average temperature difference of the optimized energy storage module 2-1 is reduced by about 5 ℃ and 6 ℃ at the charging and discharging ends, respectively. The capacity retention curve of the optimized energy storage module 2-1 is better than that of the conventional energy storage module 1-1.

Key words: expansion force, foam, energy storage module, cyclic performance