To meet the demand for high energy and long life of electric vehicles, lithium-ion batteries using Ni-Co-Mn ternary materials as cathode have become the focus of industrialization. To design a safe, reliable, and durable battery system is a necessary condition to ensure the healthy development of the new energy electric vehicle industry. The swelling force caused by the lithiumion insertion/extraction not only does harm to the safety of the battery system but also deteriorates the battery life. Moreover, the swelling force increases with the increase in the cycle. In this work, the difference in the swelling force of batteries design with different number of electrode sheets was studied. When the gap between the electrode and the aluminum shell is the same, the number of electrode sheets in the battery is higher, the swelling force is greater, and the capacity fading is faster; the swelling force is also stronger in the module. Because of the stronger swelling force in the module with more electrode sheets, the strength of each structural component needs to be designed stronger to ensure the module is safe and durable throughout the designed life. The results of this research could be instructive in designing a battery system.