Influence of cell dimensions and number of tabs on cylindrical lithium-ion cell sidewall and bottom cooling performance

The industry trend for lithium-ion battery cells for automotive applications is moving toward increased cell dimensions. For cylindrical lithium-ion battery cells, the introduction of the 46xx format is an example of this trend. To ensure a long lifetime and safe operation, lithium-ion batteries must be operated within an optimum temperature window. This is managed by cooling the cell with battery module or battery system level cooling strategies. In comparison to the state-of-the-art 21700 cell format, these 4680 lithium-ion battery cells represent an approximately 5.5x volume increase while introducing new cell design challenges: Larger cells can increase the distances between heat generation and the cooling system and require new design approaches for the internal tab configuration. Furthermore, the surface to volume and heat generation ratio shrinks with increasing cell size, leading to challenges for the cooling strategy. This paper analyzes the influence of the cell size and the number of tabs on sidewall and bottom cooling performance of cylindrical lithium-ion battery cells. Therefore, the cooling effectivity of sidewall and bottom wall active cooling of 18650, 21700, 4680 cell formats as well as different numbers of tabs was investigated from a thermal perspective. The results indicate a change of optimal cooling strategy depending on cell dimensions and number of tabs, showcasing performance optimization potentials for module and cell design.