There is ongoing discussion about which form factor is best suited for automotive applications. Recently, cylindrical cells have received increased attention since Tesla announced their 4680 cell (46 mm diameter, 80 mm height) and leading manufacturers have confirmed their interest in production of this type of cells. Especially the novel tabless electrode design [1] can be viewed as a key to enabling larger cell diameters through improved electrical and thermal homogeneity [2]. So far tab cooling of cylindrical cells was inefficient because the single tab with a small cross section acted as a choke point for heat flow [3]. For this reason current 18650 and 21700 battery packs are designed with cooling systems such as serpentine cooling that draw heat through the outer surface. However, low thermal conductivity and high temperature gradients in radial direction limit the cell diameter with this type of cooling. Cells with a tabless electrode on the other hand have drastically improved thermal connection between jellyroll and the top and bottom surfaces which makes cooling these a viable option. The resulting temperature gradients spread in axial direction with high thermal conductivity, which limits the influence of the diameter on the temperature profile.

Overall, the tabless electrode design enables a wide variety of new possibilities for engineers to design battery packs with cylindrical cells which have not yet been investigated in detail. In this study a geometrical-electrical-thermal coupled model is developed to investigate the influence of cell dimensions and cooling strategy on the performance parameters of the battery pack. Electrical-thermal cell models are parameterized and validated with state-of-the-art large-format cylindrical cells with a tabless electrode. Extensive thermal propagation simulations are performed and validated on module level to calculate the minimal cell-to-cell distance needed to ensure sufficient battery safety as a function of cell dimensions, active material energy density and cooling strategy. This study aims to generate a deeper understanding about the possibilities and advantages of future cylindrical cell battery packs.

References
[1] Tsuruta, K.; Dermer, M.E.; Dhiman, R. (2019): A CELL WITH A TABLESS ELECTRODE (EP20190809342). European Patent Office. https://patents.google.com/patent/WO2020096973A1/en?oq=WO2020096973
[2] Lee, K.-J., Smith, K., Pesaran, A. u. Kim, G.-H.: Three dimensional thermal-, electrical-, and electrochemical-coupled model for cylindrical wound large format lithium-ion batteries. Journal of Power Sources 241 (2013) 1, S. 20–32
[3] Li, S., Kirkaldy, N., Zhang, C., Gopalakrishnan, K., Amietszajew, T., Diaz, L. B., Barreras, J. V., Shams, M., Hua, X., Patel, Y., Offer, G. J. u. Marinescu, M.: Optimal cell tab design and cooling strategy for cylindrical lithium-ion batteries. Journal of Power Sources 492 (2021), S. 229594