The 18 650 and 21 700 cell format are state of the art for high-energy cylindrical lithium-ion batteries, while Tesla proposed the new 4680 format with a continuous ”tabless” design as the choice for electric vehicle applications. Using an experimentally validated multidimensional multiphysics model describing a high energy NMC811/Si-C cylindrical lithium-ion battery, the effects of tabless design and cooling topologies are evaluated for 18 650, 21 700, and 4680 cell formats under varying charging protocols. Mantle cooling is found to be the most efficient cooling topology for a segmented tab design, whereas tab cooling performs equally well for tabless cells and achieves better performance for the 4680 format. By massively reducing polarization drops (approx. 250 mV at 3C) and heat generation inside the current collectors (up to 99%), the tabless design increases cell homogeneity and enables format-independent scalability of fast-charging performance with a tab-cooling topology. In addition, the 0 to 0.8 SoC charge time can be reduced by 4 to 10 min compared to cells with a segmented tab design, resulting in 16.2 min for the 18 650 and 21 700, and 16.5 min for the larger 4680 cell format.

Cylindrical 18650 and 21700 lithium-ion batteries are produced with small gaps between the jelly roll and the case. The size of these gaps and the mechanical attachment of the jelly roll to the case can have a significant impact on the thermal and mechanical properties of cells. To investigate the influence of the state of charge (SOC) and state of health (SOH) on the size of the gap, computed tomography (CT) and gray-value analysis was conducted with various cell types at 0% and 100% SOC and after cycling. The results show a significant influence of the SOC on the gap for new cells and a substantial reduction in the gap during the first cycles.

The temperature of lithium-ion batteries is crucial in terms of performance, aging, and safety. The internal temperature, which is complicated to measure with conventional temperature sensors, plays an important role here. For this reason, numerous methods exist in the literature for determining the internal cell temperature without sensors, which are usually based on electrochemical impedance spectroscopy. This study presents a method in the time domain, based on the pulse resistance, for determining the internal cell temperature by examining the temperature behavior for the cylindrical formats 18650, 21700, and 26650 in isothermal and transient temperature states for different states of charge (SOCs). A previously validated component-resolved 2D thermal model was used to analyze the location of the calculated temperature $T_{\mathrm{R}}$ within the cell, which is still an unsolved question for pulse resistance-based temperature determination. The model comparison shows that $T_{\mathrm{R}}$ is close to the average jelly roll temperature. The differences between surface temperature and $T_{\mathrm{R}}$ depend on the SOC and cell format and range from $2.14$$\mathrm{K}$ to $2.70$$\mathrm{K}$ (18650), $3.07$$\mathrm{K}$ to $3.85$$\mathrm{K}$ (21700), and $4.74$$\mathrm{K}$ to $5.45$$\mathrm{K}$ (26650). The difference decreases for each cell format with increasing SOC and is linear dependent on the cell diameter.