Heat generation rates and anisotropic thermophysical properties of cylindrical lithium-ion battery cells with different terminal mounting configurations

Abstract

This paper investigates the variation in the heat generation rates and anisotropic thermophysical properties of cylindrical 18,650 and 21,700 lithium-nickel-manganese-cobalt-oxide (NMC) battery cells when the negative terminal is mounted at different points on the cell surface. We developed a methodology that combines experimental data with a numerical inverse heat transfer (IHT) model to quantify the differences in these properties under two strategies for connecting the negative terminal to the cell surface. In the first, the negative terminal is connected at the top rim of the cell, adjacent to the positive terminal; in the second, the negative terminal is connected at the bottom of the cell, adjacent to the negative current collector. Applying this methodology, we found that the total heat generation over 1000 s for 18,650 and 21,700 cells with the negative terminal at the top rim is higher than that for batteries with the negative terminal at the bottom by up to 4.6 % and 10.7 %, respectively. The additional heat was concentrated in the cell canisters, resulting in non-uniform heat generation across the cell volume. Without considering this non-uniformity in the numerical IHT model, the characterization process yielded 15–22 % discrepancies in the predicted thermal conductivities. By considering the canister and jelly roll of the cell as separate heat generation domains, the discrepancies were reduced below 6 % and 7 % for 18,650 and 21,700 cells, respectively. This work developed an improved battery cell characterization methodology taking into account localized heat generation and extrinsic terminal mounting effects. The results underline the importance of high-fidelity cell characterization in the battery cell design process.