Low-effort determination of heat capacity and thermal conductivity for cylindrical 18650 and 21700 lithium-ion cells

Determination of Internal Temperature Differences for Various Cylindrical Lithium-Ion Batteries Using a Pulse Resistance Approach

“…The 18650 and the 21700 cells were selected since they represent the latest nickel manganese cobalt oxide (NMC) chemistry with silicon content in the anode composite and a nickel-rich cathode material [33]. Furthermore, the 18650 was investigated in our previous studies [27,28] and the 2D thermal model of both cells (18650 and 21700) was already implemented and validated in the study of Steinhardt et al [31]. The 26650 cell's LiMn 2 O 4 (LMO) chemistry [34,35] was chosen to investigate if the relation of the R DC and temperature is altered by different chemistry.…”

“…Here, T surf is the average of T p , T c , and T n . Additionally, the surface temperature served as input for the 2D thermal model [31] for the 18650 and 21700 cells to identify the internal cell temperature distribution (T model ) during the external temperature change and investigate the relation between T R and T Model . The corresponding results are presented and discussed in Section 4.2.…”

“…A previously validated 2D thermal model was used to relate T R to the internal temperature distribution for the 18650 and 21700 cells. This model was developed and parameterized by Steinhardt et al [31] for the same cell types as used in this work. The model is a component-resolved model, which means that components such as the steel case and the current interrupt device in the positive cell pole are resolved separately.…”

“…Overall, the axisymmetric model geometry in Figure 1c defines seven domains with no heat source term, since the cells are not operated in this study. The dimensions of the geometry were either measured in [31] with a micrometer screw or taken from computed tomography scans of the cell. All simulations were run in COMSOL Multiphysics 5.4 with an adiabatic boundary in the inner core of the cell and a defined temperature for the rest of the boundaries.…”

“…Every material parameter in the model is considered isotropic except for thermal conductivity, which is defined by the in-plane and through-plane directions of the cell's jelly roll. In the study by [31], the thermal conductivity and the specific heat capacity of the electrode-separator stack were measured at three different SOCs. The measured thermal parameters at the lowest, middle, and highest SOC by [31] were used in this work for the SOC of 10%, 50%, and 90%, respectively.…”