Investigation of the Effective Thermal Conductivity of Cell Stacks of Li‐Ion Batteries

Abstract

Knowledge of the thermal transport properties of the individual battery components and their combination is required for the design of thermally optimized lithium‐ion batteries. Based on this, the limiting components can be identified and potentially improved. In this contribution, the microstructures of commercial porous electrode coatings, electrode stacks, and cell stacks are reconstructed based on experimentally determined structure parameters using a specifically developed structure generation routine. The effective thermal conductivity of the generated stacked structures is then determined by a numerical tool developed in‐house based on the finite‐volume method. The results are compared with an analytical model for fast accurate predictions which takes the morphological parameter sets and the geometry of the stacks into account. Both models are used to identify the system‐limiting components via selected simulation studies. Finally, the results of both models are compared with experimental data for commercial electrode stacks and common literature values for cell stacks.

Meta-analysis of experimental results for heat capacity and thermal conductivity in lithium-ion batteries: A critical review

“…In addition, this section does not deal with unspecific conductivities that are used in lumped thermal models [42]. Dry stack layers are also not discussed as complex models are required to determine the wet thermal conductivity from dry measurements [50,72].…”

“…The median for dry graphite coatings is 718 J kg −1 K −1 in Figure 3 a), which contains the measurement results of seven test samples. Although these coatings contain polyvinylidene fluoride (PVDF) binder (1114 J kg −1 K −1 [72]) and carbon black (650 J kg −1 K −1 [72]), the median of 718 J kg −1 K −1 is close to pure graphite with a specific heat capacity of 706.9 J kg −1 K −1 [73]. The increase compared to pure graphite depends on the weight fraction of the binder.…”

Effective Thermal Conductivity of Lithium‐Ion Battery Electrodes in Dependence on the Degree of Calendering

“…The NMC622 cathode used in this study has both a higher carbon black mass fraction and additional graphite particles, which both have a significantly higher thermal conductivity than the active material with approx. 24 W m −1 K −1 for carbon black [ 48 ] and a mean value of 130 W m −1 K −1 [ 43 ] to 139 W m −1 K −1 [ 49 ] for graphite. Furthermore, the coating of the NMC811 cathode is thicker, leading to a lower fraction of the highly conductive aluminum foil and therefore a lower effective thermal conductivity.…”

Radial Thermal Conductivity Measurements of Cylindrical Lithium-Ion Batteries—An Uncertainty Study of the Pipe Method

“…Because of the transparency and the low thickness of the separator it could not be measured as the laser did not heat the material but penetrated it. Common polymer-based separators have a thermal conductivity as low as 0.1-0.5 Wm −1 •K −1 [9,14,16,17]. Therefore, they have a great impact on heat transfer in the cell [9].…”