DOI: 10.35097/pbjzpqlkkwzaojkn
title: Thermal Material Properties of Commercial NMC532 / Graphite Lithium-Ion Battery Cell

description: In electrical automotive application lithium-ion battery cells containing a NMC532 cathode chemistry are state-of-the art[1]. To model their thermal-electrical performance during application, the thermal and electrical properties are essential. In this work, we present the thermal material properties of the coatings of the investigated NMC532 / graphite cell. These include the heat capacity measured with a differential scanning calorimeter and the density measured with a pycnometer. The temperature dependent thermal conductivity of the coatings is then calculated from the thermal diffusivity of double sided coated current collector, which is conducted with a laser flash analysis. The standard deviations with error propagation of the coatings are maximum of ≈ 7 %.
description: The commercial 3.4 Ah pouch cell contains a NMC532 / graphite cell chemistry[2]. 

The procedure is the same as already described by Cloos et al.[5]:
“The cell opening is performed at a State of Charge (SoC) of 0 % in an inert environment in a glove box. After disassembly, the anode and cathode sheets were triple washed with DMC and left to dry. For the density and heat capacity measurements, the coatings of both anode and cathode sheets were scraped off. For the thermal diffusivity measurements 18 mm double coated coins were punched from the sheets. All probes were exposed to air only very shortly before inserting them into the measurement devices. 
The experimental analysis is performed according to Oehler et al.[3]. The density measurement is done with a Micro Ultrapyc 1200e Gas (Quantachrome Instruments) pycnometer in nitrogen gas. The heat capacity is measured in a Q2000 (TA Instruments) differential scanning calorimeter in a temperature range from -40 °C to 60 °C. The thermal diffusivity measurement of the double coated coins is performed in helium atmosphere in a LFA 467 Hyperflash (NETZSCH-Gerätebau GmbH) in a temperature range from -20 °C to 60 °C. To calculate the thermal conductivity of the coatings via a serial connection[4], additional knowledge of the layer thicknesses, porosities of the coatings and the thermal material properties of the current collectors are needed. The thicknesses of the coatings and current collectors are measured with a Micromar 40 EWR (Mahr GmbH). A Balance XPE206DR precision scale (Mettler Toledo) was used to measure the mass of the coating probes. The porosity of the coating was then determined gravimetrically. All measurements were conducted at least three times. Error propagation of the standard deviation was performed for the calculated values.”[5] 

We assume the anode and cathode current collectors to be copper and aluminum respectively. The thermal conductivity at 0 °C[6], the density[5] and temperature dependent heat capacities[5] are obtained from literature.

[1] R. Schmuch, R. Wagner, G. Hörpel, T. Placke, M. Winter, Nat Energy 2018, 3, 267–278.
[2] L. Cloos, O. Queisser, A. Chahbaz, S. Paarmann, D. U. Sauer, T. Wetzel, Batteries & Supercaps 2024, 7, e202300445.
[3] D. Oehler, P. Seegert, T. Wetzel, Energy Technol. 2021, 9, 2000574.
[4] A. Loges, S. Herberger, D. Werner, T. Wetzel, Journal of Power Sources 2016, 325, 104–115.
[5] L. Cloos, S. Herberger, P. Seegert, T. Wetzel, Karlsruhe Institute of Technology 2024, DOI 10.35097/kAlrZQzUaHBxWkIj.
[6] P. Stephan, S. Kabelac, M. Kind, D. Mewes, K. Schaber, T. Wetzel, Eds. , VDI-Wärmeatlas: Fachlicher Träger VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen, Springer Berlin Heidelberg, Berlin, Heidelberg, 2019.