Lithium-ion batteries are gaining importance for other industries with smaller sales figures than electric vehicles especially because of the decrease in costs. While the big companies sell millions of devices, not-consumer focused industries have much less volume. Therefore, the manufacturers must be as efficient as possible and use the ideal operating conditions to maximize the available capacity over the lifetime. While commonly cylindrical cells are studied, the focus of research shifts towards larger cells with a higher capacity. In this work, the focus lies on the thermal parameter heat capacity of up-to-date NMC pouch cells.
The primary purpose is to compare experimentally generated data. For validation, there are two different approaches used to measure the heat capacity of the cell. While there are multiple methods to measure this parameter, most of them require specific measuring devices or are not possible in-situ. Here two tests were implemented using only a cell cycler and a climate chamber, usually available in a laboratory. One test uses a reference component with known mechanical properties and similar dimensions as the tested cell. The other test includes the electro-thermal impedance spectroscopy (ETIS), a thermal adaption of the well-known electrochemical impedance spectroscopy (EIS), using an alternating current to stimulate the temperature response of the cell. With this test concept it is possible to measure the thermal conductivity as well.
Thanks to the data gained in the experiments, thermal models should be validated in order to create a spatially resolved analysis of a single cell. This information will be used in further adaption in battery module design to estimate the heat generation and, therefore, the cooling system’s requirements.