Influence of Characterising Materials Thicknesses on the Thermal Response of Cylindrical Battery Cells

Rising concern towards environment and decarbonization has increased the demand of EVs. However, one of the major challenges for these vehicles is to achieve the same driving ranges as that of ICEs. This can be attained by increasing the power of cells without altering their sizes; conversely, this has important effects on the cell thermal behaviour. The focus of this paper is to analyse the impact of changing the characterizing materials thicknesses of collectors and electrodes of a cylindrical cell on its thermal response and to determine an optimal configuration. The CFD software considered to conduct this research uses the equivalent circuit model (ECM) to represent a cell and requires material physical properties to calculate the thermal response. In the calculations presented, resistance, capacitance, and Open Circuit Voltage (OCV) needed for the ECM are obtained from experimental measurements. The electric model provides the flow of current in the cell, that can only be elicited in the active zone. The thermal model only allows to define the active zone with equivalent material properties, such as the equivalent conductivity of the cylindrical cell in radial and axial directions. Henceforth, it is crucial to precisely define the active zone. For this, a new model has been developed for the calculation of the equivalent conductivity of a cylindrical cell. The validation of the proposed method is accomplished using perspective analysis. With the values of thermal conductivity obtained using this approach, CFD simulations are programmed, that yield the power generated by the cell and its temperature in function of charge/discharge. These are compared with the original design and allow defining the optimal thicknesses of current collectors and electrodes.