Three-dimensional layered electrochemical-thermal model for a lithium-ion pouch cell

Performance of lithium-ion pouch cell cannot be evaluated only by its external characteristics, such as the surface temperature and potential, as the internal electrochemical and thermal properties of the cell can significantly affect its performance. However, it is difficult to observe the internal thermal and electrochemical characteristics by means of experiment. Within this study a layered three-dimensional electrochemical-thermal coupled model of a lithium-ion pouch cell is proposed, then it is verified by experimental method at several discharge rates. According to this model, the spatial distribution of temperature field and heat generation rate are analyzed at four discharge rates, a fitted surface equation is presented for this battery to roughly predict the heat generation rate according to the discharge rate and depth of discharge. Afterward, several representative electrochemical properties (electric potential, electrolyte concentration, electrode current density, and mass transfer process) are investigated from the spatial perspective, which reveals the transfer process of lithium-ion and current clearly inside the battery. It is also concluded that there exists a gradient both at the plane and thickness of the electrode, and the gradient in the thickness direction is larger than that in the plane. A large gradient in temperature, lithium-ion concentration, electrode potential and current density distribution are located at the connection between tabs and electrodes.