A 3D electrochemical-thermal coupled model for electrochemical and thermal analysis of pouch-type lithium-ion batteries

Abstract A three-dimensional electrochemical-thermal coupled model is developed to investigate the interactive electrochemical and thermal characteristics of pouch-type lithium-ion batteries under natural convection conditions. The heat generation rate calculated by the electrochemical model is applied to the thermal model as the heat source, while the temperature derived from the thermal model is regarded as the initial condition for the electrochemical model. The simulations are verified by the experimental data under different discharge rates (1, 3, and 5 C). Numerical results reveal that the average particle size of electrodes directly affects the heat generation rate of the battery during the discharge process. More importantly, it is found that in the in-plane direction, the maximum local current density appears near the tabs initially and moves to the bottom side with the progress of the discharge as the regions away from tabs becomes more favorable for electrochemical reactions. The uneven distribution of local current density results in a non-uniform distribution of the heat generation rate and thus the uneven temperature distribution. In addition, the temperature gradient in the through-plane direction is relatively small under natural convection conditions. This work offers more insights into heat generation mechanisms in lithium-ion batteries, which will assist the design of efficient battery thermal management systems.