Simulation of electrochemical-thermal behavior for a 26650 lithium iron phosphate/graphite cell

A P2D electrochemical model coupled with a 2D thermal model is built and validated for a commercial type 2.3 Ah ANR26650 cell including the cathode, anode, separator, and current collectors. The spatial and temporal distribution of Li⁺ concentration on the electrode surface, the flux of Li⁺ out of the porous active particles or the local current density, the reversible/irreversible reaction heat generation rate, and the temperature distribution inside the battery are analyzed at various discharge rates. The critical thickness of the cathode is systematically studied with the correlated particle size and porosity. It is indicated that the critical thickness of the cathode increases with the particle size and porosity. In order to achieve the optimum electrochemical performance, the critical thickness of the ANR26650 battery can be estimated as 55 μm in the original model. The results indicate that the ionic ohmic heat dominates the ohmic heat generation in porous electrodes. The higher the C-rate is, the more significant role the irreversible heat plays in the generation heat. A battery thermal management system (BTMS) with water cooling plate can lower the module temperature effectively even when it is discharged at a very high C-rate.