As battery temperature greatly affects performance, safety, and life of Li-ion batteries in plug-in and electric vehicles under various driving conditions, automakers and battery suppliers are paying increased attention to thermal management for Li-ion batteries in order to reduce the high temperature excursions that could decrease the life and reduce safety of Li-Ion batteries. Currently, the lack of fundamental understanding of the heat generation mechanism due to complex electrochemical phenomena prohibits accurate estimation of the heat generation within Li-ion cells under various operating conditions. Heat from Li-ion batteries can be generated from resistive dissipation, the entropy of the cell reaction, heat of mixing, and other side chemical reactions. Each of these can be a significant source of heat under a range of circumstances.
The heat source is modeled as a combination of the heat generations due to electrochemical reactions and electrical resistance within the cell as a function of electric current, state of charge (SOC), and cell temperature. The electrochemical heat generation is computed based on the electrochemical discharge model of the battery. The electrical heating rate is calculated by the electrical current flow, which can be evaluated based on the potential distributions on the electrodes obtained from the electrochemical modeling. The model is validated by the comparison of the modeling results with the experimental measurements. The temperature distributions of the battery during discharge from the thermal model are in good agreement with those from the experimental measurements at the various discharge rates and charge rates.