Development of a Temperature-Dependent Li-ion Battery Thermal Model 2012-01-0117

The performance of lithium-ion batteries, in terms of capacity, safety, or life, is strongly dependent on operating temperature. Users and suppliers of Li-ion cells and packs must provide thermal management systems that keep the batteries operating within an acceptable temperature envelope to ensure reliable performance. The design of these systems depends on validated thermal-electrical models of battery behavior when subjected to various driving cycles and environmental conditions. A number of battery models have been developed for use in computer-aided engineering design studies, ranging in complexity from simple equivalent circuit models to multi-scale, multi-physics simulations of electro-chemical processes. One model that accomplishes a favorable compromise between simulation complexity and representative physics employs an empirical approach to capture discharge behavior as a function of current density and the depth-of-discharge (or charge depletion) on an electrode. This approach is combined with Poisson's equation, which represents voltage distribution on a 2D plate, to compute voltage and current distribution over the electrodes of a pouch-type cell during discharge. This model is limited to a one-way coupling between the electrical and thermal models of a battery, i.e., electrical effects influence the temperature response, but the temperature response can not be fed back to the electrical model. In this paper we describe how we extend the empirical model of discharge behavior to include effects of temperature, thus providing a means to create a two-way coupling between electrical and thermal behavior.