The paper presents a multidimensional modeling framework for simulating coupled thermal and electrochemical phenomena in lithium-ion batteries. Understanding the distribution of current density, potential, and temperature is critical for designing lithium-ion batteries for improved safety and durability, as well as for conducting effective design optimization studies. We have developed a model that retains the details of diffusion, migration, and charge-transfer kinetics in the various phases in a lithium-ion battery, while introducing computational techniques that allow us to efficiently calculate the transient current and temperature distributions in a three-dimensional stack. Several modeling example results are presented showing the influence of cooling system design and thermal effects on current distribution within a cell and between cells in a stack. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3591799] All rights reserved.