An accurate prediction of battery behaviors guarantees the reliability, security, and efficiency for current tasks. An electrochemical-thermal (ECT) coupling model for LiCoO2 battery is proposed to describe charge and discharge behaviors. With lumped thermal analysis, calculations of heat generation, conduction, and dissipation are added to a simplified electrochemical model. Battery mechanistic parameters are reasonably reduced and regrouped to reduce estimation complexity. Based on excitation response analysis, identification conditions are specially designed to obtain mechanistic parameters. Simulations are carried out to validate the applicability of model at different operating conditions. Simulation results of terminal voltage and surface temperature are in good agreement with actual experimental measurements at lower C rates and dynamic load currents. With proposed parameter estimation method, the simplified ECT coupling model can be applied to similar battery systems.