Lithium ion battery is considered as one of the most possible energy storage equipment for new energy vehicles (EV, HEV, etc.) because of the advantages of long cycle life, high power density and low self-discharge rate. However，the working condition for high power battery in freezing condition is so poor that its performances are strongly affected. For example, they would suffer from significant power capability losses and poor rate performance, which would restrict the acceleration performance of the electric vehicle. To evaluate those performance drawback and to make an efficient design, good mathematical models are required for system simulation especially for battery thermal management. In this paper, a three-dimensional homogenization thermal model of a 20 Ah prismatic lithium ion battery with LiFePO4 (LFP) cathode is described. This model particularly stresses on the high-ratio discharge property at low-temperature which could captures the shapes and dimensions of cell components and the spatial distributions of the temperatures. First, various discharge tests on one cell are carried out, and then, cell’s parameters and thermal characteristics are obtained. Ultimately, the three-dimensional thermal model for single-cell proposed is shown to be accurate by analyzing the simulation data and test results.