The specific heat and the heat generation rate are the key thermal properties for lithium ion battery cells. Nonetheless, there exists large scattering in data of thermal properties due to factors such as battery temperature nonuniformity during experimental measurement. In this work, a novel calorimetric method for measuring thermal properties of a lithium ion battery cell is proposed by introducing a temperature even out process to minimize the effect of the temperature difference across the battery. Through this method, the specific heat and the heat generation rate can be characterized for the electrochemical batteries. Thermal parameters of a prismatic lithium iron phosphate battery cell are determined for the wide temperature range at varying operating currents. It is found that the specific heat of the lithium ion battery cell has a linear relationship with the operating temperature, whereas the heat generation rate has a quadratic relationship with the operating current. The measured heat generation rate shows a good agreement with calculated results as per Bernardi's heat generation model. This new method allows one to obtain thermal properties of lithium ion battery cells at a lower cost and in a shorter time.