Degradation of a high capacity prismatic LiFePO4 cell with deep cycling at elevated temperature of 50 degrees C is studied by electrochemical impedance spectroscopy as well as capacity and power fading characterization at different test temperatures (45, 25, 0 and -10 degrees C. The capacity and power fade evidently becomes more severe at lower temperature. In particular, the power fade at low temperatures (e.g., 0 and -10 degrees C) rather than capacity loss is a major limitation of the LiFePO4 cell. The primary mechanism for capacity fade is loss of cyclable lithium in the cell resulting from lithium-consuming solid electrolyte interphase (SEI) layer growth and side reactions. The increased interfacial resistance (R-W) due to the catalytic growth of SEI layer on the graphite anode and increased electrolyte resistance are the main sources for power fade. (C) Elsevier B.V. All rights reserved.