Low-temperature performance of LiFePO4/C cathode in a quaternary carbonate-based electrolyte

The low-temperature performance of LiFePO4/C cathode in a quaternary carbonate-based electrolyte (1.0 M LiPF6/EC+DMC+DEC+EMC (1: 1: 1:3, v/v)) was studied. The discharge capacities of the LiFePO4/C cathode were about 134.5 mAh/g (20 degrees C), 114 mAh/g (0 degrees C), 90 mAh/g (-20 degrees C) and 69 mAh/g (-40 degrees C) using a 1C charge-discharge rate. Cyclic voltammetry measurements show obviously sluggish of the lithium insertion-extraction process of the LiFePO4/C cathode as the operation temperature falls below -20 degrees C. Electrochemical impedance analyses demonstrate that the sluggish of charge-transfer reaction on the electrolyte/LiFePO4/C interface and the decrease of lithium diffusion capability in the bulk LiFePO4 was the main performance limiting factors at low-temperature. (C) 2008 Elsevier B.V. All rights reserved.