Graphite ILiFePO4 lithium-ion battery working at the heat engine coolant temperature

Electrochemical properties of the graphite anode and the LiFePO4 cathode, working together with the 1 M LiPF6 in TMS (sulpholane) at 90 degrees C have been studied. The general aim of the investigation was to demonstrate a potential application for a Li-ion cell working in the cooling system of a car heat engine (90 degrees C). Electrodes were characterized with the use of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) as well as galvanostatic charging/discharging tests. SEM images of both electrodes after charging/discharging processes were covered with a film (electrochemical SEI formation). The charge transfer resistance at 90 degrees C, R-ct, of the C6Li vertical bar Li+ anode and the LiFePO4 cathode was 24 Omega and 110 Omega, respectively. Reversible capacity of the LiC6 anode after 10-20 cycles, at a low current rate was close to the theoretical value of 370 mAh g(-1) however an increasing current rate decreased to ca. 200 mAh g(-1) (for 1C). The reversibility of the process was close to 95%. The capacity of the LiFePO4 cathode was ca. 150 mAh g(-1), almost independent of the current rate and close to the theoretical value of 170 mAh g(-1). (C) 2014 Elsevier B.V. All rights reserved.