Preparation And Modification Of Graphite Felt Electrode Materials Used For Fe/Cr Redox Flow Battery

This article use polyacrylonitrile (PAN)-based graphite felt as the electrodes of Fe/Cr redox flow battery. Research the graphite felt electrodes in two aspects, the influence of carbonization and graphitization temperature, and the air oxidation on the performance of Fe/Cr redox flow battery.The surface morphology of graphite felt fibers is studied by Scanning Electron Microscopy (SEM), and the content of oxygen-containing functional groups is studied by Fourier Transform Infrared Spectroscopy (FTIR). Determine the best air oxidation temperature of graphite felt by TG curves. The CHI660E is used to study the electrochemical properties of graphite felt electrodes. The charge and discharge test and I-V test is conduct with a secondary battery performance tester, research graphite felt electrodes for optimum charge discharge current density, the electrical properties of the electrode and the internal resistance of the battery charge and discharge.The result show that:With the increase of carbonization temperature and graphitization temperature, the content of oxygen-containing functional groups decreases. While it was oxidized for5h at550℃in the air, the oxygen-containing functional groups increase significantly.The Fe2+/Fe3+redox exhibits an outstanding electrochemical performance, While the Cr2+/Cr3+redox exhibits poor electrochemical performance. With the conduct of carbonization, graphitization, and oxidation, the peak current of Fe2+/Fe3+redox increases, the potential difference (AEp) between the oxidation-reduction reaction gradually reduced, the ratio of the redox reaction of the peak current Ipa/IPc increases gradually, indicates the electrochemical activity and reversible of electrodes increase.The graphite felt that carbonized at1400℃, graphitized at1800℃used as electrodes, research the impact of charge and discharge current density on the performance of the battery, the current density range among40-120mA/cm2. With the charge current density increase, the voltage efficiency and the energy efficiency reduces. The Fe/Cr redox flow battery exhibits the better performance under a current density of60mA/cm2.With the increase of carbonization temperature, coulombic efficiency of the battery decreases gradually, the voltage efficiency and energy efficiency increase gradually, the charge and discharge resistance reduce. With the increase of graphitization temperature, the energy efficiency and the voltage efficiency improved, the charge and discharge resistance reduce, The impact of graphitization temperature on the resistance of graphite is significantly greater than the impact of the carbonation temperature.The graphite felt that carbonized at1400aphitized at2000℃used as electrodes, the average coulombic efficiency, voltage efficiency, energy efficiency are94.40%,83.47%,78.79%. While it was oxidation at550℃for5h, the performance of electrode improves significantly. The average coulombic efficiency, voltage efficiency, energy efficiency are94.60%,80.75%,85.36%, respectively. After several charge and discharge cycles, the battery performance is stable. Ⅰ-Ⅴ test shows that the charge and discharge resistance decrease.