关键词: 全钒液流电池, 石墨毡, 电极极化, 欧姆内阻

Abstract: An experimental setup with two external saturated calomel reference electrodes(SCE)and two flow cells was established for flow battery research application.By using this setup,the cell voltage,potentials and open circuit potentials of the positive and negative electrodes for a lab-scale flow battery single cell,could be determined simultaneously during charge-discharge(C-D) cycle test.Then,the ohmic internal resistance drop(iR drop),overpotentials at the negative and positive electrodes of the cell during C-D process,were calculated.The average iR drop accounts for about 74% of the total voltage losses during the C-D cycle at current density of 60 mA·cm-2,suggesting the voltage efficiency(VE) of vanadium redox-flow battery(VRB) single cell with graphite felt as electrodes and Nafion 117 as battery separator,was limited by the cell ohmic internal resistance.The C-D curves show that the appearance of the end-point of discharge is mainly due to the zoom of negative electrode over potential.The VRB single cell designed in this work achieves an excellent performance,with voltage and energy efficiency up to ca.89% and 85%,respectively,at C-D current density of 60 mA·cm-2,indicating structure of the cell is reasonable,and graphite felt is suitable for VRB electrode application.

Key words: all-vanadium redox-flow cell, graphite felt, electrode polarization, ohmic internal resistance