全钒液流单电池充放电行为及特性研究

建立具有外置双饱和甘汞参比电极及双液流电池的实验装置系统.使用该装置可在同一时刻同时测定小型液流单电池充放电时的电池电压、电池正负极电位及正负极开路电位,进而计算充放电过程电池的欧姆内阻降(iR)及其正负极过电位.以石墨毡为电极、Nafion 117作隔膜的全钒液流单电池,在60 mA.cm-2电流密度下,每一充放电循环的平均iR降约占总电压损耗的74%,表明该电池的电压效率受制于电池的欧姆内阻.充放电曲线显示,电池放电终点之所以出现主要是由于电池负极电位在放电末期的快速上升而引起的.本文设计的全钒单电池于60 mA.cm-2下工作时,其电压及能量效率分别达89%和85%,表明该电池结构合理,且石墨毡是钒电池合适的电极材料.

Charge-Discharge Behaviors and Properties of a Lab-Scale All-Vanadium Redox-Flow Single Cell Research Notes

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.