Perfluorosulfonated Acid Ion Exchange Membranes For Vanadium Redox Flow Battery

In order to make better use of the solar or wind and other renewable energy, it is of great importance to develop large capacity energy storage system. And all-vanadium redox flow battery(VRBs) has been one of the best choices, since its excellent charge-discharge efficiency, long operating life and other advantages. However, the high cost and serious vanadium ions permeation of ion exchange membranes, one of VRBs system's key components, have greatly influenced the application of VRBs in the long run. In this research, we prepared and modified perfluorosulfonated acid(PFSA) ion exchange membranes of different ion exchange capacities(IEC) by a solution-cast method, so as to find ways to improve the membranes'vanadium ions permeation.On the one hand, we made PFSA ion exchange membranes of three different IECs by a solution-cast method at two forming temperature, using the low cost PFSA ion exchange resin got from domestic. Through the property tests, it is find that the water uptake ratio, proton conductivity and vanadium ions permeability of the self-made PFSA membranes raise as the membranes'IEC values and forming temperature raised. While the selectivity of membranes raise as the IEC values raised and the forming temperature lowered.On the other hand, for the sake of further lower vanadium ions permeability, this research used 3-mercaptopropyl methyldimeth- oxysilane(MPMDMS) to modify the pristine PFSA ion exchange membranes with an IEC of 1.01mmol/g through an in-situ polymerizing method. According to the experiment results, the modified membranes displayed a much lower vanadium ions permeability, proton conductivity and water uptake ratio. And there is also a decreasing trend of these properties as the doping quality raised. The maxium selectivity of modified membranes was achieved from the one with a doping quality percentage of 7.58wt%.