Modification Of Membranes For Vanadium Redox Battery

With the exhaustion of fossil energy resources, such as coal, soil, natural gas, the energy crisis is increasingly severe. Further more, the slather of fossil energy resources bring us a series of austere environment and social problems that compelling human beings to exploit the clear and renewable new energy resources, for example, solar energy, wind energy, tidal energy, geothermal energy, nuclear energy, biomass energy and the like. However, solar energy, wind energy, tidal energy etc. is intermittent. For the sake of supplying energy continuously, energy storage devices should be combination with them. Vanadium redox flow battery (VRB) a kind of safe and environmentally friendly energy storage system. It is suitable for large-scale static energy storage and with the characteristic of flexible design, can be deeply discharged and low cost. So it can be combination with power plant, power grid and power emergency system to load shifting and stable supply. Whereas the contradiction between properties and cost hinders the large-scale commercial applications of VRB. The theme of this article is to prepare ion exchange membranes for VRB with low cost, high ionic conductivity and ion selectivity and long cycle life. The main contents are as follows:Taking advantage of waste Nafion 212 membrane and celgard 2730 PE film to fabricate PE-Nafion composite membrane. Comparing witn recast Nafion membrane, PE-Nafion composite membrane has higher area resistance due to hydrophobicity of PE, but lower vanadium ion permeability as its gap between ion cluster district decreased. Therefore, PE-Nafion composite membrane shows higher ion selectivity. The experimental data indicates that it is more suitable than recast Nafion membrane for VRB at the current density of 20 mA cm-2.Make use of waste Nafion 212 membrane and polyacrylonitrile(PAN) to prepare PAN/Nafion composite membrane. This kind of composite membrane shows good properties and low lost. The charge-discharge data shows that the composite membrane has high current efficiency and energy efficiency at the density of 20 and 30 mA cm-2 while comparing with recast Nafion.Vanadium solid-salt battery is a novel energy storage systerm, which employs VOSO4/(VO2)2SO4 solid electrolyte in the positive half-cell and V2(SO4)3/VSO4 solid electrolyte in the negative half-cell. Ion exchange membrane is the key component of Vanadium solid-salt battery. There are 3 kinds of ion exchange membranes, that are Nafion1135, Neosepta CMX C-1000, Selemion APS, to be used for vanadium solid-salt battery in this paper. The experimental data indicates that the vanadium solid-salt battery with Selemion APS shows better coulombic efficiency, voltage efficiency and energy efficiency than the one with Nafion1135 at low current densities. While CMX C-1000 shows poor voltage efficiency, it is only suitable for VSSB at the current density belowl0 mA·cm-2.