Studies On The Preparation And Performance Of Modified Polyvinylidene Fluoride Membranes For Vanadium Battery

Vanadium redox battery has been attracting domestic and foreign researchers’ attention for the advantages of its low cost, long cycle life, environmental protection. The membrane is the core component of vanadium battery. It can block different valence vanadium ions interpenetration and ensure that hydrogen ions in the film move freely between positive and negative poles. Polyvinylidene fluoride(PVDF) is one of macromolecular material with good heat and corrosion resistance, excellent anti-aging properties, but the membrane resistance is larger. So PVDF can’t be used as membrane of vanadium redox battery. In this paper, the characterization and performance of vanadium redox battery using modified PVDF membranes were studied.Barium titanate prepared by sol-gel method was combined with PVDF. The results of BT/PVDF membrane showed that hydrophilic and solution uptake increased with the addition of barium titanate. Solution uptake of 15%BT/PVDF membrane had maximum value, and the charge transfer resistance determined by AC impedance was small. When the addition of Ba Ti O3 powder less than 10 %, tensile strength and elastic modulus were improved and the elongation at break decreased. According to infrared spectroscopy, it was more prone to form chemical adsorption between PVDF and Ba Ti O3. Because F- would enter into oxygen octahedron of Ba Ti O3.Poly(vinylidene fluoride) membranes with Ba Ti O3 powders were grafted with styrene monomer and then sulfonated in concentrated sulfuric acid. The experimental results showed that proton conductivity reached 1.115 S/cm and solution uptake reached 161.2 % when the Ba Ti O3 content of composite proton exchange membranes was at 5 %. The addition of Ba Ti O3 decreased the permeability of V(IV) ions signi ficantly.PVDF-g-PSSA proton exchange membranes were prepared by UV-grafting. Proton conductivity was 9.16×10-4 S/cm. It was less than the membranes which were prepared by solution grafting method. Because UV-grafting time was short and Grafting rate was only 0.7 %. But this method was easy, and the process produced less damage to the membrane. So vanadium ion permeability of proton exchange membranes was better than the others.