Vanadium Redox Flow Battery Separator Performance And Modified

In this paper, different cation and anion membranes were screened. The basic characterization and electrochemistry performance were investigated. Then, more suitable membrane employing vanadium redox battery (VRB) were studied and modified. The main points can be summarized as following.In this study a range of low cost commercially available membrane were selected. The basic characterization and electrochemistry performance of different membranes in VRB were described. Compared with domestic cation and anion exchange membranes, anion exchange membrane showed higher coulombic efficiency and lower capacity loss. Anion exchange showed higher energy efficiency at low current density, cation exchange showed good electrochemical performance at higher current density. Additionally, homogeneous polyphenylene anion exchange membrane (DF-a), was selected to modify due to its better electrochemical performance and chemical stability than other domestic membranes.DF-a membrane was modified with two methods. Amphoteric ion exchange membranes were prepared by incorporated cation-exchange groups into anion exchange membrane. Modified membrane showed more suitable for application in VRB system. It showed excellent electrochemical performance to modify with the perfluorinated sulfonic acid solution (PFSA). The result indicatedthe coulombic efficiency and energy efficiency of the VRB single cell with modified membrane were increased. The values increased by 6.7% and 3.2%, respectively, which are higher than that of the VRB single cell with unmodified membrane.The hydrothermal method was employed to obtain Nafion/TiO2 hybrid membrane. Nafion/TiO2 indicated low permeability of vanadium ions. Compared with other methods, hydrothermal modified membrane didn't incorporate other ion exchange groups and decrease permeability of vanadium ions remarkably. It has been confirmed by SEM and EDX analysis of the modified membrane that Ti elements distributed uniformly in the prepared membrane. As a result, the coulombic efficiency and energy efficiency of the VRB single cell with modified Nafion membrane was higher than that of the VRB single cell with pristine Nafion membrane (The values increased by 2.5% and 1.8% at a current density of 60 mA/cm2, respectively).