Study on the Polyamine Thin Film Composite Membrane for Vanadium Battery

Vanadium redox flow battery (VRB) exhibits the advantages of independent capacity and power, easy modularization, long lifespan and high safety, which make it particularly suitable for use in large-scale energy storage systems. The separator is one of the key components of VRB, which has a significant impact on the overall performance and cost of the battery. Perfluorosulfonic acid membranes such as Nafion (DuPont) possesses the advantages of high chemical stability, high conductivity and good mechanical properties, therefore it has been widely used as commercial membrane in VRB. However, Nafion has the two main drawbacks of high vanadium ion permeability and high cost when used in VRB, which seriously restricts the commercialization process of VRB. Thin film composite (TFC) membranes have the advantages of easy regulation of the skin layer and substrate layer, simple preparation process and high ion selectivity, which make them particularly suitable for VRB system. However, traditional polyamide TFC membranes have potential problems of hydrolysis and decomposition in VRB strong acid electrolytes. In order to obtain a high stable TFC membrane for VRB application, polyethylenimine (PEI) and cyanuric chloride (CC) were used as monomers to prepare polyamine TFC membrane via interfacial polymerization (IP) method. Detailed physico-chemical and electrochemical performances of the membranes including vanadium permeability, single cell charge-discharge performances, chemical stability and long-term charge-discharge have been measured. The results showed that the vanadium permeability of MT is 3.17x10(-7) cm(2)center dot min(-1), which is dramatically lower than that of M-0 (30.89x10(-7) cm(2)center dot min(-1)) and commercial N 115 (Nafion 115, 10.91x10(-7) cm(2 center dot)min(-1)) membranes. The energy efficiency (EE) of MT membrane at 40 mA center dot cm(-2) reached up to 86.2%, which was much higher than that of M-0 (74.9%) and N 115 (80.0%) membranes. Chemical stability test proved that the permeability loss rate of MT was 4.42%, which is smaller than that of M0 (8.93%) and N 115 (4.86%). At the current density of 80 mA center dot cm(-2), the prepared TFC membrane has shown stable coulombic efficiency, voltage efficiency and energy efficiency. The TFC membrane is the ideal substitutes for commercial Nafion membrane and has great promise of application in VRB.