Polypropylene elastomer composite for the all-vanadium redox flow battery: current collector materials

In this study, a carbon-based polypropylene thermoplastic elastomer (PP-elastomer) composite for current collectors of an all-vanadium redox flow battery (VRB) was successfully prepared. The volume resistivity of the PP-elastomer composite was 0.47 Omega cm. Its tensile strength and elongation at break were 6.6 MPa and 250%, respectively. In addition, the good flow property in processing means this composite has potential for the mass industrial production of current collectors. The single cell and the cell stack of a VRB equipped with the composite current collectors were assembled for battery tests, including cyclic voltammetry, long-term performance, long-term stability, and oxidation corrosion. To evaluate the stability and the performance of the cell stack under a long-term operating condition, tests with more than 2300 charge-discharge cycles were carried out. The coulombic efficiency (CE) and voltage efficiency (VE) of the cell stack were maintained at around 93% and 80% during 2300 charge-discharge cycles, and energy efficiency (EE) held at around 75%. The results proved that a VRB equipped with composite current collectors has good stability and performance. Furthermore, long-term corrosion tests indicated that the PP-elastomer composite could endure the strong corrosion of pentavalent vanadium and concentrated sulfuric acid. The composite materials prepared in this study are more suitable than other materials for producing the current collectors. The corrosion resistance of composite materials is much better than that of the graphite, and the mechanism is also discussed.