A vanadium redox flow battery (VRFB) is one of the most promising energy storage systems (ESSs) due to its safety, durability and scalability. However, high cost of its components has been obstacle for commerciali-zation of VRFB. In this thesis, a carbon composite BP for the VRFB has been developed considering its elec-trical as well as chemical stability against strong acids. Charge/discharge tests of the VRFB using the optimal carbon composite BPs were performed to observe its energy and voltage efficiencies, from which the durabil-ity of the composite BP was estimated. Additionally, a high temperature heat treatment of carbon felt elec-trode for short process time is suggested. The change of surface morphology of the carbon felt electrode has been investigated with respect to treatment temperature and time, and, the cyclic charge/discharge tests have been conducted to verify the effects of surface treatment on the efficiency of VRFB.
Although the redox flow battery has long life cycle and flexible design advantages, low performance due to the damage of components or leakage of electrolytes are remaining concern. The main cause of the damage of components is the shunt current in the redox flow battery stack. Therefore, in this thesis, a method was developed to investigate the shunt current with independent cell design. Since the shunt current path connect-ed through the manifold in a stack, the discrete flow control with gas injection was developed, which could induce the significant reduction of shunt current. Finally, an electrolyte leakage sensor for the detection of small leakage of electrolyte over large area was developed with adhesively bonded insulating layer and con-ducting layers.