Development of a redox flow battery with multiple redox couples at both positive and negative electrolytes for high energy density

A new aqueous redox flow battery with multiple redox couples is developed based on a vanadium redox flow battery by adding Ti and Mn ions to both negative and positive electrolytes to form a V-Mn-Ti/V-Mn-Ti system. In this system, V and Mn act as redox couples at the positive electrode and V and Ti at the negative electrode. Since there are multiple redox couples in both negative and positive electrolytes, the energy density of the V-Mn-Ti/V-Mn-Ti system reaches to 39.3 Wh L−¹, which is higher than single redox couple systems such as the V/V and V/Mn systems by 86% and 27%, respectively. In addition, since the negative and positive electrolyte compositions are the same, the problem of electrolyte contamination due to ion crossover can be solved through rebalancing. After rebalancing, the energy density is restored to 98% of the initial performance. Based on the experimental results, the new V-Mn-Ti/V-Mn-Ti redox flow battery is expected to be a promising candidate for large-capacity energy storage devices.