Due to its advantages such as the absence of toxic by-products, environmental friendliness, high safety, and high energy efficiency, the all-vanadium redox flow battery (VRFB) has become one of the most widely used flow batteries. This article reviews the working principle, structure, advantages and disadvantages, and development prospects of the all-vanadium redox flow battery.​​

The active materials in the all-vanadium redox flow battery are vanadium ion solutions in different valence states. The positive electrode involves the VO²⁺/VO₂⁺ couple, and the negative electrode involves the V²⁺/V³⁺ couple. The positive and negative electrodes are separated by an ion exchange membrane. The electrolyte is stored in two storage tanks and can be increased or replaced as needed. During operation, pumps circulate the electrolyte through the cell stack, where the electrolyte remains in a flowing state during charging and discharging. The main components of a vanadium battery include the electrolyte, electrodes, selective proton exchange membrane, bipolar plates, and current collectors, as shown in the schematic diagram in Figure 2.The structure of vanadium batteries can be divided into two types: static and dynamic. In static vanadium batteries, the electrolyte solution is stationary. The structure of the dynamic vanadium battery is basically the same as that of the static battery, with the addition of one storage tank and one electrolyte circulation pump for each of the positive and negative sides. The circulation pump keeps the electrolyte in a flowing state within the battery. During operation, the electrolyte is pumped into the positive and negative half-cells where reactions occur to generate electric current. A drawback is that the external pumps consume about 2-3% of the battery's total energy.Among electrochemical energy storage technologies, the all-vanadium redox flow battery has become one of the most widely used flow batteries due to its significant advantages. Compared to other energy storage batteries, the all-vanadium redox flow battery has the following characteristics:

The battery capacity and output power are relatively independent. The capacity depends on the volume of the vanadium electrolyte and the electrolyte concentration, while the output power depends on the size of the cell stack.

During charging and discharging, only the valence state of vanadium changes, without phase changes. It allows deep discharge and has a long cycle life.It produces no toxic by-products, is environmentally friendly, has high safety, and high energy efficiency.When the system is in shutdown mode, there is no self-discharge phenomenon in the electrolyte stored in the tanks.It has a fast response speed in hot standby mode, enabling near-instantaneous charging.In case of accidental mixing of the positive and negative vanadium electrolyte solutions, recovery and regeneration are relatively easy. Compared to other flow batteries like Zn-Br and Fe-Cr, it avoids issues related to crossover contamination by different ions.

Owing to the inherent advantages and broad application fields of all-vanadium redox flow batteries, they have attracted significant global attention. Their industrialization has been strategically prioritized in Western countries, and in some countries and regions, all-vanadium redox flow batteries have already reached commercial operation levels.Future research hotspots for all-vanadium redox flow batteries will focus on improving the performance of electrode materials, developing low-cost, highly selective, long-life ion exchange membranes, and electrolytes with high concentration, high conductivity, and high stability. The aim is to enhance the battery's stability, specific energy, and energy conversion efficiency, thereby promoting the industrialization of all-vanadium redox flow batteries. Furthermore, research in fundamental areas such as the kinetics of vanadium ion electrode reactions, electrolyte theory, and novel separator membranes should be strengthened to provide a more solid foundation for the development of all-vanadium redox flow batteries. With the application of large-scale renewable energy, a vast market space is provided for all-vanadium redox flow batteries. As power system reforms deepen and incentive policies are introduced, the all-vanadium redox flow battery market is expected to experience its first major growth period soon.