Vanadium has a unique characteristic of having four different stages of oxidation. In each of the four stages, Vanadium contains a different electrical charge and is therefore used as a catalyst to store energy. In order to convert this electrical energy into a chemical compound, it requires two electrodes, called a “stack”.
This stack consists of many cells; each one contains two half-cells that are separated by a membrane. In the half-cells the electrochemical reactions take place as soon as electrolytes flow past the membranes. Hence, the reduction or oxidation leads to the charging or discharging of the battery.
The stack is connected to two different tanks and one electrolyte tank contains the positive V4+ and V5+ redox couples, the other the negative V2+ and V3+ redox couples. These energy-carrying liquids circulate through the stack by pumps.