Study on the Manufacture of High-purity Vanadium Pentoxide and Electrolyte for a Vanadium Redox Flow Battery

We investigated the hydrolytic precipitation process with regard to purification of low-purity vanadium pentoxide (V2O5) to obtain high-purity vanadium electrolyte (VE) of a vanadium redox flow battery (VRFB). The lowest purities of VE and V2O5 for VRFB, which were reviewed through the purity analysis of commercial VE, were found to be 99.98% and 99.8%, respectively. The hydrolytic precipitation process applied to V2O5 powder with 99.7% and 98.3% purity resulted in V2O5 powder with a purity higher than 99.8%. However, the V2O5 powder contained impurities such as Fe and Ga. To further improve the purity, a two-step process comprising red cake precipitation was applied. However, this process exhibited a low vanadium recovery rate; therefore, development of a new single purification process with a high vanadium recovery rate is required.