Precipitation Recovery of VO(OH)<sub>2</sub> from Sodium Metavanadate Solution and Its Application in a Vanadium Redox Flow Battery
Hee Seo Kim, Yong Jae Suh, Dae Woo Kim, Pham Tan Thong, Ho-Young Jung, Ho‐Seok Jeon, In‐Su Park, Hye-Jin Hong
Abstract
The vanadium redox flow battery has received intensive attention because of the increasing demand for safe energy storage systems. Generally, V2O5 is used for the preparation of a V electrolyte, but the synthesis of V2O5 from V leaching solution leads to significant environmental impact and requires complicated sequential reduction processes for the preparation of the V electrolyte. For sustainable V electrolyte production, we directly recovered VO(OH)2 from V leaching solution via a reduction–precipitation process using hydrazine (N2H4) as a reducing agent and used the VO(OH)2 to prepare a V electrolyte. When the V concentration was 1 M, the optimal conditions for the V recovery efficiency were a N2H4/V ratio of 1, pH 4, and a reaction time of 3 h. The effect of co-existing ions (Na, Mg, K, Fe, and Al) in the NaVO3 solution was also investigated. K exhibited the strongest adverse effect on the V recovery efficiency, and Fe and Al impurities were not removed from the recovered V compound by the washing process. A V electrolyte was prepared using the recovered VO(OH)2, and its charge–discharge performance was evaluated, revealing a high voltage efficiency (∼90.15% on average) and energy efficiency (∼86.79% on average) at a constant current density of 50 mA/cm2. These results demonstrate that directly using VO(OH)2 to prepare a V electrolyte is a simple and cost-effective process.