Vanadium is a favored electrolyte material. Sumitomo, Gildemeister and American Vanadium have been pursing various vanadium flow batteries designs. All have achieved good results for large-scale energy storage applications. However, vanadium is expensive and not easily sources. Of course, this is why Gildemeister has teamed up with American Vanadium, which has access to a significant vanadium deposit in the U.S.