I'm surprised they don't mention vanadium, with its 5 oxidation states. It's already used in commercially-available flow batteries for grid energy storage (http

I'm surprised they don't mention vanadium, with its 5 oxidation states. It's already used in commercially-available flow batteries for grid energy storage (http://www.prnewswire.com/news-releases/worlds-largest-vanadium-flow-battery-goes-online-in-usa-149083905.html http://www.prnewswire.com/news-releases/worlds-largest-vanad...).