Engineering360: "A Better Way to Store Renewable Energy"

"....a rare-earth element bismuth ferrite...."

Bismuth is not a rare earth metal. Neither are iron or oxygen (thus ferrite). Moreover, bismuth ferrite is not an element.

Unfortunately, Pumped water based energy storage still gives the best societal bang for the buck invested given how much more it contributes to society beyond just electrical energy storage and production balancing capacity.

Pumped hydro storage in the VA coal fields -

http://www.register-herald.com/news/dominion-to-invest-more-than-billion-in-va-storage-station/article_93b49db8-3c68-5c58-bb19-451bfc50a87a.html