Vanadium flow redox batteries might be good for storing intermittent renewable sources (wind, solar). Vanadium is fairly plentiful, though it is toxic. A redox flow stores charge in two liquids separated by a membrane. The cool thing is that the vanadium solution would be in both parts of the battery, as vanadium can carry extra electrons or be short a few electrons.
Another article
And of course a youtube visualization.
I'm impressed that Sumitomo is in on the project. I'm familiar with their helium compressor used in superconductor cryogenics.
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