The use of the word "rare" seems to be a reliable indicator that people have been exposed to anti-renewable propaganda.

Rare-earth elements are not rare.

"Despite their name, rare-earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, or as abundant as copper."

https://en.wikipedia.org/wiki/Rare-earth_element

And, further, many batteries and renewable power sources don't even use any Rare-earths.

As to your question, there's lots going on in storage, it wouldn't suprise me if 1/5th of the stories on a renewable tech blog were about progress and breakthroughts in various types of storage.