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The first EV with a lithium-free sodium battery hits the road in January
(www.engadget.com)
This is a most excellent place for technology news and articles.
You can buy them right now, there's more links in the 18650masterrace subreddit, but here's just one:
https://srikobatteries.com/product/sodium-ion-18650-1250mah-50a-rechargeable-battery/
However good luck finding a BMS that works for it's particular voltage range, don't think AliExpress has any yet.
I haven't seen any posts from those diy type folks experimenting with them yet. Sodium ion cells just became available within the last few months or so.