Upsides: Cheap, safe, no hard to source materials. Relatively high amount of cycles (> 5000). Downsides: somewhat low energy density, somewhat less efficient.

Upsides: Cheap, safe, no hard to source materials. Relatively high amount of cycles (> 5000). Downsides: somewhat low energy density, somewhat less efficient. CATL has been producing sodium ion batteries for some time. I think most of those so far end up in cheap Chinese EVs. Relatively few of those have found their way to the European or North American markets yet. Part of the reason is probably the lack of sodium ion battery factories outside of China (so far). It looks like Northvolt is looking to change that. It's competing with LFP and other battery chemistries. You'd use these mainly for cheap cars and possibly for grid storage.