Not an expert, but from what I read the expectation is for sodium ion batteries to get substantially cheaper than lithium, mainly due to material cost.

Lithium makes up 0.002% of the Earth's crust, meanwhile sodium is 2.36%, and there's quite a lot of it in the ocean.

https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...

The main downside is power density, which for grid storage is not as big a deal as it is for vehicles. But it will still be some years of research on sodium batteries for the cost advantage and manufacturing scale to materialize.

I’d love a shed sized battery sitting on the corner of my property if it could give me 5-7 days of power.