Different sodium based battery technologies have existed for quite a while (much longer than lithium based batteries actually), and research as well. And there were already a couple niches where some of them managed to establish some foothold, e.g. in the domain of high-temperature batteries.

But most sodium based battery types either had a too low energy density to be competitive or they had other drawbacks that - while sometimes controllable in lab or industrial conditions, made them unsuitable for common mainstream mass uses where lithium batteries are established.

Only quite recently have we reached a point where new Na battery types emerged that simultaneously 1. do not suffer of such problems, 2. have a sufficient energy density AND 3. have made it to a commercially viable alternative to the common Lithium-ion-batteries for mainstream uses. Let's hope this time is the right time for the Na battery revolution. We'll see.