A lot of discussions of the learning curves for batteries seem to bundle all of this together, but I think there are two or three different learning curves that are at different points: The most visible one is mobile batteries, where lithium-based technologies dominate and have preferred quite far down the learning curve. But then I think there is a separate curve for stationary storage, which is at a much earlier stage, with huge room for improvement, and a number of promising technologies that exist but haven't yet made it to commercial scale. And I think there's another, separate and even more nascent curve for stationary and long duration storage, where there are initial indications that some of the initial technologies might be scalable, but it's still years away, and I think it's so early that we may well see entirely different approaches come out of the labs and win this market.
But Sodium based batteries are coming into the market and would be even cheaper.