By "very slowly" you mean double the capacity per kg in the last decade at a tenth of the cost? Because that is more or less what happened in the last decade.

By "very slowly" you mean double the capacity per kg in the last decade at a tenth of the cost? Because that is more or less what happened in the last decade. If you don't believe me, the Nissan Leaf originally had 21KWH of capacity when it launched in 2010. The smallest variant of the latest model has 41 KWH. You can also get a 60KWH version. And you can actually install new batteries into an original Leaf and double the range while slightly lowering the weight. And of course those batteries are now a fraction of the cost that they were in 2010. Back then replacing the battery would have cost tens of thousands of dollars. People are getting that done for around 5K now for a battery that is literally twice the capacity. The discarded batteries typically end up being part of some grid storage solution. Another doubling in the coming decade is likely. As is further reductions in price per KWH. Maybe not 10x. But probably more than 2-3x. It's profitable now to buy expensive storage solutions for grid providers. Ten years from now that will be a lot more attractive.