It's why my recommendation is to actually go look at Toyota's tech. It's not hypothetical or in development. Their solid state batteries are known to exist and be ready to go.

"I think I found Toyota's battery" https://news.ycombinator.com/item?id=36980630

Which refers to " https://www.nature.com/articles/s41563-022-01421-z"

Maybe some patenting stuff under way? I don't know.

Toyota did predict this for a few years ago but things were shut down for the pandemic.

Fun reads: https://hn.algolia.com/?q=toyota+battery

Older teslas driving features are more reliable than the current ones. It sounds like training the AI driving systems with synthetic data is helping speed up progress. Another fn area to read.