It's a next generation Lithium battery, I've seen lithium chemistry power storage quoted as high as 600 in some prototypes so I'm guessing they cracked something in the lithium chemistry.
Given it's still lithium based I'd still think twice before chucking a bucket of water on one that's fizzing :p
As for how this battery is better I'm not an expert, but good to read if true.
Maybe you have confused it with iron phosphate, which is also fairly popular in lower cost EVs? That one has a lot of advantages, but does have relatively poor energy density.
I thought the big issue with solid-state (besides dendrites) was a lower energy density than Li-ion? What happened?