While it does use lithium it doesn't necessarily have to use the 'same chemistry' as existing technologies. Beyond that, they haven't (or maybe never will) release fully the technology so we can not know.

It uses a solid-state electrolyte which is probably big reason for capacity increase. It is the flammable liquid electrolyte that causes fires in lithium ion batteries. Solid-state electrolyte shouldn’t be flammable, that is main reason people have been researching solid-state electrolytes.