Hmm, looks like it comes down to how fast they can cool their batteries. I wonder if there's any tradeoffs. Thanks.

I'd take the sodium thing with a grain of salt (if you will), though. When there's energy there, and it releases uncontrolled, you're going to get a fire or at least a blob of molten battery. At best they're going to be more resistant to that. If they can get good power densities it's worth it just for the abundance of raw materials, though.