It boils down to: imagine asking Chevrolet to design an engine with the constraint that all of the fuel must be stored in the cylinder walls. If we want batteries that have the energy density of gasoline, this is what we want. Now you should send a tweet to @teslamotors and congratulate on them on their remarkable safety record.
Hidden deeper is an existential concern. Upon first glance, all things being equal there is no reason not to want to hang out on the upper right. However, consider a device that can provide upwards of 400 WHr/kg in under 36 seconds. This could either be