Re: "Tape has a long way to go yet, baby."
Storing more energy per volume only becomes a "bomb" if a fast uncontrolled discharge is possible. The reason some LiON batteries go pop and catch on fire isn't because they have reached some sort of bomb limit, but because of the chemistry. Some explosives that hold a half dozen orders of magnitude more energy per volume than the battery in your phone are remarkably stable against unintended explosion. If only there were some way to cause them to discharge that energy on demand at a desired rate they'd be great for grid storage (in secured areas or buried under a few meters of concrete to prevent their use as explosives by evildoers)
The guy who invented LiON batteries originally has come up with a new version that is denser, lighter, charges and discharges faster and can't go boom or catch on fire. Not only will they not catch on fire if pierced, but they will keep working even if you stab them multiple times with a knife while they're operating! Hopefully they'll figure out how to mass produce them affordably, because that will be a welcome advance.