
Tesla/Panasonic patented a new cell, larger with a greater capacity, but the require sophisticated thermal monitoring and cooling to prevent runaway thermal events. Don't know if they are in real world use at this point.

21700 batteries are becoming more common. Cordless tool manufacturers like Milwaukee and De Walt use 21700 batteries in some of their battery packs. I also have several Olight flashlights that use 21700 batteries. They typically have a 5000 mAH capacity vs. 2200-3000 mAH for the 18650.