Lithium Sulfur will be the next big thing. Half the weight and.. wait for it.. eight (8) times the energy density.
There are actually quite a few lithium battery chemistries out there that are better than what we have now. Some are far better but cost too much to make, some are far better but are too difficult to manufacture, and a lot of them are just slightly better, maybe 25 to 30 percent, but they would require re-tooling of the factories that currently make batteries.. the billion dollar investment just isn't worth getting the extra 25%.
Lithium Sulfur is another animal. Its actually cheaper to make than current lithium ion, does away with the rare cobalt, and I think the nickel too, weighs only about half as much, and has far higher energy density.
Lithium Sulfur has been known for three decades, but the battery would only last for about 10 or 20 cycles before the anode (or cathode?) would destroy itself by being coated with an undesirable side reaction. Over the last twenty or so years, with chemistry tweaks and design changes, they've been able to get them into the 100 cycle range. Far better than the original, but still not enough to market for the tech we use.
Then, sometime (last year?), the boys and girls at Drexel University were screwing with the design and trying some new stuff. One of their experiments had an unexpected result. The technique they were using had unintentionally created a form of sulfur called " mono-something gamma phase sufur bla bla bla" Anyhow, long story short, they cycled the new chemistry 4000 times with no detectable degradation, and it can be manufactured on existing equipment.
The secret was in the gamma phase sulfur. They didn't mean to put it there, it created itself due to the technique they used to making the battery. As it was explained, they used a method of vapor deposition that isn't normal, and this strange technique had the side effect of turning their sulfur compounds into this gamma phase thing.
Five to six years out. The gamma-phase sulfur has them baffled and they're trying to get a better understanding of why its happening.
Imagine an EV with a 250 mile range now having a 2000 mile range, or a drone with a 40 minute flight time clocking in an entire afternoon, or a cell phone you only have to charge once a week.. and at less than half the cost.