I was just reading an article about the state of batteries and innovation. While we've shot exponentially higher in almost all other areas of technology, the technology in batteries (a chemical reaction) has remained essentially unchanged. I believe this was the article I read, but there's a ton of knowledge out there on batteries and their relatively stagnant evolution. http://www.cnet.com/news/why-batteries-arent-getting-better/
To add to this: The magic factors everyone cares about for batteries are energy density and recharge time. The article touches on how batteries are basically layers of metal and dielectric; the more layers of metal, the higher your energy density. Electricity in batteries is a chemical process; the more reactive that chemistry the faster batteries can charge and discharge. So - the thinner and more reactive the battery design, the higher performance the battery. Which also means the higher performance your battery, the more sensitive it is to damage... and the more dramatic the results.