Batteries pose a trade-off for mobile device designers. You can use a bigger batter to get a longer run between recharges, but it will result in a device that is larger and heavier. As a result, researchers are constantly working on new technologies that can store more energy in a given amount of space. (Another way to put it is to store the same amount of energy in a smaller space.) The most popular technology these days is lithium-ion but it has its drawbacks (including occasionally catching on fire.)
SolidEnergy is a company that spun off from MIT, and its researchers think that they have a better solution. Instead of using a traditional carbon anode with a flammable liquid electrolyte, they have designed a new lithium-ion technology that is about half the size. It uses a thin film metallic anode separated from the cathode by a solid electrolyte layer made of plastic. The cathode side uses a liquid electrolyte, but one that is not flammable. The combination of solid and liquid electrolyte gives the same performance as an all liquid-electrolyte because the solid layer is very thin and does not slow down the electron transport significantly.
The result is a battery that is half the size of a traditional unit of the same storage capacity. The company has already made prototype batteries that have been tested independently to verify their increased capacity. Perhaps the best aspect of the new design is that it can be fabricated using existing battery production equipment and procedures. As a result, SolidEnergy and its partners hope to have products available on the market by 2016. This could be an enormous boon to wearable Health Tech device designers, who will be able to choose longer life, smaller size, or both compared with designs for existing battery technologies.