Batteries are a well-known problem for wearable tech. Researchers at Rice University have developed a flexible and rechargeable power resource that bypass batteries entirely in favor of supercapacitors.
James Tour, a chemist at Rice, suggests using an electrochemical capacitor a hundredth-of-an-inch thick to store power. The capacitor is easier to build than a battery, Tour says, because it uses only nickel and no lithium. (Lithium has unfortunate reactions with water and is not well-suited for clothing, which needs to be laundered.) The capacitor holds 76 percent of its charge over 10,000 charge-discharge cycles. For the chemistry geeks::
To develop the supercapacitor Tour and his fellow researchers … put a layer of nickel on a backing and then etched it with five-nanometer pores within a layer of nickel fluoride that is 900 nanometers thick. They then removed the backing and sandwiched the electrodes around an electrolyte of potassium hydroxide in polyvinyl alcohol.
Conventional Li-Ion batteries have an energy density of about 165 Wh/kg (watt-hours per kilogram). Tour reports an energy density of 38.4 khW/kg. But Tour also says that the capacitor’s power output is increased by layering the ultra-thin material.
More details in the Journal of the American Chemical Society.
Supercaps are definitely a great prospect for all sorts of mobile electronics (and even electric cars). One major advantage over a traditional battery is not only that they can discharge their power faster, but that they can also charge much faster.
My favorite bit of supercap research is the way that one group figured out how to make them out of graphene using a standard CD drive, mentioned here in a MarketPlace report: http://www.marketplace.org/topics/tech/supercapacitor-todays-energy-revolution