New flexible battery technology from researchers at the Korea Advanced Institute of Science and Technology (KAIST) has hit the highest energy density yet for this type of battery. The bendable, thin-film, lithium-ion battery could be used in things like e-paper, wearable electronics and improved piezoelectric devices for harvesting energy from movement. Imagine flexible gadgets that could be powered by bending them.
Up until now, these thin-film batteries have employed flexible organic materials that were low performing or polymer binders that were too bulky and limited the battery's density. The new battery developed by the KAIST researchers uses inorganic thin films that have a high energy density and, according to the KAIST team, performs just as well as bulk batteries.
The batteries are built by sequentially depositing several layers – a current collector, a cathode, an electrolyte, an anode, and a protective layer – on a brittle substrate made of mica. Then, the mica is manually delaminated using adhesive tape, and the battery is enclosed between two polymer sheets to improve mechanical resistance.
Bending the battery affects performance, but not to disastrous levels. With the battery constantly bent at a radius of sixteen millimeters (about the same curvature of a fifty-cent coin) the discharge capacity drops by about seven percent after 100 charge-discharge cycles, compared to a three percent drop when the battery is not bent. Voltage was shown to remain almost constant, dropping by a very modest 0.02 V after the battery was bent and released 20,000 times.
The researchers say this battery tech could be commercialized within a year. Right now they are working on a better manufacturing process that includes an automated way of delaminating the mica. That would speed things up and allow for mass production of large area flexible lithium-ion batteries. The researchers believe that stacking the thin-film batteries could lead to even greater energy density.
Below is a video of the bendable battery lighting up an LED.