One challenge organic radical batteries have faced is to be under 0.7mm thin, so they could fit into credit cards, electronic paper devices and so on. I know it may sound normal that 0.7mm is slim enough, but rest assured, in the competitive world of electronics, every millimeter counts. In this sense, by using printing technologies, NEC Corp has hit it big: its newest prototype measures only 0.3 mm.
How did they do it? It took a 0.05mm-thick polymer film to act as package for the battery and, optionally, as a circuit board. On the latter, they formed negative electrodes and on those, separators and radical polymer positive electrodes. The result allowed them to join in a display, a data communication function, advanced encryption and other power-consuming functions.
So the prototype is a 3 x 3cm battery with a capacity of 3 mAh (equivalent to a Li-ion rechargeable battery) and an output density of 5kW/L. Its potential performance includes refreshing a screen 2.000 times (!), flashing for 360 times in a row and conveying location information 35 times etc. Or you can just as well place small electronic components on the circuit board.
For those of you who are less familiar with the concept, an organic radical battery is a type of battery that makes use of an organic radical compound, just as its name suggests.
By saturating a composite positive electrode (the organic radical compound) and the carbon fibers with electrolyte, you get a flexible electrode that looks like gelatin. When the oxidation-reduction of the radical part occurs, the result is the charging and discharging of the battery.
In conclusion, I think we can all agree that a sleeker, thinner and smarter organic radical battery is one step ahead toward the future.