While we already have transparent displays, most of the circuitry and especially the batteries are not. However, Stanford researchers claim to have created the first transparent lithium-ion batteries by replacing the standard copper or aluminum foundation of a battery with a transparent silicone polymer, PDMS.
The researchers then "evaporated" a metal film over the PDMS trenches to create a conductive layer. A solution containing tiny chemical electrode models was poured into the trenches, while one piece of polymer is using positive electrodes and another negatives electrodes. In the next step, the scientists developed a transparent gel between the electrodes, which serves both as electrolyte as well as separator between the electrodes. The researchers said that the result is a battery that is about 62 percent transparent.
The problem is that this battery does not store a lot of power and is limited at about 20 watt hours per liter of electrolyte at this time, which is about comparable to a nickel-cadmium battery. More power can be added by stacking batteries on top of each other, which reduces the transparency of a battery to about 60% with three layers.
A commercial devices using the technology is not in sight yet. And it appears that cool gadgets were not the only motivation to create such a battery: "It's very exciting for doing fundamental scientific research," said Yi Cui, an associate professor of materials science and engineering and of photon science at SLAC National Accelerator Laboratory. "You can study what is happening inside batteries since they are transparent now."