They may not even know it, but I guess transparent batteries are the dream of every teenager or fancily-dressed girl out there. And the good news is that Yi Cui together with a team from the University of Stanford, have invented such a battery.
Other types of transparent electronic components had been invented before, but nobody succeeded to effectively make transparent batteries because they couldn’t store enough electricity to be used in any application.
Cui and his team devised a battery made from electrodes so thin that they can’t be observed by the naked eye, and sandwiched a transparent gel electrolyte between them.
The electrodes are made from the same materials that make a classic lithium ion battery, but they’re only 50 micrometers thick. The researchers created a mesh of such thin wires, and the squares contain no battery components, so the entire device is transparent.
To draw the mesh, they made a mold on a silicon wafer, over which them poured a polymer called PDMS, to make the negative (just like the process sculptors use). Then, they dripped a solution of electrode materials over the PDMS, which, governed by the laws of capillarity, fill the thin channels to create the thin electrodes.
Cui’s transparent battery can for the moment store 20 watt-hours per liter, about as much as a nickel-cadmium battery and about half a normal, opaque lithium ion battery can store. The researcher is nevertheless optimistic about the future, hoping to build transparent batteries that can be as effective as the opaque ones.
He envisions that reducing the thickness of the polymer substrate and making the trenches that make the electrode’s shape deeper will do the job.
With some other researchers having already invented transparent transistors and displays, Yi Cui’s transparent battery fills in a niche whose ultimate goal would be making transparent bracelet cellphones and other kinds of gadgets that would have been hard to imagine just a few years ago.