Renewable energy and batteries go hand and hand. Renewable energy sources need batteries to store the energy generated so that it can be used continuously instead of just only when the sun is shining or wind is blowing. On the flip side, batteries in our devices have to be recharged and renewable energy is the best way to accomplish that.
But what if a battery could generate the energy needed to recharge it? That's just what researchers at Kogakuin University in Japan have created. The group has developed a thin, translucent lithium-ion battery that recharges itself when exposed to direct sunlight.
Instead of plugging into a separate solar panel, the translucent battery functions both as a rechargeable battery and as a photovoltaic cell. The researchers hope that in the near future the technology will evolve into large, transparent smart windows for buildings that can generate and store energy.
This team had previously unveiled a translucent lithium-ion battery four years ago that recharged with a connected solar panel. To make the new all-in-one battery, the team made a few small tweaks to the materials, using lithium iron phosphate for the positive electrode and lithium titanate and lithium hexafluorophosphate for the negative electrode.
When the battery is exposed to sunlight it becomes tinted to about 30 percent light transmittance so that the energy can be captured. The battery stays translucent because it is so thin -- only 80 to 90 nanometers thick. Once the battery discharges, the tinting fades and the light transmittance rises to 60 percent.
The battery has an output of 3.6V and the team has successfully completed 20 charge/discharge cycles in testing.
Beyond smart building windows, the technology could also one day replace screens on our smartphones and other gadgets, letting them power themselves when used outdoors in sunlight.
This isn't the first technology to achieve energy generation and storage. Last year, researchers at Ohio State University developed a dye-sensitized mesh solar panel that could both generate electricity and store it.