Energy

World's first solar battery claimed to "run on light and air"

World's first solar battery cl...
Electron microscope images of the nanometer-sized rods of titanium dioxide that cover the surface of a piece of titanium gauze, allowing air to enter the battery to recharge it while also gathering light to generate electricity (Image: Yiying Wu, Ohio State University)
Electron microscope images of the nanometer-sized rods of titanium dioxide that cover the surface of a piece of titanium gauze, allowing air to enter the battery to recharge it while also gathering light to generate electricity (Image: Yiying Wu, Ohio State University)
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Electron microscope images of the nanometer-sized rods of titanium dioxide that cover the surface of a piece of titanium gauze, allowing air to enter the battery to recharge it while also gathering light to generate electricity (Image: Yiying Wu, Ohio State University)
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Electron microscope images of the nanometer-sized rods of titanium dioxide that cover the surface of a piece of titanium gauze, allowing air to enter the battery to recharge it while also gathering light to generate electricity (Image: Yiying Wu, Ohio State University)

Researchers at Ohio State University (OSU) have created a dye-sensitized solar cell that stores its own power by "breathing" air to decompose and re-form lithium peroxide. Its creators believe the device, which effectively combines a battery and a solar cell in one, could reduce renewable energy costs by 25 percent.

"The state of the art is to use a solar panel to capture the light, and then use a cheap battery to store the energy," explains OSU professor Yiying Wu. "We've integrated both functions into one device. Any time you can do that, you reduce cost."

This new design uses three electrodes, as opposed to the usual four. At the bottom lies a lithium plate, upon which lies a layer of electrolyte, a thin sheet of porous carbon and then another layer of electrolyte. At the top, a permeable titanium gauze mesh houses a dye-sensitive titanium dioxide photoelectrode, which looks rather like blades of grass at the 1 μm scale and generates triiodide ions under illumination. These ions then spread to the oxygen electrode surface via an iodide "shuttle," where they oxidize into lithium peroxide.

Electrons in the connected battery chemically decompose the lithium peroxide into lithium ions and oxygen, with the oxygen released into the air and lithium ions stored as lithium metal. When the battery discharges, it pulls oxygen from the surrounding environment and consumes it to re-form lithium peroxide – after which the cycle can repeat again.

The mesh is coated with a red dye called ruthenium compound to tune the wavelength of light it captures. This dye absorbs light and releases electrons, creating an electric current as new electrons are drawn from the iodide solution to replace them. Unfortunately, the dye runs out after just eight hours of charging and discharging, which is too short of a lifetime for a cost-effective rechargeable solar cell.

The researchers have done preliminary tests with a hematite (rust) photoelectrode to replace the dye-sensitized titanium oxide, with that seemingly offering comparable efficiency and "remarkably better" stability that may put its lifetime in the same ballpark as rechargeable batteries already on the market.

If they can settle on a material that gets similar efficiency (almost 100 percent of electrons retained, compared to around 80 percent in typical cells) to this titanium oxide version, while also lasting a number of years, the OSU researchers' invention could have huge repercussions in renewable energy. Broader uptake of renewables is currently limited by the high ratio of cost to energy generated and much of the cost comes from grid energy storage that loses more than 25 percent of the electricity coming in.

The US Department of Energy is funding further research, while OSU will license the solar battery to industry and seek to improve its performance.

A paper describing the research was published in the journal Nature Communications.

Source: Ohio State University

6 comments
S Michael
I see all these so called "break throughts' but never seem them on the market. Why is that???
David Leithauser
The drawback would seem to be that when the battery dies (most batteries have a limited number of charge/discharge cycles) you have to throw away the whole solar cell. Does not seem good for long term costs.
wle
believe it when it;s in cell phones til then - pie in the sky rubidium? that sounds cheap not wle
UCLABattMan
@ S Michael "Breakthroughs" occur in laboratory scale - they are proof of concept of original concepts on complex forms of physics, as applied to devices. In order the hit the market, they not only require scalability in the processing techniques (often a huge hurtle) and manageable material costs, but they have to compete with already-entrenched commercial entities. This is no small task, particularly because the Universities who enable these new technologies are not (and will not become) nearly as efficient at commercial ventures as actual market-established companies. @David Charles Leithauser You're right, and that's a good point. However, I'll just point out that Dye-Sensitized solar cells are quite cheap. For instance, Titanium Dioxide?: Check the milk carton in your fridge. TiO2 is used as a whitening agent in all kinds of things, including paint and the typical super-heated, nutrition-deficient pasteurized milk. So sure, the battery lasts let's say 2000 cycles (as most do today), and then must be disposed of. However, if your inexpensive Dye-Sensitized cell lasts 4-8 years and is a centralized generation/storage device - this could be a pretty useful technology, and potentially worth the cost. @wle Yes, you're absolutely correct. Ruthenium is far too expensive, and a great deal of work in being done in finding a cheap replacement material to act as the dye.
Don Duncan
Am I wrong in thinking the big roadblock to distributed energy production, e.g., home solar, is storage? This could be so disruptive as to end residential grid usage, and one big power monopoly is crippled. I hate monopolies.
Riaanh
@ S.Michael, research is not profit driven. It is knowledge driven. Very few of the great scientists in history has ever seen the fruits of their labour applied in commercial succesfull consumer products. Civilization has been built on the shoulders of giants. Most technological breakthroughs could not have been made without the groundwork done by other scientists. Very often the importance of this groundwork has only been realized in hindsight, with the original scientist, inventor dying in poverty.