Published on December 8th, 2014 | by Stephen Hanley0
Hybrid Solar Cell Is Also A Battery
Solar cells are great. They provide us with clean, renewable energy for free. As long as the sun is shining, that is. For decades, critics of solar power have taunted that electricity generated from fossil fuels is better because it is available any time of the day or night. But what if there was a solar cell that is also a battery and could store the electricity it makes for later use?
In an article published by Ohio State University this month, a team of researchers led by Dr. Yiying Wu, a professor of chemistry and biochemistry, say they have created a hybrid solar cell that is also a battery. Dr. Wu’s patent-pending device may bring us one step closer to the development of a system in which efficient, decentralized power generation is the norm.
The hybrid solar cell improves on current systems is by nearly eliminating inefficiency in energy transfer. Usually, up to 20% of the energy produced by a solar cell is lost as it travels to and charges a battery. But since this new device combines the solar cell and battery into one device, nearly 100% of the energy produced can be stored.
Unlike lithium-ion batteries, which have a short lifespan and are temperature sensitive, the Ohio State system uses lithium-oxygen technology. This has up to 15 times the energy density of lithium-ion batteries, almost matching the energy density of gasoline. But these so-called “air batteries” need the oxygen from air to work. Most solar cells are solid and impermeable to air.
So the team designed a novel mesh-like solar cell made from microscopic rods of titanium dioxide. The mesh makes the solar cell permeable to air while the rods were treated to capture sunlight. Normally, connecting a solar cell to a battery would require the use of four electrodes. The hybrid design uses only three.
The mesh solar panel forms the first electrode. Beneath it, the researchers placed a thin sheet of porous carbon (the second electrode) and a lithium plate (the third electrode). Between the electrodes, they sandwiched layers of electrolyte to carry electrons back and forth.
Here’s how the solar battery works: during charging, light hits the mesh solar panel and creates electrons. Inside the battery, electrons are involved in the chemical decomposition of lithium peroxide into lithium ions and oxygen. The oxygen is released into the air and the lithium ions are stored in the battery as lithium metal after capturing the electrons. When the battery discharges, it chemically consumes oxygen from the air to re-form the lithium peroxide.
This is new technology and there are hurdles to be cleared before it finds its way into production. Lithium-air batteries have been the subject of research since the 1970’s but today we are closer than ever to capturing energy from the sun and curing our addiction to energy generated by burning fossil fuels.
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