AA Carbon battery

Scientists develop potassium-oxygen battery, more efficient than AA Carbon battery

Researchers at Ohio State University claim to have developed a more efficient and reliable potassium-oxygen battery, which could provide a potential solution for energy storage in the national grid and longer-lasting batteries in mobile phones and laptops.

In this study, the Ohio State researchers detailed their findings focusing on the construction of the battery cathode, which stores the energy produced by chemical reactions in metals, such as oxygen or other metals embedded in air batteries.

Vishnu-Baba Sundaresan, a co-author of the study and a professor of mechanical and special aerospace engineering at Ohio State University, said, "If we want to provide a fully renewable option for the grid, we need an economical energy storage device that can store excess electricity and release it when we are not ready or working. Technology like this is key because it is cheap, does not use any exotic materials, and it can be produced anywhere to boost local economies.

However, in order for renewable energy to become a reliable source of energy for a regional energy grid, there needs to be a way to store excess energy collected from the sun and wind. Companies, scientists and governments around the world are working on storage solutions ranging from lithium-ion batteries, which are larger versions of many electric cars, to giant batteries the size of a big box made from the metal vanadium. Potassium-oxygen batteries have been a potential alternative for energy storage since they were invented in 2013.

A team of researchers at Ohio State University, led by chemistry professor Yiying Wu, says the battery can be more efficient than lithium-oxygen batteries while storing about twice as much energy as existing lithium-ion batteries. But potassium-oxygen batteries haven't been widely used for energy storage because, so far, they haven't been able to recharge long enough to be cost-effective.

When the team tried to make a potassium-oxygen battery as a viable storage solution, they hit a roadblock: the battery degraded with every charge but never for more than five or 10 charge cycles.

This degradation occurs because oxygen gets into the battery's anode, which damages the anode and makes the battery itself no longer rechargeable. Paul Gilmore, a doctoral student in Sundaresan's lab, began adding polymers to the cathode to see if it could protect the anode from oxygen. It turns out he was right, and the team realized that the polymer's expansion played a crucial role in its performance. Gilmore said, "The key is to find a way to bring oxygen into the battery but not let it penetrate the anode." It is understood that the design is a bit like human lungs, with air entering the battery through a fiber carbon layer and then encountering a second layer, which is slightly more porous, and finally ending in a third layer, which is almost not porous. The third layer made of a conductive polymer allows potassium ions to pass through the cathode, but restricts molecular oxygen from entering the anode. The design means that the battery can be charged at least 125 times, making the service life of potassium oxygen batteries 12 times longer than that of previous low-cost electrolytes. Sundaresan said, "This discovery shows that it is possible, but the team's tests have not yet proved that the battery can be manufactured to the scale required for grid storage. However, it does show its potential." Potassium oxygen batteries may also have potential in other applications. Gilmore added that "oxygen batteries have a higher energy density, which means they can improve the range of electric vehicles and the battery life of portable electronics, for example, and other challenges must be overcome before potassium oxygen batteries can be used in these applications." The discovery provides an alternative to lithium-ion batteries and other cobalt-dependent batteries, a material that has been called the "blood diamond of batteries." Sourcing this material is disturbing, and major companies including TESLA have announced plans to remove it from batteries completely. "It's very important that batteries for large-scale applications don't use cobalt, and it's also important that the batteries can be made cheaply," Sundaresan said. Lithium-oxygen batteries are a possible energy storage solution and are widely considered one of the most viable options, but they can be expensive and many rely on scarce resources, including cobalt. The lithium-ion batteries used in many electric vehicles cost about $100 per kilowatt-hour (about 690 yuan) based on material prices. The researchers estimate that this potassium-oxygen battery will cost about $44 per kilowatt-hour (about 300 yuan).

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