The key to better rechargeable batteries may be in your blood

Researchers at Yale have found that heme, a molecule found in blood, can improve the efficiency of lithium-oxygen batteries(Credit: Michael S. Helfenbein)

Traditional lithium-ion batteries may be on the way out, as scientists continue to overcome the obstacles holding back the longer-lasting lithium-oxygen batteries. The main issue is lack of efficiency and the build-up of lithium peroxide, which reduces the electrodes' effectiveness. But now a team at Yale has used a molecule found in blood as a catalyst that not only improved the lithium-oxygen function, but may help reduce biowaste.

Lithium-oxygen, or lithium-air batteries, have the potential to hold a charge for much longer than traditional lithium-ion batteries and extend the life of devices like phones to several weeks before they'd need to be recharged. But before those dreams can become a reality, the problems of efficiency and lithium peroxide build-up need to be solved.

Previous studies have tried to fight lithium peroxide by keeping the oxygen in the cell as a solid, and by modifying the electrode to produce lithium superoxide instead. In this case, the Yale researchers were looking for a new catalyst that allowed lithium oxide in the cell to decompose back into lithium ions and gaseous oxygen, and they found one in an unexpected place: animal blood.

The role of blood is to transport oxygen around the body, and it does so thanks to a protein called hemoglobin. The heme molecule makes up part of that protein, and the researchers found that when used in the battery, the molecule dissolved into the electrolytes. That helped to reduce the amount of energy needed for the battery to charge and discharge.

"When you breathe in air, the heme molecule absorbs oxygen from the air to your lungs and when you exhale, it transports carbon dioxide back out," says Andre Taylor, one of the study's authors. "So it has a good binding with oxygen, and we saw this as a way to enhance these promising lithium-air batteries."

So where could heme be reliably sourced? According to the researchers, it's often just disposed of as a waste product, so this new application for the molecule could help reduce the environmental impact of other industries. That green angle could also be another nail in the coffin of the notoriously dirty lithium-ion batteries.

"We're using a biomolecule that traditionally is just wasted," says Taylor. "In the animal products industry, they have to figure out some way to dispose of the blood. Here, we can take the heme molecules from these waste products and use it for renewable energy storage."

The research was published in the journal Nature Communications.

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