According to a recent Yale study, a biomolecule found in blood has the potential to improve the efficiency of lithium-oxygen batteries.

Yale School of Engineering & Applied Science professor André Taylor employed heme, a constituent of hemoglobin, as a catalyst to reduce the buildup of lithium peroxide, an oxide that covers the battery electrode and decreases efficiency of energy output. The finding aims to improve lithium-oxygen batteries, which are among the most efficient batteries ever created but lack functionality and widespread use due to oxide buildup and efficiency issues.

Furthermore, the use of heme from animal blood repurposes a common waste product in the meat industry, according to the researchers. The study was published in the journal Nature Communications on Oct. 19.

“In this work, we first report the usefulness of heme [molecules] as the catalyst part for future lithium-oxygen batteries,” lead author Won-Hee Ryu said. “We first show the possibility of heme molecules to use in future ‘green energy’ applications.”

For the study, researchers constructed a typical lithium-oxygen cell and compared the battery’s performance with and without the introduction of heme. The findings indicate that the overall charge capacity of the cell was improved with heme, and that the coulombic efficiency, a common indicator of battery effectiveness, rose from 84 to 93 percent.

While other studies have shown similar progress with the use of catalysts, Ryu said that his study is the first to demonstrate the eco-friendly potential in using heme.

“This work is very promising because using heme catalyst [molecules] extracted from blood waste is cost-effective and eco-friendly,” said Ryu. “This part should be paired with the food industry and farming industry.”

Ryu added that he decided to test the catalyst potential in heme when, after seeing bloody pictures in his wife’s anatomy textbook, he recalled that the main function of blood is to transport oxygen and realized the promising application of this in a lithium-oxygen battery.

Like most batteries, lithium-oxygen or lithium-air cells function through interactions between a negative anode, lithium, and a positive cathode, oxygen. The voltage in the system is produced as oxygen reacts with lithium ions to produce lithium peroxide and electrical energy.

“We looked at different [catalysts] and came upon heme because it helps to absorb oxygen,” Taylor said. “The heme molecules can actually bond with the oxygen to help break the oxide apart, and we saw it as a pretty interesting concept that worked out pretty well.”

According to K.M. Abraham, a professor at the Northeastern University Center for Renewable Energy Technologies and the inventor of the first lithium-air battery, research in lithium-oxygen batteries has progressed as more studies attempt to improve efficiency. Recent studies have found that these cells are among the most dense high energy batteries ever found, more comparable to gasoline in energy density than to the more-widespread lithium-ion battery used in appliances and electric vehicles. Still, despite their promise, lithium-oxygen batteries are restricted by the buildup of oxides and other limiting effects, as addressed in the Yale study.

However, some researchers were less optimistic about the study’s findings. Abraham expressed doubt as to the choice of catalyst in the study.

“One of the problems with using redox mediators [like heme] is that while they improve the performance of your positive oxygen cathode, they can also have some deleterious effects on the negative lithium anode,” Abraham said. “While it is an interesting idea, unless you can somehow prevent [heme] from reaching the negative electrode and deleteriously affecting it, I’m not sure of the practical reliability of the approach.”

Most current research in the field of lithium-oxygen batteries is attempting to expand the efficiencies for both cathodes, working toward the goal of making lithium-oxygen batteries efficient and reliable enough for widespread commercial use.

The lithium-oxygen battery was invented in 1996.