The human body delays the aging process by eliminating free oxygen radicals. A South Korean research team has applied this mechanism to lithium-air batteries to extend their life.
Ulsan National Institute of Science and Technology (UNIST) announced on Aug. 8 that a research team jointly led by Kwak Sang-gyu and Song Hyeon-gon, professors at the School of Energy and Chemical Engineering, has developed a catalyst which imitates biological responses and succeeded in improving the performance of lithium-air batteries and extending their life. The lithium–air battery is a next-generation battery which has three to five times higher energy density than lithium-ion batteries.
The lithium–air battery is light in weight and an environment friendly battery since is uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow. Until now, however, it has had a lower battery capacity and a shorter battery life due to free oxygen radicals created in the process of discharging.
The research team found a solution to the problem from the human body mechanism. The human body also produces free oxygen radicals and uses the superoxide dismutase (SOD) to remove them.
The antioxidant enzymes in the human body turn highly responsive active oxygen into peroxide ion (O₂²⁻) and oxygen (O₂). The process is called the disproportionation response. Thanks to this mechanism, cells are safely protected from free oxygen radicals.
The research team developed MA-C60 (SODm), a catalyst which imitates the mechanism of antioxidant enzymes, and applied it to the cathode of a lithium-air battery.
As a result, the catalyst converted superoxide ion (O₂⁻), an active oxygen, into peroxide ion (O₂²⁻) and oxygen (O₂), preventing additional responses caused by free oxygen radicals. In addition, substances decomposed from free radicals activated the formation of donut-shaped lithium peroxides (Li₂O₂) and improved the efficiency of the battery.
The research team explained the reason of high performance of SODm in theory through the computational chemistry method. The catalyst well absorbs and removes free radicals and reduces the possibility of side reactions on the surface of the electrodes, leading to the decline in energy needed for the disproportionation response. Consequently, the solution reactions forming lithium peroxides can be accelerated.
This mechanism is expected to be used to design various catalyst imitating the antioxidant enzymes (SDOm) and develop high-performance lithium-air batteries in the future. Song said, “The latest study will be a great help to improve the electrochemical characteristics of various high-capacity batteries that have a side reaction to free radicals as well as lithium-air batteries.”
The study was funded by Samsung Group as part of its project to nurture future technologies and the findings were published in ACS Nano, the prestigious international scientific journal.