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According to the report of the American Physicists Network on July 25th, American scientists have developed a new type of carbon fiber lithium-air battery whose energy density is now 4 times that of rechargeable lithium-ion batteries in mobile phones and automobiles. The latest issue of Energy and Environmental Science.
Last year, a scientific team led by Yang Shaohong, a professor at the Massachusetts Institute of Technology (MIT) Department of Mechanical Engineering and Materials Science and Engineering, improved the energy density of lithium-air batteries by using rare metal crystals. In theory, lithium-air batteries have a higher energy density than lithium-ion batteries because they replace bulky solid-state electrodes with a porous carbon electrode that can store energy by trapping oxygen from the air passing over it. Oxygen and lithium ions combine to form lithium oxide.
The latest research has taken a step forward and the carbon fiber electrodes produced have more pores than other carbon electrodes. Therefore, when the cell is discharged, there are more pores to store solid lithium oxide.
Robert Mitchell, a co-author of the paper and a graduate student in MIT's Department of Materials Science and Engineering, said: "We have used chemical vapor deposition to plant vertically aligned arrays of carbon nanofibers. These blanket-like arrays are high in conductivity and low in density. The energy storage 'bracket'."
Another researcher and graduate student of the MIT Mechanical Engineering Department, Beta Galant, explained that during the discharge process, lithium peroxide particles appear on the carbon fiber, and the carbon increases the weight of the battery. Therefore, the amount of carbon is minimized. It is very important to leave enough room for lithium peroxide. Lithium peroxide is the active chemical substance formed during the discharge of the lithium air battery. Yang Shaohong said: “Our new blanket-like material has more than 90% of the pore space, and its energy density is four times that of a lithium-ion battery of the same weight. Last year we have demonstrated that carbon particles can be used as lithium. Air batteries make effective electrodes, but then the carbon structure had only 70% of the pore space."
Scientists pointed out that because the arrangement of carbon-carbon electrode carbon particles is very orderly, and the carbon particles in other electrodes are very confusing, it is easier to observe the behavior of this electrode in the charging state by using a scanning electron microscope. Helping them to improve the performance of the battery also helps explain why the existing system will experience a decrease in performance after multiple charge and discharge cycles. However, the commercialization of this carbon fiber lithium air battery needs further study.
Source: Science and Technology Daily
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