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Posted: Oct 18, 2013

Nanofiber-graphene technology developed for lithium-air secondary batteries

(Nanowerk News) Will the day come to travel Seoul-Busan with an electronic vehicle? The core technology for lithium air secondary battery, the next generation high capacity battery, has been finally developed.
A research team formed by KAIST Department of Materials Science’s Professors Il-Doo Kim and Seokwoo Jeon, and Kyonggi University Department of Materials Science’s Professor Yong Joon Park has created a ‘lithium air secondary battery,’ with five times greater storage than the lithium-ion secondary battery, by developing a nano fiber-graphene composite catalyst. The research results are published Nano Letters ("Bifunctional Composite Catalysts Using Co3O4 Nanofibers Immobilized on Nonoxidized Graphene Nanoflakes for High-Capacity and Long-Cycle Li–O2 Batteries").
A cathode of a lithium-ion battery consists of graphite and an anode of the battery consists of a lithium transition metal oxide. Lithium-ion batteries are widely used in mobile phones and laptops. However, lithium-ion batteries cannot support electric vehicles, providing energy for only 160 kilometers on one full charge. The lithium air secondary battery just developed by the research team uses lithium on the cathode and oxygen on the anode. It is earning the popular acknowledgement among the next generation secondary battery research community for having lightweight mass and high energy density.
However, lithium-ion batteries remain difficult to commercialize because of its short lifespan. Lithium and oxygen meet up to form lithium oxide (Li2O2) at discharge, and decompose again at charge. In the traditional lithium air battery, this cycle does not occur smoothly and results in high resistance, thereby reducing the lifespan of the battery. It is thus essential to develop high efficiency catalyst that facilitate the formation and decomposition of lithium oxides.
The research team used electric radiation to develop a nano composite catalyst by mixing cobalt oxide nano fiber and and graphene. The performance of the battery has been maximized by settling nonoxidative graphene, which has high specific surface area and electrical conductivity, on catalyst active cobalt oxide nano fiber. Applying the nano composite catalyst on both poles of the lithium air battery resulted in an eye-opening lifespan of over 80 recharge cycles with capacity greater than 100mAh/g, five times greater than a lithium ion battery. The newly discovered charge-discharge property is the highest among the reported performances so far.
The lithium air battery is cheap to make, as the main materials are metal oxide and graphene. It is expected to support a return-trip from Seoul to Busan, a distance greater than 800 kilometers, if the lithium air battery become marketable and is applied on electronic vehicles. “There are yet more issues to resolve such as stability, but we will collaborate with other organizations to open up the era of electronic vehicles,” said Professor Il-Doo Kim. “We hope to contribute to vitalizing the fields of next generation lithium air battery by leading nanocatalyst synthesis technology, one of the core materials in the fields of secondary battery,” Professor Kim spoke of his aspiration.
Source: KAIST
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