Ulsan National Institute of Science and Technology (UNIST) announced on Feb. 14 that its research team led by professors Lee Hyun-wook and Kim Young-sik at the school of energy and chemical engineering has developed a high-performance metal electrode (carbon fiber-metal composite) through a process of impregnating liquid metal into fine gaps of carbon fiber. Using this process, the research team was able to secure a mass-production technology for lithium (Li) and sodium (Na) metal electrodes.
The researchers applied the sodium metal electrode that was mass-produced by this technology to a 10 kW seawater cell energy storage system (ESS). The system was installed in the East-West power plant in December last year and just completed a test that went on for about a month.
"Unlike previous studies that focused on improving the performance of metal batteries, we succeeded in mass production of electrode materials for commercialization. As we have carried out tests after applying the electrode material to actual equipment, we expect this technology to contribute to commercialization of high-performance metal batteries," Lee said.
The metal electrode is thought to be the next generation cathode material because it is about 10 times larger in capacity than conventional graphite electrode and has a low-driving voltage. However, it has the fundamental problem of creating twig-like crystal (dendritic crystal) formation on surface of the electrode during battery operation, which leads to reduction of performance.
To addres the problem, the team fabricated a new metal electrode by machining carbon fibers to create fine gaps and impregnating metallic liquid to the gaps. In the composites with lithium or sodium metal impregnated between carbon fibers, the formation of dendritic crystals was controlled during battery operation. In turn, this improved the stability of the metal electrode and extended the life of the battery.
Because the metal liquid seeps into contact with the carbon fiber, production of an electrode only takes about 10 seconds. Carbon fiber is highly flexible as it is a type of fabrics like cloth, and this characteristic allows the electrode to be manufactured in various forms.
Kim said, "As seawater cells utilize sodium ions in inexhaustible seawater, it is a new energy storage system that is irrelevant to resource depletion problem. Since we have developed electrodes to improve the battery performance and established mass production process, the commercialization of the seawater cell will soon be possible.”
The study will be published as a supplementary cover in the international journal Nano Letters.