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Bio-Inspired Approach

Organisms: The Beginning of Future Battery Technology

“The secondary-battery market is growing fast in the fields of small electronic devices, electric automobiles, and power storage. The “bio-inspired approach” research led by the KAIST Institute for the NanoCentury (KINC) bears significance in that it found answers, from organisms and nature, to solve difficult challenges thus far faced by secondary batteries and proved their potential. Organisms and the nature are an unlimited repository of ideas to prolong the performance and life of secondary batteries. In addition, these new solutions are expected to be commercialized without difficulty since they can be readily applied to product development in a number of industrial fields. Based on similar convergent research, KINC will further contribute to discovering effective ideas and creating high added value in a range of energy sectors.”

Development of High-capacity, Next-generation Secondary Batteries with Improved Lifespan

The material for electrodes of lithium secondary batteries has largely been transition metals that use the repetitive insertion and elimination reaction of lithium ions. However, this material has evident limitations in terms of capacity and lifespan, the two factors that characterize secondary batteries.

Various future lithium secondary batteries demonstrate several advantages, such as lower cost, larger output, and higher capacity, but the problems inherent in specific materials have reduced battery life and, therefore, have hindered commercialization. In addition, since these batteries are too heavy and require high development costs, it has been difficult to apply them to electric automobiles or other application areas that require high-energy density. In order to find new solutions to overcome high costs, reduced battery capacity, and a complicated process, researchers have, for many years, engaged in a number of research efforts involving a wide range of approaches, but without significant achievements.

Against this backdrop, the KINC research team led by Prof. Jang Wook Choi decided to try an entirely different approach by going beyond the existing development method involving screening within the scope of known materials. As a result, the researchers drew inspiration from bio-organisms and nature, and derived novel ideas from the human body. They took notice of the sagacious phenomena that have existed in the nature and organisms but did not attract attention during the human history of technological development.

The bio-inspired approach research started from two major ideas. First, the research team used the alginate polymer derived from sea mustard as an electrode binder for secondary batteries and developed secondary batteries with enhanced output density and lengthened life. For instance, a mobile-phone battery’s life ends after 300-500 charges and discharges, and therefore, they must be replaced after one to two years of use. Crystal structures including manganese are widely used as cathode materials for general batteries, but due to the inherent properties of manganese, the material is dissolved into an electrolyte within the electrodes, causing the battery life to decline. Professor Choi’s team applied the alginate binder to a secondary-battery process based on the fact that the alginate, often found in sea mustard and kelp, helps mitigate heavy-metal contamination. A combination of alginate and the secondary-battery technology proved to significantly increase the number of charges and discharges. This approach also has a competitive edge in terms of costs, which will facilitate commercialization within two to three years.

Second, the research team applied the principles of the melanic pigment working in human eyes. This idea was utilized for a study to prolong the life of the air-based batteries of the future, which will last much longer than the existing lithium-ion batteries once they are charged. Research on secondary batteries with high energy density has continued, and in the same context, there have been continued efforts to develop lithium-air cells.

One of the problems of air cells, which use air as an electrode, is that air is converted to oxygen radicals after an electrochemical reaction and these radicals attacks other electrodes, resulting in side reactions and shortened life. Due to the small number of charges and discharges, commercialization is almost impossible. The research team collaborated with Professor Haeshin Lee to come up with ideas to solve such problems and eventually directed their attention to the melanin component in human eyes, which has molecules that absorb oxygen radicals on their own, even when they receive ultraviolet rays.

Professor Choi and his research team developed bio-secondary batteries with a substantially increased number of charges and discharges and enhanced the lifespan by using synthesized melanin, namely polydopamine, which is similar to melanin found in the human body. Once this technology is commercialized, the mileage of electric cars will be dramatically lengthened in the near future so that they can run 400-500 kilometers after one charge, contributing to the dissemination of electric automobiles.

Based on these exciting ideas, the research team led by Prof. Choi is focusing on a number of natural phenomena today in an effort to develop more enhanced secondary batteries based on the continued study of the nature and organisms, an unlimited repository of ideas.

Prof. Choi, Jang-uk
2014 Annual Report

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