Professor Hor-Gil Hur's research team used microbial solution process of bacterium Shewanella to synthesize electrode material for Li-ion batteries
□ Professor Hor-Gil Hur of the School of Earth Science and Environmental Engineering at the Gwangju Institute of Science and Technology (GIST, President Seung Hyeon Moon and Vice-President Hor-Gil Hur) and Dr. Min Gyu Kim of the Pohang Accelerator Laboratory have used the bacterium Shewanella sp. strain HN-41 to make electrode material for lithium-ion batteries.
∘ The Schwannella bacterium was found in the sediments of dinosaur footprint at Haenam, and it can convert highly toxic arsenic into a yellow precipitate called arsenic sulfide. Surprisingly, the precipitated material has a unique shape of nanotubes that are several micrometers in length and has been found to exhibit semiconductor properties that can be utilized in industry.
∘ Synthesizing nanomaterials on an industrial scale requires high temperature and special equipment. However, nanomaterials produces by microorganisms can be made easily in large quantities and at low cost in an environmentally friendly process at room temperature.
□ The researchers focused on the unique structural features of the previously reported arsenic sulfide nanomaterials produced by microorganisms and studied their applicability for use in lithium-ion batteries *. Currently, lithium-ion batteries uses graphite, which is a layered structure made of carbon, as the cathode material for storing lithium ions. Similarly, microorganism-derived materials, such as arsenic sulfides (realgar, As4S4), consists of cage-like molecules with four arsenic and four sulfur atoms. There is a loosely coupled distance between the discrete molecules, and it has been confirmed that lithium ions can be freely intercalated into this space and stored by binding with the sulfur.
* Lithium-ion battery: Lithium-ion battery is used for portable electronic devices including notebooks, smart phones, and electric vehicles.
□ The research team investigated the mechanism of the reaction of arsenic sulfide nanomaterials with lithium ions through real-time structural analysis by using the Pohang Accelerator Laboratory's synchrotron radiation facility. In particular, the unique structural features of arsenic sulfide is able to maintain a stable molecular structure even during the continuous desorption process.
∘ This means that a structural problem of lithium-ion batteries that reduces its useful life from continuous breakage of its components can be solved by using this new approach.
∘ This study suggests a new method to remove toxic substances by using microorganisms and to recycle the precipitates as an energy storage and conversion material, and this method of environmentally friendly biological synthesis can improve the structural stability of Li-ion batteries.
