KIST is the only government-contributed research institute that studies and develops rechargeable batteries using magnesium. Although rechargeable magnesium batteries have significant advantages such as low cost and high capacity, they are referred to as the "next, next-generation" battery owing to numerous commercialization challenges.

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Currently, a scientist is knuckling down on rechargeable magnesium batteries, a challenging task in the research field. Dr. Minah Lee of the KIST's Energy Storage Research Center is active in various fields, from future studies to commercialization research.

Dr. Lee, studies and develops functional organic materials for next-generation batteries and has drawn attention for her bountiful research, having won the 2019 Wiley Young Researcher Award from Wiley Publications in the U.S., a global publisher specializing in academic texts. She is recognized for announcing findings on next-generation battery research consecutively in May and July after returning from maternity leave this year.

The world she dreams of through her research on next-generation batteries is a sustainable one. We paid a visit to her office in August to hear in-depth stories about her research.

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The reason why the scientific and technological community is interested in rechargeable batteries that have already been commercialized is also related to the demand for materials. Dr. Lee explained, "The demand for lithium-ion batteries is increasing with the recent growth of electric vehicles and energy storage systems, but there are concerns over supply and demand because the key raw materials, or core minerals, such as lithium and cobalt, are only found in certain regions, such as South Africa, Australia, and Africa. However, magnesium is abundantly stored on the earth's crust and can store two electrons, unlike lithium and sodium, which can only store a single electron per ion, hence, a high energy density is expected."

Nevertheless, there also are obstacles. Efficient charging and discharging of magnesium metal is challenging owing to its reactivity with the existing electrolytes. Dr. Lee explained that magnesium metal, a cathode, is easily damaged in general electrolytes, making the efficient induction of charge and discharge reactions complex. To address this issue, highly corrosive electrolytes containing excessive halogen elements have been used. The subsequent disadvantage has been the limited utilization of anodic battery parts.

High corrosivity limits the rechargeable voltage and prevents the development of high-energy batteries. Accordingly, Dr. Lee's team formed an artificial protective film on the surface of magnesium through a simple process of immersing magnesium metal to be used as a cathode in a reactive alkyl halide solution before battery assembly. This process simultaneously created a nanostructure with a large reaction area, eliminating corrosivity and enabling efficient charging and discharging of magnesium, even in general electrolytes that can be mass-produced.

Dr. Lee stated, "The magnesium metal activated by the developed technology showed an overvoltage of less than 0.2 V from the initial cycle with an efficiency of over 99.5%, suggesting that the potential for commercializing high-energy-density rechargeable batteries is increased."

There also were difficulties leading up to the publication of the study. The reaction between magnesium and reactive alkyl halide solution is one of the most critical reactions in the field of organic chemistry, known as the Grignard reaction. However, the existing academia has focused on producing soluble complex compounds, with little research on solid-state products, such as the artificial film presented in the recent study, leading to difficulties in developing proof.

Dr. Lee said, "Since this is a new material that has not been reported before, it was complicated to analyze the composition and thickness of the developed protective film and to present the reaction mechanism. Fortunately, it was possible to obtain satisfactory results by proving it using the KIST beamline in the Pohang Accelerator."

Rechargeable magnesium batteries have a long way to go as it is the next generation battery. Related to this study, Dr. Lee added, "Now that we have a cathode and an electrolyte that can be used for rechargeable magnesium batteries, the next step is to develop a suitable anode and to design a fuel cell with a high energy density and long life."

"We conducted safety tests on the batteries by piercing them with nails and detonating them. The battery to which our newly developed high flash point electrolyte was applied remained stable under the identical conditions of the nail penetration test without exploding. I remember watching the video repeatedly with the students who participated in the experiment."

Dr. Lee has also made an achievement close to commercialization with rechargeable magnesium battery research. This is by the development of a new high flash point organic carbonate electrolyte that can suppress thermal runaway and fires caused by lithium-ion batteries announced in July. This study was conducted by Dr. Jayeon Baek of the Korea Institute of Industrial Technology and Professor Donghwa Seo of the Korea Advanced Institute of Science and Technology.

According to Dr. Lee, an electrolyte is a passageway for lithium ions that determines multiple factors, including the safety, life, output, and reversible capacity of a battery. While organic carbonate electrolytes have been commercialized after extensive research and development, the linear organic carbonate that constitutes these electrolytes can be easily ignited even at room temperature and is considered the cause of battery combustion.

The research team developed a new electrolyte that does not ignite even when exposed to an ignition source at room temperature by controlling the molecular structure of the linear organic carbonate. The electrolyte's combustible gas production and self-heating decreased by 37% and 62%, respectively, even at high temperatures of 230° or higher with a charged anode. As a result, no fire or thermal runaway occurred when the new electrolyte was used in the penetration test of an actual 4Ah lithium-ion battery.

Dr. Lee explained, "From the beginning of research development, we considered a combination of conditions essential for commercialization, such as economic feasibility, environmental feasibility, mass-producibility, and compatibility with existing electrodes and components. This technology can be immediately applied to the existing lithium-ion battery manufacturing infrastructure. We are evaluating the possibility of commercializing highly safe lithium-ion batteries through collaboration with cell manufacturing companies."

However, she added, "This study confirmed that there was no combustion at 128° or lower and that heat and gas generation was significantly suppressed when exposed to a high-temperature environment. It does not mean that we have eliminated the risk of combustion or explosion of rechargeable batteries from the source," emphasizing, "We hope that our study will help reduce the frequency of fires and delay fire propagation and thermal runaway to save time for extinguishing fires."

The demand for rechargeable batteries for efficient storage and utilization of eco-friendly energy is expected to increase. As such, ensuring safety is all the more important. However, Dr. Lee argued that "Research and development alone cannot 100% guarantee safe batteries." She suggested that the development of measurement technology to determine the state of battery aging quickly and accurately should be carried out simultaneously.

She also pointed out, “In the case of electric vehicles, the battery’s safety depends on the driver’s driving habits. There are several factors to consider, such as big and minor accidents, battery overcharging, and exposure to high temperatures. Medium and large rechargeable batteries have not long been on the market, and big data has just started accumulating. It is also crucial to provide consumers with standards to accurately determine the condition of batteries based on the data.”

Dr. Lee’s interest also extends to waste batteries as she has begun studying batteries with an interest in eco-friendly energy.

She stated, “As battery use increases, waste batteries are expected to pour out in the next 5 to 10 years, but waste battery recycling technology is still not cost-effective or energy efficient. Rechargeable batteries include valuable metals such as lithium and cobalt, which are not readily available in Korea; therefore, research for recovering these resources is necessary. My team is currently developing a direct regeneration technology that will enable us to reuse anodes without decomposing them. I would like to continue contributing to creating a sustainable society through various studies."