Researchers from the Korea Institute of Science and Technology (KIST) have made a significant breakthrough in developing a nonflammable electrolyte for safer lithium-ion batteries. Led by Dr. Minah Lee of the Energy Storage Research Center at KIST, the collaborative research team also included Professor Dong-Hwa Seo of the Korea Advanced Institute of Science and Technology (KAIST), as well as Drs. Yong-Jin Kim and Jayeon Baek of the Korea Institute of Industrial Technology (KITECH).
With the growing use of lithium-ion batteries in electric vehicles and energy storage systems (ESS), concerns about fire and explosion risks have become more prominent. Battery fires occur when batteries are short-circuited due to external impacts, abuse, or aging, leading to a thermal runaway phenomenon that is challenging to extinguish and poses a high risk of personal injury. The linear organic carbonate typically used in commercial electrolytes for lithium-ion batteries has a low flash point, making it highly susceptible to catching fire even at room temperature.
Traditionally, intensive fluorination in solvent molecules or highly concentrated salts has been employed to reduce the flammability of electrolytes. However, this approach has led to decreased lithium-ion transport or incompatibility with commercial electrodes, limiting its commercial viability.
In their research, the team focused on altering the molecular structure of linear organic carbonate to prevent fire and thermal runaway in lithium-ion batteries. By simultaneously applying alkyl chain extension and alkoxy substitution to the diethyl carbonate (DEC) molecule, the researchers successfully developed a new nonflammable electrolyte called bis(2-methoxyethyl) carbonate (BMEC). This electrolyte demonstrated an enhanced flash point and ionic conductivity by increasing intermolecular interactions and solvation ability.
Compared to conventional DEC solutions, BMEC has a significantly higher flash point of 121°C, making it non-ignitable within the temperature range for conventional battery operation. Furthermore, BMEC exhibits stronger lithium salt dissociation and improved lithium-ion transport, while retaining more than 92% of the original rate capability of conventional electrolytes. In addition, BMEC reduces combustible gas evolution by 37% and heat generation by 62% compared to its conventional counterpart.
To test the stability of the new electrolyte, the research team combined it with a high nickel cathode and a graphite anode, resulting in the stable operation of 1Ah lithium-ion batteries over 500 cycles. They also conducted a nail-penetration test on a 70% charged 4Ah-level Li-ion battery, confirming the suppressed thermal runaway.
Dr. Minah Lee of KIST emphasized that the research results pave the way for designing nonflammable electrolytes without sacrificing electrochemical properties or economic feasibility. The newly developed electrolyte offers cost competitiveness and excellent compatibility with high-energy density electrode materials, making it suitable for application in conventional battery manufacturing infrastructure. Ultimately, it is expected to contribute to the development of high-performance batteries with outstanding thermal stability.
Dr. Jayeon Baek of KITECH added that the BMEC solution can be synthesized using low-cost catalysts through transesterification, allowing for easy scalability. In the future, the research team aims to develop a synthesis method using C1 gas (CO or CO2) to enhance the solution’s eco-friendliness.
The research was supported by the National Research Council of Science & Technology and the Mid-Career Research Program of the National Research Foundation of Korea, under the Ministry of Science and ICT. The findings were published in the latest issue of Energy & Environmental Science, a prestigious international journal in the field of energy and environmental science.
This latest breakthrough in developing a nonflammable electrolyte for lithium-ion batteries carries significant implications for the future of electric vehicles and energy storage systems. By addressing fire and explosion risks, this innovative electrolyte can make these technologies safer and more reliable. As further advancements are made, the widespread adoption of lithium-ion batteries in various industries is likely to continue, driving the transition towards a greener and more sustainable future.
