リチウムイオン電池でんちの発火はっかリスクりすく低減ていげんに向むけた設計変更せっけいへんこうの可能性かのうせい――新あらたな電解質でんかいしつ導入どうにゅうによる安全性向上あんぜんせいこうじょうの研究けんきゅう

Lithium-ion batteries are widely used in various products such as smartphones and automobiles, and it can be said that they are extremely safe if stored and charged properly.

However, in reality, thousands of fires have been reported around the world, and it is not uncommon for these incidents to result in serious situations involving casualties.

Lithium-ion batteries contain a flammable electrolyte, which is a solution of lithium salt dissolved in an organic solvent, serving to enable the transfer of charge.

If a battery becomes unstable due to factors such as physical damage, overcharging, extreme temperatures, or manufacturing defects, it can suddenly generate heat or catch fire, potentially leading to a chain reaction of hazardous events known as thermal runaway.

Especially in the aviation industry, many devices equipped with batteries are brought on board, so if a fire breaks out in the cabin or cargo hold, there is a risk of losing the entire aircraft.

In fact, in the case of the Airbus A321 fire accident that occurred in Busan, South Korea this January, it is highly likely that the source of the fire was a spare battery stored in the overhead compartment. Following this incident, some airlines implemented measures to restrict the carrying of similar devices.

In response to that situation, a research team at the Chinese University of Hong Kong proposed design changes to significantly improve the safety of lithium-ion batteries.

By replacing the chemicals in conventional electrolytes with new ones, rapid application is possible without making major changes to the current manufacturing process.

According to Dr. Yue Sun currently a postdoctoral researcher at Virginia Tech, By designing temperature-sensitive materials, we can ensure high performance at room temperature while maintaining excellent stability even in high-temperature environments. The group has thus overcome the previously challenging issue of balancing safety and performance.

Specifically, by using a new electrolyte containing two types of solvents, the first solvent stabilizes the battery’s chemical structure and optimizes performance at room temperature, while the second solvent takes the lead during overheating, loosening the structure and delaying reactions that could lead to thermal runaway.

In laboratory tests, the temperature increase after the nail penetration test was limited to 3.5 degrees, and there was no sudden temperature spike up to 555 degrees as seen in conventional batteries.

Furthermore, regarding battery performance and durability, the battery retains more than 80% of its capacity even after 1,000 charge cycles, reaching a level comparable to current products.

Since the new electrolyte is in liquid form, it can be easily introduced without requiring major changes to existing production lines, says Professor Liu Yizhong from the Department of Mechanical and Automation Engineering at the Chinese University of Hong Kong.

While the manufacturing of electrodes is the most difficult process, the electrolyte is in liquid form, so there is no need to introduce new equipment or add processes, which is also a major advantage.

By introducing the new method, there is a possibility that manufacturing costs may increase slightly, but it is expected that the price will be almost the same as the current product during mass production.

The research team is currently in talks with battery manufacturers about commercialization, and it may take three to five years before practical implementation.

In addition, during the testing phase, batteries were produced to operate tablet devices, but further verification is necessary to apply them to automobiles and larger equipment.

In this way, the research results on improving the safety of lithium-ion batteries have great significance for the future of the industry.