Succeeded in real-time observation of ‘Lithium-ion battery’ that expands while charging

Focused ion beam (FIB), a part of the battery analysis platform equipment developed by the Korea Institute of Science and Technology (KIST) research team. Provided by KIST
On the 26th of last month, in a double collision accident in Songpa-gu, Seoul, only electric vehicles were burned out among three vehicles. According to the statistics of the Fire Department, the safety issue of lithium-ion batteries has risen to such an extent that one out of three electric vehicle fire accidents that occurred between 2018 and 2021 were caused by battery ignition. In this situation, a real-time battery observation technology that can be used to develop safe battery devices to avoid electric vehicle fire accidents has emerged.

The Korea Institute of Science and Technology (KIST) announced on the 1st that it has succeeded in observing the expansion process of a lithium-ion battery using a silicon anode material in real time with a battery analysis platform developed by a research team led by Ahn Jae-pyeong, head of the Research Resources and Data Support Division. . The research results were published on the 8th of July in the international academic journal ‘ACS Energy Letters’.

The performance and lifespan of lithium-ion batteries are affected by internal electrode materials such as cathode and anode materials during charging and discharging. However, it was difficult to observe what was happening inside the battery because the main materials of the battery were contaminated or their characteristics changed when exposed to the atmosphere.

Director Ahn has developed a battery analysis platform that can observe the optical, electrical, and mechanical properties of battery materials and analyze the structure since 2008. Transmission electron microscopy (TEM), atomic tomography microscopy (APT), and focused ion beam (FIB) are integrated into one system and can be analyzed from various angles at once. Director Ahn said, “Exposure to the atmosphere in the process of moving samples for various observations is fatal for battery materials.

The research team observed the movement of lithium ions to the silicon-graphite anode material during charging with a battery analysis platform. Silicon-graphite anode material is known to have a charging capacity 10 times higher than that of existing graphite anode materials, so it is attracting attention as a next-generation battery material. It is known that the pores between graphite and silicon are involved in volume expansion, but the specific cause is unknown.

This study revealed that the volume expansion depends on the size of the pores. As the research team observed with the battery analysis platform, lithium ions were injected in the order of graphite, pores, and silicon during the charging process of the battery. In this case, the micro-pores absorbed lithium ions before silicon and had the effect of mitigating volume expansion, but the nano-sized pores filled the space before silicon, and thus did not reduce the volume expansion.

“As a result of observation, we have come to the conclusion that the volume expansion of silicon can be alleviated by making the pores larger or the safety of the battery can be improved by reducing the amount of silicon,” said Ahn.

According to data submitted to the National Assembly by the Ministry of Trade, Industry and Energy at the end of last year, the average dependence on foreign countries for the four key elements that make up batteries (anode material, anode material, separator, and electrolyte) is high at an average of 63.9%. As the utilization of lithium-ion batteries, such as electric vehicles and energy storage systems (ESS), is increasing day by day, the battery analysis platform will help research in developing next-generation battery devices.

General Manager Ahn said, “The competitiveness of domestic batteries depends on how well they can handle and manipulate materials.

Lee Young-ae, reporter for Donga Science [email protected]

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