▲ Dr. Ha Yun-cheol of KERI (left) and Professor Lee Yong-min of DGIST (right). (Photo courtesy of Korea Electrotechnology Research Institute)

Analysis of the Effects of Charging, Discharging, Lifespan, and Heat Generation on Lithium-ion Batteries
Contributing to the improvement of safety in smartphones, electric vehicles, and ESS

A research team from the Korea Electrotechnology Research Institute and the Daegu Gyeongbuk Institute of Science and Technology has developed a technology capable of predicting battery fires by analyzing over 1.7 million pieces of time-series data obtained from more than 1,000 experiments under various charging and discharging conditions.

The Korea Electrotechnology Research Institute (KERI) announced on the 9th that its research results on 'lithium-ion battery lifespan and heat generation characteristics analysis technology' were recognized for their high quality and published in a prestigious international academic journal in the field of electrical and electronic engineering.

The research results on 'lithium-ion battery lifespan and heat generation characteristics analysis technology,' jointly conducted by Dr. Ha Yun-cheol of the KERI Next-Generation Battery Research Center and Professor Lee Yong-min of the Daegu Gyeongbuk Institute of Science and Technology (DGIST), have been recognized for their high quality and published in a prestigious international academic journal in the field of electrical and electronic engineering.

Lithium-ion batteries are being used in various industries representing the Fourth Industrial Revolution, such as smartphones, electric vehicles, and energy storage systems (ESS).

As the persistent problem of accidents leaves a lingering sense of unease, numerous experts both at home and abroad are devoting significant effort to developing technologies for accident prevention.

Recently, electric bicycle and electric scooter batteries exploding while being charged in an apartment became a major issue, and in the case of ESS, which has recently been receiving attention, there have been more than 35 major fire accidents in Korea alone. The risk of fire or explosion has increased in proportion to the increased use of lithium-ion batteries.

One of the most important technologies for the safe use of lithium-ion batteries is 'thermal management'.

This is because battery performance deteriorates more rapidly if the temperature becomes excessively high or low. Current 'thermal management systems' are designed based on the initial characteristics of the battery and therefore fail to reflect the characteristics of batteries whose performance has degraded over long-term use.

Accordingly, the research team analyzed the impact of long-term charging and discharging processes on the lifespan and heat generation of lithium-ion batteries, and through this, developed a technology capable of predicting even battery fires.

▲ Battery accident prediction data based on statistical analysis and computational analysis techniques regarding the effects of charge/discharge conditions on battery lifespan, internal resistance, and heat generation. (Photo courtesy of Korea Electrotechnology Research Institute)

It has been scientifically revealed that even a normal battery, free from external factors such as shock or manufacturing defects, can lead to an accident if used for a long period without systematic heat management.

This study was conducted on the cylindrical battery (2.85Ah), which is the most widely produced type of lithium-ion battery. This is the result of analyzing over 1.7 million time-series data obtained from more than 1,000 experiments under various charge and discharge conditions.

▲ Experiment measuring the heat generation characteristics of a cylindrical battery (18650 type, 2.85Ah capacity). (Photo courtesy of Korea Electrotechnology Research Institute)

Unlike previous studies that presented changes in storage capacity based on battery usage cycles merely as simple numerical values, this is the world's first statistically accurate analysis of the impact of charge and discharge rates on battery lifespan and heat generation characteristics.

Furthermore, the research team independently developed a Python program capable of visualizing and statistically processing this data, successfully analyzing the long-term performance of batteries and establishing a foundation for simulations by integrating with commercial software programs.

Through this, it is expected that safety can be significantly enhanced not only for smartphones used by the majority of the public, but also for electric vehicles and ESS that use hundreds to thousands of batteries in a densely packed environment.

Dr. Ha Yun-cheol of KERI stated, “While previous findings were based merely on empirical speculation that ‘devices used for more than two years will generate more heat than new smartphones,’ our achievement is significant in that we scientifically identified the cause of the problem through statistical analysis and computational analysis techniques.” He added, “We will continue our research to dedicate ourselves to developing technologies that can help stably operate various types of batteries, such as pouch and can types.”

Recognized for its excellence, the results of this study were published in the May issue of the *Journal of Power Sources*, a world-renowned journal in the field of electrochemistry. (JCR Top 11.4%, IF=9.127)

Meanwhile, KERI is a government-funded research institute under the National Science and Technology Research Council of the Ministry of Science and ICT. This research was conducted as part of the KERI Basic Project, the Ministry of Science and ICT’s Future Materials Discovery Project, and the Ministry of Trade, Industry and Energy’s Core Technology Development Project for Strengthening PCS Competitiveness, with Tae-Jong Jeong, a doctoral student at the KERI Campus of the University of Science and Technology (UST), and Hyo-Bin Lee, a doctoral student at DGIST, participating as lead authors.