As global electric vehicle (EV) manufacturers adopt cylindrical batteries, recent research highlights that merely considering electrode curvature in battery design can mitigate issues like lithium metal deposition.
A research team, led by Professor Kyeong-Min Jeong from the School of Energy and Chemical Engineering at UNIST has elucidated the impact of electrode curvature on the electrochemical performance of cylindrical batteries and proposed an optimized electrode design that takes this curvature into account.
Cylindrical cells consist of stacked layers of cathodes, anodes, and separators, which are then tightly rolled. Typically, a single cylindrical cell for an electric vehicle contains 20 to 60 such sets of anodes and cathodes separated by separators.
The research team initiated this study based on the observation that the curvature characteristics of cylindrical cells might lead to variations in the contact area between the anode and cathode, causing the capacity ratio to deviate from ideal design values. Conventionally, designers ensure that anode capacity is larger than cathode capacity to prevent lithium metal deposition and facilitate fast charging.
The team fabricated experimental single-sheet cells that mimic various curvature conditions and conducted a comparative analysis with commercial 21700 cylindrical batteries, revealing that the capacity ratio of the electrodes varies with their radial position.
Notably, in areas with significant curvature at the center, the risk of lithium metal deposition increased markedly during low-temperature or high-voltage charging. This deposition can lead to short-circuits. Additionally, the sensitivity to curvature was found to be greater when using high-capacity high-nickel cathode materials.
To address these issues, the research team proposed a design strategy that involves adjusting the thickness of the electrodes on both sides. This approach aims to correct capacity ratio changes caused by variations in the contact area between anodes and cathodes through adjustments in electrode thickness.
First author Byeong-Jin Jeon stated, “Our findings reveal that electrode curvature is a critical design variable for cylindrical cell design. This underscores the importance of employing an advanced research approach that considers not only material properties but also electrode curvature for improving battery performance and stability.”
Professor Jeong emphasized, “This research confirms the importance of linking battery form factor with design and processing technology.” He further added, “In the context of sharp global competition, improving the capacity of materials alone is not sufficient to secure an advantage.”
This research was published online in Energy Storage Materials on the 20th of last month. The study was supported by the Ministry of Trade, Industry and Energy (MOTIE) through the performance verification platform project for high-performance battery materials and components, implemented by the Korea Institute for Advancement of Technology (KIAT).
Journal Reference
Byeong-Jin Jeon, Yeong-Hyeon Lee, and Kyeong-Min Jeong, “Unveiling the impact of electrode curvature on N/P ratio variations in cylindrical lithium-ion batteries,” Energy Storage Mater., (2025).
