A joint research team led by Professor Dooho Kim (Department of Mechanical Engineering) and Professor Jungtae Lee (Department of Plant and Environmental New Materials Engineering) at Kyung Hee University has introduced a novel battery design strategy that dramatically enhances the charging speed and stability of lithium-sulfur (Li-S) batteries.

Kyung Hee University Researchers (photo=Kyung Hee University)

By applying mechanical compression to lithium sulfide (Li₂S) electrodes, the team successfully optimized the reaction kinetics and phase transitions of the battery, enabling superior performance even under fast-charging conditions. Their research, which holds promise for electric vehicles (EVs) and high-performance portable electronics, was published on November 11 in the internationally renowned journal Advanced Functional Materials (Impact Factor: 18.5).

■ Mechanical Compression: A Game-Changer for Li-S Battery Design

Lithium-sulfur batteries are gaining attention as a next-generation energy storage solution due to their energy density being more than twice that of conventional lithium-ion batteries. However, the commercialization of Li-S batteries has been hindered by slow reaction rates and low energy efficiency, particularly during the conversion of sulfur to lithium sulfide.

To overcome these limitations, the Kyung Hee research team introduced physical changes to the electrode structure. They embedded Li₂S electrodes within narrow pores of a porous carbon structure, creating a compressed environment that induced lattice distortion. This structural deformation lowered the energy barrier for phase transitions and optimized lithium-ion transport pathways, resulting in significantly improved reaction kinetics.

X-ray diffraction (XRD) analysis confirmed micro-level distortions in the electrode’s crystal structure under compression. These distortions played a key role in enhancing phase transition reactivity. Additionally, electrochemical impedance spectroscopy (EIS) showed that the ion diffusion coefficient of the compressed electrodes increased by over 50% compared to standard electrodes, indicating much faster charge/discharge responsiveness.

Electrochemical experiments also demonstrated improved energy efficiency. Under compression, the charging voltage of Li₂S electrodes decreased from 2.1V to 1.9V, reducing charging time and increasing energy efficiency. Moreover, the compressed electrodes maintained structural stability even after multiple cycles, leading to a twofold increase in battery capacity.

■ Beyond Lithium-Sulfur: Broader Applications of the Design Strategy

The implications of this study extend beyond Li-S batteries. The research team successfully applied the mechanical compression method to other alkali-chalcogenide battery systems, proving its versatility and scalability in next-generation rechargeable battery development.

By introducing the concept of electrochemical rigidity, the team proposes a new design paradigm for fast-charging batteries—one that goes beyond conventional electrode architecture. This dual achievement of enhanced performance and mechanical stability opens the door to commercializing high-efficiency rechargeable batteries.

■ Interdisciplinary Collaboration for Scalable Innovation

The achievement stems from ongoing interdisciplinary collaboration between the two research groups. Last year, the same team improved battery performance by doping Li₂S with selenium and tellurium, which weakened the bonding strength and increased phase transition flexibility, boosting both charge/discharge speed and capacity by over 20%. The current study builds on that foundation.

“This is a meaningful outcome of sustained academic collaboration across disciplines at Kyung Hee,” said Professor Kim. “The results demonstrate the power of integrating diverse scientific approaches.” Professor Kim’s team led computational modeling using AI and big data, while Professor Lee’s team conducted advanced electrochemical and X-ray-based spectroscopy analysis.

Looking ahead, the researchers aim to further advance battery commercialization. Professor Lee commented, “We will continue to push the boundaries of innovation to realize high-performance next-generation rechargeable batteries.”

Their work is being internationally recognized as a significant advancement in materials science and energy storage technology.