Professors Duho Kim at the Department of Mechanical Engineering and Jung Tae Lee at the Department of Plant & Environmental New Resources have jointly proposed a new design approach that can drastically improve the charging speed and stability of rechargeable batteries by utilizing mechanical compression of lithium sulfide (Li₂S) electrodes. This study is expected to be a key advancement in the development of next-generation battery technology for high-performance electronic products such as electric vehicles (EVs) and portable electronic devices.
Widely regarded as a promising candidate for next-generation battery technology, lithium-sulfur batteries have an energy density more than twice that of conventional lithium-ion batteries. However, their slow reaction speed and low energy efficiency during the charge and discharge processes—when sulfur is converted to lithium sulfide (Li₂S)—pose significant challenges to achieving commercial viability. To address these issues, the research team led by Professors Kim and Lee introduced structural modifications to the electrode design.
Improving electrochemical performance through mechanical compression
The research team investigated the impact of compression on the electrochemical performance of lithium sulfide (Li₂S) electrodes. Their findings suggested that physically confining the lithium sulfide anode in the narrow pores of porous carbon created a compressive environment that distorted the lattice structure of lithium sulfide. This lattice distortion reduced the phase transition barrier and enhanced ion mobility, which resulted in faster ion diffusion and phase transition dynamics.
The accelerated reaction dynamics led to significant performance boost. The charging voltage required for the lithium sulfide anode to release lithium was reduced from 2.1V to 1.9V, which shortened the charging time and increased energy efficiency. In fact, this technological breakthrough more than doubled the capacity of lithium-sulfur batteries compared to the conventional designs. The research team demonstrated these performance improvements through impedance spectroscopy (EIS), electrochemical relaxation studies, and charge/discharge experiments.
As a result, the research team proposed a new design paradigm that enables high-speed charging by engineering electrode materials to reduce electrochemical stiffness through mechanical compression. This achievement is particularly remarkable for introducing the concept of electrochemical stiffness and pioneering an innovative approach that raises the conventional electrode design to another level. Furthermore, the research strengthens the commercial potential of next-generation rechargeable batteries that can achieve both performance enhancement and mechanical stability.
Interdisciplinary efforts for commercializing lithium-sulfur batteries
This achievement is the result of sustained interdisciplinary collaboration to address the current challenges and limitations in the design of lithium-sulfur batteries. The joint research team of Professors Duho Kim and Jung Tae Lee had already made significant progress last year with the development of a high performance lithium-sulfur battery. Building upon that success, the current study was conducted as a follow-up effort to further advance the commercialization of lithium-sulfur batteries.
Professor Kim, who led the study, remarked, “This is a meaningful result achieved through sustained academic collaboration among Kyung Hee members, and it holds even greater significance as a follow-up to last year’s success.” The research team’s contribution does not end here, as they plan to continue their efforts in designing new high-performance electrode materials. Professor Lee emphasized, “Building on our accumulated research and knowledge, we will pursue continuous innovation to develop high-performance next-generation rechargeable batteries.”
The research team's achievements received high praise internationally and were published on November 10, 2024, in the world-renowned academic journal Advanced Functional Materials (Impact Factor: 18.5) under the title, “Electro-Chemo-Mechanical Domain to Enable Less Hysteretic Fast-Charging.”