Korea University: Professor Yu Seung-ho’s Group Developed Next-Generation Lithium-Sulfur Secondary Batteries

Professor Yu Seung-ho’s group in the Department of Chemical and Biological Engineering at KU (first author: Doctor Kim Seong-jun) conducted a joint study with the research groups of Professor Hyeon Taeghwan (co-corresponding author, Seoul National University), the Director of the Center for Nanoparticle Research at the Institute for Basic Science (IBS); Professor Sung Yung-eun (co-corresponding author, Seoul National University), the Associate Director of the IBS Center for Nanoparticle Research; and Professor Back Seoin (co-corresponding author, Seogang University). They successfully modified the atomic structure of an iron single-atom electrocatalyst and enhanced the redox conversion reaction of lithium-sulfur batteries, significantly improving their performance.

On January 26 the results were published in Advanced Functional Materials (IF=18.808), a globally acclaimed international journal.

The lithium-ion secondary batteries that are currently commercially available have a high manufacturing cost due to the use of expensive raw materials, yet their energy density is low. Therefore, novel electrode materials are required for higher-capacity batteries. Sulfur has a theoretical energy storage capacity (1,675 mAh/g) about 5 times those of the current positive electrode materials used in lithium-ion batteries. In addition, the low price of sulfur can considerably reduce the unit cost of production. Moreover, since sulfur is lighter than the existing electrode materials, it can be more easily adopted, particularly, for example, by unmanned aerial vehicles. Accordingly, sulfur is drawing much attention as a new material for next-generation secondary batteries. However, lithium-sulfur batteries have drawbacks such as the dissolution into the electrolyte of the reaction intermediates generated by battery operation and the low reactivity of the reaction product lithium sulfide (Li2S). Thus, achieving high charge/discharge rates and sustaining long-term performance at high current density are a challenge, and enhancing the sulfide redox reactions is essential for realizing high performance lithium-sulfur batteries.

An iron single-atom electrocatalyst, which was originally developed for oxygen reduction reactions, was introduced to the lithium-sulfur battery system. In addition, the conventional graphene support was modified forming a highly wrinkled structure, which altered the electronic structure of the single iron atom, the active site of the electrochemical catalysis, to further improve catalytic activity. The modified local structure of the single iron atom and the improvement in catalytic activity were verified by performing various analytical experiments and density functional theory (DFT) calculation.

Professor Yu Seung-ho’s Group verified the improved electrochemical characteristics of the iron single-atom electrocatalyst by performing various electrochemical analyses, and realized high secondary battery performance, establishing an excellent lithium-sulfur battery system. The results of the study showed that the batteries could be stably operated for over 300 charge/discharge cycles at a high charge rate, fully charging the batteries within 15 minutes. In addition, the research group investigated the performance when using a large amount of active material and a small amount of electrolyte to satisfy the industrial requirements for commercialization. This demonstrated the possibility of applying the electrocatalyst, which used to be employed mostly on fuel cells, to secondary batteries, and the potential for developing lithium-sulfur batteries of excellent performance.

Professor Yu Seung-ho said, “Our study showed that electrocatalysts can be applied to batteries. I expect that the development of high-activity electrocatalytic materials can make great contributions to the improvement of the performance of next-generation batteries, including lithium-sulfur batteries.”

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