Dr. Park Jun-woo's team at KERI's Next Generation Battery Research Center has overcome a major obstacle to the commercialization of next-generation lithium–sulfur batteries and successfully developed large-area, high-capacity prototypes.
The lithium–sulfur battery, composed of sulfur as the cathode (+) and lithium metal as the anode (-), has a theoretical energy density more than eight times that of lithium-ion batteries, demonstrating significant potential. Additionally, it uses abundant sulfur (S) instead of expensive rare earth elements, making it cost-effective and environmentally friendly. As a lightweight and long-lasting secondary battery, the lithium–sulfur battery is considered a key technological field to drive the era of urban air mobility (UAM).
However, the lithium–sulfur battery generates lithium polysulfides as intermediate substances during the charge and discharge processes. These substances shuttle between the cathode and anode, causing unnecessary chemical reactions that degrade the battery's lifespan and performance. This has been the biggest obstacle to the commercialization of lithium–sulfur batteries.
To address this, Dr. Park Jun-woo's team introduced an innovative technology combining single-walled CNT (SWCNT1)) with oxygen functional groups2). SWCNT is a next-generation material with strength surpassing steel and electrical conductivity comparable to copper, while the oxygen functional group enhances the dispersion of SWCNT within the battery. This SWCNT combined with oxygen functional groups stabilizes the electrode, which can expand during charge and discharge, and effectively controls the dissolution and diffusion of lithium polysulfides. Consequently, the loss of sulfur, the active material, was significantly reduced.
1) Carbon nanomaterials are characterized by their nanoscale conductivity and hexagonal carbon structure. These include graphene, a two-dimensional planar structure often referred to as a dream material, and CNT, which features a helical structure of graphene. Among them, CNTs are divided into multi-walled and single-walled types, with single-walled CNTs being thinner, more transparent, and offering superior properties and electrical conductivity.
2) Functional group: A group of atoms or a single atom with specific chemical and physical properties.
Additionally, the high flexibility of SWCNT and the hydrophilic (solvent-friendly) nature of the oxygen functional group allow for the creation of uniform and smooth surfaces during electrode fabrication, enabling the design of large-area, high-capacity batteries. As a result, the research team was able to produce a flexible thick electrode3) with dimensions of 50x60mm and successfully assemble it into a 1,000mAh (1Ah)4) pouch-type lithium–sulfur battery prototype. This prototype demonstrates high performance, maintaining over 85% of its capacity even after 100 charge-discharge cycles.
3) Thick electrode : To increase the energy density of a battery, the electrode should be thicker, which is referred to as a thick electrode.
4) mAh (milli Ampere hour) : This is a unit that represents the capacity of a battery, indicating the amount of current that can be used over the course of one hour. 1Ah is equivalent to 1,000mAh. Currently, commercial cordless vacuum cleaners and smartphones typically contain lithium-ion batteries with capacities around 2,000–4,000mAh.
Dr. Park Jun-woo stated, "Our technology has not only overcome the biggest challenge of the lithium–sulfur battery through the combination of SWCNT and oxygen functional groups, but also achieved the design and prototype development of large-area, high-capacity flexible electrodes. This is a comprehensive result." He added, "We have laid the foundational framework that can be applied in actual industrial settings, marking a significant achievement that opens up the practical commercialization potential of next-generation lithium–sulfur batteries."
The results of this research have been recognized for their excellence and published in *Advanced Science*, one of the world's top journals in the field of materials science (first author Heo Jun-young, UST KERI Campus Ph.D. student; co-corresponding author Dr. Han Jung-tak; corresponding author Dr. Park Jun-woo). The paper's *Impact Factor* is 14.3, placing it in the top 7.18%.
KERI, which has already completed a domestic patent application, anticipates that this achievement will attract significant interest from companies in industries such as urban air mobility, aerospace, ESS, and electric vehicles, where next-generation lithium–sulfur batteries are in demand. The goal is to identify potential clients and pursue technology transfer.
Meanwhile, KERI is a government-funded research institute under the National Research Council of Science & Technology (NST) of the Ministry of Science and ICT. This research was conducted as part of the 'Global Top Strategic Research Group' project (Strategic Research Group for Innovation in Market-Leading Next-Generation Secondary Batteries) and KERI's project (lithium–sulfur batteries).
