Lightweight and flexible yet strong? Versatile fibers with dramatically improved energy storage capacity

The latest wearable devices, such as Samsung's Galaxy Ring and Apple's Vision Pro, are taking healthcare a step further and even enabling people to work virtually. Given the characteristics of wearable devices that require them to be small and lightweight, there is an inevitable limitation on battery capacity, still presenting a technical barrier to incorporating a variety of functions. In order for wearable devices to fully realize the imagined life, it is necessary to develop a lighter and more fromlessenergy storage method.

The Korea Institute of Science and Technology (KIST) announced that a joint research team led by Dr. Hyeonsu Jeong and Namdong Kim of the Center for Functional Composite Materials, Jeonbuk Branch, and Dr. Seungmin Kim of the Center for Carbon Fusion Materials has developed a fiber-like electrode material that can store energy. The fibers are strong, lightweight, and highly flexible, enabling greater freedom in wearable device form factors and the ability to be made into various shapes and applications.

Carbon nanotube fibers are flexible, lightweight, and possess excellent mechanical and electrical properties, making them a promising material for wearable devices. However, due to their small specific surface area and lack of electrochemical activity, previous studies have mainly used them as a current collector and coated their surface with active materials. However, this approach is not only uneconomical due to the high cost of additional materials and processes, but also has a high probability of separation of the active material from the fiber during long-term use or physical deformation.

To solve this problem, the KIST research team developed a fibrous electrode material with high energy storage capacity without the need for active materials. The team developed carbon nanotube fibers with both electrochemical activity and excellent physical properties by acid-treating and modifying powder-form carbon nanotubes, followed by spinning them into fibers.

The modified carbon nanotube fiber has 33 times more energy storage capacity, 3.3 times more mechanical strength, and more than 1.3 times more electrical conductivity than ordinary carbon nanotube fibers. Moreover, since the energy storage electrode material was developed using only pure carbon nanotube fibers, it can be mass-produced using wet spinning technology.

When tested with fiber shaped supercapacitors, they retained nearly 100 percent of their performance when knotted and 95 percent of their performance after 5,000 bending tests. They also performed well when woven into the wrist straps of digital watches using a combination of regular and carbon nanotube fibers, after being bent, folded, and washed.

Dr. Kim Seung-min of KIST explained the significance of the study, saying, "We have confirmed that carbon nanotubes, which have recently started to attract attention again as a conductive material for secondary batteries, can be used in a much wider range of fields." "Carbon nanotube fiber is a competitive field because we have the original technology and there is not much of a technology gap with advanced countries," said Dr. Hyeon Su Jeong, a co-researcher, adding, "We will continue our research to apply it as a core material for atypical energy storage." Another co-researcher, Dr. Nam-dong Kim, said, " We are currently conducting research to apply this technology to fiber-type batteries with higher energy density, going beyond supercapacitors. ."

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KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/

This research was supported by KIST Major Projects (ORP, K-DARPA), the Regional Leading Research Center Project (2019R1A5A8080326) of the Ministry of Science and ICT (Minister Lee Jong-ho), the Core Technology Development Project for Material Parts Industry (20017548) of the Ministry of Trade, Industry and Energy (Minister Ahn Duk-geun), and Hyundai Motor Company. The results were published as a front cover article in the international journal Advanced Energy Materials (IF 27.8, JCR 2.8%).