한국전기연구원(KERI) 절연재료연구센터 임현균·강동준 박사팀이 KIST 유정근 박사, 성균관대 김종순 교수 연구팀과의 공동연구를 통해 이차전지 분야의 ‘숨은 주역(unsung hero)’인 바인더 성능을 세계 최고 수준으로 높이면서 친환경 소재까지 사용하는 기술을 개발해 국제 저명 학술지에 논문이 게재됐다.
▲(From left, front row) KERI's research team including Dr. Kang Dong-jun and Dr. Lim Hyeon-gyun developed a binder for battery cathodes that can replace PVDF.
Realizing eco-friendliness, high performance, and low price of binder materials that are entirely dependent on imports
A 'PVDF alternative battery binder' that surpasses EU environmental regulations has been developed by domestic researchers, realizing domestic production, eco-friendliness, high performance, and low price of binder materials.
The Korea Electrotechnology Research Institute (KERI) Insulation Materials Research Center's Dr. Lim Hyeon-gyun and Dr. Kang Dong-jun's research team, together with the research teams of Dr. Yoo Jeong-geun of KIST and Professor Kim Jong-soon of Sungkyunkwan University, developed a technology to raise the performance of binders, the 'unsung hero' of the secondary battery field, to the world's highest level while also using eco-friendly materials, and the paper was published in an internationally renowned academic journal.
The electrode, which has the greatest influence on the performance of the secondary battery, is manufactured by mixing the 'active material' that generates electricity, the 'conductive material' that helps the flow of electricity, and the 'binder' with a solvent. Here, the role of the binder is to help the active material and the conductive material adhere well to the metal plate (current collector) and to physically stabilize the electrode.
Binders occupy a relatively small proportion of the electrode, so research on them has been slow, but interest is growing as demand for high-capacity, high-performance batteries increases. Currently, polyvinylidene fluoride (PVDF), a fluorinated polymer material, is mainly used as a positive electrode (+) binder material for lithium secondary batteries.
On the other hand, PVDF is dominated by some global companies from Japan and Europe, and functional problems such as decreased battery stability have been continuously raised during the utilization process.
In particular, PVDF is composed of very strong carbon (C)-fluorine (F) bonds, so it is hardly decomposed naturally, and is called a 'zombie compound'. Since it is difficult to decompose, it is known to remain in the surrounding environment for a long time and emit a significant amount of greenhouse gases when burned. Due to this environmental toxicity issue, the European Union (EU) is discussing PVDF as a target for usage regulations. Therefore, the development of binder materials that surpass PVDF is very urgent.
KERI's achievement in solving this problem is the application of 'siloxane' to the anode binder. Siloxane is a compound composed of silicon and oxygen, and has excellent electrical properties and is chemically stable. The team of Dr. Lim Hyeon-gyun and Dr. Kang Dong-jun secured a 'hybrid siloxane resin manufacturing technology' that has the advantages of both organic and inorganic materials through several years of nanocomposite technology research, and completed the development of molecular structure design and synthesis control technology that can be applied to the anode binder.
The research team also conducted several verifications through the production of a full cell using the technology. As a result, the KERI technology was confirmed to be superior, with a lifespan stability that was 1.4 times higher than that of the existing binder using PVDF. PVDF has physical and chemical stability and good adhesiveness, but it is true that there have been various problems such as swelling phenomenon and side reactions between internal substances as batteries have been developed with high capacity and high performance recently. However, KERI technology has secured performance that overcomes these limitations.
The biggest advantage of this achievement is that it is environmentally friendly and harmless to the human body as it does not contain fluorine. Not only can it avoid the EU's environmental regulations that limit the use of PVDF, but it is also expected to greatly contribute to reducing overseas dependence on anode binders that are entirely dependent on imports.
KERI’s Dr. Lim Hyeon-gyun said, “Our country’s battery industry is world-class, but we are completely dependent on imports for cathode binders as we do not have any specialized technology or companies in the country.” He added, “Our eco-friendly binder technology utilizing siloxane can replace existing PVDF and increase the safety and lifespan of products that require high-capacity batteries, such as electric vehicles.”
Meanwhile, the results of this study were recently published as a cover paper in 'Advanced Functional Materials', a world-renowned academic journal in the field of materials, in recognition of its excellence. The 'JCR Impact Factor', which evaluates the influence of academic journals, is 18.5, which puts it in the top 5% of the field.
The research team expects that this research result will receive much attention from the secondary battery industry, and aims to find companies in need and promote technology transfer. In addition, the team plans to apply the developed technology to the field of dry cathode binder materials, and plans to continue research so that the technology can be utilized in various fields such as zinc batteries and sodium batteries in addition to lithium secondary batteries.
KERI is a government-funded research institute under the National Research Council of Science and Technology of the Ministry of Science and ICT.