The Korea Electrotechnology Research Institute (KERI, Acting President Nam-Kyun Kim) is expected to popularize eco-friendly batteries that do not cause fires or explosions in the future by replacing expensive vanadium with zinc and manganese in an optimal ratio to improve battery performance and secure price competitiveness.

KERI announced on the 9th that the Next Generation Battery Research Center's Dr. Park Jun-woo's team and Pusan National University's Professor Park Min-jun's team developed a technology that overcomes the limitations of existing redox flow batteries, and the related paper received excellent reviews and was published in an internationally renowned academic journal.

Redox Flow Battery is a term that combines the words reduction, oxidation, and flow. It is a battery that generates electrical energy by moving electrons from the cathode (-) to the anode (+) with the help of an electrolyte through chemical reactions called oxidation and reduction.

Unlike existing secondary batteries, the part where the chemical reaction occurs and the part where electricity is stored are separated, so independent design of output and capacity is possible, and large capacity of the battery is possible.

Additionally, it does not emit exhaust fumes and there is no risk of fire or explosion.

Vanadium, the main core material of current redox flow batteries, is an expensive metal that we depend on for imports from China and other countries. The voltage, which determines the performance of the battery, is also lower in vanadium redox flow batteries than in commercial lithium secondary batteries, resulting in a 10-15% drop in efficiency.

Accordingly, the alternative metals utilized by KERI-Pusan National University are manganese and zinc, which are relatively inexpensive and have stable supply.

In particular, the hybrid redox flow battery is configured with a unique dual ion exchange membrane structure, enabling simultaneous use of alkaline zinc electrolyte and acidic manganese electrolyte, and can expect a high potential difference.

Of course, there were difficulties. A problem occurred when the manganese cathode active material was not restored to its original state when oxidized, but was deposited on the surface of the electrode and ion exchange membrane.

To improve the problem of manganese's low reversibility, the research team used the 'carbon reduction method' to deposit bismuth metal on the electrode surface and utilized an electrolyte containing nickel, magnesium, copper, and cobalt ions.

Bismuth has excellent electrical conductivity, which improves electron transfer, and the electrolyte, which is made at an optimal ratio through analysis of electrochemical performance characteristics, acts as a catalyst, significantly improving the stability (suppression of active material side reactions), performance, and lifespan of the battery.

The effectiveness of the developed technology was subsequently verified through various analyses, including transmission electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission (ICP-OES).

As a result, the KERI-Pusan National University hybrid zinc-manganese redox flow battery was able to secure results such as implementing a higher voltage (1.3 V -> 2.52 V) than the existing vanadium system and improving energy efficiency by more than 10%.

KERI's Dr. Park Jun-woo said, "This is a new concept redox flow battery technology that combines low-cost zinc/manganese materials and metal ion catalyst technology that can increase reversibility." He added, "This achievement will greatly contribute to expanding the distribution of next-generation long-cycle, large-capacity redox flow batteries."

The results of the related research were recently published in a paper in Energy Storage Materials, an international academic journal specializing in the energy field, in recognition of its high excellence (Impact Factor 20.831/JCR 4.2%).

KERI built the first 'Gwangju LeThe goal is to further expand and develop this development technology by utilizing the 'Dox Flow Battery Test Certification Center' and to enable the production of actual large-area/high-concentration cells, which are the key to commercialization. In addition, we plan to discover related demand companies and promote technology transfer.

Meanwhile, KERI is a government-funded research institute under the National Research Council of Science and Technology of the Ministry of Science and ICT. This research was conducted as a support project for regional industrial base institutions of the Ministry of Trade, Industry and Energy, an excellent new researcher project of the National Research Foundation of Korea, and a basic research laboratory project.