Prussian Blue, well known as a dye for jeans, is emerging as a next-generation battery material. A research team at UNIST has found a way to lower battery prices by developing a low-cost, high-performance lithium-ion battery using Prussian Blue.

UNIST (President Yong-Hoon Lee) announced on the 24th that Professor Hyun-Wook Lee's team in the Department of Energy and Chemical Engineering developed a lithium secondary battery system that significantly improved battery performance while being inexpensive, using Prussian blue as a cathode material. Performance was maximized by combining the advantages of organic and aqueous electrolytes used in existing batteries.

The improved electrolyte removes water molecules during battery operation and forms a stable protective layer on the Prussian blue surface. This allows it to maintain a stable capacity (125 mAh/g) even after more than 500 cycles. The new electrolyte significantly improves the durability of the battery, allowing it to operate stably at high output.

Existing Prussian blue cathode materials have limited energy density and life performance due to slow reaction rates in organic electrolytes and structural instability. On the other hand, by solving these problems, the utility of Prussian blue can be increased, making it a cheap and efficient battery material.

Lithium transition metal oxides, the main cathode materials of lithium-ion batteries, contain cobalt and nickel. As the prices of these resources rise, battery prices also skyrocket. This is why lithium iron phosphate, which contains cheap iron, is attracting attention.

Prussian blue is a cheap material made of iron, carbon, and nitrogen. It has low production costs and high ionic conductivity, allowing it to accommodate a variety of ions. Due to these characteristics, it is gaining attention as a next-generation battery material. However, due to limitations in utilizing lithium, not much research has been done.

Prussian Blue, an inexpensive and efficient cathode material, has shown potential to significantly reduce the price of lithium-ion batteries. It is expected that the limitations of Prussian Blue will be overcome and applied to various battery fields by optimizing its performance through electrolyte improvement.

Professor Lee Hyun-wook predicted, “The paradigm of developing cheap cathode materials may change as Prussian blue, which was looked down on in existing lithium-ion battery systems, is transformed into an attractive, low-cost cathode material.”

First author Researcher Wi Tae-woong emphasized, “Through this research, we will not only overcome the limitations of existing Prussian blue, but will also be able to contribute to the development of more efficient and stable batteries in the future.”

First author, researcher Park Chang-hyun, explained the significance of the study, saying, “This is the first study to stably operate Prussian blue in a lithium-water-based electrolyte containing water molecules in the electrolyte.”

This research was conducted with the support of the National Research Foundation of Korea's Mid-career Linkage New Researcher Follow-up Project, and was published on June 13 in Nano Letters, an international academic journal in the field of nanoscience.