A solid electrolyte has been developed using prussian-based materials, which are inexpensive and environmentally friendly materials. It is expected to significantly advance the commercialization of all-solid-state secondary batteries by simultaneously resolving the high price and environmental issues of solid electrolytes.

UNIST (President Yong-Hoon Lee) Department of Energy and Chemical Engineering Professors Hyun-Wook Lee and Seong-Kyun Jeong's team and KAIST Professor Dong-Hwa Seo's team announced on the 26th that they have developed an all-solid-state sodium secondary battery that operates even at room temperature.


Prussian Blue analogues (PBAs), an environmentally friendly material, were used as a solid electrolyte. Prussian Blue analogues are one of the blue dyes used since the 18th century and are used as a dye for jeans.

PBAs, an eco-friendly material, are commonly used as a cathode active material (positive electrode material), which is a key material for sodium secondary batteries. They have a wide ion conduction channel through which ions can move, and they are easy to synthesize. They are structurally stable and inexpensive. In addition to these advantages, their characteristics vary depending on the transition metal, and they are receiving a lot of attention.

The research team determined that the unique properties of PBAs could increase ion conductivity. They observed the change in ion conductivity while changing the type of transition metal. Through this, they confirmed that the size of the ion channel changed depending on the size of the transition metal. Materials with large ion channels exhibit high ion conductivity.

The appropriate group of materials was selected through an analysis of the interfacial stability with each positive and negative active material. The ionic conductivity and interfacial stability differed depending on the type of transition metal ion. Based on the results, the research team developed an all-solid-state sodium secondary battery using a manganese-based Prussian blue series material. The battery demonstrated a sodium ion conductivity of 0.1 mS/Cm even at room temperature, proving its potential as a solid electrolyte. It has developed a new solid electrolyte that overcomes all the shortcomings of existing sulfide electrolytes and oxide electrolytes, with excellent atmospheric stability and the possibility of a room-temperature manufacturing process.

First author Taewon Kim, a researcher in the Department of Energy and Chemical Engineering, explained, “Through this study, we applied Prussian blue, an eco-friendly material, as a solid electrolyte,” and “This study presents a new perspective on solid electrolytes.”

First author and researcher Sang-hyeok Ahn explained, “Through this study, we were able to solve the chronic problems of high prices and environmental issues of existing solid electrolytes,” and “This is research that can advance the commercialization of all-solid-state batteries in the future.”

Professor Lee Hyun-wook of the Department of Energy and Chemical Engineering also said, “I hope that the research field, which was limited to existing sulfide, oxide, and halide-based solid electrolytes, will expand its possibilities with the discovery of new materials,” and explained, “This study was able to successfully present a new solution while pointing out these aspects.”

This study was conducted with the support of the UNIST Future Leading Specialization Project and the Mid-career Linkage New Follow-up Project of the Ministry of Science and ICT and the National Research Foundation of Korea. The research results were published online on August 28 in the international journal Angewandte Chemie International Edition in the field of energy and materials.