UNIST·KAIST Develop New Solid Electrolyte Using Low-Cost Eco-Friendly Materials

Professor Hyunwook Lee and Professor Sungkyun Jeong's team from the Department of Energy and Chemical Engineering at UNIST, along with Professor Donghwa Seo's team from KAIST, have developed an all-solid-state sodium secondary battery that operates at room temperature using eco-friendly materials.

The research team used Prussian Blue analogues (PBAs), an eco-friendly material, as the solid electrolyte for the secondary battery. PBAs, which are environmentally friendly, are commonly used as cathode active materials (cathode materials), a key component of sodium secondary batteries.

PBAs have wide ion conduction channels that allow ions to move easily and can be synthesized with ease. They are also structurally stable and inexpensive. Along with these advantages, their properties vary depending on the transition metal, attracting significant attention.

The research team hypothesized that the intrinsic properties of PBAs could enhance ion conductivity and observed changes in ion conduction by varying the type of transition metal.

Through this, they confirmed that the size of the ion channels changes according to the size of the transition metal. Materials with larger ion channels exhibited higher ion conductivity.

The team selected appropriate material groups by analyzing the interfacial stability with each cathode and anode active material. Based on these results, they developed an all-solid-state sodium secondary battery using manganese-based Prussian Blue materials.

The battery demonstrated sodium ion conductivity of about 0.1 mS/cm even at room temperature, proving its potential as a solid electrolyte. It showed excellent atmospheric stability and allowed room temperature fabrication processes, overcoming the drawbacks of conventional sulfide and oxide electrolytes.

Schematic diagram of the structure of Prussian blue-based materials and schematic diagram of ion channel size according to the size of transition metals.

Professor Hyunwook Lee from the Department of Energy and Chemical Engineering stated, “I hope that the research field, which has been limited to sulfide, oxide, and halide-based solid electrolytes, will expand its possibilities through the discovery of new materials,” adding, “This study pointed out these limitations and simultaneously presented a successful new solution.”

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

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