Professor Kang Yong-mook’s group (Department of Materials Science and Engineering and KU-KIST Graduate School of Converging Science and Technology) developed a method of improving the capacity of NASICON-based Na3V2(PO4)3, which is considered a typical cathode material for sodium secondary batteries with layer structured oxides, to be as high as that of layer structured oxides.

The results of the study were published online on October 19 in the Journal of the American Chemical Society (JACS), a prominent international journal in materials science.

- Title of Paper: Activating a Multielectron Reaction of NASICON-Structured Cathodes toward High Energy Density for Sodium-Ion Batteries

Cathode materials are considered as essential components for improving the energy density of lithium secondary batteries for electric vehicles (EV). In the light of this, increasing attention is being paid worldwide to polyanion-based cathode materials, including iron phosphate-based cathode materials (LiFePO4), which possess safety advantages but relatively low energy density. For secondary batteries, sodium is increasingly seen as a possible alternative to lithium due to concerns over the shortage of lithium minerals following the explosive growth of the EV market. As for sodium secondary batteries, layer structured oxides have shown a higher energy density than those of other structures.Inspired by first-principles calculations, Professor Kang’s group theoretically proved that doping of chromium (Cr) Na3V2(PO4)3 may induce more redox reactions and improve the capacity of the materials. In addition, compared with the existing materials the group demonstrated an improvement in capacity of more than 40% through an electrochemical test at room temperature, and an improvement of both energy density and stability through a low-temperature test at -20℃.

Regarding the results, Professor Kang said, “As more emphasis is placed on the safety of EVs, polyanion-based cathodes, rather than conventional layer structured oxides-based cathodes, are drawing increasing attention, in the form of not only lithium batteries but also next-generation sodium batteries. Our work is useful because we provide a methodology for increasing the currently lower energy density of safer polyanion-based cathode materials to the level of layer structured oxides-based cathode materials. We continue our research to develop cathode materials that are as safe as iron phosphate yet have an energy density as high as layer structured oxides-based cathode materials, such as nickel-cobalt-manganese (NCM) materials that are currently spotlighted for application in not only sodium secondary batteries but also lithium secondary batteries.”

The present study by Professor Kang’s group was supported by the Mid-Career Researcher Program and the Creative Materials Discovery Program of the National Research Foundation of Korea.