A research team, led by Professor Yu Seung-ho of the Department of Chemical and Biological Engineering at Korea University, Seoul National University's Professor Yuanzhe Piao and Sogang University's Professor Back Seo-in, has fabricate nitrogen and sulfur co-doped graphene nanoribbons with stepped edges, elucidating the migration barrier and enhancing the electrochemical performance of potassium batteries.
Potassium has shown promise for large-capacity non-lithium battery cells, because it is affordable, abundant, and has a low redox potential (-2.93V) close to that of lithium ion (-3.04V). Carbon-based nanomaterials, which are chemically stable and lightweight, are popular anode materials used in potassium batteries. However, the high energy barrier between electrochemical intercalation and deintercalation of potassium ions induces adsorption/desorption reactions, resulting in the storage of potassium ions only on the surface of carbon and lowering the energy density during battery assembly. As such, the smooth intercalation/deintercalation of potassium is extremely important in obtaining high-performance potassium batteries.
While graphene structures doped with nitrogen and sulfur were effective in improving electrochemical performance, the disordered arrangement of graphene caused electrical charges to be stored on the surface of the graphene under fast charging speeds. This study presented graphene nanoribbons with well-ordered stepped edges via the electrochemical unzipping of carbon nanotubes, reducing the high energy barrier of potassium ions between charging/discharging reactions to achieve high-performance potassium-ion batteries.
Professor Yu Seung-ho’s team verified the enhanced electrochemical properties of nitrogen and sulfur co-doped graphene nanoribbons using various electrochemical analyses and established a high-performance potassium battery system. A low operating voltage was maintained, even under high-speed charging, and the system remained stable after 500 charging/discharging cycles. The migration barriers of potassium ions after nitrogen and sulfur doping were calculated via DFT, and a theoretical basis was established for the battery’s high electrochemical performance. The fabricated anode material, with its outstanding properties, shows promise in the development of potassium batteries.
Korea University Professor Yu Seung-ho said, “This study showed that graphene materials doped with other elements can be utilized as an anode material for potassium-ion batteries. Doping various elements and developing carbon materials with ordered structures will further enhance the performance of next-generation batteries.”