Novel scalable synthesis mechanism of uniform size yolk-shell microsphere by one-pot spray pyrolysis with in-situ polymerization and application as outstanding performance anodes for potassium-ion batteries

Yolk-shell structures, characterized by their unique core@void@shell architecture, have attracted increasing attention due to their tunable physical and chemical properties. These properties enable broad applications in areas such as nanoreactors, drug delivery, energy storage, biosensing, and surface-enhanced Raman scattering. However, conventional synthesis methods, such as templating and non-templating liquid-phase methods, often involve complicated multistep procedures, toxic reagents, and time-consuming procedures. Such limitations hinder their scalability and practical utilization in large-scale industrial settings. Recently, spray pyrolysis has emerged as a rapid, scalable replacement for conventional methods, offering a one-pot, continuous process with high production efficiency. This study introduces a novel strategy for synthesizing uniformly sized yolk-shell microspheres via spray pyrolysis with in-situ polymerization and control of drying agents. By systematically varying carbon sources, including citric acid, ethylene glycol, sucrose, and polyvinylpyrrolidone, we elucidated their influence on size distribution and yolk-shell formation mechanisms. The proposed formation mechanism demonstrated improved spherical morphologies and uniform size distribution, confirmed by the incorporation of drying control agents. Uniformly sized nickel oxide yolk-shell microsphere was selected as the initial target material, and enhanced yolk-shell structured nickel sulfide@C microspheres, obtained through post-treatments and carbon coating process, were applied as anode materials for potassium-ion batteries. When employed as anode materials for potassium-ion batteries, these enhanced yolk-shell structures exhibited improved electrochemical performance, highlighting their potential in next-generation energy storage. Overall, this study presents a scalable and versatile strategy for fabricating yolk-shell microspheres with tailored functionalities, thereby opening up pathways for diverse advanced technological applications. This approach not only demonstrates fundamental insights into yolk-shell formation but also provides practical guidelines for designing high-performance functional materials.

Mr. Tae Ha Kim graduated from the Department of Advanced Materials Engineering at Chungbuk National University. He is currently pursuing a master’s degree in Materials Engineering at the same university. His research focuses on the synthesis of nanomaterials via aerosol-assisted processes and their applications in various fields, particularly in energy storage, including next-generation batteries and advanced cathode and anode materials.