Synthesis of yolk‐shell‐structured iron monosulfide‐carbon microspheres and understanding of their conversion reaction for potassium‐ion storage. (14th April 2021)

• Record Type: Journal Article
• Authors: Kim, Ju Hyeong; Park, Gi Dae; Kang, Yun Chan
• Is Part Of: International journal of energy research. Volume 45:Number 10(2021)
• Page Start: 14910
• Page End: 14919
• Publication Date: 2021-04-14
• Subjects: anode materials -- iron monosulfide -- potassium‐ion batteries -- yolk‐shell microspheres; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.6767
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: Nanostructured transition metal chalcogenides (TMCs) have attracted attention as potential anode materials owing to the anticipation of next‐generation battery systems, particularly potassium‐ion batteries (PIBs). In this study, the electrochemical reaction mechanism of iron monosulfide (FeS) with potassium ions was systemically investigated for the first time. To enhance the electrochemical properties by improving the structural stability and electrical conductivity during cycling, rational strategies of introducing a yolk‐shell architecture via an aerosol process and pitch solution infiltration were applied, resulting in the formation of yolk‐shell‐structured FeS/pitch‐derived carbon composite microspheres (Y‐FeS@C). From in situ and ex situ investigations of electrodes in fully discharged and charged states, the following reaction mechanism was determined from the second cycle onward: 4Fe + 4K2 S ↔ Kx Fe2 S3 + FeS + Fe + (8 − x)K + + (8 − x)e − . The inhibition of substantial FeS crystal growth thanks to the pitch‐derived carbon encapsulation as well as the formation of metallic Fe after the initial conversion reaction contributed to the excellent electrochemical kinetic properties of Y‐FeS@C. Y‐FeS@C showed stable cycle performance (256.5 mA h g −1 for the 100th cycle at 0.5 A g −1 ) and high rate capability (113.8 mA h g −1 at 5.0 A g −1 ) as an anode material for PIBs. Abstract : In this study, for the first time, the mechanism of the electrochemical conversion reaction of iron monosulfide with potassium ions was confirmed by various techniques, including ex situ XRD, XPS, TEM, in situ EIS, and CV. Moreover, rational strategies for synthesis of a yolk‐shell architecture via an aerosol process and pitch solution infiltration were introduced.