FeCoS 2 polyhedral spherical nanoparticle decorated nitrogen doped hollow carbon nanofibers as high-performance self-supporting anodes for K-ion storage.

Herein, we present a freestanding and flexible 3D nanocomposite made of polyhedral spherical FeCoS 2 and nitrogen-doped hollow carbon nanofibers (FeCoS 2 @N-HCNFs) that is synthesized through coaxial electrospinning, high-temperature calcination, and a facile solvothermal process. As a binder-free anode composite for potassium-ion batteries (PIBs), FeCoS 2 @N-HCNF presents a high specific discharge capacity on the first lap (701.2 mA h g -1 at 100 mA g -1 ) and superior cycling stability (132.6 mA h g -1 at 3200 mA g -1 after 600 cycles). The impressive electrochemical performance can be ascribed to the unique 3D structure, such as the enormous specific surface area of the mesoporous structure beneficial for K + transfer, the three-dimensional hollow carbon nanofiber scaffold enhances the structural stability, and polyhedral spherical FeCoS 2 improves the overall specific capacity. According to the above description, the FeCoS 2 @N-HCNF anode is a promising candidate for advanced potassium-ion batteries.