FeSe2/nitrogen-doped carbon as anode material for Potassium-ion batteries

Abstract Potassium-ion batteries (PIBs) have aroused intensive interests as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage, however, the lack of high performance anode material is one of the key challenges for their development, which is mainly caused by the large size of potassium ions inducing severe volume change and pulverization of anode materials. Here, we report a FeSe2/nitrogen-doped carbon (FeSe2/NC) composite with a structure of N-doped carbon-coated FeSe2 nanoparticles anchored on thin carbon nanosheets matrix as an anode material for PIBs. Benefiting from the nanosized particles reducing the ion diffusion length, the protective carbon coating alleviating volume fluctuation, and the carbon nanosheets matrix facilitating electrons transport, the FeSe2/NC electrode delivers high capacities of 434 mA h g−1 after 70 cycles at 0.1 A g−1, and 301 mA h g−1 after 250 cycles at 1.0 A g−1. Meanwhile, the potassium storage mechanism of FeSe2 has been preliminarily investigated by using ex situ X-ray diffraction technique and high-resolution transmission electron microscopy. The remarkable performance and easy preparation demonstrate the great promise of FeSe2/NC composite as a potential anode material for PIBs.