Sheet-like structure FeF3/graphene composite as novel cathode material for Na ion batteries

Abstract

A sheet-like structure FeF₃/graphene composite is successfully synthesized by a novel and facile sol–gel method. The structure and electrochemical performance of the as-synthesized FeF₃/graphene composite are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and electrochemical measurement. The results indicate that the FeF₃ nanosheets are loaded on the surface of the graphene sheets to form the sheet-like structure hybrid. Fourier transform infrared (FTIR) spectrum confirms that C–F bonds exist in FeF₃/graphene composite, and it further indicates that a chemical bond between FeF₃ and graphene has been formed and FeF₃ can preferably stick to the surface of the graphene. The FeF₃/graphene composite as cathode material of rechargeable Na ion batteries (NIB) exhibits a fairly high initial discharge capacity of 550 mA h g⁻¹ at 0.1 C, and it still keeps a capacity of 115 mA h g⁻¹ after 50 cycles at 0.3 C at a range of 1.0–4.0 V for NIB.