Room-temperature solid-state reaction-assisted strategy to fabricate nanocomposites of N,S-codoped carbon confined FeCoS2 as high-performance anode materials for sodium-ion batteries
In this work,a facile and cost-effective solid-state reaction method for the synthesis of the nanocompos-ites(denoted as FeCoS2CNSC)of N,S-codoped carbon-confined FeCoS2 nanocrystalline was presented.By directly mixing cobalt acetate tetrahydrate,ferrous acetate,o-vanilin and o-phenylenediamine with a molar ratio of 1:1:4:2 at ambient temperature in the presence of sulfur powder,a self-assembly solid state reaction took place to give rise to the complexes of Co(Ⅱ)and Fe(Ⅱ)with a bis-Schiff base,which were evenly distributed in the sulfur powder sur-roundings.After subsequent annealing at an elevated temperature,simultaneous carbonization and sulfidization occurred,resulting in the in-situ formation of ultrafine FeCoS2 nanoparticles confined in N,S-codoped carbon matri-ces.The phase,morphology,composition,and content of each component in the nanocomposite were determined by powder X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,and thermogravimet-ric analysis.The electrochemical sodium storage performance was tested by the cyclic voltammetry and galvanostat-ic charge-discharge techniques.The results showed that the average size of the FeCoS2 particles in the optimized nanocomposite(FeCoS2 CNSC-7001)was ca.3.4 nm,which was uniformly confined in the N,S-codoped carbon matrices.When FeCoS2CNSC-7001 was used as an anode material for sodium-ion batteries,it exhibited excellent electrochemical energy storage performance in terms of long-term cycling stability and rate capability.An anode pre-pared with FeCoS2 CNSC-7001 nanocomposite exhibited significantly improved sodium-ion storage performance,where a large reversible charging capacity of 310.4 mAh-g-1 was obtained after 300 cycles at a current density of 0.1 A·g-1.Even when such an anode was cycled at a current density of 5 A·g-1,a reversible specific charging capac-ity of 146.0 mAh·g-1 can still be achieved,showing excellent electrochemical sodium storage performance.
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