Synthesis,Characterization And Electrochemical Performances Of Carbon Composite Chalcogenides

Carbon composite nano-electrode material is one of the important methods to improve the electrochemical properties of lithium/sodium ion battery electrode materials.In this paper,a method is developed for the preparation of hollow structure FeSe2/C nanospheres and hollow core-shell structures FeS2 nanospheres using the precursors of core-shell structures.It was found that hollow FeSe2/C nanospheres had good electrochemical properties when used as sodium ion batteries anode materials.In addition,the FeS2-S@C composite material was obtained by using the hollow core-shell structure FeS2@C nanosphere melting and sulfuration,when used as a sulfur electrode material for lithium-sulfur batteries,the composite also exhibits excellent performance.This paper can be mainly summarized into the following two points:1.A new method for preparing hollow structure FeSe2/C nanospheres using core-shell precursor Fe3O4@RF(resorcinol formaldehyde)nanosphere selenization and carbonization was developed.When the FeSe2/C nanospheres used as sodium ion battery anode material,coated carbon materials not only can effectively relieve volume expansion caused by FeSe2 in the process of electrochemical cycle,but also improve the conductivity of the electrode materials.The discharge specific capacity of this material was 474 mA h g-1 at 0.05 A g-1.In the meantime,the FeSe2/C nanospheres also show good rate capabilities of 364.5 mA h g-1 and 316.5 mA h g-1 at 2.0 A g-1 and 5.0 A g-1,respectively.2.Develop a hollow core-shell FeS2@C nanospheres as the carrier of sulfide-based anode materials,and excellent electrochemical properties were obtained.FeS2@C nanospheres were synthesized from the precursor of core-shell structure Fe3O4@C,and the FeS2-S@C composite materials were obtained by further melting and sulfuration.The hollow structure provides the sulphur load carrier,at the same time it effectively reduced weaving effect during the lithium sulfur batteries cycle;Secondly,FeS2 have catalytic conversion to polysulfide,its porous nanostructures can provide more active site for sulfur transformation,promote the chemical reaction during charging and discharging process;Finally,carbon composite can effectively improve the conductivity of the sulfide-based anode material,thus improving the electrochemical properties of the electrode material.The charge capacity of FeS2-S@C nanocomposite was 518.4 mA h g-1 after 60 cycles at 0.5 C;and after 200 cycles in the 0.5 C,the cycle was circulated to 500 cycles at the 1.0 C,while thereversible discharge capacity could be maintained at 387.8 mA h g-1.