Preparation And Lithium Storage Properties Of Hollow Core-shell Fe Based Sulfide@C Electrode Materials

Encouraged by the goal of"carbon peaking and carbon neutrality",lithium ion batteries have gradually become a hot spot in the new energy industry.Among them,the anode material is the key factor to determine the performance of lithium ion battery.Iron-based sulfides(such as FeS,FeS₂ and Fe_1-xS)are considered as one of the most promising anode materials for lithium ion batteries due to their high theoretical specific capacity,low price and environmental friendliness.However,its poor electronic conductivity and serious volume expansion during charging and discharging restrict its practical application.In this paper,nitrogen doped carbon coated iron disulfide（FeS₂@N-C）electrode material with hollow core-shell structure was constructed by using sulfur spheres as template combined with hydrothermal reaction and high temperature calcination.The influence of carbon coating amount and heat treatment temperature on electrode material was investigated.When the dosage of dopamine was 60 mg and the heat treatment temperature was 400℃,the best FeS₂@N-C electrode material was obtained.Under the current density of 2 A g^-1,the material can still maintain a high discharge specific capacity of 600 m Ah g^-1 after 1000 cycles,and has good rate performance.The excellent electrochemical performance is attributed to the confinement of FeS₂ nanoparticles in a carbon shell with adjustable internal void space,which provides sufficient space to buffer the volume change of FeS₂ spheres during the electrochemical process.At the same time,the outer carbon layer improves the electrical conductivity of the material,thus improving its electrochemical performance.On this basis,in order to further improve the electronic conductivity of the composites,a 3D conductive network FeS₂@N-C@rGO hollow core-shell composite was prepared by electrostatic assembly of highly conductive reduced graphene oxide.The electrode material can maintain a discharge capacity of 340 m Ah g^-1 after 700 cycles with a current density of 5 A g^-1,showing good cycle stability.The performance improvement of FeS₂@N-C@rGO composite is due to the unique structure of the hollow core shell,which alleviates the volume change of the material during lithium implantation/lithium removal.The introduction of graphene has a synergistic effect with the external carbon layer,which not only increases the conductivity of the material and improves the ionic reaction kinetics,but also further alleviates the volume expansion and improves the electrochemical performance.