Preparation And Electrochemical Performance Modification Of Metal Sulfide/C Composites

In this paper,metal sulfide/nitrogen carbon nanocomposites with excellent electrochemical properties were synthesized by using petroleum wastewater as the main raw material and structural template.The synthesis mechanism and electrochemical reaction principle of the nanocomposites were explored,and the synthesis conditions were also studied.The effect of composition and structure on the electrochemical properties of composites.Using petrochemical wastewater as the only raw material,the petrochemical wastewater was transformed into Nitrogen and Sulfur co-doped Carbon@Fe₃O₄（NS/C@Fe₃O₄）composite by in-situ thermochemical method.The effects of different hydrothermal time and heat treatment temperature on the structure and final properties of NS/C@Fe₃O₄ were also investigated.The increase of hydrothermal time is beneficial to crystallization and decrease of particle size and to the formation of disordered hard carbon.Increasing calcination temperature is also beneficial to crystallization,and the crystal volume is also increased by a small extent.For lithium ion battery,the sample without hydrothermal treatment at 700 ^oC calcinationtemperaturehasgoodelectrochemicalperformance.The NS/C@Fe₃O₄-0-700 negative electrode exhibits better cycle performance at the current density of 2 A g^-1,after 200 cycles,it decays to the minimum value of 325.06 mAh g^-1.At a high current density of 10 A g^-1,the specific discharge capacity was stabilized at109.6 mAh g^-1 after 100 cycles.For sodium ion battery,the sample calcined at 600 ^oC for 24 h has good electrochemical performance.The initial discharge specific capacity of the sample is 683 mAh g^-1 at 0.5 A g^-1 current density.After 200 cycles,the capacity was stabilized at 280 mAh g^-1,which maintained a high Coulomb efficiency,and the capacity retention rate was up to 93.3%.In order to further synthesize high performance electrode materials,we used petroleum wastewater as the organic ligand of iron metal-organic framework（Fe-MOFs）precursor and the source of sulfur,nitrogen and carbon.Iron sulfide/N-doped rigid carbon film nanocomposites with multilayer structure were synthesized.The results show that the composites prepared by hot water at 180℃for48 h and calcined at 700℃have excellent electrochemical properties.The phase composition of the synthesized materials changed obviously at different calcination temperature.Finally,it was found that only after hydrothermal treatment of the precursor,the samples calcined at 700 ^oC had pure Fe_1-xS phase.The layered pores and connected channels in the framework of the material make it easier to penetrate the electrolyte,and the lithium ion in the electrolyte can react with Fe_1-xS particles easily,and the volume expansion of the material can be alleviated.A good electrochemical performance was obtained.As a negative electrode of lithium ion battery,the initial discharge specific capacity is 1542.08 mAh g^-1 when the current density is 1 A g^-1,and the discharge specific capacity is stable at 632.16 mAh g^-1 after 200 cycles.More importantly,the chemical oxygen demand removal rate reached 80.7%in the synthesis process.Similarly,manganese sulfide/nitrogen carbon composites were prepared by hydrothermal-high temperature carbothermal reduction using petroleum wastewater as the main raw material and structural template.The results show that increasing calcination temperature and hydrothermal time are beneficial to the formation of mns phase and increase the crystallinity.For the negative electrode of lithium ion battery,the sample prepared at 600 ^oC calcination temperature has good electrochemical performance.The first discharge capacity at the current density of 0.5 A g^-1 was 1280mAh g^-1 and remained at 790 mAh g^-1 after 100 cycles.As the anode sample of sodium ion battery,600 ^oC also has good electrochemical performance,and the charge and discharge capacity can still be maintained at 250 mAh g^-1 after 115 cycles at the current density of 1 A g^-1.