Preparation And Electrochemical Properties Of Nickel-cobalt(iron) Sulfide/Carbon Composites

The contradiction between the growing demand for energy and the declining available fossil energy has become increasingly serious.The research and development of new energy storage equipment have received comprehensive attention.The most widely used batteries are lithium-ion batteries,zinc-air batteries,potassium ion battery.Compared with the abovementioned batteries,supercapacitor presents obvious advantages,such as fast charging and discharging rate,outstanding cyclic stability and remarkable power density.On this account,supercapacitor has a good development prospect and the research on electrode materials has become the main research direction.Recently,the popular and mainly used cathode materials are metal oxides and sulfides.Due to their similar electrochemical energy storage mechanism and the abundant resources in nature,Ni Co2S4 has richer electroactive sites and more excellent conductivity than single Ni sulfides and single Co sulfides,which has a relatively high specific capacitance.Nevertheless,Ni Co2S4 usually suffers from relatively poor rate retention during the charging and discharging procedure owing to the exaggerated volume alter of Ni Co2S4.Therefore,in this paper,we combine Ni Co2S4 with carbon materials through simple experimental methods to improve its rate performance.Additionally,the traditional negative electrode material of supercapacitor is carbon material.Because of its low specific capacitance,the assembled devices have low energy density.Therefore,in this paper,iron-based materials are prepared as anode with high specific capacity,and then supercapacitors with high energy density are obtained.The research contents of this paper are as follows:?1?NiCo₂O₄/CF nanofiber composites were prepared by electrospinning combined with calcination,and the target product Ni Co2S4/CF was obtained by further hydrothermal vulcanization.The specific capacity of Ni Co2S4/CF can achieve 1116 F g-1 at 1 A g-1,which is much higher than that of NiCo₂O₄/CF electrode?154.4 F g-1?.Porous carbon fibers were prepared by etching with strong acid on the basis of precursor NiCo₂O₄/CF.PCF was used as anode and Ni Co2S4/CF was used as cathode material to assemble all-solid-state asymmetric supercapacitors.The highest energy density can reach 28.8 Wh kg-1.?2?Firstly,PAN nanofiber template was prepared by electrospinning,and polypyrrole was coated on its surface.Then N-doped carbon nanotubes?NCTs?were obtained by hydrothermal method combined with calcination method.Then,the target product Ni Co2S4/NCTs was obtained by loading Ni Co2S4 nanosheets on NCTs.The specific capacity of the prepared cathode material reaches 1463 F g-1 at 1 A g-1,and remains 880 F g-1 when the current density increases to 40 A g-1.At the same time,the materials we prepared also have excellent cycling performance,after 5000 cycles,the attenuation is only 4%.?3?We obtained the nanosphere of Fe OOH by hydrolyzing Fe?NO3?3.The precursor Fe OOH and PAN were mixed and the fibrous structure of Fe OOH@PAN was obtained by electrospinning.After adsorption with thiourea and calcination,Fe_1-x S/CFs were obtained.Compared with the previously reported iron-based anode materials,it has excellent electrochemical properties: the specific capacitance is 780 F g-1?1 A g-1?,and the specific capacitance can be maintained at 313 F g-1 at 15 A g-1.At the same time,the working voltage range can be increased to-1.2-0 V.Finally,we assemble an ASC devices with the above-mentioned cathode and cathode materials.The obtained Ni Co2S4/NCTs//Fe_1-x S/CFs equipment also has excellent electrochemical performance: wide voltage range?0-1.7 V?,high specific capacity?133 F g-1 at 1 A g-1?,excellent energy density?55.4 Wh kg-1 at 882 W kg-1?,remarkable cycle performance?80.6% after 5000 cycles?.