Researches On Construction Of High Performance Cobalt-Iron Bimetallic ? Compound Electrode Materials And Relative Capacitor Devices

In recent years,with the rapid growth of the world economy,traditional fossil energy has been consumed in an unprecedented amount.In addition to its substantial reduction,a more serious problem is the incoming environmental pollution.For this reason,the protection of the environment and the sustainable development of energy have become the goals pursued by all countries in the world.With the continuous improvement of human scientific and technological level,the development of new energy has gradually attracted worldwide attention.Research on its corresponding energy storage device has also aroused worldwide attention.As a new type of energy storage device,compared to the traditional energy storage devices(capacitors and batteries),supercapacitors not only have the traditional high power density of the capacitor but also have the characteristics of high energy density of the battery.In addition,fast charging,excellent rate characteristics,safety and pollution-free features make supercapacitors unprecedented for versatile applications and development prospects in the field of energy storage.Through the existing research,we have found that the performance of supercapacitor device depends largely on its construction materials.At present,people have conducted in-depth research on nanomaterial's and found that it occupies an extremely important position in the development of supercapacitors.Among the many suitable energy storage materials,bimetallic ? compounds such as NiCo2O4,FeCo2O4,NiCo2S4,and FeCo2S4 have excellent specific capacitance,outstanding electrical conductivity and excellent redox properties make it attractive for the development of supercapacitors.In this paper,cobalt-iron bimetallic group ? compounds(FeCo2O4,FeCo2S4)and black/red phosphorus-reduced graphene oxide(BP-RP-rGO)were prepared by hydrothermal method.In addition,we analyzed their electrochemical performance through a three-electrode system,and the in-depth research on the new structural supercapacitor devices constructed by FeCo2S4 and BP-RP-rGO was carried out.The main contents are as follows:(1)we adopt a facile hydrothermal strategy to synthesize ternary FeCo2O4 directly on nickel foam A series of structure such as nano wires,nanoflake@nano wire hetero-structure and hierarchical nanospheres have been achieved via modulating the synthetic time.In addition,we studied the effect of changing the reaction time on the nanostructure of FeCo2O4,and further studied the growth mechanism of different FeCo2O4 nanostructures synthesized at different reaction times.We directly use nickel foam loaded with active materials for electrochemical testing,and found that FeCo2O4 nanoflake@nanowire hetero-structure electrode prepared at 18 h exhibits a high specific capacitance of about 969 F g-1 at 2 A g-1,as well as excellent conductivity and cycling charge and discharge stability(2)Through hydrothermal preparation method,foamed nickel is used as a conductive substrate and sodium sulfide(Na2S)is used as a sulfur source in the ion exchange process.First,different precursors are prepared by adjusting reaction times,and then the precursor is obtained after vulcanization and finally prepared.Finally,FeCo2S4 nanowire structure and FeCo2S4 ayered nanospheres structure were prepared,then we found that conpared to oxides,the conductivity and specific capacity of sulfides are greatly improved.The FeCo2S4 nano wire structure exhi-bits a high specific capacitance of about 3000 F g-1 at 2 A g-1,and has excellent rate performance and good cycle stability..(3)In order to conduct in-depth analysis and study of the practical application capabilities of FeCo2O4,FeCo2S4 and BP-RP-rGO,we have prepared a series of supercapacitor devices.First of all,we prepared PVA/KOH solid electrolyte under 95? water bath environment.Then,we use FeCo2O4 nanoflake@nanowire hetero-structure as the anode and cathode of the symmetrical supercapacitor device,while PVA-KOH gel electrolyte as the device membrane to preparation of FeCo2O4//FeCo2O4 all-solid Symmetric supercapacitor device functioned as a red LED light.Next,we used FeCo2S4 nano wire structure as the anode of asymmetric supercapacitor device,BP-RP-rGO three-dimensional composite structure and rGO as the negative electrode,and PVA-KOH gel elecltrolyte as the device separator to preparation of BP,RP-rGO//FeCo2S4 and rGO//FeCo2S4 all-solid asymmetric supercapacitor devices and three other all-so lid symmetric devices(FeCo2S4//FeCo2S4,BP-RP-rGO//BP-RP-rGO,rGO//rGO)for comparisoa It was found that BP-RP-rGO//FeCo2S4 has a larger voltage window than other devices,a higher specific capacity and a better power density and energy density,and a specific capacitance of 333 F g-1 at a current density of 1 A g-1,the maximum energy density reached 29.304 W h kg"1,and the maximum power density reached 3102.8 Wkg-1.In addition,17 red LED lamps were successfully lighted through series capacitors.It provides experimental support for the subsequent construction of higher capacity and better structured supercapacitors.