| Supercapacitors have attracted much attention because of their long service life and fast charge-discharge rate.However,the low energy density severely limits their wide application.The development of supercapacitors with high energy density and high-power density has become an urgent problem to be solved.Battery-type materials,such as transition metal oxides,phosphides,phosphates,etc.,have great potential for application as electrode materials for supercapacitors because they can provide high energy density.However,the rate performance of transition metal phosphates is unsatisfactory,because the redox reaction dominated by diffusion control in battery-type materials determines that their performance at high current densities is limited by material diffusion.The current nano-design of the electrode material to enhance its contact with the electrolyte can improve the rate performance of the material,but it cannot be widely used because of the cumbersome process and high cost.Enhancing the surface capacity behavior of battery-type materials can effectively improve the energy density of the electrode while ensuring the high-power density of the electrode by providing a fast and reversible Faraday reaction.However,few studies have focused on this.Therefore,this paper prepared a sisal-like Co3（PO4）2/Ni-Co-O@nickel foam（NF）multi-level structure self-supporting electrode（CPNO-12）through a one-step hydrothermal reaction.Thanks to the construction of the multi-level structure,the electrode has the advantages of high surface capacity behavior,high mass specific capacity,and large load per unit area(10 mg cm-2).In order to match the high specific capacity of the positive electrode,this paper also prepared a high-performance negative electrode through hydrothermal reaction and high-temperature phosphating:Fe2P/graphene@NF（FPGH）,which is an all-solid state assembled by using both as electrodes and PVA-KOH as a solid electrolyte.Supercapacitors can output high mass and volume energy density.Finally,a series of characterization and electrochemical tests were performed on the prepared materials and devices.The specific content of the topic is as follows:（1）XRD,XPS,Raman,FT-IR and other instruments show that the compositions of CPNO-12 are NF,Co3（PO4）2 and Ni-Co-O.Time-gradient SEM showed that the morphology of CPNO-12 evolved with time,and EDS showed that the internal plate-like structure and surface layer network belonged to Co3（PO4）2 and Ni-Co-O,respectively.FE-SEM,TEM and N2 adsorption/desorption tests show that the material has a graded pore structure composed of micropores,mesopores and macropores.Electrochemical tests confirmed that CPNO-12 has excellent electrochemical performance:a very high quality,area specific capacity of 2820 F g-1(28200 m F cm-2)is obtained at 5 m A cm-2;at 5～100 m A cm-2,It retained 50.4%of the initial capacity,which is much higher than that of the control sample;at 50 m A cm-2,it retains 90.9%of the initial capacity after 12000 cycles.In addition,in the mechanism analysis,CPNO-12 showed an electrochemical behavior with enhanced surface capacity behavior,and obtained a 34%capacity contribution at 0.5 m V s-1,while the overall theoretical capacitive contribution CPNO-12 was as high as 24%.（2）XRD revealed that the composition of FPGH is graphene,Fe2P,nickel foam.SEM showed that roe-shaped Fe2P clusters anchored on graphene sheets to form a multi-level structure.Electrochemical tests show that FPGH has a high mass and area specific capacity:570 F g-1(1140 m F cm-2 at 3 m A cm-2).（3）Electrochemical tests show that the assembled all-solid supercapacitor outputs an energy density of 95 Wh kg-1(32 m Wh cm-3)at 400 W kg-1(80m W cm-3),with high gravimetric and volume energy density.By successfully lighting and driving the 5 V LED sets and 5 V electric fan,the device proves that it has excellent practical application potential. |
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