| Supercapacitors（SCs）,as an energy storage device,have been widely applied in the daily electronic products,new energy vehicles,and other energy storage fields due to the advantages of fast charge and discharge,high power characteristics,and good cycles stability.However,most of the current commercial supercapacitors suffer from low capacity,narrow operating voltage windows,and low energy density.The hybrid supercapacitor assembled with a battery-type electrode and a capacitor-type electrode can effectively improve the voltage window and energy density of the supercapacitor by combining electrode materials with two different energy storage mechanisms.Transition metal compounds have relatively high theoretical capacities and are considered to be one of the ideal electrode materials for hybrid supercapacitors.Unfortunately,transition metal compounds are prone to volume expansion during long-term charging and discharging,poor electrical conductivity,and slow ion diffusion.An effective strategy to overcome this problem is to composite transition metal compounds with conductive carbon materials.Therefore,in this thesis,we design and synthesize high-performance hierarchical nanoporous carbon/transition metal compound composite electrode materials and explore their applications in hybrid supercapacitors.The study of this thesis includes the two aspects as follows:（1）Controllable synthesis of HNCMs@Ni（OH）2 composites and properties of hybrid supercapacitors.HNCMs@Ni（OH）2 composites with core-shell structure were prepared by controlled in situ deposition of nickel hydroxide nanocrystals on the surface of hierarchical nanoporous carbon spheres（HNCMs）as substrates.The effects of Ni（OH）2 deposition amount on the structure,morphology,and electrochemical properties of the composites were systematically investigated by adjusting the Ni2+concentration in the reaction system.It was found that the synthesized HNCMs@Ni（OH）2-6composites exhibited a novel“rambutan-like”microsphere morphology with a specific surface area of 286.6 m2 g-1 at a Ni2+concentration of 0.12mol L-1.The HNCMs@Ni（OH）2-6 composites exhibited the most excellent electrochemical properties at a current density of 1 A g-1.Based on its excellent electrochemical properties,the hybrid supercapacitor was constructed with HNCMs@Ni（OH）2-6 composite as the cathode and HNCMs as the anode.The energy density of the hybrid supercapacitor is as high as 41.3 Wh kg-1 at a power density of 173.3 W kg-1.After 20000cycles at a current density of 5 A g-1,the capacity retention rate was as high as 85.2%,indicating that the device has good cycling stability.（2）Controllable synthesis of HNCMs@Ni Co2S4 composites and properties of hybrid supercapacitorsHNCMs@NCS composites with core-shell structure were prepared by the controlled growth of Ni Co2S4 nanosheets and simultaneous etching of Si O2 templates on the surface of hierarchical nanoporous carbon sphere mixtures（Si HNCMs）without etched Si O2 templates as substrates by hydrothermal method.The effects of different HNCMs contents on the structural morphology and electrochemical properties of the composites were systematically investigated by adjusting the addition amount of Si HNCMs substrate in the reaction system.The synthesized HNCMs@NCS-40 composites showed a flower-like core-shell structure at a Si HNCMs addition of 40 mg.Mass specific capacitance up to 346.9m Ah g-1 at a current density of 1 A g-1 and 299.8 m Ah g-1 at a current density of 30 A g-1,showing good rate property and excellent cycling stability(81.2%of the initial capacity is maintained at 20 A g-1 for 10,000cycles).The hybrid supercapacitor was assembled with HNCMs@NCS-40 as the cathode and KOH-activated HNCMs（AHNCMs）as the anode based on the most excellent electrochemical performance demonstrated by HNCMs@NCS-40.Demonstrates an energy density of 29.5 Wh kg-1even at a power density of 24 k W kg-1,and the capacity retention rate of85.7%was achieved at 10000 cycles at 10 A g-1. |
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