| The rapid development of society and economy has brought a series of problems such as energy shortage and environmental pollution.It has become an urgent problem to be solved for the survival and health of human beings.In recent years,the search for sustainable green energy become the focus of study.As a new type of energy storage device,electrochemical capacitor has been paid much attention because of its excellent electrochemical performance and friendly to environment etc.High performance electrode materials,as one of the key factors affecting the performance of electrochemical capacitors,its research has been carried out.Two dimensional metal oxide nanomaterials have high specific surface area,high theoretical capacity and open short-range ion transport,which have high research value in the practical application of electrochemical capacitors.In this study,we prepared two-dimensional Ni(OH)2,NiO,?-Fe2O3 metal oxide nanosheets materials,combined with different preparation processes to explore and study the energy storage properties of graphene composite.The main contents are as follows:(1)Two-dimensional Ni(OH)2,NiO and ?-Fe2O3 metal oxide nanosheets materials were prepared mainly by hydrothermal method.We studied the effects of hydrothermal reaction temperature and reaction time on morphology,nanostructure and electrochemical performance of the two-dimensional Ni(OH)2 nanosheets,so as to obtain the optimal reaction conditions for energy storage performance of Ni(OH)2 nanosheets are 140 ? and 10 h.Meanwhile,the optimal annealing conditions and the electrochemical properties of the two dimensional Ni(OH)2 nanosheets and their transformation to NiO nanosheets were also investigated.(2)We used two-dimensional Ni(OH)2 nanosheets prepared by hydrothermal method and?-Fe2O3 nanoplates fabricated by solvothermal method as raw material,and obtained NFC8(the mass ratio of Ni(OH)2 and ?-Fe2O3 is 8:1)materials through the hydrothermal method by controlling the composite ratio of the two materials.The NFC8 electrode possessed a specific capacitance of 1745.33 F g-1 at a high current density of 2 A g-1,and with a 84.28% retention of capacitance after 3000 cycles galvanostatic charge-discharge at a high current density of 20 A g-1.This results indicated that the novel two-dimensional nanostructures of NFC8 has greatpotential value in the practical application of business.(3)A novel Ni(OH)2/MoS2 composite(NMCs)was synthesized by hydrothermal method by controlling the ratio of Ni(OH)2 nanosheets to the MoS2 nanosheets.The obtained NMC8(the mass ratio of Ni(OH)2 and MoS2 is 8:1)electrode has excellent electrochemical performance.It has a specific capacitance of 1677.49 F g-1 at a current density of 1 A g-1,a power density of 750 W kg-1with 57.27 W h kg-1energy density,and a 90.06% of the initial capacitance retained after 10000 cycles,which shows excellent cycle stability.(4)We have synthesized the novel nanocomposite materials of graphene with Ni(OH)2nanosheets and NiO nanosheets respectively by one step hydrothermal method.And then,the effect of graphene content on the electrochemical energy storage properties of the composite was studied by controlling the composite ratio.The specific capacity of the obtained NGC8 electrode materials(the mass ratio of Ni(OH)2 and graphene oxide is 8:1)were high up to1862.2 F g-1 at the current density of 0.8 A g-1 and had excellent stability.What's more,when the NGC8 materials were transformed to NrC8(the mass ratio of NiO and grapheme is 8:1),the electrochemical energy storage performance was still maintain excellent compared to that of the other same kind of composites. |
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