Preparation Of Carbon Nanomaterials By Direct Solid Phase Reaction Of Dimethylglyoxime With Zinc Acetate And Its Electrochemical Properties

With the continuous consumption of fossil fuels, people put more attention into the new energy field. Carbon-based materials are widely used as battery anode materials, supercapacitor electrode materials and other energy storage areas because of its high chemical stability, good electrical conductivity, low price.In this thesis, by using the direct solid state reaction, a series of carbon-based hybrid nanomaterials with nitrogen doping and hierarchical porous structure are effectively synthesized. The preparation strategy is simple, low energy-consumption and environment benign. Due to its unique component and structure, the carbon-based nanomaterial is endowed with excellent electrochemical performance when used in the lithium-ion battery and supercapacitor. The main results are as follows:(1)A porous precursor was prepared by a direct solid-state reaction at low-heating temperature using butanedione oxime and zinc acetate dihydrate as starting materials.(2)By two-step method, i.e. relatively high temperature treatment (lower than 900?) and acid etching, the porous precursor can be effectively converted to nitrogen-doped porous carbon nanomaterials (designated as NC-T-x, here NC refers to nitrogen-doped porous carbon, T is the temperature of heat treatment for the precursor,x represents the molar ratio of butanedione oxime to zinc acetate in the preparation of the precursor). Electrochemical measurements demonstrate that NC-800-2 materials show excellent electrochemical performance. For example, the NC-800-2 nanomaterial exhibits a high reversible capacity of 700 mAh g-1 after 50 cycles at a current density of 100 mA g-1, which is much higher than the theoretical capacity of commercial graphite (372 mAh g-1). Also it shows excellent electrochemical capacitor performance than that of commercial graphite. For example, it has a specific capacitance as high as 134 F g-1 at a constant charge-discharge current density of 1000 mAg-1.(3)By one-step method, i.e. a direct high temperature heat treatment (higher than 900?), the porous precursor can be effectively turned to be nitrogen-doped porous carbon through carbothermal reduction of ZnO to Zn. Since the boiling point of Zn is relatively low and the sublimation is carried out at above 900?,so the nitrogen-doped porous carbon could be directly obtained. Electrochemical measurements show that the nanostructured NC-900-2 exhibits excellent electrochemical lithium-storage performance. For example, the NC-900-2 nanomaterial can deliver a high reversible capacity of 500 mAh g-1 after 100 cycles at a current density of 100 mA g-1, which is much higher than the theoretical capacity of commercial graphite. Similarly, the NC-900-2 nanomaterial exhibits good electrochemical capacitor performance. For example, it has a specific capacitance as high as 112 F g-1 at a constant charge-discharge current density of 500 mA g-1, which is also higher than that of commercial activated carbon materials.