| Solar energy and wind energy are believed to be the most promising alternative energy, whereas they cannot work continuously which hinder the large-scale application. Meanwhile, at present, new type of energy storage devices (such as lithium ion battery and supercapacitor) have suffered from limitation in meeting the requirements of energy storage due to their low specific capacity and poor rate performance. Therefore, intensive efforts have been done to develop materials with high electrochemical properties. Carbon materials are considered to be the most prospective material in the new century, especially the porous carbon material could improve the electrochemical properties effectively due to their porous structure and high specific surface area. Moreover, micro-sized materials with a spherical morphology have the superiorities of high packing density and perfect particle mobility which lead to high power density, high volumetric energy and compact electrode layer. Consequently, how to design and prepare porous carbon microspheres become a meaningful work.For the above reasons, in this dissertation, hierarchical porous carbon microspheres (HPCM) with quantities of micropores and mesopores have been prepared by an alcohol-in-oil emulsion technique using thermoplastic phenolic formaldehyde resin (PF) as the carbon source and copper nitrate (CN) as the template precursor. The effects of synthesis factors on the morphology and structure of HPCM were investigated by SEM、TEM、XRD、BET and other test techniques. The relationship between porous structure and electrochemical performance were explored by galvanostatic charge and discharge, cyclic voltammetry and electrochemical impedance spectroscopy tests.Firstly, the effects of curing temperature, dosage of curing agent, type of solvent, volume ratio of organic solvent and oil and concentration of phenolic resin on the synthesis of microspheres were analyzed in the paper. Finally, the mechanism for the formation of HPCM was proposed. The result shows that curing temperature and dosage of curing agent affect the decomposition rate of curing agent significantly. When the curing temperature reached 150℃ and the mass ratio of phenolic resin and curing agent settled 1:0.14, uniform microspheres can be prepared. Others factors affect the preparation of microspheres similarly. In the system of ethanol or propanol, when the volume ratio of organic solvent and oil phase reached 1:2 or 1:3, we can also synthesize microspheres with good sphericity and loose internal structure.Then, in the propanol system, we prepared HPCM with different porous structure via changing the CN loading content. It was seen that, with the increase of CN, the mesopore proportion increases and the internal structure looses. Therefore, the lithium storage performance and rate property improve accordingly. The HPCM with the PF/CN mass ratio of 1:4 revealed the reversible capacity of 585 mA h g-1 at the current density of 50mA g-1. The reversible capacity still remains 480 mA h g-1 after 70 cycles, and exhibits a capacity of 200mA h g-1 when the current density was increased to 1 A g-1.Afterwards, in the ethanol system, the effects of the CN loading content and carbonization temperature on the morphologies, porous structures and capacitance behavior of HPCM were researched in detail. The results showed that the HPCM with the PF/CN mass ratio of 1:4 had the superior capacitance performance. It can maintain 148F g-1 capacitance under the current density of 0.1 A g-1 for 600 cycles with excellent cycling stability and rate performance. By carbonization at 700℃ for 2h, HPCM exhibit a capacitance of 159F g-1 at the current density of 0.1A g-1 for 200 cycles. |
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