Study On The Preparation Of Water Soluble Carbonaceous Intermediate And Its Application In Electrochemistry

In view of environmental pollution and increasingly exhausted of fossil resource,renewable resource as alternate resources attracts more and more attention, especiallyfor the energy storage devices such as lithium ion battery and supercapacitor. Watersoluble carbonaceous intermediate can soluble in water owing to abundant functionalgroups. Based on this property, no organic solvent and stabilization process is neededduring the preparation of carbon materials when using intermediate as precursor.Therefore, ACM is economic, facile, and green in carbon materials production. It isnecessary to study the forming mechanism of intermediate and develop itsapplications in energy storage.Two kinds of intermediate with different morphology were prepared in water andacetone respectively, and then various tools were used to study the structure andforming mechanism of intermediates. The results showed that the primary units ofintermediate are functionalized condensed nucleus molecular, which can disperse inalkaline solution in nanoscale. All these units were introduced onto variousO-containing groups, such as–COOH,-SO₃H,-OH,-NO₂,-C=O and so on, of which-NO₂is one of the main groups that influence the solubility of intermediate. Sphericalintermediate can be obtained using acetone to replace the water of alkaline solution.The resulting product was piled up by highly connected nano-particles with diametersof30⁵0nm, which constructed a3-D architecture also providing certain mesoporesand macropores. N2sorption analysis showed that the SBETof carbonized sphericalintermediate is292m2/g and had a wide pore size distribution from micropores tomacropores.The properties of water soluble carbonaceous intermediates derived from greenneedle coke （GNC） and their influence on the subsequent porous carbon materialswere studied. Using the intermediates is an effective way for preparingwell-developed porous carbons by KOH activation. The degree of oxidation hadsignificant effects on the structures of the intermediates and further determined thestructure and EDLC performance of the final porous carbon. Soluble intermediatesproduced better high-rate-capacitive EDLC’s electrode materials than insoluble intermediates, which can be attributed that soluble intermediates have fewercarbonaceous stacked layers, which give the short diffusion path for the electrolyteand enable a high utilization rate of the micropores.In order to further study the effect of microcrystalline structure on the poroustexture of activated carbon, another contrastive precursor, coal tar pitch from （CP）was taken into account. At the KOH/intermediate mass ratio of1.5, the porous carbonobtained exhibited surface area as high as2575m²/g and pore volume as large as1.54cm³/g, the pore size centered at2⁴nm. Electrochemical characterizationsdemonstrated that CP-derived porous carbon showed superior capacitances both inaqueous （6M KOH） and organic （1M Et4NBF4/acetonitrile） electrolytes. In aqueoussystem, the specific capacitance of CP-A5-1.5reached284F/g at a current density of0.05A/g and still maintained at195F/g at current density of100A/g. In organicsystem, the energy density of CP-A5-1.5can reach to40Wh/Kg.Based on the unique property of water solubility, intermediate was employed tocoat natural graphite, results showed that coated natural graphite show lessirreversible capacity and improved coulombic efficiency than unmodified naturalgraphite. The BET specific surface area of unmodified NFG drastically decreases aftercarbon coating. On the contrary, the R （ID/IG） value increases with the increase ofcoated amount. In order to have certain improvement in anode performance, optimumconditions for carbon coating had to be applied, under the optimum conditions, thereversible and irreversible capacity of coated sample is359.6mAh/g and30.4mAh/g,heat treatment temperature should be in the range of800-1400°C and heating rate inthe range of1-5°C/min.