Preparation And Electrochemical Performance Of Cellulose-Carbon Microspheres Via Hydrothermal Carbonization

In recent years, much attention has been attracted to the carbonaceous microshperes for many investigators, owing to the trim structure, morphology, unique thermodynamical properties, physical and chemical stabilities. Compared to different forms of functional carbonaceous materials, carbon microspheres have been motivated by the potential applications in various fields ranging from electromagnetism, biological sciences, physics, chemical industry, and materialogy. Accordingly, the synthesis of carbon spheres attracts considerable significance for both academic and industrial fields. A process, termed hydrothermal carbonization (HTC), appears especially important contributed to the low cost, renewable resource, simplicity facility, economic and environmental procedure, and has generated widespread interest recently.The thesis focused on the preparation of carbonaceous spheres materials via hydrothermal carbonization. Cellulose as raw materials was dispersed in deionized water and different mass percents of ethanol solution, respectively. The effects of various reaction parameters on superficial morphology, crystalline structure and functional group were evaluated, including carbonization temperature, reaction time, rate of charge and additive amount. Meanwhile, the carbonization mechanism of cellulose and electrochemical performance of carbon spheres through alcohol additions preliminarily were investigated.The main conclusions are summarized as follows:(1) Using cellulose as precursor and deionized water as dispersant agent, carbon microspheres were synthesized by means of hydrothermal process. Superficial morphology, crystalline structure and partical size were modulated through carbonization temperature and reaction time. The result suggest the onset of hydrothermal reaction occurred at around230℃. In the wake of reaction time lengthening, the spheroidization and morphology of products became well, whereas the partical homogeneity got low.(2) Carbonaceous spheres materials were prepared via hydrothermal method, with cellulose was dispersed in ethanol solution. The optimal reaction parameter was as follows:the ratio of charge was1.0g/25mL, mass fraction of ethanol was60wt%, carbonization temperature was320℃and time was24h. In this condition, regular morphology and uniform grain size could be synthesized successfully.(3) The shell of carbonaceous microspheres possessed directly reactive functional group, such as hydroxyl, carbonyl, carboxyl and aldehyde. Even it generated aromatization in the core. That is, not only carbonization but also functional modification could be achieved concurrently. It dispensed with the surface modification treatment in the traditional preparation of carbon materials.(4) Carbon micro-spheres which were produced by means of ethanol additives displayed graphitization and presented the improvement of reversible electric capacity in cyclic voltammetry. The electric capacity and charge-discharge time attained optimum while mass fraction of ethanol was60wt%. Meanwhile the result showed specific capacity attenuation weakened with carbon spheres got more and the degree of graphitization became higher.