【作者】 李文斌；

【导师】 王成扬；

【作者基本信息】 天津大学 ， 化学工艺， 2012， 博士

【摘要】 由于日趋严重的环境问题和化石燃料资源的日益紧缺，以生物质资源为原料制备炭材料成为一个重要的研究课题。淀粉作为制备炭材料的原料，具有绿色环保、来源广泛、可再生等特点。此外，淀粉颗粒具有天然的球型形貌，利用淀粉的这一特征可开发出球型炭材料的新型制备工艺，这对促进炭微球的研究与发展具有重要的意义。各种淀粉中，马铃薯淀粉颗粒具有最好的球型度，所以本文首先选择马铃薯淀粉为原料，通过简单的稳定化和炭化过程成功地制备出保持了马铃薯淀粉颗粒形貌的球型炭材料。制备的球型材料是一种无序硬炭，其结构中存在一定数量的微孔。直接炭化马铃薯淀粉，淀粉颗粒会膨胀并且相互融并。低温稳定化处理过程中，淀粉发生缓慢的脱水进程，同时淀粉分子链间发生交联反应，当交联反应进行到一定程度时，在随后的炭化过程中淀粉颗粒不再发泡融并，从而保持了天然淀粉颗粒的形貌特征。本文中作者也确定了稳定化过程中上述交联反应的发生机理。另外，相比惰性气氛中，空气气氛中稳定化马铃薯淀粉可以加速其失重和脱水，从而可以显著缩短稳定化所需时间。本研究将制备的马铃薯淀粉基硬炭微球用作锂离子二次电池的负极材料。随着炭化温度的升高，硬炭微球的可逆和不可逆比容量均有所降低，首次效率增加。其中，700℃炭化的硬炭微球具有最高的可逆比容量，其值为572.4mAh/g，其首次效率只有55.94%。1000℃炭化的硬炭微球0.5V以下的可逆比容量在三个样品中最高，达到了355mAh/g。1300℃炭化的硬炭微球具有最高的首次效率，其值达到了80.4%。更高炭化温度制备的硬炭微球负极材料的倍率特性提升显著。1300℃炭化的硬炭微球在大倍率放电时，放电曲线形状的保持度和可逆比容量的保持率均为最高，10C放电时，样品可逆比容量达到了0.1C放电时的88.7%。此外，马铃薯淀粉基硬炭微球负极材料具有良好的循环特性，优异的PC基电解液的兼容性，在空气氛围中长期储存可以保持稳定的电化学性能。以不同淀粉为原料，制备出了具有不同形貌和粒径分布的硬炭微球负极材料。所制备的硬炭微球材料的化学成分和结构不受原料淀粉种类的影响。其电化学性能的差异主要由微球粒径的差异而引起。较小粒径的硬炭微球材料具有更高的可逆比容量和更好的倍率特性。具有最小粒径的大米淀粉基硬炭微球材料，0.1C放电时，其可逆比容量达到了582.3mAh/g，首次效率达到了78.08%；10C放电时，其可逆比容量仍然可以达到478.2mAh/g。更多还原

【Abstract】 In view of environmental pollution and unrestrained exploitation of fossil fuel, asalternate precursors of carbon materials, biomass resources have attracted more andmore attention. Starch is green, renewable and can be obtained from various plants.Thus starch is a good biomass candidate for the preparation of kinds of carbonmaterials. Besides, starch granules naturally have spherical morphologies. Therefore,it is possible to use this characteristic to develop a new technology of spherical carbonmaterial. This can promote the research of spherical carbon materials, and widen itspotential application.Among kinds of starches, potato starch granules have relatively perfect sphericalmorphologies. In this work, we firstly prepared novel carbon spherules from potatostarch by stabilization and carbonization processes under inert atmosphere, whichpreserved the original spherical morphologies of potato starch granules. In terms ofmicrostructure, the prepared carbon material was typical of disordered hard carbonwith micropores throughout it. During direct carbonization process, starch granulesswelled and melt together. During stabilization process at200-230℃, starch wasslowly dehydrated and crosslink between starch molecules gradually took place.Because of the crosslink reaction, starch granules avoided swelling and melting in thefollowing carbonization process and the prepared carbon spherules preserved theoriginal spherical morphologies of potato starch granules. In this work, the author alsoconfirmed the mechanism of the crosslink reaction in starch granules duringstabilization. When starch was stabilized in air, weight loss and dehydration of starchwere accelerated compared with that in inert atmosphere. Thus stabilization time wasshortened greatly.The starch based spherical hard carbons was also evaluated as an anodic materialfor Li-ion secondary batteries. As carbonization temperatures increased, reversibleand irreversible specific capacities of prepared spherical hard carbons increased andinitial efficiencies decreased. The material carbonized at700℃, had the highestreversible specific capacity of572.4mAh/g with the lowest initial efficiency of55.94%; the one carbonized at1000℃had the highest reversible specific capacity of355mAh/g below0.5V and the1300℃carbonized material had the highest initial efficiency of80.4%. It was found that the potato starch based spherical hard carbonscarbonized at higher temperatures showed better high-rate discharge performances.Discharge curves of the anodic carbon material carbonized at1300℃, almost did notchange with increasing discharge rates. Discharge specific capacities of this samplehad high preserved percentages with increasing discharge rates. Even at10C, thedischarge specific capacity remained88.7%of that at0.1C. Results also showed thestarch based spherical carbon material possessed good cyclic property, excellent PCbased electrolyte compatibility and showed stable electrochemical property afterlong-time storage in atmosphere.Starting from varied starches, hard carbon spherules with different morphologiesand different particle sizes were prepared. It was found that the structures and elementcontents of the prepared carbons almost did not change with different starches.Electrochemical properties mainly affected by the particle sizes of the hard carbonspherules. Prepared carbon spherules with smaller particle sizes showed highreversible specific capacities and possessed better high-rate discharge performances.Among spherical hard carbon anodic materials prepared from different starches, ricestarch based one had the smallest particle sizes and showed good electrochemicalperformances. Discharged at0.1C the rice starch based anodic material had a specificcapacity of582.3mAh/g and an initial efficiency of78.08%; discharged at10C thisanodic material also preserved a specific capacity of478.2mAh/g.更多还原