【作者】 顾燕；

【导师】 王勇；

【作者基本信息】 上海大学 ， 化学工艺， 2013， 硕士

【摘要】 锂离子电池是上世纪90年代投放市场的新一代绿色环保电池。它因为电压高、自放电率低、无记忆效应等独特性能而受到广泛应用。而锂离子电池负极材料是制约其整体性能的关键因素之一。因此寻找新型负极材料是当今社会的一个研究热点。大部分金属、金属氧化物和金属硫化物都具有较高的理论比容量，但是它们的循环稳定性一般较差，而各种碳材料具有较好的循环稳定性能，因而，过渡金属硫化物-碳复合负极材料和过渡金属氧化物-碳复合负极材料有利于提高现有锂离子电池体系的储锂容量及循环稳定性，具有较大的潜在应用价值。本文主要以碳复合材料（如石墨烯、碳纳米管和碳纳米纤维）为研究对象，利用溶剂热法、单模微波法制备石墨烯（graphene）负载硫化钴粒子（CoS/graphene），石墨烯负载花状硫化铟（In₂S₃），石墨烯负载硫化铟纳米粒子复合材料，利用氧化铝模板法和化学气相沉积法制备碳纳米管（carbonnanotube，CNT）包覆氧化钴（CoO）和碳纳米纤维（carbon nanofiber，CNF）复合材料，并将这些材料作为锂离子电池负极材料，进行了电化学性能测试，发现它们具有较优异的储锂性能，主要结果如下：通过溶剂热法制备了花状的硫化钴（CoS）微球，并成功地制备了具有高比容量的石墨烯负载硫化钴纳米粒子。该材料在0.1C的电流密度下首次充电比容量可达1050mAh/g，循环40圈后的可逆比容量与首次可逆比容量相比，容量保持率为71.3%。该材料作为锂离子电池负极材料时在小电流下具有较高的比容量和较好的循环性能，主要是由于石墨烯与硫化钴的协同作用。在大电流下该材料同样具有较好的循环稳定性能。利用单模微波法制备出花状硫化铟（In₂S₃），并且研究反应温度和反应时间对产物的影响，结果发现，In₂S₃的晶型不随着反应温度和时间的改变而改变；花状In₂S₃的尺寸随温度的升高而增长；随着反应时间的延长，In₂S₃由粒子生长成片状，再逐步聚集成花状，随后花状In₂S₃的尺寸继续增长。利用单模微波法制备出片载花结构结构的graphene-In₂S₃和片载粒子结构结构的graphene-In₂S₃。复合物graphene-In₂S₃体系在小电流和大电流下都表现出了较优异的储锂性能。0.1C时，graphene-In₂S₃（片载花结构）和graphene-In₂S₃（片载粒子结构）的首次充电比容量分别为1249mAh/g和1056mAh/g，远大于其理论容量和单纯的In₂S₃和石墨烯的容量。循环40圈后，graphene-In₂S₃（片载花结构）和graphene-In₂S₃（片载粒子结构）的充电比容量仍然能够分别保持在657mAh/g和614mAh/g。在1C，2C和5C的电流下，两种材料均具有较高的比容量和稳定的循环性能。石墨烯的引入提高了In₂S₃电极的电导率，提高了电子传输速率，降低了电极-电解质界面阻力；石墨烯具有较好的柔韧性和机械稳定性，提高了在充放电过程中电极结构的稳定性；In₂S₃的存在阻止了石墨烯的团聚，发挥和保持与其相对应的各项性能。通过阳极氧化铝模板法和化学气相沉积法相结合成功制备了碳纳米管包覆氧化钴和碳纳米纤维（CoO-CNF@CNT）复合材料。CoO-CNF@CNT复合材料在小电流密度和大电流密度下都具有较好的循环性能。在0.1C的电流密度下，CoO-CNF@CNT复合材料首次充电比容量为920mAh/g，经过40圈循环后，可逆比容量降到630mAh/g。这主要是因为其独特的碳纳米管中有小碳纳米纤维的结构，可以有效地降低循环过程中，由于体积变化而产生的影响，碳纳米管增加了材料的导电性和机械强度，且阻止了金属氧化物纳米粒子的团聚。更多还原

【Abstract】 Lithium-ion battery is a new generation environment-friendly green batterywhich entered the market in1990s. They have been considered as the mostpromising power sources because they hold a series of considerable specificadvantages, such as high potential, high energy density, long cycle life, no memoryeffect and so on. The anode material of Li-ion battery is a key factor to control itsoverall performance. Most of metal, metal oxide and metal sulfide have highcapacities, but poor cycling stabilities. Carbon materials have good cyclingstabilities. Therefore, the preparation of carbon supported metal, metal oxide andmetal sulfide composite materials may improve the Li-ion storage properties andcycle stabilities of the present lithium battery system, which has great value ofpotential application.In this article, carbon composite materials, such as graphene nanosheet （GNS）,carbon nanotubes （CNTs） and carbon nanofibers （CNFs）, were the research targets.Graphene wrapped CoS nanoparticles and graphene-In₂S₃composites weresynthesized by the solvothermal method and microwave-assisted fast hydrothermalapproach, respectively. Carbon nanotube encapsulated CoO nanoparticles and carbonnanofibers （CoO-CNF@CNT） composite was prepared by a templated chemicalvapor deposition（CVD） method. The good electrochemical properties were foundwhen the materials were used as anode materials for Li-ion batteries.Graphene wrapped CoS nanoparticles were synthesized by a solvothermalapproach. The product was significantly different from porous CoS microspheresprepared in the absence of graphene under similar preparation conditions. Thenanocomposite exhibited an unprecedented high reversible capacity of1056mAh/gamong all cobalt sulfide-based anode materials, which still maintained71.3%after40cycles. The CoS/graphene composite was found to be better suitable as an anodematerial in terms of higher capacity and better cycling performances, which was attributed to the the synergistic action of graphene and cobalt sulfide. Good cyclingperformances area also observed at both small and high current rates.Flower-like In₂S₃was synthesized by the microwave-assisted fast hydrothermalapproach. The influence of differnent reaction temperature and time were also studied.The crystal form of In₂S₃was not changed with the change of the reaction temperatureand time. But the size of In₂S₃was increased with the rise of temperature. Thenanoflower nanostructure was formed by the self-assembly of the folded intermediateproduct of nanoparticles and nanosheets. When reaction time was increased further to30min, nanosheets were heavily folded and a heavy agglomeration of many flowerswas formed. In₂S₃-graphene nanoparticle-on-sheet and flower-on-sheet compositeswere also prepared by the same method. When fabricated as anode materials,In₂S₃-graphene composites showed extraordinary large reversible capacities and goodcycling performances and high rate capabilities at both small and high current rates.The reversible initial lithium-extraction capacities of1249mAh/g and1056mAh/gwere observed for flower-on-sheet nanostructure and nanoparticle-on-sheet at70mA/g, which larger than their theoretical values and the capacities of In₂S₃andgraphene. The charge capacities were657mAh/g and614mAh/g after40cycles,respectively. They also showed good capacities and cycling performances at largecurrents of1C，2C and5C. In comparison, the In₂S₃-graphene nanoparticle-on-sheetcomposite showed slightly lower reversible capacities but more stable cyclingperformances at both small and high currents. The presence of graphene can improvethe electrical conductivity of In₂S₃and reduce the resistance between electrode andelectrolyte interface. Graphene nanosheet also has strong toughness and mechanicalstability, improve the structural stability of In₂S₃during cycling.The presence ofIn₂S₃can prevent the agglomeration of graphene, thus maintaining their promisingproperties relative to their thin-layer structure during cycling.Carbon nanotube encapsulated CoO nanoparticles and carbon nanofibers（CoO-CNF@CNT） composite was synthesised by a templated chemical vapor deposition（CVD） method. CoO-CNF@CNT possessed good cycling performancesat both small and high current rates. The initial reversible capacity ofCoO-CNF@CNT composite was920mAh/g and the capacity reached630mAh/g upto40cycles. It was suggested that the high reversible capacity could be ascribed tothe fiber-in-tube structure and the confined volume change in the nanotube cavities.CNT can increase the electrical conductivity and mechanical strength of materials,and prevent the agglomeration of the CoO nanoparticles.更多还原