新型活性组分/石墨化介孔碳复合材料的制备及其在能源环境中的应用

【作者】 李博；

【导师】 李溪；

【作者基本信息】 复旦大学 ， 环境工程， 2013， 硕士

【摘要】 锂离子电池作为诸多化学能源之一,与其他二次电池相比,具有能量密度高,开路电压高,循环寿命长,无记忆效应,环境友好等优点,已成为当今世界极具发展潜力的新型绿色高能化学电源。负极材料是决定锂离子电池性能的重要因素之一,而传统的碳基负极材料存在能量密度低和倍率性能不佳的固有缺陷,因此开发新型廉价高效的的锂离子电池负极材料对推动新能源产业的发展具有重要的意义。锡、钛、硅、铁等元素及其氧化物是高比容量的新型负极活性组分,但锡和硅等元素及其氧化物在充放电过程中存在材料体积变化大,循环寿命不佳等缺陷,钛元素及其氧化物存在导电性差等缺陷,从而阻碍了这些活性组分在锂离子电池负极材料中的应用。研究表明,采用合适的多孔骨架材料与其形成“钢筋混凝土”的结构,能够有效的缓解活性组分的体积膨胀等问题。石墨化介孔碳材料是一种具有规则的孔道结构、良好的稳定性和电子导电性的新型碳骨架材料,本文采用简便有效的方法将锡、钛等新型活性组分以纳米颗粒的方式固载在石墨化介孔碳骨架上,充分发挥两者的优势,深入研究了其复合材料的电化学性能,开发出具有实用价值的新型活性组分掺杂的石墨化有序介孔碳锂离子电池负极材料。本文采用简单地固液球磨/模板法,以有序介孔氧化硅SBA-15为模板,以植物油为碳源,一步合成具有新型结构—金属锡纳米晶体嵌入在石墨介孔碳壁上的Sn-GMC纳米复合材料。考察了这种新型Sn-GMC纳米复合材料的结构及电化学性能。XRD、TEM、N2吸脱附分析测试结果发现金属Sn纳米晶体的含量较高,晶粒尺寸大约为3-5nm,均匀的分散在导电性良好的石墨碳壁上,并且Sn-GMC纳米复合材料具有中等的比表面积(223.9m2/g),较大的孔容(0.611cm3/g)和多级孔的有序二维六边形介孔结构；电化学测试结果表明,这种新型的结构使得Sn-GMC、内米复合材料作为锂离子电池负极材料时,表现出较高的首次库伦效率和较好的循环性能以及倍率性能。本文采用一步纳米共浇铸法制备了不同钛含量的TiO2-GC纳米复合材料,研究了不同含量的钛元素对材料结构以及电化学性能的影响,XRD、TEM以及BET测试结果表明,锐钛矿型的TiO2纳米颗粒均匀的分散在石墨化介孔碳基质中,并且这种TiO2-GC纳米复合材料具有良好的比表面积(110.28～528.95m2/g)和较大的孔容(0.063-0.351cm3/g),有利于充放电过程中锂离子的扩散；电化学测试结果表明,20TiO2-GC纳米复合材料相比于其他比例的复合材料以及石墨碳材料,具有更好的循环性能和可逆性,其初始容量高达1076mAh/g,经过50次循环后,放电容量仍保持在326mAh/g。锂离子电池中含有钴、铜、镉和锰等重金属元素,这些元素对环境和人类的健康有巨大的危害,因次,解决锂离子电池生产过程中或报废后可能造成的重金属离子污染具有重要的意义。本文以硝酸铁为铁源,豆油为碳源,采用一步纳米共浇铸法制备了不同含量的磁性Fe@y-Fe2O3/GC纳米复合材料,用于对Cu2+和Co2+离子的吸附。XRD、TEM、BET以及磁性分析等测试结果表明,磁性Fe@γ-Fe2O3纳米粒子均匀的分散在石墨碳基质中,形成具有高比表面积(249.44～701.72m2/g),大孔径(3.56～3.85nm)以及较大的饱和磁化强度(1.29～6.92emu/g)的磁性Fe@γ-Fe2O3/GC纳米复合材料。最后,将磁性Fe@γ-Fe2O3/GC纳米复合材料用于对Cu2+和Co2+离子吸附研究,并与活性炭的吸附性能比较,发现该材料表现出更好的吸附性能以及良好的磁性可回收能力。更多还原

【Abstract】 Lithium ion battery is widely used in portable electron apparatus and cars due to its highlights, such as high voltage, low discharge rate by itself little volume, light weight and nonmemeory effect. The anode material is one of the most important factors in determining the performance of lithium-ion battery. However, the traditional carbon cathode materials with low energy density and poor rate performance are difficult to meet the demand of industry, so the development of new low-cost and high-performance lithium-ion battery cathode materials has important significance to promote the development of new energy industry. Sn/Ti/Si/Fe and other elements and their oxides are new active anode material of high specific capacity, but due to expansion effect during the process of charge and discharge, the cycle performances of these materials are poor. Porous material can lead the formation of "reinforced concrete" structure with active components and effectively alleviate of the volume expansion. Graphitized mesoporous carbon (GMC) is a new type of promising carbon frame material with regular pore structure, excellent stability and electronic conductivity. This paper use Sn/Ti as active components, choose simple methods to load active components nanoparticles onto GMC frame material to develop a new type of practical active GMC based anode materials for lithium-ion batteries.New Sn-GMC nanocomposite with metallic tin nanocrystals embedded into graphitic mesoporous carbon walls has been synthesized via a simple one-step solid-liquid grinding/templating route. X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy and thermogravimetric analysis techniques are used to characterize the samples. It is observed that high content of metallic tin nanocrystals with the sizes of3-5nm are well dispersed into the highly conductive graphitic carbon walls, and synthesized tin graphitic mesoporous carbon (Sn-GMC) nanocomposite possesses ordered2D hexagonal mesostructures with moderate surface area (223.9m2/g), large pore volume (0.611cm3/g) and hierarchical porosity. Due to its novel structures, the Sn-GMC nanocomposite exhibits high initial coulombic efficiency, excellent cyclability and rate performance when employed as an anode material in lithium ion batteries.Mesostructured TiO2/graphitic carbon (TiO2-GC) composites were synthesized by a simple one-step nanocasting method. The as-prepared materials were characterized by XRD, TEM and BET. The results show that the mesostructured TiO2-GC composites have a moderate specific surface area (110.28-528.95m2/g) and large pore volume (0.063～0.351cm3/g), which are beneficial for Li+ion diffusion during charge-discharge processes. The electrochemical tests exhibit that the20TiO2-GC composite show more excellent reversibility and cyclability than other proportion of composite materials, it possesses a high initial discharge capacity of1076mAh/g, and the discharge capacity still remains326mAh/g at50th cycle.Lithium ion batteries contain heavy metals such as cobalt, copper, manganese and cadmium, which have great harm to the environment and human health. Thereby, it is very significant to remove the heavy metal ions in the waste water. Mesostructured magnetic Fe@-γFe2O3/graphitic carbon composites were synthesized through a simple one-step nanocasting route using iron nitrate and soybean oil as iron source and carbon precursor, respectively, for the gelation reaction of tetraethyl orthosilicate and citric acid. The ultimately formed magnetic Fe@γ-Fe2O3nanoparticles were homogeneous dispersed into the matrix of mesostructured carbon with graphitic frameworks. Such mesostructured magnetic Fe@γ-Fe2O3/graphitic carbon composites have a high specific surface area (249.44-701.72m2/g), large pore volume (3.56～3.85nm), and high saturation magnetization (1.29～6.92emu/g), giving the materials wide potential applications as catalyst supports or absorbents. Compared with activated carbon, Fe@γ-Fe2O3/GC composites show better adsorption performance of Cu2+and Co2+and good magnetic recoverable capacity.更多还原