石墨烯和其复合材料的制备及其电化学性能的研究

发布时间：2018-03-01 23:31

  本文关键词： 石墨烯 六溴苯 锂离子电池 金属硫化物 负极材料　出处：《天津大学》2015年博士论文　论文类型：学位论文

【摘要】：锂离子电池具有电压高、容量大、循环寿命长等优点,而被广泛应用于手机、笔记本等便携式电子设备领域,并被认为是最具应用前景的能源存储装置。为了进一步提高锂离子电池的能量密度和循环寿命,需要进一步开发新的负极材料。石墨烯作为碳家族一员,由于具有独特的二维结构、较高的比表面积和优异的电子传导速度,而成为最具潜力的锂离子电池负极材料。基于此,本文探索了不同的方法制备石墨烯,并将其用作为锂离子电池负极材料。此外,还制备了石墨烯/MoS2复合材料,研究了其电化学性能。具体研究结果如下:1.以溴化亚铜为还原剂,在不同溶剂中还原氧化石墨制备的石墨烯。结果表明在盐酸的水溶剂中合成的石墨烯性能最好,通过TEM分析发现,合成石墨烯的层数为两层。电化学测试结果表明,在100 mA·g-1电流密度下,石墨烯的可逆放电比容量为1513 mAh·g-1,循环30次后容量还能保持在1207 mAh·g-1,容量保持率为80%。增加电流密度至500 m A·g-1时,可逆容量还能够达到981 mAh·g-1,远高于石墨烯的理论比容量。2.采用Ullmann反应,以六溴苯为原料,溴化亚铜为催化剂,分别在无水无氧和空气气氛下,探索了合成石墨烯的最佳条件。结果表明,无水无氧条件下,六溴苯的加入量0.04 g,反应温度为140℃,反应时间为12 h时,合成的石墨烯质量最佳。在此条件下,空气氛围中,也可生成高质量的石墨烯。3.采用Ullmann反应,以铜片为基底和催化剂,在Ar气氛围中回流1.5 h、4h、8 h、12 h、16 h、24 h制备石墨烯。结果证明反应16 h时,制备的石墨烯质量最优为单层,通过差量法计算生成石墨烯的质量为0.1 mg,以此质量为活性物质质量则测得不的石墨烯的最高比容量为855.6 mAh·g-1。4.采用电化学方法,以六溴苯的原料,分别以泡沫铜和泡沫镍为极片,在100mA·g-1的电流密度下充放电制备石墨烯。结果表明,无论是以泡沫铜还是泡沫镍为极片充放电400次后,发现均有石墨烯生成,且具有一定的储锂性能。5.采用水热法制备了不同MoS2含量的石墨烯/MoS2复合材料,其中加入钼酸铵的量分别为0.15 g、0.20 g、0.25 g和0.30 g,并考察了12 h、24 h和36 h不同水热时间对反应的影响。结果表明,加入钼酸铵0.25 g,反应24 h时,复合材料的形貌和电化学性能最好。在100 mA·g-1电流密度下,复合材料的首次放电比容量为1680.9 mAh·g-1,经五十次循环后,容量还高达1399.3 mAh·g-1。增加电流密度至1 A·g-1,其比容量还能保持在839.1 mAh·g-1,显示了良好的储锂性能。
[Abstract]:Li-ion batteries have the advantages of high voltage, large capacity, long cycle life, and are widely used in the field of portable electronic devices, such as mobile phones, notebooks, etc. In order to further improve the energy density and cycle life of lithium-ion batteries, new anode materials need to be further developed. Because of its unique two-dimensional structure, high specific surface area and excellent electron conduction velocity, it has become the most promising anode material for lithium ion batteries. In addition, graphene / MoS2 composites were prepared and their electrochemical properties were studied. The results are as follows: 1. Copper bromide was used as reducing agent. Graphene was prepared by reducing graphite in different solvents. The results showed that the graphene synthesized in hydrochloric acid aqueous solvent had the best properties. By TEM analysis, it was found that the layer number of graphene synthesized was two layers. At 100mA 路g ~ (-1) current density, the specific discharge capacity of graphene is 1513 mAh 路g ~ (-1), the capacity of graphene can be maintained at 1207 mAh 路g ~ (-1) after 30 cycles, and the capacity retention rate is 80%. When the current density is increased to 500mA 路g ~ (-1), The reversible capacity can also reach 981 mAh 路g-1, which is much higher than that of graphene. 2. Using Ullmann reaction, using hexabromobenzene as raw material, cuprous bromide as catalyst, in anhydrous and anaerobic atmosphere and in air atmosphere, respectively, The optimum conditions for the synthesis of graphene were investigated. The results showed that under the condition of anhydrous and anaerobic conditions, when the amount of hexabromobenzene was 0.04 g, the reaction temperature was 140 鈩，

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