【作者】 姚真东；

【导师】 王久林；

【作者基本信息】 上海交通大学 ， 化学工程与技术， 2012， 硕士

【摘要】 锂硫电池由于其较高的比容量和能量密度成为新一代可循环高能电池的一个重要选择。粘结剂是硫基复合正极中一个重要的组分,极大地影响着电极的电化学性能。本次研究主要探索了三种水性粘结剂,研究了它们对硫基复合正极材料在二次锂电池中性能的影响。首先采用氧化法,将β-环糊精分子中部分羟基氧化成羰基,得到一种新型的粘结剂羰基-β-环糊精,提高了其水溶性,溶解度可达165g/100g水。其粘结强度可达0.197MPa,表现出良好的粘结性能,而且CV测试显示其在0-5伏电压范围内保持性能稳定。将羰基-β-环糊精作为粘结剂用在硫基正极上,电化学测试显示,首次可逆容量高达694.5mAh/g,50次循环后放电容量依然保有655.3mAh/g,可逆放电比容量和稳定性远远优于采用常规粘结剂PVDF、PTFE的硫基正极。SEM图显示羰基-β-环糊精基硫正极在50次循环后,表面平整,没有明显的多硫化物沉淀。初步探索了阿拉伯胶和海藻酸钠作为粘结剂对硫基正极性能的影响。采用阿拉伯胶作为粘结剂并用于锂硫电池,在0.2C条件下,首次可逆比容量可达666.7mAh/g, 50次依然可保持603.2mAh/g,循环性能稳定。将海藻酸钠作为粘结剂用于锂硫电池正极中,50次后的循环容量可达482.1mAh/g。本此研究结果表明,经过部分氧化有效地提高了β-环糊精的水溶性,作为硫基复合正极材料的粘接剂性能良好。β-环糊精相对价格便宜、使用方便、绿色环保,在高能二次电源领域具有潜在的应用价值。更多还原

【Abstract】 With the rapid development of high-energy rechargeable batteries, rechargeable lithium-sulfur batteries have attracted more attention. Among the components in the sulfur cathode, the binder plays an important role in improving its electrochemical performance, especially in regards of cycle performances. In this work, three water-soluble binders are applied in sulfur cathode to investigate the effects on the electrochemical performance of lithium-sulfur batteries in detail.A new binder, carbonyl-β-cyclodextrin, is prepared through partial oxidation, and some of its physical properties, including viscosity, pH and bonding property are studied detailedly. FT-IR shows that some of hydroxyl groups inβ-cyclodextrin molecule are oxidized to carbonyl groups, which greatly enhances its solubility in water and the solubility is 165g/100g (H2O). The shearing strength is up to 0.197MPa, showing a great bonding property, and CV result indicates that this binder remains stable between 1V and 3V and no electrochemical reaction can be observed. And then it is applied as the binder in sulfur composite. The sulfur cathode expresses a high reversible specific capacity of 694.5mAh/g and remains 655.3mAh/g even after 50 cycles. The results show that sulfur cathode using carbonyl-β-cyclodextrin expresses a higher specific capacity and better stability than that using PTFE or PVDF as the binder. The SEM indicates that a homogeneous distribution can be observed in the cathode after 50 cycles, and no severe aggregation can be found in the cathode.Arabic gum and sodium alginate are also initially studied as binders of sulfur composite cathodes to study their effects on the electrochemical performances. Sulfur composite cathode using Arabic gum as the binder shows a high specific capacity of 666.7mAh/g in the first cycle and remains 603.2mAh/g even after 50 cycles. Sodium alginate is also introduced in the sulfur cathode as a binder. And specific capacity of sulfur composite using sodium alginate as the binder is only 482.1mAh/g after 50 cycles.From these experiments, it can be concluded that carbonyl-β-cyclodextrin has a good potential application prospect due to its high water solubility, good convenience, low price, environmental friendness and stable electrochemical performances.更多还原