【作者】 郑伟；

【导师】 胡信国； 张翠芬；

【作者基本信息】 哈尔滨工业大学 ， 应用化学， 2006， 博士

【摘要】 该研究论文首先较为详细地综述了锂二次电池用硫系正极材料的研究现状和实际应用情况,选择了比容量最高的单质硫作为研究方向,考察了单质硫正极材料的商业现状,技术现状,硫系材料的发展趋势以及各种方法制备出的硫系正极材料的优势与缺点。单质硫因具有很高的能量密度、丰富的自然资源和环境友好等多种优势,成为下一代锂电池中最有发展前景的正极材料之一。但是单质硫及其放电产物导电性差,易溶于有机溶剂,使得锂-硫电池正极活性物质利用率低、循环性能差等。针对以上问题,本文设计并制备了以下三大类复合正极材料,一种是导电聚合物/硫复合材料;一种是纳米多孔导电材料/硫复合材料;另一种是纳米催化活性材料/硫复合材料。并采用H-NMR谱、FTIR光谱、XRD、元素分析、DSC和SEM等手段比较系统地对复合材料进行了表征。探索其作为锂电池正极材料的可行性。并分别把以上三大类复合材料做成正极与液态电解质或凝胶态电解质组装成金属锂电池。以充放电技术研究了不同类别复合正极的充放电性能;以扫描电镜技术观测了复合正极的表面形貌;以循环伏安技术和交流阻抗技术研究了复合正极电极的电化学性能;并初步探讨了锂-硫电池体系中充电过程、放电过程、充放电效率、自热和自放电等对体系飞梭常数的影响,推导了这些过程的机理并简要的进行了分析。采用聚氯乙烯与单质硫在一定的温度下加热处理,在熔融状态下的单质硫作为良好的脱氢氧化试剂,使聚氯乙烯主链脱氢形成具有共轭电子的导电聚合物。同时反应体系中剩下的单质硫几乎是在熔融状态下与聚乙炔相接触,冷却后形成本文所设计的聚乙炔/硫复合材料。研究发现硫与导电物质的物理分散方法对硫系材料的电化学性能有较大的影响。前处理方法对硫与聚合物的反应有较大的影响,好的前处理方法可使材料的反应能力增强。用溶液混合的方法可以使硫与聚合物分散的更好,反应变得更加容易。溶液混合是比较好的前处理方法。硫系复合材料的改性不仅可以从物理或化学的方向考虑,还可以将两种方法结合起来应用。将单质硫镶嵌入具有纳米级孔或微孔的多孔材料之中。采用分阶段加热处理的办法,将熔融状态的单质硫渗透入活性炭和多壁碳纳米管的纳米级孔或微孔之中,形成纳米级复合材料。研究发现:一方面多壁碳纳米管或活性炭具有很强的吸附能力,有效地抑制了单质硫及其放电产物不可逆的溶解到更多还原

【Abstract】 In the beginning of the paper, the present study and the actual applied complexion of cathode materials for the rechargeable lithium batteries were reviewed in detail. Our researchful purpose is the highest capacity sulfur material. We reviewed the market and technology development of sulfur positive material, compare advantage and disadvantage of sulfur positive material manufactured with different methods. Elemental sulfur is a kind of most promising cathode material for the next generation lithium batteries, due to its the highest specific capacity, abundant resources, and low toxicity. However, the insulating nature of sulfur and polysulfides and the loss of polysulfides in the liquid organic electrolyte make lithium-sulfur batteries have very low positive active material utilization and poor cyclability.In the study, three types of nano particle sulfur composite materials were designed and prepared, that is, conductive-polymer/sulfur composites and /nano-porous materials and /nano-catalyzed sulfur composite material , which can be used as advanced cathode materials for rechargeable lithium batteries. The structures and components of the resulting composites are systematically measured by means of H-NMR, FTIR, XRD, DSC, SEM, element analysis and BET. The cathodes, which were made of above-mentioned three composites, and gel polymer electrolytes were used for lithium batteries. The charge and discharge performances of different composites were studied by the charge and discharge; The structures of composites were characterized by SEM; The electrochemical properties of sulfur positive materials were characterized by cyclic voltammetry and EIS. We studied the charge process, discharge process, charge-discharge efficiency, self heat, and self-discharge of lithium-sulfur system on system shuttle constant, conduct the mechanism of these processes and simply analyse them.First to heat PVC and sulfur together at a certain temperature, where the melted sulfur being a fine dehydrogenating agent, captured hydrogen from PVC bone chain and led to an electrially conductive polymer with conjugated electrons. Remained sulfur, however, reacted with PVC almost in a melting state,更多还原