氧化物修饰碳—硫复合电极材料的制备及其电化学性能研究

发布时间：2018-06-05 23:04

本文选题：锂硫电池 + CNT　；参考：《郑州大学》2017年硕士论文

【摘要】：锂硫(Li-S)电池具有超高的理论能量密度(2600 Wh/kg),且电极材料硫储量丰富、价格便宜,已成为当前二次电池领域极具竞争力的研究体系之一。但在电极反应过程中,由于硫材料导电性差、充放电中间产物“飞梭效应”等原因,实际制备的电池往往面临容量衰减快、倍率性不强等问题,阻碍了Li-S电池的进一步应用与推广。从金属氧化物与多硫化物的界面作用出发,本研究提出以金属氧化物修饰不同碳-硫复合电极材料,探索纳米粒子吸附、壳层包覆等微结构对Li-S电池电化学性能的影响。本文主要研究内容如下:(一)纳米锑掺杂二氧化锡(Sb:SnO_2,ATO)修饰碳纳米管-硫复合电极材料的制备及其电化学性质的研究。以商用CNT为导电网络骨架,通过机械混合法将其与导电ATO纳米颗粒混合,并采用熔融法实现单质硫均匀包覆。研究表明CNT导电网络提升了电极导电性及硫负载量,而ATO颗粒则通过吸附作用抑制了“飞梭效应”。通过优化可知当ATO掺入量为2%时,电池容量衰退速率最低,其初始容量为982 mAh/g,200次循环后,容量剩余66.5%,相对于不加ATO的样品容量提高了43.8%。(二)MnO_2包覆碳化聚乙烯亚胺-硫复合电极材料的湿化学原位氧化法制备及其电化学性能研究。以线性聚乙烯亚胺(LPEI)为模板制备了具有三维贯通结构的多孔碳材料并将其负载单质硫,以KMnO4溶液为氧化剂和锰源,通过原位氧化还原反应在碳-硫复合结构表面生成一层片状MnO_2的包覆层。研究结果表明,表面MnO_2包覆层的限域效应可显著抑制多硫化锂的扩散,使得组装电池的库伦效率明显提升。适量氧化的样品在200次循环后容量剩余达485mAh/g,更重要的是其库伦效率保持在96%以上,而未氧化的样品200次循环后库伦效率仅为84%。
[Abstract]:Li-Sc battery has a high theoretical energy density of 2600 / kg 路kg ~ (-1), and its electrode material is rich in sulfur reserves and cheap in price, so it has become one of the most competitive research systems in the field of secondary battery. However, during the electrode reaction, due to the poor conductivity of sulfur materials and the "shuttle effect" of the intermediate product of charge and discharge, the batteries prepared in practice often face the problems of fast capacity attenuation and low rate, etc. It hinders the further application and popularization of Li-S battery. Based on the interfacial interaction between metal oxides and polysulfides, the effects of metal oxides on the electrochemical properties of Li-S batteries were investigated by modifying different carbon-sulfur composite electrode materials with metal oxides to explore the effects of nano-particle adsorption and shell coating on the electrochemical performance of Li-S batteries. The main contents of this paper are as follows: 1. The preparation and electrochemical properties of carbon nanotube-sulfur composite electrode modified by SB: SnO2ATO) doped with SB: SnO2ATO. Commercial CNT was used as the framework of conductive network, and it was mixed with conductive ATO nanoparticles by mechanical mixing method, and the homogeneous coating of elemental sulfur was realized by melting method. The results show that CNT network enhances the electrode conductivity and sulfur load, while ATO particles inhibit the "shuttle effect" by adsorption. The results show that when the ATO incorporation is 2, the cell capacity decline rate is the lowest, its initial capacity is 982 mg / g ~ (-1). After 200 cycles, the residual capacity is 66.5%, which is 43.8% higher than that of the sample without ATO. Preparation and Electrochemical Properties of Carbide Poly (ethyleneimide-Sulphur) Composite electrode Materials coated with MNO _ 2 by in situ Wet Chemical Oxidation method. Porous carbon materials with three dimensional penetrating structure were prepared using linear polyethylene imide (LPEI) as template and supported on elemental sulfur. KMnO4 solution was used as oxidant and manganese source. A lamellar MNO _ 2 coating was formed on the surface of carbon-sulfur composite structure by in-situ redox reaction. The results show that the limiter effect of MnO2 coating can significantly inhibit the diffusion of lithium polysulfide and increase the Coulomb efficiency of the assembled battery. After 200 cycles, the residual capacity of oxidized samples is 485 mg / g. More importantly, the Coulomb efficiency of oxidized samples remains above 96%, while that of unoxidized samples after 200 cycles is only 84%.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;TM912

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