硫化亚铜基正极材料的原位电化学制备及其储锂性能研究

发布时间：2018-03-05 06:31

本文选题：正极材料　切入点：锂离子电池　出处：《西北师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：硫化亚铜(Cu2S)由于具有较高的理论比容量(337 mAh·g-1)、较高的电子导电性(ca.104 S cm-1)、平坦的电压平台以及原料在自然界中丰富的储量,被认为是具有前景的下一代锂离子电池正极材料。然而,在实用化之前,硫化亚铜基正极材料还有些需要改进的地方。硫化亚铜电极在充放电循环过程中产生的多硫化物(Li2Sx,x2)易溶于有机电解液中,从而导致活性物质的流失,容量衰减很快。本文采用原位电化学法制备了S-C及S-PPy聚吡咯复合材料前驱体,并对其形貌、微观结构进行了研究。在此过程中铜箔既作为集电极,还作为制备Cu2S的原料。铜箔在反应过程中的腐蚀是缓和的,不会影响集电极的结构。实验结果如下:(1)利用浓硫酸对葡萄糖的脱水碳化作用,一锅法制备了前驱体S-C复合材料,再通过在铜集电极上的充放电测试过程,原位电化学法制备了Cu2S-C复合材料。复合材充放电测试结果显示,Cu2S-C复合材料具有良好的电化学循环性能,其首次可逆容量达255.4 mAh·g-1,100次循环后容量252.3 mAh·g-1,容量衰减几乎可以忽略。而且,分别在电流密度0.2 C,0.5 C,1 C(1 C=337 mA·g-1)下进行充放电性能测试,结果容量分别达232.8,207.6,183.8 mAh·g-1,倍率性能较好。SEM测试结果显示,S-C前驱体材料的形貌受复合材料中的碳含量和制备复合材料的H2SO4的浓度影响较大。同时,Cu2S-C复合材料的电化学性能与前驱体S-C复合材料中碳含量以及H2SO4的浓度有关,实验结果表明,最佳的设计碳含量为5 wt.%,合适的H2SO4浓度(所有试剂滴加完成后的浓度)为75%。(2)采用原位化学氧化聚合法制备了前驱体S-PPy复合材料,然后利用在铜集电极上充放电过程原位电化学法制备了Cu2S-PPy复合材料。实验结果显示,Cu2S-PPy复合材料具有良好的电化学循环性能和倍率性能,在0.2 C(1 C=337 mA·g-1)下首次可逆容量达297.4 mAh·g-1,50次循环后仍保持在270.2 mAh·g-1。并且研究了PPy在前驱体复合物中的含量对材料微观形貌和结构的影响。S-PPy复合材料前驱体在不同的集电极铝箔、铜箔上所发生的电化学反应机理有很大的差别,在不同的集电极上充放电电压曲线不同,不同的电压曲线代表不同的电化学反应历程。在铝箔上,发生的电化学反应完全符合Li-S电池体系的反应情况。而在铜箔上发生化学反应,原位电化学制备得到Cu2S-PPy复合材料。使用适当的电解液有利于提高电极材料的电化学性能,在Cu2S-PPy复合材料电极体系中,1M LiTFSI的DME/DOL双组分溶剂体系是比较理想的电解液。
[Abstract]:Cuprous sulphide (Cu2S) is considered to be a promising cathode material for the next generation of lithium ion batteries due to its high theoretical specific capacity of 337 mAh 路g-1C, high electronic conductivity, flat voltage platform and abundant reserves of raw materials in nature. Before application, cuprous sulphide base cathode materials need to be improved. The polysulfide Li _ 2S _ xX _ (2) produced by cuprous sulfide electrode during charge / discharge cycle is easily dissolved in organic electrolyte, which leads to the loss of active substances. The precursor of S-C and S-PPy polypyrrole composites was prepared by in situ electrochemical method, and its morphology and microstructure were studied. The corrosion of copper foil in the reaction process is mild and the structure of collector will not be affected. The experimental results are as follows: 1) the precursor S-C composite was prepared by one-pot method using concentrated sulfuric acid as dehydration and carbonation of glucose. The Cu2S-C composites were prepared by in-situ electrochemical method through the charge and discharge measurement on the copper collector. The results of charge and discharge test showed that the Cu _ 2S-C composite had good electrochemical cycling performance. The first reversible capacity is 255.4 mAh 路g-1g ~ (-1), the capacity is 252.3 mAh 路g ~ (-1) after 100 cycles, and the capacity attenuation is almost negligible. Furthermore, the charge-discharge performance is tested at the current density of 0.2 C ~ (0.5) C ~ (1) C ~ (1) C ~ (1) C ~ (1) C ~ (1) C ~ (1) ~ (3) Ma 路g-1). The results showed that the morphology of the precursor materials was influenced by the carbon content in the composites and the concentration of H _ 2SO _ 4 in the composites, and the electrochemical properties of the Cu _ 2S-C composites were also affected by the electrochemical properties of the Cu _ 2S-C composites. The energy depends on the carbon content and the concentration of H _ 2SO _ 4 in the precursor S-C composite. The experimental results show that the optimum design carbon content is 5 wt. and the suitable concentration of H _ 2SO _ 4 (after all the reagents have been added) is 75. 2. The precursor S-PPy composite was prepared by in-situ chemical oxidation polymerization. Then Cu2S-PPy composites were prepared by in-situ electrochemical method during charging and discharging process on copper collector. The experimental results show that Cu2S-PPy composite has good electrochemical cycling performance and rate performance. The initial reversible capacity reached 297.4 mAh 路g-1g ~ (-1) and remained at 270.2 mAh 路g ~ (-1) after 50 cycles. The effect of the content of PPy in the precursor complex on the microstructure and microstructure of the composite was studied. The precursor of S-PPy composite was used in different collector electrode aluminum foils. The mechanism of electrochemical reaction on copper foil is very different. The charge-discharge voltage curve is different on different collector, and different voltage curve represents different electrochemical reaction mechanism. The electrochemical reaction was completely in line with the reaction of Li-S battery system, and the electrochemical properties of the electrode materials were improved by the use of proper electrolyte, and the electrochemical reaction was carried out on copper foil and prepared by in situ electrochemistry. One M LiTFSI DME/DOL two-component solvent system is an ideal electrolyte in Cu2S-PPy composite electrode system.
【学位授予单位】：西北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O646.54;TB33

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