锂硒电池正极材料的制备与性质研究

发布时间：2018-06-23 01:00

本文选题：锂硒电池 + 正极材料　；参考：《吉林大学》2017年硕士论文

【摘要】：硒作为电极材料具有高的电子导电率和理论容积密度,因而受到了科学工作者的关注。然而,锂硒电池面临的最大的问题是电极在工作时多硒化合物的溶解及穿梭效应,从而影响了其电化学性能。针对上述问题,本论文通过制备硒/多孔材料复合物和对电池体系中隔膜的修饰两个方面对锂硒电池进行改性探究,具体内容如下:首先,我们利用模板法制备出新型多孔碳,并且通过熔融法与硒复合形成Se/Porous carbon材料,通过多种测试方法说明了硒嵌入到Porous carbon的孔中。0.5 C(1 C=675 m Ah/g)的电流密度时,1000次充放电以后放电比容量大约220m Ah/g,表现了良好的电化学稳定性。随后,我们以纸为原料,制成多孔碳作为锂硒电池的夹层,对比不加夹层、加两层夹层、加四层夹层,测试了电化学性能。结果表明,0.5 C的电流密度时经过60次循环,不加夹层放电比容量只有62 m Ah/g,加两层夹层的维持在138m Ah/g,加四层夹层的能够保持在302 m Ah/g,说明在4层paper夹层的范围内,夹层的层数与电化学性能具有线性关系。我们还对比分析了充放电曲线,发现夹层层数越多,抑制穿梭效应的效果就越好。最后,我们构建了有TiO_2纳米纤维和泡沫镍(NFF)组成的Se-TiO_2/NFF电池体系。首先我们通过静电纺丝技术合成了TiO_2纳米纤维,再将硒和TiO_2纳米纤维通过熔融过程合成得到Se-TiO_2材料,接下来把NFF(泡沫镍)作为电池的夹层放置在电极片和隔膜中间。我们进行了电化学测试,在0.5 C电流密度下,经过200圈循环以后放电比容量保持在600.3 m Ah/g,并且在30 C大倍率下容量维持在321.3 m Ah/g。优越的电化学性能主要取决于TiO_2和NFF的协同作用。同时,我们在充放电期间发现了NFF表面发生了一个氧化还原反应并对此进行了研究。综上所述,我们通过制备硒/多孔材料复合物和添加夹层修饰隔膜有效地抑制了穿梭效应,提高了电池的电子导电率和结构稳定性,优化电池的电化学动力学性质,从而提高其倍率性能、放电比容量以及循环性能。本文为锂硒电池的研究提供了理论和实验依据。
[Abstract]:Selenium as an electrode material has high electron conductivity and theoretical volume density, so it has attracted the attention of scientists. However, the biggest problem facing lithium selenium battery is the dissolving and shuttling effect of multi-selenium compounds in the electrode, which affects its electrochemical performance. In order to solve the above problems, this paper studied the modification of lithium selenium battery by preparing selenium / porous composite and modifying the membrane in the battery system. The specific contents are as follows: firstly, we prepared new porous carbon by template method. In addition, Se- / Porous carbon materials were formed by melting method combined with selenium. A variety of measurement methods show that the specific discharge capacity of selenium embedded in the pore of Porous carbon is about 220 m / g at the current density of 0.5C (1 C + 675 m Ah/g) after 1 000 charges and discharges, showing good electrochemical stability. Then we made porous carbon as the interlayer of lithium selenium battery with paper as raw material. The electrochemical performance was tested by adding two layers and four layers respectively. The results show that when the current density is 0.5 C, the discharge specific capacity is only 62 m / g without interlayer, with two layers at 138 m / g, and four layers with four layers can be kept at 302m / g, indicating that the range of four layers of paper interlayer is within the range of 4 layers. There is a linear relationship between the number of layers and electrochemical performance. We also compare the charge-discharge curves and find that the more intercalation layers, the better the suppression effect of shuttle effect. Finally, we constructed a Se-TiOS _ 2 / NFF battery system consisting of TiO-2 nanofibers and nickel foam (NFF). First, we synthesized TiO2 nanofibers by electrospinning technology, then synthesized Se-TiO2 nanofibers by melting process from selenium and TiO2 nanofibers, and then placed NFF (nickel foam) as the interlayer of the battery between the electrode sheet and the diaphragm. The electrochemical measurements show that the specific discharge capacity is kept at 600.3 m 路h / g at 0.5C current density and 321.3 m / g at 30 C at large rate after 200 cycles. Superior electrochemical performance mainly depends on the synergistic effect of TiO _ 2 and NFF. At the same time, a redox reaction on the surface of NFF was found and studied during charge and discharge. To sum up, we effectively inhibit the shuttle effect by preparing selenium / porous composite and adding interlayer modified diaphragm, improve the electronic conductivity and structural stability of the battery, and optimize the electrochemical dynamic properties of the battery. In order to improve its rate performance, discharge specific capacity and cycle performance. This paper provides theoretical and experimental basis for the study of lithium-selenium battery.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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