储氢合金及其复合材料的球磨制备和电化学性能的研究

发布时间：2018-05-04 02:24

本文选题：储氢合金 + 复合材料　；参考：《吉林大学》2017年硕士论文

【摘要】：镍金属氢化物电池(简称镍氢电池)的功率密度是由其负极材料——储氢合金的高倍率放电性能(HRD)决定的。但是,目前商用的储氢合金MmNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3)(Mm表示富铈混合稀土)在放电电流密度为3000mAg~(-1)+时的容量保留率仅为21.53%,无法满足镍氢电池在电动工具、现代军事装备、新能源汽车等高功率领域的应用。储氢合金的HRD主要受两方面的影响:氢在合金内部的扩散速率以及合金/电解液界面处的电化学反应速率。因此,为了提高储氢合金的HRD,可以通过(1)减小储氢合金的颗粒尺寸以缩短氢在其内部的扩散距离和(2)减小接触电阻和电荷转移电阻以加速界面处的电化学反应和电子传输。球磨作为一种简单有效的方法,可用于减小储氢合金的颗粒尺寸。具有良好导电性的石墨烯纳米片则能够显著降低电极材料的内阻。在本论文中,我们结合这两种策略,通过球磨法制备了储氢合金/石墨烯纳米片复合材料。详细研究了球磨时间和石墨烯纳米片的添加量对合金电化学性能的影响规律,得到了最佳的球磨时间和石墨烯纳米片添加量,从而最大幅度提高了商用储氢合金的HRD。首先,我们研究了不同球磨时间(30、45、60、90 min)对商用储氢合金放电容量及HRD的影响。当球磨时间为30 min时,该储氢合金电极在放电电流密度为3000mAg~(-1)时的容量保留率为53.0%,几乎是原始商用储氢合金电极的(21.5%)2.5倍,高于在其它球磨时间下的数据。其次,我们还研究了不同石墨烯纳米片添加量(1 wt%、1.5 wt%和2 wt%)对商用储氢合金电化学性能的影响。当添加1.5 wt%的石墨烯纳米片时,该复合材料电极具有最佳的电化学性能。其在放电电流密度为3000mAg~(-1)时的容量保留率达到68.3%,几乎是原始商用储氢合金电极的3.2倍。本论文为提高储氢合金的HRD提供了一个新的途径,而且有望应用于其它类型的储氢合金及其复合材料。
[Abstract]:The power density of Ni-MH battery is determined by the high rate discharge performance of its anode material, hydrogen storage alloy. However, the capacity retention rate of commercial hydrogen storage alloy MmNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3)(Mm (cerium rich mixed rare earth) is only 21.53 when the discharge current density is 3000mAgn-1), which can not meet the application of Ni-MH batteries in high power fields such as electric tools, modern military equipment, new energy vehicles and so on. The HRD of hydrogen storage alloy is mainly affected by the diffusion rate of hydrogen in the alloy and the electrochemical reaction rate at the interface of alloy and electrolyte. Therefore, in order to improve HRD of hydrogen storage alloy, the particle size of hydrogen storage alloy can be reduced by 1) to shorten the diffusion distance of hydrogen in its interior and to reduce the contact resistance and charge transfer resistance to accelerate the electrochemical reaction and electron transport at the interface. As a simple and effective method, ball milling can be used to reduce the particle size of hydrogen storage alloy. Graphene nanoparticles with good electrical conductivity can significantly reduce the internal resistance of electrode materials. In this thesis, the hydrogen storage alloy / graphene nanocomposites were prepared by ball milling. The effect of ball milling time and the amount of graphene nanoparticles on the electrochemical properties of the alloy was studied in detail. The optimum milling time and the amount of graphene nanocrystals were obtained, thus the HRD of commercial hydrogen storage alloys was greatly improved. Firstly, we studied the effect of different milling time on the discharge capacity and HRD of commercial hydrogen storage alloys. When the milling time is 30 min, the capacity retention rate of the hydrogen storage alloy electrode is 53.0 when the discharge current density is 3000mAgAg-1), which is almost 21.5 times of that of the original commercial hydrogen storage alloy electrode, which is higher than that under other ball milling time. Secondly, we also studied the effects of different graphene nanocrystals on the electrochemical properties of commercial hydrogen storage alloys. The composite electrode has the best electrochemical performance when 1.5 wt% graphene nanoparticles are added. When the discharge current density is 3000mAgAg-1), the capacity retention rate is 68.3%, which is almost 3.2 times that of the original commercial hydrogen storage alloy electrode. This paper provides a new way to improve the HRD of hydrogen storage alloys and is expected to be applied to other types of hydrogen storage alloys and their composites.
【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】：TG139.7

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