稀土镁合金负极对镁空气电池性能影响研究

发布时间：2018-04-24 22:01

本文选题：镁空气电池 + 稀土镁合金　；参考：《河南工业大学》2017年硕士论文

【摘要】：镁及镁合金具有密度低、电化学活性高、标准电极电位较负和电池能量密度高等优异性能,使镁合金在化学电源领域具有非常好的发展前景而作为研究的热点。然而因为镁合金的自腐蚀析氢反应严重与放电平台不稳定等问题,在很大程度上阻碍了镁合金负极材料的广泛应用。本文通过对AZ31镁合金及添加稀土元素(Y、Gd)制备的新型稀土镁合金的电化学性能和镁-空气电池放电性能做了一系列的研究,为研究出高性能镁合金负极材料提供参考依据。本论文采用线性扫描伏安曲线(LSV)、塔菲尔极化曲线(Tafel)、电化学阻抗谱(EIS)、金相实验、XRD分析及电池恒流放电等方法,主要研究了AZ31及添加Y、Gd稀土元素制备的新型镁合金的金相显微组织和电化学性能,并将新型镁合金电极与MnO2体系的空气电极以及3.5wt%NaC l电解液组成镁空气电池单体,分别测试其在5mA/cm2、10mA/cm2和20mA/cm2电流密度下的放电电压随放电时间的变化规律,并研究电池的恒流放电性能。主要研究结果如下:(1)AZ31中添加不同的稀土元素,制备AZ31-Y和AZ31-Y-Gd稀土镁合金。三类新型镁合金的金相实验和电化学性能测试中,AZ31-Y-Gd合金的组织均匀且晶粒尺寸相对最小,晶粒细化效果明显,电极的平衡电位较负且电化学活性相对较高,耐腐蚀性能最好;铸态AZ31合金的平衡电位相对较正、电荷传递过程的电阻较小,电极的耐腐蚀性最差。(2)AZ31、AZ31-Y及AZ31-Y-Gd镁负极组装的镁空气电池,其开路电压非常接近在1.60V左右。在5mA/cm2、10mA/cm2和20mA/cm2电流密度条件下放电,三类镁合金材料均在10mA/cm2电流密度下,表现出较高的放电平台和较好的放电平稳性等综合放电性能。三种新型镁负极空气电池在10mA/cm2电流密度下,AZ31-Y-Gd放电电压相对最高且放电过程电压平稳下降,总体放电效果最好;AZ31放电电压最低,且放电电压波动范围较大。(3)AZ31中添加不同含量的稀土元素Y和Gd,制备AZ31-x%RE稀土镁合金。随稀土含量的增加,组织中出现新相Al2Gd、Al2Y和Mg24Y5,组织中析出相数量增加,晶粒尺寸逐渐减小,基体组织明显细化。当稀土(Y+Gd)含量为3%时,AZ31-3%RE具有最小的晶粒尺寸和均匀的组织;电化学性能测试表明,AZ31-3%RE拥有较负的平衡电位,较高的电化学活性,在3.5wt%NaCl中的耐腐蚀性能最好,AZ31-2%RE合金表现出的电化学性能次之,AZ31-1.5%RE的平衡电位较正且电荷传递电阻较小,电化学性能较差。(4)三种AZ31-x%RE镁负极空气电池的开路电压相差不大,电压值在1.60V左右。在10mA/cm2放电电流密度下,AZ31-3%RE放电电压在1.0V左右且放电较平稳;AZ31-2%RE与AZ31-3%RE放电电压相当,但电压略有波动;AZ31-1.5%RE放电电压最低,且放电后期电压周期性波动剧烈,综合放电性能最差。
[Abstract]:Magnesium and magnesium alloys have low density, high electrochemical activity, negative electrode potential and high battery energy density, which make magnesium alloys have a very good prospect in the field of chemical power supply. However, due to the serious self-corrosion hydrogen evolution reaction and unstable discharge platform of magnesium alloys, the wide application of magnesium alloy anode materials is hindered to a great extent. In this paper, a series of studies have been done on the electrochemical properties of AZ31 magnesium alloy and the new rare earth magnesium alloy prepared by adding rare earth element, and the discharge performance of magnesia-air battery, which provides a reference for the study of high performance magnesium alloy negative electrode material. In this paper, the linear scanning voltammetry curve (LSVN), Tafer polarization curve (Tafel), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) analysis and constant current discharge of the battery were used. The metallographic microstructure and electrochemical properties of the new magnesium alloy prepared by AZ31 and YTGd rare earth element were studied. The new magnesium alloy electrode, the air electrode of MnO2 system and the 3.5wt%NaC l electrolyte were used to form the Mg-air battery monomer. The variation of discharge voltage with discharge time at 5 Ma / cm 2 10 Ma / cm 2 and 20mA/cm2 current density was measured, and the constant current discharge performance of the battery was studied. The main results are as follows: AZ31-Y and AZ31-Y-Gd rare earth magnesium alloys were prepared by adding different rare earth elements into AZ31. In the metallographic test and electrochemical performance test of three kinds of new magnesium alloys, the microstructure of AZ31-Y-Gd alloy is uniform, the grain size is relatively small, the effect of grain refinement is obvious, the equilibrium potential of electrode is relatively negative, the electrochemical activity is relatively high, and the corrosion resistance is the best. The equilibrium potential of as-cast AZ31 alloy is relatively positive, the resistance of charge transfer process is smaller, and the corrosion resistance of the electrode is the worst. The open-circuit voltage of the magnesium-air battery assembled by AZ31AZ31-Y and AZ31-Y-Gd negative electrode is very close to 1.60V. Under the conditions of 5 Ma / cm 2 10 Ma / cm 2 and 20mA/cm2 current density, the three kinds of magnesium alloys exhibit high discharge platform and good discharge stability at 10mA/cm2 current density. The discharge voltage of AZ31-Y-Gd is the highest at 10mA/cm2 current density, and the voltage of discharge process decreases steadily, the overall discharge effect is the best and the discharge voltage of AZ31 is the lowest. AZ31-x%RE rare earth magnesium alloy was prepared by adding different contents of rare earth elements Y and Gd in the range of voltage fluctuation. With the increase of rare earth content, new phases Al _ 2Gd _ 2O _ (Al _ 2Y) and mg _ (24) Y _ 5 appear in the microstructure. The number of precipitated phases in the microstructure increases, the grain size decreases gradually, and the matrix structure is refined obviously. AZ31-3RE has the smallest grain size and uniform structure when the content of rare earth is 3, and the electrochemical performance test shows that AZ31-3RE has negative equilibrium potential and high electrochemical activity. The corrosion resistance of AZ31-2RE alloy is the best in 3.5wt%NaCl. The second is the electrochemical performance of AZ31-1.5RE alloy. The equilibrium potential of AZ31-1.5RE is higher, the charge transfer resistance is smaller, and the electrochemical performance is poor. The voltage is about 1.60 V. Under the current density of 10mA/cm2 discharge, the discharge voltage of AZ31-3RE is about 1.0 V, and the discharge voltage of AZ31-2RE is about the same as that of AZ31-3%RE discharge voltage, but the voltage fluctuates slightly and the voltage of AZ31-1.5RE discharge is the lowest, and the voltage of AZ31-3RE at the later stage of discharge fluctuates sharply, and the comprehensive discharge performance is the worst.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;TM911.41

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