镁负极微观结构和含氧阴离子缓蚀剂对镁空气电池性能的影响

发布时间：2018-08-04 22:00

【摘要】：能源是保障人类生存和社会发展的重要物质基础,然而在过去的一百多年里,煤、石油以及天然气等传统能源被大量消耗,能源危机已经成为世界各国不可回避的问题。同时传统能源的使用还造成了严重的环境污染,因此开发新型绿色能源迫在眉睫。金属空气电池具有成本低、无毒、无污染、理论电压和比能量密度高等优点,是传统能源的理想替代品。镁是地球上储量居第八位的元素,具有密度低(1.74 gmL~(-1))、化学性质活泼以及电化学当量高(2.20 Ahg~(-1))等优点,是金属空气电池的理想负极材料。但由于其活泼的电化学性质,镁合金在中性盐电解液中极易被腐蚀,导致镁空气电池阳极效率很低。另一方面,镁空气电池在放电过程中,镁负极表面会产生一层主要成分为氢氧化镁的放电产物膜,电池在间歇放电时会产生严重的电压滞后现象。本论文通过极化曲线、阻抗曲线(EIS)以及析氢实验等测试方法研究了微观结构和含氧阴离子缓蚀剂对镁合金电化学性能的影响,通过连续放电测试和间歇放电测试等测试方法研究了镁负极微观结构和含氧阴离子缓蚀剂作为电解液添加剂对镁空气电池放电性能的影响,通过扫描电子显微镜(SEM)、激光共聚焦扫描显微镜(LSCM)和能谱仪(EDS)研究了镁负极表面放电产物的形貌及成分。主要研究内容如下:(1)通过预压缩变形及随后的退火处理制备了不同孪晶含量的AZ31镁合金,并研究了以这些镁合金为负极材料的镁空气电池的性能。随孪晶含量的增加,AZ31镁合金电化学活性逐渐增强,镁空气电池平均放电电压逐渐变高,电压滞后时间逐渐变短。(2)研究了织构对镁合金耐腐蚀性能以及镁空气电池放电性能的影响。当合金表面状态为机械打磨时,AZ31镁合金TD-ND面比RD-TD面具有更好的耐腐蚀性能,基于TD-ND面镁负极的镁空气电池具有更高的阳极效率。(3)通过冷轧变形和随后的退火工艺获得了不同晶粒尺寸的AZ31镁合金板材,并研究了以这些合金为负极材料的镁空气电池的性能。随晶粒尺寸的减小,AZ31镁合金电化学活性和耐腐蚀性能逐渐变好,镁空气电池阳极效率和放电电压逐渐增高。(4)Li_2CrO_4可以有效改善AZ31镁合金在3.5 wt%NaCl溶液中的耐腐蚀性能,AZ31镁合金在3.5 wt%NaCl+0.1 wt%Li_2CrO_4溶液中的腐蚀电流密度仅为在3.5 wt%NaCl溶液中的1/7。Li_2CrO_4作为电解液添加剂可以有效提高镁空气电池间歇放电阳极效率,改善镁负极表面放电产物形貌。(5)Na_3PO_4?12H_2O和NaVO_3对AZ31镁合金在0.6 M NaCl溶液中均有很好的腐蚀抑制效果。在含Na_3PO_4?12H_2O和NaVO_3的两种溶液中,镁合金表面分别会产生一层磷酸盐保护膜和一层钒酸盐保护膜,并减慢合金的自腐蚀速率。磷酸盐保护膜比钒酸盐保护膜更完整,因此Na_3PO_4?12H_2O对AZ31镁合金的腐蚀抑制效果更好。Na_3PO_4?12H_2O和NaVO_3作为电解液添加剂均可有效提高电池阳极效率,降低电池间歇放电间歇期的阳极效率损失,改善镁负极表面放电产物形貌。相比于NaVO_3而言,Na_3PO_4?12H_2O对电池阳极效率的改善效果更明显。
[Abstract]:Energy is an important material basis for the protection of human survival and social development. However, in the past more than 100 years, the traditional energy such as coal, oil and natural gas have been greatly consumed. The energy crisis has become an unavoidable problem in the world. At the same time, the use of traditional energy has also made serious environmental pollution, so the new green is developed. Energy is imminent. Metal air battery has the advantages of low cost, non-toxic, no pollution, high theoretical voltage and high specific energy density. It is an ideal substitute for traditional energy. Magnesium is the eighth element in the earth, with low density (1.74 gmL~ (-1)), active chemical properties and high electrochemical equivalent (2.20 Ahg~ (-1)). But because of its active electrochemical properties, magnesium alloys are easily corroded in neutral salt electrolyte, resulting in low anodic efficiency of magnesium air batteries. On the other hand, during the discharge process of magnesium air batteries, a layer of discharge products, mainly composed of magnesium hydroxide, is produced on the surface of magnesium negative electrode, and the battery is intermittent. In this paper, the effect of microstructure and oxygen containing anionic corrosion inhibitor on the electrochemical performance of magnesium alloys was investigated by polarization curve, impedance curve (EIS) and hydrogen evolution test. The microstructure of magnesium anode was studied by continuous discharge test and intermittent discharge test. The effect of the oxygen anion inhibitor as an electrolyte additive on the discharge performance of the magnesium air battery was studied by scanning electron microscope (SEM), laser confocal scanning microscope (LSCM) and energy spectrometer (EDS). The main contents of the study are as follows: (1) pre compression deformation and subsequent annealing are carried out. The AZ31 magnesium alloys with different twin content were prepared and the performance of magnesium air batteries with these magnesium alloys as negative materials was studied. With the increase of the twin content, the electrochemical activity of AZ31 magnesium alloy gradually increased, the average discharge voltage of magnesium air battery became higher and the voltage lag time became shorter. (2) the resistance of texture to magnesium alloy was studied. The effect of corrosion properties and the discharge performance of magnesium air battery. When the surface state of the alloy is mechanical grinding, the TD-ND surface of AZ31 magnesium alloy has better corrosion resistance than that of the RD-TD mask. The magnesium air battery based on the TD-ND surface magnesium anode has higher anode efficiency. (3) different grain sizes are obtained by cold rolling and subsequent annealing. The performance of magnesium air battery with these alloys as negative electrode was studied. With the decrease of grain size, the electrochemical activity and corrosion resistance of AZ31 magnesium alloy gradually became better, and the anode efficiency and discharge voltage of magnesium air battery increased gradually. (4) Li_2CrO_4 can effectively improve the AZ31 magnesium alloy in 3.5 wt%NaCl solution. The corrosion resistance of AZ31 magnesium alloy in 3.5 wt%NaCl+0.1 wt%Li_2CrO_4 solution is only the 1/7.Li_2CrO_4 in 3.5 wt%NaCl solution as an electrolyte additive, which can effectively improve the anodic efficiency of the intermittent discharge of magnesium air batteries and improve the surface discharge morphology of the magnesium negative electrode. (5) Na_3PO_4? 12H_2O and NaVO_3 to AZ31 magnesium The alloy has a good corrosion inhibition effect in 0.6 M NaCl solution. In the two solutions containing Na_3PO_4? 12H_2O and NaVO_3, the surface of magnesium alloy produces a layer of phosphate protection film and a layer of vanadate protective film respectively, and slows the self corrosion rate of the alloy. The phosphate protection film is more complete than the vanadate protective film, so Na_3PO_4? 12H_2O The corrosion inhibition effect on AZ31 magnesium alloy better.Na_3PO_4? 12H_2O and NaVO_3 as the electrolyte additives can effectively improve the anode efficiency of the battery, reduce the anode efficiency loss of the intermittent discharge period of the battery and improve the surface discharge product morphology of the magnesium negative electrode. Compared to NaVO_3, the improvement effect of Na_3PO_4? 12H_2O on the anode efficiency of the battery is improved. It's more obvious.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG174.42;TM911.41

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