添加镁对锂负极在碱性水溶液中放电性能和析氢反应行为的影响

Effects of Magnesium Addition on the Discharge Performance and Hydrogen Evolution Reaction Behavior of Lithium Anodes

通过测定负极放电电流、放电电位、极化曲线和析氢速率研究添加镁对锂负极在碱性水溶液中放电性能和析氢反应行为的影响。结果表明,在锂中添加0.07%Mg(质量分数)降低了锂负极的析氢速率,锂镁合金负极电流效率比纯锂负极高,放电电流密度略低于纯锂负极,高电流密度放电时放电电位比纯锂负极略有正移。极化曲线测量结果表明,Li-0.07%Mg(质量分数)合金负极开路电位比纯锂负极稍有正移,自腐蚀微电池电流密度接近纯锂负极。XRD结果表明,锂镁合金负极放电后表面膜主要由LiOH、LiOH·H2O和Mg(OH)2组成。SEM结果表明,锂镁合金负极放电后的表面膜比纯锂负极表面膜的孔隙少,即添加镁降低锂负极析氢速率与负极表面膜中形成的Mg(OH)2对提高膜的完整性有关。

The influences of magnesium addition on the discharge performance and hydrogen evolution reaction behavior were studied via measuring discharge current, discharge potential, polarization curve and hydrogen evolution rate of lithium anodes in alkali aqueous solution. The results show that the hydrogen evolution rate is decreased by adding 0.07wt%Mg to lithium anodes. It is found that the current efficiency of lithium-magnesium alloy anodes is higher than that of lithium anodes, and the discharge current density of lithium-magnesium alloy anodes is a little lower than that of lithium anodes. The discharge potential of lithium-magnesium alloy anodes is a little more positive than that of lithium anodes when the discharge current density is high. The polarization curves show that the open circuit potential of Li-0.07wt%Mg anodes is a little more positive than that of lithium anodes. The micro-cell corrosion current density of Li-0.07wt%Mg anodes is near to that of lithium anodes. The analysis of X-ray diffraction shows that after discharge the surface film of the lithium-magnesium alloy anodes mainly consists of LiOH, LiOH·H2O and some Mg（OH）2. Scanning electron microscopy images show that the surface film of lithium-magnesium alloy anodes is less porous than that of lithium anodes after discharge, namely, the decrease of hydrogen evolution rate by magnesium addition is related to the integrity of the surface film enhanced by Mg（OH）2.