退火对富铈Mm(NiCoMnAl)_5储氢合金电化学性能的影响

Effects of Annealing on Electrochemical Properties of Ce-Rich Hydrogen Storage Alloys

研究了热处理对富铈Mm(NiCoMnAl)5合金晶体结构和电化学性能的影响,实验发现热处理使合金的X射线衍射峰变尖变窄,表明热处理使合金的成分变得均匀,晶格畸变和缺陷减少;但同时,合金的过电势和充放电电势滞后明显增加,特别是在高电流密度150mA·g-1充放电,合金的充放电电极势之间产生了很大的滞后。扫描电镜结果显示,退火合金比铸态合金的晶粒更大更完整;电化学测试结果表明,热处理后合金电化学容量和循环寿命均降低。

The effects of heat treatment on the crystal structure and electrochemical properties of Ce-rich Mm(NiCoMnAl)_5 alloys were studied. The diffraction peaks of the specimens becomes narrower and sharper after heat treatment. It shows that the lattice distortion and defects decrease and more homogeneous composition is obtained after heat treatment. In the meantime, the charge/discharge overpotential and the potential hysteresis of the specimens increase after heat treatment. Especially at the high rate 150 mA·g^(-1) charge/discharge current, a large hysteresis is found between the charge/discharge electrode potential curves of alloy. SEM results show that a more integral character and larger grains can be observed in the annealed alloys. The electrochemical measurement show that the electrochemical capacity and cycle lifetime of the annealed alloys decrease.