热处理对A_5B_19型La_0.68Gd_0.2Mg_0.12Ni_3.3Co_0.3Al_0.1储氢合金微观组织和电化学性能的影响

Effects of annealing treatment on microstructure and electrochemical properties of La_(0.68)Gd_(0.2)Mg_(0.12)Ni_(3.3)Co_(0.3)Al_(0.1) hydrogen storage alloys

用感应熔炼方法熔炼A5B19型La0.68Gd0.2Mg0.12Ni3.3Co0.3Al0.1合金,并在密闭容器中对合金进行不同温度(1173～1273K)下保温16h的热处理,采用电感耦合等离子发射光谱(ICP)、X射线衍射(XRD)、电子探针显微分析方法(EPMA)和电化学测试分析方法对比研究了退火温度对合金成分、微观组织和电化学性能的影响。结果表明,A5B19型合金组织主要由Ce5Co19(Pr5Co19)型﹑PuNi3型和CaCu5型等相组成,退火后合金则形成以A5B19型(Pr5Co19和Ce5Co19)为主相的多相组织,随退火温度升高Pr5Co19型主相的相丰度逐渐增加,当T=1273K时其相丰度达到最大值87.8%(质量分数),而Ce5Co19型相仅为0.78%(质量分数)。电化学分析测试表明,退火温度对合金电极的活化性能和大电流放电特性影响不明显,但对电极容量和循环稳定性影响较大。在T=1273K退火后,合金电极放电容量为373.01mAh/g,经100次充放电循环后其电极容量保持率(S100)为90.20%,表现出较好的电化学性能。

La0.68Gd0.2Mg0.12Ni3.3CoO.3A10.1 hydrogen storage alloys were prepared by induction melting and then annealed at different temperature（1173-1273K） in the closed container for 16h. The effect of annealing tempera- ture on the microstructure and electrochemical properties of La0.68Gd0.2Mg0.12Ni3.3CoO.3A10.1 were investigated by means of inductively coupled plasma（ICP）, X-ray diffraction （XRD）, electron probe micro-analysis （EP MA） and electrochemical measurements. The results showed that the A5B19 alloys mainly consisted of Ce5Co19- type（Pr5Co19-type）, PuNi3-type and CaCus-type phase. Meanwhile, with increasing annealing temperature, Pr5Co19-type phase abundance in annealed alloys increased, and CesCo19 type phase abundance decreased. The Pr5Co19-type phase abundance was 87.75wt%, andCe5Co19-type phase abundance was only 0.78wt% when an- nealing temperature was 1273K. The electrochemical measurements showed that these alloys had little effects on activation performance under different annealing temperature, but it was great impact on electrode capacity and cycle stability. The discharge capacity of the alloys reached 373. 01mAh/g when annealing temperature was 1273K. After 100 charge-discharge cycles, the discharge capacity retention rate（S100）of the alloy electrode（T= 1273K） reached 90.2%.