薄壁铸造铸态贮氢合金的电化学性能及微观分析

Electrochemical properties and microstructures of strip cast LPC(NiCoMnAlCuFeSi)_5 and Mm(NiCoMnAl)_5 hydrogen storage alloys

讨论了壁厚(1～10mm)对无钕低铈低钴LPC(NiCoMnAlCuFeSi)5和商用成分Mm(NiCoMnAl)5铸态贮氢合金电化学性能的影响。研究发现:10mm厚的两种合金活化性能均优于1～6mm厚度合金;在0.2C充放电制度下,两种合金的放电容量对铸锭厚度均不敏感,LPC(NiCoMnAlCuFeSi)5合金的最大容量约为285mAh/g,Mm(NiCoMnAl)5合金的放电容量约为300mAh/g;在1C充放电制度下,LPC(NiCoMnAlCuFeSi)5合金的最大容量约为250mAh/g,对壁厚不敏感,Mm(NiCoMnAl)5合金的放电容量为250～280mAh/g,对壁厚敏感,并且前者显示出更好的循环稳定性。造成LPC(NiCoMnAlCuFeSi)5合金电化学性能对冷却速度不敏感的主要原因是元素Cu、Fe和Si的作用;晶胞参数和内应力等因素的交互作用也对该合金的性能有一定的影响。

The effect of thickness of ascast ingots on the electrochemical properties of LPC(NiCoMnAlCuFeSi)5 and Mm(NiCoMnAl)5 hydrogen storage alloys was discussed. It is found that both alloys with 10 mm thickness show better activation property than those with 1～6 mm thickness. The maximum discharge capacity of both alloys at 0.2 C is insensitive to the thickness of the ingots. The maximum discharge capacity of LPC(NiCoMnAlCuFeSi)5 is about 285 mAh/g, and that of Mm(NiCoMnAl)5 is about 300 mAh/g. The maximum discharge capacity of LPC(NiCoMnAlCuFeSi)5 alloy at 1 C is around 250 mAh/g and is insensitive to the thickness of ingots; and that of Mm(NiCoMnAl)5 alloy is 250～280 mAh/g and is sensitive to the thickness. It is seen that the cyclic stability of the former is much better than that of the latter. The insensitivity of the electrochemical properties of LPC(NiCoMnAlCuFeSi)5 alloy to cooling rates is possibly due to the effect of Cu, Fe and Si. The interactions of crystal parameters and internal stress can also affect its properties to certain degrees.