球磨改性对(Ti Cr)_(0.497)V_(0.42)Fe_(0.083)/30%(w)(LaRMg)(NiCoAl)_(3.5)合金复合电极材料储氢和电化学性能的影响

以钒基合金(Ti Cr)0.497V0.42Fe0.083为基体,添加30%(w)稀土系A2B7型合金(LaRMg)(NiCoAl)3.5为电催化活性材料,采用机械球磨改性制备了储氢合金复合电极材料,研究其储氢特性和电化学性能.X射线衍射(XRD)、扫描电镜(SEM)和透射电子显微镜(TEM)分析结果表明,随球磨时间增加(t=0,0.5,1,3,5,10h),复合材料颗粒逐渐细化,A2B7型合金颗粒分散并包覆在钒基合金表面上;当球磨时间t≥5h时,复合材料形成明显的复合纳米晶组织并伴有部分非晶化倾向,同时钒基合金BCC相结构的晶胞参数a和晶胞体积V均明显减小.合金储氢特性及电化学性能分析测试结果表明,铸态纯钒基合金的吸氢量为3.11%(w),而球磨复合材料的储氢量随球磨时间增加呈减小的规律,其最大储氢量为2.47%(w);球磨改性后,复合材料电极的电催化性能得到明显改善,当球磨时间t≥3h时最大放电容量达到425.8mAh·g-1,经100次充放电循环后该电极的容量保持率(C100/Cmax)为97%,表现出良好的电极循环稳定性.

Influence of Ball-Milling on Hydrogen Storage and Electrochemical Properties of (Ti Cr)0.497V0.42Fe0.083/30%(w) (LaRMg)(NiCoAl)3.5 Alloy Electrodes

Changes in phase structure, hydrogen storage and electrochemical properties of the (Ti Cr)_0.497V_0.42Fe_0.083+ 30% (w) (LaRMg)(NiCoAl)_3.5 alloy after treatment by ball-milling for different time (t=0, 0.5, 1, 3, 5, 10 h) were investigated systematically. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) showed that the particle size of the milled composite samples decreased gradually and the powder appears aggregated. The A₂B₇ alloy particles were uniformly dispersed and encapsulated on the surface of the V based alloy particles that were formed after increasing the ball-milling time. It was found that nanocrystalline composites were formed and partial amorphization occurred when the milling time was more than 5 h. The crystal parameter a and the cell volume V of the BCC phase structure in the composite both showed a decrease. Hydrogen storage capacity of the single V based alloy was 3.11%(w), with an increase in milling time hydrogen storage capacity of the milled composites decreased and the maximum hydrogen absorption capacity at room temperature approached 2.47%(w). Electrochemical studies showed that the electrochemical properties of the milled composite were enhanced and the maximum discharge capacity was 425.8 mAh·g^-1. The cyclic stability of the composite electrode improved noticeably. After 100 charge-discharge cycles the discharge capacity retention rate C₁₀₀/C_max of the milled composite electrode was 97%, and it had a better cycle life than that of the A₂B₇ type alloy electrode.