快淬纳米晶/非晶Mg2Ni1-xMnx(x=0～0.4)合金电极的电化学性能

摘要

用快淬工艺制备了纳米晶和非晶Mg2Ni型Mg2Ni1-xMnx(x=0、0.1、0.2、0.3、0.4)合金,获得长度连续,厚度约为30μm,宽度约为25mm的薄带.用XRD、HRTEM分析了快淬合金薄带的微观结构,测试了合金薄带的电化学性能及电化学交流阻抗谱(EIS),测试了电位阶跃后的阳极电流-时间相应曲线,并计算了氢在合金中的扩散系数(D).结果表明,快淬无Mn合金均具有典型的纳米晶结构,而快淬含Mn(x=0.4)合金显示了纳米晶和非晶结构,这证实Mn替代Ni有利于Mg2Ni型合金形成非晶相.Mn替代Ni及快淬处理显著地改善了合金的电化学贮氢性能,包括放电容量和电化学循环稳定性.合金的高倍率放电能力(HRD)随淬速的增加而单调上升,但随Mn替代量的变化HRD具有极大值.%The Mg2Ni-type Mg2Ni1-xMnx (x = 0, 0.1, 0. 2, 0. 3, 0.4) alloys with a nanocrystalline and amorphous structure are synthesized by melt-spinning technique. The as-spun alloy ribbons with a continuous length, a thickness of about 30μm and a width of about 25mm are obtained. The structures of the as-spun alloy ribbons were characterized by XRD and HRTEM. The electrochemical characteristics as well as the electrochemical impedance spectrums (EIS) of the as-spun alloy ribbons are measured. The semilogarithmic curves of anodic current versus time responses of the alloy were plotted by an electrochemical workstation, and the hydrogen diffusion coefficients (D) in the alloys were obtained by virtue of potential-step method. The results show that all the as-spun alloys (x=0) hold typical nanocrystalline structure, whereas the as-spun alloy (x=0. 4)displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of Mn for Ni significantly improves the electrochemical performances of the alloys, involving the discharge capacity and the electrochemical cycle stability. The high rate dischargeability (HRD) of the alloy monotonously grows with increasing the spinning rate, but it obtains a maximum value with the variation in the percent of Mn substitution.