Structure and electrochemical performances of Mg_2Ni_(1-x)Mn_x (x = 0-0.4) electrode alloys prepared by melt spinning

摘要

The melt-spinning technique is applied to the preparation of the nanocrystalline and amorphous Mg_2 Ni-type alloys with nominal compositions of Mg_2Ni_(1-x)Mn_x (x = 0, 0.1,0.2,0.3,0.4). The as-spun alloy ribbons possessing a continuous length, a thickness of about 30 μm and a width of about 25 mm were prepared. The structures of the as-spun alloy ribbons are characterized by XRD and TEM. The electrochemical performances of the as-spun alloy ribbons are measured by an automatic galvanostatic system. The results show that no amorphous structure is detected in the as-spun Mg_2Ni alloy, whereas the as-spun Mg_2Ni_(0.6)Mn_(0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni notably intensifies the amorphous forming ability of the Mg_2 Ni-type alloy. The amorphization degree of the as-spun alloys containing Mn increases with increasing spinning rate. The melt spinning also significantly enhances the electrochemical performances such as the discharge capacity and the electrochemical cycle stability of the Mn-containing alloys. Furthermore, the high rate dischargeability (HRD) of the (x ≤ 0.1) alloys increases with an increase in the spinning rate, while for the (x ≥ 0.2) alloys, the HRD exhibits a maximum value at a particular spinning rate, and it varies with the change in Mn contents of the alloys.