Of Mg <sub>, 2 </ Sub> Ni Hydrogen Storage Alloy, Preparation And Performance Improvement Study

Mg2Ni hydrogen storage alloy has been paid great attention because of its high theory capacity,low cost and abundant resource. However, it is inadequate for practical use for MH/Ni battery because of its poor kinetic property at room temperature and poor cycle life in KOH solution.To overcome these shortcomings,technics for preparing Mg2Ni alloy was studied,and effects of element substitutions(MgijM0.3(M=Mg,Al,Ti) Ni),surface modifications(Cu coating,Ni coating,Ni-Co coating and fluo--rination),ball-millings(ball-milling Mg2Ni,ball-milling Mg2Ni-10wt %Ni and ball-milling Mg2Ni-10wt%Co) and combination of them on electrochemical properties of Mg2Ni alloy were deeply studied. Phase structures and surface morphologies of Mg2Ni alloys were characterized by using X-ray diffraction(XRD) and scanning electron microscope (SEM),respectively.The mechanism of the effect of them on electrochemical properties of Mg2Ni alloy was studied by using cyclic voltammogram(CV) and electrochemical impedance spectroscopy(EIS). Results show:(DSintering temperature is an key factor for preparing Mg2Ni alloy and the most suitable temperature is 600癈 (2)Single Al or Al , Ti combined substitutions for part of Mg produce a new cubic phase in addition to Mg2Ni phase.Al and Ti substitutions not only increase discharge capacity,but also greatly improve cycle life for Mg2Ni alloy electrode.(3)Surface modifications greatly improve discharge capacity and high rate discharge capability. They except for Cu coating also improve cycle life for Mg2Ni alloy electrode.(4)Ball-millings reduce grain size and broaden width of XRD peaks of Mg2Ni phase.They also greatly increase discharge capacity and improve high rate discharge capability and cycle life for Mg2Ni alloy electrode. (5) Combining element substitutions with Ni coating and ball-milling are useful for further improving property of Mg2Ni alloy electrode. (6)Results of CV and EIS show that element substitutions,surface modifications and ball-millings all can improve electrochemical reactive activity and reduce charge transfer and H atom diffusion resistances for Mg2Ni alloy electrode.