Study On The Effect Of Co Element On The Microstructure And Electrochemical Performance Of La-Y-Ni System AB_3.5-3.8 Hydrogen Storage Alloy

The research and development of new hydrogen storage alloy electrode materials with high properties play an important role in the improvement of the properties and application of Ni-MH batteries.The new Mg-free La-Y-Ni AB_3-3.8 type hydrogen storage alloy not only has the same super lattice stacking structure and the comprehensive electrochemical properties comparable to the La-Mg-Ni type alloys,but also avoids the safety hazards caused by the high saturated vapor pressure of Mg element as well as the difficulty in controlling the composition during the melting of La-Mg-Ni type alloys.It has become an important new high-capacity rare earth Ni-type hydrogen storage alloy electrode material.However,due to the special stacking structure of the La-Y-Ni hydrogen storage alloy,it is easy to cause the instability of the stacking structure and hydrogen-induced pulverization during hydrogen absorption and desorption,which seriously affects the cyclic stability of the electrode reaction of the alloy and restricts its further application.Appropriate alloying of hydrogen storage alloys is one of the effective ways to improve the gas hydrogen storage and electrochemical properties of the alloys.In order to improve the cycling stability of the La-Y-Ni type hydrogen storage alloy electrode,this article takes the super lattice structure La-Y-Ni type alloy as the research object,and adopts XRD,SEM,EDS as well as methods like electrochemical properties testing to characterize and analyze them,it does a thorough study of the changing rules of the microstructure evolution,phase structure and electrochemical properties of the annealed alloy when the Co element partially replaces the Ni element at the B-end of A₂B₇ and A₅B₁₉ alloys.On basis of this,the microstructure and electrochemical properties of annealed alloy La_0.2Nd_0.2Y_0.6Ni_3.5-xCo_x Mn_0.2Al_0.1(x=0¹.0were investigated by adding rare earth to the A end of the alloy.The results show that the addition of Co element is beneficial to the cycle stability of La-Y-Ni type A₂B₇ and A₅B₁₉ hydrogen storage alloys,among which the improvement in cycle stability of A₅B₁₉ alloy is more obvious;For the A₅B₁₉ alloy containing rare earth Nd at the A end,when the Co content x?0.7,the capacity retention rate of the alloy electrode S100 reaches about 96%after 100 charge and discharge cycles,and the cycle stability of the alloy is significantly improved.These results lay a foundation for the future development of la-Y-Ni series hydrogen storage alloy electrode materials with high capacity and cyclic stability in the future,which own important reference and application value.