Microstructure and electrochemical characteristics of ANi3.33Mn0.17Co0.2Al0.1(A=La,Sm,Gd,Y)type hydrogen storage alloys
ANi3.33Mn0.17Co0.2Al0.1(A=La,Sm,Gd,Y)alloys were designed and prepared.The effects of A-ter-minal rare earth elements on the annealed microstructure and structure,gaseous hydrogen storage and electrochemi-cal properties of the alloys were systematically studied.The results show that the annealed microstructures of A=La,Sm,Gd alloys are mainly composed of A2B7-type(Ce2Ni7+Gd2Co7)and A5B19-type(Pr5Co19+Ce5Co19)pha-ses,while A=Y alloys are composed of Ce2Ni7,YNi3 and CaCu5-type phases.When the atomic radius rA of A ter-minal decreases in the order of rLa＞rSm＞rGd＞rY,the unit cell parameters a,c and the unit cell volume V of each phase in the alloy decrease.The plateau pressure of the hydrogen absorption PCT curve of the alloy gradually in-creased in the order of PLa(0.019 1 MPa)＞PSm(0.050 9 MPa)＞PGd(0.151 4 MPa)＞PY(0.212 9 MPa),and the maximum hydrogen storage capacity was 0.845,1.313,1.239 and 1.383 wt％,respectively.The electrochemical discharge capacities of A=La,Sm,Gd and Y alloys are 255.8,377.7,266.3 and 205.4 mAh/g,respectively,and the electrode capacity retentions S100 are 52.3％,93.5％,98.8％and 4.5％,respectively.The HRD900 of A=La and Sm alloys at 3C discharge rate is 84％～85％,and the HRD900 of A=Gd and Y alloys is 46.8％and 63.4％,respectively.With the increase of the A-terminal element rA,the volume difference Vd of the stacking unit of the su-perlattice structure and the width FWHM of the diffraction peak after the cycle gradually increase.At this time,the hydrogen-induced amorphization tendency of the alloy gradually increases,which in turn affects the electrochemical cycle stability of the alloy.A=Sm and Gd alloys not only have small rA and Vd values,but also have good corrosion resistance,so they have excellent electrochemical cycle stability(S100=94％～98％).Among them,A=Sm alloy has the best comprehensive electrochemical performance.
NETL
NSTL
万方数据
