The Research On Electrochemical Performance Of Zr-Cr-Ni AB₂ Laves Phase Hydrogen Storage Alloys

In this paper, the publications on the effect of the chemical composition on the phase structure and electrochemical properties, the preparation methods on the electrochemical properties of the ABi-type Laves phase hydrogen storage alloys were first reviewed. On this basis, the following works have been carried out: two ABa types Laves phases alloy series were chosen as the objects of study. By means of XRD analysis, SEIVL EDX and TEM investigation and electrochemical measurements, the effects of the activation pretreatment on the electrochemical properties, the chemical composition on the phase structure and electrochemical properties were studied systemically. The following results are achieved:(1) ZrCro.?Ni].3 alloys is consisted of C14, CIS Laves phase. Zr?Niio phase and little ZrC>2 phase (Zirconia), which have two structures in this alloy. One has fee phase (F) that coexisted with ZryNijo phase, the other is the high temperature tetragonal phase (T) of Zirconia, which has irregular shape. These showed the F phase coexisted with the M phase. After charged hydrogen, the lattice of C14 phase has changed a little, but the one of CIS phase has increased more.(2) This paper first put forward the composite pretreatment, which is KOH pretreatment after HF pretreatment. It is found that, after the composite pretreatment, the discharge capacity of the ZrCro.?Nii.3 alloy had been increased by 5.7%, and with the discharge current of 600mA/g, the high-rate discharge capacity also had been improved by 33% because of the decreasing of electron-transitioning resistance.(3) HF pretreatment could not produce any influence on the discharge capacity, the composite could improve it, but the KOH pretreatment and the ball-milling pretreatment could decrease it. And all of four could improve the activation capacity and high-rate discharge capacity. The ZrCrtnNiu alloys will arrived its highest discharge capacity after 25 cycles number electrochemical charge and discharge hydrogen. But the HF pretreatment and the KOH pretreatment only need 5 cycles, the ball-milling pretreatment need 15 cycles, the compositepretreatment need 7cycle. However, the composite pretreatment could increase the discharge capacity by 5.7%. With the discharge current of 600mA/g, the high-rate discharge capacity of the ZrCrojNiu alloys only 1.5%. After the KOH pretreatment, it is 15.4%. After the HF pretreatment, it is 21.1. After the composite pretreatment. it is 34.5%. After the ball-milling pretreatment, it arrived 56.4%.(4) The mechanism of HF pretreatment has been analyzed that the phase composition and its structure beget the crack, which improves the activation capacity.(5) For ZrCr0.8-xNii.2+x(x=0.0~0.2) and ZrCr0.7.xVxNii.3(x=0.0~0.4) alloys, it is found that the ZrCro.?Nii.3 alloy has the highest discharge capacity, the ZrCro.eVo iNiij alloy has the best high-rate discharge capacity. After the composite pretreatment to ZrCro.7-xVxNii.3(x=0.0~0.4) alloys, the discharge capacity of those have greatly increased. To ZrCro.6sVo.o5Ni 1.3 alloy, its increase is the greatest and is up to 15.7%. The high-rate discharge capacity is also improved.