CeMn0.25Al0.25Ni1.5+x(x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1)合金的相结构和电化学性能

研究了CeMn0.25Al0.25Ni1.5+x(x=0.0,0.3,0.5,0.7,0.9,1.1)超化学计量比合金的相结构和电化学性能。XRD、SEM和电化学性能测试结果表明:CeMn0.25Al0.25Ni1.5+x(x=0.0,0.3,0.5,0.7,0.9,1.1)合金主要含有六方的CeAl相和立方的CeNi相,合金的粒径随x值的增大而变大。Ni的超化学计量比添加能够大大提高合金的电化学活性,298K时,合金的放电容量从x=0.0时的118.3mAh/g提高到x=1.1时的200.7mAh/g;338K时,其放电容量随x值增大呈先增后减的趋势,x=0.0合金的放电容量为170.4mAh.g-1,当x=0.9时,放电容量出现最大值271.4mAh/g。合金电极的P-C-T曲线表明:随Ni超化学计量的增加,合金的平衡氢压平台斜率变小,宽度增大,平衡氢压升高,这可能是使合金电极放电容量增加的主要原因。

Phase Structure and Electrochemical Characteristics of CeMn0.25Al0.25Ni1.5+x (x =0.0, 0.3, 0.5, 0.7, 0.9, 1.1) Alloys

The phase structure and electrochemical characteristics of CeMn0.25Al0.25Ni1.5+x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys with Ni overstoichiometric addition were studied. XRD, SEM and electrochemical testing have revealed that all alloys mostly contain hexagonal CeAl phase and cubic CeNi phase, and the grain size of the alloys becomes larger with increasing Ni content. The electrochemical activity of CeMn0.25Al0.25Ni1.5+x alloys has been greatly improved by Ni overstoichiometric addition and the discharge capacity can increase from 118.3 mAh·g-1 (x=0.0) to 200.7 mAh·g-1 (x=1.1) at 298 K and from 170.4 mAh·g-1 (x=0.0) to 271.4 mAh·g-1 (x=0.9) at 338 K, respectively. The P-C-T curves show that the slopes of equilibrium hydrogen pressure plateau of CeMn0.25Al0.25Ni1.5+ x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys become flatter, longer and higher with increasing Ni content, and therefore this may be the key factor that enhances the discharge capacity of the alloys. CeMn0.25Al0.25Ni2.4 alloy is a kind of candidate anode material for MH-Ni with further optimizing compositions.