RE(Ni,Co,Mn,Ti)_5合金(RE=La,Ce,Pr,Nd)的单胞体积对电化学性能的影响

EFFECT OF UNIT CELL VOLUME OF RE(Ni, Co, Mn, Ti)_5 ALLOY (RE=La, Ce, Pr, Nd) ON ITS ELECTROCHEMICAL PROPERTIES

制备了Ｌａ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５，Ｃｅ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５，Ｐｒ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５和Ｎｄ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５四种单一稀土贮氢电极合金，分别测定了它们的单胞体积、氢化物生成焓和几个主要的电化学性能指标（包括活化循环次数、最大放电容量、高倍率放电率和容量衰退速率），以分析不同稀土元素对合金电化学性能的影响.结果表明，在四种合金中，单胞体积对合金的热力学性质和电化学性能起了决定性作用，它与合金的氢化物生成焓呈简单的线性关系，对电化学性能有双重影响，使四个主要指标随单胞体积的变化均出现极大或极小值.单胞体积本身的变化与稀土元素的周期性有关．

Four rare earth based AB(5) typed alloys, La(Ni, Co, Mn, Ti)(5), Ce(Ni, Co, Mn, Ti)(5), Pr(Ni, Co, Mn, Ti)(5) and Nd(Ni, Co, Mn, Ti)(5), were prepared and then their unit cell volumes (V-cell), standard enthalpies of metal hydride formation at 298 K (DeltaH degrees (298 K)), and main electrochemical characteristics, such as activation cycle number (n(a)), maximum discharge capacity at 50 mA/g charge/discharge rate (C-50,C-max), high-rate-dischargeability kappa (includes kappa (1) and kappa (2)), rate of decay (-dC/dn) were measured and analyzed to reveal the effects of the rare earth elements on the electrochemical properties. The results show that the unit cell volume is the key factor in determination of the alloys' thermodynamics and electrochemical properties. The standard enthalpies of metal hydride formation at 298 K (DeltaH degrees (298) (K)) are proven to vary linearly with the unit cell volume, and the four electrochemical parameters, n(a), C-50,C-max, -dC/dn and kappa, are dualistically affected by it. The change of unit cell volume is in accord with the periodic law of the rare earth element.