摘要
为了探明取代元素对非化学计量AB5型贮氢合金氢化物电极充放电性能的影响因素,对LaNi5.15,La(NiSn)5.14,La(NiSnCo)5.12,La(NiSnMn)5.12和La(NiSnCoMnAl)5.10开展了电极过程动力学的研究。采用线性极化的方法,控制电极过电势小于5mV,测量出不同荷电容量下电化学反应的交换电流密度。电极在满充电状态下i0并非最大,当电极部分放电后该值达到最大。对Co,Mn或Al部分取代形成的非化学计量多元贮氢合金的交换电流密度研究表明,Co有利于提高i0,而Mn和Al不利于提高i0。当氢化物电极中贮氢容量较小时,电极反应的交换电流密度与电极中贮氢容量存在对数值的线性关系。对于具有几乎一致的电极反应电子传递系数β的La(NiSn)5.14,La(NiSnCo)5.12,La(NiSnMn)5.12,La(NiSnCoMnAl)5.10氢化物电极,造成交换电流密度差异来源于热力学吸附平衡常数K0与反应活化能W0。含Al贮氢合金K0较低,这是影响交换电流密度的主要因素。对K0值接近的3种贮氢合金La(NiSn)5.14,La(NiSnCo)5.12,La(NiSnMn)5.12,活化能W0是造成交换电流密度不同的主要原因。
The electrochemical kinetics was studied in order to understand the effect of substitute elements on the charge/discharge performance of nonstoichiometric AB_5 hydrogen absorbing alloys LaNi_(5.15), La(NiSn)_(5.14), (La(NiSnCo)_(5.12)), La(NiSnMn)_(5.12), La(NiSnCoMnAl)_(5.10). Exchange current density of the electrochemical reaction at different charge state was measured by linear polarization method with the overpotential less than 5 mV. Exchange current density reaches the maximum after a part of capacity is released from the full charged electrodes. In contrast to Mn and Al, Co is benefit to increase the value of i^0 for the multi-component alloys with partial substitution of Co, Mn or Al for Ni. The relationship of logarithm of exchange current density and rest capacity of electrodes is linear when the rest capacity is relatively low. The difference of exchange current density is attributed to the difference of absorbing equilibrium constant K_0 and activation energy W^0 for La(NiSn)_(5.14), La(NiSnCo)_(5.12), (La(NiSnMn)_(5.12)), La(NiSnCoMnAl)_(5.10) electrodes with almost consistent transition coefficient β. The lower exchange current density for Al-substituted alloys is originated from the lower K_0. However, the difference of i^0 for La(NiSn)_(5.14), La(NiSnCo)_(5.12) and La(NiSnMn)_(5.12) which have the same K_0 is attributed to the difference of W^0.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2003年第6期647-651,共5页
Journal of the Chinese Society of Rare Earths
