硼对La_(17)Fe_(76)B_7型储氢合金结构和电化学性能的影响

Influence of Boron on Structural and Electrochemical Properties of La_(17)Fe_(76)B_7-Type Hydrogen Storage Alloy

采用中频感应熔炼-快淬方法制备了La17Fe3Mn5Al2Ni73-xBx(x=0,1,3,5)储氢合金。结构分析表明,不含B的合金为双相结构,主相为LaNi5相,第二相为La2Ni7相,含B合金均由LaNi5相、La2Ni7相和La3Ni13B2相组成,且随着B含量的增加,LaNi5相和La2Ni7相减少,La3Ni13B2相逐渐增加。电化学测试表明,随着B含量的增加,合金的活化性能、最大放电容量不同程度下降,而循环稳定性有所改善。合金电极的倍率放电能力(HRD)随着B含量的增加呈先增大后减小的趋势,表明适量的B有利于提高合金的高倍率放电性能。合金电极的交换电流密度(I0)随着B含量的增加先增大后减小,而氢在合金中的扩散系数(D)则逐渐增大,表明合金的高倍率放电性能主要取决于合金表面的电荷转移能力。

The La17Fe3Mn5Al2Ni73-xBx（x=0,1,3,5） hydrogen storage alloys were prepared using a vacuum induction-quenching furnace.The structure analysis showed that the alloy without adding boron were composed of LaNi5 phase and La2Ni7 phase,and the alloys doped with boron were composed of LaNi5 phase,La2Ni7 phase and La3Ni13B2 phase.With the increase of boron content in alloys,the LaNi5 phase and La2Ni7 phase decreased and the La3Ni13B2 phase increased gradually.The electrochemical testing showed that the activation property and the maximum discharge capacity of the alloys declined and the cyclic stability was improved when the boron content increased.The high rate dischargeability（HRD） of the alloy electrodes increased firstly and then decreased with increasing the boron content in alloys,which indicated that it is favorable for improving the high rate dischargeability of the alloy electrodes when the boron content was appropriate in alloys.With the increase of boron content in alloys,the exchange current density（I0） increased firstly and then decreased and the diffusion coefficient（D） of hydrogen in alloy bulk increased gradually,which indicated that the charge-transfer ability on the surface of alloys was the main controlling factor for the dynamics ability.