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首页> 外文期刊>International journal of hydrogen energy >A study on the microstructures and electrochemical properties of La_(0.7)Mg_(0.3)Ni_(2.45-x)Cr_xCo_(0.75)Mn_(0.1)Al_(0.2) (x = 0.00-0.20) hydrogen storage electrode alloys
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A study on the microstructures and electrochemical properties of La_(0.7)Mg_(0.3)Ni_(2.45-x)Cr_xCo_(0.75)Mn_(0.1)Al_(0.2) (x = 0.00-0.20) hydrogen storage electrode alloys

机译：La_（0.7）Mg_（0.3）Ni_（2.45-x）Cr_xCo_（0.75）Mn_（0.1）Al_（0.2）（x = 0.00-0.20）储氢电极合金的微观结构和电化学性能的研究

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In this work, the microstructures and electrochemical properties of the La_(0.7)Mg_(0.3)Ni_(2.45-x)Cr_xCo_(0.75)Mn_(0.1)Al_(0.2) (x =0.00-0.20) hydrogen storage alloys were investigated systematically for the purpose of improving the cycling stability of this type alloy. X-ray powder diffraction (XRD) analysis showed that all of the alloys mainly consisted of an (La,Mg)Ni_3 phase with PuNi_3-type structure and an LaNi_5 phase with CaCu_5-type structure. The abundance of the (La,Mg)Ni_3 phase in the alloys decreased from 69.6% to 42.9%, accordingly that of the LaNi_5 phase increased with increasing x value. With the increase of x, the lattice parameters and the unit cell volumes of the two phases increased gradually due to the larger atom radius of Cr (1.85 A) than that of the Ni (1.62 A). Electrochemical studies showed that the cycling stability (C_(100)/C_(max)) of the alloy electrodes firstly increased from 66.2% (x = 0.00) to 70.6% (x - 0.10), and then decreased to 62.8% (x = 0.20) with the increase of x value. However, the maximum discharge capacity (C_(max)) of these alloy electrodes decreased from 369.7 (x = 0.00) to 311.5mA h/g (x =0.20), and the high rate dischargeability (HRD) also showed a decreasing tendency with increasing Cr content. Further, the electrochemical impedance spectra, the linear polarization, the anodic polarization and the potential-step measurements revealed that the decrease of the HRD of this type alloy electrodes can be ascribed to the decrease of both the charge-transfer rate on the surface of the alloy electrodes and diffusion rate of the H atom in the bulk of the alloys with increasing x.
机译：在这项工作中，系统地研究了La_（0.7）Mg_（0.3）Ni_（2.45-x）Cr_xCo_（0.75）Mn_（0.1）Al_（0.2）（x = 0.00-0.20）储氢合金的微观结构和电化学性能为了改善这种合金的循环稳定性。 X射线粉末衍射（XRD）分析表明，所有合金主要由具有PuNi_3型结构的（La，Mg）Ni_3相和具有CaCu_5型结构的LaNi_5相组成。合金中（La，Mg）Ni_3相的丰度从69.6％降至42.9％，因此LaNi_5相的丰度随着x值的增加而增加。随着x的增加，由于Cr（1.85 A）的原子半径大于Ni（1.62 A）的原子半径，两相的晶格参数和晶胞体积逐渐增加。电化学研究表明，合金电极的循环稳定性（C_（100）/ C_（max））首先从66.2％（x = 0.00）增加到70.6％（x-0.10），然后下降到62.8％（x = 0.20）随着x值的增加。然而，这些合金电极的最大放电容量（C_（max））从369.7（x = 0.00）降低至311.5mA h / g（x = 0.20），并且高倍率放电率（HRD）也显示出降低的趋势。增加铬含量。此外，电化学阻抗谱，线性极化，阳极极化和电势阶跃测量表明，这种合金电极的HRD的降低可归因于表面的电荷转移率的降低。合金电极和H原子在大多数合金中的扩散速率随x的增加而增加。

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