【作者】 肖游；

【导师】 雷永泉；

【作者基本信息】 浙江大学 ， 材料学， 2005， 硕士

【摘要】 在对国内外稀土系非AB₅型贮氢合金的研究进展进行全面综述的基础上,本文确定以La-Mg-Ni-Co系贮氢电极合金作为研究对象,采用XRD分析及恒电流充放电、线性极化、恒电位阶跃放电等电化学测试技术系统地研究了La₂Mg(Ni_0.85Co_0.15)_x（x=9.0-10.5）合金的相结构、电化学性能,并从中筛选出一种综合性能较好的AB_3.2型La₂Mg(Ni_0.85Co_0.15)_9.6合金。通过采用Co元素对AB_3.2型合金中的Ni进行部分替代,研究了La₂Mg(Ni_1-xCo_x)_9.6（x=0.1-0.5）合金的相结构和电化学性能。在此基础上,进一步系统地研究了Co和Al对Ni的联合替代对AB_3.2型的La₂Mg(Ni_0.8-xCo_0.2Al_x)_9.6（x=0.01-0.03）合金以及La_2.2Mg_0.8(Ni_0.8-xCo_0.2Al_x)_9.6（x=0.01-0.03）合金的相结构和电化学性能的影响规律与机制,力求进一步提高合金的综合电化学性能。 首先系统地研究了La₂Mg(Ni_0.85Co_0.15)_x（x=9.0-10.5）合金B侧的化学计量比对合金相结构和电化学性能的影响。结果表明,上述合金及其氢化物均保持PuNi₃型结构,但合金的吸氢体积膨胀率较大（ΔV/V=24.9%-23.0%）。随着x值的增加,合金的放氢平台压力逐渐升高,最大放电容量则随之有所降低。在50mA/g电流放电的条件下,合金的最大放电容量从x=9.0时的422mAh/g,降低到x=10.5时的323.1mAh/g。研究发现,合金电极的高倍率放电性能（HRD）随x值的增加而提高,当x=10.5时的HRD₈₀₀为91.5%。经100次充放电循环后,上述合金的容量保持率(S₁₀₀)为45.2-68.5%,循环稳定性有待进一步改善。 为了提高合金的循环稳定性,采用Co元素对上述合金中的Ni进行部分替代。对La₂Mg(Ni_1-xCo_x)9.6（x=0.1-0.5）合金的研究表明,上述四元合金及其氢化物仍保持PuNi₃型结构,增大Co对Ni的替代量可使合金的吸氢体积膨胀率（ΔV/V）从x=0.1时的24.6%降低到x=0.5时的15.0%。随着x值的增大,合金的最大放电容量从x=0.1时的406.3mAh/g,降低到x=0.5时的364.5mAh/g。合金电极的高倍率性能（HRD）则随着x值的增加而提高,并在x=0.4时出现最大值(HRD₈₀₀=84.8%),然后又随x的增加下降到x=0.5时的75.1%。随着x值的增加,上述合金的循环稳定性有所提高,合金经100次充放电循环后的容量保持率S₁₀₀由x=0.1时的64.1%提高到x=0.5时的69.5%。合金循环稳定性的改善与Co含量的增加导致合金吸氢体积膨胀率的减小密切相关。 为了进一步提高合金的综合性能,从上述研究的合金中选择了一种综合性能较好的La₂Mg(Ni_0.8Co_0.2)_9.6合金为基础,进一步研究了在含Co合金中Al对Ni的部分替代对La₂Mg(Ni_0.8-xCo_0.2Al_x)_9.6（x=0.01-0.03）五元合金相结构和电化学性能的影响。结果表明,Al对Ni的上述替代进一步增大了合金的晶胞体积,并使合金的吸氢体积膨胀率有所降低。随Al含量（x）的增加,合金的最大放电容量略有降低（由x=0.01时的397.2mAh/g降低到x=0.03时的370.8mAh/g）,但合金的高倍率放电性能的降低比较显著(HRD₄₀₀从x=0.01时的50.5%降低到x=0.03时的15.1%)。另一方面,上述合金电极的循环稳定性随着Al含量的增加而有所改善,S₁₀₀从x=0.01时的57.6%提高到x=0.03时的59.7%。但合金的高倍率放电性能和循环稳定性都有待进一步改善。浙江大学硕」学位论文 为进一步提高合金的综合性能,以La22Mg08伽108一xCo02Alx)0.6（x=0.01一0.03）合金为对象,研究合金A侧L留Mg比例增大的情况下,Co和Al对Ni的联合替代对合金相结构和电化学性能的影响。结果表明,Al对Ni的上述替代进一步增大了合金的晶胞体积,并使合金的吸氢体积膨胀率有所降低。随Al含量（x）的增加,合金的最大放电容量有所降低（由x=0.ol时的394mAh/g降低到x=0.03时的373mAUg）,而合金的高倍率放电性能的降低比较显著（HRDs。。从x二0时的38.2%降低到x=0 .03时的8.3%）。在x一0.01一0.02的范围内,合金的循环稳定性随着x值的增加而得到改善, （S,。。可由x=0.01时的72.3%提高到x=0.02时的75.6%）,但当Al含量进一步增加到x=0.03时,合金的循环稳定性又有所降低（5100二62.7%）。在所研究的合金中,La22Mgo:困i0v9Co02A1001万6合金电化学综合性能相对较好,其最大放电容量喘ax=394.6mAhjg,经100次充放电循环后的容量保持率为5100=72.3%,在放电电流为4O0mA/g条件下的HRD400=67.8%,但合金的高倍率放电性能有待进一步改善。关霆添贮氢电极合金La一Mg一i一Co系合金元素替代晶体结构吸氢体积膨胀率电化学性能更多还原

【Abstract】 In this thesis, previous research works on non-AB5 type RE-based hydrogen storage alloys have been extensively reviewed. On this basis, the La-Mg-Ni-Co based hydrogen storage electrode alloys were selected as the subject of this study. By means of XRD analysis and the electrochemical test methods such as galvanostatic charge-discharge, linear polarization, potentialstatic discharge etc., the phase structure and electrochemical properties of La2Mg(Ni0.85Co0.15)x(x=9.0-10.5) alloys were studied systematically, and from which the AB3.2-type La2Mg(Ni0.85Co0.15)9.6 alloy with a better overall electrode properties was selected for further study. Then the part substitution of Co elements for Ni in AB3 2-type alloy was conducted for examining the effect of Co substitution on the phase structure and electrochemical properties of La2Mg(Ni1-xCox) 9.6 (x=0.1-0.5) alloys. Based on these works, the effect of the amount of substitutions of Co and Al for Ni on the phase structure and electrochemical properties of the La2Mg(Ni0.8-xCo0.2Alx)9.6 (x=0.01-0.03) alloys (AB3.2-type) and La2.2Mg0.8(Ni0.8-xCo0.2Alx)9.6(x=0.01-0.03) alloys (AB3.2-type) were studied in order to improve the overall electrochemical properties of the alloys.For the La2Mg(Ni0.85Co0.15)x(x=9.0-10.5) alloys, the effects of Non-stoichiometry on the phase structure and electrochemical properties were systemically investigated. It is found that the main phase of the alloys and their hydrides preserves the PuNi3 type structure but shows a large unit cell expansion rate on hydriding (△F/F=24.9%-23.0%). With increasing of x, the discharge capacity of the alloys decreases from 422mAh/g (x=9.0) to 323.1mAh/g (x=10.5). The high-rate dischargeability (HRD) of the alloy electrodes increases with increasing of x and get a maximum at x=10.5 (HRD800=91.5%). The cycling capacity retention rate of the alloys after 100 cycles (S/oo) reaches 45.2-68.5%, which needs to be further improved.For improving the cycling stability of the alloys, the Ni in La2MgNi9.6 alloy was partly substituted by Co, and the La2Mg(Ni1-xCox)9.6 (x=0.1-0.5) alloys were studied to examine the effect of Co substitution on the phase structure and electrochemical properties of the alloys. It is found that the alloys and their hydrides still preserve the PuNi3 type structure and show a noticeable decrease in unit cell expansion rate (△F/F=24.6% as x=0.1; △V/V =15.0% as x=0.5)on hydriding. The substitution leads to some decrease in discharge capacity, decreasing from 406.3 mAh/g (x=0.1) to 364.5 mAh/g (x=0.5). The high-rate dischargeability which increases with the increases of x and then decreases, pass throuth a maximum (HRD800=84.8%) at x=0.4. And the cycling stability increases with the increase of x, the cycling capacity retention rate of the alloys after 100 cycles (S100) increased from 64.1 %(x=0.1) to 69.5%(x=0.5).Based on these results, Co and Al were selected as the substitution element for Ni in a AB3.2-tpye alloy and the effect of Co and Al of substittution on the phase structure and electrochemical properties of the La2Mg(Ni0.8-xCo0.2Alx)9.6(x=0.01-0.03) alloys were investigated. It is found that the above alloys still preserve PuNi3 type structure, the increase of Al content leads to an increase in unit cell volume of the alloys but leads to a remarkable decrease in cell volume expansion on hydriding, The discharge capacity of the alloys decrease from 397.2mAh/g(x=0.01) to 370.8mAh/g(x=0.03) while the increase of x in the alloys results in a serious decrease in high-rate dischargeability (HRD400 decreases from 50.5%(x=0.01) to 15.1%(x=0.03) but an improvement in cycling stability (S100 increases from 57.6% for x=0.01 to 59.7% for x=0.03). It is found that the serious decrease of HRD of the alloys is mainly due to the decrease in both of electrocatalytic activity andthe hydrogen diffusion rate in the alloy bulk.To further improve the overall properties of the alloys, the effect of La/Mg rate and the Al substitution for Ni in the alloy on the phase structure and electrochemical properties of the La2.更多还原