稀土元素对R-Y-Ni系A_2B_7型无镁储氢合金微观结构和电化学性能的影响  

Effect of Rare Earth Elements on the Microstructure and Electrochemical Properties of Mg-Free R-Y-Ni Based A_2B_7-Type Hydrogen Storage Alloys

作　　者：姜婉婷 罗永春[1,2] 赵磊 邓安强 张国庆[1] JIANG Wan-Ting;LUO Yong-Chun;ZHAO Lei;DEN An-Qiang;ZHANG Guo-Qing(Department of Materials Science and Engineer,Lanzhou University of Technology,Lanzhou 730050,China;State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China)

机构地区：[1]兰州理工大学材料学院,兰州730050 [2]兰州理工大学有色金属先进加工与再利用省部共建国家重点实验室,兰州730050

出　　处：《无机化学学报》2018年第10期1817-1825,共9页Chinese Journal of Inorganic Chemistry

基　　金：国家自然科学基金(No.51761026)资助项目

摘　　要：采用真空电弧熔炼及退火处理制备R-Y-Ni系A_2B_7型R0.3Y0.7Ni3.25Mn0.15Al0.1(R=Y,La,Pr,Ce,Nd,Gd,Sm)储氢合金,系统研究稀土元素R对合金微观组织与结构、储氢和电化学性能的影响。XRD和SEM-EDS分析表明,合金退火组织由Ce2Ni7型主相、PuNi3型及少量Ca Cu5型相组成,Ce2Ni7型主相的晶格常数a、c及晶胞体积V均随稀土R原子半径的减小而依次降低。该合金均具有明显的吸放氢平台,常温下最大吸氢容量为1.17%~1.48%(w/w),吸氢平台压Peq为0.037~0.194 MPa。电化学分析表明,退火合金电极的电化学活化性能优良,R=La合金具有最高的放电容量(389.2 mAh·g-1)和较佳的容量保持率(充放电循环100次后的S100=85.7%),其中合金微观组织的不均匀性及稀土元素的电化学腐蚀是影响电极循环稳定性的主要原因。合金电极的高倍率放电性能(电流密度为900 m A·g-1)HRD900=71.05%~86.94%,其电极反应动力学控制步骤主要由氢原子在合金体相中的扩散速率所控制。The R-Y-Ni based A2B7-type R0.3Y0.7Ni3.25Mn0.15Al0.1(R=Y,La,Pr,Ce,Nd,Gd,Sm)alloys were prepared by vacuum arc melting and followed by annealing treatment.The effects of rare earth element R on the microstructure,hydrogen storage and electrochemical properties of the alloys were investigated systematically.XRD and SEM-EDS analysis showed that the annealed alloys mainly composed of Ce2Ni7-type main phases,minor PuNi3-type and CaCu5-type phases.The lattice constants a,c and cell volume V of the Ce2Ni7-type main phases decreased in sequence with the decreasing radius of R atoms.The annealed alloys obviously presented a hydrogen absorption/desorption platform,the maximum hydrogen storage capacities and the equilibrium hydrogen absorption pressures(Peq)at room temperature were in the range of 1.17%~1.48%(w/w)and 0.037~0.194 MPa,respectively.Electrochemical analysis showed that the electrochemical activation performance was excellent.The heterogeneity of microstructure and electrochemical oxidation corrosion of rare earth elements were main reason that affected the cycling stability of alloy electrodes.For all the alloys,the R=La alloys exhibited the highest electrochemical discharge capacity of 389.2 mAh·g^-1 and the best cyclic stability S100=85.7%(charge/discharge after 100 cycles).The high rate discharge ability HRD900(current density was 900 mA·g^-1)of the alloys was 71.05%~86.94%and the control step of the reaction kinetics was mainly controlled by the diffusion rate of the hydrogen atom in the alloys.

关 键 词：La-Y-Ni系A2B7型储氢合金 稀土元素 微观组织 储氢性能 电化学性能 

分 类 号：O646[理学—物理化学] TG139.7[理学—化学]