相转变对A_(5)B_(19)型储氢合金电化学性能的影响  

Effects of Phase Transformation on Electrochemical Properties of A_(5)B_(19)-type Hydrogen Storage Alloy

作　　者：刘红苹 李倩 LIU Hong-ping;LI Qian(Science and Technology Entrepreneurship Service Center of Xuancheng City,Xuancheng 242000,China;Baotou Research Institute of Rare Earths,Baotou 014030,China)

机构地区：[1]宣城市科技创业服务中心,安徽宣城242000 [2]包头稀土研究院,内蒙古包头014030

出　　处：《稀土》2024年第3期58-70,I0004,共14页Chinese Rare Earths

摘　　要：近年来发展起来的A_(5)B_(19)型La-Mg-Ni基超晶格储氢合金作为镍氢电池负极材料极具发展前景,但其容量和循环稳定性有待改善。以A_(5)B_(19)型La_(0.7)Mg_(0.3)Ni_(3.0)Co_(0.55)Al_(0.15)合金为研究对象,通过在1223 K下保温30 h发生相变反应,制备了以(La,Mg)_(5)Ni_(19)相为主相的超晶格合金,并研究了相变对合金电化学性能的影响和机理。结果表明,相变前合金主相为LaNi_(5)相,次要相包括(La,Mg)_(5)Ni_(19)、(La,Mg)_(2)Ni_(7)和LaMgNi_(4)相;相变过程中LaNi_(5)相与LaMgNi_(4)融化的液相发生包晶反应,与(La,Mg)_(2)Ni_(7)相发生固态扩散反应,均生成(La,Mg)_(5)Ni_(19)相。电化学结果表明,LaMgNi_(4)和LaNi_(5)相向(La,Mg)_(5)Ni_(19)相的转变提高了合金的放电容量,其C_(max)由361 mAh·g^(-1)升高到381 mAh·g^(-1);LaMgNi_(4)、(La,Mg)_(2)Ni_(7)和LaNi_(5)相向(La,Mg)_(5)Ni_(19)相的转变显著增强了合金的抗粉化/非晶和抗氧化/腐蚀能力,合金150周的容量保持率由65.6%升高至80.8%。A_(5)B_(19)-type La-Mg-Ni-based hydrogen storage alloys developed in recent years have shown great application potential as anode materials for Ni-MH batteries.But their capacity and cycle stability still need to be improved.In the present study,the superlattice La_(0.7)Mg_(0.3)Ni_(3.0)Co_(0.55)Al_(0.15)alloy with the(La,Mg)_(5)Ni_(19)main phase has been prepared by keeping the as-cast alloy at 1223 K for 30 h,and the effects of phase transformation on the electrochemical properties and the functioning mechanism are studied.It is found that the main phase of the alloy before phase transformation is LaNi_(5),and the secondary phases include(La,Mg)_(5)Ni_(19),(La,Mg)_(2)Ni_(7) and LaMgNi_(4).During phase transformation,the LaNi_(5) phase reacts with the LaMgNi_(4) liquid phase through peritectic reaction,and reacts with the(La,Mg)_(2)Ni_(7) phase through solid diffusion reaction.Electrochemical testing results show that the transformation of LaMgNi_(4) and LaNi_(5) phases to(La,Mg)_(5)Ni_(19)phase improves the alloy's discharge capacity,and the C_(max)increases from 361 to 381 mAh g^(-1).The transformation of(La,Mg)_(5)Ni_(19),(La,Mg)_(2)Ni_(7) and LaMgNi_(4) phases to(La,Mg)_(5)Ni_(19)phase enhances the anti-pulverization/amorphization and anti-oxidation/corrosion resistance of the alloy.As a positive result,the capacity retention after 150 cycles increases significantly from 65.6% to 80.8%.

关 键 词：镍氢电池 储氢合金 相转变 电化学性能 循环稳定性 

分 类 号：TG139.7[一般工业技术—材料科学与工程]