摘要
用冷坩锅磁悬浮熔炼的方法制备了不同化学计量比的La0.7Mg0.3(Ni0.85Co0.15)x (x=3.0, 3.1, 3.2, 3.3, 3.4, 3.5) 稀土镁基贮氢电极合金, 采用X射线衍射和三电极测试体系研究了合金的相结构和电化学性能.X射线衍射分析结果表明, 该系列合金均由(La, Mg)Ni3相、 (La, Mg)2Ni7相、 LaNi5相及少量杂质相组成, 为多相结构;随着化学计量比x的增加, (La, Mg)Ni3相的含量降低, 相应LaNi5相的含量增加.电化学测试结果表明, 该系列合金的最大放电容量均高于目前已商品化的稀土基AB5型贮氢电极合金的最大放电容量(310～330 mAh·g-1), 且当x=3.4时, 合金的最大放电容量可达395.4 mAh·g-1, 较AB5型合金高约30%, 是合金中各相的含量比例较为合适的结果;该系列合金活化性能、倍率放电性能良好, 并随着化学计量比x的增加得到进一步改善, 这与同时作为贮氢相和催化相的LaNi5相含量的增加有关;在电化学吸放氢循环过程中, 合金的循环稳定性较差, 有待进一步提高.
The La0.7 Mg0.3 （ Ni0.85 Co0.15 ）x （x=3.0, 3.1, 3. 2, 3. 3, 3.4, 3. 5） rare-earth Mg-based hydrogen-storage electrode alloys with different stoichiometric ratio were prepared by cold crucible melting under Ar gas atmosphere. The phase structure and electrochemical properties of these alloys were investigated by means of XRD and tri-electrode test system. XRD analyses show that all these alloys are consisted of（La, Mg）Ni3 phase, （La, Mg）2Ni7 phase and LaNis phase. The（La, Mg）Ni3 phase content decreases, and accordingly the LaNis phase content increases with increasing x from 3.0 to 3.5. The electrochemical results show that maximum discharge capacity of all these alloys is much higher than that of commercialized electrode alloys, which is 310 - 330 mAh·g^-1 The maximum discharge capacity （395.4 mAh·g^-1）, which is about 1.3 times larger than that of AB5-type alloys, can be obtained when x is 3.4 because of the appropriate phase component and content in this alloy. Activation property and high-rate dischargeability of the alloys are favorable, and can be improved with increasing x, which is attributed to the increase of LaNis phase content. However, cyclic stability of these alloys is undesired and needs to be improved during electrochemical process.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2005年第5期690-694,共5页
Chinese Journal of Rare Metals
基金
北京科技大学新金属材料国家重点实验室资助项目(20050408190)
关键词
化学计量比
稀土
镁
贮氢电极合金
相结构
电化学性能
stoichiometric ratio
rare earth
magnesium
hydrogen-storage electrode alloys
phase structure
electrochemical property
