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采用真空电弧熔炼炉熔炼储氢合金La_(1-x)Sc_(x)Ni_(3.5)(x=0~1.0),且经真空退火炉1173 K退火1周。研究了Sc含量对该合金相结构、储氢及电化学性能的影响。结果表明,该合金组织均由La_2Ni_7、LaNi_5、LaNi和Sc_2Ni_7等相组成,随着Sc含量的增加,LaNi_5相逐渐减少,La_2Ni_7和Sc_2Ni_7逐渐增加。298 K下合金电极吸放氢平台压力逐渐升高,吸氢量呈先增后减趋势,x=0.3时最大吸氢量(0.651 wt%)、平台压力均适中。随x值增大,最大放电容量C_(max)和100次充放电循环容量保持率S100均呈先增加后减小的趋势.。x介于0.3~0.5时,电极综合电化学性能较好。合适的Sc含量并经退火热处理能有效改善合金电极循环寿命。但掺入过量Sc后,合金易形成难吸氢的Sc_2Ni_7相,这是电极容量不高的主要原因,这与PCT测试结果保持一致。
The hydrogen storage alloy La_ (1-x) Sc_ (x) Ni_ (3.5) (x = 0 ~ 1.0) was melted by vacuum arc melting furnace and annealed in vacuum annealing furnace for 1 week. The effects of Sc content on the phase structure, hydrogen storage and electrochemical properties of the alloy were investigated. The results show that the microstructure of the alloy consists of La_2Ni_7, LaNi_5, LaNi and Sc_2Ni_7 phases. With the increase of Sc content, the content of LaNi_5 phase decreases and the content of La_2Ni_7 and Sc_2Ni_7 increases gradually. The pressure of hydrogen absorption and desorption platform increased gradually at 298 K, the hydrogen absorption increased first and then decreased, and the maximum hydrogen absorption (0.651 wt%) at x = 0.3 was moderate. With the increase of x value, the maximum discharge capacity C max and the retention rate S100 of 100 cycles of charging and discharging showed the trend of first increasing and then decreasing. When x is between 0.3 and 0.5, the electrode has better electrochemical performance. Appropriate Sc content and annealing heat treatment can effectively improve the cycle life of the alloy electrode. However, after the addition of excessive amount of Sc, the alloy tends to form Sc_2Ni_7 phase, which is hard to absorb hydrogen. This is the main reason for the low electrode capacity, which is consistent with the PCT test results.