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用高频感应熔炼法制备了Mm(NiCoAlMn)5储氢合金,采用模拟电池法测试了合金在238～323 K温度范围内的活化、放电容量和高倍率放电性能。结果表明:制备合金为典型AB5型储氢合金,303 K温度条件下吸氢量达到1.38%(质量分数),氢化物生成焓为32.36 kJ.mol-1H2。合金电极的活化性能、放电容量和高倍率性能受温度影响显著。室温预活化可有效改善电极的低温性能,经室温预活化后合金电极在238 K最大放电容量达到336 mAh.g-1,明显高于未经室温预活化的最大放电容量25 mAh.g-1。Mm(NiCoMn)5贮氢合金电极的高倍率性能随着温度的升高先升高后降低,273和303 K温度条件下合金保持高倍率性能良好,3C放电电流密度条件下容量保持率均高于80%;238 K温度条件下合金的大电流放电性能急剧降低,1C放电电流密度条件下容量保持率仅为10%;273 K下合金电极的综合性能最佳,最大放电容量达到340 mAh.g-1,300 mA.g-1放电电流密度下的高倍率放电比率为86%。循环伏安法测试证实,在238～323 K范围内,电极的氧化峰峰值电流(IP)与扫描速度的平方根(ν1/2)之间均存在良好的线性关系,整个电极反应受氢原子扩散控制;随着温度的降低氢扩散系数急剧下降,从而导致该合金电极的低温高倍率放电性能变差。由Arrhenius公式计算出合金中的氢扩散活化能为10.56 kJ.mol-1。
Mm (NiCoAlMn) 5 hydrogen storage alloy was prepared by high frequency induction melting method. The activation, discharge capacity and high rate discharge performance of the alloy were tested by using the simulated battery method. The results show that the prepared alloy is a typical hydrogen storage alloy of type AB5, the hydrogen uptake reaches 1.38% (mass fraction) at 303 K and the enthalpy of hydride formation is 32.36 kJ · mol-1H2. The activation performance, discharge capacity and high rate performance of the alloy electrode are significantly affected by temperature. Pre-activation at room temperature can effectively improve the low temperature performance of the electrode. After pre-activation at room temperature, the maximum discharge capacity of the alloy electrode at 336 K reaches 336 mAh.g-1, which is significantly higher than the maximum discharge capacity of 25 mAh.g-1 . The high rate performance of Mm (NiCoMn) 5 hydrogen storage alloy electrode firstly increased and then decreased with the increase of temperature, and the alloy maintained good high rate performance at 273 and 303 K, and the capacity retention rate at 3C discharge current density was higher than 80 %; The current discharge performance of the alloy at 238 K sharply decreased, and the capacity retention rate was only 10% at 1C discharge current density. The alloy electrode at 273 K had the best performance with the maximum discharge capacity of 340 mAh. The high-rate discharge rate at the discharge current density of 1,300 mA.g-1 was 86%. Cyclic voltammetry showed that there was a good linear relationship between the peak-to-peak current (IP) of the electrode and the square root of the scanning speed (ν1 / 2) in the range of 238 ~ 323 K. The whole electrode reaction was diffused by hydrogen atoms As the temperature decreases, the hydrogen diffusion coefficient decreases sharply, which leads to the deterioration of low-temperature, high-rate discharge performance of the alloy electrode. Arrhenius formula calculated by the hydrogen diffusion activation energy of the alloy is 10.56 kJ.mol-1.