颗粒度对贮氢合金MlNi_(3.65)Co_(0.75)Mn_(0.4)Al_(0.2)电化学性能的影响

Effects of Particle Size on Electrochemical Performance of MlNi_(3.65)Co_(0.75)Mn_(0.4)Al_(0.2)

研究了贮氢合金 Ml Ni3.6 5Co0 .75Mn0 .4 Al0 .2 的颗粒度及粒度分布均匀性对其电化学性能的影响。结果表明 :在2 0 0 m A/g(以贮氢合金的质量计算 ,下同 )的充放电电流下 ,合金的粒度越小 ,首次放电容量越大 ,且活化速度越快 ,但其饱和容量 (活化后稳定的放电容量 )随粒度的增大而增加 ,且在某个最佳粒度时达到最大值 ,然后又逐渐降低 ;该合金的高倍率放电容量与其粒度之间也有相同的规律 ,只是在不同的放电电流下最佳粒度值不同 ,当放电电流小于 60 0 m A/g时 ,3 0μm～ 76μm合金粉的放电容量最大 ,当放电电流等于或大于 60 0 m A/g时 ,4 0μm～ 5 0μm合金粉的放电容量最大 ;放电电流越大 ,颗粒度对合金粉电化学性能的影响越显著 ;在充放电电流为 3 0 0 m A/g时 ,除3 0μm以下的合金粉性能衰减较快外 ,其余各个粒度的合金粉的性能衰减速度几乎相等 ;均匀的粒度分布有利于合金粉电化学性能的提高。

The effects of particle size and its distribution on electrochemical performance of MlNi(3.65)Co(0.75)Mn(0.4)Al(0.2) have been systematically investigated. The experimental results show that the smaller the particle size, the larger the first discharge capacity and the earlier the saturation capacity for the charge/discharge current of 200 mA/g. However, the saturation capacity increases with increasing particle size, while the capacity declines above the optimal particle size at which the largest discharge capacity can be obtained. The particle size dependence of high-rate discharge ability is similar to that of the saturation capacity, but the optimal particle sizes are different for various discharge currents. The optimal particle size is 30 mum similar to 76 mum for the discharge currents less than 600 mA/g, while for the discharge currents of above 600 mA/g, it becomes 40 mum similar to 50 mum. The higher the discharge current, the more the affection of particle size. The cycle life test at 300 mA/g shows that the discharge capacity increases with increasing particle size. The decay rates of discharge capacity are almost the same except that of particles less than 30 mum. Uniform particle size distribution is beneficial to improving the electrochemical performance of the alloy.