Study on hydrogen storage alloy materials for Ni/MH batteries used in rail transit
The negative electrode material of nickel-metal hydride battery is very important to the low temperature performance and cycle life of the battery.The rare-earth-Mg-Ni-based hydrogen storage alloy has high capacity,easy activation and good rate discharge performance,which meets the demand of long life and low temperature discharge of nickel-metal hydride batteries of urban rail vehicles.In this work,La0.55 Sm0.20 Nd0.10 Mg0.15 Ni3.60 Al0.10 alloy was prepared by induction melting method,and followed by annealing treatment.Subsequently the microstructure and electrochemical properties of the alloys were studied.The results show that the as-cast alloy consists of Ce2 Ni7,Ce5 Co19,and LaNi5 phases.After annealing at 990℃for 8 hours,the Ce2 Ni7 and LaNi5 phases undergo peritectic reactions,and the phases in the alloy transform into Pr5 Co19,Ce5 Co19,and LaNi5 phases.The discharge capacity of annealed La0.65 Sm0.20 Mg0.15 Ni3.60 Al0.10 alloy is as high as 380 mAh/g.After 100 charge discharge cycles,the capacity retention rate is still up to 82.6%,slightly higher than that of the as cast alloy.Due to the presence of defects and in-equilibria structures on the surface and crystal phases,the surface charge transfer rate and internal hydrogen diffusion rate of as-cast alloys are both relatively faster,resulting in slightly higher rate discharge performance and low-temperature performance.The high rate discharge performance of the as-cast hydrogen storage alloy at 5C is 76%,and the discharge capacity at-40℃reach up to 208 mAh/g.All tests of Ni/MH batteries with as-cast alloy as the negative active material meet the relevant standard provisions of alkaline batteries,and the discharge capacity of 2350 cycles is still 91.8%,and the low temperature discharge capacity retention rate at-40℃reaches 97.0%.
rail transitNi/MH batteryhydrogen storage alloylong lifelow temperature discharge property
国家科技期刊平台
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