Low-Temperature Hydrogen Storage Alloy and Its Application in Ni-MH Battery

摘要

Rare earth compositions, La, Ce and Pr in Mm(NiCoMnAl)_5 hydrogen storage alloy, were arranged by uniform design method. The discharge performances and kinetics parameters including capacity, exchange current density, symmetry factor and hydrogen diffusion coefficient of the alloy at — 40℃, were tested in standard tri-elec-trode cell. And linear regression method was used to analyze the effect of rare earth compositions on the performances of hydrogen storage alloys. The results show that the capacities of the alloys are positively correlative to the square of Ce content at -40℃ and under both 0. 4 and 0. 2C rate. The kinetics parameters and hydrogen diffusion coefficient indicate that the low-temperature performances of the alloys are mainly controlled by hydrogen diffusion process, and the surface electrochemical reaction affects the low-temperature performances to a certain extent. The low-temperature discharge capacities of the battery were also tested. The results show excellent low-temperature performances. The battery delivers 69. 6% of its room-temperature capacity at -40℃ and 0. 2C rate, 77. 7% at -40 ℃ and 0.4C rate, 59. 1% at -45℃ and 0.2C rate.