Performance Comparison between AB5 and Superlattice Metal Hydride Alloys in Sealed Cells

High-power cylindrical nickel metal/hydride batteries using a misch metal-based Al-free superlattice alloy with a composition of La11.3Pr1.7Nd5.1Mg4.5Ni63.6Co13.6Zr0.2 were fabricated and evaluated against those using a standard AB(5) metal hydride alloy. At room temperature, cells made with the superlattice alloy showed a 40% lower internal resistance and a 59% lower surface charge-transfer resistance compared to cells made with the AB(5) alloy. At a low temperature (-10 degrees C), cells made with the superlattice alloy demonstrated an 18% lower internal resistance and a 60% lower surface charge-transfer resistance compared to cells made with the AB(5) alloy. Cells made with the superlattice alloy exhibited a better charge retention at -10 degrees C. A cycle life comparison in a regular cell configuration indicated that the Al-free superlattice alloy contributes to a shorter cycle life as a result of the pulverization from the lattice expansion of the main phase.