Researchers at Jilin University in China have proposed a new strategy for designing hydrogen storage alloys with high capacity and long cycling life to improve the discharge capacity and cycling life of nickel metal hydride (NiMH) batteries.

Their candidate alloy—La_0.62Mg_0.08Ce_0.2Y_0.1Ni_3.25Co_0.75Mn_0.2Al_0.3 [corresponding to (LaCeYMg) (NiCoMnAl)_4.5] exhibits a high capacity of 326.7 mAh g⁻¹ and a capacity retention of 80% after a long cycling life of 928 cycles, showing great potential for applications in nickel metal hydride batteries. A paper on their work is published in the Journal of Power Sources.

Nickel metal hydride (Ni-MH) batteries have key technology advantages for applications in new-energy vehicles, power tools, modern military devices etc. However, in order to compete with Li-ion batteries, their discharge capacity and cycling life need to be further improved, which are limited by the poor performances of their negative electrode materials—hydrogen storage alloys (HSAs).

… In this work, a novel strategy has been proposed for designing HSAs with high capacity and long cycling life by considering the structural properties, electronegativity and surface atomic coordination states. The rationality of this strategy was verified with the density functional theory (DFT) simulations and experiment results. Following this strategy, a new AB_4.5-type HSA has been designed and fabricated by employing Mg-substitution and sub-stoichiometry, which exhibits a high capacity of 326.7 mAh g⁻¹ and a long cycle life of 928 cycles.

—Wang et al.

Based on theoretical analysis and density functional theory simulation, the team determined that substituting Ni atoms inside the alloy with Mg based on the precise control of stoichiometric ratio and Mg content is critical in obtaining the higher-performance material.

Resources

• C.C. Wang, Y.T. Zhou, C.C. Yang, Q. Jiang (2018) “A strategy for designing new AB4.5-type hydrogen storage alloys with high capacity and long cycling life,” Journal of Power Sources, Volume 398, Pages 42-48 doi: 10.1016/j.jpowsour.2018.07.041