Mechanism of the enhancement of discharge rate property for Nd0.8Mg0.2(Ni0.8Co0.2)3.8 hydrogen storage alloy by magnetic annealing

For further improving the rate properties of Nd0.8Mg0.2(Ni0.8Co0.2)3.8 hydrogen storage alloy, the alloy was annealed in high magnetic fields (10 T). The results showed that the electrochemical properties and magnetic properties of Nd0.8Mg0.2(Ni0.8Co0.2)3.8 hydrogen storage alloy were considerably enhanced. And there was no change of the phase composition. The lattice constants of c and c/a ratio increased for the sample magnetically annealed, yielding uniaxial magnetic anisotropy along the c axis. The increase of c and c/a ratio enlarged interstitial volume, leading to a larger diffusion channel for hydrogen atoms, and resulted in high hydrogen storage capacity and rate properties.