Facilitation of quasi-reversible effect with rapid diffusion kinetics on Mg0.9-xTi0.1Nix high energy ball milled powders for Ni-MH batteries

Abstract

In this research work, Mg-Ti-Ni alloys had been processed through mechanical alloying route. The X-ray diffraction profile of 30 h ball milled Mg0.875Ti0.1Ni0.025 and 20 h milled Mg0.825Ti0.1Ni0.075 powders reveal the partial solid solution of Ti in Mg with induced lattice defects. Especially the 15 h milled Mg0.875Ti0.1Ni0.025 and 30 h milled Mg0.85Ti0.1Ni0.05 powders reveal that their particles are uniformly and intimately mixed with better polydispersity (%) during milling. They consists of fine crystallites (i.e. 21–40 nm in size) with more incorporated micro-strain (i.e. 0.13–0.23%). The ultra violet visible spectra reveal that the band gap energies of Mg0.9-xTi0.1Nix powders have been increased with reduction in crystallite size, increased surface area, surface energy and structural defects. The 30 h milled Mg0.85Ti0.1Ni0.05 powder transmits 46.65% of photons with increased band gap energy of 1.263 eV. The tuned bandgap energy (i.e. 1.0 eV–1.3 eV) materials with photonic transmittance (i.e. approximately 40–60%) behaviour have been attributed to the quasi reversibility of hydrogen ions with rapid diffusion kinetics. The effect of quasi-reversible has been well perceived in the cyclic voltammogram and the cyclic discharge curve with high desorption specific capacity of 531 & 424 mAh g−1 respectively for the 30 h milled Mg0.85Ti0.1Ni0.05 powder. The electrochemical impedance spectrum has been revealed an exchange ion current density of 2380 mA g−1 and low polarization resistance 36 mΩ for the 30 h milled Mg0.85Ti0.1Ni0.05 powder. The poor internal impedance leads to poor polarization and enhances the quasi-reversible behaviour.