Synthesis, stability and electrochemical properties of NiAl and NiV layered double hydroxides

Layered double hydroxides (LDH) containing NiAl or NiV of varying M(II) ∶ M(III) ratios have been prepared by coprecipitation and characterized by XRD, elemental analysis, and FT-IR. The LDHs electrochemical properties were investigated to determine their potential application as positive electrodes in Ni–Cd and NiMH batteries. Analysis of the electrochemical behavior of the LDHs indicates that the performance is not only dependant on the M(II) ∶ M(III) ratios but also on the degree of structural disorder of the material. The well-crystallized Ni5Al LDH exchanges up to 1.5 electrons in early cycles but is not stable and collapses on oxidative charging to the oxyhydroxide form. The turbostratic Ni2Al LDH exchanges more electrons (up to 1.6) and is more stable during charging. However, owing to a lower density in comparison to Ni5Al, it has a poorer loading capacity. The NiV LDHs exchange a maximum of 1.1 electrons due to the high stability of the higher oxidation states of vanadium, and thus are poor candidates for rechargeable materials.