Structural transformation and its effects on the electrochemical performances of a layered double hydroxide

When a layered double hydroxide (LDH), [Ni4Al(OH)(10)]NO3 is aged at 60 degrees C in a concentrated KOH solution (around 7 mol L-1), it transforms into beta-Ni(OH)(2); when it is cycled electrochemically, it can also transform into beta-Ni(OH)(2) but finish much sooner. In the mixture formed during the transformation, the reciprocal of the mass of the LDH is linearly related to the aging time. The electrochemical characterization of the LDH shows that the transformation impairs it performances, which leads to the decrease of the maximal number of exchanged electron per nickel atom as the charging/discharging cycling is continued. Therefore, this study reveals that the structural stability of the material, which is key to its cycle life,depends on temperature, electrolyte concentration and electrochemical cycles. It was found that high temperature cyclic performances of the LDH can be improved by lowering the concentration of electrolyte and/or adding Lu2O3. (C) Elsevier B.V. All rights reserved.