Pillared layer hydroxide powders as secondary battery electrode materials

Homogeneous decomposition of urea in aqueous solutions containing Ni²⁺ ions yields hydrated phase α-Ni(OH)₂ at temperatures higher than 50°C. Elemental and thermal analyses that are supported with the qualitative data from FTIR and Raman Spectroscopy show evidence of intercalating species in addition to water or hydroxyls. Carbon and nitrogen containing species (anions introduced from the reactants and the metal salt), have generally been predicted to be intercalating. Assuming that the generally reported reaction scheme for urea is not affected by the presence of metal ions, it is a reasonable approach to introduce OH^- and CO₃^2- ions from different sources to study their individual contributions to the precipitation. Hydroxide ion was introduced either by homogenous decomposition of hexamethylenetetramine (HMTA) or from a base such as NaOH or NH₃, while CO₃^2- was introduced either by homogeneous decomposition of trichloroacetic acid (TCAA) or from Na₂CO₃. Powders produced by HMTA decomposition were identical with the ones from urea decomposition, whereas those were produced by TCAA had the structure similar to Ni₂(CO₃)(OH)₂. When [OH^-]/[CO₃^2-] was less than unity the results were identical with the ones obtained by TCAA. For [OH^-]/[CO₃^2-] greater than one and less than 12, interstratified structures (mixture of α and β phases) were obtained. Powders were characterized using SEM, XRD, TGA/DTA, elemental analysis, particle size analysis, surface area analysis to assess the role of experimental variables on the characteristics of the powders produced.