Synthesis and Characterization of Mg Substituted LiCoO[sub 2]

Thirty stoichiometric, lithium deficient and lithium excess and samples with and were synthesized from Co–Mg mixed hydroxides, prepared by coprecipitation, and , by heating in air. X-ray diffraction was used to determine the ranges of and that gave single phase samples. Atomic absorption analysis and Rietveld refinements showed that all single phase samples had pure lithium layers containing no Mg and transition-metal layers containing excess Li (if present) and all Mg and all Co atoms. The single phase samples showed oxygen deficiency and no evidence for when and . The electrochemical studies of the excess lithium and stoichiometric samples were used to measure the rate of capacity reduction with Mg content, about per formula unit of Mg. Literature work on , , and demonstrates about the same rate of capacity reduction per formula unit of Mg.