The preparation of solid solutions of the LiAlO2−LiCoO2 system in the complete composition range is described. Powder X-ray diffraction gives direct information about the partial substitution of Co by Al atoms, together with a fractional occupancy of tetracoordinated sites by aluminum atoms. EPR of impurity Ni3+ ions and 6Li and 27Al MAS NMR spectroscopies are used to assess for cation distribution. 6Li NMR spectra show a single resonance of lithium ions in octahedral sites. 27Al NMR spectra show that the distribution of Al atoms in tetrahedral and octahedral sites changes with composition. EPR spectra evidence that Ni3+ impurity ions in the Al y Co1 - y O2 layers prefer mainly Al3+ ions as first neighbors. The potential applicability of these materials as intercalation electrodes is also evaluated in lithium anode cells. A poor lithium ion diffusivity, resulting from the presence of aluminum in both tetrahedral and octahedral sites, may limit the applicability of LiAl y Co1 - y O2 cathodes. The partial substitution of Co by Ni leads to an improvement of the electrochemical performance.

Noncrystalline solids with LiCoC 6 H 5 O 7 ‚5H 2 O and (NH 4 ) 3 LiCo(C 6 H 5 O 7 ) 2 compositions were obtained by ethanol dehydration of concentrated lithium-cobalt citrate solutions. Electron spectroscopy of solutions and solid citrates, as well as IR spectroscopy of solid citrates, reveals that in LiCoC 6 H 5 O 7 ‚5H 2 O one triionized citrate ion chelates Co 2+ while two triionized citrate ions surround Co 2+ in (NH 4 ) 3 LiCo(C 6 H 5 O 7 ) 2 . Lithium-cobalt citrates were used as precursors in the formation of lithium-cobalt mixed oxides. At 400 °C, thermal decomposition of LiCoC 6 H 5 O 7 ‚5H 2 O yields a mixture of pseudo-spinel and rhombohedral LiCoO 2 . From (NH 4 ) 3 -LiCo(C 6 H 5 O 7 ) 2 , monophase powders of rhombohedral LiCoO 2 were obtained at 400 °C, which consist of hexagonal individual particles with a diameter of 80-120 nm. This product can be annealed up to 800 °C without marked structural changes. The rhombohedral LiCoO 2 was used as active cathode material in lithium cells. Cyclic voltammogams showed little changes in the main cathodic and anodic peaks with synthesis temperature. The loss of cell capacity is limited in electrodes prepared at 400 °C from citrate precursors as compared with products of low-temperature synthetic procedures previously reported.

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