Layered lithium cobalt oxides free of localized cubic spinel-like structural phases and method of making same

A compound having the form LiαCoβAγO2, wherein A is one or more dopants having an average oxidation state N such that +2.5≦N≦+3.5, 0.90≦α≦1.10, β>0, γ≧0, and β+α=1, said compound having a substantially single phase, hexagonal layered crystal structure that is substantially free of localized cubic spinel-like structural phases, a ratio of the integrated intensity of the diffraction peak corresponding to Miller indices (110) to the integrated intensity of the diffraction peak corresponding to Miller indices (108) using powder x-ray diffraction greater than or equal to 0.7, a ratio of the integrated intensity of the diffraction peak corresponding to Miller indices (102) to the integrated intensity of the diffraction peak corresponding to Miller indices (006) using powder x-ray diffraction greater than or equal to 1.0, and no diffraction peaks using powder x-ray diffraction at a smaller scattering angle than the diffraction peak corresponding to Miller indices (003).

A compound having the formula Liα−xCoβAγO2, wherein 0≦x≦α, said compound derived by electrochemically removing x Li per formula unit from a compound having the formula LiαCoβAγO2, wherein A is one or more dopants having an average oxidation state N such that +2.5≦N≦+3.5, 0.90≦α≦1.10, β>0, γ≧0 and β+γ=1, said compound having a substantially single phase, hexagonal layered crystal structure and being substantially free of localized cubic spinel-like structural phases and wherein, in the powder x-ray diffraction pattern, there are no diffraction peaks at a smaller scattering angle than the diffraction peak corresponding to Miller indices (003).

A lithium or lithium ion secondary battery including a positive electrode comprising a compound having the formula LiαCoβAγO2, wherein A is one or more dopants having an average oxidation state N such that +2.5≦N≦+3.5, 0.90≦α≦1.10, β>0, γ≧0 and β+γ=1, said compound having a substantially single phase, hexagonal layered crystal structure and being substantially free of localized cubic spinel-like structural phases and wherein, in the powder x-ray diffraction pattern, there are no diffraction peaks at a smaller scattering angle than the diffraction peak corresponding to Miller indices (003).

A method of preparing a compound having a substantially single phase, hexagonal layered crystal structure, being substantially free of localized cubic spinel-like structural phases and having no diffraction peaks at a smaller scattering angle than the diffraction peak corresponding to Miller indices (003) in its powder x-ray diffraction pattern, the method comprising the steps of synthesizing a lithium metal oxide having the formula LiαCoβAγO2, wherein A is one or more dopants having an average oxidation state N such that +2.5≦N≦+3.5, 0.90≦α≦1.10, β>0, γ≧0 and β+γ=1, at a temperature of at least about 600° C.;

• and cooling the heated lithium metal oxide to room temperature at a rate of greater than 8° C./min;
• wherein said synthesizing step comprises synthesizing the lithium metal oxide from a cobalt source compound selected from the group consisting of Co3O4 and Co(OH)2.