A compound represented by Li.sub.Co.sub.(1-x-2y)Me.sub.x(M1M2).sub.yO.sub., (Formula (I)) wherein Me, is one or more of Li, Mg, Al, Ca, Ti, Zr, V, Cr, Mn, Fe, Ni, Cu, Zn, Ru and Sn, and wherein 0x0.3, 0<y0.4, 0.951.4, and 1.902.10 is disclosed. Further, particles including such compounds are described.

Mixed-metal oxides and lithiated mixed-metal oxides are disclosed that involve compounds according to, respectively, Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub. and Li.sub.1+Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub.. In these compounds, Me is selected from B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Ag, In, and combinations thereof; 0x1; 0y1; 0z<1; x+y+z>0; 00.5; and x+y+>0. For the mixed-metal oxides, 15. For the lithiated mixed-metal oxides, 0.11.0 and 1.93. The mixed-metal oxides and the lithiated mixed-metal oxides include particles having an average density greater than or equal to 90% of an ideal crystalline density.

A positive-electrode active material contains a lithium composite oxide containing manganese. The crystal structure of the lithium composite oxide belongs to a space group Fd-3m. The integrated intensity ratio I.sub.(111)/I.sub.(400) of a first peak I.sub.(111) on the (111) plane to a second peak I.sub.(400) on the (400) plane in an XRD pattern of the lithium composite oxide satisfies 0.05I.sub.(111)/I.sub.(400)0.90.

Disclosed is a cathode active material in which lithium cobalt oxide particles and manganese (Mn) or titanium (Ti)-containing lithium transition metal oxide particles co-exist and a method of preparing the same.

A positive electrode active material includes: a particle including a lithium composite oxide; a first layer that is provided on a surface of the particle and includes a lithium composite oxide; and a second layer that is provided on a surface of the first layer. The lithium composite oxide included in the particle and the lithium composite oxide included in the first layer have the same composition or almost the same composition, the second layer includes an oxide or a fluoride, and the lithium composite oxide included in the first layer has lower crystallinity than the lithium composite oxide included in the particle.

A positive-electrode active material contains a lithium composite oxide containing at least one selected from the group consisting of F, Cl, N, and S. The crystal structure of the lithium composite oxide belongs to a space group C2/m. An XRD pattern of the lithium composite oxide comprises a first peak within the first range of 44 degrees to 46 degrees of a diffraction angle 2 and a second peak within the second range of 18 degrees to 20 degrees of the diffraction angle 2. The ratio of the second integrated intensity of the second peak to the first integrated intensity of the first peak is within a range of 0.05 to 0.90.

Cathode active materials are provided. The cathode active material can include a plurality of cathode active compound particles. A coating is disposed over each of the cathode active compound particles. The coating can include at least one of ZrO.sub.2, La.sub.2O.sub.3, a mixture of Al.sub.2O.sub.3 and ZrO.sub.2 or a mixture of Al.sub.2O.sub.3 and La.sub.2O.sub.3. The battery cells that include the cathode active material are also provided.

A positive-electrode active material contains a lithium composite oxide, wherein the lithium composite oxide is a multiphase mixture including a first phase, of which a crystal structure belongs to a space group Fm-3m, and a second phase, of which a crystal structure belongs to a space group Fd-3m; and in an XRD pattern of the lithium composite oxide, the integrated intensity ratio I.sub.(18-20)/I.sub.(43-46) of a first maximum peak I.sub.(18-20) within a first range of 18 degrees to 20 degrees at a diffraction angle 2 to a second maximum peak I.sub.(43-46) within a second range of 43 degrees to 46 degrees at the diffraction angle 2 satisfies 0.05I.sub.(18-20)/I.sub.(43-46)0.90.

A positive-electrode active material contains a lithium composite oxide containing at least one selected from the group consisting of fluorine, chlorine, nitrogen, sulfur, bromine, and iodine. The crystal structure of the lithium composite oxide belongs to the space group R-3m. The integrated intensity ratio I.sub.(003)/I.sub.(104) of a peak intensity I.sub.(003) on the (003) plane to a peak intensity I.sub.(104) on the (104) plane in an XRD pattern of the lithium composite oxide satisfies 0.62I.sub.(003)/I.sub.(104)0.90.

A negative active material includes a carbon material. The carbon material satisfies the following relationship: 6<Gr/K<16, Gr is a graphitization degree of the carbon material, measured by means of X-ray diffraction; and K is a ratio Id/Ig of a peak intensity Id of the carbon material at a wavenumber of 1250 cm.sup.?1 to 1650 cm.sup.?1 to a peak intensity Ig of the carbon material at a wavenumber of 1500 cm.sup.?1 to 1650 cm.sup.?1, and is measured by using Raman spectroscopy, and K is 0.06 to 0.15. The negative active material according to this application can significantly improve an energy density, cycle performance, and rate performance of the electrochemical device.