Li-Ni composite oxide particles and process for producing the same, and non-aqueous electrolyte secondary battery
The present invention relates to Li-Ni composite oxide particles that exhibit a high initial discharge capacity and are excellent in thermal stability when used as a positive electrode active substance for non-aqueous electrolyte secondary batteries, and a process for producing the Li-Nicomposite oxide particles. The Li-Ni composite oxide particles of the present invention have a composition of Li x Ni 1−y−a−b Co y M1 a M2 b O 2 wherein x, y, a and b represent 1.00≦x≦1.10; 0<y≦0.25; 0<a≦0.25; and 0≦b≦0.10, respectively; M1 is at least one element selected from the group consisting of Al and Mn; and M2 is at least one element selected from the group consisting of Zr and Mg, in which a product of a metal occupancy (%) of lithium sites of the Li-Ni composite oxide as determined by Rietveld analysis of X-ray diffraction thereof and a crystallite size (nm) of the Li-Ni composite oxide as determined by the Rietveld analysis is not less than 700 and not more than 1400.
1. Li-Ni composite oxide particles having a composition of Li x Ni 1−y−a−b Co y M1 a M2 b O 2 wherein x, y, a and b represent 1.00≦x≦1.10; 0<y≦0.25; 0<a≦0.25; and 0≦b≦0.10, respectively; M1 is at least one element selected from the group consisting of Al and Mn; and M2 is at least one element selected from the group consisting of Zr and Mg, a product of a metal occupancy (%) of lithium sites of the Li-Nicomposite oxide as determined by Rietveld analysis of X-ray diffraction thereof and a crystallite size (nm) of the Li-Ni composite oxide as determined by the Rietveld analysis being not less than 700 and not more than 1400.
2. The Li-Ni composite oxide particles according to claim 1 , wherein the metal occupancy of lithium sites of the Li-Ni composite oxide as determined by the Rietveld analysis is not less than 2% and not more than 7%.
3. The Li-Ni composite oxide particles according to claim 1 , wherein the crystallite size of the Li-Ni composite oxide as determined by the Rietveld analysis is not more than 500 nm.
4. The Li-Ni composite oxide particles according to claim 1 , wherein the Li-Ni composite oxide particles have an average particle diameter of 1 to 20 μm and a BET specific surface area of 0.1 to 1.6 m 2 /g.
5. A process for producing the Li-Ni composite oxide particles as claimed in claim 1 , comprising the steps of mixing lithium compound particles and Ni-Co hydroxide particles, and calcining the resulting mixture, the Ni-Co hydroxide particles being produced by mixing an aqueous solution of a sulfuric acid salt of each metal element, an ammonia aqueous solution and a sodium hydroxide aqueous solution such that an ammonia concentration in a reaction vessel is controlled to not more than 1.4 mol/L, and a ratio of the ammonia concentration in the reaction vessel to a surplus hydroxyl group concentration in the reaction vessel is controlled to not less than 6.
6. A process for producing the Li-Ni composite oxide particles as claimed in claim 1 , comprising the steps of mixing lithium compound particles, Ni-Co hydroxide particles, and aluminum compound particles and/or zirconium compound particles, and calcining the resulting mixture, the Ni-Cohydroxide particles being produced by mixing an aqueous solution of a sulfuric acid salt of each metal element, an ammonia aqueous solution and a sodium hydroxide aqueous solution such that an ammonia concentration in a reaction vessel is controlled to not more than 1.4 mol/L, and a ratio of the ammonia concentration in the reaction vessel to a surplus hydroxyl group concentration in the reaction vessel is controlled to not less than 6.
7. A non-aqueous electrolyte secondary battery using a positive electrode comprising a positive electrode active substance comprising the Li-Nicomposite oxide particles as claimed in claim 1 .