A method for producing a lithium-transition metal composite oxide, including steps of: preparing a mixture including a lithium-containing compound and a transition metal compound; obtaining a molded body of the mixture; and sintering the molded bodies in a container having at least one vent hole, to obtain sintered bodies.

A positive electrode active material with little deterioration is provided. Positive electrode active material particles with little deterioration are provided. A power storage device with little deterioration is provided. A highly safe power storage device is provided. A novel power storage device is provided. A secondary battery includes a positive electrode and a negative electrode. In the secondary battery, the positive electrode includes a positive electrode active material; the positive electrode active material includes a crystal exhibiting a layered rock-salt crystal structure; the crystal is represented by the space group R-3m; the positive electrode active material is a particle containing lithium, cobalt, titanium, magnesium, and oxygen; the concentration of the magnesium in a surface portion of the particle is higher than the concentration of the magnesium in an inner portion of the particle; and in the positive electrode active material, the concentration of the titanium in the surface portion of the particle is higher than the concentration of the titanium in the inner portion of the particle.

The breakage or cracking of a positive electrode active material due to pressure application, repeated charging and discharging, or the like is likely to cause dissolution of a transition metal, an excessive side reaction, and the like. With a crack, unevenness, a step, roughness, or the like on the surface of a positive electrode active material, stress tends to be concentrated on part, which easily causes breakage. By contrast, with a smooth surface and a nearly spherical shape, stress concentration is alleviated; thus, breakage is unlikely to occur. Therefore, a positive electrode active material with a smooth surface and little unevenness is formed. For example, when the positive electrode active material is subjected to image analysis using a microscope image, the median value of the solidity is larger than or equal to 0.96. Alternatively, the median value of the fractal dimension of the positive electrode active material is smaller than or equal to 1.143. Alternatively, the median value of the circularity of the positive electrode active material is larger than or equal to 0.7.

Provided is a method of preparing an irreversible positive electrode additive for a secondary battery, which includes mixing Li.sub.2O, NiO, and NH.sub.4VO.sub.3 and performing thermal treatment to prepare a lithium nickel composite oxide represented by Chemical Formula 1 below, wherein the NH.sub.4VO.sub.3 is mixed in an amount of 1.5 to 6.5 parts by weight with respect to a total of 100 parts by weight of the Li.sub.2O, NiO, and NH.sub.4VO.sub.3.

Li.sub.2+aNi.sub.1−b−cM.sup.1.sub.bV.sub.cO.sub.2−dA.sub.d  [Chemical Formula 1]

In Chemical Formula 1,

M.sup.1 is at least one selected from the group consisting of Cu, Mg, Pt, Al, Co, P, W, Zr, Nb, and B, A is at least one selected from the group consisting of F, S, Cl, and Br, and 0≤a≤0.2, 0≤b≤0.5, 0.01≤c≤0.065, and 0≤d≤0.2 are satisfied.

A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

The present invention discloses a quaternary cathode material, an cathode and a battery. Particularly, the present invention provides the quaternary cathode material with a chemical structural formula: Li.sub.xNi.sub.a′Co.sub.bMn.sub.c′Al.sub.dM.sub.yO.sub.2, wherein 1x1.05,0<y0.025.0.3a′0.95,0.03b01.0.01c′0.05,0.01d0.005 and a′+b+c′+d=1; M is a dopant selecting from at least one of Zr, Al, B, Ti, Mg, Nb, Ba, Si, P, W, Sr and F. The quaternary cathode material has an α-NaFeO.sub.2 ty

A positive electrode active material to be used in a non-aqueous electrolyte secondary battery and containing a lithium transition metal compound which contains Ni in a proportion constituting 80-94 mol %, inclusive, relative to the total mole number of the metal elements other than Li, and also contains Nb in a proportion constituting 0.1-0.6 mol %, inclusive, relative thereto, the positive electrode active material being characterized in that the Nb amount n1 in a first sample solution obtained by adding 0.2 g of the lithium transition metal compound to a hydrochloric acid aqueous solution comprising 5 mL of pure water/5 mL of 35% hydrochloric acid, and the Nb amount n2 in a second sample solution obtained by immersing a filter used to filter the first sample solution in a fluonitric acid comprising 5 mL of 46% hydrofluoric acid/5 mL of 63% nitric acid satisfy the condition of 50%≤n1/(n1+n2)<75% when converted to molar quantities.

A composite metal oxide material and a preparation method thereof, a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device are provided. The composite metal oxide material includes a central core and a coating layer on the surface of the central core, in which the central core material has a chemical formula of Li.sub.5Fe.sub.xM.sub.1-xO.sub.4, 0.6≤x≤1; the coating layer material has a chemical formula of LiMO2, M is one or more metal elements with +3 valence, and the absolute value of the difference between the +3-valence ion radius of Fe and the +3-valence ion radius of M is ≤0.02 nm. The composite metal oxide material of the present disclosure makes the secondary battery have high charge capacity, high discharge capacity and long cycle life.

A positive electrode active material includes a lithium transition metal oxide having a spinel crystal structure, and a coating layer positioned on the surface of the lithium transition metal oxide, wherein the coating layer has an orthorhombic structure, and includes an oxide represented by Formula 1. A method for producing the positive electrode active material, a positive electrode including the positive electrode active material, and a lithium secondary battery, the positive electrode active material.

The cathode active material for a lithium secondary battery according to embodiments of the present invention includes a lithium-transition metal composite oxide particle including a plurality of primary particles, and the lithium-transition metal composite oxide particle includes a lithium-sulfur-containing portion formed between the primary particles. Thereby, it is possible to improve life-span properties and capacity properties by preventing the layer structure deformation of the primary particles and removing residual lithium.