The present invention relates to a positive electrode active material having improved electrical characteristics by adjusting an aspect ratio gradient of primary particles included in a secondary particle, a positive electrode including the positive electrode active material, and a lithium secondary battery using the positive electrode.

A positive electrode active material precursor for a lithium secondary battery containing at least Ni, in which S/D.sub.50 that is a ratio of a BET specific surface area S to a 50% cumulative volume particle size D.sub.50 is 2×10 to 20×10.sup.6 m/g, and, in powder X-ray diffraction measurement using a CuKα ray, A/B that is a ratio of an integrated intensity A of a diffraction peak within a range of 2θ=37.5±1° to an integrated intensity B of a diffraction peak within a range of 2θ=62.8±1° is more than 0.80 and 1.33 or less.

A lithium metal composite oxide having a layered structure, containing at least Li, Ni, and an element X, in which the element X is one or more elements selected from the group consisting of Co, Mn, Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn, L/D.sub.50 that is a ratio of an average primary particle diameter L to a 50% cumulative volume particle size D.sub.50 is 0.3 to 1.5, and, in powder X-ray diffraction measurement using a CuKα ray, a crystallite diameter A calculated from a diffraction peak within a range of 2θ=44.5±1° is 700 Å or less.

A nanoparticle cluster reduction method yields a new composition of matter including a large percentage (e.g., 75% or higher percentage) of primary nanoparticles in the new composition of matter. The particle reduction method reduces the size of nanoparticle clusters in material of the new composition of matter, allows particle reduction of specific nanoparticle cluster sizes, and allows particle reduction to primary nanoparticles. This new composition of matter can include a high permittivity and high resistivity dielectric compound. This new composition of matter, according to certain examples, has high permittivity, high resistivity, and low leakage current. In certain examples, the new composition of matter constitutes a dielectric energy storage device that is a battery with very high energy density, high operating voltage per cell, and an extended battery life cycle. An example method can include a controlled gas evolution reaction to reduce the size of nanoparticle clusters.

A cathode active material for a lithium secondary battery comprises a lithium metal oxide that has a layered crystal structure and contains nickel and aluminum. The lithium metal oxide contains 70 mol % or more of nickel based on a total number of moles of all elements excluding lithium and oxygen. A ratio of lithium sites occupied by nickel instead of lithium among all lithium sites in the lithium metal oxide is in a range from 1% to 3.5%. A weight ratio of aluminum to nickel in the lithium metal oxide is in a range from 1/550 to 1/100.

A positive electrode and a secondary battery including the same is disclosed herein. In some embodiments, a positive electrode includes a positive electrode current collector and a positive electrode mixture containing a positive electrode active material disposed thereon, the positive electrode active material includes a lithium transition metal oxide powder represented by chemical formula 1,

Li.sub.aNi.sub.xCo.sub.yM.sub.zO.sub.2-wA.sub.w  (1) M is at least one selected from the group consisting of Mn, Ti, Mg, Al, Zr, Mn and Ni, A is an oxygen-substituted halogen, and 1.00≤a≤1.05, 0.1≤x≤0.8, 0.1≤y≤0.8, 0.01≤z≤0.4, and 0≤w≤0.001, the powder having large particles which are secondary particles having an average particle diameter (D50) of 7 μm to 17 μm, and small particles which are single particles having average particle diameter (D50) of 2 μm to 7 μm, weight ratio of large particles to small particles is 5:5 to 9:1, and the positive electrode mixture has a porosity of 22% to 35%.

A process for preparing stacks of metal chalcogenide flakes includes: (a) reacting together a source of the metal atom of the target metal chalcogenide with a source of the chalcogenide atom of the target metal chalcogenide, in the presence of a spacer, so as to produce flakes of the metal chalcogenide; (b) depositing metal chalcogenide flakes obtained using step (a) onto a substrate to form a stack of assembled metal chalcogenide flakes, wherein the spacer contains an alkyl chain linked to a functional group able to bond to the metal chalcogenide surface, said alkyl chain having a length of less than 18 carbon atoms, preferably between 6 and 14 carbon atoms.

Embodiments of the present disclosure describe a magnetic substrate including a cured magnetic ink and a cured polymer resin, wherein the cured magnetic ink includes a plurality of functionalized magnetic iron oxide nanoparticles and wherein the magnetic substrate is a freestanding magnetic substrate.

A method for producing a metal composite hydroxide, which includes a first crystallization process of obtaining first metal composite hydroxide particles by supplying a first raw material aqueous solution containing a metal element and an ammonium ion donor to a reaction tank, adjusting a pH of a reaction aqueous solution in the reaction tank, and performing a crystallization reaction and a second crystallization process of forming a tungsten-concentrated layer on a surface of the first metal composite hydroxide particles and obtaining second metal composite hydroxide particles by supplying a second raw material aqueous solution containing a metal element and a more amount of tungsten than the first raw material aqueous solution and an ammonium ion donor to a reaction aqueous solution containing the first metal composite hydroxide particles, adjusting a pH of the reaction aqueous solution, and performing a crystallization reaction, and the like.

The cathode active material for a lithium secondary battery according to embodiments of the present invention includes lithium-transition metal composite oxide particles including a plurality of primary particles, and the lithium-transition metal composite oxide particles have a lithium-potassium-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.