Provided are a positive electrode active material with which a nonaqueous electrolyte secondary battery having a high energy density can be obtained, a nickel-manganese composite hydroxide suitable as a precursor of the positive electrode active material, and production methods capable of easily producing these in an industrial scale. Provided is a nickel-manganese composite hydroxide represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α and containing a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a diffraction peak of a (001) plane obtained by X-ray diffraction measurement of at least 0.10° and up to 0.40° and has a degree of sparsity/density represented by [(void area within secondary particle/cross section of secondary particle)×100](%) of at least 0.5% and up to 10%. Also provided is a production method of the nickel-manganese composite hydroxide.

Provided are a positive electrode active material with which a nonaqueous electrolyte secondary battery having a high energy density can be obtained, a nickel-manganese composite hydroxide suitable as a precursor of the positive electrode active material, and production methods capable of easily producing these in an industrial scale. Provided is a nickel-manganese composite hydroxide represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α and containing a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a diffraction peak of a (001) plane obtained by X-ray diffraction measurement of at least 0.10° and up to 0.40° and has a degree of sparsity/density represented by [(void area within secondary particle/cross section of secondary particle)×100](%) of at least 0.5% and up to 10%. Also provided is a production method of the nickel-manganese composite hydroxide.

A quantum dot luminescent material and a method of producing thereof. The quantum dot luminescent material includes a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer, and an electron injection layer. The quantum dot luminescent layer is located on the hole transport layer, and the quantum dot luminescent layer includes uniformly distributed perovskite nanodots.

The present invention relates to a metal phase transformation compound and a method for preparing the same.

Disclosed herein are a nickel-based lithium metal composite oxide, a method of preparing the same, and a lithium secondary battery including a positive electrode including the same. The nickel-based lithium metal composite oxide includes secondary particles including aggregates of primary particles, wherein a content of nickel in the nickel-based lithium metal composite oxide is 50 mol % or more, based on the total content of transition metals in the nickel-based lithium metal composite oxide, the secondary particles include large secondary particles having a particle size of 10 μm or more and small secondary particles having a particle size of 5 μm or less, and the content of nickel in the large secondary particles is larger than the content of nickel in the small secondary particles.

A method for producing a metal composite hydroxide, which includes a first crystallization process of supplying a first raw material aqueous and performing a crystallization reaction and a second crystallization process of supplying a second raw material aqueous solution containing a more amount of tungsten than the first raw material aqueous solution and performing a crystallization reaction to form a tungsten-concentrated layer and in which switching of reaction atmosphere from either atmosphere of a non-oxidizing atmosphere or an oxidizing atmosphere to the other atmosphere is performed two or more times in particle growth and the time for supplying the second raw material aqueous solution into the reaction tank in the non-oxidizing atmosphere is 50% or more with respect to the entire time for supplying the second raw material aqueous solution into the reaction tank.

A method for producing a metal composite hydroxide, which includes a first crystallization process of supplying a first raw material aqueous and performing a crystallization reaction and a second crystallization process of supplying a second raw material aqueous solution containing a more amount of tungsten than the first raw material aqueous solution and performing a crystallization reaction to form a tungsten-concentrated layer and in which switching of reaction atmosphere from either atmosphere of a non-oxidizing atmosphere or an oxidizing atmosphere to the other atmosphere is performed two or more times in particle growth and the time for supplying the second raw material aqueous solution into the reaction tank in the non-oxidizing atmosphere is 50% or more with respect to the entire time for supplying the second raw material aqueous solution into the reaction tank.

A metal composite hydroxide represented by a general formula (1): Ni.sub.1−x−yCo.sub.xMn.sub.yM.sub.z(OH).sub.2+α (where 0.02≤x≤0.3, 0.02≤y≤0.3, 0≤z≤0.05, and −0.5≤α≤0.5 are satisfied and M is at least one element selected from the group consisting of Mg, Ca, Al, Si, Fe, Cr, V, Mo, W, Nb, Ti, and Zr), in which the metal composite hydroxide contains a first particle having a core portion inside the particle and a shell portion formed around the core portion and [(D90−D10)/MV] is 0.80 or more.

A metal composite hydroxide represented by a general formula (1): Ni.sub.1−x−yCo.sub.xMn.sub.yM.sub.z(OH).sub.2+α (where 0.02≤x≤0.3, 0.02≤y≤0.3, 0≤z≤0.05, and −0.5≤α≤0.5 are satisfied and M is at least one element selected from the group consisting of Mg, Ca, Al, Si, Fe, Cr, V, Mo, W, Nb, Ti, and Zr), in which the metal composite hydroxide contains a first particle having a core portion inside the particle and a shell portion formed around the core portion and [(D90−D10)/MV] is 0.80 or more.

This positive electrode for a nonaqueous electrolyte secondary battery is provided with: a positive electrode active material including lithium composite oxide particles containing not less than 80 mol % but less than 100 mol % of Ni with respect to the total number of moles of metal elements other than Li; and a conductive material, wherein the lithium composite oxide particles include particles each having a step-like structure with three or more stacked flat surfaces having an outer edge length of 1 μm or more, and the average particle size of the conductive material is 30 nm or less.