A nickel manganese cobalt composite hydroxide, which is a precursor of a positive electrode active material, and which is composed of secondary particles to which primary particles containing a nickel, a manganese, and a cobalt are aggregated, or composed of the primary particles and the secondary particles, wherein a sodium content contained in the nickel manganese cobalt composite hydroxide is less than 0.0005% by mass. Also, a ratio of an average particle size of a lithium nickel manganese cobalt composite oxide divided by an average particle size of the nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of the lithium nickel manganese cobalt composite oxide selected randomly by a scanning electron microscope, a number that an aggregation of secondary particles is observed is 5% or less with respect to a total number of observed secondary particles.

A nickel manganese cobalt composite hydroxide, which is a precursor of a positive electrode active material, and which is composed of secondary particles to which primary particles containing a nickel, a manganese, and a cobalt are aggregated, or composed of the primary particles and the secondary particles, wherein a sodium content contained in the nickel manganese cobalt composite hydroxide is less than 0.0005% by mass. Also, a ratio of an average particle size of a lithium nickel manganese cobalt composite oxide divided by an average particle size of the nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of the lithium nickel manganese cobalt composite oxide selected randomly by a scanning electron microscope, a number that an aggregation of secondary particles is observed is 5% or less with respect to a total number of observed secondary particles.

A positive electrode active material precursor, a method of preparing the same, a positive electrode for a secondary battery and a lithium secondary battery which include the same are disclosed herein. In some embodiments, a method of preparing a positive electrode active material precursor includes adding a transition metal aqueous solution, an ammonium ion-containing solution, and a basic aqueous solution to an initial reaction solution, and performing a co-precipitation reaction to prepare a positive electrode active material precursor having an average particle diameter (D.sub.50) of 3 μm to 5 μm, wherein the transition metal aqueous solution including a nickel raw material, a cobalt raw material, and a manganese raw material, and wherein the initial reaction solution includes a metal additive, wherein the metal additive includes at least one element selected from the group consisting of Group 5 elements and Group 6 elements.

A chemical reaction device that supplies a raw material liquid into a solution and causes particles to precipitate in the solution is provided. The chemical reaction device includes an agitation tank configured to accommodate the solution, an impeller configured to agitate the solution, and a plurality of discharge parts configured to discharge the raw material liquid into the solution.

A chemical reaction device that supplies a raw material liquid into a solution and causes particles to precipitate in the solution is provided. The chemical reaction device includes an agitation tank configured to accommodate the solution, an impeller configured to agitate the solution, and a plurality of discharge parts configured to discharge the raw material liquid into the solution.

A method of recovering cobalt and nickel includes the steps of: adding alkaline to an acidic solution containing aluminum together with cobalt and nickel, adjusting pH of the acidic solution to 5 to 7, and converting the cobalt, the nickel and the aluminum into hydroxides thereof; recovering the hydroxides by solid-liquid separation, mixing the recovered hydroxides with an alkaline solution, and leaching aluminum contained in the hydroxides under a liquid condition of pH 8 or more; and recovering a cobalt hydroxide and a nickel hydroxide that aluminum is separated therefrom by solid-separation on a leachate.

A method of recovering cobalt and nickel includes the steps of: adding alkaline to an acidic solution containing aluminum together with cobalt and nickel, adjusting pH of the acidic solution to 5 to 7, and converting the cobalt, the nickel and the aluminum into hydroxides thereof; recovering the hydroxides by solid-liquid separation, mixing the recovered hydroxides with an alkaline solution, and leaching aluminum contained in the hydroxides under a liquid condition of pH 8 or more; and recovering a cobalt hydroxide and a nickel hydroxide that aluminum is separated therefrom by solid-separation on a leachate.

A secondary particle precursor, a positive electrode active material and a lithium secondary battery prepared from the same, and a method of preparing the same are disclosed herein. In some embodiments, a secondary particle precursor comprises one or more particles having a core and a shell surrounding the core, wherein a particle size (D50) of the secondary particle precursor is 6±2 μm, a particle size (D50) of the core is 1 to 5 μm, and the core has higher porosity than the shell. A positive electrode active material prepared using the secondary particle precursor has an increased press density and reduced cracking.

A secondary particle precursor, a positive electrode active material and a lithium secondary battery prepared from the same, and a method of preparing the same are disclosed herein. In some embodiments, a secondary particle precursor comprises one or more particles having a core and a shell surrounding the core, wherein a particle size (D50) of the secondary particle precursor is 6±2 μm, a particle size (D50) of the core is 1 to 5 μm, and the core has higher porosity than the shell. A positive electrode active material prepared using the secondary particle precursor has an increased press density and reduced cracking.

A positive electrode active material precursor is provided, which includes a transition metal hydroxide particle represented by Formula 1 and a cobalt oxide particle and a manganese oxide particle attached to the surface of the transition metal hydroxide particle. A preparation method thereof, a positive electrode active material prepared using the same, a positive electrode including the positive electrode active material, and a secondary battery including the positive electrode are also provided.