There are provided processes for preparing a metal hydroxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum, the process comprising: reacting a metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum with lithium hydroxide, sodium hydroxide and/or potassium hydroxide and optionally a chelating agent in order to obtain a solid comprising the metal hydroxide and a liquid comprising lithium sulfate, sodium sulfate and/or potassium sulfate; separating the liquid and the solid from one another to obtain the metal hydroxide; submitting the liquid comprising lithium sulfate, sodium sulfate and/or potassium sulfate to an electromembrane process for converting the lithium sulfate, sodium sulfate and/or potassium sulfate into lithium hydroxide, sodium hydroxide and/or potassium hydroxide respectively; reusing the sodium hydroxide obtained by the electromembrane process for reacting with the metal sulfate; and reusing the lithium hydroxide obtained by the electromembrane process for reacting with the metal sulfate and/or with the metal hydroxide.

There are provided processes for preparing a metal hydroxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum, the process comprising: reacting a metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum with lithium hydroxide, sodium hydroxide and/or potassium hydroxide and optionally a chelating agent in order to obtain a solid comprising the metal hydroxide and a liquid comprising lithium sulfate, sodium sulfate and/or potassium sulfate; separating the liquid and the solid from one another to obtain the metal hydroxide; submitting the liquid comprising lithium sulfate, sodium sulfate and/or potassium sulfate to an electromembrane process for converting the lithium sulfate, sodium sulfate and/or potassium sulfate into lithium hydroxide, sodium hydroxide and/or potassium hydroxide respectively; reusing the sodium hydroxide obtained by the electromembrane process for reacting with the metal sulfate; and reusing the lithium hydroxide obtained by the electromembrane process for reacting with the metal sulfate and/or with the metal hydroxide.

Provided are a positive electrode active material that can provide a secondary battery extremely excellent in output characteristics and having sufficient volume energy density, a nickel-manganese composite hydroxide as a precursor thereof, and methods for producing these. A nickel-manganese composite hydroxide is represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α and contains a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a (001) plane of at least 0.40° and has an average degree of sparsity/density represented by [(a void area within the secondary particle/a cross section of the secondary particle)×100] (%) falling within a range of greater than 22% and up to 40%.

Provided are a positive electrode active material that can provide a secondary battery extremely excellent in output characteristics and having sufficient volume energy density, a nickel-manganese composite hydroxide as a precursor thereof, and methods for producing these. A nickel-manganese composite hydroxide is represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α and contains a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a (001) plane of at least 0.40° and has an average degree of sparsity/density represented by [(a void area within the secondary particle/a cross section of the secondary particle)×100] (%) falling within a range of greater than 22% and up to 40%.

Ternary precursor particles used for a lithium-ion battery, the ternary precursor particles having a Ni.sub.xCo.sub.yMn.sub.z(OH).sub.2, wherein, x+y+z=1, 0<x<1, 0<y<1, 0<z<1; each ternary precursor particle is a spheroidal structure, and comprises a shell, a transition layer and a particle core; the shell is a dense structure, the particle core is a porous structure, the transition layer surrounds the particle core and is sandwiched between the shell and the particle core; each ternary precursor particle is a mixture formed by mixing the nickel hydroxide, the cobalt hydroxide and the manganese hydroxide at the atomic level; a crystallinity of the shell is greater than a crystallinity of the transition layer, and the crystallinity of the transition layer is greater than a crystallinity of the particle core.

Ternary precursor particles used for a lithium-ion battery, the ternary precursor particles having a Ni.sub.xCo.sub.yMn.sub.z(OH).sub.2, wherein, x+y+z=1, 0<x<1, 0<y<1, 0<z<1; each ternary precursor particle is a spheroidal structure, and comprises a shell, a transition layer and a particle core; the shell is a dense structure, the particle core is a porous structure, the transition layer surrounds the particle core and is sandwiched between the shell and the particle core; each ternary precursor particle is a mixture formed by mixing the nickel hydroxide, the cobalt hydroxide and the manganese hydroxide at the atomic level; a crystallinity of the shell is greater than a crystallinity of the transition layer, and the crystallinity of the transition layer is greater than a crystallinity of the particle core.

A nickel (Ni)-based active material for a lithium secondary battery, a preparing method thereof, and a lithium secondary battery including a positive electrode including the same. The Ni-based active material includes a secondary particle including a plurality of particulate structures, wherein each of the particulate structures includes a porous core portion and a shell portion including primary particles radially arranged on the porous core portion, and lithium phosphate is in the porous core portion, between the plurality of primary particles, and on the surface of the secondary particle. The Ni-based active material includes a porous inner portion including the porous core portion; and an outer portion comprising the the shell portion, and the Ni-based active material includes the porous inner portion having closed pores and the outer portion, wherein the porous inner portion has a density less than that of the outer portion, and the Ni-based active material has a net density of 4.7 g/cc or less.

A nickel (Ni)-based active material for a lithium secondary battery, a preparing method thereof, and a lithium secondary battery including a positive electrode including the same. The Ni-based active material includes a secondary particle including a plurality of particulate structures, wherein each of the particulate structures includes a porous core portion and a shell portion including primary particles radially arranged on the porous core portion, and lithium phosphate is in the porous core portion, between the plurality of primary particles, and on the surface of the secondary particle. The Ni-based active material includes a porous inner portion including the porous core portion; and an outer portion comprising the the shell portion, and the Ni-based active material includes the porous inner portion having closed pores and the outer portion, wherein the porous inner portion has a density less than that of the outer portion, and the Ni-based active material has a net density of 4.7 g/cc or less.

Provided are a positive electrode active material that can provide a secondary battery extremely excellent in output characteristics and having sufficient volume energy density, a nickel-manganese composite hydroxide as a precursor thereof, and methods for producing these. A nickel-manganese composite hydroxide is represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α, and contains a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a (001) plane of at least 0.40° and has an average degree of sparsity/density represented by [(a void area within the secondary particle/a cross section of the secondary particle)×100] (%) falling within a range of greater than 22% and up to 40%.

Provided are a positive electrode active material that can provide a secondary battery extremely excellent in output characteristics and having sufficient volume energy density, a nickel-manganese composite hydroxide as a precursor thereof, and methods for producing these. A nickel-manganese composite hydroxide is represented by General Formula (1): Ni.sub.xMn.sub.yM.sub.z(OH).sub.2+α, and contains a secondary particle formed of a plurality of flocculated primary particles. The nickel-manganese composite hydroxide has a half width of a (001) plane of at least 0.40° and has an average degree of sparsity/density represented by [(a void area within the secondary particle/a cross section of the secondary particle)×100] (%) falling within a range of greater than 22% and up to 40%.