Method of preparing positive electrode material for lithium secondary battery, positive electrode material for lithium secondary battery, and lithium secondary battery including the positive electrode material

A positive electrode material for a secondary battery, the positive electrode material comprising:

• lithium transition metal oxide particles represented by Chemical Formula 1;
• and
• an alumina coating layer formed on surfaces of the lithium transition metal oxide particles and including a γ-alumina phase in an amount of 95% or more,
• wherein a coverage of the alumina coating layer is in a range of 30% to 50% based on a total surface area of the lithium transition metal oxide particles,
• Li(1+a)(Ni(1−a−b−c)MnbCoc)On [Chemical Formula 1]
• where 0≦a≦0.1, 0≦b≦1, 0<c≦1, and n is an integer of 2 or 4.

A positive electrode for a secondary battery, the positive electrode comprising:

• a positive electrode material;
• and
• selectively a conductive agent, a binder, and a filler in addition to the positive electrode material,
• wherein the positive electrode material comprises lithium transition metal oxide particles represented by Chemical Formula 1;
• and
• an alumina coating layer formed on surfaces of the lithium transition metal oxide particles and including a γ-alumina phase in an amount of 95% or more,
• wherein a coverage of the alumina coating layer is in a range of 30% to 50% based on a total surface area of the lithium transition metal oxide particles,
• Li(1+a)(Ni(1−a−b−c)MnbCoc)On [Chemical Formula 1]
• where 0≦a≦0.1, 0≦b≦1, 0<c≦1, and n is an integer of 2 or 4.

A lithium secondary battery comprising:

• a positive electrode;
• a negative electrode;
• a separator disposed between the positive electrode and the negative electrode;
• and
• an electrolyte solution,
• wherein the positive electrode comprises a positive electrode material represented by Chemical Formula 2,
• Li(1+a)(Ni(1−a−b−c)MnbCocM′x)On [Chemical Formula 2]
• where 0≦a≦0.1, 0≦b≦1, 0<c≦1, 0<x≦1, n is an integer of 2 or 4, and M′ is Al2O3 having a gamma phase.

A method of preparing an alumina nanosol, the method comprising:

• mixing alumina nanopowder and a solvent to prepare an alumina nanopowder suspension;
• and
• dispersing the suspension with a bead mill to prepare an alumina nanosol,
• wherein the alumina nanosol comprises a γ-alumina phase in an amount of 99% of more.