Composite cathode active material, cathode and lithium battery including the composite cathode active material, and method of preparing the composite cathode active material

A composite cathode active material comprising:

• a primary particle comprising
• a core comprising a first lithium transition metal oxide represented by Formula 1,
• a shell on a surface of the core, the shell having a spinel crystal structure and comprising a dopant, and
• a polyhedral pore extending from a first surface to an opposite second surface of the polyhedral primary particle:
• LiaMO2 Formula 1
• wherein, in Formula 1, M comprises Ni and at least one non-nickel Group 4 to Group 13 element, wherein a content of Ni is about 70 mole percent or greater, based on a total content of M, and 0.9≤a≤1.1,
• wherein the first lithium transition metal oxide has a layered crystal structure belonging to an R3m space group;
• and
• wherein a sum of peak intensities defined as
• (Dopant peak intensity+Co peak intensity)/(Mn peak intensity)
• before and after Ar+ sputtering when analyzed by surface X-ray photoelectron spectroscopy of the composite cathode active material is about 5 or greater.

A method of preparing a composite cathode active material, the method comprising:

• mixing a metal-organic framework and a first lithium transition metal oxide represented by Formula 1 to prepare a mixture
• LiaMO2 Formula 1
• wherein, in Formula 1,
• M comprises Ni and at least one non-nickel Group 4 to Group 13 element,
• a content of Ni is about 70 mole percent or greater, based on a total content of M, and
• 0.9≤a≤1.1, and
• wherein the first lithium transition metal oxide has a layered crystal structure belonging to an R3m space group;
• and
• thermally treating the mixture under an oxidizing atmosphere at about 650° C. to about 800° C. for about 3 hours to about 20 hours to prepare the composite cathode active material,
• wherein the composite cathode active material comprises a polyhedral primary article comprising:
• a core comprising the first lithium transition metal oxide,
• a shell on a surface of the core, the shell having a spinel crystal structure and comprising a dopant, and
• a polyhedral pore extending from a first surface to an opposite second surface of the polyhedral primary particle.