Positive electrode active materials for lithium secondary battery, method for preparing the same and lithium secondary battery comprising the same

A positive electrode active material for a lithium secondary battery, comprising a lithiated metal oxide represented by the formula:

• LiNi(1-x-y)CoxAlyO2, wherein 0.1<x≦0.15 and 0.03<y<0.1, and wherein:
• the lithiated metal oxide is a nickel-cobalt based metallic composite having a first crystalline phase that is stable at a first temperature, and a second crystalline phase that is stable at a second temperature, the first temperature being higher than the second temperature;
• the second crystalline phase has a 003 crystalline structure having an X-ray diffraction peak intensity found in the vicinity of an X-ray diffraction-scanning angle 2θ of about 18 degrees;
• the first crystalline phase has a 104 crystalline structure having an X-ray diffraction peak intensity found in the vicinity of an X-ray diffraction-scanning angle 2θ of about 45 degrees;
• an X-ray diffraction peak intensity ratio, of the first crystalline phase to the second crystalline phase, I(104)/I(003), is in the range of from 47.8% to 49.6%;
• and
• the lithiated metal oxide is formed by calcinating a lithiated metal oxide precursor at a temperature of about 750° C. to 900° C. for about 29 to about 40 hours.

A method of preparing a positive electrode active material for a lithium secondary battery, the method comprising:

• mixing a metal oxide represented by the formula Ni(1-x-y)CoxAlyO2, where 0.1<x≦0.15 and 0.03<y<0.1 with lithium hydrates to form a mixture;
• and
• calcinating the mixture at a temperature of about 750° C. to 900° C. for about 29 to about 40 hours to form the positive electrode active material,
• wherein the positive electrode active material has an X-ray diffraction peak intensity ratio, of a first crystalline phase to a second crystalline phase, I(104)/I(003), in the range of from 47.8% to 49.6%.

A lithium secondary battery, comprising:

• an electrode assembly having a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates;
• and
• a case for housing the electrode assembly,
• wherein the positive electrode plate comprises positive electrode collector coated with a lithiated metal oxide represented by the formula:
• LiNi(1-x-y)CoxAlyO2, wherein 0.1<x≦0.15 and 0.03<y<0.1, and wherein,
• the lithiated metal oxide is a nickel-cobalt based metallic composite having a first crystalline phase that is stable at a first temperature, and a second crystalline phase that is stable at a second temperature, the first temperature being higher than the second temperature,
• the second crystalline phase has a 003 crystalline structure having an X-ray diffraction peak intensity found in the vicinity of an X-ray diffraction-scanning angle 2θ of about 18 degrees,
• the first crystalline phase has a 104 crystalline structure having an X-ray diffraction peak intensity found in the vicinity of an X-ray diffraction-scanning angle 2θ of about 45 degrees,
• an X-ray diffraction peak intensity ratio, of the first crystalline phase to the second crystalline phase (I(104)/I(003)), is in the range of from 47.8% to 49.6%;
• and
• the lithiated metal oxide is formed by calcinating a lithiated metal oxide precursor at a temperature of about 750° C. to 900° C. for about 29 to about 40 hours.