CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME
A cathode active material for a lithium secondary battery comprises a lithium metal oxide that has a layered crystal structure and contains nickel and aluminum. The lithium metal oxide contains 70 mol % or more of nickel based on a total number of moles of all elements excluding lithium and oxygen. A ratio of lithium sites occupied by nickel instead of lithium among all lithium sites in the lithium metal oxide is in a range from 1% to 3.5%. A weight ratio of aluminum to nickel in the lithium metal oxide is in a range from 1/550 to 1/100.
1 . A cathode active material for a lithium secondary battery comprising a lithium metal oxide that has a layered crystal structure and contains nickel and aluminum,
wherein the lithium metal oxide contains 70 mol % or more of nickel based on a total number of moles of all elements excluding lithium and oxygen,
a ratio of lithium sites occupied by nickel instead of lithium among all lithium sites in the lithium metal oxide is in a range from 1% to 3.5%, and
a weight ratio of aluminum to nickel in the lithium metal oxide is in a range from 1/550 to 1/100.
2 . The cathode active material for a secondary battery of claim 1 , wherein the lithium metal oxide contains 80 mol % or more of nickel based on the total number of moles of all elements excluding lithium and oxygen.
3 . The cathode active material for a secondary battery of claim 1 , wherein the ratio of the lithium sites occupied by nickel instead of lithium among all lithium sites in the lithium metal oxide is in a range from 1% to 1.5%.
4 . The cathode active material for a secondary battery of claim 1 , wherein weight ratio of aluminum to nickel in the lithium metal oxide is in a range from 1/300 to 1/150.
5 . The cathode active material for a secondary battery of claim 1 , wherein the lithium metal oxide is represented by Chemical Formula 1:
Li a Ni x Al y M 1-x-y O z [Chemical Formula 1]
wherein, in Chemical Formula 1, M includes at least one of Co, Mn, Zr, Ti, Cr, B, Mg, Ba, Si, Y, W, La and Sr, 0.9<a≤1.2, 0.7≤x≤0.99, 2≤z≤2.02, and y is a value satisfying the weight ratio of aluminum to nickel.
6 . The cathode active material for a secondary battery of claim 5 , wherein M in Chemical Formula 1 includes at least one of Co, Mn, Ti and Zr.
7 . The cathode active material for a secondary battery of claim 1 , wherein the ratio of the lithium sites occupied by nickel instead of lithium among all lithium sites is obtained by an X-ray diffraction and a Rietveld refinement.
8 . The cathode active material for a secondary battery of claim 1 , wherein the lithium metal oxide has a secondary particle structure in which primary particles are aggregated, and a crystallite size of a (104) plane of the primary particles is 150 nm or less.
9 . A lithium secondary battery, comprising:
a cathode comprising the cathode active material for a secondary battery according to claim 1 ; and
an anode facing the cathode.