Cathode active material for lithium secondary battery, and lithium secondary battery including same
View Patent ↗Proposed are a lithium secondary battery cathode active material doped with B and Sn and a lithium secondary battery including the cathode active material. The B and Sn doping enables a cathode capable of solving problems occurring in a high-nickel cathode, such as (1) an electrolyte side reaction on the surface, 2) a crystal structure collapse, 3) oxygen release, 4) inert Ni 4+ generation; 5) cation mixing, and 6) transition metal elution. This improves the life span of a lithium secondary battery.
1 . A rhombohedral structured cathode active material for a lithium secondary battery, the cathode active material comprising nickel, cobalt, and manganese, and being doped with a heteroatom,
wherein the cathode active material has a chemical formula of Li(Ni x Co y Mn 1-x-y )O 2 , wherein x is in a range of 0.40≤x≤0.96, and y is in a range of 0.01≤y≤0.30, and x+y<1 when the heteroatom is excluded,
wherein the heteroatom is at least one selected from among B and Sn, and
wherein the heteroatom is incorporated into the rhombohedral structure at a Wyckoff position selected from among 3b and 6c.
2 . The cathode active material of claim 1 , wherein a molar ratio of the lithium to the heteroatom is in a range of from 1:0.01 to 0.10.
3 . The cathode active material of claim 1 , wherein lattice parameters of the cathode active material satisfy 2.8700<a<2.8800 and 14.1800<c<14.1900.
4 . The cathode active material of claim 1 , wherein the lattice parameters of the cathode active material have values that make a c/a value fall within a range of 4.930 to 4.940.
5 . The cathode active material of claim 1 , comprising lithium layers and transition metal layers alternately stacked.
6 . The cathode active material of claim 5 , wherein the heteroatom is positioned in a tetrahedron site in the lithium layer or a tetrahedron site in the transition metal layer.
7 . The cathode active material of claim 6 , wherein the heteroatom is positioned to replace an octahedron site of a transition metal in the transition metal layer.
8 . A lithium secondary battery cathode comprising the cathode active material of claim 1 .
9 . A lithium secondary battery comprising the cathode active material of claim 1 .
10 . The lithium secondary battery of claim 9 , wherein the lithium secondary battery has a capacity retention rate of 80% or more calculated according to Equation 1 after 150 cycles of charging and discharging operations
Capacity retention rate (%) for n cycles of charging and discharging=(capacity for n-th discharging operation/capacity for first discharging operation)×100. [Equation 1]