Positive electrode active material for lithium secondary battery, positive electrode, and secondary battery
Provided is a positive electrode active material which is useful for a lithium secondary battery having a battery resistance lower than that of the conventional positive electrode active material below freezing point. The positive electrode active material for a lithium secondary battery contains at least one element selected from a group consisting of nickel, cobalt and manganese, the positive electrode active material having a layered structure and satisfying all of the following requirements (1) to (3): (1) a primary particle size is 0.1 μm to 1 μm and a secondary particle size is 1 μm to 10 μm; (2) in an X-ray powder diffraction measurement using CuKα radiation, a crystallite size in the peak within 2θ=18.7±1° is 100 Å to 1200 Å and a crystallite size in the peak within 2θ=44.6±1° is 100 Å to 700 Å; and (3) in a pore distribution obtained by a mercury intrusion method, a pore peak exists in a range where the pore size is 10 nm to 200 nm and a pore volume in the said range is 0.01 cm 3 /g to 0.05 cm 3 /g.
1. A positive electrode active material for a lithium secondary battery, the positive electrode active material having a layered structure and satisfying all of the following requirements (1) to (3):
(1) a primary particle size is greater than or equal to 0.1 μm and less than or equal to 0.49 μm and a secondary particle size is greater than or equal to 1 μm and less than or equal to 10 μm;
(2) in an X-ray powder diffraction measurement using CuKα radiation,
a crystallite size in the peak within 2θ=18.7 ±1° is 100 Å to 1200 Å and
a crystallite size in the peak within 2θ=44.6 ±1° is 100 Å to 700 Å; and
(3) in a pore distribution obtained by a mercury intrusion method,
a pore peak exists in a range where the pore size is 10 nm to 200 nm and a pore volume in the said range is 0.01 cm 3 /g to 0.05 cm 3 /g,
wherein the positive electrode active material is represented by the general formula Li a M 1 s M 2 1-s O 2 , where M 1 represents an essential metal comprising one or more of Ni, Co and Mn, M 2 represents one or more optional metal among Fe, Cu, Ti, Mg, Al, W, Zn, Zr, Ga and V, “a” is 0.9≤a≤1.2, and “s” is 0.9 ≤s≤1.
2. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the secondary particle size is greater than or equal to 1 μm and less than or equal to 5 μm.
3. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material has a BET specific surface area between about 0.8 m 2 /g to about 4 m 2 /g.
4. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material has a void in the secondary particle.
5. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material is represented by the general formula Li a Ni x Co y Mn z O 2 ,
where
0.9≤a≤1.2,
0.3<x<1,
0≤y<0.4,
0<z<0.4, and
x+y+z=1.
6. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the primary particle size is greater than or equal to 0.19 μm and less than or equal to 0.49 μm.
7. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the one or more optional metal comprises W.
8. A positive electrode for a lithium secondary battery having a positive electrode active material, the positive electrode active material having a layered structure and satisfying all of the following requirements (1) to (3):
(1) a primary particle size is greater than or equal to 0.1 μm and less than or equal to 0.49 μm and a secondary particle size is greater than or equal to 1 μm and less than or equal to 10 μm;
(2) in an X-ray powder diffraction measurement using CuK αradiation,
a crystallite size in the peak within 2θ=18.7 ±1° is 100 Å to 1200 Å and
a crystallite size in the peak within 2θ=44.6 ±1° is 100 Å to 700 Å; and
(3) in a pore distribution obtained by a mercury intrusion method,
a pore peak exists in a range where the pore size is 10 nm to 200 nm and a pore volume in the said range is 0.01 cm 3 /g to 0.05 cm 3 /g,
wherein the positive electrode active material is represented by the general formula Li a M 1 s M 2 1-s O 2 , where M 1 represents an essential metal comprising one or more of Ni, Co and Mn, M 2 represents one or more optional metal among Fe, Cu, Ti, Mg, Al, W, Zn, Zr, Ga and V, “a” is 0.9a1.2, and “s” is 0.9≤s≤1.
9. The positive electrode according to claim 8 , wherein the secondary particle size is greater than or equal to 1 μm and less than or equal to 5 μm.
10. The positive electrode according to claim 8 , wherein the positive electrode active material has a BET specific surface area between about 0.8 m 2 /g to about 4 m 2 /g.
11. The positive electrode according to claim 8 , wherein the positive electrode active material has a void in the secondary particle.
12. The positive electrode according to claim 8 , wherein the positive electrode active material is represented by the general formula Li a Ni x Co y Mn z O 2 ,
where
0.9≤a≤1.2,
0.3<x<1,
0≤y<0.4,
0<z<0.4, and
x+y+z=1.
13. The positive electrode for a lithium secondary battery according to claim 8 , wherein the one or more optional metal comprises W.
14. A lithium secondary battery having a positive electrode for a lithium secondary battery according to claim 8 .