A lithium secondary battery comprising:
a battery case; and
5 an electrode assembly and an electrolyte accommodated in
the battery case,
wherein the electrode assembly comprises a positive
electrode,
the loading amount of a positive electrode active
material layer included in the positive electrode is 9.4 mg/cm2 10
or less,
the positive electrode active material layer comprises a
first positive electrode active material and a second positive
electrode active material, and
15 the second positive electrode active material has a
smaller average particle diameter D50 than the first positive
electrode active material.
2. The lithium secondary battery of claim 1, wherein the
20 first positive electrode active material comprises a compound
represented by Formula 1 below:
[Formula 1]
Li1+x[NiaCobM1cM2d]1-xO2-yX1y
wherein, in Formula 1 above, 0.8≤a≤0.95, 0≤b≤0.2, 0≤c≤0.2,
25 0≤d≤0.1, a+b+c+d=1, 0≤x≤0.3, 0≤y≤0.2, M1 is Mn, Al, or a
55
combination thereof, M2 is at least one metal element selected
from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, In,
Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and
X1 is at least one element selected from the group consisting
5 of F, Cl, Br, I, At, P, and S.
3. The lithium secondary battery of claim 1, wherein the
second positive electrode active material comprises a compound
represented by Formula 2 below:
10 [Formula 2]
Li1+z[NigCohM3iM4j]1-zO2-wX2w
wherein, in Formula 2 above, 0.85≤g≤0.95, 0≤h≤0.15,
0≤i≤0.15, 0≤j≤0.1, g+h+i+j=1, 0≤z≤0.3, 0≤w≤0.2, M3 is Mn, Al,
or a combination thereof, M4 is at least one metal element
15 selected from the group consisting of W, Cu, Fe, V, Cr, Ti,
Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B,
and Mo, and X2 is at least one element selected from the group
consisting of F, Cl, Br, I, At, P, and S.
20 4. The lithium secondary battery of claim 1, wherein the
first positive electrode active material comprises a lithium
nickel-based oxide containing at least 80 mol% of nickel with
respect to the total number of moles of transition metals
excluding lithium.
25
56
5. The lithium secondary battery of claim 1, wherein the
first positive electrode active material comprises a lithium
nickel-based oxide containing 80-85 mol% of nickel with respect
to the total number of moles of transition metals excluding
5 lithium.
6. The lithium secondary battery of claim 1, wherein the
second positive electrode active material comprises a lithium
nickel-based oxide containing at least 85 mol% of nickel with
10 respect to the total number of moles of transition metals
excluding lithium.
7. The lithium secondary battery of claim 1, wherein the
first positive electrode active material is a secondary
15 particle in which at least 50 primary particles are aggregated
with each other.
8. The lithium secondary battery of claim 1, wherein the
second positive electrode active material is a single particle
20 composed of one primary particle, a quasi-single particle which
is an aggregate of 2 to 30 primary particles, or a combination
thereof.
9. The lithium secondary battery of claim 1, wherein the
25 first positive electrode active material has an average
57
particle diameter D50 of 8 µm to 12 µm.
10. The lithium secondary battery of claim 1, wherein the
second positive electrode active material has an average
5 particle diameter D50 of 1 µm to 7 µm.
11. The lithium secondary battery of claim 1, wherein the
weight ratio of the first positive electrode active material
and the second positive electrode active material is 7:3 to
10 9:1.
12. The lithium secondary battery of claim 1, wherein the
electrode assembly comprises a negative electrode, and
the negative electrode comprises artificial graphite as
15 a negative electrode active material.