POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY
A positive electrode active material for a lithium secondary battery that can reduce the amount of the lithium compound to be eluted and improve the cycle characteristic of the lithium secondary battery is achieved. According to an embodiment of the present invention, the positive electrode active material for a lithium secondary battery has a layered structure, contains Li, the carbon element, and the sulfur element, and satisfies 0.11≤XPS(S)/XPS(C)≤1.50. XPS(S) and XPS(C) respectively represent the abundance ratios of the sulfur element and the carbon element measured by XPS.
1 . A positive electrode active material for a lithium secondary battery having a layered structure, comprising Li, a carbon element, and a sulfur element,
wherein a formula (1) below is satisfied,
0
.
1
1
≤
XPS
(
S
)
/
XPS
(
C
)
≤
1.5
(
1
)
(in the formula (1), XPS(S) represents an abundance ratio [at %] of the sulfur element obtained from a S2p spectrum measured by X-ray photoelectron spectroscopy, and XPS(C) represents an abundance ratio [at %] of the carbon element according to a peak having a peak top at 289.5±2.0 eV obtained from a C1s spectrum measured by X-ray photoelectron spectroscopy.)
2 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a formula (2) below is satisfied,
0
.
0
2
≤
XPS
(
S
)
/
XPS
(
Li
)
≤
0.4
(
2
)
(in the formula (2), XPS(S) represents the abundance ratio [at %] of the sulfur element, and XPS(Li) represents an abundance ratio [at %] of Li obtained from a Li1s spectrum measured by X-ray photoelectron spectroscopy.)
3 . The positive electrode active material for the lithium secondary battery according to claim 1 , further comprising Ni, and at least one element X selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Al, W, Mo, Nb, Zn, Sr, Sn, Zr, La, Ce, Ga, B, Si, and P,
wherein a molar ratio of Li, Ni, the element X, and the sulfur element satisfies a formula (3) below,
Li
:
Ni
:
X
:
S
=
a
:
(
1
-
b
)
:
b
:
c
(
3
)
(in the formula (3), a, b, and c satisfy 0.90≤a≤1.2, 0<b≤0.3, and 0.001≤c≤0.05, respectively.)
4 . The positive electrode active material for the lithium secondary battery according to claim 3 ,
wherein the element X is at least one element M selected from the group consisting of Al, Mg, Ca, Sr, Zr, Ti, Co, La, and Ce, and
a formula (4) below is satisfied,
0
.
0
3
≤
XPS
(
S
)
/
(
XPS
(
C
)
+
XPS
(
Li
)
+
XPS
(
Ni
)
+
X
P
S
(
M
)
)
≤
0
.
5
0
(
4
)
(in the formula (4), XPS(S) represents the abundance ratio [at %] of the sulfur element, XPS(C) represents the abundance ratio [at %] of the carbon element, XPS(Li) represents an abundance ratio [at %] of Li obtained from a Li1s spectrum measured by X-ray photoelectron spectroscopy, XPS(Ni) represents an abundance ratio [at %] of Ni obtained from a Ni2p3 spectrum measured by X-ray photoelectron spectroscopy, and XPS(M) represents an abundance ratio [at %] of the element M obtained from a spectrum peak of the element M measured by X-ray photoelectron spectroscopy.)
5 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a formula (5) below is satisfied,
1.
≤
XPS
(
S
)
≤
5.
(
5
)
(in the formula (5), XPS(S) represents the abundance ratio [at %] of the sulfur element.)
6 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a BET specific surface area is 0.1 m 2 /g or more and 3 m 2 /g or less.
7 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a 50% cumulative volume particle diameter D50 is 5 μm or more and 30 μm or less.
8 . A positive electrode for a lithium secondary battery, comprising:
the positive electrode active material for the lithium secondary battery according to claim 1 .
9 . A lithium secondary battery comprising:
The positive electrode for the lithium secondary battery according to claim 8 .
10 . The positive electrode active material for the lithium secondary battery according to claim 2 , further comprising Ni, and at least one element X selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Al, W, Mo, Nb, Zn, Sr, Sn, Zr, La, Ce, Ga, B, Si, and P,
wherein a molar ratio of Li, Ni, the element X, and the sulfur element satisfies a formula (3) below,
Li
:
Ni
:
X
:
S
=
a
:
(
1
-
b
)
:
b
:
c
(
3
)
(in the formula (3), a, b, and c satisfy 0.90≤a≤1.2, 0<b≤0.3 and 0.001≤c≤0.05 respectively.)
11 . The positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein the element X is at least one element M selected from the group consisting of Al, Mg, Ca, Sr, Zr, Ti, Co, La, and Ce, and
a formula (4) below is satisfied,
0
.
0
3
≤
XPS
(
S
)
/
(
XPS
(
C
)
+
XPS
(
Li
)
+
XPS
(
Ni
)
+
X
P
S
(
M
)
)
≤
0
.
5
0
(
4
)
(in the formula (4), XPS(S) represents the abundance ratio [at %] of the sulfur element, XPS(C) represents the abundance ratio [at %] of the carbon element, XPS(Li) represents an abundance ratio [at %] of Li obtained from a Li1s spectrum measured by X-ray photoelectron spectroscopy, XPS(Ni) represents an abundance ratio [at %] of Ni obtained from a Ni2p3 spectrum measured by X-ray photoelectron spectroscopy, and XPS(M) represents an abundance ratio [at %] of the element M obtained from a spectrum peak of the element M measured by X-ray photoelectron spectroscopy.)
12 . The positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein a formula (5) below is satisfied,
1.
≤
XPS
(
S
)
≤
5.
(
5
)
(in the formula (5), XPS(S) represents the abundance ratio [at %] of the sulfur element.)
13 . The positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein a BET specific surface area is 0.1 m 2 /g or more and 3 m 2 /g or less.
14 . The positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein a 50% cumulative volume particle diameter D50 is 5 μm or more and 30 μm or less.