Positive electrode plate, method for preparing the same and lithium-ion secondary battery
View Patent ↗The present application discloses a positive electrode plate, a preparation method thereof, and a lithium-ion secondary battery, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film includes a positive active material which is a lithium manganese-based positive active material; and wherein the volume resistivity ρ sum of the positive electrode plate, the powder volume resistivity ρ of the positive active material under a pressure of 20 MPa and the mass percentage a of the positive active material in the positive electrode film satisfy ρ sum /ρ 97.5-a ≤3. The positive electrode plate provided in the present application enables the lithium-ion secondary battery to simultaneously have higher safety performance, rate performance and cycle performance.
1. A positive electrode plate, including a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film includes a positive active material which is a lithium manganese-based positive active material,
wherein the positive electrode plate satisfies formula (1),
ρ
sum
ρ
97.5
-
a
≤
3
formula
(
1
)
in which p sum is volume resistivity of the positive electrode plate, in kΩ·cm; ρ is powder volume resistivity of the positive active material under a pressure of 20 MPa, in kΩ·cm; a is mass percentage of the positive active material in the positive electrode film, in wt %.
2. The positive electrode plate according to claim 1 , wherein the positive electrode plate satisfies formula (2),
10
-
10
≤
ρ
sum
ρ
97.5
-
a
≤
3.
formula
(
2
)
3. The positive electrode plate according to claim 1 , wherein positive electrode plate has a volume resistivity ρ sum ≤450 kΩ·cm.
4. The positive electrode plate according to claim 1 , wherein positive electrode plate has a volume resistivity ρ sum ≤300 kΩ·cm.
5. The positive electrode plate according to claim 1 , wherein positive electrode plate has a volume resistivity ρ sum <160 kΩ·cm.
6. The positive electrode plate according to claim 1 , wherein the positive active material has a powder volume resistivity ρ under a pressure of 20 MPa between 0 to 450 kΩ·cm.
7. The positive electrode plate according to claim 1 , wherein the positive active material has a powder volume resistivity ρ under a pressure of 20 MPa between 0 to 400 kΩ·cm.
8. The positive electrode plate according to claim 1 , wherein the positive active material is present in a mass percentage from 80 wt % to 96.5 wt % in the positive electrode film.
9. The positive electrode plate according to claim 1 , wherein the lithium manganese-based positive active material includes a first lithium manganese-based positive active material according to formula (3) and a second lithium manganese-based positive active material according to formula (4),
Li 1+x Mn a Ni b M 1-a-b O 2-y A y formula (3)
Li 1+z Mn e N 2-e O 4-d B d formula (4)
where in the formula (3), −0.1 x 0.2, 0<a<1, 0 b<1, 0<a+b<1, 0 y<0.2, and M includes one or more of Co, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, A includes one or more of S, N, F, Cl, Br and I; and
in the formula (4), −0.1 z 0.2, 0<e 2, 0 d<1, and N includes one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, B includes one or more of S, N, F, Cl, Br and I.
10. The positive electrode plate according to claim 1 , wherein the mass percentage ω of Mn in the positive active material and the powder volume resistivity ρ of the positive active material under a pressure of 20 MPa satisfy the following relationship: 3≤ω·ρ/100≤200.
11. The positive electrode plate according to claim 1 , wherein the positive active material has an average particle diameter Dv50 from 1 μm to 20 μm, and the positive active material has a BET specific surface area from 0.3 m 2 /g to 1.5 m 2 /g.
12. The positive electrode plate according to claim 1 , wherein the positive electrode plate has a packing density from 3.1 g/cm 3 to 3.65 g/cm 3 .
13. A lithium-ion secondary battery including a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein the positive electrode plate is the positive electrode plate according to claim 1 .
14. A method for preparing a positive electrode plate, comprising:
mixing a first lithium manganese-based positive active material, a conductive agent, a binder, and a solvent to obtain a pre-slurry;
mixing a second lithium manganese-based positive active material with the pre-slurry to obtain a positive electrode slurry;
coating the positive electrode slurry on at least one surface of a positive electrode current collector to form a positive electrode film, thereby obtaining a positive electrode plate, wherein the positive electrode plate satisfies formula (1),
ρ
sum
ρ
97.5
-
a
≤
3
formula
(
1
)
in which ρ sum is volume resistivity of the positive electrode plate, in kΩ·cm; ρ is powder volume resistivity of the positive active material under a pressure of 20 MPa, in kΩ·cm; a is mass percentage of the positive active material in the positive electrode film, in wt %; and
wherein the first lithium manganese-based positive active material is a compound represented by formula (3), and the second lithium manganese-based positive active material is a compound represented by formula (4),
Li 1+x Mn a Ni b M 1-a-b O 2-y A y formula (3)
Li 1+z Mn e N 2-e O 4-d B d formula (4)
where in the formula (3), −0.1 x 0.2, 0<a<1, 0 b<1, 0<a+b<1, 0 y<0.2, and M includes one or more of Co, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, A includes one or more of S, N, F, Cl, Br and I; and
in the formula (4), −0.1 z 0.2, 0<e 2, 0 d<1, and N includes one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, B includes one or more of S, N, F, Cl, Br and I.