Positive electrode plate, method for preparing the same and lithium-ion secondary battery

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, the positive electrode film comprises a positive active material which is a lithium manganese-based positive active material,

wherein

the lithium manganese-based positive active material comprises a first lithium manganese-based positive active material according to formula (1-1),

Li 1+x Mn α Ni β M 1-α-β O 2-y A y   formula (1-1)

in which −0.1≤x≤0.2, 0<α<1, 0.5≤β<1, 0<α+β<1, 0≤y<0.2, and M comprises one or more of Co, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, A comprises one or more of S, N, F, Cl, Br and I; and

the positive electrode plate satisfies

ρ

sum

ρ

97.5

-

a

≤

3

,

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 %;

wherein a 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.

2. The positive electrode plate according to claim 1 , wherein the positive electrode plate satisfies

10

-

10

≤

ρ

sum

ρ

97.5

-

a

≤

3.

3. The positive electrode plate according to claim 1 , wherein the positive electrode plate satisfies

0.048

≤

ρ

sum

ρ

97.5

-

a

≤

2.684

.

4. The positive electrode plate according to claim 1 , wherein the positive electrode plate satisfies

1.017

≤

ρ

sum

ρ

97.5

-

a

≤

2.015

.

5. The positive electrode plate according to claim 1 , wherein positive electrode plate has a volume resistivity ρ sum ≤450 kΩ·cm.

6. The positive electrode plate according to claim 1 , wherein positive electrode plate has a volume resistivity ρ sum ≤160 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 450 kΩ·cm.

8. 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 90.1 to 280.3 kΩ·cm.

9. 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.

10. The positive electrode plate according to claim 1 , wherein the positive active material is present in a mass percentage from 90 wt % to 96 wt % in the positive electrode film.

11. The positive electrode plate according to claim 1 , wherein the lithium manganese-based positive active material further comprises a second lithium manganese-based positive active material according to formula (2),

Li 1+z Mn e N 2-e O 4-d B d   formula (2)

in which, −0.1≤z≤0.2, 0<e≤2, 0≤d<1, and N comprises one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, B comprises one or more of S, N, F, Cl, Br and I.

12. The positive electrode plate according to claim 1 , wherein a 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: 14.70≤ω·ρ/100≤159.16.

13. The positive electrode plate according to claim 1 , wherein the positive electrode active material is a secondary particle aggregated by primary particles.

14. The positive electrode plate according to claim 1 , wherein the positive active material has an average particle diameter Dv50 of from 1 μm to 20 μm, and the positive active material has a BET specific surface area of from 0.3 m 2 /g to 1.5 m 2 /g.

15. The positive electrode plate according to claim 1 , wherein the positive electrode plate has a compaction density of from 3.1 g/cm 3 to 3.65 g/cm 3 .

16. A lithium-ion secondary battery comprising 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 .

17. An electric vehicle comprising the lithium-ion secondary battery according to claim 16 .

18. A method for preparing a positive electrode plate, comprising:

providing a positive active material which is a lithium manganese-based positive active material, wherein the lithium manganese-based positive active material comprises a first lithium manganese-based positive active material represented by formula (1-1),

Li 1+x Mn α Ni β M 1-α-β O 2-y A y   formula (1-1)

in which −0.1≤x≤0.2, 0<α<1, 0.5≤β<1, 0<α+β<1, 0≤y<0.2, and M comprises one or more of Co, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, A comprises one or more of S, N, F, Cl, Br and I; and

mixing the positive active material, a conductive agent, a binder, and a solvent to obtain a positive electrode slurry;

applying 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

ρ

sum

ρ

97.5

-

a

≤

3

,

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 %.

19. The method according to claim 18 , wherein the lithium manganese-based positive active material further comprises a second lithium manganese-based positive active material represented by formula (2),

Li 1+z Mn e N 2-e O 4-d B d   formula (2)

in which −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;

wherein mixing the positive active material, a conductive agent, a binder, and a solvent to obtain a positive electrode slurry comprises the following steps:

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 the positive electrode slurry.