Positive electrode plate, secondary battery and power consuming device

1. A positive electrode plate, comprising:

a positive electrode current collector;

a positive electrode film layer arranged on at least one surface of the positive electrode current collector; and

a conductive undercoat layer positioned between the positive electrode current collector and the positive electrode film layer;

wherein:

the positive electrode film layer comprises a positive electrode active material comprising an inner core and a shell coating the inner core, wherein:

the inner core has a chemical formula of Li 1+x Mn 1−y A y P 1−z R z O 4 in which x is any value in a range of −0.100 to 0.100, y is any value in a range of 0.001 to 0.500, z is any value in a range of 0.001 to 0.100, A is one or more selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, R is one or more selected from the group consisting of B, Si, N, and S, and the values of x, y, and z satisfy that the entire inner core be electrically neutral; and

the shell comprises a first coating layer coating the inner core, a second coating layer coating the first coating layer, and a third coating layer coating the second coating layer, wherein:

the first coating layer comprises crystalline pyrophosphate Li a MP 2 O 7 or M b (P 2 O 7 ) c in which 0≤a≤2, 1≤b≤4, and 1≤c≤6, with the values of a, b, and c satisfying that the crystalline pyrophosphate Li a MP 2 O 7 or M b (P 2 O 7 ) c be electrically neutral, and M in each of the crystalline pyrophosphates Li a MP 2 O 7 and M b (P 2 O 7 ) c is independently one or more selected from the group consisting of Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al;

the second coating layer comprises crystalline phosphate XPO 4 in which X is one or more selected from the group consisting of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; and

the third coating layer is carbon; and

the conductive undercoat layer comprises a polymer, an aqueous binder, and a conductive agent, wherein the polymer comprises:

a first monomeric unit represented by formula 1;

a second monomeric unit including at least one selected from the group consisting of a monomeric unit represented by formula 2 and a monomeric unit represented by formula 3;

a third monomeric unit including at least one selected from the group consisting of a monomeric unit represented by formula 4 and a monomeric unit represented by formula 5; and

a fourth monomeric unit represented by formula 6, in which:

R 1 , R 2 , and R 3 each independently representing one or more of H, carboxyl, an ester group, and substituted or unsubstituted C1-C10 alkyl, C1-C10 alkoxy, C2-C10 alkenyl, and C6-C10 aryl, and

R 4 represents one or more of H and substituted or unsubstituted C1-C10 alkyl, C1-C10 alkoxy, C2-C10 alkenyl, and C6-C10 aryl;

2. The positive electrode plate according to claim 1 , wherein based on a total mass of the polymer:

a mass percentage content of the first monomeric unit M1 is in a range of 10-55%; or

a mass percentage content of the second monomeric unit M2 is in a range of 40-80%; or

a mass percentage content of the third monomeric unit M3 is greater than 0 and less than or equal to 10%; or

a mass percentage content of the fourth monomeric unit M4 is greater than 0 and less than or equal to 10%.

3. The positive electrode plate according to claim 2 , wherein M3/(M2+M3) is greater than 0 and less than or equal to 5%.

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

the polymer includes one or more selected from the group consisting of hydrogenated acrylonitrile-butadiene rubber and hydrogenated carboxylated acrylonitrile-butadiene rubber; or

a weight-average molecular weight of the polymer is in a range of 50,000 to 1,500,000.

5. The positive electrode plate according to claim 1 , wherein:

the aqueous binder includes one or more selected from the group consisting of an aqueous polyacrylic resin and derivatives of the aqueous polyacrylic resin, an aqueous amino-modified polypropylene resin and derivatives of the aqueous amino-modified polypropylene resin, and polyvinyl alcohol and derivatives of the polyvinyl alcohol; or

a weight-average molecular weight of the aqueous binder is in a range of 200,000-1,500,000.

6. The positive electrode plate according to claim 1 , wherein the conductive agent includes one or more selected from the group consisting of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

7. The positive electrode plate according to claim 1 , wherein based on a total mass of the conductive undercoat layer:

a mass percentage content of the polymer is in a range of 5-20%; or

a mass percentage content of the aqueous binder is in a range of 30-80%; or

a mass percentage content of the conductive agent is in a range of 10-50%.

8. The positive electrode plate according to claim 1 , wherein a thickness of the conductive undercoat layer is in a range of 1-20 μm.

9. The positive electrode plate according to claim 1 , wherein the positive electrode film layer further comprises one or more selected from the group consisting of an infiltration agent and a dispersing agent.

10. The positive electrode plate according to claim 9 , wherein a surface tension of the infiltration agent is in a range of 20-40 mN/m.

11. The positive electrode plate according to claim 9 , wherein the infiltration agent includes one or more selected from the group consisting of a small molecular organic solvent and a low-molecular-weight polymer.

12. The positive electrode plate according to claim 9 , wherein:

the polymer is a first polymer; and

the dispersing agent comprises a second polymer, and the second polymer comprises:

a fifth monomeric unit represented by formula 7;

a sixth monomeric unit including at least one selected from the group consisting of a monomeric unit represented by formula 8 and a monomeric unit represented by formula 9; and

a seventh monomeric unit including at least one selected from the group consisting of a monomeric unit represented by formula 10 and a monomeric unit represented by formula 11;

13. The positive electrode plate according to claim 12 , wherein based on a total mass of the second polymer:

a mass percentage content of the fifth monomeric unit M5 is in a range of 10-55%; or

a mass percentage content of the sixth monomeric unit M6 is in a range of 40-80%; or

a mass percentage content of the seventh monomeric unit M7 is greater than 0 and less than or equal to 10%.

14. The positive electrode plate according to claim 13 , wherein M7/(M6+M7) is greater than 0 and less than or equal to 5%.

15. The positive electrode plate according to claim 12 , wherein:

the second polymer is hydrogenated acrylonitrile-butadiene rubber; or

a weight-average molecular weight of the second polymer is in a range of 50,000 to 500,000.

16. The positive electrode plate according to claim 12 , wherein in the positive electrode plate, a mass ratio of the first polymer to the second polymer is in a range of 1.5-5.

17. The positive electrode plate according to claim 9 , wherein based on a total mass of the positive electrode film layer:

a mass percentage content of the dispersing agent Y1 is in a range of 0.05-1%; or

a mass percentage content of the infiltration agent Y2 is in a range of 0.05-2%.

18. The positive electrode plate according to claim 17 , wherein Y1/Y2 is in a range of 0.05-20.

19. The positive electrode plate according to claim 1 , wherein:

the crystalline pyrophosphate in the first coating layer has an interplanar spacing range of 0.293-0.470 nm and an included angle range of 18.00°-32.00° for the crystal orientation (111); and

the crystalline phosphate in the second coating layer has an interplanar spacing range of 0.244-0.425 nm and an included angle range of 20.00°-37.00° for the crystal orientation (111).

20. The positive electrode plate according to claim 1 , wherein:

in the inner core, a ratio of y to 1-y is in a range of 1:10 to 1:1; or

in the inner core, a ratio of z to 1-z is in a range of 1:9 to 1:999.