Positive Electrode Sheet, Electrode Assembly, Battery Cell, Battery, and Electrical Device

1 . A positive electrode sheet, comprising

a positive electrode current collector; and

a positive electrode active material layer;

wherein:

the positive electrode active material layer is disposed on at least one side of the positive electrode current collector in a thickness direction;

the positive electrode sheet is provided with a straight portion and to-be-bent portions;

a thickening layer is disposed on at least one side of the positive electrode current collector of at least a part of the to-be-bent portions in the thickness direction, the thickening layer is disposed between the positive electrode current collector and the positive electrode active material layer, the positive electrode active material layer covering a surface of the thickening layer is a first positive electrode active material layer, and the positive electrode active material layer located in the straight portion and connected to the first positive electrode active material layer is a second positive electrode active material layer; and

a ratio of a thickness of the first positive electrode active material layer to a thickness of the second positive electrode active material layer is 20-80%.

2 . The positive electrode sheet according to claim 1 , wherein a ratio of the thickness of the second positive electrode active material layer to a sum of the thickness of the first positive electrode active material layer and the thickening layer is 1:(0.9-1.1).

3 . The positive electrode sheet according to claim 1 , wherein the positive electrode active material layer is disposed on both sides of the positive electrode current collector in the thickness direction.

4 . The positive electrode sheet according to claim 1 , wherein a plurality of hole regions are distributed in the thickening layer, and the hole region is provided therein with a positive electrode active material for connecting the positive electrode current collector and the first positive electrode active material layer.

5 . The positive electrode sheet according to claim 4 , wherein a surface where the thickening layer is bonded to the first positive electrode active material layer is a bonding surface, and a ratio of an area of the plurality of hole regions distributed on the bonding surface to an area of the bonding surface is 20% to 50%.

6 . The positive electrode sheet according to claim 4 , wherein holes penetrating the thickening layer are distributed in the hole region of the thickening layer, the holes are filled with the positive electrode active material, and the holes have an inner diameter of 100-5000 μm.

7 . The positive electrode sheet according to claim 1 , wherein the thickening layer is made of an insulating material.

8 . The positive electrode sheet according to claim 1 , wherein:

a material of the thickening layer comprises acrylic resin and/or polyolefin resin;

the acrylic resin comprises any one or more of acrylic acid-methacrylic acid copolymer, acrylic acid-butenoic acid copolymer, acrylic acid-itaconic acid copolymer, acrylic acid-maleic acid copolymer, acrylic acid-methyl methacrylate copolymer, acrylic acid-ethyl methacrylate copolymer, acrylic acid-n-butyl methacrylate copolymer, and acrylic acid-isobutyl methacrylate copolymer; and

the polyolefin resin comprises any one or more of polypropylene, polyethylene, polybutadiene rubber, ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin, poly(butadiene-acrylonitrile), and styrene-maleic anhydride copolymer.

9 . The positive electrode sheet according to claim 1 , wherein the thickening layer is bonded to the positive electrode current collector and the first positive electrode active material layer separately.

10 . An electrode assembly, comprising:

a negative electrode sheet; and

the positive electrode sheet according to claim 1 ;

wherein:

the positive electrode sheet and the negative electrode sheet are wound or folded to form bent regions and a straight region, and the straight region is connected to the bent regions; and

the to-be-bent portions are wound or folded to form bent portions, the bent portions are located in the bent regions, and a straight portion is located in the straight region.

11 . The electrode assembly according to claim 10 , wherein the positive electrode sheet and the negative electrode sheet are wound to form a wound structure, the positive electrode current collector of the bent portion has an inner side and an outer side, and the thickening layer is disposed on the inner side of the positive electrode current collector of at least a part of the bent portions.

12 . The electrode assembly according to claim 10 , wherein the positive electrode sheet and the negative electrode sheet are wound to form a wound structure, the positive electrode sheet has a first bent portion on an innermost side, and the thickening layer is disposed on at least one side of the positive electrode current collector of the first bent portion in the thickness direction.

13 . The electrode assembly according to claim 12 , wherein the positive electrode current collector of the first bent portion is provided with an inner side and an outer side, and the thickening layer is disposed on the inner side of the positive electrode current collector of the first bent portion.

14 . The electrode assembly according to claim 12 , wherein in a winding direction, the positive electrode sheet has a second bent portion adjacent to the first bent portion, and the thickening layer is disposed on at least one side of the positive electrode current collector of the second bent portion in the thickness direction.

15 . The electrode assembly according to claim 14 , wherein the positive electrode current collector of the second bent portion is provided with an inner side and an outer side, and the thickening layer is disposed on the inner side of the positive electrode current collector of the second bent portion.

16 . The electrode assembly according to claim 14 , wherein in the winding direction, the positive electrode sheet has a third bent portion adjacent to the second bent portion, and the thickening layer is disposed on at least one side of the positive electrode current collector of the third bent portion in the thickness direction.

17 . The electrode assembly according to claim 16 , wherein the positive electrode current collector of the third bent portion is provided with an inner side and an outer side, and the thickening layer is disposed on the inner side of the positive electrode current collector of the third bent portion.

18 . The electrode assembly according to claim 16 , wherein in the winding direction, the positive electrode sheet has a fourth bent portion adjacent to the third bent portion, and the thickening layer is disposed on at least one side of the positive electrode current collector of the fourth bent portion in the thickness direction.

19 . The electrode assembly according to claim 18 , wherein the positive electrode current collector of the fourth bent portion is provided with an inner side and an outer side, and the thickening layer is disposed on the inner side of the positive electrode current collector of the fourth bent portion.

20 . The electrode assembly according to claim 10 , wherein the positive electrode sheet and the negative electrode sheet are folded to form a laminated structure, the positive electrode sheet has a fifth bent portion that clads the negative electrode sheet, and the thickening layer is disposed on at least one side of the positive electrode current collector of the fifth bent portion in the thickness direction.