Secondary battery and method for preparing the same, and electrical apparatus

Patent metadata

Field	Value
Publication number	US-2024339621-A1
Application number	US-202418746076-A
Country	US
Kind code	A1
Filing date	Jun 18, 2024
Priority date	Jun 8, 2022
Publication date	Oct 10, 2024
Grant date	—

Abstract

Provided are a secondary battery including an electrode sheet, the electrode sheet including: a current collector and an active material layer; the active material layer is provided on at least one surface of the current collector; the active material layer is divided into a first region and a second region in its thickness direction; the first region is located in a direction close to the surface of the current collector, the thickness of the first region accounts for ½ of the thickness of the active material layer, the binder content in the first region is denoted as A; the second region is located in a direction away from the surface of the current collector, the thickness of the second region accounts for ½ of the thickness of the active material layer, and the binder content in the second region is denoted as B; the electrode sheet satisfies: 1<B/A≤1.04.

First claim

What is claimed is:

1 . A secondary battery including an electrode sheet, the electrode sheet including
a current collector; and an active material layer provided on at least one surface of the current collector; the active material layer is divided into a first region and a second region in its thickness direction; the first region is located in a direction close to the surface of the current collector, the thickness of the first region accounts for ½ of the thickness of the active material layer, and a binder content of the first region is denoted as A; the second region is located in a direction away from the surface of the current collector, the thickness of the second region accounts for ½ of the thickness of the active material layer, and the binder content of the first region is denoted as B; the electrode sheet satisfies: 1<B/A≤1.04.

2 . The secondary battery according to claim 1 , wherein the electrode sheet satisfies: 1.01<B/A≤1.03.

3 . The secondary battery according to claim 1 , wherein the thickness of the active material layer is 40 μm to 180 μm; optionally, the thickness of the active material layer is 60 μm to 100 μm.

4 . The secondary battery according to claim 1 , wherein,
a porosity of the first region is 25% to 30%; and/or, a porosity of the second region is 25% to 30%.

5 . The secondary battery according to claim 1 , wherein a difference between a porosity of the first region and a porosity of the second region is ≤5%.

6 . The secondary battery according to claim 1 , wherein a porosity of the first region is the same as a porosity of the second region.

7 . The secondary battery according to claim 1 , wherein the active material layer is self-supporting.

8 . The secondary battery according to claim 1 , wherein a tensile strength of the active material layer is 0.03 MPa to 1 MPa.

9 . The secondary battery according to claim 1 , wherein the electrode sheet is a positive electrode sheet; in the active material layer, a binder includes at least one of polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

10 . The secondary battery according to claim 1 , wherein the electrode sheet is a negative electrode sheet; in the active material layer, a binder includes a polymer having a polar functional group.

11 . The secondary battery according to claim 10 , wherein a weight average molecular weight of the polymer is ≥200,000.

12 . The secondary battery according to claim 10 , wherein the polymer is selected from at least one of chain polymers and cross-network polymers.

13 . The secondary battery according to claim 10 , wherein the polymer is selected from at least one of polyacrylonitrile, polyacrylic acid, polyamide, acrylic acid-acrylonitrile copolymer and derivatives thereof, acrylic acid-acrylate copolymer and derivatives thereof, acrylic acid-acrylamide copolymer and derivatives thereof.

14 . The secondary battery according to claim 1 , wherein in the active material layer, a mass percentage of a binder is 0.5% to 5%.

15 . The secondary battery according to claim 1 , wherein the active material layer further includes an additive, and the additive includes at least one of polytetrafluoroethylene, polyethylene, polypropylene, and polyacrylonitrile.

16 . A method for preparing a secondary battery, comprising preparing an electrode sheet by the following steps:
preparing an electrode sheet slurry with a solid content greater than or equal to 65%; extruding the electrode sheet slurry to prepare an active material layer; and compounding the active material layer with a current collector to prepare the electrode sheet; wherein an active material layer is provided on at least one surface of the current collector; the active material layer is divided into a first region and a second region in its thickness direction; the first region is located in a direction close to the surface of the current collector, the thickness of the first region accounts for ½ of the thickness of the active material layer, and a binder content of the first region is denoted as A; the second region is located in a direction away from the surface of the current collector, the thickness of the second region accounts for ½ of the thickness of the active material layer, and the binder content of the first region is denoted as B; the electrode sheet satisfies: 1<B/A≤1.04.

17 . The method for preparing a secondary battery according to claim 16 , wherein the electrode sheet is a negative electrode sheet, and the solid content of the electrode sheet slurry is 68% to 74%.

18 . The method for preparing a secondary battery according to claim 16 , wherein the electrode sheet is a positive electrode sheet, and the solid content of the electrode sheet slurry is 75% to 80%.

19 . An electrical apparatus, including the secondary battery according to claim 1 or the secondary battery prepared by a method for preparing a secondary battery according to claim 16 .

Assignees

• Contemporary Amperex Technology Co Ltd

Inventors

• Deng Kaiming
• Lu Lei
• Wang yalong
• Wang Zheng
• Yu Linzhen
• Hu Changyuan
• Li Shisong
• Dai Shunhao

Classifications

• H01M2004/028

  Positive electrodes · CPC title

• H01M2004/027

  Negative electrodes · CPC title

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title

• H01M4/0411

  by extrusion · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title