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EP-4742309-A1 - NEGATIVE ELECTRODE SHEET, ELECTROCHEMICAL DEVICE, AND ELECTRONIC EQUIPMENT

EP4742309A1EP 4742309 A1EP4742309 A1EP 4742309A1EP-4742309-A1

Abstract

The present disclosure discloses a negative electrode sheet, an electrochemical device, and an electronic equipment. A specific surface area decrease rate P 0 of the negative electrode sheet is 12% to 18%; wherein P 0 =1-P, P is a ratio of a specific surface area of the negative electrode sheet under a second compaction to the specific surface area of the negative electrode sheet under a first compaction; an electrode sheet porosity ε of the negative electrode sheet is 13% or more, wherein the electrode sheet porosity is the electrode sheet porosity of the negative electrode sheet under the second compaction. The electrochemical device (especially a lithium-ion battery) containing the above can ensure excellent discharge capacity, fast charging performance, and cycle performance, and take into account excellent energy density, cycle performance, and storage performance.

Inventors

  • HOU, Shuyan

Assignees

  • AESC Japan Ltd.

Dates

Publication Date
20260513
Application Date
20251017

Claims (10)

  1. A negative electrode sheet, wherein a specific surface area decrease rate P 0 of a negative electrode sheet is 12% to 18%; wherein P 0 =1-P, P is a ratio of a specific surface area of the negative electrode sheet under a second compaction to the specific surface area of the negative electrode sheet under a first compaction; an electrode sheet porosity ε of the negative electrode sheet is 13% or more, wherein the electrode sheet porosity is the electrode sheet porosity of the negative electrode sheet under the second compaction; the second compaction is 1.80 g/cc or an ultimate compaction of the negative electrode sheet; the first compaction is 1.65 g/cc.
  2. The negative electrode sheet of claim 1, wherein the negative electrode sheet satisfies one or a plurality of following conditions a to c: a, the P 0 is 13% to 17%; b, the ε is 18% to 26%; c, an adhesive force F N of the negative electrode sheet is 25 N to 50 N.
  3. The negative electrode sheet of claim 1, wherein the negative electrode sheet comprises a negative electrode current collector, a first active material layer is disposed on at least one surface of the negative electrode current collector, a second active material layer is disposed on the first active material layer, the first active material layer comprises a first graphite material and a first binder, the second active material layer comprises a second graphite material and a second binder, and a Dv50 particle size of the first graphite material is greater than a Dv50 particle size of the second graphite material.
  4. The negative electrode sheet of claim 3, wherein the first graphite material and the second graphite material satisfy one or a plurality of following conditions a to i: a, a difference between the Dv50 particle size of the first graphite material and the Dv50 particle size of the second graphite material is 3 µ m to 7 µ m; b, a particle crushing force F 1 of the first graphite material is 30 mN to 36 mN; c, a particle crushing force F 2 of the second graphite material is 20 mN to 30 mN; d, a carbon content of the first graphite material is 99.9% or more, and the percentage is a mass percentage of the first graphite material; e, a carbon content of the second graphite material is 99.9% or more, and the percentage is a mass percentage of the first graphite material; f, the Dv50 particle size of the first graphite material is 14 µ m to 18 µ m; g, the Dv50 particle size of the second graphite material is 9 µ m to 13 µ m; h, the first graphite material is a microcrystalline graphite material; i, the second graphite material is a microcrystalline graphite material.
  5. The negative electrode sheet of claim 3, wherein the first active material layer and the second active material layer satisfy one or a plurality of following conditions a to g: a, a content of the first binder is 1.3% to 1.8%, and the percentage is a mass percentage of the first active material layer; b, a content of the second binder is 0.7% to 1.2%, and the percentage is a mass percentage of the second active material layer; c, a content of the first graphite material is 20% or more, and the percentage is a mass percentage of the first active material layer; d, a content of the second graphite material is 20% or more, and the percentage is a mass percentage of the second active material layer; e, a mass ratio of the first active material layer to the second active material layer is 1:(0.4 to 2.5); f, a thickness of the first active material layer is 50 µ m to 120 µ m; g, a thickness of the second active material layer is 50 µ m to 110 µ m.
  6. The negative electrode sheet of claim 3, wherein a preparation method of the negative electrode sheet comprises following steps: S1, applying a first negative electrode slurry layer on at least one surface of the negative electrode current collector, and the first negative electrode slurry layer comprises a first graphite material and a first binder; S2, applying a second negative electrode slurry layer on the first negative electrode slurry layer, and the second negative electrode slurry layer comprises a second graphite material and a second binder; S3, performing drying and cold pressing to obtain the negative electrode sheet.
  7. The negative electrode sheet of claim 6, wherein the first graphite material and the second graphite material satisfy one or a plurality of following conditions a to d: a, a coating density of the first negative electrode slurry layer is greater than 0.055 g/cm 2 ; b, a coating density of the second negative electrode slurry layer is greater than 0.055 g/cm 2 ; c. in step S1, the first graphite material is obtained by a pre-treatment of a first graphite precursor, and the pre-treatment comprises a surface oxidation treatment and/or a carboxylation treatment; d. in step S2, the second graphite material is obtained by a pre-treatment of the second graphite precursor, and the pre-treatment comprises a surface oxidation treatment and/or a carboxylation treatment.
  8. The negative electrode sheet of claim 7, wherein the first graphite precursor and the second graphite precursor each independently satisfy one or two of following conditions a to b: a, the first graphite precursor and the second graphite precursor independently satisfy following conditions: La ≤72 nm, Lc ≤15 nm; wherein La is a lattice constant at a 110 plane, and Lc is a lattice constant at a 002 plane; F p ≥15 mN, and F p is a particle crushing force; b, preparation methods of the first graphite precursor and the second graphite precursor each independently comprise following steps: ① performing a first mixing on a microcrystalline graphite precursor and a binder, and adding a solvent to perform a second mixing to obtain a mixture; wherein a temperature of the first mixing is 5 °C to 20 °C below a softening point of the binder; ② pressing the mixture to obtain a microcrystalline graphite rough blank; ③ laying the microcrystalline graphite rough blank at a surface of a graphitization furnace, laying a graphitized thermal insulation material on the microcrystalline graphite rough blank, and performing a graphitization treatment, and the microcrystalline graphite rough blank is subjected to a graphitization treatment to obtain a microcrystalline graphite blank body; ④ performing a crushing treatment on the microcrystalline graphite blank body.
  9. An electrochemical device, comprising the negative electrode sheet of any of claims 1 to 8.
  10. An electronic equipment, comprising the electrochemical device of claim 9.

Description

BACKGROUND Technical Field The present disclosure relates to a negative electrode sheet, an electrochemical device, and an electronic equipment. Description of Related Art Conventional natural graphite, such as flake graphite, has the characteristics of high capacity and high compaction, but is usually difficult to apply in practice due to its own defects. The capacity of artificial graphite is difficult to exceed 360 mAh/g, and it is difficult for the compaction to exceed 1.70 g/cc-1 when artificial graphite is made into an electrode sheet. Even if forced to achieve the above, the dynamics are extremely poor. Compared with conventional natural graphite and artificial graphite, microcrystalline natural graphite has the intrinsic characteristics of high capacity and good dynamics, and has excellent application prospects in high-capacity fast-charging lithium-ion batteries. Chinese patent application CN 110380050A adopts a method of asphalt impregnation filling to improve the intrinsic powder pressure of microcrystalline graphite, but this treatment reduces the pores of the material itself, significantly deteriorate the dynamics of the material itself, and has limited effect on the compaction of the electrode sheet at the electrode sheet compaction level, and the lithium-ion battery containing the above cannot guarantee excellent discharge capacity, fast charging performance, and cycle performance. Therefore, it is crucial to achieve excellent discharge capacity, fast charging performance, and cycle performance for lithium-ion batteries using graphite materials as negative electrode materials. SUMMARY In order to solve the defect that the existing lithium-ion batteries containing graphite materials cannot guarantee excellent discharge capacity, fast charging performance, and cycle performance, the present disclosure provides a negative electrode sheet, an electrochemical device, and an electronic equipment. The electrochemical device (especially the lithium-ion battery) containing the negative electrode sheet can guarantee excellent discharge capacity, fast charging performance, and cycle performance, and also take into account excellent energy density, cycle performance, and storage performance. To achieve the above object, the present disclosure adopts the following technical solutions. In a first aspect, the present disclosure provides a negative electrode sheet, wherein a specific surface area decrease rate P0 of the negative electrode sheet is 12% to 18%; wherein P0=1-P, P is a ratio of a specific surface area of the negative electrode sheet under a second compaction to the specific surface area of the negative electrode sheet under a first compaction; an electrode sheet porosity ε of the negative electrode sheet is 13% or more, wherein the electrode sheet porosity is the electrode sheet porosity of the negative electrode sheet under the second compaction;the second compaction is 1.80 g/cc or an ultimate compaction of the negative electrode sheet; the first compaction is 1.65 g/cc. In a second aspect, the present disclosure provides an electrochemical device including the negative electrode sheet. In a third aspect, the present disclosure provides an electronic equipment including the electrochemical device. The positive and progressive effects of the present disclosure are: The present disclosure provides a negative electrode sheet. By controlling and designing parameters such as the specific surface decrease rate of the negative electrode sheet and the electrode sheet porosity of the negative electrode sheet under 1.80 g/cc compaction, an electrochemical device (especially a lithium-ion battery) including the negative electrode sheet can ensure excellent discharge capacity, fast charging performance, and cycle performance, and take into account excellent energy density, cycle performance, and storage performance. DESCRIPTION OF THE EMBODIMENTS The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or the specific conditions are selected according to the product specifications. Negative electrode sheet In a negative electrode sheet provided in the first aspect of the invention, the specific surface area decrease rate P0 of the negative electrode sheet is 12% to 18%; wherein P0 =1-P, P is the ratio of the specific surface area of the negative electrode sheet under the second compaction to the specific surface area of the negative electrode sheet under the first compaction; the electrode sheet porosity ε of the negative electrode sheet is 13% or more, wherein the electrode sheet porosity is the electrode sheet porosity of the negative electrode sheet under the second compaction;the second compaction is 1.80 g/cc or the ultimate compaction of the negative electrode sh