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EP-4131475-B1 - ELECTRODE FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME

EP4131475B1EP 4131475 B1EP4131475 B1EP 4131475B1EP-4131475-B1

Inventors

  • HE, WEI
  • PENG, Chong
  • CHEN, BO
  • LI, JUNYI
  • XU, Yanming

Dates

Publication Date
20260506
Application Date
20210906

Claims (12)

  1. A negative electrode sheet, characterized by comprising: a current collector; a first active layer provided on a surface of at least one side of the current collector; and a second active layer provided on a surface of a side of the first active layer away from the current collector, the first active layer is different from the second active layer, the first active layer comprises a first active material comprising a first graphite, and the second active layer comprises a second active material comprising a second graphite; wherein, a ratio of capacity per unit mass of the first active material to specific surface area of the first active material is a first capacity ratio, and a ratio of capacity per unit mass of the second active material to specific surface area of the second active material is a second capacity ratio, a ratio of the second capacity ratio to the first capacity ratio being greater than 1; the first graphite has a greater specific surface area than the second graphite; the first active material further comprises a first silicon material, and the second active material further comprises a second silicon material, the first silicon material having a specific surface area of 1.1 m 2 /g-4.0 m 2 /g, and the second silicon material having a specific surface area of 1.1 m 2 /g-4.0 m 2 /g; the specific surface area is measured through a BET method.
  2. The negative electrode sheet according to claim 1, characterized in that the ratio of the second capacity ratio to the first capacity ratio is in the range of 1.05-1.5.
  3. The negative electrode sheet according to any one of claims 1-2, characterized in that a specific surface area of the first graphite is in the range of 1.0 m 2 /g-1.8 m 2 /g, and a specific surface area of the second graphite is in the range of 1.0 m 2 /g-1.8 m 2 /g.
  4. The negative electrode sheet according to any one of claims 1-3, characterized in that the first graphite has the same capacity per gram as that of the second graphite, and the first graphite has a specific surface area different from that of the second graphite; and/or the first active material further comprises a first silicon material, the second active material further comprises a second silicon material, the first silicon material having the same capacity per gram as that of the second silicon material, and the first silicon material having a specific surface area different from that of the second silicon material.
  5. The negative electrode sheet according to any one of claims 1-4, characterized in that the first active material further comprises a first silicon material, the second active material further comprises a second silicon material, the first silicon material accounting for 5%-40% of the first active material by mass, and the second silicon material accounting for 5%-40% of the second active material by mass.
  6. The negative electrode sheet according to claim 5, characterized in that the first silicon material accounts for 5%-20% of the first active material by mass, and the second silicon material accounts for 5%-20% of the second active material by mass.
  7. The negative electrode sheet according to any one of claims 1-6, characterized in that the first active layer comprises a first conductive agent, and the second active layer comprises a second conductive agent; and/or the first active layer comprises a first adhesive, and the second active layer comprises a second adhesive.
  8. A method of fabricating a negative electrode sheet, characterized by comprising: providing a current collector; forming, on a surface of at least one side of the current collector, a first active layer; forming, on a surface of a side of the first active layer away from the current collector, a second active layer; wherein the first active layer is different from the second active layer, the first active layer comprises a first active material comprising a first graphite, and the second active layer comprises a second active material comprising a second graphite; a ratio of capacity per unit mass of the first active material to specific surface area of the first active material is a first capacity ratio, and a ratio of capacity per unit mass of the second active material to specific surface area of the second active material is a second capacity ratio, a ratio of the second capacity ratio to the first capacity ratio being greater than 1; the first graphite has a greater specific surface area than the second graphite; the first active material further comprises a first silicon material, and the second active material further comprises a second silicon material, the first silicon material having a specific surface area of 1.1 m 2 /g-4.0 m 2 /g, and the second silicon material having a specific surface area of 1.1 m 2 /g-4.0 m 2 /g; the specific surface area is measured through a BET method.
  9. The method according to claim 8, characterized in that the ratio of the second capacity ratio to the first capacity ratio is in the range of 1.05-1.5.
  10. The method according to any one of claims 8-9, characterized in that a specific surface area of the first graphite is in the range of 1.0 m 2 /g-1.8 m 2 /g, and a specific surface area of the second graphite is in the range of 1.0 m 2 /g-1.8 m 2 /g.
  11. The method according to any one of claims 8-10, characterized in that the first graphite has the same capacity per gram as that of the second graphite, and the first graphite has a specific surface area different from that of the second graphite; and/or the first silicon material having the same capacity per gram as that of the second silicon material, and the first silicon material having a specific surface area different from that of the second silicon material.
  12. A battery, characterized by comprising the negative electrode sheet according to any one of claims 1-7.

Description

TECHNICAL FIELD The present application relates to a technical field of battery, and specifically to a negative electrode sheet, a fabricating method thereof, and a battery containing the negative electrode sheet. BACKGROUND Lithium batteries are widely used in consumer electronic products such as mobile phones and notebooks, as well as in products such as electric vehicles and electric power tools. US2019305308A1 discloses a multilayer negative electrode comprising a negative electrode current collector configured to transfer electrons between an outer lead and a negative electrode active material, a first negative electrode mixture layer formed on one surface or both surfaces of the current collector and containing natural graphite as a negative electrode active material and a second negative electrode mixture layer formed on the first negative electrode mixture layer and containing artificial graphite as a negative electrode active material, and a lithium secondary hattery including the same. WO2019187537A1 discloses a nonaqueous electrolyte secondary battery, where a negative electrode mixture layer has a first layer and a second layer formed in that order from the side of a negative electrode current collector. The first layer includes a first carbon-base active material with a 10% proof stress of less than or equal to 3 MPa, and a silicon-base active material containing Si. The second layer contains a second carbon-base active material with a 10% proof stress of greater than or equal to 5 MPa, and has a lower content ratio (mass ratio) of the silicon-base active material than the first layer. EP4037015A1 discloses a negative electrode which is provided with a negative electrode current collector, and a negative electrode mixture layer formed on the negative electrode current collector, where the negative electrode mixture layer comprises a first layer arranged on the negative electrode current collector, and a second layer arranged on the first layer; the second layer includes graphite particles A having a particle internal porosity of at most 10%: the first layer includes graphite particles B having a particle in- ternal porosity of more than 10%; and the second layer has a water contact angle of at most 50°. During the use of lithium batteries, the property of the negative electrode sheet has an important influence on the battery performance. Due to the problems such as short cycle life, expansion during cycling, and low capacity existing in the negative electrode material, it is difficult for the battery to meet the needs because of its low volumetric energy density and short cycle life. SUMMARY In view of this, the present application provides a negative electrode sheet, a fabricating method, and a battery, thereby solving the problems of short cycle life and low capacity of negative electrode materials, which result in a battery with low volumetric energy density and short cycle life. The invention is set out in the appended set of claims. To solve the above technical problems, the following solutions are provided in the present application: In a first aspect, a negative electrode sheet according to an embodiment of the present application includes: a current collector;a first active layer provided on a surface of at least one side of the current collector; anda second active layer provided on a surface of a side of the first active layer away from the current collector,where, the first active layer is different from the second active layer, the first active layer includes a first active material including a first graphite, and the second active layer includes a second active material including a second graphite; anda ratio of capacity per unit mass of the first active material to specific surface area of the first active material is a first capacity ratio, and the ratio of a capacity per unit mass of the second active material to a specific surface area of the second active material is a second capacity ratio, the ratio of the second capacity ratio to the first capacity ratio being greater than 1. Where, the ratio of the second capacity ratio to the first capacity ratio is in the range of 1.05-1.5. Where, the first active material further includes a first silicon material; and/or, the second active material further includes a second silicon material. Where, a specific surface area of the first graphite is in the range of 1.0 m2/g-1.8 m2/g, and a specific surface area of the second graphite is in the range of 1.0 m2/g-1.8 m2/g. Where, the first graphite has the same capacity per gram as that of the second graphite, and the first graphite has a specific surface area different from that of the second graphite; and/or, the first active material further includes a first silicon material, and the second active material further includes a second silicon material, the first silicon material having the same capacity per gram as that of the second silicon material, and the first silicon material having a