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CN-122003736-A - Negative electrode for secondary battery and secondary battery comprising same

CN122003736ACN 122003736 ACN122003736 ACN 122003736ACN-122003736-A

Abstract

The anode for a secondary battery of some embodiments includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer, wherein the first active material layer includes a first silicon-based active material and a first conductive material, the second active material layer includes a second silicon-based active material and a second conductive material, wherein the content of the first silicon-based active material is higher than the content of the second silicon-based active material, and a ratio of a sum of surface areas S ct of the first conductive material and the second conductive material to a sum of surface areas S st of the first silicon-based active material and the second silicon-based active material (S ct /S st ) may be 0.8 to 1.2. Some embodiments of the present invention exhibit excellent capacity, cycle characteristics, low-temperature charge and discharge properties, and rapid charge and discharge properties.

Inventors

  • LI BINGXUN
  • JIN ZHENGXUN
  • JIN XIZHEN

Assignees

  • 株式会社LG新能源

Dates

Publication Date
20260508
Application Date
20250718
Priority Date
20240719

Claims (15)

  1. 1. A negative electrode for a secondary battery, comprising: The active material device includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer, wherein: the first active material layer comprises a first silicon-based active material and a first conductive material, The second active material layer includes a second silicon-based active material and a second conductive material, The content of the first silicon-based active material is higher than the content of the second silicon-based active material, and The ratio S ct /S st of the sum of the surface areas S ct of the first and second conductive materials to the sum of the surface areas S st of the first and second silicon-based active materials is 0.8 to 1.2.
  2. 2. The negative electrode for secondary battery according to claim 1, wherein: the content of the first conductive material is higher than the content of the second conductive material.
  3. 3. The negative electrode for secondary battery according to claim 1, wherein: the ratio S c1 /S s1 of the sum of the surface areas S c1 of the first conductive material to the sum of the surface areas S s1 of the first silicon-based active material is 0.8 to 1.2, and The ratio S c2 /S s2 of the sum of the surface areas S c2 of the second conductive material to the sum of the surface areas S s2 of the second silicon-based active material is 0.8 to 1.2.
  4. 4. The negative electrode for secondary battery according to claim 1, wherein: The ratio S c1 /S s1 of the sum of the surface areas S c1 of the first conductive material to the sum of the surface areas S s1 of the first silicon-based active material is 0.9 to 1.1, and The ratio S c2 /S s2 of the sum of the specific surface areas S c2 of the second conductive material to the sum of the surface areas S s2 of the second silicon-based active material is 0.9 to 1.1.
  5. 5. The negative electrode for secondary battery according to claim 1, wherein: the first conductive material and the second conductive material comprise linear conductive materials.
  6. 6. The negative electrode for secondary battery according to claim 5, wherein: the linear conductive material comprises more than one of Carbon Nanotubes (CNTs), carbon Nanofibers (CNFs) and Vapor Grown Carbon Fibers (VGCF).
  7. 7. The negative electrode for secondary battery according to claim 5, wherein: The average length of the linear conductive material is 5 μm or more.
  8. 8. The negative electrode for secondary battery according to claim 1, wherein: The first active material layer comprises a first binder, The second active material layer contains a second binder, and The viscosity of the first adhesive is greater than the viscosity of the second adhesive.
  9. 9. The negative electrode for secondary battery according to claim 8, wherein: the viscosity of the first adhesive is at least 10 times the viscosity of the second adhesive.
  10. 10. The negative electrode for secondary battery according to claim 1, wherein: The first active material layer comprises a first carbon-based active material, The second active material layer contains a second carbon-based active material, The first and second carbon-based active materials comprise natural graphite and artificial graphite, The content of natural graphite in the first carbon-based active material is higher than that of artificial graphite, and The content of artificial graphite in the second carbon-based active material is higher than the content of natural graphite.
  11. 11. A secondary battery, comprising: A positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode, wherein: The negative electrode according to claim 1.
  12. 12. The secondary battery according to claim 11, wherein: the positive electrode includes a positive electrode active material represented by the following chemical formula 1: [ chemical formula 1] Li p Ni 1-q-r-s Co q Mn r M 1 s O 2 In the chemical formula 1, the chemical formula is shown in the drawing, M 1 is one or more elements selected from the group consisting of Al, zr, ti, mg, ta, nb, mo and Cr, and 0.9≤p≤1.5,0≤q≤1,0≤r≤0.5,0≤s≤0.1,0≤q+r+s≤1。
  13. 13. The secondary battery according to claim 11, wherein: The positive electrode includes a positive electrode active material represented by the following chemical formula 2: [ chemical formula 2] Li 1+a Fe 1-b M 2 b (PO 4-c )X c In the chemical formula 2, the chemical formula is shown in the drawing, M 2 comprises one or more elements selected from the group consisting of Al, mg, ni, co, mn, ti, ga, cu, V, nb, zr, ce, in, zn and Y, X comprises one or more elements selected from the group consisting of F, S and N, and A. b and c are respectively in the ranges of-0.5, 0-0.9 and 0-0.8.
  14. 14. The secondary battery according to claim 11, wherein: The secondary battery is a cylindrical secondary battery.
  15. 15. The secondary battery according to claim 11, wherein: The secondary battery is a secondary battery for an automobile or an ESS (energy storage system).

Description

Negative electrode for secondary battery and secondary battery comprising same Technical Field The present invention relates to a negative electrode for a secondary battery and a secondary battery including the same. More specifically, the present invention relates to a negative electrode for a secondary battery having a double-layer structure, which contains a silicon-based active material, and a secondary battery containing the negative electrode. The present application claims priority from korean patent application No. 10-2024-0095161, filed on 7 months of 2024, 19, and korean patent application No. 10-2025-0095796, filed on 16 months of 2025, 7, and korean patent application No. 10-2023-007487 and No. 10-2025-0095796, the entire contents of which are incorporated herein by reference. Background In order to reduce dependence on fossil fuels and reduce carbon emissions, the use of secondary batteries capable of long-term repeated use by recharging is increasing. Secondary batteries are used in various fields such as vehicles, portable electronic devices, and ESS (energy storage systems). Among secondary batteries, lithium secondary batteries using lithium ions as ions are favored for their excellent energy density and lifetime, resulting in active research and development. Basic performance characteristics of a lithium secondary battery, such as capacity, output, and life, are significantly affected by a negative electrode active material contained in the lithium secondary battery. Carbon-based active materials are mainly used as the negative electrode material, however, the theoretical capacity of these materials is about 372 mAh/g, which limits their ability to raise the energy density of the lithium secondary battery. Therefore, attempts are being made to use a silicon-based active material as the negative electrode active material, which has a theoretical capacity of about 4010 mAh/g, ten times or more that of a carbon-based active material. However, silicon-based active materials have a high rate of change of volume in excess of 300% during charge and discharge cycles. This causes the conductive path to break during continuous charge and discharge, rendering it ineffective as an active material. Disclosure of Invention [ Technical problem ] The technical idea of the present invention is to solve the technical problem of providing a negative electrode for a secondary battery having excellent capacity, cycle characteristics, low-temperature charge and discharge performance and rapid charge and discharge performance, and a secondary battery including the same. Technical scheme Some embodiments of the present invention capable of solving the above-described problems are as follows. The negative electrode for a secondary battery includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer, wherein the first active material layer includes a first silicon-based active material and a first conductive material, the second active material layer includes a second silicon-based active material and a second conductive material, wherein the content of the first silicon-based active material is higher than the content of the second silicon-based active material, and a ratio (S ct/Sst) of a sum of surface areas S ct of the first conductive material and the second conductive material to a sum of surface areas S st of the first silicon-based active material and the second silicon-based active material may be 0.8 to 1.2. In some embodiments, the content of the first conductive material may be higher than the content of the second conductive material. In some embodiments, the ratio of the sum of surface areas of the first conductive material S c1 to the sum of surface areas of the first silicon-based active material S s1 (S c1/Ss1) may be 0.8 to 1.2, and the ratio of the sum of surface areas of the second conductive material S c2 to the sum of surface areas of the second silicon-based active material S s2 S c2/Ss2 may be 0.8 to 1.2. In some embodiments, the ratio of the sum of surface areas of the first conductive material S c1 to the sum of surface areas of the first silicon-based active material S s1 (S c1/Ss1) may be 0.9 to 1.1, and the ratio of the sum of surface areas of the second conductive material S c2 to the sum of surface areas of the second silicon-based active material S s2 S c2/Ss2 may be 0.9 to 1.1. In some embodiments, the first conductive material and the second conductive material may comprise linear conductive materials. In some embodiments, the linear conductive material may include one or more of Carbon Nanotubes (CNTs), carbon Nanofibers (CNFs), and Vapor Grown Carbon Fibers (VGCFs). In some embodiments, the average length of the linear conductive material may be 5 μm or more. In some embodiments, the first active material layer comprises a first binder and the second active material layer comprises a se