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CN-120221583-B - High first-efficiency dry-method composite graphite electrode

CN120221583BCN 120221583 BCN120221583 BCN 120221583BCN-120221583-B

Abstract

The invention discloses a high-first-efficiency dry-method composite graphite electrode, which comprises graphite, conductive carbon materials, a PTFE adhesive and boron-containing lithium salt, wherein the mass fraction ratio of the graphite, the conductive carbon materials, the PTFE adhesive and the boron-containing lithium salt is X (100-X-Y-Z) Z: Y, wherein X is more than or equal to 90 and less than or equal to 98,1 and Z is less than or equal to 2, Y is more than or equal to 0.2 and less than or equal to 100-X-Z.

Inventors

  • ZHOU LIN
  • JIN YUXUAN
  • ZHOU QUAN

Assignees

  • 长三角物理研究中心有限公司

Dates

Publication Date
20260508
Application Date
20250331

Claims (12)

  1. 1. A high first-effect dry-method composite graphite electrode is characterized by comprising graphite, conductive carbon materials, PTFE adhesive and boron-containing lithium salt, wherein the mass fraction ratio of the graphite, the conductive carbon materials, the PTFE adhesive and the boron-containing lithium salt is X (100-X-Y-Z): Z is Y, X <98,1 > Z < 2 > is 90 <98,1 > Z < 2, and Y < (100-X-Z) is 0.2 < 100-X-Z; the boron-containing lithium salt is selected from any one or more of fluorine-containing or/and fluorine-free oxalic acid lithium borate salt and tetrafluoroboric acid lithium.
  2. 2. The high first-effect dry composite graphite electrode according to claim 1, wherein the mass fraction ratio of graphite, conductive carbon material, PTFE binder and boron-containing lithium salt is X (100-X-Y-Z): Z: Y, wherein 95< X <97,1 < Z < 2,0.4 < Y < (100-X-Z).
  3. 3. The high first-effect dry composite graphite electrode according to claim 1, wherein the mass fraction ratio of graphite, conductive carbon material, PTFE binder and boron-containing lithium salt in the high first-effect dry composite graphite electrode is X (100-X-Y-Z) Z: Y, wherein 95< X <97,1 < Z < 2,0.4 < Y < (100-X-Z), and Z: y=3.8-4.2.
  4. 4. The high first-effect dry method composite graphite electrode according to claim 1, wherein the conductive carbon material is selected from any one or more of a zero-dimensional conductive carbon material, a one-dimensional conductive carbon material and a two-dimensional conductive carbon material.
  5. 5. The high first-effect dry composite graphite electrode according to claim 1, wherein the conductive carbon material is selected from one-dimensional conductive carbon materials.
  6. 6. A battery, characterized in that the high first efficiency dry composite graphite electrode according to any one of claims 1 to 5 is used as a negative electrode.
  7. 7. The battery of claim 6, further comprising a positive electrode sheet, an electrolyte, and a separator.
  8. 8. The battery of claim 7, wherein the positive electrode sheet comprises a positive electrode active material, a positive electrode current collector, a positive electrode conductive agent, and a positive electrode binder.
  9. 9. The battery according to claim 8, wherein the positive electrode conductive agent is selected from any one or more of a carbon material, a metal material, and a conductive polymer; The positive electrode adhesive is selected from at least one of thermoplastic resin, acrylic resin, sodium carboxymethyl cellulose and styrene butadiene rubber.
  10. 10. The battery of claim 7, wherein the lithium salt added to the electrolyte is a mixed lithium salt of LiFSI and LiPF 6 .
  11. 11. The battery of claim 10, wherein the molar ratio of LiFSI to LiPF 6 in the mixed lithium salt is (2-5): 5-8.
  12. 12. The battery of claim 10, wherein the molar ratio of LiFSI to LiPF 6 in the mixed lithium salt is (4-5): 5-6.

Description

High first-efficiency dry-method composite graphite electrode Technical Field The invention belongs to the field of lithium ion batteries, and particularly relates to a high-first-efficiency dry-process composite graphite electrode. Background With the wide application of battery technology in various fields, the electrode is used as a core component of a battery, and the performance optimization of the electrode becomes a research hot spot. The dry method electrode preparation method has the advantages of simple process flow, high production efficiency, no need of using solvents and the like, and gradually becomes an important development direction of the battery electrode preparation technology. Graphite is considered to be particularly suitable for dry-process preparation of electrodes due to its excellent pressure-resistant properties, and thus dry-process preparation of negative electrode sheets using graphite as an active material has been receiving increasing attention and application. The sp2 hybridized structure of graphite imparts unique physical and chemical properties thereto. Based on the structure, the graphite negative electrode sheet has excellent cycle performance and structural stability, and has higher specific capacity. By combining the pressure resistance, the graphite can obviously improve the volume energy density of the electrode in the dry preparation process, and particularly in the electrode with high graphite content (the graphite content is more than or equal to 90 percent), the graphite has obvious advantages in the aspects of cycle stability and specific capacity. However, in a practical dry preparation process, the process of mixing the negative electrode active material graphite with a binder (e.g., PTFE binder) is challenging. Since both the PTFE binder and the graphite surface have negative charges, they repel each other during mixing, making it difficult for the binder to achieve effective bonding to the graphite. This problem not only reduces the first coulombic efficiency of the negative electrode sheet, but also limits the further development of dry-process graphite negative electrodes. To solve this problem, it is currently common to surface-coat graphite or PTFE binders, or to add additives to the electrolyte to improve compatibility between the two. However, although the bonding performance of the PTFE adhesive and graphite is improved to a certain extent by the methods, the problems of reduced capacity density of the pole piece, increased cost, possibility of side reaction and the like are brought. Therefore, how to effectively improve the first coulombic efficiency of the graphite electrode while fully playing the advantages of high stability and high energy density of the dry method preparation of the graphite electrode has become a key subject of the current battery technology research. Disclosure of Invention Aiming at the problems in the prior art, the invention provides a high-first-efficiency dry-method composite graphite electrode, solves the problem that graphite is incompatible with a PTFE adhesive, and obtains the high-first-efficiency dry-method composite graphite electrode with high first coulomb efficiency. The invention provides a high-first-effect dry-method composite graphite electrode which comprises graphite, conductive carbon materials, PTFE (polytetrafluoroethylene) adhesive and boron-containing lithium salt, wherein the mass fraction ratio of the graphite to the conductive carbon materials to the PTFE adhesive to the boron-containing lithium salt is X (100-X-Y-Z): Z: Y, wherein X is 90-98,1-Z is 2 and Y is 0.2-Y (100-X-Z). As a further scheme, in the high first-efficiency dry-method composite graphite electrode, the mass fraction ratio of graphite, conductive carbon material, PTFE binder and boron-containing lithium salt is X (100-X-Y-Z) Z: Y, wherein X is 95< X <97, Z is not less than 1 and not more than 2,0.4 and Y is not less than (100-X-Z). As a further preferable scheme, in the high-first-effect dry-method composite graphite electrode, the mass fraction ratio of graphite, conductive carbon material, PTFE binder and boron-containing lithium salt is X (100-X-Y-Z) Z: Y, wherein X is 95< X <97, Z is not less than 1 and not more than 2,0.4 and Y is not less than (100-X-Z), and Z is Y=3.8-4.2. As a further scheme, the conductive carbon material includes, but is not limited to, any one or more of a zero-dimensional conductive carbon material, a one-dimensional conductive carbon material and a two-dimensional conductive carbon material. As a further preferred embodiment, the conductive carbon material is selected from one-dimensional conductive carbon materials. As a further scheme, the boron-containing lithium salt is selected from any one or more of organic lithium borate salt and inorganic lithium borate salt. As a further preferred embodiment, the boron-containing lithium salt is selected from the group consisting of organic lithium borate sa