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CN-119674185-B - Secondary battery and electric equipment

CN119674185BCN 119674185 BCN119674185 BCN 119674185BCN-119674185-B

Abstract

The application belongs to the technical field of new energy materials, and particularly relates to a secondary battery and electric equipment. Compared with the prior art, the application can improve the energy density of the battery and improve the first coulombic efficiency and the cycle performance by selecting the first active material and the second active material with specific compositions and matching the arrangement of the first coating and the second coating. The method comprises the steps of preparing a graphite coated hard carbon material, preparing a soft carbon hard carbon composite material, coating the graphite coated hard carbon material, doping active substances by adopting a first element and a second element, improving conductivity of a negative electrode plate, improving ion diffusion kinetics, facilitating sodium ion deintercalation, and improving ion diffusion efficiency, accelerating sodium ion deintercalation, improving first coulomb efficiency and improving battery cycle performance by adopting a double-active-substance coating.

Inventors

  • LIU SHUANG
  • CHEN HONGZHE
  • AN LI
  • XU ZHONGLING

Assignees

  • 欣旺达动力科技股份有限公司

Dates

Publication Date
20260508
Application Date
20241213

Claims (13)

  1. 1. A secondary battery comprising a negative electrode tab, the negative electrode tab comprising: a current collector; The first coating is coated on at least one side surface of the current collector, the first coating contains a first active substance, the first active substance comprises a soft carbon and hard carbon composite material obtained by mixing a soft carbon material and a first hard carbon material, the first active substance contains a first element, and the first element comprises at least one of nitrogen, sulfur, phosphorus and silicon elements; The second coating is coated on the surface of the first coating, the second coating contains a second active substance, the second active substance comprises a second hard carbon material, at least part of the surface of the second hard carbon material is distributed with graphite materials, the second active substance contains a second element, and the second element comprises at least one of nitrogen, sulfur, phosphorus and silicon elements; At a test pressure of 20kN, the powder resistivity a of the first active material and the powder resistivity B of the second active material satisfy the following relationship: 1.2≤A/B≤1.8。
  2. 2. The secondary battery according to claim 1, wherein the first element comprises silicon and at least one of nitrogen, sulfur, and phosphorus.
  3. 3. The secondary battery according to claim 1, wherein the second element comprises silicon and at least one of nitrogen, sulfur, and phosphorus.
  4. 4. The secondary battery according to claim 1, wherein the soft carbon material is 20% to 50% by mass and the first element is 1% to 5% by mass based on the total mass of the first active material.
  5. 5. The secondary battery according to claim 1, wherein the graphite material is 10 to 40% by mass and the second element is 0.01 to 3% by mass based on the total mass of the second active material.
  6. 6. The secondary battery according to claim 1, wherein the powder resistivity a of the first active material is 5 to 12mΩ -cm.
  7. 7. The secondary battery according to claim 1, wherein the powder resistivity B of the second active material is 3 to 8mΩ -cm.
  8. 8. The secondary battery according to claim 1, wherein the sheet resistance of the negative electrode tab is 1 to 3mΩ.
  9. 9. The secondary battery according to claim 1, wherein the soft carbon material has a Dv50 of 6 to 12 μm and the first hard carbon material has a Dv50 of 3 to 8 μm.
  10. 10. The secondary battery according to claim 1, wherein Dv50 of the second active material is 8-14 μm.
  11. 11. The secondary battery according to any one of claims 1 to 10, wherein the first active material and the second active material are subjected to thermogravimetric analysis under an inert gas atmosphere at a test temperature of 30 to 500 ℃ and a temperature rise rate of 10 ℃ per minute, satisfying: The first active material has a percent weight loss of less than 5% over a temperature range of 200 ℃ to 400 ℃; the second active material has a percent weight loss of less than 3% over a temperature range of 200 ℃ to 400 ℃.
  12. 12. The secondary battery according to claim 11, wherein the first coating layer has a porosity of 40% to 50%, and the second coating layer has a porosity of 20% to 30%.
  13. 13. An electrical device comprising the secondary battery according to any one of claims 1 to 12.

Description

Secondary battery and electric equipment Technical Field The application belongs to the technical field of new energy materials, and particularly relates to a secondary battery and electric equipment. Background Among the novel clean energy sources, sodium ion batteries are widely paid attention to because of the advantages of abundant raw materials, low production cost and the like. As a negative electrode material of a sodium ion battery, hard carbon has irreversible loss of capacity when first discharge is performed, which consumes a large amount of electrolyte and sodium ions detached from a positive electrode, affecting the discharge capacity of the battery, thereby reducing the first coulomb efficiency of the battery. Meanwhile, the sodium ion battery has the problem of lower circulation capacity retention rate and energy density, so that the sodium ion battery needs to be improved to improve the electrochemical performance of the sodium ion battery and meet the use requirement. Disclosure of Invention Therefore, the application aims to overcome the defects of low first coulombic efficiency, low cyclic capacity retention rate, low energy density and the like of the sodium ion battery in the prior art, thereby providing a secondary battery and electric equipment. Therefore, the application provides the following technical scheme: according to an aspect of the present application, there is provided a secondary battery including a negative electrode tab including: a current collector; the first coating is coated on at least one side surface of the current collector, and contains a first active substance, wherein the first active substance comprises a soft carbon material and a first hard carbon material, the first active substance contains a first element, and the first element comprises at least one of nitrogen, sulfur, phosphorus and silicon; The second coating is coated on the surface of the first coating, the second coating contains a second active substance, the second active substance comprises a second hard carbon material, at least part of the surface of the second hard carbon material is distributed with graphite materials, the second active substance contains a second element, and the second element comprises at least one of nitrogen, sulfur, phosphorus and silicon elements. In some alternative embodiments, the first element comprises silicon and at least one of nitrogen, sulfur, and phosphorus; And/or the second element comprises silicon and at least one of nitrogen, sulfur and phosphorus. In some alternative embodiments, the soft carbon material comprises 20% -50% by mass of the total mass of the first active material, and the first element comprises 1% -5% by mass; and/or, based on the total mass of the second active substances, the mass percentage of the graphite material is 10% -40%, and the mass percentage of the second element is 0.01% -3%. In some alternative embodiments, the powder resistivity a of the first active material and the powder resistivity B of the second active material satisfy the following relationship at a test pressure of 20 kN: 1.2≤A/B≤1.8。 in some optional embodiments, the powder resistivity a of the first active material is 5-12 mΩ·cm; And/or the powder resistivity B of the second active material is 3-8mΩ & cm. In some optional embodiments, the sheet resistance of the negative electrode sheet is 1-3mΩ. In some optional embodiments, the Dv50 of the soft carbon material is 6-12 μm, and the Dv50 of the first hard carbon material is 3-8 μm; and/or the Dv50 of the second active material is 8-14 μm. In some optional embodiments, the first active material and the second active material are subjected to thermogravimetric analysis under an inert gas atmosphere, the test temperature is 30-500 ℃, the heating rate is 10 ℃ per minute, and the conditions are satisfied: The first active material has a percent weight loss of less than 5% over a temperature range of 200 ℃ to 400 ℃; the second active material has a percent weight loss of less than 3% over a temperature range of 200 ℃ to 400 ℃. In some alternative embodiments, the first coating has a porosity of 40% -50% and the second coating has a porosity of 20% -30%; and/or, the thickness of the first coating accounts for 55% -70% of the total thickness of the first coating and the second coating. According to still another aspect of the present application, there is provided an electric device including the above-described secondary battery. The technical scheme of the application has the following advantages: The secondary battery comprises a current collector, a first coating, a second coating and a second coating, wherein the first coating is coated on at least one side surface of the current collector and contains a first active substance, the first active substance comprises a soft carbon material and a first hard carbon material, the first active substance contains a first element, the first element comprises at least one of