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CN-122025830-A - Lithium-sulfur battery, preparation method thereof and electric equipment

CN122025830ACN 122025830 ACN122025830 ACN 122025830ACN-122025830-A

Abstract

The application discloses a lithium sulfur battery and a preparation method thereof, and electric equipment, wherein the lithium sulfur battery comprises a positive electrode plate, a negative electrode plate and electrolyte, the positive electrode plate comprises a positive electrode current collector, at least one side of the positive electrode current collector is provided with a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a substrate, at least part of the surface of the substrate is provided with a coating layer, the substrate comprises a sulfur-based material, and the coating layer comprises a conductive polymer; the electrolyte includes a solvent and a fluorine-containing diluent. Therefore, the conductive polymer on the surface of the positive electrode active material can swell and absorb lithium salt-solvent clusters, so that lithium polysulfide can be dissolved in the lithium salt-solvent clusters in the surface conductive polymer coating layer, the sulfur reaction is solid-liquid-solid reaction, the reaction rate is improved, the rate capability of the battery is improved, meanwhile, the probability that the lithium polysulfide shuttles to the negative electrode is reduced, the side reaction between the lithium polysulfide and the negative electrode lithium is reduced, and the capacity and the cycle performance of the battery are improved.

Inventors

  • LIANG ZIBIN
  • XU YIDA
  • ZHANG XINXIN
  • GUO BINGKUN

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (17)

  1. 1. The lithium sulfur battery is characterized by comprising a positive electrode plate, a negative electrode plate and electrolyte: The positive electrode plate comprises a positive electrode current collector, wherein at least one side of the positive electrode current collector is provided with a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a substrate, at least part of the surface of the substrate is provided with a coating layer, the substrate comprises a sulfur-based material, and the coating layer comprises a conductive polymer; The electrolyte includes a solvent and a fluorine-containing diluent.
  2. 2. The lithium sulfur battery as in claim 1, wherein, the fluorine-containing diluent comprises 1H, 5H-octafluoropentyl-1, 2-tetrafluoroethyl ether one or more of bis (2, 2-trifluoroethyl) ether, 1, 2-tetrafluoroethyl 2, 3-tetrafluoropropyl ether.
  3. 3. The lithium sulfur battery of claim 1 or 2, wherein the solvent comprises one or more of dimethyl ether, 1, 2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1, 3-dioxane.
  4. 4. A lithium sulfur battery according to claim 3 wherein the ratio of the mass ratio of the fluorine-containing diluent to the solvent is 1.25 to 19.
  5. 5. The lithium sulfur battery of claim 3 or 4 wherein the fluorine-containing diluent comprises 50% to 95% by mass based on the total mass of the electrolyte.
  6. 6. The lithium sulfur battery of any of claims 3-5 wherein the solvent is present in a mass ratio of 5% to 40% based on the total mass of the electrolyte.
  7. 7. The lithium sulfur battery of any of claims 1-6 wherein the conductive polymer comprises one or more of polyaniline, polydioxyethylthiophene, polypyrrole.
  8. 8. The lithium sulfur battery of any of claims 1-7 wherein the coating layer has a thickness of 1nm to 20nm.
  9. 9. The lithium sulfur battery of any of claims 1-8 wherein the conductive polymer has a molecular weight of 5000-100000.
  10. 10. The lithium sulfur battery of any of claims 1 to 9 wherein the positive electrode active material further comprises a conductive layer, the conductive layer being located on at least a portion of a surface of the substrate, the coating layer being located on at least a portion of a surface of the conductive layer.
  11. 11. The lithium sulfur battery of any of claims 1-10 wherein the electrolyte further comprises an electrolyte salt comprising one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorooxalato phosphate, or lithium tetrafluorooxalato phosphate.
  12. 12. The lithium sulfur battery of claim 11 wherein the electrolyte salt is present in an amount of 1% to 8% by mass based on the total mass of the electrolyte.
  13. 13. The lithium sulfur battery of any of claims 1-12 wherein the sulfur-based material comprises one or more of elemental sulfur, a sulfur selenium complex, a sulfur tellurium complex.
  14. 14. A method of making a lithium sulfur battery comprising: Mixing a conductive polymer, a sulfur-based material and a solvent for reaction, and drying to obtain a positive electrode active material, wherein the positive electrode active material comprises a matrix, at least part of the surface of the matrix is provided with a coating layer, the matrix comprises the sulfur-based material, and the coating layer comprises the conductive polymer; forming a slurry containing the positive electrode active material on at least one side of a positive electrode current collector to obtain a positive electrode sheet; and assembling the positive electrode plate, the negative electrode plate and the electrolyte into a lithium-sulfur battery, wherein the electrolyte comprises a solvent and a fluorine-containing diluent.
  15. 15. The method as recited in claim 14, further comprising: Mixing the sulfur-based material and the conductive carbon material, and heating under the protection of inert gas to form a conductive carbon layer on at least the surface of the substrate; And mixing the positive electrode active material containing the conductive carbon layer, the conductive polymer and the solvent for reaction, and drying to form the coating layer on at least part of the surface of the conductive carbon layer.
  16. 16. The method of claim 15, wherein the heating is at a temperature of 120 ℃ to 200 ℃.
  17. 17. A powered device comprising a lithium sulfur battery according to any one of claims 1-13.

Description

Lithium-sulfur battery, preparation method thereof and electric equipment Technical Field The application relates to the field of batteries, in particular to a lithium-sulfur battery, a preparation method thereof and electric equipment. Background The battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, as well as a plurality of fields such as military equipment, aerospace, and the like. The lithium-sulfur battery is a lithium battery with sulfur element as a battery anode and metal lithium as a cathode. The elementary sulfur has the characteristics of abundant reserves in the earth, low price, environmental friendliness and the like. The lithium sulfur battery using sulfur as the positive electrode material has higher material theoretical specific capacity and battery theoretical specific energy, however, the intermediate product lithium polysulfide of the lithium sulfur battery is easy to dissolve in electrolyte and can shuttle to the negative electrode metal lithium side, and side reaction occurs with the metal lithium to consume the metal lithium and form non-conductive lithium sulfide to cover the surface of the metal lithium, so that the capacity and the cycle performance are reduced. Disclosure of Invention The application provides a lithium sulfur battery, which comprises a positive electrode plate, a negative electrode plate and electrolyte, wherein the positive electrode plate comprises a positive electrode current collector, at least one side of the positive electrode current collector is provided with a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a substrate, at least part of the surface of the substrate is provided with a coating layer, the substrate comprises a sulfur-based material, the coating layer comprises a conductive polymer, and the electrolyte comprises a solvent and a fluorine-containing diluent. Therefore, the conductive polymer on the surface of the positive electrode active material can swell and absorb lithium salt-solvent clusters, so that lithium polysulfide can be dissolved in the lithium salt-solvent clusters in the surface conductive polymer coating layer, the sulfur reaction is solid-liquid-solid reaction, the reaction rate is improved, the rate capability of the battery is improved, meanwhile, the probability that the lithium polysulfide shuttles to the negative electrode is reduced, the side reaction between the lithium polysulfide and the negative electrode lithium is reduced, and the capacity and the cycle performance of the battery are improved. According to some embodiments of the present application, the fluorine-containing diluent comprises 1H, 5H-octafluoropentyl-1, 2-tetrafluoroethyl ether one or more of bis (2, 2-trifluoroethyl) ether, 1, 2-tetrafluoroethyl 2, 3-tetrafluoropropyl ether. Thus, a local high-concentration electrolyte is formed, and shuttling of lithium polysulfide is reduced. According to some embodiments of the application, the solvent comprises one or more of dimethyl ether, 1, 2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1, 3-dioxapentacyclic. Thereby, the solubility of the lithium salt is improved. According to some embodiments of the application, the ratio of the mass ratio of the fluorine-containing diluent to the solvent is 1.25-19. Thus, a locally high concentration electrolyte is formed, reducing shuttling of lithium polysulfide. According to some embodiments of the application, the fluorine-containing diluent comprises 50% -95% by mass based on the total mass of the electrolyte. According to some embodiments of the application, the solvent is present in an amount of 5% to 40% by mass based on the total mass of the electrolyte. Thus, by forming a locally high concentration electrolyte by adjusting the contents of the solvent and the fluorine-containing diluent within the above-described ranges, shuttling of lithium polysulfide is reduced. According to some embodiments of the application, the conductive polymer comprises one or more of polyaniline, polydioxyethylthiophene, polypyrrole. Therefore, the lithium salt-solvent clusters can be absorbed, so that lithium polysulfide can be dissolved in the lithium salt-solvent cl