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CN-116364857-B - Negative electrode sheet, preparation method thereof and battery

CN116364857BCN 116364857 BCN116364857 BCN 116364857BCN-116364857-B

Abstract

The invention relates to a negative plate, a preparation method thereof and a battery, wherein the negative plate comprises a current collector and an active material layer arranged on at least one surface of the current collector, and a coating is arranged on one side of the surface of the active material layer far away from the current collector; the material of the coating comprises modified lithium titanate. According to the invention, the coating containing the modified lithium titanate is arranged on the surface of the active material, so that the safety of overcharging of the battery cell can be effectively improved, the chemical stability of a negative electrode interface can be improved by the modified lithium titanate coating, the internal heat generation of overcharging is reduced, and meanwhile, the transitional lithium precipitation caused by overcharging can be effectively inhibited by the structural stability of the modified lithium titanate coating, so that the growth of lithium dendrites is inhibited, and the short circuit caused by micro-perforation of a diaphragm is greatly weakened.

Inventors

  • WANG ZHENGCHUN
  • CHEN DANDAN
  • LIU CHAN
  • HOU MIN
  • CAO HUI

Assignees

  • 上海瑞浦青创新能源有限公司
  • 瑞浦兰钧能源股份有限公司

Dates

Publication Date
20260505
Application Date
20230509

Claims (20)

  1. 1. The negative electrode plate is characterized by comprising a current collector and an active material layer arranged on at least one surface of the current collector, wherein a coating is arranged on one side, far away from the current collector, of the surface of the active material layer; The material of the coating comprises modified lithium titanate; The chemical formula of the modified lithium titanate is A x Li y TiO 3 , 3x+y=2, and x is more than or equal to 0.2 and less than or equal to 0.6; The element A in the element A x Li y TiO 3 comprises any one or a combination of at least two of La, Y, sc, al, ga, in and Tl; The modified lithium titanate has a perovskite structure.
  2. 2. The negative electrode sheet according to claim 1, wherein the active material of the active material layer includes any one or a combination of at least two of natural graphite, artificial graphite, soft carbon, hard carbon, or mesophase carbon particles.
  3. 3. The negative electrode sheet according to claim 1, wherein the active material layer has a single-sided thickness of 15 to 100 μm; and/or the single-sided surface density of the active material layer is 20-160 g/m 2 .
  4. 4. The negative electrode sheet according to claim 1, wherein the thickness of the coating layer is not more than 8-16% of the thickness of the active material layer; And/or the surface density of the coating is 10-50 g/m 2 .
  5. 5. The negative electrode sheet according to claim 1, wherein the active material layer includes an active material, a first conductive agent, and a first binder therein.
  6. 6. The negative electrode sheet according to claim 5, wherein the first conductive agent comprises carbon black and/or carbon nanotubes; and/or the first binder is any one or a combination of at least two of sodium carboxymethyl cellulose, styrene-butadiene rubber or polyvinylidene fluoride.
  7. 7. The negative electrode sheet according to claim 5, wherein in the active material layer, the mass ratio of the active material is 80 to 100% and is not 100%; And/or, in the active material layer, the mass ratio of the first conductive agent is 0-10% and is not 0; And/or, in the active material layer, the mass ratio of the first binder is 0-10% and is not 0.
  8. 8. The negative electrode sheet of claim 1, wherein the coating further comprises a second conductive agent and a second binder.
  9. 9. The negative plate of claim 8, wherein the mass ratio of the modified lithium titanate, the second conductive agent and the second binder is (94-96): 2-3.
  10. 10. The negative electrode sheet of claim 8, wherein the second binder is any one or a combination of at least two of sodium carboxymethyl cellulose, styrene-butadiene rubber, or polyvinylidene fluoride; and/or the second conductive agent comprises carbon black and/or carbon nanotubes.
  11. 11. A method for producing the negative electrode sheet according to any one of claims 1 to 10, characterized by comprising the steps of: (1) Coating the surface of a current collector with active material layer slurry, and drying to obtain an active material layer; (2) And coating the coating slurry on the surface of the active material layer, and drying to obtain the negative plate.
  12. 12. The method of claim 11, wherein the active material layer slurry in step (1) includes an active material, a first conductive agent, a first binder, and a first solvent.
  13. 13. The method of claim 12, wherein the first solvent is deionized water and/or N-methylpyrrolidone.
  14. 14. The method according to claim 11, wherein the drying temperature in step (1) is 70 to 110 ℃; And/or, the drying time in the step (1) is 30-60 min; And/or, the drying temperature in the step (2) is 80-120 ℃; And/or, the drying time in the step (2) is 30-60 min.
  15. 15. The method of claim 11, wherein the coating slurry of step (2) comprises modified lithium titanate, a second conductive agent, a second binder, and a second solvent.
  16. 16. The method of claim 15, wherein the second solvent is deionized water and/or N-methylpyrrolidone.
  17. 17. The method of preparing according to claim 15, wherein the method of preparing modified lithium titanate comprises: mixing a lithium source, a titanium source, a modified element source and a third solvent, performing ball milling, and drying to obtain a ball grinding material; and calcining the obtained ball grinding material to obtain the modified lithium titanate.
  18. 18. The method of claim 17, wherein the source of modifying element is an oxide of modifying element.
  19. 19. The method according to claim 17, wherein the third solvent is any one or a combination of at least two of ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, isoamyl alcohol, ethyl acetate, methyl acetate, propyl acetate, acetone, and methyl ethyl ketone.
  20. 20. The method of claim 17, wherein the ball milling is a double planetary ball milling; And/or the revolution speed of the ball mill is 150-400 rpm, and the rotation speed is 400-1000 rpm; and/or the ball milling time is 3-5 hours; And/or the drying temperature is 100-130 ℃; and/or the drying time is 10-15 h.

Description

Negative electrode sheet, preparation method thereof and battery Technical Field The invention belongs to the technical field of batteries, and relates to a negative plate, a preparation method thereof and a battery. Background The most important technical indexes of the power battery include energy density, safety performance, cycle life, manufacturing cost, multi-environment adaptability and the like. The advantages of the ternary battery such as high energy density, excellent low-temperature adaptability, good cycle life and the like are simultaneously and simultaneously driven with the lithium iron phosphate battery, but the lithium iron phosphate occupies the market more due to the two advantages of lower cost, safety and reliability, and the lithium battery industry in the next few years can concentrate more on reducing the cost and improving the safety. The safety of the lithium battery not only comprises the misuse limiting the use process, but also is more reflected in the reliability, namely the elimination of abnormal states such as spontaneous combustion, instant power failure and the like. The abnormal state is triggered not only by internal short circuit, high Wen Youfa and voltage exceeding the use threshold value, but also by the internal temperature of the battery core, as the internal temperature rises, the battery core sequentially generates negative electrode SEI film decomposition and negative electrode and electrolyte side reaction aggravation, further the diaphragm base film is melted, the electrolyte is gasified, the positive electrode is thermally decomposed and the electrolyte is decomposed, and then the internal of the battery core causes large-area short circuit until the thermal runaway instant black smoke, combustion and explosion. Aiming at the problems that the decomposition of the anode SEI film occurs firstly, the side reaction of the anode and the electrolyte is aggravated, the reaction temperature threshold value is increased, and the reaction degree is weakened. At present, the graphite negative electrode material has the advantages of simple processing performance, high gram capacity, large discharge interval, friendly price and the like, but has poor multiplying power performance, and the lithium removal potential of the graphite negative electrode based on a deintercalation mechanism is about 0.1V vs. Li/Li +, which is slightly higher than the lithium removal potential (0V) of metallic lithium, so that the graphite negative electrode is extremely easy to produce lithium precipitation. The growth of lithium dendrites can cause penetration of the separator, thereby easily causing safety problems. Therefore, how to overcome the defect that the graphite negative electrode is easy to produce lithium precipitation, thereby improving the safety is a technical problem which needs to be considered in the technical field of the graphite negative electrode sheet. The lithium titanate anode material coated with carbon has a higher working voltage of 1.5-1.7V, and an octahedral structure composed of titanium oxide bonds has a large amount of space gaps to provide storage and transfer of Li +, however, the higher working voltage means lower total output voltage and further low energy density, and besides, the low intrinsic electronic conductivity of lithium titanate is a bottleneck for limiting the multiplying power capability. Disclosure of Invention In view of the problems existing in the prior art, the invention provides a negative electrode sheet, a preparation method thereof and a battery, wherein a coating containing modified lithium titanate is arranged on the surface of an active material, the structure of the modified lithium titanate is an octahedral structure formed by titanium ions and surrounding six oxygen ions, a crystal skeleton is kept unchanged in the charge and discharge process, the stability and zero strain characteristics of the negative electrode in the lithium intercalation and deintercalation process are ensured, so that the safety performance of the negative electrode sheet is improved, and the modified lithium titanate can reduce the lithium intercalation working potential and optimize the electron conductivity relative to the lithium titanate, so that the multiplying power capability of the negative electrode sheet is improved. To achieve the purpose, the invention adopts the following technical scheme: in a first aspect, the present invention provides a negative electrode sheet, where the negative electrode sheet includes a current collector and an active material layer disposed on at least one surface of the current collector, and a coating layer is disposed on a side of the surface of the active material layer away from the current collector; The material of the coating comprises modified lithium titanate. According to the invention, the coating containing the modified lithium titanate is arranged on the surface of the active material, so that the saf