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CN-122025547-A - Positive plate, preparation method thereof and battery

CN122025547ACN 122025547 ACN122025547 ACN 122025547ACN-122025547-A

Abstract

The application provides a positive plate, a preparation method thereof and a battery, and belongs to the technical field of batteries. The lithium-rich material is arranged on at least one side of the current collector, and the lithium-rich material layer comprises the lithium-rich material. The first positive electrode active layer is arranged on one side, away from the current collector, of the lithium-rich material layer, and the first positive electrode active layer comprises lithium manganese iron phosphate. The second positive electrode active layer is arranged on one side, away from the lithium-rich material layer, of the first positive electrode active layer, and the second positive electrode active layer comprises a ternary material. The positive plate provided by the embodiment of the application can reduce side reactions between the lithium-rich material and other materials, improve the lithium supplementing effect, and improve the electrochemical performance, the structural stability and the cycle life of the positive plate.

Inventors

  • Lu Renxi
  • Wen Shengyao
  • LIU FANFEN
  • YUAN DINGDING
  • HUANG XIN

Assignees

  • 惠州亿纬锂能股份有限公司
  • 湖北亿纬动力有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (15)

  1. 1. A positive electrode sheet, comprising: A current collector; the lithium-rich material layer is arranged on at least one side of the current collector and comprises a lithium-rich material; The first positive electrode active layer is arranged on one side of the lithium-rich material layer, which is away from the current collector, and comprises lithium manganese iron phosphate; the second positive electrode active layer is arranged on one side, away from the lithium-rich material layer, of the first positive electrode active layer, and the second positive electrode active layer comprises ternary materials.
  2. 2. The positive plate of claim 1, wherein the lithium-rich material has a chemical formula of Li x M y O z , wherein M is at least one selected from the group consisting of Al, ni and Co, 1<x≤ 2.0,1.5≤z≤2.0; and/or the ternary material comprises at least one of nickel cobalt lithium manganate and nickel cobalt lithium aluminate.
  3. 3. The positive electrode sheet according to claim 1, wherein the thickness of the lithium-rich material layer is 10 μm to 16 μm.
  4. 4. The positive electrode sheet according to claim 1, wherein in the lithium-rich material layer, the particle diameter D50 of the lithium-rich material is 10 μm to 15 μm, and the particle diameter distribution range is 1 μm to 20 μm; and/or, in the first positive electrode active layer, the particle diameter D50 of the lithium manganese iron phosphate is 0.5-1.2 mu m, and the particle diameter distribution range is 0.1-25 mu m; And/or, in the second positive electrode active layer, the ternary material has a particle diameter D50 of 5-12 μm and a particle diameter distribution range of 5-12 μm.
  5. 5. The positive electrode sheet according to claim 1, wherein the first positive electrode active layer has a porosity of 20% to 30%; And/or, the second positive electrode active layer has a porosity of 25% -35%.
  6. 6. The positive electrode sheet of claim 1, wherein the current collector comprises a composite aluminum foil layer comprising a polymer layer and first and second aluminum foil layers disposed on opposite sides of the polymer layer.
  7. 7. The positive electrode sheet of claim 6, wherein the current collector further comprises a carbon-coated layer disposed between the composite aluminum foil layer and the lithium-rich material layer.
  8. 8. The positive electrode sheet according to claim 7, wherein the thickness of the carbon-coated layer is 0.5 μm to 1 μm.
  9. 9. The positive electrode sheet according to any one of claims 1 to 8, characterized in that a mass ratio of a total amount of the lithium iron manganese phosphate and the ternary material to the lithium-rich material is (93 to 97.8): 0.2 to 5; And/or the mass ratio of the lithium iron manganese phosphate to the ternary material is 98:2 to 50:50.
  10. 10. The positive electrode sheet according to any one of claims 1 to 8, wherein the lithium-rich material layer further comprises a first binder, the first positive electrode active layer further comprises a first conductive agent and a second binder, and the second positive electrode active layer further comprises a second conductive agent and a third binder; In the positive plate, the total mass of the lithium manganese iron phosphate and the ternary material is A, the mass of the lithium-rich material is B, the total mass of the first binder, the second binder and the third binder is C, and the total mass of the first conductive agent and the second conductive agent is D, so that the total mass of A, B, C and D= (93-97.8) is (0.2-5) is (1.2-2.5) is (0.5-2) is (0-0.5).
  11. 11. The positive electrode sheet according to claim 10, wherein the first conductive agent comprises conductive carbon black and carbon nanotubes; and/or, the second conductive agent includes conductive carbon black and carbon nanotubes.
  12. 12. The preparation method of the positive plate is characterized by comprising the following steps: Providing a current collector; providing lithium supplementing slurry comprising a lithium-rich material and a first binder, and coating the lithium supplementing slurry on at least one side of the current collector to form a lithium-rich material layer; Providing first positive electrode slurry comprising lithium manganese iron phosphate, a second binder and a first conductive agent, and coating the first positive electrode slurry on the surface of one side, facing away from the current collector, of the lithium-rich material layer to form a first positive electrode active layer; and providing a second positive electrode slurry comprising a ternary material, a third binder and a second conductive agent, coating the second positive electrode slurry on the surface of one side, facing away from the lithium-rich material layer, of the first positive electrode active layer, and forming a second positive electrode active layer to obtain the positive electrode plate.
  13. 13. The method for preparing a positive plate according to claim 12, wherein the solid content of the lithium supplementing slurry is 65% -75%; and/or the solid content of the first positive electrode slurry is 65% -75%; and/or, the solid content of the second positive electrode slurry is 65% -75%.
  14. 14. A battery comprising the positive electrode sheet according to any one of claims 1 to 11, and/or the positive electrode sheet produced by the method for producing a positive electrode sheet according to any one of claims 12 to 13.
  15. 15. The battery of claim 14, wherein the lithium-rich material in the positive electrode sheet has a chemical formula of Li a M b O c after the battery is formed, wherein M is at least one of Al, ni and Co, a is greater than or equal to 0.5 and less than or equal to 2.0,1.5 and c is greater than or equal to 2.0, and c/a is greater than or equal to 2.0 and less than or equal to 4.0.

Description

Positive plate, preparation method thereof and battery Technical Field The application relates to the technical field of batteries, in particular to a positive plate, a preparation method thereof and a battery. Background As a phosphate positive electrode material, lithium iron phosphate (LiMn l-xFexPO4, 0< x < 1) has the characteristics of good heat stability and high specific capacity of lithium iron phosphate (LiFePO 4), has a high voltage window and high specific energy of lithium manganese phosphate (LiFePO 4), has the characteristics of low cost and good safety, and is very likely to replace the lithium iron phosphate positive electrode material in future development, and is applied to the fields of power batteries, energy storage batteries and the like. However, the lithium iron manganese phosphate battery has low energy density and poor cycle performance, and becomes a limiting factor affecting the application of the lithium iron manganese phosphate battery. In order to improve the cycle life of lithium iron manganese phosphate batteries, additional high capacity lithium-supplementing materials are typically added to the positive electrode. In the related art, in supplementing lithium to the positive electrode, a small amount of high-capacity material is generally added during the preparation of the positive electrode slurry. Because the specific surface area of the lithium iron manganese phosphate is as high as 20m 2/g or more, when the anode slurry is prepared, the slurry is extremely easy to absorb environmental moisture, so that side reactions of lithium-rich materials are easy to occur, and the binder in the slurry is crosslinked, the stability and the processability of the slurry are obviously reduced, the lithium supplementing effect is poor, and the performance of the anode is influenced. Disclosure of Invention The embodiment of the application provides a positive plate, a preparation method thereof, a battery and a formation method thereof, which can reduce side reactions between a lithium-rich material and other materials, improve the lithium supplementing effect, and improve the electrochemical performance, the structural stability and the cycle life of the positive plate. In a first aspect, an embodiment of the present application provides a positive electrode sheet including: A current collector; the lithium-rich material layer is arranged on at least one side of the current collector and comprises a lithium-rich material; The first positive electrode active layer is arranged on one side of the lithium-rich material layer, which is away from the current collector, and comprises lithium manganese iron phosphate; the second positive electrode active layer is arranged on one side, away from the lithium-rich material layer, of the first positive electrode active layer, and the second positive electrode active layer comprises ternary materials. In the positive plate provided by the embodiment of the application, the lithium-rich material layer is independently arranged, so that the probability of side reaction between the lithium-rich material and other materials is reduced, the stability and the processability of the lithium-rich material layer are improved, and the lithium supplementing effect is ensured. The lithium-rich material layer is arranged close to the current collector, so that the lithium-rich material is in direct contact with the current collector, electrons can be quickly obtained by the lithium-rich material in the formation charging process, the lithium-rich material is promoted to undergo decomposition reaction, the lithium ion release efficiency is high, and the lithium supplementing effect is good. The first positive electrode active layer comprises lithium manganese iron phosphate, the second positive electrode active layer comprises ternary materials, lithium ions released by the lithium-rich material layer can sequentially pass through the first positive electrode active layer and the second positive electrode active layer to enter electrolyte, the lithium supplementing effect is exerted, the diffusion coefficient of the first positive electrode active layer is moderate, and the excessive absorption of the second positive electrode active layer to lithium ions can be reduced. And the second positive electrode active layer has high conductivity, shortens a charge transmission path and improves high-current charge and discharge capacity. Because the working voltage of the lithium iron manganese phosphate is lower than that of the ternary material, the second positive electrode active layer with the ternary material is positioned on the outer side and can preferentially remove and insert lithium, the risk of overcharging of the lithium iron manganese phosphate under high voltage is reduced, and the voltage stability is improved. The lithium iron manganese phosphate has an olivine structure, has small volume change in the charge-discharge process, can buffer the stress d