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CN-121983752-A - Separator, preparation method thereof and battery

CN121983752ACN 121983752 ACN121983752 ACN 121983752ACN-121983752-A

Abstract

The application provides a diaphragm, a preparation method thereof and a battery, and belongs to the technical field of batteries. The diaphragm comprises a base film, a first functional layer and a second functional layer, wherein the first functional layer is arranged on at least one side of the base film, the second functional layer is arranged on one side, away from the base film, of the first functional layer, the first functional layer and the second functional layer both comprise whisker-shaped ceramics and sheet-shaped ceramics, the mass ratio of the whisker-shaped ceramics to the sheet-shaped ceramics in the first functional layer is M, and the mass ratio of the whisker-shaped ceramics to the sheet-shaped ceramics in the second functional layer is N, and M is more than N. The whisker-shaped ceramic with a larger proportion in the first functional layer has higher mechanical strength, the flaky ceramic with a smaller proportion has the capability of storing and infiltrating electrolyte, meanwhile, the heat conduction network is rich, the whisker-shaped ceramic with a lower proportion has the capability of making the second functional layer have larger porosity, and the flaky ceramic with a higher proportion has the capability of electrolyte relatively stronger, so that the diaphragm with excellent structure and performance is finally formed.

Inventors

  • CHEN XINYU

Assignees

  • 湖北亿纬动力有限公司

Dates

Publication Date
20260505
Application Date
20251223

Claims (10)

  1. 1. A separator, comprising: a base film; a first functional layer disposed on at least one side of the base film, and The second functional layer is arranged on one side of the first functional layer, which is away from the base film; The first functional layer and the second functional layer both comprise whisker-shaped ceramics and sheet-shaped ceramics, the mass ratio of the whisker-shaped ceramics to the sheet-shaped ceramics in the first functional layer is M, and the mass ratio of the whisker-shaped ceramics to the sheet-shaped ceramics in the second functional layer is N, M > N.
  2. 2. The membrane of claim 1, wherein the whisker-like ceramic in the first functional layer accounts for 25% -35% of the total mass of the whisker-like ceramic and the sheet-like ceramic, the sheet-like ceramic accounts for 65% -75% of the total mass of the whisker-like ceramic and the sheet-like ceramic, and/or, In the second functional layer, the whisker-shaped ceramic accounts for 5% -15% of the total mass of the whisker-shaped ceramic and the flaky ceramic, and the flaky ceramic accounts for 85% -95% of the total mass of the whisker-shaped ceramic and the flaky ceramic.
  3. 3. The membrane of claim 1 or 2, wherein the whisker-like ceramic material comprises at least one of aluminum nitride, silicon carbide, silicon nitride, and beryllium oxide, and/or, The material of the sheet ceramic includes at least one of boehmite and boron nitride, and/or, The base film includes at least one of a polyethylene film, a polypropylene film, and a polyethylene/polypropylene film.
  4. 4. A separator according to any one of claims 1 to 3, wherein the whisker-like ceramic is a polydopamine-coated modified whisker-like ceramic, and/or, The flaky ceramic is silane coupling agent modified flaky ceramic.
  5. 5. The separator according to claim 1 to 4, wherein the first functional layer and the second functional layer each further comprise a binder, and wherein the mass ratio of the total mass of the whisker-like ceramic and the sheet-like ceramic to the binder in the first functional layer is 0.75:0.25 to 0.85:0.15, and/or, In the second functional layer, the mass ratio of the total mass of the whisker-shaped ceramic and the flaky ceramic to the binder is 0.45:0.55-0.55:0.45.
  6. 6. The membrane according to any one of claims 1 to 5, wherein the first functional layer has a porosity of 60% to 70%, and/or, The porosity of the second functional layer is 70% -80%, and/or, The porosity of the base film is 40% -60%.
  7. 7. The membrane according to any one of claims 1 to 6, wherein the first functional layer has a thickness of 1 μm to 2 μm and/or, The thickness of the second functional layer is 0.5-1 μm, and/or, The thickness of the base film is 5-12 mu m, and/or, The whisker-like ceramic has a diameter of 0.1 μm to 0.5 μm and/or, The thickness of the flaky ceramic is 0.1-0.3 mu m.
  8. 8. A method for producing the separator according to any one of claims 1 to 7, comprising: A base film is provided and is provided with a base film, Mixing whisker-shaped ceramic, flaky ceramic, a dispersing agent and a binder to obtain first slurry; Mixing the whisker-shaped ceramic, the flaky ceramic, the dispersing agent and the binder to obtain second slurry, wherein the mass ratio of the whisker-shaped ceramic to the flaky ceramic in the first slurry is larger than that of the whisker-shaped ceramic to the flaky ceramic in the second slurry; coating the first slurry on at least one side of the base film, drying, and forming a first functional layer on the base film; And coating the second slurry on one side of the first functional layer far away from the base film, drying, and forming a second functional layer on the first functional layer.
  9. 9. The method according to claim 8, wherein before mixing the whisker-like ceramic, the platelet-like ceramic and the dispersant to obtain the first slurry, mixing the whisker-like ceramic, the platelet-like ceramic and the dispersant to obtain the second slurry, further comprising: Coating and modifying the whisker-shaped ceramic by polydopamine to obtain modified whisker-shaped ceramic; And modifying the flaky ceramic by a silane coupling agent to obtain a modified flaky ceramic.
  10. 10. A battery, characterized by comprising a positive plate, a negative plate and the separator according to any one of claims 1 to 7 or the separator prepared by the preparation method of the separator according to any one of claims 8 to 9.

Description

Separator, preparation method thereof and battery Technical Field The application relates to the technical field of batteries, in particular to a diaphragm, a preparation method thereof and a battery. Background The lithium battery has the characteristics of high working voltage, high energy density and quick charge, and is widely applied to the field of new energy automobiles. The diaphragm is an important component of a lithium battery, the melting point of the polyolefin diaphragm is lower than 180 ℃, thermal shrinkage is easy to occur in a high-temperature environment, the positive electrode and the negative electrode of the battery are in direct contact to cause short circuit, the puncture resistance strength is usually lower than 120MPa, the growth and penetration of lithium dendrites are difficult to effectively block, and the battery is invalid or even a safety accident occurs. Aluminum nitride (AlN) has high thermal conductivity, high temperature resistance, high mechanical strength, boehmite (AlOOH) has low-temperature heat absorption characteristics, and in order to improve the performance of a polyolefin separator, in the related art, although the performance of the polyolefin separator can be improved by sequentially coating an aluminum nitride coating and a boehmite coating on the surface of the polyolefin separator, the aluminum nitride coating of the inner layer in the structure has limited wettability to an electrolyte, the boehmite coating of the outer layer has poor mechanical properties, and the composition and the used materials of the inner layer and the outer layer have a single structure, thereby making the performance of the separator relatively poor. Disclosure of Invention The application provides a diaphragm, a preparation method thereof and a battery, and aims to solve the problem that the diaphragm formed by the existing multilayer ceramic coating has relatively poor diaphragm performance due to the composition of different layers and the single structure of used materials. In a first aspect, embodiments of the present application provide a separator comprising: a base film; A first functional layer disposed on at least one side of the base film, and The second functional layer is arranged on one side of the first functional layer, which is away from the base film; The first functional layer and the second functional layer both comprise whisker-shaped ceramics and flake-shaped ceramics, the mass ratio of the whisker-shaped ceramics to the flake-shaped ceramics in the first functional layer is M, and the mass ratio of the whisker-shaped ceramics to the flake-shaped ceramics in the second functional layer is N, wherein M is more than N. The first functional layer and the second functional layer both comprise whisker-shaped ceramics, flaky ceramics and a binder, firstly, different whiskers are mutually entangled into a reticular framework due to the high length-diameter ratio of the whisker-shaped ceramics, meanwhile, the flaky ceramics are filled in the reticular framework formed by the whisker-shaped ceramics, so that the mechanical strength, puncture resistance and stability of the first functional layer and the second functional layer are improved, meanwhile, the binding effect of the first functional layer and the second functional layer on a base film is better, the ceramic material has certain thermal conductivity and high temperature resistance, and the thermal shrinkage rate of a diaphragm is reduced; the three-dimensional reticular framework formed by the whiskers can absorb and store a large amount of electrolyte, the contact area between the whisker-shaped ceramic and the electrolyte can be increased by the lamellar structure, the wettability of the electrolyte is improved, the mass ratio M of the whisker-shaped ceramic and the lamellar ceramic in the first functional layer is larger than the mass ratio N of the whisker-shaped ceramic and the lamellar ceramic in the second functional layer, the whisker-shaped ceramic with larger proportion in the first functional layer enables the whisker to be entangled more densely, the mechanical strength of the first functional layer is higher, the capacity of the first functional layer for storing the electrolyte and the electrolyte is adapted by the relatively dense reticular structure and the lamellar ceramic with smaller proportion, the proportion of the whisker-shaped ceramic in the second functional layer is relatively lower, the porosity of the second functional layer is relatively larger, the capacity of the lamellar structure for infiltrating the electrolyte is relatively stronger, the high porosity of the second functional layer and the high lamellar ceramic proportion enable the electrolyte to be adapted by the capacity of the whisker-shaped ceramic to store the electrolyte and the electrolyte, the gradient structure of the electrolyte is finally realized, and the heat conduction performance of the separator is excellent