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CN-122000634-A - Composite diaphragm, secondary battery thereof and electricity utilization device

CN122000634ACN 122000634 ACN122000634 ACN 122000634ACN-122000634-A

Abstract

The application discloses a composite diaphragm, a secondary battery and an electric device thereof, and relates to the technical field of batteries. The composite membrane provided by the application has the advantages that the first coating and the second coating are arranged on at least one side of the porous base membrane, wherein the first coating comprises at least two of inorganic ceramic, a porous frame material and flame retardant microcapsules, the second coating comprises polymer particles with a core layer, an intermediate layer and a shell layer, the crosslinking density of polymer A in the core layer, polymer B in the intermediate layer and polymer C in the shell layer is sequentially increased, the obtained composite membrane has excellent heat resistance and flame retardance, has good cohesiveness and can effectively improve the interfacial bonding capability, and thus the cycle performance of a secondary battery prepared subsequently can be effectively improved.

Inventors

  • ZHONG QIAOHONG
  • LIN FENG
  • HE HONGJUN
  • CHENG ZHONG

Assignees

  • 欣旺达动力科技股份有限公司

Dates

Publication Date
20260508
Application Date
20260212

Claims (16)

  1. 1. The composite membrane is characterized by comprising a porous base membrane, and a first coating and a second coating which are sequentially arranged on at least one side of the porous base membrane; The first coating comprises at least two of inorganic ceramics, porous framework materials and flame-retardant microcapsules; The second coating layer comprises polymer particles, the polymer particles comprise a core layer, an intermediate layer and a shell layer, the core layer comprises a polymer A, the intermediate layer comprises a polymer B, the shell layer comprises a polymer C, and the crosslinking density of the polymer A, the polymer B and the polymer C sequentially increases.
  2. 2. The composite separator of claim 1, wherein at least one of the following is satisfied: (1) The thickness of the porous base film is 5-16 mu m; (2) The thickness of the first coating is 1-8 mu m; (3) The thickness of the second coating is 1-6 mu m.
  3. 3. The composite separator of claim 1, wherein the first coating comprises an inorganic ceramic, a porous frame material, and flame retardant microcapsules, the first coating satisfying 0.6< y <4; Wherein y= (b×r)/(d×p); B m 2 /g is the specific surface area of the porous frame material; Rcm 3 /g is the pore volume of the porous frame material; d nm is the average particle size of the inorganic ceramic; and P nm is the thickness of the shell layer of the flame-retardant microcapsule.
  4. 4. The composite separator according to claims 1-3, wherein at least one of the following is satisfied: (1) The specific surface area B m 2 /g of the porous frame material is 2000 m 2 /g~3000 m 2 /g; (2) The pore volume R cm 3 /g of the porous frame material is 1.5 cm 3 /g~2.0 cm 3 /g; (3) The average grain diameter D nm of the inorganic ceramic is 100 nm-150 nm; (4) The thickness P nm of the shell layer of the flame-retardant microcapsule is 10 nm-50 nm.
  5. 5. The composite membrane according to claim 1, wherein the surface of the porous frame material is provided with a silane coupling agent, and the intensity ratio of the Si-O-Si asymmetric stretching vibration characteristic peak to the Si-OH stretching vibration characteristic peak of the porous frame material is more than or equal to 1.2.
  6. 6. The composite separator of claim 1, wherein at least one of the following is satisfied: (1) The inorganic ceramic comprises at least one of silicon dioxide, aluminum oxide, boehmite, magnesium oxide and barium sulfate; (2) The porous framework material comprises MOFs material, and the MOFs material comprises at least one of KAR-F02, ZIF-8, UIO-66 and MOF-177; (3) The shell layer of the flame-retardant microcapsule comprises polyurea-formaldehyde resin, and the core layer comprises melamine cyanurate; (4) The average particle diameter of the core layer of the flame-retardant microcapsule is 0.4-4.5 mu m.
  7. 7. The composite separator of claim 1, wherein the cross-link density increases in sequence by an amplitude >20%.
  8. 8. The composite separator of claim 1, wherein at least one of the following is satisfied: (1) The polymer A comprises isocyanate polymer; (2) The polymer B comprises an acrylic copolymer; (3) The polymer C comprises a cross-linked siloxane polymer; (4) The cross-linking density of the polymer A is 0.003 mol/cm 3 ~0.005mol/cm 3 ; (5) The crosslinking density of the polymer B is 0.006 mol/cm 3 ~0.008mol/cm 3 ; (6) The crosslinking density of the polymer C is 0.009 mol/cm 3 ~0.012mol/cm 3 ; (7) The thickness ratio of the core layer to the middle layer to the shell layer is (5-6): (2-3): (1-3); (8) The material of the porous base film comprises any one of polyolefin, polyvinyl alcohol and polyethylene terephthalate non-woven fabric.
  9. 9. The composite membrane of claim 1 wherein the porous base membrane has pores, the inner walls of the pores having a third coating comprising a maleic anhydride-based monomer graft polymer having a glass transition temperature of greater than or equal to 110 ℃.
  10. 10. The composite membrane of claim 9 wherein the ratio of the thickness of the third coating layer to the average pore size of the porous base membrane is 1 (1-8).
  11. 11. The composite membrane of claim 10 wherein the third coating has a thickness of 50nm to 200nm and/or the porous base membrane has an average pore size of 200nm to 600nm.
  12. 12. The composite membrane of claim 1 wherein the porous base membrane has pores, the inner walls of the pores having a fourth coating comprising an ion-conducting material having an ionic conductivity of 3 x 10 -4 S/cm or greater at 30 ℃.
  13. 13. The composite separator of claim 12, wherein the ion conducting material comprises at least one of MOFs materials, COFs materials, polythiophenes, polyanilines, sulfonated polystyrene, crystalline aluminosilicate molecular sieves, layered silicates, metal oxide nanotubes, siloxane-polymer hybrids, graphene, carbon nanotubes, carboxymethyl cellulose, hydroxyethyl cellulose.
  14. 14. The composite membrane of claim 12 wherein the ratio of the thickness of the fourth coating to the average pore size of the porous base membrane is equal to or less than 0.18.
  15. 15. A secondary battery comprising the composite separator according to any one of claims 1 to 14.
  16. 16. An electric device comprising the secondary battery according to claim 15.

Description

Composite diaphragm, secondary battery thereof and electricity utilization device Technical Field The application relates to the technical field of batteries, in particular to a composite diaphragm, a secondary battery and an electric device thereof. Background The separator, which is one of the core components of the secondary battery, mainly plays a role in separating the positive and negative electrodes, preventing short circuits, and allowing ions to pass through, and its performance directly affects the safety, cycle life, and rate performance of the battery. With the rapid development of new energy industry, high energy density, high safety and long cycle life become important development directions of secondary batteries, which puts higher demands on separator performance. Polyolefin separators are widely used because of their excellent mechanical properties and chemical stability, but have problems such as poor heat resistance (thermal shrinkage is easily generated at 120 ℃ or more), insufficient hydrophilicity (electrolyte wettability is poor), and it is difficult to satisfy the requirements of high-safety batteries. To improve these drawbacks, various modified separators have been developed by researchers, such as coating an inorganic ceramic layer on the surface of a base film to improve heat resistance, or introducing an organic coating to improve hydrophilicity. However, these modified membranes still have the disadvantages of (1) weak interfacial bonding force between the coating and the base membrane, easy peeling under long-term charge-discharge cycle or electrolyte soaking, (2) single function, difficulty in meeting multiple requirements of heat resistance, flame retardance, high ion conductivity and the like, and (3) unreasonable structural design of the coating, often increased ion transmission resistance due to improvement of performance by sacrificing porosity, and (4) lack of effective gradient function design, and incapacity of balancing various performance indexes of the membrane. Disclosure of Invention The application aims to solve the technical problems that a diaphragm is difficult to realize heat resistance, flame retardance, higher ion conduction efficiency and good cohesiveness at the same time, and provides a composite diaphragm which has excellent heat resistance, flame retardance, good electrolyte wettability, excellent cohesiveness and high ion conductivity at the same time, so that a secondary battery prepared subsequently has excellent cycle performance and lower internal resistance, and a secondary battery and an electric device thereof. To achieve the above object, according to a first aspect of the present application, there is provided a composite separator including a porous base film, and a first coating layer and a second coating layer sequentially provided on at least one side of the porous base film; The first coating comprises at least two of inorganic ceramics, porous framework materials and flame-retardant microcapsules; The second coating layer comprises polymer particles, the polymer particles comprise a core layer, an intermediate layer and a shell layer, the core layer comprises a polymer A, the intermediate layer comprises a polymer B, the shell layer comprises a polymer C, and the crosslinking density of the polymer A, the polymer B and the polymer C sequentially increases. As an embodiment of the present application, the thickness of the porous base film is 5 μm to 16 μm. As an embodiment of the application, the thickness of the first coating layer is 1-8 μm. As an embodiment of the application, the thickness of the second coating layer is 1-6 μm. As an embodiment of the present application, the first coating layer includes an inorganic ceramic, a porous frame material, and a flame retardant microcapsule, the first coating layer satisfies 0.6< y <4; Wherein y= (b×r)/(d×p); B m 2/g is the specific surface area of the porous frame material; R cm 3/g is the pore volume of the porous frame material; d nm is the average particle size of the inorganic ceramic; and P nm is the thickness of the shell layer of the flame-retardant microcapsule. As an embodiment of the present application, the specific surface area B m 2/g of the porous frame material is 2000m 2/g~3000m2/g. As an embodiment of the application, the porous frame material has a pore volume R cm 3/g of 1.5cm 3/g~2cm3/g. In an embodiment of the present application, the average particle diameter D nm of the inorganic ceramic is 100nm to 150nm. As an embodiment of the application, the thickness P nm of the shell layer of the flame-retardant microcapsule is 10 nm-50 nm. As an embodiment of the present application, the inorganic ceramic includes at least one of silica, alumina, boehmite, magnesia, and barium sulfate. As an embodiment of the application, the surface of the porous frame material is provided with a silane coupling agent, and the intensity ratio of the Si-O-Si asymmetric stretching vibration