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CN-121394778-B - Diaphragm and battery

CN121394778BCN 121394778 BCN121394778 BCN 121394778BCN-121394778-B

Abstract

The invention relates to the technical field of batteries, in particular to a diaphragm and a battery comprising the diaphragm. The diaphragm comprises a substrate layer and an organic coating layer positioned on one side or two side surfaces of the substrate layer, wherein the organic coating layer comprises organic particles, the organic particles comprise nitrogen-containing condensed ring organic matters, the molecular structure of the nitrogen-containing condensed ring organic matters is a planar structure, the molecular structure of the nitrogen-containing condensed ring organic matters comprises nitrogen-containing condensed heterocyclic rings, and the closed pore temperature of the diaphragm is 90-170 ℃. The diaphragm of the invention can reduce or even avoid the side reaction of the electrolyte and the electrode interface, reduce or even inhibit the dissolution of transition metal lithium ions in the positive electrode material, improve the high temperature safety performance of the battery, the separator also has higher puncture strength, higher thermal shrinkage resistance and higher electrolyte wettability, so that the battery has higher mechanical safety performance, lower K value and higher high-temperature cycle performance while improving the high-temperature safety performance of the battery.

Inventors

  • ZHONG JUNDONG
  • WU ZHIJIE
  • CAO XIAODONG

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260512
Application Date
20251225

Claims (14)

  1. 1. The diaphragm is characterized by comprising a substrate layer and an organic coating layer positioned on one side or two side surfaces of the substrate layer, wherein the organic coating layer comprises organic particles, the organic particles comprise nitrogen-containing condensed ring organic matters, the molecular structure of the nitrogen-containing condensed ring organic matters is a plane structure, the molecular structure of the nitrogen-containing condensed ring organic matters comprises nitrogen-containing condensed rings, the closed pore temperature of the diaphragm is 90-170 ℃, the weight ratio of the organic particles in the organic coating layer is 90-99%, and the nitrogen-containing condensed ring organic matters comprise at least one of 2-mercaptobenzimidazole and 2-mercaptobenzimidazole derivatives.
  2. 2. The separator of claim 1, wherein the separator has a closed cell temperature of 130-160 ℃; And/or the organic particles have a layered crystal structure.
  3. 3. The separator of claim 2, wherein the nitrogen-containing fused ring organic further comprises one or more of an imidazopyridine that is unsubstituted or substituted with a feature group, an imidazopyrazine that is unsubstituted or substituted with a feature group, a pyrrolopyrimidine ring that is unsubstituted or substituted with a feature group, a quinoline ring that is unsubstituted or substituted with a feature group, and a pteridine ring that is unsubstituted or substituted with a feature group.
  4. 4. A separator according to claim 3, wherein the characteristic group is selected from one or more of C1-C6 alkoxy, hydroxy, amino, carboxy, cyano, halo substituent, sulfo, mercapto, nitro and C1-C6 alkyl which is unsubstituted or substituted by substituent R, the substituent R being selected from one or more of hydroxy, amino and carboxy.
  5. 5. The separator of claim 1, wherein the nitrogen-containing fused ring organics further comprise one or more of 7-chloro-imidazopyridine, 5-bromoimidazopyrazine, 2-chloromethylimidazopyrazine, 2-amino-7H-pyrrolopyrimidine, 5-aminoquinoline, pteridin-2-amine, pteridine-2-thiol.
  6. 6. The separator of claim 1, wherein the substrate layer has a closed cell temperature of 130-170 ℃; And/or the 2-mercaptobenzimidazole derivatives include one or more of 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfobenzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole; And/or the particle size distribution of the organic particles satisfies the following relation (D 9 -D 1 )/D 5 is less than or equal to 5), wherein D 1 is Dv10 of the organic particles, the unit is mu m, D 5 is Dv50 of the organic particles, the unit is mu m, and D 9 is Dv90 of the organic particles, the unit is mu m; and/or the thickness of the organic coating is 0.2 μm to 5 μm.
  7. 7. The separator of claim 1, wherein the nitrogen-containing fused ring organic is at least one of 2-mercaptobenzimidazole, a 2-mercaptobenzimidazole derivative; And/or the components of the substrate layer comprise at least one of polyethylene and polypropylene; and/or the thickness of the substrate layer is 3 μm to 16 μm; and/or the porosity of the substrate layer is 30% -70%; and/or the average pore diameter of the substrate layer is 30nm-50nm; and/or the puncture strength of the substrate layer is 200gf-600gf; And/or the areal density of the substrate layer is 2g/m 2 -6g/m 2 ; And/or the membrane has a heat shrinkage of less than 30% after being placed at 130 ℃ for 1 hour; And/or the organic coating further comprises a first binder, wherein the weight ratio of the first binder in the organic coating is 1-10%.
  8. 8. The separator of claim 1, wherein the substrate layer comprises a plurality of fibers, the composition of the fibers comprising a first polymer comprising at least one of polyethylene, polypropylene, the fibers having a diameter of 0.02 μιη to 0.5 μιη.
  9. 9. The separator of claim 8, wherein the crystallinity of the first polymer is 40% -70%; And/or the weight average molecular weight of the polyethylene is 30 ten thousand to 60 ten thousand; And/or the components of the substrate layer further comprise polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly (p-phenylene terephthalamide), poly (m-phenylene isophthalamide) or one or more of the derivatives of the above polymers.
  10. 10. The separator of claim 7, wherein the polyethylene has a weight average molecular weight of 30-60 ten thousand; And/or the components of the substrate layer further comprise polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly (p-phenylene terephthalamide), poly (m-phenylene isophthalamide) or one or more of the derivatives of the above polymers; And/or the first binder comprises one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, styrene-acrylic latex, polyacrylonitrile, acrylic polymer, polyvinyl acetate, polyacrylic acid, polyurethane, fluorine-containing polymer or a copolymer system derived from the above polymers.
  11. 11. The separator of any of claims 1-10, wherein the organic particles have a solubility W of less than 0.8% in a test electrolyte consisting of lithium hexafluorophosphate, ethylene carbonate, methylethyl carbonate, and dimethyl carbonate at a concentration of 1mol/L and a volume ratio of 1:1:1 of ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in an environment of 135 ℃; And/or the separator satisfies the following relation of delta F being more than or equal to 40 and less than or equal to 80, wherein delta F=F 2 -F 1 ,F 1 is the peeling strength of the organic coating and the substrate layer at 25 ℃, the unit is N/m, F 2 is the peeling strength of the organic coating and the substrate layer after baking for 2 hours at 90 ℃, and the unit is N/m; And/or the diaphragm comprises a carrier layer and a glue layer positioned on one side or two side surfaces of the carrier layer, wherein the carrier layer comprises a substrate layer and an organic coating positioned on one side or two side surfaces of the substrate layer, the glue layer comprises a polymer, and the coverage rate of the glue layer on the surface of the carrier layer is 15% -50%.
  12. 12. The separator of claim 11, wherein the separator satisfies the relationship 60≤F 1 ≤80,120≤F 2 ≤140; and/or the components of the polymer of the adhesive layer comprise one or more of paraphenylene terephthalamide, m-phenylene isophthalamide, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylic polymers, phenolic resins, polyimides, furyl modified polyamides, modified phenolic resins and modified polyimides; and/or, based on the total weight of the glue layer, the weight ratio of the polymer is 30% -100%; and/or the thickness of the adhesive layer is 0.5-5 μm.
  13. 13. A battery comprising a positive electrode sheet, a negative electrode sheet, and the separator of any one of claims 1-12, the separator being located between the positive electrode sheet and the negative electrode sheet.
  14. 14. The battery according to claim 13, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on one or both side surfaces of the negative electrode current collector, the negative electrode active layer comprising a silicon-based material including one or more of elemental silicon particles, silicon oxide particles, silicon carbon composite particles, silicon nitrogen composite particles, silicon alloy particles, the silicon carbon composite particles having an average particle diameter of 5 μm to 12 μm, and a sphericity of 0.8 to 1; and/or the battery further comprises an electrolyte, wherein the electrolyte comprises a polar solvent, and the polar solvent is at least one selected from 2, 2-difluoroethyl acetate, propyl propionate, ethyl propionate, diethyl carbonate, propylene carbonate and ethylene carbonate.

Description

Diaphragm and battery Technical Field The invention relates to the technical field of batteries, in particular to a diaphragm and a battery comprising the diaphragm. Background Lithium ion batteries are used as key energy storage devices in portable electronic devices, new energy automobiles and large-scale energy storage systems. As industry technology continues to advance, the market has put forward more stringent standards for fast charge endurance and safety performance in high temperature conditions of lithium ion batteries. At present, in the long-term cycle process of a lithium ion battery, the continuous side reaction between an electrolyte and an electrode interface can lead to the generation of harmful substances such as acid, active free radicals and the like. These harmful substances corrode the solid electrolyte interface film (CEI) on the surface of the positive electrode material, resulting in elution of the transition metal, and more seriously, such side reactions tend to be accompanied by exothermic effects, particularly when the battery is at high temperature, which further accelerate the rise of the internal temperature of the battery, and the heat release caused by the side reactions further accelerates the rise of the internal temperature of the battery, and forms a vicious exothermic cycle. The vicious exothermic cycle can lead to the continuous rise of the internal temperature of the battery, and finally can cause serious safety problems such as thermal runaway and the like, thereby greatly limiting the high-temperature safety performance and the use reliability of the battery. Therefore, it is important to provide a battery capable of reducing side reactions between an electrolyte and an electrode interface and blocking an ion conduction path in time at the initial stage of temperature rise. Disclosure of Invention The research shows that the membrane with low closed pore temperature is friendly to the high temperature safety performance of the battery, but the mechanical strength of the membrane with low closed pore temperature is often insufficient, so that the K value of the battery is increased, and the battery cannot have both high temperature safety performance and low K value. In order to solve the problems that a battery cannot have higher high-temperature safety performance and higher mechanical safety performance and the battery is easy to generate thermal runaway due to side reaction of an electrolyte and an electrode interface in the prior art, the invention provides a diaphragm and the battery comprising the diaphragm. The diaphragm of the invention can reduce or even avoid the side reaction of the electrolyte and the electrode interface, reduce or even inhibit the dissolution of transition metal ions in the anode material, improve the high temperature safety performance of the battery, the separator also has higher puncture strength, higher thermal shrinkage resistance and higher electrolyte wettability, so that the battery has lower K value and higher high-temperature cycle performance while improving the high-temperature safety performance of the battery. In order to achieve the above object, according to a first aspect of the present invention, there is provided a separator comprising a base material layer and an organic coating layer located on one or both side surfaces of the base material layer, the organic coating layer comprising organic particles including nitrogen-containing condensed ring organic matter, the molecular structure of the nitrogen-containing condensed ring organic matter being a planar structure, the molecular structure of the nitrogen-containing condensed ring organic matter including nitrogen-containing condensed heterocyclic ring, the separator having a closed pore temperature of 90 ℃ to 170 ℃. A second aspect of the present invention provides a battery, wherein the battery comprises a positive electrode sheet, a negative electrode sheet, and the separator according to the first aspect of the present invention, the separator being located between the positive electrode sheet and the negative electrode sheet. Through the technical scheme, compared with the prior art, the invention has at least the following advantages: The organic particles in the diaphragm comprise nitrogen-containing condensed ring organic matters, the nitrogen-containing condensed ring organic matters have a plane conjugated large pi bond system, and nitrogen atoms in condensed rings have a pair of lone electrons, so that the nitrogen-containing condensed ring organic matters have certain coordination capacity and Lewis basicity, wherein the coordination capacity of molecules of the nitrogen-containing condensed ring organic matters can generate certain adsorption action with transition metals on the surface of positive electrode active particles, so that a compact and firm physical barrier can be formed on the surface of the positive electrode active particles, oxidation re