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CN-121261064-B - Battery cell

CN121261064BCN 121261064 BCN121261064 BCN 121261064BCN-121261064-B

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a positive plate, a negative plate, electrolyte and a diaphragm, wherein the diaphragm comprises a carrier layer and a polymer coating, the polymer coating corresponds to the positive plate and is a first polymer coating, the polymer coating corresponds to the negative plate and is a second polymer coating, the first polymer coating comprises first particles, the second polymer coating comprises second particles, the surface of the negative plate is provided with concave parts, and the battery meets the following relation formula F 1 ＜F 2 ,0.1≤M 1 /F 3 ≤1.2,F 3 =F 2 -F 1 . The battery provided by the invention can reduce risks of dislocation between the diaphragm and the positive and negative pole pieces, deformation of the electrode assembly and fragmentation of active particles in high-temperature circulation caused by the cyclic expansion of the negative pole piece in the circulation process, and can balance the binding force between the diaphragm and the negative pole piece and the interface heat dissipation performance, so that the battery has high long-circulation stability, high-temperature circulation performance and furnace temperature safety performance.

Inventors

  • WU ZHIJIE
  • CUI HONGYU

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260512
Application Date
20251208

Claims (10)

  1. 1. The battery is characterized by comprising a positive plate, a negative plate, electrolyte and a diaphragm positioned between the positive plate and the negative plate, wherein the diaphragm comprises a carrier layer and polymer coatings positioned on two side surfaces of the carrier layer, the polymer coating corresponding to the positive plate is a first polymer coating, the polymer coating corresponding to the negative plate is a second polymer coating, the first polymer coating comprises first particles distributed in a dispersing way, the components of the first particles are acrylic polymers, the second polymer coating comprises second particles distributed in a dispersing way, and the components of the second particles are acrylic polymers; F 1 ＜F 2 ,0.1≤M 1 /F 3 is less than or equal to 1.2, wherein F 3 =F 2 -F 1 ,F 1 is the coverage rate of the first particles in any 25 [ mu ] M multiplied by 19 [ mu ] M area of the surface of the first polymer coating layer, F 2 is the coverage rate of the second particles in any 25 [ mu ] M multiplied by 19 [ mu ] M area of the surface of the second polymer coating layer, and M 1 is the coverage rate of the concave parts on the surface of the negative plate; The electrolyte comprises a fluorine-containing solvent, wherein the fluorine-containing solvent comprises ethyl difluoroacetate and fluoroethylene carbonate, the weight ratio of the ethyl difluoroacetate to the fluoroethylene carbonate is 1-8.6, and the weight ratio of the fluoroethylene carbonate in the electrolyte is 5-12.5%.
  2. 2. The battery of claim 1, wherein the battery satisfies the relationship 0.3≤M 1 /F 3 ≤0.95; And/or, F 1 is 4% -35%; And/or, F 2 is 10% -45%; and/or, F 3 is 8% -35%; and/or, M 1 is 3% -17%; And/or the acrylic polymer comprises one or more of polymethyl methacrylate, polyethyl hexyl acrylate, polybutyl acrylate, acrylic monomer-acrylonitrile copolymer, styrene-acrylic monomer copolymer, acrylic monomer-acrylonitrile-ethylene copolymer, styrene-acrylic monomer-acrylonitrile copolymer, acrylic monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N, N-dimethylacrylamide copolymer, ethyl acrylate-2- (diethylamino) ethyl acrylate copolymer, ethyl acrylate-N, N-diethylacrylamide copolymer, ethyl acrylate-2- (diethylamino) ethyl acrylate.
  3. 3. The battery of claim 1, wherein the topography of the recess comprises one or more of holes, lines, and grooves; And/or the width of the concave part is 55-185 μm; And/or the depth of the concave part is 5-35 μm; and/or the spacing between adjacent concave parts is 0.9mm-1.8mm; and/or the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer positioned on one side or two side surfaces of the negative electrode current collector, wherein the negative electrode active layer comprises a silicon-based material, and the silicon-based material comprises one or more of elemental silicon particles, silicon-oxygen particles, silicon-carbon particles, silicon-nitrogen particles and silicon alloy particles.
  4. 4. The battery of claim 1, wherein the first polymer coating further comprises third particles, the third particles being agglomerated particles; and/or the second polymeric coating does not include third particles.
  5. 5. The battery of claim 4, wherein the separator satisfies the following relationship 1.5≤d 1 /d 2 ≤25, wherein d 1 is the average particle size of the secondary particles of the third particles in μm, d 2 is Dv90 of the first particles in μm; and/or the secondary particles of the third particles have an average particle diameter of 2 μm to 20 μm; And/or, the Dv90 of the first particles is 0.65 μm to 4.5 μm; and/or, at 90 ℃, the third particles are soaked in 2, 2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the third particles is less than 40%; And/or the components of the third particles comprise one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylic monomer-acrylonitrile copolymer, styrene-acrylic monomer copolymer, acrylic monomer-ethylene copolymer, styrene-acrylic monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N, N-dimethylacrylamide copolymer, ethyl acrylate-2- (diethylamino) ethyl acrylate copolymer, ethyl acrylate-N, N-diethylacrylamide copolymer, ethyl acrylate-2- (diethylamino) ethyl acrylate.
  6. 6. The battery of claim 1, wherein F 3 is 10% -25%; And/or, M 1 is 5% -11%; and/or the first particles and the second particles are the same or different; and/or the first particles have an average particle diameter of 0.5 μm to 1.2 μm; And/or the second particles have an average particle diameter of 0.5 μm to 1.2 μm; and/or, at 90 ℃, the first particles are soaked in 2, 2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the first particles is more than 70%; And/or, at 90 ℃, the second particles are soaked in 2, 2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the second particles is greater than 70%; And/or the coverage rate of the first polymer coating on the surface of the carrier layer is 10% -45%; and/or the coverage of the second polymer coating on the surface of the carrier layer is 10% -45%; and/or the separator has a thermal shrinkage of less than 10% in the stretching direction; and/or the separator has a thermal shrinkage of less than 10% in a direction perpendicular to the stretching direction; And/or the membrane has a gas permeation value of 60 s/100cc to 350 s/100cc; and/or the puncture strength of the diaphragm is greater than 120gf.
  7. 7. The battery of any of claims 1-6, wherein the fluorine-containing solvent is present in the electrolyte in an amount of 10% to 75% by weight; And/or the fluorine-containing solvent further comprises one or more of difluoro ethylene carbonate, ethyl monofluoroacetate, trifluoroethyl acetate, propyl difluoroacetate and propyl difluoroacetate.
  8. 8. The battery of claim 1, wherein the ethyl difluoroacetate comprises at least one of 2, 2-difluoroethyl acetate, 2-difluoroethyl acetate; And/or the weight ratio of the ethyl difluoroacetate in the electrolyte is 5-65%.
  9. 9. The battery of claim 1, wherein the carrier layer comprises a substrate layer and a heat resistant layer on a surface of one or both sides of the substrate layer; And/or the carrier layer comprises a substrate layer and a heat-resistant layer, wherein the aperture of the substrate layer is 25nm-50nm; and/or the carrier layer comprises a substrate layer and a heat-resistant layer, wherein the thickness of the substrate layer is 3-10 mu m; and/or the carrier layer comprises a substrate layer and a heat-resistant layer, wherein the substrate layer comprises one or more of polyethylene, polypropylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly (p-phenylene terephthalamide), poly (m-phenylene isophthalamide) or polymer derivatives thereof.
  10. 10. The battery of claim 9, wherein the heat resistant layer comprises heat resistant particles in an amount of 90-99% by weight and a first binder in an amount of 1-10% by weight, based on the total weight of the heat resistant layer; And/or the thickness of the heat-resistant layer is 0.3 μm to 4.5 μm; And/or the refractory layer comprises refractory particles and a first binder, the components of the refractory particles comprising one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silica, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3, 5-triazine-2, 4, 6-triamine, melamine cyanurate, symmetrical triamine triazine, 2, 4-diamino-6-dimethylamino-1, 3, 5-triazine, 2,4, 6-tris (2-pyridyl) triazine, 2-amino-4, 6-methoxy-1, 3, 5-triazine, lithium aluminum titanium phosphate, uracil, cytosine, guanine, 4-amino-2, 6-dihydroxypyrimidine, phenolic resin, cellulose, benzimidazole compound; And/or the heat-resistant layer comprises heat-resistant particles and a first binder, the Dv50 of the heat-resistant particles being 0.1 μm to 1.5 μm; And/or the heat-resistant layer comprises heat-resistant particles and a first binder, wherein the components of the first binder comprise polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylic adhesives, styrene-acrylic latex, polyacrylonitrile, polyvinyl acetate, polyacrylic acid, polyurethane modified polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene or one or more of the copolymer systems derived from the polymers.

Description

Battery cell Technical Field The invention relates to the technical field of batteries, in particular to a battery. Background With the increasing urgent demands of lithium ion batteries of new energy automobiles and lithium ion batteries of portable electronic devices on high energy density, silicon-based anode materials become the next generation anode materials with the highest potential due to the extremely high theoretical specific capacity. However, silicon materials undergo severe volume expansion and shrinkage during charge and discharge, and this inherent characteristic severely restricts commercial applications. In the battery circulation process, the stability of the electrode structure is damaged due to repeated severe expansion and contraction of the silicon-based negative electrode, on one hand, the expansion stress causes relative displacement between the diaphragm and the positive electrode pole piece and the negative electrode pole piece, poor interface contact is caused, an ion transmission path is blocked, long circulation performance of the battery is reduced, particularly high-temperature circulation performance of the battery is influenced, on the other hand, continuous volume deformation causes integral deformation and even cracking of the electrode assembly, active particles are broken or even fall off, the broken and fallen active particles easily pierce the diaphragm, micro-short circuit is caused, K value of the battery is increased, and macroscopic thickness change of the pole piece is aggravated, continuous mechanical stress is generated on the diaphragm, and the diaphragm is easily stretched, perforated or separated from the electrode, so that internal short circuit is caused, and serious potential safety hazard is caused. In the prior art, the schemes such as nanocrystallization, porous structure, carbon compounding, surface coating and the like, although volume expansion is relieved to a certain extent, the problems of integral structural stability of the electrode and compatibility of a pole piece-diaphragm interface in the circulation process cannot be fundamentally solved. Therefore, it is very important to invent a battery which can effectively solve the problem of poor stability of an electrolytic structure caused by the volume change of a silicon-based material and improve the stability of the electrode structure. Disclosure of Invention The invention provides a battery, aiming at solving the problems that in the prior art, the stability of an electrode assembly is poor due to the volume change of a negative electrode active material (particularly a silicon-based material), so that the long-cycle performance and the high-temperature cycle performance of the battery are reduced, and the long-cycle performance and the high-temperature safety performance are difficult to be simultaneously considered. According to the battery, the bonding strength between the diaphragm and the negative electrode plate is improved, the bonding strength between the diaphragm and the positive electrode plate is reduced, so that risks of dislocation between the diaphragm and the positive electrode plate, deformation of an electrode assembly and fragmentation of active particles in high-temperature circulation caused by the cyclic expansion of the negative electrode plate in the battery circulation process are reduced, the long-circulation stability and the high-temperature circulation performance of the battery are improved, meanwhile, the bonding force between the diaphragm and the negative electrode plate and the interface heat dissipation performance are balanced, and the safety performance of the battery in the furnace temperature is improved. In order to achieve the above object, the present invention provides a battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator between the positive electrode sheet and the negative electrode sheet, the separator comprising a support layer and polymer coatings on both side surfaces of the support layer, in which the polymer coating corresponding to the positive electrode sheet is a first polymer coating and the polymer coating corresponding to the negative electrode sheet is a second polymer coating, the first polymer coating comprising first particles having a dispersion distribution, the component of the first particles comprising an acrylic polymer, the second polymer coating comprising second particles having a dispersion distribution, the component of the second particles comprising an acrylic polymer, the surface of the negative electrode sheet being provided with recesses; The battery satisfies the following relation F 1＜F2,0.1≤M1/F3 & ltoreq.1.2, wherein F 3=F2-F1,F1 is the coverage rate of the first particles in an arbitrary 25 [ mu ] M x 19 [ mu ] M area of the surface of the first polymer coating layer, F 2 is the coverage rate of the second particles in an arbitrary 25 [ mu ] M x 19 [ mu ]