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WO2021243915A1 - 锂离子电池及其装置 - Google Patents

锂离子电池及其装置 Download PDF

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Publication number
WO2021243915A1
WO2021243915A1 PCT/CN2020/119689 CN2020119689W WO2021243915A1 WO 2021243915 A1 WO2021243915 A1 WO 2021243915A1 CN 2020119689 W CN2020119689 W CN 2020119689W WO 2021243915 A1 WO2021243915 A1 WO 2021243915A1
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Prior art keywords
lithium
lithium ion
ion battery
binder
positive electrode
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Application number
PCT/CN2020/119689
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English (en)
French (fr)
Inventor
曹警予
刘会会
李世松
马林
Original Assignee
江苏时代新能源科技有限公司
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Priority to EP20939372.7A priority Critical patent/EP4075549A4/en
Publication of WO2021243915A1 publication Critical patent/WO2021243915A1/zh
Priority to US17/814,834 priority patent/US20220384817A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application belongs to the field of batteries, and relates to a lithium ion battery and a device thereof.
  • Lithium-ion batteries are widely used in people's daily lives because of their high energy density, long cycle life, and low environmental pollution.
  • external stresses such as collisions and punctures in the application process usually cause internal short circuits, fires, and even more serious hazards. Therefore, it is very important to design and develop high-safety batteries.
  • some embodiments of the present application provide a lithium ion battery and a device thereof.
  • this application provides a lithium ion battery, including:
  • a positive electrode piece including a positive electrode current collector and a positive electrode active material layer
  • Electrolyte including non-aqueous organic solvents
  • a low swelling glue layer and an oily glue layer are sequentially arranged between the positive electrode current collector and the positive electrode active material layer;
  • the low swelling adhesive layer includes a low swelling adhesive, and the oily adhesive layer includes a first adhesive; wherein the solubility parameter SP 1 of the low swelling adhesive is lower than that of the first adhesive. Degree parameter SP 2 .
  • the solubility parameter SP 1 of the low-swelling binder is lower than the solubility parameter SP 0 of the non-aqueous organic solvent.
  • the solubility parameter SP 0 of the non-aqueous organic solvent is 20 (J/cm 3 ) 1/2 to 25 (J/cm 3 ) 1/2 , optionally 23 (J /cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1/2 .
  • the solubility parameter SP 1 of the low-swelling adhesive is 13 (J/cm 3 ) 1/2 to 18 (J/cm 3 ) 1/2 , optionally 13 ( J/cm 3 ) 1/2 ⁇ 15(J/cm 3 ) 1/2 .
  • the solubility parameter SP 2 of the first binder is 20 (J/cm 3 ) 1/2 to 29 (J/cm 3 ) 1/2 , optionally 23 ( J/cm 3 ) 1/2 ⁇ 29(J/cm 3 ) 1/2 .
  • the low-swelling binder is selected from water-based PVDF, polyacrylic acid, polyacrylate, acrylonitrile or their copolymers, oily PVDF, polyacrylic acid, polyacrylate, acrylonitrile, polystyrene One or more of ethylene, propylene modified acrylate, or copolymer of the above materials.
  • the low-swelling binder is selected from one or more of polyacrylic acid, polyacrylate, polystyrene, propylene-modified acrylate, or copolymers of the foregoing materials.
  • the content of the low-swelling binder is ⁇ 40wt%, and optionally 40wt%-80wt%.
  • the low-swelling glue layer further includes a conductive carbon material, and the conductive carbon material is selected from one or more of conductive carbon black and graphene.
  • the first adhesive is an oily adhesive
  • the oily adhesive is selected from polyvinylidene fluoride and/or polyvinylidene chloride olefin polymer materials modified by polar groups , And acrylate and acrylic copolymers.
  • the first binder is selected from carboxylic acid-modified polyvinylidene fluoride PVDF and/or carboxylic acid-modified polyvinylidene chloride PVDC.
  • the carboxylic acid is selected from acrylic acid and/or polyacrylic acid.
  • the oil-based adhesive layer further includes a first conductive material, and the first conductive material is selected from one or more of conductive carbon black, graphene, polypyrrole, and polyaniline.
  • the oily adhesive layer further includes an inorganic filler selected from the group consisting of magnesium oxide, aluminum oxide, titanium dioxide, zirconium oxide, silicon dioxide, silicon carbide, boron carbide, calcium carbonate, and silicic acid
  • an inorganic filler selected from the group consisting of magnesium oxide, aluminum oxide, titanium dioxide, zirconium oxide, silicon dioxide, silicon carbide, boron carbide, calcium carbonate, and silicic acid
  • the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is selected from lithium-containing composite metal oxides.
  • the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide and lithium nickel manganese oxide.
  • the positive electrode active material layer further includes a second binder, and the second binder is selected from optionally containing flexible chain-modified polyvinylidene fluoride and/or vinylidene fluoride.
  • the flexible chain is a long-chain alkyl or alkoxy group.
  • the second binder is selected from optionally polyvinylidene fluoride modified by styrene butyl ester, optionally polyvinylidene fluoride modified by polyethylene/propylene, and polybutyl acrylate modified One or more of flexible PVDF, polyvinylidene fluoride/butyl acrylate copolymer.
  • the thickness of the single low-swelling rubber layer T 1, the adhesive layer of oil layer thickness T 2, the positive electrode active material layer of monolayer thickness T 0 satisfies the following relationship: 0.01 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.4.
  • a device in the second aspect, includes the lithium ion battery as described above.
  • the device may include a mobile phone, a notebook computer, an electric vehicle, an electric boat, or an energy storage system.
  • Electric vehicles may include hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, or electric trucks.
  • the technical solution of the present application has at least the following advantages:
  • the lithium ion battery of the present application by providing an oily glue layer between the positive electrode current collector and the positive electrode active material layer, it can effectively wrap the battery during puncture and other processes.
  • the positive current collector and burrs block the connection with the electrode, reduce the risk of short circuit or short-circuit heat generation in the battery, and improve the safety performance of the battery.
  • the low swelling glue layer since there is a low swelling glue layer between the oily glue layer and the surface of the positive electrode current collector, the low swelling glue layer has good stability under the infiltration of electrolyte, which can ensure that the oily glue layer and the low swelling glue layer, the low swelling glue layer and the There are effective surface contact points between the surface of the positive electrode current collector, so as to achieve high adhesion and good electronic conduction network, and effectively improve the electrochemical performance of the lithium ion battery.
  • the device of the present application includes the lithium ion battery, and therefore has at least the same technical advantages as the lithium ion battery.
  • FIG. 1 is a schematic diagram of the structure of a conventional positive pole piece.
  • Fig. 2A is a schematic structural diagram of a positive pole piece according to an embodiment of the present application.
  • Fig. 2B is a schematic structural diagram of a positive pole piece according to another embodiment of the present application.
  • Fig. 3 is a perspective view of a lithium ion battery according to an embodiment of the present application.
  • Fig. 4 is an exploded view of Fig. 3.
  • Fig. 5 is a perspective view of a battery module according to an embodiment of the present application.
  • Fig. 6 is a perspective view of a battery pack according to an embodiment of the present application.
  • Fig. 7 is an exploded view of Fig. 6.
  • FIG. 8 is a schematic diagram of a device using a lithium ion battery as a power source according to an embodiment of the present application.
  • Figure 9 is the test results of the swelling performance of different adhesive layers in lithium ion electrolyte.
  • Figure 10 shows the resistance test results of the membrane before and after the bubble.
  • Figure 11 is the DC internal resistance DCR test results of lithium-ion batteries.
  • connection can be a fixed connection, or it can be a detachable connection, or an integral connection, or an electrical connection, or a signal connection; “connection” can be a direct connection or through an intermediate medium Indirectly connected.
  • the positive current collector in the positive pole piece has a relatively high resistance, and once it comes into contact with the negative pole piece, it generates the most heat, which is likely to cause safety problems. Therefore, the design and development of a more secure positive pole piece is very important to improve the safety performance of the battery.
  • the oily glue layer 522a can be made of PVDF modified with polar groups, conductive materials, and inorganic fillers, so as to satisfy high adhesion, electron transmission, and stability of the glue layer at the same time.
  • modified flexible PVDF can be introduced into the positive electrode active material layer 521a, so that while increasing the polarity difference with the oil-based glue layer 522a, the drying stress of the positive electrode active material layer 521a can be reduced. Increase the coating speed and drying temperature to effectively improve production efficiency.
  • the flexible modification of PVDF can be carried out by modification of non-polar groups such as long-chain olefin groups or long-chain ester groups. These non-polar groups improve the mutual dissolution between the positive electrode active material layer 521a and the oily glue layer 522a to a certain extent.
  • the increase in the difference in polarity also leads to the fact that in the polar electrolyte environment, the interface (for example, between the positive active material layer 521a and the oil-based glue layer 522a, or between the oil-based glue layer 522a and the surface of the positive current collector 523a )
  • the contact site is drastically reduced, which in turn causes the decrease in adhesion, the obstruction of electron transmission, and the obvious increase in DCR and heat generation, which seriously affects the electrochemical performance and safety performance of the battery.
  • the inventors have further conducted a lot of research and found that the low swelling glue layer and the oily glue layer can be arranged in the positive pole piece to realize the battery with high safety performance and electrochemical performance at the same time.
  • the first aspect of the present application relates to a lithium ion battery 5, including: a positive pole piece, including a positive current collector 523b and a positive active material layer 521b; and an electrolyte, including a non-aqueous organic solvent.
  • the positive pole piece used in the lithium ion battery 5 of the present application includes a positive current collector 523b and a positive active material layer 521b, wherein a low swelling glue layer 524 and an oil-based glue layer are sequentially arranged between the positive current collector 523b and the positive active material layer 521b 522b.
  • the low swelling glue layer 524 can be relatively close to the positive electrode current collector 523b.
  • FIG. 2A shows a schematic structural diagram of a positive electrode piece according to an embodiment of the present application, wherein the positive electrode piece includes a positive electrode current collector 523b, and a low swelling glue layer sequentially arranged on two surfaces of the positive electrode current collector 523b 524, the oil-based glue layer 522b, and the positive electrode active material layer 521b.
  • FIG. 2A only shows one form of the positive electrode sheet of the present application, that is, only two surfaces of the positive electrode current collector 523b are sequentially provided with a low-swelling glue layer 524, an oil-based glue layer 522b, and a positive electrode active. Material layer 521b.
  • a low-swelling glue layer 524, an oil-based glue layer 522b, and a positive electrode active material layer 521b may be sequentially provided on one surface of the positive electrode current collector 523b.
  • FIG. 2B a schematic structural diagram of a positive pole piece according to another embodiment of the present application is shown.
  • the positive electrode current collector 523b and burrs can be effectively wrapped during the battery puncture process, and block the connection between the positive electrode current collector 523b and the electrode. , Reduce the risk of short circuit or heat generation in the battery, and improve the safety performance of the battery.
  • the low swelling glue layer 524 exists between the oily glue layer 522b and the surface of the positive electrode current collector 523b, which changes the original point contact between the two layers, thereby increasing the contact by the way of surface contact. The site forms an effective bond while ensuring a good electron transport network, thus effectively improving the electrochemical performance of the lithium ion battery 5.
  • the positive electrode current collector 523b used in the present application has no special requirements, and the conventional positive electrode current collector 523b used in the lithium ion battery 5 can be selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the positive electrode current collector 523b is usually a structure or part that can collect current.
  • the positive electrode current collector 523b can be various materials suitable for use as the positive electrode current collector 523b of an electrochemical energy storage device in the field, for example,
  • the positive current collector 523b may include but is not limited to metal foil, and more specifically may include, but is not limited to, nickel foil and aluminum foil.
  • the low-swelling adhesive layer 524 used in the positive electrode piece of the present application includes a low-swelling binder.
  • the solubility parameter SP 1 of the low-swelling binder is lower than the solubility parameter SP 0 of the non-aqueous organic solvent.
  • the solubility parameter SP 1 of the low swelling adhesive is 13 (J/cm 3 ) 1/2 to 18 (J/cm 3 ) 1/2 .
  • SP 1 can be 13(J/cm 3 ) 1/2 ⁇ 15(J/cm 3 ) 1/2 , 13(J/cm 3 ) 1/2 ⁇ 14(J/cm 3 ) 1/2 , 14(J/cm 3 ) 1/2 ⁇ 18(J/cm 3 ) 1/2 , 14(J/cm 3 ) 1/2 ⁇ 15(J/cm 3 ) 1/2 , or 16(J/cm 3 ) 1/2 ⁇ 18(J/cm 3 ) 1/2 .
  • the low swelling binder can be selected from water-based polyvinylidene fluoride (PVDF), polyacrylic acid, polyacrylate, acrylonitrile or their copolymers, oily PVDF, polyacrylic acid, polyacrylate, One or more of acrylonitrile, polystyrene, propylene-modified acrylate, or copolymers of the above materials.
  • PVDF polyvinylidene fluoride
  • the low swelling adhesive may be selected from one or more of polyacrylic acid, polyacrylate, polystyrene, propylene-modified acrylate, or copolymers of the above materials.
  • Polystyrene and propylene-modified acrylates include one or more of polystyrene-modified acrylates, polypropylene-modified acrylates, and polystyrene and polypropylene-modified acrylates.
  • the molecular weight of the low-swelling binder may be 100,000 (w)-100w; for example, it may be 30w-80w, 30w-50w, or 50w-80w.
  • the molecular weight of the polymer is the weight average molecular weight, which can be measured in a conventional manner in the art.
  • the small-angle laser light scattering method This technique is well known to those skilled in the art.
  • the low-swelling binder is polyacrylic acid, with a molecular weight of 30w, and a solubility parameter of 14 (J/cm 3 ) 1/2 to 15 (J/cm 3 ) 1/2 .
  • the low-swelling binder is polyacrylate
  • the molecular weight is 50w
  • the solubility parameter is 16 (J/cm 3 ) 1/2 to 18 (J/cm 3 ) 1/2 .
  • the low-swelling adhesive is polystyrene, propylene-modified acrylate, with a molecular weight of 80w and a solubility parameter of 13 (J/cm 3 ) 1/2 ⁇ 14 (J/cm 3 ) 1/2 .
  • the content of the low-swelling adhesive in the low-swelling adhesive layer 524 is ⁇ 40 wt%, for example, it may be 40 wt% to 80 wt%, 40 wt% to 60 wt%, or 60 wt% to 80 wt%.
  • the low-swelling adhesive layer 524 further includes conductive carbon materials.
  • the conductive carbon material may be selected from one or more of conductive carbon black and graphene.
  • the conductive carbon black may be well-known in the art, and includes, for example, acetylene black and the like.
  • the content of the conductive carbon material in the low swelling adhesive layer 524 is 20 wt% to 60 wt%; for example, it can be 20 wt% to 40 wt%, or 40 wt% to 60 wt%, etc.
  • the single-layer thickness T 1 of the low-swelling adhesive layer 524 is 0.1 ⁇ m to 5 ⁇ m; for example, it can be 0.1 ⁇ m to 3 ⁇ m, 0.1 ⁇ m to 2 ⁇ m, 0.1 ⁇ m to 1 ⁇ m, 100 nm to 990 nm, 150 nm to 900 nm, 200nm ⁇ 800nm, 1 ⁇ m ⁇ 5 ⁇ m, 1 ⁇ m ⁇ 3 ⁇ m, 1 ⁇ m ⁇ 2 ⁇ m, 2 ⁇ m ⁇ 5 ⁇ m, or 2 ⁇ m ⁇ 3 ⁇ m, etc.
  • common organic solvents including but not limited to, for example, N-methylpyrrolidone, carbon tetrachloride, acetone, ethylene carbonate (EC), diethyl carbonate (DEC), etc.
  • solvents including but not limited to, for example, N-methylpyrrolidone, carbon tetrachloride, acetone, ethylene carbonate (EC), diethyl carbonate (DEC), etc.
  • low-swelling binders and conductive carbon materials are added at a suitable feeding ratio under room temperature environment. After being evenly dispersed and stirred by a mechanical stirring device, a low-swelling glue slurry with good dispersibility is obtained. It is then coated on the surface of the positive electrode current collector 523b. Place it in an oven to dry and remove the solvent (for example, but not limited to 100° C., 2 hours).
  • a low-swelling adhesive film can be obtained.
  • the low swelling adhesive film is immersed in the electrolyte at an appropriate temperature (for example, 70° C.), and monitored for 1 week. It was found that the mass and volume swelling rate of the low swelling film was less than 10%, indicating that its low swelling effect was very good.
  • the oily glue layer 522b used for the positive pole piece of the present application includes a first binder.
  • the solubility parameter SP 2 of the first binder is 20 (J/cm 3 ) 1/2 to 29 (J/cm 3 ) 1/2 ; for example, it may be 20 (J/cm 3 ) 1/2 ⁇ 27(J/cm 3 ) 1/2 , 20(J/cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1/2 , 20(J/cm 3 ) 1/2 ⁇ 22(J/cm 3 ) 1/2 , 23(J/cm 3 ) 1/2 ⁇ 29(J/cm 3 ) 1/2 , 23(J/cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1/2 , or 27(J/cm 3 ) 1/2 ⁇ 29(J/cm 3 ) 1/2 and so on.
  • the solubility parameter SP 2 of the first binder is higher than the solubility parameter SP 1 of the low-swelling binder.
  • the solubility parameter SP 1 of the low swelling adhesive is lower than the solubility parameter SP 2 of the first adhesive.
  • a solubility parameter SP 2 a first binder, a binder and a low solubility parameter SP swelling. 1 are relative to a non-aqueous organic solvent in terms of the electrolytic solution.
  • the first adhesive is an oily adhesive.
  • the oily binder may be selected from polyvinylidene fluoride and/or polyvinylidene chloride olefin polymer materials modified with polar groups, and copolymers of acrylate and acrylic.
  • the oily binder can be selected from carboxylic acid modified PVDF, acrylic acid modified PVDF, polyacrylic acid modified PVDF, polyvinylidene chloride (PVDC), carboxylic acid modified PVDC, One or more of acrylic-modified PVDC, PVDF copolymer, and PVDC copolymer.
  • the oily binder may be selected from one or more of acrylic-modified PVDF and polyacrylic-modified PVDF.
  • the molecular weight of the oily binder may be 30w to 500w; for example, it may be 80w to 130w, 80w to 100w, 100w to 130w, or 100w to 500w.
  • the oily binder is PVDF modified with polyacrylic acid, the molecular weight is 100w, and the solubility parameter is 23 (J/cm 3 ) 1/2 to 24 (J/cm 3 ) 1/2 .
  • the oily binder is PVDF modified with polyacrylic acid, with a molecular weight of 130w and a solubility parameter of 20 (J/cm 3 ) 1/2 to 22 (J/cm 3 ) 1/2 .
  • the oily binder is PVDF modified by polyacrylic acid, with a molecular weight of 80w and a solubility parameter of 27 (J/cm 3 ) 1/2 to 29 (J/cm 3 ) 1/2 .
  • the content of the first binder in the oily adhesive layer 522b is 40wt% to 75wt%; for example, it can be 40wt% to 60wt%, 40wt% to 50wt%, 50wt% to 75wt%, 50wt% % ⁇ 60wt%, or 60wt% ⁇ 75wt%, etc.
  • the oil-based adhesive layer 522b further includes a first conductive material.
  • the first conductive material may be selected from one or more of carbon-based conductive materials and conductive polymers.
  • the first conductive material may be selected from one or more of conductive carbon black, graphene, polypyrrole, and polyaniline.
  • the conductive carbon black may be well-known in the art, and includes, for example, acetylene black and the like.
  • the content of the first conductive material in the oily adhesive layer 522b is 20wt% to 55wt%; for example, it may be 20wt% to 40wt%, 20wt% to 30wt%, 30wt% to 45wt%, or 40wt% % ⁇ 55wt%.
  • the oily adhesive layer 522b further includes inorganic fillers.
  • the inorganic filler may be selected from magnesium oxide, aluminum oxide, titanium dioxide, zirconium oxide, silicon dioxide, silicon carbide, boron carbide, calcium carbonate, aluminum silicate, calcium silicate, potassium titanate, barium sulfate, lithium cobaltate, Lithium nickel manganese cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, silicic acid Lithium manganese, spinel lithium manganate, spinel lithium nickel manganate, lithium titanate, or modified materials coated with conductive carbon, modified materials coated with conductive metal, or conductive polymerization At least one of the modified materials covered by the substance.
  • the inorganic filler may be selected from one or more of alumina, titania, zirconia, silica, lithium iron phosphate, and carbon-coated lithium iron phosphate.
  • the inorganic filler may be selected from one or more of alumina, titania, zirconia, and silica.
  • the content of inorganic filler in the oily adhesive layer 522b is 5wt%-40wt%; for example, it may be 5wt%-20wt%, 5wt%-10wt%, 10wt%-40wt%, 10wt% -20wt%, or 20wt%-40wt%, etc.
  • the single layer thickness T 2 of the oily adhesive layer 522b is 3 ⁇ m to 15 ⁇ m; for example, it may be 3 ⁇ m to 10 ⁇ m, 3 ⁇ m to 7 ⁇ m, 3 ⁇ m to 5 ⁇ m, 5 ⁇ m to 15 ⁇ m, 5 ⁇ m to 10 ⁇ m, 5 ⁇ m to 7 ⁇ m, or 7 ⁇ m ⁇ 15 ⁇ m etc.
  • the oil-based adhesive layer 522b and the low-swelling adhesive layer 524 used in the positive pole piece of the present application can be distinguished and selected from the following two aspects: 1) particle size.
  • the thickness of the low swelling glue layer 524 is in the order of nanometer to submicrometer (for example, 100 nm to 1 ⁇ m, 100 nm to 2 ⁇ m, 100 nm to 3 ⁇ m, 100 nm to 5 ⁇ m, 100 nm to 990 nm, 150 nm to 900 nm, or 200 nm to 800 nm). Since the oily glue layer 522b introduces inorganic fillers, the thickness of the glue layer is generally on the order of micrometers. 2) Solubility parameter.
  • the solubility parameter is a parameter that characterizes the polymer-solvent interaction. It can be quantitatively characterized by cohesive energy.
  • the cohesive energy per unit volume is called the cohesive energy density, and its square root is called the solubility parameter.
  • the solubility parameter can be used as a good indicator to measure the compatibility of two materials. When the solubility parameters of the two materials are similar, they can be blended with each other and have good compatibility.
  • the solubility parameters of liquids can be obtained from their heat of evaporation.
  • the solubility parameter of the polymer can be obtained from the swelling experiment of the cross-linked polymer or the measurement of the viscosity of the dilute solution of the linear polymer.
  • the solubility parameter of the solvent that can maximize the swelling degree or intrinsic viscosity of the polymer is the solubility parameter of this polymer. This application can refer to the turbidimetric titration method to determine the solubility parameter of the binder.
  • solubility parameters of mixed solvents can be calculated according to the following formula (1):
  • ⁇ is the solubility parameter of the mixed solvent
  • ⁇ i is the solubility parameter of a certain component
  • Is the volume fraction of the certain component
  • n is an integer greater than or equal to 2.
  • the mixed solvent is a three-component solvent
  • its solubility parameter can be calculated according to the following formula (1-1):
  • ⁇ is the solubility parameter of the mixed solvent
  • ⁇ 1 is the solubility parameter of the first component
  • ⁇ 2 is the solubility parameter of the second component
  • ⁇ 3 is the solubility parameter of the third component
  • Common solvents such as ethylene carbonate (EC) have a ⁇ of 29.4 (J/cm 3 ) 1/2
  • polycarbonate (PC) has a ⁇ of 14.5 (J/cm 3 ) 1/2
  • DEC diethyl carbonate
  • the ⁇ of) is 20.3 (J/cm 3 ) 1/2
  • the solubility parameter SP 0 of the non-aqueous organic solvent of the lithium ion electrolyte is between 20 (J/cm 3 ) 1/2 and 25 (J/cm 3 ) 1/2 .
  • the low-swelling adhesive layer 524 used in the positive pole piece of this application usually selects the solubility parameter SP 1 at 13(J/cm 3 ) 1/2 ⁇ 18(J /cm 3 ) Low swelling adhesive between 1/2.
  • the low-swelling binder can be selected from, including but not limited to, for example, water-based PVDF, polyacrylic acid, polyacrylate, acrylonitrile or their copolymers, oily PVDF, polyacrylic acid, polyacrylate , Acrylonitrile, polystyrene, propylene modified acrylate, or one or more of copolymers of the above materials.
  • the solubility parameter of the low-swelling glue layer 524 and the non-aqueous organic solvent is quite different.
  • the low-swelling glue layer 524 has a small degree of swelling and high stability.
  • polar groups are usually introduced and copolymerized with structural fragments with larger solubility parameters to increase the size of the first binder, the positive electrode active material, the second conductive material, and the positive electrode current collector. 523b contact area, thereby improving the adhesion and conductivity.
  • the solubility parameter SP 2 is selected as the first binder in the range of 20 (J/cm 3 ) 1/2 to 29 (J/cm 3 ) 1/2, including but not Limited to, for example, polyvinylidene fluoride modified with polar groups (commercially available, molecular weight: 100w to 500w).
  • polar groups commercially available, molecular weight: 100w to 500w.
  • the introduction of polar groups increases the solubility parameter of the oily glue layer 522b, which is less different from the solubility parameter of the electrolyte. Therefore, the oily glue layer 522b exhibits greater swelling properties in the electrolyte.
  • the positive active material layer 521b used in the positive pole piece of the present application includes a positive active material.
  • the positive electrode active material is selected from lithium-containing composite metal oxides.
  • the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide and lithium nickel manganese oxide.
  • the lithium-containing composite metal oxide includes, but is not limited to, LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , lithium nickel cobalt manganese oxide, or lithium nickel manganese oxide.
  • the lithium nickel cobalt manganese oxide includes but is not limited to LiNi 0.8 Co 0.1 Mn 0.1 O 2 .
  • the lithium nickel manganese oxide includes but is not limited to LiNi 0.5 Mn 1.5 O 4 .
  • the molar ratio of nickel element to all transition metal elements in the positive electrode active material is 0.5-0.9; for example, 0.5-0.8.
  • the content of the positive electrode active material in the positive electrode active material layer 521b is 30% to 99.9% by weight; for example, 80% to 99%, or 90% to 97.5%, etc.
  • the positive active material layer 521b further includes a second binder.
  • the second binder may include, but is not limited to, polyvinylidene fluoride and/or polyvinylidene chloride olefin polymer material.
  • the second binder may be selected from optionally polyvinylidene fluoride and/or vinylidene fluoride modified with a flexible chain.
  • the flexible chain is a long-chain alkyl or alkoxy group.
  • the flexible chain is a C1-C6 alkyl group or alkoxy group.
  • the second binder is selected from the group consisting of optionally polyvinylidene fluoride modified by styrene butyl ester, optionally polyvinylidene fluoride modified by polyethylene/propylene, and polybutylene acrylate.
  • One or more of ester-modified PVDF and polyvinylidene fluoride/butyl acrylate copolymer are selected from the group consisting of optionally polyvinylidene fluoride modified by styrene butyl ester, optionally polyvinylidene fluoride modified by polyethylene/propylene, and polybutylene acrylate.
  • the second binder is PVDF modified with polybutyl acrylate
  • the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20 (J/cm 3 ) 1/2
  • the molecular weight It is 110w ⁇ 130w.
  • the content of the second binder in the positive active material layer 521b is 0.05 wt% to 30 wt%; for example, it can be 1 wt% to 20 wt%, 3 wt% to 10 wt%, or 4 wt% to 8 wt% %.
  • the positive active material layer 521b further includes a second conductive material.
  • the second conductive material may be selected from one or more of conductive carbon black, graphite, graphene, carbon nanotubes, and carbon nanofibers.
  • the conductive carbon black may be well-known in the art, and includes, for example, acetylene black and the like.
  • the content of the second conductive material in the positive electrode active material layer 521b is 0.05wt%-40wt%; for example, it may be 1wt%-20wt%, 3wt%-10wt%, or 4wt%-8wt% .
  • the single-layer coating thickness T 0 of the positive electrode active material layer 521b after drying is 50 ⁇ m to 300 ⁇ m; for example, it may be 70 ⁇ m to 200 ⁇ m, or 90 ⁇ m to 150 ⁇ m.
  • low-swelling adhesive layer 524 layer thickness T 1, adhesive layer 522b oily layer thickness T 2, the positive electrode active material layer 521b monolayer thickness T 0 satisfies the following relationship: 0.01 ⁇ (T 1 + T 2 )/T 0 ⁇ 0.4.
  • T 0 , T 1 , T 2 satisfy the following relationship: 0.015 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.2, 0.02 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.13, 0.02 ⁇ (T 1 + T 2 )/T 0 ⁇ 0.07, 0.02 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.05, 0.04 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.2, 0.04 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.13, 0.04 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.07, 0.05 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.2, or 0.05 ⁇ (T 1 +T 2 )/T 0 ⁇ 0.13, etc. .
  • the specific type and composition of the electrolyte used in the lithium ion battery 5 of the present application are not limited, and can be selected according to actual needs.
  • the electrolyte used in the lithium ion battery 5 is a lithium salt solution.
  • the lithium salt includes, but is not limited to, inorganic lithium salts such as LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , or LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n+1 SO 3 (n ⁇ 2) and other organic lithium salts one or more kind.
  • inorganic lithium salts such as LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 , or LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n+1 SO 3 (n ⁇ 2) and other organic lithium salts one or more kind.
  • non-aqueous organic solvents used in the electrolyte of this application include, but are not limited to, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, and diethyl carbonate.
  • Ester chain carbonates such as methyl ethyl carbonate, chain esters such as methyl propionate, cyclic esters such as ⁇ -butyrolactone, dimethoxyethane, diethyl ether, diglyme, tri One or more of chain ethers such as glyme, cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and nitriles such as acetonitrile and propionitrile.
  • the non-aqueous organic solvent of the present application is a plurality of mixed solvents, the volume content of each component is not particularly required, and can be adjusted according to the situation, as long as the technical solution of the present application can be realized.
  • the solubility parameter SP 0 of the non-aqueous organic solvent is 20 (J/cm 3 ) 1/2 to 25 (J/cm 3 ) 1/2 ; for example, it may be 20 (J/cm 3) ) 1/2 ⁇ 24(J/cm 3 ) 1/2 , 23(J/cm 3 ) 1/2 ⁇ 25(J/cm 3 ) 1/2 , 23(J/cm 3 ) 1/2 ⁇ 24 (J/cm 3 ) 1/2 etc.
  • the lithium ion battery 5 provided in the first aspect of the present application includes the positive pole piece and electrolyte as described above, the negative pole piece, and a separator disposed between the positive pole piece and the negative pole piece.
  • the negative pole piece and the separator There are no special requirements for the negative pole piece and the separator, and can be selected according to actual needs, as long as the technical solution of the present application can be realized.
  • the lithium ion battery 5 of the present application may be a capacitor, a primary battery, or a secondary battery.
  • it may be a lithium ion capacitor, a lithium ion primary battery, or a lithium ion secondary battery.
  • FIG. 3 shows a perspective view of a lithium ion battery 5 according to an embodiment of the present application
  • FIG. 4 is an exploded view of the lithium ion battery 5 shown in FIG. 3. 3 and 4,
  • the lithium ion battery 5 of the present application includes an outer package 51, an electrode assembly 52, a top cover assembly 53, and electrolyte (not shown).
  • the electrode assembly 52 is contained in the outer package 51, and the number of the electrode assembly 52 is not limited, and can be one or more.
  • the lithium ion battery 5 shown in FIG. 3 is a can type battery, but the present application is not limited to this.
  • the lithium ion battery 5 may be a pouch type battery, that is, the casing 51 is replaced by a metal plastic film and the top cover is eliminated. Component 53.
  • the lithium ion battery 5 can be assembled into the battery module 4, and the number of lithium ion batteries 5 contained in the battery module 4 can be several, and the specific number can be adjusted according to the application and capacity of the battery module 4.
  • FIG. 5 shows a perspective view of the battery module 4 according to an embodiment of the present application.
  • a plurality of lithium ion batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, a plurality of lithium ion batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a containing space, and a plurality of lithium ion batteries 5 are contained in the containing space.
  • the above-mentioned battery modules 4 can also be assembled into a battery pack 1, and the number of battery modules 4 contained in the battery pack 1 can be adjusted according to the application and capacity of the battery pack 1.
  • FIG. 6 shows a perspective view of the battery pack 1 according to an embodiment of the present application
  • FIG. 7 is an exploded view of FIG. 6.
  • the battery pack 11 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the second aspect of the present application provides a device including the lithium ion battery 5 of the first aspect of the present application.
  • the lithium ion battery 5 can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the device includes but is not limited to mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts. , Electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select the lithium ion battery 5, the battery module 4, or the battery pack 1 according to its usage requirements.
  • FIG. 8 shows a schematic diagram of a device using a lithium ion battery 5 as a power source according to an embodiment of the present application.
  • the device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • the battery pack 1 or the battery module 4 can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the device is generally required to be light and thin, and the lithium ion battery 5 of the present application can be used as a power source.
  • the low swelling binder and the conductive carbon material are dispersed and stirred in an organic solvent according to the metering ratio to obtain a low swelling glue slurry with good dispersion uniformity.
  • the low swelling glue slurry prepared above is coated on the surface of the positive electrode current collector 523b (for example, 10 ⁇ m aluminum foil) through a transfer coater at a speed of 30 m/min to obtain a low swelling glue layer 524.
  • the first binder, the first conductive material, and the inorganic filler are dispersed and stirred in N-methylpyrrolidone (NMP) according to the metering ratio to obtain an oily glue slurry with good dispersion uniformity.
  • NMP N-methylpyrrolidone
  • the oily glue slurry prepared above is coated on the aforementioned low-swelling glue layer 524 by extrusion coating at a speed of 10m/min-60m/min to obtain the oily glue layer 522b.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2
  • the second binder and the second conductive material carbon black (SP) are dissolved in the solvent N-methylpyrrolidone (NMP) according to the metering ratio, and after high-speed stirring, A uniformly dispersed positive electrode slurry was obtained.
  • the solid content is 60% by weight, and it contains 90% by weight of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , 5% by weight of polybutyl acrylate modified PVDF and 5% by weight of SP.
  • a positive electrode piece was prepared, wherein the thickness of the single layer of the positive electrode active material layer 521b was 150 ⁇ m.
  • the negative active material artificial graphite, the binder SBR emulsion, the powder of sodium carboxymethyl cellulose and the conductive carbon black are stirred at high speed in a deionized water system according to the metering ratio to obtain a uniformly dispersed negative electrode slurry.
  • the solid content is 40% by weight, and it contains 90% by weight of artificial graphite, 2% by weight of sodium carboxymethyl cellulose, 3% by weight of conductive carbon black, and 5% by weight of SBR.
  • the negative electrode slurry is coated and rolled to prepare a negative electrode piece.
  • the degree parameter is 23(J/cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1/2 , and then lithium hexafluorophosphate is added to the non-aqueous mixed organic solvent to obtain a 1mol/L lithium hexafluorophosphate solution as a lithium ion electrolyte .
  • the tabs of the positive and negative pole pieces prepared above After forming the tabs of the positive and negative pole pieces prepared above, they are separated by a 12 ⁇ m-thick polypropylene/polyethylene composite isolation film, and the sandwich structure is used to wind it to form a bare cell, and then use an aluminum-plastic film Package. After packaging, the lithium ion electrolyte prepared above is injected, and then chemical formation and aging are performed.
  • the positive pole piece and lithium ion battery 5 of this embodiment were prepared according to the above method, in which polyacrylic acid was selected as the low-swelling binder, the molecular weight was 30w, and the solubility parameter was 14(J/cm 3 ) 1/2 ⁇ 15(J/ cm 3 ) 1/2 ; the first binder in the oily adhesive layer 522b is made of polyacrylic acid modified PVDF, and the solubility parameter is 23 (J/cm 3 ) 1/2 ⁇ 24 (J/cm 3 ) 1/ 2.
  • the molecular weight is 100w; the second binder in the positive active material layer 521b is PVDF modified with polybutyl acrylate, and the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20 (J/cm 3 ) 1 /2 , the molecular weight is 110w ⁇ 130w.
  • the prepared positive electrode piece is shown in Figure 2A, including a positive electrode current collector 523b, and a low-swelling glue layer 524, an oil-based glue layer 522b and a positive electrode active material layer are sequentially coated on both surfaces of the positive electrode current collector 523b 521b.
  • the positive pole piece and the lithium ion battery 5 of this embodiment were prepared according to the above method, in which the low swelling binder was selected from polyacrylate, the molecular weight was 50w, and the solubility parameter was 16(J/cm 3 ) 1/2 ⁇ 18(J /cm 3 ) 1/2 ;
  • the first binder in the oily adhesive layer 522b is made of polyacrylic acid modified PVDF, and the solubility parameter is 23(J/cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1 /2 , the molecular weight is 100w
  • the second binder in the positive active material layer 521b is made of PVDF modified with polybutyl acrylate, and the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20 (J/cm 3 ) 1/2
  • the molecular weight is 110w ⁇ 130w.
  • the positive electrode piece prepared in this embodiment is coated with a low-swelling glue layer 524, an oil-based glue layer 522b and a positive electrode active material layer 521b on the two surfaces of the positive electrode current collector 523b in sequence.
  • the positive pole piece and lithium ion battery 5 of this embodiment are prepared according to the above method, wherein the low swelling binder is selected from polystyrene and acrylic modified acrylate, the molecular weight is 80w, and the solubility parameter is 13 (J/cm 3 ) 1/2 ⁇ 14(J/cm 3 ) 1/2 ; the first binder in the oily adhesive layer 522b is made of PVDF modified with polyacrylic acid, and the solubility parameter is 20(J/cm 3 ) 1/2 ⁇ 22 (J/cm 3 ) 1/2 , the molecular weight is 130w; the second binder in the positive active material layer 521b is polybutyl acrylate modified PVDF, and the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20(J/cm 3 ) 1/2 , the molecular weight is 110w ⁇ 130w.
  • the low swelling binder is selected from polystyrene and acrylic modified acrylate, the molecular weight is 80w, and the solub
  • the positive pole piece prepared in this embodiment is shown in FIG. 2B, that is, only one surface of the positive electrode current collector 523b is sequentially coated with a low-swelling glue layer 524, an oil-based glue layer 522b, and a positive electrode active material layer 521b.
  • the positive pole piece and lithium ion battery 5 of this embodiment are prepared according to the above method, wherein the low swelling binder is selected from polystyrene and acrylic modified acrylate, the molecular weight is 80w, and the solubility parameter is 13 (J/cm 3 ) 1/2 ⁇ 14(J/cm 3 ) 1/2 ; the first binder of the oily adhesive layer 522b is made of PVDF modified with polyacrylic acid, and the solubility parameter is 27(J/cm 3 ) 1/2 ⁇ 29( J/cm 3 ) 1/2 , the molecular weight is 80w; the second binder in the positive active material layer 521b is polybutyl acrylate modified PVDF, and the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20(J/cm 3 ) 1/2 , the molecular weight is 110w ⁇ 130w.
  • the low swelling binder is selected from polystyrene and acrylic modified acrylate
  • the molecular weight is 80w
  • the positive electrode piece prepared in this embodiment is coated with a low-swelling glue layer 524, an oil-based glue layer 522b and a positive electrode active material layer 521b on the two surfaces of the positive electrode current collector 523b in sequence.
  • This embodiment is different from Embodiment 4 in that the content of the low-swelling adhesive in the low-swelling adhesive layer 524 is 40% by weight.
  • Embodiment 4 is different from Embodiment 4 in that the content of the low swelling adhesive in the low swelling layer is 80 wt%.
  • This embodiment is different from Embodiment 4 in that the respective contents of the first adhesive, the first conductive material, and the inorganic filler in the oily adhesive layer 522b are 40 wt%, 20 wt%, and 40 wt%, respectively.
  • This embodiment is different from Embodiment 4 in that the respective contents of the first adhesive, the first conductive material, and the inorganic filler in the oily adhesive layer 522b are 75 wt%, 20 wt%, and 5 wt%, respectively.
  • This embodiment is different from Embodiment 4 in that the respective contents of the first adhesive, the first conductive material, and the inorganic filler in the oily adhesive layer 522b are 40 wt%, 55 wt%, and 5 wt%, respectively.
  • This embodiment is different from Embodiment 4 in that the respective contents of the first adhesive, the first conductive material, and the inorganic filler in the oily adhesive layer 522b are 50 wt%, 40 wt%, and 10 wt%, respectively.
  • This embodiment is different from Embodiment 4 in that the thickness of the low swelling glue layer 524 is 100 nm, and the thickness of the oily glue layer 522b is 3 ⁇ m.
  • This embodiment is different from Embodiment 4 in that the thickness of the low-swelling glue layer 524 is 1 ⁇ m, and the thickness of the oily glue layer 522b is 5 ⁇ m.
  • This embodiment is different from Embodiment 4 in that the thickness of the low-swelling glue layer 524 is 3 ⁇ m, and the thickness of the oily glue layer 522b is 7 ⁇ m.
  • This embodiment is different from Embodiment 4 in that the thickness of the low-swelling glue layer 524 is 5 ⁇ m, and the thickness of the oily glue layer 522b is 15 ⁇ m.
  • the positive pole piece of Comparative Example 1 and the lithium ion battery 5 were prepared according to the above method.
  • the Comparative Example 1 did not include the low-swelling glue layer 524.
  • the first binder in the oily glue layer 522b was selected from PVDF modified by polyacrylic acid.
  • the degree parameter is 23(J/cm 3 ) 1/2 ⁇ 24(J/cm 3 ) 1/2 , and the molecular weight is 100W;
  • the second binder in the positive active material layer 521b is made of PVDF modified with polybutyl acrylate ,
  • the solubility parameter is 19(J/cm 3 ) 1/2 ⁇ 20(J/cm 3 ) 1/2 , and the molecular weight is 110w ⁇ 130w.
  • the prepared positive pole piece as shown in FIG. 1 includes a positive electrode current collector 523a, and an oily glue layer 522a and a positive electrode active material layer 521a sequentially coated on the surface of the positive electrode current collector 523a.
  • the positive pole piece of Comparative Example 2 and the lithium ion battery 5 were prepared according to the above method, wherein only the positive electrode active material layer 521b was coated on the positive current collector 523b of Comparative Example 2.
  • the second binder in the positive active material layer 521b is PVDF modified with polybutyl acrylate, the solubility parameter is 19 (J/cm 3 ) 1/2 ⁇ 20 (J/cm 3 ) 1/2 , and the molecular weight is 110w ⁇ 130w.
  • the positive electrode piece prepared in this comparative example is coated with the positive electrode active material layer 521b only on one surface of the positive electrode current collector 523b.
  • the positive pole piece of Comparative Example 3 and the lithium ion battery 5 were prepared according to the above method.
  • a low swelling glue layer 524 and an oily glue layer 522b were sequentially arranged on the surface of the positive electrode current collector 523b.
  • the low swelling glue layer 524 was selected from PVDF modified by polyacrylic acid.
  • the solubility parameter is 27(J/cm 3 ) 1/2 ⁇ 29(J/cm 3 ) 1/2 , and the molecular weight is 80w;
  • the first binder of the oily adhesive layer 522b is made of polystyrene and acrylic modified acrylic Ester, the molecular weight is 80w, the solubility parameter is 13(J/cm 3 ) 1/2 ⁇ 14(J/cm 3 ) 1/2 ;
  • the second binder in the positive active material layer 521b is modified by polybutyl acrylate
  • the solubility parameter of PVDF is 19(J/cm 3 ) 1/2 ⁇ 20(J/cm 3 ) 1/2 , and the molecular weight is 110w ⁇ 130w.
  • the low swelling glue layer 524 and the oily glue layer 522b are glue films.
  • the different adhesive films prepared above were respectively placed in a lithium ion electrolyte, and allowed to stand in an oven at 70° C., and the weight change of the adhesive film was monitored for one week. The results are shown in FIG. 9.
  • the low-swelling adhesive layer 524 exhibits better electrolyte tolerance performance. After one week of electrolyte immersion, the weight change is less than 1%, and the swelling change of the oily glue layer 522b is as high as about 30-40%.
  • Example 1 and Comparative Example 1 Take Example 1 and Comparative Example 1 to prepare 5 positive pole pieces (20 ⁇ 90mm 2 ) of different thicknesses (100 ⁇ m, 150 ⁇ m, 200 ⁇ m, 250 ⁇ m), and place them in the lithium ion electrolyte prepared above, and place them at 70°C. After 24h, take it out in a dry room and dry it for 0.5h. Use a diaphragm resistance tester to read the diaphragm resistance on both sides of each positive pole piece every 10s, record 20 values for each sample, and take the average value. Refer to Figure 10 for the results.
  • the low-swelling adhesive layer 524 exhibits a smaller swelling rate, which can provide good adhesion and contact area between the interfaces, and ensure sufficient effective adhesion sites and electron transmission. path. It can be seen that the resistance growth trend of the positive pole piece with the three-layer coating structure of the present application before/after contacting the electrolyte is significantly smaller than that of the single-layer/double-layer coating structure.
  • Example 1 >500 >500
  • Example 2 >500 >500
  • Example 3 >500 >500
  • Example 4 >500 >500
  • Example 5 >500 >500
  • Example 6 >500 >500
  • Example 7 >500 >500
  • Example 8 >500 >500
  • Example 9 >500 455
  • Example 10 >500 460
  • Example 11 >500 312
  • Example 12 >500 >500
  • Example 13 >500 >500
  • Example 14 >500 >500 Comparative example 1 400 260 Comparative example 2 20 3.1 Comparative example 3 >500 220
  • the lithium ion batteries 5 prepared in Examples 1-14 and the lithium ion batteries 5 prepared in Comparative Examples 1-3 were tested for DCR according to the following procedures.
  • Example 1 Battery 25°C50%SOC DCR(mohm) Example 1 171 Example 2 175 Example 3 180 Example 4 169 Example 5 157 Example 6 190 Example 7 176 Example 8 182 Example 9 173 Example 10 174 Example 11 185 Example 12 172 Example 13 165 Example 14 150 Comparative example 1 197 Comparative example 2 302 Comparative example 3 263

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Abstract

本申请公开了一种锂离子电池及其装置。所述锂离子电池包括：正极极片，包括正极集流体和正极活性物质层；以及电解液，包括非水有机溶剂。其中在所述正极集流体与所述正极活性物质层之间依次设置有低溶胀胶层和油性胶层；所述低溶胀胶层包括低溶胀粘结剂，所述油性胶层包括第一粘结剂；其中所述低溶胀粘结剂的溶度参数SP 1低于所述第一粘结剂的溶度参数SP 2。

Description

锂离子电池及其装置
相关申请的交叉引用
本申请要求享有于2020年06月03日提交的名称为“锂离子电池及其装置”的中国专利申请202010492662.0的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于电池领域，涉及一种锂离子电池及其装置。
背景技术
锂离子电池因高能量密度、循环寿命长、环境污染性小而广泛应用于人们的日常生活中。然而，在应用过程中存在的外界应力如碰撞、穿刺等，通常会造成电池内部短路、着火，甚至引发更严重的危害。因此，设计开发高安全的电池至关重要。
发明内容
针对上述问题，本申请部分实施例提供一种锂离子电池及其装置。
第一方面，本申请提供一种锂离子电池，包括：
正极极片，包括正极集流体和正极活性物质层；以及
电解液，包括非水有机溶剂；
其中在所述正极集流体与所述正极活性物质层之间依次设置有低溶胀胶层和油性胶层；
所述低溶胀胶层包括低溶胀粘结剂，所述油性胶层包括第一粘结剂；其中所述低溶胀粘结剂的溶度参数SP 1低于所述第一粘结剂的溶度参数SP 2。
在本申请任意实施方式中，所述低溶胀粘结剂的溶度参数SP 1低于所述非水有机溶剂的溶度参数SP 0。
在本申请任意实施方式中，所述第一粘结剂的溶度参数SP 2与所述非水有机溶剂的溶度参数SP 0差值的绝对值≤5(J/cm 3) 1/2。
在本申请任意实施方式中，所述非水有机溶剂的溶度参数SP 0为20(J/cm 3) 1/2～25(J/cm 3) 1/2，可选的为23(J/cm 3) 1/2～24(J/cm 3) 1/2。
在本申请任意实施方式中，所述低溶胀粘结剂的溶度参数SP 1为13(J/cm 3) 1/2～18(J/cm 3) 1/2，可选的为13(J/cm 3) 1/2～15(J/cm 3) 1/2。
在本申请任意实施方式中，所述第一粘结剂的溶度参数SP 2为20(J/cm 3) 1/2～29(J/cm 3) 1/2，可选的为23(J/cm 3) 1/2～29(J/cm 3) 1/2。
在本申请任意实施方式中，所述低溶胀粘结剂选自水性PVDF、聚丙烯酸、聚 丙烯酸酯、丙烯腈或它们的共聚物，油性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。可选的，所述低溶胀粘结剂选自聚丙烯酸，聚丙烯酸酯，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。
在本申请任意实施方式中，在所述低溶胀胶层中，所述低溶胀粘结剂的含量≥40wt％，可选的为40wt％～80wt％。
在本申请任意实施方式中，所述低溶胀胶层还包括导电碳材料，所述导电碳材料选自导电炭黑、石墨烯中的一种或多种。
在本申请任意实施方式中，所述第一粘结剂为油性粘结剂，所述油性粘结剂选自极性基团改性的聚偏氟烯烃和/或聚偏氯烯烃高分子材料，以及丙烯酸酯、丙烯酸类的共聚物。可选的，所述第一粘结剂选自羧酸改性的聚偏氟乙烯PVDF和/或羧酸改性的聚偏氯乙烯PVDC。可选的，所述羧酸选自丙烯酸和/或聚丙烯酸。
在本申请任意实施方式中，所述油性胶层还包括第一导电材料，所述第一导电材料选自导电炭黑、石墨烯、聚吡咯、聚苯胺中的一种或多种。
在本申请任意实施方式中，所述油性胶层还包括无机填料，所述无机填料选自氧化镁、氧化铝、二氧化钛、氧化锆、二氧化硅、碳化硅、碳化硼、碳酸钙、硅酸铝、硅酸钙、钛酸钾、硫酸钡、钴酸锂、镍锰钴酸锂、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂、钛酸锂，或上述材料经导电碳包覆的改性材料、经导电金属包覆的改性材料或经导电聚合物包覆的改性材料中的一种或多种。
在本申请任意实施方式中，所述正极活性物质层包括正极活性物质，所述正极活性物质选自含锂复合金属氧化物。可选的，所述正极活性物质选自锂镍钴锰氧化物、锂镍锰氧化物中的一种或多种。
在本申请任意实施方式中，所述正极活性物质层还包括第二粘结剂，所述第二粘结剂选自任选的含有柔性链改性的聚偏氟乙烯和/或偏氟氯乙烯，所述柔性链为长链的烷基或烷氧基。可选的，所述第二粘结剂选自任选的被苯乙烯丁酯改性的聚偏氟乙烯、任选的被聚乙烯/丙烯改性的偏氟氯乙烯、聚丙烯酸丁酯改性的PVDF、聚偏氟乙烯/丙烯酸丁酯共聚物中的一种或多种。
在本申请任意实施方式中，所述低溶胀胶层的单层厚度T 1、所述油性胶层的单层厚度T 2、正极活性物质层单层厚度T 0满足以下关系：0.01≤(T 1+T 2)/T 0≤0.4。可选的，0.015≤(T 1+T 2)/T 0≤0.2。
第二方面，一种装置，包括如上所述的锂离子电池。所述装置可包括手机、笔记本电脑、电动车辆、电动船舶、或储能系统。电动车辆可包括混合动力电动车辆、插电式混合动力电动车辆、电动自行车、电动踏板车、电动高尔夫球车或电动卡车。
相对于现有技术，本申请的技术方案至少具有以下优势：本申请的锂离子电池中，通过在正极集流体和正极活性物质层之间设置油性胶层，可以在电池发生穿刺等过程有效包裹正极集流体和毛刺，阻隔其与电极的对接，降低电池内短路风险或短路产热，提升电池的安全性能。并且，由于油性胶层和正极集流体表面之间存在低溶胀 胶层，在电解液的浸润下该低溶胀胶层稳定性良好，可确保油性胶层与低溶胀胶层、低溶胀胶层与正极集流体表面之间具有有效的面接触位点，从而实现高粘结力和良好的电子传导网络，有效改善锂离子电池的电化学性能。
本申请的装置包括该锂离子电池，因而至少具有与锂离子电池相同的技术优势。
附图说明
图1是现有的正极极片的结构示意图。
图2A是根据本申请一实施例的正极极片的结构示意图。
图2B是根据本申请另一实施例的正极极片的结构示意图。
图3是根据本申请一实施例的锂离子电池的立体图。
图4是图3的分解图。
图5是根据本申请一实施例的电池模块的立体图。
图6是根据本申请一实施例的电池包的立体图。
图7是图6的分解图。
图8是根据本申请一实施例的锂离子电池作为电源的装置的示意图。
图9是不同胶层在锂离子电解液中的溶胀性能测试结果。
图10是泡液前后膜片的电阻测试结果。
图11是锂离子电池的直流内阻DCR测试结果。
其中，附图标记说明如下：
1：电池包；
2：上箱体；
3：下箱体；
4：电池模块；
5：锂离子电池；
51：外包装；
52：电极组件；
521a/521b：正极活性物质层；
522a/522b：油性胶层；
523a/523b：正极集流体；
524：低溶胀胶层；
53：顶盖组件。
具体实施方式
为了使本申请的目的、技术方案及优势更加清楚明白，以下结合附图及实施例，对本申请进一步详细说明。应当理解，此处所描述的具体实施方式仅仅用以解释本申请，并不用于限定本申请。
在本申请的描述中，除非另有明确的规定和限定，术语“多个(种)”是指两个(种)以上(包括两个(种))；除非另有规定或说明，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或一体地连接，或电连接，或信号连接；“连接”可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
需要理解的是，本申请实施例所描述的“上”、“下”等方位词是以附图所示的角度来进行描述的，不应理解为对本申请实施例的限定。下面通过具体的实施例并结合附图对本申请做进一步的详细描述。
本申请所使用的各种化学试剂，如无特殊说明，均为市售产品。
通常在电池内部，正极极片中的正极集流体由于电阻较大，一旦与负极极片接触产热最多，容易引发安全问题。因此，设计开发更高安全的正极极片对提升电池的安全性能至关重要。
参看图1，可通过在正极活性物质层521a和与其相邻的正极集流体523a表面之间增加一延展性良好的油性胶层522a，可以在穿刺过程有效包裹正极集流体523a和毛刺，阻隔其与电极的对接和短路产热。该油性胶层522a可选择极性基团改性的PVDF和导电材料、无机填料复合而成，以便同时满足高粘结性、电子传输和胶层的稳定性。然而，由于正极活性物质层521a和油性胶层522a中所用的粘结剂的极性相似，涂布干燥过程中两相存在相似相溶的现象，并且在高温干燥情况下，正极活性物质层521a极易发生开裂，严重影响涂布速度和效率。为此，可以在正极活性物质层521a中引入改性的柔性PVDF，使得在增大与油性胶层522a之间的极性差异的同时，可减少正极活性物质层521a的干燥应力，能够很好地提升涂布速度和干燥温度，从而有效提升生产效率。
PVDF的柔性改性可以通过非极性基团如长链烯烃基或者长链酯基等修饰来进行。这些非极性基团一定程度改善了正极活性物质层521a和油性胶层522a间的相互溶解。但极性差异增大，也导致在极性电解液环境中，界面之间(例如，正极活性物质层521a和油性胶层522a之间、或油性胶层522a和正极集流体523a的表面之间)接触位点锐减，进而造成粘结力下降、电子传输受阻、DCR及产热增加明显，从而严重影响电池的电化学性能和安全性能。
本发明人进一步进行了大量研究，发现可以通过在正极极片中设置低溶胀胶层和油性胶层，来实现电池同时兼顾较高的安全性能和电化学性能。
接下来将对本申请第一方面的锂离子电池5的各种组成、结构及参数、材料和性能等进行详细描述。
本申请第一方面涉及一种锂离子电池5，包括：正极极片，包括正极集流体523b和正极活性物质层521b；以及电解液，包括非水有机溶剂。
正极极片
用于本申请锂离子电池5的正极极片包括正极集流体523b和正极活性物质层521b，其中在正极集流体523b与正极活性物质层521b之间依次设置有低溶胀胶层524和油性胶层522b。其中低溶胀胶层524可相对靠近正极集流体523b。
图2A示出了根据本申请一实施例的正极极片的结构示意图，其中所述正极极片包括正极集流体523b，以及在所述正极集流体523b两个表面上依次设置的低溶胀胶层524、油性胶层522b和正极活性物质层521b。
需要说明的是，图2A仅示出本申请的正极极片的其中一种形式，即仅在正极集流体523b的两个表面上依次设置有低溶胀胶层524、油性胶层522b和正极活性物质层521b。在本申请的其他实施例中，例如，还可以在正极集流体523b的一个表面上依次设置有低溶胀胶层524、油性胶层522b和正极活性物质层521b。例如如图2B所示的本申请另一实施例的正极极片的结构示意图。
根据本申请的正极极片，通过在正极集流体523b和正极活性物质层521b之间设置油性胶层522b，可以在电池发生穿刺等过程有效包裹正极集流体523b和毛刺，阻隔其与电极的对接，降低电池内短路风险或短路产热，提升电池的安全性能。并且，在电解液浸泡环境中，由于油性胶层522b和正极集流体523b表面之间存在低溶胀胶层524，改变了原来两层之间的点接触方式，从而以面接触的方式增加了接触位点，形成有效的粘结，同时保证电子良好的传输网络，因此有效改善了锂离子电池5的电化学性能。
正极集流体
用于本申请的正极集流体523b没有特殊要求，可根据实际需求进行选择用于锂离子电池5的常规正极集流体523b，只要能够实现本申请的技术方案即可。在本申请一实施例中，正极集流体523b通常是可以汇集电流的结构或零件，例如正极集流体523b可以是本领域各种适用于作为电化学储能装置正极集流体523b的材料，例如，所述正极集流体523b可以是包括但不限于金属箔，更具体可以是包括但不限于镍箔、铝箔。
低溶胀胶层
在本申请一实施例中，用于本申请正极极片的低溶胀胶层524包括低溶胀粘结剂。例如，低溶胀粘结剂的溶度参数SP 1低于非水有机溶剂的溶度参数SP 0。
在本申请一实施例中，低溶胀粘结剂的溶度参数SP 1为13(J/cm 3) 1/2～18(J/cm 3) 1/2。例如，SP 1可以为13(J/cm 3) 1/2～15(J/cm 3) 1/2，13(J/cm 3) 1/2～14(J/cm 3) 1/2，14(J/cm 3) 1/2～18(J/cm 3) 1/2，14(J/cm 3) 1/2～15(J/cm 3) 1/2，或16(J/cm 3) 1/2～18(J/cm 3) 1/2。
在本申请一实施例中，低溶胀粘结剂可选自水性聚偏氟乙烯(PVDF)、聚丙烯酸、聚丙烯酸酯、丙烯腈或它们的共聚物，油性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。作为示例，低溶胀粘结剂可选自聚丙烯酸，聚丙烯酸酯，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。聚苯乙烯、丙烯改性的丙烯酸酯包括聚苯乙烯改性的丙烯酸酯、聚丙烯改性的丙烯酸酯及聚苯乙烯和聚丙烯改性的丙烯酸酯中的一种或多种。
在本申请一实施例中，低溶胀粘结剂的分子量可以为10万(w)～100w；例如可以为30w～80w，30w～50w，或50w～80w等。
根据本申请，聚合物的分子量为重均分子量，可以采用本领域的常规方式测 量。例如，小角激光光散射法。该技术是本领域技术人员熟知的。
在本申请一实施例中，低溶胀粘结剂为聚丙烯酸，分子量30w，溶度参数为14(J/cm 3) 1/2～15(J/cm 3) 1/2。
在本申请一实施例中，低溶胀粘结剂为聚丙烯酸酯，分子量50w，溶度参数为16(J/cm 3) 1/2～18(J/cm 3) 1/2。
在本申请一实施例中，低溶胀粘结剂为聚苯乙烯、丙烯改性的丙烯酸酯，分子量80w，溶度参数为13(J/cm 3) 1/2～14(J/cm 3) 1/2。
在本申请一实施例中，低溶胀粘结剂在低溶胀胶层524中的含量≥40wt％，例如可以为40wt％～80wt％，40wt％～60wt％，或60wt％～80wt％。
在本申请一实施例中，在低溶胀胶层524中，还包括导电碳材料。导电碳材料可选自导电炭黑、石墨烯中的一种或多种。导电炭黑可以是本领域公知的，例如包括乙炔黑等。可选地，导电碳材料在低溶胀胶层524的含量为20wt％-60wt％；例如可以为20wt％-40wt％，或40wt％-60wt％等。
在本申请一实施例中，低溶胀胶层524单层厚度T 1为0.1μm～5μm；例如可以为0.1μm～3μm，0.1μm～2μm，0.1μm～1μm，100nm～990nm，150nm～900nm，200nm～800nm，1μm～5μm，1μm～3μm，1μm～2μm，2μm～5μm，或2μm～3μm等。
在本申请一实施例中，以常见的有机溶剂，包括但不限于，例如N-甲基吡咯烷酮，四氯化碳、丙酮、碳酸亚乙酯(EC)、碳酸二乙酯(DEC)等中的一种或多种作为溶剂，室温环境下，以合适的投料比，加入低溶胀粘结剂和导电碳材料，利用机械搅拌设备分散搅拌均匀后，获得分散性良好的低溶胀胶浆料，然后涂布至正极集流体523b表面。将其置于烘箱内烘干并除去溶剂(例如但不限于100℃、2h)，待溶剂挥发完全后，可获得低溶胀胶膜。将该低溶胀胶膜置于电解液中适当温度下(例如70℃)浸泡，监测1周。结果发现，低溶胀胶膜的质量及体积溶胀率均小于10％，说明其低溶胀效果非常好。
油性胶层
在本申请一实施例中，用于本申请正极极片的油性胶层522b包括第一粘结剂。例如，第一粘结剂的溶度参数SP 2与非水有机溶剂的溶度参数SP 0差值的绝对值≤5(J/cm 3) 1/2。
在本申请一实施例中，第一粘结剂的溶度参数SP 2为20(J/cm 3) 1/2～29(J/cm 3) 1/2；例如可以为20(J/cm 3) 1/2～27(J/cm 3) 1/2，20(J/cm 3) 1/2～24(J/cm 3) 1/2，20(J/cm 3) 1/2～22(J/cm 3) 1/2，23(J/cm 3) 1/2～29(J/cm 3) 1/2，23(J/cm 3) 1/2～24(J/cm 3) 1/2，或27(J/cm 3) 1/2～29(J/cm 3) 1/2等。
在本申请一实施例中，第一粘结剂的溶度参数SP 2高于低溶胀粘结剂的溶度参数SP 1。换言之，低溶胀粘结剂的溶度参数SP 1低于第一粘结剂的溶度参数SP 2。第一粘结剂的溶度参数SP 2、以及低溶胀粘结剂的溶度参数SP 1均是相对于电解液的非水有机溶剂而言的。
在本申请一实施例中，第一粘结剂为油性粘结剂。例如，油性粘结剂可选自极性基团改性的聚偏氟烯烃和/或聚偏氯烯烃高分子材料，以及丙烯酸酯、丙烯酸类的共 聚物。
在本申请一实施例中，油性粘结剂可选自羧酸改性的PVDF、丙烯酸改性的PVDF、聚丙烯酸改性的PVDF、聚偏氯乙烯(PVDC)、羧酸改性的PVDC、丙烯酸改性的PVDC、PVDF共聚物、PVDC共聚物中的一种或多种。作为示例，油性粘结剂可选自丙烯酸改性的PVDF、聚丙烯酸改性的PVDF中的一种或多种。
在本申请一实施例中，油性粘结剂的分子量可以为30w～500w；例如可以为80w～130w，80w～100w，100w～130w，或100w～500w等。
在本申请一实施例中，油性粘结剂为聚丙烯酸改性的PVDF，分子量100w，溶度参数为23(J/cm 3) 1/2～24(J/cm 3) 1/2。
在本申请一实施例中，油性粘结剂为聚丙烯酸改性的PVDF，分子量130w，溶度参数为20(J/cm 3) 1/2～22(J/cm 3) 1/2。
在本申请一实施例中，油性粘结剂为聚丙烯酸改性的PVDF，分子量80w，溶度参数为27(J/cm 3) 1/2～29(J/cm 3) 1/2。
在本申请一实施例中，第一粘结剂在油性胶层522b中的含量为40wt％～75wt％；例如可以为40wt％～60wt％，40wt％～50wt％，50wt％～75wt％，50wt％～60wt％，或60wt％～75wt％等。
在本申请一实施例中，油性胶层522b中还包括第一导电材料。第一导电材料可选自碳基导电材料、导电聚合物中的一种或多种。作为示例，第一导电材料可选自导电炭黑、石墨烯、聚吡咯、聚苯胺中的一种或多种。导电炭黑可以是本领域公知的，例如包括乙炔黑等。
在本申请一实施例中，第一导电材料在油性胶层522b中的含量为20wt％～55wt％；例如可以为20wt％～40wt％，20wt％～30wt％，30wt％～45wt％，或40wt％～55wt％。
在本申请一实施例中，油性胶层522b中还包括无机填料。例如，无机填料可选自氧化镁、氧化铝、二氧化钛、氧化锆、二氧化硅、碳化硅、碳化硼、碳酸钙、硅酸铝、硅酸钙、钛酸钾、硫酸钡、钴酸锂、镍锰钴酸锂、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂、钛酸锂，或上述材料经导电碳包覆的改性材料、经导电金属包覆的改性材料或经导电聚合物包覆的改性材料中的至少一种。可选的，所述无机填料可选自氧化铝、二氧化钛、氧化锆、二氧化硅、磷酸铁锂、经碳包覆的磷酸铁锂中的一种或多种。可选的，无机填料可选自氧化铝、二氧化钛、氧化锆、二氧化硅中的一种或多种。
在本申请一实施例中，无机填料在所述油性胶层522b中的含量为5wt％～40wt％；例如可以为5wt％～20wt％，5wt％～10wt％，10wt％～40wt％，10wt％～20wt％，或20wt％～40wt％等。
在本申请一实施例中，油性胶层522b单层厚度T 2为3μm～15μm；例如可以为3μm～10μm，3μm～7μm，3μm～5μm，5μm～15μm，5μm～10μm，5μm～7μm，或7μm～15μm等。
用于本申请正极极片的油性胶层522b和低溶胀胶层524可从以下两个方面进行区别及选择：1)粒径大小。低溶胀胶层524厚度在纳米至亚微米(例如，100nm～1μm、100nm～2μm、100nm～3μm、100nm～5μm、100nm～990nm、150nm～900nm或200nm～800nm)级别。而油性胶层522b由于引入无机填料，胶层厚度一般在微米级别。2)溶度参数。溶度参数是表征聚合物-溶剂相互作用的参数。可由内聚能予以定量表征，单位体积的内聚能称为内聚能密度，其平方根称为溶度参数。溶度参数可以作为衡量两种材料是否共容的一个较好的指标。当两种材料的溶度参数相近时，它们可以互相共混且具有良好的共容性。通常液体的溶度参数可以从它们的蒸发热得到。聚合物的溶度参数可以从交联聚合物溶胀实验或线性聚合物稀溶液黏度测定得到。能使聚合物的溶胀度或特性黏数最大时的溶剂的溶度参数即为此聚合物的溶度参数。本申请可以参考浊度滴定法来测定粘结剂的溶度参数。
一般来讲，混合溶剂的溶度参数可以根据下述的公式(1)计算：
Figure PCTCN2020119689-appb-000001
其中，δ为混合溶剂的溶度参数，δ i为某一组分的溶度参数，
Figure PCTCN2020119689-appb-000002
为该某一组分的体积分数，n为大于等于2的整数。
例如，混合溶剂为三组分溶剂，其溶度参数可以根据下述的公式(1-1)计算：
Figure PCTCN2020119689-appb-000003
其中δ为混合溶剂的溶度参数，δ 1为第一组分的溶度参数，
Figure PCTCN2020119689-appb-000004
为第一组分的体积分数，δ 2为第二组分的溶度参数，
Figure PCTCN2020119689-appb-000005
为第二组分的体积分数，δ 3为第三组分的溶度参数，
Figure PCTCN2020119689-appb-000006
为第三组分的体积分数。常见溶剂例如碳酸亚乙酯(EC)的δ为29.4(J/cm 3) 1/2，聚碳酸酯(PC)的δ为14.5(J/cm 3) 1/2，碳酸二乙酯(DEC)的δ为20.3(J/cm 3) 1/2。本申请中，锂离子电解液的非水有机溶剂的溶度参数SP 0在20(J/cm 3) 1/2～25(J/cm 3) 1/2之间。
根据相似相溶的原理，针对不同的粘结剂类型，用于本申请正极极片的低溶胀胶层524通常选择溶度参数SP 1在13(J/cm 3) 1/2～18(J/cm 3) 1/2之间的低溶胀粘结剂。在本申请一实施例中，低溶胀粘结剂可选自，包括但不限于，例如水性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈或它们的共聚物，油性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。
低溶胀胶层524与非水有机溶剂的溶度参数差异较大，在电解液的浸润环境中，低溶胀胶层524的溶胀程度小、稳定性高。而对于油性胶层522b体系而言，通常引入极性基团、与溶度参数较大的结构片段共聚，来增大第一粘结剂与正极活性物质、第二导电材料，以及正极集流体523b的接触面积，从而提升粘结力和导电能力。对于本申请的油性胶层522b而言，溶度参数SP 2选用在20(J/cm 3) 1/2～29(J/cm 3) 1/2范围的第一粘结剂，包括但不限于，例如极性基团改性的聚偏氟乙烯(商购，分子量：100w～500w)。极性基团的引入增加了油性胶层522b的溶度参数，与电解液的溶度参数差异小，因此在电解液中油性胶层522b表现出较大的溶胀性等。
正极活性物质层
在本申请一实施例中，用于本申请正极极片的正极活性物质层521b包括正极活性物质。例如，该正极活性物质选自含锂复合金属氧化物。作为示例，该正极活性物质选自锂镍钴锰氧化物、锂镍锰氧化物中的一种或多种。
在本申请一实施例中，含锂复合金属氧化物包括但不限于LiCoO 2、LiNiO 2、LiMn 2O 4、锂镍钴锰氧化物、或锂镍锰氧化物等。在本申请一实施例中，锂镍钴锰氧化物包括但不限于LiNi 0.8Co 0.1Mn 0.1O 2。在本申请一实施例中，锂镍锰氧化物包括但不限于LiNi 0.5Mn 1.5O 4。
在本申请一实施例中，正极活性物质中镍元素与所有过渡金属元素的摩尔比为0.5～0.9；例如为0.5～0.8。
在本申请一具体实施例中，正极活性物质在正极活性物质层521b中的含量为30wt％～99.9wt％；例如80％～99％，或90％～97.5％等。
在本申请一实施例中，正极活性物质层521b还包括第二粘结剂。第二粘结剂可包括但不限于，聚偏氟烯烃和/或聚偏氯烯烃高分子材料。
在本申请一实施例中，第二粘结剂可选自任选的含有柔性链改性的聚偏氟乙烯和/或偏氟氯乙烯。例如，所述柔性链为长链的烷基或烷氧基。再例如，所述柔性链为C1-C6的烷基或烷氧基。
在本申请一实施例中，第二粘结剂选自任选的被苯乙烯丁酯改性的聚偏氟乙烯、任选的被聚乙烯/丙烯改性的偏氟氯乙烯、聚丙烯酸丁酯改性的PVDF、聚偏氟乙烯/丙烯酸丁酯共聚物中的一种或多种。
在本申请一实施例中，第二粘结剂为聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
在本申请一实施例中，第二粘结剂在正极活性物质层521b中的含量为0.05wt％～30wt％；例如可以为1wt％～20wt％，3wt％～10wt％，或4wt％～8wt％。
在本申请一实施例中，正极活性物质层521b还包括第二导电材料。第二导电材料可选自导电炭黑、石墨、石墨烯、碳纳米管、碳纳米纤维中的一种或多种。导电炭黑可以是本领域公知的，例如包括乙炔黑等。
在本申请一实施例中，第二导电材料在正极活性物质层521b中的含量为0.05wt％～40wt％；例如可以为1wt％～20wt％，3wt％～10wt％，或4wt％～8wt％。
在本申请一实施例中，正极活性物质层521b干燥后单层涂布厚度T 0为50μm～300μm；例如可以为70μm～200μm，或90μm～150μm。
在本申请一实施例中，低溶胀胶层524单层厚度T 1、油性胶层522b单层厚度T 2、正极活性物质层521b单层厚度T 0满足以下关系：0.01≤(T 1+T 2)/T 0≤0.4。例如，T 0、T 1、T 2满足以下关系：0.015≤(T 1+T 2)/T 0≤0.2，0.02≤(T 1+T 2)/T 0≤0.13，0.02≤(T 1+T 2)/T 0≤0.07，0.02≤(T 1+T 2)/T 0≤0.05，0.04≤(T 1+T 2)/T 0≤0.2，0.04≤(T 1+T 2)/T 0≤0.13，0.04≤(T 1+T 2)/T 0≤0.07，0.05≤(T 1+T 2)/T 0≤0.2，或0.05≤(T 1+T 2)/T 0≤0.13等。
电解液
用于本申请锂离子电池5的电解液的具体种类及组成均不受限制，可根据实际需求进行选择。在本申请一实施例中，用于锂离子电池5的电解液为锂盐溶液。在本 申请一具体实施例中，锂盐例如包括但不限于，LiClO 4、LiPF 6、LiBF 4、LiAsF 6、LiSbF 6等无机锂盐、或者LiCF 3SO 3、LiCF 3CO 2、Li 2C 2F 4(SO 3) 2、LiN(CF 3SO 2) 2、LiC(CF 3SO 2) 3、LiC nF 2n+1SO 3(n≥2)等有机锂盐中的一种或多种。
非水有机溶剂
用于本申请电解液的非水有机溶剂，例如包括但不限于，碳酸亚乙酯、碳酸亚丙酯、碳酸亚丁酯、碳酸亚乙烯酯等环状碳酸酯，碳酸二甲酯、碳酸二乙酯、碳酸甲基乙酯等链状碳酸酯，丙酸甲酯等链状酯，γ-丁内酯等环状酯，二甲氧基乙烷、二乙醚、二甘醇二甲醚、三甘醇二甲醚等链状醚，四氢呋喃、2-甲基四氢呋喃等环状醚，乙腈、丙腈等腈类中的一种或多种。当本申请的非水有机溶剂为多种混合溶剂时，各组分的体积含量没有特别要求，可根据情况进行调整，只要能够实现本申请的技术方案即可。
在本申请一实施例中，非水有机溶剂的溶度参数SP 0为20(J/cm 3) 1/2～25(J/cm 3) 1/2；例如可以为20(J/cm 3) 1/2～24(J/cm 3) 1/2，23(J/cm 3) 1/2～25(J/cm 3) 1/2，23(J/cm 3) 1/2～24(J/cm 3) 1/2等。
锂离子电池
本申请第一方面所提供的锂离子电池5，包括上文所述的正极极片和电解液，以及负极极片，和设置于正极极片和负极极片之间的隔膜。其中负极极片和隔膜没有特别要求，可根据实际需求进行选择，只要能够实现本申请的技术方案即可。
本申请的锂离子电池5可以为电容器、一次电池或二次电池。例如可以为锂离子电容器、锂离子一次电池或锂离子二次电池。
图3示出了根据本申请一实施例的锂离子电池5的立体图，图4是图3所示锂离子电池5的分解图。参看图3和图4，本申请的锂离子电池5包括外包装51、电极组件52、顶盖组件53和电解液(未示出)。其中电极组件52收容于外包装51内，电极组件52的数量不受限制，可以为一个或多个。
需要说明的是，图3所示的锂离子电池5为罐型电池，但本申请并不限于此，锂离子电池5可以是袋型电池，即壳体51由金属塑膜替代且取消顶盖组件53。
在本申请一实施例中，锂离子电池5可以组装成电池模块4，电池模块4所含的锂离子电池5的数量可以为若干个，具体数量可根据电池模块4的应用和容量来调节。图5示出了根据本申请一实施例的电池模块4的立体图。参看图5，在电池模块4中，多个锂离子电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将多个锂离子电池5进行固定。可选地，电池模块4还可以包括具有容纳空间的壳体，多个锂离子电池5容纳于该容纳空间。
在本申请一实施例中，上述电池模块4还可以组装成电池包1，电池包1所含电池模块4的数量可以根据电池包1的应用和容量进行调节。图6示出了根据本申请一实施例的电池包1的立体图，图7是图6的分解图。参看图6和图7，在电池包11中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池 模块4可以按照任意的方式排布于电池箱中。
装置
本申请第二方面提供一种装置，包括本申请第一方面的锂离子电池5。锂离子电池5可以用作该装置的电源，也可以作为该装置的能量存储单元。该装置包括但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
该装置可以根据其使用需求来选择锂离子电池5、电池模块4或电池包1。
图8示出了根据本申请一实施例的锂离子电池5作为电源的装置的示意图。该装置可以为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子电池5的高功率和高能量密度的需求，可以采用电池包1或电池模块4。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用本申请的锂离子电池5作为电源。
本领域技术人员可以理解：以上提到的本申请的不同实施方式中对于极片、电极活性物质层等的组分选择、组分含量和材料理化性能参数的各种限定或优选范围可以任意组合，其组合而得到的各种实施方式仍然在本申请范围内，且视为本说明书公开内容的一部分。
除非特别规定，本说明书中涉及的各种参数具有本领域公知的通用含义，可以按本领域公知的方法进行测量。例如，可以按照在本申请的实施例中给出的方法进行测试。另外，各种优选实施方式中给出的各种不同参数的优选范围和选项可以进行任意组合，由此得到的各种组合都视为在本申请的公开范围之内。
实施例
下面结合具体实施例，进一步阐述本发明。应理解，下文的示例性实施例仅用于举例说明，并非对本发明进行限定。除非另有声明，实施例中使用的所有试剂都可商购或按照常规方法进行合成获得，并且可直接使用而无需进一步处理。实施例中未注明的实验条件采用常规条件、或采用材料供应商或设备供应商推荐的条件。
1.正极极片的制备
1)低溶胀胶层
室温下，利用砂磨机，将低溶胀粘结剂和导电碳材料按照计量比在有机溶剂中分散搅拌，获得分散均一性良好的低溶胀胶浆料。
将上述制得的低溶胀胶浆料通过转移涂布机，在正极集流体523b(例如10μm铝箔)表面上进行涂布，速度为30m/min，得到低溶胀胶层524。
2)油性胶层
利用双行星搅拌机，将第一粘结剂和第一导电材料、无机填料按照计量比在N-甲基吡咯烷酮(NMP)中分散搅拌，获得分散均一性良好的油性胶浆料。
将上述制得的油性胶浆料采用挤压涂布方式，在上述的低溶胀胶层524上进行涂布，速度为10m/min～60m/min，得到油性胶层522b。
3)正极活性物质层
将正极活性物质(LiNi 0.8Co 0.1Mn 0.1O 2)、第二粘结剂、第二导电材料炭黑(SP)按照计量比在溶剂N-甲基吡咯烷酮(NMP)中溶解，经高速搅拌，得到分散均匀的正极浆料。其中固体含量为60wt％，包含90wt％的LiNi 0.8Co 0.1Mn 0.1O 2、5wt％的聚丙烯酸丁酯改性PVDF和5wt％的SP。将该正极浆料在上述的油性胶层522b上进一步进行涂布、辊压工序后，制得正极极片，其中正极活性物质层521b单层厚度为150μm。
2.负极极片的制备
将负极活性物质人造石墨、粘结剂SBR乳液、散剂羧甲基纤维素钠和导电炭黑按照计量比，在去离子水体系中经高速搅拌，得到分散均匀的负极浆料。其中固体含量为40wt％，包含90wt％的人造石墨、2wt％的羧甲基纤维素钠、3wt％的导电炭黑、5wt％的SBR。将该负极浆料进行涂布、辊压工序后制得负极极片。
3.锂离子电解液的制备
在充满氩气的手套箱中，将碳酸亚乙酯(EC)、碳酸二甲酯(DMC)和1,2-丙二醇碳酸酯按照体积比1:1:1混合，作为非水混合有机溶剂溶度参数为23(J/cm 3) 1/2～24(J/cm 3) 1/2，然后向该非水混合有机溶剂中加入六氟磷酸锂，得到1mol/L的六氟磷酸锂溶液，作为锂离子电解液。
4.锂离子电池5的制备
将上述制得的正、负极极片进行极耳成型后，采用12μm厚的聚丙烯/聚乙烯复合隔离膜将它们间隔隔开，采用三明治结构进行卷绕形成裸电芯，再用铝塑膜封装。封装后注入上述制得的锂离子电解液，然后进行化成和老化。
实施例1
按照上述方法制备本实施例的正极极片和锂离子电池5，其中低溶胀粘结剂选用聚丙烯酸，分子量为30w，溶度参数为14(J/cm 3) 1/2～15(J/cm 3) 1/2；油性胶层522b中的第一粘结剂选用聚丙烯酸改性的PVDF，溶度参数为23(J/cm 3) 1/2～24(J/cm 3) 1/2，分子量100w；正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
所制得的正极极片如图2A所示，包括正极集流体523b，以及在该正极集流体523b的两个表面上依次涂布有低溶胀胶层524、油性胶层522b和正极活性物质层521b。
实施例2
按照上述方法制备本实施例的正极极片和锂离子电池5，其中低溶胀粘结剂选用聚丙烯酸酯，分子量为50w，溶度参数为16(J/cm 3) 1/2～18(J/cm 3) 1/2；油性胶层522b中的第一粘结剂选用聚丙烯酸改性的PVDF，溶度参数为23(J/cm 3) 1/2～24(J/cm 3) 1/2，分子量为100w，正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
本实施例制得的正极极片是在正极集流体523b的两个表面上依次涂布有低溶胀胶层524、油性胶层522b和正极活性物质层521b。
实施例3
按照上述方法制备本实施例的正极极片和锂离子电池5，其中低溶胀粘结剂选 用聚苯乙烯、丙烯改性的丙烯酸酯，分子量为80w，溶度参数为13(J/cm 3) 1/2～14(J/cm 3) 1/2；油性胶层522b中的第一粘结剂选用聚丙烯酸改性的PVDF，溶度参数为20(J/cm 3) 1/2～22(J/cm 3) 1/2，分子量为130w；正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
本实施例制得的正极极片如图2B所示，即仅在正极集流体523b的一个表面上依次涂布有低溶胀胶层524、油性胶层522b和正极活性物质层521b。
实施例4
按照上述方法制备本实施例的正极极片和锂离子电池5，其中低溶胀粘结剂选用聚苯乙烯、丙烯改性的丙烯酸酯，分子量为80w，溶度参数为13(J/cm 3) 1/2～14(J/cm 3) 1/2；油性胶层522b的第一粘结剂选用聚丙烯酸改性的PVDF，溶度参数为27(J/cm 3) 1/2～29(J/cm 3) 1/2，分子量为80w；正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
本实施例制得的正极极片是在正极集流体523b的两个表面上依次涂布有低溶胀胶层524、油性胶层522b和正极活性物质层521b。
实施例5
本实施例与实施例4不同之处在于，低溶胀粘接剂在低溶胀胶层524中的含量为40wt％。
实施例6
本实施例与实施例4不同之处在于，低溶胀粘接剂在低溶胀层中的含量为80wt％。
实施例7
本实施例与实施例4不同之处在于，在油性胶层522b中的第一粘接剂、第一导电材料、无机填料各自的含量分别为40wt％、20wt％、40wt％。
实施例8
本实施例与实施例4不同之处在于，在油性胶层522b中的第一粘接剂、第一导电材料、无机填料各自的含量分别为75wt％、20wt％、5wt％。
实施例9
本实施例与实施例4不同之处在于，在油性胶层522b中的第一粘接剂、第一导电材料、无机填料各自的含量分别为40wt％、55wt％、5wt％。
实施例10
本实施例与实施例4不同之处在于，在油性胶层522b中的第一粘接剂、第一导电材料、无机填料各自的含量分别为50wt％、40wt％、10wt％。
实施例11
本实施例与实施例4不同之处在于，低溶胀胶层524的厚度为100nm，油性胶层522b的厚度为3μm。
实施例12
本实施例与实施例4不同之处在于，低溶胀胶层524的厚度为1μm，油性胶层522b的厚度为5μm。
实施例13
本实施例与实施例4不同之处在于，低溶胀胶层524的厚度为3μm，油性胶层522b的厚度为7μm。
实施例14
本实施例与实施例4不同之处在于，低溶胀胶层524的厚度为5μm，油性胶层522b的厚度为15μm。
对比例1
按照上述方法制备对比例1的正极极片和锂离子电池5，其中该对比例1不包含低溶胀胶层524，油性胶层522b中的第一粘结剂选用聚丙烯酸改性的PVDF，溶度参数为23(J/cm 3) 1/2～24(J/cm 3) 1/2，分子量为100W；正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
所制得的正极极片如图1所示，包括正极集流体523a，以及在该正极集流体523a表面上依次涂布的油性胶层522a和正极活性物质层521a。
对比例2
按照上述方法制备对比例2的正极极片和锂离子电池5，其中，该对比例2的正极集流体523b上仅涂布有正极活性物质层521b。正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
本对比例制得的正极极片仅在正极集流体523b的一个表面上涂布有正极活性物质层521b。
对比例3
按照上述方法制备对比例3的正极极片和锂离子电池5，在正极集流体523b表面依次设置低溶胀胶层524、油性胶层522b，其中低溶胀胶层524选用聚丙烯酸改性的PVDF，溶度参数为27(J/cm 3) 1/2～29(J/cm 3) 1/2，分子量为80w；油性胶层522b的第一粘结剂选用聚苯乙烯、丙烯改性的丙烯酸酯，分子量为80w，溶度参数为13(J/cm 3) 1/2～14(J/cm 3) 1/2；正极活性物质层521b中的第二粘结剂选用聚丙烯酸丁酯改性的PVDF，溶度参数为19(J/cm 3) 1/2～20(J/cm 3) 1/2，分子量为110w～130w。
实施例1-14、对比例1-3中的各物质用量及具体参数如表1所示。
表1
Figure PCTCN2020119689-appb-000007
性能测试
1.不同胶层在锂离子电解液中的溶胀性能测试
将上述实施例1中的低溶胀胶浆料、油性胶浆料分别稀释成7wt％的胶液，倒入铝塑膜制得的简易盒子中，放置烘箱内80℃烘干6h后，分别得到低溶胀胶层524和油性胶层522b的胶膜。
将上述制得的不同胶膜分别放置于锂离子电解液中，70℃烘箱静置，连续一周监测胶膜重量变化，结果参看图9。
从图9可以看出，相比油性胶层522b，低溶胀胶层524都表现出更好的电解液耐受性能。在在一周的电解液浸泡下，重量变化均<1％，而油性胶层522b的溶胀变化高达约30～40％。
2.泡液前后膜片电阻测试
取实施例1及对比例1制得不同厚度(100μm、150μm、200μm、250μm)的正极极片各5片(20×90mm 2)，置于上述制得的锂离子电解液中，70℃放置24h后，在干燥房环境中取出晾干0.5h。使用膜片电阻测试仪，每10s间隔读取每个正极极片两侧的膜片电阻，每个样记录20个数值，取均值，结果参看图10。
从图10可以看出，在锂离子电解液70℃的浸泡条件下，不同涂布厚度和不同涂布结构的正极极片的膜片电阻变化存在显著差异。泡液前，相比于单层涂布结构(即只有正极活性物质层521b，对比例2)和双层涂布结构(即油性胶层522b+正极活性物质层521b，对比例1)，本申请的三层涂布结构(即低溶胀胶层524+油性胶层522b+正极活性物质层521b)的正极极片表现出更小的电阻。这是因为与正极集流体523b的导电接触位点增多而导致的。进而当锂离子电解液渗入接触界面，低溶胀胶层524表现出更小的溶胀率，可以提供界面间良好的粘结力和接触面积，保证了足够有效的粘结力作用位点和电子传输通路。可以看出，本申请的具有三层涂布结构的正极极片在接触电解液前/后的电阻增长趋势明显小于单层/双层涂布结构。
3.泡液前后粘结力测试
取实施例1-14及对比例1-3的正极极片各5片(20×90mm 2)，置于上述制得的电解液溶液中，70℃放置24h后，在干燥房环境中取出晾干0.5h。将干燥后的正极极片贴在双面胶上，辊压3次后，进行180°剥离测试，拉伸速度为50mm/min，结果如下表2所示。
表2
正极极片 泡液前粘结力(N/m) 泡液后粘结力(N/m)
实施例1 ＞500 ＞500
实施例2 ＞500 ＞500
实施例3 ＞500 ＞500
实施例4 ＞500 ＞500
实施例5 ＞500 ＞500
实施例6 ＞500 ＞500
实施例7 ＞500 ＞500
实施例8 ＞500 ＞500
实施例9 ＞500 455
实施例10 ＞500 460
实施例11 ＞500 312
实施例12 ＞500 ＞500
实施例13 ＞500 ＞500
实施例14 ＞500 ＞500
对比例1 400 260
对比例2 20 3.1
对比例3 ＞500 220
从表2可以看出，本申请的正极极片在泡液前后的粘结力基本未发生任何变化，而对比例1-3的正极极片在泡液前后的粘结力明显降低。
4.锂离子电池5的DCR测试
将实施例1-14制得的锂离子电池5和对比例1-3制得的锂离子电池5分别按如下流程测试DCR。
25℃下，测试30s的DCR，具体流程如下：
25℃下静置5min；
1C电流下满充至4.3V；
静置10min；
满充下放电调整至测试不同SOC(90％，60％，50％，30％)；
依次测试4C电流下30s内，对应的DCR(采点间隔0.1s)；
静置10min。
结果参看表3和图11。
表3
电池 25℃50％SOC DCR(mohm)
实施例1 171
实施例2 175
实施例3 180
实施例4 169
实施例5 157
实施例6 190
实施例7 176
实施例8 182
实施例9 173
实施例10 174
实施例11 185
实施例12 172
实施例13 165
实施例14 150
对比例1 197
对比例2 302
对比例3 263
从表3和图11可以看出，相对于对比例1-3，本申请的锂离子电池5的DCR均有不同程度降低，其中实施例14，相比对比例1降低23.8％，相比对比例2降低50％。
根据上述说明书的揭示和教导，本领域技术人员还可以对上述实施方式进行变更和修改。因此，本发明并不局限于上面揭示和描述的具体实施方式，对本发明的一些修改和变更也应当落入本发明的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本发明构成任何限制。

Claims (18)

  1. 一种锂离子电池，包括：
    正极极片，包括正极集流体和正极活性物质层；以及
    电解液，包括非水有机溶剂；
    其中在所述正极集流体与所述正极活性物质层之间依次设置有低溶胀胶层和油性胶层；
    所述低溶胀胶层包括低溶胀粘结剂，所述油性胶层包括第一粘结剂；其中所述低溶胀粘结剂的溶度参数SP 1低于所述第一粘结剂的溶度参数SP 2。
  2. 根据权利要求1所述的锂离子电池，其中，所述低溶胀粘结剂的溶度参数SP 1低于所述非水有机溶剂的溶度参数SP 0；和/或
    所述第一粘结剂的溶度参数SP 2与所述非水有机溶剂的溶度参数SP 0差值的绝对值≤5(J/cm 3) 1/2。
  3. 根据权利要求1或2所述的锂离子电池，其中，所述非水有机溶剂的溶度参数SP 0为20(J/cm 3) 1/2～25(J/cm 3) 1/2，可选的为23(J/cm 3) 1/2～24(J/cm 3) 1/2。
  4. 根据权利要求1-3任一项所述的锂离子电池，其中，所述低溶胀粘结剂的溶度参数SP 1为13(J/cm 3) 1/2～18(J/cm 3) 1/2，可选的为13(J/cm 3) 1/2～15(J/cm 3) 1/2。
  5. 根据权利要求1-4任一项所述的锂离子电池，其中，所述第一粘结剂的溶度参数SP 2为20(J/cm 3) 1/2～29(J/cm 3) 1/2，可选的为23(J/cm 3) 1/2～29(J/cm 3) 1/2。
  6. 根据权利要求1-5任一项所述的锂离子电池，其中，所述低溶胀粘结剂选自水性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈或它们的共聚物，油性PVDF、聚丙烯酸、聚丙烯酸酯、丙烯腈，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种；可选的，所述低溶胀粘结剂选自聚丙烯酸，聚丙烯酸酯，聚苯乙烯、丙烯改性的丙烯酸酯，或上述材料的共聚物中的一种或多种。
  7. 根据权利要求1-6任一项所述的锂离子电池，其中，在所述低溶胀胶层中，所述低溶胀粘结剂的含量≥40wt％，可选的为40wt％～80wt％。
  8. 根据权利要求1-7任一项所述的锂离子电池，其中，所述低溶胀胶层还包括导电碳材料，所述导电碳材料选自导电炭黑、石墨烯中的一种或多种。
  9. 根据权利要求1-8任一项所述的锂离子电池，其中，所述第一粘结剂为油性粘结剂，所述油性粘结剂选自极性基团改性的聚偏氟烯烃和/或聚偏氯烯烃高分子材料，以及丙烯酸酯、丙烯酸类的共聚物；可选的，所述第一粘结剂选自羧酸改性的聚偏氟乙烯PVDF和/或羧酸改性的聚偏氯乙烯PVDC；可选的，所述羧酸选自丙烯酸和/或聚丙烯酸。
  10. 根据权利要求1-9任一项所述的锂离子电池，其中，所述油性胶层还包括第一导电材料，所述第一导电材料选自导电炭黑、石墨烯、聚吡咯、聚苯胺中的一种或多种。
  11. 根据权利要求1-10任一项所述的锂离子电池，其中，所述油性胶层还包括无 机填料，所述无机填料选自氧化镁、氧化铝、二氧化钛、氧化锆、二氧化硅、碳化硅、碳化硼、碳酸钙、硅酸铝、硅酸钙、钛酸钾、硫酸钡、钴酸锂、镍锰钴酸锂、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂、钛酸锂，或上述材料经导电碳包覆的改性材料、经导电金属包覆的改性材料或经导电聚合物包覆的改性材料中的一种或多种。
  12. 根据权利要求1-11任一项所述的锂离子电池，其中，所述正极活性物质层包括正极活性物质，所述正极活性物质选自含锂复合金属氧化物；可选的，所述正极活性物质选自锂镍钴锰氧化物、锂镍锰氧化物中的一种或多种。
  13. 根据权利要求1-12任一项所述的锂离子电池，其中，所述正极活性物质层还包括第二粘结剂，所述第二粘结剂选自任选的含有柔性链改性的聚偏氟乙烯和/或偏氟氯乙烯，所述柔性链为长链的烷基或烷氧基；
    可选的，所述第二粘结剂选自任选的被苯乙烯丁酯改性的聚偏氟乙烯、任选的被聚乙烯/丙烯改性的偏氟氯乙烯、聚丙烯酸丁酯改性的PVDF、聚偏氟乙烯/丙烯酸丁酯共聚物中的一种或多种。
  14. 根据权利要求1-13任一项所述的锂离子电池，其中，所述低溶胀胶层的单层厚度T 1、所述油性胶层的单层厚度T 2、正极活性物质层单层厚度T 0满足以下关系：0.01≤(T 1+T 2)/T 0≤0.4；可选的，0.015≤(T 1+T 2)/T 0≤0.2。
  15. 根据权利要求1-14任一项所述的锂离子电池，其中，所述低溶胀胶层的单层厚度T 1为0.1μm～5μm，可选的为0.1μm～3μm，可选的为0.1μm～1μm。
  16. 根据权利要求1-15任一项所述的锂离子电池，其中，所述油性胶层的单层厚度T 2为3μm～15μm，可选的为5μm～7μm。
  17. 一种装置，包括根据权利要求1-16任一项所述的锂离子电池。
  18. 根据权利要求17所述的装置，其中，所述装置包括手机、笔记本电脑、电动车辆、电动船舶、或储能系统；可选的，所述电动车辆包括混合动力电动车辆、插电式混合动力电动车辆、电动自行车、电动踏板车、电动高尔夫球车、或电动卡车。
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