WO2023179550A1 - 一种复合油基隔膜及其制备方法和二次电池 - Google Patents

一种复合油基隔膜及其制备方法和二次电池 Download PDF

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WO2023179550A1
WO2023179550A1 PCT/CN2023/082543 CN2023082543W WO2023179550A1 WO 2023179550 A1 WO2023179550 A1 WO 2023179550A1 CN 2023082543 W CN2023082543 W CN 2023082543W WO 2023179550 A1 WO2023179550 A1 WO 2023179550A1
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Prior art keywords
moisturizing
composite oil
based separator
coating
polymer
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PCT/CN2023/082543
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English (en)
French (fr)
Inventor
赖旭伦
陈杰
李载波
项海标
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惠州锂威电子科技有限公司
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Publication of WO2023179550A1 publication Critical patent/WO2023179550A1/zh

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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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/423—Polyamide resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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 invention belongs to the technical field of secondary batteries, and in particular relates to a composite oil-based separator, a preparation method thereof and a secondary battery.
  • Lithium-ion batteries have the characteristics of high operating voltage, high energy density, long cycle life, no memory effect and no pollution. They are the main energy source for various electronic products and are green, environmentally friendly and pollution-free secondary batteries. At the same time, it is in line with the development trend of energy and environmental protection in the world today, resulting in a sharp increase in the use of lithium batteries in various industries. As a result, the safety, capacity, and fast charging performance of lithium batteries have attracted more and more attention, especially in the field of fast charging. It is an urgent need to solve.
  • the four key materials of lithium-ion batteries are cathode materials, anode materials, electrolytes and separators.
  • the main function of the separator is to isolate the positive and negative electrodes and prevent electrons from passing through, while allowing ions to pass through, thereby completing the rapid transfer of lithium ions between the positive and negative electrodes during charging and discharging.
  • the liquid absorption and retention properties of the separators have become the focus of research. At present, people increase the liquid absorption and retention properties of the separator by coating a water-based polymer coating or an oil-based polymer coating on the separator.
  • the water-based separator can currently only achieve fast charging with a magnification rate below 3C, and a higher rate is An oily diaphragm is used.
  • the oily diaphragm has a large static electricity problem, which greatly affects the winding of the battery core, and the battery core qualification rate is low.
  • One of the purposes of the present invention is to provide a composite oil-based separator in view of the shortcomings of the existing technology, which can form a layer structure with water vapor on the surface of the base film, thereby reducing the electrostatic strength of the composite oil-based separator, thereby making The separator will not wrinkle when used in battery cores for winding, improving the quality of produced products.
  • a composite oil-based separator includes a base film and a moisturizing coating coated on at least one side surface of the base film.
  • the moisturizing coating includes inorganic fillers, adhesive polymers and moisturizing polymers.
  • the weight parts ratio of the adhesive polymer, moisturizing polymer and inorganic filler is 20-90:0.1-1:10-80.
  • the adhesive polymer is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride homopolymer, aramid, and fluorine-based polymers.
  • the moisturizing polymer is polyethylene glycol, polypropylene glycol, tripropylene glycol, ethylene glycol, or polyvinyl acetate. of one or more.
  • the inorganic filler is one or more of alumina, magnesium hydroxide, aluminum hydroxide, titanium dioxide, silica, and boehmite.
  • the thickness of the moisturizing coating is 0.5 ⁇ m to 5 ⁇ m.
  • the base film is PE, PP, PI, aramid, PE/PP/PE composite film or ceramic composite isolation film.
  • the base film has a melting point of 130°C to 500°C, a thickness of 3 ⁇ m to 14 ⁇ m, and a porosity of 30 ⁇ 50%, air permeability is 30sec/100cc ⁇ 300sec/100cc.
  • the second object of the present invention is to provide a method for preparing a composite oil-based separator in view of the shortcomings of the existing technology, which method is simple to operate and has good controllability.
  • a method for preparing a composite oil-based separator including the following steps:
  • Step S1 Stir and disperse part of the organic solvent and the adhesive polymer to obtain glue
  • Step S2 Add the glue liquid to the moisturizing polymer and stir and disperse to obtain the moisturizing glue liquid;
  • Step S3 Mix and disperse the remaining organic solvent and inorganic filler into the inorganic filler dispersion
  • Step S4 Mix the moisturizing glue liquid and the inorganic filler dispersion liquid, disperse, stir, and grind to obtain a moisturizing slurry;
  • Step S5 Coat the moisturizing slurry on at least one surface of the base film, solidify to form a moisturizing coating, wash and dry to obtain a composite oil-based separator.
  • step S3 also includes adding 0.01 to 5 parts by weight of a pore-forming agent to the inorganic filler dispersion.
  • step S5 coagulation is performed in a coagulation tank, the temperature of the coagulation tank is 10-18°C, the concentration of the solution in the coagulation tank is 10-40%, and the solution in the coagulation tank is NMP, DMAC, acetone, dimethyl One or more types of sulfoxides.
  • the water washing in step S5 is performed in a water washing tank, the temperature of the water washing tank is 20-30°C, the concentration of the moisturizing solution in the water washing tank is 0.1-1%, and the concentration of the organic solvent is 0.01-1%.
  • the third object of the present invention is to provide a secondary battery with good antistatic properties and liquid absorption and retention properties in view of the shortcomings of the existing technology.
  • a secondary battery includes the above composite oil-based separator.
  • a composite oil-based separator of the present invention is provided with a moisturizing coating, and is prepared by incorporating a moisturizing polymer into the oily moisturizing coating and coating to form a moisturizing coating.
  • the moisturizing coating produced has good antistatic properties, high liquid absorption/retention, high lithium ion layer rate and high cell hardness, which can significantly reduce defects caused by cell winding and improve production efficiency and product qualification rate. , the high rate cycle function of the battery core realizes the fast charging performance of the battery core.
  • Figure 1 is an SEI diagram of the composite oil-based separator of the present invention.
  • Figure 2 is a flow chart for the preparation of the composite oil-based separator of the present invention.
  • Figure 3 is a graph showing the wettability test results of Example 1 of the composite oil-based separator of the present invention.
  • Figure 4 is a graph of wettability test results of Comparative Example 1 of the present invention.
  • Figure 5 is a graph showing the wettability test results of Comparative Example 2 of the present invention.
  • a composite oil-based separator comprising a base film and a moisturizing coating coated on at least one side surface of the base film.
  • the moisturizing coating includes inorganic fillers, adhesive polymers and moisturizing polymers.
  • the composite oil-based separator of the present invention can form a layer structure with water vapor on the surface of the base film to reduce the electrostatic strength of the composite oil-based separator, so that the separator will not wrinkle when it is used in an electric core for winding.
  • the moisturizing coating of the composite oil-based separator of the present invention contains inorganic fillers.
  • the inorganic fillers play the role of skeleton support in the coating and can provide a certain degree of heat shrinkage resistance. At the same time, the inorganic particles have certain hygroscopicity and can reduce the temperature to a certain extent. Diaphragm static electricity.
  • Moisturizing polymers are hydrophilic and can absorb moisture, reducing the electrostatic strength of the separator.
  • the adhesive polymer can firmly bond the inorganic filler and the moisturizing polymer to form a stable structure.
  • the separator has lower electrostatic strength, making the composite oil-based separator of the present invention It can achieve fast charging with rate performance of 3C or above.
  • the weight parts ratio of the adhesive polymer, moisturizing polymer and inorganic filler is 20-90:0.01-1:10-80.
  • the weight parts ratio of the adhesive polymer, moisturizing polymer and inorganic filler is 20:0.01:10, 25:0.01:10, 30:0.01:10, 40:0.01:10, 50:0.01:10, 60:0.01 :10, 70:0.01:10, 80:0.01:10, 90:0.01:10, 25:0.04:15, 25:0.8:15, 25:0.9:15, 25:0.2:15, 25:0.4:30 , 25:0.4:50, 25:0.4:60, 25:0.4:80, 25:0.1:15, 27:1:10, 27:0.7:10, 20:0.1:10, 20:0.1:10.
  • the weight parts ratio of the adhesive polymer, moisturizing polymer and inorganic filler has a great influence on the performance of the moisturizing coating formed by coating. If the content of the adhesive polymer is too much, it will easily affect the moisturizing effect of the moisturizing coating, and further affect the antistatic properties of the moisturizing coating. If the content of the adhesive polymer is too little, it will easily cause the moisturizing coating to be weakly bonded.
  • Inorganic fillers It can support the moisturizing coating and give the moisturizing coating a certain mechanical strength. At the same time, the inorganic filler can increase the liquid absorption performance of the moisturizing coating, improve the liquid absorption and retention, and thereby improve the antistatic property of the moisturizing coating.
  • the adhesive polymer is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride homopolymer, aramid, and fluorine-based polymers.
  • the adhesive polymer can have a bonding effect, bonding the inorganic filler and the moisturizing polymer to form a strong reactant.
  • the melting point of the adhesive polymer is 100°C to 500°C.
  • the melting point of the adhesive polymer is 100°C, 200°C, 300°C, 400°C, or 500°C.
  • the moisturizing polymer is one or more of polyethylene glycol, polypropylene glycol, tripropylene glycol, ethylene glycol, and polyvinyl acetate.
  • the moisturizing polymer can have a moisturizing effect and make the separator have better moisturizing performance, thus reducing the electrostatic strength of the separator.
  • the inorganic filler is one or more of alumina, magnesium hydroxide, aluminum hydroxide, titanium dioxide, silica, and boehmite.
  • Inorganic fillers play the role of skeleton support in the coating and can provide a certain degree of heat shrinkage resistance.
  • the inorganic particles have certain hygroscopicity and can reduce the static electricity of the separator to a certain extent.
  • the moisturizing coating may not add inorganic fillers, or it may add inorganic fillers. Adding inorganic fillers makes the moisturizing coating more effective.
  • the thickness of the moisturizing coating is 0.5 ⁇ m to 5 ⁇ m.
  • the thickness of the moisturizing coating is 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, and 5 ⁇ m.
  • the base film is PE, PP, PI, aramid, PE/PP/PE composite film or ceramic composite film
  • the base film has a melting point of 130°C to 500°C, a thickness of 3 ⁇ m to 14 ⁇ m, and a porosity of 30 ⁇ 50%, air permeability is 30sec/100cc ⁇ 300sec/100cc.
  • the base film of the present invention can be a PE film, PP film, PI film, aramid film, PE/PP/PE composite film or ceramic composite film.
  • the melting point of the base film is 130°C to 500°C.
  • the melting point of the base film For 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 220°C, 240°C, 280°C, 320°C, 340°C, 380°C, 420°C, 460°C, 480 °C, 500°C.
  • a method for preparing a composite oil-based separator including the following steps:
  • Step S1 Stir and disperse part of the organic solvent and the adhesive polymer to obtain glue
  • Step S2 Add the glue liquid to the moisturizing polymer and stir and disperse to obtain the moisturizing glue liquid;
  • Step S3 Mix and disperse the remaining organic solvent and inorganic filler into the inorganic filler dispersion
  • Step S4 Mix the moisturizing glue liquid and the inorganic filler dispersion liquid, disperse, stir, and grind to obtain a moisturizing slurry;
  • Step S5 Coat the moisturizing slurry on at least one surface of the base film, solidify to form a moisturizing coating, wash and dry to obtain a composite oil-based separator.
  • the preparation method of a composite oil-based diaphragm of the present invention has simple and safe process, high equipment adaptability, simple operation, good controllability, and easy mass production.
  • a composite oil-based separator of the present invention is provided with a moisturizing coating.
  • the moisturizing coating is formed by incorporating a moisturizing polymer into the oily moisturizing coating.
  • the prepared moisturizing coating has good antistatic properties and high Liquid absorption/liquid retention, high lithium ion layer rate and high cell hardness make the separator used in the preparation of lithium batteries, which is not prone to wrinkles, has good production efficiency and quality, and the high-rate cycling function of the cell realizes rapid battery development. charging performance.
  • the temperature of the coagulation tank and the solution ratio of the final water washing tank are controlled to achieve high antistatic, high liquid absorption/liquid retention, high lithium ion conductivity and high cell hardness of the oil-based isolation membrane to ensure the lithium battery
  • the safety and production efficiency, as well as the high-rate cycle function of the battery core realize the fast charging performance of the battery core.
  • the coating method is any one of dip coating, extrusion coating, gravure coating, and slit coating. described
  • the organic solvent is one or more of NMP, DMAC, acetone, and dimethyl sulfoxide.
  • the present invention improves the moisturizing capacity inside the separator and incorporates a moisturizing solution through a water washing tank, so that an invisible moisturizing layer is adsorbed on the outside of the separator, thereby significantly reducing the electrostatic strength of the separator (the electrostatic strength level is the same as the water-based The coated separator is consistent), which can significantly reduce defects caused by battery core winding.
  • the present invention can first preform inside the coating, control the concentration of the coagulation bath, and improve the rapid phase separation during the phase transformation process, so that dense pores are formed on the surface of the coating, which is conducive to the rapid transmission of lithium ions and realizes High ionic conductivity of the separator.
  • step S3 also includes adding 0.01 to 5 parts by weight of a pore-forming agent to the inorganic filler dispersion.
  • the pore-forming mechanism of the pore-forming agent is the principle of phase transformation.
  • the solvent and non-solvent will diffuse into each other through the liquid film/coagulation bath interface.
  • the exchange between the organic solvent and the non-solvent reaches a certain extent. This At this time, the casting liquid becomes a thermodynamically unstable system, causing phase separation of the casting liquid.
  • the pore-forming agent is one or more of PVP, water, lithium chloride or glycerin.
  • the pore-forming agent is lithium chloride.
  • the shelf life will be reduced by 7 days from 30 days.
  • the pore-forming agent is first mixed with inorganic fillers and organic solvents, and then added to the moisturizing glue to ensure the stability of the slurry.
  • the shelf life of the moisturizing slurry can be up to 30 days.
  • step S5 coagulation is performed in a coagulation tank, the temperature of the coagulation tank is 10-18°C, the concentration of the solution in the coagulation tank is 10-40%, and the solution in the coagulation tank is NMP, DMAC, acetone, dimethyl One or more types of sulfoxides.
  • the present invention can effectively eliminate the large finger-like pores in the cross-section of the separator coating, causing the cross-section of the coating to become densely packed large pores, thereby improving the liquid absorption capacity of the separator. At the same time, it can also achieve high fluid retention capacity.
  • the temperatures of the solidification tank are 10°C, 12°C, 14°C, 16°C, and 18°C, and the solution concentrations in the solidification tank are 10%, 20%, 30%, and 40%.
  • the surface of the base film is coated with moisturizing slurry and then passes through a coagulation tank, so that the moisturizing slurry solidifies in the coagulation tank to form a moisturizing coating. Setting a certain temperature and concentration in the coagulation tank can make the moisturizing slurry coagulate better.
  • the water washing in step S5 is performed in a water washing tank, the temperature of the water washing tank is 20-30°C, the concentration of the moisturizing solution in the water washing tank is 0.1-1%, and the concentration of the organic solvent is 0.01-1%.
  • the moisturizing separator is washed in a water washing tank to wash away the residual organic solvent in the coagulation tank, and the moisturizing coating absorbs the moisturizing liquid in the water washing tank, so that the composite oil-based separator has lower antistatic strength, which is beneficial to The composite oil-based separator will not wrinkle when rolled, improving the quality of battery core production.
  • a secondary battery including the above composite oil-based separator The secondary battery of the present invention has good antistatic properties and Liquid absorption and retention.
  • a secondary battery may be a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, a calcium-ion battery, or a potassium-ion battery.
  • the following secondary battery takes a lithium ion battery as an example.
  • the lithium ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and a casing.
  • the separator separates the positive electrode sheet and the negative electrode sheet.
  • the casing is used to store the positive electrode sheet and the negative electrode sheet. Assume the positive electrode sheet, negative electrode sheet, separator and electrolyte.
  • the separator is the above-mentioned composite oil-based separator.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material.
  • the positive electrode active material can also be modified.
  • the method of modifying the positive electrode active material should be known to those skilled in the art.
  • the positive electrode active material can be modified by coating, doping, etc.
  • the material used for the modification treatment may be one or a combination of more including but not limited to Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc.
  • the positive current collector is usually a structure or part that collects current.
  • the positive current collector can be any material suitable in the art as a positive current collector for lithium ion batteries.
  • the positive current collector can be materials including but not It is limited to metal foil, etc., more specifically, it may include but is not limited to aluminum foil, etc.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector.
  • the negative electrode active material layer includes a negative electrode active material.
  • the negative electrode active material may include but is not limited to graphite, soft carbon, hard carbon, and carbon fiber. , mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium, etc.
  • the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite
  • the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon carbon composites and silicon alloys.
  • the tin-based material can be selected from one or more kinds of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode current collector is usually a structure or part that collects current.
  • the negative electrode current collector can be made of various materials in the art that are suitable as negative electrode current collectors for lithium ion batteries.
  • the negative electrode current collector can include but is not limited to Metal foil, etc., more specifically, may include but is not limited to copper foil, etc.
  • the lithium-ion battery also includes an electrolyte, which includes an organic solvent, an electrolyte lithium salt, and additives.
  • the electrolyte lithium salt can be LiPF 6 and/or LiBOB used in high-temperature electrolytes; it can also be at least one of LiBF 4 , LiBOB, and LiPF 6 used in low-temperature electrolytes; it can also be used to prevent overcharge.
  • the electrolyte may be at least one of LiBF 4 , LiBOB, LiPF 6 and LiTFSI; it may also be at least one of LiClO 4 , LiAsF 6 , LiCF 3 SO 3 and LiN(CF 3 SO 2 ) 2 .
  • the organic solvent can be cyclic carbonate, including PC, EC; it can also be chain carbonate, including DFC, DMC, or EMC; it can also be carboxylic acid esters, including MF, MA, EA, MP, etc.
  • the additives include, but are not limited to, at least one of film-forming additives, conductive additives, flame retardant additives, anti-overcharge additives, additives to control H 2 O and HF content in the electrolyte, additives to improve low-temperature performance, and multi-functional additives.
  • the housing is made of one of stainless steel and aluminum-plastic film. More preferably, the housing is made of aluminum plastic film.
  • Graphite, conductive agent superconducting carbon (Super-P), thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are made into a slurry in a mass ratio of 96:2.0:1.0:1.0 , coated on the current collector copper foil and dried at 85°C, trimmed, cut into pieces, and divided into strips. After striping, dried at 110°C for 4 hours under vacuum conditions, welded the tabs to make lithium ions. Battery negative plate.
  • LiPF 6 lithium hexafluorophosphate
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • a method for preparing a composite oil-based separator includes the following steps:
  • Step S1 Weigh 3.3 parts of polyvinylidene fluoride and 36.7 parts of polyvinylidene fluoride copolymer as the adhesive polymer, and add them to 450 parts of NMP according to the steps for stirring and dispersion.
  • the stirring speed is 30R and the dispersing speed is 2000R. Stir for 30 minutes respectively to obtain glue solution;
  • Step S2 Add 0.1 part of polyethylene glycol to the glue solution, stir and disperse, the stirring speed is 25R, the dispersion speed is 2000R, stir for 15 minutes respectively, to obtain a moisturizing glue solution;
  • Step S3 Weigh 60 parts of alumina as the inorganic filler and 0.1 part of lithium chloride as the pore-forming agent, and add them to 45 parts of NMP according to the steps for stirring and dispersion.
  • the stirring speed is 30R and the dispersing speed is 2500R. Stir for 30 minutes respectively. , obtain inorganic dispersion;
  • Step S4 Mix the moisturizing glue liquid and the inorganic filler dispersion liquid at a stirring speed of 30R and a dispersion speed of 2500R. The time is 30 minutes. After high-speed dispersion and stirring, grinding is performed. The grinding speed is 700 rpm and the grinding time is 60 minutes. After grinding, the moisturizing slurry can be obtained by filtering;
  • Step S5 Apply the moisturizing slurry to a 1.5 ⁇ m moisturizing coating on both sides of the base film, solidify to form a moisturizing coating, wash and dry to obtain a composite oil-based separator, which has high antistatic properties. As shown in Figure 1.
  • the weight parts ratio of adhesive polymer, pore-forming agent, moisturizing polymer and inorganic filler is 40:0.1:0.1:60.
  • the base film is a 5 ⁇ m PE film
  • the porosity of the PE film is 40%
  • the air permeability is 200 sec/100cc.
  • the solution in the coagulation tank is a mixture of N-methylpyrrolidone and dimethylacetamide with a mass ratio of 1:1.5.
  • the temperature of the coagulation tank is 15°C
  • the concentration of the coagulation tank is 30%
  • the concentration of polypropylene alcohol in the final water washing tank is 0.3%
  • the temperature of the final water washing tank is 25°C.
  • the above-mentioned positive electrode sheet, antistatic separator and negative electrode sheet are wound into a battery core.
  • the antistatic separator is located between the positive electrode sheet and the negative electrode sheet.
  • the positive electrode is led out by spot welding with aluminum tabs, and the negative electrode is led out by spot welding with nickel tabs; then the battery is
  • the core is placed in an aluminum-plastic packaging bag, the above-mentioned electrolyte is injected, and the lithium-ion battery is made through processes such as packaging, formation, and capacity.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 20:1.5:0.5:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 20:1.8:0.5:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 20:2:0.5:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 20:0.2:0.5:30.
  • Example 2 The difference from Example 1 is that: the weight parts of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler The number ratio is 40:0.2:0.5:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 60:0.2:0.5:30.
  • Example 1 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 80:0.2:0.5:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 40:0.2:0.8:30.
  • Example 2 The difference from Example 1 is that the weight parts ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 20:0.2:0.2:30.
  • a composite oil-based separator including a base film and a ceramic slurry and a water-based polymer slurry arranged on the surface of the base film.
  • a 2 ⁇ m ceramic coating is first coated on the base material using a slant roller gravure coater to obtain a conventional ceramic film. ; Then use a slant roller gravure coater to apply a 0.5 ⁇ m polymer coating on both sides on the ceramic membrane. After drying, a water-based polymer composite membrane is obtained.
  • a composite oil-based separator includes a laminated support layer and an organic/inorganic particle blend coating layer, and its preparation method includes the following steps:
  • Step 1 Using deionized water as the solvent, dissolve the water-based adhesive, surfactant, dispersant, thickener, etc. under normal temperature and high-speed stirring to form a solution; then add polymer particles and inorganic particles, and stir evenly at high speed. , formulated into a water-based slurry; the mass percentage of each substance in the slurry is: 1.2% water-soluble polymer thickener, 1.8% water-based dispersant, 1.5% surfactant, 3.5% water-based adhesive, 32% polymer particles and inorganic particles, 60% deionized water;
  • Step 2 Use micro-gravure roller coating to apply the aqueous slurry prepared in the first step on the support layer separator at a coating rate of 20m/min;
  • Step 3 Dry the coating film obtained in the previous step in a 60°C oven to obtain a water-based separator.
  • a micro-gravure roller is used for coating, and the coating speed is 40m/min;
  • the coating base film is a polypropylene microporous film with a porosity of 42%;
  • a three-stage oven is used for drying, and the oven temperatures at each level are 50°C. , 60°C, 65°C.
  • the thickness of the coating layer is 1.5 ⁇ m, and the thickness of the film after coating is 19 ⁇ m.
  • the separator of the present invention has better liquid absorption rate, electrostatic strength and puncture strength compared to Comparative Example 1 and Comparative Example 2.
  • the separator of the present invention is provided with a moisturizing coating, so that the separator has a good liquid absorption rate, and the liquid absorption rate is as high as 11.2%.
  • the oil-based separator of the present invention has the same electrostatic strength as the water-based separators of Comparative Examples 1 and 2, that is, the oil-based separator of the present invention has lower electrostatic strength and is less prone to wrinkles during production and use. It can be concluded from the comparison of Examples 1-10 that when the weight ratio of the adhesive polymer, pore-forming agent, moisturizing polymer, and inorganic filler is 40:0.1:0.1:60, the prepared separator has better performance.
  • Wetting test Use a 1ml syringe to take 1ml of electrolyte, drop 1 drop of electrolyte into the separator under the same area, and observe the size of the area where 1 drop of electrolyte spreads within 1 minute to compare the wettability of the separator to the electrolyte.
  • the test results of Example 1, Comparative Example 1 and Comparative Example 2 are shown in Figures 3-5 respectively.
  • Example 1 Comparative Example 1
  • Comparative Example 2 Comparative Example 2
  • the separator prepared by the present invention has better liquid absorption rate, liquid retention rate, ionic conductivity and good antistatic ability compared to the separators of Comparative Example 1 and Comparative Example 2.
  • this Example 1, Comparative Example 1 and Comparative Example 2 have greater coating porosity, stronger puncture strength, and better thermal shrinkage when they have almost the same coating film thickness and coating thickness.
  • the strength is equal to the electrostatic strength of the water-based separators of Comparative Example 1 and Comparative Example 2, that is, it has good electrostatic strength and is not prone to static electricity during use or production, and avoids wrinkles, thereby improving product quality.
  • the infiltration rate of the separator prepared by the present invention is about 1cm circle, and the infiltration area is about 3.14cm 2 .
  • the infiltration rate of the separator of Comparative Example 1 is less than that of a 1cm circle.
  • the infiltration area is less than 1cm 2 .
  • the infiltration rate of the separator of Comparative Example 2 is greater than 0.5 and less than the square area of 1cm. It can be concluded that the wettability of the separator in Example 1 of the present invention is greater than that of Comparative Examples 1 and 2, and it has better wetting effect.

Abstract

本发明属于隔膜技术领域，尤其涉及一种复合油基隔膜及其制备方法，包括基膜以及涂覆于所述基膜至少一侧表面的保湿涂层，所述保湿涂层包括无机填料、粘接聚合物以及保湿聚合物。本发明的复合油基隔膜设置有保湿涂层，能够在基膜表面形成一层具有水气的层结构，降低复合油基隔膜的静电强度，从而使隔膜应用于电芯中进行卷绕时不会发生折皱。

Description

一种复合油基隔膜及其制备方法和二次电池 技术领域
本发明属于二次电池技术领域，尤其涉及一种复合油基隔膜及其制备方法和二次电池。
背景技术
锂离子电池具有工作电压高、能量密度大、长循环寿命、无记忆效应和无污染的特点，是各类电子产品的主要能源，是绿色环保型无污染的二次电池。同时，其符合当今世界能源环保方面的发展趋势，以致在各个行业的使用量急剧增加，从而使得锂电池的安全性、容量、快充性能等越来越受到人们的重视，尤其在快速充电更是急需解决。
锂离子电池的四大关键材料为正极材料、负极材料、电解液以及隔膜。隔膜的主要作用是隔离正负极并阻止电子穿过，同时能允许离子通过，从而完成在充放电过程中锂离子在正负极之间的快速传输。在锂电池的安全性和容量的基础上，为提高电芯的快速充电性能，隔膜的吸液保液性成为人们研究的重点。目前，人们通过在隔膜上涂布水性聚合物涂层或者涂布油性聚合物涂层增加隔膜的吸液保液性，但是水性隔膜目前只能实现倍率3C以下的快充，而更高的是采用油性隔膜，然而油性隔膜由于自身静电大的问题，极其影响电芯的卷绕，电芯合格率低。
发明内容
本发明的目的之一在于：针对现有技术的不足，而提供一种复合油基隔膜，能够在基膜表面形成一层具有水气的层结构，降低复合油基隔膜的静电强度，从而使隔膜应用于电芯中进行卷绕时不会发生折皱，提高生产产品质量。
为了实现上述目的，本发明采用以下技术方案：
一种复合油基隔膜，包括基膜以及涂覆于所述基膜至少一侧表面的保湿涂层，所述保湿涂层包括无机填料、粘接聚合物以及保湿聚合物。
优选地，所述粘接聚合物、保湿聚合物、无机填料的重量份数比为20～90：0.1～1：10～80。
优选地，所述粘接聚合物为聚偏氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚偏氟乙烯均聚物、芳纶、氟类聚合物中的一种或多种。
优选地，所述保湿聚合物为聚乙二醇、聚丙烯醇、三丙二醇、乙二醇、聚醋酸乙烯酯中 的一种或多种。
优选地，所述无机填料为氧化铝、氢氧化镁、氢氧化铝、二氧化钛、二氧化硅、勃姆石中的一种或多种。
优选地，所述保湿涂层的厚度为0.5μm～5μm。
优选地，所述基膜为PE、PP、PI、芳纶、PE/PP/PE复合膜或者陶瓷复合隔离膜，基隔的熔点130℃～500℃，厚度为3μm～14μm，孔隙率为30～50％，透气度为30sec/100cc～300sec/100cc。
本发明的目的之二在于：针对现有技术的不足，而提供一种复合油基隔膜的制备方法，该方法操作简单，可控性好。
为了实现上述目的，本发明采用以下技术方案：
一种复合油基隔膜的制备方法，包括以下步骤：
步骤S1、将部分有机溶剂和粘接聚合物搅拌分散得到胶液；
步骤S2、将保湿聚合物中加入胶液搅拌分散得到保湿胶液；
步骤S3、将剩余有机溶剂和无机填料混合分散到无机填料分散液；
步骤S4、将保湿胶液和无机填料分散液混合分散搅拌，研磨，得到保湿浆料；
步骤S5、将保湿浆料涂覆于基膜的至少一表面，凝固形成保湿涂层，水洗干燥得到复合油基隔膜。
优选地，所述步骤S3还包括将0.01～5重量份数比的成孔剂添加至无机填料分散液中。
优选地，所述步骤S5中凝固在凝固槽中进行，凝固槽的温度为10～18℃，凝固槽中溶液浓度为10～40％，凝固槽中的溶液为NMP、DMAC、丙酮、二甲亚砜中的一种或多种。
优选地，所述步骤S5中水洗在水洗槽中进行，水洗槽的温度为20～30℃，水洗槽中保湿溶液浓度为0.1～1％，有机溶剂浓度为0.01～1％。
本发明的目的之三在于：针对现有技术的不足，而提供一种二次电池，具有良好的抗静电性和吸液保液性。
为了实现上述目的，本发明采用以下技术方案：
一种二次电池，包括上述的复合油基隔膜。
相对于现有技术，本发明的有益效果在于：本发明的一种复合油基隔膜，设置有保湿涂层，通过在油性保湿涂层中掺入保湿聚合物，涂布形成保湿涂层，制备出的保湿涂层具有良好的抗静电性，高吸液/保液性，高锂离子电层率以及高电芯硬度，可明显降低电芯卷绕产生的不良，提高制作效率及产品合格率，电芯的高倍率循环功能，实现电芯快充性能。
附图说明
图1是本发明的复合油基隔膜的SEI图。
图2是本发明的复合油基隔膜的制备流程图。
图3是本发明的复合油基隔膜的实施例1的浸润性测试结果图。
图4是本发明的对比例1的浸润性测试结果图。
图5是本发明的对比例2的浸润性测试结果图。
具体实施方式
1、一种复合油基隔膜，包括基膜以及涂覆于所述基膜至少一侧表面的保湿涂层，所述保湿涂层包括无机填料、粘接聚合物以及保湿聚合物。
本发明的一种复合油基隔膜，能够在基膜表面形成一层具有水气的层结构，降低复合油基隔膜的静电强度，从而使隔膜应用于电芯中进行卷绕时不会发生折皱。本发明的复合油基隔膜的保湿涂层中含有无机填料，无机填料在涂层中起到骨架支撑的作用，可以提供一定的抗热收缩性，同时无机粒子有一定吸湿性，可以一定程度降低隔膜静电。保湿聚合物具有亲水性，能够吸附水分，使隔膜静电强度下降。粘接聚合物能够使无机填料与保湿聚合物牢固粘接一起，形成稳定的结构，结合油基隔膜的特点以及上述保湿涂层使隔膜具有较低的静电强度，使本发明的复合油基隔膜可实现3C或以上的倍率性能快充。
优选地，所述粘接聚合物、保湿聚合物、无机填料的重量份数比为20～90：0.01～1：10～80。粘接聚合物、保湿聚合物、无机填料的重量份数比为20：0.01：10、25：0.01：10、30：0.01：10、40：0.01：10、50：0.01：10、60：0.01：10、70：0.01：10、80：0.01：10、90：0.01：10、25：0.04：15、25：0.8：15、25：0.9：15、25：0.2：15、25：0.4：30、25：0.4：50、25：0.4：60、25：0.4：80、25：0.1：15、27：1：10、27：0.7：10、20：0.1：10、20：0.1：10。粘接聚合物、保湿聚合物和无机填料的重量份数比对涂覆形成的保湿涂层的性能影响较大。粘接聚合物的含量过多，容易影响保湿涂层的保湿效果，进面影响保湿涂层的抗静电性能，粘接聚合物的含量过少，容易使保湿涂层粘接不牢固，无机填料能够支撑保湿涂层，使保湿涂层具有一定的机械强度，同时无机填料能够增加保湿涂层的吸液性能，提高吸液保液性，进而提高保湿涂层的抗静电性。
优选地，所述粘接聚合物为聚偏氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚偏氟乙烯均聚物、芳纶、氟类聚合物中的一种或多种。粘接聚合物能够起到粘接的效果，使无机填料与保湿聚合物粘接形成牢固的反应物。所述粘接聚合物的熔点为100℃～500℃，优选地，粘接聚合物的熔点为100℃、200℃、300℃、400℃、500℃。
优选地，所述保湿聚合物为聚乙二醇、聚丙烯醇、三丙二醇、乙二醇、聚醋酸乙烯酯中的一种或多种。保湿聚合物能够起到保湿的效果，使隔膜的保湿性能更好，从而降低隔膜的静电强度。
优选地，所述无机填料为氧化铝、氢氧化镁、氢氧化铝、二氧化钛、二氧化硅、勃姆石中的一种或多种。无机填料在涂层中起到骨架支撑的作用，可以提供一定的抗热收缩性，同时无机粒子有一定吸湿性可以一定程度降低隔膜静电。保湿涂层可以不添加无机填料，也可以添加无机填料，添加了无机填料使保湿涂层的效果更好。
优选地，所述保湿涂层的厚度为0.5μm～5μm。具体地，所述保湿涂层的厚度为0.5μm、1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm。
优选地，所述基膜为PE、PP、PI、芳纶、PE/PP/PE复合膜或者陶瓷复合膜，基隔的熔点为130℃～500℃，厚度为3μm～14μm，孔隙率为30～50％，透气度为30sec/100cc～300sec/100cc。本发明的基膜可以为PE膜、PP膜、PI膜、芳纶膜、PE/PP/PE复合膜或者陶瓷复合膜，基膜的熔点为130℃～500℃，具体地，基膜的熔点为130℃、140℃、150℃、160℃、170℃、180℃、190℃、200℃、220℃、240℃、280℃、320℃、340℃、380℃、420℃、460℃、480℃、500℃。
2、一种复合油基隔膜的制备方法，包括以下步骤：
步骤S1、将部分有机溶剂和粘接聚合物搅拌分散得到胶液；
步骤S2、将保湿聚合物中加入胶液搅拌分散得到保湿胶液；
步骤S3、将剩余有机溶剂和无机填料混合分散到无机填料分散液；
步骤S4、将保湿胶液和无机填料分散液混合分散搅拌，研磨，得到保湿浆料；
步骤S5、将保湿浆料涂覆于基膜的至少一表面，凝固形成保湿涂层，水洗干燥得到复合油基隔膜。
本发明的一种复合油基隔膜的制备方法，工艺简单、安全，设备适应性高，操作简单，可控性好，易批量生产。本发明的一种复合油基隔膜，设置有保湿涂层，通过在油性保湿涂层中掺入保湿聚合物，涂布形成保湿涂层，制备出的保湿涂层具有良好的抗静电性，高吸液/保液性，高锂离子电层率以及高电芯硬度，使隔膜应用于锂电池制备中，不易发生折皱，生产效率以及质量好，电芯的高倍率循环功能，实现电芯快充性能。同时，对凝固槽的温度和最后水洗槽的溶液配比进行管控，实现油基隔离膜的高抗静电，高吸液/保液性，高锂离子电导率和高电芯硬度，保证锂电池的安全和制作效率，以及电芯的高倍率循环功能，实现电芯快充性能。其中，涂覆方式为浸涂、挤压涂布、凹版涂布，狭缝式涂布中的任意一种。所述 有机溶剂为有机溶剂为NMP、DMAC、丙酮、二甲亚砜中的一种或多种。
本发明通过在浆料中掺入保湿聚合物，提高隔膜内部的保湿能力和通过水洗槽掺入保湿溶液，使得隔膜外部吸附一层隐形保湿层，使得隔膜静电强度明显降低(静电强度水平与水性涂覆隔膜一致)，可明显降低电芯卷绕产生的不良。
本发明通过引入成孔剂，可先在涂层内部预成型，同时控制凝固浴浓度，提高相转化过程中的快速分相，使得涂层表面形成密集的孔，利于锂离子的快速传输，实现隔膜高的离子电导率。
优选地，所述步骤S3还包括将0.01～5重量份数比的成孔剂添加至无机填料分散液中。成孔剂的成孔机理为相转化原理，当浆料浸入凝固浴后，溶剂与非溶剂将通过液膜/凝固浴界面进行相互扩散，有机溶剂与非溶剂之间的交换达到一定程度，此时铸膜液变成热力学不稳定体系，导致铸膜液发生相分离。制膜液体系分相后，溶剂、非溶剂进一步交换，发生了膜孔的凝聚、相间流动以及聚合物富相固化成膜。通过有机溶剂与凝固槽中的非溶剂是无限混合的，涂层中的有机溶剂与非溶剂相互交换，聚合物遇水成型析出，形成有微孔形状的涂层结构。所述成孔剂为PVP、水、氯化锂或甘油中的一种或多种。优选地，成孔剂为氯化锂。个别成孔剂是水性的液体，如果直接加入保湿胶液中，会出现预凝胶的风险，影响保湿胶液的稳定性和保质期，保质期会从30天降低7天。而成孔剂先与无机填料、有机溶剂混合，再加入保湿胶液中，可以确保浆料的稳定性，保湿浆料的保质期可到30天。
优选地，所述步骤S5中凝固在凝固槽中进行，凝固槽的温度为10～18℃，凝固槽中溶液浓度为10～40％，凝固槽中的溶液为NMP、DMAC、丙酮、二甲亚砜中的一种或多种。本发明通过保湿聚合物，成孔剂和凝固槽温度的协同作用，可以有效消除隔膜涂层的横截面指状大孔，使得涂层横截面变为密集的大孔，在提高隔膜吸液能力的同时也能实现高保液的能力。凝固槽的温度为10℃、12℃、14℃、16℃、18℃，凝固槽中溶液浓度为10％、20％、30％、40％。基膜表面涂覆保湿浆料后经过凝固槽，使保湿浆料在凝固槽中凝固形成保湿涂层。凝固槽设置一定的温度和设置一定的浓度可以使保湿浆料凝固效果更好。
优选地，所述步骤S5中水洗在水洗槽中进行，水洗槽的温度为20～30℃，水洗槽中保湿溶液浓度为0.1～1％，有机溶剂浓度为0.01～1％。经过凝固后，保湿隔膜在水洗槽中进行水洗，洗去凝固槽中残留的有机溶剂，而且保湿涂层在水洗槽中吸收保湿液，使复合油基隔膜具有较低的抗静电强度，有利于复合油基隔膜进行卷绕时不会发生折皱，提高电芯生产质量。
2、一种二次电池，包括上述的复合油基隔膜。本发明的二次电池具有良好的抗静电性和 吸液保液性。
一种二次电池可以为锂离子电池、钠离子电池、镁离子电池、钙离子电池、钾离子电池。优选地，下列二次电池以锂离子电池为例，锂离子电池包括正极片、负极片、隔膜、电解液以及壳体，所述隔膜将正极片和负极片分隔，所述壳体用于装设所述正极片、负极片、隔膜和电解液。所述隔膜为上述的复合油基隔膜。所述正极片包括正极集流体以及设置在正极集流体表面至少一表面的正极活性物质层，所述正极活性物质层中包括正极活性物质，正极活性物质可以是包括但不限于化学式如LiaNixCoyMzO2-bNb(其中0.95≤a≤1.2，x>0，y≥0，z≥0，且x+y+z＝1,0≤b≤1，M选自Mn、Al中的一种或多种的组合，N选自F、P、S中的一种或多种的组合)所示的化合物中的一种或多种的组合，所述正极活性物质还可以是包括但不限于LiCoO2、LiNiO2、LiVO2、LiCrO2、LiMn2O4、LiCoMnO4、Li2NiMn3O8、LiNi0.5Mn1.5O4、LiCoPO4、LiMnPO4、LiFePO4、LiNiPO4、LiCoFSO4、CuS2、FeS2、MoS2、NiS、TiS2等中的一种或多种的组合。所述正极活性物质还可以经过改性处理，对正极活性物质进行改性处理的方法对于本领域技术人员来说应该是己知的，例如，可以采用包覆、掺杂等方法对正极活性物质进行改性，改性处理所使用的材料可以是包括但不限于Al、B、P、Zr、Si、Ti、Ge、Sn、Mg、Ce、W等中的一种或多种的组合。而所述正极集流体通常是汇集电流的结构或零件，所述正极集流体可以是本领域各种适用于作为锂离子电池正极集流体的材料，例如，所述正极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铝箔等。
所述负极片包括负极集流体以及设置在负极集流体表面的负极活性物质层，负极活性物质层包括负极活性物质，所述负极活性物质可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属等中的一种或几种。其中，所述石墨可选自人造石墨、天然石墨以及改性石墨中的一种或几种；所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或几种；所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。所述负极集流体通常是汇集电流的结构或零件，所述负极集流体可以是本领域各种适用于作为锂离子电池负极集流体的材料，例如，所述负极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔等。
该锂离子电池还包括电解液，电解液包括有机溶剂、电解质锂盐和添加剂。其中，电解质锂盐可以是高温性电解液中采用的LiPF6和/或LiBOB；也可以是低温型电解液中采用的LiBF4、LiBOB、LiPF6中的至少一种；还可以是防过充型电解液中采用的LiBF4、LiBOB、LiPF6、LiTFSI中的至少一种；亦可以是LiClO4、LiAsF6、LiCF3SO3、LiN(CF3SO2)2中的至少一种。而有机溶剂可以是环状碳酸酯，包括PC、EC；也可以是链状碳酸酯，包括DFC、DMC、或 EMC；还可以是羧酸酯类，包括MF、MA、EA、MP等。而添加剂包括但不限于成膜添加剂、导电添加剂、阻燃添加剂、防过充添加剂、控制电解液中H2O和HF含量的添加剂、改善低温性能的添加剂、多功能添加剂中的至少一种。
优选地，所述壳体的材质为不锈钢、铝塑膜中的一种。更优选地，壳体为铝塑膜。
下面结合具体实施方式和说明书附图，对本发明作进一步详细的描述，但本发明的实施方式并不限于此。
实施例1
正极片的制备：
将钴酸锂、导电剂超导碳(Super-P)、粘结剂聚偏氟乙烯(PVDF)按质量比97：1.5：1.5混合均匀制成具有一定粘度的锂离子电池正极浆料，将浆料涂布在集流体铝箔上，在85℃下烘干后进行冷压；然后进行切边、裁片、分条，分条后在真空条件下以110℃烘干4小时，焊接极耳，制成锂离子电池正极片。
负极片的制备：
将石墨与导电剂超导碳(Super-P)、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按质量比96：2.0：1.0：1.0制成浆料，涂布在集流体铜箔上并在85℃下烘干，进行切边、裁片、分条，分条后在真空条件下以110℃烘干4小时，焊接极耳，制成锂离子电池负极片。
电解液的制备：
将六氟磷酸锂(LiPF6)溶解于碳酸乙烯酯(EC)、碳酸二甲酯(DMC)以及碳酸甲乙酯(EMC)组成的混合溶剂中(三者的质量比为1：2：1)，得到浓度为1mol/L的电解液。
隔膜的制备：
一种复合油基隔膜的制备方法，如图2所示，包括以下步骤：
步骤S1、称量3.3份聚偏氟乙烯和36.7份聚偏氟乙烯共聚物作为粘接聚合物，并在450份NMP中按步骤分别加入进行搅拌分散，搅拌转速为30R，分散转速为2000R，分别搅拌30min，得到胶液；
步骤S2、在胶液中加入聚乙二醇0.1份，进行搅拌分散，搅拌转速为25R，分散转速为2000R，分别搅拌15min，得到保湿胶液；
步骤S3、称量60份氧化铝作为无机填料和0.1份氯化锂作为成孔剂，并在45份NMP中按步骤分别加入进行搅拌分散，搅拌转速为30R，分散转速为2500R，分别搅拌30min，得到无机分散液；
步骤S4、保湿胶液和无机填料分散液进行混合，搅拌转速为30R，分散转速为2500R， 时间30min，高速分散搅拌均匀后，再经过研磨，研磨转速700rpm,研磨时间60min，研磨后过滤即可得到保湿浆料；
步骤S5、将保湿浆料涂覆于基膜的两侧表面各1.5μm的保湿涂层，凝固形成保湿涂层，水洗干燥得到复合油基隔膜，该复合油基隔膜具有高抗静电的性能，如图1所示。
其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为40:0.1:0.1:60。
其中，所述基膜为5μm的PE膜，PE膜的孔隙率为40％，透气度为200sec/100cc。凝固槽中溶液为N-甲基吡咯烷酮、二甲基乙酰胺按质量比为1:1.5的混合液。凝固槽温度15℃，凝固槽浓度30％，最后水洗槽聚丙烯醇浓度为0.3％，最后水洗槽温度为25℃。
锂离子电池的制备：
将上述正极片、抗静电隔膜和负极片卷绕成电芯，抗静电隔膜位于正极片和负极片之间，正极以铝极耳点焊引出，负极以镍极耳点焊引出；然后将电芯置于铝塑包装袋中，注入上述电解液，经封装、化成、容量等工序，制成锂离子电池。
实施例2
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为20：1.5：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例3
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为20：1.8：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例4
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为20：2：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例5
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为20：0.2：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例6
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份 数比为40：0.2：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例7
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为60：0.2：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例8
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为80：0.2：0.5：30。
其余与实施例1相同，这是不再赘述。
实施例9
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为40：0.2：0.8：30。
其余与实施例1相同，这是不再赘述。
实施例10
与实施例1的区别在于：其中，粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为20：0.2：0.2：30。
其余与实施例1相同，这是不再赘述。
对比例1
一种复合油基隔膜，包括基膜以及设置在基膜表面的陶瓷浆料和水性聚合物浆料，用斜线辊凹版涂布机在基材先涂面2μm陶瓷涂层，得到常规陶瓷膜；再使用斜线辊凹版涂布机在陶瓷膜上，再双面各涂布0.5μm聚合物涂层，干燥后，得到水性聚合物复合膜。
对比例2
一种复合油基隔膜，包括层叠的支撑层和有机/无机粒子共混涂覆层，其制备方法包括如下步骤：
步骤1、以去离子水作为溶剂，把水性胶黏剂、表面活性剂、分散剂、增稠剂等在常温高速搅拌下溶解，配成溶液；再加入聚合物粒子和无机粒子，高速搅拌均匀，配成水性浆料；浆料中各物质的质量百分比为：1.2％的水溶性高分子增稠剂，1.8％的水性分散剂，1.5％的表面活性剂，3.5％的水性胶黏剂，32％的聚合物粒子和无机粒子，60％的去离子水；
步骤2、采用微凹辊涂布，将第一步制备的水性浆料涂布于支撑层隔膜上，涂布速率为 20m/min；
步骤3、将第上一步得到的涂覆膜经过60℃烘箱烘干，得到水性隔膜。
其中，用微凹辊涂布，涂布速率为40m/min；涂布基膜为聚丙烯微孔膜，孔隙率为42％；使用三级烘箱进行烘干，各级烘箱温度分别为50℃，60℃，65℃。涂覆层的厚度为1.5μm，涂布后膜的厚度为19μm。
性能测试：将上述实施例1-10以及对比例1-2制备出的隔膜进行吸液率、静电强度以及刺穿强度性能测试，测试结果记录表1。
表1
由上述表1可以得出，本发明的隔膜相对于对比例1和对比例2具有更好的吸液率、静电强度和刺穿强度。本发明的隔膜设置有保湿涂层使隔膜具有良好的吸液率，吸液率高达11.2％。而且本发明的油基隔膜与对比例1和2的水性隔膜具有相同的静电强度，即本发明的油基隔膜的静电强度较低，在生产和使用过程中不易发生折皱。由实施例1-10对比得出，当设置粘接聚合物、成孔剂、保湿聚合物、无机填料的重量份数比为40:0.1:0.1:60时，制备出的隔膜具有更好的性能。
浸润性测试：用1ml针筒取电解液1ml，滴1滴电解液在相同面积下的隔膜中，观察1滴电解液在1min内扩散的面积的大小，来比较隔膜对电解液的浸润性，实施例1、对比例1以及对比例2的测试结果分别如图3-5所示。
下面将实施例1、对比例1和对比例2进行性能对比，对比结果记录表2。
表2

由上表2可以得出，本发明制备出的隔膜相对于对比例1和对比例2的隔膜具有更好的吸液率、保液率、离子电导率，具有良好的抗静电能力。具体地，本实施例1、对比例1和对比例2在具有差不多涂覆膜厚度以及涂层厚度的情况下，具有更大的涂层孔隙率、更强的穿刺强度、更好的热收缩性、更好的热收缩性、更强的干粘强度、更大的抗弯强度、更高的吸液率、保液率以及更高的离子导电率，而且本申请的油基隔膜的静电强度与对比例1和对比例2的水系隔膜的静电强度相等，即具有良好的静电强度，不易在使用或生产时发生静电现象，避免出现折皱，从而提高产品质量。
由图3可以得出，本发明制备出的隔膜的浸润率约为1cm的圆，浸润面积约为3.14cm2，由图4可以得出，对比例1的隔膜的浸润率小于1cm的圆，浸润面积小于1cm2，由图5可以得出，对比例2的隔膜的浸润率大于0.5小于1cm的正方形面积。由此可以得出，本发明实施例1隔膜的浸润性比对比例1和对比例2的浸润性大，具有更好的浸润效果。
根据上述说明书的揭示和教导，本发明所属领域的技术人员还能够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述的具体实施方式，凡是本领域技术人员在本发明的基础上所作出的任何显而易见的改进、替换或变型均属于本发明的保护范围。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 (12)

  1. 一种复合油基隔膜，其特征在于，包括基膜以及涂覆于所述基膜至少一侧表面的保湿涂层，所述保湿涂层包括无机填料、粘接聚合物以及保湿聚合物。
  2. 根据权利要求1所述的一种复合油基隔膜，其特征在于，所述粘接聚合物、保湿聚合物、无机填料的重量份数比为20～90：0.01～1：10～80。
  3. 根据权利要求1或2所述的一种复合油基隔膜，其特征在于，所述粘接聚合物为聚偏氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚偏氟乙烯均聚物、芳纶、氟类聚合物中的一种或多种。
  4. 根据权利要求1或2所述的一种复合油基隔膜，其特征在于，所述保湿聚合物为聚乙二醇、聚丙烯醇、三丙二醇、乙二醇、聚醋酸乙烯酯中的一种或多种。
  5. 根据权利要求1或2所述的一种复合油基隔膜，其特征在于，所述无机填料为氧化铝、氢氧化镁、氢氧化铝、二氧化钛、二氧化硅、勃姆石中的一种或多种。
  6. 根据权利要求1所述的一种复合油基隔膜，其特征在于，所述保湿涂层的厚度为0.5μm～5μm。
  7. 根据权利要求1或6所述的一种复合油基隔膜，其特征在于，所述基膜为PE、PP、PI、芳纶、PE/PP/PE复合膜或者陶瓷复合隔离膜，基隔的熔点为130℃～500℃，厚度为3μm～14μm，孔隙率为30～50％，透气度为30sec/100cc～300sec/100cc。
  8. 一种复合油基隔膜的制备方法，其特征在于，包括以下步骤：
    步骤S1、将部分有机溶剂和粘接聚合物搅拌分散得到胶液；
    步骤S2、将保湿聚合物中加入胶液中搅拌分散得到保湿胶液；
    步骤S3、将剩余有机溶剂和无机填料混合分散到无机填料分散液；
    步骤S4、将保湿胶液和无机填料分散液混合分散搅拌，研磨，得到保湿浆料；
    步骤S5、将保湿浆料涂覆于基膜的至少一表面，凝固形成保湿涂层，水洗干燥得到复合油基隔膜。
  9. 根据权利要求8所述的复合油基隔膜的制备方法，其特征在于，所述步骤S3还包括将0.01～5重量份数比的成孔剂添加至无机填料分散液中。
  10. 根据权利要求9所述的复合油基隔膜的制备方法，其特征在于，所述步骤S5中凝固在凝固槽中进行，凝固槽的温度为10～18℃，凝固槽中溶液浓度为10～40％，凝固槽中的溶液为NMP、DMAC、丙酮、二甲亚砜中的一种或多种。
  11. 根据权利要求10所述的复合油基隔膜的制备方法，其特征在于，所述步骤S5中水洗在水洗槽中进行，水洗槽的温度为20～30℃，水洗槽中保湿溶液浓度为0.1～1％，有机溶剂浓度为0.01～1％。
  12. 一种二次电池，其特征在于，包括权利要求1-7中任一项所述的复合油基隔膜。
PCT/CN2023/082543 2022-03-21 2023-03-20 一种复合油基隔膜及其制备方法和二次电池 WO2023179550A1 (zh)

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