WO2023130683A1 - Separator for non-aqueous electrolyte lithium secondary battery, and non-aqueous electrolyte lithium secondary battery - Google Patents

Separator for non-aqueous electrolyte lithium secondary battery, and non-aqueous electrolyte lithium secondary battery Download PDF

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WO2023130683A1
WO2023130683A1 PCT/CN2022/101851 CN2022101851W WO2023130683A1 WO 2023130683 A1 WO2023130683 A1 WO 2023130683A1 CN 2022101851 W CN2022101851 W CN 2022101851W WO 2023130683 A1 WO2023130683 A1 WO 2023130683A1
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inorganic particles
lithium secondary
secondary battery
aqueous electrolyte
coating
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PCT/CN2022/101851
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French (fr)
Chinese (zh)
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马平川
杜敬然
高飞飞
甘珊珊
张绪杰
刘杲珺
白耀宗
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中材锂膜有限公司
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Publication of WO2023130683A1 publication Critical patent/WO2023130683A1/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
    • 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
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • 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
    • 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
    • H01M50/431—Inorganic 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
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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
    • H01M50/443—Particulate 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • 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 present disclosure relates to a separator for an electrochemical element and an electrochemical element.
  • it relates to a separator for a nonaqueous electrolyte lithium secondary battery and a nonaqueous electrolyte lithium secondary battery.
  • the separator In the structure of lithium batteries, the separator is one of the key inner components.
  • the performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery.
  • a separator with excellent performance plays an important role in improving the overall performance of the battery.
  • the main function of the diaphragm is to separate the positive and negative electrodes of the battery, prevent the two electrodes from contacting and short circuit, and also have the function of allowing electrolyte ions to pass through.
  • the separator material is non-conductive, and its physical and chemical properties have a great influence on the performance of the battery.
  • the electrolyte is an organic solvent system, a diaphragm material resistant to organic solvents is required, and a high-strength thin-film polyolefin porous film is generally used.
  • polyolefin-based separators have a melting point of 200° C. or lower, they have a drawback that they shrink or melt when the battery temperature increases due to internal and/or external factors, resulting in volume changes. Therefore, there is a high possibility of a short circuit between the positive electrode and the negative electrode caused by shrinkage or melting of the separator, thereby causing unexpected accidents such as battery explosion caused by discharge.
  • organic/inorganic membranes formed by using (1) heat-resistant porous base membranes, (2) inorganic particles, and (3) binder polymers have been started.
  • Composite porous film to improve the poor thermal shrinkage properties of conventional polyolefin-based separators eg CN100502097C).
  • the active layer is mainly formed by coating the mixture of inorganic particles and binder polymer on the surface of the base film or a part of the pores in the base film, but the inorganic particles will have a negative impact on the separator during the coating process.
  • a certain pressure will cause scratches on the surface of the basement membrane, which will affect the mechanical strength of the diaphragm, especially the puncture strength.
  • the closing performance of the scratches will be insufficient, resulting in the problem of high temperature safety.
  • the purpose of the present disclosure is to provide a separator for a non-aqueous electrolyte lithium secondary battery and a non-aqueous electrolyte lithium secondary battery.
  • the separator for a non-aqueous electrolyte lithium secondary battery consists of a porous coating containing inorganic particles and The composite formation of the polyolefin porous layer, by controlling the irregularity of the inorganic particles and the hardness ratio within an appropriate range, reduces the damage caused by the inorganic particles to the polyolefin porous layer during the coating process, and completes the present disclosure.
  • the present disclosure provides a separator for a non-aqueous electrolyte lithium secondary battery, including:
  • the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of the Mohs hardness D/sphericity coefficient S is in the range of 5-20, optionally 6.5-18;
  • the sphericity coefficient S is defined as follows:
  • Vp is the particle volume
  • Sp is the particle surface area
  • the areal density per unit thickness of the inorganic particles in the porous coating is 0.7-1.5 g/m 2 / ⁇ m, optionally 0.8-1.2 g/m 2 / ⁇ m.
  • the content of the inorganic particles in the porous coating is 20wt%-95wt%, optionally 30wt%-80wt%, optionally 40wt%-70wt%.
  • binding agent comprises and is selected from polyamide, polyacrylonitrile, acrylic resin, vinyl acetate-ethylene copolymer, sodium carboxymethyl cellulose, aramid fiber, polyamide Vinyl butyraldehyde, polyvinylpyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene copolymer, epoxy resin, siloxane, modified poly One or more of olefin, polyurethane, polyvinyl alcohol, polyvinyl ether and styrene-butadiene rubber; among them, polyvinylidene fluoride and/or a copolymer of vinylidene fluoride-hexafluoropropylene is optional.
  • the total thickness of the porous coating layer containing inorganic particles is 0.5-20 ⁇ m, optionally 3-12 ⁇ m.
  • the inorganic particles include one or more selected from the following materials:
  • boehmite aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, silicon carbide, optionally aluminum oxide or boehmite.
  • the average particle size of the inorganic particles is 0.01-5 ⁇ m, optionally 0.1-2 ⁇ m, optionally 0.3-1.5 ⁇ m.
  • the polyolefin porous base membrane includes one or more copolymers or multiple blends selected from polyethylene, polypropylene, polybutene, and poly-4-methylpentene.
  • the present disclosure also provides a method for preparing a diaphragm for a non-aqueous electrolyte lithium secondary battery, comprising the following steps:
  • the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of Mohs hardness D/sphericity coefficient S is in the range of 5-20, optionally 6.5 -18; where the sphericity coefficient S is defined as follows:
  • Vp is the particle volume
  • Sp is the particle surface area
  • the porous coating coating slurry on one or both sides of the polyolefin porous base film; d. drying to obtain a separator for the non-aqueous electrolyte lithium secondary battery coated with the porous coating, Wherein the total thickness of the dried porous coating is 0.5-20 ⁇ m, optionally 3-12 ⁇ m.
  • the present disclosure also provides a lithium secondary battery, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and the separator for a non-aqueous electrolyte lithium secondary battery described in the present disclosure or the non-aqueous electrolyte lithium obtained according to the preparation method of the present disclosure.
  • a lithium secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and the separator for a non-aqueous electrolyte lithium secondary battery described in the present disclosure or the non-aqueous electrolyte lithium obtained according to the preparation method of the present disclosure.
  • Separator for secondary batteries comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and the separator for a non-aqueous electrolyte lithium secondary battery described in the present disclosure or the non-aqueous electrolyte lithium obtained according to the preparation method of the present disclosure.
  • the dispersion of inorganic particles in the porous coating is uniform, so that the separator is endowed with heat resistance and thermal shrinkage suppression, while controlling the irregularity of the inorganic particles and If the hardness ratio is in an appropriate range, the damage to the polyolefin porous layer caused by the inorganic particles during the coating process can be reduced, and the balance of ion permeability, thermal shrinkage inhibition, mechanical properties and thermal runaway shutdown uniformity can be achieved.
  • Fig. 1 is the SEM picture showing alumina particle in embodiment 1;
  • Fig. 2 is the planar SEM picture that shows the diaphragm that contains inorganic particle porous coating in embodiment 1;
  • FIG. 3 is a cross-sectional SEM image showing the inorganic particle-containing porous coating separator in Example 1.
  • polyolefin porous base film it can be selected from the previous polyolefin porous base film suitable for non-aqueous electrolyte lithium secondary battery separators, including polyethylene, polypropylene, polybutene, poly 4-formaldehyde One or more copolymers or blends of pentene.
  • the polyolefin microporous membrane may optionally contain polyethylene, and the polyethylene content may be 95% by mass or more.
  • the polyolefin porous base membrane is a single-layer polyolefin microporous membrane, and in another embodiment, the polyolefin porous base membrane is a polyolefin microporous membrane with a laminated structure of 2 or more layers.
  • the optional weight-average molecular weight (Mw) of the polyolefin contained in the polyolefin porous base film is 100,000-5 million. When the weight average molecular weight is 100,000 or more, sufficient mechanical properties can be secured. On the other hand, when the weight average molecular weight is 5 million or less, the shutdown characteristics are favorable and film formation is easy.
  • the thickness of the polyolefin porous base film is not particularly limited, and is optionally 5-30 ⁇ m.
  • the polyolefin porous base film is a porous polymer film mainly formed by stretching.
  • the polyolefin porous base film can be passed Manufactured by dry or wet methods.
  • the dry method is a method of forming micropores by forming a polyolefin film and then stretching the film at a low temperature, which causes microcracks between flakes that are crystalline parts of polyolefin.
  • the wet method is to knead polyolefin-based resin and diluent at a high temperature where the polyolefin-based resin melts to form a single phase, polyolefin and diluent are phase-separated during cooling, and the diluent is extracted to form pores therein Methods.
  • the wet method is a method of imparting mechanical strength and transparency through a stretching/extraction process after phase separation treatment. Because compared with the dry method, the wet method has thinner film thickness, uniform pore size, and excellent physical properties, so the wet method can be selected.
  • the porosity of the porous substrate is preferably 20%-60%, and the average pore diameter is 15-100nm.
  • the puncture strength of the polyolefin porous base film is preferably 200 g or more.
  • the non-aqueous electrolyte lithium secondary battery separator of the present disclosure has a porous coating layer containing inorganic particles, which is arranged on one or both sides of the polyolefin porous base film, contains inorganic particles, binder resin and has a porous pore size body layer.
  • the proportion of inorganic particles in the porous coating is 20-95wt%, optionally 30-80%, further optionally 40-70%. If the content of inorganic particles is less than 20wt%, the heat resistance of the separator, the strength and safety of the unit cells are difficult to be well reflected, while the content of inorganic particles is higher than 95%, which will easily lead to the deterioration of the adhesion of the porous coating.
  • the total thickness of the porous coating containing inorganic particles is 0.5-20 ⁇ m, optionally 3-12 ⁇ m, if less than 1 ⁇ m, the effect of thermal shrinkage and bonding will not be achieved, and if it is greater than 20 ⁇ m, the ion conductivity will decrease more obvious.
  • inorganic particles The selection and use of inorganic particles is the key to solving the technical problems described in this disclosure.
  • the selection of shape, hardness and coating density of inorganic particles affects various properties of the final separator.
  • choice of the type of inorganic particles can be selected from any inorganic filler that is stable and electrochemically stable with respect to the electrolyte, and can be selected from one or more of the following materials:
  • boehmite magnesium carbonate, magnesium sulfate, barium sulfate, calcium carbonate, wollastonite, silicon carbide, etc., optionally alumina or boehmite.
  • the Mohs hardness D of the above inorganic particle types usually has a wide range, which is 2.5-9.
  • the Mohs hardness D refers to the measured value based on the hardness of the following 10 minerals according to the definition of the general Mohs hardness D:
  • Inorganic particles express their shape parameters through the sphericity coefficient S, which is defined as follows:
  • Vp is the particle volume
  • Sp is the particle surface area
  • the sphericity coefficient S of standard geometry particles is as follows:
  • Inorganic particles can have spherical, needle-shaped, plate-shaped, spindle-shaped particles, etc. According to the experience of the prior art, generally speaking, it will be considered to choose plate-shaped inorganic particles to increase the path between the positive electrode and the negative electrode. Inhibition of dendrite short circuit has a good effect.
  • the ratio range of Mohs hardness D/sphericity coefficient S is limited.
  • the ratio is less than 5
  • the puncture strength of the diaphragm becomes worse, and the mechanical properties deteriorate.
  • the improvement of thermal shrinkage performance is not obvious, and when the ratio is greater than 20, the base film is prone to scratches. Cause irregular scratches to the base film, thereby reducing the service life of the diaphragm.
  • the average particle size of the inorganic particles is 0.01-5 ⁇ m, optionally 0.1-2 ⁇ m, optionally 0.3-1.5 ⁇ m.
  • the areal density per unit thickness of the inorganic particles in the porous coating is 0.7-1.5 g/m 2 / ⁇ m, optionally 0.8-1.2 g/m 2 / ⁇ m, When the areal density per unit thickness of the inorganic particles is higher than 1.5 g/m 2 / ⁇ m, the gas permeability is deteriorated, and when it is lower than 0.7, the heat shrinkability is greatly affected.
  • the binder resin of the porous coating in the present disclosure includes polyamide, polyacrylonitrile, acrylic resin, vinyl acetate-ethylene copolymer, sodium carboxymethyl cellulose, aramid, polyvinyl butyral, poly Vinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene copolymer, epoxy resin, siloxane, modified polyolefin, polyurethane, polyethylene One or more of alcohol, polyvinyl ether and styrene-butadiene rubber; wherein, optionally, polyvinylidene fluoride and/or a copolymer of vinylidene fluoride-hexafluoropropylene.
  • the selection of the binder is mainly to have a better fixation effect on the inorganic particles, to ensure that during the preparation of the separator, or during the storage and use of the electrochemical device with the separator for the non-aqueous electrolyte lithium secondary battery described in the present disclosure Inorganic particles will not fall off.
  • the optional molecular weight is 80,000-800,000.
  • the content of the binder and the inorganic particles in the coating liquid is optionally 6wt%-20wt%, optionally 8wt%-15wt%.
  • the solvent used for preparing the coating liquid may optionally contain a phase separation agent that induces phase separation. Therefore, the solvent used to prepare the coating liquid is optionally a mixed solvent of a good solvent and a phase separation agent.
  • the phase separation agent is mixed with a good solvent in an amount that can ensure a viscosity range suitable for coating.
  • a good solvent acetone, methyl ethyl ketone, N-methylpyrrolidone, polar amide solvents such as dimethylacetamide, diethylformamide, diethylformamide, etc. are mentioned.
  • the separating agent include water, methanol, ethanol, propanol, butanol, butylene glycol, ethylene glycol, propylene glycol, tripropylene glycol, and the like.
  • the solvent used to prepare the coating liquid may optionally contain 60 wt% or more of a good solvent and 40 wt% or less of a phase separation agent.
  • a coating slurry After the above-mentioned inorganic particles, binder and solvent are blended to form a coating slurry, optionally, firstly, use dip coating method, air knife coating method, curtain coating method, roll coating method, wire bar coating method , gravure coating method, or die coating method, etc., coating the coating composition on the above-mentioned porous substrate to form a coating film.
  • a gravure coating method or a die coating method is used as the coating method of the above-mentioned coating liquid.
  • the coating film formed on the substrate by the coating step is dried.
  • the coating composition contains thermoplastic particles, it is within the temperature range where the thermoplastic particles do not melt, the specific wind speed and The drying temperature is not particularly limited.
  • drying methods include heat transfer drying (bonding to high-heat objects), convective heat transfer (hot air), radiation heat transfer (infrared rays), and other methods (microwave, induction heating, etc.).
  • convective heat transfer or radiation heat transfer can be optionally used.
  • an optional use can be made to reduce the total mass transfer coefficient during drying while maintaining a controllable wind speed Methods.
  • the hot air can be sent in a direction parallel to the supporting substrate, parallel to the conveying direction of the substrate, or perpendicular to it.
  • the lithium secondary battery of the present disclosure has a positive electrode, a negative electrode, an electrolyte solution, and the diaphragm described in the present disclosure disposed between the positive electrode and the negative electrode, and has a structure in which the battery element and the electrolyte solution are sealed together in an external packaging material.
  • the battery element is obtained by opposing a negative electrode and a positive electrode with a separator interposed therebetween.
  • the positive electrode has, for example, a structure in which an active material layer containing a positive electrode active material and a binder resin is molded on a current collector.
  • the positive electrode active material it can be exemplified by positive electrode active materials commonly used in this field, such as lithium-containing transition metal oxides, etc., such as LiCoO 2 , LiNiO 2 , LiMn 1/2 Ni 1/2 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiMn 2 O 4 , LiFePO 4 , LiC0 1/2 Ni 1/2 O 2 , LiAl 1/4 Ni 3/4 O 2 , etc.
  • a binder resin polyvinylidene fluoride resin, a styrene-butadiene copolymer, etc. are mentioned, for example.
  • a conductive aid may also be contained, and examples thereof include carbon materials such as acetylene black, Ketjen black, and graphite powder.
  • Examples of the current collector include aluminum foil, titanium foil, stainless steel foil and the like having a thickness of 5 ⁇ m to 20 ⁇ m.
  • Examples of embodiments of the negative electrode include a structure in which an active material layer including a negative electrode active material and a binder resin is molded on a current collector.
  • the active material layer may further contain a conductive additive.
  • materials capable of electrochemically absorbing lithium can be enumerated, for example: carbon materials; alloys of silicon, tin, aluminum, etc. and lithium; Wood's alloys; and the like.
  • the binder resin, conductive additive, and current collector are substantially the same as those of the positive electrode.
  • a metal lithium foil may be used as the negative electrode instead of the negative electrode described above.
  • the electrolytic solution is a solution obtained by dissolving a lithium salt in a non-aqueous solvent.
  • a lithium salt in a non-aqueous solvent.
  • it may be a common electrolyte system in the field.
  • lithium salts include LiPF 6 , LiBF 4 , LiClO 4 and the like.
  • non-aqueous solvent for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, etc.; dimethyl carbonate, dicarbonate Chain carbonates such as ethyl ester, ethyl methyl carbonate, ethylene carbonate and their fluorine substitutes; cyclic esters such as ⁇ -butyrolactone and ⁇ -valerolactone, etc., may be used alone or in combination.
  • the thickness of the isolation base film is the thickness of the porous coating.
  • the particle size measuring apparatus Nikkiso Co., Ltd. make, MicrotracUPA150.
  • the method shown in CN111397993A is used to measure the Mohs hardness D of fine particles, and the scratches are determined with reference to standard materials.
  • This measurement method approximates the definition of the sphericity factor S.
  • the Gurley value of the porous membrane is the Gurley value of the separator provided with the porous membrane minus the Gurley value of the separator not provided with the porous membrane (ie, purely porous substrate).
  • Adhesive tape manufactured by Scotch, model 550R-12
  • Adhesive tape with a width of 12 mm and a length of 15 cm is attached to the surface of the porous layer on one side of the separator, and the separator is cut so that the width and length are the same as those of the adhesive tape.
  • the longitudinal direction was aligned with the MD direction of the separator.
  • the adhesive tape is used as a support body for peeling off one porous layer.
  • the measurement sample was left to stand in an atmosphere with a temperature of 23 ⁇ 1° C. and a relative humidity of 50 ⁇ 5% for more than 24 hours, and the following measurements were performed in the same atmosphere.
  • the adhesive tape and the porous layer immediately below it are peeled off about 10 cm together, and the laminate (1) of the adhesive tape and the porous layer is separated from the laminate (2) of the porous substrate and the other porous layer by about 10 cm.
  • the end of the laminate (1) was fixed to the upper chuck of TENSILON (RTC-1210A manufactured by Orientec), and the end of the laminate (2) was fixed to the lower chuck of TENSILON.
  • the measurement sample was suspended in the gravitational direction so that the stretching angle (the angle of the laminate (1) relative to the measurement sample) was 180°.
  • the laminate (1) was stretched at a stretching speed of 50 mm/min, and the load when the laminate (1) was peeled from the porous substrate was measured.
  • the loads from 10 mm to 40 mm after the start of the measurement were obtained at intervals of 0.4 mm, and the average value thereof was defined as the peel strength.
  • thermoplastic separator Cut the thermoplastic separator into long strips with a length of 200mm and a width of 25mm.
  • the distance between the fixtures is (100 ⁇ 5)mm, and the test speed is (50 ⁇ 10)mm/min.
  • ⁇ L The thermal shrinkage rate in the longitudinal direction of the sample, expressed in %
  • L 0 the length of the sample in the longitudinal direction before heating, in millimeters (mm);
  • ⁇ T The thermal shrinkage rate in the transverse direction of the sample, expressed in %
  • T 0 the length of the sample in the transverse direction before heating, in millimeters (mm);
  • T - the length of the sample in the transverse direction after heating, in millimeters (mm).
  • the positive electrode sheet of the present disclosure mixes layered lithium transition metal oxide LiNi 0.5 Co 0.2 Mn 0.3 O 2 with conductive agent acetylene black (SP) and binder polyvinylidene fluoride (PVDF), and the weight ratio of the three mixed is 96. : 2: 2, add the solvent N-methylpyrrolidone, mix and stir evenly to obtain the positive electrode slurry. Coat the positive electrode slurry evenly on the aluminum foil of the positive electrode current collector, then dry it at 85°C and then perform cold pressing, trimming, cutting, and slitting, and then dry it under vacuum at 85°C for 4 hours to obtain the positive electrode sheet .
  • SP conductive agent acetylene black
  • PVDF binder polyvinylidene fluoride
  • Negative electrode sheet Mix negative active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC) according to the weight ratio of 96:1:2:1, add
  • the solvent is deionized water, and the negative electrode slurry is obtained after stirring and mixing evenly. Evenly coat the negative electrode slurry on the copper foil of the negative electrode current collector. After coating, dry it at 80-90°C, perform cold pressing, edge trimming, cutting, and slitting, and then dry it under vacuum at 110°C for 4 hours , to obtain the negative pole piece.
  • the separator is in the middle of the positive pole piece and the negative pole piece, and the coating on one side of the separator faces the positive pole. sheet, and then wound into a square bare cell with a thickness of 10mm, a width of 50mm, and a length of 120mm.
  • the obtained lithium-ion secondary battery was charged to 4.2V by 1C constant current and constant voltage, and left to stand for 10 minutes; discharged to 3.0V by 1C constant current, and left to stand for 10 minutes, and the discharged electricity was recorded as Q1.
  • the above steps were taken as one cycle of charging and discharging, and 200 cycles were performed.
  • the electricity discharged in the 200th cycle is recorded as Q2.
  • the cycle performance test result is Q2/Q1 ⁇ 100%.
  • PVDF/HPF dimethylacetamide
  • DMA dimethylacetamide
  • the inorganic particles are alumina particles, Mohs hardness D8.8, average particle size 0.5 ⁇ m
  • PVDF/HPF: alumina particles weight ratio 40:60
  • alumina particles are added to the binder polymer solution to form Porous coating coating slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.71.
  • the slurry that will be used to form porous coating is coated on the two surfaces of polyethylene porous substrate by gravure roll (thickness 9 ⁇ m, porosity 55%, average pore diameter 70nm, Puncture strength 300gf), coagulated by 40% dimethylacetamide/water coagulation solution, washed with pure water, and dried at 70°C to manufacture a diaphragm with a porous coating, so that each layer of coating on the two surfaces of the porous substrate is dry.
  • the thickness is 2 ⁇ m, and the areal density of the single layer of inorganic particles is 2.2 g/m 2 .
  • Fig. 1 is the SEM figure of the aluminum oxide inorganic particles used in embodiment 1
  • Fig. 2 and Fig. 3 are the SEM image of embodiment 1 porous coating membrane plane and cross-section, can see porous coating and porous base film interface interlocking, The inorganic particles are embedded to a certain depth on the surface of the base film.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • Embodiment 7 is a diagrammatic representation of Embodiment 7:
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • the inorganic particles are selected as hydrated aluminum hydroxide particles with Mohs hardness D3 and an average particle size of 0.5 ⁇ m.
  • the weight ratio of PVDF/HPF: hydrated aluminum hydroxide particles 40:60 is added to the binder polymer solution to form a porous coating.
  • Table 1 shows the performance indexes of the separators of Examples 1-8 and Comparative Examples 1-5 and the corresponding batteries. According to Table 1, although the types of inorganic particles in Examples 1-8 change, the hardness and shape change, when the Mohs When the hardness D/sphericity coefficient S falls within the range of 5-20, the gas permeability, peeling/adhesiveness, thermal shrinkage and mechanical properties of the separator are all excellent, and the corresponding battery also shows good cycle performance. When the ratio is too high in Comparative Examples 1 and 3, the puncture strength deteriorates; when the ratio is too low in Comparative Example 2, the heat shrinkage rate and bond strength deteriorate significantly. The junction performance is relatively poor, and the air permeability becomes poor. However, when the area density per unit thickness is low in Comparative Example 5, the thermal shrinkage rate is greatly affected. The cycle performance of the corresponding battery is also not as good as that of Examples 1-8.

Abstract

A separator for a non-aqueous electrolyte lithium secondary battery and a non-aqueous electrolyte lithium secondary battery. The separator for a non-aqueous electrolyte lithium secondary battery comprises: a polyolefin porous base film; and a porous coating containing inorganic particles and formed on at least one surface of the polyolefin porous base film, wherein the Mohs hardness D of the inorganic particles is 2.5-9, a sphericity factor S is 0.2-1, a ratio range of Mohs hardness D/sphericity factor S is 5-20, and the unit thickness surface density of the inorganic particles in the porous coating is 0.7-1.5g/m2/μm. By using the specific inorganic particles, damage caused by the inorganic particles to the polyolefin porous base film during a coating process can be reduced, and the separator is guaranteed to have excellent mechanical properties, air permeability, thermal shrinkage properties and adhesive properties.

Description

非水电解液锂二次电池用隔膜及非水电解液锂二次电池Separator for nonaqueous electrolyte lithium secondary battery and nonaqueous electrolyte lithium secondary battery
相关申请的交叉引用Cross References to Related Applications
本公开要求于2022年01月05日提交中国专利局的申请号为CN202210002819.6、名称为“非水电解液锂二次电池用隔膜及非水电解液锂二次电池”的中国专利申请的优先权，其全部内容通过引用结合在本公开中。This disclosure requires submission of a Chinese patent application with the application number CN202210002819.6 and titled "Separator for non-aqueous electrolyte lithium secondary battery and non-aqueous electrolyte lithium secondary battery" submitted to the China Patent Office on January 05, 2022. Priority, the entirety of which is incorporated by reference into this disclosure.
技术领域technical field
本公开涉及电化学元件用隔膜及电化学元件。特别涉及非水电解液锂二次电池用隔膜及非水电解液锂二次电池。The present disclosure relates to a separator for an electrochemical element and an electrochemical element. In particular, it relates to a separator for a nonaqueous electrolyte lithium secondary battery and a nonaqueous electrolyte lithium secondary battery.
背景技术Background technique
锂电池的结构中，隔膜是关键的内层组件之一。隔膜的性能决定了电池的界面结构、内阻等，直接影响电池的容量、循环以及安全性能等特性，性能优异的隔膜对提高电池的综合性能具有重要的作用。隔膜的主要作用是使电池的正、负极分隔开来，防止两极接触而短路，此外还具有能使电解质离子通过的功能。隔膜材质是不导电的，其物理化学性质对电池的性能有很大的影响。对于锂二次电池而言，由于电解液为有机溶剂体系，因而需要有耐有机溶剂的隔膜材料，一般采用高强度薄膜化的聚烯烃多孔膜。In the structure of lithium batteries, the separator is one of the key inner components. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. A separator with excellent performance plays an important role in improving the overall performance of the battery. The main function of the diaphragm is to separate the positive and negative electrodes of the battery, prevent the two electrodes from contacting and short circuit, and also have the function of allowing electrolyte ions to pass through. The separator material is non-conductive, and its physical and chemical properties have a great influence on the performance of the battery. For lithium secondary batteries, since the electrolyte is an organic solvent system, a diaphragm material resistant to organic solvents is required, and a high-strength thin-film polyolefin porous film is generally used.
由于这种聚烯烃基隔膜具有200℃或更低的熔点，因此它们存在缺陷，即当电池温度因内部和/或外部因素而升高时，它们会收缩或熔融，导致体积变化。因此，存在由隔膜的收缩或熔融引起的正极和负极之间短路的很大可能性，从而导致意外事故，如由放电引起的电池***。为了防止聚烯烃多孔膜在高温下发生热收缩，现有技术中，开始通过使用(1)耐热多孔性基膜、(2)无机颗粒和(3)粘合剂聚合物形成的有机/无机复合多孔性薄膜，来改善常规聚烯烃基隔膜差的热收缩性能(例如CN100502097C)。Since such polyolefin-based separators have a melting point of 200° C. or lower, they have a drawback that they shrink or melt when the battery temperature increases due to internal and/or external factors, resulting in volume changes. Therefore, there is a high possibility of a short circuit between the positive electrode and the negative electrode caused by shrinkage or melting of the separator, thereby causing unexpected accidents such as battery explosion caused by discharge. In order to prevent thermal shrinkage of polyolefin porous membranes at high temperatures, in the prior art, organic/inorganic membranes formed by using (1) heat-resistant porous base membranes, (2) inorganic particles, and (3) binder polymers have been started. Composite porous film to improve the poor thermal shrinkage properties of conventional polyolefin-based separators (eg CN100502097C).
对于复合多孔性薄膜目前主要通过将无机颗粒和粘合剂聚合物的混合物涂覆在基膜表面或基膜中的孔的一部分形成的活性层，但是在涂覆过程中无机颗粒对隔膜会有一定的压力，因此会对基膜表面产生划痕，进而影响隔膜的机械强度，尤其是穿刺强度，另外也会出现划痕处的关闭性能不足，从而出现高温安全性的问题。For composite porous films, the active layer is mainly formed by coating the mixture of inorganic particles and binder polymer on the surface of the base film or a part of the pores in the base film, but the inorganic particles will have a negative impact on the separator during the coating process. A certain pressure will cause scratches on the surface of the basement membrane, which will affect the mechanical strength of the diaphragm, especially the puncture strength. In addition, the closing performance of the scratches will be insufficient, resulting in the problem of high temperature safety.
发明内容Contents of the invention
因此至今为止，现有技术中并没有关注在无机颗粒涂覆中可能对聚烯烃多孔层造成的损伤，进而在机械性能和安全性能上带来的不利影响。Therefore, so far, the prior art has not paid attention to the possible damage to the polyolefin porous layer during the coating of inorganic particles, and thus the adverse effects on the mechanical performance and safety performance.
本公开的目的在于提供一种非水电解液锂二次电池用隔膜及非水电解液锂二次电池，所述的非水电解液锂二次电池用隔膜由含有无机颗粒的多孔涂层和聚烯烃多孔层复合形成，通过控制无机颗粒的不规则度以及硬度之比在合适的范围内，进而减小无机颗粒在涂覆过程中对聚烯烃多孔层造成的损伤，进而完成本公开。The purpose of the present disclosure is to provide a separator for a non-aqueous electrolyte lithium secondary battery and a non-aqueous electrolyte lithium secondary battery. The separator for a non-aqueous electrolyte lithium secondary battery consists of a porous coating containing inorganic particles and The composite formation of the polyolefin porous layer, by controlling the irregularity of the inorganic particles and the hardness ratio within an appropriate range, reduces the damage caused by the inorganic particles to the polyolefin porous layer during the coating process, and completes the present disclosure.
本公开提供一种非水电解液锂二次电池用隔膜，包括：The present disclosure provides a separator for a non-aqueous electrolyte lithium secondary battery, including:
聚烯烃多孔基膜；Polyolefin porous base film;
以及形成在所述聚烯烃多孔基膜至少一个表面的含有无机颗粒的多孔涂层；And a porous coating containing inorganic particles formed on at least one surface of the polyolefin porous base film;
其中所述无机颗粒的莫氏硬度D为2.5-9，球形度系数S为0.2-1，莫氏硬度D/球形度系数S的比值范围在5-20，可选地为6.5-18；Wherein the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of the Mohs hardness D/sphericity coefficient S is in the range of 5-20, optionally 6.5-18;
其中球形度系数S的定义如下：The sphericity coefficient S is defined as follows:
Figure PCTCN2022101851-appb-000001
Figure PCTCN2022101851-appb-000001
其中，V p为颗粒体积，S p为颗粒表面积； Among them, Vp is the particle volume, Sp is the particle surface area;
并且无机颗粒在多孔涂层中的单位厚度面密度为0.7-1.5g/m 2/μm，可选地为0.8-1.2g/m 2/μm。 And the areal density per unit thickness of the inorganic particles in the porous coating is 0.7-1.5 g/m 2 /μm, optionally 0.8-1.2 g/m 2 /μm.
所述无机颗粒在多孔涂层中的含量为20wt％-95wt％，可选地为30wt％-80wt％，可选地为40wt％-70wt％。The content of the inorganic particles in the porous coating is 20wt%-95wt%, optionally 30wt%-80wt%, optionally 40wt%-70wt%.
所述多孔涂层中还含有粘结剂，所述粘结剂包括选自聚酰胺、聚丙烯腈、丙烯酸类树脂、醋酸乙烯酯-乙烯共聚物、羧甲基纤维素纳、芳纶、聚乙烯基丁醛、聚乙烯呲咯烷酮、聚偏氟乙烯、聚四氟乙烯、聚六氟丙烯、偏氟乙烯-六氟丙烯的共聚物、环氧树脂、硅氧烷类、改性聚烯烃、聚氨酯、聚乙烯醇、聚乙烯醚和丁苯橡胶中的一种或多种；其中可选聚偏氟乙烯和/或偏氟乙烯-六氟丙烯的共聚物。Also contain binding agent in described porous coating, described binding agent comprises and is selected from polyamide, polyacrylonitrile, acrylic resin, vinyl acetate-ethylene copolymer, sodium carboxymethyl cellulose, aramid fiber, polyamide Vinyl butyraldehyde, polyvinylpyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene copolymer, epoxy resin, siloxane, modified poly One or more of olefin, polyurethane, polyvinyl alcohol, polyvinyl ether and styrene-butadiene rubber; among them, polyvinylidene fluoride and/or a copolymer of vinylidene fluoride-hexafluoropropylene is optional.
在其中一个方案中，含有无机颗粒的多孔涂层的总厚度为0.5～20μm，可选地为3-12μm。In one version, the total thickness of the porous coating layer containing inorganic particles is 0.5-20 μm, optionally 3-12 μm.
所述无机颗粒包括选自下述材料中的一种或多种：The inorganic particles include one or more selected from the following materials:
基于氧化物陶瓷中的氧化铝、二氧化硅、氧化锆、氧化镁、二氧化铈、二氧化钛、氧化锌、氧化铁；Based on alumina, silica, zirconia, magnesia, ceria, titania, zinc oxide, iron oxide in oxide ceramics;
基于氮化物材料的氮化硅、氮化钛、氮化硼；Silicon nitride, titanium nitride, boron nitride based on nitride materials;
以及勃姆石、氢氧化铝、氢氧化镁、硫酸钡、碳酸钙、硅灰石、碳化硅，其中可选地为氧化铝或勃姆石。And boehmite, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, silicon carbide, optionally aluminum oxide or boehmite.
无机颗粒的平均粒径为0.01-5μm，可选地为0.1-2μm，可选地为0.3-1.5μm。The average particle size of the inorganic particles is 0.01-5 μm, optionally 0.1-2 μm, optionally 0.3-1.5 μm.
在其中一个方案中，所述聚烯烃多孔基膜包括选自聚乙烯、聚丙烯、聚丁烯、聚4-甲基戊烯中的一种或多种共聚物或多种共混物。In one solution, the polyolefin porous base membrane includes one or more copolymers or multiple blends selected from polyethylene, polypropylene, polybutene, and poly-4-methylpentene.
本公开还提供了一种非水电解液锂二次电池用隔膜的制备方法，包括如下步骤：The present disclosure also provides a method for preparing a diaphragm for a non-aqueous electrolyte lithium secondary battery, comprising the following steps:
a.制备聚烯烃多孔基膜；a. preparing polyolefin porous base film;
b.配置形成在聚烯烃多孔基膜至少一个表面的含有无机颗粒的多孔涂层涂布浆料，所述涂布浆料包括：b. configure the porous coating coating slurry containing inorganic particles formed on at least one surface of the polyolefin porous base film, the coating slurry comprising:
无机颗粒，所述无机颗粒的莫氏硬度D为2.5-9，球形度系数S为0.2-1，并且莫氏硬度D/球形度系数S的比值范围在在5-20，可选地为6.5-18；其中球形度系数S的定义如下：Inorganic particles, the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of Mohs hardness D/sphericity coefficient S is in the range of 5-20, optionally 6.5 -18; where the sphericity coefficient S is defined as follows:
Figure PCTCN2022101851-appb-000002
Figure PCTCN2022101851-appb-000002
其中，V p为颗粒体积，S p为颗粒表面积； Among them, Vp is the particle volume, Sp is the particle surface area;
粘结剂；binder;
以及溶剂；and solvents;
c.将所述多孔涂层涂布浆料均匀涂布到聚烯烃多孔基膜的一面或两面上；d.进行干燥，得到多孔涂层涂布的非水电解液锂二次电池用隔膜，其中干燥后的多孔涂层总厚度为0.5～20μm，可选地为3-12μm。c. uniformly coating the porous coating coating slurry on one or both sides of the polyolefin porous base film; d. drying to obtain a separator for the non-aqueous electrolyte lithium secondary battery coated with the porous coating, Wherein the total thickness of the dried porous coating is 0.5-20 μm, optionally 3-12 μm.
本公开还提供了一种锂二次电池，包含正极、负极、非水电解液和本公开所述的非水电解液锂二次电池用隔膜或根据本公开制备方法得到的非水电解液锂二次电池用隔膜。The present disclosure also provides a lithium secondary battery, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and the separator for a non-aqueous electrolyte lithium secondary battery described in the present disclosure or the non-aqueous electrolyte lithium obtained according to the preparation method of the present disclosure. Separator for secondary batteries.
本公开的有益效果：Beneficial effects of the present disclosure:
根据本公开得到的非水电解液锂二次电池用隔膜，无机颗粒在多孔涂层中的分散均匀，因此赋予了隔膜耐热性和抑制热收缩性，同时当控制无机颗粒的不规则度以及硬度之比在合适的范围内，能够减小无机颗粒在涂覆过程中对聚烯烃多孔层造成的损伤，实现离子透过性、热收缩抑制性、机械性能和热失控关闭均一性的平衡。According to the non-aqueous electrolyte lithium secondary battery separator obtained according to the present disclosure, the dispersion of inorganic particles in the porous coating is uniform, so that the separator is endowed with heat resistance and thermal shrinkage suppression, while controlling the irregularity of the inorganic particles and If the hardness ratio is in an appropriate range, the damage to the polyolefin porous layer caused by the inorganic particles during the coating process can be reduced, and the balance of ion permeability, thermal shrinkage inhibition, mechanical properties and thermal runaway shutdown uniformity can be achieved.
附图说明Description of drawings
图1为示出实施例1中氧化铝颗粒的SEM图；Fig. 1 is the SEM picture showing alumina particle in embodiment 1;
图2为示出实施例1中含有无机颗粒多孔涂层隔膜的平面SEM图；Fig. 2 is the planar SEM picture that shows the diaphragm that contains inorganic particle porous coating in embodiment 1;
图3为示出实施例1中含有无机颗粒多孔涂层隔膜的截面SEM图。FIG. 3 is a cross-sectional SEM image showing the inorganic particle-containing porous coating separator in Example 1. FIG.
具体实施方式Detailed ways
为了更好地解释本公开，参照本公开的实施方式详细地说明，并结合实施例进一步阐明本公开的主要内容，但本公开的内容不仅仅局限于以下实施例。实施例中未注明技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。In order to better explain the present disclosure, it is described in detail with reference to the embodiments of the present disclosure, and the main content of the present disclosure is further clarified in conjunction with examples, but the content of the present disclosure is not limited to the following examples. If the technique or condition is not indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product manual. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.
[聚烯烃多孔基膜][Porous Polyolefin Base Film]
作为聚烯烃多孔基膜，可以从以往的适用于非水电解液锂二次电池用隔膜的聚烯烃多孔基膜中进行选择，包括选自聚乙烯、聚丙烯、聚丁烯、聚4-甲基戊烯中的一种或多种共聚物或多种共混物。As the polyolefin porous base film, it can be selected from the previous polyolefin porous base film suitable for non-aqueous electrolyte lithium secondary battery separators, including polyethylene, polypropylene, polybutene, poly 4-formaldehyde One or more copolymers or blends of pentene.
从呈现关闭功能的观点考虑，聚烯烃微多孔膜可选地包含聚乙烯，作为聚乙烯的含量，可选地为95质量％以上。From the viewpoint of exhibiting a shutdown function, the polyolefin microporous membrane may optionally contain polyethylene, and the polyethylene content may be 95% by mass or more.
在其中一种实施方案中，聚烯烃多孔基膜为单层聚烯烃微多孔膜，在另一种实施方案中，聚烯烃多孔基膜为具有2层或以上层叠结构的聚烯烃微多孔膜。In one embodiment, the polyolefin porous base membrane is a single-layer polyolefin microporous membrane, and in another embodiment, the polyolefin porous base membrane is a polyolefin microporous membrane with a laminated structure of 2 or more layers.
聚烯烃多孔基膜中包含的聚烯烃可选重均分子量(Mw)为10万～500万。重均分子量为10万以上时，能够确保充分的力学物性。另一方面，重均分子量为500万以下时，关闭特性良好，并且容易成膜。The optional weight-average molecular weight (Mw) of the polyolefin contained in the polyolefin porous base film is 100,000-5 million. When the weight average molecular weight is 100,000 or more, sufficient mechanical properties can be secured. On the other hand, when the weight average molecular weight is 5 million or less, the shutdown characteristics are favorable and film formation is easy.
对聚烯烃多孔基膜的厚度没有特别限定，可选地为5-30μm。聚烯烃多孔基膜是主要由拉伸形成的多孔聚合物膜。The thickness of the polyolefin porous base film is not particularly limited, and is optionally 5-30 μm. The polyolefin porous base film is a porous polymer film mainly formed by stretching.
对根据本公开的示例性实施方案的聚烯烃多孔基膜的制造方法没有限制，只要聚烯烃多孔基膜由本领域技术人员制造即可，在示例性的实施方案中，聚烯烃多孔基膜可以通过干法或湿法来制造。干法是通过形成聚烯烃膜、然后在低温下拉伸该膜而形成微孔的方法，所述拉伸导致作为聚烯烃的结晶部分的薄片之间的微裂纹。湿法是将聚烯烃基树脂和稀释剂在聚烯烃基树脂熔融形成单相的高温下进行混炼、聚烯烃和稀释剂在冷却过程中进行相分离、然后稀释剂被提取以在其中形成孔隙的方法。湿法是在相分离处理后通过拉伸/提取工艺赋予机械强度和透明性的方法。因为与干法相比，湿法的膜厚度薄，孔径均匀，物理性能优异，所以可选湿法。There is no limit to the manufacturing method of the polyolefin porous base film according to the exemplary embodiment of the present disclosure, as long as the polyolefin porous base film is manufactured by those skilled in the art, in an exemplary embodiment, the polyolefin porous base film can be passed Manufactured by dry or wet methods. The dry method is a method of forming micropores by forming a polyolefin film and then stretching the film at a low temperature, which causes microcracks between flakes that are crystalline parts of polyolefin. The wet method is to knead polyolefin-based resin and diluent at a high temperature where the polyolefin-based resin melts to form a single phase, polyolefin and diluent are phase-separated during cooling, and the diluent is extracted to form pores therein Methods. The wet method is a method of imparting mechanical strength and transparency through a stretching/extraction process after phase separation treatment. Because compared with the dry method, the wet method has thinner film thickness, uniform pore size, and excellent physical properties, so the wet method can be selected.
从获得适当的膜电阻、关闭功能的观点考虑，多孔基材的孔隙率可选地为20％～60％，平均孔径为15～100nm。From the viewpoint of obtaining proper membrane resistance and shutdown function, the porosity of the porous substrate is preferably 20%-60%, and the average pore diameter is 15-100nm.
从提高制造成品率的观点考虑，聚烯烃多孔基膜的穿刺强度可选地为200g以上。From the viewpoint of improving manufacturing yield, the puncture strength of the polyolefin porous base film is preferably 200 g or more.
[含有无机颗粒的多孔涂层][Porous coating containing inorganic particles]
本公开的非水电解液锂二次电池用隔膜所具有的含有无机颗粒的多孔涂层是设置在聚烯烃多孔基膜的一面或两面上包含无机颗粒、粘结剂树脂并具有多孔孔径的集合体层。The non-aqueous electrolyte lithium secondary battery separator of the present disclosure has a porous coating layer containing inorganic particles, which is arranged on one or both sides of the polyolefin porous base film, contains inorganic particles, binder resin and has a porous pore size body layer.
其中无机颗粒在多孔涂层中的占比为20-95wt％，可选地为30-80％，进一步可选地为40-70％。如果无机颗粒的含量低于20wt％，隔膜的耐热性、单元电池强度和安全性难以得到很好体现，而无机颗粒的含量高于95％，容易导致多孔涂层粘结性的劣化。Wherein the proportion of inorganic particles in the porous coating is 20-95wt%, optionally 30-80%, further optionally 40-70%. If the content of inorganic particles is less than 20wt%, the heat resistance of the separator, the strength and safety of the unit cells are difficult to be well reflected, while the content of inorganic particles is higher than 95%, which will easily lead to the deterioration of the adhesion of the porous coating.
含有无机颗粒的多孔涂层的总厚度为0.5～20μm，可选地为3-12μm，如果小于1μm，则起不到热缩性和粘结的效果，如果大于20μm则会导致离子传导性下降较为明显。The total thickness of the porous coating containing inorganic particles is 0.5-20 μm, optionally 3-12 μm, if less than 1 μm, the effect of thermal shrinkage and bonding will not be achieved, and if it is greater than 20 μm, the ion conductivity will decrease more obvious.
[无机颗粒][Inorganic particles]
无机颗粒的选择和使用是影响解决本公开所述技术问题的关键，无机颗粒形状、硬度以及涂覆密度的选择，影响最终隔膜的多种性能。The selection and use of inorganic particles is the key to solving the technical problems described in this disclosure. The selection of shape, hardness and coating density of inorganic particles affects various properties of the final separator.
其中无机颗粒种类的选择，可以选择相对于电解液稳定、电化学稳定的任何无机填料，可选择包括选自下述材料中的一种或多种：Wherein the choice of the type of inorganic particles can be selected from any inorganic filler that is stable and electrochemically stable with respect to the electrolyte, and can be selected from one or more of the following materials:
基于氧化物陶瓷中的氧化铝、二氧化硅、二氧化钛、氧化锆、氧化镁、二氧化铈、二氧化钛、氧化锌、氧化铁；Based on alumina, silica, titania, zirconia, magnesia, ceria, titania, zinc oxide, iron oxide in oxide ceramics;
基于氮化物材料的氮化硅、氮化钛、氮化硼；Silicon nitride, titanium nitride, boron nitride based on nitride materials;
基于金属氢氧化物的氢氧化铝、氢氧化镁、氢氧化钙、氢氧化铬、氢氧化锆、氢氧化铈、氢氧化镍；Aluminum hydroxide, magnesium hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide based on metal hydroxides;
以及勃姆石、碳酸镁、硫酸镁、硫酸钡、碳酸钙、硅灰石、碳化硅等，其中可选地为氧化铝或勃姆石。And boehmite, magnesium carbonate, magnesium sulfate, barium sulfate, calcium carbonate, wollastonite, silicon carbide, etc., optionally alumina or boehmite.
以上无机颗粒种类的莫氏硬度D通常有较宽的范围，为2.5-9。所述莫氏硬度D指的是根据一般的莫氏硬度D的定义，以下列10种矿物的硬度为基准的测定值：The Mohs hardness D of the above inorganic particle types usually has a wide range, which is 2.5-9. The Mohs hardness D refers to the measured value based on the hardness of the following 10 minerals according to the definition of the general Mohs hardness D:
1：硫黄石、2：石膏、3：方解石、4：荧石、5：磷灰石、6；正长石、7：石英、8：黄玉、9：刚玉、10：金刚石。1: Sulphurite, 2: Gypsum, 3: Calcite, 4: Fluorite, 5: Apatite, 6: Orthoclase, 7: Quartz, 8: Topaz, 9: Corundum, 10: Diamond.
需要指出的是，即便对于同样的无机颗粒种类，由于晶型和水合度的关系，其莫氏硬度D也会存在差异。It should be pointed out that even for the same type of inorganic particles, due to the relationship between the crystal form and the degree of hydration, there will be differences in the Mohs hardness D.
无机颗粒通过球形度系数S来表达其形状参数，定义如下：Inorganic particles express their shape parameters through the sphericity coefficient S, which is defined as follows:
Figure PCTCN2022101851-appb-000003
Figure PCTCN2022101851-appb-000003
其中，V p为颗粒体积，S p为颗粒表面积； Among them, Vp is the particle volume, Sp is the particle surface area;
依据该定义，标准几何体颗粒的球形度系数S如下：According to this definition, the sphericity coefficient S of standard geometry particles is as follows:
几何体名称geometry name 球形度系数SSphericity coefficient S
四面体tetrahedron 0.6710.671
立方体cube 0.8060.806
八面体octahedron 0.8460.846
十二面体dodecahedron 0.9100.910
二十面体icosahedron 0.9390.939
理想圆锥体ideal cone 0.7940.794
半球hemisphere 0.8400.840
理想圆柱体ideal cylinder 0.8740.874
理想环面ideal torus 0.8940.894
六角化二十面体hexagonal icosahedron 0.9860.986
球体 sphere 11
无机颗粒可以具有球状、针状、板状、纺锤状等形态的颗粒，依据现有技术的经验，通常而言，会考虑选择板状无机颗粒从而增加正极和负极之间的路径，对起到抑制枝晶短路具有良好的效果。Inorganic particles can have spherical, needle-shaped, plate-shaped, spindle-shaped particles, etc. According to the experience of the prior art, generally speaking, it will be considered to choose plate-shaped inorganic particles to increase the path between the positive electrode and the negative electrode. Inhibition of dendrite short circuit has a good effect.
而对于本公开而言，从基膜划伤性和机械性能的角度考虑，限定莫氏硬度D/球形度系数S的比值范围在当该比值小于5时隔膜的穿刺强度变差，机械性能劣化严重，热收缩性能改善不明显，而当该比值大于20时，则容易出现基膜划伤，即便在硬度不太高的情况下，如果存在较为尖锐的非球形部分，也会在涂覆中对基膜造成不规则的划伤，进而降低隔膜的使用寿命。However, for the present disclosure, from the viewpoint of base film scratch and mechanical properties, the ratio range of Mohs hardness D/sphericity coefficient S is limited. When the ratio is less than 5, the puncture strength of the diaphragm becomes worse, and the mechanical properties deteriorate. Seriously, the improvement of thermal shrinkage performance is not obvious, and when the ratio is greater than 20, the base film is prone to scratches. Cause irregular scratches to the base film, thereby reducing the service life of the diaphragm.
本公开中，无机颗粒的平均粒径为0.01-5μm，可选地为0.1-2μm，可选地为0.3-1.5μm。In the present disclosure, the average particle size of the inorganic particles is 0.01-5 μm, optionally 0.1-2 μm, optionally 0.3-1.5 μm.
在本公开中，另外需要突出的发明点在于，无机颗粒在多孔涂层中的单位厚度面密度为0.7-1.5g/m 2/μm，可选地为0.8-1.2g/m 2/μm，无机颗粒单位厚度面密度高于1.5g/m 2/μm时，其透气性变差，而低于0.7时则其热收缩性受到较大影响。 In the present disclosure, another invention point that needs to be highlighted is that the areal density per unit thickness of the inorganic particles in the porous coating is 0.7-1.5 g/m 2 /μm, optionally 0.8-1.2 g/m 2 /μm, When the areal density per unit thickness of the inorganic particles is higher than 1.5 g/m 2 /μm, the gas permeability is deteriorated, and when it is lower than 0.7, the heat shrinkability is greatly affected.
作为如上所述的调节无机颗粒的球形度以及粒径分布的方法，包括使用球磨机，珠磨机，喷射磨机等粉碎无机颗粒以获得对应的球形度、粒径和粒径分布。As a method of adjusting the sphericity and particle size distribution of the inorganic particles as described above, including pulverizing the inorganic particles using a ball mill, bead mill, jet mill, etc. to obtain the corresponding sphericity, particle size and particle size distribution.
[粘结剂][binder]
本公开中多孔涂层的粘结剂树脂包括选自聚酰胺、聚丙烯腈、丙烯酸类树脂、醋酸乙烯酯-乙烯共聚物、羧甲基纤维素纳、芳纶、聚乙烯基丁醛、聚乙烯呲咯烷酮、聚偏氟乙烯、聚四氟乙烯、聚六氟丙烯、偏氟乙烯-六氟丙烯的共聚物、环氧树脂、硅氧烷类、改性聚烯烃、聚氨酯、聚乙烯醇、聚乙烯醚和丁苯橡胶中的一种或多种；其中可选地，聚偏氟乙烯和/或偏氟乙烯-六氟丙烯的共聚物。The binder resin of the porous coating in the present disclosure includes polyamide, polyacrylonitrile, acrylic resin, vinyl acetate-ethylene copolymer, sodium carboxymethyl cellulose, aramid, polyvinyl butyral, poly Vinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene copolymer, epoxy resin, siloxane, modified polyolefin, polyurethane, polyethylene One or more of alcohol, polyvinyl ether and styrene-butadiene rubber; wherein, optionally, polyvinylidene fluoride and/or a copolymer of vinylidene fluoride-hexafluoropropylene.
粘结剂的选择主要是对无机颗粒具有更好的固定作用，保证在隔膜制备过程中，或者在具有本公开所述非水电解液锂二次电池用隔膜的电化学装置在存储和使用过程中，无机颗粒不会脱落。The selection of the binder is mainly to have a better fixation effect on the inorganic particles, to ensure that during the preparation of the separator, or during the storage and use of the electrochemical device with the separator for the non-aqueous electrolyte lithium secondary battery described in the present disclosure Inorganic particles will not fall off.
基于粘结强度、成孔性能和离子透过性的考虑，当选择PVDF系粘结剂时，可选分子量为80,000-800,000。Based on the consideration of bonding strength, pore-forming performance and ion permeability, when choosing a PVDF-based binder, the optional molecular weight is 80,000-800,000.
基于形成良好的多孔结构的观点考虑，粘结剂和无机颗粒在涂布液中的含量可选地为6wt％-20wt％，可选地为8wt％-15wt％。Based on the viewpoint of forming a good porous structure, the content of the binder and the inorganic particles in the coating liquid is optionally 6wt%-20wt%, optionally 8wt%-15wt%.
[溶剂][solvent]
从形成具有良好的多孔结构的多孔层的观点考虑，用于制备涂布液的溶剂可选地包含诱发相分离的相分离剂。因此，用于制备涂布液的溶剂可选地为良溶剂与相分离剂的混合溶剂。可选地，将相分离剂以可确保适合于涂布的粘度的范围的量与良溶剂进行混 合。作为良溶剂，可举出丙酮、甲基乙基酮、N-甲基吡咯烷酮、诸如二甲基乙酰胺、二乙基甲酰胺、二乙基甲酰胺之类的极性酰胺溶剂等，作为相分离剂，可举出水、甲醇、乙醇、丙醇、丁醇、丁二醇、乙二醇、丙二醇、三丙二醇等。From the viewpoint of forming a porous layer having a good porous structure, the solvent used for preparing the coating liquid may optionally contain a phase separation agent that induces phase separation. Therefore, the solvent used to prepare the coating liquid is optionally a mixed solvent of a good solvent and a phase separation agent. Alternatively, the phase separation agent is mixed with a good solvent in an amount that can ensure a viscosity range suitable for coating. As a good solvent, acetone, methyl ethyl ketone, N-methylpyrrolidone, polar amide solvents such as dimethylacetamide, diethylformamide, diethylformamide, etc. are mentioned. Examples of the separating agent include water, methanol, ethanol, propanol, butanol, butylene glycol, ethylene glycol, propylene glycol, tripropylene glycol, and the like.
作为用于制备涂布液的溶剂，从形成良好的多孔结构的观点考虑，可选地包含60wt％以上的良溶剂，且包含40wt％以下的相分离剂。From the viewpoint of forming a good porous structure, the solvent used to prepare the coating liquid may optionally contain 60 wt% or more of a good solvent and 40 wt% or less of a phase separation agent.
[涂布方式][Coating method]
将上述无机颗粒、粘结剂和溶剂共混形成涂布浆料后，可选地，首先利用浸涂法、气刀涂布法、幕涂法、辊式涂布法、线棒涂布法、照相凹板式涂布法、或模具涂布法等方式，将涂料组合物涂布在上述多孔质基材上，形成涂膜的方法。在这些涂布方式中，可选地，照相凹板式涂布法或模具涂布法作为上述涂布液的涂布方法。After the above-mentioned inorganic particles, binder and solvent are blended to form a coating slurry, optionally, firstly, use dip coating method, air knife coating method, curtain coating method, roll coating method, wire bar coating method , gravure coating method, or die coating method, etc., coating the coating composition on the above-mentioned porous substrate to form a coating film. Among these coating methods, optionally, a gravure coating method or a die coating method is used as the coating method of the above-mentioned coating liquid.
然后，干燥通过涂布工序在基材上形成的涂膜。对于干燥条件，只要基材不因软化而产生收缩，粘结剂成分与粒子进行充分粘结，而且当涂料组合物含有热塑性粒子时，处于热塑性粒子不发生熔融的温度范围内，特定的风速及干燥温度就没有特别地限制。Then, the coating film formed on the substrate by the coating step is dried. For drying conditions, as long as the substrate does not shrink due to softening, the binder component and the particles are fully bonded, and when the coating composition contains thermoplastic particles, it is within the temperature range where the thermoplastic particles do not melt, the specific wind speed and The drying temperature is not particularly limited.
作为干燥方法，可以列举传热干燥(对高热物体的粘合)、对流传热(热风)、辐射传热(红外线)、及其他(微波、感应加热等)的方式。其中，在上述制造方法中，由于需要使宽度方向具有精密而均匀的干燥速度，因此可选地使用对流传热或辐射传热的方式。另外，在恒率干燥期间，为了在宽度方向实现均匀的干燥速度，在采用对流传热干燥方式的情况下，可选地使用在维持可控风速的同时，可以降低干燥时的总物质移动系数的方法。使用沿与支撑基材平行、与基材的输送方向平行、或垂直的方向输送热风的方式即可。Examples of drying methods include heat transfer drying (bonding to high-heat objects), convective heat transfer (hot air), radiation heat transfer (infrared rays), and other methods (microwave, induction heating, etc.). Wherein, in the above-mentioned manufacturing method, since it is required to have a precise and uniform drying speed in the width direction, convective heat transfer or radiation heat transfer can be optionally used. In addition, during constant rate drying, in order to achieve a uniform drying speed across the width, in the case of convective heat transfer drying, an optional use can be made to reduce the total mass transfer coefficient during drying while maintaining a controllable wind speed Methods. The hot air can be sent in a direction parallel to the supporting substrate, parallel to the conveying direction of the substrate, or perpendicular to it.
[锂二次电池][Lithium secondary battery]
本公开的锂二次电池具有正极、负极、电解液和配置于正极和负极之间的本公开所述的隔膜，将电池元件、电解液一同封入到外部封装材料内而成的结构，所述电池元件是使负极和正极隔着隔膜对置而得到。The lithium secondary battery of the present disclosure has a positive electrode, a negative electrode, an electrolyte solution, and the diaphragm described in the present disclosure disposed between the positive electrode and the negative electrode, and has a structure in which the battery element and the electrolyte solution are sealed together in an external packaging material. The battery element is obtained by opposing a negative electrode and a positive electrode with a separator interposed therebetween.
正极例如是含有正极活性物质及粘结剂树脂的活性物质层被成型在集电体上而得到的结构。The positive electrode has, for example, a structure in which an active material layer containing a positive electrode active material and a binder resin is molded on a current collector.
作为正极活性物质，可举例为本领域常用的正极活性材料，如含锂的过渡金属氧化物等，可举出LiCoO 2、LiNiO 2、LiMn 1/2Ni 1/2O 2、LiNi 0.5Co 0.2Mn 0.3O 2、LiMn 2O 4、LiFePO 4、 LiC0 1/2Ni 1/2O 2、LiAl 1/4Ni 3/4O 2等。作为粘结剂树脂，可举例如聚偏二氟乙烯系树脂、苯乙烯-丁二烯共聚物等。也可以含有导电助剂，可举例如乙炔黑、科琴黑、石墨粉末等碳材料。作为集电体，可列举例如厚度为5μm～20μm的铝箔、钛箔、不锈钢箔等。 As the positive electrode active material, it can be exemplified by positive electrode active materials commonly used in this field, such as lithium-containing transition metal oxides, etc., such as LiCoO 2 , LiNiO 2 , LiMn 1/2 Ni 1/2 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiMn 2 O 4 , LiFePO 4 , LiC0 1/2 Ni 1/2 O 2 , LiAl 1/4 Ni 3/4 O 2 , etc. As a binder resin, polyvinylidene fluoride resin, a styrene-butadiene copolymer, etc. are mentioned, for example. A conductive aid may also be contained, and examples thereof include carbon materials such as acetylene black, Ketjen black, and graphite powder. Examples of the current collector include aluminum foil, titanium foil, stainless steel foil and the like having a thickness of 5 μm to 20 μm.
作为负极的实施方式例，可列举包含负极活性物质和粘结剂树脂的活性物质层被成型于集电体上而成的结构。活性物质层可进一步包含导电助剂。作为负极活性物质，可列举能以电化学方式吸藏锂的材料，可列举例如：碳材料；硅、锡、铝等与锂的合金；伍德合金(Wood's alloy)；等等。粘结剂树脂、导电助剂和集电体与正极部分大体相同。另外，也可以代替上述负极而使用金属锂箔作为负极。Examples of embodiments of the negative electrode include a structure in which an active material layer including a negative electrode active material and a binder resin is molded on a current collector. The active material layer may further contain a conductive additive. As the negative electrode active material, materials capable of electrochemically absorbing lithium can be enumerated, for example: carbon materials; alloys of silicon, tin, aluminum, etc. and lithium; Wood's alloys; and the like. The binder resin, conductive additive, and current collector are substantially the same as those of the positive electrode. In addition, a metal lithium foil may be used as the negative electrode instead of the negative electrode described above.
电解液是将锂盐溶解于非水系溶剂中而得到的溶液。作为电解液的实施方式例，可以是本领域常见的电解液体系。作为锂盐，可列举例如LiPF 6、LiBF 4、LiClO 4等。作为非水系溶剂，可列举例如碳酸亚乙酯、碳酸亚丙酯、氟代碳酸亚乙酯、二氟代碳酸亚乙酯、碳酸亚乙烯酯等环状碳酸酯；碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸乙烯酯及它们的氟取代物等链状碳酸酯；γ-丁内酯、γ-戊内酯等环状酯等，它们可单独使用，也可混合使用。 The electrolytic solution is a solution obtained by dissolving a lithium salt in a non-aqueous solvent. As an embodiment of the electrolyte, it may be a common electrolyte system in the field. Examples of lithium salts include LiPF 6 , LiBF 4 , LiClO 4 and the like. As the non-aqueous solvent, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, etc.; dimethyl carbonate, dicarbonate Chain carbonates such as ethyl ester, ethyl methyl carbonate, ethylene carbonate and their fluorine substitutes; cyclic esters such as γ-butyrolactone and γ-valerolactone, etc., may be used alone or in combination.
实施例Example
以下，通过实施例说明本公开所述的隔膜及包含隔膜的锂二次电池。但是本公开的实施方式不限于以下的实施例。Hereinafter, the separator according to the present disclosure and the lithium secondary battery including the separator will be described through examples. However, embodiments of the present disclosure are not limited to the following examples.
<评价方法><Evaluation method>
(1)膜厚(1) Film thickness
先采用万分尺测试隔离基膜的厚度，然后再测试涂布之后的厚度，除去隔离基膜的厚度即为多孔涂层厚度。First use a micrometer to test the thickness of the isolation base film, and then test the thickness after coating. The thickness of the isolation base film is the thickness of the porous coating.
(2)平均粒径(2) Average particle size
使用粒径测定装置(日机装株式会社制、MicrotracUPA150)来测定。作为测定条件，设为负荷指标＝0.15～0.3、测定时间300秒，将所得到的数据中的50％粒径的数值记作粒径。It measured using the particle size measuring apparatus (Nikkiso Co., Ltd. make, MicrotracUPA150). As the measurement conditions, the load index=0.15 to 0.3 and the measurement time were set to 300 seconds, and the numerical value of the 50% particle diameter in the obtained data was described as the particle diameter.
(3)基膜平均孔径(3) Average pore size of basement membrane
用美国PMI仪器公司的AAQ-3K-A-1型压水仪对多孔膜进行孔径分布测试，采用 水做为测试液，水在压力作用下，被挤入膜的孔道内，挤入不同孔径内的水对应的压力遵循Washburn方程，从而计算出膜的一系列的孔结构参数。Use the AAQ-3K-A-1 pressure water meter of the American PMI Instrument Company to test the pore size distribution of the porous membrane. Water is used as the test liquid. The pressure corresponding to the water in the membrane follows the Washburn equation, thereby calculating a series of pore structure parameters of the membrane.
(4)莫氏硬度D(4) Mohs hardness D
采用CN111397993A所示的方法进行细小颗粒状莫氏硬度D测量，划痕参考标准物质进行等级确定。The method shown in CN111397993A is used to measure the Mohs hardness D of fine particles, and the scratches are determined with reference to standard materials.
(5)球形度系数S(5) Sphericity coefficient S
将无机颗粒的SEM图像放大20,000倍并输入到照片成像软件中，并且对每个颗粒的轮廓(二维)进行跟踪。在该分析中，彼此紧邻但彼此不附接的颗粒应被视为单独颗粒。然后，用颜色填充轮廓颗粒，并且将图像导入能够测定颗粒周长和面积的颗粒表征软件(例如IMAGE-PRO PLUS，购自Media Cybernetics,Inc.(Bethesda,Md.))中。然后，可根据以下公式计算颗粒的球形度系数S：球形度＝(周长) 2/(4π×面积)，其中周长为从颗粒的轮廓迹线导出的软件测量的周长，并且其中面积为颗粒的迹线周长内的软件测量的面积。 SEM images of inorganic particles were magnified 20,000 times and imported into photo imaging software, and the contour (two-dimensional) of each particle was tracked. Particles that are in close proximity to each other but not attached to each other should be considered as separate particles in this analysis. Outlined particles are then filled with color, and the image is imported into particle characterization software capable of determining particle perimeter and area (eg, IMAGE-PRO PLUS, available from Media Cybernetics, Inc. (Bethesda, Md.)). Then, the sphericity coefficient S of the particle can be calculated according to the following formula: sphericity = (circumference) 2 /(4π×area), where the perimeter is the software-measured perimeter derived from the particle's contour trace, and where the area The area measured by the software within the perimeter of the trajectory for the particle.
该测量方法近似于球形度系数S的定义。This measurement method approximates the definition of the sphericity factor S.
(6)Gurley透气值(6) Gurley air permeability value
裁取100mm×100mm的设有多孔膜的隔离膜样品，利用美国Gurley 4110N透气度测试仪，使用100cc的测试气体模式进行测试，记录测试气体全部通过设有多孔膜的隔离膜样品的时间，即为Gurley值。多孔膜的Gurley值为设有多孔膜的隔离膜的Gurley值减去未设有多孔膜的隔离膜(即纯多孔基材)的Gurley值。Cut a 100mm×100mm isolation membrane sample with a porous membrane, use the American Gurley 4110N air permeability tester, use the 100cc test gas mode to test, and record the time for all the test gas to pass through the isolation membrane sample with a porous membrane, that is is the Gurley value. The Gurley value of the porous membrane is the Gurley value of the separator provided with the porous membrane minus the Gurley value of the separator not provided with the porous membrane (ie, purely porous substrate).
(7)多孔基材与多孔层之间的剥离强度(7) Peel strength between porous substrate and porous layer
在隔膜的一方的多孔层表面上贴合宽度为12mm、长度为15cm的粘合胶带(Scotch制，型号550R－12)，切割隔膜，使其宽度和长度与粘合胶带的宽度和长度一致，制成测定样品。在将粘合胶带贴合于隔膜时，使长度方向与隔膜的MD方向一致。需要说明的是，粘合胶带是作为用于将一方的多孔层剥离的支持体而使用的。Adhesive tape (manufactured by Scotch, model 550R-12) with a width of 12 mm and a length of 15 cm is attached to the surface of the porous layer on one side of the separator, and the separator is cut so that the width and length are the same as those of the adhesive tape. Prepare a measurement sample. When bonding the adhesive tape to the separator, the longitudinal direction was aligned with the MD direction of the separator. In addition, the adhesive tape is used as a support body for peeling off one porous layer.
将测定样品在温度为23±1℃、相对湿度为50±5％的气氛中放置24小时以上，在相同气氛中进行以下的测定。The measurement sample was left to stand in an atmosphere with a temperature of 23±1° C. and a relative humidity of 50±5% for more than 24 hours, and the following measurements were performed in the same atmosphere.
将粘合胶带与紧邻其下方的多孔层一同剥离10cm左右，使粘合胶带和多孔层的层叠体(1)、与多孔基材和另一方的多孔层的层叠体(2)分离10cm左右。将层叠体(1)的端部固定于TENSILON(Orientec公司制RTC-1210A)的上部夹头，将层叠体(2)的端部固定于 TENSILON的下部夹头。使测定样品沿重力方向悬吊，使拉伸角度(层叠体(1)相对于测定样品的角度)成为180°。以50mm/min的拉伸速度对层叠体(1)进行拉伸，测定层叠体(1)从多孔基材剥离时的负荷。以0.4mm的间隔获取从测定开始后10mm至40mm的负荷，将其平均值作为剥离强度。The adhesive tape and the porous layer immediately below it are peeled off about 10 cm together, and the laminate (1) of the adhesive tape and the porous layer is separated from the laminate (2) of the porous substrate and the other porous layer by about 10 cm. The end of the laminate (1) was fixed to the upper chuck of TENSILON (RTC-1210A manufactured by Orientec), and the end of the laminate (2) was fixed to the lower chuck of TENSILON. The measurement sample was suspended in the gravitational direction so that the stretching angle (the angle of the laminate (1) relative to the measurement sample) was 180°. The laminate (1) was stretched at a stretching speed of 50 mm/min, and the load when the laminate (1) was peeled from the porous substrate was measured. The loads from 10 mm to 40 mm after the start of the measurement were obtained at intervals of 0.4 mm, and the average value thereof was defined as the peel strength.
(8)电极粘结强度(8) Electrode bond strength
参考GB/T 2792的要求进行测试。Test according to the requirements of GB/T 2792.
1)将A4纸和隔膜按照A4纸/隔膜/隔膜/A4纸的顺序叠放在一起，其中隔膜涂层与隔膜涂层相对；1) Stack the A4 paper and diaphragm together in the order of A4 paper/diaphragm/diaphragm/A4 paper, where the diaphragm coating is opposite to the diaphragm coating;
2)将叠放好的A4纸、隔膜进行热塑处理，温度为100℃；2) Thermoplasticize the stacked A4 paper and separator at a temperature of 100°C;
3)将热塑后的隔膜裁切成长200mm、宽25mm的长条形，夹具间距离为(100±5)mm，试验速度为(50±10)mm/min。3) Cut the thermoplastic separator into long strips with a length of 200mm and a width of 25mm. The distance between the fixtures is (100±5)mm, and the test speed is (50±10)mm/min.
(9)拉伸强度(9) Tensile strength
将固定厚度为T的测试样品沿MD(长度方向)/TD(宽度方向)用刀模分别冲切成100mm×15mm的片料，然后将片料垂直于高铁拉力机夹头且夹头上下初始高度5cm固定加紧，设置50mm/min的拉伸速率，测得最大拉力为F。Cut the test sample with a fixed thickness T into 100mm×15mm pieces along the MD (length direction)/TD (width direction) with a knife die, and then place the pieces perpendicular to the chuck of the high-speed rail tensile machine and the chuck is up and down. The height is 5cm fixed and tightened, the tensile rate is set to 50mm/min, and the measured maximum tensile force is F.
拉伸强度＝F/9.8/(15mm×T)。Tensile strength=F/9.8/(15mm×T).
(10)收缩率(10) Shrinkage
参考GB/T12027-2004的要求进行测试。Test according to the requirements of GB/T12027-2004.
1)裁剪尺寸大小为15*15cm的隔膜，在隔膜表面标记的纵向和横向，用直尺分别量取试样纵向和横向的长度；1) Cut the diaphragm with a size of 15*15cm, mark the longitudinal and transverse lengths on the diaphragm surface, and measure the longitudinal and transverse lengths of the sample with a ruler;
2)将试样平展放在夹具中，随后放在烘箱中，在130℃温度下保持60min；2) Place the sample flat in the fixture, then place it in an oven, and keep it at 130°C for 60 minutes;
3)加热结束后，取出样品，待恢复室温后，再次测量纵向和横向标记长度，按照下式分别计算收缩率，最后取几个样品的平均值作为收缩率。3) After heating, take out the sample, and after returning to room temperature, measure the longitudinal and transverse mark lengths again, calculate the shrinkage according to the following formula, and finally take the average value of several samples as the shrinkage.
Figure PCTCN2022101851-appb-000004
Figure PCTCN2022101851-appb-000004
ΔL——试样纵向方向上的热收缩率，以％表示；ΔL——The thermal shrinkage rate in the longitudinal direction of the sample, expressed in %;
L 0——试样加热前纵向方向上的长度，单位为毫米(mm)； L 0 ——the length of the sample in the longitudinal direction before heating, in millimeters (mm);
L——试样加热后纵向方向上的长度，单位为毫米(mm)；L - the length in the longitudinal direction of the sample after heating, in millimeters (mm);
ΔT——试样横向方向上的热收缩率，以％表示；ΔT——The thermal shrinkage rate in the transverse direction of the sample, expressed in %;
T 0——试样加热前横向方向上的长度，单位为毫米(mm)； T 0 ——the length of the sample in the transverse direction before heating, in millimeters (mm);
T——试样加热后横向方向上的长度，单位为毫米(mm)。T - the length of the sample in the transverse direction after heating, in millimeters (mm).
(11)隔膜穿刺强度(11) Diaphragm puncture strength
制备片状样品，固定于测试夹具下，使用高铁拉力机和针刺夹具，在穿刺测试仪上使用直径1mm的刺针，速度50mm/min进行穿刺，测得数据稳定后的顶刺力F，则计算穿刺强度(单位gf)为F/9.8*1000。Prepare a sheet sample, fix it under the test fixture, use a high-speed iron tensile machine and a needle-punching fixture, use a puncture needle with a diameter of 1mm on the puncture tester, and puncture at a speed of 50mm/min, and measure the top-puncture force F after the data is stable, then Calculate the puncture strength (unit gf) as F/9.8*1000.
(12)电池性能(12) Battery performance
本公开正极极片将层状锂过渡金属氧化物LiNi 0.5Co 0.2Mn 0.3O 2与导电剂乙炔黑(SP)、粘结剂聚偏氟乙烯(PVDF)混合，三者混合的重量比为96：2：2，加入溶剂N-甲基吡咯烷酮，混合搅拌均匀后得到正极浆料。将正极浆料均匀的涂覆在正极集流体铝箔上，随后在85℃下烘干后进行冷压、切边、裁片、分条，之后在85℃真空条件下干燥4h，得到正极极片。 The positive electrode sheet of the present disclosure mixes layered lithium transition metal oxide LiNi 0.5 Co 0.2 Mn 0.3 O 2 with conductive agent acetylene black (SP) and binder polyvinylidene fluoride (PVDF), and the weight ratio of the three mixed is 96. : 2: 2, add the solvent N-methylpyrrolidone, mix and stir evenly to obtain the positive electrode slurry. Coat the positive electrode slurry evenly on the aluminum foil of the positive electrode current collector, then dry it at 85°C and then perform cold pressing, trimming, cutting, and slitting, and then dry it under vacuum at 85°C for 4 hours to obtain the positive electrode sheet .
负极极片将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比96：1：2：1混合，加入溶剂去离子水，搅拌混合均匀后得到负极浆料。将负极浆料均匀涂覆在负极集流体铜箔上，涂覆后在80-90℃下烘干后，进行冷压、切边、裁片、分条，之后在110℃真空条件下干燥4h，得到负极极片。Negative electrode sheet Mix negative active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC) according to the weight ratio of 96:1:2:1, add The solvent is deionized water, and the negative electrode slurry is obtained after stirring and mixing evenly. Evenly coat the negative electrode slurry on the copper foil of the negative electrode current collector. After coating, dry it at 80-90°C, perform cold pressing, edge trimming, cutting, and slitting, and then dry it under vacuum at 110°C for 4 hours , to obtain the negative pole piece.
配置基础电解液，其中包括碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)和碳酸乙烯酯(EC)，三者的质量比为5:1:4。然后加入电解质盐，使电解液中LiPF 6浓度为1mol/L。 Configure the basic electrolyte, which includes dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethylene carbonate (EC), and the mass ratio of the three is 5:1:4. Then electrolyte salt was added to make the concentration of LiPF 6 in the electrolyte solution 1mol/L.
将负极极片、本公开各实施例与对比例所制备得到的隔膜、正极极片依次叠放，隔离膜处于正极极片和负极极片中间，且隔离膜一侧表面的涂层朝向正极极片，然后卷绕成厚度为10mm、宽度为50mm、长度为120mm的方形裸电芯。将裸电芯装入铝箔包装袋，在75℃下真空烘烤10h，注入非水电解液、经过真空封装、静置24h，之后用0.1C(160mA)的恒定电流充电至4.2V，然后以4.2V恒压充电至电流下降到0.05C(80mA)，然后以0.1C(160mA)的恒定电流放电至3.0V，重复3次充放电，最后以0.1C(160mA)的恒定电流充电至3.8V，即完成锂离子二次电池的制备。Stack the negative pole piece, the separator prepared by each embodiment of the present disclosure and the comparative example, and the positive pole piece in sequence, the separator is in the middle of the positive pole piece and the negative pole piece, and the coating on one side of the separator faces the positive pole. sheet, and then wound into a square bare cell with a thickness of 10mm, a width of 50mm, and a length of 120mm. Put the bare cell into an aluminum foil packaging bag, vacuum bake at 75°C for 10 hours, inject non-aqueous electrolyte, vacuum seal, and let it stand for 24 hours, then charge it to 4.2V with a constant current of 0.1C (160mA), and then charge it with 4.2V constant voltage charge until the current drops to 0.05C (80mA), then discharge to 3.0V with a constant current of 0.1C (160mA), repeat the charge and discharge 3 times, and finally charge to 3.8V with a constant current of 0.1C (160mA) , that is, the preparation of the lithium-ion secondary battery is completed.
循环性能测试：Cycle performance test:
将得到的锂离子二次电池通过1C恒流恒压充电至4.2V，静置10min；以1C恒流放电至3.0V，静置10min，放出的电量记为Q1。以上述步骤作为一个循环充放电，进行200次循环。第200次循环放出的电量记为Q2。循环性能测试结果为Q2/Q1×100％。The obtained lithium-ion secondary battery was charged to 4.2V by 1C constant current and constant voltage, and left to stand for 10 minutes; discharged to 3.0V by 1C constant current, and left to stand for 10 minutes, and the discharged electricity was recorded as Q1. The above steps were taken as one cycle of charging and discharging, and 200 cycles were performed. The electricity discharged in the 200th cycle is recorded as Q2. The cycle performance test result is Q2/Q1×100%.
实施例1：Example 1:
将40重量份PVDF/HPF(95：5，重均分子量500,000)添加到二甲基乙酰胺(DMA)分散体系中，并于35℃溶解约4小时以制备粘合剂聚合物溶液。无机颗粒为氧化铝颗粒，莫氏硬度D8.8，平均粒径0.5μm，以PVDF/HPF：氧化铝颗粒的重量比＝40:60，将氧化铝颗粒加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.71。在23℃和20％相对湿度的条件下，通过凹版辊将用于形成多孔涂层的浆料涂覆在聚乙烯多孔基板的两个表面上(厚度9μm，孔隙率55％，平均孔径70nm，穿刺强度300gf)，经40％的二甲基乙酰胺/水凝固液凝固、纯水清洗，70℃烘干以制造具有多孔涂层的隔膜，使得多孔基板的两个表面上每层涂覆干厚度为2μm，无机颗粒单层的面密度为2.2g/m 2。图1为实施例1所使用的氧化铝无机颗粒的SEM图，图2和图3为实施例1多孔涂层隔膜平面和截面的SEM图像，可以看到多孔涂层与多孔基膜界面咬合，无机颗粒嵌入基膜表面一定的深度。 40 parts by weight of PVDF/HPF (95:5, weight average molecular weight 500,000) was added to a dimethylacetamide (DMA) dispersion system, and dissolved at 35° C. for about 4 hours to prepare a binder polymer solution. The inorganic particles are alumina particles, Mohs hardness D8.8, average particle size 0.5μm, PVDF/HPF: alumina particles weight ratio = 40:60, alumina particles are added to the binder polymer solution to form Porous coating coating slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.71. Under the condition of 23 ℃ and 20% relative humidity, the slurry that will be used to form porous coating is coated on the two surfaces of polyethylene porous substrate by gravure roll (thickness 9 μ m, porosity 55%, average pore diameter 70nm, Puncture strength 300gf), coagulated by 40% dimethylacetamide/water coagulation solution, washed with pure water, and dried at 70°C to manufacture a diaphragm with a porous coating, so that each layer of coating on the two surfaces of the porous substrate is dry. The thickness is 2 μm, and the areal density of the single layer of inorganic particles is 2.2 g/m 2 . Fig. 1 is the SEM figure of the aluminum oxide inorganic particles used in embodiment 1, Fig. 2 and Fig. 3 are the SEM image of embodiment 1 porous coating membrane plane and cross-section, can see porous coating and porous base film interface interlocking, The inorganic particles are embedded to a certain depth on the surface of the base film.
实施例2：Example 2:
无机颗粒选择为氢氧化镁颗粒，莫氏硬度D5，平均粒径1μm，以PVDF/HPF：氢氧化镁颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氢氧化镁颗粒通过球磨法粉碎测得其球形度系数S为0.77。其他条件不变的情况下，无机颗粒单层的面密度为1.71g/m 2。 Inorganic particles are selected as magnesium hydroxide particles, Mohs hardness D5, average particle size 1μm, PVDF/HPF: magnesium hydroxide particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating coating Slurry, wherein the magnesium hydroxide particles are pulverized by ball milling and the sphericity coefficient S is 0.77. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 1.71g/m 2 .
实施例3：Example 3:
无机颗粒选择为勃姆石颗粒，莫氏硬度D3.5，平均粒径0.68μm，以PVDF/HPF：勃姆石颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述勃姆石颗粒通过球磨法粉碎测得其球形度系数S为0.45。其他条件不变的情况下，无机颗粒单层的面密度为2.08g/m 2。 Inorganic particles are selected as boehmite particles, Mohs hardness D3.5, average particle size 0.68μm, PVDF/HPF: boehmite particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating layer coating slurry, wherein the sphericity coefficient S of the boehmite particles measured by ball milling is 0.45. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 2.08g/m 2 .
实施例4：Example 4:
无机颗粒选择为二氧化硅颗粒，莫氏硬度D6.5，平均粒径0.03μm，以PVDF/HPF： 二氧化硅颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述二氧化硅颗粒通过球磨法粉碎测得其球形度系数S为0.98。其他条件不变的情况下，无机颗粒单层的面密度为1.66g/m 2。 Inorganic particles are selected as silica particles, Mohs hardness D6.5, average particle diameter 0.03 μm, PVDF/HPF: silica particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating layer coating slurry, wherein the silicon dioxide particles are pulverized by ball milling and the sphericity coefficient S is 0.98. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 1.66g/m 2 .
实施例5：Example 5:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.6，平均粒径0.47μm，以PVDF/HPF：氧化铝颗粒的重量比＝15:85加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.79。其他条件不变的情况下，无机颗粒单层的面密度为2.01g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.6, average particle size 0.47μm, PVDF/HPF: alumina particles weight ratio = 15:85 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.79. When other conditions remain unchanged, the areal density of a single layer of inorganic particles is 2.01 g/m 2 .
实施例6：Embodiment 6:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8，平均粒径0.1μm，以PVDF/HPF：氧化铝颗粒的重量比＝65:35加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.65。其他条件不变的情况下，无机颗粒单层的面密度为1.93g/m 2。 Inorganic particles are selected as alumina particles, Mohs hardness D8, average particle size 0.1 μm, PVDF/HPF: alumina particles weight ratio = 65:35 added to the binder polymer solution to form a porous coating coating slurry Material, wherein the aluminum oxide particles are pulverized by ball milling and the sphericity coefficient S is 0.65. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 1.93g/m 2 .
实施例7：Embodiment 7:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.8，平均粒径0.8μm，以PVDF/HPF：氧化铝颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.53。其他条件不变的情况下，无机颗粒单层的面密度为2.21g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.8, average particle size 0.8μm, PVDF/HPF: alumina particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.53. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 2.21g/m 2 .
实施例8：Embodiment 8:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.8，平均粒径1.5μm，以PVDF/HPF：氧化铝颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述二氧化硅颗粒通过球磨法粉碎测得其球形度系数S为0.94。其他条件不变的情况下，无机颗粒单层的面密度为2.14g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.8, average particle size 1.5 μm, PVDF/HPF: alumina particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the silicon dioxide particles measured by ball milling is 0.94. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 2.14g/m 2 .
比较例1：Comparative example 1:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.8，平均粒径0.5μm，以PVDF/HPF：氧化铝颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.24。其他条件不变的情况下，无机颗粒单层的面密度为2.30g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.8, average particle size 0.5 μm, PVDF/HPF: alumina particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.24. When other conditions remain unchanged, the areal density of a single layer of inorganic particles is 2.30 g/m 2 .
比较例2：Comparative example 2:
无机颗粒选择为水合氢氧化铝颗粒，莫氏硬度D3，平均粒径0.5μm，以PVDF/HPF：水合氢氧化铝颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述水合氢氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.98。其他条件不变的情况下，无机颗粒单层的面密度为1.69g/m 2。 The inorganic particles are selected as hydrated aluminum hydroxide particles with Mohs hardness D3 and an average particle size of 0.5 μm. The weight ratio of PVDF/HPF: hydrated aluminum hydroxide particles = 40:60 is added to the binder polymer solution to form a porous coating. Layer coating slurry, wherein the sphericity coefficient S of the hydrated aluminum hydroxide particles measured by ball milling is 0.98. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 1.69g/m 2 .
比较例3：Comparative example 3:
无机颗粒选择为氧化铝颗粒，莫氏硬度D7.5，平均粒径0.03μm，以PVDF/HPF：氧化铝颗粒的重量比＝40:60加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.18。其他条件不变的情况下，无机颗粒单层的面密度为1.88g/m 2。 Inorganic particles are selected as alumina particles, Mohs hardness D7.5, average particle size 0.03μm, PVDF/HPF: alumina particles weight ratio = 40:60 added to the binder polymer solution to form a porous coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.18. When other conditions remain unchanged, the areal density of the single layer of inorganic particles is 1.88g/m 2 .
比较例4：Comparative example 4:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.8，平均粒径0.5μm，以PVDF/HPF：氧化铝颗粒的重量比＝10:90加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.71。其他条件不变的情况下，无机颗粒单层的面密度为3.2g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.8, average particle size 0.5μm, PVDF/HPF:alumina particles weight ratio = 10:90 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.71. When other conditions remain unchanged, the areal density of a single layer of inorganic particles is 3.2 g/m 2 .
比较例5：Comparative example 5:
无机颗粒选择为氧化铝颗粒，莫氏硬度D8.8，平均粒径0.5μm，以PVDF/HPF：氧化铝颗粒的重量比＝80:20加入到粘合剂聚合物溶液中形成多孔涂层涂布浆料，其中所述氧化铝颗粒通过球磨法粉碎测得其球形度系数S为0.71。其他条件不变的情况下，无机颗粒单层的面密度为1.26g/m 2。 The inorganic particles are selected as alumina particles, Mohs hardness D8.8, average particle size 0.5 μm, PVDF/HPF: alumina particles weight ratio = 80:20 added to the binder polymer solution to form a porous coating coating Cloth slurry, wherein the sphericity coefficient S of the aluminum oxide particles measured by ball milling is 0.71. When other conditions remain unchanged, the areal density of a single layer of inorganic particles is 1.26g/m 2 .
表1：实施例1-8以及比较例1-5的隔膜以及相应电池的性能指标Table 1: Performance indicators of separators and corresponding batteries of Examples 1-8 and Comparative Examples 1-5
Figure PCTCN2022101851-appb-000005
Figure PCTCN2022101851-appb-000005
表1为实施例1-8以及比较例1-5的隔膜以及相应电池的性能指标，根据表1可知，实施例1-8尽管无机颗粒种类发生变化，硬度和形状发生改变，当保证莫氏硬度D/球形度系数S落在5-20范围内时，隔膜的透气性，剥离/粘结性，热收缩性和机械性能均表现优异，相应的电池也呈现出良好的循环性能，而当比较例1和3中比值过高时，穿刺强度发生劣化；比较例2中比值过低时，热收缩率和粘结强度劣化明显，同时，比较例4中单位厚度面密度高时，其粘结性能相对较差，透气性变差，而比较例5中单位厚度面密度低时，热收缩率受到较大的影响。相应电池的循环性能也不如实施例1-8的性能。Table 1 shows the performance indexes of the separators of Examples 1-8 and Comparative Examples 1-5 and the corresponding batteries. According to Table 1, although the types of inorganic particles in Examples 1-8 change, the hardness and shape change, when the Mohs When the hardness D/sphericity coefficient S falls within the range of 5-20, the gas permeability, peeling/adhesiveness, thermal shrinkage and mechanical properties of the separator are all excellent, and the corresponding battery also shows good cycle performance. When the ratio is too high in Comparative Examples 1 and 3, the puncture strength deteriorates; when the ratio is too low in Comparative Example 2, the heat shrinkage rate and bond strength deteriorate significantly. The junction performance is relatively poor, and the air permeability becomes poor. However, when the area density per unit thickness is low in Comparative Example 5, the thermal shrinkage rate is greatly affected. The cycle performance of the corresponding battery is also not as good as that of Examples 1-8.
除非明确排除或以其他方式限制，本文中引用的每一篇文献，包括任何交叉引用或相关专利或专利申请以及本申请对其要求优先权或其有益效果的任何专利申请或专利，均据此全文以引用方式并入本文。对任何文献的引用不是对其作为与本公开的任何所公开或本文受权利要求书保护的现有技术的认可，或不是对其自身或与任何一个或多个参考文献的组合提出、建议或公开任何此类公开的认可。此外，当本公开中术语的任何含义或定义与以引用方式并入的文献中相同术语的任何含义或定义矛盾时，应当服从在本公开中赋予该术语的含义或定义。Unless expressly excluded or otherwise limited, every document cited herein, including any cross-referenced or related patent or patent application and any patent application or patent to which this application claims priority or its benefit, is hereby Incorporated herein by reference in its entirety. Citation of any document is not an admission that it is prior art with respect to any disclosed or claimed herein, nor does it suggest, suggest, or suggest, by itself or in combination with any reference(s) Disclose any such public acknowledgment. Furthermore, to the extent that any meaning or definition of a term in this disclosure conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this disclosure shall govern.

Claims (10)

  1. 一种非水电解液锂二次电池用隔膜，其特征在于，所述隔膜包括：A diaphragm for a non-aqueous electrolyte lithium secondary battery, characterized in that the diaphragm comprises:
    聚烯烃多孔基膜；Polyolefin porous base film;
    以及形成在所述聚烯烃多孔基膜至少一个表面的含有无机颗粒的多孔涂层；And a porous coating containing inorganic particles formed on at least one surface of the polyolefin porous base film;
    其中所述无机颗粒的莫氏硬度D为2.5-9，球形度系数S为0.2-1，并且莫氏硬度D/球形度系数S的比值范围在5-20；Wherein the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of the Mohs hardness D/sphericity coefficient S is in the range of 5-20;
    其中球形度系数S的定义如下：The sphericity coefficient S is defined as follows:
    Figure PCTCN2022101851-appb-100001
    Figure PCTCN2022101851-appb-100001
    其中，V p为颗粒体积，S p为颗粒表面积； Among them, Vp is the particle volume, Sp is the particle surface area;
    并且无机颗粒在多孔涂层中的单位厚度面密度为0.7-1.5g/m 2/μm。 And the areal density per unit thickness of the inorganic particles in the porous coating is 0.7-1.5 g/m 2 /μm.
  2. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中无机颗粒在多孔涂层中的含量为20wt％-95wt％。The non-aqueous electrolyte lithium secondary battery separator according to claim 1, wherein the content of the inorganic particles in the porous coating is 20wt%-95wt%.
  3. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中多孔涂层还含有粘结剂，所述粘结剂包括选自聚酰胺、聚丙烯腈、丙烯酸类树脂、醋酸乙烯酯-乙烯共聚物、羧甲基纤维素纳、芳纶、聚乙烯基丁醛、聚乙烯呲咯烷酮、聚偏氟乙烯、聚四氟乙烯、聚六氟丙烯、偏氟乙烯-六氟丙烯的共聚物、环氧树脂、硅氧烷类、改性聚烯烃、聚氨酯、聚乙烯醇、聚乙烯醚和丁苯橡胶中的一种或多种。According to the diaphragm for non-aqueous electrolyte lithium secondary battery described in claim 1, wherein porous coating also contains binding agent, described binding agent comprises and is selected from polyamide, polyacrylonitrile, acrylic resin, vinyl acetate Ester-ethylene copolymer, sodium carboxymethyl cellulose, aramid, polyvinyl butyral, polyvinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoro One or more of propylene copolymers, epoxy resins, siloxanes, modified polyolefins, polyurethanes, polyvinyl alcohols, polyvinyl ethers and styrene-butadiene rubber.
  4. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中含有无机颗粒的多孔涂层的总厚度为0.5～20μm。The non-aqueous electrolyte lithium secondary battery separator according to claim 1, wherein the total thickness of the porous coating layer containing inorganic particles is 0.5-20 μm.
  5. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中无机颗粒包括选自下述材料中的一种或多种：According to the diaphragm for non-aqueous electrolyte lithium secondary battery described in claim 1, wherein inorganic particles comprise one or more selected from the following materials:
    基于氧化物陶瓷中的氧化铝、二氧化硅、氧化锆、氧化镁、二氧化铈、二氧化钛、氧化锌、氧化铁；Based on alumina, silica, zirconia, magnesia, ceria, titania, zinc oxide, iron oxide in oxide ceramics;
    基于氮化物材料的氮化硅、氮化钛、氮化硼；Silicon nitride, titanium nitride, boron nitride based on nitride materials;
    以及勃姆石、氢氧化铝、氢氧化镁、硫酸钡、碳酸钙、硅灰石、碳化硅。And boehmite, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, wollastonite, silicon carbide.
  6. 根据权利要求5中所述的非水电解液锂二次电池用隔膜，其中无机颗粒为氧化铝或勃姆石。The non-aqueous electrolyte lithium secondary battery separator according to claim 5, wherein the inorganic particles are alumina or boehmite.
  7. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中无机颗粒的平均粒径为0.01-5μm。The non-aqueous electrolyte lithium secondary battery separator according to claim 1, wherein the average particle diameter of the inorganic particles is 0.01-5 μm.
  8. 根据权利要求1中所述的非水电解液锂二次电池用隔膜，其中所述聚烯烃多孔基膜包括选自聚乙烯、聚丙烯、聚丁烯、聚4-甲基戊烯中的一种或多种共聚物或多种共混物。According to the diaphragm for non-aqueous electrolyte lithium secondary battery described in claim 1, wherein said polyolefin porous base film comprises one selected from polyethylene, polypropylene, polybutene, poly-4-methylpentene One or more copolymers or blends.
  9. 根据权利要求1中所述非水电解液锂二次电池用隔膜的制备方法，其特征在于包括如下步骤：According to the preparation method of diaphragm for non-aqueous electrolyte lithium secondary battery described in claim 1, it is characterized in that comprising the steps:
    a.制备聚烯烃多孔基膜；a. preparing polyolefin porous base film;
    b.配置形成在聚烯烃多孔基膜至少一个表面的含有无机颗粒的多孔涂层涂布浆料，所述涂布浆料包括：b. configure the porous coating coating slurry containing inorganic particles formed on at least one surface of the polyolefin porous base film, the coating slurry comprising:
    无机颗粒，所述无机颗粒的莫氏硬度D为2.5-9，球形度系数S为0.2-1，并且莫氏硬度D/球形度系数S的比值范围在在5-20；Inorganic particles, the Mohs hardness D of the inorganic particles is 2.5-9, the sphericity coefficient S is 0.2-1, and the ratio of Mohs hardness D/sphericity coefficient S is in the range of 5-20;
    其中球形度系数S的定义如下：The sphericity coefficient S is defined as follows:
    Figure PCTCN2022101851-appb-100002
    Figure PCTCN2022101851-appb-100002
    其中，V p为颗粒体积，S p为颗粒表面积； Among them, Vp is the particle volume, Sp is the particle surface area;
    粘结剂；binder;
    以及溶剂；and solvents;
    c.将所述多孔涂层涂布浆料均匀涂布到聚烯烃多孔基膜的一面或两面上；c. uniformly coating the porous coating coating slurry on one or both sides of the polyolefin porous base membrane;
    d.进行干燥，得到多孔涂层涂布的非水电解液锂二次电池用隔膜，其中干燥后的多孔涂层总厚度为0.5～20μm。d. performing drying to obtain a separator for a non-aqueous electrolyte lithium secondary battery coated with a porous coating, wherein the total thickness of the porous coating after drying is 0.5-20 μm.
  10. 一种锂二次电池，其特征在于，包含正极、负极、非水电解液和权利要求1-8之一所述的非水电解液锂二次电池用隔膜或根据权利要求9的方法得到的非水电解液锂二次电池用隔膜。A kind of lithium secondary battery, it is characterized in that, comprises positive pole, negative pole, nonaqueous electrolytic solution and the nonaqueous electrolytic solution lithium secondary battery separator described in one of claim 1-8 or obtains according to the method for claim 9 Separator for non-aqueous electrolyte lithium secondary batteries.
PCT/CN2022/101851 2022-01-05 2022-06-28 Separator for non-aqueous electrolyte lithium secondary battery, and non-aqueous electrolyte lithium secondary battery WO2023130683A1 (en)

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