CN111834591B - Porous diaphragm, preparation method thereof and lithium ion battery - Google Patents

Porous diaphragm, preparation method thereof and lithium ion battery Download PDF

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CN111834591B
CN111834591B CN201910314265.1A CN201910314265A CN111834591B CN 111834591 B CN111834591 B CN 111834591B CN 201910314265 A CN201910314265 A CN 201910314265A CN 111834591 B CN111834591 B CN 111834591B
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porous
polymer
solvent
slurry
base film
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CN111834591A (en
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龚河卿
宣博文
金丽娜
单军
何龙
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BYD Co Ltd
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BYD Co Ltd
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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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Separators (AREA)

Abstract

The porous diaphragm comprises a polyolefin base film and a polymer porous bonding layer coated on the surface of the polyolefin base film, wherein the polymer porous bonding layer is of a multi-layer wire mesh-shaped interweaving structure and has holes with the average pore diameter of 0.2-10 mu m and the porosity of 60-95%. The porous diaphragm has a special morphology structure and larger porosity, so that the whole uniformity and air permeability of the porous diaphragm are better, and a lithium ion battery prepared by the porous diaphragm has better cycle performance and rate capability.

Description

Porous diaphragm, preparation method thereof and lithium ion battery
Technical Field
The disclosure relates to the field of batteries, in particular to a porous diaphragm, a preparation method thereof and a lithium ion battery.
Background
In the construction of lithium batteries, the separator is one of the key internal layer components. The separator has a main function of separating the positive electrode and the negative electrode of the battery to prevent short circuit due to contact between the two electrodes, and also has a function of allowing electrolyte ions to pass therethrough. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The lithium ion battery diaphragm is provided with a large number of tortuous and through micropores, so that free passing of electrolyte ions can be ensured to form a charge-discharge loop; when the battery is overcharged or the temperature is increased, the diaphragm separates the positive electrode and the negative electrode of the battery through the closed-cell function so as to prevent the positive electrode and the negative electrode from being in direct contact and short circuit, and the effects of blocking current conduction and preventing the battery from overheating or even exploding are achieved. The traditional diaphragm pore-forming method is to immerse the whole bonding layer in water, and the method is too violent and is easy to cause the phenomenon of bonding layer peeling.
CN201610233725.4 discloses a preparation technology of a battery separator coating, which uses polyolefin as a base film, coats porous inorganic ceramics on both sides of the base film by a dip coating method, coats an adhesive layer on the surface of the porous inorganic ceramics by a dip coating method, and controls the aperture and porosity of the adhesive layer by controlling the drying condition. The method for controlling the aperture is commonly called as a controlled evaporation precipitation method in the industry and is commonly used for preparing an acetone system polyvinylidene fluoride coating in the industry. The method has the defects that the whole diaphragm is immersed into the glue solution in dip coating, the glue solution is attached to the surface of the diaphragm after being taken out due to viscosity, and the coating is formed after drying, so that the thickness and the surface density of the coating are inconvenient to accurately control. In addition, since the immersion coating is an open system, and a solvent (e.g., acetone) having a low boiling point is frequently used industrially for production efficiency, the organic solvent cannot be recovered well, increasing the cost of the separator coating product and the difficulty in waste liquid treatment.
CN201510069135.8 discloses a technology for preparing a porous organic coating on a non-woven fabric base film by using an immersion type phase separation method. The method comprises the steps of firstly modifying non-woven fabrics by adopting an electrostatic spinning method, then mixing a polymer and ceramics to prepare slurry, coating the slurry on the surface of a modified diaphragm, finally immersing the diaphragm in a non-solvent, and preparing a porous coating by replacing the non-solvent and the solvent. The method has the following defects: firstly, the non-woven fabric material is temporarily incompatible with the existing lithium battery porous polyolefin diaphragm system; secondly, the electrostatic spinning method has high equipment cost, large occupied area and low production efficiency, is easily interfered by the outside in the actual industrial production and is not suitable for large-scale industrial production; thirdly, the phase separation process of directly immersing the diaphragm in the non-solvent is too violent, and a relatively uniform diaphragm coating is not easy to obtain; in addition, the concentration of the organic solvent in the immersion bath gradually increases during the immersion separation process, which adversely affects the morphology of the membrane coating, and moreover, the continuous production of the membrane coating is affected by replacing the immersion bath with a pure immersion bath.
Disclosure of Invention
The purpose of the present disclosure is to provide a porous separator, a preparation method thereof and a lithium ion battery. The porous diaphragm has a special shape structure and larger porosity, so that the whole uniformity and the air permeability of the porous diaphragm are better. The lithium ion battery prepared by the porous diaphragm has better cycle performance and rate capability.
To achieve the above object, a first aspect of the present disclosure: the porous diaphragm comprises a polyolefin base film and a polymer porous bonding layer coated on the surface of the polyolefin base film, wherein the polymer porous bonding layer is of a multi-layer silk-screen-shaped interweaving structure, has holes with the average pore diameter of 0.2-10 mu m, and has the porosity of 60-95%.
Optionally, the polymer porous bonding layer contains a plurality of gathering points, and the polymer porous bonding layer presents a radial silk screen interweaving structure by taking the gathering points as centers.
Optionally, the distance between two adjacent gathering points is 300-10000 nm; the diameter of the gathering point is 10-10000 nm.
Optionally, the air permeability of the porous membrane is 100-500 sec/100 mL.
Optionally, the polymer in the polymeric porous bonding layer is a polyvinylidene fluoride homopolymer and/or a polyvinylidene fluoride-hexafluoropropylene copolymer.
Optionally, the thickness of the polymer porous bonding layer is 0.1-5 μm, preferably 0.3-3 μm; the surface density is 0.2 to 6g/m2Preferably 0.3 to 3.5g/m2。
Optionally, one or both surfaces of the polyolefin-based film have a sub-micron ceramic coating layer of at least one material selected from the group consisting of aluminum oxide, silicon oxide, calcium oxide, magnesium oxide, chromium oxide, titanium oxide, zinc oxide, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, barium sulfate, zeolite, and boehmite.
Optionally, the particle size of the material of the submicron ceramic coating is 100nm to 1 μm, and preferably 100nm to 500 nm.
In a second aspect of the present disclosure: there is provided a method of preparing a porous separator according to the first aspect of the present disclosure, the method comprising the steps of:
a. obtaining a slurry comprising a polymer and an organic solvent;
b. coating the slurry in the step a on a polyolefin base film to obtain the polyolefin base film coated with the slurry;
c. b, spraying the base film with the slurry in the step b by using a non-solvent so as to enable the non-solvent and the organic solvent to mutually diffuse to obtain a base film after the solvent is diffused;
d. and c, drying the base film after the solvent is diffused in the step c.
Optionally, in step a, the weight ratio of the polymer to the organic solvent is 1: (5-50);
the organic solvent is at least one selected from N, N-dimethylformamide, tetrahydrofuran, methyl ethyl ketone, tetramethylurea, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, triethyl phosphate, ethylene glycol ethyl ether, ethylene glycol ether ester, N-butyl acetate, cyclohexanone, diacetic acid, diisobutyl ketone, ethyl acetoacetate, butyrolactone, propylene carbonate and dimethyl phthalate.
Optionally, in step a, the organic solvent is N-methylpyrrolidone and/or dimethyl sulfoxide, and the weight ratio of the polymer to the organic solvent is 1: (10-50); or,
the organic solvent is N, N-dimethylformamide, N-dimethylacetamide or triethyl phosphate, or a combination of two or three of the N, N-dimethylformamide, the N, N-dimethylacetamide and the triethyl phosphate, and the weight ratio of the polymer to the organic solvent is 1: (15-40).
Optionally, in the step a, the slurry further contains an additive, wherein the additive comprises an organic additive and/or an inorganic additive, and the additive is used in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the slurry.
Optionally, the organic additive is at least one selected from the group consisting of polyvinyl alcohol, polybutylmethacrylate, polymethylmethacrylate, polyvinyl acetate, polyethylene oxide, polyethylene glycol, polypropylene oxide, polyethylene oxide-polypropylene oxide block copolymer, polyvinyl chloride, polycarbonate, and polyethylene oxide-alkanol copolymer; based on 100 parts by weight of the slurry, the amount of the organic additive is 0.1-10 parts by weight;
the inorganic additive is at least one selected from aluminum oxide, silicon oxide, calcium oxide, magnesium oxide, chromium oxide, titanium oxide, zinc oxide, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, barium sulfate, zeolite and boehmite, and the particle size of the inorganic additive is 100 nm-2 μm, preferably 200 nm-1 μm; the inorganic additive is used in an amount of 0.5 to 40 parts by weight based on 100 parts by weight of the slurry.
Optionally, in step c, the non-solvent comprises at least one of water, an alcohol, and a ketone;
the weight ratio of the non-solvent to the organic solvent is (1-100): 1;
the spraying conditions include: the temperature of the non-solvent is 0-100 ℃, and preferably 20-80 ℃; the spraying time is 10-3000 seconds, preferably 30-300 seconds.
Optionally, the alcohol is at least one selected from ethanol, ethylene glycol, methanol, propanol, glycerol, n-butanol, isobutanol, and benzyl alcohol; the ketone is at least one selected from acetone, butanone, 2-pentanone, methyl isobutyl ketone and cyclohexanone.
Optionally, in the step d, the drying temperature is 20-150 ℃, and preferably 50-120 ℃.
A third aspect of the disclosure: there is provided a lithium ion battery comprising a porous separator according to the first aspect of the present disclosure.
Compared with the traditional immersion phase separation method, the method can greatly reduce the impact force of the non-solvent on the diaphragm, so that the phenomenon that the coating peels off on the surface of the diaphragm is not easy to occur, thereby improving the integral uniformity of the porous diaphragm, further improving the cohesiveness of the porous diaphragm to a positive electrode and a negative electrode so as to finally improve the cycle performance of the battery. The porous diaphragm prepared by the method has a special multilayer wire mesh-shaped interweaving structure, and has larger pores and higher porosity. The method disclosed by the invention is suitable for a continuous production process, the prepared porous diaphragm has better air permeability, can form stronger viscosity on the anode and the cathode of the battery, and improves the cycle performance and the rate capability of the lithium ion battery.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:
fig. 1 and 2 are SEM electron micrographs of the porous separator prepared in example 1.
Fig. 3 and 4 are SEM electron micrographs of the porous separator prepared in example 2.
Fig. 5 and 6 are SEM electron micrographs of the porous separator prepared in example 3.
Fig. 7 and 8 are SEM electron micrographs of the porous separator prepared in example 4.
Fig. 9 and 10 are SEM electron micrographs of the porous separator prepared in example 5.
Fig. 11 and 12 are SEM electron micrographs of the porous separator prepared in comparative example 1.
Fig. 13 and 14 are SEM electron micrographs of the porous separator prepared in comparative example 2.
Fig. 15 is a positive electrode peel strength test curve of lithium ion batteries prepared from the porous separators of example 1 and comparative example 1.
Fig. 16 is a negative electrode peel strength test curve of lithium ion batteries prepared from the porous separators of example 1 and comparative example 1.
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
The first aspect of the disclosure: the porous diaphragm comprises a polyolefin base film and a polymer porous bonding layer coated on the surface of the polyolefin base film, wherein the polymer porous bonding layer is of a multi-layer silk-screen-shaped interweaving structure, has holes with the average pore diameter of 0.2-10 mu m, and has the porosity of 60-95%. Wherein the average pore size and porosity can be measured using methods well known to those skilled in the art. In the porous diaphragm disclosed by the invention, the polymer porous bonding layer has higher porosity, so that the air permeability of the porous diaphragm is better, and the transmission of lithium ions on two sides of the porous diaphragm is facilitated, thereby improving the lithium ion conductivity of the porous diaphragm and reducing the impedance.
According to the present disclosure, the shape of the multi-layer silk-net-shaped interlaced structure can refer to fig. 1 to 10, the polymer macromolecules are formed into a silk-net shape or a dendritic mutually-interpenetrating shape, and a large number of holes with larger pore diameters are formed in gaps where the silk-like polymer macromolecules are interlaced. Furthermore, the polymer porous bonding layer contains a plurality of gathering points (gathering points formed by interweaving filiform polymer macromolecules), and the polymer porous bonding layer takes the gathering points as the center to present a radial silk screen interweaving structure. Furthermore, the distance between two adjacent aggregation points can be 300-10000 nm, wherein the distance refers to the distance between any one aggregation point and the closest aggregation point; the diameter of the gathering point can be 10-10000 nm, wherein the diameter refers to the maximum three-dimensional length of the gathering point, namely the maximum distance between two points on the gathering point; the diameters and the distances of the gathering points can be observed, counted and estimated by a scanning electron microscope.
The polymer porous bonding layer of the porous diaphragm disclosed by the invention has a special multilayer wire mesh-shaped interweaving structure, and has larger-aperture holes, higher porosity and better air permeability. In the present disclosure, the porous separator may have an air permeability of 100 to 500sec/100 mL. The air permeability may be measured using methods well known to those skilled in the art.
According to the present disclosure, the polymer of the polymeric porous bonding layer may be a polyvinylidene fluoride homopolymer and/or a polyvinylidene fluoride-hexafluoropropylene copolymer. The weight average molecular weight of the polymer may be between 5 and 300 million, preferably between 20 and 150 million. When the weight average molecular weight of the polymer is too low, the polymer will not have good film-forming properties and adhesiveness to positive and negative electrodes, and when the weight average molecular weight of the polymer is too high, the difficulty of dissolution in the preparation process is high and the adhesiveness of the slurry containing the polymer is too high, which brings difficulty to the coating and feeding process.
According to the present disclosure, the polymer porous bonding layer has a uniform thickness and a surface density, for example, the thickness of the polymer porous bonding layer may be 0.1 to 5 μm, preferably 0.3 to 3 μm; the surface density is 0.2 to 6g/m2Preferably 0.3 to 3.5g/m2。
According to the present disclosure, the polyolefin-based film may be a Polyethylene (PE) -based film, a polypropylene (PP) -based film, or a polyethylene/polypropylene composite-based film. The polyethylene/polypropylene composite base film refers to a multi-layer base film obtained by compounding polyethylene and polypropylene, and the compounding sequence is not limited, and for example, polypropylene/polyethylene/polypropylene base film and the like can be used. The polyolefin-based films of the present disclosure are commercially available.
According to the present disclosure, in order to further improve the performance of the porous separator, one or both surfaces of the polyolefin-based film may have a submicron ceramic coating layer. Wherein the material of the submicron ceramic coating may be selected from alumina (Al)2O3) Silicon oxide (SiO)2) Calcium oxide (CaO), magnesium oxide (MgO), and chromium oxide (ZrO)2) Titanium oxide (TiO)2) Zinc oxide (ZnO), calcium hydroxide (Ca (OH)2) Aluminum hydroxide (Al (OH)3) Magnesium hydroxide (Mg (OH)2) Silicon carbide (SiC), barium sulfate (BaSO)4) At least one of zeolite and boehmite (AlOOH). The submicron ceramic coating made of the material can further improve the heat resistance of the porous diaphragm, and the prepared lithium ion battery has better safety. Furthermore, the particle size of the material of the submicron ceramic coating can be 100 nm-1 μm, and is preferably 100-500 nm.
In a second aspect of the present disclosure: there is provided a method of preparing a porous separator according to the first aspect of the present disclosure, the method comprising the steps of:
a. obtaining a slurry comprising a polymer and an organic solvent;
b. coating the slurry in the step a on a polyolefin base film to obtain the polyolefin base film coated with the slurry;
c. b, spraying the base film with the slurry in the step b by using a non-solvent so as to enable the non-solvent and the organic solvent to mutually diffuse to obtain a base film after the solvent is diffused;
d. and c, drying the base film after the solvent is diffused in the step c.
According to the present disclosure, in step a, the slurry may be prepared by dissolving the polymer in an organic solvent, and in order to accelerate the dissolution, the preparation may be performed under heating and stirring conditions until a clear and transparent slurry is obtained.
According to the present disclosure, in step a, the polymer may be a polyvinylidene fluoride (PVDF) homopolymer and/or a polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer. The weight average molecular weight of the polymer may be between 5 and 300 million, preferably between 20 and 150 million. When the weight average molecular weight of the polymer is too low, the polymer will not have good film-forming properties and adhesiveness to positive and negative electrodes, and when the weight average molecular weight of the polymer is too high, the difficulty of dissolution in the preparation process is high and the adhesiveness of the slurry containing the polymer is too high, which brings difficulty to the coating and feeding process.
According to the present disclosure, in the step a, the organic solvent may be at least one selected from the group consisting of N, N-Dimethylformamide (DMF), Tetrahydrofuran (THF), Methyl Ethyl Ketone (MEK), Tetramethylurea (TMU), N-Dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), triethyl phosphate (TEP), ethylene glycol ether, glycol ether ester, N-butyl acetate, cyclohexanone, diacetic acid, diisobutyl ketone (DIBK), ethyl acetoacetate, butyrolactone, propylene carbonate, and dimethyl phthalate (DMP). The organic solvent has higher boiling point, and compared with acetone used in the prior art, the organic solvent has the advantages of being safer and less in volatilization, is more favorable for solvent recovery, and reduces the production cost of products.
According to the present disclosure, in step a, the concentration of the polymer in the slurry is low, and the purpose of the present disclosure can be achieved, for example, the weight ratio of the polymer to the organic solvent may be 1: (5-50). When the amount of the polymer is within the above range, the porous bonding layer of the polymer in the prepared porous separator has a high porosity.
According to the present disclosure, different organic solvent types can adjust the viscosity of the slurry and its affinity for non-solvents and surface tension, thereby affecting the morphology of the polymeric porous bonding layer. In order to prepare a polymer porous bonding layer having a multi-layer silk-like interlaced structure, in an alternative embodiment of the present disclosure, in step a, the organic solvent may be N-methylpyrrolidone and/or dimethylsulfoxide, and then the weight ratio of the polymer to the organic solvent may be 1: (10-50). Alternatively, in another alternative embodiment of the present disclosure, the organic solvent is N, N-dimethylformamide, N-dimethylacetamide, or triethyl phosphate, or a combination of two or three thereof, and then the weight ratio of the polymer and the organic solvent may be 1: (15-40).
According to the present disclosure, in step a, in order to improve the spreading stability and shrinkage of the polymer porous bonding layer on the surface of the polyolefin-based film, the slurry may further contain an additive, which may include, for example, an organic additive and/or an inorganic additive, and may be used in an amount of 0.1 to 50 parts by weight, based on 100 parts by weight of the slurry.
Further, the organic additive may be at least one selected from the group consisting of polyvinyl alcohol (PVA), Polybutylmethacrylate (PBMA), Polymethylmethacrylate (PMMA), polyvinyl acetate (PVAc), polyethylene oxide (PEO), polyethylene glycol (PEG), polypropylene oxide (PPO), polyethylene oxide-polypropylene oxide block copolymer (PPO-PEO-PPO), polyvinyl chloride (PVC), Polycarbonate (PC), and polyethylene oxide-alkanol copolymer. The organic additive may be used in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the slurry. The organic additives of the above kind have a large surface tension and can alleviate the phenomenon of hole blocking caused by the polymer permeating into the base film.
Further, the inorganic additive may be selected from alumina (Al)2O3) Silicon oxide (SiO)2) Calcium oxide (CaO), magnesium oxide (MgO), and chromium oxide (ZrO)2) Titanium oxide (TiO)2) Zinc oxide (ZnO), calcium hydroxide (Ca (OH)2) Aluminum hydroxide (Al (OH)3) Magnesium hydroxide (Mg (OH)2) Silicon carbide (SiC), barium sulfate (BaSO)4) At least one of zeolite and boehmite (AlOOH). The inorganic additive in the above kind can greatly improve the shrinkage problem and the spreading condition of the polymer porous bonding layer on the surface of the polyolefin base film. Further, the particle size of the inorganic additive may be 100nm to 2 μm, preferably 200nm to 1 μm. If the particle size of the inorganic additive particles is too large, the thickness of the polymer porous bonding layer cannot be controlled to be thinner, and the energy density of the prepared battery is reduced; if the particle size of the inorganic additive particles is too small, agglomeration is easy to occur, so that the thickness and uniformity of the corresponding polymer porous bonding layer are difficult to control. The inorganic additive may be used in an amount of 0.5 to 40 parts by weight, based on 100 parts by weight of the slurry.
According to the disclosure, in the step b, unlike a dip coating and feeding method of a traditional production process, the polyolefin base film is spread and paved, and the slurry in the step a is uniformly coated on the polyolefin base film to obtain the polyolefin base film coated with the slurry. In this way, the thickness and areal density of the polymeric porous bonding layer can be more precisely controlled, resulting in better product consistency. The coating may include at least one of knife coating, gravure roll transfer coating, spray coating, screen printing, and transfer coating. When the coating is carried out, the running speed of the polyolefin base film can be controlled to be 1-1000 m/min, and preferably 10-500 m/min; if the walking speed is too slow, the method is unfavorable for large-scale industrial production, and if the walking speed is too fast, the impact force on the slurry is increased due to the large using amount of the non-solvent in the subsequent spraying process, and the overall uniformity of the prepared porous diaphragm is not favorable.
According to the disclosure, in step c, the base film with the slurry in step b is sprayed with a non-solvent, the sprayed small liquid beads are contacted with an organic solvent in the slurry, so that the non-solvent and the organic solvent are diffused (replaced) towards each other, liquid-liquid phase separation is further performed, and after the solvent and the non-solvent are completely replaced, the base film after the solvent is diffused is obtained. Compared with the traditional immersion phase separation method in which the whole diaphragm is immersed in the non-solvent once, the spraying mode can greatly reduce the impact force of the non-solvent on the diaphragm, so that the phenomenon that the coating is peeled off from the surface of the diaphragm is not easy to occur, and the integral uniformity of the diaphragm can be greatly improved. In addition, compared with the immersion separation, the spraying mode does not cause the accumulation of organic solvent, is more favorable for obtaining uniform and stable products and is more suitable for the continuous production process. The spraying can be carried out by conventional means, for example an atomizer. The conditions of the spraying may include: the temperature of the non-solvent is 0-100 ℃, and preferably 20-80 ℃; the spraying time is 10-3000 seconds, preferably 30-300 seconds.
According to the present disclosure, in step c, the non-solvent refers to a poor solvent for the polymer, and may include, for example, at least one of water, alcohol and ketone, preferably water. Further, the alcohol may be at least one selected from the group consisting of ethanol, ethylene glycol, methanol, propanol, glycerol, n-butanol, isobutanol, and benzyl alcohol; the ketone may be at least one selected from the group consisting of acetone, butanone, 2-pentanone, methyl isobutyl ketone, and cyclohexanone. The amount of the non-solvent can be adjusted according to the amount of the organic solvent, and specifically, the weight ratio of the non-solvent to the organic solvent can be (1-100): 1, if the using amount of the non-solvent is too small, the phase separation is not thorough, so that the porous appearance of the polymer porous bonding layer has the risk of secondary dissolution and collapse; the use of the non-solvent in an excessive amount is uneconomical and puts stress on the circulation system.
According to the disclosure, in step d, after the spraying is finished, the polymer in the slurry is cured on the polyolefin base film to form a polymer porous bonding layer, and the base film after the solvent diffusion is dried to remove the residual non-solvent on the polymer porous bonding layer. The drying temperature can be 20-150 ℃, and preferably 50-120 ℃. The drying method can include, but is not limited to, heating roller drying, oven drying, microwave radiation drying, hot air drying, or constant temperature and humidity oven drying.
The porous diaphragm prepared by the method has a polymer bonded porous layer with a multi-layer silk-screen-like interwoven structure, the layer has larger aperture and porosity, better air permeability, stronger viscosity to the anode and the cathode of the battery and improvement on the cycle performance and the rate capability of the lithium ion battery.
In a second aspect of the present disclosure, there is provided a lithium ion battery comprising the porous separator according to the first aspect of the present disclosure.
The present disclosure is further illustrated by the following examples, but is not limited thereby.
In the embodiment, a Gemini 300 model electron microscope produced by Karl Zeiss of Germany is adopted to determine the morphology of the porous bonding layer of the diaphragm polymer, and the test method comprises the following steps: cutting a porous diaphragm with a certain area, plating a layer of gold on the surface by using a gold spraying instrument, wherein the gold spraying condition is 20mA, observing under an electron microscope after 80s, and the accelerating voltage of the field emission scanning electron microscope is 7 KV.
Example 1
3 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 80 ten thousand) and 97 parts by weight of dimethyl sulfoxide as an organic solvent were mixed and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene-based film (available from Cangzhou Mingzhu, trade name RV0059) coated on one surface with a submicron alumina coating layer having a particle size of 400nm was laid on a glass plate having a smooth and flat surface, and the slurry was coated on the film using a 30 μm doctor blade at a running speed of 50 m/min. And (3) placing the base membrane coated with the slurry under an atomizer, spraying the base membrane by non-solvent pure water (60 ℃) for 300 seconds, wherein the weight ratio of the non-solvent to the organic solvent is 10, replacing and curing the non-solvent and the organic solvent, and then placing the base membrane in an oven at 70 ℃ for drying to prepare the porous membrane, wherein SEM pictures of the porous membrane are shown in figures 1 and 2, and the porous polymer bonding layer has a multi-layer silk-screen-shaped interweaving structure and is in a uniform and criss-cross dendritic shape.
Example 2
5 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 45 ten thousand) was mixed with 47.5 parts by weight of N-methylpyrrolidone and 47.5 parts by weight of dimethyl sulfoxide as an organic solvent, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (produced by BYD RM1 factory) with a submicron alumina coating layer with the grain diameter of 100nm coated on both sides is flatly laid on a glass plate with a smooth and flat surface, and then the slurry is coated on the flatly laid porous polyolefin base film by using a 120-mesh gravure roller, wherein the running speed of the base film is 500 m/min. And (3) placing the base membrane coated with the slurry under an atomizer, spraying the base membrane by non-solvent pure water (25 ℃) for 300 seconds, wherein the weight ratio of the non-solvent to the organic solvent is 1, replacing and curing the non-solvent and the organic solvent, and then placing the base membrane in an oven at 70 ℃ for drying to prepare the porous membrane, wherein SEM pictures of the porous membrane are shown in fig. 3 and fig. 4, so that the polymer porous bonding layer has a multilayer silk-screen-like interwoven structure and is in a uniform and criss-cross dendritic shape.
Example 3
5 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 15 ten thousand) was mixed with 47.425 parts by weight of N-methylpyrrolidone as an organic solvent, 47.425 parts by weight of dimethyl sulfoxide, and 0.15 part by weight of polyvinyl alcohol as an organic additive, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from a star source material and having a product number of SW309) is flatly laid on a glass plate with a smooth and flat surface, then the slurry is coated on the base film, the feeding thickness is controlled by an extrusion roller, and the running speed of the base film is 5 m/min. And (3) placing the base membrane coated with the slurry under an atomizer, spraying the base membrane by using non-solvent pure water (80 ℃) for 300 seconds, wherein the weight ratio of the non-solvent to the organic solvent is 100, replacing and curing the non-solvent and the organic solvent, and then placing the base membrane in an oven at 70 ℃ for drying to prepare the porous membrane, wherein SEM pictures of the porous membrane are shown in fig. 5 and fig. 6, so that the polymer porous bonding layer has a multi-layer silk-screen-shaped interweaving structure and is in a uniform and criss-cross dendritic shape.
Example 4
5 parts by weight of a polyvinylidene fluoride-hexafluoropropylene copolymer (weight average molecular weight: 100 ten thousand) was mixed with 47.25 parts by weight of N-methylpyrrolidone and 47.25 parts by weight of dimethyl sulfoxide as organic solvents, and 0.5 part by weight of alumina (particle diameter: 300 to 500 nm) as an inorganic additive, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from a star source material and with the trade name of SW3012) coated with a submicron alumina coating with the particle size of 300nm on the single surface is laid on a glass plate with a smooth and flat surface, and then the sizing agent is coated on the base film by a scraper with the diameter of 30 mu m, wherein the running speed of the base film is 1000 m/min. Placing the base membrane coated with the slurry under an atomizer, spraying the base membrane for 30 seconds by using non-solvent ethanol (25 ℃), wherein the weight ratio of the non-solvent to the organic solvent is 1, replacing and curing the non-solvent and the organic solvent, and then placing the base membrane in an oven at 60 ℃ for drying to prepare the porous membrane, wherein SEM pictures of the porous membrane are shown in figures 7 and 8, and the porous polymer bonding layer has a multi-layer silk-screen interweaving structure and is in a uniform and criss-cross dendritic morphology, and alumina is possibly arranged on the porous polymer bonding layer and is also possibly arranged below the porous polymer bonding layer.
Example 5
5 parts by weight of a polyvinylidene fluoride-hexafluoropropylene copolymer (weight average molecular weight: 30 ten thousand) was mixed with 94.5 parts by weight of N-methylpyrrolidone as an organic solvent and 0.5 part by weight of alumina (particle diameter: 300 to 500 nm) as an inorganic additive, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from a star source material and with the product number of SW309) with a submicron alumina coating with the particle size of 400nm coated on the single surface is flatly laid on a glass plate with a smooth and flat surface, and then the sizing agent is coated on the base film by a scraper with the diameter of 30 mu m, wherein the running speed of the base film is 30 m/min. And (3) placing the base membrane coated with the slurry under an atomizer, spraying the base membrane by using 1000 seconds of non-solvent ethanol (25 ℃), wherein the weight ratio of the non-solvent to the organic solvent is 100, replacing and curing the non-solvent and the organic solvent, and then drying the base membrane together by using a heating roller at 80 ℃ in cooperation with hot air at 80 ℃ to prepare the porous membrane, wherein SEM pictures are shown in figures 9 and 10, and the polymer porous bonding layer has a multi-layer silk-screen interweaving structure and is in a uniform criss-cross dendritic shape.
Example 6
4 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight of 75 ten thousand), 48 parts by weight of N, N-dimethylformamide as an organic solvent and 48 parts by weight of N, N-dimethylacetamide were mixed, and stirred at room temperature for 12 hours to obtain a slurry.
A polypropylene-based film (produced by BYD RM1 factory) having a submicron magnesia coating layer having a particle size of 100nm coated on one surface thereof was laid flat on a glass plate having a smooth and flat surface, and the above slurry was coated on the base film with a 30 μm doctor blade at a running speed of 50 m/min. The base film coated with the slurry was placed under an atomizer, sprayed with non-solvent pure water (75 ℃) for 300 seconds at a weight ratio of the non-solvent to the organic solvent of 10, and after the non-solvent and the organic solvent were replaced and cured, then placed in an oven at 70 ℃ to be dried, to prepare a porous separator, whose SEM photograph is similar to that of fig. 1.
Example 7
5 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight of 75 ten thousand) was mixed with 80 parts by weight of N, N-dimethylacetamide and 15 parts by weight of triethyl phosphate as an organic solvent, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene/polypropylene composite base membrane (purchased from Asahi Kasei Corp., product number Celegard) coated with a submicron titanium oxide coating layer with the particle size of 500nm on both sides is tiled on a glass plate with a smooth and flat surface, and then the slurry is coated on the tiled porous polyolefin base membrane by using a 120-mesh gravure roller, wherein the running speed of the base membrane is 300 m/min. The base film coated with the slurry was placed under an atomizer, sprayed with a non-solvent ethylene glycol (25 ℃) for 500 seconds at a weight ratio of the non-solvent to the organic solvent of 1, and after the non-solvent and the organic solvent were displaced and cured, placed in an oven at 70 ℃ to be dried, to prepare a porous separator, whose SEM photograph is similar to that of fig. 5.
Example 8
5 parts by weight of a polyvinylidene fluoride-hexafluoropropylene copolymer (weight average molecular weight: 30 ten thousand) was mixed with 50 parts by weight of N, N-dimethylformamide as an organic solvent, 30 parts by weight of N, N-dimethylacetamide, 5 parts by weight of polybutylmethacrylate as an organic additive, and 10 parts by weight of silica (particle size: 300 to 500 nm) as an inorganic additive, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from a star source material and having a commercial number of SW309) was spread on a glass plate having a smooth and flat surface, and the slurry was coated on the base film by using a 30 μm doctor blade at a running speed of 100 m/min. The base film coated with the slurry was placed under an atomizer, sprayed with a non-solvent acetone (25 ℃) for 300 seconds at a weight ratio of the non-solvent to the organic solvent of 10, and after the non-solvent and the organic solvent were replaced and cured, placed in an oven at 70 ℃ to be dried, to prepare a porous separator, whose SEM photograph is similar to that of fig. 5.
Example 9
6 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 75 ten thousand) and 94 parts by weight of methyl ethyl ketone as an organic solvent were mixed, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from a star source material and with the trade name of SW3012) coated with a submicron alumina coating with the particle size of 300nm on the single surface is laid on a glass plate with a smooth and flat surface, and then the sizing agent is coated on the base film by a scraper with the diameter of 30 mu m, wherein the running speed of the base film is 800 m/min. The base film coated with the slurry was placed under an atomizer, sprayed with non-solvent pure water (0 ℃) for 300 seconds at a weight ratio of the non-solvent to the organic solvent of 1, and after the non-solvent and the organic solvent were displaced and cured, then placed in an oven at 70 ℃ to be dried, to prepare a porous separator, whose SEM photograph is similar to that of fig. 1.
Example 10
5 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 45 ten thousand) was mixed with 47.5 parts by weight of N-methylpyrrolidone and 47.5 parts by weight of dimethyl sulfoxide as an organic solvent, and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (produced by BYD RM1 factory) with a submicron alumina coating layer with the grain diameter of 800nm coated on both sides is flatly laid on a glass plate with a smooth and flat surface, and then the slurry is coated on the flatly laid porous polyolefin base film by using a 120-mesh gravure roller, wherein the running speed of the base film is 300 m/min. And (3) placing the base membrane coated with the slurry under an atomizer, spraying the base membrane for 500 seconds by using non-solvent pure water (25 ℃), replacing and curing the non-solvent and the organic solvent by using a weight ratio of 1, and then placing the base membrane in an oven at 70 ℃ for drying to prepare the porous diaphragm.
Comparative example 1
The comparative example adopts a traditional controlled evaporation precipitation method to prepare the porous diaphragm, and the specific method comprises the following steps:
3 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 80 ten thousand) and 97 parts by weight of acetone as an organic solvent were mixed and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene base film (purchased from cangzhou bright pearl, with a trade mark of RV0059) coated with a submicron alumina coating with a particle size of 400nm on one surface is laid on a glass plate with a smooth and flat surface, then the slurry is coated on the base film by a 30-micron scraper, and after acetone is completely volatilized, the base film is placed in an oven at 70 ℃ for drying to prepare the porous diaphragm, wherein SEM pictures of the porous diaphragm are shown in figures 11 and 12, and it can be seen that a polymer bonding layer in the diaphragm is compact and has low porosity.
Comparative example 2
The porous diaphragm is prepared by adopting a traditional immersed phase separation method in the comparative example, and the specific method comprises the following steps:
3 parts by weight of a polyvinylidene fluoride homopolymer (weight average molecular weight: 80 ten thousand) and 97 parts by weight of dimethyl sulfoxide as an organic solvent were mixed and stirred at room temperature for 12 hours to obtain a slurry.
A polyethylene-based film (available from cangzhou pearl under trade designation RV0059) coated on one side with a submicron alumina coating layer having a particle size of 400nm was laid on a glass plate having a smooth and flat surface, and the above slurry was coated on the base film using a 30 μm doctor blade. Immersing the base membrane coated with the slurry into non-solvent pure water, wherein the weight ratio of the non-solvent to the organic solvent is 100, and after the non-solvent and the organic solvent are replaced and cured, placing the base membrane into an oven at 70 ℃ for drying to prepare the porous membrane, wherein SEM pictures of the porous membrane are shown in figures 13 and 14, and the polymer bonding layer in the porous membrane is relatively compact and has relatively low porosity.
Test example 1
The porous separators prepared in the test examples and comparative examples were measured for pore size, porosity, diameter and spacing of aggregation sites, thickness and areal density of the polymer porous bonding layer, and the results are shown in table 1.
The pore diameter and the porosity are tested by adopting a BET specific surface area tester under the condition of liquid nitrogen, and the average pore diameter is calculated by the following method: and selecting adsorption data according to the BET specific surface area test result, and obtaining an average pore diameter result through software by adopting a BJH function method.
The thickness of the polymer porous bonding layer is measured by adopting a diaphragm thickness gauge MahrMillimar C1216, randomly selecting five points at normal temperature and normal pressure to measure the thickness of the polymer porous bonding layer, and finally averaging to obtain the thickness of the polymer porous bonding layer by subtracting the thickness of the base film. The surface density is tested by a high-precision electronic balance instrument at normal temperature and normal pressure, and the testing method comprises the following steps: and (3) shearing a porous diaphragm with the length of 20cm and the width of 20cm, weighing, subtracting the weight of the base membrane with the same area, and dividing the difference value of the obtained weights by the area of the porous diaphragm to obtain the surface density.
TABLE 1
Figure BDA0002032569270000171
Figure BDA0002032569270000181
Test example 2
The porous separators prepared in examples and comparative examples were tested for air permeability and the results are shown in table 2.
The test method comprises the following steps: the time for 100mL of air to pass through a one-square inch area porous membrane under pressure was tested using a vent gauge model 4110N.
TABLE 2
Air permeability, sec/100mL
Example 1 192
Example 2 223
Example 3 234
Example 4 230
Example 5 246
Example 6 218
Example 7 250
Example 8 221
Example 9 253
Example 10 226
Comparative example 1 660
Comparative example 2 527
As can be seen from the results of table 2, the porous separator of the present disclosure shows better air permeability.
Test example 3
The porous separators prepared in examples and comparative examples were tested for ionic conductivity, and the results are shown in table 3.
The test method comprises the following steps: cutting a porous diaphragm into a wafer with the diameter of 17mm, drying, overlapping three layers, placing between two stainless steel electrodes, absorbing enough electrolyte (electrolyte is lithium hexafluorophosphate with the concentration of 1mol/L, organic solvent is mixed liquid obtained by mixing Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) according to the weight ratio of 1: 1: 1), sealing in a 2016 type button cell, performing an alternating current impedance experiment by adopting an electrochemical workstation (CHI 660C), wherein the frequency range of an alternating current signal is 0.01Hz to 1MHz, the potential amplitude of a sine wave is 5mV, the diameter of the stainless steel electrode is 1.58cm, and the contact area of the stainless steel plate and the porous diaphragm is 1.96cm2The thickness of the porous diaphragm is 0.00407cm, the intersection point of the linear axis and the real axis is the bulk resistance of the porous diaphragm, and the ionic conductivity of the porous diaphragm is calculated by adopting the following formula:
σ＝L/(A·R)，
wherein L represents the thickness of the porous separator, a is the contact area of the stainless steel plate and the porous separator, and R is the bulk resistance of the porous separator.
TABLE 3
Numbering Body impedance (omega) Ion conductivity (mS/cm)
Example 1 5.3 0.39
Example 2 5.5 0.38
Example 3 5.8 0.36
Example 4 5.7 0.36
Example 5 5.8 0.36
Example 6 5.4 0.39
Example 7 5.9 0.35
Example 8 5.7 0.36
Example 9 5.7 0.36
Example 10 5.8 0.36
Comparative example 1 10.1 0.21
Comparative example 2 8.9 0.23
As can be seen from table 3, the porous separator of the present disclosure shows excellent ionic conductivity.
Test example 4
The porous separators prepared in examples and comparative examples were tested for liquid absorption and the results are shown in table 4.
The test method comprises the following steps: the porous diaphragm was cut into a circular piece having a diameter of 17mm, dried, weighed, immersed in an electrolyte for 24 hours, then taken out, the liquid on the surface of the diaphragm was blotted with filter paper and the mass at that time was weighed, and the operation was carried out in a glove box filled with argon gas. The liquid absorption rate was calculated according to the following formula.
The liquid absorption (%) - (Wi-W)/WX 100%
Wherein W is the initial weight of the porous diaphragm, and Wi is the weight of the porous diaphragm after being soaked in the electrolyte for 24 hours.
TABLE 4
Imbibition rate,%
Example 1 32
Example 2 35
Example 3 30
Example 4 31
Example 5 29
Example 6 30
Example 7 28
Example 8 31
Example 9 30
Example 10 33
Comparative example 1 17
Comparative example 2 23
As can be seen from the data of table 4, the liquid absorption rate of the porous separator of the present disclosure was significantly increased compared to the comparative example.
Test example 5
The porous separators of example 1 and comparative example 1 were prepared as lithium ion batteries by the following method: in a drying room, LiCoO is added2LiCoO is prepared by winding a positive plate, a graphite negative plate and a porous diaphragm2And testing the viscosity and the peel strength of the porous diaphragm to the positive electrode and the negative electrode.
The test method comprises the following steps: dissecting the prepared lithium ion battery (subjected to 85 ℃, 4h and 1MPa hot pressing) in a full-electric state, measuring the peeling mechanical strength of the lithium ion battery by adopting a universal mechanical testing machine, and measuring the standard reference GBT 2792-2014 adhesive tape peeling strength; and the obtained positive and negative pole pieces and the diaphragm are photographed. Fig. 15 and 16 show graphs of peel strength tests of the positive and negative electrodes of the lithium ion batteries prepared in example 1 and comparative example 1, respectively. It can be seen that the porous separator of the present disclosure has higher positive electrode peel strength.
Test example 6
LiCoO was prepared as in test example 52The method for preparing the graphite soft-package polymer lithium ion battery comprises the following steps of preparing the porous diaphragms of the examples and the comparative examples into the lithium ion battery, and carrying out 25 ℃ cycle performance test on the prepared capacity-divided lithium ion battery by adopting a BK6016 type lithium ion battery performance test cabinet produced by Guangzhou Lanqi, wherein the specific method comprises the following steps: the battery is charged to 4.40V cut-off at 0.7C and 0.2C respectively; after standing for 10min, the sample was discharged to 3.0V at 0.7C or 0.2C, and the capacity retention rate was calculated according to the following formula after such cycles, and the test results are shown in Table 5.
Capacity retention (%) — capacity after cycle/initial capacity
TABLE 5
Figure BDA0002032569270000211
The results in table 5 show that the lithium ion batteries prepared using the porous separator of the present disclosure exhibit more excellent cycle performance.
Test example 7
LiCoO was prepared as in test example 52The method for preparing the graphite soft-package polymer lithium ion battery comprises the following steps of preparing the porous diaphragms of the examples and the comparative examples into the lithium ion battery, and performing 45 ℃ cycle performance test on the prepared capacity-divided lithium ion battery by adopting a BK6016 type lithium ion battery performance test cabinet produced by Guangzhou Lanqi, wherein the specific method comprises the following steps: cut off the battery charging to 4.40V at 0.7C; after standing for 10min, the solution was discharged to 3.0V at 0.7C, and the capacity retention rate was calculated by repeating the above cycles, and the results are shown in Table 6.
TABLE 6
Figure BDA0002032569270000221
The results in table 6 show that the lithium ion batteries prepared with the porous separator of the present disclosure exhibit more excellent high temperature cycling performance. It can be seen that the porous separator of the present disclosure is advantageous for improving the high temperature performance of the battery.
Test example 8
LiCoO was prepared as in test example 52The method for preparing the graphite soft-package polymer lithium ion battery comprises the following steps of preparing the porous diaphragms of the examples and the comparative examples into the lithium ion battery, and carrying out a rate discharge performance test on the prepared capacity-divided lithium ion battery by adopting a BK6016 type lithium ion battery performance test cabinet produced by Guangzhou Lanqi, wherein the specific method comprises the following steps: the cell was charged to 4.40V with a constant current and a constant voltage of 0.5C (1C-2640 mA), the cutoff current was 0.02C, left for 5min, discharged to 3.0V with 0.2C/0.5C/1C/2C/3C/4C, the discharge capacity was recorded and the capacity retention rate was calculated. The test results are shown in Table 7.
TABLE 7
Figure BDA0002032569270000231
Table 7 shows that lithium ion batteries prepared with the porous separator of the present disclosure exhibit good rate discharge performance.
The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (21)

1. A porous diaphragm is characterized by comprising a polyolefin base film and a polymer porous bonding layer coated on the surface of the polyolefin base film, wherein the polymer porous bonding layer is of a multi-layer silk-screen-shaped interweaved structure, has holes with the average pore diameter of 0.2-10 mu m, and has the porosity of 60-95%;
the polymer in the polymer porous bonding layer is polyvinylidene fluoride homopolymer and/or polyvinylidene fluoride-hexafluoropropylene copolymer;
the polymer porous bonding layer contains a plurality of gathering points, and the polymer porous bonding layer takes the gathering points as the center to present a radial silk screen interweaving structure;
the distance between two adjacent gathering points is 300-10000 nm; the diameter of the gathering point is 10-10000 nm.
2. The porous separator according to claim 1, wherein the porous separator has an air permeability of 100 to 500sec/100 mL.
3. The porous separator according to claim 1, wherein the polymer porous bonding layer has a thickness of 0.1 to 5 μm and an areal density of 0.2 to 6g/m2。
4. The porous separator according to claim 3, wherein the thickness of the polymer porous bonding layer is 0.3 to 3 μm.
5. The porous separator according to claim 3, wherein the areal density of the polymeric porous bonding layer is 0.3 to 3.5g/m2。
6. The porous separator according to claim 1, wherein one or both surfaces of the polyolefin-based film have a submicron ceramic coating layer of at least one material selected from the group consisting of alumina, silica, calcia, magnesia, chromia, titania, zinc oxide, calcia, alumina hydroxide, magnesium hydroxide, silicon carbide, barium sulfate, zeolite, and boehmite.
7. The porous separator of claim 6, wherein the particle size of the material of the sub-micron ceramic coating is 100nm to 1 μm.
8. The porous separator according to claim 7, wherein the particle size of the material of the sub-micron ceramic coating is 100 to 500 nm.
9. A method of preparing a porous separator according to any one of claims 1 to 8, comprising the steps of:
a. obtaining a slurry comprising a polymer and an organic solvent;
b. coating the slurry in the step a on a polyolefin base film to obtain the polyolefin base film coated with the slurry;
c. b, spraying the base film with the slurry in the step b by using a non-solvent so as to enable the non-solvent and the organic solvent to mutually diffuse to obtain a base film after the solvent is diffused;
d. drying the base film after the solvent is diffused in the step c;
the polymer is polyvinylidene fluoride homopolymer and/or polyvinylidene fluoride-hexafluoropropylene copolymer.
10. The method according to claim 9, wherein in step a, the weight ratio of the polymer to the organic solvent is 1: (5-50);
the organic solvent is at least one selected from N, N-dimethylformamide, tetrahydrofuran, methyl ethyl ketone, tetramethylurea, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, triethyl phosphate, ethylene glycol ethyl ether, ethylene glycol ether ester, N-butyl acetate, cyclohexanone, diacetic acid, diisobutyl ketone, ethyl acetoacetate, butyrolactone, propylene carbonate and dimethyl phthalate.
11. The method according to claim 10, wherein in step a, the organic solvent is N-methylpyrrolidone and/or dimethyl sulfoxide, and the weight ratio of the polymer to the organic solvent is 1: (10-50); or,
the organic solvent is N, N-dimethylformamide, N-dimethylacetamide or triethyl phosphate, or a combination of two or three of the N, N-dimethylformamide, the N, N-dimethylacetamide and the triethyl phosphate, and the weight ratio of the polymer to the organic solvent is 1: (15-40).
12. The method as claimed in claim 9, wherein the slurry further comprises an additive including an organic additive and/or an inorganic additive in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the slurry in step a.
13. The method according to claim 12, wherein the organic additive is at least one selected from the group consisting of polyvinyl alcohol, polybutylmethacrylate, polymethylmethacrylate, polyvinyl acetate, polyethylene oxide, polyethylene glycol, polypropylene oxide, polyethylene oxide-polypropylene oxide block copolymer, polyvinyl chloride, polycarbonate, and polyethylene oxide-alkanol copolymer; based on 100 parts by weight of the slurry, the amount of the organic additive is 0.1-10 parts by weight;
the inorganic additive is at least one selected from aluminum oxide, silicon oxide, calcium oxide, magnesium oxide, chromium oxide, titanium oxide, zinc oxide, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, barium sulfate, zeolite and boehmite, and the particle size of the inorganic additive is 100 nm-2 mu m; the inorganic additive is used in an amount of 0.5 to 40 parts by weight based on 100 parts by weight of the slurry.
14. The method of claim 13, wherein the inorganic additive has a particle size of 200nm to 1 μm.
15. The method of claim 9, wherein in step c, the non-solvent comprises at least one of water, an alcohol, and a ketone;
the weight ratio of the non-solvent to the organic solvent is (1-100): 1;
the spraying conditions include: the temperature of the non-solvent is 0-100 ℃; the spraying time is 10-3000 seconds.
16. The method according to claim 15, wherein the temperature of the non-solvent is 20 to 80 ℃.
17. The method according to claim 15, wherein the time of spraying is 30-300 seconds.
18. The method according to any one of claims 15 to 17, wherein the alcohol is at least one selected from the group consisting of ethanol, ethylene glycol, methanol, propanol, glycerol, n-butanol, isobutanol, and benzyl alcohol; the ketone is at least one selected from acetone, butanone, 2-pentanone, methyl isobutyl ketone and cyclohexanone.
19. The method according to claim 9, wherein in the step d, the temperature for drying is 20-150 ℃.
20. The method according to claim 19, wherein the temperature of the drying in step d is 50-120 ℃.
21. A lithium ion battery comprising the porous separator according to any one of claims 1 to 8.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102770984A (en) * 2010-02-25 2012-11-07 株式会社Lg化学 Manufacturing method for separator, separator made therefrom, and manufacturing method for electrochemical device containing same
CN103107301A (en) * 2013-01-17 2013-05-15 中国科学院金属研究所 Novel lithium ion battery diaphragm with inorganic coating and preparation method thereof
CN103687675A (en) * 2011-07-28 2014-03-26 住友化学株式会社 Method for manufacturing laminated porous film
CN108565379A (en) * 2018-03-19 2018-09-21 上海恩捷新材料科技股份有限公司 A kind of lithium battery diaphragm and preparation method thereof

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2741345B1 (en) * 2006-04-28 2017-09-13 LG Chem, Ltd. Separator for battery with gel polymer layer
KR101173201B1 (en) * 2010-02-25 2012-08-13 주식회사 엘지화학 Preparation method of separator, separator formed therefrom, and preparation method of electrochemical device containing the same
JP5670811B2 (en) * 2011-04-08 2015-02-18 帝人株式会社 Nonaqueous secondary battery separator and nonaqueous secondary battery
CN102617881B (en) * 2012-04-10 2013-07-17 中南大学 Preparation method of porous gel polymer lithium ion battery diaphragm
CN103113607B (en) * 2013-01-21 2015-02-04 青岛中科华联新材料有限公司 Preparation method of microporous polymer diaphragm with high-temperature self-enhancing mechanism
KR101841809B1 (en) * 2014-10-31 2018-03-23 주식회사 엘지화학 Electrode-adhesive layer composite, method of producing the same, and secondary battery comprising the same
CN104505484B (en) * 2014-12-16 2017-12-22 东莞新能源科技有限公司 A kind of organo-mineral complexing dielectric film, its preparation method and application
KR102225305B1 (en) * 2015-09-25 2021-03-10 주식회사 엘지화학 Method of Manufacturing Separator Having Inorganic Coating Layer Using Phase Separation
KR102228625B1 (en) * 2015-12-10 2021-03-15 주식회사 엘지화학 Porous separator for electric device and preparation method thereof
CN107799703A (en) * 2016-08-29 2018-03-13 比亚迪股份有限公司 A kind of composite membrane of polymer and preparation method thereof and the lithium ion battery for including it
CN107785520A (en) * 2016-08-29 2018-03-09 比亚迪股份有限公司 A kind of ceramic diaphragm and lithium ion battery and preparation method thereof
CN106784526B (en) * 2016-12-21 2019-08-09 浙江南都电源动力股份有限公司 A kind of ceramic coating membrane and preparation method thereof as lithium ion battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102770984A (en) * 2010-02-25 2012-11-07 株式会社Lg化学 Manufacturing method for separator, separator made therefrom, and manufacturing method for electrochemical device containing same
CN103687675A (en) * 2011-07-28 2014-03-26 住友化学株式会社 Method for manufacturing laminated porous film
CN103107301A (en) * 2013-01-17 2013-05-15 中国科学院金属研究所 Novel lithium ion battery diaphragm with inorganic coating and preparation method thereof
CN108565379A (en) * 2018-03-19 2018-09-21 上海恩捷新材料科技股份有限公司 A kind of lithium battery diaphragm and preparation method thereof

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