CN115395176A - Diaphragm and preparation method and application thereof - Google Patents
Diaphragm and preparation method and application thereof Download PDFInfo
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- CN115395176A CN115395176A CN202211214878.6A CN202211214878A CN115395176A CN 115395176 A CN115395176 A CN 115395176A CN 202211214878 A CN202211214878 A CN 202211214878A CN 115395176 A CN115395176 A CN 115395176A
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- 238000002360 preparation method Methods 0.000 title abstract description 22
- 239000000758 substrate Substances 0.000 claims abstract description 69
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims abstract description 41
- 239000004926 polymethyl methacrylate Substances 0.000 claims abstract description 41
- -1 polyethylene terephthalate Polymers 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims abstract description 18
- 239000004642 Polyimide Substances 0.000 claims abstract description 16
- 229920001721 polyimide Polymers 0.000 claims abstract description 16
- 229920000139 polyethylene terephthalate Polymers 0.000 claims abstract description 15
- 239000005020 polyethylene terephthalate Substances 0.000 claims abstract description 15
- 239000004696 Poly ether ether ketone Substances 0.000 claims abstract description 14
- 229920002530 polyetherether ketone Polymers 0.000 claims abstract description 14
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 2
- 229910001416 lithium ion Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
-
- 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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
- H01M50/461—Separators, membranes or diaphragms characterised by their combination with electrodes with adhesive layers between electrodes and separators
-
- 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
- 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
Abstract
The invention relates to a diaphragm and a preparation method and application thereof, wherein the diaphragm comprises a substrate and polymethyl methacrylate layers arranged on two sides of the substrate; the material of the substrate comprises any one or the combination of at least two of polyimide, polyethylene terephthalate or polyether ether ketone. The diaphragm has high porosity, good air permeability, high film breaking temperature and low thermal shrinkage; the adhesive force with the pole piece is high; the further formed battery has excellent cycle performance, rate performance and safety performance.
Description
Technical Field
The invention relates to the technical field of diaphragms, in particular to a diaphragm and a preparation method and application thereof.
Background
At present, there is a great demand for a composite separator having high safety.
CN113054324A discloses a high-safety diaphragm and a battery, wherein the diaphragm comprises a porous base material, a heat-resistant coating coated on at least one side of the porous base material, and a low-closed-cell-temperature coating coated on the porous base material or the heat-resistant coating; the heat-resistant coating comprises a heat-resistant resin; the low closed cell temperature coating comprises a self-closing cell material; the self-closing pore material comprises an adhesive self-closing resin with a low melting temperature or a low viscous flow temperature. The film breaking temperature and the heat-resistant shrinkage performance of the diaphragm are improved by arranging the heat-resistant coating, meanwhile, the low-closed-hole-temperature coating is introduced, the cohesive self-closing resin with low melting temperature or low viscous flow temperature can be quickly melted or softened at a certain temperature, the pores of the porous base film are closed, the purpose of reducing the closed hole temperature is achieved, the difference value of the closed hole temperature and the film breaking temperature is improved, the high-safety diaphragm is obtained, and the safety of the battery is enhanced.
CN106299215a discloses three microporous structure battery separators, which discloses a separator comprising a first outer layer, a second outer layer and an inner layer sandwiched therebetween, the first outer layer, the second outer layer and the inner layer having different microporous structures. The disclosed battery diaphragm with three microporous structures has multiple physical and chemical properties, is good in comprehensive performance, has high puncture strength and tensile strength while achieving lower thickness, can be applied to smaller batteries, and is not easy to damage in the installation process; meanwhile, the air permeability and porosity are good, the internal resistance is small, and the capacity and the cycle performance of the battery are improved; in addition, the composite material also has low closed pore temperature and membrane breaking temperature, and is high in safety.
However, in order to improve the long-term cycle performance and safety of the battery core, and simultaneously achieve a good interface of the high specific energy battery and improve the energy density of the battery, the development of a high-porosity, high-film-breaking and high-adhesion safety composite diaphragm is required.
In conclusion, it is important to develop a safety separator having high air permeability, high rupture strength and high adhesion.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a diaphragm, a preparation method and application thereof, wherein the diaphragm has the characteristics of high air permeability, high diaphragm rupture and high adhesion, and is high in safety.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a separator including a substrate and polymethyl methacrylate layers disposed on both sides of the substrate;
the material of the substrate includes any one or a combination of at least two of polyimide, polyethylene terephthalate, or polyetheretherketone, wherein typical but non-limiting combinations include: combinations of polyimide and polyethylene terephthalate, polyethylene terephthalate and polyetheretherketone, polyimide, polyethylene terephthalate and polyetheretherketone, and the like.
In the invention, the polymethyl methacrylate layers are arranged on the two sides of the substrate, the polymethyl methacrylate has the advantages of small particle size and light weight, the formed polymethyl methacrylate layer has excellent adhesion to the pole piece when in application, the pole piece is not easy to deform in the long-term use process, the isolating membrane is not easy to shrink, and the problem of internal short circuit can be prevented; the battery has high integral hardness and firm interlayer bonding, and reduces the risk of fire and explosion when the battery is subjected to safety such as mechanical impact, environmental thermal impact, overcharge and overdischarge. In addition, the substrates have the characteristics of high-temperature melting and high porosity, the formed diaphragm has good air permeability and high diaphragm breaking temperature, for example, polyimide (PI) is thermally decomposed at 600 ℃ and is not melted, polyethylene terephthalate (PET) can work for a long time at 210 ℃, and polyether ether ketone (PEEK) has low thermal shrinkage at 370 ℃, so that the preparation of the diaphragm with high diaphragm breaking safety and low thermal shrinkage can be realized, the safety of the battery is greatly improved, and the occurrence of thermal runaway is prevented.
In the present invention, the substrate includes a polyimide layer, a polyethylene terephthalate layer, or a polyetheretherketone layer.
In the invention, the polyimide in the polyimide layer is a main material, other materials can be mixed in the layer, and the polyethylene terephthalate layer and the polyether ether ketone layer are the same.
Preferably, the thickness of the polymethylmethacrylate layer is each independently 1-4 μm, such as 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, and the like.
Preferably, the substrate has a thickness of 5-15 μm, such as 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, and the like.
In the invention, the polymethyl methacrylate layer and the substrate are both thinner, the formed diaphragm has small integral thickness and light weight, and the specific energy of the battery can be improved.
Preferably, the porosity of the substrate is 40% -60%, such as 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, etc.
Preferably, the membrane breaking temperature of the separator is 160-500 ℃, such as 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃ and the like.
Preferably, the adhesion of the membrane to the pole piece is 10-20N/m, such as 12N/m, 14N/m, 16N/m, 18N/m, and the like.
In a second aspect, the present invention provides a method for producing the separator of the first aspect, the method comprising the steps of:
and coating polymethyl methacrylate on the surface of the substrate to form polymethyl methacrylate layers arranged on two sides of the substrate, thereby obtaining the diaphragm.
Preferably, the manner of coating comprises spot coating.
In the invention, the coating mode is preferably point-shaped coating, and compared with other coating methods, the method has the advantages of thinner coating film, better consistency and better air permeability.
Preferably, the temperature of the coating is 0-100 ℃, such as 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ and the like.
Preferably, the unreeling tension of the coating is 0.01-100N, such as 1N, 5N, 10N, 20N, 40N, 60N, 80N, etc.
Preferably, the winding tension of the coating is 0-100N and is not equal to 0N, such as 1N, 5N, 10N, 20N, 40N, 60N, 80N, etc.
Preferably, the coating is applied at a draw speed of 0.01 to 80m/min, such as 1m/min, 5m/min, 10m/min, 20m/min, 30m/min, 40m/min, 50m/min, 60m/min, 70m/min, etc., to the substrate.
Preferably, the contact pressure of the coating is 0.01-30N, such as 1N, 5N, 10N, 15N, 20N, 25N, and the like.
Preferably, the coating further comprises drying.
Preferably, the drying temperature is 50-70 deg.C, such as 52 deg.C, 54 deg.C, 56 deg.C, 58 deg.C, 60 deg.C, 62 deg.C, 64 deg.C, 66 deg.C, 68 deg.C, etc.
Preferably, the polymethyl methacrylate is coated at a density of 0.1 to 2g/m 2 For example 0.2g/m 2 、0.4g/m 2 、0.6g/m 2 、0.8g/m 2 、1g/m 2 、1.2g/m 2 、1.4g/m 2 、1.6g/m 2 、1.8g/m 2 And the like.
Preferably, when the material of the substrate comprises polyimide and/or polyether ether ketone, the preparation method of the substrate comprises electrostatic spinning.
Preferably, when the material of the substrate comprises polyethylene terephthalate, the preparation method of the substrate comprises hot pressing.
Preferably, the temperature of the hot pressing is 30 to 300 ℃, for example, 50 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃ and the like, and more preferably 100 to 150 ℃.
As a preferable technical scheme, the preparation method comprises the following steps:
the coating density on the surface of the substrate is 0.1-2g/m by means of point coating 2 The polymethyl methacrylate is prepared by controlling the coating temperature to be 0-100 ℃, the unreeling tension of coating to be 0.01-100N, the reeling tension of coating to be 0-100N and not equal to 0N, the stretching speed to the substrate to be 0.01-80m/min and the contact pressure to be 0.01-30N, and drying at 50-70 ℃ after coating to form polymethyl methacrylate layers arranged on two sides of the substrate.
In a third aspect, the present invention provides a lithium ion battery, which includes the separator of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) The diaphragm disclosed by the invention is high in porosity, good in air permeability, high in film breaking temperature and low in thermal shrinkage; the adhesive force with the pole piece is high; the further formed battery has excellent cycle performance, rate performance and safety performance.
(2) The air permeability of the diaphragm is below 240s/100mL, the diaphragm breaking temperature is above 210 ℃, the longitudinal (MD) heat shrinkage rate is within 4.0%, and the Transverse (TD) heat shrinkage rate is within 3.0%; the adhesion of the diaphragm to the pole piece is between 84 and 105N/m; the capacity retention rate of a battery formed by the diaphragm after 2000 cycles is more than 76%, and the capacity retention rate under 2C multiplying power is more than 81%; the diaphragm has good air permeability, high film breaking temperature and low thermal shrinkage; the adhesive force with the pole piece is high; the further formed battery has excellent cycle performance, rate performance and safety performance.
Drawings
FIG. 1 is a schematic view of the structure of a separator described in example 1;
wherein, 1-a substrate; a 2-polymethylmethacrylate layer.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
Example 1
The present embodiment provides a diaphragm, a schematic structural diagram of which is shown in fig. 1, where the diaphragm includes a substrate 1 and polymethyl methacrylate layers 2 disposed on two sides of the substrate;
substrate: the polyimide layer is made of polyimide, purchased from DuPont Dow and sold under the trademark of CP-8002; the thickness is 10 μm; the porosity is 40%;
polymethyl methacrylate layer: the material is polymethyl methacrylate, which is purchased from inhabitants and has the brand number of LG35; the thickness was 3 μm.
The diaphragm is prepared by the following preparation method, and the preparation method comprises the following steps:
(1) Preparation of the substrate: under the action of a high-voltage electric field, the polyimide melt is stretched into superfine fibers at the conical top of the Taylor capillary under the action of the electric field force, the electric field strength is controlled to be 10V/m, and the viscosity of the melt is 1000pcs; the diameter of the nozzle is 5 μm;
(2) Preparing a diaphragm: the coating density on the surface of the substrate is 1g/m by means of point coating 2 The polymethyl methacrylate is obtained by controlling the coating temperature to be 50 ℃, the coating unwinding tension to be 60N, the coating winding tension to be 70N, the stretching speed to the substrate to be 50m/min and the contact pressure to be 15N, and drying at 60 ℃ after coating to form polymethyl methacrylate layers arranged on two sides of the substrate.
Example 2
The embodiment provides a diaphragm, which comprises a substrate and polymethyl methacrylate layers arranged on two sides of the substrate;
substrate: the polyethylene terephthalate layer is made of polyethylene terephthalate, is purchased from Jiangyin industry and has the brand of CZ-318; the thickness is 10 μm; the porosity is 50%;
polymethyl methacrylate layer: the material is polymethyl methacrylate, japanese Sumitomo, and the brand is LG35; the thicknesses of both sides were 4 μm and 2 μm, respectively.
The diaphragm is prepared by the following preparation method, and the preparation method comprises the following steps:
(1) Preparation of the substrate: hot-pressing polyethylene terephthalate at 130 ℃ to form a substrate;
(2) Preparing a diaphragm: the coating density on the surface of the substrate is 2g/m by means of point coating 2 The coating temperature is controlled to be 100 ℃, the coating unwinding tension is 100N, the coating winding tension is 100N, the substrate drawing speed is 80m/min, the contact pressure is 30N, and after coating, drying is carried out at 70 ℃ to form polymethyl methacrylate layers arranged on two sides of the substrate, so that the diaphragm is obtained.
Example 3
The embodiment provides a diaphragm, which comprises a substrate and polymethyl methacrylate layers arranged on two sides of the substrate;
substrate: the polyether-ether-ketone layer is made of polyether-ether-ketone, is purchased from high polymer materials GmbH of Mitsui province, and has the brand number of cf30; the thickness is 5 μm; the porosity is 48%;
polymethyl methacrylate layer: the material is polymethyl methacrylate, which is purchased from inhabitants and has the brand number of LG35; the thickness was 4 μm.
The diaphragm is prepared by the following preparation method, and the preparation method comprises the following steps:
(1) Preparation of the substrate: under the action of a high-voltage electric field, the polyether-ether-ketone melt is stretched into superfine fibers at the conical top of the Taylor capillary under the action of the electric field force, the electric field strength is controlled to be 5V/m, and the viscosity of the melt is controlled to be 200pcs; the diameter of the nozzle was 0.9. Mu.m.
(2) Preparing a diaphragm: the coating density on the surface of the substrate by the way of spot coating is 1.5g/m 2 The polymethyl methacrylate is obtained by controlling the coating temperature to be 50 ℃, the coating unwinding tension to be 10N, the coating winding tension to be 10N, the stretching speed to the substrate to be 5m/min and the contact pressure to be 10N, and drying at 50 ℃ after coating to form polymethyl methacrylate layers arranged on two sides of the substrate.
Examples 4 to 7
Examples 4 to 7 are different from example 1 in that the coating densities of the polymethyl methacrylate are 0.1g/m, respectively 2 Example 4, 2g/m 2 Example 5, 0.05g/m 2 Example 6 and 2.2g/m 2 (example 7), the rest is the same as example 1.
Example 8
The difference between this example and example 1 is that the coating method is spraying, and the rest is the same as example 1.
Comparative example 1
This comparative example differs from example 1 in that the substrate was replaced with polyimide in the same thickness polyethylene (available from dow chemical under the trade designation 5220G) and the rest was the same as example 1.
Comparative example 2
The embodiment provides a diaphragm, which comprises a substrate and polymethyl methacrylate layers arranged on two sides of the substrate;
substrate: the polyethylene diaphragm is made of polypropylene and polyethylene, is purchased from maotai petrochemical, and has the brand number of EPS30R, the polyethylene diaphragm is purchased from maotai petrochemical, the total thickness of the PP/PE/PP diaphragms (purchased from Zhuhaienjie) is 5 mu m, and the thicknesses of the polyethylene layer and the polypropylene layers at two sides are the same; the porosity is 60%;
polymethyl methacrylate layer: the material is polymethyl methacrylate, which is purchased from inhabitants and has the brand number of LG35; the thickness was 1 μm.
The diaphragm is prepared by the following preparation method, and the preparation method comprises the following steps:
(1) Preparation of the substrate: preparing three layers of polypropylene which are arranged in a laminated manner by adopting a three-layer co-extrusion processing technology to form a substrate;
(2) Preparing a diaphragm: and (2) coating polymethyl methacrylate with the density of 1g/m & lt 2 & gt on the surface of the substrate in a dot coating mode, controlling the coating temperature to be 40 ℃, the unwinding tension of coating to be 20N, the winding tension of coating to be 60N, the stretching speed to the substrate to be 0.8m/min and the contact pressure to be 5N, and drying at 55 ℃ after coating to form polymethyl methacrylate layers arranged on two sides of the substrate to obtain the diaphragm.
Comparative example 3
This comparative example differs from comparative example 2 in that the substrate was replaced with a monolayer polypropylene of equal thickness, the remainder being the same as comparative example 2.
Performance testing
1. The separators described in examples 1 to 8 and comparative examples 1 to 3 were subjected to the following tests:
(1) Air permeability: 3 diaphragms are cut on the diaphragm roll at intervals of 150mm along the longitudinal direction, if the width of the diaphragm is larger than or equal to 100mm, the size of a sample is 100mm 100mm, and if the width of the diaphragm is smaller than 100mm, the size of the sample is 100mm multiplied by the width of the diaphragm. And (3) placing the diaphragm in a testing head of a ventilation instrument with a proper testing range for air permeability testing, and taking the average value of the 3 times of testing results as the air permeability of the diaphragm.
(2) Film breaking temperature: and heating the diaphragm at a set heating speed by adopting a heating resistance method, and synchronously measuring the temperature and the resistance of the diaphragm to form a temperature vs resistance relation curve. The temperature when the resistance suddenly rises is the closed pore temperature of the diaphragm, and the temperature when the resistance suddenly drops to the bottom is the film breaking temperature. The test has good repeatability, can quantitatively represent the phenomenon of closed-cell membrane rupture, and perfectly accords with the subsequent performance parameters and evaluation of the battery due to the measurement of the resistance and the temperature.
(3) Heat shrinkability: placing a stainless steel plate and two pieces of quantitative filter paper in the middle position (near the position of a temperature probe) of an oven, and controlling the temperature to enable the stainless steel plate and the filter paper to reach (150 +/-1) DEG C or (130 +/-1) DEG C. Marking the longitudinal direction and the transverse direction of the diaphragm, respectively measuring the longitudinal length and the transverse length of a test sample by using a length measuring instrument with corresponding resolution according to actual requirements, flatly placing the diaphragm on one quantitative filter paper on a stainless steel plate in the middle of the blast type constant temperature box, stacking no more than 10 diaphragms at most, pressing by using the other quantitative filter paper after the completion, placing a pressing block in the middle of the filter paper, closing the door of the constant temperature box, starting to calculate the time, and keeping the time for 2 hours at the temperature of 150 ℃ or 1 hour at the temperature of 130 ℃.
2. The separators in examples 1-8 and comparative examples 1-3 are made into soft-package batteries, wherein the preparation method of the soft-package batteries comprises the following steps: mixing 98% by mass of graphite, CMC and SBR to prepare a negative electrode slurry, mixing 99.2% by mass of sodium ferric manganate, PVDF and a conductive agent SP to prepare a positive electrode slurry, coating the prepared positive and negative electrode slurry on positive and negative current collectors, drying and welding lugs to obtain positive and negative electrode plates, and isolating the positive and negative electrode plates by winding the diaphragm into an electric core body; then, performing short circuit evaluation on the electric core body, and screening high-quality electric cores; then the materials are put into a battery shell, a battery cover is covered, and the opening is sealed by welding; and injecting electrolyte into the battery case, forming, sealing for the second time, baking by using the clamp and grading the volume to obtain the finished product of the soft package battery.
The pouch cell was tested as follows:
(1) Adhesion to the pole piece: adjusting the testing parameters of a tensile machine, wherein the testing speed is 5 +/-0.5 mm/min, the peeling length is 100 +/-10 mm, the clamp spacing is 40 +/-5 mm, the testing width is 30mm, and the front end and the tail end are 25 percent (25 mm) removed. After adjusting the parameters, the lower chuck clamps the end of the support body which is not adhered with the double-sided adhesive tape, and the upper chuck clamps the test adhesive tape. The samples were clamped with care taken to be vertical. The test is started. And reading the average peel strength value of the interface after the test is finished as the peel strength value of the sample. The average value of 3 samples is taken as the peel strength of the sample;
(2) Cycle performance: the battery cell is charged and discharged for 2000 circles in 1C current and voltage of 2.75-4.2V;
(3) Rate capability: the battery cell is charged and discharged at the rate of 2C, and the voltage is 2.75-4.2V;
(4) Safety: and (3) needle punching test: a high temperature resistant steel needle with the diameter of phi 3mm, wherein the conical angle of the needle tip is 45-60 degrees;
and (3) hot box testing: 150 ℃ for 30min, and heating from room temperature to 150 +/-2 ℃ at the speed of 5 ℃/min.
The test results are summarized in tables 1 and 2.
TABLE 1
TABLE 2
As can be seen from the analysis of the data in tables 1 and 2, the air permeability of the separator of the present invention is 240s/100mL or less, the rupture temperature is 210 ℃ or higher, the heat shrinkage in the Machine Direction (MD) is 4.0% or less, and the heat shrinkage in the Transverse Direction (TD) is 3.0% or less; the adhesion of the diaphragm to the pole piece is between 84 and 105N/m; the capacity retention rate of a battery formed by the diaphragm after 2000 cycles is more than 76%, and the capacity retention rate under 2C multiplying power is more than 81%; the diaphragm has good air permeability, high film breaking temperature and low thermal shrinkage; the adhesive force with the pole piece is high; the further formed battery has excellent cycle performance, rate performance and safety performance.
As can be seen from the analysis of comparative examples 1 to 3 and example 1, comparative examples 1 to 3 were inferior in performance to example 1, and the performance of the separator according to the present invention was confirmed to be superior.
As can be seen from the analysis of examples 4 to 7, examples 6 to 7 are inferior in performance to examples 4 to 5, and it was confirmed that the coating density of polymethyl methacrylate is 0.1 to 2.0g/m 2 The resulting separator has better performance.
As can be seen from the analysis of example 8 and example 1, example 8 is inferior in performance to example 1, and the performance of the separator formed by dot coating is better.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A diaphragm is characterized by comprising a substrate and polymethyl methacrylate layers arranged on two sides of the substrate;
the material of the substrate comprises any one or the combination of at least two of polyimide, polyethylene terephthalate or polyether ether ketone.
2. The separator according to claim 1, wherein the thickness of the polymethylmethacrylate layer is each independently 1-4 μ ι η;
preferably, the substrate has a thickness of 5-15 μm.
3. Separator according to claim 1 or 2, wherein the porosity of the substrate is 40-60%;
preferably, the membrane breaking temperature of the membrane is 160-500 ℃;
preferably, the adhesion of the membrane to the pole piece is 10-20N/m.
4. A method for preparing a separator as claimed in any one of claims 1 to 3, comprising the steps of:
and coating polymethyl methacrylate on the surface of the substrate to form polymethyl methacrylate layers arranged on two sides of the substrate, thereby obtaining the diaphragm.
5. The method according to claim 4, wherein the coating comprises dot coating;
preferably, the temperature of the coating is 0-100 ℃;
preferably, the unreeling tension of the coating is 0.01-100N;
preferably, the winding tension of the coating is 0-100N and is not equal to 0N;
preferably, the stretching speed of the substrate during coating is 0.01-80m/min;
preferably, the contact pressure of the coating is 0.01 to 30N;
preferably, the coating further comprises drying;
preferably, the temperature of the drying is 50-70 ℃;
preferably, the polymethyl methacrylate is coated at a density of 0.1 to 2g/m 2 。
6. The method according to claim 4 or 5, wherein when the material of the substrate comprises polyimide and/or polyetheretherketone, the method comprises electrospinning.
7. The method according to any one of claims 4 to 6, wherein when the material of the substrate comprises polyethylene terephthalate, the method for producing the substrate comprises hot pressing.
8. The method of claim 7, wherein the hot pressing temperature is 30 to 300 ℃.
9. The method according to any one of claims 4 to 8, characterized by comprising the steps of:
the coating density on the surface of the substrate is 0.1-2g/m by means of point coating 2 The polymethyl methacrylate is prepared by controlling the coating temperature to be 0-100 ℃, the unreeling tension of coating to be 0.01-100N, the reeling tension of coating to be 0-100N and not equal to 0N, the stretching speed to the substrate to be 0.01-80m/min and the contact pressure to be 0.01-30N, and drying at 50-70 ℃ after coating to form polymethyl methacrylate layers arranged on two sides of the substrate.
10. A lithium ion battery comprising the separator according to any one of claims 1 to 3.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104600233A (en) * | 2015-02-04 | 2015-05-06 | 厦门大学 | Thermal shutdown composite diaphragm and application thereof |
| CN106784990A (en) * | 2016-12-02 | 2017-05-31 | 国联汽车动力电池研究院有限责任公司 | A kind of long circulating nonaqueous electrolyte battery and preparation method thereof |
| CN113964453A (en) * | 2021-10-19 | 2022-01-21 | 远景动力技术(江苏)有限公司 | Composite diaphragm and preparation method and application thereof |
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2022
- 2022-09-30 CN CN202211214878.6A patent/CN115395176A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104600233A (en) * | 2015-02-04 | 2015-05-06 | 厦门大学 | Thermal shutdown composite diaphragm and application thereof |
| CN106784990A (en) * | 2016-12-02 | 2017-05-31 | 国联汽车动力电池研究院有限责任公司 | A kind of long circulating nonaqueous electrolyte battery and preparation method thereof |
| CN113964453A (en) * | 2021-10-19 | 2022-01-21 | 远景动力技术(江苏)有限公司 | Composite diaphragm and preparation method and application thereof |
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