CN117855746A - Battery separator and secondary battery - Google Patents
Battery separator and secondary battery Download PDFInfo
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- CN117855746A CN117855746A CN202311745413.8A CN202311745413A CN117855746A CN 117855746 A CN117855746 A CN 117855746A CN 202311745413 A CN202311745413 A CN 202311745413A CN 117855746 A CN117855746 A CN 117855746A
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- 239000011148 porous material Substances 0.000 abstract description 4
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
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Classifications
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- 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 provides a battery diaphragm and a secondary battery; the battery diaphragm comprises a porous substrate and a porous coating, wherein the porous coating is at least arranged on one side surface of the porous substrate, and the porous coating comprises ceramic particles, temperature-sensitive polymer microspheres and an adhesive; the air permeability value of the battery separator is more than or equal to 1500 s/100ml under the condition of baking at 130 ℃ for 2 min. According to the battery diaphragm disclosed by the application, the porous coating with the temperature-sensitive polymer microspheres is arranged on the surface, so that the battery diaphragm has a higher ventilation value under the conditions of being baked for 2min at 130 ℃, and therefore, the battery diaphragm can be endowed with lower shutdown temperature and higher closed pore rate, and the battery diaphragm has better safety when used for a secondary battery.
Description
Technical Field
The invention relates to the field of secondary batteries, in particular to a battery diaphragm and a secondary battery.
Background
In recent years, with the development of secondary batteries, battery separators have received widespread attention.
Among them, the battery separator is an important component of the battery cell in the secondary battery. With the development and application of Lithium Ion Batteries (LIBs) having high energy density, safety issues are becoming a major concern. In many safety accidents, internal short circuits are a major cause of thermal runaway of lithium ion batteries. Since direct contact between the cathode with high oxidizing property and the anode with high reducing property causes instantaneous release of a large amount of heat, the internal temperature rises sharply, and a series of exothermic reactions are initiated. These reactions generate large amounts of heat and gas, resulting in sudden increases in internal pressure and temperature, leading to thermal runaway, and ultimately to rupture, firing, or even explosion of the cell.
The PP/PE/PP battery separator with thermal response can close the micropores by melting the PE layer at around 135 ℃. However, the melting temperature of the PP layer is 165 ℃, and the melting temperature difference of PE and PP is small (30 ℃), so small temperature difference can cause melting shrinkage of the PP layer due to thermal inertia while closing the cell separator, thereby causing lib internal short circuit. The above problems are technical problems to be solved in the art.
Disclosure of Invention
The invention mainly solves the technical problem of providing a battery diaphragm with a function of shutting down micropores of a battery diaphragm substrate at low temperature and the battery diaphragm.
According to a first aspect, the present application provides a battery separator comprising a porous substrate; and
the porous coating is arranged on at least one side surface of the porous substrate, and comprises ceramic particles, temperature-sensitive polymer microspheres and an adhesive;
the air permeability value of the battery separator is more than or equal to 1500 s/100ml under the condition of baking at 130 ℃ for 2 min.
In an alternative embodiment, the cell membrane has a ventilation value of 1500 s/100ml-10000 s/100ml under conditions of baking at 130 ℃ for 2 min;
optionally, the cell separator has a gas permeation value of 2500 s/100ml to 5000 s/100ml under conditions of baking at 130 ℃ for 2 min.
In an alternative embodiment, the bonding strength of the battery separator and the pole piece is greater than or equal to 1.5N/m under the conditions of 25 ℃ and 2MPa cold pressing for 10 s;
alternatively, the bonding strength of the battery separator and the pole piece is 1.5N/m-21.1N/m under the condition of 25 ℃ and 2MPa cold pressing for 10 s.
In an alternative embodiment, the temperature sensitive polymeric microspheres have a melting point of 80 ℃ to 130 ℃, optionally 80 ℃ to 120 ℃.
In an alternative embodiment, the average particle size D50 of the temperature sensitive polymer microspheres is 200 nm to 1000 nm;
optionally, the average particle diameter D50 of the thermosensitive polymer microsphere is 250 nm-600 nm.
In an alternative embodiment, the temperature sensitive polymeric microspheres satisfy at least one of conditions (1) and (2):
(1) The temperature-sensitive polymer microsphere comprises at least one of polyoxyethylene and derivatives thereof, polyethylene, polymethyl methacrylate and ethylene-vinyl acetate copolymer;
(2) In the porous coating, the mass percentage of the temperature-sensitive polymer microsphere is 20% -90%, and 25% -75% can be selected.
In an alternative embodiment, the ceramic particles satisfy at least one of the conditions (1) to (3):
(1) The average particle diameter D50 of the ceramic particles is 100 nm-1000 nm, and is optionally 250 nm-600 nm;
(2) The ceramic particles comprise at least one of silica, aluminum oxide, boehmite, and silicon carbide particles;
(3) In the porous coating, the mass percentage of the ceramic particles is 5% -60%, and optionally 20% -60%.
In an alternative embodiment, the adhesive comprises at least one of polyvinylidene fluoride, polyurethane, polyacrylamide, polyacrylic acid, polyacrylate;
in an alternative embodiment, the battery separator satisfies at least one of the conditions (1) to (4):
(1) The thickness of the porous substrate is 3-25 mu m;
(2) The porosity of the porous base material is 30% -80%;
(3) The porous base material comprises at least one of polyolefin, aliphatic polyamide and aromatic polyamide;
(4) The thickness of the porous coating is 0.5 μm to 8 μm, alternatively 0.5 μm to 4 μm.
A second aspect of the present application provides a secondary battery comprising the above battery separator.
The beneficial effects of this application lie in: according to the battery diaphragm disclosed by the application, the porous coating with the temperature-sensitive polymer microspheres is arranged on the surface, so that the battery diaphragm has a higher ventilation value under the conditions of being baked at 130 ℃ for 2min, and therefore, the battery diaphragm can be endowed with lower shutdown temperature and higher closed pore rate, and the battery diaphragm has better safety for a secondary battery.
Drawings
FIG. 1 is a schematic view of a layered structure of a battery separator according to one embodiment of the present application;
fig. 2 is a schematic view of a layered structure of a battery separator according to another embodiment of the present application.
Reference numerals: 1. a porous coating; 2. a porous substrate.
Detailed Description
The invention will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, some operations associated with the present application have not been shown or described in the specification to avoid obscuring the core portions of the present application, and may not be necessary for a person skilled in the art to describe in detail the relevant operations based on the description herein and the general knowledge of one skilled in the art.
Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.
The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The terms "coupled" and "connected," as used herein, are intended to encompass both direct and indirect coupling (coupling), unless otherwise indicated.
In the present application, the term "secondary battery" refers to a battery that can be continuously used by activating an active material by charging after discharging the battery. Such cells typically utilize the reversibility of chemical reactions, i.e., after one chemical reaction is converted to electrical energy, the chemical system can also be repaired with electrical energy and then converted to electrical energy by the chemical reaction. Among them, more common secondary batteries include, but are not limited to, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid (or lead-storage) batteries, lithium ion batteries, polymer lithium ion batteries, sodium ion batteries, and the like.
In the present application, the term "battery separator" is an important component constituting an electric core of a secondary battery, and the battery separator is a thin film for separating positive and negative electrodes to prevent direct reaction from losing energy in the case of electrolytic reaction. The performance of the battery 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 battery diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery.
In this application, the following abbreviations of terms appear to be those known in the art and are not inconsistent, and do not pose any obstacle to the understanding of the present application by those skilled in the art, wherein:
PP, polypropylene; PE, polyethylene; the PP/PE/PP battery diaphragm is formed by sequentially compounding polypropylene, polyethylene and polypropylene according to a layered structure.
The PP/PE/PP battery separator can melt the PE layer at about 135 ℃ to shut down the battery separator, but the battery separator is shut down at the temperature due to the close melting points of the PP and PE layers, so that the PP film is easy to shrink, and the safety of the battery separator is affected.
The present application provides a battery separator comprising a porous substrate 2 and a porous coating 1.
The porous coating layer 1 is disposed at least on one side surface of the porous substrate 2, and for example, the porous coating layer 1 may be disposed on one side surface (shown in fig. 1) or opposite side surfaces (shown in fig. 2) of the porous substrate 2 by spin coating, spray coating, roll coating, screen printing, or the like, which is not specifically limited herein.
In the present application, the porous coating layer 1 includes ceramic particles, temperature-sensitive polymer microspheres, and a binder. The ceramic particles and the temperature-sensitive polymer microspheres are main bodies of the porous coating 1, and the temperature-sensitive polymer microspheres are dispersed among the ceramic particles, so that the liquid absorption and retention capacity of the battery diaphragm can be improved.
The battery separator disclosed by the application has a ventilation value of more than or equal to 1500 s/100ml under the condition of baking at 130 ℃ for 2 min. Illustratively, the gas permeation value of a battery separator under conditions of baking at 130 ℃ for 2min can be tested by: the battery diaphragm is placed at the constant temperature box of 130 ℃ for 2min, and then the battery diaphragm is taken out to test the ventilation value according to GB/T458-2008.
In some alternative embodiments, the battery separator has a ventilation value of 1500 s/100ml to 10000 s/100ml when baked at 130 ℃ for 2 min. For example, the cell separator may have a ventilation value of 1500 s/100ml, 4500 s/100ml, 6000 s/100ml, 7500s/100ml, or 10000 s/100ml.
In some alternative embodiments, the battery separator has a ventilation value of 2500 s/100ml-5000 s/100ml under conditions of baking at 130 ℃ for 2 min; for example, the cell separator may have a gas permeation value of 2500 s/100ml, 3000 s/100ml, 5000 s/100ml.
Since the battery separator disclosed in the application can make the temperature in the porous coating layer 1 under the condition of 130 ℃ and 2min bakingThe sensitive polymeric microspheres are melted, so that the ventilation value of the battery diaphragm is improved; therefore, under the abnormal working temperature of the lithium ion battery, the temperature-sensitive polymer microsphere can rapidly cut off Li between electrodes + And the transmission channel is used for inhibiting or closing the battery reaction, so that the safety of the battery is enhanced.
Meanwhile, in the preparation process of the battery cell, the battery cell needs to be hot-pressed or cold-pressed, so that each component in the battery cell can be closely attached to the battery cell, however, in the traditional hot-pressing process, heat is difficult to conduct to the battery diaphragm, and the defect of insufficient bonding strength inside the battery cell is easily caused, so that the bonding property between the battery diaphragm and an electrode in the cold pressing stage at normal temperature (25+/-5 ℃) needs to be improved while the low-temperature shutdown performance is considered. The inventor of the application researches find that the addition of the temperature-sensitive polymer microsphere in the porous coating 1 can also improve the adhesion of a battery diaphragm and an electrode in a cold pressing stage, which is probably due to the lower melting point and sensitive temperature response performance of the temperature-sensitive polymer microsphere.
According to the application, the adhesive is added into the porous coating 1, and can be adhered to the surface of the temperature-sensitive polymer microsphere, so that the adhering area of the adhesive can be enlarged, and the adhesive strength between the battery diaphragm and the pole piece disclosed by the application and the pole piece is enhanced when the battery diaphragm and the pole piece are cold pressed.
In some embodiments, the adhesive comprises at least one of polyvinylidene fluoride, polyurethane, polyacrylamide, polyacrylic acid, polyacrylate.
The bonding strength of the battery diaphragm and the pole piece is greater than or equal to 1.5N/m under the conditions of 25 ℃ and 2MPa cold pressing for 10 s.
In some embodiments, the battery separator has a bond strength of 1.5N/m to 21.1N/m with the pole piece at 25 ℃ and 2MPa cold press for 10 s. For example, the bonding strength of the battery separator with the pole piece under the condition of cold pressing for 10s at 25 ℃ and 2MPa can be 1.5N/m, 5N/m, 10N/m and 21.1N/m.
In the embodiments disclosed herein, the melting point of the temperature-sensitive polymer microspheres is 80 ℃ to 130 ℃, optionally 80 ℃ to 120 ℃. For example, the melting point of the temperature sensitive polymer microsphere may be 80 ℃, 90 ℃, 100 ℃, 110 ℃, or 120 ℃. According to the method, the temperature-sensitive polymer microsphere with the proper melting point is selected, so that the temperature-sensitive polymer microsphere can be melted at the abnormal working temperature of the battery diaphragm, and the micropores of the battery diaphragm are cut off; and cold press adhesion properties of the battery separator can be improved at room temperature.
In the embodiments disclosed herein, the average particle diameter D50 of the thermosensitive polymer microspheres is 200 nm-1000 nm. For example, the average particle size D50 of the temperature sensitive polymer microspheres may be 200 nm, 500 nm, 700 nm or 1000nm. By arranging the temperature-sensitive polymer microspheres with proper particle size, the temperature-sensitive polymer microspheres can not block the own gaps of the porous base material 2 when the battery diaphragm works normally, and can block the gaps of the porous base material 2 through melting when the battery diaphragm is at abnormal working temperature, so that the battery reaction is inhibited or shut down.
In some embodiments, the average particle size D50 of the temperature sensitive polymer microspheres is 250 nm-600 nm. For example, the average particle size D50 of the temperature sensitive polymer microspheres may be 250nm, 350 nm, 450nm, 550nm and 600nm.
In some embodiments, the mass percent of the temperature sensitive polymer microspheres is 20% -90%, alternatively 25% -75%. For example, the mass of the temperature sensitive polymer microspheres may be 25%, 35%, 45%, 55%, 65% or 75%.
In a specific example, the temperature-sensitive polymer microsphere may be at least one selected from polyoxyethylene and derivatives thereof, polyethylene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer.
In one embodiment, the ceramic particles have an average particle size D50 of 100 nm to 1000nm, optionally 250nm to 600 nm; for example, the average particle diameter D50 of the ceramic particles may be 250nm, 300 nm, 350 nm, 400 nm, 450nm, 500 nm, 550nm or 600nm.
In a specific example, the ceramic particles may be at least one selected from silica, alumina, boehmite, and silicon carbide particles.
According to the method, the particle sizes of the ceramic particles and the temperature-sensitive polymer microspheres are controlled, so that the temperature-sensitive polymer microspheres can be better dispersed in the ceramic particles.
In some embodiments, the adhesive may be at least one selected from polyvinylidene fluoride, polyurethane, polyacrylamide, polyacrylic acid, and acrylic acid ester.
More specifically, the application provides a more specific embodiment of the porous coating 1, wherein the porous coating 1 comprises the following components in percentage by mass:
20% -90% of temperature-sensitive polymer microspheres, 5% -60% of ceramic particles and 1% -20% of adhesive.
In an alternative embodiment, the porous coating 1 comprises the following components in percentage by mass:
25% -75% of temperature-sensitive polymer microspheres, 20% -60% of ceramic particles and 5% -15% of adhesive.
In addition, when the porous coating layer 1 is in the form of slurry, an aqueous solvent and a wetting agent are further included so that the porous coating layer 1 slurry can be coated on the surface of the porous substrate 2, and since a part of the volatile components exist in the components, when the porous substrate 2 is in the form of slurry, there is a certain difference in the components from the porous coating layer 1 after curing; exemplary, the present application provides an embodiment of a porous coating 1 slurry comprising the following components in mass percent:
5% -50% of temperature-sensitive polymer microspheres, 2% -15% of ceramic particles, 0.1% -10% of adhesive, 0.1% -5% of wetting agent and 30% -90% of aqueous solvent.
In an alternative embodiment, the slurry of the porous coating 1 comprises the following components in percentage by mass:
10% -40% of temperature-sensitive polymer microspheres, 2% -10% of ceramic particles, 0.1% -5% of adhesive, 0.1% -5% of wetting agent and 40% -80% of aqueous solvent.
Wherein a wetting agent is used to reduce the surface tension of the slurry of the porous coating layer 1 to facilitate the coating of the slurry of the porous coating layer 1, the wetting agent may be at least one selected from the group consisting of sodium polyacrylate, ammonium citrate, gelatin, polyethylene oxide, polyvinylpyrrolidone, polypropylene glycol, polypropylene alcohol, polypropylene, polyacrylic acid, and polyethylene glycol, by way of example. The wetting agent may be added in an amount of 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%.
Wherein an aqueous solvent is used to provide a dispersion for each group, thereby enabling uniform mixing of the components while facilitating slurry coating. The aqueous solvent may be water or a polar organic solvent miscible with water, for example.
In the present application, the porous substrate 2 serves as a battery separator body. Illustratively, the porous substrate 2 is made of at least one of polyolefin, aliphatic polyamide and aromatic polyamide. In the present embodiment, the porous substrate 2 is made of polypropylene.
In some embodiments, the thickness of the porous substrate 2 is 3 μm to 25 μm; at this thickness, the porous base material 2 has a certain toughness strength and can be wound to form a cell. Alternatively, the thickness of the porous substrate 2 is in the range of 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or any numerical composition above.
In some embodiments, the porous substrate 2 has a porosity of 30% to 80%; the porous membrane base material with the porosity range is selected to ensure Li after forming the battery cell + Is transmitted by the base station. Alternatively, the porous substrate 2 has a porosity in the range of 30%, 40%, 50%, 60%, 70%, 80% or any number of the above compositions.
In some embodiments, the thickness of the porous coating 1 is 0.5 μm to 8 μm, optionally 0.5 μm to 4 μm. The application selects the proper thickness of the porous coating 1, so that the porous substrate 2 can be well attached to the surface of the porous substrate 2, and the mechanical property of the porous substrate 2 can not be influenced.
In another embodiment of the present application, a secondary battery is provided, including the above battery separator. The secondary battery comprising the battery diaphragm can reduce the risk of thermal runaway and has better safety performance. In addition, the battery diaphragm can realize cold-pressing bonding, and the manufacturing process cost of the secondary battery is low.
In order to facilitate explanation of the effects of the present application, the present application further provides the following more specific examples and comparative examples:
example 1
Six porous substrates 2 with different thicknesses are prepared, porous coatings 1 are respectively coated on the surfaces of the six porous substrates 2, six battery diaphragm samples are obtained, and are respectively marked as samples 1 to 6, wherein the samples 1 to 5 are coated on one side, and the sample 6 is coated on two sides.
The parameters of samples 1 to 6 are shown in tables 1 and 2:
TABLE 1
| Project | Thickness of porous substrate 2 | Porous substrate 2 | Front porous coating 1 thickness | Thickness of the reverse porous substrate 2 |
| Sample 1 | 3μm | Polypropylene | 0.5μm | \ |
| Sample 2 | 25μm | Polypropylene | 8μm | \ |
| Sample 3 | 14μm | Polypropylene | 4μm | \ |
| Sample 4 | 14μm | Polypropylene | 4μm | \ |
| Sample 5 | 14μm | Polypropylene | 4μm | \ |
| Sample 6 | 14μm | Polypropylene | 2μm | 2μm |
Table 2 composition of porous coating layer 1 in samples 1 to 6
| Composition of the composition | Temperature sensitive polymer microsphere | Melting point of temperature sensitive polymer microsphere | Ceramic particles | Adhesive agent |
| Sample 1 | 20 wt% polyethylene | 80 | 60 wt% silica | 20 wt% polyvinylidene fluoride |
| Sample 2 | 90 weight percent polymethyl methacrylate | 121 | 9. 9 wt% of aluminum oxide | 1.1 wt% polyurethane |
| Sample 3 | 75 wt% ethylene-vinyl acetate copolymer | 115 | 25 wt% boehmite (Boehmite-B) | 5. 5 wt% polyacrylamide |
| Sample 4 | 25 wt% polyethylene | 120 | 60 wt% silica | 15 wt% polyvinylidene fluoride |
| Sample 5 | 50 wt% polyethylene | 100 | 40 wt% silica | 10 wt% polyvinylidene fluoride |
| Sample 6 | 50 wt% polyethylene | 100 | 40 wt% silica | 10 wt% polyvinylidene fluoride |
Comparative example one:
a polyolefin film having a thickness of 14 μm was prepared.
Control II:
a18 μm thick PP/PE/PP battery separator was prepared.
Control three:
a 14 μm thick polyolefin film was prepared, and a 4 μm thick control coating layer comprising 80% wt% silica particles and 20% wt% polyvinylidene fluoride by mass was coated on one side surface of the polyolefin film.
Embodiment two:
the samples provided in the above example one, and the comparative examples one to three were tested for initial air permeability value, final air permeability value, and adhesive strength.
Wherein, the initial ventilation value is tested according to the method disclosed in GB/T458-2008 before baking; termination ventilation values after the samples were baked at 130 ℃ for 2min, were tested according to the method disclosed in GB/T458-2008.
Wherein the adhesive strength is tested by the following method: the battery diaphragm sample is cut into 20mm multiplied by 100mm sample bars, the positive plate is cut into 20mm multiplied by 100mm as a bottom plate, and the sample bars are cold-pressed for 10 seconds under the pressure of 2MPa and the temperature of 32 ℃ to prepare a test sample. And then, testing at a speed of 100mm/min on an electronic tension machine by adopting a 180-degree direction peeling strength testing method to separate the sample strip from the positive plate, wherein the peeling strength is the bonding strength of the battery diaphragm and the pole piece (taking the average value of 5 parallel test samples as the bonding strength of the sample and the pole piece).
The specific test results are shown in table 3:
TABLE 3 Table 3
| Sample of | Initial ventilation value (s/mL) | Termination ventilation value (s/mL) | Bonding Strength (N/m) |
| Sample 1 | 59 | 1597 | 5.8 |
| Sample 2 | 410 | 1559 | 21.1 |
| Sample 3 | 236 | 4689 | 10.6 |
| Sample 4 | 231 | 1521 | 2.7 |
| Sample 5 | 243 | 2879 | 7.1 |
| Sample 6 | 242 | 6147 | 7.4 |
| Comparative example one | 221 | 81 | 0 |
| Comparative example two | 226 | 1348 | 0 |
| Comparative example three | 236 | 149 | 4.5 |
The upper surface can be seen that the final ventilation value of the samples 1 to 5 after being baked at 130 ℃ for 2min is greatly improved compared with the initial ventilation value, which indicates that the temperature-sensitive polymer microspheres in the porous coating 1 can be quickly melted after being baked at 130 ℃ for 2min, so that the pores of the porous substrate 2 are closed. The initial air permeability values of samples 3 to 5 are not much different from those of the three comparative examples, while the air permeability values of the battery separators in samples 3 to 5 are positively correlated with the coating amounts of the temperature-sensitive polymer microspheres; comparing sample 5, sample 6 and comparative example one can show that the air permeability of the porous substrate 2 can be effectively reduced, and the double-sided coating effect is better than the single-sided coating, no matter the porous coating 1 is arranged on one side of the porous substrate 2 or the porous coating 1 is arranged on the opposite sides.
Compared with the comparative examples one to three, the battery separator samples 1 to 6 provided in the present application have higher air permeability values (the higher the air permeability value, the worse the air permeability) under the conditions of baking at 130 ℃ for 2 min; the application shows that the shutdown of the battery separator can be realized at about 130 degrees, and the temperature and the rate of the closed pores are superior to those of the PP/PE/PP separator provided in the third comparison example.
Meanwhile, the battery diaphragm provided by the application also has excellent cold-pressing bonding strength with the pole piece, and the bonding strength of the diaphragm and the pole piece is more than or equal to 1.5N/m and can reach 21.1N/m at 25 ℃ and 2MPa for 10 s; because the battery diaphragm that this application provided is excellent in cold pressing bonding strength, consequently can avoid hot pressing technology in, the heat conduction is more difficult to the diaphragm, leads to the inside bonding strength of electric core not enough problem.
The foregoing description of the invention has been presented for purposes of illustration and description, and is not intended to be limiting. Several simple deductions, modifications or substitutions may also be made by a person skilled in the art to which the invention pertains, based on the idea of the invention.
Claims (10)
1. A battery separator comprising a porous substrate; and
the porous coating is arranged on at least one side surface of the porous substrate, and comprises ceramic particles, temperature-sensitive polymer microspheres and an adhesive;
the air permeability value of the battery separator is more than or equal to 1500 s/100ml under the condition of baking at 130 ℃ for 2 min.
2. The battery separator of claim 1, wherein the battery separator has a ventilation value of 1500 s/100ml to 10000 s/100ml under conditions of baking at 130 ℃ for 2 min;
optionally, the cell separator has a gas permeation value of 2500 s/100ml to 5000 s/100ml under conditions of baking at 130 ℃ for 2 min.
3. The battery separator according to claim 1, wherein the adhesive strength between the battery separator and the pole piece is greater than or equal to 1.5N/m under the conditions of 25 ℃ and 2MPa cold pressing for 10 s;
alternatively, the bonding strength of the battery separator and the pole piece is 1.5N/m-21.1N/m under the condition of 25 ℃ and 2MPa cold pressing for 10 s.
4. The battery separator of claim 1, wherein the temperature sensitive polymer microspheres have a melting point of 80 ℃ to 130 ℃, optionally 80 ℃ to 120 ℃.
5. The battery separator of claim 1, wherein the temperature sensitive polymer microspheres have an average particle size D50 of 200 nm to 1000 nm;
optionally, the average particle diameter D50 of the thermosensitive polymer microsphere is 250 nm-600 nm.
6. The battery separator of any one of claims 1 to 5 wherein the temperature sensitive polymeric microspheres satisfy at least one of conditions (1) and (2):
(1) The temperature-sensitive polymer microsphere comprises at least one of polyoxyethylene and derivatives thereof, polyethylene, polymethyl methacrylate and ethylene-vinyl acetate copolymer;
(2) In the porous coating, the mass percentage of the temperature-sensitive polymer microsphere is 20% -90%, and 25% -75% can be selected.
7. The battery separator according to any one of claims 1 to 5, wherein the ceramic particles satisfy at least one of the conditions (1) to (3):
(1) The average particle diameter D50 of the ceramic particles is 100 nm-1000 nm, and is optionally 250 nm-600 nm;
(2) The ceramic particles comprise at least one of silica, aluminum oxide, boehmite, and silicon carbide particles;
(3) In the porous coating, the mass percentage of the ceramic particles is 5% -60%, and optionally 20% -60%.
8. The battery separator according to any one of claims 1 to 5, wherein the adhesive satisfies at least one of conditions (1) and (2):
the adhesive comprises at least one of polyvinylidene fluoride, polyurethane, polyacrylamide, polyacrylic acid and polyacrylate;
(2) In the porous coating, the mass percentage of the adhesive is 1% -20%, and optionally 5% -15%.
9. The battery separator according to any one of claims 1 to 5, wherein the battery separator satisfies at least one condition of (1) to (4):
(1) The thickness of the porous substrate is 3-25 mu m;
(2) The porosity of the porous base material is 30% -80%;
(3) The porous base material comprises at least one of polyolefin, aliphatic polyamide and aromatic polyamide;
(4) The thickness of the porous coating is 0.5 μm to 8 μm, alternatively 0.5 μm to 4 μm.
10. A secondary battery comprising the battery separator according to any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311745413.8A CN117855746A (en) | 2023-12-15 | 2023-12-15 | Battery separator and secondary battery |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311745413.8A CN117855746A (en) | 2023-12-15 | 2023-12-15 | Battery separator and secondary battery |
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| Publication Number | Publication Date |
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| CN117855746A true CN117855746A (en) | 2024-04-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202311745413.8A Pending CN117855746A (en) | 2023-12-15 | 2023-12-15 | Battery separator and secondary battery |
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| Country | Link |
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| CN (1) | CN117855746A (en) |
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