A battery separator and a battery

Abstract

This application belongs to the technical field of battery materials, and particularly relates to a battery separator and a battery. The battery separator and battery provided by this application, the battery separator includes a base film layer and a heat-resistant layer disposed on at least one side of the base film layer, and the heat-resistant layer includes polymer particles; the mass ratio of the N element content to the C element content in the polymer particles is (2-10):100. In the battery separator provided by this application, the polymer particles have excellent electrolyte affinity. Compared with traditional ceramic separators, the battery separator provided by this application has excellent electrolyte wettability.

Description

Technical Field

[0001] This application belongs to the technical field of battery materials, and particularly relates to a battery separator and a battery. Background Art

[0002] Boehmite (γ-AlOOH) first loses physically adsorbed water under the action of heat. As the temperature rises, when the temperature reaches 210 °C, it begins to lose chemically adsorbed water and completely loses all water at 310 °C. Due to its excellent heat resistance and good chemical stability, it is mainly used for the coating of lithium battery cell separators. Moreover, boehmite expands when heated, and this expansion is mainly manifested as changes in lattice parameters and structural reorganization. This expansion characteristic enables boehmite to have a certain protection function in high-temperature environments, such as preventing overcharging and explosion through the closed-pore function in the application of lithium battery separators. Specifically: at lower temperatures (for example, below 300 °C), the structural changes of boehmite are mainly manifested as water loss and density increase. When the temperature rises to about 300 °C, cracks and fissures begin to appear in boehmite, indicating that its thermal expansion begins to increase significantly. At higher temperatures (for example, above 400 °C), the thermal expansion of boehmite leads to grain coarsening and pore enlargement, further increasing the thermal expansion rate. When the temperature continues to rise above 700 °C, boehmite undergoes dimensional sintering, resulting in further coarsening of crystals and pores, and the thermal expansion rate continues to increase.

[0003] During the use of boehmite, additional dispersion equipment is usually required for dispersion. Due to the irregular morphology of boehmite particles, there will inevitably be friction with the equipment during the dispersion process, causing equipment wear and introducing metal impurities into the boehmite slurry, which has a negative impact on battery performance.

[0004] To overcome the above problems, polymer particles are used in the prior art to replace boehmite as the main filler for the heat-resistant layer of battery separators. However, the polymer particles in the prior art have poor affinity for electrolytes, and the polymer coatings coated with polymer particles usually also have poor electrolyte wettability. Summary of the Invention

[0005] Aiming at the technical problems in the prior art that polymer particles have poor affinity for electrolytes and poor separator electrolyte wettability, the specific technical solution of this application is as follows:

[0006] A battery separator, comprising a base film layer and a heat-resistant layer provided on at least one side of the base film layer, wherein the heat-resistant layer comprises polymer particles; the mass ratio of the content of N element to the content of C element in the polymer particles is (2 - 10):100.

[0007] By introducing N element into the polymer particles and controlling the mass ratio of the N element content to the C element content to be (2-10):100, on the basis of maintaining the heat resistance and air permeability of the polymer particle separator, the electrolyte wettability of the polymer particles can be significantly improved, which is beneficial to improving the liquid injection efficiency in the lithium battery manufacturing process.

[0008] Preferably, the average particle size D50 of the polymer particles is 200-1000 nm, and the glass transition temperature Tg is above 150 °C.

[0009] Preferably, the polymer particles include a rigid ring structure unit, a crosslinking monomer unit, and a functional monomer unit; in the polymer particles, the mass ratio of the rigid ring structure unit, the crosslinking monomer unit, and the functional monomer unit is (60-90):(5-15):(5-25).

[0010] Preferably, the rigid ring structure unit is selected from one or more of monomer units of aromatic vinyl compounds, monomer units of maleimide and its derivatives, and monomer units of vinyl carbazole compounds; the crosslinking monomer unit is selected from one or more of bifunctional or polyfunctional (meth)acrylate monomer units, bifunctional or polyfunctional allyl monomer units, bifunctional or polyfunctional acrylamide monomer units, and bifunctional or polyfunctional vinyl monomer units; the functional monomer unit is selected from one or more of monomer units containing an amino group.

[0011] Preferably, the rigid ring structure unit is selected from one or more of styrene monomer unit, methyl styrene monomer unit, vinyl naphthalene monomer unit, vinyl toluene monomer unit, 2,4-dimethyl styrene monomer unit, ethyl styrene monomer unit, isopropyl styrene monomer unit, tert-butyl styrene monomer unit, butyl styrene monomer unit, phenyl styrene monomer unit, cyclohexyl styrene monomer unit, benzyl styrene monomer unit, isobornyl acrylate monomer unit, isobornyl methacrylate monomer unit, maleimide monomer unit, C1-C12 alkyl-substituted maleimide monomer unit, C6-C16 aryl-substituted maleimide monomer unit, and vinyl carbazole;

[0012] The crosslinking monomer unit is selected from one or more of ethylene glycol diacrylate monomer unit, polyethylene glycol diacrylate monomer unit, propylene glycol diacrylate monomer unit, dipropylene glycol diacrylate monomer unit, tripropylene glycol diacrylate monomer unit, trimethylolpropane triacrylate monomer unit, glycerol triacrylate monomer unit, pentaerythritol triacrylate monomer unit, polyethylene glycol dimethacrylate monomer unit, diethylene glycol dimethacrylate monomer unit, propylene glycol dimethacrylate monomer unit, dipropylene glycol dimethacrylate monomer unit, tripropylene glycol dimethacrylate monomer unit, trimethylolpropane trimethacrylate monomer unit, glycerol trimethacrylate monomer unit, pentaerythritol trimethacrylate monomer unit, divinylbenzene monomer unit, diallyl phthalate monomer unit, glycerol diallyl ether monomer unit, pentaerythritol diallyl ether monomer unit, pentaerythritol triallyl ether monomer unit, diallyl adipate monomer unit, N,N-methylenebisacrylamide monomer unit, allyl acrylate ether monomer unit, allyl methacrylate ether monomer unit, divinylbenzene monomer unit;

[0013] The functional monomer unit is selected from one or more of N-(2-aminoethyl)acrylamide monomer unit, N-(2-aminoethyl)methacrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, 2-(tert-butylamino)ethyl methacrylate monomer unit, dimethylaminoethyl acrylate monomer unit, dimethylaminoethyl methacrylate monomer unit, acrylamide monomer unit, methacrylamide monomer unit, N-tert-butylacrylamide monomer unit, N-isopropylacrylamide monomer unit, N,N-dimethylacrylamide monomer unit, N,N-diethylacrylamide monomer unit.

[0014] Preferably, the thickness of the heat-resistant layer is 1-4 μm.

[0015] Preferably, the heat-resistant layer further comprises a binder and optionally a thickener and a wetting agent.

[0016] Preferably, in the heat-resistant layer, the mass ratio of the polymer particles, the binder, the thickener, and the wetting agent is 100:(3-10):(0.5-5):(0.5-3).

[0017] Preferably, the base film layer is a polyolefin base film, and the polyolefin base film is selected from any one of polyethylene porous film, polypropylene porous film, polypropylene / polyethylene / polypropylene three-layer composite porous film, and polybutene porous film.

[0018] Meanwhile, the present invention also provides a battery, including the battery separator as described above. Detailed Description

[0019] The present application will be further described below in conjunction with embodiments. It should be understood that the embodiments are only used to further illustrate and explain the present application and are not used to limit the present application.

[0020] Unless otherwise defined, the technical and scientific terms in this specification have the same meanings as those commonly understood by those skilled in the art. Although methods and materials similar or equivalent to those described herein can be used in experiments or practical applications, the materials and methods are described below. In case of conflict, the present specification, including the definitions therein, shall prevail. Additionally, the materials, methods, and examples are for illustrative purposes only and are not restrictive. The present application will be further described below in conjunction with specific embodiments, but not to limit the scope of the present application.

[0021] The battery separator provided by the present invention includes a base film layer and a heat-resistant layer provided on at least one side of the base film layer. The heat-resistant layer includes polymer particles; the mass ratio of the content of N element to the content of C element in the polymer particles is (2 - 10):100.

[0022] In a specific embodiment, the mass ratio of the content of N element to the content of C element in the polymer particles is (2 - 10):100. For example, it can be 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100.

[0023] When the mass ratio of the content of N element to the content of C element is lower than 2:100, the polymer particles have insufficient affinity for the electrolyte, and the improvement effect on the wettability of the electrolyte is not obvious. When the mass ratio of the content of N element to the content of C element is higher than 10:100, the porosity of the separator becomes poor after coating, the air permeability decreases, and the dispersibility of the polymer particles becomes poor, making the preparation process more difficult.

[0024] For the above polymer particles, preferably, the average particle size D50 of the polymer particles is 200 - 1000 nm. Specifically, the average particle size D50 of the polymer particles can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm.

[0025] If the particle size of the polymer particles is too small, it is easy to cause the air permeability of the coated separator to increase too much, which cannot meet the use requirements of lithium batteries. If the particle size of the polymer particles is too large, it is easy to cause insufficient coating layers, resulting in poor heat resistance of the separator.

[0026] According to the present invention, preferably, the glass transition temperature Tg of the polymer particles is 150 °C or higher. More preferably, the glass transition temperature Tg of the polymer particles is 150 - 500 °C. Specifically, the glass transition temperature Tg of the polymer particles can be 150 °C, 200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, 500 °C. If the glass transition temperature Tg of the polymer particles is less than 150 °C, the performance of inhibiting the thermal shrinkage of the separator will decline.

[0027] In the present invention, the polymer particles can be various polymer particles commonly used in the art, as long as the mass ratio of N and C elements is controlled within the range disclosed in the present invention. Preferably, the polymer particles include a rigid ring structure unit, a crosslinking monomer unit, and a functional monomer unit. More preferably, in the polymer particles, the mass ratio of the rigid ring structure unit, the crosslinking monomer unit, and the functional monomer unit is (60 - 90):(5 - 15):(5 - 25).

[0028] The above-mentioned rigid ring structure unit is a unit formed in the polymer after polymerization of monomers having a rigid group. Specifically, the rigid ring structure unit is selected from one or more of monomer units of aromatic vinyl compounds, monomer units of maleimide and its derivatives, and monomer units of vinyl carbazole compounds. Further, the rigid ring structure unit is selected from one or more of styrene monomer unit, methylstyrene monomer unit, vinylnaphthalene monomer unit, vinyltoluene monomer unit, 2,4-dimethylstyrene monomer unit, ethylstyrene monomer unit, isopropylstyrene monomer unit, tert-butylstyrene monomer unit, butylstyrene monomer unit, phenylstyrene monomer unit, cyclohexylstyrene monomer unit, benzylstyrene monomer unit, isobornyl acrylate monomer unit, isobornyl methacrylate monomer unit, maleimide monomer unit, C1-C12 alkyl-substituted maleimide monomer unit, and C6-C16 aryl-substituted maleimide monomer unit.

[0029] The crosslinking monomer unit is a unit formed in the polymer after polymerization of crosslinking monomers. Specifically, the crosslinking monomer unit is selected from one or more of bifunctional or polyfunctional (meth)acrylate monomer units, bifunctional or polyfunctional allyl monomer units, bifunctional or polyfunctional acrylamide monomer units, and bifunctional or polyfunctional vinyl monomer units; the functional monomer unit is selected from one or more of monomer units containing an amino group.

[0030] Specifically, the crosslinking monomer unit is selected from one or more of ethylene glycol diacrylate monomer unit, polyethylene glycol diacrylate monomer unit, propylene glycol diacrylate monomer unit, dipropylene glycol diacrylate monomer unit, tripropylene glycol diacrylate monomer unit, trimethylolpropane triacrylate monomer unit, glycerol triacrylate monomer unit, pentaerythritol triacrylate monomer unit, polyethylene glycol dimethacrylate monomer unit, diethylene glycol dimethacrylate monomer unit, propylene glycol dimethacrylate monomer unit, dipropylene glycol dimethacrylate monomer unit, tripropylene glycol dimethacrylate monomer unit, trimethylolpropane trimethacrylate monomer unit, glycerol trimethacrylate monomer unit, pentaerythritol trimethacrylate monomer unit, divinylbenzene monomer unit, diallyl phthalate monomer unit, glycerol diallyl ether monomer unit, pentaerythritol diallyl ether monomer unit, pentaerythritol triallyl ether monomer unit, diallyl adipate monomer unit, N,N-methylenebisacrylamide monomer unit, allyl acrylate ether monomer unit, allyl methacrylate ether monomer unit, divinylbenzene monomer unit.

[0031] The functional monomer unit is the unit formed in the polymer after the polymerization of the functional monomer. Specifically, the functional monomer unit is selected from one or more of N-(2-aminoethyl)acrylamide monomer unit, N-(2-aminoethyl)methacrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, 2-(tert-butylamino)ethyl methacrylate monomer unit, dimethylaminoethyl acrylate monomer unit, dimethylaminoethyl methacrylate monomer unit, acrylamide monomer unit, methacrylamide monomer unit, N-tert-butylacrylamide monomer unit, N-isopropylacrylamide monomer unit, N,N-dimethylacrylamide monomer unit, N,N-diethylacrylamide monomer unit.

[0032] The functional monomer contains N element. After introducing N element into the polymer particles, the electrolyte wettability of the polymer particles can be significantly improved. This may be because the introduction of N element can effectively enhance the polarity of the polymer particles and increase the affinity with the electrolyte. Moreover, N element has good adsorption property for lithium salts in the electrolyte. After the lithium salts are adsorbed on the polymer particles containing N element, it is further beneficial to the infiltration of the electrolyte.

[0033] In the present invention, the mass ratio of the rigid cyclic structure unit, crosslinking monomer unit and functional monomer unit in the polymer particles can be based on the mass ratio of the monomer with a rigid group, crosslinking monomer and functional monomer participating in the polymerization reaction, that is, the mass ratio of the monomer with a rigid group, crosslinking monomer and functional monomer used for polymerizing to form the polymer particles is (60-90):(5-15):(5-25).

[0034] The above-mentioned polymer particles provided by the present invention can be prepared by methods commonly used in the field of chemical synthesis. For example, 0.1 - 1 part of an emulsifier, 50 - 300 parts of a solvent, and 100 parts of a monomer mixture are mixed, and a monomer emulsion is obtained after high-speed stirring. Then, nitrogen is introduced and the temperature is raised to 60 - 100 °C, and then an initiator is added. After maintaining the reaction for 4 - 10 hours, a dispersion of polymer particles can be obtained.

[0035] As is well known to those skilled in the art, the particle size of the polymer particles can be adjusted by adjusting the amount of the emulsifier used.

[0036] Among them, various conventional substances can be used as the emulsifier. The emulsifier can be an anionic emulsifier, a non-ionic emulsifier, or a combination of the two, including but not limited to sodium dodecyl sulfate, sodium dodecyl ether sulfate, and fatty alcohol polyoxyethylene ether. The initiator is usually a water-soluble initiator, including but not limited to sodium persulfate, ammonium persulfate, potassium persulfate, and hydrogen peroxide. The solvent can be deionized water. The monomer mixture is a mixture of monomers with rigid groups, cross-linking monomers, and functional monomers as described above.

[0037] In the present invention, preferably, the thickness of the heat-resistant layer is 1 - 4 μm.

[0038] If the thickness of the heat-resistant layer is too thin, the heat resistance of the separator will become poor, while if the thickness of the heat-resistant layer is too thick, the gas permeability of the separator will be poor and the internal resistance of the battery will increase.

[0039] Furthermore, the heat-resistant layer further includes a binder and optionally a thickener and a wetting agent.

[0040] Various materials commonly used in the art can be used as the binder, thickener, and wetting agent. For example, the binder can be a polyacrylate binder and / or a styrene-butadiene latex binder. The polyacrylate binder is obtained commercially. The polyacrylate binder is in the form of an emulsion, with a solid content of 45%, an average particle size D50 of 350 - 400 nm, and a glass transition temperature of -40 °C.

[0041] The thickener can be at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium polyacrylate, and lithium polyacrylate.

[0042] Existing various wetting agents can be used as the wetting agent. For example, any one or a mixture of several of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ether, and polyether-modified polysiloxane can be used.

[0043] Preferably, in the heat-resistant layer, the mass ratio of the polymer particles, binder, thickener, and wetting agent is 100:(3 - 10):(0.5 - 5):(0.5 - 3).

[0044] In a specific embodiment, the content of the binder is 3 - 10 parts, for example, it can be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts.

[0045] In a specific embodiment, the thickener is 3 - 10 parts, for example, it can be 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0046] In a specific embodiment, the content of the wetting agent is 0.5 - 3 parts, for example, it can be 0.3 parts, 0.5 parts, 0.8 parts, 1 part, 1.3 parts, 1.5 parts, 1.8 parts, 2 parts, 2.3 parts, 2.5 parts, 2.8 parts, or 3 parts.

[0047] Preferably, the base film layer is a polyolefin base film, and the polyolefin base film is selected from any one of polyethylene porous film, polypropylene porous film, polypropylene / polyethylene / polypropylene three-layer composite porous film, and polybutene porous film.

[0048] The battery separator provided by the present invention can be obtained by coating a slurry containing polymer particles on the base film layer and then drying.

[0049] The slurry may include the following components in parts by weight (converted to solid content): the mass ratio of polymer particles, binder, thickener, and wetting agent is 100:(3 - 10):(0.5 - 5):(0.5 - 3). And the solid content can be adjusted to 30 - 40 wt% by a solvent (such as deionized water).

[0050] Meanwhile, the present invention also provides a battery, including the battery separator as described above.

[0051] The battery separator provided by the present invention has good wettability to the electrolyte and low thermal shrinkage rate.

[0052] Examples

[0053] The following specifically describes and illustrates the implementation manners of the present application through specific examples. However, the following content should not be construed as any limitation to the present application. Substances used in the examples are all commercially available products if not otherwise specified. "Parts" in the examples and comparative examples all represent kg, and the composition ratios are all weight ratios.

[0054] Example 1

[0055] 0.5 parts of sodium dodecyl sulfate, 150 parts of water, and 100 parts of monomer mixture were stirred at high speed to obtain a monomer emulsion. After purging with nitrogen and heating to 80 °C, 0.5 parts of ammonium persulfate initiator were added, and the reaction was carried out at a constant temperature for 6 hours to obtain a polymer particle dispersion. The average particle size D50 of the polymer particles was detected by a laser particle size analyzer to be 450 nm. The Tg of the polymer particles was detected by a differential scanning calorimeter to be 158 °C.

[0056] The composition of the monomer mixture was styrene: vinyl carbazole: divinylbenzene: N-tert-butylacrylamide = 40:25:10:25.

[0057] Preparation of the separator with a heat-resistant layer: 250 parts of the polymer particle dispersion (containing 100 parts of polymer particles), 13.3 parts of polyacrylate binder (solid content 45%), 1 part of sodium carboxymethyl cellulose, and 0.5 part of alkylphenol polyoxyethylene ether were added, and deionized water was added to adjust the solid content to 35% to obtain a polymer particle slurry. This slurry was coated on a polyethylene film layer, and the thickness of the dried coating was controlled to be 2 μm.

[0058] Example 2

[0059] The difference between this example and Example 1 was only that the composition of the monomer mixture was styrene: vinyl carbazole: divinylbenzene: acrylamide = 40:25:10:25.

[0060] The Tg of the polymer particles was detected by a differential scanning calorimeter to be 169 °C.

[0061] Example 3

[0062] The difference between this example and Example 1 was only that the composition of the monomer mixture was isobornyl methacrylate: vinyl carbazole: divinylbenzene: acrylamide = 30:30:15:25.

[0063] The Tg of the polymer particles was detected by a differential scanning calorimeter to be 185 °C.

[0064] Example 4

[0065] The difference between this example and Example 1 was only that the composition of the monomer mixture was styrene: vinyl carbazole: divinylbenzene: N-tert-butylacrylamide = 70:20:5:5.

[0066] The Tg of the polymer particles was detected by a differential scanning calorimeter to be 152 °C.

[0067] Example 5

[0068] The difference between this example and Example 1 was only that the particle size of the polymer particles was 210 nm.

[0069] Example 6

[0070] The difference between this example and Example 1 is only that the particle size of the polymer particles is 810 nm.

[0071] Example 7

[0072] The difference between this example and Example 1 is only that the particle size of the polymer particles is 970 nm.

[0073] Example 8

[0074] The difference between this example and Example 1 is only that the coating thickness of the polymer particles is 1 μm.

[0075] Example 9

[0076] The difference between this example and Example 1 is only that the coating thickness of the polymer particles is 4 μm.

[0077] Example 10

[0078] The difference between this comparative example and Example 2 is only that the thickness of the heat-resistant layer is 0.5 μm.

[0079] Example 11

[0080] The difference between this comparative example and Example 2 is only that the thickness of the heat-resistant layer is 5 μm.

[0081] Example 12

[0082] The difference between this comparative example and Example 2 is only that the monomer mixture composition is styrene: vinylcarbazole: divinylbenzene: N-tert-butylacrylamide = 90:10:5:5.

[0083] The Tg of the polymer particles was detected by differential scanning calorimetry to be 131 °C.

[0084] Comparative Example 1

[0085] The difference between this comparative example and Example 2 is only that the monomer mixture composition is styrene: vinylcarbazole: divinylbenzene = 70:20:10.

[0086] Comparative Example 2

[0087] The difference between this comparative example and Example 2 is only that the monomer mixture composition is styrene: vinylcarbazole: divinylbenzene: acrylamide = 35:20:10:35.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 2 is that boehmite BG-611 is used to replace the polymer particles.

[0090] Performance test:

[0091] Diaphragm air permeability increase test, referring to the air permeability test in GB / T 36363-2018 "Polyolefin Diaphragms for Lithium-Ion Batteries":

[0092] Cut 3 pieces of diaphragms longitudinally spaced 150 mm apart on the film roll. If the diaphragm width ≥ 100 mm, take the sample size as 100 mm × 100 mm; if the diaphragm width < 100 mm, take the sample size as 100 mm × diaphragm width. Place the diaphragm in the test head of a permeameter suitable for the test range to conduct the air permeability time test. Take the average value of 3 test results as the air permeability time of the diaphragm, with the unit of s / 100cc. The diaphragm air permeability increase is the difference between the air permeability time of the diaphragm coated with non-conductive particles and binder and the air permeability time of the polyolefin base film, with the unit of s / 100cc.

[0093] The contents of C element and N element are detected by elemental analysis method, and the N / C ratio is the content of N element divided by the content of C element.

[0094] Electrolyte wettability test: Cut the diaphragm coated with polymer particles into strips of 5 mm * 100 mm, drop 3 μL of electrolyte onto the diaphragm strip, and measure the length of electrolyte diffusion after 1 min, with the unit of mm. The electrolyte composition is ethylene carbonate: ethyl methyl carbonate: diethyl carbonate = 3:2:5, and the concentration of lithium hexafluorophosphate is 1 mol / L.

[0095] Diaphragm heat resistance: Stack the diaphragms into 3 layers, expel the air between the films, take out and cut into samples of 100 mm * 100 mm, measure the longitudinal length M1 and transverse length T1 of the cut samples. Set the oven temperature to 130 °C respectively, after the temperature reaches, keep it warm for 1 h, put the samples into the oven, keep it warm for 1 h. After the insulation is completed, take out the diaphragm, cool for 10 min, and then measure the longitudinal length M2 and transverse length T2 of the samples. The longitudinal thermal shrinkage of the diaphragm = (M1 - M2) / M1 * 100%, and the transverse thermal shrinkage = (T1 - T2) / T1 * 100%.

[0096] Glass transition temperature test: Use a differential scanning calorimeter (Shanghai Qunhong Instrument Equipment Co., Ltd., model: DSC-100) to detect the glass transition temperatures of the core polymer and shell polymer.

[0097] Fill in the above test results in Table 1.

[0098] Table 1

[0099]

[0100] From the test results in Table 1, it can be seen that the battery diaphragm provided by the present invention has good electrolyte wettability, and at the same time has low air permeability increase and low thermal shrinkage rate.

[0101] From the test results of Comparative Example 2, Comparative Dummy Examples 1 and 2, it can be seen that when the mass ratio of N element to C element is too low, the electrolyte wettability of the battery separator is significantly reduced, while when the mass ratio of the two is too high, the air permeability increase value of the battery separator increases significantly.

[0102] From the test results of Comparative Examples 1, 5, 6, and 7, it can be seen that when the average particle size D50 of the polymer particles is relatively low, the air permeability increase value of the battery separator shows an increasing trend.

[0103] From the test results of Comparative Examples 2 and 12, it can be seen that when the glass transition temperature Tg of the polymer particles decreases, it is not conducive to suppressing the thermal shrinkage of the separator.

[0104] As described above, it is only a preferred experimental example of the present application, and it does not limit the present application in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent experimental examples of equivalent changes. However, any simple modification, equivalent change, and modification made to the above experimental examples based on the technical essence of the present application without departing from the technical solution content of the present application still fall within the protection scope of the technical solution of the present application.

Claims

1. A battery separator, characterized in that, It includes a base film layer and a heat-resistant layer provided on at least one side of the base film layer, and the heat-resistant layer includes polymer particles; The mass ratio of the content of N element to the content of C element in the polymer particles is (2-10):100; The polymer particles include a rigid ring structure unit, a crosslinking monomer unit and a functional monomer unit; in the polymer particles, the mass ratio of the rigid ring structure unit, the crosslinking monomer unit and the functional monomer unit is (60-90):(5-15):(5-25); The rigid ring structure unit is selected from one or more of monomer units of aromatic vinyl compounds, monomer units of maleimide and its derivatives, and monomer units of vinyl carbazole compounds; The crosslinking monomer unit is selected from one or more of bifunctional or polyfunctional (meth)acrylate monomer units, bifunctional or polyfunctional allyl monomer units, bifunctional or polyfunctional acrylamide monomer units, and bifunctional or polyfunctional vinyl monomer units; The heat-resistant layer further includes a binder, a thickener and a wetting agent; The average particle size D50 of the polymer particles is 200-1000 nm, and the glass transition temperature Tg is 150°C-185°C; The functional monomer unit is selected from one or more of N-(2-aminoethyl)acrylamide monomer unit, N-(2-aminoethyl)methacrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, N-(2-aminohexyl)acrylamide monomer unit, 2-(tert-butylamino)ethyl methacrylate monomer unit, dimethylaminoethyl acrylate monomer unit, dimethylaminoethyl methacrylate monomer unit, acrylamide monomer unit, methacrylamide monomer unit, N-tert-butylacrylamide monomer unit, N-isopropylacrylamide monomer unit, N,N-dimethylacrylamide monomer unit, and N,N-diethylacrylamide monomer unit; The thickness of the heat-resistant layer is 1-4 μm.

2. The battery separator according to claim 1, wherein The rigid ring structure unit is selected from one or more of styrene monomer unit, methylstyrene monomer unit, vinylnaphthalene monomer unit, vinyltoluene monomer unit, 2,4-dimethylstyrene monomer unit, ethylstyrene monomer unit, isopropylstyrene monomer unit, tert-butylstyrene monomer unit, butylstyrene monomer unit, phenylstyrene monomer unit, cyclohexylstyrene monomer unit, benzylstyrene monomer unit, isobornyl acrylate monomer unit, isobornyl methacrylate monomer unit, maleimide monomer unit, C1-C12 alkyl-substituted maleimide monomer unit, C6-C16 aryl-substituted maleimide monomer unit, and vinyl carbazole; The crosslinking monomer unit is selected from one or more of ethylene glycol diacrylate monomer unit, polyethylene glycol diacrylate monomer unit, propylene glycol diacrylate monomer unit, dipropylene glycol diacrylate monomer unit, tripropylene glycol diacrylate monomer unit, trimethylolpropane triacrylate monomer unit, glycerol triacrylate monomer unit, pentaerythritol triacrylate monomer unit, polyethylene glycol dimethacrylate monomer unit, diethylene glycol dimethacrylate monomer unit, propylene glycol dimethacrylate monomer unit, dipropylene glycol dimethacrylate monomer unit, tripropylene glycol dimethacrylate monomer unit, trimethylolpropane trimethacrylate monomer unit, glycerol trimethacrylate monomer unit, pentaerythritol trimethacrylate monomer unit, divinylbenzene monomer unit, diallyl phthalate monomer unit, glycerol diallyl ether monomer unit, pentaerythritol diallyl ether monomer unit, pentaerythritol triallyl ether monomer unit, diallyl adipate monomer unit, N,N-methylenebisacrylamide monomer unit, allyl acrylate monomer unit, allyl methacrylate monomer unit, and divinylbenzene monomer unit.

3. The battery separator according to claim 1, wherein In the heat-resistant layer, the mass ratio of the polymer particles, binder, thickener, and wetting agent is 100:(3 - 10):(0.5 - 5):(0.5 - 3).

4. The battery separator according to claim 1, wherein The base film layer is a polyolefin base film, and the polyolefin base film is selected from any one of polyethylene porous film, polypropylene porous film, polypropylene / polyethylene / polypropylene three-layer composite porous film, and polybutene porous film.

5. A battery, characterized in that, It includes the battery separator according to any one of claims 1 to 4.

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