Battery separator and method for manufacturing the same, and secondary battery

Abstract

The application relates to the technical field of battery separators, in particular to a battery separator, a preparation method thereof and a battery. The battery separator comprises a substrate and a coating layer on the surface of the substrate, and the coating layer comprises a temperature-responsive component; wherein the temperature-responsive component comprises one or more of poly-N-alkyl acrylamide, poly-N-alkyl acrylate, poly(oligoethylene glycol) acrylate, polyvinyl ether and a natural macromolecule. The application forms an electrolyte storage by arranging a continuous or discontinuous temperature-responsive coating layer, can release the stored electrolyte under the action of temperature, greatly shortens the distance to be passed by electrolyte infiltration, makes the area near the coating material be quickly infiltrated, accelerates the infiltration of the roll core, and realizes better infiltration effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery separator, in particular to a battery separator, a preparation method thereof and a battery. BACKGROUND

[0002] Electrochemical energy storage devices, such as lithium ion batteries and other secondary batteries, have high energy density, high output power, long cycle life, no memory effect, and are widely used in 3C consumer electronics, electric vehicles, large-scale energy storage, and other fields. The separator is a key component of the internal structure of the secondary battery, which has the function of conducting ions and blocking electrons, allowing ions to transmit between the positive and negative electrodes, and blocking the direct contact of the positive and negative electrodes.

[0003] The wettability of the separator and the electrolyte affects the processing and performance of the secondary battery; poor wettability can easily lead to uneven lithium precipitation or black spots on the battery interface, causing a decrease in battery capacity and other performance, and the lithium precipitation area may also cause safety problems in the later cycle.

[0004] Currently, methods to improve the wettability of the separator and the electrolyte include introducing hydrophilic ceramic coatings and hydrophilic modification of the substrate surface. These methods are effective for small-sized secondary batteries, but as the size of the battery increases, the improvement in wettability decreases. During the charging process of the battery, the volume of the electrode expands, expelling the electrolyte between the electrodes from the roll core to the surrounding roll core; during the discharging process of the battery, the expelled electrolyte reenters the roll core. After the size of the battery increases, the time required for the electrolyte to reenter the roll core and be completely wetted increases.

[0005] Based on the above problems, the present application is proposed. SUMMARY

[0006] To solve the above problems in the prior art, the present application provides a battery separator, a preparation method thereof and a secondary battery, which can achieve rapid wettability of the electrolyte in a simple and efficient manner, reduce the interface resistance of the battery, and further improve the electrochemical performance of the battery.

[0007] Based on this, the present application has the following technical solutions:

[0008] In a first aspect, the present application provides a battery separator, comprising a substrate and a coating layer on the surface of the substrate, the coating layer comprising a temperature-responsive component; wherein the temperature-responsive component comprises one or more of poly-N-alkyl acrylamide, poly-N-alkyl acrylate, poly(oligoethylene glycol) acrylate, polyvinyl ether and natural macromolecule.

[0009] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0010] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0011] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0012] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0013] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0014] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0015] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0016] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0017] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0018] The battery separator provided by the application comprises a temperature-responsive component, wherein the temperature-responsive component comprises one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan. BRIEF DESCRIPTION OF DRAWINGS

[0019] The technical solutions of the present application or the prior art will be described below more clearly. The drawings needed in the embodiments or the prior art description will be introduced simply. Obviously, some embodiments of the present application will be described below, and other drawings can be obtained by those skilled in the art without creative work.

[0020] Figure 1 is a schematic diagram of the discontinuous temperature-responsive coating in Example 1 provided by the present application.

[0021] Figure 2 is a schematic diagram of the continuous temperature-responsive coating in Example 10 provided by the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0023] In the first aspect, the present application provides a battery separator, comprising a substrate and a coating on the surface of the substrate, wherein the coating comprises a temperature-responsive component; and the temperature-responsive component comprises one or more of poly (N-alkyl acrylamide), poly (N-alkyl acrylate), poly (oligoethylene glycol) acrylate), polyvinyl ether and natural macromolecule.

[0024] In the present application, the temperature response of the temperature-responsive component refers to that when the temperature rises due to the operation of the battery, the volume phase transition of the coating occurs, and the electrolyte stored in the coating material is released due to the volume shrinkage of the particles, so that the electrolyte quickly reaches the area near the coating material, thereby accelerating the wetting of the battery interface.

[0025] In the present application, the temperature-responsive component functions to store and release electrolyte, and when the battery temperature reaches above the response temperature, the stored electrolyte in the coating material is released due to volume phase transition of the material. Specifically, the response temperature refers to the temperature at which the material begins to undergo volume phase transition, which can be adjusted by material selection or proportion control. The response threshold of the temperature-responsive component is a certain temperature range in 25-60 degrees Celsius, and when the battery is stored below the response threshold temperature, the excess electrolyte is stored in the coating material; when the battery temperature is higher than the response threshold temperature due to heat generated during operation or external temperature control, the coating material shrinks to release the electrolyte, so that the battery interface is quickly infiltrated, thereby improving the battery performance. At the same time, when stored at room temperature, the coating is in a high-swelling state, which is conducive to inhibiting the self-discharge phenomenon of the battery and improving the storage performance of the battery at room temperature.

[0026] According to a preferred embodiment of the present application, the temperature-responsive component includes one or more of poly-N-isopropyl acrylamide, poly-N,N-dimethylaminoethyl methacrylate, poly-methacrylic acid oligoethylene glycol ester, poly-methyl vinyl ether and hydroxybutyl chitosan.

[0027] In the present application, the coating containing the temperature-responsive component can be arranged on one side or both sides of the separator substrate, in a continuous or discontinuous appearance.

[0028] According to a preferred embodiment of the present application, the coverage of the coating on the surface of the substrate on the substrate is 5-50%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% and the like.

[0029] It is further found in the present application that by controlling the coverage of the coating on the surface of the substrate on the substrate in the above range, the battery performance can be further improved.

[0030] According to a preferred embodiment of the present application, the coating on the surface of the substrate further includes other components, and the other components include one or more of fluorine-containing polymers, polyacrylates and polyacrylonitriles and their homopolymers or copolymers; more preferably, the other components include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate and polyacrylonitrile.

[0031] According to a preferred embodiment of the present application, the mass ratio of the temperature-responsive component to the other component is (3-30):(70-97); further preferably, the mass ratio of the temperature-responsive component to the other component is (15-25):(75-85).

[0032] In the present application, if the content of the temperature-responsive component is too low, it is difficult to exert the temperature-responsive function, and the coating function is weakened; if the content of the temperature-responsive component is too high, it is easy to cause the coating material to swell too much, store too much electrolyte, and affect the performance of the battery cell.

[0033] According to a preferred embodiment of the present application, the thickness of the coating on the surface of the substrate is 1-7 microns, for example, 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns or 7 microns, etc.

[0034] According to a preferred embodiment of the present application, the thickness of the substrate is 3-50 microns; the porosity is 25%-65%; more preferably, the substrate comprises one of a polyethylene film, a polypropylene film, a polyimide film, a polyester film and a non-woven fabric, as well as composite films and ceramic coated films thereof.

[0035] In a second aspect, the present application provides a preparation method of the battery separator, comprising: mixing a temperature-responsive component, other components and water to obtain a mixed slurry; coating the mixed slurry on the surface of the substrate to obtain the battery separator.

[0036] According to a preferred embodiment of the present application, the coating method comprises gravure coating, microgravure coating, relief coating, array point coating or rotary spraying; preferably, the coating amount is 0.6-1.2 g / m2.

[0037] Further, the single-sided coating amount is 0.6-0.7 g / m2, and the double-sided coating amount is 1.0-1.2 g / m2.

[0038] In a third aspect, the present application provides a secondary battery comprising a positive electrode, a negative electrode and the battery separator.

[0039] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used is conventional means known to those skilled in the art.

[0040] Examples and Comparative Examples

[0041] Example 1

[0042] The present example provides a battery separator, and a preparation method thereof comprises the following steps (see the flowchart below): Figure 1 ):

[0043] Step one, mix temperature responsive component 1, other component 2 and water, wherein the temperature responsive component 1 is poly-N-isopropyl acrylamide, the other component 2 is polyvinylidene fluoride-hexafluoropropylene copolymer, prepare a coating slurry according to the mass ratio of component 1 and component 2 is 20:80, set the response temperature to 40 degrees Celsius; Step two, provide a substrate of 9 micron polyethylene film, the substrate porosity is 40%, set the ceramic coating to be single-sided 3 micron aluminum oxide; Step three, the slurry prepared in step one is coated on the substrate by using the preparation method of rotary spraying, coated on the ceramic side, the coating amount is set to 0.6 grams per square meter, and a non-continuous coated separator is prepared.

[0044] The embodiment further provides a battery, and a preparation method thereof includes:

[0045] Step four, provide positive and negative electrode sheets prepared by a conventional method, the positive and negative electrode sheets need to be matched, and a conventional electrolyte is provided; Step five, the coated separator prepared in step three, the positive and negative electrode sheets and the electrolyte are assembled into an aluminum shell battery cell, and the matched electrolyte injection amount is 800g.

[0046] The preparation parameters of other embodiments and comparative examples are shown in Table 1, wherein the schematic diagram of the discontinuous temperature responsive coating in Example 1 is shown in Figure 1 , and the schematic diagram of the continuous temperature responsive coating in Example 10 is shown in Figure 2 .

[0047] Table 1

[0048]

[0049] Test example

[0050] 1, liquid retention amount test

[0051] Test method: after the prepared multiple aluminum shell battery cells are fully placed at room temperature for 72h, they are placed at different temperatures (25 degrees Celsius / 35 degrees Celsius / 45 degrees Celsius / 55 degrees Celsius / 65 degrees Celsius) for 1h, and the free electrolyte is poured out from the aluminum shell opening in the corresponding temperature environment.

[0052] Liquid retention amount (g) = injection amount 800 - free electrolyte amount.

[0053] The test results are shown in Table 2.

[0054] Table 2

[0055]

[0056] It should be noted that the coating coverage of Example 6 and Example 10 is 100% compared with the rest of the examples, although it can ensure the liquid retention amount, but too high coverage will lead to no electrolyte immersion channel in the interface between the separator and the electrode, ion transmission is blocked, current density distribution is uneven, resulting in relatively poor electrical performance.

[0057] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery separator, characterized by, The invention comprises a substrate and a coating on the substrate surface, the coating comprising a temperature-responsive component, wherein the temperature-responsive component is poly(N-isopropylacrylamide); the coating on the substrate surface further comprises other components, wherein the other components are polyvinylidene fluoride-hexafluoropropylene copolymer; the mass ratio of the temperature-responsive component to the other components is 30:70; the coverage of the coating on the substrate surface on the substrate is 5% to 50%; the substrate is a polyethylene film; the substrate has a thickness of 9 micrometers and a porosity of 40%; the coating thickness on the substrate surface is 3 micrometers.

2. The method for preparing the battery separator according to claim 1, characterized in that, include: The temperature-responsive component, other components, and water are mixed to obtain a mixed slurry; The mixed slurry is coated onto the surface of the substrate to obtain the battery separator.

3. The method for preparing the battery separator according to claim 2, characterized in that, The coating methods include gravure coating, micro-gravure coating, relief coating, array dot coating, or rotary spraying.

4. The method for preparing the battery separator according to claim 3, characterized in that, The coating amount is 0.3 to 2.0 grams per square meter.

5. A secondary battery, characterized in that, It contains a positive electrode, a negative electrode, and a separator, wherein the separator is the battery separator as described in claim 1.

Images