Separator and method for preparing the same, secondary battery, and electrical device

Abstract

The present application provides a separator including a first porous base film, a second porous base film, and a porous coating disposed between the first and second porous base films, the porous coating including an adhesive and filler particles, and wherein at least some of the filler particles are embedded in the first porous base film to a depth of 1 μm or greater and / or at least some of the filler particles are embedded in the second porous base film to a depth of 1 μm or greater. This configuration allows the adhesive to adhere the first and second porous base films together. Furthermore, the adhesive increases the bonding strength between the porous coating and the first and / or second porous base films, effectively enhancing the separator's heat resistance and nail penetration resistance, thereby improving the reliability of the battery.

Description

[Technical Field]

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to separators and their preparation methods, secondary batteries, and electrical devices. [Background technology]

[0002] Secondary batteries have the excellent characteristics of being light, non-polluting, and having no memory effect, and are therefore widely used in various home appliances and electric vehicles.

[0003] With the continuous development of the new energy industry, users have higher usage needs for secondary batteries, and ensuring better reliability of secondary batteries and electrical devices has become a current challenge to be solved. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the technical problems existing in the background art, the present application provides a separator and a preparation method thereof, a secondary battery and an electric device for improving the reliability performance of the secondary battery and the electric device. [Means for solving the problem]

[0005] In order to achieve the above object, a first aspect of the present application provides a separator comprising a first porous base film, a second porous base film, and a porous coating provided between the first porous base film and the second porous base film, wherein the porous coating comprises an adhesive and filler particles, and the embedment depth of at least some of the filler particles into the first porous base film is 1 μm or more, and / or the embedment depth of at least some of the filler particles into the second porous base film is 1 μm or more.

[0006] Compared to the prior art, the present invention has at least the following beneficial effects: When the porous coating is located between the first porous base film and the second porous base film, the adhesive can adhere the first porous base film and the second porous base film together, and at least some of the filler particles are embedded in the first porous base film and / or the second porous base film to a depth of 1 μm or more, thereby increasing the bonding strength between the porous coating and the first porous base film and / or the second porous base film, effectively improving the heat resistance and nail penetration performance of the separator, and improving the reliability of the battery.

[0007] In any embodiment of the present application, the melting point of the first porous base film is higher than the melting point of the second porous base film, and the embedding depth of the filler particles in the first porous base film is deeper than the embedding depth of the filler particles in the second porous base film. When the separator satisfies this design, the battery can achieve both relatively good reliability and cycle performance.

[0008] In any embodiment of the present application, when the embedding depth of the filler particles into the porous base film having a high melting point is D1 and the embedding depth of the filler particles into the porous base film having a low melting point is D2, the separator satisfies 1.01≦D1 / D2≦3, preferably 1.05≦D1 / D2≦2.

[0009] In any embodiment of the present application, the embedding depth of the filler particles into the first porous base film is 1.5 μm or more, preferably 2.0 μm to 4.5 μm, and / or the embedding depth of the filler particles into the second porous base film is 1.1 μm or more, preferably 1.1 μm to 3.5 μm.

[0010] In any embodiment of the present application, the average pore size of the first porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.5 μm, and / or the average pore size of the second porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.35 μm.

[0011] In any embodiment of the present application, the volume average particle diameter Dv50 of the packing particles is 0.2 μm to 1.2 μm, and preferably 0.3 μm to 0.8 μm.

[0012] In any embodiment of the present application, the ratio of the porosity of the first porous base film to the porosity of the second porous base film is 1.01 to 3.5, and preferably 1.1 to 2.0.

[0013] In any embodiment of the present application, the porosity of the first porous base film is 40% to 80%, preferably 40% to 70%, and / or the porosity of the second porous base film is 20% to 50%, preferably 25% to 35%.

[0014] In any embodiment of the present application, the melting point of the first porous base film is 165°C to 380°C, preferably 165°C to 330°C, and / or the melting point of the second porous base film is 100°C to 250°C, preferably 130°C to 210°C.

[0015] In any embodiment of the present application, the adhesive comprises one or more of polyacrylates, acrylic acid, carboxymethyl cellulose, polyvinylidene fluoride-co-trichloroethylene copolymers, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymers, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, and cyanoethyl pullulan.

[0016] In any embodiment of the present application, the filler particles include at least one of inorganic particles, organic particles, and organometallic framework materials.

[0017] In any embodiment of the present application, the separator comprises: (1) The peel strength between the first porous base film and the porous coating is ≧5 N / m, preferably 5.5 N / m to 10 N / m; (2) The separator has a thermal shrinkage rate in the transverse direction at 250°C for 1 hour of ≦1.5%, preferably ≦1.0%; (3) At least one of the following conditions is satisfied: the thermal shrinkage rate of the separator in the longitudinal direction at 250°C for 1 hour is ≦1.5%, preferably ≦1.0%.

[0018] A second aspect of the present application provides a method for preparing a separator, comprising: providing a first porous base film and a second porous base film; preparing a porous coating slurry containing an adhesive and filler particles, and applying it to the surface of the first porous base film and / or the second porous base film to form a porous coating; and laminating the first porous base film and the second porous base film by a pressing process to form a porous coating between the first porous base film and the second porous base film, thereby obtaining a separator, wherein the embedding depth of at least some of the filler particles into the first porous base film is 1 μm or more, and / or the embedding depth of at least some of the filler particles into the second porous base film is 1 μm or more.

[0019] In any embodiment of the present application, in the crimping process, the crimping temperature is 30°C to 70°C, preferably 35°C to 50°C, and / or the crimping pressure is 2N to 30N, preferably 5N to 20N.

[0020] A third aspect of the present application provides a secondary battery including the separator of the first aspect of the present application or a separator prepared based on the method for preparing a separator of the second aspect.

[0021] In any embodiment of the present application, the secondary battery further includes a positive electrode sheet and a negative electrode sheet, and the separator is provided between the positive electrode sheet and the negative electrode sheet.

[0022] A fourth aspect of the present application provides an electrical device including the secondary battery of the third aspect of the present application.

[0023] Since the device of the present application includes the secondary battery of the present application, it has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0024] In order to more clearly describe the technical aspects of the present application, the drawings used in the present application are briefly introduced below. The drawings described below are only some embodiments of the present application, and it is obvious that those skilled in the art can obtain other drawings based on the drawings without paying creative labor.

[0025] [Figure 1] 1 is a structural schematic diagram of one embodiment of the separator of the present application. [Figure 2] FIG. 1 is a schematic diagram of one embodiment of a secondary battery. [Figure 3] FIG. 3 is an exploded view of FIG. 2. [Figure 4] FIG. 1 is a schematic diagram of one embodiment of a battery module. [Figure 5] FIG. 1 is a schematic diagram of one embodiment of a battery pack. [Figure 6] FIG. 6 is an exploded view of FIG. 5. [Figure 7] FIG. 1 is a schematic diagram of one embodiment of a device that uses a secondary battery as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are merely for the purpose of illustrating the present application and are not intended to limit the scope of the present application.

[0027] For clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an explicitly stated range, any lower limit may be combined with any other lower limit to form an explicitly stated range, and similarly, any upper limit may be combined with any other upper limit to form an explicitly stated range. Furthermore, each individually disclosed point or single numerical value may itself be combined with any other point or single numerical value as a lower limit or upper limit, or with any other lower limit or upper limit to form an explicitly stated range.

[0028] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist).

[0029] In the explanations in this paper, unless otherwise specified, "more than" and "less than" include the actual number, and "several types" in "one or several types" means two or more types.

[0030] Unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter referred to herein may be measured by various measurement methods commonly used in the art (for example, they may be tested according to the methods provided in the examples of the present application).

[0031] [Secondary battery] A secondary battery refers to a battery that can be continuously used by activating the active material through charging after discharging the battery.

[0032] Typically, a secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charge and discharge process of the battery, active ions move back and forth between the positive and negative electrode sheets, inserting and detaching them. The separator is placed between the positive and negative electrode sheets to provide isolation. The electrolyte is placed between the positive and negative electrode sheets to facilitate ion conduction.

[0033] [Separator] 1, an embodiment of the present application provides a separator 10 including a first porous base film 11, a second porous base film 12, and a porous coating 13 disposed between the first porous base film 11 and the second porous base film 12, wherein the porous coating 13 includes an adhesive 14 and filler particles 15, and the embedment depth of at least some of the filler particles 15 into the first porous base film 11 is 1 μm or more, and / or the embedment depth of at least some of the filler particles 15 into the second porous base film 12 is 1 μm or more, where a is the first embedment depth and b is the second embedment depth.

[0034] Without wishing to be limited by any theory, the separator of the present application with a specific structure can effectively improve heat resistance, but the first and second porous base films have the problem of being prone to peeling during battery use. Through extensive research, the inventors have found that when at least some of the filler particles 15 are embedded in the first porous base film 11 and / or the second porous base film 12 to a depth of 1 μm or more, the bonding strength between the porous coating 13 and the first porous base film 11 and / or the second porous base film 12 is effectively increased, thereby improving the heat resistance of the battery. Furthermore, the relatively deep inter-embedded structure allows the separator to have a relatively dense material layer, increasing the separator's ability to withstand physical breakthrough, thereby further improving the reliability of the battery.

[0035] Through further research, the inventors have found that the performance of the battery can be further improved if the separator more preferably satisfies one or more of the following design requirements.

[0036] In some embodiments, the melting point of the first porous base film 11 is higher than the melting point of the second porous base film 12, and the embedment depth of the filler particles 15 in the first porous base film 11 is deeper than the embedment depth of the filler particles 15 in the second porous base film 12. When this design is satisfied, the separator achieves both relatively high tensile strength and local material density, and effectively blocks lithium dendrites, thereby reducing the risk of separator puncture during battery cycling and further improving the reliability performance of the battery.

[0037] In any embodiment of the present application, when the embedding depth of the filler particles 15 into the porous base film with a high melting point is D1 and the embedding depth of the filler particles 15 into the porous base film with a low melting point is D2, the separator satisfies 1.01≦D1 / D2≦3, preferably 1.05≦D1 / D2≦2.

[0038] D1 / D2 may further be 1.01, 1.05, 1.3, 1.4, 1.45, 1.5, 1.83, 1.9, 2, 2.3, 2.4, 2.5, 2.53, 2.7, 2.84, 2.9, 3, etc., or may be a range consisting of any two of the above numerical values, for example, 1.01 to 1.3, 1.05 to 1.5, 1.83 to 2, 2.3 to 2.53, 2.7 to 2.84, 2.9 to 3, etc. In some embodiments, D1 / D2 may further satisfy 1.05≦D1 / D2≦2.

[0039] In any embodiment of the present application, the embedding depth of the filler particles 15 into the first porous base film 11 is 1.5 μm or more, preferably 2.0 μm to 4.5 μm, and / or the embedding depth of the filler particles 15 into the second porous base film 12 is 1.1 μm or more, preferably 1.1 μm to 3.5 μm.

[0040] The embedment depth of the filler particles 15 into the first porous base film 11 may be 1.5 μm, 1.6 μm, 1.65 μm, 2 μm, 2.2 μm, 2.3 μm, 2.5 μm, 2.7 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, etc., or may be a range consisting of any two of the above values, for example, 1.5 μm to 1.65 μm, 2 μm to 2.5 μm, 2 μm to 3 μm, 2.5 μm to 3.5 μm, 3.5 μm to 4.5 μm, 2 μm to 4.5 μm, etc. In some embodiments, the embedment depth of the filler particles 15 into the first porous base film 11 may be 2.0 μm to 4.5 μm.

[0041] The embedment depth of the filler particles 15 into the second porous base film 12 may be 1.1 μm, 1.25 μm, 1.3 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.3 μm, 2.6 μm, 2.95 μm, 3 μm, 3.2 μm, 3.3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, 7 μm, etc., or may be a range consisting of any two of the above values, for example, 1.1 μm to 1.25 μm, 1.4 μm to 2 μm, 1.8 μm to 2.95 μm, 2 μm to 3 μm, 1.1 μm to 3.5 μm, etc. In some embodiments, the embedment depth of the filler particles 15 into the second porous base film 12 may be 1.1 μm to 3.5 μm.

[0042] The embedding depth of the filler particles into the porous base film is a known value in the art and can be tested using equipment and methods known in the art. For example, it can be tested using a scanning electron microscope (e.g., ZEISS Sigma 300). For example, the procedure can be as follows: First, cut the separator into a test sample of a certain size (e.g., 6 mm x 6 mm), sandwich the test sample between two heat-conductive sheets (e.g., copper foil), and secure the test sample and the sheets with adhesive (e.g., double-sided adhesive tape). Then, press the test sample with a flat iron block of a certain mass (e.g., about 400 g) for a certain period of time (e.g., 1 hour) to minimize the gap between the test sample and the copper foil. Then, trim the edges with scissors and attach the sample to a sample holder with conductive adhesive. The sample should protrude slightly beyond the edge of the holder. Next, place the sample stage in the sample rack and lock it in place. Turn on the argon ion cross-section polisher (e.g., IB-19500CP) and apply vacuum (e.g., 10 Pa to 4 Pa). Set the argon gas flow rate (e.g., 0.15 MPa), voltage (e.g., 8 kV), and polishing time (e.g., 2 hours). Adjust the sample stage to oscillation mode and begin polishing. After polishing is complete, use a scanning electron microscope (e.g., ZEISS Sigma 300) to obtain an image of the ion-polished cross-section (CP) of the test sample. Measure the thickness of the base film and coating, respectively. Select EDS Mapping mode and test the distribution depth of the element (e.g., aluminum) contained in the filler particles into the base film as the embedment depth. For example, use the midpoint of the curve distribution as the boundary, assign the coating thickness, and subtract the values ​​for the coating thickness on both sides of the midpoint to obtain the initial value. Further measurement can be extended to the point where the content of the element (e.g., aluminum) contained in the filler particles is zero, and the value representing the embedment depth can be read.

[0043] In any embodiment of the present application, the average pore size of the first porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.5 μm, and / or the average pore size of the second porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.35 μm.

[0044] The average pore size of the first porous base film 11 may be 0.1 μm to 2 μm, for example, 0.1 μm, 0.12 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.65 μm, 0.85 μm, 1 μm, 1.2 μm, 1.35 μm, 1.5 μm, 1.75 μm, 1.85 μm, 2 μm, etc., or may be a range consisting of any two of the above numerical values, for example, 0.1 μm to 0.2 μm, 0.4 μm to 0.85 μm, 1 μm to 1.35 μm, 1.5 μm to 1.75 μm, 1.85 μm to 2 μm, etc. In some embodiments, the average pore size of the first porous base film 11 may be 0.1 μm to 0.5 μm.

[0045] The average pore size of the second porous base film 12 may be 0.1 μm to 2 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.75 μm, 0.85 μm, 1 μm, 1.2 μm, 1.5 μm, 1.75 μm, 1.85 μm, 2 μm, etc., or may be a range consisting of any two of the above values, for example, 0.1 μm to 0.2 μm, 0.1 μm to 0.35 μm, 0.3 μm to 0.75 μm, 0.85 μm to 1.2 μm, 1.5 μm to 1.75 μm, 1.85 μm to 2 μm, etc. In some embodiments, the average pore size of the second porous base film 12 may be 0.1 μm to 0.35 μm.

[0046] When the average pore diameter of the first porous base film and the average pore diameter of the second porous base film satisfy the above conditions, the separator satisfies the embedding depth of the present application and can also achieve relatively good tensile strength.

[0047] In any embodiment of the present application, the average pore size of the porous base film is tested by adopting a mercury porosimeter with reference to GB / T 21650.1-2008.

[0048] In any embodiment of the present application, the volume average particle diameter Dv50 of the filler particles 15 is 0.2 μm to 1.2 μm, and preferably 0.3 μm to 0.8 μm.

[0049] The volume average particle diameter Dv50 of the filler particles 15 may be 0.2 μm to 1.2 μm, such as 0.2 μm, 0.35 μm, 0.4 μm, 0.5 μm, 0.65 μm, 0.75 μm, 0.85 μm, 0.9 μm, 1 μm, 1.2 μm, etc., or may be a range consisting of any two of the above numerical values, such as 0.2 μm to 0.35 μm, 0.4 μm to 0.65 μm, 0.3 μm to 0.8 μm, 0.5 μm to 0.85 μm, 0.75 μm to 1 μm, etc. In some embodiments, the volume average particle diameter Dv50 of the filler particles 15 may be 0.3 μm to 0.8 μm.

[0050] The volume average particle size Dv50 of the filler particles has the meaning known in the art and represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%, and may be tested using methods known in the art, such as standard GB / T 19077-2016, and may be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0051] In any embodiment of the present application, the ratio of the porosity of the first porous base film 11 to the porosity of the second porous base film 12 is 1.01 to 3.5, and preferably 1.1 to 2.0.

[0052] The ratio of the porosity of the first porous base film 11 to the porosity of the second porous base film 12 may be 1.01, 1.5, 1.8, 2, 2.15, 2.5, 2.87, 3, 3.01, 3.15, 3.2, 3.25, 3.4, 3.5, etc., or may be a range consisting of any two of the above numerical values, for example, 1.01 to 1.8, 2 to 2.5, 2.87 to 3, 3.01 to 3.2, 3.25 to 3.5, etc.

[0053] When the ratio of the porosity of the first porous base film 11 to the porosity of the second porous base film 12 satisfies the above conditions, the separator satisfies the embedding depth of the present application while also achieving relatively good tensile strength.

[0054] In any embodiment of the present application, the porosity of the first porous base film 11 is 40% to 80%, preferably 40% to 70%, and / or the porosity of the second porous base film 12 is 20% to 50%, preferably 25% to 35%.

[0055] The porosity of the first porous base film 11 may be 40%, 50%, 55%, 58%, 60%, 65%, 70%, 72%, 73.5%, 75%, 80%, etc., or may be a range consisting of any two of the above values, for example, 40% to 50%, 55% to 58%, 60% to 70%, 72% to 73.5%, 75% to 80%, etc. In some embodiments, the porosity of the first porous base film 11 may be 40% to 70%.

[0056] The porosity of the second porous base film 12 may be 20%, 25%, 28.5%, 30%, 32%, 40%, 45%, 48%, 50%, etc., or may be a range consisting of any two of the above values, for example, 20% to 25%, 25% to 35%, 30% to 40%, 45% to 50%, etc. In some embodiments, the porosity of the second porous base film 12 may be 25% to 35%.

[0057] The porosity of the base film has a meaning known in the art and may be tested using equipment and methods known in the art, for example, the porosity of the base film may be tested using a mercury porosimeter in accordance with GB / T 21650.1-2008.

[0058] In any embodiment of the present application, the melting point of the first porous base film 11 is 165°C to 380°C, preferably 165°C to 330°C, and / or the melting point of the second porous base film 12 is 100°C to 250°C, preferably 130°C to 210°C.

[0059] The melting point of the first porous base film 11 may be 165°C, 169°C, 170°C, 176°C, 180°C, 212°C, 235°C, 256°C, 264°C, 280°C, 315°C, 330°C, 355°C, 360°C, 365°C, 380°C, etc., or may be a range consisting of any two of the above values, for example, 165°C to 176°C, 180°C to 212°C, 235°C to 280°C, 315°C to 330°C, 355°C to 360°C, 365°C to 380°C, etc. In some embodiments, the melting point of the first porous base film 11 may be 165°C to 330°C.

[0060] The melting point of the second porous base film 12 may be 100°C, 110°C, 125°C, 135°C, 141°C, 145°C, 150°C, 155°C, 160°C, 170°C, 185°C, 195°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc., or may be a range consisting of any two of the above values, for example, 100°C to 125°C, 135°C to 141°C, 145°C to 155°C, 160°C to 185°C, 195°C to 210°C, 130°C to 210°C, 220°C to 250°C, etc. In some embodiments, the melting point of the second porous base film 12 may be 130°C to 210°C.

[0061] The melting points of the first and second porous base films may be tested using equipment and methods known in the art. For example, they may be measured using differential scanning calorimetry. For specific details, reference may be made to GB / T 19466.3-2004. For example, the following method may be used: 4 to 6 mg of a test sample is weighed and placed in the sample chamber of a differential scanning calorimeter. The sample is heated from 25°C to 400°C at a rate of 10°C / min to obtain a melting endothermic curve. The temperature corresponding to the peak of the curve is the melting point of the sample.

[0062] In any embodiment of the present application, adhesive 14 includes one or more of polyacrylate, acrylic acid, carboxymethyl cellulose, polyvinylidene fluoride-co-trichloroethylene copolymer, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, and cyanoethyl pullulan.

[0063] The first porous base film 11 and the second porous base film 12 may be directly laminated by hot pressing. If the temperature is too high in the process of laminating by hot pressing, the porosity will be small and the breathability will be poor, and if the temperature is too low, the adhesion between the first porous base film 11 and the second porous base film 12 will not be strong, so it is necessary to adjust the hot pressing temperature appropriately. Preferably, the hot pressing temperature is 20°C to 50°C.

[0064] When a porous coating 13 is provided between the first porous base film 11 and the second porous base film 12 and the adhesive 14 in the porous coating 13 contains the above components, the stability of the secondary battery can be improved.

[0065] In any embodiment of the present application, the filler particles 15 include at least one of inorganic particles, organic particles, and organometallic framework materials.

[0066] Preferably, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of generating electrochemical reactions.

[0067] Preferably, the inorganic particles having a dielectric constant of 5 or more are selected from the group consisting of boehmite, alumina, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, magnesium lithium silicate, magnesium sodium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 <m<1、0<n<1)、Pb(Mg3Nb 2 / 3The adhesive layer may include at least one of )O3-PbTiO3 (abbreviated as PMN-PT) and modified inorganic particles. Preferably, the inorganic particles are modified by chemical and / or physical modification. Chemical modification methods include modification with a coupling agent (e.g., a silane coupling agent, a titanate ester coupling agent, etc.), modification with a surfactant, and modification by polymer grafting. Physical modification methods include dispersion by mechanical force, ultrasonic dispersion, and high-energy treatment. Modification treatment can reduce the aggregation of inorganic particles, resulting in a more stable and uniform structure of the adhesive layer. Furthermore, selecting a coupling agent, surfactant, or polymer with a specific functional group to modify the inorganic particles can improve the electrolyte penetration and retention properties of the adhesive layer and improve the adhesive layer's adhesion to the first and second porous base films.

[0068] Preferably, the inorganic particles having ion conductivity but not ion storage are Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, Lithium titanium aluminum phosphate Li x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3 O y3 Glass, Lithium lanthanum titanate x4 La y4 TiO3, Lithium germanium thiophosphate Li x5 Ge y5 Pz2S w , lithium nitride Li x6 N y6 , SiS2 type glass Li x7 Si y7 S z3 , and P2S5 type glass Li x8 P y8 S z4It may contain at least one of them, where 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. Thereby, the ion conductivity of the separator can be further improved.

[0069] Preferably, the inorganic particles capable of generating an electrochemical reaction may contain at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0070] Preferably, the organic particles may contain one or more of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic acid wax, polyethylene, polypropylene, cellulose, cellulose modifiers (such as carboxymethyl cellulose), melamine resin, phenol resin, polyester (such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), silicone resin, polyimide, polyamideimide, polyarylamide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyarylate ketone, and copolymers of butyl acrylate and ethyl methacrylate (such as cross-linked polymers of butyl acrylate and ethyl methacrylate).

[0071] Preferably, the organometallic frame material may contain one or more of nitrogen-containing heterocyclic ligand construction structures, organic carboxylic acid ligand construction structures, and nitrogen-containing oxygen mixed ligand construction structures.

[0072] In some embodiments, the content of the adhesive is 10% or more, preferably 10% - 30%, based on the total weight of the adhesive layer.

[0073] In some embodiments, the content of the filler may be 90% or less, preferably 40% to 90%, or 60% to 80%, by total weight of the adhesive layer.

[0074] In some embodiments, the coating may include a dispersant, such as carboxymethyl cellulose, to adjust the viscosity of the coating slurry and improve coating mass and uniformity.

[0075] In some embodiments, the dispersant content may be 25% or less, and preferably 20% or less, by total weight of the adhesive layer.

[0076] When a porous coating 13 is provided between the first porous base film 11 and the second porous base film 12, and the filling particles 15 in the porous coating 13 contain at least one of the above-mentioned inorganic particles, organic particles, and organometallic framework materials, the filling particles 15 in the porous coating 13 can further improve the heat resistance and physical performance of the separator 10, thereby increasing the stability of the secondary battery.

[0077] In any embodiment of the present application, the separator 10 satisfies at least one of the following (1) to (3). (1) The peel strength between the first porous base film and the second porous base film is ≧5 N / m, preferably 5.5 N / m to 10 N / m. (2) The separator has a thermal shrinkage rate in the transverse direction at 250°C for 1 hour of ≦1.5%, preferably ≦1.0%. (3) The thermal shrinkage rate of the separator in the longitudinal direction at 250°C for 1 hour is ≦1.5%, preferably ≦1.0%.

[0078] When at least one of the above (1) to (3) satisfies a predetermined range, the separator 10 has good heat resistance and physical properties, and can improve the stability of the secondary battery.

[0079] The thermal shrinkage rate in the transverse direction and the thermal shrinkage rate in the longitudinal direction of the separator 10 are both known in the art and may be measured using existing methods in the art. For example, sample preparation: the separator prepared as above is punched out using a press to form samples with a width of 50 mm and a length of 100 mm, five overlapping samples are taken and placed on A4 paper and fixed, and the A4 paper with the samples placed on it is then placed on a cardboard with a thickness of 1 mm to 5 mm.

[0080] Sample test: Place an A4 size paper on a cardboard box and place it in a fan oven. Set the temperature of the fan oven to 250°C. After the temperature reaches the set temperature and is maintained for 30 minutes, start timing. After the set time (1 hour in this case), measure the length and width of the separator and record the values ​​as a and b, respectively.

[0081] Calculation of heat shrinkage: Heat shrinkage in transverse direction (TD) = [(50-b) / 50] × 100%, Heat shrinkage in longitudinal direction (TD) = [(50-a) / 50] × 100%, and the average value of five duplicate samples is taken as the test result.

[0082] In any embodiment of the present application, a method for preparing a separator includes providing a first porous base film and a second porous base film; preparing a porous coating slurry containing an adhesive and filler particles, and applying the porous coating slurry to the surface of the first porous base film and / or the second porous base film to form a porous coating; and laminating the first porous base film and the second porous base film by a pressing process to provide a porous coating between the first porous base film and the second porous base film, thereby obtaining a separator, wherein the embedding depth of at least some of the filler particles into the first porous base film is 1 μm or more, and / or the embedding depth of at least some of the filler particles into the second porous base film is 1 μm or more.

[0083] In any embodiment of the present application, in the crimping process, the crimping temperature is 30°C to 70°C, preferably 35°C to 50°C, and / or the crimping pressure is 2N to 30N, preferably 5N to 20N.

[0084] In the crimping process, the crimping temperature may be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., or may be a range consisting of any two of the above values, for example, 30°C to 40°C, 40°C to 50°C, 35°C to 50°C, 50°C to 60°C, etc. In some embodiments, the crimping temperature is 35°C to 50°C.

[0085] The crimping pressure may be 2N, 5N, 7N, 10N, 12N, 15N, 17N, 20N, 23N, 55N, 27N, 30N, etc., or may be a range consisting of any two of the above values, for example, 2N to 10N, 5N to 20N, 10N to 25N, 15N to 30N, etc. In some embodiments, the crimping pressure is 5N to 20N.

[0086] By controlling the temperature and pressure in the compression bonding process within the above ranges, at least some of the filler particles are embedded in the first porous base film to a depth of 1 μm or more, and / or at least some of the filler particles are embedded in the second porous base film to a depth of 1 μm or more, which effectively increases the bonding strength between the porous coating and the first and second porous base films, improving the heat resistance of the separator and thereby enhancing the reliability of the secondary battery.

[0087] Unless otherwise specified, each of the raw materials used in the separator (for example, the first porous base film, the second porous base film, the adhesive, the filler, etc.) is commercially available.

[0088] [Positive electrode sheet] In a secondary battery, the positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer provided on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0089] The positive electrode current collector may be a conventional metal foil or a composite current collector (a composite current collector may be formed by providing a metal material on a polymer substrate). For example, the positive electrode current collector may be aluminum foil.

[0090] The positive electrode active material is not limited to a specific type, and may be any active material known in the art that can be used for the positive electrode of a secondary battery, and can be selected by a person skilled in the art according to actual needs.

[0091] For example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and modified compounds thereof. All of these materials are commercially available.

[0092] The modified compounds of the above-mentioned materials may be modified by doping and / or surface coating the materials.

[0093] The positive electrode membrane layer typically more preferably includes an adhesive, a conductive agent, and other suitable auxiliary agents.

[0094] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, conductive carbon black (Super P, SP), graphene, and carbon nanofibers.

[0095] By way of example, the adhesive may be one or more of Polymerized Styrene Butadiene Rubber (SBR), water-based acrylic resin, Polyvinylidene Difluoride (PVDF), Polytetrafluoroethylene (PTFE), Ethylene-vinyl Acetate Copolymer (EVA), Polyacrylic Acid (PAA), Carboxymethyl Cellulose (CMC), Polyvinyl Alcohol (Vinylalcohol Polymer (PVA)), and Polyvinyl Butyral (PVB).

[0096] [Negative electrode sheet] In a secondary battery, the negative electrode sheet usually includes a negative electrode current collector and a negative electrode film layer provided on the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0097] The negative electrode current collector may be a conventional metal foil or a composite current collector (e.g., a metal material may be applied to a polymer substrate to form a composite current collector). For example, the negative electrode current collector may be a copper foil.

[0098] The negative electrode active material is not limited to a specific type, and may be any active material known in the art that can be used for the negative electrode of a secondary battery. Those skilled in the art can select a material according to their needs. For example, the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. The silicon-based material may be one or more selected from elemental silicon, silicon oxide compounds (e.g., silicon oxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be one or more selected from elemental tin, stannic acid compounds, and tin alloys. All of these materials are commercially available.

[0099] In some embodiments, the negative electrode active material may include a silicon-based material to further increase the energy density of the battery.

[0100] The negative electrode film layer usually more preferably contains an adhesive, a conductive agent, and other suitable auxiliary agents.

[0101] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] By way of example, the adhesive may be one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0103] By way of example, other suitable auxiliaries may be thickening and dispersing agents (such as carboxymethylcellulose sodium, CMC-Na), PTC thermistor materials.

[0104] [Electrolyte] The secondary battery may include an electrolyte that functions to conduct ions between the positive electrode and the negative electrode. The electrolyte may include an electrolyte salt and a solvent.

[0105] By way of example, the electrolyte salt may be one or more selected from lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatephosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0106] Exemplary solvents include ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), diisopropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (Methyl The sulfone may be one or more selected from the group consisting of n-propyl propionate (MP), n-propyl propionate (PP), n-methyl butyrate (MB), n-ethyl butyrate (EB), 1,4-butylolactone (GBL), cyclobutane sulfone (tetramethylene sulfone (SF), dimethyl sulfone (methyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (diethyl sulfone (ESE)).

[0107] In some embodiments, the electrolyte solution further includes an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, an additive that improves the low-temperature performance of the battery, or an additive that can improve some performance of the battery.

[0108] In some embodiments, the secondary battery may be a lithium-ion secondary battery. When the porous coating 13 is positioned between the first porous base film 11 and the second porous base film 12, the adhesive 14 functions to adhere the first porous base film 11 and the second porous base film 12. Furthermore, the depth to which at least a portion of the filler particles 15 are embedded in the first porous base film 11 and / or the second porous base film 12 is 1 μm or more, which increases the bonding strength between the porous coating 13 and the first porous base film 11 and the second porous base film 12 and improves the reliability of the secondary battery.

[0109] In the embodiments of the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 2 shows an exemplary secondary battery 5 with a rectangular structure.

[0110] In some embodiments, the secondary battery may include an exterior body that is used to seal the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0111] In some embodiments, the exterior of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The exterior of the secondary battery may be a flexible package, such as a bag-type flexible package. The flexible package may be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0112] In some embodiments, referring to FIG. 3 , the exterior body may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding storage chamber. The housing 51 has an opening communicating with the storage chamber. The cover plate 53 may be installed to cover the opening to close the storage chamber.

[0113] The method for preparing the secondary battery of the present application is well known. In some embodiments, a secondary battery may be formed by assembling a positive electrode sheet, a separator 10, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator 10, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process, the electrode assembly may be placed in an outer casing, dried, and then an electrolyte may be injected. A battery cell may be obtained through processes such as vacuum sealing, standing, chemical conversion, and shaping. Multiple battery cells may further be connected in series, in parallel, or in a combination of series and parallel to form a battery module. Multiple battery modules may be connected in series, in parallel, or in a combination of series and parallel to form a battery pack. In some embodiments, multiple battery cells may directly form a battery pack.

[0114] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0115] The battery module 4 may include an outer shell having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0116] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0117] 5 and 6 show an example battery pack 1. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 can be attached to the lower housing 3 as a lid to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any desired configuration.

[0118] [Device] The present application further provides an electric device including the secondary battery of the present application. The battery cell, battery module, or battery pack may be a power source for the device or a power storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship, a satellite, or a power storage system.

[0119] The device may be selected as a battery cell, a battery module or a battery pack depending on the needs of its use.

[0120] 7 shows an exemplary electric device. The electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density needs of the secondary battery of the electric device, a battery pack or a battery module may be employed.

[0121] Other exemplary electrical devices may be mobile phones, tablet computers, and laptop computers.

[0122] Such electrical devices are usually required to be lightweight and may employ battery cells as a power source.

[0123] The beneficial effects of the present invention will be further explained below in connection with examples.

[0124] In order to clarify the technical problems, technical aspects, and beneficial effects that the embodiments of the present application aim to solve, the embodiments will be described in more detail below in conjunction with the embodiments and drawings. It is clear that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and will not be used as any limitation on the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without paying creative labor fall within the scope of protection of the present application.

[0125] [1. Preparation of separator] Separator 1: (1) Providing a first porous base film and a second porous base film: The first porous base film is polypropylene (PP), and the second porous base film is polyethylene (PE). The melting point of the first porous base film is 165°C, and the melting point of the second porous base film is 135°C. The porosity of the first porous base film is 55%, and the porosity of the second porous base film is 35%. The average pore size of the pore structure of the first porous base film is 0.15 μm, and the average pore size of the second porous base film is 0.12 μm.

[0126] (2) Preparation of coating slurry: The coating slurry was prepared by uniformly mixing the adhesive polyacrylate, filler particles alumina, and carboxymethyl cellulose in a ratio of 1:4:1 with an appropriate amount of deionized water as the solvent. The volume average particle diameter Dv50 of the filler particles was 0.3 μm.

[0127] (3) The above coating slurry was applied to one surface of a PE base film to form a porous coating, which was then dried in an oven for 8 seconds. The PP and PE base films were then hot-pressed. The hot-pressing temperature was 45°C, the hot-pressing pressure was 10 N, and the hot-pressing time was 5 seconds, resulting in a porous coating positioned between the PP and PE base films to form a separator. The alumina particles were embedded to a depth of 1.2 μm in the first porous base film (PP) and a depth of 1.1 μm in the second porous base film (PE).

[0128] The preparation methods for separators 2 to 12 are the same as for separator 1. The only difference is that one or more of the setting items of the average pore size of the base film or the hot pressing process are adjusted, see Table 1 for details. All other preparation methods are the same as for separator 1.

[0129] The separator 1 prepared by the above method has been tested for related performance, and the specific results are shown in Table 1.

[0130] [2. Battery Preparation] Example 1 1. Preparation of the positive electrode sheet Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (SuperP), and adhesive polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96.2:2.7:1.1 with an appropriate amount of solvent N-methylpyrrolidone (NMP) to obtain positive electrode slurry. The positive electrode slurry is then applied to the aluminum foil positive electrode current collector, followed by drying, cold pressing, striping cutting, and cutting processes to obtain a positive electrode sheet.

[0131] 2. Preparation of negative electrode sheet The negative electrode active material, artificial graphite, the conductive agent, carbon black (SuperP), the adhesive, styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na) are mixed uniformly in a mass ratio of 96.4:0.7:1.8:1.1 with an appropriate amount of deionized water as the solvent to obtain negative electrode slurry. The negative electrode slurry is then coated onto the copper foil negative electrode current collector, followed by drying, cold pressing, striping cutting, and cutting processes to obtain a negative electrode sheet.

[0132] 3. Separator The separator used is the separator 1 prepared above.

[0133] 4. Preparation of electrolyte Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 30:70 to obtain an organic solvent, and LiPF6, a thoroughly dried electrolyte salt with a concentration of 1.0 mol / L, is dissolved in the mixed solvent and mixed uniformly to obtain an electrolyte solution.

[0134] 5. Preparation of secondary batteries The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, with the separator positioned between the positive and negative electrode sheets to provide isolation, and then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer casing, and the prepared electrolyte solution is injected into the dried secondary battery. The secondary battery is then vacuum sealed, left to stand, chemically formed, and shaped to obtain the secondary battery.

[0135] The secondary batteries of Examples 2 to 10 and Comparative Examples 1 and 2 were prepared in the same manner as the secondary battery of Example 1. The difference is that different separators were used (among these, separators 1 to 10 were used in Examples 1 to 10, and separators 11 and 12 were used in Comparative Examples 1 and 2), and for details, see Table 1.

[0136] [3. Battery performance test] 1. 250℃ horizontal heat shrinkage test: Sample preparation: The separator prepared above is punched out into samples 50 mm wide and 100 mm long using a press, and five overlapping samples are placed on A4 paper and fixed in place. The A4 paper with the samples placed on it is then placed on a piece of cardboard 1 to 5 mm thick.

[0137] Sample test: Place an A4 sheet of paper on a cardboard box and place it in a blast oven. Set the oven temperature to 250°C. After the temperature reaches the set temperature and is maintained for 30 minutes, start timing. After the set time (for example, 1 hour) is reached, measure the separator width and record the value as b.

[0138] The thermal shrinkage rate in the transverse direction (TD) = [(50-b) / 50] x 100%, and the average value of five duplicate samples is taken as the test result.

[0139] 2. Nail penetration test Test at 25°C with the battery at 100% SOC. Arrange the battery in the following order: insulation pad / punctured battery cell / insulation pad / test battery cell / insulation pad. Connect the high-temperature sensing wire and start the water circulation in advance. When the temperature of the battery cell is almost entirely stable at 25°C, continue circulating for 10 minutes or more. Using a φ3mm high-temperature resistant steel needle, pierce the test battery cell at the exact center of the heat source at a needle speed of 0.01mm / s until it stops functioning (the device's displayed voltage fluctuates or drops suddenly), and record the time. The punctured battery cell refers to the punctured battery cell used as the heat source.

[0140] [Table 1]

[0141] As can be seen from Table 1, an analysis of Examples 1 to 10 and Comparative Examples 1 and 2 reveals that the depth to which the filler particles are embedded in the first porous base film and / or the second porous base film is 1 μm or more in Examples 1 to 10. This effectively improves both the heat resistance of the separator and the nail penetration test performance of the battery, thereby effectively improving the reliability of the secondary battery.

[0142] The above are only specific embodiments of the present application, and the scope of protection of the present application is not limited thereto. Those skilled in the art can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and all such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be consistent with the scope of protection of the claims.

Claims

1. a first porous base film; a second porous base film; a porous coating disposed between the first porous base film and the second porous base film; The porous coating includes an adhesive and filler particles, and at least some of the filler particles are embedded into the first porous base film to a depth of 1 μm or more, and / or at least some of the filler particles are embedded into the second porous base film to a depth of 1 μm or more. Separator.

2. The melting point of the first porous base film is higher than the melting point of the second porous base film, and the embedding depth of the filler particles in the first porous base film is greater than the embedding depth of the filler particles in the second porous base film; The separator according to claim 1 .

3. When the embedding depth of the filler particles in the first porous base film is D1 and the embedding depth of the filler particles in the second porous base film is D2, the separator satisfies 1.01≦D1 / D2≦3, preferably 1.05≦D1 / D2≦2. The separator according to claim 1 or 2.

4. The embedding depth of the filler particles into the first porous base film is 1.5 μm or more, preferably 2.0 μm to 4.5 μm; and / or The embedding depth of the filler particles into the second porous base film is 1.1 μm or more, preferably 1.1 μm to 3.5 μm. The separator according to any one of claims 1 to 3.

5. The average pore size of the first porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.5 μm, and / or the average pore size of the second porous base film is 0.1 μm to 2 μm, preferably 0.1 μm to 0.35 μm. The separator according to any one of claims 1 to 4.

6. The volume average particle diameter Dv50 of the filling particles is 0.2 μm to 1.2 μm, preferably 0.3 μm to 0.8 μm. The separator according to any one of claims 1 to 5.

7. The ratio of the porosity of the first porous base film to the porosity of the second porous base film is 1.01 to 3.5, preferably 1.1 to 2.

0. The separator according to any one of claims 1 to 6.

8. The porosity of the first porous base film is 40% to 80%, preferably 40% to 70%, and / or The porosity of the second porous base film is 20% to 50%, preferably 25% to 35%. The separator according to any one of claims 1 to 7.

9. The melting point of the first porous base film is 160°C to 380°C, preferably 165°C to 330°C, and / or the melting point of the second porous base film is 100°C to 250°C, preferably 130°C to 210°C. The separator according to any one of claims 1 to 8.

10. The adhesive may comprise one or more of polyacrylates, acrylic acid, carboxymethyl cellulose, polyvinylidene fluoride-co-trichloroethylene copolymers, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymers, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, cyanoethyl pullulan; The separator according to any one of claims 1 to 9.

11. The filler particles include at least one of inorganic particles, organic particles, and organometallic framework materials. The separator according to any one of claims 1 to 10.

12. The separator is (1) The peel strength between the first porous base film and the porous coating is ≧5 N / m, preferably 5.5 N / m to 10 N / m; (2) The thermal shrinkage rate in the transverse direction at 250°C for 1 hour is ≦1.5%, preferably ≦1.0%; (3) The thermal shrinkage rate in the longitudinal direction at 250°C for 1 hour is ≦1.5%, preferably ≦1.0%. At least one of the following three conditions is satisfied: The separator according to any one of claims 1 to 11.

13. providing a first porous base film and a second porous base film; preparing a porous coating slurry containing an adhesive and filler particles, and applying the slurry to the surface of the first porous base film and / or the second porous base film to form a porous coating; laminating the first porous base film and the second porous base film by a compression process to provide the porous coating between the first porous base film and the second porous base film, thereby obtaining the separator; At least some of the filler particles are embedded in the first porous base film to a depth of 1 μm or more, and / or at least some of the filler particles are embedded in the second porous base film to a depth of 1 μm or more. Method for preparing the separator.

14. In the crimping process, the crimping temperature is 30°C to 70°C, preferably 35°C to 50°C; and / or The pressure is 2N to 30N, preferably 5N to 20N.

14. The preparation method according to claim 13.

15. The separator comprises a separator according to any one of claims 1 to 12, or a separator prepared according to the method for preparing a separator according to claim 13 or 14. Secondary battery.

16. The battery further includes a positive electrode sheet and a negative electrode sheet, and the separator is provided between the positive electrode sheet and the negative electrode sheet. The secondary battery according to claim 15.

17. The secondary battery according to claim 15 or 16, Electrical equipment.

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