Separators, secondary batteries and power consumption devices

Abstract

The present application provides a separator including a first base film and a second base film, wherein the melting point of the second base film is lower than that of the first base film, the puncture strength of the second base film is 220 gf to 460 gf, and the puncture strength of the separator is 330 gf to 620 gf. When the puncture strengths of the first base film and the separator are within the above selected ranges, the reliability of the secondary battery can be improved.

Description

[Technical Field]

[0001] The present application relates to the field of secondary battery technology, and more particularly to separators, secondary batteries, and power consuming devices. [Background technology]

[0002] Due to their excellent characteristics of light weight, pollution-free and no memory effect, secondary batteries are widely used in various household appliances and electric vehicles. With the continuous development of the new energy industry, users' needs for the reliability of secondary batteries are increasing.

[0003] Therefore, how to make secondary batteries more reliable is a problem that must be solved urgently. 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, a secondary battery and a power consumption device, which aims to improve the reliability of the secondary battery. [Means for solving the problem]

[0005] In order to achieve the above object, a first aspect of the present application provides a separator including a first base film and a second base film, wherein the melting point of the second base film is lower than the melting point of the first base film, the puncture strength of the second base film is 220 gf to 460 gf, and the puncture strength of the separator is 330 gf to 620 gf.

[0006] Compared to the prior art, the present application has at least the following beneficial effects: the separator according to the present application has a melting point of the second base film that is lower than the melting point of the first base film, and the puncture strength of the second base film and the puncture strength of the separator are selected within the above ranges, thereby providing the separator with different degrees of puncture resistance, i.e., the puncture resistance of one side is different from that of the other side. When dealing with uneven dendrites in a battery, it is possible to prevent dendrites from penetrating the separator and causing short circuits, thereby improving the reliability of the secondary battery.

[0007] In any embodiment of the present application, the ratio of the puncture strength of the first base film to the puncture strength of the second base film is 0.2 to 0.95, and optionally 0.3 to 0.75. When the ratio of the puncture strength of the first base film to the puncture strength of the second base film satisfies the above condition, the separator has good puncture resistance and can balance other performances, thereby further improving the reliability of the secondary battery.

[0008] In any embodiment of the present application, the puncture strength of the first base film is 100 gf to 220 gf, and the puncture strength of the second base film is 260 gf to 400 gf. When the puncture strength of the first base film and / or the puncture strength of the second base film satisfy the above conditions, the separator has good puncture resistance, and the reliability of the secondary battery can be further improved.

[0009] In any embodiment of the present application, the separator comprises: (1) The transverse elongation at break of the first base film is 50% to 200%, and optionally 60% to 160%; (2) The longitudinal breaking elongation of the first base film is 40% to 700%, and optionally 80% to 600%; (3) The transverse elongation at break of the second base film is 40% to 220%, and optionally 80% to 170%; (4) The longitudinal breaking elongation of the second base film satisfies at least one of the following: 30% to 100%, and optionally 40% to 85%.

[0010] When at least one of the above items (1) to (4) of the separator satisfies a given range, the separator has better puncture resistance, thereby further improving the reliability of the secondary battery.

[0011] In any embodiment of the present application, the average filament diameter of the first base film is 60 nm to 300 nm, optionally 80 nm to 200 nm, and / or the average filament diameter of the second base film is 40 nm to 350 nm, optionally 70 nm to 180 nm. When the average filament diameter of the first base film and / or the average filament diameter of the second base film satisfy the above range, it is advantageous for keeping the puncture strength of the base film and separator within the range of the present application, and also for achieving good stretchability of the separator, thereby further improving the reliability of the secondary battery.

[0012] In any embodiment of the present application, the melting point of the first base film is 155° C. to 360° C., optionally 160° C. to 335° C., and the melting point of the second base film is 125° C. to 260° C., optionally 130° C. to 220° C. By limiting the melting points of the first base film and the second base film to within the above ranges, it is possible to ensure that the first base film and the second base film have good puncture resistance while also achieving good heat resistance.

[0013] In any embodiment of the present application, the relative molecular mass of the material of the first base film is 400,000 to 1.8 million, optionally 500,000 to 1.3 million, and / or the relative molecular mass of the material of the second base film is 300,000 to 1.5 million, optionally 400,000 to 1.1 million. When the relative molecular masses of the first base film and the second base film satisfy the above conditions, the separator has good puncture resistance, and the reliability of the secondary battery can be further improved.

[0014] In any embodiment of the present application, the thickness of the first base film is equal to or greater than the thickness of the second base film, and optionally, the ratio of the thickness of the first base film to the thickness of the second base film is 1.02 to 5, preferably 1.1 to 3.0.

[0015] In any embodiment of the present application, the thickness of the first base film is 2 μm to 14 μm, optionally 3 μm to 9 μm, and the thickness of the second base film is 2 μm to 12 μm, optionally 3 μm to 7 μm.

[0016] When the thickness of the first base film and / or the thickness of the second base film meets the above conditions, the separator has excellent puncture resistance, thereby further improving the reliability of the secondary battery and, at the same time, improving the energy density of the battery.

[0017] In any embodiment of the present application, an intermediate layer is further provided between the first base film and the second base film, the intermediate layer being provided between the first base film and the second base film, the intermediate layer including an adhesive, and optionally further including filler particles, the filler particles including at least one of inorganic particles, organic particles, and organic-metallic frame materials. When an intermediate layer is provided between the first base film and the second base film, it can not only compensate for process defects in the hot-press compounding process, but also further improve the stability of the physical properties of the separator, thereby further improving the reliability of the secondary battery.

[0018] In any embodiment of the present application, the adhesive includes one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl amylopectin. When an intermediate layer is provided between the first base film and the second base film and the adhesive in the intermediate layer includes the above-mentioned components, the reliability of the secondary battery can be improved.

[0019] In any embodiment of the present application, the separator comprises: (1) The separator has a puncture strength of 330 gf to 630 gf, and optionally 400 gf to 600 gf; (2) The separator's transverse tensile strength is ≥ 700 kg / cm 2 and selectively 1000 kg / cm 2 ~1900kg / cm 2 And, (3) The longitudinal tensile strength of the separator is ≥ 1000 kg / cm 2 and selectively 1200 kg / cm 2 ~2200kg / cm 2 And, (4) The separator has a transverse heat shrinkage rate of ≦3% at 250°C for 1 hour, and optionally ≦2.0%; (5) The separator satisfies at least one of the following: a longitudinal heat shrinkage rate at 250°C for 1 hour of ≦3%, and optionally ≦2.0%.

[0020] When at least one of the above items (1) to (5) of the separator satisfies a given range, the separator has good puncture resistance and can improve the reliability of the secondary battery.

[0021] A second aspect of the present application provides a secondary battery including the separator according to the first aspect of the present application, and when the secondary battery employs a given separator, the reliability of the secondary battery can be improved.

[0022] In any embodiment of the present application, the secondary battery further includes a positive electrode plate and a negative electrode plate, the separator is disposed between the positive electrode plate and the negative electrode plate, and the second base film of the separator faces the negative electrode plate.

[0023] The second base film of the separator faces the negative electrode plate, and the high puncture strength of the second base film increases the lithium dendrite puncture resistance effect, further improving the reliability of the secondary battery.

[0024] A third aspect of the present application provides a power consuming device, the power consuming device including the secondary battery of the second aspect of the present application. Use of a given separator in the secondary battery of the power consuming device can improve the reliability of the power consuming device.

[0025] The device of the present application includes the secondary battery of the present application, and therefore has at least the same advantages as a secondary battery. [Brief explanation of the drawings]

[0026] In order to more clearly explain the technical solution of the present application, the following briefly introduces the drawings used in the present application. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without any creative efforts. [Figure 1] 1 is a structural schematic diagram of one embodiment of the separator of the present application. FIG. [Figure 2] FIG. 2 is a structural schematic diagram of another embodiment of the separator of the present application. [Figure 3] FIG. 1 is a schematic diagram of an embodiment of a secondary battery. [Figure 4] FIG. 4 is an exploded view of FIG. 3. [Figure 5] FIG. 1 is a schematic diagram of one embodiment of a battery module. [Figure 6] FIG. 1 is a schematic diagram of one embodiment of a battery pack. [Figure 7] FIG. 7 is an exploded view of FIG. [Figure 8] FIG. 1 is a schematic diagram of an embodiment of an apparatus that uses a secondary battery as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0028] For clarity, this specification specifically discloses only some numerical ranges. However, any lower limit and any upper limit can be combined to form a range not expressly stated, and any lower limit and any other lower limit can be combined to form a range not expressly stated, and similarly, any upper limit and any other upper limit can be combined to form a range not expressly stated. Furthermore, each point or single numerical value disclosed alone may itself be combined as a lower limit or upper limit with any other point or single numerical value, or with other lower limits or upper limits, to form a range not expressly stated.

[0029] In the description of this specification, unless otherwise specified, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0030] In the description of this specification, it should be explained that unless otherwise specified, "more than" and "less than" are inclusive, and "multiple" in "one or more" means two and more than two.

[0031] Unless otherwise specified, the terms used in this application have the known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application can be measured using various measurement methods commonly used in the art (for example, can be tested using the method according to the embodiment of this application).

[0032] secondary battery A secondary battery refers to a battery that can be continuously used by activating the active material through charging after the battery has been discharged.

[0033] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During charging and discharging, active ions shuttle between the positive and negative electrodes, absorbing and desorbing. The separator is placed between the positive and negative electrodes to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0034] [Separator] Referring to FIG. 1, an embodiment of the present application provides a separator 10 including a first base film 11 and a second base film 12, wherein the melting point of the second base film 12 is lower than the melting point of the first base film 11, the puncture strength of the second base film 12 is 220 gf to 460 gf, and the puncture strength of the separator 10 is 330 gf to 620 gf.

[0035] Without wishing to be bound by any theory, the inventors have discovered through extensive research that, in a separator having a specific structure according to the present application, when the puncture strength of the second base film having a low melting point and the puncture strength of the separator are both within the above-mentioned specific ranges, the use of a specific base film in the separator can enhance the puncture resistance of the separator and improve dendrite rupture resistance. Generally, dendrite deposition occurs on the negative electrode side, which places a higher demand on the separator's puncture resistance, while the demand for puncture resistance toward the positive electrode side is relatively weaker. However, the positive electrode side may have higher demands on other performance (e.g., heat resistance to prevent thermal breakdown). Therefore, by utilizing the second base film to exhibit its excellent performance, the puncture resistance of the separator can be enhanced, and by utilizing the first base film to balance other performances of the separator, such as heat resistance, breathability, and oxidation resistance, the overall performance of the separator can be improved, thereby improving the reliability of secondary batteries.

[0036] Through further research, the inventors have discovered that the performance of the battery can be further improved if the separator selectively satisfies one or more of the following designs:

[0037] In any embodiment of the present application, the ratio of the puncture strength of the first base film 11 to the puncture strength of the second base film 12 is 0.2 to 0.95, and optionally 0.3 to 0.75. For example, the ratio of the puncture strength of the first base film 11 to the puncture strength of the second base film 12 is optionally 0.2, 0.3, 0.32, 0.41, 0.48, 0.52, 0.54, 0.66, 0.71, 0.75, 0.85, 0.89, 0.92, 0.95, or the like, or a range consisting of any two of the above values, such as 0.2 to 0.32, 0.3 to 0.75, 0.41 to 0.54, 0.48 to 0.66, 0.71 to 0.89, or 0.92 to 0.95. When the ratio of the puncture strength of the first base film to the puncture strength of the second base film satisfies the above condition, the puncture resistance and heat resistance of the first base film and the second base film can be achieved at the same time, thereby further improving the reliability of the secondary battery.

[0038] In any embodiment of the present application, the first base film 11 has a puncture strength of 100 gf to 220 gf, and / or the second base film 12 has a puncture strength of 260 gf to 400 gf. For example, the puncture strength of the first base film 11 is selectively 100 gf, 102 gf, 114 gf, 120 gf, 126 gf, 133 gf, 139 gf, 140 gf, 164 gf, 190 gf, 220 gf, etc., or a range consisting of any two of the above numerical values, such as 100 gf to 133 gf, 90 gf to 114 gf, 120 gf to 126 gf, 133 gf to 164 gf, 190 gf to 220 gf, etc. The puncture strength of the second base film 12 is optionally 260 gf, 267 gf, 277 gf, 300 gf, 323 gf, 339 gf, 361 gf, 370 gf, 400 gf, etc., or a range consisting of any two of the above values, for example, 260 gf to 300 gf, 323 gf to 361 gf, 361 gf to 400 gf, etc. When the puncture strength of the first base film and / or the puncture strength of the second base film satisfy the above conditions, the puncture resistance and heat resistance of the first base film and the second base film can be compatible. While having good puncture resistance, other performances can be balanced, thereby improving the reliability of the secondary battery.

[0039] The puncture strength of a base film or separator has a meaning known in the art and can be tested using equipment and methods known in the art. For example, puncture strength can be tested according to standard GB / T 10004-2008. Specifically, the test sample can be cut into strips, with the strip sample width being 100 mm. The 100 mm wide test specimen is attached to a sample film clamp ring and then pierced at a speed of (50±5) mm / min using a steel needle with a diameter of 1.0 mm and a tip radius of 0.5 mm. The maximum load at which the steel needle penetrates the test specimen is read. Typically, five parallel test specimens are taken at the same time, and three points are measured on each test specimen. The arithmetic average of the measurements is the final puncture strength.

[0040] In any embodiment of the present application, the separator 10 comprises: (1) The transverse breaking elongation of the first base film 11 is 50% to 200%, and optionally 60% to 160%; (2) The longitudinal breaking elongation of the first base film 11 is 40% to 700%, and optionally 80% to 600%; (3) The transverse breaking elongation of the second base film 12 is 40% to 220%, and optionally 80% to 170%; (4) The longitudinal breaking elongation of the second base film 12 satisfies at least one of the following: 30% to 100%, and optionally 40% to 85%.

[0041] When at least one of the above items (1) to (4) of the separator satisfies a given range, the separator has better puncture resistance, thereby further improving the reliability of the secondary battery.

[0042] Those skilled in the art will understand that the puncture strength of a base film can be adjusted by adjusting the inherent parameters of the base film (e.g., one or more of the average filament diameter of the base film, the relative molecular mass of the base film material, etc.) Within each parameter range according to the present application, those skilled in the art can adjust the swelling ratio of the base film by known methods, for example, by adjusting the production process of the base film (adjusting the average filament diameter of the base film, the relative molecular mass of the base film material, etc.), and can obtain a base film with the required puncture strength through a limited number of tests.

[0043] In any embodiment of the present application, the average filament diameter of the first base film 11 is 60 nm to 300 nm, optionally 80 nm to 200 nm, and / or the average filament diameter of the second base film 12 is 40 nm to 350 nm, optionally 70 nm to 180 nm.

[0044] The average filament diameter of the first base film 11 may be 60 nm, 70 nm, 75 nm, 80 nm, 96 nm, 100 nm, 124 nm, 140 nm, 172 nm, 189 nm, 200 nm, 216 nm, 238 nm, 250 nm, 264 nm, 270 nm, 283 nm, 300 nm, etc., or a range consisting of any two of the above values, for example, 60 nm to 75 nm, 70 nm to 100 nm, 124 nm to 189 nm, 172 nm to 238 nm, 264 nm to 270 nm, 283 nm to 300 nm, etc. In some embodiments, the average filament diameter of the first base film 11 may be 80 nm to 200 nm.

[0045] The average filament diameter of the second base film 12 may be 40 nm, 64 nm, 70 nm, 89 nm, 100 nm, 119 nm, 142 nm, 157 nm, 180 nm, 196 nm, 224 nm, 265 nm, 274 nm, 290 nm, 300 nm, 315 nm, 324 nm, 330 nm, 339 nm, 341 nm, 350 nm, etc., or a range consisting of any two of the above values, for example, 119 nm to 157 nm, 157 nm to 196 nm, 224 nm to 265 nm, 274 nm to 315 nm, 300 nm to 330 nm, 330 nm to 341 nm, 341 nm to 350 nm, etc. In some embodiments, the average filament diameter of the second base film 12 may be 70 nm to 100 nm.

[0046] When the average filament diameter of the first base film and / or the average filament diameter of the second base film satisfies the above range, it is advantageous for the puncture strength of the base film and separator to fall within the range of the present application, and also for the separator to have good stretchability, thereby further improving the reliability of the secondary battery.

[0047] The average filament diameter of the base film has a meaning known in the art and can be measured using known instruments and methods. For example, a scanning electron microscope (e.g., ZEISS Sigma 300) is used to obtain a scanning electron microscope (SEM) photograph of the base film in accordance with JY / T010-1996. Specifically, a test sample of length x width = 5mm x 5mm is randomly selected from the base film, and several test areas (e.g., 5) are randomly selected from the test sample, and the fiber diameter is clearly observed at a certain magnification (e.g., 10K times). Several positions (e.g., at least 30 positions) are selected on a scale to measure, and the average value of the several filament diameters is calculated, which is the average filament diameter of the base film.

[0048] In any embodiment of the present application, the melting point of the first base film 11 is 155°C to 360°C, optionally 160°C to 335°C, and the melting point of the second base film 12 is 125°C to 260°C, optionally 130°C to 220°C.

[0049] The melting point of the first base film 11 may be 155°C, 159°C, 160°C, 170°C, 186°C, 190°C, 212°C, 235°C, 246°C, 264°C, 279°C, 281°C, 312°C, 345°C, 355°C, 360°C, or the like, or may be a range consisting of any two of the above values, for example, 155°C to 170°C, 186°C to 212°C, 235°C to 279°C, 160°C to 335°C, 281°C to 312°C, 345°C to 360°C, or the like.

[0050] The melting point of the second base film 12 is 125°C, 135°C, 153°C, 171°C, 196°C, 200°C, 224°C, 235°C, 260°C, etc., or a range consisting of any two of the above values, for example, 125°C to 135°C, 153°C to 196°C, 130°C to 220°C, 196°C to 200°C, 224°C to 260°C, etc.

[0051] By limiting the melting points of the first base film and the second base film to the above ranges, it is possible to ensure that the first base film and the second base film have good puncture resistance while also achieving good heat resistance.

[0052] The melting points of the first and second base films can be measured using instruments and methods known in the art. For example, they can be measured using differential scanning calorimetry. For details, see standard GB / T 19466.3-2004. For example, the measurement can be performed as follows: 4 to 6 mg of a sample to be measured is placed in the sample chamber of a differential scanning calorimeter, and the temperature is increased from 25°C to 400°C at a heating rate of 10°C / min. A melting endothermic curve of the sample is obtained, and the temperature corresponding to the peak of the curve is the melting point of the sample.

[0053] In any embodiment of the present application, the relative molecular mass of the material of the first base film 11 is 400,000 to 1.8 million, optionally 500,000 to 1.3 million, and / or the relative molecular mass of the material of the second base film 12 is 300,000 to 1.5 million, optionally 400,000 to 1.1 million.

[0054] The relative molecular mass of the material of the first base film 11 is optionally 400,000, 450,000, 460,000, 550,000, 640,000, 750,000, 960,000, 1,200,000, 1,370,000, 1,450,000, 1,540,000, 1,620,000, 1,710,000, 1,740,000, 1,780,000, 1,800,000, etc., or a range consisting of any two of the above values, for example, 400,000 to 450,000, 450,000 to 750,000, 750,000 to 960,000, 1,200,000 to 1,370,000, 1,450,000 to 1,740,000, 1,740,000 to 1,780,000, 1,780,000 to 1,800,000, etc. In some embodiments, the relative molecular mass of the material of the first base film 11 may be 500,000 to 1,300,000.

[0055] The relative molecular mass of the material of the second base film 12 can optionally be 300,000, 390,000, 490,000, 570,000, 640,000, 660,000, 800,000, 970,000, 1,030,000, 1,140,000, 1,240,000, 1,380,000, 1,410,000, 1,440,000, 1,480,000, 1,500,000, etc., or a range consisting of any two of the above values, for example, 300,000 to 390,000, 570,000 to 660,000, 800,000 to 1,140,000, 1,140,000 to 1,440,000, 1,440,000 to 1,500,000, etc. In some embodiments, the relative molecular mass of the material of the second base film 12 can be 400,000 to 1,100,000.

[0056] Here, the magnitude of the relative molecular mass of the base film material affects the final film formation state of the base film and further affects the puncture strength of the base film. The relative molecular mass of the material affects not only the puncture strength of the base film but also other properties such as the tensile strength of the material. By limiting the relative molecular mass of the material of the first base film and the material of the second base film to the above range, the puncture strength of the first base film can be further improved, thereby reducing the probability of puncture by lithium dendrites and improving the supporting force of the first base film against the second base film, thereby improving the reliability of the secondary battery.

[0057] The relative molecular mass of the base film has a meaning known in the art and can be tested using equipment and methods known in the art, for example, using a high temperature GPC test (differential refractive index detector).

[0058] In any embodiment of the present application, the thickness of the first base film 11 is equal to or greater than the thickness of the second base film 12, and optionally the ratio of the thickness of the first base film 11 to the thickness of the second base film 12 is 1.02 to 5, preferably 1.1 to 3.0. In some embodiments, the ratio of the thickness of the first base film 11 to the thickness of the second base film 12 is optionally 1.02, 1.1, 1.2, 1.4, 1.6, 2.2, 2.8, 3.0, 3.5, 3.9, 4.1, 4.4, 4.6, 4.8, 5, etc., or a range consisting of any two of the above numerical values, for example, 1.02 to 1.2, 1.4 to 2.2, 2.8 to 3.5, 1.1 to 3.0, 3.9 to 4.4, 4.6 to 5, etc.

[0059] In any embodiment of the present application, the thickness of the first base film 11 is 2 μm to 14 μm, optionally 3 μm to 9 μm, and the thickness of the second base film 12 is 2 μm to 12 μm, optionally 3 μm to 7 μm.

[0060] The thickness of the first base film 11 is optionally 2 μm, 3.5 μm, 4 μm, 5 μm, 7 μm, 9 μm, 10 μm, 11 μm, 11.5 μm, 12 μm, 13.5 μm, 14 μm, etc., or a range consisting of any two of the above values, for example, 2 μm to 4 μm, 5 μm to 10 μm, 10 μm to 12 μm, 12 μm to 14 μm, etc. In some embodiments, the thickness of the first base film 11 may be 3 μm to 9 μm.

[0061] The thickness of the second base film 12 is optionally 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc., or a range consisting of any two of the above values, for example, 2 μm to 4 μm, 5 μm to 7 μm, 8 μm to 9 μm, 10 μm to 12 μm, etc. In some embodiments, the thickness of the second base film 12 may be 3 μm to 7 μm.

[0062] When the thickness of the first base film and / or the thickness of the second base film meets the above conditions, the separator has excellent puncture resistance, thereby improving the reliability of the secondary battery and, at the same time, improving the energy density of the battery.

[0063] The thickness of the base film can be tested using equipment and methods known in the art. For example, a lithium battery separator thickness gauge is used to measure the thickness of the base film. The test was performed in accordance with GB / T6672, "Mechanical Measurement Method for Thickness of Plastic Films and Sheets." Specifically, the following steps can be used: six sets of parallel samples are taken, and the thickness of each set of samples is measured at different positions using a multimeter thickness gauge. Each set of samples is measured at at least 20 positions, and the average thickness of the six sets of samples is the sample thickness.

[0064] The first base film 11 and the second base film 12 may be directly combined by hot pressing, but if the temperature is too high in the process of combining them by hot pressing, the porosity will decrease and the breathability will be poor, and if the temperature is too low, the adhesion between the first base film 11 and the second base film 12 will be weak, so it is necessary to adjust the hot pressing temperature appropriately. Optionally, the hot pressing temperature is 20°C to 50°C.

[0065] In any embodiment of the present application, referring to FIG. 2 , an intermediate layer 13 is further provided between the first base film 11 and the second base film 12. The intermediate layer 13 is provided between the first base film 11 and the second base film 12, and includes an adhesive. Optionally, the intermediate layer 13 further includes filler particles. Optionally, the filler particles include at least one of inorganic particles, organic particles, and organic-metallic framework materials. When an intermediate layer is provided between the first base film and the second base film, it can not only compensate for process defects during the hot-press compounding process, but also further improve the stability of the physical properties of the separator, thereby improving the reliability of the secondary battery.

[0066] In any embodiment of the present application, the adhesive includes one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl amylopectin. When an intermediate layer is provided between the first base film and the second base film and the adhesive in the intermediate layer includes the above-mentioned components, the reliability of the secondary battery can be improved.

[0067] Optionally, 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 undergoing electrochemical reactions.

[0068] Alternatively, the inorganic particles having a dielectric constant of 5 or more may be boehmite, aluminum oxide, 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 inorganic particles include at least one of PMN-PT, PO3-PbTiO3, and modified inorganic particles. Optionally, the inorganic particles may be modified chemically and / or physically. Chemical modification methods include coupling agent modification (e.g., using a silane coupling agent, titanate coupling agent, etc.), surfactant modification, and polymer graft modification. Physical modification methods may include mechanical dispersion, ultrasonic dispersion, and high-energy treatment. The modification treatment can reduce the aggregation of inorganic particles, thereby resulting in a more stable and uniform structure of the intermediate layer. Furthermore, modifying the inorganic particles by selecting a coupling agent, surfactant, or polymer with a specific functional group can improve the electrolyte wetting and retention properties of the intermediate layer and contribute to improving the adhesion of the adhesive layer to the first and second base films.

[0069] Optionally, the inorganic particles that are ionically conductive but do not store ions include 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 P z2 S 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 include 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 ionic conductivity of the separator can be further improved.

[0070] Optionally, the inorganic particles capable of undergoing an electrochemical reaction may include at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicone-based materials, tin-based materials, and lithium titanium compounds.

[0071] Optionally, the organic particles may include 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, polyaramide, polyphenylene sulfide, polysulfone, polyether sulfone, polyether ether ketone, polyaryl ether ketone, and a copolymer of butyl acrylate and ethyl methacrylate (a cross-linked polymer of butyl acrylate and ethyl methacrylate).

[0072] Optionally, the organic-metal frame material may include one or more of a nitrogen-containing heterocyclic ligand construction structure, an organic carboxylic acid ligand construction structure, and a nitrogen-containing oxygen gas mixed ligand construction structure.

[0073] In some embodiments, the content of the adhesive may be 10% or more, optionally 10% - 30%, based on the total weight of the adhesive layer.

[0074] In some embodiments, the content of the filler may be 90% or less, optionally 40% to 90%, or 60% to 80%, based on the total weight of the adhesive layer.

[0075] In some embodiments, the intermediate layer may further include a dispersant, such as carboxymethyl cellulose, which can adjust the viscosity of the intermediate layer slurry and improve the quality and uniformity of the intermediate layer.

[0076] In some embodiments, the content of the dispersant may be 25% or less, and optionally 20% or less, based on the total weight of the adhesive layer.

[0077] In any embodiment of the present application, the separator 10 comprises: (1) The separator has a puncture strength of 330 gf to 630 gf, and optionally 400 gf to 600 gf; (2) The separator's transverse tensile strength is ≥ 700 kg / cm 2 and selectively 1000 kg / cm 2 ~1900kg / cm 2 That is, (3) The longitudinal tensile strength of the separator is ≥ 1000 kg / cm 2 and selectively 1200 kg / cm 2 ~2200kg / cm 2 That is, (4) The separator 10 has a transverse heat shrinkage rate of ≦3% at 250°C for 1 hour, and optionally ≦2.0%; (5) The separator 10 satisfies at least one of the following: a longitudinal heat shrinkage rate at 250° C. for 1 hour is ≦3%, and optionally ≦2.0%.

[0078] When at least one of the above items (1) to (5) of the separator satisfies a given range, the separator has good puncture resistance and can improve the reliability of the secondary battery.

[0079] The transverse tensile strength, longitudinal tensile strength, transverse heat shrinkage rate, and longitudinal heat shrinkage rate of the base film or separator all have meanings known in the art and can be tested using equipment and methods known in the art, for example, by referring to standard GB / T 36363-2018.

[0080] Unless otherwise specified, each of the raw materials used in the separator (for example, the first base film, the second base film, the adhesive, the filler, etc.) is commercially available.

[0081] [Positive electrode plate] In a secondary battery, the positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0082] The positive electrode current collector may be a conventional metal foil sheet or a composite current collector (a metal material may be deposited on a polymer substrate to form a composite current collector). For example, the positive electrode current collector may be aluminum foil.

[0083] The specific type of the positive electrode active material is not limited, and any active material known in the art that can be used for the positive electrode of a secondary battery may be adopted, and those skilled in the art can select it according to actual needs.

[0084] 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 may include, but are not limited to, one or more of 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 may include, but are not limited to, one or more of 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.

[0085] The modifying compound for each of the above materials may be one that performs doping modification and / or surface coating modification on the material.

[0086] The positive electrode membrane layer generally further optionally contains an adhesive, a conductive agent and other optional auxiliary agents.

[0087] As an 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.

[0088] 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).

[0089] [Negative electrode plate] In a secondary battery, the negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0090] The negative electrode current collector may be a conventional metal foil sheet or a composite current collector (e.g., a metal material may be deposited on a polymer substrate to form a composite current collector). For example, the negative electrode current collector may be a copper foil.

[0091] The specific type of negative electrode active material is not limited, and any active material known in the art for use in secondary battery negative electrodes may be used. Those skilled in the art can select the material according to actual 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, silicone-based materials, and tin-based materials. Silicon-based materials may be selected from one or more of simple silicone, silicone oxide (e.g., silicon suboxide), silicone carbon composites, silicone nitrogen composites, and silicone alloys. Tin-based materials may be selected from one or more of simple tin, stannic acid compounds, and tin alloys. All of these materials are commercially available.

[0092] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicone-based material.

[0093] The negative electrode film layer generally further optionally contains an adhesive, a conductive agent and other optional 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, graphene, and carbon nanofibers.

[0095] 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).

[0096] By way of example, other optional auxiliary agents may be thickening and dispersing agents (such as sodium carboxymethylcellulose (CMC-Na)), PTC thermistor materials.

[0097] [Electrolyte] The secondary battery may include an electrolyte, which functions to conduct ions between the positive electrode and the negative electrode. The electrolyte may include an electrolyte salt and a solvent.

[0098] By way of example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0099] Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl 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 esters may be selected from one or more of: n-Propyl Propionate (MP), n-Propyl Propionate (EP), n-Propyl Propionate (PP), n-Methyl Butyrate (MB), n-Ethyl Butyrate (EB), 1,4-Butyrolactone (GBL), 1,4-Butyrolactone (SF), 1,4-Tetramethylene Sulfone (SF), 1,4-Dimethyl Sulfone (MSM), 1,4-Dimethyl Sulfone (EMS), and 1,4-Diethyl Sulfone (ESE).

[0100] In some embodiments, the electrolyte solution further includes additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature performance of the battery.

[0101] In some embodiments, the secondary battery may be a lithium ion secondary battery. In any embodiment of the present application, the second base film 12 of the separator 10 faces the negative electrode plate.

[0102] The second base film 12 of the separator 10 faces the negative electrode plate, and the second base film 12 has high puncture strength, which increases the lithium dendrite puncture resistance effect and improves the reliability of the secondary battery.

[0103] The embodiment of the present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. Figure 3 shows an example of a secondary battery 5 with a rectangular structure.

[0104] In some embodiments, the secondary battery may include an exterior body used to package the positive electrode plate, the negative electrode plate, and the electrolyte.

[0105] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and may include one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0106] 4, in some embodiments, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate together form a surrounding storage cavity. The case 51 has an opening communicating with the storage cavity, and the cover plate 53 can be installed to cover the opening to seal the storage cavity.

[0107] The method for manufacturing the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator 10, a negative electrode plate, and an electrolyte. For example, a positive electrode plate, a separator 10, and a negative electrode plate can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly can then be placed in an outer casing, dried, and then injected with an electrolyte. A battery cell can then be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping. Multiple battery cells can be further connected in series, parallel, or series-parallel to form a battery module. Multiple battery modules can be further connected in series, parallel, or series-parallel to form a battery pack. In some embodiments, multiple battery cells can directly form a battery pack.

[0108] Fig. 5 shows an example of a battery module 4. Referring to Fig. 5, the battery module 4 may include a plurality of secondary batteries 5 arranged in order along the longitudinal direction of the battery module 4. Of course, the batteries may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0109] The battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0110] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0111] 6 and 7 show an example of a battery pack 1. Referring to FIGS. 6 and 7, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed 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, forming a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0112] [Device] The present application further provides a power-consuming 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 an energy 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 an energy storage system.

[0113] A device may select a battery cell, a battery module, or a battery pack based on its usage needs.

[0114] 8 shows an example of a power consuming device. The power consuming device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of the secondary battery of the power consuming device, a battery pack or battery module may be employed.

[0115] Another example of a power consuming device may be a mobile phone, a tablet computer, or a laptop computer, which generally requires a thin design and may employ a battery cell as a power source.

[0116] The beneficial effects of the present application will be further described below in conjunction with the embodiments.

[0117] In order to make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application clearer, the following embodiments will be described in more detail in conjunction with the drawings. Obviously, the described embodiments are only some embodiments of the present application, but not all embodiments. The following description of at least one exemplary embodiment is merely explanatory in nature and does not constitute any limitation on the present application and its applications. All other embodiments obtained based on the embodiments in the present application without the need for creative efforts by those skilled in the art are within the scope of protection of the present application.

[0118] 1. Separator manufacturing Separator 1: (1) Providing a first base film and a second base film: the first base film is polypropylene (PP) and the second base film is polyethylene (PE), wherein the melting point of the first base film is 165°C and the melting point of the second base film is 135°C. The first base film has a breaking elongation in the transverse direction of 60% and a breaking elongation in the longitudinal direction of 80%. The second base film has a breaking elongation in the transverse direction of 130% and a breaking elongation in the longitudinal direction of 75%. The first base film has a puncture strength P1 of 120 gf and a puncture strength P2 of 300 gf, wherein the ratio P1 / P2 of the puncture strength P1 of the first base film to the puncture strength P2 of the second base film is 0.40.

[0119] (2) Preparation of intermediate layer slurry: Polyacrylate adhesive, alumina particles as filler, and carboxymethyl cellulose were uniformly mixed in a ratio of 1:4:1 with an appropriate amount of deionized water as solvent to prepare intermediate layer slurry.

[0120] (3) The intermediate layer slurry of step (2) is applied to one side of the second base film of step (1) to form an intermediate layer.

[0121] (4) The first base film and the second base film coated in step (3) are hot-pressed together to obtain a separator, where the intermediate layer is between the first base film and the second base film.

[0122] The manufacturing method of separator 2-11 is similar to that of separator 1, except that one or more of the melting point, material, transverse elongation at break, longitudinal elongation at break, and puncture strength of the first or second base film are adjusted, as specifically shown in Table 1. All other manufacturing methods are the same as those of the separator of Example 1.

[0123] 2. Battery manufacturing Example 1 1. Manufacturing of positive electrode plates LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (SuperP), and adhesive polyvinylidene fluoride (PVDF) were uniformly mixed in a mass ratio of 96.2:2.7:1.1 in an appropriate amount of solvent N-methylpyrrolidone (NMP) to obtain a positive electrode slurry. The positive electrode slurry was then applied to a positive electrode current collector aluminum foil, and the positive electrode plate was obtained through drying, cold pressing, slitting, and cutting processes.

[0124] 2. Manufacturing of negative electrode plates The negative electrode active material, artificial graphite, the conductive agent, carbon black (SuperP), the adhesive, styrene butadiene rubber (SBR) and carboxymethyl cellulose sodium (CMC-Na), were uniformly mixed in a mass ratio of 96.4:0.7:1.8:1.1 in an appropriate amount of deionized water solvent to obtain a negative electrode slurry. The negative electrode slurry was then applied to a negative electrode current collector copper foil, and the negative electrode plate was obtained through drying, cold pressing, slitting, and cutting processes.

[0125] 3. Separator The separator used was the separator 1 manufactured above.

[0126] 4. Electrolyte production Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 30:70 to obtain an organic solvent, and thoroughly dried electrolyte salt LiPF6 was dissolved in the mixed solvent to obtain an electrolyte solution with a concentration of 1.0 mol / L.

[0127] 5. Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate are stacked in this order, with the separator positioned between the positive electrode plate and the negative electrode plate to serve as an insulator, and the second base film is oriented toward the negative electrode plate and wound up to obtain an electrode assembly. The electrode assembly is placed in an outer casing, and the above-prepared electrolyte is injected into the secondary battery after drying. The secondary battery is then obtained through vacuum packaging, standing, chemical formation, and shaping processes.

[0128] The secondary batteries of Examples 2-9 and Comparative Examples 1-2 were manufactured using methods similar to those of the secondary battery of Example 1, except that different separators were used (here, Separator 1-9 was used in Examples 1-9, and Separator 10-11 was used in Comparative Examples 1-2). For details, see Table 1.

[0129] 3. Battery performance test 1. Needle prick test (60 min) The battery was tested under conditions of 25C and 100% SOC. The temperature-sensing wires were arranged in the following order: positive pole / negative pole / center of the large surface (approximately 5mm above the needle puncture hole) / backside of the center of the large surface / battery core explosion-proof valve. The voltage wires were arranged in the following order: V positive / negative / V positive needle / V negative needle. The multi-channel collection frequency was ≦0.1S. A φ1mm high-temperature-resistant steel needle (the cone angle of the needle tip was 30°) was used, aligned to the center of the large surface of the battery core. The needle puncture speed was 0.01mm / s. The needle was punctured into the positive pole until the voltage reached 0.5V, and continued to puncture to a depth of 3mm. This was held for 1 hour, and the meter readings were observed. If the voltage was normal and did not fluctuate, it was considered normal and not a runaway, and was marked as PASS. If the voltage fluctuated abnormally and the battery core was dead, it was marked as NP.

[0130] 2. Battery cycle performance (number of cycles) At 25°C, the secondary batteries manufactured in the examples and comparative examples were charged at a constant current of 1C to a charge cutoff voltage V1, then charged at a constant voltage of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cutoff voltage V2, allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. Following this procedure, the batteries were subjected to a cycle charge-discharge test until the battery capacity was reduced to 80%. The number of cycles at this time represents the cycle life of the battery at 25°C.

[0131] [Table 1]

[0132] As can be seen from Table 1, a comparison between Examples 1-9 and Comparative Examples 1-2 revealed that in Examples 1-9, the melting point of the second base film was lower than that of the first base film, and the puncture strength of the second base film was 220gf to 460gf, while the puncture strength of the separator was 330gf to 620gf. The batteries using the separator of the present application not only passed the needle puncture test, but also had an increased number of cycles, i.e., under similar battery performance standards, the batteries manufactured using the separator of the present application have higher reliability.

[0133] The above is merely a specific embodiment of the present application, and the scope of protection of the present application is not limited thereto. Those skilled in the art may easily devise various equivalent modifications or replacements within the technical scope disclosed in the present application, and all such equivalent modifications or replacements shall be included in the scope of protection of the present application. Therefore, the scope of protection of the present application shall be equivalent to the scope of protection of the claims.

Claims

1. A separator, a first base film; a second base film having a melting point lower than the melting point of the first base film; The separator, wherein the second base film has a puncture strength of 220 gf to 460 gf, and the separator has a puncture strength of 330 gf to 620 gf.

2. 2. The separator according to claim 1, wherein the ratio of the puncture strength of the first base film to the puncture strength of the second base film is 0.2 to 0.95, and optionally 0.3 to 0.

75.

3. The puncture strength of the first base film is 100 gf to 220 gf, and / or 3. The separator according to claim 1, wherein the second base film has a puncture strength of 260 gf to 400 gf.

4. The separator is (1) the transverse breaking elongation of the first base film is 50% to 200%, and optionally 60% to 160%; (2) The longitudinal breaking elongation of the first base film is 40% to 700%, and optionally 80% to 600%; (3) The transverse elongation at break of the second base film is 40% to 220%, and optionally 80% to 170%; (4) The separator according to any one of claims 1 to 3, wherein the longitudinal breaking elongation of the second base film is 30% to 100%, and optionally 40% to 85%.

5. the average filament diameter of the first base film is between 60 nm and 300 nm, optionally between 80 nm and 200 nm; and / or The separator according to any one of claims 1 to 4, wherein the average filament diameter of the second base film is from 40 nm to 350 nm, and optionally from 70 nm to 180 nm.

6. the melting point of the first base film is between 155°C and 360°C, optionally between 160°C and 335°C; and / or The separator according to any one of claims 1 to 5, wherein the melting point of the second base film is 125°C to 260°C, and optionally 130°C to 220°C.

7. The relative molecular mass of the material of the first base film is between 400,000 and 1,800,000, optionally between 500,000 and 1,300,000; and / or The separator according to any one of claims 1 to 6, wherein the relative molecular mass of the material of the second base film is 300,000 to 1,500,000, and optionally 400,000 to 1,100,000.

8. The separator according to any one of claims 1 to 7, wherein the thickness of the first base film is equal to or greater than the thickness of the second base film, and optionally, the ratio of the thickness of the first base film to the thickness of the second base film is 1.02 to 5, preferably 1.1 to 3.

0.

9. the thickness of the first base film is between 2 μm and 14 μm, optionally between 3 μm and 9 μm; and / or The separator according to any one of claims 1 to 8, wherein the thickness of the second base film is from 2 µm to 12 µm, and optionally from 3 µm to 7 µm.

10. The separator according to any one of claims 1 to 9, further comprising an intermediate layer, the intermediate layer being disposed between the first base film and the second base film, and the intermediate layer comprising an adhesive, optionally the intermediate layer comprising an adhesive and filler particles.

11. the adhesive comprises one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, cyanoethyl amylopectin; and / or The separator of claim 10, wherein the filler particles include at least one of inorganic particles, organic particles, and organic-metallic frame materials.

12. The separator is (1) The separator has a puncture strength of 330 gf to 630 gf, and optionally 400 gf to 600 gf; (2) The separator has a lateral tensile strength of 700 kg / cm or more. ２ and optionally 1000 kg / cm ２ ~1900kg / cm ２ That is, (3) The separator has a longitudinal tensile strength of ≥ 1000 kg / cm ２ and optionally 1200 kg / cm ２ ~2200kg / cm ２ That is, (4) The separator has a transverse heat shrinkage rate of ≦3%, optionally ≦2.0%, at 250° C. for 1 hour; (5) The separator according to any one of claims 1 to 11, wherein the separator has a longitudinal heat shrinkage rate of ≦3% at 250°C for 1 hour, and optionally ≦2.0%.

13. A secondary battery comprising the separator according to claim 1 .

14. 14. The secondary battery according to claim 13, comprising a positive electrode plate and a negative electrode plate, the separator being disposed between the positive electrode plate and the negative electrode plate, and the second base film facing the negative electrode plate.

15. A power consuming device comprising the secondary battery according to claim 13 or 14.

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