Separator, secondary battery and power consuming device

Abstract

According to the present application, there is provided a separator, the separator comprising a first base film and a second base film, the melting point of the second base film being lower than that of the first base film, the transverse direction breaking elongation of the second base film being higher than the longitudinal direction breaking elongation of the second base film, and the longitudinal direction breaking elongation of the second base film being lower than 100%. The separator according to the present application can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of secondary batteries.

Description

[Technical Field]

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

[0002] Due to their distinctive features of light weight, pollution-free and no memory effect, secondary batteries are widely used in various consumer electronic products and electric vehicles. With the development of the new energy industry, users have higher usage requirements for the reliability performance of secondary batteries.

[0003] Therefore, how to provide a secondary battery with better reliability is a current issue that must be resolved as soon as possible. Summary of 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 to improve the reliability performance of the secondary battery.

[0005] In order to achieve the above object, according to a first aspect of the present application, a separator is provided, which includes 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 transverse breaking elongation of the second base film is higher than the longitudinal breaking elongation of the second base film, and the longitudinal breaking elongation of the second base film is lower than 100%.

[0006] Compared to the prior art, the present application has at least the following beneficial effects: In the separator according to the present application, the melting point of the first base film is higher than that of the second base film, which can improve the heat resistance of the separator; the transverse breaking elongation of the second base film is greater than the longitudinal breaking elongation of the second base film, and the longitudinal breaking elongation of the second base film is less than 100%, which can effectively improve the nail penetration resistance of the separator and prevent metal 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 transverse breaking elongation of the second base film to the longitudinal breaking elongation of the second base film is 1.05-4.5, optionally 1.2-3.0, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0008] In any embodiment of the present application, the longitudinal breaking elongation of the second base film is 30%-90%, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0009] In any embodiment of the present application, the transverse breaking elongation of the first base film is smaller than the longitudinal breaking elongation of the first base film, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0010] In any embodiment of the present application, the ratio of the transverse breaking elongation of the first base film to the longitudinal breaking elongation of the first base film is 0.05-0.5, optionally 0.1-0.3, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0011] In any embodiment of the present application, the separator comprises: (1) The transverse breaking elongation of the first base film is 30%-250%, and optionally 40%-200%; (2) The longitudinal breaking elongation of the first base film is 40%-1000%, and optionally 400%-800%; and (3) The transverse breaking elongation of the second base film is 50%-250%, and optionally 100%-180%; At least one of the following is satisfied.

[0012] When the separator satisfies the given ranges for at least one of the above (1) to (3), the nail penetration resistance of the separator can be effectively improved and metal dendrites can be prevented from penetrating the separator and causing a short circuit, thereby further improving the reliability performance of the secondary battery.

[0013] In any embodiment of the present application, the transverse tensile strength of the second base film is smaller than the longitudinal tensile strength of the second base film, and optionally the ratio of the transverse tensile strength of the second base film to the longitudinal tensile strength of the second base film is 0.4-0.95, and more optionally 0.6-0.9, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby further improving the reliability performance of the secondary battery.

[0014] In any embodiment of the present application, the transverse tensile strength of the first base film is smaller than the longitudinal tensile strength of the first base film, and the ratio of the transverse tensile strength of the first base film to the longitudinal tensile strength of the first base film is 0.2-0.9, optionally 0.3-0.6, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby further improving the reliability performance of the secondary battery.

[0015] In any embodiment of the present application, the cross-directional tensile strength of the first base film is less than the cross-directional tensile strength of the second base film, and / or the longitudinal tensile strength of the first base film is less than the longitudinal tensile strength of the second base film.

[0016] When the transverse tensile strength of the first base film is smaller than the transverse tensile strength of the second base film and the longitudinal tensile strength of the first base film is smaller than the longitudinal tensile strength of the second base film, the nail penetration resistance of the separator can be effectively improved and metal dendrites can be prevented from penetrating the separator and causing short circuits, thereby further improving the reliability performance of the secondary battery.

[0017] In any embodiment of the present application, the separator comprises: (1) The transverse tensile strength of the first base film is 100 kgf / cm 2 -1000Kgf / cm 2 and optionally 200Kgf / cm 2 -750Kgf / cm 2 That is, (2) The longitudinal tensile strength of the first base film is 700 kgf / cm 2 -2500Kgf / cm 2 and optionally 1000Kgf / cm 2 -1900Kgf / cm 2 That is, (3) The transverse tensile strength of the second base film is 1200 kgf / cm 2 -3800Kgf / cm 2and optionally 2000Kgf / cm 2 -3500Kgf / cm 2 and (4) The longitudinal tensile strength of the second base film is 1800 kgf / cm 2 -5500Kgf / cm 2 and optionally 2100Kgf / cm 2 -3500Kgf / cm 2 That is, At least one of the following is satisfied.

[0018] When the separator satisfies the given ranges for at least one of the above (1) to (4), the nail penetration resistance of the separator can be effectively improved and metal dendrites can be prevented from penetrating the separator and causing a short circuit, thereby further improving the reliability performance of the secondary battery.

[0019] In any embodiment of the present application, the melting point of the first base film is 160° C.-370° C., optionally 170° C.-350° C., and / or the melting point of the second base film is 120° C.-280° C., optionally 130° C.-260° C. When the melting points of the first base film and the second base film satisfy the above conditions, the separator has good heat resistance and physical properties, thereby improving the reliability of the secondary battery.

[0020] 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 and comprising an adhesive, and optionally the intermediate layer comprising an adhesive and filler particles.

[0021] 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 of the base film, but also improve the stability of the physical properties of the separator, thereby improving the reliability performance of the secondary battery.

[0022] In one embodiment of the present application, the adhesive may include one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichlorostyrene copolymer, polyethylene pyrrolidone, 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-branched starch, and / or the filler particles may include at least one of inorganic particles, organic particles, and organic-metallic frame materials. An intermediate layer is provided between the first base film and the second base film, and when the adhesive and / or filler particles in the intermediate layer include the above components, the reliability of the secondary battery can be improved.

[0023] In any embodiment of the present application, the separator comprises: (1) The separator has a transverse elongation at break of 50%-220%, and optionally 70%-170%; (2) The longitudinal elongation at break of the separator is 30%-150%, and optionally 40%-100%; (3) The separator's transverse tensile strength is 1200 kgf / cm 2 -4000Kgf / cm 2 and optionally 2100Kgf / cm 2 -3600Kgf / cm 2 That is, (4) The separator's longitudinal tensile strength is 1900 kgf / cm 2 -5500Kgf / cm 2 and optionally 2200Kgf / cm 2 -3700Kgf / cm 2 That is, (5) The separator has a transverse heat shrinkage of ≦2%, optionally ≦1.0%, at 250°C for 1 hour; and (6) The separator has a longitudinal heat shrinkage rate of ≦2% at 250°C for 1 hour, and optionally ≦1.0%; At least one of the following is satisfied.

[0024] When the separator satisfies at least one of the above (1)-(6) within the given range, the separator has good heat resistance and physical properties, thereby improving the reliability of the secondary battery.

[0025] According to a second aspect of the present application, there is provided a secondary battery including the separator of any one of the above aspects. When the given separator is used in a secondary battery, the reliability performance of the secondary battery can be improved.

[0026] In any embodiment of the present application, the secondary battery further includes a positive electrode sheet and a negative electrode sheet, the separator is disposed between the positive electrode sheet and the negative electrode sheet, and the second base film is disposed on the negative electrode sheet side. When the secondary battery employs the given separator, it can improve the effect of resisting puncture by metal dendrites and suppress dendrite precipitation, thereby improving the reliability performance of the secondary battery.

[0027] According to a third aspect of the present application, there is provided a power consuming device including the secondary battery of the second aspect of the present application. When the secondary battery of the power consuming device employs the given separator, the reliability performance of the power consuming device can be improved.

[0028] The device of the present application includes the secondary battery of the present application, and therefore has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0029] In order to more clearly explain the technical solution of the present application, the drawings used in the present application will be briefly described below. The drawings described below are only some examples 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.

[0030] [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 one embodiment of a secondary battery powered device. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present application will be further described below in connection with specific embodiments. It should be understood that these specific embodiments are used only to illustrate the present application, rather than limiting the scope of the present application.

[0032] For clarity, this specification specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with any other lower limit to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each point or single numerical value disclosed individually can itself be combined with any other point or single numerical value as a lower limit or upper limit, or can be combined with other lower limits or upper limits to form an unspecified range.

[0033] In the description herein, the term "or" is inclusive unless otherwise specified. That is, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy 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 both A and B are true (or exist).

[0034] In the description of this specification, unless otherwise specified, the terms "more than or equal to" and "less than or equal to" are inclusive, and "multiple types" in "one or more types" means two types and more than two types.

[0035] Unless otherwise specified, the terms used herein have the well-known meanings that are commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter described herein can be measured using various measurement methods commonly used in the art (for example, can be tested using the methods described in the examples of this specification).

[0036] secondary battery A secondary battery is a battery that can be used continuously by activating the active material through charging after discharging.

[0037] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During charging and discharging of the battery, active ions are repeatedly absorbed and released between the positive and negative electrode sheets. The separator, located between the positive and negative electrode sheets, acts as a barrier. The electrolyte acts as an ion conductor between the positive and negative electrode sheets.

[0038] [Separator] Referring to FIG. 1, according to an embodiment of the present application, a separator 10 is provided, which includes 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 transverse breaking elongation of the second base film 12 is higher than the longitudinal breaking elongation of the second base film 12, and the longitudinal breaking elongation of the second base film 12 is lower than 100%.

[0039] Without intending to be limited by any theory, the inventors have conducted extensive research and discovered the following: In the specific separator structure of the present application, the melting point of the first base film is higher than that of the second base film, which can improve the heat resistance of the separator; by making the transverse breaking elongation of the second base film greater than the longitudinal breaking elongation of the second base film and making the longitudinal breaking elongation of the second base film less than 100%, the nail penetration resistance of the separator can be effectively improved and metal dendrites can be prevented from penetrating the separator and causing short circuits, thereby improving the reliability of the secondary battery.

[0040] As a result of further research, the present inventors have found that the performance of the battery can be further improved if the separator selectively satisfies one or more of the following designs.

[0041] The materials of the first base film 11 and the second base film 12 are not particularly limited, and any known base film having good chemical stability and strength stability can be selected. The material of the first base film 11 and the material of the second base film 12 of the separator 10 may be the same or different. In some embodiments, the first base film 11 and the second base film 12 may be selected from one or more of polyolefin, polyether, polyether ether ketone, polyethylene terephthalate, polyimide, polytetrafluoroethylene, polyvinylidene tetrafluoride, polyvinyl alcohol, glass fiber, nonwoven fabric, polyolefin, and polyvinylidene fluoride.

[0042] In any embodiment of the present application, the ratio of the transverse breaking elongation of the second base film 12 to the longitudinal breaking elongation of the second base film 12 is 1.05-4.5, optionally 1.2-3.0, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery. For example, the ratio of the transverse breaking elongation of the second base film 12 to the longitudinal breaking elongation of the second base film 12 may be 1.05, 1.2, 1.5, 2.0, 2.15, 2.755, 3.0, 3.13, 3.5, 3.88, 4.0, 4.15, 4.25, 4.35, 4.5, etc., or may be a range consisting of any two of the above values, such as 1.05-2.0, 1.2-3.0, 2.15-2.755, 3.0-3.5, 3.88-4.25, 4.35-4.5, etc.

[0043] In any embodiment of the present application, the longitudinal breaking elongation of the second base film 12 is 30%-90%, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability of the secondary battery. For example, the longitudinal breaking elongation of the second base film 12 may be 30%, 35%, 38%, 40%, 43%, 50%, 60%, 68%, 70%, 75%, 78%, 80%, 85%, 90%, etc., or a range consisting of any two of the above values, such as 30%-40%, 40%-60%, 68%-75%, 80%-90%, etc.

[0044] In any embodiment of the present application, the transverse breaking elongation of the first base film 11 is smaller than the longitudinal breaking elongation of the first base film 11, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0045] In any embodiment of the present application, the ratio of the transverse breaking elongation of the first base film 11 to the longitudinal breaking elongation of the first base film 11 is 0.05-0.5, optionally 0.1-0.3, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery. For example, the ratio of the transverse breaking elongation of the first base film 11 to the longitudinal breaking elongation of the first base film 11 may be 0.05, 0.09, 0.1, 0.13, 0.15, 0.19, 0.2, 0.25, 0.28, 0.3, 0.34, 0.36, 0.4, 0.42, 0.45, 0.5, or a range consisting of any two of the above values, such as 0.05-0.09, 0.1-0.15, 0.15-0.19, 0.1-0.3, 0.2-0.25, 0.28-0.34, 0.34-0.36, 0.4-0.42, 0.42-0.5, etc.

[0046] In any embodiment of the present application, the separator 10 comprises: (1) The transverse breaking elongation of the first base film 11 is 30%-250%, and optionally 40%-200%; (2) The longitudinal breaking elongation of the first base film 11 is 40%-1000%, and optionally 400%-800%; and (3) The transverse breaking elongation of the second base film 12 is 50%-250%, and optionally 100%-180%; At least one of the following is satisfied.

[0047] When the separator satisfies the given ranges for at least one of the above (1) to (3), the nail penetration resistance of the separator can be effectively improved, and metal dendrites can be prevented from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0048] In any embodiment of the present application, the transverse tensile strength of the second base film 12 is smaller than the longitudinal tensile strength of the second base film 12, and optionally the ratio of the transverse tensile strength of the second base film 12 to the longitudinal tensile strength of the second base film 12 is 0.4-0.95, and more preferably 0.6-0.9, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery. For example, the ratio of the transverse tensile strength of the second base film 12 to the longitudinal tensile strength of the second base film 12 may be 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.83, 0.85, 0.9, 0.95, or a range consisting of any two of the above values, such as 0.4-0.5, 0.55-0.6, 0.6-0.9, 0.65-0.75, 0.75-0.8, 0.8-0.85, 0.85-0.9, 0.9-0.95, etc.

[0049] In any embodiment of the present application, the transverse tensile strength of the first base film 11 is smaller than the longitudinal tensile strength of the first base film 11, and the ratio of the transverse tensile strength of the first base film 11 to the longitudinal tensile strength of the first base film 11 is 0.2-0.9, optionally 0.3-0.6, which can effectively improve the nail penetration resistance of the separator and prevent metal dendrites from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery. For example, the ratio of the transverse tensile strength of the first base film 11 to the transverse tensile strength of the second base film 12 may be 0.2, 0.25, 0.28, 0.3, 0.35, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, 0.78, 0.8, 0.82, 0.85, 0.9, etc., or may be a range consisting of any two of the above values, such as 0.2-0.25, 0.15-0.3, 0.25-0.4, 0.35-0.6, 0.3-0.6, 0.4-0.55, 0.55-0.7, 0.7-0.9, etc.

[0050] In any embodiment of the present application, the cross-directional tensile strength of the first base film 11 is less than the cross-directional tensile strength of the second base film 12, and / or the longitudinal tensile strength of the first base film 11 is less than the longitudinal tensile strength of the second base film 12.

[0051] When the transverse tensile strength of the first base film is smaller than the transverse tensile strength of the second base film and / or the longitudinal tensile strength of the first base film is smaller than the longitudinal tensile strength of the second base film, the nail penetration resistance of the separator can be effectively improved and metal dendrites can be prevented from penetrating the separator and causing a short circuit, thereby improving the reliability performance of the secondary battery.

[0052] In any embodiment of the present application, the separator 10 comprises: (1) The transverse tensile strength of the first base film 11 is 100 kgf / cm 2 -1000Kgf / cm 2 and optionally 200Kgf / cm 2 -750Kgf / cm 2 That is, (2) The longitudinal tensile strength of the first base film 11 is 700 kgf / cm 2 -2500Kgf / cm 2 and optionally 1000Kgf / cm 2 -1900Kgf / cm 2 That is, (3) The transverse tensile strength of the second base film 12 is 1200 kgf / cm 2 -3800Kgf / cm 2 and optionally 2000Kgf / cm 2 -3500Kgf / cm 2 and (4) The second base film 12 has a longitudinal tensile strength of 1800 kgf / cm 2 -5500Kgf / cm 2 and optionally 2100Kgf / cm 2 -3500Kgf / cm 2 That is, At least one of the following is satisfied.

[0053] When the separator satisfies the given ranges for at least one of the above (1) to (4), the nail penetration resistance of the separator can be effectively improved, and metal dendrites can be prevented from penetrating the separator and causing short circuits, thereby improving the reliability performance of the secondary battery.

[0054] The transverse tensile strength, longitudinal tensile strength, transverse heat shrinkage rate, and longitudinal heat shrinkage rate of the base film or separator all have the meanings known in the art and can be tested using devices and methods known in the art, for example, by referring to standard GB / T 36363-2018.

[0055] In any embodiment of the present application, the melting point of the first base film 11 may be 160° C.-370° C., optionally 170° C.-350° C. For example, it may be 160° C., 165° C., 170° C., 180° C., 196° C., 200° C., 225° C., 235° C., 245° C., 260° C., 280° C., 290° C., 300° C., 315° C., 320° C., 330° C., 350° C., 370° C., or a range consisting of any two of the above values, such as 160° C.-170° C., 180° C.-235° C., 225° C.-280° C., 290° C.-315° C., 350° C.-370° C., etc. In some examples, the melting point of the second base film 12 may be 120° C.-280° C., optionally 130° C.-160° C. For example, it may be 120°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 180°C, 185°C, 190°C, 196°C, 200°C, 215°C, 220°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, or a range consisting of any two of the above values, such as 120°C-185°C, 130°C-250°C, 245°C-255°C, 130°C-160°C, etc.

[0056] The melting points of the first and second base films can be tested using known devices and methods in the art. For example, they can be measured using differential scanning calorimetry. For example, see standard GB / T 19466.3-2004. For example, they can be measured according to the following method: 4-6 mg of the sample to be measured is placed in the sample chamber of the differential scanning calorimeter, and the temperature is increased from 25°C to 400°C at a rate of 10°C / min to obtain a melting endothermic curve of the sample. The temperature corresponding to the peak value of the curve is the melting point of the sample.

[0057] The first base film 11 and the second base film 12 may be directly combined by hot pressing. During the hot pressing process, if the temperature is too high, the porosity will be small and the air permeability will be poor, while if the temperature is too low, the adhesion between the first base film 11 and the second base film 12 will be insufficient. Therefore, it is necessary to adjust the hot pressing temperature appropriately. Optionally, the hot pressing temperature is 20°C-50°C. Referring to FIG. 2 , in any embodiment of the present application, an intermediate layer 13 may be further provided between the first base film 11 and the second base film 12, and the intermediate layer 13 includes an adhesive. Optionally, the intermediate layer includes an adhesive and filler particles. Optionally, the filler particles include at least one of inorganic particles, organic particles, and an organic-metallic framework material.

[0058] 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 electrochemical reactions.

[0059] Alternatively, the inorganic particles having a dielectric constant of 5 or more may be 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 nitride, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, aluminum magnesium silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyroxene, 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 / 3 The inorganic particles may include at least one of PMN-PT, PO3-PbTiO3 (abbreviated as PMN-PT), and modified inorganic particles thereof. Optionally, the inorganic particles may be modified chemically and / or physically. Chemical modification methods include coupling agent modification (e.g., silane coupling agents, titanate ester coupling agents, etc.), surfactant modification, and polymer graft modification. Physical modification methods include mechanical dispersion, ultrasonic dispersion, and high-energy treatment. Modification treatment can reduce the aggregation of inorganic particles, thereby making the adhesive layer more stable and uniform. Furthermore, modifying the inorganic particles by selecting a coupling agent, surfactant, or polymer with a specific functional group can improve the electrolyte penetration and retention properties of the adhesive layer and the adhesion of the adhesive layer to the first and second base films.

[0060] Optionally, the inorganic particles that are ionically conductive but do not store ions 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 type glass, lithium lanthanum titanate Li 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 z4 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.

[0061] Optionally, the inorganic particles capable of 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.

[0062] Alternatively, the organic particles may comprise one or more of polycarbonate, polythienyl, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifiers (e.g., carboxymethyl cellulose), melamine resin, phenolic resin, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), organosilicon resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, and copolymers of butyl acrylate and ethyl methacrylate (e.g., crosslinked polymers of butyl acrylate and ethyl methacrylate).

[0063] Optionally, the organic-metal framework material may include one or more of nitrogen-containing heterocyclic ligand structures, organic carboxylic acid ligand structures, and nitrogen-containing oxygen-mixed ligand structures.

[0064] In some embodiments, the adhesive content may be 10% or more, optionally 10%-30%, based on the total weight of the adhesive layer.

[0065] In some embodiments, the filler content may be up to 90% based on the total weight of the adhesive layer, optionally 40%-90%, 60%-80%.

[0066] 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.

[0067] In some embodiments, the dispersant content may be 25% or less, and optionally 20% or less, based on the total weight of the adhesive layer.

[0068] 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 of the base film, but also improve the stability of the physical properties of the separator, thereby improving the reliability performance of the secondary battery.

[0069] In some embodiments of the present application, the adhesive may include one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichlorostyrene copolymer, polyethylene pyrrolidone, 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-branched starch. An intermediate layer may be provided between the first base film and the second base film. When the adhesive in the intermediate layer includes any of the above components, the reliability of the secondary battery can be improved. In some embodiments, carboxymethyl cellulose may be used as a thickener to adjust the viscosity of the slurry.

[0070] In any embodiment of the present application, the separator comprises: (1) The separator 10 has a transverse breaking elongation of 50%-220%, and optionally 70%-170%; (2) The longitudinal breaking elongation of the separator 10 is 30%-150%, and optionally 40%-100%; (3) The separator 10 has a transverse tensile strength of 1200-4000 kgf / cm 2 and optionally 2100-3600Kgf / cm 2 That is, (4) The longitudinal tensile strength of the separator 10 is 1900-5500 kgf / cm 2 and optionally 2200-3700Kgf / cm 2 That is, (5) The separator 10 has a transverse heat shrinkage of ≦2% at 250° C. for 1 hour, and optionally ≦1.0%; and (6) The longitudinal heat shrinkage rate of the separator 10 at 250°C for 1 hour is ≦2%, and optionally ≦1.0%; At least one of the following is satisfied.

[0071] When the separator satisfies at least one of the above (1)-(6) within the given range, the separator has good heat resistance and physical properties, thereby improving the reliability of the secondary battery.

[0072] Unless otherwise specified, each of the raw materials used in the separator (eg, first base film, second base film, adhesive, filler, etc.) is commercially available.

[0073] According to the present application, a secondary battery including the separator 10 of any of the above aspects is provided. When a secondary battery employs the given separator, the reliability of the secondary battery can be improved.

[0074] [Positive electrode sheet] In a secondary battery, the positive electrode sheet generally 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.

[0075] The positive electrode current collector may be a conventional metal foil or a composite current collector (a composite current collector may be formed by applying a metal material to a polymer substrate). For example, the positive electrode current collector may be an aluminum foil.

[0076] The specific type of positive electrode active material is not limited, and any active material known in the art that can be used for a secondary battery positive electrode may be employed, and a person skilled in the art can select the material according to actual needs.

[0077] 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 their respective modified compounds. 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 their modified compounds. 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 their modified compounds. All of these materials are commercially available.

[0078] The modified compounds of the above-mentioned materials may be obtained by subjecting the materials to doping modification and / or surface coating modification.

[0079] The positive electrode film layer generally further optionally contains an adhesive, a conductive agent, and other optional auxiliary agents.

[0080] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon spots, carbon nanotubes, conductive carbon black (Super P, SP), graphene, and carbon nanofibers.

[0081] 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).

[0082] [Negative electrode sheet] In a secondary battery, the negative electrode sheet generally 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.

[0083] 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.

[0084] The specific type of negative electrode active material is not limited, and may be any active material known in the art for use in secondary battery negative electrodes. Those skilled in the art can select the 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 selected from one or more of elemental silicon, silicon oxide compounds (e.g., silicon oxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, stannic oxide compounds, and tin alloys. All of these materials are commercially available.

[0085] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicon-based material.

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

[0087] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon spots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] 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 alcohol butyral (PVB).

[0089] For example, other optional auxiliary agents may be thickening and dispersing agents (such as carboxymethylcellulose sodium, CMC-Na), PTC thermistor materials.

[0090] [Electrolyte] The secondary battery may include an electrolyte that functions as ion conduction between the positive electrode and the negative electrode. The electrolyte may include an electrolyte salt and a solvent.

[0091] 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 bisfluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluoro(oxalato)borate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0092] Examples of 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 (MP), ethyl propionate (Ethyl The compound may be selected from one or more of the following: n-Propanoate (EP), n-Propyl Propionate (PP), Methyl Butyrate (MB), Ethyl Butyrate (EB), 1,4-Butyrolactone (GBL), Tetramethylene Sulfone (SF), Dimethyl Sulfone (Methyl Sulfone (MSM), Methyl Ethyl Sulfone (EMS), and Diethyl Sulfone (ESE).

[0093] 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, or an additive that can improve some performance of the battery, 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.

[0094] In some embodiments, the secondary battery may be a lithium-ion secondary battery. In any embodiment of the present application, the separator 10 is provided between the positive electrode sheet and the negative electrode sheet, and the second base film 12 is disposed on the negative electrode sheet side.

[0095] Because base films with low tensile strength have good heat resistance, a first base film with low longitudinal tensile strength is positioned on the positive electrode side to demonstrate its excellent heat resistance. Because base films with high longitudinal tensile strength have good physical properties and are less susceptible to puncture by metal dendrites, a second base film with high longitudinal tensile strength is positioned on the negative electrode side to demonstrate its excellent physical properties and suppress dendrite deposition. By positioning the first base film with good heat resistance on the positive electrode side and the second base film with good physical properties on the negative electrode side, the resistance to puncture by metal dendrites can be improved, thereby improving the reliability of the secondary battery.

[0096] In the embodiment 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 3 shows an example of a secondary battery 5 with a rectangular structure.

[0097] In some embodiments, the secondary battery may include an outer casing. The outer casing is used to package the positive electrode sheet, the negative electrode sheet, and the electrolyte. The first base film 11 of the separator 10 is disposed on the positive electrode sheet side.

[0098] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may be a soft pack such as a bag-type soft pack. The material of the soft pack may be plastic, and may include, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0099] 4, in some embodiments, the exterior may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are surrounded to form a storage chamber. The housing 51 has an opening communicating with the storage chamber, and the cover plate 53 can be installed to cover the opening to close the storage chamber.

[0100] Methods for manufacturing the secondary battery of the present application are 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, a positive electrode sheet, a separator 10, and a negative electrode sheet may be wound and / or stacked to form an electrode component, the electrode component may be placed in a housing, dried, and then an electrolyte may be injected. A single battery may be obtained by vacuum packaging, standing, chemical formation, molding, or other processes. Multiple single batteries may be further connected in series, parallel, or series-parallel to form a battery module. Multiple battery modules may be further connected in series, parallel, or series-parallel to form a battery pack. In some embodiments, multiple single batteries may directly form a battery pack.

[0101] Fig. 5 shows an example of a battery module 4. Referring to Fig. 5, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, any other layout method may also be used. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0102] The battery module 4 may further include a case having an accommodating space for accommodating a plurality of secondary batteries 5.

[0103] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack is adjustable depending on the application and capacity of the battery pack.

[0104] 6 and 7 show an example 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 provided in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be attached to the lower box body 3 as a lid to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0105] [Device] The present application further provides a power-consuming device including the secondary battery of the present application. The battery alone, the battery module, or the 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 mobility 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.

[0106] The device can be configured to use a single battery, a battery module, or a battery pack depending on its usage needs.

[0107] 8 shows an example power consuming device. The power consuming device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack or battery module may be employed to meet the high power and high energy density demands of the secondary battery of the power consuming device.

[0108] Another example of a power consuming device may be a mobile phone, tablet, or laptop, which generally requires a low profile and low weight and may employ a battery alone as a power source.

[0109] The beneficial effects of the present invention will be further explained below in conjunction with examples.

[0110] In order to clarify the technical problems, technical solutions, and beneficial effects that the embodiments of the present application aim to solve, the following will be described in more detail in conjunction with the embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. The following description of at least one exemplary embodiment is, in fact, merely illustrative and should not be used as any limitation on the present application and its application. 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.

[0111] 1. Separator manufacturing

[0112] First separator: (1) Provide a first base film and a second base film. The first base film is made of polypropylene (PP), with a melting point of 165°C, a transverse breaking elongation of 40%, a longitudinal breaking elongation of 400%, and a transverse tensile strength T1 of 400Kgf / cm. 2 , longitudinal tensile strength L1 900Kgf / cm 2 Meet the following.

[0113] The second base film is made of polyethylene (PE), with a melting point of 135°C, a transverse breaking elongation of 105%, a longitudinal breaking elongation of 50%, and a transverse tensile strength T2 of 1400 kgf / cm. 2 , longitudinal tensile strength L2 1700Kgf / cm 2 Meet the following.

[0114] The ratio T1 / T2 of the transverse tensile strength T1 of the first base film to the transverse tensile strength T2 of the second base film is 0.29, and the ratio L1 / L2 of the longitudinal tensile strength L1 of the first base film to the longitudinal tensile strength L2 of the second base film is 0.53.

[0115] (2) Prepare the intermediate layer slurry: The adhesive polyacrylate, the filler alumina particles, and the carboxymethyl cellulose are uniformly mixed in a ratio of 1:4:1 with an appropriate amount of solvent deionized water to produce the intermediate layer slurry.

[0116] (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.

[0117] (4) The first base film and the second base film after coating in step (3) are hot-pressed together to obtain a separator, and the intermediate layer is located between the first base film and the second base film.

[0118] The manufacturing methods of separators 2 to 13 are the same as those of separator 1, except that one or more of the melting point, material, transverse direction breaking elongation, longitudinal direction breaking elongation, transverse direction tensile strength, or longitudinal direction tensile strength of the base film are adjusted. For details, see Table 1. All other manufacturing methods are the same as those of the separator of Example 1.

[0119] The first separator prepared by the above method is subjected to relevant performance tests, the results of which are shown in Table 1.

[0120] 2. Battery manufacturing

[0121] Example 1

[0122] 1. Manufacturing of positive electrode sheets Cathode active material LiNi 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, dried, cold pressed, cut into strips, and cut into a positive electrode sheet.

[0123] 2. Manufacturing of negative electrode sheets The negative electrode active material artificial graphite, the conductive agent carbon black (SuperP), the adhesive styrene butadiene rubber (SBR), and the 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 as a 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 sheet was obtained by performing drying, cold pressing, cutting into strips, and cutting processes.

[0124] 3. Separator The separator used was the first separator produced above.

[0125] 4. Electrolyte production Ethylene carbonate (EC) and methyl ethyl 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.

[0126] 5. Secondary battery manufacturing The positive electrode sheet, separator, and negative electrode sheet were stacked in this order, with the separator between the positive electrode sheet and the negative electrode sheet to serve as a cutoff, and then wound to obtain an electrode component. The electrode component was placed in an outer casing, and the above-prepared electrolyte solution was injected into the dried secondary battery, which was then vacuum packaged, left to stand, chemically converted, and molded to obtain a secondary battery.

[0127] The manufacturing method of Example 2-11 is the same as that of the secondary battery of Comparative Example 1-2 and that of Example 1, but differs in that different separators are used (Example 1-11 employs separators 1 to 11, and Comparative Example 1-2 employs separators 12 to 13). Specifically, see Table 1.

[0128] 3. Battery performance test

[0129] 1. 250℃ transverse heat shrinkage test Sample preparation: The separator prepared above was punched out into samples 50 mm wide and 100 mm long using a press, and five parallel samples were placed on top of an A4 sheet of paper and fixed in place. The A4 sheet of paper containing the samples was then placed on top of cardboard with a thickness of 1 mm to 5 mm.

[0130] Sample test: An A4 sheet of paper placed on a piece of cardboard was placed in a blast oven, the temperature of the blast oven was set to 250°C, and after the temperature reached the set temperature and stabilized for 30 minutes, timing began. After the set time (1 hour in this application) was reached, the width of the separator was measured and the value was represented as a.

[0131] Heat shrinkage calculation: Transverse direction (TD) heat shrinkage = [(50-a) / 50] x 100%, and the average value of five parallel samples was used as the test result.

[0132] 2. Nail penetration resistance The test was conducted at 25°C and with the battery at 100% SOC. The order of placement was insulation pad / punctured battery cell / insulation pad / battery cell to be tested / insulation pad. A high-temperature resistant thermocouple was connected, and the water cycle was started promptly. Once the temperature of the large area of ​​the battery cell stabilized at 25°C, the cycle continued for at least 10 minutes. A 3mm high-temperature resistant steel needle was used, facing the center of the heat source, at a puncture speed of 0.01mm / s, until the punctured battery cell failed and burned. Changes in the voltage and other values ​​of the battery cell to be tested were monitored. When the battery failed (when the voltage displayed on the device fluctuated or dropped suddenly), the test stopped and the length of time was recorded. If the voltage and other values ​​remained unchanged, the test passed. The punctured battery cell refers to a battery cell that had already been punctured and was used as the heat source.

[0133] [Table 1]

[0134] As can be seen from Table 1, in Examples 1-11, the melting point of the second base film is lower than the melting point of the first base film, the transverse breaking elongation of the second base film is higher than the longitudinal breaking elongation of the second base film, and the longitudinal breaking elongation of the second base film is lower than 100%, and the battery using this separator has improved resistance to nail penetration and higher battery reliability.

[0135] In Comparative Example 1-2, the second base film has a transverse breaking elongation equal to or less than the longitudinal breaking elongation of the second base film, and is poor in heat resistance and nail penetration resistance, which is likely to cause battery safety problems.

[0136] The above are only specific embodiments of the present application, and the scope of protection of the present application is not limited thereto. Anyone skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be in accordance with the scope of protection of the claims.

Claims

1. A separator, a first base film and a second base film; The melting point of the second base film is lower than the melting point of the first base film, A separator, wherein the breaking elongation in the transverse direction of the second base film is greater than the breaking elongation in the longitudinal direction of the second base film, and the breaking elongation in the longitudinal direction of the second base film is less than 100%.

2. 2. The separator according to claim 1, wherein the ratio of the transverse breaking elongation of the second base film to the longitudinal breaking elongation of the second base film is 1.05-4.5, and optionally 1.2-3.

0.

3. The separator according to claim 1 or 2, wherein the second base film has a longitudinal breaking elongation of 30% to 90%.

4. 4. The separator according to claim 1, wherein the first base film has a breaking elongation in the transverse direction that is smaller than the breaking elongation in the longitudinal direction of the first base film.

5. The separator according to any one of claims 1 to 4, wherein the ratio of the transverse breaking elongation of the first base film to the longitudinal breaking elongation of the first base film is 0.05-0.5, and optionally 0.1-0.

3.

6. The separator is (1) The transverse breaking elongation of the first base film is 30%-250%, and optionally 40%-200%; (2) The longitudinal breaking elongation of the first base film is 40%-1000%, and optionally 400%-800%; and (3) The transverse breaking elongation of the second base film is 50%-250%, and optionally 100%-180%; The separator according to any one of claims 1 to 5, which satisfies at least one of the above.

7. The separator according to any one of claims 1 to 6, wherein the transverse tensile strength of the second base film is smaller than the longitudinal tensile strength of the second base film, and optionally the ratio of the transverse tensile strength of the second base film to the longitudinal tensile strength of the second base film is 0.4-0.95, and more preferably 0.6-0.

9.

8. The separator according to any one of claims 1 to 7, wherein the transverse tensile strength of the first base film is smaller than the longitudinal tensile strength of the first base film, and the ratio of the transverse tensile strength of the first base film to the longitudinal tensile strength of the first base film is 0.2-0.9, optionally 0.3-0.

6.

9. The cross-directional tensile strength of the first base film is less than the cross-directional tensile strength of the second base film; and / or The separator according to any one of claims 1 to 8, wherein the first base film has a longitudinal tensile strength smaller than the second base film.

10. The separator is (1) The transverse tensile strength of the first base film is 100 kgf / cm ２ -1000Kgf / cm ２ and optionally 200 kgf / cm ２ -750Kgf / cm ２ That is, (2) The first base film has a longitudinal tensile strength of 700 kgf / cm ２ -2500Kgf / cm ２ and optionally 1000 Kgf / cm ２ -1900Kgf / cm ２ That is, (3) The transverse tensile strength of the second base film is 1200 kgf / cm ２ -3800Kgf / cm ２ and optionally 2000 Kgf / cm ２ -3500Kgf / cm ２ and (4) The second base film has a longitudinal tensile strength of 1800 kgf / cm ２ -5500Kgf / cm ２ and optionally 2100 Kgf / cm ２ -3500Kgf / cm ２ That is, The separator according to any one of claims 1 to 9, which satisfies at least one of the above.

11. the melting point of the first base film is 160°C-370°C, optionally 170°C-350°C; and / or The separator according to any one of claims 1 to 10, wherein the melting point of the second base film is 120°C-280°C, and optionally 130°C-260°C.

12. The separator according to any one of claims 1 to 11, further comprising an intermediate layer, the intermediate layer being provided between the first base film and the second base film and comprising an adhesive, and optionally comprising an adhesive and filler particles.

13. the adhesive comprises one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichlorostyrene copolymer, polyethylene pyrrolidone, 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 branched starch; and / or The separator of claim 12, wherein the filler particles comprise at least one of inorganic particles, organic particles, and organic-metallic frame materials.

14. The separator is (1) the separator has a transverse breaking elongation of 50%-220%, optionally 70%-170%; (2) The longitudinal breaking elongation of the separator is 30%-150%, and optionally 40%-100%; (3) The separator has a transverse tensile strength of 1200 kgf / cm ２ -4000Kgf / cm ２ and optionally 2100 Kgf / cm ２ -3600Kgf / cm ２ That is, (4) The separator has a longitudinal tensile strength of 1900 kgf / cm ２ -5500Kgf / cm ２ and optionally 2200 Kgf / cm ２ -3700Kgf / cm ２ That is, (5) The separator has a transverse heat shrinkage of ≦2%, optionally ≦1.0%, at 250° C. for 1 hour; and (6) The separator has a longitudinal heat shrinkage of ≦2% at 250° C. for 1 hour, and optionally ≦1.0%; The separator according to any one of claims 1 to 13, which satisfies at least one of the above.

15. A secondary battery comprising the separator according to any one of claims 1 to 14.

16. 16. The secondary battery according to claim 15, further comprising a positive electrode sheet and a negative electrode sheet, the separator being provided between the positive electrode sheet and the negative electrode sheet, and the second base film being disposed on the side of the negative electrode sheet.

17. A power consuming device comprising the secondary battery of claim 15.

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