Separator and manufacturing method thereof, secondary battery and power consumption device

Abstract

The present application provides a separator comprising a first base film and a second base film, wherein the melting point of the second base film is higher than that of the first base film, and wherein the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator is denoted as T, where T1 / T2≧1.02 and 0.3≦T1 / T≦0.7. By setting the relationship between the thicknesses of the first base film and the second base film and the relationship between the melting points of the first base film and the second base film, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

Description

[Technical Field]

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

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

[0003] With the continuous development of the new energy industry, users are increasingly demanding the use of secondary batteries. However, batteries generate heat during use, and poor heat resistance poses a safety risk.

[0004] Therefore, how to improve the heat resistance of secondary batteries is currently an issue that needs to be resolved as soon as possible. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a separator and a manufacturing method thereof, a secondary battery, and a power consumption device, which are intended to improve the heat resistance and high-temperature cycle performance of a secondary battery.

[0006] In order to achieve the above object, a first aspect of the present application provides a separator comprising a first base film and a second base film, wherein the melting point of the second base film is higher than the melting point of the first base film, the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator (total thickness of the separator) is denoted as T, and T1 / T2≧1.02 and 0.3≦T1 / T≦0.7.

[0007] Compared with the prior art, the present application has at least the following beneficial effects: By setting the relationship between the thicknesses of the first and second base films and the relationship between the melting points of the first and second base films, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0008] In any embodiment of the present application, 1.2≦T1 / T2≦4.0 When the thickness ratio of the first base film to the second base film satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0009] In any embodiment of the present application, 0.35≦T1 / T≦0.6. When the ratio of the thickness of the first base film to the total thickness of the separator satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0010] In any embodiment of the present application, T≦17 μm, and optionally 4 μm≦T≦15 μm. When the separator total thickness satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0011] In any embodiment of the present application, T1≦12 μm, and optionally 3 μm≦T1≦8 μm. When the thickness of the first base film satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0012] In any embodiment of the present application, T2≦12 μm, and optionally 2 μm≦T2≦7 μm. When the thickness of the second base film satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0013] In any embodiment of the present application, the ratio of the melting point of the first base film to the melting point of the second base film is 1.05 or more and 2.50 or less, and optionally 1.5-2.5. When the ratio of the melting point of the first base film to the melting point of the second base film satisfies the above condition, the separator has good heat resistance and can effectively improve the high-temperature cycle performance of the battery.

[0014] In any embodiment of the present application, the melting point of the first base film is 120° C.-270° C., optionally 135° C.-260° C., and / or the melting point of the second base film is 160° C.-330° C., optionally 180° C.-320° C. When the melting points of the first base film and the second base film respectively satisfy the above conditions, the separator can have good heat resistance and the high-temperature cycle performance of the battery can be effectively improved.

[0015] In any embodiment of the present application, the first base film and the second base film are each independently selected from at least one of polyolefins and their derivatives, halogenated polyolefins and their derivatives, polyethers and their derivatives, polyetheretherketones and their derivatives, polyesters and their derivatives, polyimides and their derivatives, polyvinyl alcohols and their derivatives, polytetrafluoroethylenes and their derivatives, polyvinyl fluorides and their derivatives, polyvinylidene fluorides and their derivatives, and polyethylene terephthalate and its derivatives. When the materials of the first base film and the second base film are selected from at least one of the above materials, the separator has good heat resistance and the high-temperature cycle performance of the battery can be effectively improved.

[0016] In any embodiment of the present application, an adhesive layer is further provided between the first base film and the second base film, the adhesive layer including an adhesive, and optionally the adhesive layer including an adhesive and a filler. When an adhesive 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 improving the reliability of the secondary battery.

[0017] 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. An adhesive layer is provided between the first base film and the second base film, and the adhesive in the adhesive layer includes the above-mentioned components, thereby improving the reliability of the secondary battery.

[0018] In any embodiment of the present application, the thickness of the adhesive layer is 4 μm or less, and optionally 0.5-2.5 μm. When the thickness of the adhesive layer is within the predetermined range, the reliability of the secondary battery can be improved.

[0019] A second aspect of the present application provides a method for manufacturing a separator. The method includes providing a first base film and a second base film, the second base film having a melting point higher than that of the first base film, and combining the first and second base films to obtain a separator, where the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator is denoted as T, and the ratio T1 / T2 is 1.02 and 0.3≦T1 / T≦0.7. The manufactured separator can improve the heat resistance of a battery and effectively improve the high-temperature cycling performance of the battery.

[0020] A third aspect of the present application provides a secondary battery, the secondary battery including the separator of the first aspect of the present application or the separator produced by the method of the second aspect of the present application. When the secondary battery employs the specified separator, the heat resistance of the secondary battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0021] 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, the first base film faces the negative electrode plate, and the thickness of the first base film facing the negative electrode plate is larger, which provides more spare space for the easily swellable material in the separator, thereby improving the heat resistance of the secondary battery and effectively improving the high-temperature cycle performance of the battery.

[0022] A fourth aspect of the present application provides a power consuming device, the power consuming device including the secondary battery of the third aspect of the present application. Using a given separator in the secondary battery of the power consuming device can improve the heat resistance and reliability of the power consuming device.

[0023] 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]

[0024] 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] 1 is a structural schematic diagram of one embodiment of the separator of the present application. FIG. [Figure 3] 1 is a flowchart of one embodiment of a method for manufacturing a separator of the present application. [Figure 4] FIG. 1 is a schematic diagram of an embodiment of a secondary battery. [Figure 5] FIG. 5 is an exploded view of FIG. [Figure 6] FIG. 1 is a schematic diagram of one embodiment of a battery module. [Figure 7] FIG. 1 is a schematic diagram of one embodiment of a battery pack. [Figure 8] FIG. 8 is an exploded view of FIG. [Figure 9] 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

[0025] The present application will be further described below in conjunction with the detailed description of the present invention. 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.

[0026] For clarity, this specification specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form an open range, and any lower limit can be combined with another lower limit to form an open range, and similarly, any upper limit can be combined with another upper limit to form an open range. Furthermore, each point or single numerical value disclosed alone can be used as a lower limit or upper limit in combination with any other point or single numerical value, or in combination with other lower limits or upper limits to form an open range.

[0027] 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).

[0028] 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.

[0029] Unless otherwise specified, the terms used in this application have the 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 methods described in the examples of this application).

[0030] ●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.

[0031] 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.

[0032] [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 is higher than the melting point of the first base film, the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator is denoted as T, where T1 / T2≧1.02 and 0.3≦T1 / T≦0.7.

[0033] Without wishing to be bound by any theory, the inventors have found through extensive research that, in the separator structure according to the present application, by controlling the ratio of the separator thickness to the base film thickness within the above range, the high-temperature cycle performance of the battery can be effectively improved while ensuring heat resistance. This is because when the separator, especially the separator base film, is immersed in the electrolyte for a long time during battery use, volumetric swelling occurs, which is likely to cause hipot defects. The specific thickness ratio design according to the present application contributes to increasing the gap in the battery core, providing spare space for materials in the separator that are prone to swelling, while not affecting the separator's heat resistance, thereby effectively improving the high-temperature cycle performance of the battery.

[0034] As a result of intensive research, the present inventors have found that the performance of a secondary battery can be further improved when the separator of the present application satisfies the above conditions and, in addition, selectively satisfies one or more of the following conditions:

[0035] In any embodiment of the present application, 1.2≦T1 / T2≦4.0. For example, the ratio of the thickness of the first base film to the thickness of the second base film may be optionally 1.2, 1.25, 1.32, 1.46, 1.58, 1.67, 1.91, 2.05, 2.25, 2.56, 2.78, 2.99, 3.15, 3.46, 3.88, 4.0, etc., or a range consisting of any two of the above values. For example, the thickness ratio of the first base film to the second base film may optionally be 1.02-1.11, 1.05-1.20, 1.10-1.50, 1.10-1.86, 1.10-2.51, 1.10-3.04, 1.45-3.70, 1.67-2.50, 1.75-2.33, 2.33-2.50, 2.50-3.50, 3.50-4.00, 3.30-3.50, 3.20-3.60, 1.75-2.50, 1.2-1.46, 1.32-1.67, 1.58-2.05, 2.25-2.99, 2.78-3.15, 3.46-4.0, etc. When the thickness ratio between the first base film and the second base film satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0036] In any embodiment of the present application, the ratio of T1 / T to the total thickness of the separator is 0.35≦T1 / T≦0.6. The ratio of the thickness of the first base film to the total thickness of the separator is 0.35 or more and 0.6 or less. The ratio of the thickness of the first base film to the total thickness of the separator is optionally 0.35, 0.37, 0.40, 0.44, 0.47, 0.51, 0.55, 0.58, 0.60, etc., or a range consisting of any two of the above values. For example, the ratio of the thickness of the first base film to the total thickness of the separator may optionally be 0.35-0.42, 0.42-0.53, 0.50-0.61, 0.58-0.64, 0.53-0.58, 0.47-0.54, 0.50-0.60, 0.42-0.56, 0.54-0.60, 0.46-0.59, 0.53-0.57, 0.42-0.50, 0.50-0.56, 0.40-0.47, 0.37-0.58, 0.47-0.60, 0.51-0.60, 0.44-0.51, 0.54-0.60, etc. In this embodiment, when the ratio of the thickness of the first base film to the total thickness of the separator satisfies the above condition, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0037] In any embodiment of the present application, the thickness of the separator is T≦17 μm, and optionally 4 μm≦T≦15 μm.

[0038] In some embodiments, the separator thickness is optionally 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 9 μm, 10 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, etc., or a range consisting of any two of the foregoing values. For example, the separator thickness is optionally 3 μm-15 μm, 3 μm-13 μm, 3 μm-10 μm, 3 μm-9 μm, 5 μm-17 μm, 5 μm-15 μm, 5 μm-12 μm, 5 μm-10 μm, 6 μm-15 μm, 6 μm-13 μm, 7 μm-17 μm, 7 μm-15 μm, 7 μm-12 μm, 9 μm-17 μm, 9 μm-15 μm, 10 μm-15 μm, etc.

[0039] In any embodiment of the present application, the thickness of the first base film is T1≦12 μm, and optionally 3 μm≦T1≦8 μm.

[0040] In some embodiments, the thickness of the first base film is optionally 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 9 μm, 10 μm, 12 μm, etc., or a range consisting of any two of the foregoing values. For example, the thickness of the first base film is optionally 2 μm-12 μm, 2 μm-10 μm, 2 μm-8 μm, 3 μm-12 μm, 3 μm-10 μm, 3 μm-8 μm, 5 μm-12 μm, 5 μm-10 μm, 6 μm-12 μm, 6 μm-10 μm, 7 μm-12 μm, 7 μm-10 μm, etc.

[0041] In any embodiment of the present application, the thickness of the second base film is T2≦12 μm, and optionally 2 μm≦T2≦7 μm.

[0042] In some embodiments, the thickness of the second base film is optionally 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 11 μm, 12 μm, etc., or a range consisting of any two of the foregoing values. For example, the thickness of the first base film is optionally 2 μm-12 μm, 2 μm-10 μm, 2 μm-7 μm, 2 μm-5 μm, 3 μm-12 μm, 3 μm-10 μm, 3 μm-7 μm, 3 μm-5 μm, 5 μm-12 μm, 5 μm-10 μm, 6 μm-12 μm, 6 μm-10 μm, 7 μm-12 μm, 7 μm-10 μm, etc.

[0043] When the thickness of the separator, the thickness of the first base film, and the thickness of the second base film are within the above ranges, the heat resistance of the battery can be improved and the high-temperature cycle performance of the battery can be effectively improved.

[0044] According to some embodiments, the thickness of the base film can be tested using equipment and methods known in the art, specifically, by taking six sets of parallel samples and measuring the thickness of each set of samples at different locations using a multimeter thickness gauge, with at least 20 measurements being taken for each set of samples, and the average thickness of the six sets of samples is the thickness of the base film.

[0045] In any embodiment of the present application, the ratio of the melting point of the first base film to the melting point of the second base film is 1.05-2.50, optionally 1.5-2.5. For example, the ratio of the melting point of the first base film to the melting point of the second base film is 1.05, 1.06, 1.08, 1.1, 1.2, 1.24, 1.38, 1.44, 1.54, 1.72, 1.95, 2.12, 2.30, 2.45, 2.49, 2.50, or a range consisting of any two of the above values. For example, the ratio of the melting point of the first base film to the melting point of the second base film may be 1.05-1.24, 1.05-1.38, 1.05-1.54, 1.05-1.72, 1.05-1.95, 1.05-2.30, 1.05-2.45, 1.08-1.24, 1.08-1.38, 1.08-1.54, 1.08-1.72, 1.08-1.95, 1.08-2.30, 1.08-2.45, 1.08-2.5, 1.1-1.24, 1.1-1.38, 1.1-1.54, 1.1 -1.72, 1.1-1.95, 1.1-2.30, 1.1-2.45, 1.1-2.5, 1.2-1.24, 1.2-1.38, 1.2-1.54, 1.2-1.72, 1.2-1.95, 1.2-2.30, 1.2-2.45, 1.2-2.5, 1.38-1.54, 1.38-1.72, 1.38-1.95, 1.38-2.30, 1.38-2.45, 1.38-2.5, 1.72-1.95, 1.95-2.30, 2.12-2.49, 2.45-2.50, etc. 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 the high-temperature cycle performance of the battery can be effectively improved.

[0046] In some embodiments of the present application, the melting point of the first base film is 120°C-270°C, optionally 135°C-260°C, and / or the melting point of the second base film is 160°C-330°C, optionally 180°C-320°C. For example, in some embodiments, the melting point of the first base film is 120°C, 138°C, 149°C, 160°C, 170°C, 186°C, 195°C, 232°C, 240°C, 257°C, 270°C, etc., or a range consisting of any two of the above values. For example, the melting point of the first base film is 120°C-165°C, 149°C-186°C, 160°C-189°C, 186°C-195°C, or 232°C-240°C. In some embodiments, the melting point of the second base film is 160°C, 171°C, 194°C, 212°C, 240°C, 267°C, 295°C, 316°C, 325°C, 330°C, or a range consisting of any two of the above values. For example, the melting point of the second base film is 160°C-180°C, 171°C-210°C, 210°C-240°C, 240°C-272°C, or 272°C-330°C.

[0047] A melting point that is too high or too low will affect the physical performance of the base film material, and by limiting the melting points of the first base film and the second base film, and their ratio, within the above range, the heat resistance of the first base film and the second base film can be improved, and the high-temperature cycle performance of the battery can be effectively improved.

[0048] According to some embodiments, the melting points of the first base film and the second base film have meanings known in the art and can be measured using 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, they can be measured using the following method: A 4-6 mg sample 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.

[0049] In any embodiment of the present application, the materials of the first base film and the second base film can be independently selected from at least one of polyolefins and their derivatives, halogenated polyolefins and their derivatives, polyethers and their derivatives, polyetheretherketones and their derivatives, polyesters and their derivatives, polyimides and their derivatives, polyvinyl alcohols and their derivatives, polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, polyvinylidene fluoride and its derivatives, and polyethylene terephthalate and its derivatives. Here, the term "derivative" generally refers to a product derived by replacing a hydrogen atom or atomic group in a compound with another atom or atomic group. Using at least one of the above materials for the first base film and the second base film can provide the first base film and the second base film with good chemical stability, provide the separator with good heat resistance, and effectively improve the high-temperature cycling performance of the battery.

[0050] Referring to FIG. 2, an example of the present application provides a separator 10 including a first base film 11 and a second base film 12. In some embodiments of the present application, an adhesive layer 13 is further provided between the first base film 11 and the second base film 12. The adhesive layer includes an adhesive, and optionally, the adhesive layer includes an adhesive and a filler. The adhesive layer between the first and second base films can compensate for some process defects during the hot-press compounding process and further improve the stability of the separator's physical properties (e.g., tensile strength, puncture strength, heat resistance, etc.), thereby improving the reliability of secondary batteries. The presence of a filler between the first and second base films can also reduce the risk of powder shedding.

[0051] 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 adhesive layer is provided between the first base film and the second base film and the adhesive in the adhesive layer includes the above-mentioned components, the heat resistance and physical performance of the separator can be further improved, thereby improving the reliability of the secondary battery.

[0052] In any embodiment of the present application, the filler includes at least one of inorganic particles, organic particles, and an organic-metallic frame material. Optionally, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or greater, inorganic particles that are ionic conductive but do not store ions, and inorganic particles that can undergo electrochemical reactions.

[0053] Optionally, the inorganic particles having a dielectric constant of 5 or more include 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), Pb1-mLamZr1-nTinO3 (abbreviated as PLZT), and 0. <m<1、0<n<1)、Pb(Mg3Nb 2 / 3The adhesive may include at least one of )O3-PbTiO3 (abbreviated as PMN-PT) and modified inorganic particles. Optionally, the inorganic particles may be modified chemically and / or physically. The chemical modification may include coupling agent modification (e.g., using a silane coupling agent, a titanate coupling agent, etc.), surfactant modification, polymer graft modification, etc. The physical modification may include mechanical dispersion, ultrasonic dispersion, high-energy treatment, etc. The modification treatment can reduce the aggregation of the inorganic particles, thereby resulting in a more stable and uniform structure of the adhesive layer. Furthermore, by selecting a coupling agent, surfactant, or polymer with a specific functional group to modify the inorganic particles, the adhesive layer's wetting and retention properties with respect to the electrolyte can be improved, contributing to improved adhesion of the adhesive layer to the first and second base films.

[0054] 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 z4including 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.

[0055] Optionally, the inorganic particles capable of undergoing the 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.

[0056] 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 copolymers of butyl acrylate and ethyl methacrylate (crosslinked polymers of butyl acrylate and ethyl methacrylate).

[0057] Optionally, the organic-metal frame material may include one or more of nitrogen-containing heterocyclic ligand building structures, organic carboxylic acid ligand building structures, and nitrogen-containing oxygen gas mixed ligand building structures.

[0058] 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.

[0059] 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%.

[0060] In some embodiments, the adhesive layer may further include a dispersant, such as carboxymethyl cellulose, which can adjust the viscosity of the adhesive layer slurry and improve the quality and uniformity of the adhesive layer.

[0061] 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.

[0062] In one embodiment of the present application, the thickness of the adhesive layer is 4 μm or less, and optionally 0.5-2.5 μm. When the thickness of the adhesive layer is within this range, the reliability of the secondary battery can be improved. At the same time, when combined with the base film, the heat resistance and high-temperature cycle performance of the battery can be improved.

[0063] According to some embodiments, the thickness of the adhesive layer can be tested using equipment and methods known in the art. Specifically, a scanning electron microscope (e.g., ZEISS Sigma 300) is used to obtain a cross-sectional scanning electron microscope (SEM) photograph of the separator according to JY / T010-1996. For example, the thickness can be tested according to the following method: Randomly select multiple areas on the cross section of the separator, measure the thickness of the adhesive layer at least five times at a certain magnification, and calculate the average value of the measurements from different areas.

[0064] [Separator manufacturing method] The present application also provides a method for manufacturing a separator according to the present application. Referring to Figure 3, the present application provides a method for manufacturing a separator. The method includes the following steps: S10: Providing a first base film and a second base film, the melting point of the second base film being higher than the melting point of the first base film.

[0065] S20: The first base film and the second base film are combined to obtain a separator.

[0066] Here, the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator is denoted as T, and T1 / T2≧1.02 and 0.3≦T1 / T≦0.7.

[0067] The first and second base films may be directly combined by hot pressing, but if the temperature is too high during the hot pressing process, the porosity will be small and the breathability will be poor, and if the temperature is too low, the adhesion between the first and second base films will be weak, so it is necessary to adjust the hot pressing temperature appropriately. Optionally, the hot pressing temperature is 20°C-50°C.

[0068] In any embodiment of the present application, the manufacturing method further includes providing an adhesive layer slurry containing an adhesive, and applying the adhesive layer slurry to a first base film and / or a second base film followed by compounding.

[0069] Optionally, the adhesive layer slurry contains an adhesive and a filler, which allows an adhesive layer to be formed between the first base film and the second base film, improving the physical performance of the separator and the reliability of the secondary battery.

[0070] Unless otherwise specified, each of the raw materials used in the method for producing the separator (for example, the first base film, the second base film, the adhesive, the filler, etc.) is commercially available.

[0071] [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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The modifying compound for each of the above materials may be one that performs doping modification and / or surface coating modification on the material.

[0076] The positive electrode membrane layer generally further optionally contains an adhesive, a conductive agent and other optional auxiliary agents.

[0077] 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, Super P (SP), graphene, and carbon nanofibers.

[0078] 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), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0079] [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.

[0080] 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.

[0081] 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 their 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.

[0082] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicone-based material.

[0083] The negative electrode film layer generally further optionally contains an adhesive, a conductive agent and other optional auxiliary agents.

[0084] 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.

[0085] 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).

[0086] For example, other optional auxiliaries may be thickening and dispersing agents (such as sodium carboxymethylcellulose CMC-Na), PTC thermistor materials.

[0087] [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.

[0088] 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).

[0089] Examples of solvents 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 hydroxybenzoates may be selected from one or more of the following: n-Propyl Propionate (MP), n-Ethyl Propanoate (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-Butyrolactone (MSM), 1,4-Butyrolactone (MES), and 1,4-Butyrolactone (ESE).

[0090] 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.

[0091] In some embodiments, the secondary battery may be a lithium-ion secondary battery. In any embodiment of the present application, the secondary battery includes a positive electrode plate, a negative electrode plate, and a separator, and the separator is disposed between the positive electrode plate and the negative electrode plate, and the separator may be the separator of any of the above embodiments.

[0092] In some embodiments, in a secondary battery, the first base film of the separator faces the negative electrode plate. That is, the thicker side of the base film faces the negative electrode plate. If lithium dendrites precipitate on the negative electrode side, the separator can withstand the lithium dendrites more effectively, reducing the risk of the separator being pierced and causing a short circuit between the positive and negative electrodes. At the same time, the melting point of the second base film facing the positive electrode plate is higher than that of the first base film, allowing it to withstand higher temperatures and reducing the risk of the separator being destroyed by heat and causing a short circuit between the positive and negative electrodes. This improves the reliability of the secondary battery.

[0093] The embodiments of the present application are not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. Figure 4 shows an example of a secondary battery 5 with a rectangular structure.

[0094] In some embodiments, the secondary battery may include an exterior body used to package the positive electrode plate, the negative electrode plate, the separator, and the electrolyte.

[0095] 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-like pouch. The material of the pouch may be plastic, and may include, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0096] 5, 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.

[0097] The manufacturing method of 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, a negative electrode plate, and an electrolyte. For example, a positive electrode plate, a separator, and a negative electrode plate can be formed into an electrode assembly by 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 be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping. A plurality of battery cells can be further connected in series, parallel, or series-parallel to form a battery module. A plurality of battery modules can be further connected in series, parallel, or series-parallel to form a battery pack. In some embodiments, a plurality of battery cells can directly form a battery pack.

[0098] Fig. 6 shows an example of a battery module 4. Referring to Fig. 6, a plurality of secondary batteries 5 may be 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.

[0099] 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.

[0100] 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.

[0101] 7 and 8 show an example of a battery pack 1. Referring to FIGS. 7 and 8, 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 may be provided with a lid on the lower housing 3 to form 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.

[0102] ●Device The present application further provides an electric consumption 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.

[0103] A device may select a battery cell, a battery module, or a battery pack based on its usage needs.

[0104] 9 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.

[0105] 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.

[0106] The beneficial effects of the present application will be further explained below in conjunction with examples.

[0107] 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. Of course, the described embodiments are only a part of the embodiments of the present application, but not all of the 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 by those skilled in the art based on the embodiments in the present application without any creative effort are within the scope of protection of the present application.

[0108] 1. Battery manufacturing Example 1 1. Manufacturing of positive electrode plates Positive electrode 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, and after drying, cold pressing, slitting, cutting, and other processes, a positive electrode plate was obtained.

[0109] 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 after drying, cold pressing, slitting, and cutting processes.

[0110] 3. Separator manufacturing (1) A first base film is provided, the material of which is polyethylene (PE), the thickness of which is 7 μm, and the melting point of which is 135°C.

[0111] (2) A second base film is provided, the material of which is polypropylene (PP), the thickness of which is 6 μm, and the melting point of which is 165°C.

[0112] (3) Preparation of adhesive layer slurry: Boehmite, polyacrylate, and carboxymethyl cellulose were uniformly mixed in a ratio of 4:1:1 with an appropriate amount of deionized water as a solvent to prepare an adhesive layer slurry.

[0113] (4) The adhesive layer slurry from step (3) is applied to a PE base film to form an adhesive layer, and the PP and PE base films are hot-pressed together so that the adhesive layer is located between the PP base film and the PE base film, thereby producing a separator. The thickness of the adhesive layer is 2 μm.

[0114] 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. Thoroughly dried electrolyte salt LiPF6 was dissolved in the mixed solvent, and the concentration of the electrolyte salt was 1.0 mol / L. After uniform mixing, an electrolyte solution was obtained.

[0115] 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 then wound to obtain an electrode assembly. The electrode assembly is placed in an outer casing, and the prepared electrolyte solution is injected into the dried case. The secondary battery is obtained through vacuum packaging, standing, chemical formation, and shaping processes.

[0116] The secondary batteries of Examples 2-10 and Comparative Examples 1-4 were manufactured using methods similar to that of the secondary battery of Example 1, except that different separators were used. See Table 1 for details.

[0117] 2. Performance test (1) High-temperature cycle performance of the battery At 60°C, the batteries of the above examples and comparative examples were charged at a constant current of 1 C until the voltage reached 3.65 V, then charged at a constant voltage of 3.65 V until the current was ≦0.05 C, and then discharged at a constant current of 1 C until the voltage reached 2.5 V. This constitutes one charge / discharge process, and the discharge capacity at this stage is recorded as the discharge capacity of the first cycle of the battery. The charge / discharge cycle was repeated in this manner, and the number of cycles when the capacity decreased to 80% was recorded.

[0118] Test results of battery performance for each example and comparative example [Table 1]

[0119] As can be seen from Table 1, in Examples 1-10, the thickness of the first base film (T1), the thickness of the second base film (T2), and the total thickness of the separator (T) satisfy the relationships T1 / T2≧1.02 and 0.3≦T1 / T≦0.7, and the batteries manufactured thereby have good cycle life and higher reliability.

[0120] 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 set forth in the present application, and all such 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 higher than the melting point of the first base film; A separator, wherein the thickness of the first base film is denoted as T1, the thickness of the second base film is denoted as T2, and the total thickness of the separator is denoted as T, and T1 / T2≧1.02 and 0.3≦T1 / T≦0.

7.

2. 2. The separator according to claim 1, wherein 1.2≦T1 / T2≦4.

0.

3. The separator according to claim 1 or 2, wherein 0.35≦T1 / T≦0.

6.

4. 4. The separator of claim 1, wherein T≦17 μm, and optionally 4 μm≦T≦15 μm.

5. T1≦12 μm, optionally 3 μm≦T1≦8 μm, and / or 5. The separator of claim 1, wherein T2≦12 μm, and optionally 2 μm≦T2≦7 μm.

6. The separator according to any one of claims 1 to 5, wherein the ratio of the melting point of the second base film to the melting point of the first base film is 1.05-2.5, and optionally 1.5-2.

5.

7. The melting point of the first base film is 120°C-270°C, optionally 135°C-260°C, and / or The separator according to any one of claims 1 to 6, wherein the melting point of the second base film is 160°C-330°C, and optionally 180°C-320°C.

8. 8. The separator according to claim 1, wherein the first base film and the second base film are each independently selected from at least one of polyolefins and derivatives thereof, halogenated polyolefins and derivatives thereof, polyethers and derivatives thereof, polyether ether ketones and derivatives thereof, polyesters and derivatives thereof, polyimides and derivatives thereof, polyvinyl alcohols and derivatives thereof, polytetrafluoroethylenes and derivatives thereof, polyvinyl fluorides and derivatives thereof, polyvinylidene fluorides and derivatives thereof, and polyethylene terephthalate and derivatives thereof.

9. 9. The separator according to claim 1, further comprising an adhesive layer between the first base film and the second base film, the adhesive layer including an adhesive, optionally the adhesive layer including an adhesive and a filler, optionally the filler including at least one of inorganic particles, organic particles, and an organic-metallic frame material.

10. The separator of claim 9, wherein the thickness of the adhesive layer is 4 μm or less, and optionally 0.5-2.5 μm.

11. 11. The separator of claim 9 or 10, wherein 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, and cyanoethyl amylopectin.

12. A method for manufacturing a separator, comprising: Providing a first base film and a second base film, wherein the melting point of the second base film is higher than the melting point of the first base film; and combining the first base film and the second base film to obtain the separator, wherein, when a thickness of the first base film is denoted as T1, a thickness of the second base film is denoted as T2, and a total thickness of the separator is denoted as T, T1 / T2≧1.02 and 0.3≦T1 / T≦0.

7.

13. The manufacturing method includes: providing an adhesive layer slurry comprising an adhesive; and applying the adhesive layer slurry to the first base film and / or the second base film, followed by compounding; Optionally, the adhesive layer slurry comprises an adhesive and a filler.

14. A secondary battery comprising the separator according to any one of claims 1 to 11 or the separator produced by the method of claims 12 or 13.

15. 15. The secondary battery according to claim 14, further comprising a positive electrode plate and a negative electrode plate, wherein the separator is provided between the positive electrode plate and the negative electrode plate, and the first base film faces the negative electrode plate.

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

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