Separator, secondary battery and power consuming device

Abstract

The present application provides a separator, which includes a first base film and a second base film, wherein the melting point of the second base film is lower than that of the first base film, and where the porosity of the first base film is P1 and the porosity of the second base film is P2, the ratio P1 / P2 is 1.02≦P1≦3. A base film with a high porosity has high breathability, and therefore the first base film with a high porosity exhibits excellent breathability. A base film with a low porosity has high strength, and therefore the second base film with a low porosity exhibits good strength and is less likely to be penetrated by lithium dendrites. Therefore, by using a combination of the first base film and the second base film, the present application provides a separator with good breathability and strength, thereby improving the reliability and cycle characteristics of secondary batteries.

Description

[Technical Field]

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

[0002] Secondary batteries have the notable characteristics of being lightweight, non-polluting and having no memory effect, and are widely used in various consumer electronic products and electric vehicles.

[0003] With the continuous development of the new energy industry, users are placing higher requirements on secondary batteries, for example, some secondary batteries have ion transport limitations, which reduces the cycle life of the battery.

[0004] Therefore, how to make secondary batteries have good cycle characteristics is an urgent issue to be solved. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a separator, a secondary battery, and a power consuming device that aim to improve the cycle characteristics of a secondary battery.

[0006] To achieve the above object, according to a first aspect of the present application, a separator is provided, comprising 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, and where the porosity of the first base film is P1 and the porosity of the second base film is P2, 1.02≦P1 / P2≦3.

[0007] Compared to the prior art, the present application has at least the following beneficial effects. When the melting point of the second base film is lower than that of the first base film and 1.02≦P1 / P2≦3, the breathability and strength of the first and second base films are better balanced. A base film with high porosity has high breathability, and a first base film with high porosity exhibits excellent breathability. A base film with low porosity has high strength, and a second base film with low porosity exhibits good strength and is less likely to be penetrated by dendrites. Therefore, by using the first and second base films provided by the present application, and combining two base films with 1.02≦P1 / P2≦3, the separator has good breathability and strength, thereby improving the reliability and cycle characteristics of secondary batteries.

[0008] In any embodiment of the present application, 1.05≦P1 / P2≦2.5. When 1.05≦P1 / P2≦2.5, the breathability and strength of the first base film and the second base film are better balanced. As a result, the separator has good breathability and strength, and the reliability and cycle characteristics of the secondary battery can be improved.

[0009] In any embodiment of the present application, the porosity of the first base film is 30% to 90%, optionally 35% to 85%, and / or the porosity of the second base film is 30% to 70%, optionally 35% to 45%.

[0010] When the porosity of the first base film is 30% to 90% and / or the porosity of the second base film is 30% to 70%, the breathability and strength of the first base film and the second base film are better balanced. As a result, the separator has good breathability and strength, and the reliability and cycle characteristics of the secondary battery can be improved. When the porosity of the first base film is 35% to 85% and / or the porosity of the second base film is 35% to 45%, the breathability and strength of the separator can be further improved, and therefore the reliability and cycle characteristics of the secondary battery can be improved.

[0011] In any embodiment of the present application, the ratio of the average pore size of the first base film to the average pore size of the second base film is 0.05 to 80, and optionally 0.2 to 40. The smaller the average pore size, the smaller the space occupied by the average pore area, the larger the space occupied by the fiber threads of the base film, and the stronger the base film. Conversely, the smaller the space occupied by the fiber threads of the base film, the larger the average pore area of ​​the separator and the better the breathability. By setting the average pore size ratio within the above range, the separator can achieve both breathability and strength, improving the reliability and cycle characteristics of the separator.

[0012] In any embodiment of the present application, the average pore size of the first base film is larger than the average pore size of the second base film, which satisfies the porosity requirements of the two base films, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0013] In any embodiment of the present application, the first base film has an average pore size of 100 nm to 4000 nm, optionally 100 nm to 2000 nm, and / or the second base film has an average pore size of 50 nm to 2000 nm, optionally 50 nm to 500 nm, which satisfies the porosity requirements of the two base films, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0014] In any embodiment of the present application, the tensile strength in the transverse direction of the first base film is smaller than the tensile strength in the longitudinal direction of the first base film, and the ratio of the tensile strength in the transverse direction of the first base film to the tensile strength in the longitudinal direction of the first base film is 0.2 to 0.8, and optionally 0.3 to 0.6, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0015] In any embodiment of the present application, the tensile strength in the transverse direction of the second base film is smaller than the tensile strength in the longitudinal direction of the second base film, and optionally the ratio of the tensile strength in the transverse direction of the second base film to the tensile strength in the longitudinal direction of the second base film is 0.45 to 0.9, and optionally 0.6 to 0.8, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0016] In any embodiment of the present application, the tensile strength in the transverse direction of the first base film is lower than the tensile strength in the transverse direction of the second base film, and / or the tensile strength in the longitudinal direction of the first base film is lower than the tensile strength in the longitudinal direction of the second base film, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0017] In any embodiment of the present application, the separator satisfies at least one of the following (1) to (4).

[0018] (1) The transverse tensile strength of the first base film is 150 to 900 kgf / cm 2 and selectively 200 to 750 kgf / cm 2 is.

[0019] (2) The first base film has a longitudinal tensile strength of 800 to 2500 kgf / cm 2 and selectively 1100~1900Kgf / cm 2 is.

[0020] (3) The transverse tensile strength of the second base film is 1500 to 3600 kgf / cm 2 and selectively 1800~3300Kgf / cm 2 is.

[0021] (4) The second base film has a longitudinal tensile strength of 1900 to 4000 kgf / cm 2 and selectively 2000~3500Kgf / cm 2 is.

[0022] When the separator satisfies the ranges shown in at least one of the above items (1) to (4), the separator has good breathability and strength, and the reliability and cycle characteristics of the secondary battery can be improved.

[0023] In any embodiment of the present application, the ratio of the thickness of the first base film to the thickness of the second base film is 1.02 or more, and optionally 1.2 to 3.0, so that the separator has good breathability and strength, and the reliability and cycle characteristics of the secondary battery can be improved.

[0024] In any embodiment of the present application, the thickness of the first base film is 2 μm to 12 μm, and optionally 3 μm to 6 μm, and / or the thickness of the second base film is 2 μm to 12 μm, and optionally 3 μm to 5 μm, thereby providing the separator with good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0025] 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 3.0 or less, and optionally 1.1 or more and 2.5 or less, so that the separator has good breathability and strength, as well as heat resistance, and can improve the reliability and cycle characteristics of the secondary battery.

[0026] In any embodiment of the present application, the melting point of the first base film is 160° C. to 360° C., and optionally 180° C. to 350° C., and / or the melting point of the second base film is 120° C. to 280° C., and optionally 130° C. to 265° C. This allows the separator to have good breathability and strength, as well as heat resistance, and can improve the reliability and cycle characteristics of the secondary battery.

[0027] 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, polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, polyvinylidene fluoride and its derivatives, and polyethylene terephthalate and its derivatives. When the first base film and the second base film are each made of at least one of the above materials, maintaining the porosity of the separator within an appropriate range improves the breathability and strength of the separator when combined, thereby improving the reliability and cycle characteristics of the secondary battery.

[0028] In any embodiment of the present application, an adhesive layer containing a binder is further disposed between the first base film and the second base film, and optionally, the adhesive layer contains a binder and a filler. When an adhesive layer is disposed between the first base film and the second base film and contains a binder and a filler, the separator can have high strength, heat resistance, and breathability. The reliability and cycle characteristics of the secondary battery can be improved.

[0029] In some embodiments of the present application, the binder may include one or more of polyacrylic acid ester, 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 disposed between the first base film and the second base film and the binder in the adhesive layer includes the above-mentioned components, the separator can have high strength, heat resistance, and breathability. This can improve the reliability and cycle characteristics of secondary batteries.

[0030] In any embodiment of the present application, the filler comprises at least one of inorganic particles, organic particles, and organic-metal frameworks. When an adhesive layer is disposed between the first base film and the second base film, and the filler in the adhesive layer comprises at least one of inorganic particles, organic particles, and organic-metal frameworks, the filler in the adhesive layer can further improve the heat resistance and strength of the separator, thereby improving the reliability of the secondary battery.

[0031] In any embodiment of the present application, the thickness of the adhesive layer is 0.3 μm or more, and optionally 0.5 to 2 μm. When the thickness of the adhesive layer is within the above range, the separator has good breathability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0032] In any embodiment of the present application, the separator has an air permeability of 200 s / 100 cc to 400 s / 100 cc, optionally 250 s / 100 cc to 320 s / 100 cc, and / or a porosity of 25% to 80%, optionally 35% to 55%. When the separator satisfies the ranges specified in at least one of the above characteristics, the separator can have good air permeability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0033] According to a second aspect of the present application, there is provided a method for manufacturing a separator, including the steps of providing 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, and the ratio of the porosity of the first base film to the porosity of the second base film being 1.02≦P1 / P2≦3, and combining the first base film and the second base film to obtain a separator, which can have good breathability and strength and can improve the reliability and cycle characteristics of secondary batteries.

[0034] In any embodiment of the present application, the manufacturing method further includes the steps of providing an adhesive layer paste containing a binder, and applying the adhesive layer paste to a first base film and / or a second base film to form an adhesive layer, and after compounding, the adhesive layer is located between the first base film and the second base film.

[0035] The adhesive layer paste further includes a filler, and optionally the filler includes at least one of inorganic particles, organic particles, and organic-metal frameworks, which allows the separator to have good breathability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0036] According to a third aspect of the present application, there is provided a secondary battery including the separator according to the first aspect of the present application or a separator manufactured by the separator manufacturing method according to the second aspect of the present application. When the secondary battery uses the separator, the reliability and cycle characteristics of the secondary battery can be improved.

[0037] In any embodiment of the present application, the secondary battery further includes a positive electrode sheet and a negative electrode sheet, and the second base film faces the negative electrode sheet. The second base film has low porosity, high strength, and can enhance the performance of being resistant to dendrite penetration, while the first base film has good heat resistance and faces the positive electrode, improving the thermal shock resistance of the separator.

[0038] According to a fourth aspect of the present application, there is provided a power consuming device including the secondary battery of the third aspect of the present application. When the secondary battery of the power consuming device uses the separator shown, the reliability of the power consuming device can be improved.

[0039] The device of the present application includes the secondary battery provided by the present application, and therefore has at least the same advantages as a secondary battery.

[0040] In order to more clearly describe the technical solutions of the present application, the following briefly describes the drawings used in the present application. It should be understood that the drawings shown below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without creative efforts. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is a structural schematic diagram of an embodiment of the separator of the present application. [Figure 2] 1 is a structural schematic diagram of an embodiment of the separator of the present application. [Figure 3] FIG. 1 is a schematic diagram of an embodiment of a secondary battery. [Figure 4] FIG. 4 is an exploded view of FIG. 3. [Figure 5] FIG. 1 is a schematic diagram of one embodiment of a battery module. [Figure 6] FIG. 1 is a schematic diagram of one embodiment of a battery pack. [Figure 7] FIG. 7 is an exploded view of FIG. [Figure 8]FIG. 1 is a schematic diagram of an embodiment of an apparatus that uses a secondary battery as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present application will be further described below with reference to specific embodiments, which are merely for the purpose of illustrating the present application and are not intended to limit the scope of the present application.

[0043] For the sake of brevity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unstated range, and any lower limit may be combined with another lower limit to form an unstated range, and similarly, any upper limit may be combined with any other upper limit to form an unstated range. Furthermore, each point or individual numerical value disclosed alone can serve as a lower or upper limit, and can be combined with any other point or individual numerical value, or with other lower or upper limits, to form an unstated range.

[0044] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by either A being true (or present) and B being false (or not present), or A being false (or not present) and B being true (or present), or both A and B being true (or present).

[0045] In the description of this specification, it should be noted that unless otherwise stated, "more than" and "less than" are inclusive, and the meaning of "plurality" in "one or more" is two and more than two.

[0046] Unless otherwise specified, the terms used herein have the same meaning as 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, they can be measured according to the methods shown in the examples of the present application).

[0047] secondary battery A secondary battery is a battery that can be continuously used by activating the active material through charging after discharging.

[0048] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charge and discharge process, active ions are inserted and removed between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets to separate them. The electrolyte conducts ions between the positive and negative electrode sheets.

[0049] [Separator] 1, an embodiment of the present application provides a separator 10, which includes a first base film 11 and a second base film 12. The melting point of the second base film 12 is lower than the melting point of the first base film 11, and when the porosity of the first base film 11 is P1 and the porosity of the second base film 12 is P2, the relationship is 1.02≦P1 / P2≦3.

[0050] While not wishing to be limited by any theory, the inventors, after extensive research, believed that their initial understanding that combining two types of base films with good porosity ultimately improves the breathability of the separator and aids in ion transport was accurate. However, current experimental results show that the effect is unclear, and that good breathability can lead to insufficient strength and the possibility of breakage, which can cause a short circuit between the positive and negative electrodes and pose a safety risk.

[0051] When the porosity ratio of the first base film to the second base film is 1.02≦P1 / P2≦3, the breathability and strength of the first base film and the second base film are better balanced. A base film with a high porosity has good breathability, and therefore the first base film with a high porosity exhibits its excellent breathability. A base film with a low porosity has good strength and is less susceptible to dendrites, and therefore the second base film with a low porosity exhibits its excellent strength. This allows the separator to have good breathability and strength, improving the reliability and cycle characteristics of the secondary battery.

[0052] In any embodiment of the present application, 1.02≦P1 / P2≦3, and optionally 1.05≦P1 / P2≦2.5. P1 / P2 may be 1.02, 1.05, 1.13, 1.2, 1.3, 1.4, 1.5, 2.0, 2.3, 2.55, 3.0, or a range consisting of any two of the above values. For example, it may be 1.02 to 1.13, 1.05 to 1.2, 1.2 to 2.5, 1.5 to 2.0, 1.2 to 1.5, 2.0 to 2.5, 2.5 to 3.0, or 1.5 to 2.8. In this embodiment, the breathability and strength of the first base film and the second base film are better balanced, thereby providing the separator with good breathability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0053] In any embodiment of the present application, the porosity of the first base film is 30% to 90%, optionally 35% to 85%, and / or the porosity of the second base film is 30% to 70%, optionally 35% to 45%. For example, the porosity of the first base film may be 30%, 35%, 38%, 40%, 50%, 55%, 60%, 70%, 75%, 80%, 85%, 90%, or a range consisting of any two of the above values. For example, the porosity of the first base film may further be 30% to 40%, 35% to 45%, 50% to 70%, 75% to 80%, 80% to 90%, etc. The porosity of the second base film may be 30%, 35%, 40%, 45%, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values. For example, it may be 30% to 40%, 45%, 50% to 60%, 65% to 70%, or the like.

[0054] When the porosity of the first base film is 30% to 90% and / or the porosity of the second base film is 30% to 70%, the breathability and strength of the first and second base films are better balanced. A base film with a high porosity has good breathability and exhibits excellent breathability, while a base film with a low porosity has good strength and exhibits good strength and is less likely to be penetrated by dendrites. This allows the separator to have good breathability and strength, improving the reliability and cycle characteristics of the secondary battery.

[0055] According to some embodiments, porosity has a meaning known in the art and can be measured using known devices and methods. For example, it can be measured with reference to GB / T 24586-2009. The measurement method is as follows: A separator or substrate is punched into a small circular sheet sample with a diameter of 14 mm, the thickness is measured, and the apparent volume V1 of the separator or substrate is calculated according to the cylinder volume calculation formula. Referring to GB / T 24586-2009, an inert gas such as helium or nitrogen is used as a medium, and the actual volume V2 of the separator or substrate is measured using a true density measurement device by the gas displacement method. The porosity of the separator or substrate = (V1 - V2) / V1 × 100%. The measurement device may be an AccuPyc II 1340 fully automatic true density measurement device from Micromeritics, USA.

[0056] In any embodiment of the present application, the ratio of the average pore size of the first base film to the average pore size of the second base film is 0.05 to 80, and optionally 0.2 to 40. The ratio of the average pore size of the first base film to the average pore size of the second base film may be 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 6.0, 9.0, 13.0, 18.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0, 70.0, 80.0, etc., or may be a range consisting of any two of the above values. For example, it may further be 0.05 to 0.2, 0.2 to 1, 1 to 5, 5 to 8, 8 to 10, 10 to 14, 15 to 20, 20 to 30, 30 to 40, 40 to 60, 60 to 80, etc.

[0057] The smaller the average pore size, the smaller the space occupied by the average pore area, the larger the space occupied by the fiber threads of the base film, and the stronger the base film. Conversely, the smaller the space occupied by the fiber threads of the base film, the larger the average pore area of ​​the separator and the better the breathability. By setting the average pore size ratio within the above range, the separator can achieve both breathability and strength, improving the reliability and cycle characteristics of the separator.

[0058] In any embodiment of the present application, the average pore size of the first base film is larger than the average pore size of the second base film.

[0059] In any embodiment of the present application, the average pore size of the first base film is 100 nm to 4000 nm, and optionally 100 nm to 2000 nm. For example, the average pore size of the pore structure of the first base film may be 100 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 255 nm, 285 nm, 300 nm, 325 nm, 350 nm, 400 nm, 500 nm, 750 nm, 855 nm, 955 nm, 1000 nm, 1250 nm, 1350 nm, 1500 nm, 1750 nm, 1850 nm, 2000 nm, 2300 nm, 2500 nm, 2700 nm, 3000 nm, 3300 nm, 3600 nm, 4000 nm, or a range consisting of any two of the above values. For example, it may further be 100 nm to 150 nm, 100 nm to 400 nm, 120 nm to 200 nm, 200 nm to 250 nm, 235 nm to 285 nm, 300 nm to 350 nm, 100 nm to 2000 nm, 325 nm to 2000 nm, 350 nm to 1850 nm, 400 nm to 1750 nm, 500 nm to 1500 nm, 750 nm to 1350 nm, 855 nm to 1250 nm, 2000 nm to 3000 nm, 3000 nm to 4000 nm, 2500 nm to 3500 nm, 1000 to 3000 nm, 1000 to 4000 nm, etc.

[0060] The average pore size of the second base film is 50 nm to 2000 nm, and optionally 50 nm to 500 nm. For example, the average pore size of the pore structure of the second base film may be 50 nm, 75 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 225 nm, 255 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 1000 nm, 1250 nm, 1400 nm, 1500 nm, 1650 nm, 1800 nm, 1900 nm, or 2000 nm, or may be a range consisting of any two of the above values. For example, it may be 50 nm to 100 nm, 100 nm to 150 nm, 150 nm to 200 nm, 200 nm to 255 nm, 250 nm to 300 nm, 100 nm to 300 nm, 50 nm to 500 nm, 400 nm to 1900 nm, 500 nm to 1800 nm, 600 nm to 1650 nm, 700 nm to 1500 nm, 800 nm to 1400 nm, 1000 nm to 1250 nm, 1000 nm to 1900 nm, 1000 nm to 2000 nm, etc. The porosity requirements of the two base films can be satisfactorily met, thereby allowing the separator to have good breathability and strength, and improving the reliability and cycle characteristics of the secondary battery.

[0061] According to some embodiments, the average pore size has a meaning known in the art and can be measured using methods known in the art, for example, using a mercury porosimeter and with reference to GB / T 21650.1-2008.

[0062] In any embodiment of the present application, the tensile strength in the transverse direction of the first base film is smaller than the tensile strength in the longitudinal direction of the first base film, which increases the ductility of the separator in the transverse direction, making it more resistant to punctures by dendrites and suppressing dendrite growth.

[0063] In any embodiment of the present application, the ratio of the tensile strength in the transverse direction of the first base film to the tensile strength in the longitudinal direction of the first base film is 0.2 to 0.8, and optionally 0.3 to 0.6. The ratio of the tensile strength in the transverse direction of the first base film to the tensile strength in the longitudinal direction of the first base film may be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.53, 0.62, 0.70, 0.75, 0.8, etc., or may be a range consisting of any two of the above values. For example, it may be 0.2 to 0.3, 0.28 to 0.31, 0.38 to 0.42, 0.32 to 0.36, 0.42 to 0.51, 0.52 to 0.55, 0.55 to 0.61, 0.62 to 0.7, 0.7 to 0.75, 0.75 to 0.8, etc.

[0064] By setting it in this way, the porosity of the first base film and the second base film can be balanced to satisfy 1.02≦P1 / P2≦3, which ensures the breathability of the separator while increasing the strength of the separator, improving its ability to withstand stress deformation, further improving the reliability of the battery, and extending the cycle life.

[0065] In any embodiment of the present application, the tensile strength in the transverse direction of the second base film is smaller than the tensile strength in the longitudinal direction of the second base film, which increases the ductility of the separator in the transverse direction, making it more resistant to punctures by dendrites and the like, while simultaneously suppressing dendrite growth.

[0066] In any embodiment of the present application, the ratio of the tensile strength in the transverse direction of the second base film to the tensile strength in the longitudinal direction of the second base film is 0.45 to 0.9, and optionally 0.6 to 0.8. The ratio of the tensile strength in the transverse direction of the second base film to the tensile strength in the longitudinal direction of the second base film may be 0.45, 0.5, 0.53, 0.62, 0.70, 0.75, 0.8, 0.85, 0.90, etc., or may be a range consisting of any two of the above values. For example, it may be 0.45 to 0.49, 0.49 to 0.53, 0.54 to 0.59, 0.60 to 0.64, 0.66 to 0.70, 0.72 to 0.75, 0.76 to 0.81, 0.82 to 0.9, etc. By setting it in this way, the porosity of the first base film and the second base film can be balanced to satisfy 1.02≦P1 / P2≦3, which ensures the breathability of the separator while increasing the strength of the separator, improving its ability to withstand stress deformation, further improving the reliability of the battery, and extending the cycle life.

[0067] In any embodiment of the present application, the lateral tensile strength of the first base film is lower than the lateral tensile strength of the second base film, which allows the porosities of the first and second base films to be balanced, satisfying 1.02≦P1 / P2≦3, thereby increasing the separator's strength while ensuring its breathability, improving its ability to withstand stress deformation, and further improving the reliability of the battery and extending its cycle life.

[0068] In any embodiment of the present application, the longitudinal tensile strength of the first base film is lower than the longitudinal tensile strength of the second base film, which allows the porosities of the first and second base films to be balanced to satisfy 1.02≦P1 / P2≦3, thereby increasing the separator's strength while ensuring its breathability, improving its ability to withstand stress deformation, and further improving the reliability of the battery and extending its cycle life.

[0069] In any embodiment of the present application, the first base film has a transverse tensile strength of 150 to 900 kgf / cm 2 and selectively 200 to 750 kgf / cm 2 For example, 150Kgf / cm 2 , 200Kgf / cm 2 , 280Kgf / cm 2 , 360Kgf / cm 2 , 420Kgf / cm 2 , 550Kgf / cm 2 , 650Kgf / cm 2 , 680Kgf / cm 2 , 750Kgf / cm 2 Or it may be a range consisting of any two of the above values. For example, it may be 150 to 200 kgf / cm 2 , 200~280Kgf / cm 2 , 280~350Kgf / cm 2 , 360~420Kgf / cm 2 , 450~550Kgf / cm 2 , 580~680Kgf / cm 2 , 650~680Kgf / cm 2 , 650~750Kgf / cm 2 etc. may also be used.

[0070] In any embodiment of the present application, the first base film has a longitudinal tensile strength of 800 to 2500 kgf / cm 2 and selectively 1100~1900Kgf / cm 2 For example, 800Kgf / cm 2 , 880Kgf / cm 2 , 960Kgf / cm 2 , 1080Kgf / cm 2 , 1150Kgf / cm 2 , 1320Kgf / cm 2 , 1550Kgf / cm 2 , 1680Kgf / cm 2 , 1750Kgf / cm 2 , 1850Kgf / cm 2 , 1980Kgf / cm 2 , 2050Kgf / cm2 , 2280Kgf / cm 2 , 2500Kgf / cm 2 Or, it may be a range consisting of any two of the above values. For example, it may be 800 to 880 kgf / cm 2 , 880~960Kgf / cm 2 , 960~1080Kgf / cm 2 , 1080~1150Kgf / cm 2 , 1150~1320Kgf / cm 2 , 1320~1550Kgf / cm 2 , 1550~1680Kgf / cm 2 , 1750~1980Kgf / cm 2 , 1950~2280Kgf / cm 2 , 2250~2500Kgf / cm 2 etc. may also be used.

[0071] In any embodiment of the present application, the second base film has a transverse tensile strength of 1500 to 3600 kgf / cm 2 and selectively 1800~3300Kgf / cm 2 For example, 1500Kgf / cm 2 , 1680Kgf / cm 2 , 1860Kgf / cm 2 , 1980Kgf / cm 2 , 2150Kgf / cm 2 , 2320Kgf / cm 2 , 2550Kgf / cm 2 , 2680Kgf / cm 2 , 2750Kgf / cm 2 , 2850Kgf / cm 2 , 2980Kgf / cm 2 , 3050Kgf / cm 2 , 3280Kgf / cm 2 , 3300Kgf / cm 2 Or it may be a range consisting of any two of the above values. For example, it may be 1500 to 1880 kgf / cm 2 , 1880~1960Kgf / cm 2 , 1960~2080Kgf / cm2 , 2080~2150Kgf / cm 2 , 2150~2320Kgf / cm 2 , 2320~2550Kgf / cm 2 , 2550~2680Kgf / cm 2 , 2750~2980Kgf / cm 2 , 2950~3280Kgf / cm 2 , 3250~3300Kgf / cm 2 etc. may also be used.

[0072] In any embodiment of the present application, the second base film has a longitudinal tensile strength of 1900 to 4000 kgf / cm 2 and selectively 2000~3500Kgf / cm 2 For example, 1900Kgf / cm 2 , 1980Kgf / cm 2 , 2060Kgf / cm 2 , 2180Kgf / cm 2 , 2250Kgf / cm 2 , 2320Kgf / cm 2 , 2550Kgf / cm 2 , 2680Kgf / cm 2 , 2750Kgf / cm 2 , 2850Kgf / cm 2 , 2980Kgf / cm 2 , 3050Kgf / cm 2 , 3280Kgf / cm 2 , 3300Kgf / cm 2 , 3550Kgf / cm 2 , 3780Kgf / cm 2 , 4000Kgf / cm 2 Or, it may be a range consisting of any two of the above values. For example, it may be 1900 to 1980 kgf / cm 2 , 1980~2060Kgf / cm 2 , 1960~2080Kgf / cm 2 , 2080~2150Kgf / cm 2 , 2150~2320Kgf / cm 2 , 2320~2550Kgf / cm 2, 2550~2680Kgf / cm 2 , 2750~2980Kgf / cm 2 , 2950~3280Kgf / cm 2 , 3250~3300Kgf / cm 2 , 3150~3380Kgf / cm 2 , 3450~3680Kgf / cm 2 , 3850~4000Kgf / cm 2 By setting the ratios in this manner, the porosities of the first and second base films can be balanced to satisfy 1.02≦P1 / P2≦3, and the separator can be made stronger while ensuring the breathability of the separator, improving its ability to withstand stress deformation, further improving the reliability of the battery, and extending the cycle life.

[0073] The transverse tensile strength (MD) and longitudinal tensile strength (TD) of the separator or base film are both defined as known in the art and can be measured using methods known in the art, for example, by referring to standard GB / T 36363-2018.

[0074] In any embodiment of the present application, the thickness of the first base film is 2 μm to 12 μm, and optionally 3 μm to 6 μm. For example, it may be 2 μm, 2.5 μm, 2.6 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, or a range consisting of any two of the above values. For example, it may further be 1 μm to 2.5 μm, 2 μm to 2.6 μm, 3 μm to 6 μm, 5 μm to 9 μm, 10 μm to 12 μm, etc.

[0075] In some embodiments, the thickness of the second base film is 2 μm to 12 μm, and optionally 3 μm to 5 μm. For example, it may be 2 μm, 3 μm, 3.5 μm, 5 μm, 9 μm, 10 μm, 12 μm, or a range consisting of any two of the above values. For example, it may further be 2 μm to 3.5 μm, 3 μm to 5 μm, 5 μm to 6 μm, 9 μm to 12 μm, etc.

[0076] When the thickness of the first base film and the second base film is 2 μm to 12 μm, the breathability and strength of the base film can be balanced, and the separator thickness can more easily meet the energy density usage requirements of the battery, provided that the breathability and strength of the separator meet the requirements.

[0077] According to some embodiments, thickness has a meaning known in the art and can be measured using methods known in the art, for example, by taking six sets of parallel samples and measuring the thickness of each set of samples at different positions using a thickness measuring micrometer, measuring at least 20 positions for each set of samples, and determining the average thickness of the six sets of samples as the thickness of the base film.

[0078] 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 3.0 or less, and optionally 1.1 or more and 2.5 or less. For example, the ratio of the melting point of the first base film to the melting point of the second base film in degrees Celsius may be 1.05, 1.1, 1.2, 1.3, 1.35, 1.5, 1.6, 1.75, 1.95, 2.0, 2.2, 2.5, 2.6, 2.7, 2.9, 3.0, or a range consisting of any two of the above values. For example, it may further be 1.05 to 1.2, 1.2 to 1.4, 1.35 to 1.5, 1.5 to 1.65, 1.6 to 1.75, 1.1 to 2.0, 1.1 to 2.5, 1.95 to 2.1, 2.2 to 2.5, 2.5 to 3.0, etc. In some embodiments, the ratio of the melting point in degrees Celsius of the first base film to the melting point in degrees Celsius of the second base film may be between 1.1 and 2.5.

[0079] When 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 3.0 or less, the first base film with a high melting point mainly contributes to its heat resistance; in other words, a base film with a high porosity has a high melting point and good heat resistance. The second base film with a low porosity mainly contributes to its strength; therefore, by combining the two, the separator can have both high strength and heat resistance. When the ratio of the melting point of the first base film to the melting point of the second base film is selectively 1.1 or more and 2.5 or less, the strength and heat resistance of the separator can be further improved.

[0080] In any embodiment of the present application, the melting point of the first base film may be 160°C to 360°C, for example, 160°C, 165°C, 170°C, 180°C, 196°C, 200°C, 235°C, 245°C, 260°C, 280°C, 290°C, 300°C, 315°C, 320°C, 330°C, 340°C, 350°C, 360°C, or a range consisting of any two of the above values. For example, it may further be 160°C to 170°C, 180°C to 235°C, 180°C to 350°C, 225°C to 280°C, 290°C to 315°C, 300°C to 360°C, etc. In some embodiments, the melting point of the first base film is optionally 180°C to 350°C. The melting point of the second base film may be 120°C to 280°C, for example, 120°C, 130°C, 135°C, 140°C, 150°C, 155°C, 180°C, 200°C, 230°C, 265°C, 280°C, or a range consisting of any two of the above values. For example, it may further be 120°C to 135°C, 130°C to 150°C, 135°C to 150°C, 145°C to 155°C, 150°C to 250°C, 250°C to 280°C, 300°C to 265°C, 120°C to 280°C, etc. In some embodiments, the melting point of the second base film is optionally 130°C to 265°C. Optionally, it is 130°C to 265°C.

[0081] When the melting point of the first base film is 160°C to 360°C and / or the melting point of the second base film is 120°C to 280°C, the melting point of the first base film is higher than that of the second base film, and the first base film with a higher melting point mainly contributes to the heat resistance, while the second base film with higher strength mainly contributes to the strength. Therefore, by combining the two, the separator can have both high strength and heat resistance. When the melting point of the first base film is selectively 180°C to 350°C and / or the melting point of the second base film is selectively 130°C to 265°C, the strength and heat resistance of the separator can be further improved.

[0082] According to some embodiments, the melting point has a meaning known in the art and can be measured using methods known in the art. For example, it can be measured using differential scanning calorimetry. For specific examples, see standard GB / T 19466.3-2004. For example, it can be measured according to the following method: 4-6 mg of a sample to be measured is placed in the sample box 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 value of the curve is the melting point of the sample.

[0083] As a result of extensive research, the present inventors have discovered 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:

[0084] The materials of the first and second base films are not particularly limited, and any known base film having good chemical stability and strength stability can be selected. The materials of the first and second base films of the separator may be the same or different.

[0085] 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, polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, polyvinylidene fluoride and its derivatives, and polyethylene terephthalate and its derivatives. Derivatives generally refer to products derived by replacing hydrogen atoms or atomic groups in a compound with other atoms or atomic groups. When the first base film and the second base film are each made of at least one of the above materials, maintaining the porosity of the separator within an appropriate range can improve the breathability and strength of the separator when combined, thereby improving the reliability and cycle characteristics of the secondary battery.

[0086] Referring to Figure 1, an embodiment of the present application provides a separator 10, which includes a first base film 11 and a second base film 12. An adhesive layer 13 containing a binder is further disposed between the first base film 11 and the second base film 12. Optionally, the adhesive layer contains a binder and a filler. The adhesive layer disposed between the first and second base films not only compensates for process shortcomings in the hot-press compounding process of the base films, but also further improves the physical properties of the separator (e.g., tensile strength, puncture resistance, heat resistance, etc.), thereby improving the reliability of secondary batteries. The filler is disposed between the first and second base films, thereby avoiding the problem of powder shedding.

[0087] The first and second base films can be directly combined by hot pressing, but if the temperature is too high during the hot pressing process, the porosity will decrease and the breathability will decrease, 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. Preferably, the hot pressing temperature is 20°C to 50°C.

[0088] In some embodiments of the present application, the binder may include one or more of polyacrylic acid ester, 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 disposed between the first base film and the second base film and the binder in the adhesive layer includes the above-mentioned components, the separator can have high strength, heat resistance, and breathability. This can improve the reliability and cycle characteristics of secondary batteries.

[0089] In any embodiment of the present application, the filler comprises at least one of inorganic particles, organic particles, and metal-organic frameworks.

[0090] Optionally, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of generating electrical and chemical reactions.

[0091] Alternatively, the inorganic particles having a dielectric constant of 5 or more may be boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, magnesium lithium silicate, magnesium sodium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 <m<1、0<n<1)、Pb(Mg3Nb 2 / 3 The inorganic particles may include at least one of )O3-PbTiO3 (abbreviated as PMN-PT) and modified inorganic particles. Optionally, the modification of each inorganic particle may be chemical and / or physical. The chemical modification may include coupling agent modification (e.g., using a silane coupling agent, titanate coupling agent, etc.), surfactant modification, graft polymer modification, etc. The physical modification may include mechanical dispersion, ultrasonic dispersion, high-energy treatment, etc. The modification treatment may reduce the aggregation of inorganic particles, thereby resulting in a more stable and uniform adhesive layer. Furthermore, modifying the inorganic particles by selecting a coupling agent, surfactant, or polymer with a specific functional group can improve the wetting and retention properties of the adhesive layer with respect to the electrolyte, further contributing to improving the adhesion of the adhesive layer to the first and second base films.

[0092] 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 series 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 series glass Li x7 Si y7 S z3 and P2S5 series glass Li x8 P y8 S z4 At least one of them may be included, and 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.

[0093] Optionally, the inorganic particles capable of selectively causing the electrical and chemical reactions may include 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.

[0094] Optionally, the organic particles may include one or more of polycarbonate, polythiophene, 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), silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, copolymer of butyl acrylate and ethyl methacrylate (e.g., crosslinked polymer of butyl acrylate and ethyl methacrylate).

[0095] Optionally, the metal-organic framework may include one or more of a nitrogen-containing heterocyclic ligand framework, an organic carboxylic acid-based ligand framework, and a nitrogen-oxygen mixed ligand framework.

[0096] In some embodiments, the content of the binder may be 10% or more, and optionally 10% to 30%, based on the total weight of the adhesive layer.

[0097] In some embodiments, the content of the filler may be 90% or less, optionally 40%-90%, or 60%-80% based on the total weight of the adhesive layer.

[0098] In some embodiments, the adhesive layer may further include a dispersant, such as carboxymethyl cellulose, which can adjust the viscosity of the adhesive layer paste and improve the quality and uniformity of the adhesive layer.

[0099] 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.

[0100] When an adhesive layer is disposed between the first base film and the second base film, and the filler in the adhesive layer includes at least one of the inorganic particles, organic particles, and organic-metallic structures, the filler in the adhesive layer can further improve the heat resistance and strength of the separator, thereby improving the reliability of the secondary battery.

[0101] In any embodiment of the present application, the thickness of the adhesive layer is 0.3 μm or more, and optionally 0.5 to 2 μm. When the thickness of the adhesive layer is within the specified range, the reliability of the secondary battery can be improved.

[0102] In any embodiment of the present application, the separator has an air permeability of 200 s / 100 cc to 400 s / 100 cc, optionally 250 s / 100 cc to 320 s / 100 cc, and / or a porosity of 25% to 80%. When the separator satisfies the ranges indicated in at least one of the above characteristics, the separator can have good air permeability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0103] In one embodiment of the present application, there is provided a method for manufacturing a separator, including the steps of: providing 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, and the ratio of the porosity of the first base film to the porosity of the second base film being 1.02≦P1 / P2≦3; and combining the first base film and the second base film to obtain a separator, which can have good breathability and strength and can improve the reliability and cycle characteristics of a secondary battery.

[0104] In any embodiment of the present application, the manufacturing method further includes the steps of providing an adhesive layer paste containing a binder, and applying the adhesive layer paste to a first base film and / or a second base film to form an adhesive layer, and after compounding, the adhesive layer is located between the first base film and the second base film.

[0105] The adhesive layer paste further includes a filler, and optionally the filler includes at least one of inorganic particles, organic particles, and organic-metal frameworks, which allows the separator to have good breathability and strength, thereby improving the reliability and cycle characteristics of the secondary battery.

[0106] In any embodiment of the present application, an adhesive layer paste including a binder is prepared, and the adhesive layer paste is coated on the first base film and / or the second base film and then further combined. Optionally, the adhesive layer paste includes a binder and a filler. When the adhesive layer paste is coated on the first base film and / or the second base film and then further combined, and the adhesive layer paste includes the above components, the reliability of the secondary battery can be improved.

[0107] Unless otherwise specified, each of the raw materials used in the separator (for example, the first base film, the second base film, the binder, the filler, etc.) can be obtained commercially.

[0108] In any embodiment of the present application, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator provided in any of the above embodiments of the present application or a separator manufactured by the separator manufacturing method of any of the above embodiments, the separator being disposed between the positive electrode sheet and the negative electrode sheet. When the secondary battery uses the separator shown, the reliability and cycle characteristics of the secondary battery can be improved.

[0109] In any embodiment of the present application, the second base film of the separator faces the negative electrode sheet, the first base film has good heat resistance and faces the positive electrode, and the second base film has high strength and faces the negative electrode, which can increase the effect of preventing penetration by lithium dendrites and improve the reliability of the secondary battery.

[0110] In any of the embodiments of the present application, a power consuming device includes the secondary battery of any of the above embodiments of the present application. When the secondary battery of the power consuming device uses the separator shown, the reliability of the power consuming device can be improved.

[0111] The device of the present application includes the secondary battery provided by the present application, and therefore has at least the same advantages as a secondary battery.

[0112] [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 including a positive electrode active material.

[0113] The positive electrode current collector can be a conventional metal foil or a composite current collector (which may be a composite current collector formed by placing a metal material on a polymer substrate). For example, the positive electrode current collector can be aluminum foil.

[0114] The specific type of the positive electrode active material is not particularly limited, and active materials known in the art for use in positive electrodes of secondary batteries may be used, and those skilled in the art may select the material according to their actual needs.

[0115] For example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and modified compounds thereof. All of these materials are commercially available.

[0116] The modifying compounds for each of the above materials can perform doping modification and / or surface coating modification on the material.

[0117] The positive electrode film layer generally further optionally contains a binder, a conductive agent, and other optional auxiliary agents.

[0118] By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, conductive carbon black (Super P, SP), graphene, and carbon nanofibers.

[0119] By way of example, the binder 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).

[0120] [Negative electrode sheet] In a secondary battery, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector and including a negative electrode active material.

[0121] The negative electrode current collector may be a conventional metal foil or a composite current collector (e.g., a composite current collector formed by placing a metal material on a polymer substrate). For example, the negative electrode current collector may be a copper foil.

[0122] The specific type of the negative electrode active material is not particularly limited, and active materials known in the art for use in negative electrodes of secondary batteries can be used, and 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, silicon-based materials, and tin-based materials. The silicon-based material may be selected from one or more of silicon elemental, silicon oxide (e.g., silicon oxide), silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may be selected from one or more of tin elemental, tin oxide, and tin alloy. All of these materials are commercially available.

[0123] In some embodiments, the negative electrode active material may include a silicon-based material to further improve the energy density of the battery.

[0124] The negative electrode film layer generally further optionally contains a binder, a conductive agent, and other optional auxiliary agents.

[0125] By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] By way of example, the binder may include 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).

[0127] For example, other optional auxiliary agents may be thickening and dispersing agents (such as sodium carboxymethylcellulose (CMC-Na)) and PTC thermistor materials.

[0128] [Electrolyte] The secondary battery may include an electrolyte, which serves to conduct ions between the positive electrode and the negative electrode, and may include an electrolyte salt and a solvent.

[0129] 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 bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), lithium tetrafluorooxalatophosphate (LiTFOP).

[0130] Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (Methyl Propionate (MP), Ethyl Propanoate (EP), n-Propyl Propionate (PP), Methyl Butyrate (MB), Ethyl Butyrate (EB), 1,4-Butyrolactone (GBL), Sulfolane (Tetramethylene Sulfone (SF), Methyl Sulfone (MSM), Methyl Ethyl Sulfone (EMS), and Diethyl Sulfone (ESE).

[0131] 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 / or an additive that can improve specific battery performance, such as an additive that improves the overcharge characteristics of the battery, an additive that improves the high-temperature characteristics of the battery, or an additive that improves the low-temperature characteristics of the battery.

[0132] In some embodiments, the secondary battery may be a lithium ion secondary battery. In any embodiment of the present application, the second base film of the separator faces the negative electrode sheet.

[0133] When the porosity of the first base film is greater than that of the second base film, the first and second base films can effectively complement each other in terms of breathability and strength. A base film with a high porosity has good breathability, so the first base film with a high porosity exhibits its excellent breathability, while a base film with a low porosity has good strength and is less likely to be penetrated by lithium dendrites. This allows the separator to have good breathability and strength, improving the reliability of the secondary battery.

[0134] The embodiment of the present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. Figure 3 shows a secondary battery 5 having a rectangular structure as an example.

[0135] In some embodiments, the secondary battery may include a housing material that encapsulates the positive electrode sheet, the negative electrode sheet, and the electrolyte, with the second base film of the separator facing the negative electrode sheet.

[0136] In some embodiments, the exterior material of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior material of the secondary battery may be a soft pack such as a pouch-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).

[0137] 4, in some embodiments, the exterior material 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 a storage cavity surrounded by the bottom plate and the side plate is formed. The housing 51 has an opening communicating with the storage cavity, and the cover plate 53 may cover the opening to seal the storage cavity.

[0138] The method for manufacturing the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed from a positive electrode sheet, a separator, and a negative electrode sheet through a winding process and / or a lamination process. The electrode assembly can then be placed in a housing, dried, and then an electrolyte can be injected. A battery cell can then be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. Multiple battery cells can be further connected in series, parallel, or series-parallel to form a battery module. Multiple battery modules can be further connected in series, parallel, or series-parallel to form a battery pack. In some embodiments, multiple battery cells can be further connected directly to form a battery pack.

[0139] FIG. 5 shows an example of a battery module 4. Referring to FIG. 5, in the battery module 4, a plurality of secondary batteries 5 can be arranged in order along the length of the battery module 4. Of course, any other arrangement method may be used. The plurality of secondary batteries 5 can also be fixed by fasteners.

[0140] The battery module 4 may further include an outer case having a storage space for storing a plurality of secondary batteries 5.

[0141] In some embodiments, the battery modules can 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.

[0142] 6 and 7 show an example of a battery pack 1. Referring to FIGS. 6 and 7, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 can be fitted over the lower housing 3 to form a sealed space for accommodating the plurality of battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0143] [Device] The present application further provides a power consumption device including the secondary battery of the present application. The battery cell, battery module, or battery pack may be used as a power source for the device or as an energy storage element 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), a train, a ship, a satellite, or an energy storage system.

[0144] The device can select a battery cell, a battery module, or a battery pack depending on its usage conditions.

[0145] 8 shows an example of a power consuming device. The power consuming device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements for the secondary battery of the power consuming device, a battery pack or a battery module may be used.

[0146] Another example of a power consuming device may be a mobile phone, a tablet computer, or a laptop computer, which generally require a light and thin design and may use a battery cell as a power source.

[0147] The device of the present application includes the secondary battery provided by the present application, and therefore has at least the same advantages as a secondary battery.

[0148] The beneficial effects of the present invention will be further explained below with reference to examples.

[0149] In order to clarify the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application, the present application will be described in more detail below with reference to the embodiments and drawings. It should be noted that the described embodiments are only some of the embodiments of the present application, and are not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative and does not limit the present application and its applications in any way. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without requiring creative efforts fall within the scope of protection of the present application.

[0150] 1. Separator manufacturing Separator 1: (1) Provide a first base film and a second base film. The material of the first base film includes polypropylene (PP), and the material of the second base film includes polyethylene (PE). Control the porosity ratio of the first base film to the second base film within a target range.

[0151] (2) Preparation of adhesive layer paste: Boehmite, polyacrylic acid ester, and carboxymethyl cellulose are uniformly mixed in a mass ratio of 4:1:1 in an appropriate amount of deionized water as a solvent to prepare an adhesive layer paste.

[0152] (3) The adhesive layer paste described in step (2) is compounded on at least one side of the first base film and the second base film described in step (1) to form an adhesive layer.

[0153] The manufacturing method of the separators of Examples 2 to 11 was the same as that of the separator of Example 1, except that the material or porosity of the base film was adjusted.

[0154] Separators 1 to 11 further satisfy the following: The tensile strength in the transverse direction of the first base film is smaller than the tensile strength in the longitudinal direction of the first base film, and the ratio of the tensile strength in the transverse direction of the first base film to the tensile strength in the longitudinal direction of the first base film is 0.2 to 0.8. The tensile strength in the transverse direction of the second base film is smaller than the tensile strength in the longitudinal direction of the second base film, and the ratio of the tensile strength in the transverse direction of the second base film to the tensile strength in the longitudinal direction of the second base film is 0.45 to 0.9. The tensile strength in the transverse direction of the first base film is smaller than the tensile strength in the transverse direction of the second base film, and the tensile strength in the longitudinal direction of the first base film is smaller than the tensile strength in the longitudinal direction of the second base film. The tensile strength in the transverse direction of the first base film in Example 1 was 600 Kgf / cm 2 and the longitudinal tensile strength of the first base film is 1250 Kgf / cm 2 and the transverse tensile strength of the second base film is 1350 Kgf / cm 2 The tensile strength of the second base film in the machine direction is 1700 Kgf / cm 2 The separator's transverse tensile strength is 1650 Kgf / cm 2 The longitudinal tensile strength of the separator is 2700 Kgf / cm 2 The transverse tensile strength of the first base film in Example 6 was 550 Kgf / cm 2and the longitudinal tensile strength of the first base film is 700 Kgf / cm 2 and the transverse tensile strength of the second base film is 650 Kgf / cm 2 and the tensile strength of the second base film in the machine direction is 1300 Kgf / cm 2 The separator's transverse tensile strength is 800 Kgf / cm 2 The longitudinal tensile strength of the separator is 2000 Kgf / cm 2 The transverse tensile strength of the first base film in Example 9 was 550 kgf / cm 2 and the longitudinal tensile strength of the first base film is 700 Kgf / cm 2 and the transverse tensile strength of the second base film is 1450 Kgf / cm 2 The tensile strength of the second base film in the machine direction is 1850 Kgf / cm 2 The separator's transverse tensile strength is 1500 Kgf / cm 2 The longitudinal tensile strength of the separator is 2500 Kgf / cm 2 is.

[0155] The separator manufactured by the above method was subjected to relevant performance tests, and the specific results are shown in Table 1.

[0156] 2. Battery manufacturing Example 1 1. Manufacturing of positive electrode sheets Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (SuperP), and binder polyvinylidene fluoride (PVDF) were mixed uniformly 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 paste. This paste was then applied to a positive electrode current collector aluminum foil, followed by drying, cold pressing, slitting, and cutting to obtain a positive electrode sheet. The areal density of the positive electrode was 0.207 mg / mm 2 and the green density is 3.5 g / cm 3 is.

[0157] 2. Manufacturing of negative electrode sheets The negative electrode active material, artificial graphite, the conductive agent, carbon black (SuperP), the binder, styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na) were mixed uniformly 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 paste, which was then dried, cold pressed, slit, and cut to obtain a negative electrode sheet. The areal density of the negative electrode was 0.126 mg / mm 2 and the green density is 1.7 g / cm 3 is.

[0158] 3. Separator The separator used is the separator 1 manufactured as described above.

[0159] 4. Electrolyte production Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 30:70 to obtain an organic solvent, and the thoroughly dried electrolyte salt LiPF6 is dissolved in the mixed solvent to obtain an electrolyte solution with a concentration of 1.0 mol / L.

[0160] 5. Secondary battery manufacturing The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, with the separator between them to separate them, and then wound up to obtain an electrode assembly. The electrode assembly is placed in a housing, and the above-prepared electrolyte is injected into the secondary battery after drying. The secondary battery is then vacuum sealed, left to stand, chemically formed, and shaped to obtain the secondary battery.

[0161] The secondary batteries of Examples 2 to 11 and Comparative Examples 1 to 3 were manufactured using the same method as the secondary battery of Example 1, except that different separators were used (Separators 1 to 11 were used in Examples 1 to 11, and Separators 11 and 14 were used in Comparative Examples 1 to 3), as specifically shown in Table 1.

[0162] Unless otherwise specified, each of the raw materials used in the separator (for example, the first base film, the second base film, the binder, the filler, etc.) can be obtained commercially.

[0163] 3. Battery performance test 1. 250℃ heat shrinkage test The method for testing the heat shrinkage rate of the separator is as follows.

[0164] (1) Sample preparation: Punch out samples 50 mm wide and 100 mm long using a press. Five to ten parallel samples are used. Place the sample on a glass plate and secure all four edges with paper clips. (2) Test: Set up a blast oven and set the temperature to the specified temperature, for example, 250°C. After the temperature reaches the set temperature and stabilizes for 60 minutes, place the glass plate in the oven and time it for 1 hour. Measure the length of the separator and mark each value as a. (3) Calculation: The shrinkage rate in the longitudinal direction is A = (100 - a) / 100 * 100%, record the value of A, and take the average of the five measurements.

[0165] 2. Battery cycle characteristic test Measurement method for the total battery capacity retention rate at 25°C: At 25°C, charge to 4.55V at a constant current of 1C, then charge at a constant voltage of 4.55V until the current drops to 0.05C. Discharge to 2.5V at a constant current of 1C to obtain the first-cycle discharge specific capacity (Cd1). Repeat charge and discharge in this manner up to the 100th cycle, and obtain the discharge specific capacity after n cycles of the lithium-ion battery, denoted as Cdn. Capacity retention rate = discharge specific capacity after n cycles / discharge specific capacity at the first cycle.

[0166] [Table 1]

[0167] As can be seen from Table 1, in Examples 1 to 11, the porosity (P1) of the first base film and the porosity (P2) of the second base film satisfy the relationship 1.02≦P1 / P2≦3, and at the same time, the melting point of the second base film is lower than the melting point of the first base film. Batteries manufactured using the separator provided herein have higher capacity retention and safety reliability.

[0168] The above are only specific embodiments of the present application, and the scope of protection of the present application is not limited thereto. Those skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and all such 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 based on the scope of protection of the claims.

Claims

1. A separator, A first base film; a second base film, wherein the melting point of the second base film is lower than the melting point of the first base film; A separator in which, when the porosity of the first base film is P1 and the porosity of the second base film is P2, 1.02≦P1 / P2≦3.

2. The separator according to claim 1, wherein 1.05≦P1 / P2≦2.

5.

3. The porosity of the first base film is 30% to 90%, optionally 35% to 85%; and / or The separator according to claim 1 or 2, wherein the porosity of the second base film is 30% to 70%, and optionally 35% to 45%.

4. the ratio of the average pore size of the first base film to the average pore size of the second base film is 0.05 to 80, and optionally 0.2 to 40; Optionally, the average pore size of the first base film is larger than the average pore size of the second base film; Alternatively, the average pore size of the first base film is 100 nm to 4000 nm, and preferably 100 nm to 2000 nm; Optionally, the second base film has an average pore size of 50 nm to 2000 nm, optionally 50 nm to 500 nm.

5. The separator according to any one of claims 1 to 4, 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 to 0.8, optionally 0.3 to 0.

6.

6. The separator according to any one of claims 1 to 5, 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 0.45 to 0.9, and optionally 0.6 to 0.

8.

7. 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 6, wherein the first base film has a longitudinal tensile strength lower than the second base film.

8. The first base film has a transverse tensile strength of 150 to 900 kgf / cm ２ and optionally 200 to 750 kgf / cm ２ (1) and The first base film has a longitudinal tensile strength of 800 to 2500 kgf / cm ２ and optionally 1100 to 1900 kgf / cm ２ (2) and The second base film has a transverse tensile strength of 1500 to 3600 kgf / cm ２ and optionally 1800 to 3300 kgf / cm ２ (3) and The second base film has a longitudinal tensile strength of 1900 to 4000 kgf / cm ２ and optionally 2000 to 3500 kgf / cm ２ The separator according to any one of claims 1 to 7, wherein at least one of the following conditions (4) is satisfied:

9. The separator according to any one of claims 1 to 8, wherein the ratio of the thickness of the first base film to the thickness of the second base film is 1.02 or more, and optionally 1.2 to 3.

0.

10. The thickness of the first base film is 2 μm to 12 μm, optionally 3 μm to 6 μm; and / or The separator according to any one of claims 1 to 9, wherein the thickness of the second base film is 2µm to 12µm, and optionally 3µm to 5µm.

11. The separator according to any one of claims 1 to 10, wherein 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 3.0 or less, and optionally 1.1 or more and 2.5 or less.

12. The melting point of the first base film is between 160°C and 360°C, and optionally between 180°C and 350°C; and / or The separator according to any one of claims 1 to 11, wherein the melting point of the second base film is 120°C to 280°C, and optionally 130°C to 265°C.

13. The separator according to any one of claims 1 to 12, 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.

14. The adhesive layer is disposed between the first base film and the second base film and further includes an adhesive layer containing a binder. Optionally, the adhesive layer comprises a binder and a filler.

15. 15. The separator of claim 14, wherein the binder 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.

16. The separator according to claim 14 or 15, wherein the filler comprises at least one of inorganic particles, organic particles, and organic-metallic frameworks.

17. The separator according to any one of claims 14 to 16, wherein the thickness of the adhesive layer is 0.3 µm or more, and optionally 0.5 to 2 µm.

18. The separator has an air permeability of 200 s / 100 cc to 400 s / 100 cc, and optionally 250 s / 100 cc to 320 s / 100 cc; and / or The separator according to any one of claims 1 to 17, wherein the porosity of the separator is between 25% and 80%, and optionally between 35% and 55%.

19. providing 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, and the porosity of the first base film is P1 and the porosity of the second base film is P2, where P1 / P2 is 1.02≦P1 / P2≦3; and combining the first base film and the second base film to obtain the separator.

20. providing an adhesive layer paste comprising a binder; The adhesive layer paste is applied to the first base film and / or the second base film to form an adhesive layer, and after combining, the adhesive layer is located between the first base film and the second base film; 20. The method for manufacturing a separator according to claim 19, wherein optionally, the adhesive layer paste further comprises a filler, and optionally, the filler comprises at least one of inorganic particles, organic particles, and organic-metallic frameworks.

21. A secondary battery comprising the separator according to any one of claims 1 to 20, or a separator produced by the production method according to claim 19 or 20.

22. The secondary battery according to claim 21 , further comprising a positive electrode sheet and a negative electrode sheet, wherein the second base film faces the negative electrode sheet.

23. 23. A power consuming device comprising the secondary battery according to claim 21 or 22.

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