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

Abstract

The present application provides a separator, a method for manufacturing the same, and a secondary battery and a power consumption device related thereto. The separator includes a porous substrate and a coating provided on at least one surface of the porous substrate. The coating includes a three-dimensional skeleton structure and a filler, and at least a part of the filler is filled in the three-dimensional skeleton structure. Along the thickness direction of the separator, the average pore area of the coating is denoted as S1, and the average pore area of the porous substrate is denoted as S2, and 0 < S1 / S2 < 1. The present application can achieve both high energy density, high thermal safety performance, good cycle performance and kinetic performance in the secondary battery.

Description

[Technical Field]

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

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As the applications and popularity of secondary batteries increase, their safety issues, especially thermal safety issues, have received increasing attention. However, current methods for improving the thermal safety performance of secondary batteries often fail to balance the energy density and service life of secondary batteries. Therefore, how to achieve high energy density, high thermal safety performance, and good cycle and dynamic performance in secondary batteries is an important issue in secondary battery design. Summary of the Invention

[0003] An object of the present application is to provide a separator, a manufacturing method thereof, and related secondary batteries and power consumption devices, which can provide secondary batteries with high energy density, high thermal safety performance, and good cycle performance and dynamic performance.

[0004] A first aspect of the present application provides a separator, the separator comprising a porous substrate and a coating disposed on at least one surface of the porous substrate, wherein the coating comprises a three-dimensional framework and a filler, and at least a portion of the filler is filled in the three-dimensional framework, and an average pore area of the coating is denoted as S1, an average pore area of the porous substrate is denoted as S2, and an average pore area of the porous substrate is denoted as 0. <S1 / S2<1である。

[0005] In the research process, the inventor included a three-dimensional skeleton structure and a filler in the coating, filled at least a part of the filler into the three-dimensional skeleton structure, and made the average pore area S1 of the coating and the average pore area S2 of the porous substrate satisfy 0 < S1 / S2 < 1, so that the separator can have both high heat resistance and high ionic conductivity, and surprisingly found that the secondary battery can have both high energy density, high thermal safety performance, good cycle performance and kinetic performance.

[0006] In any embodiment of the present application, 0.06 ≤ S1 / S2 < 1, and optionally, 0.30 ≤ S1 / S2 ≤ 0.97.

[0007] In any embodiment of the present application, 0.0002 μm 2 ≤ S1 ≤ 0.0080 μm 2 and optionally, 0.0004 μm 2 ≤ S1 ≤ 0.0050 μm 2 When the average pore area S1 of the coating is within the above range, the heat resistance of the separator can be improved, while not hindering the transmission of active ions, thereby enabling the secondary battery to better achieve both high energy density, high thermal safety performance, good cycle performance and kinetic performance.

[0008] In any embodiment of the present application, 0.0005 μm 2 ≤ S2 ≤ 0.0100 μm 2 and optionally, 0.0008 μm 2 ≤ S2 ≤ 0.0080 μm 2 When the average pore area S2 of the porous substrate is within the above range, it is advantageous for improving the ionic conductivity of the separator and the performance of the secondary battery in terms of capacity utilization.

[0009] In any embodiment of the present application, the average pore size of the separator is denoted as d1, the average pore size of the porous substrate is denoted as d2, and d1 / d2 is < 1, and optionally 0.3 ≦ d1 / d2 ≦ 0.8. When the ratio d1 / d2 of the average pore size d1 of the separator to the average pore size d2 of the porous substrate is within the above range, the separator can also have relatively high ionic conductivity under the premise of ensuring high heat resistance.

[0010] In one embodiment of the present application, 15 nm≦d1≦50 nm, and optionally 20 nm≦d1≦40 nm. When the average pore diameter d1 of the separator is within the above range, the heat resistance of the separator can be improved without impeding the transmission of active ions, thereby enabling the secondary battery to better achieve high energy density, high thermal safety performance, and good cycle performance and kinetic performance.

[0011] In one embodiment of the present application, 25 nm≦d2≦60 nm, and optionally 30 nm≦d2≦50 nm. When the average pore diameter d2 of the porous substrate is within the above range, it is advantageous to improve the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0012] In any embodiment of the present application, the areal density of the coating is denoted as ρ1, the areal density of the porous substrate is denoted as ρ2, and ρ1 / ρ2 is 0.15≦ρ1 / ρ2≦0.80, and optionally 0.20≦ρ1 / ρ2≦0.50. When ρ1 / ρ2 is within the above range, it is advantageous for the coating to have high heat resistance, and it is also advantageous for the secondary battery to achieve both high energy density and high thermal safety performance.

[0013] In any embodiment of the present application, optionally, 0.50 g / m 2 ≦ρ1≦1.50g / m 2 , and more selectively, 0.75 g / m 2 ≦ρ1≦1.40g / m 2When the surface density ρ1 of the coating is within the above range, it is advantageous for the secondary battery to achieve both high energy density and high thermal safety performance, and the coating can have an appropriate average pore area, which can further improve the heat resistance and ionic conductivity of the separator.

[0014] In any embodiment of the present application, optionally, 1.50 g / m 2 ≦ρ2≦4.50g / m 2 , and more selectively, 2.00 g / m 2 ≦ρ2≦4.00g / m 2 When the areal density ρ2 of the porous substrate is within the above range, the porous substrate can have an appropriate average pore area, which is also advantageous in improving the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0015] In any embodiment of the present application, the porosity of the separator is denoted as P1, the porosity of the porous substrate is denoted as P2, and 0.4≦P2 / P1<1, optionally 0.55≦P2 / P1≦0.85. When P2 / P1 is within the above range, it is advantageous for the secondary battery to achieve high thermal safety performance and good cycle performance and dynamic performance at the same time.

[0016] In any embodiment of the present application, 20%≦P1≦60%, and optionally 25%≦P1≦45%. When the porosity P1 of the separator is within the above range, it is advantageous for the secondary battery to achieve high thermal safety performance and good cycle performance and dynamic performance at the same time.

[0017] In one embodiment of the present application, 15%≦P2≦45%, and optionally 20%≦P2≦40%. When the porosity P2 of the porous substrate is within the above range, it is advantageous to improve the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0018] In one embodiment of the present application, the filler includes a first filler, and the first filler has an average particle size of ≦150 nm, optionally 15 nm to 120 nm. The first filler has the advantages of a relatively small average particle size, a large specific surface area, and high affinity with the three-dimensional skeletal structure, thereby enabling better contact with the three-dimensional skeletal structure and providing a stable spatial network structure in the coating, thereby increasing the ionic conductivity of the separator and improving the separator's heat resistance and electrolyte infiltration and retention properties. Furthermore, when the average particle size of the first filler is within the above range, the coating can have an appropriate average pore area, further improving the separator's heat resistance and ionic conductivity.

[0019] In any embodiment of the present application, the first filler comprises at least one of primary particles and secondary particles.

[0020] In any embodiment of the present application, the average particle size of the first filler in the form of primary particles is 15 nm to 80 nm, and optionally 30 nm to 75 nm.

[0021] In any embodiment of the present application, the average particle size of the first filler in the form of secondary particles is 50 nm to 150 nm, and optionally 55 nm to 120 nm.

[0022] In one embodiment of the present application, the first filler includes at least one of inorganic particles and organic particles, optionally including at least one of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicone oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride, optionally including at least one of boehmite, aluminum oxide, barium sulfate, magnesium oxide, silicone oxide, titanium oxide, zinc oxide, cerium oxide, and barium titanate, and optionally including at least one of polystyrene particles, polyacrylic wax particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, and polyaryletherketone particles.

[0023] In any embodiment of the present application, the first filler comprises inorganic particles, and the crystalline form of the inorganic particles comprises at least one of a θ crystalline form, a γ crystalline form, and an η crystalline form, and optionally, the crystalline form of the inorganic particles comprises at least one of a θ crystalline form and a γ crystalline form.

[0024] In any embodiment of the present application, the content of the θ crystalline inorganic particles is ≧50 wt %, and optionally 60 wt % to 82 wt %, based on the total weight of the inorganic particles in the first filler.

[0025] In any embodiment of the present application, the content of the inorganic particles in the γ crystalline form is ≧10 wt %, and optionally 17 wt % to 38 wt %, based on the total weight of the inorganic particles in the first filler.

[0026] In any embodiment of the present application, the content of inorganic particles of the η crystalline form is ≦5 wt %, optionally ≦1.5 wt %, based on the total weight of the inorganic particles in the first filler.

[0027] Selection of a first filler having a different crystal form contributes to improving at least one of the heat resistance, ionic conductivity, and electrolyte wetting and retention properties of the separator.

[0028] In any embodiment of the present application, the BET specific surface area of the first filler is ≥ 15 m 2 / g, and selectively 18m 2 / g~65m 2 When the BET specific surface area of the first filler is within the above range, the coating can have an appropriate average pore area, the heat resistance and ionic conductivity of the separator can be further improved, and the affinity between the first filler and the three-dimensional framework structure can be improved, so that the coating has a more stable spatial network structure, and the separator has higher heat resistance and higher ionic conductivity.

[0029] In one embodiment of the present application, the content of the first filler is ≧55 wt %, and optionally 60 wt % to 90 wt %, based on the total weight of the coating. When the content of the first filler is within this range, the coating can have an appropriate average pore area, which can further improve the heat resistance and ionic conductivity of the separator. It is also advantageous for the coating to have a more stable spatial network structure, which can further improve the heat resistance and ionic conductivity of the separator.

[0030] In any embodiment of the present application, the filler further includes a second filler, and the second filler has an average particle size larger than that of the first filler. The second filler having a relatively large particle size can better support the coating, reduce shrinkage of the first filler, and reduce the amount of adhesive used, thereby improving the heat resistance of the separator. The second filler having a relatively large particle size and a relatively small amount used can contribute to the coating having a more porous structure and a lower moisture content, further improving the ionic conductivity and electrolyte wetting and retention properties of the separator.

[0031] In any embodiment of the present application, the average particle size of the second filler is 400 nm or less, and optionally 100 nm to 300 nm.

[0032] In any embodiment of the present application, the second filler has a primary particle morphology.

[0033] In any embodiment of the present application, the BET specific surface area of the second filler is ≦15 m 2 / g, and selectively 7m 2 / g~12m 2 When the BET specific surface area of the second filler is within the above range, the coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved. The supporting effect of the second filler can also be better exerted, the moisture content of the coating can be reduced, and the coating can maintain a stable pore structure during long-term charge and discharge, which is more favorable for ion transmission, and at the same time, the heat resistance of the separator can also be improved.

[0034] In one embodiment of the present application, the content of the second filler is ≦20 wt %, preferably 2 wt % to 15 wt %, based on the total weight of the coating. When the content of the second filler is within this range, the coating can have an appropriate average pore area, further improving the heat resistance and ionic conductivity of the separator, and further enhancing the supporting effect of the second filler, reducing the moisture content of the coating, allowing the coating to maintain a stable pore structure during long-term charge and discharge, further benefiting ion transmission, while also improving the heat resistance of the separator.

[0035] In any embodiment of the present application, the second filler comprises at least one of inorganic particles and organic particles.

[0036] In one embodiment of the present application, the second filler comprises inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles comprises at least one of an α-crystalline form and a γ-crystalline form, and optionally comprises an α-crystalline form. The α-crystalline second filler has the advantages of high hardness, good heat resistance, low dielectric constant, high safety, and high true density, which can further improve the heat resistance of the coating.

[0037] In any embodiment of the present application, the second filler comprises inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles comprises an α-crystalline form, and the content of the α-crystalline form inorganic particles is ≧80 wt %, and optionally 90 wt % to 100 wt %, based on the total weight of the inorganic particles in the form of primary particles in the second filler.

[0038] In any embodiment of the present application, the content of the three-dimensional framework structure is ≦40 wt %, and optionally 5 wt % to 25 wt %, based on the total weight of the coating. When the content of the three-dimensional framework structure is within this range, the coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0039] In any embodiment of the present application, the three-dimensional framework structure is formed of a fibrous material, and the shape of the fibrous material optionally includes at least one of a rod-like shape, a tubular shape, a rod-like shape, and a fiber-like shape.

[0040] In any embodiment of the present application, the average diameter of the material constituting the three-dimensional framework is ≦40 nm, and optionally 10 nm to 35 nm. When the average diameter of the material constituting the three-dimensional framework is within the above range, the material constituting the three-dimensional framework and the filler come into contact with each other, contributing to the formation of an integrated effect.

[0041] In any embodiment of the present application, the average length of the material constituting the three-dimensional framework is 100 nm to 800 nm, and optionally 200 nm to 600 nm. When the average length of the material constituting the three-dimensional framework is within an appropriate range, the heat resistance and ionic conductivity of the separator can be further improved.

[0042] In any embodiment of the present application, the aspect ratio of the material constituting the three-dimensional framework is 5 to 60, and optionally 10 to 30. When the aspect ratio of the material constituting the three-dimensional framework is within an appropriate range, the heat resistance and ionic conductivity of the separator can be further improved.

[0043] In any embodiment of the present application, the material constituting the three-dimensional framework structure includes at least one of an organic material and an inorganic material. Optionally, the organic material includes at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers. Optionally, the nanocellulose includes at least one of cellulose nanofibers, cellulose nanocrystals, and bacterial nanocellulose. Optionally, the inorganic material includes at least one of halloysite nanotubes, nanorod-shaped aluminum oxide, nanorod-shaped boehmite, nanorod-shaped silica, and glass fibers.

[0044] In any embodiment of the present application, the material constituting the three-dimensional skeletal structure includes nanocellulose.

[0045] In any embodiment of the present application, the nanocellulose comprises hydroxyl groups and anionic modifying groups.

[0046] In one embodiment of the present application, the anion-modifying group includes at least one of an amine group, a carboxyl group, a sulfonic acid group, a boric acid group, and a phosphate group, and optionally includes at least one of a sulfonic acid group, a boric acid group, and a phosphate group. When nanocellulose has the specific anion-modifying group, it can effectively improve the heat resistance of the separator, improving the thermal safety performance of the secondary battery, while also improving the adhesive strength between the coating and the porous substrate. When nanocellulose has the specific anion-modifying group, it can further help the nanocellulose and the filler to abut against each other to form an integrated effect, thereby allowing the coating to have a more stable spatial network structure, thereby improving the separator's electrolyte penetration and retention properties, improving the separator's ionic conductivity and voltage breakdown characteristics, and further benefiting the integration of high-voltage positive electrode active materials, and further improving the energy density of the secondary battery. The presence of anionic modifying groups can also reduce the proportion of hydroxyl groups, thereby ensuring that the coating slurry has an appropriate viscosity, which is more advantageous for application, and thereby improving the production efficiency and coating uniformity of the separator.

[0047] In any embodiment of the present application, the molar ratio of the anion modifying groups to the hydroxyl groups is 1:4 to 4:1, and optionally 2:3 to 7:3. When the molar ratio of the anion modifying groups to the hydroxyl groups is within an appropriate range, the heat resistance, ionic conductivity, and electrolyte infiltration and retention properties of the separator can be further improved.

[0048] In any embodiment of the present application, the coating further comprises a non-particulate adhesive. Optionally, the non-particulate adhesive comprises a water-based adhesive.

[0049] In one embodiment of the present application, the content of the non-particulate adhesive in the coating is ≦2 wt % based on the total weight of the coating. The three-dimensional framework structure and filler in the coating can form a stable spatial network structure, thereby maintaining high adhesiveness for the separator while reducing the amount of adhesive used.

[0050] In any embodiment of the present application, the thickness of the porous substrate is ≦8 μm, and optionally 3 μm to 6 μm. The coating of the present application can significantly improve the heat resistance of the separator, allowing for the selection of a thinner porous substrate, thereby contributing to improving the energy density of the secondary battery.

[0051] In any embodiment of the present application, the thickness of the coating is ≦2 μm, and optionally 0.5 μm to 1.3 μm. The coating of the present application has high heat resistance, which allows the coating thickness to be reduced and the energy density of the secondary battery to be further improved. In the present application, the coating thickness refers to the thickness of the coating located on one side of the porous substrate.

[0052] In one embodiment of the present application, the separator further includes an adhesive layer disposed on at least a portion of the surface of the coating, the adhesive layer including a particulate adhesive. The adhesive layer not only prevents the coating from falling off and improves the safety of the secondary battery, but also improves the interface between the separator and the electrodes, thereby improving the cycle performance of the secondary battery.

[0053] In any embodiment of the present application, the particulate adhesive includes at least one of an acrylate-based monomer homopolymer or copolymer, an acrylic-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer.

[0054] In any embodiment of the present application, the separator has a longitudinal heat shrinkage rate at 150°C for 1 hour of ≦6%, and optionally 0.5% to 4%.

[0055] In any embodiment of the present application, the separator has a transverse heat shrinkage rate at 150°C for 1 hour of ≦6%, and optionally 0.5% to 4%.

[0056] The separator of the present application has low thermal shrinkage in both the transverse and longitudinal directions at a high temperature of 150° C., thereby improving the safety of the secondary battery.

[0057] In any embodiment of the present application, the ionic conductivity of the separator is ≧0.6 ms / cm 2 and selectively ≧0.9ms / cm 2 The separator of the present application has high ionic conductivity, and thus can improve the cycle performance and / or dynamic performance of the secondary battery.

[0058] In any embodiment of the present application, the separator has a resistance value of ≦1.3 Ω, and optionally ≦1.0 Ω. The separator of the present application has a low resistance value, which can improve the cycle performance and / or kinetic performance of the secondary battery.

[0059] In any embodiment of the present application, the separator has a longitudinal tensile strength of ≥ 2000 kg / cm 2 and selectively 2500 kg / cm 2 ~4500kg / cm 2 is.

[0060] In any embodiment of the present application, the separator has a transverse tensile strength of ≥ 2000 kg / cm 2 and selectively 2500 kg / cm 2 ~4500kg / cm 2 is.

[0061] The separator of the present application has high tensile strength in both the horizontal and vertical directions, so that the probability of the separator being damaged when the secondary battery expands is relatively low, thereby improving the safety of the secondary battery.

[0062] In any embodiment of the present application, the wetted length of the separator is ≧30 mm, and optionally 30 mm to 80 mm.

[0063] In any embodiment of the present application, the wetting speed of the separator is ≧3 mm / s, and optionally 3 mm / s to 10 mm / s.

[0064] The separator of the present application has good electrolyte infiltration and retention properties, and therefore can improve the ionic conductivity of the separator and the capacity development properties of the secondary battery.

[0065] In any embodiment of the present application, the separator has an air permeability of ≦300 s / 100 mL, and optionally 100 s / 100 mL to 230 s / 100 mL. The separator of the present application has good air permeability, which can improve ion conductivity and secondary battery capacity development characteristics.

[0066] A second aspect of the present application provides a method for producing the separator of the first aspect of the present application, the method comprising the steps of: providing a porous substrate; mixing a material constituting the three-dimensional framework structure and a filler in a predetermined ratio in a solvent, and then uniformly stirring the mixture at a certain shear rate to prepare a coating slurry; and applying the coating slurry to at least one surface of the porous substrate and drying it to obtain a separator, wherein the separator comprises a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating comprising a three-dimensional framework structure and a filler, at least a portion of the filler being filled in the three-dimensional framework structure, an average pore area of the coating along the thickness direction of the separator is denoted as S1, an average pore area of the porous substrate is denoted as S2, and an average pore area of the porous substrate is denoted as 0. <S1 / S2<1である。

[0067] In any embodiment of the present application, the shear rate is ≦30 m / s, and optionally 15 m / s to 30 m / s. When the shear rate is within the above range, the coating after drying can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0068] In any embodiment of the present application, the solid content of the coating slurry is 8% to 30%, and optionally 10% to 20%.

[0069] In any embodiment of the present application, the coating surface density of the coating slurry on one side is 0.50 g / m 2 ~1.50g / m 2 and optionally 0.75 g / m 2 ~1.40g / m 2 When the surface density of the coating slurry is within the above range, the coating after drying can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can also be further improved.

[0070] In any embodiment of the present application, the coating slurry has a thickness of ≦2 μm on one side, and optionally 0.5 μm to 1.3 μm. When the coating slurry has a thickness within the above range, the coating after drying can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0071] In any embodiment of the present application, the method further comprises applying a slurry containing a particulate adhesive to at least a portion of the surface of the coating and drying to form an adhesive layer.

[0072] A third aspect of the present application provides a secondary battery, the secondary battery comprising the separator of the first aspect of the present application or comprising a separator produced by the method of the second aspect of the present application.

[0073] 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.

[0074] The separator of the present application can provide a secondary battery with high energy density, high thermal safety performance, and good cycle performance and dynamic performance at the same time, and the power consumption device of the present application includes a secondary battery according to the present application and therefore has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0075] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of 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 making any creative efforts. In the drawings, the drawings are not necessarily drawn to actual scale. [Figure 1] 1 is a schematic diagram of one embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of an embodiment of the secondary battery of FIG. 1. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of the present application including a secondary battery-powered power consuming device; DETAILED DESCRIPTION OF THE INVENTION

[0076] Hereinafter, with appropriate reference to the drawings, specific disclosed embodiments of the separator of the present application, its manufacturing method, and related secondary batteries and power consumption devices will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or repeated description of structures that are actually the same may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0077] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values and 3, 4, and 5 are listed as maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. In this application, unless otherwise specified, the numerical range "ab" is a shorthand notation for any combination of real numbers from a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have already been listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0079] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0080] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0081] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0082] Unless otherwise stated, in this application, the term "or" is inclusive. For example, 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).

[0083] Unless otherwise stated, in this application, the terms "first," "second," etc. are not intended to describe a particular order or hierarchy, but rather to distinguish between different objects.

[0084] Unless otherwise specified, terms used in this application have the known meanings commonly understood by those skilled in the art.

[0085] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be tested using various test methods commonly used in the art, and can be measured, for example, according to the test methods given in the examples of this application.

[0086] Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is installed between the positive electrode plate and the negative electrode plate and serves mainly to prevent short circuits between the positive and negative electrodes, while allowing active ions to pass freely through the separator to complete a circuit.

[0087] With the increasing application and popularity of secondary batteries, people's demands for the energy density and dynamic performance of secondary batteries are increasing. Thinning the separator is an effective way to improve the energy density of secondary batteries. The separators currently used in commercial secondary batteries are generally polyolefin porous membranes, such as porous polyethylene membranes, porous polypropylene membranes, or polypropylene / polyethylene / polypropylene three-layer composite membranes, with melting points ranging from 130°C to 160°C. Therefore, as the separator becomes thinner, its heat resistance deteriorates. When exposed to heat, significant thermal contraction occurs, leading to direct contact between the positive and negative electrodes inside the battery, causing an internal short circuit and increasing the safety risks of secondary batteries.

[0088] To solve the above problems, the current approach is to coat a heat-resistant inorganic ceramic layer on a polyolefin porous membrane, which increases the mechanical strength of the separator, reduces the degree of shrinkage of the separator when heated, and reduces the risk of short-circuiting between the positive and negative electrodes inside the battery. However, the inventors discovered through further research that the inorganic ceramic layer has limited effect on improving the heat resistance of the separator. To ensure high heat resistance of the separator, the coating thickness of the inorganic ceramic layer needs to be increased, but this extends the transmission distance of active ions, affecting the cycle performance and dynamic performance of the secondary battery, and at the same time, it is impossible to balance the energy density of the secondary battery.

[0089] Therefore, it is often difficult for conventional separators to achieve both high energy density, high thermal safety performance, and good cycle performance and kinetic performance in secondary batteries.

[0090] In the research process, the inventor discovered surprisingly that by installing a coating containing a three-dimensional skeleton structure and a filler on the surface of the separator porous substrate and making the average pore area of the coating smaller than that of the porous substrate, it is possible to achieve both high heat resistance and high ionic conductivity in the separator, and further achieve both high energy density, high thermal safety performance, good cycle performance, and kinetic performance in secondary batteries.

[0091] Separator Specifically, the first aspect of the embodiment of the present application provides a separator.

[0092] The separator includes a porous substrate and a coating provided on at least one surface of the porous substrate. The coating includes a three-dimensional skeleton structure and a filler, and at least a part of the filler is filled in the three-dimensional skeleton structure. Along the thickness direction of the separator, the average pore area of the coating is denoted as S1, and the average pore area of the porous substrate is denoted as S2, and 0 < S1 / S2 < 1. In the present application, the "three-dimensional skeleton structure" refers to a structure having a three-dimensional spatial shape and having a certain void, and it can be formed by abutting against each other with the materials constituting the three-dimensional skeleton structure.

[0093] In the process of studying the heat resistance of the separator, the inventor discovered that the heat resistance of the current coating (such as an inorganic ceramic layer, etc.) on the surface of the porous substrate is low. In order to ensure that the coating has high heat resistance, it is generally necessary to increase the thickness of the coating, but this will result in losses in the energy density, cycle performance, and kinetic performance of the secondary battery.

[0094] In further research, the inventors included a three-dimensional skeletal structure and a filler in the coating, filled at least a part of the filler into the three-dimensional skeletal structure, and made the average pore area S1 of the coating and the average pore area S2 of the porous substrate satisfy 0 < S1 / S2 < 1, so that the separator can have both high heat resistance and high ionic conductivity, and the secondary battery can have both high energy density, high thermal safety performance, and good cycle performance and kinetic performance.

[0095] The coating includes a three-dimensional skeletal structure and a filler, and at least a part of the filler is filled into the three-dimensional skeletal structure, so that the filler and the three-dimensional skeletal structure contribute to forming an intercalation effect, thereby improving the heat resistance of the separator, reducing the degree of shrinkage when the separator receives heat, reducing the short-circuit risk between the positive electrode and the negative electrode, and not only giving the secondary battery high thermal safety performance, but also maintaining a high adhesive strength between the coating and the porous substrate, and avoiding the filler from falling off during the long-term charge and discharge process of the secondary battery. Also, when at least a part of the filler is filled into the three-dimensional skeletal structure, since there are relatively many contact sites between the filler and the three-dimensional skeletal structure, the amount of adhesive used in the coating can be reduced, thereby effectively reducing the risk of clogging of the pores of the adhesive, and further improving the cycle performance and kinetic performance of the secondary battery. In some embodiments, at least a part of the filler is filled into the three-dimensional skeletal structure, and other parts of the filler may be located on the surface of the three-dimensional skeletal structure and / or the interface between the three-dimensional skeletal structure and the porous substrate, and a small amount of the filler may be embedded in the porous substrate at the interface position between the three-dimensional skeletal structure and the porous substrate. For example, in the winding process of the electrode assembly, due to the action of external pressure, a small amount of the filler at the interface position is embedded in the matrix and / or pores of the porous substrate.

[0096] Because the average pore area S1 of the coating is smaller than the average pore area S2 of the porous substrate, the coating can have high heat resistance. Because the coating of the present application has high heat resistance, the coating thickness (for example, the coating thickness may be 2 μm or less) can be reduced, shortening the transmission distance of the active ions, and the secondary battery can achieve both higher energy density and good cycle performance and dynamic performance. Furthermore, because the coating of the present application has high heat resistance, a thinner porous substrate can be selected, thereby further improving the energy density of the secondary battery.

[0097] In further studies, the inventors have also found that it is preferable that the ratio S1 / S2 of the average pore area S1 of the coating to the average pore area S2 of the porous substrate is not too small. If S1 / S2 is too small, the average pore area of the coating is often relatively small, which may hinder the transmission of active ions and affect the cycle performance and / or kinetic performance of the secondary battery. In some embodiments, 0.06≦S1 / S2<1, optionally 0.10≦S1 / S2≦0.99, 0.20≦S1 / S2≦0.98, 0.30≦S1 / S2≦0.97, 0.30≦S1 / S2≦0.80, 0.30≦S1 / S2≦0.70, 0.35≦S1 / S2≦0.94, 0.35≦S1 / S2≦0.85, 0.40≦S1 / S2≦0.92, 0.40≦S1 / S2≦0.80, 0.40≦S1 / S2≦0.70, 0.45≦S1 / S2≦0.90.

[0098] In some embodiments, the coating has an average pore area S1 of 0.0002 μm 2 ≦S1≦0.0080μm 2 and selectively, 0.0004 μm 2 ≦S1≦0.0050μm 2 , 0.0008 μm 2 ≦S1≦0.0048μm 2When the average pore area S1 of the coating is within the above range, the heat resistance of the separator can be improved without impeding the transmission of active ions, thereby enabling the secondary battery to better achieve high energy density, high thermal safety performance, and good cycle performance and kinetic performance.

[0099] In some embodiments, the average pore area S of the porous substrate is 0.0005 μm 2 ≦S2≦0.0100μm 2 and selectively, 0.0008 μm 2 ≦S2≦0.0080μm 2 When the average pore area S2 of the porous substrate is within the above range, it is advantageous for improving the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0100] In the present application, the average pore area S1 of the separator coating and the average pore area S2 of the separator porous substrate can be obtained by examining the cross-sectional image of the separator.

[0101] The average pore area S1 of the separator coating refers to the ratio of the total pore area of the coating in a cross-sectional image of the separator to the number of pores in the coating.

[0102] The average pore area S2 of the porous substrate of the separator means the ratio of the total pore area of the porous substrate to the number of pores in the porous substrate in a cross-sectional image of the separator.

[0103] In this application, the cross-sectional image of the separator is an image taken along the thickness direction of the separator. A test separator sample of a certain size (e.g., 15 mm × 15 mm) is cut from any region of the separator and cut under refrigeration conditions (e.g., -80 °C) using an ion beam polishing device (e.g., Hitachi Arblade 5000) to obtain the separator cross section. Referring to JY / T010-1996, a scanning electron microscope (e.g., ZEISS Sigma 300 scanning electron microscope, Germany) is used to obtain an SEM image of the separator cross section (magnification may be 1000x to 30000x), and an image processing detection system (e.g., EHOLLY Separator Detection System 2022-0408) is used to obtain the average pore area S1 of the separator coating and the average pore area S2 of the separator porous substrate by a multi-stage binarization method.

[0104] When cutting using an ion beam polishing device, the test sample may be wrapped in copper or aluminum foil before cutting. When obtaining SEM images of the separator cross section, the test sample may be sprayed with gold.

[0105] The image processing detection system can be used to obtain the pore area data of the separator coating and the porous substrate, respectively, and then the Mintab software can be used to obtain the pore area distribution map and average pore area of the separator coating and the porous substrate, respectively. The ratio of the total pore area of the separator coating to the number of pores in the coating is the average pore area S1 of the separator coating, and the ratio of the total pore area of the separator porous substrate to the number of pores in the porous substrate is the average pore area S2 of the separator porous substrate.

[0106] In some embodiments, the average pore size of the separator is denoted as d1, the average pore size of the porous substrate is denoted as d2, and d1 / d2<1, and optionally 0.2≦d1 / d2≦0.9, 0.3≦d1 / d2≦0.8, or 0.4≦d1 / d2≦0.7. When the ratio d1 / d2 of the average pore size d1 of the separator to the average pore size d2 of the porous substrate is within the above range, the separator can have relatively high ionic conductivity while ensuring high heat resistance.

[0107] In some embodiments, the average pore diameter d1 of the separator satisfies 15 nm≦d1≦50 nm, and optionally 20 nm≦d1≦40 nm. When the average pore diameter d1 of the separator is within the above range, the heat resistance of the separator can be improved without impeding the transmission of active ions, thereby enabling the secondary battery to better achieve high energy density, high thermal safety performance, and good cycle performance and kinetic performance.

[0108] In some embodiments, the average pore diameter d2 of the porous substrate satisfies 25 nm≦d2≦60 nm, and optionally 30 nm≦d2≦50 nm. When the average pore diameter d2 of the porous substrate is within the above range, it is advantageous to improve the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0109] The average pore size d1 of the separator and the average pore size d2 of the porous substrate can be measured using a capillary porosity analyzer (bubble point method). An exemplary test method is as follows: a circular sample with a diameter of 25 mm is taken, 3-5 drops of infiltration liquid are placed on it, and after the sample is completely infiltrated, it is placed in a mold. An inert gas is then used to extrude the infiltration liquid through the pores in the test sample. The extrusion pressure and flow rate are inversely proportional to the pore size. Software sampling and pressure-to-pore size conversion analysis are used to obtain the average pore size of the test sample. The measurement device can be a PMI CFP 1500 pore size analyzer, and the test pressure can be 100 psi to 350 psi.

[0110] In some embodiments, the areal density of the coating is denoted as ρ1, the areal density of the porous substrate is denoted as ρ2, and ρ1 / ρ2 is 0.15≦ρ1 / ρ2≦0.80, and optionally 0.20≦ρ1 / ρ2≦0.50. When ρ1 / ρ2 is within the above range, it is advantageous for the coating to have high heat resistance, and it is also advantageous for the secondary battery to have both high energy density and high thermal safety performance.

[0111] In some embodiments, the areal density of the coating, ρ, is 0.50 g / m 2 ≦ρ1≦1.50g / m 2 and optionally, 0.60 g / m 2 ≦ρ1≦1.40g / m 2 , 0.75g / m 2 ≦ρ1≦1.40g / m 2 , 0.75g / m 2 ≦ρ1≦1.30g / m 2 The above is satisfied. When the surface density ρ1 of the coating is within the above range, it is advantageous for the secondary battery to achieve both high energy density and high thermal safety performance. When the surface density ρ1 of the coating is within the above range, the coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved. In this application, the surface density of the coating means the surface density of the coating located on one side of the porous substrate.

[0112] In some embodiments, the areal density ρ of the porous substrate is 1.50 g / m 2 ≦ρ2≦4.50g / m 2 and optionally, 2.00 g / m 2 ≦ρ2≦4.00g / m 2 When the areal density ρ2 of the porous substrate is within the above range, the porous substrate can have an appropriate average pore area, which is also advantageous in improving the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0113] In some embodiments, the porosity of the separator is denoted as P1, the porosity of the porous substrate is denoted as P2, and 0.4≦P2 / P1<1, and optionally 0.55≦P2 / P1≦0.85. When P2 / P1 is within the above range, it is advantageous for the secondary battery to achieve high thermal safety performance and good cycle performance and dynamic performance at the same time.

[0114] In some embodiments, the porosity P1 of the separator satisfies 20%≦P1≦60%, and optionally 25%≦P1≦45%. When the porosity P1 of the separator is within the above range, it is advantageous for the secondary battery to have high thermal safety performance and good cycle performance and dynamic performance.

[0115] In some embodiments, the porosity P2 of the porous substrate satisfies 15%≦P2≦45%, and optionally 20%≦P2≦40%. When the porosity P2 of the porous substrate is within the above range, it is advantageous to improve the ionic conductivity of the separator and the capacity development characteristics of the secondary battery.

[0116] The porosity P1 of the separator and the porosity P2 of the porous substrate can be tested in accordance with GB / T 24586-2009. The test method is as follows: the separator or porous 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 porous substrate is calculated according to the cylindrical volume calculation formula. Referring to GB / T 24586-2009, an inert gas such as helium or nitrogen is used as the medium, and the gas displacement method is used to measure the true volume V2 of the separator or porous substrate with a true density measuring instrument. The porosity of the separator or porous substrate = (V1 - V2) / V1 × 100%. The test instrument may be a fully automatic true density measuring instrument, model AccuPyc II 1340, manufactured by Micromeritics, USA.

[0117] In some embodiments, the thickness of the porous substrate is ≦8 μm, and optionally 3 μm to 6 μm. The coating of the present application can significantly improve the heat resistance of the separator, allowing for the selection of a thinner porous substrate, thereby contributing to improving the energy density of the secondary battery.

[0118] In some embodiments, the thickness of the coating is ≦2 μm, and optionally 0.5 μm to 1.3 μm. The coating of the present application has high heat resistance, which allows the coating thickness to be reduced and the energy density of the secondary battery to be further improved. In the present application, the coating thickness refers to the thickness of the coating located on one side of the porous substrate.

[0119] The present application does not particularly limit the material of the porous substrate, and any known substrate having good chemical and mechanical stability can be selected. For example, the porous substrate may include at least one of a porous polyolefin resin film (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The porous substrate may be a single-layer film or a multi-layer composite film. When the porous substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0120] In some embodiments, the filler comprises a first filler, and the first filler has an average particle size of ≦150 nm, optionally 15 nm to 150 nm, or 15 nm to 120 nm.

[0121] The first filler has the advantages of a relatively small average particle size, a large specific surface area, and a high affinity with the three-dimensional framework, which allows for better contact with the three-dimensional framework and a stable spatial network structure in the coating, thereby increasing the ionic conductivity of the separator and improving the separator's heat resistance and electrolyte infiltration and retention properties. Furthermore, secondary batteries using the separator of the present application can achieve high thermal safety performance, long service life, and good cycle and dynamic performance. Furthermore, when the average particle size of the first filler is within the above range, the coating can have an appropriate average pore area, further improving the separator's heat resistance and ionic conductivity.

[0122] In some embodiments, the first filler comprises at least one of primary particles and secondary particles.

[0123] In some embodiments, the average particle size of the first filler in the form of primary particles is 15 nm to 80 nm, optionally 20 nm to 80 nm, or 30 nm to 75 nm.

[0124] In some embodiments, the average particle size of the first filler in the form of secondary particles is 50 nm to 150 nm, optionally 50 nm to 135 nm, 50 nm to 120 nm, 55 nm to 150 nm, 55 nm to 135 nm, or 55 nm to 120 nm.

[0125] In some embodiments, the BET specific surface area of the first filler is ≥ 15 m 2 / g, and selectively 18m 2 / g~65m 2 When the BET specific surface area of the first filler is within the above range, the coating can have an appropriate average pore area, the heat resistance and ionic conductivity of the separator can be further improved, and the affinity between the first filler and the three-dimensional framework structure can be improved, so that the coating has a more stable spatial network structure, and the separator has higher heat resistance and higher ionic conductivity.

[0126] In some embodiments, the first filler includes at least one of inorganic particles and organic particles, and selectively includes inorganic particles or a combination of inorganic particles and organic particles. Inorganic particles have the characteristics of high hardness, high thermal stability, and being difficult to decompose. Since they usually have hydroxyl groups on their surfaces, they are likely to construct with materials forming a three-dimensional skeletal structure (such as nanocellulose, etc.) to form a stable spatial network structure. Organic particles have the characteristics of good thermal stability and being difficult to decompose. At the same time, when the internal temperature of the secondary battery reaches the melting point of the organic particles due to overcharge abuse, thermal abuse, etc., the organic particles can further melt and be inhaled into the pores of the porous substrate by capillary action to play a role in closing pores and blocking, which is advantageous for improving the safety of the secondary battery.

[0127] Selectively, the inorganic particles include at least one of boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon oxide SiO x (0 < x ≤ 2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium dioxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), and magnesium fluoride (MgF2). Further selectively, the inorganic particles include at least one of boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), silicon oxide SiO x (0 < x ≤ 2), titanium oxide (TiO2), zinc oxide (ZnO), cerium oxide (CeO2), and barium titanate (BaTiO3).

[0128] Optionally, the organic particles include at least one of polystyrene particles, polyacrylic wax particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, and polyaryletherketone particles.

[0129] In some embodiments, the first filler comprises inorganic particles, and the crystalline form of the inorganic particles comprises at least one of theta, gamma, and eta crystal forms. Optionally, the crystalline form of the inorganic particles comprises at least one of theta and gamma crystal forms.

[0130] The inorganic particles of the θ crystal form have diffraction peaks at 2θ of 36.68°±0.2° and 31.21°±0.2° in an X-ray diffraction spectrum measured using an X-ray diffractometer. In some embodiments, the content of the inorganic particles of the θ crystal form in the first filler may be ≧50 wt %, and optionally 60 wt % to 82 wt %, based on the total weight of the inorganic particles in the first filler.

[0131] The γ-crystalline inorganic particles have diffraction peaks at 2θ of 66.95°±0.2° and 45.91°±0.2° in an X-ray diffraction spectrum measured using an X-ray diffractometer. In some embodiments, the content of the γ-crystalline inorganic particles in the first filler may be ≧10 wt%, and optionally 17 wt% to 38 wt%, based on the total weight of the inorganic particles in the first filler.

[0132] The inorganic particles of the η-crystalline form have diffraction peaks at 2θ of 31.89°±0.2° and 19.37°±0.2° in an X-ray diffraction spectrum measured using an X-ray diffractometer. In some embodiments, the content of the inorganic particles of the η-crystalline form in the first filler may be ≦5 wt %, optionally ≦1.5 wt %, and further optionally ≦1 wt %, based on the total weight of the inorganic particles in the first filler.

[0133] Inorganic particles with a θ crystal form have an appropriate specific surface area and hardness, which can better simultaneously improve the heat resistance and ionic conductivity of the separator, while inorganic particles with a γ crystal form and an η crystal form have the advantage of a large specific surface area.

[0134] Selection of a first filler having a different crystal form contributes to improving at least one of the heat resistance, ionic conductivity, and electrolyte wetting and retention properties of the separator.

[0135] In some embodiments, the first filler may comprise inorganic particles, and the crystalline forms of the inorganic particles may include θ crystalline form, γ crystalline form, and η crystalline form, and the content of θ crystalline form inorganic particles in the first filler may be 60 wt% to 82 wt%, the content of γ crystalline form inorganic particles may be 17 wt% to 38 wt%, and the content of η crystalline form inorganic particles may be ≦1.5 wt%, all based on the total weight of the inorganic particles in the first filler.

[0136] X-ray diffraction spectra of inorganic particles can be obtained by the following method: After drying the inorganic particles, they are ground in a mortar (e.g., an agate mortar) for 30 minutes, and then tested using an X-ray diffractometer (e.g., a Miniflex 600-C) to obtain X-ray diffraction spectra. The test can be performed using a Cu target, a Ni filter, a tube pressure of 40 kV, a tube current of 15 mA, and a continuous scan range of 5°-80°.

[0137] In some embodiments, the first filler may include inorganic particles, which can be produced by the following method: subjecting a precursor solution of inorganic particles to an oxidation reaction by high-pressure sputtering, followed by heating at 600°C to 900°C (e.g., for 1 hour to 3 hours) to form inorganic particles in the form of primary particles, and then further drying at 150°C to 250°C (e.g., for 30 minutes to 60 minutes) to obtain inorganic particles in the form of secondary particles after self-assembly of the primary particles.

[0138] In some embodiments, the content of the first filler is ≧55 wt %, preferably 60 wt % to 90 wt %, based on the total weight of the coating. When the content of the first filler is within this range, the coating can have an appropriate average pore area, which can further improve the heat resistance and ionic conductivity of the separator. It is also advantageous for the coating to have a more stable spatial network structure, which can further improve the heat resistance and ionic conductivity of the separator.

[0139] In some embodiments, the filler comprises a first filler and a second filler, and the second filler has an average particle size greater than the average particle size of the first filler.

[0140] The second filler having a relatively large particle size can better exert its supporting effect in the coating, reduce the shrinkage of the first filler, and reduce the amount of adhesive used, thereby improving the heat resistance of the separator; when the second filler has a relatively large particle size and is used in a relatively small amount, it can contribute to the coating having a more porous structure and a lower water content, further improving the ionic conductivity and the electrolyte wetting and retention properties of the separator.

[0141] In some embodiments, the second filler has an average particle size of 400 nm or less, preferably 100 nm to 300 nm. When the average particle size of the second filler is within this range, the coating can have an appropriate average pore area, further improving the heat resistance and ionic conductivity of the separator, and also better exerting the supporting effect of the second filler, reducing the moisture content of the coating, allowing the coating to maintain a stable pore structure during long-term charge and discharge, further benefiting ion transmission, and simultaneously improving the heat resistance of the separator.

[0142] In some embodiments, the BET specific surface area of the second filler is ≦15 m 2 / g, and selectively 7m 2 / g~12m 2 When the BET specific surface area of the second filler is within the above range, the coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved. The supporting effect of the second filler can also be better exerted, the moisture content of the coating can be reduced, and the coating can maintain a stable pore structure during long-term charge and discharge, which is more favorable for ion transmission, and at the same time, the heat resistance of the separator can also be improved.

[0143] In some embodiments, the second filler comprises at least one of inorganic particles and organic particles.

[0144] In some embodiments, the inorganic particles may include at least one 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.

[0145] 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 coating composition includes 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, 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 inorganic particles, thereby resulting in a more stable and uniform spatial network structure of the coating. Furthermore, selecting a coupling agent, surfactant, or polymer with a specific functional group to modify the inorganic particles can improve the electrolyte wetting and retention properties of the coating and also contribute to improving the adhesion of the coating to the porous substrate.

[0146] 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 Tiz1 (PO4)3, (LiAlTiP) x3 O y3 type glass, lithium lanthanum titanate Li x4 La y4 TiO3, lithium germanium thiophosphate Li x5 Ge y5 P z2 S w , lithium nitride Li x6 N y6 , SiS2 type glass Li x7 Si y7 S z3 and P2S5 type glass Li x8 P y8 S z4 contains 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.

[0147] Optionally, the inorganic particles capable of undergoing an electrochemical reaction 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.

[0148] In some embodiments, the organic particles include, but are not limited to, at least one of polyethylene particles, polypropylene particles, cellulose, cellulose modifiers (e.g., carboxymethyl cellulose), melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), silicone resin particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and copolymers of butyl acrylate and ethyl methacrylate (e.g., crosslinked polymers of butyl acrylate and ethyl methacrylate).

[0149] In some embodiments, the second filler has a primary particle morphology.

[0150] In some embodiments, the second filler comprises inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles comprises at least one of α-crystalline form and γ-crystalline form, and optionally comprises α-crystalline form. The α-crystalline second filler has the advantages of high hardness, good heat resistance, low dielectric constant, high safety, and high true density, which can further improve the heat resistance of the coating.

[0151] In some embodiments, the second filler comprises inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles comprises α-crystalline form, and the content of the α-crystalline form inorganic particles is ≧80 wt%, optionally 85 wt% to 100 wt%, 90 wt% to 100 wt%, or 95 wt% to 100 wt%, based on the total weight of the inorganic particles in the form of primary particles in the second filler.

[0152] The α-crystalline inorganic particles have diffraction peaks at 2θ of 57.48°±0.2° and 43.34°±0.2° in an X-ray diffraction spectrum measured using an X-ray diffractometer.

[0153] In some embodiments, the content of the second filler is ≦20 wt %, preferably 2 wt % to 15 wt %, based on the total weight of the coating. When the content of the second filler is within this range, the coating can have an appropriate average pore area, further improving the heat resistance and ionic conductivity of the separator, and further exerting the supporting effect of the second filler, reducing the moisture content of the coating, allowing the coating to maintain a stable pore structure during long-term charge and discharge, further benefiting ion transmission, while also improving the heat resistance of the separator.

[0154] In some embodiments, the three-dimensional framework may be formed of fibers, and the shape of the fibers may optionally include at least one of rod-like, tubular (e.g., hollow tubular), rod-like, and fibrous. A material with an appropriate shape is advantageous for the three-dimensional framework and the filler to form a stable spatial network structure, thereby further improving the heat resistance and ionic conductivity of the separator. In this application, the term "fibrous" refers to a material with an aspect ratio of 5 or more.

[0155] In some embodiments, the average diameter of the material constituting the three-dimensional framework is ≦40 nm, and optionally 10 nm to 35 nm. When the average diameter of the material constituting the three-dimensional framework is within this range, the material constituting the three-dimensional framework and the filler come into contact with each other, contributing to the formation of an integrated effect. Furthermore, the following situation can be effectively avoided: if the average diameter of the material constituting the three-dimensional framework is too large, the entanglement effect of the resulting three-dimensional framework may be insufficient, which may result in insufficient heat resistance, voltage breakdown resistance, and other properties of the separator.

[0156] In some embodiments, the average length of the material constituting the three-dimensional framework is 100 nm to 800 nm, and preferably 200 nm to 600 nm. When the average length of the material constituting the three-dimensional framework is within an appropriate range, the heat resistance and ionic conductivity of the separator can be further improved. Furthermore, the following situations can be effectively avoided: if the average length of the material constituting the three-dimensional framework is too short, the contact effect between the three-dimensional framework and the filler is relatively poor, resulting in poor heat resistance of the coating. Furthermore, during the drying process of the coating, the three-dimensional framework is prone to collapse due to insufficient support from the filler, which is likely to cause pore clogging problems and hinder ion transmission and moisture discharge, which may affect the thermal safety performance, cycle performance, and dynamic performance of the secondary battery. If the average length of the material constituting the three-dimensional framework is too long, the viscosity of the coating slurry is high and the fluidity is poor, which may affect the application of the coating slurry and further affect the quality of the coating, such as the heat resistance and ionic conductivity of the separator.

[0157] In some embodiments, the aspect ratio of the material constituting the three-dimensional framework is 5 to 60, and preferably 10 to 30. When the aspect ratio of the material constituting the three-dimensional framework is within an appropriate range, the heat resistance and ionic conductivity of the separator can be further improved. Furthermore, the following situation can be effectively avoided: if the aspect ratio of the material constituting the three-dimensional framework is too small, the contact effect between the three-dimensional framework and the filler is relatively poor, resulting in poor heat resistance of the coating. Furthermore, during the drying process of the coating, the three-dimensional framework is prone to collapse due to insufficient support from the filler, and furthermore, pore clogging problems are likely to occur, hindering ion transmission and moisture discharge, which may affect the thermal safety performance, cycle performance, and dynamic performance of the secondary battery. If the aspect ratio of the material constituting the three-dimensional framework is too large, the ionic conductivity of the separator may be reduced, which may ultimately result in poor cycle performance and / or dynamic performance of the secondary battery.

[0158] The average length and average diameter of the material constituting the three-dimensional skeletal structure can be measured by the following method: a 3.6 mm × 3.6 mm sample is cut out from any region of the separator, and the micromorphology of the coating in the sample is mapped using a scanning electron microscope (e.g., ZEISS Sigma 300) in high vacuum mode at an operating voltage of 3 kV and a magnification of 30,000 times. SEM images are obtained based on the obtained SEM images, and length statistics are performed on multiple (e.g., five or more) test regions, each with a size of 0.5 μm × 0.5 μm. The average length value obtained in each test region is then used as the average length of the material constituting the three-dimensional skeletal structure. Based on the obtained SEM images, Nano Measurer particle size distribution statistical software is used to select multiple (e.g., five or more) test regions and perform diameter statistics, each with a size of 0.5 μm × 0.5 μm. The average diameter value obtained in each test region is then used as the average diameter of the material constituting the three-dimensional skeletal structure.

[0159] In some embodiments, the material constituting the three-dimensional framework includes at least one of an organic material and an inorganic material. The material constituting the three-dimensional framework is not particularly limited as long as it has electrical insulation, electrochemical stability, and stability against an electrolyte, and may be an organic material or an inorganic material.

[0160] In some embodiments, the organic material comprises at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers. In some embodiments, the inorganic material comprises at least one of halloysite nanotubes, nanorod aluminum oxide, nanorod boehmite, nanorod silica, and glass fibers.

[0161] In some embodiments, the material constituting the three-dimensional framework comprises nanocellulose. Optionally, the nanocellulose comprises at least one of cellulose nanofibers (CNF, also known as nanofibril cellulose or microfibrillated cellulose), cellulose nanocrystals (CNC, also known as nanocrystalline cellulose), and bacterial nanocellulose (BNC, also known as bacterial cellulose or microbial cellulose). Optionally, the nanocellulose comprises cellulose nanocrystals, which have the advantage of high crystallinity and can therefore better improve the heat resistance of the separator.

[0162] Nanocellulose is a general term for cellulose whose size in any dimension is nanoscale (e.g., within 100 nm), and it possesses the properties of cellulose but also nanoparticles. Nanocellulose can be a polymeric nanomaterial extracted from natural sources such as wood or cotton by one or more means, including chemical, physical, and biological methods. Its advantages include widespread availability, low cost, biodegradability, high elastic modulus, and high specific surface area. It is an excellent alternative to traditional petrochemical resources and can effectively alleviate issues such as environmental pollution and petrochemical resource shortages. Nanocellulose also has excellent high-temperature resistance and a relatively small volume change after heating, thereby improving the heat resistance of separators. At the same time, nanocellulose's density is relatively low compared to traditional inorganic ceramic particles, thereby reducing the weight of secondary batteries and improving their weight-to-weight energy density. Furthermore, the three-dimensional framework structure of nanocellulose has tiny nanopores that prevent current leakage, allowing separators to achieve both good electrolyte infiltration and retention properties and good voltage breakdown resistance.

[0163] In some embodiments, the nanocellulose comprises hydroxyl groups and anionic modifying groups.

[0164] In some embodiments, the anion-modifying groups optionally include at least one of an amine group, a carboxyl group, a sulfonic acid group, a boric acid group, and a phosphate group, and further optionally include at least one of a sulfonic acid group, a boric acid group, and a phosphate group.

[0165] Through further research, the inventors discovered that nanocellulose containing the specific anion-modifying groups effectively improves the heat resistance of the separator, improving the thermal safety performance of the secondary battery, while also improving the adhesive strength between the coating and the porous substrate. The specific anion-modifying groups in nanocellulose also favorably integrate the nanocellulose and filler, resulting in a more stable spatial network structure for the coating. This improves the separator's electrolyte penetration and retention properties, improves the separator's ionic conductivity and voltage breakdown characteristics, and further enhances the alignment of high-voltage positive electrode active materials, further improving the energy density of the secondary battery. The presence of the anion-modifying groups also reduces the proportion of hydroxyl groups, ensuring the coating slurry has an appropriate viscosity, which is beneficial for application and thereby improves separator production efficiency and coating uniformity.

[0166] In some embodiments, the molar ratio of the anion-modifying groups to the hydroxyl groups is 1:4 to 4:1, preferably 2:3 to 7:3. When the molar ratio of the anion-modifying groups to the hydroxyl groups is within an appropriate range, the separator's heat resistance, ionic conductivity, and electrolyte penetration and retention properties can be further improved. The following situation can also be effectively avoided: if the molar ratio of the anion-modifying groups to the hydroxyl groups is too low, the additional improvement effect of the anion-modifying groups on the separator's heat resistance and ionic conductivity may be insignificant; if the molar ratio of the anion-modifying groups to the hydroxyl groups is too high, the separator's electrolyte penetration and retention properties may be poor, affecting the cycle performance and / or dynamic performance of the secondary battery and further reducing the separator's heat resistance, potentially affecting the improvement in the thermal safety performance of the secondary battery.

[0167] The type of anionic modifying groups in nanocellulose can be determined by infrared spectroscopy. For example, the type of anionic modifying groups can be determined by examining the infrared spectrum of the material and determining the characteristic peaks contained therein. Specifically, infrared spectroscopy analysis can be performed on the material using instruments and methods known in the art, such as an infrared spectrometer (e.g., an IS10 Fourier transform infrared spectrometer manufactured by Nicolet, USA) in accordance with GB / T 6040-2019 General Methods for Infrared Spectroscopy.

[0168] In some embodiments, the material constituting the three-dimensional framework contains a sulfonic acid group, and the content of sulfur element in the material constituting the three-dimensional framework is ≧0.1 wt %, optionally 0.2 wt % to 0.5 wt %, based on the total weight of the material constituting the three-dimensional framework.

[0169] The sulfur content of the three-dimensional framework material can be measured as follows: After drying the three-dimensional framework material, it is ground in a mortar (e.g., an agate mortar) for 30 minutes and then tested using an X-ray diffractometer (e.g., a Miniflex 600-C) to determine the sulfur content. The test uses a Cu target, a Ni filter, a tube pressure of 40 kV, a tube current of 15 mA, and a continuous scan range of 5°-80°.

[0170] In some embodiments, the content of the three-dimensional framework structure is ≦40 wt %, and optionally 5 wt % to 25 wt %, based on the total weight of the coating. When the content of the three-dimensional framework structure is within this range, the coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0171] In some embodiments, the coating further includes a non-particulate adhesive. The present application is not particularly limited to the type of non-particulate adhesive, and any known material with good adhesive properties may be selected. Optionally, the non-particulate adhesive includes a water-based adhesive, which has the advantages of high thermodynamic stability and environmental friendliness, making it advantageous for the production and application of coating slurries. For example, the water-based adhesive may include at least one of a water-based acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate monomer, or a copolymer with other copolymerizable monomers), polyvinyl alcohol (PVA), an isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0172] In some embodiments, the content of the non-particulate adhesive in the coating is ≦2 wt % based on the total weight of the coating. The three-dimensional framework and filler in the coating can form a stable spatial network structure, thereby maintaining high adhesiveness of the separator while reducing the amount of adhesive used.

[0173] In some embodiments, the separator further includes an adhesive layer disposed on at least a portion of the surface of the coating, the adhesive layer including a particulate adhesive. The adhesive layer not only prevents the coating from peeling off and improves the safety of the secondary battery, but also improves the interface between the separator and the electrodes, thereby improving the cycle performance of the secondary battery.

[0174] Optionally, the particulate adhesive includes at least one of an acrylate-based monomer homopolymer or copolymer, an acrylic-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer, and the copolymerizable monomer includes at least one of an acrylate-based monomer, an acrylic-based monomer, an olefin monomer, a halogen-containing olefin monomer, a fluoroether-based monomer, etc., but is not limited thereto.

[0175] Optionally, the particulate adhesive includes a vinylidene fluoride polymer, such as a homopolymer of vinylidene fluoride monomer (VDF) and / or a copolymer of a copolymerizable monomer with vinylidene fluoride monomer. The copolymerizable monomer may be at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylate-based monomer, an acrylic-based monomer, and a fluoroether-based monomer. Optionally, the copolymerizable monomer may include at least one of trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl) ether (e.g., perfluoro(methyl vinyl) ether PMVE, perfluoro(ethyl vinyl) ether PEVE, perfluoro(propyl vinyl) ether PPVE), perfluoro(1,3-dioxole), and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD).

[0176] In some embodiments, the separator has a longitudinal heat shrinkage rate of ≦6%, optionally 0.5% to 4%, at 150° C. for 1 hour.

[0177] In some embodiments, the separator has a transverse heat shrinkage of ≦6%, optionally 0.5% to 4%, at 150° C. for 1 hour.

[0178] The separator of the present application has low thermal shrinkage in both the transverse and longitudinal directions at a high temperature of 150° C., thereby improving the safety of the secondary battery.

[0179] In some embodiments, the separator has an ionic conductivity of ≥ 0.6 ms / cm 2 and selectively ≧0.9ms / cm 2 is.

[0180] The separator of the present application has high ionic conductivity, which can improve the cycle performance and / or dynamic performance of the secondary battery.

[0181] In some embodiments, the separator has a resistance of ≦1.3Ω, optionally ≦1.0Ω.

[0182] The separator of the present application has a low resistance value, which can improve the cycle performance and / or dynamic performance of the secondary battery.

[0183] In some embodiments, the separator has a longitudinal tensile strength of ≥ 2000 kg / cm 2 and selectively 2500 kg / cm 2 ~4500kg / cm 2 is.

[0184] In some embodiments, the separator has a transverse tensile strength of ≥ 2000 kg / cm 2 and selectively 2500 kg / cm 2 ~4500kg / cm 2 is.

[0185] The separator of the present application has high tensile strength in both the horizontal and vertical directions, so that the probability of the separator being damaged when the secondary battery expands is relatively low, thereby improving the safety of the secondary battery.

[0186] In some embodiments, the separator has a wetted length of ≧30 mm, optionally between 30 mm and 80 mm.

[0187] In some embodiments, the wetting rate of the separator is ≧3 mm / s, optionally 3 mm / s to 10 mm / s.

[0188] The separator of the present application has good electrolyte infiltration and retention properties, and therefore can improve the ionic conductivity of the separator and the capacity development properties of the secondary battery.

[0189] In some embodiments, the separator has an air permeability of ≦300 s / 100 mL, optionally between 100 s / 100 mL and 230 s / 100 mL.

[0190] The separator of the present application has good air permeability, and therefore can improve ion conductivity and secondary battery capacity development characteristics.

[0191] In this application, the average particle size of a material (e.g., a first filler, a second filler) has a meaning known in the art and can be measured using equipment and methods known in the art. For example, the material or separator may be measured using a scanning electron microscope, a transmission electron microscope, or a particle size distribution analyzer to obtain an image, and a plurality of test particles (e.g., 10 or more) (e.g., having a first filler, a second filler) may be randomly selected from the image, and the average length of the shortest diagonal lines of the particles may be calculated and used as the average particle size.

[0192] In this application, the specific surface area of a material (e.g., a first filler, a second filler) has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be tested using the nitrogen gas adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the Brunauer Emmett Teller (BET) method. Alternatively, the nitrogen gas adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, Inc., USA.

[0193] In this application, the heat shrinkage rate, tensile strength, and air permeability of the separator all have meanings known in the art and can be measured using methods known in the art, for example, they may be tested in accordance with standard GB / T 36363-2018.

[0194] In this application, the separator wetting length and wetting rate have meanings known in the art and can be measured using methods known in the art. An exemplary test method is as follows: a separator is cut into a 5 mm wide, 100 mm long sample. Both ends of the sample are clamped and placed horizontally. 0.5 mg of electrolyte is dropped into the center of the sample. After a predetermined time (1 minute in this application), a photograph is taken to measure the diffusion length of the electrolyte, thereby obtaining the separator wetting length and wetting rate. To ensure the accuracy of the test results, multiple samples (e.g., 5-10) can be tested, and the test results are obtained by calculating the average value. The electrolyte can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent. Thoroughly dried LiPF6 is dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0195] The ionic conductivity and resistance of the separator can be determined by AC impedance spectroscopy. Specifically, the separator is cut into a circular sheet of a certain area, dried, and then placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, the sheet is sealed to form a button battery, and AC impedance spectroscopy is performed.

[0196] It should be noted that the coating parameters (e.g., areal density, thickness, etc.) of the separator are all coating parameters on one side of the porous substrate. When the coating is applied to both sides of the porous substrate, if the coating parameters on either side satisfy the present application, it is considered to fall within the protection scope of the present application.

[0197] Manufacturing method A second aspect of the present application provides a method for manufacturing the separator of the first aspect of the present application, the method comprising the steps of: providing a porous substrate; mixing a material constituting the three-dimensional framework structure and a filler in a predetermined ratio in a solvent, and then uniformly stirring the mixture at a certain shear rate to prepare a coating slurry; and applying the coating slurry to at least one surface of the porous substrate and drying it to obtain a separator, wherein the separator comprises a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating comprising a three-dimensional framework structure and a filler, at least a portion of the filler being filled in the three-dimensional framework structure, an average pore area of the coating along the thickness direction of the separator is denoted as S1, an average pore area of the porous substrate is denoted as S2, and an average pore area of the porous substrate is denoted as S3. <S1 / S2<1である。

[0198] In some embodiments, the solvent used in preparing the coating slurry may be water, for example, deionized water.

[0199] In some embodiments, the coating slurry may further include other ingredients, such as dispersants, wetting agents, adhesives, and the like.

[0200] In some embodiments, the shear rate is ≦30 m / s, and optionally 15 m / s to 30 m / s. When the shear rate is within this range, the dried coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0201] In some embodiments, the solid content of the coating slurry is between 8% and 30%, and optionally between 10% and 20%.

[0202] In some embodiments, the coating slurry has a surface density of 0.50 g / m 2 ~1.50g / m 2 and optionally 0.75 g / m 2 ~1.40g / m 2 When the surface density of the coating slurry is within the above range, the coating after drying can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can also be further improved.

[0203] In some embodiments, the coating slurry has a thickness of ≦2 μm, preferably 0.5 μm to 1.3 μm, on one side. When the coating slurry has a thickness within this range, the dried coating can have an appropriate average pore area, and the heat resistance and ionic conductivity of the separator can be further improved.

[0204] In some embodiments, the material for forming the three-dimensional framework may include at least one of an organic material and an inorganic material. Optionally, the organic material includes at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers. Optionally, the inorganic material includes at least one of halloysite nanotubes, nanorod-shaped aluminum oxide, nanorod-shaped boehmite, nanorod-shaped silica, and glass fibers. In some embodiments, the material for forming the three-dimensional framework may include nanocellulose, and optionally cellulose nanocrystals (CNC, also known as cellulose nanocrystals or nanocrystalline cellulose).

[0205] In some embodiments, the nanocellulose can be obtained by the following method: providing a cellulose powder with a whiteness of ≥ 80%, mixing the resulting cellulose powder with a modifying solution to react, then washing to remove impurities to obtain cellulose nanocrystals, adjusting the pH of the resulting cellulose nanocrystals to neutral, and then grinding and cutting them to obtain nanocellulose.

[0206] Alternatively, the cellulose powder having a whiteness of 80% or greater may be commercially available or may be obtained using a chemical method (e.g., acid hydrolysis, alkali treatment, Tempo catalytic oxidation), a biological method (e.g., enzyme treatment), a mechanical method (e.g., ultrafine grinding, ultrasonic crushing, high-pressure homogenization), etc. The fiber raw material for producing the cellulose powder having a whiteness of 80% or greater may include at least one of plant fibers, such as cotton fibers (e.g., cotton wool fibers, cotton fiber), hemp fibers (e.g., sisal fibers, ramie fibers, jute fibers, flax fibers, hemp fibers, abaca fibers, etc.), braun fibers, wood fibers, bamboo fibers, and grass fibers.

[0207] In some embodiments, the cellulose powder having a whiteness of 80% or greater can also be produced by the following method: after opening the fiber raw material and removing the scum, the raw material is cooked in an alkaline solution (for example, an aqueous NaOH solution, the concentration of which may be 4 wt% to 20 wt%, and optionally 5 wt% to 15 wt%), and then sequentially washed with water to remove impurities (for example, washed 3 to 6 times), bleached (for example, sodium hypochlorite and / or hydrogen peroxide solution may be used), pickled to remove impurities, washed with water to remove impurities, drained, and dried in an air stream to obtain a cellulose powder.

[0208] In some embodiments, the modifying solution may be an acid solution (e.g., aqueous sulfuric acid, aqueous boric acid, aqueous phosphoric acid, aqueous acetic acid) or an alkaline solution (e.g., organic solvent urea solution). Optionally, the modifying solution is an acid solution.

[0209] Alternatively, the concentration of the acid solution may be 5 wt% to 80 wt%. When a sulfuric acid aqueous solution is selected as the modifying solution, a cellulose powder having sulfonic acid groups can be obtained by adjusting the concentration of the acid solution to 40 wt% to 80 wt%. When a boric acid aqueous solution is selected as the modifying solution, a cellulose powder having boric acid groups can be obtained by adjusting the concentration of the acid solution to 5 wt% to 10 wt%. When a phosphoric acid aqueous solution is selected as the modifying solution, a cellulose powder having phosphate groups can be obtained by adjusting the concentration of the acid solution to 45 wt% to 75 wt%. When an acetic acid aqueous solution is selected as the modifying solution, a cellulose powder having carboxylic acid groups can be obtained by adjusting the concentration of the acid solution to 40 wt% to 80 wt%.

[0210] Alternatively, the urea organic solvent solution is a urea xylene solution, thereby obtaining a cellulose powder having an amine group.

[0211] In some embodiments, the mass ratio of the cellulose powder to the modifying solution is 1:2.5 to 1:50, optionally 1:5 to 1:30.

[0212] When a sulfuric acid aqueous solution is selected as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When a boric acid aqueous solution is selected as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:20 to 1:50. When a phosphoric acid aqueous solution is selected as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When an acetic acid aqueous solution is selected as the modifying solution, the mass ratio of the cellulose powder to the acid solution may be 1:5 to 1:30. When a urea organic solvent solution is selected as the modifying solution, the mass ratio of the cellulose powder to the urea organic solvent solution may be 1:4 to 1:40.

[0213] In some embodiments, when the modifying solution is an acid solution, the reaction may be carried out at a temperature of 80°C or less, or optionally at a temperature of 30°C to 60°C, and the reaction time between the cellulose powder and the modifying solution may be 0.5 hours to 4 hours, or optionally 1 hour to 3 hours.

[0214] In some embodiments, when the modifying solution is an alkaline solution, the reaction may be carried out at a temperature of 100°C to 145°C, and the reaction time between the cellulose powder and the modifying solution may be 1 hour to 5 hours.

[0215] In some embodiments, grinding may be performed using a grinder, and cutting may be performed using a high-pressure homogenizer. By adjusting the grinding parameters of the grinder (e.g., grinding frequency, grinding time, etc.) and the cutting parameters of the high-pressure homogenizer, nanocellulose having different average diameters and / or different average lengths can be obtained.

[0216] In some embodiments, a coater may be used to apply the coating slurry. The present application does not particularly limit the model number of the coater, and for example, a commercially available coater may be used. The coater may include an intaglio roller, and the intaglio roller is used to transfer the slurry onto the porous substrate.

[0217] In some embodiments, the coating slurry may be applied by transfer coating, spin spray coating, dip coating, or the like.

[0218] In some embodiments, the method further comprises applying a slurry containing a particulate adhesive to at least a portion of the surface of the coating and allowing it to dry to form an adhesive layer.

[0219] The separator manufacturing method of the present application produces and obtains a coating in a single application, greatly simplifying the separator manufacturing process flow.

[0220] Parameters such as some raw materials used in the manufacturing method of the separator of the present application and their contents can be referred to the separator of the first aspect of the embodiment of the present application, and will not be further described here.

[0221] Unless otherwise specified, each of the raw materials used in the manufacturing method of the separator of the present application is commercially available.

[0222] secondary battery A third aspect of the present invention provides a secondary battery.

[0223] A secondary battery, also known as a rechargeable battery or storage battery, is a battery that can be continuously used by activating the active material through charging after discharging. Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and mainly serves to prevent short circuits between the positive electrode and the negative electrode and allows active ions to pass through.

[0224] The present application is not particularly limited to the type of secondary battery, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, etc., and in particular, the secondary battery may be a lithium ion secondary battery.

[0225] A secondary battery according to a third aspect of the present application includes the separator according to the first aspect of the present application or a separator manufactured by the method according to the second aspect of the present application, the separator being interposed between the positive electrode plate and the negative electrode plate, and optionally having the coating according to the present application on at least one side of the separator close to the negative electrode plate. This allows the secondary battery according to the present application to achieve high energy density, high thermal safety performance, and good cycle and dynamic performance.

[0226] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces facing each other in a thickness direction thereof, and the positive electrode film layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0227] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate, and a respective modified compound. Examples of the lithium transition metal oxide may include, but are not limited to, at least one 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 a respective modified compound. Examples of the lithium-containing phosphate may include, but are not limited to, at least one of lithium iron phosphate, a lithium iron phosphate-carbon composite, lithium manganese phosphate, a lithium manganese phosphate-carbon composite, lithium manganese iron phosphate, a lithium manganese iron phosphate-carbon composite, and a respective modified compound.

[0228] In some embodiments, in order to further improve the energy density of the secondary battery, the cathode active material used in the lithium-ion battery has a general formula of Li a Ni b Co c M d O e A f and may include at least one of lithium transition metal oxides and modified compounds thereof. 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is at least one selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is at least one selected from N, F, S, and Cl.

[0229] For example, the cathode active material used in the lithium-ion battery may include at least one of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi<着 0.85 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4.

[0230] When the secondary battery of the present application is a sodium-ion battery, the cathode active material may include, but is not limited to, at least one of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue-based materials.

[0231] For example, the cathode active material used in the sodium-ion battery may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi It should be noted that there seems to be an incorrect tag "着0000121" in the original text which should be corrected before accurate translation. The above translation is based on the existing text as much as possible.1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue-based materials, general formula X p M' q (PO4) r O x Y 3-x The compound may contain at least one material represented by the general formula X p M' q (PO4) r O x Y 3-x In, 0 <p≦4、0<q≦2、1≦r≦3、0≦x≦2であり、Xは、H + , Li + , Na + , K. + and NH4 + wherein M' is a transition metal cation, optionally at least one of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn; and Y is a halogen anion, optionally at least one of F, Cl, and Br.

[0232] In the present application, the modifying compound for each of the positive electrode active materials is a compound that modifies the positive electrode active material by doping and / or surface coating.

[0233] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent, and the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the positive electrode conductive agent is ≦5 wt %, based on the total weight of the positive electrode film layer.

[0234] In some embodiments, the positive electrode film layer optionally further includes a positive electrode adhesive. The present application is not particularly limited to the type of the positive electrode adhesive. For example, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage content of the positive electrode adhesive is ≦5 wt %, based on the total weight of the positive electrode film layer.

[0235] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet is aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0236] The positive electrode film layer is typically obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other optional components in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0237] [Negative electrode plate] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces facing each other in a thickness direction thereof, and the negative electrode film layer is disposed on one or both of the two facing surfaces of the negative electrode current collector.

[0238] The negative electrode active material may be any negative electrode active material for secondary batteries known in the art. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may include at least one of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy material. The tin-based material may include at least one of a tin element, a tin oxide, and a tin alloy material.

[0239] In some embodiments, the negative electrode film layer optionally further includes a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent, and for example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage content of the negative electrode conductive agent is ≦5 wt%.

[0240] In some embodiments, the negative electrode film layer optionally further includes a negative electrode adhesive. The present application is not particularly limited to the type of the negative electrode adhesive. For example, the negative electrode adhesive may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic acid-based resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative electrode adhesive is ≦5 wt %, based on the total weight of the negative electrode film layer.

[0241] In some embodiments, the negative electrode membrane layer further optionally contains other additives. For example, the other additives may include a thickener, such as carboxymethylcellulose sodium (CMC-Na), a PTC thermistor material, etc. In some embodiments, the mass percentage content of the other additives is ≦2 wt %, based on the total weight of the negative electrode membrane layer.

[0242] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet is copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0243] The negative electrode film layer is typically obtained by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliary agents in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0244] The negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described herein further includes a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate described herein further includes a protective layer covering the surface of the negative electrode film layer.

[0245] [Electrolyte] During the charge and discharge process of the secondary battery, active ions are absorbed and released by moving back and forth between the positive and negative electrodes, and the electrolyte serves to conduct the active ions between the positive and negative electrodes. The present application does not particularly limit the type of electrolyte, and it can be selected according to actual needs.

[0246] The electrolyte solution includes an electrolyte salt and a solvent, and the types of the electrolyte salt and the solvent are not specifically limited and may be selected according to actual needs.

[0247] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt may include at least one 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).

[0248] When the secondary battery of the present application is a sodium-ion battery, for example, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluoro(oxalato)borate (NaDFOB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobis(oxalato)phosphate (NaDFOP), and sodium tetrafluoro(oxalato)phosphate (NaTFOP).

[0249] By way of example, the solvent may include, but is not limited to, at least one of 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), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0250] In some embodiments, the electrolyte solution may further optionally contain 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 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 power performance of the battery.

[0251] In some embodiments, the positive electrode plate, the separator, and the negative electrode plate may be fabricated into an electrode assembly by a winding process and / or a stacking process.

[0252] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0253] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0254] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 with a rectangular structure.

[0255] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0256] The method for manufacturing the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly can be placed in an outer casing, dried, and then injected with an electrolyte. The secondary battery can be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0257] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0258] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0259] Optionally, 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.

[0260] 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 may be adjusted according to the application and capacity of the battery pack.

[0261] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, 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 covers the lower housing 3 and is used 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.

[0262] power consumption equipment A fourth aspect of the present application provides a power consuming device, the power consuming device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), 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, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0263] The power consumption device may select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0264] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0265] Other examples of power consuming devices include mobile phones, tablet computers, notebook computers, etc. These power consuming devices generally require a thin design and can employ secondary batteries as their power source.

[0266] Example The following examples will more specifically describe the contents disclosed in this application, and these examples are for illustrative purposes only, as various modifications and variations within the scope of the contents disclosed in this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are by weight, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further treatment, and all equipment used in the examples can be obtained commercially.

[0267] Production of nanocellulose C1 Cellulose powder production The cotton linters were opened in a cotton opener to remove scum, then steamed in a 5 wt% NaOH aqueous solution at 150°C for 2 hours, then sequentially washed with water to remove impurities (washed three times), bleached with sodium hypochlorite, washed with dilute hydrochloric acid to remove impurities, washed with water to remove impurities (washed once), drained, and dried in an air stream to obtain cotton cellulose powder with a whiteness of ≥85%.

[0268] esterification of cellulose 1 kg of the obtained cotton cellulose powder was mixed with 30 kg of 60 wt% aqueous sulfuric acid solution and reacted for 1.5 hours at 55°C to 60°C. After the reaction was completed, the mixture was washed with water to remove impurities (three times), filtered, and the acid was removed to remove impurities, yielding cellulose nanocrystals with sulfonic acid groups.

[0269] Neutralization of cellulose The pH of the cellulose nanocrystals with sulfonic acid groups was first adjusted to neutral using a 10 wt% NaOH aqueous solution, then polished with a polishing machine, and then nanoscale cutting was performed using a high-pressure homogenizer device to obtain nanocellulose with sulfonic acid group-modified groups having an average length of 500 nm and an average diameter of 22 nm, and the molar ratio of sulfonic acid groups to hydroxyl groups was 5:3.

[0270] The molar ratio of anionic modifying groups to hydroxyl groups in nanocellulose can be measured using the following method: the hydroxyl group value (the number of milligrams of potassium hydroxide equivalent to the hydroxyl group content per gram of sample) of raw cellulose and nanocellulose is measured according to the phthalic anhydride method in GB / T 12008.3-2009. The resulting value is expressed in mg KOH / g, which is then converted to mmol / g to represent the hydroxyl group content. Subtracting the hydroxyl group content of nanocellulose from the hydroxyl group content of raw cellulose yields the anionic modifying group content (i.e., the content of modified hydroxyl groups), which can then be used to calculate the molar ratio of anionic modifying groups to hydroxyl groups.

[0271] Production of nanocellulose C2 Unmodified nanocellulose, with an average length of 500 nm and an average diameter of 22 nm, product number CNWS-50, purchased from Zhongke Leiming (Beijing) Technology Co., Ltd., can be further processed using a grinder and / or a high-pressure homogenizer to obtain nanocellulose with different average diameters and / or different average lengths.

[0272] Example 1 Separator manufacturing A PE porous substrate is provided: the thickness is 4.8 μm and the porosity is 32%.

[0273] Preparation of coating slurry: The nanocellulose C1 produced above, the first filler aluminum oxide (secondary particle form, average particle size 75 nm), and the adhesive aqueous polyacrylic acid were mixed uniformly with an appropriate amount of deionized water solvent in a mass ratio of 16:83:1, and then stirred at a shear rate of 23 m / s to obtain a coating slurry with a solids content of 15 wt%. The contents of the α, θ, γ, and η crystal forms in the first filler were 1.1 wt%, 68.7 wt%, 29.6 wt%, and 0.6 wt%, respectively, based on the total weight of the first filler.

[0274] Coating: The prepared coating slurry was applied to two surfaces of the PE porous substrate using a coater, and then dried and slit to obtain a separator. The thickness of the coating on one side of the PE porous substrate was 0.8 μm, and the surface density was 1.25 g / m. 2 is.

[0275] Positive electrode plate manufacturing Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were uniformly mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry was then applied to a positive electrode current collector aluminum foil, and after processes such as drying, cold pressing, slitting, and cutting, a positive electrode plate was obtained.

[0276] Negative electrode plate manufacturing The negative electrode active material, artificial graphite, the conductive agent, carbon black (Super P), 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 mixture was dried, cold pressed, slit, and cut to obtain a negative electrode plate.

[0277] Electrolyte production Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 30:70 to obtain an organic solvent, and thoroughly dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0278] Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate were stacked in this order and wound to obtain an electrode assembly. The electrode assembly was then placed in an outer casing, dried, and then an electrolyte was added. After undergoing processes such as vacuum packaging, standing, chemical conversion, and shaping, a secondary battery was obtained.

[0279] Example 2-16 The secondary batteries were manufactured in the same manner as in Example 1, with the differences shown in Table 1. The second filler in Examples 12-15 was in the form of primary particles, and the crystalline form of the second filler was mainly α-crystalline, with a mass proportion of 99% or more based on the total weight of the second filler.

[0280] Comparative Example 1 The secondary battery was manufactured in the same manner as in Example 1, except for the manufacturing process of the separator.

[0281] A PE porous substrate is provided: the thickness is 4.8 μm and the porosity is 32%.

[0282] Preparation of coating slurry: Aluminum oxide (average particle size 600 nm, primary particle form, α-crystalline mass fraction ≥ 99%) and adhesive were mixed in a mass ratio of 94:6, dissolved in deionized water, and then stirred at a shear rate of 23 m / s to obtain a coating slurry with a solid content of 38 wt%.

[0283] Coating: The prepared coating slurry was applied to two surfaces of the PE porous substrate using a coater, and then dried and slit to obtain a separator. The coating thickness on one side of the PE porous substrate was 1.7 μm, and the surface density was 1.80 g / m. 2 is.

[0284] Testing part (1) Separator ionic conductivity test The ionic conductivity of the separator was measured using AC impedance spectroscopy. Specifically, the separator was cut into circular sheets of a certain area, dried, and then placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, the sheets were sealed to form a button cell battery. An AC impedance spectroscopy experiment was performed using an electrochemical workstation, a Shanghai Chenhua CHI 660C electrochemical workstation, with an AC signal frequency range of 0.01 Hz to 1 MHz and a sinusoidal potential amplitude of 5 mV. For accuracy, the average value of five parallel samples was taken as the test result.

[0285] The electrolyte solution used was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:50:20 to obtain an organic solvent, and then dissolving thoroughly dried LiPF6 in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0286] (2) Average pore area test of coating and porous substrate A test separator sample of a certain size (e.g., 15 mm x 15 mm) is cut from any region of the separator, wrapped in copper foil, and then cut using an ion beam polishing device (e.g., Hitachi Arblade 5000) under frozen conditions (e.g., -80°C) to obtain a cross-section of the separator sample. The separator sample is then gold-sprayed, and, referring to JY / T010-1996, scanned using a scanning electron microscope (e.g., Sigma 300 scanning electron microscope from ZEISS, Germany) to obtain an SEM image of the separator cross-section (magnification can be 1,000x to 30,000x). An image processing detection system (e.g., EHOLLY Separator Detection System 2022-0408) is used to obtain the average pore area S1 of the separator coating and the average pore area S2 of the separator porous substrate using a multi-stage binarization method. The ratio of the total pore area of the separator coating to the number of pores in the coating is the average pore area of the separator coating S1, and the ratio of the total pore area of the separator porous substrate to the number of pores in the porous substrate is the average pore area of the separator porous substrate S2. For accuracy, the average value of five parallel samples is taken as the test result.

[0287] (3) Separator heat shrinkage test Sample preparation: The separator prepared above is punched into samples with a width of 50 mm and a length of 100 mm using a press, and five parallel samples are placed on A4 paper and fixed in place. Next, the A4 paper containing the samples is placed on a cardboard box with a thickness of 1 mm to 5 mm.

[0288] Sample test: Place an A4 sheet of paper on a piece of cardboard and place it in a ventilated oven. Set the oven temperature to 150°C. After the temperature reaches the set temperature and stabilizes for 30 minutes, start timing. After the set time (1 hour in this application) is reached, measure the length and width of the separator and mark the values as a and b respectively.

[0289] Calculation of heat shrinkage rate: Machine direction (MD) heat shrinkage rate = [(100-a) / 100] x 100%, Transverse direction (TD) heat shrinkage rate = [(50-b) / 50] x 100%, the average value of five parallel samples is taken as the test result.

[0290] (4) Hot box test of secondary batteries At 25°C, the rechargeable batteries were charged at a constant current of 1C to 4.2V, and then continued constant voltage charging until the current reached ≤0.05C. After 5 minutes of rest, each rechargeable battery was then tested in a DHG-9070A DHG series high-temperature oven with a fixture. The temperature was increased from room temperature to 80°C + / -2°C at a rate of 5°C / min and maintained at that temperature for 30 minutes. The temperature was then increased at a rate of 5°C / min, with each 5°C increase being maintained for 30 minutes. The temperature change on the surface of the rechargeable battery was monitored during the heating process. The oven temperature at which the temperature began to rise rapidly was the hot box expiration temperature of the rechargeable battery. A higher hot box expiration temperature indicates better thermal safety performance of the rechargeable battery. For accuracy, the average value of five parallel samples was taken as the test result.

[0291] 5. Secondary battery cycle performance test At 25°C, the secondary battery was charged at a constant current of 1C to 4.2V, and then continued to be charged at a constant voltage of 0.05C. At this point, the secondary battery was fully charged. The charge capacity at this point, i.e., the first charge capacity, was recorded. After allowing the secondary battery to stand for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This constitutes one cycle charge / discharge process, and the discharge capacity at this point, i.e., the first discharge capacity, was recorded. The secondary battery was subjected to a cycle charge / discharge test according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 1000 cycles at 25°C = discharge capacity after 1000 cycles / discharge capacity at first cycle × 100%. For accuracy, the average value of five parallel samples was taken as the test result.

[0292] As can be seen from Table 2, in Examples 1-16, a coating containing nanocellulose (constituting a three-dimensional skeleton structure) and a filler is provided on two surfaces of the porous substrate of the separator, and by reasonably controlling the average pore area S1 of the coating and the average pore area S2 of the porous substrate to satisfy 0 < S1 / S2 < 1, it is possible to achieve both a low thermal shrinkage rate and a high ionic conductivity for the separator, and further achieve both a high thermal safety performance and a good cycle performance for the secondary battery.

[0293] It should be noted that this application is not limited to the above embodiments. The above embodiments are illustrative, and embodiments having substantially the same configuration and the same effects within the technical idea of the technical solution of this application are all included within the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications that those skilled in the art can conceive for the embodiments, and other modes constituted by combining some components in the embodiments are also included within the scope of this application.

Explanation of Reference Numerals

[0294] 1: Battery pack, 2: Upper housing, 3: Lower housing, 4: Battery module, 5: Secondary battery, 51: Case, 52: Electrode assembly, 53: Cover plate.

[0295]

Table 1

[0296]

Table 2

Claims

1. A separator comprising a porous substrate and a coating disposed on at least one surface of the porous substrate, wherein the coating comprises a three-dimensional framework and a filler, at least a portion of the filler is filled in the three-dimensional framework, and an average pore area of the coating along a thickness direction of the separator is S １ and the average pore area of the porous substrate is S ２ and 0<S １ / S ２ < 1, separator.

2. 0.06≦S １ / S ２ < 1, optionally, 0.30≦S １ / S ２ 2. The separator of claim 1, wherein the ρ is ≦0.

97.

3. 0.0002 μm ２ ≦S １ ≦0.0080 μm ２ and optionally 0.0004 μm ２ ≦S １ ≦0.0050 μm ２ and / or 0.0005 μm ２ ≦S ２ ≦0.0100 μm ２ and optionally 0.0008 μm ２ ≦S ２ ≦0.0080 μm ２ The separator according to claim 1 or 2,

4. The average pore diameter of the separator is d １ and the average pore diameter of the porous substrate is represented by d ２ and d １ / d ２ <1, Optionally, 0.3≦d １ / d ２ ≦0.8, Optionally, 15 nm≦d １ ≦50 nm, and more optionally, 20 nm≦d １ ≦40 nm, Optionally, 25 nm≦d ２ ≦60 nm, and more optionally, 30 nm≦d ２ 4. The separator of claim 1, wherein the thickness is ≦50 nm.

5. The areal density of the coating is ρ １ and the surface density of the porous substrate is expressed as ρ ２ and 0.15≦ρ １ / ρ ２ ≦0.80, Optionally, 0.20≦ρ １ / ρ ２ ≦0.50, Optionally, 0.50 g / m ２ ≦ρ １ ≦1.50 g / m ２ and more preferably 0.75 g / m ２ ≦ρ １ ≦1.40 g / m ２ and Optionally, 1.50 g / m ２ ≦ρ ２ ≦4.50 g / m ２ and more optionally, 2.00 g / m ２ ≦ρ ２ ≦4.00 g / m ２ The separator according to claim 1 , wherein

6. The porosity of the separator is P １ and the porosity of the porous substrate is represented by P ２ and 0.4≦P ２ / P １ <1, Optionally, 0.55≦P ２ / P １ ≦0.85, Optionally, 20%≦P １ ≦60%, and more optionally, 25%≦P １ ≦45%; Optionally, 15%≦P ２ ≦45%, and more optionally, 20%≦P ２ 6. The separator of claim 1, wherein the porosity is ≦40%.

7. The separator according to any one of claims 1 to 6, wherein the filler comprises a first filler, and the first filler has an average particle size of ≦150 nm, optionally 15 nm to 120 nm.

8. the first filler includes at least one of primary particles and secondary particles; Optionally, the average particle size of the first filler in the form of primary particles is 15 nm to 80 nm, optionally 30 nm to 75 nm; Optionally, the average particle size of the first filler in the form of secondary particles is 50 nm to 150 nm, and optionally 55 nm to 120 nm.

9. the first filler includes at least one of inorganic particles and organic particles; Alternatively, the inorganic particles include at least one of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicone oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride; more preferably, the inorganic particles include at least one of boehmite, aluminum oxide, barium sulfate, magnesium oxide, silicone oxide, titanium oxide, zinc oxide, cerium oxide, and barium titanate; 9. The separator according to claim 7, wherein the organic particles optionally include at least one of polystyrene particles, polyacrylic wax particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, and polyaryletherketone particles.

10. The first filler includes inorganic particles, and the crystalline form of the inorganic particles includes at least one of a θ crystalline form, a γ crystalline form, and an η crystalline form; Optionally, the crystalline form of the inorganic particles includes at least one of a θ crystalline form and a γ crystalline form; Preferably, the content of the θ crystalline inorganic particles is ≧50 wt %, more preferably 60 wt % to 82 wt %, based on the total weight of the inorganic particles in the first filler; Preferably, the content of the inorganic particles in the gamma crystalline form is ≧10 wt %, more preferably 17 wt % to 38 wt %, based on the total weight of the inorganic particles in the first filler.

10. The separator according to claim 7, wherein the content of the inorganic particles of the η crystalline form is ≦5 wt %, and further preferably ≦1.5 wt %, based on the total weight of the inorganic particles in the first filler.

11. The BET specific surface area of the first filler is ≥ 15 m ２ / g, and optionally 18m ２ / g~65m ２ / g, and / or The separator according to any one of claims 7 to 10, wherein the content of the first filler is ≧55 wt%, and optionally 60 wt% to 90 wt%, based on the total weight of the coating.

12. the filler further comprises a second filler, the second filler having an average particle size larger than the average particle size of the first filler; Optionally, the average particle size of the second filler is 400 nm or less, and optionally 100 nm to 300 nm.

13. The second filler is (1) The second filler has a primary particle form; (2) The BET specific surface area of the second filler is ≦15 m ２ / g, and optionally 7m ２ / g~12m ２ / g, and (3) the content of the second filler is ≦20 wt %, optionally 2 wt % to 15 wt %, based on the total weight of the coating; (4) The second filler contains at least one of inorganic particles and organic particles; (5) The second filler contains inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles includes at least one of an α-crystalline form and a γ-crystalline form, and selectively includes the α-crystalline form; (6) The separator according to claim 12, wherein the second filler contains inorganic particles in a primary particle form, and the crystalline form of the inorganic particles in a primary particle form includes an α-crystalline form, and the content of the α-crystalline inorganic particles is ≧80 wt %, and optionally 90 wt % to 100 wt %, based on the total weight of the inorganic particles in a primary particle form in the second filler.

14. The separator according to any one of claims 1 to 13, wherein the content of the three-dimensional framework structure is ≦40 wt %, and optionally 5 wt % to 25 wt %, based on the total weight of the coating.

15. The separator according to claim 1 , wherein the three-dimensional skeletal structure is formed of fibrous material, and the shape of the fibrous material selectively includes at least one of a rod shape, a tubular shape, a rod shape, and a fiber shape.

16. the average diameter of the material constituting the three-dimensional framework is ≦40 nm, and optionally 10 nm to 35 nm; the average length of the material constituting the three-dimensional framework is 100 nm to 800 nm, and optionally 200 nm to 600 nm; The separator according to any one of claims 1 to 15, wherein the aspect ratio of the material constituting the three-dimensional framework structure is 5 to 60, and optionally 10 to 30.

17. the material constituting the three-dimensional framework includes at least one of an organic material and an inorganic material; Optionally, the organic material comprises at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers; and optionally, the nanocellulose comprises at least one of cellulose nanofibers, cellulose nanocrystals, and bacterial nanocellulose; Optionally, the inorganic material includes at least one of halloysite nanotubes, nanorod-shaped aluminum oxide, nanorod-shaped boehmite, nanorod-shaped silica, and glass fibers.

18. The material constituting the three-dimensional skeletal structure includes nanocellulose, Optionally, the nanocellulose comprises hydroxyl groups and anionic modifying groups; Optionally, the anion-modifying group comprises at least one of an amine group, a carboxyl group, a sulfonic acid group, a boric acid group, and a phosphate group, and further optionally comprises at least one of a sulfonic acid group, a boric acid group, and a phosphate group; Optionally, the molar ratio of the anion-modifying groups to the hydroxyl groups is from 1:4 to 4:1, and further optionally from 2:3 to 7:

3.

19. the coating further comprises a non-particulate adhesive; Optionally, the non-particulate adhesive comprises a water-based adhesive; Optionally, the content of the non-particulate adhesive in the coating is ≦2 wt %, based on the total weight of the coating.

20. the thickness of the porous substrate is ≦8 μm, optionally 3 μm to 6 μm; and / or The separator of any one of claims 1 to 19, wherein the coating has a thickness of ≦2 μm, optionally between 0.5 μm and 1.3 μm.

21. the separator further includes an adhesive layer disposed on at least a portion of the surface of the coating, the adhesive layer including a particulate adhesive; Optionally, the particulate adhesive includes at least one of an acrylate-based monomer homopolymer or copolymer, an acrylic-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer.

22. The separator is (1) The separator has a longitudinal heat shrinkage rate of ≦6%, optionally 0.5% to 4%, at 150°C for 1 hour; (2) The separator has a transverse heat shrinkage rate of ≦6%, optionally 0.5% to 4%, at 150°C for 1 hour; (3) The ionic conductivity of the separator is ≧0.6 ms / cm ２ and optionally ≧0.9 ms / cm ２ and (4) The resistance value of the separator is ≦1.3Ω, and optionally ≦1.0Ω; (5) The separator has a longitudinal tensile strength of ≥ 2000 kg / cm ２ and optionally 2500 kg / cm ２ ~4500kg / cm ２ and (6) The separator has a lateral tensile strength of ≥ 2000 kg / cm ２ and optionally 2500 kg / cm ２ ~4500kg / cm ２ and (7) The wet length of the separator is ≧30 mm, and optionally 30 mm to 80 mm; (8) The wetting speed of the separator is ≧3 mm / s, and optionally 3 mm / s to 10 mm / s; (9) The separator according to any one of claims 1 to 21, wherein the separator has an air permeability of ≦300 s / 100 mL, and optionally 100 s / 100 mL to 230 s / 100 mL.

23. 23. A method for producing a separator according to any one of claims 1 to 22, the method comprising the steps of: providing a porous substrate; mixing a material constituting the three-dimensional framework and a filler in a predetermined ratio in a solvent, and then uniformly stirring the mixture at a constant shear rate to prepare a coating slurry; and applying the coating slurry to at least one surface of the porous substrate and drying it to obtain a separator, wherein the separator comprises a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating comprising a three-dimensional framework and a filler, at least a portion of the filler being filled in the three-dimensional framework, and an average pore area of the coating along a thickness direction of the separator is S １ and the average pore area of the porous substrate is represented by S ２ and 0<S １ / S ２ <1> A method for manufacturing a separator.

24. the shear rate is ≦30 m / s, optionally between 15 m / s and 30 m / s; and / or the solids content of the coating slurry is between 8% and 30%, optionally between 10% and 20%; and / or The coating surface density of the coating slurry on one side is 0.50 g / m ２ ~1.50g / m ２ and optionally 0.75 g / m ２ ~1.40g / m ２ and / or 24. The method of claim 23, wherein the coating thickness of the coating slurry on one side is ≦2 μm, and optionally 0.5 μm to 1.3 μm.

25. 25. The method of claim 23 or 24, further comprising applying a slurry containing a particulate adhesive to at least a portion of the surface of the coating and drying to form an adhesive layer.

26. 26. A secondary battery comprising the separator of any one of claims 1 to 22 or a separator produced by the method of any one of claims 23 to 25.

27. 27. A power consuming device comprising the secondary battery of claim 26.

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