Secondary battery and power consumption device

Abstract

This application relates to a secondary battery, which includes a negative electrode plate and a separator. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. When the capacity per unit area of the negative electrode film layer is C and the void volume per unit area of the separator is V, the secondary battery satisfies 0.05 cm 3 / Ah ≤ V / C ≤ 0.3 cm 3 / Ah, where the unit of C is mAh and the unit of V is cm 3 . Also, this application relates to a power consumption device including the secondary battery, and the secondary battery has good cycle performance.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and particularly to secondary batteries and power consumption devices.

Background Art

[0002] In recent years, secondary batteries have been widely applied in many fields such as energy storage power systems like hydraulic, thermal, wind, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the leapfrog development of secondary batteries, higher requirements are also imposed on their energy density, cycle performance, etc. How to improve the use performance of batteries is the direction that those skilled in the art are constantly striving for.

Summary of the Invention

[0003] This application is made in view of the above problems, and aims to provide a secondary battery having good cycle performance.

[0004] To achieve the above object, the first aspect of this application provides a secondary battery including a negative electrode plate and a separator, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. When the capacity per unit area of the negative electrode film layer is C and the void volume per unit area of the separator is V, the secondary battery satisfies 0.05 cm 3 / Ah ≤ V / C ≤ 0.3 cm 3 / Ah, where the unit of C is mAh and the unit of V is cm 3 ³.

[0005] The secondary battery of this application ensures that the ratio of the void volume of the separator to the capacity per unit area of the negative electrode film layer satisfies the above range, thereby ensuring the wettability of the separator and the capacity of the negative electrode, and giving the corresponding battery good cycle performance.

[0006] In any embodiment, 0.07 cm 3 / Ah ≤ V / C ≤ 0.25 cm3 / Ah, and optionally, 0.08 cm 3 / Ah ≤ V / C ≤ 0.2 cm 3 / Ah. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0007] In any embodiment, C is 2 to 8 mAh, optionally 2.3 to 5.5 mAh, and further optionally 2.3 to 5.0 mAh. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0008] In any embodiment, V is 2×10 -4 ~20×10 -4 cm 3 optionally 2×10 -4 ~15×10 -4 cm 3 and further optionally 4×10 -4 ~10×10 -4 cm 3 Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0009] In any embodiment, the areal density of the negative electrode film layer is 0.002 g / cm 2 ~0.02 g / cm 2 optionally 0.006 to 0.015 g / cm 2 and further optionally 0.005 to 0.007 g / cm 2 Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0010] In any embodiment, the thickness of the negative electrode film layer is 0.03 to 0.24 mm, and optionally, 0.08 to 0.16 mm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0011] In any embodiment, the separator includes a base film and a coating provided on at least one side of the base film, and the coating includes first polymer particles and second polymer particles. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0012] In any embodiment, the number-based average diameter of the first polymer particles is larger than the number-based average diameter of the second polymer particles. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0013] In any embodiment, the number-based average diameter of the first polymer particles is 2 to 8 μm, and optionally 3 to 7 μm. And / or, the number-based average diameter of the second polymer particles is 50 to 800 nm, and optionally 100 to 600 nm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0014] In any embodiment, the content of the first polymer particles is 15% or less based on the weight of the coating. And / or, the content of the second polymer particles is 30% or less based on the weight of the coating. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0015] In any embodiment, the first polymer particles include at least one of a homopolymer or copolymer of fluoroalkenyl monomer units, a homopolymer or copolymer of olefin monomer units, a homopolymer or copolymer of unsaturated nitrile monomer units, a homopolymer or copolymer of alkylene oxide-based monomer units, a homopolymer or copolymer of acrylate-based monomer units, a homopolymer or copolymer of imide-based monomer units, and a modified compound of each of the above homopolymers or copolymers, and / or the second polymer particles include at least one of a homopolymer or copolymer of unsaturated nitrile-based monomer units, a homopolymer or copolymer of fluoroalkenyl monomer units, a homopolymer or copolymer of styrene-based monomer units, and a modified compound of the above homopolymers or copolymers. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0016] In any embodiment, the coating further includes inorganic particles, and optionally, the volume average diameter of the inorganic particles is 0.1 to 2 μm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0017] In any embodiment, the thickness of the base film is 5 to 16 μm, and / or the thickness of the coating is 1 to 5 μm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0018] In any embodiment, the ratio of the thickness of the coating on one side to the thickness of the base film is 0.1 to 1.5. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0019] In any embodiment, the air permeability of the separator is 370 s or less, and optionally 100 - 250 s. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0020] In any embodiment, the porosity of the separator is 20% - 60%. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0021] Moreover, in the second aspect of the present application, a power consumption device is further provided, which is characterized by including the secondary battery described in the first aspect of the present application.

[0022] By guaranteeing that the ratio of the void volume of the separator to the capacity per unit area of the negative electrode film layer in the secondary battery of the present application satisfies the above range, it is ensured that the void volume of the separator is sufficiently large, and at the same time, it is guaranteed that the negative electrode film layer has a sufficient capacity per unit area, enabling the corresponding battery to have good cycle performance.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0024] Hereinafter, embodiments specifically disclosing the secondary battery and the power consumption device of the present application will be described in detail with appropriate reference to the drawings. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of structures that are actually the same may be omitted. This is to avoid the following description from becoming unnecessarily long and to enable those skilled in the art to easily understand. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and do not limit the theme described in the claims.

[0025] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit, and the given range is limited by selecting one lower limit and one upper limit. The selected lower limit and upper limit define the boundary of a specific range. The range thus limited may or may not include the end values, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, when ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also understood to be conceivable. Note that if 1 and 2 are listed as the minimum range values and 3, 4, and 5 are listed as the maximum range values, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all conceivable. In the present application, unless otherwise specified, the numerical range of "a - b" represents a shortened expression of any real number combination of a - b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are listed in this specification, and "0 - 5" is only a shortened expression of the combination of these numerical values. Also, when a certain parameter is expressed as an integer ≧ 2, it corresponds to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and alternative embodiments of the present application can be combined with each other to form a new technical solution.

[0027] Unless otherwise specified, all the technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0028] Unless otherwise specified, all the steps of this application may be performed in sequence or randomly, and preferably, they are performed in sequence. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0029] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application represent an open type and may also be a closed type. For example, the "comprising" and "including" may further include or contain other components not listed, or may include or contain only the components listed.

[0030] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the conditions where A is true (or exists) and B is false (or does not exist), A is false (or does not exist) but B is true (or exists), and both A and B are true (or exist) satisfy "A or B".

[0031] At present, the improvement of the separator is usually achieved by applying a ceramic coating and / or an adhesive coating on the base film. After the pressure inside the battery increases, the adhesive coating is crushed and flattened, blocking the ion passage between the separator and the electrode plate, resulting in insufficient wetting of the electrolyte, and even problems such as black spots and lithium precipitation. In addition, in the improvement of the separator, the cooperation with the positive and negative electrodes is not considered. Therefore, the improvement of the conventional secondary battery, especially the separator, requires further improvement. The inventor has found through research that when the void volume of the separator in the secondary battery and the capacity per unit area of the negative electrode film layer have a specific relationship, the capacity of the negative electrode can be guaranteed together with the wetting ability of the separator, and thus the corresponding secondary battery has good cycle performance.

[0032] Secondary battery In some embodiments, the first aspect of the present application provides a secondary battery including a negative electrode plate and a separator, the negative electrode plate including a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. Assuming that the capacity per unit area of the negative electrode film layer is C and the void volume per unit area of the separator is V, the secondary battery satisfies 0.05 cm 3 / Ah ≤ V / C ≤ 0.3 cm 3 / Ah, where the unit of C is mAh and the unit of V is cm 3 is.

[0033] The secondary battery of the present application ensures the wettability of the separator and the capacity of the negative electrode by making the ratio of the void volume of the separator to the capacity per unit area of the negative electrode film layer satisfy the above range, giving the corresponding battery good cycle performance.

[0034] In some embodiments, C is the capacity per unit area of the negative electrode film layer, that is, the capacity per 1 cm 2 of the negative electrode film layer (also called per 1 cm 2 of the negative electrode plate).

[0035] In some embodiments, V is the void volume per unit area of the separator, i.e., the void volume per 1 cm of the separator. 2 It is the void volume per centimeter.

[0036] In some embodiments, V / C is 0.05 cm 3 / Ah, 0.07 cm 3 / Ah, 0.08 cm 3 / Ah, 0.09 cm 3 / Ah, 0.1 cm 3 / Ah, 0.15 cm 3 / Ah, 0.18 cm 3 / Ah, 0.20 cm 3 / Ah, 0.24 cm 3 / Ah, 0.25 cm 3 / Ah, 0.28 cm 3 / Ah, 0.3 cm 3 / Ah, or may be within the range consisting of any two of the above values. Those skilled in the art can make adjustments and selections as needed.

[0037] In some embodiments, C is 2 to 8 mAh, optionally 2.3 to 5.5 mAh, and more optionally 2.3 to 5.0 mAh, and V is 2 to 20×10 -4 cm 3 and optionally 2 to 15×10 -4 cm 3 and more optionally 4 to 10×10 -4 cm 3 is.

[0038] In some embodiments, the void volume per unit area of the separator is the void volume of the separator at the self-generated pressure inside the battery. Generally, the self-generated pressure inside the battery is 0 to 10 MPa.

[0039] In some embodiments, 0.07 cm 3 / Ah ≤ V / C ≤ 0.25 cm 3 / Ah, C is 2 to 8 mAh, and V is 2×10 -4 ~20×10 -4 cm3 This can further guarantee the wetting ability of the separator and the capacity of the negative electrode, and endow the corresponding battery with good cycle performance.

[0040] In some embodiments, 0.08 cm 3 / Ah ≤ V / C ≤ 0.2 cm 3 / Ah, where C is 2 to 8 mAh and V is 2.5×10 -4 ~15×10 -4 cm 3 This can further guarantee the wetting ability of the separator and the capacity of the negative electrode, and endow the corresponding battery with good cycle performance.

[0041] In some embodiments, 0.08 cm 3 / Ah ≤ V / C ≤ 0.3 cm 3 / Ah, where C is 2 to 8 mAh and V is 2 to 20×10 -4 cm 3 This can further guarantee the wetting ability of the separator and the capacity of the negative electrode, and endow the corresponding battery with good cycle performance.

[0042] In some embodiments, 0.07 cm 3 / Ah ≤ V / C ≤ 0.25 cm 3 / Ah, where C is 2 to 8 mAh and V is 0.2×10 -3 ~1.2×10 -3 cm 3 This can further guarantee the wetting ability of the separator and the capacity of the negative electrode, and endow the corresponding battery with good cycle performance.

[0043] In some embodiments, 0.05 cm 3 / Ah ≤ V / C ≤ 0.2 cm 3 / Ah, where C is 2 to 8 mAh and V is 0.16×10 -3 ~1.0×10 -3It is cm3. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0044] In some embodiments, 0.15 cm 3 / Ah ≤ V / C ≤ 0.25 cm 3 / Ah, where C is 2.4 to 2.9 mAh and V is 0.4×10 -3 ~0.6×10 -3 cm3.

[0045] In some embodiments, the areal density of the negative electrode film layer is 0.002 to 0.02 g / cm 2 optionally 0.006 to 0.015 g / cm 2 optionally 0.005 to 0.007 g / cm 2 Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0046] In some embodiments, the negative electrode film layer contains 80 to 99%, optionally 93 to 97%, of negative electrode active material based on the weight of the negative electrode film layer. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0047] In some embodiments, the thickness of the negative electrode film layer is 0.03 to 0.24 mm. Optionally, it is 0.08 to 0.16 mm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0048] In any embodiment, the separator includes a base film and a coating provided on at least one side of the base film, and the coating includes first polymer particles and second polymer particles. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0049] In any embodiment, the number-based average diameter of the first polymer particles is larger than the number-based average diameter of the second polymer particles.

[0050] In some embodiments, the number-based average diameter of the first polymer particles is 2 to 8 μm, optionally 3 to 7 μm, and / or the number-based average diameter of the second polymer particles is 50 to 800 nm, optionally 100 to 600 nm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0051] In some embodiments, the content of the first polymer particles is 15% or less based on the weight of the coating, and / or the content of the second polymer particles is 30% or less based on the weight of the coating. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0052] In some embodiments, the first polymer particles include at least one of a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of an olefin monomer unit, a homopolymer or copolymer of an unsaturated nitrile monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an imide-based monomer unit, and a modified compound of each of the above homopolymers or copolymers, and / or the second polymer particles include at least one of a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, and a modified compound of the above homopolymers or copolymers. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0053] In some embodiments, in the coating, the first polymer particles can include one or more of a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of an olefin monomer unit, a homopolymer or copolymer of an unsaturated nitrile monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an imide-based monomer unit, and a modified compound of each of the above homopolymers or copolymers.

[0054] In some embodiments, the fluoroalkenyl monomer unit can be selected from one or more of difluoroethylene, vinylidene fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene.

[0055] In some embodiments, the olefin monomer unit can be selected from one or more of ethylene, propylene, butadiene, isoprene, and the like.

[0056] In some embodiments, the unsaturated nitrile monomer unit can be selected from one or more of acrylonitrile, methacrylonitrile, and the like.

[0057] In some embodiments, the alkylene oxide monomer unit can be selected from one or more of ethylene oxide, propylene oxide, and the like.

[0058] In some embodiments, the acrylate monomer unit can be selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, butyl (meth)acrylate, isooctyl (meth)acrylate, and the like.

[0059] In some embodiments, the first polymer particles include one or more of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, polyacrylate, polymethacrylate, copolymers of different fluoroalkenyl monomer units, copolymers of fluoroalkenyl monomer units and olefin monomer units, copolymers of fluoroalkenyl monomer units and acrylic monomer units, copolymers of fluoroalkenyl monomer units and acrylate monomer units, polyvinylpyrrolidone, polyimide, polyethylene oxide (PEO), and modified compounds of the above homopolymers or polymers.

[0060] In some embodiments, the first polymer particles include one or more of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer (PADF-HFP), vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, polyvinylpyrrolidone, polyimide, polyethylene oxide (PEO), styrene-vinyl acetate-pyrrolidone copolymer, and modified compounds of the above polymers.

[0061] According to some examples, the modified compound of each homopolymer or copolymer refers to a modified compound obtained by copolymerizing a monomer unit in each homopolymer or copolymer and a monomer unit containing a specific functional group. For example, a modified compound can be obtained by copolymerizing a fluoroalkenyl monomer unit and a compound containing a carboxyl group-containing functional group.

[0062] In some embodiments, the number average molecular weight of the first polymer particles is 10,000 to 100,000 according to the vapor phase osmometry method.

[0063] In some embodiments, in the coating, the content of the first polymer particles is 0% to 15%, optionally 2% to 15%, and optionally 5 to 10% based on the weight of the coating. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0064] In some embodiments, the coating includes 0% to 30%, optionally 10 to 25%, and further optionally 15 to 20% of second polymer particles based on the weight of the coating. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0065] In some embodiments, the second polymer particles mainly function as a binder and can include one or more of a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, and a modified compound of each of the above homopolymers or copolymers.

[0066] In some embodiments, the second polymer particles may be one or more of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and polystyrene (PS).

[0067] In some embodiments, the number average molecular weight of the second polymer particles is 300,000 to 800,000 as determined by vapor phase osmometry.

[0068] In some embodiments, the coating further includes inorganic particles. Optionally, the volume average diameter of the inorganic particles is 0.1 to 2 μm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0069] In some embodiments, the volume average diameter D V50 of the inorganic particles is 0.1 to 2 μm, optionally 0.3 to 0.7 μm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0070] In the present application, the volume average diameter D v50 of the inorganic particles has the meaning well-known in the art and can be measured using devices and methods known in the art. For example, referring to GB / T 19077-2016 laser diffraction particle size distribution method, it can be measured using a laser particle size analyzer (for example, Master Size 3000).

[0071] In this application, the particle size and number-based average diameter of the organic particles can be measured by devices and methods known in the art. For example, a scanning electron microscope (e.g., ZEISS Sigma 300) is used to obtain a scanning electron microscope (SEM) photograph of the separator with reference to JY / T010-1996. As an example, it can be measured by the following method. Arbitrarily collect one test sample with a length × width = 50 mm × 100 mm on the separator, randomly collect a plurality of test regions (e.g., 5) in the test sample, and at a certain magnification (e.g., 500 times when measuring the first organic particle and 1000 times when measuring the second organic particle), read the particle size of each organic particle in each test region (that is, take the distance between the two farthest points on the organic particle as the particle size of the organic particle), count the number and particle size values of the organic particles in each test region, take the arithmetic mean value of the particle sizes of the organic particles in each test region, that is, the number-based average diameter of the organic particles in the test sample. To ensure the accuracy of the test results, the above test can be repeated with a plurality of test samples (e.g., 10), and the average value of each test sample can be used as the final test result.

[0072] In some embodiments, the inorganic particles can include one or more of alumina (Al2O3), boehmite (γ-AlOOH), barium titanate (BaTiO3), titanium dioxide (TiO2), magnesium oxide (MgO), barium sulfate (BaSO4), magnesium hydroxide (Mg(OH)2), silica (SiO2), tin dioxide (SnO2), calcium oxide (CaO), zinc oxide (ZnO), zirconia (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), ceria (CeO2), strontium titanate (SrTiO3), magnesium fluoride (MgF2), clay, glass powder, boron nitride, and aluminum nitride. For example, the inorganic particles can include one or more of alumina, boehmite, barium titanate, titanium dioxide, magnesium oxide, clay, glass powder, boron nitride, and aluminum nitride. Optionally, the inorganic particles can include one or more of alumina (Al2O3) and boehmite (γ-AlOOH).

[0073] In some embodiments, in the coating, the content of the inorganic particles is 60% to 100% based on the weight of the coating.

[0074] In one embodiment, the coating includes 65 to 80% inorganic particles, 6 to 12% first polymer particles, and 15 to 20% second polymer particles based on the weight of the coating.

[0075] In some embodiments, other organic compounds can also be included in the coating, for example, polymers for improving heat resistance, dispersants, wetting agents, other types of adhesives, etc. can be included. The above other organic compounds are all non-particulate substances in the coating. This application does not particularly limit the types of the above other organic compounds, and any known materials having good improvement performance can be selected and used.

[0076] This application does not particularly limit the material of the base film, and any known base film having good chemical stability and mechanical stability can be selected and used, for example, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film may be a single-layer film or a multi-layer composite film. When the base film is a multi-layer composite film, the materials of each layer may be the same or different.

[0077] In some embodiments, measured by a scanning electron microscope, the thickness of the base film is 5 to 16 μm, and the thickness of the coating on one side is 1 to 10 μm, optionally 2 to 5 μm. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0078] In the present application, the thickness of the coating is the vertical distance from the protruding top formed by the first polymer particles to the horizontal line of the base film surface.

[0079] In some embodiments, the ratio of the thickness of the one-sided coating to the thickness of the base film is 0.1 to 1.5, optionally 0.25 to 1.0, and further optionally 0.4 to 0.85. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0080] In some embodiments, the air permeability (Gurley value) of the separator is measured according to ASTM-D726(B) for 100 mL of gas permeation and is 370 seconds or less, optionally 100 to 250 seconds, and further optionally 150 to 200 seconds. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0081] In some embodiments, the porosity of the coating is 20% to 98%, optionally 25% to 40%, and further optionally 28% to 35%. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0082] In some embodiments, the porosity of the separator is measured according to ASTM D-2873 and is 20% to 60%, optionally 30% to 40%. Thereby, the wetting ability of the separator and the capacity of the negative electrode can be further guaranteed, and the corresponding battery can be provided with good cycle performance.

[0083] Hereinafter, the secondary battery and the power consumption device according to the present application will be described with reference to the drawings as appropriate.

[0084] In one embodiment of the present application, a secondary battery is provided.

[0085] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions reciprocate between the positive electrode plate and the negative electrode plate for intercalation and deintercalation. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short - circuiting between the positive and negative electrodes and allowing ions to pass through.

[0086] Positive electrode plate 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 the positive electrode film layer contains a positive electrode active material.

[0087] As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on either one or both of the two opposing surfaces of the positive electrode current collector.

[0088] In some embodiments, the positive electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, an aluminum foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. Here, the metal materials include, but are not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer material substrates include substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0089] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery well-known in the art. By way of example, the positive electrode active material may include at least one material among lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides are lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which may be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05It may include, but is not limited to, at least one of O2) and its modified compounds. Examples of lithium-containing phosphates with an olivine structure include lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, but are not limited thereto.

[0090] In some embodiments, the positive electrode film layer may further optionally include an adhesive. As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene polymer, and a fluorine-containing acrylate resin. Based on the total weight of the positive electrode film layer, the weight ratio of the adhesive in the positive electrode film layer is 0 to 20% by weight.

[0091] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black or ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the positive electrode film layer, the weight ratio of the conductive agent in the positive electrode film layer is 0 to 20% by weight.

[0092] In some embodiments, the positive electrode plate may be manufactured by the following method. The above components for manufacturing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, where the solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s. The positive electrode slurry is applied to the surface of the positive electrode current collector and dried, and then a positive electrode plate is formed through cold pressing by a cold rolling machine. The consolidation density of the positive electrode plate is 2.0-3.6 g / cm 3 , optionally 2.3-3.5 g / cm 3 .

[0093] Negative electrode plate 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 the negative electrode film layer contains a negative electrode active material.

[0094] For example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is disposed on one or both of the two opposite surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, a copper foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material on the polymer material base. Here, the metal material includes, but is not limited to, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc., and the polymer material base is a base such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0096] In some embodiments, the negative electrode active material may adopt a negative electrode active material for batteries well known in the art. By way of example, the negative electrode active material may include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, this application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may be used. These negative electrode active materials may be used alone or in combination of two or more. Based on the total weight of the negative electrode film layer, the weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100% by weight.

[0097] In some embodiments, the negative electrode film layer may optionally further include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Based on the total weight of the negative electrode film layer, the weight ratio of the adhesive in the negative electrode film layer is 0 to 30% by weight.

[0098] In some embodiments, the negative electrode film layer may optionally further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, carbon black (such as acetylene black or ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the negative electrode film layer, the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight.

[0099] In some embodiments, the negative electrode film layer may optionally further contain other auxiliaries, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). Based on the total weight of the negative electrode film layer, the weight ratio of the other auxiliaries in the negative electrode film layer is 0 to 15% by weight.

[0100] In some embodiments, the negative electrode plate may be manufactured by the following method. The above components for manufacturing the negative electrode plate, such as the negative electrode active material, the conductive agent, the adhesive and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, where the solid content of the negative electrode slurry is 30 to 70 wt%, and the viscosity at room temperature is adjusted to 2000 to 10000 mPa·s. The obtained negative electrode slurry is applied to a negative electrode current collector, and after passing through a drying process, it is subjected to cold pressing, for example, rolling, to obtain a negative electrode plate. The consolidation density of the negative electrode plate is 0.5 to 2.0 g / m 3 is.

[0101] The mass M of the negative electrode active material in the negative electrode film layer per unit area can be obtained by weighing with a standard balance.

[0102] The thickness T of the negative electrode film layer can be obtained by measuring with a micrometer. For example, a micrometer with the product number Mitutoyo 293 - 100 and an accuracy of 0.1 μm may be used for measurement. It should be noted that the thickness of the negative electrode film layer described in the present invention refers to the thickness of the negative electrode film layer in the negative electrode plate for battery assembly after consolidation by cold pressing.

[0103] Electrolyte The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The present application does not specifically limit the type of the electrolyte, and it can be selected according to the needs. For example, the electrolyte may be liquid, gel-like or all-solid.

[0104] In some embodiments, the electrolyte employs an electrolytic solution. The electrolytic solution contains an electrolyte salt and a solvent.

[0105] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), 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 (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP). The concentration of the electrolyte salt is generally 0.5 to 5 mol / L.

[0106] In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), 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), 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), and ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0107] In some embodiments, the electrolyte solution may optionally further contain an additive. For example, the additive may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some performances of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, and the like.

[0108] Separator In some embodiments, the secondary battery further includes the separator described in the first aspect of the present application.

[0109] In some embodiments, the thickness of the separator is 5 to 40 μm, optionally 7 to 20 μm.

[0110] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator may be used to manufacture an electrode assembly by a winding process or a lamination process.

[0111] In some embodiments, the secondary battery may include an exterior body. The exterior body may be used to package the electrode assembly and the electrolyte.

[0112] In some embodiments, the exterior body of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, a steel case, etc. The exterior body of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0113] The present application is not particularly limited to the shape of the secondary battery, and it may be cylindrical, square, or any other arbitrary shape. For example, FIG. 1 shows a secondary battery 5 having a square structure as an example.

[0114] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form an accommodation cavity. The case 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can close the accommodation cavity by covering the opening. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodation cavity. The electrolytic solution infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to the actual specific requirements.

[0115] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0116] In the battery module, a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module. Of course, they may be arranged according to any other method. Further, the plurality of secondary batteries 5 may be fixed with a fastener.

[0117] Optionally, the battery module may further include a housing having an accommodation space, and a plurality of secondary batteries 5 are accommodated in the accommodation space.

[0118] In some embodiments, the above battery module may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0119] The battery pack may include a battery box and a plurality of battery modules installed in the battery box. The battery box includes an upper housing and a lower housing, and the upper housing is provided to cover the lower housing and can form a sealed space for accommodating the battery modules. The plurality of battery modules may be arranged in the battery box according to an arbitrary method.

[0120] Furthermore, the present application further provides a power consumption device, which includes at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit of the power consumption device. The power consumption device may include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, and satellites, energy storage systems, etc.

[0121] As the power consumption device, a secondary battery, battery module, or battery pack can be selected according to the requirements in its use.

[0122] Figure 3 shows an example of a power consumption device. The power consumption device is, for example, a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements for high power and high energy density of the secondary battery of the power consumption device, a battery pack or a battery module can be adopted.

[0123] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Generally, weight reduction is required for such a device, and a secondary battery can be adopted as the power source.

[0124] Embodiment To more clearly illustrate the technical problems, technical solutions, and beneficial effects to be solved by this application, the following will further elaborate on this application in conjunction with examples and drawings. Obviously, the described examples are only some examples of this application, not all examples. The description of at least one of the following exemplary examples is for illustrative purposes only and not a limitation on this application and its applications. Based on the examples of this application, all other examples obtained without the need for creative efforts by those skilled in the art shall fall within the protection scope of this application.

[0125] In the examples, when specific technologies or conditions are not specified, they are carried out according to the technologies or conditions described in the literature of the technical field or the product handling instructions. For the reagents or instruments used, those not specified by the manufacturer are all common products that can be purchased commercially.

[0126] I. Examples Example 1 1) Manufacture of the positive electrode plate The positive electrode active material NCM811, conductive carbon black SP, and adhesive PVDF are dispersed and uniformly mixed in the solvent NMP at a weight ratio of 98:1:1 to obtain a positive electrode slurry, and its solid content is 75%. The positive electrode slurry is uniformly coated on the aluminum foil of the positive electrode current collector, and after drying and cold pressing, a positive electrode plate is obtained, and its coating amount per unit area is 0.39 g / 1540.25 mm 2 is.

[0127] 2) Manufacture of the negative electrode plate The negative electrode active material (graphite and silicon monoxide SiO), thickener sodium carboxymethyl cellulose, adhesive styrene butadiene rubber, and conductive agent acetylene black are mixed according to a mass ratio of 96.5:1:1:1, deionized water is added, and a negative electrode slurry is obtained by the action of a vacuum stirrer. The solid content is 55%. Here, silicon monoxide SiO accounts for 5% by weight in the negative electrode active material. The negative electrode slurry is uniformly coated on a copper foil. After drying the copper foil at room temperature, it is transferred to a drying oven at 120 °C and dried for 1 h, and then through cold pressing and slitting processes, a negative electrode plate is obtained. The coating amount per unit area is 0.2 g / 1540.25 mm 2 is obtained. The thickness of the negative electrode film layer is 0.158 mm.

[0128] 3) Manufacturing of the separator (1) Provide a PE substrate. For example, the thickness of the substrate is 7 μm and the porosity is 37%. (2) Prepare a coating slurry. Alumina of inorganic particles (Al2O3, Dv50 is 500 nm), sodium carboxymethyl cellulose (CMC-Na) as a dispersant, and organosilicon-modified polyether as a wetting agent are uniformly mixed in deionized water according to a weight ratio of 98:1:1 to obtain a coating slurry with a solid content of 38% (by weight).

[0129] (3) Coat the coating slurry prepared in step (2) on one side surface of the PE substrate with a coater, and obtain a separator through processes such as drying and slitting. Here, the number of lines of the gravure roll of the coater is 125 LPI, the coating speed is 50 m / min, the coating line speed ratio is 1.15, the drying temperature is 50 °C, and the drying time is 25 s. The single-sided coating weight per unit area of the separator is 2.3 g / m 2 is obtained.

[0130] 4) Manufacturing of the electrolyte The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Here, the volume ratio of EC, EMC, and DEC is 20:20:60. In a glove box with an argon gas atmosphere having a water content <10 ppm, sufficiently dried lithium salt LiPF6 was dissolved in the organic solvent and uniformly mixed to obtain an electrolytic solution. Here, the concentration of the lithium salt is 1 mol / L.

[0131] 5) Manufacture of the battery The positive electrode plate, the separator, and the negative electrode plate were laminated in order, and the separator was positioned between the positive and negative electrode plates to perform an isolation function. After winding into a rectangular bare cell, an aluminum plastic film was inserted, and after baking at 80°C to remove moisture, 63 g of the corresponding non-aqueous electrolytic solution was injected and sealed. Through processes such as standing, hot and cold pressing, forming, clamping, and capacity sorting, a finished battery with a capacity of 35 Ah was obtained.

[0132] Examples 2 to 8 Except for changing the thickness of the base film of the separator, the surface density of the negative electrode, and the thickness of the separator coating respectively, the manufacturing steps of Example 1 were repeated. Details are shown in Table 1.

[0133] Example 9 In step (2) of manufacturing the separator, except that the weight ratio of alumina (Al2O3, Dv50 is 500 nm) as inorganic particles, styrene-vinyl acetate-pyrrolidone polymer (number average molecular weight is 80,000) as the first polymer particles, sodium carboxymethyl cellulose (CMC-Na) as a dispersant, and organosilicon-modified polyether as a wetting agent is 90:8:1:1, the manufacturing steps of Example 3 were repeated.

[0134] Example 10 3) In step (2) of separator production, repeat the production steps of Example 3, except that the weight ratio of alumina (Al2O3, Dv50 is 500 nm) as inorganic particles, styrene-vinyl acetate-pyrrolidone polymer (number average molecular weight is 80,000) as the first polymer particles, polyvinylidene fluoride (number average molecular weight is 500,000) as the second polymer particles, carboxymethyl cellulose sodium (CMC-Na) as the dispersant, and organosilicon-modified polyether as the wetting agent is 75:8:15:1:1.

[0135] Example 11 3) In step (2) of separator production, repeat the production steps of Example 3, except that the weight ratio of alumina (Al2O3, Dv50 is 500 nm) as inorganic particles, styrene-vinyl acetate-pyrrolidone polymer (number average molecular weight is 80,000) as the first polymer particles, polyvinylidene fluoride (number average molecular weight is 500,000) as the second polymer particles, carboxymethyl cellulose sodium (CMC-Na) as the dispersant, and organosilicon-modified polyether as the wetting agent is 68:10:20:1:1.

[0136] Example 12 3) In step (2) of separator production, repeat the production steps of Example 3, except that the weight ratio of alumina (Al2O3, Dv50 is 500 nm) as inorganic particles, polyvinylidene fluoride (number average molecular weight is 500,000) as the second polymer particles, carboxymethyl cellulose sodium (CMC-Na) as the dispersant, and organosilicon-modified polyether as the wetting agent is 78:20:1:1.

[0137] Comparative Example 1: The V / C value is higher than the protection scope of the present invention 1) The coating amount per unit area of the positive electrode plate is 0.164 g / 1540.25 mm2, 2) The coating amount per unit area of the negative electrode plate is 0.084 g / 1540.25 mm2, 3) The thickness of the separator used in step (1) of separator production is 12 μm, and the one-sided coating weight per unit area of the separator in step (3) is 8 g / m 2 Repeat the production steps of Example 1, except for this.

[0138] Comparative Example 2 1) The coating amount per unit area of the positive electrode plate is 0.57 g / 1540.25 mm 2 and 2) the coating amount per unit area of the negative electrode plate is 0.29 g / 1540.25 mm 2 and 3) the thickness of the separator used in step (1) of separator production is 5 μm, and the inorganic particles alumina (Al2O3, Dv50 is 500 nm), the first polymer particles styrene-vinyl acetate-pyrrolidone polymer (number average molecular weight is 80,000), the second polymer particles polyvinylidene fluoride (number average molecular weight is 500,000), the dispersant sodium carboxymethyl cellulose (CMC-Na), and the wetting agent organosilicon-modified polyether are in a weight ratio of 94:2:2:1:1. Repeat the manufacturing steps of Example 10 except for this.

[0139] Summarize the product parameters of each example and comparative example in Table 1.

[0140]

Table 1

[0141] II. Performance Test 1. Cycle Performance Test Put the battery into an oven at 25°C and let it stand for 2 h, then conduct a charge-discharge test. Charge at a constant current of 0.5C until 4.25V, then continue charging at a constant voltage. Cut off after the charging current is less than 0.05C, interrupt for 30 minutes, discharge at a constant current of 0.5C until 2.5V, interrupt for 30 minutes, and record the corresponding discharge capacity as the initial discharge capacity. The above is regarded as one charge-discharge cycle of the battery. Repeat until the battery capacity decays to 80% of the initial value, and record the number of cycles.

[0142] 2. Test Method for Capacity C per Unit Area of the Negative Electrode Film Layer Fully discharge the cell, remove the negative electrode membrane from the cell in a vacuum drying environment, then immerse the electrode plate in excess DMC for more than 2 hours, take it out and dry it in a vacuum drying oven at 60 °C or higher. Punch it into wafers with a diameter of 1.4 cm (area 1.5386 cm2) in the drying environment. In the glove box, use a lithium metal sheet as the counter electrode, select the ceglard composite membrane as the separator, add the electrolyte to form a button cell, and use a LAND series battery tester to perform charge and discharge tests on the battery to obtain the capacity C of the fabricated wafer.

[0143] 3. Test method for the void volume V per unit area of the separator Cut the separator to be tested into rectangular samples with certain longitudinal and transverse dimensions. Measure and calculate the apparent volume V1 of the sample, and V1 = S×d (where S is the separator area and can be measured by length × width, the unit is cm 2 is. d is the thickness of the separator, the unit is cm and can be directly measured). Adopt the AccuPyc II1340 true density meter, refer to the measurement method of porosity in GB / T 24586-2009, utilize the helium replacement method, and in accordance with Archimedes' principle and Boyle's law (PV = nRT), accurately measure the true volume V2 of the material to be measured, and the unit is cm 3 and the void volume V = V1 - V2.

[0144] III. Test results of each example and comparative example Batteries of each example and comparative example were manufactured according to the above method, and the measurement results of each performance parameter are as shown in Table 2 below.

[0145] Table 2 Battery performance of each example and comparative example TIFF2025519615000002.tif89155

[0146] From the above examples and comparative examples, it can be seen that the secondary battery of this application has good cycle performance and the initial discharge capacity is maintained at a high level.

[0147] It should be noted that this application is not limited to the above embodiments. The above embodiments are examples, and embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of this application and exhibit the same effects 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 can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some components in the embodiments are also included within the scope of this application.

Explanation of Reference Numerals

[0148] 5. Secondary battery; 51. Case; 52. Electrode assembly; 53. Cover plate; 6. Power consumption device.

Claims

1. A secondary battery including a negative electrode plate and a separator, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. When the capacitance per unit area of the negative electrode film layer is C and the void volume per unit area of the separator is V, the secondary battery has 0.05 cm 3 / Ah ≤ V / C ≤ 0.3 cm 3 / Ah, where the unit of C is mAh and the unit of V is cm 3 3. A secondary battery, characterized in that it satisfies the above conditions.

2. 0.07 cm 3 / Ah ≤ V / C ≤ 0.25 cm 3 / Ah, and optionally, 0.08 cm 3 / Ah ≤ V / C ≤ 0.2 cm 3 The secondary battery according to claim 1, characterized in that it is / Ah

3. The secondary battery according to claim 1 or 2, wherein C is 2 to 8 mAh, optionally 2.3 to 5.5 mAh, and further optionally 2.3 to 5.0 mAh.

4. V is 2 × 10 -4 to 20 × 10 -4 cm 3 and optionally 2 × 10 -4 to 15 × 10 -4 cm 3 and further optionally 4 × 10 -4 to 10 × 10 -4 cm 3 The secondary battery according to any one of claims 1 to 3, characterized in that it is so.

5. The areal density of the negative electrode film layer is 0.002 g / cm 2 to 0.02 g / cm 2 and optionally 0.006 to 0.015 g / cm 2 and further optionally 0.005 to 0.007 g / cm 2 The secondary battery according to any one of claims 1 to 4, characterized in that it is so.

6. The secondary battery according to any one of claims 1 to 5, wherein the thickness of the negative electrode film layer is 0.03 to 0.24 mm, and optionally 0.08 to 0.16 mm.

7. The secondary battery according to any one of claims 1 to 6, wherein the separator includes a base film and a coating provided on at least one side of the base film, and the coating includes first polymer particles and second polymer particles.

8. The secondary battery according to claim 7, wherein the number-based average diameter of the first polymer particles is larger than the number-based average diameter of the second polymer particles.

9. The secondary battery according to claim 7 or 8, wherein the number-based average diameter of the first polymer particles is 2 to 8 μm, optionally 3 to 7 μm, and / or the number-based average diameter of the second polymer particles is 50 to 800 nm, optionally 100 to 600 nm.

10. The secondary battery according to any one of claims 7 to 9, wherein the content of the first polymer particles is 15% or less based on the weight of the coating, and / or the content of the second polymer particles is 30% or less based on the weight of the coating.

11. The first polymer particles contain at least one of a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of an olefin monomer unit, a homopolymer or copolymer of an unsaturated nitrile monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an imide-based monomer unit, and a modified compound of each of the above homopolymers or copolymers, and / or the second polymer particles contain at least one of a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of a fluoroalkenyl monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, and a modified compound of the above homopolymers or copolymers. The secondary battery according to any one of claims 7 to 10, characterized in that.

12. The coating further contains inorganic particles, and optionally, the volume average diameter of the inorganic particles is 0.1 to 2 μm. The secondary battery according to any one of claims 7 to 11, characterized in that.

13. The thickness of the base film is 5 to 16 μm, and / or the thickness of the coating is 1 to 5 μm. The secondary battery according to any one of claims 7 to 12, characterized in that.

14. The ratio of the thickness of the coating on one side to the thickness of the base film is 0.1 to 1.

5. The secondary battery according to any one of claims 7 to 13, characterized in that.

15. The air permeability of the separator is 370 s or less, and optionally 100 to 250 s. The secondary battery according to any one of claims 1 to 14, characterized in that.

16. The porosity of the separator is 20% to 60%. The secondary battery according to any one of claims 1 to 15, characterized in that.

17. A power consumption device, comprising the secondary battery according to any one of claims 1 to 16. The power consumption device is characterized in that.

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