Electrode assembly, secondary battery, battery module, battery pack, and electric device including the same

Abstract

An electrode assembly (52) and a secondary battery (5), a battery module (4), a battery pack (1), and an electrical device comprising the electrode assembly (52) are provided. The electrode assembly (52) includes an aqueous positive electrode and a negative electrode. The aqueous positive electrode includes a positive current collector (101) and a positive electrode film (102) on at least one surface of the positive current collector (101), the positive electrode film (102) including a positive active material. The negative electrode includes a negative current collector and a negative electrode film on at least one surface of the negative current collector, the negative electrode film including a negative active material. At least a portion of the surface of the aqueous positive electrode is provided with a plurality of first micropores, satisfying: 0.001% ≤ (S12×H12×D1) / (S11×C1×H11) ≤ 1%. At least a portion of the surface of the negative electrode is provided with a plurality of second micropores, satisfying: 0 < (S22×H22×D2) / (S21×C2×H21) ≤ 2.5%.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an electrode assembly and a secondary battery, battery module, battery pack and power-consuming device containing the same. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the application and promotion of secondary batteries, their cost and environmental pollution issues have received increasing attention. The positive electrode is one of the key factors determining the performance of a secondary battery. The solvents used in existing positive electrode slurries are usually oil-based solvents, such as N-methylpyrrolidone (NMP). However, NMP has drawbacks such as high usage, volatility, difficulty in recycling, high toxicity, and high cost, which not only cause serious environmental pollution but also harm human health. Aqueous positive electrode slurries using water as a solvent have attracted increasing attention from researchers due to their low cost and environmental friendliness. However, aqueous positive electrode sheets suffer from high water content and poor capacity utilization, thus limiting their practical application. Summary of the Invention

[0003] The purpose of this application is to provide an electrode assembly and a secondary battery, battery module, battery pack and power device containing the same, so that the electrode assembly using an aqueous positive electrode and the secondary battery, battery module, battery pack and power device containing the same have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.

[0004] A first aspect of this application provides an electrode assembly, including an aqueous positive electrode and a negative electrode. The aqueous positive electrode includes a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, the positive electrode film layer comprising a positive active material. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, the negative electrode film layer comprising a negative active material. At least a portion of the surface of the aqueous positive electrode is provided with a plurality of first micropores, satisfying: 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤1%, H 11 μm represents the thickness of the aqueous positive electrode sheet, H 12 μm represents the depth of the first micropore, S 11 m 2 S represents the area of ​​the positive electrode plate of the water system. 12 m 2The total area of ​​the plurality of first micropores is represented by C1g / cc, the compaction density of the aqueous positive electrode sheet is represented by D1μm, and the volume average particle size Dv50 of the positive electrode active material is represented by D1μm. The negative electrode sheet has at least a portion of its surface provided with a plurality of second micropores, and satisfies: 0 < (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.5%, H 21 μm represents the thickness of the negative electrode sheet, H 22 μm represents the depth of the second micropore, S 21 m 2 S represents the area of ​​the negative electrode sheet. 22 m 2 C2g / cc represents the total area of ​​the plurality of second micropores, C2g / cc represents the compaction density of the negative electrode sheet, and D2μm represents the volume average particle size Dv50 of the negative electrode active material.

[0005] In the electrode assembly of this application, the aqueous positive electrode sheet satisfies 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤1%, negative electrode plate satisfies 0<(S) 22 ×H 22 ×D2) / (S 21 ×C2×H 21 With a moisture content of ≤2.5%, the electrode assembly can have low moisture content, high electrolyte wetting rate and high drying rate. When applied to secondary batteries, it can enable secondary batteries to have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.

[0006] In any embodiment of this application, 0.05% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 0.15% ≤ 0.5%; optionally, 0.15% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ≤0.25%.

[0007] (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11Within the aforementioned range, the electrode assembly can possess low surface impedance and good interfacial properties, thereby enabling secondary batteries using this electrode assembly to exhibit excellent electrochemical performance, such as high cycle stability, high capacity utilization, and low internal resistance. Furthermore, (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 Within the above range, the aqueous positive electrode sheet can also maintain good mechanical properties.

[0008] In any embodiment of this application, 0.2% ≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.0%; optionally, 0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ≤1.0%.

[0009] (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 Within the aforementioned range, the negative electrode not only possesses a high electrolyte wetting rate but also exhibits low surface impedance and excellent interfacial properties. Therefore, secondary batteries using the electrode assembly of this application can possess high cycle stability, high capacity utilization, and low internal resistance. Furthermore, (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 Within the above range, the negative electrode sheet can also maintain good mechanical properties.

[0010] In any embodiment of this application, 0 < S 12 / S 11 ≤2%, optionally, 0.4% ≤S 12 / S 11 ≤0.6%.

[0011] When the ratio of the total area of ​​the multiple first micropores to the area of ​​the aqueous positive electrode is within the above range, the aqueous positive electrode can possess good mechanical properties and a suitable porosity, which is conducive to water drainage and electrolyte wetting. In addition, it can also enable the aqueous positive electrode to have suitable electron conduction channels and active ion transport channels.

[0012] In any embodiment of this application, 30% ≤ H 12 / H 11≤100%, optionally, 60% ≤H 12 / H 11 ≤100%.

[0013] The ratio of the depth of the first micropore to the thickness of the aqueous positive electrode sheet is within the above range, which not only ensures that the aqueous positive electrode sheet has a high drying rate and a high electrolyte wetting rate, but also ensures that the aqueous positive electrode sheet has good mechanical properties.

[0014] In any embodiment of this application, C1 is 2.0-3.0, and optionally 2.3-2.7.

[0015] By controlling the compaction density of the aqueous positive electrode sheet within a suitable range, the positive active material particles in the positive electrode film layer can be brought into close contact, increasing the content of positive active material per unit volume, thereby improving the energy density of the secondary battery.

[0016] In any embodiment of this application, D1 is 0.5-1.5, and optionally 0.8-1.3.

[0017] When the volume average particle size Dv50 of the positive electrode active material is within the above range, the diffusion path of active ions can be shortened, thereby further improving the energy density, cycle performance and rate performance of the secondary battery.

[0018] In any embodiment of this application, 0 < S 22 / S 21 ≤0.2%, optionally, 0.04% ≤S 22 / S 21 ≤0.06%.

[0019] When the ratio of the total area of ​​the multiple second micropores to the area of ​​the negative electrode sheet is within the above range, the negative electrode sheet can have good mechanical properties, as well as suitable porosity and high capacity. This is beneficial to improving the electrolyte wetting rate and capacity utilization of the electrode assembly. In addition, it can also enable the negative electrode sheet to have suitable electron conduction channels and active ion transport channels.

[0020] In any embodiment of this application, 30% ≤ H 22 / H 21 ≤100%, optionally, 60% ≤H 22 / H 21 ≤100%.

[0021] The ratio of the depth of the second micropore to the thickness of the negative electrode sheet is within the above range, which not only ensures that the negative electrode sheet has a high electrolyte wetting rate, but also ensures that the negative electrode sheet has good mechanical properties.

[0022] In any embodiment of this application, C2 is 1.2-2.0, and optionally 1.4-1.8.

[0023] By controlling the compaction density of the negative electrode sheet within a suitable range, the particles of the negative electrode active material in the negative electrode film layer can be in close contact, increasing the content of negative electrode active material per unit volume, thereby improving the energy density of the secondary battery.

[0024] In any embodiment of this application, D2 is 12-20, and optionally 15-19.

[0025] When the volume average particle size Dv50 of the negative electrode active material is within the above range, the diffusion path of active ions can be shortened, thereby further improving the energy density, cycle performance and rate performance of the secondary battery.

[0026] In any embodiment of this application, the electrode assembly satisfies: 0.1 ≤ A / B ≤ 1.0, optionally, 0.25 ≤ A / B ≤ 0.50, where A represents (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 B represents (S) 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ).

[0027] When the A / B value is within the above range, the electrolyte wetting rate of the electrode assembly can be further improved, and it is more conducive to the rapid removal of residual moisture from the electrode assembly during the drying process, thereby enabling the secondary battery to have low impedance, high energy density and high cycle capacity retention.

[0028] In any embodiment of this application, the electrode assembly satisfies: S3 / S 22 ≥5%, optionally, 8% ≤ S3 / S 22 ≤70%, S3m 2 This represents the overlapping area of ​​the plurality of first micropores and the plurality of second micropores.

[0029] The overlapping area of ​​the first micropore on the surface of the aqueous positive electrode and the second micropore on the surface of the negative electrode is within the aforementioned range, which facilitates the formation of channels between the first and second micropores and the micropores in the separator. This promotes the rapid removal of residual moisture from the electrode assembly and increases the electrolyte wetting rate of the electrode assembly. Therefore, the electrode assembly of this application, when applied to a secondary battery, enables the secondary battery to have low impedance, high energy density, and high cycle capacity retention.

[0030] In any embodiment of this application, the morphology of each first micropore is a regular shape or an irregular shape. Optionally, the morphology of each first micropore includes a circle, a rectangle or a square.

[0031] In any embodiment of this application, the equivalent diameter of each first micropore is 1μm-200μm, and optionally 50μm-180μm.

[0032] With the equivalent diameter of the first micropore within the aforementioned range, the aqueous positive electrode can possess excellent mechanical properties, such as high strength and good flexibility, while ensuring low moisture content, high electrolyte wetting rate, and high drying rate. Therefore, the electrode assembly exhibits a high electrolyte wetting rate and good processing performance, resulting in secondary batteries using this electrode assembly that also possess excellent electrochemical performance and high energy output.

[0033] In any embodiment of this application, the center-to-center distance between adjacent first micropores is 1mm-10mm.

[0034] The center-to-center distance between adjacent first micropores is within the aforementioned range, allowing the first micropores to be appropriately distributed on the surface of the aqueous positive electrode sheet. This prevents the distribution of the first micropores from becoming too dense, thus maintaining good mechanical properties of the aqueous positive electrode sheet.

[0035] In any embodiment of this application, the plurality of first micropores are arranged in an array.

[0036] In any embodiment of this application, the morphology of each second micropore is a regular shape or an irregular shape. Optionally, the morphology of each second micropore includes a circle, a rectangle or a square.

[0037] In any embodiment of this application, the equivalent diameter of each second micropore is 1μm-200μm, and optionally 50μm-150μm.

[0038] The equivalent diameter of the second micropore is within the aforementioned range, which ensures that the negative electrode sheet has a high electrolyte wetting rate while also giving it good mechanical properties, such as high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte wetting rate and good processing performance, and consequently, the secondary battery using this electrode assembly can also have good electrochemical performance and high energy production.

[0039] In any embodiment of this application, the center-to-center distance between adjacent second micropores is 1mm-10mm.

[0040] The center-to-center distance between adjacent second micropores is within the aforementioned range, allowing the second micropores to be appropriately distributed on the surface of the negative electrode. This prevents the second micropores from being too densely distributed, thus maintaining good mechanical properties of the negative electrode.

[0041] In any embodiment of this application, the plurality of second micropores are arranged in an array.

[0042] In any embodiment of this application, the positive electrode film layer further includes one or more of an aqueous adhesive and a conductive agent.

[0043] In any embodiment of this application, the aqueous adhesive includes methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginate and its salts, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymer and its derivatives or mixtures thereof.

[0044] In any embodiment of this application, the aqueous adhesive comprises a compound mixture of xanthan gum and polyethyleneimine. Optionally, the mass ratio of xanthan gum to polyethyleneimine is 2:1 to 0.2:2.8. Optionally, the number average molecular weight of the xanthan gum is 300,000 to 2,000,000. Optionally, the number average molecular weight of the polyethyleneimine is 2,000 to 50,000.

[0045] In any embodiment of this application, the aqueous adhesive comprises a compound mixture of acrylonitrile-acrylic acid copolymer and polyethyleneimine. Optionally, the mass ratio of the acrylonitrile-acrylic acid copolymer to the polyethyleneimine is 2:1 to 0.2:2.8. Optionally, the number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300,000 to 2,000,000. Optionally, the number average molecular weight of the polyethyleneimine is 2,000 to 70,000.

[0046] In any embodiment of this application, the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0047] A second aspect of this application provides a secondary battery that includes the electrode assembly of the first aspect of this application.

[0048] A third aspect of this application provides a battery module that includes the secondary battery of the second aspect of this application.

[0049] The fourth aspect of this application provides a battery pack, which includes one of the secondary battery of the second aspect of this application and the battery module of the third aspect.

[0050] The fifth aspect of this application provides an electrical device that includes at least one of the secondary battery of the second aspect of this application, the battery module of the third aspect, and the battery pack of the fourth aspect.

[0051] The secondary battery of this application features low moisture content, high electrolyte wetting rate, and high drying rate. It also boasts high energy density, good cycle performance, low internal resistance, low cost, and environmental friendliness. The battery modules, battery packs, and power devices of this application include the secondary battery provided herein and therefore possess at least the same advantages as the described secondary battery. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0053] Figure 1 This is a cross-sectional schematic diagram of one embodiment of the water-based positive electrode sheet of this application.

[0054] Figure 2 This is a cross-sectional schematic diagram of another embodiment of the water-based positive electrode sheet of this application.

[0055] Figure 3 This is a schematic diagram of one embodiment of the secondary battery of this application.

[0056] Figure 4 yes Figure 3 An exploded view of the implementation method of the secondary battery.

[0057] Figure 5 This is a schematic diagram of one embodiment of the battery module of this application.

[0058] Figure 6 This is a schematic diagram of one embodiment of the battery pack of this application.

[0059] Figure 7 yes Figure 6 An exploded view of an embodiment of the battery pack shown.

[0060] Figure 8 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0061] The accompanying drawings are not necessarily drawn to scale. The reference numerals are explained as follows: 101 Positive current collector, 102 Positive electrode film, 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0062] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrode assembly, secondary battery, battery module, battery pack, and power-consuming device included herein. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a thorough understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0063] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0065] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0066] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0067] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0068] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0069] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0070] In this application, the term "about" is used to describe and indicate small variations, and when used in conjunction with numerical values, the term may refer to a range of variations less than or equal to ±10% of the numerical value.

[0071] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0072] In this description, unless otherwise stated, “multiple,” “many,” or “more” means two, two, or more than two.

[0073] With the application and promotion of secondary batteries, their cost and environmental pollution issues have received increasing attention. Aqueous cathode slurries using water as a solvent have attracted growing attention from researchers due to their low cost and environmental friendliness. However, the inventors have discovered that aqueous cathode slurries often use binders with hydrophilic groups, and these hydrophilic groups and the solvent water can significantly affect the performance of secondary batteries. Aqueous cathode sheets prepared using aqueous cathode slurries retain some moisture, which is difficult to remove during the drying process. Therefore, when current aqueous cathode sheets are used in secondary batteries, the residual moisture not only affects the wetting performance of the cathode sheet but also causes side reactions with the electrolyte and electrode active materials inside the battery, leading to increased irreversible loss of active ions, reduced battery energy density, and excessively rapid capacity decay. In addition, it can also cause battery swelling and increased self-discharge.

[0074] Currently, most related technologies reduce the moisture content of aqueous cathode sheets by adjusting the formulation of the cathode slurry or the preparation process of the cathode sheet. Adjusting the cathode slurry formulation, for example, by adding anhydrous ethanol to the aqueous cathode slurry, can reduce the residual moisture content in the aqueous cathode sheet to some extent. However, the addition of ethanol to the aqueous cathode slurry introduces active hydroxyl groups that affect the interfacial performance of the secondary battery, leading to phenomena such as lithium plating and interfacial black spots. This not only reduces the cycle performance of the secondary battery but also introduces safety hazards. Adjusting the cathode sheet preparation process, such as controlling the solid content of the aqueous cathode slurry and using a combination of hot coating, cold pressing, and vacuum baking to prepare the cathode sheet, can effectively accelerate moisture evaporation and reduce residual moisture in the aqueous cathode sheet, but it correspondingly increases the preparation cost of the aqueous cathode sheet and reduces the production capacity of the secondary battery.

[0075] After in-depth consideration, the inventors designed an electrode assembly based on its structure. This electrode assembly has low moisture content, high electrolyte wetting rate and high drying rate. It also features high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.

[0076] Electrode assembly

[0077] The first aspect of this application provides an electrode assembly, which includes an aqueous positive electrode and a negative electrode.

[0078] The aqueous positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material. At least a portion of the surface of the aqueous positive electrode sheet has a plurality of first micropores, and satisfies: 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11×C1×H 11 )≤1%, H 11 μm represents the thickness of the aqueous positive electrode sheet, H 12 μm represents the depth of the first micropore, S 11 m 2 S represents the area of ​​the positive electrode plate of the water system. 12 m 2 C1g / cc represents the total area of ​​the plurality of first micropores, C1g / cc represents the compaction density of the aqueous positive electrode sheet, and D1μm represents the volume average particle size Dv50 of the positive electrode active material.

[0079] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material. At least a portion of the surface of the negative electrode sheet has a plurality of second micropores, and satisfies: 0 < (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.5%, H 21 μm represents the thickness of the negative electrode sheet, H 22 μm represents the depth of the second micropore, S 21 m 2 S represents the area of ​​the negative electrode sheet. 22 m 2 C2g / cc represents the total area of ​​the plurality of second micropores, C2g / cc represents the compaction density of the negative electrode sheet, and D2μm represents the volume average particle size Dv50 of the negative electrode active material.

[0080] Not intending to be limited by any theory or explanation, the inventors unexpectedly discovered that at least a portion of the surface of the aqueous positive electrode sheet has multiple first micropores, and that in the aqueous positive electrode sheet (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 When the value of is within the aforementioned range, residual water in the aqueous positive electrode sheet can be easily removed, thereby improving the interfacial performance of the electrode assembly and reducing the risks of electrode assembly swelling, self-discharge, and corrosion. Furthermore, the presence of the aforementioned first micropores on the surface of the aqueous positive electrode sheet increases its porosity, thus facilitating a faster electrolyte wetting rate. It also significantly shortens the lithium-ion diffusion distance, effectively reducing lithium-ion mass transfer resistance and lowering the battery's internal resistance. Therefore, the electrode assembly of this application, when applied to secondary batteries, not only reduces the risks of swelling, self-discharge, and corrosion in secondary batteries but also improves the energy density, cycle performance, and rate performance of secondary batteries.

[0081] Furthermore, not intended to be limited to any theory or explanation, in the electrode assembly of this application, at least a portion of the surface of the negative electrode sheet is provided with a plurality of second micropores, and in the negative electrode sheet (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 Within the aforementioned range, the value of [value] not only further enhances the lithium-ion transport capacity of the negative electrode and increases the electrolyte wetting rate, but also facilitates the capacity utilization of the positive electrode active material. Therefore, secondary batteries using the electrode assembly of this application possess excellent electrochemical performance and high energy density.

[0082] The inventors discovered that (S) 12 ×H 12 ×D1) / (S 11 ×C1×H 11 When the percentage is less than 0.001%, the aqueous positive electrode sheet exhibits at least one of the following conditions: the ratio S of the total area of ​​the plurality of first micropores to the area of ​​the aqueous positive electrode sheet is less than 0.001%. 12 / S 11 The ratio H of the depth of the smaller, first micropore to the thickness of the aqueous positive electrode sheet. 12 / H 11 The smaller particle size (D1) of the positive electrode active material and the larger compaction density (C1) of the aqueous positive electrode sheet result in smaller spacing and tighter contact between the positive electrode active material particles. This leads to fewer active ion transport channels, higher internal resistance in the secondary battery, and poor electrolyte wetting performance, which is detrimental to battery capacity. Furthermore, the limited moisture drainage channels in the aqueous positive electrode sheet make it difficult for moisture to drain quickly during the drying process, resulting in higher residual moisture levels and a higher risk of gas expansion, self-discharge, and corrosion in the secondary battery.

[0083] The inventors discovered that (S) 12 ×H 12 ×D1) / (S 11 ×C1×H 11 When the percentage is greater than 1%, the aqueous positive electrode sheet exhibits at least one of the following conditions: the ratio S of the total area of ​​the plurality of first micropores to the area of ​​the aqueous positive electrode sheet is greater than 1%. 12 / S 11 The ratio H of the depth of the larger, first micropore to the thickness of the aqueous positive electrode sheet. 12 / H 11 The positive electrode active material has a larger volume average particle size D1, while the aqueous positive electrode sheet has a smaller compaction density C1. As a result, the energy density of the secondary battery decreases significantly.

[0084] The inventors discovered that (S) 22 ×H 22 ×D2) / (S21 ×C2×H 21 When the ratio S is greater than 2.5%, the negative electrode sheet has at least one of the following conditions: the ratio S of the total area of ​​the plurality of second micropores to the area of ​​the negative electrode sheet is greater than 2.5%. 22 / S 21 The ratio H of the depth of the larger, second micropore to the thickness of the negative electrode sheet. 22 / H 21 The negative electrode active material has a larger volume average particle size D2 and a smaller compaction density C2. As a result, the energy density of the secondary battery decreases significantly.

[0085] In the electrode assembly of this application, the aqueous positive electrode sheet satisfies 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤1%, negative electrode plate satisfies 0<(S) 22 ×H 22 ×D2) / (S 21 ×C2×H 21 With a moisture content of ≤2.5%, the electrode assembly can have low moisture content, high electrolyte wetting rate and high drying rate. When applied to secondary batteries, it can enable secondary batteries to have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.

[0086] Possible reasons include: First, the surfaces of both the aqueous positive and negative electrode sheets are provided with micropores, allowing the electrolyte to wet the electrode assembly not only horizontally along the electrode / separator but also vertically through the network of micropores in the electrode sheet and the separator during the secondary battery assembly process. Second, the micropores on the surfaces of both the aqueous positive and negative electrode sheets allow residual moisture in the electrodes to be quickly discharged to the outside of the electrode assembly during the drying process, thereby further reducing the moisture content of the electrode assembly. Third, a reasonable combination of micropores on the electrode surface, electrode compaction density, and active material particle size ensures that both the aqueous positive and negative electrode sheets have suitable electron conduction channels and active ion transport channels.

[0087] In some embodiments, the aqueous positive electrode sheet may satisfy: 0.05% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 0.05% ≤ 0.5%, 0.05% ≤ (S) 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.45%, 0.05%≤(S 12 ×H12 ×D1) / (S 11 ×C1×H 11 )≤0.4%,0.05%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.35%,0.05%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.3%,0.05%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.25%,0.05%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.2%,0.05%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.15%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.5%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.45%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.4%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.35%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.3%,0.1%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.25%,0.1%≤(S 12 ×H 12 ×D1) / (S 11×C1×H 11 )≤0.2%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.5%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.45%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.4%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.35%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.3%,0.15%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.25%,0.2%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.5%,0.2%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.45%,0.2%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.4%,0.2%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.35%,0.2%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.3%,0.25%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11)≤0.5%, 0.25%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≤0.45% or 0.25%≤(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ≤0.4%.

[0088] Not intended to be limited to any theory or explanation, the inventors' research found that (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 Within the aforementioned range, moisture in the aqueous positive electrode sheet can be rapidly discharged to the outside of the electrode assembly during the drying process, thereby further reducing the moisture content of the positive electrode sheet and increasing the electrolyte wetting rate and drying rate of the electrode assembly. As a result, the electrode assembly can possess low surface impedance and good interfacial properties, enabling secondary batteries using this electrode assembly to exhibit excellent electrochemical performance, such as high cycle stability, high capacity utilization, and low internal resistance. Furthermore, (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 Within the aforementioned range, the aqueous positive electrode sheet can also maintain good mechanical properties. Therefore, the positive electrode sheet is less prone to deformation during the assembly and processing of the electrode assembly. Consequently, the electrode assembly not only maintains good electrochemical performance during processing and assembly but also possesses high power generation.

[0089] In some embodiments, the negative electrode may satisfy: 0.2% ≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.0%, 0.2%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.8%, 0.2%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.5%, 0.2%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.2%, 0.2%≤(S 22 ×H22 ×D2) / (S 21 ×C2×H 21 )≤1.0%,0.2%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤0.8%,0.2%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤0.5%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.0%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.8%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.5%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.2%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.0%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤0.8%,0.3%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤0.5%,0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.0%,0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.8%,0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H21 )≤1.5%, 0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.2%, 0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.0%, 0.4%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤0.8%, 0.5%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤2.0%, 0.5%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.8%, 0.5%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.5%, 0.5%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.2%, 0.5%≤(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≤1.0% or 0.5%≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ≤0.8%.

[0090] Not intended to be limited to any theory or explanation, the inventors' research found that (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 Within the aforementioned range, the negative electrode not only possesses a high electrolyte wetting rate but also exhibits low surface impedance and excellent interfacial properties. Therefore, secondary batteries using the electrode assembly of this application can possess high cycle stability, high capacity utilization, and low internal resistance. Furthermore, (S 22 ×H 22 ×D2) / (S 21 ×C2×H21 Within the aforementioned range, the negative electrode sheet can also maintain good mechanical properties. Therefore, the negative electrode sheet is less prone to deformation during the assembly and processing of the electrode assembly. Consequently, the electrode assembly not only maintains good electrochemical performance during processing and assembly but also possesses high production capacity.

[0091] In some implementations, the ratio of the total area of ​​the plurality of first micropores to the area of ​​the aqueous positive electrode sheet satisfies 0 < S 12 / S 11 ≤2%. For example, 0.1% ≤ S 12 / S 11 ≤2%, 0.1%≤S 12 / S 11 ≤1.8%, 0.1%≤S 12 / S 11 ≤1.5%, 0.1%≤S 12 / S 11 ≤1.2%, 0.1%≤S 12 / S 11 ≤1%, 0.1%≤S 12 / S 11 ≤0.8%, 0.1%≤S 12 / S 11 ≤0.6%, 0.2%≤S 12 / S 11 ≤2%, 0.2%≤S 12 / S 11 ≤1.8%, 0.2%≤S 12 / S 11 ≤1.5%, 0.2%≤S 12 / S 11 ≤1.2%, 0.2%≤S 12 / S 11 ≤1%, 0.2%≤S 12 / S 11 ≤0.8%, 0.2%≤S 12 / S 11 ≤0.6%, 0.3%≤S 12 / S 11 ≤2%, 0.3%≤S 12 / S 11 ≤1.8%, 0.3%≤S 12 / S 11 ≤1.5%, 0.3%≤S 12 / S 11 ≤1.2%, 0.3%≤S 12 / S 11 ≤1%, 0.3%≤S 12 / S 11 ≤0.8%, 0.3%≤S12 / S 11 ≤0.6%, 0.4%≤S 12 / S 11 ≤2%, 0.4%≤S 12 / S 11 ≤1.8%, 0.4%≤S 12 / S 11 ≤1.5%, 0.4%≤S 12 / S 11 ≤1.2%, 0.4%≤S 12 / S 11 ≤1%, 0.4%≤S 12 / S 11 ≤0.8%, 0.4%≤S 12 / S 11 ≤0.6%, 0.5%≤S 12 / S 11 ≤2%, 0.5%≤S 12 / S 11 ≤1.8%, 0.5%≤S 12 / S 11 ≤1.5%, 0.5%≤S 12 / S 11 ≤1.2%, 0.5%≤S 12 / S 11 ≤1%, 0.5%≤S 12 / S 11 ≤0.8% or 0.5% ≤S 12 / S 11 ≤0.6%.

[0092] Not intended to be limited by any particular theory or explanation, the ratio of the total area of ​​the multiple micropores to the area of ​​the aqueous positive electrode sheet within the aforementioned range enables the aqueous positive electrode sheet to possess good mechanical properties. This reduces the risk of irreversible deformation of the aqueous positive electrode sheet during processing, thereby increasing the productivity of the electrode assembly. Furthermore, this ratio also ensures the aqueous positive electrode sheet has suitable porosity, facilitating water drainage and electrolyte wetting. Additionally, this ratio also provides suitable electron conduction channels and active ion transport channels. Therefore, when applied to secondary batteries, this electrode assembly enables the secondary battery to exhibit high productivity, high cycle stability, high capacity utilization, and low internal resistance.

[0093] In some embodiments, the ratio of the depth of the first micropore to the thickness of the aqueous positive electrode sheet satisfies 30% ≤ H. 12 / H 11 ≤100%. For example, 30% ≤ H12 / H 11 ≤90%, 30% ≤ H 12 / H 11 ≤80%, 30% ≤ H 12 / H 11 ≤70%, 30% ≤ H 12 / H 11 ≤60%, 30% ≤ H 12 / H 11 ≤50%, 30% ≤ H 12 / H 11 ≤40%, 40% ≤ H 12 / H 11 ≤100%, 40% ≤ H 12 / H 11 ≤90%, 40% ≤ H 12 / H 11 ≤80%, 40% ≤ H 12 / H 11 ≤70%, 40% ≤ H 12 / H 11 ≤60%, 40% ≤ H 12 / H 11 ≤50%, 50% ≤ H 12 / H 11 ≤100%, 50% ≤ H 12 / H 11 ≤90%, 50% ≤ H 12 / H 11 ≤80%, 50% ≤ H 12 / H 11 ≤70%, 50% ≤ H 12 / H 11 ≤60%, 60% ≤ H 12 / H 11 ≤100%, 60% ≤ H 12 / H 11 ≤90%, 60% ≤ H 12 / H 11 ≤80%, 60% ≤ H 12 / H 11 ≤70%, 70% ≤ H 12 / H 11 ≤100%, 70% ≤ H 12 / H 11 ≤90%, 70% ≤ H 12 / H 11 ≤80%, 80% ≤ H 12 / H 11 ≤100%, 80% ≤ H 12 / H 11 ≤90% or 90% ≤ H12 / H 11 ≤100%.

[0094] In this application, the depth of the first micropore can be less than or equal to the thickness of the aqueous positive electrode sheet. When H 12 / H 11 When the value is 100%, the first micropore can be a through hole that penetrates the positive electrode sheet.

[0095] Not intended to be limited by any theory or explanation, the ratio of the depth of the first micropore to the thickness of the aqueous positive electrode sheet within the aforementioned range not only ensures a high drying rate and a high electrolyte wetting rate for the aqueous positive electrode sheet, but also guarantees good mechanical properties. Therefore, the electrode assembly of this application possesses excellent interfacial performance, low surface resistance, and high processing efficiency. When applied to secondary batteries, it enables the secondary batteries to exhibit good cycle performance, good rate performance, and high production capacity.

[0096] C1g / cc represents the compaction density of the aqueous positive electrode. In some embodiments, C1 can be 2.0-3.0, for example, C1 can be about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3.0, or within any range of the above values. In some embodiments, C1 is optionally 2.3-2.7.

[0097] By controlling the compaction density of the aqueous positive electrode sheet within a suitable range, the positive active material particles in the positive electrode film layer can be brought into close contact, increasing the content of positive active material per unit volume, thereby improving the energy density of the secondary battery.

[0098] D1μm represents the volume average particle size Dv50 of the positive electrode active material. In some embodiments, D1 can be 0.5-1.5, for example, D1 can be about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, or within any range of the above values. In some embodiments, D1 is optionally 0.8-1.3.

[0099] When the volume average particle size Dv50 of the positive electrode active material is within the aforementioned range, the diffusion path of active ions can be shortened. Therefore, the electrode assembly of this application, when applied to a secondary battery, can further improve the energy density, cycle performance, and rate performance of the secondary battery.

[0100] Furthermore, in the control electrode assembly, the ratio S of the total area of ​​multiple first micropores to the area of ​​the aqueous positive electrode sheet... 12 / S 11 The ratio H of the depth of the first micropore to the thickness of the aqueous positive electrode sheet. 12 / H 11 The compaction density C1 of the aqueous positive electrode sheet and the volume average particle size D1 of the positive electrode active material are within the above ranges, which is beneficial for controlling (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 This is within the scope of this application. Therefore, the electrode assembly of this application, when applied to a secondary battery, can not only reduce the risks of secondary battery swelling, self-discharge, and corrosion, but also improve the energy density, cycle performance, and rate performance of the secondary battery.

[0101] In some implementations, the ratio of the total area of ​​the plurality of second micropores to the area of ​​the negative electrode sheet can satisfy: 0 < S 22 / S 21 ≤0.2%. For example, 0.02% ≤S 22 / S 21 ≤0.2%, 0.02%≤S 22 / S 21 ≤0.18%, 0.02%≤S 22 / S 21 ≤0.16%, 0.02%≤S 22 / S 21 ≤0.14%, 0.02%≤S 22 / S 21 ≤0.12%, 0.02%≤S 22 / S 21 ≤0.1%, 0.02%≤S 22 / S 21 ≤0.08%, 0.02%≤S 22 / S 21 ≤0.06%, 0.02%≤S 22 / S 21 ≤0.04%, 0.04%≤S 22 / S 21 ≤0.2%, 0.04%≤S 22 / S 21 ≤0.18%, 0.04%≤S 22 / S 21 ≤0.16%, 0.04%≤S 22 / S 21 ≤0.14%, 0.04%≤S 22 / S 21 ≤0.12%, 0.04%≤S 22 / S 21 ≤0.1%, 0.04%≤S 22 / S 21 ≤0.08%, 0.04%≤S 22 / S21 ≤0.06%, 0.06%≤S 22 / S 21 ≤0.2%, 0.06%≤S 22 / S 21 ≤0.18%, 0.06%≤S 22 / S 21 ≤0.16%, 0.06%≤S 22 / S 21 ≤0.14%, 0.06%≤S 22 / S 21 ≤0.12%, 0.06%≤S 22 / S 21 ≤0.1% or 0.06% ≤S 22 / S 21 ≤0.08%.

[0102] Not intended to be limited by any particular theory or explanation, the ratio of the total area of ​​the multiple second micropores to the area of ​​the negative electrode sheet within the aforementioned range enables the negative electrode sheet to possess good mechanical properties. This reduces the risk of irreversible deformation of the negative electrode sheet during processing, thereby increasing the productivity of the electrode assembly. Furthermore, this ratio also allows the negative electrode sheet to have suitable porosity and high capacity, which is beneficial for improving the electrolyte wetting rate and capacity utilization of the electrode assembly. In addition, this ratio also enables the negative electrode sheet to possess suitable electron conduction channels and active ion transport channels. Therefore, when applied to secondary batteries, the electrode assembly enables the secondary battery to have high productivity, high cycle stability, high capacity utilization, and low internal resistance.

[0103] In some embodiments, the ratio of the depth of the second micropore to the thickness of the negative electrode sheet can satisfy: 30% ≤ H 22 / H 21 ≤100%, 30%≤H 22 / H 21 ≤90%, 30%≤H 22 / H 21 ≤80%, 30%≤H 22 / H 21 ≤70%, 30%≤H 22 / H 21 ≤60%, 40%≤H 22 / H 21 ≤100%, 40%≤H 22 / H 21 ≤90%, 40%≤H 22 / H 21 ≤80%, 40% ≤H 22 / H21 ≤70%, 40%≤H 22 / H 21 ≤60%, 50%≤H 22 / H 21 ≤100%, 50%≤H 22 / H 21 ≤90%, 50%≤H 22 / H 21 ≤80%, 50%≤H 22 / H 21 ≤70%, 60%≤H 22 / H 21 ≤100%, 60%≤H 22 / H 21 ≤90%, 60%≤H 22 / H 21 ≤80%, 70%≤H 22 / H 21 ≤100%, 70%≤H 22 / H 21 ≤90%, 70%≤H 22 / H 21 ≤80%, 80%≤H 22 / H 21 ≤100%, 80%≤H 22 / H 21 ≤90% or 90%≤H 22 / H 21 ≤100%.

[0104] In this application, the depth of the second micropore can be less than or equal to the thickness of the negative electrode sheet. When H 22 / H 21 When the value is 100%, the second micropore can be a through hole that penetrates the negative electrode sheet.

[0105] Not intended to be limited by any theory or explanation, the ratio of the depth of the second micropore to the thickness of the negative electrode sheet within the aforementioned range not only ensures a high electrolyte wetting rate for the negative electrode sheet but also guarantees good mechanical properties. Therefore, the electrode assembly of this application possesses excellent interfacial performance, low surface resistance, and high processing efficiency. When applied to secondary batteries, it enables the secondary batteries to exhibit good cycle performance, good rate performance, and high production capacity.

[0106] C2g / cc represents the compaction density of the negative electrode. In some embodiments, C2 can be 1.2-2.0, for example, C2 can be about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, or within any range of the above values. In some embodiments, C2 is optionally 1.4-1.8.

[0107] By controlling the compaction density of the negative electrode sheet within a suitable range, the particles of the negative electrode active material in the negative electrode film layer can be in close contact, increasing the content of negative electrode active material per unit volume, thereby improving the energy density of the secondary battery.

[0108] D2μm represents the volume average particle size Dv50 of the negative electrode active material. In some embodiments, D2 can be 12-20, for example, D2 can be about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, or within any range of the above values. In some embodiments, D2 may optionally be 15-19.

[0109] When the volume average particle size Dv50 of the negative electrode active material is within the aforementioned range, the diffusion path of active ions can be shortened. Therefore, the electrode assembly of this application, when applied to a secondary battery, can further improve the energy density, cycle performance, and rate performance of the secondary battery.

[0110] Furthermore, in the control electrode assembly, the ratio S of the total area of ​​multiple second micropores to the area of ​​the negative electrode sheet... 22 / S 21 The ratio H of the depth of the second micropore to the thickness of the negative electrode sheet 22 / H 21 The compaction density C2 of the negative electrode sheet and the volume average particle size D2 of the negative electrode active material are within the above ranges, which is beneficial for controlling (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 This is within the scope of this application. Therefore, the electrode assembly of this application, when applied to a secondary battery, enables the secondary battery to possess excellent electrochemical performance and high energy density.

[0111] In some embodiments, the electrode assembly may satisfy: 0.10 ≤ A / B ≤ 1.0, where A represents (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 B represents (S) 22 ×H 22 ×D2) / (S 21 ×C2×H 21For example, 0.10≤A / B≤0.75, 0.10≤A / B≤0.50, 0.10≤A / B≤0.50, 0.10≤A / B≤0.25, 0.15≤A / B≤1.0, 0.15≤A / B≤0.75, 0.15≤A / B≤0.50, 0.15≤A / B≤0.25, 0.20≤A / B≤1.0, 0.20≤A / B≤0.75, 0.20≤A / B≤0.50, 0.20≤A / B≤0. 25, 0.25≤A / B≤1.0, 0.25≤A / B≤0.75, 0.25≤A / B≤0.50, 0.30≤A / B≤1.0, 0.30≤A / B≤0.75, 0.30≤A / B≤0.50, 0.35≤A / B≤1.0, 0.35≤A / B≤0.75, 0.35≤A / B≤0.50, 0.40≤A / B≤1.0, 0.40≤A / B≤0.75 or 0.40≤A / B≤0.50.

[0112] Not intended to be limited by any theory or explanation, a value of A / B within the aforementioned range can fully leverage the advantages of both the aqueous positive and negative electrode plates, as well as their synergistic effect. This further improves the electrolyte wetting rate of the electrode assembly and facilitates the rapid removal of residual moisture during the drying process. Therefore, the electrode assembly of this application, when applied to a secondary battery, enables the secondary battery to exhibit low impedance, high energy density, and high cycle capacity retention.

[0113] In some embodiments, the electrode assembly may satisfy: S3 / S 22 ≥5%, for example, S3 / S 22 It can be approximately 5%, approximately 8%, approximately 10%, approximately 15%, approximately 20%, approximately 25%, approximately 30%, approximately 35%, approximately 40%, approximately 45%, approximately 50%, approximately 55%, approximately 60%, approximately 65%, approximately 70%, approximately 75%, approximately 80%, approximately 85%, approximately 90%, approximately 95%, approximately 100%, or within any range of the above values. Wherein, S3m 2 This represents the overlapping area of ​​the plurality of first micropores and the plurality of second micropores.

[0114] In some embodiments, the electrode assembly may satisfy: 8% ≤ S3 / S 22 ≤85%, 8%≤S3 / S 22 ≤80%, 8%≤S3 / S 22 ≤75%, 8%≤S3 / S 22 ≤70%, 15%≤S3 / S 22 ≤85%, 15%≤S3 / S 22 ≤80%, 15%≤S3 / S 22≤75%, 15%≤S3 / S 22 ≤70%, 25%≤S3 / S 22 ≤85%, 25%≤S3 / S 22 ≤80%, 25%≤S3 / S 22 ≤75%, 25%≤S3 / S 22 ≤70%, 40%≤S3 / S 22 ≤85%, 40%≤S3 / S 22 ≤80%, 40%≤S3 / S 22 ≤75% or 40% ≤S3 / S 22 ≤70%.

[0115] Not intended to be limited by any theory or explanation, the overlapping area of ​​the first micropore on the surface of the aqueous positive electrode and the second micropore on the surface of the negative electrode is within the aforementioned range. This facilitates the formation of channels between the first and second micropores and the micropores in the separator, thereby promoting the rapid removal of residual moisture from the electrode assembly and increasing the electrolyte wetting rate of the electrode assembly. Therefore, the electrode assembly of this application, when applied to a secondary battery, enables the secondary battery to exhibit low impedance, high energy density, and high cycle capacity retention.

[0116] This application does not limit the morphology of the first micropores; the morphologies of each first micropore may be the same or different. In some embodiments, the morphology of each first micropore may be a regular shape or an irregular shape. In some embodiments, the morphology of each first micropore may include a circle, a rectangle, or a square.

[0117] In some embodiments, the equivalent diameter of each first micropore can be 1 μm-200 μm, for example, it can be about 5 μm, about 10 μm, about 20 μm, about 50 μm, about 80 μm, about 100 μm, about 120 μm, about 150 μm, about 180 μm, about 200 μm, or within any range of the above values. In some embodiments, the equivalent diameter of each first micropore can be 5 μm-180 μm, 10 μm-180 μm, 20 μm-180 μm, 30 μm-180 μm, 50 μm-180 μm, 5 μm-150 μm, 10 μm-150 μm, 20 μm-150 μm, 30 μm-150 μm, or 50 μm-150 μm.

[0118] The equivalent diameter of each first micropore can be the diameter of a circle with an area equal to that of each first micropore. When the equivalent diameter of the first micropore is within the aforementioned range, it ensures that the aqueous positive electrode has low moisture content, a high electrolyte wetting rate, and a high drying rate, while also giving the aqueous positive electrode good mechanical properties, such as high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte wetting rate and good processing performance, and consequently, the secondary battery using this electrode assembly can also have good electrochemical performance and high energy production.

[0119] In some embodiments, the center-to-center distance between adjacent first micropores can be 1mm-10mm, for example, it can be about 1mm, about 2mm, about 3mm, about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, about 9mm, about 10mm or within any of the above values.

[0120] Not intended to be limited by any theory or explanation, the center-to-center distance between adjacent first micropores within the aforementioned range allows for a suitable distribution of the first micropores on the surface of the aqueous positive electrode. This prevents the distribution of the first micropores from becoming too dense, thus maintaining good mechanical properties of the aqueous positive electrode.

[0121] This application does not limit the distribution of the plurality of first micropores. In some embodiments, the plurality of first micropores may be distributed in an array.

[0122] This application does not limit the morphology of the second micropores; the morphologies of each second micropore may be the same or different. In some embodiments, the morphology of each second micropore may be a regular shape or an irregular shape. In some embodiments, the morphology of each second micropore may include a circle, a rectangle, or a square.

[0123] In some embodiments, the equivalent diameter of each second micropore can be 1 μm-200 μm, for example, it can be about 5 μm, about 10 μm, about 20 μm, about 50 μm, about 80 μm, about 100 μm, about 120 μm, about 150 μm, about 180 μm, about 200 μm, or within any range of the above values. In some embodiments, the equivalent diameter of each second micropore can be 5 μm-180 μm, 10 μm-180 μm, 20 μm-180 μm, 30 μm-180 μm, 50 μm-180 μm, 5 μm-150 μm, 10 μm-150 μm, 20 μm-150 μm, 30 μm-150 μm, or 50 μm-150 μm.

[0124] The equivalent diameter of each second micropore can be the diameter of a circle with an area equal to that of each second micropore. When the equivalent diameter of the second micropore is within the aforementioned range, it ensures that the negative electrode sheet has good mechanical properties while maintaining a high electrolyte wetting rate; for example, it can give the negative electrode sheet high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte wetting rate and good processing performance, and consequently, the secondary battery using this electrode assembly can also have good electrochemical performance and high energy production.

[0125] In some embodiments, the center-to-center distance between adjacent second micropores can be 1mm-10mm, for example, it can be about 1mm, about 2mm, about 3mm, about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, about 9mm, about 10mm or within any of the above values.

[0126] Not intended to be limited by any theory or explanation, the center-to-center distance between adjacent second micropores within the aforementioned range allows for a suitable distribution of the second micropores on the surface of the negative electrode. This prevents the second micropores from being too densely distributed, thus maintaining good mechanical properties of the negative electrode.

[0127] This application does not limit the distribution of the plurality of second micropores. In some embodiments, the plurality of second micropores may be distributed in an array.

[0128] In this application, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer can be located on either or both of the two opposite surfaces of the positive current collector. The negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer can be located on either or both of the two opposite surfaces of the negative current collector.

[0129] It should be noted that the thickness H of the aqueous positive electrode sheet... 11 H represents the sum of the thicknesses of the positive current collector and the positive electrode film, and the thickness of the negative electrode sheet. 21 This represents the sum of the thicknesses of the negative electrode current collector and the negative electrode film. Figure 1 This is a cross-sectional schematic diagram of a partial embodiment of the aqueous positive electrode sheet of this application. Figure 2 This is a cross-sectional schematic diagram of another embodiment of the aqueous positive electrode sheet of this application. (See diagram below.) Figure 1 and Figure 2 As shown, the positive electrode film layer 102 is disposed on both sides of the positive electrode current collector 101, wherein, Figure 1 This indicates that the ratio of the depth of the first micropore to the thickness of the positive electrode is less than 100%, i.e., H. 12 Less than H 11 ; Figure 2 This indicates that the first micropore is a through-hole that penetrates the positive electrode plate, at which point H12 equals H 11 In this application, the arrangement of the second micropores on the surface of the negative electrode is similar to that of the aqueous positive electrode.

[0130] In the electrode assembly of this application, the type of positive electrode active material is not specifically limited, and any positive electrode active material known in the art for use in secondary batteries can be used. In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides, lithium phosphates with an olivine structure, and their respective modified compounds. The modified compounds of the above-mentioned positive electrode active materials may be used for doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.

[0131] As an example, lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. As an example, olivine-structured lithium phosphates may include one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds. These cathode active materials may be used alone or in combination of two or more.

[0132] Optionally, the positive electrode active material may include one or more of lithium phosphates with an olivine structure and their modified compounds.

[0133] In some embodiments, the positive electrode film layer may further include one or more of an aqueous binder and a conductive agent. The aqueous binder can bond the positive electrode active material, conductive agent, etc., to the current collector, enhancing the electronic contact between the positive electrode active material and the conductive agent, as well as between the positive electrode active material and the positive electrode current collector, and stabilizing the structure of the positive electrode sheet. Compared to oil-based binders, such as polyvinylidene fluoride, aqueous binders are lower in cost, more environmentally friendly, and safer to use.

[0134] The aqueous adhesive may comprise an aqueous dispersion or emulsion with a solid component content of 5% or more. The aqueous adhesive may also comprise a solid that can form a stable dispersion with a solid component content of 1% or more with water. In some embodiments, the aqueous adhesive comprises soluble polysaccharides and their derivatives, water-soluble or aqueous dispersion polymers, or mixtures thereof. For example, the aqueous adhesive may include methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginate and its salts, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymers and their derivatives, or mixtures thereof.

[0135] In some embodiments, the aqueous adhesive may comprise a compound mixture of xanthan gum and polyethyleneimine. Optionally, the mass ratio of xanthan gum to polyethyleneimine may be 2:1 to 0.2:2.8. Optionally, the number average molecular weight of the xanthan gum may be 300,000 to 2,000,000. Optionally, the number average molecular weight of the polyethyleneimine may be 2,000 to 50,000.

[0136] In some embodiments, the aqueous adhesive may comprise a blend of acrylonitrile-acrylic acid copolymer and polyethyleneimine. Optionally, the mass ratio of the acrylonitrile-acrylic acid copolymer to the polyethyleneimine may be 2:1 to 0.2:2.8. Optionally, the number average molecular weight of the acrylonitrile-acrylic acid copolymer may be 300,000 to 2,000,000. Optionally, the number average molecular weight of the polyethyleneimine may be 2,000 to 70,000.

[0137] Not intended to be limited to any theory or explanation, the aqueous binder selected from the aforementioned substances can further enhance the electronic contact between the positive electrode active material and the conductive agent, as well as between the positive electrode active material and the positive electrode current collector, thereby better stabilizing the structure of the positive electrode sheet. Therefore, the electrode assembly of this application, when applied to a secondary battery, enables the secondary battery to possess high cycle stability and low internal resistance.

[0138] This application does not impose any particular limitation on the type of conductive agent used in the positive electrode film. In some embodiments, the conductive agent may include one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0139] In the electrode assembly of this application, the positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing positive electrode active material, aqueous binder, conductive agent, and any other components in deionized water and stirring until homogeneous.

[0140] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0141] In the electrode assembly of this application, the negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry coating is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or water, but is not limited thereto. As an example, the binder used for the negative electrode film layer may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). As an example, the conductive agent used for the negative electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Other optional additives may include thickeners (e.g., sodium carboxymethyl cellulose, CMC), one or more PTC thermistor materials.

[0142] The type of negative electrode active material is not specifically limited, and any negative electrode active material known in the art for use in secondary batteries can be used. As examples, negative electrode active materials may include one or more of graphite, soft carbon, hard carbon, mesophase carbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys. This application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0143] The type of negative electrode current collector is not specifically limited and can be selected according to actual needs. For example, the negative electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, the negative electrode current collector can be copper foil. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can be selected from one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material base layer can be selected from one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0144] Furthermore, in the electrode assembly of this application, the negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) disposed between the negative electrode current collector and the negative electrode film layer. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0145] In the electrode assembly of this application, the implementation method of the first and second micro-holes is not specifically limited and can be achieved using methods known in the art. In some embodiments, the means of setting the first and second micro-holes on the electrode surface can include any one or a combination of laser drilling, mechanical punching, or other methods. For example, when using laser drilling, the lasers can be arranged vertically in a staggered manner, a suitable drilling array can be set according to the requirements of the drilling process, and an appropriate laser energy can be selected according to the required micro-hole depth.

[0146] In some embodiments, the electrode assembly further includes a separator. The separator is disposed between the aqueous positive electrode and the negative electrode, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0147] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0148] In some embodiments, the aqueous positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0149] In this application, the thickness of the film and the electrode are defined in a way known in the art and can be tested using methods known in the art, such as a micrometer.

[0150] In this application, the volume average particle size Dv50 of the material has a well-known meaning in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 50%, which can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0151] In this application, the compaction density of the electrode sheet has a meaning known in the art and can be tested using methods known in the art. The compaction density of the electrode sheet = the areal density of the film layer / the thickness of the film layer. The areal density of the film layer has a meaning known in the art and can be tested using methods known in the art. For example, take an electrode sheet that is single-sided coated and cold-pressed (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off first), cut it into small discs, and weigh them; then wipe off the film layer of the weighed electrode sheet and weigh the current collector. The areal density of the film layer = (weight of the small disc - weight of the current collector) / area of ​​the small disc.

[0152] Secondary batteries

[0153] A second aspect of this application provides a secondary battery, including the electrode assembly and electrolyte of the first aspect of this application. The electrolyte serves to conduct active ions between the positive and negative electrode plates. This application does not specifically limit the type of electrolyte and can select it according to needs. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0154] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0155] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include one or more selected from 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0156] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more selected from 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), butyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0157] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0158] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0159] In some implementations, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0160] This application does not impose any particular limitation on the shape of the secondary battery; it can be a flat, rectangular, or other shape. Figure 3 This is an example of a cuboid-shaped secondary battery 5.

[0161] In some implementations, such as Figure 4 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 of the first aspect of this application is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted as needed.

[0162] The method for preparing the secondary battery described in this application is well known. In some embodiments, the electrode assembly can be placed in an outer package, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0163] Battery modules and battery packs

[0164] The secondary battery according to this application can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0165] Figure 5 This is a schematic diagram of battery module 4 as an example. Figure 5 As shown, in battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0166] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0167] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0168] Figure 6 and Figure 7 This is a schematic diagram of battery pack 1 as an example. Figure 6 and Figure 7 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0169] Electrical appliances

[0170] This application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack described in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0171] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0172] Figure 8 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0173] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0174] Example

[0175] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0176] The secondary batteries of Examples 1 to 25 and Comparative Examples 4 to 10 were all prepared according to the following method.

[0177] (1) Preparation of aqueous positive electrode sheet

[0178] Lithium iron phosphate (LiFePO4), conductive carbon black, and aqueous binder were mixed uniformly at a mass ratio of 96:1:3. An appropriate amount of deionized water was added to obtain a positive electrode slurry with a solid content of 50%. The positive electrode slurry was uniformly coated onto the surface of the positive electrode current collector, and after drying, a double-sided coated aqueous positive electrode sheet was obtained. The aqueous binder was a compound of polyacrylonitrile-acrylate copolymer LA-133 (purchased from Sichuan Yindile Technology Co., Ltd.) and polyethyleneimine, in which the mass ratio of LA-133 to polyethyleneimine was 1:1.

[0179] A laser drilling device is used to drill holes in the aqueous positive electrode sheet, thereby creating multiple first micropores on the surface of the aqueous positive electrode sheet. The equivalent diameter d1 (μm) of the first micropore, the center-to-center distance L1 (mm) between adjacent first micropores, and the ratio S of the total area of ​​the multiple first micropores to the area of ​​the aqueous positive electrode sheet are defined. 12 / S 11 The ratio H of the depth of the first micropore to the thickness of the aqueous positive electrode sheet. 12 / H 11The compaction density C1 (g / cc) of the aqueous positive electrode sheet, the volume average particle size D1 (μm) of the positive electrode active material, and (S) 12 ×H 12 ×D1) / (S 11 ×C1×H 11 The results are shown in Table 1.

[0180] (2) Preparation of negative electrode sheet

[0181] Artificial graphite (anode active material), conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) are mixed in a mass ratio of 96.2:1.8:0.8:1.2. An appropriate amount of deionized water is added and the mixture is stirred evenly to obtain a cathode slurry. The cathode slurry is then uniformly coated onto the surface of the cathode current collector and dried to obtain a double-sided coated cathode sheet.

[0182] A laser drilling device is used to drill holes in the negative electrode sheet, thereby creating multiple second micropores on the surface of the negative electrode sheet. The equivalent diameter d2 (μm) of the second micropores, the center-to-center distance L2 (mm) between adjacent second micropores, and the ratio S of the total area of ​​the multiple second micropores to the area of ​​the negative electrode sheet are determined. 22 / S 21 The ratio H of the depth of the second micropore to the thickness of the negative electrode sheet 22 / H 21 The compaction density C2 (g / cc) of the negative electrode sheet, the volume average particle size D2 (μm) of the negative electrode active material, and (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 The results are shown in Table 1.

[0183] (3) Preparation of electrolyte

[0184] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly at a volume ratio of 3:7. 12.5% ​​LiPF6 was added and dissolved in the organic solvent and stirred evenly to obtain the electrolyte.

[0185] (4) Separating membrane

[0186] Polypropylene film is used as the separator.

[0187] (5) Preparation of secondary batteries

[0188] The aqueous positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the aqueous positive and negative electrodes to provide isolation. The stacked aqueous positive electrode, separator, and negative electrode are then wound to form an electrode assembly. After welding tabs to the electrode assembly, it is placed in an aluminum casing and baked to remove moisture. Electrolyte is injected into the aluminum casing, which is then sealed to obtain a non-charged battery. The non-charged battery is then subjected to a series of processes, including settling, hot and cold pressing, formation, shaping, and capacity testing, to obtain a secondary battery.

[0189] Comparative Example 1

[0190] The preparation processes of the aqueous positive electrode, negative electrode, separator, electrolyte, and secondary battery are basically the same as in Example 1, except that no holes are drilled on the surface of the aqueous positive and negative electrodes.

[0191] Comparative Examples 2-3

[0192] The preparation processes of the aqueous positive electrode, negative electrode, separator, electrolyte, and secondary battery are basically the same as those in Example 1, except that Comparative Example 2 did not have holes drilled on the surface of the negative electrode, and Comparative Example 3 did not have holes drilled on the surface of the aqueous positive electrode.

[0193] Test section

[0194] (1) Electrolyte wetting performance test of electrode assembly

[0195] The uncharged batteries obtained from each embodiment and comparative example were left to stand for different periods before undergoing their first charge test. The initial charge current was set to 0.1C (51.2A), and the charging cutoff voltage was set to 3.65V. After charging, the batteries were disassembled in a drying room, and the large area of ​​the negative electrode was observed to show the grayish-white color of lithium deposition. If a black area was found on the surface, it indicated that the electrolyte wetting was insufficient; if no black area was found, it indicated that the electrolyte had completely wetted the negative electrode. The shortest time required for the electrolyte to completely wet the negative electrode was recorded. During the test, a group was set up for every half-hour increase in wetting time. Three electrode assemblies were disassembled for each group for evaluation. The shortest time required for all three electrode assemblies to simultaneously meet the requirement of complete electrolyte wetting of the negative electrode was taken as the electrolyte wetting time T1 of the electrode assembly.

[0196] (2) Drying performance test of secondary batteries

[0197] The unfilled batteries obtained from each embodiment and comparative example were placed in a vacuum oven for drying performance testing. The oven temperature was set to 105°C, and the water content of the batteries was measured every 1 hour. Batteries with a water content below 200 ppm (mass concentration) were considered dried, and the drying time T2 was recorded.

[0198] (3) Initial capacity and cycle performance testing of secondary batteries

[0199] The secondary battery was charged and discharged using a battery tester. The charging and discharging voltage was set to 2.5V to 3.65V, and the charging and discharging current was set to 1C (512A). The discharge capacity after the first cycle and after 300 cycles were read.

[0200] The average discharge capacity of the three secondary batteries after the first cycle is taken as the initial capacity of the secondary battery.

[0201] The capacity retention rate of a secondary battery after 300 cycles = (discharge capacity after 300 cycles / discharge capacity after the first cycle) × 100%.

[0202] (4) DC resistance (DCR) test of secondary battery

[0203] At 25℃, the secondary battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the voltage V1 was recorded. The secondary battery was then discharged at a constant current of 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance after the first cycle is expressed as (V2-V1) / (1 / 3C). The above steps were repeated, and the internal resistance of the secondary battery after 300 cycles was recorded.

[0204] The parameters for each embodiment and comparative example are shown in Table 1, and the test results are shown in Table 2.

[0205]

[0206]

[0207] Table 2

[0208]

[0209] As can be seen from Tables 1 and 2, in the electrode assemblies of Examples 1-25, the aqueous positive and negative electrode plates meet the conditions defined in this application, enabling the secondary battery to have high initial capacity, high electrolyte wetting rate and high drying rate, while the secondary battery also has high cycle capacity retention rate and low internal resistance.

[0210] In Comparative Examples 1-3, the aqueous positive and / or negative electrode surfaces lack micropores, resulting in very low electrolyte wetting and drying rates for the electrode assembly, and a significant amount of moisture tends to remain within the electrode assembly. Consequently, the secondary batteries using this electrode assembly exhibit high internal resistance and poor cycle performance. Comparative Examples 4-5 incorporate micropores on both the aqueous positive and negative electrode surfaces; however, in the prepared aqueous positive electrode, (S... 12 ×H 12×D1) / (S 11 ×C1×H 11 When the concentration of electrolyte in the electrode assembly is less than 0.001%, the electrolyte wetting rate and drying rate are slightly increased compared to Comparative Examples 1-3, but the improvement is not significant, and consequently, the improvement in the cycle performance of the secondary battery is also not significant. Comparative Examples 6-7 have micropores on the surface of both the aqueous positive and negative electrode sheets; however, in the prepared aqueous positive electrode sheet, (S... 12 ×H 12 ×D1) / (S 11 ×C1×H 11 The concentration of S is greater than 1%, which significantly reduces the energy density of the secondary battery. Comparative Examples 8-10 have micropores on the surfaces of both the positive and negative electrodes in an aqueous system; however, in the prepared negative electrode, (S...) 22 ×H 22 ×D2) / (S 21 ×C2×H 21 The energy density of the secondary battery is significantly reduced as the energy density is greater than 2.5%.

[0211] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode assembly comprising an aqueous positive electrode and a negative electrode, wherein, The aqueous positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material; The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material; The aqueous positive electrode sheet has at least a plurality of first micropores on a portion of its surface, and satisfies the following: 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 1%, H 11 μm represents the thickness of the aqueous positive electrode sheet, H 12 μm represents the depth of the first micropore, S 11 m 2 S represents the area of ​​the positive electrode plate of the water system. 12 m 2 C1 represents the total area of ​​the plurality of first micropores, C1 g / cc represents the compaction density of the aqueous positive electrode sheet, and D1 μm represents the volume average particle size Dv50 of the positive electrode active material. The negative electrode sheet has at least a portion of its surface with multiple second micropores, and satisfies the following conditions: 0<(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.5%, H 21 μm represents the thickness of the negative electrode sheet, H 22 μm represents the depth of the second micropore, S 21 m 2 S represents the area of ​​the negative electrode sheet. 22 m 2 C2 represents the total area of ​​the plurality of second micropores, C2 g / cc represents the compaction density of the negative electrode sheet, and D2 μm represents the volume average particle size Dv50 of the negative electrode active material.

2. The electrode assembly according to claim 1, wherein, 0.05% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 0.5%。 3. The electrode assembly according to claim 2, wherein, 0.15% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 0.25%。 4. The electrode assembly according to claim 1, wherein, 0.2% ≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.0%。 5. The electrode assembly according to claim 4, wherein, 0.4% ≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 1.0%。 6. The electrode assembly according to claim 1, wherein, 0 < S 12 / S 11 ≤ 2%; and / or, 30% ≤ H 12 / H 11 ≤ 100%; and / or, C1 is 2.0-3.0; and / or, D1 is 0.5-1.

5.

7. The electrode assembly according to claim 6, wherein, 0.4% ≤ S 12 / S 11 ≤ 0.6%; and / or, 60% ≤ H 12 / H 11 ≤ 100%; and / or, C1 is 2.3-2.7; and / or, D1 is 0.8-1.

3.

8. The electrode assembly according to claim 1, wherein, 0 < S 22 / S 21 ≤ 0.2%; and / or, 30% ≤ H 22 / H 21 ≤ 100%; and / or, C2 is 1.2-2.0; and / or, D2 is 12-20.

9. The electrode assembly according to claim 8, wherein, 0.04% ≤ S 22 / S 21 ≤ 0.06%; and / or, 60% ≤ H 22 / H 21 ≤ 100%; and / or, C2 is 1.4-1.8; and / or, D2 is 15-19.

10. The electrode assembly according to claim 1, wherein, The electrode assembly satisfies: 0.1 ≤ A / B ≤ 1.0, where A represents (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 B represents (S) 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ).

11. The electrode assembly of claim 10, wherein, 0.25 ≤ A / B ≤ 0.

50.

12. The electrode assembly according to claim 1, wherein, The electrode assembly satisfies: S3 / S 22 ≥ 5%, S3 m 2 This represents the overlapping area of ​​the plurality of first micropores and the plurality of second micropores.

13. The electrode assembly according to claim 12, wherein, 8% ≤ S3 / S 22 ≤ 70%.

14. The electrode assembly according to any one of claims 1-13, wherein, The first micropore satisfies at least one of the following conditions (1) to (4): (1) The morphology of each first micropore includes circular, rectangular or square; (2) The equivalent diameter of each first micropore is 1μm-200μm; (3) The center-to-center distance between adjacent first micropores is 1mm-10mm; (4) The plurality of first micropores are arranged in an array.

15. The electrode assembly of claim 14, wherein, The equivalent diameter of each first micropore is 50μm-180μm.

16. The electrode assembly according to any one of claims 1-13, wherein, The second micropore satisfies at least one of the following conditions (1) to (4): (1) The morphology of each second micropore includes circular, rectangular or square shapes; (2) The equivalent diameter of each second micropore is 1μm-200μm; (3) The center-to-center distance between adjacent second micropores is 1mm-10mm; (4) The plurality of second micropores are arranged in an array.

17. The electrode assembly of claim 16, wherein, The equivalent diameter of each second micropore is 50μm-150μm.

18. The electrode assembly according to claim 1, wherein, The positive electrode film layer also includes one or more of the following: an aqueous binder and a conductive agent.

19. The electrode assembly of claim 18, wherein, The aqueous adhesive includes one or more of the following: methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginate and its salts, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymer, and derivatives of acrylonitrile-acrylic acid copolymer.

20. The electrode assembly of claim 18, wherein, The conductive agent includes one or more of superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

21. The electrode assembly according to claim 19, wherein, The water-based adhesive comprises a compound mixture of xanthan gum and polyethyleneimine.

22. The electrode assembly according to claim 21, wherein, The mass ratio of xanthan gum to polyethyleneimine is 2:1 to 0.2:2.

8.

23. The electrode assembly according to claim 21, wherein, The number average molecular weight of the xanthan gum is 300,000-2,000,000.

24. The electrode assembly of claim 21, wherein, The number average molecular weight of the polyethyleneimine is 2000-50000.

25. The electrode assembly according to claim 19, wherein, The water-based adhesive comprises a blend of acrylonitrile-acrylic acid copolymer and polyethyleneimine.

26. The electrode assembly of claim 25, wherein, The mass ratio of the acrylonitrile-acrylic acid copolymer to the polyethyleneimine is 2:1-0.2:2.

8.

27. The electrode assembly of claim 25, wherein, The number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300,000-2,000,000.

28. The electrode assembly according to claim 25, wherein, The number average molecular weight of the polyethyleneimine is 2000-70000.

29. A secondary battery comprising an electrolyte and an electrode assembly according to any one of claims 1-28.

30. A battery module comprising the secondary battery according to claim 29.

31. A battery pack comprising one of the secondary battery according to claim 29 and the battery module according to claim 30.

32. An electrical device comprising at least one of the secondary battery according to claim 29, the battery module according to claim 30, and the battery pack according to claim 31.

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