Electrode Assembly and Secondary Battery, Battery Module, Battery Pack, and Power Consumption Device Containing the Same

Abstract

The present invention provides an electrode assembly, and a secondary battery, a battery module, a battery pack, and a power consumption device each including the electrode assembly. The electrode assembly includes an aqueous positive electrode sheet and an aqueous negative electrode sheet, the aqueous positive electrode sheet includes a positive electrode current collector and a positive electrode film layer including a positive electrode active material and located on at least one surface of the positive electrode current collector, the aqueous negative electrode sheet includes a negative electrode current collector and a negative electrode film layer including a negative electrode active material and located on at least one surface of the negative electrode current collector, a plurality of first pores are provided on at least a portion of the surface of the aqueous positive electrode sheet, and the aqueous positive electrode sheet has a pH of 0.001%≦(S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 )≦1%, a plurality of second pores are provided on at least a portion of the surface of the negative electrode sheet, and 0<(S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 )≦2.5%. Figure 3

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and specifically relates to an electrode assembly, a secondary battery, a battery module, a battery pack, and a power consumption device including the same.

Background Art

[0002] In recent years, secondary batteries have been widely applied in multiple fields such as energy storage power systems including hydroelectric, thermal, wind, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military devices, aerospace, etc. With the application and popularization of secondary batteries, their cost problems and environmental pollution problems have attracted increasing attention. The positive electrode sheet is one of the important factors determining the performance of secondary batteries. The solvents used in conventional positive electrode slurries are usually oil-based solvents, such as N-methylpyrrolidone (NMP). However, NMP has defects such as high usage, easy volatility, difficult recovery, high toxicity, and high cost, which not only causes serious pollution to the environment but also harms human health. Aqueous positive electrode slurries using water as a solvent have attracted more and more attention from researchers because of their characteristics of low cost and environmental friendliness. However, the practical application of aqueous positive electrode sheets is limited because they have the disadvantages of high water content and poor capacity performance.

Summary of the Invention

[0003] An object of this application is to provide an electrode assembly, a secondary battery, a battery module, a battery pack, and a power consumption device including the same. Thereby, the electrode assembly using an aqueous positive electrode sheet and the secondary battery, battery module, battery pack, and power consumption device including the same have the characteristics of high energy density, good cycle performance, low internal resistance, low cost, and environmental friendliness.

[0004] The first aspect of this application is an electrode assembly comprising an aqueous positive electrode sheet and a negative electrode sheet, The aqueous positive electrode sheet includes a positive electrode current collector and a positive electrode film layer on at least one surface of the positive electrode current collector, and contains a positive electrode active material. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, and contains a negative electrode active material. A plurality of first pores are provided on at least a part of the surface of the aqueous positive electrode sheet, and 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 1% is satisfied, where H 11 μm represents the thickness of the aqueous positive electrode sheet, H 12 μm represents the depth of the first pores, S 11 m 2 represents the area of the aqueous positive electrode sheet, S 12 m 2 represents the total area of the plurality of first pores, C1 g / cc represents the compression density of the aqueous positive electrode sheet, and D1 μm represents the volume average particle diameter Dv50 of the positive electrode active material. A plurality of second pores are provided on at least a part of the surface of the negative electrode sheet, and 0 < (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.5% is satisfied. H 21 μm represents the thickness of the negative electrode sheet, H 22 μm represents the depth of the second pores, S 21 m 2 represents the area of the negative electrode sheet, S 22 m 2 represents the total area of the plurality of second pores, C2 g / cc represents the compression density of the negative electrode sheet, and D2 μm represents the volume average particle diameter Dv50 of the negative electrode active material, providing an electrode assembly.

[0005] In the electrode assembly of the present application, the aqueous positive electrode sheet satisfies 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 1%, and the negative electrode sheet satisfies 0 < (S 22×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.5% is satisfied, the electrode assembly can have a low water content, a high electrolyte impregnation rate, and a high drying rate. When applied to a secondary battery, the secondary battery can have high energy density, good cycle performance, low internal resistance, low cost, and environmentally friendly characteristics.

[0006] In any embodiment of the present application, 0.05% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 0.5%, and 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 11 ) is within the above range, the electrode assembly can have low surface impedance and good interfacial performance, whereby the secondary battery applied with the electrode assembly can have good electrochemical performance, such as high cycle stability, high capacity utilization, and low internal resistance. Also, when (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) is within the above range, the aqueous positive electrode sheet can also maintain good mechanical performance.

[0008] In any embodiment of the present application, 0.2% ≤ (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.0%, and 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 ) is within the above range, the negative electrode sheet can have a high electrolyte impregnation rate, while having a low surface impedance and good interfacial performance. Thereby, the secondary battery applying the electrode assembly of the present application can have high cycle stability, high capacity performance, and low internal resistance. Also, (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) is within the above range, the negative electrode sheet can maintain good mechanical performance.

[0010] In any embodiment of the present application, 0 < S 12 / S 11 ≦2%, and optionally, 0.4% ≦ S 12 / S 11 ≦0.6%.

[0011] When the ratio of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is within the above range, the aqueous positive electrode sheet can have good mechanical performance and appropriate porosity, which is advantageous for water discharge and electrolyte impregnation. Also, the aqueous positive electrode sheet can also have an appropriate electron conduction path and active ion transport path.

[0012] In any embodiment of the present application, 30% ≦ H 12 / H 11 ≦100%, and optionally, 60% ≦ H 12 / H 11 ≦100%.

[0013] When the ratio of the depth of the first pores to the thickness of the aqueous positive electrode sheet is within the above range, it can be guaranteed that the aqueous positive electrode sheet not only has a high drying rate and a high electrolyte impregnation rate, but also has good mechanical performance.

[0014] In any embodiment of the present application, C1 is 2.0 to 3.0, and optionally 2.3 to 2.7.

[0015] When the compression density of the aqueous positive electrode sheet is controlled within an appropriate range, the positive electrode active material particles in the positive electrode film layer can be adhered to each other, and the content of the positive electrode active material per unit volume can be improved. Thereby, the energy density of the secondary battery can be improved.

[0016] In any embodiment of the present application, D1 is 0.5 to 1.5, and optionally 0.8 to 1.3.

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

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

[0019] When the ratio of the total area of the plurality of second pores to the area of the negative electrode sheet is within the above range, the negative electrode sheet can have good mechanical properties, appropriate porosity, and high capacity, which is advantageous for the impregnation rate and capacity performance of the electrolyte of the electrode assembly. In addition, the negative electrode sheet can also have an appropriate electron conduction path and active ion transport path.

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

[0021] When the ratio of the depth of the second pores to the thickness of the negative electrode sheet is within the above range, the negative electrode sheet can not only have a high electrolyte impregnation rate, but also ensure good mechanical performance.

[0022] In any embodiment of the present application, C2 is 1.2 to 2.0, and optionally 1.4 to 1.8.

[0023] When the tap density of the negative electrode sheet is controlled within an appropriate range, the particles of the negative electrode active material in the negative electrode film layer can be adhered, and the content of the negative electrode active material per unit volume can be improved, thereby improving the energy density of the secondary battery.

[0024] In any embodiment of the present application, D2 is 12 to 20, and optionally 15 to 19.

[0025] When the volume average particle diameter Dv50 of the negative electrode active material is within the above range, the diffusion path of the 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 the present application, the electrode assembly satisfies 0.1 ≦ A / B ≦ 1.0, and optionally 0.25 ≦ A / B ≦ 0.50, where A is (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ), and B is (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ).

[0027] When the value of A / B is within the above range, the electrolyte impregnation rate of the electrode assembly can be further improved, and it is also advantageous for quickly discharging the moisture remaining in the drying process of the electrode assembly. Thereby, the secondary battery can have a low impedance, a high energy density and a high cycle capacity retention rate.

[0028] In any embodiment of the present application, the electrode assembly is S3 / S 22 ≧5%, optionally, 8% ≦ S3 / S 22 ≦70% is satisfied, and S3m 2 represents the overlapping area between the plurality of first pores and the plurality of second pores.

[0029] When the overlapping area between the first pores on the surface of the aqueous positive electrode sheet and the second pores on the surface of the negative electrode sheet is within the above range, it is advantageous for the pores in the first pores, the second pores, and the separator to form a passage. Thereby, it is advantageous for the rapid discharge of the moisture remaining in the electrode assembly, and the impregnation rate of the electrolyte of the electrode assembly can be improved. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have a low impedance, a high energy density, and a high cycle capacity retention rate.

[0030] In any embodiment of the present application, the form of each first pore is a regular shape or an irregular shape, and optionally, the form of each first pore includes a circle, a rectangle, or a square.

[0031] In any embodiment of the present application, the equivalent diameter of each first pore is 1 μm to 200 μm, and optionally, it is 50 μm to 180 μm.

[0032] When the equivalent diameter of the first pores is within the above range, on the premise of ensuring that the aqueous positive electrode sheet has a low water content, a high impregnation rate of the electrolyte, and a high drying rate, the aqueous positive electrode sheet can have good mechanical properties. For example, the aqueous positive electrode sheet can have high strength and good flexibility. Therefore, the electrode assembly can have a high impregnation rate of the electrolyte and good processing performance, whereby the secondary battery applied with the electrode assembly can have good electrochemical performance and a high yield.

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

[0034] When the center - to - center distance between adjacent first pores is within the above range, the first pores can be appropriately distributed on the surface of the aqueous positive electrode sheet. Thereby, in order to avoid the distribution of the first pores being too dense, the aqueous positive electrode sheet can maintain good mechanical performance.

[0035] In any embodiment of the present application, the plurality of first pores are distributed in an array.

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

[0037] In any embodiment of the present application, the equivalent diameter of each second pore is 1 μm to 200 μm, and optionally, it is 50 μm to 150 μm.

[0038] When the equivalent diameter of the second pores is within the above range, on the premise of ensuring that the negative electrode sheet has a high electrolyte impregnation rate, the negative electrode sheet can have good mechanical performance. For example, the negative electrode sheet can have high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte impregnation rate and good processing performance, and thereby, the secondary battery applying the electrode assembly can have good electrochemical performance and a high yield. [[ID=..]]

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

[0040] When the center - to - center distance between adjacent second pores is within the above range, the second pores can be appropriately distributed on the surface of the negative electrode sheet. Thereby, in order to avoid the distribution of the second pores being too dense, the negative electrode sheet can maintain good mechanical performance.

[0041] In any embodiment of the present application, the plurality of second pores are distributed in an array.

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

[0043] In any embodiment of the present application, the aqueous adhesive includes methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymer and its derivatives, or a mixture thereof.

[0044] In any embodiment of the present application, the aqueous adhesive includes a composite mixture of xanthan gum and polyethyleneimine. Optionally, the mass ratio of the xanthan gum to the 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 the present application, the aqueous adhesive includes a composite mixture of an 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 the present 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] The second aspect of the present application provides a secondary battery including the electrode assembly of the first aspect of the present application.

[0048] The third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.

[0049] The fourth aspect of the present application provides a battery pack including one of the secondary battery of the second aspect of the present application and the battery module of the third aspect.

[0050] The fifth aspect of the present application provides a power consumption device including at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.

[0051] The secondary battery of the present application has a low moisture content, a high impregnation rate of the electrolyte, and a high drying rate. The secondary battery of the present application further has the characteristics of high energy density, good cycle performance, low internal resistance, low cost, and environmental friendliness. Since the battery module, battery pack, and power consumption device of the present application include the secondary battery according to the present application, they have at least the same advantages as the secondary battery.

Brief Description of Drawings

[0052] To more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without creative effort.

[0053]

Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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Figure 8

[0061] In the drawings, it is not necessarily drawn to actual scale. Here, the description of the reference numerals is as follows. 101 Positive electrode current collector, 102 Positive electrode film layer, 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Case, 52 Electrode assembly, 53 Cover plate.

Embodiments for Carrying Out the Invention

[0062] Hereinafter, embodiments specifically disclosing the electrode assembly of the present application and the secondary battery, battery module, battery pack, and power consumption device including the same will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate the understanding of those skilled in the art. Also, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0063] The "ranges" disclosed in this application are limited in the form of a lower limit and an upper limit. A given range is limited by selecting one lower limit and one upper limit, and the selected lower limit and upper limit particularly define the boundaries of the range. The ranges limited in such a manner may or may not include the 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 enumerated for a specific parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also contemplated. Further, if the minimum range values 1 and 2, and the maximum range values 3, 4, and 5 are enumerated, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all contemplated. In this application, unless otherwise explained, the numerical range "a - b" represents a reduced expression of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" represents all real numbers between 0 and 5 in this specification, and "0 - 5" is a reduced expression of combinations of these numbers. Also, when a parameter is expressed as an integer ≧ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] Unless otherwise specified, all embodiments and selectable embodiments of this application can be combined with each other to form a new technical solution, and such a technical solution should be regarded as being included in the disclosure content of this application.

[0065] Unless otherwise specified, all technical features and selectable technical features of this application can be combined with each other to form a new technical solution, and such a technical solution should be regarded as being included in the disclosure content of this application.

[0066] Unless otherwise specified, all steps of the present application can be performed in order, can be performed randomly, and preferably are performed in order. For example, when the method includes steps (a) and (b), it means that the method can include steps (a) and (b) performed in order, and can also include steps (b) and (a) performed in order. For example, when it is stated that the method can further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), can also include steps (a), (c), and (b), and can further include steps (c), (a), and (b), etc.

[0067] Unless otherwise specified, the terms "having", "comprising", and "including" referred to in the present application are open-ended and can also be closed-ended. For example, the above "having", "comprising", and "including" can further have, comprise, or include other components not listed, and can also have, comprise, or include only the listed components.

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

[0069] Unless otherwise specified, in the present application, terms such as "first", "second", etc. are for distinguishing different objects and not for explaining a specific order or a master-slave relationship.

[0070] In the present application, the term "about" is used to explain or interpret a small change. When combined with a numerical value, the term can refer to a change range of ±10% or less of the said numerical value.

[0071] In the description of this specification, unless otherwise specified, "above" and "below" include that number.

[0072] In the description of this specification, unless otherwise specified, "multiple types" and "multiple" mean two or more types.

[0073] With the application and popularization of secondary batteries, their cost problems and environmental pollution problems have attracted more and more attention. Aqueous positive electrode slurry using water as a solvent has attracted more and more attention from researchers because of its characteristics of low cost and environmental friendliness. However, as a result of the research by the inventors, it has been found that aqueous positive electrode slurry often employs adhesives having hydrophilic groups. These hydrophilic groups and solvent water have a great influence on the performance of secondary batteries. The aqueous positive electrode sheet manufactured using the aqueous positive electrode slurry has some residual moisture and is difficult to be removed during the drying process. Thereby, when the current aqueous positive electrode sheet is applied to a secondary battery, the residual moisture not only affects the impregnation property of the positive electrode sheet, but also causes side reactions with the electrolyte, electrode active material, etc. inside the battery, resulting in an increase in irreversible loss of active ions, a reduction in the energy density of the battery, a too-fast attenuation of the capacity, as well as gas expansion of the battery, an increase in self-discharge, etc.

[0074] Currently, in the related art, the water content of the aqueous positive electrode sheet is often reduced by adjusting the formulation of the positive electrode slurry or the manufacturing process of the positive electrode sheet. Here, by adjusting the formulation of the positive electrode slurry, for example, by adding anhydrous ethanol to the aqueous positive electrode slurry, the water content remaining in the aqueous positive electrode sheet can be reduced to a certain extent. However, when ethanol is added to the aqueous positive electrode slurry, the hydroxyl groups of the introduced active groups affect the interfacial performance of the secondary battery, causing phenomena such as lithium precipitation and dark spots on the interface. As a result, not only does the cycle performance of the secondary battery decrease, but also potential safety risks are brought about. By adjusting the manufacturing process of the positive electrode sheet, for example, controlling the solid content of the aqueous positive electrode slurry and adopting a process combining hot coating, cold rolling, and vacuum baking to manufacture the positive electrode sheet, the volatilization of water can be effectively accelerated and the water remaining in the aqueous positive electrode sheet can be reduced. However, accordingly, the manufacturing cost of the aqueous positive electrode sheet increases and the yield of the secondary battery decreases.

[0075] As a result of intensive research, the inventors designed an electrode assembly that can have a low water content, a high electrolyte impregnation rate, and a high drying rate from the structure of the electrode assembly. The electrode assembly can further have the characteristics of high energy density, good cycle performance, low internal resistance, low cost, and environmental friendliness. Electrode assembly

[0076] The first aspect of the present application provides an electrode assembly including an aqueous positive electrode sheet and a negative electrode sheet.

[0077] The aqueous positive electrode sheet includes a positive electrode current collector and a positive electrode film layer on at least one surface of the positive electrode current collector, containing a positive electrode active material. A plurality of first pores are provided on at least a part of the surface of the aqueous positive electrode sheet, and 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 1% is satisfied, where H 11 μm represents the thickness of the aqueous positive electrode sheet, and H12 μm represents the depth of the first pores, and S 11 m 2 represents the area of the aqueous positive electrode sheet, and S 12 m 2 represents the total area of the plurality of first pores, C1 g / cc represents the tap density of the aqueous positive electrode sheet, and D1 μm represents the volume average particle diameter Dv50 of the positive electrode active material.

[0078] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material, and a negative electrode film layer on at least one surface of the negative electrode current collector. A plurality of second pores are provided on at least a part of the surface of the negative electrode sheet, and 0 < (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.5% is satisfied, where H 21 μm represents the thickness of the negative electrode sheet, H 22 μm represents the depth of the second pores, S 21 m 2 represents the area of the negative electrode sheet, and S 22 m 2 represents the total area of the plurality of second pores, C2 g / cc represents the tap density of the negative electrode sheet, and D2 μm represents the volume average particle diameter Dv50 of the negative electrode active material.

[0079] Although not intended to be limited by any theory or interpretation, the inventors have surprisingly provided a plurality of first pores on at least a part of the surface of the aqueous positive electrode sheet, and (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11By setting the value of to within the above range, it becomes easier to remove the moisture remaining in the aqueous positive electrode sheet, thereby improving the interfacial performance of the electrode assembly and reducing the risks of gas expansion, self-discharge, and corrosion of the electrode assembly. Further, when the first pores are provided on the surface of the aqueous positive electrode sheet, while it is advantageous for increasing the porosity of the positive electrode sheet and the impregnation rate of the electrolytic solution, the diffusion distance of lithium ions can be significantly shortened, thereby effectively reducing the transfer resistance of lithium ions and reducing the internal resistance of the battery. Therefore, it has been found that when the electrode assembly of the present application is applied to a secondary battery, not only can the risks of gas expansion, self-discharge, and corrosion of the secondary battery be reduced, but also the energy density, cycle performance, and rate performance of the secondary battery can be improved.

[0080] Also, although not intended to be limited by any theory or interpretation, in the electrode assembly of the present application, a plurality of second pores are provided on at least a part of the surface of the negative electrode sheet, and (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) is set within the above range, the transport ability of lithium ions in the negative electrode sheet can be further improved, not only the impregnation rate of the electrolytic solution can be increased, but also it is advantageous for the capacity exhibition of the positive electrode active material. Thereby, a secondary battery applying the electrode assembly of the present application can have good electrochemical performance and a high energy density.

[0081] The inventors have found through research that when (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) is less than 0.001%, the ratio S 12 / S 11 of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is small, and the ratio H 12 / H 11There is at least one of the following situations: the area S is small, the volume average particle size D1 of the positive electrode active material is small, and the tap density C1 of the aqueous positive electrode sheet is large. As a result, the distance between the positive electrode active material particles is small and the contact is tight, so there are few transport paths for active ions, the internal resistance of the secondary battery is high, the impregnation performance of the electrolytic solution is poor, which is disadvantageous for the battery capacity to be exerted. In addition, there are few water discharge paths in the aqueous positive electrode sheet, and it is difficult for water to be quickly discharged during the drying process, so it is found that the residual amount of water is high, and the risks of gas expansion, self-discharge and corrosion of the secondary battery are high.

[0082] The inventors have found through research that when (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) is greater than 1%, the aqueous positive electrode sheet has at least one of the following situations: the ratio S 12 / S 11 of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is large, the ratio H 12 / H 11 of the depth of the first pore to the thickness of the aqueous positive electrode sheet is large, the volume average particle size D1 of the positive electrode active material is large, and the tap density C1 of the aqueous positive electrode sheet is small. As a result, it is found that the energy density of the secondary battery is significantly reduced.

[0083] The inventors have found through research that when (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) is greater than 2.5%, the negative electrode sheet has at least one of the following situations: the ratio S 22 / S 21 of the total area of the plurality of second pores to the area of the negative electrode sheet is large, the ratio H 22 / H 21 of the depth of the second pore to the thickness of the negative electrode sheet is large, the volume average particle size D2 of the negative electrode active material is large, and the tap density C2 of the negative electrode sheet is small. As a result, it is found that the energy density of the secondary battery is significantly reduced.

[0084] In the electrode assembly of the present application, when the aqueous positive electrode sheet satisfies 0.001% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 1%, and the negative electrode sheet satisfies 0 < (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) ≤ 2.5%, the electrode assembly can have a low water content, a high electrolyte impregnation rate, and a high drying rate. When applied to a secondary battery, the secondary battery can have high energy density, good cycle performance, low internal resistance, low cost, and environmentally friendly characteristics.

[0085] Possible reasons are as follows. First, when pores are provided on the surfaces of both the aqueous positive electrode sheet and the negative electrode sheet, during the assembly process of the secondary battery, the electrolyte can impregnate the electrode assembly not only along the horizontal direction of the electrode sheet / separator but also through the network composed of the pores of the electrode sheet and the pores of the separator along the vertical direction of the electrode sheet. Second, when pores are provided on the surfaces of both the aqueous positive electrode sheet and the negative electrode sheet, the water remaining in the electrode sheet can be quickly discharged to the outside of the electrode assembly during the drying process of the electrode assembly, thereby further reducing the water content of the electrode assembly. Finally, by reasonably combining the pores on the surface of the electrode sheet, the compression density of the electrode sheet, and the particle size of the active material particles, it can be ensured that the aqueous positive electrode sheet and the negative electrode sheet have appropriate electron conduction paths and active ion transport paths at the same time.

[0086] In some embodiments, the aqueous positive electrode sheet satisfies 0.05% ≤ (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) ≤ 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% can be satisfied.

[0087] Although not intended to be limited to any theory or interpretation, the inventors have found through research that when (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) is within the above range, the moisture in the aqueous positive electrode sheet can be quickly discharged to the outside of the electrode assembly during the drying process of the electrode assembly, so that the moisture content of the positive electrode sheet can be further reduced, and the impregnation rate and drying rate of the electrolyte of the electrode assembly can be improved. Thereby, the electrode assembly has a low surface impedance and good interfacial performance, and the secondary battery applying the electrode assembly can have good electrochemical performance, for example, high cycle stability, high capacity performance and low internal resistance. Also, when (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ) is within the above range, the aqueous positive electrode sheet can also maintain good mechanical performance. Thereby, the positive electrode sheet is not easily deformed during the process of assembling and processing the electrode assembly. Therefore, it has been found that the electrode assembly can not only maintain good electrochemical performance during the process of processing and assembling, but also have a high yield.

[0088] In some embodiments, the negative electrode sheet has 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 ×H 22 ×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×H 21 )≦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% can be satisfied.

[0089] Although not intended to be limited to any theory or interpretation, the inventors' research has shown that when (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) is within the above range, the negative electrode sheet can have a high electrolyte impregnation rate, low surface impedance, and good interfacial performance. As a result, the secondary battery applying the electrode assembly of the present application can have high cycle stability, high capacity performance, and low internal resistance. Also, when (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) is within the above range, the negative electrode sheet can maintain good mechanical performance. As a result, the negative electrode sheet is less likely to deform during the assembly and processing of the electrode assembly. Therefore, it has been found that the electrode assembly can not only maintain good electrochemical performance during the processing and assembly process but also have a high yield.

[0090] In some embodiments, the ratio of the total area of the plurality of first pores 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 / S11 ≤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% ≤ S 12 / 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%.

[0091] Although not intended to be limited to any theory or interpretation, when the ratio of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is within the above range, the aqueous positive electrode sheet can have good mechanical properties. Thereby, the risk that the aqueous positive electrode sheet is irreversibly deformed during the processing can be reduced, and the yield of the electrode assembly can be improved. When the ratio of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is within the above range, the aqueous positive electrode sheet can have an appropriate porosity, which is advantageous for the discharge of moisture and the impregnation of the electrolytic solution. Further, when the ratio of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet is within the above range, the aqueous positive electrode sheet can also have an appropriate electron conduction path and an active ion transport path. Therefore, when the electrode assembly is applied to a secondary battery, the secondary battery can have a high yield, high cycle stability, high capacity performance, and low internal resistance.

[0092] In some embodiments, the ratio of the depth of the first pores to the thickness of the aqueous positive electrode sheet satisfies 30% ≦ H 12 / H 11 ≦ 100%. For example, 30% ≦ H 12 / 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% ≤ H 12 / H 11 ≤100%.

[0093] In the present application, the depth of the first pores may be less than or equal to the thickness of the aqueous positive electrode sheet. H 12 / H 11 When it is 100%, the first pores may be through holes penetrating the positive electrode sheet.

[0094] Although not intended to be limited by any theory or interpretation, when the ratio of the depth of the first pores to the thickness of the aqueous positive electrode sheet is within the above range, the aqueous positive electrode sheet not only has a high drying rate and a high electrolyte impregnation rate, but also can ensure good mechanical properties. Therefore, the electrode assembly of the present application can have good interfacial performance, low surface impedance, and high processing efficiency. When applied to a secondary battery, the secondary battery can have good cycle performance, good rate performance, and high yield.

[0095] C1 g / cc represents the tap density of the aqueous positive electrode sheet. In some embodiments, C1 may be from 2.0 to 3.0. For example, C1 may 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 a range consisting of any of these numerical values. In some embodiments, C1 is optionally from 2.3 to 2.7.

[0096] When the tap density of the aqueous positive electrode sheet is controlled within an appropriate range, the particles of the positive electrode active material in the positive electrode film layer can be adhered, and the content of the positive electrode active material per unit volume can be improved, thereby improving the energy density of the secondary battery.

[0097] D1 μm represents the volume average particle diameter Dv50 of the positive electrode active material. In some embodiments, D1 may be from 0.5 to 1.5. For example, D1 may 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 a range consisting of any of these numerical values. In some embodiments, D1 is optionally from 0.8 to 1.3.

[0098] When the volume average particle diameter Dv50 of the positive electrode active material is within the above range, the diffusion path of the active ions can be shortened. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0099] Also, for the electrode assembly, the ratio S of the total area of the plurality of first pores to the area of the aqueous positive electrode sheet 12 / S 11 the ratio H of the depth of the first pores to the thickness of the aqueous positive electrode sheet 12 / H 11 When the tap density C1 of the aqueous positive electrode sheet and the volume average particle diameter D1 of the positive electrode active material are within the above ranges, (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11It is advantageous to control within the scope of the present application. Therefore, when the electrode assembly of the present application is applied to a secondary battery, it can not only reduce the risks of gas expansion, self-discharge, and corrosion of the secondary battery, but also improve the energy density, cycle performance, and rate performance of the secondary battery.

[0100] In some embodiments, the ratio of the total area of the plurality of second pores to the area of the negative electrode sheet satisfies 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 / S 21 ≤ 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%.

[0101] Although not intended to be limited by any theory or interpretation, when the ratio of the total area of the plurality of second pores to the area of the negative electrode sheet is within the above range, the negative electrode sheet can have good mechanical properties. Thereby, the risk of irreversible deformation of the negative electrode sheet during the processing can be reduced, and the yield of the electrode assembly can be improved. When the ratio of the total area of the plurality of second pores to the area of the negative electrode sheet is within the above range, the negative electrode sheet can have an appropriate porosity and high capacity, which is advantageous for improving the impregnation rate and capacity performance of the electrolyte of the electrode assembly. Also, when the ratio of the total area of the plurality of second pores to the area of the negative electrode sheet is within the above range, the negative electrode sheet can also have an appropriate electron conduction path and active ion transport path. Therefore, when the electrode assembly is applied to a secondary battery, the secondary battery can have a high yield, high cycle stability, high capacity performance, and low internal resistance.

[0102] In some embodiments, the ratio of the depth of the second pores to the thickness of the negative electrode sheet is 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% ≤ H22 / H 21 ≤90%, 40% ≤ H 22 / H 21 ≤80%, 40% ≤ H 22 / H 21 ≤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 can satisfy ≤100%.

[0103] In the present application, the depth of the second pore may be less than or equal to the thickness of the negative electrode sheet. H 22 / H 21 When it is 100%, the second pore may be a through hole penetrating the negative electrode sheet.

[0104] Although not intended to be limited by any theory or interpretation, when the ratio of the depth of the second pores to the thickness of the negative electrode sheet is within the above range, the negative electrode sheet not only has a high electrolyte impregnation rate but also can be guaranteed to have good mechanical performance. Therefore, the electrode assembly of the present application can have good interfacial performance, low surface impedance, and high processing efficiency. When applied to a secondary battery, the secondary battery can have good cycle performance, good rate performance, and high yield.

[0105] C2 g / cc represents the tap density of the negative electrode sheet. In some embodiments, C2 may be 1.2 to 2.0. For example, C2 may 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 a range consisting of any of the above numerical values. In some embodiments, C2 can be selectively 1.4 to 1.8.

[0106] When the tap density of the negative electrode sheet is controlled within an appropriate range, the particles of the negative electrode active material in the negative electrode film layer can be adhered, and the content of the negative electrode active material per unit volume can be improved, thereby improving the energy density of the secondary battery.

[0107] D2 μm represents the volume average particle diameter Dv50 of the negative electrode active material. In some embodiments, D2 may be 12 to 20. For example, D2 may be about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, or within a range consisting of any of these numerical values. In some embodiments, D2 can be selectively 15 to 19.

[0108] When the volume average particle diameter Dv50 of the negative electrode active material is within the above range, the diffusion path of the active ions can be shortened. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the energy density, cycle performance, and rate performance of the secondary battery can be further improved.

[0109] Also, for the electrode assembly, the ratio S of the total area of a plurality of second pores to the area of the negative electrode sheet22 / S 21 and the ratio H of the depth of the second pore to the thickness of the negative electrode sheet 22 / H 21 When the pressure density C2 of the negative electrode sheet and the volume average particle diameter D2 of the negative electrode active material are within the above ranges, it is advantageous to control (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) within the scope of the present application. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have good electrochemical performance and high energy density.

[0110] In some embodiments, the electrode assembly can satisfy 0.10 ≦ A / B ≦ 1.0. A represents (S 12 ×H 12 ×D1) / (S 11 ×C1×H 11 ), and B represents (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ). For 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.

[0111] Although not intended to be limited to any theory or interpretation, when the value of A / B is within the above range, the respective advantages of the aqueous positive electrode sheet and the negative electrode sheet and the synergistic effect between the two can be fully exerted, thereby further improving the impregnation rate of the electrolytic solution of the electrode assembly and advantageously discharging the moisture remaining in the drying process of the electrode assembly quickly. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have a low impedance, a high energy density, and a high cycle capacity retention rate.

[0112] In some embodiments, the electrode assembly has S3 / S 22 which can satisfy ≧5%. For example, S3 / S 22 can be about 5%, about 8%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 100%, or within a range consisting of any of the above values. Here, S3m 2 represents the overlapping area of the plurality of first pores and the plurality of second pores.

[0113] In some embodiments, the electrode assembly has 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 It can satisfy ≦ 70%.

[0114] Although not intended to be limited to any theory or interpretation, when the overlapping area between the first pores on the surface of the aqueous positive electrode sheet and the second pores on the surface of the negative electrode sheet is within the above range, it is advantageous for the pores in the first pores, the second pores, and the separator to form a passage, thereby facilitating the rapid discharge of the moisture remaining in the electrode assembly and improving the impregnation rate of the electrolyte in the electrode assembly. Therefore, when the electrode assembly of the present application is applied to a secondary battery, it can have a low impedance, a high energy density, and a high cycle capacity retention rate.

[0115] In the present application, the form of the first pores is not limited, and the forms of the respective first pores may be the same or different. In some embodiments, the form of each first pore can be a regular shape or an irregular shape. In some embodiments, the form of each first pore can include a circular shape, a rectangular shape, or a square shape.

[0116] In some embodiments, the equivalent diameter of each first pore may be 1 μm to 200 μm, for example, 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 a range consisting of any of the above numerical values. In some embodiments, the equivalent diameter of each first pore may be 5 μm to 180 μm, 10 μm to 180 μm, 20 μm to 180 μm, 30 μm to 180 μm, 50 μm to 180 μm, 5 μm to 150 μm, 10 μm to 150 μm, 20 μm to 150 μm, 30 μm to 150 μm, or 50 μm to 150 μm.

[0117] The equivalent diameter of each first pore may be the diameter of a circle having the same area as each first pore. When the equivalent diameter of the first pore is within the above range, on the premise of ensuring that the aqueous positive electrode sheet has a low water content, a high impregnation rate of the electrolytic solution, and a high drying rate, it can have good mechanical properties, for example, high strength and good flexibility. Therefore, the electrode assembly can have a high impregnation rate of the electrolytic solution and good processing performance, whereby the secondary battery applying the electrode assembly can also have good electrochemical performance and a high yield.

[0118] In some embodiments, the center-to-center distance between adjacent first pores may be 1 mm to 10 mm, for example, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, or a range consisting of any of the above values.

[0119] Although not intended to be limited by any theory or interpretation, when the center-to-center distance between adjacent first pores is within the above range, the first pores can be appropriately distributed on the surface of the aqueous positive electrode sheet. Thereby, in order to avoid the distribution of the first pores becoming excessively dense, the aqueous positive electrode sheet can maintain good mechanical properties.

[0120] This application does not limit the distribution pattern of the plurality of first pores. In some embodiments, the plurality of first pores may be distributed in an array.

[0121] The form of the second pores is not limited in this application, but the forms of each second pore may be the same or different. In some embodiments, the form of each second pore can be a regular shape or an irregular shape. In some embodiments, the form of each second pore can include a circle, a rectangle, or a square.

[0122] In some embodiments, the equivalent diameter of each second pore may be from 1 μm to 200 μm, for example, 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 a range consisting of any of the above values. In some embodiments, the equivalent diameter of each second pore may be from 5 μm to 180 μm, from 10 μm to 180 μm, from 20 μm to 180 μm, from 30 μm to 180 μm, from 50 μm to 180 μm, from 5 μm to 150 μm, from 10 μm to 150 μm, from 20 μm to 150 μm, from 30 μm to 150 μm, or from 50 μm to 150 μm.

[0123] The equivalent diameter of each second pore may be the diameter of a circle having the same area as each second pore. When the equivalent diameter of the second pore is within the above range, on the premise of ensuring that the negative electrode sheet has a high electrolyte impregnation rate, it can have good mechanical properties, for example, high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte impregnation rate and good processing performance. Thereby, the secondary battery applying the electrode assembly can also have good electrochemical performance and a high yield.

[0124] In some embodiments, the center-to-center distance between adjacent second pores may be from 1 mm to 10 mm, for example, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, or a range consisting of any of the above values.

[0125] Although not intended to be limited by any theory or interpretation, when the center-to-center distance between adjacent second pores is within the above range, the second pores can be appropriately distributed on the surface of the negative electrode sheet. Thereby, in order to avoid the distribution of the second pores becoming excessively dense, the negative electrode sheet can maintain good mechanical properties.

[0126] This application does not limit the distribution pattern of the plurality of second pores. In some embodiments, the plurality of second pores may be distributed in an array.

[0127] In the present application, the positive electrode current collector has two opposing surfaces in its thickness direction. The positive electrode film layer can be located on one or both of the two opposing surfaces of the positive electrode current collector. The negative electrode current collector has two opposing surfaces in its thickness direction. The negative electrode film layer can be located on one or both of the two opposing surfaces of the negative electrode current collector.

[0128] Note that the thickness H of the aqueous positive electrode sheet 11 represents the sum of the thicknesses of the positive electrode current collector and the positive electrode film layer. The thickness H of the negative electrode sheet 21 represents the sum of the thicknesses of the negative electrode current collector and the negative electrode film layer. FIG. 1 is a schematic cross-sectional view of a partial embodiment of the aqueous positive electrode sheet of the present application. FIG. 2 is a schematic cross-sectional view of another partial embodiment of the aqueous positive electrode sheet of the present application. As shown in FIGS. 1 and 2, the positive electrode film layer 102 is provided on both sides of the positive electrode current collector 101. Among them, in FIG. 1, the ratio of the depth of the first pore to the thickness of the positive electrode sheet is less than 100%, that is, H 12 is smaller than H 11 . FIG. 2 shows that the first pore is a through hole penetrating the positive electrode sheet. At this time, H 12 is equal to H 11 . In the present application, the installation situation of the second pores on the surface of the negative electrode sheet is similar to that of the aqueous positive electrode sheet.

[0129] In the electrode assembly of the present application, the type of the positive electrode active material is not specifically limited, and a positive electrode active material for a secondary battery known in the art can be adopted. In some embodiments, the positive electrode active material can include one or more of lithium transition metal oxides, lithium-containing phosphates having an olivine structure, and modified compounds thereof. The modified compounds of the above positive electrode active materials can perform doping modification, surface coating modification, or both doping modification and surface coating modification on the positive electrode active material.

[0130] As an example, the lithium transition metal oxide can 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 modified compounds. As an example, the olivine-structured lithium-containing phosphate can include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. These cathode active materials may be used alone, or two or more of them may be used in combination.

[0131] Optionally, the cathode active material can include one or more of the olivine-structured lithium-containing phosphate and its modified compounds.

[0132] In some embodiments, the cathode film layer can further include one or more of an aqueous adhesive and a conductive agent. The aqueous adhesive can adhere the cathode active material, the conductive agent, etc. to the current collector, strengthen the electron contact between the cathode active material and the conductive agent, and between the cathode active material and the cathode current collector, and stabilize the structure of the cathode sheet. The aqueous adhesive has a lower cost, is more environmentally friendly, and can be used more safely than oil-based adhesives such as polyvinylidene fluoride.

[0133] The aqueous adhesive can include an aqueous dispersion or emulsion having a solid content of 5% or more. The aqueous adhesive can further include a solid capable of forming a stable dispersion with water and having a solid content of 1% or more. In some embodiments, the aqueous adhesive includes soluble polysaccharides and their derivatives, water-soluble or aqueous-dispersible polymer polymers or mixtures thereof. For example, the aqueous adhesive can include methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymers and their derivatives, or mixtures thereof.

[0134] In some embodiments, the aqueous adhesive can include a composite mixture of xanthan gum and polyethyleneimine. Optionally, the mass ratio of the xanthan gum to the 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.

[0135] In some embodiments, the aqueous adhesive can include a composite mixture of an 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.

[0136] Although not intended to be limited to any theory or interpretation, when the aqueous adhesive is selected from the above substances, the structure of the positive electrode sheet can be better stabilized in order to further strengthen the electron contact between the positive electrode active material and the conductive agent, and between the positive electrode active material and the positive electrode current collector. Thereby, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have high cycle stability and low internal resistance.

[0137] The present application does not particularly limit the type of the conductive agent used in the positive electrode film layer. 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.

[0138] In the electrode assembly of the present application, the positive electrode film layer is usually formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an aqueous adhesive, a conductive agent, and any other components in deionized water and uniformly stirring them.

[0139] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can 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 include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0140] In the electrode assembly of the present application, the negative electrode film layer is usually formed by applying a negative electrode slurry to a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliaries in a solvent and uniformly stirring them. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or water. As an example, the adhesive used for the negative electrode film layer can include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (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 can include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Other optional auxiliaries can include one or more of a thickener (e.g., sodium carboxymethyl cellulose CMC) and PTC thermistor materials.

[0141] The type of the negative electrode active material is not particularly limited, and a negative electrode active material for a secondary battery known in the art can be adopted. As an example, the negative electrode active material can include one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fiber, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include one or more of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials can include one or more of tin alone, tin oxide, and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials used as secondary battery negative electrode active materials can be used. These negative electrode active materials can be used alone or in combination of two or more.

[0142] The type of the negative electrode current collector is not specifically limited and can be selected according to actual requirements. For example, a metal foil or a composite current collector can be used as the negative electrode current collector. As an example of the metal foil, a copper foil can be adopted as the negative electrode current collector. The composite current collector can 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 is one or more selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may be one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0143] In addition, in the electrode assembly of the present application, the negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet described in the present application may further include a conductive primer layer (for example, composed of a conductive agent and an adhesive) provided between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0144] In the electrode assembly of the present application, the realization methods of the first pores and the second pores are not specifically limited and can be realized by using known means in this field. In some embodiments, the means for providing the first pores and the second pores on the surface of the electrode sheet can include any one method or a combination thereof, such as laser perforation and mechanical perforation. For example, when laser perforation is adopted, the lasers can be arranged with a vertical shift, an appropriate perforation array can be installed according to the requirements of the perforation process, and an appropriate laser energy can be selected according to the required depth of the pores.

[0145] In some embodiments, the electrode assembly further includes a separator. The separator is provided between the aqueous positive electrode sheet and the negative electrode sheet, mainly serving to prevent short - circuit between the positive and negative electrodes and allowing active ions to pass through. In the present application, the type of the separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0146] For example, the material of the separator can 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 can be the same or different.

[0147] In some embodiments, the aqueous positive electrode sheet, the separator, and the negative electrode sheet can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0148] In the present application, the thickness of the membrane layer and the electrode sheet has a meaning known in the art and can be measured by methods known in the art. For example, it can be measured using a spiral micrometer.

[0149] In the present application, the volume - average particle diameter Dv50 of the material has a meaning known in the art, indicating the particle diameter corresponding when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by known equipment and methods in the art. For example, referring to GB / T 19077 - 2016 Laser Diffraction Method for Particle Size Distribution, it can be easily measured using a laser particle size analyzer, such as the Mastersizer2000E type laser particle size analyzer of Malvern Panalytical Ltd. in the UK.

[0150] In the present application, the pressure density of the electrode sheet has the meaning known in the art and can be measured by a method known in the art. The pressure 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 the meaning known in the art and can be measured by adopting a method known in the art. For example, take an electrode sheet after being coated on one side and cold-pressed (if it is an electrode sheet coated on both sides, first, the film layer on one side can be wiped off and removed), punch it into small wafers, weigh its weight, and then wipe off and remove the film layer of the weighed electrode sheet and weigh the weight of the current collector. The areal density of the film layer = (the weight of the small wafer - the weight of the current collector) / the area of the small wafer. Secondary battery

[0151] The second aspect of the present application provides a secondary battery including the electrode assembly and the electrolyte of the first aspect of the present application. The electrolyte serves to conduct active ions between the positive electrode sheet and the negative electrode sheet. In the present application, the type of the electrolyte is not specifically limited and is selected as needed. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

[0152] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution contains an electrolyte salt and a solvent.

[0153] The type of electrolyte salt is not particularly limited and is selected according to actual requirements. In some embodiments, by way of example, the electrolyte salt may be one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium difluoromethanesulfonimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoroborate (LiDFOB), lithium diborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodiphosphate (LiDFOP), and lithium tetrafluoroborate (LiTFOP).

[0154] The type of solvent is not particularly limited and is selected according to actual requirements. In some embodiments, by way of 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), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0155] In some embodiments, the electrolytic solution may further optionally contain an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, an additive that can improve certain performance of the battery, such as an additive that improves the overcharging performance of the battery, an additive that improves the high-temperature performance of the battery, an additive that improves the low-temperature output performance of the battery, and the like.

[0156] The secondary battery may have an exterior package. The exterior package is used to seal the electrode assembly and the electrolyte described above.

[0157] In some embodiments, the exterior package of the secondary battery may be a rigid case such as a rigid plastic case, an aluminum case, or a steel case. The exterior package of the secondary battery may also be a soft pack, such as a pouch soft pack. The material of the soft pack may be a plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.

[0158] In the present application, the shape of the secondary battery is not particularly limited, and it may be a flat body, a rectangular parallelepiped, or other shapes. FIG. 3 shows, as an example, a secondary battery 5 having a rectangular parallelepiped structure.

[0159] In some embodiments, as shown in FIG. 4, the exterior package may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and side plates connected to the bottom plate, and a storage cavity is formed by enclosing the bottom plate and the side plates. The case 51 has an opening communicating with the storage cavity, and the cover plate 53 covers the opening to seal the storage cavity. The electrode assembly 52 of the first aspect of the embodiment of the present application is enclosed in the storage cavity. The electrolytic solution is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be adjusted as needed.

[0160] The manufacturing method of the secondary battery of the present application is known. In some embodiments, the electrode assembly is placed in the exterior packaging, the electrolytic solution is injected after drying, and through processes such as vacuum sealing, standing, formation, and shaping, a secondary battery can be obtained. Battery module and battery pack

[0161] The secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural, and the specific number can be adjusted according to the use and capacity of the battery module.

[0162] FIG. 5 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 5, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4, and of course, they may be arranged in any other manner. Furthermore, these plurality of secondary batteries 5 may be fixed by fastening tools.

[0163] Optionally, the battery module 4 may further include a housing having an accommodation space for accommodating a plurality of secondary batteries 5.

[0164] In some embodiments, the above battery module may be assembled into a battery pack. The number of battery modules included in the battery pack can be adjusted according to the use and capacity of the battery pack.

[0165] FIGS. 6 and 7 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 6 and 7, the battery pack 1 can include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and is used to form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 can be arbitrarily arranged within the battery case. Power consumption device

[0166] Embodiments of the present application further provide a power consumption device including at least one of a secondary battery, a battery module, or a battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage unit of the power consumption device. The power consumption device may be a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

[0167] The power consumption device can select a secondary battery, a battery module, or a battery pack according to its usage requirements.

[0168] FIG. 8 is a schematic diagram of a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. In order to meet the requirements for high power and high energy density of the power consumption device, a battery pack or a battery module can be adopted.

[0169] Another example of the power consumption device may be a mobile phone, a tablet computer, a notebook computer, etc. The power consumption device is usually required to be thin, and a secondary battery can be adopted as a power source. Example

[0170] The following examples specifically illustrate the content disclosed in the present application. These examples are only used for illustration, and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the content disclosed in the present application. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass. In addition, all reagents used in the examples can be purchased or synthesized according to conventional methods, and can be directly used without further treatment. Also, all the devices used in the examples can be purchased.

[0171] The secondary batteries of Examples 1 to 25 and Comparative Examples 4 to 10 were fabricated by the following method.

[0172] ( (1) Preparation of aqueous positive electrode sheet

[0173] Lithium iron phosphate as the cathode active material, conductive carbon black as the conductive agent, and an aqueous adhesive were uniformly mixed at a mass ratio of 96:1:3, and an appropriate amount of deionized water was added to obtain a cathode slurry with a solid content of 50%. The cathode slurry was uniformly coated on the surface of the cathode current collector and dried to obtain an aqueous cathode sheet coated on both sides. The aqueous adhesive is a blend of polyacrylonitrile-acrylic acid ester copolymer LA-133 (purchased from Sichuan Yindi Le Technology Co., Ltd.) and polyethyleneimine. In this blend, the mass ratio of LA-133 to polyethyleneimine is 1:1.

[0174] By using a laser drilling device to drill the aqueous cathode sheet, a plurality of first pores were provided on the surface of the aqueous cathode sheet. The equivalent diameter d1 (μm) of the first pores, the center-to-center distance L1 (mm) between adjacent first pores, the ratio S of the total area of the plurality of first pores to the area of the aqueous cathode sheet 12 / S 11 The ratio H of the depth of the first pores to the thickness of the aqueous cathode sheet 12 / H 11 The tap density C1 (g / cc) of the aqueous cathode sheet, the volume average particle size D1 (μm) of the cathode active material, (S 12 ×H 12 ×D1) / (S11 ×C1×H 11 ) are shown in Table 1A and Table 1B, respectively.

[0175] (2) Preparation of negative electrode sheet

[0176] Artificial graphite as the anode active material, conductive carbon black as the conductive agent, styrene-butadiene rubber (SBR) as the adhesive, and sodium carboxymethyl cellulose (CMC) as the thickener were mixed at a mass ratio of 96.2:1.8:0.8:1.2. Then, an appropriate amount of deionized water was added and uniformly mixed to obtain an anode slurry. The anode slurry was uniformly coated on the surface of the anode current collector and dried to obtain an anode sheet coated on both sides.

[0177] By using a laser drilling device to drill the anode sheet, a plurality of second pores are provided on the surface of the anode sheet. The equivalent diameter d2 (μm) of the second pores, the center-to-center distance L2 (mm) between adjacent second pores, the ratio S of the total area of the plurality of second pores to the area of the anode sheet 22 / S 21 , the ratio H of the depth of the second pores to the thickness of the anode sheet 22 / H 21 , the tap density C2 (g / cc) of the anode sheet, the volume average particle diameter D2 (μm) of the anode active material, (S 22 ×H 22 ×D2) / (S 21 ×C2×H 21 ) are shown in Table 1A and Table 1B, respectively.

[0178] (3) Preparation of electrolyte

[0179] In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC), which are organic solvents, were uniformly mixed at a volume ratio of 3:7, 12.5% of LiPF6 was added and dissolved in the organic solvent, and uniformly stirred to obtain an electrolyte.

[0180] (4) Separator

[0181] A polypropylene film was used as the separator.

[0182] (5) Preparation of secondary battery

[0183] The aqueous positive electrode sheet, separator, and negative electrode sheet were laminated in sequence so that the separator was positioned between the aqueous positive electrode sheet and the negative electrode sheet to play a role of isolation. The laminated aqueous positive electrode sheet, separator, and negative electrode sheet were wound to obtain an electrode assembly. After welding tabs to the electrode assembly, the electrode assembly was placed in an aluminum case, baked to remove moisture, and after injecting an electrolyte into the aluminum case, it was sealed to obtain a non-charged battery. Through processes such as standing, hot and cold pressing, formation, shaping, and capacity testing in sequence for the non-charged battery, a secondary battery was obtained.

[0184] Comparative Example 1

[0185] The production process of the aqueous positive electrode sheet, negative electrode sheet, separator, electrolyte, and secondary battery is basically the same as that of Example 1, but the difference is that the surfaces of the aqueous positive electrode sheet and the negative electrode sheet are not perforated.

[0186] Comparative Examples 2 - 3

[0187] The production process of the aqueous positive electrode sheet, negative electrode sheet, separator, electrolyte, and secondary battery is basically the same as that of Example 1, but the differences are that in Comparative Example 2, the surface of the negative electrode sheet is not perforated, and in Comparative Example 3, the surface of the aqueous positive electrode sheet is not perforated. Test part

[0188] (1) Test on the impregnation performance of the electrolyte of the electrode assembly

[0189] The non-charged batteries obtained in each example and comparative example were allowed to stand for different periods of time, and then the first charge test was carried out. The current for the first charge was set at 0.1C (51.2 A), and the charge cut-off voltage was set at 3.65 V. After the charge was completed, the battery was disassembled in a drying chamber, and it was observed whether or not a grayish-white color appeared after lithium deposition in a large-area region of the negative electrode sheet. If a black region was exposed on the surface, it indicated that the impregnation of the electrolyte was insufficient. If no black region was exposed on the surface, it indicated that the electrolyte completely impregnated the negative electrode sheet. The shortest time required for the electrolyte to completely impregnate the negative electrode sheet was recorded. Each time the impregnation time was increased by half an hour during the test, one group was set up. Each group disassembled three electrode assemblies for determination. The shortest time required for the three electrode assemblies to simultaneously meet the condition that the electrolyte completely impregnates the negative electrode sheet was defined as the electrolyte impregnation time T1 of the electrode assembly.

[0190] (2) Test of the drying performance of the secondary battery

[0191] The batteries obtained in each example and comparative example were placed in a case, and the drying performance test was carried out by putting them into a vacuum oven without injecting liquid. The oven temperature was set at 105 °C, and they were taken out every 1 h to measure the moisture content of the battery. When the moisture content of the battery was less than 200 ppm (mass concentration), it was considered to be already dried, and the drying time T2 was recorded.

[0192] (3) Test of the initial capacity and cycle performance of the secondary battery

[0193] For the secondary battery, a charge-discharge test was carried out using a battery test machine. Here, the charge-discharge voltage was 2.5 V to 3.65 V, the charge-discharge current was 1C (512 A), and the discharge capacity after the first cycle and the discharge capacity after 300 cycles of the secondary battery were read.

[0194] The average value of the discharge capacities of the three secondary batteries after the first cycle was defined as the initial capacity of the secondary battery.

[0195] The capacity retention rate of the secondary battery after 300 cycles = (discharge capacity after 300 cycles / discharge capacity after the first cycle) × 100%.

[0196] (4) Test of DC resistance impedance (DCR) of secondary battery

[0197] At 25 °C, the secondary battery was charged to 3.65 V at a constant current of 1 / 3C, and then charged at a constant voltage of 3.65 V until the current reached 0.05C. After standing for 5 min, the voltage V1 at that time was recorded. The secondary battery was discharged at a constant current of 1 / 3C for 30 s, and the voltage V2 at that time was recorded. The internal resistance after the first cycle is indicated by (V2~V1) / (1 / 3C). While repeating the above procedure, the internal resistance of the secondary battery after 300 cycles was recorded.

[0198] The parameters of each example and comparative example are shown in Table 1A and Table 1B, and the test results are shown in Table 2.

Table 1A

Table 1B

Table 2

[0199] As can be seen from Table 1A, Table 1B and Table 2, in the electrode assemblies of Examples 1 to 25, when the aqueous positive electrode sheet and the negative electrode sheet satisfy the conditions limited in the present application, the secondary battery can have a high initial capacity, a high impregnation rate of the electrolyte and a high drying rate, and can also have a high cycle capacity retention rate and a low internal resistance.

[0200] In Comparative Examples 1 to 3, pores are not provided on the surfaces of the aqueous positive electrode sheet and / or the negative electrode sheet, the impregnation rate and the drying rate of the electrolyte of the electrode assembly are very low, and a large amount of moisture easily remains in the electrode assembly. Thereby, the secondary battery applying the electrode assembly has a high internal resistance and poor thermal performance. In Comparative Examples 4 to 5, pores are provided on the surfaces of both the aqueous positive electrode sheet and the negative electrode sheet. However, in the produced aqueous positive electrode sheet, (S 12 ×H12 × D1) / (S 11 × C1 × H 11 ) is less than 0.001%. In this case, the impregnation rate and drying rate of the electrolyte of the electrode assembly increased slightly compared to Comparative Examples 1 to 3, but the improvement effect was not obvious, and furthermore, the improvement effect on the cycle performance of the secondary battery was not obvious either. In Comparative Examples 6 to 7, pores were provided on the surfaces of both the aqueous positive electrode sheet and the negative electrode sheet. However, in the produced aqueous positive electrode sheet, (S 12 × H 12 × D1) / (S 11 × C1 × H 11 ) was greater than 1%, so the energy density of the secondary battery was significantly reduced. In Comparative Examples 8 to 10, pores were provided on the surfaces of both the aqueous positive electrode sheet and the negative electrode sheet. However, in the produced negative electrode sheet, (S 22 × H 22 × D2) / (S 21 × C2 × H 21 ) was greater than 2.5%, so the energy density of the secondary battery was significantly reduced.

[0201] Note that the present application is not limited to the above embodiments. The above embodiments are merely illustrative, and embodiments having a configuration substantially the same as the technical idea within the scope of the technical solution of the present application and exhibiting the same operational effects are all included in the technical scope of the present application. Also, forms in which various modifications conceivable by those skilled in the art are added to the embodiments and other forms constructed by combining some of the components in the embodiments without departing from the spirit of the present application are also included in the scope of the present application.

Claims

1. An electrode assembly comprising a water-based positive electrode sheet and a negative electrode sheet, wherein the water-based positive electrode sheet includes a positive electrode current collector and a positive electrode film layer on at least one surface of the positive electrode current collector, the positive electrode film layer containing a positive electrode active material, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, the negative electrode film layer containing a negative electrode active material, A plurality of first pores are provided on at least a part of the surface of the aqueous positive electrode sheet, and 0.00001 ≦ (S １２ × H １２ × D １ ) / (S １１ × C １ × H １１ ) ≦ 0.01 is satisfied, H １１ μm represents the thickness of the aqueous positive electrode sheet, H １２ μm represents the depth of the first pores, S １１ m ２ represents the area of the aqueous positive electrode sheet, S １２ m ２ represents the total area of the plurality of first pores, C １ g / cc represents the tap density of the aqueous positive electrode sheet, D １ μm represents the volume average particle diameter Dv50 of the positive electrode active material, A plurality of second pores are provided on at least a part of the surface of the negative electrode sheet, and 0 < (S ２２ × H ２２ × D ２ ) / (S ２１ × C ２ × H ２１ ) ≤ 0.025 is satisfied, H ２１ μm represents the thickness of the negative electrode sheet, H ２２ μm represents the depth of the second pores, S ２１ m ２ represents the area of the negative electrode sheet, S ２２ m ２ represents the total area of the plurality of second pores, C ２ g / cc represents the tap density of the negative electrode sheet, D ２ μm represents the volume average particle diameter Dv50 of the negative electrode active material, 0 < S １２ / S １１ ≤ 0.02, and 0.3 ≤ H １２ / H １１ ≤ 1, C １ is 2.0 to 3.0, D １ is 0.5 to 1.5, the equivalent diameter of each first pore is 1 μm to 200 μm, and the center-to-center distance between adjacent said first pores is 1 mm to 10 mm 0 < S ２２ / S ２１ ≤ 0.002, and 0.3 ≤ H ２２ / H ２１ ≤ 1, C ２ is 1.2 to 2.0, D ２ is 12 to 20, the equivalent diameter of each second pore is 1 μm to 200 μm, and the center - to - center distance between adjacent second pores is 1 mm to 10 mm The electrode assembly is S ３ / S ２２ satisfies S ３ m ２ represents the overlapping area between the plurality of first pores and the plurality of second pores, the electrode assembly.

2. 0.0005 ≤ (S １２ × H １２ × D １ ) / (S １１ × C １ × H １１ ) ≤ 0.005, the electrode assembly according to claim 1.

3. 0.002 ≤ (S ２２ × H ２２ × D ２ ) / (S ２１ × C ２ × H ２１ ) ≤ 0.02, the electrode assembly according to claim 1.

4. The electrode assembly satisfies 0.1 ≦ A / B ≦ 1.0, where A is (S １２ × H １２ × D １ ) / (S １１ × C １ × H １１ ), and B is (S ２２ × H ２２ × D ２ ) / (S ２１ × C ２ × H ２１ ). The electrode assembly according to any one of claims 1 to 3

5. The electrode assembly according to any one of Claims 1 to 3, wherein the first pores satisfy at least one of the following conditions (1) to (2). (1) The form of each first pore is a regular shape or an irregular shape. (2) The plurality of first pores are distributed in an array.

6. The electrode assembly according to any one of Claims 1 to 3, wherein the second pores satisfy at least one of the following conditions (1) to (2). (1) The form of each second pore is a regular shape or an irregular shape. (2) The plurality of second pores are distributed in an array.

7. The electrode assembly according to any one of Claims 1 to 3, wherein the positive electrode film layer further contains one or more of an aqueous adhesive and a conductive agent.

8. The electrode assembly according to Claim 7, wherein the aqueous adhesive contains a composite mixture of xanthan gum and polyethyleneimine.

9. The electrode assembly according to Claim 7, wherein the aqueous adhesive contains a composite mixture of acrylonitrile-acrylic acid copolymer and polyethyleneimine.

10. A secondary battery including an electrolyte and the electrode assembly according to any one of Claims 1 to 3.

11. A battery module including the secondary battery according to Claim 10.

12. A battery pack including one of the secondary battery according to Claim 10 and the battery module according to Claim 11.

13. A power consumption device including at least one of the secondary battery according to Claim 10, the battery module according to Claim 11, and the battery pack according to Claim 12.

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