CN116417685A

CN116417685A - Electrode assembly, method for manufacturing same, secondary battery, battery module, battery pack, and electricity using device

Info

Publication number: CN116417685A
Application number: CN202111657694.2A
Authority: CN
Inventors: 何晓宁; 刘成勇; 薛文文; 钟成斌
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2023-07-11

Abstract

The application provides an electrode assembly, a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive pole piece is provided with more than one positive pole bending part and more than one positive pole straight part connected with the positive pole bending parts, and at least one positive pole bending part in the positive pole piece is a first bending part; the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part; at least one part of the surface of the first bending part is attached with a blocking layer, and the blocking layer is used for blocking at least one part of active ions which are separated from the first bending part from being embedded into the second bending part; ion conductivity lambda of the first bending part ₁ Ion conductivity lambda with positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ < 1. The safety performance of the secondary battery can be enhanced.

Description

Electrode assembly, method for manufacturing same, secondary battery, battery module, battery pack, and electricity using device

Technical Field

The application belongs to the technical field of batteries, and particularly relates to an electrode assembly, a preparation method of the electrode assembly, a secondary battery, a battery module, a battery pack and an electric device.

Background

In recent years, secondary batteries are widely used in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace, and the like. With the application and popularization of secondary batteries, the safety problem of the secondary batteries is becoming more and more concerned, and if the safety problem of the secondary batteries cannot be guaranteed, the secondary batteries cannot be used. Therefore, how to enhance the safety performance of the secondary battery is a technical problem to be solved at present.

Disclosure of Invention

The present application is directed to an electrode assembly, a method of manufacturing the same, a secondary battery, a battery module, a battery pack, and an electric device, which are directed to enhancing safety performance of the secondary battery.

The first aspect of the application provides an electrode assembly, which comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate is provided with more than one positive electrode bending part and more than one positive electrode straight part connected with the positive electrode bending part, and at least one positive electrode bending part in the positive electrode plate is a first bending part; the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part; a blocking layer is attached to at least a part of the surface of the first bending part and used for blocking at least a part of active ions which are separated from the first bending part from being embedded into the second bending part; the ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

According to the method, the situation that active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced through a simple positive electrode plate treatment process, so that the safety performance of the electrode assembly is remarkably improved. In the first embodiment of the present applicationIn the electrode assembly of the aspect, the barrier layer is attached to at least a part of a surface of the first bent portion, so that the first bent portion has lower ion conductivity. When the electrode assembly is charged, at least one part of active ions separated from the first bending part cannot be embedded into the adjacent second bending part due to being blocked by the blocking layer, so that the condition that the active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced, and the safety performance of the electrode assembly is obviously improved. The ionic conductivity lambda of the first bending part ₁ And the energy density of the electrode assembly is not 0, so that the condition that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly is effectively avoided.

In any embodiment of the present application, 0 < λ ₁ /λ ₂ Less than or equal to 0.9. At the moment, the condition that active ions are reduced to form metal simple substances in the bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced

In any embodiment of the present application, the electrode assembly has a winding structure, and in the winding structure, at least an innermost one of the positive electrode sheets is the first bending portion, and at least an innermost one of the negative electrode sheets is the second bending portion. The probability of the active ions to be reduced to form the metal simple substance is highest at the anode bending part at the innermost side of the winding structure, so that the safety performance of the electrode assembly can be remarkably improved by the arrangement.

In any embodiment of the present application, the barrier layer is attached to one or both surfaces of the first bend.

In any embodiment of the present application, the barrier layer is attached to 80% -100% of the surface of the first bending portion facing the second bending portion. At the moment, the condition that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In any embodiment of the present application, the barrier layer has a thickness of 0.1 μm to 20 μm. Optionally, the thickness of the barrier layer is 0.5 μm to 10 μm. When the thickness of the barrier layer is in a proper range, the situation that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In any embodiment of the present application, the barrier layer comprises a polymer component and an inorganic component comprising a conductive active ion component or a combination of a conductive active ion component and a filler component. The conductive active ion component can enable the barrier layer to have certain ion conductivity, so that the situation that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In any embodiment of the present application, the conductive active ion component comprises at least one selected from the group consisting of electrolyte salts, fast ion conductors.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of inorganic component.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of conductive active ion component.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of electrolyte salt.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of fast ion conductor.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 5-45% of electrolyte salt and 5-70% of fast ion conductor.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of conductive active ion component and 1-10% of filler component.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of electrolyte salt and 1-10% of filler component.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of fast ion conductor and 1-10% of filler component.

In any embodiment of the present application, the barrier layer comprises, based on the total mass of the barrier layer: 5 to 90 percent of polymer component, 4.5 to 45 percent of electrolyte salt, 4.5 to 70 percent of fast ion conductor and 1 to 10 percent of filler component.

In any embodiment of the present application, the electrolyte salt comprises a material selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorophosphate, lithium difluorodioxaato phosphate, lithium tetrafluorooxalato phosphate, naPF ₆ 、NaClO ₄ 、NaBCl ₄ 、NaSO ₃ CF ₃ 、Na(CH ₃ )C ₆ H ₄ SO ₃ One or more of them.

In any embodiment of the present application, the fast ion conductor comprises a material selected from garnet type LLZO, perovskite type LLTO, NASICON type LATP, NASICON type LAGP, li ₂ S-GeS ₂ 、Li ₂ S-P ₂ S ₅ 、Li ₂ S-B ₂ S ₃ 、Li ₂ S-SiS ₂ 、Li ₂ S-SiS ₂ -P ₂ S ₅ 、Li ₂ S-SeS ₂ -P ₂ S ₅ 、Li ₂ S-SnS ₂ -P ₂ S ₅ 、Li ₂ S-Al ₂ S ₃ -P ₂ S ₅ 、Li ₂ O-B ₂ O ₃ -P ₂ O ₅ 、Li ₂ O-B ₂ O ₃ -SiO ₂ 、Li ₂ O-SeO ₂ -B ₂ O ₃ 、Li ₃ PO ₄ -Li ₂ S-SiS ₂ 、Na ₃ PS ₄ 、Na ₂ S-P ₂ S ₅ One or more of them.

In any embodiment of the present application, the filler component includes at least one selected from inorganic ceramics. Optionally, the inorganic ceramic comprises one or more selected from aluminum oxide, boehmite, calcium carbonate, calcium silicate, potassium titanate, barium sulfate, hydrotalcite, montmorillonite, spinel, mullite, -, silicon dioxide, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, zirconium carbide.

In any embodiment herein, the polymer component comprises one or more selected from the group consisting of polyacrylonitrile, polyacrylate, polyether, fluoropolymer, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, polyurethane, ethylene-vinyl acetate copolymer, and modified compounds thereof. Alternatively, the polyacrylate is selected from polymethyl methacrylate. Optionally, the polyether includes one or more selected from polyethylene oxide and polypropylene oxide. Optionally, the fluoropolymer comprises a polymer selected from vinylidene fluoride homopolymers or copolymers. Further, the fluorine-containing polymer comprises one or more of vinylidene fluoride homopolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

A second aspect of the present application provides a method for preparing an electrode assembly, comprising the steps of: step 1, providing a positive pole piece and a negative pole piece; step 2, winding the positive electrode plate and the negative electrode plate to form an electrode assembly, wherein the positive electrode plate is provided with more than one positive electrode bending part and is matched with the positive electrode The positive electrode bending parts are connected with positive electrode straight parts, and at least one positive electrode bending part in the positive electrode plate is a first bending part; the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part; a blocking layer is attached to at least a part of the surface of the first bending part and used for blocking at least a part of active ions which are separated from the first bending part from being embedded into the second bending part; the ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

In any embodiment of the present application, the method for preparing the positive electrode sheet includes the steps of: step 101, providing an initial positive electrode plate and slurry for forming the barrier layer, wherein the initial positive electrode plate comprises a positive electrode current collector and a positive electrode film layer which is arranged on at least one surface of the positive electrode current collector and comprises a positive electrode active material; and 102, coating the slurry on at least a part of the surface of the initial positive electrode sheet for forming the first bending part through winding so as to form the barrier layer after drying. The preparation method can ensure the continuity of the production of the positive electrode plate, has strong compatibility with the existing equipment, and can effectively improve the safety performance of the electrode assembly under the condition of smaller weight increment of the electrode assembly.

In any embodiment of the present application, the slurry includes a solvent, a polymer component, and an inorganic component including a conductive active ion component or a combination of a conductive active ion component and a filler component. Optionally, the conductive active ion component comprises at least one selected from the group consisting of electrolyte salts, fast ion conductors.

A third aspect of the present application provides a secondary battery comprising the electrode assembly of the first aspect of the present application, or the electrode assembly prepared according to the method of the second aspect of the present application.

A fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.

A fifth aspect of the present application provides a battery pack comprising the battery module of the fourth aspect of the present application.

A sixth aspect of the present application provides an electric device comprising at least one of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect, and the battery pack of the fifth aspect.

The method can effectively improve the safety performance of the secondary battery while the weight gain of the secondary battery is small and the energy density of the secondary battery is excessively reduced through a simple positive electrode plate treatment process. The battery module, the battery pack, and the power consumption device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the drawings that are required to be used in the embodiments of the present application. It is apparent that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained from the drawings without inventive work for those of ordinary skill in the art.

Fig. 1 is a schematic view of an embodiment of an electrode assembly of the present application.

Fig. 2 is a flow chart of a method of making an electrode assembly of the present application.

Fig. 3 is a schematic flow chart of a method for preparing a positive electrode sheet according to some embodiments of the present application.

Fig. 4 is a schematic view of an embodiment of a secondary battery of the present application.

Fig. 5 is an exploded schematic view of the secondary battery shown in fig. 4.

Fig. 6 is a schematic view of an embodiment of a battery module of the present application.

Fig. 7 is a schematic view of an embodiment of a battery pack of the present application.

Fig. 8 is an exploded view of the battery pack shown in fig. 7.

Fig. 9 is a schematic diagram of an embodiment of an electrical device including the secondary battery of the present application as a power source.

In the drawings, the drawings are not necessarily to scale.

Detailed Description

Hereinafter, embodiments of an electrode assembly, a method of manufacturing the same, a secondary battery, a battery module, a battery pack, and an electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, and such solutions should be considered to be included in the disclosure of the present application, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, if not specifically stated, and such technical solutions should be considered as included in the disclosure of the present application.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

The terms "coupled," "connected," and "connected," as used herein, are defined in a broad sense as connected, either permanently connected, detachably connected, or integrally connected, unless otherwise specified; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

The term "attached" in this application refers to being attached by adhesion, coating, or the like, unless otherwise specified.

The terms "first," "second," "third," "fourth," and the like in this application, unless otherwise specified, are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order.

In the present application, the term "active ion" refers to an ion capable of being inserted and extracted back and forth between the positive and negative electrodes of the secondary battery, including, but not limited to, lithium ion, sodium ion, and the like, unless otherwise specified.

The term "plurality" as used herein refers to more than two (including two).

In the present application, the secondary battery may include a lithium ion battery, a sodium ion battery, and the like, which is not limited by the embodiment of the present application. The secondary battery may be an aqueous battery or an oil battery, and the embodiment of the present application is not limited thereto. The secondary battery may have a flat body, a rectangular parallelepiped, or other shape, etc., and the embodiment of the present application is not limited thereto.

Secondary batteries, also referred to as rechargeable batteries or secondary batteries, refer to batteries that can be continuously used by activating an active material by charging after the battery is discharged. In general, a secondary battery includes an electrode assembly including a positive electrode tab, a negative electrode tab, and a separator, and an electrolyte. The positive pole piece comprises a positive current collector and a positive film layer, wherein the positive film layer is coated on the surface of the positive current collector, and the positive film layer comprises a positive active material. The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer, wherein the negative electrode film layer is coated on the surface of the negative electrode current collector, and the negative electrode film layer comprises a negative electrode active material. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile, active ions can pass through the isolating film. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

When the secondary battery is charged, active ions are extracted from the positive electrode active material of the positive electrode film layer and are embedded into the negative electrode active material of the negative electrode film layer, but abnormal conditions may occur, for example, the storage sites for the active ions which can be provided by the negative electrode film layer are insufficient, the resistance of the active ions to be embedded into the negative electrode active material is too large, or the active ions which are extracted from the positive electrode active material too quickly but are extracted cannot be embedded into the negative electrode active material in an equivalent amount, and part of the active ions which cannot be embedded into the negative electrode active material can only obtain electrons on the surface of the negative electrode plate and reduce to form metal elements.

The formation of the metal simple substance not only increases the irreversible consumption of the active ions, greatly shortens the cycle life of the secondary battery, but also limits the dynamic properties of the secondary battery, such as the quick charge property. In addition, the metal simple substance, such as lithium simple substance, is relatively active, and can react with the organic solvent in the electrolyte at a lower temperature, so that the self-heating initial temperature of the secondary battery is reduced, the self-heating rate is increased, and the safety of the secondary battery is seriously compromised. In addition, the metal simple substance continuously grows, dendrites can be formed on the surface of the negative electrode plate, and the dendrites continuously grow and easily puncture the isolating film to cause short circuit in the secondary battery, so that risks such as combustion and explosion are possibly caused.

The inventor finds that in the research and development process, the radius of the positive electrode plate is far larger than that of the adjacent negative electrode plate in the bending region of the winding electrode assembly, especially in the innermost region of the bending region, so that the number of active ion storage sites which can be provided by the negative electrode film layer in the region is far smaller than that of active ions which can be extracted from the adjacent positive electrode film layer. Therefore, when the secondary battery is charged, the situation that active ions are reduced in the negative electrode plate to form metal simple substance easily occurs in the area, so that the safety performance of the secondary battery is seriously affected.

In view of this, the inventors have improved the structure of the electrode assembly and have proposed an electrode assembly having significantly improved safety performance.

A first aspect of embodiments of the present application provides an electrode assembly comprising a positive electrode sheet and a negative electrode sheet. Wherein the positive electrode plate is provided with more than one positive electrode bending part and one positive electrode bending partThe positive electrode straight part is connected with the positive electrode bending part, and at least one positive electrode bending part in the positive electrode plate is a first bending part; the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part; a blocking layer is attached to at least a part of the surface of the first bending part and used for blocking at least a part of active ions which are separated from the first bending part from being embedded into the second bending part; the ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

According to the method, the situation that active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced through a simple positive electrode plate treatment process, so that the safety performance of the electrode assembly is remarkably improved. In the electrode assembly of the first aspect of the embodiments of the present application, the barrier layer is attached to at least a part of the surface of the first bending part, so that the first bending part has lower ion conductivity. When the electrode assembly is charged, at least one part of active ions separated from the first bending part cannot be embedded into the adjacent second bending part due to being blocked by the blocking layer, so that the condition that the active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced, and the safety performance of the electrode assembly is obviously improved. Therefore, although the number of active ion storage sites which can be provided by the negative electrode film layer of the bending region of the electrode assembly is unchanged, the number of active ions which are taken out of the positive electrode film layer and can be embedded into the negative electrode film layer is reduced, so that the condition that the active ions are reduced to form metal simple substances in the bending region of the electrode assembly is effectively reduced. The ionic conductivity lambda of the first bending part ₁ And is not 0, which means that the barrier layer has a certain active ion conductivity, so that part of active ions released from the first bending part can be embedded into the adjacent second bending part during charging, and further, the active ion reduction formation in the bending region of the electrode assembly is effectively avoided while the energy density of the electrode assembly is excessively reducedThe case of elemental metals.

The electrode assembly can be subjected to less weight increment through a simple positive electrode plate treatment process, and the safety performance of the electrode assembly can be effectively improved while the energy density of the electrode assembly is excessively reduced.

In some embodiments, optionally, 0 < lambda ₁ /λ ₂ ≤0.9，0＜λ ₁ /λ ₂ ≤0.8，0＜λ ₁ /λ ₂ ≤0.7，0＜λ ₁ /λ ₂ ≤0.6，0＜λ ₁ /λ ₂ ≤0.5，0＜λ ₁ /λ ₂ ≤0.4，0＜λ ₁ /λ ₂ ≤0.3，0＜λ ₁ /λ ₂ ≤0.2，0＜λ ₁ /λ ₂ ≤0.1，0.1≤λ ₁ /λ ₂ ＜1，0.1≤λ ₁ /λ ₂ ≤0.9，0.1≤λ ₁ /λ ₂ ≤0.8，0.1≤λ ₁ /λ ₂ ≤0.7，0.1≤λ ₁ /λ ₂ ≤0.6，0.1≤λ ₁ /λ ₂ ≤0.5，0.1≤λ ₁ /λ ₂ ≤0.4，0.1≤λ ₁ /λ ₂ ≤0.3，0.1≤λ ₁ /λ ₂ ≤0.2，0.2≤λ ₁ /λ ₂ ＜1，0.2≤λ ₁ /λ ₂ ≤0.9，0.2≤λ ₁ /λ ₂ ≤0.8，0.2≤λ ₁ /λ ₂ ≤0.7，0.2≤λ ₁ /λ ₂ ≤0.6，0.2≤λ ₁ /λ ₂ ≤0.5，0.2≤λ ₁ /λ ₂ ≤0.4，0.2≤λ ₁ /λ ₂ ≤0.3，0.3≤λ ₁ /λ ₂ ＜1，0.3≤λ ₁ /λ ₂ ≤0.9，0.3≤λ ₁ /λ ₂ ≤0.8，0.3≤λ ₁ /λ ₂ ≤0.7，0.3≤λ ₁ /λ ₂ ≤0.6，0.3≤λ ₁ /λ ₂ ≤0.5，0.3≤λ ₁ /λ ₂ ≤0.4，0.4≤λ ₁ /λ ₂ ＜1，0.4≤λ ₁ /λ ₂ ≤0.9，0.4≤λ ₁ /λ ₂ ≤0.8，0.4≤λ ₁ /λ ₂ ≤0.7，0.4≤λ ₁ /λ ₂ ≤0.6，0.4≤λ ₁ /λ ₂ ≤0.5，0.5≤λ ₁ /λ ₂ ＜1，0.5≤λ ₁ /λ ₂ ≤0.9，0.5≤λ ₁ /λ ₂ ≤0.8，0.5≤λ ₁ /λ ₂ Not more than 0.7, or not less than 0.5 +.lambda. ₁ /λ ₂ Less than or equal to 0.6. At the moment, the condition that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In some embodiments, the electrode assembly has a coiled structure, and in the coiled structure, at least an innermost one of the positive electrode sheets is the first bend and at least an innermost one of the negative electrode sheets is the second bend. The probability of the active ions to be reduced to form the metal simple substance is highest at the anode bending part at the innermost side of the winding structure, so that the safety performance of the electrode assembly can be remarkably improved by the arrangement.

In some embodiments, the barrier layer is attached to one or both surfaces of the first bend.

In some embodiments, the barrier layer is attached to a portion or all of the surface of the first bend that faces the second bend. For example, 80% -100% of the surface of the first bending portion facing the second bending portion is attached with the barrier layer. Optionally, the barrier layer is attached to 80% -95% of the surface of the first bending part facing the second bending part. At the moment, the condition that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In some embodiments, the barrier layer has a thickness of 0.1 μm to 20 μm. Alternatively, the barrier layer has a thickness of 0.1 μm to 20 μm,0.1 μm to 18 μm,0.1 μm to 16 μm,0.1 μm to 14 μm,0.1 μm to 12 μm,0.1 μm to 10 μm,0.1 μm to 8 μm,0.1 μm to 6 μm,0.1 μm to 4 μm,0.1 μm to 2 μm,0.5 μm to 20 μm,0.5 μm to 18 μm,0.5 μm to 16 μm,0.5 μm to 14 μm,0.5 μm to 12 μm,0.5 μm to 10 μm,0.5 μm to 8 μm,0.5 μm to 6 μm,0.5 μm to 4 μm,0.5 μm to 2 μm,1 μm to 20 μm,1 μm to 18 μm,1 μm to 16 μm,1 μm to 14 μm,1 μm to 1 μm,1 μm to 12 μm. When the thickness of the barrier layer is in a proper range, the situation that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In some embodiments, the barrier layer includes a polymer component and an inorganic component including a conductive active ion component or a combination of a conductive active ion component and a filler component. The conductive active ion component can enable the barrier layer to have certain ion conductivity, so that the situation that active ions are reduced to form a metal simple substance in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced. Optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5% -90% of polymer component; 10 to 95 percent of inorganic component.

In some embodiments, the conductive active ion component comprises at least one selected from the group consisting of electrolyte salts, fast ion conductors (also known as inorganic solid electrolytes).

In some embodiments, the inorganic component includes a conductive active ion component and does not include a filler component. Optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of conductive active ion component. For example, in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of electrolyte salt; in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of fast ion conductor; in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 5-45% of electrolyte salt and 5-70% of fast ion conductor.

In some embodiments, the inorganic component comprises a combination of a conductive active ion component and a filler component. Optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of conductive active ion component and 1-10% of filler component. For example, in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of electrolyte salt and 1-10% of filler component; in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of fast ion conductor and 1-10% of filler component; in some embodiments, the barrier layer comprises, based on the total mass of the barrier layer: 5 to 90 percent of polymer component, 4.5 to 45 percent of electrolyte salt, 4.5 to 70 percent of fast ion conductor and 1 to 10 percent of filler component.

The type of electrolyte salt is not particularly limited in the present application, and in some embodiments, the electrolyte salt includes, but is not limited to, one or more of lithium salt, sodium salt. Alternatively, the lithium salt comprises a compound selected from lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium bis (fluorosulfonyl) imide (LiLSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium difluorooxalato borate (LiBOB), lithium difluorophosphate (LiPO) ₂ F ₂ ) One or more of lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP). Alternatively, the sodium salt comprises a salt selected from the group consisting of NaPF ₆ 、NaClO ₄ 、NaBCl ₄ 、NaSO ₃ CF ₃ 、Na(CH ₃ )C ₆ H ₄ SO ₃ One or more of them.

The type of the fast ion conductor is not particularly limited, and may include, for example, one or more selected from a crystalline solid electrolyte, an amorphous solid electrolyte, and a composite solid electrolyte. In some embodiments, the fast ion conductor comprises a material selected from garnet type LLZO (lithium lanthanum zirconium oxide), perovskite type LLTO (lithium lanthanum titanium oxide), NASICON type LATP (lithium aluminum titanium phosphate), NASICON type LAGP (lithium aluminum germanium phosphate), li ₂ S-GeS ₂ 、Li ₂ S-P ₂ S ₅ 、Li ₂ S-B ₂ S ₃ 、Li ₂ S-SiS ₂ 、Li ₂ S-SiS ₂ -P ₂ S ₅ 、Li ₂ S-SeS ₂ -P ₂ S ₅ 、Li ₂ S-SnS ₂ -P ₂ S ₅ 、Li ₂ S-Al ₂ S ₃ -P ₂ S ₅ 、Li ₂ O-B ₂ O ₃ -P ₂ O ₅ 、Li ₂ O-B ₂ O ₃ -SiO ₂ 、Li ₂ O-SeO ₂ -B ₂ O ₃ 、Li ₃ PO ₄ -Li ₂ S-SiS ₂ 、Na ₃ PS ₄ 、Na ₂ S-P ₂ S ₅ One or more of them.

The kind of the filler component is not particularly limited in the present application, and in some embodiments, the filler component includes at least one selected from inorganic ceramics. As an example, the inorganic ceramic includes one or more selected from aluminum oxide, boehmite, calcium carbonate, calcium silicate, potassium titanate, barium sulfate, hydrotalcite, montmorillonite, spinel, mullite, silica, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, zirconium carbide.

The kind of the polymer component, which may bond the electrolyte salt, the fast ion conductor, and the filler component together to form the barrier layer, is not particularly limited herein. In some embodiments, the polymer comprises one or more selected from the group consisting of Polyacrylonitrile (PAN), polyacrylate, polyether, fluoropolymer, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, polyurethane, ethylene-vinyl acetate copolymer, and modified compounds thereof.

The term "polyacrylate" refers to the generic name for a series of polymers made from the self-polymerization of ester monomers of acrylic acid and its derivatives, and its homologs, or their predominant copolymerization with other monomers. Optionally, the polyacrylate is selected from polymethyl methacrylate (PMMA).

The term "polyether" refers to a class of polymers that contain-O-in the backbone structure of the molecular chain. Optionally, the polyether includes one or more selected from polyethylene oxide (PEO) and polypropylene oxide (PPO).

The term "fluoropolymer" refers to a class of polymers in which part or all of H is replaced by F. Optionally, the fluoropolymer comprises a polymer selected from vinylidene fluoride homopolymers or copolymers. For example, the fluorine-containing polymer includes one or more of vinylidene fluoride homopolymer (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (P (VDF-HFP)), vinylidene fluoride-trifluoroethylene copolymer (P (VDF-TrFE)), vinylidene fluoride-chlorotrifluoroethylene copolymer (PCTFE), vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

In some embodiments, the polymer component may be selected from polymers capable of conducting active ions, such as one or more of polyacrylonitrile, polymethyl methacrylate, polyether, fluoropolymer, and modified compounds thereof. The polymers can enable the barrier layer to have proper ion conductivity, so that the situation that active ions are reduced to form metal simple substances in a bending region of the electrode assembly can be effectively avoided while the energy density of the electrode assembly is excessively reduced.

In the electrode assembly of the present application, the ionic conductivity lambda of the first bent portion may be made by adjusting one or more of the kind of the polymer component, the content of the polymer component, the kind of the electrolyte salt, the content of the electrolyte salt, the kind of the fast ion conductor, the content of the fast ion conductor, the kind of the inorganic ceramic, the content of the inorganic ceramic, the thickness of the barrier layer, and the like ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

An electrode assembly according to a first aspect of the embodiment of the present application will be described in detail with reference to fig. 1.

Fig. 1 is a schematic view of an embodiment of an electrode assembly of the present application. As shown in fig. 1, the electrode assembly 52 includes a positive electrode tab 11 and a negative electrode tab 12.

The positive electrode tab 11 includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposing in the thickness direction thereof, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

The positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metal material may include one or more selected from aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy. As an example, the polymer material base layer may include one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

The positive electrode film layer typically comprises a positive electrode active material, an optional binder, and an optional conductive agent. The positive electrode film layer is usually formed by coating positive electrode slurry on a positive electrode current collector, drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, the binder for the positive electrode film layer may include one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin. As an example, the conductive agent for the positive electrode film layer may include one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

The positive electrode active material may be a positive electrode active material for a secondary battery, which is known in the art.

When the secondary battery of the present application is a lithium ion battery, the positive electrode active material may include one or more selected from lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxide may include, but are not limited to, 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 aluminum oxide, and modified compounds thereof. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate-carbon composites, lithium manganese phosphate-carbon composites, lithium manganese phosphate-iron, lithium manganese phosphate-carbon composites, and their respective modified compounds. The present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for lithium ion batteries may be used. These positive electrode active materials may be used alone or in combination of two or more.

In some embodiments, in order to further increase the energy density of the secondary battery, the positive electrode active material for a lithium ion battery may include one or more selected from the group consisting of lithium transition metal oxides represented by formula 1 and modified compounds thereof,

Li _a Ni _b Co _c M _d O _e A _f the method comprises the steps of (1),

in the formula 1, a is more than or equal to 0.8 and less than or equal to 1.2,0.5, B is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than 1, d is more than 0 and less than or equal to 1, e is more than or equal to 1 and less than or equal to 0 and less than or equal to 1, M is selected from one or more of Mn, al, zr, zn, cu, cr, mg, fe, V, ti and B, and A is selected from one or more of N, F, S and Cl.

As an example, the positive electrode active material for a lithium ion battery may include a material selected from LiCoO ₂ 、LiNiO ₂ 、LiMnO ₂ 、LiMn ₂ O ₄ 、LiNi _1/3 Co _1/3 Mn _1/3 O ₂ 、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ 、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.85 Co _0.15 Al _0.05 O ₂ 、LiFePO ₄ 、LiMnPO ₄ One or more of them.

When the secondary battery of the present application is a sodium ion battery, the positive electrode active material may include a material selected from sodium transition metal oxides Na _x MO ₂ (M is one or more transition metals, preferably one or more of Mn, fe, ni, co, V, cu, cr, wherein x is more than 0 and less than or equal to 1), polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates and the like), prussian blue materials. The present application is not limited to these materials, and other conventionally known materials that can be used as a positive electrode active material of a sodium ion battery may be used. These positive electrode active materials may be used alone or in combination of two or more.

As an example, the positive electrode active material for a sodium ion battery may include a material selected from the group consisting of NaFeO ₂ 、NaCoO ₂ 、NaCrO ₂ 、NaMnO ₂ 、NaNiO ₂ 、NaNi _1/2 Ti _1/2 O ₂ 、NaNi _1/2 Mn _1/2 O ₂ 、Na _2/3 Fe _1/3 Mn _2/3 O ₂ 、NaNi _1/3 Co _1/3 Mn _1/3 O ₂ 、NaFePO ₄ 、NaMnPO ₄ 、NaCoPO ₄ Prussian blue material with general formula A _a M _b (PO ₄ ) _c O _x Y _3-x One or more of the materials of (a) are used. Wherein A is selected from H ⁺ 、Li ⁺ 、Na ⁺ 、K ⁺ NH and NH ₄ ⁺ One or more of the following; m is a transition metal cation, preferably one or more of V, ti, mn, fe, co, ni, cu and Zn; y is halogen anion, preferably one or more of F, cl and Br; a is more than 0 and less than or equal to 4, b is more than 0 and less than or equal to 2, c is more than or equal to 1 and less than or equal to 3, and x is more than or equal to 0 and less than or equal to 2.

In the present application, the modifying compound for each positive electrode active material may be a doping modification or a surface coating modification of the positive electrode active material.

The negative electrode tab 12 includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the anode current collector has two surfaces opposing in the own thickness direction, and the anode film layer is provided on either or both of the two opposing surfaces of the anode current collector.

The negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metal material may include one or more selected from copper, copper alloy, nickel alloy, titanium alloy, silver alloy. As an example, the polymer material base layer may include one or more selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

The negative electrode film layer typically comprises a negative electrode active material, an optional binder, an optional conductive agent, and other optional adjuvants. The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector, drying and cold pressing. The negative electrode slurry coating is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliaries in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto. As an example, the binder for the negative electrode film layer may include one or more selected from 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), carboxymethyl chitosan (CMCS). As an example, the conductive agent for the negative electrode film layer may include one or more selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Other optional adjuvants may include thickeners (e.g., sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.

The negative electrode active material may employ a negative electrode active material for a secondary battery, which is well known in the art. As an example, the anode active material may include one or more selected from natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate. The silicon-based material may comprise one or more selected from elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy material. The tin-based material may include one or more selected from elemental tin, tin oxides, tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as a secondary battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

The negative electrode tab 12 of the present application does not exclude other additional functional layers than the negative electrode film layer. For example, in some embodiments, the negative electrode tab 12 of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on a surface of the negative electrode current collector, sandwiched between the negative electrode current collector and the negative electrode film layer. In other embodiments, the negative electrode tab 12 of the present application further includes a protective layer that covers the surface of the negative electrode film layer.

In some embodiments, the electrode assembly 52 further includes a separator 13, and the separator 13 is disposed between the positive electrode tab 11 and the negative electrode tab 12 to function as a separator. The type of the separator 13 is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used. In some embodiments, the material of the isolation film 13 may be one or more selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator 13 may be a single-layer film or a multilayer composite film. When the separator 13 is a multilayer composite film, the materials of the respective layers are the same or different.

The electrode assembly 52 may be of various shapes, for example, the electrode assembly 52 may be of a flat body, a rectangular parallelepiped, or other shapes.

As shown in fig. 1, in some embodiments, the electrode assembly 52 is a flat body, and the positive electrode tab 11 and the negative electrode tab 12 are wound in the winding direction a and form a winding structure including a bending region B and a flat region C connected to the bending region B. In the embodiment of the present application, the winding direction a is a direction in which the positive electrode tab 11 and the negative electrode tab 12 are circumferentially wound from inside to outside. In fig. 1, the winding direction a is clockwise.

The positive electrode tab 11 and the negative electrode tab 12 each include one or more bending portions located in the bending region B. The bending region B is a region of the electrode assembly 52 having a bending structure, and both the portion of the positive electrode tab 11 located in the bending region B (i.e., the positive electrode bending portion 111 of the positive electrode tab 11) and the portion of the negative electrode tab 12 located in the bending region B (i.e., the negative electrode bending portion 121 of the negative electrode tab 12) are bent. Illustratively, the positive electrode bent portion 111 of the positive electrode tab 11 and the negative electrode bent portion 121 of the negative electrode tab 12 are bent in a substantially circular arc shape.

Illustratively, in the bending region B, the positive electrode bending portion 111 of the positive electrode tab 11 and the negative electrode bending portion 121 of the negative electrode tab 12 are arranged in a staggered manner, that is, in the bending region B, one negative electrode bending portion 121 of the negative electrode tab 12, one positive electrode bending portion 111 of the positive electrode tab 11, and one negative electrode bending portion 121 … … of the negative electrode tab 12 are sequentially arranged. Alternatively, the innermost one of the positive electrode bent portions 111 of the positive electrode tab 11 is located outside the innermost one of the negative electrode bent portions 121 of the negative electrode tab 12.

Positive electrode tab 11 and negative electrode tab 12 also each include one or more straight portions located in straight region C. The flat region C is a region of the electrode assembly 52 having a flat structure. Alternatively, the bending areas B are two and are respectively connected to two ends of the flat area C.

The portion of the positive electrode tab 11 located in the flat region C (i.e., the positive electrode flat portion 112 of the positive electrode tab 11) and the portion of the negative electrode tab 12 located in the flat region C (i.e., the negative electrode flat portion 122 of the negative electrode tab 12) are disposed substantially flat. The surfaces of the positive straight portion 112 of the positive electrode tab 11 and the negative straight portion 122 of the negative electrode tab 12 are both generally planar.

At least one positive electrode bent portion 111 in the positive electrode tab 11 is a first bent portion 111a. In the positive electrode tab 11, the first bending portion 111a may be one or more. In the positive electrode sheet 11, all positive electrode bent portions 111 may be the first bent portions 111a, or some positive electrode bent portions 111 may be the first bent portions 111a. For example, a part of the positive electrode bent portion 111 in the positive electrode sheet 11 is a first bent portion 111a, and another part of the positive electrode bent portion 111 is a third bent portion.

At least one anode bent portion 121 in the anode tab 12 is a second bent portion 121a adjacent to the first bent portion 111a. In the negative electrode tab 12, the second bending portion 121a may be one or more. In the negative electrode tab 12, all the negative electrode bent portions 121 may be the second bent portions 121a, or part of the negative electrode bent portions 121 may be the second bent portions 121a. For example, a part of the negative electrode bent portions 121 in the negative electrode tab 12 is a second bent portion 121a, and another part of the negative electrode bent portions 121 is a fourth bent portion.

At least a part of the surface of the first bent portion 111a is attached with a barrier layer 111b, while the surface of the third bent portion is not attached with the barrier layer 111b, the surface of the positive electrode flat portion 112 is not attached with the barrier layer 111b, and the ion conductivity lambda of the first bent portion 111a ₁ Ion conductivity lambda with positive electrode flat portion 112 ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ < 1. According to the method, the situation that active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced through a simple positive electrode plate treatment process, so that the safety performance of the electrode assembly is remarkably improved. At least a part of the surface of the first bent portion 111a is attached with a barrier layer 111b, so that the first bent portion 111a has a lower ion conductivity. During charging, at least a part of the active ions separated from the first bending part 111a cannot be embedded into the adjacent second bending part 121a due to being blocked by the blocking layer 111b, so that the situation that the active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced, and the safety performance of the electrode assembly is remarkably improved. Ion conductivity lambda of first bending part 111a ₁ And the energy density of the electrode assembly is not 0, which means that the barrier layer 111b has a certain active ion conduction capability, so that part of active ions separated from the first bending part 111a can be embedded into the adjacent second bending part 121a during charging, and the situation that the active ions are reduced to form a metal simple substance in the bending region of the electrode assembly is effectively avoided while the energy density of the electrode assembly is excessively reduced.

In some embodiments, at least the innermost one of the positive electrode tabs 11 is the first bend 111a and at least the innermost one of the negative electrode tabs 12 is the second bend 121a. The probability of the occurrence of the reduction of the active ions to form the metal simple substance is highest at the anode bent portion 121 at the innermost side of the winding structure, and thus, such arrangement can significantly improve the safety performance of the electrode assembly.

According to the formula λ=d/RS, λ represents ion conductivity, d represents thickness, R represents ion resistance, S represents area, and the ratio of ion conductivity of the positive electrode sheet of the same specification is equivalent to the reciprocal of the ratio of ion resistance thereof, so that the ion resistance R of the first bending portion can be measured by respectively ₁ And an ionic resistor R of the positive electrode straight part ₂ Further calculating to obtain the ionic conductivity lambda of the first bending part ₁ And ion conductivity lambda of positive electrode flat part ₂ Ratio lambda ₁ /λ ₂ And lambda is ₁ /λ ₂ ＝R ₂ /R ₁ . Ion resistor R of first bending part of positive pole piece ₁ And an ionic resistor R of the positive electrode straight part ₂ The measurement may be performed using instruments and methods well known in the art, for example, using ac impedance methods. In order to facilitate calculation, discs with the same area can be cut from the first bending part and the positive straight part of the positive pole piece respectively, and then the discs are assembled with the isolating film and the lithium metal sheet to form a half battery respectively; injecting electrolyte, testing by adopting an electrochemical alternating current impedance method of an electrochemical workstation, and drawing a Nyquist diagram; and analyzing the obtained Nyquist diagram by using an equivalent circuit curve fitting method, and taking the semicircular diameter, namely the charge transfer resistance Rct, as the resistance of the test positive electrode plate. The test voltage may be 10mV and the test frequency may be 0.1 Hz-100K Hz.

When the half battery is prepared, when the positive electrode plate is coated on two sides, water or other solvents can be used for wiping off a film layer on one side; the area of the lithium metal sheet can be larger than that of the positive electrode sheet; in addition, since the electrolyte has a low contribution to the half-cell resistance, which is negligible, the composition of the electrolyte is not particularly limited in the preparation of the half-cell, and electrolytes conventional in the art may be used. For example, the electrolyte may be obtained by: mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a volume ratio of 1:1 to obtain an organic solvent, and dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in the organic solvent to obtain an electrolyte, wherein the concentration of LiFSI is 1mol/L.

It should be noted that, the positive electrode sheet can be directly obtained from freshly prepared cold-pressed positive electrode sheet or obtained from the secondary battery during the test. Among them, an exemplary method of obtaining a positive electrode sheet from a secondary battery is as follows: and disassembling the secondary battery after fully placing the secondary battery, soaking the positive electrode plate in an organic solvent (for example, dimethyl carbonate) for a period of time (for example, 30 min), and then taking out the positive electrode plate and drying the positive electrode plate at a certain temperature and for a certain time (for example, 80 ℃ for 6 h).

Method for preparing electrode assembly

A second aspect of embodiments of the present application provides a method of manufacturing an electrode assembly.

Fig. 2 is a flow chart of a method of making an electrode assembly of the present application. As shown in fig. 2, the method for manufacturing an electrode assembly according to the second aspect of the embodiment of the present application includes: step 1, providing a positive pole piece and a negative pole piece; and 2, winding the positive electrode plate and the negative electrode plate to form an electrode assembly. The positive pole piece is provided with more than one positive pole bending part and more than one positive pole straight part connected with the positive pole bending parts, and at least one positive pole bending part in the positive pole piece is a first bending part; the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part; a blocking layer is attached to at least a part of the surface of the first bending part and used for blocking at least a part of active ions which are separated from the first bending part from being embedded into the second bending part; the ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

The positive pole piece and the negative pole piece are both in a strip-shaped structure. The positive electrode plate and the negative electrode plate can be sequentially stacked, and then more than two circles of positive electrode plates and negative electrode plates are wound to form the electrode assembly.

Fig. 3 is a schematic flow chart of a method for preparing a positive electrode sheet according to some embodiments of the present application. As shown in fig. 3, the preparation method of the positive electrode sheet according to some embodiments of the present application includes: step 101, providing an initial positive electrode plate and slurry for forming the barrier layer, wherein the initial positive electrode plate comprises a positive electrode current collector and a positive electrode film layer which is arranged on at least one surface of the positive electrode current collector and comprises a positive electrode active material; and 102, coating the slurry on at least a part of the surface of the initial positive electrode sheet for forming the first bending part through winding so as to form the barrier layer after drying.

The exemplary preparation method of the positive electrode plate can ensure the production continuity of the positive electrode plate, has strong compatibility with the existing equipment, and can effectively improve the safety performance of the electrode assembly under the condition of small weight increment of the electrode assembly.

The application method of the slurry is not particularly limited, and may be doctor blade coating, gravure coating, slit coating, dip coating, spray coating, or the like.

In some embodiments, the slurry includes a solvent, a polymer component, and an inorganic component including a conductive active ion component or a combination of a conductive active ion component and a filler component. Optionally, the conductive active ion component comprises at least one selected from the group consisting of electrolyte salts, fast ion conductors. The kind of the solvent is not particularly limited in this application, and may be selected according to actual requirements. For example, in some embodiments, the solvent may be N-methylpyrrolidone (NMP).

The method for manufacturing an electrode assembly according to the second aspect of the embodiment of the present application may manufacture the electrode assembly according to the first aspect of the embodiment of the present application. It should be noted that, for the relevant structure of the electrode assembly prepared by the above-mentioned preparation method of the electrode assembly, reference may be made to the electrode assemblies provided in the examples of the first aspect of the embodiments of the present application.

Secondary battery

A third aspect of the embodiments provides a secondary battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly is an electrode assembly of the first aspect of the embodiments or an electrode assembly prepared by a method of the second aspect of the embodiments.

The type of the secondary battery is not particularly limited in the present application, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, or the like.

The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

The kind of the electrolyte salt is not particularly limited and may be selected according to actual requirements. For example, the electrolyte salt includes one or more selected from lithium salts for lithium ion batteries, sodium salts for sodium ion batteries. As an example, the lithium salt includes a lithium salt selected from lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium bis (fluorosulfonyl) imide (LiLSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium difluorooxalato borate (LiBOB), lithium difluorophosphate (LiPO) ₂ F ₂ ) One or more of lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP). As an example, the sodium salt includes a salt selected from the group consisting of NaPF ₆ 、NaClO ₄ 、NaBCl ₄ 、NaSO ₃ CF ₃ 、Na(CH ₃ )C ₆ H ₄ SO ₃ One or more of them.

The kind of the solvent is not particularly limited and may be selected according to actual demands. In some embodiments, as an example, the solvent may include one or more selected from Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl 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), dimethylsulfone (MSM), methylsulfone (EMS), and diethylsulfone (ESE).

In some embodiments, additives are optionally also included in the electrolyte. For example, the additives may include negative electrode film-forming additives, or may include positive electrode film-forming additives, or may include additives that improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature performance of the battery, additives that improve the low temperature power performance of the battery, and the like.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The soft bag can be made of one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

The shape of the secondary battery is not particularly limited in the present application, and may be a flat body, a rectangular parallelepiped, or other shapes. Fig. 4 shows a secondary battery 5 having a rectangular parallelepiped structure as an example.

In some embodiments, as shown in fig. 5, the overpack may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround to form a receiving cavity. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 is used to cover the opening to close the accommodation chamber. The electrode assembly 52 of the first aspect of the present embodiment or the electrode assembly 52 prepared according to the method of the second aspect of the present embodiment is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the secondary battery 5 may be one or several, and may be adjusted according to the need.

Methods of manufacturing secondary batteries of the present application are known, including at least the steps of manufacturing electrode assemblies according to the second aspect of the embodiments of the present application. In some embodiments, the electrode assembly may be placed in an external package, dried, and then injected with an electrolyte, and subjected to vacuum packaging, standing, formation, shaping, and the like to obtain a secondary battery.

In some embodiments of the present application, the secondary batteries 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 may be adjusted according to the application and capacity of the battery module.

Fig. 6 is a schematic diagram of the battery module 4 as an example. As shown in fig. 6, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

Fig. 7 and 8 are schematic views of the battery pack 1 as an example. As shown in fig. 7 and 8, a battery box and a plurality of battery modules 4 provided in the battery box may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used for covering the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

Power utilization device

The embodiment also provides an electric device comprising at least one of the secondary battery, the battery module, or the battery pack of the application. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The electric device may be, but is not limited to, a mobile device (e.g., a cellular phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

The power consumption device may select a secondary battery, a battery module, or a battery pack according to its use requirements.

Fig. 9 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the power device, a battery pack or battery module may be employed.

As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. The electric device is required to be light and thin, and a secondary battery can be used as a power source.

Examples

The following examples more particularly describe the disclosure of the present application, which are intended as illustrative only, since numerous modifications and variations within the scope of the disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.

Comparative example 1

The positive electrode active material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM 523), conductive agent carbon black (Super P) and binder polyvinylidene fluoride (PVDF) are uniformly mixed in solvent N-methylpyrrolidone (NMP) according to the mass ratio of 91.6:1.8:6.6 to prepare positive electrode slurry; coating the prepared positive electrode slurry on one surface of an aluminum foil current collector, drying in an oven, and cold pressing And obtaining the positive pole piece.

Examples 1 to 21

The polymer, the electrolyte salt, the fast ion conductor and the inorganic ceramic are mixed according to the compositions and the mass percentages shown in table 1 respectively, and then uniformly mixed in a solvent of N-methylpyrrolidone (NMP) to prepare a coating slurry. In order to more intuitively observe the capacity exertion condition of the positive electrode sheet, the coating slurry was uniformly coated on the whole surface of the positive electrode sheet prepared in comparative example 1, to obtain the positive electrode sheets of examples 1 to 21.

Cutting the positive electrode plates prepared in comparative example 1 and examples 1-21 into wafers with the same area, and respectively assembling the wafers with a separation film and a lithium metal sheet to form a half cell; injecting electrolyte, testing by adopting an electrochemical alternating current impedance method of a strong force transmission (Solartron) 1470ECellTest multichannel electrochemical workstation, and drawing a Nyquist diagram; and analyzing the obtained Nyquist diagram by using Zview software by using an equivalent circuit curve fitting method, wherein the semicircular diameter, namely the charge transfer resistor Rct is used as the resistance of the half battery. The test voltage may be 10mV and the test frequency may be 0.1 Hz-100 KHz. The isolating film adopts a porous PE film. The preparation process of the electrolyte is as follows: mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a volume ratio of 1:1 to obtain an organic solvent, and dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in the organic solvent to obtain an electrolyte, wherein the concentration of LiFSI is 1mol/L.

Ion conductivity lambda of the positive electrode sheets prepared in examples 1 to 21 ₁ Ion conductivity lambda of the positive electrode sheet prepared in comparative example 1 ₂ Ratio lambda ₁ /λ ₂ The inverse of the ratio of the resistances of half cells obtained by the above-described test methods for the positive electrode tabs prepared in examples 1 to 21 to the resistances of half cells obtained by the above-described test methods for the positive electrode tab prepared in comparative example 1 can be used. The test results are shown in table 1.

Next, the capacity of the positive electrode sheet was observed.

First, the positive electrode sheets prepared in comparative example 1 and examples 1 to 21 were prepared into a soft pack battery according to the following procedure.

Preparing a negative electrode plate: fully stirring and mixing negative electrode active material graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethylcellulose (CMC-Na) in a proper amount of solvent deionized water according to a mass ratio of 95.4:1.5:2.5:0.6 to form uniform negative electrode slurry; and uniformly coating the negative electrode slurry on one surface of a copper foil current collector, and drying and cold pressing to obtain a negative electrode plate.

Preparation of a separation film: porous PE films were used.

Preparation of electrolyte: mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a volume ratio of 1:1 to obtain an organic solvent, and dissolving lithium bis (fluorosulfonyl) imide (LiFSI) in the organic solvent to obtain an electrolyte, wherein the concentration of LiFSI is 1mol/L.

Preparation of a soft package battery: sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate to obtain an electrode assembly; and placing the electrode assembly in an outer packaging aluminum plastic film, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other procedures to obtain the soft package battery.

And then testing the capacity performance of the soft package battery by adopting a battery charging and discharging machine.

Standing the soft-packed battery for 5 minutes, charging to 4.25V at a constant current of 0.33C (46 mA), and then charging to a constant voltage of 4.25V until the current is less than 0.05C, thereby obtaining the first-circle charging capacity of the battery; after standing for 5 minutes, the battery was discharged to 2.8V at a constant current of 0.33C, thereby obtaining the first-turn discharge capacity of the battery. The test results are shown in table 1.

As can be seen from the test results in table 1, after a barrier layer is coated on the surface of the positive electrode sheet, the effect of blocking the migration of active ions and reducing the capacity of the positive electrode sheet can be achieved. Therefore, after the barrier layer is applied to the bending region of the electrode assembly, the condition that active ions are reduced to form a metal simple substance in the bending region of the electrode assembly can be effectively reduced, and the safety performance of the electrode assembly is obviously improved.

As can be seen from the test results in table 1, the capacity of the soft-pack battery can be adjusted by adjusting the composition of the barrier layer, so that the application can properly adjust the specific types of each component and the specific content of each component of the barrier layer according to the specific conditions of the capacities of the bending regions of different electrode assemblies, thereby achieving the best effect, and not only remarkably improving the safety performance of the electrode assemblies, but also excessively reducing the energy density of the electrode assemblies.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

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Claims

1. An electrode assembly comprising a positive electrode plate and a negative electrode plate, characterized in that,

the positive electrode plate is provided with more than one positive electrode bending part and more than one positive electrode straight part connected with the positive electrode bending parts, and at least one positive electrode bending part in the positive electrode plate is a first bending part;

the negative electrode plate is provided with more than one negative electrode bending part and more than one negative electrode straight part connected with the negative electrode bending parts, and at least one negative electrode bending part in the negative electrode plate is a second bending part adjacent to the first bending part;

a blocking layer is attached to at least a part of the surface of the first bending part and used for blocking at least a part of active ions which are separated from the first bending part from being embedded into the second bending part;

The ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ < 1, alternatively 0 < lambda ₁ /λ ₂ ≤0.9。

2. The electrode assembly according to claim 1, wherein the electrode assembly has a winding structure, and in the winding structure, at least an innermost one of the positive electrode sheets is the first bending portion, and at least an innermost one of the negative electrode sheets is the second bending portion.

3. The electrode assembly of claim 1 or 2, wherein the barrier layer is attached to one or both surfaces of the first bend.

4. The electrode assembly of any one of claims 1-3, wherein the barrier layer is attached to 80-100% of the surface of the first bend facing the second bend.

5. The electrode assembly of any one of claims 1-4, wherein the barrier layer has a thickness of 0.1 μιη to 20 μιη, optionally 0.5 μιη to 10 μιη.

6. The electrode assembly of any one of claims 1-5, wherein the barrier layer comprises a polymer component and an inorganic component comprising a conductive active ion component or a combination of a conductive active ion component and a filler component,

Optionally, the conductive active ion component comprises at least one selected from the group consisting of electrolyte salts, fast ion conductors.

7. The electrode assembly of claim 6, wherein the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of inorganic component.

8. The electrode assembly of claim 7, wherein the electrode assembly comprises,

the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of conductive active ion component;

optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of electrolyte salt;

optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component and 10-95% of fast ion conductor;

optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 5-45% of electrolyte salt and 5-70% of fast ion conductor.

9. The electrode assembly of claim 7, wherein the electrode assembly comprises,

the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of conductive active ion component and 1-10% of filler component;

Optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of electrolyte salt and 1-10% of filler component;

optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5-90% of polymer component, 9-94% of fast ion conductor and 1-10% of filler component;

optionally, the barrier layer comprises, based on the total mass of the barrier layer: 5 to 90 percent of polymer component, 4.5 to 45 percent of electrolyte salt, 4.5 to 70 percent of fast ion conductor and 1 to 10 percent of filler component.

10. The electrode assembly of any one of claims 6-9, wherein the electrolyte salt comprises a material selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluorooxalato phosphateLithium, naPF ₆ 、NaClO ₄ 、NaBCl ₄ 、NaSO ₃ CF ₃ 、Na(CH ₃ )C ₆ H ₄ SO ₃ One or more of the following; and/or the number of the groups of groups,

the fast ion conductor comprises a material selected from garnet type LLZO, perovskite type LLTO, NASICON type LATP, NASICON type LAGP, li ₂ S-GeS ₂ 、Li ₂ S-P ₂ S ₅ 、Li ₂ S-B ₂ S ₃ 、Li ₂ S-SiS ₂ 、Li ₂ S-SiS ₂ -P ₂ S ₅ 、Li ₂ S-SeS ₂ -P ₂ S ₅ 、Li ₂ S-SnS ₂ -P ₂ S ₅ 、Li ₂ S-Al ₂ S ₃ -P ₂ S ₅ 、Li ₂ O-B ₂ O ₃ -P ₂ O ₅ 、Li ₂ O-B ₂ O ₃ -SiO ₂ 、Li ₂ O-SeO ₂ -B ₂ O ₃ 、Li ₃ PO ₄ -Li ₂ S-SiS ₂ 、Na ₃ PS ₄ 、Na ₂ S-P ₂ S ₅ One or more of them.

11. The electrode assembly of any one of claims 6-10, wherein the filler component comprises at least one selected from the group consisting of inorganic ceramics, optionally the inorganic ceramics comprises one or more selected from the group consisting of alumina, boehmite, calcium carbonate, calcium silicate, potassium titanate, barium sulfate, hydrotalcite, montmorillonite, spinel, mullite, silica, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, boron carbide, silicon carbide, zirconium carbide.

12. The electrode assembly according to any one of claims 6 to 11, wherein the polymer comprises one or more selected from the group consisting of polyacrylonitrile, polyacrylate, polyether, fluoropolymer, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, polyurethane, ethylene-vinyl acetate copolymer, and modified compounds thereof,

alternatively, the polyacrylate is selected from polymethyl methacrylate;

optionally, the polyether comprises one or more selected from polyethylene oxide and polypropylene oxide,

optionally, the fluoropolymer comprises a vinylidene fluoride homopolymer or copolymer, optionally, the fluoropolymer comprises one or more of a vinylidene fluoride homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-chlorotrifluoroethylene copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, and a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

13. A method for preparing an electrode assembly, comprising the steps of:

step 1, providing a positive pole piece and a negative pole piece;

step 2, winding the positive electrode sheet and the negative electrode sheet to form an electrode assembly,

wherein,,

the ionic conductivity lambda of the first bending part ₁ Ion conductivity lambda with the positive electrode flat portion ₂ The ratio satisfies 0 < lambda ₁ /λ ₂ ＜1。

14. The method according to claim 13, wherein the method for preparing the positive electrode sheet comprises the steps of:

Step 101, providing an initial positive electrode plate and slurry for forming the barrier layer, wherein the initial positive electrode plate comprises a positive electrode current collector and a positive electrode film layer which is arranged on at least one surface of the positive electrode current collector and comprises a positive electrode active material;

and 102, coating the slurry on at least a part of the surface of the initial positive electrode sheet for forming the first bending part through winding so as to form the barrier layer after drying.

15. The method of claim 14, wherein the slurry comprises a solvent, a polymer component, and an inorganic component comprising a conductive active ion component or a combination of a conductive active ion component and a filler component,

16. A secondary battery comprising one of the electrode assembly according to any one of claims 1 to 12, and the electrode assembly prepared according to the method of any one of claims 13 to 15.

17. A battery module comprising the secondary battery according to claim 16.

18. A battery pack comprising one of the secondary battery according to claim 16 and the battery module according to claim 17.

19. An electric device comprising at least one of the secondary battery according to claim 16, the battery module according to claim 17, and the battery pack according to claim 18.