CN217822877U

CN217822877U - Electrode assembly, battery cell, battery and power consumption device

Info

Publication number: CN217822877U
Application number: CN202221539374.7U
Authority: CN
Inventors: 韩志松; 李彦朋
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-06-20
Filing date: 2022-06-20
Publication date: 2022-11-15
Anticipated expiration: 2032-06-20

Abstract

The application relates to an electrode assembly, a battery monomer, a battery and an electric device. The electrode assembly has a flat region and a corner region connecting the flat region; at least one corner part in the positive plate is a first corner part, and at least one straight part in the positive plate is a first straight part connected with the first corner part; the first corner portion includes a first current collecting portion, and the first straight portion includes a second current collecting portion; the mass per unit area of the first collecting portion is smaller than that of the second collecting portion. Since the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion, the current flowing through the first corner portion is smaller than that flowing through the first straight portion in the unit area. Accordingly, the lithium ion release amount of the first corner part is smaller than that of the first flat part in unit area, so that the lithium ions provided by the first corner part are balanced with the lithium-embedded active sites provided by the corresponding negative electrode plate, and the corner lithium precipitation phenomenon is reduced.

Description

Electrode assembly, battery cell, battery and electric device

Technical Field

The present application relates to the field of battery technologies, and in particular, to an electrode assembly, a battery cell, a battery, and an electric device.

Background

Energy conservation and emission reduction are the key points of sustainable development of the automobile industry, and electric vehicles become important components of the sustainable development of the automobile industry due to the advantages of energy conservation and environmental protection. For electric vehicles, battery technology is an important factor in its development.

The electrode assembly, which is a critical component of the battery and is usually formed by winding or stacking, is subject to a lithium precipitation phenomenon at the corner positions, so that the service performance and safety performance of the battery are greatly reduced.

SUMMERY OF THE UTILITY MODEL

In view of the above problems, the present application provides an electrode assembly, a battery cell, a battery and an electric device, which can effectively reduce the phenomenon that lithium is separated from corners of the electrode assembly, thereby improving the service performance and safety performance of the battery.

In a first aspect, the present application provides an electrode assembly having a flat region and a corner region connecting the flat region;

the electrode assembly includes a positive electrode tab including a plurality of corner portions located in the corner region and a plurality of straight portions located in the straight region;

at least one corner part in the positive plate is a first corner part, and at least one straight part in the positive plate is a first straight part connected with the first corner part; the first corner portion comprises a first header portion, and the first straight portion comprises a second header portion; the mass per unit area of the first current collecting part is smaller than that of the second current collecting part.

Since the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion, the current flowing through the first corner portion is smaller than that flowing through the first flat portion in the unit area. Accordingly, the lithium ion release amount of the first corner part is smaller than that of the first flat part in unit area, so that the lithium ions provided by the first corner part are balanced with the lithium-embedded active sites provided by the corresponding negative electrode plate, and the corner lithium precipitation phenomenon is reduced.

In some embodiments, each of the corner portions of the positive electrode sheet is the first corner portion, and each of the straight portions of the positive electrode sheet is the first straight portion. Thus, each corner portion of the positive electrode tab is made to flow a smaller current than each straight portion. Accordingly, the lithium ion extraction amount of each corner part is smaller than that of each straight part in a unit area, so that the lithium ions provided by each corner part are balanced with the lithium-embedded active sites provided by the corresponding negative electrode piece, and the corner lithium separation phenomenon is reduced.

In some embodiments, the mass per unit area of the first header portion ranges from: 18g/m ² -148.5g/m ² The mass range per unit area of the second collecting part is as follows: 20g/m ² -150g/m ² . When the mass per unit area of the first current collector and the mass per unit area of the second current collector are set within the above ranges, the corner lithium deposition phenomenon can be further improved.

In some embodiments, the first corner portion further comprises a first active material portion coated on a surface of the first header portion;

the first current collecting part is provided with an opening in the thickness direction, and the aperture of the opening is smaller than the particle size of active particles in the first active material part. The first current collecting part is provided with the opening in the thickness direction, so that the mass of the unit area of the first current collecting part is reduced, the current of the first corner part is smaller than that of the first straight part, the lithium ion extraction amount of the first corner part is reduced in the unit area, the lithium ions provided by the first corner part and the negative electrode lithium-embedded active site are balanced, and the corner lithium extraction phenomenon is reduced. Meanwhile, the first corner part is provided with the opening, so that the surface roughness of the first current collecting part can be improved, the bonding force between the first active material part of the first corner part and the first current collecting part is improved, and the material falling problem of the corner area is improved. And the first current collecting part is provided with the opening, so that the weight of the first current collecting part can be reduced, the weight of the whole current collector is reduced, and the energy density of the electrode assembly is improved.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 0.1 μm to 200 μm, the pore size of the open pores being in the range of: 0.05 μm to 100 μm. With the arrangement, the particle size of the active particles and the pore diameter of the open pores in the first active material part are in proper ranges, so that the phenomenon of corner lithium precipitation is greatly reduced.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 0.1-0.5 μm, and the pore diameter of the open pore is in the range of 0.05-0.1 μm.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 0.5-1 μm, and the pore diameter of the open pore is in the range of 0.05-0.5 μm.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 1-10 μm, and the pore diameter of the open pore is in the range of 0.05-1 μm.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 10-30 μm, and the pore diameter of the open pore is in the range of 0.05-10 μm.

In some embodiments, the particle size of the active particles in the first active material portion ranges from: 100-200 μm, and the pore diameter of the open pore is in the range of 0.05-100 μm.

The particle size of the active particles in the first active material portion and the pore diameter of the open pores are matched with each other, so that the particle size of the active particles in the first active material portion and the pore diameter of the open pores are in proper ranges, and the phenomenon of corner lithium precipitation is greatly reduced.

In some embodiments, the proportion of the total area of the first header portion occupied by the aperture area of all of the apertures in the first header portion is: 1 to 10 percent. Assuming that the thickness of the first collecting portion at each portion of the first corner portion is the same, the mass per unit area of the first collecting portion is related only to the proportion of the aperture area of the opening to the total area of the first collecting portion. When the proportion of the pore area of all the open pores in the first collecting part to the total area of the first collecting part is: when the concentration is 1% -10%, on the basis of conveniently opening the holes, the proportion of the hole area of all the holes occupying the total area of the first current collecting part is in a reasonable range, and the corner lithium precipitation phenomenon is weakened.

In some embodiments, a thickness of the first current collecting portion is less than a thickness of the second current collecting portion. By setting the thickness of the first current collecting portion to be smaller than that of the second current collecting portion, the current flowing through the first corner portion is smaller than the current flowing through the first straight portion per unit area. Accordingly, the lithium ion release amount of the first corner part is smaller than that of the first flat part in unit area, so that the lithium ions provided by the first corner part and the lithium-embedded active sites provided by the corresponding negative electrode piece are balanced, and the corner lithium precipitation phenomenon is reduced.

In a second aspect, the present application provides a battery cell comprising an electrode assembly as described in the above embodiments.

In a third aspect, the present application provides a battery comprising a battery cell as described in the above embodiments.

In a fourth aspect, the present application provides an electrical device comprising a battery as described in the above embodiments.

The above description is only an overview of the technical solutions of the present application, and the present application may be implemented in accordance with the content of the description so as to make the technical means of the present application more clearly understood, and the detailed description of the present application will be given below in order to make the above and other objects, features, and advantages of the present application more clearly understood.

Drawings

FIG. 1 is a schematic structural view of a vehicle according to some embodiments of the present application;

FIG. 2 is an exploded view of a battery according to some embodiments of the present application;

fig. 3 is an exploded view of a battery cell according to some embodiments of the present disclosure;

FIG. 4 is a schematic structural view of an electrode assembly according to an embodiment of the present application;

FIG. 5 is a schematic view of a positive electrode tab of the electrode assembly shown in FIG. 4;

fig. 6 is a sectional view of the positive electrode tab shown in fig. 5;

FIG. 7 is a schematic view of the structure of another positive electrode tab of the electrode assembly shown in FIG. 4;

fig. 8 is a sectional view of the positive electrode tab shown in fig. 7;

fig. 9 is a schematic view of the structure of still another positive electrode tab of the electrode assembly shown in fig. 4;

fig. 10 is a sectional view of the positive electrode tab shown in fig. 9.

1000. A vehicle; 100. a battery; 200. a controller; 300. a motor; 10. a box body; 11. a first portion; 12. a second portion; 20. a battery cell; 21. an end cap; 21a, electrode terminals; 22. a housing; 23. an electrode assembly; 231. a positive plate; 2311. a current collector; 2312. an active material layer; 2313. opening a hole; 2314. a corner portion; 2315. a straight portion; 232. a negative plate; 233. a diaphragm; A. a flat area; B. a corner region; 24. and (7) a tab.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only used to illustrate the technical solutions of the present application more clearly, and therefore are only used as examples, and the protection scope of the present application is not limited thereby.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof, in the description and claims of this application and the description of the above figures are intended to cover non-exclusive inclusions.

In the description of the embodiments of the present application, the technical terms "first", "second", and the like are used only for distinguishing different objects, and are not to be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary-secondary relationship of the technical features indicated. In the description of the embodiments of the present application, "a plurality" means two or more unless specifically defined otherwise.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein may be combined with other embodiments.

In the description of the embodiments of the present application, the term "and/or" is only one kind of association relationship describing an associated object, and means that three relationships may exist, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

In the description of the embodiments of the present application, the term "plurality" refers to two or more (including two), and similarly, "plural sets" refers to two or more (including two), and "plural pieces" refers to two or more (including two).

In the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the directions or positional relationships indicated in the drawings, and are only for convenience of description of the embodiments of the present application and for simplicity of description, but do not indicate or imply that the referred device or element must have a specific direction, be constructed and operated in a specific direction, and thus, should not be construed as limiting the embodiments of the present application.

In the description of the embodiments of the present application, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are used in a broad sense, and for example, may be fixedly connected, detachably connected, or integrated; mechanical connection or electrical connection is also possible; either directly or indirectly through intervening media, either internally or in any other relationship. Specific meanings of the above terms in the embodiments of the present application can be understood by those of ordinary skill in the art according to specific situations.

At present, the application of the power battery is more and more extensive from the development of market situation. The power battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles and the like, and a plurality of fields such as military equipment and aerospace. With the continuous expansion of the application field of the power battery, the market demand is also continuously expanding.

The present inventors have noted that during cycling of the battery, the positive electrode active material and the negative electrode active material can intercalate or deintercalate lithium ions, i.e., lithium ions can deintercalate from the positive electrode active material and intercalate into the negative electrode active material. In a battery formed by winding the electrode assembly, the active material layer of one surface of the positive electrode sheet is bent and stacked in the corner region of the electrode assembly, and the active material layer of the negative electrode sheet opposite to the surface is bent and pulled, so that the amount of the positive electrode active material is not uniform with the amount of the negative electrode active material, and thus, the lithium intercalation active site of the negative electrode is insufficient. When the negative electrode has insufficient lithium-intercalation active sites, lithium ions which cannot be intercalated into the negative electrode can only obtain electrons on the surface of the negative electrode, so that a silvery white metallic lithium simple substance is formed, and the phenomenon of corner lithium precipitation is caused. The lithium separation not only reduces the performance of the battery and greatly shortens the cycle life, but also limits the quick charge capacity of the battery and possibly causes disastrous results such as combustion, explosion and the like.

In order to alleviate the problem of corner lithium deposition, the applicant researches and discovers that in a corner region, the amount of lithium ions transferred from the positive electrode to the negative electrode can be reduced, so that the lithium ions provided by the positive electrode are balanced with the lithium intercalation active sites of the negative electrode, and the occurrence of the corner lithium deposition phenomenon is reduced. Alternatively, in the corner region, the negative electrode lithium intercalation active sites can be increased, so that the lithium ions provided by the positive electrode and the negative electrode lithium intercalation active sites are balanced, and the corner lithium precipitation phenomenon is reduced.

In view of the above, the inventors have conducted intensive studies to design an electrode assembly having a flat region and a corner region connecting the flat regions in order to alleviate the corner lithium deposition problem. The electrode assembly includes a positive electrode tab including a plurality of corner portions located at the corner regions and a plurality of flat portions located at the flat regions. At least one corner part in the positive plate is a first corner part, and at least one straight part in the positive plate is a first straight part connected with the first corner part. The first corner portion includes a first current collecting portion, and the second straight portion includes a second current collecting portion. The mass per unit area of the first current collecting part is smaller than that of the second current collecting part.

In such an electrode assembly, since the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion, the current flowing through the first corner portion is smaller than that flowing through the first straight portion in the unit area. Accordingly, the lithium ion release amount of the first corner part is smaller than that of the first flat part in unit area, so that the lithium ions provided by the first corner part and the lithium-embedded active sites provided by the corresponding negative electrode piece are balanced, and the corner lithium precipitation phenomenon is reduced.

The electrode assembly disclosed in the embodiment of the application can be used in electric devices such as vehicles, ships or aircrafts, but not limited to. The power supply system with the electric device formed by the electrode assembly, the battery monomer, the battery and the like disclosed by the application can be used, so that the lithium precipitation phenomenon in a corner area is reduced, and the service performance and the safety performance of the battery are improved.

The embodiment of the application provides an electric device using a battery as a power supply, wherein the electric device can be but is not limited to a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, a battery car, an electric automobile, a ship, a spacecraft and the like. The electric toy may include a stationary or mobile electric toy, such as a game machine, an electric car toy, an electric ship toy, an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, etc.

For convenience of description, the following embodiment is described with reference to fig. 1, taking an electric device according to an embodiment of the present application as an example of a vehicle 1000.

The vehicle 1000 may be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile may be a pure electric automobile, a hybrid electric automobile, or a range-extended automobile, etc. Referring to fig. 2, a battery 100 is provided inside a vehicle 1000, and the battery 100 may be provided at the bottom or the head or the tail of the vehicle 1000. The battery 100 may be used for power supply of the vehicle 1000, for example, the battery 100 may serve as an operation power source of the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300, the controller 200 being configured to control the battery 100 to supply power to the motor 300, for example, for starting, navigation, and operational power requirements while the vehicle 1000 is traveling.

In some embodiments of the present application, the battery 100 may be used not only as an operating power source of the vehicle 1000, but also as a driving power source of the vehicle 1000, instead of or in part of fuel or natural gas, to provide driving power for the vehicle 1000.

The battery 100 includes a case 10 and a battery cell 20, and the battery cell 20 is accommodated in the case 10. The case 10 is used to provide a receiving space for the battery cell 20, and the case 10 may have various structures. In some embodiments, the case 10 may include a first portion 11 and a second portion 12, the first portion 11 and the second portion 12 cover each other, and the first portion 11 and the second portion 12 together define a receiving space for receiving the battery cell 20. The second part 12 may be a hollow structure with one open end, the first part 11 may be a plate-shaped structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a containing space; the first portion 11 and the second portion 12 may be both hollow structures with one side open, and the open side of the first portion 11 may cover the open side of the second portion 12. Of course, the box 10 formed by the first and second portions 11 and 12 may have various shapes, such as a cylinder, a rectangular parallelepiped, and the like.

In the battery 100, the number of the battery cells 20 may be multiple, and the multiple battery cells 20 may be connected in series or in parallel or in series-parallel, where in series-parallel refers to both series connection and parallel connection among the multiple battery cells 20. The plurality of battery cells 20 can be directly connected in series or in parallel or in series-parallel, and the whole formed by the plurality of battery cells 20 is accommodated in the box body 10; of course, the battery 100 may also be formed by connecting a plurality of battery cells 20 in series, in parallel, or in series-parallel to form a battery 100 module, and then connecting a plurality of battery 100 modules in series, in parallel, or in series-parallel to form a whole, and accommodating the whole in the case 10. The battery 100 may further include other structures, for example, the battery 100 may further include a bus member for achieving electrical connection between the plurality of battery cells 20.

The battery cell 20 refers to the smallest unit constituting the battery 100. Referring to fig. 3, a battery cell 20 includes an end cap 21, a case 22, an electrode assembly 23, and other functional components.

The end cap 21 refers to a member that covers an opening of the case 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 may be adapted to the shape of the housing 22 to fit the housing 22. Alternatively, the end cap 21 may be made of a material (e.g., an aluminum alloy) having certain hardness and strength, so that the end cap 21 is not easily deformed when being extruded and collided, and the single battery 20 may have higher structural strength and improved safety performance. The end cap 21 may be provided with functional components such as the electrode terminals 21 a. The electrode terminals 21a may be used to be electrically connected with the electrode assembly 23 for outputting or inputting electric energy of the battery cells 20. In some embodiments, the end cap 21 may further include a pressure relief mechanism for relieving the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold value. The material of the end cap 21 may also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited in this embodiment. In some embodiments, insulation may also be provided on the inside of the end cap 21, which may be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. Illustratively, the insulator may be plastic, rubber, or the like.

The case 22 is an assembly for mating with the end cap 21 to form an internal environment of the battery cell 20, wherein the formed internal environment may be used to house the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 may be separate components, and an opening may be provided in the housing 22, and the opening may be covered by the end cap 21 to form the internal environment of the battery cell 20. The end cap 21 and the housing 22 may be integrated, and specifically, the end cap 21 and the housing 22 may form a common connecting surface before other components are inserted into the housing, and when it is required to seal the inside of the housing 22, the end cap 21 covers the housing 22. The housing 22 may be a variety of shapes and sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the case 22 may be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 may be various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited in the embodiments of the present invention.

The electrode assembly 23 is a part in which electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 23 may be contained within the case 22. Referring to fig. 4, the electrode assembly 23 is mainly formed by winding or stacking a positive electrode sheet 231 and a negative electrode sheet 232, and a separator 233 is generally disposed between the positive electrode sheet 231 and the negative electrode sheet 232. The portions of the positive and

negative electrode tabs

231 and 232 having the active material constitute the body portion of the electrode assembly 23, and the portions of the positive and

negative electrode tabs

231 and 232 having no active material each constitute the tab 24. The positive electrode tab 24 and the negative electrode tab 24 may be located together at one end of the main body portion or separately at both ends of the main body portion. During the charge and discharge of the battery 100, the positive and negative active materials react with the electrolyte, and the tab 24 is connected to the electrode terminal 21a to form a current loop.

Referring to fig. 4, the present application provides an electrode assembly 23 having a flat region a and a corner region B connecting the flat regions a. The electrode assembly 23 includes the positive electrode tab 231, and the positive electrode tab 231 includes a plurality of corner portions 2314 located at the corner region B and a plurality of flat portions 2315 located at the flat region a. Among them, at least one corner portion 2314 in the positive electrode tab 231 is a first corner portion, and at least one straight portion 2315 in the positive electrode tab 231 is a first straight portion connecting the first corner portions. The first corner portion includes a first current collecting portion, and the first flat portion includes a second current collecting portion. The mass per unit area of the first current collecting part is smaller than that of the second current collecting part.

The electrode assembly 23 is a wound structure formed by winding, that is, the wound structure includes the above-described straight regions a and corner regions B.

The flat region a is a region where there is no bending or bending of the electrode assembly 23, that is, a region where there is no undulation. The corner region B is a region where there is a bend or bend in the electrode assembly 23, that is, a region having undulations. Each corner region B connects every two adjacent flat regions a, and correspondingly, each flat region a also connects every two adjacent corner regions B. Specifically, the electrode assembly 23 has two straight regions a and two corner regions B, which are sequentially staggered from the two straight regions a.

The corner portion 2314 and the flat portion 2315 are both part of the positive electrode tab 231, wherein the corner portion 2314 is located at the corner region B of the electrode assembly 23 and the flat portion 2315 is located at the flat region a of the positive electrode tab 231. The straight portion 2315 is a portion of the positive electrode tab 231 where there is no bending or bending, that is, where there is no undulation. The corner portion 2314 is a portion where the positive electrode tab 231 is bent or curved, that is, a portion having undulations. Each corner portion 2314 connects every adjacent two of the flat portions 2315, and each flat portion 2315 connects every adjacent two of the corner portions 2314, respectively. The number of the corner portions 2314 and the flat portions 2315 included in the positive electrode tab 231 is not limited.

One of the corner portions 2314 of the positive electrode sheet 231 is a first corner portion, or both of the corner portions 2314 are first corner portions, or all of the corner portions 2314 are first corner portions. Which corner portions 2314 in the positive electrode sheet 231 are the first corner portions can be determined as necessary. The first flat portion is a flat portion 2315 connected to the first corner portion.

The positive electrode tab 231 includes a current collector 2311, and the first current collecting portion and the second current collecting portion are both part of the current collector 2311. Meanwhile, the first current collecting portion is also a part of the first corner portion, and the second current collecting portion is a part of the first straight portion.

Of the first collecting partThe mass per unit area is the mass of the first current collecting part per unit area, i.e. the areal density of the first current collecting part, and the unit is g/m ² And (4) showing. Similarly, the "mass per unit area of the second current collecting portion" is the mass per unit area of the second current collecting portion, that is, the areal density of the second current collecting portion.

Since the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion, the current flowing through the first corner portion is smaller than that flowing through the first straight portion in the unit area. Accordingly, the lithium ion release amount of the first corner portion is smaller than that of the first flat portion in a unit area, so that the lithium ions provided by the first corner portion are balanced with the lithium intercalation active sites provided by the corresponding negative electrode sheet 232, and the corner lithium precipitation phenomenon is reduced.

If the current flowing through the second current collecting portion meets the design requirement in the unit area, that is, when the current flowing through the second current collecting portion reaches the first preset value in the unit area, the lithium is not separated from the negative electrode sheet 232 located on the inner side. Since the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion, compared with the first preset value, the current is reduced, so that the lithium intercalation active site provided by the part of the negative electrode sheet 232 corresponding to the first corner portion is balanced with the lithium ions provided by the first corner portion, and the corner lithium deposition phenomenon is reduced.

According to some embodiments of the present application, alternatively, each corner portion 2314 of the positive electrode tab 231 is a first corner portion, and each straight portion 2315 of the positive electrode tab 231 is a first straight portion. Thus, each corner portion 2314 of the positive electrode tab 231 is made to flow a smaller current than each flat portion 2315. Accordingly, the lithium ion extraction amount of each corner 2314 is smaller than that of each flat portion 2315 per unit area, so that the lithium ions provided at each corner 2314 are balanced with the lithium intercalation active sites provided at the corresponding negative electrode tab 232, thereby reducing the corner lithium deposition phenomenon.

According to some embodiments of the present application, optionally, the mass per unit area of the first collecting part ranges from: 18g/m ² -148.5g/m ² The mass range per unit area of the second collecting part is as follows: 20g/m ² -150g/m ² 。

When the mass per unit area of the first current collector and the mass per unit area of the second current collector are set within the above ranges, the corner lithium deposition phenomenon can be further improved.

According to some embodiments of the present application, optionally, with reference to fig. 5-8, the first corner portion further comprises a first active material portion coated on a surface of the first header portion. The first current collector is provided with openings 2313 in the thickness direction, and the diameters of the openings 2313 are smaller than the particle size of the active material in the first active material portion.

The positive electrode sheet 231 includes an active material layer 2312 coated on the surface of the current collector 2311, and the first active material portion is a part of the active material layer 2312.

The current collector 2311 is typically aluminum foil, and the active material in the active material layer 2312 is typically selected from lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganese, lithium nickel cobalt aluminum, and the like.

The thickness direction of the first current collecting part is a connecting line direction of two side surfaces of the first current collecting part coated with the first active material part. The opening 2313 is a through hole penetrating through the first current collecting portion in the thickness direction. The meaning that the pore diameter of the opening 2313 is smaller than the particle diameter of the active particles in the first active material portion is: the size of the opening 2313 is smaller than that of the active particles in the first active material portion so that the active particles cannot enter the opening 2313. The cross-sectional shape of the openings 2313 is not limited to circular (see fig. 5 and 6), but may be other shapes such as rectangular (see fig. 7 and 8), diamond (see fig. 9 and 10), or other irregular patterns.

The first current collecting portion is provided with the opening 2313 in the thickness direction, so that the unit area mass of the first current collecting portion is reduced, and the current of the first corner portion is smaller than that of the first straight portion. In a unit area, the lithium ion extraction amount of the first corner part is reduced, so that the lithium ions provided by the first corner part and the lithium insertion active sites of the negative electrode are balanced, and the corner lithium separation phenomenon is reduced. Meanwhile, the first corner part is provided with the opening 2313, so that the surface roughness of the first current collecting part can be improved, the bonding force between the first active material part and the first current collecting part of the first corner part is improved, and the material falling problem of the corner region B is solved. And the first current collecting part has the opening 2313, the weight of the first current collecting part can be reduced, thereby reducing the weight of the entire current collector 2311 and increasing the energy density of the electrode assembly 23.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 0.1 μm to 200 μm, and the pore diameter of the opening 2313 is in the range of: 0.05 μm to 100 μm.

Since the larger the particle diameter of the active particles, the longer the lithium ion transport path and the smaller the number of extracted lithium ions per unit time, the smaller the number of lithium ions reaching the negative electrode sheet 232, the less likely lithium is to be separated. And the larger the aperture of the opening 2313 is, the more uneven the current is, the more the electron transport path is blocked, the less the amount of extracted lithium ions is, and the less lithium is easily separated out.

With the above arrangement, the particle diameter of the active particles in the first active material portion and the pore diameter of the opening 2313 are both in an appropriate range, and the occurrence of corner lithium deposition is greatly reduced.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 0.1 μm to 0.5 μm, and the aperture of the openings 2313 is in the range of 0.05 μm to 0.1. Mu.m. For example, the active particles can be LiFePO ₄ Small particle size.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 0.5-1 μm, and the aperture of the opening 2313 is in the range of 0.05-0.5. Mu.m. For example, the active particles may be LiFePO ₄ And (4) large grain size.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 1 μm to 10 μm, and the pore diameter of the opening 2313 is in the range of 0.05 μm to 1 μm. For example, the active particles may be single crystals of NCM.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 10-30 μm, and the aperture of the opening 2313 is in the range of 0.05-10 μm. For example, the active particles may be NCM polycrystals.

According to some embodiments of the application, optionally, the particle size of the active particles in the first active material portion ranges from: 100 μm to 200 μm, and the pore diameter of the opening 2313 is in the range of 0.05 μm to 100. Mu.m. For example, the active particles can be made of ultra-large particle size materials.

The different combinations of the particle size of the active particles in the first active material portion and the pore size of the opening 2313 make the particle size of the active particles in the first active material portion and the pore size of the opening 2313 in proper ranges, so that the corner lithium deposition phenomenon is greatly reduced.

According to some embodiments of the present application, optionally, a ratio of the aperture area of all the apertures 2313 in the first header portion to the total area of the first header portion is: 1 to 10 percent.

Assuming that the thickness of the first collecting portion at each portion of the first corner portion is the same, the mass per unit area of the first collecting portion is related only to the proportion of the aperture area of the opening 2313 occupying the total area of the first collecting portion. When the hole areas of all the openings 2313 in the first current collecting portion occupy the total area of the first current collecting portion, the ratio is: 1% -10%, on the basis of conveniently opening the openings 2313, the proportion of the hole areas of all the openings 2313 occupying the total area of the first current collecting part is in a reasonable range, and the corner lithium precipitation phenomenon is weakened.

Specifically, when the particle diameter of the active particles in the first active material portion ranges from: 0.1 μm to 0.5 μm, and the aperture of the openings 2313 is in the range of 0.05 μm to 0.1 μm, the proportion of the pore area of all the openings 2313 in the first current collecting portion occupying the total area of the first current collecting portion is set to 10%. When the particle diameter of the active particles in the first active material portion ranges: when the aperture of the openings 2313 ranges from 0.05 to 0.5 μm, the proportion of the pore area of all the openings 2313 in the first current collecting portion occupying the total area of the first current collecting portion is set to 8%. When the particle diameter of the active particles in the first active material portion ranges: when the aperture of the openings 2313 ranges from 0.05 μm to 1 μm, the proportion of the pore area of all the openings 2313 in the first current collecting portion to the total area of the first current collecting portion is set to be 5%. When the particle diameter of the active particles in the first active material portion ranges: when the diameter of the openings 2313 ranges from 0.05 to 10 μm, the ratio of the area of all the openings 2313 in the first current collector to the total area of the first current collector is set to 3%. When the particle diameter of the active particles in the first active material portion ranges: when the aperture of the openings 2313 ranges from 0.05 μm to 100 μm, the proportion of the pore area of all the openings 2313 in the first current collecting portion to the total area of the first current collecting portion is set to be 1%.

The following comparative examples and examples are given:

the positive active materials used in the comparative examples and examples were all LiFePO ₄ Reversible capacity of 143mAh/g and coating surface density of 342g/m ² The active substance content is 97%; the negative active materials are all artificial graphite, the reversible capacity is 355mAh/g, and the coating surface density is 150g/m ² The active substance content is 96%; CB is 1.075. The charging and discharging current is 100A, and the charging and discharging voltage is 2.5V-3.65V.

The design value of CB is larger than 1 in general, so that the lithium ions extracted from the positive electrode can be inserted into the negative electrode.

Wherein, anode represents a negative electrode, cathode represents a positive electrode, CW (coating weight) is coating surface density, loading represents the percentage of active material (active material, binder, additive, etc. are contained in general slurry), and capacity represents active material capacity.

Here, all the corner portions 2314 where the positive electrode tab 231 is provided are first corner portions, and all the straight portions 2315 are first straight portions.

The cycle performance of the secondary battery was tested as follows:

charging to 3.8V at 45 deg.C under constant current of 1C, constant voltage to 0.05C, standing for 30min, discharging to 2.0V at 1C, and repeating the above steps. And (4) until the battery cell begins to separate lithium, and recording the cycle number at the moment. (if the battery capacity is 100Ah,1C = 100A)

The method for detecting lithium separation comprises the following steps: and extracting the standing voltage and time data of the battery cell with different cycle turns, drawing a dV/dt and time curve, and if an inflection point appears in dV/dt of the lithium analysis battery cell and a lithium analysis signal appears, proving that the battery cell analyzes lithium (dV is voltage differential and dt is time differential).

As can be seen from the above table, examples 1 to 12 (the mass per unit area of the first current collecting portion is smaller than that of the second current collecting portion) all had larger number of lithium deposition cycles than comparative example 1 (the mass per unit area of the first current collecting portion is equal to that of the second current collecting portion), and all proved to improve the lithium deposition phenomenon.

The mass per unit area of the first current collecting portion in example 1 is smaller than that in example 2, the ratio of the pore area of the first current collecting portion in example 1 is larger than that in example 2, and the number of lithium deposition turns in example 1 is larger than that in example 2. The mass per unit area of the first current collecting portion in example 9 is smaller than that in example 10, the ratio of the pore area of the first current collecting portion in example 9 is larger than that in example 10, and the number of lithium deposition starts in example 9 is larger than that in example 10. The mass per unit area of the first current collecting portion in example 11 was larger than that in example 12, the ratio of the pore area of the first current collecting portion in example 12 was larger than that in example 11, and the number of lithium deposition started in example 12 was larger than that in example 11. Under the same other conditions, it was confirmed that the smaller the mass per unit area of the first current collecting portion, that is, the larger the pore area occupying ratio, the better the corner lithium deposition improving effect.

The particle size of the active particles in example 3 was larger than that of the active particles in example 4, and the number of lithium ions released from example 3 was larger than that of example 4. The particle size of the active particles in example 7 was larger than that of the active particles in example 6, and the number of lithium ions released from example 7 was larger than that of example 6. Under the same other conditions, it was confirmed that the larger the particle size of the active particles, the better the effect of improving corner lithium deposition.

The aperture of the opening 2313 of the first current collecting portion in example 5 is smaller than that of the opening 2313 of the first current collecting portion in example 6, and the number of lithium deposition starts in example 6 is larger than that in example 5. The aperture of the opening 2313 of the first current collecting portion in example 7 is smaller than that of the opening 2313 of the first current collecting portion in example 8, and the number of lithium deposition turns at the beginning of example 8 is larger than that of the lithium deposition turns at the beginning of example 7. Under otherwise identical conditions, it was demonstrated that the larger the pore size, the better the effect of improving corner lithium extraction.

According to some embodiments of the present application, optionally, a thickness of the first current collecting portion is less than a thickness of the second current collecting portion.

By setting the thickness of the first current collecting portion to be smaller than the thickness of the second current collecting portion, the current flowing through the first corner portion per unit area is smaller than the current flowing through the first flat portion. Accordingly, the lithium ion release amount of the first corner portion is smaller than that of the first flat portion per unit area, so that the lithium ions provided by the first corner portion are balanced with the lithium intercalation active sites provided by the corresponding negative electrode sheet 232, and the corner lithium precipitation phenomenon is reduced.

According to some embodiments of the present application, there is also provided a battery cell 20 including the electrode assembly 23 of any of the above aspects.

According to some embodiments of the present application, the present application also provides a battery 100 including the battery cell 20 of any of the above aspects.

According to some embodiments of the present application, the present application further provides an electric device, which includes the battery 100 according to any of the above aspects, and the battery 100 is used to provide electric energy for the electric device.

The powered device may be any of the aforementioned devices or systems that employ battery 100.

According to some embodiments of the present application, an electrode assembly 23 is provided, the electrode assembly 23 having a straight region a and a corner region B connecting the straight regions a. The electrode assembly 23 includes a positive electrode tab 231, and the positive electrode tab 231 includes a plurality of corner portions 2314 located at a corner region B and a plurality of straight portions 2315 located at a straight region a. Here, all the corner portions 2314 of the positive electrode sheet 231 are first corner portions, and all the straight portions 2315 of the positive electrode sheet 231 are first straight portions. The first corner portion includes a first current collecting portion, and the second straight portion 2315 includes a second current collecting portion. The mass per unit area of the first current collecting part is smaller than that of the second current collecting part.

The first current collector is provided with openings 2313 in the thickness direction, and the diameters of the openings 2313 are smaller than the particle size of the active material in the first active material portion.

The first current collecting part is provided with the opening 2313 in the thickness direction, so that the mass of the unit area of the first current collecting part is reduced, the current of the first corner part is smaller than that of the first straight part, the lithium ion extraction amount of the first corner part is reduced in the unit area, the lithium ions provided by the first corner part and the negative electrode lithium intercalation active site are balanced, and the corner lithium precipitation phenomenon is reduced. Meanwhile, the first corner part is provided with the opening 2313, so that the surface roughness of the first current collecting part can be improved, the bonding force between the first active material part and the first current collecting part of the first corner part is improved, and the material falling problem of the corner region B is solved. And the first current collecting part has the opening 2313, the weight of the first current collecting part can be reduced, thereby reducing the weight of the entire current collector 2311 and increasing the energy density of the electrode assembly 23.

All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the utility model. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An electrode assembly, wherein the electrode assembly has a flat region and a corner region connecting the flat regions;

the electrode assembly includes a positive electrode tab including a plurality of corner portions located in the corner regions and a plurality of straight portions located in the straight regions;

at least one corner part in the positive plate is a first corner part, and at least one straight part in the positive plate is a first straight part connected with the first corner part; the first corner portion includes a first header portion, and the first flat portion includes a second header portion; the mass per unit area of the first current collecting part is smaller than that of the second current collecting part.

2. The electrode assembly according to claim 1, wherein each of said corner portions of said positive electrode tab is said first corner portion, and each of said straight portions of said positive electrode tab is said first straight portion.

3. The electrode assembly according to claim 1, wherein the first current collecting part has a mass per unit area ranging from: 18g/m ² -148.5g/m ² The mass range per unit area of the second collecting part is as follows: 20g/m ² -150g/m ² 。

4. The electrode assembly of claim 1, wherein the first corner portion further comprises a first active material portion coated on a surface of the first current collector portion;

the first current collecting part is provided with an opening in the thickness direction, and the aperture of the opening is smaller than the particle size of active particles in the first active material part.

5. The electrode assembly according to claim 4, wherein the particle diameter of the active particles in the first active material portion is in a range of: 0.1 μm to 200 μm, the pore size of the open pores being in the range of: 0.05 μm to 100 μm.

6. The electrode assembly according to claim 5, wherein the particle diameter of the active particles in the first active material portion is in a range of: 0.1-0.5 μm, and the pore diameter of the open pore is in the range of 0.05-0.1 μm.

7. The electrode assembly according to claim 5, wherein the particle diameter of the active particles in the first active material portion is in a range of: 0.5-1 μm, and the pore diameter of the open pore is in the range of 0.05-0.5 μm.

8. The electrode assembly according to claim 5, wherein the particle diameter of the active particles in the first active material portion is in a range of: 1-10 μm, and the pore diameter of the open pore is in the range of 0.05-1 μm.

9. The electrode assembly according to claim 5, wherein the particle diameter of the active particles in the first active material portion is in a range of: 10-30 μm, and the pore diameter of the open pore is in the range of 0.05-10 μm.

10. The electrode assembly according to claim 5, wherein the particle diameter of the active particles in the first active material portion is in a range of: 100-200 μm, and the pore diameter of the open pore is in the range of 0.05-100 μm.

11. The electrode assembly according to any one of claims 4 to 10, wherein the proportion of the pore area of all the openings in the first current collecting portion occupying the total area of the first current collecting portion is: 1 to 10 percent.

12. The electrode assembly according to claim 1, wherein the thickness of the first current collecting part is less than the thickness of the second current collecting part.

13. A battery cell comprising an electrode assembly according to any one of claims 1 to 12.

14. A battery comprising the cell of claim 13.

15. An electric device comprising the battery of claim 14.