CN116435714B

CN116435714B - Electrode assembly, manufacturing method, battery cell, battery and electric equipment

Info

Publication number: CN116435714B
Application number: CN202310680450.9A
Authority: CN
Inventors: 常雯; 付成华; 郭锁刚; 朱小刚; 叶永煌
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-06-09
Filing date: 2023-06-09
Publication date: 2024-02-02
Anticipated expiration: 2043-06-09
Also published as: CN116435714A

Abstract

The application discloses an electrode assembly, a manufacturing method, a battery cell, a battery and electric equipment. The battery assembly includes a first pole piece, a second pole piece, and a separator. The first pole piece is a positive pole piece. The second pole piece is a negative pole piece. The second pole piece and the first pole piece are oppositely arranged. The diaphragm is arranged between the first pole piece and the second pole piece and is used for separating the first pole piece and the second pole piece. The electrode assembly is bent at least one position, and at least one bending part of the first pole piece wrapping the second pole piece is formed; at least part of the first pole piece and the second pole piece at the bending part are tightly attached to the diaphragm. The first pole piece comprises a first current collector and a first active material layer, the first active material layer is arranged on the surface of the first current collector, and grooves are formed in the first active material layer at least at part of the bending part. The technical scheme provided by the application can improve the reliability of the battery.

Description

Electrode assembly, manufacturing method, battery cell, battery and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to an electrode assembly, a manufacturing method, a battery cell, a battery and electric equipment.

Background

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

In the development of battery technology, how to improve the reliability of a battery is a technical problem that needs to be solved in battery technology.

Disclosure of Invention

The application provides an electrode assembly, a manufacturing method, a battery monomer, a battery and electric equipment.

The application is realized by the following technical scheme:

in a first aspect, the present application provides a battery assembly comprising a first pole piece, a second pole piece, and a separator. The first pole piece is a positive pole piece. The second pole piece is a negative pole piece. The second pole piece and the first pole piece are oppositely arranged. The diaphragm is arranged between the first pole piece and the second pole piece and is used for separating the first pole piece and the second pole piece. The electrode assembly is bent at least one position, and at least one bending part of the first pole piece wrapping the second pole piece is formed; at least part of the first pole piece and the second pole piece at the bending part are tightly attached to the diaphragm. The first pole piece comprises a first current collector and a first active material layer, the first active material layer is arranged on the surface of the first current collector, and grooves are formed in at least part of the first active material layer at the bent parts.

In the scheme, the first pole piece and the second pole piece at least at part of the bending part are tightly attached to the diaphragm, so that the transmission distance of lithium ions at the bending part is reduced, the migration capacity of the lithium ions is improved based on the dynamic performance, the risk of occurrence of a lithium precipitation phenomenon is reduced, and the reliability of the battery monomer is improved. Meanwhile, at the bending part, the anode plate is coated with the cathode plate, namely the area of active substances of the anode plate is larger than that of active substances of the cathode plate, so that a higher lithium separation risk exists.

According to some embodiments of the present application, the first pole piece is a positive pole piece and the second pole piece is a negative pole piece.

In the kink department, the positive pole piece cladding negative pole piece, the area of the active material of positive pole piece is greater than the area of the active material of negative pole piece promptly, so there is higher lithium risk of separating out, for this reason, in the above-mentioned scheme, through setting up positive pole piece and the negative pole piece of at least some kink department as all closely laminating with the diaphragm for lithium ion's transmission distance in kink department reduces, based on dynamic performance, lithium ion's migration ability improves, has reduced the risk that lithium phenomenon takes place, has improved the reliability of battery monomer.

According to some embodiments of the present application, the first pole piece comprises a first current collector and a first active material layer, the first active material layer is disposed on a surface of the first current collector, the second pole piece comprises a second current collector and a second active material layer, and the second active material layer is disposed on a surface of the second current collector. At least a portion of the first active material layer and the second active material layer at the bend are both connected to the separator.

In the scheme, the first active material layer is connected with the diaphragm, and the second active material layer is connected with the diaphragm, so that the first pole piece, the second pole piece and the diaphragm are tightly attached to each other, the transmission distance of lithium ions at the bent part is effectively reduced, the migration capacity of the lithium ions is improved, the risk of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

According to some embodiments of the present application, at least a portion of the first active material layer and the second active material layer at the bend are both thermally press-compounded with the separator.

In the scheme, through the hot pressing process, the first active material layer, the second active material layer and the diaphragm are compounded into a whole, the first pole piece, the second pole piece and the diaphragm are tightly attached to each other, the transmission distance of lithium ions at the bent part is effectively reduced, the migration capability of the lithium ions is improved, the risk of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

According to some embodiments of the present application, in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the first pole piece, the second pole piece and the diaphragm are stacked and thermally pressed and compounded into a whole.

In the scheme, the first pole piece, the second pole piece and the diaphragm are laminated and compounded into a whole in a spreading state, namely before the electrode assembly is formed by bending, so that compared with the scheme of local hot-pressing compounding, the manufacturing difficulty can be reduced, and the manufacturing efficiency can be improved; on the other hand can make first pole piece, second pole piece and diaphragm closely laminate each other, reduce the transmission distance of lithium ion in kink department effectively, improve the migration ability of lithium ion, reduce the risk that the lithium phenomenon takes place of separating out, improved the single reliability of battery.

According to some embodiments of the application, the depth of the groove is D, the thickness of the first active material layer is D, and D/D is more than or equal to 30%.

In the above scheme, the depth of the groove is too small, namely the quantity of the active substances on the positive electrode plate is too small by arranging the groove to realize reduction, which means that the active substances on the positive electrode plate are too much, and the problem of insufficient lithium intercalation space of the negative electrode plate exists.

According to some embodiments of the present application, D/D is 80% or more.

In the scheme, the depth D of the groove and the thickness D of the first active material layer are limited, so that D/D is more than or equal to 80%, the amount of positive electrode active materials at the corner is reduced as much as possible, the second active material layer has a certain lithium intercalation space for accommodating lithium ions, the risk of lithium precipitation caused by insufficient lithium intercalation space is effectively reduced, and the reliability of the battery is improved.

According to some embodiments of the present application, the groove is located in a preset area; the preset area is an area which extends to two sides by 6mm or less respectively by taking the central line of the bending part as a reference along the extending direction of the first pole piece in the state that the first pole piece is unfolded.

In the above-mentioned scheme, if the region that the recess is located is too big, then probably cause the risk that energy density descends, perhaps set up the recess in surpassing in predetermineeing the region, can cause and can't improve the problem that leads to the lithium precipitation because of the excessive volume of positive pole piece active material, therefore, through limiting the position of the region that the recess is located, namely set up the recess as the central line of kink as the benchmark, extend the region within 6mm to both sides respectively, on the one hand can not influence the energy density of battery as far as possible, on the other hand can be aimed at corner region department, reduce the lithium precipitation risk because of the excessive volume of positive pole active material.

According to some embodiments of the application, a surface of the diaphragm facing the second pole piece is provided with a lithium-absorbing layer, and a surface of the lithium-absorbing layer facing away from the diaphragm is provided with an insulating layer.

In the scheme, when the diaphragm is bent to form the corner part, the insulating layer is broken by stress at the corner part so as to expose the lithium absorption layer, and the exposed lithium absorption layer can absorb lithium ions which cannot be absorbed by the negative electrode plate, so that the risk of lithium precipitation is reduced, and the reliability of the battery is improved.

According to some embodiments of the present application, the first electrode sheet, the second electrode sheet, and the separator are stacked and repeatedly bent to form a plurality of bent portions, the electrode assembly includes a plurality of flat portions, the plurality of flat portions are stacked, and two adjacent flat portions are connected through the bent portions.

To increase the energy density of the battery, the current electrode assembly includes a laminated electrode assembly. At present, an electrode assembly comprising a single-piece laminated electrode plate, namely a plurality of positive electrode plates and a plurality of positive electrode plates are laminated mutually, however, the electrode assembly has the risk of internal lap short circuit of a battery caused by edge burrs; on the other hand, through setting up first pole piece and the second pole piece of at least some kink department as all closely laminating with the diaphragm for the transmission distance of lithium ion in kink department reduces, based on dynamic performance, and the migration ability of lithium ion improves, has reduced the risk that the lithium phenomenon takes place, has improved the reliability of battery monomer.

According to some embodiments of the application, the number of the first pole pieces is n, the number of the second pole pieces is n+1, and the n+1 second pole pieces comprise a first sub-pole piece and a second sub-pole piece, wherein n is larger than or equal to 1. In the state that the first pole piece, the second pole piece and the diaphragm are unfolded, all the first pole pieces are positioned between the first sub pole pieces and the second sub pole pieces along the stacking direction.

In the scheme, the number of the second pole pieces is one more than that of the first pole pieces, and the two sides of each first pole piece are respectively corresponding to the second pole pieces, namely, the two sides of each first pole piece can be provided with the active material layer, so that the energy density of the battery can be improved.

According to some embodiments of the present application, in a state in which the first pole piece, the second pole piece, and the diaphragm are expanded, a surface of the first sub-pole piece facing away from the first pole piece is a first surface, and a surface of the second sub-pole piece facing away from the first pole piece is a second surface; the first surface and the second surface are respectively provided with a first protection layer.

In the above solution, the first surface is the surface of the first sub-sheet exposed to the outside, which may be without an active material layer, i.e. in some embodiments, the first surface may be regarded as an empty foil area of the current collector. Similarly, the second surface is the surface of the second sub-sheet exposed to the outside, which may be without an active material layer, i.e. in some embodiments, the second surface may be regarded as an empty foil area of the current collector. Therefore, the first protective layers are respectively arranged on the first surface and the second surface, so that the risk of corrosion caused by exposure of current collectors of the first sub-pole piece and the second sub-pole piece can be effectively reduced, and the battery has higher reliability.

According to some embodiments of the present application, in a state in which the first pole piece, the second pole piece, and the diaphragm are expanded, a surface of the first sub-pole piece facing away from the first pole piece is a first surface, and a surface of the second sub-pole piece facing away from the first pole piece is a second surface; the first surface and the second surface are respectively provided with a first connecting layer. The first connection layers between two adjacent flat portions are connected to each other in the stacking direction.

In the scheme, the first connecting layers are respectively arranged on the first surface and the second surface, so that the straight parts can be effectively stuck to each other, the structure of the electrode assembly is compact, and the volume energy density of the electrode assembly is effectively improved.

According to some embodiments of the present application, the number of first pole pieces is the same as the number of second pole pieces. The first pole piece comprises a third sub-pole piece, and the second pole piece comprises a fourth sub-pole piece. In the state that the first pole piece, the second pole piece and the diaphragm are unfolded, all the diaphragms are positioned between the third sub-pole piece and the fourth sub-pole piece along the stacking direction.

In the scheme, the number of the first pole pieces is the same as that of the second pole pieces, so that the specifications of the first pole pieces and the second pole pieces correspond, for example, the arrangement positions of the active material layers correspond, the coating efficiency of the pole pieces can be improved, and the manufacturing efficiency of the battery can be improved.

According to some embodiments of the present application, in a state where the first pole piece, the second pole piece and the diaphragm are unfolded, a surface of the third sub-pole piece, which faces away from the diaphragm, is a third surface, and the third surface is provided with a second protection layer.

In the above solution, the third surface is the surface of the third sub-sheet exposed to the outside, which may be provided without an active material layer, i.e. in some embodiments, the third surface may be regarded as an empty foil area of the current collector. Therefore, by arranging the second protective layer on the third surface, the risk of corrosion of the current collector of the third sub-pole piece caused by exposure to the outside can be effectively reduced, and the battery has higher reliability.

According to some embodiments of the present application, in a state where the first pole piece, the second pole piece, and the diaphragm are unfolded, a surface of the fourth sub-pole piece facing away from the diaphragm is a fourth surface, and the fourth surface is provided with a third protection layer.

In the above solution, the fourth surface is the surface of the fourth sub-pole piece exposed to the outside, which may be without an active material layer, i.e. in some embodiments, the fourth surface may be regarded as an empty foil area of the current collector. Therefore, by arranging the third protective layer on the fourth surface, the risk of corrosion of the fourth sub-pole piece caused by exposure to the outside can be effectively reduced, and the battery has higher reliability.

According to some embodiments of the present application, in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, a surface of the third sub-pole piece, which faces away from the diaphragm, is a third surface, and the third surface is provided with a second connection layer. The second connection layers between two adjacent flat portions and facing each other are connected to each other in the stacking direction.

In the scheme, the second connecting layer is arranged on the third surface, so that the straight parts can be effectively stuck to each other through the second connecting layer, the structure of the electrode assembly is compact, and the volume energy density of the electrode assembly is effectively improved.

According to some embodiments of the present application, in a state where the first pole piece, the second pole piece, and the diaphragm are unfolded, a surface of the fourth sub-pole piece facing away from the diaphragm is a fourth surface, and the fourth surface is provided with a third connection layer. The third connection layers between two adjacent flat portions are connected to each other in the stacking direction.

In the scheme, the third connecting layer is arranged on the fourth surface, so that the straight parts can be effectively stuck to each other through the third connecting layer, the structure of the electrode assembly is compact, and the volume energy density of the electrode assembly is effectively improved.

In a second aspect, some embodiments of the present application also provide a method of manufacturing an electrode assembly, including the steps of:

the first pole piece, the diaphragm and the second pole piece are arranged in a stacked mode and are combined into a whole to form a composite structure, the first pole piece is a positive pole piece, the second pole piece is a negative pole piece, and a first active material layer of the first pole piece is provided with a groove;

and bending the composite structure at least one position, forming at least one bending part of the first pole piece coating the second pole piece, and positioning the groove at the bending part.

In the scheme, on the one hand, through setting up first pole piece, diaphragm and second pole piece range upon range of and compound in an organic whole, can make the transmission distance of lithium ion in kink department reduce, based on dynamic performance, can improve the migration ability of lithium ion, reduced the risk that the lithium phenomenon takes place of separating out, improved the single reliability of battery. On the other hand, the first active material layer at the bending part is provided with the grooves so as to reduce the quantity of the first active material layer, so that the second active material layer has a certain lithium intercalation space for accommodating lithium ions, the risk of lithium precipitation caused by insufficient lithium intercalation space is effectively reduced, and the reliability of the battery is improved.

According to some embodiments of the present application, the first pole piece, the diaphragm and the second pole piece are stacked and combined into one body, and include:

the first pole piece, the diaphragm and the second pole piece are arranged in a laminated mode and are combined into a whole in a hot pressing mode.

In the scheme, through the hot pressing process, the first active material layer, the second active material layer and the diaphragm can be compounded into a whole efficiently, the first pole piece, the second pole piece and the diaphragm can be tightly attached to each other, the transmission distance of lithium ions at the bent part is effectively reduced, the migration capability of the lithium ions is improved, the risk of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

According to some embodiments of the present application, the bending the composite structure at least one position and forming at least one bending portion of the first pole piece wrapping the second pole piece includes:

the composite structure is repeatedly bent to form an electrode assembly, the electrode assembly comprises a plurality of straight parts and a plurality of bending parts, the plurality of straight parts are arranged in a lamination mode in the lamination direction of the first pole piece, the diaphragm and the second pole piece in a lamination mode, and two adjacent straight parts are connected through the bending parts.

In the scheme, the composite structure is repeatedly bent to form the electrode assembly, so that the electrode assembly is compact in structure, and the volume energy density of the battery is improved.

In a third aspect, some embodiments of the present application further provide a battery cell, the battery cell including a housing, and the electrode assembly provided in any one of the first aspects, the electrode assembly being disposed inside the housing.

In a fourth aspect, some embodiments of the present application further provide a battery, the battery including the battery cell provided in the third aspect.

In a fifth aspect, some embodiments of the present application further provide an electrical device, where the electrical device includes the battery cell provided in the third aspect.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic illustration of a vehicle in some embodiments of the present application;

FIG. 2 is an exploded perspective view of a battery provided in some embodiments of the present application;

FIG. 3 is an exploded perspective view of a battery cell according to some embodiments of the present application;

FIG. 4 is a schematic view of a partial structure of an electrode assembly in some embodiments of the present application;

FIG. 5 is a schematic illustration of an electrode assembly without compaction in some embodiments of the present application;

FIG. 6 is a schematic illustration of an electrode assembly after compaction in some embodiments of the present application;

FIG. 7 is a schematic illustration of a partial structure of a first pole piece in some embodiments of the present application;

FIG. 8 is a schematic illustration of a first pole piece, a second pole piece, and a separator in some embodiments of the present application;

FIG. 9 is a schematic illustration of an electrode assembly without compaction in some embodiments of the present application;

FIG. 10 is a schematic illustration of an electrode assembly after compaction in some embodiments of the present application;

FIG. 11 is a schematic illustration of an electrode assembly according to further embodiments of the present application, without compaction;

FIG. 12 is a schematic illustration of an electrode assembly after compaction according to further embodiments of the present application;

FIG. 13 is a schematic view of a first pole piece, the second pole piece, and the separator in an expanded state in accordance with further embodiments of the present application;

FIG. 14 is a schematic view of a first pole piece, the second pole piece, and the separator in an expanded state in accordance with further embodiments of the present application;

FIG. 15 is a schematic view of a first pole piece, the second pole piece, and the separator in an expanded state in accordance with further embodiments of the present application;

FIG. 16 is a schematic illustration of a first pole piece, the second pole piece, and the separator in an expanded state in accordance with further embodiments of the present application;

fig. 17 is a flow chart of a method of manufacturing an electrode assembly in some embodiments of the present application.

Icon: 11-an electrode assembly; 11 a-a bend; 11 b-a straight portion; 30-a first pole piece; 30 a-a third sub-pole piece; 31-a first current collector; 32-a first active material layer; 33-grooves; 34-a second protective layer; 35-a second connection layer; 40-a second pole piece; 40 a-a first sub-pole piece; 40 b-a second sub-pole piece; 40 c-a fourth sub-pole piece; 41-a second current collector; 42-a second active material layer; 43-a first protective layer; 44-a first connection layer; 45-a third protective layer; 46-a third connection layer; 50-a separator; 51-a lithium-absorbing layer; 52-an insulating layer; 1000-vehicle; 100-cell; 200-a controller; 300-motor; 10-battery cell; 20-a box body; 21-an upper box body; 22-lower box body; 60-a housing; 61-a housing; 62-end caps; 63-electrode terminals; 64-liquid injection hole.

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

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 in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description and claims of the present application and in the description of the figures above are intended to cover non-exclusive inclusions. The terms first, second and the like in the description and in the claims or in the above-described figures, are used for distinguishing between different objects and not necessarily for describing a particular sequential or chronological order.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases 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.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "attached" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; 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 "and/or" in this application is merely an association relation describing an associated object, and indicates that three relations may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In this application, the character "/" generally indicates that the associated object is an or relationship.

In the embodiments of the present application, the same reference numerals denote the same components, and in the interest of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, etc. dimensions of the various components in the embodiments of the present application, as well as the overall thickness, length, width, etc. dimensions of the integrated device, are illustrative only and should not be construed as limiting the present application in any way.

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

In the present application, the battery cells may include lithium ion secondary battery cells, lithium ion primary battery cells, lithium sulfur battery cells, sodium lithium ion battery cells, sodium ion battery cells, or magnesium ion battery cells, and the embodiment of the present application is not limited thereto. The battery cells may be cylindrical, flat, rectangular, or otherwise shaped, as well as the embodiments herein are not limited in this regard.

Reference to a battery in embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. The battery generally includes a case for enclosing one or more battery cells. The case body can prevent liquid or other foreign matters from affecting the charge or discharge of the battery cells.

The battery cell comprises an electrode assembly and electrolyte, wherein the electrode assembly consists of a positive electrode plate, a negative electrode plate and a diaphragm. The battery cell mainly relies on metal ions to move between the positive pole piece and the negative pole piece to work. The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is coated on the surface of the positive electrode current collector, the positive electrode current collector without the positive electrode active material layer protrudes out of the positive electrode current collector coated with the positive electrode active material layer, and the positive electrode current collector without the positive electrode active material layer is used as a positive electrode lug. Taking a lithium ion battery as an example, the material of the positive electrode current collector may be aluminum, and the positive electrode active material may be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate or the like. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is coated on the surface of the negative electrode current collector, the negative electrode current collector without the negative electrode active material layer protrudes out of the negative electrode current collector coated with the negative electrode active material layer, and the negative electrode current collector without the negative electrode active material layer is used as a negative electrode lug. The material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon, silicon, or the like. The separator may be made of PP (polypropylene) or PE (polyethylene). The diaphragm has electronic insulation and is used for isolating adjacent positive pole pieces and negative pole pieces and preventing the adjacent positive pole pieces and negative pole pieces from being short-circuited. The diaphragm has a large number of through micropores, can ensure free passage of electrolyte ions and has good permeability to lithium ions, so the diaphragm can not substantially block passage of lithium ions. In addition, the electrode assembly may be a wound structure or a lamination structure, and the embodiment of the present application is not limited thereto.

In order to make the battery cell smaller in volume and higher in energy density, the negative electrode sheet, the positive electrode sheet and the separator in the electrode assembly of the battery cell may be wound or folded and then compacted. Whether wound or folded, the electrode assembly is bent at least one position to form a positive electrode sheet wrapping a negative electrode sheet, or a negative electrode sheet wrapping a bent portion of the positive electrode sheet.

When the battery monomer is charged, metal ions, such as lithium ions, are deintercalated from the positive electrode plate and are embedded into the negative electrode plate, but abnormal conditions, such as insufficient lithium embedding space of the negative electrode plate, overlarge distance between the negative electrode plate and the positive electrode plate, overlarge resistance of lithium ions to be embedded into the negative electrode plate or too fast deintercalation of lithium ions from the positive electrode plate, and the deintercalated lithium ions cannot be equally embedded into the negative electrode active material layer of the negative electrode plate, and the lithium ions which cannot be embedded into the negative electrode plate can only obtain electrons on the surface of the negative electrode plate, so that a metal lithium simple substance is formed, namely a lithium precipitation phenomenon. The lithium separation not only reduces the performance of the lithium ion battery monomer and shortens the cycle life greatly, but also limits the quick charge capacity of the lithium ion battery monomer. In addition, when lithium ion battery is separated, the separated lithium metal is very active, and can react with electrolyte at a lower temperature, so that the self-heating initial temperature of the battery monomer is reduced, the self-heating rate is increased, and the safety of the battery monomer is seriously endangered. Furthermore, when lithium is severely separated, lithium crystals can be formed on the surface of the negative electrode plate by the separated lithium ions, and the lithium crystals are easy to puncture the diaphragm, so that the adjacent positive electrode plate and the negative electrode plate have short circuit risks, and the reliability of the battery is affected.

Further research shows that the reason for the lithium precipitation phenomenon is that after the electrode assembly is bent, the distance between the adjacent first pole piece and the second pole piece at the bent part is larger, the transmission distance of lithium ions is larger, the lithium ion migration capacity is reduced due to the influence of dynamic performance, and the lithium precipitation phenomenon is easy to occur at the bent part, so that the reliability of the battery is influenced.

In view of this, some embodiments of the present application provide an electrode assembly, through setting the first pole piece and the second pole piece of at least some kinks to all closely laminate with the diaphragm for the transmission distance of lithium ion in kink department reduces, based on dynamic performance, and the migration ability of lithium ion improves, has reduced the risk that the lithium phenomenon of separating out takes place, has improved the reliability of battery monomer.

The technical scheme described by the embodiment of the application is suitable for the battery and the electric equipment using the battery.

The electric equipment can be vehicles, mobile phones, portable equipment, notebook computers, ships, spacecrafts, electric toys, electric tools and the like. Spacecraft including airplanes, rockets, space planes, spacecraft, and the like; the electric toy includes fixed or mobile electric toys, such as a game machine, an electric car toy, an electric ship toy, and an electric airplane toy; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railroad power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete shakers, and electric planers, among others. The embodiment of the application does not limit the electric equipment in particular.

For convenience of description, the following embodiments take the electric device as the vehicle 1000 as an example.

Referring to fig. 1, fig. 1 is a schematic diagram of a vehicle 1000 according to some embodiments of the present application. The vehicle 1000 may be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or a range-extended vehicle. The battery 100 is provided in the interior of the 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 be used as an operating power source of the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, the controller 200 being configured to control the battery 100 to power the motor 300, for example, for operating power requirements during start-up, navigation, and travel of the vehicle 1000.

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

Referring to fig. 2, fig. 2 is an exploded perspective view of a battery 100 according to some embodiments of the present application. The battery 100 includes a case 20 and a battery cell 10, and the battery cell 10 is accommodated in the case 20. The case 20 is used to provide an accommodating space for the battery cell 10, and the case 20 may have various structures. In some embodiments, the case 20 may include an upper case 21 and a lower case 22, the upper case 21 and the lower case 22 being overlapped with each other, the upper case 21 and the lower case 22 together defining an accommodating space for accommodating the battery cell 10. The lower case 22 may have a hollow structure with one end opened, the upper case 21 may have a plate-shaped structure, and the upper case 21 covers the opening side of the lower case 22, so that the upper case 21 and the lower case 22 together define an accommodating space; the upper case 21 and the lower case 22 may be hollow structures each having one side opened, and the opening side of the upper case 21 may be closed to the opening side of the lower case 22. Of course, the case 20 formed by the upper case 21 and the lower case 22 may be of various shapes, such as a cylinder, a rectangular parallelepiped, etc.

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

Wherein each battery cell 10 may be a secondary battery cell or a primary battery cell; but not limited to, lithium sulfur battery cells, sodium ion battery cells, or magnesium ion battery cells.

Fig. 3 is an exploded view of battery cell 10 in some embodiments of the present application. The battery cell 10 includes a case 60, and an electrode assembly 11 accommodated in the case 60.

As shown in fig. 3, the case 60 includes a case 61 and an end cap 62, the case 61 having a receiving chamber, the case 61 having an opening so that the electrode assembly 11 can be received in the receiving chamber of the case 61. The end cap 62 is configured to close the opening of the housing 61. The end cap 62 is provided at an electrode terminal 63 for electrical connection with a tab of the electrode assembly 11, to achieve charge and discharge of the battery cell. After the electrode assembly 11 is accommodated in the case, an electrolyte may be injected into the accommodating chamber through the injection hole 64 provided at the end cap 62.

The case 60 is dependent on the shape of the one or more electrode assemblies 11 combined, and for example, the case 60 may be a hollow rectangular parallelepiped or a hollow square or a hollow cylinder. In some embodiments of the present application, the housing 60 may be made of a material that is a conductive metal, such as aluminum or an aluminum alloy, or the like. The housing may also be made of plastic.

Referring to fig. 4, fig. 4 is a schematic diagram illustrating a partial structure of an electrode assembly 11 according to some embodiments of the present application.

The battery assembly includes a first pole piece 30, a second pole piece 40, and a separator 50. The first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece. The second pole piece 40 is disposed opposite the first pole piece 30. A separator 50 is disposed between the first and second pole pieces 30, 40 for separating the first and second pole pieces 30, 40. The electrode assembly 11 is bent at least one position, and forms at least one bent portion 11a of the first electrode sheet 30 covering the second electrode sheet 40; at least a portion of the first and second pole pieces 30, 40 at the bend 11a are in close contact with the diaphragm 50. The first electrode sheet 30 includes a first current collector 31 and a first active material layer 32, the first active material layer 32 is disposed on a surface of the first current collector 31, and at least a portion of the first active material layer 32 at the bending portion 11a is provided with a groove 33 (see fig. 5 and 7, fig. 5 is a schematic view of an electrode assembly not compacted in some embodiments of the present application, and fig. 6 is a schematic view of an electrode assembly compacted in some embodiments of the present application).

In some embodiments, whether rolled or folded, the electrode assembly 11 is bent at least one location and forms a positive electrode tab wrapped around a negative electrode tab, or a negative electrode tab wrapped around a bent portion 11a of the positive electrode tab. At the bent portion 11a, the area of the pole piece on the inner side is smaller than that of the pole piece on the outer side. In some embodiments, the electrode assembly 11 is bent at least one position and forms a positive electrode tab coating a negative electrode tab, or a portion of the negative electrode tab coating the positive electrode tab may be referred to as a bent portion 11a.

After the electrode assembly 11 is bent, the bent portion 11a is positioned between two parallel flat portions 11b, and both ends of the bent portion 11a are respectively connected to the adjacent two flat portions 11b. In fig. 4, the bent portion 11a is located between two flat portions 11b and has an arc shape. In other embodiments, the bent portion 11a is located between two flat portions 11b and may be flat, such as in fig. 5.

The bent portion 11a may be understood as a portion where the second electrode sheet 40 having a relatively large area can be covered by the first electrode sheet having a relatively small area at the bent position of the electrode assembly 11.

The polarity of the positive pole piece is opposite to that of the negative pole piece. The positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector. In some embodiments, the two opposite surfaces of the positive electrode current collector may be provided with positive electrode active material layers, respectively. In some embodiments, one surface of the positive electrode current collector may be provided with a positive electrode active material layer. The negative electrode tab may include a negative electrode current collector and a negative electrode active material layer disposed on a surface of the negative electrode current collector. In some embodiments, the two opposite surfaces of the negative electrode current collector may be provided with negative electrode active material layers, respectively. In some embodiments, one surface of the anode current collector may be provided with an anode active material layer.

In some embodiments, when the first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece, at least part of the positive pole piece and the negative pole piece can be tightly attached to the diaphragm 50 in the bending portion 11a formed by wrapping the positive pole piece with the negative pole piece; in the bending part 11a formed by wrapping the anode plate with the cathode plate, at least part of the cathode plate and the anode plate can be tightly attached to the diaphragm 50. In other embodiments, when the first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece, at least part of the positive pole piece and the negative pole piece can be tightly attached to the diaphragm 50 in the bending portion 11a formed by wrapping the positive pole piece with the negative pole piece; in the bent portion 11a formed by wrapping the positive electrode sheet with the negative electrode sheet, the negative electrode sheet and the positive electrode sheet may not be tightly bonded with the separator 50.

When the first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece. In the above scheme, the positive electrode plate and the negative electrode plate at least at part of the bent part 11a are arranged to be tightly attached to the diaphragm 50, so that the transmission distance of lithium ions at the bent part 11a is reduced, the migration capability of lithium ions is improved based on the dynamic performance, the occurrence risk of lithium precipitation is reduced, and the reliability of a battery cell is improved.

In other embodiments, first pole piece 30 is a negative pole piece and second pole piece 40 is a positive pole piece. In the bending part 11a formed by wrapping the anode plate with the cathode plate, at least part of the anode plate and the cathode plate can be tightly attached to the diaphragm 50; in the bending part 11a formed by wrapping the anode plate with the cathode plate, at least part of the cathode plate and the anode plate can be tightly attached to the diaphragm 50.

Referring to fig. 5 and 6, fig. 6 is a schematic diagram of an electrode assembly 11 according to some embodiments of the present application after being compacted. In fig. 5, the electrode assembly 11 is shown continuously folded in a zigzag shape. In fig. 5 and 6, it can be seen that the electrode assembly 11 is formed with a plurality of bent portions 11a, and the polarities of the electrode sheets having a smaller area and the polarities of the electrode sheets having a larger area are alternately changed in the bent portions 11a at different positions because they are continuously folded in a zigzag shape. For example, in two adjacent bending portions 11a, one bending portion 11a is a positive electrode sheet and coats a negative electrode sheet, and the other bending portion 11a is a negative electrode sheet and coats a positive electrode sheet.

By "at least a portion of the first pole piece 30 and the second pole piece 40 at the bent portion 11a are both tightly attached to the separator 50" it is understood that at the bent portion 11a, a portion or all of the first pole piece 30 and the second pole piece 40 are both tightly attached to the separator 50, and the gap is smaller or no gap exists at the tightly attached portion, so as to solve the problem of larger distance between the first pole piece 30 and the second pole piece 40.

In some embodiments, the first pole piece 30 and the second pole piece 40 may be respectively connected with the diaphragm 50 to achieve at least a portion of the first pole piece 30 and the second pole piece 40 at the bending portion 11a to be tightly adhered to the diaphragm 50. In some embodiments, first pole piece 30 and second pole piece 40 may be attached to diaphragm 50 by adhesive, welding, or heat and pressure bonding. In other embodiments, first pole piece 30 and second pole piece 40 may be riveted, clamped, etc. to diaphragm 50 via a connector.

The grooves 33 are groove-like structures formed in the first active material layer 32, and the purpose of providing the grooves 33 includes reducing the amount of the first active material layer 32.

At the bent portion 11a, the first active material layer 32 of the first pole piece 30 is provided with a groove 33. In some embodiments, the first active material layer 32 of the first pole piece 30 may also be provided with grooves 33 at the non-bent portion 11 a.

In some embodiments, the shape of the groove 33 includes, but is not limited to, circular, square, triangular, or other shapes.

In some embodiments, when the shape of the groove 33 is circular, the aperture of the groove 33 may be 1um-100um, for example, the aperture of the groove 33 may be any of 1um, 2um, 3um … um, 99um, or 100um, or any value between two adjacent values. In some embodiments, when the shape of the groove 33 is circular, the aperture of the groove 33 may be 5um-40um, for example, the aperture of the groove 33 may be any of 5um, 6um, 7um … um, 39um, or 40um, or any value between two adjacent values.

In the above scheme, by setting the first pole piece 30 and the second pole piece 40 at least at part of the bent portion 11a to be tightly attached to the diaphragm 50, the transmission distance of lithium ions at the bent portion 11a is reduced, the migration capability of lithium ions is improved based on dynamic performance, the risk of occurrence of lithium precipitation is reduced, and the reliability of the battery cell is improved.

When the first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece. In the above-mentioned scheme, in the bent portion 11a, the groove 33 is formed in at least part of the first active material layer 32 to reduce the amount of the first active material layer 32, so that the second active material layer 42 has a certain lithium intercalation space to accommodate lithium ions, thereby effectively reducing the risk of lithium precipitation due to insufficient lithium intercalation space and improving the reliability of the battery.

According to some embodiments of the present application, referring to fig. 4 to 6, the first electrode sheet 30 includes a first current collector 31 and a first active material layer 32, the first active material layer 32 is disposed on a surface of the first current collector 31, the second electrode sheet 40 includes a second current collector 41 and a second active material layer 42, and the second active material layer 42 is disposed on a surface of the second current collector 41. At least a portion of the first active material layer 32 and the second active material layer 42 at the bend 11a are connected to the separator 50.

In some embodiments, the first electrode sheet 30 is connected to the separator 50 through the first active material layer 32, and the second electrode sheet 40 is connected to the separator 50 through the second active material layer 42, such that the first electrode sheet 30, the separator 50, and the second electrode sheet 40 are in close proximity to each other, such that the spacing between the first active material layer 32 and the second active material layer 42 is reduced, reducing the transmission distance of lithium ions at the bend 11 a.

In the above scheme, the first active material layer 32 is connected with the diaphragm 50, and the second active material layer 42 is connected with the diaphragm 50, so that the first pole piece 30, the second pole piece 40 and the diaphragm 50 are tightly attached to each other, the transmission distance of lithium ions at the bent part 11a is effectively reduced, the migration capability of lithium ions is improved, the risk of occurrence of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

In other embodiments, first pole piece 30 and second pole piece 40 may be connected to diaphragm 50 by a connector, for example, first pole piece 30 and second pole piece 40 may be clamped to diaphragm 50 by a clamping jaw or structure having a clamping effect.

According to some embodiments of the present application, at least a portion of first active material layer 32 and second active material layer 42 at bend 11a are both thermally and compression compounded with separator 50.

In some embodiments, at the bent portion 11a, a portion of the first active material layer 32, a portion of the second active material layer 42, and the separator 50 are combined into one body through a hot pressing process. In some embodiments, at the bent portion 11a, the first active material layer 32, the second active material layer 42, and the separator 50 are combined into one body through a hot pressing process. In other embodiments, the first active material layer 32, the second active material layer 42 and the separator 50 are all integrated by a hot pressing process, and then bent to form the bent portion 11a.

In some embodiments, the hot pressing temperature of the first active material layer 32, the second active material layer 42, and the separator 50 may be between 60 degrees celsius and 90 degrees celsius, for example, 60 degrees celsius, 61 degrees celsius, 62 degrees celsius … degrees celsius, or 90 degrees celsius.

In the above scheme, through the hot pressing process, the first active material layer 32, the second active material layer 42 and the diaphragm 50 can be compounded into a whole, so that the first pole piece 30, the second pole piece 40 and the diaphragm 50 are tightly attached to each other, the transmission distance of lithium ions at the bent part 11a is effectively reduced, the migration capability of lithium ions is improved, the risk of occurrence of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

According to some embodiments of the present application, in a state in which the first pole piece 30, the second pole piece 40, and the separator 50 are unfolded, the first pole piece 30, the second pole piece 40, and the separator 50 are stacked and thermally pressed and compounded as one body.

In some embodiments, before the first pole piece 30, the second pole piece 40 and the diaphragm 50 are wound or folded, the first pole piece 30, the second pole piece 40 and the diaphragm 50 may be stacked so that the first pole piece 30, the second pole piece 40 and the diaphragm 50 are hot-pressed and compounded into a whole through a hot-pressing process in a state that the diaphragm 50 separates the first pole piece 30 and the second pole piece 40, that is, the first pole piece 30, the second pole piece 40 and the diaphragm 50 are hot-pressed and compounded into a whole along the length direction of the first pole piece 30, the second pole piece 40 and the diaphragm 50, and the first pole piece 30, the second pole piece 40 and the diaphragm 50 are closely attached.

In the above-mentioned scheme, before the electrode assembly 11 is formed in the unfolded state, that is, before being folded, the first electrode sheet 30, the second electrode sheet 40 and the separator 50 are laminated and thermally pressed and compounded into a whole, on one hand, compared with the scheme of local thermal pressing and compounding, the manufacturing difficulty can be reduced, and the manufacturing efficiency can be improved; on the other hand, the first pole piece 30, the second pole piece 40 and the diaphragm 50 can be tightly attached to each other, so that the transmission distance of lithium ions at the bent part 11a is effectively reduced, the migration capability of the lithium ions is improved, the risk of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

In other embodiments, the first pole piece 30, the second pole piece 40 and the diaphragm 50 may be stacked such that the first pole piece 30, the second pole piece 40 and the diaphragm 50 are thermally pressed and compounded by a thermal pressing process in a state where the diaphragm 50 separates the first pole piece 30 and the second pole piece 40, that is, a local part of the first pole piece 30, the second pole piece 40 and the diaphragm 50 along the length direction of the first pole piece 30, the second pole piece 40 and the diaphragm 50 is thermally pressed and integrated with the first pole piece 30, the second pole piece 40 and the diaphragm 50, and the local part may correspond to a bending part 11a formed after winding or folding.

According to some embodiments of the present application, referring to FIG. 7, the depth of the groove 33 is D and the thickness of the first active material layer 32 is D, satisfying D/D.gtoreq.30%.

The depth d of the groove 33 can be understood as the thickness of the active material that decreases in the thickness direction of the first active material layer 32.

The larger the value of D/D, the larger the amount of active material that the first active material layer 32 reduces due to the grooves 33.

In some embodiments, D/D may take on the value 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, or any value between two adjacent values. When D/D is equal to 100%, it can be understood that the first active material layer 32 is not present at the portion of the groove 33.

In the above scheme, the depth of the groove 33 is too small, that is, the amount of the active material of the positive electrode sheet is too small by arranging the groove 33 to reduce, which means that the active material on the positive electrode sheet is too much, and the problem of insufficient lithium intercalation space of the negative electrode sheet exists, therefore, the depth D of the groove 33 and the thickness D of the first active material layer 32 are limited, so that D/D is more than or equal to 30%, and the second active material layer 42 has a certain lithium intercalation space to accommodate lithium ions, thereby effectively reducing the risk of lithium precipitation caused by insufficient lithium intercalation space and improving the reliability of the battery.

According to some embodiments of the present application, D/D is 80% or more.

In the above scheme, the depth D of the groove 33 and the thickness D of the first active material layer 32 are defined so that D/D is greater than or equal to 80%, so that the amount of the positive electrode active material at the corner portion is reduced as much as possible, and the second active material layer 42 has a certain lithium intercalation space for accommodating lithium ions, thereby effectively reducing the risk of lithium precipitation caused by insufficient lithium intercalation space and improving the reliability of the battery.

According to some embodiments of the present application, referring to fig. 6, the groove 33 is located in a predetermined area. The predetermined region is a region extending by 6mm or less to both sides with respect to the center line of the bent portion 11a in the extending direction of the first pole piece 30 in the state where the first pole piece 30 is extended.

Referring to fig. 6, after the electrode assembly 11 is bent, the bent portion 11a is positioned between two parallel straight portions 11b, and both ends of the bent portion 11a are connected to the adjacent two straight portions 11b, respectively. The center line of the bent portion 11a is denoted by a reference numeral "a" in fig. 6 with a broken line, and the center line of the bent portion 11a may refer to a line between adjacent two flat portions 11b and equidistant from the two flat portions 11b when the electrode assembly 11 is compacted.

By "a region extending within 6mm on each side" is understood a region extending by 6mm or less on each side of the center line, along the first pole piece 30, respectively, with respect to the center line. For example, after the electrode assembly 11 is expanded, two line segments parallel to the reference line are divided by measuring a value of 6mm or less to both sides with a line segment bisecting the two straight portions 11b as the reference line, and the region divided by the two parallel line segments can be regarded as a preset region.

In some embodiments, the grooves 33 may be provided in regions extending within 5mm to both sides, respectively, with respect to the center line of the bent portion 11 a.

In the above-mentioned scheme, if the area where the groove 33 is located is too large, there is a risk that the energy density may be reduced, or if the groove 33 is set to be out of the preset area, there is a problem that the lithium precipitation caused by the excessive amount of the active material of the positive electrode sheet cannot be improved.

Referring to fig. 8, fig. 8 is a schematic diagram of a first pole piece 30, a second pole piece 40, and a separator 50 according to some embodiments of the present application. The surface of the diaphragm 50 facing the second pole piece 40 is provided with a lithium-absorbing layer 51, and the surface of the lithium-absorbing layer 51 facing away from the diaphragm 50 is provided with an insulating layer 52.

A diaphragm 50 is positioned between first pole piece 30 and second pole piece 40. The surface of the separator 50 facing the second pole piece 40 is provided with a lithium absorbing layer 51. The lithium absorbing layer 51 may be a graphite layer, a silicon oxide layer, a tin oxide layer, a copper oxide layer, or a zinc oxide layer. The role of the lithium absorbing layer 51 includes absorbing lithium ions or elemental lithium that the negative electrode tab fails to absorb.

The insulating layer 52 has insulating features, the insulating layer 52 being arranged on the surface of the lithium-absorbing layer 51 facing away from the separator 50, i.e. the insulating layer 52 is located between the lithium-absorbing layer 51 and the second pole piece 40. In some embodiments, the insulation layer 52 has a density of 98% or more, and is dense, ensuring that the lithium-absorbing layer 51 is not exposed first, avoiding premature reaction with lithium ions and consuming additional lithium ions.

In the above scheme, when the diaphragm 50 is bent to form a corner, the insulating layer 52 is broken by stress at the corner to expose the lithium absorbing layer 51, and the exposed lithium absorbing layer 51 can absorb the lithium simple substance which cannot be absorbed by the negative electrode piece, so that the risk of lithium precipitation is reduced, and the reliability of the battery is improved.

Referring to fig. 5, fig. 5 illustrates a portion of an electrode assembly 11 of a laminated structure, according to some embodiments of the present application. The first electrode sheet 30, the second electrode sheet 40 and the separator 50 are stacked and repeatedly bent to form a plurality of bent portions 11a, the electrode assembly 11 includes a plurality of straight portions 11b, the plurality of straight portions 11b are stacked, and adjacent two straight portions 11b are connected by the bent portions 11 a.

In fig. 5, it can be understood that the first electrode sheet 30, the separator 50, and the second electrode sheet 40 are continuously folded in a zigzag shape after being laminated to form the electrode assembly 11.

To increase the energy density of the battery, the present electrode assembly 11 includes a laminated electrode assembly 11. At present, in the laminated electrode assembly including a single laminated electrode sheet, that is, a plurality of positive electrode sheets and a plurality of positive electrode sheets are laminated with each other, however, the electrode assembly 11 has a risk of internal lap short circuit of the battery due to edge burrs, and therefore, in the above scheme, on one hand, the first electrode sheet 30, the second electrode sheet 40 and the separator 50 in the electrode assembly 11 are all in a strip-shaped structure, and the first electrode sheet 30, the second electrode sheet 40 and the separator 50 are laminated and repeatedly bent, so that the problem of edge burrs can be overcome, thereby reducing the risk of internal lap short circuit of the battery; on the other hand, by arranging the first pole piece 30 and the second pole piece 40 at least at part of the bent portion 11a to be in close contact with the separator 50, the transmission distance of lithium ions at the bent portion 11a is reduced, the migration capability of lithium ions is improved based on the dynamic performance, the risk of occurrence of a lithium precipitation phenomenon is reduced, and the reliability of the battery cell is improved.

Referring to fig. 9 and 10, fig. 9 is a schematic diagram of an uncompacted electrode assembly 11 according to some embodiments of the present application, and fig. 10 is a schematic diagram of an uncompacted electrode assembly 11 according to some embodiments of the present application. The number of the first pole pieces 30 is n, the number of the second pole pieces 40 is n+1, and the n+1 second pole pieces 40 comprise a first sub-pole piece 40a and a second sub-pole piece 40b, wherein n is more than or equal to 1. In the state where the first pole piece 30, the second pole piece 40, and the separator 50 are expanded, all the first pole pieces 30 are located between the first sub-pole piece 40a and the second sub-pole piece 40b in the lamination direction.

In some embodiments, first pole piece 30 may be a positive pole piece and second pole piece 40 may be a negative pole piece. n may be 1, referring to fig. 9, the number of the first pole pieces 30 may be one, the number of the second pole pieces 40 may be two, and the two second pole pieces 40 are divided into a first sub-pole piece 40a and a second sub-pole piece 40b, and the first sub-pole piece 40a and the second sub-pole piece 40b are two second pole pieces 40 located at the outermost sides. Referring to fig. 9, the first pole piece 30 is located between the first sub-pole piece 40a and the second sub-pole piece 40b, and the first pole piece 30 and the first sub-pole piece 40a are separated by a diaphragm 50, and the first pole piece 30 and the second sub-pole piece 40b are separated by the diaphragm 50. The first active material layer 32 is provided on both surfaces of the first electrode sheet 30 to correspond to the second active material layer 42 on the first sub-electrode sheet 40a and the second active material layer 42 on the second sub-electrode sheet 40b, respectively.

In other embodiments, n may be other integers greater than 1, e.g., n is 2, 3, 4, etc.

In the above scheme, the number of the second pole pieces 40 is one more than the number of the first pole pieces 30, and the two sides of each first pole piece 30 are respectively corresponding to the second pole pieces 40, that is, the two sides of each first pole piece 30 can be provided with the active material layer, so that the energy density of the battery can be improved.

Referring to fig. 11 and 12, fig. 11 is a schematic view of an electrode assembly 11 according to another embodiment of the present application, and fig. 12 is a schematic view of an electrode assembly 11 according to another embodiment of the present application after being compacted.

In the state where the first pole piece 30, the second pole piece 40, and the separator 50 are expanded, the surface of the first sub-pole piece 40a facing away from the first pole piece 30 is a first surface, and the surface of the second sub-pole piece 40b facing away from the first pole piece 30 is a second surface. The first surface and the second surface are provided with a first protective layer 43, respectively.

Referring to fig. 13, fig. 13 is a schematic view illustrating a state in which the first pole piece 30, the second pole piece 40, and the separator 50 are unfolded according to other embodiments of the present application.

The first surface is the surface of the first sub-pole piece 40a facing away from the first pole piece 30. The surface of the second current collector 41 of the first sub-tab 40a facing the first tab 30 is provided with a second active material layer 42 to correspond to the first active material layer 32 of the first tab 30. The surface of the second current collector 41 of the first sub-pole piece 40a facing away from the first pole piece 30 is not provided with the second active material layer 42. The first protective layer 43 is disposed on the first surface, which is understood to mean that the surface of the second current collector 41 of the first sub-pole piece 40a facing away from the first pole piece 30 is provided with the first protective layer 43.

The second surface is the surface of the second sub-pole piece 40b facing away from the first pole piece 30. The surface of the second current collector 41 of the second sub-tab 40b facing the first tab 30 is provided with a second active material layer 42 to correspond to the first active material layer 32 of the first tab 30. The surface of the second current collector 41 of the second sub-pole piece 40b facing away from the first pole piece 30 is not provided with the second active material layer 42. The first protective layer 43 is disposed on the second surface, it being understood that the surface of the second current collector 41 of the second sub-pole piece 40b facing away from the first pole piece 30 is provided with the first protective layer 43.

The first protective layer 43 may be an insulating protective layer or a polymer layer. In some embodiments, the first protective layer 43 may be a paint having insulating characteristics applied to the first and second surfaces.

In the above solution, the first surface is the surface of the first sub-sheet 40a exposed to the outside, which may be free of an active material layer, i.e. in some embodiments, the first surface may be regarded as an empty foil area of the current collector. Similarly, the second surface is the surface of the second sub-sheet 40b that is exposed to the outside, which may not be provided with an active material layer, i.e., in some embodiments, the second surface may be regarded as an empty foil region of the current collector. Therefore, by providing the first protective layer 43 on the first surface and the second surface respectively, the risk of corrosion of the current collectors of the first sub-pole piece 40a and the second sub-pole piece 40b caused by exposure to the outside can be effectively reduced, so that the battery has higher reliability.

Referring to fig. 14, fig. 14 is a schematic view illustrating the state in which the first pole piece 30, the second pole piece 40, and the separator 50 are unfolded according to other embodiments of the present application. According to some embodiments of the present application, in the state in which the first pole piece 30, the second pole piece 40, and the separator 50 are expanded, the surface of the first sub-pole piece 40a facing away from the first pole piece 30 is a first surface, and the surface of the second sub-pole piece 40b facing away from the first pole piece 30 is a second surface; the first and second surfaces are provided with a first connection layer 44, respectively. The first connection layers 44 between two adjacent straight portions 11b are connected to each other in the stacking direction.

The point at which the first connection layers 44 between the adjacent two straight portions 11b are connected to each other is indicated by an arrow labeled "C" in fig. 12.

In some embodiments, the first connection layer 44 may be a hot melt adhesive layer, and the first connection layer 44 between the two flat portions 11b can be thermally melted to be integrated with each other through a thermal pressing process when the first and second pole pieces 30 and 40 and the separator 50 are pressed.

In the above-mentioned scheme, by providing the first connection layer 44 on the first surface and the second surface, respectively, the flat portions 11b can be effectively adhered to each other, so that the structure of the electrode assembly 11 is compact, and the volumetric energy density of the electrode assembly 11 is effectively improved.

Referring to fig. 5 and 6, the number of first pole pieces 30 is the same as the number of second pole pieces 40, according to some embodiments of the present application. The first pole piece 30 includes a third sub-pole piece 30a and the second pole piece 40 includes a fourth sub-pole piece 40c. In the state where the first pole piece 30, the second pole piece 40, and the separator 50 are expanded, all the separators 50 are located between the third sub-pole piece 30a and the fourth sub-pole piece 40c in the lamination direction.

In some embodiments, the number of first pole pieces 30 is the same as the number of second pole pieces 40, e.g., in fig. 5, the number of first pole pieces 30 and second pole pieces 40 are one; or the number of the first pole piece 30 and the second pole piece 40 are integers greater than one, for example, the number of the first pole piece 30 and the second pole piece 40 are two, three, four, or the like.

In the state where the first pole piece 30, the second pole piece 40, and the separator 50 are expanded, the third sub-pole piece 30a is one of the first pole pieces 30 at the outermost side, and the fourth sub-pole piece 40c is one of the second pole pieces 40 at the outermost side.

In the above scheme, the number of the first pole pieces 30 is the same as the number of the second pole pieces 40, so that the specifications of the first pole pieces 30 and the second pole pieces 40 correspond, for example, the setting positions of the active material layers correspond, thereby improving the coating efficiency of the pole pieces and the manufacturing efficiency of the battery.

Referring to fig. 15, fig. 15 is a schematic view illustrating a state in which the first pole piece 30, the second pole piece 40, and the separator 50 are unfolded according to other embodiments of the present application. In the state in which the first pole piece 30, the second pole piece 40, and the diaphragm 50 are expanded, the surface of the third sub-pole piece 30a facing away from the diaphragm 50 is a third surface, and the third surface is provided with the second protective layer 34.

The surface of the third sub-sheet 30a facing away from the separator 50 is a third surface, which may be understood as a surface of the first current collector 31 of the third sub-sheet 30a where the first active material layer 32 is not provided.

The second protective layer 34 may be an insulating coating or a polymer layer. In some embodiments, the second protective layer 34 may be a paint having insulating features applied to the third surface.

In the above-described embodiment, the third surface is the surface of the third sub-sheet 30a exposed to the outside, which may be provided without an active material layer, i.e., in some embodiments, the third surface may be regarded as an empty foil region of the current collector. Therefore, by providing the second protective layer 34 on the third surface, the risk of corrosion of the current collector of the third sub-pole piece 30a caused by exposure to the outside can be effectively reduced, so that the battery has higher reliability.

According to some embodiments of the present application, referring to fig. 15, in the state in which the first pole piece 30, the second pole piece 40, and the diaphragm 50 are unfolded, the surface of the fourth sub-pole piece 40c facing away from the diaphragm 50 is a fourth surface, and the fourth surface is provided with a third protection layer 45.

The surface of the fourth sub-pole piece 40c facing away from the separator 50 is a fourth surface, which may be understood as a surface of the second current collector 41 of the fourth sub-pole piece 40c not provided with the second active material layer 42.

The third protective layer 45 may be an insulating coating or a polymer layer. In some embodiments, the third protective layer 45 may be a paint having insulating features applied to the third surface.

In the above solution, the fourth surface is the surface of the fourth sub-pole piece 40c exposed to the outside, which may be provided without an active material layer, i.e. in some embodiments, the fourth surface may be regarded as an empty foil area of the current collector. Therefore, by providing the third protection layer 45 on the fourth surface, the risk of corrosion of the fourth sub-pole piece 40c caused by exposure to the outside can be effectively reduced, so that the battery has higher reliability.

Referring to fig. 16, fig. 16 is a schematic illustration of the expanded state of first pole piece 30, second pole piece 40, and separator 50 according to other embodiments of the present application. In the state in which the first pole piece 30, the second pole piece 40, and the diaphragm 50 are unfolded, the surface of the third sub-pole piece 30a facing away from the diaphragm 50 is a third surface, and the third surface is provided with the second connection layer 35. The second connection layers 35 between two adjacent flat portions 11b and facing each other in the lamination direction are connected to each other.

In some embodiments, the second connection layer 35 may be a hot melt adhesive layer, and the second connection layer 35 between the two flat portions 11b can be thermally melted to be integrated with each other through a thermal pressing process while the first and second pole pieces 30 and 40 and the separator 50 are pressed. "second connection layers 35 facing each other are connected to each other", and in the bending region, two adjacent second connection layers 35 are connected to each other.

For ease of understanding, the point where the second connection layer 35 between the adjacent two straight portions 11b is connected to each other is indicated by an arrow mark "F" in fig. 6.

In the above-mentioned scheme, by providing the second connection layer 35 on the third surface, the flat portions 11b can be effectively adhered to each other by the second connection layer 35, so that the structure of the electrode assembly 11 is compact, and the volumetric energy density of the electrode assembly 11 is effectively improved.

According to some embodiments of the present application, referring to fig. 16, in the state in which the first pole piece 30, the second pole piece 40, and the separator 50 are unfolded, the surface of the fourth sub-pole piece 40c facing away from the separator 50 is a fourth surface, and the fourth surface is provided with the third connection layer 46. The third connection layers 46 between two adjacent straight portions 11b are connected to each other in the lamination direction.

In some embodiments, the third connection layer 46 may be a hot melt adhesive layer, and the third connection layer 46 between the two flat portions 11b can be thermally melted to be integrated with each other through a thermal pressing process when the first and second pole pieces 30 and 40 and the separator 50 are pressed.

For ease of understanding, the point at which the third connection layer 46 between the adjacent two straight portions 11b is connected to each other is indicated by an arrow mark "E" in fig. 6.

In the above-mentioned scheme, by providing the third connection layer 46 on the fourth surface, the flat portions 11b can be effectively adhered to each other by the third connection layer 46, so that the structure of the electrode assembly 11 is compact, and the volumetric energy density of the electrode assembly 11 is effectively improved.

According to some embodiments of the present application, there is provided a method of manufacturing an electrode assembly 11. Referring to fig. 17, fig. 17 is a flow chart of a method of manufacturing an electrode assembly 11 according to some embodiments of the present application.

The manufacturing method 2000 of the electrode assembly 11 includes the steps of:

s1, a first pole piece 30, a diaphragm 50 and a second pole piece 40 are arranged in a laminated mode and are combined into a whole to form a composite structure, the first pole piece 30 is an anode pole piece, the second pole piece 40 is a cathode pole piece, and a first active material layer 32 of the first pole piece 30 is provided with a groove 33;

S2, bending the composite structure at least one position, forming at least one bending part 11a of the first pole piece 30 wrapping the second pole piece 40, and positioning the groove 33 at the bending part 11a.

In step S1, the first electrode sheet 30, the diaphragm 50, and the second electrode sheet 40 are stacked and reset as a unit, so that the first electrode sheet 30 and the second electrode sheet 40 can be tightly attached to the diaphragm 50. And a groove 33 is provided in the first active material layer 32 of the first electrode sheet 30 so that the groove 33 corresponds to the position of the bent portion 11a after the step S2.

In step S2, the composite structure formed in step S1 is bent at least one position by winding or folding to form at least one bending portion 11a.

In the above scheme, on the one hand, through setting up and compounding in an organic whole first pole piece 30, diaphragm 50 and second pole piece 40 range upon range of, can make the transmission distance of lithium ion in kink 11a department reduce, based on the dynamic performance, can improve the migration ability of lithium ion, reduced the risk that the lithium phenomenon takes place of separating out, improved the reliability of battery monomer. On the other hand, the grooves 33 are formed in the first active material layer 32 to reduce the amount of the first active material layer 32, so that the second active material layer 42 has a certain lithium intercalation space for accommodating lithium ions, and therefore, the risk of lithium precipitation caused by insufficient lithium intercalation space is effectively reduced, and the reliability of the battery is improved.

According to some embodiments of the present application, step S1, the first pole piece 30, the diaphragm 50 and the second pole piece 40 are stacked and combined into one body, including: the first pole piece 30, the diaphragm 50 and the second pole piece 40 are laminated and thermally pressed and combined into a whole.

In some embodiments, in step 1, the first electrode sheet 30, the separator 50, and the second electrode sheet 40, which are stacked, are combined into one body through a hot pressing process.

In some embodiments, all of the parts of the first pole piece 30, the diaphragm 50, and the second pole piece 40 that are stacked are combined into one body through a hot pressing process.

In the above scheme, through the hot pressing process, the first active material layer 32, the second active material layer 42 and the diaphragm 50 can be efficiently combined into a whole, so that the first pole piece 30, the second pole piece 40 and the diaphragm 50 are tightly attached to each other, the transmission distance of lithium ions at the bent part 11a is effectively reduced, the migration capability of lithium ions is improved, the risk of occurrence of lithium precipitation is reduced, and the reliability of the battery monomer is improved.

According to some embodiments of the present application, step S2, bending the composite structure at least one position and forming at least one bending portion 11a of the first pole piece 30 wrapping the second pole piece 40, includes:

The composite structure is repeatedly bent to form the electrode assembly 11, the electrode assembly 11 includes a plurality of straight portions 11b and a plurality of bent portions 11a, the plurality of straight portions 11b are stacked in a stacking direction of the first electrode sheet 30, the separator 50 and the second electrode sheet 40, and adjacent two straight portions 11b are connected through the bent portions 11 a.

In step S2, the composite structure may be continuously folded in a zigzag shape to form the electrode assembly 11.

In the above-mentioned scheme, through repeatedly bending the composite structure so as to form the electrode assembly 11, the electrode assembly 11 can be made compact in structure, and the volumetric energy density of the battery can be improved.

According to some embodiments of the present application, there is also provided a battery cell including a case, and the electrode assembly 11 provided above, the electrode assembly 11 being disposed inside the case.

There is also provided, in accordance with some embodiments of the present application, a battery including the battery cells provided above.

According to some embodiments of the present application, there is also provided an electrical device including the battery cell provided above.

According to some embodiments of the present application, an electrode assembly 11 is provided, see fig. 5 and 6, the battery assembly comprising a first pole piece 30, a second pole piece 40, and a separator 50. The second pole piece 40 is disposed opposite the first pole piece 30. A separator 50 is disposed between the first and second pole pieces 30, 40 for separating the first and second pole pieces 30, 40. The first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece. The number of first pole pieces 30 is the same as the number of second pole pieces 40 and is one. The first pole piece 30, the diaphragm 50 and the second pole piece 40 are laminated and thermally pressed and combined into a whole. The first electrode sheet 30, the separator 50 and the second electrode sheet 40, which are heat-pressed and combined in one body, are continuously folded in a zigzag shape to form the electrode assembly 11. The electrode assembly 11 is formed by continuously folding in a zigzag shape to have straight portions 11b and bent portions 11a, the bent portions 11a being located between adjacent two of the straight portions 11b and connecting the adjacent two of the straight portions 11b.

In some embodiments, at the bent portion 11a, the first active material layer 32 of the first electrode sheet 30 is provided with a groove 33, the groove 33 may have a circular shape, an inner diameter of the groove 33 may be 10um, and a depth of the groove 33 may be consistent with a thickness of the first active material layer 32. The grooves 33 may be distributed in a region extending to both sides by 2mm or less with respect to the center line of the bent portion 11 a.

In some embodiments, the surface of the separator 50 facing the second pole piece 40 (i.e., the surface facing the negative pole piece) is provided with a lithium-absorbing layer 51, and the surface of the lithium-absorbing layer 51 facing away from the separator 50 is provided with an insulating layer 52. The insulating layer 52 may be a ceramic layer, and the thickness of the ceramic layer may be 1um. The thickness of the lithium absorbing layer 51 may be 1um.

According to some embodiments of the present application, an electrode assembly 11 is provided, see fig. 9 and 10, the battery assembly including a first electrode sheet 30, a second electrode sheet 40, and a separator 50. The second pole piece 40 is disposed opposite the first pole piece 30. A separator 50 is disposed between the first and second pole pieces 30, 40 for separating the first and second pole pieces 30, 40. The first pole piece 30 is a positive pole piece and the second pole piece 40 is a negative pole piece. The number of second pole pieces 40 is two, including a first sub-pole piece 40a and a second sub-pole piece 40b. The number of first pole pieces 30 is one. The first sub-pole piece 40a, the diaphragm 50, the first pole piece 30, the diaphragm 50 and the second sub-pole piece 40b are laminated and thermally pressed and combined into a whole. The first sub-electrode sheet 40a, the separator 50, the first electrode sheet 30, the separator 50, and the second sub-electrode sheet 40b, which are integrally heat-pressed, are continuously folded in a zigzag shape to form the electrode assembly 11. The electrode assembly 11 is formed by continuously folding in a zigzag shape to have straight portions 11b and bent portions 11a, the bent portions 11a being located between adjacent two of the straight portions 11b and connecting the adjacent two of the straight portions 11b.

In some embodiments, referring to fig. 14, the surface of the first and second sub-pole pieces 40a and 40b where the active material layer is not provided is provided with a first connection layer 44, and the first connection layer 44 may be a hot melt adhesive layer. The hot melt adhesive layer of the folded electrode assembly 11 makes the bonding between the electrode layers more tight after hot pressing.

In some embodiments, referring to fig. 7, the first active material layer 32 of the first electrode sheet 30 is provided with grooves 33, the grooves 33 may be circular, the inner diameter of the grooves 33 may be 10um, and the depth of the grooves 33 may be consistent with the thickness of the first active material layer 32. The grooves 33 may be distributed in a region extending to both sides by 2mm or less with respect to the center line of the bent portion 11 a. In other embodiments, the depth of the grooves 33 may be 50% of the thickness of the first active material layer 32.

In some embodiments, referring to fig. 14, the surfaces of the first and second sub-pole pieces 40a and 40b, which are not provided with the active material layer, are provided with a first protective layer 43, and the first protective layer 43 may be an insulating protective layer.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An electrode assembly, comprising:

the first pole piece is a positive pole piece;

the second pole piece is a negative pole piece and is arranged opposite to the first pole piece;

the diaphragm is arranged between the first pole piece and the second pole piece and used for separating the first pole piece from the second pole piece, a lithium absorption layer is arranged on the surface of the diaphragm facing the second pole piece, and an insulating layer is arranged on the surface of the lithium absorption layer, which is far away from the diaphragm;

the electrode assembly is bent at least one position, and at least one bending part of the first pole piece wrapping the second pole piece is formed; at least part of the first pole piece and the second pole piece at the bending part are tightly attached to the diaphragm; the first pole piece comprises a first current collector and a first active material layer, the first active material layer is arranged on the surface of the first current collector, and grooves are formed in at least part of the first active material layer at the bending part;

when the electrode assembly is bent to form a corner part, the insulating layer at the corner part is stressed to be broken so as to expose the lithium absorbing layer, and the exposed lithium absorbing layer is used for absorbing lithium ions which cannot be absorbed by the negative electrode plate.

2. The electrode assembly of claim 1, wherein the electrode assembly comprises,

the first pole piece comprises a first current collector and a first active material layer, the first active material layer is arranged on the surface of the first current collector, the second pole piece comprises a second current collector and a second active material layer, and the second active material layer is arranged on the surface of the second current collector;

at least a portion of the first active material layer and the second active material layer at the bend are both connected to the separator.

3. The electrode assembly of claim 2, wherein the electrode assembly comprises,

and at least part of the first active material layer and the second active material layer at the bending part are compounded with the diaphragm through hot pressing.

4. The electrode assembly of claim 3, wherein the electrode assembly comprises,

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the first pole piece, the second pole piece and the diaphragm are arranged in a laminated mode and are combined into a whole through hot pressing.

5. The electrode assembly of claim 1, wherein the electrode assembly comprises,

the depth of the groove is D, the thickness of the first active material layer is D, and D/D is more than or equal to 30%.

6. The electrode assembly of claim 5, wherein the electrode assembly comprises,

satisfying the requirement, the D/D is more than or equal to 80 percent.

7. The electrode assembly of claim 1, wherein the electrode assembly comprises,

the groove is positioned in a preset area;

the preset area is an area which extends to two sides by 6mm or less respectively by taking the central line of the bending part as a reference along the extending direction of the first pole piece in the state that the first pole piece is unfolded.

8. The electrode assembly according to any one of claim 1 to 7, wherein,

the electrode assembly comprises a plurality of straight parts, wherein the plurality of straight parts are arranged in a stacked mode, and two adjacent straight parts are connected through the bending parts.

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

the number of the first pole pieces is n, the number of the second pole pieces is n+1, and all the second pole pieces comprise a first sub-pole piece and a second sub-pole piece, wherein n is more than or equal to 1;

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, all the first pole pieces are positioned between the first sub pole pieces and the second sub pole pieces along the stacking direction.

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

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the first sub-pole piece, which is away from the first pole piece, is a first surface, and the surface of the second sub-pole piece, which is away from the first pole piece, is a second surface; the first surface and the second surface are respectively provided with a first protection layer.

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

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the first sub-pole piece, which is away from the first pole piece, is a first surface, and the surface of the second sub-pole piece, which is away from the first pole piece, is a second surface; the first surface and the second surface are respectively provided with a first connecting layer;

the first connection layers between two adjacent flat portions are connected to each other in the stacking direction.

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

the number of the first pole pieces is the same as the number of the second pole pieces; all the first pole pieces comprise a third sub-pole piece, and all the second pole pieces comprise a fourth sub-pole piece;

In the state that the first pole piece, the second pole piece and the diaphragm are unfolded, all the diaphragms are positioned between the third sub-pole piece and the fourth sub-pole piece along the stacking direction.

13. The electrode assembly of claim 12 wherein the electrode assembly,

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the third sub pole piece, which is away from the diaphragm, is a third surface, and a second protection layer is arranged on the third surface.

14. The electrode assembly of claim 12 wherein the electrode assembly,

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the fourth sub-pole piece, which is away from the diaphragm, is a fourth surface, and a third protection layer is arranged on the fourth surface.

15. The electrode assembly of claim 12 wherein the electrode assembly,

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the third sub-pole piece, which is away from the diaphragm, is a third surface, and a second connecting layer is arranged on the third surface;

the second connection layers between two adjacent flat portions and facing each other are connected to each other in the stacking direction.

16. The electrode assembly of claim 12 wherein the electrode assembly,

in the state that the first pole piece, the second pole piece and the diaphragm are unfolded, the surface of the fourth sub-pole piece, which is away from the diaphragm, is a fourth surface, and a third connecting layer is arranged on the fourth surface;

the third connection layers between two adjacent flat portions are connected to each other in the lamination direction.

17. A method of manufacturing an electrode assembly, comprising the steps of:

the lithium ion battery comprises a first pole piece, a diaphragm and a second pole piece, wherein the first pole piece, the diaphragm and the second pole piece are arranged in a stacked mode and are combined into a whole to form a composite structure, the first pole piece is a positive pole piece, the second pole piece is a negative pole piece, a first active material layer of the first pole piece is provided with a groove, the surface of the diaphragm facing the second pole piece is provided with a lithium absorption layer, and the surface of the lithium absorption layer, which is far away from the diaphragm, is provided with an insulating layer;

and bending the composite structure at least one position, forming at least one bending part for wrapping the second pole piece by the first pole piece, wherein the groove is positioned at the bending part, and when the electrode assembly is bent to form a corner part, the insulating layer positioned at the corner part is stressed and broken to expose the lithium absorbing layer, and the exposed lithium absorbing layer is used for absorbing lithium ions which cannot be absorbed by the negative pole piece.

18. The method of manufacturing an electrode assembly according to claim 17, wherein,

the first pole piece, the diaphragm and the second pole piece are arranged in a lamination mode and are combined into a whole, and the device comprises:

19. The method for manufacturing an electrode assembly according to claim 17 or 18, wherein,

the bending of the composite structure at least one position and the formation of at least one bending part of the first pole piece coating the second pole piece comprise:

20. A battery cell, comprising:

a housing, and the electrode assembly of any one of claims 1-16 disposed inside the housing.

21. A battery comprising the cell of claim 20.

22. A powered device comprising the battery cell of claim 20.