CN116565341B

CN116565341B - Electrode assembly, battery cell and electric equipment

Info

Publication number: CN116565341B
Application number: CN202310835191.2A
Authority: CN
Inventors: 张国文
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2023-07-10
Filing date: 2023-07-10
Publication date: 2023-10-03
Anticipated expiration: 2043-07-10
Also published as: CN116565341A

Abstract

The embodiment of the application provides an electrode assembly, an electric core and electric equipment, wherein the electrode assembly is of a winding type structure and comprises: the negative electrode plate comprises a negative electrode initial section, a negative electrode middle section and a negative electrode tail-collecting section which are sequentially connected in the winding direction, wherein the negative electrode initial section is provided with a negative electrode active material on one side only, and the negative electrode middle section is provided with a negative electrode active material on both sides; the cathode initial section comprises a first sub-section, a second sub-section and a first bending section, wherein the first sub-section and the second sub-Duan Cengdie are arranged, the first bending section is connected with the first sub-section and the second sub-section, and a cathode active material is not arranged on one surface of the first sub-section and the second sub-section, which are opposite to each other; the most inner ring of the positive plate comprises a second bending section, and the first bending section is positioned at the inner side of the second bending section and is opposite to the second bending section.

Description

Electrode assembly, battery cell and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to an electrode assembly, an electric core and electric equipment.

Background

The battery is widely applied to the fields of portable electronic equipment, electric vehicles, electric tools, unmanned aerial vehicles, energy storage equipment and the like. The reliability of the battery is a non-negligible problem in the manufacturing process of the battery. Therefore, how to improve the reliability of the battery is a technical problem to be solved in the battery technology.

Disclosure of Invention

The application provides an electrode assembly, an electric core and electric equipment.

The application is realized by the following technical scheme:

in a first aspect, an embodiment of the present application provides an electrode assembly, which is a rolled structure, including: the negative electrode plate comprises a negative electrode initial section, a negative electrode middle section and a negative electrode tail-collecting section which are sequentially connected in the winding direction, wherein the negative electrode initial section is provided with a negative electrode active material on one surface only, and the negative electrode middle section is provided with a negative electrode active material on both surfaces; the cathode starting section comprises a first subsection, a second subsection and a first bending section, the first subsection and the second subsection Duan Cengdie are arranged, the first bending section is connected with the first subsection and the second subsection, and the cathode active material is not arranged on one surface of the first subsection and the second subsection, which are opposite to each other; the innermost ring of the positive plate comprises a second bending section, and the first bending section is positioned at the inner side of the second bending section and is opposite to the second bending section.

According to the electrode assembly provided by the embodiment of the application, the anode active material is not arranged on one surface of the anode initial section, the anode initial section is bent to form the first sub-section and the second sub-section which are overlapped with each other, and the anode active material is not arranged on the side surfaces of the first sub-section and the second sub-section which face each other, so that the size of the electrode assembly in the thickness direction is reduced, meanwhile, the first bending section of the anode initial section is opposite to the second bending section of the innermost ring of the cathode plate, the probability of metal precipitation (such as lithium precipitation) at the corner of the innermost ring of the cathode plate can be reduced, the inner side surface of the second bending section does not need to be attached with protective adhesive, the problem that the second bending section breaks is solved, and the probability of metal precipitation of the non-adhesive surface of the second bending section is reduced.

According to some embodiments of the application, the membrane comprises: the third bending section is arranged between the inner side surface of the second bending section and the outer side surface of the first bending section, and the inner side surface of the second bending section and the outer side surface of the first bending section are respectively attached to the third bending section. Therefore, positive ions (such as lithium ions) separated from the second bending section can be very easily inserted into the first bending section, so that the moving distance of the positive ions in the electrolyte is greatly reduced, the problem that metal is separated out from the first bending section is solved, the original protective adhesive arranged on the inner side surface of the second bending section can be eliminated, and the problem that the inner side surface of the second bending section is easy to break is effectively improved.

According to some embodiments of the application, an end of the first subsection away from the first bending section is a starting end of the negative plate, and the starting end of the negative plate is flush with the starting end of the separator. Therefore, the condition that a plurality of layers of diaphragms are overlapped on the innermost ring of the electrode assembly is avoided, the thickness of the electrode assembly is increased due to the fact that the innermost ring is provided with the plurality of layers of overlapped diaphragms, and then the energy density loss of the electrode assembly in the thickness direction is reduced.

According to some embodiments of the application, the ending end of the negative electrode tab is flush with the ending end of the separator. Therefore, the diaphragm tail-collecting section can completely cover the outer side face of the negative plate tail-collecting section, and the using amount of the diaphragm is reduced, so that the production cost of the battery cell is reduced.

According to some embodiments of the application, the overlapping length of the first and second sub-segments in the length direction of the negative electrode sheet is 0.5mm-10mm. Therefore, by utilizing the structure that the anode initial sections are mutually overlapped after being bent, the thickness difference between the sum of the thicknesses of the first sub-section and the second sub-section after being overlapped and the thickness difference of the anode middle section coated on two sides can be effectively reduced, the flatness of the inner ring of the electrode assembly is ensured, and poor adhesion of the inner ring of the electrode assembly after hot pressing is prevented.

According to some embodiments of the application, the overlapping length of the first and second sub-segments in the length direction of the negative electrode sheet is 2mm-5mm. Therefore, by utilizing the structure that the anode initial sections are mutually overlapped after being bent, the thickness difference between the sum of the thicknesses of the first sub-section and the second sub-section after being overlapped and the thickness difference of the anode middle section coated on two sides can be effectively reduced, the flatness of the inner ring of the electrode assembly is ensured, and poor adhesion of the inner ring of the electrode assembly after hot pressing is prevented.

According to some embodiments of the application, one end of the first sub-section and one end of the second sub-section are connected to the first bending section, respectively, and the other end of the second sub-section is connected to one end of the negative electrode middle section, and the other end of the first sub-section is spaced apart from a projection of the one end of the negative electrode middle section in a thickness direction of the electrode assembly to form a separation gap. Since the other end of the first sub-section is not overlapped with the negative electrode intermediate section in the thickness direction, the probability of an increase in thickness of the electrode assembly and occurrence of problems affecting the flatness of the inner ring and poor adhesion of the inner ring is further reduced.

According to some embodiments of the application, the size of the separation gap in the winding direction is 0-5mm. It is thus ensured that the other end of the first sub-section is spaced apart from the projection of the one end of the negative electrode intermediate section in the thickness direction of the electrode assembly to form a separation gap, while also reducing the energy density loss of the electrode assembly in the winding direction due to the excessive separation gap.

According to some embodiments of the application, the size of the separation gap in the winding direction is 0-2mm. It is thus ensured that the other end of the first sub-section is spaced apart from the projection of the one end of the negative electrode intermediate section in the thickness direction of the electrode assembly to form a separation gap, while also reducing the energy density loss of the electrode assembly in the winding direction due to the excessive separation gap.

According to some embodiments of the application, an insulating layer is provided on an inner side surface of the innermost ring of the positive electrode sheet in a region facing the separation gap. By arranging the insulating layer in the area where the inner side surface of the innermost ring of the positive plate is opposite to the separation gap, positive ions (such as lithium ions) separated from the area where the inner side surface of the innermost ring of the positive plate is opposite to the separation gap can be blocked by the insulating layer when the battery cell is charged, and the probability of precipitation of the positive ions on the area where the inner side surface of the innermost ring of the positive plate is opposite to the separation gap on the second subsection is reduced.

According to some embodiments of the application, one end of the first sub-section and one end of the second sub-section are respectively connected to the first bending section, the other end of the second sub-section is connected to one end of the negative electrode middle section, a part of the first sub-section overlaps the second sub-section, and another part of the first sub-section overlaps the negative electrode middle section. The second subsection is not provided with the exposed negative current collector, so that an insulating layer is not required to be arranged on the inner side surface of the innermost ring of the positive plate, and the forming process of the battery cell and the production cost of the battery cell are reduced at least to a certain extent.

According to some embodiments of the present application, the innermost ring of the positive electrode sheet further includes a first straight section and a second straight section, the second bending section connects the first straight section and the second straight section, and an end of the first straight section away from the second bending section is a starting end of the positive electrode sheet;

the first sub-segment is located between the second sub-segment and the first straight segment or the first sub-segment is located between the second sub-segment and the second straight segment in a thickness direction of the electrode assembly. Therefore, the direction from the first bending section toward the other end of the first sub-section is the same as or opposite to the winding direction of the positive electrode sheet.

According to some embodiments of the application, the membrane comprises: and a first separator located on the side of the anode starting section having the anode active material. The separator is arranged on the surface of the cathode initial section with the cathode active material, so that the thickness of the first sub-section and the second sub-section after being overlapped can be reduced, and the energy density loss of the battery cell in the thickness direction is reduced.

According to some embodiments of the application, the diaphragm further comprises: and a second separator located on a side of the anode starting section having no anode active material. Therefore, the cathode initial section can be protected more effectively, and meanwhile, the effect that the separator is arranged on only one side of the cathode initial section is achieved without special process steps, so that the forming process of the electrode assembly is greatly reduced.

According to some embodiments of the application, the negative electrode pigtail section is provided with a negative electrode active material on only one side, the side of the negative electrode pigtail section not provided with a negative electrode active material facing the outside of the electrode assembly. Therefore, the outer side of the negative electrode tail-collecting section does not participate in the reaction of deintercalation ions, and therefore, the negative electrode tail-collecting section only sets negative electrode active substances on one surface facing the interior of the electrode assembly, and the negative electrode tail-collecting section does not set negative electrode active substances on the side surface facing the outer side of the electrode assembly, so that the production cost of the electrode assembly is reduced.

According to some embodiments of the application, the positive electrode sheet includes a positive electrode start section, a positive electrode intermediate section, and a positive electrode end-receiving section that are sequentially connected in a winding direction, the positive electrode start section being provided with a positive electrode active material on both sides, the positive electrode intermediate section being provided with a positive electrode active material on both sides, the positive electrode end-receiving section being provided with a positive electrode active material on both sides. Therefore, the battery core is ensured to have enough capacity and excellent battery performance, and the energy density loss caused by the fact that the positive electrode plate is not coated with the positive electrode active material is reduced.

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

In a third aspect, the present application provides an electrical device, including the above-mentioned electrical core.

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 as limiting the scope, and 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 view of an electrode assembly according to a first embodiment of the present application;

fig. 2 is a schematic view of an electrode assembly provided near an inner end portion according to a first embodiment of the present application;

fig. 3 is a schematic view of a negative electrode starting section of an electrode assembly according to a first embodiment of the present application;

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

fig. 5 is a schematic view of an electrode assembly provided near an inner end portion according to a second embodiment of the present application;

Fig. 6 is a schematic view of a negative electrode starting section of an electrode assembly according to a second embodiment of the present application;

fig. 7 is a schematic view of an electrode assembly according to a third embodiment of the present application;

fig. 8 is a schematic view of an electrode assembly provided near an inner end portion according to a third embodiment of the present application;

fig. 9 is a schematic view of a negative electrode initial section of an electrode assembly according to a third embodiment of the present application.

Icon:

the electrode assembly 100 is provided with a plurality of electrodes,

positive electrode sheet 110, second bent section 111, first straight section 112, second straight section 113, positive electrode starting section 114, positive electrode intermediate section 115, positive electrode terminating section 116,

the negative electrode tab 120, the negative electrode starting section 121, the first sub-section 121a, the second sub-section 121b, the first bent section 121c, the negative electrode intermediate section 122, the negative electrode ending section 123, the negative electrode current collector 102, the negative electrode active material 103,

the third bending section 131, the first diaphragm 132, the second diaphragm 133,

an insulating layer 140 separating the gaps 101, and a thickness direction X of the electrode assembly.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying 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 of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the 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 of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.

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. Those of skill in the art will explicitly and implicitly appreciate that the described embodiments of the application may be combined with 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 above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

The term "and/or" in the present application is merely an association relation describing the association object, and indicates that three kinds of relations may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In the present application, the character "/" generally indicates that the front and rear related objects are an or relationship.

The term "plurality" as used herein means two or more (including two), and similarly, "plural sets" means two or more (including two), and "plural sheets" means two or more (including two).

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the embodiments of the present application, it should be noted that, the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship conventionally put in place when the product of this application is used, or the orientation or positional relationship conventionally understood by those skilled in the art, is merely for convenience of describing the present application and simplifying the description, and is not indicative or implying that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

The existing MMT (Mid-Tab) structure is generally wound by adopting a winding needle to clamp a diaphragm, so that four layers of diaphragms exist in the innermost ring, the thickness of a battery cell is increased, and the problem of energy density loss of the battery cell in the thickness direction occurs.

In order to solve the above-described problems, the related art may solve the following problems: the positive plate and the negative plate adopt a butt-inserted structure. The structure of the opposite insertion is as follows: the positive electrode sheet and the negative electrode sheet are wound in opposite directions, that is, the direction of the initial end of the positive electrode sheet is opposite to the direction of the initial end of the negative electrode sheet, for example, in the first direction, the initial end of the positive electrode sheet faces one side in the first direction, and the initial end of the negative electrode sheet faces the other side in the first direction. Or the initial end of the positive electrode sheet faces the first corner of the innermost ring of the negative electrode sheet in the winding direction, and the initial end of the negative electrode sheet faces the first corner of the innermost ring of the positive electrode sheet in the winding direction.

Meanwhile, lithium-precipitating protective glue is attached to the inner side of the corner of the innermost ring of the positive plate, which is opposite to the starting end of the negative plate, but in this way, the problems that the corner of the innermost ring of the positive plate is easy to break, the low capacity of a finished battery cell is affected, and lithium is precipitated on the non-rubberizing surface of the positive plate are caused.

Therefore, the embodiment of the application provides an electrode assembly, which not only can solve the problem of the increase of the thickness of a battery cell caused by the multi-layer diaphragm at the innermost ring of the electrode assembly, but also can reduce the probability of attaching protective adhesive at the corner of the innermost ring of the positive plate, thereby causing the problem of breakage at the corner of the innermost ring of the positive plate.

In the prior art, the protection glue is attached to the corner of the innermost ring of the positive plate, because the corner of the innermost ring of the positive plate is opposite to the starting end of the negative electrode, positive ions (such as lithium ions) at the corner of the innermost ring of the positive plate are separated from the positive plate in the charging process and then enter the electrolyte, and the positive ions separated from the corner of the innermost ring of the positive plate are fully embedded due to the insufficient area of the starting end of the negative electrode, so that the positive ions are precipitated on the surface of the starting end of the negative electrode and form crystal branches on the surface of the starting end of the negative electrode. In the scheme of the prior art, the protection glue is attached to the corner of the innermost ring of the positive plate, and the protection glue is tightly adhered to the inner side surface of the corner of the innermost ring of the positive plate, so that the protection glue prevents the inner side surface of the innermost corner of the positive plate from being separated from positive ions outwards, and therefore excessive positive ions are not embedded into the starting end of the negative electrode, and at the moment, the corner of the innermost ring of the positive plate and the end part of the starting section of the negative electrode do not participate in charge-discharge reaction.

However, the protection glue is attached to the corner of the innermost ring of the positive plate, although the corner of the innermost ring of the positive plate can be blocked from being separated from positive ions, in the process of winding the positive plate, the protection glue is arranged at the corner of the innermost ring of the positive plate, so that the whole thickness of the corner is increased, the same bending degree is achieved at the corner of the innermost ring of the positive plate, the protection glue at the corner of the innermost ring of the positive plate is necessarily extruded, the protection glue is deformed after being extruded, the generated elastic force is further applied to the corner of the innermost ring of the positive plate, so that the bending difficulty of the corner of the innermost ring of the positive plate is increased, the positive ions separated from the corner of the innermost ring of the positive plate are very easy to break when the same bending degree is achieved at the corner of the innermost ring of the positive plate, and are blocked by the protection glue, and can not penetrate through the end part of the starting section of the negative electrode, and are directly separated out of the non-adhesive surface of the positive plate, so that the battery performance is reduced, the cycle life is prolonged, the battery is easy to cause a disaster, and the battery is easy to burn and explode.

The electrode assembly of the embodiment of the application can be applied to a battery cell, the electrode assembly is of a winding type structure, the battery cell can be a soft-package battery cell or a hard-shell battery cell, and the soft-package battery cell generally has higher energy density and better heat dissipation performance and is suitable for some high-end application scenes, such as mobile phones, computers and the like. The hard shell battery core has better protection performance and longer service life, and is suitable for some severe working environments. The specific limitation is not particularly limited herein.

The battery cells may be, but are not limited to, lithium ion battery cells, sodium lithium ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium sulfur battery cells, magnesium ion battery cells, and the like.

As shown in fig. 1, 4 and 7, according to an electrode assembly 100 of an embodiment of the present application, the electrode assembly 100 may be a roll-to-roll structure, and the electrode assembly 100 includes: the positive plate 110, the negative plate 120 and the diaphragm are arranged between the negative plate 120 and the positive plate 110, and the winding structure is a structure formed by winding the positive plate 110, the negative plate 120 and the diaphragm so as to store electric energy. During the charge and discharge of the battery cell, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive electrode tab 110 and the negative electrode tab 120. The separator is disposed between the positive electrode sheet 110 and the negative electrode sheet 120, and can prevent the positive and negative electrodes from being shorted, and can pass active ions.

The positive electrode sheet 110 may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector. Similarly, the negative electrode sheet 120 may include the negative electrode current collector 102 and the negative electrode active material 103 disposed on at least one surface of the negative electrode current collector 102. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.

As an example, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, surface-silver-treated aluminum, surface-silver-treated stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, titanium, or the like can be used. The composite current collector may include a polymeric material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used.

The negative electrode active material 103 may employ a negative electrode active material 103 for a battery known in the art. As an example, the anode active material 103 may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the battery anode active material 103 may be used. These negative electrode active materials 103 may be used alone or in combination of two or more.

As an example, the main material of the separator may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited. The separator may be a single member located between the positive and negative electrodes, or may be attached to the surfaces of the positive and negative electrodes.

In some embodiments, the separator is a solid state electrolyte. The solid electrolyte is arranged between the anode and the cathode and plays roles in transmitting ions and isolating the anode and the cathode.

As shown in fig. 1, 4 and 7, the negative electrode tab 120 may include a negative electrode start section 121, a negative electrode intermediate section 122 and a negative electrode end section 123 connected in sequence in the winding direction. After the rolled negative electrode sheet 120 is unwound, the part that is wound at the beginning is the negative electrode starting section 121, the part that is wound in the middle is the negative electrode intermediate section 122, and the part that is wound at the end is the negative electrode ending section 123. That is, the negative electrode start section 121 is located at the innermost side of the wound negative electrode sheet 120, and the negative electrode end section 123 is located at the outermost side of the negative electrode sheet 120.

In some embodiments of the present application, as shown in fig. 3, the anode starting section 121 is provided with the anode active material 103 on only one side, and the anode intermediate section 122 is provided with the anode active material 103 on both sides. That is, the anode current collector 102 of the anode starting section 121 is provided with the anode active material 103 on one side in the thickness direction, and is not provided with the anode active material 103 on the other side in the thickness direction. And the anode intermediate section 122 is connected to the anode starting section 121, and the anode intermediate section 122 is provided with the anode active material 103 on both sides in the thickness direction, so that the anode starting section 121 needs single-sided coating, and the anode intermediate section 122 needs double-sided coating.

In some embodiments of the present application, as shown in fig. 3, 6 and 9, the anode starting section 121 includes a first sub-section 121a, a second sub-section 121b and a first bent section 121c, the first sub-section 121a and the second sub-section 121b being stacked, the first bent section 121c being connected between the first sub-section 121a and the second sub-section 121b, and one surface of the first sub-section 121a and the second sub-section 121b opposite to each other being not provided with the anode active material 103.

The first and second sub-segments 121a and 121c and 121b are sequentially connected in the winding direction of the electrode assembly 100, and the first and second sub-segments 121a and 121b may be stacked in the thickness direction of the electrode assembly 100. That is, the anode starting section 121 is bent toward one direction so that one portion thereof overlaps another portion thereof. Immediately after the electrode assembly 100 is wound, the electrode assembly 100 needs to be pre-pressed after the winding needle is withdrawn from the electrode assembly 100, so that the electrode assembly 100 is pressed into a structure having different lengths and thicknesses, the thickness of the electrode assembly 100 is smaller than the length of the electrode assembly 100, and the thickness direction of the electrode assembly 100 is shown in the X direction of fig. 1, 4 and 7.

In the embodiment of the present application, the anode starting section 121 is bent to form the first and second sub-sections 121a and 121b stacked on each other, the first and second sub-sections 121a and 121b are both part of the anode sheet, the side surfaces of the first and second sub-sections 121a and 121b facing each other do not participate in the reaction of the deintercalation positive ions, and thus the anode active material 103 is not provided on the side surfaces of the anode current collector 102 facing each other at the part of the first and second sub-sections 121a and 121b, and since the first bent section 121c is connected between the first and second sub-sections 121a and 121b, and the inner side surfaces of the first bent section 121c also do not participate in the reaction of the deintercalation positive ions, the inner side surfaces of the part of the anode current collector 102 on the first bent section 121c also do not need to be provided with the anode active material 103.

As shown in fig. 3 in particular, the negative electrode active material 103 is not provided on the side surfaces of the negative electrode current collector 102 facing each other of the portions on the first and second sub-segments 121a and 121b, and the negative electrode active material 103 is provided on the side surfaces of the portions on the first and second sub-segments 121a and 121b facing away from each other. And the portion of the anode current collector 102 located at the anode intermediate section 122 is provided with the anode active material 103 on both sides in the thickness direction of the electrode assembly 100.

Since the first and second sub-segments 121a and 121b are each provided with no anode active material 103 on one side and the first and second sub-segments 121a and 121b are not provided with anode active material 103 on the side facing each other, the anode starting segments 121 of the electrode assembly 100 are stacked together, but the stacked first and second sub-segments 121a and 121b also contain only two layers of anode active material 103, that is, the anode active material 103, the anode current collector 102, and the anode active material 103 in this order in the thickness direction, the problem of excessive size of the electrode assembly 100 in the thickness direction does not occur.

The thickness of the negative electrode current collector 102 alone is very small, and the thickness of the negative electrode sheet 120 is mainly the thickness of the negative electrode active material 103 on one or both sides of the negative electrode current collector 102; therefore, in the embodiment of the application, after the first sub-segment 121a and the second sub-segment 121b are stacked, compared with the anode middle segment 122 provided with the anode active material 103 on both sides, the first sub-segment 121a and the second sub-segment 121b only have one layer of anode current collector 102, so that the thicknesses of the stacked first sub-segment 121a and second sub-segment 121b are not greatly different from the thicknesses of the anode middle segment 122, the transition between the stacked first sub-segment 121a and second sub-segment 121b and the anode middle segment 122 is smoother, and the stacked first sub-segment 121a and second sub-segment 121b do not have excessive influence on the energy density loss of the electrode assembly 100 in the thickness direction.

In some embodiments of the present application, as shown in fig. 2, 5 and 8, the innermost ring of the positive electrode sheet 110 includes a second bending section 111, and the first bending section 121c is located inside the second bending section 111 and is disposed opposite to the second bending section 111. Since the first and second sub-sections 121a and 121b each extend in the length direction of the battery cell assembly 100 and the first bent section 121c connects the first and second sub-sections 121a and 121b, it can be said that the first bent section 121c is connected to the same-side ends of the first and second sub-sections 121a and 121b in the length direction of the electrode assembly 100. Thus, the first bending section 121c and the second bending section 111 being disposed opposite to each other means that the first bending section 121c and the second bending section 111 are disposed opposite to each other in the length direction of the electrode assembly 100.

It can be understood that the innermost ring of the positive electrode sheet 110 not only includes the second bending section 111, but also includes two flat sections connected to two ends of the first bending section 111, which will be described in detail later, and will not be repeated here.

Therefore, during charging, the portion facing the second bending section 111 is no longer the end of the anode starting section 121, but the first bending section 121c, the portion of the first bending section 121c facing the second bending section 111 may be configured as an arc surface, while the portion of the second bending section 111 facing the first bending section 121c may also be configured as an arc surface, the opposite portion being face-to-face, so that the side of the first bending section 121c facing the second bending section 111 has sufficient positions for positive ions precipitated from the second bending section 111 to be embedded.

Positive ions (e.g., lithium ions) precipitated from the second bending section 111 can be fully inserted into the first bending section 121c, and the first bending section 121c has enough negative electrode excess, so that a protective adhesive does not need to be arranged on the inner side of the second bending section 111, and the probability of breakage at the corner of the innermost ring of the positive electrode sheet 110 and precipitation of metal on the negative electrode initial section 121 is effectively reduced.

According to the electrode assembly 100 of the embodiment of the application, the first bending section 121c of the anode initial section 121 is opposite to the second bending section 111 of the innermost ring of the cathode sheet 110, and the risk of metal precipitation (such as lithium precipitation) at the corner of the innermost ring of the cathode sheet 110 can be effectively reduced by bending the anode initial section 121 to form the first subsection 121a and the second subsection 121b stacked on each other, and the side surfaces of the first subsection 121a and the second subsection 121b facing each other are not provided with the anode active material 103, so that the size of the electrode assembly 100 in the thickness direction is reduced, and the probability of metal precipitation at the non-rubberized surface of the second bending section 111 is reduced.

In some embodiments of the present application, as shown in fig. 2, 5 and 8, the diaphragm includes: the third bending section 131, the third bending section 131 is disposed between the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c, and the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c are respectively attached to the third bending section 131.

The inner side of the second bending section 111 refers to a side of the second bending section 111 facing the center of the electrode assembly 100, and the outer side of the first bending section 121c refers to a side of the first bending section 121c facing away from the center of the electrode assembly 100. The third bending section 131 in the diaphragm is sandwiched between the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c, the inner side surface of the second bending section 111 is in close contact with one side surface of the third bending section 131, and the outer side surface of the first bending section 121c is in close contact with the other side surface of the third bending section 131.

Because the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c are attached to the third bending section 131, the distance between the second bending section 111 and the first bending section 121c is very close, positive ions (such as lithium ions) detached from the second bending section 111 can be very easily embedded into the first bending section 121c, the moving distance of the positive ions in electrolyte is greatly reduced, the problem that positive metal is precipitated on the first bending section 121c is avoided, the original protective adhesive arranged on the inner side surface of the second bending section 111 can be omitted, the inner side surface of the second bending section 111 is not extruded by the protective adhesive after bending, and the probability of fracture problem of the inner side surface of the second bending section 111 is effectively reduced.

In some embodiments of the present application, the end of the first subsection 121a away from the first bending section 121c is the starting end of the negative electrode sheet 120, and the starting end of the negative electrode sheet 120 is flush with the starting end of the separator. The starting end of the negative electrode sheet 120 is the innermost end of the negative electrode sheet 120 in the winding direction, and the starting end of the separator is the innermost end of the separator in the winding direction.

The fact that the starting end of the negative electrode sheet 120 and the starting end of the separator are flush means that the starting end of the negative electrode sheet 120 and the starting end of the separator are located at substantially the same position in the winding direction, and the fact that the starting end of the negative electrode sheet 120 and the starting end of the separator are located at the same position in the winding direction may cause that the starting ends of the negative electrode sheet 120 and the separator exceed the starting end of the separator by a certain distance or the starting end of the separator exceeds the starting end of the negative electrode sheet 120 by a certain distance due to errors possibly caused by the process. For example, the distance of the starting end of the negative electrode sheet 120 beyond the starting end of the separator in the winding direction is not more than 5mm, or the distance of the starting end of the separator beyond the starting end of the negative electrode sheet 120 in the winding direction is not more than 5mm.

Since the starting end of the negative electrode sheet 120 is flush with the starting end of the separator, the innermost ring of the electrode assembly 100 does not have a multi-layered separator stack, and the thickness of the electrode assembly 100 is increased due to the provision of the multi-layered separator at the innermost ring, thereby reducing the energy density loss of the electrode assembly 100 in the thickness direction.

In some embodiments of the application, the trailing end of the negative electrode tab 120 is flush with the trailing end of the separator. The ending end of the negative electrode sheet 120 refers to an end of the negative electrode sheet 120 located outermost in the winding direction, and the ending end of the separator refers to an end of the separator located outermost in the winding direction.

The fact that the ending end of the negative electrode sheet 120 is flush with the ending end of the separator means that the ending end of the negative electrode sheet 120 and the ending end of the separator are at the same position in the winding direction. Flush may refer to that the tail end of the negative electrode sheet 120 and the tail end of the separator are completely the same in position in the winding direction, and the tail end of the negative electrode sheet 120 does not exceed the tail end of the separator nor the tail end of the separator; or the ending end of the negative electrode sheet 120 exceeds the ending end of the diaphragm by a certain distance, and the ending end of the diaphragm exceeds the ending end of the negative electrode sheet 120 by a certain distance, so long as the distance is ensured to be in a smaller range. For example, the distance by which the trailing end of the negative electrode sheet 120 exceeds the trailing end of the separator in the winding direction is not more than 5mm, or the distance by which the trailing end of the separator exceeds the trailing end of the negative electrode sheet 120 in the winding direction is not more than 5mm.

Because the tail end of the negative plate 120 is flush with the tail end of the diaphragm, the diaphragm tail end can completely cover the outer side surface of the tail end of the negative plate 120, and the use amount of the diaphragm is reduced, so that the production cost of the battery cell is reduced. Therefore, the ending section of the negative electrode plate 120 can be completely coated by the diaphragm ending section, the outermost ring of the negative electrode plate 120 cannot be exposed, the situation that the outermost ring of the negative electrode plate 120 contacts with the shell of the battery cell cannot occur, and further the corrosion phenomenon of the negative electrode plate 120 is reduced.

According to some embodiments of the application, the overlapping length of the first and second subsections 121a, 121b in the length direction of the negative electrode sheet 120 is 0.5mm-10mm. The first and second sub-segments 121a and 121b are stacked, wherein the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120 satisfies the above range. Thus, the structure that the anode starting sections 121 are folded and then stacked can be utilized, and the thickness difference between the sum of the thicknesses of the stacked first sub-section 121a and second sub-section 121b and the thickness of the double-sided coated anode intermediate section 122 can be effectively reduced, so that the flatness of the inner ring of the electrode assembly 100 is ensured, and poor adhesion of the inner ring of the electrode assembly 100 after hot pressing can be prevented.

For example, the overlapping length of the first and second subsections 121a and 121b in the length direction of the negative electrode sheet 120 may be 0.5mm, 2mm, 4mm, 6mm, 8mm, 10mm. The present application does not limit the specific value of the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the anode sheet 120 as long as the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the anode sheet 120 satisfies the above range.

In some embodiments of the present application, the overlapping length of the first and second subsections 121a and 121b in the length direction of the negative electrode sheet 120 is 2mm to 5mm. For example, the overlapping length of the first and second subsections 121a and 121b in the length direction of the negative electrode sheet 120 may be 2mm, 3mm, 4mm, 5mm. The present application does not limit the specific value of the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the anode sheet 120 as long as the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the anode sheet 120 satisfies the above range.

It can be understood that, when the electrode assembly 100 is wound and the clamping needle is opened, the length direction of the negative electrode sheet 120 is the winding direction of the electrode assembly 100. In some embodiments of the present application, as shown in fig. 1-2, or as shown in fig. 3-4, the first and second sub-sections 121a and 121b extend in the length direction Y of the electrode assembly 100, and thus the overlapping length of the first and second sub-sections 121a and 121b in the length direction of the negative electrode sheet 120 is the overlapping length of the first and second sub-sections 121a and 121b in the length direction Y of the electrode assembly 100.

The overlapping portions of the first and second sub-segments 121a and 121b in the thickness direction may be adhesively fixed, and the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120 directly affects the adhesive strength of the first and second sub-segments 121a and 121 b. The larger the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120, the greater the bonding strength of the first and second sub-segments 121a and 121b, the smaller the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120, and the smaller the bonding strength of the first and second sub-segments 121a and 121 b. The overlapping length of the first sub-segment 121a and the second sub-segment 121b in the length direction of the negative electrode sheet 120 meets the above conditions, so that the bonding strength of the first sub-segment 121a and the second sub-segment 121b can be effectively ensured, the bonding of the first sub-segment 121a and the second sub-segment 121b is firmer, and the probability of separating the first sub-segment 121a and the second sub-segment 121b when the battery cell falls is reduced.

In addition, the longer the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120, the smaller the size of the first and second sub-segments 121a and 121b as a whole in the length direction of the electrode assembly 100, of the negative electrode initial segment 121 of the same length; the shorter the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120, the larger the size of the first and second sub-segments 121a and 121b as a whole in the length direction of the electrode assembly 100. Therefore, while the overlapping length of the first and second sub-segments 121a and 121b in the length direction of the negative electrode sheet 120 satisfies the above-described conditions, not only can the adhesive property between the first and second sub-segments 121a and 121b be ensured, but also the size of the first and second sub-segments 121a and 121b as a whole in the length direction of the electrode assembly 100 can be ensured not to be excessively large, thereby reducing the energy density loss of the electrode assembly 100 in the winding direction.

It should be noted that, in the embodiment of the present application, the length direction of the electrode assembly 100 is shown in the Y direction in fig. 1, 4 and 7.

In some embodiments of the present application, as shown in fig. 3 and 6, one end of the first sub-segment 121a and one end of the second sub-segment 121b are connected to the first bent segment 121c, respectively, the other end of the second sub-segment 121b is connected to one end of the negative electrode middle segment 122, and the other end of the first sub-segment 121a is spaced apart from the projection of the one end of the negative electrode middle segment 122 in the thickness direction of the electrode assembly 100 to form the separation gap 101.

That is, in the winding direction, the first sub-section 121a, the first bending section 121C, and the second sub-section 121b are sequentially connected, the first bending section 121C may be configured in a "C" shape, the first sub-section 121a may be connected to one end of the first bending section 121C, and the second sub-section 121b may be connected to the other end of the second bending section 111. The projection of the other end of the first sub-section 121a in the thickness direction of the electrode assembly 100 may fall onto the second sub-section 121b, and the other end of the first sub-section 121a is spaced apart from the projection of the one end of the negative electrode intermediate section 122 in the thickness direction of the electrode assembly 100.

Immediately after the winding of the electrode assembly 100 is completed, it is necessary to withdraw the winding needle from the electrode assembly 100, and then the innermost jaw of the electrode assembly 100 is moved toward both sides, thereby drawing the circular cross section of the electrode assembly 100 into a flat cross section. At this time, the direction of spacing between the sides of the electrode assembly, which are closely spaced and facing each other, is the thickness direction of the electrode assembly in the embodiment of the present application, and a specific direction may be the X direction shown in fig. 1, 4 and 7.

In addition, the larger the separation gap 101 is, the smaller the overlapping portion of the first and second sub-segments 121a and 121b is after the lamination of the cathode starting segments 121 of the same length, and the length of the overlapping portion of the first and second sub-segments 121a and 121b directly affects the bonding strength between the first and second sub-segments 121a and 121 b. That is, the longer the overlapping portion of the first and second sub-segments 121a and 121b, the greater the bonding strength between the first and second sub-segments 121a and 121b, and the shorter the overlapping portion of the first and second sub-segments 121a and 121b, the smaller the bonding strength between the first and second sub-segments 121a and 121 b.

The separation gap 101 is thus ensured to be within a certain range, so that the problem that a part of the first sub-section 121a overlaps the negative electrode middle section 122 in the thickness direction of the electrode assembly 100, which in turn causes the sum of the thicknesses of the folded first and second sub-sections 121a and 121b to be too large, is alleviated, and the first and second sub-sections 121a and 121b are ensured to have a sufficient overlapping length in the winding direction, so that the adhesive strength between the first and second sub-sections 121a and 121b is ensured, and the energy density loss of the electrode assembly 100 in the winding direction due to the excessive separation gap 101 is reduced.

The first and second sub-segments 121a and 121b are stacked in the thickness direction of the electrode assembly 100, and the sides of the first and second sub-segments 121a and 121b facing each other are not provided with the anode active material 103, thereby reducing the thickness of the first and second sub-segments 121a and 121b stacked on each other in the thickness direction of the electrode assembly 100. In addition, since the other end of the first sub-segment 121a is not overlapped with the negative electrode middle segment 122 in the thickness direction, the probability of an increase in the thickness of the electrode assembly, problems affecting the flatness of the inner ring and poor adhesion of the inner ring, is further reduced.

In some embodiments of the application, the size of the separation gap 101 in the winding direction is 0-5mm. That is, the distance between the projection of the other end of the first sub-segment 121a in the thickness direction of the electrode assembly 100 and the projection of the one end of the negative electrode intermediate segment 122 in the thickness direction of the electrode assembly 100 is 0 to 5mm. For example, the dimensions of the separation gap 101 in the winding direction may be 1mm, 3mm, and 5mm. The embodiment of the present application does not limit the size of the separation gap 101 in the winding direction, as long as the separation gap 101 satisfies the above-described range.

Since the size of the separation gap 101 in the winding direction is 0 to 5mm, it is ensured that the other end of the first sub-section 121a is spaced apart from the projection of the one end of the negative electrode middle section 122 in the thickness direction of the electrode assembly 100 to form the separation gap 101, while also reducing the energy density loss of the electrode assembly 100 in the winding direction due to the excessive separation gap 101.

In addition, the thickness of the first and second sub-segments 121a and 121b stacked on each other in the thickness direction of the electrode assembly 100 is reduced. Since the other end of the first sub-segment 121a is not overlapped with the negative electrode middle segment 122 in the thickness direction, problems of the increased thickness of the electrode assembly 100, affecting the flatness of the inner ring, and poor adhesion of the inner ring are further avoided.

If the other end of the first sub-segment 121a overlaps the anode intermediate segment 122, the size of the overlap region in the thickness direction increases, and the stacked structure of the overlap region in the thickness direction is the anode active material layer 103, the anode current collector 102, and the anode active material 103 in this order. The overlap region is therefore sufficiently increased by a layer of the anode active material 103 as compared to the first and second subsections 121a and 121b after stacking, and the dimension of the anode active material 103 in the thickness direction is much larger than the thickness of the anode current collector 102. Obviously, the other end of the first sub-section 121a is overlapped with the negative electrode middle section 122, and there are problems in that the thickness of the electrode assembly 100 increases, and the flatness of the inner ring and the adhesion failure of the inner ring are affected.

In some embodiments of the application, the size of the separation gap 101 in the winding direction is 0-2mm. That is, the distance of the projection of the separation gap 101 in the thickness direction of the electrode assembly 100 is 0-2mm. For example, the dimensions of the separation gap 101 in the winding direction may be 0.5mm, 1mm, 1.5mm, and 2mm. The embodiment of the present application does not limit the size of the separation gap 101 in the winding direction, as long as the separation gap 101 satisfies the above-described range.

Since the size of the separation gap 101 in the winding direction is 0-2mm, the size of the first and second sub-segments 121a and 121b stacked on each other in the thickness direction of the electrode assembly 100 is reduced. In addition, since the other end of the first sub-section 121a is not overlapped with the negative electrode middle section 122 in the thickness direction, problems of the increased thickness of the electrode assembly 100, affecting the flatness of the inner ring, and poor adhesion of the inner ring are further avoided.

In some embodiments of the present application, as shown in fig. 2, 5 and 8, an insulation layer 140 is disposed on an inner side surface of an innermost ring of the positive electrode sheet 110, and the insulation layer 140 is opposite to the separation gap 101.

As mentioned in the above-described embodiment, the other end of the first sub-section 121a is spaced apart from the projection of the one end of the negative electrode intermediate section 122 in the thickness direction of the electrode assembly 100 to form the separation gap 101. Because the second subsection 121b and the first subsection 121a are both provided with the negative electrode active material 103 on one surface, and because of the existence of the separation gap 101, a part of the negative electrode current collector 102 is exposed in the area of the second subsection 121b opposite to the separation gap 101, if the insulating layer 140 is not arranged at the innermost ring of the positive electrode plate 110 and the insulating layer 140 opposite to the separation gap 101, positive ions (such as lithium ions) separated from the part of the innermost ring of the positive electrode plate 110 opposite to the separation gap 101 can be separated out on the exposed negative electrode current collector 102, thereby causing the performance of the battery core to be reduced, greatly shortening the cycle life, limiting the quick charge capacity of the battery, and possibly causing catastrophic consequences such as combustion, explosion and the like.

By providing the insulating layer 140 in the region where the inner side surface of the innermost ring of the positive electrode sheet 110 is opposite to the separation gap 101, the insulating layer 140 is bonded to the region where the inner side surface of the innermost ring of the positive electrode sheet 110 is opposite to the separation gap 101 during charging of the battery cell, so that the insulating layer 140 prevents positive ions from separating out from the region where the inner side surface of the innermost ring of the positive electrode sheet 110 is opposite to the separation gap 101, thereby reducing the probability of positive ions precipitating on the region where the second subsection 121b is opposite to the separation gap 101.

In other words, the reaction of the deintercalating positive ions does not take place between the region of the inner side surface of the innermost ring of the positive electrode sheet 110 facing the separation gap 101 and the region of the second subsection 121b facing the separation gap 101, and the charge and discharge process does not take place between the region of the inner side surface of the innermost ring of the positive electrode sheet 110 facing the separation gap 101 and the region of the second subsection 121b facing the separation gap 101.

In some embodiments of the present application, as shown in fig. 8 and 9, one end of the first sub-segment 121a and one end of the second sub-segment 121b are connected to the first bending segment 121c, respectively, the other end of the second sub-segment 121b is connected to one end of the negative electrode middle segment 122, a portion of the first sub-segment 121a overlaps the second sub-segment 121b, and another portion of the first sub-segment 121a overlaps the negative electrode middle segment 122.

That is, in the winding direction, the first sub-section 121a, the first bending section 121C, and the second sub-section 121b are sequentially connected, the first bending section 121C may be configured in a "C" shape, the first sub-section 121a may be connected to one end of the first bending section 121C, and the second sub-section 121b may be connected to the other end of the second bending section 111.

The projection of the other end of the first sub-segment 121a in the thickness direction of the electrode assembly 100 may fall onto the negative electrode middle segment 122 such that a portion of the first sub-segment 121a overlaps the second sub-segment 121b in the thickness direction of the electrode assembly 100 and another portion of the second sub-segment 121b overlaps the negative electrode middle segment 122 in the thickness direction of the electrode assembly 100.

Therefore, the second subsection 121b is not provided with the exposed negative current collector 102, so that the inner side surface of the innermost ring of the positive plate 110 is not required to be provided with the insulating layer 140, and the forming process of the battery cell and the production cost of the battery cell are reduced at least to a certain extent.

In some embodiments of the present application, as shown in fig. 2, 5 and 8, the innermost ring of the positive electrode sheet 110 further includes a first flat section 112 and a second flat section 113, the second bending section 111 is connected between the first flat section 112 and the second flat section 113, and an end of the first flat section 112 away from the second bending section 111 is a starting end of the positive electrode sheet 110.

The first sub-section 121a is located between the second sub-section 121b and the first straight section 112, or the first sub-section 121a is located between the second sub-section 121b and the second straight section 113 in the thickness direction of the electrode assembly 100.

In one embodiment of the present application, the starting end of the positive electrode sheet 110 is not disposed on the second bending section 111, but is disposed on the first straight section 112 connected to the second bending section 111, and the first sub-section 121a is located between the second sub-section 121b and the first straight section 112 in the thickness direction of the electrode assembly 100. Therefore, the direction from the first bending section 121c toward the other end of the first sub-section 121a is opposite to the winding direction of the positive electrode sheet 110.

In another embodiment of the present application, the starting end of the positive electrode tab 110 is disposed on the first straight section 112 connected to the second bent section 111, and the first sub-section 121a is located between the second sub-section 121b and the second straight section 113 in the thickness direction of the electrode assembly 100. Accordingly, the direction from the first bending section 121c toward the other end of the first sub-section 121a is the same as the winding direction of the positive electrode sheet 110.

The electrode assembly 100 in the embodiment of the present application does not limit the bending direction of the first subsection 121a compared to the second subsection 121b, as long as the side surface of the first subsection 121a on which the negative electrode active material 103 is not disposed is ensured to be opposite to the side surface of the second subsection 121b on which the negative electrode active material 103 is not disposed.

According to some embodiments of the present application, as shown in fig. 3, the separator includes a first separator 132, and the first separator 132 is located on the side of the anode starting section 121 having the anode active material 103. The first separator 132 is disposed between the side of the anode starting section 121 having the anode active material 103 and the innermost ring of the cathode, thereby reducing the probability of occurrence of a short circuit phenomenon due to contact between the side of the anode starting section 121 having the anode active material 103 and the innermost ring of the cathode, while also ensuring that active ions between the side of the anode starting section 121 having the anode active material 103 and the innermost ring of the cathode can pass through.

In addition, the separator is provided only on the side having the anode active material 103 in the anode starting section 121 of the present application, and the thickness of the first and second sub-sections 121a and 121b after stacking can be reduced, thereby reducing the energy density loss of the battery cell in the thickness direction.

That is, the first and second sub-segments 121a and 121b do not have a separator between sides of the first and second sub-segments 121a and 121b facing each other after being stacked, thereby reducing not only the thickness of the electrode assembly but also the manufacturing cost of the electrode assembly 100. In addition, the sides of the first and second sub-segments 121a and 121b facing each other may be bonded, thereby further reducing the thickness of the electrode assembly 100 and reducing the energy density loss of the battery cells in the thickness direction.

In some embodiments of the present application, in order to reduce the overall thickness of the first and second subsections 121a and 121b after stacking, the first separator 132 is closely adhered to the anode active material 103 on the anode starting section 121. Thereby effectively reducing excessive impact on the overall thickness of the first and second subsections 121a, 121b after stacking due to the presence of the first diaphragm 132.

In some embodiments of the present application, as shown in fig. 6 and 9, the separator further includes a second separator 133, and the second separator 133 is located on the side of the anode starting section 121 having no anode active material 103. That is, in this embodiment, the separator includes: a first separator 132 and a second separator 133, the first separator 132 being provided on the side of the anode starting section 121 on which the anode active material 103 is provided, and the second separator 133 being provided on the side of the anode starting section 121 on which the anode active material 103 is not provided. Therefore, the cathode starting section 121 can be more effectively protected, and the effect that the separator is arranged on only one surface of the cathode starting section 121 is achieved without specially arranging process steps, so that the difficulty of the forming process of the electrode assembly 100 is greatly reduced.

That is, the first and second sub-sections 121a and 121b are provided with a diaphragm between the sides of the first and second sub-sections 121a and 121b facing each other after being stacked. The first and second sub-sections 121a and 121b may be respectively bonded to the second separator 133 such that although the separator is provided between the first and second sub-sections 121a and 121b, the gap width between the first and second sub-sections 121a and 121b is reduced as much as possible, and the influence on the thickness of the electrode assembly 100 due to the third separator 133 provided between the first and second sub-sections 121a and 121b is reduced.

In some embodiments of the present application, in order to reduce the overall thickness of the stacked first and second sub-sections 121a and 121b, the first separator 132 is tightly attached to the anode active material 103 on the anode starting section 121, and the second separator 133 is attached to the side of the anode starting section 121 where the anode active material 103 is not provided, that is, the second separator 133 is attached to the anode current collector 102 exposed on the anode starting section 121. Thereby effectively reducing excessive impact on the overall thickness of the first and second subsections 121a, 121b after stacking due to the presence of the first and second diaphragms 132, 121 b.

In some embodiments of the present application, the negative electrode collecting section 123 is provided with the negative electrode active material 103 only on one side, and the side of the negative electrode collecting section 123 where the negative electrode active material 103 is not provided faces the outside of the electrode assembly 100. That is, the electrode assembly 100 of the embodiment of the present application is terminated by the negative electrode sheet 120, and since the side of the negative electrode terminating segment 123 facing the outside of the electrode assembly 100 is no longer opposite to the positive electrode sheet 110, the outside of the negative electrode terminating segment 123 no longer participates in the reaction of the deintercalation ions, so that the negative electrode terminating segment 123 only sets the negative electrode active material 103 on the side facing the inside of the electrode assembly 100, and the negative electrode active material 103 is no longer set on the side of the negative electrode terminating segment 123 facing the outside of the electrode assembly 100, thereby reducing the production cost of the electrode assembly 100.

According to some embodiments of the present application, as shown in fig. 1, 4 and 7, the positive electrode sheet 110 includes a positive electrode start section 114, a positive electrode intermediate section 115 and a positive electrode end-receiving section 116 that are sequentially connected in the winding direction, the positive electrode start section 114 being provided with the negative electrode active material 103 on both sides, the positive electrode intermediate section 115 being provided with the negative electrode active material 103 on both sides, and the positive electrode end-receiving section 116 being provided with the negative electrode active material 103 on both sides.

The positive electrode start section 114 is disposed at the innermost side of the positive electrode sheet 110 in the winding direction, the positive electrode end-receiving section 116 is disposed at the outermost side of the positive electrode sheet 110 in the winding direction, and the positive electrode intermediate section 115 is disposed between the positive electrode start section 114 and the positive electrode end-receiving section 116 in the winding direction.

Since the electrode assembly 100 is not terminated by the positive electrode terminating segment 116, and both sides of the positive electrode starting segment 114 are opposite to the negative electrode starting segment 121 or the negative electrode intermediate segment 122, the positive electrode starting segment 114, the positive electrode intermediate segment 115, and the positive electrode terminating segment 116 are coated with the positive electrode active material on both sides. Therefore, the battery cell is ensured to have enough capacity and excellent battery performance. The energy density loss occurring due to the non-coating of the positive electrode active material on the positive electrode sheet 110 is reduced. In addition, compared with the interval coating, the continuous coating on the positive plate 110 can also reduce the difficulty of the coating process and improve the production efficiency of the positive plate 110.

An electrode assembly 100 according to an embodiment of the present application is described in detail below.

The electrode assembly 100 is a winding structure, the electrode assembly 100 includes a positive electrode sheet 110, a negative electrode sheet 120, and a separator disposed between the positive electrode sheet 110 and the negative electrode sheet 120, the negative electrode sheet 120 includes a negative electrode start section 121, a negative electrode intermediate section 122, and a negative electrode end-receiving section 123 in a winding direction, the negative electrode start section 121 is provided with a negative electrode active material 103 only on one side, and the negative electrode intermediate section 122 is provided with a negative electrode active material 103 on both sides.

The anode starting section 121 is bent to form a first sub-section 121a, a first bent section 121c, and a second sub-section 121b, which are sequentially connected in the winding direction, the first sub-section 121a and the second sub-section 121b are stacked, and the side surfaces of the first sub-section 121a and the second sub-section 121b facing each other are not provided with the anode active material 103, and the innermost ring of the cathode sheet 110 includes a second bent section 111, and the first bent section 121c is located inside the second bent section 111 and is disposed opposite to the second bent section 111. The diaphragm comprises a third bending section 131, the third bending section 131 is arranged between the first bending section 121c and the second bending section 111, and the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c are respectively attached to the third bending section 131.

The separator includes: the third bending section 131, the third bending section 131 is disposed between the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c, and the inner side surface of the second bending section 111 and the outer side surface of the first bending section 121c are respectively attached to the third bending section 131. The end of the first subsection 121a far away from the first bending section 121c is the starting end of the negative electrode plate 120, the starting end of the negative electrode plate 120 is flush with the starting end of the diaphragm, and the ending end of the negative electrode plate 120 is flush with the ending end of the diaphragm. The overlapping length of the first and second subsections 121a and 121b in the length direction of the negative electrode sheet 120 is 0.5mm to 10mm.

One end of the first sub-segment 121a and one end of the second sub-segment 121b are connected to the first bending segment 121c, respectively, and the other end of the second sub-segment 121b is connected to the negative electrode middle segment 122, and the other end of the first sub-segment 121a is spaced apart from the projection of the one end of the negative electrode middle segment 122 in the thickness direction of the electrode assembly 100 to form the separation gap 101. The size of the separation gap 101 in the winding direction is 0 to 5mm. An insulating layer 140 is disposed on the inner side surface of the innermost ring of the positive electrode sheet 110, and the insulating layer 140 is opposite to the separation gap 101.

Alternatively, one end of the first sub-segment 121a and one end of the second sub-segment 121b are connected to the first bending segment 121c, respectively, the other end of the second sub-segment 121b is connected to one end of the negative electrode middle segment 122, a portion of the first sub-segment 121a overlaps the second sub-segment 121b, and another portion of the first sub-segment 121a overlaps the negative electrode middle segment 122.

The innermost ring of the positive electrode sheet 110 further includes a first flat section 112 and a second flat section 113, the second bending section 111 is connected between the first flat section 112 and the second flat section 113, and one end of the first flat section 112 away from the second bending section 111 is a starting end of the positive electrode sheet 110. The first sub-section 121a is located between the second sub-section 121b and the first straight section 112, or the first sub-section 121a is located between the second sub-section 121b and the second straight section 113 in the thickness direction of the electrode assembly 100.

The separator includes a first separator 132, the first separator 132 is located on the side of the anode starting section 121 having the anode active material 103, the first separator 132 is provided only on the side having the anode active material 103 in the anode starting section 121, and the separator is not provided on the side not provided with the anode active material 103.

The anode starting section 121 and the anode ending section 123 are both single-sided coated with active material, and the anode intermediate section 122 is double-sided coated with active material. The positive electrode sheet 110 includes a positive electrode start section 114, a positive electrode intermediate section 115, and a positive electrode end-receiving section 116, which are sequentially connected in the winding direction, wherein the positive electrode start section 114, the positive electrode intermediate section 115, and the positive electrode end-receiving section 116 are coated with an active material on both sides.

The battery cell according to the embodiment of the present application is briefly described below.

The battery cell according to the embodiment of the application comprises the electrode assembly 100 of the embodiment, and the battery cell according to the embodiment of the application is provided with the electrode assembly 100, so that the battery cell can cancel the protective adhesive at the innermost ring corner of the positive electrode, and reduce the probability of fracture at the innermost ring corner of the positive electrode and the problem of metal precipitation of a non-adhesive surface generated by the fracture.

The following briefly describes the electric equipment according to the embodiment of the present application.

The embodiment of the application provides electric equipment using a battery cell as a power supply, wherein the electric equipment can be, but is not limited to, a mobile phone, a tablet personal computer, a notebook computer, an electric toy, an electric tool, an electric bicycle, an electric motorcycle, an electric automobile, a ship, a spacecraft and the like. Among them, the electric toy may include fixed or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric plane toys, and the like, and the spacecraft may include planes, rockets, space planes, and spacecraft, and the like.

The electric equipment comprises the electric core, the electric energy of the electric component on the electric equipment can be provided by the electric core, and meanwhile, if the electric equipment is provided with the power generation equipment, the power generation equipment can also charge the electric core. Because the electric equipment provided by the embodiment of the application is provided with the electric core, the electric equipment has longer endurance, the electric core is not easy to damage, and the use experience of a user is improved.

While the application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims

1. An electrode assembly, wherein the electrode assembly is of a rolled configuration, the electrode assembly comprising:

the negative electrode plate comprises a negative electrode initial section, a negative electrode middle section and a negative electrode tail-collecting section which are sequentially connected in the winding direction, wherein the negative electrode initial section is provided with a negative electrode active material on one surface only, and the negative electrode middle section is provided with a negative electrode active material on both surfaces;

the cathode starting section comprises a first subsection, a second subsection and a first bending section, the first subsection and the second subsection Duan Cengdie are arranged, the first bending section is connected with the first subsection and the second subsection, and the cathode active material is not arranged on one surface of the first subsection and the second subsection, which are opposite to each other; the innermost ring of the positive plate comprises a second bending section, and the first bending section is positioned on the inner side of the second bending section and is opposite to the second bending section;

The initial end of the positive electrode sheet faces to a first corner of the innermost ring of the negative electrode sheet in the winding direction, and the first corner is the first corner of the negative electrode middle section in the winding direction; the first bending section of the negative electrode plate faces to the first corner of the innermost ring of the positive electrode plate in the winding direction, and the first corner of the innermost ring of the positive electrode plate in the winding direction is the second bending section.

2. The electrode assembly of claim 1, wherein the separator comprises: the third bending section is arranged between the inner side surface of the second bending section and the outer side surface of the first bending section, and the inner side surface of the second bending section and the outer side surface of the first bending section are respectively attached to the third bending section.

3. The electrode assembly of claim 1, wherein an end of the first sub-segment distal from the first bent segment is a beginning end of the negative electrode tab, the beginning end of the negative electrode tab being flush with the beginning end of the separator.

4. The electrode assembly of claim 1, wherein the trailing end of the negative electrode tab is flush with the trailing end of the separator.

5. The electrode assembly of claim 1, wherein the overlapping length of the first and second subsections in the length direction of the negative electrode sheet is 0.5mm-10mm.

6. The electrode assembly of claim 5, wherein the overlapping length of the first and second subsections in the length direction of the negative electrode tab is 2mm-5mm.

7. The electrode assembly of claim 1, wherein one end of the first sub-segment and one end of the second sub-segment are connected to the first bent segment, respectively, and the other end of the second sub-segment is connected to one end of the negative electrode intermediate segment, and the other end of the first sub-segment is spaced apart from a projection of the one end of the negative electrode intermediate segment in a thickness direction of the electrode assembly to form a separation gap.

8. The electrode assembly according to claim 7, wherein the size of the separation gap in the winding direction is 0-5mm.

9. The electrode assembly of claim 8, wherein the size of the separation gap in the winding direction is 0-2mm.

10. The electrode assembly according to claim 7, wherein an insulating layer is provided on an inner side surface of the innermost ring of the positive electrode sheet in a region facing the separation gap.

11. The electrode assembly of claim 1, wherein one end of the first sub-segment and one end of the second sub-segment are connected to the first bent segment, respectively, the other end of the second sub-segment is connected to one end of the negative electrode middle segment, a portion of the first sub-segment overlaps the second sub-segment, and another portion of the first sub-segment overlaps the negative electrode middle segment.

12. The electrode assembly of claim 7 or 11, wherein the innermost ring of the positive electrode tab further comprises a first straight section and a second straight section, the second bent section connecting the first straight section and the second straight section, an end of the first straight section remote from the second bent section being a starting end of the positive electrode tab;

the first sub-segment is located between the second sub-segment and the first straight segment or the first sub-segment is located between the second sub-segment and the second straight segment in a thickness direction of the electrode assembly.

13. The electrode assembly of claim 1, wherein the separator comprises: and a first separator located on the side of the anode starting section having the anode active material.

14. The electrode assembly of claim 13, wherein the separator further comprises: and a second separator located on a side of the anode starting section having no anode active material.

15. The electrode assembly according to claim 1, wherein the negative electrode collecting section is provided with a negative electrode active material only on one side, and the side of the negative electrode collecting section, on which the negative electrode active material is not provided, faces the outside of the electrode assembly.

16. The electrode assembly according to claim 1, wherein the positive electrode sheet includes a positive electrode start section, a positive electrode intermediate section, and a positive electrode end-receiving section that are sequentially connected in a winding direction, the positive electrode start section being provided with a positive electrode active material on both sides, the positive electrode intermediate section being provided with a positive electrode active material on both sides, the positive electrode end-receiving section being provided with a positive electrode active material on both sides.

17. A cell, comprising: the electrode assembly of any one of claims 1-16.

18. A powered device comprising the electrical core of claim 17.