Electrode assembly and battery

Abstract

The utility model provides an electrode assembly and a battery, the electrode assembly has a coiled structure, comprises a pole piece, and is characterized in that the pole piece comprises a current collector and an active substance layer, the active substance layer is arranged on at least one side surface of the current collector, the active substance layer comprises a first region and a second region, and the current collector comprises a third region; the first region, the second region and the third region which are arranged on the surface of the same side of the current collector are sequentially and adjacently arranged along the winding direction of the electrode assembly; the pole piece further comprises a first protective layer, one part of the first protective layer covers the second area, and the other part of the first protective layer covers the surface of the third area on the same side as the second area; in the thickness direction of the pole piece, the size of the active material layer in the first area is H1, the size of the active material layer in the second area is H2, the third area is not provided with the active material layer, and H2 is larger than or equal to 0 and smaller than H1, so that the ineffective thickness generated by the first protective layer is reduced or eliminated, and the energy density of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrode assembly and a battery. Background Art

[0002] Lithium-ion batteries have the advantages of high specific energy, strong endurance, long cycle life, wide operating range, short charging time, and large current discharge. They are widely used in power fields such as electric vehicles, as well as consumer fields such as mobile phones, watches, tablets, and notebooks.

[0003] At present, in order to improve the fast charging performance of batteries, the central-lug structure in lithium-ion batteries has been widely used. In order to make the electrode assembly firmly connected, a protective layer is affixed to the electrode assembly. The setting of the protective layer increases the ineffective thickness of the battery and reduces the energy density of the battery. Utility Model Content

[0004] In view of this, the present application provides an electrode assembly, which reduces the ineffective thickness of the battery and improves the energy density of the battery. In addition, the present application also provides a battery having the above electrode assembly.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] An electrode assembly having a wound structure, comprising a pole piece, the pole piece comprising a current collector and an active material layer, the active material layer being arranged on at least one side surface of the current collector, the active material layer comprising a first region and a second region, and the current collector comprising a third region;

[0007] Along the winding direction of the electrode assembly, the first region, the second region, and the third region that are sequentially adjacent to each other are located on the same side surface of the current collector;

[0008] The pole piece further includes a first protective layer, a portion of the first protective layer covers the second region, and another portion of the first protective layer covers the surface of the third region on the same side as the second region;

[0009] Along the thickness direction of the electrode sheet, the size of the active material layer in the first region is H1, the size of the active material layer in the second region is H2, and no active material layer is provided in the third region, wherein 0≤H2

[0010] Optionally, in the above electrode assembly, 2μm≤H2

[0011] Optionally, in the above electrode assembly, along the thickness direction of the electrode sheet, the size of the first protective layer is A1, wherein H1-H2=(2A1±5) μm.

[0012] ​​Optionally, in the above electrode assembly, along the length direction of the electrode sheet, the size of the second region is B, wherein 2 mm ≤ B ≤ 8 mm;

[0013] Along the width direction of the pole piece, the size of the second region is less than or equal to the width of the pole piece.

[0014] Optionally, in the above electrode assembly, a recessed portion is provided on the surface of the third region; and / or,

[0015] The circumscribed circle diameter of the recessed portion is D, wherein 30 μm≤D≤90 μm; and / or,

[0016] Along the thickness direction of the pole piece, the size of the recessed portion is H3, wherein 1 μm≤H3≤3 μm.

[0017] Optionally, the electrode assembly further includes a first surface, a second surface opposite to the first surface, and at least one second protective layer, one end of the second protective layer is fixed to the first surface, and the other end of the second protective layer is fixed to the second surface;

[0018] The pole piece further comprises a first groove, and along the thickness direction of the electrode assembly, the projection of the second protective layer falls within the projection of the first groove;

[0019] The first surface and the second surface are perpendicular to a thickness direction of the electrode assembly.

[0020] Optionally, in the above electrode assembly, the first groove is provided with one, and along the thickness direction of the electrode assembly, the size of the first groove is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm; or,

[0021] There are multiple first grooves, and along the thickness direction of the pole piece assembly, the projections of the multiple first grooves overlap. The total size of the multiple first grooves is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm.

[0022] Optionally, the electrode assembly further includes a first surface, a second surface opposite to the first surface, at least one third protective layer and a second groove, along the thickness direction of the electrode assembly, the projection of the third protective layer falls within the projection of the second groove, along the winding direction of the electrode assembly, the pole piece has a tail section, wherein,

[0023] The end section is arranged on the first surface, and the third protective layer is fixed on the end section and the first surface; or,

[0024] The end section is arranged on the second surface, and the third protective layer is fixed on the end section and the second surface.

[0025] Optionally, in the above electrode assembly, along the thickness direction of the electrode sheet, the size of the second groove is H5, and the size of the third protective layer is A3, wherein A3-H5=±5μm.

[0026] Optionally, in the above electrode assembly, there is a gap between the first protective layer and the second region along the length direction of the electrode piece.

[0027] A battery cell comprises the electrode assembly described in any one of the above items.

[0028] The present application provides an electrode assembly, which has a winding structure and includes a pole piece. Specifically, the pole piece includes a current collector, an active material layer and a first protective layer, the active material layer is arranged on at least one side of the current collector, the active material layer has a first region and a second region, the current collector has a third region, along the winding direction of the electrode assembly, the first region, the second region and the third region on the same side of the current collector are arranged adjacent to each other in sequence, wherein a part of the first protective layer covers the second region, and another part covers the third region on the same side as the second region, along the thickness direction of the electrode, the size of the active material layer in the first region is H1, the size of the active material layer in the second region is H2, and the third region is not provided with an active material layer, wherein 0≤H2 BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0030] Figure 1 It is a schematic diagram of the winding core structure of the prior art;

[0031] Figure 2 It is a schematic diagram of the structure of the positive electrode sheet in the prior art;

[0032] Figure 3 A schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present application;

[0033] Figure 4 A schematic diagram of the structure of another positive electrode sheet provided in an embodiment of the present application;

[0034] Figure 5 ​A schematic diagram of a winding core structure provided in an embodiment of the present application.

[0035] 1. Pole piece; 11. Positive electrode piece; 12. Negative electrode piece; 13. Pole ear; 111. Terminal position;

[0036] 2. active material layer; 21. first region; 22. second region;

[0037] 211, first groove; 222, second groove;

[0038] 2111, first embedded groove; 2112, second embedded groove; 2113, third embedded groove; 2114, fourth embedded groove; 2115, fifth embedded groove; 2116, sixth embedded groove;

[0039] 3. Current collector; 31. Third region;

[0040] 4. first protective layer; 41. first section; 42. last section;

[0041] 5. First surface; 6. Second surface; 7. Third protective layer; 8. Gap. DETAILED DESCRIPTION

[0042] The present application provides an electrode assembly, which reduces the ineffective thickness of a battery and improves the energy density of the battery. In addition, the present application also provides a battery having the electrode assembly.

[0043] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] like Figure 1-Figure 5As shown, an embodiment of the present application provides an electrode assembly, which has a winding structure and includes a pole piece 1, wherein the pole ear 13 on the pole piece 1 is a central structure. Specifically, the pole piece 1 includes a current collector 3 and an active material layer 2, the active material layer 2 is arranged on at least one side surface of the current collector 3, the active material layer 2 includes a first region 21 and a second region 22, the current collector 3 includes a third region 31, along the winding direction of the electrode assembly, the first region 21, the second region 22 and the third region 31 are sequentially arranged adjacent to each other on the same side of the current collector 3, wherein the surfaces of the second region 22 and the third region 31 located on the same side of the current collector 3 are simultaneously covered with a first protective layer 4, in the thickness direction of the pole piece 1, the size of the first region 21 located on the same side of the current collector is greater than the size of the second region 22, and the size of the second region 22 is greater than or equal to zero, that is, because the thickness of the second region 22 is less than the thickness of the first region 21, the first protective layer 4 covers the second region 22, and the ineffective thickness of this position is reduced, thereby improving the energy density of the battery.

[0045] It should be noted that the first protective layer 4 can be insulating tape such as rubber tape, acrylic tape, SIS tape, etc., and can also be an inorganic insulating layer such as boehmite insulating layer, AI2O3 insulating layer, MgO insulating layer, etc.

[0046] For ease of understanding and explanation, taking a certain embodiment of the present application as a reference, after the positive electrode sheet 11 and the negative electrode sheet 12 are wound, the current collector of the positive electrode sheet 11 is located at the outermost side of the winding core, and various types of protective layers arranged on the winding core are fixed on the outermost current collector 3. The understanding of the following scheme can be based on this.

[0047] Further, such as Figure 3 As shown, the thickness of the active material layer 2 in the second region 22 has the following numerical relationship, 2μm≤H2

[0048] In some optional embodiments, such as Figure 5 and Figure 3 ​As shown, along the thickness direction of the pole piece 1, the size of the first protective layer 4 is A1, where H1-H2 = (2A1 ± 5) μm. Taking the embodiment of the present application as an example, after the electrode assembly is wound, it has two maximum surface planes arranged opposite to each other, which are called the first surface 5 and the second surface 6. The positive electrode sheet 11 is located at the outermost side of the battery cell, and the terminal position 111 of the positive electrode sheet 11 is connected to the first section 41 of the first protective layer 4. It should be noted that the terminal position 111 of the positive electrode sheet 11 is provided with two overlapping projections in the thickness direction of the pole piece 1, and the two terminal positions 111 are both located on the active material layer 2 opposite to the first surface 5. After the first protective layer 4 is wound along the winding direction of the pole piece 1, the tail section 42 of the first protective layer 4 is located on the second surface 6, and in the thickness direction of the electrode assembly, the projections of the first section 41 and the tail section 42 overlap. In actual production, in the thickness direction of the electrode assembly, the projections of the first section 41 and the tail section 42 of the first protective layer 4 are misaligned, and the general misalignment distance is 0 to 3 mm.

[0049] Because there are two terminal positions 111 of the positive electrode sheet 11, two first protective layers 4 are provided, that is, the two first protective layers 4 have two leading sections 41 and two trailing sections 42. In the thickness direction of the electrode assembly, compared with the electrode assembly body, the thickness of four first protective layers 4 is increased, namely 4A1. In order to offset the invalid thickness caused by the addition of the first protective layer 4, in the thickness direction of the electrode assembly, the size of the first region 21 is equal to the sum of the size of the second region 22 plus the size of the first protective layer 4, so that the thickness of the first protective layer 4 can be completely offset. Figure 5 As shown, in the present embodiment, two second regions 22 are provided and are respectively located at the terminal position 111 of the positive electrode sheet 11. Preferably, the thickness of the two second regions 22 is the same, and each second region 22 can offset the thickness of the two first protective layers 4, that is, H1-H2=2A1. It should be noted that there are inevitable errors in actual production, so H1-H2=(2A1±5)μm.

[0050] In some other embodiments, one second region 22 may be set, in which case the thickness of the second region 22 shall satisfy H1-H2=(4A1±5) μm; alternatively, two second regions 22 may be set, but the thicknesses of the two second regions 22 are different, but the thickness of the first protective layer 4 can be completely eliminated in the thickness direction of the electrode assembly.

[0051] In an optional embodiment, if Figure 3As shown, along the length direction of the pole piece 1, the size of the second region 22 is B, where 2mm≤B≤8mm; along the width direction of the pole piece 1, the size of the second region 22 is greater than or equal to the width of the pole piece 1. In this way, the short circuit between the current collector 3 and the active material layer on the negative electrode sheet can be better avoided, thereby improving the safety performance of the battery and ensuring the energy density of the battery.

[0052] In an optional embodiment, the surface of the third region 31 is provided with a recessed portion (not shown in the figure), by which the roughness of the surface of the third region 31 is increased. It should be noted that the shape of the recessed portion provided in the third region 31 can be a regular pattern, such as a circular or rectangular groove, etc., and the shape of the recessed portion provided in the third region 31 can also be an irregular pattern, such as a pit, etc. The third region 31 is a blank area, that is, an area where no active layer is provided on the current collector 3, a part of the first protective layer 4 covers the third region 31, and the firmness of the connection between the first protective layer 4 and the current collector 3 is enhanced by the recessed portion provided on the surface of the third region 31.

[0053] And / or, the diameter of the circumscribed circle of the recessed portion is D, wherein 30μm≤D≤90μm, that is, when the bottom of the recessed portion has an arc, the diameter of its circumscribed circle is D, and 30μm≤D≤90μm. Compared with the current collector 3 in the blank area, the recessed portion of this size can enhance the firmness of the connection between the first protective layer 4 and the current collector 3 without affecting the normal operation of the current collector 3.

[0054] And / or, along the thickness direction of the pole piece 1, the size of the recessed portion is H3, wherein 1μm≤H3≤3μm, that is, the depth of the recessed portion is H3, and 1μm≤H3≤3μm. Compared with the thickness of the current collector 3, the recessed portion does not penetrate the current collector 3, that is, it does not interfere with the normal operation of the current collector 3, and at the same time strengthens the firmness of the connection between the first protective layer 4 and the current collector 3.

[0055] In some other optional embodiments, the surface of the third region 31 may not be provided with a recessed portion, that is, the surface of the third region 31 is a smooth surface of the current collector 3. In order to ensure that the first protective layer 4 is firmly connected to the surface of the third region 31, a first protective layer 4 with a higher viscosity coefficient may be used.

[0056] In an optional embodiment, if Figure 4 and Figure 5As shown, it also includes a first surface 5, a second surface 6 opposite to the first surface 5, and at least one second protective layer (not shown in the figure), one end of the second protective layer is fixed to the first surface 5, and the other end of the second protective layer is fixed to the second surface 6; the pole piece 1 also includes a first groove 211, along the thickness direction of the electrode assembly, the projection of the second protective layer falls into the projection of the first groove 211; the first surface 5 and the second surface 6 are perpendicular to the thickness direction of the electrode assembly. It should be noted that the first surface 5 and the second surface 6 are the two largest surfaces set opposite to each other after the electrode assembly is wound. After the electrode assembly is wound, one end of the second protective layer is fixed to the first surface 5 of the electrode assembly, and the other end of the second protective layer is wound around the thickness area of ​​the electrode assembly and fixed on the second surface 6, so as to tighten and shape the positive and negative plates and diaphragms at the top and bottom of the electrode assembly, and reduce the probability of bruises when the winding core is put into the shell. The above-mentioned second protective layer may include one of rubber adhesive tape, acrylic adhesive tape, and SIS adhesive.

[0057] In the thickness direction of the electrode assembly, the second protective layer increases the ineffective thickness of the electrode assembly and reduces the energy density of the battery. The pole piece 1 is provided with a first groove 211 to eliminate part or all of the ineffective thickness increased by the second protective layer, thereby improving the energy density of the battery. It should be noted that there is a misalignment between the projections of the two ends of the second protective layer, and the general misalignment distance is 0 to 3 mm. This misalignment is a processing error in actual production.

[0058] Specifically, after the electrode assembly is wound, the active material layer 2 located on the positive electrode sheet 11 is also in a wound shape, wherein a portion of the active material layer 2 is arranged parallel to the first surface 5, and the portion of the active material layer 2 includes multiple layers, and a first groove 211 is provided on one or more of the multiple layers to reduce the ineffective thickness of the second protective layer.

[0059] It should be noted that one or more first grooves 211 are provided, the second protective layer located on the first surface 5 is the first part, and the second protective layer located on the second surface 6 is the second part. In actual production, the widths of the first part and the second part are the same, and the lengths of the first part and the second part may be different. The length and width of the first groove 211 are both greater than or equal to the length and width of the larger one between the first part and the second part.

[0060] In some other optional embodiments, the first groove 211 may also be provided on the negative electrode sheet 12 , and in the thickness direction of the electrode assembly, the projection of the second protective layer falls within the projection of the first groove.

[0061] Further, the first groove 211 is provided with one, and along the thickness direction of the electrode assembly, the size of the first groove 211 is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm, that is, the first groove 211 is provided with one, and the depth of the first groove 211 is used to offset the thickness of the second protective layer on the electrode assembly, that is, A2-H4=±5μm, and it should be noted that ±5μm is a processing error in actual production. In this embodiment, the first groove 211 is provided on any active material layer 2 parallel to the first surface 5, preferably, it is provided on the active material layer 2 on the opposite side of the current collector 3 located on the first surface 5 or on the second surface 6.

[0062] Alternatively, a plurality of first grooves 211 are provided, and along the thickness direction of the electrode assembly, the projections of the plurality of first grooves 211 overlap, the total size of the plurality of first grooves 211 is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm, that is, the total thickness of the plurality of first grooves 211 is used to offset the thickness of the second protective layer, thereby improving the energy density of the battery.

[0063] In the embodiment of the present application, preferably, a first groove 211 is provided on the active material layer 2 opposite to the current collector 3 of the positive electrode sheet 11, three second protective layers are provided, and six first grooves 211 are provided. For the convenience of explanation, the first grooves 211 are divided into groups, and each group of first grooves 211 includes two embedded grooves, and the projections of the two embedded grooves in the thickness direction of the electrode assembly overlap with each other, and the total thickness of each two embedded grooves can offset the invalid thickness generated by a second protective layer, such as the third embedded groove 2113 and the second embedded groove 2112, the fourth embedded groove 2114 and the first embedded groove 2111, the fifth embedded groove 2115 and the sixth embedded groove 2116.

[0064] In other optional embodiments, when the electrode assembly is a stacked structure formed by a positive electrode sheet, a negative electrode sheet, and a separator, the two ends of the second protective layer are arranged on the two largest surfaces of the stacked structure, one end of the second protective layer is fixed on the first surface, and the other end bypasses the thickness area of ​​the stacked structure and is fixed on the second surface. In the thickness direction of the stacked structure, the projections of the two ends of the second protective layer overlap with each other, and the first groove 211 can be arranged on the active material layer of any stack or multiple stacks. Preferably, the first groove 211 is arranged on the active material layer of the first surface 5 and / or the second surface 6 of the stacked structure. It should be noted that the function of the second protective layer arranged on the stacked structure is the same as that of the second protective layer arranged on the roll battery.

[0065] In an optional embodiment, if Figure 4 and Figure 5As shown, it also includes a first surface 5, a second surface 6 opposite to the first surface 5, at least one third protective layer 7 and a second groove 222. Along the thickness direction of the electrode assembly, the projection of the third protective layer 7 falls into the projection of the second groove 222. Along the winding direction of the electrode assembly, the pole piece 1 has a tail section 42, wherein the tail section 42 is arranged on the first surface 5, and the third protective layer 7 is fixed on the tail section 42 and the first surface 5; or, the tail section 42 is arranged on the second surface 6, and the third protective layer 7 is fixed on the tail section 42 and the second surface 6. It should be noted that one end of the third protective layer 7 is fixed on the tail section 42, and the other end is fixed on the first surface 5 or the second surface 6 to prevent the electrode assembly from scattering after winding, so as to ensure the integrity of the electrode assembly. In an embodiment of the present application, the third protective layer 7 may include one of rubber tape, acrylic tape, and SIS tape. A second groove 222 is provided on the pole piece 1. In the thickness direction of the electrode assembly, the projection of the third protective layer 7 falls into the second groove 222. The second groove 222 may be provided on any one or more active material layers 2 after winding is completed to partially offset or completely offset the ineffective thickness generated by the third protective layer 7, thereby improving the energy density of the battery.

[0066] In the embodiment of the present application, preferably, when the third protective layer 7 is arranged on the first surface 5, the second groove 222 is arranged on the active material layer 2 opposite to the current collector 3 of the first surface 5; when the third protective layer 7 is arranged on the second surface 6, the second groove 222 is arranged on the active material layer 2 opposite to the current collector 3 of the second surface 6. In this way, the ineffective thickness generated by the third protective layer 7 can be better partially or completely offset, thereby improving the energy density of the battery.

[0067] Furthermore, along the thickness direction of the pole piece 1, the size of the second groove 222 is H5, and the size of the third protective layer 7 is A3, wherein A3-H5=±5μm, that is, the depth of the second groove 222 is used to completely offset the thickness of the third protective layer 7. It should be noted that ±5μm is a processing error in actual production.

[0068] In some other embodiments, A3 - H5 ≥ 5 μm. In this case, the second groove 222 can also partially offset the thickness of the third protection layer 7 .

[0069] In an optional embodiment, there is a gap 8 between the first protective layer 4 and the second region 22 along the length direction of the electrode 1. In this way, the yield of the electrode 1 process is improved, the content of the electrolyte is increased, and the cycle life of lithium ions is improved.

[0070] In addition, the present application also provides a battery, which includes the above-mentioned electrode assembly. For the beneficial effects of the battery brought by the above-mentioned electrode assembly, please refer to the above-mentioned description of the electrode assembly, which will not be repeated here.

[0071] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0072] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0073] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0074] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0075] It should be understood that the qualifiers "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present application are only used to more clearly explain the technical solutions and cannot be used to limit the scope of protection of the present application.

[0076] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. An electrode assembly having a wound structure, comprising a pole piece, characterized in that: The pole piece comprises a current collector and an active material layer, wherein the active material layer is arranged on at least one side surface of the current collector, the active material layer comprises a first region and a second region, and the current collector comprises a third region; Along the winding direction of the electrode assembly, the first region, the second region, and the third region that are sequentially adjacent to each other are located on the same side surface of the current collector; The pole piece further includes a first protective layer, a portion of the first protective layer covers the second region, and another portion of the first protective layer covers the surface of the third region on the same side as the second region; Along the thickness direction of the electrode sheet, the size of the active material layer in the first region is H1, the size of the active material layer in the second region is H2, and no active material layer is provided in the third region, wherein 0≤H2<H1.

2. The electrode assembly according to claim 1, characterized in that: 2μm≤H2<H1.

3. The electrode assembly according to claim 1, characterized in that: Along the thickness direction of the pole piece, the size of the first protective layer is A1, wherein H1-H2=(2A1±5) μm.

4. The electrode assembly according to claim 1, characterized in that: Along the length direction of the pole piece, the size of the second area is B, wherein 2 mm ≤ B ≤ 8 mm; Along the width direction of the pole piece, the size of the second region is less than or equal to the width of the pole piece.

5. The electrode assembly according to claim 1, characterized in that: The surface of the third region is provided with a recessed portion; and / or, The circumscribed circle diameter of the recessed portion is D, wherein 30 μm≤D≤90 μm; and / or, Along the thickness direction of the pole piece, the size of the recessed portion is H3, wherein 1 μm≤H3≤3 μm.

6. The electrode assembly according to claim 1, characterized in that: It also includes a first surface, a second surface opposite to the first surface, and at least one second protective layer, one end of the second protective layer is fixed to the first surface, and the other end of the second protective layer is fixed to the second surface; The pole piece further comprises a first groove, and along the thickness direction of the electrode assembly, the projection of the second protective layer falls within the projection of the first groove; The first surface and the second surface are perpendicular to a thickness direction of the electrode assembly.

7. The electrode assembly according to claim 6, characterized in that: The first groove is provided with one, and along the thickness direction of the pole piece assembly, the size of the first groove is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm; or, There are multiple first grooves, and along the thickness direction of the pole piece assembly, the projections of the multiple first grooves overlap. The total size of the multiple first grooves is H4, and the size of the second protective layer is A2, wherein A2-H4=±5μm.

8. The electrode assembly according to claim 1, characterized in that: It also includes a first surface, a second surface opposite to the first surface, at least one third protective layer and a second groove, along the thickness direction of the electrode assembly, the projection of the third protective layer falls within the projection of the second groove, along the winding direction of the electrode assembly, the pole piece has a tail section, wherein, The end section is arranged on the first surface, and the third protective layer is fixed on the end section and the first surface; or, The end section is arranged on the second surface, and the third protective layer is fixed on the end section and the second surface.

9. The electrode assembly according to claim 8, characterized in that: Along the thickness direction of the pole piece, the size of the second groove is H5, and the size of the third protective layer is A3, wherein A3-H5=±5 μm.

10. The electrode assembly according to claim 1, characterized in that: Along the length direction of the pole piece, there is a gap between the first protective layer and the second region.

11. A battery, characterized in that: The electrode assembly comprises the electrode assembly according to any one of claims 1 to 10.

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