Electrode assembly and battery

Abstract

The present application provides an electrode assembly and a battery, wherein the electrode assembly includes at least two pole pieces stacked on each other and having opposite polarities, a diaphragm is arranged between each two adjacent pole pieces, the pole piece includes a current collector and an active material layer, and the active material layer covers two opposite surfaces of the current collector; one of the two adjacent pole pieces is provided with a groove, and in the pole piece provided with the groove, the notch of the groove is located on the surface of the active material layer away from the current collector, and the bottom wall of the groove is the current collector; the other of the two adjacent pole pieces is provided with an avoidance groove, and the avoidance groove is arranged opposite to the groove; the current collector in the groove is connected with a pole ear, and the projection of the avoidance groove on the pole piece with the groove completely covers the pole ear located in the groove. The avoidance groove can reduce the thickness increase caused by the pole ear, and therefore, the electrode assembly and the battery provided by the present application can reduce the thickness of the electrode assembly, so as to reduce the volume of the electrode assembly and improve the energy density of the battery.

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 large capacity, small size, light weight and green environmental protection, and have been widely used in industries such as digital electronic products and electric vehicles.

[0003] In the related art, the electrode assembly includes a pole piece, on which a pole ear is provided, and the pole piece is electrically connected to an external circuit structure through the pole ear.

[0004] However, the thickness of some areas of the electrode assembly is relatively large, resulting in a low energy density of the battery. Summary of the invention

[0005] In view of the above problems, embodiments of the present application provide an electrode assembly and a battery, which can reduce the thickness of a partial area of ​​the electrode assembly, thereby improving the energy density of the battery.

[0006] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0007] A first aspect of an embodiment of the present application provides an electrode assembly, comprising: at least two electrode sheets stacked on each other and having opposite polarities, a separator being disposed between each two adjacent electrode sheets, the electrode sheet comprising a current collector and an active material layer, the active material layer covering two opposite surfaces of the current collector;

[0008] One of the two adjacent pole pieces is provided with a groove, and in the pole piece provided with the groove, the notch of the groove is located on the surface of the active material layer away from the current collector, and the bottom wall of the groove is the current collector;

[0009] The other of the two adjacent pole pieces is provided with an avoidance groove, and the avoidance groove is arranged opposite to the groove;

[0010] The current collector in the groove is connected with a pole ear, and the projection of the avoidance groove on the pole piece with the groove completely covers the pole ear located in the groove.

[0011] The electrode assembly provided in the embodiment of the present application includes at least two electrode sheets stacked on each other and having opposite polarities, and a diaphragm is provided between each two adjacent electrode sheets to electrically isolate the two adjacent electrode sheets. A pole ear is provided on one of the electrode sheets, and a avoidance groove is provided on the other electrode sheet adjacent to the pole ear. The avoidance groove can reduce the thickness increase caused by the pole ear, thereby reducing the thickness of the electrode assembly, reducing the volume of the electrode assembly, and improving the energy density of the battery.

[0012] In a possible implementation, the at least two pole pieces include a first pole piece and a second pole piece with opposite polarities, the first pole piece includes a first current collector and a first active material layer, and the first active material layer is disposed on two opposite surfaces of the first current collector;

[0013] The groove includes a first groove, the avoidance groove includes a first avoidance groove, and the pole ear includes a first pole ear; the first groove is located in the first pole sheet, the notch of the first groove is located on the surface of the first active material layer away from the first current collector, the bottom wall of the first groove is the first current collector, and the first current collector in the first groove is connected to the first pole ear;

[0014] A second pole piece adjacent to the first pole piece is provided with a first avoidance groove, and the first avoidance groove is arranged opposite to the first groove;

[0015] The projection of the first avoidance groove on the first pole piece completely covers the first pole ear located in the first groove.

[0016] In a possible implementation, the second pole piece includes a second current collector and a second active material layer, and the second active material layer is disposed on two opposite surfaces of the second current collector;

[0017] The groove includes a second groove, the avoidance groove includes a second avoidance groove, and the pole ear includes a second pole ear; the second groove is located in the second pole sheet, the notch of the second groove is located on the surface of the second active material layer away from the second current collector, the bottom wall of the second groove is the second current collector, and the second current collector in the second groove is connected to the second pole ear;

[0018] The first pole piece adjacent to the second pole piece is provided with a second avoidance groove, and the second avoidance groove is arranged opposite to the second groove;

[0019] The projection of the second avoidance groove on the second pole piece completely covers the second pole ear located in the second groove.

[0020] In a possible implementation, a protective layer is disposed between the diaphragm adjacent to the pole tab and the pole tab, and the protective layer completely covers the groove.

[0021] In a possible implementation, an isolation layer is provided between the diaphragm adjacent to the avoidance groove and the avoidance groove, and the isolation layer completely covers the avoidance groove.

[0022] In a possible implementation, the thickness of the pole ear in the groove is equal to the groove depth of the groove, and part of the diaphragm, part of the protective layer and part of the isolation layer located between the avoidance groove and the groove are all inserted in the avoidance groove;

[0023] Alternatively, the thickness of the pole ear in the groove is greater than the groove depth of the groove, and part of the diaphragm, part of the protective layer, part of the isolation layer and part of the pole ear located between the avoidance groove and the groove are all inserted in the avoidance groove.

[0024] In a possible implementation, in a pole piece provided with a groove, the current collector is welded to the pole ear to form a weld mark, at least part of the weld mark is located on the surface of the pole ear facing away from the current collector, and bulges in a direction away from the current collector to form a first bulge;

[0025] The projection of the groove on the current collector, and the active material layer located on the side of the current collector away from the groove is within the projection of the current collector.

[0026] In a possible implementation, in a pole piece provided with a groove, a weld mark penetrates the pole ear along the thickness direction of the current collector, and the weld mark is located in a partial area close to the pole ear in the thickness direction of the current collector;

[0027] Or, in a pole piece provided with a groove, along the thickness direction of the current collector, the weld mark penetrates the pole ear and the current collector, the weld mark on the side of the current collector away from the pole ear bulges toward the side away from the pole ear to form a second bulge, and the active material layer on the side of the current collector away from the groove covers the second bulge;

[0028] Or, in a pole piece provided with a groove, the weld mark includes an outer edge portion and a middle portion, and the outer edge portion is arranged around the outside of the middle portion;

[0029] Along the thickness direction of the current collector, the middle portion penetrates the pole ear, and the middle portion is located in a partial area close to the pole ear in the thickness direction of the current collector;

[0030] Along the thickness direction of the current collector, the outer edge portion penetrates the electrode ear and the current collector, and the outer edge portion located on the side of the current collector away from the electrode ear protrudes toward the side away from the electrode ear to form a second protrusion, and the active material layer on the side of the current collector away from the groove covers the second protrusion.

[0031] In a possible implementation, in a pole piece provided with an avoidance groove:

[0032] The length of the avoidance groove along the first direction of the pole piece ranges from 1 mm to 40 mm;

[0033] And / or, the length of the avoidance groove along the second direction of the pole piece ranges from 1 mm to 30 mm;

[0034] and / or, along the second direction of the pole piece, the avoidance groove is located in the middle section of the pole piece, and the distance between the avoidance groove and the end of the pole piece is 1 / 4-3 / 4 of the length of the pole piece;

[0035] And / or, the groove depth of the avoidance groove ranges from 0.01 mm to 0.2 mm;

[0036] The first direction is perpendicular to the second direction.

[0037] In a possible implementation, in a pole piece provided with a groove:

[0038] The length of the groove along the first direction of the pole piece ranges from 1 mm to 40 mm;

[0039] And / or, the length of the groove along the second direction of the pole piece ranges from 1 mm to 30 mm;

[0040] and / or, along the second direction of the pole piece, the groove is located in the middle section of the pole piece, and the distance between the groove and the end of the pole piece is 1 / 3-2 / 3 of the length of the pole piece;

[0041] and / or, the distance between the electrode ear located in the groove and the active material layer located in the groove is in the range of 0.001 mm to 5 mm;

[0042] And / or, the thickness of the tab is in the range of 0.01 mm to 1 mm;

[0043] and / or, the groove depth ranges from 0.01 mm to 0.2 mm;

[0044] The first direction is perpendicular to the second direction.

[0045] A second aspect of an embodiment of the present application provides a battery, comprising the electrode assembly of the first aspect.

[0046] The battery provided in the embodiment of the present application includes an electrode assembly, the electrode assembly includes at least two pole pieces stacked on each other and having opposite polarities, and a diaphragm is provided between each two adjacent pole pieces to electrically isolate the two adjacent pole pieces. A pole ear is provided on one of the pole pieces, and a avoidance groove is provided on the other pole piece adjacent to the pole ear, and the avoidance groove can reduce the thickness increase caused by the pole ear, thereby reducing the thickness of the electrode assembly, reducing the volume of the electrode assembly, and improving the energy density of the battery.

[0047] The construction of the present application and its other inventive objectives and beneficial effects will be more clearly understood through the description of the preferred embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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 some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 A cross-sectional view of an electrode assembly provided in an embodiment of the present application;

[0050] Figure 2 A cross-sectional view of a pole piece provided in an embodiment of the present application;

[0051] Figure 3 A top view of a pole piece provided in an embodiment of the present application;

[0052] Figure 4 A top view of another pole piece provided in an embodiment of the present application;

[0053] Figure 5 A top view of another pole piece provided in an embodiment of the present application;

[0054] Figure 6 A cross-sectional view of another pole piece provided in an embodiment of the present application;

[0055] Figure 7 A cross-sectional view of another electrode assembly provided in an embodiment of the present application;

[0056] Figure 8 A cross-sectional view of another electrode assembly provided in an embodiment of the present application;

[0057] Fig. 9 for Figure 8 Schematic diagram of the enlarged structure of part C.

[0058] Description of reference numerals:

[0059] 1-Electrode assembly;

[0060] 100-pole piece;

[0061] 110- first pole piece;

[0062] 120- second pole piece;

[0063] 200-diaphragm;

[0064] 11-Current collector;

[0065] 12-active material layer;

[0066] 121-groove;

[0067] 1211-first groove;

[0068] 1212-second groove;

[0069] 20-ear;

[0070] 21- first pole lug;

[0071] 22- second pole lug;

[0072] 30- welding area;

[0073] 40-protective layer;

[0074] 41- first protective layer;

[0075] 42- second protective layer;

[0076] 50- auxiliary adhesive layer;

[0077] 60-avoidance slot;

[0078] 61-First avoidance slot;

[0079] 62-Second avoidance slot;

[0080] 70- isolation layer;

[0081] 71- first isolation layer;

[0082] 72 - Second isolation layer. DETAILED DESCRIPTION

[0083] The electrode assembly includes two pole pieces with opposite polarities, and a diaphragm is arranged between the two adjacent pole pieces to electrically isolate the two adjacent pole pieces. The pole pieces are connected with pole ears.

[0084] However, the pole lug has a certain thickness. In the area of ​​the pole piece where the pole lug is connected, the thickness of the pole piece increases due to the provision of the pole lug, thereby increasing the thickness of the electrode assembly, making the volume of the electrode assembly larger, and reducing the energy density of the battery.

[0085] In view of the above technical problems, the embodiments of the present application provide an electrode assembly and a battery, wherein the electrode assembly includes at least two electrode sheets stacked on each other and having opposite polarities, and a diaphragm is provided between each two adjacent electrode sheets to electrically isolate the two adjacent electrode sheets. A pole ear is provided on one of the electrode sheets, and a avoidance groove is provided on the other electrode sheet adjacent to the pole ear. The avoidance groove can reduce the thickness increase caused by the pole ear, thereby reducing the thickness of the electrode assembly, reducing the volume of the electrode assembly, and improving the energy density of the battery.

[0086] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are 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.

[0087] The present application embodiment provides a pole piece 100, such as Figure 1 and 2As shown, the pole piece 100 includes a current collector 11 and an active material layer 12, and the pole piece 100 can be a negative pole piece or a positive pole piece. It can be determined according to the specific selection of the materials of the current collector 11 and each active material layer 12. For example, when the current collector 11 is aluminum foil and the material of the active material layer 12 is a positive electrode active material such as a ternary material or lithium iron phosphate, the pole piece 100 is a positive pole piece; the active material layer 12 on the positive pole piece is a positive electrode active material layer. When the current collector 11 is copper foil and the material of the active material layer 12 is a negative electrode active material such as graphite or silicon-based, the pole piece 100 is a negative pole piece, and the active material layer 12 on the negative pole piece is a negative electrode active material layer.

[0088] The current collector 11 includes two surfaces arranged opposite to each other, and the active material layer 12 is arranged on the two surfaces respectively. The surface of the current collector 11 refers to the two largest and opposite surfaces of the current collector 11 for coating the active material layer 12. The active material layer 12 in the pole piece 100 of the present application can be coated on only one surface of the current collector 11, or on both surfaces of the current collector 11 at the same time.

[0089] like Figure 1 and Figure 2 As shown, a groove 121 is provided in the active material layer 12 on one surface of the electrode sheet, and the groove 121 exposes part of the surface of the current collector 11. The groove 121 can be formed by removing the corresponding part of the active material layer 12 by cleaning to expose the current collector 11. Since the active material layer 12 at the groove 121 is removed, the thickness of the electrode assembly can be reduced.

[0090] The cleaning method may be laser cleaning, mechanical cleaning or foam cleaning, etc. This application does not limit the cleaning method.

[0091] The electrode tab 20 is disposed in the groove 121, and the electrode tab 20 is electrically connected to the surface of the exposed current collector 11. The surface of the electrode tab 20 away from the current collector 11 is covered with a protective layer 40, which can prevent the welding burrs formed by the electrode tab 20 and the current collector 11 from piercing the film layer outside the electrode sheet 100, thereby affecting the performance or safety of the battery. The protective layer 40 can completely cover the groove 121.

[0092] The active material layer 12 on the side of the current collector 11 facing away from the pole ear 20 that is opposite to the groove 121 is not removed but retained. At this time, the projection of the groove 121 on the current collector 11 is located within the projection of the active material layer 12 on the side of the current collector 11 away from the pole ear 20. That is, the active material layer 12 on the back of the groove 121 is not removed, the exposed area of ​​the current collector 11 is small, and the activity of the pole piece 100 is high.

[0093] In some embodiments, such as Figure 3As shown, the electrode tab 20 and the current collector 11 form a welding area 30 at the connection, and the welding area 30 may have multiple weld marks, and the multiple weld marks are arranged at intervals. The energy input to form a single weld mark is small, which can reduce the impact on the active material layer 12 near the welding area 30.

[0094] For example, the electrode tab 20 and the current collector 11 may be connected by laser welding, and the laser is irradiated from a side of the electrode tab 20 away from the current collector 11 to perform welding.

[0095] In some embodiments, the thickness of the protective layer 40 may range from 0.001 mm to 0.1 mm. For example, the thickness of the protective layer 40 may be 0.001 mm, 0.005 mm, 0.01 mm, 0.012 mm, 0.05 mm, or 0.1 mm. When the thickness of the protective layer 40 is less than this range, the protective layer 40 is thinner and the protective effect of the protective layer 40 is poorer. When the thickness of the protective layer 40 is greater than this range, the protective layer 40 is thicker and will occupy more internal space of the battery.

[0096] In some embodiments, such as Figure 4 As shown, the tab 20 in the groove 121 is spaced apart from the active material layer 12 in the groove 121. There is a space between the edge of the tab 20 and the notch edge of the groove 121 to prevent the tab 20 from affecting the active material layer 12 in the groove 121 during the connection process.

[0097] Specifically, Figure 4 As shown, the distance between the tab 20 located in the groove 121 and the active material layer 12 located at the groove 121 is L1, and the range of the distance L1 can be 0.001mm-5mm. For example, the distance L1 can be 0.001mm, 0.01mm, 0.05mm, 0.1mm, 0.5mm, 1mm, 3mm or 5mm, etc. This can avoid L1 being too small, causing the tab 20 to easily affect the active material layer 12 at the groove 121 during the welding process. It can also avoid L1 being too large, requiring more active material layer 12 to be cleaned, which affects the energy density of the battery.

[0098] In some embodiments, the thickness of the current collector 11 may range from 0.001 mm to 0.02 mm. For example, the thickness of the current collector 11 may be 0.001 mm, 0.003 mm, 0.006 mm, 0.01 mm, 0.013 mm, 0.016 mm or 0.02 mm, etc., and the present application does not limit this.

[0099] It should be noted that if Figure 4As shown, the width direction of the pole piece 100 can be a first direction, that is, the direction shown by Y in the figure; the length direction of the pole piece 100 can be a second direction, that is, the direction shown by X in the figure; the first direction and the second direction can be perpendicular to each other. The thickness direction of the pole piece 100 can be consistent with the thickness direction of the pole ear 20, the electrode assembly 1 and the battery. The width direction and the length direction in the embodiment of the present application are only for the convenience of description and do not mean any size limitation. For example, the width may be greater than, less than or equal to the length.

[0100] In some embodiments, the groove 121 may be located in the middle of the length direction (i.e., the second direction X) of the current collector 11, and the forces exerted on the groove 121 by the two ends of the pole piece 100 are relatively consistent and balanced. If the groove 121 is disposed at the end of the pole piece 100, the forces exerted on the groove 121 by the two ends of the pole piece 100 are uneven, causing the active material layer 12 at the groove 121 to easily fall off.

[0101] Specifically, Figure 4 As shown, the distance between the groove 121 and the end of the current collector 11 in the length direction is L2, the length of the current collector 11 is L3, and the ratio of L2 / L3 can range from 1 / 3 to 2 / 3. For example, the ratio of L2 / L3 can be 1 / 3, 2 / 4, 3 / 5 or 2 / 3, etc., so as to avoid L2 / L3 being too small or too large, and the groove 121 being subjected to uneven force from both ends of the pole piece 100.

[0102] In some embodiments, the depth of the groove 121 ranges from 0.01 mm to 0.2 mm. For example, the depth of the groove 121 may be 0.01 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.07 mm, 0.1 mm or 0.2 mm. This can prevent the active material layer 12 from being too thin, resulting in a low energy density of the battery. It can also prevent the active material layer 12 from being too thick, resulting in the active material layer 12 near the surface of the current collector 11 not being utilized, and the utilization rate of the active material in the active material layer 12 being low.

[0103] like Figure 4 As shown, the length of the groove 121 along the first direction Y of the pole piece 100 is L4, and the range of L4 can be 1mm-40mm. For example, L4 can be 1mm, 2mm, 5mm, 10mm, 15mm, 20mm, 30mm or 40mm. This can avoid L4 being too small, resulting in a small connectable area between the pole ear 20 and the current collector 11. It can also avoid L4 being too large, resulting in more removal of the active material layer 12, which has a greater impact on the energy density of the battery.

[0104] like Figure 4As shown, the length of the groove 121 along the second direction X of the pole piece 100 is L5, and the length L5 may range from 1 mm to 30 mm. For example, L5 may be 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm or 30 mm, etc. The principle is similar to that of the length value L4, and will not be repeated here.

[0105] The thickness of the tab 20 may range from 0.01 mm to 1 mm. For example, the thickness of the tab 20 may be 0.01 mm, 0.03 mm, 0.05 mm, 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm or 1 mm. This can prevent the tab 20 from being too thin, which may result in a larger resistance of the tab 20 and a poorer current carrying capacity of the tab 20. It can also prevent the tab 20 from being too thick, which may occupy more internal space of the battery.

[0106] The length of the tab 20 along the first direction Y may range from 5 mm to 200 mm. For example, the length of the tab 20 along the first direction Y is 5 mm, 10 mm, 20 mm, 25 mm, 50 mm, 75 mm, 100 mm, 150 mm or 200 mm, etc. This can prevent the tab 20 from being too short, resulting in a smaller area for connection between the tab 20 and the current collector 11 and lower connection strength. It can also prevent the tab 20 from being too long, which will occupy more internal space of the battery.

[0107] The length of the tab 20 along the second direction X may range from 1 mm to 20 mm. For example, the length of the tab 20 along the second direction X is 1 mm, 5 mm, 6 mm, 10 mm, 15 mm or 20 mm. This can prevent the tab 20 from being too narrow, resulting in a smaller area for connection between the tab 20 and the current collector 11 and lower connection strength. It can also prevent the tab 20 from being too wide, which will occupy more internal space of the battery.

[0108] like Figure 3 As shown, an auxiliary adhesive layer 50 may be further provided on the pole piece 100, and the pole tab 20 is inserted in the auxiliary adhesive layer 50. After the pole piece 100 forms the electrode assembly 1, the outside of the electrode assembly 1 may be wrapped with a plastic shell to protect the electrode assembly 1. The auxiliary adhesive layer 50 may be used to seal (using hot melt sealing) the gap between the pole tab 20 and the plastic shell.

[0109] The electrode assembly 1 provided in the embodiment of the present application will be described in detail below with reference to the accompanying drawings.

[0110] The electrode assembly 1 provided in the embodiment of the present application is as follows Figure 1 and Figure 7As shown, the electrode assembly 1 can be applied to a battery. The electrode assembly 1 may include at least two pole pieces 100 stacked on each other and having opposite polarities, and the pole pieces 100 with opposite polarities respectively form the positive pole piece and the negative pole piece of the battery. In order to avoid contact short circuit between the positive and negative pole pieces, a diaphragm 200 is provided between each two adjacent pole pieces 100, and the pole pieces 100 with opposite polarities are electrically isolated by the diaphragm 200. At least one of the pole pieces 100 may be the pole piece 100 in the above-mentioned embodiment.

[0111] In this embodiment, one of the two adjacent pole pieces 100 is the pole piece 100 in the above embodiment, that is, the groove 121 in the above embodiment is provided in one of the two adjacent pole pieces 100. The other of the two adjacent pole pieces 100 is provided with an avoidance groove 60, and the avoidance groove 60 and the groove 121 are arranged opposite to each other along the thickness direction of the electrode assembly 1.

[0112] The avoidance groove 60 and the notch of the groove 121 may be arranged to face each other, or the avoidance groove 60 and the notch of the groove 121 may be arranged to face each other.

[0113] It can be realized that the groove 121 can be close to the edge of the electrode 100 in the width direction, and the side of the groove 121 close to the edge is open. That is, there is no active material layer 12 on the outer side of the groove 121 close to the edge, and the active material layer 12 is provided on the outer side of the groove 121 away from the edge. Along the width direction of the electrode 100, the length of the groove 121 is less than the length of the current collector 11.

[0114] The projection of the avoidance groove 60 on the pole piece 100 having the groove 121 completely covers the pole ear 20 located in the groove 121. That is, the portion of the pole ear 20 located in the groove 121 is smaller than the avoidance groove 60, and the avoidance groove 60 can play a better avoidance role for the pole ear 20, reduce the thickness increase of the pole ear 20 on the electrode assembly 1, thereby reducing the volume of the electrode assembly 1 and improving the energy density of the battery.

[0115] The avoidance groove 60 can be formed by removing the corresponding portion of the active material layer 12 through cleaning to expose the current collector 11. Since the active material layer 12 at the avoidance groove 60 is removed, the thickness of the electrode assembly 1 at the corresponding portion of the avoidance groove 60 can be reduced. The cleaning method can be laser cleaning, mechanical cleaning, or foam cleaning, and the present application does not limit the cleaning method.

[0116] In some embodiments, in a pole piece provided with an avoidance groove 60 , the avoidance groove 60 may be located in the middle section of the pole piece 100 in the length direction, and the active material layer 12 at the avoidance groove 60 is subjected to a relatively consistent and balanced force from both ends of the pole piece 100 .

[0117] like Figure 4-Figure 6As shown, the distance between the avoidance groove 60 and the end of the pole piece 100 in the length direction is L6, the length of the pole piece 100 is L3, and the ratio of L6 / L3 can range from 1 / 4 to 3 / 4. For example, the ratio of L6 / L3 can be 1 / 4, 2 / 5, 1 / 2, 3 / 5 or 3 / 4. When the ratio of L6 / L3 is within this range, the avoidance groove 60 is subjected to a relatively uniform force from both ends of the pole piece 100. In addition, as Figure 7 As shown in the dotted box B, when the ratio of L6 / L3 is within this range, the groove 121 and the avoidance groove 60 in the dotted box B can easily meet the relative setting requirements.

[0118] In some embodiments, the depth of the avoidance groove 60 ranges from 0.01 mm to 0.2 mm. For example, the depth of the avoidance groove 60 can be 0.01 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.07 mm, 0.1 mm or 0.2 mm. The depth principle is similar to that of the groove 121 and will not be described in detail.

[0119] like Figure 4 and Figure 5 As shown, the length of the avoidance groove 60 along the first direction Y of the pole piece 100 is in the range of 1mm-40mm. For example, the length of the avoidance groove 60 along the first direction Y of the pole piece 100 can be 1mm, 2mm, 5mm, 10mm, 15mm, 20mm, 30mm or 40mm, etc., so as to avoid the avoidance groove 60 being unable to avoid the pole ear 20 well due to the length being too small. It can also avoid the avoidance groove 60 being too large, resulting in low activity of the pole piece 100.

[0120] The length of the avoidance groove 60 along the second direction X of the pole piece 100 ranges from 1 mm to 30 mm. For example, the length of the avoidance groove 60 along the second direction X of the pole piece 100 may be 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, 25 mm or 30 mm, etc. The principle is similar to the length of the avoidance groove 60 along the first direction Y of the pole piece 100, and will not be repeated.

[0121] In some embodiments, such as Figure 7 As shown, a protective layer 40 is disposed between the diaphragm 200 adjacent to the pole ear 20 and the pole ear, and the protective layer 40 completely covers the groove 121 to prevent the groove 121 from affecting the adjacent diaphragm 200. The protective layer 40 may be disposed on the surface of the pole ear 20 facing the diaphragm 200, or the protective layer 40 may be disposed on the surface of the diaphragm 200 facing the pole ear 20.

[0122] In some embodiments, continue as Figure 7As shown, an isolation layer 70 is disposed between the diaphragm 200 adjacent to the avoidance groove 60 and the avoidance groove 60, and the isolation layer 70 completely covers the avoidance groove 60 to prevent the avoidance groove 60 from affecting the adjacent diaphragm 200. The isolation layer 70 may be disposed on the surface of the avoidance groove 60 facing the diaphragm 200, or the isolation layer 70 may be disposed on the surface of the diaphragm 200 facing the avoidance groove 60.

[0123] In some embodiments, the thickness of the isolation layer 70 may range from 0.001 mm to 0.1 mm. For example, the thickness of the isolation layer 70 may be 0.001 mm, 0.005 mm, 0.01 mm, 0.012 mm, 0.05 mm or 0.1 mm, etc. The principle is similar to the thickness of the protective layer 40 and will not be described in detail.

[0124] like Figure 7 As shown in the dotted box B, when the thickness of the pole ear 20 in the groove 121 is equal to the groove depth of the groove 121, part of the diaphragm 200, part of the protective layer 40 and part of the isolation layer 70 between the avoidance groove 60 and the groove 121 are all squeezed into the avoidance groove 60 by the pole ear 20. In this way, the thickness of the electrode assembly 1 is prevented from increasing due to the provision of the pole ear 20, and the energy density of the battery is guaranteed.

[0125] In other examples, such as Figure 7 As shown in the dotted box B, when the thickness of the pole ear 20 in the groove 121 is greater than the depth of the groove 121, part of the diaphragm 200, part of the protective layer 40, and part of the isolation layer 70 between the relatively arranged avoidance groove 60 and the groove 121 all enter the avoidance groove 60 under the extrusion of the pole ear 20. In addition, part of the pole ear 20 protrudes from the groove 121 and is located in the avoidance groove 60. In this way, the thickness of the electrode assembly 1 is prevented from increasing due to the provision of the pole ear 20. In addition, due to the presence of the avoidance groove 60, the pole ear 20 can be set thicker, thereby reducing the resistance of the pole ear 20 and improving the current capacity of the pole ear 20.

[0126] In some embodiments, in a pole piece 100 provided with a groove 121, the current collector 11 is welded to the pole ear 20 to form a weld mark, at least part of the weld mark is located on the surface of the pole ear 20 facing away from the current collector 11, and protrudes in a direction away from the current collector 11 to form a first protrusion, the projection of the groove 121 on the current collector 11, and the active material layer 12 located on the side of the current collector 11 facing away from the groove 121 is within the projection of the current collector 11.

[0127] In some examples, in the pole piece 100 provided with the groove 121, the weld mark penetrates the pole ear 20 along the thickness direction of the current collector 11, and the weld mark is located in a partial area close to the pole ear 20 in the thickness direction of the current collector 11. At this time, the weld mark is formed on the side of the pole ear 20 away from the current collector 11, while the surface of the current collector 11 away from the pole ear 20 does not form the weld mark, and the surface of the current collector 11 away from the pole ear 20 is a plane. In this way, the weld mark has little effect on the active material layer 12 on the side of the current collector 11 away from the pole ear 20.

[0128] In other examples, in the pole piece 100 provided with the groove 121, the weld mark penetrates the pole ear 20 and the current collector 11 along the thickness direction of the current collector 11. At this time, the weld mark can be observed on the surface of the pole ear 20 facing away from the current collector 11, and on the surface of the current collector 11 facing away from the pole ear 20. Among them, the weld mark on the side of the current collector 11 facing away from the pole ear 20 is covered by the active material layer 12, which can reduce the influence of the weld mark on the diaphragm on this side. The weld mark on the side of the current collector 11 facing away from the pole ear 20 bulges toward the side facing away from the pole ear 20, thereby forming a second bulge.

[0129] In some other examples, in a pole piece 100 provided with a groove 121, in one weld mark, part of the weld mark passes through the pole ear 20 and the current collector 11; another part of the weld mark passes through the pole ear 20 and is located in a partial area close to the pole ear 20 in the thickness direction of the current collector 11. For example, the weld mark includes an outer edge portion and a middle portion, and the outer edge portion is arranged on the outside of the middle portion. Along the thickness direction of the current collector 11, the outer edge portion passes through the pole ear 20 and the current collector 11, and the outer edge portion located on the side of the current collector 11 away from the pole ear 20 bulges toward the side away from the pole ear 20. At this time, the outer edge portion of the weld mark can be observed on the surface of the current collector 11 away from the pole ear 20. The outer edge portion located on the side of the current collector 11 away from the pole ear 20 bulges toward the side away from the pole ear 20, thereby forming a second bulge. Among them, the outer edge portion located on the side of the current collector 11 away from the pole ear 20 is covered by the active material layer 12, which can reduce the influence of the outer edge portion on the diaphragm on that side.

[0130] The middle portion passes through the tab 20 along the thickness direction of the current collector 11, and is located in a partial area close to the tab 20 in the thickness direction of the current collector 11. At this time, the middle portion of the weld mark cannot be observed on the surface of the current collector 11 away from the tab 20.

[0131] In a specific implementation, at least two pole pieces 100 may include a first pole piece 110 and a second pole piece 120, and the first pole piece 110 and the second pole piece 120 have opposite polarities. One of the first pole piece 110 and the second pole piece 120 is used to form a positive pole piece, and the other of the first pole piece 110 and the second pole piece 120 is used to form a negative pole piece.

[0132] The first pole piece 110 and the second pole piece 120 are stacked on each other. In order to avoid short circuit between the first pole piece 110 and the second pole piece 120 , a diaphragm 200 is disposed between adjacent first pole pieces 110 and second pole pieces 120 , and the diaphragm 200 is used to electrically insulate the first pole piece 110 and the second pole piece 120 .

[0133] In some examples, the electrode assembly 1 may be a wound electrode assembly 1. The first electrode sheet 110 and the second electrode sheet 120 are both one, and the first electrode sheet 110, the separator 200 and the second electrode sheet 120 stacked in sequence are wound around a winding center to form a winding structure.

[0134] In some other examples, the electrode assembly 1 may be a laminated electrode assembly 1. There are multiple first pole pieces 110 and multiple second pole pieces 120, and the multiple first pole pieces 110 and the multiple second pole pieces 120 are alternately stacked in the same direction, and a diaphragm 200 is provided between each adjacent first pole piece 110 and second pole piece 120 to electrically insulate the first pole piece 110 and the second pole piece 120.

[0135] The embodiment of the present application is described in detail by taking a wound electrode assembly 1 as an example.

[0136] In some embodiments, such as Figure 8 and Fig. 9 As shown, in some examples, the first electrode sheet 110 includes a first current collector and a first active material layer, and the first active material layer is disposed on two opposite surfaces of the first current collector.

[0137] In some examples, the second electrode sheet 120 includes a second current collector and a second active material layer, and the second active material layer is disposed on two opposite surfaces of the second current collector.

[0138] In some other examples, the groove 121 may include a first groove 1211 , the avoidance groove 60 may include a first avoidance groove 61 , and the pole tab 20 may include a first pole tab 21 .

[0139] In some other examples, the groove 121 includes a second groove 1212 , the avoidance groove 60 includes a second avoidance groove 62 , and the pole tab 20 includes a second pole tab 22 .

[0140] The first pole piece 110 is provided with a first groove 1211, and the first groove 1211 exposes the surface of the first current collector. The notch of the first groove 1211 is located on the surface of the first active material layer away from the first current collector, and the bottom wall of the first groove 1211 is the first current collector. The current collector 11 in the first groove 1211 is connected to the first pole ear 21. Among them, the second pole piece 120 adjacent to the first pole piece 110 is provided with a first avoidance groove 61, and the first avoidance groove 61 is located in the second active material layer of the second pole piece 120 close to the first groove 1211. The first avoidance groove 61 and the first groove 1211 are arranged opposite to each other along the thickness direction of the electrode assembly 1. The first avoidance groove 61 can reduce the thickness of part of the electrode assembly 1 to ensure the energy density of the battery.

[0141] The projection of the first avoidance groove 61 on the first pole piece 110 completely covers the first pole tab 21 located in the first groove 1211 , thereby forming a better avoidance effect for the first pole tab 21 .

[0142] In the first pole piece 110, a first protective layer 41 is provided on the side of the first pole tab 21 away from the first current collector, thereby protecting the adjacent separator 200. The first protective layer 41 may be located on the surface of the first pole tab 21 away from the first current collector, or the first protective layer 41 may be located on the surface of the separator 200 adjacent to the first pole tab 21 facing the first pole tab 21.

[0143] The first protection layer 41 completely covers the first groove 1211 .

[0144] A first isolation layer 71 is provided between the diaphragm 200 adjacent to the first avoidance groove 61 and the first avoidance groove 61, thereby protecting the adjacent diaphragm 200. The first isolation layer 71 may be located on the surface of the first avoidance groove 61 facing the first groove 1211, or the first isolation layer 71 may be located on the surface of the diaphragm 200 adjacent to the first avoidance groove 61 close to the first avoidance groove 61.

[0145] The first isolation layer 71 completely covers the first avoiding groove 61 .

[0146] In some embodiments, such as Figure 8As shown, a second groove 1212 is provided on the second pole piece 120, and the second groove 1212 exposes the surface of the second current collector. The notch of the second groove 1212 is located on the surface of the second active material layer away from the second current collector, and the bottom wall of the second groove 1212 is the second current collector. The second current collector in the second groove 1212 is connected to the second pole ear 22. Among them, a second avoidance groove 62 is provided in the first pole piece 110 adjacent to the second pole piece 120, and the second avoidance groove 62 is located in the first active material layer of the first pole piece 110 near the second groove 1212, and the second avoidance groove 62 and the second groove 1212 are arranged opposite to each other along the thickness direction of the electrode assembly 1. The second avoidance groove 62 can reduce the thickness of part of the electrode assembly 1 to ensure the energy density of the battery.

[0147] The projection of the second avoidance groove 62 on the second pole piece 120 completely covers the second pole tab 22 located in the second groove 1212 , thereby forming a better avoidance effect for the second pole tab 22 .

[0148] In the second pole piece 120, a second protective layer 42 is provided on the side of the second pole tab 22 facing away from the second current collector, thereby protecting the adjacent separator 200. The second protective layer 42 may be located on the surface of the second pole tab 22 facing away from the second current collector, or the second protective layer 42 may be located on the surface of the separator 200 adjacent to the second pole tab 22 facing the second pole tab 22.

[0149] The second protection layer 42 completely covers the second groove 1212 .

[0150] A second isolation layer 72 is provided between the diaphragm 200 adjacent to the second avoidance groove 62 and the second avoidance groove 62, thereby protecting the adjacent diaphragm 200. The second isolation layer 72 may be located on the surface of the second avoidance groove 62 facing the second groove 1212, or the second isolation layer 72 may be located on the surface of the diaphragm 200 adjacent to the second avoidance groove 62 close to the second avoidance groove 62.

[0151] The second isolation layer 72 completely covers the second avoiding groove 62 .

[0152] It should be noted that, in the embodiment of the present application, the first groove 1211 may be provided only on the first pole piece 110, or the second groove 1212 may be provided only on the second pole piece 120, or the first groove 1211 may be provided on the first pole piece 110 and the second groove 1212 may be provided on the second pole piece 120. The embodiment of the present application does not limit the arrangement of the first groove 1211 and the second groove 1212.

[0153] In addition, the first avoidance groove 61 may be provided only on the second pole piece 120; or, the second avoidance groove 62 may be provided only on the first pole piece 110; or, the first avoidance groove 61 may be provided on the second pole piece 120, and the second avoidance groove 62 may be provided on the first pole piece 110. The embodiment of the present application does not limit the arrangement of the first avoidance groove 61 and the second avoidance groove 62.

[0154] In addition, an embodiment of the present application further provides a battery, which includes the electrode assembly 1 in the above embodiment.

[0155] It should be noted here that the numerical values ​​and numerical ranges involved in the embodiments of the present application are approximate values. Due to the influence of the manufacturing process, there may be a certain range of errors, which can be considered negligible by those skilled in the art.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrode assembly, characterized in that: include: At least two pole pieces stacked on each other and having opposite polarities, a diaphragm is arranged between each two adjacent pole pieces, the pole piece comprises a current collector and an active material layer, and the active material layer covers two opposite surfaces of the current collector; One of the two adjacent pole pieces is provided with a groove, and in the pole piece provided with the groove, the notch of the groove is located on the surface of the active material layer away from the current collector, and the bottom wall of the groove is the current collector; The other of the two adjacent pole pieces is provided with an avoidance groove, and the avoidance groove is arranged opposite to the groove; The current collector in the groove is connected to a pole lug, and the projection of the avoidance groove on the pole piece having the groove completely covers the pole lug in the groove; In the pole piece provided with the groove, the current collector is welded to the pole ear to form a plurality of weld marks, the plurality of weld marks are arranged at intervals, at least part of the weld marks are located on the surface of the pole ear away from the current collector, and protrude in a direction away from the current collector to form a first protrusion; The projection of the groove on the current collector, the active material layer located on the side of the current collector away from the groove is within the projection of the current collector; In the pole piece provided with the groove, the weld mark includes an outer edge portion and a middle portion, the outer edge portion is arranged on the outside of the middle portion; along the thickness direction of the current collector, the middle portion passes through the pole ear, and the middle portion is located in a partial area close to the pole ear in the thickness direction of the current collector; along the thickness direction of the current collector, the outer edge portion passes through the pole ear and the current collector, and the outer edge portion located on the side of the current collector away from the pole ear protrudes toward the side away from the pole ear to form a second protrusion, and the active material layer on the side of the current collector away from the groove covers the second protrusion.

2. The electrode assembly according to claim 1, characterized in that: At least two of the pole pieces include a first pole piece and a second pole piece with opposite polarities, the first pole piece includes a first current collector and a first active material layer, and the first active material layer is arranged on two opposite surfaces of the first current collector; The groove includes a first groove, the avoidance groove includes a first avoidance groove, and the pole ear includes a first pole ear; the first groove is located in the first pole sheet, the notch of the first groove is located on the surface of the first active material layer away from the first current collector, the bottom wall of the first groove is the first current collector, and the first current collector in the first groove is connected to the first pole ear; The second pole piece adjacent to the first pole piece is provided with the first avoidance groove, and the first avoidance groove is arranged opposite to the first groove; The projection of the first avoidance groove on the first pole piece completely covers the first pole ear located in the first groove.

3. The electrode assembly according to claim 2, characterized in that: The second pole piece includes a second current collector and a second active material layer, and the second active material layer is arranged on two opposite surfaces of the second current collector; The groove includes a second groove, the avoidance groove includes a second avoidance groove, and the pole ear includes a second pole ear; the second groove is located in the second pole sheet, the notch of the second groove is located on the surface of the second active material layer away from the second current collector, the bottom wall of the second groove is the second current collector, and the second current collector in the second groove is connected to the second pole ear; The first pole piece adjacent to the second pole piece is provided with the second avoidance groove, and the second avoidance groove is arranged opposite to the second groove; The projection of the second avoidance groove on the second pole piece completely covers the second pole ear located in the second groove.

4. The electrode assembly according to any one of claims 1 to 3, characterized in that: A protective layer is arranged between the diaphragm adjacent to the pole lug and the pole lug, and the protective layer completely covers the groove.

5. The electrode assembly according to claim 4, characterized in that: An isolation layer is arranged between the diaphragm adjacent to the avoidance groove and the avoidance groove, and the isolation layer completely covers the avoidance groove.

6. The electrode assembly according to claim 5, characterized in that: The thickness of the pole ear in the groove is equal to the groove depth of the groove, and part of the diaphragm, part of the protective layer and part of the isolation layer located between the avoidance groove and the groove are all inserted in the avoidance groove; Alternatively, the thickness of the pole lug in the groove is greater than the groove depth of the groove, and part of the diaphragm, part of the protective layer, part of the isolation layer and part of the pole lug located between the avoidance groove and the groove are all inserted into the avoidance groove.

7. The electrode assembly according to any one of claims 1 to 3, characterized in that: In the pole piece provided with the avoidance groove: The length of the avoidance groove along the first direction of the pole piece ranges from 1 mm to 40 mm; And / or, the length of the avoidance groove along the second direction of the pole piece ranges from 1 mm to 30 mm; And / or, along the second direction of the pole piece, the avoidance groove is located in the middle section of the pole piece, and the distance between the avoidance groove and the end of the pole piece is 1 / 4-3 / 4 of the length of the pole piece; And / or, the groove depth of the avoidance groove ranges from 0.01 mm to 0.2 mm; The first direction is perpendicular to the second direction.

8. The electrode assembly according to any one of claims 1 to 3, characterized in that: In the pole piece provided with the groove: The length of the groove along the first direction of the pole piece ranges from 1 mm to 40 mm; And / or, the length of the groove along the second direction of the pole piece ranges from 1 mm to 30 mm; And / or, along the second direction of the pole piece, the groove is located in the middle section of the pole piece, and the distance between the groove and the end of the pole piece is 1 / 3-2 / 3 of the length of the pole piece; And / or, the distance between the electrode ear located in the groove and the active material layer located in the groove is in the range of 0.001 mm to 5 mm; And / or, the thickness of the tab is in the range of 0.01 mm to 1 mm; And / or, the groove depth of the groove ranges from 0.01 mm to 0.2 mm; The first direction is perpendicular to the second direction.

9. A battery, characterized in that: The electrode assembly comprises any one of claims 1 to 8.

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