Pole piece and battery cell

Abstract

The utility model provides a pole piece and a battery cell, the pole piece comprises a current collector and an active substance layer arranged on the surface of at least one side of the current collector, the pole piece comprises a single-sided area, the active substance layer is arranged on one side of the current collector located in the single-sided area, and the active substance layer located in the single-sided area is provided with a groove. According to the present invention, the grooves are formed in the active material layer of the single-sided region, such that the bending degree of the single-sided region of the pole piece can be alleviated, and the adhesion between the single-sided region of the pole piece and the diaphragm can be improved when the pole piece is assembled into the battery cell so as to shorten the lithium ion transmission path of the battery cell during the charging and discharging process, and solve the problems of lithium precipitation, black spots and the like.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a pole piece and a battery cell. Background Art

[0002] Lithium-ion batteries have become the main power source for consumer electronics and electric vehicles due to their many advantages. With people's growing demand, lithium-ion batteries are gradually developing towards fast charging, long life, high energy density and high safety.

[0003] In order to increase the energy density of lithium-ion batteries, the compaction density of the pole piece is usually increased. Since the two sides of the single-sided area of ​​the battery pole piece are subjected to different stresses, the pole piece bends toward the side where the active material layer is not set. The greater the compaction density, the greater the bending of the pole piece. When the pole piece is assembled into a battery cell, the greater the bending of the pole piece, the worse the adhesion between the pole piece and the diaphragm, and a gap will be generated between the two, causing the transmission path of lithium ions to become longer during the charge and discharge process of the battery cell, which is prone to lithium precipitation, black spots and other problems. Summary of the invention

[0004] In view of this, the present application provides a pole piece, which solves the problems of large bending of the pole piece and poor adhesion between the pole piece and the diaphragm. The present application also provides a battery cell including the pole piece.

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

[0006] A pole piece, comprising a current collector and an active material layer arranged on at least one side of the current collector, wherein the pole piece comprises a single-sided area, and the active material layer is arranged on one side of the current collector located in the single-sided area.

[0007] The active material layer located in the single-side area is provided with a groove.

[0008] Optionally, the area of ​​the region where the groove is set in the active material layer in the single-sided area is S1, and the area of ​​the active material layer in the single-sided area is S2, wherein S1 and S2 satisfy: S1 = (0.05-0.7) * S2.

[0009] Optional,

[0010] In a direction perpendicular to the active material layer, the depth of the groove is L, wherein 3 μm≤L≤2000 μm; and / or,

[0011] The outer diameter of the notch of the groove is D, wherein 0.2 mm≤D≤5 mm.

[0012] Optionally, the depth of the groove in a direction perpendicular to the active material layer is L, and the bending radius of the pole piece is R, wherein L and R satisfy: L:R≥0.005.

[0013] Optionally, a protrusion is provided on a side of the current collector in the single-sided area facing away from the active material layer, and a protruding direction of the protrusion is the same as a recessed direction of the groove.

[0014] Optionally, the protrusion height of the protrusion is the same as the recessed depth of the groove.

[0015] Optionally, at least two protrusions are provided, and a recessed portion is formed between adjacent protrusions.

[0016] Optionally, in a direction perpendicular to the active material layer,

[0017] The depth of the protrusion is M, wherein 2 μm≤M≤1700 μm; and / or,

[0018] The depth of the recessed portion is N, wherein 0.05 mm≤N≤1.5 mm.

[0019] Optionally, the bottom of the groove is a plane or an arc-shaped surface, and / or

[0020] The side wall of the groove is a plane or an arc surface.

[0021] Optionally, the grooves are provided with at least two, and / or

[0022] The notch of the groove is at least one of a circular shape, a polygonal shape and an elliptical shape.

[0023] A battery cell comprises a negative electrode sheet, a positive electrode sheet and a separator arranged between the negative electrode sheet and the positive electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is any one of the electrode sheets described above.

[0024] Optionally, adhesive tape is provided on both sides of the battery cell in the first direction, and the adhesive tape at least covers a portion of the protrusions in the single-sided area.

[0025] Optionally, the single-sided area is located on the outside of the battery cell, and the groove of the single-sided area is recessed in a direction away from the center of the battery cell.

[0026] Optionally, the battery cell further includes a negative electrode lug connected to the negative electrode sheet and a positive electrode lug connected to the positive electrode sheet, and in the second direction, the groove in the single-sided area overlaps with at least one of the positive electrode lug and the negative electrode lug.

[0027] Optionally, the groove of the single-sided area and the folded section of the diaphragm at least partially overlap.

[0028] Optionally, the battery cell is a wound battery cell, and the groove in the single-sided area of ​​the positive electrode sheet exceeds the end of the active material layer of the negative electrode sheet.

[0029] Optionally, the peeling force between the active material layer and the separator in the single-sided area with the groove is F1, and the peeling force between the active material layer and the separator without the groove is F2, wherein F1 and F2 satisfy: F1>F2.

[0030] Optionally, F1 and F2 satisfy: F1 = (1.1-5) * F2.

[0031] Optionally, the battery cell is a wound battery cell, and the groove is located in a straight section and / or an arc section of the wound battery cell.

[0032] The pole piece provided in the present application has a groove in the active material layer on a single side area, which can alleviate the bending degree of the single side area of ​​the pole piece, thereby improving the adhesion between the single side area of ​​the pole piece and the diaphragm when the pole piece is assembled into a battery cell, thereby shortening the transmission path of lithium ions in the battery cell during the charge and discharge process, and alleviating problems such as lithium plating and black spots. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 A front view of a pole piece provided by the prior art;

[0035] Figure 2 A front view of the pole piece provided in this embodiment;

[0036] Figure 3 It is a top view of the pole piece;

[0037] Figure 4 for Figure 2 A partial enlarged view of

[0038] Figure 5 A top view of the pole piece after the groove is set;

[0039] Figure 6 A partial enlarged view of the protrusions provided on the pole piece;

[0040] Figure 7 It is a front view of the battery cell;

[0041] Figure 8 This is a schematic diagram of 3D depth synthesis at the groove;

[0042] Fig. 9 It is a line graph between the capacity ratio and the number of cycles of the experimental group and the control group;

[0043] Fig.10 It is a line graph between thickness expansion and cycle number for the experimental group and the control group.

[0044] exist Figure 1-Figure 10 middle:

[0045] 1-pole piece, 2-groove, 3-protrusion, 4-positive electrode piece, 5-negative electrode piece, 6-diaphragm, 7-positive electrode ear, 8-negative electrode ear, 9-straight section, 10-arc section;

[0046] 101 - single-sided area, 102 - double-sided area, 103 - current collector, 104 - active material layer. DETAILED DESCRIPTION

[0047] The present application provides a pole piece and a battery cell including the pole piece.

[0048] 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.

[0049] like Figures 1 to 10 As shown, an embodiment of the present application provides a pole piece 1, wherein the pole piece 1 and the diaphragm 6 constitute a battery cell, and the battery cell, the housing, and the components constitute a battery, which is installed on an electrical device and provides electrical energy for the electrical device. The pole piece 1 mainly includes a current collector 103 and an active material layer 104 disposed on at least one side of the current collector 103, and the pole piece 1 includes a single-sided area 101, and the active material layer 104 is disposed on one side of the current collector 103 located in the single-sided area 101. Exemplarily, taking a wound battery cell as an example, the pole piece 1 of the wound battery cell includes a single-sided area 101 and a double-sided area 102, and the current collector 103 located in the single-sided area 101 is coated with the active material layer 104 on only one side, and the current collector 103 located in the double-sided area 102 is coated with the active material layer 104 on both sides.

[0050] Specifically, the active material layer 104 located in the single-sided area 101 is provided with a groove 2. The groove 2 can destroy the stress inside the active material layer 104 area of ​​the single-sided area 101, thereby improving the bending degree of the single-sided area 101 after being rolled by a pressure roller. The bending degree of the single-sided area 101 is reduced, and the adhesion between the electrode sheet 1 and the diaphragm 6 will be improved after the electrode sheet 1 is assembled into a battery cell, so that the electrode sheet 1 provided with the single-sided area 101 and the diaphragm 6 are more firmly bonded, and the gap between the electrode sheet 1 and the diaphragm 6 can be reduced, or the gap between the electrode sheet 1 and the diaphragm 6 can be avoided, thereby avoiding the length of the transmission path of lithium ions during the charging and discharging process of the battery, alleviating or even avoiding problems such as lithium deposition or black spots in the battery.

[0051] It should also be noted that the type of the electrode sheet 1 is not limited, and the electrode sheet 1 can be a positive electrode sheet 4 or a negative electrode sheet 5 .

[0052] In addition, since the groove 2 is opened on the active material layer 104 of the single-sided area 101 of the electrode 1, after the electrode 1 is assembled into a battery cell and the electrolyte is injected, the groove 2 can store more electrolyte, which can also increase the liquid storage capacity of the battery cell, thereby improving the performance of the battery.

[0053] It should also be noted that there is no limitation on the number and arrangement of the grooves 2 , and one or more grooves 2 may be provided. When multiple grooves 2 are provided, the grooves 2 are preferably arranged in an array, which can further alleviate the bending degree of the single-sided area 101 of the pole piece 1 .

[0054] The electrode 1 of the above structure has a groove 2 formed in the active material layer 104 on the single-sided area 101, which can alleviate the bending degree of the single-sided area 101 of the electrode 1, thereby improving the adhesion between the single-sided area 101 of the electrode 1 and the diaphragm 6 when the electrode 1 is assembled into a battery cell, thereby shortening the transmission path of lithium ions in the battery cell during charging and discharging, and alleviating problems such as lithium plating and black spots.

[0055] In some embodiments, the area of ​​the active material layer 104 in the single-sided area 101 where the groove 2 is set is S1, and the area of ​​the active material layer 104 in the single-sided area 101 is S2, wherein S1 and S2 satisfy: S1 = (0.05-0.7) * S2. Specifically, ensuring that the above relationship is satisfied between S1 and S2 can avoid the opening area of ​​the groove 2 being too small, avoiding the groove 2 from having the effect of not alleviating the bending of the pole piece 1, and can avoid the opening area of ​​the groove 2 being too large, avoiding causing the energy density of the pole piece 1 to drop too much.

[0056] Illustratively, S1 may be 0.05S2, 0.1S2, 0.2S2, 0.3S2, 0.4S2, 0.5S2, 0.6S2, 0.7S2, and so on.

[0057] In some embodiments, in the direction perpendicular to the active material layer 104, the depth of the groove 2 is L, where 3μm≤L≤2000μm. Ensuring that the depth of the groove 2 is within the above range can prevent the groove 2 from being too small, and prevent the groove 2 from failing to alleviate the curvature of the pole piece 1, and can also prevent the problem of the pole piece 1 being too large and causing the curvature of the pole piece 1 to be too large, resulting in poor adhesion of the diaphragm 6. Such a setting can greatly alleviate the curvature of the pole piece 1.

[0058] It should be noted that the direction perpendicular to the active material layer 104 is Figure 4 In the direction indicated by the double-headed arrow Y, the depth of the groove 2 is the dimension of the groove 2 in the direction indicated by the double-headed arrow Y.

[0059] For example, the depth L of the groove 2 may be 3 μm, 10 μm, 50 μm, 100 μm, 200 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, etc.

[0060] In some embodiments, the outer diameter of the notch of the groove 2 is D, where 0.2 mm ≤ D ≤ 5 mm. Specifically, ensuring that the groove 2 is within the above range can prevent the outer diameter of the groove 2 from being too small, preventing the groove 2 from failing to alleviate the bending degree of the pole piece 1, and can prevent the outer diameter of the groove 2 from being too large, which will deteriorate the effect of alleviating the bending degree of the pole piece 1. Such a setting can improve the effect of alleviating the bending degree of the pole piece 1.

[0061] It should be noted that when the slot is circular, the outer diameter of the slot refers to the diameter of the slot; when the slot is non-circular such as polygonal, elliptical or irregular, the outer diameter of the slot refers to the diameter of the circumscribed circle of the slot.

[0062] It should also be noted that when the notch is a circular notch, the outer diameter of the notch is the Figure 2 The dimension in the direction indicated by the double-headed arrow X.

[0063] Exemplarily, the outer diameter D of the groove 2 may be 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0064] In some embodiments, the depth of the groove 2 in the direction perpendicular to the active material layer 104 is L, and the bending radius of the pole piece 1 is R, where L and R satisfy: L: R ≥ 0.005. Specifically, ensuring that the depth of the groove 2 in the direction of the active material layer 104 and the bending radius of the pole piece 1 are within the above range can greatly alleviate the degree of bending of the single-sided area 101 of the pole piece 1, thereby alleviating the problems of lithium deposition, black spots, etc. of the battery composed of the pole piece 1.

[0065] Illustratively, L:R can be 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.08, 0.1, and the like.

[0066] In some embodiments, a protrusion 3 is provided on the side of the current collector 103 of the single-sided area 101 facing away from the active material layer 104, and the protruding direction of the protrusion 3 is the same as the recessed direction of the groove 2. The protrusion 3 can also alleviate the curvature of the single-sided area 101 of the pole piece 1. In this way, when the groove 2 alleviates the curvature of the single-sided area 101 of the pole piece 1, the protrusion 3 can also alleviate the above-mentioned curvature, and can avoid excessive reduction of the active material in the active material layer 104, thereby avoiding excessive reduction of the energy density of the battery.

[0067] In some embodiments, the protrusion height of the protrusion 3 is the same as the recess depth of the groove 2. Exemplarily, the protrusion height of the protrusion 3 and the recess depth of the groove 2 are ensured to be the same, so that both can alleviate the bending degree of the pole piece 1 at the same time, and ensure that the above values ​​are the same, which can avoid the thickness of the pole piece 1 from increasing and avoid the energy density of the battery composed of the pole piece 1 from decreasing.

[0068] In some embodiments, at least two protrusions 3 are provided, and a recessed portion is formed between adjacent protrusions 3. When the pole piece 1 provided with the protrusions 3 is assembled into a battery cell, the recessed portions between adjacent protrusions 3 can also store electrolyte, thereby improving the battery's liquid storage capacity and thus improving the performance of the battery cell.

[0069] In some embodiments, in the direction perpendicular to the active material layer 104, the depth of the protrusion 3 is M, where 2μm≤M≤1700μm, ensuring that the depth of the protrusion 3 is within the above range, which can avoid the protrusion 3 being too small, avoiding the protrusion 3 from failing to alleviate the curvature of the electrode 1, and avoiding the problem of the protrusion 3 being too deep causing the curvature of the electrode 1 to be too large. Such a setting can alleviate the curvature of the electrode 1 and make the electrode 1 form a regular size of the battery cell.

[0070] For example, the depth of the protrusion 3 may be 2 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 500 μm, 1000 μm, 1500 μm, 1700 μm, etc.

[0071] In some embodiments, the depth of the recess is N, where 0.05mm≤N≤1.5mm, ensuring that the depth of the recess is within the above range. This can prevent the recess from being too shallow to increase the liquid storage capacity of the battery cell composed of the electrode 1, and can also prevent the recess from being too deep to cause the energy density of the battery cell composed of the electrode 1 to decrease. Such a setting can prevent the electrode 1 from being bent too much, thereby alleviating problems such as lithium deposition and black spots in the battery composed of the electrode 1.

[0072] Illustratively, the depth of the recessed portion may be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.12 mm, 0.15 mm, or the like.

[0073] In some embodiments, the bottom of the groove 2 is a plane or an arc surface, and the side wall of the groove 2 is a plane or an arc surface. Here, the shapes of the bottom and side walls of the groove 2 are defined, and the bottom and side walls of the groove 2 can be planes or arc surfaces. In this way, the groove 2 can alleviate the bending degree of the pole piece 1.

[0074] In some embodiments, at least two grooves 2 are provided, and the notches of the grooves 2 are at least one of circular, polygonal and elliptical. It should be noted that the shapes of the notches of at least two grooves 2 can be the same or different. Grooves 2 of different shapes have different capacities for storing electrolyte, and grooves 2 of different shapes have different functions for alleviating the curvature of the electrode 1. Grooves 2 of different shapes can be selected according to the required capacity for storing electrolyte and the required relief of the curvature of the electrode 1.

[0075] In this embodiment, a preferred implementation is provided, in which a plurality of grooves 2 are provided and arranged in an array, so that the bending degree of the electrode piece 1 can be reduced while avoiding excessive reduction in the content of the active material layer 104 at the position where the grooves 2 are opened in the electrode piece 1.

[0076] A battery cell includes a negative electrode sheet 5, a positive electrode sheet 4, and a separator 6 disposed between the negative electrode sheet 5 and the positive electrode sheet 4, wherein the positive electrode sheet 4 and / or the negative electrode sheet 5 is any one of the above-mentioned electrode sheets 1. Since the battery cell includes the above-mentioned electrode sheet 1, the beneficial effects of the battery cell brought by the electrode sheet 1 refer to the above content and will not be repeated here.

[0077] In some embodiments, adhesive tape is provided on both sides of the battery cell in the first direction, and the adhesive tape at least covers part of the protrusion 3 of the single-sided area 101. Specifically, after the electrode 1 is assembled into a battery cell, the active material layer 104 of the single-sided area 101 of the electrode 1 faces the center of the battery cell, and the protrusion 3 is located on the side away from the center of the battery cell. The adhesive tape covers part of the protrusion 3 of the single-sided area 101, which can increase the contact area between the adhesive tape and the single-sided area 101, thereby improving the stability of the adhesive tape bonding to the single-sided area 101, making the battery cell more secure.

[0078] It should be noted that the first direction refers to Figure 7 The direction indicated by the double-headed arrow A or the direction indicated by the double-headed arrow B.

[0079] In some embodiments, the single-sided area 101 is located outside the battery cell, and the groove 2 of the single-sided area 101 is recessed in a direction away from the center of the battery cell. Specifically, the electrode sheet 1 provided with the single-sided area 101 can be a positive electrode sheet 4 or a negative electrode sheet 5, and the groove 2 of the single-sided area 101 is recessed in a direction away from the center of the battery cell, which can improve the ability of the battery cell provided with the electrode sheet 1 to store electrolyte, and facilitate the transmission of lithium ions between the positive electrode sheet 4 and the negative electrode sheet 5.

[0080] In some embodiments, the battery cell further includes a negative electrode ear 8 connected to the negative electrode sheet 5 and a positive electrode ear 7 connected to the positive electrode sheet 4. In the second direction, the groove 2 of the single-sided area 101 overlaps with at least one of the positive electrode ear 7 and the negative electrode ear 8. In this way, the arrangement area of ​​the groove 2 can be guaranteed, and the groove 2 can be arranged more evenly on the single-sided area 101, thereby better relieving the bending degree of the electrode sheet 1, so as to alleviate the lithium deposition, black spots and other phenomena of the battery composed of the battery cell.

[0081] It should be noted that the second direction refers to Figure 7 The direction indicated by the double-headed arrow A or the direction indicated by the double-headed arrow B.

[0082] Furthermore, in some embodiments, the groove 2 of the single-sided area 101 and the folded section of the diaphragm 6 at least partially overlap. Such an arrangement can further ensure the uniformity of the arrangement of the groove 2 in the single-sided area 101, further ensure the arrangement area of ​​the groove 2, and further make the arrangement of the groove 2 in the single-sided area 101 more uniform, thereby better relieving the bending degree of the pole piece 1, so as to alleviate the lithium deposition, black spots and other phenomena of the battery composed of the battery cell.

[0083] In some embodiments, the battery cell is a wound battery cell, and the groove 2 of the single-sided area 101 of the positive electrode sheet 4 exceeds the end of the active material layer 104 of the negative electrode sheet 5. When the above-mentioned electrode sheets 1 are combined into a wound battery cell and the single-sided area 101 of the positive electrode sheet 4 is located at the outermost circle, see Figure 7 The arrangement shown in this way can alleviate the degree of bending of the single-sided area 101 of the positive electrode sheet 4. At the same time, grooving on the active material layer 104 in the positive electrode sheet 4 can reduce the content of active material on the positive electrode sheet 4, so that the content of active material in this area is less than the content of the active material layer 104 of the negative electrode sheet 5 corresponding to this area, and lithium deposition in this area can be avoided during the subsequent battery charging and discharging process.

[0084] In some embodiments, the peeling force between the active material layer 104 of the single-sided area 101 with the groove 2 and the diaphragm 6 is F1, and the peeling force between the active material layer 104 and the diaphragm 6 without the groove 2 is F2, wherein F1 and F2 satisfy: F1>F2. Such a setting can improve the bonding stability between the active material layer 104 of the single-sided area 101 with the groove 2 and the diaphragm 6, thereby reducing the gap between the single-sided area 101 with the groove 2 and the active material layer 104 of the other polar pole piece 1, thereby reducing the transmission path of lithium ions during battery charging and discharging, and improving the battery life.

[0085] Furthermore, in some embodiments, F1 and F2 satisfy the relationship: F1 = (1.1-5) * F2. Specifically, ensuring that F1 and F2 satisfy the above relationship can further alleviate the gap between the pole pieces 1 formed by the bending of the single-sided area 101 of the pole piece 1, thereby improving the stability of the battery.

[0086] Illustratively, F1 may be 1.1F2, 1.2F2, 1.5F2, 1.8F2, 2F2, 2.5F2, 3F2, 4F2, 4.5F2, 5F2, and so on.

[0087] In some embodiments, the battery cell is a wound battery cell, and the groove 2 is located in the straight section 9 and / or arc section 10 of the wound battery cell. Such an arrangement can further ensure the uniformity of the arrangement of the groove 2 in the single-sided area 101, further ensure the arrangement area of ​​the groove 2, and further make the arrangement of the groove 2 in the single-sided area 101 more uniform, thereby better relieving the bending degree of the pole piece 1, so as to alleviate the lithium deposition, black spots and other phenomena of the battery composed of the battery cell.

[0088] Taking the electrode sheet 1 as the positive electrode sheet 4, whose single-side area 101 has a length of 120 mm and a width of 80 mm as an example, the following experiment is conducted, and the specific steps are as follows:

[0089] In the experimental group, after the electrode 1 is rolled normally, a special roller is used to process the single-side area 101 of the electrode 1 under a pressure of 0.5 MPa before winding, so that a groove 2 is formed on the active material layer 104 of the single-side area 101;

[0090] The depth of groove 2 is 0.3 mm, the diameter is 2 mm, and the total area of ​​groove 2 is about 314 mm 2 , due to the presence of the groove 2 , when the electrode 1 is laid flat on the experimental table, the maximum curling height of the active material layer 104 in the single-sided area 101 of the electrode 1 is less than 1 mm;

[0091] In the normal group, after the pole piece 1 is rolled, no special treatment is performed. When the pole piece 1 is laid flat on the test bench, the maximum curling height of the single-side area 101 of the pole piece 1 is ≥8mm;

[0092] After the winding of the experimental group and the normal group batteries was completed, the batteries continued to flow. After the capacity division was completed, the batteries were disassembled to test the peeling force between the positive electrode sheet 4 and the separator 6. The peeling force F1 between the single-sided area 101 of the positive electrode sheet 4 of the experimental group battery and the separator 6 was 0.032 N / mm, and the peeling force F2 of other areas without the groove 2 was 0.015 N / mm.

[0093] The battery cycle performance of the experimental group and the normal group was tested. Under the conditions of 25℃ 2C / 2C charge and discharge, after 700 cycles, the capacity retention rate of the normal group battery was 85.6%, and the thickness expansion rate was 9.75%. The capacity retention rate of the experimental group battery was 89.3%, and the thickness expansion rate was 6.38%. The performance of the experimental group battery was significantly better than that of the normal group battery.

[0094] The higher thickness expansion rate of the normal group of batteries is mainly due to the bulges at the top and bottom of the battery in the height direction. Disassembly revealed that lithium deposition occurred in the two folds of the outermost circle of the battery, while the experimental group of batteries did not have this problem. The analysis is mainly based on the normal group of batteries. The single-sided area 101 has not been treated, and the stress in the coating of the pole piece 1 still exists, resulting in relatively poor adhesion between the positive electrode 4 and the diaphragm 6. This phenomenon worsens during high-rate cycling, leading to lithium deposition. The experimental group of batteries has dents in the single-sided coating area. The dents destroy the stress in the coating of the pole piece 1, reduce the curling height of the pole piece 1, and make the pole piece 1 more "flat", which improves the adhesion between it and the diaphragm 6, thereby improving the performance of the battery.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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. A pole piece, comprising a current collector and an active material layer disposed on at least one side of the current collector, wherein the pole piece comprises a single-sided region, and the active material layer is disposed on one side of the current collector located in the single-sided region, characterized in that: The active material layer located in the single-side area is provided with a groove.

2. The pole piece according to claim 1, characterized in that: The area of ​​the active material layer in the single-sided region where the groove is set is S1, and the area of ​​the active material layer in the single-sided region is S2, wherein S1 and S2 satisfy: S1 = (0.05-0.7) * S2.

3. The pole piece according to claim 1, characterized in that: In a direction perpendicular to the active material layer, the depth of the groove is L, wherein 3 μm≤L≤2000 μm; and / or, The outer diameter of the notch of the groove is D, wherein 0.2 mm≤D≤5 mm.

4. The pole piece according to claim 1, characterized in that: The depth of the groove in the direction perpendicular to the active material layer is L, and the bending radius of the pole piece is R, wherein L and R satisfy: L:R≥0.

005.

5. The pole piece according to claim 1, characterized in that: A protrusion is arranged on the side of the current collector in the single-sided area facing away from the active material layer, and a protruding direction of the protrusion is the same as a recessed direction of the groove.

6. The pole piece according to claim 5, characterized in that: The protrusion height of the protrusion is the same as the recess depth of the groove.

7. The pole piece according to claim 5, characterized in that: At least two protrusions are provided, and a recessed portion is formed between adjacent protrusions.

8. The pole piece according to claim 7, characterized in that: In the direction perpendicular to the active material layer, The depth of the protrusion is M, wherein 2 μm≤M≤1700 μm; and / or, The depth of the recessed portion is N, wherein 0.05 mm≤N≤1.5 mm.

9. The pole piece according to claim 1, characterized in that: The bottom of the groove is a plane or an arc surface, and / or The side wall of the groove is a plane or an arc surface.

10. The pole piece according to claim 1, characterized in that: The grooves are provided with at least two, and / or The notch of the groove is at least one of a circular shape, a polygonal shape and an elliptical shape.

11. A battery cell, characterized in that: It comprises a negative electrode sheet, a positive electrode sheet and a separator arranged between the negative electrode sheet and the positive electrode sheet, and the positive electrode sheet and / or the negative electrode sheet is the electrode sheet as described in any one of claims 1-10.

12. The battery cell according to claim 11, characterized in that: Adhesive tape is arranged on both sides of the battery cell in the first direction, and the adhesive tape at least covers a portion of the protrusions in the single-sided area.

13. The battery cell according to claim 11, characterized in that: The single-sided area is located outside the battery cell, and the groove of the single-sided area is recessed in a direction away from the center of the battery cell.

14. The battery cell according to claim 11, characterized in that: The battery cell further includes a negative electrode tab connected to the negative electrode sheet and a positive electrode tab connected to the positive electrode sheet, and in the second direction, the groove in the single-sided area overlaps with at least one of the positive electrode tab and the negative electrode tab.

15. The battery cell according to claim 11, characterized in that: The groove of the single-sided area and the folded section of the diaphragm at least partially overlap.

16. The battery cell according to claim 11, characterized in that: The battery cell is a wound battery cell, and the groove in the single-sided area of ​​the positive electrode sheet exceeds the end of the active material layer of the negative electrode sheet.

17. The battery cell according to claim 11, characterized in that: The peeling force between the active material layer and the separator in the single-sided area with the groove is F1, and the peeling force between the active material layer and the separator without the groove is F2, wherein F1 and F2 satisfy: F1>F2.

18. The battery cell according to claim 17, characterized in that: F1 and F2 satisfy: F1 = (1.1-5) * F2.

19. The battery cell according to claim 11, characterized in that: The battery core is a wound battery core, and the groove is located in a straight section and / or an arc section of the wound battery core.

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