Positive plate, battery cell and lithium ion secondary battery

Abstract

The utility model relates to the field of batteries, and discloses a positive plate, a battery cell and a lithium ion secondary battery, the positive plate comprises a current collector, an active material layer, a protective layer and a first tab; the surface of the current collector comprises a paste coating area and a protection area, the active material layer is located in the paste coating area, the protection layer is located in the protection area, the protection area is located between the active material layer and the first tab, and the first tab extends outwards from the current collector in the first direction; the active material layer comprises a concave part area, the concave part area comprises at least one concave part, and in the first direction, the distance between the concave part area and the protective layer ranges from 0 mm to 20 mm. The active material layer of the positive plate is provided with the concave part, so that the infiltration effect of the positive plate can be improved, the CB value of the battery cell can be improved, and the problem of lithium precipitation of the battery cell comprising the positive plate is solved. The protective layer plays a role in protecting the active substance layer when the first tab is formed by cutting, and meanwhile, burrs formed by cutting can be prevented from puncturing the diaphragm, so that short circuit of the battery cell is avoided.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a positive electrode sheet, a battery cell and a lithium-ion secondary battery. Background Art

[0002] Lithium-ion battery is a rechargeable battery that mainly relies on the movement of lithium ions between the positive and negative electrodes to work. + Insertion and deinsertion back and forth between the two electrodes: During charging, Li + It is deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the process is reversed during discharge.

[0003] In multi-electrode lithium batteries, the positive electrode current collector is covered with an active material layer and a protective layer, and tabs extend outward from the positive electrode current collector. During the charge and discharge cycles of multi-electrode lithium batteries, the electrodes can experience severe lithium deposition, which in turn causes battery expansion, severely impacting battery performance in terms of rate capability, lifespan, and safety. Utility Model Content

[0004] The purpose of this application is to provide a positive electrode sheet, a battery cell and a lithium-ion secondary battery to improve the lithium plating problem of the battery and enhance the performance of the battery.

[0005] In order to solve the above technical problems, the present application provides a positive electrode sheet, comprising: a current collector, an active material layer, a protective layer and a first electrode tab;

[0006] The surface of the current collector includes a paste coating area and a protection area, the active material layer is located in the paste coating area, the protection layer is located in the protection area, and the protection area is located between the active material layer and the first electrode tab, and the first electrode tab extends outward from the current collector along a first direction;

[0007] The active material layer includes a recessed area, the recessed area includes at least one recessed portion, and in the first direction, a distance between the recessed area and the protective layer ranges from 0 to 20 mm.

[0008] Optionally, the recessed area includes a first recessed area and / or a second recessed area, the first recessed area is located at an edge portion of the active material layer in the first direction, and the second recessed area is located in a middle portion of the active material layer in the first direction.

[0009] Optionally, the width of the first recessed area ranges from 1 mm to 20 mm.

[0010] and / or, the width of the edge region of the active material layer is in the range of 0 to 20 mm,

[0011] And / or, the ratio of the width of the first concave area to the width of the edge area is in the range of (0.5-5): 1,

[0012] The edge region is a region between the first recessed region and a side edge of the active material layer.

[0013] Optionally, the distance between the recessed area and the protective layer is greater than zero; and / or the width of the edge area of ​​the active material layer is greater than zero.

[0014] Optionally, it also includes:

[0015] A splicing area is located between adjacent recessed areas.

[0016] Optionally, the length of the first joint area between the first recessed areas ranges from 0.1 mm to 10 mm.

[0017] and / or, the width of the second joint area between the second recessed areas is in the range of 0.1 mm to 10 mm,

[0018] And / or, the width of the third splicing area between the first recessed area and the second recessed area is in the range of 0.1 mm to 10 mm.

[0019] Optionally, a ratio of an area of ​​the first joint region to an area of ​​the first recess region is in a range of 0.001 to 0.2;

[0020] And / or, the ratio of the area of ​​the second splicing area to the area of ​​the second recessed area is in the range of 0.001 to 0.5.

[0021] Optionally, a ratio of a width of the first splicing area to a width of an edge area of ​​the active material layer is in a range of (0.2-20):1.

[0022] Optionally, it also includes:

[0023] The safety coating is located between the active material layer and the current collector.

[0024] Optionally, the recess comprises a recessed hole and / or a groove.

[0025] Optionally, the aperture of the concave hole ranges from 30 μm to 300 μm.

[0026] and / or, the depth of the concave hole ranges from 2 μm to 30 μm,

[0027] And / or, the distance between the concave holes ranges from 50 μm to 2000 μm;

[0028] And / or, the groove diameter ranges from 30 μm to 200 μm,

[0029] and / or, the depth of the groove ranges from 2 μm to 40 μm,

[0030] And / or, the distance between the grooves ranges from 100 μm to 5000 μm.

[0031] Optionally, the active material layer includes a first active material layer partition and a second active material layer partition, the thickness of the first active material layer partition is smaller than that of the second active material layer partition, and the first active material layer partition is located between the protective layer and the second active material layer partition.

[0032] Optionally, the thickness ratio of the first active material layer partition to the second active material layer partition is in the range of (0.2-5):1;

[0033] and / or, the distance between the first active material layer partition and the protective layer is in the range of 1 to 10 mm;

[0034] And / or, a depth ratio of the concave portion located in the first active material layer partition to the concave portion located in the second active material layer partition is in a range of (0.2-5):1.

[0035] Optionally, the ratio of the width of the protective layer to the width of the recess is in the range of (0.5~80):1, and / or the ratio of the thickness of the protection layer to the depth of the recess is in the range of (0.5~5:1), and / or the ratio of the depth of the recess to the thickness of the remaining active material layer at the location of the recess is in the range of 1:(1~30).

[0036] Optionally, the width of the protective layer ranges from 0.1 mm to 4 mm.

[0037] And / or, the thickness of the protective layer ranges from 10 μm to 60 μm.

[0038] Optionally, the number of the first tabs is at least two.

[0039] The present application also provides a battery cell, comprising any one of the above-mentioned positive electrode sheet, negative electrode sheet, separator and second electrode tab;

[0040] The separator is located between the positive electrode sheet and the negative electrode sheet, and the second electrode tab is connected to the first electrode tab in the positive electrode sheet.

[0041] Optionally, the first electrode tab includes a welding area, and the distance between the welding area and the recessed area on the positive electrode sheet ranges from 2 mm to 20 mm, and / or the distance between the welding area and the protective layer on the positive electrode sheet ranges from 5 mm to 20 mm.

[0042] Optionally, the N / P ratio between the positive electrode sheet and the negative electrode sheet is in the range of 1.01 to 1.20.

[0043] And / or, the angle between the first electrode tab and the recessed area ranges from 0° to 90°.

[0044] Optionally, the battery cell includes the positive electrode sheet, the separator, and the negative electrode sheet that are stacked and wound together. The positive electrode sheet includes a bending area and a straight area, and the bending area contains a concave portion.

[0045] Optionally, splicing areas are distributed between adjacent recessed areas.

[0046] Optionally, the edge area of ​​the positive electrode sheet contains the recess.

[0047] The present application also provides a lithium-ion secondary battery, which includes any one of the above-mentioned battery cells and membrane shells, wherein the battery cell is located in the membrane shell, and the second electrode tab is exposed outside the membrane shell.

[0048] A positive electrode sheet provided in the present application includes: a current collector, an active material layer, a protective layer and a first electrode tab; the surface of the current collector includes a pasted area and a protected area, the active material layer is located in the pasted area, the protective layer is located in the protected area, the protected area is located between the active material layer and the first electrode tab, and the first electrode tab extends outward from the current collector along a first direction; the active material layer includes a recessed area, the recessed area includes at least one recess, and in the first direction, the distance between the recessed area and the protective layer ranges from 0 to 20 mm.

[0049] It can be seen that the positive electrode sheet in the present application includes a current collector, an active material layer, a protective layer and a first pole ear. The active material layer has a recess. On the one hand, it increases the contact area between the electrode liquid and the positive electrode sheet, improving the wetting effect of the positive electrode sheet. On the other hand, it can also reduce the active material on the positive electrode sheet and improve the CB value (Cell Balance, cell balance coefficient, also known as N / P ratio) of the battery, thereby improving the lithium plating problem of the multi-pole ear battery cell including the positive electrode sheet, thereby improving the rate performance and cycle performance of the battery including the multi-pole ear battery cell, and improving the safety and service life of the battery. In addition, the protective layer is located in the area near the first pole ear on the current collector, which can protect the active material layer when cutting to form the first pole ear. At the same time, it can also prevent the burrs generated when cutting to form the first pole ear from piercing the diaphragm, thereby avoiding short circuit of the battery cell.

[0050] In addition, the present application also provides a battery cell and a lithium-ion secondary battery including the above-mentioned positive electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0052] Figure 1 A top view of a positive electrode provided in an embodiment of the present application Figure 1 ;

[0053] Figure 2 A schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present application Figure 1 ;

[0054] Figure 3 A top view of a positive electrode provided in an embodiment of the present application Figure 2 ;

[0055] Figure 4 A top view of a positive electrode provided in an embodiment of the present application Figure 3 ;

[0056] Figure 5 A top view of a positive electrode provided in an embodiment of the present application Figure 4 ;

[0057] Figure 6 A schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present application Figure 2 ;

[0058] Figure 7 A partial top view of a positive electrode provided in an embodiment of the present application Figure 1 ;

[0059] Figure 8 A partial top view of a positive electrode provided in an embodiment of the present application Figure 2 ;

[0060] Figure 9 A schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present application Figure 3 ;

[0061] Figure 10 A schematic diagram of a first tab on a positive electrode sheet provided in an embodiment of the present application being bent to form a whole;

[0062] Figure 11 A side view of a positive electrode sheet provided in an embodiment of the present application;

[0063] Figure 12 A top view of a positive electrode provided in an embodiment of the present application Figure 5 ;

[0064] Figure 13 A schematic structural diagram of a wound battery cell provided in an embodiment of the present application;

[0065] In the figure, 1. current collector, 2. active material layer, 3. protective layer, 4. first electrode ear, 5. first splicing area, 6. second splicing area, 7. third splicing area, 8. safety coating, 9. negative electrode current collector, 10. negative electrode active material layer, 11. third electrode ear, 21. first recessed area, 22. second active material layer partition, 23. first active material layer partition, 24. second recessed area, 25. recess, 26. edge area, 41. welding area, 100. positive electrode sheet, 200. diaphragm, 300. negative electrode sheet. DETAILED DESCRIPTION

[0066] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a 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 those skilled in the art without making any creative efforts are within the scope of protection of the present application.

[0067] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0068] As mentioned in the background technology section, during high-rate cycle charge and discharge, lithium-ion batteries will experience severe lithium deposition in the electrodes, which will lead to battery swelling and seriously affect the battery's performance in terms of rate, life, and safety.

[0069] In view of this, the present application provides a positive electrode sheet 100, please refer to Figures 1 to 2 ,include:

[0070] Current collector 1, active material layer 2, protective layer 3 and first electrode tab 4;

[0071] The surface of the current collector 1 includes a pasted area and a protected area. The active material layer 2 is located in the pasted area, and the protective layer 3 is located in the protected area. The protected area is located between the active material layer 2 and the first electrode tab 4. The first electrode tab 4 extends outward from the current collector 1 along the first direction X.

[0072] The active material layer 2 includes a recessed area, which includes at least one recessed portion 25 . In the first direction, a distance between the recessed area and the protective layer is in a range of 0 to 20 mm.

[0073] The first direction X is the width direction of the positive electrode sheet 100 .

[0074] The current collector 1 may be aluminum foil, and the material of the active material layer 2 may be lithium cobalt oxide, ternary nickel-cobalt-manganese material, ternary nickel-cobalt-aluminum material, lithium iron phosphate, lithium manganese iron phosphate, etc., which are not limited in this embodiment.

[0075] The active material layer 2 may be located on the first surface of the current collector 1, or on the second surface of the current collector 1, or on both the first and second surfaces of the current collector 1. The first and second surfaces of the current collector 1 are two surfaces that are opposite in the third direction. For example, the first and second surfaces of the current collector 1 may be the upper and lower surfaces, respectively.

[0076] When the positive electrode sheet 100 is made into a battery cell, an active material layer 2 is provided on the side of the positive electrode sheet 100 corresponding to the negative electrode sheet. That is, when the positive electrode sheet 100 is located in the innermost layer or outermost layer of the battery cell, the active material layer 2 is provided on the first surface or the second surface of the current collector 1; when the positive electrode sheet 100 is located in the middle position, the active material layer 2 is provided on both the first surface and the second surface of the current collector 1.

[0077] When the active material layer 2 is located on both the first and second surfaces of the current collector 1 , the active material layers 2 on the first and second surfaces at both ends in the length direction may be aligned at one end and staggered at the other end.

[0078] It should be noted that in this embodiment, the active material layer 2 on one side of the current collector 1 is not limited and can be set at will.

[0079] As an implementation method, the number of active material layers 2 located on a single surface of the current collector 1 is one.

[0080] As another possible embodiment, the number of active material layers 2 located on a single surface of the current collector 1 is two or more.

[0081] The recessed portion 25 is formed by the surface of the active material layer 2 being recessed in the third direction Z and / or in a direction opposite to the third direction Z.

[0082] The third direction Z is the direction of the thickness of the positive electrode sheet 100 , and the first direction X is perpendicular to the third direction Z.

[0083] For example, when the positive electrode sheet 100 is placed horizontally, the third direction Z points upward, and the recess 25 on the active material layer 2 on the upper surface of the current collector 1 is recessed from the surface of the active material layer 2 along the direction opposite to the third direction Z, and the recess 25 on the active material layer 2 on the lower surface of the current collector 1 is recessed from the surface of the active material layer 2 along the third direction Z.

[0084] The first electrode tab 4 is electrically connected to the current collector 1 and extends away from the current collector 1 , that is, along the first direction X (that is, the width direction of the positive electrode sheet 100 ). The width herein refers to the distance in the first direction X.

[0085] It should be noted that the thickness of the active material layer 2 is not limited in this embodiment and can be set at will.

[0086] As an implementable embodiment, the thickness of the active material layer 2 can be 20 μm to 150 μm, which can adapt to high energy density thick electrode sheets and is also compatible with high rate thin electrode sheets.

[0087] There are gaps between adjacent first electrode tabs 4 . The gaps between adjacent first electrode tabs 4 can be equal or unequal, which is not specifically limited in this embodiment.

[0088] The protective layer 3 and the active material layer 2 are distributed along the first direction X, and the protective layer 3 is located between the active material layer 2 and the first electrode tab 4 .

[0089] The recesses 25 in the recess area can be arranged in a matrix or irregularly, and the specific number of the recess area and the recesses 25 is not limited in this embodiment. The distance D1 between the recesses 25 can be equal.

[0090] The recessed portion 25 can be formed by laser or mechanical means, and can be formed after the active material layer 2 is coated or rolled.

[0091] The distance between the recessed area and the protective layer 3 is not specifically limited in this embodiment and depends on the circumstances. For example, the distance D2 between the recessed area and the protective layer 3 can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc. The positive electrode sheet 100 in this embodiment includes a current collector 1, an active material layer 2, a protective layer 3 and a first electrode tab 4. The active material layer 2 has a recessed portion 25. On the one hand, it increases the contact area between the electrode liquid and the positive electrode sheet 100, thereby improving the wetting effect of the positive electrode sheet 100. On the other hand, it can also reduce the active material on the positive electrode sheet 100 and improve the CB (Cell Balance) value of the battery having the positive electrode sheet, thereby improving the lithium plating problem of the battery cell including the positive electrode sheet 100, thereby improving the rate performance and cycle performance of the battery including the battery cell, and improving the safety and service life of the battery. In addition, the protective layer 3 is located in the area near the first pole tab 4 on the current collector 1, which can protect the active material layer 2 when cutting to form the first pole tab 4. At the same time, it can also prevent the burrs generated when cutting to form the first pole tab 4 from piercing the diaphragm 200, thereby avoiding short circuit of the battery cell.

[0092] Based on the above embodiments, in one embodiment of the present application, Figure 1 As shown,

[0093] The recessed area includes a first recessed area 21 , and the first recessed area 21 is located at an edge portion of the active material layer in the first direction.

[0094] The number of the first recessed areas 21 may be one or more than two, which is not limited in this embodiment.

[0095] In this embodiment, the first recessed area 21 is located at the edge of the positive electrode sheet 100 and extends along the second direction Y. This can solve the problem of lithium deposition at the edge of the battery cell. The recessed area can be distributed on the edge near the protective layer 3 and the edge away from the protective layer 3.

[0096] The second direction Y is the length direction of the positive electrode sheet 100 , and the second direction Y is perpendicular to the third direction Z and the first direction X. The lengths herein are all distances in the second direction Y.

[0097] Based on the above embodiments, in one embodiment of the present application, Figure 3 As shown, the recessed area is a second recessed area 24 , and the second recessed area 24 is located in the middle part of the active material layer in the first direction.

[0098] The number of the second concave regions 24 can be one or more than two, which is not limited in this embodiment.

[0099] In this embodiment, the second recessed area 24 extends along the width direction of the positive electrode sheet 100. When the positive electrode sheet 100 is made into a wound battery cell, the recessed area corresponds to the curved arc area of ​​the battery cell, which can solve the problem of lithium deposition in the curved arc area of ​​the battery cell.

[0100] The distance D2 between the second recessed area 24 and the protective layer 3 can range from 0 to 10 mm, preferably from 0.2 mm to 1.5 mm, which can significantly improve the impact of the active material powder that falls on the protective layer 3 when the recessed portion 25 is formed, significantly improve the problem of the process interruption zone, and at the same time avoid damaging the protective layer 3 when the recessed portion 25 is formed.

[0101] Based on the above embodiments, in one embodiment of the present application, Figure 4 As shown, the recessed area includes a first recessed area 21 and a second recessed area 24 , wherein the first recessed area 21 is located at the edge of the active material layer in the first direction, and the second recessed area 24 is located in the middle of the active material layer in the first direction.

[0102] In this embodiment, a first recessed area 21 is distributed at the edge portion of the positive electrode sheet 100, and a second recessed area 24 is distributed in the middle portion between the edge portions. When the positive electrode sheet 100 is made into a wound battery cell, the second recessed area 24 in the middle portion is located in the bending arc area of ​​the battery cell. Therefore, in this embodiment, the positive electrode sheet 100 can solve the problem of lithium deposition in the edge portion and the bending arc area.

[0103] In one embodiment of the present application, the width W1 of the first recessed area 21 may be in the range of 1 mm to 20 mm, preferably 3 mm to 8 mm, so as to solve the problem of lithium plating while avoiding excessive capacity loss.

[0104] Illustratively, the width W1 of the first recessed area 21 may be 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, 10 mm, 15 mm, 17 mm, 19 mm, 20 mm, etc.

[0105] In one embodiment of the present application, the distance D2 between the first recessed area 21 close to the protective layer 3 and the protective layer 3 can be in the range of 0 to 10 mm, preferably 0.2 mm to 1.5 mm, which can significantly improve the impact of the active material powder falling on the protective layer 3 when making the recess 25, significantly improve the process interruption band problem, and at the same time avoid damaging the protective layer 3 when making the recess 25.

[0106] Illustratively, the distance D2 between the first recessed area 21 and the protective layer 3 may be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc.

[0107] In one embodiment of the present application, the width W2 of the edge region 26 of the active material layer 2 can range from 0 to 20 mm, preferably from 0.2 mm to 1.5 mm. The edge region 26 of the active material layer 2 is the area between the first recessed region 21 and the side of the active material layer 2 .

[0108] Illustratively, the width W2 of the edge region 26 may be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 14 mm, 18 mm, 20 mm, etc.

[0109] The bonding force between the active material layer 2 and the current collector 1 at the edge is relatively poor. Setting a certain width of the edge area 26 can, on the one hand, prevent the laser from acting on the edge of the active material layer 2 when making the recess 25 and causing powder to fall off. On the other hand, it can also avoid cracks in the active material layer 2 when making the recess 25, thereby damaging the current collector 1.

[0110] In one embodiment of the present application, the ratio of the width W1 of the first recessed area 21 to the width W2 of the edge area 26 can be in the range of (0.5-5):1, so as to avoid the laser acting on the active material layer 2 when forming the recessed portion 25, resulting in powder loss in the edge area 26.

[0111] For example, the ratio of the width W1 of the first recessed area 21 to the width W2 of the edge area 26 may be 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, etc.

[0112] In one embodiment of the present application, the distance between the recessed area and the protective layer 3 is greater than zero; and / or the width of the edge area 26 of the active material layer 2 is greater than zero.

[0113] The distance between the recessed area and the protective layer 3 is greater than zero, which can prevent powder from falling off the edge of the active material layer 2 when forming the recessed area 25 .

[0114] The width of the edge region 26 of the active material layer 2 is greater than zero, so as to prevent powder from falling off the edge of the active material layer 2 when forming the recess 25 .

[0115] Please refer to Figure 5 Based on any of the above embodiments, in one embodiment of the present application, the positive electrode sheet 100 may further include:

[0116] The splicing area is located between adjacent recessed areas.

[0117] There is no recess 25 in the splicing area. The splicing area can not only reduce the reduction of the active material layer 2 and enhance the structural stability of the positive electrode material, but also serve as a stress buffer when the positive electrode sheet 100 is subjected to tensile stress during the winding process, thereby preventing the positive electrode sheet 100 from breaking; and can indirectly improve the stress release during the battery cell cycle.

[0118] In one embodiment of the present application, the length L1 of the first splicing area 5 located between the first recessed areas 21 can range from 0.1 mm to 10 mm. For example, the length L1 of the first splicing area 5 can be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 7.0 mm, 8.0 mm, 9.0 mm, 10.0 mm, etc.

[0119] In one embodiment of the present application, the width W3 of the second splicing area 6 located between the second recessed areas 24 can range from 0.1 mm to 10 mm. For example, the width W3 of the second splicing area 6 can be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 7.0 mm, 8.0 mm, 9.0 mm, 10.0 mm, etc.

[0120] In one embodiment of the present application, when a first recessed area 21 is distributed in the edge portion of the positive electrode sheet 100 and a second recessed area 24 is distributed in the middle portion between the edge portions, the width W4 of the third splicing area 7 located between the first recessed area 21 and the second recessed area 24 ranges from 0.1 mm to 10 mm. For example, the width W4 of the third splicing area 7 can be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 7.0 mm, 8.0 mm, 9.0 mm, 10.0 mm, etc.

[0121] As an implementable embodiment, the ratio of the area of ​​the first splicing area 5 to the area of ​​the first recessed area 21 may be in the range of 0.001 to 0.2.

[0122] Illustratively, the ratio of the area of ​​the first splicing region 5 to the area of ​​the first recessed region 21 may be 0.001, 0.005, 0.01, 0.015, 0.02, 0.05, 0.1, 0.15, 0.2, etc.

[0123] The size of the ratio of the area of ​​the first splicing area 5 to the area of ​​the first recessed area 21 can be adjusted by adjusting the size of the area of ​​the first splicing area 5 and the size of the area of ​​the first recessed area 21 .

[0124] The dynamic performance at the first splicing area 5 is weaker than that of the first recessed area 21 . The area of ​​the first splicing area 5 is set smaller, much smaller than the area of ​​the first recessed area 21 , so as to minimize the negative impact of the weak dynamic performance brought by the first splicing area 5 .

[0125] When the ratio of the area of ​​the first splicing area 5 to the area of ​​the first recessed area 21 is less than 0.001, overlapping is likely to occur between adjacent recesses 25 in the first recessed area 21, affecting the quality of the recesses 25. When the ratio of the area of ​​the first splicing area to the area of ​​the first recessed area is greater than 0.2, the CB value and liquid retention of the battery cell decrease. Therefore, the ratio of the area of ​​the first splicing area to the area of ​​the first recessed area is set at 0.001~0.2.

[0126] Table 1 shows the relationship between the ratio of the area of ​​the first splicing area 5 to the area of ​​the first recessed area 21 and the CB value and liquid retention of the battery cell.

[0127] Table 1

[0128]

[0129] As an implementation method, the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 may be in the range of 0.001 to 0.5.

[0130] Illustratively, the ratio of the area of ​​the second splicing region 6 to the area of ​​the second recessed region 24 may be 0.001, 0.004, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0131] The size of the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 can be adjusted by adjusting the size of the area of ​​the second splicing area 6 and the size of the area of ​​the second recessed area 24 .

[0132] The dynamic performance at the second splicing area 6 is weaker than that of the second recessed area 24 . The area of ​​the second splicing area 6 is set smaller, much smaller than the area of ​​the second recessed area 24 , so as to minimize the negative impact of the weak dynamic performance brought by the second splicing area 6 .

[0133] When the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 is less than 0.001, overlapping is likely to occur between adjacent recesses 25 in the second recessed area 24, affecting the quality of the recesses 25. When the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 is greater than 0.5, the CB value and liquid retention of the battery cell decrease. Therefore, the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 is set at 0.001~0.5.

[0134] Table 2 shows the relationship between the ratio of the area of ​​the second splicing area 6 to the area of ​​the second recessed area 24 and the battery CB value and liquid retention capacity.

[0135] Table 2

[0136]

[0137] Based on any of the above embodiments, in one embodiment of the present application, the ratio of the width of the first splicing area 5 to the width of the edge area 26 of the active material layer 2 can be in the range of (0.2-20):1.

[0138] For example, the ratio of the width of the first splicing area 5 to the width of the edge area 26 can be 0.2:1, 1:1, 5:1, 10:1, 15:1, 20:1, etc.

[0139] like Figure 6 As shown, based on any of the above embodiments, in one embodiment of the present application, the positive electrode sheet 100 may further include:

[0140] The safety coating 8 is located between the active material layer 2 and the current collector 1 .

[0141] The safety coating 8 may be a conductive ceramic coating or other conductive layers.

[0142] It should be noted that when the active material layer 2 is distributed on both the first surface and the second surface of the current collector 1, the safety coating 8 can be between the active material layer 2 and the current collector 1 on either side of the current collector 1, or the safety coating 8 can be distributed on both sides of the current collector 1.

[0143] The safety coating 8 can reduce the damage to the current collector 1 caused by the laser energy transmission when the recess 25 is formed by laser, thereby reducing the probability of damage to the current collector 1 .

[0144] like Figures 2 to 6 As shown, based on any of the above embodiments, in one embodiment of the present application, the recess 25 includes a recessed hole and / or a groove.

[0145] The concave hole and / or groove may be funnel-shaped in cross section, ie, the size thereof gradually decreases along the concave direction.

[0146] In this embodiment, the size of the concave hole is not limited and depends on the situation.

[0147] As an implementation method, the pore diameter a of the concave hole can range from 30μm to 300μm, and / or the depth h1 of the concave hole can range from 2μm to 30μm, and / or the distance D1 between the concave holes can range from 50μm to 2000μm, so as to improve the problem of lithium plating and reduce energy loss.

[0148] The aperture a of the concave holes is preferably in the range of 50 μm to 200 μm, the depth h1 of the concave holes is preferably in the range of 3 μm to 20 μm, and the distance D1 between the concave holes is preferably in the range of 100 μm to 500 μm.

[0149] Illustratively, the pore diameter a of the concave hole can be 30 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc.; the depth h1 of the concave hole can be 2 μm, 3 μm, 8 μm, 10 μm, 15 μm, 20 μm, 30 μm, etc.; the distance D1 between the concave holes can be 50 μm, 100 μm, 200 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, etc.

[0150] The relationship between the aperture of the concave hole and the battery liquid retention capacity is shown in Table 3.

[0151] Table 3

[0152]

[0153] When the concave pore diameter a is less than 30μm, the liquid retention is small. When the concave pore diameter a is greater than 300μm, although the liquid retention is relatively large, it will lead to a lower CB value. Therefore, when the concave pore diameter a is controlled between 30μm and 300μm, the battery liquid retention is relatively good, avoiding a CB value that is too small. It can also ensure energy density and reduce energy loss while controlling electrolyte costs.

[0154] The relationship between the distance between the concave holes and the battery liquid retention capacity is shown in Table 4.

[0155] When the pit spacing D1 is less than 50μm, the liquid retention is large, but the distance between adjacent pits is too small, which easily causes overlap between adjacent pits, affecting the quality of the pits. When the pit spacing D1 is greater than 2000μm, although the liquid retention is relatively large, it will lead to a lower CB value. Therefore, when the pit spacing D1 is controlled between 50μm and 2000μm, the battery liquid retention is relatively good, avoiding a too small CB value, and can also ensure energy density and reduce energy loss while controlling electrolyte costs.

[0156] Table 4

[0157]

[0158] In this embodiment, the size of the groove is not limited and depends on the specific situation.

[0159] As an implementation method, the groove diameter ranges from 30μm to 200μm, and / or the groove depth ranges from 2μm to 40μm, and / or the distance between the grooves ranges from 100μm to 5000μm, so as to improve the problem of lithium plating and reduce energy loss.

[0160] The groove diameter is preferably in the range of 50 μm to 150 μm, the groove depth is preferably in the range of 3 μm to 30 μm, and the distance between the grooves is preferably in the range of 1000 μm to 3000 μm.

[0161] Exemplarily, the groove diameter can be 30μm, 50μm, 100μm, 150μm, 200μm; the groove depth can be 2μm, 3μm, 10μm, 15μm, 20μm, 30μm, 40μm, etc.; the distance between the grooves can be 100μm, 500μm, 1000μm, 1500μm, 2000μm, 3000μm, 4000μm, 5000μm, etc.

[0162] On the basis of any of the above embodiments, in one embodiment of the present application, adjacent first recessed areas 21 are aligned with each other in the first direction X, such as Figure 5 Alternatively, adjacent first recessed areas 21 are staggered in the first direction X, as shown in FIG. Figure 7 shown.

[0163] The first recessed area 21 may be completely aligned, e.g. Figure 5 As shown, it can also be staggered by a certain distance, such as Figure 7 As shown, the offset distance A in the first direction X can range from 0 to 2 mm.

[0164] For example, the staggered distance A between adjacent first recessed areas 21 in the first direction X may be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, etc.

[0165] Based on any of the above embodiments, in one embodiment of the present application, adjacent second recessed areas 24 are aligned with each other in the second direction Y, or adjacent second recessed areas 24 are staggered with each other in the second direction Y; wherein the second direction Y is perpendicular to the first direction X.

[0166] The second recessed area 24 may be perfectly aligned, e.g. Figure 5 As shown, it can also be staggered by a certain distance, such as Figure 8 As shown, the offset distance B in the second direction Y can range from 0 to 2 mm.

[0167] For example, the staggered distance B between adjacent second recessed areas 24 in the second direction Y may be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, etc.

[0168] Based on any of the above embodiments, in one embodiment of the present application, the active material layer 2 includes a first active material layer partition 23 and a second active material layer partition 22, the thickness of the first active material layer partition 23 is smaller than that of the second active material layer partition 22, and the first active material layer partition 23 is at least located between the protective layer 3 and the second active material layer partition 22.

[0169] As an embodiment, the first active material layer partition 23 is located between the protective layer 3 and the second active material layer partition 22 , that is, the first active material layer partition 23 , the second active material layer partition 22 and the protective layer 3 are in the same horizontal plane and are all located on the surface of the current collector 1 .

[0170] As another possible implementation, the first active material layer partition 23 may also be located between the protective layer 3 and the current collector 1 , that is, the protective layer 3 is located on the surface of the first active material layer partition 23 .

[0171] In the present application, there is no limitation on the thickness relationship between the first active material layer partition 23 and the second active material layer partition 22 , which depends on the specific situation.

[0172] In one embodiment of the present application, the thickness ratio of the first active material layer partition 23 to the second active material layer partition 22 may be in the range of (0.2-5):1.

[0173] Illustratively, the thickness ratio of the first active material layer partition 23 to the second active material layer partition 22 may be 0.2:1, 0.5:1, 0.8:1, 0.9:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, etc.

[0174] It should be noted that, in this embodiment, the distance D3 between the first active material layer partition 23 and the protective layer 3 is not limited and can be set arbitrarily.

[0175] In one embodiment of the present application, the distance D3 between the first active material layer partition 23 and the protective layer 3 is in the range of 1 to 10 mm to avoid damage to the protective layer 3 when forming the recess 25 on the first active material layer partition 23 .

[0176] The first active material layer partition 23 and the second active material layer partition 22 may both be provided with recesses 25 . In the present application, there is no limitation on the depth relationship between the recesses 25 in the first active material layer partition 23 and the second active material layer partition 22 .

[0177] As an implementation method, the depth ratio of the concave portion 25 located in the first active material layer partition 23 to the concave portion 25 located in the second active material layer partition 22 is in a range of (0.2-5):1.

[0178] For example, the depth ratio of the recess 25 in the first active material layer partition 23 to the recess 25 in the second active material layer partition 22 may be 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, etc.

[0179] The first active material layer partition 23 is relatively thin, resulting in poor contact with the separator 200 when fabricated into a battery cell. Furthermore, the presence of the recess 25 reduces the amount of positive electrode active material, thereby improving the CB value. Furthermore, the enhanced wetting of the electrolyte into the active material layer 2 improves the dynamic performance of the positive electrode sheet 100.

[0180] Based on any of the above embodiments, in one embodiment of the present application, the ratio of the width W5 of the protective layer 3 to the width of the recess 25 can be in the range of (0.5~80):1, and / or the ratio of the thickness of the protection zone to the depth of the recess 25 can be in the range of (0.5~5:1), and / or the ratio of the depth of the recess 25 to the thickness of the remaining active material layer 2 at the location of the recess 25 can be in the range of 1:(1~30) to obtain a better CB value and liquid retention amount.

[0181] When the concave portion 25 is a concave hole, the width of the concave portion 25 is the hole diameter; when the concave portion 25 is a groove, the width of the concave portion 25 is the groove diameter.

[0182] For example, when the active material layer 2 is distributed on the first surface of the current collector 1, the ratio of the depth of the recess 25 to the thickness of the active material layer 2 remaining at the location of the recess 25 is the ratio of the depth of the recess 25 above the active material layer 2 on the first surface of the current collector 1 to the thickness of the active material layer 2 below the recess 25 on the first surface of the current collector 1. Exemplarily, when the thickness of the active material layer 2 on the first surface of the current collector 1 is a and the depth of the recess 25 is b, the thickness of the active material layer 2 remaining at the location of the recess 25 is ab.

[0183] The ratio of the depth of the recess 25 to the thickness of the active material layer 2 remaining at the location of the recess 25 is preferably in the range of 1:(5-15), for example, 1:1, 1:5, 1:10, 1:15, 1:20, 1:30, etc.

[0184] The ratio of the depth of recess 25 to the thickness of active material layer 2 where recess 25 is located can be adjusted by adjusting the depth of recess 25 and the thickness of active material layer 2 where recess 25 is located.

[0185] Table 5 shows the relationship between the ratio of the depth of the recess 25 to the thickness of the active material layer 2 where the recess 25 is located, the CB value, and the liquid retention amount.

[0186] When the ratio of the depth of the recess 25 to the thickness of the active material layer 2 remaining at the location of the recess 25 is less than 1:1, the CB value of the battery is relatively small. When the ratio of the depth of the recess 25 to the thickness of the active material layer 2 remaining at the location of the recess 25 is greater than 1:30, the liquid retention of the battery is reduced. Therefore, the ratio of the depth of the recess 25 to the thickness of the active material layer 2 where the recess 25 is located is controlled within a range of 1:1 to 1:30, so that the CB value and liquid retention of the battery are both at a good level.

[0187] Table 5

[0188]

[0189] Based on any of the above embodiments, in one embodiment of the present application, the width W5 of the protective layer 3 ranges from 0.1 mm to 4 mm, and / or the thickness h2 of the protective layer 3 ranges from 10 μm to 60 μm, so as to provide good protection for the current collector 1 when cutting and manufacturing the first electrode tab 4.

[0190] For example, the width W5 of the protective layer 3 may be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, etc.; the thickness h2 of the protective layer 3 may be 10 μm, 30 μm, 50 μm, 60 μm, etc.

[0191] Based on any of the above implementations, in one embodiment of the present application, the number of the first electrode tabs 4 is at least two.

[0192] The specific number of the first electrode tabs 4 is not limited in this embodiment and depends on the circumstances.

[0193] Based on any of the above implementations, in one embodiment of the present application, the protective layer includes any one or any combination of the following:

[0194] A ceramic layer, a composite protective layer, and a film layer, wherein the composite protective layer comprises a stacked aluminum oxide layer and a boehmite layer.

[0195] The adhesive film layer may be a PI (Polyimide) adhesive film or a PAA (Polyacrylic acid) adhesive film, etc., which is not limited in this embodiment.

[0196] When using ceramic layer and composite protective layer, the hardness of the protection zone can be improved; when using film layer, the roller-pressure breakage can be improved.

[0197] Based on any of the above embodiments, in one embodiment of the present application, the projection of the recess 25 on the active material layer 2 located on the first surface of the current collector 1 on the current collector 1 and the projection of the recess 25 on the active material layer 2 located on the second surface of the current collector 1 on the current collector 1 are staggered with each other, or the projection of the recess 25 on the active material layer 2 located on the first surface of the current collector 1 on the current collector 1 and the projection of the recess 25 on the active material layer 2 located on the second surface of the current collector 1 on the current collector 1 overlap.

[0198] The active material layer 2 is distributed on both the first and second surfaces of the current collector 1. The recesses 25 can be produced by laser drilling. Laser drilling in the active material layer 2 may damage the current collector 1. Preferably, the recesses 25 on the active material layer 2 on the first and second surfaces of the current collector 1 are staggered. This can reduce the effect of laser energy on the same location on the current collector 1, reduce the probability of damage to the current collector 1, and improve the yield of the current collector 1.

[0199] Please refer to Figure 10 , the present application also provides a battery cell, the battery cell comprising the positive electrode sheet, the negative electrode sheet, the separator and the second electrode tab of any one of the above embodiments;

[0200] The diaphragm is located between the positive electrode sheet and the negative electrode sheet, and the second electrode tab is connected to the first electrode tab 4 in the positive electrode sheet.

[0201] like Figure 10 As shown, a plurality of first electrode tabs 4 on the positive electrode sheet are bent and connected together, and the connected whole can be electrically connected to an external circuit.

[0202] The first electrode tab 4 and the second electrode tab may be connected by welding to enhance the connection strength between the first electrode tab 4 and the second electrode tab.

[0203] In the extending direction perpendicular to the first electrode tab 4 , the welding portion of the first electrode tab 4 and the second electrode tab may completely overlap or may not completely overlap, which is not limited in the present application.

[0204] The separator and the negative electrode sheet can refer to the relevant technology and will not be described in detail here.

[0205] It should be noted that the negative electrode sheet is also connected to a third electrode tab.

[0206] Based on any of the above embodiments, in one embodiment of the present application, the N / P ratio between the positive electrode sheet 100 and the negative electrode sheet 300 is in the range of 1.01 to 1.20, so as to achieve the best performance, cycle life and safety of the battery.

[0207] The N / P ratio preferably ranges from 1.01 to 1.10. For example, the N / P ratio can be 1.01, 1.02, 1.05, 1.1, 1.15, 1.20, etc.

[0208] The formula for calculating the N / P ratio is:

[0209] ; (1)

[0210] Where C1 is the capacity of the negative electrode sheet (300 volts), mA.h; C2 is the capacity of the positive electrode sheet (100 volts), mA.h; m1 is the mass of the negative electrode sheet (300 volts), g; m2 is the mass of the positive electrode sheet (100 volts), g; ρ1 is the surface density of the negative electrode sheet (300 volts), g / cm 2 ; ρ2 is the surface density of the positive electrode sheet 100, g / cm 2 .

[0211] Among them, the capacity of the negative electrode active material (C1 / m1) can be obtained by preparing a button battery through the electrode sheet based on the exerted capacity. The surface density of the positive and negative electrode sheets 300 can be obtained by fixed area mass / fixed area. The recess 25 on the positive electrode sheet 100 affects the size of the positive electrode surface density.

[0212] The capacity of the negative electrode active material can be 300mA.h / g~370mA.h / g, and the capacity of the positive electrode active material can be 160mA.h / g~200mA.h / g; the negative electrode surface density can be 20g / m 2 ~180g / m 2 , positive electrode surface density 50g / m 2 ~300g / m 2 .

[0213] Based on any of the above embodiments, in one embodiment of the present application, Figure 11 As shown, the angle α between the first electrode tab 4 and the recessed area on the positive electrode sheet can range from 0° to 90°, thereby significantly increasing the energy density of the battery cell.

[0214] For example, the angle α between the first electrode tab 4 and the recessed region may be 0°, 30°, 45°, 60°, 90°, etc.

[0215] Based on any of the above embodiments, in one embodiment of the present application, Figure 12 As shown, the first electrode tab 4 includes a welding area 41, and the distance D4 between the welding area 41 and the recessed area on the positive electrode sheet ranges from 2 mm to 20 mm, and / or, the distance D5 between the welding area 41 and the protective layer 3 on the positive electrode sheet ranges from 5 mm to 20 mm, so as to avoid adverse effects on the protective layer 3 and the recessed area 25 during welding.

[0216] The distance D4 between the welding area 41 and the recessed area is preferably in the range of 3 mm to 10 mm, for example, 3 mm, 5 mm, 8 mm, 10 mm, etc.

[0217] In one embodiment of the present application, Figure 13 As shown, the battery cell includes the positive electrode sheet 100 , the separator 200 , and the negative electrode sheet 300 which are stacked and wound. The positive electrode sheet 100 includes a bending area and a straight area, and the bending area includes a concave portion 25 .

[0218] The negative electrode sheet 300 includes a negative electrode current collector 9 , a negative electrode active material layer 10 located on at least one surface of the negative electrode current collector 9 , and a third electrode tab 11 .

[0219] Based on the above embodiments, in one embodiment of the present application, in a battery cell including the positive electrode sheet, the diaphragm, and the negative electrode sheet arranged in a stacked and wound manner, a splicing area is distributed between adjacent recessed areas. The splicing area can serve as a stress buffer zone for the positive electrode sheet 100 to reduce the possibility of the positive electrode sheet 100 breaking.

[0220] Based on the above embodiment, in one embodiment of the present application, in a battery cell comprising the stacked and wound positive electrode sheet, the separator, and the negative electrode sheet, the edge region of the positive electrode sheet includes the recessed portion. That is, both the edge region and the bend region include recessed portions, thereby resolving the problem of lithium deposition in the edge region and the bend region.

[0221] The present application also provides a lithium-ion secondary battery, which includes a battery cell and a membrane shell according to any one of the above embodiments, wherein the battery cell is located in the membrane shell, and the second electrode tab is exposed outside the membrane shell.

[0222] The membrane shell can be aluminum foil or the like.

[0223] The lithium-ion secondary battery may be a wound battery or a laminated battery, which is not limited in this embodiment.

[0224] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0225] The above is a detailed introduction to the positive electrode sheet, battery cell and lithium-ion secondary battery provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A positive electrode sheet, characterized in that: include: Current collector, active material layer, protective layer and first electrode tab; The surface of the current collector includes a paste coating area and a protection area, the active material layer is located in the paste coating area, the protection layer is located in the protection area, and the protection area is located between the active material layer and the first electrode tab, and the first electrode tab extends outward from the current collector along a first direction; The active material layer includes a recessed area, the recessed area includes at least one recessed portion, and in the first direction, a distance between the recessed area and the protective layer ranges from 0 to 20 mm.

2. The positive electrode sheet according to claim 1, wherein: The recessed area includes a first recessed area and / or a second recessed area. The first recessed area is located at an edge portion of the active material layer in the first direction. The second recessed area is located at a middle portion of the active material layer in the first direction.

3. The positive electrode sheet according to claim 2, wherein: The width of the first concave area ranges from 1 mm to 20 mm; and / or, the width of the edge region of the active material layer is in the range of 0 to 20 mm; And / or, the ratio of the width of the first recessed area to the width of the edge area is in the range of (0.5-5):1; The edge region is a region between the first recessed region and a side edge of the active material layer.

4. The positive electrode sheet according to claim 3, wherein: The distance between the recessed area and the protective layer is greater than zero; and / or the width of the edge area of ​​the active material layer is greater than zero.

5. The positive electrode sheet according to any one of claims 1 to 3, characterized in that: Also includes: A splicing area is located between adjacent recessed areas.

6. The positive electrode sheet according to claim 2, wherein: The length of the first splicing area between the first recessed areas ranges from 0.1 mm to 10 mm; and / or, the width of the second splicing area between the second recessed areas is in the range of 0.1 mm to 10 mm; And / or, the width of the third splicing area between the first recessed area and the second recessed area is in the range of 0.1 mm to 10 mm.

7. The positive electrode sheet according to claim 6, wherein: The ratio of the area of ​​the first splicing area to the area of ​​the first recessed area is in a range of 0.001 to 0.2; And / or, the ratio of the area of ​​the second splicing area to the area of ​​the second recessed area is in the range of 0.001 to 0.

5.

8. The positive electrode sheet according to claim 6, wherein: The ratio of the width of the first splicing area to the width of the edge area of ​​the active material layer is in the range of (0.2-20):

1.

9. The positive electrode sheet according to claim 1, wherein: Also includes: The safety coating is located between the active material layer and the current collector.

10. The positive electrode sheet according to any one of claims 1 to 9, characterized in that: The recessed portion includes a recessed hole and / or a groove.

11. The positive electrode sheet according to claim 10, wherein: The pore size of the concave hole ranges from 30 μm to 300 μm; And / or, the depth of the concave hole ranges from 2 μm to 30 μm; And / or, the distance between the concave holes ranges from 50 μm to 2000 μm; And / or, the groove diameter ranges from 30 μm to 200 μm; And / or, the depth of the groove ranges from 2 μm to 40 μm; And / or, the distance between the grooves ranges from 100 μm to 5000 μm.

12. The positive electrode sheet according to claim 1, wherein: The active material layer includes a first active material layer partition and a second active material layer partition, the first active material layer partition is thinner than the second active material layer partition, and the first active material layer partition is at least partially located between the protective layer and the second active material layer partition.

13. The positive electrode sheet according to claim 12, wherein: The thickness ratio of the first active material layer partition to the second active material layer partition is in the range of (0.2-5):1; and / or, the distance between the first active material layer partition and the protective layer is in the range of 1 to 10 mm; And / or, a depth ratio of the concave portion located in the first active material layer partition to the concave portion located in the second active material layer partition is in a range of (0.2-5):

1.

14. The positive electrode sheet according to claim 1, wherein: The ratio of the width of the protective layer to the width of the recess is in the range of (0.5~80):1, and / or the ratio of the thickness of the protective layer to the depth of the recess is in the range of (0.5~5:1), and / or the ratio of the depth of the recess to the thickness of the remaining active material layer at the location of the recess is in the range of 1:(1~30).

15. The positive electrode sheet according to claim 1, wherein: The width of the protective layer ranges from 0.1 mm to 4 mm; And / or, the thickness of the protective layer ranges from 10 μm to 60 μm.

16. The positive electrode sheet according to claim 1, wherein: The number of the first electrode tabs is at least two.

17. A battery cell, characterized in that: The battery cell comprises the positive electrode sheet according to any one of claims 1 to 16, a negative electrode sheet, a separator and a second tab; The separator is located between the positive electrode sheet and the negative electrode sheet, and the second electrode tab is connected to the first electrode tab in the positive electrode sheet.

18. The battery cell according to claim 17, wherein: The first electrode tab includes a welding area, and the distance between the welding area and the recessed area on the positive electrode sheet ranges from 2 mm to 20 mm; And / or, the distance between the welding area and the protective layer on the positive electrode sheet ranges from 5 mm to 20 mm.

19. The battery cell according to claim 17, wherein: The N / P ratio between the positive electrode sheet and the negative electrode sheet is in the range of 1.01 to 1.20; And / or, the angle between the first electrode tab and the recessed area on the positive electrode sheet ranges from 0° to 90°.

20. The battery cell according to claim 17, wherein: The battery cell includes the positive electrode sheet, the separator, and the negative electrode sheet that are stacked and wound together. The positive electrode sheet includes a bending area and a straight area, and the bending area contains a concave portion.

21. The battery cell according to claim 20, wherein: There are splicing areas distributed between adjacent recessed areas.

22. The battery cell according to any one of claims 17 to 21, characterized in that: The edge area of ​​the positive electrode sheet contains the recess.

23. A lithium ion secondary battery, characterized in that: The lithium-ion secondary battery comprises the battery core and membrane shell according to any one of claims 17 to 22, wherein the battery core is located in the membrane shell, and the second electrode tab is exposed outside the membrane shell.

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