Positive plate and battery

Abstract

The utility model discloses a positive plate which comprises a current collector, a first active material layer and a second active material layer, the first active material layer and the second active material layer are coated on different surfaces of the current collector, and the first active material layer and the second active material layer form a single-surface coating area and a double-surface coating area on the current collector; a plurality of reinforcing ribs are arranged in a transition area of the single-side coating area and the double-side coating area, and the transition area comprises a first part located in the single-side coating area and a second part located in the double-side coating area. The positive plate has the beneficial effects that the reinforcing ribs are arranged in the transition area of the single-sided and double-sided coating areas of the positive plate, so that the tensile strength of the positive plate in the transition area is improved, the positive plate can bear higher pressure without deformation or rupture, and the problem that the positive plate is broken due to expansion of a negative electrode material is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium-ion batteries, and more specifically, to a positive electrode sheet and a battery. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in industrial applications due to their high energy density, long cycle life, low self-discharge, and no memory effect. Especially in the field of civilian drones, extremely high requirements are put forward for the energy density and power performance of the battery cells.

[0003] To meet the demand for ultra-high energy density, an effective method at present is to replace a part of graphite with silicon in the electrode sheet of the battery cell to obtain a higher specific capacity, reduce the weight of the battery cell, and improve the energy density of the battery. In most current lithium-ion batteries, the active materials coated on both sides of the positive electrode sheet are not completely symmetrical, and there is often a coating length difference (i.e., there are single-sided coating areas and double-sided coating areas) to improve the energy density of the battery cell. Since the positive aluminum current collector itself is relatively brittle and has poor tensile strength, and there is a thickness difference at the single-sided and double-sided junction area of the positive electrode sheet, this place becomes the weakest stress concentration point on the positive electrode sheet. As is well known, during the cyclic charge and discharge process, the volume of silicon expands by up to 400%, and in the electrode sheet doped with silicon, the thickness difference between full charge and empty charge is 70%. During long-term cyclic charge and discharge, the negative electrode sheet also continuously expands and contracts, and the corresponding positive electrode is constantly squeezed by the negative electrode sheet. Due to the existence of the thickness difference at its single-sided and double-sided junction area, it also becomes the place where the electrode sheet is most likely to break, and the macroscopic manifestation is that the capacity of the battery suddenly drops like a cliff, and the discharge capacity is severely insufficient. Summary of the Utility Model

[0004] To solve the problem that during the cycle of a lithium-ion battery, due to the continuous expansion and contraction of the negative electrode sheet, the transition area of the single-sided and double-sided paste coating on the positive electrode sheet is prone to electrode sheet breakage, the purpose of the present utility model is to provide a positive electrode sheet and a battery.

[0005] On the one hand, the present utility model provides a positive electrode sheet, which includes:

[0006] A current collector, a first active material layer and a second active material layer coated on different surfaces of the current collector, and the first active material layer and the second active material layer form a single-sided coating area and a double-sided coating area on the current collector;

[0007] A plurality of reinforcing ribs are provided in the transition area between the single-sided coating area and the double-sided coating area, where the transition includes a first part located in the single-sided coating area and a second part located in the double-sided coating area.

[0008] As an implementation manner of the present utility model, the multiple reinforcing ribs are provided at least at one of the first part and the second part within the transition region.

[0009] As an implementation manner of the present utility model, the multiple reinforcing ribs form a reinforcing rib region in the transition region, and the included angle between the extending direction of the multiple reinforcing ribs and the length direction of the current collector is 0 - 180°.

[0010] As an implementation manner of the present utility model, the extending direction of the multiple reinforcing ribs is parallel, inclined or perpendicular to the length direction of the current collector.

[0011] As an implementation manner of the present utility model, the multiple reinforcing ribs include at least one first reinforcing rib and at least one second reinforcing rib, and the first reinforcing rib and the second reinforcing rib are arranged in a cross - setting.

[0012] As an implementation manner of the present utility model, the width of the reinforcing rib region is 3 - 20 mm, the thickness of the current collector is 5 - 30 μm, and the thicknesses of the first active material layer and the second active material layer are 30 - 200 μm respectively.

[0013] As an implementation manner of the present utility model, the width of the reinforcing rib region is L mm, the thickness of the current collector is M μm, and the thickness difference between the first active material layer and the second active material layer is N μm. L, M and N satisfy at least one of the following formula (1) and formula (2):

[0014] 0.150 ≤ L / M ≤ 4.2 formula (1),

[0015] L / N ≥ 0.1 formula (2),

[0016] where 3 ≤ L ≤ 20, 5 ≤ M ≤ 30, 0 < N ≤ 30.

[0017] As an implementation manner of the present utility model, L and M satisfy the following formula (3):

[0018] 0.35 ≤ L / M ≤ 2 formula (3),

[0019] where 3 ≤ L ≤ 20, 5 ≤ M ≤ 30.

[0020] As an implementation manner of the present utility model, the height of the reinforcing rib region is 33% - 100% of the width of the current collector.

[0021] As an implementation manner of the present utility model, the width of the reinforcing rib is 0.5 - 2.2 mm, the thickness of the reinforcing rib is 10 - 200 μm, and the interval between two adjacent reinforcing ribs is 0.5 - 4 mm.

[0022] On the other hand, the present utility model also provides a battery, and the battery includes the above-mentioned positive electrode sheet.

[0023] The beneficial effects of the present utility model are as follows: by arranging reinforcing ribs in the transition area of the single-sided and double-sided coating areas of the positive electrode sheet, the tensile strength of the positive electrode sheet in this transition area is improved, enabling it to withstand greater pressure without deformation or rupture, and avoiding the problem of the positive electrode sheet breaking due to the expansion of the negative electrode material. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present utility model, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative labor.

[0025] Figure 1 It is a schematic structural view of a positive electrode sheet according to an embodiment of the present utility model.

[0026] Figure 2 It is a top view of a positive electrode sheet according to an embodiment of the present utility model.

[0027] Figure 3 It is a top view of a positive electrode sheet according to another embodiment of the present utility model.

[0028] Figure 4 It is a top view of a positive electrode sheet according to another embodiment of the present utility model.

[0029] Figure 5 For Figure 4 It is a sectional view of the positive electrode sheet shown in the A-A direction.

[0030] Figure 6 It is a top view of a positive electrode sheet according to another embodiment of the present utility model.

[0031] Figure 7 It is a top view of a positive electrode sheet according to another embodiment of the present utility model.

[0032] Figure 8 It is a top view of a positive electrode sheet according to another embodiment of the present utility model. Detailed Embodiments

[0033] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

[0034] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present utility model, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0035] In addition, in the description of the present utility model, the terms used are only for illustrative purposes and are not intended to limit the scope of the present utility model. The terms "comprising" and / or "including" are used to specify the existence of the described elements, steps, operations, and / or components, but do not exclude the existence or addition of one or more other elements, steps, operations, and / or components. The terms "first", "second", etc. may be used to describe various elements, do not represent an order, and do not limit these elements. In addition, in the description of the present utility model, unless otherwise specified, the meaning of "a plurality of" is two or more. These terms are only used to distinguish one element from another. In combination with the following drawings, these and / or other aspects become obvious, and it is easier for those of ordinary skill in the art to understand the description of the embodiments of the present utility model. The drawings are only used to depict the embodiments of the present utility model for illustrative purposes. Those skilled in the art will easily recognize from the following description that alternative embodiments of the structure and method shown in the present utility model can be adopted without departing from the principles described in the present utility model.

[0036] Figure 1 It is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present utility model.

[0037] As Figure 1 shown, the positive electrode sheet includes:

[0038] A current collector 30, a first active material layer 10 and a second active material layer 20 coated on different surfaces of the current collector 30, and the first active material layer 10 and the second active material layer 20 form a single-sided coating area and a double-sided coating area on the current collector 30;

[0039] A plurality of reinforcing ribs are provided in the transition region 40 between the single-sided coating area and the double-sided coating area to improve the strength of the positive electrode sheet in the transition region 40, where the transition region 40 includes a first part located in the single-sided coating area and a second part located in the double-sided coating area.

[0040] Specifically, the first active material layer 10 and the second active material layer 20 are coated on opposite surfaces of the current collector 30. For example, the first active material layer 10 is coated on the upper surface of the current collector 30, and the second active material layer 20 is coated on the lower surface of the current collector 30. Among them, the coating length of the first active material layer 10 on the upper surface of the current collector 30 is shorter, and the coating length of the second active material layer 20 on the lower surface of the current collector 30 is longer. The overlapping area of the first active material layer 10 and the second active material layer 20 in the length direction of the current collector 30 forms a double-sided coating area of the positive electrode sheet, and the area where the second active material layer 20 extends beyond in the length direction of the current collector 30 forms a single-sided coating area of the positive electrode sheet. The part where the double-sided coating area transitions to the single-sided coating area forms a transition area 40. For example Figure 1 The part outlined by the dotted line in the figure is the transition area 40 of the positive electrode sheet. A plurality of reinforcing ribs are provided at the position of the transition area 40 to solve the stress concentration problem caused by the single-sided and double-sided coating areas in the transition area 40. During the cyclic charge and discharge process of the battery, as the negative electrode sheet continuously expands and contracts, the plurality of reinforcing ribs can effectively disperse the stress concentration caused by the uneven thickness of the transition area 40, improve the tensile and compressive resistance of the positive electrode sheet in the transition area 40, and thus avoid the problem of electrode sheet fracture caused by the expansion and contraction of the negative electrode sheet.

[0041] In one example, the first active material layer 10 and the second active material layer 20 have the same composition. For example, the first active material layer 10 and the second active material layer 20 include a positive electrode active material, and / or a binder, and / or a conductive agent, and / or a solvent. The positive electrode active material includes one or more mixtures of lithium nickel cobalt manganese oxide materials, lithium cobalt oxide materials, lithium nickel cobalt aluminum oxide materials, lithium manganese oxide materials, lithium iron phosphate materials, and lithium-rich manganese-based materials; the binder is one or more mixtures of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyimide, or polyethylene; the conductive agent is one or more mixtures of conductive ceramics, carbon black, graphite, graphene, polyaniline, polypyrrole, Ketjen black, acetylene black, and carbon nanotubes; the solvent is one or more mixtures of N-methylpyrrolidone, water, ethanol, and polyethylene glycol. The current collector 30 is aluminum foil or any other foil material.

[0042] It should be noted that the reinforcing ribs of the present application are provided on the positive electrode sheet, that is, after the coating of the first active material layer 10 and the second active material layer 20 is completed, the obtained positive electrode sheet is then processed with reinforcing ribs. In this way, it can ensure the balanced distribution of the amount of active material on both sides of the current collector 30, maintain the consistency of lithium deintercalation of the positive electrode, and avoid the problem of lithium plating caused by uneven active material on both sides of the current collector 30.

[0043] An alternative embodiment is that multiple reinforcing ribs are provided at least at one of the first part and the second part of the transition region 40. For example, the reinforcing ribs are provided on the double-sided coating area within the transition region 40.

[0044] Alternatively, as another embodiment, the reinforcing ribs are provided on the single-sided coating area within the transition region 40;

[0045] Alternatively, as another embodiment, the reinforcing ribs are provided on both the double-sided coating area and the single-sided coating area within the transition region 40.

[0046] For example Figure 2 As shown, multiple reinforcing ribs 4011 are provided on both the double-sided coating area and the single-sided coating area within the transition region 40, that is, the orthographic projection of the reinforcing rib region 401 formed by the multiple reinforcing ribs 4011 is located on the first active material layer 10 and the current collector 30 within the transition region 40. Another example Figure 3 As shown, multiple reinforcing ribs 4021 are provided on the single-sided coating area of the transition region 40, that is, the orthographic projection of the reinforcing rib region 402 formed by the multiple reinforcing ribs 4021 is located on the current collector 30 within the transition region 40. The above are only exemplary descriptions of the positions where the reinforcing ribs are provided. The reinforcing ribs can also be provided within the transition region 40 in other ways, and the present application does not specifically limit their setting methods.

[0047] An alternative embodiment is that multiple reinforcing ribs form a reinforcing rib region in the transition region 40, and the extension direction of the multiple reinforcing ribs forms an angle of 0 - 180° with the length direction of the current collector 30. For example, the extension direction of the reinforcing ribs forms an angle of any one or more of 0°, 30°, 45°, 75°, 90°, 110°, 145°, 160°, and 170° with the length direction of the current collector 30.

[0048] For the convenience of description, the direction of the X-axis in the accompanying drawings of the specification represents the length direction of the current collector 30, and the direction of the Y-axis represents the width direction of the current collector 30. It can be understood that the multiple reinforcing ribs can be provided within the transition region 40 with the same or different extension directions.

[0049] An alternative embodiment is that multiple reinforcing ribs include at least one first reinforcing rib and at least one second reinforcing rib, and the first reinforcing rib and the second reinforcing rib are arranged crosswise.

[0050] Specifically, as Figure 2 , Figure 3 or Figure 8 As shown, the multiple reinforcing ribs are arranged in two extension manners and are arranged in an intersecting manner within the transition region 40.

[0051] Figure 2Among them, multiple reinforcing ribs 4011 are arranged in the single-sided coating area and the double-sided coating area within the transition region 40. Among them, the extending directions of a part of the reinforcing ribs 4011 are set at 0° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is parallel to the length direction of the current collector), and the extending directions of another part of the reinforcing ribs 4011 are set at 90° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is perpendicular to the length direction of the current collector).

[0052] Figure 3 Among them, multiple reinforcing ribs 4021 are arranged in the single-sided coating area within the transition region 40. Among them, the extending directions of some of the reinforcing ribs 4021 are set at 0° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is parallel to the length direction of the current collector), and the extending directions of some of the reinforcing ribs 4011 are set at 90° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is perpendicular to the length direction of the current collector).

[0053] Figure 8 Among them, multiple reinforcing ribs 4061 are arranged in the single-sided coating area and the double-sided coating area within the transition region 40. Among them, the extending directions of some of the reinforcing ribs 4061 are set at 45° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is inclined with respect to the length direction of the current collector), and the extending directions of some of the reinforcing ribs 4061 are set at 135° with respect to the length direction of the current collector 30 (that is, the extending direction of the reinforcing rib is inclined with respect to the length direction of the current collector).

[0054] Alternatively, as another embodiment, multiple reinforcing ribs are arranged in the transition region 40 with the same extending direction.

[0055] Specifically, as Figure 4 、 Figure 6 or Figure 7 shown, Figure 4 Among them, the extending directions of multiple reinforcing ribs 4031 are all arranged in the transition region 40 parallel to the length direction of the current collector 30; Figure 6 Among them, the extending directions of multiple reinforcing ribs 4041 are all arranged in the transition region 40 perpendicular to the length direction of the current collector 30; and then Figure 7 Among them, the extending directions of multiple reinforcing ribs 4051 are all inclined at the same angle with respect to the length direction of the current collector 30.

[0056] Preferably, the extending direction of the reinforcing rib is parallel, inclined or perpendicular to the length direction of the current collector.

[0057] Continue to refer to Figure 4, a plurality of reinforcing ribs 4031 are parallel to each other and extend along the length direction of the current collector 30. Specifically, the plurality of reinforcing ribs 4031 are horizontally arranged in the double-sided coating area and the single-sided coating area within the positive electrode sheet transition region 40. That is, the orthographic projection of the reinforcing rib region 403 formed by the plurality of reinforcing ribs 4031 is located on the first active material layer 10 and the current collector 30 within the transition region 40. It can not only more effectively decompose the stress concentration in the transition region 40 and improve the tensile and compressive capabilities of the positive electrode sheet, but also simplify the processing procedure of the reinforcing ribs. Only one rolling is required to complete the treatment of the reinforcing ribs, avoiding the adverse effects brought by multiple rollings on the electrode sheet.

[0058] Continue to refer to Figure 6 , a plurality of reinforcing ribs 4041 are parallel to each other and extend along the width direction of the current collector 30. Specifically, the plurality of reinforcing ribs 4041 are vertically arranged in the double-sided coating area and the single-sided coating area within the positive electrode sheet transition region 40. That is, the orthographic projection of the reinforcing rib region 404 formed by the plurality of reinforcing ribs 4041 is located on the first active material layer 10 and the current collector 30 within the transition region 40. It can not only more effectively decompose the stress concentration in the transition region 40 and improve the tensile and compressive capabilities of the positive electrode sheet, but also simplify the processing procedure of the reinforcing ribs. Only one rolling is required to complete the treatment of the reinforcing ribs, avoiding the adverse effects brought by multiple rollings on the electrode sheet.

[0059] Continue to refer to Figure 7 , a plurality of reinforcing ribs 4051 are parallel to each other and extend along a direction inclined to the length direction of the current collector 30. Specifically, the plurality of reinforcing ribs 4051 are inclined and arranged in the double-sided coating area and the single-sided coating area within the positive electrode sheet transition region 40. That is, the orthographic projection of the reinforcing rib region 405 formed by the plurality of reinforcing ribs 4051 is located on the first active material layer 10 and the current collector 30 within the transition region 40. It can not only more effectively decompose the stress concentration in the transition region 40 and improve the tensile and compressive capabilities of the positive electrode sheet, but also simplify the processing procedure of the reinforcing ribs. Only one rolling is required to complete the treatment of the reinforcing ribs, avoiding the adverse effects brought by multiple rollings on the electrode sheet.

[0060] An optional implementation manner is that a plurality of reinforcing ribs form a reinforcing rib region in the transition region 40. Among them, the length of the reinforcing rib region in the X-axis direction is the width of the reinforcing rib region, and the length of the reinforcing rib region in the Y-axis direction is the height of the reinforcing rib region.

[0061] For example, refer to Figure 2-7 , where Figure 2 , in it, a plurality of reinforcing ribs 4011 intersect to form a reinforcing rib region 401; Figure 3 , in it, a plurality of reinforcing ribs 4021 intersect to form a reinforcing rib region 402; Figure 4 , in it, a plurality of reinforcing ribs 4031 are horizontally arranged to form a reinforcing rib region 403;Figure 6 In it, multiple reinforcing ribs 4041 are vertically arranged to form a reinforcing rib region 404; Figure 7 In it, multiple reinforcing ribs 4051 are inclined to form a reinforcing rib region 405.

[0062] Preferably, the width of the reinforcing rib region is 3 - 20 mm, the thickness of the current collector 30 is 5 - 30 μm, and the thicknesses of the first active material layer 10 and the second active material layer 10 are 30 - 200 μm respectively.

[0063] More preferably, the thicknesses of the first active material layer 10 and the second active material layer 20 are different, and the width L (mm) of the reinforcing rib region, the thickness M (μm) of the current collector 30, and the thickness difference N (μm) between the first active material layer 10 and the second active material layer 20 satisfy the following relationships:

[0064] 0.150 ≤ L / M ≤ 4.2 Equation (1),

[0065] L / N ≥ 0.1 Equation (2),

[0066] wherein, 3 ≤ L ≤ 20, 5 ≤ M ≤ 30, 0 < N ≤ 30.

[0067] It is not difficult to understand that the thinner the aluminum foil used, the wider the width of the required reinforcing rib region of the positive electrode sheet to improve the tensile and compressive abilities of the positive electrode sheet.

[0068] For example, the ratio of the width of the reinforcing rib region to the thickness of the current collector is 0.5, 0.8, 1.0, 1.2, 1.6, 2.0, 2.5, 3.0, 3.5, 3.8 or 4.0, etc. When the positive electrode sheet meets the above range, it can solve the problem of the positive electrode sheet breaking while taking into account the optimal energy density of the battery cell. When the ratio of the width of the reinforcing rib region to the thickness of the current collector is less than 0.15, the reinforcing rib cannot play the role of releasing the concentrated stress, and the positive electrode sheet will still break after being squeezed by the negative electrode sheet several times; when the ratio of the width of the reinforcing rib region to the thickness of the current collector is greater than 4.2, it will cause too long grooves or protrusions in the foil or the active material coating area, resulting in unevenness on the surface of the battery cell, increasing the thickness of the battery cell, and reducing the energy density of the battery cell.

[0069] At the same time, it can be understood that the greater the thickness difference between the first active material layer 10 and the second active material layer 20, the more serious the stress concentration that occurs during the expansion and contraction of the negative electrode sheet in the positive electrode sheet, and a wider reinforcing rib region needs to be set to better relieve the stress concentration in the transition region 40. However, the thickness difference between the first active material layer 10 and the second active material layer 20 needs to be controlled within the range of 0 - 30 μm. If the thickness difference between the two is set too large, the stress concentration on the side with the thinner active material layer is serious, and the electrode sheet will curl towards the thinner side, resulting in the unusability of the electrode sheet.

[0070] For example, the ratio of the width of the ribbed area to the thickness difference between the first active material layer 10 and the second active material layer 20 is 0.12, 0.13, 0.15, 0.16, 0.18, or 2.0, etc. When the positive electrode sheet meets the above range, the problem of breakage of the positive electrode sheet can be solved, and at the same time, the interfacial lithium deposition caused by the problem of the detachment speed of the active layer can be prevented. If the ratio of the rib width to the thickness difference between the first active material layer 10 and the second active material layer 20 is less than 0.1, the ribbed area is too narrow to achieve the effect of dispersing stress concentration.

[0071] Preferably, L and M satisfy the following formula (3):

[0072] 0.35 ≤ L / M ≤ 2 Formula (3), where 3 ≤ L ≤ 20 and 5 ≤ M ≤ 30.

[0073] In an alternative embodiment, the height of the ribbed area is 33% - 100% of the width of the current collector 30. For example, the height of the ribbed area can be set to be equal to the width of the current collector 30. If the height of the ribbed area is too small, less than 1 / 3 of the width of the current collector 30, the ribs cannot effectively release the stress of the electrode sheet, and thus it is impossible to avoid the breakage of the positive electrode sheet due to stress concentration.

[0074] In an alternative embodiment, the width L of the rib is 0.5 - 2.2 mm. For example, the width L of the rib is 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, or 2 mm, etc. If the width of the rib is too narrow, the curvature of the current collector 30 will become larger, easily causing the current collector 30 to break; if the width of the rib is too large, the curvature of the current collector 30 is insufficient, and the stress cannot be effectively decomposed, and it will still be concentrated in the transition region 40, unable to effectively relieve stress concentration.

[0075] The thickness H of the rib is 10 - 200 μm. For example, the thickness H of the rib is 50 - 180 μm, 80 - 160 μm, 70 - 120 μm, or 100 - 160, etc. If the thickness of the rib is too small, it cannot achieve the effect of strengthening the current collector 30 in the transition region, and there is no obvious difference from the flat current collector 30; if the thickness of the rib is too thick, the current collector 30 will be severely curled, affecting the flatness of the battery cell.

[0076] The spacing D between two adjacent reinforcing ribs is 0.5 - 4 mm. For example, the spacing D between two adjacent reinforcing ribs is 0.8 mm, 1.2 mm, 1.6 mm, 2.0 mm, 2.8 mm, 3.0 mm, 3.5 mm, or 3.8 mm, etc. If the spacing between two adjacent reinforcing ribs is too large, this interval may cover the entire stress concentration area, and the bending degree of the current collector 30 is insufficient. The stress concentration caused by the expansion of the negative electrode still accumulates in the transition area 40, and the problem of the positive electrode sheet fracture caused by stress concentration cannot be effectively solved. If the spacing between two adjacent reinforcing ribs is too small, the bending degree of the current collector 30 is too large, and the current collector 30 will be overstretched during processing, resulting in the fracture of the current collector 30 during processing.

[0077] Among them, the test methods for the width of the reinforcing rib, the thickness of the reinforcing rib, and the spacing between two adjacent reinforcing ribs can all be measured by a common 2.5D size measuring instrument or a microscope scale in the industry.

[0078] As Figure 5 shown, it shows the structure of the reinforcing rib. The reinforcing rib 4031 is a groove that is concave along the thickness direction of the positive electrode sheet. After the positive electrode sheet is processed with the reinforcing rib, more electrolyte can be accommodated in the groove, thereby improving the cycle life of the battery cell. Figure 5 In it, L is the width of the reinforcing rib 4031, H is the thickness of the reinforcing rib 4031, and D is the spacing between two adjacent reinforcing ribs 4031.

[0079] The processing technology of this groove can be implemented in any process steps such as pole piece rolling, die cutting, winding, etc. The reinforcing rib groove in this application is processed in the die cutting process, and a flexible pressure roller is used to press the positive electrode sheet to form the reinforcing rib. During the pressing process, the contacts between the first active material layer 10, the second active material layer 20 and the pressure roller are all flexible contacts, which can avoid the problem of particle breakage caused by overpressing of the active material material and the performance failure of the positive electrode sheet.

[0080] The present utility model also provides a battery, and the battery includes the above-mentioned positive electrode sheet.

[0081] The following uses specific examples and comparative examples to illustrate the effect of relieving stress concentration during the charge and discharge process of the positive electrode sheet described in this application.

[0082] 6 groups of examples

[0083] This group of examples is used to illustrate the influence of the treatment of the positive electrode sheet with the reinforcing rib on the effect of relieving stress concentration. Specifically:

[0084] Example 1-1

[0085] (1) Prepare a positive electrode sheet with a reinforcing rib pretreatment

[0086] The positive electrode active material lithium nickel cobalt manganese oxide (NCM) material, binder polyvinylidene fluoride, and conductive agent carbon black are stirred and mixed at a ratio of 97 wt%: 2 wt%: 1 wt%. Solvent N-methylpyrrolidone is added for mixing, shearing, and stirring to form a uniformly dispersed slurry mixture solution. The solid content of the slurry is 65%. After the slurry is mixed evenly, it is uniformly coated on both sides of the aluminum foil, and the thickness of the positive electrode active material layer on one side is 70 μm.

[0087] After the initial positive electrode sheet is dried, a reinforcing rib processing device commonly used in the current industry is used to perform reinforcing rib treatment on the positive electrode sheet in the single-sided and double-sided coating transition area. In the examples listed this time, the width of the reinforcing rib area can cover the arc area of the winding structure. The height of the reinforcing rib area is equal to the width of the positive electrode sheet. The ratio of the width of the reinforcing rib area to the thickness of the foil is 1.0 times. The ratio of the width of the reinforcing rib area to the thickness difference between the active material layers on both sides of the positive electrode sheet is 1.6 times.

[0088] In Example 1-1, the extending directions of some of the reinforcing ribs are parallel to the length direction of the current collector, and the extending directions of some of the reinforcing ribs are perpendicular to the length direction of the current collector. Among them, the width of the reinforcing rib area is 8 mm, of which 4 mm is located on the double-sided coating area, and the other 4 mm is located on the single-sided coating area, as Figure 2 shown. The width L of each reinforcing rib is 1 mm, the interval D between adjacent two reinforcing ribs is 2 mm, and the thickness H of the reinforcing rib is 100 μm. After using the reinforcing rib processing device to process the single-sided and double-sided coating transition area according to the above parameters, a positive electrode sheet is obtained.

[0089] (2) Preparation of the battery

[0090] The positive electrode sheet obtained in step (1) is wound, welded, and encapsulated with a negative electrode sheet (silicon-doped graphite) and a separator, electrolyte is injected, and then formation, secondary sealing, and grading are carried out to obtain a battery, and then its performance is tested.

[0091] Example 1-2

[0092] The difference from Example 1-1 is that in step (1), all the reinforcing ribs are provided on the single-sided coating area, and the reinforcing rib treatment avoids the double-sided coating area, as Figure 3 shown. Under the same other conditions, a positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0093] Example 1-3

[0094] The difference from Example 1-1 is that the extending directions of all the reinforcing ribs are parallel to the length direction of the current collector, as Figure 4 shown. Under the same other conditions, a positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0095] Examples 1-4

[0096] It is different from Example 1-1 in that the extending directions of all the reinforcing ribs are perpendicular to the length direction of the current collector, as shown schematically Figure 6 . With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0097] Example 1-5

[0098] It is different from Example 1-1 in that the extending directions of all the reinforcing ribs form a 45° angle with the length direction of the current collector, as shown schematically Figure 7 . With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0099] Comparative Example 1

[0100] (1) Prepare a positive electrode sheet without reinforcing rib treatment

[0101] The positive electrode active material lithium nickel cobalt manganese oxide (NCM) material, binder polyvinylidene fluoride, and conductive agent carbon black are stirred and mixed in a ratio of 97 wt%: 2 wt%: 1 wt%. Solvent N-methylpyrrolidone is added for mixing, shearing, and stirring to form a uniformly dispersed slurry mixture solution, and the solid content of the slurry is 65%. After the slurry is mixed evenly, it is uniformly coated on both sides of the aluminum foil, and the single-sided thickness of the positive electrode active material layer is 70 μm. Subsequently, the electrode sheet is dried to obtain a positive electrode sheet.

[0102] (2) Prepare a battery

[0103] The positive electrode sheet obtained in step (1) is laminated and encapsulated with a negative electrode sheet (silicon-doped graphite) and a separator, electrolyte is injected, and then formation, second sealing, and grading are carried out to obtain a battery, and its performance is immediately tested.

[0104] Perform performance tests on the batteries prepared in Examples 1-1 to 1-5 and Comparative Example 1

[0105] Each battery is charged at a constant current rate of 2C at 45 °C, with a cut-off current of 0.05C rate, and then discharged at a constant current rate of 4C, and the voltage range is 2.0 - 4.3V. This is one charge-discharge cycle. For each sample, 10 batteries are taken, and each is subjected to 200 cycles. After the cycles are completed, the batteries are disassembled to observe the fracture conditions of their electrode sheets and compare them. The data are shown in Table 1.

[0106] Table 1 Fracture conditions of the positive electrode sheets of the batteries corresponding to Examples 1-1 to 1-5 and Comparative Example 1

[0107] Example Fracture ratio of disassembled battery positive electrode Comparative Example 1 8 / 10 Example 1-1 0 / 10 Example 1-2 0 / 10 Example 1-3 0 / 10 Example 1-4 0 / 10 Example 1-5 0 / 10

[0108] In the table, the fracture ratio of the disassembled battery cathode plate refers to the ratio of the number of batteries with cathode plate fracture caused by anode swelling during the battery cycle to the number of batteries taken, where 10 batteries are taken from each sample for disassembly.

[0109] According to the data in Table 1: For the batteries corresponding to Examples 1-1 to 1-5, no cathode plate fracture occurred during the cycle, while among the 10 samples of the battery corresponding to Comparative Example 1, 8 had pole piece fractures. Through comparison of the above test results, it can be seen that strengthening rib treatment in the transition region of the cathode plate can effectively alleviate the problem of cathode plate fracture caused by stress concentration during the battery cycle. From the test results of Examples 1-1 and 1-2, it can be seen that whether the strengthening rib treatment is carried out in the double-sided coating area or the single-sided coating area and the double-sided coating area of the transition region, the problem of stress concentration can be alleviated; from the test results of Examples 1-3 to 1-5, it can be seen that when the extension direction of the strengthening rib is parallel, perpendicular or inclined to the length of the current collector, the problem of stress concentration can also be alleviated.

[0110] 10 groups of examples

[0111] This group of examples is used to illustrate the influence of the ratio of the width of the strengthening rib region to the thickness of the foil on the effect.

[0112] This group of examples is carried out with reference to Example 1-1. The difference is that the width of the strengthening rib region (while keeping the foil thickness unchanged) is changed to adjust the ratio of the width of the strengthening rib region to the thickness of the foil. Specifically:

[0113] Example 2-1

[0114] The ratio of the width of the strengthening rib region to the thickness of the foil is 0.2, the foil thickness is 5 μm, the width of the strengthening rib region is 1 mm, the width of each strengthening rib is 0.5 mm, and the other conditions are the same. A cathode plate is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0115] Example 2-2

[0116] The ratio of the width of the strengthening rib region to the thickness of the foil is 0.5, the foil thickness is 5 μm, the width of the strengthening rib region is 2.5 mm, the width of each strengthening rib is 0.5 mm, and the other conditions are the same. A cathode plate is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0117] Example 2-3

[0118] The ratio of the width of the ribbed area to the thickness of the foil is 1.0. The thickness of the foil is 5 μm, the width of the ribbed area is 5 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0119] Example 2-4

[0120] The ratio of the width of the ribbed area to the thickness of the foil is 1.5. The thickness of the foil is 5 μm, the width of the ribbed area is 7.5 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0121] Example 2-5

[0122] The ratio of the width of the ribbed area to the thickness of the foil is 2.0. The thickness of the foil is 5 μm, the width of the ribbed area is 10.0 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0123] Example 2-6

[0124] The ratio of the width of the ribbed area to the thickness of the foil is 2.5. The thickness of the foil is 5 μm, the width of the ribbed area is 12.5 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0125] Example 2-7

[0126] The ratio of the width of the ribbed area to the thickness of the foil is 3.0. The thickness of the foil is 5 μm, the width of the ribbed area is 15 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0127] Example 2-8

[0128] The ratio of the width of the ribbed area to the thickness of the foil is 3.5. The thickness of the foil is 5 μm, the width of the ribbed area is 17.5 mm, and the width of each rib is 0.5 mm. With the remaining conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0129] Example 2-9

[0130] The ratio of the width of the ribbed area to the thickness of the foil is 4.0. The thickness of the foil is 5 μm, the width of the ribbed area is 20 mm, and the width of each rib is 0.5 mm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0131] Comparative Example 2

[0132] The ratio of the width of the ribbed area to the thickness of the foil is 0.1. The thickness of the foil is 5 μm, the width of the ribbed area is 0.5 mm, and the width of each rib is 0.5 mm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0133] Perform performance tests on the batteries prepared in Examples 2-1 to 2-9 and Comparative Example 2

[0134] Charge each battery at a constant current of 2C rate at 45 °C until the cut-off current is 0.05C rate, and then discharge it at a constant current of 4C rate. The voltage range is 2.0 - 4.3V. This is one charge-discharge cycle. Take 10 batteries for each sample, and each is subjected to 200 cycles. After the cycles are completed, disassemble the batteries to observe the fracture conditions of their electrode sheets and make comparisons. The data is shown in Table 2.

[0135] Table 2 Fracture conditions of the positive electrode sheets of the corresponding batteries in Examples 2-1 to 2-9 and Comparative Example 2

[0136]

[0137]

[0138] According to the data in Table 2: For the batteries corresponding to Examples 2-1, 2-2, 2-4, 2-6, 2-7, 2-8, and 2-9, no fracture of the positive electrode sheet occurred during the cycling process; for the battery corresponding to Example 2-3, 2 out of 10 samples had fracture of the positive electrode sheet during the cycling process; for the battery corresponding to Example 2-5, 1 out of 10 samples had fracture of the positive electrode sheet during the cycling process. Among them, the fracture situations of Example 2-3 and Example 2-5 are within the acceptable error range. For the battery corresponding to Comparative Example 2, 7 out of 10 samples had fracture of the electrode sheet. From the comparison of the above test results, it can be seen that when the ratio of the width of the ribbed area to the thickness of the foil is less than 0.15, the rib treatment cannot play the role of alleviating stress concentration; while when the ratio of the width of the ribbed area to the thickness of the foil is in the range of 0.15 - 4.0, the rib treatment can effectively alleviate the stress concentration problem in the transition area.

[0139] Example 6 group

[0140] This group of embodiments is used to illustrate the influence of the ratio of the width of the reinforcing rib area to the thickness of the foil on the fracture of the electrode sheet and the energy density of the battery.

[0141] This group of embodiments is carried out with reference to Embodiment 1-1. The difference is that the thickness of the foil is changed (while keeping the width of the reinforcing rib area unchanged) to adjust the ratio of the width of the reinforcing rib area to the thickness of the foil. Specifically:

[0142] Example 3-1

[0143] The ratio of the width of the reinforcing rib area to the thickness of the foil is 0.35, the width of the reinforcing rib area is 10 mm, the thickness of the foil is 28 μm, the width of each reinforcing rib is 0.5 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0144] Example 3-2

[0145] The ratio of the width of the reinforcing rib area to the thickness of the foil is 0.5, the width of the reinforcing rib area is 10 mm, the thickness of the foil is 20 μm, the width of each reinforcing rib is 0.5 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0146] Example 3-3

[0147] The ratio of the width of the reinforcing rib area to the thickness of the foil is 1.0, the width of the reinforcing rib area is 10 mm, the thickness of the foil is 10 μm, the width of each reinforcing rib is 0.5 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0148] Example 3-4

[0149] The ratio of the width of the reinforcing rib area to the thickness of the foil is 1.5, the width of the reinforcing rib area is 10 mm, the thickness of the foil is 6.7 μm, the width of each reinforcing rib is 0.5 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0150] Example 3-5

[0151] The ratio of the width of the reinforcing rib area to the thickness of the foil is 2.0, the width of the reinforcing rib area is 10 mm, the thickness of the foil is 5 μm, the width of each reinforcing rib is 0.5 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0152] Comparative Example 3

[0153] The ratio of the width of the ribbed area to the thickness of the foil is 0.33. The width of the ribbed area is 10 mm, the thickness of the foil is 30 μm, and the width of each rib is 0.5 mm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0154] The batteries prepared in Examples 3-1 to 3-5 and Comparative Example 3 are subjected to performance tests.

[0155] Each battery is charged at a constant current of 2C at 45 °C until the cut-off current of 0.05C, and then discharged at a constant current of 4C. The voltage range is 2.0 - 4.3 V. This is one charge-discharge cycle. For each sample, 10 batteries are taken, and each is subjected to 200 cycles. After the cycles are completed, the energy density of the battery is calculated, the battery is disassembled to observe the fracture condition of its electrode sheet, and comparisons are made. The data are shown in Table 3.

[0156] Table 3 Energy density of the batteries corresponding to Examples 3-1 to 3-5 and Comparative Example 3 and the fracture condition of the positive electrode sheet

[0157] Example Fracture ratio of disassembled battery positive electrode Energy density (Wh / kg) Comparative Example 3 0 / 10 320 Example 3-1 0 / 10 324 Example 3-2 0 / 10 340 Example 3-3 0 / 10 360 Example 3-4 0 / 10 366 Example 3-5 1 / 10 370

[0158] According to the data in Table 3: For the batteries corresponding to Examples 3-1 to 3-4 and Comparative Example 3, no fracture of the positive electrode sheet occurred during the cycling process; for the battery corresponding to Example 3-5, 1 out of 10 samples had a fracture of the positive electrode sheet during the cycling process. The fracture of the positive electrode sheet in Example 3-5 is within the acceptable error range. The energy density of the battery corresponding to Comparative Example 3 is 320 Wh / kg, and the energy densities of the batteries corresponding to Examples 3-1 to 3-5 increase in sequence. The energy density of the battery corresponding to Example 3-5 is 370 Wh / kg, which is significantly higher than that of the battery corresponding to Comparative Example 3. From the comparison of the above test results, it can be seen that when the ratio of the width of the ribbed area to the thickness of the foil is 0.33, although the rib treatment can relieve stress concentration, due to the relatively large thickness of the foil, it will have an adverse impact on the energy density of the battery; when the ratio of the width of the ribbed area to the thickness of the foil is in the range of 0.35 - 2.0, the rib treatment can not only effectively relieve the stress concentration problem in the transition area, but also, because the corresponding foil thickness is relatively small, it will not cause a significant reduction in the energy density of the battery.

[0159] Example 4 group

[0160] This group of examples is used to illustrate the influence of the ratio of the width of the ribbed area to the thickness difference between the first active material layer and the second active material layer on the effect.

[0161] This group of embodiments is carried out with reference to Embodiment 1-1. The difference is that the width of the reinforcing rib region is changed (while keeping the thickness difference between the first active material layer and the second active material layer unchanged) to adjust the ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer. Specifically:

[0162] Example 4-1

[0163] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.2. The thickness difference between the first active material layer and the second active material layer is 20 μm, the width of the reinforcing rib region is 4.0 mm, the width of each reinforcing rib is 1 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0164] Example 4-2

[0165] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.5. The thickness difference between the first active material layer and the second active material layer is 20 μm, the width of the reinforcing rib region is 10 mm, the width of each reinforcing rib is 1 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0166] Example 4-3

[0167] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.8. The thickness difference between the first active material layer and the second active material layer is 20 μm, the width of the reinforcing rib region is 16 mm, the width of each reinforcing rib is 1 mm, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Embodiment 1-1, and then its performance is tested.

[0168] The batteries prepared in Examples 4-1 to 4-3 are subjected to performance tests

[0169] Each battery is charged at a constant current of 2C at 45 °C until the cut-off current is 0.05C, and then discharged at a constant current of 4C, and the voltage range is 2.0 - 4.3V. This is one charge-discharge cycle. For each sample, 10 batteries are taken, and each is subjected to 200 cycles. After the cycles are completed, the batteries are disassembled to observe the fracture conditions of their electrode sheets and compare them. The data is shown in Table 4.

[0170] Table 4 Fracture conditions of the positive electrode sheets of the batteries corresponding to Examples 4-1 to 4-3

[0171] Example Fracture ratio of disassembled battery positive electrode Example 4-1 0 / 10 Example 4-2 0 / 10 Example 4-3 0 / 10

[0172] According to the data in Table 4: For the batteries corresponding to Examples 4-1 to 4-3, no fracture of the positive electrode sheet occurred during the cycling process. From the comparison of the above test results, it can be seen that when the ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.2 or more, the reinforcing rib treatment can effectively alleviate the problem of positive electrode sheet fracture caused by stress concentration during battery cycling.

[0173] Example 5 group

[0174] This group of examples is used to illustrate the influence of the ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer on the fracture of the electrode sheet and the situation of lithium deposition at the interface.

[0175] This group of examples is carried out with reference to Example 1-1. The difference is that the thickness difference between the first active material layer and the second active material layer is changed (while keeping the width of the reinforcing rib region unchanged) to adjust the ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer. Specifically:

[0176] Example 5-1

[0177] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.1, the width of the reinforcing rib region is 3 mm, and the thickness difference between the first active material layer and the second active material layer is 30 μm. Under the same other conditions, a positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0178] Example 5-2

[0179] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 0.5, the width of the reinforcing rib region is 3 mm, and the thickness difference between the first active material layer and the second active material layer is 6 μm. Under the same other conditions, a positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0180] Example 5-3

[0181] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 1.0, the width of the reinforcing rib region is 3 mm, and the thickness difference between the first active material layer and the second active material layer is 3 μm. Under the same other conditions, a positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0182] Example 5-4

[0183] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 1.5. The width of the reinforcing rib region is 3 mm, and the thickness difference between the first active material layer and the second active material layer is 2 μm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0184] Example 5-5

[0185] The ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is 2.0. The width of the reinforcing rib region is 3 mm, and the thickness difference between the first active material layer and the second active material layer is 1.5 μm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0186] Perform performance tests on the batteries prepared in Examples 5-1 to 5-5

[0187] Charge each battery at a constant current of 2C at 45 °C until the cut-off current is 0.05C, and then discharge it at a constant current of 4C. The voltage range is 2.0 - 4.3V. This is one charge-discharge cycle. Take 10 batteries for each sample, and each battery undergoes 200 cycles. After the cycles are completed, disassemble the batteries to observe the fracture situation of the electrode sheets and the lithium deposition at the interface, and make comparisons. The data is shown in Table 5.

[0188] Table 5 Fracture situation of the positive electrode sheets and lithium deposition at the interface of the batteries corresponding to Examples 5-1 to 5-5

[0189] Example Fracture ratio of disassembled battery positive electrode Interfacial lithium plating situation Example 5-1 0 / 10 No lithium plating Example 5-2 0 / 10 No lithium plating Example 5-3 0 / 10 No lithium plating Example 5-4 0 / 10 No lithium plating Example 5-5 0 / 10 No lithium plating

[0190] According to the data in Table 5: For the batteries corresponding to Examples 5-1 to 5-5, no fracture of the positive electrode sheet occurred during the cycling process. At the same time, no lithium deposition at the interface occurred in Examples 5-1 to 5-5 either. Through the comparison of the above test results, it can be seen that when the ratio of the width of the reinforcing rib region to the thickness difference between the first active material layer and the second active material layer is greater than 0.1, the reinforcing rib treatment can not only effectively alleviate the problem of positive electrode sheet fracture caused by stress concentration during battery cycling; at the same time, because the corresponding thickness difference between the first active material layer and the second active material layer is relatively small, it can also effectively improve the problem of lithium deposition at the interface.

[0191] Example 8 group

[0192] This group of examples is used to illustrate the influence of the height of the reinforcing rib region on the effect.

[0193] This group of examples is carried out with reference to Example 1-1. The difference is that the height of the reinforcing rib region is changed. Specifically:

[0194] Example 6-1

[0195] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 33% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0196] Example 6-2

[0197] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 40% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0198] Example 6-3

[0199] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 50% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0200] Example 6-4

[0201] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 60% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0202] Example 6-5

[0203] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 70% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0204] Example 6-6

[0205] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 80% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0206] Example 6-7

[0207] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 100% of the width of the current collector, and the remaining conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0208] Comparative Example 6

[0209] The difference from Example 1-1 is that in step (1), the height of the reinforcing rib is 30% of the width of the current collector, and the other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0210] Each battery is charged at a constant current of 2C at 45 °C until the cut-off current is 0.05C, and then discharged at a constant current of 4C with a voltage range of 2.0 - 4.3V. This is one charge-discharge cycle. For each sample, 10 batteries are taken, and each is subjected to 200 cycles. After the cycles are completed, the batteries are disassembled to observe the fracture of the electrode sheets and compare them. The data is shown in Table 6.

[0211] Table 6 Fracture conditions of the positive electrode sheets of the batteries corresponding to Examples 6-1 to 6-7 and Comparative Example 6

[0212] Example Fracture ratio of disassembled battery positive electrode Comparative Example 6 9 / 10 Example 6-1 2 / 10 Example 6-2 1 / 10 Example 6-3 0 / 10 Example 6-4 0 / 10 Example 6-5 1 / 10 Example 6-6 0 / 10 Example 6-7 0 / 10

[0213] According to the data in Table 6: For the batteries corresponding to Examples 6-3, 6-4, 6-6, and 6-7, no fracture of the positive electrode sheet occurred during the cycling process. For the battery corresponding to Example 6-1, 2 out of 10 samples had fractures of the positive electrode sheet during the cycling process; for the batteries corresponding to Examples 6-2 and 6-5, 1 out of 10 samples had fractures of the positive electrode sheet during the cycling process. Among them, the fracture situations of Examples 6-1, 6-2, and 6-5 are within the acceptable error range. For the battery corresponding to Comparative Example 6, 9 out of 10 samples had fractures of the electrode sheet. By comparing the above test results, it can be seen that when the height of the reinforcing rib area is 30% of the width of the current collector, the treatment with the reinforcing rib cannot relieve the stress concentration problem of the positive electrode sheet in the transition area. When the height of the reinforcing rib area is 33% - 100% of the width of the current collector, the treatment with the reinforcing rib can effectively relieve the problem of fracture of the positive electrode sheet caused by stress concentration during the battery cycling process.

[0214] Example 3 group

[0215] This group of examples is used to illustrate the influence of the width and thickness of the reinforcing rib on the effect.

[0216] Example 7-1

[0217] The difference from Example 1-1 is that in step (1), the width L of the reinforcing rib is 1.5 mm, the interval D between two adjacent reinforcing ribs is 1.5 mm, and the thickness H of the reinforcing rib is 100 μm. The other conditions are the same. A positive electrode sheet is obtained, and a battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0218] Example 7-2

[0219] The difference from Example 1-1 is that in step (1), the width L of the reinforcing rib is 1.5 mm, the interval D between two adjacent reinforcing ribs is 1.5 mm, and the thickness H of the reinforcing rib is 70 μm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0220] Example 7-3

[0221] The difference from Example 1-1 is that in step (1), the width L of the reinforcing rib is 2 mm, the interval D between two adjacent reinforcing ribs is 1.5 mm, and the thickness H of the reinforcing rib is 70 μm. With other conditions being the same, a positive electrode sheet is obtained. A battery is assembled according to step (2) in Example 1-1, and then its performance is tested.

[0222] Perform performance tests on the batteries prepared in Examples 7-1 to 7-3

[0223] Charge each battery at a constant current of 2C at 45 °C until the cut-off current is 0.05C, and then discharge it at a constant current of 4C with the voltage range of 2.0 - 4.3 V. This is one charge-discharge cycle. Take 10 batteries for each sample, and each battery is subjected to 200 cycles. After the cycles are completed, disassemble the battery to observe the fracture situation of its electrode sheet and make comparisons. The data is shown in Table 7.

[0224] Table 7 Fracture situations of the positive electrode sheets of the corresponding batteries in Examples 7-1 to 7-3

[0225] Example Fracture ratio of disassembled battery positive electrode Example 7-1 0 / 10 Example 7-2 0 / 10 Example 7-3 0 / 10

[0226] According to the data in Table 7: There is no fracture of the positive electrode sheet in the corresponding batteries in Examples 7-1 to 7-3 during the cycling process. By comparing Example 7-1 and Example 7-2, it can be seen that when the width L of the reinforcing rib is 1.5 mm, the interval D between two adjacent reinforcing ribs is 1.5 mm, and the thickness H of the reinforcing rib is 70 μm and 100 μm, the treatment of the reinforcing rib can relieve the stress concentration problem of the positive electrode sheet in the transition region. By comparing Example 7-2 and Example 7-3, it can be seen that when the interval D between two adjacent reinforcing ribs is 1.5 mm, the thickness H of the reinforcing rib is 70 μm, and the width L of the reinforcing rib is 1.5 mm and 2.0 mm, the treatment of the reinforcing rib can relieve the stress concentration problem of the positive electrode sheet in the transition region.

[0227] In the specification provided here, a large number of specific details are described. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0228] In addition, those of ordinary skill in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments means that it is within the scope of the present utility model and forms different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0229] Those skilled in the art should understand that although the present utility model has been described with reference to exemplary embodiments, various changes can be made and its elements can be replaced with equivalents without departing from the scope of the present utility model. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present utility model without departing from the essential scope of the present utility model. Therefore, the present utility model is not limited to the specific embodiments disclosed, but the present utility model will include all embodiments falling within the scope of the appended claims.

Claims

1. A positive electrode sheet, comprising a current collector, a first active material layer and a second active material layer coated on different surfaces of the current collector, wherein the first active material layer and the second active material layer form a single-sided coating area and a double-sided coating area on the current collector, and is characterized in that: A plurality of reinforcing ribs are provided in a transition region between the single-sided coating area and the double-sided coating area, wherein the transition region includes a first part located in the single-sided coating area and a second part located in the double-sided coating area.

2. The positive electrode sheet according to claim 1, characterized in that, The plurality of reinforcing ribs are provided in at least one of the first part and the second part within the transition region.

3. The positive electrode sheet according to claim 1, characterized in that, The plurality of reinforcing ribs form a reinforcing rib region in the transition region, and an included angle between an extending direction of the plurality of reinforcing ribs and a length direction of the current collector is 0-180°.

4. The positive electrode sheet according to claim 3, characterized in that, The extending direction of the plurality of reinforcing ribs is parallel, inclined or perpendicular to the length direction of the current collector.

5. The positive electrode sheet according to claim 3, wherein, The plurality of reinforcing ribs include at least one first reinforcing rib and at least one second reinforcing rib, and the first reinforcing rib and the second reinforcing rib are arranged in a cross manner.

6. The positive electrode sheet according to claim 3, characterized in that, A width of the reinforcing rib region is 3-20 mm, a thickness of the current collector is 5-30 μm, and thicknesses of the first active material layer and the second active material layer are 30-200 μm respectively.

7. The positive electrode sheet according to claim 3, wherein The width of the reinforcing rib region is L mm, the thickness of the current collector is M μm, and a thickness difference between the first active material layer and the second active material layer is N μm, and L, M and N satisfy at least one of the following formula (1) and formula (2): 0.150≤L / M≤4.2 Formula (1), L / N≥0.1 Formula (2), where 3≤L≤20, 5≤M≤30, 0<N≤30.

8. The positive electrode sheet according to claim 7, characterized in that, L and M satisfy the following formula (3): 0.35≤L / M≤2 Formula (3), where 3≤L≤20, 5≤M≤30.

9. The positive electrode sheet according to claim 3, characterized in that, A height of the reinforcing rib region is 33%-100% of a width of the current collector.

10. The positive electrode sheet according to claim 1, characterized in that, A width of the reinforcing rib is 0.5-2.2 mm, a thickness of the reinforcing rib is 10-200 μm, and a spacing between two adjacent reinforcing ribs is 0.5-4 mm.

11. A battery, characterized in that, The battery includes the positive electrode sheet according to any one of claims 1-10.

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