Positive electrode sheet and battery

Abstract

The present disclosure relates to the field of batteries, and in particular to a positive electrode sheet. The positive electrode sheet of the present disclosure comprises a positive current collector and a positive active material layer on at least one side surface of the positive current collector, wherein the positive active material layer comprises a first groove, the positive current collector comprises a tab connecting area located in the first groove, and a positive tab is located in the first groove and connected to the tab connecting area; the positive active material layer comprises a second groove, and the second groove is located in an edge area on one side or two sides of the positive current collector in the width direction; and the tab connecting area comprises a third groove. The positive electrode sheet provided in the present disclosure can effectively relieve edge lithium precipitation under a high-rate charging system, and improve the cycle performance and the capacity retention rate of batteries.

Description

Positive electrode sheet and battery Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular to a positive electrode sheet and a battery comprising the positive electrode sheet.

[0002] Background of the Invention

[0003] Lithium-ion batteries are high-capacity, long-life, and environmentally friendly batteries widely used in new energy and electric vehicle applications. With the development of society and the economy, higher requirements are being placed on battery energy density, lifespan, safety, and cost. The development of lithium-ion batteries with high specific energy, long life, high safety, and low cost is urgently needed.

[0004] However, the edges of the electrodes of current lithium-ion batteries will produce lithium plating under high-rate charging conditions, resulting in an abnormal increase in the thickness of the battery cell, rapid degradation of battery performance, and also affecting the battery capacity and cycle performance. Summary of the Invention

[0005] The purpose of the present disclosure is to overcome the problem of lithium deposition at the edge of the electrode in the prior art and to provide a positive electrode that can effectively alleviate the lithium deposition at the edge of the electrode or electrode assembly under a high-rate charging system.

[0006] The present disclosure also provides a battery comprising the above-mentioned positive electrode sheet, which can improve the capacity and cycle performance of the battery.

[0007] In order to achieve the above objectives, the present disclosure provides the following technical solutions:

[0008] A first aspect of the present disclosure provides a positive electrode sheet, comprising a positive current collector and a positive active material layer on at least one side of the positive current collector, wherein the positive active material layer contains a first groove, the positive current collector includes a tab connection area located in the first groove, and the positive tab is located in the first groove and connected to the tab connection area; the positive active material layer contains a second groove, and the second groove is located on one side or both sides of the edge area in the width direction of the positive current collector; and the tab connection area contains a third groove.

[0009] A second aspect of the present disclosure provides a battery, comprising the positive electrode sheet according to the first aspect of the present disclosure.

[0010] Through the above technical solution, the present disclosure has at least the following beneficial effects compared with the prior art:

[0011] (1) The positive electrode sheet disclosed in the present invention has a third groove in the tab connection area, which can increase the surface area of ​​the tab connection area. When the tab is welded to the tab connection area, the heat dissipation efficiency of the tab connection area is effectively improved, thereby improving the performance of the tab positive electrode sheet. Moreover, the welding stability of the positive tab can be improved to avoid an increase in battery impedance.

[0012] (2) The positive electrode sheet disclosed in the present invention has a second groove and a third groove formed in both the positive active material layer and the tab connection area. On the one hand, the NP ratio of the second groove can be increased to avoid lithium deposition in the tab connection area. On the other hand, the overall groove formation can reduce the preparation process and improve the production efficiency of the tab electrode sheet.

[0013] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1 is a side view of a positive electrode sheet in the prior art;

[0015] FIG2 is a top view of a positive electrode sheet provided in one embodiment of the present disclosure;

[0016] FIG3 is a cross-sectional view taken along line AA in FIG1 ;

[0017] Figure 4 is an enlarged view of point B in Figure 3;

[0018] FIG5 is a top view of the positive electrode sheet with the positive electrode ear installed;

[0019] FIG6 is a top view of the lower positive electrode sheet in another embodiment;

[0020] FIG7 is a top view of the positive electrode sheet in another embodiment;

[0021] FIG8 is a partial schematic diagram of a positive active material layer having a second groove;

[0022] FIG9 is a partial schematic diagram of a third groove formed in the tab connection area;

[0023] FIG10 is a partial schematic diagram of the tab connection area connecting the positive tab and forming a third groove;

[0024] FIG11 is a partial enlarged view of the positive active material layer in FIG3 ;

[0025] FIG12 is a partial enlarged view of the tab connection area of ​​FIG3;

[0026] FIG13 is a schematic diagram of a third groove formed in the lower tab connection area according to an embodiment;

[0027] FIG14 is a schematic diagram of a laser array of a second groove or a third groove;

[0028] FIG15 is a schematic diagram of a laser array according to one embodiment;

[0029] FIG16 is a schematic diagram of a laser array under another embodiment;

[0030] FIG17 is a schematic diagram of laser grooving in an embodiment after providing a positive electrode tab;

[0031] FIG18 is a schematic diagram of laser grooving in another embodiment after the positive electrode tab is provided;

[0032] FIG19 is a schematic diagram of another embodiment in which a third groove is provided in the lower tab connection area;

[0033] FIG20 is a SEM schematic diagram of a third groove formed in the tab connection area;

[0034] FIG21 is a partial enlarged view of FIG20;

[0035] FIG22 is a SEM diagram of a second groove formed in the positive active material layer and a third groove formed in the tab connection region;

[0036] FIG23 is a partial enlarged view of FIG22;

[0037] FIG24 is a schematic diagram showing an EDS analysis of the third groove in the tab connection area according to an embodiment of the present disclosure.

[0038] In Figures 1-23:

[0039] 1-positive electrode sheet, 2-first groove, 3-positive electrode ear, 4-second groove, 5-third groove, 6-fourth groove, 7-transition area;

[0040] 11-positive current collector, 12-positive active material layer, 41-convex portion, 42-groove portion, 51-depressed portion, 52-convex portion;

[0041] 111-ear connection area. DETAILED DESCRIPTION

[0042] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0043] The pores of conventional lithium-ion batteries are highly complex, which is not conducive to the diffusion of lithium ions. Therefore, under larger charging currents, polarization will increase, and lithium deposition may occur on the negative electrode surface. Especially under high-rate charging systems, lithium deposition is likely to occur along the upper and lower edges of the negative electrode width, which will lead to increased polarization at the lithium deposition site, continuous consumption of electrolyte, increased impedance, and abnormal increase in battery cell thickness, and rapid degradation of battery performance. In addition, since the electrodes of ordinary lithium-ion batteries are thicker, the electrolyte cannot penetrate into the interior of the electrode, resulting in insufficient liquid retention in the electrode, thereby affecting the capacity and cycle life of the lithium-ion battery.

[0044] Based on this, as shown in Figures 2 to 23, the present disclosure provides a positive electrode sheet 1, which forms a winding structure or a stacked structure with the negative electrode sheet and the separator. The winding structure can then form a battery together with the shell, electrolyte and other structures.

[0045] A positive electrode sheet 1 includes a positive current collector 11 and a positive active material layer 12 on at least one side of the positive current collector 11, the positive active material layer 12 includes a first groove 2, the positive current collector 11 includes a tab connection area 111 located in the first groove 2, and the positive tab 3 is located in the first groove 2 and connected to the tab connection area 111; the positive active material layer 12 includes a second groove 4, and the second groove 4 is located in the edge area on one side or both sides in the width direction of the positive current collector 11; the tab connection area 111 includes a third groove 5.

[0046] In the present disclosure, the second groove 4 opened on the positive active material layer 12 can be opened on the positive active material layer 12 on one side of the positive current collector 11, or on the positive active material layer 12 on both sides of the positive current collector 11. By providing the second groove on the positive active material layer, the pore tortuosity of the electrode can be reduced, which is beneficial to the Li + Rapid diffusion in the electrode increases Li + The diffusion coefficient is beneficial to enhancing the mass transfer of the positive electrode and reducing the ionic impedance; moreover, by opening a second groove on the positive active material layer, the infiltration effect and infiltration speed of the electrolyte can be increased, and the liquid storage capacity of the electrode can be increased, thereby effectively alleviating the lithium plating phenomenon at the edge of the electrode and improving the battery cycle life and capacity retention rate at high rates.

[0047] Furthermore, in some embodiments, the second groove 4 is provided on one or both sides of the width direction of the positive current collector 11. This reduces the content of the positive active material layer 12 in the positive electrode sheet 1 on one or both sides of the width direction of the positive current collector 11, which is equivalent to increasing the CB value of the battery cell on one or both sides of the width direction of the positive current collector. In this way, during charging, the content of lithium ions moving from one or both sides of the width direction of the positive electrode sheet 1 to the corresponding area of ​​the negative electrode sheet is reduced, thereby alleviating lithium deposition at the edge of the width direction of the negative electrode sheet. In some preferred embodiments, the second groove 4 is provided on both sides of the width direction of the positive current collector 11.

[0048] Furthermore, opening a third groove 5 in the tab connection area 111 can increase the surface area of ​​the tab connection area, and effectively improve the heat dissipation efficiency of the tab connection area when the tab is welded to the tab connection area, thereby improving the pole piece performance of the tab positive electrode sheet and improving the cycle performance and capacity retention rate of the battery; moreover, the increase in the surface area of ​​the tab connection area can also improve the welding stability of the positive tab and avoid an increase in battery impedance.

[0049] Moreover, since the positive electrode sheet disclosed herein is a tab-type positive electrode sheet including a first groove and a tab connection area, the welding stability of the positive electrode tab will directly affect the performance of the tab and the battery. Therefore, in order to further improve the welding stability of the positive electrode tab, the positive electrode sheet disclosed herein further controls the distribution of the content of each element in the third groove, minimizing the impact of the high-temperature etching of the laser on the tab connection area when the third groove is opened, ensuring that the content of each element in the third groove is appropriate when the positive electrode tab is welded, thereby avoiding poor welding of the tab positive electrode sheet and affecting the performance of the tab, thereby avoiding an increase in battery impedance and improving the capacity and cycle performance of the battery. In addition, simultaneously opening the second groove and the third groove in the positive active material layer and the tab connection area can reduce the preparation process and improve the production efficiency of the tab pole sheet.

[0050] In the present disclosure, the number of first grooves 2 is not limited. One first groove 2 is provided, opened on the positive active material layer 12 on one side of the positive current collector 11. Two first grooves 2 can also be provided, and the first grooves 2 are opened on the positive active material layer 12 on both sides of the positive current collector 11. Accordingly, the number of second grooves 4 and third grooves 5 is not limited. One or more second grooves 4 can be provided, and one or more third grooves 5 can also be provided.

[0051] In the present disclosure, the width direction of the positive current collector 11 refers to the width direction of the positive electrode sheet 1 in the unfolded state, that is, the direction indicated by the double-headed arrow Y in Figure 2. M is the dimension of the area where the second groove 4 is located in the width direction of the positive current collector 11, and N is the dimension of the positive active material layer 12 in the width direction of the positive current collector 11. It should also be noted that the area where the second groove 4 is located refers to the area of ​​the positive active material layer 12 where the second groove 4 is provided.

[0052] In order to further adjust the element distribution of the third groove and improve the performance of the pole piece, in some embodiments, the third groove also contains the elements O, Co, C and F. In terms of the mass percentage of each element, the Al content is 70% to 85%, the O content is 1% to 5%, the C content is 10% to 20%, the Co content is 0.5% to 2%, and the F content is 0.1% to 1%.

[0053] Illustratively, the Al content may be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, or 85%.

[0054] For example, the content of O may be 1%, 2%, 3%, 4% or 5%.

[0055] For example, the C content may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0056] Illustratively, the Co content may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%.

[0057] For example, the content of F may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0058] It should be noted that the C and O elements in the third groove are formed by laser high-temperature etching during the process of opening the third groove, and the Co and F elements are the positive active material layer materials remaining when cleaning the tab groove and / or the positive active material layer materials that are sputtered and remain on the tab connection area by laser high-temperature etching during the process of opening the second groove. However, if the content of the above-mentioned C, O, Co, and F elements stated in the process of opening the third groove is too high, it will reduce the welding stability between the positive tab and the tab connection area. Therefore, in order to reduce the impact of the laser high-temperature etching process on the tab connection area, it is necessary to control the content distribution of each element in the third groove. Among them, the higher the Al content and the lower the C and O content, the smaller the high-temperature etching effect of the laser on the aluminum foil. This can minimize the poor welding of the tab positive plate in the presence of process errors, thereby stabilizing the performance of the plate and avoiding an increase in battery impedance.

[0059] Furthermore, the elements contained in the second groove include Al, O, Co, C and F;

[0060] In some embodiments, in the second groove, based on the mass percentage of each element, the Al content is 0.2% to 1.2%, the O content is 25% to 40%, the C content is 15% to 30%, the Co content is 40% to 55%, and the F content is 0.01% to 1%.

[0061] For example, the Al content may be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1% or 1.2%.

[0062] Illustratively, the O content can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.

[0063] Illustratively, the C content may be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%.

[0064] Illustratively, the Co content may be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%.

[0065] Illustratively, the content of F may be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0066] It should be noted that the C, O, Co, and F elements in the second groove can represent the content of active material in the positive active material layer. When the content distribution of each element in the second groove conforms to the above-mentioned specific range, it means that the composition of the positive active material layer has not changed before and after the opening of the second groove, and the laser high-temperature etching process has a low impact on the active material in the positive active material layer, thereby avoiding affecting the battery performance.

[0067] In addition, in order to further alleviate edge lithium deposition and improve the capacity and cycle performance of the battery. In some embodiments of the positive electrode sheet disclosed herein, as shown in FIG2 , in the width direction of the positive current collector 11, the size of the area where the second groove 4 is located is M, and the size of the positive active material layer 12 is N, wherein M and N satisfy: 0.1N≤M≤N. Ensuring that the size of the area where the second groove 4 is located is within the above range can significantly alleviate the effect of lithium deposition on both sides of the width direction of the negative electrode sheet.

[0068] Illustratively, the value of M can be 0.1N, 0.2N, 0.3N, 0.4N, 0.5N, 0.6N, 0.7N, 0.8N, 0.9N or N.

[0069] In some embodiments, referring to Figures 2 and 5, in the width direction of the positive current collector 11, the size of the connection area between the positive tab 3 and the tab connection area 111 is O, and the size of the tab connection area 111 is P, wherein O and P satisfy: P≥O+k1, and 2mm≤k1≤4mm (for example, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.9mm, 3.8mm, 3.9mm or 4mm). Specifically, the positive electrode sheet 1 is welded to the tab connection area 111 to achieve connection between the positive electrode tab 3 and the tab connection area 111, thereby achieving electrical connection between the positive electrode tab 3 and the positive electrode sheet 1. In order to ensure the contact area between the positive electrode tab 3 and the tab connection area 111, the positive electrode tab 3 and the tab connection area 111 satisfy the above-mentioned relationship, so that the positive electrode tab 3 can be completely welded to the positive current collector 11, avoiding the positive electrode tab 3 from extending onto the positive active material layer 12, thereby avoiding increasing the ineffective thickness of the battery cell, thereby avoiding a reduction in the energy density of the battery cell.

[0070] It should be noted that the width direction of the positive current collector 11 refers to the width direction of the positive electrode sheet 1 in the unfolded state, that is, the direction indicated by the double-headed arrow Y in Figure 2, then O is the size of the connection area between the positive tab 3 and the tab connection area 111 in the width direction of the positive current collector 11, and P is the size of the tab connection area 111 in the width direction of the positive current collector 11.

[0071] In some embodiments, referring to Figures 2 and 5, the third groove 5 is arranged in the edge area of ​​the positive current collector 11 adjacent to the tab connection area 111. In the width direction of the positive current collector 11, the size of the area where the third groove 5 is located is Q, and the size of the tab connection area 111 is P, wherein P and Q satisfy: Q = (0.1P~P)+k2, and -0.5mm≤k2≤-0.1mm (for example, -0.5mm, -0.4mm, -0.3mm, -0.2mm or -0.1mm) or 0.1mm≤k2≤0.5mm (for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm or 0.5mm). Specifically, the dimensions of the area where the third groove 5 is located and the tab connection area are ensured to be within the above-mentioned range. Firstly, it is ensured that the third groove can be arranged in the area close to the edge of the tab connection area, thereby ensuring that the groove is arranged as a whole with the edge of the positive active material layer, thereby improving the NP ratio at the tab connection and avoiding lithium deposition in the tab connection area. Secondly, the welding stability of the positive tab is improved to avoid an increase in battery impedance. Thirdly, the current density at the positive tab is large, the polarization is large, and the electrolyte loss is large. The third groove can increase the storage capacity of the electrolyte at the positive tab. Fourthly, the third groove is arranged in the edge area in the width direction adjacent to the tab connection area, and the second groove is arranged on one side or both sides of the width direction of the positive active material layer. The second groove and the third groove can be opened simultaneously by the laser array, thereby improving the groove opening efficiency, improving the work efficiency, and thereby improving the processing and production efficiency of the battery.

[0072] It should be noted that the width direction of the positive current collector 11 refers to the width direction of the positive electrode sheet 1 in the unfolded state, that is, the direction indicated by the double-headed arrow Y in Figure 2. Q is the size of the area where the third groove 5 is located in the width direction of the positive current collector 11, and P is the size of the tab connection area 111 in the width direction of the positive current collector 11.

[0073] In some embodiments, please refer to Figures 11 and 12. Figure 11 is a partial enlarged view of the positive active material layer in Figure 3, and Figure 12 is a partial enlarged view of the tab connection area in Figure 3; in the direction perpendicular to the positive current collector 11, the size of the second groove 4 is H1, and H1 satisfies: 0.03(ρ*10) / p≤H1≤(ρ*10) / p, where p is the compaction density of the positive active material layer, in g / cm 3 ρ is the surface density of the positive active material layer, in mg / cm 2.

[0074] In some embodiments, please refer to Figure 12, which is a local enlarged view of the tab connection area of ​​Figure 3. The size of the third groove 5 is H2, in μm, and the size of the tab connection area 111 is H, wherein H2 and H satisfy: 0.1H≤H2<0.5H.

[0075] It should be noted that the above relationship 0.03(ρ*10) / p≤H1≤(ρ*10) / p can be expressed as 0.03×the thickness of the positive active material layer≤H1≤the thickness of the positive active material layer. It can be understood that if the groove depth H1 of the second groove 4 is less than 0.03 of the thickness of the positive active material layer, the groove depth H1 of the second groove is too small, and the benefit of setting the second groove in the positive active material layer will be small, and the effect of avoiding lithium plating and improving battery performance will not be obvious; if the groove depth H1 of the second groove is greater than the thickness of the positive active material layer, the groove depth H1 of the second groove is too large, which will cause a large capacity loss to the battery on the one hand, and may cause perforation of the positive current collector on the other hand.

[0076] The thickness H of the positive current collector and the depth H2 of the third groove satisfy the relationship 0.1H ≤ H2 < 0.5H. By controlling the depth of the third groove to satisfy this relationship, when the third grooves are provided on both sides of the tab connection area, the tab connection area can be prevented from being opened, thereby preventing the performance of the battery in which the positive electrode sheet is installed. If the tab connection area is opened, the groove diameter will be correspondingly increased, which will reduce the effective welding area of ​​the positive tab and even cause the positive tab to be welded loose, affecting the performance of the positive tab.

[0077] It should be noted that the direction perpendicular to the positive current collector 11 refers to the direction perpendicular to the positive current collector 11 when the positive electrode sheet 1 is in the unfolded state, that is, the direction indicated by the double-headed arrow Z in Figure 3. H1 is the dimension of the second groove 4 in the direction perpendicular to the positive current collector 11, that is, the groove depth of the second groove, H2 is the dimension of the third groove 5 in the direction perpendicular to the positive current collector 11, that is, the groove depth of the third groove, and H is the dimension of the tab connection area 111 in the direction perpendicular to the positive current collector 11.

[0078] In some embodiments, please refer to Figure 8, which is a partial schematic diagram of the second groove opened in the positive active material layer. At least one second groove 4 is provided, and the spacing between adjacent second grooves 4 is L1. The outer diameter of the cross section of the second groove 4 is D1, wherein L1 and D1 satisfy: 50μm≤L1≤1000μm, preferably 100μm≤L1≤300μm; 20μm≤D1≤500μm, preferably 20μm≤D1≤100μm.

[0079] For example, the interval L1 between adjacent second grooves 4 is 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, 800 μm or 1000 μm. The cross-sectional outer diameter D1 of the second groove 4 is 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 200 μm, 300 μm or 500 μm.

[0080] In some embodiments, please refer to Figure 9, which is a partial schematic diagram of a third groove opened in the tab connection area. At least one third groove 5 is provided, and the spacing between adjacent third grooves 5 is L2. The outer diameter of the cross section of the third groove 5 is D2, wherein L2 and D2 satisfy: 50μm≤L2≤1000μm, preferably 100μm≤L2≤300μm; 20μm≤D2≤500μm, preferably 20μm≤D2≤100μm.

[0081] For example, the interval L2 between adjacent third grooves 5 is 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, 800 μm or 1000 μm, and the cross-sectional outer diameter D2 of the third groove 5 is 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 200 μm, 300 μm or 500 μm.

[0082] Specifically, setting the spacing of the second grooves 4 and the outer diameter of the cross section of the second grooves 4 within the above range can ensure the electrolyte storage capacity of the second grooves 4, prevent lithium deposition on the negative electrode sheet, and have little impact on the positive active material layer 12. The same effect is achieved by setting the third grooves 5 within the range.

[0083] It should be noted that the spacing between adjacent second grooves 4 refers to the distance between the groove centers of adjacent second grooves 4. When the cross-section of the second groove 4 is circular, the outer diameter of the cross-section of the second groove 4 is the diameter of the circle. When the cross-section of the second groove 4 is of other shapes, the outer diameter of the cross-section of the second groove 4 is the diameter of the circumscribed circle of the cross-section. Similarly, the spacing between adjacent third grooves 5 and the outer diameter of the cross-section of the third groove 5 are similar and will not be further described here.

[0084] In addition, one second groove 4 may be provided, and one corresponding third groove 5 may also be provided.

[0085] In some embodiments, please refer to Figures 22 and 23. Figure 22 is an SEM schematic diagram of the second groove opened in the positive active material layer and the third groove opened in the electrode tab connection area. Figure 23 is a partial enlarged view of Figure 22. The second groove 4 includes at least one protrusion 41 and at least one groove portion 42 located between adjacent protrusions 41. The cross-sectional outer diameter of the groove portion 42 is D3, and the cross-sectional outer diameter of the protrusion 41 is D4, wherein D3 and D4 satisfy: 10μm≤D3≤100μm, 5μm≤D4≤30μm; preferably, the cross-sectional outer diameter of the groove portion 42 is 10μm≤D3≤30μm, and the cross-sectional outer diameter of the protrusion 41 is 10μm≤D4≤20μm.

[0086] Illustratively, the outer diameter D3 of the cross section of the groove portion 42 is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm.

[0087] Illustratively, the outer diameter D4 of the cross section of the protrusion 41 is 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0088] It should be noted that the cross-sectional outer diameters of the protrusion 41 and the groove 42 are expressed the same as the cross-sectional outer diameter of the second groove 4 and are not repeated here. D3 is the cross-sectional outer diameter of the groove 42, and D4 is the cross-sectional outer diameter of the protrusion 41. D3 and D4 are not shown in the figure.

[0089] In some embodiments, referring to Figures 8-12, in the direction perpendicular to the positive current collector 11, the size of the second groove 4 is H1, and the size of the third groove 5 is H2; the cross-sectional outer diameter of the second groove 4 is D1, and the cross-sectional outer diameter of the third groove 5 is D2; wherein, H1 and H2 satisfy: 0μm

[0090] ​It should be further explained that in the process of processing the material strip into the positive electrode sheet 1, first, the positive active material layer 12 is coated on the material strip, and then the material strip is initially cut, and then the electrode sheet is rolled by a roller press, and then the material strip is secondary cut to form the positive electrode sheet 1. The laser grooving process of the positive electrode sheet 1 can be between the initial cutting and the secondary cutting of the material strip, or after the secondary cutting. It should be noted that when the laser grooves the positive electrode sheet 1 between the initial cutting and the secondary cutting, it can ensure that the groove position of the positive electrode sheet 1 is located at the edge area in the width direction of the positive active material layer 12, thereby avoiding lithium deposition in the edge area in the width direction of the negative electrode sheet when the battery cell composed of the positive electrode sheet 1 is in operation.

[0091] In some embodiments, referring to Figures 20-21, the third groove 5 includes a recessed portion 51 that is recessed in the tab connection area 111 and a protruding portion 52 that surrounds the recessed portion 51 and protrudes relative to the tab connection area 111, wherein the outer diameter of the protruding portion 52 is 0.5μm to 8μm (for example, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, or 8μm). It should be noted that the outer diameter of the protruding portion 52 refers to the diameter width of a raised circular ring formed on the outer edge of the third groove 5. The protruding portion 52 is made of aluminum oxide. The protruding portion 52 can further increase the contact area between the tab connection area 111 and the positive tab 3, thereby further improving the heat dissipation efficiency when welding the tab. In addition, the protruding portion can increase the impedance at the tab, reduce the current density at the tab, reduce the positive electrode de-insertion speed around the tab, and further improve the performance of the pole piece.

[0092] In some embodiments, referring to Figures 20 and 21 , the recess 51 includes at least one concentric annular portion, and the outer diameter of the at least one concentric annular portion decreases as the depth of the third groove 5 increases. When a laser is used to drill a hole in the tab connection area 111, at a specific laser power, as the hole depth increases, at least one concentric annular portion is formed. The effect of the laser is weakened as the groove depth increases, thus preventing perforation.

[0093] In some embodiments, referring to Figures 2-13 , the positive active material layer 12 on both sides of the positive current collector 11 is provided with a first groove 2, and the two first grooves 2 are symmetrically arranged about the plane where the tab connection area 111 is located. Specifically, to improve the charging efficiency of the battery, the tab is usually thicker. To compensate for the ineffective thickness of the positive tab 3, a first groove 2 is provided on the positive active material layer 12 on both sides of the positive current collector 11, and the two first grooves 2 are symmetrically arranged about the plane where the tab connection area 111 is located.

[0094] Furthermore, in some embodiments, please refer to FIG13 , which is a schematic diagram of a third groove formed in the tab connection region under one embodiment. Third grooves 5 are formed on both sides of the tab connection region 111. In a direction perpendicular to the tab connection region 111, the third grooves 5 on both sides of the tab connection region 111 have an overlapping area, and the area of ​​the overlapping area accounts for 1% to 40% of the total cross-sectional area of ​​the third grooves 5 on one side of the tab connection region 111. Specifically, when the third grooves 5 are formed on both sides of the tab connection region 111, the projections of the third grooves 5 on both sides of the tab connection region 111 in a direction perpendicular to the positive current collector 11 will have a partial overlapping area. By controlling this overlapping area within an appropriate range, the possibility of perforation of the third grooves 5 is further reduced, the tab welding yield is guaranteed, and the proportion of the overlapping area is ensured within the above range. This can minimize the tab connection region 111 from being too small in the direction perpendicular to the positive current collector 11, thereby improving the structural stability of the tab connection region 111.

[0095] Furthermore, third grooves 5 are provided on both sides of the tab connection area 111, and in the direction perpendicular to the tab connection area 111, the third grooves 5 on both sides of the tab connection area 111 are staggered. This arrangement further ensures the stability of the structure of the tab connection area 111 and completely avoids the appearance of through grooves in the tab connection area 111.

[0096] In some embodiments, please refer to FIG22, which is a SEM diagram of a second groove formed in the positive active material layer and a third groove formed in the tab connection area. A fourth groove 6 is formed in the transition area 7 between the positive active material layer 12 and the tab connection area 111. Specifically, the fourth groove 6 is formed in the boundary area between the positive active material layer 12 and the tab connection area 111. The various parameters and properties of the fourth groove 6 can be the same as those of the second groove 4, or the same as those of the third groove 5. Alternatively, a portion of the fourth groove 6 can be the same as the second groove 4 and a portion of the fourth groove 6 can be the same as the third groove 5. Details will not be repeated here.

[0097] In addition, the fourth groove 6 may not be provided in the transition area 7 between the positive active material layer 12 and the tab connection area 111. Since the content of the positive active material layer 12 in the transition area 7 is less than the content of the positive active material layer 12 on the corresponding negative electrode sheet, the probability of lithium deposition in this area itself is relatively small. If the fourth groove 6 is not provided in the transition area 7, the negative electrode sheet corresponding to this area will usually not deposit lithium.

[0098] In some embodiments, please refer to Figure 14, which is a schematic diagram of the laser array of the second groove or the third groove. The second groove 4 forms at least one array unit, and the distance L4 between adjacent array units is 0μm to 1000μm (for example, 0μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm or 1000μm). Preferably, the distance between adjacent array units is 0μm to 200μm. And / or, the third groove 5 forms at least one array unit, and the distance L4 between adjacent array units is 0 μm to 1000 μm (for example, 0 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm), preferably, the distance between adjacent array units is 0 to 200 μm. Furthermore, the length of the positive electrode sheet 1 along the length direction of the positive current collector 11 is L, and the length of a single array unit is L3. The number of matrix channel regions N can be calculated as L / (L3+L4)+1.

[0099] It should be noted that the length direction of the positive current collector 11 refers to the length direction of the positive current collector 11 when the positive electrode sheet 1 is in the unfolded state, that is, the direction indicated by the double-headed arrow X in FIG. 1 or FIG. 2 .

[0100] It should also be noted that the third groove 5 in the tab connection area 111 can be formed by etching with one laser array, for example: the laser array E in Figure 15 or Figure 17; the third groove 5 in the tab connection area 111 can be formed by etching with two laser arrays, for example: the laser array F and the laser array G in Figure 16 or Figure 18.

[0101] In some embodiments, referring to FIG19 , the area of ​​the tab connection region 111 where the third groove 5 is not formed is connected to the positive tab 3. Specifically, when the positive tab 3 is welded to the tab welding region, the tab can be completely aligned with the tab connection region 111, ensuring welding stability and making the positive tab 3 more firmly connected and less likely to fall off.

[0102] In some embodiments, referring to Figures 6 and 7, the cross-sectional shape of the second groove 4 is a strip, and the arrangement direction of the second groove 4 is parallel to the width direction of the positive current collector 11, as shown in Figure 6, and / or the arrangement direction of the second groove 4 is parallel to the length direction of the positive current collector 11, as shown in Figure 7. The cross-sectional shape of the third groove 5 is a strip, and the arrangement direction of the third groove 5 is parallel to the width direction of the positive current collector 11, and / or the arrangement direction of the third groove 5 is parallel to the length direction of the positive current collector 11.

[0103] Specifically, the second grooves 4 are arranged in a strip shape. One or more second grooves 4 can be provided. The second grooves 4 can be parallel to both the width direction and the length direction of the positive current collector 11. When the second grooves 4 are arranged in a strip shape and the positive electrode sheet 1 is assembled into a battery cell, when the electrolyte is injected into the battery cell, the electrolyte flows along the second grooves 4, which can further improve the electrolyte infiltration efficiency and accelerate the electrolyte infiltration into the positive electrode sheet 1. Furthermore, the second grooves 4 include at least one strip groove in at least one direction, such as a crisscross or cross-shaped strip groove. Such an arrangement can further improve the electrolyte infiltration efficiency.

[0104] In addition, the arrangement of the third groove 5 and the fourth groove 6 may be similar to the arrangement of the second groove 4 described above, and will not be described in detail here.

[0105] In addition, the cross-sectional shape of the second groove 4 can be circular, elliptical or polygonal. The same is true for the third groove 5 and the fourth groove 6.

[0106] The second aspect of the present disclosure provides a battery, which includes the positive electrode sheet of the first aspect of the present disclosure. The beneficial effects of the positive electrode sheet 1 of the battery can be found in the above content and will not be repeated here.

[0107] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0108] The following examples are for a battery cell with a tab-center structure. The negative electrode sheet, positive electrode sheet, and battery are manufactured according to the following processes:

[0109] Example 1

[0110] 1. Preparation of negative electrode sheet

[0111] Artificial graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were placed in deionized water in a mass ratio of 97.2:0.5:1.3:1 and stirred evenly to prepare a negative electrode slurry; the negative electrode slurry was evenly coated on a negative electrode current collector, and the negative electrode sheet was prepared by drying, rolling, slitting, cleaning, and sheeting.

[0112] 2. Preparation of positive electrode

[0113] Lithium cobalt oxide, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF were placed in NMP at a mass ratio of 97.60:1.35:1.05 and stirred to prepare a positive electrode slurry. This positive electrode active material slurry was evenly coated on both sides of an aluminum foil (9μm thick). The slurry was then dried, rolled, slit, and cleaned. The cleaned positive electrode sheet was laser treated to form multiple second grooves along the edge of the positive active material layer of the positive electrode sheet. The dimension M of the second grooves was 10μm. Specifically, the multiple second grooves formed multiple array units, with the spacing L4 between any two adjacent matrix units in the multiple array units being 50μm. The spacing L1 between any two adjacent second grooves was 150μm, the diameter D1 of a single second groove was 100μm, and the groove depth H1 of a single second groove was 12μm. The laser power used to form the second grooves was 30%, and the laser drilling rate was 8000-20000mm / s. To reduce manufacturing complexity, this embodiment uses the same laser power and laser drilling rate when setting the third groove in the tab connection area. This means the second and third grooves are simultaneously formed in a single high-temperature laser etching process. Therefore, the parameters of the third groove are the same as those of the second groove: L2 is 150μm, D2 is 100μm, H2 is 12μm, and the dimension Q of the area where the third groove is located is 10μm. The laser-drilled positive electrode sheet is then processed into a sheet to produce the positive electrode sheet. Furthermore, the third groove is formed on both sides of the tab connection area of ​​the positive electrode sheet in Example 1, and the grooves are formed using the same high-temperature laser etching parameters on both sides.

[0114] Other dimensional parameters of the above-mentioned positive electrode sheet are as follows: the size N of the positive active material layer of the positive electrode sheet is 80.8 μm, the groove depth H of the tab connection area is 9 μm, the size P of the tab connection area is 26.5 μm, and the compaction density p of the positive active material layer of the positive electrode sheet is 13.66 g / cm 3 The surface density ρ of the positive active material layer of the positive electrode is 4.15 mg / cm 2 .

[0115] The positive electrode sheet prepared in Example 1 was subjected to energy spectrum analysis (EDS). As shown in Figure 24, the contents of Al, O, Co, C and F in one of the third grooves were measured as follows: Al content was 80.2%, O content was 1.6%, C content was 16.3%, Co content was 1.3%, and F content was 0.6%.

[0116] The contents of Al, O, Co, C, and F in one of the second grooves are as follows: Al content is 0.7%, O content is 30.1%, C content is 19.2%, Co content is 50%, and F content is 0.01%.

[0117] When the elements in the second groove and the third groove of the positive electrode sheet meet the above-mentioned element content distribution, the battery preparation steps can be continued.

[0118] 3. Preparation of batteries

[0119] The separator of this application adopts an 8μm thick substrate + ceramic + glue-coated separator. The electrolyte includes lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), wherein the molar ratio of the three is DEC:EC:EMC=1:1:1. The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in sequence and wound into a wound structure battery cell. After the battery cell is packaged, injected, formed, and secondarily sealed, a lithium-ion battery is obtained.

[0120] Example 2 group

[0121] The second embodiment was carried out in accordance with the first embodiment, except that the contents of the elements in the third groove were changed, as shown in Table 1.

[0122] Comparative Example 1

[0123] Comparative Example 1 was carried out with reference to Example 1, except that no grooves were provided in the positive active material layer and the tab connection area. The corresponding content distribution in Table 1 is the EDS test result of the positive active material layer without the second groove and the tab connection area without the third groove, as shown in Table 1.

[0124] Table 1

[0125] The cell capacity, capacity decay, and lithium deposition at the tab (around the first groove) of the lithium-ion batteries obtained in Examples 1-2 and Comparative Example 1 were evaluated (as shown in Table 2). The specific testing method is as follows:

[0126] (1) Lithium-ion battery cell capacity test

[0127] The lithium-ion battery cells obtained in the above Examples 1-2 and Comparative Example 1 were capacity tested on a blue electric test cabinet. Within the upper and lower limits of the usable voltage specified for the battery cells, they were discharged to the lower limit voltage at 25°C ± 2°C and 0.2C, and allowed to stand for 10 minutes; charged to the upper limit voltage at 0.7C, cut off at 0.025C, and allowed to stand for 10 minutes; discharged to the lower limit voltage at 0.2C, and then an initial capacity test was performed. The capacity obtained at this time is the initial capacity (mAh) of the battery cell. The test results are recorded in Table 2.

[0128] (2) Capacity retention test of lithium-ion batteries

[0129] The lithium-ion batteries obtained in the above Examples 1-2 and Comparative Example 1 were subjected to charge and discharge cycle tests on a blue electric test cabinet battery charge and discharge test cabinet. The test conditions were 25°C ± 2°C, 3.7C / 0.7C charge and discharge, and the capacity retention rate of the battery at 1000T cycle was recorded and the test results were recorded in Table 2.

[0130] (3) Lithium deposition test

[0131] The lithium-ion batteries obtained in the above-mentioned Examples 1-2 and Comparative Example 1 were charged and discharged under the test conditions of Test (2). The charge and discharge cycle was repeated for 400T (or 800T), and the battery was fully charged after the end. The battery cells were disassembled in a dry room environment to observe the lithium deposition on the surface of the tab (around the first groove). The degree of lithium deposition is divided into four levels: no lithium deposition, slight lithium deposition, lithium deposition, and severe lithium deposition. Slight lithium deposition means that a linear lithium deposition phenomenon occurs around the first groove; lithium deposition means that the lithium deposition around the first groove is slightly diffused to other areas; severe lithium deposition means that the lithium deposition has diffused from the first groove to other areas; wherein, lithium deposition is a lithium deposition situation between slight lithium deposition and severe lithium deposition. The test results are recorded in Table 2.

[0132] Table 2

[0133] Example 3 group

[0134] The third embodiment was carried out in accordance with the first embodiment, except that the size M of the second groove and the size Q of the third groove were changed, as shown in Tables 3-1 and 3-2.

[0135] Example 4 Group

[0136] The fourth embodiment was carried out with reference to the first embodiment, except that L1 of the second groove and L2 of the third groove were changed, as shown in Tables 3-1 and 3-2.

[0137] Example 5 group

[0138] The fifth embodiment was carried out in accordance with the first embodiment, except that D1 and H1 of the second groove and D2 and H2 of the third groove were changed, as shown in Tables 3-1 and 3-2.

[0139] Example 6

[0140] Example 6 is carried out with reference to Example 1, except that the negative electrode sheet is provided with a negative electrode sheet groove by using the same laser etching process as the positive electrode sheet, as shown in Tables 3-1 and 3-2.

[0141] Example 7

[0142] Example 7 is carried out with reference to Example 1, except that the third groove is not provided in the tab connection area of ​​the positive electrode sheet, as shown in Tables 3-1 and 3-2.

[0143] Comparative Example 2

[0144] Comparative Example 2 was carried out with reference to Example 1, except that the negative electrode was provided with a negative electrode groove using the same laser etching process as the positive electrode, while the positive electrode was not provided with a groove, as shown in Tables 3-1 and 3-2.

[0145] Table 3-1

[0146] Table 3-2

[0147] (In Table 3-2, "√" indicates that H1 meets the relationship with the thickness of the positive active material layer, that is, 0.03 × thickness of the positive active material layer ≤ H1 ≤ thickness of the positive active material layer, and "×" indicates that H1 does not meet the relationship with the thickness of the positive active material layer)

[0148] Example 8 Group

[0149] The dimensions of the protrusion and the groove in the second groove of Example 1 are as follows: the outer diameter D3 of the cross section of the groove is 50 μm, and the outer diameter D4 of the cross section of the protrusion is 15 μm.

[0150] Example 8-1 was carried out in the same manner as Example 1, except that the laser power and laser drilling rate of the high-temperature etching were changed so that the outer diameter of the cross section of the groove portion D3 was measured to be 10 μm, and the outer diameter of the cross section of the protrusion portion D4 was measured to be 25 μm;

[0151] Example 8-2 was carried out in the same manner as Example 1, except that the laser power and laser drilling rate of the high-temperature etching were changed so that the outer diameter D3 of the cross section of the groove portion was measured to be 90 μm, and the outer diameter D4 of the cross section of the protrusion portion was measured to be 6 μm.

[0152] Example 8-3 was carried out with reference to Example 1, except that the laser power and laser drilling rate of the high-temperature etching were changed so that the outer diameter of the cross section of the groove portion D3 was measured to be 120 μm, and the outer diameter of the cross section of the protrusion portion D4 was measured to be 3 μm;

[0153] Example 8-4 is carried out with reference to Example 1, except that the laser power and laser drilling rate of high-temperature etching are changed so that the measured cross-sectional outer diameter D3 of the groove portion is 50 μm, and the cross-sectional outer diameter D4 of the protrusion portion is 50 μm.

[0154] The cell capacity, capacity decay, and edge lithium deposition of the lithium-ion batteries obtained in the above examples and comparative examples were evaluated (as shown in Table 4). The specific test method is as follows:

[0155] (1) Lithium-ion battery cell capacity test

[0156] The lithium-ion battery cells obtained in the examples and comparative examples were capacity tested on a blue electric test cabinet. Within the upper and lower limits of the usable voltage specified for the battery cells, they were discharged to the lower limit voltage at 25°C ± 2°C and 0.2C, and allowed to stand for 10 minutes; charged to the upper limit voltage at 0.7C, cut off at 0.025C, and allowed to stand for 10 minutes; discharged to the lower limit voltage at 0.2C, and then an initial capacity test was performed. The capacity obtained at this time is the initial capacity (mAh) of the battery cell, which is recorded in Table 4.

[0157] (2) Cycling performance and capacity retention test of lithium-ion batteries

[0158] The lithium-ion batteries obtained in the examples and comparative examples were subjected to charge and discharge cycle tests on a blue electric test cabinet battery charge and discharge test cabinet. The test conditions were 25°C ± 2°C, 3.7C / 0.7C charge and discharge, and the capacity retention rate / % of the battery at 1000T cycle was examined and the test results are recorded in Table 4.

[0159] (3) Testing of the cycle performance and lithium deposition of lithium-ion batteries

[0160] The lithium-ion batteries obtained in the examples and comparative examples were charged and discharged under the test conditions of test (2). The charge and discharge cycle was repeated for 400T (or 800T). After the charge and discharge cycle was completed, the battery was fully charged and the battery cells were disassembled in a dry room to observe the lithium deposition on the positive electrode surface. The degree of lithium deposition was divided into four levels: no lithium deposition, slight lithium deposition at the edge, lithium deposition at the edge, and severe lithium deposition at the edge. Slight lithium deposition at the edge means that a line-like lithium deposition phenomenon appears at the edge and is gray; lithium deposition at the edge means that the lithium deposition slightly diffuses into the interior of the electrode on the basis of slight lithium deposition at the edge, and is also gray; severe lithium deposition at the edge means that the lithium deposition has diffused from the edge of the electrode to the interior of the electrode, and the color of the deposition at the edge is metallic silver; wherein, lithium deposition at the edge is a lithium deposition situation between slight lithium deposition and severe lithium deposition. The test results are recorded in Table 4.

[0161] Table 4

[0162] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A positive electrode sheet, comprising a positive current collector and a positive active material layer on at least one side of the positive current collector, characterized in that: The positive active material layer comprises a first groove, the positive current collector comprises a tab connection region located in the first groove, and the positive tab is located in the first groove and connected to the tab connection region; Wherein, the positive active material layer comprises a second groove, and the second groove is located at one side or both sides of the edge region in the width direction of the positive current collector; The tab connection area includes a third groove.

2. The positive electrode sheet according to claim 1, characterized in that: The elements contained in the third groove include Al; Preferably, the elements contained in the third groove are Al, O, Co, C and F. In terms of the mass percentage of each element, the content of Al is 70% to 85%, the content of O is 1% to 5%, the content of C is 10% to 20%, the content of Co is 0.5% to 2%, and the content of F is 0.1% to 1%.

3. The positive electrode sheet according to claim 1 or 2, characterized in that: The elements contained in the second groove are Al, O, Co, C and F; Preferably, in the second groove, based on the mass percentage of each element, the content of Al is 0.2% to 1.2%, the content of O is 25% to 40%, the content of C is 15% to 30%, the content of Co is 40% to 55%, and the content of F is 0.01% to 1%.

4. The positive electrode sheet according to any one of claims 1 to 3, characterized in that: In the width direction of the positive current collector, the size of the region where the second groove is located is M, and the size of the positive active material layer is N, wherein M and N satisfy: 0.1N≤M≤N.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The third groove is located at the edge area of ​​the positive current collector in the width direction of the tab connection area. In the width direction of the positive current collector, the size of the area where the third groove is located is Q, and the size of the pole ear connection area is P, wherein P and Q satisfy: Q = (0.1P~P)+k2, and -0.5mm≤k2≤-0.1mm or 0.1mm≤k2≤0.5mm.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: In a direction perpendicular to the positive current collector, a size of the second groove is H1; The H1 satisfies: 0.03(ρ*10) / p≤H1≤(ρ*10) / p, wherein p is the compaction density of the positive active material layer, and ρ is the surface density of the positive active material layer; And / or, in a direction perpendicular to the positive current collector, a size of the third groove is H2, a size of the tab connection region is H, and H2 and H satisfy: 0.1H≤H2<0.5H.

7. The positive electrode sheet according to any one of claims 1 to 6, characterized in that: There is at least one second groove, and the spacing between adjacent second grooves is L1. The outer diameter of the cross section of the second groove is D1, wherein L1 and D1 satisfy: 50 μm≤L1≤1000 μm; 20 μm≤D1≤500 μm; And / or, at least one third groove is provided, and the interval between adjacent third grooves is L2, and the outer diameter of the cross section of the third groove is D2, wherein L2 and D2 satisfy: 50μm≤L2≤1000μm; 20μm≤D2≤500μm.

8. The positive electrode sheet according to any one of claims 1 to 7, characterized in that: In a direction perpendicular to the positive current collector, a size of the second groove is H1, and a size of the third groove is H2; The cross-sectional outer diameter of the second groove is D1, and the cross-sectional outer diameter of the third groove is D2; Among them, H1 and H2 satisfy: 0μm<H1-H2≤40μm; D1 and D2 satisfy: 0μm<D1-D2≤20μm.

9. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: The second groove contains at least one protruding portion and at least one groove portion located between adjacent protruding portions, the cross-sectional outer diameter of the groove portion is D3, and the cross-sectional outer diameter of the protruding portion is D4, wherein D3 and D4 satisfy: 10μm≤D3≤100μm, 5μm≤D4≤30μm.

10. The positive electrode sheet according to any one of claims 1 to 9, characterized in that: The third groove includes a concave portion sunken in the tab connection area and a convex portion surrounding the concave portion and protruding relative to the tab connection area, and the outer diameter of the convex portion is 0.5 μm to 8 μm; And / or, the recessed portion includes at least one concentric annular portion, and the outer diameter of at least one of the concentric annular portions decreases in a direction in which the groove depth of the third groove increases.

11. The positive electrode sheet according to any one of claims 1 to 10, characterized in that: Both sides of the pole tab connection area include the third groove, and in the vertical direction of the positive current collector, the third grooves on both sides of the pole tab connection area have overlapping areas, and the area of ​​the overlapping areas accounts for 1% to 40% of the total cross-sectional area of ​​the third grooves on one side of the pole tab connection area.

12. The positive electrode sheet according to any one of claims 1 to 11, characterized in that: A transition region between the positive active material layer and the tab connection region includes a fourth groove.

13. The positive electrode sheet according to any one of claims 1 to 12, characterized in that: The second groove forms at least one array unit, and the distance between adjacent array units is 0 μm to 1000 μm; And / or, the third groove forms at least one array unit, and the distance between adjacent array units is 0 μm to 1000 μm.

14. The positive electrode sheet according to any one of claims 1 to 13, characterized in that: The area of ​​the tab connection region where the third groove is not formed is connected to the positive tab.

15. A battery, characterized in that: A positive electrode sheet comprising any one of claims 1 to 14.

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