Secondary battery and electrical device

Abstract

Provided in the present application are a secondary battery and an electrical device. The secondary battery comprises a positive electrode sheet, a positive electrode tab and an adhesive tape, the positive electrode sheet being provided with a recess, and the positive electrode tab being connected to the positive electrode sheet; the adhesive tape is affixed to the positive electrode sheet and covers the recess and the positive electrode tab; the adhesive tape comprises a base material layer and a bonding layer, and the base material layer has pores allowing metal cations to pass through, the porosity of the base material layer being φ, wherein 30%≤φ≤60%; in the thickness direction of a positive electrode current collector, the projection area of the base material layer is S1, and the overlapping area of the projection of the bonding layer and the projection of the base material layer is S2, wherein 20%≤S2 / S1≤45%. The present application enables the adhesive tape to have lower impedance, thus reducing the probability of lithium plating or formation of purple spots of the secondary battery, enabling the secondary battery to have better dynamic performance, and allowing metal cations to pass through the adhesive tape, so as to improve the discharge capacity of the secondary battery.

Description

Secondary batteries and electrical equipment CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese patent application CN202410383519.6, entitled “Secondary Batteries and Electrical Equipment,” filed on March 31, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a secondary battery and an electrical device. Background Art

[0003] With the rapid development of electronic information technology, various electronic devices are becoming more intelligent and multifunctional, placing increasing demands on battery discharge capacity. Therefore, improving battery discharge capacity has become a pressing issue in the battery industry. Summary of the Invention

[0004] The present application provides a secondary battery and an electrical device, which can increase the discharge capacity of the secondary battery.

[0005] In a first aspect, the present application provides a secondary battery comprising a positive electrode sheet, a positive electrode tab, and adhesive tape, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector along a thickness direction thereof, wherein the positive electrode active material layer is provided with a groove, and the positive electrode current collector comprises a first region, wherein the first region is exposed in the groove;

[0006] At least a portion of the positive electrode tab is disposed in the groove and connected to the first region;

[0007] The adhesive tape is attached to the positive electrode active material layer and covers the groove and the positive electrode tab, the adhesive tape includes a substrate layer and an adhesive layer, the adhesive layer is provided on the surface of the substrate layer facing the positive electrode tab, the substrate layer has pores allowing metal cations to pass through, and the porosity of the substrate layer is φ, which satisfies 30%≤φ≤60%;

[0008] Along the thickness direction of the positive electrode current collector, the projection area of ​​the substrate layer is S1, and the overlapping area of ​​the projection of the adhesive layer and the projection of the substrate layer is S2, satisfying 20%≤S2 / S1≤45%.

[0009] In the above technical solution, the porosity φ of the substrate layer satisfies 30%≤φ≤60%. When the porosity φ of the substrate layer is greater than or equal to 30%, the metal cations can pass through the substrate layer, so that the part of the positive electrode active material layer covered by the adhesive tape can also absorb and release the metal cations, so that the effective area of ​​the positive electrode active material layer is larger, and the discharge capacity of the secondary battery can be improved; when the porosity φ of the substrate layer is less than or equal to 60%, the possibility of deformation of the adhesive tape during the preparation process of the secondary battery can be reduced, and the shrinkage rate of the adhesive tape at high temperature can be lower, which can improve the high-temperature external short performance of the secondary battery, and thus improve the safety performance of the secondary battery.

[0010] Along the thickness direction of the positive electrode current collector, the projected area of ​​the substrate layer is S1, and the overlapping area of ​​the projection of the adhesive layer and the projection of the substrate layer is S2, satisfying 20%≤S2 / S1≤45%. When S2 / S1 is greater than or equal to 20%, the area of ​​the adhesive layer can be larger, so that the bonding force between the adhesive tape and the positive electrode sheet is stronger, and the insulation reliability of the adhesive tape to the positive electrode tab is higher, which can reduce the possibility of thermal runaway of the secondary battery; when S2 / S1 is less than or equal to 45%, the area of ​​the adhesive layer is smaller, which can reduce the impedance of the adhesive tape, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and can make the dynamic performance of the secondary battery better, and can make the area of ​​the positive electrode active material layer blocked by the adhesive layer smaller, so that more metal cations can pass through the adhesive tape, thereby improving the discharge capacity of the secondary battery.

[0011] In some embodiments of the present application, 25% ≤ S2 / S1 ≤ 35%. When S2 / S1 is greater than or equal to 25%, the area of ​​the adhesive layer can be further increased, thereby increasing the bonding force between the adhesive tape and the positive electrode tab, increasing the insulation reliability of the adhesive tape on the positive electrode tab, and reducing the possibility of thermal runaway of the secondary battery. When S2 / S1 is less than or equal to 35%, the area of ​​the adhesive layer can be further decreased, reducing the impedance of the adhesive tape, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, improving the dynamic performance of the secondary battery, and reducing the area of ​​the positive electrode active material layer blocked by the adhesive layer, allowing more metal cations to pass through the adhesive tape, thereby increasing the discharge capacity of the secondary battery.

[0012] In some embodiments of the present application, the adhesive layer includes a plurality of adhesive portions, and the plurality of adhesive portions are spaced apart from each other.

[0013] In the above technical solution, the adhesive layer includes a plurality of adhesive portions, which are spaced apart from each other, so that the adhesive force between the adhesive tape and the positive electrode sheet is more evenly distributed, thereby making the adhesive strength between the adhesive tape and the positive electrode sheet higher. The insulation reliability of the adhesive tape to the positive electrode tab is higher, which can reduce the possibility of thermal runaway of the secondary battery. The area of ​​the adhesive layer can be controlled by adjusting the area of ​​each adhesive portion.

[0014] In some embodiments of the present application, the bonding portion is linear, extends along a first direction, and a plurality of bonding portions are spaced apart along a second direction; the first direction, the second direction, and the thickness direction of the positive electrode current collector are perpendicular to each other.

[0015] In the above technical solution, the bonding portion is linear, extending along the first direction, and multiple bonding portions are spaced apart along the second direction; the first direction, the second direction, and the thickness direction of the positive electrode collector are perpendicular to each other, which can make the bonding strength between the adhesive tape and the positive electrode sheet higher, and the insulation reliability of the adhesive tape to the positive electrode tab higher, which can reduce the possibility of thermal runaway of the secondary battery.

[0016] In some embodiments of the present application, the width of the bonding portion along the second direction is W, satisfying 1mm≤W≤2mm; the spacing distance between two adjacent bonding portions along the second direction is G1, satisfying 3mm≤G1≤5mm.

[0017] In the above technical solution, when W is greater than or equal to 1 mm, the width of the bonding portion along the second direction can be larger, the bonding strength between the bonding portion and the positive electrode sheet can be higher, the insulation reliability of the adhesive tape to the positive electrode tab can be higher, and the possibility of thermal runaway of the secondary battery can be reduced; when W is less than or equal to 2 mm, the width of the bonding portion along the second direction can be smaller, the impedance of the adhesive tape can be reduced, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and the kinetic performance of the secondary battery can be better, and the area of ​​the positive electrode active material layer blocked by the bonding portion can be smaller, so that more metal cations can pass through the adhesive tape, thereby increasing the discharge capacity of the secondary battery.

[0018] When G1 is greater than or equal to 3 mm, the spacing distance between two adjacent bonding parts along the second direction is larger, which can reduce the impedance of the adhesive paper, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and can make the secondary battery have better dynamic performance, and can allow more metal cations to pass through the adhesive paper, thereby increasing the discharge capacity of the secondary battery; when G1 is less than or equal to 5 mm, there can be more space on the substrate layer for setting the bonding part, the bonding strength between the adhesive layer and the positive electrode sheet is higher, the insulation reliability of the adhesive paper to the positive electrode ear is higher, and the possibility of thermal runaway of the secondary battery can be reduced.

[0019] In some embodiments of the present application, the plurality of bonding portions are arranged in an array, and the diameter of the circumscribed circle of the projection of the bonding portion along the thickness direction of the positive electrode current collector is D, satisfying 2.5 mm ≤ D ≤ 3.5 mm; the spacing distance between two adjacent bonding portions is G2, satisfying 2 mm ≤ G2 ≤ ​​3 mm.

[0020] In the above technical solution, the multiple adhesive parts are arranged in an array, which can make the adhesive force between the adhesive tape and the positive electrode sheet more evenly distributed, thereby making the adhesive strength between the adhesive tape and the positive electrode sheet higher, and the insulation reliability of the adhesive tape to the positive electrode tab is higher, which can reduce the possibility of thermal runaway of the secondary battery.

[0021] When D is greater than or equal to 2.5 mm, the area of ​​the bonding portion can be larger, the bonding strength between the bonding portion and the positive electrode sheet can be higher, the insulation reliability of the adhesive tape to the positive electrode tab can be higher, and the possibility of thermal runaway of the secondary battery can be reduced; when D is less than or equal to 3.5 mm, the area of ​​the bonding portion can be smaller, the impedance of the adhesive tape can be reduced, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and the kinetic performance of the secondary battery can be better, and the area of ​​the positive electrode active material layer blocked by the bonding portion is smaller, which can allow more metal cations to pass through the adhesive tape, thereby increasing the discharge capacity of the secondary battery.

[0022] When G2 is greater than or equal to 2 mm, the spacing between two adjacent bonding parts along the second direction can be larger, which can reduce the impedance of the adhesive tape, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and can make the secondary battery have better dynamic performance, and can allow more metal cations to pass through the adhesive tape, thereby increasing the discharge capacity of the secondary battery; when G2 is less than or equal to 3 mm, there can be more space on the substrate layer for setting the bonding part, the bonding strength between the adhesive layer and the positive electrode sheet is higher, the insulation reliability of the adhesive tape to the positive electrode ear is higher, and the possibility of thermal runaway of the secondary battery can be reduced.

[0023] In some embodiments of the present application, the maximum spacing distance between two adjacent bonding portions is G3, and the minimum spacing distance is G4, satisfying 1mm≤G4<G3≤7mm.

[0024] In the above technical solution, G4<G3, that is, the multiple bonding parts are unevenly distributed, which can make the preparation of the bonding parts less difficult. When G3 and G4 are greater than or equal to 1mm, the maximum spacing distance between two adjacent bonding parts can be larger, which can reduce the impedance of the adhesive tape, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and can improve the dynamic performance of the secondary battery. It can also allow more metal cations to pass through the adhesive tape, thereby increasing the discharge capacity of the secondary battery. When G3 and G4 are less than or equal to 7mm, there can be more space on the substrate layer for setting the bonding part, the bonding strength between the adhesive layer and the positive electrode sheet is higher, and the insulation reliability of the adhesive tape to the positive electrode tab is higher, which can reduce the possibility of thermal runaway of the secondary battery.

[0025] In some embodiments of the present application, along the thickness direction of the positive electrode current collector, the bonding layer at least partially overlaps with the projection of the positive electrode tab.

[0026] In the above technical solution, along the thickness direction of the positive electrode current collector, the projection of the adhesive layer and the positive electrode tab at least partially overlaps, so that at least part of the adhesive layer can be attached to the positive electrode tab, so that the bonding strength between the adhesive tape and the positive electrode tab is high, the insulation reliability of the adhesive tape to the positive electrode tab is high, and the possibility of thermal runaway of the secondary battery can be reduced.

[0027] In some embodiments of the present application, along the thickness direction of the positive electrode current collector, the overlapping area of ​​the projection of the positive electrode tab and the positive electrode sheet is S3, and the overlapping area of ​​the projection of the adhesive layer and the positive electrode tab is S4, satisfying 40%≤S4 / S3≤100%.

[0028] In the above technical solution, 40%≤S4 / S3≤100%, which can make the overlapping area between the adhesive layer and the projection of the positive electrode tab larger, thereby making the bonding area between the adhesive tape and the positive electrode tab larger, the bonding strength between the adhesive tape and the positive electrode tab higher, and the insulation reliability of the adhesive tape to the positive electrode tab higher, which can reduce the possibility of thermal runaway of the secondary battery.

[0029] In some embodiments of the present application, the bonding force between the adhesive tape and the positive electrode plate is F, which satisfies 30 N / m≤F≤140 N / m.

[0030] In the above technical solution, when the bonding force F between the adhesive tape and the positive electrode sheet is greater than or equal to 30 N / m, the bonding force between the adhesive tape and the positive electrode sheet can be stronger, the insulation reliability of the adhesive tape to the positive electrode tab is higher, and the possibility of thermal runaway of the secondary battery can be reduced; because the bonding force F between the adhesive tape and the positive electrode sheet is positively correlated with the area and thickness of the adhesive layer, when the bonding force F between the adhesive tape and the positive electrode sheet is less than or equal to 140 N / m, the area and / or thickness of the adhesive layer can be smaller, reducing the space occupied by the adhesive layer, thereby reducing the impact on the discharge capacity of the secondary battery.

[0031] In some embodiments of the present application, the thickness of the substrate layer is H1, satisfying 6 μm≤H1≤20 μm.

[0032] In the above technical solution, when the thickness H1 of the substrate layer is greater than or equal to 6 μm, the burrs of the positive electrode tab are not easy to pass through the adhesive tape and contact the negative electrode plate, thereby reducing the possibility of short circuit of the secondary battery; when the thickness H1 of the substrate layer is less than or equal to 20 μm, the impedance of the adhesive tape can be reduced, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and the dynamic performance of the secondary battery can be better, and the size of the adhesive tape in the thickness direction of the positive electrode current collector can be smaller, so that the impact on the discharge capacity of the secondary battery is smaller.

[0033] In some embodiments of the present application, 8 μm≤H1≤12 μm.

[0034] In the above technical solution, when the thickness H1 of the substrate layer is greater than or equal to 8 μm, it can further prevent the burrs of the positive electrode tab from passing through the adhesive tape and contacting the negative electrode tab, thereby reducing the possibility of short circuit in the secondary battery; when the thickness H1 of the substrate layer is less than or equal to 12 μm, it can further reduce the impedance of the adhesive tape, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and can make the dynamic performance of the secondary battery better, and can further make the size of the adhesive tape in the thickness direction of the positive electrode current collector smaller, so that the impact on the discharge capacity of the secondary battery is smaller.

[0035] In some embodiments of the present application, the substrate layer is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film, and non-woven fabric.

[0036] In the above technical solution, the substrate layer is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose membrane, and non-woven fabric, so that the substrate layer has pores and the porosity can reach 30% to 60%.

[0037] In some embodiments of the present application, the thickness of the adhesive layer is H2, satisfying 3μm≤H2≤5μm.

[0038] In the above technical solution, when the thickness H2 of the adhesive layer is greater than or equal to 3 μm, the adhesive force of the adhesive paper can be stronger, the adhesive paper is not easy to fall off, the insulation reliability of the adhesive paper to the positive electrode tab is higher, and the burrs of the positive electrode tab are not easy to pass through the adhesive paper and contact the negative electrode tab, thereby reducing the possibility of short circuit in the secondary battery; when the thickness H2 of the adhesive layer is less than or equal to 5 μm, the impedance of the adhesive paper can be reduced, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery, and the dynamic performance of the secondary battery can be better, and the size of the adhesive paper in the thickness direction of the positive electrode current collector can be smaller, so that the impact on the discharge capacity of the secondary battery is smaller.

[0039] In some embodiments of the present application, the adhesive layer is made of at least one of polyacrylate, polyolefin, acrylate, polyacrylic acid and derivatives thereof.

[0040] In the above technical solution, the adhesive layer is made of at least one of polyacrylate, polyolefin, acrylate, polyacrylic acid and derivatives thereof, which can make the adhesive layer have a stronger adhesive force.

[0041] In a second aspect, the present application provides an electrical device, comprising the secondary battery as described above, wherein the secondary battery is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can also be obtained based on these drawings.

[0043] FIG1 is a schematic structural diagram of a secondary battery provided by some embodiments of the present application from one perspective;

[0044] FIG2 is a schematic cross-sectional view of a partial structure of a secondary battery provided in some embodiments of the present application;

[0045] FIG3 is a schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application;

[0046] FIG4 is a schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application;

[0047] FIG5 is a schematic cross-sectional view of a partial structure of a secondary battery provided in some embodiments of the present application;

[0048] FIG6 is a schematic diagram of the structure of adhesive tape for secondary batteries provided in some embodiments of the present application;

[0049] FIG7 is a schematic structural diagram of adhesive tape for secondary batteries provided in other embodiments of the present application;

[0050] FIG8 is a schematic structural diagram of adhesive tape for secondary batteries provided in other embodiments of the present application;

[0051] FIG9 is a schematic diagram of a partial structure of a secondary battery provided in some other embodiments of the present application.

[0052] Icons: 10 - Secondary battery; 100 - Positive electrode sheet; 110 - Positive electrode current collector; 111 - Base layer; 112 - Conductive layer; 120 - Positive electrode active material layer; 121 - Groove; 200 - Positive electrode tab; 300 - Adhesive tape; 310 - Base material layer; 320 - Adhesive layer; 321 - Adhesive portion; 400 - Negative electrode sheet; 500 - Negative electrode tab; 600 - Separator; 700 - Housing; X - Thickness direction of positive electrode current collector; Y - First direction; Z - Second direction.

[0053] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0054] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0055] The terms "first", "second" and the like in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0056] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0057] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0058] With the development of the new energy industry, batteries are gradually developing towards high discharge capacity. In the electrode assembly of a secondary battery, in order to install the tabs, it is necessary to remove part of the active material layer on the electrode sheet to leak out the current collector to form a groove, so that part of the current collector of the electrode sheet is exposed in the groove, so that the tabs accommodated in the groove can be electrically connected to the current collector. And in order to reduce the possibility of short circuit between the positive electrode sheet and the negative electrode sheet, it is necessary to set adhesive tape on the active material layer to cover the tabs and grooves. The part of the active material layer blocked by the adhesive tape cannot absorb and release metal ions, which will reduce the discharge capacity of the secondary battery.

[0059] In order to improve the discharge capacity of an electrochemical device, the present application provides a secondary battery, including a positive electrode sheet, a positive electrode tab and adhesive tape, the positive electrode sheet including a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector along the thickness direction thereof, the positive electrode active material layer being provided with a groove, the positive electrode collector including a first region, the first region being exposed in the groove; at least a portion of the positive electrode tab being arranged in the groove and connected to the first region; the adhesive tape being attached to the positive electrode active material layer and covering the groove and the positive electrode tab, the adhesive tape including a substrate layer and an adhesive layer, the adhesive layer being arranged on the surface of the substrate layer facing the positive electrode tab, the substrate layer having pores allowing metal cations to pass through, the porosity of the substrate layer being φ, satisfying 30%≤φ≤60%; along the thickness direction of the positive electrode collector, the projected area of ​​the substrate layer is S1, the overlapping area of ​​the projection of the adhesive layer and the projection of the substrate layer is S2, satisfying 20%≤S2 / S1≤45%.

[0060] In a secondary battery of this structure, when the porosity φ of the substrate layer is 30%-60%, metal cations can pass through the substrate layer, thereby allowing the portion of the positive electrode active material layer covered by the adhesive tape to absorb and release metal cations, thereby increasing the effective area of ​​the positive electrode active material layer, thereby improving the discharge capacity of the secondary battery, and reducing the possibility of deformation of the adhesive tape during the secondary battery preparation process. The shrinkage rate of the adhesive tape at high temperatures is also low, thereby improving the high-temperature short circuit performance of the secondary battery and thereby improving the safety performance of the secondary battery. Along the thickness direction of the positive electrode current collector, the projected area of ​​the substrate layer is S1, and the overlapping area of ​​the projection of the adhesive layer and the projection of the substrate layer is S2, satisfying 20%≤S2 / S1≤45%. This not only strengthens the adhesion between the adhesive tape and the positive electrode tab, but also increases the insulation reliability of the adhesive tape to the positive electrode tab, thereby reducing the possibility of thermal runaway of the secondary battery, and reduces the area of ​​the positive electrode active material layer blocked by the adhesive layer, allowing more metal cations to pass through the adhesive tape, thereby improving the discharge capacity of the secondary battery.

[0061] The secondary battery in the embodiment of the present application can be a lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., and the embodiment of the present application is not limited thereto. The secondary battery can be cylindrical, flat, rectangular, or other shapes, and the embodiment of the present application is not limited thereto.

[0062] The embodiments of the present application provide an electrical device that uses a secondary battery as a power source. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, and the like.

[0063] Referring to Figures 1 to 6, Figure 1 is a structural schematic diagram of a secondary battery provided in some embodiments of the present application from one perspective; Figure 2 is a cross-sectional schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application; Figure 3 is a schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application; Figure 4 is a schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application; Figure 5 is a cross-sectional schematic diagram of a partial structure of a secondary battery provided in some embodiments of the present application; and Figure 6 is a structural schematic diagram of the adhesive tape of the secondary battery provided in some embodiments of the present application.

[0064] The present embodiment provides a secondary battery 10, comprising a positive electrode sheet 100, a positive electrode tab 200, and adhesive tape 300. The positive electrode sheet 100 comprises a positive electrode current collector 110 and a positive electrode active material layer 120 disposed on a surface of the positive electrode current collector 110 along its thickness direction. The positive electrode active material layer 120 is provided with a groove 121. The positive electrode current collector 110 comprises a first region, which is exposed in the groove 121. At least a portion of the positive electrode tab 200 is disposed in the groove 121 and is connected to the first region. The adhesive tape 300 is adhered to the positive electrode active material layer 120 and covers the groove 121 and the positive electrode tab 200.

[0065] In some embodiments, the adhesive tape 300 includes a substrate layer 310 and an adhesive layer 320. The adhesive layer 320 is disposed on the surface of the substrate layer 310 facing the positive electrode tab 200. The substrate layer 310 has pores that allow metal cations to pass through. The porosity of the substrate layer 310 is φ, which satisfies 30% ≤ φ ≤ 60%. For example, φ can be 30%, 45%, or 60%.

[0066] By making the porosity φ of the substrate layer 310 satisfy 30%≤φ≤60%, when the porosity φ of the substrate layer 310 is greater than or equal to 30%, the metal cations can pass through the substrate layer 310, so that the portion of the positive electrode active material layer 120 covered by the adhesive tape 300 can also absorb and release the metal cations, making the effective area of ​​the positive electrode active material layer 120 larger, and improving the discharge capacity of the secondary battery 10; when the porosity φ of the substrate layer 310 is less than or equal to 60%, the possibility of deformation of the adhesive tape 300 during the preparation process of the secondary battery 10 can be reduced, and the shrinkage rate of the adhesive tape 300 at high temperature can be lowered, which can improve the secondary battery. Therefore, when the porosity φ of the substrate layer 310 is 30%-60%, the metal cations can pass through the substrate layer 310, so that the part of the positive electrode active material layer 120 covered by the adhesive tape 300 can also realize the absorption and release of metal cations, making the effective area of ​​the positive electrode active material layer 120 larger, which can increase the discharge capacity of the secondary battery 10, and reduce the possibility of deformation of the adhesive tape 300 during the preparation process of the secondary battery 10, and can make the shrinkage rate of the adhesive tape 300 at high temperature lower, which can improve the high temperature external short performance of the secondary battery, and thus improve the safety performance of the secondary battery.

[0067] In some embodiments, along the thickness direction X of the positive electrode current collector, the projected area of ​​the substrate layer 310 is S1, and the overlapping area of ​​the projection of the adhesive layer 320 and the projection of the substrate layer 310 is S2, satisfying 20% ​​≤ S2 / S1 ≤ 45%. For example, S2 / S1 can be 20%, 30%, or 45%.

[0068] When S2 / S1 is greater than or equal to 20%, the area of ​​the adhesive layer 320 can be larger, so that the bonding force between the adhesive tape 300 and the positive electrode sheet 100 is stronger, and the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is higher, which can reduce the possibility of thermal runaway of the secondary battery 10; when S2 / S1 is less than or equal to 45%, the area of ​​the adhesive layer 320 is smaller, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and make the area of ​​the positive electrode active material layer 120 blocked by the adhesive layer 320 smaller, so that more metal cations can pass through the adhesive tape 300. , thereby improving the discharge capacity of the secondary battery 10; therefore, when S2 / S1 is 20%-45%, it can not only make the adhesion between the tape 300 and the positive electrode sheet 100 stronger, but also make the insulation reliability of the tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10, but also reduce the impedance of the tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better, and can make the area of ​​the positive electrode active material layer 120 blocked by the adhesive layer 320 smaller, which can allow more metal cations to pass through the tape 300, thereby improving the discharge capacity of the secondary battery 10.

[0069] In some embodiments, 25%≤S2 / S1≤35%. For example, S2 / S1 can be 25%, 30%, or 35%.

[0070] When S2 / S1 is greater than or equal to 25%, the area of ​​the adhesive layer 320 can be further increased, thereby making the bonding force between the adhesive tape 300 and the positive electrode sheet 100 stronger, and the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10; when S2 / S1 is less than or equal to 35%, the area of ​​the adhesive layer 320 can be further decreased, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and making the dynamic performance of the secondary battery 10 better, and making the area of ​​the positive electrode active material layer 120 blocked by the adhesive layer 320 smaller, which can allow more metal cations to pass through the adhesive tape 320. 00, thereby improving the discharge capacity of the secondary battery 10; therefore, when S2 / S1 is 25%-35%, it can not only further make the adhesion between the tape 300 and the positive electrode sheet 100 stronger, but also make the insulation reliability of the tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10, but also reduce the impedance of the tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better, and can further make the area of ​​the positive electrode active material layer 120 blocked by the adhesive layer 320 smaller, which can allow more metal cations to pass through the tape 300, thereby improving the discharge capacity of the secondary battery 10.

[0071] 6 , in some embodiments, the adhesive layer 320 includes a plurality of adhesive portions 321 , and the plurality of adhesive portions 321 are spaced apart from each other.

[0072] By making the adhesive layer 320 include multiple adhesive parts 321, and the multiple adhesive parts 321 are arranged at intervals from each other, the adhesive force distribution between the adhesive paper 300 and the positive electrode sheet 100 can be made more uniform, thereby making the adhesive strength between the adhesive paper 300 and the positive electrode sheet 100 higher. The insulation reliability of the adhesive paper 300 to the positive electrode tab 200 is higher, which can reduce the possibility of thermal runaway of the secondary battery 10. The area of ​​the adhesive layer 320 can be controlled by adjusting the area of ​​each adhesive part 321.

[0073] In some embodiments, the bonding portion 321 is linear and extends along a first direction Y. Multiple bonding portions 321 are spaced apart along a second direction Z. The first direction Y, the second direction Z, and the thickness direction X of the positive electrode current collector are perpendicular to each other.

[0074] By making the bonding portion 321 linear, the bonding portion 321 extends along the first direction Y, and multiple bonding portions 321 are spaced apart along the second direction Z; the first direction Y, the second direction Z, and the thickness direction X of the positive electrode collector are perpendicular to each other, so that the bonding strength between the adhesive tape 300 and the positive electrode sheet 100 is high, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is high, and the possibility of thermal runaway of the secondary battery 10 can be reduced.

[0075] In some embodiments, the width of the adhesive portion 321 along the second direction Z is W, which satisfies 1 mm ≤ W ≤ 2 mm. For example, W can be 1 mm, 1.5 mm, or 2 mm.

[0076] When W is greater than or equal to 1 mm, the width of the adhesive portion 321 along the second direction Z can be larger, the bonding strength between the adhesive portion 321 and the positive electrode sheet 100 is higher, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is higher, and the possibility of thermal runaway of the secondary battery 10 can be reduced; when W is less than or equal to 2 mm, the width of the adhesive portion 321 along the second direction Z can be smaller, the impedance of the adhesive tape 300 can be reduced, and the possibility of lithium deposition or purple spots in the secondary battery 10 can be reduced, and the dynamic performance of the secondary battery 10 can be better, and the area of ​​the positive electrode active material layer 120 blocked by the adhesive portion 321 is smaller, which can More metal cations can pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10; therefore, when W is 1mm-2mm, it can not only make the bonding strength between the adhesive portion 321 and the positive electrode sheet 100 higher, but also make the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10, but also reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10.

[0077] In some embodiments, the distance between two adjacent adhesive portions 321 along the second direction Z is G1, which satisfies 3mm≤G1≤5mm. For example, G1 can be 3mm, 4mm, or 5mm.

[0078] When G1 is greater than or equal to 3 mm, the impedance of the adhesive tape 300 can be reduced, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and the dynamic performance of the secondary battery 10 can be improved. In addition, the spacing between two adjacent adhesive portions 321 along the second direction Z can be larger, which can allow more metal cations to pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10. When G1 is less than or equal to 5 mm, more space can be left on the substrate layer 310 for arranging the adhesive portion 321, and the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 is higher, and the adhesive tape 300 has a better bond to the positive electrode tab 2. 00 has a higher insulation reliability, which can reduce the possibility of thermal runaway of the secondary battery 10; therefore, when G1 is 3mm-5mm, it can reduce the impedance of the tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the tape 300, thereby increasing the discharge capacity of the secondary battery 10, and can make the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 higher, and the insulation reliability of the tape 300 to the positive electrode tab 200 is higher, which can reduce the possibility of thermal runaway of the secondary battery 10.

[0079] In some embodiments, the plurality of adhesive portions 321 are arranged in an array.

[0080] By arranging the multiple adhesive portions 321 in an array, the adhesive force between the adhesive tape 300 and the positive electrode sheet 100 can be distributed more evenly, thereby increasing the adhesive strength between the adhesive tape 300 and the positive electrode sheet 100. The adhesive tape 300 has a higher insulation reliability for the positive electrode tab 200, which can reduce the possibility of thermal runaway of the secondary battery 10.

[0081] Refer to FIG. 7 , which is a schematic structural diagram of adhesive tape for secondary batteries provided in other embodiments of the present application.

[0082] In some embodiments, the diameter of the circumscribed circle of the projection of the bonding portion 321 along the thickness direction X of the positive electrode current collector is D, which satisfies 2.5 mm ≤ D ≤ 3.5 mm. For example, D can be 2.5 mm, 3 mm, or 3.5 mm.

[0083] When D is greater than or equal to 2.5 mm, the area of ​​the adhesive portion 321 can be larger, the bonding strength between the adhesive portion 321 and the positive electrode sheet 100 is higher, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is higher, and the possibility of thermal runaway of the secondary battery 10 can be reduced; when D is less than or equal to 3.5 mm, the area of ​​the adhesive portion 321 can be smaller, the impedance of the adhesive tape 300 can be reduced, and the possibility of lithium deposition or purple spots in the secondary battery 10 can be reduced, and the dynamic performance of the secondary battery 10 can be better, and the area of ​​the positive electrode active material layer 120 blocked by the adhesive portion 321 is smaller, which can make more metal Metal cations pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10; therefore, when D is 2.5mm-3.5mm, it can not only make the bonding strength between the adhesive portion 321 and the positive electrode sheet 100 higher, but also make the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10, but also reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10.

[0084] In some embodiments, the distance between two adjacent bonding portions 321 is G2, which satisfies 2 mm ≤ G2 ≤ ​​3 mm. For example, G2 can be 2 mm, 2.5 mm, or 3 mm.

[0085] When G2 is greater than or equal to 2 mm, the distance between two adjacent adhesive portions 321 along the second direction Z can be larger, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the adhesive tape 300, thereby improving the discharge capacity of the secondary battery 10; when G2 is less than or equal to 3 mm, it can make more space on the substrate layer 310 for arranging the adhesive portion 321, the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 is higher, and the adhesive tape 300 is more secure to the positive electrode tab 2 00 has a higher insulation reliability, which can reduce the possibility of thermal runaway of the secondary battery 10; therefore, when G2 is 2mm-3mm, it can reduce the impedance of the tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the tape 300, thereby increasing the discharge capacity of the secondary battery 10, and can make the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 higher, and the insulation reliability of the tape 300 to the positive electrode tab 200 is higher, which can reduce the possibility of thermal runaway of the secondary battery 10.

[0086] Refer to FIG8 , which is a schematic structural diagram of adhesive tape for secondary batteries provided in other embodiments of the present application.

[0087] In some embodiments, the maximum spacing distance between two adjacent bonding portions 321 is G3, and the minimum spacing distance is G4, satisfying 1mm≤G4<G3≤7mm. For example, G4 can be 1mm, 3mm, or 5mm. For example, G3 can be 3mm, 5mm, or 7mm.

[0088] By making G4 < G3, that is, multiple bonding parts 321 are unevenly distributed, the difficulty of preparing the bonding parts 321 can be reduced. When G3 and G4 are greater than or equal to 1mm, the maximum spacing distance between two adjacent bonding parts 321 can be larger, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and can allow more metal cations to pass through the adhesive tape 300, thereby increasing the discharge capacity of the secondary battery 10; when G3 and G4 are less than or equal to 7mm, there can be more space on the substrate layer 310 for setting the bonding part 321, the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 is higher, and the adhesive tape 300 is closer to the positive electrode tab. The insulation reliability of 200 is high, which can reduce the possibility of thermal runaway of the secondary battery 10; therefore, when G3 and G4 are 1mm-7mm, it can reduce the impedance of the tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and can make the dynamic performance of the secondary battery 10 better, and can make more metal cations pass through the tape 300, thereby increasing the discharge capacity of the secondary battery 10, and can make the bonding strength between the adhesive layer 320 and the positive electrode sheet 100 higher. The insulation reliability of the tape 300 to the positive electrode tab 200 is high, which can reduce the possibility of thermal runaway of the secondary battery 10.

[0089] In some embodiments, along the thickness direction X of the positive electrode current collector, the bonding layer 320 at least partially overlaps with the projection of the positive electrode tab 200 .

[0090] By making the projections of the adhesive layer 320 and the positive electrode tab 200 at least partially overlap along the thickness direction X of the positive electrode current collector, at least a portion of the adhesive layer 320 can be attached to the positive electrode tab 200, so that the bonding strength between the adhesive tape 300 and the positive electrode tab 200 is high, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is high, and the possibility of thermal runaway of the secondary battery 10 can be reduced.

[0091] Refer to FIG9 , which is a schematic diagram of a partial structure of a secondary battery provided in some other embodiments of the present application.

[0092] In some embodiments, along the thickness direction X of the positive electrode current collector, the overlapping area of ​​the projection of the positive electrode tab 200 and the positive electrode sheet 100 is S3, and the overlapping area of ​​the projection of the adhesive layer 320 and the positive electrode tab 200 is S4, satisfying 40% ≤ S4 / S3 ≤ 100%. For example, S4 / S3 can be 40%, 70%, or 100%.

[0093] By ensuring that 40% ≤ S4 / S3 ≤ 100%, the overlapping area between the projection of the adhesive layer 320 and the positive electrode tab 200 can be made larger, thereby making the bonding area between the adhesive tape 300 and the positive electrode tab 200 larger, the bonding strength between the adhesive tape 300 and the positive electrode tab 200 higher, and the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10.

[0094] In some embodiments, the adhesive force F between the adhesive tape 300 and the positive electrode sheet 100 satisfies 30 N / m≤F≤140 N / m. For example, F can be 30 N / m, 80 N / m, or 140 N / m.

[0095] When the bonding force F between the adhesive tape 300 and the positive electrode sheet 100 is greater than or equal to 30 N / m, the bonding force between the adhesive tape 300 and the positive electrode sheet 100 is strong, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is high, and the possibility of thermal runaway of the secondary battery 10 can be reduced; since the bonding force F between the adhesive tape 300 and the positive electrode sheet 100 is positively correlated with the area and thickness of the adhesive layer 320, when the bonding force F between the adhesive tape 300 and the positive electrode sheet 100 is less than or equal to 140 N / m, the area and thickness of the adhesive layer 320 can be increased. / or the thickness is small, reducing the space occupied by the adhesive layer 320, thereby making the impact on the discharge capacity of the secondary battery 10 smaller; therefore, when the bonding force F between the adhesive tape 300 and the positive electrode sheet 100 is 30N / m-140N / m, it can not only make the bonding force between the adhesive tape 300 and the positive electrode sheet 100 stronger, but also make the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 higher, which can reduce the possibility of thermal runaway of the secondary battery 10, but also reduce the space occupied by the adhesive layer 320, thereby making the impact on the discharge capacity of the secondary battery 10 smaller.

[0096] In some embodiments, the thickness of the substrate layer 310 is H1, which satisfies 6 μm≤H1≤20 μm. For example, H1 can be 6 μm, 13 μm, or 20 μm.

[0097] When the thickness H1 of the substrate layer 310 is greater than or equal to 6 μm, the burrs of the positive electrode tab 200 are less likely to pass through the adhesive tape 300 and contact the negative electrode tab, thereby reducing the possibility of short circuit of the secondary battery 10. When the thickness H1 of the substrate layer 310 is less than or equal to 20 μm, the size of the adhesive tape 300 in the thickness direction X of the positive electrode current collector can be smaller, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and improving the dynamic performance of the secondary battery 10. And the impact on the discharge capacity of the secondary battery 10 is smaller; therefore, when the thickness H1 of the substrate layer 310 is 6μm-20μm, it can not only prevent the burrs of the positive electrode tab 200 from easily passing through the adhesive tape 300 and contacting the negative electrode plate, thereby reducing the possibility of short circuit of the secondary battery 10, but also reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better and have less impact on the discharge capacity of the secondary battery 10.

[0098] In some embodiments, 8 μm ≤ H1 ≤ 12 μm. For example, H1 may be 8 μm, 10 μm, or 12 μm.

[0099] When the thickness H1 of the substrate layer 310 is greater than or equal to 8 μm, it is possible to further prevent the burrs of the positive electrode tab 200 from passing through the adhesive tape 300 and contacting the negative electrode tab, thereby reducing the possibility of short circuit of the secondary battery 10; when the thickness H1 of the substrate layer 310 is less than or equal to 12 μm, it is possible to further reduce the size of the adhesive tape 300 in the thickness direction X of the positive electrode current collector, thereby further reducing the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and thus improving the dynamic performance of the secondary battery 10. And it has less impact on the discharge capacity of the secondary battery 10; therefore, when the thickness H1 of the substrate layer 310 is 8μm-12μm, it can further prevent the burrs of the positive electrode tab 200 from passing through the adhesive tape 300 and contacting the negative electrode plate, thereby reducing the possibility of short circuit of the secondary battery 10, and can further reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better and further reduce the impact on the discharge capacity of the secondary battery 10.

[0100] In some embodiments, the substrate layer 310 is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film, and non-woven fabric.

[0101] The substrate layer 310 is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film, and non-woven fabric, so that the substrate layer 310 has pores, and the porosity can reach 30% to 60%.

[0102] In some embodiments, the thickness of the adhesive layer 320 is H2, which satisfies 3 μm≤H2≤5 μm. For example, H2 can be 3 μm, 4 μm, or 5 μm.

[0103] When the thickness H2 of the adhesive layer 320 is greater than or equal to 3 μm, the adhesive force of the adhesive tape 300 is stronger, the adhesive tape 300 is not easy to fall off, the insulation reliability of the adhesive tape 300 to the positive electrode tab 200 is higher, and the burrs of the positive electrode tab 200 are not easy to pass through the adhesive tape 300 and contact the negative electrode sheet, thereby reducing the possibility of short circuit of the secondary battery 10; when the thickness H2 of the adhesive layer 320 is less than or equal to 5 μm, the size of the adhesive tape 300 in the thickness direction X of the positive electrode current collector can be smaller, which can reduce the impedance of the adhesive tape 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, and making the dynamic performance of the secondary battery 10 better. And the impact on the discharge capacity of the secondary battery 10 is smaller; therefore, when the thickness H2 of the adhesive layer 320 is 3μm-5μm, the adhesion of the adhesive paper 300 can be stronger, the adhesive paper 300 is not easy to fall off, the insulation reliability of the adhesive paper 300 to the positive electrode tab 200 is higher, and the burrs of the positive electrode tab 200 are not easy to pass through the adhesive paper 300 and contact the negative electrode tab, thereby reducing the possibility of short circuit of the secondary battery 10, and reducing the impedance of the adhesive paper 300, thereby reducing the possibility of lithium deposition or purple spots in the secondary battery 10, which can make the dynamic performance of the secondary battery 10 better and have less impact on the discharge capacity of the secondary battery 10.

[0104] In some embodiments, the adhesive layer 320 is made of at least one of polyacrylate, polyolefin, acrylate, polyacrylic acid, and derivatives thereof.

[0105] By making the adhesive layer 320 be made of at least one of polyacrylate, polyolefin, acrylate, polyacrylic acid and derivatives thereof, the adhesive force of the adhesive layer 320 can be made stronger.

[0106] Referring to Figures 1 and 2, in some embodiments, a secondary battery 10 further includes a negative electrode sheet 400, a negative electrode tab 500, a separator 600, and a housing 700. The positive electrode sheet 100, separator 600, and negative electrode sheet 400 are stacked, and the housing 700 is used to accommodate the positive electrode sheet 100, separator 600, negative electrode sheet 400, and electrolyte. Secondary batteries primarily operate by the movement of metal ions between the positive electrode sheet 100 and the negative electrode sheet 400. The negative electrode sheet 400 includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode tab 500 is connected to the negative electrode current collector to enable electrical energy input or output from the negative electrode sheet 400 through the negative electrode tab. Taking lithium-ion batteries as an example, the negative electrode current collector can be made of copper, and the negative electrode active material can be made of carbon or silicon materials. The separator 600 can be made of polypropylene (PP) or polyethylene (PE), among others. The electrolyte may include an organic solvent, an electrolyte lithium salt, and the like.

[0107] 2 , in some embodiments, the positive electrode sheet 100 , the separator 600 , and the negative electrode sheet 400 are wound to form a wound structure.

[0108] In other embodiments, the positive electrode sheet 100 , the separator 600 , and the negative electrode sheet 400 may also be stacked to form a laminated structure.

[0109] In some embodiments, the secondary battery 10 is configured in a rectangular parallelepiped shape.

[0110] 5 , in some embodiments, the positive electrode current collector 110 may be a composite current collector, comprising a base layer 111 and two conductive layers 112 , wherein the conductive layers 112 are disposed on both sides of the base layer 111 along its thickness direction.

[0111] See Table 1, in which H1 is the thickness of the substrate layer; φ is the porosity of the substrate layer; S2 is the overlapping area of ​​the projection of the bonding layer 320 and the projection of the substrate layer 310 along the thickness direction X of the positive electrode current collector; S1 is the projected area of ​​the substrate layer 310 along the thickness direction X of the positive electrode current collector; "ordered point shape" means that the projection of multiple bonding portions along the thickness direction X of the positive electrode current collector is circular, and the multiple bonding portions are arranged in an array; "disordered point shape" means that the projection of multiple bonding portions along the thickness direction X of the positive electrode current collector is circular, and the multiple bonding portions are arranged in an array; "disordered point shape" means that the projection of multiple bonding portions along the thickness direction X of the positive electrode current collector is circular. The projection in the direction X of the positive electrode collector is circular, and the spacing distances between the multiple bonding parts are different; H2 is the thickness of the bonding layer; "bonding part spacing" is the spacing distance between two adjacent bonding parts; S3 is the overlapping area of ​​the projection of the positive electrode tab and the positive electrode sheet along the thickness direction X of the positive electrode collector; S4 is the overlapping area of ​​the projection of the bonding layer and the positive electrode tab along the thickness direction X of the positive electrode collector; F is the bonding force between the adhesive tape and the positive electrode sheet; R is the buckle resistance value of the secondary battery.

[0112] The examples and comparative examples of the present application were prepared as follows, and the specific parameters can be seen in Table 1.

[0113] The preparation method of the secondary battery is as follows:

[0114] (1) Preparation of positive electrode sheet: Lithium cobalt oxide, conductive agent and binder polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone (NMP) solution at a mass ratio of 97.2:1.5:1.3 to prepare positive electrode active material layer slurry. Pass through a 200-mesh sieve to prepare positive electrode active material layer slurry with a solid content of 70%-75%. Use a coating machine to apply the positive electrode active material layer slurry to the surface of the positive electrode current collector with a coating thickness of 90 microns. The width of the positive electrode sheet is 70 mm and the length of the positive electrode sheet is 1400 mm. After cold pressing and slitting, the positive electrode sheet is obtained.

[0115] (2) Assembling the positive electrode sheet and the positive electrode tab: providing a groove in the positive electrode active material layer so that the first region of the positive electrode current collector is exposed in the groove; preparing the positive electrode tab and connecting the positive electrode tab to the first region.

[0116] (3) Preparation and assembly of adhesive tape: An adhesive (the adhesive can be polyacrylate, polyolefin, acrylate, polyacrylic acid, etc., and polymethyl acrylate is used in this application) is applied to one side of the polypropylene substrate layer using a micro-gravure plate. A release agent is applied to the other side of the substrate layer. After winding, the adhesive tape is divided into strips to prepare an adhesive tape roll with an adhesive layer on the surface. The adhesive tape is cut and attached to the positive electrode active material layer so that the adhesive tape covers the groove and the positive electrode tab.

[0117] (4) Preparation of negative electrode sheets: Graphite, a negative electrode active material, sodium carboxymethyl cellulose, a negative electrode thickener, and styrene-butadiene rubber, a negative electrode binder, are mixed in a mass ratio of 98:1:1. Deionized water is then added as a solvent and stirred evenly to form a negative electrode active material layer slurry. The mixture is passed through a 200-mesh sieve to form a negative electrode active material layer slurry with a solid content of 40%-45%. Copper foil is used as the negative electrode current collector, and the negative electrode active material layer slurry is applied to the negative electrode current collector. After drying at 80°C, cold pressing, and slitting, the negative electrode sheets are obtained.

[0118] (5) Assembling the negative electrode sheet and the negative electrode tab: providing a second groove in the negative electrode active material layer so that the second region of the negative electrode current collector is exposed in the groove; preparing the negative electrode tab and connecting the negative electrode tab to the second region.

[0119] (6) Diaphragm preparation: The base material of the diaphragm is 8 μm thick polyethylene (PE). A 2 μm alumina ceramic layer is coated on each of the two opposite surfaces of the base material. Finally, 2.5 mg / cm2 of the binder polyvinylidene fluoride (PVDF) is coated on each side of the ceramic layer and dried.

[0120] (7) Preparation of electrolyte: In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate and a non-aqueous organic solvent (propylene carbonate (PC): ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:0.5:1, weight ratio) are prepared to prepare a basic electrolyte, and LiPF6 is added and mixed uniformly to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0121] (8) Preparation of secondary batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrode sheets to act as an insulator, and then wound to form an electrode assembly. The electrode assembly is placed in an outer packaging aluminum-plastic film, dehydrated at 80°C, injected with the above-mentioned electrolyte, and packaged. After the formation, degassing, and trimming processes, a secondary battery is obtained.

[0122] Table 1 Preparation parameters and performance test of secondary batteries

[0123] The method for testing the porosity of the substrate layer of the adhesive tape is:

[0124] (1) Remove the adhesive tape from the positive electrode and soak it in toluene at 45°C for 10 hours, repeating twice to obtain a substrate layer sample. Use a micrometer to measure the thickness h of the substrate layer sample and take the average of 10 measurements.

[0125] (2) Calculate the porosity of the substrate layer as φ = [1-m / (s*h*ρ)]*100%, where m is the mass of the substrate layer sample and ρ is the true density of the substrate layer material.

[0126] True density test method for substrate layer material:

[0127] (1) Take a substrate layer sample with an area greater than 0.35 cm2 and use a true density tester (AccuPycⅡ1340) to measure the true volume V of the substrate layer sample in a helium environment. The true volume V is the volume of the substrate layer sample excluding the pores.

[0128] (2) Using an electronic balance to measure the weight of the substrate layer sample is M, and the true density ρ = M / V.

[0129] The test method for the projected area ratio S2 / S1 of the adhesive layer to the substrate layer is:

[0130] (1) Place the adhesive tape under a scanning electron microscope (SEM) and take an image at an acceleration voltage (Extra High Tension) of EHT = 3 kV and a magnification of approximately 1000 times.

[0131] (2) Using imageJ software, the adhesive layer area was identified by threshold segmentation, and S2 / S1 was calculated = the area of ​​the adhesive layer in the field of view / the area of ​​the adhesive tape in the field of view.

[0132] The test method for the ratio S4 / S3 of the area of ​​the bonding layer to the area S3 of the tab on the pole piece is:

[0133] (1) Use a micrometer to measure the length L1 and width L2 of the pole piece on the tab. The area S3 of the tab on the pole piece is equal to L1*L2.

[0134] (2) Place the adhesive tape under a scanning electron microscope (SEM) and take an image at an acceleration voltage (Extra High Tension) of EHT = 3 kV and a magnification of approximately 1000 times.

[0135] (3) Using imageJ software, the adhesive layer area was identified by threshold segmentation, and S4 / S3 was calculated as the area of ​​the adhesive layer in the field of view / L1*L2.

[0136] The method for testing the adhesion between the adhesive tape and the positive electrode is:

[0137] (1) Punch the positive electrode sheet with adhesive tape into 54.2*72.5mm samples.

[0138] (2) Place the sample on a tensile testing machine, set the tensile testing machine to a test speed of 50 mm / min, and pre-stretch the sample by 5 mm.

[0139] (3) After pre-stretching, the force, displacement and other data of the tensile testing machine are reset to zero, and the sample is tested again at a test speed of 50 mm / min. When the stretching length of the tensile testing machine is 40 mm, the tensile force is recorded as the bonding force between the adhesive tape and the positive electrode sheet.

[0140] The test method for high temperature external short circuit performance of secondary batteries is:

[0141] (1) Place the secondary battery in an environment with a temperature of 23±2℃.

[0142] (2) Charge the secondary battery to the battery's charge cut-off voltage (e.g., 4.45V) at a constant current of 0.7C and charge the secondary battery to 0.02C at a constant voltage.

[0143] (3) Place the secondary battery in a test environment at 57±5℃. After the surface temperature of the battery cell reaches the test temperature, let it stand for 30 minutes. Use load resistors of different resistance values ​​(between 60-100mΩ) to short-circuit the positive and negative poles of the battery. The test time is 24 hours.

[0144] (4) Judgment criteria: No fire, no explosion, and the sample surface temperature does not exceed 130℃.

[0145] The detection method of the buckle resistance value of the secondary battery is:

[0146] (1) The secondary battery sample was allowed to stand for 5 minutes; the secondary battery sample was charged to 4.5V at a constant voltage of 0.5C, and then the secondary battery sample was charged to 4.5V at a constant current of 0.1C, and allowed to stand for 10 minutes; the secondary battery sample was discharged to 3V at a constant voltage of 0.5C;

[0147] (2) Let the secondary battery sample stand for 3 minutes; charge the secondary battery sample to 4.5V at a constant voltage of 0.5C, let it stand for 10 minutes, and discharge the secondary battery sample to 1V at a constant voltage of 0.5C. The voltage at this time is taken as V1;

[0148] (3) After standing for 1 hour, the voltage of the secondary battery is taken as V2, and the buckle resistance value of the secondary battery is R = (V1-V2) / (the current value corresponding to 0.5C discharge).

[0149] According to Table 1, the following conclusions can be drawn:

[0150] Referring to Comparative Example 1 and Examples 1-33, the adhesive tape in Comparative Example 1 includes only a substrate layer and no adhesive layer, while the adhesive tape in the present application includes both a substrate layer and an adhesive layer, which improves the adhesive tape's bonding performance and increases the secondary battery's buckle resistance. When the porosity φ of the substrate layer satisfies 30% ≤ φ ≤ 60%, and the bonding between the adhesive layer and the substrate layer satisfies 20% ≤ S2 / S1 ≤ 45%, the secondary battery's dynamic performance is improved and the likelihood of lithium deposition or purple spots forming in the secondary battery is reduced.

[0151] As shown in Comparative Examples 2-9 and Examples 1-6, a higher porosity φ of the substrate layer results in a lower buckle resistance and better dynamic performance of the secondary battery, but also worse high-temperature short circuit performance. In Comparative Example 2, where the substrate layer had a porosity φ of less than 30%, the buckle resistance of the secondary battery was high, affecting its dynamic performance. In Comparative Example 3, where the substrate layer had a porosity φ of greater than 60%, the adhesive tape was susceptible to deformation, increasing the risk of short circuiting the secondary battery.

[0152]

[0153] Referring to Comparative Examples 4-5 and Examples 4, 7-10, along the thickness direction of the positive electrode current collector, a smaller ratio (S2 / S1) of the overlapping area of ​​the adhesive layer's projection to the substrate layer's projection, and a smaller bonded portion, results in a lower buckle resistance and improved dynamic performance of the secondary battery. However, in Comparative Example 4, where S2 / S1 is less than 20%, the adhesive tape exhibits low adhesion; and in Comparative Example 5, where S2 / S1 is greater than 45%, the adhesive layer's larger area blocks metal cations from passing through the tape, impacting the secondary battery's discharge capacity.

[0154] Referring to Examples 11-13, when the shape of the bonding portion is an ordered point shape (for example, circular bonding portions arranged in a matrix), the smaller the size of the bonding portion, the smaller the buckling resistance value of the secondary battery, and the better the dynamic performance of the secondary battery.

[0155] Referring to Examples 14-15, when the shape of the bonding portion is an ordered point shape (for example, circular bonding portions arranged in a matrix), the larger the spacing between the bonding portions, the smaller the buckling resistance value of the secondary battery, and the better the dynamic performance of the secondary battery.

[0156] Referring to Examples 16-18, when the shape of the bonding portion is disordered dots (for example, irregularly arranged circular bonding portions), the larger the spacing between the bonding portions, the smaller the buckling resistance value of the secondary battery, and the better the dynamic performance of the secondary battery.

[0157] Referring to Examples 19-21, when the adhesive portion is coated on the positive electrode tab, along the thickness direction X of the positive electrode current collector, the larger the ratio S4 / S3 of the overlapping area of ​​the adhesive layer and the projection of the positive electrode tab to the overlapping area of ​​the projection of the positive electrode tab and the positive electrode sheet, the greater the adhesion force of the adhesive paper, which can reduce the risk of the adhesive paper falling off, thereby reducing the possibility of thermal runaway of the secondary battery.

[0158] Referring to Examples 4 and 22-25, the smaller the thickness of the substrate layer, the smaller the buckling resistance value of the secondary battery, and the better the dynamic performance of the secondary battery.

[0159] Referring to Examples 4, 26-27, the smaller the thickness of the bonding portion, the smaller the bonding force, but the smaller the buckling resistance value of the secondary battery, and the better the dynamic performance of the secondary battery.

[0160] Referring to Examples 4, 28-33, the substrate layer made of PP (polypropylene) material has a smaller buckling resistance value of the secondary battery and better dynamic performance of the secondary battery; secondly, the substrate layer made of cellulose film and PE (polyethylene) material has a relatively small buckling resistance value of the secondary battery and relatively good dynamic performance of the secondary battery.

[0161] An embodiment of the present application provides an electrical device, including the secondary battery 10 provided in any of the above embodiments, and the secondary battery 10 is used to provide electrical energy.

[0162] The electric device may be any of the aforementioned devices or systems using the secondary battery 10 .

[0163] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0164] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A secondary battery, characterized in that: include: A positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector along a thickness direction thereof, wherein the positive electrode active material layer is provided with a groove, and the positive electrode current collector comprises a first region, wherein the first region is exposed in the groove; a positive electrode tab, at least partially disposed in the groove and connected to the first region; A tape is attached to the positive electrode active material layer and covers the groove and the positive electrode tab, the tape comprising a substrate layer and an adhesive layer, the adhesive layer being disposed on a surface of the substrate layer facing the positive electrode tab, the substrate layer having pores allowing metal cations to pass through, and the porosity of the substrate layer being φ, satisfying 30%≤φ≤60%; Along the thickness direction of the positive electrode current collector, the projection area of ​​the substrate layer is S1, and the overlapping area of ​​the projection of the adhesive layer and the projection of the substrate layer is S2, satisfying 20%≤S2 / S1≤45%.

2. The secondary battery according to claim 1, wherein 25%≤S2 / S1≤35%.

3. The secondary battery according to claim 1, wherein The adhesive layer includes a plurality of adhesive portions, and the plurality of adhesive portions are arranged at intervals from each other.

4. The secondary battery according to claim 3, wherein The bonding portion is linear and extends along a first direction. A plurality of bonding portions are spaced apart along a second direction. The first direction, the second direction, and the thickness direction of the positive electrode current collector are perpendicular to each other.

5. The secondary battery according to claim 4, wherein The width of the bonding portion along the second direction is W, satisfying 1mm≤W≤2mm; the spacing distance between two adjacent bonding portions along the second direction is G1, satisfying 3mm≤G1≤5mm.

6. The secondary battery according to claim 3, wherein The plurality of bonding portions are arranged in an array, and the diameter of the circumscribed circle of the projection of the bonding portion along the thickness direction of the positive electrode current collector is D, satisfying 2.5mm≤D≤3.5mm; the interval distance between two adjacent bonding portions is G2, satisfying 2mm≤G2≤3mm.

7. The secondary battery according to claim 3, wherein The maximum spacing distance between two adjacent bonding portions is G3, and the minimum spacing distance is G4, satisfying 1mm≤G4<G3≤7mm.

8. The secondary battery according to claim 1, wherein Along the thickness direction of the positive electrode current collector, the adhesive layer at least partially overlaps with the projection of the positive electrode tab.

9. The secondary battery according to claim 8, characterized in that Along the thickness direction of the positive electrode current collector, the overlapping area of ​​the projection of the positive electrode tab and the positive electrode sheet is S3, and the overlapping area of ​​the projection of the adhesive layer and the positive electrode tab is S4, satisfying 40%≤S4 / S3≤100%.

10. The secondary battery according to claim 1, wherein The bonding force between the adhesive tape and the positive electrode plate is F, which satisfies 30 N / m≤F≤140 N / m.

11. The secondary battery according to claim 1, wherein The thickness of the substrate layer is H1, which satisfies 6 μm≤H1≤20 μm.

12. The secondary battery according to claim 11, wherein 8μm≤H1≤12μm.

13. The secondary battery according to claim 1, wherein The substrate layer is made of at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film, and non-woven fabric.

14. The secondary battery according to claim 1, wherein The thickness of the adhesive layer is H2, which satisfies 3 μm≤H2≤5 μm.

15. The secondary battery according to claim 1, wherein The adhesive layer is made of at least one of polyacrylate, polyolefin, acrylate, polyacrylic acid and derivatives thereof.

16. An electrical device, characterized in that: The secondary battery according to any one of claims 1 to 15 is used to provide electrical energy.

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