Secondary battery and electric device

Abstract

A secondary battery and an electric device. An electrode assembly (10) of the secondary battery comprises a positive electrode sheet (100), a separator (200), a negative electrode sheet (300) and a first-type adhesive tape (400) that are stacked, wherein the first-type adhesive tape (400) comprises a substrate layer (401), the thickness H of the substrate layer (401) satisfying 8 μm≤H≤20 μm, and the porosity φ of the substrate layer (401) satisfying 20％≤φ≤60％; the positive electrode sheet (100) comprises a positive electrode tab (140), and a positive current collector (110), a first positive active material layer (120) and a second positive active material layer (130) that are stacked; the first positive active material layer (120) is provided with a first recess (121), and the positive electrode tab (140) is accommodated in the first recess (121); and the first-type adhesive tape (400) comprises a first adhesive tape (410), the first adhesive tape (410) being attached to the first positive active material layer (120) and covering the first recess (121) and the positive electrode tab (140). The substrate layer (401) allows metal cations to pass therethrough, such that the part of the first positive active material layer (120) covered by the first-type adhesive tape (400) can also absorb and release the metal cations, thereby increasing the effective area of the first positive active material layer (120) and improving 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 CN202410383505.4, 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 also developing towards intelligence and multi-functionality, and the requirements for battery discharge capacity are becoming increasingly higher. Therefore, how to improve the discharge capacity of batteries has become an urgent problem to be solved in the battery field. Summary of the Invention

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

[0005] In a first aspect, the present application provides a secondary battery comprising a housing, an electrolyte, and an electrode assembly, wherein the electrode assembly and the electrolyte are contained in the housing, the electrode assembly comprising a positive electrode sheet, a separator, a negative electrode sheet, and a first type of adhesive tape, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0006] The first type of adhesive tape includes a substrate layer, the substrate layer has a thickness H, which satisfies 8μm≤H≤20μm; the substrate layer has pores that allow metal cations to pass through, and the porosity of the substrate layer is φ, which satisfies 20%≤φ≤60%;

[0007] The positive electrode includes:

[0008] positive electrode current collector;

[0009] a first positive electrode active material layer, disposed on one side of the positive electrode current collector, the first positive electrode active material layer being provided with a first groove, and a portion of the positive electrode current collector being exposed in the first groove;

[0010] a second positive electrode active material layer, disposed on a side of the positive electrode current collector opposite to the first positive electrode active material layer;

[0011] The positive electrode tab is accommodated in the first groove and is electrically connected to the positive electrode current collector;

[0012] The first type of adhesive tape includes a first adhesive tape, which is attached to the first positive electrode active material layer and covers the first groove and the positive electrode tab.

[0013] In the above technical solution, the first type of adhesive tape includes a substrate layer, and the thickness of the substrate layer is H, which satisfies 8μm≤H≤20μm. On the one hand, it can prevent the burrs of the positive electrode tab from easily passing through the first type of adhesive tape and contacting the negative electrode tab; on the other hand, it can make the first type of adhesive tape smaller in the thickness direction of the positive electrode current collector, with smaller impedance and less impact on the discharge capacity of the secondary battery; the substrate layer has pores that allow metal cations to pass through, and the porosity of the substrate layer is φ, which satisfies 20%≤φ≤60%. On the one hand, the metal cations can pass through the first type of adhesive tape, so that the part of the first positive electrode active material layer covered by the first type of adhesive tape can also realize metal cation absorption and release, thereby making the effective area of ​​the first positive electrode active material layer larger and improving the discharge capacity of the secondary battery; on the other hand, it can reduce the possibility of deformation of the first type of adhesive tape during the preparation process of the secondary battery.

[0014] In some embodiments, the porosity of the substrate layer is φ, which satisfies 30%≤φ≤55%.

[0015] In the above technical solution, by ensuring that the porosity φ of the substrate layer satisfies 30%≤φ≤55%, on the one hand, it can make it easier for metal cations to pass through the first type of adhesive paper, accelerate the speed at which metal cations pass through the first type of adhesive paper, and reduce the possibility of metal cation precipitation; on the other hand, it can further reduce the possibility of deformation of the first type of adhesive paper during the preparation process of the secondary battery.

[0016] In some embodiments, the substrate layer is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, or aramid.

[0017] In the above technical solution, the substrate layer is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex or aramid, so that the substrate layer has pores, and the porosity can reach 20% to 60%.

[0018] In some embodiments, the thickness of the substrate layer is H, satisfying 8 μm≤H≤16 μm.

[0019] In the above technical solution, by making the thickness of the substrate layer satisfy 8μm≤H≤16μm, on the one hand, it can further make it difficult for the burrs of the positive electrode tab to pass through the first type of tape and contact the negative electrode plate; on the other hand, the size of the first type of tape in the thickness direction of the positive electrode current collector can be made smaller, which has less impact on the discharge capacity of the secondary battery.

[0020] In some embodiments, the thickness of the substrate layer is H, satisfying 10 μm≤H≤16 μm.

[0021] In the above technical solution, by making the thickness of the substrate layer satisfy 10μm≤H≤16μm, on the one hand, it can further make it difficult for the burrs of the positive electrode tab to pass through the first type of tape and contact the negative electrode plate; on the other hand, the size of the first type of tape in the thickness direction of the positive electrode current collector can be made smaller, which has less impact on the discharge capacity of the secondary battery.

[0022] In some embodiments, the thickness of the substrate layer is H, the porosity of the substrate layer is φ, and 14≤H / φ≤67 is satisfied.

[0023] In the above technical solution, since the value of H / φ in the substrate layer is positively correlated with the impedance of the substrate layer, by making the thickness H of the substrate layer and the porosity φ of the substrate layer satisfy 14≤H / φ≤67, on the one hand, the substrate layer can have a certain impedance, which is convenient for the preparation of the substrate layer; on the other hand, the impedance of the substrate layer can be made smaller, thereby reducing the probability of metal ion precipitation in the secondary battery.

[0024] In some embodiments, the first type of adhesive tape further includes an adhesive layer, which is made of at least one of polyolefin, polyacrylate, polyacrylic acid and derivatives thereof, and is laminated with the base material layer.

[0025] In the above technical solution, by arranging an adhesive layer on the first type of adhesive tape, the adhesive layer and the base material layer are stacked, which can facilitate the attachment of the first type of adhesive tape and make the position of the first type of adhesive tape more stable after attachment; by making the adhesive layer made of at least one of polyolefin, polyacrylate, polyacrylic acid and its derivatives, the adhesive layer can have better viscosity.

[0026] In some embodiments, a second groove is provided at a position of the second positive electrode active material layer corresponding to the first groove, and a portion of the positive electrode current collector is exposed in the second groove;

[0027] The first type of adhesive tape further includes a second adhesive tape, which is attached to the second positive electrode active material layer and covers the second groove.

[0028] In the above technical solution, by attaching the second tape to the second positive electrode active material layer and covering the second groove, it can play an insulating role between the positive electrode plate and the negative electrode plate, reducing the possibility of contact between the positive electrode tab and the negative electrode plate, thereby improving the reliability of the secondary battery; and the part of the second positive electrode active material layer blocked by the second tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0029] In some embodiments, the negative electrode plate comprises:

[0030] negative electrode current collector;

[0031] A first negative electrode active material layer is provided on one side of the negative electrode current collector;

[0032] a second negative electrode active material layer, disposed on a side of the negative electrode current collector opposite to the first negative electrode active material layer;

[0033] The first type of tape includes a third tape, which is attached to the first negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the third tape.

[0034] In the above technical solution, by attaching the third tape to the first negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the third tape, which can play an insulating role between the positive electrode sheet and the negative electrode sheet, and since the projection of the positive electrode tab is covered by the projection of the third tape, the insulation effect of the third tape can be better, reducing the possibility of contact between the positive electrode tab and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the part of the first negative electrode active material layer blocked by the third tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0035] In some embodiments, the first type of tape further includes a fourth tape, which is attached to the second negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the fourth tape.

[0036] In the above technical solution, by attaching the fourth tape to the second negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the fourth tape, which can play an insulating role between the positive electrode sheet and the negative electrode sheet, and since the projection of the positive electrode tab is covered by the projection of the fourth tape, the insulation effect of the fourth tape can be better, reducing the possibility of contact between the positive electrode tab and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the part of the second negative electrode active material layer blocked by the fourth tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0037] In some embodiments, along the length direction of the positive electrode current collector, the width of the third tape is smaller than the width of the first tape, and the width of the fourth tape is smaller than the width of the first tape.

[0038] In the above technical solution, although metal cations can pass through the first type of tape, the speed at which the active material layer blocked by the first type of tape absorbs and releases metal cations will still be affected by the first type of tape. The larger the area of ​​the active material layer blocked by the first type of tape, the slower the speed at which the metal cations are absorbed and released. Therefore, by making the width of the third tape smaller than the width of the first tape and the width of the fourth tape smaller than the width of the first tape along the length direction of the positive electrode current collector, the area of ​​the first positive electrode active material layer and the second positive electrode active material layer blocked by the first type of tape can be larger than the area of ​​the first negative electrode active material layer and the second negative electrode active material layer blocked by the first type of tape, thereby making the speed at which the first positive electrode active material layer and the second positive electrode active material layer absorb and release metal cations smaller than the speed at which the first negative electrode active material layer and the second negative electrode active material layer absorb and release metal cations, thereby reducing the possibility of metal ion precipitation in the secondary battery.

[0039] In some embodiments, the negative electrode plate comprises:

[0040] negative electrode current collector;

[0041] a first negative electrode active material layer disposed on one side of the negative electrode current collector, the first negative electrode active material layer being provided with a third groove, and a portion of the negative electrode current collector being exposed in the third groove;

[0042] a second negative electrode active material layer, disposed on a side of the negative electrode current collector opposite to the first negative electrode active material layer;

[0043] The negative electrode tab is accommodated in the third groove, and the negative electrode tab is connected to the negative electrode current collector;

[0044] The first type of adhesive tape includes a fifth adhesive tape, which is attached to the first negative electrode active material layer and covers the third groove and the negative electrode tab.

[0045] In the above technical solution, the negative electrode tab is placed in the third groove and connected to the negative electrode current collector, so that the external device can be electrically connected to the negative electrode current collector through the negative electrode tab; by attaching the fifth tape to the first negative electrode active material layer and covering the third groove and the negative electrode tab, it can play an insulating role between the positive electrode sheet and the negative electrode sheet, reducing the possibility of contact between the negative electrode current collector, the negative electrode tab and the positive electrode collector; and the part of the first negative electrode active material layer blocked by the fifth tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0046] In some embodiments, a fourth groove is provided at a position of the second negative electrode active material layer corresponding to the third groove, and a portion of the negative electrode current collector is exposed in the fourth groove;

[0047] The first type of adhesive tape includes a sixth adhesive tape, which is attached to the second negative electrode active material layer and covers the fourth groove.

[0048] In the above technical solution, by attaching the sixth tape to the second negative electrode active material layer and covering the fourth groove, it can play an insulating role between the positive electrode plate and the negative electrode plate, reducing the possibility of contact between the negative electrode collector and the positive electrode collector, thereby improving the reliability of the secondary battery; and the part of the second negative electrode active material layer blocked by the sixth tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0049] In some embodiments, the electrode assembly also includes a second type of tape, the base material of the second type of tape is non-porous, and the second type of tape includes a seventh tape and an eighth tape. The seventh tape is attached to the first positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the seventh tape; the eighth tape is attached to the second positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the eighth tape.

[0050] In the above technical solution, by setting the seventh tape and the eighth tape, and making the seventh tape attached to the first positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the seventh tape; the eighth tape is attached to the second positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the eighth tape; it can play an insulating role between the positive electrode sheet and the negative electrode sheet, and because the projection of the negative electrode tab is covered by the projections of the seventh tape and the eighth tape, the insulation effect of the seventh tape and the eighth tape can be better, reducing the possibility of contact between the negative electrode tab and the positive electrode current collector, thereby improving the reliability of the secondary battery; because the third groove for accommodating the negative electrode tab has no active material and cannot receive metal cations, by making the substrate of the second type of tape non-porous, the part of the first positive electrode active material layer blocked by the seventh tape and the part of the second positive electrode active material layer blocked by the eighth tape cannot release metal cations, which can reduce the possibility of metal ion precipitation in the secondary battery.

[0051] In some embodiments, the first type of adhesive tape includes a ninth adhesive tape, which is disposed at the tail end of the positive electrode sheet, with a portion thereof attached to the first positive electrode active material layer and another portion thereof attached to the positive electrode current collector.

[0052] In the above technical solution, by setting the ninth tape at the tail end of the positive electrode sheet, with one part attached to the first positive electrode active material layer and the other part attached to the positive electrode collector, it can play an insulating role between the positive electrode sheet and the negative electrode sheet, reducing the possibility of contact between the positive electrode collector and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the part of the first positive electrode active material layer blocked by the ninth tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0053] In some embodiments, the first type of adhesive tape includes a tenth adhesive tape, which is disposed at the tail end of the positive electrode sheet, with a portion thereof attached to the second positive electrode active material layer and another portion thereof attached to the positive electrode current collector.

[0054] In the above technical solution, by setting the tenth tape at the tail end of the positive electrode sheet, with one part attached to the second positive electrode active material layer and the other part attached to the positive electrode collector, it can play an insulating role between the positive electrode sheet and the negative electrode sheet, reducing the possibility of contact between the positive electrode collector and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the part of the first positive electrode active material layer blocked by the ninth tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0055] 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

[0056] 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.

[0057] FIG1 is a schematic cross-sectional view of an electrode assembly of a secondary battery provided in some embodiments of the present application;

[0058] FIG2 is a schematic diagram of a partially enlarged structure of a portion A of the electrode assembly in FIG1 ;

[0059] FIG3 is a schematic cross-sectional view of a partial structure of a secondary battery provided in some embodiments of the present application;

[0060] FIG4 is a schematic cross-sectional view of the first type of adhesive tape for secondary batteries provided in some embodiments of the present application.

[0061] Icons: 10-electrode assembly; 100-positive electrode sheet; 110-positive electrode current collector; 120-first positive electrode active material layer; 121-first groove; 130-second positive electrode active material layer; 131-second groove; 140-positive electrode tab; 200-separator; 300-negative electrode sheet; 310-negative electrode current collector; 320-first negative electrode active material layer; 321-third groove; 330-second negative electrode active material layer; 331-fourth groove; 400-first type of adhesive tape; 401-base material layer; 402-adhesive layer; 410-first adhesive tape; 420-second adhesive tape; 430-third adhesive tape; 440-fourth adhesive tape; 450-fifth adhesive tape; 460-sixth adhesive tape; 470-ninth adhesive tape; 480-tenth adhesive tape; 510-seventh adhesive tape; 520-eighth adhesive tape.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] In order to improve the discharge capacity of the electrochemical device, the present application provides a secondary battery, including a shell, an electrolyte and an electrode assembly, the electrode assembly and the electrolyte are accommodated in the shell, the electrode assembly includes a positive electrode sheet, a separator, a negative electrode sheet and a first type of adhesive tape, the separator is arranged between the positive electrode sheet and the negative electrode sheet; the first type of adhesive tape includes a substrate layer, the thickness of the substrate layer is H, and satisfies 8μm≤H≤20μm; the substrate layer has pores that allow metal cations to pass through, and the porosity of the substrate layer is φ, and satisfies 20%≤φ≤60%; the positive electrode sheet ... A current collector, a first positive electrode active material layer, a second positive electrode active material layer and a positive electrode tab, the first positive electrode active material layer is arranged on one side of the positive electrode current collector, the first positive electrode active material layer is provided with a first groove, and a portion of the positive electrode current collector is exposed in the first groove; the second positive electrode active material layer is arranged on the side of the positive electrode current collector opposite to the first positive electrode active material layer; the positive electrode tab is accommodated in the first groove, and the positive electrode tab is electrically connected to the positive electrode collector; the first type of adhesive tape includes the first adhesive tape, the first adhesive tape is attached to the first positive electrode active material layer and covers the first groove and the positive electrode tab.

[0069] In a secondary battery of this structure, the first type of tape includes a substrate layer, the thickness of the substrate layer is H, satisfying 8μm≤H≤20μm. On the one hand, it can prevent the burrs of the positive electrode tab from easily passing through the first type of tape and contacting the negative electrode tab; on the other hand, it can make the first type of tape smaller in the thickness direction of the positive electrode current collector, and have less impact on the discharge capacity of the secondary battery; the substrate layer has pores that allow metal cations to pass through, and the porosity of the substrate layer is φ, satisfying 20%≤φ≤60%. On the one hand, it allows metal cations to pass through the first type of tape, so that the part of the first positive electrode active material layer covered by the first type of tape can also realize metal cation absorption and release, thereby making the effective area of ​​the first positive electrode active material layer larger and improving the discharge capacity of the secondary battery; on the other hand, it can reduce the possibility of deformation of the first type of tape during the preparation process of the secondary battery.

[0070] 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.

[0071] 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.

[0072] Referring to Figures 1 to 3, Figure 1 is a schematic cross-sectional structural diagram of an electrode assembly of a secondary battery provided in some embodiments of the present application; Figure 2 is a schematic enlarged structural diagram of a portion A of the electrode assembly in Figure 1; and Figure 3 is a schematic cross-sectional structural diagram of a portion of a secondary battery provided in some embodiments of the present application.

[0073] An embodiment of the present application provides a secondary battery, which includes a shell (not shown in the figure), an electrolyte (not shown in the figure) and an electrode assembly 10. The electrode assembly 10 and the electrolyte are accommodated in the shell. The electrode assembly 10 includes a positive electrode sheet 100, an isolation membrane 200, a negative electrode sheet 300 and a first type of adhesive tape 400. The isolation membrane 200 is arranged between the positive electrode sheet 100 and the negative electrode sheet 300.

[0074] In some embodiments, the positive electrode sheet 100 includes a positive electrode collector 110, a first positive electrode active material layer 120, a second positive electrode active material layer 130 and a positive electrode tab 140. The first positive electrode active material layer 120 is arranged on one side of the positive electrode collector 110, and the first positive electrode active material layer 120 is provided with a first groove 121, and a portion of the positive electrode collector 110 is exposed in the first groove 121; the second positive electrode active material layer 130 is arranged on the side of the positive electrode collector 110 opposite to the first positive electrode active material layer 120; the positive electrode tab 140 is accommodated in the first groove 121, and the positive electrode tab 140 is electrically connected to the positive electrode collector 110.

[0075] Taking a lithium-ion battery as an example, the material of the positive electrode current collector 110 can be aluminum, and the first positive electrode active material layer 120 and the second positive electrode active material layer 130 can be lithium cobalt oxide, lithium iron phosphate, a ternary material, or lithium manganese oxide. The material of the positive electrode tab 140 can be the same as that of the positive electrode current collector 110 to facilitate welding of the positive electrode tab 140 and the positive electrode current collector 110.

[0076] The material of the isolation film may be polypropylene (PP) or polyethylene (PE), etc. The electrolyte may include an organic solvent, an electrolyte lithium salt, etc.

[0077]

[0078] In some embodiments, the first type of adhesive tape 400 includes a first adhesive tape 410, which is attached to the first positive electrode active material layer 120 and covers the first groove 121 and the positive electrode tab 140, and can play an insulating role between the positive electrode plate 100 and the negative electrode plate 300, reducing the possibility of contact between the positive electrode tab 140 and the negative electrode plate 300.

[0079] In some embodiments, the first type of adhesive tape 400 includes a substrate layer 401 , and the thickness of the substrate layer 401 is H, satisfying 8 μm≤H≤20 μm. For example, H can be 8 μm, 14 μm, or 20 μm.

[0080] By ensuring that the thickness H of the substrate layer 401 satisfies 8μm≤H≤20μm, on the one hand, it is possible to prevent the burrs of the positive electrode tab 140 from easily passing through the first type of tape 400 and contacting the negative electrode plate 300; on the other hand, the size of the first type of tape 400 in the thickness direction of the positive electrode current collector 110 can be made smaller, thereby having less impact on the discharge capacity of the secondary battery.

[0081] In some embodiments, the substrate layer 401 has pores that allow metal cations to pass through, and the porosity of the substrate layer 401 is φ, which satisfies 20% ≤ φ ≤ 60%. For example, φ can be 20%, 40%, or 60%. On the one hand, this allows the metal cations to pass through the first-type adhesive tape 400, so that the portion of the first positive active material layer 120 covered by the first-type adhesive tape 400 can also absorb and release the metal cations, thereby increasing the effective area of ​​the first positive active material layer 120 and improving the discharge capacity of the secondary battery. On the other hand, it can reduce the possibility of deformation of the first-type adhesive tape 400 during the secondary battery manufacturing process.

[0082] In some embodiments, the porosity of substrate layer 401 is φ, which satisfies 30% ≤ φ ≤ 55%. For example, φ can be 30%, 37%, or 55%. On the one hand, this allows metal cations to more easily pass through first-type adhesive tape 400, accelerating the rate at which metal cations pass through first-type adhesive tape 400 and reducing the possibility of metal cation precipitation. On the other hand, it further reduces the possibility of deformation of first-type adhesive tape 400 during the preparation of the secondary battery.

[0083] In some embodiments, the substrate layer 401 is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, or aramid, so that the substrate layer 401 has pores, and the porosity can reach 20% to 60%.

[0084] In some embodiments, the substrate layer 401 may be a non-woven fabric, a film, or a composite film made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, or aramid. For example, the substrate layer 401 may be a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, a polypropylene-polyethylene-polypropylene porous composite film, or the like.

[0085] In some embodiments, the thickness of the substrate layer 401 is H, which satisfies 8 μm ≤ H ≤ 16 μm. For example, H can be 8 μm, 12 μm, or 16 μm. On the one hand, this can further prevent burrs on the positive electrode tab 140 from penetrating the first type of adhesive tape 400 and contacting the negative electrode tab 300. On the other hand, it can reduce the size of the first type of adhesive tape 400 in the thickness direction of the positive electrode current collector 110, thereby minimizing the impact on the discharge capacity of the secondary battery.

[0086] In some embodiments, the thickness of the substrate layer 401 is H, which satisfies 10 μm≤H≤16 μm. For example, H can be 10 μm, 13 μm, or 16 μm.

[0087] .

[0088] In some embodiments, the thickness of the substrate layer 401 is H, the porosity of the substrate layer 401 is φ, and 14≤H / φ≤67 is satisfied. For example, H / φ can be 14, 40, or 67.

[0089] Since the value of H / φ in the substrate layer 401 is positively correlated with the impedance of the substrate layer 401, by making the thickness H of the substrate layer 401 and the porosity φ of the substrate layer 401 satisfy 14≤H / φ≤67, on the one hand, the substrate layer 401 can have a certain impedance, which facilitates the preparation of the substrate layer 401; on the other hand, the impedance of the substrate layer 401 can be made smaller, thereby reducing the probability of metal ion precipitation in the secondary battery.

[0090] Refer to FIG4 , which is a schematic cross-sectional view of the first type of adhesive tape for secondary batteries provided in some embodiments of the present application.

[0091] In some embodiments, the first type of adhesive tape 400 further includes an adhesive layer 402 , and the adhesive layer 402 is stacked with the base material layer 401 .

[0092] By providing the adhesive layer 402 on the first type of adhesive tape 400 so that the adhesive layer 402 and the base material layer 401 are stacked, the first type of adhesive tape 400 can be easily attached and the position of the first type of adhesive tape 400 can be more stable after attachment.

[0093] In some embodiments, the adhesive layer 402 is made of at least one of polyolefin, polyacrylate, polyacrylic acid, and derivatives thereof, which can make the adhesive layer 402 have better adhesion.

[0094] Referring to Figures 1 to 3, in some embodiments, a second groove 131 is provided at a position of the second positive electrode active material layer 130 corresponding to the first groove 121, and a portion of the positive electrode current collector 110 is exposed in the second groove 131; the first type of tape 400 also includes a second tape 420, which is attached to the second positive electrode active material layer 130 and covers the second groove 131.

[0095] The second groove 131 is provided at a position of the second positive active material layer 130 corresponding to the first groove 121 , that is, the projections of the first groove 121 and the second groove 131 in the thickness direction of the positive current collector 110 overlap.

[0096] By attaching the second tape 420 to the second positive active material layer 130 and covering the second groove 131, it can provide insulation between the positive electrode sheet 100 and the negative electrode sheet 300, reducing the possibility of contact between the positive electrode current collector 110 and the negative electrode sheet 300, thereby improving the reliability of the secondary battery. In addition, the portion of the second positive active material layer 130 blocked by the second tape 420 can absorb and release metal cations, thereby increasing the discharge capacity of the secondary battery.

[0097] In some embodiments, the negative electrode sheet 300 includes a negative electrode current collector 310, a first negative electrode active material layer 320 and a second negative electrode active material layer 330, wherein the first negative electrode active material layer 320 is arranged on one side of the negative electrode current collector 310; the second negative electrode active material layer 330 is arranged on the side of the negative electrode current collector 310 opposite to the first negative electrode active material layer 320.

[0098] Taking a lithium-ion battery as an example, the material of the negative electrode current collector 310 may be copper, and the first negative electrode active material layer 320 and the second negative electrode active material layer 330 may be carbon materials or silicon materials.

[0099] In some embodiments, the first type of adhesive tape 400 includes a third adhesive tape 430, which is attached to the first negative active material layer 320. Along the thickness direction of the negative current collector 310, the projection of the positive electrode tab 140 is located within the projection of the third adhesive tape 430. This provides insulation between the positive electrode sheet 100 and the negative electrode sheet 300. Furthermore, since the projection of the positive electrode tab 140 is covered by the projection of the third adhesive tape 430, the insulation effect of the third adhesive tape 430 is improved, reducing the possibility of contact between the positive electrode tab 140 and the negative electrode sheet 300, thereby improving the reliability of the secondary battery. Furthermore, the portion of the first negative active material layer 320 shielded by the third adhesive tape 430 can absorb and release metal cations, thereby improving the discharge capacity of the secondary battery.

[0100] Among them, the total thickness of the first adhesive tape 410, the isolation film 200 and the third adhesive tape 430 is the isolation thickness between the positive electrode tab 140 and the negative electrode current collector 310, that is, the burrs on the positive electrode tab 140 can only contact the negative electrode current collector 310 after passing through the first adhesive tape 410, the isolation film 200 and the third adhesive tape 430 in sequence.

[0101] In some embodiments, the first type of tape 400 further includes a fourth tape 440 , which is attached to the second negative active material layer 330 , and along the thickness direction of the negative current collector 310 , the projection of the positive electrode tab 140 is located within the projection of the fourth tape 440 .

[0102] By attaching the fourth tape 440 to the second negative active material layer 330, and along the thickness direction of the negative current collector 310, the projection of the positive electrode tab 140 is located within the projection of the fourth tape 440, which can play an insulating role between the positive electrode sheet 100 and the negative electrode sheet 300, and since the projection of the positive electrode tab 140 is covered by the projection of the fourth tape 440, the insulation effect of the fourth tape 440 can be better, reducing the possibility of contact between the positive electrode tab 140 and the negative electrode sheet 300, thereby improving the reliability of the secondary battery; and the part of the second negative active material layer 330 blocked by the fourth tape 440 can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0103] Among them, the total thickness of the second adhesive tape 420, the isolation film 200 and the fourth adhesive tape 440 is the isolation thickness between the positive electrode collector 110 and the negative electrode collector 310, that is, the burrs on the positive electrode collector 110 can only contact the negative electrode collector 310 after passing through the second adhesive tape 420, the isolation film 200 and the fourth adhesive tape 440 in sequence.

[0104] In some embodiments, along the length direction of the positive electrode current collector 110 , the width of the third tape 430 is smaller than the width of the first tape 410 , and the width of the fourth tape 440 is smaller than the width of the first tape 410 .

[0105] Since the metal cations can pass through the first type of tape 400, the speed of absorbing and releasing the metal cations in the portion of the active material layer blocked by the first type of tape 400 will still be affected by the first type of tape 400. The larger the area of ​​the active material layer blocked by the first type of tape 400, the slower the speed of absorbing and releasing the metal cations. Therefore, by making the width of the third tape 430 smaller than the width of the first tape 410 and the width of the fourth tape 440 smaller than the width of the first tape 410 along the length direction of the positive electrode current collector 110, the first type of tape 400 can be made smaller. The area of ​​the positive electrode active material layer 120 and the second positive electrode active material layer 130 blocked by the first type of adhesive tape 400 is larger than the area of ​​the first negative electrode active material layer 320 and the second negative electrode active material layer 330 blocked by the first type of adhesive tape 400, so that the speed at which the first positive electrode active material layer 120 and the second positive electrode active material layer 130 absorb and release metal cations is lower than the speed at which the first negative electrode active material layer 320 and the second negative electrode active material layer 330 absorb and release metal cations, which can reduce the possibility of metal ion precipitation in the secondary battery.

[0106] In some embodiments, the first negative electrode active material layer 320 is provided with a third groove 321 , and a portion of the negative electrode current collector 310 is exposed in the third groove 321 ; the negative electrode plate 300 further includes a negative electrode tab 340 , which is accommodated in the third groove 321 and connected to the negative electrode current collector 310 .

[0107] By electrically connecting the negative electrode tab 340 to the negative electrode current collector 310 , an external device can be electrically connected to the negative electrode current collector 310 through the negative electrode tab 340 .

[0108] In some embodiments, the first type of adhesive tape 400 includes a fifth adhesive tape 450 . The fifth adhesive tape 450 is attached to the first negative electrode active material layer 320 and covers the third groove 321 and the negative electrode tab 340 .

[0109] By accommodating the negative electrode tab 340 in the third groove 321 and connecting the negative electrode tab 340 to the negative electrode current collector 310, an external device can be electrically connected to the negative electrode current collector 310 through the negative electrode tab 340; by attaching the fifth tape 450 to the first negative electrode active material layer 320 and covering the third groove 321 and the negative electrode tab 340, it can play an insulating role between the positive electrode sheet 100 and the negative electrode sheet 300, reducing the possibility of contact between the negative electrode current collector 310, the negative electrode tab 340 and the positive electrode current collector 110; and the portion of the first negative electrode active material layer 320 blocked by the fifth tape 450 can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0110] In some embodiments, a fourth groove 331 is provided at a position corresponding to the third groove 321 of the second negative electrode active material layer 330 , and a portion of the negative electrode current collector 310 is exposed in the fourth groove 331 ; the first type of tape 400 includes a sixth tape 460 , which is attached to the second negative electrode active material layer 330 and covers the fourth groove 331 .

[0111] The fourth groove 331 is provided at a position of the second negative active material layer 330 corresponding to the third groove 321 , that is, the projections of the third groove 321 and the fourth groove 331 in the thickness direction of the negative current collector 310 overlap.

[0112] By attaching the sixth tape 460 to the second negative electrode active material layer 330 and covering the fourth groove 331, it can play an insulating role between the positive electrode plate 100 and the negative electrode plate 300, reducing the possibility of contact between the negative electrode collector 310 and the positive electrode collector 110, thereby improving the reliability of the secondary battery; and the part of the second negative electrode active material layer 330 blocked by the sixth tape 460 can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0113] In some embodiments, the electrode assembly 10 further includes a second type of adhesive tape, the substrate of which is non-porous. The second type of adhesive tape includes a seventh adhesive tape 510 and an eighth adhesive tape 520. The seventh adhesive tape 510 is attached to the first positive active material layer 120, and along the thickness direction of the positive current collector 110, the projection of the negative electrode tab 340 is located within the projection of the seventh adhesive tape 510. The eighth adhesive tape 520 is attached to the second positive active material layer 130, and along the thickness direction of the positive current collector 110, the projection of the negative electrode tab 340 is located within the projection of the eighth adhesive tape 520. The substrate of the second type of adhesive tape is non-porous, that is, the second type of adhesive tape does not allow metal cations to pass through.

[0114] This provides insulation between the positive electrode sheet 100 and the negative electrode sheet 300. Furthermore, since the projection of the negative electrode tab 340 is covered by the projections of the seventh and eighth adhesive tapes 510 and 520, the third adhesive tape 430 provides a better insulation effect, reducing the possibility of contact between the negative electrode tab 340 and the positive electrode current collector 110, thereby improving the reliability of the secondary battery. Since the third recess 321 for accommodating the negative electrode tab 340 contains no active material and cannot receive metal cations, by ensuring that the substrate of the second type of adhesive tape is free of pores, the portion of the first positive electrode active material layer 120 obscured by the seventh adhesive tape 510 and the portion of the second positive electrode active material layer 130 obscured by the eighth adhesive tape 520 cannot release metal cations, thereby reducing the possibility of metal ion precipitation in the secondary battery.

[0115] Among them, the adhesive tape with a porosity of less than 5% is non-porous adhesive tape.

[0116] Among them, the total thickness of the fifth adhesive tape 450, the isolation film 200 and the seventh adhesive tape 510 is the isolation thickness between the negative electrode tab 340 and the positive electrode current collector 110, that is, the burrs on the negative electrode tab 340 can only contact the positive electrode current collector 110 after passing through the fifth adhesive tape 450, the isolation film 200 and the seventh adhesive tape 510 in sequence.

[0117] Among them, the total thickness of the sixth tape 460, the isolation film 200 and the eighth tape 520 is the isolation thickness between the negative electrode collector 310 and the positive electrode collector 110, that is, the burrs on the negative electrode collector 310 can only contact the positive electrode collector 110 after passing through the sixth tape 460, the isolation film 200 and the eighth tape 520 in sequence.

[0118] In some embodiments, the first type of adhesive tape 400 includes a ninth adhesive tape 470, which is disposed at the rear end of the positive electrode sheet 100, with a portion attached to the first positive electrode active material layer 120 and another portion attached to the positive electrode current collector 110. This can provide insulation between the positive electrode sheet 100 and the negative electrode sheet 300, reducing the likelihood of contact between the positive electrode current collector 110 and the negative electrode sheet 300, thereby improving the reliability of the secondary battery. Furthermore, the portion of the first positive electrode active material layer 120 shielded by the ninth adhesive tape 470 can absorb and release metal cations, thereby improving the discharge capacity of the secondary battery.

[0119] In some embodiments, the first type of adhesive tape 400 includes a tenth adhesive tape 480 , which is disposed at the tail end of the positive electrode sheet 100 , with a portion attached to the second positive active material layer 130 and another portion attached to the positive current collector 110 .

[0120] This can serve as an insulator between the positive electrode sheet 100 and the negative electrode sheet 300, reduce the possibility of contact between the positive electrode collector 110 and the negative electrode sheet 300, and thus improve the reliability of the secondary battery; and the portion of the first positive electrode active material layer 120 blocked by the ninth adhesive tape 470 can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0121] In other embodiments, the third adhesive tape 430 , the fourth adhesive tape 440 , the fifth adhesive tape 450 , and the sixth adhesive tape 460 may also be the second type of adhesive tape, which is not limited here.

[0122] For example, in some embodiments, the first adhesive tape 410 , the second adhesive tape 420 , the third adhesive tape 430 , the fourth adhesive tape 440 , the ninth adhesive tape 470 , and the tenth adhesive tape 480 are first-type adhesive tapes, while the seventh adhesive tape 510 , the eighth adhesive tape 520 , the fifth adhesive tape 450 , and the sixth adhesive tape 460 are second-type adhesive tapes.

[0123] For example, in some embodiments, the first adhesive tape 410, the second adhesive tape 420, the ninth adhesive tape 470, and the tenth adhesive tape 480 are first-type adhesive tapes, while the third adhesive tape 430, the fourth adhesive tape 440, the seventh adhesive tape 510, the eighth adhesive tape 520, the fifth adhesive tape 450, and the sixth adhesive tape 460 are second-type adhesive tapes.

[0124] For example, in some embodiments, the first adhesive tape 410, the second adhesive tape 420, the ninth adhesive tape 470, the tenth adhesive tape 480, the fifth adhesive tape 450, and the sixth adhesive tape 460 are first-type adhesive tapes, while the third adhesive tape 430, the fourth adhesive tape 440, the seventh adhesive tape 510, and the eighth adhesive tape 520 are second-type adhesive tapes.

[0125] For example, in some embodiments, the first adhesive tape 410, the second adhesive tape 420, the third adhesive tape 430, the fourth adhesive tape 440, the ninth adhesive tape 470, and the tenth adhesive tape 480 are first-type adhesive tapes, while the fifth adhesive tape 450, the sixth adhesive tape 460, the seventh adhesive tape 510, and the eighth adhesive tape 520 are second-type adhesive tapes.

[0126] See Table 1, in which φ is the porosity of the substrate layer 401 of the first type of adhesive tape 400. H is the thickness of the substrate layer 401 of the first type of adhesive tape 400, in μm. See Figures 2 and 3. In Figures 2 and 3, the position of the positive electrode tab 140 away from the positive electrode current collector 110 is position 1, and the first adhesive tape 410 is attached to cover the first groove 121 and the positive electrode tab 140; the position where the second groove 131 is located is position 2, and the second adhesive tape 420 is attached to the second positive electrode active material layer 130 and covers the second groove 131; in Figure 2, the position on the first positive electrode active material layer 120 along the thickness direction of the positive electrode current collector 110 corresponding to the negative electrode tab 340 is position 3, and the seventh adhesive tape 510 is attached to the second positive electrode active material layer 130 and covers the second groove 131. Attached to the position of the first positive electrode active material layer 120 corresponding to the negative electrode tab 340; in Figure 2, the position on the second positive electrode active material layer 130 along the thickness direction of the positive electrode current collector 110 corresponding to the negative electrode tab 340 is position 4, and the eighth adhesive tape 520 is attached to the position of the second positive electrode active material layer 130 corresponding to the negative electrode tab 340; the tail of the second positive electrode active material layer 130 is position 5, and part of the tenth adhesive tape 480 is attached to the tail of the second positive electrode active material layer 130, and the other part is attached to the positive electrode current collector 1 10; the tail of the first positive electrode active material layer 120 is position 6, part of the ninth adhesive tape 470 is attached to the tail of the first positive electrode active material layer 120, and the other part is attached to the positive electrode current collector 110; the position corresponding to the positive electrode tab 140 along the thickness direction of the negative electrode current collector 310 on the first negative electrode active material layer 320 in Figure 2 is position 7, and the third adhesive tape 430 is attached to the position of the first negative electrode active material layer 320 corresponding to the positive electrode tab 140; the second negative electrode active material layer 330 along the thickness direction of the negative electrode current collector in Figure 2 The position corresponding to the positive electrode tab 140 in the thickness direction of 310 is position 8, and the fourth adhesive tape 440 is attached to the position of the second negative electrode active material layer 330 corresponding to the positive electrode tab 140; the position of the negative electrode tab 340 away from the negative electrode current collector 310 in Figures 2 and 3 is position 9, and the fifth adhesive tape 450 is attached to cover the third groove 321 and the negative electrode tab 340; the position where the fourth groove 331 is located is position 10, and the sixth adhesive tape 460 is attached to the second negative electrode active material layer 330 and covers the fourth groove 331. H1 is the sum of the thickness of the two layers of the first type of adhesive tape and the thickness of the separator (i.e., the thickness of the separator between the tab and the current collector or between the positive electrode current collector and the negative electrode current collector), in μm. Q is the discharge capacity of the secondary battery, in mAh. The thickness of the separator 200 is 8 μm.

[0127] The examples and comparative examples were prepared according to the parameters in Table 1, as follows:

[0128] The preparation method of the secondary battery is as follows:

[0129] (1) Preparation of the first type of adhesive tape: A water-based polyacrylate is used as an adhesive using a micro-gravure plate and coated on one side of the polypropylene substrate layer. A release agent is coated on the other side of the substrate layer. After winding, the adhesive tape is divided into strips to prepare a roll of adhesive tape.

[0130] (2) Preparation of negative electrode sheet: 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 added 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 coated on the negative electrode current collector. After drying at 80°C, cold pressing, and slitting, the negative electrode sheet is obtained.

[0131] Table 1 Preparation parameters and performance test of secondary batteries

[0132] (3) Preparation of isolation membrane: The substrate of the isolation membrane is 8 μm thick polyethylene (PE). A 2 μm alumina ceramic layer is coated on each of the two opposite surfaces of the substrate. Finally, 2.5 mg / cm2 of the binder polyvinylidene fluoride (PVDF) is coated on each side of the ceramic layer and dried.

[0133] (4) 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.

[0134] (5) Preparation of negative 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 base coating sheet 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.

[0135] (6) Preparation of electrochemical device: 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 provide isolation, 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.

[0136] The porosity test method of the first type of adhesive tape is:

[0137] (1) The first type of adhesive tape was removed from the electrode, and the first type of adhesive tape was soaked in toluene solvent at 45°C for 10 hours, and the soaking was repeated twice to obtain a substrate layer sample of the first type of adhesive tape.

[0138] (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, s is the area of ​​the substrate layer sample, h is the thickness of the substrate layer sample, and ρ is the true density of the substrate layer material.

[0139] True density test method for substrate layer material:

[0140] (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.

[0141] (2) Using an electronic balance to measure the weight of the substrate layer sample is M, and the true density ρ = M / V.

[0142] The method for testing the thickness of the first type of adhesive tape is:

[0143] (1) The first type of adhesive tape was removed from the electrode, and the first type of adhesive tape was soaked in toluene solvent at 45°C for 10 hours, and the soaking was repeated twice to obtain a substrate layer sample of the first type of adhesive tape.

[0144] (2) Randomly measure the thickness of the substrate layer sample at 6 locations, calculate the average value, and obtain the thickness of the first type of adhesive tape.

[0145] The method for testing the discharge capacity of secondary batteries is:

[0146] (1) Place the secondary battery in an environment at 25°C.

[0147] (2) Charge the secondary battery to the battery's charge cut-off voltage (e.g., 4.5V) at a constant current of 0.2C and charge the secondary battery to 0.02C at a constant voltage.

[0148] (3) Let the secondary battery stand for 10 minutes.

[0149] (4) Discharge the secondary battery at a constant current of 0.1C to the battery's discharge cut-off voltage (e.g., 3.0V), and extract the discharge capacity of the secondary battery.

[0150] The short circuit test method for secondary batteries is:

[0151] The resistance between the positive electrode tab 140 and the negative electrode tab 340 of the electrode assembly 10 is tested by a high voltage test (Hi-pot test). If the resistance between the positive electrode tab 140 and the negative electrode tab 340 is less than 20MΩ, it is determined that the electrode assembly 10 is short-circuited; otherwise, the electrode assembly 10 is not short-circuited.

[0152] According to Table 1, the following conclusions can be drawn:

[0153] (1) Referring to Comparative Examples 1 to 3 and Examples 1, 9 to 14, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 3, 4, 9, and 10. When the thickness of the first type of adhesive tape is 8 μm, by making the porosity of the first type of adhesive tape 20% to 60%, the capacity of the secondary battery can be increased and the discharge capacity of the secondary battery can be improved.

[0154] (2) Referring to Examples 1 to 14, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 3, 4, 9, and 10. The porosity of the first type of adhesive tape is 20% to 60%, the thickness of the first type of adhesive tape is 8μm to 20μm, and H / φ is 14 to 67. The capacity of the secondary battery is large and the discharge capacity of the secondary battery is high.

[0155] (3) Referring to Comparative Examples 1 to 4, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 3, 4, 9, and 10. When the porosity of the first type of adhesive tape is 20%, if the thickness of the first type of adhesive tape is too small, for example, the thickness of the first type of adhesive tape in Comparative Example 4 is 6 μm (less than 8 μm), although the capacity of the secondary battery is relatively high, the first type of adhesive tape cannot achieve a good insulation effect, and a short circuit problem will occur.

[0156] (4) Referring to Comparative Example 5 and Examples 2, 4, and 8, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 3, 4, 9, and 10. When the thickness of the first type of adhesive tape is 10 μm, if the porosity of the first type of adhesive tape is too large, for example, the porosity of the first type of adhesive tape in Comparative Example 5 is 65% (greater than 60%), although the capacity of the secondary battery is large, the first type of adhesive tape is deformed during stretching and cutting, resulting in a change in the actual thickness of the first type of adhesive tape.

[0157] (5) Referring to Comparative Example 6 and Examples 7 and 14, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 3, 4, 9, and 10. When the porosity of the first type of adhesive tape is 55%, if the thickness of the first type of adhesive tape is too large, for example, the thickness of the first type of adhesive tape in Comparative Example 6 is 25 μm (greater than 20 μm), the impedance of the first type of adhesive tape is too large, resulting in a smaller discharge capacity of the secondary battery, affecting the energy density of the secondary battery, and the secondary battery is at risk of metal ion precipitation.

[0158] (6) Referring to Examples 15 to 18, the first type of adhesive tape is set at positions 1, 2, 5, and 6, or the first type of adhesive tape is set at positions 1, 2, 5, 6, 9, and 10, or the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, or the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, 6, 9, and 10, and the porosity of the first type of adhesive tape is 20% to 60%, the thickness of the first type of adhesive tape is 8μm to 20μm, the discharge capacity of the secondary battery is large, and the energy density of the secondary battery is high.

[0159] (7) Referring to Comparative Example 7 and Example 16, the first type of adhesive tape was set at positions 1, 2, 5, 6, 9, and 10, and the second type of adhesive tape was set at positions 7 and 8 in Comparative Example 7. Although the capacity of the secondary battery increased, the CB value (Ce11Balance, the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area) at positions 7 and 8 was insufficient, and there was a problem of metal ion precipitation.

[0160] (8) Referring to Comparative Example 8 and Example 18, the first type of adhesive tape is set at positions 1, 2, 7, 8, 9, and 10, while the second type of adhesive tape is set at positions 5 and 6 in Comparative Example 8, and the first type of adhesive tape is set at positions 5 and 6 in Example 18. The discharge capacity of the secondary battery is significantly larger, and the energy density of the secondary battery is higher.

[0161] (9) Referring to Comparative Example 9 and Example 17, the first type of adhesive tape is set at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is set at positions 9 and 10. In Example 17, the second type of adhesive tape is set at positions 3 and 4, and in Comparative Example 9, the first type of adhesive tape is set at positions 3 and 4. This will result in insufficient CB values ​​at positions 3 and 4, and the problem of metal ion precipitation.

[0162] An embodiment of the present application provides an electrical device, comprising a secondary battery according to any of the above solutions, wherein the secondary battery is used to provide electrical energy to the electrical device.

[0163] The electric device may be any of the aforementioned devices or systems using secondary batteries.

[0164] 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.

[0165] 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 comprising a housing, an electrolyte, and an electrode assembly, wherein the electrode assembly and the electrolyte are housed in the housing, wherein: The electrode assembly includes a positive electrode sheet, a separator, a negative electrode sheet, and a first type of adhesive tape, wherein the separator is provided between the positive electrode sheet and the negative electrode sheet; The first type of adhesive tape includes a substrate layer, the thickness of the substrate layer is H, and satisfies 8μm≤H≤20μm; The substrate layer has pores that allow metal cations to pass through, and the porosity of the substrate layer is φ, which satisfies 20%≤φ≤60%; The positive electrode plate comprises: positive electrode current collector; a first positive electrode active material layer, disposed on one side of the positive electrode current collector, wherein the first positive electrode active material layer is provided with a first groove, and a portion of the positive electrode current collector is exposed in the first groove; a second positive electrode active material layer, disposed on a side of the positive electrode current collector opposite to the first positive electrode active material layer; a positive electrode tab, accommodated in the first groove, the positive electrode tab being electrically connected to the positive electrode current collector; The first type of adhesive tape includes a first adhesive tape, which is attached to the first positive electrode active material layer and covers the first groove and the positive electrode tab.

2. The secondary battery according to claim 1, wherein The porosity of the substrate layer is φ, which satisfies 30%≤φ≤55%.

3. The secondary battery according to claim 1, wherein The substrate layer is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex or aramid.

4. The secondary battery according to claim 1, wherein The thickness of the substrate layer is H, which satisfies 8 μm≤H≤16 μm.

5. The secondary battery according to claim 1, wherein The thickness of the substrate layer is H, which satisfies 10 μm≤H≤16 μm.

6. The secondary battery according to claim 1, wherein The thickness of the substrate layer is H, and the porosity of the substrate layer is φ, which satisfies 14≤H / φ≤67.

7. The secondary battery according to claim 1, wherein The first type of adhesive tape further includes an adhesive layer, which is made of at least one of polyolefin, polyacrylate, polyacrylic acid and derivatives thereof, and is laminated with the base material layer.

8. The secondary battery according to claim 1, wherein A second groove is provided at a position of the second positive electrode active material layer corresponding to the first groove, and a portion of the positive electrode current collector is exposed in the second groove; The first type of adhesive tape further includes a second adhesive tape, and the second adhesive tape is attached to the second positive electrode active material layer and covers the second groove.

9. The secondary battery according to claim 1, wherein The negative electrode plate comprises: negative electrode current collector; a first negative electrode active material layer, disposed on one side of the negative electrode current collector; a second negative electrode active material layer, disposed on a side of the negative electrode current collector opposite to the first negative electrode active material layer; The first type of tape includes a third tape, which is attached to the first negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the third tape.

10. The secondary battery according to claim 9, wherein The first type of tape also includes a fourth tape, which is attached to the second negative electrode active material layer, and along the thickness direction of the negative electrode current collector, the projection of the positive electrode tab is located within the projection of the fourth tape.

11. The secondary battery according to claim 10, wherein: Along the length direction of the positive electrode current collector, the width of the third tape is smaller than that of the first tape, and the width of the fourth tape is smaller than that of the first tape.

12. The secondary battery according to claim 1, wherein The negative electrode plate comprises: negative electrode current collector; a first negative electrode active material layer disposed on one side of the negative electrode current collector, wherein the first negative electrode active material layer is provided with a third groove, and a portion of the negative electrode current collector is exposed in the third groove; a second negative electrode active material layer, disposed on a side of the negative electrode current collector opposite to the first negative electrode active material layer; a negative electrode tab, accommodated in the third groove, wherein the negative electrode tab is connected to the negative electrode current collector; The first type of adhesive tape includes a fifth adhesive tape, which is attached to the first negative electrode active material layer and covers the third groove and the negative electrode tab.

13. The secondary battery according to claim 12, characterized in that A fourth groove is provided at a position of the second negative electrode active material layer corresponding to the third groove, and a portion of the negative electrode current collector is exposed in the fourth groove; The first type of adhesive tape includes a sixth adhesive tape, and the sixth adhesive tape is attached to the second negative electrode active material layer and covers the fourth groove.

14. The secondary battery according to claim 1 or 12, characterized in that: The electrode assembly also includes a second type of tape, the base material of the second type of tape has no pores, and the second type of tape includes a seventh tape and an eighth tape. The seventh tape is attached to the first positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the seventh tape; the eighth tape is attached to the second positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the projection of the negative electrode tab is located within the projection of the eighth tape.

15. The secondary battery according to claim 1, wherein The first type of adhesive tape includes a ninth adhesive tape, which is arranged at the tail end of the positive electrode plate, with a portion thereof attached to the first positive electrode active material layer and another portion thereof attached to the positive electrode current collector.

16. The secondary battery according to claim 15, characterized in that The first type of adhesive tape includes a tenth adhesive tape, which is arranged at the tail end of the positive electrode plate, with a portion thereof attached to the second positive electrode active material layer and another portion thereof attached to the positive electrode current collector.

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

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