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-references to related applications

[0001] This application claims priority to Chinese patent application CN202410383505.4, entitled "Secondary Battery and Electrical Equipment", filed on March 31, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and more specifically, to a secondary battery and an electrical device. Background Technology

[0003] With the rapid development of electronic information technology, various electronic devices are also moving towards intelligence and multifunctionality, placing increasingly higher demands on battery discharge capacity. Therefore, improving battery discharge capacity has become a pressing issue in the battery industry. Summary of the Invention

[0004] This application provides a secondary battery and electrical device that can improve the discharge capacity of an electrochemical device.

[0005] In a first aspect, this application provides a secondary battery, including a casing, an electrolyte and an electrode assembly, wherein the electrode assembly and the electrolyte are housed in the casing, and the electrode assembly includes a positive electrode, a separator, a negative electrode and a first type of adhesive paper, wherein the separator is disposed between the positive electrode and the negative electrode.

[0006] The first type of adhesive paper includes a substrate layer with a thickness of H, satisfying 8μm≤H≤20μm; 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%;

[0007] Positive electrode plates include:

[0008] Positive current collector;

[0009] A first positive electrode active material layer is disposed on one side of the positive electrode current collector. The first positive electrode active material layer is provided with a first groove, and a part of the positive electrode current collector is exposed in the first groove.

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

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

[0012] The first type of adhesive tape includes a first adhesive tape, which is attached to a 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 paper includes a substrate layer with a thickness of H, satisfying 8μm≤H≤20μm. On the one hand, this makes it difficult for burrs on the positive electrode tab to penetrate the first type of adhesive paper and contact the negative electrode sheet; on the other hand, it makes the first type of adhesive paper smaller in the thickness direction of the positive electrode current collector, resulting in lower 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, satisfying 20%≤φ≤60%. On the one hand, this allows metal cations to pass through the first type of adhesive paper, so that the portion of the first positive electrode active material layer covered by the first type of adhesive paper can also achieve 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 reduces the possibility of deformation of the first type of adhesive paper during the preparation of the secondary battery.

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

[0015] In the above technical solution, by ensuring that the porosity φ of the substrate layer meets the requirement of 30%≤φ≤55%, on the one hand, it makes it easier for metal cations to pass through the first type of adhesive paper, accelerates the speed at which metal cations pass through the first type of adhesive paper, and reduces 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 of secondary batteries.

[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, which satisfies 8μm≤H≤16μm.

[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 the burrs of the positive electrode tab less likely to penetrate the first type of adhesive paper and come into contact with the negative electrode sheet; on the other hand, it can make the size of the first type of adhesive paper smaller in the thickness direction of the positive electrode current collector, and have less impact on the discharge capacity of the secondary battery.

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

[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 the burrs of the positive electrode tab less likely to penetrate the first type of adhesive paper and come into contact with the negative electrode sheet; on the other hand, it can make the size of the first type of adhesive paper smaller in the thickness direction of the positive electrode current collector, and have less impact on the discharge capacity of the secondary battery.

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

[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 made of at least one of polyolefin, polyacrylate, polyacrylic acid and its derivatives, and the adhesive layer is stacked with the substrate layer.

[0025] In the above technical solution, by providing an adhesive layer in the first type of adhesive paper, the adhesive layer and the substrate layer are stacked, which facilitates the application of the first type of adhesive paper and makes the first type of adhesive paper more stable after application; by making the adhesive layer made of at least one of polyolefin, polyacrylate, polyacrylic acid and its derivatives, the adhesiveness of the adhesive layer is better.

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

[0027] The first type of adhesive tape also 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 adhesive 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, reduce the possibility of contact between the positive electrode tab and the negative electrode plate, and thus improve the reliability of the secondary battery; and the part of the second positive electrode active material layer covered by the second adhesive tape can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0029] In some embodiments, the negative electrode sheet includes:

[0030] Negative electrode current collector;

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

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

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

[0034] In the above technical solution, by attaching the third adhesive tape to the first negative electrode active material layer, and with the projection of the positive electrode tab located within the projection of the third adhesive tape along the thickness direction of the negative electrode current collector, it can provide insulation between the positive electrode sheet and the negative electrode sheet. Furthermore, since the projection of the positive electrode tab is covered by the projection of the third adhesive tape, the insulation effect of the third adhesive tape is better, reducing the possibility of contact between the positive electrode tab and the negative electrode sheet, thereby improving the reliability of the secondary battery. In addition, the portion of the first negative electrode active material layer covered by the third adhesive 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 adhesive tape further includes a fourth adhesive tape, which is attached to the second negative electrode active material layer, and the projection of the positive electrode tab is located within the projection of the fourth adhesive tape along the thickness direction of the negative electrode current collector.

[0036] In the above technical solution, by attaching the fourth adhesive tape to the second negative electrode active material layer, and with the projection of the positive electrode tab located within the projection of the fourth adhesive tape along the thickness direction of the negative electrode current collector, it can provide insulation between the positive and negative electrode sheets. Furthermore, since the projection of the positive electrode tab is covered by the projection of the fourth adhesive tape, the insulation effect of the fourth adhesive tape is improved, reducing the possibility of contact between the positive electrode tab and the negative electrode sheet, thereby improving the reliability of the secondary battery. In addition, the portion of the second negative electrode active material layer covered by the fourth adhesive 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 current collector, the width of the third adhesive tape is smaller than the width of the first adhesive tape, and the width of the fourth adhesive tape is smaller than the width of the first adhesive tape.

[0038] In the above technical solution, although metal cations can pass through the first type of adhesive paper, the absorption and release rate of metal cations in the active material layer blocked by the first type of adhesive paper is still affected by the first type of adhesive paper. The larger the area of ​​the active material layer blocked by the first type of adhesive paper, the slower the absorption and release rate of metal cations. Therefore, by making the width of the third adhesive paper smaller than the width of the first adhesive paper and the width of the fourth adhesive paper smaller than the width of the first adhesive paper 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 adhesive paper is 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 adhesive paper. This makes the absorption and release rate of metal cations in the first positive electrode active material layer and the second positive electrode active material layer smaller than the absorption and release rate of metal cations in the first negative electrode active material layer and the second negative electrode active material layer, thereby reducing the possibility of metal ion deposition in the secondary battery.

[0039] In some embodiments, the negative electrode sheet includes:

[0040] Negative electrode current collector;

[0041] The first negative electrode active material layer is disposed on one side of the negative electrode current collector. The first negative electrode active material layer is provided with a third groove, and a part of the negative electrode current collector is exposed in the third groove.

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

[0043] The negative electrode tab is housed in the third groove and is connected to the negative 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, by placing the negative electrode tab in the third groove and connecting the negative electrode tab to the negative electrode current collector, an external device can be electrically connected to the negative electrode current collector through the negative electrode tab; by attaching the fifth adhesive 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 plate and the negative electrode plate, reducing the possibility of contact between the negative electrode current collector, the negative electrode tab and the positive electrode current collector; and the part of the first negative electrode active material layer covered by the fifth adhesive 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 the position corresponding to the third groove of the second negative electrode active material layer, 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 adhesive paper to the second negative electrode active material layer and covering the fourth groove, it can play an insulating role between the positive electrode and the negative electrode, reduce the possibility of contact between the negative electrode current collector and the positive electrode current collector, and thus improve the reliability of the secondary battery; and the part of the second negative electrode active material layer covered by the sixth adhesive paper can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

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

[0050] In the above technical solution, by setting a seventh adhesive sheet and an eighth adhesive sheet, with the seventh adhesive sheet attached to the first positive electrode active material layer and the projection of the negative electrode tab located within the projection of the seventh adhesive sheet along the thickness direction of the positive electrode current collector; and the eighth adhesive sheet attached to the second positive electrode active material layer and the projection of the negative electrode tab located within the projection of the eighth adhesive sheet along the thickness direction of the positive electrode current collector, the insulation between the positive and negative electrode sheets can be achieved. Furthermore, since the projection of the negative electrode tab is covered by the projections of the seventh and eighth adhesive sheets, the insulation effect of the seventh and eighth adhesive sheets is improved, reducing the possibility of contact between the negative electrode tab and the positive electrode current collector, thereby improving the reliability of the secondary battery. Since the third groove used to accommodate the negative electrode tab has no active material and cannot receive metal cations, by making the substrate of the second type of adhesive sheet non-porous, the portion of the first positive electrode active material layer blocked by the seventh adhesive sheet and the portion of the second positive electrode active material layer blocked by the eighth adhesive sheet cannot release metal cations, thus reducing the possibility of metal ion deposition 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 attached to the first positive electrode active material layer and another portion attached to the positive electrode current collector.

[0052] In the above technical solution, by placing the ninth adhesive paper at the tail end of the positive electrode sheet, with a portion attached to the first positive electrode active material layer and another portion attached to the positive electrode current collector, it can serve as an insulator between the positive and negative electrode sheets, reducing the possibility of contact between the positive electrode current collector and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the portion of the first positive electrode active material layer covered by the ninth adhesive paper can absorb and release metal cations, thereby improving 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 attached to the second positive electrode active material layer and another portion attached to the positive electrode current collector.

[0054] In the above technical solution, by placing the tenth adhesive tape at the tail end of the positive electrode sheet, with a portion attached to the second positive electrode active material layer and another portion attached to the positive electrode current collector, it can serve as an insulator between the positive and negative electrode sheets, reducing the possibility of contact between the positive electrode current collector and the negative electrode sheet, thereby improving the reliability of the secondary battery; and the portion of the first positive electrode active material layer covered by the ninth adhesive tape can absorb and release metal cations, thereby improving the discharge capacity of the secondary battery.

[0055] Secondly, this application provides an electrical device including a secondary battery as described above, the secondary battery being used to provide electrical energy. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings.

[0057] Figure 1 is a cross-sectional view of the electrode assembly of a secondary battery provided in some embodiments of this application;

[0058] Figure 2 is a partially enlarged structural diagram of point A in the electrode assembly in Figure 1;

[0059] Figure 3 is a cross-sectional schematic diagram of a partial structure of a secondary battery provided in some embodiments of this application;

[0060] Figure 4 is a cross-sectional view of the first type of adhesive tape for secondary batteries provided in some embodiments of this application.

[0061] Icons: 10-Electrode assembly; 100-Positive electrode sheet; 110-Positive current collector; 120-First positive active material layer; 121-First groove; 130-Second positive active material layer; 131-Second groove; 140-Positive electrode tab; 200-Separating membrane; 300-Negative electrode sheet; 310-Negative current collector; 320-First negative active material layer; 321-Third groove; 330-Second negative active material layer; 331-Fourth groove; 400-First type of adhesive tape; 401-Substrate 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. Specific embodiments.

[0062] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application 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 meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having" and any variations thereof in the specification, claims and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0064] The terms "first," "second," etc., in the specification, claims, or the accompanying drawings of this application are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0065] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0066] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0067] With the development of the new energy industry, batteries are gradually moving towards higher discharge capacity. In the electrode assembly of a secondary battery, to install the tabs, a portion of the active material layer needs to be removed from the electrode to expose the current collector, forming a groove. This exposes the current collector portion of the electrode, allowing the tab housed in the groove to make electrical connection with the current collector. Furthermore, to reduce the possibility of short circuits between the positive and negative electrodes, adhesive tape is applied to the active material layer to cover the tabs and grooves. The portion of the active material layer covered by the adhesive tape cannot absorb and release metal ions, reducing the discharge capacity of the secondary battery.

[0068] To improve the discharge capacity of an electrochemical device, this application provides a secondary battery, including a casing, an electrolyte, and an electrode assembly. The electrode assembly and electrolyte are housed in the casing. The electrode assembly includes a positive electrode, a separator, a negative electrode, and a first type of adhesive paper. The separator is disposed between the positive and negative electrode. The first type of adhesive paper includes a substrate layer with a thickness H, satisfying 8μm≤H≤20μm. 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%. The positive electrode includes a positive electrode... The device comprises 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 disposed on one side of the positive electrode current collector and has a first groove, through which a portion of the positive electrode current collector is exposed. The second positive electrode active material layer is disposed on the side opposite to the first positive electrode active material layer. The positive electrode tab is housed in the first groove and is electrically connected to the positive electrode current collector. A first type of adhesive tape includes a first adhesive tape that is attached to the first positive electrode active material layer and covers the first groove and the positive electrode tab.

[0069] In this type of secondary battery, the first type of adhesive paper includes a substrate layer with a thickness of H, satisfying 8μm≤H≤20μm. On the one hand, this prevents burrs on the positive electrode tab from easily penetrating the first type of adhesive paper and contacting the negative electrode sheet. On the other hand, it allows the first type of adhesive paper to have a smaller dimension in the thickness direction of the positive electrode current collector, thus having a smaller 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, this allows metal cations to pass through the first type of adhesive paper, so that the portion of the first positive electrode active material layer covered by the first type of adhesive paper can also achieve the absorption and release of metal cations, thereby increasing the effective area of ​​the first positive electrode active material layer and improving the discharge capacity of the secondary battery. On the other hand, it reduces the possibility of deformation of the first type of adhesive paper during the preparation of the secondary battery.

[0070] The secondary battery in this application embodiment can be a lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., and this application embodiment is not limited to this. The secondary battery can be cylindrical, flat, cuboid, or other shapes, etc., and this application embodiment is not limited to this either.

[0071] This application provides an electrical device that uses a secondary battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0072] Referring to Figures 1 to 3, Figure 1 is a cross-sectional view of the electrode assembly of a secondary battery provided in some embodiments of this application; Figure 2 is a partially enlarged view of the electrode assembly at point A in Figure 1; and Figure 3 is a cross-sectional view of a portion of the structure of a secondary battery provided in some embodiments of this application.

[0073] This application provides a secondary battery, which includes a casing (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 housed in the casing. The electrode assembly 10 includes a positive electrode 100, a separator 200, a negative electrode 300, and a first type of adhesive paper 400. The separator 200 is disposed between the positive electrode 100 and the negative electrode 300.

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

[0075] Taking a lithium-ion battery as an example, the positive electrode current collector 110 can be made of 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, ternary materials, or lithium manganese oxide, etc. The material of the positive electrode tab 140 can be the same as that of the positive electrode current collector 110, which facilitates the welding of the positive electrode tab 140 to the positive electrode current collector 110.

[0076] The separator can be made of polypropylene (PP) or polyethylene (PE), etc. The electrolyte can include organic solvents, lithium salts, 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. It can serve as an insulation between the positive electrode plate 100 and the negative electrode plate 300, reducing the possibility of the positive electrode tab 140 coming into contact with the negative electrode plate 300.

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

[0080] By ensuring that the thickness H of the substrate layer 401 satisfies 8μm≤H≤20μm, on the one hand, the burrs of the positive electrode tab 140 are less likely to penetrate the first type of adhesive paper 400 and come into contact with the negative electrode sheet 300; on the other hand, the size of the first type of adhesive paper 400 in the thickness direction of the positive electrode current collector 110 is smaller, thus 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 φ of the substrate layer 401 satisfies 20% ≤ φ ≤ 60%, for example, φ can be 20%, 40%, or 60%, etc. On the one hand, this allows metal cations to pass through the first type of adhesive paper 400, thereby enabling the portion of the first positive electrode active material layer 120 covered by the first type of adhesive paper 400 to also absorb and release metal cations, thus making the effective area of ​​the first positive electrode active material layer 120 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 paper 400 during the preparation of the secondary battery.

[0082] In some embodiments, the porosity φ of the substrate layer 401 satisfies 30% ≤ φ ≤ 55%, for example, φ can be 30%, 37%, or 55%. On the one hand, this allows metal cations to pass through the first type of adhesive paper 400 more easily, accelerating the passage of metal cations through the first type of adhesive paper 400 and reducing 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 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, such 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 nonwoven fabric, membrane, or composite membrane 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 membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, a polypropylene-polyethylene-polypropylene porous composite membrane, etc.

[0085] In some embodiments, the thickness of the substrate layer 401 is H, satisfying 8μm≤H≤16μm, for example, H can be 8μm, 12μm, or 16μm. On the one hand, this further makes it less likely for the burrs of the positive electrode tab 140 to penetrate the first type of adhesive paper 400 and come into contact with the negative electrode sheet 300; on the other hand, it makes the size of the first type of adhesive paper 400 smaller in the thickness direction of the positive electrode current collector 110, thus having a smaller impact on the discharge capacity of the secondary battery.

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

[0087] .

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

[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] Referring to Figure 4, Figure 4 is a cross-sectional view of the first type of adhesive tape for secondary batteries provided in some embodiments of this application.

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

[0092] By providing an adhesive layer 402 on the first type of adhesive tape 400, and stacking the adhesive layer 402 with the substrate layer 401, it is easier to attach the first type of adhesive tape 400, making the first type of adhesive tape 400 more stable after attachment.

[0093] In some embodiments, the adhesive layer 402 is made of at least one of polyolefin, polyacrylate, polyacrylic acid and its derivatives, which enables the adhesive layer 402 to have good adhesion.

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

[0095] The second positive electrode active material layer 130 is provided with a second groove 131 at the position 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 electrode current collector 110 overlap.

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

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

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

[0099] In some embodiments, the first type of adhesive tape 400 includes a third adhesive tape 430, which is attached to the first negative electrode active material layer 320. Along the thickness direction of the negative electrode current collector 310, the projection of the positive electrode tab 140 lies within the projection of the third adhesive tape 430. This provides insulation between the positive electrode sheet 100 and the negative electrode sheet 300. 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 electrode active material layer 320 blocked by the third adhesive tape 430 can absorb and release metal cations, increasing the discharge capacity of the secondary battery.

[0100] The total thickness of the first adhesive tape 410, the separator 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 separator 200, and the third adhesive tape 430 in sequence.

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

[0102] By attaching the fourth adhesive tape 440 to the second negative electrode active material layer 330, and with the projection of the positive electrode tab 140 located within the projection of the fourth adhesive tape 440 along the thickness direction of the negative electrode current collector 310, it can provide insulation between the positive electrode plate 100 and the negative electrode plate 300. Furthermore, since the projection of the positive electrode tab 140 is covered by the projection of the fourth adhesive tape 440, the insulation effect of the fourth adhesive tape 440 is improved, reducing the possibility of contact between the positive electrode tab 140 and the negative electrode plate 300, thereby improving the reliability of the secondary battery. In addition, the portion of the second negative electrode active material layer 330 that is blocked by the fourth adhesive tape 440 can absorb and release metal cations, which can improve the discharge capacity of the secondary battery.

[0103] The total thickness of the second adhesive tape 420, the separator 200, and the fourth adhesive tape 440 is the isolation thickness between the positive current collector 110 and the negative current collector 310. That is, the burrs on the positive current collector 110 can only contact the negative current collector 310 after passing through the second adhesive tape 420, the separator 200, and the fourth adhesive tape 440 in sequence.

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

[0105] Although metal cations can pass through the first type of adhesive tape 400, the absorption and release rate of metal cations in the active material layer partially blocked by the first type of adhesive tape 400 is still affected by the first type of adhesive tape 400. The larger the area of ​​the active material layer blocked by the first type of adhesive tape 400, the slower the absorption and release rate of metal cations. Therefore, by making the width of the third adhesive tape 430 smaller than the width of the first adhesive tape 410 and the width of the fourth adhesive tape 440 smaller than the width of the first adhesive tape 410 along the length direction of the positive electrode current collector 110, the first... The area of ​​the positive electrode active material layer 120 and the second positive electrode active material layer 130 that is covered by the first type of adhesive paper 400 is greater than the area of ​​the first negative electrode active material layer 320 and the second negative electrode active material layer 330 that is covered by the first type of adhesive paper 400. As a result, the rate 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 less than the rate 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 sheet 300 also 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 via the negative electrode tab 340.

[0108] In some embodiments, the first type of adhesive tape 400 includes a fifth adhesive tape 450, which 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 housing 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 adhesive tape 450 to the first negative electrode active material layer 320 and covering the third groove 321 and the negative electrode tab 340, insulation can be provided between the positive electrode plate 100 and the negative electrode plate 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. Furthermore, the portion of the first negative electrode active material layer 320 covered by the fifth adhesive tape 450 can absorb and release metal cations, thereby improving the discharge capacity of the secondary battery.

[0110] In some embodiments, a fourth groove 331 is provided at the 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 adhesive tape 400 includes a sixth adhesive tape 460, which is attached to the second negative electrode active material layer 330 and covers the fourth groove 331.

[0111] The second negative electrode active material layer 330 is provided with a fourth groove 331 at the position 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 electrode current collector 310 overlap.

[0112] By attaching the sixth adhesive tape 460 to the second negative electrode active material layer 330 and covering the fourth groove 331, it can serve as an insulator between the positive electrode 100 and the negative electrode 300, reducing the possibility of contact between the negative electrode current collector 310 and the positive electrode current collector 110, thereby improving the reliability of the secondary battery; and the portion of the second negative electrode active material layer 330 covered by the sixth adhesive tape 460 can absorb and release metal cations, thereby improving 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 the second type of adhesive tape 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 electrode active material layer 120, and the projection of the negative electrode tab 340 is located within the projection of the seventh adhesive tape 510 along the thickness direction of the positive electrode current collector 110. The eighth adhesive tape 520 is attached to the second positive electrode active material layer 130, and the projection of the negative electrode tab 340 is located within the projection of the eighth adhesive tape 520 along the thickness direction of the positive electrode current collector 110. The substrate of the second type of adhesive tape is non-porous, meaning that the second type of adhesive tape does not allow metal cations to pass through.

[0114] This provides insulation between the positive electrode 100 and the negative electrode 300. Furthermore, since the projection of the negative electrode tab 340 is covered by the projections of the seventh adhesive tape 510 and the eighth adhesive tape 520, the insulation effect of the third adhesive tape 430 is improved, reducing the possibility of the negative electrode tab 340 contacting the positive current collector 110, thereby improving the reliability of the secondary battery. Because the third groove 321 used to accommodate the negative electrode tab 340 lacks active material and cannot receive metal cations, by making the substrate of the second type of adhesive tape non-porous, the portion of the first positive electrode active material layer 120 covered by the seventh adhesive tape 510 and the portion of the second positive electrode active material layer 130 covered by the eighth adhesive tape 520 cannot release metal cations, thus reducing the possibility of metal ion deposition in the secondary battery.

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

[0116] The total thickness of the fifth adhesive tape 450, the separator 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 separator 200, and the seventh adhesive tape 510 in sequence.

[0117] The total thickness of the sixth adhesive tape 460, the separator 200, and the eighth adhesive tape 520 is the isolation thickness between the negative current collector 310 and the positive current collector 110. That is, the burrs on the negative current collector 310 can only contact the positive current collector 110 after passing through the sixth adhesive tape 460, the separator 200, and the eighth adhesive 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 tail end of the positive electrode 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 provides insulation between the positive electrode 100 and the negative electrode 300, reducing the possibility of contact between the positive electrode current collector 110 and the negative electrode 300, thereby improving the reliability of the secondary battery. Furthermore, the portion of the first positive electrode active material layer 120 covered by the ninth adhesive tape 470 can absorb and release metal cations, thereby increasing 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 100, and a portion of it is attached to the second positive electrode active material layer 130, while another portion is attached to the positive electrode current collector 110.

[0120] This provides insulation between the positive electrode 100 and the negative electrode 300, reducing the possibility of contact between the positive current collector 110 and the negative electrode 300, thereby improving the reliability of the secondary battery. Furthermore, the portion of the first positive electrode active material layer 120 that is covered by the ninth adhesive paper 470 can absorb and release metal cations, thereby increasing 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 second type adhesive tapes, and no limitation is made 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-class 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-class 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-class 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-class 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-class 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-class 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-class 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-class adhesive tapes.

[0126] Referring to Table 1, φ represents the porosity of the substrate layer 401 of the first type of adhesive tape 400. H represents the thickness of the substrate layer 401 of the first type of adhesive tape 400, in μm. Referring to 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, where the first adhesive tape 410 is attached and covers the first groove 121 and the positive electrode tab 140; the position where the second groove 131 is located is position 2, where 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, where the seventh adhesive tape 510 is located. The first positive electrode active material layer 120 is attached to the position 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 second positive electrode active material layer 130 at the position 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 110. 10; Position 6 is the tail of the first positive electrode active material layer 120. 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; Position 7 is the position on the first negative electrode active material layer 320 along the thickness direction of the negative electrode current collector 310 corresponding to the positive electrode tab 140. The third adhesive tape 430 is attached to the first negative electrode active material layer 320 at the position corresponding to the positive electrode tab 140; Position 7 is the position on the second negative electrode active material layer 330 along the thickness direction of the negative electrode current collector 110. Position 8 corresponds to the thickness direction of the positive electrode tab 140. The fourth adhesive tape 440 is attached to the second negative electrode active material layer 330 at the position corresponding to the positive electrode tab 140. In Figures 2 and 3, position 9 is the side of the negative electrode tab 340 furthest from the negative electrode current collector 310. The fifth adhesive tape 450 is attached to and covers the third groove 321 and the negative electrode tab 340. Position 10 is the location of the fourth groove 331. 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 first-type adhesive tape and the thickness of the separator (i.e., the separation thickness 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 separator 200 has a thickness of 8 μm.

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

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

[0129] (1) Preparation of the first type of adhesive paper: A water-based polyacrylate is used as an adhesive by microgravure 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 paper is slit into rolls.

[0130] (2) Preparation of the negative electrode sheet: Graphite (negative electrode active material), sodium carboxymethyl cellulose (negative electrode thickener), and styrene-butadiene rubber (negative electrode binder) were mixed at a mass ratio of 98:1:1. Deionized water was added and stirred until homogeneous to form a negative electrode active material slurry. The slurry was passed through a 200-mesh sieve and had a solid content of 40%-45%. Copper foil was used as the negative electrode current collector, and the negative electrode active material slurry was coated onto the current collector. After drying at 80℃, cold pressing, and slitting, the negative electrode sheet was obtained.

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

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

[0133] (4) Electrolyte preparation: Under 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, by weight) were used to prepare a basic electrolyte. LiPF6 was then added and mixed evenly to obtain the electrolyte, wherein the concentration of LiPF6 was 1 mol / L.

[0134] (5) Preparation of the negative electrode sheet: Lithium cobalt oxide, conductive agent, and binder polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) solution at a mass ratio of 97.2:1.5:1.3 to prepare a positive electrode active material layer slurry. The slurry was passed through a 200-mesh sieve and had a solid content of 70%-75%. The positive electrode active material layer slurry was coated onto the surface of the positive electrode undercoat sheet using a coating machine. The coating thickness was 90 micrometers, the width of the positive electrode sheet was 70 millimeters, and the length of the positive electrode sheet was 1400 millimeters. After cold pressing and slitting, the positive electrode sheet was obtained.

[0135] (6) Preparation of the electrochemical device: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an outer aluminum-plastic film, and after removing moisture at 80°C, the electrolyte is injected and the assembly is sealed. After formation, degassing, and edge trimming processes, a secondary battery is obtained.

[0136] The method for detecting the porosity of the first type of adhesive tape is as follows:

[0137] (1) Remove the first type of adhesive paper from the electrode sheet and soak it in toluene solvent at 45°C for 10 hours. Repeat this process twice to obtain the substrate layer sample of the first type of adhesive paper.

[0138] (2) Calculate the porosity of the substrate layer 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 testing method for substrate layer materials:

[0140] (1) Take a substrate layer sample with an area > 0.35 cm2 and use a true density tester (AccuPycⅡ1340) to measure the true volume V of the substrate layer sample in a helium atmosphere. The true volume V is the volume of the substrate layer sample excluding pores.

[0141] (2) The weight of the substrate layer sample was measured using an electronic balance. The true density was ρ = M / V.

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

[0143] (1) Remove the first type of adhesive paper from the electrode sheet and soak it in toluene solvent at 45°C for 10 hours. Repeat this process twice to obtain the substrate layer sample of the first type of adhesive paper.

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

[0145] The method for testing the discharge capacity of a secondary battery is as follows:

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

[0147] (2) Charge the secondary battery with a constant current of 0.2C to the battery’s charging cutoff voltage (e.g., 4.5V), and charge the secondary battery with a constant voltage to 0.02C.

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

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

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

[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 withstand test. If the resistance between the positive electrode tab 140 and the negative electrode tab 340 is less than 20MΩ, the electrode assembly 10 is determined to be short-circuited; otherwise, the electrode assembly 10 is not short-circuited.

[0152] Based on 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 paper is placed at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive paper is placed at positions 3, 4, 9, and 10. When the thickness of the first type of adhesive paper is 8 μm, by making the porosity of the first type of adhesive paper 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 placed at positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is placed 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 8 μm to 20 μm, and the H / φ is 14 to 67. The secondary batteries have relatively large capacities and high discharge capacities.

[0155] (3) Referring to Comparative Examples 1 to 4, the first type of adhesive tape is placed in positions 1, 2, 7, 8, 5, and 6, and the second type of adhesive tape is placed in 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 high, the first type of adhesive tape cannot achieve a good insulation effect, and a short circuit will occur.

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

[0157] (5) Referring to Comparative Example 6 and Examples 7 and 14, the first type of adhesive paper is set at positions 1, 2, 7, 8, 5 and 6, and the second type of adhesive paper is set at positions 3, 4, 9 and 10. When the porosity of the first type of adhesive paper is 55%, if the thickness of the first type of adhesive paper is too large, for example, the thickness of the first type of adhesive paper in Comparative Example 6 is 25 μm (greater than 20 μm), the impedance of the first type of adhesive paper will be too large, resulting in a smaller discharge capacity of the secondary battery, affecting the energy density of the secondary battery, and the secondary battery will have the 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. The porosity of the first type of adhesive tape is 20% to 60%, and the thickness of the first type of adhesive tape is 8 μm to 20 μm. The discharge capacity of the secondary battery is relatively large, and the energy density of the secondary battery is relatively high.

[0159] (7) Referring to Comparative Example 7 and Example 16, the first type of adhesive tape was placed at positions 1, 2, 5, 6, 9 and 10. In Comparative Example 7, the second type of adhesive tape was placed at positions 7 and 8. Although the capacity of the secondary battery was increased, the CB value (Ce11 Balance, the ratio of negative electrode capacity per unit area to positive electrode capacity per unit area) at positions 7 and 8 was insufficient, resulting in the 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. However, in Example 17, the second type of adhesive tape is set at positions 3 and 4, while 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, leading to the problem of metal ion precipitation.

[0162] This application provides an electrical device including a secondary battery of any of the above-described solutions, the secondary battery being used to provide electrical energy to the electrical device.

[0163] The electrical equipment can be any of the aforementioned devices or systems that use secondary batteries.

[0164] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0165] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A secondary battery, comprising a casing, an electrolyte, and an electrode assembly, wherein the electrode assembly and the electrolyte are housed within the casing, characterized in that, The electrode assembly includes a positive electrode sheet, a separator, a negative electrode sheet, and a first type of adhesive paper, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet; The first type of adhesive tape includes a substrate layer, the thickness of which is H, satisfying 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 sheet includes: Positive current collector; A first positive electrode active material layer is disposed 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 disposed on the side of the positive electrode current collector opposite to the first positive electrode active material layer; A positive electrode tab is housed in the first groove, and the positive electrode tab is electrically connected to the positive 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, characterized in that, The porosity φ of the substrate layer satisfies 30% ≤ φ ≤ 55%.

3. The secondary battery according to claim 1, characterized in that, 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, characterized in that, The thickness of the substrate layer is H, which satisfies 8μm≤H≤16μm.

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

6. The secondary battery according to claim 1, characterized in that, The thickness of the substrate layer is H, and the porosity of the substrate layer is φ, satisfying 14≤H / φ≤67.

7. The secondary battery according to claim 1, characterized in that, The first type of adhesive tape further includes an adhesive layer, which is made of at least one of polyolefin, polyacrylate, polyacrylic acid and its derivatives, and the adhesive layer is stacked with the substrate layer.

8. The secondary battery according to claim 1, characterized in that, The second positive electrode active material layer has a second groove at the position 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 also includes a second adhesive tape, which is attached to the second positive electrode active material layer and covers the second groove.

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

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

11. The secondary battery according to claim 10, characterized in that, Along the length of the positive current collector, the width of the third adhesive tape is smaller than the width of the first adhesive tape, and the width of the fourth adhesive tape is smaller than the width of the first adhesive tape.

12. The secondary battery according to claim 1, characterized in that, The negative electrode sheet includes: Negative electrode current collector; A first negative electrode active material layer is disposed on one side of the negative electrode current collector. 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. The second negative electrode active material layer is disposed on the side of the negative electrode current collector opposite to the first negative electrode active material layer; A negative electrode tab is housed in the third groove, and the negative electrode tab is connected to the negative 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 the position corresponding to the third groove in the second negative electrode active material layer, 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, which 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 further includes a second type of adhesive tape. The substrate of the second type of adhesive tape is non-porous. The second type of adhesive tape includes a seventh adhesive tape and an eighth adhesive tape. The seventh adhesive 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 adhesive tape. The eighth adhesive 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 adhesive tape.

15. The secondary battery according to claim 1, characterized in that, 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 attached to the first positive electrode active material layer and another portion 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 disposed at the tail end of the positive electrode sheet, with a portion attached to the second positive electrode active material layer and another portion attached to the positive electrode current collector.

17. An electrical appliance, characterized in that, Includes a secondary battery as described in any one of claims 1 to 16, wherein the secondary battery is used to provide electrical energy.

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