Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery comprises a shell, an electrode assembly, a positive electrode lug and porous gummed paper, the electrode assembly is housed within the housing. The electrode assembly is of a winding structure. The positive pole piece comprises a positive current collector and positive active material layers, the positive active material layers are arranged on two surfaces, which are oppositely arranged along the thickness direction, of the positive current collector, and the positive active material layers are provided with grooves exposed out of the positive current collector; the positive pole lug comprises a connecting part arranged in the groove, and the connecting part is electrically connected with the positive pole current collector. The porous gummed paper comprises a glue layer, and the glue layer comprises a first bonding part at least bonded with the connecting part and a second bonding part bonded with the positive active material layer. The second bonding parts are arranged on two opposite sides of the first bonding part along the length direction of the positive pole piece. The second bonding part is thicker than the first bonding part. The possibility that ions deintercalated from the positive electrode active material layer are attached to the edge of the pored gummed paper is reduced, and the risk that the pored gummed paper is degummed is reduced.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Art

[0002] Current secondary batteries generally include a housing and an electrode assembly, wherein the housing is filled with an electrolyte and the electrode assembly is contained in the housing. The electrode assembly includes a negative electrode sheet, a positive electrode sheet and a diaphragm, wherein the diaphragm separates the negative electrode sheet and the positive electrode sheet, and the negative electrode sheet and the positive electrode sheet exchange ions through the electrolyte. Among them, the negative electrode sheet is provided with a negative electrode tab for leading out the negative electrode of the electrode assembly, and the positive electrode sheet is provided with a positive electrode tab for leading out the positive electrode of the electrode assembly. Summary of the invention

[0003] For secondary batteries in the prior art (such as lithium-ion batteries), the inventors have found that green glue is often required to be applied at the connection position between the positive electrode tab and the positive electrode sheet. At this time, at least part of the green glue covers the surface of the positive electrode sheet. When the lithium ions in the positive electrode sheet move toward the negative electrode sheet under the influence of the potential difference, since the green glue itself cannot allow the lithium ions to pass through, the lithium ions tend to move first along the length or width direction of the positive electrode sheet to the edge of the green glue, and then move toward the negative electrode sheet. In this case, the lithium ions are easily attached to the edge of the green glue, causing lithium deposition at the edge of the green glue, thereby resulting in a loss of capacity of the secondary battery.

[0004] In view of the above situation, it is necessary to provide a secondary battery that is beneficial to improving the capacity of the secondary battery.

[0005] The first aspect of the present application provides a secondary battery, comprising a housing, an electrode assembly, a positive electrode tab and a perforated adhesive tape. The electrode assembly is contained in the housing. The electrode assembly comprises a wound negative electrode sheet, a positive electrode sheet and a separator, and the separator separates the negative electrode sheet and the positive electrode sheet. The positive electrode sheet comprises a positive electrode collector and a positive electrode active material layer, the positive electrode active material layer is arranged on two surfaces of the positive electrode collector that are arranged opposite to each other along the thickness direction, and the positive electrode active material layer is provided with a groove exposing the positive electrode collector. The positive electrode tab comprises a connecting portion arranged in the groove, and the connecting portion is electrically connected to the positive electrode collector. The perforated adhesive tape comprises an adhesive layer, and the adhesive layer comprises a first adhesive portion at least bonded to the connecting portion and a second adhesive portion bonded to the positive electrode active material layer. Along the first direction, the second adhesive portion is arranged on opposite sides of the first adhesive portion, and the first direction is the length direction of the positive electrode sheet. Along the second direction, the thickness of the first adhesive portion is H1, the thickness of the second adhesive portion is H2, and the second direction is the thickness direction of the positive electrode sheet, and H2>H1.

[0006] The perforated adhesive tape can provide a moving channel for the ions released from the positive electrode active material layer, which is conducive to reducing the possibility of the ions released from the positive electrode active material layer adhering to the edge of the perforated adhesive tape, so that the ions released from the positive electrode active material layer can work normally, which is conducive to improving the capacity of the secondary battery. In addition, the thickness of the second adhesive portion is greater than the thickness of the first adhesive portion, which can enhance the bonding strength between the second adhesive portion and the positive electrode active material layer, which is conducive to reducing the possibility of the second adhesive portion in the wound structure electrode assembly relative to the positive electrode active material layer warping, thereby helping to reduce the risk of debonding of the perforated adhesive tape.

[0007] In one or more of the above embodiments, along the second direction, the projection of the perforated tape covers the projection of the groove. Along the first direction, the width of the groove is M, and the width of the perforated tape is W0. Along the third direction, the length of the groove is N, the length of the perforated tape is L0, and the third direction is the width direction of the positive electrode sheet. 1.1≤W0 / M≤2, and / or 1.3≤L0 / N≤2.3. By setting 1.1≤W0 / M and / or 1.3≤L0 / N, the portion of the perforated tape that exceeds the groove is not too small, which is beneficial to reduce the possibility of thermal shrinkage of the perforated tape causing the positive current collector to be exposed, thereby helping to reduce the risk of short circuit. By setting W0 / M≤2 and / or L0 / N≤2.3, the portion of the perforated tape that exceeds the groove is not too large, which is beneficial to reduce the possibility of the perforated tape being located at the corner position, and is beneficial to alleviate the problem that the second bonding portion is more likely to warp at the corner position.

[0008] In one or more of the above embodiments, 15mm≤M≤20mm, 7mm≤N≤13mm.

[0009] In one or more of the above embodiments, along the first direction, the width of the first adhesive portion is W1, the width of the second adhesive portion is W2, and 1.5≤W1 / W2≤4. By setting 1.5≤W1 / W2, the thinner first adhesive portion can account for a higher proportion in the perforated adhesive tape, which is beneficial to reducing the overall impedance of the perforated adhesive tape and improving the energy density of the secondary battery. By setting W1 / W2≤4, the thicker second adhesive portion can account for a higher proportion in the perforated adhesive tape, which is beneficial to improving the overall bonding performance of the perforated adhesive tape, thereby reducing the risk of debonding of the perforated adhesive tape.

[0010] In one or more of the above embodiments, 2×10 4 um 2 ≤H2×W2≤8×10 4 um 2 By setting 2×10 4 um 2≤H2×W2, when the proportion of the second adhesive portion in the porous adhesive tape is low, the thickness of the second adhesive portion can be kept small, which is beneficial to maintaining the bonding strength between the porous adhesive tape and the positive electrode active material layer, thereby reducing the risk of debonding of the porous adhesive tape. 4 um 2 When the proportion of the second adhesive portion in the perforated adhesive tape is high, while ensuring that the perforated adhesive tape has the required bonding strength, the thickness of the second adhesive portion can be not too large, which is beneficial to reducing the overall impedance of the perforated adhesive tape and reducing the loss of secondary battery energy density.

[0011] In one or more of the above embodiments, 2≤H2 / H1≤4. By setting 2≤H2 / H1, the difference in thickness between the second adhesive portion and the first adhesive portion can be not too small, which is beneficial to improve the bonding strength between the perforated adhesive tape and the positive electrode active material layer, thereby helping to reduce the risk of debonding of the perforated adhesive tape. By setting H2 / H1≤4, the difference in thickness between the second adhesive portion and the first adhesive portion can be not too large, which is beneficial to improve the flatness of the local interface of the positive electrode sheet where the perforated adhesive tape is provided, while ensuring that the perforated adhesive tape has the required bonding strength.

[0012] In one or more of the above embodiments, 2um≤H1≤4um.

[0013] In one or more of the above embodiments, the porous adhesive tape includes a base layer, which is arranged on the side of the adhesive layer away from the groove. The material of the adhesive layer includes a polymer and an inert substance, the polymer includes at least one of polyacrylate, polyacrylic acid, acrylic acid, ethylene acrylic copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, rubber, carboxymethyl cellulose, polyurethane and epoxy resin hot melt adhesive, and the inert substance includes at least one of boehmite, diaspore, halloysite and quartz sand. The material of the base layer includes at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose membrane isolation membrane and non-woven fabric. By making the material of the adhesive layer include the above substances and making the material of the base layer include the above substances, it is possible to facilitate the porous adhesive tape to form a channel for the movement of ions for embedding and de-embedding.

[0014] In one or more of the above embodiments, the porosity of the base layer is 25% to 55%. In this case, the porosity of the base layer is not too small, which can increase the permeability of the ions to be deintercalated through the base layer, which is beneficial to improving the energy density of the secondary battery. The porosity of the base layer is not too large, which is beneficial to reduce the possibility of the glue layer overflowing from the base layer, and when the positive electrode tab is welded to the positive electrode collector, it can reduce the possibility of welding burrs passing through the base layer, which is beneficial to reduce the risk of short circuit.

[0015] In one or more of the above embodiments, the air permeability of the glue layer is 200Sed / 100mL to 700Sed / 100mL. In this case, the air permeability of the glue layer is not too small. When the positive electrode tab is welded to the positive electrode current collector, the possibility of welding burrs passing through the glue layer can be reduced, which is beneficial to reducing the risk of short circuit. The air permeability of the glue layer is not too large, which can increase the transmittance of the embedded and de-embedded ions through the glue layer, which is beneficial to improving the energy density of the secondary battery.

[0016] In one or more of the above embodiments, along the second direction, the thickness of the base layer is 8um to 25um. In this case, the thickness of the base layer is not too small, and when the positive electrode tab is welded to the positive electrode current collector, the possibility of welding burrs piercing the base layer can be reduced, which is conducive to reducing the risk of short circuit. The thickness of the base layer is not too large, which is conducive to improving the energy density of the secondary battery.

[0017] In one or more of the above embodiments, the adhesive force of the second adhesive portion against peeling from the positive electrode active material layer is 60N / m to 140N / m in the opposite direction of the second direction. In this case, the adhesive force of the second adhesive portion against peeling from the positive electrode active material layer is not too small, so that the second adhesive portion can still be well bonded to the positive electrode active material layer after multiple charge and discharge cycles, which is beneficial to reduce the risk of debonding of the perforated adhesive tape. The adhesive force of the second adhesive portion against peeling from the positive electrode active material layer is not too large, which can facilitate the preparation of a perforated adhesive tape that meets the requirements.

[0018] The second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application. The secondary battery of the first aspect of the present application can reduce the possibility of ions deintercalated from the positive electrode active material layer adhering to the edge of the porous adhesive tape, which is beneficial to increase the capacity of the secondary battery, thereby facilitating the endurance of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A front view of a secondary battery provided in accordance with an embodiment of the present application.

[0020] Figure 2 For an embodiment of the present application Figure 1 The cross-section of the housing is omitted along section line AA.

[0021] Figure 3 A top view of a perforated adhesive tape provided in an embodiment of the present application attached to a positive electrode plate.

[0022] Figure 4 A front view of a perforated adhesive tape provided in an embodiment of the present application attached to a positive electrode plate.

[0023] Figure 5An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0024] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, housing; 20, electrode assembly; 201, straight section; 202, bent section; 21, positive electrode plate; 211, positive electrode current collector; 212, positive electrode active material layer; 2121, groove; 22, negative electrode plate; 221, negative electrode current collector; 222, negative electrode active material layer; 23, separator; 30, positive electrode ear; 31, connecting part; 40, perforated adhesive tape; 41, adhesive layer; 411, first bonding part; 412, second bonding part; 42, base layer; 50, negative electrode ear; 60, ear glue; X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0026] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0027] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0028] The terms "first", "second", etc. are only used to distinguish different objects and shall not be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the indicated technical features.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0030] It should be understood that, considering the actual processing tolerance factors, in the technical solution of the present application, when the two elements are arranged parallel / vertically and in the same direction, there may be a certain angle between the two elements, and a tolerance of 0-±10% is allowed between the two elements. A tolerance of 0-±10% is allowed between the two elements greater than, equal to or less than.

[0031] The embodiment of the present application provides a secondary battery, including a housing, an electrode assembly, a positive electrode tab and a perforated adhesive tape. The electrode assembly is contained in the housing. The electrode assembly includes a wound negative electrode sheet, a positive electrode sheet and a separator, and the separator separates the negative electrode sheet and the positive electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer, the positive electrode active material layer is arranged on two surfaces of the positive electrode collector that are arranged opposite to each other along the thickness direction, and the positive electrode active material layer is provided with a groove exposing the positive electrode collector. The positive electrode tab includes a connecting portion arranged in the groove, and the connecting portion is electrically connected to the positive electrode collector. The perforated adhesive tape includes an adhesive layer, and the adhesive layer includes a first adhesive portion bonded to at least the connecting portion and a second adhesive portion bonded to the positive electrode active material layer. Along the first direction, the second adhesive portion is arranged on opposite sides of the first adhesive portion, and the first direction is the length direction of the positive electrode sheet. Along the second direction, the thickness of the first adhesive portion is H1, the thickness of the second adhesive portion is H2, and the second direction is the thickness direction of the positive electrode sheet, and H2>H1.

[0032] In the secondary battery of the present application, the perforated adhesive tape can provide a moving channel for the ions deintercalated from the positive electrode active material layer, which is conducive to reducing the possibility of the ions deintercalated from the positive electrode active material layer adhering to the edge of the perforated adhesive tape, so that the ions deintercalated from the positive electrode active material layer can work normally, which is conducive to improving the capacity of the secondary battery. In addition, the thickness of the second adhesive portion is greater than the thickness of the first adhesive portion, which can enhance the bonding strength between the second adhesive portion and the positive electrode active material layer, which is conducive to reducing the possibility of the second adhesive portion in the wound structure electrode assembly relative to the positive electrode active material layer warping, thereby helping to reduce the risk of debonding of the perforated adhesive tape.

[0033] Some embodiments of the present application will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0034] See also Figures 1 to 4 An embodiment of the present application provides a secondary battery 100 , including a housing 10 , an electrode assembly 20 , a positive electrode tab 30 , and a perforated adhesive tape 40 .

[0035] The shell 10 can be a hard shell or a soft shell, wherein the material of the hard shell includes steel and the material of the soft shell includes an aluminum-plastic film. The shell 10 is provided with a receiving cavity for the electrode assembly 20 to be accommodated in the shell 10. The receiving cavity is filled with an electrolyte, and the electrolyte includes an electrolyte salt. The electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the electrolyte salt includes but is not limited to at least one of lithium hexafluorophosphate (LiPF6), bistrifluoromethanesulfonyl imide lithium LiN(CF3SO2)2 (LiTFSI), bis(fluorosulfonyl)imide lithium Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4) or lithium trifluoromethanesulfonate (LiCF3SO3).

[0036] See also Figure 2 The electrode assembly 20 includes a positive electrode sheet 21, a negative electrode sheet 22 and a separator 23 which are wound, and the separator 23 separates the positive electrode sheet 21 and the negative electrode sheet 22. The first separator 23, a single positive electrode sheet 21, a single negative electrode sheet 22 and a second separator 23 are stacked in sequence, and the positive electrode sheet 21, the negative electrode sheet 22 and the separator 23 are wound as a whole. When viewed in a direction parallel to the winding axis, each winding layer of the electrode assembly 20 includes a straight section 201 and a bent section 202, and the bent section 202 of the nth layer connects the straight section 201 of the nth layer and the straight section 201 of the n+1th layer, where n is a positive integer.

[0037] In some embodiments, the positive electrode sheet 21 includes a positive electrode current collector 211 and a positive electrode active material layer 212, and the positive electrode active material layer 212 is disposed on two opposite sides of the positive electrode current collector 211 along the thickness direction. The negative electrode sheet 22 includes a negative electrode current collector 221 and a negative electrode active material layer 222, and the negative electrode active material layer 222 is disposed on two opposite sides of the negative electrode current collector 221 along the thickness direction.

[0038] In some embodiments, the material of the positive electrode current collector 211 includes but is not limited to aluminum foil and aluminum alloy foil, and the material of the negative electrode current collector 221 includes but is not limited to copper foil, copper alloy foil, nickel foil, titanium foil, foamed nickel and foamed copper.

[0039] Please refer to Figure 3 and Figure 4In some embodiments, the positive electrode active material layer 212 is provided with a groove 2121, and the concave direction of the groove 2121 is toward the positive electrode collector 211, so that the positive electrode active material layer 212 exposes the positive electrode collector 211. The positive electrode tab 30 includes a connecting portion 31, and the connecting portion 31 is electrically connected to the positive electrode collector 211. The so-called connecting portion 31 refers to the portion of the positive electrode tab 30 disposed in the groove 2121. In some embodiments, the secondary battery 100 includes a negative electrode tab 50, and the negative electrode tab 50 is electrically connected to the negative electrode collector 221. The positive electrode tab 30 and the negative electrode tab 50 extend out of the outer shell 10 and are insulated and sealed with the outer shell 10 by the tab glue 60 (see Figure 1 ).

[0040] In some embodiments, the positive electrode tab 30 is connected to the positive electrode current collector 211 by welding, and the negative electrode tab 50 is connected to the negative electrode current collector 221 by welding.

[0041] In some embodiments, the perforated adhesive tape 40 includes an adhesive layer 41, and the adhesive layer 41 includes a first adhesive portion 411 and a second adhesive portion 412. The second adhesive portion 412 is disposed on opposite sides of the first adhesive portion 411 along a first direction X, and the first direction X is the length direction of the positive electrode sheet 21. The so-called first adhesive portion 411 refers to the portion of the perforated adhesive tape 40 that overlaps at least with the projection of the connecting portion 31 along the thickness direction of the adhesive layer 41. It should be understood that when the length of the first adhesive portion 411 is greater than the length of the groove 2121, the first adhesive portion 411 is also bonded to the positive active material layer 212 along the length direction of the positive electrode tab 30. The so-called second adhesive portion 412 refers to the portion of the perforated adhesive tape 40 that is bonded to the positive active material layer 212 along the length direction of the positive electrode sheet 21.

[0042] In some embodiments, see Figure 4 The adhesive layer 41 includes a transition area 413 , and the transition area 413 connects the first adhesive portion 411 and the second adhesive portion 412 .

[0043] Along the second direction Y, the thickness of the first adhesive portion 411 is H1, and the thickness of the second adhesive portion 412 is H2. The second direction Y is the thickness direction of the positive electrode sheet 21, and H2>H1. Among them, the thickness H1 of the first adhesive portion 411 and / or the thickness H2 of the second adhesive portion 412 may be uneven. For example, along the direction from the second adhesive portion 412 to the first adhesive portion 411, the thickness of the second adhesive portion 412 may gradually decrease, but the minimum thickness of the second adhesive portion 412 is greater than the maximum thickness of the first adhesive portion 411. There is a smooth transition or a step transition between the first adhesive portion 411 and the second adhesive portion 412. The so-called step transition refers to the sudden rise of the thickness of the first adhesive portion 411 to the thickness of the second adhesive portion 412, and when the adhesive layer 41 includes a transition zone 413, the thickness of the transition zone 413 may be equal to its thickness at the connection point between the first adhesive portion 411 or the second adhesive portion 412. The so-called smooth transition means that the thickness of the first bonding portion 411 gradually increases to the thickness of the second bonding portion 412, and when the adhesive layer 41 includes a transition zone 413, the thickness of the transition zone 413 can gradually increase from the thickness at the connection with the first bonding portion 411 to the thickness at the connection with the second bonding portion 412. Figure 4 In the illustrated viewing angle, the first adhesive portion 411 and the second adhesive portion 412 are substantially flush with each other on a surface facing away from the positive electrode tab 30 .

[0044] The above-mentioned perforated adhesive tape 40 can provide a moving channel for the ions released from the positive electrode active material layer 212, which is conducive to reducing the possibility of the ions released from the positive electrode active material layer 212 adhering to the edge of the perforated adhesive tape 40, so that the ions released from the positive electrode active material layer 212 can work normally, which is conducive to improving the capacity of the secondary battery 100. In addition, the thickness of the second adhesive portion 412 is greater than the thickness of the first adhesive portion 411, which can enhance the bonding strength between the second adhesive portion 412 and the positive electrode active material layer 212, which is conducive to reducing the possibility of the second adhesive portion 412 in the wound structure electrode assembly 20 relative to the positive electrode active material layer 212 warping, thereby helping to reduce the risk of debonding of the perforated adhesive tape 40.

[0045] It should be understood that by enhancing the bonding strength between the second bonding portion 412 and the positive electrode active material layer 212, when the positive electrode tab 30 is arranged near the corner position of the electrode assembly 20, the possibility of warping of the second bonding portion 412 of the perforated adhesive tape 40 under the action of stress can be more effectively reduced. The so-called corner position refers to the connection position between the straight section 201 and the bent section 202.

[0046] In some embodiments, the perforated adhesive tape 40 includes a base layer 42, which is disposed on a side of the adhesive layer 41 away from the groove 2121. It should be understood that when the perforated adhesive tape 40 includes the adhesive layer 41 and the base layer 42, along the thickness direction of the perforated adhesive tape 40, the projection of the base layer 42 coincides with the projection of the adhesive layer 41. The width of the perforated adhesive tape 40 is the width of the adhesive layer 41 or the base layer 42, and the length of the perforated adhesive tape 40 is the length of the adhesive layer 41 or the base layer 42.

[0047] In some embodiments, the material of the positive electrode active material layer 212 includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide. The material of the negative electrode active material layer 222 includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material. In the process of lithium ions being deintercalated from the positive electrode active material layer 212 and moving toward the negative electrode plate 22, it is helpful to reduce the possibility of lithium ions adhering to the edge of the porous adhesive tape 40.

[0048] In some embodiments, the positive electrode active material layer 212 further includes at least one of a positive electrode conductor and a positive electrode binder, and the negative electrode active material layer 222 further includes at least one of a negative electrode conductor, a thickener, and a negative electrode binder. The mass ratio of each material in the positive electrode active material layer 212 and the negative electrode active material layer 222 can be selected by those skilled in the art according to actual needs.

[0049] In some embodiments, the material of the separator 23 includes, but is not limited to, at least one of polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (such as polyethylene terephthalate (PET) films), cellulose, polyimide (PI), polyamide (PA), spandex, and aramid. The type of the separator 23 includes, but is not limited to, at least one of a woven membrane, a nonwoven membrane, a microporous membrane, a composite membrane, a rolled membrane, and a spun membrane.

[0050] In some embodiments, along the second direction Y, the projection of the perforated tape 40 covers the projection of the groove 2121. Along the first direction X, the width of the groove 2121 is M, and the width of the perforated tape 40 is W0. 1.1≤W0 / M≤2. For example, the values ​​of W0 / M are 1.1, 1.3, 1.6 and 2. By setting 1.1≤W0 / M, the portion of the perforated tape 40 that exceeds the groove 2121 can be less than that, which is beneficial to reduce the possibility of the positive electrode current collector 211 being exposed due to heat shrinkage of the perforated tape 40, thereby helping to reduce the risk of short circuit. By setting W0 / M≤2, the portion of the perforated tape 40 that exceeds the groove 2121 can be less than that, which is beneficial to reduce the possibility of the perforated tape 40 being located at the corner position, and is beneficial to alleviate the problem that the second adhesive portion 412 is more likely to warp at the corner position.

[0051] In some embodiments, 15 mm ≤ M ≤ 20 mm. For example, the value of M is 15 mm, 16 mm, 18 mm, and 20 mm. As an example, when the value of M is 20 mm, the value of W0 can be selected from any value between 22 mm and 40 mm.

[0052] In some embodiments, along the second direction Y, the projection of the perforated adhesive tape 40 covers the projection of the groove 2121. Along the third direction Z, the length of the groove 2121 is N, the length of the perforated adhesive tape 40 is L0, and the third direction Z is the width direction of the positive electrode sheet 21. 1.3≤L0 / N≤2.3. For example, the values ​​of L0 / N are 1.3, 1.5, 1.8 and 2.3. By setting 1.3≤L0 / N, the portion of the perforated adhesive tape 40 that exceeds the groove 2121 is not too small, which is conducive to reducing the possibility of the positive electrode current collector 211 being exposed due to heat shrinkage of the perforated adhesive tape 40, thereby helping to reduce the risk of short circuit. By setting L0 / N≤2.3, the portion of the perforated adhesive tape 40 that exceeds the groove 2121 is not too large, which is conducive to reducing the possibility of the perforated adhesive tape 40 being located at the corner position, and is conducive to alleviating the problem that the second bonding portion 412 is more likely to warp at the corner position.

[0053] In some embodiments, 7 mm ≤ N ≤ 13 mm. For example, the value of N is 7 mm, 8 mm, 10 mm, and 13 mm. As an example, when the value of N is 10 mm, the value of L0 can be selected from any value between 13 mm and 23 mm.

[0054] In some embodiments, along the first direction X, the width of the first adhesive portion 411 is W1, the width of the second adhesive portion 412 is W2, and 1.5≤W1 / W2≤4. For example, the values ​​of W1 / W2 are 1.5, 2, 2.5, 3, and 4. By setting 1.5≤W1 / W2, the thinner first adhesive portion 411 can occupy a higher proportion in the perforated adhesive tape 40, which is beneficial to reducing the overall impedance of the perforated adhesive tape 40 and improving the energy density of the secondary battery 100. By setting W1 / W2≤4, the thicker second adhesive portion 412 can occupy a higher proportion in the perforated adhesive tape 40, which is beneficial to improving the overall bonding performance of the perforated adhesive tape 40, thereby reducing the risk of debonding of the perforated adhesive tape 40. It should be understood that the width of the second adhesive portion 412 refers to the total width of the second adhesive portion 412 provided on the opposite sides of the first adhesive portion 411, that is, W2=W0-W1. When the adhesive layer 41 includes the transition zone 413 , W2 = W0 − W1 − the total width of the transition zone 413 .

[0055] In some embodiments, 2×10 4 um 2 ≤H2×W2≤8×10 4 um 2By setting 2×10 4 um 2 ≤H2×W2, when the proportion of the second adhesive portion 412 in the porous adhesive tape 40 is low, the thickness of the second adhesive portion 412 can be kept small, which is beneficial to maintain the bonding strength between the porous adhesive tape 40 and the positive electrode active material layer 212, thereby reducing the risk of debonding of the porous adhesive tape 40. 4 um 2 When the proportion of the second adhesive portion 412 in the perforated adhesive tape 40 is relatively high, under the premise of ensuring that the perforated adhesive tape 40 has the required bonding strength, the thickness of the second adhesive portion 412 can be not too large, which is beneficial to reducing the overall impedance of the perforated adhesive tape 40 and reducing the loss of energy density of the secondary battery 100.

[0056] In some embodiments, 2≤H2 / H1≤4. For example, the value of H2 / H1 is 2, 2.5, 3, 3.5 and 4. By setting 2≤H2 / H1, the difference in thickness between the second adhesive portion 412 and the first adhesive portion 411 can be not too small, which is beneficial to improve the bonding strength between the perforated adhesive tape 40 and the positive electrode active material layer 212, thereby helping to reduce the risk of debonding of the perforated adhesive tape 40. By setting H2 / H1≤4, the difference in thickness between the second adhesive portion 412 and the first adhesive portion 411 can be not too large, which is beneficial to improve the flatness of the local interface of the positive electrode sheet 21 where the perforated adhesive tape 40 is provided, while ensuring that the perforated adhesive tape 40 has the required bonding strength.

[0057] In some embodiments, 2um≤H1≤4um. For example, the value of H1 is 2um, 3um and 4um. As an example, when the value of H1 is 3um, the value of H2 can be selected from any value between 6mm and 12mm.

[0058] In some embodiments, the material of the adhesive layer 41 includes a polymer and an inert substance, the polymer includes at least one of polyacrylate, polyacrylic acid, acrylic acid, ethylene acrylic copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, rubber, carboxymethyl cellulose, polyurethane and epoxy resin hot melt adhesive, and the inert substance includes at least one of boehmite, diaspore, halloysite and quartz sand. The material of the base layer 42 includes at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose membrane isolation membrane and non-woven fabric. By making the material of the adhesive layer 41 include the above substances and making the material of the base layer 42 include the above substances, it is possible to facilitate the porous adhesive tape 40 to form a channel for the movement of the embedded and de-embedded ions.

[0059] In some embodiments, the air permeability of the glue layer 41 is 200Sed / 100mL to 700Sed / 100mL. For example, the air permeability of the glue layer 41 is 200Sed / 100mL, 300Sed / 100mL, 500Sed / 100mL and 700Sed / 100mL. In this case, the air permeability of the glue layer 41 is not too small. When the positive electrode tab 30 is welded to the positive electrode current collector 211, the possibility of welding burrs passing through the glue layer 41 can be reduced, which is beneficial to reducing the risk of short circuit. The air permeability of the glue layer 41 is not too large, which can increase the transmittance of the embedded ions through the glue layer 41, which is beneficial to increase the energy density of the secondary battery 100. The unit Sed / 100mL refers to the time taken to pass through 100mL of gas in seconds.

[0060] The present application has no particular restrictions on the method for regulating the air permeability of the adhesive layer 41, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating the mass ratio of the inert substance and the high molecular polymer in the adhesive layer 41. Generally speaking, the more the content of the inert substance in the adhesive layer 41, the smaller the air permeability value of the adhesive layer 41; the less the content of the inert substance in the adhesive layer 41, the greater the air permeability value of the adhesive layer 41.

[0061] In some embodiments, the porosity of the base layer 42 is 25% to 55%. For example, the porosity of the base layer 42 is 25%, 35%, 45% and 55%. In this case, the porosity of the base layer 42 is not too small, which can improve the permeability of the ions to be extracted through the base layer 42, which is beneficial to improve the energy density of the secondary battery 100. The porosity of the base layer 42 is not too large, which is beneficial to reduce the possibility of the glue layer 41 overflowing from the base layer 42, and when the positive electrode tab 30 is welded to the positive electrode collector 211, it is possible to reduce the possibility of welding burrs passing through the base layer 42, which is beneficial to reduce the risk of short circuit.

[0062] The present application has no particular restrictions on the method for regulating the porosity of the base layer 42, as long as the purpose of the present application can be achieved. For example, the method can be achieved by regulating the biaxial stretching ratio of the base layer 42.

[0063] The porosity of the base layer 42 and the air permeability of the adhesive layer 41 will affect the permeability of the de-embedded ions through the porous adhesive tape 40. When the porosity of the base layer 42 is large and the air permeability of the adhesive layer 41 is small, the permeability of the ions is greatly restricted by the adhesive layer 41; when the air permeability of the adhesive layer 41 is large and the porosity of the base layer 42 is small, the permeability of the ions is greatly restricted by the base layer 42. Therefore, the present application can set a linkage relationship of 400Sed / 100mL≤air permeability of adhesive layer 41 / porosity of base layer 42≤1400Sed / 100mL to comprehensively consider the air permeability of the adhesive layer 41 and the porosity of the base layer 42, so as to further improve the permeability of the de-embedded ions through the porous adhesive tape 40.

[0064] In some embodiments, along the second direction Y, the thickness of the base layer 42 is 8um to 25um. For example, the thickness of the base layer 42 is 8um, 10um, 15um, 20um and 25um. In this case, the thickness of the base layer 42 is not too small, and when the positive electrode tab 30 is welded to the positive electrode collector 211, the possibility of the welding burr piercing the base layer 42 can be reduced, which is beneficial to reduce the risk of short circuit. The thickness of the base layer 42 is not too large, which is beneficial to improve the energy density of the secondary battery 100. Among them, the thickness of the perforated adhesive tape 40 can be obtained by adding the thickness of the first adhesive portion 411 and the thickness of the second adhesive portion 412 to the thickness of the base layer 42.

[0065] In some embodiments, along the opposite direction of the second direction Y, the adhesive force of the second adhesive portion 412 to resist peeling from the positive active material layer 212 is 60N / m to 140N / m. For example, the adhesive force of the second adhesive portion 412 to resist peeling from the positive active material layer 212 is 60N / m, 70N / m, 80N / m, 100N / m and 140N / m. In this case, the adhesive force of the second adhesive portion 412 to resist peeling from the positive active material layer 212 is not too small, so that the second adhesive portion 412 can still be well bonded to the positive active material layer 212 after multiple charge and discharge cycles, which is beneficial to reduce the risk of debonding of the perforated adhesive tape 40. The adhesive force of the second adhesive portion 412 to resist peeling from the positive active material layer 212 is not too large, which can facilitate the preparation of a perforated adhesive tape 40 that meets the requirements. It should be understood that since the adhesive force of the second adhesive portion 412 is greater than the adhesive force of the first adhesive portion 411, when measuring the pulling force required to peel the perforated adhesive tape 40 from the positive electrode sheet 21 in the opposite direction of the second direction Y, the measured value can be considered to be the adhesive force of the second adhesive portion 412 to resist peeling from the positive electrode active material layer 212, and can also be considered to be the adhesive force of the perforated adhesive tape 40.

[0066] See also Figure 5The embodiment of the present application also provides an electric device 1000, which includes the secondary battery 100 involved in any of the above embodiments. The secondary battery 100 of the present application can reduce the possibility of ions released from the positive electrode active material layer 212 adhering to the edge of the porous adhesive tape 40, which is conducive to improving the capacity of the secondary battery 100, thereby improving the endurance of the electric device 1000. The electric device 1000 includes but is not limited to electronic devices such as e-book players, mobile phones, fax machines, copiers, printers, headphones, video recorders, LCD TVs, recorders, radios, cameras, tablet computers, and laptop computers.

[0067] In order to verify the effect of the solution provided in the present application on the secondary battery 100, the inventor of the present application conducted the following experiment, which includes 3 groups of comparative examples and 50 groups of embodiments, each group of comparative examples and embodiments includes 4 secondary batteries 100, and the number of each secondary battery 100 is 20. Each secondary battery 100 is subsequently used for lithium deposition test, cycle test, external short performance test and energy density determination.

[0068] The preparation process of the secondary battery 100 in Example 1 includes the following steps: <Preparation of Perforated Tape 40> After mixing the inert substance boehmite and polymethyl acrylate, ethyl acetate is added as a solvent, and stirred evenly to obtain a glue layer slurry with a solid content of 20wt%. Among them, the mass ratio of the inert substance to the polymethyl acrylate is 1:1, and the inert substance includes a first inert substance having a particle size greater than 300nm and less than or equal to 900nm and a second inert substance having a particle size greater than or equal to 50nm and less than or equal to 300nm, and the average particle size of the first inert substance is 600nm, and the average particle size of the second inert substance is 140nm. The particle number ratio of the first inert substance to the second inert substance is 3:2. Among them, the particle size refers to a single particle size of a single particle size, which can also be understood as an equivalent particle size. The average particle size refers to the average particle size obtained by selecting several arbitrary regions on the surface of the glue layer 41, measuring the particle size of the inert substance particles in the region, and calculating the average value. The above-mentioned "several" can be one or more than two. The present application does not particularly limit the area size of the above-mentioned "any area", and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the method for regulating the particle size of the inert substance, as long as the purpose of the present application can be achieved. For example, it can be achieved by crushing and screening. The present application has no particular restrictions on the method for regulating the average particle size of the inert substance, as long as the purpose of the present application can be achieved. For example, after the film is prepared by the process of the present application, its average particle size can be tested by combining a scanning electron microscope, and the inert substance particles of the desired particle size can be selected. When testing the average particle size of the particles, 50 particles are selected to test the average value of the maximum circumscribed circle diameter of their outer contour as the average particle size of the particles.

[0069] The above-mentioned adhesive layer slurry is coated on the surface of a release film polyethylene terephthalate (PET) film with a release force of 10g by a micro-concave roller, and is dried at 110°C to form an adhesive layer 41 with a thickness of 3um. Then, the adhesive layer 41 is compounded with a porous substrate (a biaxially oriented polypropylene (BOPP film) with a thickness of 14um (manufacturer: Dalian Eco Energy Technology Co., Ltd., model: ECO-9)) at the winding position, and the adhesive layer 41 is transferred to the surface of the porous substrate, and the intermediate product with a release film and a porous substrate is obtained by winding; the porous substrate side of the intermediate product (the opposite side of the adhesive layer 41) is coated with a silicone release agent (manufacturer: Dow Corning) by a micro-concave roller, and after drying, the release film is removed while the porous substrate is rolled up to obtain a porous adhesive paper 40.

[0070] Among them, the air permeability of the adhesive layer 41 is 350Sed / 100mL, the width W1 of the first adhesive part 411 is 18um, the width W2 of the second adhesive part 412 is 9um, the thickness H1 of the first adhesive part 411 is 3um, the thickness H2 of the second adhesive part 412 is 9um, the porosity of the base layer 42 is 45%, the thickness of the base layer 42 is 14um, the width W0 of the porous adhesive tape 40 is 27um, the length L0 of the porous adhesive tape 40 is 20um, and the bonding force of the porous adhesive tape 40 is 100N / m.

[0071] <Preparation of Positive Electrode Sheet 21> The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97.2:1.5:1.3, and NMP is added as a solvent. The mixture is stirred under the action of a vacuum mixer until the solid content is 72wt% and the system is uniform. The positive electrode slurry is evenly coated on one surface of an aluminum foil (i.e., the positive electrode current collector 211) with a thickness of 10um, and dried at 85°C to obtain a positive electrode sheet 21 with a single-sided coating of a positive electrode active material layer 212 (thickness 50um). Afterwards, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet 21 with a double-sided coating of a positive electrode active material layer 212. A groove 2121 is formed in the positive electrode active material layer 212 on one surface, and an aluminum tab (i.e., positive electrode tab 30) is cold pressed, cut, and welded in the groove 2121. The width M of the groove 2121 is 18um, and the length N of the groove 2121 is 10um. A perforated adhesive tape 40 is bonded to the positive electrode tab 30 and the positive electrode active material layer 212 to obtain a positive electrode sheet 21 with a specification of 70mm×1400mm for standby use.

[0072] <Preparation of Negative Electrode Sheet 22> The negative electrode active material graphite, the negative electrode thickener sodium carboxymethyl cellulose, and the negative electrode binder styrene butadiene rubber are mixed in a mass ratio of 98.2:0.8:1.0, and then deionized water is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 42wt% and the system is uniform. The negative electrode slurry is evenly coated on one surface of a copper foil (i.e., the negative electrode current collector 221) with a thickness of 8um, and dried at 85°C to obtain a negative electrode sheet 22 with a single-sided coating of a negative electrode active material layer 222 (thickness 60um). After that, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet 22 with a double-sided coating of a negative electrode active material layer 222. After cold pressing, cutting, and welding of nickel tabs (i.e., negative tabs 50), a negative electrode sheet 22 with a specification of 74mm×1408mm is obtained for standby use.

[0073] <Preparation of Separator 23> The base film of the diaphragm 23 is 8um thick polyethylene (PE), and a 2um thick alumina ceramic layer is coated on both surfaces of the base film of the diaphragm 23 along its thickness direction, and finally a 2.5mg / cm thick alumina ceramic layer is coated on both surfaces of the ceramic layer along its thickness direction. 2 The diaphragm 23 is obtained by drying the PVDF binder.

[0074] <Preparation of Electrolyte> In an environment with a water content of less than 10ppm, non-aqueous organic solvents propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are prepared into a basic electrolyte in a mass ratio of 1:1:0.5:1, and lithium hexafluorophosphate (LiPF6) is added and mixed evenly to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0075] <Preparation of Secondary Battery 100> The positive electrode sheet 21, negative electrode sheet 22 and separator 23 prepared above are stacked and then wound to obtain a wound structure electrode assembly 20. The electrode assembly 20 is placed in an aluminum-plastic film packaging bag, and after drying, an electrolyte is injected, and a secondary battery 100 is obtained through vacuum packaging, standing, formation, capacity, degassing, trimming and other processes.

[0076] Among them, along the thickness direction of the electrode assembly 20, the corresponding positions of the two negative electrode sheets 22 adjacent to the positive electrode sheet 21 of the winding layer where the positive electrode tab 30 is located are bonded with insulating tape (manufacturer: Todi Chemical (Shanghai) Co., Ltd., model: T4116BR), and the corresponding positions of the two positive electrode sheets 21 adjacent to the negative electrode sheet 22 of the winding layer where the negative electrode tab 50 is located are bonded with insulating tape.

[0077] The preparation process of the secondary battery 100 in Comparative Examples 1 to 3 is basically the same as that in Example 1, the difference is that the secondary battery 100 in Comparative Example 1 uses traditional green glue, and the secondary batteries 100 in Comparative Examples 2 and 3 use perforated adhesive tape 40, but the thickness of the second adhesive portion 412 is less than or equal to the thickness of the first adhesive portion 411.

[0078] The manufacturing process of the secondary battery 100 in Embodiments 2 to 5 is substantially the same as that in Embodiment 1, except that the thickness of the second adhesive portion 412 in Embodiments 2 to 5 is different from that in Embodiment 1.

[0079] The preparation process of the secondary battery 100 in Examples 6 to 10 is substantially the same as that in Example 1, except that the width W0 and the length L0 of the perforated tape 40 in Examples 10 to 14 are different from those in Example 1.

[0080] The manufacturing process of the secondary battery 100 in Examples 11 to 16 is substantially the same as that in Example 1, except that the widths of the first adhesive portion 411 and the second adhesive portion 412 in Examples 11 to 16 are different from those in Example 1.

[0081] The preparation process of the secondary battery 100 in Examples 17 to 28 is substantially the same as that in Example 1, except that the width and thickness of the second adhesive portion 412 in Examples 17 to 28 are different from those in Example 1.

[0082] The preparation process of the secondary battery 100 in Examples 29 to 37 is substantially the same as that in Example 1, except that the air permeability of the glue layer 41 and the porosity of the base layer 42 in Examples 29 to 37 are different from those in Example 1.

[0083] The preparation process of the secondary battery 100 in Examples 38 to 43 is substantially the same as that in Example 1, except that the thickness of the base layer 42 in Examples 38 to 43 is different from that in Example 1.

[0084] The preparation process of the secondary battery 100 in Examples 44 to 49 is substantially the same as that in Example 1, except that the adhesive force of the perforated adhesive tape 40 in Examples 44 to 49 is different from that in Example 1.

[0085] After the secondary batteries 100 in the comparative examples and the embodiments are prepared, a lithium deposition test is performed on all the secondary batteries 100 in each group, and the lithium deposition is observed at the edge of the perforated adhesive tape 40; a cycle test is performed on all the secondary batteries 100 in each group, and the perforated adhesive tape 40 is observed to fall off and move; an external short circuit performance test is performed on all the secondary batteries 100 in each group, and the passing of the short circuit test of the secondary batteries 100 is observed. After the test, the experimental results are recorded in Tables 1 to 6.

[0086] The specific process of lithium extraction test is as follows: 1) The secondary battery 100 is directly charged at a low temperature (12° C.) at a rate of 1.5C to a set voltage of 4.45V, and discharged at a rate of 1.5C to 3V, for a cycle of 10 cls; 2) Disassemble the secondary battery 100 and observe whether lithium deposition occurs at the edge of the perforated adhesive tape 40. Count the number of secondary batteries 100 with lithium deposition at the edge of the perforated adhesive tape 40 in each group, and count the number of secondary batteries 100 with lithium deposition at the edge of the perforated adhesive tape 40 in this group of experiments as F. Then, the occurrence rate of lithium deposition at the edge of the perforated adhesive tape 40 in this group of experiments is F / 20.

[0087] The specific process of the cycle test is as follows: 1) Maintain the test temperature at 25°C; 2) The secondary battery 100 was left to stand for 30 min; 3) 1.3C constant current charging to 4.1V, then constant voltage charging to 1C; 4) 1C constant current charge to 4.2V, then constant voltage charge to 0.7C; 5) 0.7C constant current charge to 4.3V, then constant voltage charge to 0.025C; 6) Let stand for 5 minutes; 7) 0.7C constant current discharge to 3V; 8) Let stand for 5 minutes; 9) Repeat steps 3 to 8 800 times; 10) Disassemble the secondary batteries 100 and observe whether the perforated adhesive tape 40 is fallen off or displaced. Count the number of secondary batteries 100 with the perforated adhesive tape 40 falling off or displaced in each group. The number of secondary batteries 100 with the perforated adhesive tape 40 falling off or displaced in this group of experiments is F. The lithium plating rate at the edge of the perforated adhesive tape 40 in this group of experiments is F / 20.

[0088] The specific process of the external short performance test is: 1) Place the secondary battery 100 in an environment of 23±2°C; 2) charging the secondary battery 100 to a charging cut-off voltage of 4.45V at a constant current of 0.7C and charging the secondary battery 100 to a constant voltage of 0.02C; 3) Place the secondary battery 100 in a 57±5℃ test environment. When the surface temperature of the secondary battery 100 reaches the test temperature, leave it alone for 30 minutes. Use a load resistor with a resistance of 60mΩ to short-circuit the positive and negative electrodes of the secondary battery 100. The test time is 24 hours.

[0089] 4) Count the number of secondary batteries 100 in each group that pass the external short circuit performance test, and count the number of secondary batteries 100 that pass the external short circuit performance test in this group of experiments as F, and the short circuit test pass rate of this group of experiments is F / 20. Among them, the judgment criteria for passing the external short circuit performance test are: the secondary battery 100 does not catch fire, does not explode, and the surface temperature does not exceed 130°C.

[0090] Method for determining the parameters involved in this application: Determine the energy density of the secondary battery 100: Take the factory outer packaging label of the secondary battery 100 as an example. When the voltage range marked on the factory outer packaging of the secondary battery 100 is 3.0V to 4.45V, the charging cut-off voltage is 4.45V and the discharging cut-off voltage is 3.0V. In a 25°C environment, use 0.2C direct charging to 4.45V, charge to 0.025C full charge at 4.45V constant voltage, and discharge to 3.0V at 0.2C current after full charge. Repeat the above process 3 times, and take the average capacity as the actual capacity. Among them, the energy density of the secondary battery 100 = actual capacity × discharge platform / (volume of the secondary battery 100).

[0091] Steps for removing the perforated adhesive tape 40 from the secondary battery 100: disassemble the secondary battery 100 in an environment of room temperature (25±1°C) and humidity less than 20%, separate the positive electrode sheet 21, the negative electrode sheet 22, and the separator 23, and tear the perforated adhesive tape 40 off the positive electrode sheet 21 with tweezers.

[0092] Determine the adhesive strength of the second adhesive portion 412 against peeling from the positive electrode active material layer 212: After taking out the perforated adhesive tape 40 from the secondary battery 100, take a sample of the 100mm×300mm perforated adhesive tape 40 and the positive electrode sheet 21, wrap the taken sample with paper on top and bottom, and use a die cutter and a punch to punch out into a 54.2mm×72.5mm sample; neatly stack the punched perforated adhesive tape 40 and the positive electrode sheet 21, place the stacked sample in the middle of the cardboard, and cover it with a 150mm×160mm clamp cardboard; put the stacked sample into the flat press to adjust the pressure , adjust the air pressure, pressure = 2KG; use a die cutter and a punching machine to punch the perforated adhesive tape 40 into small strips of 72.5mm×15mm, separate the perforated adhesive tape 40 from the positive electrode plate 21, connect the sample with A4 paper with a width of 15mm, and stick wrinkle glue on both sides of the connection to complete the sample production; turn on the high-speed rail tensile testing machine, and set it in sequence: adhesion test, speed 50mm / min, starting fixture spacing 40mm; click "Start" to pre-stretch about 5mm; after pre-stretching, reset the force, displacement, etc. to zero, start the test, and measure at least 5 samples in each group.

[0093] Determine the air permeability of the adhesive layer 41: After taking the perforated adhesive tape 40 out of the secondary battery 100, measure the air permeability of the perforated adhesive tape 40, and then place the perforated adhesive tape 40 in a mixed solvent of toluene and ethyl acetate (the mass ratio of toluene to ethyl acetate is 7:3) and water, respectively, stir at 50°C for 20 minutes and then take it out, dry it at 100°C for 2 hours until there is no solution, obtain the base layer 42, and measure the air permeability of the base layer 42. When measuring the air permeability of the sample, place the perforated adhesive tape 40 and the base layer 42 on the air permeability tester in turn, press the start button, and the test is completed after five seconds. Repeat the experiment 5 times for each sample and take the average value. The air permeability of the adhesive layer 41 = the air permeability of the perforated adhesive tape 40 - the air permeability of the base layer 42.

[0094] Determine the thickness of the base layer 42: After the perforated adhesive tape 40 is taken out from the secondary battery 100, the perforated adhesive tape 40 is placed in N-methylpyrrolidone (NMP), stirred at 50°C for 20 minutes, taken out, and dried at 100°C for 2 hours until there is no solution, thereby obtaining the base layer 42. The thickness of 6 locations of the base layer 42 sample is randomly measured, and the average value is calculated to obtain the thickness of the base layer 42.

[0095] Determine the porosity of the base layer 42: After obtaining the base layer 42 from the porous adhesive tape 40, calculate the porosity of the base layer 42 as φ=[1-m(s×h×p)]×100%, wherein m is the mass of the base layer 42 sample, s is the projected area of ​​the base layer 42 sample along its thickness direction, h is the thickness of the base layer 42 sample, and p is the density of the base layer 42 material.

[0096] Determine the thickness of the first adhesive portion 411 and the second adhesive portion 412: After taking the perforated adhesive tape 40 out of the secondary battery 100, use a micrometer to randomly measure the middle thickness of the perforated adhesive tape 40 of 5 samples, calculate the average value, subtract the thickness of the base layer 42, and obtain the thickness of the first adhesive portion 411; use a micrometer to randomly measure the thickness of both sides of the perforated adhesive tape 40 of 5 samples, calculate the average value, subtract the thickness of the base layer 42, and obtain the thickness of the second adhesive portion 412.

[0097] Table 1 In Table 1, the lithium plating rate at the edge of the porous adhesive tape 40 in Examples 1 to 10 is significantly lower than the lithium plating rate at the edge of the porous adhesive tape 40 in Comparative Example 1. That is, by providing the porous adhesive tape 40, the porous adhesive tape 40 can provide a moving channel for the deintercalated ions, which is beneficial to reduce the possibility of the deintercalated ions adhering to the edge of the porous adhesive tape 40. The failure rate of the porous adhesive tape 40 in Examples 1 to 10 is significantly lower than the failure rate of the porous adhesive tape 40 in Comparative Examples 2 and 3. That is, by providing the thickness of the second adhesive portion 412 to be greater than the thickness of the first adhesive portion 411, the risk of debonding of the porous adhesive tape 40 in the secondary battery 100 is reduced.

[0098] In Table 1, according to Examples 1 to 5, the failure rate of the perforated adhesive tape 40 in Examples 2 to 5 is significantly lower than that in Example 1, and the failure rates of the perforated adhesive tape 40 in Examples 4 and 5 are equivalent. That is, the present application is conducive to further reducing the risk of debonding of the perforated adhesive tape 40 in the secondary battery 100 by setting 2≤H2 / H1. By setting H2 / H1≤4, it is possible to improve the flatness of the local interface of the positive electrode sheet 21 where the perforated adhesive tape 40 is provided, while ensuring that the perforated adhesive tape 40 has the required bonding strength.

[0099] In Table 1, according to Examples 6 to 10, the short-circuit test pass rate of the secondary battery 100 in Examples 7 to 10 is significantly greater than the short-circuit test pass rate of the secondary battery 100 in Example 6, and the short-circuit test pass rates of the secondary battery 100 in Examples 9 and 10 are equivalent. In other words, the present application is conducive to reducing the risk of short circuit by setting 1.1≤W0 / M and 1.3≤L0 / N. By setting W0 / M≤2 and L0 / N≤2.3, the part of the perforated tape 40 that exceeds the groove 2121 can be not too large while ensuring that the risk of short circuit is not easy to occur, which is conducive to reducing the possibility of the perforated tape 40 being in a corner position, thereby helping to alleviate the problem that the perforated tape 40 is more likely to warp at the corner position.

[0100] Table 2 In Table 2, as the value of W1 / W2 gradually increases, the proportion of the first adhesive portion 411 gradually increases, and the proportion of the second adhesive portion 412 gradually decreases. The failure rate of the perforated adhesive tape 40 in Examples 11 to 15 is significantly lower than the failure rate of the perforated adhesive tape 40 in Example 16, and the energy density of the secondary battery 100 in Examples 11 to 16 gradually increases. In other words, the present application is conducive to improving the energy density of the secondary battery 100 by setting 1.5≤W1 / W2. By setting W1 / W2≤4, it is conducive to reducing the risk of debonding of the perforated adhesive tape 40.

[0101] Table 3 In Table 3, the failure rate of the perforated adhesive tape 40 in Examples 19 to 28 is significantly lower than that in Examples 17 and 18, and the energy density of the secondary battery 100 in Examples 17 to 26 is significantly higher than that in Examples 27 and 28. That is, the present application sets 2×10 4 um 2 ≤H2×W2, which is helpful to reduce the risk of debonding of the porous adhesive tape 40. By setting H2×W2≤8×10 4 um 2 , which is beneficial to reducing the loss of energy density of the secondary battery 100.

[0102] Table 4 In Table 4, the short circuit test pass rate of the secondary battery 100 in Examples 32 to 36 is significantly greater than the short circuit test pass rate of the secondary battery 100 in Example 31, and the energy density of the secondary battery 100 in Examples 31 to 35 is significantly greater than the energy density of the secondary battery 100 in Example 36. That is, the present application is conducive to reducing the risk of short circuit by setting the air permeability of the glue layer 41 to be greater than or equal to 200Sed / 100mL. By setting the air permeability of the glue layer 41 to be less than or equal to 700Sed / 100mL, it is conducive to improving the energy density of the secondary battery 100.

[0103] In Table 4, the energy density of the secondary battery 100 in Example 30, Example 33, Example 37 and Example 38 is significantly greater than the energy density of the secondary battery 100 in Example 29, and the short circuit test pass rate of the secondary battery 100 in Example 29, Example 30, Example 33 and Example 37 is significantly greater than the short circuit test pass rate of the secondary battery 100 in Example 38. That is, the present application is conducive to improving the energy density of the secondary battery 100 by setting the porosity of the base layer 42 to be greater than or equal to 25%. By setting the porosity of the base layer 42 to be less than or equal to 55%, it is conducive to reducing the risk of short circuit.

[0104] Table 5 In Table 5, the energy density of the secondary battery 100 in Examples 39 to 43 is significantly greater than the energy density of the secondary battery 100 in Example 44, and the short circuit test pass rate of the secondary battery 100 in Examples 40 to 44 is significantly greater than the short circuit test pass rate of the secondary battery 100 in Example 39. That is, the present application is conducive to reducing the risk of short circuit by setting the thickness of the base layer 42 to be greater than or equal to 8um. By setting the thickness of the base layer 42 to be less than or equal to 25um, it is conducive to improving the energy density of the secondary battery 100.

[0105] Table 6 In Table 6, the failure rate of the perforated adhesive tape 40 in Examples 46 to 50 is significantly lower than that in Example 45, and the failure rates of the perforated adhesive tape 40 in Examples 49 and 50 are equivalent. That is, the present application is conducive to reducing the risk of debonding by setting the adhesive force of the perforated adhesive tape 40 to be greater than or equal to 60 N / m. By setting the adhesive force of the perforated adhesive tape 40 to be less than or equal to 140 N / m, it is easy to prepare the perforated adhesive tape 40 that meets the requirements while ensuring that the perforated adhesive tape 40 is not prone to debonding.

[0106] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not intended to limit the present application. As long as they are within the essential scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, characterized in that: include: shell; An electrode assembly, the electrode assembly is accommodated in the housing; the electrode assembly comprises a negative electrode sheet, a positive electrode sheet and a separator which are wound together, the separator separates the negative electrode sheet and the positive electrode sheet; the positive electrode sheet comprises a positive current collector and a positive active material layer, the positive active material layer is arranged on two surfaces of the positive current collector which are arranged opposite to each other in the thickness direction, and the positive active material layer is provided with a groove which exposes the positive current collector; A positive electrode tab, the positive electrode tab comprising a connecting portion disposed in the groove, the connecting portion being electrically connected to the positive electrode current collector; Perforated adhesive tape, the perforated adhesive tape includes an adhesive layer, the adhesive layer includes a first adhesive portion bonded to at least the connecting portion and a second adhesive portion bonded to the positive electrode active material layer; along a first direction, the second adhesive portion is arranged on opposite sides of the first adhesive portion, and the first direction is the length direction of the positive electrode sheet; along a second direction, the thickness of the first adhesive portion is H1, the thickness of the second adhesive portion is H2, and the second direction is the thickness direction of the positive electrode sheet; H2>H1.

2. The secondary battery according to claim 1, characterized in that: Along the second direction, the projection of the perforated adhesive tape covers the projection of the groove; along the first direction, the width of the groove is M, and the width of the perforated adhesive tape is W0; along the third direction, the length of the groove is N, and the length of the perforated adhesive tape is L0, and the third direction is the width direction of the positive electrode sheet; 1.1≤W0 / M≤2, and / or 1.3≤L0 / N≤2.

3.

3. The secondary battery according to claim 2, characterized in that: 15mm≤M≤20mm, 7mm≤N≤13mm.

4. The secondary battery according to claim 1, characterized in that: Along the first direction, the width of the first adhesive portion is W1, the width of the second adhesive portion is W2, and 1.5≤W1 / W2≤4.

5. The secondary battery according to claim 4, characterized in that: 2×10 4 one 2 ≤H2×W2≤8×10 4 one 2 。 6. The secondary battery according to claim 1, characterized in that: 2≤H2 / H1≤4.

7. The secondary battery according to claim 6, characterized in that: 2um≤H1≤4um.

8. The secondary battery according to claim 1, characterized in that: The porous adhesive tape includes a base layer, which is arranged on a side of the adhesive layer away from the groove; the material of the adhesive layer includes a high molecular polymer and an inert substance, the high molecular polymer includes at least one of polyacrylate, polyacrylic acid, acrylic acid, ethylene acrylic copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, rubber, carboxymethyl cellulose, polyurethane and epoxy resin hot melt adhesive, and the inert substance includes at least one of boehmite, diaspore, halloysite and quartz sand; the material of the base layer includes at least one of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene, microporous polyolefin, cellulose film isolation membrane and non-woven fabric.

9. The secondary battery according to claim 8, characterized in that: The porosity of the base layer is 25% to 55%.

10. The secondary battery according to claim 8, characterized in that: The air permeability of the adhesive layer is 200Sed / 100mL to 700Sed / 100mL.

11. The secondary battery according to claim 8, characterized in that: Along the second direction, the thickness of the base layer is 8 um to 25 um.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: In the direction opposite to the second direction, the second adhesive portion has an adhesive force of 60 N / m to 140 N / m that resists separation from the positive electrode active material layer.

13. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 12.

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