Secondary battery and electronic device

Abstract

The invention discloses a secondary battery and electronic equipment, the secondary battery comprises a shell, an electrode assembly and a first tab, the electrode assembly is arranged in the shell, the electrode assembly comprises a first pole piece, an isolating membrane and a second pole piece, the isolating membrane is arranged between the first pole piece and the second pole piece, one end of the first tab is electrically connected with the first pole piece, and the other end of the first tab is electrically connected with the second pole piece. And the other end of the first tab extends out of the shell. The secondary battery further comprises a first adhesive layer, the first adhesive layer is arranged on the first pole piece, and the first adhesive layer covers at least part of the first tab. The first adhesive layer comprises a heat insulation layer and a bonding layer, and the bonding layer is bonded between the heat insulation layer and the first tab along the thickness direction of the first pole piece. Heat transfer to the isolating membrane can be effectively reduced, damage to the isolating membrane is reduced, and then positive and negative electrode contact short circuit is reduced. And moreover, the first adhesive layer can also play a role in bonding and fixing the first tab and the first pole piece, so that the electric connection stability of the first tab and the first pole piece can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, high energy efficiency and long cycle life, and are widely used in the fields of consumer electronics and power storage equipment. When a lithium-ion battery short-circuits, the current density at the tab is high and the temperature rise is high, which can easily cause the separator adjacent to the tab to melt and rupture, causing the positive and negative electrodes to contact and cause an internal short circuit, posing a safety risk. Summary of the invention

[0003] The present application aims to provide a secondary battery and an electronic device, aiming to reduce the technical problem that the battery is prone to internal short circuit.

[0004] This application adopts the following technical solutions:

[0005] In the first aspect, the present application proposes a secondary battery, comprising a housing, an electrode assembly and a first pole lug, wherein the electrode assembly is disposed in the housing, the electrode assembly comprises a first pole piece, a separator and a second pole piece, the separator is disposed between the first pole piece and the second pole piece, one end of the first pole lug is electrically connected to the first pole piece, and the other end of the first pole lug extends out of the housing. The secondary battery also comprises a first adhesive layer, the first adhesive layer is disposed on the first pole piece, and the first adhesive layer covers at least a portion of the first pole lug. The first adhesive layer comprises a heat insulating layer and an adhesive layer, and the adhesive layer is bonded between the heat insulating layer and the first pole lug along the thickness direction of the first pole piece.

[0006] By providing a heat-insulating layer in the first adhesive layer, the heat transfer to the isolation membrane can be effectively reduced, the damage of the isolation membrane can be reduced, and the risk of short circuit between the positive and negative electrodes can be reduced. In addition, the first adhesive layer can also play the role of bonding and fixing the first pole ear and the first pole piece, which helps to improve the electrical connection stability between the first pole ear and the first pole piece, reduce the loosening or displacement of the first pole ear during use, and reduce the increase in resistance and heat generation caused by poor contact. At the same time, the first adhesive layer can cover the burrs, weld marks, etc. on the first pole ear, which can reduce the puncture of the isolation membrane by the burrs, weld marks, etc., and thus reduce the occurrence of short circuits.

[0007] In another technical solution of the present application, the first adhesive layer also includes a substrate layer, and a heat-insulating layer is provided between the substrate layer and the adhesive layer. The substrate layer has a certain strength and can provide support for the adhesive layer and the heat-insulating layer, so that the first adhesive layer maintains a complete shape and structure, so as to facilitate the gluing operation of the first adhesive layer. In addition, the substrate layer has a certain dimensional stability and can adapt to external humidity and temperature changes.

[0008] In another technical solution of the present application, the bonding layer is partially bonded to the substrate layer, so that the combination of the substrate layer, the thermal insulation layer and the bonding layer forms an integral structure. The thermal insulation layer effectively blocks heat transfer and reduces melting, breakage and tearing of the isolation membrane. The substrate layer provides support and insulation properties. The bonding layer ensures that the first adhesive layer is firmly attached to the first pole ear, which can effectively improve the structural stability and thermal insulation of the first adhesive layer.

[0009] In another technical solution of the present application, the thermal insulation layer includes a plurality of thermal insulation particles, and the bonding layer is partially bonded between two adjacent thermal insulation particles. The bonding layer can firmly bond the thermal insulation particles together to form a stable thermal insulation structure, which can reduce the displacement or shedding of the thermal insulation particles and maintain the integrity of the thermal insulation layer. In addition, the bonding layer fills the gaps between the thermal insulation particles, making the thermal insulation layer more compact and reducing the transfer of heat through the gaps.

[0010] In another technical solution of the present application, along the width direction of the first pole piece, the first pole piece includes a first edge and a second edge, one end of the first pole ear and one end of the first adhesive layer both extend out of the first edge, and the other end of the first adhesive layer is located between the other end of the first pole ear and the second edge. It is convenient for the first adhesive layer to cover the portion of the first pole ear located on the first pole piece, reducing the hot-melt isolation film of the first pole ear. In addition, it is possible to reduce the first adhesive layer from extending beyond the first pole piece in the width direction of the first pole piece, which can not only reduce the impact on the energy density of the secondary battery, but also reduce the occurrence of short circuits.

[0011] In another technical solution of the present application, along the width direction of the first pole piece, the length of the portion where the first adhesive layer covers the first pole piece is L1, 20mm≤L1≤30mm, which can reduce the melting of the isolation film of the first pole ear, reduce the occurrence of short circuits, and reduce the impact on energy density.

[0012] In another technical solution of the present application, the first pole piece includes a first current collector and a first active material layer. Along the thickness direction of the first current collector, the first active material layer is stacked on at least one surface of the first current collector. The first active material layer is provided with a first groove, and the first pole ear portion is provided in the first groove. The first adhesive layer is provided on the surface of the first active material layer away from the first current collector. Along the thickness direction of the first pole piece, the first adhesive layer covers the first groove. Within the projection range of the first pole piece, along the width direction of the first pole piece, the length of the portion of the first adhesive layer covering the first pole piece is L1, and the length of the first groove is L3, 1mm≤L1-L3≤3mm. On the one hand, the first groove is fully covered to reduce the melting isolation film of the first pole ear, and on the other hand, the influence of the first adhesive layer on the energy density of the secondary battery is reduced.

[0013] In another technical solution of the present application, along the length direction of the first pole piece, the width of the first adhesive layer is W0, and the width of the first pole ear is W2, wherein 4mm≤(W0-W2)≤20mm. In this way, the width W0 of the first adhesive layer is greater than the width W2 of the first pole ear, that is, there is a first adhesive layer of a certain width not covering the first pole ear on both sides of the width direction of the first pole ear, and the setting of 4mm≤(W0-W2)≤20mm can reduce the melting of the isolation film in the heat radiation area on the one hand, and on the other hand, because the first adhesive layer not covering the first pole ear is at least partially attached to the first active material layer, the above setting can reduce the influence of the first adhesive layer on the energy density.

[0014] In some embodiments, the housing includes an edge seal, and the first pole ear extends out of the housing from the edge seal. The secondary battery also includes a first seal, the first seal is disposed between the edge seal and the first pole ear, and the first adhesive layer is partially disposed between the edge seal and the first seal, so that the first adhesive layer can effectively isolate the first pole ear and the isolation film in the housing, further reducing the occurrence of short circuits.

[0015] In some embodiments, along the thickness direction of the first pole piece, the thickness of the thermal insulation layer is T, 10μm≤T≤50μm, which improves the thermal insulation performance of the first adhesive layer while improving the bonding layer of the first adhesive layer and reducing the impact of the first adhesive layer on the energy density of the secondary battery.

[0016] In some embodiments, the thermal insulation layer includes at least one of hollow silica microspheres, silica aerogels, or alumina aerogels. Hollow silica microspheres have a hollow structure and can effectively reduce the conduction of heat. Silica aerogels are materials with a nanoporous structure and have a low thermal conductivity, which can hinder the transfer of heat in the aerogel, thereby achieving thermal insulation performance. Alumina aerogels have good chemical stability and can reduce erosion and oxidation by electrolytes, so as to maintain long-term stable thermal insulation performance.

[0017] In some embodiments, the substrate layer comprises at least one of polyester and polypropylene. In other embodiments, the adhesive layer comprises at least one of polyacrylate, silicone or polyurethane.

[0018] In a second aspect, the present application further proposes an electronic device, comprising a secondary battery as in any embodiment of the first aspect above.

[0019] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the subsequent description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are exemplarily described by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and the figures in the drawings do not constitute proportional limitations unless otherwise stated.

[0021] Figure 1 A structural view of a secondary battery according to some embodiments of the present application;

[0022] Figure 2 A schematic diagram of the stacking structure of an electrode assembly in some embodiments of the present application;

[0023] Figure 3 A schematic diagram of the winding structure of an electrode assembly in some embodiments of the present application;

[0024] Figure 4 A schematic diagram of a stacked structure of a first pole piece, an isolation film, and a second pole piece in some embodiments of the present application;

[0025] Figure 5 This is a schematic structural diagram of a first pole piece in some embodiments of the present application;

[0026] Figure 6 This is a schematic structural diagram of a first pole piece in some embodiments of the present application;

[0027] Figure 7 This is a schematic diagram of the structure of the first adhesive layer of some embodiments of the present application;

[0028] Figure 8 This is a schematic diagram of the structure of the first adhesive layer of some embodiments of the present application;

[0029] Fig. 9 A partial structural schematic diagram of a first pole piece in some embodiments of the present application;

[0030] Fig.10 A partial structural schematic diagram of a first pole piece in some embodiments of the present application;

[0031] Fig.11 A partial structural schematic diagram of a first pole piece in some embodiments of the present application;

[0032] Fig.12 for Figure 1 A partial enlarged view of point A in the middle.

[0033] Description of reference numerals:

[0034] 1000. Secondary battery;

[0035] 100. Electrode assembly;

[0036] 10, first pole piece; 10a, first edge; 10b, second edge; 11, first current collector; 11a, first empty foil area; 111, first surface; 112, second surface; 12, first active material layer; 121, first groove;

[0037] 20. second pole piece; 21. second current collector; 211. third surface; 212. fourth surface; 22. second active material layer;

[0038] 30. Isolation film;

[0039] 40. first adhesive layer; 41. heat insulation layer; 411. heat insulation particles; 42. base material layer; 43. bonding layer;

[0040] 50. Second adhesive layer;

[0041] 200, shell; 210, edge sealing;

[0042] 300, first pole lug;

[0043] 310, first part; 320, second part; 330, third part;

[0044] 400, second pole lug;

[0045] 500. First sealing member. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly 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, not all of the embodiments.

[0047] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0048] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0049] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0050] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0051] In the first aspect, the present application proposes a secondary battery 1000, please refer to Figure 1 The secondary battery 1000 includes an electrode assembly 100 , a shell 200 and an electrolyte (not shown in the figure). The shell 200 can accommodate the electrode assembly 100 and the electrolyte. The electrolyte infiltrates the electrode assembly 100 in the shell 200 .

[0052] For the electrode assembly 100, the electrode assembly 100 includes a first electrode sheet 10, a second electrode sheet 20 and a separator 30. The electrode assembly 100 may adopt a laminated structure, please refer to Figure 2 , a plurality of first pole pieces 10 and a plurality of second pole pieces 20 are alternately stacked along a third direction Z (thickness direction of the first pole piece 10 and / or the second pole piece 20), and an isolation film 30 is disposed between adjacent first pole pieces 10 and second pole pieces 20, and the isolation film 30 is used to insulate and separate the first pole piece 10 and the second pole piece 20. In some other embodiments, please refer to Figure 3 The electrode assembly 100 may also adopt a winding structure, for example, the first electrode sheet 10 , the isolation film 30 and the second electrode sheet 20 are stacked and wound to form a wound electrode assembly 100 .

[0053] Please refer to Figure 4 The first pole piece 10 includes a first current collector 11 and a first active material layer 12. The first current collector 11 is a conductive substrate of the first pole piece 10 and can be made of an overall flat aluminum foil. The aluminum foil has certain strength and ductility. In the production process such as winding or lamination, the aluminum foil is not easy to break or deform, so as to ensure the structural integrity of the first pole piece 10. In some other embodiments, the first current collector 11 can also be made of titanium foil, nickel foil or stainless steel foil.

[0054] The first active material layer 12 may be disposed on at least one surface of the first current collector 11 in the thickness direction (third direction Z), for example, along the third direction Z, the first current collector 11 includes a first surface 111 and a second surface 112 disposed opposite to each other, and the first active material layer 12 may be disposed on the first surface 111 and / or the second surface 112. The first active material layer 12 includes a positive electrode active material, a conductive agent, and an adhesive, etc., and the above-mentioned material components are mixed and stirred evenly and applied to the first surface 111 and / or the second surface 112, thereby obtaining the first active material layer 12. Among them, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, or lithium iron manganese phosphate.

[0055] Please refer to Figure 4 The second pole piece 20 includes a second current collector 21 and a second active material layer 22. The second current collector 21 is used as a conductive substrate of the second pole piece 20, and can be made of an overall flat copper foil. The copper foil has certain strength and ductility. In the production process such as winding or lamination, the copper foil is not easy to break or deform, so as to ensure the structural integrity of the second pole piece 20. In some other embodiments, the second current collector 21 can also be made of titanium foil, nickel foil, stainless steel foil or silver foil.

[0056] The second active material layer 22 may be disposed on at least one surface of the second current collector 21 in the thickness direction (third direction Z), for example, along the third direction Z, the second current collector 21 includes a third surface 211 and a fourth surface 212 disposed opposite to each other, and the second active material layer 22 may be disposed on the third surface 211 and / or the fourth surface 212. The second active material layer 22 includes a negative electrode active material, a conductive agent, and an adhesive, etc., such materials are mixed and stirred evenly and coated on the third surface 211 and / or the fourth surface 212, thereby obtaining the second active material layer 22. Among them, the negative electrode active material includes one or more of graphite, soft carbon, hard carbon, carbon fiber, elemental silicon, silicon oxide, silicon alloy, etc.

[0057] In some embodiments, the secondary battery 1000 further includes a first electrode tab 300. Figure 5 , the first pole ear 300 is connected to the first pole piece 10. For example, the first current collector 11 has a first empty foil area 11a where the first active material layer 12 is not provided, a portion of the first pole ear 300 is provided in the first empty foil area 11a, and is electrically connected to the first current collector 11, and the connection method includes but is not limited to welding, clamping or conductive adhesive bonding. Another portion of the first pole ear 300 can directly extend out of the housing 200 for electrical connection to an external circuit. In some other embodiments, the first pole ear 300 can also be provided integrally with the first current collector 11, for example, the first pole ear 300 is directly die-cut and cut out of the first current collector 11.

[0058] Alternatively, please refer to Figure 6 The first active material layer 12 is provided with a first groove 121. For example, the first groove 121 is opened in the first active material layer 12 by laser cleaning or foaming process, so that part of the first current collector 11 is exposed. A part of the first pole ear 300 is arranged in the first groove 121 and is electrically connected to the first current collector 11. The connection method includes but is not limited to welding, clamping or conductive adhesive bonding. Another part of the first pole ear 300 can be directly extended out of the housing 200 for electrical connection with an external circuit.

[0059] The inventors of the present application have found that the tabs are the main channels for current in and out of the secondary battery 1000. In the secondary battery 1000, the cross-sectional area of ​​the tabs is relatively small, while the area of ​​the pole pieces is relatively large. When the current flows from the large-area pole pieces to the small-area tabs, current concentration will occur. High-density current will cause severe heating at the tabs, which may easily cause the isolation film 30 adjacent to the tabs to melt and shrink or break, resulting in a short circuit between the positive and negative electrodes.

[0060] To reduce the above problems, in the embodiments of this application, please refer to Figure 5 and Figure 6 The secondary battery 1000 further includes a first adhesive layer 40, which is disposed on the first electrode sheet 10 and covers at least a portion of the first electrode tab 300. Figure 7 The first adhesive layer 40 includes a heat insulating layer 41 and an adhesive layer 43 . Along the thickness direction (third direction Z) of the first pole piece 10 , the adhesive layer 43 is bonded between the heat insulating layer 41 and the first pole tab 300 .

[0061] In the embodiment of the present application, by providing a heat insulating layer 41 in the first adhesive layer 40, the heat transfer to the isolation film 30 can be effectively reduced, the shrinkage or damage of the isolation film 30 can be reduced, and the occurrence of positive and negative contact short circuits can be reduced. In addition, the first adhesive layer 40 can also play a role in bonding and fixing the first pole ear 300 and the first pole piece 10, which helps to improve the electrical connection stability between the first pole ear 300 and the first pole piece 10, reduce the loosening or displacement of the first pole ear 300 during use, and thus reduce the increase in resistance and heating problems caused by poor contact. At the same time, the first adhesive layer 40 can cover the burrs of the first pole ear 300 (such as welding burrs or cutting burrs, etc.) and the burrs of the first pole ear 300 and the first pole piece 10 (such as welding burrs or cutting burrs, etc.), which can reduce the burrs from piercing the isolation film 30, thereby reducing the occurrence of short circuits.

[0062] In some embodiments, please refer to Figure 8The first adhesive layer 40 further includes a substrate layer 42, and a heat insulating layer 41 is disposed between the substrate layer 42 and the adhesive layer 43. The substrate layer 42 has a certain strength, and can provide support for the adhesive layer 43 and the heat insulating layer 41, so that the first adhesive layer 40 maintains a complete shape and structure, so as to facilitate the gluing operation of the first adhesive layer 40. In addition, the substrate layer 42 has a certain dimensional stability, and can adapt to external humidity and temperature changes.

[0063] For the material of the substrate layer 42, at least one of polyester or polypropylene can be used. Polyester material has high mechanical strength, can provide good mechanical support for the adhesive layer 43 and the heat insulation layer 41, and polyester has a low thermal expansion coefficient and hygroscopic expansion coefficient, can maintain a stable size under different temperature and humidity conditions, and at the same time, polyester has good corrosion resistance, can reduce corrosion by electrolyte. Polypropylene has good insulation, can effectively insulate the first pole ear 300 and the second pole piece 20, and the first pole piece 10 and the second pole piece 20, and polypropylene has good tolerance to chemical substances such as acids, alkalis, and salts, can reduce corrosion by chemical substances such as electrolytes inside the secondary battery 1000.

[0064] As for the material of the heat insulation layer 41 , the heat insulation layer 41 may be made of at least one of silicon oxide hollow microspheres, silicon dioxide aerogel or aluminum oxide aerogel.

[0065] Silica hollow microspheres have a hollow structure, which can effectively reduce the conduction of heat. When heat passes through the hollow microspheres, it needs to go through a longer path, and multiple reflections and scattering will occur in the hollow part, thereby reducing the transfer of heat. In addition, silica hollow microspheres have good chemical stability, which can reduce corrosion by electrolytes.

[0066] Silica aerogel is a material with a nanoporous structure and a low thermal conductivity, which can hinder the transfer of heat in the aerogel, thereby achieving thermal insulation performance. In addition, silica aerogel has excellent high temperature resistance and can maintain a stable structure and performance at higher temperatures.

[0067] Alumina aerogel has high mechanical strength, which enables the alumina aerogel insulation layer 41 to better withstand external forces during the assembly and use of the secondary battery 1000, and is not prone to breakage and deformation. It also has good chemical stability, which can reduce erosion and oxidation by the electrolyte, so as to maintain long-term stable insulation performance. Alumina aerogel also has adjustable properties. By changing the preparation process and parameters of alumina aerogel, its properties, such as thermal conductivity, porosity, mechanical strength, etc., can be adjusted, so that the alumina aerogel insulation layer 41 can be customized according to the needs of different secondary batteries 1000, so as to meet the requirements of various application scenarios.

[0068] As for the material of the adhesive layer 43, the adhesive layer 43 includes at least one of polyacrylate, silicone or polyurethane. Polyacrylate has good bonding performance, good flexibility and elasticity, and can adapt to the volume change of the battery during the charging and discharging process. Silicone has excellent high temperature resistance and can maintain stable bonding performance at higher temperatures. Polyurethane has good moisture resistance and can maintain stable bonding performance in a humid environment, which can effectively reduce the penetration of moisture, thereby ensuring the bonding effect of the first adhesive layer 40.

[0069] In some embodiments, part of the adhesive layer 43 is bonded to the substrate layer 42, so that the combination of the substrate layer 42, the thermal insulation layer 41 and the adhesive layer 43 forms an integral structure, the thermal insulation layer 41 effectively blocks heat transfer, reduces melting, damage and tearing of the isolation film 30, the substrate layer 42 provides support and insulation performance, and the adhesive layer 43 ensures that the first adhesive layer 40 is firmly attached to the first electrode tab 300, which can effectively improve the structural stability and thermal insulation of the first adhesive layer 40. In some other embodiments, the adhesive layer 43 and the substrate layer 42 can also be used to cover the thermal insulation layer 41, which can also improve the structural stability of the first adhesive layer 40.

[0070] In some other embodiments, the thermal insulation layer 41 includes a plurality of thermal insulation particles 411, and the bonding layer 43 is partially bonded between two adjacent thermal insulation particles 411. The bonding layer 43 can firmly bond the thermal insulation particles 411 together to form a stable thermal insulation structure, which can reduce the displacement or shedding of the thermal insulation particles 411 and maintain the integrity of the thermal insulation layer 41. In addition, the bonding layer 43 fills the gaps between the thermal insulation particles 411, making the thermal insulation layer 41 more compact, which can reduce the heat transfer through the gaps on the one hand, and improve the structural stability of the thermal insulation layer 41 on the other hand.

[0071] As for the thickness of the thermal insulation layer 41, if the thickness of the thermal insulation layer 41 is too small, the thermal insulation performance of the first adhesive layer 40 will be affected. A thicker thermal insulation layer 41 will affect the energy density on the one hand, especially for the pole piece with the first groove 121 connected to the first pole tab 300, the thermal insulation layer 41 occupies a larger thickness space of the first pole piece 10, and on the other hand, a thicker thermal insulation layer 41 may affect the bonding performance of the adhesive layer 43. For example, when the thermal insulation layer 41 is coated with the adhesive layer 43 and the substrate layer 42, the thicker thermal insulation layer 41 requires more adhesive layers 43 to coat, and the portion of the adhesive layer 43 bonding the first pole piece 10 and the first pole tab 300 is relatively small, which may easily lead to insufficient bonding strength.

[0072] In the embodiments of this application, please refer to Figure 8Along the thickness direction of the first pole piece 10 (the third direction Z), the thickness of the thermal insulation layer 41 is T, 10μm≤T≤50μm, which can improve the thermal insulation performance of the first adhesive layer 40 while improving the adhesive layer 43 of the first adhesive layer 40 and reducing the influence of the first adhesive layer 40 on the energy density of the secondary battery 1000.

[0073] When the first groove 121 is opened in the first active material layer 12 to connect the first electrode tab 300, the heat insulation layer 41 can be set only in the second part 40b, and the second part 40b can be partially accommodated in the first groove 121, so that the second part 40b occupies less thickness of the first electrode sheet 10. Since the first part 40a and the third part 40c are not provided with the heat insulation layer 41, they are thinner themselves and occupy less space in the thickness direction (third direction Z) of the first electrode sheet 10, so that the first adhesive layer 40 can be thinner as a whole, thereby reducing the influence of the first adhesive layer 40 on the energy density of the secondary battery 1000.

[0074] For the thickness of the substrate layer 42 and the adhesive layer 43, please refer to Figure 8 , the thickness of the substrate layer 42 is T1, 4μm≤T1≤16μm, which provides better mechanical strength and reduces the impact on the energy density of the secondary battery 1000. The thickness of the bonding layer 43 is T2, 2μm≤T2≤16μm, which improves the bonding strength while reducing the casting of the first adhesive layer 40 and reducing the impact of energy density. It should be noted that when the bonding layer 43 bonds part of the substrate layer 42, T2 does not include the part that occupies the thickness of the thermal insulation layer 41, and T2 is only the thickness of the bonding layer 43 on the side of the thermal insulation layer 41 facing the first pole piece 10. For the thickness measurement of each layer of the first adhesive layer 40, after cutting the first adhesive layer 40 to expose each layer, the thickness of each layer can be observed and measured by microscopy.

[0075] The first electrode 300 has a heat radiation area, and the temperature of the heat radiation area is relatively high, and there is also a risk of melting the isolation film 30. Fig. 9 , along the width direction (second direction Y) of the first pole piece 10, the first pole piece 10 includes a first edge 10a and a second edge 10b, one end of the first pole tab 300 and one end of the first adhesive layer 40 both extend out of the first edge 10a, and the other end of the first adhesive layer 40 is located between the other end of the first pole tab 300 and the second edge 10b. In this way, the first adhesive layer 40 can be reduced from exceeding the first pole piece 10 in the width direction of the first pole piece 10, thereby reducing the influence of the first adhesive layer 40 on the energy density.

[0076] For example, the width of the first pole piece 10 is W, and along the width direction of the first pole piece 10 (the second direction Y), the length of the portion of the first adhesive layer 40 covering the first pole piece 10 is L1, and within the range of the first pole piece 10, the length of the first pole ear 300 is L2, and 2mm≤L1-L2≤W-L2. By defining L1-L2≥2mm, it is convenient for the first adhesive layer 40 to cover the portion of the first pole ear 300 located on the first pole piece 10, and reduce the first pole ear 300 from hot melting the isolation film 30. In addition, by defining L1-L2≤W-L2, the first adhesive layer 40 is reduced from exceeding the first pole piece 10 in the width direction of the first pole piece 10, and the isolation film 30 can be reduced from melting in the heat radiation area, which can not only reduce the impact on the energy density of the secondary battery 1000, but also reduce the occurrence of short circuits. Optionally, 20mm≤L1≤30mm can reduce the melting of the isolation film 30 by the first pole ear 300, reduce the occurrence of short circuits, and reduce the impact on energy density.

[0077] When the first groove 121 is opened in the first active material layer 12 to connect the first electrode tab 300, please refer to Fig.10 , the first adhesive layer 40 is arranged on the surface of the first active material layer 12 away from the first current collector 11, along the thickness direction of the first pole piece 10 (the third direction Z), the first adhesive layer 40 covers the first groove 121, within the projection range of the first pole piece 10, along the width direction of the first pole piece 10 (the second direction Y), the length of the first adhesive layer 40 is L1, the length of the first groove 121 is L3, 1mm≤L1-L3≤3mm. Because the first adhesive layer 40 is directly arranged on the first active material layer 12, the first adhesive layer 40 occupies the thickness space of the first pole piece 10, affecting the energy density of the secondary battery 1000. In the present application, by limiting 1mm≤L1-L3≤3mm, on the one hand, the first groove 121 is fully covered to reduce the melting of the isolation film 30 of the first pole piece 300, and on the other hand, the influence of the first adhesive layer 40 on the energy density of the secondary battery 1000 is reduced.

[0078] As for the width of the first adhesive layer 40, its width is greater than that of the first tab 300, and the heat radiation area of ​​the first tab 300 also extends to both sides of the width direction (second direction Y) of the first tab 300. For example, please refer to Fig.11 In the width direction of the first electrode tab 300, the first adhesive layer 40 can be divided into a first part 40a, a second part 40b and a third part 40c. Along the length direction of the first electrode sheet 10 (the first direction X), the second part 40b is connected between the first part 40a and the third part 40c.

[0079] Along the thickness direction of the first pole piece 10 (third direction Z), within the projection range of the first pole piece 10, the projection of the first pole ear 300 overlaps with the projection of the second part 40b, that is, the width of the first pole ear 300 is equal to the width of the second part 40b. The second part 40b reduces the direct contact between the first pole ear 300 and the isolation film 30, which can reduce the melting of the isolation film 30 by the first pole ear 300. Along the length direction of the first pole piece 10 (first direction X), the width of the first glue layer 40 is W0, and the width of the first pole ear 300 is W2, where 4mm≤(W0-W2)≤20mm. On the one hand, the melting of the isolation film 30 in the heat radiation area is reduced, and on the other hand, the influence of the first part 40a on the energy density is reduced. The width of the first portion 40a is W1, and the width of the third portion 40c is W3. It can be understood that W0-W2=W1+W3, W1 and W3 can be equal or unequal, 2mm≤W1≤10mm, on the one hand, the melting isolation film 30 in the heat radiation area is reduced, and on the other hand, the influence of the first portion 40a on the energy density is reduced. Based on the same inventive concept, the width of the third portion 40c is W3, 2mm≤W3≤10mm, on the one hand, the melting isolation film 30 in the heat radiation area is reduced, and on the other hand, the influence of the third portion 40c on the energy density is reduced.

[0080] In some embodiments, please refer to Figure 1 and Fig.12 The shell 200 includes a sealing edge 210, and the first pole ear 300 extends out of the shell 200 from the sealing edge 210. The secondary battery 1000 also includes a first sealing member 500, which is arranged between the sealing edge and the first pole ear 300, and the first adhesive layer 40 is partially arranged between the sealing edge and the first sealing member 500, so that the first adhesive layer 40 can effectively isolate the first pole ear 300 and the isolation film 30 in the shell 200, further reducing the occurrence of short circuit.

[0081] For example, along the extension direction (second direction Y) of the first tab 300, the bonding length between the first adhesive layer 40 and the first sealant 500 is W4, 0.2mm≤W4≤2mm. The first adhesive layer 40 penetrates into the edge seal part, which can reduce the exposure of the first tab 300 due to the shrinkage of the first adhesive layer 40 and reduce the melting of the isolation film 30 by the first tab 300. At the same time, the influence of the first adhesive layer 40 on the edge seal packaging strength can be reduced.

[0082] As for the second pole piece 20, in some embodiments, the secondary battery 1000 further includes a second pole tab 400, one end of which is connected to the first pole piece 10, and the other end of the second pole tab 400 extends out of the housing 200. Similar to the first pole piece 10, the second pole tab 400 may also be provided with a heat insulation layer 41, which may reduce the melting of the isolation film 30 by the second pole tab 400, thereby reducing the occurrence of short circuits.

[0083] In the second aspect, the present application also proposes an electronic device, including a secondary battery 1000 as described in any embodiment of the first aspect above. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices include but are not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles and spacecrafts, etc.

[0084] Embodiment 1:

[0085] <Preparation of positive electrode sheet>

[0086] The positive electrode active material lithium cobalt oxide (LiCoO2), the conductive agent conductive carbon black (Super P), and the binder polyvinylidene fluoride are mixed in a mass ratio of 98.0:1.0:1.0, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%. After vacuum stirring, the positive electrode slurry is obtained. Aluminum foil with a thickness of 8μm is selected as the positive electrode current collector, and the positive electrode slurry is evenly coated on one surface of the positive electrode current collector aluminum foil, and the coating weight is 0.158mg / mm 2 . A first empty foil area is reserved on the first surface, and the positive electrode ear (first ear) of the aluminum sheet is welded in the first empty foil area. The width W2 of the positive electrode ear is 6 mm, and the length L2 of the part of the positive electrode ear located on the positive electrode sheet in the width direction of the positive electrode sheet is 18 mm. Dry at 110°C to obtain a positive electrode sheet coated with a positive electrode active material layer on one side. Afterwards, repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. The specifications of the positive electrode sheet are 69.4 mm × 1600 mm, and the thickness of the single-sided positive electrode active material layer is 39.35 μm.

[0087] <Preparation of negative electrode sheet>

[0088] Artificial graphite, binder styrene butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97.7:0.8:1.5, and deionized water was added as a solvent to prepare a slurry with a solid content of 50wt%. After being stirred evenly with a vacuum mixer, the negative electrode slurry was obtained. A copper foil with a thickness of 5μm was selected as the negative electrode current collector, and the negative electrode slurry was evenly coated on one surface of the negative electrode current collector copper foil, with a coating weight of 0.07mg / mm 2, and reserve a second empty foil area on the copper foil, and weld the nickel sheet negative electrode tab (second tab) in the second empty foil area. Dry at 120°C to obtain a single-sided negative electrode sheet. After the above steps are completed, the single-sided coating of the negative electrode sheet has been completed. After that, repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of the negative electrode active material layer. The specifications of the negative electrode sheet are 74mm×1816mm, and the thickness of the single-sided negative electrode active material layer is 54.5μm.

[0089] <Preparation of Separator Film>

[0090] A polyethylene (PE) porous film with a thickness of 7 μm was used as the isolation membrane.

[0091] <Electrolyte Preparation>

[0092] In a dry argon atmosphere, ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and then lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0093] <Preparation of lithium-ion batteries>

[0094] Polyester is used as the substrate layer, and a silicon oxide hollow microsphere insulation layer with a thickness T of 20 mm is set on the surface of the polyester, and then a bonding layer is compounded on the side of the insulation layer away from the substrate layer, so that the substrate layer, the insulation layer and the bonding layer form a first adhesive layer. The first base layer is set on the above-mentioned first pole ear and covers the first pole ear. Along the width direction of the positive electrode sheet, the length L1 of the part of the first adhesive layer covering the positive electrode sheet is 20 mm. Along the length direction of the positive electrode sheet, the width W0 of the first adhesive layer is 16 mm, the width of the part of the first adhesive layer that exceeds one side of the first pole ear (the first part) is 5 mm, and the width of the part that exceeds the other side (the third part) is 5 mm. The above-prepared separator, positive electrode sheet, separator, and negative electrode sheet are stacked in order, wound to obtain an electrode assembly, the pole ears are welded, and the electrode assembly is placed in the shell. After the positive electrode is led out, the cover plate is covered. After dehydration at 80°C, the electrolyte is injected for packaging.

[0095] Short circuit test method: After the lithium-ion battery is fully charged at room temperature, place it in a 55±2℃ test furnace and monitor the surface temperature of the lithium-ion battery. When the surface temperature of the lithium-ion battery reaches 55±2℃, let it stand for 30 minutes, and use a 60±20mΩ load resistor to short-circuit the positive and negative electrodes of the lithium-ion battery. The test ends when one of the following conditions is met: 1) The test time reaches 24h; 2) The surface temperature of the lithium-ion battery returns to the ambient temperature ±20℃. Short circuit test pass standard: The lithium-ion battery does not catch fire or explode; otherwise it is considered to be failed. Each group tests 20 samples, the number of failures is X, and the failure rate is X / 20.

[0096] Different from Example 1, the relevant parameters in Examples 2 to 30 and Comparative Example 1 are shown in Table 1 below, and the change of W0-W2 in other embodiments is achieved by keeping the tab width W2 unchanged and adjusting the first glue layer width W0.

[0097] Table 1

[0098]

[0099]

[0100] According to Table 1 above, combined with Examples 1 to 30 and Comparative Example 1, it can be seen that when a heat insulating layer is provided on the first adhesive layer, the risk of short circuit failure of the lithium ion battery can be effectively reduced. By providing a heat insulating layer in the first adhesive layer, the heat transfer to the isolation film can be effectively reduced, the melting damage of the isolation film can be reduced, and the short circuit of the positive and negative electrodes can be reduced.

[0101] In combination with Examples 1 to 8, in Example 1 and Examples 3 to 8, the first adhesive layer can better cover the heat radiation area of ​​the first tab, and the short-circuit failure risk is lower than that of Example 2. The short-circuit failure rate of Example 7 is consistent with that of Example 8, that is, continuing to increase the size of L1 will not further improve the short-circuit test performance of the battery. In Example 7, the length of the first adhesive layer is smaller, and the impact on the energy density is small. Therefore, in the embodiments of the present application, in combination with Example 1 and Examples 3 to 7, it can be selected that 20mm≤L1≤30mm.

[0102] In combination with Examples 9 to 20, the short-circuit failure rate in Examples 11 to 20 is lower than that in Examples 9 and 10. Compared with Example 18, the short-circuit test performance of Examples 19 and 20 has not been further improved. The width of the first adhesive layer in Example 18 is smaller, which not only has a lower short-circuit failure rate, but also has a smaller impact on energy density. At the same time, it can also reduce the dislocation, folding or deformation caused by the excessive length of the first adhesive layer during the adhesive bonding process. In combination with Examples 11 to 18, in the embodiments of the present application, 4mm≤(W0-W2)≤20mm can be selected.

[0103] In combination with Example 21 to Example 30, the short circuit risk in Example 22 to Example 30 is lower than that in Example 21. Compared with Example 29, the short circuit test performance of Example 30 has not been further improved. In Example 29, the thickness of the thermal insulation layer is less than that of Example 30, which can reduce the impact of the thickness of the thermal insulation layer on the bonding performance of the first adhesive layer, reduce the deformation or displacement of the first adhesive layer, and reduce the impact on the energy density of the lithium-ion battery. Therefore, in this application, 10μm≤T≤50μm can be selected.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present application as described above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A secondary battery, comprising a housing, an electrode assembly and a first pole ear, wherein the electrode assembly is disposed in the housing, the electrode assembly comprises a first pole piece, a separator and a second pole piece, the separator is disposed between the first pole piece and the second pole piece, one end of the first pole ear is electrically connected to the first pole piece, and the other end of the first pole ear extends out of the housing, characterized in that: The secondary battery further includes a first glue layer; The first adhesive layer is disposed on the first pole piece, and the first adhesive layer covers at least a portion of the first pole lug; The first adhesive layer includes a heat insulating layer and an adhesive layer. Along the thickness direction of the first pole piece, the adhesive layer is bonded between the heat insulating layer and the first pole tab.

2. The secondary battery according to claim 1, characterized in that: The first adhesive layer further includes a substrate layer, and the heat insulation layer is arranged between the substrate layer and the adhesive layer.

3. The secondary battery according to claim 2, characterized in that: The adhesive layer is partially bonded to the base material layer; and / or the thermal insulation layer includes a plurality of thermal insulation particles, and the adhesive layer is partially bonded between two adjacent thermal insulation particles.

4. The secondary battery according to claim 1, characterized in that: Along the width direction of the first pole piece, the first pole piece includes a first edge and a second edge opposite to each other, one end of the first pole ear and one end of the first adhesive layer both extend out of the first edge, and the other end of the first adhesive layer is located between the other end of the first pole ear and the second edge.

5. The secondary battery according to claim 4, characterized in that: Along the width direction of the first pole piece, the length of the portion where the first adhesive layer covers the first pole piece is L1, and 20 mm ≤ L1 ≤ 30 mm.

6. The secondary battery according to claim 1, characterized in that: The first pole piece includes a first current collector and a first active material layer. The first active material layer is stacked on at least one surface of the first current collector along the thickness direction of the first current collector. The first active material layer is provided with a first groove, and the first pole lug portion is provided in the first groove. The first adhesive layer is arranged on the surface of the first active material layer away from the first current collector, and along the thickness direction of the first pole piece, the first adhesive layer covers the first groove; along the width direction of the first pole piece, the length of the part of the first adhesive layer covering the first pole piece is L1, and the length of the first groove is L3, 1mm≤L1-L3≤3mm.

7. The secondary battery according to claim 1, characterized in that: Along the length direction of the first pole piece, the width of the first glue layer is W0, and the width of the first pole ear is W2, wherein 4mm≤(W0-W2)≤20mm.

8. The secondary battery according to claim 1, characterized in that: The shell includes a sealed edge, and the first pole tab extends out of the shell from the sealed edge; The secondary battery further includes a first sealant, which is disposed between the edge seal and the first electrode tab, and the first adhesive layer is partially disposed between the edge seal and the first sealant.

9. The secondary battery according to claim 1, characterized in that: Along the thickness direction of the first pole piece, the thickness of the thermal insulation layer is T, 10 μm≤T≤50 μm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The heat insulation layer includes at least one of hollow silicon oxide microspheres, silicon dioxide aerogel or aluminum oxide aerogel.

11. The secondary battery according to claim 2, characterized in that: The substrate layer comprises at least one of polyester and polypropylene; and / or, The adhesive layer includes at least one of polyacrylate, silicone or polyurethane.

12. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 11.

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