Secondary battery and electronic apparatus

Abstract

A secondary battery and an electronic apparatus. The secondary battery comprises a casing, an electrode assembly and an electrolyte accommodated in the casing, a metal plate connected to the electrode assembly, and an adhesive member. The electrode assembly comprises a first electrode sheet and a second electrode sheet which are stacked, the first electrode sheet comprises a first electrode sheet layer, and the second electrode sheet comprises a second electrode sheet layer arranged adjacent to the first electrode sheet layer. The electrode assembly comprises a first end and a second end which are opposite one another. The adhesive member is adhered to the electrode assembly and the casing. The adhesive member comprises a first edge located on one side of the first end and a second edge located on one side of the second end. The distance between the first end and the first edge is L1 mm, the distance between the second end and the second edge is L2 mm, and L1>L2. The electrode assembly comprises a first area and a second area which are sequentially connected in a first direction, the adhesive member is disposed in the second area, and the distance between the first electrode sheet layer and the second electrode sheet layer located in the first area is greater than the distance between the first electrode sheet layer and the second electrode sheet layer located in the second area.

Description

Secondary batteries and electronic devices 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] Secondary batteries are widely used in electric vehicles and consumer electronics due to their high energy density, high output power, and long cycle life. However, lithium-ion secondary batteries are prone to lithium deposition during cycling. This deposition not only degrades battery performance and significantly shortens cycle life, but also limits the battery's fast-charging capacity and can potentially lead to catastrophic consequences such as combustion and explosion.

[0003] Summary of the Invention

[0004] One purpose of the present application is to provide a secondary battery and an electronic device that can improve the lithium plating phenomenon.

[0005] In a first aspect, the present application provides a secondary battery comprising a housing, an electrode assembly, and a metal plate. The electrode assembly is housed within the housing, and the metal plate is connected to the electrode assembly and extends outside the housing in a first direction. The electrode assembly comprises a first electrode plate, a separator, and a second electrode plate stacked in sequence along a second direction perpendicular to the first direction. The first electrode plate comprises a first electrode plate layer, and the second electrode plate comprises a second electrode plate layer disposed adjacent to the first electrode plate layer in the second direction. The secondary battery further comprises an adhesive, and the electrode assembly further comprises a first surface, the adhesive being disposed on the first surface and bonding the electrode assembly to the housing. In the first direction, the first surface comprises a first end and a second end opposing each other. The adhesive comprises a first side and a second side opposing each other in the first direction, the first side being closer to the first end than the second side, the first end having a distance L1 from the first side, and the second end having a distance L2 from the second side, where L1>L2. The electrode assembly comprises a first region and a second region connected in sequence along the first direction. The adhesive is disposed in the second region, and the spacing between the first electrode plate layer and the second electrode plate layer in the first region is greater than the spacing between the first electrode plate layer and the second electrode plate layer in the second region.

[0006] The secondary battery of the present application configures an adhesive on the surface of the electrode assembly and makes the distance L1 between the first side of the adhesive and the first end of the electrode assembly greater than the distance L2 between the second side of the adhesive and the second end of the electrode assembly. During the manufacturing pressurization process, the second area of ​​the electrode assembly is subjected to greater pressure than the first area, thereby making the spacing between the first electrode layer and the second electrode layer located in the first area greater than the spacing between the first electrode layer and the second electrode layer located in the second area. The first area retains more electrolyte, which is beneficial to improving the lithium plating phenomenon at the location of the first area.

[0007] According to some embodiments of the present application, in the first direction, the length of the electrode assembly is L, 0.3≤L1 / L≤0.6, to ensure that during the manufacturing pressurization process, the second region of the electrode assembly is subjected to greater pressure than the first region, thereby making the distance between the first electrode layer and the second electrode layer located in the first region greater than the distance between the first electrode layer and the second electrode layer located in the second region, while ensuring that the electrode assembly is firmly bonded to the shell, which is conducive to improving the drop pass rate and reducing the impact of the adhesive on the volume energy density.

[0008] According to some embodiments of the present application, 0.35≤L1 / L≤0.45 is more conducive to maintaining appropriate bonding performance, improving the drop pass rate, and reducing the impact on the volume energy density, and ensuring that the pressure on the second area is greater than that on the first area, thereby making the distance between the first pole piece layer and the second pole piece layer located in the first area greater than the distance between the first pole piece layer and the second pole piece layer located in the second area.

[0009] According to some embodiments of the present application, 0≤L2 / L≤0.2 is conducive to maintaining appropriate bonding performance, improving the drop pass rate, and ensuring that the pressure on the second area is greater than that on the first area, thereby making the distance between the first electrode layer and the second electrode layer located in the first area greater than the distance between the first electrode layer and the second electrode layer located in the second area.

[0010] According to some embodiments of the present application, 0.05≤L2 / L≤0.1 is more conducive to maintaining appropriate bonding performance, improving the drop pass rate, and ensuring that the pressure on the second area is greater than that on the first area, thereby making the distance between the first electrode layer and the second electrode layer located in the first area greater than the distance between the first electrode layer and the second electrode layer located in the second area, which is conducive to improving the lithium plating problem.

[0011] According to some embodiments of the present application, in a third direction perpendicular to both the first direction and the second direction, the first surface includes a third end and a fourth end relative to each other, the adhesive includes a third side located on one side of the third end and a fourth side located on one side of the fourth end, and the first side, the third side, the second side and the fourth side are connected in sequence; in the third direction, the width of the electrode assembly is W, the distance between the third end and the third side is W1, the distance between the fourth end and the fourth side is W2mm, 0≤W1 / W≤0.3, 0≤W2 / W≤0.3, which is conducive to ensuring firm bonding between the electrode assembly and the shell and improving the drop pass rate.

[0012] According to some embodiments of the present application, 0.1≤W1 / W≤0.25, 0.1≤W2 / W≤0.25.

[0013] According to some embodiments of the present application, the adhesive includes a plurality of sub-adhesives, which are arranged at intervals on the first surface, and the spacing between two adjacent sub-adhesives is less than or equal to the smaller of the widths of the two adjacent sub-adhesives, ensuring that there is sufficient bonding area between the adhesive and the electrode assembly and the shell, and the plurality of sub-adhesives arranged at intervals can disperse stress, thereby improving the drop pass rate.

[0014] According to some embodiments of the present application, the electrode assembly is provided as a wound structure.

[0015] According to some embodiments of the present application, the metal plate includes a first metal plate, the first metal plate being welded to the first electrode piece, forming a weld mark between the first metal plate and the first electrode piece; the secondary battery further includes an insulating layer, the insulating layer covering the weld mark and a portion of the first metal plate. The provision of the insulating layer can reduce the risk of puncture of the diaphragm due to burrs from the weld mark, thereby reducing the risk of short circuit between the first electrode piece and the second electrode piece.

[0016] According to some embodiments of the present application, when viewed along the second direction, the adhesive member does not overlap with the first metal plate, and the adhesive member does not overlap with the insulating layer, which is beneficial to improving the volume energy density.

[0017] According to some embodiments of the present application, the adhesive member includes a first adhesive layer, a base material layer, and a second adhesive layer stacked in sequence, the first adhesive layer is bonded to the shell, and the second adhesive layer is bonded to the electrode assembly.

[0018] According to some embodiments of the present application, the thickness of the adhesive is 10 to 50 mm. When the thickness of the adhesive is within this range, during the manufacturing pressurization process, the pressure applied to the first region and the second region is significantly different, thereby producing an electrode assembly in which the spacing between the first and second electrode sheet layers in the first region is greater than the spacing between the first and second electrode sheet layers in the second region.

[0019] According to some embodiments of the present application, the thickness of the adhesive is 18 to 30 mm.

[0020] A second aspect of the present application provides an electronic device comprising any of the above-mentioned secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a view of a secondary battery provided in one embodiment of the present application viewed along a second direction.

[0022] FIG2 is a view of an electrode assembly provided in one embodiment of the present application observed along a first direction.

[0023] FIG3 is an enlarged view of point III shown in FIG2 .

[0024] FIG4 is a view of the electrode assembly provided in one embodiment of the present application viewed along a direction opposite to the second direction.

[0025] FIG5 is a schematic cross-sectional view of an adhesive member provided in one embodiment of the present application.

[0026] FIG6 is a view of the electrode assembly provided in one embodiment of the present application observed along the second direction.

[0027] Description of Main Component Symbols Secondary Battery 100 Housing 10 Electrode Assembly 20 First Metal Plate 31 Second Metal Plate 32 Main Body 11 Packaging 12 First Electrode Sheet 21 First Electrode Sheet Layer 21a Second Electrode Sheet 22 Second Electrode Sheet Layer 22a Separator 23 First Current Collector 211 First Active Material Layer 212 Second Current Collector 221 Second Active Material Layer 222 First Surface 201 Second Surface 202 First End 201a Second End 201b Adhesive 50 First Edge 50a Second Edge 50b First Region 20a Second Region 20b Weld Stamp 25 Insulation Layer 26, 27 Third End 201c Fourth End 201d Third Edge 50c Fourth Edge 50d First Adhesive Layer 501 Base Layer 502 Second Adhesive Layer 503 First Direction X Second Direction Z Third Direction Y Sub-Adhesive 51 First Edge 51a Second Edge51b Third edge 51c Fourth edge 51d

[0028] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used 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.

[0030] Below, embodiments of the present application will be described in detail. However, the present application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments illustrated herein. Rather, these exemplary embodiments are provided to make the present application thorough and detailed for those skilled in the art.

[0031] In addition, for the sake of brevity and clarity, the size or thickness of various components, layers may be amplified in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, or when element A is referred to as "connecting" to element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0032] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0033] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0034] It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part without departing from the teachings of the exemplary embodiments.

[0035] Referring to Figure 1 , one embodiment of the present application provides a secondary battery 100 comprising a housing 10, an electrode assembly 20, an electrolyte, and a metal plate. The electrode assembly 20 and the electrolyte are housed within the housing 10. The metal plate is connected to the electrode assembly 20 and extends from one side of the housing 10 in a first direction X for connection to external components. In this embodiment, the metal plate comprises a first metal plate 31 and a second metal plate 32, which are located on the same side of the secondary battery 100.

[0036] The housing 10 can be a packaging bag encapsulated with an encapsulation film (such as an aluminum-plastic film or a steel-plastic film), that is, the secondary battery 100 is a soft-pack battery. Specifically, the housing 10 includes a main body 11 and an encapsulation portion 12. The main body 11 is provided with a housing cavity for accommodating the electrode assembly 20. The encapsulation portion 12 extends from the edge of the main body 11 and is used to seal the main body 11. The first metal plate 31 and the second metal plate 32 extend through the encapsulation portion 12 along the first direction X. In other embodiments, the housing 10 is a metal housing, such as a steel shell or an aluminum shell.

[0037] Referring to Figure 2, the electrode assembly 20 includes a first electrode sheet 21, a second electrode sheet 22, and a separator 23 disposed between the first electrode sheet 21 and the second electrode sheet 22. In this embodiment, the electrode assembly 20 is configured as a wound structure, wherein the first electrode sheet 21, separator 23, and second electrode sheet 22 are stacked in sequence along a second direction Z perpendicular to the first direction X and then wound to form the wound structure. The wound structure has a flat portion and a curved portion, wherein the flat portion is the portion of the first electrode sheet 21, separator 23, or second electrode sheet 22 that extends straight after being wound, and the curved portion is the portion of the first electrode sheet 21, separator 23, or second electrode sheet 22 that extends curved after being wound. In other embodiments, the electrode assembly 20 is configured as a laminated structure, wherein the first electrode sheet 21, separator 23, and second electrode sheet 22 are alternately stacked along the second direction Z to form the laminated structure. The first electrode sheet 21 includes a first electrode sheet layer 21a, and the second electrode sheet 22 includes a second electrode sheet layer 22a disposed adjacent to the first electrode sheet layer 21a in the second direction Z. When the electrode assembly 20 is configured as a wound structure, the first electrode layer 21a is a layer of a multi-layer electrode sheet formed by winding the first electrode sheet 21, and the second electrode layer 22a is a layer of a multi-layer electrode sheet formed by winding the second electrode sheet. When the electrode assembly 20 is configured as a laminated structure, the first electrode layer 21a is one of the stacked plurality of first electrode sheets 21, and the second electrode layer 22a is one of the stacked plurality of second electrode sheets 22.

[0038] The first electrode sheet 21 includes a first current collector 211 and a first active material layer 212 disposed on at least one surface of the first current collector 211. The second electrode sheet 22 includes a second current collector 221 and a second active material layer 222 disposed on at least one surface of the second current collector 221. A first metal plate 31 is connected to the first current collector 211, and a second metal plate 32 is connected to the second current collector 221. In this embodiment, the first electrode sheet 21 is a positive electrode sheet, and the second electrode sheet 22 is a negative electrode sheet. The first current collector 211 can be any known current collector, such as aluminum foil, aluminum alloy foil, or a composite current collector. The second current collector 221 can be any known current collector, such as copper foil, copper alloy foil, or a composite current collector. The first active material layer 212 includes a positive electrode active material, which may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and combinations thereof. The second active material layer 222 includes a negative electrode active material, which can be selected from at least one of graphite materials, alloy materials, lithium metal, and alloys thereof. The graphite material can be selected from at least one of artificial graphite and natural graphite; the alloy material can be selected from at least one of silicon, silicon oxide, tin, and titanium sulfide. The first and second active material layers 212 and 222 may also include a conductive agent and a binder. The conductive agent may include at least one of conductive carbon black, carbon nanotubes, carbon fibers, or graphene; the binder may include at least one of styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, or sodium carboxymethyl cellulose.

[0039] Referring to Figures 1, 2, and 4, the electrode assembly 20 further includes a first surface 201 and a second surface 202 that are opposed to each other in the second direction Z. The first surface 201 is formed by the outermost surfaces of the first electrode piece 21, the second electrode piece 22, and / or the diaphragm 23 on one side in the second direction Z, while the second surface 202 is formed by the outermost surfaces of the first electrode piece 21, the second electrode piece 22, and / or the diaphragm 23 on the other side in the second direction Z. In the first direction X, the first surface 201 includes opposing first and second ends 201a, 201b, with the first end 201a being closer to the metal plate than the second end 201b. As viewed along the second direction Z, the first and second metal plates 31, 32 protrude from the electrode assembly 20 from the first end 201a.

[0040] Referring to Figures 1 and 4, the secondary battery 100 also includes an adhesive 50. The adhesive 50 is disposed on the first surface 201 and bonds the electrode assembly 20 and the shell 10. In the first direction X, the adhesive 50 includes a first edge 50a located on the side of the first end 201a and a second edge 50b located on the side of the second end 201b. The first edge 50a and the second edge 50b are opposite to each other in the first direction X, and the first edge 50a is closer to the first end 201a than the second edge 50b. The distance between the first end 201a and the first edge 50a is L1, and the distance between the second end 201b and the second edge 50b is L2, where L1>L2. By configuring the adhesive 50, the bonding force between the electrode assembly 20 and the shell 10 is improved, the risk of relative displacement between the electrode assembly 20 and the shell 10 is reduced, and the drop pass rate is thereby improved. In addition, by configuring the adhesive 50, the thickness of the area of ​​the secondary battery 100 opposite to the adhesive 50 is larger. During the manufacturing pressurization process of the secondary battery 100, the area opposite to the adhesive 50 is subjected to less pressure and less compression than other areas, so that the distance between the first electrode layer 21a and the second electrode layer 22a in this area is larger, which can retain more electrolyte and is beneficial to improving the lithium plating phenomenon in this area.

[0041] Referring to Figures 1, 2, and 4, the electrode assembly 20 further includes a first region 20a and a second region 20b connected sequentially along a first direction X, with an adhesive 50 disposed in the second region 20b. Specifically, when viewed along the second direction Z, the portion of the electrode assembly 20 covered by the adhesive 50 serves as the second region 20b, while the portion of the electrode assembly 20 not covered by the adhesive 50 serves as the first region 20a. The spacing between the first electrode layer 21a and the second electrode layer 22a in the first region 20a is greater than the spacing between the first electrode layer 21a and the second electrode layer 22a in the second region 20b. This allows the first region 20a to retain more electrolyte than the second region 20b, thereby improving lithium deposition in the first region 20a.

[0042] Referring to FIG. 3 , in some embodiments, the first metal plate 31 is welded to the first current collector 211. A weld mark 25 is formed between the first metal plate 31 and the first current collector 211. The electrode assembly 20 further includes an insulating layer 26. The insulating layer 26 is disposed on the surface of the first current collector 211 facing away from the weld mark 25 and covers the weld mark 25 to reduce the risk of puncture of the separator 23 due to weld mark burrs and reduce the risk of contact short circuit between the first and second electrode sheets 21 and 22. The insulating layer 26 can also be disposed on the surface of the first current collector 211 where the first metal plate 31 is disposed, covering the weld mark 25 and a portion of the first metal plate 31 to further reduce the risk of puncture of the separator 23 due to weld mark burrs. The insulating layer 26 comprises an insulating material selected from at least one of polyethylene, polypropylene, phenolic resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, or polyurethane.

[0043] In some embodiments, the second metal plate 32 is welded to the second current collector 221, and a weld mark (not shown) is formed between the second metal plate 32 and the second current collector 221. The electrode assembly 20 further includes an insulating layer 27. The insulating layer 27 is disposed on the surface of the second current collector 221 facing away from the corresponding weld mark and covers the corresponding weld mark to reduce the occurrence of puncture of the diaphragm 23 due to weld mark burrs. The material of the insulating layer 27 and the material of the insulating layer 26 can be the same or different. In some embodiments, the insulating layer 27 includes at least one of polyethylene, polypropylene, phenolic resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, or polyurethane.

[0044] Referring to Figure 1 , when viewed along the second direction Z, the adhesive member 50 does not overlap with the first metal plate 31 or the insulating layer 26. This avoids the problem of increased overall thickness of the secondary battery 100 due to overlap, thereby improving volumetric energy density.

[0045] In some embodiments, the length of the electrode assembly 20 in the first direction X is L mm, and 0.3 ≤ L1 / L ≤ 0.6. For example, L1 / L is 0.3, 0.4, 0.5, 0.6, etc. When L1 / L satisfies the above range, the adhesive 50 has sufficient dimensions in the first direction X to ensure a firm bond between the electrode assembly 20 and the housing 10, thereby improving the drop pass rate. The adhesive 50 can also avoid the metal plate in the first direction X, thereby reducing its impact on the volumetric energy density. At the same time, during the manufacturing pressurization process, the second region 20b of the electrode assembly 20 is subjected to greater pressure than the first region 20a, thereby making the distance between the first electrode layer 21a and the second electrode layer 22a in the first region 20a greater than the distance between the first electrode layer 21a and the second electrode layer 22a in the second region 20b. Preferably, 0.35≤L1 / L≤0.45, which is more conducive to maintaining appropriate bonding performance, improving the drop pass rate, and reducing the impact on the volume energy density, and ensuring that the pressure on the second area is greater than that on the first area, thereby making the distance between the first electrode layer 21a and the second electrode layer 22a located in the first area greater than the distance between the first electrode layer 21a and the second electrode layer 22a located in the second area.

[0046] In some embodiments, 0 ≤ L2 / L ≤ 0.2. For example, L2 / L is 0, 0.1, 0.2, etc. When L2 / L satisfies the above range, the adhesive 50 has sufficient dimensions in the first direction X to ensure a secure bond between the electrode assembly 20 and the housing 10, thereby improving the drop pass rate. Furthermore, during the manufacturing pressurization process, the second region 20b of the electrode assembly 20 is subjected to greater pressure than the first region 20a, thereby increasing the spacing between the first electrode layer 21a and the second electrode layer 22a in the first region 20a to be greater than the spacing between the first electrode layer 21a and the second electrode layer 22a in the second region 20b. Preferably, 0.05≤L2 / L≤0.1, which has a better effect on improving the drop pass rate, while ensuring that during the manufacturing pressurization process, the pressure applied to the second area 20b of the electrode assembly 20 is greater than that of the first area 20a, thereby making the distance between the first electrode layer 21a and the second electrode layer 22a located in the first area 20a greater than the distance between the first electrode layer 21a and the second electrode layer 22a located in the second area 20b.

[0047] In some embodiments, in a third direction Y perpendicular to both the first direction X and the second direction Z, the first surface 201 includes a third end 201c and a fourth end 201d, and the adhesive member 50 includes a third side 50c located on the side of the third end 201c and a fourth side 50d located on the side of the fourth end 201d. The first side 50a, the third side 50c, the second side 50b, and the fourth side 50d are sequentially connected. In the third direction Y, the electrode assembly has a width of W mm, a distance between the third end 201c and the third side 50c of W1 mm, and a distance between the fourth end 201d and the fourth side 50d of W2 mm, with 0 ≤ W1 / W ≤ 0.3 and 0 ≤ W2 / W ≤ 0.3. For example, W1 / W and W2 / W are 0, 0.1, 0.2, 0.3, etc. When W1 / W and W2 / W meet the above ranges, the adhesive 50 has sufficient size in the third direction Y to ensure that the electrode assembly 20 is firmly bonded to the shell 10. Preferably, 0.1≤W1 / W≤0.25, 0.1≤W2 / W≤0.25. The curved portion of the electrode assembly 20 with a wound structure is tighter than the flat portion. If the distance between the adhesive 50 and the third side 50c or the fourth side 50d in the third direction Y is too small, the curved portion of the electrode assembly 20 may be easily pulled and damaged during a fall. When W1 / W and W2 / W are greater than or equal to 0.1, the risk of the curved portion of the electrode assembly 20 being pulled and damaged during a fall can be reduced.

[0048] Referring to Figure 5 , in some embodiments, adhesive member 50 includes a first adhesive layer 501, a base material layer 502, and a second adhesive layer 503 stacked in sequence. First adhesive layer 501 is bonded to the housing, and second adhesive layer 503 is bonded to the electrode assembly. Base material layer 502 comprises an insulating material selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Each of first adhesive layer 501 and second adhesive layer 503 may be a pressure-sensitive adhesive or a hot-melt adhesive. In some embodiments, the first adhesive layer 501 is a hot melt adhesive and includes at least one of polymethyl methacrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer or polyimide, and the second adhesive layer 503 is a pressure-sensitive adhesive and includes at least one of polyethylene oxide, acrylonitrile-styrene-butadiene copolymer, styrene-butadiene copolymer, polyvinyl alcohol, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polymethyl methacrylate, polypropylene, polyethylene or polyamide.

[0049] In some embodiments, the thickness of the adhesive 50 is 10 to 50 mm, the thickness of the substrate layer 502 is 2 to 30 mm, the thickness of the first adhesive layer 501 is 2 to 10 mm, and the thickness of the second adhesive layer 503 is 2 to 10 mm. When the thickness of the adhesive 50 is within the above range, during the pressurization process of manufacturing the secondary battery 100, the pressure difference between the first region 20a and the second region 20b is significant, resulting in a significantly larger spacing between the first electrode layer 21a and the second electrode layer 22a in the first region 20a than between the first electrode layer 21a and the second electrode layer 22a in the second region 20b, which helps to improve lithium plating. When the thickness of the first adhesive layer 501 / the second adhesive layer 503 is less than 2 mm, the thickness is too thin, the adhesion is insufficient, and the fixing ability is weak. When the thickness of the first adhesive layer 501 / the second adhesive layer 503 is greater than 10 mm, the thickness is too thick, and bubbles and adhesive overflow are likely to occur. Preferably, the thickness of the adhesive member 50 is 18-30 mm, the thickness of the base material layer 502 is 10-15 mm, the thickness of the first adhesive layer 501 is 4-8 mm, and the thickness of the second adhesive layer 503 is 4-8 mm.

[0050] Referring to Figure 6, in some embodiments, the adhesive 50 includes a plurality of sub-adhesives 51. The plurality of sub-adhesives 51 are spaced apart on the first surface 201. Figure 6 shows two sub-adhesives 51. The number of sub-adhesives 51 can be set according to actual needs. Each sub-adhesive 51 includes a first edge 51a located on one side of the first end 201a, a second edge 51b located on one side of the second end 201b, a third edge 51c located on one side of the third end 201c, and a fourth edge 51d located on one side of the fourth end 201d. The first edge 51a, the third edge 51c, the second edge 51b, and the fourth edge 51d are connected in sequence. In this embodiment, the plurality of sub-adhesives 51 are spaced apart on the first surface 201 along the third direction Y. The first edges 51a of the multiple sub-adhesive elements 51 on one side in the first direction X collectively constitute the first side 50a of the adhesive element 50. The second edges 51b of the multiple sub-adhesive elements 51 on the other side in the first direction X collectively constitute the second side 50b of the adhesive element 50. The third edge 51c of the outermost sub-adhesive element 51 on one side in the third direction Y constitutes the third side 50c of the adhesive element 50. The fourth edge 51d of the outermost sub-adhesive element 51 on the other side in the third direction Y constitutes the fourth side 50d of the adhesive element 50. In the third direction Y, the spacing between two adjacent sub-adhesive elements 51 is less than or equal to the smaller of the widths of the two adjacent sub-adhesive elements 51, ensuring sufficient bonding area between the adhesive element 50 and the electrode assembly 20 and the housing 10. The multiple sub-adhesive elements 51 spaced apart can also disperse stress, thereby improving the drop pass rate. When the spacing between two adjacent sub-adhesives 51 is greater than the smaller of the widths of the two adjacent sub-adhesives 51 , the shell 10 pulls the sub-adhesives 51 during the falling process, and the resulting pulling force can easily cause part of the electrode assembly 20 located between the two adjacent sub-adhesives 51 to be pulled and damaged.

[0051] In another embodiment, multiple sub-adhesive elements 51 are spaced apart on the first surface 201 along the first direction X. A first edge 51a of the outermost sub-adhesive element 51 on one side of the first direction X constitutes a first side 50a of the adhesive element 50, a second edge 51b of the outermost sub-adhesive element 51 on the other side of the first direction X constitutes a second side 50b of the adhesive element 50, third edges 51c of the multiple sub-adhesive elements 51 on one side of the third direction Y collectively constitute a third side 50c of the adhesive element 50, and fourth edges 51d of the multiple sub-adhesive elements 51 on the other side of the third direction Y collectively constitute a fourth side 50d of the adhesive element 50. In the first direction X, the spacing between two adjacent sub-adhesive elements 51 is less than or equal to the smaller of the widths of the two adjacent sub-adhesive elements 51.

[0052] One embodiment of the present application further provides an electronic device comprising any of the above-described secondary batteries. The electronic device of the present application may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0053] The performance of the secondary battery provided in this application is described below through specific examples and comparative examples.

[0054] Example 1-1

[0055] Preparation of the positive electrode sheet: The positive electrode active material (lithium cobalt oxide), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) are dissolved in N-methylpyrrolidone solution at a weight ratio of 97.5:1:1.5 to form a positive electrode slurry with a solid content of 75%. Using aluminum foil as a current collector, the positive electrode slurry is applied to the surface of the positive electrode current collector to form the positive electrode active material layer. The negative electrode sheet is then cold pressed and cut.

[0056] Preparation of the negative electrode sheet: The negative electrode active material (graphite), conductive agent (conductive carbon black), thickener (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) are mixed in a mass ratio of 97.5:1:0.5:1. Deionized water is then added as a solvent and stirred to obtain a negative electrode slurry with a solid content of 50 wt%. Using copper foil as a current collector, the negative electrode slurry is applied to the surface of the negative electrode current collector to form the negative electrode active material layer. The negative electrode sheet is then cold pressed and cut into pieces.

[0057] Preparation of isolation film: Polyethylene film is selected as the isolation film.

[0058] Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) are mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 and the organic solvent are mixed in a weight ratio of 8:92 to obtain an electrolyte.

[0059] Preparation of a lithium-ion battery: The positive electrode sheet, polyethylene separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and then wound to form an electrode assembly. An adhesive is bonded to the surface of the electrode assembly, and the electrode assembly is placed in an aluminum-plastic film packaging bag. Heat-pressed at a preset pressure is applied, and the lithium-ion battery is obtained after liquid injection and formation. The spacing between the first electrode sheet layer in the first region and the second electrode sheet layer in the second region is greater. The electrode assembly has a length (L) of 86 mm and a width (W) of 62 mm. The adhesive comprises two sub-adhesives, each 50 mm long and 20 mm wide, with a spacing of 1 mm between the two sub-adhesives. The distance (L1) between the first side of the adhesive and the first end of the electrode assembly is 31 mm, the distance (L2) between the second side and the second end is 5 mm, the distance (W1) between the third side and the third end is 13 mm, and the distance (W2) between the fourth side and the fourth end is 8 mm.

[0060] Examples 1-2 to 1-18 and Comparative Examples 1-4

[0061] The difference from Example 1-1 is that at least one of L1 and L2 is different. Specific parameters are shown in Table 1.

[0062] The drop test and lithium deposition test were performed on each embodiment and comparative example, and the test results are shown in Table 1.

[0063] Test the distance between the first pole piece layer and the second pole piece layer:

[0064] The cross section is scanned using a CT device to measure the distance between the first pole piece layer and the second pole piece layer in the first region and the distance between the first pole piece layer and the second pole piece layer in the second region.

[0065] Drop test:

[0066] The lithium-ion batteries were preconditioned at 25°C and allowed to rest at room temperature for 60 minutes. The voltage of the lithium-ion batteries was then measured before the drop test. The batteries were then placed in a fixture and dropped from a height of 1.5m using a drop device in the following sequence: head-to-tail-head right corner-tail right corner-head left corner-tail left corner (angle: 45±15°), repeated six times. After the drop, the lithium-ion battery voltage was measured and recorded. The appearance of the lithium-ion batteries was inspected and photographed before and after the test. The drop test passing criteria were: no smoke, no leakage, and a voltage drop of <30mV. The voltage drop was measured using an internal resistance meter before and after the drop, with the voltage drop being the difference between the two values. Twenty samples were drop tested, and the drop pass rate was calculated as the number of samples that passed the drop test divided by 20.

[0067] Lithium deposition test:

[0068] At 25°C, charge the lithium-ion battery to 4.30V at a constant current of X (X = 1, 2, 3) C, then charge to 0.05C at a constant voltage of 4.30V and let it rest for 5 minutes; then discharge to 2.0V at a constant current of 1C and let it rest for 5 minutes. This is considered a cycle. After repeating 10 cycles, disassemble the battery in a fully charged state to obtain the negative electrode sheet. If any area of ​​the negative electrode sheet opposite to the first area is greater than or equal to 2mm 2 If lithium deposition occurs in the area of ​​the sample, it is determined to be lithium deposition. Take 20 samples for lithium deposition test, and X / 20 means that the number of samples with lithium deposition is X.

[0069] Table 1

[0070] By comparing the various embodiments and comparative examples in Table 1, it can be seen that when L1>L2, the probability of lithium deposition in the lithium-ion battery is lower. This is because when L1 is greater than L2, during the manufacturing pressurization process, the second region of the electrode assembly is subjected to greater pressure than the first region, thereby making the distance between the first electrode layer and the second electrode layer located in the first region greater than the distance between the first electrode layer and the second electrode layer located in the second region. The first region retains more electrolyte, thereby improving the lithium deposition phenomenon in the first region.

[0071] As can be seen from Table 1, compared with Examples 1-2, 1-3, 1-9, and 1-10, Examples 1-1 and 1-4 to 1-8 satisfy 0.3≤L1 / L≤0.6. When 0.3≤L1 / L≤0.6 is satisfied, the adhesive has sufficient dimensions in the first direction to ensure a firm bond between the electrode assembly and the housing, which is beneficial to improving the drop pass rate; and it can also ensure that during the manufacturing pressurization process, the pressure on the second region of the electrode assembly is greater than that on the first region, thereby making the spacing between the first electrode layer and the second electrode layer in the first region greater than the spacing between the first electrode layer and the second electrode layer in the second region, which is beneficial to improving lithium plating. Therefore, the drop pass rate is higher and the amount of lithium plating is less. Among Examples 1-1 and 1-4 to 1-8, Examples 1-1, 1-6, and 1-7 satisfy 0.35≤L1 / L≤0.45, and the effect of improving lithium plating and drop pass rate is better.

[0072] As can be seen from Table 1, compared with Examples 1-17 and 1-18, Examples 1-11 to 1-16 meet 0≤L2 / L≤0.2. When 0≤L2 / L≤0.2 is met, the adhesive has sufficient size in the first direction to ensure a firm bond between the electrode assembly and the housing, which is beneficial to improving the drop pass rate; and it can also ensure that during the manufacturing pressurization process, the pressure on the second region of the electrode assembly is greater than that on the first region, thereby making the spacing between the first electrode layer and the second electrode layer in the first region greater than the spacing between the first electrode layer and the second electrode layer in the second region, which is beneficial to improving lithium plating. Therefore, the drop pass rate is higher and the amount of lithium plating is less. Among Examples 1-11 to 1-16, Examples 1-12 to 1-14 meet 0.05≤L2 / L≤0.1, and the effect of improving the drop pass rate is better.

[0073] Example 2-1 to Example 2-18

[0074] The difference from Example 1-1 is that at least one of W1 and W2 is different. Specific parameters are shown in Table 2. Drop tests and lithium deposition tests were performed on each example, and the test results are shown in Table 2.

[0075] Table 2

[0076] As can be seen from Table 2, compared with Examples 2-8 and 2-9, Examples 2-1 to 2-7 and 1-1 meet 0≤W1 / W≤0.3. When 0≤W1 / W≤0.3 is met, the adhesive has sufficient size in the third direction Y to ensure a strong bond between the electrode assembly and the shell, so the drop pass rate is higher. It can also be seen from Table 2 that the W1 / W ratio does not affect lithium deposition. Among Examples 2-1 to 2-7 and 1-1, Examples 2-3 to 2-6 and 1-1 meet 0.1≤W1 / W≤0.25, and the effect of improving the drop pass rate is better.

[0077] As can be seen from Table 2, compared with Examples 2-17 and 2-18, Examples 2-10 to 2-16 and 1-1 meet 0≤W2 / W≤0.3. When 0≤W2 / W≤0.3 is met, the adhesive has sufficient size in the third direction Y to ensure a strong bond between the electrode assembly and the shell, so the drop pass rate is higher. It can also be seen from Table 2 that the W2 / W ratio does not affect lithium deposition. Among Examples 2-10 to 2-16 and 1-1, Examples 2-12 to 2-15 and 1-1 meet 0.1≤W2 / W≤0.25, and the effect of improving the drop pass rate is better.

[0078] Example 3-1 to Example 3-5

[0079] The difference from Example 1-1 lies in the difference in the width of the sub-adhesive members and the spacing between adjacent sub-adhesive members. See Table 3 for specific parameters. The number of sub-adhesive members is always two, designated as the first sub-adhesive member and the second sub-adhesive member in Table 3. The two sub-adhesive members are of equal length. The widths of the two sub-adhesive members may be equal or different depending on the embodiment. Each embodiment was subjected to a drop test and a lithium deposition test. The test results are shown in Table 3.

[0080] Table 3

[0081] As shown in Table 3, compared to Examples 3-3 to 3-8, Examples 1-1, 3-1, 3-2, 3-9, and 3-11 all meet the requirement that the spacing between adjacent sub-adhesive components is less than the smaller of the widths of two adjacent sub-adhesive components. This ensures sufficient bonding area between the adhesive component and the electrode assembly and the housing. Furthermore, the multiple sub-adhesive components spaced apart can disperse stress, resulting in a higher drop pass rate. Table 3 also shows that the spacing between adjacent sub-adhesive components does not affect lithium deposition.

[0082] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A secondary battery, comprising a housing, an electrode assembly, and a metal plate. The electrode assembly is accommodated in the housing. The metal plate is connected to the electrode assembly and extends out of the housing in a first direction. The electrode assembly includes a first electrode tab, a separator, and a second electrode tab that are sequentially stacked in a second direction perpendicular to the first direction. The first electrode tab includes a first electrode tab layer, and the second electrode tab includes a second electrode tab layer that is disposed adjacent to the first electrode tab layer in the second direction. It is characterized in that, the secondary battery further includes an adhesive member, and the electrode assembly further includes a first surface. The adhesive member is disposed on the first surface and bonds the electrode assembly and the housing; in the first direction, the first surface includes opposite first and second ends, the adhesive member includes first and second sides that are opposite in the first direction, the first side is closer to the first end than the second side, the distance between the first end and the first side is L1, the distance between the second end and the second side is L2, and L1 > L2; the electrode assembly includes a first region and a second region that are sequentially connected in the first direction. The adhesive member is disposed in the second region, and the distance between the first electrode tab layer and the second electrode tab layer in the first region is greater than the distance between the first electrode tab layer and the second electrode tab layer in the second region.

2. The secondary battery according to claim 1, characterized in that, in the first direction, the length of the electrode assembly is L, and 0.3 ≤ L1 / L ≤ 0.

6.

3. The secondary battery according to claim 2, characterized in that, 0.35 ≤ L1 / L ≤ 0.

45.

4. The secondary battery according to claim 1, characterized in that, 0 ≤ L2 / L ≤ 0.

2.

5. The secondary battery according to claim 4, wherein, 0.05 ≤ L2 / L ≤ 0.

1.

6. The secondary battery according to claim 1, wherein in a third direction perpendicular to both the first direction and the second direction, the first surface includes opposite third and fourth ends, the adhesive member includes a third side on one side of the third end and a fourth side on one side of the fourth end, and the first side, the third side, the second side, and the fourth side are sequentially connected; in the third direction, the width of the electrode assembly is W, the distance between the third end and the third side is W1, the distance between the fourth end and the fourth side is W2, and 0 ≤ W1 / W ≤ 0.3, 0 ≤ W2 / W ≤ 0.

3.

7. The secondary battery according to claim 6, wherein, 0.1 ≤ W1 / W ≤ 0.25, 0.1 ≤ W2 / W ≤ 0.

25.

8. The secondary battery according to claim 1, wherein the adhesive member includes a plurality of sub - adhesive members, and the plurality of sub - adhesive members are spaced apart on the first surface, and the distance between adjacent two sub - adhesive members is less than or equal to the smaller one of the widths of the adjacent two sub - adhesive members.

9. The secondary battery according to claim 1, wherein, the electrode assembly is arranged as a wound structure.

10. The secondary battery according to claim 9, characterized in that, the metal plate includes a first metal plate, the first metal plate is welded to the first electrode tab, and a welding mark is formed between the first metal plate and the first electrode tab; the secondary battery further includes an insulating layer, and the insulating layer covers the welding mark and part of the first metal plate.

11. The secondary battery according to claim 10, wherein, in the second direction, the adhesive member does not overlap with the first metal plate, and the adhesive member and the insulating layer do not overlap.

12. The secondary battery according to claim 1, wherein the adhesive member includes a first adhesive layer, a base material layer, and a second adhesive layer that are sequentially stacked. The first adhesive layer is bonded to the housing, and the second adhesive layer is bonded to the electrode assembly.

13. The secondary battery according to claim 12, characterized in that, The thickness of the bonding member is 10 to 50 mm.

14. The secondary battery according to claim 13, characterized in that, The thickness of the bonding member is 18 to 30 mm.

15. An electronic device, characterized in that, It includes a secondary battery according to any one of claims 1-14.

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