Secondary battery and electric device

Abstract

The present application discloses a secondary battery and an electric device. The secondary battery comprises a case, an electrode assembly, and first bonding members. The case comprises a first shell and a second shell welded to each other. The electrode assembly comprises first electrode sheets, second electrode sheets, and separators. Any separator is provided with a main body portion and an extension portion. In a first direction, the main body portions overlap the first electrode sheets, and the extension portions extend beyond the first electrode sheets. Each first bonding member comprises a first portion, a second portion, and a third portion that are sequentially arranged; the electrode assembly comprises a first surface and a second surface; the first portions are bonded to the first surface; the third portions are bonded to the second surface; when viewed in the first direction, the portion of each extension portion that is not covered by the corresponding first bonding member exceeds beyond the corresponding second portion in a second direction; each second portion is provided with a plurality of first holes; and the first holes run through the corresponding second portion in the second direction. The secondary battery is beneficial to reducing the interference of the extension portions on the welding of the first shell and the second shell, and taking into account the degree of infiltration of the electrode assembly.

Description

Secondary batteries and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202510322122.0, filed on March 18, 2025, entitled "Secondary Battery and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of energy storage technology, and specifically relates to a secondary battery and electrical equipment. Background Technology

[0003] Currently, the electrode components of stacked secondary batteries are typically encapsulated in steel shells to improve the strength and safety of the batteries. The shell usually consists of two parts, which are connected by a welding process. Summary of the Invention

[0004] The inventors of this application have discovered that when the electrode assembly of a secondary battery is installed into the casing, part of the separator may extend between the two parts of the casing that need to be welded together, interfering with the welding process of the casing, causing insufficient sealing at the welding position of the casing, resulting in a loss of yield.

[0005] In view of the above situation, it is necessary to provide a secondary battery to reduce the possibility of the separator interfering with the welding of the casing.

[0006] A first aspect of this application provides a secondary battery, which includes a casing, an electrode assembly, and at least one first adhesive member. The casing is made of a metallic material and includes a first casing and a second casing. The first casing and the second casing are disposed opposite to each other along a first direction. The first casing is welded to the second casing and together with the second casing forms a receiving cavity; the first direction is the thickness direction of the secondary battery. The electrode assembly is housed in the receiving cavity and includes a first electrode, a second electrode, and a separator. The first electrode and the second electrode have opposite polarities. Multiple first electrodes and multiple second electrodes are alternately stacked. Along the first direction, the orthographic projection of the second electrode is located within the orthographic projection range of the first electrode. A separator is disposed between any adjacent first electrode and second electrode. Each separator has a main body and an extension. When viewed along the first direction, the main body coincides with the first electrode, and the extension connects to the main body and extends beyond the first electrode. The first adhesive member includes a first part, a second part, and a third part arranged sequentially. The electrode assembly includes a first surface and a second surface arranged opposite each other along a first direction. The first part is bonded to the first surface, the third part is bonded to the second surface, and the second part connects the first part and the second part, and bonds a portion of the extension. Along a second direction, the portion of the extension is located between the first electrode and the second part, and the second direction is perpendicular to the first direction. Viewed along the first direction, the portion of the extension not covered by the first adhesive member extends beyond the second part in the second direction. The second part has multiple first holes, which penetrate the second part along the second direction.

[0007] In this secondary battery, the portion of the extension not covered by the first adhesive extends beyond the second portion in the second direction. In other words, the first adhesive applies pressure to the extension of the separator, causing the portion of the extension covered by the second portion to converge and be constrained towards the electrode assembly. This helps to reduce the possibility of the extension interfering with the connection between the first and second housings. Furthermore, the second portion has a first hole, which helps to increase the degree of electrolyte wetting of the electrode assembly, thereby reducing lithium plating in the secondary battery.

[0008] In one or more embodiments of this application, when viewed along the first direction, the width of the portion of the extension not covered by the first adhesive that extends beyond the second portion in the second direction is D, where 0.02mm≤D≤0.3mm. The fact that the portion of the extension not covered by the first adhesive extends beyond the second portion in the second direction by at least 0.02mm ensures that the pressure exerted by the first adhesive on the extension is not too low, thus improving the binding effect of the first adhesive on the release liner. Furthermore, the fact that the portion of the extension not covered by the first adhesive extends beyond the second portion in the second direction by at least 0.3mm reduces the likelihood of the extension entering the connection portion between the first and second housings.

[0009] In one or more embodiments of this application, viewed along a first direction, the first electrode includes a first side edge, and a first adhesive member covers at least a portion of the first side edge; along the extending direction of the first side edge, the total length of the plurality of first adhesive members is L1, and the length of the first side edge is L, where 0.7L≤L1≤L. Setting L1≥0.7L ensures that the ratio of the total length of the first adhesive member to the length of the first side edge is not too small, which is beneficial for improving the binding effect of the separator; setting L1≤L ensures that the ratio of the total length of the first adhesive member to the length of the first side edge is not too large, which is beneficial for saving materials.

[0010] In one or more embodiments of this application, in a first adhesive member, along the second direction, the orthographic projection area of ​​the second portion is S, and the total orthographic projection area of ​​the first hole is S1, where 0.2S ≤ S1 ≤ 0.65S. Setting S1 ≥ 0.2S ensures that the area ratio of the first hole to the second portion is not too small, which is beneficial for improving the electrolyte wetting effect of the electrode assembly; setting S1 ≤ 0.65S ensures that the area ratio of the first hole to the second portion is not too large, which is beneficial for improving the structural strength of the second portion.

[0011] In one or more embodiments of this application, the second portion includes a central region. Along the first direction, the width of the central region is equal to the width of the second portion. Along the third direction, the second portion includes a first end and a second end disposed opposite to each other. The length of the second portion is L2, and the length from the central region to both the first and second ends is 0.25L2. The first, second, and third directions are mutually perpendicular. The orthographic projection area of ​​the central region along the second direction is S2, and the total area of ​​the first hole located in the central region is S3, where 0.5S3≤S2. Setting S2≥0.5S3 ensures that the ratio of the area of ​​the first hole in the central region to the area of ​​the central region is not too small, which is beneficial to improving the electrolyte wetting effect of the electrode assembly.

[0012] In one or more embodiments of this application, the minimum distance from the first hole to the first surface along the first direction is D1, where D1 ≥ 0.8 mm. This helps to reduce the possibility of the separator protruding from the first hole, thereby reducing the possibility of the separator affecting the welding of the first housing and the second housing.

[0013] In one or more embodiments of this application, the minimum distance from the first hole to the second surface along the first direction is D2, where D2 ≥ 0.8 mm. This helps to reduce the possibility of the separator protruding from the first hole, thereby reducing the possibility of the separator affecting the welding of the first and second housings.

[0014] In one or more embodiments of this application, along the second direction, the projected area of ​​any first hole is S4, 0.24 mm. 2 ≤S4≤0.8mm 2 Set S4 ≥ 0.24 mm2 The area of ​​the first hole should not be too small, which is beneficial to improving the degree of electrolyte wetting of the electrode assembly. S4 should be set to ≤ 0.8 mm. 2 The area of ​​the first hole should not be too large, which helps to reduce the possibility of the separator membrane protruding from the first hole, thereby reducing the possibility of the separator membrane affecting the welding of the first shell and the second shell.

[0015] In one or more embodiments of this application, viewed along a first direction, the first electrode includes a first side, a second side, and a third side. A first adhesive member covers at least a portion of the first side. The second and third sides are disposed opposite to each other along the extending direction of the first side. The second side and the first side are smoothly connected by a first arc, with the second side perpendicular to the first side. The third side and the first side are smoothly connected by a second arc, with the third side perpendicular to the first side. The radius of the first arc is R1. Along the extending direction of the first side, the minimum distance between the first adhesive member and the second side is D3, where R1 + 0.2 mm ≤ D3. This reduces the likelihood of the first adhesive member adhering to the first arc, thereby increasing the contact area between the first adhesive member and the electrode assembly and reducing the possibility of the first adhesive member detaching.

[0016] In one or more embodiments of this application, the radius of the second arc is R2, and the minimum distance between the first adhesive and the third side along the extension direction of the first side is D4, where R2 + 0.2 mm ≤ D4. This reduces the likelihood of the first adhesive adhering to the second arc, thereby increasing the contact area between the first adhesive and the electrode assembly and reducing the possibility of the first adhesive detaching.

[0017] In one or more embodiments of this application, the width of the portion of the first part overlapping the first surface along the second direction is W1, where 1.5mm ≤ W1 ≤ 5mm. Setting W1 ≥ 1.5mm helps to increase the bonding area between the first part and the electrode assembly, thereby improving the stability of the connection between the first adhesive and the electrode assembly; setting W1 ≤ 5mm helps to save materials.

[0018] In one or more embodiments of this application, when the separator is flattened, the minimum width of the extension along the second direction is W2, where 0.1mm ≤ W2 ≤ 2mm. Setting W2 ≥ 0.1mm is beneficial for improving the insulation effect of the separator on the first and second electrodes, allowing for leeway for separator shrinkage and changes in the relative position of the separator and the electrodes, and reducing the possibility of short circuit between the first and second electrodes. Setting W2 ≤ 2mm is beneficial for saving materials and also for reducing the possibility of the separator interfering with the welding of the first and second housings.

[0019] In one or more embodiments of this application, along the second direction, the distance between the first electrode and the inner surface of the casing is W3, where 1mm ≤ W3 ≤ 2mm. Setting W3 ≥ 1mm ensures that the distance between the electrode assembly and the inner surface of the casing is not too small, which helps reduce the difficulty of inserting the electrode assembly into the casing and reduces the possibility of the casing squeezing the electrode assembly, thereby reducing lithium plating. In addition, it also helps reduce the possibility of the separator affecting the welding of the first and second casings. Setting W3 ≤ 2mm ensures that the distance between the electrode assembly and the inner surface of the casing is not too large, which helps to improve the energy density of the secondary battery.

[0020] A second aspect of the embodiments of this application provides an electrical device that includes a secondary battery as described in any of the foregoing embodiments. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of a secondary battery in one embodiment of this application.

[0022] Figure 2 is an exploded view of the secondary battery structure in one embodiment of this application.

[0023] Figure 3 is an exploded view of the secondary battery structure in one embodiment of this application.

[0024] Figure 4 is a schematic diagram of the cross-sectional structure at point IV-IV in Figure 1.

[0025] Figure 5 is a schematic diagram of the cross-sectional structure at point VV in Figure 2.

[0026] Figure 6 is a partial structural schematic diagram of the secondary battery in one embodiment of this application.

[0027] Figure 7 is a schematic diagram of the connection structure between the electrode assembly and the first adhesive in one embodiment of this application.

[0028] Figure 8 is a schematic diagram showing the relative positional relationship between the first electrode and the flattened separator in one embodiment of this application.

[0029] Figure 9 is a schematic diagram of the structure of an electrical device in one embodiment of this application.

[0030] Key Component Symbols: Secondary Battery 100; Casing 10; First Casing 11; Second Casing 12; Electrode Assembly 20; First Electrode 21; First Side 211; Second Side 212; Third Side 213; First Arc 214; Second Arc 215; Second Electrode 22; Separator 23; Main Body 231; Extension 232; Positive Electrode 201; Positive Current Collector 2011; Positive Active Material Layer 2012; Negative Electrode 202; Negative Current Collector 2021; Negative Active Material Layer 2022; First Surface 20a; Second Surface 20b; First Adhesive 30; First Part 31; Second Part 32; Third Part 33; First Hole 321; Central Region 32a; First End32b Second terminal 32c Connection terminal 40 Pole post 41 Pole lug bundle 42 Electrical equipment 1000 First direction X Second direction Y Third direction Z

[0031] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0033] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0036] In the description of the embodiments of this application, the term "perpendicular" is used to describe the ideal state between two components. In actual production or use, two components may exist in a state that is approximately perpendicular. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be approximately straight lines or planes. From a macroscopic perspective, if the overall extension direction is a straight line or plane, the component can be considered as a "straight line" or "plane".

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Where there is no conflict, the various embodiments in this application can be combined with each other.

[0038] An embodiment of this application provides a secondary battery, which includes a casing, an electrode assembly, and at least one first adhesive member. The casing is made of a metal material and includes a first casing and a second casing. The first casing and the second casing are disposed opposite to each other along a first direction. The first casing is welded to the second casing and together with the second casing forms a receiving cavity; the first direction is the thickness direction of the secondary battery. The electrode assembly is housed in the receiving cavity and includes a first electrode, a second electrode, and a separator. The first electrode and the second electrode have opposite polarities. Multiple first electrodes and multiple second electrodes are alternately stacked. Along the first direction, the orthographic projection of the second electrode is located within the orthographic projection range of the first electrode. A separator is disposed between any adjacent first electrode and second electrode. Each separator has a main body and an extension. When viewed along the first direction, the main body coincides with the first electrode, and the extension connects to the main body and extends beyond the first electrode. The first adhesive member includes a first part, a second part, and a third part arranged sequentially. The electrode assembly includes a first surface and a second surface arranged opposite each other along a first direction. The first part is bonded to the first surface, the third part is bonded to the second surface, and the second part connects the first part and the second part, and bonds a portion of the extension. Along a second direction, the portion of the extension is located between the first electrode and the second part, and the second direction is perpendicular to the first direction. Viewed along the first direction, the portion of the extension not covered by the first adhesive member extends beyond the second part in the second direction. The second part has multiple first holes, which penetrate the second part along the second direction.

[0039] In this secondary battery, the portion of the extension not covered by the first adhesive extends beyond the second portion in the second direction. In other words, the first adhesive applies pressure to the extension of the separator, causing the portion of the extension covered by the second portion to converge and be constrained towards the electrode assembly. This helps to reduce the possibility of the extension interfering with the connection between the first and second housings. Furthermore, the second portion has a first hole, which helps to increase the degree of electrolyte wetting of the electrode assembly, thereby reducing lithium plating in the secondary battery.

[0040] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0041] As shown in Figures 1 and 2, an embodiment of this application provides a secondary battery 100, which includes a housing 10 and an electrode assembly 20. The electrode assembly 20 is housed within the housing 10 and is used to store and release electrical energy.

[0042] In some embodiments, as shown in FIG1 and FIG2, the housing 10 is made of metal material and includes a first housing 11 and a second housing 12. The first housing 11 and the second housing 12 are disposed opposite to each other along a first direction X. The first housing 11 is welded to the second housing 12 and together with the second housing 12 forms a receiving cavity. The electrode assembly 20 is accommodated in the receiving cavity. The first direction X is the thickness direction of the secondary battery 100.

[0043] In some embodiments, as shown in FIG4, the electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separator 23. The first electrode 21 and the second electrode 22 have opposite polarities; in other words, one of the first electrode 21 and the second electrode 22 is a positive electrode 201, and the other is a negative electrode 202. Multiple first electrodes 21 and multiple second electrodes 22 are alternately stacked. Along the first direction X, the orthographic projection of the second electrode 22 lies within the orthographic projection range of the first electrode 21. A separator 23 is disposed between any adjacent first electrode 21 and second electrode 22 to insulate them from each other. Each separator 23 can be formed as a single separator 23; or, a single separator 23 can be folded to form a multilayer structure; or, the separator 23 can be a bag-like structure to house the electrode.

[0044] In some embodiments, as shown in FIG4, the positive electrode 201 includes a positive current collector 2011 and a positive active material layer 2012, wherein the positive active material layer 2012 is disposed on one or both sides of the positive current collector 2011 along its thickness direction.

[0045] In some embodiments, when the outermost electrode of the electrode assembly 20 is a positive electrode 201, the outermost positive electrode 201 is provided with a positive active material layer 2012 only on the surface of the positive current collector 2011 facing the interior of the electrode assembly 20. Here, "outermost layer" refers to the outermost layer considering only the relative positional relationship between the electrodes.

[0046] In some embodiments, the positive current collector 2011 is a metal layer. As an example, the positive current collector 2011 may be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil.

[0047] In some embodiments, the positive electrode active material layer 2012 includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0048] In some embodiments, as shown in FIG4, the negative electrode 202 includes a negative electrode current collector 2021 and a negative electrode active material layer 2022, wherein the negative electrode active material layer 2022 is disposed on one or both sides of the negative electrode current collector 2021 along its thickness direction.

[0049] In some embodiments, when the outermost electrode of the electrode assembly 20 is a negative electrode 202, the outermost negative electrode 202 is provided with a negative electrode active material layer 2022 only on the surface of the negative electrode current collector 2021 facing the interior of the electrode assembly 20. Here, "outermost layer" refers to the outermost layer considering only the relative positional relationship between the electrodes.

[0050] In some embodiments, the negative electrode current collector 2021 is a metal layer. As an example, the negative electrode current collector 2021 may be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as copper foil.

[0051] In some embodiments, the negative electrode active material layer 2022 includes a negative electrode active material, which includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials.

[0052] In some embodiments, the material of the separator 23 is one of polyethylene film, polypropylene film, polyester film or polyimide film.

[0053] In some embodiments, the secondary battery 100 further includes an electrolyte (not shown), which is contained in the housing 10 and used for ion transport. The electrolyte can be liquid, solid, or gel.

[0054] In some embodiments, the electrolyte comprises an electrolyte salt. The electrolyte salt comprises at least one of an organic lithium salt or an inorganic lithium salt.

[0055] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0056] In some embodiments, as shown in Figures 4 and 5, any layer of the separator 23 has a main body 231 and an extension 232. When viewed along the first direction X, the main body 231 overlaps with the first electrode 21, the extension 232 connects to the main body 231, and the extension 232 extends beyond the first electrode 21. As shown in Figures 2 and 3, the secondary battery 100 further includes at least one first adhesive member 30. The first adhesive member 30 includes a first portion 31, a second portion 32, and a third portion 33 arranged sequentially. The electrode assembly 20 includes a first surface 20a and a second surface 20b arranged opposite each other along a first direction X. The first portion 31 is bonded to the first surface 20a, the third portion 33 is bonded to the second surface 20b, and the second portion 32 connects the first portion 31 and the second portion 32 and bonds a portion of the extension 232. Along a second direction Y, the portion of the extension 232 is located between the first electrode 21 and the second portion 32. The second direction Y is perpendicular to the first direction X. When viewed along the first direction X, the portion of the extension 232 not covered by the first adhesive member 30 extends beyond the second portion 32 in the second direction Y. The second portion 32 has a plurality of first holes 321, which penetrate the second portion 32 along the second direction Y.

[0057] In this secondary battery 100, the portion of the extension 232 not covered by the first adhesive 30 extends beyond the second portion 32 in the second direction Y. In other words, the first adhesive 30 applies pressure to the extension 232 of the separator 23, causing the portion of the extension 232 covered by the second portion 32 to converge and be constrained towards the electrode assembly 20, thereby reducing the possibility of the extension 232 interfering with the connection between the first housing 11 and the second housing 12. Furthermore, the second portion 32 has a first hole 321, which helps to increase the degree of electrolyte wetting of the electrode assembly 20, thereby reducing lithium plating in the secondary battery 100.

[0058] In some embodiments, as shown in FIG6, when viewed along the first direction X, the portion of the extension 232 not covered by the first adhesive 30 extends beyond the second portion 32 in the second direction Y by a width D, where 0.02mm≤D≤0.3mm. Setting the portion of the extension 232 not covered by the first adhesive 30 to extend beyond the second portion 32 in the second direction Y by at least 0.02mm ensures that the pressure exerted by the first adhesive 30 on the extension 232 is not too weak, thus improving the binding effect of the first adhesive 30 on the release membrane 23. Setting the portion of the extension 232 not covered by the first adhesive 30 to extend beyond the second portion 32 in the second direction Y by at least 0.3mm also helps reduce the possibility of the extension 232 entering the connection portion between the first housing 11 and the second housing 12.

[0059] In some embodiments, as shown in FIG6, viewed along the first direction X, the first electrode 21 includes a first side 211, and the first adhesive member 30 covers at least a portion of the first side 211. Along the extending direction of the first side 211, the total length of the first adhesive member 30 is L1, and the length of the first side 211 is L, where 0.7L≤L1≤L. Setting L1≥0.7L ensures that the ratio of the total length of the first adhesive member 30 to the length of the first side 211 is not too small, which is beneficial for improving the binding effect of the separator 23; setting L1≤L ensures that the ratio of the total length of the first adhesive member 30 to the length of the first side 211 is not too large, which is beneficial for saving material. In this embodiment, the first adhesive member 30 provided on the first side 211 can be one or more. When multiple first adhesive members 30 are provided, the total length of the first adhesive members 30 refers to the sum of the lengths of the first adhesive members 30 provided on the first side 211. Multiple first adhesive members 30 can be spaced apart. Compared to the connection method where the first adhesive members 30 are connected by edges or partially overlapped, the spaced arrangement can save material and improve the degree of electrolyte wetting of the electrode assembly 20. It should be noted that in some embodiments, the first side 211 of the electrode assembly 20 is smoothly connected to other sides by an arc. When determining the length of the first side 211, only the straight extension is considered, excluding the arc. The boundary between the first side 211 and the arc is the inflection point between them.

[0060] In some embodiments, in a first adhesive member 30, along the second direction Y, the projected area of ​​the second portion 32 is S, and the total projected area of ​​the first hole 321 is S1, where 0.2S ≤ S1 ≤ 0.65S. Setting S1 ≥ 0.2S ensures that the area ratio of the first hole 321 to the second portion 32 is not too small, which is beneficial for improving the electrolyte wetting effect of the electrode assembly 20; setting S1 ≤ 0.65S ensures that the area ratio of the first hole 321 to the second portion 32 is not too large, which is beneficial for improving the structural strength of the second portion 32.

[0061] In some embodiments, as shown in FIG7, the second portion 32 includes a central region 32a. Along the first direction X, the width of the central region 32a is equal to the width of the second portion 32. Along the third direction Z, the second portion 32 includes a first end 32b and a second end 32c disposed opposite to each other. The length of the second portion 32 is L2, and the length from the central region 32a to the first end 32b and to the second end 32c is 0.25L2. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. The orthographic projection area of ​​the central region 32a along the second direction Y is S2, and the total area of ​​the first hole 321 located in the central region 32a is S3, where 0.5S3≤S2. Setting S2≥0.5S3 ensures that the ratio of the area of ​​the first hole 321 located in the central region 32a to the area of ​​the central region 32a is not too small, which is beneficial to improving the electrolyte wetting effect of the electrode assembly 20.

[0062] In some embodiments, as shown in FIG7, the minimum distance from the first hole 321 to the first surface 20a along the first direction X is D1, where D1 ≥ 0.8 mm. This helps to reduce the possibility of the isolation membrane 23 protruding from the first hole 321, thereby helping to reduce the possibility of the isolation membrane 23 affecting the welding of the first housing 11 and the second housing 12.

[0063] In some embodiments, as shown in FIG7, the minimum distance from the first hole 321 to the second surface 20b along the first direction X is D2, where D2 ≥ 0.8 mm. This helps to reduce the possibility of the isolation membrane 23 protruding from the first hole 321, thereby reducing the possibility of the isolation membrane 23 affecting the welding of the first housing 11 and the second housing 12.

[0064] In some embodiments, along the second direction Y, the projected area of ​​any first hole 321 is S4, 0.24 mm. 2 ≤S4≤0.8mm 2 Set S4 ≥ 0.24 mm 2 The area of ​​the first hole 321 should not be too small, which is beneficial to improving the degree of electrolyte wetting of the electrode assembly 20. S4 is set to ≤ 0.8 mm. 2 The area of ​​the first hole 321 is not too large, which helps to reduce the possibility of the isolation membrane 23 protruding from the first hole 321, thereby reducing the possibility of the isolation membrane 23 affecting the welding of the first housing 11 and the second housing 12.

[0065] In some embodiments, as shown in FIG6, viewed along a first direction X, the first electrode 21 includes a first side 211, a second side 212, and a third side 213. A first adhesive 30 covers at least a portion of the first side 211. The second side 212 and the third side 213 are disposed opposite each other along the extending direction of the first side 211. The second side 212 and the first side 211 are smoothly connected by a first arc 214, and the second side 212 is perpendicular to the first side 211. The third side 213 and the first side 211 are smoothly connected by a second arc 215, and the third side 213 is perpendicular to the first side 211.

[0066] In some embodiments, as shown in FIG6, the radius of the first arc 214 is R1, and the minimum distance between the first adhesive 30 and the second side 212 along the extension direction of the first side 211 is D3, where R1 + 0.2 mm ≤ D3. This reduces the likelihood of the first adhesive 30 adhering to the first arc 214, thereby increasing the contact area between the first adhesive 30 and the electrode assembly 20 and reducing the possibility of the first adhesive 30 detaching.

[0067] In some embodiments, as shown in FIG6, the radius of the second arc 215 is R2, and the minimum distance between the first adhesive 30 and the third side 213 along the extension direction of the first side 211 is D4, where R2 + 0.2 mm ≤ D4. This reduces the likelihood of the first adhesive 30 adhering to the second arc 215, thereby increasing the contact area between the first adhesive 30 and the electrode assembly 20 and reducing the possibility of the first adhesive 30 detaching.

[0068] In some embodiments, the width of the portion of the first part 31 overlapping with the first surface 20a along the second direction Y is W1, where 1.5mm ≤ W1 ≤ 5mm. Setting W1 ≥ 1.5mm helps to increase the bonding area between the first part 31 and the electrode assembly 20, thereby improving the stability of the connection between the first adhesive 30 and the electrode assembly 20; setting W1 ≤ 5mm helps to save materials.

[0069] In some embodiments, as shown in FIG8, when the separator 23 is flattened, the minimum width of the extension 232 along the second direction Y is W2, 0.1mm≤W2≤2mm. Setting W2≥0.1mm is beneficial to improving the insulation effect of the separator 23 on the first electrode 21 and the second electrode 22, leaving room for the inward shrinkage of the separator 23 and the relative position change of the separator 23 and the electrode, and reducing the possibility of short circuit between the first electrode 21 and the second electrode 22; setting W2≤2mm is beneficial to saving materials on the one hand, and to reducing the possibility of the separator 23 interfering with the welding of the first housing 11 and the second housing 12 on the other hand. In the embodiments of this application, when calculating W2, the width of the separator 23 along the second direction Y is measured first, and then the width of the first electrode 21 along the second direction Y is measured, W2 = (width of the separator 23 along the second direction Y - width of the first electrode 21 along the third direction Z) / 2. It should be noted that, in this embodiment, the flattened state of the separator 23 refers to the flattened state of the single-layer separator 23 located between the first electrode 21 and the second electrode 22. For a scheme in which a single separator 23 is folded in a Z-shape to form a multi-layer structure, the separator 23 of different layers is divided by the creases produced by the folding.

[0070] In some embodiments, as shown in FIG6, the distance between the first electrode 21 and the inner surface of the housing 10 along the second direction Y is W3, where 1mm ≤ W3 ≤ 2mm. Setting W3 ≥ 1mm ensures that the distance between the electrode assembly 20 and the inner surface of the housing 10 is not too small, which helps to reduce the difficulty of inserting the electrode assembly 20 into the housing and reduces the possibility of the housing 10 squeezing the electrode assembly 20, thereby reducing lithium plating. In addition, it also helps to reduce the possibility of the separator 23 affecting the welding of the first housing 11 and the second housing 12. Setting W3 ≤ 2mm ensures that the distance between the electrode assembly 20 and the inner surface of the housing 10 is not too large, which helps to improve the energy density of the secondary battery 100.

[0071] In some embodiments, as shown in Figures 1 and 4, the secondary battery 100 further includes a connection terminal 40, which is connected to the electrode assembly 20 and is located on the side of the electrode assembly 20 along the third direction Z. A portion of the connection terminal extends out of the housing 100, and the connection terminal 40 is used to connect the secondary battery to an external circuit.

[0072] In some embodiments, as shown in FIG4, the connection terminal 40 includes a pole post 41 and a tab bundle 42. The tab bundle 42 includes a plurality of tabs, each tab being connected to an electrode plate. The tabs are gathered together along a first direction X to form the tab bundle 42. The tab bundle 42 is connected to the pole post 41. The pole post 41 is connected to the housing 10 and exposed to the outside of the housing 10. The pole post 41 is used to connect the electrode assembly 20 to an external circuit.

[0073] As shown in FIG9, an embodiment of this application further provides an electrical device 1000, which includes a secondary battery 100 as described in any of the foregoing embodiments.

[0074] In some embodiments, the electrical device 1000 includes, but is not limited to, a mobile phone, a laptop computer, an electric toy, and a power tool.

[0075] To verify the effectiveness of the technical solutions in the embodiments of this application, the inventors conducted the following experiments. The experiments included 32 experimental groups, of which 2 groups were comparative examples and the remaining 30 groups were implementation examples. The number of secondary batteries 100 in each group was determined based on the number of tests it participated in subsequently.

[0076] The preparation process of the secondary battery 100 in Example 1 includes the following steps:

[0077] (1) Preparation of positive electrode 201: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNTs (carbon nanotubes), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material with a solid content of 75 wt%, and the mixture was stirred evenly for later use. A 10 μm thick aluminum foil was used as the positive electrode current collector 2011. The above active material was uniformly coated onto one side of the positive electrode current collector 2011 using a slot coater, and then dried at 90°C to obtain a positive electrode 201 with a single-sided coating of the positive electrode active material. At this time, the thickness of the positive electrode active material layer 2012 was 50 μm. The above coating steps were then repeated on the other side of the positive electrode current collector 2011. The coated positive electrode sheet 201 is then cold-pressed, resulting in a positive electrode active material layer 2012 thickness of 35 μm. The area of ​​the positive electrode current collector 2011 not covered by the positive electrode active material layer 2012 is the positive electrode empty foil area, which is then die-cut to obtain the positive electrode tab. It should be noted that multiple positive electrode sheets 201 are prepared in this step, with two positive electrode sheets 201 having the positive electrode active material layer 2012 coated only on one side of the positive electrode current collector 2011, serving as the two outermost electrodes of the electrode assembly 20.

[0078] (2) Preparation of negative electrode 202: Artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2. Deionized water was added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and the mixture was stirred evenly for later use. A copper foil with a thickness of 10 μm was used as the negative electrode current collector 2021. The above negative electrode active material was uniformly coated onto one side of the negative electrode current collector 2021 using a slot coater, and then dried at 110°C to obtain a negative electrode 202 with a single-sided coating of negative electrode active material layer 2022. At this time, the thickness of the negative electrode active material layer 2022 was 55 μm. The above steps were then repeated on the other side of the negative electrode current collector 2021 to obtain a negative electrode 202 with negative electrode active material layers 2022 coated on both sides. The coated negative electrode sheet 202 is then cold-pressed, and the thickness of the negative electrode active material layer 2022 after cold pressing is 45μm. The area of ​​the negative electrode current collector 2021 that is not covered by the negative electrode active material layer 2022 is the negative electrode empty foil area, and the negative electrode empty foil area is die-cut to obtain the negative electrode tab;

[0079] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0080] (4) Preparation of the isolation membrane 23: A 7 μm thick porous polyethylene polymer film was used as the isolation membrane 23;

[0081] (5) Preparation of electrode assembly 20: Multiple positive electrode sheets 201, multiple separators 23 and multiple negative electrode sheets 202 are stacked alternately along the first direction XX; positive electrode tabs are gathered and welded along the first direction X to form a positive electrode tab bundle, and negative electrode tabs are gathered and welded along the first direction X to form a negative electrode tab bundle; a first adhesive member 30 is bonded to the periphery of the electrode assembly 20 to bind the extension 232 of the separator 23, and a first hole 321 is provided on the first adhesive member 30;

[0082] (6) Assembly of the secondary battery 100: The electrode assembly 20 is placed into the second housing 12 with a receiving cavity, and the first housing 11 is welded to the second housing 12. After electrolyte injection, encapsulation, settling, hot pressing and other processes are performed to obtain the secondary battery 100. In the obtained secondary battery 100, D1 = D2.

[0083] The preparation process of the secondary battery 100 in Comparative Example 1 is basically the same as that in Example 1. The difference is that the electrode assembly 20 of the secondary battery 100 in Comparative Example 1 is not bonded to the first adhesive 30.

[0084] The preparation process of the secondary battery 100 in Comparative Example 2 is basically the same as that in Example 1. The difference is that the first adhesive 30 of the secondary battery 100 in Comparative Example 2 does not have a first hole 321.

[0085] The preparation process of the secondary battery 100 in Examples 2 to 30 is basically the same as that in Example 1. The difference is that some parameters of the secondary battery 100 in Examples 2 to 30 are different from those in Example 1. The specific differences are recorded in the experimental results table.

[0086] After the secondary batteries 100 in each experimental group were prepared, the following experiments were conducted, and the experimental results were recorded in the table.

[0087] 1. Sealing test

[0088] Ten secondary batteries 100 were randomly selected from each experimental group for a sealing test, and no further tests were conducted on the selected secondary batteries 100.

[0089] The sealing test specifically includes the following steps:

[0090] 1) Determine the testing standards

[0091] In the experiments of this application, the acceptable threshold for leakage rate was set to be less than or equal to 1 × 10⁻⁶. -7 Pa·m 3 / s;

[0092] 2) Prepare equipment and materials

[0093] Required equipment includes: a helium mass spectrometer leak detector (sensitivity ≤ 1×10⁻⁶). -8 Pa·m 3 / s), special fixtures or vacuum chambers (adapted to the size of the battery cells to avoid deformation), high-purity helium (≥99.999%), vacuum pump sets and battery cell pretreatment equipment.

[0094] 3) Pretreatment of secondary batteries 100

[0095] Cleaning: Remove residual electrolyte and dust from the surface of the secondary battery 100;

[0096] Drying: Bake at 50℃ for 2 hours to reduce internal moisture interference;

[0097] Let stand: Cool to room temperature to avoid thermal expansion and contraction affecting the seal.

[0098] 4) Leak testing of secondary battery 100 was performed using the vacuum hood method.

[0099] The vacuum chamber method involves placing the secondary battery 100 into a sealed vacuum chamber, evacuating it, filling it with helium, and detecting changes in the helium concentration inside the chamber to assess the sealing performance of the secondary battery 100's casing 10. The method specifically includes the following steps:

[0100] ① Fix the secondary battery 100 inside the vacuum chamber, ensuring the sealing ring fits snugly to prevent deformation caused by external pressure;

[0101] ② Start the vacuum pump group and evacuate in stages. Specifically, first use a mechanical pump to pre-evacuate to 1 Pa, and then use a molecular pump to evacuate to ≤1×10-3 Pa.

[0102] ③ Inject helium into the vacuum chamber to the set pressure, which is 500 Pa in this experiment;

[0103] ④ Monitor the leakage rate with a helium mass spectrometer for 5 minutes;

[0104] ⑤ Record and calculate the peak leakage rate Q. If it exceeds the threshold, it is considered unqualified.

[0105] The calculation formula is: Q=(ΔC˙V) / t; where, ΔC: helium concentration change, V: vacuum chamber volume, t: detection time;

[0106] ⑥ Use a helium recovery system to reduce losses and discharge residual helium to a safe concentration (<1%).

[0107] 5) Result Determination and Processing

[0108] If the leakage rate is ≤1×10 -7 Pa·m 3 If the leakage rate is / s, then the secondary battery 100 is considered to have no concentrated leakage points and is judged to be qualified; otherwise, it is unqualified. Record the number of qualified secondary batteries 100 and calculate the pass rate of the sealing test, and record it in Table 1.

[0109] 6) Count the number of explosion points

[0110] The secondary batteries 100 used in the test were observed using a high-powered microscope. The total number of burst points in each experimental group was counted and recorded in Table 1.

[0111] 2. Wetting test

[0112] Ten secondary batteries 100 were randomly selected from each experimental group for wettability testing, and no other tests were performed on the selected secondary batteries 100.

[0113] The wettability test process specifically includes the following steps:

[0114] At 25°C, the secondary battery is charged at a constant current of 0.5C until the voltage reaches the full charge voltage, then charged at a constant voltage of the full charge voltage until the current reaches 0.05C, and discharged at 0.2C until the voltage reaches 3.0V; this process is repeated 10 times.

[0115] Then, the secondary battery 100 was disassembled and the lithium plating area in the center of the secondary battery 100 was observed. If the lithium plating area was ≤5%, the secondary battery 100 was considered to be qualified in terms of electrolyte wetting. The number of qualified secondary batteries 100 was recorded in Table 1.

[0116] Table 1 Note: In Table 1, " / " indicates that the data is not found.

[0117] As shown in Table 1, in Examples 1 to 30, the electrode assembly 20 of the secondary battery 100 is provided with a first adhesive 30 to constrain the extension 232 of the separator 23. Compared with Comparative Example 1, the secondary batteries 100 in Examples 1 to 30 have fewer burst points and a higher pass rate in the sealing test. It can be seen that the first adhesive 30 applies pressure to the extension 232 of the separator 23, causing the part of the extension 232 covered by the second part 32 to converge and be constrained towards the electrode assembly 20, thereby reducing the possibility of the extension 232 interfering with the connection between the first housing 11 and the second housing 12. Compared with Comparative Example 2, the secondary batteries 100 in Examples 1 to 30 have a higher pass rate in the wettability test. It can be seen that the second part 32 has a first hole 321, which helps to improve the degree of electrolyte wettability of the electrode assembly 20, thereby reducing lithium plating in the secondary battery 100.

[0118] In Examples 1 to 3, the secondary battery 100 satisfies 0.02mm≤D≤0.3mm. Compared with Example 4, the secondary battery 100 in Examples 1 to 3 has fewer burst points and a higher pass rate in the sealing test. It can be seen that the portion of the extension 232 not covered by the first adhesive 30 extends beyond the second portion 32 in the second direction Y by no more than 0.3mm, which helps to reduce the possibility of the extension 232 entering the connection portion of the first housing 11 and the second housing 12. On this basis, the portion of the extension 232 not covered by the first adhesive 30 extends beyond the second portion 32 in the second direction Y by no less than 0.02mm, so that the pressure of the first adhesive 30 on the extension 232 is not too small, which helps to improve the binding effect of the first adhesive 30 on the separator 23.

[0119] In Examples 2, 6, and 7, the secondary battery 100 satisfies L1 / L≥0.7. Compared to Example 5, the secondary battery 100 in Examples 2, 6, and 7 has fewer burst points and a higher pass rate in the sealing test. It can be seen that setting L1≥0.7L ensures that the ratio of the total length of the first adhesive member 30 to the length of the first side 211 is not too small, which is beneficial to improving the binding effect of the separator 23. On this basis, setting L1≤L ensures that the ratio of the total length of the first adhesive member 30 to the length of the first side 211 is not too large, which is beneficial to saving materials.

[0120] In Examples 2, 9, and 10, the secondary battery 100 satisfies 0.2S≤S1≤0.65S. Compared to Example 8, the secondary batteries 100 in Examples 2, 9, and 10 have a higher pass rate in the wettability test. It can be seen that setting S1≥0.2S ensures that the area ratio of the first hole 321 to the second part 32 is not too small, which is beneficial to improving the effect of electrolyte wetting of the electrode assembly 20. Furthermore, there is no significant difference in the pass rate of the secondary battery 100 in Examples 10 and 11 in the wettability test. It can be seen that setting S1≤0.65S ensures that the area ratio of the first hole 321 to the second part 32 is not too large, which is beneficial to improving the structural strength of the second part 32.

[0121] In Examples 2, 13, and 14, the secondary battery 100 satisfies 0.5S3≤S2. Compared with Example 12, the secondary battery 100 in Examples 2, 13, and 14 has a higher pass rate in the wettability test. It can be seen that by setting S2≥0.5S3, the ratio of the area of ​​the first hole 321 in the central region 32a to the area of ​​the central region 32a is not too small, which is beneficial to improving the effect of electrolyte wetting of the electrode assembly 20.

[0122] In Examples 2 and 16, the secondary battery 100 satisfies D1≥0.8mm. Compared with Example 15, the secondary battery 100 in Examples 2 and 16 has fewer burst points and a higher pass rate in the sealing test. It can be seen that setting D1≥0.8mm is beneficial to reducing the possibility of the separator 23 protruding from the first hole 321, thereby reducing the possibility of the separator 23 affecting the welding of the first housing 11 and the second housing 12.

[0123] In Examples 2, 17, and 18, the secondary battery 100 meets the requirement of 0.24 mm. 2 ≤S4≤0.8mm 2 Compared to Example 19, the secondary batteries 100 in Examples 2, 17, and 18 have fewer burst points and a higher pass rate in the sealing test. This demonstrates that setting S4 ≤ 0.8 mm is effective. 2The area of ​​the first hole 321 is not too large, which helps to reduce the possibility of the separator 23 protruding from the first hole 321, thereby reducing the possibility of the separator 23 affecting the welding of the first housing 11 and the second housing 12; based on this, S4 is set to ≥ 0.24 mm. 2 The area of ​​the first hole 321 is not too small, which is conducive to the electrolyte passing through the first hole 321, thereby increasing the degree of electrolyte wetting of the electrode assembly 20.

[0124] 3. Tensile test

[0125] In Examples 2, 20 to 22, 10 secondary batteries 100 were randomly selected for tensile testing, and no other tests were performed on the selected secondary batteries 100.

[0126] The tensile test process specifically includes the following steps:

[0127] Discharge the secondary battery 100 to 3.0V, then disassemble the secondary battery 100. Remove the outermost electrode of the electrode assembly 20 and the first adhesive piece 30 bonded to it as a whole, and wipe the electrolyte off the surface with a lint-free paper. Then cut the first adhesive piece 30 and the outermost electrode into strip-shaped samples. Along the length of the sample, adhere the side of the outermost electrode without the first adhesive piece 30 to the steel plate using double-sided adhesive (Nitto 5000NS), with an adhesion length of not less than 15mm. The steel plate was fixed in the corresponding position on the high-speed rail tensile testing machine. One end of the first adhesive component 30 on the other side of the sample was pulled up and clamped in the clamp. The part of the first adhesive component 30 that was pulled up made an angle of 180° with the steel plate in space. The clamp pulled the sample at a speed of 5±0.2 mm / s. The average tensile force in the stable region was recorded as the peel strength between the first adhesive component 30 and the first electrode 21. The peel strength of the secondary batteries 100 in the same group was taken as the average value, and the unit was N / mm. The stable region refers to the part of the graph where the tensile force of the clamp pulling the first adhesive component 30 does not change significantly over time. The test results are recorded in Table 2.

[0128] Table 2

[0129] As can be seen from Table 2, in Examples 2, 21, and 22, the secondary battery 100 satisfies 1.5mm≤W1. Compared with Example 20, the secondary battery 100 in Examples 2, 21, and 22 has a higher average peel strength in the tensile test. It can be seen that setting W1≥1.5mm is beneficial to increasing the bonding area between the first part 31 and the electrode assembly 20, thereby improving the stability of the connection between the first adhesive 30 and the electrode assembly 20. On this basis, setting W1≤5mm is beneficial to saving materials.

[0130] 4. Withstand Voltage Test (Hi-pot Test)

[0131] In Examples 2, 23 to 26, 10 secondary batteries 100 were randomly selected for voltage withstand testing, and no other tests were performed on the selected secondary batteries 100.

[0132] The withstand voltage test process specifically includes the following steps:

[0133] The experiment consists of two parts: a roller test and a Hi-pot test performed sequentially. The roller test process includes the following steps:

[0134] 1) Preparation before testing

[0135] Environmental conditions: Temperature 25℃, Humidity 75%RH;

[0136] Battery status: Fully charged to 100% SOC;

[0137] Equipment calibration: Ensure that parameters such as roller speed and drop height meet the standards;

[0138] 2) Test parameter settings

[0139] Roller specifications: Inner wall is made of stainless steel, diameter 1.5m, width 50cm;

[0140] Rotational speed: 5 revolutions per minute;

[0141] Number of tests: 100 cycles (one cycle = 1 clockwise rotation + 1 counterclockwise rotation);

[0142] Drop height: The secondary battery 100 is dropped freely from the highest point of the inner wall of the drum to the bottom (simulating a drop impact of 1-1.5m);

[0143] 3) Test Procedure

[0144] Secure the battery cell: Fix the secondary battery 100 to the inner wall of the drum using clamps, ensuring that it is not loose;

[0145] Start the test: Run the roller at the set speed and record the number of tests and the time.

[0146] Real-time monitoring:

[0147] • Observe for signs of leakage, smoke, fire, explosion, etc.

[0148] • Monitor the surface temperature of the secondary battery 100 (immediate shutdown is required if the temperature exceeds 80°C);

[0149] 4) Post-test evaluation

[0150] • Visual inspection: Deformation, damage, and electrolyte leakage of the casing; stop testing if damage is found.

[0151] • If no breakage or leakage occurs, continue with the Hi-pot test.

[0152] The specific process of the Hi-pot test is as follows:

[0153] Connect the secondary battery 100 to the high-voltage tester. Detect the leakage current generated by the electrode assembly 20 under the test voltage output by the high-voltage tester. Then calculate the resistance value: test voltage / leakage current. Compare the calculated resistance value with the set judgment resistor. If the detected resistance value is greater than or equal to the preset value, the tested product is deemed to have passed the test (OK). If the detected resistance value is less than the preset value, the test voltage is instantly cut off, and the tested product is deemed to have failed the test (NG). In this test, the preset value of the judgment resistor is 5mΩ. When the measured resistance value is less than 5mΩ, it indicates that the battery can conduct but the resistance value is too small, indicating a short circuit. The product is deemed NG. The presence of a short circuit may reflect the shrinkage of the separator, causing a short circuit between the positive and negative electrodes. When the resistance value is greater than or equal to 5mΩ, the product is deemed OK. Calculate the number of secondary batteries that pass the test. The test pass rate = number of secondary batteries that pass the test / 10. The test structure is recorded in Table 3.

[0154] Table 3

[0155] As shown in Tables 1 and 3, in Examples 2 and 24 to 25, the secondary battery 100 satisfies 0.1mm ≤ W2 ≤ 2mm. Compared with Example 23, the secondary battery 100 in Examples 2 and 24 to 25 has a higher pass rate in the Hi-pot test. It can be seen that setting W2 ≥ 0.1mm is beneficial to improving the insulation effect of the separator 23 on the first electrode 21 and the second electrode 22, leaving room for the inward shrinkage of the separator 23 and the relative position change of the separator 23 and the electrode, and reducing the possibility of short circuit between the first electrode 21 and the second electrode 22. Compared with Example 26, the secondary battery 100 in Examples 2 and 24 to 25 has fewer burst points and a higher pass rate in the sealing test. It can be seen that setting W2 ≤ 2mm is beneficial to reducing the possibility of the separator 23 interfering with the welding of the first shell 11 and the second shell 12.

[0156] 5. Energy density test

[0157] In Examples 2, 27 to 30, 10 secondary batteries were randomly selected for energy density testing, and no further testing was conducted on the selected secondary batteries.

[0158] The energy density testing process specifically includes the following steps:

[0159] Place the secondary battery 100 in a 25°C constant temperature chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge the secondary battery 100 at a constant current of 0.5C until it reaches the full charge voltage, then charge it at a constant voltage of 0.05C until the current reaches 0.2C, and discharge it at 0.2C until the voltage reaches 3.0V. Record the discharge energy.

[0160] Volumetric energy density = Discharge energy / (Length of secondary battery × Width of secondary battery × Thickness).

[0161] The volumetric energy density of the 10 secondary batteries 100 in the experimental group participating in the test should be taken as the average value, and the test results are recorded in Table 4.

[0162] Table 4

[0163] As shown in Tables 1 and 4, in Examples 2, 28, and 29, the secondary battery 100 satisfies 1mm ≤ W3 ≤ 2mm. Compared to Example 27, the secondary batteries 100 in Examples 2, 28, and 29 have fewer burst points and a higher pass rate in the sealing test. It is evident that setting W3 ≥ 1mm ensures that the distance between the electrode assembly 20 and the inner surface of the housing 10 is not too small, which helps to reduce the possibility of the separator affecting the welding of the first housing 11 and the second housing 12. Compared to Example 30, the secondary batteries 100 in Examples 2, 28, and 29 have a higher average volumetric energy density. It is evident that setting W3 ≤ 2mm ensures that the distance between the electrode assembly 20 and the inner surface of the housing 10 is not too large, which helps to improve the energy density of the secondary battery 100.

[0164] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application.

Claims

1. A secondary battery, characterized in that, include: The housing is made of metal and includes a first housing and a second housing. The first housing and the second housing are disposed opposite to each other along a first direction. The first housing is welded to the second housing and together with the second housing forms a receiving cavity. The first direction is the thickness direction of the secondary battery. An electrode assembly is housed in the receiving cavity. The electrode assembly includes a first electrode, a second electrode, and a separating membrane. The first electrode and the second electrode have opposite polarities. Multiple first electrodes and multiple second electrodes are alternately stacked. Along the first direction, the orthographic projection of the second electrode is located within the orthographic projection range of the first electrode. A layer of the separating membrane is disposed between any adjacent first electrode and second electrode. Each layer of the separating membrane has a main body and an extension. When viewed along the first direction, the main body coincides with the first electrode, and the extension connects to the main body and extends beyond the first electrode. At least one first adhesive member, the first adhesive member comprising a first part, a second part and a third part arranged sequentially, the electrode assembly comprising a first surface and a second surface arranged opposite to each other along a first direction, the first part being bonded to the first surface, the third part being bonded to the second surface, the second part connecting the first part and the second part and bonding a portion of the extension, the extension being located between the first electrode and the second part along a second direction, the second direction being perpendicular to the first direction; When viewed along the first direction, the portion of the extension not covered by the first adhesive extends beyond the second portion in the second direction; The second part has a plurality of first holes, which penetrate the second part along the second direction.

2. The secondary battery as described in claim 1, characterized in that, Viewed along the first direction, the portion of the extension not covered by the first adhesive extends beyond the second portion by a width D in the second direction, where 0.02mm≤D≤0.3mm.

3. The secondary battery as described in claim 1, characterized in that, Viewed along the first direction, the first electrode includes a first side, and the first adhesive covers at least a portion of the first side; Along the extension direction of the first side, the total length of the plurality of first adhesive members is L1, the length of the first side is L, and 0.7L≤L1≤L.

4. The secondary battery as described in any one of claims 1-3, characterized in that, In one of the first adhesive components, along the second direction, the orthographic projection area of ​​the second portion is S, and the total orthographic projection area of ​​the first hole is S1, where 0.2S≤S1≤0.65S.

5. The secondary battery as described in claim 4, characterized in that, The second part includes a central region, and the width of the central region along the first direction is equal to the width of the second part; Along the third direction, the second part includes a first end and a second end that are disposed opposite to each other, the length of the second part is L2, and the length of the central region from the first end and the second end is 0.25L2; the first direction, the second direction and the third direction are perpendicular to each other; The orthographic projection area of ​​the central region along the second direction is S2, and the total area of ​​the first hole located in the central region is S3, where 0.5S2≤S3.

6. The secondary battery as described in claim 1, characterized in that, Along the first direction, the minimum distance from the first hole to the first surface is D1, where D1 ≥ 0.8 mm; and / or Along the first direction, the minimum distance from the first hole to the second surface is D2, where D2 ≥ 0.8 mm.

7. The secondary battery as described in claim 1, characterized in that, Along the second direction, the projected area of ​​any one of the first holes is S4, 0.24 mm. 2 ≤S4≤0.8mm 2 .

8. The secondary battery as described in claim 1, characterized in that, Viewed along the first direction, the first electrode includes a first side, a second side, and a third side, the first adhesive covers at least a portion of the first side, and the second side and the third side are disposed opposite to each other along the extending direction of the first side; The second side and the first side are smoothly connected by a first arc, and the second side is perpendicular to the first side; The third side and the first side are smoothly connected by a second arc, and the third side is perpendicular to the first side; The secondary battery satisfies at least one of conditions a and b: a. The radius of the first arc is R1, and the minimum distance between the first adhesive and the second side along the extension direction of the first side is D3, where R1+0.2mm≤D3; b. The radius of the second arc is R2. Along the extension direction of the first side, the minimum distance between the first adhesive and the third side is D4, where R2 + 0.2 mm ≤ D4.

9. The secondary battery as described in claim 1, characterized in that, The width of the portion of the first part that overlaps with the first surface along the second direction is W1, where 1.5mm ≤ W1 ≤ 5mm.

10. The secondary battery as described in claim 1, characterized in that, When the isolation film is flattened, the minimum width of the extension along the second direction is W2, where 0.1mm ≤ W2 ≤ 2mm.

11. The secondary battery as described in claim 1, characterized in that, Along the second direction, the distance between the first electrode and the inner surface of the housing is W3, where 1mm ≤ W3 ≤ 2mm.

12. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 11.

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