Secondary batteries, methods for manufacturing secondary batteries, and electronic devices for them.

Abstract

This application discloses a secondary battery, a method for manufacturing a secondary battery, and an electronic device. The secondary battery includes a casing, an electrolyte, and an electrode assembly, with the electrode assembly and electrolyte disposed within the casing. The electrode assembly includes at least two electrode composites and a plurality of first electrodes stacked together. Each electrode composite includes a second electrode and two separators. Each separator includes a first portion, a second portion, and a third portion, with the third portion connected between the first and second portions. The first portions of the two separators are bonded together to form a first composite portion, and the second portions of the two separators are bonded together to form a second composite portion. Parts of the first composite portions of the at least two electrode composites are stacked and bonded together to form a first composite element, and parts of the second composite portions of the at least two electrode composites are stacked and bonded together to form a second composite element. This application can improve the drop performance of the secondary battery and enhance its safety performance while reducing energy density loss.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a secondary battery, a method for manufacturing the secondary battery, and an electronic device thereof. Background Technology

[0002] Stacked batteries are widely used in electronic products such as mobile phones and laptops, and have extremely high requirements for battery safety performance. During a drop, the electrolyte can easily impact the separator of the electrode assembly, causing the separator to shrink and potentially leading to a short circuit between the cathode and anode electrodes.

[0003] In related technologies, to improve the safety performance of batteries during drops, adhesive wrapping is usually applied to the sides and bottom of the electrode assembly. However, applying adhesive wrapping increases the thickness of the electrode assembly, which is not conducive to improving the energy density of the battery. Currently, the separator edge thermal bonding method is usually used to prevent separator shrinkage. However, the redundancy after separator edge thermal bonding is not properly handled, which can easily lead to an increase in battery width and the risk of separator entering the packaging shell, resulting in poor sealing. Summary of the Invention

[0004] In view of this, it is necessary to provide a secondary battery that can improve the drop performance and enhance safety performance while reducing battery energy density loss.

[0005] An embodiment of the first aspect of this application provides a secondary battery, including: a casing, an electrolyte, and an electrode assembly, wherein the electrode assembly and the electrolyte are disposed in the casing; the electrode assembly includes at least two electrode composites and a plurality of first electrodes stacked together, the electrode composites being disposed between two adjacent first electrodes. Each electrode composite includes a second electrode and two separators stacked together, the second electrodes having opposite polarities to the first electrodes. Along the width direction of the electrode assembly, each separator includes a first portion, a second portion, and a third portion, the third portion being connected between the first and second portions; a second electrode is disposed between the third portions of the two separators; the first portions of the two separators are bonded together to form a first composite portion; and the second portions of the two separators are bonded together to form a second composite portion. Parts of the first composite portions of at least two electrode composites are stacked and bonded together to form a first composite element; and parts of the second composite portions of at least two electrode composites are stacked and bonded together to form a second composite element. The third part, the second electrode, and the first electrode are stacked to form the main body of the electrode assembly. Along the width direction of the electrode assembly, the main body has a first side and a second side opposite to each other. The first composite part tapers towards the first side, and the second composite part tapers towards the second side. The housing includes a first shell part and a second shell part. Along the thickness direction of the electrode assembly, the depth of the first shell part is less than the depth of the second shell part, and the first composite part extends towards the second shell part.

[0006] By bonding portions of the first and second composite parts of the two electrode composites together, the bonding strength and structural strength between the separators on both sides of the electrode assembly in the width direction are improved. This makes it less likely for the separators to separate when the electrolyte impacts the first and second parts, reducing the risk of short circuits between the first and second electrodes. Compared to the case where the first and second composite parts are not closed, closing them on both sides of the main body helps to reduce the overall width of the electrode assembly, thereby increasing the energy density of the secondary battery. Compared to the first shell, the second shell has a deep pit surface. The first composite part faces the deep pit surface of the shell, allowing the end of the first composite part away from the main body to face the deep pit surface. This makes it less likely for the end of the first composite part to extend into the connection between the first and second shells, which is beneficial for shell encapsulation and improves the sealing performance. The secondary battery in this embodiment can improve the drop performance of the secondary battery and enhance its safety performance while reducing energy density loss.

[0007] In at least one embodiment, along the thickness direction of the electrode assembly, the first composite portions of at least two electrode composites are inclined toward the same side and partially stacked and bonded to form a first composite.

[0008] Relative to a single first composite part, the first composite parts are tilted toward the same side and laminated together, and the thickness of at least a portion of the thickness of the at least two first composite parts after lamination is superimposed, which can further improve the structural strength of the first composite parts.

[0009] In at least one embodiment, along the thickness direction of the electrode assembly, the second composite portions of at least two electrode composites are inclined toward the same side and partially stacked and bonded to form a second composite.

[0010] In contrast to a single second composite part, the second composite parts are stacked and bonded together with the same inclination towards the same side, and the thickness of at least a portion of the two stacked second composite parts is superimposed, which can further improve the structural strength of the second composite parts.

[0011] In at least one embodiment, along the thickness direction of the electrode assembly, the first composite portions of at least two electrode composites are brought together in a direction that brings them closer to each other and are partially stacked and bonded to form a first composite. The first composite is inclined toward one side of the electrode assembly in the thickness direction and is brought together in a direction that brings it closer to the first side.

[0012] At least two first composite parts are bonded together by being brought close together. The thickness of the first composite part formed after bonding is superimposed, thereby improving the structural strength at the location of the first composite part, making it less likely for the separators of the secondary battery to separate due to electrolyte impact during a drop. The first composite part is tilted and gathered on the first side, which can reduce the dimension of the electrode assembly in the width direction, thereby helping to reduce the volume of the secondary battery and reduce the volumetric energy density loss of the secondary battery.

[0013] In at least one embodiment, along the thickness direction of the electrode assembly, the second composite portions of at least two electrode composites are brought closer to each other and partially stacked and bonded to form a second composite, the second composite being inclined toward one side of the electrode assembly thickness direction and brought closer to the second side.

[0014] At least two second composite parts are bonded together by being brought close together. The resulting second composite parts have overlapping thicknesses, thereby increasing the structural strength at the location of the second composite parts. This makes it less likely for the separators of the secondary battery to separate due to electrolyte impact during a drop. In addition, the tilting and convergence of the second composite parts to the second side can further reduce the width dimension of the electrode assembly, which helps to reduce the volume of the secondary battery and reduce the volumetric energy density loss of the secondary battery.

[0015] In at least one embodiment, the end of the second composite member away from the third portion extends toward the interior of the second shell portion.

[0016] The end of the second composite part away from the main body can face the pit surface, so that the end of the second composite part is not easy to extend into the position where the first shell part and the second shell part are connected, which is beneficial to the encapsulation of the shell.

[0017] In at least one embodiment, the width of the first portion along the width direction of the electrode assembly is D1, 0.9mm≤D1≤2.0mm; and / or, the width of the second portion along the width direction of the electrode assembly is D2, 0.9mm≤D2≤2.0mm.

[0018] When the width of the first part is satisfied (0.9mm ≤ D1 ≤ 2.0mm), the width of the first part is not too small, so that the first part has sufficient length to bond with the adjacent first part, and the width of the first part is not too large, thus not occupying the volume of the secondary battery and causing a loss in the volumetric energy density of the secondary battery. Similarly, when the width of the second part is satisfied (0.9mm ≤ D2 ≤ 2.0mm), the width of the second part is not too small, so that the second part has sufficient length to bond with the adjacent second part, and the width of the second part is not too large, thus not occupying the volume of the secondary battery and causing a loss in the volumetric energy density of the secondary battery.

[0019] In at least one embodiment, the adhesive force between two adjacent diaphragms is F, where 2N / 10mm≤F≤5N / 10mm.

[0020] When 2N / 10mm≤F≤5N / 10mm is satisfied, there is sufficient adhesion between the diaphragms, making it less likely for the diaphragms to separate from each other, which is beneficial to the formation of the first composite and the second composite.

[0021] In at least one embodiment, the housing includes a main body and side seals. The main body has a cavity in which an electrode assembly is disposed. A first housing portion has a first extension disposed on both sides of the first housing portion in its width direction. A second housing portion has a second extension disposed on both sides of the second housing portion in its width direction. Along a direction away from the main body, the first extension and the second extension gradually converge to form a side seal. The side seal includes an unsealed area and an encapsulated area. The unsealed area is the region where the first extension and the second extension gradually converge but are not adhered to each other, and the encapsulated area is the region where the first extension and the second extension adhere to each other. The unsealed area connects the encapsulated area and the main body, and communicates with the cavity. Along the width direction of the housing, the width of the unsealed area is W, where 0.5mm ≤ W ≤ 1mm.

[0022] By gathering the first and second parts of the separator to the first and second sides, the first and second parts are limited, making it difficult for the first and second composite components to enter the unsealed area, reducing the risk of the separator entering the unsealed area. This allows the width of the unsealed area to be designed to be smaller, i.e., W≤1mm, resulting in a smaller overall width of the side sealing edge, which is beneficial to improving the volumetric energy density of the secondary battery. In addition, W≥0.5 avoids interference between the sealing head and the cell body, preventing damage to the cell.

[0023] In at least one embodiment, 0.5mm ≤ W ≤ 0.7mm.

[0024] While reducing stress concentration at the side sealing edge, further reduce the volumetric energy density loss of the secondary battery.

[0025] In at least one embodiment, the housing includes a main body and side seals. The main body has a cavity in which an electrode assembly is disposed. A first housing portion has a first extension located on both sides of the first housing portion in its width direction. A second housing portion has a second extension located on both sides of the second housing portion in its width direction. Along a direction away from the main body, the first extension and the second extension gradually converge to form a side seal. The side seal is a double-folded edge, and the side seal converges on both sides of the main body in its width direction. The thickness of the secondary battery is H1, and the height of the side seal along the thickness direction of the secondary battery is H2, where H2 ≤ H1 ≤ 2.4 mm.

[0026] The folding of the side seals helps reduce the thickness of the secondary battery. The height of the folded side seals does not exceed the overall thickness of the secondary battery, which facilitates the design of ultra-thin secondary batteries, reducing their volume and increasing their volumetric energy density.

[0027] The second aspect of this application provides a method for manufacturing a secondary battery, used to manufacture the secondary battery in any of the above embodiments. The method for manufacturing the secondary battery includes:

[0028] Lamination: Electrode composites are laminated between two adjacent first electrodes, with at least two electrode composites having their first composite portions stacked together, and at least two electrode composites having their second composite portions stacked together; at least two electrode composites are laminated with multiple first electrodes to form an electrode assembly. Thermal bonding: The first composite portions are heated to bond the stacked first composite portions together, and the second composite portions are heated to bond the stacked second composite portions together.

[0029] The thermal bonding process enables different first composite parts to bond together, thereby improving the structural strength at the location of the first composite part; it also enables different second composite parts to bond together, thereby improving the structural strength at the location of the second composite part. This makes it less likely for the parts to be washed away by the electrolyte when the secondary battery is dropped, thus improving the overall drop resistance of the secondary battery.

[0030] In at least one embodiment, the lamination step further includes preparing an electrode composite, the electrode composite preparation step including: providing two isolation films and a plurality of second electrodes; stacking the second electrodes between the two isolation films along the thickness direction of the isolation films; spacing the plurality of second electrodes between the two isolation films along the length direction of the isolation films, the two isolation films and the plurality of second electrodes forming a composite component; and cutting the isolation films using a laser cutting process at positions between two adjacent second electrodes along the length direction of the composite component, so that the composite component is separated to form a plurality of electrode composites.

[0031] The preparation of electrode composites facilitates the fabrication of multiple electrode composites. Furthermore, the laser cutting process enables the separation of different electrode composites. Simultaneously, the high temperature generated by laser cutting can melt and fuse the diaphragm at the cutting location, improving the structural stability between the diaphragm and the second electrode in a single electrode composite.

[0032] In at least one embodiment, the thermal bonding step includes: heat-pressing to bring the first composite portion toward the main body of the electrode assembly, wherein during the bringing-to-close process, the first composite portions of at least two electrode composites are inclined on the same side along the thickness direction of the electrode assembly, and the inclined first composite portions approach and bond with each other; heat-pressing to bring the second composite portion toward the main body of the electrode assembly, wherein during the bringing-to-close process, the second composite portion is inclined on the same side along the thickness direction of the electrode assembly, and the inclined second composite portions approach and bond with each other.

[0033] The hot stamping process facilitates the deformation of the first and second composite parts, allowing them to converge on both sides of the main body. Furthermore, the high temperature of the hot stamping activates the adhesiveness of the first and second composite parts, causing them to bond together. This improves the stability of the first and second composite parts converging on the main body and enhances the structural strength of the electrode assembly.

[0034] In at least one embodiment, the thermal bonding step includes: along the thickness direction of the electrode assembly, hot-pressing at least two mutually stacked first composite parts to be brought closer to each other, and the hot-pressed first composite parts are partially bonded to each other; along the thickness direction of the electrode assembly, hot-pressing at least two mutually stacked second composite parts to be brought closer to each other, and the hot-pressed second composite parts are partially bonded to each other.

[0035] Compared to a single first composite part, the thickness of at least two first composite parts bonded together is superimposed, thereby improving the structural strength at the location of the first composite part; compared to a single second composite part, the thickness of at least two second composite parts bonded together is superimposed, making it less likely for the separators of the secondary battery to be separated by electrolyte impact during drop, thus improving the drop performance of the secondary battery.

[0036] In at least one embodiment, the thermal bonding step includes: pushing a first composite portion along the thickness direction of the electrode assembly using a heat-pressing member, such that the laminated adhesive portion of the first composite portion is inclined toward the same side of the thickness direction of the electrode assembly; and pushing a second composite portion along the thickness direction of the electrode assembly using a heat-pressing member, such that the laminated adhesive portion of the second composite portion is inclined toward the same side of the thickness direction of the electrode assembly.

[0037] When the first composite layer and the second composite layer are tilted to the same side, the width dimension of the electrode assembly can be reduced, which helps to reduce the volume of the secondary battery and reduce the volumetric energy density loss of the secondary battery.

[0038] In at least one embodiment, the method of manufacturing a secondary battery further includes: encapsulation: an electrode assembly is inserted into a first shell portion of a housing, such that the end of a first composite portion away from the third portion is received in a second shell portion, and the end of a second composite portion away from the third portion is received in the second shell portion, and the second shell portion of the housing covers the first shell portion; along the thickness direction of the electrode assembly, the depth of the first shell portion is less than the depth of the second shell portion.

[0039] By housing the ends of the first composite portion and the second composite portion away from the third portion in the first housing portion, the influence of the housing encapsulation can be reduced by reducing the distance between the ends of the first composite portion and the second composite portion away from the third portion and the connection between the first housing portion and the second housing portion.

[0040] An embodiment of the third aspect of this application provides an electronic device including the secondary battery in any of the above embodiments.

[0041] In secondary batteries for electronic devices, bonding and bonding between separators can improve the battery's drop resistance, thus making the electronic device less susceptible to damage from drops. Attached Figure Description

[0042] Figure 1 This is a perspective view of a secondary battery in one embodiment of this application.

[0043] Figure 2 This is a cross-sectional view of an electrode assembly in one embodiment of this application.

[0044] Figure 3 This is a cross-sectional view of the diaphragm in one embodiment of this application.

[0045] Figure 4 This is a cross-sectional view of an electrode composite in one embodiment of this application.

[0046] Figure 5 This is a cross-sectional view of the electrode assembly in one embodiment of this application, showing the laminated and bonded state of the first composite part.

[0047] Figure 6 This is a cross-sectional view of an electrode assembly in one embodiment of the present application, showing the first composite portion tilted toward the same side in the thickness direction of the electrode assembly.

[0048] Figure 7 This is a cross-sectional view of the electrode composite in one embodiment of this application with the diaphragm in the deployed state.

[0049] Figure 8 This is a cross-sectional view of a secondary battery in one embodiment of this application.

[0050] Figure 9 This is a cross-sectional view of a secondary battery in another embodiment of this application.

[0051] Figure 10 This is a cross-sectional view showing the side sealing edge of the housing in one embodiment of this application.

[0052] Figure 11 This is a schematic diagram illustrating the stacking steps in one embodiment of this application.

[0053] Figure 12 This is a cross-sectional view of the composite component in one embodiment of this application.

[0054] Figure 13 This is a top view of one embodiment of the present application, showing the stacked state of the isolation diaphragm and the second electrode.

[0055] Figure 14 This is a schematic diagram illustrating the processing state of the electrode assembly by the thermal bonding equipment in one embodiment of this application.

[0056] Figure 15 This is a schematic diagram of an electronic device in one embodiment of this application.

[0057] Explanation of main component symbols

[0058] 1000, Electronic device; 100, Secondary battery; 10, Electrode assembly; 10a, Main body; 101, First side; 102, Second side; 11, First electrode; 111, First current collector; 112, First active material layer; 12, Electrode composite; 121, Second electrode; 1211, Second current collector; 1212, Second active material layer; 122, Separator; 122a, First composite part; 122b, Second composite part; 122c, First composite component; 122d, Second composite component; 1221, Base film; 1222, Adhesive layer; 1223, First part; 1223a, First end; 1224, Second part; 12 24a, Second end; 1225, Third part; 20, Shell; 20a, Shell body; 20b, Side seal; 201, Cavity; 202, Unsealed area; 203, Encapsulated area; 204, First curved section; 205, First extension section; 206, Second curved section; 207, Second extension section; 22, First shell part; 211, First extension part; 21, Second shell part; 221, Second extension part; 200, Device body; 300, Isolation diaphragm; 400, Composite component; X, First direction; Y, Second direction; L1, Centerline; 2000, Thermal composite equipment; 2001, Bearing component; 2002, Upper pressing component; 2003, Hot stamping component.

[0059] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Stacked batteries are widely used in electronic products such as mobile phones and laptops, and have extremely high requirements for battery safety performance. During a drop, the electrolyte can easily impact the separator of the electrode assembly, causing the separator to shrink and potentially leading to a short circuit between the cathode and anode electrodes.

[0064] In related technologies, to improve the safety performance of batteries during drops, adhesive wrapping is usually applied to the sides and bottom of the electrode assembly. However, applying adhesive wrapping increases the thickness of the electrode assembly, which is not conducive to improving the energy density of the battery. Currently, the separator edge thermal bonding method is usually used to prevent separator shrinkage. However, the redundancy after separator edge thermal bonding is not properly handled, which can easily lead to an increase in battery width and the risk of separator entering the packaging shell, resulting in poor sealing.

[0065] This application provides a secondary battery, including: a casing, an electrolyte, and an electrode assembly, with the electrode assembly and electrolyte disposed within the casing. The electrode assembly includes at least two stacked electrode composites and a plurality of first electrodes, with the electrode composites disposed between adjacent first electrodes. Each electrode composite includes stacked second electrodes and two separators, the second electrodes having opposite polarities to the first electrodes. Along the width direction of the electrode assembly, each separator includes a first portion, a second portion, and a third portion, the third portion connecting the first and second portions, and the second electrode disposed between the third portions of the two separators. The first portions of the two separators are bonded together to form a first composite portion, and the second portions of the two separators are bonded together to form a second composite portion. Parts of the first composite portions of the at least two electrode composites are stacked and bonded together to form a first composite element, and parts of the second composite portions of the at least two electrode composites are stacked and bonded together to form a second composite element. The third part, the second electrode, and the first electrode are stacked to form the main body of the electrode assembly. Along the width direction of the electrode assembly, the main body has a first side and a second side opposite to each other. The first composite part tapers towards the first side, and the second composite part tapers towards the second side. The housing includes a first shell part and a second shell part. Along the thickness direction of the electrode assembly, the depth of the first shell part is less than the depth of the second shell part, and the first composite part extends towards the second shell part.

[0066] By bonding portions of the first and second composite parts of the two electrode composites together, the bonding strength and structural strength between the separators on both sides of the electrode assembly in the width direction are improved. This makes it less likely for the separators to separate when the electrolyte impacts the first and second parts, reducing the risk of short circuits between the first and second electrodes. Compared to the case where the first and second composite parts are not closed, closing them on both sides of the main body helps to reduce the overall width of the electrode assembly, thereby increasing the energy density of the secondary battery. Compared to the first shell, the second shell has a deep pit surface. The first composite part faces the deep pit surface of the shell, allowing the end of the first composite part away from the main body to face the deep pit surface. This makes it less likely for the end of the first composite part to extend into the connection between the first and second shells, which is beneficial for shell encapsulation and improves the sealing performance. The secondary battery in this embodiment can improve the drop performance of the secondary battery and enhance its safety performance while reducing energy density loss.

[0067] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0068] like Figure 1 and Figure 2 As shown, a first embodiment of this application provides a secondary battery 100, which includes an electrode assembly 10, a housing 20, and an electrolyte (not shown). The electrode assembly 10 and the electrolyte are disposed within the housing 20. The electrode assembly 10 includes at least two electrode composites 12 and a plurality of first electrodes 11 stacked together, with the electrode composites 12 disposed between adjacent first electrodes 11. The electrode composites 12 include second electrodes 121 and two separators 122 stacked together.

[0069] In some embodiments, the housing 20 is a flexible packaging bag, such as an aluminum-plastic film. In other embodiments, the housing 20 is a rigid outer shell, such as a plastic shell, or a metal shell including at least one of steel alloys, aluminum alloys, and copper alloys.

[0070] In some embodiments, an electrolyte (not shown) is injected into the housing 20, and the electrolyte components include solvents, electrolyte salts, and additives.

[0071] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0072] 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).

[0073] In some embodiments, the first electrode 11 and the second electrode 121 have opposite polarities. For example, the first electrode 11 is an anode electrode and the second electrode 121 is a cathode electrode. Another example is that the first electrode 11 is a cathode electrode and the second electrode 121 is an anode electrode.

[0074] Please see Figure 2 In some embodiments, the first electrode 11 includes a first current collector 111 and a first active material layer 112. The first active material layer 112 is disposed on at least one surface of the first current collector 111 along its thickness direction, and a diaphragm 122 is disposed between the first active material layer 112 and the second electrode 121. The thickness direction of the first current collector 111 is a first direction X. For example, the first active material layer 112 is disposed on both sides of the first current collector 111.

[0075] Please see Figure 2 In some embodiments, the second electrode 121 includes a second current collector 1211 and a second active material layer 1212. Along the thickness direction of the second electrode 121, the second current collector 1211 has two opposing surfaces, and the thickness direction of the second electrode 121 is consistent with the thickness direction of the second current collector 1211. At least one of the second current collectors 1211 is provided with the second active material layer 1212; for example, both surfaces of the second current collector 1211 are provided with the second active material layer 1212.

[0076] Taking the first electrode 11 as the anode electrode and the second electrode 121 as the cathode electrode as an example, the first current collector 111 and the second current collector 1211 can be metal layers. The first current collector 111 can be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 1211 can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0077] Taking the first electrode 11 as the anode electrode and the second electrode 121 as the cathode electrode as an example, the first active material layer 112 is anode-polarized and includes an anode active material, which may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials. The second active material layer 1212 is cathode-polarized and includes a cathode active material, which may include 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.

[0078] Please see Figure 3In some embodiments, the diaphragm 122 includes a base membrane 1221. Along the thickness direction of the base membrane 1221, the base membrane 1221 has two surfaces, and an adhesive layer 1222 is provided on each surface so that when the diaphragm 122 is combined with the second electrode 121, the diaphragm 122 and the second electrode 121 can be bonded together.

[0079] Please see Figure 4 In some embodiments, along the width direction of the electrode assembly 10, the diaphragm 122 includes a first portion 1223, a second portion 1224, and a third portion 1225, with the third portion 1225 connected between the first portion 1223 and the second portion 1224. A second electrode 121 is disposed between the third portions 1225 of the two diaphragms 122. The thickness direction of the electrode assembly 10 is a first direction X, and the width direction of the electrode assembly 10 is a second direction Y. Figure 4 As shown, the second electrode 121 and the two diaphragms 122 are stacked along the thickness direction of the electrode assembly 10. The first portions 1223 of the two diaphragms 122 are bonded together to form a first composite portion 122a, and the second portions 1224 of the two diaphragms 122 are bonded together to form a second composite portion 122b.

[0080] At least two electrode composites 12 have portions of their first composite portion 122a stacked and bonded together to form a first composite 122c, and portions of their second composite portion 122b stacked and bonded together to form a second composite 122d.

[0081] By bonding portions of the first composite portion 122a and the second composite portion 122b of the two electrode composites 12 together, the bonding strength and structural strength between the separators 122 on both sides of the electrode assembly 10 in the width direction are improved. This makes it less likely for the separators 122 to separate when the electrolyte impacts the first portion 1223 and the second portion 1224, reducing the risk of short circuit between the first electrode 11 and the second electrode 121. Compared to the method of attaching adhesive to the sides and bottom of the electrode assembly 10, the volume of the secondary battery 100 is reduced, thereby improving the drop performance of the secondary battery 100 and enhancing its safety performance while reducing energy density loss.

[0082] Please see Figure 2 and Figure 4In some embodiments, the third portion 1225, the second electrode 121, and the first electrode 11 are stacked to form the main body 10a of the electrode assembly 10. Along the width direction of the electrode assembly 10, the main body 10a has a first side 101 and a second side 102 opposite to each other. The first composite portion 122a is drawn closer to the first side 101. The first composite portion 122a is drawn closer to the first side 101. The drawing closer to the first side 101 can be along the thickness direction of the electrode assembly 10, upward or downward, so that the first composite portion 122a is drawn closer to or even attached to the first side 101 after being drawn closer. The second composite portion 122b is drawn closer to the second side 102. The drawing closer to the second side 102 can be along the thickness direction of the electrode assembly 10, upward or downward, so that the second composite portion 122b is drawn closer to or even attached to the second side 102 after being drawn closer. Figure 4 The first composite part 122a and the second composite part 122b are shown in an unfolded state. Figure 2 The state after the first composite part 122a and the second composite part 122b are closed is shown.

[0083] Compared to the case where the first composite portion 122a and the second composite portion 122b are not closed, the first composite portion 122a and the second composite portion 122b are closed on both sides of the main body portion 10a, which helps to reduce the overall width of the electrode assembly 10 and thereby increase the energy density of the secondary battery 100.

[0084] Please see Figure 2 In some embodiments, along the thickness direction of the electrode assembly 10, the first composite portions 122a of at least two electrode composites 12 are inclined toward the same side and partially stacked and bonded to form a first composite 122c. For example... Figure 2 As shown in the figure, the electrode assembly 10 includes three first electrode plates 11 and two electrode plate composites 12 as an example. The first composite parts 122a are all tilted towards the same side and converge towards the first side 101 of the main body part 10a by tilting.

[0085] Relative to a single first composite portion 122a, at least two first composite portions 122a are tilted toward the same side and stacked and bonded together. The thickness of at least a portion of the stacked first composite portions 122a is superimposed, which can further improve the structural strength of the first composite portion 122a.

[0086] Please see Figure 2In some embodiments, along the thickness direction of the electrode assembly 10, at least two second composite portions 122b of the electrode composites 12 are inclined toward the same side and partially stacked and bonded to form a second composite 122d. The second composite portions 122b are all inclined toward the same side and converge toward the second side 102 of the main body portion 10a by this inclination. By shaping the first composite portion 122a and the second composite portion 122b, the impact of the unfolding of the first portion 1223 and the second portion 1224 of the diaphragm 122 on the encapsulation of the housing 20 is reduced.

[0087] Relative to a single second composite portion 122b, the second composite portions 122b are inclined toward the same side and are stacked and bonded together. The thickness of at least a portion of the stacked second composite portions 122b is superimposed, which can further improve the structural strength of the second composite portions 122b.

[0088] Please see Figure 5 and Figure 6 In some embodiments, along the thickness direction of the electrode assembly 10, the first composite portions 122a of at least two electrode composites 12 converge toward each other and are partially stacked and bonded to form a first composite 122c. The first composite 122c is inclined toward one side of the electrode assembly 10 in the thickness direction and converges toward the first side 101.

[0089] For example, in the thickness direction of the electrode assembly 10, the electrode assembly 10 has a center line L1, and the first composite portions 122a located on both sides of the center line L1 converge toward the center line L1, so that the first composite portions 122a are bonded to each other near the center line L1, and the bonded first composite portions 122a form a first composite 122c that is inclined toward one side of the center line L1. Figure 5 The image shows the state after the first composite part 122a is brought together towards the center line L1 and partially laminated and bonded. Figure 6 The image shows the state in which the laminated bonding portion (first composite 122c) of the first composite part 122a is tilted toward one side of the electrode assembly 10 in the thickness direction.

[0090] At least two first composite parts 122a are bonded together by being brought close together. The thickness of the first composite part 122c formed after bonding is the sum of the thicknesses of the two first composite parts 122a, thereby improving the structural strength at the location of the first composite part 122c. This makes it less likely for the separators 122 of the secondary battery 100 to separate due to electrolyte impact during a drop. After the first composite part 122c is tilted and gathered on the first side 101, the dimension in the width direction of the electrode assembly 10 can be reduced, which helps to reduce the volume of the secondary battery 100 and reduce the volumetric energy density loss of the secondary battery 100.

[0091] Please see Figure 5 and Figure 6In some embodiments, along the thickness direction of the electrode assembly 10, the second composite portions 122b of at least two electrode composites 12 converge toward each other and are partially stacked and bonded to form a second composite 122d, the second composite 122d being inclined toward one side of the electrode assembly 10 in the thickness direction.

[0092] For example, in the thickness direction of the electrode assembly 10, the second composite portions 122b located on both sides of the center line L1 converge toward the center line L1, thereby causing the second composite portions 122b to adhere to each other near the center line L1, and the second composite portions 122b after being adhered to each other form a second composite 122d that is inclined toward one side of the center line L1. Figure 5 The image shows the state after the second composite part 122b is converged towards the center line L1 and partially laminated and bonded. Figure 6 The image shows the state in which the laminated bonding portion (second composite 122d) of the second composite part 122b is tilted toward one side of the electrode assembly 10 in the thickness direction.

[0093] At least two second composite portions 122b are bonded together by being brought close together. The thickness of the second composite member 122d formed after bonding is the sum of the thicknesses of the at least two second composite portions 122b, thereby improving the structural strength at the location of the second composite member 122d. This makes it less likely for the separators 122 of the secondary battery 100 to separate due to electrolyte impact during a drop. In addition, the tilting and convergence of the second composite member 122d to the second side 102 can further reduce the width dimension of the electrode assembly 10, thereby helping to reduce the volume of the secondary battery 100 and reduce the volumetric energy density loss of the secondary battery 100.

[0094] Please see Figure 7 In some embodiments, along the width direction of the electrode assembly 10, the width of the second electrode 121 is the same as the width of the third portion 1225, and the first portion 1223 and the third portion 1225 are the portions of the diaphragm 122 that extend beyond the width of the second electrode 121. The width of the first portion 1223 and the width of the second portion 1224 are the widths in the width direction of the electrode assembly 10 when unfolded.

[0095] Please see Figure 7 In some embodiments, the width of the first portion 1223 along the width direction of the electrode assembly 10 is D1, where 0.9mm ≤ D1 ≤ 2.0mm. Satisfying 0.9mm ≤ D1 ≤ 2.0mm ensures that the width of the first portion 1223 is not too small, allowing it to have sufficient length to bond with adjacent portions, and preventing it from occupying too much space in the secondary battery 100, thus minimizing volumetric energy density loss in the secondary battery 100.

[0096] Please see Figure 7In some embodiments, the width of the second portion 1224 along the width direction of the electrode assembly 10 is D2, where 0.9mm ≤ D2 ≤ 2.0mm. Satisfying 0.9mm ≤ D2 ≤ 2.0mm ensures that the width of the second portion 1224 is not too small, allowing it to have sufficient length to bond with adjacent portions, and preventing it from occupying too much space in the secondary battery 100, thus minimizing volumetric energy density loss in the secondary battery 100.

[0097] In some embodiments, the adhesive force between two adjacent diaphragms 122 is F, where 2N / 10mm ≤ F ≤ 5N / 10mm. For example, the diaphragms 122 are melted and bonded together by the high temperature generated by laser cutting, thus providing adhesive force between the diaphragms 122. When 2N / 10mm ≤ F ≤ 5N / 10mm is satisfied, the diaphragms 122 have sufficient adhesive force, making it less likely for them to separate, which is beneficial for the formation of the first composite 122c and the second composite 122d.

[0098] Please see Figure 8 or Figure 9 In some embodiments, the housing 20 includes a first housing portion 22 and a second housing portion 21. Along the thickness direction of the electrode assembly 10, the depth of the first housing portion 22 is less than the depth of the second housing portion 21. The first composite member 122c extends toward the second housing portion 21, that is, the end of the first composite member 122c away from the third portion 1225 extends toward the second housing portion 21 and away from the first housing portion 22. The depth directions of the first housing portion 22 and the second housing portion 21 are consistent with the thickness direction of the electrode assembly 10. As shown in the figure, the end of the first composite member 122c away from the third portion 1225 is the first end 1223a.

[0099] Compared to the first shell portion 22, the second shell portion 21 has a deep pit surface. The first composite part 122c formed by the first composite part 122a faces the deep pit surface of the shell 20, so that the end of the first composite part 122a away from the main body portion 10a can face the deep pit surface. This makes it difficult for the end of the first composite part 122c to extend into the position where the first shell portion 22 and the second shell portion 21 are connected, which is beneficial to the encapsulation of the shell 20 and improves the sealing performance of the encapsulation.

[0100] Please see Figure 8 or Figure 9 In some embodiments, the second composite 122d extends toward the second shell portion 21, that is, the end of the second composite 122b away from the third portion 1225 extends toward the interior of the second shell portion 21 and away from the first shell portion 22. As shown in the figure, the end of the second composite 122b away from the third portion 1225 is the second end 1224a.

[0101] The second composite part 122d formed by the second composite part 122b faces the deep pit surface of the housing 20. The end of the second composite part 122b away from the main body part 10a can face the deep pit surface, which further makes it difficult for the end of the second composite part 122b to extend into the position where the first housing part 22 and the second housing part 21 are connected, which is beneficial to the encapsulation of the housing 20 and improves the sealing performance of the encapsulation.

[0102] Please see Figure 10 In some embodiments, the housing 20 includes a housing body 20a and side sealing edges 20b. The housing body 20a has a cavity 201 in which the electrode assembly 10 is disposed. A first housing portion 22 has a first extension 211 disposed on both sides of the first housing portion 22 in the width direction. A second housing portion 21 has a second extension 221 disposed on both sides of the second housing portion 21 in the width direction. Along a direction away from the main body portion 10a, the first extension 211 and the second extension 221 gradually converge to fit together to form the side sealing edges 20b. The width direction of the first housing portion 22 and the width direction of the second housing portion 21 are the second direction Y shown in the figure.

[0103] Please see Figure 10 In some embodiments, the side seal 20b includes an unsealed area 202 and a sealed area 203. The unsealed area 202 is the region where the first extension 211 and the second extension 221 gradually converge and are not adhered to each other. The sealed area 203 is the region where the first extension 211 and the second extension 221 adhere to each other. The unsealed area 202 connects the sealed area 203 and the shell body 20a, and communicates with the cavity 201. Along the width direction of the shell 20, the width of the unsealed area 202 is W, 0.5mm≤W≤1mm. The width direction of the shell 20 is the second direction Y shown in the figure.

[0104] By bringing the first portion 1223 and the second portion 1224 of the separator 122 together to the first side 101 and the second side 102, the first portion 1223 and the second portion 1224 are confined, making it difficult for the first composite component 122c and the second composite component 122d to enter the unsealed area 202. This reduces the risk of the separator 122 entering the unsealed area 202, thereby allowing the width of the unsealed area 202 to be designed to be smaller, i.e., W≤1mm. This also makes the overall width of the side seal edge 20b smaller, which is beneficial to improving the volumetric energy density of the secondary battery 100. In addition, W≥0.5mm, which is beneficial to the transition from the unsealed area 202 to the encapsulation area 203, reduces stress concentration, and makes the side seal edge 20b less prone to breakage.

[0105] In some embodiments, 0.5mm ≤ W ≤ 0.7mm. This further reduces the volumetric energy density loss of the secondary battery 100 while minimizing stress concentration at the side seal 20b.

[0106] Please see Figure 10 In some embodiments, the side seal 20b is a double-folded edge, and the side seal 20b is gathered to both sides in the width direction of the shell body 20a. Taking the side seal 20b on one side of the width direction of the first shell portion 22 as an example, the side seal 20b includes a first curved section 204, a first extension section 205, a second curved section 206, and a second extension section 207 connected in sequence. The first extension section 205 and the second extension section 207 extend along the thickness direction of the secondary battery 100, which is the first direction X shown in the figure. In the width direction of the secondary battery 100, the second extension section 207 is located between the first extension section 205 and the main body portion 10a. The width direction of the secondary battery 100 is the second direction Y shown in the figure. In the thickness direction of the secondary battery 100, the first curved section 204 and the second curved section 206 are arranged opposite to each other. The side seal 20b is bent and gathered on both sides of the width direction of the first shell 22, which helps to reduce the volume of the secondary battery 100 and increase the energy density of the secondary battery 100.

[0107] Please see Figure 10 In some embodiments, the thickness of the secondary battery 100 is H1, and the height of the side seal 20b along the thickness direction of the secondary battery 100 is H2, where H2≤H1≤2.4mm. The reduction in the thickness of the side seal 20b helps to decrease the thickness of the secondary battery 100. The height of the reduced side seal 20b does not exceed the overall thickness of the secondary battery 100, thus facilitating the design of an ultra-thin secondary battery 100, reducing its volume, and increasing its volumetric energy density.

[0108] This application also provides a method for manufacturing a secondary battery 100, used to manufacture the secondary battery 100 in any of the above embodiments. The method for manufacturing the secondary battery 100 includes:

[0109] Stacking: The electrode composite 12 is stacked between two adjacent first electrodes 11, with at least two first composite portions 122a of the electrode composite 12 being stacked with each other, and at least two second composite portions 122b of the electrode composite 12 being stacked with each other; at least two electrode composites 12 and a plurality of first electrodes 11 are stacked to form an electrode assembly 10. Figure 11 This is a diagram illustrating the stacking steps.

[0110] Thermal bonding: The first composite part 122a is heated to bond the stacked first composite parts 122a together, and the second composite part 122b is heated to bond the stacked second composite parts 122b together.

[0111] The thermal bonding process enables different first composite parts 122a to bond together, thereby improving the structural strength at the location of the first composite part 122a; it also enables different second composite parts 122b to bond together, thereby improving the structural strength at the location of the second composite part 122b. This makes it less likely for the parts of the secondary battery 100 to be broken apart by the electrolyte when it is dropped, thereby improving the overall drop resistance of the secondary battery 100.

[0112] In some embodiments, the lamination step further includes preparing an electrode composite 12, the step of preparing the electrode composite 12 including:

[0113] Two isolation diaphragms 300 and multiple second electrodes 121 are provided;

[0114] like Figure 12 and Figure 13 As shown, along the thickness direction of the isolation diaphragm 300, second electrode plates 121 are stacked between two isolation diaphragms 300; along the length direction of the isolation diaphragm 300, multiple second electrode plates 121 are spaced apart between two isolation diaphragms 300, and the two isolation diaphragms 300 and the multiple second electrode plates 121 are combined to form a composite assembly 400. The length direction of the isolation diaphragm 300 is the width direction of the electrode assembly 10.

[0115] Along the length of the composite component 400, the separator 300 is cut using a laser cutting process between two adjacent second electrode plates 121, so that the separator 300 is separated to form multiple separators 122, and the composite component 400 is separated to form multiple electrode composites 12. Figure 10 and Figure 11 The dashed line L2 in the diagram is used to indicate the location of the laser cutting.

[0116] The preparation of the electrode composite 12 facilitates the fabrication of multiple electrode composites 12. Furthermore, the laser cutting process enables the separation of different electrode composites 12. Simultaneously, the high temperature generated by laser cutting can melt and connect the diaphragm 122 at the cutting location, improving the structural stability between the diaphragm 122 and the second electrode 121 of a single electrode composite 12.

[0117] In some embodiments, the second electrode 121 and the diaphragm 122 are bonded together by high-temperature hot pressing, thereby improving the bonding stability between the second electrode 121 and the diaphragm 122.

[0118] Please refer to the following in order. Figure 11 and Figure 2 In some embodiments, the thermal bonding step includes:

[0119] The first composite part 122a is brought closer to the main body part 10a of the electrode assembly 10 by heat treatment. During the bringing-up process, the first composite parts 122a of at least two electrode composites 12 are inclined on the same side along the thickness direction of the electrode assembly 10, and the inclined first composite parts 122a are bonded to each other.

[0120] The second composite part 122b is brought closer to the main body part 10a of the electrode assembly 10 by heat treatment. During the bringing process, the second composite part 122b is tilted on the same side along the thickness direction of the electrode assembly 10, and the tilted second composite parts 122b are bonded to each other.

[0121] In some embodiments, the inclined first composite portions 122a are bonded together to form a first composite 122c, and the inclined second composite portions 122b are bonded together to form a second composite 122d.

[0122] Through a thermal bonding step, the first composite part 122a and the second composite part 122b are separated from each other. Figure 11 The state shown Figure 2 The state transition is shown. Through the hot stamping process, on the one hand, the first composite part 122a and the second composite part 122b can be easily deformed, so that the first composite part 122a and the second composite part 122b can be gathered on both sides of the main body part 10a; on the other hand, the high temperature of the hot stamping can activate the adhesiveness of the first composite part 122a and the second composite part 122b, thereby making the first composite part 122a bonded to each other and the second composite part 122b bonded to each other, improving the stability of the first composite part 122a and the second composite part 122b gathered on the main body part 10a, and improving the structural strength of the electrode assembly 10.

[0123] Please refer to the following in order. Figure 11 , Figure 5 and Figure 6 In some embodiments, the thermal bonding step includes:

[0124] Along the thickness direction of the electrode assembly 10, at least two stacked first composite parts 122a are brought closer to each other by hot pressing, and the first composite parts 122a are partially bonded to each other after hot pressing.

[0125] Along the thickness direction of the electrode assembly 10, at least two stacked second composite parts 122b are brought closer to each other by hot pressing, and the hot-pressed second composite parts 122b are partially bonded to each other.

[0126] Through a thermal bonding step, the first composite part 122a and the second composite part 122b are separated from each other. Figure 11 The states shown are sequentially directed to Figure 5 , Figure 6 The state transition is shown.

[0127] In some embodiments, the first composite parts 122a are partially bonded together by hot pressing to form a first composite 122c, and the second composite parts 122b are partially bonded together by hot pressing to form a second composite 122d.

[0128] Compared to a single first composite part 122a, the thickness of at least two first composite parts 122a bonded together is superimposed, thereby improving the structural strength at the location of the first composite part 122a; compared to a single second composite part 122b, the thickness of at least two second composite parts 122b bonded together is superimposed, making it less likely for the separators 122 of the secondary battery 100 to be separated by electrolyte impact during drop, thereby improving the drop performance of the secondary battery 100.

[0129] Please see Figure 14 In some embodiments, the first composite portion 122a or the second composite portion 122b of the electrode assembly 10 is processed by a thermal bonding apparatus 2000. The thermal bonding apparatus 2000 includes a carrier 2001, an upper pressure member 2002, and a heat-pressing member 2003. The electrode assembly 10 is placed on the carrier 2001, and the upper pressure member 2002 is placed above the electrode assembly 10 to fix the electrode assembly 10. Then, the first composite portion 122a and the second composite portion 122b of the electrode assembly 10 are processed by the heat-pressing member 2003.

[0130] Please see Figure 14 In some embodiments, the thermal bonding step includes:

[0131] The first composite part 122a is pushed along the thickness direction of the electrode assembly 10 by the hot stamping element 2003, so that the laminated and bonded portion of the first composite part 122a is tilted toward the same side of the thickness direction of the electrode assembly 10.

[0132] The second composite portion 122b is pushed along the thickness direction of the electrode assembly 10 by the hot stamping element 2003, so that the laminated and bonded portion of the second composite portion 122b is tilted toward the same side of the thickness direction of the electrode assembly 10.

[0133] When the portions of the first composite part 122a and the second composite part 122b are stacked and bonded together, tilting them to the same side can reduce the size of the electrode assembly 10 in the width direction, thereby helping to reduce the volume of the secondary battery 100 and reduce the volumetric energy density loss of the secondary battery 100.

[0134] Please see Figure 8 or Figure 9 In some embodiments, the method for manufacturing the secondary battery 100 further includes:

[0135] Encapsulation: The electrode assembly 10 is inserted into the second shell portion 21 of the housing 20, such that the end of the first composite portion 122a away from the third portion 1225 is received in the second shell portion 21, and the end of the second composite portion 122b away from the third portion 1225 is received in the second shell portion 21. The second shell portion 21 of the housing 20 covers the first shell portion 22. Along the thickness direction of the electrode assembly 10, the depth of the first shell portion 22 is less than the depth of the second shell portion 21.

[0136] By housing the ends of the first composite portion 122a and the second composite portion 122b away from the third portion 1225 in the second shell portion 21, the distance between the ends of the first composite portion 122a and the second composite portion 122b away from the third portion 1225 and the connection between the first shell portion 22 and the second shell portion 21 can be reduced, thereby reducing the impact of the shell 20 encapsulation and improving the sealing performance of the encapsulation.

[0137] Please see Figure 15 The embodiments of this application also provide an electronic device 1000, including the secondary battery 100 in any of the above embodiments. In the secondary battery 100 of the electronic device 1000, the adhesive bonding between the separators 122 helps to improve the drop resistance of the secondary battery 100, thereby making the electronic device 1000 less susceptible to damage from drops.

[0138] In some embodiments, the electronic device 1000 may be a mobile phone, a laptop computer, a tablet computer, a drone, a power tool, an electric toy, a game console, a video recorder, a portable recorder, a radio, or a smartwatch, etc., which will not be listed here.

[0139] In some embodiments, the electronic device 1000 further includes a device body 200, and a secondary battery 100 is mounted on the device body 200. Since the electronic device 1000 adopts the technical solution of the secondary battery 100 in any of the above embodiments, it has at least the beneficial effects brought about by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described in detail here.

[0140] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of 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's disclosure.

Claims

1. A secondary battery, characterized in that, include: A housing and an electrode assembly, wherein the electrode assembly is disposed in the housing; the electrode assembly includes at least two electrode composites and a plurality of first electrodes stacked together, wherein the electrode composites are disposed between two adjacent first electrodes; The electrode composite includes a second electrode and two diaphragms stacked together, the second electrode having the opposite polarity to the first electrode; along the width direction of the electrode assembly, the diaphragm includes a first part, a second part, and a third part, the third part being connected between the first part and the second part, the second electrode being disposed between the third parts of the two diaphragms, the first parts of the two diaphragms being bonded together to form a first composite part, and the second parts of the two diaphragms being bonded together to form a second composite part; At least two electrode composites have portions of their first composite parts stacked and bonded together to form a first composite, and at least two electrode composites have portions of their second composite parts stacked and bonded together to form a second composite; the third part, the second electrode, and the first electrode are stacked to form the main body of the electrode assembly. Along the width direction of the electrode assembly, the main body has opposing first and second sides. The first composite is recessed toward the first side, and the second composite is recessed toward the second side. The housing includes a first housing portion and a second housing portion, and along the thickness direction of the electrode assembly, the depth of the first housing portion is less than the depth of the second housing portion; The first composite component extends toward the second shell portion; along the thickness direction of the electrode assembly, at least two first composite portions of the electrode composites are inclined toward the same side and partially stacked and bonded to form the first composite component; along the width direction of the electrode assembly, the width of the first portion is D1, 0.9mm≤D1≤2.0mm; and / or, The second composite part extends toward the interior of the second shell portion from the end away from the third portion. Along the thickness direction of the electrode assembly, the second composite portions of at least two electrode composites are inclined toward the same side and partially stacked and bonded to form the second composite part. Along the width direction of the electrode assembly, the width of the second portion is D2, 0.9mm≤D2≤2.0mm.

2. The secondary battery as described in claim 1, characterized in that, Along the thickness direction of the electrode assembly, at least two of the first composite portions of the electrode composites are brought closer to each other and partially stacked and bonded to form the first composite, and the first composite is inclined toward one side of the thickness direction of the electrode assembly and brought closer to the first side.

3. The secondary battery as described in claim 2, characterized in that, Along the thickness direction of the electrode assembly, at least two of the second composite portions of the electrode composites are brought closer to each other and partially stacked and bonded to form the second composite, and the second composite is inclined toward one side of the thickness direction of the electrode assembly and brought closer to the second side.

4. The secondary battery as described in claim 1, characterized in that, The adhesive force between two adjacent diaphragms is F, where 2N / 10mm≤F≤5N / 10mm.

5. The secondary battery as described in claim 1, characterized in that, The housing includes a main body and side sealing edges. The main body has a cavity, and the electrode assembly is disposed in the cavity. The first housing portion has a first extension portion, which is disposed on both sides of the width direction of the first housing portion. The second housing portion has a second extension portion, which is disposed on both sides of the width direction of the second housing portion. Along the direction away from the main body, the first extension portion and the second extension portion gradually converge to fit together to form the side sealing edges. The side sealing edge includes an unsealed area and a sealed area. The unsealed area is the region where the first extension and the second extension gradually converge and are not attached. The sealed area is the region where the first extension and the second extension are attached to each other. The unsealed area is connected between the sealed area and the shell body, and the unsealed area communicates with the cavity. Along the width direction of the shell, the width of the unsealed area is W, 0.5mm≤W≤1mm.

6. The secondary battery as described in claim 5, characterized in that, 0.5mm≤W≤0.7mm.

7. The secondary battery as described in claim 1, characterized in that, The housing includes a main body and side seals. The main body has a cavity, and the electrode assembly is disposed in the cavity. The first housing portion has a first extension, which is disposed on both sides of the width direction of the first housing portion. The second housing portion has a second extension, which is disposed on both sides of the width direction of the second housing portion. Along the direction away from the main body, the first extension and the second extension gradually converge to fit together to form the side seals. The side seals are double-folded edges, and the side seals converge on both sides of the width direction of the main body. The thickness of the secondary battery is H1, and the height of the side seal along the thickness direction of the secondary battery is H2, where H2≤H1≤2.4mm.

8. A method for manufacturing a secondary battery, used to manufacture a secondary battery as described in any one of claims 1 to 7, characterized in that, include: Stacking: The electrode composites are stacked between two adjacent first electrodes, the first composite portions of at least two electrode composites are stacked with each other, and the second composite portions of at least two electrode composites are stacked with each other; at least two electrode composites and a plurality of first electrodes are stacked to form an electrode assembly; Thermal bonding: The first composite part is heated to bond the stacked first composite parts together, and the second composite part is heated to bond the stacked second composite parts together.

9. The method for manufacturing a secondary battery as described in claim 8, characterized in that, The lamination step further includes preparing an electrode composite, the preparation of the electrode composite step including: Provides two isolation diaphragms and multiple second electrodes; Along the thickness direction of the isolation diaphragm, the second electrode is stacked between the two isolation diaphragms; Along the length of the isolation diaphragm, a plurality of second electrodes are spaced apart between two isolation diaphragms, and the two isolation diaphragms and the plurality of second electrodes are combined to form a composite component; Along the length of the composite component, the separator is cut using a laser cutting process at the position between two adjacent second electrodes, so that the composite component is separated to form multiple electrode composites.

10. The method for manufacturing a secondary battery as described in claim 9, characterized in that, The thermal bonding step includes: The first composite part is brought closer to the main body of the electrode assembly by heat treatment. During the bringing-back process, the first composite parts of at least two electrode composites are inclined on the same side along the thickness direction of the electrode assembly, and the inclined first composite parts are bonded to each other. The second composite part is brought closer to the main body of the electrode assembly by heat treatment. During the bringing-back process, the second composite part is tilted on the same side along the thickness direction of the electrode assembly, and the tilted second composite parts are bonded to each other.

11. The method for manufacturing a secondary battery as described in claim 8, characterized in that, The thermal bonding step includes: Along the thickness direction of the electrode assembly, at least two stacked first composite parts are brought closer to each other by hot pressing, and the first composite parts are partially bonded to each other after hot pressing. Along the thickness direction of the electrode assembly, at least two stacked second composite parts are brought closer together by hot pressing, and the hot-pressed second composite parts are partially bonded to each other.

12. The method for manufacturing a secondary battery as described in claim 11, characterized in that, The thermal bonding step includes: The first composite part is pushed along the thickness direction of the electrode assembly by a hot stamping element, so that the laminated and bonded portion of the first composite part is tilted toward the same side of the thickness direction of the electrode assembly. The second composite part is pushed along the thickness direction of the electrode assembly by a hot stamping element, so that the laminated and bonded portion of the second composite part is tilted toward the same side of the thickness direction of the electrode assembly.

13. The method for manufacturing a secondary battery as described in claim 10 or 12, characterized in that, The method for manufacturing the secondary battery further includes: Encapsulation: The electrode assembly is installed in the first shell portion of the housing, such that the end of the first composite portion away from the third portion is received in the first shell portion, and the end of the second composite portion away from the third portion is received in the first shell portion, and the second shell portion of the housing covers the first shell portion; along the thickness direction of the electrode assembly, the depth of the first shell portion is greater than the depth of the second shell portion.

14. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 7.

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