Secondary battery, method for manufacturing secondary battery, and electronic device

Abstract

The invention discloses a secondary battery, a manufacturing method of the secondary battery and an electronic device, the secondary battery comprises a shell, electrolyte and an electrode assembly, and the electrode assembly and the electrolyte are arranged in the shell. The electrode assembly comprises at least two pole piece composites and a plurality of first pole pieces which are arranged in a stacked mode. And the pole piece complex comprises a second pole piece and two diaphragms. The diaphragm comprises a first part, a second part and a third part, and the third part is connected between the first part and the second part. The first parts of the two diaphragms are mutually adhered to form a first composite part, and the second parts of the two diaphragms are mutually adhered to form a second composite part. The parts of the first composite parts of the at least two pole piece composites are mutually laminated and bonded to form a first composite piece, and the parts of the second composite parts of the at least two pole piece composites are mutually laminated and bonded to form a second composite piece. On the premise of reducing the energy density loss of the secondary battery, the falling performance of the secondary battery is improved, and the safety performance of the secondary battery is improved.

Description

Technical Field

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

[0002] Laminated batteries are widely used in electronic products such as mobile phones and laptops, which have extremely high requirements for battery safety. When the battery falls, the electrolyte easily impacts the diaphragm of the electrode assembly, causing the diaphragm to shrink, which in turn causes the cathode and anode electrodes to short-circuit.

[0003] In the related art, in order to improve the safety performance of the battery during the falling process, glue is usually pasted on the side and bottom of the electrode assembly. However, pasting the glue will increase the thickness of the electrode assembly, which is not conducive to improving the energy density of the battery. Currently, the diaphragm edge heat composite method is usually adopted to prevent the diaphragm from shrinking. However, the redundancy of the diaphragm edge after heat composite is not properly handled, which may easily lead to an increase in the battery width and the risk of the diaphragm entering the packaging shell and causing poor packaging. Summary of the invention

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

[0005] The embodiment of the first aspect of the present application provides a secondary battery, comprising: a shell, an electrolyte and an electrode assembly, wherein the electrode assembly and the electrolyte are arranged in the shell; the electrode assembly comprises at least two stacked electrode sheet complexes and a plurality of first electrode sheets, wherein the electrode sheet complex is arranged between two adjacent first electrode sheets. The electrode sheet complex comprises a stacked second electrode sheet and two diaphragms, wherein the second electrode sheet has an opposite polarity to the first electrode sheet. Along the width direction of the electrode assembly, the diaphragm comprises a first part, a second part and a third part, wherein the third part is connected between the first part and the second part, and the second electrode sheet is arranged between the third parts of the two diaphragms, wherein the first parts of the two diaphragms are bonded to each other to form a first composite part, and the second parts of the two diaphragms are bonded to each other to form a second composite part. Parts of the first composite parts of at least two electrode sheet complexes are stacked and bonded to each other to form a first composite part, and parts of the second composite parts of at least two electrode sheet complexes are stacked and bonded to each other to form a second composite part. The third part, the second pole piece and the first pole piece 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 is gathered in a direction close to the first side, and the second composite part is gathered in a direction close to the second side. The shell 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 toward the second shell part.

[0006] By bonding the first composite part and the second composite part of the two electrode sheet composites to each other, the bonding strength and structural strength between the diaphragms on both sides of the electrode assembly in the width direction are improved, so that when the electrolyte impacts the first part and the second part, the diaphragms are not easily separated from each other, reducing the risk of short circuit between the first electrode sheet and the second electrode sheet. Compared with the situation where the first composite part and the second composite part are not folded together, the first composite part and the second composite part are folded together on both sides of the main body, which is conducive to reducing the overall width of the electrode assembly, thereby improving the energy density of the secondary battery. Compared with the first shell, the second shell is a deep pit surface, and the first composite part faces the deep pit surface of the shell, so that the end of the first composite part away from the main body can face the deep pit surface, so that the end of the first composite part is not easy to extend into the position where the first shell and the second shell are connected, which is conducive to the packaging of the shell and improves the sealing of the packaging. The secondary battery in the embodiment of the present application can improve the drop performance of the secondary battery and improve the safety performance of the secondary battery under the premise of reducing the loss of energy density of the secondary battery.

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

[0008] Compared with a single first composite part, the first composite parts are stacked and bonded while being tilted toward the same side, and at least part of the thickness of at least two stacked first composite parts overlap, 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 parts of at least two electrode sheet composites are inclined toward the same side and are partially stacked and bonded to form a second composite member.

[0010] Compared with a single second composite part, the second composite parts are stacked and bonded while being tilted toward the same side, and at least part of the thickness of at least two stacked second composite parts overlap, 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 parts of at least two pole piece composites are gathered in a direction close to each other and partially stacked and bonded to form a first composite part, and the first composite part is inclined toward one side in the thickness direction of the electrode assembly and gathered in a direction close to the first side.

[0012] At least two first composite parts are bonded to each other by being close to each other, and the thickness of the first composite parts formed after bonding is superimposed, thereby improving the structural strength at the position of the first composite parts, so that the diaphragms of the secondary battery are not easily separated by the impact of the electrolyte during the fall process. After the first composite parts are tilted and gathered at the first side, the width direction of the electrode assembly can be reduced, which is conducive to reducing the volume of the secondary battery and reducing the volume energy density loss of the secondary battery.

[0013] In at least one embodiment, along the thickness direction of the electrode assembly, the second composite parts of at least two pole piece composites are gathered in a direction close to each other and partially stacked and bonded to form a second composite part, and the second composite part is inclined toward one side in the thickness direction of the electrode assembly and gathered in a direction close to the second side.

[0014] At least two second composite parts are bonded to each other by being close to each other, and the thickness of the second composite parts formed after bonding is superimposed, thereby improving the structural strength at the position of the second composite parts, so that the separators of the secondary battery are not easily separated by the impact of the electrolyte during the fall process. In addition, after the second composite parts are tilted and gathered at the second side, the width direction of the electrode assembly can be further reduced, which is conducive to reducing the volume of the secondary battery and reducing the volume energy density loss of the secondary battery.

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

[0016] One end of the second composite part away from the main body can face the deep 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 packaging of the shell.

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

[0018] When 0.9mm≤D1≤2.0mm is satisfied, the width of the first part is not too small, so that the first part has enough length to bond with the adjacent first part, and the first part is not too wide to occupy the volume of the secondary battery, and the secondary battery volume energy density loss is not easy to cause. When 0.9mm≤D2≤2.0mm is satisfied, the width of the second part is not too small, so that the second part has enough length to bond with the adjacent second part, and the second part is not too wide to occupy the volume of the secondary battery, and the secondary battery volume energy density loss is not easy to cause.

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

[0020] When 2N / 10mm≤F≤5N / 10mm is satisfied, the separators have sufficient bonding force, and the separators are not easily separated from each other, which is beneficial to the formation of the first composite member and the second composite member.

[0021] In at least one embodiment, the shell includes a shell body and a side seal, the shell body has a cavity, and the electrode assembly is arranged in the cavity; the first shell portion has a first extension portion, and the first extension portion is arranged on both sides of the width direction of the first shell portion; the second shell portion has a second extension portion, and the second extension portion is arranged on both sides of the width direction of the second shell portion; along the direction away from the main body, the first extension portion and the second extension portion gradually converge to fit to form a side seal. The side seal includes an unsealed area and a packaging area, the unsealed area is an area where the first extension portion and the second extension portion gradually converge and do not fit, and the packaging area is an area where the first extension portion and the second extension portion fit each other; the unsealed area is connected between the packaging area and the shell body, and the unsealed area is connected to the cavity. Along the width direction of the shell, the width of the unsealed area is W, 0.5mm≤W≤1mm.

[0022] By gathering the first part and the second part of the diaphragm at the first side and the second side, the first part and the second part are limited, making it difficult for the first composite part and the second composite part to enter the unsealed area, reducing the risk of the diaphragm entering the unsealed area, so that the width of the unsealed area can be designed to be smaller, that is, W≤1mm, so that the overall width of the side seal is also smaller, which is beneficial to the improvement of the volume energy density of the secondary battery; in addition, W≥0.5 avoids interference between the head and the battery body and crushing of the battery cell.

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

[0024] Under the premise of reducing the stress concentration of the side sealing edge, the volume energy density loss of the secondary battery is further reduced.

[0025] In at least one embodiment, the shell includes a shell body and a side seal, the shell body has a cavity, and the electrode assembly is arranged in the cavity; the first shell has a first extension, and the first extension is arranged on both sides of the width direction of the first shell; the second shell has a second extension, and the second extension is arranged on both sides of the width direction of the second shell; along the direction away from the main body, the first extension and the second extension gradually converge to fit to form a side seal, the side seal is a double fold, and the side seal is gathered on both sides of the width direction of the shell 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, H2≤H1≤2.4mm.

[0026] The side seals are gathered together to reduce the thickness of the secondary battery. The height of the gathered side seals does not exceed the overall thickness of the secondary battery, which is beneficial to the design of ultra-thin secondary batteries, reduces the volume of the secondary battery, and increases the volume energy density of the secondary battery.

[0027] An embodiment of a second aspect of the present application provides a method for manufacturing a secondary battery, which is used to manufacture the secondary battery in any of the above embodiments. The method for manufacturing the secondary battery includes: Lamination: The electrode composite is stacked between two adjacent first electrode sheets, the first composite parts of at least two electrode composites are stacked, and the second composite parts of at least two electrode composites are stacked; at least two electrode composites and multiple first electrode sheets are stacked to form an electrode assembly. Thermal composite: The first composite parts are heated to make the stacked first composite parts bonded to each other, and the second composite parts are heated to make the stacked second composite parts bonded to each other.

[0028] Through the thermal composite step, different first composite parts can be bonded to each other, thereby improving the structural strength at the position of the first composite parts; different second composite parts can be bonded to each other, thereby improving the structural strength at the position of the second composite parts, so that when the secondary battery falls, the parts are not easily washed apart by the electrolyte, thereby improving the overall anti-fall performance of the secondary battery.

[0029] In at least one embodiment, the stacking step also includes preparing a pole piece complex, and the step of preparing the pole piece complex includes: providing two isolation membranes and a plurality of second pole pieces; stacking the second pole pieces between the two isolation membranes along the thickness direction of the isolation membranes; spacing the plurality of second pole pieces between the two isolation membranes along the length direction of the isolation membranes, and the two isolation membranes and the plurality of second pole pieces are combined to form a composite component; along the length direction of the composite component, cutting the isolation membrane at the position between two adjacent second pole pieces using a laser cutting process to separate the composite component to form a plurality of pole piece complexes.

[0030] The step of preparing the pole piece complex facilitates the production of multiple pole piece complexes. In addition, the step of laser cutting can achieve the separation between different pole piece complexes. At the same time, the high temperature generated by laser cutting can also melt and connect the diaphragm at the cutting position, thereby improving the structural stability between the diaphragm of a single pole piece complex and the second pole piece.

[0031] In at least one embodiment, the thermal composite step includes: hot blanching so that the first composite part is gathered toward the main body of the electrode assembly, and during the gathering process, the first composite parts of at least two electrode composites are inclined along the same side of the thickness direction of the electrode assembly, and the inclined first composite parts are close to each other and bonded; hot blanching so that the second composite part is gathered toward the main body of the electrode assembly, and during the gathering process, the second composite parts are inclined along the same side of the thickness direction of the electrode assembly, and the inclined second composite parts are close to each other and bonded.

[0032] The hot stamping process can facilitate the deformation of the first composite part and the second composite part, so that the first composite part and the second composite part can be gathered on both sides of the main body; on the other hand, the high temperature of hot stamping can activate the viscosity of the second composite part of the first composite part, so that the first composite parts close to each other are bonded to each other, and the second composite parts close to each other are bonded to each other, thereby improving the stability of the first composite part and the second composite part being gathered to the main body and improving the structural strength of the electrode assembly.

[0033] In at least one embodiment, the thermal composite step includes: along the thickness direction of the electrode assembly, at least two mutually stacked first composite parts are brought together in a direction close to each other by hot pressing, and the first composite parts that have been hot pressed are partially bonded to each other; along the thickness direction of the electrode assembly, at least two mutually stacked second composite parts are brought together in a direction close to each other by hot pressing, and the second composite parts that have been hot pressed are partially bonded to each other.

[0034] Compared with a single first composite part, the thickness of at least two first composite parts bonded to each other overlap, thereby improving the structural strength at the position of the first composite part; compared with a single second composite part, the thickness of at least two second composite parts bonded to each other overlap, making it difficult for the diaphragms of the secondary battery to be separated by the impact of the electrolyte during the falling process, thereby improving the falling performance of the secondary battery.

[0035] In at least one embodiment, the thermal composite step includes: pushing the first composite part along the thickness direction of the electrode assembly by a hot stamping piece so that the stacked bonding parts of the first composite part are inclined toward the same side of the thickness direction of the electrode assembly; pushing the second composite part along the thickness direction of the electrode assembly by a hot stamping piece so that the stacked bonding parts of the second composite part are inclined toward the same side of the thickness direction of the electrode assembly.

[0036] When the laminated and bonded parts of the first composite part and the laminated and bonded parts of the second composite part are tilted toward the same side, the width dimension of the electrode assembly can be reduced, thereby facilitating reduction in the volume of the secondary battery and reducing the volume energy density loss of the secondary battery.

[0037] In at least one embodiment, the manufacturing method of the secondary battery also includes: packaging: the electrode assembly is installed into the first shell portion of the shell, so that the end of the first composite part away from the third part is accommodated in the second shell portion, and the end of the second composite part away from the third part is accommodated in the second shell portion, and the second shell portion of the shell 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.

[0038] By accommodating the ends of the first composite part and the second composite part away from the third part in the first shell part, the ends of the first composite part and the second composite part away from the third part can be reduced toward the connection between the first shell part and the second shell part, thereby reducing the impact of the shell packaging.

[0039] An embodiment of a third aspect of the present application provides an electronic device, comprising the secondary battery in any of the above embodiments.

[0040] In the secondary battery in the electronic device, the bonding and compounding between the separators is beneficial to improving the anti-drop performance of the secondary battery, so that the electronic device is not easily damaged by falling. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a three-dimensional diagram of a secondary battery in one embodiment of the present application.

[0042] Figure 2 is a cross-sectional view of an electrode assembly in one embodiment of the present application.

[0043] Figure 3 is a cross-sectional view of a diaphragm in one embodiment of the present application.

[0044] Figure 4 It is a cross-sectional view of a pole piece complex in one embodiment of the present application.

[0045] Figure 5 The electrode assembly in one embodiment of the present application is a cross-sectional view showing the stacking and bonding state of the first composite part.

[0046] Figure 6 The electrode assembly in one embodiment of the present application is a cross-sectional view showing a state in which the first composite portion is inclined toward the same side in the thickness direction of the electrode assembly.

[0047] Figure 7 It is a cross-sectional view of a pole piece complex in one embodiment of the present application when the diaphragm is in an expanded state.

[0048] Figure 8 is a cross-sectional view of a secondary battery in one embodiment of the present application.

[0049] Fig. 9 is a cross-sectional view of a secondary battery in another embodiment of the present application.

[0050] Fig.10 It is a cross-sectional view showing the side sealing of the shell in one embodiment of the present application.

[0051] Fig.11 It is a schematic diagram showing the stacking steps in one embodiment of the present application.

[0052] Fig.12 is a cross-sectional view of a composite component in one embodiment of the present application.

[0053] Fig.13 It is a top view showing the stacking state of the isolation diaphragm and the second pole piece in one embodiment of the present application.

[0054] Fig.14 It is a schematic diagram showing the processing state of an electrode assembly by a thermal composite device in one embodiment of the present application.

[0055] Fig.15 is a schematic diagram of an electronic device in one embodiment of the present application.

[0056] Main component symbols 1000, electronic device; 100, secondary battery; 10, electrode assembly; 10a, main body; 101, first side; 102, second side; 11, first pole piece; 111, first current collector; 112, first active material layer; 12, pole piece composite; 121, second pole piece; 1211, second current collector; 1212, second active material layer; 122, separator; 122a, first composite part; 122b, second composite part; 122c, first composite member; 122d, second composite member; 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, packaging area; 204, first bending section; 205, first extension section; 206, second bending section; 207, second extension section; 22, first shell; 211, first extension section; 21, second shell; 221, second extension section; 200, device body; 300, isolation diaphragm; 400, composite component; X, first direction; Y, second direction; L1, center line; 2000, thermal composite equipment; 2001, carrier; 2002, upper pressure piece; 2003, hot stamping piece.

[0057] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0060] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0061] Laminated batteries are widely used in electronic products such as mobile phones and laptops, which have extremely high requirements for battery safety. When the battery falls, the electrolyte easily impacts the diaphragm of the electrode assembly, causing the diaphragm to shrink, which in turn causes the cathode and anode electrodes to short-circuit.

[0062] In the related art, in order to improve the safety performance of the battery during the falling process, glue is usually pasted on the side and bottom of the electrode assembly. However, pasting the glue will increase the thickness of the electrode assembly, which is not conducive to improving the energy density of the battery. Currently, the diaphragm edge heat composite method is usually adopted to prevent the diaphragm from shrinking. However, the redundancy of the diaphragm edge after heat composite is not properly handled, which may easily lead to an increase in the battery width and the risk of the diaphragm entering the packaging shell and causing poor packaging.

[0063] An embodiment of the present application provides a secondary battery, comprising: a shell, an electrolyte and an electrode assembly, wherein the electrode assembly and the electrolyte are arranged in the shell. The electrode assembly comprises at least two stacked electrode sheet complexes and a plurality of first electrode sheets, wherein the electrode sheet complex is arranged between two adjacent first electrode sheets. The electrode sheet complex comprises a stacked second electrode sheet and two diaphragms, wherein the second electrode sheet has an opposite polarity to the first electrode sheet. Along the width direction of the electrode assembly, the diaphragm comprises a first part, a second part and a third part, wherein the third part is connected between the first part and the second part, and the second electrode sheet is arranged between the third parts of the two diaphragms. The first parts of the two diaphragms are bonded to each other to form a first composite part, and the second parts of the two diaphragms are bonded to each other to form a second composite part. Parts of the first composite parts of at least two electrode sheet complexes are stacked and bonded to each other to form a first composite part, and parts of the second composite parts of at least two electrode sheet complexes are stacked and bonded to each other to form a second composite part. The third part, the second pole piece and the first pole piece 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 is gathered in a direction close to the first side, and the second composite part is gathered in a direction close to the second side. The shell 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 toward the second shell part.

[0064] By bonding the first composite part and the second composite part of the two electrode sheet composites to each other, the bonding strength and structural strength between the diaphragms on both sides of the electrode assembly in the width direction are improved, so that when the electrolyte impacts the first part and the second part, the diaphragms are not easily separated from each other, reducing the risk of short circuit between the first electrode sheet and the second electrode sheet. Compared with the situation where the first composite part and the second composite part are not folded together, the first composite part and the second composite part are folded together on both sides of the main body, which is conducive to reducing the overall width of the electrode assembly, thereby improving the energy density of the secondary battery. Compared with the first shell part, the second shell part is a deep pit surface, and the first composite part faces the deep pit surface of the shell, so that the end of the first composite part away from the main body can face the deep pit surface, so that the end of the first composite part is not easy to extend into the position where the first shell part and the second shell part are connected, which is conducive to the packaging of the shell and improves the sealing of the packaging. The secondary battery in the embodiment of the present application can improve the drop performance of the secondary battery and improve the safety performance of the secondary battery under the premise of reducing the loss of battery energy density.

[0065] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0066] like Figure 1 and Figure 2 As shown, the first embodiment of the present application provides a secondary battery 100, which includes an electrode assembly 10, a housing 20 and an electrolyte (not shown), wherein the electrode assembly 10 and the electrolyte are arranged in the housing 20. The electrode assembly 10 includes at least two stacked pole piece complexes 12 and a plurality of first pole pieces 11, wherein the pole piece complex 12 is arranged between two adjacent first pole pieces 11. The pole piece complex 12 includes a stacked second pole piece 121 and two diaphragms 122.

[0067] 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 hard shell, such as a plastic shell, or a metal shell including at least one of a steel alloy, an aluminum alloy, and a copper alloy.

[0068] In some embodiments, an electrolyte (not shown) is injected into the housing 20 , and the electrolyte components include a solvent, an electrolyte salt, and an additive.

[0069] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0070] In some embodiments, the electrolyte salt includes but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)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).

[0071] In some embodiments, the polarities of the first electrode piece 11 and the second electrode piece 121 are opposite. For example, the first electrode piece 11 is an anode electrode piece, and the second electrode piece 121 is a cathode electrode piece. For another example, the first electrode piece 11 is a cathode electrode piece, and the second electrode piece 121 is an anode electrode piece.

[0072] See also Figure 2 In some embodiments, the first pole piece 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 the thickness direction of the first current collector 111, and the separator 122 is disposed between the first active material layer 112 and the second pole piece 121. The thickness direction of the first current collector 111 is the first direction X. For example, the first active material layer 112 is disposed on both surfaces of the first current collector 111.

[0073] See also 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 oppositely disposed 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, the second active material layer 1212 is provided on both surfaces of the second current collector 1211.

[0074] Taking the first pole piece 11 as an anode pole piece and the second pole piece 121 as a cathode pole piece as an example, the first current collector 111 and the second current collector 1211 may be metal layers. The first current collector 111 may be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 1211 may be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0075] Taking the first pole piece 11 as an anode pole piece and the second pole piece 121 as a cathode pole piece as an example, the polarity of the first active material layer 112 is anode, and the first active material layer 112 includes anode active materials, and the anode active materials may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, silicon-carbon materials, etc. The polarity of the second active material layer 1212 is cathode, and the second active material layer 1212 includes cathode active materials, and the cathode active materials 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, etc.

[0076] See also Figure 3In some embodiments, the diaphragm 122 includes a base film 1221. Along the thickness direction of the base film 1221, the base film 1221 has two surfaces, and an adhesive layer 1222 is provided on each surface so that when the diaphragm 122 and the second pole piece 121 are compounded, the diaphragm 122 and the second pole piece 121 can be bonded.

[0077] See also 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, the third portion 1225 is connected between the first portion 1223 and the second portion 1224, and the second electrode sheet 121 is disposed between the third portions 1225 of the two diaphragms 122. The thickness direction of the electrode assembly 10 is the first direction X, and the width direction of the electrode assembly 10 is the second direction Y. Figure 4 As shown, the second electrode sheet 121 and the two separators 122 are stacked along the thickness direction of the electrode assembly 10. The first parts 1223 of the two separators 122 are bonded to each other to form a first composite part 122a, and the second parts 1224 of the two separators 122 are bonded to each other to form a second composite part 122b.

[0078] Parts of the first composite parts 122a of at least two pole piece composites 12 are stacked and bonded to form a first composite member 122c, and parts of the second composite parts 122b of at least two pole piece composites 12 are stacked and bonded to form a second composite member 122d.

[0079] By bonding the first composite part 122a and the second composite part 122b of the two electrode composite bodies 12 to each other, the bonding strength and structural strength between the separators 122 on both sides of the electrode assembly 10 in the width direction are improved, so that when the electrolyte impacts the first part 1223 and the second part 1224, the separators 122 are not easily separated from each other, reducing the risk of short circuit between the first electrode 11 and the second electrode 121. Compared with the solution of pasting the wrapping glue on the side and bottom of the electrode assembly 10, the volume of the secondary battery 100 is reduced, so that the drop performance of the secondary battery 100 can be improved while reducing the energy density loss of the secondary battery 100, and the safety performance of the secondary battery 100 can be improved.

[0080] See also Figure 2 and Figure 4In some embodiments, the third portion 1225, the second electrode sheet 121, and the first electrode sheet 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, and the first composite portion 122a is gathered in a direction close to the first side 101. The first composite portion 122a is gathered in a direction close to the first side 101, which can be along the thickness direction of the electrode assembly 10, upward or downward, so that the first composite portion 122a is close to or even attached to the first side 101 after being gathered; the second composite portion 122b is gathered in a direction close to the second side 102. The second composite portion 122b is gathered in a direction close to the second side 102, which can be along the thickness direction of the electrode assembly 10, upward or downward, so that the second composite portion 122b is close to or even attached to the second side 102 after being gathered. Figure 4 The first composite part 122a and the second composite part 122b are shown in an unclosed state. Figure 2 The first composite portion 122a and the second composite portion 122b are shown in a collapsed state.

[0081] Compared with the case where the first composite part 122a and the second composite part 122b are not collapsed, the first composite part 122a and the second composite part 122b are collapsed at both sides of the main body 10a, which is beneficial to reduce the overall width of the electrode assembly 10 and thus improve the energy density of the secondary battery 100.

[0082] See also Figure 2 In some embodiments, along the thickness direction of the electrode assembly 10, the first composite parts 122a of at least two electrode composites 12 are inclined toward the same side and partially stacked and bonded to form a first composite member 122c. Figure 2 As shown, the figure takes the electrode assembly 10 including three first pole pieces 11 and two pole piece composites 12 as an example for illustration, the first composite parts 122a are all inclined toward the same side and are gathered toward the first side 101 of the main body 10a by inclination.

[0083] Compared with a single first composite part 122a, at least two first composite parts 122a are stacked and bonded while being tilted toward the same side. After stacking, at least part of the thickness of the at least two first composite parts 122a overlap, which can further improve the structural strength of the first composite part 122a.

[0084] See also Figure 2In some embodiments, along the thickness direction of the electrode assembly 10, the second composite parts 122b of at least two electrode composites 12 are inclined toward the same side and partially stacked and bonded to form a second composite part 122d. The second composite parts 122b are all inclined toward the same side and are gathered toward the second side 102 of the main body 10a by inclination. By shaping the first composite part 122a and the second composite part 122b, the influence of the expansion of the first part 1223 and the second part 1224 of the diaphragm 122 on the packaging of the housing 20 is reduced.

[0085] Compared with a single second composite part 122b, the second composite parts 122b are stacked and bonded while being tilted toward the same side. At least part of the thickness of at least two stacked second composite parts 122b overlaps, which can further improve the structural strength of the second composite part 122b.

[0086] See also Figure 5 and Figure 6 In some embodiments, along the thickness direction of the electrode assembly 10, the first composite parts 122a of at least two electrode composites 12 are gathered in a direction close to each other and partially stacked and bonded to form a first composite part 122c, and the first composite part 122c is inclined toward one side in the thickness direction of the electrode assembly 10 and gathered in a direction close to the first side 101.

[0087] For example, in the thickness direction of the electrode assembly 10, the electrode assembly 10 has a center line L1, and the first composite parts 122a located on both sides of the center line L1 are both converged toward the center line L1, so that the first composite parts 122a are bonded to each other near the center line L1. After being bonded to each other, the first composite parts 122a form a first composite part 122c that is inclined to one side of the center line L1. Figure 5 FIG. 1 shows the state where the first composite portion 122a is gathered toward the center line L1 and partially laminated and bonded. Figure 6 , a state in which the laminated bonding portion (first composite member 122 c ) of the first composite portion 122 a is inclined toward one side in the thickness direction of the electrode assembly 10 is shown.

[0088] At least two first composite parts 122a are bonded to each other by being close to each other, and the thickness of the first composite part 122c formed after bonding is the superposition of the thickness of at least two first composite parts 122a, thereby improving the structural strength at the position of the first composite part 122c, so that the separators 122 are not easily separated by the impact of the electrolyte during the falling process of the secondary battery 100. After the first composite part 122c is tilted and gathered at the first side 101, the width direction of the electrode assembly 10 can be reduced, which is conducive to reducing the volume of the secondary battery 100 and reducing the volume energy density loss of the secondary battery 100.

[0089] See also Figure 5 and Figure 6In some embodiments, along the thickness direction of the electrode assembly 10, the second composite parts 122b of at least two electrode sheet composites 12 are gathered in a direction close to each other and partially stacked and bonded to form a second composite part 122d, and the second composite part 122d is inclined toward one side in the thickness direction of the electrode assembly 10.

[0090] For example, in the thickness direction of the electrode assembly 10, the second composite parts 122b located on both sides of the center line L1 are both converged toward the center line L1, so that the second composite parts 122b are bonded to each other near the center line L1, and the second composite parts 122b after bonding to each other form a second composite part 122d inclined to one side of the center line L1. Figure 5 The second composite part 122b is shown in the state after being gathered toward the center line L1 and partially laminated and bonded. Figure 6 , a state in which the laminated bonding portion (second composite member 122 d ) of the second composite portion 122 b is inclined toward one side in the thickness direction of the electrode assembly 10 is shown.

[0091] At least two second composite parts 122b are bonded to each other by being close to each other, and the thickness of the second composite part 122d formed after bonding is the superposition of the thickness of at least two second composite parts 122b, thereby improving the structural strength at the position of the second composite part 122d, so that the separators 122 are not easily separated by the impact of the electrolyte during the falling process of the secondary battery 100. In addition, after the second composite part 122d is tilted and gathered at the second side 102, the width direction of the electrode assembly 10 can be further reduced, which is conducive to reducing the volume of the secondary battery 100 and reducing the volume energy density loss of the secondary battery 100.

[0092] See also Figure 7 In some embodiments, along the width direction of the electrode assembly 10, the width of the second electrode sheet 121 is the same as the width of the third portion 1225, and the first portion 1223 and the third portion 1225 are portions of the diaphragm 122 that extend beyond the width of the second electrode sheet 121. The width of the first portion 1223 and the width of the second portion 1224 are the widths of the electrode assembly 10 in the width direction when unfolded.

[0093] See also Figure 7 In some embodiments, along the width direction of the electrode assembly 10, the width of the first portion 1223 is D1, 0.9 mm ≤ D1 ≤ 2.0 mm. When 0.9 mm ≤ D1 ≤ 2.0 mm is satisfied, the width of the first portion 1223 is not too small, so that the first portion 1223 has enough length to bond with the adjacent first portion 1223, and the first portion 1223 is not too wide to occupy the volume of the secondary battery 100, and is not likely to cause a loss of volume energy density of the secondary battery 100.

[0094] See also Figure 7In some embodiments, along the width direction of the electrode assembly 10, the width of the second portion 1224 is D2, 0.9 mm ≤ D2 ≤ 2.0 mm. When 0.9 mm ≤ D2 ≤ 2.0 mm is satisfied, the width of the second portion 1224 is not too small, so that the second portion 1224 has enough length to bond with the adjacent second portion 1224, and the second portion 1224 is not too wide to occupy the volume of the secondary battery 100, and is not likely to cause a loss of volume energy density of the secondary battery 100.

[0095] In some embodiments, the bonding force between two adjacent diaphragms 122 is F, 2N / 10mm≤F≤5N / 10mm. For example, the high temperature generated by laser cutting of the diaphragms 122 causes the diaphragms 122 to melt and bond to each other, so that there is bonding force between the diaphragms 122. When 2N / 10mm≤F≤5N / 10mm is satisfied, there is sufficient bonding force between the diaphragms 122, and it is not easy to cause the diaphragms 122 to separate from each other, which is conducive to the formation of the first composite member 122c and the second composite member 122d.

[0096] See also Figure 8 or Fig. 9 In some embodiments, the shell 20 includes a first shell portion 22 and a second shell portion 21. 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 2121. The first composite member 122c extends toward the second shell portion 2121, that is, the end of the first composite member 122c away from the third portion 1225 extends toward the second shell portion 21 and away from the first shell portion 22. The depth direction of the first shell portion 22 and the second shell portion 2121 is 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.

[0097] Compared with the first shell portion 22, the second shell portion 21 is a deep pit surface. The first composite part 122c formed by the first composite part 122a faces the deep pit surface of the shell body 20, so that the end of the first composite part 122a away from the main body portion 10a can face the deep pit surface, so that the end of the first composite part 122c is not easy to extend into the position where the first shell portion 22 and the second shell portion 21 are connected, which is beneficial to the packaging of the shell body 20 and improves the sealing of the packaging.

[0098] See also Figure 8 or Fig. 9 In some embodiments, the second composite part 122d extends toward the second shell 21, that is, the end of the second composite part 122b away from the third part 1225 extends toward the inside of the second shell 21 and away from the first shell 22. As shown in the figure, the end of the second composite part 122b away from the third part 1225 is the second end 1224a.

[0099] The second composite part 122d formed by the second composite part 122b faces the deep pit surface of the shell 20, and 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 shell part 22 and the second shell part 21 are connected, which is beneficial to the packaging of the shell 20 and improves the sealing of the packaging.

[0100] See also Fig.10 In some embodiments, the shell 20 includes a shell body 20a and a side sealing edge 20b, the shell body 20a has a cavity 201, and the electrode assembly 10 is disposed in the cavity 201. The first shell 22 has a first extension 211, and the first extension 211 is disposed on both sides of the width direction of the first shell 22. The second shell 21 has a second extension 221, and the second extension 221 is disposed on both sides of the width direction of the second shell 21. Along the direction away from the main body 10a, the first extension 211 and the second extension 221 gradually converge to fit to form the side sealing edge 20b. The width direction of the first shell 22 and the width direction of the second shell 21 are the second direction Y shown in the figure.

[0101] See also Fig.10 In some embodiments, the side sealing edge 20b includes an unsealed area 202 and a packaging area 203. The unsealed area 202 is an area where the first extension portion 211 and the second extension portion 221 are gradually gathered and not attached, and the packaging area 203 is an area where the first extension portion 211 and the second extension portion 221 are attached to each other; the unsealed area 202 is connected between the packaging area 203 and the shell body 20a, and the unsealed area 202 is connected to 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.

[0102] By gathering the first part 1223 and the second part 1224 of the diaphragm 122 at the first side 101 and the second side 102, the first part 1223 and the second part 1224 are limited, so that the first composite part 122c and the second composite part 122d are not easy to enter the unsealed area 202, thereby reducing the risk of the diaphragm 122 entering the unsealed area 202, so that the width of the unsealed area 202 can be designed to be smaller, that is, W≤1mm, so that the overall width of the side sealing edge 20b is also smaller, which is beneficial to the improvement of the volume 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 packaging area 203, reducing stress concentration, and making the side sealing edge 20b not easy to break.

[0103] In some embodiments, 0.5 mm ≤ W ≤ 0.7 mm. On the premise of reducing the stress concentration of the side sealing edge 20 b , the volume energy density loss of the secondary battery 100 is further reduced.

[0104] See also Fig.10 In some embodiments, the side seal 20b is a double folded edge, and the side seal 20b is gathered on both sides of the shell body 20a in the width direction. Taking the side seal 20b on one side in 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, and the first extension section 205 and the second extension section 207 extend along the thickness direction of the secondary battery 100, and the thickness direction of the secondary battery 100 is the first direction X shown in the figure. And 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 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 sealing edges 20 b are bent and gathered at both sides of the first shell portion 22 in the width direction, which is beneficial to reducing the volume of the secondary battery 100 and improving the energy density of the secondary battery 100 .

[0105] See also Fig.10 In some embodiments, the thickness of the secondary battery 100 is H1, and the height of the side sealing edge 20b along the thickness direction of the secondary battery 100 is H2, where H2≤H1≤2.4mm. The folding of the side sealing edge 20b is conducive to reducing the thickness of the secondary battery 100. The height of the folded side sealing edge 20b does not exceed the overall thickness of the secondary battery 100, which is conducive to the design of the ultra-thin secondary battery 100, reduces the volume of the secondary battery 100, and improves the volume energy density of the secondary battery 100.

[0106] The embodiment of the present application also provides a method for manufacturing a secondary battery 100, which is used to manufacture the secondary battery 100 in any of the above embodiments. The method for manufacturing the secondary battery 100 includes: Stacking: The pole piece complex 12 is stacked between two adjacent first pole pieces 11, the first composite parts 122a of at least two pole piece complexes 12 are stacked on each other, and the second composite parts 122b of at least two pole piece complexes 12 are stacked on each other; at least two pole piece complexes 12 and multiple first pole pieces 11 are stacked to form an electrode assembly 10. Fig.11 It is a schematic diagram of the stacking steps.

[0107] Thermal bonding: The first bonding parts 122a are heated so that the first bonding parts 122a stacked on each other are bonded to each other, and the second bonding parts 122b are heated so that the second bonding parts 122b stacked on each other are bonded to each other.

[0108] Through the thermal composite step, different first composite parts 122a can be bonded to each other, thereby improving the structural strength at the position of the first composite part 122a; different second composite parts 122b can be bonded to each other, thereby improving the structural strength at the position of the second composite part 122b, so that when the secondary battery 100 falls, the parts are not easily washed apart by the electrolyte, thereby improving the overall anti-drop performance of the secondary battery 100.

[0109] In some embodiments, the lamination step further includes preparing a pole piece composite 12, and the step of preparing the pole piece composite 12 includes: Providing two isolation diaphragms 300 and a plurality of second pole pieces 121; like Fig.12 and Fig.13 As shown, along the thickness direction of the isolation diaphragm 300, the second pole piece 121 is stacked between two isolation diaphragms 300; along the length direction of the isolation diaphragm 300, multiple second pole pieces 121 are spaced between two isolation diaphragms 300, and the two isolation diaphragms 300 and the multiple second pole pieces 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.

[0110] Along the length direction of the composite component 400 , the isolation diaphragm 300 is cut by laser cutting process between two adjacent second pole pieces 121 , so that the isolation diaphragm 300 is separated into a plurality of diaphragms 122 , and the composite component 400 is separated into a plurality of pole piece complexes 12 . Fig.10 and Fig.11 The dotted line L2 in FIG. 1 is used to indicate the position of laser cutting.

[0111] The step of preparing the pole piece complex 12 facilitates the production of multiple pole piece complexes 12. In addition, the step of laser cutting can achieve the separation between different pole piece complexes 12. At the same time, the high temperature generated by the laser cutting can also melt and connect the diaphragm 122 at the cutting position, thereby improving the structural stability between the diaphragm 122 and the second pole piece 121 of a single pole piece complex 12.

[0112] In some embodiments, the second pole piece 121 and the diaphragm 122 are laminated by high-temperature hot pressing, so that the second pole piece 121 and the diaphragm 122 are bonded, thereby improving the bonding stability between the second pole piece 121 and the diaphragm 122 .

[0113] Please refer to Fig.11 and Figure 2 In some embodiments, the thermal compounding step includes: The first composite parts 122a are folded toward the main body 10a of the electrode assembly 10 by hot stamping. During the folding process, the first composite parts 122a of at least two electrode composites 12 are tilted along the same side in the thickness direction of the electrode assembly 10, and the tilted first composite parts 122a are bonded to each other. The second composite parts 122b are retracted toward the main body 10a of the electrode assembly 10 by hot stamping. During the retraction process, the second composite parts 122b are inclined along the same side in the thickness direction of the electrode assembly 10, and the inclined second composite parts 122b are bonded to each other.

[0114] In some embodiments, the inclined first composite parts 122a are bonded to each other to form a first composite member 122c, and the inclined second composite parts 122b are bonded to each other to form a second composite member 122d.

[0115] Through the thermal bonding step, the first bonding part 122a and the second bonding part 122b are formed from Fig.11 The status shown is 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 10a; on the other hand, the high temperature of hot stamping can activate the viscosity of the first composite part 122a and the second composite part 122b, so that the first composite parts 122a are bonded to each other, and the second composite parts 122b are bonded to each other, thereby improving the stability of the first composite part 122a and the second composite part 122b being gathered to the main body 10a, and improving the structural strength of the electrode assembly 10.

[0116] Please refer to Fig.11 , Figure 5 and Figure 6 In some embodiments, the thermal compounding step includes: Along the thickness direction of the electrode assembly 10, at least two mutually stacked first composite parts 122a are brought together in a direction close to each other by hot pressing, and the first composite parts 122a that have been hot pressed are partially bonded to each other; Along the thickness direction of the electrode assembly 10 , at least two mutually stacked second composite parts 122 b are brought together toward each other through hot pressing, and the second composite parts 122 b that have been hot pressed are partially bonded to each other.

[0117] Through the thermal bonding step, the first bonding part 122a and the second bonding part 122b are formed from Fig.11 The status shown is Figure 5 , Figure 6 State transitions are shown.

[0118] In some embodiments, the first composite parts 122a that have been subjected to heat pressing are partially bonded to each other to form a first composite member 122c, and the second composite parts 122b that have been subjected to heat pressing are partially bonded to each other to form a second composite member 122d.

[0119] Compared with a single first composite part 122a, the thickness of at least two first composite parts 122a bonded to each other overlap, thereby improving the structural strength at the position of the first composite part 122a; compared with a single second composite part 122b, the thickness of at least two second composite parts 122b bonded to each other overlap, making it difficult for the diaphragms 122 of the secondary battery 100 to be separated by the impact of the electrolyte during the falling process, thereby improving the falling performance of the secondary battery 100.

[0120] See also Fig.14 In some embodiments, the first composite part 122a or the second composite part 122b of the electrode assembly 10 is processed by a thermal composite device 2000. The thermal composite device 2000 includes a carrier 2001, an upper pressing member 2002, and a hot stamping member 2003. The electrode assembly 10 is placed on the carrier 2001, and the upper pressing member 2002 is placed above the electrode assembly 10 to fix the electrode assembly 10. Then, the first composite part 122a and the second composite part 122b of the electrode assembly 10 are processed by the hot stamping member 2003.

[0121] See also Fig.14 In some embodiments, the thermal compounding step includes: The first composite part 122a is pushed along the thickness direction of the electrode assembly 10 by the hot stamping member 2003, so that the stacked bonding parts of the first composite part 122a are inclined toward the same side in the thickness direction of the electrode assembly 10; The second composite part 122 b is pushed along the thickness direction of the electrode assembly 10 by the hot stamping member 2003 , so that the stacked bonding parts of the second composite part 122 b are inclined toward the same side in the thickness direction of the electrode assembly 10 .

[0122] When the stacked and bonded parts of the first composite part 122a and the stacked and bonded parts of the second composite part 122b are tilted toward the same side, the width dimension of the electrode assembly 10 can be reduced, thereby facilitating the reduction of the volume of the secondary battery 100 and reducing the volume energy density loss of the secondary battery 100.

[0123] See also Figure 8 or Fig. 9 In some embodiments, the method for manufacturing the secondary battery 100 further includes: Packaging: The electrode assembly 10 is installed in the second shell portion 21 of the shell 20, so that the end of the first composite portion 122a away from the third portion 1225 is accommodated in the second shell portion 21, and the end of the second composite portion 122b away from the third portion 1225 is accommodated in the second shell portion 21, and the second shell portion 21 of the shell 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.

[0124] By accommodating the ends of the first composite part 122a and the second composite part 122b away from the third part 1225 in the second shell part 21, the connection between the ends of the first composite part 122a and the second composite part 122b away from the third part 1225 and the first shell part 22 and the second shell part 21 can be reduced, thereby reducing the impact of the shell 20 packaging and improving the sealing of the packaging.

[0125] See also Fig.15 The embodiment of the present application further provides an electronic device 1000, comprising the secondary battery 100 in any of the above embodiments. In the secondary battery 100 in the electronic device 1000, the bonding and compounding between the separators 122 is conducive to improving the anti-drop performance of the secondary battery 100, so that the electronic device 1000 is not easily damaged by falling.

[0126] 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 smart watch, etc., which are not listed one by one here.

[0127] In some embodiments, the electronic device 1000 further includes a device body 200, and the secondary battery 100 is installed in 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 by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described one by one here.

[0128] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

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 comprises at least two stacked electrode sheet complexes and a plurality of first electrode sheets, wherein the electrode sheet complex is disposed between two adjacent first electrode sheets; The electrode composite comprises a second electrode and two diaphragms which are stacked, wherein the second electrode has an opposite polarity to the first electrode; along the width direction of the electrode assembly, the diaphragm comprises a first portion, a second portion and a third portion, wherein the third portion is connected between the first portion and the second portion, and the second electrode is arranged between the third portions of the two diaphragms, wherein the first portions of the two diaphragms are bonded to each other to form a first composite portion, and the second portions of the two diaphragms are bonded to each other to form a second composite portion; The first composite parts of at least two of the electrode composites are partially stacked and bonded to form a first composite part, and the second composite parts of at least two of the electrode composites are partially stacked and bonded to form a second composite part; the third part, the second electrode and the first electrode are stacked to form a main body of the electrode assembly, and 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 is arranged in a direction close to the first side, and the second composite part is arranged in a direction close to the second side; The shell includes a first shell portion and a second 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. The first composite component is extended toward the second shell portion.

2. The secondary battery according to claim 1, wherein: Along the thickness direction of the electrode assembly, the first composite parts of at least two of the electrode sheet composites are inclined toward the same side and are partially stacked and bonded to form the first composite member.

3. The secondary battery according to claim 2, characterized in that: Along the thickness direction of the electrode assembly, the second composite parts of at least two of the electrode sheet composites are inclined toward the same side and are partially stacked and bonded to form a second composite member.

4. The secondary battery according to claim 1, wherein: Along the thickness direction of the electrode assembly, the first composite parts of at least two of the electrode sheet composites are gathered towards each other and partially stacked and bonded to form the first composite part, and the first composite part is inclined toward one side in the thickness direction of the electrode assembly and gathered towards the first side.

5. The secondary battery according to claim 4, characterized in that: Along the thickness direction of the electrode assembly, the second composite parts of at least two of the electrode sheet composites are gathered towards each other and partially stacked and bonded to form the second composite part, and the second composite part is inclined toward one side in the thickness direction of the electrode assembly and gathered towards the second side.

6. The secondary battery according to claim 1, wherein: One end of the second composite component away from the third portion extends toward the interior of the second shell portion.

7. The secondary battery according to claim 1, wherein: Along the width direction of the electrode assembly, the width of the first portion is D1, 0.9 mm ≤ D1 ≤ 2.0 mm; and / or, Along the width direction of the electrode assembly, the width of the second portion is D2, 0.9 mm≤D2≤2.0 mm.

8. The secondary battery according to claim 1, wherein: The bonding force between two adjacent separators is F, 2N / 10mm≤F≤5N / 10mm.

9. The secondary battery according to claim 1, wherein: The shell comprises a shell body and a side sealing edge, the shell body has a cavity, the electrode assembly is arranged in the cavity; the first shell portion has a first extension portion, the first extension portion is arranged on both sides of the first shell portion in a width direction; the second shell portion has a second extension portion, the second extension portion is arranged on both sides of the second shell portion in a width direction; along the direction away from the main body, the first extension portion and the second extension portion are gradually gathered together to fit together to form the side sealing edge; The side sealing edge includes an unsealed area and a packaged area, wherein the unsealed area is an area where the first extension portion and the second extension portion are gradually gathered and not attached, and the packaged area is an area where the first extension portion and the second extension portion are attached to each other; the unsealed area is connected between the packaged area and the shell body, and the unsealed area is in communication with the cavity; Along the width direction of the shell, the width of the unsealed area is W, 0.5mm≤W≤1mm.

10. The secondary battery according to claim 9, characterized in that 0.5mm≤W≤0.7mm.

11. The secondary battery according to claim 1, wherein The shell comprises a shell body and a side seal, the shell body has a cavity, the electrode assembly is arranged in the cavity; the first shell portion has a first extension portion, the first extension portion is arranged on both sides of the first shell portion in the width direction; the second shell portion has a second extension portion, the second extension portion is arranged on both sides of the second shell portion in the width direction; along the direction away from the main body, the first extension portion and the second extension portion are gradually gathered to fit together to form the side seal, the side seal is a double folded edge, and the side seal is gathered on both sides of the shell body in the width direction; The thickness of the secondary battery is H1, and along the thickness direction of the secondary battery, the height of the side seal is H2, where H2≤H1≤2.4 mm.

12. A method for manufacturing a secondary battery, for manufacturing the secondary battery according to any one of claims 1 to 11, characterized in that: include: Stacking: stacking the electrode sheet complex between two adjacent first electrode sheets, the first composite parts of at least two electrode sheet complexes are stacked on each other, and the second composite parts of at least two electrode sheet complexes are stacked on each other; at least two electrode sheet complexes and a plurality of the first electrode sheets are stacked to form an electrode assembly; Thermal bonding: The first bonding parts are bonded to each other by heating the first bonding parts, and the second bonding parts are bonded to each other by heating the second bonding parts.

13. The method for manufacturing a secondary battery according to claim 12, wherein: The lamination step further includes preparing a pole piece composite, and the step of preparing the pole piece composite includes: Providing two isolation diaphragms and a plurality of second pole pieces; The second pole piece is stacked between two isolation diaphragms along the thickness direction of the isolation diaphragms; Along the length direction of the isolation diaphragm, a plurality of the second pole pieces are spaced between two isolation diaphragms, and the two isolation diaphragms and the plurality of the second pole pieces are combined to form a composite assembly; The isolation membrane is cut along the length direction of the composite component at a position between two adjacent second pole pieces by using a laser cutting process, so that the composite component is separated to form a plurality of pole piece composites.

14. The method for manufacturing a secondary battery according to claim 13, wherein: The thermal compounding step comprises: The first composite parts are gathered toward the main body of the electrode assembly by hot stamping. During the gathering process, the first composite parts of at least two electrode composites are tilted along the same side in the thickness direction of the electrode assembly, and the tilted first composite parts are bonded to each other; The second composite parts are gathered toward the main body of the electrode assembly by hot stamping. During the gathering process, the second composite parts are inclined along the same side in the thickness direction of the electrode assembly, and the inclined second composite parts are bonded to each other.

15. The method for manufacturing a secondary battery according to claim 12, wherein: The thermal compounding step comprises: Along the thickness direction of the electrode assembly, at least two mutually stacked first composite parts are brought together in a direction close to each other by heat pressing, and the first composite parts after heat pressing are partially bonded to each other; Along the thickness direction of the electrode assembly, at least two mutually stacked second composite parts are brought together in a direction close to each other by heat pressing, and the second composite parts that have been heat pressed are partially bonded to each other.

16. The method for manufacturing a secondary battery according to claim 15, wherein: The thermal compounding step comprises: Pushing the first composite part along the thickness direction of the electrode assembly by a hot stamping piece so that the stacked bonding parts of the first composite part are inclined toward the same side in 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 member, so that the stacked bonding parts of the second composite part are inclined toward the same side in the thickness direction of the electrode assembly.

17. The method for manufacturing a secondary battery according to claim 14 or 16, characterized in that: The method for manufacturing the secondary battery further includes: Packaging: The electrode assembly is installed in the first shell portion of the shell, so that the end of the first composite part away from the third part is accommodated in the first shell portion, and the end of the second composite part away from the third part is accommodated in the first shell portion, and the second shell portion of the shell 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.

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

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