Secondary battery and electric device

Abstract

A secondary battery (100, 200) and an electric device (1). The secondary battery (100, 200) comprises a housing (10), an electrode assembly (20), multiple first tabs (30), and a first adapter (50). The electrode assembly (20) has a laminated structure and comprises multiple first electrode sheets (21) stacked in a first direction (X). Each first electrode sheet (21) comprises a first current collector (210) and a first active material layer (211). The first current collector (210) comprises a first side (2101), a second side (2102), a third side (2103), and a fourth side (2104). The second side (2102) and the fourth side (2104) are arranged opposite to each other in a second direction (Y), and the first side (2101) and the third side (2103) are arranged opposite to each other in a third direction (Z). The dimension W1 of the first side (2101) and the dimension L1 of the second side (2102) satisfy: 1<L1 / W1≤5. Each first tab (30) is integrally formed with a corresponding first current collector (210) and extends out of the first current collector (210) from the first side (2101); and when viewed from the first direction (X), the first tab (30) is connected to a corresponding first active material layer (211) at the first side (2101). The dimension of each first tab (30) in the second direction (Y) is equal to the dimension of a corresponding first side (2101) in the second direction (Y). The first adapter (50) is electrically connected to the first tabs (30) and the housing (10). The energy density and electrolyte infiltration efficiency of the secondary battery (100, 200) are improved, and the first tabs (30) do not require die cutting.

Description

Secondary batteries and electrical devices Technical Field

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

[0002] Secondary batteries (such as lithium-ion batteries) are widely used in electronic products such as mobile devices, power tools, and electric vehicles. Secondary batteries with a laminated structure typically consist of stacked electrodes and tabs connected to the electrodes. The tabs are integrally connected to the current collectors of the electrodes and are manufactured using a die-cutting process.

[0003] However, tabs can take up space within a secondary battery, reducing its energy density. Furthermore, tabs can cause localized poor wetting of the electrode sheet, impacting the battery's cycling performance. Furthermore, tabs manufactured using a die-cutting process have low electrical and thermal conductivity, and the die-cutting process reduces production efficiency and increases costs.

[0004] Summary of the Invention

[0005] In view of this, it is necessary to provide a secondary battery that can solve at least one of the above technical problems.

[0006] In addition, it is also necessary to provide an electrical device having the above-mentioned secondary battery.

[0007] In a first aspect, the present application provides a secondary battery comprising a housing, at least one electrode assembly disposed within the housing, and a plurality of first electrode tabs. Each electrode assembly is a laminated structure and includes a plurality of first electrode sheets stacked in a first direction. The first electrode sheet includes a first current collector and a first material layer disposed on the first current collector. The first current collector includes a first side, a second side, a third side, and a fourth side connected end to end. The second side and the fourth side are disposed opposite each other in the second direction, and the first side and the third side are disposed opposite each other in the third direction, with the first, second, and third directions being perpendicular to each other. The dimension of the first side in the second direction is W1, and the dimension of the second side in the third direction is L1, where 1 < L1 / W1 ≤ 5. The first electrode tab is integrally disposed with the first current collector and extends from the first side. When viewed in the first direction, the first electrode tab contacts the first material layer at the first side. The dimension of the first electrode tab in the second direction is W2, where W2 = W1. The secondary battery also includes a first adapter electrically connected to the plurality of first electrode tabs and further connected to the housing.

[0008] In the secondary battery of the present application, by providing a first electrode tab extending from the first side to the first current collector, the space occupied by the first electrode tab in the housing is reduced, thereby helping to reduce the impact of the first electrode tab on the energy density of the secondary battery. Furthermore, during injection, the electrolyte can enter the interlayer gap of the electrode sheet from both ends of the electrode assembly in the second direction, and the required infiltration distance of the electrolyte is shorter, which is conducive to the electrolyte fully infiltrating the electrode assembly and improving the electrolyte infiltration efficiency, improving the interface during the cycle, and improving the cycle performance of the secondary battery. In addition, the first electrode tab does not need to be die-cut, so the conduction area of ​​current and heat is increased, which is not only conducive to improving electrical and thermal conductivity, but also to improving production efficiency and reducing production costs. Moreover, since 1<L1 / W1≤5, the conduction distance of electrons in the first current collector from the third side along the third direction to the first side can be reduced, thereby reducing the risk of uneven electron density distribution or increased internal resistance, thereby further improving the interface during the cycle and improving the cycle performance of the secondary battery.

[0009] In some possible implementations, the first tab includes a first segment connected to the first side and a second segment connected to the first segment, with the second segment being bent relative to the first segment. The plurality of second segments form a first connecting portion, and the first adapter is connected to the first connecting portion. This helps reduce the space occupied by the first tab on one side of the electrode assembly in the third direction, thereby increasing the energy density of the secondary battery.

[0010] In some possible implementations, the plurality of first tabs are divided into N tab groups, where N is a positive integer. Each tab group includes a first tab bundle and a second tab bundle, wherein the first segment of the first tab in the first tab bundle and the first segment of the first tab in the second tab bundle extend away from each other, and the second segment of the first tab in the second tab bundle and the second segment of the first tab in the second tab bundle extend toward each other. By independently bending each tab bundle, the length required for stacking the second segments of the first tab after bending is reduced, thereby reducing the overall weight and production cost of the secondary battery.

[0011] In some possible implementations, there is one electrode assembly, and the N electrode tab groups are all connected to the first electrode piece of the electrode assembly.

[0012] In some possible implementations, there are multiple electrode assemblies, and N tab groups are respectively connected to the first pole pieces of the multiple electrode assemblies. By dividing the first tabs connected to the multiple electrode assemblies into an even number of tab bundles and bending each tab bundle independently, the first tabs are bent so that the length required for the second sections to be stacked on each other is shorter, thereby reducing the overall weight and production cost of the secondary battery. In addition, when at least one electrode assembly has a quality problem, the problematic electrode assembly (and other electrode assemblies welded to the electrode assembly) can be removed separately to avoid the risk of all electrode assemblies being scrapped at the same time when the first tabs of all electrode assemblies are bent together.

[0013] In some possible implementations, there are two electrode assemblies, and N is 1. A first tab bundle is connected to the first electrode sheet of one electrode assembly, and a second tab bundle is connected to the first electrode sheet of another electrode assembly. By bending the first tabs connected to the same electrode assembly to form the first tab bundle or the second tab bundle, the bending of the first tab reduces the length required for stacking the second tabs, thereby reducing the overall weight and production cost of the secondary battery.

[0014] In some possible implementations, the first adapter includes N connection regions and a transition region connected to each connection region, with the transition region being bent relative to the connection region. The connection region is located on the side of the first connecting portion facing the electrode assembly and is connected to the second segment of the first tab in the first and second tab bundles. The transition region is connected to the housing. The N connection regions correspond one-to-one to the N tab groups, thereby facilitating connection of the first adapter to each tab group.

[0015] In some possible implementations, the second segments of the first tabs in the first tab bundle are stacked and welded together to form a first welded region, thereby improving the connection strength between the second segments. The connection region is welded to the second segments to form a second welded region, thereby improving the weld strength between the connection region and the second segments. Furthermore, stacking and welding the second segments together facilitates connection between the connection region and the second segment of each first tab in the corresponding tab bundle.

[0016] In some possible implementations, when viewed from a third direction, the first welding area and the second welding area overlap, thereby improving the stability of the welding between the second segments at the first welding area.

[0017] In some possible implementations, when viewed from the third direction, the first welding region is located between 0 and 1 / 3 of the thickness of the electrode assembly in the first direction. Therefore, the second segments in each tab group are fully welded together, allowing the first tab in each tab group to be connected to the first adapter.

[0018] In some possible implementations, the secondary battery further includes a first insulating member disposed on a side of the connection region facing the electrode assembly in the third direction. The first insulating member can cover burrs or weld marks on the connection region, reducing the risk of such burrs or weld marks piercing the first segment of the first tab.

[0019] In some possible implementations, the secondary battery further includes a second insulating member disposed in the third direction on a side of the first connecting portion facing away from the connection region. The second insulating member can cover burrs or weld marks on the first connecting portion, thereby reducing damage to the housing caused by such burrs or weld marks.

[0020] In some possible implementations, the first and second tab bundles contain the same number of first tabs. This allows the second segments of each tab bundle to be welded using the same welding parameters, improving weld uniformity and enhancing the smoothness of the structure within the housing.

[0021] In some possible implementations, along the direction in which the first tab extends from the first side, the length of the first tab is D, the thickness of the electrode assembly in the first direction is T, and T / 3 ≤ D ≤ 2T / 3. This allows the first tabs of each tab bundle to be stacked between the folded second segments to facilitate welding and fixation, while also minimizing the impact of overlapping second segments of different tab bundles on the energy density or weight of the secondary battery.

[0022] In some possible implementations, the secondary battery further includes multiple second electrode tabs. The electrode assembly further includes multiple second electrode sheets stacked in a first direction. The second electrode sheet includes a second current collector and a second active material layer disposed on a surface of the second current collector. The second current collector includes a fifth side, a sixth side, a seventh side, and an eighth side connected end to end. The sixth and eighth sides are disposed opposite each other in the second direction, and the fifth and seventh sides are disposed opposite each other in the third direction. The dimension of the fifth side in the second direction is W3, and the dimension of the sixth side in the third direction is L2, where 1 < L2 / W3 ≤ 5. The second electrode tab is integrally formed with the second current collector and extends from the fifth side. When viewed from the first direction, the second electrode tab contacts the second active material layer at the fifth side. The dimension of the second electrode tab in the second direction is W4, where W4 = W3. The secondary battery further includes a second adapter electrically connected to the multiple second electrode tabs and further connected to the housing. By having the second electrode tab extend from the fifth side of the second current collector, the space occupied by the second electrode tab within the housing is reduced, thereby reducing the impact of the second electrode tab on the energy density of the secondary battery. Furthermore, during injection, the electrolyte can enter the interlayer gaps between the electrode sheets from both ends of the electrode assembly in the second direction. This shortens the distance required for the electrolyte to penetrate the electrode assembly, thereby facilitating full electrolyte penetration and improving electrolyte wetting efficiency. Furthermore, since the second tab does not require die-cutting, the area for current and heat conduction is increased, which not only improves electrical and thermal conductivity but also increases production efficiency and reduces costs.

[0023] In some possible implementations, the first electrode tab and the second electrode tab are respectively located at two opposite ends of the electrode assembly in the third direction.

[0024] In some possible implementations, the secondary battery is a square-shell battery, and the shell is made of metal. The shell includes a first end wall and a second end wall arranged opposite to each other in a second direction, a side wall connected between the first end wall and the second end wall, and a first pole and a second pole. The first pole and the second pole are both arranged on the first end wall or both arranged on the side wall. The first adapter is connected to the first pole, and the second adapter is connected to the second pole. Therefore, the first pole and the second pole can respectively present the same electrical polarity as the first pole piece and the second pole piece, and the first pole and the second pole can be used to connect external components.

[0025] In some possible implementations, the housing is a packaging bag. The housing includes a receiving portion and a sealed edge connected to the receiving portion. The electrode assembly is disposed within the receiving portion. The first adapter and the second adapter both extend from the sealed edge into the housing. Thus, the first adapter and the second adapter can be used to connect to external components.

[0026] The second aspect of the present application further provides an electrical device comprising a battery compartment and the above secondary battery. The electrical device is powered by the above secondary battery, and the energy density and electrolyte infiltration efficiency of the secondary battery are improved, and the first tab of the secondary battery does not need to be die-cut. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0028] FIG1 is a schematic structural diagram of a secondary battery provided in some examples according to one embodiment of the present application.

[0029] FIG. 2A is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some embodiments.

[0030] FIG. 2B is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some other embodiments.

[0031] FIG3 is a cross-sectional view of the secondary battery shown in FIG1 along the cutting line III-III in some embodiments (the separator is omitted).

[0032] FIG. 4 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line IV-IV in some embodiments.

[0033] FIG5 is a schematic structural diagram of the first adapter of the secondary battery shown in FIG4 when viewed from a third direction.

[0034] FIG6 is a schematic structural diagram of the secondary battery of the present application in other embodiments.

[0035] FIG. 7 is a cross-sectional view of the secondary battery shown in FIG. 6 along the cutting line VII-VII.

[0036] FIG. 8 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some other embodiments.

[0037] FIG. 9 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line IV-IV in some other embodiments.

[0038] FIG10 is a schematic structural diagram of the first adapter of the secondary battery shown in FIG9 when viewed from a third direction.

[0039] FIG. 11 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some further embodiments.

[0040] FIG. 12 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some other embodiments.

[0041] FIG13 is a schematic structural diagram of a secondary battery provided in another embodiment of the present application.

[0042] FIG14 is a cross-sectional view of the secondary battery shown in FIG13 along the cutting line XIII-XIII.

[0043] FIG15 is a schematic structural diagram of an electrical device provided in one embodiment of the present application.

[0044] Description of Main Component Symbols Electric device 1 Housing 10 First end wall 11 Second end wall 12 Side wall 13 First electrode post 14 Second electrode post 15 Accommodation portion 16 Edge seal 17 Electrode assembly 20 First electrode sheet 21 Second electrode sheet 22 Separator 23 First electrode tab 30 Electrode tab group 30A First electrode tab bundle 30B Second electrode tab bundle 30C First segment 31 Second segment 32 Second electrode tab 40 First adapter 50 Connection area 51 Transfer area 52 Second adapter 60 First insulating member 70 Second insulating member 80 Secondary battery 100 Battery compartment 101 First opening 111 Second opening 112 First current collector 210 First active material layer 211 Insulating layer 212 Second current collector 220 Second active material layer 221 First connecting portion 320 First portion 521 Second portion 522 First side 2101 Second side 2102 Third side 2103 Fourth side 2104 Fifth side 2201 Sixth side 2202 Seventh side 2203 Eighth side 2204 First direction X Second direction YThird direction Z First side X1 Second side X2 First material layer H First welding area S1 Second welding area S2 Length D Thickness T Dimensions W1, W2, W3, W4, L1, L2,

[0045] The following specific implementation methods will further illustrate this application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0047] Below, embodiments of the present application will be described in detail. However, the present application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments illustrated herein. Rather, these exemplary embodiments are provided to make the present application thorough and detailed for those skilled in the art.

[0048] In addition, for the sake of brevity and clarity, the size or thickness of various components, layers may be exaggerated in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0049] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0050] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0051] Spatial related terms, such as "on" etc., can be used herein for convenient description, to describe the relationship between an element or feature and another element (multiple elements) or feature (multiple features) as illustrated in the figure. It should be understood that, in addition to the directions described in the figure, spatial related terms are intended to include different directions of equipment or devices in use or operation. For example, if the equipment in the figure is turned over, the elements described as "above" or "on" other elements or features will be oriented "below" or "below" other elements or features. Therefore, the exemplary term "on" can include the direction above and below. It should be understood that although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part, without departing from the teachings of the exemplary embodiments.

[0052] As used herein, "parallel" and "perpendicular" are used to describe an ideal state between two components. In actual production or use, there may be a state between two components that is approximately parallel or perpendicular. For example, in combination with numerical descriptions, parallel can refer to the angle between two straight lines being between ±10°, parallel can also refer to the dihedral angle between two planes being between ±10°, and parallel can also refer to the angle between a straight line and a plane being between ±10°. Perpendicular can refer to the angle between two straight lines being between 90±10°, perpendicular can also refer to the dihedral angle between two planes being between 90±10°, and perpendicular can also refer to the angle between a straight line and a plane being between 90±10°. The two components described as "parallel" or "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or "plane" if its overall extension direction is a straight line or plane.

[0053] In this application, the relationship between parameter values ​​that is greater than, less than, or not equal to the design relationship needs to exclude the reasonable error of the measuring equipment.

[0054] Referring to Figures 1 to 4 , one embodiment of the present application provides a secondary battery 100 comprising a housing 10, at least one electrode assembly 20 and an electrolyte (not shown) disposed within the housing 10, a first electrode tab 30, and a second electrode tab 40. Figures 1 to 4 illustrate the embodiment with one electrode assembly 20. As shown in Figures 2A to 4 , each electrode assembly 20 is a laminated structure comprising a plurality of first electrode sheets 21, a plurality of second electrode sheets 22, and a plurality of separators 23. In the laminated structure, the first electrode sheets 21 and the second electrode sheets 22 are alternately stacked, with one second electrode sheet 22 disposed between every two adjacent first electrode sheets 21, and one first electrode sheet 21 disposed between every two adjacent second electrode sheets 22. Separator membranes 23 are disposed between adjacent first electrode sheets 21 and second electrode sheets 22. Separator membranes 23 are used to prevent direct contact between the first electrode sheets 21 and the second electrode sheets 22, thereby reducing the possibility of a contact short between the first electrode sheets 21 and the second electrode sheets 22. The first electrode tab 30 is electrically connected to the first electrode piece 21 , and the second electrode tab 40 is electrically connected to the second electrode piece 22 .

[0055] In some embodiments, the housing 10 is made of metal. The housing 10 includes a first end wall 11 and a second end wall 12 disposed opposite each other, a side wall 13 connected between the first end wall 11 and the second end wall 12, and a first terminal 14 and a second terminal 15, respectively, disposed on the first end wall 11. The first terminal 14 and the second terminal 15 are electrically isolated from the first end wall 11. The first end wall 11 and the second end wall 12 may be arranged parallel to each other. In some embodiments, the secondary battery 100 is a prismatic battery. The side wall 13 and the second end wall 12 may be integrally formed, and the first end wall 11 and the side wall 13 may be welded or clamped together. The housing 10 may be entirely made of steel. For example, the steel housing may contain the elements Fe and C. The steel housing may also contain one or more of the elements Ni, Co, Al, Mn, Cr, Cu, Mg, Mo, S, Si, Ti, V, Pb, Sb, N, and P. For example, the first end wall 11 may be made of steel, and the second end wall 12 and the side wall 13 may also be made of steel. As shown in FIG3 , the first end wall 11 is provided with a first opening 111 and a second opening 112 spaced apart from each other. The first pole 14 and the second pole 15 can be mounted on the first opening 111 and the second opening 112 respectively by bonding or riveting.

[0056] In which, a three-dimensional coordinate system is established based on a first direction X, a second direction Y, and a third direction Z that are perpendicular to each other. In the description of the embodiments of the present application, the first direction X is the stacking direction of the plurality of first pole pieces 21. Although the first direction X is indicated in Figures 1 to 4 as having a specific vector direction to illustrate the stacking direction of the plurality of first pole pieces 21, it can be understood that the opposite direction of the above-mentioned indicated direction can also be the stacking direction of the plurality of first pole pieces 21. As shown in Figure 2A, the first direction X has a first side X1 and a second side X2 opposite to the first side X1. The second direction Y is the direction from the second end wall 12 to the first end wall 11. The third direction Z is the direction from the first pole 14 to the second pole 15.

[0057] As shown in Figures 2A and 4, the first electrode sheet 21 includes a first current collector 210 and a first active material layer 211 stacked in a first direction X. The first electrode sheet 21 can be a positive electrode sheet. Accordingly, the first current collector 210 can be a positive electrode current collector, and the first active material layer 211 can be a positive electrode active material layer. The second electrode sheet 22 includes a second current collector 220 and a second active material layer 221 stacked. The second electrode sheet 22 can be a negative electrode sheet. Accordingly, the second current collector 220 can be a negative electrode current collector, and the second active material layer 221 can be a negative electrode active material layer.

[0058] The positive electrode current collector may be made of aluminum foil or nickel foil, and the negative electrode current collector may be made of at least one of copper foil, nickel foil or carbon-based current collector. The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material includes a compound that can reversibly embed and deintercalate lithium ions (lithiated intercalation compound). In some embodiments, the positive electrode active material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive electrode active material is selected from lithium cobaltate (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) or at least one of lithium iron phosphate (LiFePO4).

[0059] The negative electrode active material layer contains a negative electrode active material, which is a negative electrode active material known in the art that can reversibly deintercalate active ions, and is not limited in this application. For example, it can be a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium. Among them, graphite can be selected from a combination of one or more of artificial graphite, natural graphite and modified graphite; silicon-based materials can be selected from a combination of one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; tin-based materials can be selected from a combination of one or more of elemental tin, tin oxide compounds, and tin alloys.

[0060] The isolation film 23 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene have a good effect on improving short circuits.

[0061] As shown in Figure 3, when viewed from the first direction X, the first current collector 210 may be roughly rectangular, including a first side 2101, a second side 2102, a third side 2103, and a fourth side 2104, connected end to end. The second side 2102 and the fourth side 2104 are disposed opposite each other in the second direction Y, while the first side 2101 and the third side 2103 are disposed opposite each other in the third direction Z. In the second direction Y, the second side 2102 is closer to the first and second poles 14 and 15 than the fourth side 2104. The dimension of the first side 2101 in the second direction Y is defined as W1, and the dimension of the second side 2102 in the third direction Z is defined as L1, where 1 < L1 / W1 ≤ 5. It can be understood that when the first current collector 210 is approximately rectangular, the dimension of the third side 2103 in the second direction Y is approximately the same as the dimension of the first side 2101 in the second direction Y, and the dimension of the fourth side 2104 in the third direction Z is approximately the same as the dimension of the second side 2102 in the third direction Z. Therefore, the first side 2101 and the third side 2103 are the short sides of the first current collector 210, and the direction in which the first side 2101 or the third side 2103 extends is the second direction Y; the second side 2102 and the fourth side 2104 are the long sides of the first current collector 210, and the direction in which the second side 2102 or the fourth side 2104 extends is the third direction Z. The first electrode tab 30 is integrally provided with the first current collector 210 and extends from the first side 2101 (the short side). The direction in which the first electrode tab 30 extends from the electrode assembly 30 is the third direction Z. The dimension of the first electrode tab 30 in the second direction Y is equal to the dimension of the first side 2101 in the second direction Y. The dimension of the first electrode tab 30 in the second direction Y is defined as W2, where W2 = W1. Therefore, the first electrode tab 30 does not need to be die-cut. During production, the positive electrode active slurry can be coated on the surface of the first current collector 210, and an empty foil area can be reserved at the edge of the first current collector 210. After the positive electrode active slurry is dried, the reserved empty foil area forms the first electrode tab 30. In the embodiment of the present application, since the first electrode tab 30 and the first current collector 210 are integrally provided, the first edge 2101 of the first current collector 210 can be a virtual dividing line between the first electrode tab 30 and the first current collector 210. As shown in Figures 2A and 3, when viewed from the first direction X, the first electrode tab 30 is in contact with the first material layer H, i.e., the first active material layer 211, at the first edge 2101.

[0062] As shown in FIG2A , in some embodiments, the first electrode tab 30 extends from the electrode assembly 20 in the third direction Z, and the first electrode tab 30 is bent. The first electrode tab 30 includes a first segment 31 connected to the first side 2101 and a second segment 32 connected to the first segment 31, with the second segment 32 bent relative to the first segment 31. The bent configuration of the first electrode tab 30 helps reduce the space occupied by the first electrode tab 30 on one side of the electrode assembly 20 in the third direction Z, thereby improving the energy density of the secondary battery 100.

[0063] Among them, when the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode, in order to reduce the risk of lithium plating of the negative electrode, it can be arranged in the third direction Z, with the edge of the second electrode 22 exceeding the edge of the first electrode 21, and the edge of the isolation film 23 exceeding the edge of the second electrode 22. As shown in Figure 2B, in other embodiments, in order to reduce the risk of short circuit caused by the contact between the bent first electrode 30 and the edge of the second electrode 22 (such as the isolation film 23 shrinks at high temperature, the first electrode 30 may contact the edge of the second electrode 22 in the event of falling, collision, etc.), the first electrode 21 can also be arranged to further include an insulating layer 212 provided on the first current collector 210, and the first active material layer 211 and the insulating layer 212 are connected to each other in the third direction Z. In the third direction Z, the edge of the insulating layer 212 exceeds the edge of the second electrode 22. At this time, the first active material layer 211 and the insulating layer 212 together form a first material layer H. As shown in FIG2B , when viewed from the first direction X, the first electrode tab 30 is in contact with the first material layer H at the first edge 2101. More specifically, the first electrode tab 30 is in contact with the insulating layer 212 of the first material layer H at the first edge 2101. In this way, even if the separator 23 shrinks at high temperatures, the insulating layer 212 can reduce the risk of short circuiting caused by the edge contact between the first electrode tab 30 and the second electrode piece 22. Among them, the insulating layer 212 includes inorganic particles and polymers, the inorganic particles include at least one of aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate, and the polymer includes at least one of polypropylene alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamide-imide, styrene-butadiene rubber, polyvinyl alcohol, polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, water-based acrylic resin, carboxymethyl cellulose or sodium carboxymethyl cellulose.

[0064] As shown in FIG3 , when viewed from the first direction X, the second current collector 220 may also be substantially rectangular, comprising a fifth side 2201, a sixth side 2202, a seventh side 2203, and an eighth side 2204, connected end to end. The sixth side 2202 and the eighth side 2204 are disposed opposite each other in the second direction Y, while the fifth side 2201 and the seventh side 2203 are disposed opposite each other in the third direction Z. The first side 2101 and the seventh side 2203 are located at one end of the electrode assembly 20 in the third direction Z, while the third side 2103 and the fifth side 2201 are located at the other end of the electrode assembly 20 in the third direction Z. In the second direction Y, the sixth side 2202 is closer to the first electrode post 14 and the second electrode post 15 than the eighth side 2204. The second side 2102 and the sixth side 2202 are located at one end of the electrode assembly 20 in the second direction Y, while the fourth side 2104 and the eighth side 2204 are located at the other end of the electrode assembly 20 in the second direction Y. The dimension of the fifth side 2201 in the second direction Y is W3, and the dimension of the sixth side 2202 in the third direction Z is L2, where 1<L2 / W3≤5. It can be understood that when the second current collector 220 is substantially rectangular, the dimension of the seventh side 2203 in the second direction Y is substantially the same as the dimension of the fifth side 2201 in the second direction Y, and the dimension of the eighth side 2204 in the third direction Z is substantially the same as the dimension of the sixth side 2202 in the third direction Z. Therefore, the fifth side 2201 and the seventh side 2203 are the short sides of the second current collector 220, while the sixth side 2202 and the eighth side 2204 are the long sides of the second current collector 220. The second electrode tab 40 is integrally provided with the second current collector 220 and extends from the fifth side 2201 (the short side). The direction in which the second electrode tab 40 extends from the electrode assembly 30 is the third direction Z. The dimension of the second electrode tab 40 in the second direction Y is equal to the dimension of the fifth side 2201 in the second direction Y. The dimension of the second electrode tab 40 in the second direction Y is defined as W4, where W4 = W3. Therefore, the second electrode tab 40 does not require die-cutting. During fabrication, the negative electrode active slurry can be applied to the surface of the second current collector 220, and a blank foil area can be reserved at the edge of the second current collector 220. After the negative electrode active slurry is dried, the reserved blank foil area forms the second electrode tab 40. In the embodiment of the present application, since the second electrode tab 40 is integrally provided with the second current collector 220, the fifth side 2201 of the second current collector 220 can serve as a virtual dividing line between the second electrode tab 40 and the second current collector 220. As shown in Figure 3, when viewed from the first direction X, the second electrode tab 40 contacts the second active material layer 221 at the fifth side 2201. In some embodiments, the first electrode tab 30 and the second electrode tab 40 are located at opposite ends of the electrode assembly 20 in the third direction Z. The first electrode tab 30 extends from the second side X2 of the electrode assembly 20, and the second electrode tab 40 extends from the first side X1 of the electrode assembly 20.

[0065] As shown in FIG3 , when viewed from the first direction X, the first electrode sheet 21 and the second electrode sheet 22 overlap. When the first electrode sheet 21 is a positive electrode sheet and the second electrode sheet 22 is a negative electrode sheet, to reduce the risk of lithium plating in the negative electrode sheet, the second electrode sheet 22 can be arranged to extend from the first electrode sheet 21 along the second direction Y and the third direction Z from the area overlapping with the first electrode sheet 21. Therefore, in the third direction Z, the seventh side 2203 is closer to the side wall 13 than the first side 2101, and the fifth side 2201 is closer to the side wall 13 than the third side 2103. In the second direction Y, the sixth side 2202 is closer to the first and second pole posts 14 and 15 than the second side 2102, and the eighth side 2204 is farther away from the first and second pole posts 14 and 15 than the fourth side 2104.

[0066] As shown in Figures 2A to 5, the secondary battery 100 further includes a first adapter 50 and a second adapter 60 (the second adapter 60 is shown in Figures 2A and 3). The first adapter 50 is electrically connected to the plurality of first electrode tabs 30, and the second adapter 60 is electrically connected to the plurality of second electrode tabs 40. In some embodiments, the second segments 32 of the plurality of first electrode tabs 30 collectively form a first connecting portion 320, and the first adapter 50 is connected to the first connecting portion 320.

[0067] The first adapter 50 and the second adapter 60 are also connected to the housing 10. In some embodiments, when the housing 10 is made of metal, the first adapter 50 is connected to the first pole 14 and the second adapter 60 is connected to the second pole 15. Therefore, the first pole 14 and the second pole 15 can have opposite polarities, so that the secondary battery 100 can power external components (not shown). For example, when the first pole piece 21 is a positive pole piece and the second pole piece 22 is a negative pole piece, the first pole piece 14 has a positive polarity and the second pole piece 15 has a negative polarity. Moreover, when the first adapter 50 connects the first pole tab 30 to the first pole 14 and the second adapter 60 connects the second pole tab 40 to the second pole 15, the first pole tab 30 and the second pole tab 40 are guided to the same end of the electrode assembly 20 by the two adapters. Referring to Figures 6 and 7 , in other embodiments, two adapters may also guide the first electrode tab 30 and the second electrode tab 40 to opposite ends of the electrode assembly 20 in the third direction Z. For example, the first electrode post 14 and the second electrode post 15 are both provided on the sidewall 13, and the first electrode post 14 and the second electrode post 15 are arranged opposite each other in the third direction Z. The first adapter 50 connects the first electrode tab 30 to the first electrode post 14, and the second adapter 60 connects the second electrode tab 40 to the second electrode post 15. By using two adapters to guide the first electrode tab 30 and the second electrode tab 40 to the same end or opposite ends of the electrode assembly 20, the application range of the secondary battery 100 is broadened.

[0068] In some embodiments, the first adapter 50 can be made of aluminum, nickel, copper, steel, or nickel-plated copper. The second adapter 60 can be made of aluminum, nickel, copper, steel, or nickel-plated copper. To reduce the impact of the first adapter 50 and the second adapter 60 on the energy density of the secondary battery 100, the width of the first adapter 50 in the first direction X can be set to not exceed the thickness T of the electrode assembly 20 in the first direction X, and the width of the second adapter 60 in the first direction X can be set to not exceed the thickness T of the electrode assembly 20 in the first direction X. Furthermore, the thickness of the first adapter 50 can be 0.08 mm to 2.0 mm, and the thickness of the second adapter 60 can be 0.08 mm to 2.0 mm.

[0069] In the secondary battery 100 of the present application, by providing the first electrode tab 30 so as to extend the first current collector 210 from the first side 2101 (short side), the space occupied by the first electrode tab 30 in the housing 10 is reduced, thereby helping to reduce the impact of the first electrode tab 30 on the energy density of the secondary battery 100. Furthermore, during injection, the electrolyte can enter the interlayer gap of the electrode sheet from both ends of the electrode assembly 20 in the second direction Y, and the required infiltration distance of the electrolyte is shorter, which is conducive to the electrolyte fully infiltrating the electrode assembly 20 and improving the electrolyte infiltration efficiency, improving the interface during the cycle, reducing the capacity attenuation caused by lithium plating, black spots, purple spots, etc., and improving the cycle performance of the secondary battery 100. In addition, the first electrode tab 30 does not need to be die-cut, so the conduction area of ​​current and heat is increased, which is not only conducive to improving the electrical and thermal conductivity, but also conducive to improving production efficiency and reducing production costs.

[0070] Similarly, by providing the second electrode tab 40 so that the second current collector 220 extends from the fifth side 2201 (short side), the space occupied by the second electrode tab 40 within the housing 10 is reduced, thereby helping to reduce the impact of the second electrode tab 40 on the energy density of the secondary battery 100. Furthermore, during injection, the electrolyte can enter the interlayer gap between the electrode sheets from both ends of the electrode assembly 20 in the second direction Y. The required infiltration distance of the electrolyte is shorter, which is conducive to the electrolyte fully infiltrating the electrode assembly 20 and improving the electrolyte infiltration efficiency, improving the interface during the cycle process, reducing capacity attenuation caused by lithium plating, black spots, purple spots, etc., and improving the cycle performance of the secondary battery 100. In addition, the second electrode tab 40 does not need to be die-cut, so the conduction area of ​​current and heat is increased, which not only helps to improve the electrical and thermal conductivity, but also helps to improve production efficiency and reduce production costs.

[0071] Moreover, in the present application, since 1 < L1 / W1 ≤ 5, the conduction distance of electrons in the first current collector 210 from the third side 2103 along the third direction Z to the first side 2101 is reduced, thereby reducing the risk of uneven electron density distribution or increased internal resistance, thereby further improving the interface during the cycle process and enhancing the cycle performance of the secondary battery 100. Furthermore, when 1 < L2 / W3 ≤ 5, the conduction distance of electrons in the second current collector 220 from the seventh side 2203 along the third direction Z to the fifth side 2201 can be reduced, thereby reducing the risk of uneven electron density distribution or increased internal resistance.

[0072] In some embodiments, the plurality of first tabs 30 are divided into N tab groups 30A, where N is a positive integer. As shown in FIG2A , when there is only one electrode assembly 20, the N tab groups 30A are all connected to the first electrode sheet 21 of the electrode assembly 20. Each tab group 30A includes a first tab bundle 30B and a second tab bundle 30C, meaning that the plurality of first tabs 30 are divided into an even number of tab bundles. For example, when N=1, the plurality of first tabs 30 are divided into two tab bundles; when N=2, the plurality of first tabs 30 are divided into four tab bundles.

[0073] The first segments 31 of the first tab bundle 30B and the first segments 31 of the second tab bundle 30C extend away from each other, while the second segments 32 of the first tab bundle 30B and the second segments 32 of the second tab bundle 30C extend toward each other, so that the first tab bundle 30B and the second tab bundle 30C can each form a substantially U-shaped structure. The second segments 32 of the first tab bundle 30B and the second tab bundle 30C can be stacked together, thereby facilitating the simultaneous electrical connection of the first adapter 50 to all of the second segments 32 in each tab bundle. In some embodiments, the first tabs 30 in the first tab bundle 30B or the second tab bundle 30C are bent to form a roughly U-shaped structure, so that the first tab bundle 30B or the second tab bundle 30C has an innermost layer and an outermost layer, wherein the innermost layer of the first tab bundle 30B refers to the first tab 30 in the first tab bundle 30B connected to the first adapter 50, and the outermost layer of the first tab bundle 30B refers to the first tab 30 in the first tab bundle 30B that is farthest from the first adapter 50 along the stacking direction. Compared to a solution in which all first tabs 30 are bent together (e.g., all first tabs 30 are first extended toward the first side X1 and then toward the second side X2), by dividing the plurality of first tabs 30 into an even number of tab bundles and independently bending each tab bundle, the length required to stack the second segments 32 after the first tabs 30 are bent is reduced. This is particularly true when the electrode assembly 20 has a large thickness T in the first direction X (in which case the required length of the first tabs 30 is greater when all first tabs 30 are bent together). This significantly reduces the length required to bend the first tabs 30, thereby reducing the overall weight and production cost of the secondary battery 100. Furthermore, to reduce the length required to bend the second tabs 40, the plurality of second tabs 40 can also be divided into an even number of tab bundles. The manner in which the plurality of first tabs 30 are bundled can be the same as or different from the manner in which the plurality of second tabs 40 are bundled.

[0074] As shown in Figures 2A to 5, in some embodiments, the first adapter 50 includes N connection areas 51 and a transition area 52 connected to each connection area 51, with the transition area 52 being bent relative to the connection area 51. The N connection areas 51 correspond one-to-one to the N tab groups 30A. For example, when the plurality of first tabs 30 include one tab group 30A, the first adapter 50 includes one connection area 51. In other embodiments, as shown in Figures 8 to 10, when the plurality of first tabs 30 include two tab groups 30A, the first adapter 50 includes two connection areas 51. Each connection area 51 of the first adapter 50 is located on the side of the first connecting portion 320 facing the electrode assembly 20, and each connection area 51 is connected to the second segment 32 of the first tab bundle 30B and the second segment 32 of the second tab bundle 30C. The transition area 52 of the first adapter 50 is connected to the housing 10 (for example, the transition area 52 is connected to the first electrode post 14). As shown in Figures 2A and 3, in some embodiments, each connection region 51 is located between the electrode assembly 20 and the side wall 13 of the housing 10 in the third direction Z. When viewed from the third direction Z, the connection region 51 overlaps with the second segment 32 to which it is connected, and the connection region 51 extends from the overlapping region with the second segment 32 in the second direction Y. The transition region 52 is located between the electrode assembly 20 and the first end wall 11 of the housing 10 in the second direction Y. When viewed from the third direction Z, the transition region 52 extends from its connection with the connection region 51 in the third direction Z, and the transition region 52 extends to overlap with the first electrode 14. The connection region 51 and the transition region 52 may both be sheet-like structures, with the plane of the connection region 51 extending along the first direction X and the second direction Y, and the plane of the transition region 52 extending along the first direction X and the third direction Z. The second adapter 60 may have a structure similar to that of the first adapter 50, which will not be described in detail.

[0075] As shown in FIG2A and FIG8 , in some embodiments, the second segments 32 of the first or second tab bundles 30B or 30C are stacked and welded to form a first welded region S1, thereby improving the connection strength between the second segments 32. The connection region 51 is welded to the second segments 32 to form a second welded region S2, thereby improving the weld strength between the connection region 51 and the second segments 32. When manufacturing the secondary battery 100, the first or second tab bundles 30B or 30C can be first bent using a welding head to stack the second segments 32. The second segments 32 of the first or second tab bundles 30B or 30C are then pre-welded to improve the connection strength between the second segments 32. Subsequently, the connection region 51 of the first adapter 50 is stacked on the side of the second segments 32 facing the electrode assembly 20, and the connection region 51 is then welded to the second segments 32 using a welding head. Pre-welding the second segments 32 facilitates the connection between the connection region 51 and the second segment 32 of each first tab 30 of the first or second tab bundles 30B or 30C.

[0076] The first tab bundle 30B and the second tab bundle 30C in a tab group 30A can include the same number of first tabs 30. This allows the second segments 32 of the first tab bundle 30B and the second segments 32 of the second tab bundle 30C to be welded using the same welding parameters (e.g., welding time, welding temperature, etc.). This eliminates the need for frequent parameter adjustments when welding different tab bundles, simplifies the manufacturing process, and improves the uniformity of welding quality. Furthermore, this also helps improve the flatness of the structure within the housing 10.

[0077] As shown in Figures 2A and 8, in some embodiments, the first welding region S1 and the second welding region S2 overlap when viewed from the third direction Z, thereby improving the stability of the weld between the second segments 32 at the first welding region S1. In other embodiments, the first welding region S1 and the second welding region S2 may be separated when viewed from the third direction Z, thereby reducing the risk of over-welding at the first welding region S1.

[0078] In some embodiments, when viewed from the third direction Z, the first welding region S1 is located between 0 and 1 / 3 of the thickness T of the electrode assembly 20 in the first direction X. When the electrode assembly 20 is divided into three equal regions having the same thickness in the first direction X, when viewed from the third direction Z, the first welding region S1 may overlap with any of the three equal regions located closer to the outside in the first direction X. This ensures that the second segments 32 in each tab group 30A are fully welded, thereby facilitating the connection of the first tab 30 in each tab group 30A to the first adapter 50.

[0079] As shown in FIG2A , in some embodiments, the length of the first tab 30 along the direction in which the first tab 30 extends from the first side 2101 is D, and the thickness of the electrode assembly 20 in the first direction X is T, where T / 3 ≤ D ≤ 2T / 3. This allows the first tabs 30 of the first tab bundle 30B or the second tab bundle 30C to be stacked between the folded second segments 32 to facilitate welding and fixation, while also minimizing the impact of overlapping second segments 32 of the first tab bundle 30B and second tab bundle 30C on the energy density or weight of the secondary battery 100. It will be appreciated that the direction in which the first tab 30 extends from the first side 2101 is a curved direction. The length D of the first tab 30 is the sum of the lengths of the first segment 31 and the second segment 32 along the curved direction.

[0080] Referring to Figures 11 and 12, in other embodiments, there are multiple electrode assemblies 20. The multiple electrode assemblies 20 are connected in parallel or in series, thereby increasing the supply voltage of the secondary battery 100. In this case, N tab groups 30A are respectively connected to the first electrode sheets 21 of the multiple electrode assemblies 20, and each tab group 30A includes a first tab bundle 30B and a second tab bundle 30C. That is, this embodiment divides the first tabs 30 connected to the multiple electrode assemblies 20 into an even number of tab bundles, and each tab bundle is bent independently. Figure 11 shows that there are two electrode assemblies 20 and one tab group 30A. The first tab bundle 30B of the tab group 30A is connected to one of the electrode assemblies 20, and the second tab bundle 30C is connected to the other electrode assembly 20. The first adapter 50 includes a connection area 51, and the first tab bundle 30B and the second tab bundle 30C are both connected to the connection area 51. Figure 12 shows that there are two electrode assemblies 20 and two tab groups 30A. The two tab groups 30A are connected one-to-one with the two electrode assemblies 20. Correspondingly, the first adapter 50 includes two connection areas 51, and the first tab bundle 30B and the second tab bundle 30C of each tab group 30A are connected to the same connection area 51.

[0081] In this way, after the first tab 30 is bent, the length required for the second section 32 to be stacked together is shortened. This significantly reduces the length required to bend the first tab 30, particularly when the electrode assembly 20 is thick in the first direction X. This embodiment can significantly reduce the length required to bend the first tab 30, thereby reducing the overall weight and production cost of the secondary battery 100. Furthermore, if at least one electrode assembly 20 has a quality problem, the problematic electrode assembly 20 (and any other electrode assemblies 20 welded to it) can be removed separately, avoiding the risk of simultaneously rendering all electrode assemblies 20 useless if the first tabs 30 of all electrode assemblies 20 are bent simultaneously. Multiple electrode assemblies 20 can be stacked in the first direction X.

[0082] In some other embodiments, the plurality of first tabs 30 may not be grouped. In this case, all first tabs 30 are bent together (e.g., all first tabs 30 are first extended toward the first side X1 and then toward the second side X2), thereby reducing the number of welding times and simplifying the process.

[0083] As shown in FIG2A , in some embodiments, the secondary battery 100 further includes a first insulating member 70 , which is disposed on the side of the connection region 51 facing the electrode assembly 20 in the third direction Z. The first insulating member 70 can cover burrs or weld marks on the connection region 51 (burrs may be generated when cutting the first adapter 50 , and weld marks may be generated when welding the connection region 51 to the second segment 32 , but this application is not limited thereto), reducing the risk of such burrs or weld marks piercing the first segment 31 of the first electrode tab 30 , thereby reducing the risk of the first electrode tab 30 being easily broken during mechanical abuse. The first insulating member 70 can be a single-sided adhesive comprising an insulating material, and the insulating material can be selected from at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, or polyethylene glycol. In other embodiments, the first insulating member 70 can also be a ceramic coating. The thickness of the first insulating member 70 can be 0.01 mm to 0.1 mm.

[0084] The secondary battery 100 may further include a second insulating member 80, which is provided on the side of the first connecting portion 320 facing away from the connecting area 51 in the third direction Z. The second insulating member 80 may cover the burrs or weld marks on the first connecting portion 320, thereby reducing the damage caused to the housing 10 by the burrs or weld marks. The second insulating member 80 may be a single-sided adhesive comprising an insulating material, and the insulating material may be selected from at least one of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, or polyethylene glycol. In other embodiments, the second insulating member 80 may also be a ceramic coating. The thickness of the second insulating member 80 may be 0.01 mm to 0.1 mm. A similar insulating member may also be provided on the side of the connecting area of ​​the second adapter 60 facing the electrode assembly 20, and a similar insulating member may also be provided on the side of the second connecting portion (not shown) formed by the second tab 40 facing away from the connecting area, which will not be described in detail.

[0085] Please refer to Figures 13 and 14. Another embodiment of the present application also provides a secondary battery 200. The difference from the above-mentioned secondary battery 100 is that the shell 10 is a packaging bag, that is, the secondary battery 200 can be a soft-pack battery. For example, the shell 10 can be a packaging bag obtained by packaging with a packaging film (such as an aluminum-plastic film). The shell 10 includes a accommodating portion 16 and a sealing edge 17 connected to the accommodating portion 16. The electrode assembly 20 is arranged in the accommodating portion 16. The first adapter 50 and the second adapter 60 both extend out of the shell 10 from the sealing edge 17. The first adapter 50 and the second adapter 60 are used to connect to an external device (not shown). In this embodiment, the second direction Y is the direction in which the transition area 52 of the first adapter 50 extends out of the sealing edge 17, and is also the direction in which the transition area of ​​the second adapter 60 extends out of the sealing edge 17. The third direction Z is the arrangement direction of the transition area 52 of the first adapter 50 and the transition area of ​​the second adapter 60.

[0086] The transition region 52 includes a first portion 521 and a second portion 522, which are connected to each other. The first portion 521 is connected to the connection region 51, and the second portion 522 is connected to the edge seal 17. To facilitate the transition region 52 extending beyond the edge seal 17, the plane containing the first portion 521 can be configured to extend along the first direction X and the third direction Z, while the plane containing the second portion 522 can extend along the second direction Y and the third direction Z (i.e., along the plane containing the edge seal 17). In other words, the second portion 522 is bent relative to the first portion 521.

[0087] The secondary battery 100 (or secondary battery 200 ) of the present application may be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery.

[0088] Referring to FIG15 , one embodiment of the present application further provides an electrical device 1 comprising a battery compartment 101 and a secondary battery 100 (or secondary battery 200) housed in the battery compartment 101. The electrical device 1 is powered by the secondary battery 100, and the energy density and electrolyte infiltration efficiency of the secondary battery 100 are improved, and the first tab 30 of the secondary battery 100 does not require die-cutting. In some embodiments, the electrical device 1 of the present application may be, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0089] The performance of the secondary battery provided in this application is described below through specific examples and comparative examples. The present application is described using a secondary battery comprising a prismatic battery having a single electrode assembly, wherein the first electrode sheet is a positive electrode sheet, and the second electrode sheet is a negative electrode sheet, as an example, and in conjunction with specific preparation processes and testing methods. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0090] Example 1

[0091] (1) Preparation of the first electrode: The positive electrode active material lithium iron phosphate (LiFePO4), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 96.5:1.5:2, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and stirred evenly. The slurry is evenly coated on one surface of a current collector aluminum foil with a thickness of 12μm, leaving an empty foil area at the edge of the aluminum foil, and then dried at 90°C to obtain an active material layer with a coating thickness of 74μm. The above coating steps are repeated on the other surface of the aluminum foil to obtain a double-sided coated first electrode sheet, and the empty foil area is the first electrode tab. The first electrode tab is integrally connected to the first side of the aluminum foil, the dimension W1 of the first side in the second direction is 100mm, the dimension W2 of the first electrode tab in the second direction is 100mm, and the dimension L1 of the second side of the aluminum foil in the third direction is 110mm.

[0092] (2) Preparation of the second electrode sheet: The negative electrode active material artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, deionized water is added as a solvent, and a slurry with a weight percentage of 70 wt% is prepared and stirred evenly. The slurry is evenly coated on one surface of a current collector copper foil with a thickness of 8 μm, and an empty foil area is reserved at the edge of the copper foil. It is dried at 110°C to obtain an active material layer with a coating thickness of 58 μm. The above steps are repeated on the other surface of the copper foil to obtain a double-sided coated second electrode sheet, and the empty foil area is the second electrode tab. Among them, the second electrode tab is integrally connected to the fifth side of the copper foil. The dimension W3 of the fifth side in the second direction is 103 mm, and the dimension W4 of the second electrode tab in the second direction is both 103 mm. The dimension L2 of the sixth side of the copper foil in the third direction is 113 mm.

[0093] (3) Preparation of electrolyte: In a dry argon atmosphere, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed at a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0094] (4) Preparation of isolation film: A polyethylene (PE) film with a thickness of 9 μm was selected.

[0095] (5) Assembly of secondary battery: The first electrode sheet, the separator, and the second electrode sheet are stacked in sequence to obtain an electrode assembly with a laminated structure, and the electrode assembly is placed in a housing. Then, the first tab is stacked and welded to the first adapter, and the first adapter is welded to the first pole. The material of the first adapter is aluminum. The second tab is stacked and welded to the second adapter, and the second adapter is welded to the second pole. The material of the second adapter is copper. Then, the electrolyte is injected into the housing and the top cover is welded. After standing and forming, a secondary battery is obtained.

[0096] Examples 2-4 and Comparative Example 1

[0097] The difference from Example 1 lies in the value of L1 / W1.

[0098] Ten secondary batteries of each comparative example and embodiment were taken for energy density and cycle performance tests.

[0099] The energy density test steps are as follows: 1) At a test temperature of 25°C, charge the battery at a constant current of 0.2C to 3.650V, cycle to 0.02C, and let it rest for 10 minutes. Then discharge it at a constant current of 0.2C to 2.5V and let it rest for 10 minutes to obtain the battery's discharge capacity D. After charging the battery at a constant current of 0.2C to 3.35V, then charging it at a constant voltage of 0.02C to 3.35V, use an optical detector to measure the length, width, and height of the secondary battery to calculate the volume T. Energy density (ED) = D / T, expressed in Wh / L. Then, calculate the average energy density of the 10 samples.

[0100] The cycle test steps are as follows: 1) At a test temperature of 25°C, let the battery stand for 30 minutes to allow it to reach a constant temperature; 2) Charge the battery, specifically: 0.5C constant current charging to 3.650V, CV to 0.02C, and then discharge it to 2.5V at a constant current of 0.5C. This is one charge and discharge cycle, and the capacity of the first discharge is 100%; 2) Repeat the charge and discharge cycle 800 times; 3) Disassemble the electrode assembly and check whether there are black spots, purple spots or lithium plating on the surface of the second pole piece. If no black spots, purple spots or lithium plating are found on the second pole piece, check whether there are any spots greater than or equal to 2mm on the second pole piece. 2 If black spots, purple spots or lithium deposition appear in the area of ​​the test tube, the test has passed. Then, the pass rate of the test of the test tube for 100 samples is calculated.

[0101] Table 1

[0102] It can be seen from the test results in Table 1 that compared with Comparative Example 1, Examples 1-3 improve the energy density of the secondary battery by arranging the first electrode tab to extend the first current collector from the shorter first side and the second electrode tab to extend the second current collector from the shorter fifth side; and when injecting liquid, it is beneficial for the electrolyte to fully infiltrate the electrode assembly and improve the infiltration efficiency of the electrolyte, so that the interface during the cycle is improved and the cycle performance of the secondary battery is improved.

[0103] Compared with Comparative Example 2, Examples 1-3 reduce the conduction distance of electrons in the first current collector and the second current collector by setting 1<L1 / W1≤5 and 1<L2 / W3≤5, thereby reducing the risk of uneven electron density distribution or increased internal resistance, thereby improving the cycle performance of the secondary battery.

[0104] The above disclosure is only a preferred embodiment of the present application and certainly cannot be used to limit the present application. Therefore, equivalent changes made based on the present application are still within the scope covered by the present application.

Claims

1. A secondary battery comprising a housing, at least one electrode assembly disposed in the housing, and a plurality of first tabs, each of the electrode assemblies being a laminate structure and comprising a plurality of first tabs stacked in a first direction, wherein: The first pole piece includes a first current collector and a first material layer provided on the first current collector, the first current collector includes a first side, a second side, a third side, and a fourth side connected end to end, the second side and the fourth side are arranged opposite to each other in a second direction, the first side and the third side are arranged opposite to each other in a third direction, and the first direction, the second direction, and the third direction are perpendicular to each other; The dimension of the first side in the second direction is W1, the dimension of the second side in the third direction is L1, 1<L1 / W1≤5, the first electrode tab is integrally provided with the first current collector and extends from the first side. When viewed from the first direction, the first electrode tab is in contact with the first material layer at the first side; the dimension of the first electrode tab in the second direction is W2, W2=W1; The secondary battery further includes a first adapter, which is electrically connected to the plurality of first tabs and is further connected to the housing.

2. The secondary battery according to claim 1, wherein The first tab includes a first segment connected to the first side and a second segment connected to the first segment. The second segment is bent relative to the first segment. A plurality of the second segments form a first connecting portion. The first adapter is connected to the first connecting portion.

3. The secondary battery according to claim 2, wherein The multiple first pole tabs are divided into N pole tab groups, where N is a positive integer. Each of the pole tab groups includes a first pole tab bundle and a second pole tab bundle. The first segment of the first pole tab in the first pole tab bundle and the first segment of the first pole tab in the second pole tab bundle extend in directions away from each other, and the second segment of the first pole tab in the first pole tab bundle and the second segment of the first pole tab in the second pole tab bundle extend in directions approaching each other.

4. The secondary battery according to claim 3, wherein The number of the electrode assembly is one, and the N electrode tab groups are all connected to the first electrode sheet of the electrode assembly.

5. The secondary battery according to claim 3, wherein There are multiple electrode assemblies, and the N electrode tab groups are respectively connected to the first electrode sheets of the multiple electrode assemblies.

6. The secondary battery according to claim 3, wherein The number of the electrode assemblies is two, N is 1, the first electrode tab bundle is connected to the first electrode piece of one electrode assembly, and the second electrode tab bundle is connected to the first electrode piece of another electrode assembly.

7. The secondary battery according to claim 3, wherein The first adapter includes N connection areas and a transition area connected to each of the connection areas, the transition area is bent compared to the connection area, the connection area is arranged on the side of the first connection part facing the electrode assembly, the connection area is connected to the first pole tab bundle and the second section of the first pole tab in the second pole tab bundle, and the transition area is connected to the shell.

8. The secondary battery according to claim 7, wherein The second sections of the first tabs in the first tab bundle are stacked and welded to form a first welding area, and the connecting area is welded to the second section to form a second welding area.

9. The secondary battery according to claim 8, wherein When viewed from the third direction, the first welding area and the second welding area overlap.

10. The secondary battery according to claim 8, wherein When observed from the third direction, the first welding area is located at 0 to 1 / 3 of the thickness of the electrode assembly in the first direction.

11. The secondary battery according to claim 7, wherein The secondary battery further includes a first insulating member disposed on a side of the connection area facing the electrode assembly in the third direction.

12. The secondary battery according to claim 7, wherein The secondary battery further includes a second insulating member disposed on a side of the first connection portion facing away from the connection area in the third direction.

13. The secondary battery according to claim 3, wherein The number of the first tab ears included in the first tab ear bundle and the second tab ear bundle is the same.

14. The secondary battery according to claim 1, wherein Along the direction in which the first tab ear extends from the first side, the length of the first tab ear is D, and the thickness of the electrode assembly in the first direction is T, where T / 3 ≤ D ≤ 2T / 3.

15. The secondary battery according to claim 1, wherein The secondary battery further includes a plurality of second tab ears, and the electrode assembly further includes a plurality of second electrode sheets stacked in the first direction; The second electrode sheet includes a second current collector and a second active material layer disposed on the second current collector. The second current collector includes a fifth side, a sixth side, a seventh side, and an eighth side that are sequentially connected end to end. The sixth side and the eighth side are oppositely disposed in the second direction, and the fifth side and the seventh side are oppositely disposed in the third direction; The dimension of the fifth side in the second direction is W3, and the dimension of the sixth side in the third direction is L2, where W3 < L2. The second tab ear is integrally provided with the second current collector and extends out of the second current collector from the fifth side. When observed from the first direction, the second tab ear is in contact with the second active material layer at the fifth side; the dimension of the second tab ear in the second direction is W4, and W4 = W3; The secondary battery further includes a second adapter electrically connected to the plurality of second tab ears, and the second adapter is further connected to the housing.

16. The secondary battery according to claim 15, wherein The first tab ear and the second tab ear are respectively located at opposite ends of the electrode assembly in the third direction.

17. The secondary battery according to claim 16, wherein The secondary battery is a square shell battery. The housing is made of metal and includes a first end wall and a second end wall oppositely disposed in the second direction, a side wall connected between the first end wall and the second end wall, a first pole column, and a second pole column. The first pole column and the second pole column are both disposed on the first end wall or both disposed on the side wall. The first adapter is connected to the first pole column, and the second adapter is connected to the second pole column.

18. The secondary battery according to claim 16, wherein The housing is a packaging bag, which includes a containing portion and a sealing edge connected to the containing portion. The electrode assembly is disposed in the containing portion, and the first adapter and the second adapter both extend out of the housing from the sealing edge.

19. An electrical device comprising a battery compartment, wherein: The electrical device further includes a secondary battery according to any one of claims 1 to 18, and the secondary battery is accommodated in the battery compartment.

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