Secondary battery and battery pack
By designing tapered tabs and widened contact areas for the adapter plates, the problem of overcurrent temperature rise in power batteries was solved, the welding process was simplified and equipment wear was reduced, and the manufacturability and packaging reliability of the battery pack were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2026-03-24
AI Technical Summary
In existing technologies, the temperature rise of the tabs and adapter plates of power batteries is too high during overcurrent, which increases the difficulty of welding process and wears the welding teeth. Furthermore, the requirements for welding equipment are increased during high-current charging and discharging, affecting the manufacturability and packaging reliability of the battery pack.
A tapered first tab and a correspondingly widened contact area of the adapter plate were designed. By reducing the thickness of the adapter plate and optimizing the welding position, the electron flow area is increased, the transmission path is changed, the overcurrent temperature rise is reduced, and the requirements for welding process and equipment are reduced.
It effectively reduces overcurrent temperature rise, simplifies welding process, reduces wear on welding equipment, improves battery pack manufacturability and packaging reliability, and meets the requirements of high-current charging and discharging.
Smart Images
Figure CN224036581U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a secondary battery and a battery pack. Background Technology
[0002] With the development of the new energy industry, lithium-ion batteries are widely used in daily life. Among them, power batteries have flourished in the automotive industry due to policy support and environmental protection reasons. To ensure that electric vehicles and gasoline vehicles have the same driving range, power batteries are becoming increasingly larger and thicker. Power batteries are further classified into pouch batteries, prismatic batteries, and cylindrical batteries based on their shape. Utility Model Content
[0003] In view of the problems existing in the related technologies, the purpose of this utility model is to provide a secondary battery and battery pack, so as to at least reduce the overcurrent temperature rise at the first electrode and the first adapter piece.
[0004] To achieve the above objectives, this utility model provides a secondary battery, comprising: an electrode assembly including a first electrode and a first tab, wherein the first tab extends from the first electrode along the length direction of the electrode assembly, wherein the first tab tapers from one end to the other in a tapered shape along a direction away from the first electrode, and one end of the first tab extends continuously from one edge of the first electrode to the other edge along the width direction of the electrode assembly; a first adapter piece, wherein the first tab has a first edge and a second edge facing away from each other along the width direction, the contact area between the first adapter piece and the first tab is tapered and extends from the first edge to the second edge, and the first adapter piece and the first tab are electrically connected in the contact area.
[0005] In some embodiments, the first adapter has a thinned portion that is thinned in the thickness direction of the electrode assembly, at least a portion of the contact area is located within the thinned portion, and the projection of the first tab along the thickness direction at least partially falls into the thinned portion.
[0006] In some embodiments, the electrode assembly includes a plurality of stacked first electrode sheets and a plurality of first tabs, the plurality of first tabs extending from the plurality of first electrode sheets in a one-to-one correspondence, the plurality of first tabs converging into a first tab group, the first tab group being electrically connected to the thinning portion, the projection of the first tab group along the thickness direction falling entirely into the thinning portion, and along the length direction, the thinning portion having a root and an end facing away from each other, the end being farther away from the first electrode sheet than the root, and the thickness of the root being less than the thickness of the end.
[0007] In some embodiments, the secondary battery further includes: a packaging film encapsulating the electrode assembly and having a sealing portion for sealing the electrode assembly; along the length direction, the first adapter piece has opposing first adapter piece edges and second adapter piece edges, the second adapter piece edge being farther away from the first electrode sheet than the first adapter piece edge; along the width direction, the first adapter piece has opposing third adapter piece edges and fourth adapter piece edges; the sealing portion is disposed along at least a portion of the third adapter piece edges and the fourth adapter piece edges; the first adapter piece is provided with rounded corners at a first position and a second position, the first position being the position where the first adapter piece edge meets the third adapter piece edge, and the second position being the position where the first adapter piece edge meets the fourth adapter piece edge.
[0008] In some embodiments, the adapter sheet has an unthinned portion, and the thickness of the unthinned portion is greater than the thickness of the thinned portion along the thickness direction of the electrode assembly. The unthinned portion is disposed between the thinned portion and the edge of the third adapter sheet and the edge of the fourth adapter sheet. The thinned portion is located inside the packaging film, and the projection of the sealing portion along the thickness direction is offset from the thinned portion.
[0009] In some embodiments, the thinning portion extends from the edge of the third adapter piece to the edge of the fourth adapter piece, a portion of the thinning portion is located within the packaging film, and the projection of the sealing portion along the thickness direction falls on the thinning portion.
[0010] In some embodiments, the first adapter piece is welded to the first electrode tab in the contact area, and the weld mark extends along the first edge, the other end, and the second edge.
[0011] In some embodiments, when projected along the thickness direction of the electrode assembly, the first tab is trapezoidal in shape, and the end of the first adapter piece for connecting to the first tab is trapezoidal in shape.
[0012] In some embodiments, the electrode assembly further includes a second electrode plate and a second tab, wherein the second tab extends from the second electrode plate along the length direction, and the first tab and the second tab are located at both ends of the electrode assembly, and the second tab extends continuously from one edge of the second electrode plate to the other edge along the width direction.
[0013] Embodiments of this application also provide a battery pack, including any of the aforementioned secondary batteries.
[0014] The beneficial technical effects of this utility model are as follows:
[0015] Compared with the prior art, the embodiments of this application widen the first electrode tab and the corresponding portion of the first adapter piece, thereby widening the contact area between the two, thus increasing the electron exit on the first electrode piece, changing the electron transport path, increasing the electron flow area, and thus reducing the flow temperature rise. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 A schematic diagram of a prior art electrode assembly is shown.
[0018] Figure 2 A schematic diagram of a prior art adapter is shown.
[0019] Figure 3 A schematic diagram of the prior art electrode tab and adapter plate after welding is shown.
[0020] Figure 4 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.
[0021] Figure 5 A first electrode and a first electrode tab are shown according to some embodiments of this application.
[0022] Figure 6 An adapter piece according to a first embodiment of this application is shown.
[0023] Figure 7 A schematic diagram showing the electrical connection between the first electrode tab and the adapter plate of the first embodiment is shown.
[0024] Figure 8 The magnified edge is shown Figure 7 The cross-sectional view taken from line AA.
[0025] Figure 9 A first adapter piece according to a second embodiment of this application is shown. Detailed Implementation
[0026] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.
[0027] Embodiments of this application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are indicated by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.
[0028] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, these terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.
[0029] In this specification, unless otherwise specified or limited, relative terms such as “central,” “longitudinal,” “lateral,” “front,” “rear,” “right,” “left,” “inner,” “outer,” “lower,” “higher,” “horizontal,” “vertical,” “above,” “below,” “above,” “below,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or depicted in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.
[0030] For ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.
[0031] With the rapid development of power batteries, more stringent requirements are being placed on their manufacturing processes. Pouch batteries are widely used due to their high energy density and high assembly rate. The manufacturing process of pouch batteries typically includes: coating, rolling, slitting, die-cutting, welding (using technologies such as ultrasonic vibration to connect the tabs and adapters to achieve electronic conduction), encapsulation, baking, electrolyte injection, formation, high-temperature aging, capacity testing, K-test (voltage drop of the battery over a specific time interval), SOC (state of charge) adjustment, OCV (open circuit voltage) testing, and final inspection. Due to range anxiety and cost considerations, pouch batteries are becoming increasingly larger in capacity and thickness, thus placing increasingly higher demands on manufacturing processes. Especially with increased battery thickness, the number of electrode layers in the battery increases, leading to an increase in the number of welding layers for the tabs, further increasing the requirements for welding technology and manufacturing difficulty. Furthermore, the increased number of welding layers leads to increased wear rate of the welding teeth, increased frequency of welding tooth replacement, and increased equipment maintenance costs.
[0032] Figure 1 A schematic diagram of the prior art electrode assembly (JR) 4 after being cut, stacked, and hot-pressed is shown. Figure 2 A schematic diagram of the prior art adapter 2 is shown. Figure 3 A schematic diagram is shown of the prior art after the tab 3 and the adapter 2 are welded (e.g., by ultrasonic vibration technology). The prior art tab 3 is die-cut so that its width differs from that of the electrode 1. During battery charging and discharging, electrons will concentrate in the tab 3. As the required charging and discharging speed of the battery increases, the rapid charging and discharging leads to an increasingly higher rate of electron transport at the tab 3, resulting in a larger current and more severe heat generation at the tab 3.
[0033] As battery capacity increases, the corresponding electrode assembly 4 becomes thicker. To reduce overcurrent temperature rise, the thickness of the adapter piece 2 (perpendicular to the length direction L and width direction W) also increases. The thickness of the positive electrode adapter piece increases from 0.4 mm to 0.5 mm to 0.6 mm, and the thickness of the negative electrode adapter piece increases from 0.2 mm to 0.3 mm to 0.4 mm. With the increase in the number of electrode layers 1 and the increase in the thickness of the adapter piece 2, the requirements for welding process parameters and weld teeth become increasingly stringent, and the processing difficulty increases.
[0034] This utility model provides an electronic device 1000. For ease of explanation, the following embodiments will use a vehicle as an example to illustrate the electronic device 1000. Figure 4This illustration shows an electronic device 1000 in an embodiment of this application when it is a vehicle. A battery pack 1002 is installed inside the vehicle, and the battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The working part of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The battery pack 1002 provides electrical power for the vehicle's operation or the operation of its internal electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part is a unit component that can obtain electrical power from the battery pack 1002 and perform corresponding tasks, such as a fan blade rotation unit or a vacuum cleaner's suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1000.
[0035] Figure 5 A first electrode 10 and a first electrode tab 20 according to some embodiments of this application are shown. Figure 6 An adapter piece 30 according to a first embodiment of this application is shown. Figure 7 A schematic diagram showing the electrical connection between the first tab 20 and the adapter piece 30 of the first embodiment is shown. Figure 8 The magnified edge is shown Figure 7 A cross-sectional view taken from line AA, where solder mark 40 is not shown.
[0036] Embodiments of this application provide a secondary battery, including an electrode assembly 50 and a tab 30. The electrode assembly 50 includes a first electrode 10 and a second electrode with opposite polarities, and a separator located between the first electrode 10 and the second electrode. The first electrode 10 is one of a positive electrode and a negative electrode, and the second electrode is the other of a positive electrode and a negative electrode. The electrode assembly 50 also includes a first tab 20 and a second tab corresponding to the first electrode 10 and the second electrode, respectively. The first tab 20 extends from the first electrode 10 along the length direction L of the electrode assembly 50, and the second tab extends from the second electrode along the length direction L.
[0037] See Figure 5Along the direction away from the first electrode 10, the first electrode tab 20 gradually tapers from one end 24 to the other end 26, forming a tapered shape. Along the width direction W of the electrode assembly 50, the aforementioned end 24 of the first electrode tab 20 extends continuously from one edge of the first electrode 10 to the other edge (e.g., ...). Figure 5 As shown, it extends continuously from the upper edge to the lower edge of the first electrode 10. Along the width direction W, the first electrode tab 20 has a first edge 21 and a second edge 22 facing away from each other. The contact area where the first adapter piece 30 is electrically connected to the first electrode tab 20 is also tapered, and the contact area extends from the first edge 21 to the second edge 22 of the first electrode tab 20.
[0038] Compared to the prior art, the embodiments of this application widen the corresponding portions of the first tab 20 and the first adapter piece 30, thereby widening their contact area. This increases the electron exit point on the first tab 10, alters the electron transport path, and increases the electron flow area, thus reducing the overcurrent temperature rise. Therefore, it eliminates the need to thicken the tab or adapter piece as in the prior art, enabling the use of thinner tabs or adapter pieces to meet larger charge and discharge current requirements. This avoids the need to increase welding process parameters (amplitude, energy, power), reduces the requirements for welding teeth, and lowers the processing difficulty.
[0039] The electrode assembly 50 in this embodiment is a stacked body with the first tab 20 and the second tab located at both ends of the electrode assembly 50. Therefore, the first tab 20 and the second tab will not contact each other and cause a short circuit. The second tab can also be similar to the first tab 20, that is, it extends continuously from one edge of the second tab to the other along the width direction W, while increasing the size of the second tab and reducing the overcurrent temperature rise at the second tab. Correspondingly, the configuration of the second adapter piece welded to the second tab is similar to that of the first adapter piece 30.
[0040] In some embodiments, when projected along the thickness direction T of the electrode assembly 50, the first tab 20 is trapezoidal (trumpet-shaped), and the end of the first adapter piece 30 used to connect with the first tab 20 is trapezoidal (trumpet-shaped). That is, the shapes of the two correspond, and the shape of the contact area between them is also trapezoidal (trumpet-shaped).
[0041] The first adapter piece 30 has a thinning portion (groove) 36 that is thinned in the thickness direction T of the electrode assembly 50. The thickness of the first adapter piece 30 at the thinning portion 36 is, for example, 0.1 mm to 0.3 mm, and the thickness at other portions is, for example, 0.4 mm to 0.6 mm. At least a portion of the contact area is located within the thinning portion 36, and the projection of the first tab 20 along the thickness direction T at least partially falls into the thinning portion 36. In the embodiments of this application, the thinning portion 36 is provided in the area of the first adapter piece 30 that accommodates the first tab 20. At least a portion of the first tab 36 overlaps in the thinning portion 36, which at least partially reduces the total thickness of the first tab 36 and the first adapter piece 30, which is beneficial for utilizing the thickness space of the secondary battery in this area. The mechanism of ultrasonic welding is physical welding through high-frequency vibration of the welding head. The embodiments of this application at least partially reduce the total thickness of the first tab 36 and the first adapter piece 30, which can reduce welding power, reduce the requirements for welding process and welding teeth, improve manufacturability, and reduce wear on the welding head. The secondary battery is, for example, a pouch battery, which includes a packaging film (e.g., an aluminum-plastic film) encapsulating the electrode assembly. The first tab 20 and the first adapter piece 30 are welded together. The surface of the solder mark 40 is often uneven and may produce burrs. The portion of the packaging film that adheres to the solder mark 40 may be punctured by the solder mark 40. The embodiments of this application at least partially reduce the total thickness of the first tab 36 and the first adapter piece 30, thus reducing the risk of the solder mark 40 formed by the welding of the two puncturing the packaging film.
[0042] Electrode assembly 50 includes a plurality of stacked first electrode layers 10 and a plurality of first electrode tabs 20, the plurality of first electrode tabs 20 extending from the plurality of first electrode layers 10 in a one-to-one correspondence, see [reference]. Figure 7 and Figure 8 The plurality of first electrode tabs 20 are converged to form a first electrode tab assembly 120. The first electrode tab assembly 120 is electrically connected to the thinning portion 36, and the projection of the first electrode tab assembly 120 along the thickness direction T entirely falls into the thinning portion 36. Along the length direction L, the thinning portion 36 has a root portion 360 and an end portion 362 facing away from each other. The end portion 362 is farther away from the first electrode sheet 10 than the root portion 360, and the thickness of the root portion 360 is less than the thickness of the end portion 362. The plurality of first electrode tabs 20 are first ultrasonically pre-welded to form the first electrode tab assembly 120, and then the first electrode tab assembly 120 is welded to the adapter piece 30. When the plurality of first electrode tabs 20 converge, Figure 8In the cross-sectional view shown, the portion where the outermost tab 20 connects to the first electrode 20 is arc-shaped. This means that the thickness of the portion of the first tab assembly 120 connected to the first electrode 10 is increased. If the root 360 of the thinned portion 36 is thick, it is easy to interfere with the bottommost first tab 20 of the first tab assembly 120, posing a risk that the root 360 may cut or damage the bottommost first tab 20, or even cause the first tab 20 to tear. The embodiments of this application further thin the root 360 of the thinned portion 36, which can alleviate the problem of the first tab 20 tearing.
[0043] Along the length direction L, the first adapter piece 30 has a first adapter piece edge 31 and a second adapter piece edge 32 facing away from each other. The second adapter piece edge 32 is farther away from the first electrode 10 than the first adapter piece edge 31. Along the width direction W, the first adapter piece 30 has a third adapter piece edge 33 and a fourth adapter piece edge 34 facing away from each other. When the secondary battery is a pouch battery, the packaging film has a sealing portion for sealing the electrode assembly 50. The sealing portion is provided along at least a portion of the third adapter piece edge 33 and the fourth adapter piece edge 34. The first adapter piece 30 has rounded corners (R-corners) at a first position 301 and a second position 302. The first position 301 is the position where the first adapter piece edge 31 and the third adapter piece edge 33 meet, and the second position 302 is the position where the first adapter piece edge 31 and the fourth adapter piece edge 34 meet. If the first adapter piece 30 has sharp corners at the first position 301 and the second position 302, it is easy to puncture the packaging film during the assembly and use of the soft-pack battery. In the embodiments of this application, the first adapter piece 30 is set with rounded corners at the first position 301 and the second position 302, which is more friendly to the packaging film of the soft-pack battery and can prevent the first adapter piece 30 from puncturing the packaging film at the first position 301 and the second position 302, thus preventing the seal from failing.
[0044] See Figure 7The first adapter piece has unthinned portions 38 located on both sides of the thinned portion 36. Along the thickness direction T of the electrode assembly 50, the thickness of the unthinned portions 38 is greater than the thickness of the thinned portion 36. The unthinned portions 38 are disposed between the thinned portion 36 and the edges 33 and 34 of the third and fourth adapter pieces. When the electrode assembly 50 is sealed with a packaging film, the sealing portion of the packaging film on the first adapter piece 30 is sealed at the sealant 60, the thinned portion 36 is located inside the packaging film, and the portion of the first adapter piece 30 located to the left of the sealant 60 is located outside the packaging film. The projection of the sealing portion along the thickness direction T is offset from the thinned portion 36. The thinned portion 36 and the unthinned portion 38 have different thicknesses, resulting in a height difference between them. The connection between the two forms a step. If the sealing portion partially seals on the thinned portion 36 and partially seals on the unthinned portion 38 (i.e., across the step formed by the thinned portion 36 and the unthinned portion 38), the seal is prone to failure at the step position, leading to leakage. In the embodiments of this application, the sealing portion of the packaging film is staggered from the thinned portion 36 to avoid seal failure.
[0045] Figure 9 A first adapter piece 30 according to a second embodiment of this application is shown, wherein the thinned portion 36 extends from the edge 33 of the third adapter piece to the edge 34 of the fourth adapter piece. That is, unlike the first embodiment, there are no unthinned portions 38 on either side of the thinned portion 36. When the electrode assembly 50 is sealed using a packaging film, a portion of the thinned portion 36 is located inside the packaging film, and the projection of the sealing portion of the packaging film along the thickness direction T falls on the thinned portion 36. In the second embodiment, a portion of the thinned portion 36 is located inside the packaging film, and a portion is located outside the packaging film; the sealing portion of the packaging film is located at the thinned portion 36, which can reduce the overall thickness of the first adapter piece 30 and the packaging film after encapsulation.
[0046] In the first and second embodiments, the first adapter piece 30 and the first electrode tab 20 are welded at their contact area, and the weld mark 40 is as follows: Figure 7 As shown, extending along the first edge 21, the other end 26, and the second edge 22 of the first tab 20, the welding trajectory can be lengthened, the welding impedance reduced, the current-carrying area further increased, and the current-carrying effect enhanced. The solder mark 40 in the embodiments of this application is not limited to the shape shown in the figure; the solder mark 40 can also be a line segment shape. Because the area of the contact region is increased, especially the width of the contact region, the welding trajectory of the solder mark 40 between the first adapter piece 30 and the first tab 20 can be lengthened.
[0047] The embodiments of this application optimize the structure at the welding position between the first tab 20 and the first adapter piece 30, thereby reducing the difficulty of the welding process, reducing the requirements for welding equipment, improving product manufacturability, reducing overcurrent temperature rise during high-current charging and discharging, extending the service life of the packaging film seal at this position, and improving the manufacturability and packaging reliability of the secondary battery.
[0048] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.
Claims
1. A secondary battery, characterized in that, include: The electrode assembly includes a first electrode plate and a first electrode tab, wherein the first electrode tab extends from the first electrode plate along the length direction of the electrode assembly. Wherein, along the direction away from the first electrode, the first tab gradually tapers from one end to the other to form a tapered shape, and along the width direction of the electrode assembly, one end of the first tab extends continuously from one edge of the first electrode to the other edge. The first adapter piece, along the width direction, has a first edge and a second edge facing away from each other, the contact area between the first adapter piece and the first electrode is tapered and extends from the first edge to the second edge, and the first adapter piece and the first electrode are electrically connected in the contact area.
2. The secondary battery according to claim 1, characterized in that, The first adapter has a thinned portion that is thinned in the thickness direction of the electrode assembly, at least a portion of the contact area is located within the thinned portion, and at least a portion of the projection of the first tab along the thickness direction falls into the thinned portion.
3. The secondary battery according to claim 2, characterized in that, The electrode assembly includes a plurality of stacked first electrode plates and a plurality of first electrode tabs, with each plurality of first electrode tabs extending from the plurality of first electrode plates in a corresponding manner. Multiple layers of the first tabs converge to form a first tab group, which is electrically connected to the thinning section. The projection of the first tab group along the thickness direction entirely falls into the thinning section. Along the length direction, the thinned portion has a root and an end facing away from each other, the end being farther away from the first electrode than the root, and the thickness of the root being less than the thickness of the end.
4. The secondary battery according to any one of claims 1 to 3, characterized in that, Also includes: A packaging film encapsulates the electrode assembly and has a sealing portion that seals the electrode assembly. Along the length direction, the first adapter piece has a first adapter piece edge and a second adapter piece edge facing away from each other, the second adapter piece edge being farther away from the first electrode piece than the first adapter piece edge. Along the width direction, the first adapter piece has opposing third and fourth adapter piece edges. The sealing portion is provided along at least a portion of the edges of the third adapter piece and the fourth adapter piece. The first adapter piece is provided with rounded corners at a first position and a second position. The first position is the position where the edge of the first adapter piece meets the edge of the third adapter piece, and the second position is the position where the edge of the first adapter piece meets the edge of the fourth adapter piece.
5. The secondary battery according to claim 4, characterized in that, The first adapter piece has an unthinned portion, and along the thickness direction of the electrode assembly, the thickness of the unthinned portion is greater than the thickness of the thinned portion. The unthinned portion is disposed between the thinned portion and the edges of the third and fourth adapter pieces. The thinning portion is located inside the packaging film, and the projection of the sealing portion along the thickness direction is offset from the thinning portion.
6. The secondary battery according to claim 4, characterized in that, The first adapter piece has a thinned portion that decreases in thickness direction of the electrode assembly, the thinned portion extending from the edge of the third adapter piece to the edge of the fourth adapter piece. The thinned portion is located within the packaging film, and the projection of the sealing portion along the thickness direction falls on the thinned portion.
7. The secondary battery according to any one of claims 1 to 3, characterized in that, The first adapter piece is welded to the first electrode tab in the contact area, and the weld mark extends along the first edge, the other end, and the second edge.
8. The secondary battery according to any one of claims 1 to 3, characterized in that, Projecting along the thickness direction of the electrode assembly, the first tab is trapezoidal in shape, and the end of the first adapter piece used to connect with the first tab is also trapezoidal in shape.
9. The secondary battery according to any one of claims 1 to 3, characterized in that, The electrode assembly also includes: The second electrode plate and the second electrode tab, along the length direction, the second electrode tab extending from the second electrode plate, and the first electrode tab and the second electrode tab located at both ends of the electrode assembly. Along the width direction, the second electrode tab extends continuously from one edge of the second electrode sheet to the other edge.
10. A battery pack, characterized in that, Includes the secondary battery as described in any one of claims 1 to 9.