Secondary battery

Abstract

The present application relates to a secondary battery, which comprises: a flexible shell, the flexible shell comprises two first side surfaces arranged at an interval along a first direction and two second side surfaces arranged at an interval along a second direction, the first side surfaces and the second side surfaces are connected end to end, and the thickness of the second side surfaces is greater than the thickness of the first side surfaces; the two top covers are arranged in a spaced mode in the third direction, a battery cell cavity is formed after the two top covers are connected with the flexible shell, and the faces, facing the battery cell cavity, of the two top covers are a first plane and a second plane respectively; and the pole piece assembly comprises a plurality of positive pole pieces and a plurality of negative pole pieces, the plurality of positive pole pieces and the plurality of negative pole pieces are staggered and stacked in the battery cell cavity along the third direction, and two ends of the pole piece assembly are respectively attached to the first plane and the second plane. The problem that a traditional secondary battery pole piece assembly does not have the function of shifting and moving in the direction in the pole piece plane direction is solved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a secondary battery. Background Technology

[0002] Rechargeable batteries utilize a stacking process, which involves precisely stacking individual electrode sheets into a cell. This process generates electricity through the movement of lithium ions. Compared to winding, stacking offers superior battery performance, boasting advantages in energy density, safety, and cycle life. Rechargeable batteries also offer higher space utilization than wound batteries. Especially with the trend towards larger prismatic battery sizes, stacking technology is expected to see widespread adoption. Rechargeable batteries are widely used in both power and energy storage applications, becoming an essential technology for both long and short battery cells, and gradually becoming the mainstream technology for large-cell batteries.

[0003] In related technologies, the electrode assembly of a secondary battery is not designed and manufactured to have the function of offset movement along the length or width direction in the electrode plane. Utility Model Content

[0004] This application provides a secondary battery that solves the problem that the electrode assembly of traditional secondary batteries does not have the function of offset movement along the length or width direction in the electrode plane in terms of design and manufacturing.

[0005] In a first aspect, embodiments of this application provide a secondary battery, comprising:

[0006] A flexible shell, the flexible shell including two first side surfaces spaced apart along a first direction and two second side surfaces spaced apart along a second direction, the first side surfaces and the second side surfaces being connected end to end, and the thickness of the second side surface being greater than the thickness of the first side surface;

[0007] Two top covers are spaced apart along a third direction and connected to the flexible shell to form a cell chamber. The sides of the two top covers facing the cell chamber are a first plane and a second plane, respectively.

[0008] An electrode assembly includes multiple positive electrode plates and multiple negative electrode plates, which are stacked alternately in the cell cavity along the third direction, and the two ends of the electrode assembly are respectively attached to the first plane and the second plane.

[0009] In one embodiment, the first plane and the second plane are parallel to each other and inclined along a fourth direction, wherein the angle between the fourth direction and the first direction is an acute angle.

[0010] In one embodiment, the positive electrode includes a positive electrode coating, and the negative electrode includes a negative electrode coating;

[0011] Along a third direction, the projection of the negative electrode coating covers the projection of the adjacent positive electrode coating, and along the first direction, both ends of the negative electrode coating exceed the positive electrode coating by a first preset distance, and along the second direction, both ends of the negative electrode coating exceed the positive electrode coating by a second preset distance, wherein the first preset distance is greater than the second preset distance.

[0012] In one embodiment, the size of the negative electrode is larger than the size of the positive electrode;

[0013] Alternatively, the size of the negative electrode sheet is the same as that of the positive electrode sheet, and there is an uncoated area around the positive electrode sheet where no positive electrode coating is applied, so that the projection of the negative electrode coating along the third direction covers the projection of the adjacent positive electrode coating along the third direction.

[0014] In one embodiment, the first plane and the second plane are parallel to each other and inclined along a fourth direction.

[0015] For each positive electrode, the electrode assembly includes a negative electrode above the positive electrode and a negative electrode below the positive electrode. Along the fourth direction, the positive electrode includes a first end a and a second end b, and the height of the first end a is greater than the height of the second end b.

[0016] The positive electrode sheet has an uncoated area on the side of the negative electrode sheet above it at the second end b, and the width of the uncoated area along the fourth direction is greater than 2 mm.

[0017] The positive electrode sheet has an uncoated area on the side of the negative electrode sheet near the bottom, at the first end a, and the width of the uncoated area along the fourth direction is greater than 2 mm.

[0018] In one embodiment, the negative electrode sheet is provided with a negative electrode tab on one side along the second direction, and the plurality of negative electrode tabs are electrically connected to the negative electrode post on the top cover after being electrically connected through a negative electrode conductive element.

[0019] A positive electrode tab is provided on the other side of the positive electrode sheet along the second direction. After multiple positive electrode tabs are electrically connected through a positive electrode conductive element, they are electrically connected to the positive electrode post on the top cover.

[0020] In one embodiment, the negative electrode conductive element includes a negative electrode connecting line, which is sequentially electrically connected to a plurality of negative electrode tabs, and the length of the negative electrode connecting line between adjacent negative electrode tabs exceeds a first preset length.

[0021] The positive electrode conductive component includes a positive electrode connecting line, which is sequentially electrically connected to a plurality of positive electrode tabs, and the length of the positive electrode connecting line between adjacent positive electrode tabs exceeds a second preset length.

[0022] In one embodiment, the size range of the electrode assembly along the first and second directions is [a, 2a], and the size range of the electrode assembly along the third direction is [10a, 20a], where a is a positive number.

[0023] In one embodiment, the secondary battery further includes a separator that extends in an S-shape along a third-direction path and is disposed between the negative electrode and the adjacent positive electrode.

[0024] In one embodiment, the flexible shell is welded to the top cover, the thickness of the first side is in the range of 250mm-350mm, and the thickness of the second side is in the range of 350mm-450mm.

[0025] The beneficial effects of the technical solutions provided in this application include:

[0026] By increasing the thickness of the second side (which is thicker than the first side), a more stable support structure is provided for the electrode assembly. This thickness difference not only enhances the strength and rigidity of the battery casing but also effectively restricts the movement of the electrode assembly in the second direction. When the electrode assembly shifts along the second direction, the thicker second side of the flexible casing can resist the tendency of the electrode assembly to move due to external forces, thereby maintaining the relative stability of the electrode assembly. Because the thickness of the first side of the flexible casing is less than the thickness of the second side, the electrode assembly tends to shift along the first direction, which can restrict the translational direction of the electrode assembly, enhance the flexibility and adaptability of the battery, and effectively solve the problem that the electrode assembly of traditional secondary batteries does not have the function of shifting along the length or width direction in the electrode plane. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a front view schematic diagram of a secondary battery.

[0029] Figure 2 This is a front view schematic diagram of a portion of the electrodes in the first embodiment of the electrode assembly;

[0030] Figure 3 This is a side view of a portion of the electrodes in the first embodiment of the electrode assembly.

[0031] Figure 4This is a front view schematic diagram of a portion of the electrodes in the second embodiment of the electrode assembly;

[0032] Figure 5 This is a side view of a portion of the electrodes in the second embodiment of the electrode assembly;

[0033] Figure 6 This is a front view schematic diagram of some of the electrodes in the third embodiment of the electrode assembly;

[0034] Figure 7 This is a schematic diagram of the bending path of the positive electrode conductive component;

[0035] Figure 8 for Figure 1 A side view diagram.

[0036] In the diagram: 1. Top cover; 2. Electrode assembly; 21. Negative electrode; 22. Positive electrode; 23. Negative electrode coating; 24. Positive electrode coating; 25. Uncoated area; 3. Negative electrode tab; 4. Negative electrode conductive component; 5. Positive electrode tab; 6. Positive electrode conductive component. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0038] This application provides a secondary battery that solves the problem that the electrode assembly of traditional secondary batteries does not have the function of offset movement along the length or width direction in the electrode plane in terms of design and manufacturing.

[0039] It should be noted that the first direction mentioned below refers to... Figure 1 The X-axis direction (i.e., the left-right direction) is the second direction. Figure 3 The Y-axis direction (i.e., the front-to-back direction) and the third direction are... Figure 1 The Z-axis direction (i.e., the up-down direction) and the fourth direction are... Figure 1 The S-axis direction (i.e., the direction in which the electrode assembly 2 tilts left and right).

[0040] like Figure 1As shown in the figure, this application embodiment provides a flexible battery, which includes: a flexible shell (not shown in the figure), the flexible shell including two first side surfaces spaced apart along a first direction and two second side surfaces spaced apart along a second direction, the first side surfaces and the second side surfaces being connected end to end, and the thickness of the second side surface being greater than the thickness of the first side surface; two top covers 1, the two top covers 1 being spaced apart along a third direction and connected to the flexible shell to form a cell chamber, the sides of the two top covers 1 facing the cell chamber being a first plane and a second plane, respectively; an electrode assembly 2, the electrode assembly 2 including a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 21, the plurality of positive electrode sheets 22 and the plurality of negative electrode sheets 21 being stacked alternately along a third direction in the cell chamber, and the two ends of the electrode assembly 2 being respectively attached to the first plane and the second plane.

[0041] In this embodiment, the flexible shell includes two first side surfaces spaced apart along a first direction (left-right direction) and two second side surfaces spaced apart along a second direction (front-back direction). The first and second side surfaces are connected end-to-end to form the basic framework of the battery. In particular, the thickness of the second side surfaces is greater than the thickness of the first side surfaces. This design can enhance the structural strength of the battery in the second direction while maintaining overall flexibility. Two top covers 1 are spaced apart along a third direction (up-down direction) and are connected to the flexible shell to form a cell chamber. The sides of these two top covers facing the cell chamber are the first plane and the second plane, respectively, providing a stable support surface for the stacking of the electrode assembly 2. The electrode assembly 2 includes multiple positive electrode sheets 22 and multiple... Each negative electrode 21 is staggered and stacked in the cell cavity along a third direction (vertical direction). Importantly, the two ends of the electrode assembly 2 are respectively attached to the first plane and the second plane. This design can ensure the stability and positional accuracy of the electrode assembly inside the battery. Due to the use of a flexible shell and the design that the thickness of the first side is less than the thickness of the second side, the secondary battery can shift and move to a certain extent along the first direction (i.e., the length or width direction), thereby improving the adaptability and flexibility of the battery. Because it has the function of shifting and moving along the electrode plane direction, the secondary battery can be used in more diverse application scenarios, especially performing well in occasions where the battery needs to have a certain deformation capability.

[0042] In one implementation, such as Figure 1 As shown, the first plane and the second plane are parallel to each other and inclined along the fourth direction, and the angle between the fourth direction and the first direction is an acute angle.

[0043] In this embodiment, the design of the first and second planes being parallel to each other and inclined along the fourth direction facilitates the offset of the electrode assembly 2 along the first direction. That is, the positive electrode 22 and the negative electrode 21 are misaligned along the fourth direction, thereby achieving the offset of the electrode assembly 2 along the first direction. This design provides an inclined support surface for the electrode assembly 2, making it easier for the electrode assembly 2 to offset or adjust its position along the first direction (i.e., the left-right direction) when subjected to external forces or changes in internal stress.

[0044] In one implementation, such as Figure 2 and Figure 3 As shown, as Figure 4 and Figure 5 As shown in Figure 6, the positive electrode 22 includes a positive electrode coating 24, and the negative electrode 21 includes a negative electrode coating 23. Along a third direction, the projection of the negative electrode coating 23 covers the projection of the adjacent positive electrode coating 24. Along a first direction, both ends of the negative electrode coating 23 extend beyond the positive electrode coating 24 by a first preset distance, and along a second direction, both ends of the negative electrode coating 23 extend beyond the positive electrode coating 24 by a second preset distance. The first preset distance is greater than the second preset distance.

[0045] In this embodiment, along a third direction (i.e., the thickness direction of the battery), the projection of the negative electrode coating 23 overlaps the projection of the adjacent positive electrode coating 24. This means that during the charging and discharging process of the battery, the negative electrode material can provide a larger area to receive or release lithium ions, thereby reducing the local excessive concentration of lithium ions on the negative electrode surface and lowering the risk of lithium plating. Along both the first direction (i.e., the length direction of the battery) and the second direction (i.e., the width direction of the battery), both ends of the negative electrode coating 23 extend beyond the positive electrode coating 24 by a certain preset distance. This design further ensures the uniform distribution of lithium ions on the negative electrode surface. In particular, the design that the first preset distance is greater than the second preset distance, by increasing the amount of extension of the negative electrode coating 23 in the length direction, can more effectively prevent lithium plating when the electrode assembly is offset along the first direction.

[0046] In one implementation, such as Figure 2 and Figure 3 As shown, the size of the negative electrode 21 is larger than the size of the positive electrode 22.

[0047] In this embodiment, during the charging process, lithium ions are deintercalated from the positive electrode and intercalated into the negative electrode. If the space of the negative electrode is insufficient, the lithium intercalation space will be insufficient, which will increase the resistance of lithium ions intercalating into the negative electrode. Therefore, the negative electrode 21 is designed to be larger than the positive electrode 22 to ensure that there is enough lithium intercalation space. In this way, during the charging process, lithium ions can smoothly migrate from the positive electrode to the negative electrode and intercalate into the negative electrode material, without being deposited on the surface of the negative electrode due to insufficient space.

[0048] In one implementation, such as Figure 4 and Figure 5 As shown, the size of the negative electrode 21 is the same as that of the positive electrode 22, and there is an uncoated area 25 around the positive electrode 22 that is not coated with the positive electrode coating, so that the projection of the negative electrode coating 23 along the third direction covers the projection of the adjacent positive electrode coating 24 along the third direction.

[0049] In this embodiment, the size of the negative electrode 21 is the same as that of the positive electrode 22, but there is an uncoated area 25 around the positive electrode 22 where the positive electrode coating is not coated. This design ensures that the projection of the negative electrode coating 23 along a third direction can cover the projection of the adjacent positive electrode coating 24 along a third direction. By retaining the uncoated area 25 around the positive electrode 22, it can be ensured that the negative electrode coating 23 can completely cover the edge of the positive electrode coating 24 during battery assembly, thereby preventing local overcharging or over-discharging caused by uneven distribution of lithium ions during charging and discharging. Since the negative electrode 21 completely covers the coating of the positive electrode 22 and leaves a certain margin around it, this helps to maintain a uniform distribution of lithium ions during charging and discharging, reducing the risk of local overcharging or over-discharging, thereby reducing the possibility of lithium plating.

[0050] In one implementation, such as Figure 6 As shown, the first plane and the second plane are parallel to each other and inclined along the fourth direction. For each positive electrode 22, the electrode assembly 2 includes a negative electrode 21 located above the positive electrode 22 and a negative electrode 21 located below the positive electrode 22. The positive electrode 22 along the fourth direction includes a first end a and a second end b, and the height of the first end a is greater than the height of the second end b. An uncoated area 25 is provided on the side of the positive electrode 22 near the upper negative electrode 21 at the second end b, and the width of the uncoated area 25 along the fourth direction is greater than 2 mm. An uncoated area 25 is provided on the side of the positive electrode 22 near the lower negative electrode 21 at the first end a, and the width of the uncoated area 25 along the fourth direction is greater than 2 mm.

[0051] In this embodiment, for each positive electrode 22, the electrode assembly 2 includes a negative electrode 21 located above it and a negative electrode 21 located below it. The first plane and the second plane are parallel to each other and inclined along the fourth direction, which causes the positive electrode 22 to also be inclined along the fourth direction, having a first end a and a second end b, wherein the height of the first end a is greater than the height of the second end b. Since the positive electrode 22 and the negative electrode 21 have a certain thickness and are placed in the housing, the first end a of the side of the positive electrode 22 close to the upper negative electrode 21 can be covered by the negative electrode 21. Since the positive electrode 22 cannot be completely covered by the negative electrode 21 at its second end (b), an uncoated area 25 is provided at the second end (b) of the positive electrode 22 near the upper negative electrode 21. The width of this uncoated area 25 along the fourth direction is greater than 2 mm. This design helps to reduce local overcharging caused by uneven lithium ion distribution during charging, as lithium ions are extracted from the positive electrode 22 and embedded in the upper negative electrode 21. Similarly, an uncoated area 25 is provided at the first end (a) of the positive electrode 22 near the lower negative electrode 21, and the width of this uncoated area 25 along the fourth direction is also greater than 2 mm. This design also helps to optimize the distribution of lithium ions, reduce local overcharging or over-discharging, and further reduce the possibility of lithium plating.

[0052] In one implementation, such as Figure 1 As shown, a negative electrode tab 3 is provided on one side of the negative electrode plate 21 along the second direction. Multiple negative electrode tabs 3 are electrically connected via a negative electrode conductive element 4, and then electrically connected to the negative electrode post on the top cover 1; as shown... Figure 7 As shown, a positive electrode tab 5 is provided on the other side of the positive electrode plate 22 along the second direction. After multiple positive electrode tabs 5 are electrically connected through the positive electrode conductive member 6, they are electrically connected to the positive electrode post on the top cover 1.

[0053] In this embodiment, multiple negative electrode tabs 3 on the negative electrode plate 21 are electrically connected through negative electrode conductive elements 4 (which may be a conductive sheet, conductive wire, or conductive strip) to form a unified negative current collection path. This path is ultimately connected to the negative terminal on the top cover 1 of the battery, thereby allowing current to flow out from inside the battery and supply external circuits. Similarly, multiple positive electrode tabs 5 on the positive electrode plate 22 are electrically connected through positive electrode conductive elements 6 to form a unified positive current collection path. This path is connected to the positive terminal on the top cover 1 of the battery, allowing current to flow into the battery from external circuits. This design not only ensures the effective transmission of current inside the battery but also improves the overall performance and safety of the battery. By distributing the positive and negative electrode tabs and their conductive elements at intervals along the second direction, local overheating inside the battery can be minimized, thereby improving the battery's efficiency and cycle life.

[0054] In one implementation, such as Figure 8 As shown, the negative electrode conductive component 4 includes a negative electrode connecting wire, which is sequentially electrically connected to a plurality of negative electrode tabs 3, and the length of the negative electrode connecting wire between adjacent negative electrode tabs 3 exceeds a first preset length; as shown Figure 7 As shown, the positive electrode conductive element 6 includes a positive electrode connecting line, which is sequentially electrically connected to a plurality of positive electrode tabs 5, and the length of the positive electrode connecting line between adjacent positive electrode tabs 5 exceeds a second preset length.

[0055] In this embodiment, the negative electrode conductive element 4 is electrically connected to multiple negative electrode tabs 3 in sequence via negative electrode connecting lines, and the length of the negative electrode connecting lines between adjacent negative electrode tabs 3 exceeds a first preset length; the positive electrode conductive element 6 is electrically connected to multiple positive electrode tabs 5 in sequence via positive electrode connecting lines, and the length of the positive electrode connecting lines between adjacent positive electrode tabs 5 exceeds a second preset length; the length of the negative electrode connecting lines between adjacent negative electrode tabs 3 is designed to exceed the first preset length, which provides sufficient flexibility and redundancy to accommodate the offset of the positive and negative electrode plates of the electrode assembly 2; the length of the positive electrode connecting lines between adjacent positive electrode tabs 5 is also designed to exceed the second preset length, which is also to provide sufficient flexibility and redundancy.

[0056] In one implementation, such as Figure 1 and Figure 7 As shown, the negative electrode conductive element 4 and the positive electrode conductive element 6 are arranged to extend in an S-shape or zigzag path along a third direction.

[0057] In this embodiment, the bent negative electrode conductive element 4 and positive electrode conductive element 6 provide sufficient length requirements when the electrode sheet is offset along the first direction, providing sufficient displacement length, which helps to extend the service life of the conductive element.

[0058] In one implementation, such as Figure 1 and Figure 7 As shown, the negative electrode tab 3 and the positive electrode tab 5 are distributed along the fourth direction in the middle region of their respective electrode plates.

[0059] In one embodiment, the size range of the electrode assembly along the first and second directions is [a, 2a], and the size range of the electrode assembly along the third direction is [10a, 20a], where a is a positive number.

[0060] In this embodiment, for example, 'a' can be equal to 1cm, 2cm, or 3cm, etc. The thickness of the negative electrode 21 and the positive electrode 22 along the third direction is set to be ten to twenty times the length of the negative electrode 21 and the positive electrode 22 along the first direction or the width of the negative electrode 21 and the positive electrode 22 along the second direction. This makes the contact area of ​​the electrodes in the planes of the first and second directions smaller, reduces the moving resistance between the electrodes, and further improves the offset tendency of the negative electrode 21 and the positive electrode 22 along the first direction.

[0061] In one embodiment, a diaphragm is also included, which is S-shaped along a third-direction extension path and disposed between the negative electrode 21 and its adjacent positive electrode 22.

[0062] In this embodiment, the separator extends in an S-shape along a third direction and is disposed between the negative electrode 21 and its adjacent positive electrode 22 to ensure effective isolation between the negative electrode 21 and the positive electrode 22 and prevent the battery from short-circuiting.

[0063] In one embodiment, no adhesive is applied between the diaphragm and the adjacent negative electrode coating 23 and positive electrode coating 24.

[0064] In this embodiment, no adhesive is applied between the separator and the adjacent negative electrode coating 23 and positive electrode coating 24, which simplifies the battery manufacturing process and ensures the offset effect between the electrodes along the first direction.

[0065] In one embodiment, the flexible shell is welded to the top cover 1, the thickness of the first side is in the range of 250mm-350mm, and the thickness of the second side is in the range of 350mm-450mm. Preferably, the difference between the thickness of the second side and the thickness of the first side is in the range of 50mm-150mm.

[0066] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0067] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A secondary battery characterized by comprising: It comprises: a flexible shell comprising two first sides arranged in a first direction and two second sides arranged in a second direction, the first and second sides are connected head to tail, the thickness of the second side is greater than the thickness of the first side; two top covers (1), the two top covers (1) are arranged in a third direction and connected with the flexible shell to form a cell cavity, one side of the two top covers (1) facing the cell cavity is a first plane and a second plane respectively; a pole piece assembly (2) comprising a plurality of positive pole pieces (22) and a plurality of negative pole pieces (21), the plurality of positive pole pieces (22) and the plurality of negative pole pieces (21) are arranged in the cell cavity in a staggered manner along the third direction, and the two ends of the pole piece assembly (2) are attached to the first plane and the second plane respectively.

2. The secondary battery of claim 1, wherein: the first plane and the second plane are parallel to each other and arranged in a fourth direction at an acute angle with the first direction.

3. The secondary battery according to claim 1 or 2, wherein the positive pole piece (22) comprises a positive coating layer (24), and the negative pole piece (21) comprises a negative coating layer (23); in the third direction, the projection of the negative coating layer (23) covers the projection of the adjacent positive coating layer (24), and in the first direction, the two ends of the negative coating layer (23) exceed the positive coating layer (24) by a first preset distance, and in the second direction, the two ends of the negative coating layer (23) exceed the positive coating layer (24) by a second preset distance, the first preset distance being greater than the second preset distance.

4. The secondary battery according to claim 3, wherein the size of the negative pole piece (21) is greater than the size of the positive pole piece (22); alternatively, the size of the negative pole piece (21) is consistent with the size of the positive pole piece (22), and there is an uncoated area (25) around the positive pole piece (22) without positive coating, so that the projection of the negative coating layer (23) along the third direction covers the projection of the adjacent positive coating layer (24) along the third direction.

5. The secondary battery according to claim 4, wherein the first plane and the second plane are parallel to each other and arranged in a fourth direction at an acute angle with the first direction, for each positive pole piece (22), the pole piece assembly (2) comprises a negative pole piece (21) above the positive pole piece (22) and a negative pole piece (21) below the positive pole piece (22), the positive pole piece (22) comprises a first end a and a second end b along the fourth direction, the height of the first end a is greater than the height of the second end b; the uncoated area (25) is provided on the second end b of the side of the positive pole piece (22) close to the negative pole piece (21) above, and the width of the uncoated area (25) along the fourth direction is greater than 2mm; the uncoated area (25) is provided on the first end a of the side of the positive pole piece (22) close to the negative pole piece (21) below, and the width of the uncoated area (25) along the fourth direction is greater than 2mm.

6. The secondary battery of claim 1 or 2, wherein: The negative electrode sheet (21) is provided with a negative electrode tab (3) on one side along the second direction, and a plurality of negative electrode tabs (3) are electrically connected through a negative electrode conductive member (4) and then electrically connected with a negative electrode column on the top cover (1); The positive electrode sheet (22) is provided with a positive electrode tab (5) on the other side along the second direction, and a plurality of positive electrode tabs (5) are electrically connected through a positive electrode conductive member (6) and then electrically connected with a positive electrode column on the top cover (1).

7. The secondary battery of claim 6, wherein The negative electrode conductive member (4) comprises a negative electrode connecting line, the negative electrode connecting line is sequentially electrically connected with a plurality of negative electrode tabs (3), and the length of the negative electrode connecting line between adjacent negative electrode tabs (3) exceeds a first preset length; The positive electrode conductive member (6) comprises a positive electrode connecting line, the positive electrode connecting line is sequentially electrically connected with a plurality of positive electrode tabs (5), and the length of the positive electrode connecting line between adjacent positive electrode tabs (5) exceeds a second preset length.

8. The secondary battery according to claim 1 or 2, wherein The size range of the electrode sheet assembly along the first direction and the second direction is [a, 2a], and the size range of the electrode sheet assembly along the third direction is [10a, 20a], a being a positive number.

9. The secondary battery according to claim 1 or 2, wherein The secondary battery further comprises a diaphragm, the extension path of the diaphragm along the third direction is S-shaped and is arranged between the negative electrode sheet (21) and the adjacent positive electrode sheet (22).

10. The secondary battery according to claim 1 or 2, wherein The flexible shell is welded to the top cover (1), the thickness of the first side surface ranges from 250mm to 350mm, and the thickness of the second side surface ranges from 350mm to 450mm.

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