Battery cell and electronic device

Abstract

The invention discloses a battery cell and an electronic device. The battery cell comprises an electrode assembly, a packaging bag, a first tab and a first bonding piece, the electrode assembly is flat and comprises a first surface. The packaging bag comprises a top sealing part. The first face comprises a first area, a second area and a third area which are sequentially connected in the third direction. The second area comprises a first edge and a second edge which are oppositely arranged along the third direction; and the first edge and the second edge are respectively positioned on two sides of the first tab in the third direction along extension lines of the first direction. In the second direction, the first bonding piece is located between the packaging bag and the first face, and the first bonding piece is bonded to the surface, facing the first face, of the packaging bag. The orthographic projection of the first bonding piece in the second direction covers at least part of the first area and / or at least part of the third area. The first bonding piece comprises at least one first edge, at least part of the first edge abuts against the main body part, and the distance D between the upper edge, in the first direction, of the first edge and the lower edge, in the first direction, of the top sealing part is smaller than or equal to 10 mm.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and particularly relates to an electric core and an electronic device. Background Art

[0002] During the external short circuit or thermal box test of the electric core, a large amount of redox gases are generated due to the thermal chemical reaction inside the electric core when it is heated, and the internal pressure of the electric core increases and a heat accumulation phenomenon occurs. The existing packaging bag of the electric core cannot relieve pressure in time, resulting in a reduction in the safety performance of the electric core. Summary of the Invention

[0003] In view of the above situation, it is necessary to provide an electric core that can solve the above problems.

[0004] An embodiment of the present application provides an electric core, which includes an electrode assembly, a packaging bag, a first tab, and a first bonding member. The electrode assembly is flat, and the electrode assembly includes a first end face, a second end face, a first surface, and a second surface. The first end face and the second end face are arranged opposite to each other along a first direction, and the first surface and the second surface are arranged opposite to each other along a second direction. The packaging bag includes a main body portion and a top sealing portion. The electrode assembly is disposed in the main body portion. Along the first direction, the top sealing portion is located on one side of the first end face. Along the first direction, one end of the first tab is electrically connected to the electrode assembly, and the other end of the first tab extends out from the top sealing portion. The first surface includes a first region, a second region, and a third region that are sequentially connected along a third direction. When observed along the second direction, the second region includes a first edge and a second edge that are arranged opposite to each other along the third direction. Both the first edge and the second edge extend along the first direction, and the extension lines of the first edge and the second edge along the first direction are respectively located on both sides of the first tab in the third direction. Along the second direction, the first bonding member is located between the packaging bag and the first surface, and the first bonding member is bonded to the surface of the packaging bag facing the first surface. The orthographic projection of the first bonding member in the second direction covers at least part of the first region; and / or, the orthographic projection of the first bonding member in the second direction covers at least part of the third region. The first bonding member includes at least one first edge, the orthographic projection of the first edge in the second direction extends along the first direction, at least part of the first edge abuts against the main body portion, and the distance between the upper edge of the first edge in the first direction and the lower edge of the top sealing portion in the first direction is D, where D ≤ 10 mm. Herein, the second direction is the thickness direction of the electric core, and the first direction, the second direction, and the third direction are perpendicular to each other in pairs.

[0005] When the above-mentioned battery cell is subjected to an external short circuit or a hot box test, the internal pressure of the battery cell increases and heat accumulation occurs. The first bonding member can guide the gas to concentrate on the first encapsulation weak area of the top seal portion. At least a part of the first edge abuts against the main body portion, and the distance D between the upper edge of the first edge in the first direction and the lower edge of the top seal portion in the first direction is ≤ 10 mm. One end of the first edge close to the top seal portion will pull the first encapsulation weak area of the top seal portion to form a first crease. The part of the top seal portion provided with the first crease is more likely to deform compared to other parts of the packaging bag, so that the first encapsulation weak area of the top seal portion can be timely opened for pressure relief under the action of stress, reducing heat accumulation and improving the safety performance of the battery cell.

[0006] In some embodiments of the present application, D ≤ 4 mm. This further reduces the distance between the upper edge of the first edge in the first direction and the lower edge of the top seal portion in the first direction, making it easier for the first encapsulation weak area to form a first crease, so that the first encapsulation weak area of the top seal portion can be timely opened for pressure relief under the action of stress, reducing heat accumulation and further improving the safety performance of the battery cell.

[0007] In some embodiments of the present application, the battery cell further includes a second tab. The second tab and the first tab are arranged at intervals in the third direction. Along the first direction, one end of the second tab is electrically connected to the electrode assembly, and the other end of the second tab extends out from the top seal portion. The third area includes a fourth area, a fifth area, and a sixth area connected in sequence along the third direction. When observed along the second direction, the fifth area includes a fifth edge and a sixth edge arranged oppositely along the third direction. Both the fifth edge and the sixth edge extend along the first direction, and the extension lines of the fifth edge and the sixth edge along the first direction are respectively located on both sides of the second tab in the third direction. The positive projection of the first bonding member in the second direction covers at least a part of the fourth area; and / or, the positive projection of the first bonding member in the second direction covers at least a part of the sixth area. The first edge abuts against the packaging bag, and one end of the first edge close to the top seal portion will pull the second encapsulation weak area of the top seal portion to form a second crease. The part of the top seal portion provided with the first crease and the second crease is more likely to deform compared to other parts of the packaging bag, so that the first encapsulation weak area and the second weak area of the top seal portion can be timely opened for pressure relief under the action of stress, reducing heat accumulation and improving the safety performance of the battery cell.

[0008] In some embodiments of the present application, the first tab includes a third edge and a fourth edge that are oppositely arranged in the third direction. In the third direction, the third edge is closer to the first edge than the fourth edge. In the second direction, the projection area of the first adhesive member in the first area is the first projection area. The first projection area includes a first side and a second side that are oppositely arranged in the third direction. In the third direction, the second side is closer to the first edge than the first side. In the third direction, the distance between the extension line of the second side along the first direction and the third edge is D1, where 0mm ≤ D1 ≤ 5mm, so that the portion of the first adhesive member located in the first area corresponds to the first weak area of the top seal, thereby facilitating the end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0009] In some embodiments of the present application, 0mm ≤ D1 ≤ 3mm, so as to further make the portion of the first adhesive member located in the first area correspond to the first weak area of the top seal, thereby facilitating the end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0010] In some embodiments of the present application, in the second direction, the projection area of the first adhesive member in the third area is the third projection area. The third projection area includes a third side and a fourth side that are oppositely arranged in the third direction. In the third direction, the third side is closer to the second edge than the fourth side. In the third direction, the distance between the extension line of the third side along the first direction and the fourth edge is D2, where 0mm ≤ D2 ≤ 5mm, so that the portion of the first adhesive member located in the third area corresponds to the first weak area of the top seal, thereby facilitating the end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0011] In some embodiments of the present application, 0mm ≤ D2 ≤ 3mm, so as to further make the portion of the first adhesive member located in the third area correspond to the first weak area of the top seal, thereby facilitating the end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0012] In some embodiments of the present application, the first surface includes a top edge and a bottom edge that are oppositely arranged in the first direction. The top edge is connected to the first end face, and the bottom edge is connected to the second end face. In the first direction, the distance between the top edge and the bottom edge is D3. In the first direction, compared with the bottom edge, the first projection area is closer to the top edge, and the length of the first projection area is D4, where D4 / D3 ≥ 20%, so that the portion of the first adhesive member located in the first area meets the requirements of its own structural strength and facilitates the end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0013] In some embodiments of the present application, along the first direction, compared with the bottom edge, the third projection area is closer to the top edge, and the length of the third projection area is D5, where D5 / D3 ≥ 20%, so that the part of the first adhesive located in the third area meets the requirements of its own structural strength, and it is convenient for one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0014] In some embodiments of the present application, D4 / D3 > 50%, so that the part of the first adhesive located in the first area meets the requirements of its own structural strength. The part of the first adhesive located in the upper half area of the first area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first adhesive located in the lower half area of the first area can reduce the risk of deformation of the corresponding area of the packaging bag, facilitate guiding the gas to concentrate on the first encapsulation weak area of the top seal, and further facilitate the first encapsulation weak area of the top seal to be opened and relieved of pressure in time under the action of stress.

[0015] In some embodiments of the present application, D5 / D3 > 50%, so that the part of the first adhesive located in the third area meets the requirements of its own structural strength. The part of the first adhesive located in the upper half area of the third area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first adhesive located in the lower half area of the third area can reduce the risk of deformation of the corresponding area of the packaging bag, facilitate guiding the gas to concentrate on the first encapsulation weak area of the top seal, and further facilitate the first encapsulation weak area of the top seal to be opened and relieved of pressure in time under the action of stress.

[0016] In some embodiments of the present application, along the second direction, the thickness of the first adhesive is T1, where 1μm ≤ T1 ≤ 50μm, so as to facilitate one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, and is beneficial to improving the energy density of the battery cell.

[0017] In some embodiments of the present application, 10μm ≤ T1 ≤ 40μm, to further facilitate one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, and is beneficial to improving the energy density of the battery cell.

[0018] In some embodiments of the present application, the first adhesive is bonded to the first surface. The first surface includes a top edge and a bottom edge that are oppositely arranged along the first direction, the top edge is connected to the first end face, and the bottom edge is connected to the second end face. Along the second direction, the projection area of the first adhesive on the first surface includes a fifth edge and a sixth edge that are oppositely arranged along the first direction, the fifth edge is closer to the top edge than the sixth edge, and the distance between the fifth edge and the top edge is D6, where 0mm ≤ D6 ≤ 6mm, so as to facilitate one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease.

[0019] In some embodiments of the present application, 0 mm ≤ D6 ≤ 2 mm. This is to facilitate the end of the first edge close to the top seal pulling the first encapsulation weak area of the top seal to form a first crease.

[0020] In some embodiments of the present application, when the temperature is 120 °C to 140 °C, the peel strength between the first surface adhered to both sides of the first adhesive and the packaging bag is σ1, and the peel strength of the top seal is σ2, and σ1 > σ2. This is to enable the first encapsulation weak area and the second encapsulation weak area of the top seal to be promptly opened for pressure relief under the action of stress when the internal pressure of the battery cell increases and heat accumulation occurs, reduce heat accumulation, and improve the safety performance of the battery cell.

[0021] In some embodiments of the present application, 0.55 N / mm ≤ σ1 ≤ 0.78 N / mm, 0.1 N / mm ≤ σ2 ≤ 0.5 N / mm, so that σ1 > σ2.

[0022] In some embodiments of the present application, the material of the first adhesive includes at least one of a fluorinated rubber binder and a silicone-based binder. The material of the fluorinated rubber binder includes at least one of fluorinated rubber and perfluororubber. The material of the silicone-based binder includes a silicone-based polymer.

[0023] In some embodiments of the present application, the battery cell further includes a first tab glue. Along the thickness direction of the first tab, the first tab glue wraps the first tab. Along the second direction, at least a part of the first tab glue overlaps with the top seal. Along the direction from the main body to the top seal, the overlapping area of the first tab glue and the top seal includes an inner unsealed area and a middle seal area arranged in sequence. At least a part of the first adhesive is located in the inner unsealed area to facilitate the end of the first edge close to the top seal forming a first crease in the first encapsulation weak area of the top seal.

[0024] In some embodiments of the present application, along the first direction, the length of the first adhesive extending into the inner unsealed area is L1, and 0.5 mm ≤ L1 ≤ 1 mm. This is to facilitate the end of the first edge close to the top seal abutting against the encapsulation weak area of the top seal to form a first crease, and is beneficial to improving the encapsulation stability of the top seal.

[0025] In some embodiments of the present application, when the temperature is 120 °C to 140 °C, the tensile strength of the main body of the first adhesive is set as P1, and the tensile strength of the top seal is P2, and P1 > P2. This is to enable the top seal to be opened for pressure relief before the main body deforms at high temperature, reduce heat accumulation, and improve the safety performance of the battery cell. In some embodiments of the present application, 5 MPa ≤ P2 ≤ 20 MPa, and P1 > 20 MPa. This is to enable the top seal to have a certain strength, reduce the risk of electrolyte leakage in the battery cell, and at the same time enable the top seal to be opened for pressure relief before the main body deforms at high temperature, reduce heat accumulation, and improve the safety performance of the battery cell.

[0026] In some embodiments of the present application, the material of the first bonding member includes at least one of epoxy resin and acrylic resin.

[0027] An embodiment of the present application further provides an electronic device, which includes any one of the secondary batteries in the above embodiments. Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of a battery cell in an embodiment of the present application.

[0029] Figure 2 is Figure 1 a cross-sectional view along the section line A-A.

[0030] Figure 3 is a schematic structural diagram of the third region in an embodiment of the present application.

[0031] Figure 4 is a schematic structural diagram of the first bonding member in an embodiment of the present application.

[0032] Figure 5 is a schematic structural diagram of the first bonding member in an embodiment of the present application.

[0033] Figure 6 is a schematic structural diagram of a battery cell in another embodiment of the present application.

[0034] Figure 7 is Figure 6 a cross-sectional view along the section line B-B.

[0035] Figure 8 is a schematic structural diagram of an electronic device in an embodiment of the present application.

[0036] Description of the Main Element Symbols

[0037] Battery cell 100

[0038] Electronic device 200

[0039] Electrode assembly 10

[0040] First end face 11

[0041] Second end face 12

[0042] First face 13

[0043] First region 131

[0044] Second region 132

[0045] First edge 1321

[0046] Second edge 1322

[0047] Third Zone 133

[0048] Fourth Zone 134

[0049] Fifth Zone 135

[0050] Fifth Edge 1351

[0051] Sixth Edge 1352

[0052] Sixth Zone 136

[0053] Top Edge 13A

[0054] Bottom Edge 13B

[0055] Packaging Bag 20

[0056] Main Body 21

[0057] Top Sealing Part 22

[0058] R Corner 221

[0059] First Tab 30

[0060] Third Edge 31

[0061] Fourth Edge 32

[0062] First Adhesive Part 40

[0063] First Edge 41

[0064] First Projection Area 42

[0065] First Side 421

[0066] Second Side 422

[0067] Third Projection Area 43

[0068] Third Side 431

[0069] Fourth Side 432

[0070] Fifth Side 44

[0071] Sixth Side 45

[0072] Second Tab 50

[0073] First Tab Adhesive 60

[0074] Inner Unsealed Area 61

[0075] Middle Sealing Area 62

[0076] Outer Unsealed Area 63

[0077] The first direction Z

[0078] The second direction X

[0079] The third direction Y

[0080] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. Specific embodiments

[0081] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0082] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element. When an element is considered to be "disposed" on another element, it can be directly disposed on the other element or there may be an intermediate element.

[0083] When a value is considered to be "equal" to another value, it means that the two are equal within a set deviation, and the set deviation range is within 5%. That is to say, when at least one of the two values fluctuates within the set deviation range, even if their values are not equal, they are still determined to be approximately equal. When the ratio of a value to another value is "1:1", it means that the two are equal within a set deviation, and the set deviation range is within 5%. That is to say, when at least one of the two values fluctuates within the set deviation range, even if their values are not equal, they are still determined to have an equal ratio.

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. The term "overlap" used herein means that the projected parts of two components overlap or the projections of two components coincide.

[0085] Embodiments of the present application provide a battery cell, which includes an electrode assembly, a packaging bag, a first tab, and a first adhesive. The electrode assembly is flat and includes a first end face, a second end face, a first surface, and a second surface. The first end face and the second end face are oppositely arranged along a first direction, and the first surface and the second surface are oppositely arranged along a second direction. The packaging bag includes a main body portion and a top-sealing portion. The electrode assembly is disposed in the main body portion. Along the first direction, the top-sealing portion is located on one side of the first end face. Along the first direction, one end of the first tab is electrically connected to the electrode assembly, and the other end of the first tab extends out from the top-sealing portion. The first surface includes a first region, a second region, and a third region that are sequentially connected along a third direction. When observed along the second direction, the second region includes a first edge and a second edge that are oppositely arranged along the third direction. Both the first edge and the second edge extend along the first direction, and the extension lines of the first edge and the second edge along the first direction are respectively located on both sides of the first tab in the third direction. Along the second direction, the first adhesive is located between the packaging bag and the first surface. The orthographic projection of the first adhesive in the second direction covers at least part of the first region; and / or, the orthographic projection of the first adhesive in the second direction covers at least part of the third region. The first adhesive includes at least one first edge. The orthographic projection of the first edge in the second direction extends along the first direction. At least part of the first edge abuts against the main body portion, and the distance D between the upper edge of the first edge in the first direction and the lower edge of the top-sealing portion in the first direction is ≤ 10 mm. Wherein, the second direction is the thickness direction of the battery cell, and the first direction, the second direction, and the third direction are perpendicular to each other in pairs.

[0086] During external short circuit or hot box test of the above battery cell, the internal pressure of the battery cell increases and heat accumulation occurs. The first adhesive can guide the gas to concentrate on the first encapsulation weak area of the top-sealing portion. The orthographic projection of the first edge in the second direction extends along the first direction. At least part of the first edge abuts against the main body portion, and the distance D between the upper edge of the first edge in the first direction and the lower edge of the top-sealing portion in the first direction is ≤ 10 mm. One end of the first edge close to the top-sealing portion will pull the first encapsulation weak area of the top-sealing portion to form a first crease. The part of the top-sealing portion provided with the first crease is more likely to deform compared with other parts of the packaging bag, so that the first encapsulation weak area of the top-sealing portion can be opened in time to relieve pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery cell.

[0087] The following will further illustrate the embodiments of the present application with reference to the accompanying drawings.

[0088] Please refer to Figure 1 and Figure 2 Together, an embodiment of the present application provides a battery cell 100. The battery cell 100 includes an electrode assembly 10, a packaging bag 20, a first tab 30, and a first adhesive 40.

[0089] The electrode assembly 10 is formed by winding or stacking a positive electrode tab, a separator membrane, and a negative electrode tab arranged in sequence. The electrode assembly 10 is used to convert chemical energy into electrical energy. The length direction of the electrode assembly 10 is the first direction Z, the thickness direction of the electrode assembly 10 is the second direction X, and the width direction of the electrode assembly 10 is the third direction Y. The first direction Z, the second direction X, and the third direction Y are perpendicular to each other in pairs.

[0090] The electrode assembly 10 includes a first end face 11, a second end face 12, a first face 13, and a second face 14. The first end face 11 and the second end face 12 are arranged opposite to each other along the first direction Z, and the first face 13 and the second face 14 are arranged opposite to each other along the second direction X.

[0091] The packaging bag 20 includes a main body portion 21 and a top sealing portion 22. The main body portion 21 refers to the portion of the packaging film where the punching is set, and the top sealing portion 22 refers to the portion where the packaging film is overlapped and joined. The electrode assembly 10 is disposed within the main body portion 21. Along the first direction Z, one end of the first tab 30 is electrically connected to the electrode assembly 10, and the other end of the first tab 30 extends out from the top sealing portion 22. The first tab 30 is configured to be electrically connected to an external circuit. The thickness of the first tab 30 itself will affect the packaging strength of the top sealing portion 22 near the first tab 30, causing the portions on both sides of the top sealing portion 22 corresponding to the first tab 30 in the third direction Y to form a first packaging weak area compared to other portions of the packaging bag 20.

[0092] The first face 13 includes a first region 131, a second region 132, and a third region 133 that are sequentially connected along the third direction Y. When observed along the second direction X, the second region 132 includes a first edge 1321 and a second edge 1322 that are arranged opposite to each other along the third direction Y. Both the first edge 1321 and the second edge 1322 extend along the first direction Z, and the extension lines of the first edge 1321 and the second edge 1322 along the first direction Z are respectively located on both sides of the first tab 30 in the third direction Y.

[0093] Along the second direction X, the first adhesive member 40 is located between the packaging bag 20 and the first face 13. The orthographic projection of the first adhesive member 40 in the second direction X covers at least part of the first region 131, and / or the orthographic projection of the first adhesive member 40 in the second direction X covers at least part of the third region 133.

[0094] The first adhesive member 40 includes at least one first edge 41. At least part of the first edge 41 abuts against the main body portion 21, and the distance D between the upper edge of the first edge 41 in the first direction Z and the lower edge of the top sealing portion 22 in the first direction Z is D ≤ 10 mm. One end of the first edge 41 close to the top sealing portion 22 will pull the first packaging weak area of the top sealing portion 22 to form a first crease. The portion of the top sealing portion 22 provided with the first crease is more likely to deform compared to other portions of the packaging bag 20.

[0095] Optionally, the first bonding member 40 is provided with a first edge 41 at the portion located in the first region 131, and / or the first bonding member 40 is provided with a first edge 41 at the portion located in the third region 133. Wherein, in the first direction Z, there is an R corner 221 at the connection between the top sealing portion 22 and the main body portion 21, and the lower edge of the top sealing portion 22 in the first direction Z refers to an edge passing through the R corner 221 and perpendicular to the first direction Z. Wherein, the positive projection of the first edge 41 in the second direction X extending along the first direction Z means that the first edge 41 is not necessarily parallel to the first direction Z, the first edge 41 may be inclined at a certain angle relative to the second direction X, and the first edge 41 may also be curved or in other forms, and the present application does not limit this.

[0096] When the above-mentioned battery cell 100 is subjected to an external short circuit or a hot box test, the internal pressure of the battery cell 100 increases and heat accumulation occurs. The first bonding member 40 can guide the gas to concentrate on the first encapsulation weak area of the top sealing portion 22. The first edge 41 abuts against the packaging bag 20, and one end of the first edge 41 close to the top sealing portion 22 will pull the first encapsulation weak area of the top sealing portion 22 to form a first crease. The portion of the top sealing portion 22 provided with the first crease is more likely to deform compared to other portions of the packaging bag 20, so that the first encapsulation weak area of the top sealing portion 22 can be opened in time to relieve pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery cell 100.

[0097] Please refer to Figure 3 , in some embodiments, the battery cell 100 further includes a second tab 50, and the second tab 50 and the first tab 30 are arranged at intervals along the third direction Y. Along the first direction Z, one end of the second tab 50 is electrically connected to the electrode assembly 10, and the other end of the second tab 50 extends out from the top sealing portion 22. The polarity of the second tab 50 is opposite to the polarity of the first tab 30 to facilitate forming a complete current loop with the external circuit. The thickness of the second tab 50 itself will affect the encapsulation strength of the top sealing portion 22 near the second tab 50, so that the portions of the top sealing portion 22 corresponding to both sides of the second tab 50 in the third direction Y form a second encapsulation weak area compared to other portions of the packaging bag 20 except the first encapsulation weak area.

[0098] The third region 133 includes a fourth region 134, a fifth region 135, and a sixth region 136 that are sequentially connected along the third direction Y. When observing along the second direction X, the fifth region 135 includes a fifth edge 1351 and a sixth edge 1352 that are oppositely arranged along the third direction Y. Both the fifth edge 1351 and the sixth edge 1352 extend along the first direction Z, and the extension lines of the fifth edge 1351 and the sixth edge 1352 along the first direction Z are respectively located on both sides of the second tab 50 in the third direction Y.

[0099] The orthographic projection of the first adhesive member 40 in the second direction X covers at least part of the fourth region 134; and / or, the orthographic projection of the first adhesive member 40 in the second direction X covers at least part of the sixth region 136. Optionally, a first edge 41 is provided at the portion of the first adhesive member 40 located in the fourth region 134, and / or, a first edge 41 is provided at the portion of the first adhesive member 40 located in the sixth region 136. At least part of the first edge 41 abuts against the main body portion 21, and one end of the first edge 41 close to the top sealing portion 22 pulls the second encapsulation weak area of the top sealing portion 22 to form a second crease. The portions of the top sealing portion 22 provided with the first crease and the second crease are more likely to deform compared to other portions of the packaging bag 20, so that the first encapsulation weak area and the second weak area of the top sealing portion 22 can be opened in time under the action of stress to relieve pressure, reduce heat accumulation, and improve the safety performance of the battery cell 100.

[0100] It should be noted that the dimensional relationship between the portions of the first adhesive member 40 located on both sides of the fifth region 135 along the third direction Y and the second pole ear 50, and the dimensional relationship between the portions of the first adhesive member 40 located on both sides of the second region 132 along the third direction Y and the first pole ear 30 are substantially the same. In this application, the dimensional relationship between the portions of the first adhesive member 40 located on both sides of the second region 132 along the third direction Y and the first pole ear 30 is taken as an example for description.

[0101] Please refer to Figure 1 and Figure 3 , in some embodiments, the first pole ear 30 includes a third edge 31 and a fourth edge 32 that are oppositely arranged along the third direction Y. Along the third direction Y, the third edge 31 is closer to the first edge 1321 than the fourth edge 32.

[0102] Along the second direction X, the projection area of the first adhesive member 40 in the first region 131 is the first projection area 42. The first projection area 42 includes a first side 421 and a second side 422 that are oppositely arranged along the third direction Y. Along the third direction Y, the second side 422 is closer to the first edge 1321 than the first side 421. Along the third direction Y, the distance between the extension line of the second side 422 along the first direction Z and the third edge 31 is D1, and 0mm ≤ D1 ≤ 5mm, so that the portion of the first adhesive member 40 located in the first region 131 corresponds to the first weak area of the top sealing portion 22, and thus it is convenient for one end of the first edge 41 close to the top sealing portion 22 to pull the first encapsulation weak area of the top sealing portion 22 to form a first crease.

[0103] Optionally, D1 is one of 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, and any other arbitrary value within the range of 0mm ≤ D1 ≤ 5mm.

[0104] Further, 0 mm ≤ D1 ≤ 3 mm, so as to further make the part of the first bonding member 40 located in the first region 131 correspond to the first weak region of the top sealing portion 22, thereby facilitating one end of the first edge 41 close to the top sealing portion 22 to pull the first packaging weak region of the top sealing portion 22 to form a first crease.

[0105] It should be noted that the extension line of the second side 422 is schematically represented by a line on the same straight line as the second side 422.

[0106] Please refer to Figure 1 and Figure 3 In some embodiments, along the second direction X, the projection area of the first bonding member 40 in the third region 133 is the third projection area 43. The third projection area 43 includes a third side 431 and a fourth side 432 that are oppositely arranged along the third direction Y. Along the third direction Y, the third side 431 is closer to the second edge 1322 than the fourth side 432. Along the third direction Y, the distance between the extension line of the third side 431 along the first direction Z and the fourth edge 32 is D2, and 0 mm ≤ D2 ≤ 5 mm, so as to make the part of the first bonding member 40 located in the third region 133 correspond to the first weak region of the top sealing portion 22, thereby facilitating one end of the first edge 41 close to the top sealing portion 22 to pull the first packaging weak region of the top sealing portion 22 to form a first crease.

[0107] Optionally, D2 is one of 0 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm and any other arbitrary value within the range of 0 mm ≤ D2 ≤ 5 mm.

[0108] Further, 0 mm ≤ D2 ≤ 3 mm, so as to further make the part of the first bonding member 40 located in the third region 133 correspond to the first weak region of the top sealing portion 22, thereby facilitating one end of the first edge 41 close to the top sealing portion 22 to pull the first packaging weak region of the top sealing portion 22 to form a first crease.

[0109] It should be noted that the extension line of the third side 431 is schematically represented by a line on the same straight line as the third side 431.

[0110] Please refer to Figure 1 and Figure 3 In some embodiments, the first surface 13 includes a top edge 13A and a bottom edge 13B that are oppositely arranged along the first direction Z. The top edge 13A is connected to the first end face 11, and the bottom edge 13B is connected to the second end face 12. Along the first direction Z, the distance between the top edge 13A and the bottom edge 13B is D3.

[0111] In some embodiments, along the first direction Z, the first projection area 42 is close to the top edge 13A, the length of the first projection area 42 is D4, and D4 / D3≥20%, that is, the first projection area 42 is located in the upper half area of the first area 131 in the first direction Z, so that the part of the first adhesive member 40 located in the first area 131 meets the requirements of its own structural strength, and it is convenient for one end of the first edge 41 close to the top seal part 22 to pull the first encapsulation weak area of the top seal part 22 to form a first crease.

[0112] Optionally, D4 / D3 is one of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, 100% and any other value within the range.

[0113] In some embodiments, along the first direction Z, the third projection area 43 is close to the top edge 13A, the length of the third projection area 43 is D5, and D5 / D3≥20%, that is, the third projection area 43 is located in the upper half area of the third area 133 in the first direction Z, so that the part of the first adhesive member 40 located in the third area 133 meets the requirements of its own structural strength, and it is convenient for one end of the first edge 41 close to the top seal part 22 to pull the first encapsulation weak area of the top seal part 22 to form a first crease.

[0114] Optionally, D5 / D3 is one of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, 100% and any other value within the range.

[0115] Please refer to Figure 4 and Figure 5 In some embodiments, D4 / D3>50%, that is, the first projection area 42 extends from the upper half area of the first area 131 in the first direction Z to the lower half area of the first area 131 in the first direction Z, so that the part of the first adhesive member 40 located in the first area 131 meets the requirements of its own structural strength. The part of the first adhesive member 40 located in the upper half area of the first area 131 can pull the first encapsulation weak area of the top seal part 22 to form a first crease. The part of the first adhesive member 40 located in the lower half area of the first area 131 can reduce the risk of deformation of the corresponding area of the packaging bag 20, facilitate guiding the gas to concentrate on the first encapsulation weak area of the top seal part 22, and further facilitate the first encapsulation weak area of the top seal part 22 to be opened and depressurized in time under the action of stress.

[0116] Optionally, D4 / D3 is one of 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% and any other value within the range of D4 / D3>50%.

[0117] In some embodiments, D5 / D3 > 50%, that is, the third projection area 43 extends from the upper half area of the third area 133 in the first direction Z to the lower half area of the third area 133 in the first direction Z, so that the portion of the first adhesive member 40 located in the third area 133 meets the requirements of its own structural strength. The portion of the first adhesive member 40 located in the upper half area of the third area 133 can pull the first encapsulation weak area of the top seal portion 22 to form a first crease. The portion of the first adhesive member 40 located in the lower half area of the third area 133 can reduce the risk of deformation of the corresponding area of the packaging bag 20, facilitate guiding the gas to concentrate on the first encapsulation weak area of the top seal portion 22, and further facilitate the first encapsulation weak area of the top seal portion 22 to be opened and depressurized in time under the action of stress.

[0118] Optionally, D2 / D3 is one of 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% and any other value within the range of D5 / D3 > 50%.

[0119] Please refer to Figure 2 , in some embodiments, along the second direction X, the thickness of the first adhesive member 40 is T1, and 1 μm ≤ T1 ≤ 50 μm. When T1 is too small (less than 1 μm), the pulling effect of the end of the first edge 41 close to the top seal portion 22 on the first encapsulation weak area of the top seal portion 22 is likely to be weakened. When T1 is too large (greater than 50 μm), it is easy for the first adhesive member 40 to occupy a relatively large space in the packaging bag 20, resulting in a decrease in the energy density of the battery cell 100. By defining 1 μm ≤ T1 ≤ 50 μm, it is convenient for the end of the first edge 41 close to the top seal portion 22 to pull the first encapsulation weak area of the top seal portion 22 to form a first crease, and it is beneficial to improve the energy density of the battery cell 100.

[0120] Optionally, T1 is one of 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm and any other value within the range of 1 μm ≤ T1 ≤ 50 μm.

[0121] Furthermore, 10 μm ≤ T1 ≤ 40 μm, which further facilitates the end of the first edge 41 close to the top seal portion 22 to pull the first encapsulation weak area of the top seal portion 22 to form a first crease, and is beneficial to further improve the energy density of the battery cell 100.

[0122] Please refer to Figure 2 , in some embodiments, the first adhesive member 40 is adhered to the first surface 13 to improve the structural stability between the electrode assembly 10 and the packaging bag 20, and facilitate the first adhesive member 40 to guide the gas to concentrate on the top seal portion 22.

[0123] In some embodiments, the first adhesive member 40 is adhered to the first surface 13. When the temperature is between 120°C and 140°C, the peel strength between the first surface 13 adhered to both sides of the first adhesive member 40 and the packaging bag 20 is σ1, and the peel strength of the top seal portion 22 is σ2, where σ1 > σ2. When the internal pressure of the battery cell 100 increases and heat accumulation occurs, the first encapsulation weak area and the second encapsulation weak area of the top seal portion 22 can be promptly opened to relieve pressure under the action of stress, reducing heat accumulation and improving the safety performance of the battery cell 100.

[0124] In some embodiments, 0.55 N / mm ≤ σ1 ≤ 0.78 N / mm, 0.1 N / mm ≤ σ2 ≤ 0.5 N / mm, so as to facilitate σ1 > σ2.

[0125] Optionally, σ1 is one of 0.55 N / mm, 0.56 N / mm, 0.57 N / mm, 0.58 N / mm, 0.59 N / mm, 0.6 N / mm, 0.65 N / mm, 0.7 N / mm, 0.75 N / mm, 0.78 N / mm, and any other value within the range of 0.55 N / mm ≤ σ1 ≤ 0.78 N / mm; σ2 is one of 0.1 N / mm, 0.15 N / mm, 0.2 N / mm, 0.25 N / mm, 0.3 N / mm, 0.35 N / mm, 0.4 N / mm, 0.45 N / mm, 0.5 N / mm, and any other value within the range of 0.1 N / mm ≤ σ2 ≤ 0.5 N / mm.

[0126] In some embodiments, the first adhesive member 40 is adhered to the first surface 13. Optionally, the material of the first adhesive member 40 includes at least one of a fluorinated rubber binder and a silicone-based binder.

[0127] The material of the fluorinated rubber binder includes at least one of fluorinated rubber or perfluororubber as the main polymer, and the mass percentage content of the main polymer in the fluorinated rubber binder ranges from 30% to 60%. In addition, the fluorinated rubber binder also includes a solvent, a crosslinking agent, a filler, a stabilizer, and an antioxidant. Common solvent materials mainly include toluene, xylene, acetone, etc. Common crosslinking agent materials mainly include peroxides or polyolefins. Common fillers include silica, calcium carbonate, etc. Common stabilizers and antioxidants include phenolic antioxidants, phosphoramide stabilizers, etc. Among them, by adjusting the mass percentage content of the main polymer in the fluorinated rubber glue, the peel strength σ1 between the first adhesive member 40 and the packaging bag 20 can be regulated. The higher the mass percentage content of the main polymer, the greater σ1.

[0128] The materials of the silicone-based binder include silicone polymers, and a common silicone polymer is polydimethylsiloxane. The mass percentage content of the silicone polymer in the silicone binder ranges from 20% to 50%. In addition, the silicone-based binder also includes a cross-linking agent, a catalyst, a filler, a plasticizer, a stabilizer, and an antioxidant. A common cross-linking agent is a silane coupling agent. Common catalysts include organotin compounds, organic acids, etc. Common fillers include silica, talcum powder, calcium carbonate, etc. Common plasticizers include silicone oil, phthalate esters, etc. Common stabilizers and antioxidants include phenolic antioxidants, phosphoramide stabilizers, etc. Among them, by adjusting the mass percentage content of the silicone polymer in the silicone-based binder, the peel strength σ1 between the first bonding member 40 and the packaging bag 20 can be regulated. The higher the mass percentage content of the silicone polymer, the greater σ1 is.

[0129] The peel strength of the top seal portion 22 is mainly regulated by parameters such as the heat-sealing temperature and heat-sealing pressure during heat-sealing.

[0130] Please refer to Figure 1 and Figure 3 , in some embodiments, along the second direction X, the projection area of the first bonding member 40 on the first surface 13 includes a fifth side 44 and a sixth side 45 that are oppositely arranged along the first direction Z. The fifth side 44 is closer to the top edge 13A than the sixth side 45. The distance between the fifth side 44 and the top edge 13A is D6, and 0mm ≤ D6 ≤ 6mm, so as to facilitate one end of the first edge 41 close to the top seal portion 22 to pull the first encapsulation weak area of the top seal portion 22 to form a first crease.

[0131] Optionally, D6 is one of 0mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, and any other value within the range of 0mm ≤ D6 ≤ 6mm.

[0132] Please refer to Figure 6 and Figure 7 , in some embodiments, the first bonding member 40 is bonded to the surface of the packaging bag 20 facing the first surface 13.

[0133] In some embodiments, the battery cell 100 further includes a first tab glue 60. Along the thickness direction of the first tab 30, the first tab glue 60 wraps the first tab 30. Along the second direction X, at least a part of the first tab glue 60 overlaps with the top sealing part 22. Along the direction from the main body part 21 to the top sealing part 22, the overlapping area of the first tab glue 60 and the top sealing part 22 includes an inner unsealed area 61, a middle sealing area 62, and an outer unsealed area 63 arranged in sequence. Among them, the middle sealing area 62 refers to the area of the top sealing part 22 that has been hot-pressed. The inner unsealed area 61 is located on the side of the middle sealing area 62 close to the electrode assembly 10 and has not been hot-pressed. The outer unsealed area 63 is located on the side of the middle sealing area 52 far from the electrode assembly 10 and has not been hot-pressed. At least a part of the first bonding member 40 is located in the inner unsealed area 61, so that one end of the first edge 41 close to the top sealing part 22 forms a first crease in the first packaging weak area of the top sealing part 22. Among them, please refer to Figure 2 , in the first direction Z, there is an R corner 221 at the connection between the top sealing part 22 and the main body part 21. The lower edge of the top sealing part 22 in the first direction Z refers to an edge that passes through the R corner 221 and is perpendicular to the first direction Z. The lower edge of the inner unsealed area 61 in the first direction Z is the lower edge of the top sealing part 22 in the first direction Z.

[0134] Please refer to Figure 6 , in some embodiments, along the first direction Z, the length of the first bonding member 40 extending into the inner unsealed area 61 is L1, and 0.5mm ≤ L1 ≤ 1mm. When L1 is too small (less than 0.5mm), it is easy to make one end of the first edge 41 close to the top sealing part 22 difficult to abut against the first packaging weak area of the top sealing part 22, thus making it difficult to form the first crease. When L1 is too large (greater than 1mm), it is easy for the first bonding member 40 to interfere with the middle sealing area 62, resulting in a reduction in the packaging strength of the top sealing part 22. By defining 0.5mm ≤ L1 ≤ 1mm, it is convenient for one end of the first edge 41 close to the top sealing part 22 to abut against the packaging weak area of the top sealing part 22 to form the first crease, and it is beneficial to improve the packaging stability of the top sealing part 22. Among them, the length of the first bonding member 40 extending into the inner unsealed area 61 is the distance between the edge of the first bonding member 40 located in the inner unsealed area 61 and the lower edge of the inner unsealed area 61 in the first direction Z.

[0135] Optionally, L1 is one of 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, and any other arbitrary value within the range of 0.5mm ≤ L1 ≤ 1mm.

[0136] In some embodiments, when the temperature is 120°C to 140°C, the tensile strength of the main body part 21 provided with the first bonding member 40 is P1, and the tensile strength of the top sealing part 22 is P2, and P1 > P2. So that before the main body part 21 deforms at high temperature, the top sealing part 22 can be opened to release pressure, reduce heat accumulation, and improve the safety performance of the battery cell 100.

[0137] Optionally, 5 MPa ≤ P1 ≤ 20 MPa and P2 > 20 MPa. Since the tensile strength = bonding force / bonding area, on the premise that the bonding area of the top sealing part 22 is constant, the lower the tensile strength of the top sealing part 22, the lower the corresponding bonding force. When the bonding force of the top sealing part 22 is too low, risks such as easy electrolyte leakage of the battery cell 100 may occur. When the tensile strength of the top sealing part 22 is too large, the bonding force of the top sealing part 22 with the same bonding area is stronger, and the top sealing part 22 is less likely to be flushed open at high temperatures, affecting the safety performance of the battery cell 100 at high temperatures. By selecting P2 > 20 MPa, the packaging bag 20 provided with the first bonding member 40 is not easily deformed at high temperatures, facilitating the concentration of gas towards the first encapsulation weak area of the top sealing part 22, and further facilitating the first encapsulation weak area of the top sealing part 22 to be flushed open in time under the action of stress to relieve pressure.

[0138] Optionally, the material of the first bonding member 40 includes at least one of epoxy resin and acrylic resin. The optional epoxy resins include bisphenol A epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, etc. The optional acrylic resins include methyl methacrylate, 2-hydroxyethyl methacrylate, polyurethane acrylate, epoxy acrylate, etc. In addition to the above epoxy resin materials or acrylic resin materials, the material of the first bonding member 40 may also include curing agents, fillers, diluents, coupling agents, etc. Common curing agent materials include diaminodiphenyl sulfone, vinyltriamine, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, etc. Common fillers include silica, calcium carbonate, aluminum oxide, glass fiber, carbon fiber, etc. Common diluents include acetone, toluene, alkyl glycidyl ether, butyl glycidyl ether, etc. Common coupling agents include γ-aminopropyltriethoxysilane, etc. Among them, the strength of the first bonding member 40 can be adjusted by regulating the mass percentage content of epoxy resin or acrylic resin in the material of the first bonding member 40, and correspondingly, the tensile strength of the packaging bag 20 provided with the first bonding member 40 can be adjusted. The higher the mass percentage content of epoxy resin or acrylic resin in the material of the first bonding member 40, the greater the strength of the first bonding member 40, and correspondingly, the greater the tensile strength of the packaging bag 20 provided with the first bonding member 40.

[0139] Please refer to Figure 8 , an embodiment of the present application further provides an electronic device 200, including the battery cell 100 in any of the above embodiments. Optionally, the electronic device 200 may be a device with a rechargeable battery such as a mobile phone, a tablet computer, a notebook computer, a smart wearable product (e.g., a smart watch, a smart bracelet), a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, etc.

[0140] In the above-mentioned battery cell 100 and electronic device 200, when the battery cell 100 is subjected to an external short circuit or a hot box test, the internal pressure of the battery cell 100 increases and heat accumulation occurs. The first bonding member 40 can guide the gas to concentrate on the first encapsulation weak area of the top seal portion 22. The first edge 41 abuts against the packaging bag 20, and one end of the first edge 41 close to the top seal portion 22 will pull the first encapsulation weak area of the top seal portion 22 to form a first crease. The part of the top seal portion 22 provided with the first crease is more likely to deform compared to other parts of the packaging bag 20, so that the first encapsulation weak area of the top seal portion 22 can be opened in time to release pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery cell 100.

[0141] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0142] 1. Battery cell hot box test

[0143] 130°C hot box test: Under the condition of 25°C, the lithium-ion battery charged at a constant current of 2C to 4.5V and then charged at a constant voltage of 4.5V until the current is 0.02C is placed in a test chamber with circulating air convection, a temperature of 25°C, and a humidity of 80%. After standing for 5 minutes, the test chamber is heated to 130°C at a rate of 5°C / min, and kept at 130°C unchanged. After 1 hour, the test is stopped, and it is checked whether the lithium-ion battery catches fire or explodes. Passing the test means that it does not catch fire or explode.

[0144] 130°C hot box test passing rate = number of lithium-ion batteries passing the hot box test at 130°C / total number of lithium-ion batteries in the hot box test at 130°C (5).

[0145] 132°C hot box test: Under the condition of 25°C, the lithium-ion battery charged at a constant current of 2C to 4.5V and then charged at a constant voltage of 4.5V until the current is 0.02C is placed in a test chamber with circulating air convection, a temperature of 25°C, and a humidity of 80%. After standing for 5 minutes, the test chamber is heated to 132°C at a rate of 5°C / min, and kept at 132°C unchanged. After 1 hour, the test is stopped, and it is checked whether the lithium-ion battery catches fire or explodes.

[0146] 132°C hot box test passing rate = number of lithium-ion batteries passing the hot box test at 132°C / total number of lithium-ion batteries in the hot box test at 132°C (5).

[0147] 2. Encapsulation strength test

[0148] Soak the battery cell in red ink for 12 h. Take out the battery cell from the red ink, corrode the nylon layer in the encapsulation film at the top-sealing part with aqua regia, and corrode the metal layer in the encapsulation film at the top-sealing part with hydrochloric acid solution to expose the polymer layer in the encapsulation film. Rinse with clean water, and use an optical microscope to observe whether the polymer layer in the encapsulation film at the top-sealing part is penetrated by red ink. If it is penetrated by red ink, it indicates that there is a liquid leakage channel in the polymer layer of the encapsulation film at the top-sealing part, and it is judged as NG; if it is not penetrated by red ink, it is judged as OK. For each group of examples and comparative examples, 20 battery cells are taken for testing, and the number of battery cells passing the test is X1, and the test passing rate is X1 / 20.

[0149] 3. Volume energy density test: The volume energy density test steps are as follows: 1) Under the environmental condition of 25 °C, let the battery cell stand for 10 min, charge it at a constant current of 0.2C to 4.5V, charge it at a constant voltage to 0.02C, and stand for 5 min; then discharge it at a constant current of 0.2C to 3V and stand for 5 min, and record the discharge capacity C0; 2) Measure the length, width and thickness of the battery cell through a PPG battery thickness measuring instrument, and calculate through the following formula: Volume energy density = platform voltage × C0 / (length × width × thickness).

[0150] For each group of examples and comparative examples, 5 battery cells are taken to test the volume energy density and then the average value is recorded in the table.

[0151] 4. Battery cell size measurement

[0152] D, D1, D2, D3, D4, D5, D6, T1, L1 are measured through crystal glue slicing test. Specifically, discharge the battery cell to 0% SOC (State of Charge), wrap the whole battery cell with acrylate polyurethane, dry it at 25 °C for 24 h. After the acrylate polyurethane is completely cured on the surface of the battery cell, use a diamond wire saw to cut a specific part of the battery cell at a speed of 0.5 mm / s, and then polish the cutting surface on a grinding disc until the cutting surface is smooth, and observe and measure the relevant dimensions under a metallurgical microscope.

[0153] Among them, during the measurement of D, D3, D4, D5, D6, T1, L1, the cutting position is the first surface and the cutting line needs to pass through the first tab and / or the second tab, and the cutting direction is along the first direction. During the measurement of D1, D2, the cutting position is the first surface and the cutting line needs to pass through the first bonding part, and the cutting direction is along the third direction. When measuring, what needs to be measured is the distance from the extension line of the first bonding part in the first direction to the edge of the tab.

[0154] 5. Peel strength measurement

[0155] σ1 and σ2 are measured by a high-speed tensile testing machine. When measuring σ1, the battery cell 100 is discharged to 0% SOC (state of charge), and then the battery cell is disassembled. The first bonding member, the first surface on both sides of the first bonding member, and the packaging bag are taken down as a whole, and the electrolyte on the surface is wiped with lint-free paper. Then it is cut into strip samples with a size of 5 mm × 10 mm, and the samples are placed in an oven and heated to 140 °C. Along the length direction of the sample, the surface of the first surface of the sample facing away from the first bonding member is adhered to the steel plate through double-sided tape (Nitto 5000NS), and the adhesion length is not less than 3 mm. The steel plate is fixed at the corresponding position of the high-speed tensile testing machine, the part of the packaging bag in the sample is pulled up, and the sample is clamped in the chuck. The included angle between the pulled-up part of the sample and the steel plate in space is 180°. The chuck pulls the sample at a speed of 50 mm / min, and the average value of the tensile force in the stable area finally measured is recorded as the peel strength σ1, with the unit of N / mm.

[0156] When measuring σ2, the battery cell 100 is preheated in an oven to 140 °C, and then the battery cell 100 is fixed on the lower fixture of the high-speed tensile testing machine. The top-sealing part needs to be in close contact with the fixture to avoid unnecessary displacement during the test; the top-sealing part is clamped with the upper fixture. Set the test speed to 10 mm / min, start the tensile testing machine, and start applying tensile force. Record the tensile force-displacement curve until the top-sealing part opens. Record the tensile force value when the top-sealing part opens as σ2, with the unit of N / mm.

[0157] For each group of examples and comparative examples, 5 battery cells 100 are taken to measure σ1 and σ2, and then the average value is recorded in the table.

[0158] 6. Tensile strength measurement:

[0159] P1 and P2 are measured by a universal material testing machine. When measuring P1, a test specimen with a length of 150 mm and a width of 3 ± 0.2 mm (retaining the middle seal area) is cut out from the top-sealing part using a laser cutting machine. The accurate width w1 and thickness h1 of the specimen are measured using a laser thickness gauge and recorded. The specimen is placed in an oven and heated to 140 °C, and then both ends of the specimen are clamped in the test machine fixture. Set the tensile speed to 50 mm / min, start the test machine until the specimen breaks, and record the maximum tensile force value (unit: N) and the elongation at break. Calculate the tensile strength (unit: MPa) = maximum tensile force (N) / specimen cross-sectional area (mm 2 ), where the specimen cross-sectional area = w1 × h1.

[0160] When measuring P2, cut the packaging bag with the first adhesive into a dumbbell-shaped specimen with a length of 150 mm and a width of 15 mm. Use a micrometer to measure the thickness h2 of the specimen and record it. Put the specimen into an oven and heat it to 140 °C. Then clamp both ends of the specimen in the test machine fixture, set the tensile speed to 50 mm / min, start the test machine until the specimen breaks, and record the maximum tensile force value (unit: N) and the elongation at break. Calculate the tensile strength (unit: MPa) = maximum tensile force (N) / specimen cross-sectional area (mm 2 ), where the specimen cross-sectional area = specimen width (15 mm) × h2.

[0161] Example 1:

[0162] A battery cell, with an initial thickness of 4.8 mm, a length of 87 mm, and a width of 64 mm at 50% SOC. The assembly process is as follows:

[0163] (1) Preparation of the negative electrode sheet: Mix the negative electrode active material artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, and formulate a slurry with a weight percentage of 50 wt%. Stir evenly, coat the slurry on one surface of the copper foil, and then dry it at 90 °C to obtain a negative electrode sheet with a single-sided coating of the negative electrode active material layer. When preparing a double-sided coated negative electrode sheet, repeat the above steps on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet with a negative electrode active material layer. Then cold-press the coated electrode sheet to a thickness of 105 μm, use a laser to remove part of the negative electrode active material on the negative electrode active material to set a groove, and weld the first tab to the copper foil exposed in the groove.

[0164] (2) Preparation of the positive electrode sheet: Mix the positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, and formulate a slurry with a solid content of 75 wt%. Stir evenly. Paste a foaming agent on the aluminum foil, coat the slurry on one surface of the aluminum foil, and then dry it at 90 °C to obtain a positive electrode sheet with a single-sided coating of the positive electrode active material. When preparing a double-sided coated positive electrode sheet, repeat the above coating steps on the other surface of the aluminum foil. Then cold-press the coated electrode sheet to a thickness of 95 μm, tear off the foaming agent to obtain a groove exposing the empty aluminum foil, and weld the second tab to the aluminum foil exposed in the groove.

[0165] (3) Preparation of electrolyte: In a dry argon atmosphere, first, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent and dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0166] (4) Preparation of separator: A separator with a three-layer structure is used, which includes an adhesive layer, a substrate layer, and an adhesive layer arranged in a stacked manner. The material of the first substrate layer is polyethylene (PE), the adhesive in the adhesive layer is PVDF, and the adhesive layer also contains inorganic particles boehmite.

[0167] (5) Preparation of the first adhesive paste: A first adhesive paste is prepared by mixing fluororubber, toluene, polyethylene, and silicon dioxide according to a mass percentage ratio of 50%:40%:5%:5%.

[0168] (6) Preparation of electrode assembly: The positive electrode sheet, separator, and negative electrode sheet are wound, and the first adhesive paste is coated on the first surface of the electrode assembly. Then, the first adhesive paste is thermally cured, and the positive projection of the first adhesive in the second direction covers at least part of the first area and at least part of the third area.

[0169] (7) Cell assembly: The formed aluminum-plastic film with a pit is placed in an assembly fixture with the pit surface facing up, and the electrode assembly is placed in the pit and pressed tightly by applying an external force. Then, another formed aluminum-plastic film with a pit is covered on the electrode assembly with the pit surface facing down, and the four sides of the two aluminum-plastic films are heat-sealed by a hot-pressing method, and the first edge of the first adhesive abuts against the packaging bag.

[0170] (8) Liquid injection and encapsulation: The electrolyte is injected into the assembled electrode assembly, and after processes such as vacuum encapsulation, standing, hot pressing formation, and shaping, the hot pressing temperature (60 °C to 120 °C) and pressure (0.5 Mpa to 3.0 Mpa) are adjusted during the hot pressing formation process to activate the first adhesive to bond with the packaging bag, thus obtaining the cell.

[0171] Comparative example 1: The first adhesive is not provided in the electrode assembly. Except for this, other parameters of comparative example 1 are the same as those of example 1.

[0172] Comparative example 2: The distance D between the first edge provided in the first area and the top sealing part is 12 mm, and the distance D between the first edge provided in the third area and the top sealing part is 12 mm. Except for this, other parameters of comparative example 2 are the same as those of example 1.

[0173] Table 1

[0174] (Other parameters of examples 2 to 10 are the same as those of example 1 except for the parameters involved in Table 1)

[0175]

[0176]

[0177] Note: In Table 1, "\ " means that the parameter is not included.

[0178] It can be seen from Comparative Example 1, Example 1, and Examples 6 to 10 that by the positive projection of the first adhesive member in the second direction covering at least part of the first region; and / or, the positive projection of the first adhesive member in the second direction covering at least part of the third region, and the first edge abutting against the packaging bag, the passing rate of the hot box test can be improved. Further, by providing a fourth region and / or a sixth region in the third region, and the first edge in the fourth region and / or the sixth region abutting against the packaging bag, the passing rate of the hot box test can be further improved. This is because when the battery core is short-circuited externally or tested in a hot box, the internal pressure of the battery core increases and heat accumulation occurs. The first adhesive member can guide the gas to concentrate on the first weak packaging region of the top seal. The first edge abuts against the packaging bag, and the end of the first edge close to the top seal will pull the first weak packaging region of the top seal to form a first crease. The part of the top seal with the first crease is more likely to deform compared to other parts of the packaging bag, so that the first weak packaging region of the top seal can be opened in time to relieve pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery core.

[0179] It can be seen from Comparative Example 2 and Examples 1 to 5 that when the distance D between the first edge and the top seal is D ≤ 10 mm, the passing rate of the hot box test of the battery core can be significantly improved. This is because the end of the first edge close to the top seal will pull the first weak packaging region of the top seal to form a first crease. The part of the top seal with the first crease is more likely to deform compared to other parts of the packaging bag, so that the first weak packaging region of the top seal can be opened in time to relieve pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery core. Further, when D ≤ 4 mm, the passing rate of the special test of the battery core can be further improved. This is because the distance between the upper edge of the first edge in the first direction and the lower edge of the top seal in the first direction is further reduced, and the first weak packaging region is more likely to form a first crease, so that the first weak packaging region of the top seal can be opened in time to relieve pressure under the action of stress, reduce heat accumulation, and thus further improve the safety performance of the battery core.

[0180] Table 2

[0181] (For Examples 11 to 50, other parameters except those involved in Table 2 are the same as those in Example 1)

[0182]

[0183]

[0184]

[0185] As can be seen from Example 1 and Examples 11 to 14, by defining 0 mm ≤ D1 ≤ 5 mm, the passing rate of the hot box test can be improved. When D1 > 5 mm, due to the thickness of the first tab, the length of the encapsulation weak area near the first tab is limited. When the edge of the first adhesive is too far from the edge of the first tab, the position where the first adhesive is set has exceeded the encapsulation weak area, and the first crease generated by the first edge also correspondingly exceeds the encapsulation weak area, resulting in poor effect of the top seal being promptly opened to relieve pressure at high temperature, which affects the passing rate of the hot box test. Further, by defining 0 mm ≤ D1 ≤ 3 mm, the passing rate of the hot box test can be further improved.

[0186] As can be seen from Example 1 and Examples 15 to 18, by defining 0 mm ≤ D2 ≤ 5 mm, the passing rate of the hot box test can be improved. When D2 > 5 mm, due to the thickness of the first tab, the length of the encapsulation weak area near the first tab is limited. When the edge of the first adhesive is too far from the edge of the first tab, the position where the first adhesive is set has exceeded the encapsulation weak area, and the first crease generated by the first edge also correspondingly exceeds the encapsulation weak area, resulting in poor effect of the top seal being promptly opened to relieve pressure at high temperature, which affects the passing rate of the hot box test. Further, by defining 0 mm ≤ D2 ≤ 3 mm, the passing rate of the hot box test can be further improved.

[0187] As can be seen from Example 1 and Examples 19 to 24, by defining 20% ≤ D4 / D3 ≤ 50%, the passing rate of the hot box test can be improved. The first projection area is located in the upper half area of the first area in the first direction, so that the part of the first adhesive located in the first area meets the requirements of its own structural strength, and it is convenient for one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, which is convenient for the top seal to be promptly opened to relieve pressure at high temperature, so as to improve the passing rate of the hot box test of the battery cell. Further, D4 / D3 > 50%, that is, the first projection area extends from the upper half area of the first area in the first direction to the lower half area of the first area in the first direction, so that the part of the first adhesive located in the first area meets the requirements of its own structural strength. The part of the first adhesive located in the upper half area of the first area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first adhesive located in the lower half area of the first area can reduce the risk of deformation of the corresponding area of the packaging bag, which is convenient for guiding the gas to concentrate on the first encapsulation weak area of the top seal, and then it is convenient for the first encapsulation weak area of the top seal to be promptly opened to relieve pressure under the action of stress, thereby further improving the passing rate of the hot box test of the battery cell.

[0188] As can be seen from Example 1 and Examples 25 to 30, by defining 20% ≤ D5 / D3 ≤ 50%, the passing rate of the hot box test can be improved. The third projection area is located in the upper half area of the third area in the first direction, so that the part of the first bonding member located in the third area meets the requirements of its own structural strength, and it is convenient for one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, which is convenient for the top seal to be quickly opened to release pressure at high temperature, so as to improve the passing rate of the hot box test of the battery cell. Further, when D5 / D3 > 50%, that is, the third projection area extends from the upper half area of the third area in the first direction to the lower half area of the third area in the first direction, so that the part of the first bonding member located in the third area meets the requirements of its own structural strength. The part of the first bonding member located in the upper half area of the third area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first bonding member located in the lower half area of the third area 3 can reduce the risk of deformation of the corresponding area of the packaging bag 20, which is convenient for guiding the gas to concentrate on the first encapsulation weak area of the top seal, and then it is convenient for the first encapsulation weak area of the top seal to be quickly opened to release pressure under the action of stress, thereby further improving the passing rate of the hot box test of the battery cell.

[0189] As can be seen from Example 1 and Examples 31 to 36, when T1 < 1μm, the improvement effect on the hot box performance of the battery cell is not good. When T1 > 50μm, the volume energy density of the battery cell is severely lost. By selecting 1μm ≤ T1 ≤ 50μm, the passing rate of the hot box test of the battery cell can be improved while taking into account the volume energy density of the battery cell. Further, it is preferably 10μm ≤ T1 ≤ 40μm to further balance the hot box performance and volume energy density of the battery cell.

[0190] As can be seen from Example 1 and Examples 37 to 40, when D6 > 6mm, the distance between the first edge and the top seal in the first direction is relatively far, and the effect of the first edge pulling the first encapsulation weak area of the top seal to form a first crease is poor, and the improvement effect on the timely opening of the top seal to release pressure at high temperature is poor. By defining 0mm ≤ D6 ≤ 6mm, a first crease can be formed in the first encapsulation weak area, so that the top seal can be quickly opened to release pressure at high temperature, and the passing rate of the hot box test can be improved. Further, by defining 0mm ≤ D6 ≤ 2mm, the passing rate of the hot box test can be further improved.

[0191] As can be seen from Examples 42 to 44, by setting σ1 > σ2, the passing rate of the hot box test can be improved. This is because when the internal pressure of the battery cell increases and heat accumulation occurs, the top seal forms an encapsulation weak area compared with other parts of the packaging bag, which is beneficial to the top seal being quickly opened to release pressure under the action of stress, reducing heat accumulation, and improving the safety performance of the battery cell.

[0192] As can be seen from Example 1, Example 41, Example 42, Example 45 and Example 46, when σ2 remains unchanged, as σ1 increases, the passing rate of the hot box test gradually increases. However, when σ1 is too large, it is easy to cause deformation or tearing of the outermost pole piece of the battery cell 100. Therefore, by selecting 0.55 N / mm ≤ σ1 ≤ 0.78 N / mm, the hot box performance and other performances of the battery cell 100 are taken into account.

[0193] As can be seen from Example 1 and Example 47 to Example 50, when σ1 remains unchanged, as σ2 decreases, the passing rate of the hot box test gradually increases. However, when σ2 is too small, the encapsulation strength of the top sealing part 221 is too low, which is likely to cause other problems such as electrolyte leakage. Therefore, by selecting 0.1 N / mm ≤ σ2 ≤ 0.5 N / mm, the hot box performance of the battery cell 100 and the encapsulation strength of the top sealing part 221 are taken into account.

[0194] Example 51:

[0195] A battery cell with an initial thickness of 4.8 mm, a length of 87 mm, and a width of 64 mm at 50% SOC. The assembly process is as follows:

[0196] (1) Preparation of the negative electrode sheet: Mix artificial graphite as the negative electrode active material, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, and formulate a slurry with a weight percentage of 50 wt%. Stir evenly, coat the slurry on one surface of the copper foil, and then dry it at 90 °C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side. When preparing a double-sided coated negative electrode sheet, repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a negative electrode active material layer coated on both sides. Then cold-press the coated electrode sheet to a thickness of 105 μm, use a laser to remove part of the negative electrode active material on the negative electrode active material to set a groove, and weld the first pole ear to the copper foil exposed in the groove.

[0197] (2) Preparation of the positive electrode sheet: Mix lithium cobalt oxide (LiCoO2) as the positive electrode active material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, and formulate a slurry with a solid content of 75 wt%. Stir evenly. Paste a foaming adhesive on the aluminum foil, coat the slurry on one surface of the aluminum foil, and then dry it at 90 °C to obtain a positive electrode sheet with a positive electrode active material coated on one side. When preparing a double-sided coated positive electrode sheet, repeat the above coating steps on the other surface of the aluminum foil. Then cold-press the coated electrode sheet to a thickness of 95 μm, tear off the foaming adhesive to obtain a groove exposing the empty aluminum foil, and weld the second pole ear to the aluminum foil exposed in the groove.

[0198] (3) Preparation of electrolyte: In a dry argon atmosphere, first, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent and dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0199] (4) Preparation of separator: A separator with a three-layer structure is used, which includes an adhesive layer, a substrate layer, and an adhesive layer arranged in a stacked manner. The material of the first substrate layer is polyethylene (PE), the binder in the adhesive layer is PVDF, and the adhesive layer also contains inorganic particles boehmite.

[0200] (5) Preparation of a packaging bag provided with a first bonding member: A first bonding member slurry is prepared by mixing methyl methacrylate, acetone, diaminodiphenyl sulfone, silicon dioxide, and benzoyl peroxide according to a mass percentage ratio of 60%:30%:3%:5%:2%. The first bonding member slurry is coated on the aluminum-plastic film, where the coating area corresponds to the projection area of the first zone along the second direction on the packaging bag and the projection area of the third zone along the second direction on the packaging bag. Then, the first bonding member slurry is thermally cured.

[0201] (6) Preparation of electrode assembly: The positive electrode sheet, separator, and negative electrode sheet are wound.

[0202] (7) Cell assembly: The aluminum-plastic film formed with a punched hole is placed in an assembly fixture with the hole surface facing up, and the electrode assembly is placed in the hole and pressed tightly by applying an external force. Then, another aluminum-plastic film formed with a punched hole is covered on the electrode assembly with the hole surface facing down, and the four sides of the two aluminum-plastic films are heat-sealed by means of hot pressing.

[0203] (8) Liquid injection and encapsulation: The electrolyte is injected into the assembled electrode assembly, and through processes such as vacuum encapsulation, standing, hot pressing formation, and shaping, the cell is obtained.

[0204] Comparative Example 3: The distance D between the first edge located within the projection area of the first zone along the second direction on the packaging bag and the top sealing portion is 12 mm, and the distance D between the first edge located within the projection area of the third zone along the second direction on the packaging bag and the top sealing portion is 12 mm. Except for this, all other parameters of Comparative Example 3 are the same as those of Example 51.

[0205] Table 3

[0206] (For Examples 52 to 60, all other parameters except those involved in Table 3 are the same as those of Example 51)

[0207]

[0208] Note: In Table 3, "\ " indicates that the parameter is not included.

[0209] It can be seen from Comparative Example 1, Example 51, and Examples 56 to 60 that by the positive projection of the first adhesive member in the second direction covering at least part of the first region; and / or, the positive projection of the first adhesive member in the second direction covering at least part of the third region, the passing rate of the hot box test can be improved. Further, by providing a fourth region and / or a sixth region in the third region, and the first edge in the fourth region and / or the sixth region abutting against the packaging bag, the passing rate of the hot box test can be further improved. This is because when the battery cell undergoes an external short circuit or a hot box test, the internal pressure of the battery cell increases and heat accumulation occurs. The first adhesive member can guide the gas to concentrate on the first weak packaging area of the top seal. One end of the first edge close to the top seal will pull the first weak packaging area of the top seal to form a first crease. The part of the top seal with the first crease is more likely to deform compared to other parts of the packaging bag, so that the first weak packaging area of the top seal can be opened in time to release pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery cell.

[0210] It can be seen from Comparative Example 3 and Examples 51 to 55 that when the distance D between the first edge and the top seal is D ≤ 10 mm, the passing rate of the hot box test of the battery cell can be significantly improved. This is because one end of the first edge close to the top seal will pull the first weak packaging area of the top seal to form a first crease. The part of the top seal with the first crease is more likely to deform compared to other parts of the packaging bag, so that the first weak packaging area of the top seal can be opened in time to release pressure under the action of stress, reduce heat accumulation, and improve the safety performance of the battery cell. Further, when D ≤ 4 mm, the passing rate of the special test of the battery cell can be further improved. This is because the distance between the upper edge of the first edge in the first direction and the lower edge of the top seal in the first direction is further reduced, and the first weak packaging area is more likely to form a first crease, so that the first weak packaging area of the top seal can be opened in time to release pressure under the action of stress, reduce heat accumulation, and thus further improve the safety performance of the battery cell.

[0211] Table 4

[0212] (For Examples 61 to 100, other parameters except those involved in Table 4 are the same as those in Example 51)

[0213]

[0214]

[0215]

[0216]

[0217] As can be seen from Example 51 and Examples 61 to 64, by defining 0 mm ≤ D1 ≤ 5 mm, the passing rate of the hot box test can be improved. When D1 > 5 mm, due to the limited length of the encapsulation weak area near the first tab caused by the thickness of the first tab, when the edge of the first bonding member is too far from the edge of the first tab, the position where the first bonding member is set has exceeded the encapsulation weak area, and the first crease generated by the first edge also correspondingly exceeds the encapsulation weak area, resulting in poor effect of the top seal being promptly opened and relieved of pressure at high temperature, which affects the passing rate of the hot box test. Further, by defining 0 mm ≤ D1 ≤ 3 mm, the passing rate of the hot box test can be further improved.

[0218] As can be seen from Example 51 and Examples 65 to 68, by defining 0 mm ≤ D2 ≤ 5 mm, the passing rate of the hot box test can be improved. When D2 > 5 mm, due to the limited length of the encapsulation weak area near the first tab caused by the thickness of the first tab, when the edge of the first bonding member is too far from the edge of the first tab, the position where the first bonding member is set has exceeded the encapsulation weak area, and the first crease generated by the first edge also correspondingly exceeds the encapsulation weak area, resulting in poor effect of the top seal being promptly opened and relieved of pressure at high temperature, which affects the passing rate of the hot box test. Further, by defining 0 mm ≤ D2 ≤ 3 mm, the passing rate of the hot box test can be further improved.

[0219] As can be seen from Example 51 and Examples 69 to 74, by defining 20% ≤ D4 / D3 ≤ 50%, the passing rate of the hot box test can be improved. The first projection area is located in the upper half area of the first area in the first direction, so that the part of the first bonding member located in the first area meets the requirements of its own structural strength, and it is convenient for one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, facilitating the top seal to be promptly opened and relieved of pressure at high temperature, so as to improve the passing rate of the hot box test of the battery cell. Further, when D4 / D3 > 50%, that is, the first projection area extends from the upper half area of the first area in the first direction to the lower half area of the first area in the first direction, so that the part of the first bonding member 0 located in the first area meets the requirements of its own structural strength. The part of the first bonding member located in the upper half area of the first area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first bonding member located in the lower half area of the first area can reduce the risk of deformation of the corresponding area of the packaging bag, facilitating the gas to concentrate towards the first encapsulation weak area of the top seal, and then facilitating the first encapsulation weak area of the top seal to be promptly opened and relieved of pressure under the action of stress, thereby further improving the passing rate of the hot box test of the battery cell.

[0220] As can be seen from Example 51 and Examples 75 to 80, by limiting 20% ≤ D5 / D3 ≤ 50%, the passing rate of the hot box test can be improved. The third projection area is located in the upper half area of the third area in the first direction, so that the part of the first adhesive located in the third area meets the requirements of its own structural strength, and it is convenient for one end of the first edge close to the top seal to pull the first encapsulation weak area of the top seal to form a first crease, which is convenient for the top seal to be promptly opened to relieve pressure at high temperature, so as to improve the passing rate of the hot box test of the battery cell. Further, when D5 / D3 > 50%, that is, the third projection area extends from the upper half area of the third area in the first direction to the lower half area of the third area in the first direction, so that the part of the first adhesive located in the third area meets the requirements of its own structural strength. The part of the first adhesive located in the upper half area of the third area can pull the first encapsulation weak area of the top seal to form a first crease. The part of the first adhesive located in the lower half area of the third area 3 can reduce the risk of deformation of the corresponding area of the packaging bag 20, which is convenient for guiding the gas to concentrate on the first encapsulation weak area of the top seal, and further convenient for the first encapsulation weak area of the top seal to be promptly opened to relieve pressure under the action of stress, thereby further improving the passing rate of the hot box test of the battery cell.

[0221] As can be seen from Example 51 and Examples 81 to 86, when T1 < 1 μm, the improvement effect on the hot box performance of the battery cell is not good. When T1 > 50 μm, the volumetric energy density loss of the battery cell is serious. By selecting 1 μm ≤ T1 ≤ 50 μm, the passing rate of the hot box test of the battery cell can be improved while taking into account the volumetric energy density of the battery cell. Further, it is preferably 10 μm ≤ T1 ≤ 40 μm to further balance the hot box performance and volumetric energy density of the battery cell.

[0222] As can be seen from Example 51, Examples 87 to 92, and Example 100, when L1 < 0.5 mm, the size of the first adhesive extending into the inner unsealed area is too small, and the improvement effect on the passing rate of the hot box test is not good. When L1 > 1 mm, the size of the first adhesive extending into the inner unsealed area is too large, resulting in too low a passing rate of the encapsulation strength test. Therefore, in order to balance the passing rate of the hot box test and the passing rate of the encapsulation strength test of the battery cell, 0.5 mm ≤ L1 ≤ 1 mm is selected.

[0223] As can be seen from Example 51 and Examples 93 to 98, when P1 remains unchanged, as P2 decreases, the passing rate of the hot box test gradually increases. This is because the smaller P2 is, the easier the top seal is to be opened, so as to relieve pressure and reduce the heat accumulation inside the battery cell. At the same time, the smaller P2 is, the lower the passing rate of the encapsulation strength test of the battery cell. Therefore, in order to balance the passing rate of the hot box test and the passing rate of the encapsulation strength test of the battery cell, 5 MPa ≤ P2 ≤ 20 MPa is selected.

[0224] As can be seen from Examples 97 to 99, when P1 > P2, the passing rate of the hot box test of the battery cell is better; when P2 > P1, the passing rate of the hot box test of the battery cell is worse. This is because when P1 > P2, before the main body deforms at high temperature, the top seal can be opened to release pressure, reducing heat accumulation and improving the safety performance of the battery cell. On the contrary, when P2 > P1, the main body is prone to deformation before the top seal is opened, and the deformation of the main body is not conducive to the concentration of gas towards the top seal position, resulting in the top seal being more difficult to open, thus deteriorating the hot box performance of the battery cell.

[0225] The above is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be covered within the disclosure scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: An electrode assembly, wherein the electrode assembly is flat, and comprises a first end surface, a second end surface, a first surface, and a second surface, wherein the first end surface and the second end surface are arranged opposite to each other along a first direction, and the first surface and the second surface are arranged opposite to each other along a second direction; A packaging bag, the packaging bag comprising a main body and a top seal, the electrode assembly is arranged in the main body, and along the first direction, the top seal is located at one side of the first end surface; a first electrode tab, wherein one end of the first electrode tab is electrically connected to the electrode assembly along the first direction, and the other end of the first electrode tab extends from the top seal portion; the first surface comprises a first region, a second region and a third region sequentially connected along a third direction, and when viewed along the second direction, the second region comprises a first edge and a second edge oppositely arranged along the third direction, the first edge and the second edge both extend along the first direction, and extension lines of the first edge and the second edge along the first direction are respectively located on both sides of the first electrode tab in the third direction; A first adhesive member, along the second direction, the first adhesive member is located between the packaging bag and the first surface, and the first adhesive member is adhered to the surface of the packaging bag facing the first surface; the orthographic projection of the first adhesive member in the second direction covers at least a portion of the first area; and / or the orthographic projection of the first adhesive member in the second direction covers at least a portion of the third area; The first adhesive member includes at least one first edge, the orthographic projection of the first edge in the second direction extends along the first direction, at least part of the first edge abuts against the main body, and a distance D between an upper edge of the first edge in the first direction and a lower edge of the top seal portion in the first direction is ≤10 mm; The second direction is the thickness direction of the battery cell, and the first direction, the second direction and the third direction are perpendicular to each other.

2. The battery cell according to claim 1, characterized in that: D≤4mm.

3. The battery cell according to claim 1, characterized in that: The battery cell further includes a second pole lug, the second pole lug and the first pole lug are arranged at intervals along the third direction; along the first direction, one end of the second pole lug is electrically connected to the electrode assembly, and the other end of the second pole lug extends from the top seal portion; The third region includes a fourth region, a fifth region and a sixth region sequentially connected along the third direction. When viewed along the second direction, the fifth region includes a fifth edge and a sixth edge that are oppositely arranged along the third direction. Both the fifth edge and the sixth edge extend along the first direction. Extension lines of the fifth edge and the sixth edge along the first direction are respectively located on both sides of the second pole ear in the third direction. The orthographic projection of the first adhesive in the second direction covers at least a portion of the fourth area; and / or, An orthographic projection of the first adhesive in the second direction covers at least a portion of the sixth area.

4. The battery cell according to claim 1, characterized in that: The first electrode tab comprises a third edge and a fourth edge disposed opposite to each other along the third direction, wherein along the third direction, the third edge is closer to the first edge than the fourth edge; Along the second direction, the projection area of the first adhesive in the first area is the first projection area. The first projection area includes a first side and a second side that are oppositely arranged along the third direction. Along the third direction, the second side is closer to the first edge than the first side. Along the third direction, the distance between the extension line of the second side along the first direction and the third edge is D1, where 0mm ≤ D1 ≤ 5mm; and / or, Along the second direction, the projection area of the first adhesive in the third area is the third projection area. The third projection area includes a third side and a fourth side that are oppositely arranged along the third direction. Along the third direction, the third side is closer to the second edge than the fourth side. Along the third direction, the distance between the extension line of the third side along the first direction and the fourth edge is D2, where 0mm ≤ D2 ≤ 5mm.

5. The battery cell according to claim 4, characterized in that: 0mm ≤ D1 ≤ 3mm; and / or, 0mm ≤ D2 ≤ 3mm.

6. The battery cell according to claim 4, characterized in that: The first surface includes a top edge and a bottom edge that are oppositely arranged along the first direction. The top edge connects the first end face, and the bottom edge connects the second end face. Along the first direction, the distance between the top edge and the bottom edge is D3; Along the first direction, compared with the bottom edge, the first projection area is closer to the top edge. The length of the first projection area is D4, and D4 / D3 ≥ 20%; and / or, Along the first direction, compared with the bottom edge, the third projection area is closer to the top edge. The length of the third projection area is D5, and D5 / D3 ≥ 20%.

7. The battery cell according to claim 6, characterized in that: D4 / D3 > 50%; and / or, D5 / D3 > 50%.

8. The battery cell according to claim 1, characterized in that: Along the second direction, the thickness of the first adhesive is T1, where 1μm ≤ T1 ≤ 50μm.

9. The battery cell according to claim 8, characterized in that: 10μm ≤ T1 ≤ 40μm.

10. The battery cell according to any one of claims 1 to 9, characterized in that: The first adhesive is also bonded to the first surface; The first surface includes a top edge and a bottom edge that are oppositely arranged along the first direction. The top edge connects the first end face, and the bottom edge connects the second end face; Along the second direction, the projection area of the first adhesive on the first surface includes a fifth side and a sixth side that are oppositely arranged along the first direction. The fifth side is closer to the top edge than the sixth side; The distance between the fifth side and the top edge is D6, where 0mm ≤ D6 ≤ 6mm.

11. The battery cell according to claim 10, characterized in that: 0mm ≤ D6 ≤ 2mm.

12. The battery cell according to claim 10, characterized in that: When the temperature is 120°C to 140°C, the peel strength between the first surface and the packaging bag bonded to both sides of the first adhesive is σ1, and the peel strength of the top seal is σ2, where σ1 > σ2.

13. The battery cell according to claim 12, characterized in that: 0.55N / mm ≤ σ1 ≤ 0.78N / mm, 0.1N / mm ≤ σ2 ≤ 0.5N / mm.

14. The battery cell according to claim 10, characterized in that: The material of the first adhesive includes at least one of a fluorinated rubber binder and a silicone-based binder; the material of the fluorinated rubber binder includes at least one of fluorinated rubber and perfluororubber; the material of the silicone-based binder includes a silicone-based polymer.

15. The battery cell according to any one of claims 1 to 9, wherein The battery cell further comprises a first pole ear glue, wherein the first pole ear glue wraps the first pole ear along the thickness direction of the first pole ear; along the second direction, at least a portion of the first pole ear glue overlaps with the top seal portion; along the direction from the main body portion to the top seal portion, the overlapping area of ​​the first pole ear glue and the top seal portion comprises an inner unsealed area and a middle sealed area which are sequentially arranged; At least a portion of the first adhesive member is located in the inner unsealed area.

16. The battery cell according to claim 15, characterized in that: Along the first direction, the first adhesive extends into the inner unsealed area by a length L1, 0.5 mm ≤ L1 ≤ 1 mm.

17. The battery cell according to claim 15, characterized in that: When the temperature is 120° C. to 140° C., the tensile strength of the main body of the first adhesive is set to P1, the tensile strength of the top sealing part is set to P2, and P1>P2.

18. The battery cell according to claim 17, characterized in that: 5MPa≤P2≤20MPa, P1>20MPa.

19. The battery cell according to claim 15, characterized in that: The material of the first adhesive member includes at least one of epoxy resin and acrylic resin.

20. An electronic device, characterized in that: The electronic device comprises the battery cell as claimed in any one of claims 1 to 19.

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