Secondary battery and electronic apparatus

Abstract

A secondary battery (100) and an electronic apparatus (1000), the secondary battery (100) comprising a housing (10) and an electrode assembly (20), the electrode assembly (20) being accommodated in the housing (10), and the electrode assembly (20) being configured to bend towards a first direction (X). The electrode assembly (20) comprises a first electrode plate (21) and a second electrode plate (22), the first electrode plate (21) comprising a first current collector (211) and a first active material layer (212) arranged in a stacked manner, and the first current collector (211) having a first face (211a) and a second face (211b) oppositely arranged along a thickness direction of the first electrode plate (21). The first current collector (211) comprises a first coating area (2111), a first face (211a) and a second face (211b) of the first coating area (2111) both provided with the first active material layer (212). The second electrode plate (22) comprises a second current collector (221) and a second active material layer (222) arranged in a stacked manner. Multiple first protrusions (213) are formed on the surface of the first electrode plate (21), the multiple first protrusions (213) being located in the first coating area (2111). By means of providing first protrusions (213) located in the first coating area (2111), the stress of the bent first electrode plate (21) is dispersed, facilitating the first electrode plate (21) maintaining a bent shape, and thereby reducing the risk of deformation of the first electrode plate (21).

Description

Secondary battery and electronic device Technical Field

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

[0002] To meet usage requirements, some secondary batteries are designed with curved or arc-shaped structures, and the electrode assemblies within the secondary batteries are also curved or arc-shaped. However, when the electrode sheets in the electrode assemblies are bent, the active material particles on the sheets are squeezed or stretched, and then the pressure is released, which can easily cause the sheets to deform and rebound, resulting in deformation problems such as reduced curvature and flattening of the secondary batteries.

[0003] Summary of the Invention

[0004] In view of this, the present application provides a secondary battery and an electronic device, aiming to suppress deformation and rebound of the electrode.

[0005] In a first aspect of the present application, a secondary battery is provided. The secondary battery includes a housing and an electrode assembly, wherein the electrode assembly is accommodated in the housing and is bent in a first direction. The electrode assembly includes a first pole piece and a second pole piece. The first pole piece includes a first current collector and a first active material layer that are stacked together. Along the thickness direction of the first pole piece, the first current collector has a first surface and a second surface that are oppositely arranged. The first current collector includes a first coating area, and the first surface and the second surface of the first coating area are both provided with a first active material layer. The second pole piece includes a second current collector and a second active material layer that are stacked together. A plurality of first protrusions are formed on the surface of the first pole piece, and the plurality of first protrusions are located in the first coating area.

[0006] In the above embodiment, the first protrusion is located in the first coating area, which can disperse the stress of the bent first pole piece and suppress the deformation and rebound of the first pole piece, thereby facilitating the maintenance of the shape of the first pole piece after bending, reducing the risk of a large gap between the first pole piece and the second pole piece and the generation of black spots in the electrode assembly, and improving the reliability of the electrode assembly. In addition, the first protrusion suppressing the deformation and rebound of the first pole piece is also beneficial for solving the problem of deformation such as the reduction and equalization of the overall curvature of the electrode assembly. When the overall curvature of the electrode assembly remains basically unchanged, the secondary battery is not prone to large deformation, and the reserved space of the battery compartment for accommodating the secondary battery can also be reduced, which is beneficial for the installation of the secondary battery and improves the reliability and applicability of the secondary battery.

[0007] In some embodiments, the second current collector has a third surface and a fourth surface disposed opposite each other along the thickness direction of the second pole piece. The second current collector includes a second coating region, and the second active material layer is disposed on both the third surface and the fourth surface of the second coating region. A plurality of second protrusions are formed on the surface of the second pole piece, and the plurality of second protrusions are located in the second coating region.

[0008] In the above embodiment, the second protrusion can disperse the stress of the bent second pole piece, suppressing deformation and rebound of the second pole piece, thereby helping to maintain the bent shape of the second pole piece. The tendency of deformation and rebound of both the first and second pole pieces is suppressed, which helps to further reduce the risk of excessive gap between the first and second pole pieces and the appearance of black spots in the electrode assembly, thereby further improving the reliability of the electrode assembly.

[0009] In some embodiments, along the first direction, the electrode assembly includes a first portion and a second portion disposed sequentially, and the plurality of first protrusions are located in a first coating region of the second portion.

[0010] In the above embodiment, the plurality of first protrusions are located in the first coating area in the second portion, so that the first protrusions are arranged on the first pole piece close to the protruding side of the electrode assembly, which is beneficial for making the effect of suppressing the flattening of the electrode assembly more obvious.

[0011] In some embodiments, along the first direction, the thickness of the electrode assembly is D, the thickness of the second portion is D1, and 3×D / 4≤D1≤D is satisfied.

[0012] In the above embodiment, when the thickness D1 of the second part satisfies the condition of 3×D / 4≤D1≤D, the thickness of the electrode assembly occupied by the first pole piece provided with the first protrusion can be increased, which is beneficial to further suppress the deformation of the electrode assembly after bending and reduce the risk of the curvature of the electrode assembly being reduced or flattened.

[0013] In some embodiments, the shape of the first protrusion is one of a dot protrusion, a mesh protrusion and a stripe protrusion, and / or the shape of the second protrusion is one of a dot protrusion, a mesh protrusion and a stripe protrusion.

[0014] In some embodiments, the shape of the first protrusion is different from the shape of the second protrusion.

[0015] In the above embodiment, the shape of the first protrusion is different from the shape of the second protrusion, which allows the patterns of the first protrusion and the second protrusion of different shapes to be staggered, which is beneficial to increase the friction between the first pole piece, the second pole piece and the diaphragm, and suppress the risk of slippage between the first pole piece and the second pole piece, thereby improving the reliability of the motor assembly.

[0016] In some embodiments, when the first pole piece is flattened, when observed along the first direction, the sum of the areas of the plurality of first protrusions is S1, and the area of ​​the first pole piece is S2, satisfying: S1 ≥ 0.06 × S2.

[0017] In the above embodiment, when the sum S1 of the areas of the plurality of first protrusions satisfies the condition S1 ≥ 0.06×S2, it is beneficial to improve the dispersion effect of the plurality of first protrusions on the overall stress of the first pole piece, thereby improving the suppression of deformation of the first pole piece after bending.

[0018] In some embodiments, along the first direction, the thickness of the first electrode corresponding to the first coating area is T1, and the height of the first protrusion is H1, satisfying 0.01×T1≤H1≤0.14×T1.

[0019] In the above embodiment, when the height H1 of the first protrusion satisfies the condition of 0.01×T1≤H1≤0.14×T1, it is beneficial to improve the stress dispersion effect of the second protrusion on the second pole piece, thereby further suppressing the deformation of the second pole piece after bending, and in the embodiment where the second protrusion is pressed out by an embossing roller, satisfying this condition is also beneficial to reducing the risk of damage to the second pole piece due to excessive pressure applied by the embossing roller, or reducing the risk of damage to the second pole piece due to excessive local deformation of the second pole piece.

[0020] In some embodiments, the distance between any two adjacent first protrusions is F1, which satisfies 1.5 mm ≤ F1 ≤ 3 mm.

[0021] In the above embodiment, when the distance F1 between any two adjacent first protrusions satisfies the condition of 1.5mm≤F1≤3mm, it is beneficial to disperse the stress of the first pole piece, further suppress the deformation of the first pole piece after bending, and the electrode assembly is not prone to black spots.

[0022] In some embodiments, when viewed along the first direction, the width of the first protrusion is R1, satisfying R1 ≥ 1 mm.

[0023] In the above embodiment, when the width of the first protrusion is R1 and satisfies the condition R1 ≥ 1 mm, it is beneficial to improve the stress dispersion effect of the first protrusion on the first pole piece, thereby further suppressing the deformation of the first pole piece after bending, and the electrode assembly is not prone to black spots.

[0024] In some embodiments, the first coating area includes a first area having a first protrusion; when the first pole piece is in a flattened state, the first pole piece has a first boundary line and a second boundary line arranged opposite to each other along a second direction, the second direction is perpendicular to the first direction, the minimum distance between the first area and the first boundary line is L1, and the minimum distance between the first area and the second boundary line is L2, satisfying: 1mm≤L1≤7mm, 1mm≤L2≤7mm.

[0025] In the above embodiment, when the minimum distance L1 between the first area and the first boundary line and the minimum distance L2 between the first area and the second boundary line meet the conditions of 1mm≤L1≤7mm, 1mm≤L2≤7mm, it is beneficial to reduce the risk of the embossing roller pressing the cutting position of the first pole piece in the second direction, thereby reducing the risk of damage to the first pole piece.

[0026] In some embodiments, the first coating region includes a first area having a first protrusion; when the first electrode piece is flattened, the first electrode piece has a third boundary line and a fourth boundary line arranged opposite each other along a third direction, with the first direction being perpendicular to both the second and third directions. The minimum distance between the first area and the third boundary line is L3, and the minimum distance between the first area and the fourth boundary line is L4, satisfying the following conditions: 1mm≤L3≤7mm, 1mm≤L4≤7mm.

[0027] In the above embodiment, when the minimum distance between the first area and the third boundary line is L3 and the minimum distance between the first area and the fourth boundary line L4 satisfies the conditions of 1mm≤L3≤7mm, 1mm≤L4≤7mm, it is beneficial to reduce the risk of the embossing roller pressing the cutting position of the first pole piece in the third direction, thereby reducing the risk of damage to the first pole piece.

[0028] In some embodiments, the first electrode piece is an anode electrode piece, and the second electrode piece is a cathode electrode piece.

[0029] In the above embodiment, by providing the first protrusion on the surface of the first electrode piece of the anode, the effect of suppressing the flattening of the electrode assembly is more obvious.

[0030] In some embodiments, along the length direction of the first pole piece, the total length of the first pole piece is greater than the total length of the second pole piece.

[0031] In the above embodiment, the total length of the first pole piece is greater than the total length of the second pole piece, which is beneficial for reducing the risk of lithium plating in the electrode assembly.

[0032] In some embodiments, along the first direction, the thickness of the first current collector is P1, satisfying: 4um≤P1≤16um, the thickness of the second current collector is P2, satisfying 8um≤P2≤16um, the thickness of the first active material layer is C1, satisfying 50um≤C1≤200um, and the thickness of the second active material layer is C2, satisfying 50um≤C2≤200um.

[0033] In some embodiments, the first current collector further includes a third coating region, wherein a first surface of the third coating region is provided with a first active material layer, and a second surface of the third coating region is not provided with the first active material layer. A plurality of third protrusions are formed on a surface of the first electrode piece, and the plurality of third protrusions are located in the third coating region.

[0034] In the above embodiment, multiple third protrusions are located in the third coating area, which can further disperse the stress of the bent first pole piece and suppress the deformation and rebound of the first pole piece, thereby facilitating maintaining the shape of the first pole piece after bending, reducing the risk of a large gap between the first pole piece and the second pole piece and the generation of black spots in the electrode assembly, and improving the reliability of the electrode assembly.

[0035] In some embodiments, the housing is a packaging bag.

[0036] In a second aspect of the present application, an electronic device is provided, which includes the secondary battery in any one of the above embodiments.

[0037] In the above embodiment, the problem of the curved secondary battery becoming flat is alleviated, which is beneficial to improving the reliability of the secondary battery, thereby facilitating reduction of the reserved space of the battery compartment in the electronic device and improving the reliability of the electronic device.

[0038] The secondary battery in the present application includes a shell and an electrode assembly housed in the shell, the electrode assembly is bent in a first direction, and the electrode assembly includes a first pole piece and a second pole piece. The first pole piece includes a first current collector and a first active material layer that are stacked, and the second pole piece includes a second current collector and a second active material layer that are stacked. A plurality of first protrusions are formed on the surface of the first pole piece, and the plurality of first protrusions are located in the first coating area of ​​the first current collector, so that the stress of the bent first pole piece can be dispersed, and the deformation and rebound of the first pole piece can be suppressed, thereby facilitating the maintenance of the shape of the first pole piece after bending, reducing the risk of a large gap between the first pole piece and the second pole piece and the generation of black spots on the electrode assembly, and improving the reliability of the electrode assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0040] FIG2 is a cross-sectional view of a secondary battery provided in another embodiment of the present application.

[0041] FIG3 is a side view of a first pole piece provided in one embodiment of the present application.

[0042] FIG4 is a side view of a second pole piece provided in one embodiment of the present application.

[0043] FIG5 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0044] FIG6 is a front view of a first pole piece provided in one embodiment of the present application.

[0045] FIG7 is a front view of a first pole piece provided in another embodiment of the present application.

[0046] FIG8 is a front view of a first pole piece provided in another embodiment of the present application.

[0047] FIG9 is a front view of a second pole piece provided in one embodiment of the present application.

[0048] FIG10 is a front view of a second pole piece provided in another embodiment of the present application.

[0049] FIG11 is a front view of a second pole piece provided in another embodiment of the present application.

[0050] FIG12 is a side view of a first pole piece provided in another embodiment of the present application.

[0051] FIG13 is a side view of a second pole piece provided in another embodiment of the present application.

[0052] FIG14 is a schematic diagram of an electronic device provided in an embodiment of the present application.

[0053] DESCRIPTION OF KEY EMBODIMENTS Secondary battery 100 Housing 10 Electrode assembly 20 First portion 20a Second portion 20b First pole sheet 21 First current collector 211 First surface 211a Second surface 211b First coated area 2111 First region 211c Third coated area 2112 First uncoated area 2113 First active material layer 212 First protrusion 213 First recess 214 Third protrusion 215 Third recess 216 First boundary line 21a Second boundary line 21b Third boundary line 21c Fourth boundary line 21d Second pole sheet 22 Second current collector 221 Third surface 221a Fourth surface 221b Second coated area 2211 Second region 221c Fourth coated area 2212 Second uncoated area2213 Second active material layer 222 Second convex portion 223 Second concave portion 224 Fourth convex portion 225 Fourth concave portion 226 Separator 23 Device body 200 Electronic device 1000 First direction X Second direction Y Third direction Z DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0055] It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it may be directly disposed on the other component or there may be an intermediate component.

[0056] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0057] The terms "first", "second", etc. appearing in this article are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the technical features indicated.

[0058] The term "perpendicular" used in this document describes an ideal relationship between two components. In actual production or use, two components may be approximately perpendicular to each other. For example, in numerical terms, perpendicularity can refer to the angle between two lines being within 90°±10°, the dihedral angle between two planes being within 90°±10°, or the angle between a line and a plane being within 90°±10°.

[0059] It should be noted that when a parameter is greater than, equal to, or less than a certain endpoint value, it should be understood that the endpoint value is allowed to have a tolerance of ±10%. For example, if the ratio of A to B is greater than 10, it should be understood to include the case where the ratio of A to B is greater than 9, and also include the case where the ratio of A to B is greater than 11.

[0060] It should be understood that the dimensions of the layers, regions, films, plates, blocks, columns, projections, recesses, etc. shown in the drawings are provided for better understanding and more convenient description, and the present application is not limited to the dimensions shown in the drawings. Elements not relevant to the description are omitted from the details of this specification in order to make the present invention clear.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0062] The present application discloses a secondary battery, which includes a housing and an electrode assembly. The electrode assembly is accommodated in the housing, and the electrode assembly is bent in a first direction. The electrode assembly includes a first pole piece and a second pole piece. The first pole piece includes a first current collector and a first active material layer that are stacked together. Along the thickness direction of the first pole piece, the first current collector has a first surface and a second surface that are oppositely arranged. The first current collector includes a first coating area, and the first surface and the second surface of the first coating area are both provided with a first active material layer. The second pole piece includes a second current collector and a second active material layer that are stacked together. A plurality of first protrusions are formed on the surface of the first pole piece, and the plurality of first protrusions are located in the first coating area.

[0063] The first protrusion, located in the first coating area, can disperse the stress of the bent first electrode sheet, suppressing its deformation and rebound, thereby helping to maintain the bent shape of the first electrode sheet. This reduces the risk of a large gap between the first and second electrode sheets and the formation of black spots in the electrode assembly, thereby improving the reliability of the electrode assembly. Furthermore, suppressing the deformation and rebound of the first electrode sheet also helps address deformation issues such as reduced overall curvature and equalization of the electrode assembly, reducing the required space in the battery compartment housing the secondary battery, facilitating installation of the secondary battery, and improving its reliability and applicability.

[0064] The following will describe some embodiments of the present application with reference to the accompanying drawings. Unless there is a conflict, the following embodiments and features thereof may be combined with each other.

[0065] Referring to FIG. 1 , an embodiment of the present application provides a secondary battery 100 , which includes a housing 10 and an electrode assembly 20 . The electrode assembly 20 is accommodated in the housing 10 and is bent in a first direction X. The first direction X is the bending direction of the electrode assembly 20 , and is defined as the direction from the concave side of the bent electrode assembly 20 toward the convex side.

[0066] In some embodiments, the housing 10 is a flexible packaging bag, such as an aluminum-plastic film. In other embodiments, the housing 10 is a hard shell, such as a plastic shell, or a metal shell including at least one of steel alloy, aluminum alloy, and copper alloy.

[0067] In some embodiments, an electrolyte (not shown) may be injected into the housing 10 , and the electrolyte components include a solvent, a lithium salt, and an additive.

[0068] In some embodiments, referring to FIG1 , an electrode assembly 20 includes a first electrode piece 21 and a second electrode piece 22. The first electrode piece 21 and the second electrode piece 22 have different polarities. For example, the first electrode piece 21 is an anode electrode piece, and the second electrode piece 22 is a cathode electrode piece; or in another example, the first electrode piece 21 is a cathode electrode piece, and the second electrode piece 22 is an anode electrode piece.

[0069] In some embodiments, referring to FIG. 1 , the first pole piece 21 and the second pole piece 22 are stacked along a first direction X to form a laminate structure, and the first pole piece 21 and the second pole piece 22 in the laminate structure are bent toward the first direction X.

[0070] In some other embodiments, referring to FIG. 2 , the first pole piece 21 and the second pole piece 22 are stacked and wound to form a wound structure.

[0071] In some embodiments, referring to FIG. 1 and FIG. 2 , the electrode assembly 20 further includes a diaphragm 23 . The diaphragm 23 is disposed between the first electrode piece 21 and the second electrode piece 22 . The diaphragm 23 is used to isolate the first electrode piece 21 from the second electrode piece 22 .

[0072] In some embodiments, referring to FIG3 , the first electrode sheet 21 includes a first current collector 211 and a first active material layer 212 that are stacked. When the first electrode sheet 21 is flattened, the first current collector 211 has a first surface 211a and a second surface 211b that are opposite each other along the thickness direction of the first electrode sheet 21. The first current collector 211 includes a first coating region 2111. The first active material layer 212 is provided on both the first surface 211a and the second surface 211b of the first coating region 2111. The first coating region 2111 is a double-sided coating region.

[0073] In some embodiments, referring to FIG. 4 , the second electrode sheet 22 includes a stacked second current collector 221 and a second active material layer 222. When the second electrode sheet 22 is flattened, the second current collector 221 has a third surface 221a and a fourth surface 221b that are opposite each other along the thickness direction of the second electrode sheet 22. The second current collector 221 includes a second coating region 2211. The second active material layer 222 is provided on both the third surface 221a and the fourth surface 221b of the second coating region 2211. The second coating region 2211 is a double-sided coating region.

[0074] In some embodiments, referring to FIG3 , the first current collector 211 further includes a third coating region 2112 . The first active material layer 212 is provided on the first surface 211a of the third coating region 2112 , while the second active material layer 222 is not provided on the second surface 211b of the third coating region 2112 . The third coating region 2112 is a single-sided coating region.

[0075] In some embodiments, referring to FIG4 , the second current collector 221 further includes a fourth coating region 2212 . The third surface 221 a of the fourth coating region 2212 is provided with a second active material layer 222 , while the fourth surface 221 b of the fourth coating region 2212 is not provided with the second active material layer 222 . The third coating region 2112 is a single-sided coating region.

[0076] In some embodiments, the first electrode sheet 21 and the second electrode sheet 22 are arranged in a wound structure, and the second current collector 221 further includes a second uncoated area 2213. The second active material layer 222 is not provided on the third surface 221a and the fourth surface 221b of the second uncoated area 2213. The second uncoated area 2213 is a blank foil area.

[0077] Taking the first electrode piece 21 as an anode electrode piece and the second electrode piece 22 as a cathode electrode piece as an example, the first current collector 211 and the second current collector 221 can be metal layers. The first current collector 211 can be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 221 can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0078] Taking the first electrode 21 as an anode electrode and the second electrode 22 as a cathode electrode as an example, the polarity of the first active material layer 212 is anodic, and the first active material layer 212 includes an anode active material. The anode active material may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, silicon-carbon material, etc. The polarity of the second active material layer 222 is cathodic, and the second active material layer 222 includes a cathode active material. The cathode active material may include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide, etc.

[0079] In some embodiments, referring to FIG3 , a plurality of first protrusions 213 are formed on the surface of the first pole piece 21, and the plurality of first protrusions 213 are located in the first coating area 2111. The plurality of first protrusions 213 being located in the first coating area 2111 can be understood as meaning that when the first pole piece 21 is flattened and viewed along the thickness direction of the first pole piece 21, the first protrusions 213 are located within the first coating area 2111.

[0080] In related art, the electrode assembly 20 of a curved secondary battery 100 is curved. The first and second electrode sheets 21, 22 of the electrode assembly 20 are bent, which compresses or stretches the active materials on the first and second electrode sheets 21, 22. After the pressure on the compressed or stretched active materials is released, the first and second electrode sheets 21, 22 tend to deform and rebound. Research has found that this deformation and rebound of the first and second electrode sheets 21, 22 can easily lead to an excessively large gap between them or cause black spots on the outermost layer of the electrode assembly 20.

[0081] The present application provides a first protrusion 213 on the first electrode sheet 21. The first protrusion 213 is located in the first coating area 2111 and can disperse the stress of the bent first electrode sheet 21, thereby suppressing the deformation and rebound of the first electrode sheet 21. This helps maintain the shape of the first electrode sheet 21 after bending, reduces the risk of a large gap between the first electrode sheet 21 and the second electrode sheet 22 and the generation of black spots on the electrode assembly 20, and improves the reliability of the electrode assembly 20. In addition, the first protrusion 213 suppressing the deformation and rebound of the first electrode sheet 21 also helps solve the problem of reducing the overall curvature and equalizing the deformation of the electrode assembly 20. When the overall curvature of the electrode assembly 20 remains basically unchanged, the secondary battery 100 is not prone to significant deformation, and the reserved space of the battery compartment for accommodating the secondary battery 100 can also be reduced, which is conducive to the installation of the secondary battery 100 and improves the reliability and applicability of the secondary battery 100.

[0082] It is understandable that when the gap between the first electrode sheet 21 and the second electrode sheet 22 is too large, causing electrolyte bridge failure, black spots will appear on the electrode assembly 20. Whether black spots appear can be verified by disassembling the secondary battery 100 and observing the appearance of the electrode assembly 20.

[0083] In some embodiments, referring to FIG4 , a plurality of second protrusions 223 are formed on the surface of the second pole piece 22. The plurality of second protrusions 223 are located in the second coating region 2211. The second protrusions 223 can disperse the stress of the bent second pole piece 22, thereby suppressing deformation and rebound of the second pole piece 22, thereby facilitating the maintenance of the bent shape of the second pole piece 22. The deformation and rebound tendencies of the first pole piece 21 and the second pole piece 22 are both suppressed, which further reduces the risk of excessive gaps between the first pole piece 21 and the second pole piece 22 and the appearance of black spots in the electrode assembly 20, thereby further improving the reliability of the electrode assembly 20.

[0084] In some embodiments, the first pole piece 21 is subjected to an embossing process to form the first protrusion 213 , and the second pole piece 22 is subjected to an embossing process to form the second protrusion 223 .

[0085] The embossing process is described using the example of the first pole piece 21 using the embossing process. The embossing process for the first pole piece 21 involves contacting one side of the first pole piece 21 with a rubberized roller, and contacting the other side of the first pole piece 21 with an embossing roller with protrusions. The embossing roller applies pressure to the first pole piece 21, causing the side of the first pole piece 21 in contact with the rubberized roller to bulge, forming a first protrusion 213. The embossing process for forming the first protrusion 213 and the second protrusion 223 is advantageous in improving the efficiency of forming the first protrusion 213.

[0086] In some embodiments, as shown in Figures 3 and 4 , the first protrusion 213 is formed by embossing the first pole piece 21, and the surface of the first pole piece 21 facing away from the first protrusion 213 forms the first concave portion 214. The second protrusion 223 is formed by embossing the second pole piece 22, and the surface of the second pole piece 22 facing away from the second protrusion 223 forms the second concave portion 224.

[0087] In some embodiments, the first protrusion 213 and the second protrusion 223 are arranged to protrude toward the first direction X.

[0088] In some embodiments, the first protrusion 213 and the second protrusion 223 are arranged to protrude in a direction opposite to the first direction X.

[0089] In some embodiments, one of the first protrusion 213 and the second protrusion 223 is protruded toward the first direction X, and the other is protruded toward a direction opposite to the first direction X.

[0090] In some other embodiments, the first electrode plate 21 may be subjected to other processes to form the first protrusion 213 and the second protrusion 223 . For example, a protrusion made of the same material as the first current collector may be connected to the first current collector to form the first protrusion 213 and the second protrusion 223 .

[0091] In some embodiments, referring to FIG. 3 to FIG. 5 , along the first direction X, the electrode assembly 20 includes a first portion 20 a and a second portion 20 b sequentially arranged, and a plurality of first protrusions 213 are located in the first coating region 2111 of the second portion 20 b .

[0092] Along the first direction X, the second portion 20b is closer to the convex side of the electrode assembly 20 after bending than the first portion 20a. In the curved electrode assembly 20, the first pole piece 21 near the convex side of the electrode assembly 20 is subjected to greater stress and is more likely to deform and rebound. Providing the first protrusion 213 on the first pole piece 21 near the convex side of the electrode assembly 20 helps to more significantly suppress the flattening of the electrode assembly 20.

[0093] It can be understood that when the first pole piece 21 and the second pole piece 22 are a laminated structure, the second part 20b includes one or more layers of independent first pole piece 21; when the first pole piece 21 and the second pole piece 22 are a winding structure, the second part 20b includes a part of the first pole piece 21 or multiple parts arranged at intervals. For example, along the first direction X, the second part 20b includes a straight section in the outermost circle of the first pole piece 21 close to the protruding side of the electrode assembly 20, and the second part 20b also includes a straight section in the second outer circle of the first pole piece 21 close to the protruding side of the electrode assembly 20.

[0094] In some embodiments, the first protrusion 213 is not located in the first coating area 2111 in the second part 20b. This arrangement allows the first protrusion 213 to be located in the portion of the first pole piece 21 that is easier to flatten, and the first protrusion 213 is omitted in the portion of the first pole piece 21 that is not easy to flatten, thereby saving steps and improving production efficiency.

[0095] In some other embodiments, a plurality of first protrusions 213 are located in the first portion 20 a and the second portion 20 b , which increases the distribution area of ​​the first protrusions 213 and helps to further suppress deformation and rebound of the first pole piece 21 .

[0096] In some embodiments, referring to Figures 3 to 5 , multiple second protrusions 223 are located in the second coating region 2211 of the second portion 20b. In a curved electrode assembly 20, the second pole piece 22 near the protruding side of the electrode assembly 20 is subjected to greater stress and is more susceptible to deformation and rebound. The multiple second protrusions 223 are located in the second coating region 2211 of the second portion 20b, so that the second protrusions 223 are located on the second pole piece 22 near the protruding side of the electrode assembly 20, thereby more effectively preventing the electrode assembly 20 from flattening.

[0097] It can be understood that when the first pole piece 21 and the second pole piece 22 are a laminated structure, the second part 20b includes one or more layers of independent second pole pieces 22; when the first pole piece 21 and the second pole piece 22 are a winding structure, the second part 20b includes a part of the second pole piece 22 or multiple parts arranged at intervals. For example, along the first direction X, the second part 20b includes a straight section in the outermost circle of the second pole piece 22 close to the protruding side of the electrode assembly 20, and the second part 20b also includes a straight section in the second outer circle of the second pole piece 22 close to the protruding side of the electrode assembly 20.

[0098] In some embodiments, the second protrusion 223 is not located in the second coating area 2211 in the second part 20b. This arrangement allows the second protrusion 223 to be located in the portion of the second pole piece 22 that is easier to flatten, and the second protrusion 223 is omitted in the portion of the second pole piece 22 that is not easy to flatten, thereby saving processes and improving production efficiency.

[0099] In some other embodiments, a plurality of second protrusions 223 are located in the first portion 20 a and the second portion 20 b , which increases the distribution area of ​​the second protrusions 223 and helps to further suppress deformation and rebound of the second pole piece 22 .

[0100] In some embodiments, referring to Figures 3 and 5 , a plurality of first protrusions 213 are located in a first coating region 2111 of the second portion 20b. Along the first direction X, the thickness of the electrode assembly 20 is D, and the thickness of the second portion 20b is D1, satisfying the relationship 3×D / 4≤D1≤D. This arrangement can increase the thickness of the electrode assembly 20 occupied by the first electrode sheet 21 having the first protrusions 213, further suppressing deformation of the electrode assembly 20 after bending and reducing the risk of the electrode assembly 20 becoming flat or having its curvature reduced.

[0101] In some embodiments, referring to Figures 4 and 5 , multiple second protrusions 223 are located in the second coating region 2211 of the second portion 20b. Along the first direction X, the thickness of the electrode assembly 20 is D, and the thickness of the second portion 20b is D1, satisfying the relationship 3×D / 4≤D1≤D. This arrangement can increase the thickness of the electrode assembly 20 occupied by the second electrode sheet 22 having the second protrusions 223, further suppressing deformation of the electrode assembly 20 after bending and reducing the risk of the electrode assembly 20 becoming flat or having its curvature reduced.

[0102] In some embodiments, referring to Figures 3 to 5 , a plurality of first protrusions 213 are located in the first coating area 2111 of the second portion 20b, and a plurality of second protrusions 223 are located in the second coating area 2211 of the second portion 20b, satisfying 3×D / 4≤D1≤D. This arrangement allows the thickness of the electrode sheet having the first and second protrusions 213, 223 to account for at least three-quarters of the thickness of the electrode assembly 20, further suppressing deformation of the electrode assembly 20 after bending and reducing the risk of the electrode assembly 20 becoming flat or reduced in curvature.

[0103] In some embodiments, the first pole piece 21 and the second pole piece 22 are a laminated structure, the first protrusion 213 can be provided on any one or more layers of the first pole piece 21, and the second protrusion 223 can be provided on any one or more layers of the second pole piece 22. The specific settings are not listed one by one.

[0104] In some other embodiments, the first pole piece 21 and the second pole piece 22 are of a winding structure, the first protrusion 213 can be provided on any part or multiple discontinuous parts of the first pole piece 21, and the second protrusion 223 can be provided on any part or multiple discontinuous parts of the second pole piece 22. The specific settings are no longer listed one by one.

[0105] In some embodiments, referring to FIG. 6 to FIG. 8 , the shape of the first protrusion 213 is one of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0106] In some embodiments, referring to FIG. 9 to FIG. 11 , the second protrusion 223 is in the shape of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0107] The first protrusion 213 and the second protrusion 223 can be embossed using an embossing roller. For example, a spherical embossing roller with spherical protrusions on its surface can be used to emboss dot-shaped protrusions on the first pole piece 21, and a spherical embossing roller can be used to emboss dot-shaped protrusions on the second pole piece 22. A mesh embossing roller with mesh protrusions on its surface can be used to emboss a reticulated protrusion on the first pole piece 21, and a mesh embossing roller can be used to emboss a reticulated protrusion on the second pole piece 22. A striped embossing roller with striped protrusions on its surface can be used to emboss a striped protrusion on the first pole piece 21, and a striped embossing roller can be used to emboss a striped protrusion on the second pole piece 22.

[0108] In some embodiments, referring to Figures 6 and 9 , the first protrusion 213 is in the form of a dot-shaped protrusion, and the second protrusion 223 is in the form of a dot-shaped protrusion. Compared to protrusions of other shapes, dot-shaped protrusions are less likely to damage the first active material layer 212 of the first electrode sheet 21 and the second active material layer 222 of the second electrode sheet 22, thereby improving the reliability of the electrode assembly 20.

[0109] In some embodiments, referring to Figures 6 to 11, the shape of the first protrusion 213 is different from the shape of the second protrusion 223, which allows the patterns of the first protrusion 213 and the second protrusion 223 with different shapes to be staggered, which is beneficial to increase the friction between the first pole piece 21, the second pole piece 22 and the diaphragm 23, thereby suppressing the risk of slippage between the first pole piece 21 and the second pole piece 22, thereby improving the reliability of the motor assembly.

[0110] For example, one of the first convex portion 213 and the second convex portion 223 is configured as a dot-shaped convex portion, and the other of the first convex portion 213 and the second convex portion 223 is configured as a mesh-shaped convex portion.

[0111] For another example, one of the first convex portion 213 and the second convex portion 223 is configured as a dot-shaped convex portion, and the other of the first convex portion 213 and the second convex portion 223 is configured as a stripe-shaped convex portion.

[0112] For another example, one of the first convex portion 213 and the second convex portion 223 is configured as a striped convex portion, and the other of the first convex portion 213 and the second convex portion 223 is configured as a mesh convex portion.

[0113] In some embodiments, referring to Figures 6 to 8, the first coating area 2111 includes a first area 211c having a first protrusion 213; when the first electrode 21 is in a flattened state, the first electrode 21 has a first boundary line 21a and a second boundary line 21b relatively arranged along the second direction Y, and the first electrode 21 has a third boundary line 21c and a fourth boundary line 21d relatively arranged along the third direction Z, and the first direction X is perpendicular to the second direction Y and the third direction Z.

[0114] In some embodiments, the minimum distance between the first area 211c and the first boundary line 21a is L1, and the minimum distance between the first area 211c and the second boundary line 21b is L2, satisfying: 1mm≤L1≤7mm, 1mm≤L2≤7mm, which is beneficial to reducing the risk of the embossing roller pressing on the cutting position of the first pole piece 21 in the second direction Y, thereby reducing the risk of damage to the first pole piece 21.

[0115] As an example, L1 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm, and L2 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm.

[0116] In some embodiments, the minimum distance between the first area 211c and the third boundary line 21c is L3, and the minimum distance between the first area 211c and the fourth boundary line 21d is L4, satisfying: 1mm≤L3≤7mm, 1mm≤L4≤7mm, which is beneficial to reducing the risk of the embossing roller pressing on the cutting position of the first pole piece 21 in the third direction Z, thereby reducing the risk of damage to the first pole piece 21.

[0117] As an example, L3 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm. L4 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm.

[0118] In some embodiments, referring to FIG6 , when the first pole piece 21 is flattened and viewed along the first direction X, the sum of the areas of the plurality of first protrusions 213 is S1, and the area of ​​the first pole piece 21 is S2, satisfying the condition: S1 ≥ 0.06 × S2. When the sum of the areas of the plurality of first protrusions 213 S1 satisfies this condition, the plurality of first protrusions 213 can effectively disperse the stress of the first pole piece 21 as a whole, thereby further suppressing deformation of the first pole piece 21 after bending. As an example, S1 = 0.12 × S2.

[0119] In some embodiments, referring to Figures 9 to 11, the second coating area 2211 includes a second area 221c having a second protrusion 223. The distance between the second area 221c and the boundary lines of the second pole piece 22 in the second direction Y and the third direction Z can be specifically referred to the distance between the above-mentioned first area 211c and the first boundary line 21a, the second boundary line 21b, the third boundary line 21c and the fourth boundary line 21d, which will not be repeated here.

[0120] In some embodiments, along the length direction of the first electrode piece 21, the total length of the first electrode piece 21 is greater than the total length of the second electrode piece 22, and the first electrode piece 21 is the anode electrode piece and the second electrode piece 22 is the cathode electrode piece, which is beneficial to reduce the risk of lithium plating in the electrode assembly 20.

[0121] In some embodiments, referring to FIG9 , when the second pole piece 22 is flattened and viewed along the first direction X, the sum of the areas of the second protrusions 223 is S3, and the area of ​​the second pole piece 22 is S4, satisfying the condition: S3 ≥ 0.06 × S4. When the sum of the areas of the plurality of second protrusions 223, S3, satisfies this condition, the plurality of second protrusions 223 can effectively disperse the stress of the second pole piece 22 as a whole, thereby effectively suppressing deformation of the second pole piece 22 after bending. As an example, S3 = 0.12 × S4.

[0122] It can be understood that the sum S1 of the areas of the plurality of first protrusions 213 is the sum of the areas of all first protrusions 213 on the first pole piece 21. The sum S1 of the areas of the plurality of first protrusions 213 can be calculated by calculating the area of ​​a single first protrusion 213 when the first pole piece 21 is flattened, and then multiplying the area of ​​the single first protrusion 213 by the number of first protrusions 213 to obtain the sum S1 of the areas of the plurality of first protrusions 213.

[0123] The sum S3 of the areas of the plurality of second protrusions 223 is the sum of the areas of all second protrusions 223 on the second pole piece 22. The sum S3 of the areas of the plurality of second protrusions 223 can be calculated by calculating the area of ​​a single second protrusion 223 when the second pole piece 22 is flattened, and then multiplying the area of ​​the single second protrusion 223 by the number of second protrusions 223 to obtain the sum S3 of the areas of the plurality of second protrusions 223.

[0124] In some embodiments, referring to FIG6 , the distance between any two adjacent first protrusions 213 is F1, satisfying 1.5 mm ≤ F1 ≤ 3 mm. When this condition is met, it is beneficial to disperse the stress of the first electrode piece 21 , and is beneficial to further suppress the deformation of the first electrode piece 21 after bending, and the electrode assembly 20 is not prone to black spots.

[0125] As an illustrative example, F1 may specifically be 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm or 3 mm.

[0126] In some embodiments, referring to FIG. 9 , the distance between any two adjacent second protrusions 223 is F2, satisfying 1.5 mm ≤ F2 ≤ 3 mm. When this condition is met, it is beneficial to disperse the stress of the second pole piece 22 , and is beneficial to further suppress the deformation of the second pole piece 22 after bending, and the electrode assembly 20 is not prone to black spots.

[0127] As an illustrative example, F2 may specifically be 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm or 3 mm.

[0128] In some embodiments, referring to Figures 6 to 8, when observed along the first direction X, the width of the first protrusion 213 is R1, satisfying R1 ≥ 1 mm. When this condition is met, it is beneficial to improve the stress dispersion effect of the first protrusion 213 on the first pole piece 21, thereby further suppressing the deformation of the first pole piece 21 after bending, and the electrode assembly 20 is not prone to black spots.

[0129] As an illustrative example, R1 may specifically be 1 mm, 1.2 mm, 1.5 mm, 2 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm or 3 mm.

[0130] It can be understood that when the first protrusion 213 is a dot-shaped protrusion, the first protrusion 213 is circular, and the width R1 of the first protrusion 213 is the diameter of the first protrusion 213. When the first protrusion 213 is a stripe-shaped protrusion, the length direction of the first protrusion 213 is the extension direction of the stripe protrusion, the width direction of the first protrusion 213 is the direction of arrangement of the multiple first protrusions 213, and the width R1 of the first protrusion 213 is the width of the first protrusion 213 along the arrangement direction. When the first protrusion 213 is a reticulated protrusion, a single first protrusion 213 is actually an inclined stripe protrusion, the length direction of the first protrusion 213 is the extension direction of the stripe protrusion, the width direction of the first protrusion 213 is the direction of arrangement of the multiple first protrusions 213, and the width R1 of the first protrusion 213 is the width of the first protrusion 213 along the arrangement direction.

[0131] In some embodiments, referring to Figures 9 to 11 , the width of the second protrusion 223 as viewed along the first direction X is R2, satisfying R2 ≥ 1 mm. Meeting this condition facilitates improving the stress dispersion effect of the second protrusion 223 on the second electrode sheet 22, thereby further suppressing deformation of the second electrode sheet 22 after bending, and making the electrode assembly 20 less susceptible to black spots. The definition of the width R2 of the second protrusion 223 can refer to the definition of the width R1 of the first protrusion 213 described above, and will not be repeated here.

[0132] In some embodiments, please refer to Figure 12. Along the first direction X, the thickness of the first coating area 2111 of the first pole piece 21 is T1, and the height of the first protrusion 213 is H1, satisfying 0.01×T1≤H1≤0.14×T1. When this condition is met, it is beneficial to improve the stress dispersion effect of the first protrusion 213 on the first pole piece 21, thereby further suppressing the deformation of the first pole piece 21 after bending. In the embodiment where the first protrusion 213 is pressed out by an embossing roller, satisfying this condition is also beneficial to reducing the risk of damage to the first pole piece 21 caused by excessive pressure applied by the embossing roller, or reducing the risk of damage to the first pole piece 21 due to excessive local deformation of the first pole piece 21.

[0133] The thickness T1 of the first electrode 21 corresponding to the first coating area 2111 is the sum of the thicknesses of the first current collector 211, the first active material layer 212 on the first surface 211a, and the second active material layer 222 on the second surface 211b in the first coating area 2111. The height H1 of the first protrusion 213 is the height of the largest of the plurality of first protrusions 213.

[0134] In some embodiments, please refer to Figure 13. Along the first direction X, the thickness of the second coating area 2211 of the second pole piece 22 is T2, and the height of the second protrusion 223 is H2, satisfying 0.01×T2≤H2≤0.14×T2. When this condition is met, it is beneficial to improve the stress dispersion effect of the second protrusion 223 on the second pole piece 22, thereby further suppressing the deformation of the second pole piece 22 after bending. In the embodiment where the second protrusion 223 is pressed out by an embossing roller, meeting this condition is also beneficial to reducing the risk of damage to the second pole piece 22 caused by excessive pressure applied by the embossing roller, or reducing the risk of damage to the second pole piece 22 due to excessive local deformation of the second pole piece 22.

[0135] The thickness T2 of the second electrode sheet 22 corresponding to the second coating area 2211 is the sum of the thicknesses of the second current collector 221, the second active material layer 222 on the third surface 221a, and the second active material layer 222 on the fourth surface 221b in the second coating area 2211. The height H2 of the second protrusion 223 is the height of the largest of the plurality of second protrusions 223.

[0136] Taking the first electrode piece 21 as an anode electrode piece and the second electrode piece 22 as a cathode electrode piece as an example, the height of the first protrusion 213 is H1 = 0.01×T1 and the height of the second protrusion 223 is H2 = 0.14×T2.

[0137] In some embodiments, referring to Figures 12 and 13, along the first direction X, the thickness of the first current collector 211 is P1, satisfying: 4um≤P1≤16um, the thickness of the second current collector 221 is P2, satisfying 8um≤P2≤16um, the thickness of the first active material layer 212 is C1, satisfying 50um≤C1≤200um, and the thickness of the second active material layer 222 is C2, satisfying 50um≤C2≤200um.

[0138] As an example, P1 can be 4um, 6um, 8um, 10um, 12um, 14um, or 16um. P2 can be 8um, 10um, 12um, 14um, or 16um. C1 can be 50um, 60um, 70um, 80um, 100um, 120um, 140um, 160um, 170um, 180um, 190um, or 200um. C2 can be 50um, 60um, 70um, 80um, 100um, 120um, 140um, 160um, 170um, 180um, 190um, or 200um.

[0139] In some embodiments, the first electrode piece 21 is an anode electrode piece, the first current collector 211 is copper foil, the polarity of the first active material layer 212 is anodic, and the first active material includes graphite. The second electrode piece 22 is a cathode electrode piece, the second current collector 221 is aluminum foil, and the second active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0140] Among them, during the bending process of the first pole piece 21, the graphite particles in the first active material layer 212 squeeze each other, deform and store stress. After the first pole piece 21 is bent, the graphite particles release the stress, resulting in the extension of the graphite particles on the first current collector 211 being greater than the extension of the first current collector 211 of the copper foil, so that the first pole piece 21 is prone to deformation after bending. By setting the first protrusion 213 on the surface of the first pole piece 21, the effect of suppressing the flattening of the electrode assembly 20 is more obvious.

[0141] In some embodiments, referring to Figure 12, a plurality of third protrusions 215 are formed on the surface of the first pole piece 21, and the plurality of third protrusions 215 are located in the third coating area 2112, which can further disperse the stress of the bent first pole piece 21, and play a role in suppressing the deformation and rebound of the first pole piece 21, thereby facilitating the maintenance of the shape of the first pole piece 21 after bending, reducing the risk of a large gap between the first pole piece 21 and the second pole piece 22 and the generation of black spots in the electrode assembly 20, and improving the reliability of the electrode assembly 20.

[0142] In some embodiments, referring to FIG. 13 , a plurality of fourth protrusions 225 are formed on the surface of the second pole piece 22, and the plurality of fourth protrusions 225 are located in the fourth coating area 2212, which can further disperse the stress of the bent second pole piece 22, and suppress the deformation and rebound of the second pole piece 22, thereby facilitating the maintenance of the shape of the second pole piece 22 after bending, reducing the risk of a large gap between the first pole piece 21 and the second pole piece 22 and the generation of black spots in the electrode assembly 20, and improving the reliability of the electrode assembly 20.

[0143] In some embodiments, referring to Figures 12 and 13 , the third protrusion 215 is formed by embossing the first pole piece 21, and the surface of the first pole piece 21 facing away from the third protrusion 215 forms the third recess 216. The fourth protrusion 225 is formed by embossing the second pole piece 22, and the surface of the second pole piece 22 facing away from the fourth protrusion 225 forms the fourth recess 226.

[0144] In some embodiments, referring to Figures 12 and 13 , the first electrode sheet 21 and the second electrode sheet 22 are arranged in a wound structure, and the first current collector 211 further includes a first uncoated region 2113. The first active material layer 212 is not provided on the first surface 211a or the second surface 211b of the first uncoated region 2113. The first uncoated region 2113 is a blank foil region.

[0145] Referring to FIG. 14 , an embodiment of the present application further provides an electronic device 1000 . The electronic device 1000 includes the secondary battery 100 in any of the above embodiments.

[0146] In some embodiments, the electronic device 1000 may be a mobile phone, a laptop computer, a tablet computer, a drone, a power tool, a power toy, a game console, a video recorder, a portable recorder, a radio, or a smart watch, etc., which are not listed here one by one.

[0147] In some embodiments, the electronic device 1000 further includes a device body 200, and the secondary battery 100 is installed in the device body 200. Since the electronic device 1000 adopts the technical solution of the secondary battery 100 in any of the above embodiments, it has at least the beneficial effects brought about by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described in detail here.

[0148] In addition, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the substantive scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery (100), characterized in that: The secondary battery (100) comprises a housing (10) and an electrode assembly (20), wherein the electrode assembly (20) is accommodated in the housing (10), the electrode assembly (20) is bent toward a first direction (X), and the electrode assembly (20) comprises: A first pole piece (21), comprising a first current collector (211) and a first active material layer (212) which are stacked, wherein along the thickness direction of the first pole piece (21), the first current collector (211) has a first surface (211a) and a second surface (211b) which are arranged opposite to each other; the first current collector (211) comprises a first coating area (2111), and the first surface (211a) and the second surface (211b) of the first coating area (2111) are both provided with the first active material layer (212); A second pole piece (22) comprising a second current collector (221) and a second active material layer (222) which are stacked; A plurality of first protrusions (213) are formed on the surface of the first pole piece (21), and the plurality of first protrusions (213) are located in the first coating area (2111).

2. The secondary battery (100) according to claim 1, characterized in that: Along the thickness direction of the second pole piece (22), the second current collector (221) has a third surface (221a) and a fourth surface (221b) arranged opposite to each other, the second current collector (221) comprises a second coating area (2211), and the third surface (221a) and the fourth surface (221b) of the second coating area (2211) are both provided with the second active material layer (222); A plurality of second protrusions (223) are formed on the surface of the second pole piece (22), and the plurality of second protrusions (223) are located in the second coating area (2211).

3. The secondary battery (100) according to claim 2, characterized in that: Along the first direction (X), the electrode assembly (20) includes a first portion (20a) and a second portion (20b) arranged in sequence, and the plurality of first protrusions (213) are located in the first coating area (2111) in the second portion (20b).

4. The secondary battery (100) according to claim 3, characterized in that: Along the first direction (X), the thickness of the electrode assembly (20) is D, and the thickness of the second portion (20b) is D1, satisfying 3D / 4≤D1≤D.

5. The secondary battery (100) according to any one of claims 2 to 4, characterized in that: The shape of the first protrusion (213) is one of a dot-shaped protrusion, a mesh-shaped protrusion and a striped protrusion, and / or the shape of the second protrusion (223) is one of a dot-shaped protrusion, a mesh-shaped protrusion and a striped protrusion.

6. The secondary battery (100) according to any one of claims 2 to 5, characterized in that: The shape of the first convex portion (213) is different from the shape of the second convex portion (223).

7. The secondary battery (100) according to any one of claims 1 to 6, characterized in that: When the first pole piece (21) is flattened, when observed along the first direction (X), the sum of the areas of the plurality of first protrusions (213) is S1, and the area of ​​the first pole piece (21) is S2, satisfying: S1≥0.06S2.

8. The secondary battery (100) according to any one of claims 1 to 7, characterized in that: Along the first direction (X), the thickness of the first pole piece (21) corresponding to the first coating area (2111) is T1, and the height of the first protrusion (213) is H1, satisfying 0.01T1≤H1≤0.14T1.

9. The secondary battery (100) according to any one of claims 1 to 8, characterized in that: The distance between any two adjacent first protrusions (213) is F1, satisfying 1.5 mm ≤ F1 ≤ 3 mm.

10. The secondary battery (100) according to any one of claims 1 to 9, characterized in that: Observed along the first direction (X), the width of the first protrusion (213) is R1, satisfying R1≥1 mm.

11. The secondary battery (100) according to any one of claims 1 to 10, characterized in that: The first coating area (2111) comprises a first region (211c) provided with the first protrusion (213); in a flattened state of the first pole piece (21), the first pole piece (21) has a first boundary line (21a) and a second boundary line (21b) arranged relatively along a second direction (Y), the first pole piece (21) has a third boundary line (21c) and a fourth boundary line (21d) arranged relatively along a third direction (Z), and the first direction (X), the second direction (Y) and the third direction (Z) are perpendicular to each other; The minimum distance between the first area (211c) and the first boundary line (21a) is L1, the minimum distance between the first area (211c) and the second boundary line (21b) is L2, 1mm≤L1≤7mm, 1mm≤L2≤7mm; or The minimum distance between the first area (211c) and the third boundary line (21c) is L3, and the minimum distance between the first area (211c) and the fourth boundary line (21d) is L4, 1mm≤L3≤7mm, 1mm≤L4≤7mm.

12. The secondary battery (100) according to any one of claims 1 to 11, characterized in that: The first pole piece (21) is an anode pole piece, and the second pole piece (22) is a cathode pole piece.

13. The secondary battery (100) according to any one of claims 1 to 12, characterized in that: The first current collector (211) further comprises a third coating region (2112), the first surface (211a) of the third coating region (2112) is provided with the first active material layer (212), and the second surface (211b) of the third coating region (2112) is not provided with the first active material layer (212); A plurality of third protrusions (215) are formed on the surface of the first pole piece (21), and the plurality of third protrusions (215) are located in the third coating area (2112).

14. The secondary battery (100) according to any one of claims 1 to 13, characterized in that: The shell (10) is a packaging bag.

15. An electronic device (1000), characterized in that: The invention comprises the secondary battery (100) as claimed in any one of claims 1 to 14.

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