Secondary battery and electronic device

Abstract

Disclosed in the present application are a secondary battery and an electronic device. The secondary battery comprises a packaging bag, an electrode assembly, a first tab, a first insulating adhesive tape and a second insulating adhesive tape, wherein the electrode assembly is accommodated in the packaging bag; the first tab is electrically connected to the electrode assembly and extends out of the packaging bag in a first direction; the electrode assembly is of a wound structure and comprises a first end face, a first side surface, a first arc-shaped face and a second side surface, wherein the first side surface, the first arc-shaped face and the second side surface are arranged around a periphery of the first end face; the first insulating adhesive tape comprises an adhesive tape body and a first extension, wherein the adhesive tape body is bonded to the first side surface, the first arc-shaped face and the second side surface, respectively, the first extension extends beyond a negative electrode plate of the electrode assembly in the first direction, and the first extension comprises a first section and a second section; and the second insulating adhesive tape is bonded to the first end surface, the first section and the second section, respectively. In this way, the present application can increase the thermal chamber test pass rate of the secondary battery.

Description

Secondary battery and electronic device

[0001] This application claims priority to the prior application with application number 202410346291.3 filed with the State Intellectual Property Office of China on March 25, 2024, entitled “Secondary Batteries and Electronic Devices”. The contents of the above-mentioned prior application are incorporated into this text by introduction. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a secondary battery and an electronic device. Background Art

[0003] Secondary batteries have been widely used in consumer electronics, electric vehicles, electric two-wheeled vehicles, power tools, etc. As market demand expands, people have put forward higher requirements for the reliability of secondary batteries.

[0004] Application Contents

[0005] The purpose of this application is to provide a secondary battery and an electronic device, aiming to improve the reliability of the secondary battery.

[0006] According to a first aspect of the present application, a secondary battery is provided, comprising: a packaging bag, an electrode assembly, a first tab, a first insulating tape and a second insulating tape. The electrode assembly is housed in the packaging bag. The first tab is electrically connected to the electrode assembly and extends out of the packaging bag along a first direction. The electrode assembly is in a wound structure and comprises a first end face, a first side surface, a first curved surface and a second side surface, wherein the first side surface, the first curved surface and the second side surface are arranged around the periphery of the first end face. The first insulating tape comprises a tape body and a first extension. The tape body is respectively bonded to the first side surface, the first curved surface and the second side surface. The first extension extends beyond the negative electrode sheet of the electrode assembly along the first direction, and the first extension comprises a first partition and a second partition. Along the second direction, the first partition and the second partition are arranged relative to each other, wherein the second direction is perpendicular to the first direction. The second insulating tape is respectively bonded to the first end face, the first partition and the second partition.

[0007] In the secondary battery involved in the present application, the positive electrode sheet, the negative electrode sheet and the isolation membrane are bonded together by the second insulating tape and the first insulating tape to form an integral structure, thereby improving the integrity of the electrode assembly, thereby reducing the risk of at least one of the positive electrode sheet, the negative electrode sheet and the isolation membrane being dislocated under vibration or impact conditions due to lack of restriction.

[0008] On this basis, under the fixing action of the second insulating tape, the first partition and the second partition can be bent toward the inner circle of the electrode assembly, thereby driving the end surface of the isolation membrane on one side in the first direction close to the first curved surface to fold inward, thereby forming a blocking structure that blocks part of the gas from passing through, so that during the hot box test of the secondary battery, the heat-generated gas can be concentrated and rushed out of the packaging bag from the position close to the first pole ear, thereby improving the hot box test pass rate of the secondary battery.

[0009] In one or more optional embodiments above, the second insulating tape includes a first portion, a second portion, and a third portion. The first portion is bonded to the first end face, the first partition, and the second partition, respectively. The second portion is connected to a side edge of the first portion along the second direction and is bonded to the first side surface and the tape body, respectively. The third portion is connected to the other side edge of the first portion along the second direction and is bonded to the second side surface and the tape body, respectively. In the second direction, the projection of the second portion and the projection of the tape body on the first side surface have a first overlapping area, and the projection of the third portion and the projection of the tape body on the second side surface have a second overlapping area.

[0010] Because the second insulating tape and the first insulating tape overlap on both the first and second side surfaces, the thickness of the overlapping area in the second direction is greater than the thickness of the portion surrounding the first curved surface in the second direction. Therefore, during the subsequent hot pressing process, the force applied to the portion surrounding the first curved surface is less than that applied to the overlapping area. As a result, the spacing between adjacent electrode pieces around the first curved surface is slightly greater than the spacing between adjacent electrode pieces in the overlapping area. This improves electrolyte wettability on the first curved surface, thereby mitigating the risk of lithium deposition around the portion surrounding the first curved surface due to insufficient electrolyte.

[0011] In one or more of the above optional embodiments, 0.2<W1 / W≤0.7, and 1<W2 / W tab ≤3, limiting W1 and W2 to this value range can not only improve the hot box test pass rate of the secondary battery, but also improve the lithium plating of the secondary battery. Among them, the width of the electrode assembly in the third direction is W mm; the width of the first insulating tape in the third direction is W1 mm; the width of the first tab in the third direction is W tab mm; the width of the second insulating tape in the third direction is W2 mm, wherein the third direction, the second direction and the first direction are perpendicular to each other.

[0012] In one or more optional embodiments above, 0.3≤W1 / W≤0.5, thereby the hot box test pass rate of the secondary battery and the probability of lithium plating or not plating lithium on the negative electrode plate are both better.

[0013] In one or more of the above optional embodiments, 1.5≤W2 / W tab≤2.5, thus the hot box test pass rate of the secondary battery and the probability of lithium plating or not plating lithium on the negative electrode are both relatively good.

[0014] In one or more of the above optional embodiments, 0 < W3 / W1 ≤ 0.5, and 0.8 < W4 / W3 ≤ 1.1; the width of the first overlapping region in the third direction is W3 mm; and the width of the second overlapping region in the third direction is W4 mm. Thus, the areas of the first overlapping region and the second overlapping region are both within a certain range. This allows the first and second insulating tapes to maintain excellent bonding strength, thereby maintaining the effective function of the barrier structure formed by the second insulating tape, the first partition, and the second partition. It also reduces interface problems caused by the area difference between the first and second overlapping regions during the subsequent hot pressing process.

[0015] In one or more optional embodiments above, the packaging bag is made of aluminum-plastic film. The electrode assembly includes a negative electrode sheet and a positive electrode sheet that are stacked and wound. Along the winding direction of the electrode assembly, the positive electrode sheet has a winding end end, and the negative electrode sheet has a protruding portion that extends beyond the winding end end. The protruding portion and the winding end end are both located on one side of the electrode assembly in the second direction, and the protruding portion and the winding end end are arranged on two adjacent electrode sheet layers. Along the second direction, the projection of the protruding portion falls within the projection of the first insulating tape. With such a design, the first insulating tape can play a role in restraining the electrode assembly to maintain the structural integrity and stability of the winding structure. In addition, since the protruding portion of the negative electrode sheet still has the die-cut surface of the negative electrode current collector exposed to the outside, the first insulating tape is arranged between the protruding portion and the packaging bag, which can also reduce the situation where the burrs on the die-cut surface pierce the isolation film and directly contact the packaging bag made of aluminum-plastic film under some working conditions.

[0016] In one or more of the above optional embodiments, 1 < L2 / L1 ≤ 1.1; the length of the negative electrode sheet in the first direction is L1 mm; and the length of the first insulating tape in the first direction is L2 mm. Limiting L2 to this value range improves the contact between the negative electrode sheet and the packaging bag, thereby preventing corrosion of the aluminum layer in the packaging bag, while also reducing the risk of the first extension extending into the sealing area of ​​the packaging bag due to excessive extension.

[0017] In one or more of the above optional embodiments, the first insulating tape and the second insulating tape each independently include a base layer and an adhesive layer disposed on the base layer. The base layer includes at least one of polyethylene terephthalate, polyimide, or polypropylene. The adhesive layer includes at least one of a rubber system, acrylic acid, or styrene-isoprene-styrene.

[0018] In one or more optional embodiments above, the substrate layer is made of polyethylene terephthalate, and / or the adhesive layer is made of styrene-isoprene-styrene.

[0019] According to a second aspect of the present application, there is provided an electrical device comprising the secondary battery described above.

[0020] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the following description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0022] FIG1 is a schematic structural diagram of a secondary battery provided in one embodiment of the present application;

[0023] FIG2 is a schematic structural diagram of another secondary battery provided by one embodiment of the present application;

[0024] FIG3 is a schematic structural diagram of another secondary battery provided in one embodiment of the present application;

[0025] FIG4 is a perspective view of the structure of the secondary battery shown in FIG1 without a packaging bag;

[0026] FIG5 is a top view of an electrode assembly in the secondary battery shown in FIG1 ;

[0027] FIG6 is a top view of another electrode assembly in the secondary battery shown in FIG1 ;

[0028] FIG7 is a structural schematic diagram of the secondary battery shown in FIG1 when no packaging bag is assembled, viewed from the front on the first side surface;

[0029] FIG8 is a schematic structural diagram of the secondary battery shown in FIG1 when no packaging bag is assembled, viewed from the front on the second side surface;

[0030] 10. Packaging bags;

[0031] 20. Electrode assembly; 201. First end surface; 202. Second end surface; 203. Peripheral surface; 2031. First side surface; 2032. First curved surface; 2033. Second side surface; 2034. Second curved surface; 21. First separator; 22. Negative electrode sheet; 221. Protruding portion; 23. Second separator; 24. Positive electrode sheet; 24a. Winding termination end;

[0032] 31. First terminal tab; 32. Second terminal tab;

[0033] 41. First insulating tape; 411. Tape body; 412. First extension; 412a. First partition; 412b. Second partition; 413. Second extension;

[0034] 42. Second insulating tape; 421. First part; 422. Second part; 423. Third part;

[0035] 431, first overlapping area; 432, second overlapping area;

[0036] X, first direction; Y, second direction; Z, third direction; S, winding direction. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0038] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0039] In the description of this application, it should be noted that, unless otherwise specified or limited, the terms "mounted" and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0040] The term "perpendicular" is used to describe the ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular between the two components. For example, combined with numerical descriptions, perpendicular can refer to the angle between two straight lines being in the range of 90°±10°, perpendicular can also refer to the dihedral angle between two planes being in the range of 90°±10°, and perpendicular can also refer to the angle between a straight line and a plane being in the range of 90°±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if the overall extension direction is a straight line or a plane.

[0041] The term "parallel" is used to describe the ideal state between two components. In actual production or use, there may be a state of approximate parallelism between the two components. For example, combined with numerical descriptions, parallel can refer to the angle between two straight lines being in the range of 180°±10°, parallel can also refer to the dihedral angle between two planes being in the range of 180°±10°, and parallel can also refer to the angle between a straight line and a plane being in the range of 180°±10°. The two components described as "parallel" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if its overall extension direction is a straight line or a plane.

[0042] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0043] For ease of description, as shown in FIG1 to FIG8 , a three-dimensional rectangular coordinate system is established with the length direction of the secondary battery as the first direction X, the thickness direction of the secondary battery as the second direction Y, and the width direction of the secondary battery as the third direction Z.

[0044] In some embodiments, the first direction X is parallel to the relative direction of the first end face 201 and the second end face 202 in the electrode assembly 20 to be described below; in addition, the first direction X is also parallel to the extension direction of the first electrode tab 31 to be described below.

[0045] In some embodiments, the second direction Y is parallel to the direction in which the first side surface 2031 and the second side surface 2033 in the electrode assembly 20 are relatively arranged, which will be described in detail below. In addition, the second direction Y is also parallel to the direction in which the pole pieces in the electrode assembly 20 are stacked, which will be described in detail below.

[0046] In some embodiments, the third direction Z is parallel to the direction in which the first curved surface 2032 and the second curved surface 2034 in the electrode assembly 20 are relatively set, which will be described in detail below. In addition, the third direction Z is also parallel to the direction in which the first electrode tab 31 and the second electrode tab 32 are relatively set, which will be described in detail below.

[0047] Figure 1 is a schematic diagram of the structure of a secondary battery provided by one embodiment of the present application, Figure 2 is a schematic diagram of the structure of another secondary battery provided by one embodiment of the present application, and Figure 3 is a schematic diagram of the structure of yet another secondary battery provided by one embodiment of the present application. First, referring to any of Figures 1 to 3, the secondary battery includes: a packaging bag 10; an electrode assembly 20, which is placed within the packaging bag 10; one end of a first electrode tab 31 and one end of a second electrode tab 32 are both electrically connected to the electrode assembly 20 within the packaging bag 10; the other end of the first electrode tab 31 and the other end of the second electrode tab 32 extend outside the packaging bag 10 to electrically connect to an external device to enable the input or output of electrical energy.

[0048] In some embodiments, the packaging bag 10 is made of a packaging film. The packaging film includes, from the inside out, a first polymer layer (not shown), a metal layer (not shown), and a second polymer layer (not shown). The first polymer layer melts at a predetermined temperature and has adhesive properties to facilitate packaging of the packaging bag 10. The metal layer is used to reduce the infiltration of moisture into the packaging bag 10, thereby allowing for gas-liquid exchange with the electrolyte. The second polymer layer reduces air permeation into the packaging bag 10 and improves the packaging bag 10's deformability.

[0049] As an example, the first polymer layer may be made of polypropylene, so that the first polymer layer is difficult to be melted or swelled by the electrolyte, thereby reducing the risk of corrosion of the metal layer adjacent to the first polymer layer.

[0050] As an example, the metal layer can be made of aluminum, which reacts with oxygen in the air to form a dense oxide film to prevent moisture from penetrating into the interior of the packaging bag 10 .

[0051] As an example, the second polymer layer may be made of nylon material.

[0052] Of course, the specific selection of the packaging bag 10 is actually diverse and is not limited to being made of the aforementioned packaging film.

[0053] The electrode assembly 20 includes a positive electrode sheet 24, a negative electrode sheet 22, and a separator separating the positive electrode sheet 24 and the negative electrode sheet 22. In a specific embodiment, there is only one positive electrode sheet 24 and one negative electrode sheet 22, and both are strip-shaped. The positive electrode sheet 24, the separator, and the negative electrode sheet 22 are stacked in sequence and wound two or more times to form a wound structure. One of the positive electrode sheet 24 and the negative electrode sheet 22 is electrically connected to the first electrode tab 31, and the other is electrically connected to the second electrode tab 32. For ease of description, the following embodiments are illustrated by exemplifying that the positive electrode sheet 24 is electrically connected to the first electrode tab 31 and the negative electrode sheet 22 is electrically connected to the second electrode tab 32.

[0054] The positive electrode sheet 24 includes a positive electrode current collector (not shown) and a positive electrode active material layer (not shown) coated on at least one surface of the positive electrode current collector.

[0055] The positive electrode current collector includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al and combinations thereof.

[0056] The positive electrode active material layer includes a positive electrode active material (not shown), which includes but is not limited to one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium nickel oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium iron phosphate and lithium-rich manganese-based materials.

[0057] The negative electrode sheet 22 includes a negative electrode current collector (not shown) and a negative electrode active material layer (not shown) coated on at least one surface of the negative electrode current collector.

[0058] The negative electrode current collector includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al and combinations thereof.

[0059] The negative electrode active material layer includes a negative electrode active material (not shown), which can be selected from at least one of a graphite material, an alloy material, lithium metal, and alloys thereof. The graphite material can be selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, graphene, and mesocarbon microbeads; the alloy material can be selected from at least one of a silicon-based material, a tin-based material, and titanium sulfide.

[0060] Please refer to any of the figures in Figures 1 to 3 in conjunction with Figure 5 or Figure 6. In some embodiments, the electrode assembly 20 is generally a flat wound structure and includes: a first end surface 201, a second end surface 202, and a peripheral surface 203; the first end surface 201 is located on one side of the wound structure along the first direction X; the second end surface 202 is located on the other side of the wound structure along the first direction X; the peripheral surface 203 is located between the first end surface 201 and the second end surface 202 and is respectively connected to the peripheral edge of the first end surface 201 and the peripheral edge of the second end surface 202; the peripheral surface 203 The first end surface 201 includes a first side surface 2031, a first curved surface 2032, a second side surface 2033, and a second curved surface 2034. The first side surface 2031, the first curved surface 2032, the second side surface 2033, and the second curved surface 2034 are sequentially arranged around the circumference of the wound structure in a direction opposite to the winding direction S of the wound structure. The first side surface 2031 and the second side surface 2033 are arranged opposite each other in the second direction Y, and the first curved surface 2032 and the second curved surface 2034 are arranged opposite each other in the third direction Z. The first end surface 201 may be composed of the positive electrode sheet 24, the negative electrode sheet 22, and the separator on one side in the first direction X. The second end surface 202 may be composed of the positive electrode sheet 24, the negative electrode sheet 22, and the separator on the other side in the first direction X.

[0061] It is worth mentioning that, based on the safety and reliability of the secondary battery, the electrode assembly 20 in each embodiment of the present application should meet the following requirements: the width of the separator in the first direction X should be greater than the width of the negative electrode sheet 22 in the first direction X, and the width of the negative electrode sheet 22 in the first direction X should be greater than the width of the positive electrode sheet 24 in the first direction X. As a result, the separator can provide an additional safety margin to reduce the possibility of a short circuit due to direct contact between the positive electrode sheet 24 and the negative electrode sheet 22.

[0062] In some embodiments, the first end surface 201 or the second end surface 202 may be a plane, a curved surface, or an irregular surface.

[0063] Regarding the first electrode tab 31, in some embodiments, the first electrode tab 31 includes a first metal strip (not shown) and a first electrode tab glue (not shown); one end of the first metal strip is electrically connected to the positive electrode plate 24 in the packaging bag 10, and the other end of the first metal strip extends out of the packaging bag 10; the first electrode tab glue is arranged around the outer circumference of the first metal strip and sandwiched between the first metal strip and the packaging bag 10.

[0064] It is understood that the various embodiments of the present application do not specifically limit the connection method between the first electrode tab 31 and the positive electrode sheet 24. For example, in some embodiments, the first electrode tab 31 and the positive electrode sheet 24 are independent components, and the first metal strip can be fixed to the positive electrode sheet 24 by welding, riveting, or conductive adhesive bonding. For another example, in other embodiments, the first electrode tab 31 and the positive electrode current collector are different parts of the same component. The first electrode tab 31 and the positive electrode current collector can be obtained by die-cutting a foil, and then an active material layer is coated on at least one surface of the positive electrode current collector to form the positive electrode sheet 24.

[0065] Regarding the second electrode tab 32, in some embodiments, the second electrode tab 32 includes a second metal strip (not shown) and a second electrode tab glue (not shown); one end of the second metal strip is electrically connected to the negative electrode plate 22 in the packaging bag 10, and the other end of the second metal strip extends outside the packaging bag 10; the second electrode tab glue is arranged around the outer circumference of the second metal strip and sandwiched between the second metal strip and the packaging bag 10.

[0066] It is understood that the various embodiments of the present application do not specifically limit the connection method between the second electrode tab 32 and the negative electrode plate 22. Since the connection method between the second electrode tab 32 and the negative electrode plate 22 is similar to the connection method between the first electrode tab 31 and the positive electrode plate 24, the relevant description can be referred to the first electrode tab 31 and the positive electrode plate 24, and will not be further elaborated here.

[0067] For ease of description, the example in which the first electrode tab 31 and the second electrode tab 32 both extend from the same side of the electrode assembly 20 is used. Figures 1, 2, and 4 also show that in some embodiments, the first electrode tab 31 and the second electrode tab 32 are spaced apart in the third direction Z, thereby improving the space utilization of the secondary battery. Specifically, the other end of the first metal strip and the other end of the second metal strip both extend outside the packaging bag 10 from the first end surface 201.

[0068] Of course, the arrangement of the first and second tabs 31, 32 can also be adjusted based on actual usage requirements. As shown in FIG3 , in other embodiments, the first and second tabs 31, 32 each extend from opposite sides of the packaging bag 10 along the first direction X. Specifically, the other end of the first metal strip extends outside the packaging bag 10 from the first end surface 201, and the other end of the second metal strip extends outside the packaging bag 10 from the second end surface 202.

[0069] Furthermore, the first electrode tab 31 is closer to the second arcuate surface 2034 than the first arcuate surface 2032 , and the second electrode tab 32 is closer to the second arcuate surface 2034 than the first arcuate surface 2032 .

[0070] As shown in any of the figures in Figures 1 to 4, in some embodiments, the secondary battery includes a first insulating tape 41, which is roughly U-shaped when viewed from the first direction X, and includes a tape body 411 and a first protruding portion 412 integrally connected to the tape body 411. The tape body 411 is respectively bonded to the first side surface 2031, the first curved surface 2032 and the second side surface 2033, and the first protruding portion 412 extends beyond one side end surface of the negative electrode plate 22 in the first direction X.

[0071] The benefits of such a setting can be reflected in the following two aspects. First, because the first insulating tape 41 has a certain mechanical strength, the forced bending of the part of the first extension portion 412 extending out of the first end face 201 can prevent the end face of one side of the negative electrode plate 22 in the first direction X from directly contacting the packaging bag 10 made of aluminum-plastic film, thereby improving the situation where the negative electrode plate 22 and the packaging bag 10 contact and corrode the aluminum layer in the packaging bag 10; second, by adding the first insulating tape 41, the thickness of the portion of the electrode assembly 20 where the first insulating tape 41 is located can be balanced with the thickness of the portion of the electrode assembly 20 where the connection between the first tab 31 and the electrode assembly 20 is located, thereby improving the interface problem of the electrode assembly 20 caused by uneven force in the subsequent hot pressing process.

[0072] Furthermore, the first insulating tape 41 includes a second extension portion 413 connected to the tape body 411 , and the second extension portion 413 extends out of the second end surface 202 along the first direction X. Similarly, the corrosion of the aluminum layer in the packaging bag 10 caused by the contact between the negative electrode sheet 22 and the packaging bag 10 can also be improved.

[0073] Please refer to the example shown in FIG. 4 in combination with FIG. 5 or FIG. 6 . In some embodiments, in the second direction Y, the projection of the protruding portion 221 completely falls within the projection of the first insulating tape 41 .

[0074] For ease of description, the winding structure includes a first separator 21, a negative electrode sheet 22, a second separator 23 and a positive electrode sheet 24 as an example. The first separator 21, the negative electrode sheet 22, the second separator 23 and the positive electrode sheet 24 are stacked and wound in sequence to form the aforementioned flat winding structure. Among them, along the winding direction S of the winding structure, the positive electrode sheet 24 has a winding end end 24a, and the negative electrode sheet 22 has a protruding portion 221 that protrudes beyond the winding end end 24a. The first insulating tape 41 is respectively bonded to the winding end end 24a and the protruding portion 221. In the second direction Y, the projection of the protruding portion 221 falls within the projection of the first insulating tape 41. With this design, the first insulating tape 41 can play the role of binding the electrode assembly 20 to maintain the structural integrity and stability of the winding structure. In addition, since the protruding portion 221 of the negative electrode plate 22 still has the die-cut surface of the negative electrode collector exposed, the first insulating tape 41 is arranged between the protruding portion 221 and the packaging bag 10, which can also reduce the situation where the burrs on the die-cut surface pierce the isolation film and directly contact the packaging bag 10 made of aluminum-plastic film under some working conditions.

[0075] Continuing with Figures 7 and 8 , in some embodiments, 1 < L2 / L1 ≤ 1.1; wherein the length of the negative electrode tab 22 in the first direction X is L1 mm, and the length of the first insulating tape 41 in the first direction X is L2 mm. Limiting L2 to this value range improves the contact between the negative electrode tab 22 and the packaging bag 10, thereby preventing corrosion of the aluminum layer within the packaging bag 10, while also reducing the risk of the first extension 412 extending excessively into the seal area of ​​the packaging bag 10. As an example, the length L1 of the negative electrode tab 22 in the first direction X can be 1.01L1, 1.02L1, 1.03L1, 1.04L1, 1.05L1, 1.055L1, 1.058L1, 1.06L1, 1.065L1, 1.07L1, 1.072L1, 1.08L1, 1.085L1, 1.09L1, 1.098L1, 1.1L1 or a range consisting of any two of the above.

[0076] It should be noted that if the first insulating tape 41 is divided into the tape body 411 and the first extension 412, then the length of the negative electrode tab 22 in the first direction X mentioned here specifically refers to the distance between the side edge of the first extension 412 and the side edge of the tape body 411 in the first direction X. If the first insulating tape 41 is divided into the tape body 411, the first extension 412, and the second extension 413, then the length of the negative electrode tab 22 in the first direction X mentioned here specifically refers to the distance between the side edge of the first extension 412 and the side edge of the second extension 413 in the first direction X.

[0077] In some embodiments, the first insulating tape 41 includes a base material layer (not shown) and an adhesive layer (not shown) disposed on the base material layer. The base material layer may have a certain degree of mechanical strength, electrical insulation, and thermal stability to maintain long-term stability even when immersed in an electrolyte environment; the adhesive layer may have a certain degree of adhesion and thermal stability to resist corrosion from the alkaline environment of the electrolyte while remaining difficult to fall off or shift during use.

[0078] The substrate layer includes at least one of polyethylene terephthalate, polyimide or polypropylene. As an example, the substrate layer is made of polyethylene terephthalate.

[0079] The adhesive layer includes at least one of a rubber system, acrylic acid or styrene-isoprene-styrene. As an example, the adhesive layer is made of styrene-isoprene-styrene.

[0080] Please refer to the examples shown in FIG. 6 or FIG. 5 in conjunction with FIG. 7 and FIG. 8 . In some embodiments, the first protruding portion 412 may be divided into a first partition 412 a and a second partition 412 b that are oppositely disposed along the first direction X.

[0081] The secondary battery includes a second insulating tape 42, which is substantially U-shaped when viewed from a third direction Z and includes a first portion 421, a second portion 422, and a third portion 423.

[0082] The first portion 421 is bonded to the first end surface 201 , the first partition 412 a and the second partition 412 b . In other words, the first portion 421 is bonded to the first extension 412 and one end surface of the positive electrode tab 24 , the negative electrode tab 22 and the separator in the first direction X.

[0083] The second part 422 is integrally connected to a side edge of the first part 421 along the second direction Y and is respectively bonded to the first side surface 2031 and the tape body 411. In the second direction Y, the projection of the second part 422 and the projection of the tape body 411 on the first side surface 2031 have a first overlapping area 431.

[0084] The third part 423 is integrally connected to the other side edge of the first part 421 along the second direction Y and is respectively bonded to the second side surface 2033 and the tape body 411. In the second direction Y, the projection of the third part 423 and the projection of the tape body 411 on the second side surface 2033 have a second overlapping area 432.

[0085] In the secondary battery involved in the present application, the positive electrode sheet 24, the negative electrode sheet 22 and the isolation membrane are bonded together by the second insulating tape 42 and the first insulating tape 41 to form an integral structure, thereby improving the integrity of the electrode assembly 20, thereby reducing the risk of at least one of the positive electrode sheet 24, the negative electrode sheet 22 and the isolation membrane being dislocated under vibration or impact conditions due to lack of restriction.

[0086] On this basis, under the fixing action of the second insulating tape 42, the first partition 412a and the second partition 412b can be bent toward the inner circle of the electrode assembly 20, thereby driving the isolation membrane to fold inward on one side of the first direction X close to the part of the end surface of the first curved surface 2032, thereby forming a blocking structure that blocks part of the gas from passing through, so that during the hot box test of the secondary battery, the heat-generated gas can be concentrated and rushed out of the packaging bag 10 from the position close to the first pole ear 31, thereby improving the hot box test pass rate of the secondary battery.

[0087] Finally, the second insulating tape 42 and the first insulating tape 41 overlap on both the first side surface 2031 and the second side surface 2033. This means that the thickness of the overlapping region in the second direction Y is greater than the thickness of the portion surrounding the first curved surface 2032 in the second direction Y. Therefore, during the subsequent hot pressing process, the force applied to the portion surrounding the first curved surface 2032 is less than that applied to the overlapping region. As a result, the spacing between adjacent electrode pieces surrounding the first curved surface 2032 is slightly greater than the spacing between adjacent electrode pieces in the overlapping region. This improves electrolyte wettability of the first curved surface 2032, thereby mitigating the risk of lithium deposition around the first curved surface 2032 due to insufficient electrolyte.

[0088] Of course, the structure of the second insulating tape 42 is not limited to this, and its shape can be adaptively adjusted according to actual usage. For example, as shown in Figure 2, in other embodiments, the second insulating tape 42 only has a first portion 421, that is, the second insulating tape 42 has a generally sheet-like structure, which is adhered to the first end surface 201, the first partition 412a, and the second partition 412b. As a result, the second insulating tape 42 and the first insulating tape 41 do not overlap on the first side surface 2031 and the second side surface 2033, and thus no longer have the function of improving the lithium deposition around the first curved surface 2032 due to insufficient electrolyte.

[0089] It should be noted that the second insulating tape 42 is disposed on one side of the electrode assembly 20 in the first direction X. The width of the second insulating tape 42 in the third direction Z directly affects the wettability of the portion surrounding the first curved surface 2032. Specifically, the greater the width of the second insulating tape 42 in the third direction Z, the worse the wettability of the portion surrounding the first curved surface 2032. Therefore, the width of the second insulating tape 42 in the third direction Z should not be equal to or greater than the maximum distance from the edge of the second insulating tape 42 near the first tab 31 to the first curved surface 2032.

[0090] It should also be noted that the reason why the heat-generating gas can be concentrated and rush out of the packaging bag 10 from the position near the first pole ear 31 is that, for the packaging bag 10 made of aluminum-plastic film, when the same hot pressing pressure is applied to the first pole ear 31 and the sealing area adjacent to the first pole ear 31, since the first metal belt is made of metal, some heat will be dissipated, so that the bonding strength of the first pole ear glue is less than the bonding strength of the sealing area other than the first pole ear glue. Therefore, in the hot box test, the heat-generating gas can be concentrated and rush out of the packaging bag 10 from the position near the first pole ear 31.

[0091] In some embodiments, the second insulating tape 42 includes a base material layer (not shown) and an adhesive layer (not shown) disposed on the base material layer. It should be noted that the structure and function of the base material layer of the second insulating tape 42 are similar to those of the base material layer of the first insulating tape 41, and the structure and function of the adhesive layer of the second insulating tape 42 are similar to those of the first insulating tape 41. These details will not be further elaborated here; please refer to the relevant description of the first insulating tape 41.

[0092] As shown in FIG. 7 or FIG. 8 , in some embodiments, 0.2<W1 / W≤0.7, and 1<W2 / W tab ≤3; limiting W1 and W2 to this value range can not only improve the hot box test pass rate of the secondary battery, but also improve the lithium plating of the secondary battery. Among them, the width of the electrode assembly 20 in the third direction Z is W mm; the width of the first insulating tape 41 in the third direction Z is W1 mm; the width of the first tab 31 in the third direction Z is W tab mm; the width of the second insulating tape 42 in the third direction Z is W2 mm.

[0093] Furthermore, 0.3≤W1 / W≤0.5; and / or, 1.5≤W3 / W tab ≤2.5. With this design, when either W1 or W2 is satisfied, the hot box test pass rate of the secondary battery and the probability of lithium plating or not plating on the negative electrode are both better.

[0094] 7 or 8 , in some embodiments, 0<W3 / W1≤0.5, and 0.8<W4 / W3≤1.1; wherein the width of the first overlapping region 431 in the third direction Z is W3 mm; and the width of the second overlapping region 432 in the third direction Z is W4 mm.

[0095] The present application is further described below with reference to the following examples and comparative examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by weight. It should be understood that these examples are intended only to illustrate the present application and are not intended to limit the scope of the present application.

[0096] Example 1-1

[0097] Preparation of positive electrode sheet:

[0098] The positive electrode active material (lithium cobalt oxide), conductive agent (conductive carbon black and carbon nanotubes), and binder (polyvinylidene fluoride) are dissolved in N-methylpyrrolidone solution at a weight ratio of 97.5:1:1.5 to form a positive electrode slurry with a solid content of 75%. Using aluminum foil as a current collector, the positive electrode slurry is applied to the surface of the positive electrode current collector to form the positive electrode active material layer. The positive electrode sheets are then dried, cold pressed, and cut.

[0099] Preparation of negative electrode sheet:

[0100] The negative electrode active material (graphite), conductive agent (conductive carbon black), thickener (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) were mixed in a mass ratio of 97.5:1:0.5:1. Deionized water was then added as a solvent and stirred evenly to produce a negative electrode slurry with a solid content of 50%. Using copper foil as a current collector, the negative electrode slurry was applied to the surface of the negative electrode current collector to form the negative electrode active material layer. The negative electrode sheets were then dried, cold-pressed, and cut.

[0101] Preparation of isolation membrane:

[0102] Polyethylene film is selected as the isolation film.

[0103] Preparation of electrolyte:

[0104] Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) are mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 and the organic solvent are mixed in a weight ratio of 8:92 to obtain an electrolyte.

[0105] Preparation of secondary batteries:

[0106] The first separator, the negative electrode sheet, the second separator and the positive electrode sheet are stacked in sequence, wound to obtain an electrode assembly, and the first and second tabs are welded; then the first insulating tape is first pasted, and the second insulating tape is pasted on the first end face, the first partition and the second partition respectively; the second insulating tape is then pasted between the first partition and the second partition of the first insulating tape; the electrode assembly is hot pressed; furthermore, the electrode assembly is placed in an aluminum-plastic film packaging bag, with the first and second tabs both extending out of the packaging bag, and after drying, the electrolyte is injected, and after vacuum packaging, standing, formation, degassing, trimming and other processes, a secondary battery with a length of 80 mm, a width of 60 mm and a thickness of 5 mm is obtained.

[0107] Comparative Example 1-1: The difference from Example 1-1 is that only the first insulating tape is bonded.

[0108] Comparative Example 1-2: The difference from Example 1-1 is that only the second insulating tape is bonded.

[0109] Comparative Example 1-3: The difference from Example 1-1 is that the second insulating tape is only bonded to the first end surface but not to the first partition and the second partition.

[0110] The following describes the test methods for each parameter of this application

[0111] Electrode assembly length test

[0112] The secondary battery was disassembled, left to stand for 1 hour, and the thickness was measured using a vernier caliper to obtain data on the length of the electrode assembly (the distance between the first end face and the second end face in the first direction).

[0113] Electrode assembly width test

[0114] The secondary battery was disassembled, left to stand for 1 hour, and the thickness was measured using a vernier caliper to obtain the width of the electrode assembly (the distance between the first curved surface and the second curved surface in the third direction).

[0115] Electrode assembly thickness test

[0116] The secondary battery was disassembled, left to stand for 1 hour, and the thickness was measured using a vernier caliper to obtain the thickness data of the electrode assembly (the distance between the first side surface and the second side surface in the second direction).

[0117] Hot box test

[0118] At 25°C, the secondary battery was allowed to rest for 5 minutes, then charged at a constant current of 0.5C to 4.5V. It was then charged at a constant voltage of 4.5V to 0.025C and allowed to rest for 60 minutes. The secondary battery was then subjected to a hot box test. Before the hot box test, the secondary battery was inspected and photographed. A temperature sensor was attached. The secondary battery was placed vertically in a hot box and heated from 25°C to 130°C at a rate of 5°C / minute for 60 minutes. If the secondary battery did not catch fire or explode, it was considered to have passed the hot box test. A total of 100 secondary battery samples were tested. The number of batteries that passed the hot box test was counted, and the hot box test pass rate was calculated.

[0119] Lithium deposition test

[0120] Place the secondary battery at a test temperature of 25°C for 30 minutes, and then charge it to 4.53V according to the following charging steps:

[0121] (1) 4C CC to 4.3V, CV to 3.2C;

[0122] (2) 3.2C CC to 4.35V, CV to 2.5C;

[0123] (3) 2.5C CC to 4.4V, CV to 2C;

[0124] (4) 2C CC to 4.45V, CV to 1.5C;

[0125] (5) 1.5C CC to 4.53V, CV to 0.28C;

[0126] After standing for 30 minutes, discharge according to the following steps:

[0127] (1) 1.5C DC to 3.3V,

[0128] (2) 0.7C DC to 3V.

[0129] The above charge and discharge process is one cycle. After repeating 700 cycles, when the battery is in a fully charged state (the battery is designed to have a maximum voltage of 4.53V), the secondary battery is disassembled to obtain the negative electrode. If the lithium deposition area on the surface of the negative electrode is greater than or equal to 2mm 2 , it is determined to be lithium deposition.

[0130] Table 1

[0131] As shown in Table 1, the hot box test pass rate for the case where the second insulating tape was bonded to the first insulating tape at the first end face was higher than that for Comparative Examples 1-1, 1-2, and 1-3, and Example 1. This is likely because, under the fixing effect of the second insulating tape, both the first and second partitions can bend toward the inner ring of the electrode assembly, thereby driving the portion of the end face of the separator in the first direction near the first curved surface to fold inward, thereby forming a barrier structure that partially blocks the passage of gas. This allows the hot gas generated by the secondary battery to be concentrated and discharged from the packaging bag near the first tab during the hot box test, thereby improving the hot box test pass rate for the secondary battery.

[0132] Example 1-2 to Example 1-18

[0133] The difference from Example 1-1 is that the width W1 of the first insulating tape in the third direction is different from the width W2 of the second insulating tape in the third direction. Each example was subjected to a hot box test and a lithium deposition test. The example parameters and test results are shown in Table 2.

[0134] Table 2

[0135] It can be seen from Table 2 that, under the premise that the width W3 of the third direction of the first overlapping area in Examples 1-2 to 1-9 is constant, the width W4 of the third direction of the second overlapping area is constant, and the width W2 of the third direction of the second insulating tape is constant, by comparing Examples 1-2 to 1-8 with Examples 1-1 and 1-9, it can be seen that when 0.2<W1 / W≤0.7 is satisfied, the hot box test pass rate of the secondary battery and the probability of no lithium deposition on the first curved surface are both better; especially when 0.3≤W1 / W≤0.5 is satisfied, the hot box test pass rate of the secondary battery and the probability of no lithium deposition on the first curved surface are even better.

[0136] Under the premise that the width W3 of the first overlapping area in the third direction is constant, the width W4 of the second overlapping area in the third direction is constant, and the width W1 of the first insulating tape in the third direction is constant in Examples 1-10 to 1-17, it can be seen from the comparison between Examples 1-11 to 1-16 and Examples 1-10 and 1-17 that 1<W2 / W tab When ≤3, the hot box test pass rate of the secondary battery and the probability of no lithium deposition on the first curved surface are both better; especially when 1.5≤W2 / W tab When W2 / W tabWhen it is greater than 3, even if the hot box test pass rate of the secondary battery and the probability of no lithium deposition on the first curved surface are both relatively good, the second insulating tape is too wide and covers a larger area of ​​the first end surface, resulting in poor electrolyte wettability and the area is prone to problems such as lithium deposition black spots.

[0137] This may be because the positions of the first overlapping area and the second overlapping area depend not only on the width of the first insulating tape in the third direction, but also on the width of the second insulating tape in the third direction. Specifically, when W1 / W≤0.2, and W2 / W tab When W1 / W>0.7, the barrier structure formed by the second insulating tape, the first partition and the second partition gradually loses its function, and the hot box test pass rate of the secondary battery gradually decreases. When W2 / W>0.7, the barrier structure formed by the second insulating tape, the first partition and the second partition gradually loses its function, and the hot box test pass rate of the secondary battery gradually decreases. tab When the ratio is greater than 0.7, the second insulating tape covers a larger area of ​​the first end face, resulting in poor electrolyte wettability in the covered area, and further lithium deposition on the negative electrode sheet.

[0138] Therefore, W1 and W2 satisfy: 0.2<W1 / W≤0.7, and 1<W2 / W tab ≤3. It can not only improve the passing rate of hot box test of secondary batteries, but also improve the lithium plating of secondary batteries.

[0139] The difference from Example 1-1 is that the width W2 of the second insulating tape in the third direction, the width W3 of the first overlapping region in the third direction, and the width W4 of the second overlapping region in the third direction are different. Hot box testing and lithium deposition testing were performed on each example. The parameters and test results of the examples are shown in Table 3.

[0140] Table 3

[0141] It can be seen from Table 3 that, compared with Example 2-5, when W3 and W4 satisfy: 0<W3 / W1≤0.5, and 0.8<W4 / W3≤1.1, the areas of the first overlapping region and the second overlapping region are both within a certain range. At this time, the first insulating tape and the second insulating tape can maintain a relatively good bonding strength to maintain the effective function of the barrier structure formed by the second insulating tape, the first partition and the second partition; it can also reduce the interface problems formed in the subsequent hot pressing process due to the area difference between the first overlapping region and the second overlapping region.

[0142] Based on the same technical concept, one embodiment of the present application further provides an electronic device comprising any of the above-mentioned secondary batteries. The electronic device of the present application may be, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0143] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A secondary battery comprising a packaging bag, an electrode assembly, and a first tab, wherein the electrode assembly is housed in the packaging bag, the first tab being electrically connected to the electrode assembly and extending out of the packaging bag in a first direction; the electrode assembly being in a wound structure and comprising a first end surface, a first side surface, a first curved surface, and a second side surface, wherein the first side surface, the first curved surface, and the second side surface are arranged around a periphery of the first end surface; characterized in that: The secondary battery comprises a first insulating tape and a second insulating tape; The first insulating tape comprises a tape body and a first extension portion, wherein the tape body is respectively bonded to the first side surface, the first curved surface, and the second side surface; The first extension extends beyond the negative electrode sheet of the electrode assembly along a first direction, the first extension includes a first partition and a second partition, the first partition and the second partition are arranged opposite to each other along a second direction, wherein the second direction is perpendicular to the first direction and is a thickness direction of the electrode assembly; The second insulating tape is respectively bonded to the first end surface, the first partition and the second partition.

2. The secondary battery according to claim 1, wherein The second insulating tape comprises a first part, a second part and a third part; The first part is respectively bonded to the first end surface, the first partition and the second partition; The second portion is connected to a side edge of the first portion along the second direction and is bonded to the first side surface and the adhesive tape body respectively; The third portion is connected to the other side edge of the first portion along the second direction and is bonded to the second side surface and the adhesive tape body respectively; In the second direction, the projection of the second portion and the projection of the tape body have a first overlapping area on the first side surface, and the projection of the third portion and the projection of the tape body have a second overlapping area on the second side surface.

3. The secondary battery according to claim 2, wherein 0.2<W1 / W≤0.7, and 1<W2 / W tab ≤3; The width of the electrode assembly in the third direction is W mm; The width of the first insulating tape in the third direction is W1 mm; The width of the first tab in the third direction is W tab mm; The width of the second insulating tape in the third direction is W2 mm, wherein the third direction, the second direction and the first direction are perpendicular to each other.

4. The secondary battery according to claim 3, wherein 0.3≤W1 / W≤0.5; and / or 1.5≤W2 / W tab ≤2.

5.

5. The secondary battery according to claim 3, wherein 0<W3 / W1≤0.5, and 0.8<W4 / W3≤1.1; The width of the first overlapping area in the third direction is W3 mm; The width of the second overlapping area in the third direction is W4 mm.

6. The secondary battery according to any one of claims 2 to 5, characterized in that: The packaging bag is made of aluminum-plastic film; The electrode assembly includes a stacked and wound negative electrode sheet and a positive electrode sheet; along the winding direction of the electrode assembly, the positive electrode sheet has a winding end end, and the negative electrode sheet has a protruding portion that extends beyond the winding end end; the protruding portion and the winding end end are both located on one side of the electrode assembly in the second direction, and the protruding portion and the winding end end are arranged on two adjacent electrode sheet layers; Along the second direction, the orthographic projection of the protruding portion falls within the orthographic projection of the first insulating tape.

7. The secondary battery according to claim 6, characterized in that 1<L2 / L1≤1.1; The length of the negative electrode plate in the first direction is L1 mm; The length of the first insulating tape in the first direction is L2 mm.

8. The secondary battery according to any one of claims 1 to 5, characterized in that: The first insulating tape and the second insulating tape each independently include a base material layer and an adhesive layer provided on the base material layer; The substrate layer comprises at least one of polyethylene terephthalate, polyimide or polypropylene; The adhesive layer includes at least one of a rubber system, acrylic acid or styrene-isoprene-styrene.

9. The secondary battery according to claim 8, characterized in that The substrate layer is made of polyethylene terephthalate; and / or The adhesive layer is made of styrene-isoprene-styrene.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The electrode assembly includes a second end surface; the second end surface is located on the other side of the winding structure along the first direction, and the first end surface is located on one side of the winding structure along the first direction; The first insulating tape includes a second extending portion connected to the tape body, and the second extending portion extends out of the second end surface along the first direction.

11. The secondary battery according to claim 10, wherein The first end surface or the second end surface is a plane or a curved surface.

12. The secondary battery according to any one of claims 1 to 9, characterized in that: The secondary battery includes a second electrode tab; one end of the second electrode tab is electrically connected to the electrode assembly in the packaging bag, and the other end of the second electrode tab extends out of the packaging bag.

13. The secondary battery according to claim 12, characterized in that The second electrode tab and the first electrode tab both extend out of the packaging bag from the same side of the electrode assembly.

14. The secondary battery according to any one of claims 1 to 9, characterized in that: The first tab includes a first metal strip and a first tab glue; one end of the first metal strip is electrically connected to one pole of the electrode assembly in the packaging bag, and the other end of the first metal strip extends out of the packaging bag; the first tab glue is arranged around the outer circumference of the first metal strip and is sandwiched between the first metal strip and the packaging bag.

15. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 14.

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