Battery and electric device

Abstract

A battery and an electric device. The battery comprises a case, an electrode assembly, and an adhesive member. The electrode assembly is accommodated in the case, and comprises a plurality of layers of electrode sheets stacked in a first direction. Each electrode sheet comprises a main body region and a thinned region, and the thickness of the thinned region is less than the thickness of the main body region. The electrode assembly comprises a first surface, and a region of the first surface coinciding with the thinned region in the first direction is a first region. The adhesive member bonds the case and the first surface, the adhesive member comprises a first adhesive member, the first adhesive member at least partially overlaps the first region, and the first adhesive member comprises a first substrate and a first adhesive layer which are stacked in the first direction. In the first direction, the surface of the first substrate distant from the first adhesive layer covers a part of the first surface, and the surface of the first adhesive layer distant from the first substrate is bonded to a part of the case; or in the first direction, the surface of the first adhesive layer distant from the first substrate is bonded to a part of the first surface, and the surface of the first substrate distant from the first adhesive layer covers a part of the case.

Description

Batteries and electrical equipment Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a battery and an electrical device. Background Technology

[0002] Rechargeable batteries (such as lithium-ion batteries) are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, and long cycle life. The safety performance of rechargeable batteries is a major public concern.

[0003] During battery electrode manufacturing, the uncured slurry of the active material layer is fluid. At the boundary between the active material layer and the empty foil area, a thinning zone is formed due to the natural leveling of the slurry. The thickness of this thinned zone is less than that of the normal central area. This thinned zone is located at the head of the cell after winding or stacking, specifically on the side where the tabs extend. Over multiple layers, this results in the thickness at the cell head being less than that in the center. The presence of this thinned zone at the cell head creates gaps between the positive and negative electrodes, making the cell prone to lithium plating and other abnormalities during cycling, severely impacting its cycle performance and safety.

[0004] When a battery is dropped or shaken, the internal cells are prone to shifting and impacting the battery casing, potentially causing casing damage and leakage. There is also a risk of separator shrinkage leading to a short circuit, compromising safety. Currently, adhesives are typically used to bond the cells and casing, fixing them relatively in place and preventing cell shifting during drops or other impacts, thus improving safety. However, there is a tensile force between the adhesive and the casing. This force pulls on the outermost electrode, increasing the gap between the positive and negative electrodes and worsening lithium plating. Summary of the Invention

[0005] One objective of this application is to propose a battery and electrical device that can improve the problem of lithium deposition in the electrode thinning zone.

[0006] This application provides a battery in its first aspect, comprising a housing, an electrode assembly, and an adhesive. The electrode assembly is housed within the housing and includes multiple layers of electrode sheets stacked along a first direction, the first direction being the thickness direction of the electrode sheets. Each electrode sheet includes a current collector and an active material layer, the active material layer being disposed on at least one surface of the current collector. The active material layer includes a main region and a thinned region, wherein, along the first direction, the average thickness of the main region is T3, and the average thickness of the thinned region is T4, where T3 > T4. The electrode assembly includes a first surface facing the housing, the region of the first surface overlapping the thinned region along the first direction being a first region. The adhesive adheres to the housing and the first surface. The adhesive includes a first adhesive member, which at least partially overlaps with the first region along the first direction. The first adhesive member includes a first substrate and a first adhesive layer stacked along the first direction. Along the first direction, the surface of the first substrate away from the first adhesive layer covers a portion of the first surface, and the surface of the first adhesive layer away from the first substrate adheres to a portion of the housing; or, along the first direction, the surface of the first adhesive layer away from the first substrate adheres to a portion of the first surface, and the surface of the first substrate away from the first adhesive layer covers a portion of the housing.

[0007] The battery provided in this application is configured with a first adhesive member that at least partially overlaps with the thinned area of ​​the electrode. The first adhesive member covers a portion of the first surface and is bonded to the casing, or the first adhesive member covers a portion of the casing and is bonded to the first surface. That is, the first adhesive member is set as a single-sided adhesive, so that the tensile force generated between the adhesive member and the casing is not easily directly applied to the thinned area, thereby reducing the risk of increased gap between the thinned areas of adjacent electrodes, improving edge lithium plating, and improving cycle performance.

[0008] Based on the first aspect, in some possible implementations, the material of the first substrate includes one or more of polyethylene terephthalate, polyimide, polyethylene, polypropylene, polyvinyl chloride, kraft paper, cotton cloth, synthetic fiber cloth, metal foil, and glass fiber; the material of the first adhesive layer includes one or more of rubber-based adhesive, silicone-based adhesive, hot melt adhesive, water-based adhesive, polyurethane-based adhesive, epoxy-based adhesive, and polyimide-based adhesive.

[0009] Based on the first aspect, in some possible implementations, the electrode assembly further includes electrode terminals, the extension direction of which is a second direction, perpendicular to the first direction. Along the second direction, the width of the area overlapping the first adhesive with the first region is W, and the width of the thinned region is W1, where 0.7 ≤ W / W1 ≤ 1.1. When W / W1 ≥ 0.7, the first adhesive has a certain width in the first region, which can reduce the increase in gap between the thinned regions of adjacent electrodes caused by the tensile force between the adhesive and the shell. At the same time, it helps to increase the thickness consistency between the thinned region and the main body region in the second direction, reducing the risk of lithium plating in the thinned region due to undervoltage. By limiting the upper limit of W / W1 to 1.1, the risk of the electrode assembly moving within the shell due to excessively large single-sided adhesive area is reduced, improving the battery's drop resistance. At the same time, it reduces the phenomenon of overvoltage in the main body region caused by excessively large overlapping area between the first adhesive and the main body region. Overvoltage will increase the risk of poor electrolyte wetting in the main body region, increasing the risk of lithium plating in the main body region.

[0010] Based on the first aspect, among some possible implementations, 0.8≤W / W1≤1.0 is more effective in reducing lithium plating and improving drop resistance.

[0011] Based on the first aspect, in some possible implementations, the area where the first surface overlaps with the main body region in the first direction is the second region. The adhesive further includes a second adhesive component. Along the first direction, the second adhesive component at least partially overlaps with the second region. The second adhesive component includes a second substrate, a second adhesive layer, and a third adhesive layer stacked along the first direction. The second adhesive layer and the third adhesive layer are disposed on two opposite surfaces of the second substrate along the first direction. The surface of the second adhesive layer away from the second substrate is used to bond the housing, and the surface of the third adhesive layer away from the second substrate is used to bond the first surface. By providing the second adhesive component in the second region overlapping with the main body region, and by using a double-sided adhesive component to bond one side to the second region and the other side to the housing, the drop resistance of the electrode assembly is improved. Furthermore, the second adhesive component can reduce the risk of undervoltage in the main body region and reduce the risk of lithium plating in the main body region.

[0012] Based on the first aspect, in some possible implementations, the electrode assembly further includes electrode terminals, the extension direction of which is a second direction, and a third direction perpendicular to both the first and second directions; viewed from the first direction, the first adhesive member includes a first edge and a second edge disposed opposite to each other along the third direction, the second adhesive member includes a third edge and a fourth edge disposed opposite to each other along the third direction, and the projection area of ​​the electrode assembly along the first direction includes a fifth edge and a sixth edge disposed opposite to each other along the third direction; along the third direction, the fifth edge, the first edge, the second edge, and the sixth edge are arranged sequentially; along the third direction, the fifth edge, the third edge, the fourth edge, and the sixth edge are arranged sequentially; the distance between the first edge and the fifth edge along the third direction is L1, the distance between the second edge and the sixth edge along the third direction is L2, the distance between the third edge and the fifth edge along the third direction is L3, and the distance between the fourth edge and the sixth edge along the third direction is L4; 0≤|L1-L2|≤4mm, and / or, 0≤|L3-L4|≤4mm. The above limitations ensure that the first adhesive and / or the second adhesive are not too offset relative to the electrode assembly in the third direction. If the first adhesive and / or the second adhesive are offset too much in the third direction, it will increase the risk of uneven force on the electrode assembly in the third direction and affect the drop resistance performance of the electrode assembly.

[0013] Based on the first aspect, in some possible implementations, along the third direction, the length of the first adhesive is W2, the width of the second adhesive is W3, and the width of the projection area of ​​the electrode assembly along the first direction is W4, 0.5≤W2 / W4≤1, and / or 0.5≤W3 / W4≤1, which is beneficial to improving lithium plating and drop performance.

[0014] Based on the first aspect, in some possible implementations, 0.6≤W2 / W4≤0.8, and / or 0.6≤W3 / W4≤0.8, the effect of improving lithium plating and drop performance is better.

[0015] Based on the first aspect, in some possible implementations, W2 > W3. The width of the first adhesive in the second direction is generally smaller than the length of the second adhesive in the second direction. Because the first adhesive has a large area, the probability of air bubbles appearing in the bonding process is relatively small, so it can be set to W2 > W3.

[0016] Based on the first aspect, in some possible implementations, the first adhesive and the second adhesive are integrally configured.

[0017] Based on the first aspect, in some possible implementations, the first adhesive and the second adhesive are separately disposed; along the second direction, the first adhesive includes a seventh edge and an eighth edge disposed opposite to each other, and the second adhesive includes a ninth edge and a tenth edge disposed opposite to each other, the straight-line distance between the eighth edge and the ninth edge along the second direction is L5, 0≤L5≤5mm. By setting L5≥0, the overlap of the first adhesive and the second adhesive is reduced. If the first adhesive and the second adhesive overlap, the thickness of the overlapping area will increase, affecting the volumetric energy density of the electrode assembly and the thickness consistency of the electrode assembly in the second direction; by limiting L5≤5mm, the distance between the first adhesive and the second adhesive in the second direction is reduced. If the area of ​​the electrode assembly not covered by the first adhesive or the second adhesive is too large, the risk of the electrode assembly moving within the housing will increase, affecting the drop resistance performance of the electrode assembly. At the same time, the area not covered by the first adhesive or the second adhesive is prone to undervoltage, resulting in a high risk of lithium plating in the undervoltage area. By limiting 0≤L5≤5mm, it is beneficial to reduce the impact of the first and second adhesives on the volumetric energy density of the electrode assembly, to improve the risk of lithium plating caused by undervoltage or overvoltage, and to improve the drop resistance of the electrode assembly.

[0018] Based on the first aspect, in some possible implementations, the thickness of the first adhesive is greater than the thickness of the second adhesive in the first direction. During hot pressing formation, the thickness of the first adhesive exceeding that of the second adhesive can be used to compensate for the thickness of the thinned region, thereby reducing the gap between the thinned regions of adjacent electrodes and improving the problems of poor adhesion and easy lithium plating in the thinned region.

[0019] Based on the first aspect, in some possible implementations, in the first direction, the thickness of the first substrate is greater than the thickness of the second substrate, or the thickness of the first adhesive layer is greater than the total thickness of the second adhesive layer and the third adhesive layer.

[0020] Based on the first aspect, in some possible implementations, in the first direction, the thickness of the first adhesive is T1, the thickness of the second adhesive is T2, and 1.1 ≤ T1 / T2 ≤ 2. The thickness ratio of the first adhesive and the second adhesive is within the above range, ensuring that the thickness difference between the two adhesives is not too small and cannot compensate for the thickness difference between the thinned region and the main body region. This allows the first adhesive to improve the degree of lithium plating in the thinned region. Simultaneously, the thickness difference between the first adhesive and the second adhesive is not too large, reducing the difficulty of electrolyte wetting in the thinned region caused by overpressure at the first adhesive coverage location, and also reducing the overall thickness unevenness of the electrode assembly.

[0021] Based on the first aspect, in some possible implementations, 1.4≤T1 / T2≤1.8, in order to further balance the poor adhesion of the thinned region, the improvement of lithium plating problem, and the thinned region without overpressure and the thickness uniformity of the electrode assembly.

[0022] Based on the first aspect, in some possible implementations, along the second direction, the width of the thinned region is W1, where 1mm≤W1≤10mm.

[0023] Based on the first aspect, in some possible implementations, the electrode assembly further includes electrode terminals extending in a second direction, with the thinned region extending along the second direction to the edge of the electrode sheet.

[0024] A second aspect of this application provides an electrical device including any of the batteries described above. Attached Figure Description

[0025] Figure 1 is a schematic diagram of a battery provided in one embodiment of this application, viewed along a first direction.

[0026] Figure 2 is a cross-sectional view of the battery shown in Figure 1 along AA.

[0027] Figure 3 is a partial schematic diagram of a multilayer electrode sheet with adhesive provided according to an embodiment of this application.

[0028] Figure 4 is a partial schematic diagram of a multilayer electrode sheet provided with an adhesive element according to another embodiment of this application.

[0029] Figure 5 is a schematic diagram of an electrode assembly with adhesive provided according to an embodiment of this application, viewed along a first direction.

[0030] Figure 6 is a schematic diagram of an electrode assembly with adhesive provided according to another embodiment of this application, viewed along a first direction.

[0031] Figure 7 is a partial schematic diagram of an electrode assembly with an adhesive provided according to another embodiment of this application.

[0032] Figure 8 is a schematic diagram of an electrical device provided in one embodiment of this application.

[0033] Key Component Symbols: Battery 100, Casing 10, Electrode Assembly 20, Electrode Terminal 30, Electrode 21, Main Body Region 21A, Thinning Region 21B, First Gap G1, Second Gap G2, First Surface 22, First Region 22B, Second Region 22A, First Adhesive 41, First Substrate 411, First Adhesive Layer 412, Second Adhesive 421, Second Adhesive Layer 422, Third Adhesive Layer 423, First Edge 41A, Second Edge 41B, Third Edge 42A, Fourth Edge 42B, Fifth Edge 20A, Sixth Edge 20B, Seventh Edge 41C, Eighth Edge 41D, Ninth Edge 42C, Tenth Edge 42D, Positive Electrode 220, Positive Current Collector 221, Positive Active Material Layer 222, Negative Electrode 210, Negative Current Collector 211, Negative Active Material Layer 212, Separator 230, Electrical Equipment 1, First Direction Z, Second Direction X, Third Direction Y.

[0034] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0035] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0036] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to provide a thorough and detailed understanding of this application to those skilled in the art.

[0037] Additionally, for brevity and clarity, the dimensions or thicknesses of various components and layers may be enlarged in the accompanying drawings. Throughout the text, the same numerical values ​​refer to the same elements. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more of the associated enumerated items. Furthermore, it should be understood that when element A is referred to as "connecting" element B, or when element A is referred to as "attached" to element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0038] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".

[0039] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0040] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, the first element, component, region, layer, or portion discussed below may be referred to as the second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0041] Referring to Figures 1 and 2, one embodiment of this application provides a battery 100, including a housing 10, an electrode assembly 20, and electrode terminals 30. The electrode assembly 20 is housed within the housing 10, and the electrode terminals 30 are connected to the electrode assembly 20 and extend from one side of the housing 10 along a second direction X to connect to external components. In this application, the second direction X refers to the longitudinal direction of the electrode assembly 20. In this embodiment, there are two electrode terminals 30, designated as a positive terminal and a negative terminal, and both electrode terminals 30 are located on the same side of the battery 100 in the second direction X. In other embodiments, the number of electrode terminals 30 may be greater than two, and multiple electrode terminals 30 may be located on different sides of the battery 100.

[0042] Referring to Figure 3, the electrode assembly 20 includes multiple layers of electrode sheets 21 stacked along a first direction Z. In this application, the first direction Z is the thickness direction of the electrode sheet 21, and the first direction Z is perpendicular to the second direction X. The electrode sheet 21 includes a current collector and an active material layer. The active material layer is disposed on at least one surface of the current collector and includes a main region 21A and a thinned region 21B. The thinned region 21B is connected to the main region 21A and located at at least one edge of the main region 21A. In some embodiments, the main region 21A and the thinned region 21B are sequentially disposed along the second direction X. In the first direction Z, the average thickness T4 of the thinned region 21B is less than the average thickness T3 of the main region 21A, and the first gap G1 between the thinned regions 21B of two adjacent electrode sheets 21 is greater than the second gap G2 between the main regions 21A. In some embodiments, the main regions 21A have the same thickness, and the thickness of the thinned regions 21B decreases sequentially from the main region 21A along the second direction X. In some implementations, the minimum thickness of the main body region 21A is greater than the maximum thickness of the thinned region 21B.

[0043] Referring to Figures 2 and 3, the electrode assembly 20 includes a first surface 22 facing the housing 10, and the battery 100 includes an adhesive 40 that bonds the first surface 22 and the housing 10. The area of ​​the first surface 22 that overlaps with the thinned region 21B in the first direction Z is designated as a first region 22B. The adhesive 40 includes a first adhesive 41. Along the first direction Z, the first adhesive 41 at least partially overlaps with the first region 22B.

[0044] The first adhesive component 41 includes a first substrate 411 and a first adhesive layer 412 stacked along the first direction Z. Along the first direction Z, the surface of the first substrate 411 away from the first adhesive layer 412 covers a portion of the first surface 22, and the surface of the first adhesive layer 412 away from the first substrate 411 adheres to a portion of the housing 10. When the first adhesive layer 412 generates a tensile force with the housing 10 due to its adhesiveness, this tensile force is less likely to directly act on the first region 22B through the first substrate 411, increasing the first gap G1 between the thinned regions 21B. This improves the lithium plating in the thinned region 21B and the deterioration of electrode adhesion caused by the increased first gap G1, thereby improving the cycle performance of the battery.

[0045] When the first adhesive layer 412 is bonded to a portion of the housing 10 on the surface of the first substrate 411 away from the first adhesive layer 412, the surface of the first substrate 411 away from the first adhesive layer 412 may or may not be bonded to the portion of the first surface 22 it covers. In some embodiments, the first substrate 411 includes an adhesive to make the first substrate 411 tacky, thereby enabling the first substrate 411 to bond to the first surface 22. The adhesive includes, but is not limited to, one or more of rubber-based adhesives, silicone-based adhesives, water-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, and polyimide-based adhesives.

[0046] In some embodiments, along the first direction Z, the bonding force between the surface of the first substrate 411 away from the first adhesive layer 412 and a portion of the first surface 22 is F1, and the bonding force between the surface of the first adhesive layer 412 away from the first substrate 411 and a portion of the shell 10 is F2, where 0 ≤ F1 ≤ 0.01 N / mm and 0.1 N / mm ≤ F2 ≤ 1 N / mm. When F1 and F2 are within the above ranges, it is beneficial to prevent the tensile force generated between the first adhesive layer 412 and the shell 10 from directly acting on the first region 22B through the first substrate 411, thereby increasing the first gap G1 between the thinned regions 21B and improving the lithium plating problem in the thinned regions 21B.

[0047] Referring to Figure 4, in another embodiment, along the first direction Z, the first adhesive layer 412 is bonded to the first surface 22 away from the surface of the first substrate 411, and the first substrate 411 is covered by the housing 10 away from the surface of the first adhesive layer 412. When the adhesive member 40 generates a tensile force with the housing 10 due to its adhesiveness, this tensile force is less likely to directly act on the first region 22B through the first adhesive layer 412, thereby increasing the first gap G1 between the thinned regions 21B, improving lithium plating in the thinned region 21B caused by the increase in the first gap G1, and improving cycle performance.

[0048] When the first adhesive layer 412 is bonded to the first surface 22 on the surface of the first substrate 411 away from the first adhesive layer 412, the surface of the first substrate 411 away from the first adhesive layer 412 may or may not be bonded to the portion of the housing 10 it covers. In some embodiments, the first substrate 411 includes an adhesive to make the first substrate 411 tacky, thereby bonding the first substrate 411 to the housing 10. The adhesive includes, but is not limited to, one or more of rubber-based adhesives, silicone-based adhesives, water-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, and polyimide-based adhesives.

[0049] In some embodiments, along the first direction Z, the adhesive force between the surface of the first substrate 411 away from the first adhesive layer 412 and a portion of the housing 10 is F1, and the adhesive force between the surface of the first adhesive layer 412 away from the first substrate 411 and a portion of the first surface 22 is F2, where 0 ≤ F1 ≤ 0.01 N / mm and 0.1 N / mm ≤ F2 ≤ 1 N / mm. When F1 and F2 are within the above ranges, it is beneficial to prevent the tensile force generated between the adhesive member 40 and the housing 10 from directly acting on the first region 22B through the first adhesive layer 412, thereby increasing the first gap G1 between the thinned regions 21B.

[0050] In some embodiments, the material of the first substrate 411 includes one or more of polyethylene terephthalate, polyimide, polyethylene, polypropylene, polyvinyl chloride, kraft paper, cotton cloth, synthetic fiber cloth, metal foil, and glass fiber. In some embodiments, the material of the first adhesive layer 412 includes one or more of rubber-based adhesives, silicone-based adhesives, hot melt adhesives, water-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, and polyimide-based adhesives.

[0051] In some embodiments, the casing 10 can be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), an aluminum-plastic film, or a steel-plastic film, etc. It is understood that when the casing 10 is an aluminum-plastic film or a steel-plastic film, and the first substrate 411 is selected from the aforementioned polymers, the hot-pressing temperature during the hot-pressing formation process is lower than the melting temperature of the polymer in the casing 10 and the first substrate 411, so that the first substrate 411 in the resulting battery 100 will not adhere to the casing 10.

[0052] Referring to Figure 3, along the second direction X, the width of the area where the first adhesive 41 overlaps with the first region 22B is W, and the width of the thinned region 21B is W1. In some embodiments, 0.7 ≤ W / W1 ≤ 1.1. When W / W1 is within the above range, it is beneficial to improve the consistency of the thickness of the thinned region 21B in the second direction X, reduce the risk of undervoltage problems during hot pressing formation of the thinned region 21B, reduce the risk of lithium plating, and improve cycle performance; it is also beneficial to improve the consistency of the thickness of the thinned region 21B and the main body region 21A in the second direction X, reduce the risk of overvoltage problems during hot pressing formation of the main body region 21A, and reduce the risk of lithium plating; and the first adhesive 41 has suitable adhesion to the electrode assembly 20 or the housing 10, improving the battery's drop resistance. When W / W1 < 0.7, the first adhesive 41 is too narrow along the second direction X, resulting in poor thickness consistency of the thinned region 21B along the second direction X, which easily leads to undervoltage problems and lithium plating. Furthermore, the adhesion between the first adhesive 41 and the electrode assembly 20 or the housing 10 is insufficient, affecting drop performance. When W / W1 > 1.1, the first adhesive 41 is too wide along the second direction X, overlapping with the main body region 21A. The thickness of the main body region 21A and the thinned region 21B are inconsistent, making the main body region 21A prone to overvoltage and lithium plating. Moreover, the excessively wide first adhesive 41 results in insufficient adhesion between the adhesive 40 as a whole and the electrode assembly 20 and the housing 10, affecting the battery's drop resistance.

[0053] In some implementations, 0.8 ≤ W / W1 ≤ 1.0 is more effective in reducing lithium plating and improving drop performance.

[0054] In some embodiments, the width W1 of the thinned region 21B along the second direction X is 1 mm to 10 mm. For example, W1 is a range of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any two of these values.

[0055] Referring to Figures 2 and 3, the area where the first surface 22 overlaps with the main body region 21A in the first direction Z is the second region 22A. In some embodiments, the adhesive 40 includes a second adhesive 42. Along the first direction Z, the second adhesive 42 at least partially overlaps with the second region 22A. The second adhesive 42 includes a second substrate 421, a second adhesive layer 422, and a third adhesive layer 423 stacked along the first direction Z, with the second adhesive layer 422 and the third adhesive layer 423 disposed on two opposite surfaces of the second substrate 421 along the first direction Z. Along the first direction Z, the second adhesive layer 422 adheres to the surface of the housing 10 away from the second substrate 421, and the third adhesive layer adheres to the first surface of the housing away from the surface of the second substrate 421.

[0056] In some embodiments, the second substrate 421 comprises one or more of polyethylene terephthalate, polyimide, polyethylene, polypropylene, polyvinyl chloride, kraft paper, cotton cloth, synthetic fiber cloth, metal foil, and glass fiber. In some embodiments, the second adhesive layer 422 and the third adhesive layer 423 each comprise one or more of rubber-based adhesives, silicone-based adhesives, hot melt adhesives, water-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, and polyimide-based adhesives.

[0057] Referring to Figure 5, the projection area of ​​the first adhesive member 41 along the first direction Z includes a first edge 41A and a second edge 41B arranged opposite each other along the third direction Y. The projection area of ​​the second adhesive member 42 along the first direction Z includes a third edge 42A and a fourth edge 42B arranged opposite each other along the third direction Y. The projection area of ​​the electrode assembly 20 along the first direction Z includes a fifth edge 20A and a sixth edge 20B arranged opposite each other along the third direction Y. The third direction Y is perpendicular to both the first direction Z and the second direction X, and the third direction Y is the width direction of the electrode assembly 20. The first edge 41A, the third edge 42A, and the fifth edge 20A are located on the same side of the electrode assembly 20 in the third direction Y, and the second edge 41B, the fourth edge 42B, and the sixth edge 20B are located on the other side of the electrode assembly 20 in the third direction Y. The straight-line distance between the first edge 41A and the fifth edge 20A along the third direction Y is L1; the straight-line distance between the second edge 41B and the sixth edge 20B along the third direction Y is L2; ​​the straight-line distance between the third edge 42A and the fifth edge 20A along the third direction Y is L3; and the straight-line distance between the fourth edge 42B and the sixth edge 20B along the third direction Y is L4.

[0058] In some embodiments, 0≤|L1-L2|≤4mm. When the absolute value of the difference between L1 and L2 is within the above range, the first adhesive 41 tends to be located in the middle position of the electrode assembly 20 in the third direction Y, which is beneficial to make the stress applied by the housing 10 to the first adhesive 41 uniformly distributed and improve the drop resistance performance.

[0059] In some embodiments, 0 ≤ |L3-L4| ≤ 4 mm. When the absolute value of the difference between L3 and L4 is within the above range, the second adhesive 42 tends to be located in the middle position of the electrode assembly 20 in the third direction Y, which is beneficial to make the stress applied by the housing 10 to the second adhesive 42 uniformly distributed and improve the drop resistance.

[0060] Along the third direction Y, the length of the first adhesive member 41 is W2, the length of the second adhesive member 42 is W3, and the width of the projection area of ​​the electrode assembly 20 along the first direction Z in the third direction Y is W4. In some embodiments, 0.5 ≤ W2 / W4 ≤ 1. When W2 and W4 are within the above range, the first adhesive member 41 has a suitable adhesive force with the electrode assembly 20 or the housing 10, improving drop performance; and it is beneficial to improve the consistency of the thickness of the thinned region 21B in the third direction Y, reducing the risk of undervoltage problems during hot pressing formation of the thinned region 21B, and reducing the risk of lithium plating. When W2 / W4 < 0.5, the first adhesive member 41 is too narrow along the third direction Y, the consistency of the thickness of the thinned region 21B in the third direction Y is poor, and undervoltage problems are prone to occur, causing lithium plating. When W2 / W4 > 1, the first adhesive 41 is too wide along the third direction Y. When the first adhesive 41 is bonded to the electrode assembly 20, air bubbles may be generated, affecting the bonding effect and drop performance.

[0061] In some implementations, 0.6 ≤ W2 / W4 ≤ 0.8 improves lithium plating and drop performance even more.

[0062] In some embodiments, 0.5 ≤ W3 / W4 ≤ 1. When W3 and W4 are within the above range, the second adhesive 41 has suitable adhesion to the electrode assembly 20 or the housing 10, improving drop performance; and it helps to ensure the consistency of the thickness of the main body region 21A in the third direction Y, reducing the risk of undervoltage problems during hot pressing formation of the main body region 21A and reducing the risk of lithium plating. When W2 / W4 < 0.5, the second adhesive 42 is too narrow along the third direction Y, and the consistency of the thickness of the thinned region 21B along the third direction Y is poor, which easily leads to undervoltage problems and causes lithium plating. When W2 / W4 > 1, the second adhesive 42 is too wide along the third direction Y, and air bubbles may be generated when the second adhesive 42 is bonded to the electrode assembly 20 or the housing 10, affecting the bonding effect and drop performance.

[0063] In some implementations, 0.6 ≤ W3 / W4 ≤ 0.8 improves lithium plating and drop performance even more.

[0064] In some embodiments, W2 > W3. Since the thinned region 21B has a smaller width in the second direction X, the first adhesive 41 covering the thinned region 21B is less likely to generate air bubbles when it is bonded to the electrode assembly 20 or the housing 10. Therefore, the width of the first adhesive 41 in the third direction Y can be designed to be greater than the width of the second adhesive 42 in the third direction Y.

[0065] Referring to Figure 5, in some embodiments, the first adhesive member 41 and the second adhesive member 42 are separately disposed. Along the second direction X, the first adhesive member 41 and the second adhesive member 42 are adjacent to or separate from each other.

[0066] Along the second direction X, the first adhesive member 41 includes a seventh edge 41C and an eighth edge 41D disposed opposite to each other, and the second adhesive member 42 includes a ninth edge 42C and a tenth edge 42D disposed opposite to each other. The seventh edge 41C and the ninth edge 42C are located on the same side of the electrode assembly 20 in the second direction X, and the eighth edge 41D and the tenth edge 42D are located on the other side of the electrode assembly 20 in the second direction X. The straight-line distance between the eighth edge 41D and the ninth edge 42C along the second direction X is L5. In some embodiments, 0 ≤ L5 ≤ 5 mm. When L5 is within the above range, the risk of overlap between the first adhesive member 41 and the second adhesive member 42 can be reduced, thereby reducing the risk of overpressure due to overlap; and the area covered by the adhesive member 40 on the electrode assembly 20 is large enough to improve drop performance.

[0067] Please refer to Figure 6. In some embodiments, the first adhesive 41 and the second adhesive 42 are integrally formed for easy processing.

[0068] Referring to Figure 7, in some embodiments, the thickness of the first adhesive 41 is greater than the thickness of the second adhesive 42 in the first direction Z. During hot pressing formation, the thickness of the first adhesive 41 exceeding that of the second adhesive 42 can be used to compensate for the thickness of the thinned region 21B, thereby reducing the gap G1 between the thinned regions 21B and improving the lithium plating problem.

[0069] In some embodiments, in the first direction Z, the thickness of the first substrate 411 is greater than the thickness of the second substrate 421, so that the thickness of the first adhesive 41 is greater than the thickness of the second adhesive 42.

[0070] In some embodiments, in the first direction Z, the thickness of the first adhesive layer 412 is greater than the total thickness of the second adhesive layer 422 and the third adhesive layer 423, so that the thickness of the first adhesive member 41 is greater than the thickness of the second adhesive member 42.

[0071] Referring to Figure 4, in some embodiments, the multilayer electrode 21 includes alternating layers of positive electrode 220 and negative electrode 210. The positive electrode 220 includes a positive current collector 221 and a positive active material layer 222 disposed on at least one surface of the positive current collector 221. The negative electrode 210 includes a negative current collector 211 and a negative active material layer 212 disposed on at least one surface of the negative current collector 211. During the process of coating the active material layer slurry to form the active material layer, at the boundary between the active material layer slurry and the empty foil area of ​​the current collector, as the active material layer slurry flows towards the edge of the current collector, the volume and flow rate of the active material layer slurry gradually decrease, thereby forming a thinning region 21B.

[0072] In some embodiments, the two outermost layers of the multilayer electrode 21 in the first direction Z are provided with an active material layer on one side, that is, one side of the electrode is provided with an active material layer; the remaining electrodes are provided with active material layers on both sides, that is, the two opposite sides of the electrode along the first direction Z are provided with active material layers.

[0073] In the first direction Z, the thickness of the first adhesive 41 is T1, and the thickness of the second adhesive 42 is T2. In some embodiments, 1.1 ≤ T1 / T2 ≤ 2, and further, 1.4 ≤ T1 / T2 ≤ 1.8. When T1 and T2 satisfy the above proportional relationship, the thickness of the first adhesive 41 exceeding that of the second adhesive 42 can compensate for the overall thickness difference of the thinned region 21B, thereby reducing the gap G1 between each thinned region 21B, improving the lithium plating effect, and reducing the problems of overvoltage in the thinned region and poor overall thickness uniformity of the electrode assembly caused by excessive difference between T1 and T2. Generally, T1 ranges from 27.5 μm to 70 μm, and T2 ranges from 25 μm to 35 μm.

[0074] In some embodiments, the positive current collector 221 may be a metal foil or a composite current collector. For example, as a metal foil, it may be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0075] In some embodiments, the positive electrode active material layer 222 may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active material layers of batteries may also be used. These positive electrode active material layers may use only one type or a combination of two or more types. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds.

[0076] In some embodiments, the negative electrode current collector 211 may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it may be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0077] In some embodiments, the negative electrode active material layer 212 may employ a negative electrode active material layer for batteries known in the art. As an example, the negative electrode active material layer may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active material layers for batteries may also be used. These negative electrode active material layers may be used alone or in combination of two or more.

[0078] Referring to Figure 4, in some embodiments, the electrode assembly 20 includes a separator 230 disposed between the positive electrode 220 and the negative electrode 210. The separator 230 can be any known porous separator with good chemical and mechanical stability.

[0079] In some embodiments, the electrode assembly 20 is a stacked structure. The positive electrode 220, the separator 230, and the negative electrode 210 are stacked sequentially to form the stacked structure.

[0080] In some embodiments, the electrode assembly 20 is a wound structure. The positive electrode 220, the separator 230, and the negative electrode 210 are stacked in sequence and then wound to form a wound structure.

[0081] In some embodiments, the battery 100 includes an electrolyte that acts as a conductor of ions between the positive electrode 220 and the negative electrode 210. The electrolyte can be liquid or solid. Liquid electrolytes include an electrolyte salt and a solvent, while solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0082] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0083] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0084] In some embodiments, the polymer solid electrolyte can be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymer, polyionic liquid-lithium salt, cellulose, etc.

[0085] In some embodiments, the inorganic solid electrolyte may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0086] In some embodiments, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to a polymer solid electrolyte.

[0087] In some embodiments, the electrode assembly 20 may be cylindrical, flat, polygonal, or square in shape.

[0088] Please refer to Figure 8. One embodiment of this application also provides an electrical device 1, including any of the batteries 100 described above. The electrical device of this application may be, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0089] The performance of the battery provided in this application will be described below through specific embodiments and comparative examples.

[0090] Example 1-1

[0091] Preparation of the positive electrode sheet: Positive active material (lithium cobalt oxide), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) are dissolved in an N-methylpyrrolidone solution at a weight ratio of 97.5:1:1.5 to form a positive active material slurry with a solid content of 75 wt%. Using aluminum foil as a current collector, the positive active material slurry is coated onto the surface of the current collector to obtain the positive active material layer. Subsequently, it is cold-pressed and cut to obtain the positive electrode sheet.

[0092] Preparation of the negative electrode sheet: The negative electrode active material (graphite), conductive agent (conductive carbon black), thickener (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) are mixed in a mass ratio of 97.5:1:0.5:1. Deionized water is then added as a solvent, and the mixture is stirred until homogeneous, resulting in a negative electrode active material slurry with a solid content of 50 wt%. Copper foil is used as the current collector, and the negative electrode active material slurry is coated onto the surface of the current collector to obtain the negative electrode active material layer. Subsequently, the negative electrode sheet is obtained through cold pressing and cutting.

[0093] Preparation of the diaphragm: Polyethylene film was selected as the diaphragm.

[0094] Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propylene propionate (PP), and vinylene carbonate (VC) were mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 and the organic solvent were mixed in a weight ratio of 8:92 to obtain the electrolyte.

[0095] The preparation of a lithium-ion battery involves stacking a positive electrode, a separator, and a negative electrode in sequence, with the separator positioned between the positive and negative electrodes to obtain an electrode assembly. An adhesive is then bonded to the first surface of the electrode assembly. This adhesive includes a first adhesive and a second adhesive, where the projection of the first adhesive along a first direction lies within a first region, and the projection of the second adhesive along the first direction lies within a second region. The electrode assembly is placed in an aluminum-plastic film packaging bag and hot-pressed under a preset pressure. After electrolyte injection and formation, a lithium-ion battery is obtained. The first adhesive layer bonds to the casing.

[0096] Examples 1-2

[0097] The difference from Embodiment 1-1 is that the first adhesive layer adheres to the electrode assembly.

[0098] Comparative Example 1

[0099] The difference from Embodiment 1-1 is that the first adhesive also includes a second adhesive layer, which adheres to the electrode assembly.

[0100] Examples 2-1 to 2-18

[0101] The difference from Example 1-1 is that at least one of W / W1, W2 / W3, W2 / W4, and W3 / W4 is different.

[0102] Examples 3-1 to 3-9

[0103] The difference from Example 1-1 is that at least one of L1-L2, L3-L4, and L5 is different.

[0104] Examples 4-1 to 4-8

[0105] The difference from Example 1-1 is that the values ​​of T1 / T2 are different.

[0106] The test methods for each parameter of this application are described below.

[0107] (1) Thickness test:

[0108] Delineation of the thinning region and the main region: The thickness of the middle part of the electrode is measured using an offline laser instrument. Then, starting from the first test point, the thickness of the electrode is measured every 0.5 mm along the second direction towards the edge of the electrode. When the thickness difference between two adjacent tests is greater than or equal to 0.01 mm, this point is defined as the boundary between the main region and the thinning region. A straight line extending along the third direction through this point is the boundary line between the main region and the thinning region.

[0109] In the embodiments and comparative examples of this application, the thickness of multiple points on the outermost electrode of the electrode assembly is measured to confirm the location of the thinned area and the main area of ​​the outermost electrode, wherein the outermost electrode is a positive electrode with a single-sided coating of active material layer.

[0110] Disassemble the battery, take the positive or negative electrode sheet, select three points in the thinned area from the direction of the thinned area toward the main area, use a laser thickness gauge to measure the thickness of the active material layer at the three points, and take the average value to obtain the average thickness of the thinned area.

[0111] Disassemble the secondary battery, take the positive or negative electrode sheet, select five points in the main body area away from the thinning area, use a laser thickness gauge to measure the thickness of the active material layer at these five points, and take the average value to obtain the average thickness of the main body area.

[0112] In the embodiments and comparative examples of this application, the thickness of the thinned region and the main region of the outermost electrode of the electrode assembly are measured using the above method, wherein the outermost electrode is a positive electrode with a single-sided coating of active material layer.

[0113] Disassemble the secondary battery, remove the adhesive components, and use a laser thickness gauge to measure the thickness of the first and second adhesive components.

[0114] (2) Adhesion test:

[0115] Disassemble the battery, removing the packaging bag, adhesive components, and the electrodes bonded to them as a single unit. Cut the assembly into 25mm x 25mm strips. Using a peel tester, fix the sample in a fixture and slowly peel off the adhesive components, measuring the force required for peeling. The peeling speed was 50mm / min, and the peeling angle was 180°. Calculate the average peel force, converting it to adhesive force based on the sample width, denoted as F, in N / mm.

[0116] (3) Cyclic capacity retention test:

[0117] At 25°C, charge the lithium-ion battery according to the following charging steps:

[0118] (1) Constant current at 1.65C to 4.10V, constant voltage at 1.55C to cutoff;

[0119] (2) Constant current at 1.55C to 4.20V, constant voltage at 1.4C to cutoff;

[0120] (3) Constant current at 1.4C to 4.24V, constant voltage at 1.1C to cutoff;

[0121] (4) Constant current at 1.1C to 4.27V, constant voltage at 0.7C to cutoff;

[0122] (5) Maintain constant current at 0.7C to 4.30V, and constant voltage at 0.4C to cut off;

[0123] (6) Maintain a constant current of 0.4C to 4.5V, and a constant voltage to C / 40 cutoff.

[0124] The above charge-discharge process constitutes one cycle. Record the discharge capacity after the first cycle as the initial discharge capacity. Repeat the above charge-discharge process 1000 times, and record the discharge capacity after 1000 cycles as the final discharge capacity. Capacity retention rate = (Final discharge capacity / Initial discharge capacity) × 100%.

[0125] (4) Lithium plating test:

[0126] After repeating the above charging and discharging process for 1000 cycles, the battery was disassembled in a fully charged state to obtain the negative electrode sheet adjacent to the outermost single-sided positive electrode. The presence or absence of lithium plating at the interface of the thinned region of the negative electrode sheet and the proportion of the area of ​​the lithium plating region to the area of ​​the thinned region of the negative electrode sheet were observed; and the proportion of the area of ​​the lithium plating region to the area of ​​the main body region of the negative electrode sheet was also observed.

[0127] The severity of lithium deposition is assessed by the ratio of the area of ​​the lithium-deposited region to the area of ​​the thinned region of the negative electrode sheet, or the ratio of the area of ​​the lithium-deposited region to the area of ​​the main region of the negative electrode sheet. Specifically: no lithium deposition: lithium-deposited area equals 0; slight lithium deposition: 0 < lithium-deposited area / thinned region area or main region area ≤ 5%; moderate lithium deposition: 5% < lithium-deposited area / thinned region area or main region area ≤ 15%; severe lithium deposition: lithium-deposited area / thinned region area or main region area > 15%.

[0128] (5) Drop test:

[0129] Lithium-ion batteries were pretreated at 25°C and left to stand at room temperature for 60 minutes before the drop test. The batteries were then placed in a clamp and dropped freely from a height of 1.5m using a drop tester in the following sequence: head-tail-head right corner-tail right corner-head left corner-tail left corner (angle: 45±15°), repeated 6 times. The battery voltage was measured and recorded after each drop. The appearance of the batteries was inspected and photographed before and after the test. The drop test pass criteria were: no smoke, no leakage, and voltage drop <30mV. The voltage drop was measured using an internal resistance meter, comparing the battery voltage before and after the drop. Twenty samples were taken from each group for the drop test. The drop pass rate was calculated as the number of samples that passed the drop test / 20.

[0130] Table 1

[0131] As can be seen from the experimental data of Examples 1-1 and Comparative Example 1 in Table 1, setting the first adhesive in at least part of the first region can reduce the risk of increased spacing and poor adhesion between the outermost electrode and the adjacent separator caused by the thinning region being stretched, compared with the solution of setting adhesive layers on both layers of the substrate in the prior art. This can reduce the degree of lithium plating in the thinning region and improve the cycle performance of the battery.

[0132] Table 2

[0133] A comparison of the experimental data from Examples 1-1 and 2-1 to 2-6 in Table 2 shows that when 0.7 ≤ W / W1 ≤ 1.1, the lithium plating area in the thinned region is relatively smaller, resulting in better battery cycle performance. When W / W1 < 0.7, the first adhesive does not cover the first region with sufficient area, leading to a larger gap between the thinned region of the outermost electrode and its adjacent separator, resulting in a larger lithium plating area in the thinned region, which negatively impacts battery cycle performance. When W / W1 > 1.1, the first adhesive covers part of the second region, increasing the risk of overvoltage in the main region. The second region also experiences increased lithium plating area due to poor electrolyte wetting, affecting the overall battery cycle performance. Furthermore, the excessively large area of ​​the first adhesive also negatively impacts the battery's drop resistance. To balance the degree of lithium plating in the thinned region, the degree of lithium plating in the main region, and the battery's drop resistance, it is necessary to limit the value to 0.7 ≤ W / W1 ≤ 1.1. More preferably, 0.8 ≤ W / W1 ≤ 1.0.

[0134] A comparison of experimental data from Examples 1-1 and 2-7 to 2-12 shows that when the ratio of the width W2 of the first adhesive component in the third direction to the width W4 of the electrode assembly in the third direction is 0.5 ≤ W2 / W4 ≤ 1, as the ratio of W2 / W4 increases, the coverage area of ​​the thinned region by the first adhesive component increases, the lithium plating area of ​​the thinned region gradually decreases, the cycle performance of the battery improves, and the drop resistance of the battery is improved. When W2 / W4 < 0.5, the thinned region is not sufficiently covered. The presence of a first adhesive layer covering the thinned area results in a large gap and poor adhesion between the thinned area and the adjacent separator, leading to a larger lithium plating area and thus affecting the overall cycle performance of the battery. Furthermore, if the area of ​​the first adhesive layer is too small, the battery's drop resistance is poor. When W2 / W4 > 1, the first adhesive layer extends beyond the width of the electrode assembly in the third direction, not only increasing the size of the electrode assembly in the width direction and affecting the battery's volumetric energy density, but also negatively impacting the battery's drop resistance to some extent. Therefore, a value of 0.5 ≤ W2 / W4 ≤ 1 is specified, and more preferably, 0.6 ≤ W2 / W4 ≤ 0.8.

[0135] A comparison of experimental data from Examples 1-1 and 2-13 to 2-18 shows that when the ratio of the width W3 of the second adhesive component in the third direction to the width W4 of the electrode assembly in the third direction is 0.5 ≤ W3 / W4 ≤ 1, as the W3 / W4 ratio increases, the coverage area of ​​the second adhesive component over the main body region increases, reducing the risk of undervoltage in the main body region. The lithium plating area in the main body region gradually decreases, the cycle performance of the battery improves, and the battery's drop resistance is improved. Moreover, compared to the first adhesive component, the second adhesive component is made of double-sided adhesive, and generally the coverage area of ​​the second adhesive component is larger than that of the first adhesive component. Therefore, W3 / W4 is more favorable than W2 / W4. W4 has a more significant impact on the battery's drop resistance. When W3 / W4 < 0.5, the main body area is not covered by a sufficiently large area of ​​the second adhesive, increasing the risk of undervoltage in the main body area and resulting in a larger lithium plating area, which in turn affects the overall cycle performance of the battery. Furthermore, if the area of ​​the second adhesive is too small, the electrode assembly is prone to shifting relative to the casing, leading to poor drop resistance. When W3 / W4 > 1, the second adhesive extends beyond the width of the electrode assembly in the third direction, not only increasing the size of the electrode assembly in the width direction and affecting the volumetric energy density of the battery, but also affecting the drop resistance to some extent due to the adhesive size exceeding the electrode assembly size. Therefore, 0.5 ≤ W3 / W4 ≤ 1 is limited, and more preferably 0.6 ≤ W3 / W4 ≤ 0.8.

[0136] Table 3

[0137] By comparing the experimental data of Examples 1-1 and 3-1 to 3-3 in Table 3, it can be seen that when 0≤|L1-L2|≤4mm, the deviation of the first adhesive member from the centerline of the electrode assembly in the third direction is not large, the lithium plating area of ​​the thinned region is relatively small, and the cycle performance of the battery is good. When |L1-L2|>4mm, the deviation of the first adhesive member from the centerline of the electrode assembly in the third direction is large, which easily makes the adhesion between the thinned region of the outermost electrode sheet and the adjacent separator worse and the spacing larger, thereby increasing the lithium plating area of ​​the thinned region and affecting the cycle performance of the battery.

[0138] A comparison of experimental data from Examples 1-1 and 3-4 to 3-6 shows that when 0 ≤ |L3-L4| ≤ 4 mm, the second adhesive component has a small deviation from the centerline of the electrode assembly in the third direction, resulting in a relatively small lithium plating area in the main body region and good battery cycle performance. When |L3-L4| > 4 mm, the second adhesive component has a large deviation from the centerline of the electrode assembly in the third direction, which easily leads to a decrease in the adhesion force and a larger gap between the main body region of the outermost electrode sheet and the adjacent separator, thereby increasing the lithium plating area in the main body region and affecting the battery cycle performance. Furthermore, the second adhesive component is not centered relative to the electrode assembly in the third direction, which easily leads to uneven stress on the electrode assembly in the third direction, thus affecting its drop resistance performance.

[0139] Table 4

[0140] A comparison of the experimental data from Examples 1-1, 4-1, and 4-2 in Table 4 shows that when the thickness T1 of the first adhesive is greater than the thickness T2 of the second adhesive, the improvement in the lithium plating area of ​​the thinned region is more significant. This is because the thickness of the first adhesive exceeding that of the second adhesive can compensate for the thickness of the thinned region, resulting in a smaller gap between the thinned regions and improving the lithium plating problem. A comparison of the experimental data from Examples 1-1 and 4-3 to 4-8 shows that when 1.1 ≤ T1 / T2 ≤ 2, the lithium plating area of ​​the thinned region is smaller, and the battery cycle performance is better; furthermore, 1.4 ≤ T1 / T2 ≤ 1.8 is preferred. When T1 / T2 ≥ 2, the lithium plating area of ​​the thinned region shows an increasing trend. This is because the difference between the thickness of the first adhesive and the thickness of the second adhesive is large, leading to overpressure in the thinned region, making electrolyte wetting difficult, thus increasing the lithium plating area and decreasing the battery cycle performance.

[0141] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. A battery, characterized in that, include: case; An electrode assembly is housed within the housing. The electrode assembly includes multiple layers of electrode sheets stacked along a first direction, which is the thickness direction of the electrode sheets. Each electrode sheet includes a current collector and an active material layer, the active material layer being disposed on at least one surface of the current collector. The active material layer includes a main region and a thinned region. In the first direction, the average thickness of the main region is T3, and the average thickness of the thinned region is T4, where T3 > T4. The electrode assembly includes a first surface facing the housing, and the region of the first surface that coincides with the thinned region in the first direction is a first region. as well as An adhesive for bonding the housing and the first surface, the adhesive comprising a first adhesive element along the first direction, the first adhesive element at least partially overlapping the first region, the first adhesive element comprising a first substrate and a first adhesive layer stacked along the first direction; Along the first direction, the surface of the first substrate away from the first adhesive layer covers a portion of the first surface, and the surface of the first adhesive layer away from the first substrate adheres to a portion of the housing; or, Along the first direction, the first adhesive layer adheres to a portion of the first surface away from the surface of the first substrate, and the surface of the first substrate away from the surface of the first adhesive layer covers a portion of the housing.

2. The battery as described in claim 1, characterized in that, The material of the first substrate includes one or more of polyethylene terephthalate, polyimide, polyethylene, polypropylene, polyvinyl chloride, kraft paper, cotton cloth, synthetic fiber cloth, metal foil, and glass fiber; the material of the first adhesive layer includes one or more of rubber-based adhesive, silicone-based adhesive, hot melt adhesive, water-based adhesive, polyurethane-based adhesive, epoxy-based adhesive, and polyimide-based adhesive.

3. The battery as described in claim 1, characterized in that, The electrode assembly further includes electrode terminals, the electrode terminals extending in a second direction, the second direction being perpendicular to the first direction; along the second direction, the width of the area where the first adhesive overlaps with the first region is W, and the width of the thinned region is W1, 0.7≤W / W1≤1.

1.

4. The battery as described in claim 3, characterized in that, 0.8≤W / W1≤1.

0.

5. The battery as described in claim 1, characterized in that, The area of ​​the first surface that coincides with the main body area in the first direction is the second region. The adhesive also includes a second adhesive. Along the first direction, the second adhesive at least partially overlaps with the second region. The second adhesive includes a second substrate, a second adhesive layer, and a third adhesive layer stacked along the first direction. The second adhesive layer and the third adhesive layer are disposed on two surfaces of the second substrate that are opposite to each other along the first direction. The surface of the second adhesive layer away from the second substrate is bonded to the housing, and the surface of the third adhesive layer away from the second substrate is bonded to the first surface.

6. The battery as described in claim 5, characterized in that, The electrode assembly further includes electrode terminals, the extension direction of which is a second direction, and a third direction perpendicular to both the first and second directions. Viewed from the first direction, the first adhesive member includes a first edge and a second edge disposed opposite to each other along the third direction; the second adhesive member includes a third edge and a fourth edge disposed opposite to each other along the third direction; the projection area of ​​the electrode assembly along the first direction includes a fifth edge and a sixth edge disposed opposite to each other along the third direction; along the third direction, the fifth edge, the first edge, the second edge, and the sixth edge are arranged sequentially; along the third direction, the fifth edge, the third edge, the fourth edge, and the sixth edge are arranged sequentially; the distance between the first edge and the fifth edge along the third direction is L1, the distance between the second edge and the sixth edge along the third direction is L2, the distance between the third edge and the fifth edge along the third direction is L3, and the distance between the fourth edge and the sixth edge along the third direction is L4; 0≤|L1-L2|≤4mm, and / or, 0≤|L3-L4|≤4mm.

7. The battery as described in claim 5, characterized in that, The electrode assembly further includes electrode terminals, the extension direction of which is a second direction, and a third direction is perpendicular to both the first direction and the second direction. Along the third direction, the length of the first adhesive is W2, the width of the second adhesive is W3, and the width of the projection area of ​​the electrode assembly along the first direction in the third direction is W4, 0.5≤W2 / W4≤1, and / or, 0.5≤W3 / W4≤1.

8. The battery as claimed in claim 7, characterized in that, 0.6≤W2 / W4≤0.8, and / or, 0.6≤W3 / W4≤0.

8.

9. The battery as described in claim 7 or 8, characterized in that, W2 > W3.

10. The battery as claimed in claim 5, characterized in that, The first adhesive and the second adhesive are integrally formed.

11. The battery as claimed in claim 5, characterized in that, The first adhesive and the second adhesive are separately disposed; the electrode assembly further includes an electrode terminal, the electrode terminal extending in a second direction, along the second direction, the first adhesive includes a seventh edge and an eighth edge disposed opposite to each other, and the second adhesive includes a ninth edge and a tenth edge disposed opposite to each other; Along the second direction, the seventh edge, the eighth edge, the ninth edge, and the tenth edge are arranged in sequence; the distance between the eighth edge and the ninth edge along the second direction is L5, 0≤L5≤5mm.

12. The battery as claimed in claim 5, characterized in that, In the first direction, the thickness of the first adhesive is greater than the thickness of the second adhesive.

13. The battery as claimed in claim 12, characterized in that, In the first direction, the thickness of the first substrate is greater than the thickness of the second substrate, or the thickness of the first adhesive layer is greater than the total thickness of the second adhesive layer and the third adhesive layer.

14. The battery as claimed in claim 12, characterized in that, In the first direction, the thickness of the first adhesive is T1, the thickness of the second adhesive is T2, and 1.1≤T1 / T2≤2.

15. The battery as claimed in claim 14, characterized in that, 1.4≤T1 / T2≤1.

8.

16. The battery as claimed in claim 1, characterized in that, The electrode assembly further includes an electrode terminal, the electrode terminal extending in a second direction, the second direction being perpendicular to the first direction; along the second direction, the width of the thinning region is W1, 1mm≤W1≤10mm.

17. The battery as claimed in claim 1, characterized in that, The electrode assembly further includes electrode terminals, the electrode terminals extending in a second direction, and the thinning region extending along the second direction to the edge of the electrode sheet.

18. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1-17.

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