Electrochemical device and electronic apparatus

Abstract

The invention provides an electrochemical device and electronic equipment, and relates to the technical field of electrochemical energy storage. The electrochemical device comprises an electrode assembly, a packaging bag, a tab and tab glue, the electrode assembly is contained in the packaging bag, the packaging bag comprises a sealing part, the tab is connected to the electrode assembly and extends out of the sealing part, the tab glue is arranged on the side wall of the tab in the circumferential direction, and the tab glue is in a closed type; the tab glue comprises a first glue layer, a second glue layer and a third glue layer which are sequentially connected from inside to outside, the inner side of the first glue layer is connected to the tab, and the outer side of the third glue layer is connected to the inner side of the sealing part; the relation among the melting point T1 of the first adhesive layer, the melting point T2 of the second adhesive layer and the melting point T3 of the third adhesive layer meets T1lt; t2lt; t3; wherein 130 DEG C < = T1 < = 150 DEG C, 160 DEG C < = T2 < = 180 DEG C, and 190 DEG C < = T3 < = 200 DEG C; and the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer is 110-210 microns along the thickness direction of the tab. The electrochemical device is high in safety performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical energy storage, in particular to an electrochemical device and an electronic device. BACKGROUND

[0002] At present, in the manufacturing process of electrochemical devices, the battery quality is greatly affected by the cell packaging, especially the top edge heat sealing of soft package cells, i.e. top sealing, which needs to seal the outer tab (with tab adhesive) with the packaging bag by heat sealing to isolate the inside of the cell from the outside, preventing external air and moisture from entering the cell; at the same time, preventing electrolyte from leaking to the outside of the cell.

[0003] However, due to the common use of a structure combining a strip-shaped metal conductive sheet and tab adhesive for the outer tab, during heat sealing, the adhesive overflows at the steps at both ends of the tab in the heat sealing area, making it a weak point of the packaging, which becomes a high-risk area of leakage during subsequent use of the cell. At the same time, if defective products occur during packaging, the resulting defective products can only be scrapped, greatly affecting the production effect. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provides an electrochemical device and an electronic device.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: In a first aspect, an electrochemical device is provided, comprising an electrode assembly, a packaging bag, a tab and a tab adhesive, the electrode assembly is contained in the packaging bag, the packaging bag comprises a sealing portion, the tab is connected to the electrode assembly and extends from the sealing portion, the tab adhesive is arranged on the side wall of the tab in the circumferential direction, the tab adhesive is in a closed type, the tab adhesive comprises a first adhesive layer, a second adhesive layer and a third adhesive layer connected in sequence from inside to outside, the inside of the first adhesive layer is connected to the tab, and the outside of the third adhesive layer is connected to the inside of the sealing portion; the relationship between the melting point T1 of the first adhesive layer, the melting point T2 of the second adhesive layer and the melting point T3 of the third adhesive layer satisfies T1 < T2 < T3; wherein 130℃ ≤ T1 ≤ 150℃, 160℃ ≤ T2 ≤ 180℃, and 190℃ ≤ T3 ≤ 200℃; In the thickness direction of the tab, the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer is 110-210μm.

[0006] In some embodiments, in the thickness direction of the tab, the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer is 135-185μm.

[0007] In some embodiments, along the thickness direction of the tab, the thickness percentage of the first adhesive layer is 20-30%, the thickness percentage of the second adhesive layer is 40-50%, and the thickness percentage of the third adhesive layer is 20-30%, based on the sum of the thicknesses of the first, second, and third adhesive layers.

[0008] In some embodiments, the tab adhesive comprises a first side portion and a second side portion, which are connected between the top portion and the bottom portion and are disposed on both sides of the tab along the width direction of the tab.

[0009] In some embodiments, along the width direction of the tab, the first and second side portions comprise a fourth adhesive layer and a fifth adhesive layer stacked in sequence; along the thickness direction of the tab, both ends of the fourth adhesive layer are in contact with the first adhesive layer and at least part of the second adhesive layer; both ends of the fifth adhesive layer are in contact with at least part of the second adhesive layer and the third adhesive layer; the first, second, third, fourth, and fifth adhesive layers form a ring structure; the relationship between the melting point T4 of the fourth adhesive layer and the melting point T5 of the fifth adhesive layer satisfies T4>T5, wherein 180℃≤T4≤200℃ and 160℃≤T5<180℃.

[0010] In some embodiments, the thickness percentage of the fourth adhesive layer is 40-50% and the thickness percentage of the fifth adhesive layer is 50-60%, based on the sum of the thicknesses of the fourth and fifth adhesive layers.

[0011] In some embodiments, along the width direction of the tab, the first and second side portions comprise a fourth adhesive layer, a fifth adhesive layer, and a sixth adhesive layer stacked in sequence; along the thickness direction of the tab, both ends of the fourth adhesive layer are in contact with the first adhesive layer; both ends of the fifth adhesive layer are in contact with the second adhesive layer, and both ends of the sixth adhesive layer are in contact with the third adhesive layer; the first, second, third, fourth, fifth, and sixth adhesive layers form a ring structure; the relationship between the melting point T4 of the fourth adhesive layer, the melting point T5 of the fifth adhesive layer, and the melting point T6 of the sixth adhesive layer satisfies T4>T5>T6, wherein 180℃≤T4≤200℃, 160℃≤T5<180℃, and 130℃≤T6≤150℃.

[0012] In some embodiments, the thickness percentage of the fourth adhesive layer is 25-35%, the thickness percentage of the fifth adhesive layer is 30-40%, and the thickness percentage of the sixth adhesive layer is 25-35%, based on the sum of the thicknesses of the fourth, fifth, and sixth adhesive layers.

[0013] In some embodiments, the fourth adhesive layer comprises polyethylene and silica, the mass percentage of the silica is 3-6% based on the mass of the fourth adhesive layer.

[0014] In some embodiments, the fifth adhesive layer comprises polypropylene and glass microbeads, the mass percentage of the glass microbeads is 8-12% based on the mass of the fifth adhesive layer.

[0015] In some embodiments, the sixth adhesive layer comprises polyethylene and talcum powder, the mass percentage of the talcum powder is 4-7% based on the mass of the sixth adhesive layer.

[0016] In some embodiments, the tab adhesive comprises a top portion and a bottom portion, the top portion and the bottom portion are oppositely arranged in the extending direction of the tab, the top portion is located outside the sealing portion, and the bottom portion is located inside the packaging bag; the length of the top portion protruding out of the sealing portion is 1.5-3mm, and the length of the bottom portion protruding out of the sealing portion is 0.8-2mm.

[0017] In some embodiments, the third adhesive layer comprises polypropylene, polytetrafluoroethylene and phase change microcapsules, the mass percentage of the polytetrafluoroethylene is 15-20% and the mass percentage of the phase change microcapsules is 5-8% based on the mass of the third adhesive layer.

[0018] In some embodiments, the second adhesive layer comprises polypropylene, polyethylene and graphene, the mass percentage of the polyethylene is 20-40% and the mass percentage of the graphene is 3-5% based on the mass of the second adhesive layer.

[0019] In some embodiments, the first adhesive layer comprises polyethylene and calcium carbonate, the mass percentage of the calcium carbonate is 2-4% based on the mass of the first adhesive layer.

[0020] In a second aspect, an electronic device is provided, comprising the electrochemical device.

[0021] Compared with the prior art, the application has the following beneficial effects: The application controls the melting points of the first glue layer, the second glue layer and the third glue layer in the tab glue, and the sum of the thicknesses of the first glue layer, the second glue layer and the third glue layer in the thickness direction of the tab, so that the tab glue maintains a stable structure during heat sealing or pressure relief. Specifically, during the heat sealing of the tab glue, the third glue layer is first heated and melted, the third glue layer has the highest melting point, which is beneficial to reduce the risk of short circuit between the packaging bag and the tab due to over-melting of the third glue layer when heated, improve the sealing effect, and reduce the risk of liquid leakage. The second glue layer plays a role in heat conduction and support, transferring heat to the first glue layer, connecting the inside of the first glue layer to the tab, and improving the adhesion between the first glue layer and the tab. At the same time, it reduces the risk of glue overflow caused by the deformation rate of the first glue layer due to pressure and high temperature, thereby reducing the risk of corrosion and liquid leakage at the tab caused by poor packaging of the electrode assembly; thereby improving the safety performance of the electrochemical device. In the pressure relief process, when the temperature of the electrode assembly abnormally rises, the temperature of the tab also rises accordingly. When the melting point range of the first glue layer is reached, the first glue layer will melt to reduce the packaging strength of the connection area between the first glue layer and the packaging bag, thereby reducing the packaging strength between the tab glue and the packaging bag, so that the gas generated at high temperature can be easily discharged from the connection area between the tab glue and the packaging bag, reducing the accumulation of heat and the degree of deformation inside the electrode assembly, and improving the safety of the electrochemical device. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of an electrochemical device in an embodiment of the application; Figure 2 It is a top view schematic diagram of the tab glue of an electrochemical device in an embodiment of the application; Figure 3 It is a top view schematic diagram of the tab glue of an electrochemical device in an embodiment of the application; Figure 4 It is a top view schematic diagram of the tab glue of an electrochemical device in an embodiment of the application.

[0023] Explanation of main element symbols Electrochemical device 100 Electrode assembly 10 Packaging bag 20 Sealing part 21 Tab 30 Tab glue 40 First glue layer 41 Second glue layer 42 Third glue layer 43 Top 44 Bottom 45 First side 46 Second side 47 Fourth glue layer 51 Fifth adhesive layer 52 Sixth adhesive layer 53 Thickness direction Z Extension direction X Width direction Y The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0024] For the purposes of this application, a more complete description will be provided below. However, the present application can be implemented in numerous ways, not just the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0025] As used herein the terms "about" and "substantially" mean approximately or nearly, as in "about 90%," "substantially defect free," or "substantially oriented," to name a few. "Made from" is synonymous with "comprising." As used herein the terms "comprising" "including," "having" "with" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a step, a method, an article, or an apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0026] The transitional phrase "consisting of" excludes any element, step, or ingredient not specified. If used in the claims, this phrase shall not be construed to mean that the noted elements or steps are essential to the practice of the application. When the phrase "consisting of is followed by a list of elements or steps, the list is to be construed as meaning that the claimed application includes only the elements or steps in the list, and not any other elements or steps not specifically recited.

[0027] When expressing a range, concentration, or other value or parameter either as a range, a preferred range, or a series of upper preferred values and lower preferred values, it is to be understood that every range of values between the upper and lower preferred values are specifically contemplated regardless of whether such specific range is explicitly stated herein. For example, where a range of "1-5" is disclosed, the disclosure is to be interpreted to include ranges of "1-4," "1-3," "1-2," "1-2 and 4-5," "1-3 and 5," etc. When numerical ranges are disclosed herein, unless explicitly stated otherwise, the range is intended to include the end values and all integers and fractions within that range.

[0028] In these embodiments, the parts and percentages described are by mass unless otherwise indicated.

[0029] "Parts by mass" means a basic unit of measurement that indicates the mass ratio relationship of multiple components, 1 part can represent an arbitrary unit of mass, such as can be expressed as 1 g, can also be expressed as 2.689 g, etc. If we say that the mass of component A is a parts, and the mass of component B is b parts, it means that the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK, and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It must not be misunderstood that, unlike the parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0030] "and / or" is used to indicate that one or both of the described situations can occur, for example, A and / or B includes (A and B) and (A or B).

[0031] <General definitions> The term "porous substrate" refers to a substrate having pores or voids inside. The material used as the porous substrate can be an organic material or an inorganic material, as long as the material is an electrically insulating material. Any porous substrate having electrical insulation can be used in the present application.

[0032] The term "polymer" refers to a natural high molecular compound or a synthetic high molecular compound prepared by polymerizing the same or different types of monomers. The synthetic high molecular compound includes, but is not limited to, homopolymer, copolymer, terpolymer, multipolymer, and interpolymer.

[0033] The term "inorganic filler" refers to a non-conductive substance. Some non-limiting examples of inorganic fillers include metal oxides, as well as non-oxide materials and non-metallic materials.

[0034] The term "volume distribution particle size D50" refers to the particle size that reaches 50% of the volume accumulation from the small particle size in the particle size distribution on the volume basis of the material.

[0035] The reference to "embodiment", "part of embodiment", "one embodiment", "another embodiment", "specific embodiment" or "part of embodiment" throughout the specification means that at least one embodiment or example in the present application contains the specific features, structures, materials or characteristics described in the embodiment or example.

[0036] The content of the present application is further described in conjunction with the accompanying drawings.

[0037] As Figure 1As shown, in the first aspect of the present application, an electrochemical device 100 is provided. The electrochemical device 100 includes an electrode assembly 10, a packaging bag 20, tab 30, and tab glue 40. The electrode assembly 10 includes a positive electrode plate, a separator, and a negative electrode plate, which are formed by stacking or winding; the electrode assembly 10 is accommodated in the packaging bag 20 for storing or releasing electrical energy. The packaging bag 20 includes a sealing portion 21. The tab 30 is connected to the electrode assembly 10 and extends out from the sealing portion 21. The portion of the tab 30 extending out of the sealing portion 21 is used to connect to a circuit board assembly or an external electrical device.

[0038] Optionally, the battery 100 includes two tabs 30. The two tabs 30 are arranged at intervals and are respectively connected to the positive electrode plate and the negative electrode plate in the electrode assembly 10, so that the polarities of the two tabs 30 are opposite.

[0039] As Figure 2 shown, the tab glue 40 is arranged on the side wall of the tab 30 along the circumferential direction. The tab glue 40 is of a closed type. The tab glue 40 includes a first glue layer 41, a second glue layer 42, and a third glue layer 43 that are connected in sequence from the inside to the outside. The inner side of the first glue layer 41 is connected to the tab 30, and the outer side of the third glue layer 43 is connected to the inner side of the sealing portion 21.

[0040] The relationship among the melting point T1 of the first glue layer, the melting point T2 of the second glue layer, and the melting point T3 of the third glue layer satisfies: T1 < T2 < T3; where, 130°C ≤ T1 ≤ 150°C, 160°C ≤ T2 ≤ 180°C, 190°C ≤ T3 ≤ 200°C. During the heat sealing process of the tab glue, the third glue layer 43 is first heated and melted. The melting point of the third glue layer 43 is the highest, which is beneficial to reducing the risk of short circuit between the packaging bag 20 and the tab 30 caused by over-melting of the third glue layer 43 during heating, improving the sealing effect, and reducing the risk of liquid leakage; the second glue layer 42 plays a role in heat conduction and support, transferring heat to the first glue layer 41, making the inner side of the first glue layer 41 connected to the tab 30, and improving the adhesion between the first glue layer 41 and the tab 30; at the same time, reducing the risk of glue overflow caused by the deformation rate of the first glue layer 41 due to pressure and high temperature, and further reducing the risk of corrosion of the electrode assembly 10 and liquid leakage at the tab 30 due to poor encapsulation; thereby improving the safety performance of the electrochemical device.

[0041] When the temperature of the electrode assembly 10 rises abnormally, the temperature of the tab 30 also rises accordingly. When reaching the melting point range of the first glue layer 41, the first glue layer 41 will melt to reduce the encapsulation strength of the connection area between the first glue layer 41 and the packaging bag 20, and further reduce the encapsulation strength between the tab glue 40 and the packaging bag 20, so as to facilitate the gas generated at high temperature to rush out of the connection area between the tab glue 40 and the packaging bag 20, reduce the heat accumulation and deformation degree inside the electrode assembly, and improve the safety of the electrochemical device.

[0042] By setting the lower limit of the melting point of the first adhesive layer 41 to 130℃, the risk of melting of the first adhesive layer 41 when the electrode assembly 10 normally heats up is reduced; by setting the upper limit of the melting point of the first adhesive layer 41 to 150℃, the first adhesive layer 41 melts within the melting point range of 130℃ to 150℃, reducing the risk of further increasing the electrode assembly temperature after increasing to 150℃, which poses a safety hazard.

[0043] Optionally, T1 can be one or a range value consisting of any two of 130℃, 132℃, 134℃, 136℃, 138℃, 140℃, 142℃, 144℃, 146℃, 148℃, 150℃.

[0044] Optionally, T2 can be one or a range value consisting of any two of 160℃, 162℃, 164℃, 166℃, 168℃, 170℃, 172℃, 174℃, 176℃, 178℃, 180℃.

[0045] Optionally, T3 can be one or a range value consisting of any two of 190℃, 191℃, 192℃, 193℃, 194℃, 195℃, 196℃, 197℃, 198℃, 199℃, 200℃.

[0046] In some embodiments, the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer along the thickness direction of the tab is 110-210μm. While limiting the packaging volume occupied by the tab adhesive, the melting points of the first adhesive layer, the second adhesive layer and the third adhesive layer are adapted to the heat sealing temperature of the electrochemical device 100, improving the sealing effect of the tab adhesive and thus improving the safety performance of the electrochemical device.

[0047] Optionally, the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer along the thickness direction of the tab can be one or a range value consisting of any two of 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, 200μm, 205μm, 210μm; preferably 135-185μm.

[0048] In some embodiments, along the thickness direction of the tab, the thickness percentage of the first adhesive layer is 20-30%, the thickness percentage of the second adhesive layer is 40-60%, and the thickness percentage of the third adhesive layer is 20-30%, based on the sum of the thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer; during packaging, the packaging bag 20 and the tab adhesive 40 can be completely fused without obvious interface, thereby improving the packaging strength between the tab adhesive 40 and the packaging bag 20, improving the sealing effect, and reducing the risk of liquid leakage. The thickness of the second adhesive layer 42 is higher than the thicknesses of the first adhesive layer 41 and the third adhesive layer 43, which can ensure that the second adhesive layer 42 is not over-fused or not fused enough when heated during packaging, so that the second adhesive layer 42 and the first adhesive layer 41 and the third adhesive layer 43 do not have an interface or delamination, which reduces the packaging strength.

[0049] Optionally, the thickness percentage of the first adhesive layer 41 is one or a range value consisting of any two of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0050] Optionally, the thickness percentage of the second adhesive layer 42 is one or a range value consisting of any two of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%.

[0051] Optionally, the thickness percentage of the third adhesive layer 43 can be one or a range value consisting of any two of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0052] It should be noted that during the packaging process, the first adhesive layer 41 is in contact with the tab 30, and the thickness of the first adhesive layer 41 at the position corresponding to the tab 30 will decrease under the extrusion of the tab 30. In this application, the thickness of the first adhesive layer 41 is the initial thickness of the first adhesive layer 41 before being extruded by the tab 30, i.e. Figure 2 In this application, the thickness of the first adhesive layer 41 at the position corresponding to the tab 30 is the initial thickness of the first adhesive layer 41 before being extruded by the tab 30.

[0053] Further, the thickness percentage of the second adhesive layer 42 is 44-50% to further improve the stability of the second adhesive layer 42 in supporting between the tab 30 and the sealing portion 21, thereby improving the safety performance of the electrochemical device 100.

[0054] It is understood that, in some embodiments, provided that the thickness of the second adhesive layer 42 is greater than the thickness of the third adhesive layer 43, the thickness of the first adhesive layer 41 of the third adhesive layer is greater than the thickness of the third adhesive layer 43, or the thickness of the first adhesive layer 41 is less than the thickness of the third adhesive layer 43, can enable the second adhesive layer 42 to have higher structural strength than the first adhesive layer 41 and the third adhesive layer 43, so that the second adhesive layer 42 has sufficient structural strength to play a supporting role in the tab 30 and the first encapsulation edge 21.

[0055] In some embodiments, along the width direction of the tab, the tab adhesive includes a first side portion 46 and a second side portion 47, the first side portion 46 and the second side portion 47 being connected between the top 44 and the bottom 45, and being disposed on both sides of the tab 30 along the width direction Y of the tab 30.

[0056] Along the width direction Y of the tab, the distance between the first side portion 46 and the second side portion 47 is 4.0-8.0 mm to increase the extension length of the bottom within the packaging bag 20, thereby increasing the sealing strength of the tab.

[0057] In some embodiments, along the width direction Y of the tab, the distance between the side of the tab 30 facing the first side 46 and the first side 46 is 0.8-1.5mm, and the distance between the side of the tab 30 facing the second side 47 and the second side 47 is 0.8-1.5mm, so that the tab adhesive 40 protrudes from both sides of the tab 30 in the width direction Y of the tab 30, thereby improving the sealing effect of the tab adhesive 40.

[0058] In some embodiments, along the width direction Y of the tab 30, the tab 30 is centrally disposed between the first side portion 46 and the second side portion 47, that is, the distance between the side of the tab 30 facing the first side portion 46 and the first side portion 46 is equal to the distance between the side of the tab 30 facing the second side portion 47 and the second side portion 47, so that the force on both sides of the tab 30 is uniform.

[0059] In some implementations, such as Figure 3 As shown, along the width direction Y of the tab, the first side portion 46 and the second side portion 47 include a fourth adhesive layer 51 and a fifth adhesive layer 52 stacked sequentially; along the thickness direction Z of the tab, the two ends of the fourth adhesive layer 51 are in contact with the first adhesive layer 41 and at least a portion of the second adhesive layer 42; the two ends of the fifth adhesive layer 52 are in contact with at least a portion of the second adhesive layer 42 and the third adhesive layer 43; the first adhesive layer 41, the second adhesive layer 42, the third adhesive layer 43, the fourth adhesive layer 51 and the fifth adhesive layer 52 together form a ring structure; the relationship between the melting point T4 of the fourth adhesive layer 51 and the melting point T5 of the fifth adhesive layer 52 satisfies: T4>T5, where 180℃≤T4≤200℃, 160℃≤T5<180℃.

[0060] In this application, the first side portion and the second side portion include the fourth adhesive layer and the fifth adhesive layer of the above structure, which can further improve the high temperature resistance and sealing performance of the tab adhesive.

[0061] In some embodiments, the thickness percentage of the fourth adhesive layer is 40-50% and the thickness percentage of the fifth adhesive layer is 50-60%, based on the sum of the thicknesses of the fourth and fifth adhesive layers.

[0062] In this application, the thickness percentages of the fourth and fifth adhesive layers are within the aforementioned range, which helps to ensure the layering melting and interfacial bonding strength during the heat sealing process, and optimizes the structural rigidity and sealing integrity in the tab width direction.

[0063] Specifically, based on the sum of the thicknesses of the fourth adhesive layer and the fifth adhesive layer, the thickness percentage of the fourth adhesive layer can be a range of one or any two of the following: 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, and 50%.

[0064] Specifically, based on the sum of the thicknesses of the fourth and fifth adhesive layers, the thickness percentage of the fifth adhesive layer can be a range of one or any two of the following: 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%.

[0065] In some implementations, such as Figure 4 As shown, along the width direction Y of the tab, the first side portion 46 and the second side portion 47 include a fourth adhesive layer 51, a fifth adhesive layer 52 and a sixth adhesive layer 53 stacked sequentially. Along the thickness direction Z of the tab, the two ends of the fourth adhesive layer 51 are in contact with the first adhesive layer 41; the two ends of the fifth adhesive layer 52 are in contact with the second adhesive layer 42; and the two ends of the sixth adhesive layer 53 are in contact with the third adhesive layer 43. The first adhesive layer 41, the second adhesive layer 42, the third adhesive layer 43, the fourth adhesive layer 51, the fifth adhesive layer 52 and the sixth adhesive layer 53 together form a ring structure. The relationship between the melting point T4 of the fourth adhesive layer 51, the melting point T5 of the fifth adhesive layer and the melting point T6 of the sixth adhesive layer satisfies: T4>T5>T6, where 180℃≤T4≤200℃, 160℃≤T5<180℃, and 130℃≤T6≤150℃.

[0066] In this application, the first side and the second side include the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer of the above structure, which can prevent the edge temperature of the first side and the second side from being too low, resulting in sealing failure.

[0067] It is understandable that both ends of the fourth adhesive layer 51 can be in contact with at least a portion of the second adhesive layer 42.

[0068] It can be understood that the two ends of the fifth adhesive layer 52 can be in contact with at least one of at least part of the first adhesive layer 41 and at least part of the third adhesive layer 43.

[0069] It can be understood that the two ends of the sixth adhesive layer 53 can be in contact with at least part of the second adhesive layer 42.

[0070] Specifically, T4 can be one or a range value formed by any two of 180℃, 182℃, 184℃, 186℃, 188℃, 190℃, 192℃, 194℃, 196℃, 198℃, 200℃.

[0071] Specifically, T5 can be one or a range value formed by any two of 160℃, 162℃, 164℃, 166℃, 168℃, 170℃, 172℃, 174℃, 175℃, 177℃, 179℃.

[0072] Specifically, T6 can be one or a range value formed by any two of 130℃, 132℃, 134℃, 136℃, 138℃, 140℃, 142℃, 144℃, 146℃, 148℃, 150℃.

[0073] In some embodiments, based on the sum of the thicknesses of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer, the thickness percentage of the fourth adhesive layer is 25-35%, the thickness percentage of the fifth adhesive layer is 30-40%, and the thickness percentage of the sixth adhesive layer is 25-35%.

[0074] In this application, based on the sum of the thicknesses of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer, the thickness percentages of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer are within the above range, which is beneficial to improve the sealing reliability of heat sealing, strengthen the structural stability of the side structure, and also optimize the balanced stability of pressure relief.

[0075] If the thickness percentage of the fourth adhesive layer is too high, the first adhesive layer is not fully melted during heat sealing, and is not tightly bonded with the first adhesive layer, which is easy to cause interlayer gaps; at the same time, it will also inhibit the decrease of the packaging strength during pressure relief, leading to poor gas discharge, increasing the risk of high internal pressure in the battery; if the thickness percentage of the fourth adhesive layer is too low, it will lead to insufficient structural support of the tab adhesive, and the tab adhesive will be dissolved and cracked during heat sealing or pressure relief, which will damage the closed structure of the tab adhesive, and the high temperature resistance of the tab adhesive will be weakened, and the tab adhesive will be easy to stick or fail to seal at high temperature.

[0076] If the thickness percentage of the fifth adhesive layer is too high, the tab adhesive melts excessively during the heat sealing process, which is prone to overflow and increases the risk of liquid leakage. At the same time, the rigidity of the side tab adhesive is insufficient to resist internal pressure fluctuations. If the thickness percentage of the fifth adhesive layer is too low, the fourth and sixth adhesive layers cannot be effectively connected to the first, second, and third adhesive layers, and interface gaps may occur between the layers, resulting in insufficient tightness and increased liquid leakage channels, which increases the heat box test liquid leakage rate.

[0077] If the thickness percentage of the sixth adhesive layer is too high, it melts excessively at the beginning of heat sealing, which is prone to excessive adhesion with the aluminum plastic film. When the pressure is released, it softens too quickly, causing a sudden drop in packaging strength, which leads to excessive leakage of electrolyte. If the thickness percentage of the sixth adhesive layer is too low, the sealing and filling are insufficient, and it cannot completely cover the small gaps on the inside of the sealing part. Air and moisture can easily enter the battery interior. The anti-adhesion performance is weakened, and the incidence of adhesion with the inner wall of the packaging bag increases at high temperatures.

[0078] Specifically, based on the sum of the thicknesses of the fourth, fifth, and sixth adhesive layers, the thickness percentage of the fourth adhesive layer can be in the range of one or any two of 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%.

[0079] Specifically, based on the sum of the thicknesses of the fourth, fifth, and sixth adhesive layers, the thickness percentage of the fifth adhesive layer can be in the range of one or any two of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%.

[0080] Specifically, based on the sum of the thicknesses of the fourth, fifth, and sixth adhesive layers, the thickness percentage of the fifth adhesive layer can be in the range of one or any two of 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%.

[0081] In some embodiments, the fourth adhesive layer includes polyethylene and silicon dioxide, and the mass percentage of the silicon dioxide in the fourth adhesive layer is 3-6% based on the mass of the fourth adhesive layer. In this application, the addition of silicon dioxide in the fourth adhesive layer helps to improve the mechanical strength and heat resistance of the fourth adhesive layer, while optimizing the melt flowability of the fourth adhesive layer.

[0082] Specifically, the mass percentage of the silicon dioxide can be in the range of one or any two of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6% based on the mass of the fourth adhesive layer.

[0083] In some embodiments, the particle size Dv50 of the silica is 40-80 nm, for example, can be one or a range value consisting of any two of 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm.

[0084] The particle size Dv50 of the silica within the above range is beneficial to improve the dispersibility of the silica in the polyethylene. When the particle size Dv50 of the silica is <40 nm, the silica is prone to agglomeration, resulting in the formation of defects in the fourth adhesive layer, reducing the sealing effect and mechanical properties. When the particle size Dv50 of the silica is >80 nm, the interfacial bonding area of the silica and the polyethylene is reduced, making it difficult to fully play the reinforcing role, and the continuity of the fourth adhesive layer may be damaged during heat sealing.

[0085] In some embodiments, the fifth adhesive layer comprises polypropylene and glass beads, and the mass percentage of the glass beads in the fifth adhesive layer is 8-12% based on the mass of the fifth adhesive layer. In this application, the addition of glass beads in the fifth adhesive layer is beneficial to reduce the density of the fifth adhesive layer, while improving the structural rigidity, cushioning performance and high-temperature deformation resistance of the fifth adhesive layer.

[0086] Specifically, the mass percentage of the glass beads in the fifth adhesive layer can be one or a range value consisting of any two of 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12% based on the mass of the fifth adhesive layer.

[0087] In some embodiments, the Dv50 of the glass beads is 60-100 nm, for example, can be one or a range value consisting of any two of 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm. The particle size Dv50 of the glass beads within the above range can simultaneously consider the compactness and processing fluidity of the fifth adhesive layer. When the particle size Dv50 of the glass beads is <60 nm, the hollow structure of the glass beads is prone to be damaged during processing, and cannot fully play the role of lightweight and support. When the particle size Dv50 of the glass beads is >100 nm, the glass beads are difficult to disperse uniformly in the fifth adhesive layer, which may result in the existence of pores in the fifth adhesive layer, reducing the sealing effect and mechanical strength of the fifth adhesive layer.

[0088] In some embodiments, the sixth adhesive layer comprises polyethylene and talc, and the mass percentage of the talc in the sixth adhesive layer is 4-7% based on the mass of the sixth adhesive layer. In the sixth adhesive layer, the addition of talc is beneficial to improve the heat resistance and anti-blocking performance of the sixth adhesive layer, while improving the interfacial bonding stability of the sixth adhesive layer and the sealing part.

[0089] Specifically, based on the mass of the sixth adhesive layer, the mass percentage of the talcum powder can be in the range of one or any two of 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%.

[0090] In some embodiments, the particle size Dv50 of the talcum powder is 50-90 nm, for example, can be in the range of one or any two of 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm. The particle size Dv50 of the talcum powder in the above range is beneficial to achieve a balance between the processing performance and sealing performance of the sixth adhesive layer. When the particle size Dv50 of the talcum powder is less than 50 nm, the layered structure of the talcum powder is prone to stacking and agglomeration, resulting in stress concentration in the sixth adhesive layer, affecting the flexibility and interfacial bonding force of the sixth adhesive layer. When the particle size Dv50 of the talcum powder is greater than 90 nm, the compatibility of the talcum powder with polyethylene decreases, which may form a small gap in the sixth adhesive layer, reducing the density of the sixth adhesive layer.

[0091] In some embodiments, the tab adhesive includes a bottom 45 and a top 44, the top 44 and the bottom 45 are oppositely arranged in the extension direction (X direction) of the tab, the top 44 is located outside the sealing portion 21, and the bottom 45 is located inside the packaging bag 20; the length of the top 44 protruding out of the sealing portion 21 is 1.5-3 mm, and the length of the bottom 45 protruding out of the sealing portion 21 is 0.8-2 mm; to reduce the risk of the tab 30 leaking and contacting the metal material in the packaging belt 20 to cause short circuit, thereby improving the safety performance of the electrochemical device 100.

[0092] Specifically, the length of the top portion protruding out of the sealing portion can be in the range of one or any two of 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm; preferably 2.0-2.5 mm.

[0093] Specifically, the length of the bottom portion protruding out of the sealing portion can be in the range of one or any two of 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm; preferably 1.2-1.5 mm.

[0094] In some embodiments, the third adhesive layer includes polypropylene, polytetrafluoroethylene, and phase change microcapsules, based on the mass of the third adhesive layer, the mass percentage of polytetrafluoroethylene is 15-20%, and the mass percentage of phase change microcapsules is 5-8%.

[0095] In this application, the third adhesive layer adds polytetrafluoroethylene, which can improve the flexibility and impact resistance of the third adhesive layer 43, thereby improving the packaging strength between the tab adhesive 40 and the packaging bag 20.

[0096] It can be understood that the phase change microcapsule includes a core material and a wall material, the core material includes a paraffin wax with a melting point of 195-205℃, and the wall material is a melamine formaldehyde resin. When the heat sealing temperature exceeds 200℃, the phase change microcapsule is broken, the core material is released, heat is absorbed to form a heat insulation layer, local overheating and melting of the tab adhesive are avoided, and the risk of tab adhesive overflow is reduced.

[0097] Specifically, the mass percentage content of polytetrafluoroethylene based on the mass of the third adhesive layer can be in a range value composed of one or any two of 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, and 20%.

[0098] Specifically, the mass percentage content of the phase change microcapsule based on the mass of the third adhesive layer can be in a range value composed of one or any two of 5%, 5.5%, 6%, 6.5%, 7%, and 7.5%.

[0099] In some embodiments, the second adhesive layer includes polypropylene, polyethylene, and graphene, and the mass percentage content of polyethylene based on the mass of the second adhesive layer is 20-40%, and the mass percentage content of graphene is 3-5%.

[0100] It can be understood that, by the high thermal conductivity of graphene in the second adhesive layer, the heat of the first adhesive layer can be quickly conducted to the third adhesive layer, the temperature difference of adjacent areas is reduced, the melting point transition between the first adhesive layer to the third adhesive layer is smooth, and the interlayer stress is reduced.

[0101] Specifically, the mass percentage content of polyethylene based on the mass of the second adhesive layer can be in a range value composed of one or any two of 20%, 23%, 25%, 28%, 30%, 32%, 35%, 37%, and 40%.

[0102] Specifically, the mass percentage content of graphene based on the mass of the second adhesive layer can be in a range value composed of one or any two of 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, and 5%.

[0103] In some embodiments, the thickness of the graphene is 5-10 nm, and the flake diameter is 1-5 μm.

[0104] Specifically, the thickness of the graphene can be in a range value composed of one or any two of 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm.

[0105] Specifically, the flake diameter of the graphene can be in a range value composed of one or any two of 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm.

[0106] In some embodiments, the first adhesive layer comprises polyethylene and calcium carbonate, and the mass percentage of calcium carbonate is 2-4% based on the mass of the first adhesive layer.

[0107] It can be understood that the calcium carbonate can improve the mechanical properties of the third adhesive layer, and can reduce the problem of over-melting and glue overflow of the sealing area during heat sealing due to poor packaging parallelism, excessive packaging pressure or excessive packaging temperature, thereby reducing the problems of battery corrosion, electrolyte leakage at the tab, etc. caused by the contact between the tab and the packaging bag.

[0108] Specifically, the mass percentage of calcium carbonate can be 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4% or a range value consisting of any two of them based on the mass of the first adhesive layer.

[0109] In some embodiments, the particle size D50 of the calcium carbonate is 50-100 nm, for example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range value consisting of any two of them.

[0110] The electrochemical device provided by the present application includes any device in which an electrochemical reaction occurs to convert chemical energy and electrical energy into each other, and specific non-limiting examples include all kinds of primary electrochemical devices, secondary electrochemical devices, fuel electrochemical devices, solar electrochemical devices, or capacitors. In particular, the electrochemical device is a lithium secondary electrochemical device, including a lithium metal secondary electrochemical device, a lithium ion secondary electrochemical device, a lithium polymer secondary electrochemical device, or a lithium ion polymer secondary electrochemical device.

[0111] The present application provides an electronic device comprising any one of the electrochemical devices described herein.

[0112] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art.

[0113] The use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art. According to some embodiments of the present application, the electronic device includes but is not limited to a mobile phone, a mobile phone, a smart phone, a notebook computer, a tablet computer, a wearable device, a smart watch, a smart bracelet, smart glasses, a mobile power supply, a television, a game console, a gamepad, a digital camera, a smart speaker, earphones, a keyboard, a mouse, a display, a drone, a sound system, a household appliance, a toy, a power tool, a car, a motorcycle, an electric bicycle, a bicycle, a robot, a robot dog, an industrial robot, a humanoid robot, etc.

[0114] <TEST METHODS> 1. Peel strength: According to: GB / T 2792-2014; Sample: Take 15mm wide, ≥100mm long "tab-tab adhesive-seal" sample, 5 parallel samples for each interface; Equipment: Electronic tensile testing machine Parameters: 23℃±2℃, 50%±5% humidity, 300mm / min speed, 180° peeling; Results: Take the average value of the effective maximum tensile force, unit N / 15mm; 2. Heat radiation adhesion occurrence rate: Purpose: Measure the adhesion risk of tab adhesive to the inner wall of the packaging bag at high temperature; Sample: 100 qualified electrochemical devices (remove external accessories, retain the core structure); Equipment: Heat radiation test box; Parameters: 130℃±2℃, 1000W / m² radiation intensity, constant temperature for 2h; Results: After cooling, observe and count the proportion of samples that need ≥5N force to separate or are damaged after separation, unit %; 3. Heat box test: According to: IEC 61960-3:2017; Sample: 100 devices that have completed charge and discharge cycles, measure the initial mass; Equipment: Precision heat box; Parameters: Increase temperature to 130℃±2℃ at 5℃ / min, constant temperature for 16h; Results: After cooling, weigh and check fluorescence under ultraviolet light (365nm), count the proportion of samples with mass difference ≥0.05g or fluorescence, unit %.

[0115] Example 1 <Preparation of negative electrode sheet> A negative electrode slurry was obtained by fully stirring and mixing negative electrode active material (artificial graphite), conductive agent (Super P), binder (styrene-butadiene rubber), and thickening agent (sodium carboxymethyl cellulose) in a mass ratio of 98.1:0.5:0.7:0.7 in a deionized water solvent system. The negative electrode slurry was coated on a negative electrode current collector copper foil, dried, cold-pressed, and slitted, and then dried at 85℃ under vacuum for 6h, and the tab was welded to obtain the negative electrode sheet. The thickness of the negative electrode active layer was 115μm.

[0116] <Preparation of positive electrode sheet> The positive electrode active material (lithium cobaltate), the conductive agent (Super P) and the binder (polyvinylidene fluoride) were mixed uniformly in N-methylpyrrolidone solvent at a mass ratio of 98:1.2:0.8, to obtain a positive electrode slurry; the positive electrode slurry was coated on the current collector aluminum foil, dried at 85°C, then cold-pressed, followed by edge cutting and slitting, and then dried at 85°C under vacuum for 6h, and the tab was welded, to obtain a positive electrode sheet; wherein the thickness of the positive electrode active layer was 100μm.

[0117] <Preparation of electrolyte> Ethylene carbonate (EC), dimethyl carbonate (DMC) and ethylene carbonate (EC) were mixed uniformly at a mass ratio of 1:1:1 at room temperature in an argon-filled glove box (H2O<1ppm, O2<1ppm), and then dehydrated with 4Å molecular sieves to obtain a non-aqueous organic solvent; Lithium salt LiPF6 was added to the non-aqueous organic solvent and mixed uniformly to obtain an electrolyte, wherein the molar concentration of lithium salt LiPF6 was 1M.

[0118] <Preparation of separator> A polyethylene / polypropylene porous film with a thickness of 8μm was used as the separator.

[0119] <Preparation of tab adhesive> The first mixture was obtained by uniformly mixing polyethylene with a mass percentage of 98% and calcium carbonate (particle size Dv50 of 80nm) with a mass percentage of 2%; The second mixture was obtained by uniformly mixing polypropylene with a mass percentage of 68%, polyethylene with a mass percentage of 29% and graphene with a mass percentage of 3%; The third mixture was obtained by uniformly mixing polypropylene with a mass percentage of 77%, polytetrafluoroethylene with a mass percentage of 18% and phase change microcapsules with a mass percentage of 5%; wherein the core material of the phase change microcapsules was paraffin with a melting point of 200°C, and the wall material was melamine formaldehyde resin.

[0120] The first mixture, the second mixture and the third mixture were passed through a multi-channel co-extrusion die to obtain a tab adhesive as shown in Figure 2 ; wherein, along the thickness direction of the tab, the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer on one side was 160μm, the thickness percentage of the first adhesive layer was 25% based on the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer on one side, the thickness percentage of the second adhesive layer was 50%, and the thickness percentage of the third adhesive layer was 25%; the melting point of the first adhesive layer was T1=130°C, the melting point of the second adhesive layer was T2=173°C, and the melting point of the third adhesive layer was T3=195°C.

[0121] <Preparation of electrochemical device> The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and the electrode assembly is obtained by winding; the electrode assembly is placed in a packaging bag, the tab adhesive is arranged between the packaging bag and the tab, and then a 1.5 mm wide heat sealing head is used for heat sealing to obtain a secondary battery as shown in Figure 1 The heat sealing temperature is 180°C, the heat sealing pressure is 0.3 MPa, and the heat sealing time is 1S; wherein, along the tab extension direction, the length of the top protruding out of the sealing part is 2.5 mm, and the length of the bottom protruding out of the sealing part is 1.5 mm.

[0122] Examples 2-16 and Comparative Examples 1-8 The difference from Example 1 is that at least one of the melting point of the first adhesive layer, the melting point of the second adhesive layer, the melting point of the third adhesive layer, the sum of the thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer, the thickness percentage of the first adhesive layer, the thickness percentage of the second adhesive layer and the thickness percentage of the third adhesive layer is different, and the specific parameters are shown in Table 1.

[0123] Example 17 The difference from Example 1 is that the preparation of the tab adhesive is different.

[0124] The preparation of the tab adhesive of the present example includes the following steps: Mix polyethylene with a mass percentage of 98% and calcium carbonate (particle size Dv50 of 80 nm) with a mass percentage of 2% uniformly to obtain a first mixture; Mix polypropylene with a mass percentage of 68%, polyethylene with a mass percentage of 29% and graphene with a mass percentage of 3% uniformly to obtain a second mixture; Mix polypropylene with a mass percentage of 77%, polytetrafluoroethylene with a mass percentage of 18% and phase change microcapsules with a mass percentage of 5% uniformly to obtain a third mixture; wherein the core material of the phase change microcapsules is paraffin with a melting point of 200°C, and the wall material is melamine formaldehyde resin; Extrude the first mixture, the second mixture and the third mixture through a multi-channel co-extrusion die to form a front part and a rear part; Mix polyethylene with a mass percentage of 94% and silicon dioxide (particle size Dv50 = 80 nm) with a mass percentage of 6% uniformly to obtain a fourth mixture; Mix glass beads with a mass percentage of 92% and glass beads with a mass percentage of 8% (particle size Dv50 = 100 nm) uniformly to obtain a fifth mixture; Extrude the fourth mixture and the fifth mixture through a multi-channel co-extrusion die to form a first side part and a second side part; The front part, the rear part, the first side part and the second side part are hot-pressed and combined under the condition of a temperature of 160℃ and a pressure of 0.2MPa for 10s to obtain the tab adhesive as shown in Figure 3 Wherein, along the thickness direction Z of the tab, the front part and the back part are arranged on both sides of the tab, along the width direction Y of the tab, the first side part and the second side part are arranged on both sides of the tab; the front part, the back part, the first side part and the second side part form a ring structure; Along the thickness direction Z of the tab, the front part and the back part include the first adhesive layer, the second adhesive layer and the third adhesive layer which are stacked in sequence, one side of the first adhesive layer is in contact with the tab, and the second adhesive layer is between the first adhesive layer and the third adhesive layer; the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer on one side is 160μm, the thickness percentage of the first adhesive layer is 25% based on the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer, the thickness percentage of the second adhesive layer is 50%, and the thickness percentage of the third adhesive layer is 25%; the melting point T1 of the first adhesive layer is 130℃, the melting point T2 of the second adhesive layer is 173℃, and the melting point T3 of the third adhesive layer is 195℃; Along the width direction Y of the tab, the first side part and the second side part include the fourth adhesive layer and the fifth adhesive layer which are stacked in sequence, one side of the fourth adhesive layer is in contact with the tab; the fourth adhesive layer is between the tab and the fifth adhesive layer; the melting point T4 of the fourth adhesive layer is 200℃, and the melting point of the fifth adhesive layer is 180℃; Along the thickness direction Z of the tab, both ends of the fourth adhesive layer are in contact with the first adhesive layer and at least part of the second adhesive layer; both ends of the fifth adhesive layer are in contact with at least part of the second adhesive layer and the third adhesive layer; Along the width direction Y of the tab, the total thickness of the fourth adhesive layer and the fifth adhesive layer on one side is 1mm, the thickness percentage of the fourth adhesive layer is 45% based on the total thickness of the fourth adhesive layer and the fifth adhesive layer, and the thickness percentage of the fifth adhesive layer is 55%.

[0125] Example 18 The difference from Example 1 is that the preparation of the tab adhesive is different.

[0126] The preparation of the tab adhesive of the present example includes the following steps: The first mixed material is obtained by uniformly mixing polyethylene with a mass percentage of 98% and calcium carbonate (particle size Dv50 is 80nm) with a mass percentage of 2%; The second mixed material is obtained by uniformly mixing polypropylene with a mass percentage of 68%, polyethylene with a mass percentage of 29% and graphene with a mass percentage of 3%; ​Mixing the polypropylene with a mass percentage of 77%, the polytetrafluoroethylene with a mass percentage of 18% and the phase change microcapsules with a mass percentage of 5% to obtain a third mixture; wherein the core material of the phase change microcapsules is paraffin with a melting point of 200℃, and the wall material is melamine formaldehyde resin; Extruding the first mixture, the second mixture and the third mixture through a multi-channel co-extrusion die to form the front part and the rear part; Mixing the polyethylene with a mass percentage of 97% and the silicon dioxide (particle size Dv50=40nm) with a mass percentage of 3% to obtain a fourth mixture; Mixing the glass microbeads with a mass percentage of 88% and the glass microbeads (particle size Dv50=60nm) with a mass percentage of 12% to obtain a fifth mixture; Mixing the polyethylene with a mass percentage of 95% and the talcum powder (particle size Dv50=70nm) with a mass percentage of 5% to obtain a sixth mixture; Extruding the fourth mixture and the fifth mixture through a multi-channel co-extrusion die to form the first side part and the second side part; Hot-pressing the front part, the rear part, the first side part and the second side part at a temperature of 170℃ and a pressure of 0.22MPa for 15s to obtain the tab adhesive as shown in Figure 4 ; Wherein, along the thickness direction Z of the tab, the front part and the rear part are arranged on both sides of the tab, and along the width direction Y of the tab, the first side part and the second side part are arranged on both sides of the tab; the front part, the rear part, the first side part and the second side part form a ring structure; Along the thickness direction Z of the tab, the front part and the rear part include the first adhesive layer, the second adhesive layer and the third adhesive layer which are stacked in sequence, one side of the first adhesive layer is in contact with the tab, and the second adhesive layer is between the first adhesive layer and the third adhesive layer; the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer is 160μm, the thickness percentage of the first adhesive layer is 25%, the thickness percentage of the second adhesive layer is 50%, and the thickness percentage of the third adhesive layer is 25% based on the total thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer; the melting point T1 of the first adhesive layer is 130℃, the melting point T2 of the second adhesive layer is 173℃, and the melting point T3 of the third adhesive layer is 195℃; Along the width direction Y of the tab, the first side part and the second side part include the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer which are stacked in sequence; one side of the fourth adhesive layer is in contact with the tab, and the fifth adhesive layer is between the fourth adhesive layer and the sixth adhesive layer; the melting point T4 of the fourth adhesive layer is 180℃, the melting point of the fifth adhesive layer is 160℃, and the melting point T6 of the sixth adhesive layer is 140℃; Along the thickness direction Z of the tab, two ends of the fourth adhesive layer are in contact with the first adhesive layer, two ends of the fifth adhesive layer are in contact with at least part of the first adhesive layer, the second adhesive layer and at least part of the third adhesive layer, and two ends of the sixth adhesive layer are in contact with the third adhesive layer; Along the width direction Y of the tab, the total thickness of the single side of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer is 1 mm, the thickness percentage of the fourth adhesive layer is 30% based on the total thickness of the single side of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer, the thickness percentage of the fifth adhesive layer is 40%, and the thickness percentage of the sixth adhesive layer is 30%.

[0127] Table 1 Note: The total thickness of the single side refers to the sum of the single side thicknesses of the first adhesive layer, the second adhesive layer and the third adhesive layer along the thickness direction of the tab.

[0128] Table 2 Performance test results of examples and comparative examples From the experimental data in Table 1 and Table 2, it can be seen that the peeling strength of the tab adhesive in the electrochemical device of the present application is high, and the occurrence rate of heat radiation adhesion and heat sealing overflow during the heat sealing process is low, and the heat box test liquid leakage rate is low; it shows that the thermal safety of the electrochemical device of the present application is high.

[0129] Finally, it should be explained that the above examples are used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced with the same, without departing from the essence and scope of the technical solutions of the present application.

Claims

1. An electrochemical device, comprising an electrode assembly, a packaging bag, a tab, and a tab adhesive, wherein the electrode assembly is accommodated in the packaging bag, the tab is connected to the electrode assembly and extends from a sealed portion of the packaging bag, the tab adhesive is circumferentially arranged on a side wall of the tab, the tab adhesive is in a closed form, the tab adhesive comprises a first adhesive layer, a second adhesive layer, and a third adhesive layer connected in sequence from inside to outside, an inner side of the first adhesive layer is connected to the tab, an outer side of the third adhesive layer is connected to an inner side of the sealed portion, a relationship among a melting point T1 of the first adhesive layer, a melting point T2 of the second adhesive layer, and a melting point T3 of the third adhesive layer satisfies T1 < T2 < T3, wherein 130℃ ≤ T1 ≤ 150℃, 160℃ ≤ T2 ≤ 180℃, and 190℃ ≤ T3 ≤ 200℃, a sum of thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer in a thickness direction of the tab is 110-210μm, the sum of thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer in the thickness direction of the tab is 135-185μm, a percentage of the thickness of the first adhesive layer based on the sum of thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer in the thickness direction of the tab is 20-30%, a percentage of the thickness of the second adhesive layer based on the sum of thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer in the thickness direction of the tab is 40-60%, and a percentage of the thickness of the third adhesive layer based on the sum of thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer in the thickness direction of the tab is 20-30%, the tab adhesive comprises a first side portion and a second side portion, the first side portion and the second side portion are connected between the top portion and the bottom portion and are arranged on both sides of the tab in a width direction of the tab, the first side portion and the second side portion comprise a fourth adhesive layer and a fifth adhesive layer stacked in sequence in the width direction of the tab, both ends of the fourth adhesive layer are in contact with the first adhesive layer and at least part of the second adhesive layer in the thickness direction of the tab, both ends of the fifth adhesive layer are in contact with at least part of the second adhesive layer and the third adhesive layer in the thickness direction of the tab, the first adhesive layer, the second adhesive layer, the third adhesive layer, the fourth adhesive layer, and the fifth adhesive layer form a ring structure, a relationship between a melting point T4 of the fourth adhesive layer and a melting point T5 of the fifth adhesive layer satisfies T4 > T5, wherein 180℃ ≤ T4 ≤ 200℃ and 160℃ ≤ T5 < 180℃, a percentage of the thickness of the fourth adhesive layer based on a sum of thicknesses of the fourth adhesive layer and the fifth adhesive layer is 40-50%, and a percentage of the thickness of the fifth adhesive layer based on the sum of thicknesses of the fourth adhesive layer and the fifth adhesive layer is 50-60%. ​ ​ ​ ​ 2. The electrochemical device of claim 1, wherein, ​ 3. The electrochemical device of claim 1, wherein, ​ 4. The electrochemical device of claim 1, wherein, ​ 5. The electrochemical device of claim 4, wherein, ​ 6. The electrochemical device of claim 5, wherein, ​ 7. The electrochemical device of claim 4, wherein The first side portion and the second side portion comprise, in sequence, a fourth adhesive layer, a fifth adhesive layer and a sixth adhesive layer along the width direction of the tab, and the two ends of the fourth adhesive layer are in contact with the first adhesive layer along the thickness direction of the tab; the two ends of the fifth adhesive layer are in contact with the second adhesive layer, and the two ends of the sixth adhesive layer are in contact with the third adhesive layer; the first adhesive layer, the second adhesive layer, the third adhesive layer, the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer form a ring structure; the relationship between the melting point T4 of the fourth adhesive layer, the melting point T5 of the fifth adhesive layer and the melting point T6 of the sixth adhesive layer satisfies: T4>T5>T6, wherein 180℃≤T4≤200℃, 160℃≤T5<180℃, and 130℃≤T6≤150℃.

8. The electrochemical device of claim 7, wherein The thickness percentage of the fourth adhesive layer is 25-35% based on the sum of the thicknesses of the fourth adhesive layer, the fifth adhesive layer and the sixth adhesive layer; the thickness percentage of the fifth adhesive layer is 30-40%; and the thickness percentage of the sixth adhesive layer is 25-35%.

9. The electrochemical device of claim 4 or 7, wherein The fourth adhesive layer comprises polyethylene and silicon dioxide, and the mass percentage of the silicon dioxide is 3-6% based on the mass of the fourth adhesive layer. The fifth adhesive layer comprises polypropylene and glass microbeads, and the mass percentage of the glass microbeads is 8-12% based on the mass of the fifth adhesive layer.

10. The electrochemical device of claim 7, wherein The sixth adhesive layer comprises polyethylene and talcum powder, and the mass percentage of the talcum powder is 4-7% based on the mass of the sixth adhesive layer.

11. The electrochemical device of claim 1, wherein, The tab adhesive comprises a bottom portion and a top portion, the top portion and the bottom portion are oppositely arranged along the extension direction of the tab, the top portion is located outside the sealing portion, and the bottom portion is located inside the packaging bag; the length of the top portion protruding out of the sealing portion is 1.5-3mm, and the length of the bottom portion protruding out of the sealing portion is 0.8-2mm.

12. The electrochemical device of claim 1, wherein, The third adhesive layer comprises polypropylene, polytetrafluoroethylene and phase change microcapsules, and the mass percentage of the polytetrafluoroethylene is 15-20% and the mass percentage of the phase change microcapsules is 5-8% based on the mass of the third adhesive layer. The second adhesive layer comprises polypropylene, polyethylene and graphene, and the mass percentage of the polyethylene is 20-40% and the mass percentage of the graphene is 3-5% based on the mass of the second adhesive layer. The first adhesive layer comprises polyethylene and calcium carbonate, and the mass percentage of the calcium carbonate is 2-4% based on the mass of the first adhesive layer.

13. An electronic device, comprising: The electrochemical device comprises the tab adhesive as claimed in any one of claims 1-12.

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