Gums and electrochemical devices comprising the same

Abstract

The application discloses a kind of glue material and the electrochemical device (30) comprising it, glue material includes glue film (10), glue film (10) includes bonding layer (101) and first functional layer (102), wherein, first functional layer (102) includes synthetic rubber and additive, and additive includes wax or high molecular surfactant.Glue material is adjusted by being provided with first functional layer (102) with synthetic rubber and additive, and the adhesion of the surface of both sides of its glue film (10) can be adjusted by heat treatment and / or pressure treatment, and the penetration and / or migration between layers in glue film (10) is avoided, to improve the safety performance of electrochemical device (30).

Description

Technical Field

[0001] This application relates to the fields of interfacial bonding and energy storage, specifically to an adhesive material having a substrate-free adhesive film and an electrochemical device containing therein, particularly a lithium-ion battery. Background Technology

[0002] With technological advancements and increasing demand for mobile devices, the need for electrochemical devices (such as lithium-ion batteries) has grown significantly. As electrochemical devices employ electrode components with high energy density and high discharge performance, the safety requirements for other components have also become more stringent.

[0003] In practical applications, electrode components in electrochemical devices often require adhesives to secure them to the housing / encapsulation. Currently used adhesives consist of a substrate and an adhesive layer, which present at least the following problems: 1) The substrate is too thick, leading to energy density loss, and the burrs from the substrate cutting process pose a risk of puncturing the diaphragm; 2) The adhesive layer can detach from the substrate, failing to effectively bind the electrode components, and in severe cases, causing delamination between the electrode components and the housing, thus losing its protective effect. Substrate-free adhesive films can solve these problems and are gradually gaining commercial application in actual production.

[0004] However, in existing substrate-free adhesive films, the adhesive surface and the hot-melt layer easily interpenetrate, resulting in high surface adhesion at room temperature, which is detrimental to the fabrication of electrochemical devices. Furthermore, under external forces, the significant difference between the bonding forces at the hot-melt layer and the adhesive layer limits the occurrence of interfacial damage between the adhesive film and its attached material (e.g., the electrochemical device casing, such as aluminum foil), thereby threatening the safety performance of the electrochemical device.

[0005] In view of this, it is indeed necessary to study and improve the adhesive material in order to enhance its safety in the use of electrochemical devices. Summary of the Invention

[0006] This application provides an adhesive material having a substrate-free adhesive film and an electrochemical device comprising the same, thereby solving at least one problem existing in the relevant field to some extent.

[0007] In one aspect of this application, an adhesive material is provided, comprising: an adhesive film. The adhesive film includes an adhesive layer and a first functional layer. The first functional layer comprises synthetic rubber and additives, wherein the additives include wax or a polymeric surfactant. By providing a first functional layer containing synthetic rubber and additives, the adhesive material of this application can adjust the adhesion between the two surfaces of its adhesive film through heat treatment and / or pressure treatment, and prevent penetration and / or migration between layers in the adhesive film, thereby improving the safety performance of electrochemical devices.

[0008] According to some embodiments of this application, the adhesion strength of the first functional layer at 23°C to 26°C is 0.01 N / mm to 0.05 N / mm.

[0009] According to some embodiments of this application, the adhesive strength of the first functional layer after hot pressing is 0.05 N / mm to 1.0 N / mm.

[0010] According to some embodiments of this application, the adhesive material further includes release paper. The release paper is disposed on the surface of the adhesive layer facing away from the first functional layer.

[0011] In another aspect of this application, an electrochemical device is provided, comprising an electrode assembly, a housing, and the aforementioned adhesive film. An adhesive layer of the adhesive film is disposed on the outer surface of the electrode assembly. A first functional layer of the adhesive film is disposed on the surface of the adhesive layer facing away from the electrode assembly and in contact with the inner surface of the housing. The adhesive film secures the electrode assembly and the housing.

[0012] According to some embodiments of this application, the adhesion force of the adhesive layer to the outer surface of the electrode assembly is 0.05 N / mm to 1.0 N / mm, and the adhesion force of the first functional layer to the inner surface of the housing is 0.05 N / mm to 1.0 N / mm.

[0013] According to some embodiments of this application, the mass ratio of the additive is 0.5% to 5.0% based on the total weight of the first functional layer.

[0014] According to some embodiments of this application, the mass ratio of the additive is preferably 1.0% to 4.0%.

[0015] According to some embodiments of this application, the synthetic rubber includes one or more of styrene-butadiene rubber, nitrile rubber, butyl rubber, chloroprene rubber, polysulfide rubber, polyurethane rubber, polyacrylate rubber, chlorosulfonated polyethylene rubber, silicone rubber, fluororubber, cis-butadiene rubber, isoprene rubber, or ethylene propylene rubber.

[0016] According to some embodiments of this application, the wax comprises one or more of paraffin wax, sasol wax, polyethylene wax, or polypropylene wax.

[0017] According to some embodiments of this application, the polymeric surfactant comprises one or more of the following components: polyacrylamide, polyacrylamide copolymer, polyacrylic acid, polyacrylic acid copolymer, polybutenoic acid, polybutenoic acid copolymer, maleic anhydride copolymer, polyethylene imide, polymaleamide, polymaleamide derivative, quaternized polyacrylamide, polydimethylamine cyclopropane, polyvinyl alcohol, polyvinyl alcohol esterification product, polyvinyl alcohol acetalization product, or polyethylene oxide-propylene oxide.

[0018] According to some embodiments of this application, the adhesive layer comprises one or more of acrylic, polypropylene, synthetic rubber (SIS), polyethylene, or polyamide.

[0019] According to some embodiments of this application, the dyne value of the adhesive layer is 30 mN / m to 48 mN / m, and the dyne value of the first functional layer is 30 mN / m to 48 mN / m.

[0020] According to some embodiments of this application, the thickness of the adhesive layer is 1 μm to 15 μm, the thickness of the first functional layer is 1 μm to 15 μm, and the thickness of the first functional layer is greater than or equal to the thickness of the adhesive layer.

[0021] According to some embodiments of this application, the adhesive film in the adhesive material further includes: a second functional layer disposed between the adhesive layer and the first functional layer, the second functional layer including a thermally conductive filler, the content of the thermally conductive filler being 5% to 50% based on the total weight of the second functional layer.

[0022] According to some embodiments of this application, the content of the thermally conductive filler is 20% to ~40%.

[0023] According to some embodiments of this application, the thermally conductive filler comprises one or more of diamond, graphite, graphene, alumina, boron nitride, silicon dioxide, or calcium oxide.

[0024] According to some embodiments of this application, the thickness of the second functional layer is 5 μm to 20 μm.

[0025] The adhesive material of this application, by eliminating the substrate, can reduce the thickness of the adhesive material to increase energy density and eliminate the phenomenon of adhesive layer detachment from the substrate, ensuring the fixation of the electrode assembly and improving the drop resistance of the electrochemical device. Simultaneously, by setting the composition of each layer of the adhesive film, the substrate-free adhesive film of this application can ensure that there is no penetration / migration from the first functional layer and the adhesive layer to the surface of another layer before and after heat / pressure treatment, thereby optimizing the fabrication process of the electrochemical device. Under strong external force, the adhesive film in the electrochemical device will undergo cohesive failure at the interface between the first functional layer and the adhesive layer, releasing stress and preventing interface damage between the adhesive film and its adhered material. This avoids failure phenomena such as voltage drop, leakage, overheating, smoke, and fire caused by aluminum foil tearing, further improving the safety of the lithium-ion electrochemical device.

[0026] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0027] The accompanying drawings, necessary for describing embodiments of this application or the prior art, will be briefly described below to facilitate the depiction of embodiments of this application. It is obvious that the drawings described below represent only a portion of the embodiments in this application. Those skilled in the art will be able to derive other embodiments from the structures illustrated in these drawings without requiring inventive effort.

[0028] Figure 1 This is a cross-sectional structural diagram of an adhesive material according to some embodiments of this application.

[0029] Figure 2 This is a cross-sectional structural diagram of an adhesive material according to other embodiments of this application.

[0030] Figure 3 This is a cross-sectional structural schematic diagram of an electrochemical device according to some embodiments of this application. Detailed Implementation

[0031] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0032] Unless otherwise expressly stated, the terms used herein have the meanings indicated below.

[0033] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the terms may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two numerical values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two numerical values ​​can be considered “generally” the same.

[0034] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "one or more of," "one or more of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "one or more of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "one or more of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0035] Furthermore, for ease of description, "first," "second," "third," etc., may be used in this document to distinguish different components of a figure or a series of figures. Unless otherwise specified or limited, "first," "second," "third," etc., are not intended to describe the corresponding components.

[0036] In this field, adhesives used to fix electrochemical devices and bond their electrode components to the housing are generally composed of a substrate and an adhesive layer. However, since the substrate itself has a certain thickness, using this adhesive to bond the electrode components to the housing increases the overall thickness of the electrochemical device, leading to a loss in overall energy density. Simultaneously, the substrate material may develop burrs during the slitting process, potentially puncturing the diaphragm of the electrode component and posing a potential safety risk to the electrochemical device. Furthermore, because the adhesive force of the adhesive layer to the substrate is not consistent with its adhesive force to the attached material, the adhesive layer can detach from the contact point between the adhesive layer and the substrate, failing to effectively fix the electrode component. In severe cases, relative movement between the electrode component and the housing can cause severe wear at both ends, easily leading to overheating, smoke, or even fire in the electrochemical device.

[0037] Chinese patent CN105449255B discloses a substrate-free adhesive film. This substrate-free adhesive film comprises an adhesive layer and a functional layer (hot melt layer) of a composite material consisting of a pressure-sensitive adhesive with initial tack or a pressure-sensitive adhesive without initial tack and a temperature-sensitive adhesive that is not tacky at room temperature. It can remain unbonded to the packaging shell (outer shell) without heat treatment and / or pressure treatment, but bond to the shell after pressure is applied, thereby optimizing the packaging process of electrode components. However, a stable interface cannot be formed between the adhesive layer and the hot melt layer of this substrate-free adhesive film. The materials of the adhesive layer and the hot melt layer easily interpenetrate, causing the surface tack of the hot melt layer to automatically increase after being left at room temperature for a period of time, which is detrimental to the packaging process of electrode components. In addition, since the adhesive force of the adhesive layer surface to its attached object is greater than that of the hot melt layer surface to its attached object, when subjected to external force, the interface damage of the substrate-free adhesive film often occurs between the functional layer surface and its attached object. In severe cases, the interface damage of the adhesive film can lead to tearing or breakage of the aluminum foil of the outer shell, thereby threatening the safety of the electrochemical device.

[0038] In view of the above problems, according to one aspect of this application, an embodiment of this application provides a substrate-free adhesive film. This substrate-free adhesive film, by adding wax and / or polymeric surfactants to the functional layer, can effectively maintain the interface between the adhesive layer and the functional layer, reducing mutual penetration between the adhesive layer and the functional layer, thereby optimizing the packaging process of the electrode assembly. Simultaneously, under external force, the adhesive film of this application can undergo cohesive failure at the interface between its adhesive layer and the functional layer, buffering stress and preventing damage to the adhesive interface of the attached object. Under strong external force, the adhesive film of this application can peel off at the interface between its adhesive layer and the functional layer, thereby protecting the integrity of both the electrode assembly and the housing, and preventing breakage or damage to the electrochemical device.

[0039] Figure 1 This is a cross-sectional schematic diagram of the adhesive material according to some embodiments of this application.

[0040] like Figure 1 As shown, some embodiments of this application provide an adhesive material, which includes an adhesive film 10. The adhesive film 10 is a substrate-free adhesive film, which includes an adhesive layer 101 and a first functional layer 102. The first functional layer 102 contains synthetic rubber and additives, and the additives include one or more of waxes or polymeric surfactants.

[0041] The first functional layer 102 is a heat-sensitive and / or pressure-sensitive layer, meaning that its adhesion to contact materials (e.g., aluminum foil, PP layer of packaging bags, etc.) increases after heat treatment and / or pressure treatment. In some embodiments, without heat treatment and / or pressure treatment, the adhesion of the first functional layer 102 at room temperature is 0.01 N / mm to 0.05 N / mm, where "room temperature" refers to a temperature in the range of 23°C to 26°C. In some embodiments, after heat treatment and / or pressure treatment, the adhesion of the first functional layer 102 is 0.05 N / mm to 1.0 N / mm. In this document, the terms "heat treatment" refer to a sample being in contact with or placed in an object / environment at a relatively high temperature (above room temperature) for a period of time; "pressure treatment" refers to a sample being subjected to a certain amount of pressure for a period of time; and "hot pressing" refers to a sample being in contact with or placed in an object / environment at a relatively high temperature (above room temperature) for a period of time while simultaneously being subjected to a certain amount of pressure. Those skilled in the art can adjust the parameters of "heat treatment," "pressure treatment," or "hot pressing" according to the actual material and viscosity requirements. In some embodiments, the adhesion strength of the first functional layer 102 after hot pressing is 0.05 N / mm to 1.0 N / mm, wherein the hot pressing temperature is set at 55°C to 85°C, the applied pressure is 0.3 MPa to 2 MPa, and the time is 5 mins to 120 mins.

[0042] The term "adhesion force" in this article refers to the vertical peel force between the bonded sample and the sample to be bonded when subjected to external force. It can be obtained by peel force test according to standard GB / T2792-2014. For specific implementation details, please refer to the specific examples section below.

[0043] In some embodiments, the mass ratio of additives in the first functional layer 102, based on the total weight of the first functional layer 102, is 0.5% to 5.0%. In some embodiments, the mass ratio of additives is approximately 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or a range of values ​​formed by any two of the above. The wax and / or polymeric surfactants in the additives have low polarity and anti-corrosion properties, exhibiting strong polar binding force to the synthetic rubber of the first functional layer 102 and incompatibility with the adhesive layer material, thereby preventing the first functional layer 102 from interpenetrating with the adhesive layer 101. In some embodiments, the first functional layer 102 can adjust its adhesion to the shell material by adjusting the composition and mass ratio of the additives. In some embodiments, the mass ratio of additives in the first functional layer 102 is 1.0% to 4.0% to achieve optimal cohesive structure disruption effect.

[0044] In some embodiments, the wax in the additive comprises one or more of paraffin wax, sasol wax, polyethylene wax, or polypropylene wax. In some embodiments, polyethylene wax is added to the first functional layer 102, wherein the polyethylene wax has excellent cold resistance, heat resistance, chemical resistance, and abrasion resistance, which can further improve the processing performance of the first functional layer. In some embodiments, polypropylene wax is added to the first functional layer 102, wherein the polypropylene wax has characteristics such as high melting point, low melt density, good lubricity, and good dispersibility, which can make the first functional layer easier to distribute evenly. In some embodiments, sasol wax is added to the first functional layer 102, wherein the shorter side chains of sasol wax contain long-chain aliphatic hydrocarbons, which have better electrical conductivity, higher melting point, and hardness, and can improve the heat resistance of the first functional layer. In some embodiments, paraffin wax is added to the first functional layer 102, wherein the paraffin wax is a mixture of hydrocarbons with 18 to 30 carbon atoms, containing 80% to 95% straight-chain alkanes, less than 20% alkanes with individual branches, and monocyclic cycloalkanes with long side chains. In some embodiments, the chemical structural formula of paraffin wax is as follows:

[0045]

[0046] In some embodiments, the polymeric surfactant in the additive comprises one or more of the following components: polyacrylamide, polyacrylamide copolymer, polyacrylic acid, polyacrylic acid copolymer, polybutyric acid, polybutyric acid copolymer, maleic anhydride copolymer, polyethylene imide, polymaleamide, polymaleamide derivative, quaternized polyacrylamide, polydimethylamine cyclopropane, polyvinyl alcohol, polyvinyl alcohol esterification product, polyvinyl alcohol acetalization product, or polyethylene oxide-propylene oxide. Substrate-free film delamination effect is better when using the above-mentioned polymeric surfactant.

[0047] In some embodiments, the synthetic rubber (SIS) in the first functional layer 102 includes one or more of styrene-butadiene rubber, nitrile rubber, butyl rubber, chloroprene rubber, polysulfide rubber, polyurethane rubber, polyacrylate rubber, chlorosulfonated polyethylene rubber, silicone rubber, fluororubber, cis-butadiene rubber, isoprene rubber, or ethylene propylene rubber.

[0048] In some embodiments, the composition of the first functional layer 102 can be determined by Fourier transform infrared spectroscopy. In this document, the composition of the first functional layer 102 is determined according to standard GB / T 21186-2007, wherein a special prism (e.g., a KRS-5 prism made of TlBr and TLI) is used at 250 cm⁻¹. -1The sample is sandwiched between two transparent surfaces. Incident light, after multiple reflections in the sample and prism, reaches the detector. The depth of the incident light reaching the sample surface depends on the incident wavelength, the incident angle, and the refractive indices of the prism and the sample. In some embodiments, the composition of the first functional layer 102 can be determined based on the position and intensity of the absorption peak detected by the detector. In some embodiments, based on standard GB / T21186-2007, the first functional layer of this application can be [value missing] within the range of 100~1700 cm⁻¹. -1 (1450 cm) -1 Methyl CH3, 1465 cm -1 Methylene CH2, 1340 cm -1 Methionine (CH), 1270 cm -1 Sulfate salt, 1200 cm -1 Sulfonates, 1430 & 1560 cm -1 Fatty acid salts, 1220 & 1100 cm -1 Sulfate salt, 1100 cm -1 Hydroxyl group, 1700 cm -1 carbonyl), 2000~2800cm -1 (2700 cm) -1 (carboxyl group) and 3000~3500cm -1 (3300 cm) -1 amide, 3100 cm -1 Characteristic absorption peaks appear in the paragraphs containing aliphatic ammonium salts.

[0049] In some embodiments, adhesive layer 101 may comprise any suitable adhesive material in the art. In some embodiments, adhesive layer 101 comprises one or more of acrylic, polypropylene, synthetic rubber (SIS), polyethylene, or polyamide.

[0050] refer to Figure 1In some embodiments, the thickness of the adhesive layer 101 is from 1 μm to 15 μm. In some embodiments, the thickness of the adhesive layer 101 can be less than or equal to 3 μm. In some embodiments, the thickness of the first functional layer 102 is from 1 μm to 15 μm. In some embodiments, the thickness of the first functional layer 102 can be less than or equal to 5 μm. In some embodiments, the thickness of the first functional layer 102 is greater than the thickness of the adhesive layer 101 to further reduce the possibility of the adhesive layer 101 penetrating the first functional layer 102. In some embodiments, the total thickness of the adhesive film 10 is from 2 μm to 30 μm. In some embodiments, the total thickness of the adhesive film 10 can be less than or equal to 8 μm to improve the volumetric energy density of the electrochemical device. In other embodiments, the total thickness of the adhesive film 10 is approximately, for example, about 2 μm, about 4 μm, about 6 μm, about 8 μm, about 10 μm, about 15 μm, about 20 μm, about 30 μm, or a range of any two of these values.

[0051] In some embodiments, the permeation between the adhesive layer 101 and the first functional layer 102 can be measured by the dyne values ​​of their respective surfaces. The term "dyne value" as used herein refers to the surface tension coefficient, defined as the force exerted between adjacent portions of a liquid / colloid surface per unit length, which can be obtained using a dyne pen test, as detailed in the specific embodiments section below. If the adhesive layer 101 permeates into the first functional layer 102, the composition of adjacent surfaces of the first functional layer 102 will change, resulting in a change in its dyne value. Conversely, if the first functional layer 102 permeates into the adhesive layer 101, the dyne value of the adhesive layer 101 surface will also change. In some embodiments, after the film 10 is placed at room temperature for 12 hours, there is no significant change in the dyne values ​​of the adhesive layer 101 and the first functional layer surface 102 on both sides. In some embodiments, the dyne value of the first functional layer 102 after heat treatment and / or pressure treatment does not change significantly. In some embodiments, the dyne value of the adhesive layer 101 is between 30 mN / m and 48 mN / m. In some embodiments, the dyne value of the first functional layer 102 is 30 mN / m to 48 mN / m.

[0052] Those skilled in the art will understand that the coverage of the adhesive film on the surface of the object to which it is attached can be adjusted according to the specific requirements of the application scenario. In some embodiments, the coverage of the adhesive film on the surface of the object to which it is attached is 10% to 95%.

[0053] refer to Figure 1 In some embodiments, the adhesive material may further include release paper 103, which is disposed on the surface of the adhesive layer 101 of the adhesive film 10 facing away from the first functional layer 102.

[0054] Those skilled in the art will understand that the release paper 103 in the adhesive material is used to prevent the surface of the adhesive layer 101 from contacting a non-attached target surface or itself, thereby avoiding adhesion between the adhesive layer and the non-attached target surface or itself during the use of the adhesive material. Those skilled in the art can select any suitable release paper material or size according to actual needs. In some embodiments, the release paper can be disposed on one side of any exposed surface of the adhesive layer of the adhesive film, for example, but not limited to, the surface of the adhesive layer facing away from the first functional layer or the surface on the side of the adhesive layer. In some embodiments, the release paper can be disposed simultaneously on both the exposed surface of the adhesive layer of the adhesive film and the exposed surface of the first functional layer, for example, but not limited to, the surface of the first functional layer facing away from the adhesive layer or the surface on the side of the first functional layer. In some embodiments, the release paper can be removed after the adhesive film is applied. In some embodiments, the release paper comprises a single-sided silicone release film or a double-sided silicone release film.

[0055] Figure 2 This is a cross-sectional schematic diagram of the adhesive material according to another embodiment of this application.

[0056] like Figure 2 As shown in another embodiment of this application, the adhesive film 10 of the adhesive material further includes a second functional layer 104, which is disposed between the adhesive layer 101 and the first functional layer 102. The second functional layer 104 is a heat dissipation layer with a high thermal conductivity. The second functional layer 104 can provide heat dissipation channels to dissipate the heat generated inside the electrode assembly, thereby eliminating heat concentration in the electrode assembly, avoiding heat accumulation in the electrochemical device, and improving the safety of the electrochemical device. In some embodiments, the thermal conductivity of the second functional layer 104 is higher than that of the adhesive layer 101 and / or the first functional layer 102.

[0057] In some embodiments, the second functional layer 104 includes a thermally conductive filler to improve its thermal conductivity. In some embodiments, the second functional layer 104 may also include a thermally conductive gel. Without departing from the spirit of this application, the thermally conductive filler and thermally conductive gel can be any suitable material in the art. In some embodiments, the thermally conductive gel is a polysiloxane. In some embodiments, the thermally conductive filler includes one or more of diamond, graphite, graphene, alumina, boron nitride, silicon dioxide, or calcium oxide. Based on the total weight of the second functional layer 104, in some embodiments, the content of the thermally conductive filler is 5% to 50%; in some embodiments, the content of the thermally conductive filler is approximately 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range of values ​​formed by any two of the above. In some embodiments, the content of the thermally conductive filler is 20% to 40% to maintain a certain level of adhesion while providing a certain level of thermal conductivity, thereby making the multilayer structure of the adhesive film more stable.

[0058] In some embodiments, the second functional layer 104 further comprises an adhesive material comprising one or more of acrylic, polypropylene, synthetic rubber (SIS), polyethylene, or polyamide to improve the structural stability of the second functional layer 104 and the adhesion of the adhesive film. In some embodiments, the content of the adhesive material is 5% to 30% by weight of the second functional layer 104.

[0059] In some embodiments, the thickness of the second functional layer 104 is 5 μm to 20 μm.

[0060] In some embodiments, the second functional layer 104 can completely cover the adhesive layer 101. In some embodiments, the second functional layer 104 can partially cover the adhesive layer 101. It should be understood that, without departing from the spirit of this application, those skilled in the art can configure the distribution range of the second functional layer in the adhesive film according to actual heat dissipation needs. In some embodiments, the distribution of the second functional layer in the adhesive film can be set according to the heat concentration area corresponding to the electrode assembly.

[0061] Figure 3 This is a cross-sectional schematic diagram of an electrochemical device according to some embodiments of this application.

[0062] like Figure 3 As shown, according to another aspect of this application, some embodiments of this application provide an electrochemical device 30, which includes: an electrode assembly 301, a housing 302, and a film 10 as described in the above embodiments, wherein the adhesive layer 101 of the film 10 is disposed on the outer surface of the electrode assembly 301, and the first functional layer 102 of the film 10 is disposed on the surface of the adhesive layer facing away from the electrode assembly 301 and in contact with the inner surface of the housing 302, and the film 10 fixes the electrode assembly 301 and the housing 302.

[0063] In some embodiments, the adhesion force of the adhesive layer 101 to the outer surface of the electrode assembly 301 is 0.05 N / mm to 1.0 N / mm. In some embodiments, the adhesion force of the first functional layer 102 to the inner surface of the housing is 0.05 N / mm to 1.0 N / mm. In some embodiments, under external force, the cohesive failure of the adhesive film itself at the interface between the adhesive layer and the first functional layer can be optimized, further improving the protection of the adhesive film for the outer surface of the electrode assembly 301 and the inner surface of the housing 302.

[0064] In some embodiments, the housing is a soft-pack aluminum-plastic film. It should be understood that, without departing from the spirit of this application, the housing 302 can be any common electrochemical device encapsulation structure in the art. In some embodiments, the housing is a square aluminum shell or a cylindrical aluminum shell.

[0065] In some embodiments, the electrode assembly includes a positive electrode, a separator, and a negative electrode. It should be understood that, although... Figure 3 The embodiments described herein employ a wound electrode assembly; however, without departing from the spirit of this application, the electrode assembly may be any suitable electrode assembly in the art, and is not limited thereto. In some embodiments, the electrode assembly may be a stacked structure or a multi-tab structure. In some embodiments, the electrochemical device is a lithium-ion battery.

[0066] In some embodiments, the positive electrode comprises a positive current collector and a positive active material layer. The positive current collector may be aluminum foil or nickel foil; however, other positive current collectors commonly used in the art may be used without limitation. In some embodiments, the positive active material layer comprises a positive active material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as "positive active material capable of absorbing / releasing lithium Li"). Examples of positive active materials capable of absorbing / releasing lithium (Li) may include one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0067] In some embodiments, the positive electrode active material layer may further comprise at least one of a binder and a conductive agent. The binder comprises one or more of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The conductive agent comprises one or more of carbon nanotubes, conductive carbon black, acetylene black, graphene, and Ketjen black. It should be understood that those skilled in the art may select conventional binders and conductive agents according to actual needs, and are not limited thereto.

[0068] In some embodiments, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector may be copper foil or nickel foil; however, other negative electrode current collectors commonly used in the art may be used without limitation. In some embodiments, the negative electrode active material layer comprises a negative electrode active material capable of absorbing and releasing lithium (Li), including, but not limited to, one or more of carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN3, lithium metal, metallic and semi-metallic elements that form alloys with lithium, polymer materials, and combinations thereof. In some embodiments, the negative electrode active material layer may further comprise at least one of a binder and a conductive agent. The conductive agent and binder of the negative electrode active material layer are similar to those of the conductive agent and binder of the positive electrode active material layer described above, and will not be repeated here.

[0069] In some embodiments, the separator includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. For example, polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. Polyethylene and polypropylene, in particular, are effective in preventing short circuits and can improve battery stability through a turn-off effect. It should be understood that those skilled in the art can select conventional separators according to actual needs, without being limited thereto.

[0070] The electrochemical device of this application also includes an electrolyte comprising a lithium salt and a non-aqueous solvent.

[0071] In some embodiments, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, LiPF6 is chosen as the lithium salt because it provides high ionic conductivity and improves cycling characteristics.

[0072] The non-aqueous solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, other organic solvents, or any combination thereof.

[0073] The aforementioned carbonate compounds may be chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or any combination thereof.

[0074] Examples of other organic solvents mentioned above include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and any combination thereof.

[0075] In some embodiments, the non-aqueous solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, and any combination thereof.

[0076] In some embodiments, the non-aqueous solvent is a mixture of dioxolane (DOL) and dimethyl ether (DME) in a volume ratio of 0.5-2.

[0077] It should be understood that the preparation methods of the positive electrode, negative electrode, separator, and electrolyte in the embodiments of this application can be any suitable conventional method in the art, without departing from the spirit of this application, and are not limited thereto, as needed. In one embodiment of the method for manufacturing an electrochemical device, the method for preparing a lithium-ion battery includes: sequentially winding, folding, or stacking the negative electrode, separator, and positive electrode into an electrode assembly; adhering the adhesive film in the adhesive material of the above embodiments to the outer surface of the electrode assembly through an adhesive layer; then loading the electrode assembly with the adhesive film adhering to it into a housing, such as an aluminum-plastic film, and injecting electrolyte; then performing a hot-pressing process on the lithium-ion battery housing containing the electrode assembly to bond the adhesive film on the outer surface of the electrode assembly to the inner surface of the housing; and then obtaining a lithium-ion battery through subsequent vacuum sealing, settling, formation, shaping, and other processes.

[0078] Although the above example uses a lithium-ion battery, those skilled in the art, upon reading this application, will realize that the adhesive film of the adhesive material described in this application can be used in other suitable electrochemical devices. Such electrochemical devices include any device in which an electrochemical reaction occurs, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0079] Some embodiments of this application further provide an electronic device that includes the electrochemical device described in the embodiments of this application.

[0080] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, 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, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc. Specific Implementation

[0082] The following are some specific embodiments and comparative examples, and the test methods and results of their electrochemical devices (lithium-ion batteries) and GB / T2792-2014 peel force test, dyne value test, GB / T21186-2007 Fourier transform infrared spectroscopy test, thickness reduction test, drop performance test and heat dissipation test are provided to better illustrate the technical solution of this application.

[0083] I. Testing Methods

[0084] 1.1 GB / T2792-2014 Peel Strength Test:

[0085] The test object was attached to aluminum foil using a high-speed rail tensile testing machine (ASR-1021, Guangdong ASR Instruments Technology Co., Ltd.), and then cut into 20mm pieces. A 60mm strip-shaped sample, the length and width of which can be adjusted proportionally according to actual conditions, is used. Along the length of the sample to be tested, the surface of the sample used to test the adhesion to the sample is adhered to a steel plate using strong adhesive, with an adhesion length of not less than 40mm. The steel plate is fixed at the corresponding position on the high-speed rail tensile testing machine. The other end of the sample not adhered to the steel plate is pulled up, and the sample is placed into the clamp using a connector or directly to clamp it, making it bond with the sample surface on the steel plate. The angle between the pulled-up sample portion and the steel plate in space is 180°. The clamp pulls the sample at a speed of 50mm / min, and the average tensile force in the stable region is recorded as the adhesion force.

[0086] 1.2 Dyne value test:

[0087] The test is conducted using a dyne tester. The tester is held perpendicular to the surface of the object being tested, and a straight line is drawn evenly on the surface. After 2 to 3 seconds, observe whether the surface contracts and forms droplets. Judgment methods: ① If the line is evenly distributed without any droplets, the surface tension of the object is higher than the value marked on the dyne tester; ② If the line slowly contracts, the surface tension of the object is slightly lower than the value marked on the dyne tester; ③ If the line contracts immediately and forms droplets, the surface tension of the object is much lower than the value marked on the dyne tester. Continue using different dyne testers with different dyne values ​​until the closest dyne value is obtained as the dyne value for the object being tested.

[0088] 1.3 GB / T21186-2007 Fourier Transform Infrared Spectroscopy Test:

[0089] Fourier transform infrared (FTIR) spectra of the analytes were measured using a Nicolet iS50 (Thermo Fisher Scientific) spectrometer. Total reflectance (ATR) can be used for infrared spectroscopy determination along the depth and surface of the sample. A special prism (KRS-5 prism made of TlBr and TLI) was used at 250 cm⁻¹. -1 The detector is constructed by sandwiching the sample (which is transparent above) between its two sides. Incident light is reflected multiple times by the sample and the prism before reaching the detector. The depth to which the incident light reaches the surface of the sample depends on the incident wavelength, the incident angle, and the refractive indices of the prism and the sample. The absorption wavelength of the incident light upon reaching the detector is recorded, and the composition of the sample is determined by the intensity and position of the absorbed wavelength.

[0090] 1.4 1.8m drop test:

[0091] Ten electrochemical devices (lithium-ion batteries) to be tested were charged to full charge voltage at a constant current rate of 0.5C at room temperature, and then charged to full charge state at a constant voltage rate of 0.05C. The lithium-ion battery voltage was then adjusted to 68% SOC. The voltage and internal resistance were measured to ensure that the lithium-ion battery voltage was between 3.94V and 3.99V. Using a constant voltage tester and a drop-specific metal or plastic mold (shaped and sized to simulate a real mobile phone), the lithium-ion battery was placed in the constant voltage tester. After the mold was pressed against the lithium-ion battery (within 1 minute), air compression was immediately applied, and a 5kg pressure block was used to press the lithium-ion battery for 7 seconds. The battery was then left to stand for 1 hour, and the voltage and internal resistance were measured again. The battery was inspected for damage, leakage, swelling, corrosion, etc. After completion, the cover of the drop-specific metal or plastic mold was closed and the screws were tightened to complete the drop test preparation.

[0092] Manual drop test: Drop the battery freely from a height of 1.8m in six directions as follows: head -> tail -> head right corner -> tail right corner -> head left corner -> tail left corner (angle: 45±15 degrees), repeating 7 rounds. If leakage, overheating, smoke, or fire is observed after each round, stop dropping. If none of the above occurs after the entire drop cycle, the drop test is considered passed. After the drop test, remove the lithium-ion battery and allow it to stand at room temperature for 24 hours. Then measure the voltage and internal resistance, and record whether the discharge voltage drops by more than 50mV.

[0093] 1.5-1 m extreme drop test:

[0094] Ten electrochemical devices (lithium-ion batteries) to be tested were charged to full charge voltage at a constant current rate of 0.5C at room temperature, and then charged to full charge state at a constant voltage rate of 0.05C. The lithium-ion battery voltage was then adjusted to 68% SOC. The voltage and internal resistance were measured to ensure that the lithium-ion battery voltage was between 3.94V and 3.99V. Using a constant voltage tester and a drop-specific metal or plastic mold (shaped and sized to simulate a real mobile phone), the lithium-ion battery was placed in the constant voltage tester. After the mold was pressed against the lithium-ion battery (within 1 minute), air compression was immediately applied, and a 5kg pressure block was used to press the lithium-ion battery for 7 seconds. The battery was then left to stand for 1 hour, and the voltage and internal resistance were measured again. The battery was inspected for damage, leakage, swelling, corrosion, etc. After completion, the cover of the drop-specific metal or plastic mold was closed and the screws were tightened to complete the drop test preparation.

[0095] Manual drop test: Drop freely from a height of 1 m in the following order from 6 directions: head -> tail -> head right corner -> tail right corner -> head left corner -> tail left corner (angle: 45±15 degrees). Stop the drop if leakage, heat, smoke, fire, or voltage drop exceeds 50mV, and record the number of drops to the 1 m limit.

[0096] 1.6 Heat dissipation test:

[0097] Thermocouples were embedded inside the electrochemical device (lithium-ion battery) under test. Two miniature thermocouples used 80 μm diameter wires; one thermocouple was embedded in the center of the electrode assembly, and the other was placed at the interface between the electrode assembly and the casing. Additionally, a thermocouple was attached to the outer surface of the pouch cell to monitor the battery surface temperature. The lithium-ion battery was first discharged at 0.5C to 2.8V, then allowed to stand for 30 minutes. It was then charged at a constant current of 0.5C to full charge voltage at room temperature, and then charged at a constant voltage to a current of 0.05C. The battery was then placed horizontally in a temperature chamber with the thermocouples facing upwards, and temperature changes at different charge / discharge rates of 1C and 7C were recorded.

[0098] II. Preparation Method

[0099] 2.1 Preparation of the positive electrode

[0100] Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75%, and the mixture was stirred evenly. The slurry was uniformly coated onto aluminum foil for the positive electrode current collector and dried at 90°C. Subsequently, the positive electrode was obtained after cold pressing, cutting, and slitting.

[0101] 2.2 Preparation of Electrolyte

[0102] In an environment with a water content of less than 150 ppm (in a dry argon atmosphere), a solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC) = 20:30:20:28:2, mass ratio) at a mass ratio of 8:92 is used as the electrolyte for lithium-ion batteries.

[0103] 2.3 Preparation of the negative electrode

[0104] Copper foil was used as the negative electrode current collector. A layer of graphite slurry was uniformly coated on the surface of the copper foil. The slurry composition was a combination of 97.7 wt% artificial graphite, 1.3 wt% sodium carboxymethyl cellulose (CMC-Na), and 1.0 wt% styrene-butadiene rubber (SBR), and dried at 90°C. After cold pressing, cutting, and slitting, the negative electrode was dried under vacuum at 85°C for 4 hours.

[0105] 2.4 Preparation of Lithium-ion Batteries

[0106] A polyethylene film with a thickness of 15 μm was used as the separator. The positive electrode, separator, and negative electrode were stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation. After removing moisture from the stacked electrode assembly at 80°C, a dry electrode assembly was obtained, and a lithium-ion battery was prepared according to the following embodiments.

[0107] Example 1

[0108] Acrylic is used as the adhesive layer material, and synthetic rubber and additives are mixed to form the first functional layer slurry. The types and proportions of the synthetic rubber and polypropylene wax are shown in the table below. The adhesive layer material is coated onto release paper to form an adhesive layer, and the first functional layer slurry is coated onto the adhesive layer to form the first functional layer. The thickness of both the adhesive layer and the first functional layer is 5 μm.

[0109] The dry electrode assembly is attached to both sides with a substrate-free adhesive film and placed in a soft aluminum-plastic molded packaging bag. The top side is sealed and vacuum-baked at 80°C for 8 hours. Subsequently, electrolyte is injected, and after formation, capacity testing, and degassing processes, a square soft-pack lithium-ion battery with a thickness / width / height of 5.2 mm, 63 mm, and 76 mm, respectively, is produced.

[0110] Example 2-11

[0111] The preparation method is largely the same as in Example 1, except that the type of synthetic rubber in the first functional layer slurry and / or the ratio of it to the additives are different. Please refer to the following example table for details.

[0112] Examples 12-15

[0113] The preparation method is largely the same as that in Example 3, except that the types of additives in the first functional layer slurry are different. Please refer to the table of the following examples for details.

[0114] Examples 16-18

[0115] The preparation method is largely the same as that in Example 3, except that the thickness of the first functional layer is different, as detailed in Table 1.

[0116] Examples 19-22

[0117] The preparation method is largely the same as that in Example 3, except that the adhesive material of the adhesive layer is different, as detailed in Table 2.

[0118] Examples 23-24

[0119] The preparation method is largely the same as that in Example 3, except that the thickness of the adhesive layer is different, as detailed in Table 2.

[0120] Example 25

[0121] The preparation method is largely the same as in Example 3, except that in Example 25, after forming the adhesive layer, a second functional layer coating is further formed by mixing 50 wt% thermally conductive gel, 40 wt% thermally conductive filler, and 10 wt% binder. The types and proportions of the thermally conductive gel, thermally conductive filler, and binder are shown in Table 3. Subsequently, the second functional layer coating is applied to the adhesive layer to form the second functional layer, and a first functional layer slurry is applied to the second functional layer to form the first functional layer. The thickness of the adhesive layer is 5 μm, the thickness of the first functional layer is 5 μm, and the thickness of the second functional layer is 10 μm.

[0122] Examples 26-36

[0123] The preparation method is largely the same as that of Example 25, except that the types or proportions of thermally conductive gels or binders are different, as detailed in Table 3.

[0124] Examples 37-39

[0125] The preparation method is largely the same as that in Example 25, except that the thickness of the second functional layer is different, as detailed in Table 3.

[0126] Comparative Examples 1-3

[0127] The preparation method is roughly the same as that of Comparative Example 1, except that only synthetic rubber was used in the preparation of the first functional layer slurry, and the thickness of the first functional layer is different. Please refer to Table 1 for details.

[0128] Comparative Example 4

[0129] Commercially available double-sided adhesive is used as the adhesive material. The double-sided adhesive is attached to both sides of the electrode assembly and then placed in a soft aluminum-plastic molded packaging bag. The top side is sealed and the battery is vacuum-baked at 80°C for 8 hours. Subsequently, electrolyte is injected, and after formation, capacity testing, and degassing processes, a square soft-pack lithium-ion battery with a thickness / width / height of 5.2 mm, 63 mm, and 76 mm, respectively, is produced.

[0130] Comparative Example 5

[0131] The preparation method is roughly the same as that of Comparative Example 4, except that the double-sided adhesive is only attached to one side of the electrode assembly.

[0132] Comparative Example 6

[0133] The preparation method is roughly the same as that of Comparative Example 5, except that the double-sided adhesive is only attached to the other side of the electrode assembly.

[0134] III. Comparison Results

[0135] 3.1 Comparison of Substrate-Free Adhesive Film Composition

[0136] The difference between the lithium-ion batteries in Examples 1-15 and Comparative Examples 1-6 lies in the composition of the adhesive film or the first functional layer of the adhesive film. The structural parameters of the first functional layer and the results of the adhesion test, dyne test and drop test are recorded in Table 1 below.

[0137] Table 1

[0138]

[0139]

[0140] Referring to Table 1, this application effectively adjusts the adhesive strength of the first functional layer by adding additives containing wax or polymeric surfactants to the first functional layer of the substrate-free adhesive film. This allows the adhesive strength to differ between the first functional layer and the first functional layer after hot pressing, thereby optimizing the encapsulation process of the electrode assembly. Simultaneously, the addition of additives to the adhesive film in this application maintains the dyne value of the first functional layer surface within a certain range, preserving the interface between the first functional layer and the adhesive layer and preventing penetration between them. This allows the adhesive film to release stress through cohesive failure at the interface between the first functional layer and the adhesive layer when subjected to external force, improving its performance in drop tests. Referring to Examples 1-15 and Comparative Examples 1-6, the first functional layer with added additives effectively adjusts the surface viscosity after hot pressing, preventing excessive viscosity from damaging the electrode assembly or the surface of the casing. Simultaneously, it maintains the dyne value of the first functional layer to optimize the processing requirements of the lithium-ion battery. The lithium-ion battery using the substrate-free adhesive film in this application can maintain a stable voltage output for the vast majority of cases after being subjected to external impact.

[0141] Comparing Examples 1-6 with Comparative Example 1, it can be seen that by adjusting the proportion of additives in the first functional layer of the substrate-free adhesive film of this application, the surface dyn value of the first functional layer can be changed, affecting the interface stability between the first functional layer and the adhesive layer, and thus affecting its drop test performance. Referring to Examples 1-5, it can be seen that the adhesive film with the additive mass ratio range provided in the embodiments of this application has a dyn value ranging from 30 dyn / cm to 48 dyn / cm, the interface between the first functional layer and the adhesive layer is relatively stable, and its lithium-ion battery has better drop test performance.

[0142] Comparing Example 3 with Comparative Examples 4-6, compared to lithium-ion batteries using conventional double-sided adhesive, the lithium-ion batteries of this application, after being subjected to strong external impacts, can maintain their outer casing without damage, fire, or leakage. This demonstrates that the lithium-ion batteries using a substrate-free adhesive film in this application can effectively improve their safety performance against strong external impacts. In the 1m extreme drop test, the number of drops it can withstand is far greater than that of the lithium-ion batteries using conventional double-sided adhesive in the comparative examples, indicating that this application can still effectively improve its safety performance even with lower external impacts.

[0143] 3.2 Comparison of substrate-free adhesive film thickness

[0144] The difference between the lithium-ion batteries in Example 3 and Examples 16-18 and Examples 23-24 is that the thickness of the first functional layer and / or adhesive layer of the adhesive film is different. The thickness of the first functional layer, the thickness of the adhesive layer, the material of the adhesive layer, the results of the adhesion test and the drop test of the lithium-ion battery are recorded in Table 2 below.

[0145] Table 2

[0146]

[0147] Referring to Table 2, a comparison of Examples 3, 16-18, and 23-24 reveals that if the thickness of the first functional layer or adhesive layer in the substrate-free adhesive film of this application is too low, its adhesive strength will decrease, affecting the interface maintenance between the first functional layer and the adhesive layer. This prevents the adhesive film from releasing stress through cohesive failure at the interface, thus affecting its drop test performance. In the examples, the lithium-ion battery adhesive film with a first functional layer thickness greater than or equal to the adhesive layer thickness exhibits better interface maintenance between the first functional layer and the adhesive layer, resulting in superior drop test performance. A comparison of Examples 3 and 19-22 shows that the adhesive strength of the adhesive layer on the outer surface of the electrode assembly in this application is affected by its material and thickness; that is, the adhesive strength of the adhesive layer on the outer surface of the electrode assembly can be changed by adjusting the thickness and adhesive material of the adhesive layer.

[0148] 3.3 Heat dissipation test results

[0149] The difference between the lithium-ion batteries in Example 3 and Examples 25-39 is that the encapsulant film has a second functional layer. The thickness of the second functional layer, the composition of the second functional layer, the results of the adhesion test, and the drop test and heat dissipation test of the lithium-ion battery are recorded in Table 3 below.

[0150] Table 3

[0151]

[0152] Referring to Table 3, it can be seen that in Examples 25-39, by using a substrate-free adhesive film with a second functional layer, the heat dissipation of the lithium-ion battery can be effectively improved, thereby effectively reducing the temperature rise of its electrode components during charging and avoiding overheating of the battery at high charging rates. Furthermore, comparing Examples 3 with Examples 25-39, it can be seen that the substrate-free adhesive film with a second functional layer in this application still exhibits good safety performance in the drop test structure of its lithium-ion battery.

[0153] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0154] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrochemical device comprising: an electrode assembly, a housing, and a film, said film including an adhesive layer and a first functional layer, wherein, The first functional layer comprises synthetic rubber and additives, including waxes or polymeric surfactants, and the adhesive strength of the first functional layer after hot pressing is 0.05 N / mm to 1.0 N / mm; The adhesive layer of the adhesive film is disposed on the outer surface of the electrode assembly of the electrochemical device, and the first functional layer of the adhesive film is disposed on the surface of the adhesive layer facing away from the electrode assembly and in contact with the inner surface of the housing. The adhesive film fixes the electrode assembly and the housing. The wax comprises one or more of paraffin wax, sasol wax, polyethylene wax, or polypropylene wax; The polymeric surfactant comprises one or more of the following components: polyacrylamide, polyacrylamide copolymer, polyacrylic acid, polyacrylic acid copolymer, polybutenoic acid, polybutenoic acid copolymer, maleic anhydride copolymer, polyethylene imide, polymaleamide, polymaleamide derivative, quaternized polyacrylamide, polydimethylamine cyclopropane, polyvinyl alcohol, polyvinyl alcohol esterification product, polyvinyl alcohol acetalization product, or polyethylene oxide-propylene oxide; The adhesive layer comprises one or more of acrylic, polypropylene, synthetic rubber, polyethylene, or polyamide.

2. The electrochemical device according to claim 1, wherein the adhesion strength of the first functional layer at 23°C to 26°C is 0.01 N / mm to 0.05 N / mm.

3. The electrochemical device according to claim 1, wherein the surface of the adhesive layer facing away from the first functional layer is provided with release paper.

4. The electrochemical device according to claim 1, wherein the adhesion force of the adhesive layer to the outer surface of the electrode assembly is 0.05 N / mm to 1.0 N / mm, and the adhesion force of the first functional layer to the inner surface of the housing is 0.05 N / mm to 1.0 N / mm.

5. The electrochemical device according to claim 1, wherein the mass ratio of the additive is 0.5% to 5.0% based on the total weight of the first functional layer.

6. The electrochemical device according to claim 5, wherein the mass ratio of the additive is 1.0% to 4.0%.

7. The electrochemical device according to claim 1, wherein the synthetic rubber comprises one or more of styrene-butadiene rubber, nitrile rubber, butyl rubber, chloroprene rubber, polysulfide rubber, polyurethane rubber, polyacrylate rubber, chlorosulfonated polyethylene rubber, silicone rubber, fluororubber, cis-butadiene rubber, isoprene rubber, or ethylene propylene rubber.

8. The electrochemical device according to claim 1, wherein the dyne value of the adhesive layer is from 30 mN / m to 48 mN / m, and the dyne value of the first functional layer is from 30 mN / m to 48 mN / m.

9. The electrochemical device according to claim 1, wherein the thickness of the adhesive layer is 1 μm to 15 μm, the thickness of the first functional layer is 1 μm to 15 μm, and the thickness of the first functional layer is greater than or equal to the thickness of the adhesive layer.

10. The electrochemical device of claim 1, wherein the adhesive film further comprises: a second functional layer disposed between the adhesive layer and the first functional layer, wherein the second functional layer comprises a thermally conductive filler, and the content of the thermally conductive filler is 5% to 50% based on the total weight of the second functional layer.

11. The electrochemical device according to claim 10, wherein the content of the thermally conductive filler is 20% to 40%.

12. The electrochemical device according to claim 10, wherein the heat-conducting filler comprises one or more of diamond, graphite, graphene, alumina, boron nitride, silicon dioxide, or calcium oxide.

13. The electrochemical device according to claim 10, wherein the thickness of the second functional layer is from 5 μm to 20 μm.

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