Background
With the continuous development of power battery technology, the requirements for light weight and high energy density of the battery cell are gradually increased, and the cost reduction of the battery cell in the consumer market is also extremely challenging. At present, the application of the composite conductive film with a multilayer structure as a current collector instead of the traditional copper-aluminum foil is gradually mature. The composite conductive film with low cost and high quality has positive significance for the development of power batteries.
SUMMERY OF THE UTILITY MODEL
The application aims to provide a conductive film and a pole piece so as to solve the technical problems of low compactness, low elongation at break and high resistivity of the conductive film.
The application also aims to clarify the relative structural relationship among the bonding layer, the transition layer, the protective layer and the functional layer, so that the structure, physical properties and cost of the whole conductive film are more reasonably controlled.
In a first aspect, an embodiment of the present application provides a conductive film, which includes a base film and a structural layer, where the structural layer is disposed on two sides of the base film. The structural layer comprises a transition layer and a functional layer which are sequentially arranged on the base film, the transition layer and the functional layer are metal layers, and the thickness of the transition layer is 1% -4% of the thickness of the functional layer.
The conductive film improves the structural layer, a transition layer is arranged between the base film and the functional layer, the transition layer is a metal layer and has conductivity, and the transition layer has better compactness and lower resistivity, so that the compactness of the conductive film is improved, and the resistivity of the conductive film is reduced. The thickness of the transition layer is 1% -4% of the thickness of the functional layer, and the structure reduces the process cost and the thickness of the structural layer while the conductive film has better compactness and lower resistivity.
In a possible implementation manner, the preparation process of the transition layer comprises at least one of a magnetron sputtering method, an alkaline electroplating method and chemical plating, and the preparation process of the functional layer comprises one or two of an evaporation method and a water electroplating method. In one possible implementation, the metallic material of the transition layer and the functional layer includes at least one of Cu, Ni, Cr, NiCu alloy, and NiCr alloy.
The transition layer and the functional layer respectively adopt different processes to obtain layer structures with different performances, so that the transition layer and the functional layer have better conductivity and have better compactness and lower resistivity.
At one kind canIn the realization mode of the energy, the structural layer further comprises a bonding layer arranged between the transition layer and the base film, and the thickness of the bonding layer is 0.1% -2% of that of the functional layer. The material of the bonding layer is metal, and the thickness of the bonding layer is 0.2% -0.5% of that of the functional layer. Or the material of the bonding layer is nonmetal, and the thickness of the bonding layer is 0.5% -2% of that of the functional layer. The bonding layer is a metal layer, and the metal material of the bonding layer comprises at least one of Ni, Cr, NiCu alloy, NiCr alloy and NiV alloy. Or the bonding layer is a non-metal layer, and the non-metal material of the bonding layer comprises polytetrafluoroethylene, polypropylene, polyethylene, titanium nitride and NbOx(1≤x≤2.5)、SiC、Si3N4、SiOx(1.5≤x≤2)、AlOx(x is more than or equal to 1 and less than or equal to 1.5), polyvinylidene chloride and/or melamine.
The bonding layer plays the effect of connecting base film and transition layer, improves the adhesive strength of layer structure. The bonding layer with the thickness proportion enables the base film and the transition layer to have good bonding force.
In a possible implementation manner, the structural layer further includes a protective layer disposed on the surface of the functional layer, and the thickness of the protective layer is 0.1% -6% of the thickness of the functional layer. The protective layer is a metal layer, and the metal material of the protective layer comprises at least one of Ni, Cr, NiCu alloy, NiCr alloy and NiCu alloy. Or the protective layer is a non-metal layer, and the non-metal material of the protective layer comprises at least one of glucose complex and potassium dichromate.
The functional layer plays a role in protecting the functional layer from oxidation. The protective layer of this thickness proportion has when better protection, has reduced the thickness of protective layer, reduces the discharge capacity in the course of working, reduce cost.
In one possible implementation, the thickness of the base film is 1.2 μm to 12 μm and the thickness of the functional layer is 300-1500 nm.
The structure enables the structure layer to be thinner than that of the existing conductive film, and more active substances can be coated in the area in the manufacturing process of the lithium battery. The battery cell with the same volume can contain more layers of pole pieces when the thickness of the active substances coated on the pole pieces is the same, and finally the energy density of the battery cell can be improved by 0.5-2%.
In a second aspect, a pole piece is provided, which comprises the conductive film and an active material coated on the conductive film. Because the conducting film provided by the application has better conducting performance and tensile mechanical property and has a thinner structural layer, the pole piece has better conducting performance and tensile mechanical property.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like refer to orientations or positional relationships based on orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the application usually place when using, are only used for convenience of description and simplification of description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present application.
The current multilayer structure composite conductive film generally comprises a base film, a functional layer and a protective layer, wherein the functional layer is used as a conductive layer to play a conductive role, and the protective layer is used for protecting the functional layer. On the basis of the existing multilayer structure composite conductive film, a bonding layer is added to improve the adhesion between the base film and the functional layer. With the development of power batteries, the requirements on structures such as pole pieces and conductive films are gradually increased.
Under the requirement, the inventor of the application provides the improvement of the structural layer through the research on the multi-layer structure composite conductive thin film structure, the transition layer is arranged between the bonding layer and the functional layer, the transition layer has better compactness and lower resistivity, and meanwhile, the transition layer is a metal layer, has conductive performance and cannot influence the overcurrent capacity of the conductive film. Some embodiments of the present application will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1, fig. 2 and fig. 3, fig. 1 to fig. 3 are schematic structural diagrams of three different conductive films 100 provided in this embodiment.
The embodiment provides a conductive film 100, which includes a base film 110 and a structural layer 120, wherein the structural layer 120 is disposed on both sides of the base film 110. It is understood that the base film 110 has opposite first and second surfaces, the first surface being provided with the first structural layer 120 and the second surface being provided with the second structural layer 120. In this embodiment, the structures of the first structural layer 120 and the second structural layer 120 are the same, and in other embodiments of the present application, the first structural layer 120 may be different from the second structural layer 120, and the specific structure may be changed as needed.
The base film 110 in the embodiment of the present application is a flexible film material, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), Polyimide (PI), polypropylene (PP), Polyethylene (PE), Polyphenylene Sulfide (PPs), and the like, and the base film 110 plays a role of a base support in the conductive film 100. The thickness of the base film 110 in the embodiment of the present application is 1.2 μm to 12 μm, and alternatively, the thickness of the base film 110 may be 1.2 μm, 2 μm, 3.5 μm, 4 μm, 5 μm, or 6 μm.
The structural layer 120 in the embodiment of the present application includes an adhesive layer 121, a transition layer 122, a functional layer 123, and a protective layer 124 sequentially disposed on the base film 110. The adhesive layers 121 are disposed on both surfaces of the base film 110, and serve to connect the base film 110 and the transition layer 122. The transition layer 122 is disposed on the surface of the bonding layer 121, and plays a role in improving electrical conductivity and enhancing compactness. The functional layer 123 is disposed on the surface of the transition layer 122, and mainly plays a role in conducting electricity. The protective layer 124 is disposed on the surface of the functional layer 123, and plays a role in protecting the functional layer 123 and preventing oxidation. In other embodiments of the present application, the adhesive layer 121 and the protective layer 124 may be selectively disposed as needed. Referring to fig. 2 and 3, the structural layer in fig. 2 only includes the transition layer 122 and the functional layer 123, and the structural layer in fig. 3 only includes the transition layer 122, the functional layer 123 and the protective layer 124.
The transition layer 122 and the functional layer 123 in the present application are made of the same material, and are both metal layers, which have a conductive effect. In some embodiments of the present application, the metal materials of the transition layer 122 and the functional layer 123 include at least one of Cu, Ni, Cr, NiCu alloy, and NiCr alloy. However, the transition layer 122 and the functional layer 123 adopt different preparation processes, so that the transition layer 122 has higher compactness and lower resistivity. Through the research of the inventor of the present application, the preparation process of the transition layer 122 includes at least one of a magnetron sputtering method, an alkaline electroplating method, and a chemical plating method, and the preparation process of the functional layer 123 includes one or both of an evaporation method and a water electroplating method. By adopting the preparation process, the transition layer 122 with high compactness is obtained, the compactness of the conductive film 100 is improved, and the light holes of the conductive film 100 are reduced.
Since the preparation process of the transition layer 122 is more demanding and costly than the preparation process of the functional layer 123, the thickness of the transition layer 122 is generally smaller than that of the functional layer 123 in order to reduce the cost. Through the research of the inventor of the present application, the thickness of the transition layer 122 is 1% to 4% of the thickness of the functional layer 123. The structure improves the compactness of the conductive film 100, reduces the light holes of the conductive film 100, reduces the resistivity of the conductive film 100 and improves the elongation of the conductive film 100 while the conductive film 100 has certain conductive performance. Optionally, the thickness of the transition layer 122 is 1%, 5%, 10%, 15%, 20%, 25%, or 30% of the thickness of the functional layer 123.
On the basis of the above layer structure, in order to provide a better adhesive force between the base film 110 and the transition layer 122, the thickness of the adhesive layer 121 in the embodiment of the present application is 0.1% to 2% of the thickness of the functional layer 123. The layer structure enables the adhesion between the base film 110 and the transition layer 122 to reach more than 100-300N/m. Alternatively, the thickness of the adhesive layer 121 is 0.1%, 0.5%, 1%, 2%, 5%, 6%, 8%, or 10% of the thickness of the functional layer 123.
In the embodiment of the present application, the material of the adhesive layer 121 is metal or nonmetal. When the adhesion layer 121 is a metal layer, the metal material of the adhesion layer 121 includes at least one of Ni, Cr, NiCu alloy, NiCr alloy, and NiV alloy, and the thickness of the adhesion layer 121 is preferably 0.2% to 0.5% of the thickness of the functional layer 123. When the bonding layer 121 is a non-metal layer, the non-metal material of the bonding layer 121 includes polytetrafluoroethylene, polypropylene, polyethylene, titanium nitride, and NbOx(1≤x≤2.5)、SiC、Si3N4、 SiOx(1.5≤x≤2)、AlOx(x is not less than 1 and not more than 1.5), polyvinylidene chloride (PVDC) and melamine, and the thickness of the adhesive layer 121 is preferably 0.5 to 2% of the thickness of the functional layer 123.
On the basis of the layer structure, in order to reduce the thickness of the structural layer 120 to a greater extent, reduce the amount of sewage discharged during the processing, and reduce the cost, in some embodiments of the present application, the thickness of the protective layer 124 is 0.1% to 6% of the thickness of the functional layer 123. The layer structure has better protection to the functional layer 123, and simultaneously reduces the thickness of the protective layer 124. Further, the thickness of the protective layer 124 is 3% to 7% of the thickness of the functional layer 123. Optionally, the thickness of the protective layer 124 is 0.1%, 1%, 2%, 3%, 5%, 7%, 8%, or 10% of the thickness of the functional layer 123.
In the embodiment of the present application, the material of the protection layer 124 is metal or nonmetal. When the bonding layer 121 is a metal layer, the metal material of the protection layer 124 includes at least one of Ni, Cr, NiCu alloy, NiCr alloy, and NiCu alloy. When the protective layer 124 is a non-metal layer, the non-metal material of the protective layer 124 includes at least one of a glucose complex and potassium dichromate.
The existing multilayer structure composite conductive film has a wider limitation on the structure of each layer, but the application defines the relative structural relationship among the adhesive layer 121, the transition layer 122, the protective layer 124 and the functional layer 123, so that the structure, physical properties and cost of the whole conductive film 100 are more reasonably controlled.
In the embodiment of the application, the thickness of the functional layer 123 is 300-1500nm, and the thickness proportion relationship of the structural layer 120 enables the conductive film 100 to have physical properties such as good adhesion, oxidation resistance, conductivity and the like. This structure allows the structural layer 120 to be thinner than the structural layer 120 of the prior art conductive film 100, and more active material can be applied to this region during the lithium battery manufacturing process. The battery cell with the same volume can contain more layers of pole pieces when the thickness of the active substances coated on the pole pieces is the same, and finally the energy density of the battery cell can be improved by 0.5-2%.
The conductive film 100 has the characteristic of double-sided conductivity, and the sheet resistance of the film surface is 300-10m omega; film surface resistivity 1.8X 10E-8-2.5×10E-8Omega, m, the film surface TD and MD breaking elongation is more than or equal to 3 percent; the film surface TD and MD tensile strength are more than or equal to 200 MPa; the surface tension test dyne value is more than or equal to 38. It is demonstrated that the conductive film 100 provided by the present application has good conductivity and tensile mechanical propertiesCan be widely applied to the field of power batteries.
The present application also provides a pole piece (not shown) comprising the above-described conductive film 100 and an active material coated on the conductive film 100. Because the conductive film 100 provided by the application has better conductive performance and tensile mechanical property and has a thinner structural layer 120, the pole piece has better conductive performance and tensile mechanical property.
The conductive film provided by the application can be prepared by the following steps:
1. preparing the bonding layer. The preparation process of the bonding layer in the embodiment of the application comprises at least one of physical vapor deposition and chemical vapor deposition.
The physical vapor deposition method comprises the following steps: placing the base film coil stock in a vacuum coating machine, sealing the vacuum chamber, and gradually vacuumizing until the vacuum degree reaches 10-4-10-1Pa, adopting magnetron sputtering or crucible high-frequency heating or resistance heating or electron beam heating as deposition source, the deposited material is metallic nickel, chromium, nickel alloy, chromium alloy or nonmetal SiC, Si3N4、SiO2Or Al2O3The purity is more than or equal to 99.9 percent, the winding and unwinding speed is adjusted, and evaporated atoms or molecules form a coating layer, namely a bonding layer, on the moving base film;
the chemical vapor deposition method comprises: placing the base film coil stock in a vacuum coating machine, sealing the vacuum chamber, and gradually vacuumizing until the vacuum degree reaches 10-4-10-1Pa, adopting a crucible high-frequency heating mode or a resistance heating mode or an electron beam heating mode as an evaporation source, and introducing compressed oxygen by utilizing an oxygen introducing structure of an oxygen delivery mechanism near the evaporation source or between the evaporation source and the surface close to the tympanic membrane or near the main drum to adjust the ventilation quantity. The evaporation source evaporation raw materials are metal aluminum wire, aluminum ingot and silicon, the purity is more than or equal to 99.9 percent, the winding and unwinding speed is adjusted, the evaporated atoms react with oxygen and form a layer of SiO on the moving base filmx(x is more than or equal to 1.5 and less than or equal to 2) or AlOx(x is more than or equal to 1 and less than or equal to 1.5), namely the bonding layer.
2. And preparing a transition layer. The preparation process of the transition layer in the embodiment of the application comprises at least one of a magnetron sputtering method, an alkaline electroplating method and chemical plating.
The magnetron sputtering method comprises the following steps: placing the film roll coated with the bonding layer into a vacuum coating machine, sealing the vacuum chamber, and gradually vacuumizing until the vacuum degree reaches 10-5-10-1Pa, exciting a metal with the purity of more than or equal to 99.9 percent such as copper by adopting a magnetron sputtering mode, adjusting the unwinding speed, the winding speed and the evaporation capacity, forming a metal layer such as a copper plating layer on the surface of the film plated with the bonding layer, and repeating the steps for a plurality of times according to actual needs to obtain a transition layer with a certain thickness;
the alkaline plating includes:
placing the conductive film coil material plated with the bonding layer in reel-to-reel hydroelectric plating equipment, adjusting the film surface square resistance of the conductive film to be 50-2 omega, adjusting the proper winding and unwinding speed, current, copper ion concentration, brightener concentration, adjuvant concentration, pH value and electrolyte temperature, depositing 5-300nm each time according to actual needs, and repeating for a plurality of times to obtain a transition layer with a certain thickness;
the chemical plating comprises the following steps: the film coil stock plated with the metal or metal alloy bonding layer is placed in a roll-to-roll chemical coating device, sodium salt is used as main salt, copper sulfate is used as main raw material, sodium potassium tartrate, EDTA disodium salt and the like are used as complexing agents, sodium hydroxide is used for adjusting the pH value to be 11.5-13, formaldehyde is used as reducing agent, potassium ferrocyanide, alpha' -bipyridine, methyl dichlorosilane and the like are used as stabilizing agents, the proper winding and unwinding speed is adjusted, and a transition layer with a certain thickness is obtained by repeating for a plurality of times according to actual needs.
3. And preparing the functional layer. The preparation process of the functional layer in the embodiment of the application comprises one or two of an evaporation method and a water electroplating method.
The evaporation method comprises the following steps: placing the film coil coated with the transition layer into a vacuum coating machine, sealing the vacuum chamber, and gradually vacuumizing until the vacuum degree reaches 10-4-10-1Pa, heating metal such as copper with purity of 99.9% or more by high-frequency heating in crucible or resistance heating or electron gun-accelerated electron evaporationAdjusting the unreeling speed, the reeling speed and the evaporation amount, continuously melting and evaporating copper in the evaporation source, forming a metal layer such as a copper plating layer on the surface of the transition layer, and repeating the steps for a plurality of times according to actual needs to obtain a functional layer with a certain thickness;
the water electroplating method comprises the following steps: placing the conductive film coil material plated with the transition layer in reel-to-reel hydroelectric plating equipment, adjusting the film surface square resistance of the conductive film to 10000-20m omega, adjusting the proper winding and unwinding speed, current, copper ion concentration, brightener concentration, adjuvant concentration, pH value and electrolyte temperature, depositing for 2-2500nm each time according to actual needs, and repeating for a plurality of times to obtain a functional layer with a certain thickness;
4. and preparing a protective layer. The preparation process of the protective layer in the embodiment of the application comprises at least one of a physical vapor deposition method, a magnetron sputtering method, a water electroplating method and a coating method.
The physical vapor deposition method comprises the following steps: putting the coil material coated with the functional layer into a vacuum chamber of a vacuum coating machine which can reciprocate on one side or two sides, sealing the vacuum chamber, and vacuumizing step by step until the vacuum degree reaches 10-4-10-1Pa, adopting a crucible high-frequency heating mode or a resistance heating mode or an electron beam heating mode as an evaporation source, wherein the evaporation source evaporation raw material is metallic nickel, chromium, nickel alloy and chromium alloy, the purity is more than or equal to 99.9%, the unwinding speed and the winding speed are adjusted, and evaporated atoms or molecules form a layer of coating, namely a protective layer, on the surface of the functional layer;
the magnetron sputtering method comprises the following steps: putting the coil material coated with the functional layer into a vacuum chamber of a vacuum coating machine which can reciprocate on one side or two sides, sealing the vacuum chamber, and vacuumizing step by step until the vacuum degree reaches 10-5-10-1Pa, coating a film on the functional layer on the surface of the film by utilizing magnetron sputtering, wherein the target material is nickel or chromium or nickel alloy or chromium alloy, the purity of the target material is more than or equal to 99.9 percent, the unwinding speed and the winding speed are adjusted, and sputtered ions form a magnetron sputtering coating, namely a protective layer, on the surface of the functional layer;
the water electroplating method comprises the following steps: the coil material plated with the functional layer is placed into roll-to-roll water electroplating equipment or a device, the material is immersed into a solution in a solution pool in a winding and membrane-moving mode, potassium dichromate or glucose or other organic matters with oxidation resistance are dissolved in the solution pool, and a layer of plating layer, namely a protective layer, can be formed on the surface of the functional layer by adjusting proper winding and unwinding speed, current, concentration, pH value and temperature;
the coating method comprises the following steps: the coil material plated with the functional layer is placed into single-side or double-side coil-to-coil surface coating equipment or a device, the material passes through the coating device in a mode of winding and film-passing, the coating device can uniformly coat potassium dichromate or glucose or other organic matters with oxidation resistance on the surface of the functional layer, and a coating layer, namely a protective layer, can be formed on the surface of the functional layer by adjusting the proper winding and unwinding speed.
The thickness proportion of the coating of the multilayer structure can produce the current collector with stable quality through a curing production process. On the premise of ensuring the overcurrent capacity of the current collector, the current collector also has better physical properties such as adhesive force, oxidation resistance, conductivity and the like.
Example 1
The embodiment provides a conductive film, which comprises a base film and a structural layer, wherein the structural layer is arranged on two sides of the base film. The structural layer comprises a bonding layer, a transition layer, a functional layer and a protective layer which are sequentially arranged on the base film. The thickness of the base film was 4 μm and the thickness of the functional layer was 1500 nm.
The transition layer and the functional layer are copper-plated layers, and the thickness of the transition layer is 10% of that of the functional layer. The adhesive layer is a Ni metal layer, and the thickness of the adhesive layer is 6% of that of the functional layer. The protective layer is a glucose complex non-metal layer, and the thickness of the protective layer is 5% of that of the functional layer.
Example 2
The embodiment provides a conductive film, which comprises a base film and a structural layer, wherein the structural layer is arranged on two sides of the base film. The structural layer comprises a bonding layer, a transition layer, a functional layer and a protective layer which are sequentially arranged on the base film. The thickness of the base film was 3.5 μm and the thickness of the functional layer was 300 nm.
The transition layer and the functional layer are copper-plated layers, and the thickness of the transition layer is15% of the thickness of the functional layer. The bonding layer is Si3N4And the thickness of the bonding layer is 2% of that of the functional layer. The protective layer is a NiCu alloy metal layer, and the thickness of the protective layer is 1% of the thickness of the functional layer.
Example 3
The embodiment provides a conductive film, which comprises a base film and a structural layer, wherein the structural layer is arranged on two sides of the base film. The structural layer comprises a bonding layer, a transition layer, a functional layer and a protective layer which are sequentially arranged on the base film. The thickness of the base film was 6 μm and the thickness of the functional layer was 1000 nm.
The transition layer and the functional layer are copper-plated layers, and the thickness of the transition layer is 20% of that of the functional layer. The bonding layer is a NiCu alloy metal layer, and the thickness of the bonding layer is 10% of that of the functional layer. The protective layer is a potassium dichromate non-metal layer, and the thickness of the protective layer is 8% of that of the functional layer.
Example 4
This embodiment provides a conductive film, which is different from embodiment 1 only in that: the structural layer of the conductive film is not provided with an adhesive layer.
Example 5
This embodiment provides a conductive film, which is different from embodiment 1 only in that: the structure layer of the conductive film is not provided with a protective layer.
Comparative example 1
This comparative example provides a conductive film, differing from example 1 only in that: the structural layer of the conductive film has no transition layer.
Comparative example 2
This comparative example provides a conductive film, differing from example 1 only in that: the thickness of the transition layer of the conductive film is 0.01% of the thickness of the functional layer.
Test examples
SEM examination was performed on the conductive films provided in example 1 and comparative examples 1 to 2 to examine the densification property. Fig. 4 is a result of detection of the conductive film provided in example 1, fig. 5 is a result of detection of the conductive film provided in comparative example 1, and fig. 6 is a result of detection of the conductive film provided in comparative example 2. As can be seen from the figure, the conductive film of example 1 had a uniform surface and no spots, while the conductive films of comparative examples 1 and 2 had a rougher surface and more spots.
The resistivity of the conductive films provided in the examples 1-5 and the comparative examples 1-2 is detected by adopting a multipoint test fitting algorithm of a daily internal resistance meter, and the method comprises the following steps:
1. the samples were cut into small strips with a gauge of 15mm by 210 mm.
2. A marker is used to mark every 20mm on the sample, with all points lying on the sample mid-line.
3. Resistance values of 20mm, 40mm, 60mm, 80mm … were measured using a probe resistance test line aligned to the position of the red dot in the plot, testing until the end of the substrate, and recording the position and resistance.
4. And repeating the steps, testing 3 parallel samples for each sample, drawing the measurement data by taking the measurement distance as an abscissa and the resistance as an ordinate, performing linear fitting, and reading the slope k.
5. The resistivity ρ (sample width 15mm, coating thickness by weight) was calculated according to the formula k ρ/(width × coating thickness).
The conductive films provided in examples 1 to 5 and comparative examples 1 to 2 were subjected to adhesion test, which specifically includes the following steps: taking a double-sided adhesive tape with the width of 20mm and the length of 100mm, adhering the double-sided adhesive tape on a table for standby, taking a test sample, adhering the test sample on the surface of the double-sided adhesive tape to cover the double-sided adhesive tape, then stealing redundant samples, and carrying out peeling test on the samples by using adhesive tapes with different adhesive forces, wherein the adhesive tapes with different gradients of 300-one-100N/m are generally selected for testing, and the adhesive force grade is confirmed when the adhesive tapes are not peeled.
The conductive films provided in examples 1 to 5 and comparative examples 1 to 2 were subjected to oxidation resistance tests by the following method: the surface change of the conductive film was observed under the environment of a relative humidity of less than 60% and a normal temperature, and the oxidation resistance time (days) was recorded.
The test results are given in the following table:
TABLE 1 Properties of the conductive films
As can be seen from table 1, the conductive film layer structures provided in embodiments 1 to 3 include the adhesive layer, the transition layer, the functional layer, and the protective layer, and the thickness ratio of each layer is within the range provided in the present application, so that the conductive film has higher compactness, lower resistivity, and better oxidation resistance, and the layer structure of the conductive film has better adhesive strength. Comparative example 1 does not have a transition layer, so that the conductive film has low compactness and high resistivity. The transition layer in comparative example 2 is thinner and does not achieve better densification and lower resistivity.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.