Composite current collector and preparation method therefor, and lithium-ion battery

Abstract

A composite current collector and a preparation method therefor, and a lithium-ion battery. The composite current collector comprises: a polymer base film (1); a metal layer (2) arranged on at least one side surface of the polymer base film (1); and an organic protective layer (3) arranged on the surface of the metal layer (2) along the direction away from the polymer base film (1), wherein the material of the organic protective layer (3) is composed of polypyrrole and a silane material in a mass ratio of (80-99.5):(0.5-20), and the polypyrrole is prepared by coating a pyrrole material on the metal layer (2) by means of in-situ polymerization.

Description

Composite current collector, preparation method thereof and lithium ion battery TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, for example, a composite current collector, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] At present, the composite current collector based on the high polymer film has been widely concerned and applied in the new energy industry. The preparation of the composite current collector usually adopts the method of physical vapor deposition (PVD) to deposit a metal layer on the high polymer film (such as polyester or polyolefin, etc.), so as to prepare a composite current collector with good conductivity. Compared with the traditional current collector (copper foil or aluminum foil, etc.), the composite current collector based on the high polymer film has the characteristics of low cost, light weight and good internal insulation. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when applied in the battery.

[0003] However, since the metal layer material of the composite current collector, copper and aluminum metal, has strong reducibility and is easy to be oxidized, the conductivity of the composite current collector is poor, which affects its use. Therefore, a protective layer is usually arranged on the surface of the composite current collector to protect the metal material from being oxidized. At present, the inorganic passivation method, i.e. the method of hexavalent chromium treatment, is usually used to generate an oxide layer on the surface of the metal layer of the composite current collector in situ by using hexavalent chromium, so as to protect the metal layer from being oxidized. However, the hexavalent chromium used in the preparation process is highly hazardous and can easily harm human health, and the wastewater generated in the process can pollute the water body and cause a series of environmental problems. In order to solve this problem, organic protective layers have begun to enter the research field of people. A representative organic protective layer is polypyrrole. However, due to the hydrophobicity of polypyrrole and the relatively low surface roughness of the composite current collector, the adhesion between polypyrrole and the composite current collector is poor when polypyrrole is compounded on the composite current collector, which leads to poor oxidation resistance and stability of the prepared composite current collector.

[0004] Therefore, it is urgent to design a protective layer to solve the problem of poor oxidation resistance and stability of the composite current collector caused by the weak adhesion between polypyrrole and the metal layer in the composite current collector. SUMMARY

[0005] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of protection of the claims.

[0006] The application provides a composite current collector, a preparation method thereof and a lithium ion battery. The application introduces a specific mass ratio of polypyrrole and silane material to cooperatively construct an organic protective layer. The polar oxygen-containing group in the silane material can form a strong intermolecular force with the metal atoms in the metal layer and the nitrogen atoms in the polypyrrole, and the non-polar alkyl group in the silane material can form a strong intermolecular force with the polypyrrole. Therefore, the silane material can be used as a bridge to promote the close combination between the metal layer and the organic protective layer in the composite current collector, thereby improving the oxidation resistance of the composite current collector and the performance stability of the composite current collector based on the organic protective layer in the application process, and facilitating the promotion and application of the composite current collector.

[0007] In a first aspect, the application provides a composite current collector, which comprises:

[0008] a polymer base film;

[0009] a metal layer arranged on at least one side surface of the polymer base film;

[0010] an organic protective layer arranged on the surface of the metal layer in a direction away from the polymer base film;

[0011] wherein the material of the organic protective layer is composed of polypyrrole and silane material with a mass ratio of (80-99.5):(0.5-20), and the polypyrrole is prepared by in-situ polymerization of pyrrole material coated on the metal layer.

[0012] The application introduces a specific mass ratio of polypyrrole and silane material to cooperatively construct an organic protective layer. The polar oxygen-containing group in the silane material can form a strong intermolecular force with the metal atoms in the metal layer and the nitrogen atoms in the polypyrrole, and the non-polar alkyl group in the silane material can form a strong intermolecular force with the polypyrrole. Therefore, the silane material can be used as a bridge to promote the close combination between the metal layer and the organic protective layer in the composite current collector, thereby improving the oxidation resistance of the composite current collector and the performance stability of the composite current collector based on the organic protective layer in the application process, and facilitating the promotion and application of the composite current collector.

[0013] In the application, the mass ratio of polypyrrole and silane material is (80-99.5):(0.5-20), wherein the selected range of polypyrrole “80-99.5” can be 80, 85, 90, 95 or 99.5, and the selected range of silane material “0.5-20” can be 0.5, 1, 5, 10, 15 or 20.

[0014] In the present application, if the mass ratio of polypyrrole and silane material is too small, i.e. the content of polypyrrole is too low, the prepared organic protective layer has poor oxidation resistance; if the mass ratio of polypyrrole and silane material is too large, i.e. the content of silane material is too low, the adhesion between the prepared organic protective layer and the metal layer is low, and the stability is poor.

[0015] As an optional technical solution of the present application, the mass content of the silane material is 0.5-20wt%, for example, it can be 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt% or 20wt% and the like, and optionally 5-10wt%.

[0016] In the present application, if the mass content of the silane coupling agent is too low, the adhesion between the prepared organic protective layer and the metal layer is low, and the stability is poor; if the mass content of the silane coupling agent is too high, the adhesion between the prepared organic protective layer and the metal layer cannot be further improved significantly, and the content of polypyrrole is reduced, resulting in poor oxidation resistance of the prepared protective layer.

[0017] In an embodiment, the silane material is a silane coupling agent containing an isocyanate group.

[0018] In an embodiment, the silane coupling agent containing an isocyanate group includes any one of 3-isocyanate propyl triethoxysilane, 3-isocyanate propyl trimethoxysilane, 3-isocyanate propyl methyl dimethoxysilane or 1,3,5-tris(trimethoxysilylpropyl) isocyanurate or a combination of at least two.

[0019] The present application selects a silane material containing an isocyanate group because the isocyanate group in the molecule can react with the amine group on the polypyrrole, so that the silane material and the polypyrrole can be tightly combined through a chemical bond, thereby improving the compactness and stability of the organic protective layer and improving the protection effect.

[0020] It should be noted that the molecule in polypyrrole contains an amine group as an inherent property, and the structural formula is as follows:

[0021] In an embodiment, the group in the silane material further includes any one of halogen, hydroxyl, amino or mercapto or a combination of at least two.

[0022] As an optional technical solution of the present application, the thickness of the organic protective layer is 5-100nm, for example, it can be 5nm, 10nm, 20nm, 40nm, 60nm, 80nm or 100nm and the like.

[0023] In the present application, if the thickness of the organic protective layer is too thin, the effect is not obvious, and if the thickness of the organic protective layer is too thick, the conductivity of the composite current collector is poor and affects the improvement of the energy density of the battery.

[0024] In one embodiment, the thickness of the organic protective layer is less than or equal to 10% of the thickness of the metal layer, for example, the thickness of the organic protective layer can be 10%, 8%, 6%, 4% or 2% of the thickness of the metal layer, etc.

[0025] In the present application, if the thickness of the organic protective layer is greater than 10% of the thickness of the metal layer, the performance improvement is not obvious, and the conductivity of the composite current collector is poor and affects the improvement of the energy density of the battery.

[0026] In one embodiment, the organic protective layer is at least 2 layers, and the content of silane material in the single-layer organic protective layer decreases in the direction away from the polymer base film.

[0027] In the present application, on the one hand, the preparation of the multi-layer organic protective layer can ensure that the reaction is more complete, and can further improve the production efficiency, on the other hand, the gradient reduction of the silane material content in each layer of the protective layer can take into account the comprehensive effect of the protective layer density, the bonding force between the protective layer and the metal layer and the corrosion resistance.

[0028] As an optional technical solution of the present application, the material of the metal layer includes elemental metal and / or metal alloy, which can be an elemental metal.

[0029] In one embodiment, the elemental metal includes copper and / or aluminum, and the metal alloy includes aluminum alloy and / or copper alloy.

[0030] In one embodiment, the thickness of the metal layer is 500-2000nm, for example, it can be 500nm, 1000nm, 1500nm or 2000nm, etc., and optionally 700-1200nm.

[0031] In the present application, if the metal layer is too thin, the conductivity is poor, and if the metal layer is too thick, the prepared composite current collector is too thick and heavy, which is not conducive to improving the energy density of the battery. Considering the conductivity and taking into account the improvement of the energy density, the optional thickness is 700-1200nm.

[0032] In one embodiment, the material of the polymer base film comprises any one of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), or polyimide (PI) or a combination of at least two thereof.

[0033] In one embodiment, the thickness of the polymer base film is 1-10 μm, for example, 1 μm, 3 μm, 5 μm, 7 μm, or 9 μm, etc.

[0034] In the present application, the thickness of the polymer base film is 1-10 μm, considering the application requirements of the composite current collector, and taking into account the difficulty and cost of the preparation process.

[0035] In a second aspect, the present application provides a preparation method of the composite current collector according to the first aspect, comprising the following steps:

[0036] Preparation of a metal layer and an organic protective layer on at least one side surface of the polymer base film in sequence;

[0037] The material of the organic protective layer is composed of polypyrrole and silane material in a mass ratio of (80-99.5):(0.5-20), and the polypyrrole is prepared by in-situ polymerization of pyrrole material coated on the metal layer.

[0038] The preparation method provided by the present application is simple and easy to operate, and is environmentally friendly and harmless.

[0039] As an optional technical solution of the present application, a metal layer and an organic protective layer are prepared on both side surfaces of the polymer base film in sequence, and the preparation method of the organic protective layer comprises two-stage dip coating process, and the specific steps comprise:

[0040] The composite film containing double-sided metal layer is placed in the first dip coating liquid for one-time dip coating, and then placed in the second dip coating liquid for two-time dip coating to obtain the organic protective layer.

[0041] The solute of the first dip coating liquid comprises pyrrole and silane material, and the second dip coating liquid is an oxidizing agent solution.

[0042] In the present application, the oxidizing agent solution not only promotes the polymerization of pyrrole, but also corrodes the metal layer, which is beneficial to increase the roughness of the surface of the metal layer, and further increase the adhesion between the metal layer and the organic protective layer. As an optional technical solution of the present application, the concentration of pyrrole in the first dip-coating solution is 0.5-10 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 7 mol / L or 9 mol / L, etc.

[0043] In one embodiment, the solvent of the first dip-coating solution includes ethanol.

[0044] In one embodiment, the solute in the oxidizing agent solution includes any one or a combination of at least two of ferric chloride, ammonium persulfate, sodium persulfate or hydrogen peroxide.

[0045] In one embodiment, the concentration of the oxidizing agent solution is 0.2-2 mol / L, for example, it can be 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, etc.

[0046] In one embodiment, the time of the first dip-coating is 0.5-5 min, for example, it can be 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min, etc.

[0047] In the present application, if the time of the first dip-coating is too short, the saturation adsorption of the dip-coating solution cannot be achieved, and if the time of the first dip-coating is too long, the carrying capacity of the dip-coating solution cannot be further improved.

[0048] In one embodiment, the time of the second dip-coating is 0.5-10 min, for example, it can be 0.5 min, 1 min, 3 min, 5 min, 7 min, 9 min or 10 min, etc.

[0049] In the present application, if the time of the second dip-coating is too short, the reaction is not sufficient, and the thickness of the generated protective layer is relatively thin, and the protective effect is poor; as the reaction time is prolonged, the reaction gradually reaches equilibrium, and further increasing the time makes the time of the second dip-coating too long, and the reaction cannot be further promoted.

[0050] In one embodiment, after the second dip-coating, post-treatment is further performed, and the steps of the post-treatment include water washing, extrusion liquid removal and drying treatment.

[0051] In one embodiment, the temperature of the drying treatment is 50-90℃, for example, it can be 50℃, 60℃, 70℃, 80℃ or 90℃, etc.

[0052] In one embodiment, the drying process is performed for 1-5 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes, etc.

[0053] As an optional technical solution of the present application, the preparation method of the metal layer comprises any one or a combination of at least two of physical vapor deposition, electroplating or chemical plating.

[0054] As an optional technical solution of the present application, the preparation method comprises the following steps:

[0055] (1) using any one or a combination of at least two of physical vapor deposition, electroplating or chemical plating to deposit a metal layer on both sides of the polymer-based film, to obtain a composite film with double-sided metal layers;

[0056] (2) placing the composite film with double-sided metal layers in an ethanol solution containing pyrrole and silane coupling agent, performing one-time dip coating for 0.5-5 minutes, then placing the one-time dip coated composite film in an oxidizing agent solution with a concentration of 0.2-2 mol / L, performing two-time dip coating for 0.5-10 minutes, then performing water washing and extrusion liquid removal, and subsequently performing drying treatment at 50-90℃ for 1-5 minutes, to obtain a composite current collector with an in-situ formed organic protective layer;

[0057] In the ethanol solution containing pyrrole and silane coupling agent, the concentration of pyrrole is 0.5-10 mol / L.

[0058] It should be noted that in-situ formation refers to the polymerization reaction of pyrrole on the surface of the metal layer.

[0059] In a third aspect, the present application provides a lithium ion battery, wherein the electrode tab of the lithium ion battery comprises the composite current collector according to the first aspect or prepared by the preparation method according to the second aspect.

[0060] The numerical range described in the present application includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed, and for the sake of brevity and simplicity, the present application does not list all the specific point values included in the range.

[0061] Compared with the related art, the present application has the following beneficial effects:

[0062] (1) When the organic protective layer is constructed on the surface of the composite current collector, the specific mass ratio of polypyrrole and silane material is introduced for synergistic cooperation. The polar oxygen-containing group in the silane material can form a strong intermolecular force between the metal atoms in the metal layer and the nitrogen atoms in the polypyrrole, and the non-polar alkyl group in the silane material can form a strong intermolecular force between the polypyrrole. A kind of organic framework is constructed, which can promote the close combination between the metal layer and the organic protective layer in the composite current collector, thereby improving the oxidation resistance of the composite current collector. The composite current collector based on the organic protective layer has stable performance during application, which is conducive to promoting the popularization and application of the composite current collector.

[0063] (2) The preparation method provided by the present application is simple and easy to operate, and is environmentally friendly and harmless.

[0064] Other aspects can become apparent from a consideration of the drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0065] The drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used to explain the technical solutions of the present application together with the embodiments of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0066] FIG. 1 is a structural schematic diagram of the composite current collector prepared in Example 1 of the present application.

[0067] Among them, 1-polymer base film; 2-metal layer; 3-organic protective layer. DETAILED DESCRIPTION

[0068] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0069] Example 1

[0070] The present embodiment provides a kind of composite current collector, its structural schematic diagram as shown in Figure 1, the composite current collector includes:

[0071] Polymer base film 1, material is PET film, thickness is 4.5 μm;

[0072] Metal layer 2 is arranged on the two side surfaces of the polymer base film, the material of the metal layer 2 is elemental copper, and the single-sided thickness is 1000 nm;

[0073] Organic protective layer 3 is arranged on the surface of the metal layer 2 along the direction away from the polymer base film 1, and the thickness of the organic protective layer 3 is 10 nm on one side;

[0074] The material of the organic protective layer 3 is composed of polypyrrole and silane material with a mass ratio of 99.5:0.5, the silane material is 3-isocyanate propyl triethoxysilane, the mass content of the silane material is 0.5wt% based on the mass of the organic protective layer 3, and the polypyrrole is prepared by in-situ polymerization of pyrrole material coated on the metal layer.

[0075] The embodiment also provides a preparation method of the composite current collector.

[0076] (1) The PET film prepared by the biaxial stretching method is placed in a vacuum evaporation machine, and copper metal is deposited on both sides of the PET film, that is, high-purity copper wire (purity greater than 99.99%) in a metal evaporation chamber is melted and evaporated at a high temperature of 1500°C, and the metal atoms after evaporation pass through the cooling system in the vacuum coating chamber and are deposited on both sides of the PET film to form a double-sided metal layer 2, thereby obtaining a composite film with the double-sided metal layer 2;

[0077] (2) The composite film with the double-sided metal layer 2 is placed in an ethanol solution containing pyrrole and silane material, and is subjected to one-time dip coating for 2 min, then the composite film after one-time dip coating is placed in an aqueous ferric chloride solution with a concentration of 0.5 mol / L, and is subjected to secondary dip coating for 4 min, and after the end of the dip coating, the composite film is cleaned with pure water, squeezed by a squeeze roller to remove liquid, and then is placed in an oven at 70°C for drying treatment for 5 min, thereby obtaining a composite current collector with an organic protective layer 3.

[0078] In the ethanol solution containing pyrrole and silane material, the concentration of pyrrole is 1 mol / L, and the mass ratio of the silane material to pyrrole is 0.5:99.5, and the silane material is 3-isocyanate propyl trimethoxysilane.

[0079] Example 2

[0080] The difference between the embodiment and example 1 is that the 3-isocyanate propyl triethoxysilane in step (2) is replaced by 3-isocyanate propyl trimethoxysilane.

[0081] The rest of the preparation method and parameters are consistent with those of example 1.

[0082] Example 3

[0083] The difference between the embodiment and example 1 is that the 3-isocyanate propyl triethoxysilane in step (2) is replaced by 3-isocyanate propyl trimethoxysilane.

[0084] The rest of the preparation method and parameters are consistent with those of example 1.

[0085] Example 4

[0086] The difference between this example and Example 1 is that 3-isocyanate propyl triethoxysilane in step (2) is replaced by 1,3,5-tris(trimethoxysilylpropyl) isocyanurate.

[0087] The rest of the preparation method and parameters are consistent with Example 1.

[0088] Example 5

[0089] The difference between this example and Example 1 is that the mass content of silane material in the organic protective layer is 10wt%, that is, the mass ratio of silane material and pyrrole in step (2) is adjusted to 10:90.

[0090] The rest of the preparation method and parameters are consistent with Example 1.

[0091] Example 6

[0092] The difference between this example and Example 1 is that the mass content of silane material in the organic protective layer is 20wt%, that is, the mass ratio of silane material and pyrrole in step (2) is adjusted to 20:80.

[0093] The rest of the preparation method and parameters are consistent with Example 1.

[0094] Example 7

[0095] The difference between this example and Example 1 is that the concentration of pyrrole in step (2) is 0.5mol / L.

[0096] The rest of the preparation method and parameters are consistent with Example 1.

[0097] Example 8

[0098] The difference between this example and Example 1 is that the concentration of pyrrole in step (2) is 10mol / L.

[0099] The rest of the preparation method and parameters are consistent with Example 1.

[0100] Example 9

[0101] The difference between this example and Example 1 is that the time of one-time dip coating in step (2) is 0.5min.

[0102] The rest of the preparation method and parameters are consistent with Example 1.

[0103] Example 10

[0104] The difference between this example and Example 1 is that the time of one-time dip coating in step (2) is 5min.

[0105] The rest of the preparation method and parameters are consistent with Example 1.

[0106] Example 11

[0107] The difference between this example and Example 1 is that the concentration of the aqueous ferric chloride solution in step (2) is 0.2 mol / L.

[0108] The rest of the preparation method and parameters are consistent with Example 1.

[0109] Example 12

[0110] The difference between this example and Example 1 is that the concentration of the aqueous ferric chloride solution in step (2) is 2 mol / L.

[0111] The rest of the preparation method and parameters are consistent with Example 1.

[0112] Example 13

[0113] The difference between this example and Example 1 is that the time of the secondary dip-coating in step (2) is 0.5 min.

[0114] The rest of the preparation method and parameters are consistent with Example 1.

[0115] Example 14

[0116] The difference between this example and Example 1 is that the time of the secondary dip-coating in step (2) is 10 min.

[0117] The rest of the preparation method and parameters are consistent with Example 1.

[0118] Example 15

[0119] The difference between this example and Example 1 is that the material of the metal layer is elemental aluminum, i.e. in step (1), high-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber is melted and evaporated at a high temperature of 1300°C.

[0120] The rest of the preparation method and parameters are consistent with Example 1.

[0121] Example 16

[0122] The difference between this example and Example 1 is that the concentration of the pyrrole in step (2) is 0.3 mol / L.

[0123] The rest of the preparation method and parameters are consistent with Example 1.

[0124] Example 17

[0125] The difference between this example and Example 1 is that the concentration of the pyrrole in step (2) is 11 mol / L.

[0126] The rest of the preparation method and parameters are consistent with Example 1.

[0127] Example 18

[0128] The difference between this example and Example 1 is that the time for one-time dip-coating in step (2) is 0.3 min.

[0129] The rest of the preparation method and parameters are consistent with Example 1.

[0130] Example 19

[0131] The difference between this example and Example 1 is that the time for one-time dip-coating in step (2) is 6 min.

[0132] The rest of the preparation method and parameters are consistent with Example 1.

[0133] Example 20

[0134] The difference between this example and Example 1 is that the concentration of the aqueous ferric chloride solution in step (2) is 0.1 mol / L.

[0135] The rest of the preparation method and parameters are consistent with Example 1.

[0136] Example 21

[0137] The difference between this example and Example 1 is that the concentration of the aqueous ferric chloride solution in step (2) is 2.2 mol / L.

[0138] The rest of the preparation method and parameters are consistent with Example 1.

[0139] Example 22

[0140] The difference between this example and Example 1 is that the time for two-time dip-coating in step (2) is 0.3 min.

[0141] The rest of the preparation method and parameters are consistent with Example 1.

[0142] Example 23

[0143] The difference between this example and Example 1 is that the time for two-time dip-coating in step (2) is 11 min.

[0144] The rest of the preparation method and parameters are consistent with Example 1.

[0145] Comparative Example 1

[0146] The difference between this example and Example 1 is that the organic protective layer only contains polypyrrone, i.e. the ethanol solution containing pyrrone and 3-isocyanate propyl triethoxysilane in step (2) is replaced by an ethanol solution containing only pyrrone.

[0147] The remaining preparation method and parameters are consistent with Example 1.

[0148] Comparative Example 2

[0149] The difference between this comparative example and Example 15 is that the organic protective layer only contains polypyrole, i.e. the ethanol solution containing polypyrole and 3-isocyanate propyl triethoxysilane in step (2) is replaced by an ethanol solution containing only polypyrole.

[0150] The remaining preparation method and parameters are consistent with Example 15.

[0151] Comparative Example 3

[0152] The difference between this comparative example and Example 1 is that the organic protective layer only contains silane material, i.e. the ethanol solution containing polypyrole and 3-isocyanate propyl triethoxysilane in step (2) is replaced by an ethanol solution containing only 3-isocyanate propyl triethoxysilane.

[0153] The remaining preparation method and parameters are consistent with Example 1.

[0154] Comparative Example 4

[0155] The difference between this example and Example 1 is that the mass content of silane material in the organic protective layer is 0.3wt%, and the mass ratio of polypyrole to silane material is 99.7:0.3.

[0156] The remaining preparation method and parameters are consistent with Example 1.

[0157] Comparative Example 5

[0158] The difference between this example and Example 1 is that the mass content of silane material in the organic protective layer is 22wt%, and the mass ratio of polypyrole to silane material is 78:22.

[0159] The remaining preparation method and parameters are consistent with Example 1.

[0160] Comparative Example 6

[0161] The difference between this example and Example 1 is that 3-isocyanate propyl triethoxysilane is replaced by vinyl triethoxysilane in step (2).

[0162] The remaining preparation method and parameters are consistent with Example 1.

[0163] Performance Test

[0164] The conductive properties, thickness of the organic protective layer and oxidation resistance of the composite current collectors prepared in the above examples and comparative examples were evaluated to verify that the organic protective layer prepared in the application improves the oxidation resistance of the composite current collector without affecting the conductive properties of the composite current collector. Specifically as follows:

[0165] ①Conductive properties: characterized by sheet resistance, specifically, the prepared flat composite current collector sample was placed on a sample stage, and a four-probe sheet resistance meter was used to test the sheet resistance of the sample.

[0166] ②Oxidation resistance: indirectly characterized by the change in sheet resistance before and after baking, specifically, the prepared flat composite current collector sample and the composite current collector sample after baking at 150°C for 30 min were placed on a sample stage, and a four-probe sheet resistance meter was used to test the sheet resistance of the sample. The change in sheet resistance before and after baking was compared, and the smaller the change, the better the oxidation resistance.

[0167] ③Stability of the protective layer: a 3M TM Scotch TM 600 transparent film tape with a width of 20 mm was attached to the above prepared composite current collector, and a roller was used to press twice, then the tape was peeled off at an angle of 45°, the area where the tape was peeled off was marked, and placed in an oven at 150°C for 30 min. After baking, the sheet resistance of the marked area was tested. If the sheet resistance changes greatly, it means that the protective layer is peeled off from the surface of the composite current collector, i.e. the stability of the composite current collector based on the protective layer is poor.

[0168] ④Thickness characterization of the organic protective layer of the composite current collector: the prepared composite copper current collector was prepared according to the sample preparation requirements of focused ion beam field emission microscope (FIB-SEM), then the sample was placed in FIB-SEM, and the sample was cut to prepare a cross-section sample using an ion beam. After the cross-section sample was prepared, the cross-section was observed using a field emission microscope lens at a magnification of 50,000 times, and after adjusting the clarity, the thickness of the protective layer in the cross-section morphology photo was measured using the measurement software of the electron microscope, thereby obtaining the thickness data of the organic protective layer.

[0169] The above test results are shown in Table 1.

[0170] Table 1

[0171] Analysis:

[0172] From Examples 1-23 and Comparative Example 1, compared with the composite current collector with the polyazole protective layer without adding the silane material, the composite current collector prepared in the application has a smaller change in square resistance before and after baking at 150°C, and a smaller change in square resistance after 150°C baking for 30 min before and after the protective layer is peeled off by the adhesive tape, indicating that the anti-oxidation performance of the organic protective layer prepared in the application and the adhesion to the metal layer are significantly improved.

[0173] From Examples 1, 5, 6, Comparative Example 4 and Comparative Example 5, increasing the content of the silane coupling agent in the organic protective layer can make the change in square resistance of the composite current collector before and after baking at 150°C decrease first and then increase, and the change in square resistance after 150°C baking for 30 min before and after the protective layer is peeled off by the adhesive tape decrease first and then increase, which is because increasing the content of the silane coupling agent in the protective layer can improve the stability of the organic protective layer and the adhesion to the metal layer, and further improve the anti-oxidation performance of the prepared composite current collector, but too high silane content can cause poor conductivity of the composite current collector. In addition, too low silane content, i.e. too large mass ratio of polyazole to silane material, can cause large change in square resistance after 150°C baking for 30 min before and after the protective layer is peeled off by the adhesive tape.

[0174] From Examples 1, 7, 8, 16 and 17, increasing the concentration of pyrrole in the first dip-coating liquid can increase the thickness of the organic protective layer, decrease the change in square resistance of the composite current collector before and after baking at 150°C first and then keep unchanged, and keep the change in square resistance after 150°C baking for 30 min before and after the organic protective layer is peeled off by the adhesive tape unchanged. The change in square resistance of the composite current collector before and after baking at 150°C decreases first and then keeps unchanged due to the increase in the thickness of the organic protective layer, and the adhesion of the organic protective layer to the metal layer keeps unchanged due to the unchanged content of the silane coupling agent in the organic protective layer, resulting in the change in square resistance after 150°C baking for 30 min before and after the protective layer is peeled off by the adhesive tape unchanged. When the concentration of pyrrole in the first dip-coating liquid is too low, the prepared protective layer is too thin and not dense enough, resulting in poor protection effect; when the concentration of pyrrole in the first dip-coating liquid is too high, the prepared protective layer is too thick, and the protection effect cannot be further improved, and the square resistance of the composite current collector becomes large and the conductivity becomes poor.

[0175] From Example 1, Example 9, Example 10, Example 18 and Example 19, it can be seen that increasing the time of primary dipping, the thickness of the organic protective layer first increases and then remains unchanged, the sheet resistance change amount of the composite current collector before and after 150°C baking first decreases and then remains unchanged, and the sheet resistance change amount of the organic protective layer after the tape is peeled off before and after 150°C baking for 30 min remains unchanged. The sheet resistance change amount of the composite current collector before and after 150°C baking first decreases and then remains unchanged due to the thickness of the organic protective layer first increasing and then remaining unchanged, and the adhesion between the organic protective layer and the metal layer remains unchanged due to the unchanged content of the silane coupling agent in the organic protective layer, resulting in the sheet resistance change amount of the organic protective layer after the tape is peeled off before and after 150°C baking for 30 min remaining unchanged. When the time of primary dipping is too short, the prepared protective layer is relatively thin, resulting in poor protection effect; when the time of primary dipping is too long, the thickness of the prepared protective layer cannot be further improved, thereby the protection effect cannot be further improved, and the preparation efficiency is reduced.

[0176] From Example 1, Example 11, Example 12, Example 20 and Example 21, it can be seen that increasing the concentration of the aqueous ferric chloride solution, the thickness of the organic protective layer first increases and then remains unchanged, and the sheet resistance change amount of the composite current collector before and after 150°C baking first decreases and then remains unchanged, which is due to the thickness of the organic protective layer first increasing and then remaining unchanged. When the concentration of the aqueous ferric chloride solution is too low, the reactivity with pyrrole is affected, resulting in a relatively thin and not dense protective layer, which leads to poor protection effect; when the concentration of the aqueous ferric chloride solution is too high, the thickness of the prepared protective layer cannot be further improved, thereby the protection effect cannot be further improved, and the preparation cost is increased.

[0177] From Example 1, Example 13, Example 14, Example 22 and Example 23, it can be seen that increasing the time of secondary dipping, the thickness of the organic protective layer first increases and then remains unchanged, and the sheet resistance change amount of the composite current collector before and after 150°C baking first decreases and then remains unchanged, which is due to the thickness of the organic protective layer first increasing and then remaining unchanged. When the time of secondary dipping is too short, the reaction is incomplete, the prepared protective layer is relatively thin, and the protection effect is poor; when the time of secondary dipping is too long, the thickness of the prepared protective layer cannot be further improved, thereby the protection effect cannot be further improved, and the preparation efficiency is reduced.

[0178] From Examples 1-4, it can be seen that adding a silane coupling agent containing an isocyanate group as a silane material can achieve better application effect.

[0179] Applicants state that the process of the present application is illustrated by the above examples, but the present application is not limited to the process steps described above, i.e., it is not meant that the present application must rely on the process steps described above in order to be practiced. It should be apparent to those skilled in the art that any modifications to the present application, equivalent substitutions of the materials selected by the present application, additions of auxiliary ingredients, choices of specific modes, etc., all fall within the scope of protection and disclosure of the present application.

Claims

1. A composite current collector, comprising: a polymer substrate film; a metal layer disposed on at least one side surface of the polymer substrate film; an organic protective layer disposed on a surface of the metal layer in a direction away from the polymer substrate film; wherein the material of the organic protective layer is composed of a mass ratio of (80-99.5) : (0.5-20) of polypyrrole and silane material, the polypyrrole is prepared by in-situ polymerization of pyrrole material coated on the metal layer.

2. The composite current collector of claim 1, wherein, The mass content of the silane material is 0.5-20 wt% based on the mass of the organic protective layer.

3. The composite current collector of claim 1 or 2, wherein, The silane material is a silane coupling agent containing isocyanate groups.

4. The composite current collector of claim 3, wherein, The silane coupling agent containing isocyanate groups includes any one or a combination of at least two of 3-isocyanate propyl triethoxysilane, 3-isocyanate propyl trimethoxysilane, 3-isocyanate propyl methyl dimethoxysilane or 1, 3, 5-tris (trimethoxysilylpropyl) isocyanurate.

5. The composite current collector of any one of claims 1-4, wherein, The group in the silane material further includes any one or a combination of at least two of halogen, hydroxyl, amino or mercapto.

6. The composite current collector of any one of claims 1-5, wherein, The thickness of the organic protective layer is 5-100 nm; Optionally, the thickness of the organic protective layer is less than or equal to 10% of the thickness of the metal layer.

7. The composite current collector of any one of claims 1-6, wherein, The organic protective layer is at least 2 layers, and the content of silane material in a single layer of the organic protective layer decreases in a gradient in a direction away from the polymer substrate film.

8. The composite current collector of any one of claims 1-7, wherein, The material of the metal layer includes elemental metal and / or metal alloy; Optionally, the elemental metal includes copper and / or aluminum, and the metal alloy includes aluminum alloy and / or copper alloy.

9. The composite current collector of any one of claims 1-8, wherein, The thickness of the metal layer is 500-2000 nm, and optionally 700-1200 nm. Optionally, the thickness of the polymer substrate film is 1-10 μm. 10.A method for preparing the composite current collector according to any one of claims 1-9, comprising the following steps: sequentially preparing a metal layer and an organic protective layer on at least one side surface of a polymer substrate film; the material of the organic protective layer is composed of a mass ratio of (80-99.5) : (0.5-20) of polypyrrole and silane material, the polypyrrole is prepared by in-situ polymerization of pyrrole material coated on the metal layer.

11. The production method according to claim 10, wherein sequentially preparing a metal layer and an organic protective layer on both side surfaces of a polymer substrate film, the preparation method of the organic protective layer includes a two-stage dip coating process, and the specific steps include: placing a composite film containing a double-sided metal layer in a first dip coating solution for one-time dip coating, and then placing it in a second dip coating solution for two-time dip coating to obtain the organic protective layer; wherein the solute of the first dip coating solution includes pyrrole and silane material, and the second dip coating solution is an oxidizing agent solution.

12. The method of making according to claim 11, wherein, The concentration of pyrrole in the first dip coating solution is 0.5-10 mol / L; Optionally, the solute in the oxidizing agent solution includes any one or a combination of at least two of ferric chloride, ammonium persulfate, sodium persulfate or hydrogen peroxide; Optionally, the concentration of the oxidizing agent solution is 0.2-2 mol / L.

13. The production method according to claim 11 or 12, wherein, The time of the one-time dip coating is 0.5-5 min; Optionally, the time of the two-time dip coating is 0.5-10 min.

14. The preparation method of claim 10, comprising the following steps: (1) depositing a metal layer on both sides of the polymer-based film by any one or a combination of at least two of physical vapor deposition, electroplating or electroless plating, to obtain a composite film with double-sided metal layer; (2) immersing the composite film with double-sided metal layer in an ethanol solution containing pyrrole and silane coupling agent for 0.5-5 min, then immersing the once-immersed composite film in an oxidant solution with a concentration of 0.2-2 mol / L for 0.5-10 min, followed by water washing and squeezing to remove liquid, and then drying at 50-90 °C for 1-5 min, to obtain a composite current collector with in-situ formed organic protective layer; wherein the concentration of pyrrole in the ethanol solution containing pyrrole and silane coupling agent is 0.5-10 mol / L.

15. A lithium-ion battery, wherein, The electrode tab of the lithium ion battery comprises the composite current collector of any one of claims 1-9 or prepared by the preparation method of any one of claims 10-14.

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