Conductive adhesive and preparation method thereof, current collector, electrode and battery

Abstract

This application provides a conductive binder, a preparation method thereof, a current collector, an electrode, and a battery. The conductive binder comprises a first polymer binder grafted with conductive groups and a second polymer binder grafted with conductive groups. The molecular weight of the first polymer binder is greater than that of the second polymer binder. In this application, polymer binders of different molecular weights are used to effectively graft conductive groups onto the polymer binder. The low-molecular-weight polymer binder is able to penetrate the surface of the conductive binder, thus enabling the conductive binder to possess both conductivity and adhesive properties.

Description

Technical Field

[0001] The present application relates to the technical field of adhesives, and in particular to a conductive adhesive and a preparation method thereof, a current collector, an electrode and a battery. Background Art

[0002] Lithium-ion batteries have been widely used in consumer electronics, electric vehicles, and other fields. The market has also placed higher demands on their energy density, cycle life, and safety. Current collector conductive primer technology can effectively reduce the contact resistance between the electrode material and the current collector, increase the adhesion between the electrode material and the current collector, reduce the battery's internal resistance, and extend battery life.

[0003] However, a certain amount of binder is required during the preparation of the conductive coating current collector. The binder itself is not conductive. Adding too much will cause the conductive performance of the conductive coating to decrease. At the same time, an overly thick conductive coating will also affect the overall conductive effect of the electrode. Adding too little will not be able to bond the conductive material well.

[0004] Therefore, how to improve the conductivity and adhesion of the conductive coating current collector has become an urgent problem that needs to be solved. Summary of the Invention

[0005] Based on this, it is necessary to provide a conductive adhesive and its preparation method, a current collector, an electrode and a battery, so that the adhesive has conductivity and adhesion while improving the conductivity and adhesion of the conductive coating current collector.

[0006] In a first aspect, the present application provides a conductive adhesive, comprising a first polymer binder grafted with a conductive group and a second polymer binder grafted with a conductive group, wherein the molecular weight of the first polymer binder is greater than that of the second polymer binder.

[0007] In some embodiments of the present application, the conductive adhesive is prepared by polymerization of raw materials including a first polymer, a second polymer, a conductive monomer, and an initiator; the molecular weight of the first polymer is greater than that of the second polymer.

[0008] In some embodiments of the present application, the mass ratio of the first polymer to the second polymer is (10-50):1, for example, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1.

[0009] In some embodiments of the present application, the mass ratio of the initiator to the conductive monomer is 1:(10-150), for example, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130, 1:140 or 1:150.

[0010] In some embodiments of the present application, the molecular weight of the first polymer is 100,000 to 400,000, for example, 100,000, 130,000, 160,000, 190,000, 220,000, 250,000, 280,000, 310,000, 340,000, 370,000 or 400,000.

[0011] In some embodiments of the present application, the molecular weight of the second polymer is 500 to 50,000, for example, 500, 1,000, 2,500, 5,000, 7,500, 10,000, 15,000, 20,000, 30,000, 40,000 or 50,000.

[0012] In some embodiments of the present application, the ratio of the mass of the conductive group to the total mass of the first polymer binder and the second polymer binder is 1:(10-50), for example, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50.

[0013] In some embodiments of the present application, the conductive group includes at least one of polyaniline, polypyrrole, polythiophene, polyparaphenylene and polyphenyleneacetylene.

[0014] In some embodiments of the present application, the first polymer and the second polymer are each independently selected from at least one of polyacrylic acid, polyvinylidene fluoride and styrene-butadiene emulsion.

[0015] In some embodiments of the present application, the conductive monomer includes at least one of a polyaniline monomer, a polypyrrole monomer, a polythiophene monomer, a polyparaphenylene monomer, and a polyphenyleneacetylene monomer.

[0016] In some embodiments of the present application, the initiator includes a persulfate compound, and optionally, the persulfate compound includes sodium persulfate.

[0017] In a second aspect, the present application provides a method for preparing the conductive adhesive as described in the first aspect, the method for preparing the conductive adhesive comprising:

[0018] The conductive adhesive is prepared by mixing a first polymer, a second polymer, a conductive monomer and an initiator in a solvent, polymerizing the conductive monomer at 0-5°C to generate conductive groups, and grafting the conductive groups onto the first polymer and the second polymer. For example, the reaction temperature is 0°C, 1°C, 2°C, 3°C, 4°C or 5°C.

[0019] In some embodiments of the present application, the conductive monomer and the initiator are mixed and then added to the mixture of the first polymer and the second polymer.

[0020] In some embodiments of the present application, the reaction time of the preparation method is 8 to 20 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours.

[0021] In some embodiments of the present application, the preparation method is carried out under stirring conditions.

[0022] In a third aspect, the present application provides a current collector comprising a substrate and a conductive layer disposed on at least one surface of the substrate, wherein the conductive layer comprises a conductive agent and the conductive adhesive as described in the first aspect.

[0023] In some embodiments of the present application, the mass ratio of the conductive agent to the conductive adhesive is 1:(0.2-1.25), for example, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0 or 1:1.25.

[0024] In some embodiments of the present application, the conductive agent includes at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, and a two-dimensional conductive agent.

[0025] In some embodiments of the present application, the zero-dimensional conductive agent includes conductive carbon black and / or acetylene black, the one-dimensional conductive agent includes carbon nanotubes, and the two-dimensional conductive agent includes graphite and / or graphene.

[0026] In a fourth aspect, the present application provides an electrode, comprising a current collector and an active layer disposed on at least one side of the current collector, wherein the current collector is the current collector described in the third aspect.

[0027] In a fifth aspect, the present application provides a battery, comprising the electrode as described in the fourth aspect.

[0028] This application has the following beneficial effects:

[0029] The present application utilizes a conductive group grafted binder and adopts polymer binders of different molecular weights. Since the high molecular weight polymer binder has a large number of grafting sites, the conductive groups can be evenly grafted to the surface of the high molecular weight polymer binder, thereby improving the grafting rate of the conductive groups. In addition, due to the molecular chain length of the high molecular weight polymer, the steric hindrance effect is utilized to reduce the polymerization ability of the low molecular weight polymer binder, and the low molecular weight polymer binder can easily penetrate into the surface of the conductive binder, thereby increasing the bonding sites, so that the conductive binder has both adhesiveness and improved conductivity. DETAILED DESCRIPTION

[0030] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] As used herein, "ranges" are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, i.e., any lower limit may be combined with any upper limit to form a range.

[0033] A first aspect of an embodiment of the present application provides a conductive adhesive, comprising a first polymer binder grafted with a conductive group and a second polymer binder grafted with a conductive group, wherein the molecular weight of the first polymer binder is greater than that of the second polymer binder.

[0034] The present application utilizes a conductive group grafted binder and adopts polymer binders of different molecular weights. Since the high molecular weight polymer binder has a large number of grafting sites, the conductive groups can be evenly grafted to the surface of the high molecular weight polymer binder, thereby improving the grafting rate of the conductive groups. In addition, due to the molecular chain length of the high molecular weight polymer, the steric hindrance effect is utilized to reduce the polymerization ability of the low molecular weight polymer binder, and the low molecular weight polymer binder can easily penetrate into the surface of the conductive binder, thereby increasing the bonding sites, so that the conductive binder has both adhesiveness and improved conductivity.

[0035] In some embodiments, the conductive adhesive is prepared from raw materials including a first polymer, a second polymer, a conductive monomer, and an initiator through a polymerization reaction; the molecular weight of the first polymer is greater than that of the second polymer.

[0036] In some embodiments, the mass ratio of the initiator to the conductive monomer is 1:(10-150).

[0037] In some embodiments, the mass ratio of the first polymer to the second polymer is (10-50):1. In the present application, by controlling the mass ratio of polymers with different molecular weights, the conductive groups are grafted onto the binder substrate and the conductive groups are distributed, thereby ensuring conductivity and adhesion. If the high molecular weight matrix accounts for a relatively large proportion, the conductive layer may be brittle and have low adhesion. If the low molecular weight matrix accounts for a relatively large proportion, the conductive layer may have low cohesive strength and be easily damaged.

[0038] In some embodiments, the molecular weight of the first polymer is 100,000 to 400,000. In this application, by selecting the molecular weight of the first polymer to be 100,000 to 400,000, the conductive adhesive has both solubility and stability, and the conductive groups can be evenly grafted onto the high molecular weight substrate, effectively ensuring the conductivity of the conductive adhesive.

[0039] In some embodiments, the molecular weight of the second polymer is 500 to 50000. In this application, by selecting the molecular weight of the second polymer to be 500 to 50000, the low molecular weight polymer can effectively penetrate into the substrate surface during the preparation process, improving adhesion without affecting the grafting effect.

[0040] In some embodiments, the ratio of the mass of the conductive monomer to the total mass of the first polymer and the second polymer is 1:(10-50). In this application, a combination of polymer binders of different molecular weights is used to effectively increase the grafting rate of the conductive groups, achieving both grafting rate and conductivity. If the mass proportion of the conductive groups is too large, the grafting rate is too high and difficult to achieve. If the total mass proportion of the polymer binder is too large, the grafting rate is too low, resulting in low conductivity.

[0041] In some embodiments, the conductive group includes at least one of polyaniline, polypyrrole, polythiophene, polyparaphenylene, and polyphenyleneacetylene.

[0042] In some embodiments, the first polymer and the second polymer are each independently selected from at least one of polyacrylic acid, polyvinylidene fluoride, and styrene-butadiene emulsion.

[0043] In some embodiments, the conductive monomer includes at least one of a polyaniline monomer, a polypyrrole monomer, a polythiophene monomer, a polyparaphenylene monomer, and a polyphenyleneacetylene monomer.

[0044] In some embodiments, the initiator comprises a persulfate compound, optionally comprising sodium persulfate.

[0045] A second aspect of the embodiments of the present application provides a method for preparing the conductive adhesive as described in the first aspect, the method for preparing the conductive adhesive comprising:

[0046] The first polymer, the second polymer, the conductive monomer and the initiator are mixed in a solvent, the conductive monomer is polymerized at 0-5° C. to generate conductive groups, and the conductive groups are grafted onto the first polymer and the second polymer to prepare the conductive adhesive.

[0047] Low-temperature polymerization is used in the present application to first avoid violent polymerization during the grafting process, reduce the possibility of violent polymerization of the polymer binder, and improve the grafting effect of the conductive group. Furthermore, due to the steric effect of the first polymer binder with a high molecular weight, the second polymer binder with a low molecular weight penetrates into the surface of the substrate, increasing the bonding sites, thereby improving the adhesion of the conductive adhesive. In addition, the high molecular weight matrix can effectively ensure the grafting uniformity of the conductive matrix, so that the prepared conductive adhesive has both conductivity and adhesion.

[0048] In some embodiments, the preparation process is carried out in an ice-water bath, that is, the reaction temperature during the preparation process is 0°C, which effectively avoids violent polymerization during the grafting process, reduces the possibility of polymerization of the polymer binder, and improves the grafting effect of the conductive group.

[0049] In some embodiments, the conductive monomer and the initiator are mixed and then added to the mixture of the first polymer and the second polymer.

[0050] In some embodiments, the reaction time of the preparation method is 8 to 20 hours. In this application, a low-temperature reaction is adopted and a long polymerization reaction is utilized to reduce the polymerization of the polymer binder while improving the uniformity of the grafting distribution of the conductive group on the polymer binder, effectively ensuring the grafting rate and adhesion.

[0051] In some embodiments, the mixture of the conductive monomer and the initiator is added at a rate of 1 ml / min to 10 ml / min.

[0052] In some embodiments, the preparation method is carried out under stirring conditions.

[0053] Exemplarily, a method for preparing the conductive adhesive is provided, which specifically comprises:

[0054] An initiator and a conductive monomer in a mass ratio of 1:(10-150) are weighed and mixed with a solvent to form a mixed liquid. A first polymer and a second polymer in a mass ratio of (10-50):1 are weighed and mixed with a solvent to form a polymer binder solution. The mixed liquid is added to the polymer binder solution at a rate of 1 ml / min to 10 ml / min at 0-5°C to cause a polymerization reaction. After stirring for 8-20 hours, the conductive monomer undergoes a polymerization reaction to generate a conductive group, and the conductive group is grafted onto the first polymer and the second polymer to prepare the conductive binder. The solvent can be water.

[0055] A third aspect of the embodiments of the present application provides a current collector, which includes a substrate and a conductive layer disposed on at least one surface of the substrate, wherein the conductive layer includes a conductive agent and the conductive adhesive as described in the first aspect.

[0056] In the present application, a conductive adhesive and a conductive agent are used to form a conductive layer. The grafted conductive groups in the conductive adhesive can form electrical conduction with the conductive agent, thereby increasing the conductive path and improving the conductive performance.

[0057] In some embodiments, the substrate includes aluminum foil, copper foil, composite aluminum foil, or composite copper foil.

[0058] In some embodiments, the mass ratio of the conductive agent to the conductive adhesive is 1:(0.2-1.25).

[0059] In some embodiments, the conductive agent includes at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, and a two-dimensional conductive agent. Alternatively, the conductive agent includes a combination of at least two of the zero-dimensional conductive agent, the one-dimensional conductive agent, and the two-dimensional conductive agent. In this application, conductive agents of multiple dimensions are used in conjunction with the conductive adhesive. The conductive agent can form a physical entanglement with the graft structure in the conductive adhesive, and the cross-entanglement improves the stability and conductivity of the conductive layer.

[0060] In some embodiments, the zero-dimensional conductive agent comprises conductive carbon black and / or acetylene black, the one-dimensional conductive agent comprises carbon nanotubes, and the two-dimensional conductive agent comprises graphite and / or graphene.

[0061] Exemplarily, a method for preparing the above-mentioned current collector is provided, which specifically includes:

[0062] A conductive agent and a conductive binder are weighed in a mass ratio of 1:0.2 to 1.25, a solvent is added, and the mixture is mixed and dispersed for 2 to 10 hours to prepare a conductive slurry. The conductive slurry is applied to the surface of the substrate and dried at 80 to 120° C. to prepare the current collector.

[0063] A fourth aspect of the present application provides an electrode, comprising a current collector and an active layer disposed on at least one side of the current collector, wherein the current collector is the current collector described in the third aspect.

[0064] Optionally, the electrode is a positive electrode, and the active layer is a positive electrode active layer. For example, the positive electrode active material in the positive electrode active layer includes a ternary material or a lithium iron phosphate material.

[0065] Optionally, the electrode is a negative electrode, and the active layer is a negative electrode active layer. For example, the negative electrode material in the negative electrode active layer includes graphite.

[0066] A fifth aspect of the present application provides a battery, comprising the electrode as described in the fourth aspect.

[0067] Optionally, the battery is a lithium-ion battery, comprising a battery cell and a shell, wherein the shell is injected with an electrolyte, and the battery cell is immersed in the electrolyte, wherein the battery cell can be a wound battery cell or a stacked battery cell. Taking the stacked battery cell as an example, the battery cell includes a stacked positive electrode, a separator and a negative electrode, wherein the positive electrode and / or the negative electrode adopts the electrode described in the fourth aspect.

[0068] Example 1

[0069] (1) Conductive adhesive

[0070] 1 kg of polyaniline monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyacrylic acid (molecular weight of 150,000) and low molecular weight polyacrylic acid (molecular weight of 25,000) were weighed in a mass ratio of 20:1 and mixed with water to form 40 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 0°C to react. After stirring for 16 hours, the conductive adhesive was prepared.

[0071] (2) Current collector

[0072] Weigh 10 kg of conductive carbon black and carbon nanotubes, the mass ratio of conductive carbon black and carbon nanotubes is 1:1, and 8 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25% is added with water to prepare a conductive slurry with a solid content of 8%. After mixing and dispersing for 4 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 100°C, a conductive layer is formed to prepare the current collector.

[0073] Example 2

[0074] (1) Conductive adhesive

[0075] 1 kg of polyaniline monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyacrylic acid (molecular weight of 200,000) and low molecular weight polyacrylic acid (molecular weight of 500) were weighed in a mass ratio of 30:1 and mixed with water to form 80 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 0°C to react. After stirring for 12 hours, the conductive adhesive was prepared.

[0076] (2) Current collector

[0077] Weigh 10 kg of conductive carbon black and carbon nanotubes, the mass ratio of conductive carbon black to carbon nanotubes is 1:2, and 10 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25% is added with water to prepare a conductive slurry with a solid content of 8%. After mixing and dispersing for 6 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 100°C, a conductive layer is formed to prepare the current collector.

[0078] Example 3

[0079] (1) Conductive adhesive

[0080] 1 kg of polyaniline monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyacrylic acid (molecular weight of 300,000) and low molecular weight polyacrylic acid (molecular weight of 50,000) were weighed in a mass ratio of 20:1 and mixed with water to form 160 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 0°C to react. After stirring for 10 hours, the conductive adhesive was prepared.

[0081] (2) Current collector

[0082] Weigh 10 kg of conductive carbon black and graphene, the mass ratio of conductive carbon black and graphene is 1:1, 16 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25%, add water to prepare a conductive slurry with a solid content of 8%, after mixing and dispersing for 8 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 100°C, a conductive layer is formed to prepare the current collector.

[0083] Example 4

[0084] (1) Conductive adhesive

[0085] 1 kg of polyaniline monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyacrylic acid (molecular weight of 400,000) and low molecular weight polyacrylic acid (molecular weight of 30,000) were weighed in a mass ratio of 50:1 and mixed with water to form 60 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 0°C to react. After stirring for 10 hours, the conductive adhesive was prepared.

[0086] (2) Current collector

[0087] Weigh 10 kg of conductive carbon black and graphite, the mass ratio of conductive carbon black and graphite is 1:1, 25 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25%, add water to prepare a conductive slurry with a solid content of 8%. After mixing and dispersing for 8 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 105°C, a conductive layer is formed to prepare the current collector.

[0088] Example 5

[0089] (1) Conductive adhesive

[0090] 1 kg of polyaniline monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyacrylic acid (molecular weight of 500,000) and low molecular weight polyacrylic acid (molecular weight of 5000) were weighed in a mass ratio of 10:1 and mixed with water to form 200 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 0°C to react. After stirring for 10 hours, the conductive adhesive was prepared.

[0091] (2) Current collector

[0092] Weigh 10 kg of conductive carbon black and carbon nanotubes, the mass ratio of conductive carbon black to graphene is 1:1, 50 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25%, add water to prepare a conductive slurry with a solid content of 8%. After mixing and dispersing for 8 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 105°C, a conductive layer is formed to prepare the current collector.

[0093] Example 6

[0094] (1) Conductive adhesive

[0095] 1 kg of polyphenylene acetylene monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, a high molecular weight styrene butadiene emulsion (molecular weight of 350,000) and a low molecular weight styrene butadiene emulsion (molecular weight of 10,000) with a mass ratio of 40:1 were weighed and mixed with water to form 120 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 5°C to react. After stirring for 8 hours, the conductive adhesive was prepared.

[0096] (2) Current collector

[0097] Weigh 10 kg of carbon nanotubes and graphene, the mass ratio of carbon nanotubes and graphene is 1:1, and 40 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25% is added with water to prepare a conductive slurry with a solid content of 8%. After mixing and dispersing for 10 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm. The substrate is an aluminum foil with a thickness of 13 μm. After drying at 120°C, a conductive layer is formed to prepare the current collector.

[0098] Example 7

[0099] (1) Conductive adhesive

[0100] 1 kg of polyparaphenylene monomer and 0.1 kg of sodium persulfate were weighed and mixed to form a mixed solution. Then, high molecular weight polyvinylidene fluoride (molecular weight of 200,000) and low molecular weight polyvinylidene fluoride (molecular weight of 15,000) were weighed in a mass ratio of 25:1 and mixed with water to form 100 kg of a polymer binder solution with a solid content of 25%. The mixed solution was added to the polymer binder solution at a rate of 2 ml / min at 2°C to react. After stirring for 20 hours, the conductive adhesive was prepared.

[0101] (2) Current collector

[0102] Weigh 10 kg of acetylene black, carbon nanotubes and graphene, the mass ratio of acetylene black, carbon nanotubes and graphene is 1:1:1, 20 kg of the above-mentioned conductive adhesive solution with a mass fraction of 25%, add water to prepare a conductive slurry with a solid content of 8%, after mixing and dispersing for 6 hours, the conductive slurry is coated on both sides of the substrate with a coating thickness of 1 μm, the substrate is an aluminum foil with a thickness of 13 μm, and a conductive layer is formed after drying at 80°C to prepare the current collector.

[0103] Example 8

[0104] This embodiment provides a conductive adhesive and a current collector. Compared with Example 2, the difference is that the conductive agent 10 kg of conductive carbon black in the current collector is replaced with 10 kg of conductive graphite, and the remaining parameters and steps are exactly the same as Example 1.

[0105] Example 9

[0106] This embodiment provides a conductive adhesive and a current collector. Compared with Example 3, the difference is that the mixing and dispersion time during the preparation of the current collector is 10 hours, and the other parameters and steps are exactly the same as Example 1.

[0107] Example 10

[0108] This embodiment provides a conductive adhesive and a current collector. Compared with Example 4, the difference is that the drying temperature during the preparation of the current collector is 120° C., and the other parameters and steps are exactly the same as Example 1.

[0109] Example 11

[0110] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the mass ratio of the first polymer to the second polymer is 5:1, and the other parameters and steps are exactly the same as those in Example 1.

[0111] Example 12

[0112] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the mass ratio of the first polymer to the second polymer is 60:1, and the other parameters and steps are exactly the same as those in Example 1.

[0113] Example 13

[0114] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the molecular weight of the high molecular weight polyacrylic acid is 80,000, and the other parameters and steps are exactly the same as those in Example 1.

[0115] Example 14

[0116] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the molecular weight of the high molecular weight polyacrylic acid is 600,000, and the other parameters and steps are exactly the same as those in Example 1.

[0117] Example 15

[0118] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the molecular weight of the low molecular weight polyacrylic acid is 300, and the other parameters and steps are exactly the same as those in Example 1.

[0119] Example 16

[0120] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the molecular weight of the low molecular weight polyacrylic acid is 60,000, and the other parameters and steps are exactly the same as those in Example 1.

[0121] Example 17

[0122] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the mass of the polyaniline monomer is 2 kg, and the other parameters and steps are exactly the same as those in Example 1.

[0123] Example 18

[0124] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the mass of the polyaniline monomer is 0.1 kg, and the other parameters and steps are exactly the same as those in Example 1.

[0125] Example 19

[0126] This embodiment provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the conductive agent in the current collector only uses conductive carbon black and does not include carbon nanotubes. The remaining parameters and steps are exactly the same as Example 1.

[0127] Comparative Example 1

[0128] This comparative example provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the reaction temperature during the preparation of the conductive adhesive is 10° C., and the other parameters and steps are exactly the same as those in Example 1.

[0129] Comparative Example 2

[0130] This comparative example provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the low molecular weight polyacrylic acid is replaced with an equal mass of high molecular weight polyacrylic acid (molecular weight of 250,000), and the remaining parameters and steps are exactly the same as Example 1.

[0131] Comparative Example 3

[0132] This comparative example provides a conductive adhesive and a current collector. Compared with Example 1, the difference is that the high molecular weight polyacrylic acid is replaced by an equal mass of low molecular weight polyacrylic acid (molecular weight of 25,000), and the remaining parameters and steps are exactly the same as Example 1.

[0133] The surface resistance, penetration resistance and conductive layer peeling force performance tests of the current collectors prepared in the above examples and comparative examples were performed. The test results are shown in Table 1. The test method specifically includes:

[0134] (1) Surface resistance: tested with a four-probe resistance meter (probe type, full pressure stroke).

[0135] (2) Penetration resistance: The electrode resistance meter was used for testing. The highly conductive coating current collectors prepared in the above embodiments and comparative examples were cut into 5 cm × 5 cm squares, placed under the test head, and maintained at a test pressure of 0.3t for 5 seconds.

[0136] (3) Peel force test: 3M610 tape was used, 180° peeling, gauge length 100 mm, speed 50 mm / min.

[0137] Table 1

[0138]

[0139]

[0140] From the table above we can see that:

[0141] (1) Comparing Example 1 with Examples 11-12, it can be seen that in the present application, by controlling the mass ratio of polymers with different molecular weights, the conductive groups are grafted onto the adhesive substrate and the conductive groups are distributed, thereby ensuring conductivity and adhesion.

[0142] (2) Comparing Example 1 with Examples 13-14, it can be seen that in this application, by selecting the molecular weight of the first polymer to be 100,000 to 400,000, the conductive adhesive has both solubility and stability, and the conductive groups can be evenly grafted onto the second polymer adhesive, effectively ensuring the conductivity of the conductive adhesive.

[0143] (3) Comparing Example 1 with Examples 15-16, it can be seen that in the present application, by selecting the molecular weight of the second polymer to be 500 to 50,000, the low molecular weight polymer can effectively penetrate into the surface of the substrate during the preparation process, thereby improving the adhesion and not affecting the grafting effect.

[0144] (4) Comparing Example 1 with Examples 17-18, it can be seen that the combination of the first polymer and the second polymer in the present application effectively improves the grafting rate of the conductive group, achieving both grafting rate and conductivity.

[0145] (5) Compared with Example 19, it can be seen that in this application, conductive agents of various dimensions are used in conjunction with the conductive adhesive. The conductive agent can form a physical entanglement with the grafted structure in the conductive adhesive, and the cross-entanglement improves the stability and conductivity of the conductive layer.

[0146] (6) Comparing Example 1 with Comparative Example 1, it can be seen that the use of an ice-water bath in the present application first effectively avoids the occurrence of violent polymerization during the grafting process, reduces the possibility of polymerization of the binder matrix, and improves the grafting effect of the conductive group.

[0147] (7) When Example 1 is compared with Comparative Examples 2-3, it can be seen that when polymer binders with different molecular weights are used, since the high molecular weight polymer binder has a large number of grafting sites, the conductive groups can be evenly grafted to the surface of the high molecular weight polymer binder, thereby improving the grafting rate of the conductive groups. In addition, due to the molecular chain length of the high molecular weight polymer, the polymerization ability of the low molecular weight polymer binder is reduced by utilizing the steric hindrance effect, and the low molecular weight polymer binder can easily penetrate into the surface of the conductive binder, thereby increasing the bonding sites, so that the conductive binder has both adhesive properties and improved conductivity.

[0148] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A conductive adhesive, characterized in that: The conductive binder comprises a first polymer binder grafted with a conductive group and a second polymer binder grafted with a conductive group, wherein the molecular weight of the first polymer binder is greater than the molecular weight of the second polymer binder; The conductive adhesive is prepared by the following preparation method, comprising: The conductive adhesive is prepared by mixing a first polymer, a second polymer, a conductive monomer, and an initiator in a solvent, polymerizing the conductive monomer at 0-5° C. to generate conductive groups, and grafting the conductive groups onto the first polymer and the second polymer. The molecular weight of the first polymer is 100,000 to 400,000, the molecular weight of the second polymer is 500 to 50,000, and the mass ratio of the first polymer to the second polymer is (10 to 50):1; the ratio of the mass of the conductive monomer to the total mass of the first polymer and the second polymer is 1:(10 to 50).

2. The conductive adhesive according to claim 1, wherein The mass ratio of the initiator to the conductive monomer is 1:(10-150).

3. The conductive adhesive according to claim 1 or 2, wherein: One or more of the following conditions are met: 1) The conductive group includes at least one of polyaniline, polypyrrole, polythiophene, polyparaphenylene and polyphenylene acetylene; 2) The first polymer and the second polymer are each independently selected from at least one of polyacrylic acid, polyvinylidene fluoride and styrene-butadiene emulsion; 3) The conductive monomer includes at least one of a polyaniline monomer, a polypyrrole monomer, a polythiophene monomer, a polyparaphenylene monomer, and a polyphenyleneacetylene monomer; 4) The initiator includes a persulfate compound.

4. The conductive adhesive according to claim 3, wherein The persulfate compound includes sodium persulfate.

5. A method for preparing the conductive adhesive according to any one of claims 1 to 4, characterized in that: The preparation method of the conductive adhesive comprises: The conductive adhesive is prepared by mixing a first polymer, a second polymer, a conductive monomer and an initiator in a solvent, polymerizing the conductive monomer at 0-5° C. to generate conductive groups, and grafting the conductive groups onto the first polymer and the second polymer.

6. The method for preparing the conductive adhesive according to claim 5, wherein: One or more of the following conditions are met: 1) The conductive monomer and the initiator are mixed and added to the mixture of the first polymer and the second polymer; 2) The reaction time of the preparation method is 8 to 20 hours; 3) The preparation method is carried out under stirring conditions.

7. A current collector, characterized in that: The current collector includes a substrate and a conductive layer disposed on at least one surface of the substrate, wherein the conductive layer includes a conductive agent and the conductive adhesive according to any one of claims 1 to 4.

8. The current collector according to claim 7, wherein: One or more of the following conditions are met: 1) The mass ratio of the conductive agent to the conductive adhesive is 1:(0.2-1.25); 2) The conductive agent includes at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, and a two-dimensional conductive agent; 3) The zero-dimensional conductive agent includes conductive carbon black and / or acetylene black; the one-dimensional conductive agent includes carbon nanotubes; and the two-dimensional conductive agent includes graphite and / or graphene.

9. An electrode, characterized in that The electrode includes a current collector and an active layer disposed on at least one side of the current collector. The current collector is the current collector according to claim 7 or 8.

10. A battery, characterized in that: The battery comprises the electrode according to claim 9.

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