Conductive slurry for carbon-coated current collector, preparation method of conductive slurry and lithium ion battery

Abstract

The invention provides conductive paste for a carbon-coated current collector, a preparation method of the conductive paste and a lithium ion battery. The conductive paste comprises a wetting aid, a water-based glue solution, a carbon material and a solvent, the lubrication aid comprises a polyfunctional group compound as shown in a formula I; r1 is a fluorine substituent group, and R2 is a silicon oxygen substituent group. The multifunctional group compound introduced into the conductive paste contains amino, fluorine substituent and silica substituent, and the amino can act with the surface of an active substance to generate hydrogen bonds, so that the binding force of a current collector and the active substance is enhanced, and the stripping force of a pole piece is improved; the silicon-oxygen substituent group can form an interface layer with good affinity with the surface of an active substance in the conductive slurry, and can also reduce the friction coefficient of the surface of the foil material, so that the foil leakage rate is greatly reduced; the fluorine substituent group can obviously improve the interface property of the conductive slurry and the surface of the foil material, is beneficial to the wetting process, has lower surface energy, and is beneficial to spreading of the conductive slurry on the surface of the foil material, so that the foil leakage rate is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a conductive slurry for a carbon-coated current collector, a preparation method thereof, and a lithium ion battery. Background Art

[0002] With the advancement of lithium-ion battery technology, the positive electrode current collector of lithium-ion batteries includes but is not limited to ordinary aluminum foil. Carbon-coated aluminum foil has also been gradually used in recent years, especially in lithium iron phosphate batteries. Carbon-coated aluminum foil can effectively improve the adhesion between the active material and the current collector, reduce the internal resistance of the battery, reduce polarization, and improve the battery life and consistency. Therefore, it is particularly important to prepare carbon-coated aluminum foil with excellent performance. However, the aluminum foil in the carbon-coated aluminum foil requires a large amount of rolling oil during the preparation process, and these rolling oils cannot be completely removed in the final stage of aluminum foil production, resulting in residual oil stains on the surface of the aluminum foil. The conductive slurry is mostly water-based and is incompatible with the oil stains on the surface of the aluminum foil. The slurry is not easy to spread on the aluminum foil, and a large amount of coating leakage will occur during coating, affecting the appearance and use of the carbon-coated aluminum foil, increasing the internal resistance of the battery, and affecting the battery life.

[0003] To this end, researchers have made improvements. For example, the prior art discloses a carbon-coated current collector and its preparation method and application. The preparation method includes the following steps: (1) pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing to obtain a conductive carbon material premix; (2) mixing the conductive carbon material premix with deionized water, a binder, a wetting dispersant, and lithium carbonate, and dispersing to obtain a conductive slurry; (3) coating the conductive slurry obtained in step (2) on the surface of the current collector and baking to obtain the carbon-coated current collector. The wetting dispersant includes any one of n-pentanol, ethanol, methanol, isopropanol, or sodium dodecylbenzenesulfonate, or a combination of at least two. The prior art also provides a carbon-coated current collector and its preparation method and application. The carbon-coated current collector includes a current collector substrate and a carbon-coated layer on at least one side of the current collector substrate; the carbon-coated layer includes a conductive agent, a binder, and a cross-linking agent; the binder includes a polyacrylic polymer and polystyrene microspheres. The prior art also discloses a lithium-ion battery negative electrode sheet comprising a carbon-coated current collector and an active layer coated on the surface of the carbon-coated current collector. The carbon-coated current collector comprises a copper foil and a carbon layer coated on the surface of the copper foil. The active layer comprises an active material, a first binder, and a first conductive agent, while the carbon layer comprises a second binder and a second conductive agent. While the above prior art can, to a certain extent, improve the slurry's leaking coating and enhance the adhesion between the active material and the current collector, the effect is not significant and requires further optimization.

[0004] Therefore, how to significantly improve the spreading of the conductive paste on the foil, reduce the foil leakage rate, and significantly enhance the bonding force between the active material and the current collector, and improve the electrode peeling force, is a hot topic that needs to be studied urgently. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a conductive paste for carbon-coated current collectors, a preparation method thereof, and a lithium-ion battery. The present invention introduces a multifunctional compound as shown in Formula I into the conductive paste, wherein the multifunctional compound contains an amino group, a fluorine substituent, and a silicon-oxygen substituent. The amino group has a certain polarity and alkalinity, and can react with the surface of the active material to produce hydrogen bonds, which is beneficial to enhancing the binding force between the current collector and the active material, thereby improving the electrode peeling force; the silicon-oxygen substituent has good flexibility and low surface energy, and can form an interface layer with good affinity with the surface of the active material in the conductive paste, and it can also reduce the friction coefficient of the foil surface, so that the conductive paste can be better spread on the foil, thereby greatly reducing the foil leakage rate; the fluorine substituent can significantly improve the interface properties between the conductive paste and the foil surface, which is beneficial to the wetting process, and it has a low surface energy, which helps the conductive paste spread on the foil surface, thereby greatly reducing the foil leakage rate.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a conductive paste for a carbon-coated current collector, wherein the conductive paste comprises a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0008] Wherein, the wetting agent includes a multifunctional compound as shown in Formula I:

[0009]

[0010] Wherein, R1 is a fluorine substituent, and R2 is a silicon-oxygen substituent.

[0011] The present invention introduces a multifunctional group compound as shown in Formula I into the conductive paste, wherein the multifunctional group compound contains an amino group, a fluorine substituent and a silicon oxygen substituent. The amino group has certain polarity and alkalinity and can react with the surface of the active material to produce hydrogen bonds, which is beneficial to enhancing the binding force between the current collector and the active material, thereby improving the electrode peeling force; the silicon oxygen substituent has good flexibility and low surface energy, and can form an interface layer with good affinity with the surface of the active material in the conductive paste, and can also reduce the friction coefficient of the foil surface, so that the conductive paste can be better spread on the foil, thereby greatly reducing the foil leakage rate; the fluorine substituent can significantly improve the interface properties between the conductive paste and the foil surface, which is beneficial to the wetting process, and has a low surface energy, which helps the conductive paste to spread on the foil surface, thereby greatly reducing the foil leakage rate.

[0012] In the present invention, the amino group, fluorine substituent, and siloxy substituent cooperate with each other. The amino group and siloxy group form a dual bond through hydrogen bonding and covalent bonding, greatly improving the adhesion between the conductive paste and the foil. The fluorine substituent reduces the surface tension gradient, which can cooperate with the low viscosity of the siloxy chain to significantly improve the uniformity of the conductive paste coating thickness. Therefore, the three synergistically can effectively regulate the surface tension and viscosity of the conductive paste, greatly improving the spreading effect of the conductive paste on the foil surface, thereby greatly reducing the foil leakage rate, and also significantly improving the peeling force of the electrode.

[0013] Preferably, the fluorine substituent is selected from any one of a fluorine atom, a fluorinated alkyl group, a fluorinated alkenyl group, a fluorinated alkynyl group, a fluorinated alkoxy group, a fluorinated acyl group or a fluorinated aryl group.

[0014] Preferably, the siloxy substituent includes any one of a methoxysilyl group, an ethoxysilyl group, a trimethylsilyl group, a phenylsilyl group or a fluorine-containing silyl group.

[0015] Preferably, the multifunctional compound is selected from at least one of the following compounds;

[0016]

[0017] In the present invention, The CAS number is 660449-55-8; The CAS number is 2169267-73-4; The CAS number is 205700-47-6.

[0018] Preferably, the aqueous adhesive includes any one of polyacrylic acid adhesive, acrylate adhesive, acrylamide adhesive or polyurethane adhesive, and silane coupling agent adhesive, or a combination of at least two of them.

[0019] In the present invention, the aqueous glue has the following functions: a binder, which helps to bond the various components in the conductive paste together and firmly combine the paste with the foil; a dispersant, which makes the carbon material uniformly dispersed in the paste system; a rheology regulator, which can adjust the rheological properties of the conductive paste to ensure that the paste has good construction performance; a conductive auxiliary agent, which has an auxiliary effect of improving the overall conductivity of the conductive paste; and a protective agent, which has the function of protecting the carbon material from the influence of the external environment and improving the performance stability and service life of the paste.

[0020] Preferably, the carbon material includes any one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fiber, or a combination of at least two thereof.

[0021] Preferably, the mass ratio of the wetting agent, aqueous glue and carbon material is (1-5): (60-80): (10-30), wherein the selection range of the wetting agent "1-5" can be, for example, 1, 2, 3, 4 or 5, the selection range of the aqueous glue "60-80" can be, for example, 60, 65, 70, 75 or 80, and the selection range of the carbon material "10-30" can be, for example, 10, 15, 20, 25 or 30, etc.

[0022] In the present invention, if the mass ratio of the wetting agent to the carbon material is too small, it is not conducive to the uniform dispersion of the carbon material, and the spreading effect of the slurry is poor, which is not conducive to reducing the foil leakage rate; if the mass ratio of the wetting agent to the carbon material is too large, it is not conducive to improving the adhesion of the conductive slurry.

[0023] In the present invention, an appropriate amount of aqueous glue is used in synergistic combination with a wetting agent and a carbon material, which helps to fully improve the dispersibility of the conductive paste and enhance the bonding force of the carbon material. At the same time, it can also reduce the contact resistance between the carbon material and the foil, optimize the coating performance of the conductive paste, and make it easier for the conductive paste to spread evenly on the surface of the foil.

[0024] Preferably, based on 100% by mass of the conductive paste, the mass fraction of the wetting agent is 0.2-0.8%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7% or 0.8%.

[0025] In the present invention, a suitable wetting agent helps to fully enhance the bonding force between the foil and the active material, and can also fully adjust the wettability of the conductive paste, so that the conductive paste can be better spread on the foil and reduce the foil leakage rate.

[0026] Preferably, the solvent comprises water.

[0027] In a second aspect, the present invention provides a method for preparing the conductive paste for the carbon-coated current collector as described in the first aspect, the preparation method comprising the following steps:

[0028] The wetting agent, aqueous glue, carbon material and solvent are mixed to obtain the conductive slurry for the carbon-coated current collector.

[0029] Preferably, the mixing method comprises:

[0030] (a) a wetting agent and a solvent are mixed for a first time to obtain a first dispersion; and the first dispersion and the aqueous glue are mixed for a second time to obtain a second dispersion.

[0031] (b) mixing the second dispersion liquid and the carbon material.

[0032] The mixing method provided by the present invention can further improve the mixing effect, so that the components are mixed more evenly and the dispersion effect is better.

[0033] Preferably, in step (a), vacuum stirring and dispersion are performed independently and sequentially during the first mixing and the second mixing.

[0034] In this invention, stirring in a vacuum environment effectively removes air and other volatile gases from the slurry, allowing the materials to fully contact and mix in an environment free of gas interference. This more evenly distributes the components under stirring, contributing to the formation of a stable and consistently performing conductive slurry. Furthermore, the vacuum environment reduces oxygen contact with the materials, lowering the risk of oxidation and preserving their properties.

[0035] In the present invention, the dispersion process further refines particles such as carbon materials and evenly disperses them in the slurry. The dispersion process also creates a stable suspension system for the various components in the slurry, ensuring the stability of the conductive slurry during storage and use. Furthermore, the well-dispersed conductive slurry exhibits improved rheological and coating properties, helping to reduce foil leakage.

[0036] Preferably, the vacuum stirring rate is 150-350 rpm, for example, 150 rpm, 200 rpm, 250 rpm, 300 rpm or 350 rpm.

[0037] In the present invention, an appropriate vacuum stirring rate can allow the carbon material, solvent, aqueous glue and wetting agent and other components to fully contact and mix in a vacuum environment, avoiding the occurrence of local uneven mixing or agglomeration caused by excessive stirring, and also helps bubbles to escape quickly from the slurry, avoiding damage to the material structure and performance due to excessively high stirring rate.

[0038] Preferably, the dispersion speed is 500-700 rpm, for example, 500 rpm, 550 rpm, 600 rpm, 650 rpm or 700 rpm.

[0039] In this invention, an appropriate dispersion rate provides sufficient shear and impact forces to break up agglomerated particles, evenly distributing them in the slurry as individual particles or small aggregates. This improves particle dispersion and, in turn, enhances the conductivity and stability of the conductive slurry. While achieving good dispersion, the particles maintain an appropriate size and surface properties, facilitating subsequent processing and application while reducing foil leakage.

[0040] Preferably, the dispersion time is 30-50 min, for example, 30 min, 35 min, 40 min, 45 min or 50 min.

[0041] Preferably, the mixing method in step (b) includes:

[0042] The carbon material is added to the second dispersion liquid in multiple times and mixed.

[0043] In the present invention, adding the carbon material in multiple steps helps to disperse it more fully in the solution. Compared to adding a large amount of carbon material all at once, adding it in steps allows the carbon material more time to fully contact and interact with the components in the solution, such as the wetting agent and aqueous glue, reducing the occurrence of agglomeration and thus improving the dispersion uniformity of the carbon material in the solution. Furthermore, it helps to optimize the mixing effect, improve the stability and rheological properties of the slurry, making it more suitable for subsequent processes such as coating, and reducing the foil leakage rate.

[0044] It should be noted that the present invention has no limitation on “multiple times”, as long as it is greater than or equal to 2 times, for example, it can be 2 times, 3 times, 4 times or 5 times.

[0045] Preferably, the carbon material is added in multiple times, and stirring and dispersion are performed after each addition.

[0046] Preferably, the stirring rate is 150-300 rpm, for example, 150 rpm, 200 rpm, 250 rpm, 300 rpm or 350 rpm.

[0047] Preferably, the dispersion speed is 500-700 rpm, for example, 500 rpm, 550 rpm, 600 rpm, 650 rpm or 700 rpm.

[0048] Preferably, the dispersion time is 30-50 min, for example, 30 min, 35 min, 40 min, 45 min or 50 min.

[0049] In a third aspect, the present invention provides a carbon-coated current collector, which includes a foil and a conductive coating arranged on the surface of the foil. The conductive coating is prepared by the conductive slurry for the carbon-coated current collector described in the first aspect, or the conductive coating is prepared by the conductive slurry prepared by the preparation method described in the second aspect.

[0050] It should be noted that the present invention does not limit the type of foil material. For example, it can be aluminum foil.

[0051] Preferably, the thickness of the conductive coating is 0.5-1 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm.

[0052] In the present invention, the conductive coating with appropriate thickness not only helps to improve the bonding force between the foil material and the active material, but also has an excellent spreading effect, greatly reducing the foil leakage rate.

[0053] In a fourth aspect, the present invention provides a lithium-ion battery, comprising the carbon-coated current collector as described in the third aspect.

[0054] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The present invention introduces a multifunctional group compound as shown in Formula I into the conductive paste, wherein the multifunctional group compound contains an amino group, a fluorine substituent and a silicon oxygen substituent. The amino group has certain polarity and alkalinity and can react with the surface of the active material to produce hydrogen bonds, which is beneficial to enhancing the binding force between the current collector and the active material, thereby improving the electrode peeling force; the silicon oxygen substituent has good flexibility and low surface energy, and can form an interface layer with good affinity with the surface of the active material in the conductive paste, and can also reduce the friction coefficient of the foil surface, so that the conductive paste can be better spread on the foil, thereby greatly reducing the foil leakage rate; the fluorine substituent can significantly improve the interface properties between the conductive paste and the foil surface, which is beneficial to the wetting process, and has a low surface energy, which helps the conductive paste to spread on the foil surface, thereby greatly reducing the foil leakage rate. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0058] Example 1

[0059] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0060] Wherein, the wetting agent is a multifunctional compound as shown below:

[0061]

[0062] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:60:10; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0063] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0064] (1) 1 g of a wetting agent and 429 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 60 g of an aqueous glue to obtain a second dispersion.

[0065] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0066] (2) 10 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0067] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0068] Example 2

[0069] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0070] Wherein, the wetting agent is a multifunctional compound as shown below:

[0071]

[0072] The aqueous glue is an acrylic glue; the carbon material is conductive graphite; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:10; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0073] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0074] (1) 1 g of a wetting agent and 419 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0075] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 150 rpm, the dispersion rate was 500 rpm, and the dispersion time was 50 min.

[0076] (2) 10 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0077] The stirring rate was 200 rpm, the dispersion rate was 500 rpm, and the dispersion time was 50 min.

[0078] Example 3

[0079] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0080] Wherein, the wetting agent is a multifunctional compound as shown below:

[0081]

[0082] The aqueous glue is acrylamide glue; the carbon material is carbon nanotubes; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:80:10; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0083] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0084] (1) 1 g of a wetting agent and 409 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 80 g of an aqueous glue to obtain a second dispersion.

[0085] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 350 rpm, the dispersion rate was 700 rpm, and the dispersion time was 30 min.

[0086] (2) 10 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0087] The stirring rate was 150 rpm, the dispersion rate was 700 rpm, and the dispersion time was 40 min.

[0088] Example 4

[0089] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0090] Wherein, the wetting agent is a multifunctional compound as shown below:

[0091]

[0092] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0093] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0094] (1) 1 g of a wetting agent and 409 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0095] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0096] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0097] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0098] Example 5

[0099] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0100] Wherein, the wetting agent is a multifunctional compound as shown below:

[0101]

[0102] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:30; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0103] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0104] (1) 1 g of a wetting agent and 399 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0105] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0106] (2) 30 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0107] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0108] Example 6

[0109] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0110] Wherein, the wetting agent is a multifunctional compound as shown below:

[0111]

[0112] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:90:10; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0113] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0114] (1) 1 g of a wetting agent and 399 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 90 g of an aqueous glue to obtain a second dispersion.

[0115] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0116] (2) 10 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0117] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0118] Example 7

[0119] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0120] Wherein, the wetting agent is a multifunctional compound as shown below:

[0121]

[0122] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:90:40; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.2%; and the solvent is water.

[0123] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0124] (1) 1 g of a wetting agent and 369 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 90 g of an aqueous glue to obtain a second dispersion.

[0125] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0126] (2) 40 g of carbon material was added to the second dispersion liquid in three times, and the mixture was stirred and dispersed after each addition to obtain the conductive slurry for the carbon-coated current collector.

[0127] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0128] Example 8

[0129] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0130] Wherein, the wetting agent is a multifunctional compound as shown below:

[0131]

[0132] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.5%; and the solvent is water.

[0133] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0134] (1) 1 g of a wetting agent and 109 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0135] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0136] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0137] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0138] Example 9

[0139] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0140] Wherein, the wetting agent is a multifunctional compound as shown below:

[0141]

[0142] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.8%; and the solvent is water.

[0143] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0144] (1) 1 g of a wetting agent and 34 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0145] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0146] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0147] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0148] Example 10

[0149] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0150] Wherein, the wetting agent is a multifunctional compound as shown below:

[0151]

[0152] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 1%; and the solvent is water.

[0153] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0154] (1) 1 g of a wetting agent and 9 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0155] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0156] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0157] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0158] Example 11

[0159] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0160] Wherein, the wetting agent is a multifunctional compound as shown below:

[0161]

[0162] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.5%; and the solvent is water.

[0163] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0164] (1) 1 g of a wetting agent and 109 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0165] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0166] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0167] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0168] Example 12

[0169] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0170] Wherein, the wetting agent is a multifunctional compound as shown below:

[0171]

[0172] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.5%; and the solvent is water.

[0173] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0174] (1) 1 g of a wetting agent and 109 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion was mixed with 70 g of an aqueous glue to obtain a second dispersion.

[0175] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0176] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0177] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0178] Example 13

[0179] This embodiment provides a conductive paste for a carbon-coated current collector, wherein the conductive paste includes a wetting agent, an aqueous glue, a carbon material, and a solvent.

[0180] Wherein, the wetting agent is a multifunctional compound as shown below:

[0181]

[0182] The aqueous glue is polyacrylic acid glue; the carbon material is conductive carbon black; the mass ratio of the wetting agent, the aqueous glue and the carbon material is 1:70:20; based on the mass of the conductive paste being 100%, the mass fraction of the wetting agent is 0.1%; and the solvent is water.

[0183] This embodiment also provides a method for preparing the conductive slurry for the carbon-coated current collector, the preparation method comprising the following steps:

[0184] (1) 1 g of a wetting agent and 909 g of water were mixed in a blender to obtain a first dispersion; and the first dispersion and 70 g of an aqueous glue were mixed to obtain a second dispersion.

[0185] The first mixing and the second mixing processes were independently and sequentially performed with vacuum stirring and dispersion, the vacuum stirring rate was 250 rpm, the dispersion rate was 600 rpm, and the dispersion time was 40 min.

[0186] (2) 20 g of carbon material was added to the second dispersion liquid in three times, and stirring and dispersing were performed after each addition to obtain the conductive paste for the carbon-coated current collector.

[0187] The stirring rate was 300 rpm, the dispersion rate was 600 rpm, and the dispersion time was 30 min.

[0188] Comparative Example 1

[0189] The difference between this comparative example and Example 8 is that the wetting agent is replaced with isopropyl alcohol of equal mass.

[0190] The remaining preparation methods and parameters remained the same as in Example 8.

[0191] Comparative Example 2

[0192] The difference between this comparative example and Example 8 is that the wetting agent is replaced by the following multifunctional compound (CAS No.: 14791-78-7):

[0193]

[0194] The remaining preparation methods and parameters remained the same as in Example 8.

[0195] Comparative Example 3

[0196] The difference between this comparative example and Example 8 is that the wetting agent is replaced by the following multifunctional compound (CAS No.: 113984-68-2):

[0197]

[0198] The remaining preparation methods and parameters remained the same as in Example 8.

[0199] Comparative Example 4

[0200] The difference between this comparative example and Example 8 is that the wetting agent is replaced by the following multifunctional compound (CAS No.: 121942-75-4):

[0201]

[0202] The remaining preparation methods and parameters remained the same as in Example 8.

[0203] Comparative Example 5

[0204] The difference between this comparative example and Example 8 is that the aqueous glue is replaced with water of equal mass.

[0205] The remaining preparation methods and parameters remained the same as in Example 8.

[0206] Performance Testing

[0207] 1. The conductive pastes provided in the above examples and comparative examples were respectively subjected to contact angle tests on aluminum foil.

[0208] 2. The conductive pastes provided in the above embodiments and comparative examples were coated on aluminum foil respectively, and after drying, they were inspected using a three-coordinate measuring instrument. The number of foil leakage points was recorded under a magnification of 2W.

[0209] 3. The conductive pastes provided in the above embodiment and comparative example were respectively coated on aluminum foil to prepare negative electrode sheets, and then the obtained negative electrode sheets were subjected to a peeling force test using a universal tensile testing machine.

[0210] The above test results are shown in Table 1.

[0211] Table 1

[0212]

[0213]

[0214] analyze:

[0215] As shown in Table 1, by comparing Example 1, Example 2, Example 3, Example 4, Example 5, Example 6 and Example 7, it can be seen that when the ratio of wetting agent: aqueous glue: carbon material = 1:70:20, the performance is optimal; by comparing Example 4, Example 8, Example 9, Example 10 and Example 13, it can be seen that when the wetting agent content is 0.5%, the performance is optimal; by comparing Example 8, Example 11, Example 12, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, it can be seen that when the wetting agent contains amino, siloxy substituents and fluorine substituents at the same time, the performance is optimal; by comparing Example 8 and Comparative Example 5, it can be seen that the aqueous glue plays an important role in improving the wettability of the conductive paste, reducing the foil leakage rate and improving the peeling force of the electrode. In summary, Example 8 of the present invention is the best and can significantly improve the performance of the electrode.

[0216] It should be noted that while the present invention illustrates the process method through the above-described embodiments, the present invention is not limited to the above-described process steps, and does not necessarily rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A conductive paste for carbon-coated current collector, characterized in that: The conductive paste includes a wetting agent, an aqueous glue, a carbon material and a solvent; Wherein, the wetting agent includes a multifunctional compound as shown in Formula I: Wherein, R1 is a fluorine substituent, and R2 is a silicon-oxygen substituent.

2. The conductive paste for carbon-coated current collector according to claim 1, characterized in that: The fluorine substituent is selected from any one of a fluorine atom, a fluorinated alkyl group, a fluorinated alkenyl group, a fluorinated alkynyl group, a fluorinated alkoxy group, a fluorinated acyl group or a fluorinated aryl group; Preferably, the siloxy substituent includes any one of a methoxysilyl group, an ethoxysilyl group, a trimethylsilyl group, a phenylsilyl group or a fluorine-containing silyl group.

3. The conductive paste for carbon-coated current collector according to claim 1 or 2, characterized in that: The multifunctional compound is selected from at least one of the following compounds; 4. The conductive paste for carbon-coated current collector according to any one of claims 1 to 3, characterized in that: The aqueous glue includes any one or a combination of at least two of polyacrylic acid glue, acrylate glue, acrylamide glue or polyurethane glue, and silane coupling agent glue; Preferably, the carbon material includes any one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fiber, or a combination of at least two thereof; Preferably, the mass ratio of the wetting agent, the aqueous glue and the carbon material is (1-5):(60-80):(10-30); Preferably, based on 100% by mass of the conductive paste, the mass fraction of the wetting agent is 0.2-0.8%.

5. A method for preparing a conductive slurry for a carbon-coated current collector according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: The wetting agent, aqueous glue, carbon material and solvent are mixed to obtain the conductive slurry for the carbon-coated current collector.

6. The preparation method according to claim 5, characterized in that The mixing method includes: (a) mixing a wetting agent and a solvent to obtain a first dispersion; and mixing the first dispersion and the aqueous glue to obtain a second dispersion; (b) mixing the second dispersion liquid and the carbon material.

7. The preparation method according to claim 6, characterized in that Step (a) vacuum stirring and dispersion are performed independently and sequentially during the first mixing and the second mixing; Preferably, the vacuum stirring rate is 150-350 rpm; Preferably, the dispersion rate is 500-700 rpm; Preferably, the dispersion time is 30-50 min.

8. The preparation method according to claim 6, characterized in that The mixing method of step (b) includes: adding the carbon material into the second dispersion liquid in multiple batches and mixing; Preferably, the carbon material is added in multiple times, and is stirred and dispersed after each addition; Preferably, the stirring rate is 150-300 rpm; Preferably, the dispersion rate is 500-700 rpm; Preferably, the dispersion time is 30-50 min.

9. A carbon-coated current collector, characterized in that: The carbon-coated current collector includes a foil and a conductive coating arranged on the surface of the foil. The conductive coating is prepared by the conductive slurry for the carbon-coated current collector according to any one of claims 1 to 4, or the conductive coating is prepared by the conductive slurry prepared by the preparation method according to any one of claims 5 to 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the carbon-coated current collector according to claim 9.

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