Carbon-coated aluminum foil process, preparation method thereof and lithium ion battery

Abstract

The invention relates to a carbon-coated aluminum foil process, a carbon-coated aluminum foil preparation method and a lithium ion battery, the carbon-coated aluminum foil comprises an aluminum foil substrate, and the surface of the aluminum foil substrate is provided with a coated and cured conductive composite layer; the conductive composite layer comprises the following components in parts by weight: 5-7 parts of conductive carbon black, 3-5 parts of conductive graphite, 0.8-1.2 parts of a functional additive, 1.2-2.0 parts of a dispersant and 40-50 parts of a binder, and the thickness of the conductive composite layer is 0.4-1.8 [mu] m. The conductive network construction efficiency is high, the overall conductivity is high, no toxic waste gas is discharged in the production process, NMP recovery equipment does not need to be matched, and the production environmental protection cost and the safety risk are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon-coated aluminum foil technology, specifically to a carbon-coated aluminum foil process and preparation method, and to lithium-ion batteries. Background Technology

[0002] With the deepening application of lithium-ion batteries in the new energy field, carbon-coated aluminum foil, as a key material for the positive electrode current collector, directly affects the energy density, cycle life, and safety of the battery. Aluminum foil plays a crucial role in lithium-ion batteries as the current collector. Its surface carries the active material and simultaneously gathers electrons generated by the positive electrode active material to the external circuit to form current. Utilizing functional coatings to treat the surface of the battery's positive electrode current collector can improve the adhesion between the active material and the current collector and enhance the positive electrode's ability to collect micro-currents from the active material, thereby improving the battery's rate performance. Therefore, the carbon coating slurry applied to the current collector surface needs to possess excellent conductivity.

[0003] A Chinese patent document with publication number CN115621469A discloses a carbon coating slurry for improving conductivity and adhesion and its drying and molding process. The following raw materials are weighed in parts by weight: 10 parts graphene powder, 10 parts carbon nanotubes, 10 parts sodium carboxymethyl cellulose, and 200 parts water. They are added to a flask and mixed to prepare a mixed slurry. The particle size of the graphene powder is less than 120-150 μm. The mixed slurry is placed in an ultrasonic disperser and ultrasonically treated for 3 hours to obtain a conductive slurry. Then, 10 parts of polyvinylidene fluoride are dissolved in 100 parts of N-methylpyrrolidone to prepare an adhesive slurry.

[0004] The above-mentioned carbon coating slurry uses graphene as the conductive phase. Although graphene powder has good dispersibility, the single conductive agent is prone to agglomeration, resulting in low efficiency in building the conductive network. The overall conductivity of the carbon-coated aluminum foil is weak. In addition, the carbon coating slurry uses a large amount of N-methylpyrrolidone (NMP) organic solvent. NMP is toxic and volatile, posing environmental and safety hazards in production. Furthermore, the solvent recovery process is complex and costly, which does not meet the current requirements for green manufacturing of lithium batteries. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a carbon-coated aluminum foil process and its preparation method and a lithium-ion battery. The conductive network construction efficiency is high, the overall conductivity is strong, and there is no toxic waste gas emission during the production process. No matching NMP recovery equipment is required, which greatly reduces the environmental protection costs and safety risks of production.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A carbon-coated aluminum foil process includes an aluminum foil substrate. The surface of the aluminum foil substrate is coated with a conductive composite layer, which is then cured via a three-stage gradient drying process. The thickness of the conductive composite layer is 0.4 μm to 1.8 μm. The conductive composite layer comprises the following components in the following weight ratio: conductive carbon black: conductive graphite: functional additives: compound dispersant: binder = (5-7): (3-5): (0.8-1.2): (1.2-2.0): (40-50). The three-stage gradient drying temperatures are 40℃-60℃, 80℃-120℃, and 50℃-70℃, respectively, and the curing temperature is controlled at 100℃-140℃.

[0008] In one embodiment, the composite conductive phase consists of conductive carbon black and conductive graphite, wherein the conductive carbon black comprises 5 to 7 parts by weight and the conductive graphite comprises 3 to 5 parts by weight. For example, the conductive carbon black can be 5, 6, or 7 parts, and the conductive graphite can be 3, 4, or 5 parts. Specific values ​​within the aforementioned ranges are not exhaustively listed here for space limitations and for the sake of brevity.

[0009] In one embodiment, the functional additive is 0.8 to 1.2 parts by weight, for example, 0.8, 0.9, 1.0, or 1.2 parts by weight. The functional additive is composed of a rheology modifier, a coupling agent, and an antifoaming agent. The rheology modifier improves the leveling properties of the coating, the coupling agent enhances the interfacial bonding between the conductive phase and the binder, and the antifoaming agent eliminates bubbles generated during the preparation process.

[0010] In one embodiment, the dispersant is in the amount of 1.2 to 2.0 parts by weight, for example, 1.2, 1.3, 1.6, 1.8, or 2.0 parts by weight, and the dispersant is a compound dispersant of PVP and CMC-Li.

[0011] In one embodiment, the adhesive is in the form of 40 to 50 parts by weight, for example, 40, 44, 46, or 50 parts, and the adhesive is one of acrylic resin, water-based styrene-acrylic emulsion, or a mixture thereof.

[0012] In one embodiment, the thickness of the conductive composite layer is 0.4 μm to 1.8 μm, and can be 0.4 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.5 μm, 1.8 μm, or specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0013] Preferably, the conductive carbon black is acetylene black with a particle size of 21 nm to 55 nm, and the conductive graphite is reduced graphene oxide with a sheet thickness d ≤ 4.5 nm.

[0014] Preferably, the adhesive is one of acrylic resin, water-based styrene-acrylic emulsion, or a mixture thereof.

[0015] Preferably, the compound dispersant is composed of PVP and CMC-Li, wherein the weight ratio of PVP to CMC-Li is 1.6:1.

[0016] Another object of the present invention is to provide a method for preparing carbon-coated aluminum foil, comprising the following steps:

[0017] Step 1: Prepare the carbon coating slurry according to the component ratio;

[0018] Step 2: The carbon coating slurry obtained in Step 1 is applied to the surface of the aluminum foil substrate using a micro-gravure plate, and then cured and shaped by a three-stage gradient drying process to obtain a carbon-coated aluminum foil with a conductive composite layer. The three-stage gradient drying temperatures are 40℃~60℃, 80℃~120℃, and 50℃~70℃ respectively, and the curing temperature is controlled at 100℃~140℃.

[0019] Preferably, the preparation of the carbon coating slurry in step one includes the following steps:

[0020] S1, Preparation of premixed solvent: PVP dispersant and deionized water are added to a dispersion vessel and stirred at 1200 rpm for 5 min until completely dissolved to obtain a premixed solvent;

[0021] S2, Conductive agent premixing and dispersion: Dispersant CMC-Li is dry-mixed with 1 / 3 weight of conductive carbon black to obtain mixture I. The dispersion vessel is stirred at a high speed of 1500 rpm. Mixture I is sprinkled into the premixed solvent in small amounts several times. After the addition is completed, stirring is continued for 15 minutes until the material is completely dispersed.

[0022] S3, Conductive agent supplementation and dispersion: Add the remaining 2 / 3 weight of conductive carbon black and conductive graphite to the dispersion vessel, first stir at a low speed of 800 rpm for 5 minutes to initially mix, then increase to a high speed of 1800 rpm for 10 minutes to disperse, and obtain mixture II.

[0023] S4, Conductive slurry sand milling: Transfer mixture II into a sand mill and mill it at 2500 rpm for 2-3 hours, controlling the slurry particle size D50≤0.8μm;

[0024] S5, Stabilization and Dispersion of Conductive Paste: Cool the slurry after sand milling to below 35°C, stir at a low speed of 500 rpm, slowly add binder to the slurry, and continue stirring for 20 minutes until uniform after the addition is complete to prevent the slurry from breaking the emulsion and gel.

[0025] S6, Slurry viscosity control: Add functional additives to the slurry, stir at low speed of 500 rpm for 10 min until uniformly dispersed, and then add a small amount of deionized water to adjust the viscosity of the slurry at 25℃ to 2200 mPa·s~2800 mPa·s.

[0026] S7, Filtration and Degassing: The adjusted slurry is filtered through a 200-mesh filter to remove impurities and agglomerated particles. After filtration, it is allowed to stand for 15 minutes to degas, resulting in a coatable carbon coating slurry.

[0027] Preferably, the conductive carbon black in S2 is SP conductive carbon black, and the binder in S5 is water-based acrylic resin.

[0028] Preferably, the functional additive in S6 is a mixture of rheology modifier, coupling agent, and defoamer. Based on the total weight of the functional additives, the rheology modifier accounts for 10%–20%, the coupling agent accounts for 40%–50%, and the defoamer accounts for 30%–40%. The rheology modifier can be 11%, 13%, 14%, 17%, or 18%; the coupling agent can be 42%, 44%, 46%, or 49%; and the defoamer can be 31%, 32%, 35%, or 38%. Specific values ​​within the above ranges are not exhaustively listed here for space limitations and for the sake of brevity.

[0029] The present invention also provides a lithium-ion battery, wherein the positive electrode current collector of the battery is a carbon-coated aluminum foil, which is prepared by the above-described preparation method.

[0030] In summary, the advantages of this invention are:

[0031] 1. This invention employs a design that combines at least two carbon-based conductive agents to synergistically enhance conductivity and dispersion stability, thereby improving conductivity efficiency while also ensuring slurry dispersion.

[0032] 2. The functional additives in this invention are composed of a rheology modifier, a coupling agent, and an antifoaming agent. The rheology modifier improves the leveling properties of the coating, thereby solving the problems of pinholes and uneven thickness. The coupling agent enhances the interfacial bonding between the conductive phase and the binder, thereby solving the problems of coating peeling and powder shedding during circulation. The antifoaming agent eliminates bubbles generated during the preparation process, avoiding defects such as pinholes and pitting.

[0033] 3. In this invention, the compound dispersant is a combination of PVP and CMC-Li to achieve synergistic dispersion. PVP can be quickly adsorbed on the surface of carbon-based conductive agents, providing steric hindrance to inhibit initial agglomeration; CMC-Li can improve the colloidal stability of the slurry, achieving long-term anti-settling, thus achieving the dual effect of rapid dispersion and long-term stability, perfectly suited for high specific surface area carbon-based conductive agents.

[0034] 4. In this invention, the conductive agent is a combination of acetylene black and reduced graphene oxide, which can form a three-dimensional conductive network with point-like conductivity and sheet-like overlap, thereby constructing a dense conductive path without the need to add excessive conductive agent.

[0035] 5. This invention adopts a stepwise addition of conductive agent, which effectively reduces the difficulty of dispersion from the feeding method and prevents the phenomenon of hard agglomerates with wet outer layer and dry internal agglomeration when a large amount of powder is added at one time. Moreover, without using organic solvents and relying only on the aqueous dispersion system, it greatly improves the dispersion uniformity of the conductive phase, reduces agglomerated particles, and reduces the load on subsequent sand milling.

[0036] 6. The solvent used in this invention is deionized water, and there is no toxic waste gas emission during the production process. There is no need for supporting NMP recovery equipment, which greatly reduces the environmental protection costs and safety risks of production. In addition, deionized water is free of external impurity ions, which avoids the electrode system from being contaminated, reduces battery self-discharge and side reactions, and further improves battery life and safety.

[0037] 7. Compared with traditional lithium-ion batteries, the lithium-ion battery provided by this invention reduces the proportion of inactive materials. Under the same volume and mass, it can reserve more space for positive electrode active materials, effectively improving the volumetric energy density and gravimetric energy density of the battery, which meets the development needs of power batteries and consumer batteries for high energy density. Detailed Implementation

[0038] To more clearly illustrate the overall concept of the present invention, the present invention will be further described below with reference to specific embodiments. It should be understood that the terms "upper," "lower," "left," "right," "longitudinal," "lateral," "inner," "outer," "vertical," "horizontal," "top," and "bottom," etc., which indicate orientation or positional relationship, are based solely on orientation or positional relationship and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device / component referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0039] In one embodiment, the carbon coating slurry for lithium-ion batteries comprises the following components in parts by weight: a compounded conductive phase: 8-12 parts by weight, the compounded conductive phase being obtained by compounding at least two carbon-based conductive agents to synergistically improve the conductivity and dispersion stability of the slurry; a solvent: 130-150 parts by weight, the solvent being deionized water; functional additives: 0.8-1.2 parts by weight, the functional additives being composed of a rheology modifier, a coupling agent, and an antifoamer, wherein the rheology modifier improves the coating leveling properties, the coupling agent enhances the interfacial bonding between the conductive phase and the binder, and the antifoamer eliminates bubbles generated during the preparation process; a dispersant: 1.2-2.0 parts by weight, the dispersant being a compound dispersant of PVP and CMC-Li; and a binder: 40-50 parts by weight, the binder being one of acrylic resin, aqueous styrene-acrylic emulsion, or a mixture thereof; the viscosity of the carbon coating slurry at 25°C is 2200 mPa·s to 2800 mPa·s.

[0040] The above technical solution employs a design that combines at least two carbon-based conductive agents to synergistically enhance conductivity and dispersion stability, thereby improving conductivity efficiency while simultaneously ensuring slurry dispersion. The functional additives consist of a combination of rheology modifiers, coupling agents, and defoamers. The rheology modifier improves coating leveling, thus addressing issues such as pinholes and uneven thickness. The coupling agent enhances the interfacial bonding between the conductive phase and the binder, resolving coating peeling and powder shedding during recycling. The defoamer eliminates bubbles generated during preparation, preventing defects such as pinholes and pitting. The solvent is deionized water, resulting in no toxic waste gas emissions during production and eliminating the need for NMP recovery equipment, significantly reducing environmental costs and safety risks. Furthermore, deionized water is free of exogenous impurity ions, preventing electrode contamination, reducing battery self-discharge and side reactions, and further improving battery life and safety.

[0041] In one embodiment, the weight parts of the composite conductive phase are 8 to 12 parts, for example, 8 parts, 8.5 parts, 9 parts, 9.2 parts, 10 parts, 12 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0042] In one embodiment, the composite conductive phase consists of conductive carbon black and conductive graphite, wherein the conductive carbon black comprises 5 to 7 parts by weight and the conductive graphite comprises 3 to 5 parts by weight. For example, the conductive carbon black can be 5, 6, or 7 parts, and the conductive graphite can be 3, 4, or 5 parts. Specific values ​​within the aforementioned ranges are not exhaustively listed here for space limitations and for the sake of brevity.

[0043] In one embodiment, the solvent is 130 to 150 parts by weight, and the solvent is deionized water, for example, 130 parts, 135 parts, 141 parts, 146 parts, or 150 parts.

[0044] In one embodiment, the functional additive is 0.8 to 1.2 parts by weight, for example, 0.8, 0.9, 1.0, or 1.2 parts by weight. The functional additive is composed of a rheology modifier, a coupling agent, and an antifoaming agent. The rheology modifier improves the leveling properties of the coating, the coupling agent enhances the interfacial bonding between the conductive phase and the binder, and the antifoaming agent eliminates bubbles generated during the preparation process.

[0045] In one embodiment, the dispersant is in the amount of 1.2 to 2.0 parts by weight, for example, 1.2, 1.3, 1.6, 1.8, or 2.0 parts by weight, and the dispersant is a compound dispersant of PVP and CMC-Li.

[0046] In one embodiment, the adhesive is in the form of 40 to 50 parts by weight, for example, 40, 44, 46, or 50 parts, and the adhesive is one of acrylic resin, water-based styrene-acrylic emulsion, or a mixture thereof.

[0047] In one embodiment, the viscosity of the carbon coating slurry at 25°C is 2200 mPa·s to 2800 mPa·s, for example, it can be 2200 mPa·s, 2300 mPa·s, 2400 mPa·s, 2500 mPa·s, or 2800 mPa·s.

[0048] In one embodiment, the conductive carbon black is acetylene black with a particle size of 21 nm to 55 nm, such as 22 nm, 24 nm, 29 nm, 33 nm, or 47 nm; the conductive graphite is reduced graphene oxide with a sheet thickness d ≤ 4.5 nm, such as 1.1 nm, 1.5 nm, 1.8 nm, 2 nm, 2.5 nm, 3.5 nm, or 4.2 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list all the specific values ​​included in the range. The conductive agent is a combination of acetylene black and reduced graphene oxide, which can form a three-dimensional conductive network of point-like conductivity and sheet-like overlap, thereby constructing a dense conductive pathway without the need to add excessive conductive agent.

[0049] In another embodiment, the conductive carbon black is one or more mixtures of SP conductive carbon black, EC conductive carbon black, and XC conductive carbon black.

[0050] In one embodiment, the carbon coating slurry is prepared by adding a composite conductive phase in two steps: first, one-third of the composite conductive phase is added, followed by stirring at 1500 rpm for 15 minutes; second, the remaining two-thirds of the composite conductive phase is added, followed by stirring at 800 rpm for 5 minutes, and then dispersing at 1800 rpm for 10 minutes. This process ensures uniform dispersion of the slurry, prevents large particle agglomeration, results in more stable rheological properties, and reduces viscosity fluctuations. This provides a guarantee for precise viscosity control to 2200 mPa·s–2800 mPa·s. Simultaneously, reducing agglomerated particles avoids defects such as pinholes, pitting, and uneven thickness during subsequent coating, thereby improving the electrode yield.

[0051] In one embodiment, the solid content of the carbon coating slurry is 25% to 35%, for example, it can be 26%, 29%, 31%, 33%, 34%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0052] In one embodiment, based on the total weight of the functional additives, the functional additives contain 10% to 20% rheology modifiers, 40% to 50% coupling agents, and 30% to 40% defoamers. The rheology modifiers can be 11%, 13%, 14%, 17%, or 18%, the coupling agents can be 42%, 44%, 46%, or 49%, and the defoamers can be 31%, 32%, 35%, or 38%. Specific values ​​between these ranges are not exhaustively listed here for space limitations and for the sake of brevity.

[0053] In one embodiment, the defoamer is one of TEGO902W, BYK-024, BYK-028, or a mixture thereof.

[0054] In one embodiment, the coupling agent is one of KH550, KH560, KH580, or a mixture thereof.

[0055] In one embodiment, the compound dispersant is composed of PVP and CMC-Li, wherein the weight ratio of PVP to CMC-Li is 1.6:1. The compound dispersant uses a combination of PVP and CMC-Li to achieve synergistic dispersion enhancement. PVP can rapidly adsorb onto the surface of the carbon-based conductive agent, providing steric hindrance to inhibit initial agglomeration; CMC-Li can improve the colloidal stability of the slurry, achieving long-term anti-settling effects, thus achieving the dual effects of rapid dispersion and long-term stability, perfectly suited for high specific surface area carbon-based conductive agents.

[0056] Example 1

[0057] This invention also provides a method for preparing a carbon coating slurry for lithium-ion batteries, comprising the following steps:

[0058] S1, Preparation of premixed solvent: PVP dispersant and deionized water are added to a dispersion vessel and stirred at 1200 rpm for 5 min until completely dissolved to obtain a premixed solvent;

[0059] S2, Conductive agent premixing and dispersion: Dispersant CMC-Li is dry-mixed with 1 / 3 weight of conductive carbon black to obtain mixture I. The dispersion vessel is stirred at a high speed of 1500 rpm. Mixture I is sprinkled into the premixed solvent in small amounts several times. After the addition is completed, stirring is continued for 15 minutes until the material is completely dispersed.

[0060] S3, Conductive agent supplementation and dispersion: Add the remaining 2 / 3 weight of conductive carbon black and conductive graphite to the dispersion vessel, first stir at a low speed of 800 rpm for 5 minutes to initially mix, then increase to a high speed of 1800 rpm for 10 minutes to disperse, and obtain mixture II.

[0061] S4, Plasma grinding: Transfer mixture II into a sand mill and grind it at 2500 rpm for 2-3 hours, controlling the slurry particle size D50≤0.8μm;

[0062] S5, Stabilization and Dispersion of Conductive Paste: Cool the slurry after sand milling to below 35°C, stir at a low speed of 500 rpm, slowly add binder to the slurry, and continue stirring for 20 minutes until uniform after the addition is complete to prevent the slurry from breaking the emulsion and gel.

[0063] S6, Slurry viscosity control: Add functional additives to the slurry, stir at low speed of 500 rpm for 10 min until uniformly dispersed, and then add a small amount of deionized water to adjust the viscosity of the slurry at 25℃ to 2200 mPa·s~2800 mPa·s.

[0064] S7, Filtration and Degassing: The adjusted slurry is filtered through a 200-mesh filter to remove impurities and agglomerated particles. After filtration, it is allowed to stand for 15 minutes to degas, resulting in a coatable carbon coating slurry.

[0065] Example 2

[0066] This embodiment provides a carbon coating slurry for lithium-ion batteries. The raw materials for preparation include, by weight: 30g of conductive carbon black, 20g of conductive graphite, 705g of deionized water, 5g of KH550, 8g of compound dispersant, and 230g of acrylic resin.

[0067] In this embodiment, the compound dispersant is composed of PVP and CMC-Li, wherein the weight ratio of PVP to CMC-Li is 1.6:1, and the compound dispersant is 8g, of which 8g is PVP and 5g is CMC-Li.

[0068] In this embodiment, the feeding ratio is based on 1 part by weight of functional additive. The feeding ratio of each component is as follows: 6 parts by weight of conductive carbon black, 4 parts by weight of conductive graphite, 141 parts by weight of deionized water, 1 part by weight of functional additive, 1.6 parts by weight of dispersant, and 46 parts by weight of acrylic resin.

[0069] Preparation steps:

[0070] S1, Preparation of premixed solvent: Add 8g PVP and 705g deionized water to the dispersion vessel, and stir at 1200rpm for 5min until the dispersant PVP is completely dissolved to obtain the premixed solvent;

[0071] S2, Conductive agent premixing and dispersion: Mix 5g CMC-Li and 10g SP conductive carbon black evenly to obtain mixture I. Keep the dispersion vessel stirring at 1500rpm. Sprinkle mixture I into the premixed solvent in small amounts several times. After the addition is complete, continue stirring for 15min until the material is completely dispersed.

[0072] S3, Conductive agent supplementation and dispersion: Add the remaining 20g SP conductive carbon black and 20g conductive graphite to the dispersion vessel, first stir at a low speed of 800rpm for 5min to initially mix, then increase to a high speed of 1800rpm for 10min to disperse, to obtain mixture II;

[0073] S4, Plasma grinding: Transfer mixture II into a sand mill and grind it at 2500 rpm for 2-3 hours, controlling the slurry particle size D50≤0.8μm;

[0074] S5, Stabilization and Dispersion of Conductive Paste: Cool the slurry after sand milling to below 35°C, stir at a low speed of 500 rpm, slowly add 230g of water-based styrene-acrylic emulsion binder to the slurry, and continue stirring for 20 minutes until uniform after the addition is completed to prevent the slurry from breaking the emulsion and gelling.

[0075] S6, Slurry viscosity control: Add 5g of functional additive KH550 to the slurry, stir at low speed of 500rpm for 10min until uniformly dispersed, and then add a small amount of deionized water to adjust the viscosity of the slurry at 25℃ to 2200mPa・s~2800mPa·s.

[0076] S7, Filtration and Degassing: The adjusted slurry is filtered through a 200-mesh filter to remove impurities and agglomerated particles. After filtration, it is allowed to stand for 15 minutes to degas, resulting in a coatable carbon coating slurry.

[0077] Example 3

[0078] This embodiment provides a carbon coating slurry for lithium-ion batteries. The raw materials for preparation include, by weight: 25g of conductive carbon black, 15g of conductive graphite, 650g of deionized water, 4g of KH550, 6g of compound dispersant, and 200g of acrylic resin.

[0079] The difference between this embodiment and Embodiment 2 is that the weight proportions of each component in the raw materials are different.

[0080] In this embodiment, the feeding ratio is based on 0.8 parts by weight of functional additives, and the components are added as follows: 5 parts by weight of conductive carbon black, 3 parts by weight of conductive graphite, 130 parts by weight of deionized water, 0.8 parts by weight of functional additives, 1.2 parts by weight of dispersant, and 40 parts by weight of acrylic resin.

[0081] The preparation steps in this embodiment are detailed in Example 2 and will not be repeated here.

[0082] Example 4

[0083] This embodiment provides a carbon coating slurry for lithium-ion batteries. The raw materials for preparation include, by weight: 35g of conductive carbon black, 25g of conductive graphite, 750g of deionized water, 6g of KH550, 10g of compound dispersant, and 250g of acrylic resin.

[0084] The difference between this embodiment and Embodiment 2 is that the weight proportions of each component in the raw materials are different.

[0085] In this embodiment, the feeding ratio is based on 1.2 parts by weight of functional additives. The feeding ratio of each component is as follows: 7 parts by weight of conductive carbon black, 5 parts by weight of conductive graphite, 150 parts by weight of deionized water, 1.2 parts by weight of functional additives, 2.0 parts by weight of dispersant, and 50 parts by weight of acrylic resin.

[0086] The preparation steps in this embodiment are detailed in Example 2 and will not be repeated here.

[0087] Example 5

[0088] This embodiment provides a carbon-coated aluminum foil, wherein a conductive composite layer is coated and cured on the surface of the aluminum foil substrate, and the thickness of the conductive composite layer is 0.4 μm to 1.8 μm. In this embodiment, the conductive composite layer is prepared by coating the aluminum foil substrate surface with the carbon-coating slurry described in Embodiments 2, 3, and 4 and curing it.

[0089] Example 6

[0090] This embodiment provides a method for preparing carbon-coated aluminum foil, including the following steps:

[0091] Step 1: Prepare the carbon coating slurry according to the component ratio;

[0092] Step 2: The carbon coating slurry obtained in Step 1 is applied to the surface of the aluminum foil substrate using a micro-gravure plate, and then cured and shaped by a three-stage gradient drying process to obtain a carbon-coated aluminum foil with a conductive composite layer. The three-stage gradient drying temperatures are 40℃~60℃, 80℃~120℃, and 50℃~70℃ respectively, and the curing temperature is controlled at 100~140℃.

[0093] In step one of this embodiment, the carbon coating slurry is prepared using the component ratios described in Examples 2 to 4. For details, please refer to Examples 2, 3, and 4; they will not be repeated here.

[0094] Example 7

[0095] This embodiment provides a lithium-ion battery, wherein the positive electrode current collector of the battery is a carbon-coated aluminum foil, which is prepared by the above-described method for preparing carbon-coated aluminum foil.

[0096] In this embodiment, the carbonized aluminum foil used is the same as that in Example 5. For details, please refer to Example 5, which will not be repeated here.

[0097] The method for preparing carbon-coated aluminum foil in this embodiment adopts the method for preparing carbon-coated aluminum foil in Example 6. For details, please refer to Example 6, which will not be repeated here.

[0098] In addition to the preferred embodiments described above, there are other embodiments of the present invention. Those skilled in the art can make various changes and modifications based on the present invention, and all such changes and modifications should fall within the scope defined by the appended claims, as long as they do not depart from the spirit of the present invention.

Claims

1. A carbon-coated aluminum foil process, comprising an aluminum foil substrate, characterized in that, The aluminum foil substrate has a conductive composite layer formed by coating and three-stage gradient drying and curing. The thickness of the conductive composite layer is 0.4μm to 1.8μm. The conductive composite layer includes the following components in the following weight ratio: conductive carbon black: conductive graphite: functional additives: compound dispersant: binder = (5-7): (3-5): (0.8-1.2): (1.2-2.0): (40-50). The three-stage gradient drying temperature is 40℃-60℃, 80℃-120℃, and 50℃-70℃ respectively. The curing temperature is controlled at 100℃-140℃.

2. The carbon-coated aluminum foil process according to claim 1, characterized in that, The conductive carbon black is acetylene black with a particle size of 21 nm to 55 nm, and the conductive graphite is reduced graphene oxide with a sheet thickness d ≤ 4.5 nm.

3. The carbon-coated aluminum foil process according to claim 1, characterized in that, The adhesive is one of acrylic resin, water-based styrene-acrylic emulsion, or a mixture thereof.

4. The carbon-coated aluminum foil process according to claim 1, characterized in that, The compound dispersant is composed of PVP and CMC-Li, wherein the weight ratio of PVP to CMC-Li is 1.6:

1.

5. The method for preparing carbon-coated aluminum foil according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Prepare the carbon coating slurry according to the component ratio; Step 2: The carbon coating slurry obtained in Step 1 is applied to the surface of the aluminum foil substrate using a micro-gravure plate, and then cured and shaped by a three-stage gradient drying process to obtain a carbon-coated aluminum foil with a conductive composite layer.

6. The method for preparing carbon-coated aluminum foil according to claim 5, characterized in that, The preparation of the carbon coating slurry in step one includes the following steps: S1, Preparation of premixed solvent: PVP dispersant and deionized water are added to a dispersion vessel and stirred at 1200 rpm for 5 min until completely dissolved to obtain a premixed solvent; S2, Conductive agent premixing and dispersion: Dispersant CMC-Li is dry-mixed with 1 / 3 weight of conductive carbon black to obtain mixture I. The dispersion vessel is stirred at a high speed of 1500 rpm. Mixture I is sprinkled into the premixed solvent in small amounts several times. After the addition is completed, stirring is continued for 15 minutes until the material is completely dispersed. S3, Conductive agent supplementation and dispersion: Add the remaining 2 / 3 weight of conductive carbon black and conductive graphite to the dispersion vessel, first stir at a low speed of 800 rpm for 5 minutes to initially mix, then increase to a high speed of 1800 rpm for 10 minutes to disperse, and obtain mixture II. S4, Conductive slurry sand milling: Transfer mixture II into a sand mill and mill it at 2500 rpm for 2-3 hours, controlling the slurry particle size D50≤0.8μm; S5, Stabilization and Dispersion of Conductive Paste: Cool the slurry after sand milling to below 35°C, stir at a low speed of 500 rpm, slowly add binder to the slurry, and continue stirring for 20 minutes until uniform after the addition is complete to prevent the slurry from breaking the emulsion and gel. S6, Slurry viscosity control: Add functional additives to the slurry, stir at low speed of 500 rpm for 10 min until uniformly dispersed, and then add a small amount of deionized water to adjust the viscosity of the slurry at 25℃ to 2200 mPa·s~2800 mPa·s. S7, Filtration and Degassing: The adjusted slurry is filtered through a 200-mesh filter to remove impurities and agglomerated particles. After filtration, it is allowed to stand for 15 minutes to degas, resulting in a coatable carbon coating slurry.

7. The method for preparing carbon-coated aluminum foil according to claim 6, characterized in that, The conductive carbon black in S2 is SP conductive carbon black, and the binder in S5 is water-based acrylic resin.

8. The method for preparing carbon-coated aluminum foil according to claim 6, characterized in that, The functional additive in S6 is a mixture of rheology modifier, coupling agent and defoamer. Based on the total weight of the functional additive, the rheology modifier accounts for 10% to 20%, the coupling agent accounts for 40% to 50%, and the defoamer accounts for 30% to 40%.

9. A lithium-ion battery, characterized in that, The positive electrode current collector of the battery is the carbon-coated aluminum foil according to any one of claims 1 to 4, and the carbon-coated aluminum foil is prepared by the method according to any one of claims 5 to 8.