Composite aluminum foil and process for producing the same

Abstract

The application discloses a composite aluminum foil and a preparation process thereof, and relates to the technical field of electronic materials. The composite aluminum foil comprises, from top to bottom, an upper layer, an intermediate layer and a lower layer. The upper layer and the lower layer are both aluminum foils, and the thicknesses of the upper layer and the lower layer are both 4-5 mu m. The intermediate layer is a composite material, and the thickness of the intermediate layer is 2-3 mu m. The composite material raw material comprises, by weight, 40-60 parts of polyimide, 10-25 parts of polyether ether ketone, 5-15 parts of modified nano-aluminum oxide, 3-10 parts of a conductive agent, 1-2 parts of Wood alloy, 5-12 parts of a binder, 20-30 parts of a solvent and 2-6 parts of an additive. The conductive agent is porous conductive carbon black modified by a styrene-maleic anhydride copolymer. The composite aluminum foil provided by the application has excellent mechanical properties and can effectively prevent the performance of burr penetration after a needle penetration test.

Description

Technical Field

[0001] This application relates to the field of electronic materials technology, and in particular to a composite aluminum foil and its preparation process. Background Technology

[0002] As the lithium battery industry relentlessly pursues maximum energy density, aluminum foil, as the positive electrode current collector, is undergoing a "thinning" revolution. Currently, the mainstream aluminum foil thickness has gradually decreased from the early 20μm to 12μm, with some companies already mass-producing 8μm aluminum foil, which reduces weight by 38% compared to the traditional 13μm aluminum foil and increases cell energy density by 5-8%. However, the reduced aluminum foil thickness leads to decreased mechanical strength and makes it more prone to producing metal burrs during needle penetration tests.

[0003] The lithium battery nail penetration test is one of the core tests for assessing battery safety. Conventional aluminum foil, used as the positive electrode current collector, is prone to generating metal burrs under nail penetration impact. These burrs form a low-resistance short-circuit loop with the negative electrode graphite, causing current concentration and a surge in Joule heating. This ignites lithium intercalation compounds in the electrolyte and graphite, leading to thermal runaway and fire. To suppress this pathway, the industry has proposed a "metal-polymer-metal" sandwich composite current collector: the outer metal layer is thinned to less than 5µm, melting first upon nail penetration; the middle insulating polymer layer can deform to encapsulate the burrs, blocking the short-circuit current and dispersing mechanical stress.

[0004] However, existing polymer interlayers only provide mechanical insulation and cannot actively regulate electrical conductivity with temperature; if the metal layer does not melt completely or overheats locally, there is still a risk of secondary thermal runaway. Summary of the Invention

[0005] In order to provide a composite aluminum foil based on the synergistic optimization of polymer mechanical properties and PTC effect, this application provides a composite aluminum foil and its preparation process.

[0006] This application provides a composite aluminum foil, which adopts the following technical solution:

[0007] A composite aluminum foil comprises, from top to bottom, an upper layer, a middle layer, and a lower layer; the upper and lower layers are both aluminum foils with a thickness of 5 μm; the middle layer is a composite material with a thickness of 3 μm.

[0008] The raw materials of the composite material include, by weight: 40-60 parts polyimide, 10-25 parts polyether ether ketone, 5-15 parts modified nano alumina, 3-10 parts conductive agent, 1-2 parts Wood's alloy, 5-12 parts binder, 20-30 parts solvent, and 2-6 parts additives.

[0009] Preferably, the conductive agent is styrene-maleic anhydride copolymer modified porous conductive carbon black.

[0010] Preferably, the adhesive is polyvinylidene fluoride.

[0011] Preferably, the solvent is N-methylpyrrolidone.

[0012] Preferably, the additives include dispersants, defoamers, and thickeners.

[0013] Preferably, the styrene-maleic anhydride copolymer-modified porous conductive carbon black is prepared from the following raw materials in parts by weight: 5-10 parts porous conductive carbon black, 95-96.5 parts N-methylpyrrolidone, and 1.5-3 parts styrene-maleic anhydride copolymer.

[0014] Preferably, the method for preparing the porous conductive carbon black includes the following steps:

[0015] Nitrogen gas is introduced into a tube furnace, which is then filled with an inert gas atmosphere and heated to 1000-1200℃. Then, conductive carbon black is placed into the tube furnace, and active gas carbon dioxide is introduced to maintain the temperature for 3-5 hours. After the temperature drops to room temperature, it is removed to obtain porous conductive carbon black.

[0016] Preferably, the preparation method of the styrene-maleic anhydride copolymer modified porous conductive carbon black includes the following steps:

[0017] After mixing N-methylpyrrolidone and styrene-maleic anhydride copolymer, the mixture was dispersed at a stirring speed of 300-500 rpm for 30-50 min to obtain a mixture. Then, porous conductive carbon black and zirconium beads were added to the mixture and dispersed by shaking for 6-8 h. The mixture was then purified several times through a PVDF microfiltration membrane and dried in a vacuum environment at 70-80℃ for 24-30 h to obtain styrene-maleic anhydride copolymer modified porous conductive carbon black.

[0018] Preferably, the modified nano-alumina is prepared from the following raw materials in parts by weight: 10-20 parts nano-alumina, 100-200 parts ethanol, 0.02-0.04 parts n-hexadecyltrimethoxysilane, and 0.01-0.02 parts titanate coupling agent.

[0019] Preferably, the method for preparing the modified nano-alumina includes the following steps:

[0020] Nano-alumina was uniformly dispersed in ethanol, and n-hexadecyltrimethoxysilane was added dropwise. The mixture was then uniformly dispersed at 800-1000 rpm for 110-130 min. The mixture was then heated at 110-130℃ for 3-5 h to evaporate the ethanol, thus obtaining pre-modified nano-alumina. Subsequently, a titanate coupling agent was uniformly dispersed into the pre-modified nano-alumina, and the mixture was heated again at 110-130℃ for 30-60 min, thus obtaining modified nano-alumina.

[0021] The present application provides a process for preparing composite aluminum foil, which adopts the following technical solution:

[0022] A process for preparing composite aluminum foil includes the following steps:

[0023] S1. Mix 40-60 parts of polyimide, 10-25 parts of polyetheretherketone (PEEK), 5-15 parts of modified nano-alumina, 3-10 parts of conductive agent, 1-2 parts of Wood's alloy, 5-12 parts of binder, 20-30 parts of solvent, and 2-6 parts of additives, and stir at 1000-1500 rpm for 30-60 minutes. Then, degas under vacuum to obtain the composite material.

[0024] S2. After wiping the surface of the aluminum foil to be treated with acetone and corona treatment, the composite material is coated on the lower aluminum foil using gravure printing at a speed of 8-12 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.2-0.3 MPa. After drying at 80-120℃ for 3-5 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. After hot pressing and shaping treatment, the composite aluminum foil is obtained.

[0025] Preferably, the hot pressing and shaping process includes a preheating and pressing stage, a main hot pressing stage, and a cold pressing and shaping stage; the preheating and pressing stage has a temperature of 150-180℃, a pressure of 0.5-1.0MPa, and a time of 5-10min; the main hot pressing stage has a temperature of 200-230℃, a pressure of 2.0-4.0MPa, and a time of 15-30min; and the cold pressing and shaping stage has a temperature of 30-40℃, a pressure of 1.0-2.0MPa, and a time of 10-15min.

[0026] In summary, this application includes at least one of the following beneficial technical effects:

[0027] 1. This application adopts a PI / PEEK blend system. The high temperature resistance of PI and the high toughness of PEEK complement each other, effectively improving the tensile strength of the composite material. Under the impact of the needle punch test, the polymer interlayer absorbs energy through high toughness deformation, significantly improving the burr suppression rate and completely avoiding membrane puncture. It not only meets the mechanical buffering requirements under needle punch impact, but also ensures the structural stability under high temperature environment.

[0028] 2. This application also adds Wood alloy, which undergoes "micro-melting" during the preheating and pressing stage at 150-180℃, flowing and filling the gaps between the carbon fiber-carbon black network to form a "metal-polymer" interpenetrating structure, improving interlayer shear strength and avoiding the risk of being punctured again by burrs after softening at high temperature.

[0029] 3. The porous carbon black provided in this application undergoes high-temperature activation treatment at 1000-1200℃, resulting in increased specific surface area and improved electrical conductivity. Surface grafting modification with styrene-maleic anhydride copolymer enhances interfacial compatibility with the PI / PEEK matrix, reducing high-temperature agglomeration. Modified nano-alumina, through dual modification with hexadecyltrimethoxysilane and titanate coupling agent, forms a three-dimensional thermally conductive network in the intermediate layer, enabling rapid diffusion of localized heat from needle penetration and inhibiting thermal runaway. The modified filler exhibits improved dispersion uniformity and significantly enhanced interfacial bonding strength, reducing thermal conductivity degradation caused by agglomeration.

[0030] 4. The synergistic effect of Wood's alloy and conductive agent: When the local temperature rises to 200-230℃, Wood's alloy completely melts and expands, pushing away the adjacent conductive particles. At the same time, the movement of PI chain segments increases the tunnel distance, the resistance jumps by 3-4 orders of magnitude, cuts off the short circuit current, and reduces the Joule heat by two orders of magnitude, forming a "melting + current limiting" double insurance, and significantly reducing the probability of secondary thermal runaway. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the embodiments.

[0032] The chemical reagents used in the preparation examples, embodiments, and comparative examples provided in this invention are all commercially available products, and their brands and manufacturers are as follows:

[0033] Polyimide, Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0034] Polyetheretherketone (PEEK), Shanghai E.E. Chemical Technology Co., Ltd.

[0035] Wood's alloy, Shanghai Bohr Chemical Reagent Co., Ltd.;

[0036] Polyvinylidene fluoride (PVDF), Shanghai Flucon Chemical Co., Ltd.

[0037] Styrene-maleic anhydride copolymer, Guangdong Wengjiang Chemical Reagent Co., Ltd., PA29007;

[0038] Titanate coupling agents, Wuhan Camic Technology Co., Ltd.

[0039] Preparation Example 1: Preparation of Porous Conductive Carbon Black Modified by Styrene-Maleic Anhydride Copolymer

[0040] Preparation Example 1.1

[0041] S1. Nitrogen gas is introduced into a tube furnace, and the tube furnace is filled with an inert gas atmosphere and heated to 1000℃; then 10g of conductive carbon black is placed into the tube furnace; active gas carbon dioxide is introduced and the temperature is maintained for 3 hours; after the temperature drops to room temperature, it is taken out to obtain porous conductive carbon black.

[0042] S2. 95g of N-methylpyrrolidone and 3g of styrene-maleic anhydride copolymer were mixed and dispersed at 300rpm for 30min to obtain a mixture. Then, 5g of porous conductive carbon black and 5g of zirconium beads were added to the mixture and dispersed by shaking for 6h. The mixture was then purified three times through a PVDF microfiltration membrane and dried in a vacuum environment at 70℃ for 24h to obtain styrene-maleic anhydride copolymer modified porous conductive carbon black.

[0043] Preparation Example 1.2

[0044] S1. Nitrogen gas is introduced into a tube furnace, and the tube furnace is filled with an inert gas atmosphere and heated to 1100℃; then 10g of conductive carbon black is placed into the tube furnace; active gas carbon dioxide is introduced and the temperature is maintained for 4 hours; after the temperature drops to room temperature, it is taken out to obtain porous conductive carbon black.

[0045] S2. 95.75g of N-methylpyrrolidone and 2.25g of styrene-maleic anhydride copolymer were mixed and dispersed at 400rpm for 40min to obtain a mixture. Then, 7.5g of porous conductive carbon black and 7.5g of zirconium beads were added to the mixture and dispersed by shaking for 7h. The mixture was then purified four times through a PVDF microfiltration membrane and dried in a vacuum environment at 75℃ for 27h to obtain styrene-maleic anhydride copolymer modified porous conductive carbon black.

[0046] Preparation Example 1.3

[0047] S1. Nitrogen gas is introduced into a tube furnace, and the tube furnace is filled with an inert gas atmosphere and heated to 1200℃; then 10g of conductive carbon black is placed into the tube furnace; active gas carbon dioxide is introduced and the temperature is maintained for 5 hours; after the temperature drops to room temperature, it is taken out to obtain porous conductive carbon black.

[0048] S2. 96.5g of N-methylpyrrolidone and 1.5g of styrene-maleic anhydride copolymer were mixed and dispersed at a stirring speed of 500rpm for 50min to obtain a mixture. Then, 10g of porous conductive carbon black and 10g of zirconium beads were added to the mixture and dispersed by shaking for 8h. The mixture was then purified five times through a PVDF microfiltration membrane and dried in a vacuum environment at 80℃ for 30h to obtain styrene-maleic anhydride copolymer modified porous conductive carbon black.

[0049] Preparation Example 2: Preparation of Modified Nano-Alumina

[0050] Preparation Example 2.1

[0051] 10g of nano-alumina was uniformly dispersed in 100g of ethanol, and 0.02g of n-hexadecyltrimethoxysilane was added dropwise. The mixture was then uniformly dispersed at 800 rpm for 110 min, followed by heating at 110℃ for 3 h to evaporate the ethanol, thus obtaining pre-modified nano-alumina. Subsequently, 0.01g of titanate coupling agent was uniformly dispersed into the pre-modified nano-alumina, and the mixture was heated again at 110℃ for 30 min, thus obtaining modified nano-alumina.

[0052] Preparation Example 2.2

[0053] 15g of nano-alumina was uniformly dispersed in 150g of ethanol, and 0.03g of n-hexadecyltrimethoxysilane was added dropwise. The mixture was then uniformly dispersed at 900 rpm for 120 min, followed by heating at 120℃ for 4 h to evaporate the ethanol, thus obtaining pre-modified nano-alumina. Subsequently, 0.015g of titanate coupling agent was uniformly dispersed into the pre-modified nano-alumina, and the mixture was heated again at 120℃ for 45 min, thus obtaining modified nano-alumina.

[0054] Preparation Example 2.3

[0055] 20g of nano-alumina was uniformly dispersed in 200g of ethanol, and 0.04g of n-hexadecyltrimethoxysilane was added dropwise. The mixture was then uniformly dispersed at 1000 rpm for 130 min, followed by heating at 130℃ for 5 h to evaporate the ethanol, thus obtaining pre-modified nano-alumina. Subsequently, 0.02g of titanate coupling agent was uniformly dispersed into the pre-modified nano-alumina, and the mixture was heated again at 130℃ for 60 min, thus obtaining modified nano-alumina.

[0056] Example 1

[0057] S1. 40g of polyimide, 10g of polyetheretherketone, 5g of modified nano-alumina prepared in Preparation Example 2.1, 3g of styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1, 1g of Wood's alloy, 5g of polyvinylidene fluoride binder, 20g of N-methylpyrrolidone solvent, and 2g of additives were mixed and stirred at 1000rpm for 30min, followed by vacuum degassing to obtain the composite material;

[0058] S2. After wiping the surface of the aluminum foil to be treated with acetone and undergoing corona treatment, the composite material is coated onto the lower aluminum foil using a laser-engraved gravure roller at a rate of 8 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.2 MPa. After drying at 80°C for 5 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. Following hot-pressing and shaping, a composite aluminum foil is obtained where both the upper and lower layers are 5 μm thick, and the middle layer is a 3 μm thick composite material. The hot-pressing and shaping process includes a preheating and pressing stage, a main hot-pressing stage, and a cold-pressing and shaping stage. The preheating and pressing stage has a temperature of 150°C, a pressure of 0.5 MPa, and a time of 5 minutes. The main hot-pressing stage has a temperature of 200°C, a pressure of 2.0 MPa, and a time of 15 minutes. The cold-pressing and shaping stage has a temperature of 30°C, a pressure of 1.0 MPa, and a time of 10 minutes.

[0059] The additives include 0.9g of dispersant BYK-190, 0.3g of defoamer (organic silicone defoamer Tego-902), and 0.8g of thickener sodium carboxymethyl cellulose.

[0060] Example 2

[0061] S1. Mix 50g of polyimide, 7.5g of polyetheretherketone, 10g of modified nano-alumina prepared in Preparation Example 2.1, 6.5g of styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1, 1.5g of Wood's alloy, 8.5g of polyvinylidene fluoride binder, 25g of N-methylpyrrolidone solvent, and 4g of additives, and stir at 1000rpm for 30min. Then, degas under vacuum to obtain the composite material.

[0062] S2. After wiping the surface of the aluminum foil to be treated with acetone and undergoing corona treatment, the composite material is coated onto the lower aluminum foil using a laser-engraved gravure roller at a rate of 8 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.2 MPa. After drying at 80°C for 5 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. Following hot-pressing and shaping, a composite aluminum foil is obtained where both the upper and lower layers are 5 μm thick, and the middle layer is a 3 μm thick composite material. The hot-pressing and shaping process includes a preheating and pressing stage, a main hot-pressing stage, and a cold-pressing and shaping stage. The preheating and pressing stage has a temperature of 150°C, a pressure of 0.5 MPa, and a time of 5 minutes. The main hot-pressing stage has a temperature of 200°C, a pressure of 2.0 MPa, and a time of 15 minutes. The cold-pressing and shaping stage has a temperature of 30°C, a pressure of 1.0 MPa, and a time of 10 minutes.

[0063] The additives include 1.8g of dispersant BYK-190, 0.6g of defoamer (organic silicone defoamer Tego-902), and 1.6g of thickener sodium carboxymethyl cellulose.

[0064] Example 3

[0065] S1. 60g of polyimide, 25g of polyetheretherketone, 15g of modified nano-alumina prepared in Preparation Example 2.1, 10g of styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1, 2g of Wood's alloy, 12g of polyvinylidene fluoride binder, 30g of N-methylpyrrolidone solvent, and 6g of additives were mixed and stirred at 1000rpm for 30min, followed by vacuum degassing to obtain the composite material;

[0066] S2. After wiping the surface of the aluminum foil to be treated with acetone and undergoing corona treatment, the composite material is coated onto the lower aluminum foil using a laser-engraved gravure roller at a rate of 8 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.2 MPa. After drying at 80°C for 5 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. Following hot-pressing and shaping, a composite aluminum foil is obtained where both the upper and lower layers are 5 μm thick, and the middle layer is a 3 μm thick composite material. The hot-pressing and shaping process includes a preheating and pressing stage, a main hot-pressing stage, and a cold-pressing and shaping stage. The preheating and pressing stage has a temperature of 150°C, a pressure of 0.5 MPa, and a time of 5 minutes. The main hot-pressing stage has a temperature of 200°C, a pressure of 2.0 MPa, and a time of 15 minutes. The cold-pressing and shaping stage has a temperature of 30°C, a pressure of 1.0 MPa, and a time of 10 minutes.

[0067] The additives include 2.7g of dispersant BYK-190, 0.9g of defoamer organosilicon defoamer Tego-902, and 2.4g of thickener sodium carboxymethyl cellulose.

[0068] Example 4

[0069] S1. 40g of polyimide, 10g of polyetheretherketone, 5g of modified nano-alumina prepared in Preparation Example 2.1, 3g of styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1, 1g of Wood's alloy, 5g of polyvinylidene fluoride binder, 20g of N-methylpyrrolidone solvent, and 2g of additives were mixed and stirred at 1250rpm for 45min, followed by vacuum degassing to obtain the composite material;

[0070] S2. After wiping the surface of the aluminum foil to be treated with acetone and undergoing corona treatment, the composite material is coated onto the lower aluminum foil using a laser-engraved gravure roller at a speed of 10 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.25 MPa. After drying at 100°C for 4 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. Following hot pressing and shaping, a composite aluminum foil is obtained where both the upper and lower layers are 5 μm thick, and the middle layer is a 3 μm thick composite material. The hot pressing and shaping process includes a preheating stage, a main hot pressing stage, and a cold pressing and shaping stage. The preheating stage has a temperature of 165°C, a pressure of 0.75 MPa, and a time of 7.5 minutes; the main hot pressing stage has a temperature of 215°C, a pressure of 3.0 MPa, and a time of 22 minutes; and the cold pressing and shaping stage has a temperature of 35°C, a pressure of 1.5 MPa, and a time of 13 minutes.

[0071] The additives include 0.9g of dispersant BYK-190, 0.3g of defoamer (organic silicone defoamer Tego-902), and 0.8g of thickener sodium carboxymethyl cellulose.

[0072] Example 5

[0073] S1. 40g of polyimide, 10g of polyetheretherketone, 5g of modified nano-alumina prepared in Preparation Example 2.1, 3g of styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1, 1g of Wood's alloy, 5g of polyvinylidene fluoride binder, 20g of N-methylpyrrolidone solvent, and 2g of additives were mixed and stirred at 1500rpm for 60min, followed by vacuum degassing to obtain the composite material;

[0074] S2. After wiping the surface of the aluminum foil to be treated with acetone and undergoing corona treatment, the composite material is coated onto the lower aluminum foil using a laser-engraved gravure roller at a speed of 12 meters per minute, with a 250-mesh anilox roller and a doctor blade pressure of 0.3 MPa. After drying at 120°C for 3 minutes, the upper aluminum foil is covered under the coating in an environment with humidity ≤50%. Following hot pressing and shaping, a composite aluminum foil is obtained where both the upper and lower layers are 5 μm thick, and the middle layer is a 3 μm thick composite material. The hot pressing and shaping process includes a preheating and pressing stage, a main hot pressing stage, and a cold pressing and shaping stage. The preheating and pressing stage has a temperature of 180°C, a pressure of 1.0 MPa, and a time of 10 minutes; the main hot pressing stage has a temperature of 230°C, a pressure of 4.0 MPa, and a time of 30 minutes; and the cold pressing and shaping stage has a temperature of 40°C, a pressure of 2.0 MPa, and a time of 15 minutes.

[0075] The additives include 0.9g of dispersant BYK-190, 0.3g of defoamer (organic silicone defoamer Tego-902), and 0.8g of thickener sodium carboxymethyl cellulose.

[0076] Example 6

[0077] The difference between Example 6 and Example 1 is that the modified nano-alumina used in Example 6 was prepared from Preparation Example 2.2.

[0078] Example 7

[0079] The difference between Example 7 and Example 1 is that the modified nano-alumina used in Example 7 was prepared from Preparation Example 2.3.

[0080] Example 8

[0081] The difference between Example 8 and Example 1 is that the styrene-maleic anhydride copolymer modified porous conductive carbon black used in Example 8 was prepared from Preparation Example 1.2.

[0082] Example 9

[0083] The difference between Example 9 and Example 1 is that the styrene-maleic anhydride copolymer modified porous conductive carbon black used in Example 9 was prepared from Preparation Example 1.3.

[0084] Comparative Example 1

[0085] The difference between Comparative Example 1 and Example 1 is that no polyether ether ketone was added in Comparative Example 1.

[0086] Comparative Example 2

[0087] The difference between Comparative Example 2 and Example 1 is that Wood's alloy is not added in Comparative Example 2.

[0088] Comparative Example 3

[0089] The difference between Comparative Example 3 and Example 1 is that an equal amount of unmodified nano-alumina was used in Comparative Example 3 instead of the modified nano-alumina prepared in Preparation Example 2.1.

[0090] Comparative Example 4

[0091] The difference between Comparative Example 4 and Example 1 is that an equal amount of conductive carbon black was used in Comparative Example 4 instead of the styrene-maleic anhydride copolymer modified porous conductive carbon black prepared in Preparation Example 1.1.

[0092] Performance testing

[0093] 1. The composite aluminum foils obtained in Examples 1-9 and Comparative Examples 1-4 were subjected to needle penetration tests: a needle with a diameter of 3 mm and a penetration speed of 3 mm / s were used. The battery was fully charged to 4.25V and the needle penetration test was performed to determine whether the composite aluminum foil passed the needle penetration test.

[0094] The specific test results are as follows:

[0095] Table 1 Performance Test Results

[0096]

[0097] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite aluminum foil, characterized by: From top to bottom, the upper layer, the middle layer, the lower layer; the upper layer and the lower layer are aluminum foil, thickness is 5um; The middle layer is a composite material, thickness is 3um; The composite material raw material includes 40-60 parts of polyimide, 10-25 parts of polyether ether ketone, 5-15 parts of modified nano alumina, 3-10 parts of conductive agent, 1-2 parts of wood alloy, 5-12 parts of binder, 20-30 parts of solvent and 2-6 parts of auxiliary agent by weight; The conductive agent is styrene-maleic anhydride copolymer modified porous conductive carbon black; The styrene-maleic anhydride copolymer modified porous conductive carbon black is prepared from the following raw materials by weight: 5-10 parts of porous conductive carbon black, 95-96.5 parts of N-methyl pyrrolidone and 1.5-3 parts of styrene-maleic anhydride copolymer; The preparation method of the porous conductive carbon black comprises the following steps: Nitrogen is introduced into the tube furnace, and the tube furnace is heated to 1000-1200℃ after being filled with inert gas atmosphere; then the conductive carbon black is put into the tube furnace; active gas carbon dioxide is introduced, and the temperature is maintained for 3-5h; after the temperature is reduced to room temperature, it is taken out, and the porous conductive carbon black is obtained; The preparation method of the styrene-maleic anhydride copolymer modified porous conductive carbon black comprises the following steps: The N-methyl pyrrolidone and the styrene-maleic anhydride copolymer are mixed, then dispersed at a stirring speed of 300-500rpm for 30-50min to obtain a mixed solution; then the porous conductive carbon black and zirconium beads are added into the mixed solution, and oscillation dispersion is carried out for 6-8h, then purified several times through PVDF microfiltration membrane, and then dried in a vacuum environment at 70-80℃ for 24-30h to obtain the styrene-maleic anhydride copolymer modified porous conductive carbon black.

2. The composite aluminum foil according to claim 1, wherein: The binder is polyvinylidene fluoride; The solvent is N-methyl pyrrolidone; The auxiliary agent includes dispersant, defoaming agent and thickening agent.

3. The composite aluminum foil according to claim 1, wherein: The modified nano alumina is prepared from the following raw materials by weight: 10-20 parts of nano alumina, 100-200 parts of ethanol, 0.02-0.04 parts of n-hexadecyl trimethoxysilane and 0.01-0.02 parts of titanate coupling agent.

4. The composite aluminum foil according to claim 3, wherein: The preparation method of the modified nano alumina comprises the following steps: The nano alumina is uniformly dispersed in ethanol, n-hexadecyl trimethoxysilane is added dropwise, then uniformly dispersed at 800-1000rpm for 110-130min, then heated and treated at 110-130℃ for 3-5h to evaporate ethanol, and the pre-modified nano alumina is obtained; then the titanate coupling agent is uniformly dispersed into the pre-modified nano alumina, and heated again at 110-130℃ for 30-60min; the modified nano alumina is obtained.

5. The process for producing a composite aluminum foil according to any one of claims 1 to 4, characterized in that: The following steps are included: S1. 40-60 parts of polyimide, 10-25 parts of polyether ether ketone, 5-15 parts of modified nano alumina, 3-10 parts of conductive agent, 1-2 parts of wood alloy, 5-12 parts of binder, 20-30 parts of solvent and 2-6 parts of auxiliary agent are mixed, then stirred at a stirring speed of 1000-1500rpm for 30-60min, and then vacuum degassing to obtain a composite material; S2. The surface of the aluminum foil to be treated is wiped with acetone and treated by corona discharge; the composite material is coated on the lower aluminum foil by gravure printing at a speed of 8-12 m / min, the screen roller is 250 mesh, the doctor blade pressure is 0.2-0.3 MPa, and after drying at 80-120℃ for 3-5 min, the upper aluminum foil is covered in a humidity ≤50% environment, and after heat pressing and shaping, the composite aluminum foil is prepared.

6. The process for producing a composite aluminum foil according to claim 5, wherein: The heat pressing and shaping treatment comprises a pre-heat pressing stage, a main heat pressing stage and a cold pressing and shaping stage; the pre-heat pressing stage has a temperature of 150-180℃, a pressure of 0.5-1.0 MPa and a time of 5-10 min; the main heat pressing stage has a temperature of 200-230℃, a pressure of 2.0-4.0 MPa and a time of 15-30 min; and the cold pressing and shaping stage has a temperature of 30-40℃, a pressure of 1.0-2.0 MPa and a time of 10-15 min.

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