Method for producing a battery foil and battery foil

Abstract

The present application belongs to the technical field of aluminum-based alloy battery foil, and particularly relates to a production method of battery foil and the battery foil, comprising the following preparation steps: sending aluminum ingot into a casting and rolling machine for casting and rolling, annealing to obtain aluminum foil, pretreating the aluminum foil in an inert atmosphere by using sodium hydroxide solution and deionized water, soaking the pretreated aluminum foil in a modified liquid in an inert atmosphere, reacting, taking out, washing, soaking in a carbon black suspension, taking out, obtaining a composite aluminum foil, placing the composite aluminum foil in an inert atmosphere, heating and reacting, drying under reduced pressure, cooling, and obtaining the battery foil. The present application can improve the current transmission capacity of the battery foil and adapt to the requirement of large-current discharge.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aluminum-based alloy battery foil, and particularly relates to a production method of battery foil and the battery foil. BACKGROUND

[0002] The battery foil is a current collector material in the battery, which plays a role of carrying active material and conducting current. The commonly used battery foil carrier for the positive electrode is aluminum foil. Aluminum is easy to react with oxygen in the air and form a dense aluminum oxide film on its surface with a thickness of 2-5 nm. Although the aluminum oxide film can prevent the aluminum foil from being further corroded, it has a high resistivity, which forms a significant resistance barrier in the electron transport process. The electrons need to rely on the tunneling effect for transmission, and the thickness of the naturally formed aluminum oxide film is in the range of significant attenuation of the tunneling effect, so the electron transmission efficiency is low.

[0003] A Chinese invention patent with the publication number CN117352738B discloses a carbon-coated aluminum foil. The preparation method includes the following steps: adding a solvent and a conductive agent into a binder, stirring and mixing uniformly, high-speed dispersing at 2000 rpm for 30 min under the condition of cooling water condensation, standing for 1 h, filtering the obtained slurry with a filter cloth with a pore size of 1 um, obtaining a conductive coating liquid, uniformly coating the conductive coating liquid on the surface of a clean aluminum foil, preheating in hot air at 60-110 DEG C, and then irradiating under UV light to solidify the conductive coating liquid on the surface of the aluminum foil, thereby obtaining the carbon-coated aluminum foil. In this scheme, the surface of the aluminum foil is coated with a carbon layer, and the conductive particles in the carbon layer form a large number of dense contact points on the surface of the aluminum oxide film, thereby constructing multiple parallel tunneling paths, which effectively reduces the interface resistance between the aluminum foil and the carbon layer. However, there is still an aluminum oxide film between the carbon layer and the aluminum foil, and the electron transmission still relies on the tunneling effect. The interface resistance between the carbon layer and the aluminum foil is higher than 10 mΩ·cm 2 , and the current transmission capacity is relatively limited. In the application scenarios of fast charging equipment and other large current discharges, the battery foil of some high-performance batteries requires that the interface resistance between the conductive composite layer and the aluminum foil be less than 5 mΩ·cm 2 , so as to meet the demand for efficient current transmission. Therefore, the carbon-coated aluminum foil prepared by the above patent cannot meet the strict requirements of high-performance batteries for low interface resistance. SUMMARY

[0004] The present application provides a production method of battery foil and the battery foil, which reduces the interface resistance between the composite layer and the aluminum foil, improves the current transmission capacity of the battery foil, and meets the requirement of large current discharge.

[0005] To solve the above problems, the present application adopts the following technical scheme:

[0006] A production method of battery foil, comprising the following steps:

[0007] S1, sending the aluminum ingot into a casting and rolling machine to be cast and rolled, annealing, obtaining an aluminum foil, in an inert atmosphere, soaking the aluminum foil in a sodium hydroxide solution, taking out, soaking in deionized water, taking out, and storing in anhydrous ethanol to obtain a pretreated aluminum foil;

[0008] S2, adding an acetic acid solution to the n-propanol solution, stirring and mixing, adding octenyltrimethoxysilane, stirring and reacting, obtaining a modified liquid, in an inert atmosphere, soaking the pretreated aluminum foil in the flowing modified liquid, reacting, taking out, washing, soaking in a flowing carbon black suspension, taking out, and obtaining a composite aluminum foil;

[0009] S3, placing the composite aluminum foil in an inert atmosphere, heating and reacting, drying under reduced pressure, and cooling to obtain a battery foil;

[0010] The carbon black suspension is prepared by adding ethylene glycol diacrylate and dibenzoyl peroxide to n-propanol, stirring and mixing, adding hydrophilic modified carbon black and deionized water, and stirring and mixing to obtain a carbon black suspension.

[0011] The aluminum foil is soaked in a sodium hydroxide solution to remove the surface aluminum oxide film and form a bare aluminum surface, then soaked in deionized water, and when part of the aluminum is in contact with the deionized water, a hydrated aluminum oxide is generated, introducing hydroxyl groups on the aluminum surface. The pretreated aluminum foil is placed in a modification solution containing silanol with a carbon-carbon double bond obtained by hydrolysis of octenyltrimethoxysilane. Condensation occurs between the hydroxyl groups on the bare aluminum surface and the silanol of the siloxane, generating Si-O-Al bonds, and the siloxane is grafted onto the bare aluminum surface, thereby introducing carbon-carbon double bonds onto the surface of the aluminum foil. Then, the aluminum foil is soaked in a flowing carbon black suspension. Under the combined action of n-propanol reducing surface tension and convection enhancing mass transfer, the hydrophilic modified carbon black, ethylene glycol diacrylate, and dibenzoyl peroxide fully contact the surface of the aluminum foil, forming a composite layer on the surface of the aluminum foil containing hydrophilic modified carbon black and polymerizable organic matter, and obtaining a composite aluminum foil. The composite aluminum foil is heated in an inert atmosphere. Under the initiation of dibenzoyl peroxide, radical copolymerization occurs between siloxane and ethylene glycol diacrylate through carbon-carbon double bonds, forming an organic crosslinked network, and carbon black is uniformly dispersed in the organic crosslinked network. Then, the organic crosslinked network is subjected to reduced pressure drying, n-propanol and deionized water are evaporated, the organic crosslinked network shrinks, the hydrophilic modified carbon black approaches each other and the bare aluminum surface, forming a carbon black conductive network embedded between the organic crosslinked network, and obtaining a battery foil. The surface of the battery foil has a composite layer composed of an organic crosslinked network and a carbon black conductive network. After the battery foil is in contact with air, the contact between the bare aluminum surface covered by carbon black and oxygen is physically blocked, effectively inhibiting the formation of an aluminum oxide film in this area. The carbon black in this part directly adheres to the bare aluminum surface, forming a low-impedance interface, and electrons can be directly transmitted to the aluminum foil through the carbon black adhering to the bare aluminum surface without relying on tunneling effect, achieving efficient electron transmission and meeting the demand for large current discharge.

[0012] The carbon black suspension is composed of an aqueous phase and an organic component. The aqueous phase is deionized water, and the organic component is dibenzoyl peroxide and ethylene glycol diacrylate. Dibenzoyl peroxide can be dissolved in ethylene glycol diacrylate, ethylene glycol diacrylate can be miscible with n-propanol, and n-propanol can be miscible with water. Therefore, n-propanol can be used as a cosolvent to promote the mixing of the organic component and the aqueous phase, forming a uniform continuous phase. The surface of the hydrophilic modified carbon black has hydrophilic functional groups, which improves the dispersion stability of the carbon black in the continuous phase and is beneficial to the formation of a uniform carbon black suspension.

[0013] The aluminum foil grafted with carbon-carbon double bond on the surface is immersed in the carbon black suspension, and n-propanol is used as a low surface tension solvent to reduce the overall surface tension of the carbon black suspension, promote the spreading of the carbon black suspension on the surface of the aluminum foil, and make the carbon black uniformly distributed in the carbon black suspension. The carbon black can diffuse to the surface of the aluminum foil under the action of Brownian motion and convection and contact the surface of the aluminum foil, laying a foundation for the subsequent direct contact between the carbon black and the bare aluminum surface to form a low impedance interface; n-propanol can connect with water molecules through hydrogen bonds, and can also form a uniform solution with ethylene glycol diacrylate and dibenzoyl peroxide. Under the bridging action of n-propanol, the carbon black suspension will not phase separate, and ethylene glycol diacrylate and dibenzoyl peroxide can diffuse to the surface of the aluminum foil to provide a molecular distribution foundation and reaction environment for the subsequent free radical polymerization reaction.

[0014] The ethylene glycol diacrylate in the carbon black suspension contains a long ethylene glycol segment, which can improve the flexibility of the organic cross-linked network, so that it can bend and deform synchronously with the aluminum foil, reduce the peeling between the composite layer and the aluminum foil when bearing bending stress, and improve the use stability of the battery foil.

[0015] The battery foil surface has a composite layer composed of an organic cross-linked network and a carbon black conductive network embedded therein. The connection between the organic cross-linked network and the aluminum foil is achieved through Si-O-Al bonds, which have a bond energy greater than 350 kJ / mol and a decomposition temperature above 250℃. The Si-O-Al bond has strong stability, which can effectively fix the composite layer on the surface of the aluminum foil, avoid the peeling or falling off of the composite layer from the surface of the aluminum foil under the action of long-term cycling or mechanical stress, and improve the long-term stability of the use performance of the battery foil.

[0016] Further, in the step S1, the concentration of the sodium hydroxide solution is 3wt%, the aluminum foil is immersed in the sodium hydroxide solution for 2min, and the aluminum foil is immersed in the deionized water for 20s.

[0017] Immersing the aluminum foil in the sodium hydroxide solution for 2min can effectively remove the oxide layer on the surface of the aluminum foil to form a bare aluminum surface; immersing the aluminum foil with the bare surface in the deionized water for only 20 seconds can cause a hydration oxidation reaction on only part of the bare aluminum surface to generate surface hydroxyl groups, while still retaining part of the unoxidized bare aluminum surface, thereby laying a foundation for the subsequent direct contact with the carbon black to form a low impedance interface.

[0018] Further, the modification liquid is prepared by the following method: mixing n-propanol and deionized water to obtain an n-propanol solution, adding an acetic acid solution to adjust the pH to 5, adding octenyltrimethoxysilane, and stirring at 400rpm for 2h to obtain the modification liquid.

[0019] The octenyl trimethoxysilane is hydrolyzed in an acidic environment to generate siloxane containing silicon hydroxyl and carbon-carbon double bond, the modified liquid maintains a weak acid environment before and after the reaction, and the pretreated aluminum foil is soaked in the modified liquid. Due to the moderate concentration of hydrogen ions, only part of the silicon hydroxyl of the siloxane is protonated to form an electrophilic silicon center, and part of the hydroxyl on the surface of the aluminum foil is still in a deprotonated state. The deprotonated hydroxyl on the surface of the aluminum foil can act as a nucleophile to attack the silicon atom in the protonated silicon hydroxyl, and then a condensation reaction occurs to form a Si-O-Al bond. At the same time, the siloxane contains octenyl as a branched chain, which has a large steric hindrance, and the self-condensation between the silicon hydroxyl of the siloxane is not easy to occur, so the silicon hydroxyl is more inclined to condense with the hydroxyl on the surface of the aluminum foil which has a smaller steric hindrance. The number of siloxane grafted on the surface of the aluminum foil is large, and the density of carbon-carbon double bond is large, which provides a large number of active sites for the subsequent free radical polymerization reaction. In addition, in the weak acid environment, the reaction rate of aluminum with hydrogen ions is slow, which effectively reduces the loss of aluminum components in the aluminum foil.

[0020] Further, in the preparation process of the carbon black suspension, ethylene glycol diacrylate and dibenzoyl peroxide are added to n-propanol, stirred at 460 rpm for 4 min, and then the hydrophilic modified carbon black is added multiple times under continuous stirring. After all the carbon black is added, stir at 650 rpm for 1 h, add deionized water, and stir at 530 rpm for 10 min to obtain the carbon black suspension.

[0021] Further, in the step S2, the pretreated aluminum foil is soaked in the flowing modified liquid for 1.5 h, taken out, washed with anhydrous ethanol, and then soaked in the flowing carbon black suspension for 1 h to obtain the composite aluminum foil.

[0022] The carbon black suspension is always in a flowing state, which can improve the mass transfer efficiency by forced convection, inhibit the agglomeration and sedimentation of carbon black, and make the carbon black, ethylene glycol diacrylate and dibenzoyl peroxide diffuse synchronously and uniformly to the surface of the aluminum foil, so as to promote the formation of a uniform composite layer on the surface of the aluminum foil, and lay a foundation for the subsequent construction of a uniform organic crosslinked network and a carbon black conductive network.

[0023] Further, in the step S3, the composite aluminum foil is placed in an inert atmosphere at 40℃, and heated to 75℃ under normal pressure for 2 h. First, the temperature is adjusted to 58℃, and then the absolute pressure is adjusted to 21.3 kPa for 2 h. The temperature is increased to 63℃ for 2 h, and then increased to 75℃ for 3 h. The pressure is restored to normal, and the temperature of the inert atmosphere is reduced to room temperature to obtain the battery foil.

[0024] In the environment of absolute pressure 21.3kPa, the boiling point of n-propanol is about 56.5℃, and the boiling point of water is about 60.8℃, the temperature is controlled at 58℃ first, so that n-propanol is slowly volatilized, then the temperature is adjusted to 63℃, so that deionized water is slowly volatilized, and finally the temperature is raised to 75℃, so that the remaining n-propanol and deionized water are further removed, which is beneficial to form a dense and uniform organic crosslinked network.

[0025] Further, the hydrophilic modified carbon black is prepared by adding carbon black into nitric acid solution, ultrasonic dispersion for 10min, 300rpm stirring for 4h, deionized water washing, drying, to obtain hydrophilic modified carbon black.

[0026] Further, in the preparation process of the hydrophilic modified carbon black, the carbon black after deionized water washing is placed in a-50℃ environment for freeze drying for 24h.

[0027] Further, the concentration of the nitric acid solution is 40-50wt%.

[0028] The carbon black and 40-50wt% nitric acid solution undergo oxidation reaction, and carboxyl functional groups are introduced on the carbon black, the hydrophilicity of the carboxyl is strong, the dispersion degree of the carbon black in deionized water is improved, and it is helpful to form a uniform carbon black suspension.

[0029] A battery foil is prepared by the above-mentioned battery foil preparation method, which is obtained by sequentially immersing an aluminum foil into a modified liquid and a carbon black suspension, and then drying; the chemical composition of the aluminum foil, in terms of mass percentage, is: silicon 0.18-0.20%, iron 0.13-0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, and the balance is aluminum; the modified liquid comprises the following raw materials in mass parts: n-propanol 200-220 parts, deionized water 17-25 parts, and octenyltrimethoxysilane 50-57 parts; the carbon black suspension comprises the following raw materials in mass parts: ethylene glycol diacrylate 30-40 parts, dibenzoyl peroxide 1.1-1.4 parts, n-propanol 100-107 parts, hydrophilic modified carbon black 40-48 parts, and deionized water 55-63 parts; the hydrophilic modified carbon black comprises the following raw materials in mass parts: carbon black 5-6 parts and nitric acid solution 75-90 parts.

[0030] The beneficial effects of the present application are:

[0031] The present application introduces hydroxyl groups on the surface of the aluminum foil while preserving the bare aluminum surface by pretreating the aluminum foil with sodium hydroxide solution and deionized water, immerses the pretreated aluminum foil in a modification liquid, the modification liquid contains silicon-containing hydroxyl groups and siloxane with carbon-carbon double bonds generated by the hydrolysis of octenyltrimethoxysilane, the silicon-containing hydroxyl groups and the aluminum foil surface hydroxyl groups undergo dehydration condensation to form Si-O-Al bonds, the siloxane is grafted on the surface of the aluminum foil, then the aluminum foil is immersed in a carbon black suspension, the carbon black, ethylene glycol diacrylate and dibenzoyl peroxide in the carbon black suspension are combined on the surface of the aluminum foil, under the thermal initiation of dibenzoyl peroxide, the carbon-carbon double bonds of ethylene glycol diacrylate and siloxane compounds undergo free radical copolymerization to form an organic crosslinked network wrapping the carbon black, after drying, the organic crosslinked network shrinks, the carbon black approaches each other and the bare aluminum surface, forming a carbon black conductive network in contact with the bare aluminum surface, obtaining a battery foil, electrons can directly move along the conductive network to the carbon black in contact with the bare aluminum surface, directly transmitting electrons to the aluminum foil, without relying on the tunneling effect, achieving efficient electron transmission and meeting the demand for large current discharge.

[0032] The battery foil surface has a composite layer composed of an organic crosslinked network and a carbon black conductive network embedded therein, in the construction process of the organic crosslinked network, the silicon-containing hydroxyl groups of siloxane condense with the hydroxyl groups on the surface of the aluminum foil to form Si-O-Al bonds, since the siloxane contains carbon-carbon double bonds, it can be used as a functional component to undergo free radical copolymerization with ethylene glycol diacrylate to construct an organic crosslinked network, therefore, the organic crosslinked network and the aluminum foil are connected by Si-O-Al bonds as a connecting bridge, the Si-O-Al bond has high bond energy and strong stability, effectively enhancing the interfacial bonding force between the composite layer and the aluminum foil, making it not easy to peel off or fall off from the surface of the aluminum foil, improving the use stability of the battery foil. DETAILED DESCRIPTION

[0033] Preparation Example One

[0034] 60g of carbon black was added to 800g of 45wt% nitric acid solution, ultrasonic dispersion for 10min, 300rpm stirring for 4h, deionized water washing for 3 times, -50℃ freeze drying for 24 hours, to obtain hydrophilic modified carbon black; 30g of ethylene glycol diacrylate, 1.1g of dibenzoyl peroxide was added to 100g of n-propanol, 460rpm stirring for 4min, under the condition of 600rpm, 10g of hydrophilic modified carbon black was added every 5min, a total of 4 times, after all the addition, 650rpm stirring for 1h, 55g of deionized water was added, 530rpm stirring for 10min, to obtain a carbon black suspension.

[0035] Preparation Example Two

[0036] Put 55 g of carbon black into 750 g of 50 wt% nitric acid solution, ultrasonic dispersion for 10 min, 300 rpm stirring for 4 h, deionized water washing for 3 times, -50℃ freeze drying for 24 hours, to obtain hydrophilic modified carbon black; Put 35 g of ethylene glycol diacrylate, 1.4 g of dibenzoyl peroxide into 107 g of n-propanol, 460 rpm stirring for 4 min, under the condition of 600 rpm, every 5 min, add 12 g of hydrophilic modified carbon black, a total of 4 times, after all added, 650 rpm stirring for 1 h, add 60 g of deionized water, 530 rpm stirring for 10 min, to obtain carbon black suspension.

[0037] Preparation Example Three

[0038] Put 50 g of carbon black into 900 g of 40 wt% nitric acid solution, ultrasonic dispersion for 10 min, 300 rpm stirring for 4 h, deionized water washing for 3 times, -50℃ freeze drying for 24 hours, to obtain hydrophilic modified carbon black; Put 40 g of ethylene glycol diacrylate, 1.2 g of dibenzoyl peroxide into 104 g of n-propanol, 460 rpm stirring for 4 min, under the condition of 600 rpm, every 5 min, add 11 g of hydrophilic modified carbon black, a total of 4 times, after all added, 650 rpm stirring for 1 h, add 63 g of deionized water, 530 rpm stirring for 10 min, to obtain carbon black suspension.

[0039] Example One

[0040] Select aluminum ingot as raw material, put the aluminum ingot into the casting and rolling machine for casting and rolling, annealing, to obtain aluminum foil with a thickness of 15 μm, the chemical composition of the aluminum foil is: silicon 0.18%, iron 0.13%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, the balance is aluminum, in a nitrogen atmosphere, take 10 g of aluminum foil and put it into a 3 wt% sodium hydroxide solution for 2 min, take it out and put it into deionized water for 20 s, take it out and put it into anhydrous ethanol for storage, to complete the pretreatment of the aluminum foil.

[0041] Put 20 g of deionized water into 200 g of n-propanol, adjust the pH to 5 by adding 3 wt% acetic acid solution, mix 50 g of octenyltrimethoxysilane, 400 rpm stirring for 2 h, to obtain modified liquid, put the modified liquid in a nitrogen atmosphere, use a circulating pump to control the flow rate of the modified liquid to be 50 g / min, soak the pretreated aluminum foil in the flowing modified liquid for 1.5 h, take it out and wash it with anhydrous ethanol, to obtain modified aluminum foil; Put the carbon black suspension in a nitrogen atmosphere, use a circulating pump to control the flow rate of the carbon black suspension to be 60 g / min, soak the modified aluminum foil in the flowing carbon black suspension for 1 h, take it out, to obtain composite aluminum foil.

[0042] The composite aluminum foil is placed into a nitrogen-filled vacuum drying oven for solidification, the pressure is set to normal pressure, the temperature is 40℃, nitrogen is continuously introduced, the temperature is increased to 75℃ at a speed of 15℃ / h, the temperature is maintained for 2h, the temperature is decreased to 58℃, the absolute pressure is adjusted to 21.3kPa, the temperature is maintained for 2h, the temperature is increased to 63℃ and maintained for 2h, the temperature is increased to 75℃ and maintained for 3h, the pressure is restored to normal pressure, and the temperature is decreased to room temperature at a speed of 20℃ / h to obtain a battery foil.

[0043] The carbon black suspension used in this example is prepared by Preparation Example One.

[0044] Example Two

[0045] The aluminum ingot is sent to a casting and rolling machine for casting and rolling, and annealing to obtain an aluminum foil with a thickness of 15μm. The chemical composition of the aluminum foil is as follows in terms of mass percentage: silicon 0.20%, iron 0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, and the balance being aluminum. In a nitrogen atmosphere, 10g of the aluminum foil is placed into a 3wt% sodium hydroxide solution for immersion for 2min, taken out and placed into deionized water for immersion for 20s, and taken out and placed into anhydrous ethanol for storage for standby, to complete the pretreatment of the aluminum foil.

[0046] In 210g of n-propanol, 17g of deionized water is added, a 3wt% acetic acid solution is added to adjust the pH to 5, and 52g of octenyltrimethoxysilane is added and mixed, and stirred at 400rpm for 2h to obtain a modification liquid. The modification liquid is placed in a nitrogen atmosphere, a circulating pump is used to control the flow rate of the modification liquid to be 50g / min, the pretreated aluminum foil is immersed in the flowing modification liquid for 1.5h, taken out, and washed with anhydrous ethanol to obtain a modified aluminum foil. The carbon black suspension is placed in a nitrogen atmosphere, a circulating pump is used to control the flow rate of the carbon black suspension to be 60g / min, the modified aluminum foil is immersed in the flowing carbon black suspension for 1h, taken out, and a composite aluminum foil is obtained.

[0047] The composite aluminum foil is placed into a nitrogen-filled vacuum drying oven for solidification, the pressure is set to normal pressure, the temperature is 40℃, nitrogen is continuously introduced, the temperature is increased to 75℃ at a speed of 15℃ / h, the temperature is maintained for 2h, the temperature is decreased to 58℃, the absolute pressure is adjusted to 21.3kPa, the temperature is maintained for 2h, the temperature is increased to 63℃ and maintained for 2h, the temperature is increased to 75℃ and maintained for 3h, the pressure is restored to normal pressure, and the temperature is decreased to room temperature at a speed of 20℃ / h to obtain a battery foil.

[0048] The carbon black suspension used in this example is prepared by Preparation Example One.

[0049] Example Three

[0050] The aluminum ingot is sent to a casting and rolling machine for casting and rolling, and annealing, to obtain an aluminum foil with a thickness of 15 μm. The chemical composition of the aluminum foil is as follows in terms of mass percentage: silicon 0.19%, iron 0.13%, copper ≤ 0.02%, manganese ≤ 0.01%, titanium ≤ 0.03%, and the balance being aluminum. In a nitrogen atmosphere, 10 g of the aluminum foil is placed in a 3 wt% sodium hydroxide solution for 2 min, taken out and placed in deionized water for 20 s, taken out and placed in anhydrous ethanol for storage, to complete the pretreatment of the aluminum foil.

[0051] In 205 g of n-propanol, 19 g of deionized water is added, a 3 wt% acetic acid solution is added to adjust the pH to 5, and 54 g of octenyltrimethoxysilane is added and mixed, stirred at 400 rpm for 2 h, to obtain a modified liquid. The modified liquid is placed in a nitrogen atmosphere, and a circulating pump is used to control the flow rate of the modified liquid to be 50 g / min. The pretreated aluminum foil is soaked in the flowing modified liquid for 1.5 h, taken out and washed with anhydrous ethanol, to obtain a modified aluminum foil. The carbon black suspension is placed in a nitrogen atmosphere, and a circulating pump is used to control the flow rate of the carbon black suspension to be 60 g / min. The modified aluminum foil is soaked in the flowing carbon black suspension for 1 h, taken out, to obtain a composite aluminum foil.

[0052] The composite aluminum foil is placed in a nitrogen-filled vacuum drying box for curing. The pressure is set to normal pressure, the temperature is set to 40℃, nitrogen is continuously introduced, the temperature is raised to 75℃ at a rate of 15℃ / h, and the temperature is maintained for 2 h. The temperature is lowered to 58℃, the absolute pressure is adjusted to 21.3 kPa, and the temperature is maintained for 2 h. The temperature is raised to 63℃ and maintained for 2 h. The temperature is raised to 75℃ and maintained for 3 h. The pressure is returned to normal pressure, and the temperature is lowered to room temperature at a rate of 20℃ / h, to obtain a battery foil.

[0053] The carbon black suspension used in this example is prepared according to Preparation Example Two.

[0054] Example Four

[0055] The aluminum ingot is sent to a casting and rolling machine for casting and rolling, and annealing, to obtain an aluminum foil with a thickness of 15 μm. The chemical composition of the aluminum foil is as follows in terms of mass percentage: silicon 0.19%, iron 0.13%, copper ≤ 0.02%, manganese ≤ 0.01%, titanium ≤ 0.03%, and the balance being aluminum. In a nitrogen atmosphere, 10 g of the aluminum foil is placed in a 3 wt% sodium hydroxide solution for 2 min, taken out and placed in deionized water for 20 s, taken out and placed in anhydrous ethanol for storage, to complete the pretreatment of the aluminum foil.

[0056] In 220 g of n-propanol, 25 g of deionized water was added, 3 wt% acetic acid solution was added to adjust the pH to 5, 57 g of octenyltrimethoxysilane was added and mixed, stirred at 400 rpm for 2 h to obtain a modified liquid, the modified liquid was placed in a nitrogen atmosphere, and the flow rate of the modified liquid was controlled to be 50 g / min by using a circulating pump, the pretreated aluminum foil was soaked in the flowing modified liquid for 1.5 h, taken out, washed with anhydrous ethanol, and a modified aluminum foil was obtained; the carbon black suspension was placed in a nitrogen atmosphere, the flow rate of the carbon black suspension was controlled to be 60 g / min by using a circulating pump, the modified aluminum foil was soaked in the flowing carbon black suspension for 1 h, taken out, and a composite aluminum foil was obtained.

[0057] The composite aluminum foil was placed in a nitrogen-filled vacuum drying oven for curing, the pressure was set to normal pressure, the temperature was 40℃, the nitrogen was continuously introduced, the temperature was increased to 75℃ at a rate of 15℃ / h, the temperature was kept for 2 h, the temperature was decreased to 58℃, the absolute pressure was adjusted to 21.3 kPa, the temperature was kept for 2 h, the temperature was increased to 63℃ and kept for 2 h, the temperature was increased to 75℃ and kept for 3 h, the pressure was restored to normal pressure, and the temperature was decreased to room temperature at a rate of 20℃ / h, and a battery foil was obtained.

[0058] The carbon black suspension used in this example was prepared by Preparation Example Two.

[0059] Example Five

[0060] The aluminum ingot was sent to a casting and rolling machine for casting and rolling, and annealing to obtain an aluminum foil with a thickness of 15 μm. The chemical composition of the aluminum foil was as follows: silicon 0.19%, iron 0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, and the balance being aluminum. In a nitrogen atmosphere, 10 g of the aluminum foil was soaked in a 3 wt% sodium hydroxide solution for 2 min, taken out and soaked in deionized water for 20 s, taken out and stored in anhydrous ethanol for standby, and the pretreatment of the aluminum foil was completed.

[0061] In 215 g of n-propanol, 23 g of deionized water was added, 3 wt% acetic acid solution was added to adjust the pH to 5, 53 g of octenyltrimethoxysilane was added and mixed, stirred at 400 rpm for 2 h to obtain a modified liquid, the modified liquid was placed in a nitrogen atmosphere, and the flow rate of the modified liquid was controlled to be 50 g / min by using a circulating pump, the pretreated aluminum foil was soaked in the flowing modified liquid for 1.5 h, taken out, washed with anhydrous ethanol, and a modified aluminum foil was obtained; the carbon black suspension was placed in a nitrogen atmosphere, the flow rate of the carbon black suspension was controlled to be 60 g / min by using a circulating pump, the modified aluminum foil was soaked in the flowing carbon black suspension for 1 h, taken out, and a composite aluminum foil was obtained.

[0062] The composite aluminum foil is placed into a nitrogen-filled vacuum drying oven for solidification, the pressure is set as normal pressure, the temperature is 40℃, nitrogen is continuously introduced, the temperature is increased to 75℃ at a speed of 15℃ / h, the temperature is kept for 2h, the temperature is decreased to 58℃, the absolute pressure is adjusted to 21.3kPa, the temperature is kept for 2h, the temperature is increased to 63℃ and kept for 2h, the temperature is increased to 75℃ and kept for 3h, the pressure is returned to normal pressure, the temperature is decreased to room temperature at a speed of 20℃ / h, and a battery foil is obtained.

[0063] The carbon black suspension used in the example is prepared by Preparation Example Three.

[0064] Example Six

[0065] Aluminum ingots are selected as raw materials, the aluminum ingots are sent into a casting and rolling machine for casting and rolling, and annealing, so that an aluminum foil with a thickness of 15μm is obtained, the chemical composition of the aluminum foil is as follows in terms of mass percentage: silicon 0.18%, iron 0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, and the balance is aluminum, 10g of the aluminum foil is placed into a 3wt% sodium hydroxide solution in a nitrogen atmosphere for 2min, taken out and placed into deionized water for 20s, taken out and placed into anhydrous ethanol for storage, and the pretreatment of the aluminum foil is completed.

[0066] In 217g of n-propanol, 22g of deionized water is added, a 3wt% acetic acid solution is added to adjust the pH to 5, 51g of octenyltrimethoxysilane is added and uniformly mixed, and stirring is performed at 400rpm for 2h, so that a modification liquid is obtained, the modification liquid is placed in a nitrogen atmosphere, a circulating pump is used to control the flow rate of the modification liquid to be 50g / min, the pretreated aluminum foil is soaked in the flowing modification liquid for 1.5h, taken out and washed with anhydrous ethanol, so that a modified aluminum foil is obtained, the carbon black suspension is placed in a nitrogen atmosphere, a circulating pump is used to control the flow rate of the carbon black suspension to be 60g / min, the modified aluminum foil is soaked in the flowing carbon black suspension for 1h, taken out, and a composite aluminum foil is obtained.

[0067] The composite aluminum foil is placed into a nitrogen-filled vacuum drying oven for solidification, the pressure is set as normal pressure, the temperature is 40℃, nitrogen is continuously introduced, the temperature is increased to 75℃ at a speed of 15℃ / h, the temperature is kept for 2h, the temperature is decreased to 58℃, the absolute pressure is adjusted to 21.3kPa, the temperature is kept for 2h, the temperature is increased to 63℃ and kept for 2h, the temperature is increased to 75℃ and kept for 3h, the pressure is returned to normal pressure, the temperature is decreased to room temperature at a speed of 20℃ / h, and a battery foil is obtained.

[0068] The carbon black suspension used in the example is prepared by Preparation Example Three.

[0069] The present application also sets up a comparative example and carries out related tests.

[0070] Comparative Example One

[0071] Comparative Example 1 differs from Example 6 in that the aluminum foil in Comparative Example 1 is not pretreated, and the remaining steps and environmental conditions are the same as in Example 6, to prepare a battery foil.

[0072] Comparative Example 2

[0073] Comparative Example 2 differs from Example 6 in that no dibenzoyl peroxide is added to the carbon black suspension, and the remaining steps and environmental conditions are the same as in Example 6, to prepare a battery foil.

[0074] Comparative Example 3

[0075] The preparation method of the Chinese invention patent with publication number CN117352738B is used to coat a carbon layer on the surface of an aluminum foil, and the carbon layer serves as a composite layer for electron transmission, to prepare a battery foil.

[0076] Battery foil performance test

[0077] For each battery foil sample prepared in Examples 1-6 and Comparative Examples 1-3, the contact resistance between the composite layer and the aluminum foil is tested using the Kelvin four-wire method, the adhesion between the composite layer and the aluminum foil of each sample is tested using the grid method, and the fatigue resistance of the composite layer is tested using a bending fatigue testing machine, with a bending angle of 90° and a bending frequency of 40 times / min. After 5000 bending cycles, the surface of the bending area is observed using a magnifying glass, the area of the composite layer peeling region is recorded, and the peeling rate is calculated. The contact resistance, adhesion grade, and peeling rate of each sample are shown in Table 1.

[0078] Table 1

[0079]

[0080] According to the analysis in Table 1, compared with Comparative Examples 1 and 3, the contact resistance between the composite layer and the aluminum foil of the battery foils prepared in Examples 1-6 is lower, indicating that pretreatment of the aluminum foil can produce a bare aluminum surface. Under the surrounding and pushing of the organic cross-linked network, part of the carbon black directly contacts the bare aluminum surface, and there is no oxidation layer between the two, effectively reducing the contact resistance between the aluminum foil and the composite layer to meet the need for large current discharge. Compared with Comparative Example 2, the adhesion of the composite layer prepared in Examples 1-6 is good, and the peeling rate is low, indicating that the method of fixing the composite layer on the surface of the aluminum foil through Si-O-Al bonds can effectively increase the interfacial bonding strength between the composite layer and the aluminum foil, and improve the use stability of the battery foil.

Claims

1. A method for producing battery foil, characterized in that, Includes the following steps: S1. The aluminum ingot is fed into the casting and rolling mill for casting and rolling, annealing, and aluminum foil is obtained. In an inert atmosphere, the aluminum foil is immersed in sodium hydroxide solution, taken out, and immersed in deionized water for 20 seconds. It is then taken out and stored in anhydrous ethanol to obtain pretreated aluminum foil. S2. Add acetic acid solution to n-propanol solution and mix well. Add octenyltrimethoxysilane and stir to react to obtain modified solution. Under inert atmosphere, immerse the pretreated aluminum foil in the flowing modified solution and react for 1.5 h. Take it out, wash with anhydrous ethanol, immerse in flowing carbon black suspension for 1 h, take it out, and obtain composite aluminum foil. S3. Place the composite aluminum foil in an inert atmosphere at 40°C, heat it to 75°C under normal pressure, keep it at that temperature for 2 hours to carry out the reaction, dry it under reduced pressure, and cool it to obtain the battery foil. The carbon black suspension was prepared by adding ethylene glycol diacrylate and benzoyl peroxide to n-propanol, stirring and mixing, then adding hydrophilic modified carbon black and deionized water and stirring and mixing to obtain the carbon black suspension. The chemical composition of the aluminum foil, by mass percentage, is: silicon 0.18-0.20%, iron 0.13-0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, with the balance being aluminum; the modified solution includes the following raw materials by mass: n-propanol 200-220 parts, deionized water 17-25 parts, octenyltrimethoxysilane 50-57 parts; the carbon black suspension includes the following raw materials by mass: ethylene glycol diacrylate 30-40 parts, benzoyl peroxide 1.1-1.4 parts, n-propanol 100-107 parts, hydrophilic modified carbon black 40-48 parts, deionized water 55-63 parts; the hydrophilic modified carbon black includes the following raw materials by mass: carbon black 5-6 parts, nitric acid solution 75-90 parts.

2. The method for producing battery foil according to claim 1, characterized in that, In step S1, the concentration of the sodium hydroxide solution is 3 wt%, and the aluminum foil is immersed in the sodium hydroxide solution for 2 minutes.

3. The method for producing battery foil according to claim 2, characterized in that, The modified solution is prepared by mixing n-propanol with deionized water to obtain a n-propanol solution, adding acetic acid solution to adjust the pH to 5, adding octenyltrimethoxysilane, and stirring at 400 rpm for 2 hours to obtain the modified solution.

4. The method for producing battery foil according to claim 3, characterized in that, In the preparation of the carbon black suspension, ethylene glycol diacrylate and benzoyl peroxide are added to n-propanol and stirred at 460 rpm for 4 min. Hydrophilic modified carbon black is added multiple times under continuous stirring. After all the carbon black is added, the mixture is stirred at 650 rpm for 1 h. Deionized water is then added and stirred at 530 rpm for 10 min to obtain the carbon black suspension.

5. A method for producing battery foil according to claim 4, characterized in that, In step S3, the temperature is first adjusted to 58°C, then the absolute pressure is adjusted to 21.3 kPa, and the temperature is maintained for 2 hours. The temperature is then raised to 63°C and maintained for 2 hours, then raised to 75°C and maintained for 3 hours. The pressure is then restored to normal, and the temperature of the inert atmosphere is lowered to room temperature to obtain the battery foil.

6. A method for producing battery foil according to claim 5, characterized in that, The hydrophilic modified carbon black was prepared by adding carbon black to a nitric acid solution, ultrasonically dispersing for 10 min, stirring at 300 rpm for 4 h, washing with deionized water, and drying to obtain the hydrophilic modified carbon black.

7. A method for producing battery foil according to claim 6, characterized in that, In the preparation process of the hydrophilic modified carbon black, the carbon black washed with deionized water is freeze-dried in an environment of -50℃ for 24 hours.

8. A method for producing battery foil according to claim 7, characterized in that, The concentration of the nitric acid solution is 40-50 wt%.

9. A battery foil, prepared by the method for preparing the battery foil according to any one of claims 1-8.

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