Production method of battery foil and battery foil

Abstract

The invention belongs to the technical field of aluminum-based alloy battery foils, and particularly relates to a battery foil production method and a battery foil, and the battery foil production method comprises the following preparation steps: feeding an aluminum ingot into a cast rolling machine for cast rolling and annealing to obtain an aluminum foil, in an inert atmosphere, pretreating the aluminum foil by adopting a sodium hydroxide solution and deionized water, and in the inert atmosphere, carrying out heat treatment on the aluminum foil to obtain the aluminum foil. And soaking the pretreated aluminum foil in the modification liquid, reacting, taking out, washing, soaking in the carbon black suspension, taking out to obtain a composite aluminum foil, putting the composite aluminum foil in an inert atmosphere, heating for reacting, drying under reduced pressure, and cooling to obtain the battery foil. The current transmission capability of the battery foil can be improved, and the high-current discharge requirement is met.

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 bearing active material and conducting current. The bearing body of the commonly used battery foil of the positive electrode is an aluminum foil. Aluminum is easy to react with oxygen in the air to form a dense aluminum oxide film on the 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 transmission 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 uniformly mixing, 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 the 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 depends 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: A production method of battery foil, comprising the following steps: S1, send the aluminum ingot into the casting and rolling machine for casting and rolling, annealing, to obtain aluminum foil, in an inert atmosphere, the aluminum foil is soaked in sodium hydroxide solution, taken out, put into deionized water, taken out, put into anhydrous ethanol, to obtain pretreated aluminum foil; S2, adding acetic acid solution to the n-propanol solution, mixing, adding octenyl trimethoxysilane, stirring and reacting to obtain a modified liquid, in an inert atmosphere, the pretreated aluminum foil is soaked in the flowing modified liquid, reacting, taking out, washing, soaking in the flowing carbon black suspension, taking out, to obtain a composite aluminum foil; S3, the composite aluminum foil is put into an inert atmosphere, heated, dried under reduced pressure, cooled, to obtain a battery foil; The carbon black suspension is prepared by adding ethylene glycol diacrylate and dibenzoyl peroxide into n-propanol, stirring and mixing, adding hydrophilic modified carbon black and deionized water, stirring and mixing, to obtain the carbon black suspension.

[0006] The aluminum foil is soaked in sodium hydroxide solution to remove the surface aluminum oxide film and form a bare aluminum surface, then soaked in deionized water, part of the aluminum contacts with deionized water to generate hydrated aluminum oxide, introducing hydroxyl groups on the aluminum surface, the pretreated aluminum foil is put into the modified liquid, which contains silanol and carbon-carbon double bond obtained by hydrolysis of octenyl trimethoxysilane, condensation reaction occurs between the hydroxyl groups on the bare aluminum surface and the silanol of the siloxane to generate Si-O-Al bond, grafting siloxane on the bare aluminum surface, thereby introducing carbon-carbon double bond on the surface of the aluminum foil, then soaking in the 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 with the surface of the aluminum foil, forming a composite layer containing hydrophilic modified carbon black and polymerizable organic matter on the surface of the aluminum foil, to obtain a composite aluminum foil, the composite aluminum foil is put into an inert atmosphere and heated, under the initiation of dibenzoyl peroxide, radical copolymerization occurs between siloxane and ethylene glycol diacrylate through carbon-carbon double bond to form an organic matter crosslinked network, carbon black is uniformly dispersed in the organic matter crosslinked network, then the organic matter crosslinked network is dried under reduced pressure, n-propanol and deionized water evaporate, the organic matter 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 matter crosslinked network, to obtain a battery foil, the surface of the battery foil has a composite layer composed of organic matter crosslinked network and carbon black conductive network, after the battery foil contacts with air, the contact between the bare aluminum surface covered by carbon black and oxygen is physically blocked, effectively inhibiting the formation of aluminum oxide film in this area, part of the carbon black directly adheres to the bare aluminum surface, forming a low impedance interface, electrons can be directly transmitted to the aluminum foil through the carbon black adhering to the bare aluminum surface, without relying on tunneling effect, realizing efficient electron transmission and meeting the demand of large current discharge.

[0007] 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. The dibenzoyl peroxide can be dissolved in the ethylene glycol diacrylate, the ethylene glycol diacrylate can be mutually soluble with the n-propanol, and the n-propanol can be mutually soluble with water. Therefore, the n-propanol can be used as a co-solvent to promote the mixing of the organic component and the aqueous phase, form a uniform continuous phase, and improve the dispersion stability of the hydrophilic modified carbon black in the continuous phase, which is beneficial to the formation of a uniform carbon black suspension.

[0008] The aluminum foil with surface grafted carbon-carbon double bonds is immersed in the carbon black suspension. The n-propanol is used as a low surface tension solvent to reduce the overall surface tension of the carbon black suspension, promote its spreading on the surface of the aluminum foil, and promote the uniform distribution of the carbon black in the carbon black suspension. The carbon black can diffuse to the surface of the aluminum foil and contact the surface of the aluminum foil under the action of Brownian motion and convection, which lays a foundation for the subsequent direct contact between the carbon black and the bare aluminum surface. The n-propanol can connect water molecules through hydrogen bonds and form a uniform solution with ethylene glycol diacrylate and dibenzoyl peroxide. Under the bridging action of the n-propanol, the carbon black suspension will not phase separate, and the ethylene glycol diacrylate and dibenzoyl peroxide can diffuse to the surface of the aluminum foil to provide a molecular distribution basis and reaction environment for the subsequent free radical polymerization reaction.

[0009] 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, enable it to bend and deform synchronously with the aluminum foil, reduce the peeling between the composite layer and the aluminum foil when subjected to bending stress, and improve the use stability of the battery foil.

[0010] The battery foil surface has a composite layer composed of an organic cross-linked network and a carbon black conductive network embedded therein. The Si-O-Al bond is used as the connecting bond between the organic cross-linked network and the aluminum foil. The bond energy of the Si-O-Al bond is greater than 350 kJ / mol, and the decomposition temperature is above 250℃. The stability is strong, which can effectively fix the composite layer on the surface of the aluminum foil, avoid its peeling or falling off 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.

[0011] Further, in the step S1, the concentration of the sodium hydroxide solution is 3wt%, the immersion time of the aluminum foil in the sodium hydroxide solution is 2min, and the immersion time of the aluminum foil in the deionized water is 20s.

[0012] The aluminum foil is immersed in sodium hydroxide solution for 2 min, and the oxide layer on the surface of the aluminum foil can be effectively removed to form a bare aluminum surface; the surface-exposed aluminum foil is immersed in deionized water for only 20 s, the immersion time is relatively short, only part of the bare aluminum surface will undergo hydration oxidation reaction to generate surface hydroxyl groups, and part of the bare aluminum surface is still unoxidized, which lays a foundation for subsequent direct contact with carbon black to form a low-impedance interface.

[0013] Further, the modification liquid is prepared by mixing n-propanol and deionized water to obtain an n-propanol solution, adding an acetic acid solution to adjust the pH to 5, and adding octenyltrimethoxysilane, stirring at 400 rpm for 2 h to obtain the modification liquid.

[0014] The octenyltrimethoxysilane undergoes hydrolysis reaction in an acidic environment to generate siloxane containing silicon hydroxyl and carbon-carbon double bond, and the modification liquid always maintains a weak acid environment before and after the reaction. The pretreated aluminum foil is immersed in the modification liquid. Due to the moderate concentration of hydrogen ions, only part of the silicon hydroxyl groups of the siloxane are protonated to form electrophilic silicon centers, and part of the hydroxyl groups on the surface of the aluminum foil are still in deprotonated state. The deprotonated hydroxyl groups on the surface of the aluminum foil can act as nucleophiles to attack the silicon atoms in the protonated silicon hydroxyl groups, and then condensation reaction occurs to form Si-O-Al bonds. At the same time, the siloxane contains octenyl as a branched chain, which has large steric hindrance, and the self-condensation between the silicon hydroxyl groups of the siloxane is not easy to occur, so the silicon hydroxyl groups tend to condense with the hydroxyl groups on the aluminum surface which have small 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 abundant 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.

[0015] 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, the mixture is stirred at 650 rpm for 1 h, deionized water is added, and the mixture is stirred at 530 rpm for 10 min to obtain the carbon black suspension.

[0016] Further, in the step S2, the pretreated aluminum foil is immersed in the flowing modification liquid for 1.5 h, taken out, washed with anhydrous ethanol, and then immersed in the flowing carbon black suspension for 1 h to obtain the composite aluminum foil.

[0017] 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 carbon black conductive network.

[0018] Further, in the step S3, the composite aluminum foil is placed in an inert atmosphere at 40℃, and is heated to 75℃ under normal pressure for 2h, the temperature is first adjusted to 58℃, then the absolute pressure is adjusted to 21.3kPa, and is kept for 2h, the temperature is raised to 63℃ for 2h, the temperature is raised to 75℃ for 3h, the normal pressure is restored, and the temperature of the inert atmosphere is reduced to room temperature, to obtain the battery foil.

[0019] In an environment with an absolute pressure of 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 first controlled to 58℃ to make n-propanol slowly volatilize, then the temperature is adjusted to 63℃ to make deionized water slowly volatilize, and finally the temperature is raised to 75℃ to further remove the residual n-propanol and deionized water, which is beneficial to form a dense and uniform organic crosslinked network.

[0020] Further, the hydrophilic modified carbon black is prepared by adding carbon black into a nitric acid solution, ultrasonic dispersion for 10min, 300rpm stirring for 4h, deionized water washing, and drying to obtain the hydrophilic modified carbon black.

[0021] Further, in the preparation process of the hydrophilic modified carbon black, the carbon black after deionized water washing is placed in an environment at-50℃ for freeze drying for 24h.

[0022] Further, the concentration of the nitric acid solution is 40-50wt%.

[0023] The carbon black and the 40-50wt% nitric acid solution undergo an oxidation reaction, and a carboxyl functional group is introduced on the carbon black, the hydrophilicity of the carboxyl group 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.

[0024] A battery foil is prepared by the above-mentioned preparation method of the battery foil, and is obtained by sequentially placing an aluminum foil into a modified liquid and a carbon black suspension for soaking, and 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; and 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.

[0025] The beneficial effects of the present application are: 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, immersing the pretreated aluminum foil in a modification liquid, the modification liquid containing silicon-containing hydroxyl groups and siloxane with carbon-carbon double bonds generated by the hydrolysis of octenyltrimethoxysilane, the silicon-containing hydroxyl groups undergoing dehydration condensation with the hydroxyl groups on the surface of the aluminum foil to generate Si-O-Al bonds, the siloxane being grafted onto the surface of the aluminum foil, then immersing the aluminum foil in a carbon black suspension, the carbon black, ethylene glycol diacrylate and dibenzoyl peroxide in the carbon black suspension being combined on the surface of the aluminum foil, under the thermal initiation of dibenzoyl peroxide, the carbon-carbon double bonds of the ethylene glycol diacrylate and the siloxane compound undergoing free radical copolymerization to generate an organic crosslinked network wrapping the carbon black, the organic crosslinked network shrinking after drying, the carbon black and the bare aluminum surface approaching each other, forming a carbon black conductive network in contact with the bare aluminum surface, obtaining a battery foil, electrons moving directly along the conductive network to the carbon black in contact with the bare aluminum surface, directly delivering the electrons to the aluminum foil, without relying on the tunneling effect, achieving efficient electron transmission, meeting the demand for large current discharge.

[0026] The battery foil 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 the siloxane condense with the hydroxyl groups on the surface of the aluminum foil to generate 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 the organic crosslinked network, therefore the organic crosslinked network and the aluminum foil are connected by the Si-O-Al bonds as a connecting bridge, the Si-O-Al bonds have 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

[0027] Preparation Example One 60g of carbon black was added to 800g of 45wt% nitric acid solution, ultrasonically dispersed for 10min, stirred at 300rpm for 4h, washed with deionized water for 3 times, freeze-dried at-50℃ for 24 hours, to obtain hydrophilic modified carbon black; 30g of ethylene glycol diacrylate and 1.1g of dibenzoyl peroxide were added to 100g of n-propanol, stirred at 460rpm for 4min, 10g of hydrophilic modified carbon black was added every 5min under the condition of 600rpm, a total of 4 times, after all were added, stirred at 650rpm for 1h, 55g of deionized water was added, stirred at 530rpm for 10min, to obtain a carbon black suspension.

[0028] Preparation Example Two Add 55 g of carbon black to 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; add 35 g of ethylene glycol diacrylate, 1.4 g of dibenzoyl peroxide to 107 g of n-propanol, 460 rpm stirring for 4 min, under the condition of 600 rpm, add 12 g of hydrophilic modified carbon black every 5 min, 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.

[0029] Preparation Example Three Add 50 g of carbon black to 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; add 40 g of ethylene glycol diacrylate, 1.2 g of dibenzoyl peroxide to 104 g of n-propanol, 460 rpm stirring for 4 min, under the condition of 600 rpm, add 11 g of hydrophilic modified carbon black every 5 min, 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.

[0030] Example One Select aluminum ingot as raw material, send 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 0.18% of silicon, 0.13% of iron, ≤0.02% of copper, ≤0.01% of manganese, ≤0.03% of titanium, and the balance of aluminum, in a nitrogen atmosphere, take 10 g of aluminum foil and immerse it in a 3 wt% sodium hydroxide solution for 2 min, take it out and immerse it in deionized water for 20 s, and then take it out and store it in anhydrous ethanol for standby, to complete the pretreatment of the aluminum foil.

[0031] Add 20 g of deionized water to 200 g of n-propanol, add 3 wt% acetic acid solution to adjust the pH to 5, add 50 g of octenyltrimethoxysilane and mix, 400 rpm stirring for 2 h, to obtain a modified liquid, place 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, immerse the pretreated aluminum foil in the flowing modified liquid for 1.5 h, take it out and wash it with anhydrous ethanol, to obtain a modified aluminum foil; place 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, immerse the modified aluminum foil in the flowing carbon black suspension for 1 h, take it out, to obtain a composite aluminum foil.

[0032] 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, the temperature is decreased to room temperature at a speed of 20℃ / h, and a battery foil is obtained.

[0033] The carbon black suspension used in this example is prepared by Preparation Example One.

[0034] Example Two 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, 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.

[0035] In 210g of n-propanol, 17g of deionized water is added, a 3wt% acetic acid solution is added to adjust the pH to 5, 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 soaked 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 soaked in the flowing carbon black suspension for 1h, taken out, and a composite aluminum foil is obtained.

[0036] 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, the temperature is decreased to room temperature at a speed of 20℃ / h, and a battery foil is obtained.

[0037] The carbon black suspension used in this example is prepared by Preparation Example One.

[0038] Example Three 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 for later use, to complete the pretreatment of the aluminum foil.

[0039] 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, and a composite aluminum foil is obtained.

[0040] 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, the temperature is maintained for 2 h, the temperature is lowered to 58℃, the absolute pressure is adjusted to 21.3 kPa, 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.

[0041] The carbon black suspension used in this example is prepared according to Preparation Example Two.

[0042] Example Four 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 0.20%, 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 for later use, to complete the pretreatment of the aluminum foil.

[0043] 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.

[0044] 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.

[0045] The carbon black suspension used in this example was prepared by Preparation Example Two.

[0046] Example Five 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 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, and the pretreatment of the aluminum foil was completed.

[0047] 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.

[0048] 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 DEG C, nitrogen is continuously introduced, the temperature is increased to 75 DEG C at a speed of 15 DEG C / h, the temperature is kept for 2 h, the temperature is decreased to 58 DEG C, the absolute pressure is adjusted to 21.3 kPa, the temperature is kept for 2 h, the temperature is increased to 63 DEG C and kept for 2 h, the temperature is increased to 75 DEG C and kept for 3 h, the normal pressure is restored, the temperature is decreased to room temperature at a speed of 20 DEG C / h, and a battery foil is obtained.

[0049] The carbon black suspension used in the example is prepared by Preparation Example Three.

[0050] Example Six Aluminum ingot is selected as a raw material, the aluminum ingot is sent into a casting and rolling machine for casting and rolling, and annealing is performed, so that an aluminum foil with a thickness of 15 μm 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, 10 g of the aluminum foil is placed into a 3wt% sodium hydroxide solution in a nitrogen atmosphere for 2 min, taken out and placed into deionized water for 20 s, taken out and placed into anhydrous ethanol for storage, and the pretreatment of the aluminum foil is completed.

[0051] In 217 g of n-propanol, 22 g of deionized water is added, a 3wt% acetic acid solution is added to adjust the pH to 5, 51 g of octenyltrimethoxysilane is added and uniformly mixed, and stirring is performed at 400 rpm for 2 h, 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 50 g / min, the pretreated aluminum foil is soaked in the flowing modification liquid for 1.5 h, 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 60 g / min, the modified aluminum foil is soaked in the flowing carbon black suspension for 1 h, taken out, and a composite aluminum foil is obtained.

[0052] 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 DEG C, nitrogen is continuously introduced, the temperature is increased to 75 DEG C at a speed of 15 DEG C / h, the temperature is kept for 2 h, the temperature is decreased to 58 DEG C, the absolute pressure is adjusted to 21.3 kPa, the temperature is kept for 2 h, the temperature is increased to 63 DEG C and kept for 2 h, the temperature is increased to 75 DEG C and kept for 3 h, the normal pressure is restored, the temperature is decreased to room temperature at a speed of 20 DEG C / h, and a battery foil is obtained.

[0053] The carbon black suspension used in the example is prepared by Preparation Example Three.

[0054] The present application also sets up a comparative example and carries out related tests.

[0055] Comparative Example One 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.

[0056] Comparative Example 2 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.

[0057] Comparative Example 3 A carbon layer is coated on the surface of an aluminum foil using the preparation method of the Chinese invention patent with publication number CN117352738B, and the carbon layer serves as a composite layer for electron transmission, to prepare a battery foil.

[0058] Battery foil performance test 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 tester, 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 peeling region of the composite layer is recorded, and the peeling rate is calculated. The contact resistance, adhesion grade, and peeling rate of each sample are shown in Table 1.

[0059] Table 1

[0060] 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 of producing a battery foil, characterized by, The method comprises the following steps: S1, sending an aluminum ingot into a casting and rolling machine to perform casting and rolling, annealing, and obtaining an aluminum foil, and 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; S2, adding an acetic acid solution into the n-propanol solution and mixing, adding octenyltrimethoxysilane, stirring and reacting to obtain a modified liquid, and in an inert atmosphere, soaking the pretreated aluminum foil in the flowing modified liquid, reacting, taking out, washing, and soaking in a flowing carbon black suspension to obtain a composite aluminum foil; S3, placing the composite aluminum foil in an inert atmosphere, and performing temperature rising, pressure reduction, drying, and cooling to obtain a battery foil; The carbon black suspension is prepared by adding ethylene glycol diacrylate and dibenzoyl peroxide into n-propanol, stirring and mixing, adding hydrophilic modified carbon black and deionized water, and stirring and mixing to obtain the carbon black suspension.

2. The method of producing a battery foil according to claim 1, wherein In the step S1, the concentration of the sodium hydroxide solution is 3 wt%, the soaking time of the aluminum foil in the sodium hydroxide solution is 2 min, and the soaking time of the aluminum foil in the deionized water is 20 s.

3. The method of claim 2, wherein the step of applying the electrolyte solution is performed after the step of applying the protective layer. The modified liquid is prepared by mixing n-propanol and deionized water to obtain an n-propanol solution, adding an acetic acid solution to adjust the pH to 5, and adding octenyltrimethoxysilane, and stirring at 400 rpm for 2 h to obtain the modified liquid.

4. The method of producing a battery foil according to claim 3, wherein In the preparation process of the carbon black suspension, ethylene glycol diacrylate and dibenzoyl peroxide are added into n-propanol, and the stirring speed is 460 rpm and the stirring time is 4 min, the hydrophilic modified carbon black is added multiple times under continuous stirring, after all the hydrophilic modified carbon black is added, the stirring speed is 650 rpm and the stirring time is 1 h, deionized water is added, and the stirring speed is 530 rpm and the stirring time is 10 min to obtain the carbon black suspension.

5. The method of producing a battery foil according to claim 4, wherein 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 soaked in the flowing carbon black suspension for 1 h to obtain the composite aluminum foil.

6. The method of producing a battery foil according to claim 5, wherein In the step S3, the composite aluminum foil is placed in an inert atmosphere at 40℃, and the temperature is raised to 75℃ under normal pressure for 2 h, the temperature is first adjusted to 58℃, then 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 restored to normal, the temperature of the inert atmosphere is reduced to room temperature, and the battery foil is obtained.

7. The method of producing a battery foil according to claim 6, wherein The hydrophilic modified carbon black is prepared by adding carbon black into a nitric acid solution, ultrasonic dispersion for 10 min, stirring at 300 rpm for 4 h, deionized water washing, and drying to obtain the hydrophilic modified carbon black.

8. The method of producing a battery foil according to claim 7, wherein In the preparation process of the hydrophilic modified carbon black, the carbon black washed with deionized water is placed in a-50℃ environment for freeze-drying for 24 h.

9. The method of producing a battery foil according to claim 8, wherein The concentration of the nitric acid solution is 40-50 wt%.

10. A battery foil prepared by the method of any one of claims 1 to 9, characterized in that, The aluminum foil is sequentially immersed in a modification liquid and a carbon black suspension, and then dried to obtain the product; the chemical composition of the aluminum foil is as follows in terms of mass percentage: silicon 0.18-0.20%, iron 0.13-0.14%, copper ≤0.02%, manganese ≤0.01%, titanium ≤0.03%, and the balance being aluminum; the modification liquid comprises the following raw materials in terms of mass: 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 terms of mass: 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 terms of mass: carbon black 5-6 parts and nitric acid solution 75-90 parts.

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