Composite aluminum foil and preparation method thereof, positive pole piece and battery

Abstract

The invention provides a composite aluminum foil and a preparation method thereof, a positive pole piece and a battery. The composite aluminum foil comprises a base film, first aluminum layers covering the two surfaces of the base film and second aluminum layers covering the surfaces of the first aluminum layers, and the sheet resistance of the first aluminum layers is smaller than 45 m omega / square; the second aluminum layer has a microporous structure, the average pore size of the microporous structure is 0.5-10 [mu] m, and the pore density is 500-1000 / m < 2 >; and the surface of the second aluminum layer is also provided with an aluminum oxide film. The composite aluminum foil provided by the invention has excellent needling performance, the needling passing rate can be effectively improved, and the risk of short circuit in a battery cell is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery cell technology, and relates to a composite aluminum foil and its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] With the rapid development of the new energy battery industry, battery safety has become a focus of industry attention. Composite foil, as a crucial component of battery structure, directly impacts battery safety and stability. Currently, composite foil is primarily prepared through vapor deposition, a process that forms a composite structure with specific functions by depositing a metal layer onto the substrate surface.

[0003] In existing technologies, vapor deposition processes have been widely applied in various fields. For example, some literature discloses an LED vapor deposition process that includes selecting a substrate, performing a first vapor deposition using tin as the plating layer, applying a reinforcing agent and baking it before performing a second vapor deposition, ultimately improving the brightness of the LED light and the conductivity of the panel. Other literature introduces a metallized thin film for rail transit locomotives and its processing technology, which involves first vapor deposition of an aluminum plating layer on an insulating base film, followed by a second vapor deposition to form a tin plating layer. This effectively prevents the aluminum plating layer from oxidizing and improves the working stability of the capacitor under AC high voltage and high current conditions.

[0004] In the field of thin film preparation, some literature discloses a method for preparing a high-strength, reverse-side aluminum-coated VMPET film. This method involves strictly controlling process parameters to perform aluminum deposition on the non-corona-electrode surface of the PET base film, and employing plasma treatment technology during the aluminum deposition process. Other literature provides a method for preparing a conductive thin film, which includes a first vapor deposition to form a first metal layer on the film substrate surface, followed by surface roughening treatment and a second vapor deposition to form a second metal layer, effectively avoiding wrinkling and perforation problems in the film.

[0005] In the field of capacitor films, some literature describes a method for preparing a thickened all-aluminum metallized capacitor film. This method involves depositing an aluminum film on the surface of the dielectric layer with a sheet resistance controlled at 6-12 Ω / □, and then depositing a thickened aluminum or zinc-aluminum reinforcing layer on the aluminum film with a sheet resistance controlled at 1-4 Ω / □. By utilizing the characteristic that aluminum is easily oxidized in air to form dense aluminum oxide, the oxidation resistance of the metallized film is improved.

[0006] Although existing technologies have conducted some research on composite foils and their preparation methods, there are still significant shortcomings in their application to the new energy battery industry. Firstly, existing composite foils offer limited improvement in needle penetration resistance and cannot effectively address the mechanical damage that batteries may encounter during use. Secondly, the bonding strength between the composite foil and the battery pack is insufficient, making it prone to separation during battery operation and leading to a decline in battery performance. These problems severely limit the role of composite foils in improving battery safety, making it difficult to effectively reduce the risk of short circuits within the cell and failing to meet the increasingly stringent safety requirements of new energy batteries. Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Given the above situation, it is necessary to address the problems that existing composite foils have limited effectiveness in improving needle punching, poor adhesion to the material area, and difficulty in effectively reducing the risk of short circuits and thermal runaway within the battery cell.

[0009] Solution for solving the problem

[0010] The present invention first provides a composite aluminum foil, wherein the composite aluminum foil includes a base film, a first aluminum layer covering two surfaces of the base film, and a second aluminum layer covering the surface of the first aluminum layer.

[0011] Wherein, the sheet resistance of the first aluminum layer is <45mΩ / □;

[0012] The second aluminum layer has a microporous structure with an average pore size of 0.5~10μm and a pore density of 500~1000 pores / m³. 2 ;

[0013] The surface of the second aluminum layer also has an aluminum oxide film.

[0014] According to the composite aluminum foil of the present invention, the thickness of the first aluminum layer is 0.2~2μm; and / or,

[0015] The thickness of the second aluminum layer is 0.1~1μm; and / or,

[0016] The thickness ratio of the first aluminum layer to the second aluminum layer is 9:1 to 1:1.

[0017] According to the composite aluminum foil of the present invention, the thickness of the alumina film is 5~20 nm.

[0018] According to the composite aluminum foil of the present invention, the base film is at least one selected from PI, PET, and PP; and / or,

[0019] The thickness of the base film is 3~10μm.

[0020] This invention also provides a method for preparing composite aluminum foil according to the present invention, comprising the following steps:

[0021] S1: Aluminum plating is performed on both surfaces of the base film to form the first aluminum layer;

[0022] S2: A second aluminum layer is formed by secondary aluminum plating on the surface of the first aluminum layer, resulting in a foil with secondary aluminum plating;

[0023] S3: The aluminum-plated foil is etched with a salt solution to obtain an etched foil.

[0024] S4: The etched foil is placed in an acid solution for passivation to form an aluminum oxide film on the surface of the second aluminum layer, thereby obtaining a composite aluminum foil.

[0025] According to the preparation method of the present invention, the purity of the raw aluminum used in the primary aluminum plating is 99.999% or higher; and / or,

[0026] The purity of the aluminum used in the secondary aluminum plating is 99.0~99.9%.

[0027] According to the preparation method of the present invention, the methods for primary aluminum plating and secondary aluminum plating include vapor deposition and / or magnetron sputtering.

[0028] According to the preparation method of the present invention, the salt solution includes at least one selected from NaCl solution, BaCl2 solution, CaCl2 solution, NH4Cl solution, CuCl2 solution, and FeCl3 solution, and the concentration of the salt solution is 0.5~3 mol / L; and / or,

[0029] The salt solution corrosion treatment time is 2~12 hours.

[0030] According to the preparation method of the present invention, the acid solution includes at least one selected from hydrochloric acid solution, nitric acid solution, boric acid solution, and sulfuric acid solution, and the concentration of the acid solution is 0.05~0.5 mol / L; and / or,

[0031] The temperature of the acid solution is 25~90℃; and / or,

[0032] The passivation is performed under the condition of applying a voltage of 200~500V for 1~20min.

[0033] According to the preparation method of the present invention, the preparation method further includes a washing step, wherein the washing is performed at room temperature for 1 to 10 minutes.

[0034] The present invention also provides a positive electrode sheet with improved needle penetration performance, comprising a composite aluminum foil according to the present invention and a positive active material layer coated on the composite aluminum foil; the needle penetration rate of the positive electrode sheet is more than 50%.

[0035] Furthermore, the present invention also provides a battery comprising a positive electrode sheet according to the present invention.

[0036] The effects of the invention

[0037] 1. The composite aluminum foil preparation method provided by the present invention adopts a combination of secondary aluminum plating, salt solution corrosion and acid solution stepwise anodizing treatment, which makes the prepared composite aluminum foil have excellent needle punching performance and can effectively improve the needle punching pass rate. Compared with the traditional method, the needle punching safety performance is improved by nearly 3 times, which significantly reduces the risk of short circuit in the battery cell. At the same time, the alumina film structure generated on the surface of the composite aluminum foil through passivation treatment significantly enhances the bonding force of the positive electrode material pre-composite aluminum foil, solving the problem of poor bonding force between the composite aluminum foil and the material area.

[0038] 2. The preparation method provided by this invention further improves the performance stability of composite aluminum foil and the safety of batteries by controlling the purity of raw materials during multiple aluminum plating processes and conducting in-depth research on surface post-treatment processes.

[0039] 3. The composite aluminum foil provided by this invention can effectively reduce the risk of battery thermal runaway and improve the safety of new energy batteries. Attached Figure Description

[0040] Figure 1 A schematic diagram of the composite aluminum foil of the present invention is shown;

[0041] Figure 2 A schematic flowchart of the preparation method of the composite aluminum foil of the present invention is shown.

[0042] Explanation of icon numbers:

[0043] 1. Base film; 2. First aluminum layer; 3. Second aluminum layer. Detailed Implementation

[0044] The present invention will now be described in detail. The descriptions of the technical features described below are based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0045] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0046] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0047] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0048] In this specification, the terms "optional" or "optional" are used to indicate the use or omission of certain substances, components, procedures, application conditions, etc.

[0049] In this instruction manual, "normal temperature" or "room temperature" refers to an indoor ambient temperature of "23±2℃".

[0050] All unit names used in this manual are international standard unit names, and unless otherwise stated, the "%" indicates weight or mass percentage.

[0051] In this specification, the terms "substantially" and "essentially" are used to indicate that the standard deviation from the theoretical model, theoretical data, or target data is within a range of 2%, preferably 1%, and more preferably 0.8%.

[0052] In this specification, the terms “comprising” and / or “including” are used to indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0054] <First Aspect>

[0055] A first aspect of the present invention provides a composite aluminum foil, wherein the composite aluminum foil includes a base film, a first aluminum layer covering two surfaces of the base film, and a second aluminum layer covering the surface of the first aluminum layer.

[0056] Wherein, the sheet resistance of the first aluminum layer is <45mΩ / □;

[0057] The second aluminum layer has a microporous structure with an average pore size of 0.5~10μm and a pore density of 500~1000 pores / m³. 2 ;

[0058] The surface of the second aluminum layer also has an aluminum oxide film.

[0059] The layer structure of the composite aluminum foil of the present invention can be found in [reference needed]. Figure 1As shown, 1 is the base film, 2 is the first aluminum layer, and 3 is the second aluminum layer.

[0060] (Base membrane)

[0061] The base film of this invention is primarily provided as a carrier for the aluminum layer.

[0062] The present invention does not specifically limit the type of the base film, and it can be a polymer resin base film commonly used in the art, such as at least one of PI (polyimide), PET (polyethylene terephthalate), and PP (polypropylene). By using a polymer resin as the base film, since the insulating resin layer is non-conductive and has a high resistance, the short-circuit resistance of the battery under abnormal conditions can be increased, thereby significantly reducing the short-circuit current and greatly reducing the heat generated during short circuits, thus improving the battery safety performance.

[0063] In some specific implementations, the thickness of the base film can be 3~10μm, preferably 4.5~8μm, for example, it can be 3.5μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc.

[0064] (First aluminum layer)

[0065] The first aluminum layer of the present invention is a dense layer. By forming a dense first aluminum layer on the surface of the base film, the corrosion of the base film by the electrolyte caused by phenomena such as pinholes can be prevented, as well as the possible peeling between the base film and the aluminum coating.

[0066] The sheet resistance of the first aluminum layer of the present invention is <45mΩ / □, for example, it can be 40mΩ / □, 35mΩ / □, 30mΩ / □, 25mΩ / □, 20mΩ / □, 18mΩ / □, 15mΩ / □, 12mΩ / □, 10mΩ / □, 5mΩ / □, etc.

[0067] In some specific implementations, the thickness of the first aluminum layer can be 0.2~2μm, for example, it can be 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, etc.

[0068] (Second aluminum layer)

[0069] The second aluminum layer of the present invention is a microporous layer with a microporous structure. Due to the presence of micropores, it can break more quickly during the needle punching process, and the probability of generating aluminum burrs is lower. It also forms point short circuits faster and with a higher probability, thereby effectively improving the needle punching performance of the composite aluminum foil, facilitating rapid breakage during the needle punching process, and addressing mechanical damage that the battery may encounter during use.

[0070] In this invention, the average pore size of the microporous structure is 0.5~10μm, for example, it can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc.; the pore density is 500~1000 pores / m². 2 For example, it can be 550 per m 2 600 pieces / m 2 650 pieces / m 2 700 pieces / m 2 750 pieces / m 2 800 pieces / m 2 850 pieces / m 2 900 pieces / m 2 950 pieces / m 2 By controlling the microporous structure of the second aluminum layer within the aforementioned range, the needle-punching performance of the composite aluminum foil can be effectively improved.

[0071] In some specific implementations, the thickness of the second aluminum layer can be 0.1~1μm, for example, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, etc. By forming a thin aluminum layer on the substrate surface, due to the thinness of the conductive layers (first aluminum layer and second aluminum layer), the local conductive network is interrupted under abnormal conditions such as nail penetration, which can prevent large-area internal short circuits in the electrochemical device. This effectively confines the damage to the electrochemical device caused by nail penetration to the puncture site, forming only a "point break" that does not affect the normal operation of the electrochemical device, thereby improving battery safety.

[0072] In some specific implementation schemes, on the one hand, in order to maintain the density of the first aluminum layer formed by high-purity aluminum with a purity of 99.999% or higher, the first aluminum layer cannot be too thin; on the other hand, in order to break more quickly during the needle punching process, the thickness of the second aluminum layer with a microporous structure formed by aluminum with a purity of 99.0~99.9% must be moderate. Therefore, the thickness ratio of the first aluminum layer to the second aluminum layer can be 9:1 to 1:1, for example, 8:1, 6:1, 5:1, 4:1, 2:1, etc.

[0073] Furthermore, the surface of the second aluminum layer of the present invention also has an aluminum oxide film. The aluminum oxide film can significantly enhance the adhesion between the positive electrode coating and the composite aluminum foil. In addition, the aluminum oxide film structure can also improve the corrosion resistance of the foil in the electrolyte and the specific capacity of the battery.

[0074] In some specific implementations, the thickness of the alumina film can be 5~20nm, for example, 8nm, 10nm, 12nm, 15nm, 18nm, etc.

[0075] The composite aluminum foil of the present invention has excellent needle-punching performance, which can effectively improve the needle-punching pass rate. Compared with the traditional method, the needle-punching safety performance is improved by nearly 3 times, which greatly reduces the risk of short circuit and thermal runaway in the cell and improves the safety of new energy batteries.

[0076] <Second aspect>

[0077] A second aspect of the present invention provides a method for preparing composite aluminum foil, comprising the following steps:

[0078] S1: Aluminum plating is performed on both surfaces of the base film to form the first aluminum layer;

[0079] S2: A second aluminum layer is formed by secondary aluminum plating on the surface of the first aluminum layer, resulting in a foil with secondary aluminum plating;

[0080] S3: The aluminum-plated foil is etched with a salt solution to obtain an etched foil.

[0081] S4: The etched foil is placed in an acid solution for passivation to form an aluminum oxide film on the surface of the second aluminum layer, thereby obtaining a composite aluminum foil.

[0082] The type and specifications of the base film, as well as the specifications of the first aluminum layer and the second aluminum layer, are the same as those described in the first aspect, and will not be repeated here.

[0083] The present invention does not particularly limit the method used for aluminum plating, and commonly used aluminum plating methods in the art can be used, such as vapor deposition and / or magnetron sputtering, wherein vapor deposition is preferred.

[0084] In some more specific embodiments, when the aluminum plating method employs vapor deposition, the preparation flow chart can be found here. Figure 2 As shown.

[0085] (Step S1)

[0086] Step S1 of the present invention is a single aluminum plating step. Specifically, a first aluminum layer is formed by single aluminum plating on both surfaces of the base film.

[0087] In some specific implementations, the purity of the raw aluminum used in the primary aluminum plating can be above 99.999%. When high-purity raw aluminum is used in the primary aluminum plating, a dense first aluminum layer can be formed on the surface of the base film, preventing corrosion of the PET by the electrolyte due to pinholes and other phenomena, as well as possible peeling between the PET and the aluminum coating.

[0088] In some specific implementations, when aluminum is deposited by vapor deposition, the roller system in the equipment used for vapor deposition is at least one of sponge rollers, rubber rollers, or adsorption rollers; the vapor deposition method can be one of suspension coating, roller coating, direct coating, electron beam coating, resistive coating, etc.

[0089] In some specific implementations, an evaporation boat is used as the evaporation source during the vapor deposition process, and the film feeding speed of the thin film substrate is 10~500m / min, for example, it can be 50m / min, 100m / min, 150m / min, 200m / min, 250m / min, 300m / min, 350m / min, 400m / min, 450m / min, etc.; the wire feeding speed of the evaporation boat is 100~1000mm / s, for example, it can be 200mm / s, 300mm / s, 400mm / s, 500mm / s, 600mm / s, 700mm / s, 800mm / s, 900mm / s, etc.

[0090] (Step S2)

[0091] Step S2 of the present invention is a secondary aluminum plating step. Specifically, a second aluminum layer is formed by secondary aluminum plating on the surface of the first aluminum layer to obtain a secondary aluminum-plated foil.

[0092] In some specific implementation schemes, the purity of the raw aluminum used for secondary aluminum plating can be 99.0~99.9%, for example, 99.2%, 99.5%, 99.6%, 99.7%, 99.8%, etc. When the purity of the raw aluminum is 99.0~99.9%, impurity particles are present. The particle size of the impurity particles is usually between submicron and micron. The purity of raw aluminum, such as aluminum wire, and its corresponding impurities are shown in Table 1. Using raw aluminum containing impurities for secondary aluminum plating can form a second aluminum layer containing impurities, which serves as a prerequisite for the next step of chemical etching to form micropores.

[0093] Table 1. Aluminum wire purity grades and corresponding impurities

[0094]

[0095] This invention employs a multi-stage aluminum plating process, and strictly controls the purity of different raw aluminum materials during each plating stage, which lays the foundation for the formation of micropores.

[0096] (Step S3)

[0097] Step S3 of this invention is an etching process. Specifically, the aluminum-plated foil is etched using a salt solution to obtain an etched foil. Through etching, a microporous structure can be formed on the second aluminum layer. Due to the presence of micropores, it can break more quickly during needle punching, and the probability of aluminum burrs is lower. Point short circuits are formed faster and more frequently, thus effectively improving the needle punching performance of the composite aluminum foil, facilitating rapid breakage during needle punching, and addressing potential mechanical damage to the battery during use.

[0098] In some specific embodiments, the salt solution may include at least one of NaCl solution, BaCl2 solution, CaCl2 solution, NH4Cl solution, CuCl2 solution, FeCl3 solution, etc.; the concentration of the salt solution may be 0.5~3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, etc.

[0099] In some specific implementations, the salt solution corrosion treatment time is 2 to 12 hours, for example, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, etc.

[0100] (Step S4)

[0101] Step S4 of this invention is a passivation process. Specifically, the etched foil is placed in an acid solution for passivation to obtain a passivated foil. Passivation generates an alumina film structure on the surface of the composite aluminum foil, which significantly enhances the adhesion between the positive electrode coating and the composite aluminum foil. In addition, the alumina film structure can also improve the corrosion resistance of the foil in the electrolyte and the specific capacity of the battery.

[0102] In some specific embodiments, the acid solution may include at least one of hydrochloric acid solution, nitric acid solution, boric acid solution, and sulfuric acid solution; the concentration of the acid solution may be 0.05~0.5 mol / L, for example, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, etc.

[0103] In some specific implementations, the temperature of the acid solution is 25~90℃, for example, it can be 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, etc.

[0104] In some specific implementations, the passivation is performed under the condition of applying a voltage, which can be 200~500V, for example, 250V, 300V, 350V, 400V, 450V, etc.; the voltage application time is 1~20min, for example, 5min, 10min, 15min, etc.

[0105] (Other steps)

[0106] The preparation method of the present invention may further include a post-processing step, such as washing. The washing step can remove acidic substances from the surface of the composite aluminum foil.

[0107] In some specific implementations, the washing process can be carried out at room temperature for 1 to 10 minutes, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, etc.

[0108] In some specific embodiments, the washing is performed using solvents such as N-methylpyrrolidone (NMP).

[0109] This invention employs a combination of secondary aluminum plating, salt solution corrosion, and stepwise acid solution anodizing, resulting in composite aluminum foil with excellent needle-punching performance. This effectively improves the needle-punching pass rate and, compared to traditional methods, enhances needle-punching safety performance by nearly three times, significantly reducing the risk of short circuits within the battery cell.

[0110] <Third aspect>

[0111] A third aspect of the present invention provides a positive electrode sheet for improving needle penetration rate, comprising a composite aluminum foil as described in the first aspect and a positive active material layer coated on the composite aluminum foil.

[0112] The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0113] The present invention does not particularly limit the types of positive electrode active material, conductive agent and binder, and commonly used positive electrode active material, conductive agent and binder in the art can be used.

[0114] In some specific implementations, the active material layer includes a positive electrode active material, a conductive agent SP (conductive carbon black), a binder PVDF (polyvinylidene fluoride), and carbon nanotubes (CNTs), used in a mass ratio of 96:1:2:1.

[0115] The needle penetration rate of the positive electrode sheet of the present invention is 50% or more, preferably 70% or more, more preferably 80% or more, for example, it can be 55%, 60%, 65%, 75%, 85%, etc.

[0116] <Fourth Aspect>

[0117] A fourth aspect of the present invention provides a battery comprising a positive electrode as described in the third aspect of the present invention.

[0118] Example

[0119] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0120] Comparative Example 1

[0121] Positive electrode preparation: A positive electrode active material slurry is uniformly coated onto the surface of a 12μm ordinary aluminum foil. The positive electrode active material slurry includes Ni positive electrode active material in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0122] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0123] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0124] Comparative Example 2

[0125] Preparation of composite aluminum foil:

[0126] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 1μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 37mΩ / □.

[0127] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0128] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0129] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0130] Comparative Example 3

[0131] Preparation of composite aluminum foil:

[0132] S1: 99.0% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 1μm. An evaporation boat is used as the evaporation source during the evaporation process. The film substrate feed speed is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance coating. The sheet resistance of the first aluminum layer is approximately 48mΩ / □.

[0133] S2: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 10 μm and a pore density of 2000 pcs / m³. 2 .

[0134] S3: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0135] S4: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0136] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0137] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0138] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0139] Example 1

[0140] Preparation of composite aluminum foil:

[0141] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feed speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 39mΩ / □.

[0142] S2: Aluminum wire with 99.0% purity is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0143] S3: The aluminum foil after secondary vapor deposition is etched in a 1 mol / L NaCl solution for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 1 μm and a pore density of 1000 pcs / m³. 2 .

[0144] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0145] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0146] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0147] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0148] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0149] Example 2

[0150] Preparation of composite aluminum foil:

[0151] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 8μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance coating. The sheet resistance of the first aluminum layer is approximately 37mΩ / □.

[0152] S2: Aluminum wire with 99.0% purity is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0153] S3: The aluminum foil after secondary vapor deposition is etched in a 1 mol / L NaCl solution for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 1 μm and a pore density of 1000 pcs / m³. 2 .

[0154] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0155] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0156] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0157] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0158] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0159] Example 3

[0160] Preparation of composite aluminum foil:

[0161] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 4.5 μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8 μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50 m / min, and the wire feed speed of the evaporation boat is 500 mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 43 mΩ / □.

[0162] S2: Aluminum wire with 99.0% purity is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0163] S3: The aluminum foil after secondary vapor deposition is etched in a 1 mol / L NaCl solution for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 1 μm and a pore density of 1000 pcs / m³. 2 .

[0164] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0165] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0166] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0167] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0168] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0169] Example 4

[0170] Preparation of composite aluminum foil:

[0171] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.7μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feed speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 38mΩ / □.

[0172] S2: 99.0% pure aluminum wire is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in the vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.3 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 7:3. The evaporation boat is also used as the evaporation source in the secondary vapor deposition process, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0173] S3: The aluminum foil after secondary vapor deposition is etched in a 1 mol / L NaCl solution for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 1 μm and a pore density of 1000 pcs / m³. 2 .

[0174] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0175] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0176] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0177] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0178] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0179] Example 5

[0180] Preparation of composite aluminum foil:

[0181] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.6μm. An evaporation boat is used as the evaporation source during the evaporation process. The film substrate feed speed is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 39mΩ / □.

[0182] S2: 99.0% pure aluminum wire is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in the vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.4 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 6:4. The evaporation boat is also used as the evaporation source in the secondary vapor deposition process, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0183] S3: The aluminum foil after secondary vapor deposition is etched in a 1 mol / L NaCl solution for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 1 μm and a pore density of 1000 pcs / m³. 2 .

[0184] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0185] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0186] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0187] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0188] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0189] Example 6

[0190] Preparation of composite aluminum foil:

[0191] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film substrate feed speed is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 39mΩ / □.

[0192] S2: 99.5% pure aluminum wire is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0193] S3: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 800 nm and a pore density of 800 pcs / m³. 2 .

[0194] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0195] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0196] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0197] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0198] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0199] Example 7

[0200] Preparation of composite aluminum foil:

[0201] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film substrate feed speed is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 39mΩ / □.

[0202] S2: 99.7% pure aluminum wire is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0203] S3: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 650 nm and a pore density of 700 pcs / m³. 2 .

[0204] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0205] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0206] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0207] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0208] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0209] Example 8

[0210] Preparation of composite aluminum foil:

[0211] S1: 99.999% pure aluminum wire is selected as the raw material, and PET is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film substrate feed speed is 50m / min, and the wire feeding speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 39mΩ / □.

[0212] S2: 99.9% pure aluminum wire is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0213] S3: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 500 nm and a pore density of 600 pcs / m³. 2 .

[0214] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0215] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0216] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0217] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0218] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0219] Example 9

[0220] Preparation of composite aluminum foil:

[0221] S1: 99.999% pure aluminum wire is selected as the raw material, and PP is used as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feed speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 47mΩ / □.

[0222] S2: Aluminum wire with 99.0% purity is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0223] S3: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 500 nm and a pore density of 600 pcs / m³. 2 .

[0224] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0225] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0226] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0227] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0228] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0229] Example 10

[0230] Preparation of composite aluminum foil:

[0231] S1: 99.999% pure aluminum wire is selected as the raw material, and PI is selected as the base film with a thickness of 6μm. The first aluminum layer is formed by a single vapor deposition process in an evaporation equipment. The thickness of the first aluminum layer is controlled to be 0.8μm. An evaporation boat is used as the evaporation source during the evaporation process. The film feed speed of the substrate is 50m / min, and the wire feed speed of the evaporation boat is 500mm / s. The roller system in the evaporation equipment is made of rubber rollers. The evaporation method is resistance deposition. The sheet resistance of the first aluminum layer is approximately 37mΩ / □.

[0232] S2: Aluminum wire with 99.0% purity is used as raw material, and a second aluminum layer is formed through secondary vapor deposition in a vapor deposition equipment. The thickness of the second aluminum layer is controlled at 0.2 μm. The ratio of the thickness of the first aluminum layer to the thickness of the second aluminum layer is 4:1. In the secondary vapor deposition process, an evaporation boat is used as the evaporation source, and the film feed speed of the thin film substrate and the wire feeding speed of the evaporation boat are the same as in the primary vapor deposition. The roller system and vapor deposition method in the secondary vapor deposition equipment are the same as in the primary vapor deposition.

[0233] S3: The aluminum foil after secondary vapor deposition is placed in a 1 mol / L NaCl solution for etching treatment for 8 hours. This gives the second aluminum layer a microporous structure with an average micropore size of 500 nm and a pore density of 600 pcs / m³. 2 .

[0234] S4: The etched aluminum foil is placed in a 0.5 mol / L boric acid solution at 60℃, and the aluminum surface is passivated under a voltage of 200V for 5 minutes. An aluminum oxide film with a thickness of 20 nm is formed on the surface of the second aluminum layer.

[0235] S5: Wash the passivated composite aluminum foil with NMP at room temperature for 5 minutes.

[0236] Positive electrode preparation: A positive electrode active material slurry is uniformly coated on the surface of a composite aluminum foil, wherein the positive electrode active material slurry includes positive electrode active material Ni in a mass ratio of 96:1:2:1. 0.8 Co 0.1 Mn 0.1 The positive electrode slurry contains conductive agent SP, binder PVDF and carbon nanotubes (CNTs) and solvent NMP, with a solid content of approximately 75 wt%.

[0237] Negative electrode preparation: The negative electrode active material slurry is uniformly coated on the surface of a 6μm ordinary copper foil. The negative electrode active material slurry includes graphite + SiC, conductive agent SP, binder PVDF and carbon nanotubes CNTs in a mass ratio of 94:2:2:2, and deionized water as a solvent. The solid content of the negative electrode slurry is about 45wt%.

[0238] Cell assembly and testing: The positive and negative electrode plates are stacked to form 30 10Ah soft-pack cells for nail penetration testing.

[0239] Performance testing

[0240] 1. The battery cells obtained in the examples and comparative examples were subjected to needle penetration tests according to the new national standard GB38031-2020, using 3mm tungsten steel needles with a 45° tip angle and a needle penetration speed of 1mm / s. The results are shown in Table 2.

[0241] Table 2. Needle penetration performance test results of the battery cells obtained in the examples and comparative examples.

[0242]

[0243] As can be seen from Table 1, the composite aluminum foil cells obtained in Examples 1-10 of the present invention have a needle penetration performance that is more than 3 times higher than that of the conventional aluminum foil cells in Comparative Example 1. They have excellent needle penetration performance, which greatly reduces the risk of short circuits in the cells and improves the safety of new energy batteries.

[0244] As can be seen from Examples 1-3, the needle punching pass rate can be improved with the increase of substrate thickness; as can be seen from Examples 1, 4-5, the needle punching pass rate is improved with the increase of the thickness ratio of the second aluminum layer and the increase of the electrode porosity, indicating that the pore structure can effectively improve the needle punching performance of aluminum foil; as can be seen from Examples 6-8, the needle punching pass rate decreases with the increase of the purity of the second aluminum layer raw material, because the increase of purity reduces the number of pores, which is not conducive to the effective improvement of needle punching performance, further proving that the pore structure has a significant improving effect on needle punching performance; as can be seen from Examples 9-10, aluminum foil with excellent needle punching performance can be obtained when using various substrates.

[0245] The aluminum foil prepared in Comparative Example 2 does not contain a second aluminum layer with a microporous structure, making it difficult to effectively improve the needle penetration performance of the battery cell. It still has a high risk of short circuit, and the safety of the battery cannot be effectively guaranteed.

[0246] The aluminum foil prepared in Comparative Example 3 does not contain a first aluminum layer with a dense structure. Although the needle-punching performance is improved to some extent, the improvement effect is limited and safety risks still exist.

[0247] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0248] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A composite aluminum foil, characterized in that, The composite aluminum foil includes a base film, a first aluminum layer covering two surfaces of the base film, and a second aluminum layer covering the surface of the first aluminum layer. Wherein, the sheet resistance of the first aluminum layer is <45mΩ / □; The second aluminum layer has a microporous structure with an average pore size of 0.5~10μm and a pore density of 500~1000 pores / m³. 2 ; The surface of the second aluminum layer also has an aluminum oxide film.

2. The composite aluminum foil according to claim 1, characterized in that, The thickness of the first aluminum layer is 0.2~2μm; and / or, The thickness of the second aluminum layer is 0.1~1μm; and / or, The thickness ratio of the first aluminum layer to the second aluminum layer is 9:1 to 1:

1.

3. The composite aluminum foil according to claim 1 or 2, characterized in that, The thickness of the alumina film is 5~20nm.

4. The composite aluminum foil according to any one of claims 1 to 3, characterized in that, The base film is at least one of PI, PET, and PP; and / or, The thickness of the base film is 3~10μm.

5. A method for preparing composite aluminum foil according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Aluminum plating is performed on both surfaces of the base film to form the first aluminum layer; S2: A second aluminum layer is formed by secondary aluminum plating on the surface of the first aluminum layer, resulting in a foil with secondary aluminum plating; S3: The aluminum-plated foil is etched with a salt solution to obtain an etched foil. S4: The etched foil is placed in an acid solution for passivation to form an aluminum oxide film on the surface of the second aluminum layer, thereby obtaining a composite aluminum foil.

6. The preparation method according to claim 5, characterized in that, The purity of the aluminum used in a single metallization process is 99.999% or higher; and / or, The purity of the aluminum used in the secondary aluminum plating is 99.0~99.9%.

7. The preparation method according to claim 5 or 6, characterized in that, Methods for primary and secondary aluminum plating include vapor deposition and / or magnetron sputtering.

8. The preparation method according to any one of claims 5 to 7, characterized in that, The salt solution includes at least one selected from NaCl solution, BaCl2 solution, CaCl2 solution, NH4Cl solution, CuCl2 solution, and FeCl3 solution, and the concentration of the salt solution is 0.5~3 mol / L; and / or, The salt solution corrosion treatment time is 2~12 hours.

9. The preparation method according to any one of claims 5 to 8, characterized in that, The acid solution includes at least one selected from hydrochloric acid solution, nitric acid solution, boric acid solution, and sulfuric acid solution, and the concentration of the acid solution is 0.05~0.5 mol / L; and / or, The temperature of the acid solution is 25~90℃; and / or, The passivation is performed under the condition of applying a voltage of 200~500V for 1~20min.

10. The preparation method according to any one of claims 5 to 9, characterized in that, The preparation method further includes a washing step, wherein the washing is performed at room temperature for 1 to 10 minutes.

11. A positive electrode sheet for improving needle penetration performance, characterized in that, It includes the composite aluminum foil according to any one of claims 1 to 4 and the positive electrode active material layer coated on the composite aluminum foil; the needle penetration rate of the positive electrode sheet is more than 50%.

12. A battery, characterized in that, Including the positive electrode sheet according to claim 11.

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