Anodizing film forming process of battery cell aluminum shell and battery cell

Abstract

This invention provides an anodizing film formation process for aluminum battery cell shells and the battery cell itself, solving the problems of scratches, damage, bubbles, wrinkles, and other defects that easily occur during production, affecting not only appearance but also potentially damaging battery cell function. The film formation process includes the following steps: S1, degreasing; S2, neutralization; S3, room temperature hard anodizing; S4, sealing; S5, dust removal. This invention makes it possible to perform thick film anodizing at room temperature, taking into account not only the wear resistance, corrosion resistance, insulation, thermal stability, and high hardness of the oxide film, but also the superior flexibility of the oxide film compared to low-temperature hard anodizing films. Furthermore, the room temperature hard anodized aluminum film has passed various reliability tests for battery cell shells. This invention not only enables mass production of anodized films for aluminum battery cell shells but also improves upon the brittle and hard defects of thick anodized films on other aluminum materials. The room temperature hard anodizing method also offers advantages such as low processing energy consumption and high breakdown voltage resistance.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology and relates to a battery cell coating film, particularly an anodizing film formation process for an aluminum battery cell shell and the battery cell itself. Background Technology

[0002] Currently, the aluminum casings of new energy vehicle battery cells are primarily made of polypropylene or polyester to isolate individual cells and prevent them from affecting other cells due to various malfunctions. However, defects such as scratches, breakage, bubbles, and wrinkles are prone to occur during the production process, which not only affect the appearance but may also impair the product's functionality.

[0003] For example, Chinese patent literature has disclosed anodizing solution, battery casing, and their insulation protection method and application [Chinese Patent No.: 202111163688.1]. This invention relates to the field of battery technology, specifically to anodizing solution, battery casing, and their insulation protection method and application. The battery casing provided by this invention includes a casing body and a protective layer disposed on the surface of the casing body. The protective layer material is a composite material formed of alumina and polyaniline. The battery casing provided by this invention can greatly improve the insulation performance and corrosion resistance of the battery casing.

[0004] The above technical solution requires alumina as the protective layer, but also polyaniline as a composite material, so the protective performance of the composite film still needs to be improved. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing an anodizing film formation process for aluminum casings of battery cells and a battery cell itself. This process uses an electrolyte with a specific composition ratio to perform an electrochemical room-temperature hard anodizing process on the aluminum casing, resulting in the formation of a high-performance aluminum oxide film on its surface.

[0006] The objective of this invention can be achieved through the following technical solution: an anodizing film formation process for aluminum casing of battery cells, comprising the following steps:

[0007] S1. Place the aluminum casing of the battery cell in a degreasing tank and soak it in a degreasing and deionized aqueous solution. The degreasing agent removes the oil stains from the surface of the aluminum casing of the battery cell by dissolving, saponifying, wetting, penetrating and dispersing the dirt.

[0008] S2. Place the aluminum casing of the battery cell in a neutralization tank and immerse it in a neutralized deionized aqueous solution at 15-25°C, consisting of sulfuric acid content of 150-200 g / L and ferric nitrate content of 20-30 g / L, to remove the residual ash on the surface of the aluminum casing of the battery cell.

[0009] S3. Place the aluminum casing of the battery cell in an oxidation tank and immerse it in an aqueous deionized acid solution containing 100-200 g / L sulfuric acid, 10-30 g / L oxalic acid, 10-30 g / L citric acid, and 10-30 g / L tartaric acid at 20-30°C while passing an electric current through it, so that an aluminum oxide film is formed on the surface of the aluminum material under the action of oxidation at room temperature.

[0010] S4. Place the aluminum shell of the battery cell in a sealing tank and immerse it in a sealing deionized water solution containing 8-10 g / L nickel acetate, 1-3 g / L sodium benzenesulfonate, and 0.2-0.7 g / L sodium acetate at 93-97°C. The nickel acetate hydrolyzes and fills the oxide film pores. At the same time, the high temperature converts the amorphous alumina into trihydrated alumina, causing volume expansion to seal the oxide film pores.

[0011] S5. Place the aluminum casing of the battery cell in a dust removal tank and immerse it in a deionized water solution with a sulfuric acid content of 150-200 g / L at 15-25°C. The hydrogen ions in the deionized water solution neutralize the residual hydroxide ions on the aluminum casing of the battery cell.

[0012] In the above-mentioned anodizing film formation process of aluminum casing for battery cells, in step S1, the degreasing tank is specifically made of 304 stainless steel.

[0013] In the above-mentioned anodizing film formation process of aluminum battery cell casing, in step S1, the degreasing and deionized aqueous solution is composed of sodium carbonate with a content of 20-30 g / L, sodium silicate with a content of 20-30 g / L, sodium gluconate with a content of 10-20 g / L, and sodium dodecylbenzene sulfonate as a surfactant with a content of 1-2 g / L; the temperature of the degreasing and deionized aqueous solution is 50-60°C, and the immersion time of the aluminum battery cell casing in the degreasing and deionized aqueous solution is 1-5 minutes.

[0014] In the above-mentioned anodizing film formation process of aluminum battery cell shell, in step S2, the neutralization tank is specifically made of polypropylene; the aluminum battery cell shell is immersed in the neutralization deionized water solution for 1 to 3 minutes, utilizing the strong oxidizing properties of ferric ions to remove dust, whiten, and brighten the aluminum material without damaging it.

[0015] In the above-mentioned anodizing film formation process of aluminum casing of battery cell, in step S3, the oxidation tank is specifically made of polypropylene material, graphite plates are fixed on both sides of the oxidation tank, and a copper V-shaped seat is fixed on the top of the oxidation tank. The graphite plates and the copper V-shaped seat form a closed circuit under the action of an applied current.

[0016] In the above-mentioned anodic oxidation film formation process of aluminum battery cell shell, in step S3, the current density of the deionized aluminum oxide aqueous solution is 2-2.5 A / dm2, the immersion time of the aluminum battery cell shell in the deionized aluminum oxide aqueous solution is 60-120 minutes, and the thickness of the aluminum oxide film is 60-100 μm.

[0017] In the above-mentioned anodizing film formation process of aluminum battery cell shell, in step S4, the sealing tank is specifically made of 304 stainless steel; the aluminum battery cell shell is immersed in the sealing deionized high-temperature aqueous solution for 60-80 minutes; the alumina and inorganic salt ions combine with water to form a hydroxy inorganic acid salt to achieve the effect of sealing the membrane pores, while the amorphous alumina is converted into trihydrated alumina and expands in volume by about 30% to fill the micro membrane pores.

[0018] In the above-mentioned anodizing film formation process of aluminum battery cell casing, in step S5, the ash removal tank is specifically made of polypropylene material; the immersion time of the aluminum battery cell casing in the ash removal deionized water solution is 1 to 3 minutes.

[0019] A battery cell comprising an insulating film for the aluminum shell of the battery cell, produced by the anodizing film forming process described above.

[0020] Compared with existing technologies, the anodizing film formation process of the aluminum shell of this battery cell and the battery cell itself have the following advantages:

[0021] 1. This invention makes it possible to perform thick film oxidation at room temperature. It not only takes into account the wear resistance, corrosion resistance, insulation, thermal stability and high hardness of the oxide film, but also the flexibility of the oxide film far exceeds that of low temperature hard oxide film. In addition, the room temperature hard alumina film has passed various reliability tests of the aluminum shell of the battery cell.

[0022] 2. This invention can not only realize the mass production of aluminum shell oxidation film of battery cells, but also improve the defects of hard and brittle thick films of other aluminum materials.

[0023] 3. This invention uses room temperature hard anodizing, which also has the advantages of low processing energy consumption and high breakdown voltage resistance. Attached Figure Description

[0024] Figure 1 This is a flowchart of the anodizing film formation process for the aluminum casing of this battery cell. Detailed Implementation

[0025] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments.

[0026] Example 1

[0027] An anodizing film formation process for an aluminum casing of a battery cell includes the following steps:

[0028] S1. Place the aluminum casing of the battery cell in a degreasing tank, specifically a tank made of 304 stainless steel. Immerse the aluminum casing at 50-60℃ in a deionized aqueous solution containing 20-30 g / L sodium carbonate, 20-30 g / L sodium silicate, 10-20 g / L sodium gluconate, and 1-2 g / L sodium dodecylbenzene sulfonate (a surfactant) for 1-5 minutes. The degreasing agent utilizes its dissolving, saponifying, wetting, penetrating, and dispersing properties to remove oil from the surface of the aluminum casing. The chemical reaction between grease and alkali produces soap and glycerin.

[0029] S2. Place the aluminum casing of the battery cell in a neutralization tank, specifically a tank made of polypropylene. Immerse the aluminum casing in a neutralized deionized aqueous solution at 15-25℃ for 1-3 minutes, consisting of 150-200 g / L sulfuric acid and 20-30 g / L ferric nitrate. The hydrogen ions and ferric ions in the neutralized deionized aqueous solution neutralize residual hydroxide ions and ash on the aluminum casing. The strong oxidizing property of ferric ions removes ash, whitens, and brightens the aluminum without damaging it.

[0030] S3. Place the aluminum shell of the battery cell in the oxidation tank. The oxidation tank is made of polypropylene. Graphite plates are fixed on both sides of the oxidation tank, and a copper V-shaped seat is fixed on the top of the oxidation tank. The graphite plates and the copper V-shaped seat form a closed circuit under the action of an applied current.

[0031] The aluminum casing of the battery cell is immersed in an oxidizing deionized water solution containing 100-200 g / L sulfuric acid, 10-30 g / L oxalic acid, 10-30 g / L citric acid, and 10-30 g / L tartaric acid at 20-30℃ for 60-120 minutes, while a current density of 2-2.5 A / dm2 is passed through it, so that an aluminum oxide film with a thickness of 60-100 μm is formed on the surface of the aluminum material under the action of oxidation at room temperature.

[0032] Adding 10–30 g / L of oxalic acid utilizes its non-porous, dense inner layer and porous outer layer, as well as the low solubility of the solution in aluminum alloys and their oxide films, to obtain a thicker film with high density, good corrosion resistance, high hardness, strong oxidation resistance, high insulation voltage, and stable insulation performance.

[0033] Adding 10-30 g / L of citric acid mainly controls the acidity of the bath and increases the ion concentration in the bath to enhance the conductivity of the bath. At the same time, it acts as a complexing agent to capture metal ions generated during the anodizing process, preventing them from redepositing back onto the anode during the oxidation process, thereby ensuring the uniformity and tightness of the oxide film layer and enhancing the wear resistance, corrosion resistance and hardness of the oxide film.

[0034] Adding 10–30 g / L of tartaric acid utilizes its low solubility in aluminum alloy oxide films to obtain thicker films with low porosity, good uniformity, high hardness, strong corrosion resistance, and high insulation voltage.

[0035] S4. Place the aluminum casing of the battery cell in a sealing tank, specifically a tank made of 304 stainless steel. Immerse the aluminum casing at 93–97°C in a sealing deionized aqueous solution containing 8–10 g / L nickel acetate, 1–3 g / L sodium benzenesulfonate, and 0.2–0.7 g / L sodium acetate for 60–80 minutes. This process utilizes the combination of alumina and inorganic salt ions with water to form a hydroxyl inorganic acid salt, thereby sealing the membrane pores. Simultaneously, the amorphous alumina transforms into trihydrated alumina, expanding in volume by approximately 30% to fill the micropores.

[0036] Sodium benzenesulfonate can undergo ion exchange with the solution, thereby reducing the ion concentration in the sealing agent and lowering the viscosity; at the same time, sodium benzenesulfonate can also strongly bind with water molecules, improving the fluidity of the sealing solution.

[0037] S5. Place the aluminum casing of the battery cell in a dust removal tank, which is specifically made of polypropylene. Immerse the aluminum casing of the battery cell in a deionized water solution with a sulfuric acid content of 150-200 g / L at 15-25℃ for 1-3 minutes. The hydrogen ions in the deionized water solution neutralize the residual hydroxide ions on the aluminum casing of the battery cell.

[0038] The advantages of this room-temperature hard anodizing process compared to the low-temperature hard anodizing process are as follows:

[0039]

[0040] As shown in the table above, the present invention uses room temperature hard anodizing, which has advantages such as low processing energy consumption, high breakdown voltage resistance, and high flexibility of the finished oxide film.

[0041] Compared with existing technologies, the anodizing film formation process for the aluminum casing of this battery cell has the following advantages:

[0042] 1. This invention makes it possible to perform thick film oxidation at room temperature. It not only takes into account the wear resistance, corrosion resistance, insulation, thermal stability and high hardness of the oxide film, but also the flexibility of the oxide film far exceeds that of low temperature hard oxide film. In addition, the room temperature hard alumina film has passed various reliability tests of the aluminum shell of the battery cell.

[0043] 2. This invention can not only realize the mass production of aluminum shell oxidation film of battery cells, but also improve the defects of hard and brittle thick films of other aluminum materials.

[0044] 3. This invention uses room temperature hard anodizing, which also has the advantages of low processing energy consumption and high breakdown voltage resistance.

[0045] Example 2

[0046] Based on Embodiment 1, the difference in this embodiment is as follows:

[0047] A battery cell comprising an insulating film for the aluminum shell of the battery cell, produced by the anodizing film forming process described above.

[0048] The test results of the aluminum casing insulation film of the battery cell are shown in the table below:

[0049]

[0050] Compared with existing technologies, this battery cell has the following advantages:

[0051] 1. This invention makes it possible to perform thick film oxidation at room temperature. It not only takes into account the wear resistance, corrosion resistance, insulation, thermal stability and high hardness of the oxide film, but also the flexibility of the oxide film far exceeds that of low temperature hard oxide film. In addition, the room temperature hard alumina film has passed various reliability tests of the aluminum shell of the battery cell.

[0052] 2. This invention can not only realize the mass production of aluminum shell oxidation film of battery cells, but also improve the defects of hard and brittle thick films of other aluminum materials.

[0053] 3. This invention uses room temperature hard anodizing, which also has the advantages of low processing energy consumption and high breakdown voltage resistance.

[0054] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. An anodizing film formation process for aluminum casing of a battery cell, characterized in that, Includes the following steps: S1. Place the aluminum casing of the battery cell in a degreasing tank and soak it in a degreasing and deionized aqueous solution. Based on the chemical reaction between grease and alkali to produce soap and glycerin, the oil stains on the surface of the aluminum casing of the battery cell are removed. S2. Place the aluminum casing of the battery cell in a neutralization tank and immerse it in a neutralized deionized aqueous solution at 15-25°C, consisting of sulfuric acid content of 150-200 g / L and ferric nitrate content of 20-30 g / L, to remove the residual ash on the surface of the aluminum casing of the battery cell. S3. Place the aluminum casing of the battery cell in an oxidation tank and immerse it in an aqueous deionized acid solution containing 100-200 g / L sulfuric acid, 10-30 g / L oxalic acid, 10-30 g / L citric acid, and 10-30 g / L tartaric acid at 20-30°C while passing an electric current through it, so that an aluminum oxide film is formed on the surface of the aluminum material under the action of oxidation at room temperature. In step S3, the current density of the deionized aluminum oxide aqueous solution is 2 to 2.5 A / dm2, the immersion time of the aluminum shell of the battery cell in the deionized aluminum oxide aqueous solution is 60 to 120 minutes, and the thickness of the aluminum oxide film is 60 to 100 μm. S4. Place the aluminum shell of the battery cell in a sealing tank and immerse it in a sealing deionized water solution containing 8-10 g / L nickel acetate, 1-3 g / L sodium benzenesulfonate, and 0.2-0.7 g / L sodium acetate at 93-97°C. The nickel acetate hydrolyzes and fills the oxide film pores. At the same time, the high temperature converts the amorphous alumina into trihydrated alumina, causing volume expansion to seal the oxide film pores. S5. Place the aluminum casing of the battery cell in a dust removal tank and immerse it in a deionized water solution with a sulfuric acid content of 150-200 g / L at 15-25°C. The hydrogen ions in the deionized water solution neutralize the residual hydroxide ions on the aluminum casing of the battery cell.

2. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S1, the degreasing tank is specifically made of 304 stainless steel.

3. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S1, the degreased and deionized aqueous solution is composed of sodium carbonate (20-30 g / L), sodium silicate (20-30 g / L), sodium gluconate (10-20 g / L), and sodium dodecylbenzene sulfonate (1-2 g / L); the temperature of the degreased and deionized aqueous solution is 50-60°C, and the aluminum shell of the battery cell is immersed in the degreased and deionized aqueous solution for 1-5 minutes.

4. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S2, the neutralization tank is specifically made of polypropylene; the aluminum casing of the battery cell is immersed in the neutralization and deionization aqueous solution for 1 to 3 minutes.

5. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S3, the oxidation tank is specifically made of polypropylene, graphite plates are fixed on both sides of the oxidation tank, and a copper V-shaped seat is fixed on the top of the oxidation tank. The graphite plates and the copper V-shaped seat form a closed circuit under the action of an applied current.

6. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S4, the sealing tank is made of 304 stainless steel; the aluminum shell of the battery cell is immersed in the sealing deionized high-temperature aqueous solution for 60 to 80 minutes.

7. The anodizing film formation process for the aluminum casing of the battery cell as described in claim 1, characterized in that, In step S5, the ash removal tank is specifically made of polypropylene; the aluminum casing of the battery cell is immersed in the ash removal and deionization aqueous solution for 1 to 3 minutes.

8. A battery cell, characterized in that, Including the insulating film of the aluminum shell of the battery cell made by the anodizing film forming process of the aluminum shell of the battery cell as described in any one of claims 1 to 7.

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