A battery steel shell electroplating process

Abstract

This application specifically discloses a battery steel casing electroplating process. The battery steel casing electroplating process includes the following steps: S1, pre-cleaning the steel casing; S2, placing the pre-cleaned steel casing in a primary electroplating solution for a primary electroplating operation; the primary electroplating solution includes 280-300 g / L of nickel sulfate; the electroplating temperature in the primary electroplating operation is 40-45℃, and the current density is 40-60 mA / cm². 2 S3. After the first electroplating operation, a nickel-plated steel shell is obtained; S4. The nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation; the electroplating temperature in the secondary electroplating operation is 50-55℃, and the current density is 25-40mA / cm². 2 A nickel / titanium composite layer is formed on the surface of the nickel-plated steel shell to obtain a battery steel shell; wherein, the secondary electroplating solution is obtained by mixing the electroplating solution after the primary electroplating operation with an additive; the additive includes nano-titanium dioxide. This application has the advantages of improving the adhesion of the coating on the steel shell surface, corrosion resistance, and wear resistance.

Description

Technical Field

[0001] This application relates to the field of metal surface treatment technology, and in particular to an electroplating process for battery steel casings. Background Technology

[0002] With the booming development of industries such as portable communication devices, laptops, word processors, and power tools, the lithium battery industry has increasingly higher requirements for the performance of battery casing materials. The casing of a lithium-ion power battery is not merely a sealed container; it plays a crucial role in the battery's storage and safety performance. On one hand, the battery casing material must have excellent resistance to electrolyte corrosion, as this directly affects the lifespan of the lithium battery. On the other hand, when encountering complex and variable conditions such as impacts, bumps, and strong vibrations caused by high-speed braking, the steel casing must withstand short-term, high-impact loads. Therefore, the steel casing also plays a significant role in the safety performance of the lithium battery.

[0003] In existing technologies, battery structural components such as the steel casing and top cover are generally nickel-plated. However, nickel plating may lead to excessive porosity in the steel casing and top cover due to process issues, reducing corrosion resistance. Secondly, nickel plating generates significant internal stress, which may cause the plating to crack or peel off during the stamping process of the steel casing. All of these defects can lead to corrosion of the steel casing battery during use, resulting in leakage, short circuits, and other problems. Summary of the Invention

[0004] To address the problems in the prior art, this application provides a battery steel shell electroplating process.

[0005] In a first aspect, this application provides a battery steel casing electroplating process, employing the following technical solution:

[0006] A battery steel casing electroplating process includes the following steps:

[0007] S1, Pre-cleaning treatment of the steel shell;

[0008] S2, the pre-cleaned steel shell is placed in a primary electroplating solution for a primary electroplating operation; the primary electroplating solution includes 280-300 g / L of nickel sulfate; the electroplating temperature of the primary electroplating operation is 40-45℃, and the current density is 40-60 mA / cm². 2 After one electroplating operation, a nickel-plated steel shell is obtained;

[0009] S3, the nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation; the electroplating temperature during the secondary electroplating operation is 50-55℃, and the current density is 25-40mA / cm². 2 A nickel / titanium composite layer is formed on the surface of the nickel-plated steel shell to obtain a battery steel shell.

[0010] The secondary electroplating solution is obtained by mixing the electroplating solution after the primary electroplating operation with an additive; the additive includes nano-titanium dioxide.

[0011] The amount of the additive added to the electroplating solution after the electroplating operation is 10-13 g / L.

[0012] Preferably, the pre-cleaning process in S1 includes degreasing, primary water washing, acid washing, and secondary water washing.

[0013] Preferably, after the secondary electroplating operation in S3 is completed, a process including recycling, washing and drying is performed to obtain the battery steel shell.

[0014] This application achieves the formation of a nickel layer and a relatively dense nickel / titanium composite layer on the surface of a steel shell through two electroplating operations, by controlling the current density and electroplating temperature during both operations. On one hand, the nickel layer provides a good bond between the steel shell and the nickel / titanium composite layer, avoiding poor bonding between heterogeneous metals and significantly improving the adhesion stability of the nickel / titanium composite layer, thus contributing to improved wear resistance and corrosion resistance of the electroplated layer. On the other hand, the combination of the nickel layer and the nickel / titanium composite layer prevents excessive porosity on the plating surface or excessive internal stress that could cause cracking or peeling of the plating during stretching of the steel shell, significantly improving the stability, conductivity, and weldability of the plating on the steel shell surface, thereby meeting the requirements of high-performance, high-capacity batteries.

[0015] Preferably, the primary electroplating solution further includes 6-9 g / L of citric acid.

[0016] Preferably, the pH value of the primary electroplating solution is 5-6.

[0017] Preferably, the electroplating time in a single electroplating operation is 90-115 minutes.

[0018] Adjusting the composition, pH value, and time of the primary electroplating solution helps form a nickel layer of suitable thickness on the steel shell surface. This provides an adhesion substrate for subsequent nickel / titanium composite layer electroplating, significantly improving the adhesion stability of the nickel / titanium composite layer on the steel shell, thereby significantly improving the corrosion resistance and wear resistance of the steel shell surface layer. When the nickel layer is too thin, it is prone to peeling off during deep hole forming and grooving after pre-plating, leading to rusting of the steel shell. When the nickel layer is too thick, the pack solder joints are not firmly connected and are prone to detachment during the resistance welding of the entire battery cell module (cell pack).

[0019] Preferably, the pH of the secondary electroplating solution is 5-6.

[0020] Preferably, the electroplating time in the secondary electroplating operation is 30-50 minutes.

[0021] Adjusting the pH value of the secondary electroplating solution and the time during the secondary electroplating operation helps to form a nickel / titanium composite layer of suitable thickness on the surface of the steel shell. When the nickel / titanium composite layer is too thin, the distribution of TiO2 is insufficient, which leads to a decrease in the wear resistance and corrosion resistance of the coating, and the coating may also be torn during the steel shell forming process. When the nickel / titanium composite layer is too thick, it will affect the welding connection of the pack welding piece.

[0022] Preferably, the particle size of the additive is 30-50 nm.

[0023] By adjusting the particle size of the additives to meet the above range, it is helpful to form a dense, uniform nickel / titanium composite layer with low porosity, which helps to improve the film resistance and corrosion resistance of the coating on the steel shell surface.

[0024] Preferably, the additive added in S3 needs to undergo surface activation treatment, which includes the following steps:

[0025] Take a portion of the liquid from the electroplating solution after the electroplating operation is completed, mix it with the additive particles (solid-liquid ratio 10-15 g / L), add a surfactant (the amount of surfactant added is 1-1.5 g / L according to the solid-liquid ratio), and then disperse it by ultrasonication.

[0026] Preferably, the surfactant comprises sodium dodecylbenzenesulfonate.

[0027] By performing surface activation treatment on the additives, the dispersibility of the nano-additives in the electroplating solution after a single electroplating operation can be improved, avoiding agglomeration. This helps to improve the homogeneity of the nickel / titanium composite layer, thereby significantly reducing the porosity of the nickel / titanium composite layer and improving its corrosion resistance and wear resistance.

[0028] Secondly, this application provides a battery steel casing, which adopts the following technical solution:

[0029] A battery steel casing is prepared by the above-mentioned electroplating process.

[0030] Preferably, the battery steel shell includes a nickel / titanium composite layer, a nickel layer, and a steel shell substrate arranged sequentially from top to bottom.

[0031] Preferably, the thickness of the nickel / titanium composite layer is 1-2 μm, and the thickness of the nickel layer is 1-2 μm. Detailed Implementation

[0032] To better understand and implement this application, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of this application, and not all of them.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0034] Unless otherwise stated, all numerical values ​​for the amounts of expressed components, reaction conditions, etc., used in the specification and claims are to be understood as being modified by the term "about". Therefore, unless otherwise indicated, the numerical parameters set forth herein are approximate values ​​that can be varied to obtain the desired performance.

[0035] The word “and / or” as used in this article refers to one or all of the elements mentioned.

[0036] The terms "include" and "contain" as used in this article cover both cases where only the mentioned elements exist and cases where other unmentioned elements exist in addition to the mentioned elements.

[0037] All percentages in this application are weight percentages unless otherwise stated.

[0038] Unless otherwise stated, the terms “a,” “an,” “an,” and “the” as used in this specification are intended to include “at least one” or “one or more.” For example, “a component” refers to one or more components, and therefore more than one component may be considered and may be employed or used in the implementation of the described embodiments.

[0039] Example 1

[0040] A battery steel casing electroplating process includes the following steps:

[0041] S1, pre-cleaning treatment of the steel shell including degreasing, first water washing, pickling and second water washing processes;

[0042] S2, the pre-cleaned steel shell is placed in a primary electroplating solution for a primary electroplating operation. The primary electroplating solution comprises 300 g / L nickel sulfate and 8 g / L citric acid, with a pH of 5.5. The electroplating temperature during the primary operation is 40℃, and the current density is 50 mA / cm². 2 The electroplating time is 90 minutes, and after one electroplating operation, a nickel-plated steel shell (nickel layer thickness is 1.4 μm) is obtained.

[0043] S3, the nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation. The electroplating temperature during the secondary electroplating operation is 55℃, and the current density is 30mA / cm². 2 A nickel / titanium composite layer (with a thickness of 1.82 μm) is formed on the surface of the aforementioned nickel-plated steel shell.

[0044] The aforementioned secondary electroplating solution is obtained by mixing the electroplating solution after the first electroplating operation with an additive (nano titanium dioxide with a particle size of 50nm). The amount of additive added to the electroplating solution after the first electroplating operation is 12g / L.

[0045] S4, after the secondary electroplating operation is completed, processes including recycling, washing and drying are carried out to obtain the battery steel shell.

[0046] Example 2

[0047] A battery steel casing electroplating process includes the following steps:

[0048] S1, pre-cleaning treatment of the steel shell including degreasing, first water washing, pickling and second water washing processes;

[0049] S2, the pre-cleaned steel shell is placed in a primary electroplating solution for a primary electroplating operation. The primary electroplating solution comprises 280 g / L nickel sulfate and 6 g / L citric acid, with a pH of 6. The electroplating temperature during the primary operation is 45℃, and the current density is 60 mA / cm². 2 The electroplating time is 100 minutes, and after one electroplating operation, a nickel-plated steel shell (nickel layer thickness is 1.52 μm) is obtained.

[0050] S3, the nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation. The electroplating temperature during the secondary electroplating operation is 55℃, and the current density is 40mA / cm². 2 A nickel / titanium composite layer (with a thickness of 1.85 μm) is formed on the surface of the aforementioned nickel-plated steel shell.

[0051] The aforementioned secondary electroplating solution is obtained by mixing the electroplating solution after the first electroplating operation with an additive (nano titanium dioxide with a particle size of 60nm). The amount of additive added to the electroplating solution after the first electroplating operation is 14g / L.

[0052] S4, after the secondary electroplating operation is completed, processes including recycling, washing and drying are carried out to obtain the battery steel shell.

[0053] Example 3

[0054] A battery steel casing electroplating process includes the following steps:

[0055] S1, pre-cleaning treatment of the steel shell including degreasing, first water washing, pickling and second water washing processes;

[0056] S2, the pre-cleaned steel shell is placed in a primary electroplating solution for a primary electroplating operation. The primary electroplating solution comprises 300 g / L nickel sulfate and 9 g / L citric acid, with a pH of 5. The electroplating temperature during the primary operation is 40℃, and the current density is 40 mA / cm². 2 The electroplating time was 110 minutes, and after one electroplating operation, a nickel-plated steel shell (nickel layer thickness was 1.48 μm) was obtained.

[0057] S3, the nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation. The electroplating temperature during the secondary electroplating operation is 50℃, and the current density is 25mA / cm². 2 A nickel / titanium composite layer (with a thickness of 1.73 μm) is formed on the surface of the aforementioned nickel-plated steel shell.

[0058] The aforementioned secondary electroplating solution is obtained by mixing the electroplating solution after the first electroplating operation with an additive (nano titanium dioxide with a particle size of 40nm). The amount of additive added to the electroplating solution after the first electroplating operation is 10g / L.

[0059] S4, after the secondary electroplating operation is completed, processes including recycling, washing and drying are carried out to obtain the battery steel shell.

[0060] Example 4

[0061] The difference between this embodiment and Embodiment 1 is that the particle size of the additive is 15-20 nm; the other steps and parameter settings are consistent with Embodiment 1.

[0062] Example 5

[0063] The difference between this embodiment and Embodiment 1 is that the particle size of the additive is 60-70 nm; the other steps and parameter settings are consistent with Embodiment 1.

[0064] Example 6

[0065] The difference between this embodiment and Embodiment 1 is that the additive used in this embodiment has undergone surface activation treatment. The surface activation treatment steps are as follows:

[0066] Take a portion of the liquid from the electroplating solution after one electroplating operation and mix it with additive particles at a solid-liquid mixing ratio of 10 g / L. Then, add sodium dodecylbenzenesulfonate to the resulting solid-liquid mixture at a solid-liquid ratio of 1.3 g / L and ultrasonically disperse for 3 hours.

[0067] All other steps and parameter settings are consistent with those in Example 1.

[0068] Example 7

[0069] The difference between this embodiment and Embodiment 1 is that the electroplating time in one electroplating operation is 50 minutes; the other steps and parameter settings are consistent with Embodiment 1.

[0070] Example 8

[0071] The difference between this embodiment and Embodiment 1 is that the electroplating time in one electroplating operation is 150 minutes; the other steps and parameter settings are consistent with Embodiment 1.

[0072] Example 9

[0073] The difference between this embodiment and Embodiment 1 is that the electroplating time in the secondary electroplating operation is 20 minutes; the other steps and parameter settings are consistent with Embodiment 1.

[0074] Example 10

[0075] The difference between this embodiment and Embodiment 1 is that the electroplating time in the secondary electroplating operation is 70 minutes; the other steps and parameter settings are consistent with Embodiment 1.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that the surface of the steel shell is not electroplated.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that only one electroplating operation is performed on the pre-cleaned steel shell surface to form a nickel layer with a thickness of 1.4 μm; other steps and parameter settings are consistent with Example 1.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 1 is that a composite electroplating solution was used to perform electroplating on the pre-cleaned steel shell surface. After the electroplating operation, a nickel / titanium composite layer was formed on the surface of the steel shell, and the thickness of the nickel / titanium composite layer was 1.82 μm. Other steps and parameter settings were consistent with those in Example 1.

[0082] Test methods

[0083] I. Microhardness Test of Coating

[0084] The battery steel shells prepared by the electroplating process in the above embodiments and comparative examples were subjected to coating microhardness test. The surface coating hardness was tested using an ultramicro hardness tester. Five sites at different locations were selected during the test, and the average value was taken. The load was 100g and the loading time was 20s.

[0085] II. Coating Corrosion Resistance Test

[0086] The corrosion resistance of the battery steel shells prepared by the electroplating process in the above embodiments and comparative examples was tested. A salt spray test was conducted at 25°C (using a 5wt% sodium chloride solution, spray pressure 1.00±0.01 kgf / cm²). 2 After 40 days of storage, the quality loss is recorded.

[0087] Table 1

[0088] Serial Number Microhardness / HV NaCl tolerance mass loss / mg Example 1 170 1.2 Example 2 168 1.2 Example 3 175 1.3 Example 4 156 1.5 Example 5 178 1.6 Example 6 179 1.1 Example 7 151 1.9 Example 8 185 1.5 Example 9 147 1.3 Example 10 182 1.4 Comparative Example 1 135 3.8 Comparative Example 2 158 3.3 Comparative Example 3 155 3.1

[0089] Based on Example 1, Comparative Examples 1-3, and Table 1, it can be seen that by controlling the current density and electroplating temperature during the two electroplating operations, this application can form a coating on the surface of the steel shell consisting of a nickel layer and a relatively dense nickel / titanium composite layer. The nickel layer forms a good connection between the steel shell and the nickel / titanium composite layer, avoiding poor bonding between heterogeneous metals, thereby significantly improving the adhesion stability of the nickel / titanium composite layer. Furthermore, the combination of the nickel layer and the nickel / titanium composite layer can prevent the coating surface from having excessive porosity or the coating from cracking or peeling off during tensile stress. The coating on the steel shell surface has strong adhesion, high microhardness, and minimal mass loss after salt spray testing, exhibiting excellent corrosion resistance.

[0090] Combining Examples 1-5 and Table 1, it can be seen that when the particle size of the additive is too small or too large, it is not conducive to the formation of a dense and uniform nickel / titanium composite layer in the second electroplating. In Example 4, the microhardness of the coating is significantly reduced, while in Example 5, the corrosion resistance of the steel shell is significantly reduced.

[0091] Based on Examples 1 and 6 and Table 1, it can be seen that by using ammonium dodecyl sulfonate, the dispersibility of the additive nano-titanium dioxide in the electroplating solution of the second electroplating operation can be significantly improved, which helps to form a dense and uniform nickel / titanium composite layer, significantly improves the microhardness of the coating, and reduces the mass loss of the steel shell in the salt spray test and improves the corrosion resistance of the steel shell.

[0092] Combining Examples 1, 7-8 and Table 1, it can be seen that by controlling the first electroplating time within a suitable range, the nickel layer thickness can be adjusted to remain within a reasonable range, avoiding plating peeling due to a thin nickel layer, and significantly improving the wear resistance and corrosion resistance of the plating. Although the mass loss of the steel shell after the salt spray test is not significantly improved compared to Example 1 when the nickel layer is too thick, an excessively thick nickel layer will be detrimental to improving the weldability of the steel shell.

[0093] Based on Examples 1, 9-10, and Table 1, it can be seen that by controlling the second electroplating time within a suitable range, the thickness of the nickel / titanium composite layer can be adjusted to maintain a reasonable range, which helps to improve the wear resistance and corrosion resistance of the shell. Although the mass loss of the steel shell after the salt spray test is not significantly improved compared to Example 1 when the nickel / titanium composite layer thickness is too high, an excessively thick nickel / titanium composite layer will be detrimental to improving the weldability of the steel shell.

[0094] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application, but such modifications or substitutions are all within the scope of protection of this application.

Claims

1. A battery steel casing electroplating process, characterized in that, Includes the following steps: S1, Pre-cleaning treatment of the steel shell; S2, the pre-cleaned steel shell is placed in a primary electroplating solution for a primary electroplating operation; the primary electroplating solution includes 280-300 g / L of nickel sulfate, and the pH value of the primary electroplating solution is 5-6; the electroplating temperature in the primary electroplating operation is 40-45℃, and the current density is 40-60 mA / cm². 2 After one electroplating operation, a nickel-plated steel shell is obtained; S3, the nickel-plated steel shell is placed in a secondary electroplating solution for a secondary electroplating operation; the electroplating temperature during the secondary electroplating operation is 50-55℃, and the current density is 25-40mA / cm². 2 A nickel / titanium composite layer is formed on the surface of the nickel-plated steel shell to obtain a battery steel shell. The secondary electroplating solution is obtained by mixing the electroplating solution after the primary electroplating operation with an additive; the additive includes nano titanium dioxide, and the particle size of the additive is 30-50 nm. The amount of the additive added to the electroplating solution after the electroplating operation is 10-13 g / L.

2. The battery steel casing electroplating process according to claim 1, characterized in that: The primary electroplating solution also includes 6-9 g / L of citric acid.

3. The battery steel casing electroplating process according to claim 1, characterized in that: The electroplating time in a single electroplating operation is 90-115 minutes.

4. The battery steel casing electroplating process according to claim 1, characterized in that: The pH of the secondary electroplating solution is 5-6.

5. The battery steel casing electroplating process according to claim 1, characterized in that: The electroplating time in the secondary electroplating operation is 30-50 minutes.

6. The battery steel casing electroplating process according to any one of claims 1-5, characterized in that: The additive used in S3 requires surface activation treatment, which includes the following steps: A portion of the liquid is measured from the electroplating solution after the electroplating operation is completed, mixed with the additive particles, and then ultrasonically dispersed after adding a surfactant.

7. The battery steel casing electroplating process according to claim 6, characterized in that: The surfactant includes sodium dodecylbenzenesulfonate.

8. A battery steel casing, characterized in that: It is prepared by any one of the electroplating processes according to claims 1-7.