Electroplating process for battery steel shell

Abstract

The invention particularly discloses a battery steel shell electroplating process. A battery steel shell electroplating process comprises the following steps that S1, a steel shell is subjected to pre-cleaning treatment; s2, the pre-cleaned steel shell is placed in a primary electroplating solution to be subjected to primary electroplating operation; the primary electroplating solution comprises 280-300 g / L of nickel sulfate; the electroplating temperature in the primary electroplating operation is 40-45 DEG C, the current density is 40-60 mA / cm < 2 >, and the nickel-plated steel shell is obtained after the primary electroplating operation is finished; s3, the nickel-plated steel shell is placed in a secondary electroplating solution to be subjected to secondary electroplating operation; the electroplating temperature in the secondary electroplating operation is 50-55 DEG C, the current density is 25-40 mA / cm < 2 >, a nickel / titanium composite layer is formed on the surface of the nickel-plated steel shell, and the battery steel shell is obtained; wherein the secondary electroplating liquid is obtained by mixing the electroplating liquid obtained after the primary electroplating operation is finished with an additive; the additive comprises nano titanium dioxide. The method has the advantage of improving the binding force, corrosion resistance and wear resistance of the coating on the surface of the steel shell.

Description

Technical Field

[0001] The present application relates to the technical field of metal surface treatment, and in particular to a battery steel shell electroplating process. Background Art

[0002] With the booming development of industries such as portable communication devices, laptops, word processors and power tools, the lithium battery industry has higher and higher requirements for the performance of battery shell materials. The shell of lithium-ion power batteries is not only a sealed container, but also plays a vital role in the storage performance and safety performance of the battery. On the one hand, the battery shell material must have good resistance to electrolyte corrosion. The corrosion resistance of the shell material directly affects the service life of the lithium battery; on the other hand, when encountering complex and changeable situations such as collisions, bumps, and strong shocks caused by high-speed braking, the steel shell must withstand short-term strong impact loads, so the steel shell also plays a major role in the safety performance of lithium batteries.

[0003] In the prior art, the structural parts of the battery, such as the steel shell and the top cover, are generally set to a nickel-plated structure. However, nickel plating may cause the porosity of the steel shell and the top cover to be too large due to process problems, thereby reducing the corrosion resistance. Secondly, nickel plating will produce large internal stress, and the coating may crack or fall off during the stamping process of the steel shell. The above defects will cause the steel shell battery to corrode during use, leading to leakage, short circuit, etc. Summary of the invention

[0004] In order to solve the problems in the prior art, the present application provides a battery steel shell electroplating process.

[0005] In the first aspect, the present application provides a battery steel shell electroplating process, which adopts the following technical solution:

[0006] A battery steel shell electroplating process comprises the following steps:

[0007] S1, pre-cleaning the steel shell;

[0008] S2, placing the pre-cleaned steel shell 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° C., and the current density is 40-60 mA / cm 2 , after one electroplating operation, a nickel-plated steel shell is obtained;

[0009] S3, placing the nickel-plated steel shell in a secondary electroplating solution for secondary electroplating operation; the electroplating temperature in the secondary electroplating operation is 50-55° C., and the current density is 25-40 mA / cm 2 , forming a nickel / titanium composite layer on the surface of the nickel-plated steel shell to obtain a battery steel shell;

[0010] 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;

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

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

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

[0014] The present application performs two electroplating operations and controls the current density and the electroplating temperature during the two electroplating operations, so as to form a nickel layer and a relatively dense nickel / titanium composite layer on the surface of the steel shell; on the one hand, the nickel layer can form a good connection between the steel shell and the nickel / titanium composite layer to avoid the poor bonding of heterogeneous metals, thereby significantly improving the adhesion stability of the nickel / titanium composite layer and helping to improve the wear resistance and corrosion resistance of the electroplated layer; on the other hand, the nickel layer and the nickel / titanium composite layer cooperate to avoid excessive porosity on the surface of the coating or cracking or shedding of the coating when the steel shell is stretched due to large internal stress, thereby significantly improving the stability, conductivity and welding performance of the coating on the surface of the steel shell, thereby meeting the requirements of high-performance and high-capacity batteries.

[0015] Preferably, the primary electroplating solution further comprises 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 one electroplating operation is 90-115 min.

[0018] By adjusting the composition of the primary plating solution, the pH value of the primary plating solution and the time of the primary plating operation, it is helpful to form a nickel layer of appropriate thickness on the surface of the steel shell, thereby providing an adhesion base for the subsequent electroplating of the nickel / titanium composite layer, significantly improving the adhesion stability of the nickel / titanium composite layer on the steel shell, and thus significantly improving the corrosion resistance and wear resistance of the surface shell of the steel shell. When the nickel layer is thin, the coating is easily detached during deep hole forming and grooving after pre-nickel plating, causing the steel shell to rust; when the nickel layer is thick, when the battery module (battery pack) is welded as a whole group of resistors, the pack welding piece is not firmly connected and is easy to fall off.

[0019] Preferably, the pH of the secondary plating 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 plating solution and the time of the secondary plating operation is helpful to form a nickel / titanium composite layer of appropriate thickness on the surface of the steel shell. When the nickel / titanium composite layer is thin, TiO 2 The distribution amount is insufficient, resulting in 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 thickness of the nickel / titanium composite layer is thick, it will affect the welding connectivity 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 additive to meet the above range, it helps to form a dense, uniform, low-porosity nickel / titanium composite layer, which helps to improve the film resistance and corrosion resistance of the steel shell surface coating.

[0024] Preferably, the additive added in S3 needs to be subjected to surface activation treatment, and the surface activation treatment comprises the following steps:

[0025] A portion of the liquid is measured from the electroplating solution after the electroplating operation is completed, mixed with the additive particles (solid-liquid ratio of 10-15 g / L), and a surfactant is added (the amount of surfactant added is based on the solid-liquid ratio of 1-1.5 g / L) and then ultrasonically dispersed.

[0026] Preferably, the surfactant comprises sodium dodecylbenzene sulfonate.

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

[0028] In the second aspect, the present application provides a battery steel shell, which adopts the following technical solution:

[0029] A battery steel shell is prepared by the above electroplating process.

[0030] Preferably, the battery steel shell comprises a nickel / titanium composite layer, a nickel layer and a steel shell base arranged in sequence 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 DESCRIPTION

[0032] For better understanding and implementation, the technical solution of the present application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] Unless otherwise indicated, all numerical values ​​expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties desired to be obtained.

[0035] As used herein, "and / or" means one or all of the mentioned elements.

[0036] As used herein, “including” and “comprising” encompasses the case where only the stated elements are present as well as the case where there are other elements other than the stated elements.

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

[0038] Unless otherwise indicated, "a", "an", "an" and "the" used in this specification are intended to include "at least one" or "one or more". For example, "a component" means one or more components, so more than one component may be considered and may be employed or used in the implementation of the embodiment.

[0039] Example 1

[0040] A battery steel shell electroplating process comprises the following steps:

[0041] S1, pre-cleaning the steel shell including degreasing, primary water washing, pickling and secondary water washing processes;

[0042] S2, placing the pre-cleaned steel shell in a primary electroplating solution for a primary electroplating operation, wherein the primary electroplating solution includes 300 g / L nickel sulfate and 8 g / L citric acid, and the pH value of the primary electroplating solution is 5.5; the electroplating temperature in the primary electroplating operation is 40°C, and the current density is 50 mA / cm 2 , the electroplating time is 90min, and a nickel-plated steel shell (the thickness of the nickel layer is 1.4μm) is obtained after one electroplating operation;

[0043] S3, placing the nickel-plated steel shell in a secondary electroplating solution for secondary electroplating operation, wherein the electroplating temperature in the secondary electroplating operation is 55° C. and the current density is 30 mA / cm 2 , forming a nickel / titanium composite layer on the surface of the nickel-plated steel shell (the thickness of the nickel / titanium composite layer is 1.82 μm);

[0044] The 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 50 nm), and the amount of the additive in the electroplating solution after the first electroplating operation is 12 g / L.

[0045] S4, after the secondary electroplating operation is completed, a process including recovery, water washing and drying is performed to obtain a battery steel shell.

[0046] Example 2

[0047] A battery steel shell electroplating process comprises the following steps:

[0048] S1, pre-cleaning the steel shell including degreasing, primary water washing, pickling and secondary water washing processes;

[0049] S2, placing the pre-cleaned steel shell in a primary electroplating solution for a primary electroplating operation, wherein the primary electroplating solution includes 280 g / L nickel sulfate and 6 g / L citric acid, and the pH value of the primary electroplating solution is 6; the electroplating temperature in the primary electroplating operation is 45°C, and the current density is 60 mA / cm 2 , the electroplating time is 100min, and a nickel-plated steel shell (the thickness of the nickel layer is 1.52μm) is obtained after one electroplating operation;

[0050] S3, placing the nickel-plated steel shell in a secondary electroplating solution for secondary electroplating operation, wherein the electroplating temperature in the secondary electroplating operation is 55° C. and the current density is 40 mA / cm 2 , forming a nickel / titanium composite layer on the surface of the nickel-plated steel shell (the thickness of the nickel / titanium composite layer is 1.85 μm);

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

[0052] S4, after the secondary electroplating operation is completed, a process including recovery, water washing and drying is performed to obtain a battery steel shell.

[0053] Example 3

[0054] A battery steel shell electroplating process comprises the following steps:

[0055] S1, pre-cleaning the steel shell including degreasing, primary water washing, pickling and secondary water washing processes;

[0056] S2, placing the pre-cleaned steel shell in a primary electroplating solution for a primary electroplating operation, wherein the primary electroplating solution includes 300 g / L nickel sulfate and 9 g / L citric acid, and the pH value of the primary electroplating solution is 5; the electroplating temperature in the primary electroplating operation is 40°C, and the current density is 40 mA / cm 2 , the electroplating time is 110min, and a nickel-plated steel shell (the thickness of the nickel layer is 1.48μm) is obtained after one electroplating operation;

[0057] S3, placing the nickel-plated steel shell in a secondary electroplating solution for secondary electroplating operation, wherein the electroplating temperature in the secondary electroplating operation is 50° C. and the current density is 25 mA / cm 2 , forming a nickel / titanium composite layer on the surface of the nickel-plated steel shell (the thickness of the nickel / titanium composite layer is 1.73 μm);

[0058] The 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 40 nm), and the amount of the additive in the electroplating solution after the first electroplating operation is 10 g / L.

[0059] S4, after the secondary electroplating operation is completed, a process including recovery, water washing and drying is performed to obtain a 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; 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; other steps and parameter settings are consistent with those in embodiment 1.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 1 is that the additive used in this embodiment is further subjected to surface activation treatment, and the steps of the surface activation treatment are:

[0066] Part of the liquid is measured from the electroplating solution after one electroplating operation is completed, and mixed with the additive particles at a solid-liquid mixing ratio of 10 g / L. Then, sodium dodecylbenzene sulfonate is added to the obtained solid-liquid mixture at a solid-liquid ratio of 1.3 g / L, and ultrasonically dispersed for 3 hours.

[0067] The 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 those in 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 those in 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 those in 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 those in 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, and the thickness of the nickel layer is 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 is used to perform electroplating on the surface of the pre-cleaned steel shell. After the electroplating operation, a nickel / titanium composite layer is formed on the surface of the steel shell, and the thickness of the nickel / titanium composite layer is 1.82 μm. Other steps and parameter settings are consistent with those in Example 1.

[0082] Test Method

[0083] 1. Microhardness test of coating

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

[0085] 2. Test of corrosion resistance of coating

[0086] The battery steel shells prepared by the electroplating process in the above embodiment and comparative example were subjected to a corrosion resistance test of the coating, and a salt spray test was performed in an environment of 25°C (using a 5wt% sodium chloride solution and a spray pressure of 1.00±0.01kgf / cm 2 ), and the mass loss was recorded after storage for 40 days.

[0087] Table 1

[0088] Serial number Microhardness / HV NaCl resistance 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] In combination with Example 1, Comparative Examples 1-3 and Table 1, it can be seen that the present application can form a coating consisting of a nickel layer and a relatively dense nickel / titanium composite layer on the surface of the steel shell by controlling the current density and the electroplating temperature during the two electroplating operations. The nickel layer forms a good connection between the steel shell and the nickel / titanium composite layer, avoiding the poor bonding of heterogeneous metals, thereby significantly improving the adhesion stability of the nickel / titanium composite layer. Moreover, the nickel layer and the nickel / titanium composite layer cooperate to avoid excessive porosity on the surface of the coating or cracking or shedding of the coating when the steel shell is stretched due to large internal stress. The coating on the surface of the steel shell has strong bonding strength and high microhardness, and the mass loss of the steel shell after the salt spray test is small, and the corrosion resistance is excellent.

[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 second electroplating to form a dense and uniform nickel / titanium composite layer. The microhardness of the coating in Example 4 is significantly reduced, and the corrosion resistance of the steel shell in Example 5 is significantly reduced.

[0091] In combination with Example 1, Example 6 and Table 1, it can be seen that by using ammonium dodecylsulfonate, 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 improve the microhardness of the coating, and reduce the mass loss of the steel shell in the salt spray test and improve the corrosion resistance of the steel shell.

[0092] In combination with Example 1, Examples 7-8 and Table 1, it can be seen that by controlling the first electroplating time to be kept within an appropriate range, the thickness of the nickel layer can be adjusted to be kept within a reasonable range, thereby avoiding the shedding of the coating due to the thin nickel layer, and significantly improving the wear resistance and corrosion resistance of the coating. Although when the nickel layer is too thick, the mass loss of the steel shell after the salt spray test is not significantly improved compared with Example 1, a too thick nickel layer will be unfavorable for improving the welding performance of the steel shell.

[0093] Combining Example 1, Examples 9-10 and Table 1, it can be seen that by controlling the second electroplating time to be within a suitable range, the thickness of the nickel / titanium composite layer can be adjusted to be within a reasonable range, which helps to improve the wear resistance and corrosion resistance of the shell layer; although the mass loss of the steel shell after the salt spray test is not significantly improved compared with Example 1 when the thickness of the nickel / titanium composite layer is too high, the excessive thickness of the nickel / titanium composite layer will be unfavorable for improving the welding performance of the steel shell

[0094] The above embodiments are only used to illustrate the technical solution of the present application rather than to limit the protection scope of the present application. Although the present application is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solution of the present application can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present application.

Claims

1. A battery steel shell electroplating process, characterized in that: The steps include: S1, pre-cleaning the steel shell; S2, placing the pre-cleaned steel shell 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° C., and the current density is 40-60 mA / cm 2 , after one electroplating operation, a nickel-plated steel shell is obtained; S3, placing the nickel-plated steel shell in a secondary electroplating solution for secondary electroplating operation; the electroplating temperature in the secondary electroplating operation is 50-55° C., and the current density is 25-40 mA / cm 2 , forming a nickel / titanium composite layer 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; The amount of the additive added to the electroplating solution after the first electroplating operation is completed is 10-13 g / L.

2. The battery steel shell 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 shell electroplating process according to claim 1, characterized in that: The pH value of the primary electroplating solution is 5-6.

4. The battery steel shell electroplating process according to claim 1, characterized in that: The plating time in one plating operation is 90-115 minutes.

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

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

7. The battery steel shell electroplating process according to claim 1, characterized in that: The particle size of the additive is 30-50 nm.

8. The battery steel shell electroplating process according to any one of claims 1 to 7, characterized in that: The additive used in S3 needs to be subjected to surface activation treatment, and the surface activation treatment includes the following steps: A portion of the liquid is measured from the electroplating solution after the first electroplating operation is completed, mixed with the additive particles, and then ultrasonically dispersed after adding a surfactant.

9. The battery steel shell electroplating process according to claim 8, characterized in that: The surfactant includes sodium dodecylbenzene sulfonate.

10. A battery steel shell, characterized in that: The invention is prepared by the electroplating process described in any one of claims 1 to 9.