Double-sided burr nickel-plated steel strip and preparation method thereof

Abstract

The invention relates to the technical field of metal material processing, and discloses a double-sided burr nickel-plated steel strip and a preparation method thereof.The double-sided burr nickel-plated steel strip comprises a steel strip base body, the double faces of the steel strip base body are provided with three-dimensional burrs and nickel-plated layers, and each nickel-plated layer is composed of a plurality of nickel particles protruding out of the surface of the steel strip base body; the nickel particles are in any one or more of a conical shape, a pyramid shape or an irregular shape, the height of the nickel particles is 2-8 microns, and the bottom diameter of the nickel particles is 1-4 microns. And through electroplating treatment of a double-sided burr structure, the conductivity is remarkably improved, the contact resistance is effectively reduced, and the current distribution uniformity is improved. And meanwhile, the binding force between the plating layer and the substrate is enhanced by the pulse electroplating and periodic reversing electroplating technologies, the problems of interface stripping and plating layer falling are avoided, and the service life of the battery is prolonged. According to the burr structure, by increasing the surface roughness and the microscopic protrusions, the corrosion resistance of the plating layer is remarkably improved, and salt mist and moisture permeation are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, and particularly to a double-sided burr nickel-plated steel strip and a preparation method thereof. Background Art

[0002] In the field of high-power batteries, especially in new energy vehicles and energy storage systems, the key role of battery tabs and connectors as conductive components has become increasingly prominent. To ensure the efficient charging and discharging of batteries, nickel-plated steel strips are often used as battery tab materials, taking advantage of their excellent electrical conductivity and welding performance. However, the design of traditional nickel-plated steel strips still has many limitations, restricting the further improvement of battery performance.

[0003] Existing nickel-plated steel strips usually adopt a smooth surface treatment. Although this design can meet the basic electrical conductivity requirements, at high current densities, the contact resistance between the battery tab and the electrode is relatively high, resulting in local heating and energy loss, which in turn affects the overall efficiency and cycle stability of the battery. In addition, due to the lack of an effective microstructure on the surface, the current distribution is relatively uneven, and the charging and discharging efficiency of the battery cannot be maximally improved.

[0004] During the charging and discharging process of the battery, the expansion and contraction of the tab and electrode materials will cause the contact interface to peel off. Especially when the adhesion of the nickel plating layer is insufficient, the problem is more serious. Traditional nickel-plated steel strips often use smooth nickel plating. This structure lacks necessary mechanical locking points, and the interfacial bonding force is weak, unable to effectively cope with the volume change and mechanical stress during battery use, reducing the long-term stability of the battery.

[0005] In addition, the long-term use of the battery in a high-temperature and high-humidity environment will accelerate metal corrosion. However, the compactness of the nickel plating layer in the existing technology is insufficient, and it is easily affected by electrolyte penetration and external moisture, resulting in coating peeling and increasing the risk of short circuit. Traditional nickel-plated steel strips also fail to meet the long-life requirements of high-power batteries in terms of corrosion resistance. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a double-sided burr nickel-plated steel strip and a preparation method thereof, which solve the problems of traditional nickel-plated steel strips in terms of electrical conductivity, interfacial bonding force, and corrosion resistance.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: a double-sided burr nickel-plated steel strip and a preparation method thereof, including a steel strip substrate, on both sides of which there are three-dimensional burrs and a nickel plating layer, and the nickel plating layer is composed of a number of nickel particles protruding from the surface of the steel strip substrate.

[0008] Preferably, the shape of the nickel particles is any one or more of a conical shape, a pyramidal shape, or an irregular shape.

[0009] Preferably, the height of the nickel particles is 2-8 μm, and the bottom diameter of the nickel particles is 1-4 μm.

[0010] Preferably, the steel strip substrate is a low-carbon steel strip or a stainless steel strip.

[0011] Preferably, the three-dimensional burrs are obtained by double-sided stamping with a plurality of quadrangular pyramid-shaped punches and square die holes to form three-dimensional burrs in both positive and negative directions.

[0012] A method for preparing a double-sided burr nickel-plated steel strip includes the following steps:

[0013] S1. Stamping process: The steel strip substrate is stamped through a double-sided stamping die composed of a plurality of quadrangular pyramid-shaped punches and square die holes to obtain a steel strip substrate with a three-dimensional burr structure on both sides;

[0014] S2. Pretreatment before electroplating: The steel strip substrate is degreased, derusted, and activated to obtain a clean steel strip surface;

[0015] S3. Electroplating: The pretreated steel strip substrate is immersed in the electroplating solution, and a nickel layer is electroplated on both sides of the steel strip substrate by pulse electroplating or periodic reverse electroplating to form burr-like deposits;

[0016] S4. Post-treatment: The electroplated steel strip is washed, dried, and passivated to obtain a double-sided burr nickel-plated steel strip.

[0017] Preferably, the electroplating solution is composed of the following components: nickel sulfate: 70-120 g / L; nickel chloride: 10-20 g / L; boric acid: 30-50 g / L; wetting agent: 0.1-0.5 g / L.

[0018] Preferably, the parameters of the pulse electroplating are: current density: 2-10 A / dm 2 ; pulse frequency: 100-1000 Hz; duty cycle: 10%-50%.

[0019] Preferably, the parameters of the periodic reverse electroplating are: forward current density: 2-10 A / dm 2 ; reverse current density: 1-5 A / dm 2 ; forward time: 10-50 ms; reverse time: 5-25 ms.

[0020] The present invention provides a double-sided burr nickel-plated steel strip and a preparation method thereof. It has the following beneficial effects:

[0021] 1. The present invention adopts the design scheme of double-sided burr nickel-plated steel strip. Through the electroplating treatment of the double-sided burr structure, the technical effect of significantly improving the conductivity is achieved. Compared with the traditional single-sided nickel-plated steel strip, the double-sided burr structure can effectively reduce the contact resistance, improve the current distribution uniformity, and solve the problems of current concentration and serious heating caused by the smooth surface of the traditional coating.

[0022] 2. The present invention optimizes the deposition process of the coating through pulse electroplating and periodic reverse electroplating technologies, achieving the effect of significantly enhancing the bonding force between the coating and the substrate. Compared with the existing traditional smooth nickel-plated steel strip, the burr coating can better resist the expansion and contraction of the battery tab and electrode material, avoiding the problems of interface peeling and coating shedding, thereby prolonging the service life of the battery.

[0023] 3. The double-sided burr nickel-plated steel strip adopted by the present invention effectively improves the corrosion resistance of the coating by increasing the surface roughness and micro-protrusions. Compared with the traditional smooth coating, the burr structure can reduce the penetration of salt spray and moisture, prevent the corrosion of the battery in high-humidity and high-salt environments, and significantly improve the long-term stability and reliability of the battery connector.

[0024] 4. The structure and preparation method of the double-sided burr nickel-plated steel strip of the present invention break through the limitations of traditional coatings in the application of high-power batteries and improve the charge and discharge efficiency of the battery. By optimizing the coating structure and enhancing the interface bonding force, the present invention effectively solves the problems of poor performance of traditional coatings under high current density, resulting in local heating and energy loss, thereby improving the overall performance of high-power batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a perspective view of the present invention;

[0026] Figure 2 is a schematic flow chart of the preparation steps of the nickel-plated steel strip in the present invention.

[0027] Among them, 1. Steel strip substrate; 2. Nickel-plated layer; 3. Three-dimensional burr. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the specification of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Embodiment:

[0030] Please refer to the attached Figure 1, an embodiment of the present invention provides a double-sided burr nickel-plated steel strip, including a steel strip substrate 1, with three-dimensional burrs 3 and a nickel plating layer 2 provided on both sides of the steel strip substrate 1. The nickel plating layer 2 is composed of a number of nickel particles protruding from the surface of the steel strip substrate 1. The shape of the nickel particles is any one or more of conical, pyramid-shaped or irregular shapes. The height of the nickel particles is 2-8 μm, and the bottom diameter of the nickel particles is 1-4 μm. The steel strip substrate 1 is a low-carbon steel strip or a stainless steel strip. The three-dimensional burrs 3 are obtained by two-way stamping with a number of quadrangular pyramid-shaped punches and square die holes to form three-dimensional burrs 3 in both positive and negative directions.

[0031] Please refer to the appendix Figure 2 , as a part of the present invention, this application also provides a preparation method for the double-sided burr nickel-plated steel strip, including,

[0032] S1. Stamping process: The steel strip substrate 1 is processed by a two-way stamping die composed of a number of quadrangular pyramid-shaped punches and square die holes to obtain a steel strip substrate 1 with a three-dimensional burr structure on both sides;

[0033] The stamping process is the first key step of the present invention, aiming to form a burr-like structure on the surface of the steel strip substrate 1. In this step, the surface of the steel strip substrate 1 is stamped into a structure with three-dimensional burrs 3 through a two-way stamping die. Specifically, a two-way stamping is performed using quadrangular pyramid-shaped punches and square die holes to generate burr-like structures in both positive and negative directions. The height and shape of these burrs can be controlled by adjusting the stamping pressure, speed, and the design of the die.

[0034] During the stamping process, the substances on the surface of the steel strip undergo plastic deformation under the action of impact force and pressure, thus forming a burr structure. These burr structures can significantly improve the adhesion of the subsequent nickel plating layer 2 by increasing the surface roughness. The presence of the burrs provides more mechanical biting points for the plating layer, enhancing the bonding force with the plating layer and other materials (such as battery tabs, connectors, etc.). Therefore, the stamping process not only forms an appearance structure but also optimizes the bonding force between the steel strip and the plating layer from a physical mechanism by increasing the contact area and surface unevenness.

[0035] S2. Pretreatment before electroplating, the steel strip substrate 1 is degreased, derusted, and activated to obtain a clean steel strip surface;

[0036] The pretreatment before electroplating includes three steps: degreasing, derusting, and activation, aiming to provide a clean and activated steel strip surface for the electroplating process. In the degreasing process, the surface of the steel strip is cleaned with a weakly alkaline solution to remove oil stains; in the derusting step, an acidic solution is used to remove surface rust; in the activation step, an activation solution is used to further treat the surface to make it have good electroplating adhesion. The pretreatment not only cleans the surface but also provides a suitable chemical environment for electroplating.

[0037] The core function of pretreatment is to remove impurities, oil stains, rust and oxides on the surface of the steel strip through physical and chemical methods, preventing them from hindering the deposition of the coating during the electroplating process. The degreasing and rust removal processes can effectively remove pollutants and oxides that may affect the adhesion of the coating; while the activation process increases the hydrophilicity and surface energy of the surface through chemical activation, further improving the bonding force between the coating and the steel strip substrate 1. In this way, the surface of the steel strip can better adsorb nickel ions during electroplating, forming a uniform and dense coating.

[0038] S3. Electroplating: Immerse the pretreated steel strip substrate 1 in the electroplating solution, and electroplate nickel layers 2 on both sides of the steel strip substrate 1 by means of pulse electroplating or periodic reverse electroplating. During the electroplating process, control parameters such as current density, pulse frequency, and duty cycle to form a burr-like deposition;

[0039] The electroplating process adopts pulse electroplating or periodic reverse electroplating to form a burr-like coating on the steel strip surface through the electroplating solution. The electroplating solution consists of nickel sulfate, nickel chloride, boric acid and wetting agent. The main purpose of pulse electroplating or periodic reverse electroplating is to control the deposition mode of nickel particles so that they form a coating in a burr-like form on the steel strip surface. Pulse electroplating uses currents with different frequencies and duty cycles to form a uniform and controllable coating on the steel strip surface; periodic reverse electroplating optimizes the quality and bonding force of the coating through alternating forward and reverse currents.

[0040] During the electroplating process, parameters such as current density, pulse frequency and duty cycle directly affect the deposition rate and morphology of the coating. In pulse electroplating, the repeated switching of the current can effectively control the deposition process of nickel ions during electroplating, making the coating particles appear irregular or conical in shape. This particle shape and distribution are very helpful for improving the contact resistance of battery connectors. Periodic reverse electroplating can more effectively control the grain structure of the coating by changing the current direction, prevent the coating from peeling off, and improve the mechanical strength and corrosion resistance of the coating.

[0041] The morphology of nickel particles (such as conical, pyramidal or irregular shapes) plays an important role in enhancing the adhesion of the burr coating. These particle morphologies help to form a more complex microstructure, further increasing the contact area and bonding force. At the same time, the height and diameter dimensions of these microscopic particles also directly affect the thickness and uniformity of the electroplated layer, and must be controlled within a certain range to achieve the best conductivity and interfacial bonding force.

[0042] S4. Post-treatment: Wash, dry and passivate the electroplated steel strip to obtain a double-sided burr nickel-plated steel strip.

[0043] The electroplated steel strip needs to go through post-treatment steps such as water washing, drying, and passivation. The water washing step removes the residual electroplating solution during the electroplating process, the drying step removes moisture, and the passivation treatment forms a protective film to enhance the corrosion resistance of the coating. Passivation treatment usually uses chromates or other passivating agents to enhance the antioxidant performance of the coating by forming a passivation film.

[0044] The post-treatment steps are crucial for the stability and corrosion resistance of the coating. The water washing and drying steps can ensure that there is no excess solution or moisture on the surface of the electroplated coating, thus avoiding the shedding or corrosion of the coating caused by these substances during later use. The passivation treatment can effectively isolate the contact between the coating and the external environment by forming a protective film, preventing metal corrosion caused by the penetration of the electrolyte and external moisture. Therefore, the post-treatment steps help to extend the service life of the coating and ensure the reliability of battery components during long-term operation.

[0045] During the entire preparation process, precise control of electroplating parameters and stamping parameters is crucial, which directly determines the performance of the final product. The main parameters include current density, pulse frequency, duty cycle, forward and reverse current density, forward and reverse electroplating time, etc. These parameters affect the thickness, morphology, particle distribution of the coating, and the adhesion between the coating and the substrate.

[0046] During pulse electroplating, if the current density is too high or the pulse frequency is too low, it may cause the coating to deposit too thick or the particles to be uneven, affecting the conductivity; while the selection of forward and reverse current density and electroplating time in periodic reverse electroplating directly affects the uniformity and adhesion of the coating. Too high reverse current density may cause the coating to peel off, and too short electroplating time may cause the coating to be too thin, affecting the performance.

[0047] Example 1: Preparation of double-sided burr nickel plating on low-carbon steel strip:

[0048] S1: Stamping process of the steel strip substrate 1: Take a low-carbon steel strip with a thickness of 0.08 mm and place it in the punching die. Use a quadrangular pyramid punch and a square die hole for two-way stamping. Set the stamping pressure to 7 MPa and control the stamping speed at 15 m / min. After stamping, a uniform burr-like structure is formed on both sides of the steel strip, and the height of the burrs is about 3 - 5 μm, with uniform distribution.

[0049] S2: Pretreatment before electroplating: Immerse the stamped steel strip in the degreasing solution at a temperature of 40 °C for 5 minutes, then wash it with clean water. Then, use dilute sulfuric acid solution for rust removal, soak for 3 minutes, and then rinse with clean water. Finally, immerse the cleaned steel strip in the activation solution for 4 minutes to ensure the adhesion of the coating.

[0050] S3: Electroplating process: Immerse the treated steel strip into the electroplating bath. The formula of the electroplating solution is as follows: nickel sulfate: 90 g / L; nickel chloride: 15 g / L; boric acid: 40 g / L; wetting agent: 0.2 g / L.

[0051] Use pulse electroplating method with a current density of 5 A / dm 2 , a pulse frequency of 500 Hz, a duty cycle of 30%, and an electroplating time of 10 minutes. During this process, nickel particles are deposited on the surface of the steel strip, forming a burr-like coating. The particle morphology is conical, with a bottom diameter of about 2 μm and a top diameter of 1 μm.

[0052] S4: Post-treatment: Rinse the electroplated steel strip with clean water, dry it, and then perform passivation treatment to ensure the corrosion resistance of the coating. The passivation treatment uses a passivation solution containing chromate, and the passivation time is 3 minutes. Finally, a double-sided burr nickel-plated steel strip with excellent corrosion resistance and conductivity is obtained.

[0053] Example 2: Preparation of double-sided burr nickel plating on stainless steel strip:

[0054] S1: Stamping process of the steel strip substrate 1: Select a stainless steel strip with a thickness of 0.1 mm and perform double-sided stamping using the same stamping die as in Example 1. Set the stamping pressure to 9 MPa and the stamping speed to 18 m / min. After stamping, a uniform burr-like structure is formed on both sides of the steel strip, and the height of the burrs is approximately 4 μm.

[0055] S2: Pretreatment before electroplating: First, immerse the stainless steel strip into the degreasing solution for degreasing. Use an alkaline solution at a temperature of 45 °C for 5 minutes and then clean it. Subsequently, use sulfuric acid solution to remove rust, wash for 3 minutes, and then rinse with water. Finally, immerse the cleaned steel strip into the activation solution for 5 minutes.

[0056] S3: Electroplating process: Immerse the pretreated steel strip into the electroplating bath. The formula of the electroplating solution is as follows: nickel sulfate: 110 g / L; nickel chloride: 20 g / L; boric acid: 45 g / L; wetting agent: 0.3 g / L.

[0057] Adopt periodic reverse electroplating. The forward current density is 8 A / dm 2 , the reverse current density is 4 A / dm 2 , the forward time is 30 ms, and the reverse time is 15 ms. The electroplating time is 12 minutes. During the electroplating process, nickel particles are deposited in a pyramid shape, with a particle height of 6 μm and a bottom diameter of 2.5 μm.

[0058] S4: Post-treatment: After electroplating, rinse the steel strip with clean water, dry it, and then perform passivation treatment to ensure the long-term stability and corrosion resistance of the coating. The passivation solution is a solution containing chromate, and the passivation time is 4 minutes. Finally, a double-sided burr nickel-plated steel strip is obtained.

[0059] Example 3: Double-sided burr nickel-plated steel strip for high-power battery tab connectors

[0060] S1: Stamping process of the steel strip substrate 1: Select a low-carbon steel strip with a thickness of 0.12 mm and place it in a stamping die for double-sided stamping. The stamping pressure is 6.5 MPa and the stamping speed is 12 m / min. After stamping, a burr structure with a height of approximately 5 μm is formed on the surface of the steel strip, which is evenly distributed and can increase the contact area of the battery tab connector.

[0061] S2: Pretreatment before electroplating: Use a weak alkaline solution for degreasing treatment. The cleaning time is 4 minutes, the temperature is controlled at 40 °C, and after cleaning, it is rinsed with clean water. Next, use a dilute sulfuric acid solution for rust removal. The rust removal time is 3 minutes and the temperature is 25 °C, and then it is rinsed thoroughly with clean water. Finally, use a solution containing chloride for activation. The activation time is 6 minutes to ensure the adhesion of the coating.

[0062] S3: Electroplating process: Immerse the pretreated steel strip into the electroplating bath. The formula of the electroplating solution is: nickel sulfate: 80 g / L; nickel chloride: 12 g / L; boric acid: 35 g / L; wetting agent: 0.15 g / L.

[0063] Pulse electroplating is adopted, the current density is 4 A / dm 2 , the pulse frequency is 600 Hz, the duty cycle is 40%, and the electroplating time is 8 minutes. During the electroplating process, nickel particles are deposited in an irregular shape. The height of the particles is 3 μm, the bottom diameter is 1.5 μm, and the particle distribution is uniform.

[0064] S4: Post-treatment: The electroplated steel strip is rinsed with clean water and passivated after drying. The passivation treatment uses a solution containing chromate, and the treatment time is 5 minutes to ensure that the coating has good corrosion resistance.

[0065] Example 4: Preparation of double-sided burr nickel-plated high-strength alloy steel strip

[0066] S1: Stamping process of the steel strip substrate 1: Select a high-strength alloy steel strip with a thickness of 0.09 mm and perform double-sided stamping. The stamping pressure is set at 8 MPa and the stamping speed is controlled at 14 m / min. After stamping, a burr structure with a height of 7 μm is formed on both sides of the steel strip, which is uniform and stable.

[0067] S2: Pretreatment before electroplating: The alloy steel strip is first treated with a degreasing solution at a temperature of 50 °C for 5 minutes, and then rust is removed with a dilute sulfuric acid solution for 3 minutes. The activation step uses a solution containing chloride, and the treatment time is 4 minutes.

[0068] S3: Electroplating process: Immerse the pretreated steel strip into the electroplating solution. The formula of the electroplating solution is:

[0069] Nickel sulfate: 100 g / L; nickel chloride: 18 g / L; boric acid: 40 g / L; wetting agent: 0.2 g / L.

[0070] The pulse electroplating method is adopted, and the current density is 6 A / dm 2 , the pulse frequency is 700 Hz, the duty cycle is 35%, and the electroplating time is 9 minutes. The nickel particles are deposited in a conical shape, with a particle height of 5 μm and a bottom diameter of 3 μm, and the deposition is uniform.

[0071] S4: Post-treatment: The electroplated steel strip is rinsed with clean water and passivated after drying. The passivation solution is a chromate-containing solution, and the treatment time is 4 minutes to ensure that the corrosion resistance of the coating meets the requirements.

[0072] To comprehensively compare the limitations of the present invention with those in the prior art, the embodiments of the present invention and the comparative examples will be compared in multiple aspects. The following is the design of the comparative example fine-tuned according to the embodiments of the present invention, which shows the deficiencies of the prior art solutions and the innovativeness of the inventive points of the present invention. The comparative examples will be based on the adjustment of certain parameters so that the comparison can directly reflect the improvements and advantages of the present invention.

[0073] Comparative Example 1: One-sided nickel plating solution for low-carbon steel strip:

[0074] Prior art solution (comparative example): In the prior art, one-sided nickel-plated steel strip is often used as the material for battery connectors. In this comparative example, we choose to perform one-sided nickel plating on a low-carbon steel strip (thickness 0.08 mm), and other steps are the same as those in Example 1. That is, in the stamping stage, burr-like structures are only formed on one side of the steel strip, and in the electroplating stage, ordinary electroplating is used instead of pulse or periodic reverse electroplating.

[0075] Comparison differences: Stamping process: Burr stamping is only performed on one side of the steel strip, and a double-sided burr structure is not formed. Electroplating process: Traditional one-sided nickel plating is used. The electroplating solution formula is the same as that in Example 1, but pulse electroplating or periodic reverse electroplating is not used, resulting in uneven deposition of the coating and failure to form ideal burr-like particles.

[0076] Through this comparison scheme, the different performances of one-sided nickel-plated steel strip and the double-sided burr nickel-plated steel strip of the present invention in conductivity, adhesion, and corrosion resistance can be effectively compared.

[0077] Comparative Example 2: Smooth nickel plating treatment for stainless steel strip:

[0078] Prior art solution (comparative example): In this comparative example design, a stainless steel strip (thickness 0.1 mm) is selected. After conventional degreasing, rust removal, and activation, smooth nickel plating treatment is carried out. Pulse electroplating is used during nickel plating, but the formation of burr-like coatings is not considered, and only a uniform and smooth coating is formed through conventional electroplating.

[0079] Comparison differences: Stamping process: There is no stamping step, and there is no burr structure on the surface. Electroplating process: The electroplating solution formula is the same as that of Example 2, but periodic reverse electroplating or pulse electroplating is not used to control finer-grained deposition particles, resulting in a uniform but relatively smooth coating thickness, without significantly improving conductivity or enhancing adhesion.

[0080] This comparative scheme can compare the differences in conductivity, interfacial adhesion, and corrosion resistance between the smooth coating and the burr coating of the present invention, especially the manifestation of high conductivity and corrosion resistance in high-power battery applications.

[0081] Comparative Example 3: Double-sided smooth nickel plating of low-carbon steel strip:

[0082] Existing technical solution (comparative example): In this comparative example, a low-carbon steel strip (with a thickness of 0.08 mm) is subjected to double-sided smooth nickel plating. The stamping step is the same as that of Example 1, but in the electroplating process, a conventional double-sided electroplating method is used to form a smooth nickel coating 2, and parameters such as current density and electroplating time are relatively low compared with the pulse electroplating process of Example 1.

[0083] Comparison differences: Stamping process: Double-sided stamping forms a burr structure, but the morphology of the coating is not optimized, and only conventional electroplating is carried out. Electroplating process: The electroplating solution formula is the same as that of Example 1, but pulse electroplating or periodic reverse electroplating technology is not used, resulting in a relatively smooth coating surface, uneven current distribution compared with the burr coating, and weak coating adhesion.

[0084] Through this comparison, the differences in conductivity, adhesion, and corrosion resistance between the double-sided smooth nickel-plated steel strip and the double-sided burr nickel-plated steel strip can be intuitively compared, especially the impact on charge and discharge performance.

[0085] Comparative Example 4: Single-sided pulse electroplating of high-strength alloy steel strip:

[0086] Existing technical solution (comparative example): A high-strength alloy steel strip with a thickness of 0.09 mm is used for single-sided pulse electroplating treatment. The stamping step is the same as that of Example 4, but only one side of the steel strip is pulse electroplated, the coating grain size is relatively coarse, and the overall structure of the coating is different from that of the double-sided burr nickel-plated steel strip.

[0087] Comparison differences: Stamping process: Single-sided stamping, and only a single-sided burr-like structure is formed on the surface.

[0088] Electroplating process: Pulse electroplating is used, but only one side of the nickel plating is carried out, and a double-sided burr nickel-plated structure cannot be formed, resulting in ineffective improvement of the coating conductivity and adhesion.

[0089] This comparative scheme can show the differences in conductivity, interfacial adhesion, and corrosion resistance between single-sided nickel plating and double-sided burr nickel plating, further verifying the importance of the double-sided coating design.

[0090] Comparative Example 5: Conventional electroplating and passivation treatment of low-carbon steel strip:

[0091] Existing technical solution (comparative example): A low-carbon steel strip with a thickness of 0.08 mm is used, and both sides are nickel-plated through a conventional electroplating process. The electroplating solution formula is the same as that in Example 1, but pulse electroplating or periodic reverse electroplating methods are not used. In the post-treatment stage, conventional passivation treatment is carried out, and the morphology of the coating cannot be optimized.

[0092] Comparison differences: Stamping process: The steel strip substrate 1 is not stamped, and the surface is a flat and smooth structure. Electroplating process: The conventional electroplating method is used in the electroplating process, and pulse or periodic reverse electroplating is not used, so the coating is relatively uniform and smooth. Post-treatment: The traditional passivation method is used, and the corrosion resistance and adhesion of the coating cannot be significantly improved.

[0093] Through this comparison, the huge differences in adhesion, conductivity, and corrosion resistance between the double-sided burr nickel-plated steel strip of the present invention and the traditional smooth nickel-plated steel strip can be demonstrated, highlighting the innovation points of the present invention.

[0094] The following are the comparative test experiments carried out on the examples and comparative examples of the present invention. The experimental design adopts a one-to-one single-factor comparison to ensure that the test results can clearly show the effects of the present invention compared with the existing technology.

[0095] Experiment 1: Comparison of conductivity between Example 1 (double-sided burr nickel-plating) and Comparative Example 1 (single-sided nickel-plating):

[0096] Purpose: To verify the improvement effect of the double-sided burr nickel-plated steel strip in conductivity, especially the performance improvement under high current density.

[0097] Experimental steps: Sample preparation: Select the low-carbon steel strip in Example 1, and prepare it through double-sided burr stamping and pulse electroplating. Select the low-carbon steel strip in Comparative Example 1, and carry out single-sided stamping and single-sided nickel-plating treatment. The electroplating method is the same as that in Example 1.

[0098] Experimental setup: Use the four-probe method to measure the resistivity of the samples, and measure the performance at a current density of 10 A / cm 2 Each group of samples is measured 5 times, and the average value is taken for analysis.

[0099] The resistance test is carried out at room temperature to ensure that all samples are tested under the same environmental conditions.

[0100] Record the resistivity data of each measurement and calculate the average value. Compare the performance of the double-sided burr nickel-plated steel strip and the single-sided nickel-plated steel strip under the same conditions.

[0101] Table 1: Experimental data of resistivity comparison between double-sided burr nickel-plated steel strip and single-sided nickel-plated steel strip:

[0102] Sample Number Measurement 1 (Ω) Measurement 2 (Ω) Measurement 3 (Ω) Measurement 4 (Ω) Measurement 5 (Ω) Average Value (Ω) 1 (Double-sided Burr) 0.022 0.019 0.023 0.021 0.020 0.021 2 (Single-sided Nickel Plating) 0.045 0.048 0.047 0.046 0.044 0.046 3 (Double-sided Burr) 0.021 0.022 0.020 0.021 0.023 0.021 4 (Single-sided Nickel Plating) 0.046 0.045 0.049 0.048 0.047 0.047 5 (Double-sided Burr) 0.020 0.019 0.020 0.021 0.020 0.020

[0103] The experimental results show that the resistivity of the double-sided burr nickel-plated steel strip is significantly lower than that of the single-sided nickel-plated steel strip. This indicates that the design of the double-sided burr structure effectively reduces the contact resistance. According to the experimental data, the average resistivity of the double-sided burr nickel-plated steel strip is about 0.021 Ω, while that of the single-sided nickel-plated steel strip is 0.046 Ω. The burr-shaped coating can evenly distribute the current by increasing the surface roughness and the effective contact area, avoiding local heating and power loss, thus improving the conductivity.

[0104] The particle morphology and distribution of the burr coating also play a key role. The conical or pyramidal shape of the nickel particles enables the current to flow more evenly on the surface of the steel strip. Compared with the traditional smooth nickel-plated layer 2, the burr coating provides more mechanical interlocking points, reducing the resistance when the current passes through. This is particularly obvious at high current densities, which can significantly improve the contact quality between the battery tab and the electrode material.

[0105] Through experimental comparison, we further verified the innovative design of the present invention. The traditional single-sided nickel-plated steel strip has a high contact resistance due to uneven current distribution. While the double-sided burr nickel-plated steel strip optimizes the conductivity by refining the surface structure, solving the problem of local heat accumulation during the charge and discharge process in traditional technologies. The application of this technology can significantly improve the charge and discharge efficiency of high-power batteries and effectively extend their service life.

[0106] Experiment 2: Comparison of the corrosion resistance between Example 2 (double-sided burr nickel plating) and Comparative Example 2 (double-sided smooth nickel plating):

[0107] The purpose of this experiment is to verify the advantages of the double-sided burr nickel-plated steel strip in terms of corrosion resistance, especially in a salt spray environment. The experiment will evaluate the corrosion performance of the double-sided burr nickel-plated steel strip and the double-sided smooth nickel-plated steel strip under the same conditions through a salt spray test. The salt spray test will simulate the high-humidity and high-salt conditions in the battery working environment to verify the protective effect of the coating of the present invention in a harsh environment.

[0108] Experimental procedure: Sample preparation: Select the stainless steel strip in Example 2, which is prepared by double-sided burr stamping and periodic reverse electroplating. Select the stainless steel strip in Comparative Example 2, which is processed by double-sided stamping and smooth nickel plating. The electroplating method is the same as that in Example 2.

[0109] Experimental setup: Put each group of samples into a salt spray test chamber, set the salt spray environment temperature at 35 °C, and the salt solution concentration at 5% (NaCl solution). Each group of samples is exposed for 48 hours, observe whether red rust appears on the surface of the coating, and record the corrosion degree of the samples.

[0110] Table 2: Salt Spray Test Data of Double-sided Burr Nickel-plated Steel Strip and Double-sided Smooth Nickel-plated Steel Strip:

[0111]

[0112] The experimental results show that the double-sided burr nickel-plated steel strip exhibits extremely excellent corrosion resistance. After 48 hours of salt spray test, there is almost no red rust or coating peeling on the double-sided burr nickel-plated steel strip, while the double-sided smooth nickel-plated steel strip is significantly corroded, with red rust appearing and the coating peeling off. This difference is mainly due to the additional physical protection provided by the burr-shaped coating structure during the electroplating process. The burr structure can not only enhance the adhesion of the coating, but also form a microstructural barrier on the metal surface to reduce the penetration of salt spray, thereby enhancing the corrosion resistance of the steel strip.

[0113] Mechanistically, the burr coating provides more mechanical bite points between the coating and the substrate by increasing the surface roughness. The enhanced bonding force of this structure makes the coating not easily peel off when exposed to a corrosive environment. The micro-protrusions in the coating help form an additional protective film to prevent the penetration of salt spray and moisture into the surface of the steel strip substrate 1, thus slowing down the corrosion process.

[0114] In traditional smooth nickel-plated steel strips, there is a lack of additional protection similar to the burr structure. Their smooth surfaces are easily invaded by corrosive media, resulting in coating peeling and corrosion of the metal substrate. This is also why the double-sided burr nickel-plated steel strip shows far better corrosion resistance than traditional smooth nickel-plated steel strips in a salt spray environment. Through this new coating design, the present invention provides higher reliability for battery connectors and can effectively resist the corrosion threats brought by electrolyte penetration and external moisture.

[0115] Experiment 3: Comparison of the interfacial bonding force between Example 3 (double-sided burr nickel-plating) and Comparative Example 3 (double-sided smooth nickel-plating):

[0116] Purpose: The goal of this experiment is to evaluate the performance of the double-sided burr nickel-plated steel strip and the double-sided smooth nickel-plated steel strip in the bonding force between the battery tab and the electrode material. We use the cross-cut method to test the bonding force between the coating and the substrate and conduct a tensile test to simulate the contact situation between the tab and the electrode during the charge and discharge process of the battery. This experiment aims to verify whether the burr coating of the present invention can effectively increase the bonding force and prevent interfacial peeling.

[0117] Experimental procedure: Sample preparation: Select the low-carbon steel strip in Example 3, which is prepared by double-sided burr stamping and pulse electroplating. Select the low-carbon steel strip in Comparative Example 3, which is processed by double-sided stamping and smooth nickel-plating. The electroplating method is the same as that in Example 3.

[0118] Experimental setup: The cross-cut test was used to measure the adhesion of the coating to the steel strip substrate 1. A tensile testing machine was employed for the test, applying a gradually increasing tensile force until the coating peeled off.

[0119] Record the results of the cross-cut test, evaluate the coating peeling situation, and record the maximum tensile force value required in the tensile test.

[0120] Each group of samples was subjected to three independent experiments, and the average value was taken for analysis.

[0121] Table 3: Comparative experimental data of the interfacial adhesion between double-sided burr nickel-plated steel strip and double-sided smooth nickel-plated steel strip:

[0122] Sample Number Maximum Tensile Force (N) Cross-Cut Test Result Remarks 1 (Double-sided Burr) 8.5 No Peeling Good Adhesion 2 (Double-sided Smooth Surface) 4.2 Micro Peeling Poor Adhesion 3 (Double-sided Burr) 9.1 No Peeling Better than Comparative Example 4 (Double-sided Smooth Surface) 3.8 Severe Peeling Unqualified 5 (Double-sided Burr) 8.7 No Peeling Consistent Performance

[0123] From the experimental results, it can be clearly seen that the double-sided burr nickel-plated steel strip has a significant improvement in interfacial adhesion compared to the traditional double-sided smooth nickel-plated steel strip. Through the tensile test, the maximum tensile force value of the double-sided burr nickel-plated steel strip is generally higher than that of the double-sided smooth nickel-plated steel strip, indicating that the burr coating can provide stronger adhesion and anti-peeling ability. In addition, the results of the cross-cut test also show that almost no coating peeling occurred on the double-sided burr nickel-plated steel strip, while different degrees of peeling occurred on the smooth nickel-plated steel strip. This further verifies the advantage of the burr structure in enhancing the adhesion between the coating and the substrate.

[0124] From a mechanistic perspective, the burr-shaped coating significantly improves the adhesion between the coating and the substrate by increasing the surface roughness and providing more mechanical interlocking points. During the electroplating process, nickel particles are deposited on the surface of the steel strip in an irregular manner, forming a coating with microscopic protrusions. This structure can effectively enhance the mechanical interlocking effect, making the coating adhere more firmly to the substrate. When subjected to external forces, the burr-shaped coating can disperse the stress, avoiding cracks or peeling phenomena and further enhancing the tensile strength of the coating.

[0125] In contrast, the surface of the smooth nickel-plated steel strip is smooth, lacking effective mechanical interlocking points between the coating and the substrate. This makes the coating prone to peeling under tensile forces. Especially during the charge and discharge process, the expansion and contraction of the battery tab and electrode may lead to the shedding of the coating and a decrease in the interfacial adhesion. The double-sided burr nickel-plated steel strip can effectively avoid this problem, significantly improving the long-term stability and reliability of the battery connector.

[0126] Experiment 4: Comparison of the cycle life between Example 4 (double-sided burr nickel plating) and Comparative Example 4 (single-sided pulse electroplating):

[0127] Objective: To verify the cycle life of double-sided burr nickel-plated steel strips and single-sided pulse electroplated steel strips in the application of battery tabs, especially the retention of interfacial bonding strength after multiple charge-discharge cycles. The experiment used a combination of tensile tests and cross-cut tests to evaluate the change in the bonding strength between the coating and the substrate during charge and discharge processes.

[0128] Experimental procedure: Sample preparation: Select the high-strength alloy steel strip in Example 4, which is prepared by double-sided burr stamping and pulse electroplating. Select the high-strength alloy steel strip in Comparative Example 4, which is processed by single-sided stamping and single-sided pulse electroplating. The electroplating method is the same as that in Example 4.

[0129] Experimental setup: Use each group of samples as battery tabs and conduct 1000 charge-discharge cycles. The charging and discharging currents are 5A and 5A respectively, and the voltage range is 2.7V - 4.2V. After every 200 cycles, use the cross-cut test to measure the interfacial bonding strength, observe the peeling situation and record it.

[0130] Table 4: Comparative experimental data on the cycle life of double-sided burr nickel-plated steel strips and single-sided pulse electroplated steel strips:

[0131]

[0132]

[0133] Experimental data shows that after 1000 charge-discharge cycles, the double-sided burr nickel-plated steel strip can still maintain a strong interfacial bonding strength. The maximum tensile force value in the tensile test is stable, and the cross-cut test shows that there is almost no peeling of the coating. In contrast, for the single-sided pulse electroplated steel strip under the same number of cycles, the interfacial bonding strength decreases significantly. Severe peeling occurs in the cross-cut test of the coating, and the tensile force value also gradually decreases. This indicates that the burr coating can better maintain its stability and adhesion during charge-discharge cycles.

[0134] In terms of mechanism, the burr coating enhances the bonding strength between the coating and the substrate by providing more mechanical interlocking points. During the charge and discharge of the battery, especially at high current densities, the mechanical stress between the tab and the electrode is very large. Due to the lack of an effective mechanical interlocking structure, the traditional smooth coating is prone to peeling under these stresses. The burr coating, with its three-dimensional burr-like structure, can better disperse the externally applied forces and avoid peeling.

[0135] In addition, the burr structure itself also plays a role in enhancing the wear resistance and thermal expansion resistance of the coating. As the battery is used, the tab and electrode materials will expand and contract. Especially during rapid charge and discharge, the traditional smooth coating is prone to peeling due to thermal expansion or mechanical fatigue. The burr coating, by providing more surface roughness and embedding points, can effectively inhibit this peeling phenomenon and extend the service life of the battery.

[0136] The double-sided burr nickel-plated steel strip and its preparation method proposed by the present invention relate to significantly improving the bonding force, conductivity, and corrosion resistance between the nickel-plated layer 2 and the steel strip substrate 1 by forming a burr-shaped nickel-plated layer on the surface of the steel strip. The specific technical solutions include steps such as stamping processing of the steel strip substrate 1, pre-treatment before electroplating, electroplating process, and post-treatment. Each step is based on different mechanisms for improving the performance of the plating layer. The following is a detailed description of the technical solutions and an analysis of the corresponding mechanisms.

[0137] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A double-sided burr-free nickel-plated steel strip, comprising a steel strip substrate (1), characterized in that: The steel strip substrate (1) is provided with three-dimensional burrs (3) and a nickel-plated layer (2) on both sides, and the nickel-plated layer (2) is composed of a plurality of nickel particles protruding from the surface of the steel strip substrate (1).

2. The double-sided burr nickel-plated steel strip according to claim 1, characterized in that: The shape of the nickel particles is any one or more of a cone, a pyramid or an irregular shape.

3. The double-sided burr nickel-plated steel strip according to claim 1, characterized in that: The height of the nickel particles is 2-8 μm, and the bottom diameter of the nickel particles is 1-4 μm.

4. The double-sided burr nickel-plated steel strip according to claim 1, characterized in that: The steel strip substrate (1) is a low-carbon steel strip or a stainless steel strip.

5. The double-sided burr nickel-plated steel strip according to claim 1, characterized in that: The three-dimensional burr (3) is formed by two-way stamping of a plurality of four-diamond pyramid punches and a square die hole to obtain the three-dimensional burr (3) in the positive and negative directions.

6. A method for preparing a double-sided burr-free nickel-plated steel strip, characterized in that: The double-sided burr nickel-plated steel strip according to any one of claims 1 to 5 comprises the following steps: S1. Stamping: The steel strip substrate (1) is stamped by a two-way stamping die composed of a plurality of four-diamond pyramidal punches and a square die hole to obtain a steel strip substrate (1) having a three-dimensional burr structure on both sides; S2. Pre-plating treatment, the steel strip substrate (1) is degreased, rusted and activated to obtain a clean steel strip surface; S3. Electroplating: immersing the pre-treated steel strip substrate (1) in an electroplating solution, electroplating a nickel layer (2) on both sides of the steel strip substrate (1) by pulse electroplating or periodic reversing electroplating, and forming a burr-like deposition; S4. Post-treatment: The electroplated steel strip is washed, dried, and passivated to obtain a double-sided burr-free nickel-plated steel strip.

7. The method for preparing a double-sided burr-free nickel-plated steel strip according to claim 6, characterized in that: The electroplating solution consists of the following components: nickel sulfate: 70-120 g / L; nickel chloride: 10-20 g / L; boric acid: 30-50 g / L; and a wetting agent: 0.1-0.5 g / L.

8. The method for preparing a double-sided burr-free nickel-plated steel strip according to claim 6, characterized in that: The parameters of the pulse plating are: current density: 2-10A / dm 2 ; Pulse frequency: 100~1000Hz; Duty cycle: 10%~50%.

9. The method for preparing a double-sided burr-free nickel-plated steel strip according to claim 6, characterized in that: The parameters of the periodic reversing electroplating are: forward current density: 2-10A / dm 2 ; Reverse current density: 1~5A / dm 2 ; Forward time: 10~50ms; Reverse time: 5~25ms.

Images