High-toughness low-surface-density foamed nickel and preparation method thereof

Abstract

The invention discloses high-toughness low-surface-density foamed nickel and a preparation method thereof, and belongs to the field of porous metal materials. The method comprises the following steps: firstly, carrying out blending foaming on polyether type polyurethane and polyester type polyurethane to form a gradient hole sponge matrix; then, conducting through PVD (Physical Vapor Deposition); gradient electrodeposition is carried out for three times, a high-toughness nickel layer with a thin and dense surface is formed by adopting low current density for the first time, and a high-strength core nickel layer with a thick and sparse interior is formed by adopting high chloride ion concentration pulse electroplating for the second time; and finally, crystal grains are optimized and stress is eliminated through multi-stage atmosphere heat treatment. The total surface density of the prepared foamed nickel is smaller than or equal to 200 g / m < 2 >, and the foamed nickel has excellent mechanical strength, conductivity and flexibility, is particularly suitable for a flexible battery current collector, effectively solves the problems of brittle fracture and performance degradation of low-surface-density foamed nickel in the prior art, and remarkably reduces the cost of raw materials.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of porous metal material preparation, in particular to high-toughness low-area-density foamed nickel and a preparation method thereof. BACKGROUND

[0002] As a kind of three-dimensional porous metal material, foamed nickel is widely used in the fields of battery electrodes, catalyst carriers and the like due to its high specific surface area and excellent electrical conductivity. With the development of flexible electronic devices, higher requirements are put forward for the low area density and high toughness of foamed nickel.

[0003] However, the traditional foamed nickel faces severe challenges in realizing low area density (≤200 g / m 2 ). First, the reduction of nickel consumption directly leads to insufficient material mechanical strength and decreased electrical conductivity; second, the cost of nickel material accounts for more than 60% in the existing production process, and high area density means high cost, so reducing the area density is the key to controlling the cost, but the performance bottleneck has not been broken through; third, low area density foamed nickel is prone to brittle fracture in bending or folding applications, which limits its commercial application in flexible batteries.

[0004] Therefore, it is of great significance to develop a foamed nickel preparation method with high toughness and low area density. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a high-toughness low-area-density foamed nickel and a preparation method thereof. The method significantly improves the flexibility of foamed nickel by designing a substrate blending and foaming process, gradient electrodeposition and toughness optimization heat treatment process, while ensuring that the area density is ≤200 g / m 2 .

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a high-toughness low-area-density foamed nickel preparation method, which comprises the following steps:

[0008] S1, preparing a substrate: blending and foaming polyether type PU (20-30 wt%) and polyester type PU (70-80 wt%) to form a sponge substrate with a gradient pore structure of surface layer fine pores and inner layer coarse pores, which provides a new pore structure for low-density foamed nickel, the polyester type PU provides high tensile strength and tear resistance to support the skeleton structure, and the ether bond flexible segment (-O-) in the polyether type PU significantly improves the elongation at break of the substrate, avoiding the risk of brittle fracture in subsequent processes;

[0009] S2, Physical Vapor Deposition (PVD): A layer of metallic nickel is uniformly deposited on the sponge substrate prepared in step S1 using conventional physical vapor deposition method to make it conductive, providing a basis for subsequent electrodeposition;

[0010] S3, Gradient Electrodeposition: This step is crucial for forming the gradient density structure, and involves three electrodeposition processes sequentially.

[0011] First electrodeposition (low-density layer): The electroplating solution formula includes: NiSO4·7H2O (300±15g / L), NiCl2·6H2O (40±15g / L), boric acid (30-45g / L), sodium dodecyl sulfate (0.05-0.08g / L), and water. The electroplating process parameters include: electroplating current density of 1-10A / dm³. 2 The electroplating time is 1-20 min, the electroplating speed is 0.1-1 m / min, the anode area ratio is 1:1, and the plating solution temperature is 40-60℃; the pH value of the plating solution is 4-5.5. Through the first electrodeposition treatment, a layer with a density of approximately 40-60 g / m² is deposited on the surface of the conductive sponge. 2 A dense but thin nickel layer with fine fibrous strands, which mainly provides flexibility and impact resistance, is washed with pure water after electroplating.

[0012] Second electrodeposition (high-density layer): The electroplating solution formulation includes: NiSO4·7H2O (280±15g / L), NiCl2·6H2O (80±15g / L), boric acid (30-45g / L), sodium dodecyl sulfate (0.05-0.08g / L), and water. A pulse electroplating process is used for the second electrodeposition. The electroplating process parameters include: electroplating current density of 1-30A / dm2, electroplating time of 1-30min, electroplating speed of 0.1-1m / min, and anode area ratio of 1:4; the pulse parameters are: forward current 20±5A / dm2. 2 Reverse current -8±5A / dm 2 The forward pulse width is 10ms and the reverse pulse width is 2ms. During the second electrodeposition process, the deep plating ability of the plating solution can be improved by increasing the concentration of chloride ions in the electroplating solution. Combined with the coarse pore structure of the inner layer of the sponge substrate, nickel metal can be preferentially deposited inside, thereby improving the effect of the inner metal plating layer of the foam nickel. As a result, a thicker nickel layer is deposited inside and on the surface of the sponge substrate, forming a high-density core layer with coarse and sparse ribs in the core layer.

[0013] Third time of electrodeposition (high density layer): the process parameters are basically the same as the second time of electrodeposition, but the anode area ratio is adjusted to 4:1 to balance the deposition effect of the two sides of the sponge substrate A and B, and to ensure that the density gradient of the final product in the thickness direction is symmetrical, after three times of electrodeposition treatment, the gradient surface density structure of the foamed nickel with the surface density of the outer layer lower than that of the inner layer is obtained, the gradient surface density structure of the foamed nickel is divided into three layers of A surface, middle layer and B surface along the thickness direction, and the surface density ratio is 1:2:1, the filaments of the A surface and the B surface are thin and dense, which provide flexibility and impact resistance, and the filaments of the inner layer are thick and sparse, which are used to enhance the overall mechanical stability;

[0014] S4, toughness optimization heat treatment: the foamed nickel after electrodeposition is subjected to multi-stage heat treatment in a protective atmosphere, specifically including:

[0015] S41, under the conditions of N2:H2 (1:2-3) atmosphere, 4-8 L / min flow and temperature of 300-500 DEG C, heat preservation for 1-60 minutes, and then promote the directional growth and preliminary refinement of nickel grains;

[0016] S42, heat preservation for 2-8 minutes under the conditions of 600-700 DEG C, H2 atmosphere (3±0.5 L / min) to completely eliminate the internal stress generated by electrodeposition;

[0017] Finally, cooling is carried out by nitrogen blowing assisted water cooling, the cooling rate is greater than or equal to 5 DEG C / s, the synergistic optimization of grain refinement, stress release and interface strengthening is realized, the metal toughness of the foamed nickel is improved, and the mechanical properties and electrical properties of the foamed nickel are enhanced.

[0018] In the second aspect, the present application provides a high-toughness low-surface-density foamed nickel prepared by the above-mentioned method, which has a total surface density of less than or equal to 200 g / m 2 , and has a three-layer gradient surface density structure of A surface, middle layer and B surface along the thickness direction, and the surface density ratio is 1:2:1, wherein the filaments of the A surface and the B surface are thin and dense, which are used to ensure the flexibility of the product, and the filaments of the inner layer are thick and sparse, which are used to ensure the overall strength of the product.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. Excellent mechanical properties: through the design of polyether / polyester PU blended substrate and gradient electrodeposition, the structure of "soft outside and hard inside" is realized, high tensile strength, high tear resistance and high bending fatigue life are simultaneously obtained at low surface density, and the problem of brittle fracture is solved.

[0021] 2. Good electrical conductivity: the pulse plating process forms a dense and uniform plating layer, which, combined with the internal high-density metal layer, ensures excellent overall electrical conductivity.

[0022] 3. Significant cost advantage: the total surface density is less than or equal to 200 g / m2 This significantly reduced the amount of nickel used, directly lowering the cost of raw materials.

[0023] 4. High process controllability: By adjusting the electrodeposition and heat treatment parameters, the density gradient, mechanical properties and electrical conductivity of nickel foam can be precisely controlled to meet the needs of different application scenarios.

[0024] 5. Broad application prospects: It is particularly suitable for flexible battery electrode current collectors that require repeated bending and folding, and can also be used in other lightweight applications such as catalysis and filtration. Attached Figure Description

[0025] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the embodiments described below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0026] Figure 1 This is a flowchart of a method for preparing high-toughness, low-area-density nickel foam according to some embodiments of this application.

[0027] Figure 2 These are 50x SEM images of the cross-sections of the nickel foam products prepared in Example 1 and Comparative Example 1.

[0028] Figure 3 These are 5000x SEM images of the electrodeposited grains on the surface of the nickel foam products prepared in Example 1 and Comparative Example 1.

[0029] Figure 4 This is a 1000x SEM image of the nickel foam products prepared in Example 1 and Comparative Example 1 under ductile fracture conditions. Detailed Implementation

[0030] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Example 1

[0032] S1. Matrix preparation: 25wt% polyether PU and 75wt% polyester PU are blended and foamed at normal pressure to form a sponge matrix with a thickness of 1.6mm. The sponge matrix exhibits a gradient structure with a surface pore size of 50μm and an inner pore size of 200μm.

[0033] S2, PVD conductivity: The sponge matrix prepared in step S1 is fed into a PVD device, and a 0.1 μm thick nickel layer is deposited under vacuum conditions.

[0034] S3, gradient electrodeposition:

[0035] First electrodeposition: NiSO4·7H2O 300 g / L, NiCl2·6H2O 40 g / L, boric acid 35 g / L, and sodium dodecyl sulfate 0.06 g / L were added to the solvent water, and the electrodeposition was carried out at 5 A / dm³. 2 Electroplating at a current density of 10 minutes resulted in the deposition of a layer with a surface density of 50 g / m² on the sponge substrate surface. 2 A dense but relatively thin nickel layer is formed, wherein the plating bath temperature is 50℃ and pH=5, and the plating is washed with pure water after the first electroplating is completed.

[0036] Second electrodeposition: NiSO4·7H2O 280 g / L, NiCl2·6H2O 80 g / L, boric acid 35 g / L, and sodium dodecyl sulfate 0.06 g / L were added to the solvent water, using a pulsed power supply (forward current 20 A / dm²). 2 Forward pulse width 10ms; reverse current -8A / dm 2 (Reverse pulse width 2ms), two anode area ratio of 1:4, electroplating for 15 minutes;

[0037] Third electrodeposition: Using the same electroplating solution and electroplating parameters as the second, the ratio of the two anode areas was adjusted to 4:1, and electroplating was performed for 15 minutes to obtain a gradient surface density structure of nickel foam with an outer surface density lower than that of the inner surface density. This gradient surface density structure of nickel foam is divided into three layers along the thickness direction: surface A, middle layer, and surface B, with a surface density ratio of 1:2:1.

[0038] S4. Heat treatment: The electrodeposited nickel foam is heated at 400℃ for 30 minutes under an atmosphere of N2:H2 volume ratio of 1:3 and flow rate of 5L / min; then the atmosphere is switched to pure H2 with a flow rate of 3L / min and heated at 650℃ for 5 minutes; finally, it is purged with nitrogen and immersed in water for rapid cooling at a cooling rate of ≥5℃ / s to obtain the final nickel foam product.

[0039] S5. Calculate the total areal density and nickel content of the obtained foamed nickel product.

[0040] Example 2

[0041] S1. Matrix preparation: 20wt% polyether PU and 80wt% polyester PU are blended and foamed at normal pressure to form a sponge matrix with a thickness of 1.6mm. The sponge matrix exhibits a gradient structure with a surface pore size of 50μm and an inner pore size of 200μm.

[0042] S2, PVD conductivity: The sponge matrix prepared in step S1 is fed into a PVD device, and a 0.1 μm thick nickel layer is deposited under vacuum conditions.

[0043] S3, gradient electrodeposition:

[0044] First electrodeposition: NiSO4·7H2O 285 g / L, NiCl2·6H2O 25 g / L, boric acid 30 g / L, and sodium dodecyl sulfate 0.05 g / L were added to the solvent water, and the electrodeposition was carried out at 10 A / dm³. 2 Electroplating at a current density of 1 minute deposits a layer with a density of 40 g / m² on the surface of the sponge substrate. 2 A dense but relatively thin nickel layer is formed, wherein the plating bath temperature is 60℃ and pH=5.5, and the plating is washed with pure water after the first electroplating is completed.

[0045] Second electrodeposition: NiSO4·7H2O 265g / L and NiCl2·6H2O 65g / L, boric acid 30g / L, and sodium dodecyl sulfate 0.05g / L were added to the solvent water, using a pulsed power supply (forward current 15A / dm). 2 Forward pulse width 10ms; reverse current -5A / dm 2 (Reverse pulse width 2ms), two anode area ratio of 1:4, electroplating for 30 minutes;

[0046] Third electrodeposition: Using the same plating solution and electroplating parameters as the second, the ratio of the two anode areas was adjusted to 4:1, and electroplating was performed for 30 minutes to obtain a gradient surface density structure of nickel foam with an outer surface density lower than that of the inner surface density. This gradient surface density structure of nickel foam is divided into three layers along the thickness direction: surface A, middle layer, and surface B, with a surface density ratio of 1:2:1.

[0047] S4. Heat treatment: The electrodeposited nickel foam is heated at 500℃ for 1 minute in an atmosphere with a N2:H2 volume ratio of 1:2 and a flow rate of 8L / min. Then, the atmosphere is switched to pure H2 with a flow rate of 3.5L / min and heated at 700℃ for 2 minutes. Finally, it is purged with nitrogen and immersed in water for rapid cooling at a cooling rate of ≥5℃ / s to obtain the final nickel foam product.

[0048] S5. Calculate the total areal density and nickel content of the foamed nickel product.

[0049] Example 3

[0050] S1. Matrix preparation: 30wt% polyether PU and 70wt% polyester PU are blended and foamed at normal pressure to form a sponge matrix with a thickness of 1.6mm. The sponge matrix exhibits a gradient structure with a surface pore size of 50μm and an inner pore size of 200μm.

[0051] S2, PVD conductivity: The sponge matrix prepared in step S1 is fed into a PVD device, and a 0.1 μm thick nickel layer is deposited under vacuum conditions.

[0052] S3, gradient electrodeposition:

[0053] First electrodeposition: NiSO4·7H2O 315 g / L, NiCl2·6H2O 55 g / L, boric acid 45 g / L, and sodium dodecyl sulfate 0.08 g / L were added to the solvent water, and the electrodeposition was carried out at 1 A / dm³. 2 Electroplating at a current density of 20 minutes resulted in the deposition of a layer with a surface density of 60 g / m² on the sponge substrate surface. 2 A dense but relatively thin nickel layer is formed, wherein the plating bath temperature is 40℃ and pH=4, and the plating is washed with pure water after the first electroplating is completed.

[0054] Second electrodeposition: NiSO4·7H2O 295g / L and NiCl2·6H2O 95g / L, boric acid 30g / L, and sodium dodecyl sulfate 0.08g / L were added to the solvent water, using a pulsed power supply (forward current 25A / dm). 2 Forward pulse width 10ms; reverse current -13A / dm 2 (Reverse pulse width 2ms), two anode area ratio of 1:4, electroplating for 1 minute;

[0055] Third electrodeposition: Using the same plating solution and electroplating parameters as the second, the ratio of the two anode areas was adjusted to 4:1, and electroplating was performed for 1 minute to obtain a gradient surface density structure of nickel foam with an outer surface density lower than that of the inner surface. This gradient surface density structure of nickel foam is divided into three layers along the thickness direction: surface A, middle layer, and surface B, with a surface density ratio of 1:2:1.

[0056] S4. Heat treatment: The electrodeposited nickel foam is heated at 300℃ for 60 minutes under an atmosphere of N2:H2 volume ratio of 1:2.5 and flow rate of 4L / min; then the atmosphere is switched to pure H2 with a flow rate of 2.5L / min and heated at 600℃ for 8 minutes; finally, it is purged with nitrogen and immersed in water for rapid cooling at a cooling rate ≥5℃ / s to obtain the final nickel foam product.

[0057] S5. Calculate the total areal density and nickel content of the obtained foamed nickel product.

[0058] Comparative Example 1

[0059] Compared with Example 1, the difference is that: Comparative Example 1 uses a polyester-type PU single matrix material, and the electrodeposition process uses two high-density layer electroplating (i.e. the second electrodeposition and the third electrodeposition in Example 1), and the total areal density and nickel material ratio of the obtained foam nickel product are calculated.

[0060] The products obtained in Examples 1-3 and Comparative Example 1 were subjected to performance tests, including longitudinal strength, transverse strength, longitudinal resistivity, transverse resistivity, and resistance to cracking at 180° flexural angle. The units for longitudinal and transverse strength are N / 20mm, and the units for longitudinal and transverse resistivity are mΩ·100*10mm.2 The performance test results are shown in Table 1.

[0061] Table 1. Performance test results of the products prepared in Examples 1-3 and Comparative Example 1

[0062]

[0063] As can be seen from Table 1, the areal density of the nickel foam products obtained in Examples 1-3 is all below 170 g / m³. 2 The longitudinal resistivity is greater than 29 N / 20 mm, the transverse resistivity is greater than 18 N / 20 mm, and the longitudinal resistivity is greater than 66 mΩ.

[0064] Ω·100*10mm 2 The transverse resistivity is greater than 86 mΩ·100*10 mm. 2 The number of times it can withstand a 180° bend and crack resistance is greater than 7; while the areal density of the nickel foam product prepared by the traditional method is only 165 g / m³. 2 The longitudinal resistivity is 16 N / 20 mm, the transverse resistivity is 10 N / 20 mm, and the longitudinal resistivity is 97 mΩ·100*10 mm. 2 The lateral resistivity is 137 mΩ·100*10 mm 2 The number of times the material resisted cracking after bending 180° was 4. Therefore, compared with Comparative Example 1, the areal density of Examples 1-3 is comparable to that of Comparative Example 1. The transverse and longitudinal resistivity values ​​of Examples 1-3 are much greater than those of Comparative Example 1. The transverse and longitudinal resistivity of Examples 1-3 are much smaller than those of Comparative Example 1. The number of times the material resisted cracking after bending 180° in Examples 1-3 is also much greater than that in Comparative Example 1. Moreover, the proportion of nickel material in Examples 1-3 is only 36%, which is much lower than 55% in Comparative Example 1.

[0065] from Figures 2-4 It can be seen from this that Figure 2 a shows a 50x SEM image of the cross-section of the nickel foam product prepared in Example 1. Figure 2 b shows a 50x SEM image of the cross-section of the nickel foam product prepared in Comparative Example 1. Figure 3 a shows a 5000x SEM image of the electrodeposited grains on the surface of the nickel foam product prepared in Example 1. Figure 3 b shows a 5000x SEM image of the electrodeposited grains on the surface of the nickel foam product prepared in Comparative Example 1. Figure 4 a shows a 1000x SEM image of the nickel foam product prepared in Example 1 under ductile fracture conditions. Figure 4b shows a 1000x SEM image of the nickel foam product prepared in Comparative Example 1 under ductile fracture conditions. The nickel foam product obtained in Example 1 exhibits a gradient areal density structure and fine surface grains, while the nickel foam product obtained in Comparative Example 1 has a uniform porous structure and rough surface grains. At the same time, under ductile fracture conditions, the nickel foam product obtained in Example 1 exhibits a fracture morphology of metal extension, while the nickel foam product obtained in Comparative Example 1 has a smooth fracture surface and poor metal ductility under ductile fracture conditions.

[0066] In summary, the high-toughness, low-area-density foam nickel preparation method provided by this invention produces foam nickel with excellent mechanical strength, conductivity, and flexibility, making it particularly suitable for flexible battery current collectors. It effectively solves the problems of brittle fracture and performance degradation of low-area-density foam nickel in the prior art, while significantly reducing raw material costs.

[0067] The above provides a detailed description of a high-toughness, low-area-density nickel foam and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for preparing high-toughness, low-area-density nickel foam, characterized in that, The method includes the following steps: S1. Blend polyether polyurethane and polyester polyurethane at a predetermined mass percentage and foam to form a sponge matrix with a gradient pore structure of fine pores on the surface and coarse pores in the inner layer. S2. A layer of metallic nickel is uniformly deposited on the surface of the sponge substrate using physical vapor deposition to form a conductive sponge. S3. Perform three electrodepositions on the conductive sponge in sequence. The first electrodeposition uses a low current density and short time process to form a low-density nickel layer on the surface of the conductive sponge. The second and third electrodepositions both use a high current density and pulse electroplating process to form a high-density nickel layer inside the low-density nickel layer and the conductive sponge, so that the final foam nickel has a gradient areal density structure, and the gradient areal density structure foam nickel is divided into three layers along the thickness direction: surface A, middle layer and surface B. S4. The electrodeposited nickel foam is subjected to multi-stage gradient heat treatment under a protective atmosphere, followed by rapid cooling at a preset cooling rate.

2. The method for preparing high-toughness, low-area-density nickel foam as described in claim 1, characterized in that, In step S1, the preset mass percentage of polyether polyurethane to polyester polyurethane is 20-30%: 70-80%.

3. The method for preparing high-toughness, low-area-density nickel foam as described in claim 2, characterized in that, In step S3, the composition of the electroplating solution for the first electrodeposition includes:

4. The method for preparing high-toughness, low-area-density nickel foam as described in claim 3, characterized in that, In step S3, the process conditions for the first electrodeposition are: electroplating current density of 1-10 A / dm³. 2 The electroplating time is 1-20 min, the electroplating solution temperature is 40-60℃, the pH value is 4-5.5, the electroplating speed is 0.1-1 m / min, and the anode area ratio is 1:

1.

5. The method for preparing high-toughness, low-area-density nickel foam as described in claim 4, characterized in that, In step S3, the electroplating solutions for the second and third electrodepositions include:

6. The method for preparing high-toughness, low-area-density nickel foam as described in claim 5, characterized in that, In step S3, the process conditions for the second electrodeposition are: forward current density of 15-25 A / dm³. 2 The reverse current density is -3 to -13 A / dm. 2 The forward pulse width is 10ms, the reverse pulse width is 2ms, the electroplating time is 1-30min, the electroplating speed is 0.1-1m / min, and the anode area ratio is 1:

4.

7. The method for preparing high-toughness, low-area-density nickel foam as described in claim 6, characterized in that, In step S3, the process conditions for the second electrodeposition are: forward current density of 15-25 A / dm³. 2 The reverse current density is -3 to -13 A / dm. 2 The forward pulse width is 10ms, the reverse pulse width is 2ms, the electroplating time is 1-30min, the electroplating speed is 0.1-1m / min, and the anode area ratio is 4:

1.

8. The method for preparing high-toughness, low-area-density nickel foam as described in claim 7, characterized in that, Step S4 specifically includes: S41. Under a mixed atmosphere of nitrogen and hydrogen with a volume ratio of 1:2-3, control the flow rate to be 4-8 L / min and the temperature to be 300-500℃ for 1-60 minutes. S42. Under a hydrogen atmosphere, control the flow rate to 2.5-3.5 L / min and the temperature to 600-700℃ and hold for 2-8 minutes; S43. Nitrogen purging-assisted water cooling is used to cool the heat-treated nickel foam, wherein the preset cooling rate is ≥5℃ / s.

9. A high-toughness, low-area-density nickel foam, characterized in that, This nickel foam is prepared based on the high-toughness, low-area-density nickel foam preparation method according to any one of claims 1-8, and its total area-density is ≤200g / m³. 2 It has a three-layer gradient surface density structure along the thickness direction, consisting of surface A, middle layer, and surface B, with a surface density ratio of 1:2:1 for surface A, middle layer, and surface B.

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