Low-resistance high-weatherability surface modified silver-coated nickel powder, and preparation method and application thereof

Abstract

This invention proposes a low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, its preparation method, and its application. The preparation method includes: chemically plating silver onto the surface of nickel powder under weak acid conditions to obtain silver-coated nickel powder; and grafting an organic modifier onto the surface of the silver-coated nickel powder to obtain the surface-modified silver-coated nickel powder. The organic modifier includes thiol compounds and thiol amino acids. This invention prepares a dense silver layer through chemical silver plating under weak acid conditions, thus ensuring complete silver coating, improving conductivity and weather resistance. The grafting of organic modifiers provides protection and improves the compatibility of the silver-coated nickel powder with the resin matrix. The resulting surface-modified silver-coated nickel powder exhibits excellent acid and alkali resistance and high stability in harsh environments. When used in HJT battery conductive pastes, it simultaneously achieves low resistivity and high weather resistance.

Description

Technical Field

[0001] This invention relates to the field of HJT battery technology, and in particular to a low-resistance, high-weather-resistant surface-modified silver-coated nickel powder, its preparation method, and its application. Background Technology

[0002] Heterojunction (HJT) solar cells, as a type of high-efficiency solar cell, require low-temperature curing (typically below 200°C) in their fabrication process, thus necessitating low-temperature conductive silver paste. Currently, silver powder is the primary conductive filler used in HJT cell pastes; however, silver powder is expensive and prone to migration in high-humidity environments, affecting cell reliability. To reduce costs, silver-coated copper powder has been proposed as an alternative, but the copper core is easily oxidized and exhibits poor stability in acidic and alkaline environments, resulting in insufficient weather resistance of the paste. Silver-coated nickel powder combines the low cost of the nickel core with the high conductivity of the silver layer; however, traditional silver-coated nickel powder has a discontinuous and non-dense silver layer coating, poor compatibility with the resin matrix, and poor dispersibility, affecting the paste's conductivity and long-term stability.

[0003] In recent years, chemical silver plating technology has been used to prepare silver-coated nickel powder. However, this process often uses silver ammonia solution under alkaline conditions, which easily leads to a rough, porous silver layer and poor environmental performance. While surface modification technology is crucial, existing modifiers (such as silane coupling agents) have weak adhesion to the silver layer and cannot effectively improve dispersibility. Therefore, developing a method for preparing silver-coated nickel powder with low resistance, high weather resistance, and good dispersibility is of great significance for promoting the development of HJT battery slurries. Summary of the Invention

[0004] Based on the technical problems existing in the background art, this invention proposes a low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, its preparation method, and its application. A dense silver layer is prepared by chemically plating silver under weak acid conditions, thus ensuring complete silver coating and improving conductivity and weather resistance. Protection is achieved by grafting organic modifiers, and the compatibility between the silver-coated nickel powder and the resin matrix is ​​improved. The resulting surface-modified silver-coated nickel powder exhibits excellent acid and alkali resistance and high stability in harsh environments. When used in HJT battery conductive paste, it simultaneously achieves low resistivity and high weather resistance.

[0005] The present invention proposes a method for preparing low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, comprising the following steps:

[0006] S1. The surface of nickel powder is chemically plated with silver under weak acid conditions to obtain silver-coated nickel powder;

[0007] S2. Graft an organic modifier onto the surface of the silver-coated nickel powder to obtain the surface-modified silver-coated nickel powder; wherein the organic modifier includes thiol compounds and thiol amino acids.

[0008] In this invention, a dense silver layer is prepared under weakly acidic conditions. The resistivity of the silver-coated nickel powder is low, close to that of silver powder. Subsequently, an organic modifier is grafted to achieve protection, resulting in better acid and alkali resistance than silver-coated copper powder, and high stability in harsh environments. The organic modifier is a combination of thiol compounds and thiol amino acids. The strong coordination of the thiol groups of the two compounds forms a strong chemical bond on the surface of the silver layer. At the same time, the carboxyl and amino functional groups at the molecular ends generate strong interactions (hydrogen bonds, etc.) with the resin matrix, constructing a stable organic-inorganic hybrid interface. Ultimately, this results in uniform dispersion of the powder in the HJT battery conductive slurry, significantly reduced agglomeration, lower percolation threshold, and enhanced interfacial bonding.

[0009] Preferably, in step S1, the chemical silver plating of the nickel powder surface under weak acid conditions specifically includes: adding the nickel powder to a reducing agent solution and mixing it, then adding a silver source acidic solution, adjusting the pH of the system to 6-6.5, and then carrying out a reduction reaction to obtain the silver-coated nickel powder.

[0010] Preferably, the reducing agent solution comprises a complexing agent and a reducing agent;

[0011] The complexing agent is at least one of triethylamine, triethanolamine, diethylenetriamine, ethylenediamine, or disodium ethylenediaminetetraacetate (EDTA-2Na), and the reducing agent is at least one of glucose, fructose, ascorbic acid, sodium borohydride, or potassium sodium tartrate.

[0012] In this invention, while performing chemical silver plating under weak acid conditions, a complexing agent (EDTA-2Na and ethylenediamine) and a reducing agent (ascorbic acid and glucose) are selected to make the silver layer more dense.

[0013] Preferably, the silver source acidic solution includes a silver salt; the silver salt is at least one selected from silver nitrate, silver methanesulfonate, or silver iodide.

[0014] The pH of the silver source acidic solution is 2-3.

[0015] Preferably, the reduction reaction is carried out at a temperature of 20-60°C for 1-3 hours.

[0016] Preferably, in step S1, before chemically plating silver onto the surface of the nickel powder, the nickel powder is further subjected to alkali washing and acid washing in sequence;

[0017] The pH of the alkaline wash is 10-11, and the pH of the acid wash is 6-7.

[0018] Preferably, in step S2, grafting an organic modification layer onto the surface of the silver-coated nickel powder specifically includes: dispersing the silver-coated nickel powder in an alcohol-water mixed solvent, adding a thiol compound and a thiol amino acid, adjusting the pH of the system to 8-9, and then stirring the reaction to obtain the surface-modified silver-coated nickel powder.

[0019] The general structural formula of the thiol compound is: The general structural formula of the thiol amino acid is: R1 is an alkyl group with 2-6 carbon atoms, and R2 is an alkyl group with 3-10 carbon atoms.

[0020] In this invention, a complex system of thiol compounds and thiol amino acids is used to organically modify the surface of a silver layer. On the one hand, the strong coordination between the thiol groups and silver, as well as the multipolar functional groups such as carboxyl and amino groups, significantly improve the dispersibility and interfacial bonding strength of the powder in the resin matrix. On the other hand, by controlling the number of carbon atoms in the alkyl groups of both compounds, the complex system is ensured to have certain hydrophobic properties, further enhancing its compatibility with nonpolar resin matrices. Furthermore, the small-molecule thiol compounds and the large-molecule thiol amino acids can be mutually compatible, and after grafting, a dense, stable, and functionally rich organic-inorganic hybrid interfacial layer can be constructed on the powder surface, which also improves its dispersion stability in the resin system.

[0021] Preferably, the thiol compound is mercaptopropionic acid, and the thiol amino acid is D-penicillamine; the mass ratio of mercaptopropionic acid to D-penicillamine is 1-3:1.

[0022] In this invention, mercaptopropionic acid (MPA, HS-CH2-CH2-COOH) and D-penicillamine ((CH3)2C(SH)-CH(NH2)-COOH) are combined as organic modifiers for the following three reasons:

[0023] Coordination chemistry principle: Both mercaptopropionic acid and D-penicillamine contain thiol groups (-SH) with strong coordination ability. Their lone pair electrons can efficiently coordinate with the empty orbitals of silver atoms to form a strong Ag-S covalent bond (bond energy about 217 kJ / mol). This coordination effect is thermodynamically far superior to physical adsorption that relies solely on van der Waals forces.

[0024] Steric hindrance and synergistic effect: Mercaptopropionic acid has a small molecular size and good chain segment flexibility, which can quickly diffuse and adsorb onto the surface of the silver layer to form a high-coverage monolayer basis; D-penicillamine contains not only thiol and carboxyl groups, but also amino (-NH2) and a hydrophobic tert-butyl group. Its multifunctional characteristics can provide richer interfacial interactions: thiol groups bond with silver, while carboxyl and amino groups can form hydrogen bonds or ionic bonds with polar groups (such as epoxy and hydroxyl groups) in the resin matrix, significantly enhancing the interfacial binding force; its large steric hindrance can also generate a stronger stereorepulsion effect, further preventing powder agglomeration.

[0025] Synergistic effect of dual modifiers: The small molecule MPA can quickly occupy the active sites on the surface of the silver layer, while the slightly larger molecule penicillamine can intersect between them, "anchoring" itself to the silver layer through multiple forces, and forming a hydrogen bond network with the carboxyl groups of MPA, together constructing a dense, stable and functional group-rich organic-inorganic hybrid interface layer; this interface layer can effectively reduce the surface energy of the powder, and greatly improve its dispersion stability in the resin system through electrostatic repulsion (carboxyl groups are negatively charged by ionization) and steric hindrance effect.

[0026] In this invention, the coordination behavior of the organic modifier was also simulated using density functional theory (DFT) calculations (using B3LYP functionals).

[0027] Adsorption of mercaptopropionic acid on the Ag(111) surface: The most stable configuration is that the mercapto-SH group is perpendicularly coordinated to the Ag surface, with an adsorption energy (E_ads) of -1.78 eV; charge distribution analysis shows that 0.20 eV is transferred from Ag atoms to S atoms. - This forms a strong covalent Ag-S bond;

[0028] Adsorption of penicillamine on the Ag(111) surface: The most stable configuration is bidentate coordination of mercapto-SH and carboxyl-O, with an adsorption energy as high as -2.45 eV, which is significantly higher than that of single mercapto coordination (-1.82 eV). This indicates that the multifunctionality of penicillamine enables it to anchor on the silver surface in a more stable mode.

[0029] Molecular dynamics simulations show that the pre-adsorbed MPA provides a pre-organized interface for penicillamine. The amino group (-NH2) of penicillamine can form hydrogen bonds with the carboxyl group (-COOH) of MPA, further stabilizing the modified layer. This synergistic effect makes the composite modified layer denser and more stable than the film formed by a single modifier.

[0030] Preferably, in step S2, the temperature of the stirring reaction is 40-60℃ and the time is 1-3h.

[0031] Preferably, in step S2, before grafting the organic modified layer onto the surface of the silver-coated nickel powder, the method further includes grafting an epoxy silane coupling agent onto the surface of the silver-coated nickel powder.

[0032] Preferably, the epoxy silane coupling agent is at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, or γ-glycidoxypropylmethyldimethoxysilane.

[0033] In this invention, silver-coated nickel powder is first surface modified using a silane coupling agent with epoxy-active reaction sites, and then an organic modifier is added for grafting reaction. The ring-opening reaction of epoxy and mercapto groups can be used to achieve chemical bonding of the organic modifier on the surface of the silver-coated nickel powder, ultimately obtaining surface-modified silver-coated nickel powder with better dispersion stability.

[0034] The present invention also proposes a low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, which is prepared by the above-mentioned preparation method.

[0035] In this invention, the surface-modified silver-coated nickel powder is essentially a multi-layered core-shell structure of "nickel core-silver layer-organic modification layer".

[0036] This invention also proposes the application of the above-mentioned low-resistance, high-weather-resistant surface-modified silver-coated nickel powder in HJT battery conductive paste.

[0037] The beneficial effects of the low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder described in this invention are as follows:

[0038] (1) Traditional silver plating process for nickel powder uses silver ammonia solution. Under alkaline conditions, the silver layer is discontinuous and not dense, with high resistivity and poor environmental performance. This invention uses weak acid conditions to plating silver, which prepares a denser and more continuous silver layer, avoids the use of silver ammonia solution, and improves conductivity and weather resistance.

[0039] (2) Traditional silver-coated nickel powder has poor surface modification effect, the modifier has weak bonding with the silver layer, poor dispersibility, and affects the uniformity and conductivity of the slurry; the present invention designs a compound of thiol compounds and thiol amino acids as an organic modification layer to improve the compatibility between silver-coated nickel powder and resin matrix and improve dispersibility.

[0040] (3) The present invention applies the surface-modified silver-coated nickel powder to the low-temperature conductive silver paste of HJT battery, achieving the technical effects of low resistance, high weather resistance, conductivity close to silver powder, and superior to silver-coated copper powder. Attached Figure Description

[0041] Figure 1 This is a cross-sectional electron microscope image of the surface-modified silver-coated nickel powder described in Example 1 of the present invention;

[0042] Figure 2 This is an overall electron microscope image of the surface-modified silver-coated nickel powder described in Example 1 of the present invention. Detailed Implementation

[0043] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0044] Example 1

[0045] A low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder is prepared by the following method:

[0046] (1) Commercially available spherical nickel powder (D50 particle size of 5μm) was added to deionized water and dispersed evenly. Then, sodium hydroxide solution (concentration of 1mol / L) was added to adjust the pH of the system to 10.5. After stirring for 30min, the surface oil was removed. Then, dilute nitric acid solution (concentration of 1mol / L) was added to adjust the pH of the system to 6.5. After stirring for 30min, the surface oxide layer was removed. After standing for 30min, most of the supernatant was extracted, and a small amount of acid was retained as a liquid seal to prevent the nickel powder from oxidizing, thus obtaining pretreated nickel powder.

[0047] (2) A complexing agent consisting of disodium ethylenediaminetetraacetate (EDTA-2Na) and ethylenediamine (molar ratio 1:1) and a reducing agent consisting of ascorbic acid and glucose (molar ratio 1:1) are added to water and dispersed evenly. Then, the pretreated nickel powder is added and stirred until well mixed. A nitric acid solution containing silver nitrate (pH 2.4) is added, and a sodium hydroxide solution (concentration 1 mol / L) is added dropwise to maintain the pH of the reaction system to 6.3 ± 0.1. The amount of complexing agent added is 50 wt% of the spherical nickel powder, the amount of reducing agent added is 30 wt% of the spherical nickel powder, and the amount of silver nitrate added is 15 wt% of the spherical nickel powder. The mixture is stirred at 40°C for 1 h to ensure silver coating. The mixture is then filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 4 h to obtain silver-coated nickel powder.

[0048] (3) The above silver-coated nickel powder was added to a mixed solvent of ethanol and water (volume ratio of 4:1) and dispersed evenly. Then, an organic modifier including mercaptopropionic acid and D-penicillamine (mass ratio of 2:1) was added. The amount of organic modifier added was 1.5% of the mass of the silver-coated nickel powder. Dilute ammonia was added to adjust the pH of the system to 8.5. The reaction was stirred with ultrasonic assistance (power of 100W) at 50°C for 2 hours. The mixture was then filtered, washed with ethanol, and vacuum dried at 60°C for 4 hours to obtain the low-resistance, high-weather-resistant surface-modified silver-coated nickel powder. Its microstructure is as shown in the figure. Figure 1 , 2 .

[0049] Example 2

[0050] A low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder is prepared by the following method:

[0051] (1) Commercially available spherical nickel powder (D50 particle size of 5μm) was added to deionized water and dispersed evenly. Then, sodium hydroxide solution (concentration of 1mol / L) was added to adjust the pH of the system to 10.5. After stirring for 30min, the surface oil was removed. Then, dilute nitric acid solution (concentration of 1mol / L) was added to adjust the pH of the system to 6.5. After stirring for 30min, the surface oxide layer was removed. After standing for 30min, most of the supernatant was extracted, and a small amount of acid was retained as a liquid seal to prevent the nickel powder from oxidizing, thus obtaining pretreated nickel powder.

[0052] (2) A complexing agent consisting of disodium ethylenediaminetetraacetate (EDTA-2Na) and triethanolamine (molar ratio 1:1) and a reducing agent consisting of sodium potassium tartrate and glucose (molar ratio 1:1) are added to water and dispersed evenly. Then, the pretreated nickel powder is added and stirred until well mixed. A nitric acid solution containing silver nitrate (pH 2.0) is added, and a sodium hydroxide solution (concentration 1 mol / L) is added dropwise to maintain the reaction system at pH 6.3 ± 0.1. The amount of complexing agent added is 30 wt% of the spherical nickel powder, the amount of reducing agent added is 25 wt% of the spherical nickel powder, and the amount of silver nitrate added is 15 wt% of the spherical nickel powder. The reaction is stirred at 60°C for 1 h to ensure silver coating. The mixture is filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 4 h to obtain silver-coated nickel powder.

[0053] (3) The above silver-coated nickel powder is added to a mixed solvent of ethanol and water (volume ratio of 4:1) and dispersed evenly. Then, an organic modifier including mercaptopropionic acid and D-penicillamine (mass ratio of 1:1) is added. The amount of organic modifier added is 1.5% of the mass of the silver-coated nickel powder. Then, dilute ammonia is added to adjust the pH of the system to 8.5. The reaction is stirred with ultrasonic assistance (power of 100W) at 60°C for 1 hour. The mixture is then filtered, washed with ethanol, and vacuum dried at 60°C for 4 hours to obtain the low-resistance, high-weather-resistant surface-modified silver-coated nickel powder.

[0054] Example 3

[0055] A low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder is prepared by the following method:

[0056] (1) Commercially available spherical nickel powder (D50 particle size of 5μm) was added to deionized water and dispersed evenly. Then, sodium hydroxide solution (concentration of 1mol / L) was added to adjust the pH of the system to 10.5. After stirring for 30min, the surface oil was removed. Then, dilute nitric acid solution (concentration of 1mol / L) was added to adjust the pH of the system to 6.5. After stirring for 30min, the surface oxide layer was removed. After standing for 30min, most of the supernatant was extracted, and a small amount of acid was retained as a liquid seal to prevent the nickel powder from oxidizing, thus obtaining pretreated nickel powder.

[0057] (2) A complexing agent including disodium ethylenediaminetetraacetate (EDTA-2Na) and diethylenetriamine (molar ratio of 1:1) and a reducing agent including sodium potassium tartrate and ascorbic acid (molar ratio of 1:1) are added to water and dispersed evenly. Then, the pretreated nickel powder is added and stirred and mixed. A nitric acid solution containing silver nitrate (pH 2.4) is added, and a sodium hydroxide solution (concentration of 1 mol / L) is added dropwise to maintain the pH of the reaction system to 6.3 ± 0.1. The amount of complexing agent added is 70 wt% of the spherical nickel powder, the amount of reducing agent added is 50 wt% of the spherical nickel powder, and the amount of silver nitrate added is 30 wt% of the spherical nickel powder. The reaction is stirred at 40°C for 3 h to ensure silver coating. The mixture is filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 4 h to obtain silver-coated nickel powder.

[0058] (3) The above silver-coated nickel powder is added to a mixed solvent of ethanol and water (volume ratio of 4:1) and dispersed evenly. Then, an organic modifier including mercaptopropionic acid and D-penicillamine (mass ratio of 3:1) is added. The amount of organic modifier added is 1.5% of the mass of the silver-coated nickel powder. Then, dilute ammonia is added to adjust the pH of the system to 8.5. The reaction is stirred with ultrasonic assistance (power of 100W) at 40°C for 3 hours. The mixture is then filtered, washed with ethanol, and vacuum dried at 60°C for 4 hours to obtain the low-resistance, high-weather-resistant surface-modified silver-coated nickel powder.

[0059] Example 4

[0060] A low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder is prepared by the following method:

[0061] (1) Commercially available spherical nickel powder (D50 particle size of 5μm) was added to deionized water and dispersed evenly. Then, sodium hydroxide solution (concentration of 1mol / L) was added to adjust the pH of the system to 10.5. After stirring for 30min, the surface oil was removed. Then, dilute nitric acid solution (concentration of 1mol / L) was added to adjust the pH of the system to 6.5. After stirring for 30min, the surface oxide layer was removed. After standing for 30min, most of the supernatant was extracted, and a small amount of acid was retained as a liquid seal to prevent the nickel powder from oxidizing, thus obtaining pretreated nickel powder.

[0062] (2) A complexing agent consisting of disodium ethylenediaminetetraacetate (EDTA-2Na) and ethylenediamine (molar ratio 1:1) and a reducing agent consisting of ascorbic acid and glucose (molar ratio 1:1) are added to water and dispersed evenly. Then, the pretreated nickel powder is added and stirred until well mixed. A nitric acid solution containing silver nitrate (pH 2.4) is added, and a sodium hydroxide solution (concentration 1 mol / L) is added dropwise to maintain the pH of the reaction system to 6.3 ± 0.1. The amount of complexing agent added is 50 wt% of the spherical nickel powder, the amount of reducing agent added is 30 wt% of the spherical nickel powder, and the amount of silver nitrate added is 15 wt% of the spherical nickel powder. The mixture is stirred at 40°C for 1 h to ensure silver coating. The mixture is then filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 4 h to obtain silver-coated nickel powder.

[0063] (3) The above silver-coated nickel powder was added to isopropanol and dispersed evenly. Then γ-glycidyl etheroxypropyltriethoxysilane was added. The amount of γ-glycidyl etheroxypropyltriethoxysilane added was 3wt% of the mass of the silver-coated nickel powder. The mixture was stirred at 60°C for 1 hour and filtered to obtain epoxy-coated silver-coated nickel powder.

[0064] (4) The above epoxy-oxidized silver-coated nickel powder is added to a mixed solvent of ethanol and water (volume ratio of 4:1) and dispersed evenly. Then, an organic modifier including mercaptopropionic acid and D-penicillamine (mass ratio of 2:1) is added. The amount of organic modifier added is 1.5% of the mass of the silver-coated nickel powder. Dilute ammonia water is added to adjust the pH of the system to 8.5. The reaction is stirred with ultrasonic assistance (power of 100W) at 50°C for 2 hours. The mixture is then filtered, washed with ethanol, and vacuum dried at 60°C for 4 hours to obtain the low-resistance, high-weather-resistant surface-modified silver-coated nickel powder.

[0065] Comparative Example 1

[0066] A surface-modified silver-coated nickel powder is prepared according to the preparation method described in Example 1. Except in step (2), a complexing agent including disodium ethylenediaminetetraacetate (EDTA-2Na) and ethylenediamine (molar ratio of 1:1) and a reducing agent including ascorbic acid and glucose (molar ratio of 1:1) are added to water and dispersed evenly. Then, the pretreated nickel powder is added and stirred and mixed. Then, a silver ammonia solution is added. The silver ammonia solution is obtained by adding silver nitrate to deionized water and slowly adding ammonia water under stirring until the brown precipitate is completely dissolved. The amount of complexing agent added is 50 wt% of the spherical nickel powder, the amount of reducing agent added is 30 wt% of the spherical nickel powder, and the amount of silver nitrate added is 15 wt% of the spherical nickel powder. The mixture is stirred at 40°C for 1 h to ensure silver coating. The mixture is then filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 4 h to obtain silver-coated nickel powder.

[0067] Comparative Example 2

[0068] A low-resistance, high-weather-resistant surface-modified silver-coated nickel powder is prepared according to the preparation method described in Example 1, except that in step (3), only D-penicillamine organic modifier is added.

[0069] Comparative Example 3

[0070] A low-resistance, high-weather-resistant surface-modified silver-coated nickel powder is prepared according to the preparation method described in Example 1, except that in step (3), an organic modifier including mercaptopropionic acid and L-cysteine ​​(mass ratio of 2:1) is added.

[0071] Performance testing:

[0072] 0.5g of the surface-modified silver-coated nickel powder described in the above examples and comparative examples were added to 3mL of 90% acetic acid, and the color change was observed. The results are shown in Table 1 below:

[0073] Table 1 Results of acid resistance test

[0074]

[0075] As can be seen from Table 1, the acid resistance of the silver-coated nickel powder of the present invention is close to that of silver powder and significantly better than that of silver-coated copper powder, thanks to the dense silver layer.

[0076] 0.5g of the surface-modified silver-coated nickel powder described in the above examples and comparative examples were added to 3mL of 25% ammonia water, and the color change was observed. The results are shown in Table 2 below:

[0077] Table 2 Results of Alkali Resistance Test

[0078]

[0079] As can be seen from Table 2, the alkali resistance of the silver-coated nickel powder of the present invention is close to that of silver powder and significantly better than that of silver-coated copper powder, thanks to the dense silver layer.

[0080] Preparation and performance testing of low-temperature conductive silver paste for HJT batteries:

[0081] Slurry composition: epoxy resin (40wt%), solvent (butyl carbitol acetate, 30wt%), conductive filler (25wt%, which are the surface-modified silver-coated nickel powders described in the examples and comparative examples respectively), additive (dispersant BYK-163, 5wt%).

[0082] Preparation process: Epoxy resin, solvent and additives are mixed and stirred at high speed. Conductive filler is added and pre-stirred. After mixing, the mixture is added to a centrifugal degassing machine and mixed evenly. The fineness is then ground to below 10μm by a three-roll mill to obtain a uniform slurry.

[0083] Conductivity testing: Prepare standard electrode patterns and test line resistivity and contact resistivity (four-probe method).

[0084] Table 3 Test results of conductive paste performance

[0085]

[0086] As can be seen from Table 3, the conductivity of the silver-coated nickel powder described in this invention is close to that of silver powder and significantly better than that of silver-coated copper powder, thanks to the dense silver layer and good dispersibility.

[0087] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, characterized in that, Includes the following steps: S1. The surface of nickel powder is chemically plated with silver under weak acid conditions to obtain silver-coated nickel powder; S2. Graft an organic modifier onto the surface of the silver-coated nickel powder to obtain the surface-modified silver-coated nickel powder; wherein, the organic modifier includes thiol compounds and thiol amino acids; In step S1, before chemically plating silver onto the surface of the nickel powder, the nickel powder is subjected to alkali washing and acid washing in sequence. After standing, the supernatant is extracted and a small amount of acid is retained as a liquid seal. In step S1, the process of chemically plating silver onto the surface of nickel powder under weak acid conditions specifically includes: adding nickel powder to a reducing agent solution and mixing it thoroughly, then adding an acidic silver source solution, adjusting the pH of the system to 6-6.5, and then carrying out a reduction reaction to obtain the silver-coated nickel powder. In step S2, grafting an organic modification layer onto the surface of silver-coated nickel powder specifically includes: dispersing silver-coated nickel powder in an alcohol-water mixed solvent, adding thiol compounds and thiol amino acids, adjusting the pH of the system to 8-9, and stirring the reaction to obtain the surface-modified silver-coated nickel powder. The general structural formula of the thiol compound is: The general structural formula of the thiol amino acid is: R1 is an alkyl group with 2-6 carbon atoms, and R2 is an alkyl group with 3-10 carbon atoms.

2. The preparation method of low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder according to claim 1, characterized in that, The reducing agent solution includes a complexing agent and a reducing agent; The complexing agent is at least one of triethylamine, triethanolamine, diethylenetriamine, ethylenediamine, or disodium ethylenediaminetetraacetate, and the reducing agent is at least one of glucose, fructose, ascorbic acid, sodium borohydride, or potassium sodium tartrate. The silver source acidic solution includes a silver salt; the silver salt is at least one of silver nitrate, silver methanesulfonate, or silver iodide. The pH of the silver source acidic solution is 2-3.

3. The preparation method of low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder according to claim 1, characterized in that, The reduction reaction is carried out at a temperature of 20-60℃ for 1-3 hours.

4. The method for preparing low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder according to any one of claims 1-3, characterized in that, In step S1, the pH of the alkaline wash is 10-11, and the pH of the acid wash is 6-7.

5. The preparation method of low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder according to claim 1, characterized in that, The thiol compound is mercaptopropionic acid, and the thiol amino acid is D-penicillamine; the mass ratio of mercaptopropionic acid to D-penicillamine is 1-3:

1.

6. The method for preparing low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder according to claim 1, characterized in that, In step S2, the temperature of the stirring reaction is 40-60℃ and the time is 1-3h.

7. A low-resistivity, high-weather-resistant surface-modified silver-coated nickel powder, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. The application of the low-resistance, high-weather-resistant surface-modified silver-coated nickel powder as described in claim 7 in the conductive paste of HJT batteries.

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