Small-particle-size silver-plated copper powder and preparation method and application thereof

Abstract

The invention discloses a small-particle-size silver-plated copper powder and a preparation method and application thereof, and relates to the technical field of metal powder surface treatment and composite powder preparation. The preparation method of the silver-plated copper powder comprises the following steps: S1, cleaning the surface of the copper powder; S2, in the presence of a solvent, mixing copper salt, copper powder and an organic surface treatment agent uniformly, and adjusting the system to alkalinity, then adding a first reducing agent to perform a first reduction reaction to obtain a modified copper powder; S3, uniformly dispersing the modified copper powder in a solution containing a silver source, and then adding a second reducing agent to perform a second reduction reaction to form an activation center on the surface of the copper powder; S4, adding a third reducing agent to the solution obtained in step S3, and then dripping a solution containing silver ions to perform a third reduction reaction to obtain a silver-plated copper powder. The silver-plated copper powder of the invention has a dense silver layer on the surface, a low volume resistivity, and excellent comprehensive performance, and its preparation method is simple and easy to realize industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of metal powder surface treatment and composite powder preparation, and in particular to small-particle-size silver-plated copper powder and a preparation method and application thereof. Background Art

[0002] Photovoltaic power generation is the process in which the internal charge distribution of silicon wafers changes after being exposed to light, converting light energy into electrical energy. Photovoltaic conversion efficiency is the core indicator of photovoltaic cells. For every 1% increase in photovoltaic conversion efficiency, the cost per kilowatt-hour can be reduced by 5-7%. After years of development of photovoltaic power generation technology, along with the advancement of materials and technology, the photovoltaic conversion efficiency of photovoltaic cells is also gradually improving. Photovoltaic silver paste is the most important auxiliary material for photovoltaic cells besides silicon wafers. Photovoltaic silver paste is printed on both sides of silicon wafers as an electrode material and plays an important conductive role. The performance of silver paste directly affects the photovoltaic conversion efficiency of photovoltaic cells and the output power of components.

[0003] Photovoltaic cells are mainly divided into P-type (including BSF and PERC) and N-type (including TopCon and HJT). Currently, the photoelectric conversion efficiency of P-type cells is lower than that of N-type cells and is close to the theoretical limit; therefore, future development will mainly focus on N-type cells. Among them, TopCon cells can be directly upgraded from PERC cell production lines, with low investment costs, and have become the mainstream cell type in the early stage; HJT cells are relatively backward in development due to the great differences in production process with PERC cell technology, the complete incompatibility of core equipment, and high investment and production costs; however, HJT cells have the advantages of higher photoelectric conversion efficiency and simple preparation process. In the future, with further cost reduction and efficiency improvement, HJT cells are expected to catch up with better performance and lower supply and demand steps.

[0004] Photovoltaic silver paste is the main auxiliary material of photovoltaic cells. Since both P-type cells and N-type TopCon cells are sintered at high temperatures, the conductive powder in the paste can only use silver powder with excellent oxidation resistance and conductivity, resulting in a high cost of conductive powder, accounting for about 80~95%, so it is urgent to reduce the cost of conductive powder. Since HJT cells use a low-temperature (<250℃) sintering process, there is room for silver-plated copper powder (conductivity is equivalent to silver powder, and the oxidation resistance temperature is lower than silver powder) to replace silver powder to reduce costs; and HJT silver paste requires the conductive powder particle size to be as small as possible.

[0005] Patents CN103252505A and CN105127449A both adopt a direct replacement silver plating method, which has a simple process, but is not conducive to the continuous deposition of silver on the surface of the copper powder, resulting in low silver content and poor density of the silver layer; Patents CN113976881A, CN115889767A, and CN117943552A all adopt a direct chemical reduction silver plating method, and patents CN101774025A, CN106086837A, CN107626917A, and CN115156529A all adopt a method of first surface acid washing / alkali washing and then reduction silver plating. Since there is no surface activation step, it is easy to cause the density and uniformity of the silver layer on the copper powder surface to be poor, and some require multiple silver plating.

[0006] Therefore, it is very necessary to provide a copper powder silver plating method with simple and easy-to-control process, high conductivity and dense plating layer. Summary of the invention

[0007] The purpose of the invention is to overcome the problems of poor density and uniformity of the silver layer on the surface of the silver-plated product in the prior art, and to provide a preparation method of silver-plated copper powder with simple and easy-to-control process, high conductivity and dense coating, which can realize industrial production.

[0008] In order to achieve the above object, the first object of the present invention is to provide a method for preparing small-particle-size silver-plated copper powder, comprising the following steps:

[0009] S1. Clean the surface of copper powder;

[0010] S2, copper powder surface treatment: in the presence of a solvent, copper salt, copper powder and an organic surface treatment agent are mixed evenly, and the system is adjusted to be alkaline, and then a first reducing agent is added to perform a first reduction reaction to obtain modified copper powder;

[0011] S3, formation of activation centers: uniformly mixing the modified copper powder and the silver source in a solvent, and then adding a second reducing agent to perform a second reduction reaction to form activation centers on the surface of the copper powder;

[0012] S4, silver plating: adding a third reducing agent to the solution obtained in step S3, and then dropping a solution containing silver ions to perform a third reduction reaction to obtain silver-plated copper powder.

[0013] The second object of the present invention is to provide a silver-plated copper powder obtained by the aforementioned preparation method.

[0014] The third object of the present invention is to provide the application of the aforementioned silver-plated copper powder in photovoltaic silver paste.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention first introduces an organic network on the surface of copper powder, and then reduces silver ions in the organic network to generate silver activation points. The surface silver activation points are evenly distributed, have good binding force on the copper surface, and are not easy to fall off; and due to the limitation of the pore size of the organic network, the surface silver activation points are of equal size, which is conducive to the subsequent formation of a uniform and dense silver layer.

[0017] 2. The smaller the copper powder particle size, the easier it is for the copper powder to agglomerate. Since the present invention performs organic surface treatment on the copper powder, the dispersibility of the product silver-plated copper powder is greatly improved, which is beneficial to improving its application performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The SEM images of the silver-plated copper powder obtained in Example 1, wherein the left image is a low-magnification panoramic image of the silver-plated copper powder, and the right image is a high-magnification single-particle image of the silver-plated copper powder;

[0019] Figure 2 : is a SEM image of the silver-plated copper powder obtained in Comparative Example 1, wherein the left image is a low-magnification panoramic image of the silver-plated copper powder, and the right image is a high-magnification single-particle image of the silver-plated copper powder;

[0020] Figure 3 : is a SEM image of the silver-plated copper powder obtained in Comparative Example 2, wherein the left image is a low-magnification panoramic image of the silver-plated copper powder, and the right image is a high-magnification single-particle image of the silver-plated copper powder;

[0021] Figure 4 is a thermogravimetric analysis diagram of the silver-plated copper powder obtained in Example 1;

[0022] Figure 5 is a SEM image of the silver-plated copper powder obtained in Comparative Example 3;

[0023] Figure 6 This is the SEM image of the silver-plated copper powder obtained in Comparative Example 7. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments and diagrams.

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] The present invention provides a method for preparing small-particle-size silver-plated copper powder, comprising the following steps:

[0027] S1. Clean the surface of copper powder;

[0028] S2, copper powder surface treatment: in the presence of a solvent, copper salt, copper powder and an organic surface treatment agent are mixed evenly, and the system is adjusted to be alkaline, and then a first reducing agent is added to perform a first reduction reaction to obtain modified copper powder;

[0029] S3, formation of activation centers: uniformly mixing the modified copper powder and the silver source in a solvent, and then adding a second reducing agent to perform a second reduction reaction to form activation centers on the surface of the copper powder;

[0030] S4, silver plating: adding a third reducing agent to the solution obtained in step S3, and then dropping a solution containing silver ions to perform a third reduction reaction to obtain silver-plated copper powder.

[0031] In the present invention, the surface cleaning process of the copper powder can be known to those skilled in the art, such as pickling the copper powder. Exemplarily, the surface cleaning method of the copper powder includes: placing the copper powder in dilute sulfuric acid for mechanical stirring to remove the oxide layer on the surface of the copper powder, and finally washing it with deionized water.

[0032] The method for preparing the silver-plated copper powder provided by the present invention is suitable for silver plating on the surface of copper powders with different particle sizes, especially small-particle copper powder, because the smaller the copper powder particle size, the more difficult it is to disperse, and it will obviously agglomerate during silver plating, so that a complete and dense silver coating cannot be formed, resulting in poor performance of the silver-plated copper powder. Therefore, the copper powder of the present invention is preferably a gas-atomized or water-atomized copper powder with a median particle size of 1 to 10 μm. Those skilled in the art can select the size of the copper powder according to actual needs. For example, the median particle size of the copper powder is 1 to 10 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value in the range of any two of the above values.

[0033] The present invention innovatively uses copper ions and organic surface treatment agents to surface treat copper powder, and can form an organic network on the surface of copper powder; then a small amount of silver source is added to reduce silver ions in the organic network to generate silver activation points, and due to the limitation of the pores of the organic network, uniformly distributed and uniformly sized silver activation points can be formed on the surface of the copper powder, thereby preparing a uniform and dense silver plating layer. Under preferred conditions, the method for surface treatment of copper powder includes: adding an organic surface treatment agent to a solvent and dissolving it, adding a copper salt aqueous solution and copper powder after complete dissolution, and stirring at a constant temperature of 60-100°C for 3-6h; finally, adding an appropriate amount of an alkali source and a first reducing agent to perform a first reduction reaction until the solution changes from blue to transparent, at which time an organic metal network is generated on the surface of the copper powder, and filtering and washing after natural cooling to room temperature to obtain a modified copper powder. Preferably, the solvent used to dissolve the organic surface treatment agent can be known to a person skilled in the art, for example, it can be at least one of N,N-dimethylformamide, deionized water, and ethanol. By stirring the organic surface treatment agent, copper salt aqueous solution and copper powder at a constant temperature of 60-100°C for 3-6 hours, the copper ions and organic matter can be better combined. By adding an alkali source to adjust the system to alkaline, the copper ions can undergo a first reduction reaction with the reducing agent under alkaline conditions, thereby reducing the copper ions and combining them on the surface of the copper powder, which helps to build an organic network on the surface of the copper powder.

[0034] In the present invention, an organic surface treatment agent that can form an organic metal network with copper ions is selected. Since the small-particle copper powder raw material has a large specific surface area, the organic metal network can be adsorbed on the surface of the copper powder; under preferred conditions, the organic surface treatment agent is selected from terephthalic acid, 5-nitro-isophthalic acid, trimesic acid, 4-amino-1,2,4-triazole, 5-carboxyl-benzotriazole, 2,3,6,7,10,11-hexaaminotriphenyl hexahydrochloride, 4,4'-diamino-2,2'-bipyridine and 5,5'-diamino-2,2'-bipyridine. In some preferred embodiments of the present invention, the addition amount of the organic surface treatment agent is 0.5-5% of the mass of the copper powder, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value in the range of any two of the above values.

[0035] In the present invention, a copper salt with good solubility is selected, which is conducive to the formation of the subsequent metal organic network and improves the uniformity of the organic metal network on the surface of the copper powder; the type of the copper salt can be known to the technicians in the relevant field, for example, it can be at least one of copper chloride, copper nitrate and copper acetate. In addition, it is also necessary to control the amount of copper salt added in the present invention. When the amount added is too low, the surface organic network formed is incomplete; when the amount added is too high, a free organic metal network is formed, which is not conducive to subsequent silver plating, resulting in the formation of nano-scale silver ions in the subsequent silver plating process. In some preferred embodiments of the present invention, the amount of copper salt added is 1-3% of the mass of the copper powder, for example, it can be 1%, 1.5%, 2%, 2.5%, 3% or any value in the range of any two of the above values.

[0036] In the present invention, if the content of silver ions in the surface active center is too low, it is not conducive to the subsequent formation of a dense silver layer, and the conductivity and antioxidant properties of the silver-plated copper powder are reduced; if the content of silver ions in the surface active center is too high, the performance of the copper powder does not change significantly, but the cost will increase. In some preferred embodiments of the present invention, in step S3, the amount of silver source added is 0.1-1% of the mass of the copper powder; for example, it can be 0.1%, 0.25%, 0.4%, 0.55%, 0.7%, 0.85%, 1% or any value in the range of any two of the above values.

[0037] According to the present invention, the method for forming the activation center includes: firstly, adding a silver source to a mixed solvent to dissolve it, and then adding the modified copper powder of step S2 to disperse it evenly; then adding glucose to reduce the silver ions to metallic silver to obtain the activation center; specifically, the method for forming the activation center includes: firstly, adding silver nitrate to a mixed solvent of N,N-dimethylformamide, deionized water and ethanol to dissolve it, and then adding the modified copper powder of S2 to disperse it evenly; the silver ions are adsorbed in the organic metal network on the surface of the copper powder, and then adding glucose to reduce the silver ions to metallic silver to obtain the activation center.

[0038] In step S4, the solution containing silver ions is a silver amine complex solution, and the preparation method of the silver amine complex solution can be known to those skilled in the art. Exemplarily, the preparation method of the silver amine complex solution includes: dissolving silver nitrate with deionized water, and then adding a complexing agent to prepare a silver amine complex solution. The complexing agent in the silver amine complex solution is selected from at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine. In the present invention, the amount of silver powder used can be known to those skilled in the art. Exemplarily, in terms of silver, the silver content of the silver amine complex solution is 9.9-42.9% of the mass of the copper powder.

[0039] In the present invention, the first reducing agent, the second reducing agent and the third reducing agent are each independently selected from at least one of glucose, vitamin C, sodium citrate and potassium sodium tartrate.

[0040] The invention also provides silver-plated copper powder prepared by the preparation method.

[0041] Preferably, the particle size of the silver-plated copper powder is 1-10 μm.

[0042] Preferably, the surface silver content of the silver-plated copper powder is 9-30%.

[0043] Preferably, the volume resistivity of the silver-plated copper powder is less than 6×10 -5 Ω·cm.

[0044] Preferably, the anti-oxidation temperature of the silver-plated copper powder is greater than 260°C; further preferably, the anti-oxidation temperature of the silver-plated copper powder is greater than 280°C.

[0045] The invention also provides application of the silver-plated copper powder in photovoltaic silver paste.

[0046] The present invention will be described in detail below through examples.

[0047] Example 1

[0048] S1. Clean the surface of the copper powder. Weigh 120g of deionized water and pour it into the reactor. Slowly add 7.5g of sulfuric acid, then add 60g of copper powder (median particle size 4μm), and mechanically stir at a speed of 500r / min for 30min to remove the oxide layer on the surface of the copper powder. Finally, wash it with deionized water to obtain copper powder without an oxide layer on the surface.

[0049] S2, copper powder surface treatment: 100g N,N-dimethylformamide, 100g deionized water, and 100g ethanol were weighed and mixed to prepare a mixed solvent; 0.6g (1% relative to the mass of copper) of organic surface treatment agent 4,4'-diamino-2,2'-bipyridine was weighed and ultrasonically dissolved in the mixed solvent, and after complete dissolution, 0.6g of copper chloride and 60g of copper powder treated in step S1 were added in sequence, and mechanical stirring was performed at a speed of 500r / min, followed by heat preservation at 80°C for 6h; finally, 0.36g of sodium hydroxide and 0.4g of glucose were added in sequence to reduce the solution until the solution changed from blue to colorless and transparent, and an organic metal network was generated on the surface of the copper powder. After naturally cooling to room temperature, the solution was filtered and washed to obtain modified copper powder;

[0050] S3, formation of activation center: 100g N,N-dimethylformamide, 100g deionized water and 100g ethanol were weighed and mixed to prepare a mixed solvent; 0.12g silver nitrate was weighed and added to the mixed solvent, and after it was completely dissolved, 60g of the copper powder treated in step S2 was added, and mechanical stirring was performed at a speed of 500r / min, and 0.12g glucose was added at the same time to reduce the silver ions to metallic silver, and an activation center was formed on the surface of the copper powder;

[0051] S4, silver plating: weigh 10.5g of silver nitrate and dissolve it in 100g of deionized water. After the solution is completely dissolved, add 10.5g of diethylenetriamine to obtain a silver amine complex solution for later use; weigh 6g of glucose and add it to the reaction solution obtained in the above step S3, ultrasonically dissolve the glucose completely, then heat the temperature to 50°C, slowly add the silver amine complex solution and react for 30min; finally, filter and wash the reaction solution, and vacuum dry it at 80°C for 2h to obtain 66.5g of silver-plated copper powder.

[0052] Figure 1 This is the SEM image of the silver-plated copper powder obtained in Example 1. Figure 1 It can be seen that the silver-plated layer on the surface of the silver-plated copper powder obtained in Example 1 has a high density and there are basically no silver particles on the surface of the silver-plated layer, indicating that a dense and highly uniform silver-plated layer can be prepared on the surface of the copper powder by the method of Example 1.

[0053] Figure 4 This is the thermogravimetric analysis diagram of the silver-plated copper powder obtained in Example 1. Figure 4 It can be seen that the silver-plated nickel powder prepared in Example 1 has good anti-oxidation performance (>280°C).

[0054] Comparative Example 1

[0055] The method of Example 1 is followed, except that the organic metal network treatment in step S2 is not performed, and the process directly proceeds to step S3 activation and step S4 silver plating.

[0056] Comparative Example 2

[0057] The method of Comparative Example 1 is followed, except that the surface activation treatment of S3 is not performed, and the silver plating step of S4 is directly performed.

[0058] The performance test results of the silver-plated copper powder obtained in Example 1 and Comparative Examples 1-2 are shown in Table 1.

[0059] Table 1

[0060]

[0061] Figure 2 and Figure 3 The following are SEM images of the silver-plated copper powders obtained in Comparative Examples 1 and 2, respectively.

[0062] Combined with Table 1 Figure 1-3 It can be seen that the surface organic networking treatment and surface silver activation treatment of copper powder can effectively improve the comprehensive performance of silver-plated copper powder. If the preparation process does not contain step S2, that is, the surface organic networking treatment is not carried out, and silver is directly plated after silver activation, the anti-oxidation temperature of the product silver-plated copper powder is reduced, and pure silver particles appear in the product, and the flatness of the silver layer on the surface of the silver-plated copper powder deteriorates. If the preparation process does not contain steps S2 and S3, that is, the surface organic networking treatment and surface silver activation steps are removed at the same time, and silver is directly plated on the surface of the copper powder, the anti-oxidation temperature of the product silver-plated copper powder continues to decrease, the volume resistivity increases significantly, a large number of silver particles appear in the product, and the surface silver layer flatness is very poor.

[0063] Examples 2-4 and Comparative Examples 3-4

[0064] The method of Example 1 is followed, except that the amount of the organic surface treatment agent (4,4'-diamino-2,2'-bipyridine) added is adjusted, as shown in Table 2.

[0065] The performance test results of the silver-plated copper powder obtained in Examples 2-4 and Comparative Examples 3-4 are shown in Table 2.

[0066] Table 2

[0067]

[0068] It can be seen from Table 2 that as the addition amount of the organic surface treatment agent 4,4'-diamino-2,2'-bipyridine increases from 0.5% to 5%, the performance of the product silver-plated copper powder does not change significantly; when it continues to increase to 7% or decreases to 0.1%, the performance of the product silver-plated copper powder deteriorates (the volume resistivity increases slightly, and the anti-oxidation temperature decreases slightly). The reason for this is that when the organic surface treatment agent exceeds a certain level, the excess organic surface treatment agent fails to form an effective metal organic network agglomeration on the copper powder surface, resulting in copper powder agglomeration, which is not conducive to subsequent silver plating. Figure 5 This is the SEM image of the silver-plated copper powder obtained in Comparative Example 3, showing a large amount of agglomeration, which confirms the analysis.

[0069] Embodiment 5~7

[0070] The method of Example 1 is followed, except that the type of organic surface treatment agent is changed, as shown in Table 3.

[0071] The performance test results of the silver-plated copper powder obtained in Examples 5 to 7 are shown in Table 3.

[0072] Table 3

[0073]

[0074] It can be seen from Table 3 that there is no significant difference in the performance of silver-plated copper powder prepared by using different types of organic surface treatment agents; considering the production cost comprehensively, low-cost organic surface treatment agents should be selected as much as possible on the basis of stable product performance.

[0075] Example 8 and Comparative Examples 5-6

[0076] The method of Example 1 is followed, except that the amount of copper salt added during surface treatment is adjusted, as shown in Table 4.

[0077] The performance test results of the silver-plated copper powder obtained in Example 8 and Comparative Examples 5-6 are shown in Table 4.

[0078] Table 4

[0079]

[0080] It can be seen from Table 4 that by adjusting the amount of copper salt added, it is found that when the amount of copper salt added is 1~3%, the performance of the obtained silver-plated copper powder is equivalent; when the amount of copper salt added is further increased to 5%, the volume resistivity of the obtained silver-plated copper powder increases, and the other properties have no obvious changes. The reason for this is that the added copper salt will eventually be reduced to cuprous oxide with poor conductivity in the metal network and combined with the surface of the copper powder, so excessive addition will lead to an increase in the volume resistivity of the silver-plated copper powder (poor conductivity); when the amount of copper salt added is reduced to 0.5%, due to insufficient organic network formation, the subsequent silver activation points on the copper powder surface are insufficient, so a small amount of pure silver particles will appear in the product silver-plated copper powder, and due to the reduced density of the local silver layer on the copper powder surface, the antioxidant performance of the silver-plated copper powder is reduced.

[0081] Examples 9 to 12 and Comparative Example 7

[0082] The method of Example 1 is followed, except that the amount of silver nitrate added during the formation of the activation center is adjusted, as shown in Table 5.

[0083] The performance test results of the silver-plated copper powder obtained in Examples 9 to 12 and Comparative Example 7 are shown in Table 5.

[0084] Table 5

[0085]

[0086] From Table 5 and combined Figure 6 It can be seen that by comparing different activated silver nitrate addition amounts, when the activated silver nitrate addition amount is too low, the surface silver activation points are insufficient, the surface of the obtained silver-plated copper powder has more gaps, and the volume resistivity of the silver-plated copper powder increases, and the antioxidant temperature decreases; when the activated silver nitrate addition amount is sufficient, the performance of the obtained silver-plated copper powder is stable; continuing to increase the activated silver nitrate addition amount, the performance of the obtained silver-plated copper powder has no further improvement; considering the comprehensive cost, use as little activated silver nitrate as possible during activation.

[0087] Comparative Example 8

[0088] The method of Example 1 is different from that in step S2, the mixed solution is not subjected to heat preservation treatment. The specific steps are as follows:

[0089] S1, copper powder surface cleaning process is the same as in Example 1;

[0090] S2, copper powder surface treatment: 100g N,N-dimethylformamide, 100g deionized water, and 100g ethanol were weighed and mixed to prepare a mixed solvent; 0.6g (1% of the mass of copper) of organic surface treatment agent 4,4'-diamino-2,2'-bipyridine was weighed and ultrasonically dissolved in the mixed solvent, and after complete dissolution, 0.6g of copper chloride and 60g of copper powder treated in step S1 were added in sequence, and mechanical stirring was performed at a speed of 500r / min to mix evenly; finally, 0.36g of sodium hydroxide and 0.4g of glucose were added in sequence to reduce the solution until the solution changed from blue to transparent, and an organic metal network was generated on the surface of the copper powder. After naturally cooling to room temperature, the solution was filtered and washed to obtain modified copper powder;

[0091] S3, the process for forming the activation center is the same as that in Example 1;

[0092] S4: The silver plating process is the same as in Example 1.

[0093] The performance test results of the silver-plated copper powder obtained in Comparative Example 8 are shown in Table 6.

[0094] Table 6

[0095]

[0096] It can be seen from Table 6 that if the mixed solution is not subjected to heat preservation treatment during the surface treatment of the copper powder, the combination of copper ions and the organic surface treatment agent is poor, and the surface of the copper powder cannot be effectively modified, resulting in the deterioration of the comprehensive performance of the silver-plated copper powder.

[0097] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing small-particle-size silver-plated copper powder, characterized in that: The following steps are involved: S1. Clean the surface of copper powder; S2, copper powder surface treatment: in the presence of a solvent, copper salt, copper powder and an organic surface treatment agent are mixed evenly, and the system is adjusted to be alkaline, and then a first reducing agent is added to perform a first reduction reaction to obtain modified copper powder; S3, formation of activation centers: uniformly mixing the modified copper powder and the silver source in a solvent, and then adding a second reducing agent to perform a second reduction reaction to form activation centers on the surface of the copper powder; S4, silver plating: adding a third reducing agent to the solution obtained in step S3, and then dropping a solution containing silver ions to perform a third reduction reaction to obtain silver-plated copper powder; In step S2, the organic surface treatment agent is selected from at least one of terephthalic acid, 5-nitro-isophthalic acid, trimesic acid, 4-amino-1,2,4-triazole, 5-carboxyl-benzotriazole, 2,3,6,7,10,11-hexaaminotriphenyl hexahydrochloride, 4,4′-diamino-2,2′-bipyridine and 5,5′-diamino-2,2′-bipyridine; In step S2, the mixing conditions include: keeping warm at 60-100° C. for 3-6 hours; In step S2, the amount of the organic surface treatment agent added is 0.5-5% of the mass of the copper powder; In step S2, the amount of copper salt added is 1-3% of the mass of copper powder; In step S3, the amount of the silver source added is 0.1-1% of the mass of the copper powder.

2. The preparation method according to claim 1, characterized in that: In step S2, the copper salt is at least one of copper chloride, copper nitrate and copper acetate.

3. The preparation method according to claim 1, characterized in that: In step S4, the solution containing silver ions is a silver amine complex solution; The complexing agent in the silver amine complexing solution is selected from at least one of ethylenediamine, diethylenetriamine and triethylenetetramine.

4. The preparation method according to claim 1, characterized in that: The first reducing agent, the second reducing agent and the third reducing agent are each independently selected from at least one of glucose, vitamin C, sodium citrate and potassium sodium tartrate; The median particle size of the copper powder is 1-10 μm.

5. A silver-plated copper powder prepared by the method according to any one of claims 1 to 4; The particle size of the silver-plated copper powder is 1-10 μm; The surface silver content of the silver-plated copper powder is 9-30%; The volume resistivity of the silver-plated copper powder is less than 6×10 -5 Ω·cm; The anti-oxidation temperature of the silver-plated copper powder is greater than 260°C.

6. Application of the silver-plated copper powder according to claim 5 in photovoltaic silver paste.

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