Preparation method and application of silver-coated copper powder with high compactness

Abstract

This invention discloses a method for preparing and applying highly dense silver-coated copper powder. The method comprises the following steps: First, in a first solvent, pretreated copper powder, a copper complexing agent, a dispersant, p-benzoquinone, and slow-release microspheres coated with a reducing agent are mixed, and the pH is adjusted to 10-11.5 to obtain a first mixture; then, silver ammonia solution is added, and the reaction proceeds to obtain a second mixture; wherein the redox potential during the reaction is 0.6-0.75V; finally, the second mixture is cooled, washed, and dried, and then processed by an air jet mill to obtain the final product. This method eliminates the need for a complex silver liquid / reducing agent dropwise control system, requiring only temperature and stirring control. The reaction endpoint is determined by monitoring the ORP, which helps reduce operational difficulty and uncertainty in industrial scale-up. Furthermore, the resulting silver-coated copper powder exhibits advantages such as high density and low volume resistivity.

Description

Technical Field

[0001] This invention relates to the field of silver-coated copper materials technology, and in particular to a method for preparing and applying highly dense silver-coated copper powder. Background Technology

[0002] Silver-coated copper powder is a powder material in which silver is coated on the surface of copper. Because it can replace silver powder to reduce costs, it has broad application prospects in fields such as conductive pastes. Currently, the main methods for preparing silver-coated copper powder include chemical silver plating, mechanical alloying, sol-gel method, and melt atomization method. Among these, chemical silver plating is currently the most mainstream and widely used method for preparing silver-coated copper powder, with advantages such as low cost, good coating adhesion, and excellent conductivity.

[0003] Among related technologies, although chemical silver plating has significant advantages, it still faces many drawbacks in industrial applications, such as difficulty in ensuring the density and uniformity of the coating, complex process control, and unstable coating quality. In actual preparation, the displacement method often results in a non-uniform coating with a "dotted" appearance; while the reduction method tends to cause homogeneous nucleation, leading to the formation of independent silver particles in the solution, resulting in a loose coating, powder agglomeration, and affecting density. Furthermore, the unstable coating quality is a critical drawback. Because the chemical reaction process is affected by numerous factors such as temperature, pH, reactant concentration, type and dropping rate of the complexing / reducing agent, and stirring intensity, the interaction between these parameters means that even slight fluctuations in conditions can lead to unstable coating quality.

[0004] Therefore, there is an urgent need to develop a method for preparing silver-coated copper powder that can effectively improve the density and uniformity of the coating and has good stability. Summary of the Invention

[0005] The first objective of this invention is to provide a method for preparing silver-coated copper powder.

[0006] The second objective of this invention is to provide a silver-coated copper powder.

[0007] The third aspect of this invention aims to provide a method for preparing the above-mentioned silver-coated copper powder or the application of the silver-coated copper powder in the preparation of conductive materials.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a method for preparing silver-coated copper powder, comprising the following steps: S1. In the first solvent, pretreated copper powder, copper complexing agent, dispersant, p-benzoquinone and slow-release microspheres coated with reducing agent are mixed, and the pH value is adjusted to 10~11.5 to obtain the first mixture; S2. Add silver ammonia solution to the first mixture and react to obtain a second mixture; wherein the redox potential during the reaction is 0.6~0.75V; S3. The second mixture is cooled, washed and dried, and then processed by an air jet mill to obtain the final product.

[0009] The preparation method according to embodiments of the present invention has at least the following beneficial effects: (1) This invention achieves precise control of the chemical silver plating process through multiple synergistic control. Specifically, this invention uses "ascorbic acid-slow-release microspheres" as a stable reduction power source and forms a reaction power buffer system with ORP regulator, which fundamentally solves the problem of loose and uneven coating caused by uncontrolled reaction rate in traditional processes, so that silver ions can be deposited layer by layer and in an orderly and dense manner on the surface of copper core.

[0010] (2) The silver-coated copper powder preparation method of the present invention eliminates the complex silver liquid / reducing agent dropwise control system. It only requires temperature and stirring. The reaction endpoint is determined by monitoring ORP, which helps to reduce the difficulty of operation and the uncertainty of industrial scale-up.

[0011] (3) The silver-coated copper powder prepared by the method of the present invention has good density and low volume resistivity. The present invention achieves control through the intrinsic physicochemical properties of the materials (PLGA microspheres, p-benzoquinone) rather than relying on complex external equipment, which makes the product quality (coating density and uniformity) more consistent and reproducible. In addition, the method of the present invention is suitable for preparing products with low silver content, because the stable reaction kinetics allow extremely thin silver layers to grow in a continuous and defect-free manner, thereby achieving high density and oxidation resistance even with low silver content.

[0012] In some embodiments of the present invention, the method for obtaining the pretreated copper powder includes: dispersing the copper powder in a nitric acid solution with a volume concentration of 0.5% to 2%, subjecting it to ultrasonic treatment, and then washing it to obtain the copper powder.

[0013] In some embodiments of the present invention, the method for preparing the sustained-release microspheres coated with the reducing agent includes: S11. Add the reducing agent and polyester polymer to the second solvent to obtain an organic phase mixture; S12. The organic phase mixture is mixed with an emulsifier solution with a mass concentration of 0.8%~1.2%, reacted, and then centrifuged, washed and dried to obtain the final product.

[0014] In some embodiments of the present invention, the second solvent is selected from at least one of dichloromethane, ethyl acetate, and acetone.

[0015] In some embodiments of the present invention, the reducing agent is selected from at least one of ascorbic acid and glucose.

[0016] In some embodiments of the present invention, the polyester polymer is selected from at least one of polylactic acid-glycolic acid copolymer and polylactic acid.

[0017] In some embodiments of the present invention, the emulsifier is selected from at least one of polyvinyl alcohol and polyvinylpyrrolidone.

[0018] In some embodiments of the present invention, the mass ratio of the reducing agent to the polyester polymer is 1:1.5~2.5.

[0019] In some embodiments of the present invention, the volume ratio of the organic phase mixture to the emulsifier solution is 80:250~350.

[0020] In some embodiments of the present invention, the first solvent includes water; And / or, the copper complexing agent is selected from at least one of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine and their sodium salts; And / or, the dispersant is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, methylcellulose, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; And / or, in step S2, the mass ratio of silver nitrate to ammonia in the silver ammonia solution is 5~6:1; And / or, the reaction in step S2 is carried out at a temperature of 30~50℃ for 1~4h.

[0021] In some embodiments of the present invention, the first mixture comprises, by weight, 60-100 parts of pretreated copper powder, 1.5-2.5 parts of copper complexing agent, 0.5-1.5 parts of dispersant, 0.05-0.15 parts of p-benzoquinone, and 8-12 parts of slow-release microspheres coated with reducing agent.

[0022] In some embodiments of the present invention, the volume ratio of the first mixture to the silver ammonia solution is 400~600:180~250.

[0023] In some embodiments of the present invention, the pressure of the air jet milling process is 0.5~0.8MPa; the time is 0.2~1h.

[0024] In a second aspect, the present invention provides a silver-coated copper powder, which is prepared by any of the preparation methods described in the first aspect.

[0025] A third aspect of the present invention provides the application of the preparation method as described in the first aspect or the silver-coated copper powder as described in the second aspect in the preparation of conductive materials.

[0026] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 The image shows an electron microscope image of silver-coated copper powder prepared using the method described in Example 1 of this invention. Figure 2 The image shows an electron microscope image of silver-coated copper powder prepared using the method described in Example 2 of this invention. Figure 3 The image shows an electron microscope image of silver-coated copper powder prepared using the method described in Example 3 of this invention. Detailed Implementation

[0028] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0029] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0030] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] In the description of this invention, the reference term "and / or" includes all and any combination of one or more of the associated listed items.

[0032] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] Example 1 This embodiment provides a method for preparing highly dense silver-coated copper powder, the specific steps of which are as follows: 1. Copper powder pretreatment: 80 g of spherical copper powder (D) 50 The spherical copper powder (2.5 μm) was dispersed in 500 mL of 1.5% dilute nitric acid solution and sonicated for 10 min to remove the oxide layer on the surface of the spherical copper powder. Then it was repeatedly washed with deionized water until neutral, and finally washed once with ethanol for later use.

[0034] 2. Preparation of ascorbic acid-PLGA sustained-release microspheres: This embodiment uses an emulsion-solvent evaporation method to prepare ascorbic acid-PLGA sustained-release microspheres, specifically including the following steps: 2 g of ascorbic acid and 4 g of polylactic acid-glycolic acid copolymer (PLGA) were dissolved in 80 mL of dichloromethane to form an organic phase. This organic phase was then poured into 300 mL of an aqueous solution containing 1% polyvinyl alcohol (PVA) and emulsified under high-speed stirring at 5000 rpm to form an emulsion. The emulsion was then continuously stirred at 40 °C to allow the dichloromethane to evaporate and solidify into microspheres. Finally, after centrifugation, washing, and freeze-drying, ascorbic acid-PLGA sustained-release microspheres were obtained.

[0035] 3. Chemical plating process with redox potential controlled: S1. Add 500 mL of deionized water to the reaction vessel, then add 2 g of EDTA-2Na (a complexing agent to stabilize free Cu) sequentially. 2+ 1 g of polyvinylpyrrolidone (dispersant, PVP K30), 0.1 g of p-benzoquinone (ORP regulator), 80 g of the pretreated spherical copper powder, and 10 g of ascorbic acid-PLGA sustained-release microspheres were added. The reactor was then stirred and heated, with the reaction system temperature controlled at 50±1℃. The initial pH was adjusted to 10.5 by adding dilute NaOH solution dropwise.

[0036] S2. Add the pre-prepared silver ammonia solution to the reaction vessel. The silver ammonia solution is prepared as follows: Dissolve 8g of silver nitrate in 200mL of deionized water, and add 6mL of 28% ammonia solution dropwise while stirring until the solution is just clear.

[0037] S3. Turn on the online oxidation-reduction potential (ORP) monitor and maintain the ORP value stably within the range of 0.70V±0.02V by controlling the temperature and stirring rate of the reaction system. The reaction time is 2 h.

[0038] Due to the sustained-release effect of PLGA microspheres and the buffering effect of p-benzoquinone, violent reactions can be effectively avoided without the addition of any solution. Simultaneously, the continuous release of ascorbic acid from the PLGA microspheres and the sustained buffering effect of the p-benzoquinone / hydroquinone couple facilitate the smooth reduction and deposition of silver ions on the copper powder surface.

[0039] 4. Post-processing and densification: The above reaction solution was cooled to room temperature (25±2℃), filtered, and the solid phase was collected and washed three times alternately with deionized water and ethanol to remove impurities. The filter cake was then dried in a vacuum oven at 60℃ for 12 h. Finally, the dried powder was subjected to an air jet mill at a pressure of 0.6 MPa for 0.5 h. After processing, silver-coated copper powder was obtained, and its electron micrograph is shown below. Figure 1 As shown.

[0040] The densification post-processing step can effectively break up soft agglomerates and further "forge" the powder surface through mechanical force, making the silver layer denser and smoother and improving sphericity.

[0041] Example 2 This embodiment provides a method for preparing highly dense silver-coated copper powder, the specific steps of which are as follows: 1. Copper powder pretreatment: Disperse 80 g of spherical copper powder in 500 mL of 1.5% dilute nitric acid solution and sonicate for 10 min to remove the oxide layer on the surface of the spherical copper powder; then wash repeatedly with deionized water until neutral, and finally wash once with ethanol for later use.

[0042] 2. Preparation of ascorbic acid-PLA sustained-release microspheres: This embodiment uses an emulsion-solvent evaporation method to prepare ascorbic acid-PLA sustained-release microspheres, specifically including the following steps: 2 g of ascorbic acid and 4 g of polylactic acid (PLA, Mw approximately 60,000) were dissolved together in 80 mL of dichloromethane to form an organic phase. This organic phase was then poured into 300 mL of an aqueous solution containing 1% polyvinyl alcohol (PVA) and emulsified under high-speed stirring at 5000 rpm to form an emulsion. The emulsion was then continuously stirred at 40 °C to allow the dichloromethane to evaporate and solidify into microspheres. Finally, after centrifugation, washing, and freeze-drying, ascorbic acid-PLA sustained-release microspheres were obtained.

[0043] 3. Chemical plating process with redox potential controlled: S1. Add 500 mL of deionized water to the reaction vessel, then add 2 g of EDTA-2Na (a complexing agent to stabilize free Cu) sequentially. 2+1 g of polyvinylpyrrolidone (dispersant, PVP K30), 0.1 g of p-benzoquinone (ORP regulator), 80 g of the pretreated spherical copper powder, and 10 g of ascorbic acid-PLA sustained-release microspheres were added. The reactor was then stirred and heated, with the reaction system temperature controlled at 50±1℃. The initial pH was adjusted to 10.5 by adding dilute NaOH solution dropwise.

[0044] S2. Add the pre-prepared silver ammonia solution to the reaction vessel. The silver ammonia solution is prepared as follows: Dissolve 8g of silver nitrate in 200mL of deionized water, and add ammonia dropwise while stirring until the solution is just clear.

[0045] S3. Turn on the online oxidation-reduction potential (ORP) monitor. By controlling the temperature and stirring rate of the reaction system, the ORP value is kept stable in the range of 0.70V±0.02V. The reaction time is 2 hours. After the reaction is completed, the ORP value will drop significantly, indicating that the reaction is basically completed.

[0046] 4. Post-processing and densification: The above reaction solution was cooled to room temperature (25±2℃), filtered, and the solid phase was collected and washed three times alternately with deionized water and ethanol to remove impurities. The filter cake was then dried in a vacuum oven at 60℃ for 12 h. Finally, the dried powder was subjected to an air jet mill at a pressure of 0.6 MPa for 0.5 h. After processing, silver-coated copper powder was obtained, and its electron micrograph is shown below. Figure 2 As shown.

[0047] Example 3 This embodiment provides a method for preparing highly dense silver-coated copper powder, the specific steps of which are as follows: 1. Copper powder pretreatment: Disperse 80 g of spherical copper powder in 500 mL of 1.5% dilute nitric acid solution and sonicate for 10 min to remove the oxide layer on the surface of the spherical copper powder; then wash repeatedly with deionized water until neutral, and finally wash once with ethanol for later use.

[0048] 2. Preparation of ascorbic acid-PLGA sustained-release microspheres: This embodiment uses an emulsion-solvent evaporation method to prepare ascorbic acid-PLGA sustained-release microspheres, specifically including the following steps: 2 g of ascorbic acid and 4 g of polylactic acid-glycolic acid copolymer were dissolved in 80 mL of dichloromethane to form an organic phase. This organic phase was then poured into 300 mL of an aqueous solution containing 1% polyvinyl alcohol and emulsified at 5000 rpm to form an emulsion. The emulsion was then continuously stirred at 40 °C to allow the dichloromethane to evaporate and solidify into microspheres. Finally, after centrifugation, washing, and freeze-drying, ascorbic acid-PLGA sustained-release microspheres were obtained.

[0049] 3. Chemical plating process with redox potential controlled: S1. Add 500 mL of deionized water to the reactor, followed by 2 g of triethylenetetramine, 1 g of polyvinylpyrrolidone, 0.1 g of p-benzoquinone, 80 g of the pretreated spherical copper powder, and 10 g of ascorbic acid-PLGA sustained-release microspheres. Then, start stirring and heating in the reactor, controlling the reaction system temperature at 50±1℃, and adjust the initial pH value to 10.5 by adding dilute NaOH solution dropwise.

[0050] S2. Add the pre-prepared silver ammonia solution to the reaction vessel. The silver ammonia solution is prepared as follows: Dissolve 8g of silver nitrate in 200mL of deionized water, and add ammonia dropwise while stirring until the solution is just clear.

[0051] S3. Turn on the online oxidation-reduction potential (ORP) monitor. By controlling the temperature and stirring rate of the reaction system, the ORP value is kept stable in the range of 0.70V±0.02V. The reaction time is 2 hours. After the reaction is completed, the ORP value will drop significantly, indicating that the reaction is basically completed.

[0052] 4. Post-processing and densification: The above reaction solution was cooled to room temperature (25±2℃), filtered, and the solid phase was collected and washed three times alternately with deionized water and ethanol to remove impurities. The filter cake was then dried in a vacuum oven at 60℃ for 12 h. Finally, the dried powder was subjected to an air jet mill at a pressure of 0.6 MPa for 0.5 h. After processing, silver-coated copper powder was obtained, and its electron micrograph is shown below. Figure 3 As shown.

[0053] Comparative Example 1 This comparative example provides a method for preparing silver-coated copper powder, which differs from Example 1 in that: the ascorbic acid is not coated with a slow-release material, but is directly added in an equal amount during the chemical plating process with redox potential controlled.

[0054] The remaining steps are the same as in Example 1.

[0055] Comparative Example 2 This comparative example provides a method for preparing silver-coated copper powder, which differs from Example 1 in that the mass ratio of ascorbic acid to polylactic acid-glycolic acid copolymer is 1:5 during the preparation of ascorbic acid-PLGA sustained-release microspheres.

[0056] The remaining steps are the same as in Example 1.

[0057] Comparative Example 3 This comparative example provides a method for preparing silver-coated copper powder, which differs from Example 1 in that: in the electroless plating process with redox potential controlled, p-benzoquinone was not added, and the ORP value was not controlled.

[0058] The remaining steps are the same as in Example 1.

[0059] Comparative Example 4 This comparative example provides a method for preparing silver-coated copper powder, which differs from Example 1 in that: in the electroless plating process with redox potential controlled, p-benzoquinone is replaced with nitrosobenzene, and the ORP value in the reaction system is stably maintained in the range of 0.5±0.02V.

[0060] The remaining steps are the same as in Example 1.

[0061] Comparative Example 5 This comparative example provides a method for preparing silver-coated copper powder, which differs from Example 1 in that the densification process is different. Specifically, after the chemical plating process is completed, the reaction solution is cooled to room temperature (25±2℃), filtered, the solid phase is collected, and washed three times alternately with deionized water and ethanol to remove impurities; then the filter cake is dried in a vacuum oven at 60℃ for 12 h to obtain the final product.

[0062] The remaining steps are the same as in Example 1.

[0063] Detection example This test example examines the particle size, density, oxidation resistance, and volume resistivity of the silver-coated copper powders prepared in Examples 1-3 and Comparative Examples 1-5, where: (1) Particle size detection: Laser diffraction method is used for detection. For specific methods, refer to GB / T 19077-2024 "Laser diffraction method for particle size analysis".

[0064] (2) Oxygen content detection: Refer to GB / T 5158.1-2011 "Determination of oxygen content by reduction method of metal powder - Part 4: Determination of total oxygen by reduction-extraction method".

[0065] (3) Acid resistance test: 5 g of the silver-coated copper powder to be tested was placed in 30 g of acetic acid solution (10 wt% water, 90 wt% acetic acid), stirred thoroughly for 30 s, and the color change time of the supernatant was observed.

[0066] (4) Volume resistivity test: Refer to GB / T 35019-2018 for the pressing method in micron-sized silver-coated copper powder.

[0067] The specific test results are shown in Table 1.

[0068] Table 1

[0069] The above test results show that the present invention can prepare silver-coated copper powder with high density, low oxygen content and high conductivity by controlling the supply of reducing agent through slow-release microspheres, combining ORP regulators (such as p-benzoquinone) to stabilize the reaction potential, and then processing it after air jet milling. The oxygen content and acid resistance time of the silver-coated copper powder reflect the density and integrity of its coating.

[0070] Compared to Example 1, Comparative Example 1 did not use slow-release microspheres but directly added ascorbic acid. The results showed increased oxygen content, shortened acid resistance time, and increased resistivity. This indicates that the one-time release of the reducing agent led to an uncontrolled reaction rate, rapid reduction of silver ions, and the formation of an uneven coating, potentially containing pores that exposed and oxidized the copper nuclei. While Comparative Example 2 used slow-release microspheres, the excessively thick coating (1:5) resulted in a slow release of the reducing agent, leading to insufficient reducing agent for silver ions, incomplete coating growth, and partial exposure of the copper nuclei. This resulted in even higher oxygen content and further deterioration of acid resistance time and conductivity.

[0071] Compared to Example 1, Comparative Example 3, which did not add the ORP regulator p-benzoquinone, showed that due to the lack of potential regulation, the redox potential of the reaction system was unstable, leading to excessively rapid local reactions, the formation of a loose structure, or homogeneous nucleation producing free silver particles, affecting the density of the coating, resulting in increased oxygen content and decreased acid resistance time. In Comparative Example 4, which used nitrosobenzene instead of p-benzoquinone, the test results showed a significant increase in oxygen content, a shortened acid resistance time, and an increased volume resistivity. This may be due to insufficient reduction kinetics caused by a lower potential, resulting in a slow silver deposition rate and an inability to form a continuous coating, leading to severe copper oxidation and the most significant overall decline in performance indicators.

[0072] Furthermore, Comparative Example 5 did not undergo air jet milling, lacking the final "physical densification" step. Test results showed a significant decrease in density and an increase in volume resistivity. This may be related to the presence of soft agglomerates in the dried powder after electroless plating, and the insufficient smoothness and density of the plating surface, with the presence of nanoscale pores or protrusions. These microscopic defects provide channels for oxygen and corrosive media to penetrate the copper nucleus. After air jet milling, the mechanical energy generated by high-speed collisions effectively disperses the soft agglomerates, and the "forging" effect causes micro-plastic deformation of the plating metal, compressing the micropores and making the surface smoother and denser.

[0073] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing silver-coated copper powder, characterized in that, Includes the following steps: S1. In the first solvent, pretreated copper powder, copper complexing agent, dispersant, p-benzoquinone and slow-release microspheres coated with reducing agent are mixed, and the pH value is adjusted to 10~11.5 to obtain the first mixture; S2. Add silver ammonia solution to the first mixture and react to obtain a second mixture; wherein the redox potential during the reaction is 0.6~0.75V; S3. The second mixture is cooled, washed and dried, and then processed by an air jet mill to obtain the final product.

2. The preparation method according to claim 1, characterized in that, The method for obtaining the pretreated copper powder includes: dispersing the copper powder in a nitric acid solution with a volume concentration of 0.5% to 2%, ultrasonically treating it, and then washing it to obtain the copper powder.

3. The preparation method according to claim 1, characterized in that, The method for preparing the sustained-release microspheres coated with the reducing agent includes: S11. Add the reducing agent and polyester polymer to the second solvent to obtain an organic phase mixture; S12. The organic phase mixture is mixed with an emulsifier solution with a mass concentration of 0.8%~1.2%, reacted, and then centrifuged, washed and dried to obtain the final product.

4. The preparation method according to claim 3, characterized in that, The second solvent is selected from at least one of dichloromethane, ethyl acetate, and acetone; And / or, the reducing agent is selected from at least one of ascorbic acid and glucose; And / or, the polyester polymer is selected from at least one of polylactic acid-glycolic acid copolymer and polylactic acid; And / or, the emulsifier is selected from at least one of polyvinyl alcohol and polyvinylpyrrolidone.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the reducing agent to the polyester polymer is 1:1.5~2.5; And / or, the volume ratio of the organic phase mixture to the emulsifier solution is 80:250~350.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The first solvent includes water; And / or, the copper complexing agent is selected from at least one of ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine and their sodium salts; And / or, the dispersant is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, methylcellulose, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; And / or, in step S2, the mass ratio of silver nitrate to ammonia in the silver ammonia solution is 5~6:1; And / or, the reaction in step S2 is carried out at a temperature of 30~50℃ for 1~4h.

7. The preparation method according to claim 6, characterized in that, The first mixture comprises, by weight, 60-100 parts of pretreated copper powder, 1.5-2.5 parts of copper complexing agent, 0.5-1.5 parts of dispersant, 0.05-0.15 parts of p-benzoquinone and 8-12 parts of slow-release microspheres coated with reducing agent; And / or, the volume ratio of the first mixture to the silver ammonia solution is 400~600:180~250.

8. The preparation method according to claim 6, characterized in that, The pressure of the air jet mill treatment is 0.5~0.8MPa; the time is 0.2~1 h.

9. A silver-coated copper powder, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

10. The preparation method according to any one of claims 1 to 8 or the application of the silver-coated copper powder according to claim 9 in the preparation of conductive materials.

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