A method for preparing flower-like spherical silver powder

Abstract

This invention discloses a method for preparing flower-shaped spherical silver powder, comprising the following steps: (1) first preparing a silver nitrate solution, then adding sodium polydithiodipropane sulfonate to the silver nitrate solution and stirring until fully dissolved to obtain a precursor solution; (2) first preparing a reducing agent solution, then adding a dispersant and stirring until uniformly mixed to obtain a reducing agent-dispersant mixed solution; (3) under light-protected conditions, adding the above precursor solution and the above reducing agent-dispersant mixed solution dropwise into deionized water that is being stirred, and aging the solution after the addition is complete to obtain a silver paste solution; (4) centrifuging, washing and drying the silver paste solution sequentially to obtain flower-shaped spherical silver powder. This invention has the advantages of being simple, efficient, low-cost, and having a large process window, which is beneficial for subsequent commercial mass production.

Description

Technical Field

[0001] This invention belongs to the field of conductive material preparation technology, specifically relating to a method for preparing flower-shaped spherical silver powder. Background Technology

[0002] Silver possesses unique antibacterial, conductive, and catalytic properties, leading to its wide application in microelectronics, catalysts, biomedicine, and conductive pastes. Currently, researchers both domestically and internationally have developed and prepared silver microparticles with various special morphologies, including but not limited to spherical, plate-like, dendritic, cubic, flower-like, linear, and triangular shapes. Among these, flower-shaped silver powder has attracted significant attention due to its unique physicochemical properties.

[0003] In recent years, the photovoltaic industry has experienced rapid development, and conductive silver paste is a key material in photovoltaic cells. The importance of silver powder as the conductive phase in conductive silver paste is self-evident. Currently, photovoltaic technology is advancing towards the third generation of technological revolution, with High-JT (High-Temperature Joint) technology gaining widespread favor among photovoltaic companies. HJT cells require low-temperature silver paste, which demands silver powder with excellent low-temperature sintering characteristics and volume resistivity. Silver nanowires are not considered due to their high manufacturing cost. The orientation of micro / nano-sheet silver powder during printing can lead to uneven conductivity. Flower-shaped silver powder has more contact points and better low-temperature sintering activity, making it more suitable as the conductive phase in low-temperature silver paste.

[0004] Currently, existing technologies for preparing micro / nano-scale flower-like silver powder often employ liquid-phase chemical reduction methods. However, most reaction systems suffer from problems such as complex processes, environmental unfriendliness, high energy consumption, poor repeatability, numerous impurities, and unstable flower-like structures in the silver powder. The technical solutions disclosed in CN 103273082 A and CN 103551589 A introduce iron elements during the preparation process, which are difficult to clean completely. Residual iron elements can cause problems such as poor conductivity and short lifespan in photovoltaic silver paste, and the prepared silver powder exhibits an indistinct flower-like structure and unstable morphology. The technical solution disclosed in CN 114192769 A prepares silver powder with obvious flower-like structural features, but its preparation process is overly cumbersome, has many sources of error, and the sphericity of the prepared flower-like silver powder is not high, making it prone to breakpoints during subsequent printing, leading to reduced conductivity of the silver paste. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing flower-shaped spherical silver powder.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing flower-shaped spherical silver powder includes the following steps:

[0008] (1) First, prepare a silver nitrate solution, then add sodium polydisulfide dipropane sulfonate (SPS) to the silver nitrate solution and stir until fully dissolved to obtain a precursor solution;

[0009] (2) First, prepare a reducing agent solution, then add a dispersant and stir until the mixture is homogeneous to obtain a reducing agent-dispersant mixed solution;

[0010] (3) In a light-protected environment at 28-32℃, equal volumes of the above precursor solution and the above reducing agent-dispersant mixed solution are symmetrically added dropwise to the deionized water being stirred at a rate of 1-2 mL / s. After the addition is completed, the reaction is kept at a temperature for 4-6 min, and then aged at room temperature to obtain the silver paste solution.

[0011] (4) The silver paste solution is centrifuged, washed and dried in sequence to obtain flower-shaped spherical silver powder.

[0012] In a preferred embodiment of the present invention, the molar ratio of sodium polydisulfide dipropane sulfonate (SPS) to silver nitrate is 0.001 to 0.005:1, and the concentration of the silver nitrate solution is 0.2-0.3 mol / L.

[0013] In a preferred embodiment of the present invention, the reducing agent is ascorbic acid, and the concentration of the reducing agent solution is 0.1-0.2 mol / L.

[0014] In a preferred embodiment of the present invention, the dispersant is at least one of xanthan gum, polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC-Na), and alkyl glycoside (APG).

[0015] More preferably, the dispersant is composed of polyvinylpyrrolidone and alkyl glycoside.

[0016] More preferably, the dispersant is an alkyl glycoside.

[0017] More preferably, the dispersant is composed of sodium carboxymethyl cellulose and alkyl glycoside.

[0018] In a preferred embodiment of the present invention, the reducing agent is ascorbic acid; the dispersant is composed of polyvinylpyrrolidone and alkyl glycoside, or alkyl glycoside, or sodium carboxymethyl cellulose and alkyl glycoside.

[0019] A flower-shaped spherical silver powder is prepared by the above-described method.

[0020] The beneficial effects of this invention are:

[0021] 1. The flower-shaped spherical silver powder obtained by this invention is formed by the self-assembly of silver nanosheets with a thickness of about 40 nm, and the particle size ranges from 1 to 3 μm. The surface-level nanostructure of this flower-shaped spherical silver powder can greatly increase the contact area between silver powder particles, forming a uniform conductive network.

[0022] 2. This invention belongs to the liquid phase chemical reduction method. SPS is added to the precursor solution to control the formation of a continuous and stable sheet-like structure in the system. Adding a dispersant to the reducing agent solution can promote the self-assembly of silver nanosheets into flower-shaped spherical silver powder, effectively preventing the agglomeration of the formed silver powder.

[0023] 3. This invention does not introduce seed crystals, and it can be self-assembled in one step. Moreover, there is no need to adjust the pH, temperature, etc. of the reaction system during the reaction process. It has the advantages of being simple, efficient, low cost, and having a large process window, which is conducive to subsequent commercial mass production. Attached Figure Description

[0024] Figure 1 This is a 5000x SEM image of the flower-shaped spherical silver powder prepared in Example 1 of the present invention (one small division on the scale bar in the image represents 1 μm).

[0025] Figure 2 This is a 10,000x SEM image of the flower-shaped spherical silver powder prepared in Example 1 of the present invention (one small division on the scale bar represents 100 nm).

[0026] Figure 3 This is a 10,000x SEM image of the flower-shaped spherical silver powder prepared in Example 2 of the present invention (one small division on the scale bar represents 100 nm).

[0027] Figure 4 This is a 5000x SEM image of the comparative silver powder prepared in Comparative Example 1 of this invention (one small division on the scale bar in the image represents 1 μm).

[0028] Figure 5 This is a 5000x SEM image of the comparative silver powder prepared in Comparative Example 2 of this invention (one small division on the scale bar represents 1 μm). Detailed Implementation

[0029] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0030] Example 1

[0031] (1) Preparation of precursor solution: First, prepare 25 mL of 0.25 mol / L silver nitrate solution, then add 0.006 g SPS to the silver nitrate solution and stir magnetically for 5 to 8 min until fully dissolved to obtain the precursor solution.

[0032] (2) Preparation of reducing agent-dispersant mixed solution: First, prepare 25 mL of 0.15 mol / L ascorbic acid solution, then weigh 0.003 g PVP and 0.005 g APG and add them to the ascorbic acid solution. Stir magnetically for 2 min to obtain reducing agent-dispersant mixed solution.

[0033] (3) Under the light-protected environment at 30°C, the above precursor solution and the above reducing agent-dispersant mixed solution were symmetrically added dropwise to the deionized water being stirred at a rate of 2 mL / s (the deionized water was heated in a water bath at 30°C). After the addition was completed, the reaction was kept at the temperature for 5 min, and then aged at room temperature for 10 min to obtain the silver paste solution.

[0034] (4) The silver paste solution was centrifuged, washed and dried in sequence to obtain flower-shaped spherical silver powder. Among them: the centrifugation parameters were 10000 r / min for 3 min; the washing method was to wash 3 times with deionized water and 2 times with anhydrous ethanol; the drying conditions were to dry in a forced-air drying oven at 60℃ for 8 h.

[0035] Example 2

[0036] (1) Preparation of precursor solution: First, prepare 25 mL of 0.25 mol / L silver nitrate solution, then add 0.006 g SPS and 0.003 g PVP to the silver nitrate solution, and stir magnetically for 5 to 8 minutes until fully dissolved to obtain the precursor solution.

[0037] (2) Preparation of reducing agent-dispersant mixed solution: Prepare 25 mL of 0.15 mol / L ascorbic acid solution, then weigh 0.005 g APG and add it to the ascorbic acid solution. Stir magnetically for 2 min to obtain reducing agent-dispersant mixed solution.

[0038] (3) Under the light-protected environment at 30°C, the above precursor solution and the above reducing agent-dispersant mixed solution were symmetrically added dropwise to the deionized water being stirred at a rate of 2 mL / s (the deionized water was heated in a water bath at 30°C). After the addition was completed, the reaction was kept at the temperature for 5 min, and then aged at room temperature for 10 min to obtain the silver paste solution.

[0039] (4) The silver paste solution was centrifuged, washed and dried in sequence to obtain flower-shaped spherical silver powder. Among them: the centrifugation parameters were 10000 r / min for 3 min; the washing method was to wash 3 times with deionized water and 2 times with anhydrous ethanol; the drying conditions were to dry in a forced-air drying oven at 60℃ for 8 h.

[0040] Example 3

[0041] (1) Preparation of precursor solution: First, prepare 25 mL of 0.25 mol / L silver nitrate solution, then add 0.006 g SPS to the silver nitrate solution and stir magnetically for 5 to 8 min until fully dissolved to obtain the precursor solution.

[0042] (2) Preparation of reducing agent-dispersant mixed solution: First, prepare 25 mL of 0.15 mol / L ascorbic acid solution, then weigh 0.003 g CMC-Na and 0.005 g APG and add them to the ascorbic acid solution. Stir magnetically for 2 min to obtain reducing agent-dispersant mixed solution.

[0043] (3) Under the light-protected environment at 30°C, the above precursor solution and the above reducing agent-dispersant mixed solution were symmetrically added dropwise to the deionized water being stirred at a rate of 2 mL / s (the deionized water was heated in a water bath at 30°C). After the addition was completed, the reaction was kept at the temperature for 5 min, and then aged at room temperature for 10 min to obtain the silver paste solution.

[0044] (4) The silver paste solution was centrifuged, washed and dried in sequence to obtain flower-shaped spherical silver powder. Among them: the centrifugation parameters were 10000 r / min for 3 min; the washing method was to wash 3 times with deionized water and 2 times with anhydrous ethanol; the drying conditions were to dry in a forced-air drying oven at 60℃ for 8 h.

[0045] Comparative Example 1

[0046] (1) Preparation of precursor solution: Weigh silver nitrate and add deionized water to prepare 25 mL of 0.25 mol / L silver nitrate solution.

[0047] (2) Preparation of reducing agent-dispersant mixed solution: First, prepare 25 mL of 0.15 mol / L ascorbic acid solution, then weigh 0.003 g PVP and 0.005 g APG and add them to the ascorbic acid solution. Stir magnetically for 2 min to obtain reducing agent-dispersant mixed solution.

[0048] (3) Under the light-protected environment at 30°C, the above precursor solution and the above reducing agent-dispersant mixed solution were symmetrically added dropwise to the deionized water being stirred at a rate of 2 mL / s (the deionized water was heated in a water bath at 30°C). After the addition was completed, the reaction was kept at the temperature for 5 min, and then aged at room temperature for 10 min to obtain the silver paste solution.

[0049] (4) The silver paste solution was centrifuged, washed and dried in sequence to obtain the comparative silver powder. Among them: the centrifugation parameters were 10000 r / min for 3 min; the washing method was washing with deionized water 3 times and washing with anhydrous ethanol 2 times; the drying conditions were drying in a forced-air drying oven at 60℃ for 8 h.

[0050] The difference between Comparative Example 1 and Example 1 is that SPS was not added to the precursor solution.

[0051] Comparative Example 2

[0052] (1) Preparation of precursor solution: First, prepare 25 mL of 0.25 mol / L silver nitrate solution, then add 0.006 g SPS to the silver nitrate solution and stir magnetically for 5 to 8 min until fully dissolved to obtain the precursor solution.

[0053] (2) Preparation of reducing agent solution: Weigh ascorbic acid, add deionized water, and prepare 25 mL of 0.15 mol / L ascorbic acid solution.

[0054] (3) Under the light-protected environment at 30°C, the above precursor solution and the above reducing agent solution were symmetrically added dropwise to the deionized water being stirred at a rate of 2 mL / s (the deionized water was heated in a water bath at 30°C). After the addition was completed, the reaction was kept at the temperature for 5 min, and then aged at room temperature for 10 min to obtain the silver paste solution.

[0055] (4) The silver paste solution was centrifuged, washed and dried in sequence to obtain the comparative silver powder. Among them: the centrifugation parameters were 10000 r / min for 3 min; the washing method was washing with deionized water 3 times and washing with anhydrous ethanol 2 times; the drying conditions were drying in a forced-air drying oven at 60℃ for 8 h.

[0056] The difference between Comparative Example 2 and Example 1 is that no dispersant was added to the reducing agent solution.

[0057] Depend on Figure 1 and Figure 2 It can be seen that the flower-shaped spherical silver powder prepared in Example 1 of the present invention is formed by the self-assembly of silver nanosheets with a thickness of 40 nm, and the flower as a whole presents a spherical shape, with more contact sites on its surface than a smooth sphere.

[0058] Depend on Figure 3 It can be seen that the flower-like structure of the spherical silver powder prepared in Example 2 of the present invention is more obvious, but the sphericity is not as good as that of the silver powder prepared in Example 1.

[0059] Depend on Figure 4 and Figure 5 It can be seen that, in Comparative Example 1, without the addition of SPS, the silver powder obtained was generally spherical, but almost without flower-like structure, and the silver powder particles were uneven in size; in Comparative Example 2, without the addition of dispersant, the silver powder obtained was generally flat boat-shaped, and the flat boat was still composed of thin silver flakes, but it failed to self-assemble into flower-like spherical silver powder and had poor dispersibility.

[0060] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing flower-shaped spherical silver powder, characterized in that: Includes the following steps: (1) First, prepare a silver nitrate solution, then add sodium polydisulfide dipropane sulfonate to the silver nitrate solution and stir until fully dissolved to obtain a precursor solution. The molar ratio of sodium polydisulfide dipropane sulfonate to silver nitrate is 0.001 to 0.005:1, and the concentration of the silver nitrate solution is 0.2 to 0.3 mol / L. (2) First, prepare a reducing agent solution, then add a dispersant and stir until the mixture is uniform to obtain a reducing agent-dispersant mixed solution. The reducing agent is ascorbic acid and the dispersant is at least one of xanthan gum, polyvinylpyrrolidone, sodium carboxymethyl cellulose and alkyl glycoside. (3) In a light-protected environment at 28-32℃, equal volumes of the above precursor solution and the above reducing agent-dispersant mixed solution are symmetrically added dropwise to the deionized water being stirred at a rate of 1-2 mL / s. After the addition is completed, the reaction is kept at a temperature for 4-6 min, and then aged at room temperature to obtain the silver paste solution. (4) The silver paste solution is centrifuged, washed and dried in sequence to obtain flower-shaped spherical silver powder.

2. The preparation method according to claim 1, characterized in that: The concentration of the reducing agent solution is 0.1-0.2 mol / L.

3. The preparation method according to claim 1, characterized in that: The dispersant is composed of polyvinylpyrrolidone and alkyl glycosides.

4. The preparation method according to claim 1, characterized in that: The dispersant is an alkyl glycoside.

5. The preparation method according to claim 1, characterized in that: The dispersant is composed of sodium carboxymethyl cellulose and alkyl glycosides.

6. The preparation method according to claim 1, characterized in that: The reducing agent is ascorbic acid; the dispersant is composed of polyvinylpyrrolidone and alkyl glycoside, or alkyl glycoside, or sodium carboxymethyl cellulose and alkyl glycoside.

7. A flower-shaped spherical silver powder, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 6.

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