High-sphericity-degree surface porous silver powder and preparation method and application thereof

Abstract

The invention discloses high-sphericity-degree surface porous silver powder and a preparation method and application thereof, and belongs to the technical field of metal powder material preparation. In the preparation process of the silver powder, the silver seed crystal is added to induce nucleation, the polycrystalline seed crystal provides a template for uniform growth of silver ions, meanwhile, the added auxiliaries are adsorbed to the surfaces of the silver particles through functional groups, surface energy is reduced, growth in the aspheric surface direction is limited, the silver particles evenly grow in the radial direction through cooperation of the silver seed crystal and the auxiliaries, and therefore the silver powder is obtained. The sphericity degree of the silver powder is improved; in addition, due to the fact that the auxiliary contains carbon-carbon double bonds and carboxyl groups, accurate regulation and control of the morphology of the silver powder are achieved through the synergistic effect of the carbon-carbon double bonds and the carboxyl groups, the carboxyl groups are adsorbed to the surfaces of secondary particles through the coordination effect, tight agglomeration of the secondary particles is prevented, and the sphericity degree is improved; due to the weak polarity of the carbon-carbon double bonds, proper distances are kept between secondary particles, and loosely-stacked silver powder with a porous structure is obtained; through cooperation of the components, the silver powder with the high sphericity degree and the porous surface is prepared.

Description

Technical Field

[0001] This invention belongs to the field of metal powder material preparation technology, specifically relating to a high sphericity porous silver powder, its preparation method, and its application. Background Technology

[0002] Silver powder is indispensable in fields such as electronics, information technology, and energy catalysis due to its excellent electrical conductivity, thermal conductivity, and chemical stability. Among them, spherical silver powder has excellent flowability and packing properties, making it a core raw material for electronic pastes; silver powder with a porous surface structure provides more active sites in catalytic reactions due to its large specific surface area, and can optimize the conductive network in electrode materials.

[0003] Currently, the existing liquid-phase reduction method for preparing silver powder often faces the challenge of simultaneously achieving sphericity and porosity. While spherical silver powder can be obtained by simply controlling the reduction rate, its surface is mostly dense with a low specific surface area. On the other hand, increasing surface porosity can easily lead to a decrease in sphericity due to surface structure disorder, making it difficult to accurately grasp the mechanism and control product performance.

[0004] Therefore, it is of great significance to develop a silver powder preparation method that can simultaneously achieve high sphericity and a porous surface structure that is easy to control. Summary of the Invention

[0005] The purpose of this invention is to provide a porous silver powder with high sphericity, its preparation method, and its applications. This addresses the problem of simultaneously achieving sphericity and porosity in existing liquid-phase reduction methods for preparing silver powder.

[0006] In a first aspect, the present invention provides a method for preparing highly spherical porous silver powder, comprising the following steps: adding a silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, and then aging the solution to obtain a silver seed solution; providing a second silver nitrate solution, a second reducing agent solution, and an auxiliary agent solution respectively; mixing the second reducing agent solution and the auxiliary agent solution and adding the mixture to the silver seed solution; then adding the second silver nitrate solution and a coating agent to react and obtain a mother liquor; centrifuging the mother liquor; washing and drying the resulting precipitate to obtain highly spherical porous silver powder; wherein the auxiliary agent in the auxiliary agent solution includes a low molecular weight organic acid containing both carbon-carbon double bonds and carboxyl groups.

[0007] In this invention, the inventors discovered that during the preparation of silver powder, the addition of silver seed crystals induces nucleation. The polycrystalline seed crystals provide a template for the uniform growth of silver ions. Simultaneously, the added additives adsorb onto the surface of the silver particles through functional groups, reducing surface energy and limiting growth in non-spherical directions. The synergy between the silver seed crystals and the additives enables the silver particles to grow uniformly radially, improving the sphericity of the silver powder. Furthermore, since the additives contain carbon-carbon double bonds and carboxyl groups, their synergistic effect allows for precise control of the silver powder morphology. Specifically, the carboxyl groups adsorb onto the surface of secondary particles through coordination, preventing their tight aggregation and improving sphericity. The weak polarity of the carbon-carbon double bonds maintains an appropriate distance between secondary particles, resulting in loosely packed silver powder with a porous structure. Through the synergistic combination of the above components, a silver powder with a highly spherical and porous surface is prepared.

[0008] In some embodiments, in the step of aging after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the silver ammonia solution is obtained by adding ammonia water to a first silver nitrate solution until the solution becomes clear, and the concentration of the first silver nitrate solution is 0.1-0.5 g / L.

[0009] In some embodiments, in the step of aging after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the first reducing agent in the mixed solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride, and the concentration of the first reducing agent is 0.005-0.3 mol / L; the stabilizer in the mixed solution includes at least one of polyethylene glycol, polyvinyl alcohol, polyethylene glycol monomethyl ether, polyvinylpyrrolidone, Tween, Span, chitosan, sodium carboxymethyl cellulose, xanthan gum, and gum arabic, and the concentration of the stabilizer is 0.002-0.3 mol / L.

[0010] In some implementations, the aging process after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer specifically includes aging for 20-40 minutes at a temperature of 20-60°C.

[0011] In some embodiments, in the steps of providing the second silver nitrate solution, the second reducing agent solution, and the auxiliary agent solution respectively, the concentration of the second silver nitrate solution is 0.4-2.5 mol / L, the concentration of the second reducing agent solution is 0.05-0.6 mol / L, and the concentration of the auxiliary agent solution is 0.008-1.8 mol / L; wherein the second reducing agent in the second reducing agent solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride.

[0012] In some embodiments, the low molecular weight organic acid containing both carbon-carbon double bonds and carboxyl groups includes at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0013] In some embodiments, in the step of reacting after the continued addition of the second silver nitrate solution and the coating agent, the addition rate of the second silver nitrate solution is 0.1-2.5 L / s; the coating agent includes at least one of oleic acid, lauric acid, stearic acid, ethyl laurate, myristic acid, and oleamide, and the amount of the coating agent is 0.06-1.25% of the mass of the second silver nitrate.

[0014] In some embodiments, the reaction step after the addition of the second silver nitrate solution and the coating agent specifically includes reacting for 10-30 min under stirring at a rate of 200-600 r / min and / or under static conditions.

[0015] In a second aspect, the present invention provides a porous silver powder with high sphericity, which is prepared by any of the above preparation methods.

[0016] In a third aspect, the present invention provides the application of highly spherical porous silver powder as described above in solar cell pastes.

[0017] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention induces nucleation by adding silver seed crystals during the preparation of silver powder. The polycrystalline seed crystals provide a template for the uniform growth of silver ions. Simultaneously, the added additives adsorb onto the surface of silver particles through functional groups, reducing surface energy and limiting growth in non-spherical directions. Through the synergy of silver seed crystals and additives, silver particles grow uniformly in the radial direction, improving the sphericity of the silver powder. In addition, since the additives contain carbon-carbon double bonds and carboxyl groups, the two work synergistically to achieve precise control of the morphology of the silver powder. The carboxyl groups adsorb onto the surface of secondary particles through coordination, preventing their tight aggregation and improving sphericity. The weak polarity of the carbon-carbon double bonds maintains an appropriate distance between secondary particles, resulting in loosely packed silver powder with a porous structure. Through the synergistic combination of the above components, a silver powder with a porous surface and high sphericity is prepared. Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation method of porous silver powder with high sphericity surface in this invention; Figure 2 This is an electron microscope image of the highly spherical porous silver powder with a surface prepared in Example 1 of the present invention; Figure 3 This is an electron microscope image of the highly spherical porous silver powder prepared in Example 2 of the present invention; Figure 4 This is an electron microscope image of the highly spherical porous silver powder with a surface prepared in Example 3 of the present invention; Figure 5 This is an electron microscope image of the silver powder prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0021] Currently, existing liquid-phase reduction methods for preparing silver powder have the problem of simultaneously achieving good sphericity and porosity.

[0022] To address the challenge of balancing sphericity and porosity in existing liquid-phase reduction methods for silver powder preparation, this invention provides a highly spherical porous silver powder, its preparation method, and its applications.

[0023] In a first aspect, the present invention provides a method for preparing highly spherical porous silver powder, comprising the following steps: adding a silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, and then aging the solution to obtain a silver seed solution; providing a second silver nitrate solution, a second reducing agent solution, and an auxiliary agent solution respectively; mixing the second reducing agent solution and the auxiliary agent solution and adding the mixture to the silver seed solution; then adding the second silver nitrate solution and a coating agent to react and obtain a mother liquor; centrifuging the mother liquor; washing and drying the resulting precipitate to obtain highly spherical porous silver powder; wherein the auxiliary agent in the auxiliary agent solution includes a low molecular weight organic acid containing both carbon-carbon double bonds and carboxyl groups.

[0024] In the preparation method provided by this invention, silver seed crystals are added to induce nucleation. The polycrystalline seed crystals provide a template for the uniform growth of silver ions. At the same time, the added additives are adsorbed on the surface of silver particles through functional groups, reducing the surface energy and restricting growth in the non-spherical direction. Through the synergy of silver seed crystals and additives, silver particles grow uniformly in the radial direction, improving the sphericity of silver powder. In addition, since the additives contain carbon-carbon double bonds and carboxyl groups, the two achieve precise control of the morphology of silver powder through synergistic effects. Among them, the carboxyl groups are adsorbed on the surface of secondary particles through coordination, preventing them from agglomerating tightly and improving sphericity. The weak polarity of carbon-carbon double bonds keeps the secondary particles at an appropriate distance, resulting in loosely packed silver powder with a porous structure. Through the synergistic combination of the above components, a silver powder with a porous surface and high sphericity is prepared.

[0025] In some embodiments, in the step of aging after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the silver ammonia solution is obtained by adding ammonia water to a first silver nitrate solution until the solution becomes clear, and the concentration of the first silver nitrate solution is 0.1-0.5 g / L.

[0026] Understandably, the preparation method of silver ammonia solution can adopt conventional methods in the existing technology, as long as it can be used to efficiently prepare silver seed crystals.

[0027] In some embodiments, in the step of aging after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the first reducing agent in the mixed solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride, and the concentration of the first reducing agent is 0.005-0.3 mol / L; the stabilizer in the mixed solution includes at least one of polyethylene glycol, polyvinyl alcohol, polyethylene glycol monomethyl ether, polyvinylpyrrolidone, Tween, Span, chitosan, sodium carboxymethyl cellulose, xanthan gum, and gum arabic, and the concentration of the stabilizer is 0.002-0.3 mol / L.

[0028] In this invention, by controlling the concentrations of the first reducing agent and the stabilizer within a specific range, they can react efficiently with the silver ammonia solution, thereby obtaining high-performance silver seed crystals, which facilitate the subsequent preparation of highly spherical, porous silver powder using the silver seed crystals as raw materials.

[0029] In some implementations, the aging process after adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer specifically includes aging for 20-40 minutes at a temperature of 20-60°C.

[0030] In this invention, by controlling the temperature and time of aging treatment within a specific range, the reaction can be completed, resulting in high-performance silver seed crystals, which facilitate the subsequent preparation of highly spherical, porous silver powder using the silver seed crystals as raw materials.

[0031] In some embodiments, in the steps of providing the second silver nitrate solution, the second reducing agent solution, and the auxiliary agent solution respectively, the concentration of the second silver nitrate solution is 0.4-2.5 mol / L, the concentration of the second reducing agent solution is 0.05-0.6 mol / L, and the concentration of the auxiliary agent solution is 0.008-1.8 mol / L; wherein the second reducing agent in the second reducing agent solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride.

[0032] In this invention, by controlling the concentrations of the second silver nitrate solution, the second reducing agent solution, and the auxiliary agent solution within a specific range, the reaction can be completed, which is beneficial for obtaining silver powder with a highly spherical and porous surface.

[0033] In some embodiments, the low molecular weight organic acid containing both carbon-carbon double bonds and carboxyl groups includes at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0034] Understandably, the types of low-molecular-weight organic acids containing both carbon-carbon double bonds and carboxyl groups can be conventionally adjusted according to actual usage needs, as long as they contain both carbon-carbon double bonds and carboxyl groups and can precisely control the morphology of silver powder. For example, in this invention, the low-molecular-weight organic acids preferably include at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0035] In some embodiments, in the step of reacting after the continued addition of the second silver nitrate solution and the coating agent, the addition rate of the second silver nitrate solution is 0.1-2.5 L / s; the coating agent includes at least one of oleic acid, lauric acid, stearic acid, ethyl laurate, myristic acid, and oleamide, and the amount of the coating agent is 0.06-1.25% of the mass of the second silver nitrate.

[0036] In this invention, by controlling the addition rate of the second silver nitrate solution and adding a coating agent, the interface stability can be enhanced, the porosity can be increased, and silver powder with a porous structure and high sphericity can be obtained.

[0037] Understandably, the type and amount of coating agent can be adjusted according to actual usage needs, as long as it can enhance interfacial stability and improve pore opening rate. For example, in this invention, the coating agent preferably includes at least one of oleic acid, lauric acid, stearic acid, ethyl laurate, myristic acid, and oleamide, and the amount of coating agent is preferably 0.06-1.25% of the mass of the second silver nitrate.

[0038] In some embodiments, the reaction step after the addition of the second silver nitrate solution and the coating agent specifically includes reacting for 10-30 min under stirring at a rate of 200-600 r / min and / or under static conditions.

[0039] In this invention, the reaction can be carried out under stirring or under stillness; and the reaction conditions are mild, the equipment requirements are low, and it is easy to scale up industrially.

[0040] In some embodiments, the steps of centrifuging the mother liquor and washing and drying the resulting precipitate include washing with deionized water and an organic solvent (preferably anhydrous ethanol) respectively, preferably 3-6 times; drying includes drying at a temperature of 60-90°C for 8-15 hours.

[0041] In a second aspect, the present invention provides a porous silver powder with high sphericity, which is prepared by any of the above preparation methods.

[0042] In some implementations, the specific surface area of ​​the highly spherical porous silver powder is 0.6-1.2 m². 2 / g, D50 particle size is 1.2-1.6μm.

[0043] The silver powder provided in this invention has a good specific surface area, uniform particle size distribution, high sphericity, and a porous structure.

[0044] In a third aspect, the present invention provides the application of highly spherical porous silver powder as described above in solar cell pastes.

[0045] In this invention, when high-sphericity porous silver powder is applied to solar cell paste, it can form a continuous and dense conductive network, exhibiting good conductivity, and therefore has good application prospects.

[0046] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0047] Please see Figure 1 The flowchart illustrates the preparation method of the high-sphericity porous silver powder according to the present invention. Specifically, the preparation method of the high-sphericity porous silver powder includes the following steps: adding silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, and then aging it to obtain a silver seed solution; providing a second silver nitrate solution, a second reducing agent solution, and an auxiliary agent solution respectively; mixing the second reducing agent solution and the auxiliary agent solution and adding them to the silver seed solution; then continuing to add the second silver nitrate solution and a coating agent and reacting to obtain a mother liquor; centrifuging the mother liquor; washing and drying the resulting precipitate to obtain the high-sphericity porous silver powder.

[0048] Example 1 A method for preparing porous silver powder with high sphericity includes the following steps: S1. Seed preparation: Dissolve 0.3g of silver nitrate in 1.8L of deionized water, add ammonia until the solution is clear to obtain silver ammonia solution, add the silver ammonia solution to 500mL of a mixed solution containing 0.44g of ascorbic acid and 2g of polyethylene alcohol, react and age at 40℃ for 30min to obtain silver seed solution.

[0049] S2. Silver powder preparation: Prepare 0.5 mol / L silver nitrate solution (400 mL), 0.5 mol / L ascorbic acid solution (200 mL), and 1.2 mol / L maleic acid solution (25 mL) respectively. Before the reaction, mix the ascorbic acid solution and maleic acid solution evenly, add 0.2 g of the silver seed crystals prepared in step S1, and then rapidly add the silver nitrate solution to the mixed solution at a rate of 0.3 L / s. After the addition is complete, pour 0.1 g of oleic acid into the reaction system, and react for 20 min under static conditions to obtain the mother liquor.

[0050] S3. Silver powder post-treatment: After the reaction, the precipitate was separated by centrifugation and washed three times each with deionized water and anhydrous ethanol. The precipitate was then dried in an 80℃ forced-air drying oven for 12 hours to obtain high sphericity porous silver powder.

[0051] Example 2 A method for preparing porous silver powder with high sphericity includes the following steps: S1. Seed preparation: Dissolve 0.5g of silver nitrate in 1.0L of deionized water, add ammonia until the solution is clear to obtain silver ammonia solution, add the silver ammonia solution to 600mL of a mixed solution containing 0.3g of formaldehyde and 1.5g of polyvinylpyrrolidone, react and age at 30℃ for 25min to obtain silver seed solution.

[0052] S2. Silver powder preparation: Prepare 1.0 mol / L silver nitrate solution (200 mL), 0.1 mol / L formaldehyde solution (500 mL), and 0.9 mol / L acrylic acid solution (30 mL) respectively. Before the reaction, mix the formaldehyde solution and acrylic acid solution evenly, add 0.5 g of the silver seed crystals prepared in step S1, and then quickly add the silver nitrate solution to the mixed solution at a rate of 0.5 L / s. After the addition is complete, pour lauric acid (0.2 g) into the reaction system and react for 20 min at a stirring rate of 300 r / min to obtain the mother liquor.

[0053] S3. Silver powder post-treatment: After the reaction is completed, the precipitate is separated by centrifugation and washed 4 times each with deionized water and anhydrous ethanol. The precipitate is then dried in an 80℃ forced-air drying oven for 10 hours to obtain high sphericity porous silver powder.

[0054] Example 3 A method for preparing porous silver powder with high sphericity includes the following steps: S1. Seed preparation: Dissolve 0.4g of silver nitrate in 1.2L of deionized water, add ammonia until the solution is clear to obtain silver ammonia solution, add the silver ammonia solution to 550mL of a mixed solution containing 0.25g of sodium borohydride and 1.8g of chitosan, react and age at 50℃ for 35min to obtain silver seed solution.

[0055] S2. Silver powder preparation: Prepare 2.0 mol / L silver nitrate solution (100 mL), 0.2 mol / L sodium borohydride solution (250 mL), and 0.8 mol / L fumaric acid solution (25 mL) respectively. Before the reaction, mix the sodium borohydride solution and fumaric acid solution evenly, add 0.25 g of the silver seed crystals prepared in step S1, and then rapidly add the silver nitrate solution to the mixed solution at a rate of 2.0 L / s. After the addition is complete, pour stearic acid (0.3 g) into the reaction system, and react for 25 min under static conditions to obtain the mother liquor.

[0056] S3. Silver powder post-treatment: After the reaction is completed, the precipitate is separated by centrifugation and washed 5 times each with deionized water and anhydrous ethanol. The precipitate is then dried in an 85℃ forced-air drying oven for 14 hours to obtain high sphericity porous silver powder.

[0057] Comparative Example 1 The preparation method of silver powder in this comparative example is basically the same as that in Example 1. The difference is that maleic acid solution is not added in step S2 to obtain silver powder.

[0058] Comparative Example 2 The preparation method of silver powder in this comparative example is basically the same as that in Example 1. The difference is that step S1 is not performed, and maleic acid solution is not added in step S2 to obtain silver powder.

[0059] Comparative Example 3 The preparation method of silver powder in this comparative example is basically the same as that in Example 1. The difference is that in step S2, maleic acid solution is replaced with styrene solution (containing only carbon-carbon double bonds) to obtain silver powder.

[0060] Comparative Example 4 The preparation method of silver powder in this comparative example is basically the same as that in Example 1. The difference is that in step S2, maleic acid solution is replaced with styrene solution (containing only carboxyl groups) to obtain silver powder.

[0061] Performance testing Electron microscopy was performed on the high sphericity porous silver powders prepared in Examples 1-3 and the silver powder prepared in Comparative Example 1. The results are as follows: Figure 2-5 As shown.

[0062] from Figure 2-5As can be seen, the silver powder prepared in Examples 1-3 has high sphericity and a porous surface; while the silver powder prepared in the comparative example has poor sphericity and a dense surface.

[0063] Furthermore, the D50 particle size and specific surface area of ​​the high sphericity porous silver powder prepared in Examples 1-3 and the silver powder prepared in Comparative Examples 1-4 were tested. The D50 particle size was tested using a Malvern laser particle size analyzer, and the specific surface area was tested using a Bestech BSD-BET400. The results are shown in Table 1 below.

[0064] Table 1 Test Results

[0065] As can be seen from Table 1, the silver powders prepared in Examples 1-3 exhibit high sphericity, significant surface porosity, and a specific surface area ranging from 0.6 to 1.2 m². 2 Within the range of / g, the particle size distribution is uniform. When applied to solar cell paste, it exhibits excellent flowability and packing properties, forming a continuous and dense conductive network with good conductivity. In Comparative Example 1 (no additives), Comparative Example 2 (no additives or silver seeds), and Comparative Examples 3 and 4 (with different types of additives), the results showed that the sphericity of the prepared silver powder decreased, the porous structure was destroyed, particles agglomerated, the specific surface area was significantly reduced, and the performance was significantly degraded.

[0066] The above results indicate that, in this invention, silver powder with a highly spherical and porous surface is obtained through the synergistic effect of specific additives and silver seeds.

[0067] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0068] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing porous silver powder with high sphericity, characterized in that, Includes the following steps: After adding the silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the solution is aged to obtain a silver seed solution. A second silver nitrate solution, a second reducing agent solution, and an auxiliary agent solution are provided respectively. The second reducing agent solution and the auxiliary agent solution are mixed and then added to the silver seed solution. Then, the second silver nitrate solution and the coating agent are added and reacted to obtain the mother liquor. The mother liquor was centrifuged, and the resulting precipitate was washed and dried to obtain highly spherical porous silver powder. The additives in the additive solution include low molecular weight organic acids that simultaneously contain carbon-carbon double bonds and carboxyl groups.

2. The preparation method according to claim 1, characterized in that, In the step of aging after adding silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the silver ammonia solution is obtained by adding ammonia water to a first silver nitrate solution until the solution becomes clear, and the concentration of the first silver nitrate solution is 0.1-0.5 g / L.

3. The preparation method according to claim 1, characterized in that, In the step of aging after adding silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the first reducing agent in the mixed solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride, and the concentration of the first reducing agent is 0.005-0.3 mol / L. The stabilizer in the mixed solution includes at least one of polyethylene glycol, polyvinyl alcohol, polyethylene glycol monomethyl ether, polyvinylpyrrolidone, Tween, Span, chitosan, sodium carboxymethyl cellulose, xanthan gum, and gum arabic, and the concentration of the stabilizer is 0.002-0.3 mol / L.

4. The preparation method according to claim 1, characterized in that, In the step of adding silver ammonia solution to a mixed solution containing a first reducing agent and a stabilizer, the aging process specifically includes aging for 20-40 minutes at a temperature of 20-60°C.

5. The preparation method according to claim 1, characterized in that, In the steps of providing the second silver nitrate solution, the second reducing agent solution, and the auxiliary agent solution respectively, the concentration of the second silver nitrate solution is 0.4-2.5 mol / L, the concentration of the second reducing agent solution is 0.05-0.6 mol / L, and the concentration of the auxiliary agent solution is 0.008-1.8 mol / L. The second reducing agent in the second reducing agent solution includes at least one of ascorbic acid, formaldehyde, hydrazine hydrate, and sodium borohydride.

6. The preparation method according to claim 5, characterized in that, The low molecular weight organic acids containing both carbon-carbon double bonds and carboxyl groups include at least one of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

7. The preparation method according to claim 1, characterized in that, In the step of reacting after adding the second silver nitrate solution and the coating agent, the addition rate of the second silver nitrate solution is 0.1-2.5 L / s; The coating agent includes at least one of oleic acid, lauric acid, stearic acid, ethyl laurate, myristic acid, and oleamide, and the amount of the coating agent is 0.06-1.25% of the mass of the second silver nitrate.

8. The preparation method according to claim 1, characterized in that, The reaction step after adding the second silver nitrate solution and coating agent specifically includes reacting for 10-30 minutes under stirring conditions of 200-600 r / min and / or standing conditions.

9. A porous silver powder with high sphericity, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the high sphericity surface porous silver powder as described in claim 9 in solar cell paste.

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