Flake-stacked porous silver powder and preparation method thereof

Abstract

The present application relates to a flaky stacked porous silver powder and a preparation method thereof, the preparation method comprising: configuring a first solution, a second solution, a third solution and a fourth solution, the first solution comprising silver nitrate, the second solution comprising a reducing agent, at least one of the first solution and the second solution further comprising a crystal form disruptor, the third solution comprising a seed crystal and a dispersant, and the fourth solution comprising a surfactant; adjusting the pH value of the second solution to a preset value and then adding the second solution to the third solution for reaction to obtain a reaction solution; adding the fourth solution to the reaction solution for surface treatment to obtain a silver powder slurry; separating the flaky stacked porous silver powder from the silver powder slurry, the flaky stacked porous silver powder being a porous structure formed by flaky stacking, thereby being able to prepare a flaky stacked porous silver powder having a high specific surface area, so as to achieve high sintering activity of the silver powder, and having broad application prospects in the field of photovoltaic silver paste.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of new precious metal materials, and in particular to a flaky stacked porous silver powder and a preparation method thereof. Background Art

[0002] Silver powder material is a key material for solar cell electrodes, accounting for more than 85% of the silver paste. Its particle size, morphology, unit cell size, etc. will affect the sintering activity of silver powder. The sintering activity of silver powder directly determines the open circuit voltage, which in turn affects the photoelectric conversion efficiency of crystalline silicon solar cells. Therefore, the development of silver powder with high sintering activity is of great significance to improve the photoelectric conversion efficiency.

[0003] However, the silver powder in the prior art has the problem of low sintering activity. Summary of the invention

[0004] The purpose of the present application is to provide a flaky stacked porous silver powder and a preparation method thereof, so as to prepare a flaky stacked porous silver powder with a high specific surface area, thereby achieving high sintering activity of the silver powder.

[0005] The embodiment of the present application provides a method for preparing flaky porous silver powder, which comprises: preparing a first solution, a second solution, a third solution and a fourth solution, wherein the first solution comprises silver nitrate, the second solution comprises a reducing agent, at least one of the first solution and the second solution further comprises a crystal form disruptor, the third solution comprises a seed crystal and a dispersant, and the fourth solution comprises a surfactant; after adjusting the pH value of the second solution to a preset value, the second solution and the first solution are added to the third solution for reaction to obtain a reaction solution; the fourth solution is added to the reaction solution for surface treatment to obtain a silver powder slurry; and the flaky porous silver powder is separated from the silver powder slurry, wherein the flaky porous silver powder is a porous structure formed by flaky accumulation.

[0006] The first solution contains a crystal form disruptor, and the mass concentration of silver nitrate in the first solution is 30-45%, and the mass concentration of the crystal form disruptor in the first solution is 0-1‰.

[0007] The second solution contains a crystal form disruptor, and the mass concentration of the reducing agent in the second solution is 15-25%, the mass concentration of the crystal form disruptor in the second solution is 0.2-1‰, and the ratio of the mass of the reducing agent in the second solution to the mass of silver nitrate in the first solution is 40-60%.

[0008] The ratio of the mass of the seed crystals in the third solution to the mass of the silver nitrate in the first solution is 0.1-1%, and the ratio of the mass of the dispersant in the third solution to the mass of the silver nitrate in the first solution is 5-25%.

[0009] Wherein, the mass ratio of the surfactant in the fourth solution to the mass ratio of the silver nitrate in the first solution is 1-5%.

[0010] Wherein, the crystal form interfering agent is one or more of copper stearate, calcium stearate, sodium citrate, potassium citrate, calcium citrate, magnesium citrate and citric acid.

[0011] The method comprises: adjusting the pH value of the second solution to a preset value and then adding the second solution to a third solution for reaction to obtain a reaction liquid, comprising: adding a pH adjuster to the second solution, adjusting the pH value of the second solution to a preset value and then adding the second solution to a third solution for reaction to obtain a reaction liquid, wherein the pH adjuster is one or more of ammonia water, sodium hydroxide, sodium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid and sulfuric acid, and the preset value is 5 to 8.

[0012] The time when the first solution is added into the third solution is 10 to 60 seconds earlier than the time when the second solution is added into the third solution.

[0013] Wherein, the surfactant is one or more of caprylic acid, oleic acid, stearic acid, palmitic acid, lauric acid, dodecylamine, tetradecylamine, hexadecylamine and oleylamine.

[0014] The embodiment of the present application also provides a flaky stacked porous silver powder, which is prepared by any of the above-mentioned methods for preparing flaky stacked porous silver powder.

[0015] The present application provides a flaky stacked porous silver powder and a preparation method thereof. The first solution, the second solution, the third solution and the fourth solution are configured. The first solution contains silver nitrate, the second solution contains a reducing agent, at least one of the first solution and the second solution further contains a crystal disruptor, the third solution contains a seed crystal and a dispersant, and the fourth solution contains a surfactant. The pH value of the second solution is adjusted to a preset value and then added to the third solution for reaction with the first solution to obtain a reaction solution. The fourth solution is then added to the reaction solution for surface treatment to obtain a silver powder slurry, and the flaky stacked porous silver powder is separated from the silver powder slurry. The flaky stacked porous silver powder is a porous structure formed by flaky stacking, so that the purpose of controlling the morphology of the silver powder can be achieved through the interaction between the crystal disruptor and the reaction pH value, so as to prepare a flaky stacked porous silver powder with a unique morphology and a high specific surface area, thereby achieving high sintering activity of the silver powder, and having broad application prospects in the field of photovoltaic silver paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0017] Figure 1It is a schematic flow chart of a method for preparing a flaky stacked porous silver powder provided in an embodiment of the present application;

[0018] Figure 2 is a scanning electron microscope image of the flaky stacked porous silver powder prepared by the method for preparing the flaky stacked porous silver powder provided in Example 1 of the present application;

[0019] Figure 3 is a scanning electron microscope image of the flaky stacked porous silver powder prepared by the method for preparing the flaky stacked porous silver powder provided in Example 2 of the present application;

[0020] Figure 4 is a scanning electron microscope image of the flaky stacked porous silver powder prepared by the method for preparing the flaky stacked porous silver powder provided in Example 3 of the present application;

[0021] Figure 5 is a scanning electron microscope image of the flaky stacked porous silver powder prepared by the method for preparing the flaky stacked porous silver powder provided in Example 4 of the present application;

[0022] Figure 6 This is a scanning electron microscope image of the flaky porous silver powder prepared by the method for preparing the flaky porous silver powder provided in Example 5 of the present application. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0024] In the following description of the present application, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0025] In the following description of the present application, the terms "first\second\third" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0027] Silver powder material is a key material for solar cell electrodes, accounting for more than 85% of the silver paste. Its particle size, morphology, unit cell size, etc. will affect the sintering activity of silver powder. The sintering activity of silver powder directly determines the open circuit voltage, which in turn affects the photoelectric conversion efficiency of crystalline silicon solar cells. Therefore, the development of silver powder with high sintering activity is of great significance to improve the photoelectric conversion efficiency.

[0028] At present, the main silver powder on the market is spherical, which has good fluidity, high dispersibility, and easy to control shape and size. In order to improve the sintering activity of spherical silver powder, the particle size can be reduced or the specific surface area can be increased. The smaller the particle size of the silver powder, the finer the unit cell, and the higher the sintering activity of the silver powder, but the change in particle size will cause significant changes in other properties. For example, too small a particle size will cause the fluidity of the silver paste to deteriorate. In addition, the solution of increasing the surface roughness of the silver powder in the related art can only appropriately increase the specific surface area of ​​the silver powder, so it cannot effectively solve the problem of low sintering activity of the silver powder.

[0029] In view of the above problems, an embodiment of the present application provides a flaky porous silver powder and a preparation method thereof, wherein a first solution, a second solution, a third solution and a fourth solution are configured, wherein the first solution contains silver nitrate, the second solution contains a reducing agent, at least one of the first solution and the second solution further contains a crystal form interfering agent, the third solution contains a seed crystal and a dispersant, and the fourth solution contains a surfactant. After the pH value of the second solution is adjusted to a preset value, the second solution is added to the third solution with the first solution for reaction to obtain a reaction solution, and then the fourth solution is added to the reaction solution for surface treatment to obtain a silver powder slurry, and flaky porous silver powder is separated from the silver powder slurry. The flaky porous silver powder is a porous structure formed by flaky accumulation, so that compared with the method of increasing the specific surface area of ​​the silver powder by increasing the wrinkles or roughness of the silver powder surface, a flaky porous silver powder with a larger specific surface area can be obtained, so as to more effectively achieve the high sintering activity of the silver powder, and has a broader application prospect in the field of photovoltaic silver paste.

[0030] The following is a detailed description with reference to specific embodiments. It should be noted that the serial numbers of the following embodiments are not intended to limit the preferred order of the embodiments.

[0031] See also Figure 1 , Figure 1 : is a schematic diagram of a method for preparing a flaky porous silver powder provided in an embodiment of the present application. The specific process of the method for preparing a flaky porous silver powder can be as follows:

[0032] Step S11. prepare a first solution, a second solution, a third solution and a fourth solution, wherein the first solution comprises silver nitrate, the second solution comprises a reducing agent, at least one of the first solution and the second solution further comprises a crystal form disruptor, the third solution comprises a seed crystal and a dispersant, and the fourth solution comprises a surfactant.

[0033] Wherein, the reducing agent can be one or more of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde and acetaldehyde, and in some examples, the reducing agent can be ascorbic acid. The crystal form interfering agent can be one or more of copper stearate, calcium stearate, sodium citrate, potassium citrate, calcium citrate, magnesium citrate and citric acid, and in some examples, the crystal form interfering agent can be sodium citrate. The dispersant can be one or more of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, gum arabic, gelatin and tween, and in some examples, the dispersant can be polyvinyl pyrrolidone. The surfactant can be one or more of caprylic acid, oleic acid, stearic acid, palmitic acid, lauric acid, dodecylamine, tetradecylamine, hexadecylamine and oleylamine, and in some examples, the surfactant can be oleic acid.

[0034] In some embodiments, the first solution may contain a crystal form disruptor (eg, sodium citrate), and the mass concentration of silver nitrate in the first solution may be 30-45%, and the mass concentration of the crystal form disruptor in the first solution may be 0-1‰.

[0035] Specifically, preparing the first solution may include: adding silver nitrate and a crystal interfering agent into ultrapure water, and stirring and dissolving them to obtain the first solution.

[0036] In some embodiments, the second solution may contain a crystal form disruptor (e.g., sodium citrate), and the mass concentration of the reducing agent (e.g., ascorbic acid) in the second solution may be 15-25%, the mass concentration of the crystal form disruptor in the second solution may be 0.2-1‰, and the ratio of the mass of the reducing agent in the second solution to the mass of silver nitrate in the first solution may be 40-60%.

[0037] Specifically, preparing the second solution may include: adding a reducing agent and a crystal form interfering agent into ultrapure water, and stirring and dissolving them to obtain the second solution.

[0038] In some specific embodiments, the first solution and the second solution may both contain a crystal form interfering agent, and the crystal form interfering agent contained in the first solution may be the same as or different from the crystal form interfering agent contained in the second solution.

[0039] In some embodiments, the ratio of the mass of the seed crystals in the third solution to the mass of the silver nitrate in the first solution may be 0.1-1%, and the ratio of the mass of the dispersant (e.g., polyvinyl pyrrolidone) in the third solution to the mass of the silver nitrate in the first solution may be 5-25%. The seed crystals contained in the third solution may be silver seed crystals, and their particle size may be nanometer-sized, that is, the seed crystals contained in the third solution may be nano silver seed crystals.

[0040] Specifically, preparing the third solution may include: weighing a certain amount of seed solution, adding an appropriate amount of ultrapure water and ultrasonically dispersing for a period of time (for example, 5 minutes) to obtain a target seed solution (that is, the seed solution after dilution and dispersion), and adding a dispersant and an appropriate amount of a reducing agent to the ultrapure water, stirring and dissolving to obtain a neutralized solution; then, adding the target seed solution to the neutralized solution, stirring evenly to obtain the third solution.

[0041] The seed solution can be obtained from the market or prepared by yourself. In some examples, the preparation process of the seed solution may include: adding 0.64g of adipic acid to a reducing agent solution containing 79.5g of ascorbic acid and a mass fraction of 12%, stirring evenly, adding a silver nitrate solution containing 300g of silver nitrate and a mass fraction of 18%, moving the mixed solution to a hydrothermal reactor and placing it in a 120°C oven, heating for 45 minutes and standing for 30 minutes to obtain a seed solution.

[0042] Specifically, the seed solution may be a nano silver seed solution.

[0043] In some embodiments, the ratio of the mass of the surfactant (eg, oleic acid) in the fourth solution to the mass of the silver nitrate in the first solution may be 1-5%.

[0044] Specifically, preparing the fourth solution may include: stirring and mixing the surfactant and ethanol evenly to obtain the fourth solution.

[0045] In some specific embodiments, the method for preparing the flaky stacked porous silver powder may further include: controlling the temperature of the first solution, the second solution and the third solution at 5-25°C.

[0046] Step S12: adjusting the pH value of the second solution to a preset value and then adding the second solution and the first solution to the third solution for reaction to obtain a reaction solution.

[0047] The preset value may be 5 to 8, for example, 7.4 or 7.7.

[0048] The time of adding the first solution to the third solution can be earlier than the time of adding the second solution to the third solution, for example, 10 to 60 seconds earlier than the time of adding the second solution to the third solution. The duration of adding the first solution to the third solution can be 2 to 5 minutes, and the duration of adding the second solution to the third solution can be 2 to 5 minutes.

[0049] In some embodiments, the above step S12 may include: adding a pH adjuster to the second solution, adjusting the pH value of the second solution to a preset value, and then adding the pH adjuster to the third solution to react with the first solution to obtain a reaction solution. The pH adjuster may be one or more of ammonia water, sodium hydroxide, sodium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid and sulfuric acid. In some examples, the pH adjuster may be ammonia water and nitric acid.

[0050] Specifically, a pH adjuster (e.g., ammonia water and nitric acid) can be added to the second solution to adjust the pH value of the second solution to 5-8, and then the first solution and the second solution are added to the third solution at a stirring time of 1-6 min and 1-6 min, respectively, under stirring conditions, for example, at a stirring speed of 100-400 r / min, to react to obtain a reaction solution, wherein the first solution can be added to the third solution 10-60 s earlier than the second solution.

[0051] Moreover, in a specific implementation, 36 mL of nitric acid can be added to the first solution, and aqueous ammonia can be added to the second solution to adjust the pH value of the second solution to 7.7 or 7.4, and then the first solution and the second solution are added to the third solution at a stirring speed of 300 r / min to react to obtain a reaction solution, wherein the first solution can be added to the third solution 15 s or 35 s earlier than the second solution, and the first solution and the second solution can be completely added in 4 min 30 s and 3 min 20 s, respectively.

[0052] Step S13: adding the fourth solution to the reaction solution for surface treatment to obtain a silver powder slurry.

[0053] Specifically, the fourth solution may be added to the reaction solution for surface treatment, and the silver powder slurry may be obtained after stirring for 5 to 15 minutes.

[0054] Furthermore, in a specific implementation, after obtaining the above reaction solution, the fourth solution and 100 g of ammonia water may be added to the above reaction solution for surface treatment, and the silver powder slurry may be obtained after stirring for 10 minutes.

[0055] Step S14: separating the flaky porous silver powder from the silver powder slurry. The flaky porous silver powder is a porous structure formed by flaky accumulation.

[0056] Specifically, the silver powder slurry can be subjected to solid-liquid separation, the separated solid can be washed, and the washed solid can be dried at a preset drying temperature and a preset drying time to obtain a flaky stacked porous silver powder. The preset drying temperature can be 40 to 60° C., and the preset drying time can be 60 to 120 minutes.

[0057] Moreover, in a specific implementation, after obtaining the above-mentioned silver powder slurry, the above-mentioned silver powder slurry can be separated into solid and liquid, and the separated solid can be washed with ultrapure water, and then the washed solid can be dried at 60°C for 120 minutes to obtain the target silver powder (that is, the above-mentioned flaky stacked porous silver powder).

[0058] It should be noted that the flaky stacked porous silver powder obtained after the completion of the above step S14 does not increase the specific surface area of ​​the silver powder by increasing the wrinkles or roughness of the silver powder surface, but is a porous spherical silver powder formed by the accumulation of flaky structures. This is a new silver powder structure, which is effectively distinguished from other irregular spherical silver powders, has the advantages of good dispersibility, narrow size distribution, large specific surface area, high sintering activity, etc., which is beneficial to improving the open circuit voltage of crystalline silicon solar cells and has broad application prospects in the field of photovoltaic silver paste.

[0059] Furthermore, the inventors of the present application have discovered that the silver powder morphology can be precisely controlled through the interaction between the crystal disruptor and the reaction pH value to prepare silver powder with unique morphology and surface properties (ie, flaky stacked porous silver powder).

[0060] In some embodiments, the particle size of the flaky porous silver powder obtained after step 14 is completed may be 1.0 to 2.0 μm. The tap density of the flaky porous silver powder obtained after step 14 is completed may be greater than or equal to 5.1 g / cm 3 .

[0061] Furthermore, for ease of understanding, the present application is further described in detail below through five specific embodiments (ie, Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4 and Embodiment 5).

[0062] Example 1

[0063] In Example 1, the specific process of the preparation method of the flaky stacked porous silver powder can be as follows:

[0064] Step S21. Prepare a first solution, a second solution, a third solution and a fourth solution, including: taking 1g of seed solution, adding 30mL of ultrapure water, and ultrasonically dispersing for 5min to obtain a target seed solution (i.e., a diluted and dispersed seed solution); weighing 1100g of silver nitrate solid, preparing a silver nitrate solution with a mass fraction of 35%, and then adding 0.9g of sodium citrate to dissolve to obtain a first solution; weighing 550g of ascorbic acid solid, preparing a reducing agent solution with a mass fraction of 25%, and then adding 0.75g of sodium citrate to dissolve to obtain a second solution; weighing 88g of ascorbic acid solid, preparing a neutralizing solution with a mass concentration of 3%, and then adding 170g of polyvinyl pyrrolidone as a dispersant, stirring until completely dissolved, adding the target seed solution, and stirring evenly to obtain a third solution; weighing 7g of oleic acid and 200g of ethanol, stirring and mixing evenly to obtain a fourth solution; controlling the temperature of the first solution, the second solution and the third solution at 15°C.

[0065] Step S22. Add 36 mL of nitric acid to the first solution, and add aqueous ammonia to the second solution to adjust the pH value of the second solution to 7.7, and then add the first solution and the second solution to the third solution for reaction at a stirring speed of 300 r / min to obtain a reaction solution, wherein the first solution is added to the third solution 15 s earlier than the second solution, and the first solution and the second solution take 4 min 30 s and 3 min 20 s to be fully added, respectively.

[0066] Step S23. Add the fourth solution and 100 g of ammonia water to the reaction solution for surface treatment, and stir for 10 min to obtain a silver powder slurry.

[0067] Step S24: separate the silver powder slurry into solid and liquid, and wash the separated solid with ultrapure water, and then bake the washed solid in an oven at 60° C. for 120 min to obtain silver powder A1.

[0068] Example 2

[0069] The preparation method of the flaky stacked porous silver powder provided in Example 2 is basically the same as the preparation method of the flaky stacked porous silver powder provided in Example 1, except that: in Example 2, 1.65 g of sodium citrate was added to the reducing agent solution, but no sodium citrate was added to the silver nitrate solution; aqueous ammonia was added to the second solution to adjust the pH to 7.4; and the first solution was added to the third solution 35 s earlier than the second solution.

[0070] Accordingly, in Example 2, the specific process of the method for preparing the flaky stacked porous silver powder can be as follows:

[0071] Step S31. Prepare a first solution, a second solution, a third solution and a fourth solution, including: taking 1g of seed solution, adding 30mL of ultrapure water, and ultrasonically dispersing for 5min to obtain a target seed solution (i.e., a diluted and dispersed seed solution); weighing 1100g of silver nitrate solid, preparing a silver nitrate solution with a mass fraction of 35%, and obtaining a first solution; weighing 550g of ascorbic acid solid, preparing a reducing agent solution with a mass fraction of 25%, and then adding 1.65g of sodium citrate to dissolve to obtain a second solution; weighing 88g of ascorbic acid solid, preparing a neutralizing solution with a mass concentration of 3%, and then adding 170g of polyvinyl pyrrolidone as a dispersant, stirring until completely dissolved, and then adding the target seed solution, stirring evenly, to obtain a third solution; weighing 7g of oleic acid and 200g of ethanol, stirring and mixing evenly to obtain a fourth solution; controlling the temperature of the first solution, the second solution and the third solution at 15°C.

[0072] Step S32. Add 36 mL of nitric acid to the first solution, and add aqueous ammonia to the second solution to adjust the pH value of the second solution to 7.4, and then add the first solution and the second solution to the third solution for reaction at a stirring speed of 300 r / min to obtain a reaction solution, wherein the first solution is added to the third solution 35 s earlier than the second solution, and the first solution and the second solution take 4 min 30 s and 3 min 20 s to be added respectively.

[0073] Step S33. Add the fourth solution and 100 g of ammonia water to the reaction solution for surface treatment, and stir for 10 min to obtain a silver powder slurry.

[0074] Step S34. Separate the silver powder slurry into solid and liquid, and wash the separated solid with ultrapure water. Then, bake the washed solid in an oven at 60° C. for 120 min to obtain silver powder A2.

[0075] Example 3

[0076] The method for preparing the flaky porous silver powder provided in Example 3 is basically the same as the method for preparing the flaky porous silver powder provided in Example 2, except that the mass of sodium citrate added to the reducing agent solution is adjusted from 1.65 g to 3.3 g. Accordingly, in Example 3, the specific process of the method for preparing the flaky porous silver powder can be as follows:

[0077] Step S41. Prepare a first solution, a second solution, a third solution and a fourth solution, including: taking 1 g of a seed solution, adding 30 mL of ultrapure water, and ultrasonically dispersing for 5 minutes to obtain a target seed solution (i.e., a diluted and dispersed seed solution); weighing 1100 g of silver nitrate solid, preparing a silver nitrate solution with a mass fraction of 35%, and obtaining a first solution; weighing 550 g of ascorbic acid solid, preparing a reducing agent solution with a mass fraction of 25%, and then adding 3.3 g of sodium citrate to dissolve to obtain a second solution; weighing 88 g of ascorbic acid solid, preparing a neutralizing solution with a mass concentration of 3%, and then adding 170 g of polyvinyl pyrrolidone as a dispersant, stirring until completely dissolved, and then adding the target seed solution, stirring evenly to obtain a third solution; weighing 7 g of oleic acid and 200 g of ethanol, stirring and mixing evenly to obtain a fourth solution; controlling the temperature of the first solution, the second solution and the third solution at 15°C.

[0078] Step S42. Add 36 mL of nitric acid to the first solution, and add aqueous ammonia to the second solution to adjust the pH value of the second solution to 7.4, and then add the first solution and the second solution to the third solution for reaction at a stirring speed of 300 r / min to obtain a reaction solution, wherein the first solution is added to the third solution 35 s earlier than the second solution, and the first solution and the second solution take 4 min 30 s and 3 min 20 s to be added respectively.

[0079] Step S43: Add the fourth solution and 100 g of ammonia water to the reaction solution for surface treatment, and stir for 10 min to obtain a silver powder slurry.

[0080] Step S44: separate the silver powder slurry into solid and liquid, and wash the separated solid with ultrapure water, and then place the washed solid in an oven at 60° C. and bake for 120 min to obtain silver powder A3.

[0081] Example 4

[0082] The method for preparing the flaky porous silver powder provided in Example 4 is basically the same as the method for preparing the flaky porous silver powder provided in Example 2, except that: in Example 4, 1.65 g of sodium citrate is added to the silver nitrate solution, and no sodium citrate is added to the reducing agent solution. Accordingly, in Example 4, the specific process of the method for preparing the flaky porous silver powder can be as follows:

[0083] Step S51. prepare a first solution, a second solution, a third solution and a fourth solution, including: taking 1 g of a seed solution, adding 30 mL of ultrapure water, and ultrasonically dispersing for 5 minutes to obtain a target seed solution (i.e., a seed solution after dilution and dispersion); weighing 1100 g of solid silver nitrate, and then adding 1.65 g of sodium citrate to dissolve, to prepare a silver nitrate solution with a mass fraction of 35%, to obtain a first solution; weighing 550 g of solid ascorbic acid, and preparing a reducing agent solution with a mass fraction of 25%, to obtain a second solution; weighing 88 g of solid ascorbic acid, and preparing a neutralizing solution with a mass concentration of 3%, and then adding 170 g of polyvinyl pyrrolidone as a dispersant, stirring until completely dissolved, and then adding the target seed solution, stirring evenly, to obtain a third solution; weighing 7 g of oleic acid and 200 g of ethanol, stirring and mixing evenly, to obtain a fourth solution; controlling the temperature of the first solution, the second solution and the third solution at 15°C.

[0084] Step S52. Add 36 mL of nitric acid to the first solution, and add aqueous ammonia to the second solution to adjust the pH value of the second solution to 7.4, and then add the first solution and the second solution to the third solution for reaction at a stirring speed of 300 r / min to obtain a reaction solution, wherein the first solution is added to the third solution 35 s earlier than the second solution, and the first solution and the second solution take 4 min 30 s and 3 min 20 s to be added respectively.

[0085] Step S53: Add the fourth solution and 100 g of ammonia water to the reaction solution for surface treatment, and stir for 10 min to obtain a silver powder slurry.

[0086] Step S54: separate the silver powder slurry into solid and liquid, and wash the separated solid with ultrapure water, and then place the washed solid in an oven at 60° C. and bake for 120 min to obtain silver powder A4.

[0087] Example 5

[0088] The method for preparing the flaky porous silver powder provided in Example 5 is basically the same as the method for preparing the flaky porous silver powder provided in Example 2, except that in Example 5, 0.9 g of sodium citrate is added to the silver nitrate solution and 0.75 g of sodium citrate is added to the reducing agent solution. Accordingly, in Example 5, the specific process of the method for preparing the flaky porous silver powder can be as follows:

[0089] Step S61. Prepare a first solution, a second solution, a third solution and a fourth solution, including: taking 1 g of a seed solution, adding 30 mL of ultrapure water, and ultrasonically dispersing for 5 minutes to obtain a target seed solution (i.e., a diluted and dispersed seed solution); weighing 1100 g of silver nitrate solid, preparing a silver nitrate solution with a mass fraction of 35%, and then adding 0.9 g of sodium citrate to dissolve to obtain a first solution; weighing 550 g of ascorbic acid solid, preparing a reducing agent solution with a mass fraction of 25%, and then adding 0.75 g of sodium citrate to dissolve to obtain a second solution; weighing 88 g of ascorbic acid solid, preparing a neutralizing solution with a mass concentration of 3%, and then adding 170 g of polyvinyl pyrrolidone as a dispersant, stirring until completely dissolved, and then adding the target seed solution, stirring evenly to obtain a third solution; weighing 7 g of oleic acid and 200 g of ethanol, stirring and mixing evenly to obtain a fourth solution; controlling the temperature of the first solution, the second solution and the third solution at 15°C.

[0090] Step S62. Add 36 mL of nitric acid to the first solution, and add aqueous ammonia to the second solution to adjust the pH value of the second solution to 7.4, and then add the first solution and the second solution to the third solution for reaction at a stirring speed of 300 r / min to obtain a reaction solution, wherein the first solution is added to the third solution 35 s earlier than the second solution, and the first solution and the second solution take 4 min 30 s and 3 min 20 s to be added respectively.

[0091] Step S63. Add the fourth solution and 100 g of ammonia water to the reaction solution for surface treatment, and stir for 10 min to obtain a silver powder slurry.

[0092] Step S64: separate the silver powder slurry into solid and liquid, and wash the separated solid with ultrapure water, and then place the washed solid in an oven at 60° C. and bake for 120 min to obtain silver powder A5.

[0093] Specifically, by testing the silver powder A1, silver powder A2, silver powder A3, silver powder A4 and silver powder A5 prepared in the above-mentioned embodiment 1, embodiment 2, embodiment 3, embodiment 4 and embodiment 5, the performance parameter results of each silver powder A1 / A2 / A3 / A4 / A5 are shown in the following table 1. Among them, the silver powder A1, silver powder A2, silver powder A3, silver powder A4 and silver powder A5 prepared in the above-mentioned embodiment 1, embodiment 2, embodiment 3, embodiment 4 and embodiment 5 can be tested by using a Better laser particle size analyzer to obtain the particle size of each silver powder A1 / A2 / A3 / A4 / A5 (as shown in the following table 1). In addition, the silver powder A1, silver powder A2, silver powder A3, silver powder A4 and silver powder A5 prepared in the above-mentioned embodiment 1, embodiment 2, embodiment 3, embodiment 4 and embodiment 5 can be tested by using a Better tap density meter to obtain the tap density of each silver powder A1 / A2 / A3 / A4 / A5 (as shown in the following table 1). The silver powder A1, silver powder A2, silver powder A3, silver powder A4 and silver powder A5 prepared in the above-mentioned Example 1, Example 2, Example 3, Example 4 and Example 5 can also be tested to obtain the specific surface area of ​​each silver powder A1 / A2 / A3 / A4 / A5 (as shown in the following Table 1).

[0094] Table 1

[0095]

[0096] Referring to Table 1, in combination with Example 1 and Example 5, and in combination with Figure 2 and Figure 6 It can be known that, when the crystal form disruptor (i.e., sodium citrate) is added to both the oxidizing solution (i.e., the first solution) and the reducing solution (i.e., the second solution), Example 1 adjusts the pH value of the reducing solution (i.e., the second solution) to a larger value, which is more conducive to the growth and accumulation of the flaky structure. The obtained silver powder A1 has more divergent flaky structures and a higher specific surface area, but the corresponding tap density is lower.

[0097] Referring to Table 1, in combination with Example 2, Example 4 and Example 5, and in combination with Figure 3 , Figure 5 and Figure 6 It can be seen that in Example 2 and Example 4, by adding equal amounts of crystal interfering agents to the oxidizing solution or the reducing solution alone, the surface microstructure of the obtained silver powder A2 / A4 is closer to thick sheet or block accumulation, so the structure is denser, the tap density is higher, and the corresponding specific surface area is smaller.

[0098] Referring to Table 1, in combination with Example 2 and Example 3, and in combination with Figure 3 and Figure 4It can be seen that in Example 3, the amount of crystal form disruptor is increased, and the surface microstructure of the obtained silver powder A3 is a thin sheet stacking, the structure is looser, the specific surface area is significantly increased, and the tap density is significantly reduced. This is because the increase in crystal form disruptor has a stronger inhibitory effect on the growth of specific crystal faces of silver powder, resulting in a thinner sheet structure.

[0099] Generally speaking, the larger the specific surface area of ​​silver powder, the higher its surface activity, and the easier it is for the modulated silver paste to form a dense conductive film during the sintering process, which can enhance the contact between silver powder particles and significantly improve the conductivity of the conductive film, thereby resulting in a high open circuit voltage and high photoelectric conversion efficiency.

[0100] In addition, the morphology of silver powder can be precisely controlled by adjusting the reaction pH value and crystal disruptors, so that the silver powder has a higher specific surface area and higher sintering activity, thus having broad application prospects in the field of photovoltaic silver paste.

[0101] As can be seen from the above, the method for preparing flaky porous silver powder provided in this embodiment is through configuring a first solution, a second solution, a third solution and a fourth solution, the first solution contains silver nitrate, the second solution contains a reducing agent, at least one of the first solution and the second solution also contains a crystal form interfering agent, the third solution contains a seed crystal and a dispersant, the fourth solution contains a surfactant, and the pH value of the second solution is adjusted to a preset value and then added to the third solution with the first solution for reaction to obtain a reaction liquid, and then the fourth solution is added to the reaction liquid for surface treatment to obtain a silver powder slurry, and the flaky porous silver powder is separated from the silver powder slurry. The flaky porous silver powder is a porous structure formed by flaky accumulation, so that the flaky porous silver powder with a high specific surface area can be prepared to achieve high sintering activity of the silver powder, which has broad application prospects in the field of photovoltaic silver paste.

[0102] In order to better implement the method for preparing the flaky porous silver powder provided in the embodiment of the present application, the embodiment of the present application also provides a flaky porous silver powder (such as Figure 2 , Figure 3 , Figure 4 , Figure 5 or Figure 6 As shown), the flaky stacked porous silver powder is prepared by the preparation method of the flaky stacked porous silver powder provided by any of the above embodiments.

[0103] Specifically, the flaky stacked porous silver powder can be a porous structure formed by flaky stacking, thereby ensuring that the flaky stacked porous silver powder can have a high specific surface area, can achieve high sintering activity, and has broad application prospects in the field of photovoltaic silver paste.

[0104] In some embodiments, the particle size of the flaky porous silver powder may be 1.0 to 2.0 μm. The tap density of the flaky porous silver powder may be greater than or equal to 5.1 g / cm 3 .

[0105] Furthermore, it should be noted that the flaky stacked porous silver powder in the embodiment of the present application is prepared by the preparation method of the flaky stacked porous silver powder provided by any of the above embodiments, and therefore has all the same beneficial effects, which will not be described in detail in this embodiment.

[0106] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0107] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing flaky porous silver powder, characterized in that: include: A first solution, a second solution, a third solution and a fourth solution are configured, wherein the first solution comprises silver nitrate, the second solution comprises a reducing agent, at least one of the first solution and the second solution further comprises a crystal form disruptor, the third solution comprises a seed crystal and a dispersant, and the fourth solution comprises a surfactant, wherein the first solution comprises the crystal form disruptor, and the mass concentration of the silver nitrate in the first solution is 30-45%, the mass concentration of the crystal form disruptor in the first solution is 0-1‰, the second solution comprises the crystal form disruptor, and the mass concentration of the reducing agent in the second solution is 15-25%, the mass concentration of the crystal form disruptor in the second solution is 0.2-1‰, the ratio of the mass of the reducing agent in the second solution to the mass of the silver nitrate in the first solution is 40-60%, and the crystal form disruptor is one or more of copper stearate, calcium stearate, sodium citrate, potassium citrate, calcium citrate, magnesium citrate and citric acid; The pH value of the second solution is adjusted to a preset value, and then added to the third solution together with the first solution to react to obtain a reaction solution; adding the fourth solution to the reaction solution for surface treatment to obtain a silver powder slurry; Separating flaky porous silver powder from the silver powder slurry, wherein the flaky porous silver powder is a porous structure formed by flaky accumulation; The step of adjusting the pH value of the second solution to a preset value and then adding the second solution to the third solution to react with the first solution to obtain a reaction solution comprises: A reaction liquid is obtained by adding a pH adjusting agent to the second solution, adjusting the pH value of the second solution to a preset value, and then adding the second solution to the third solution for reaction with the first solution, wherein the pH adjusting agent is one or more of ammonia water, sodium hydroxide, sodium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid and sulfuric acid, the preset value is 5 to 8, and the first solution is added to the third solution 10 to 60 seconds earlier than the second solution is added to the third solution.

2. The preparation method according to claim 1, characterized in that: The ratio of the mass of the seed crystals in the third solution to the mass of the silver nitrate in the first solution is 0.1-1%, and the ratio of the mass of the dispersant in the third solution to the mass of the silver nitrate in the first solution is 5-25%.

3. The preparation method according to claim 1, characterized in that: The ratio of the mass of the surfactant in the fourth solution to the mass of the silver nitrate in the first solution is 1-5%.

4. The preparation method according to claim 1, characterized in that: The surfactant is one or more of caprylic acid, oleic acid, stearic acid, palmitic acid, lauric acid, dodecylamine, tetradecylamine, hexadecylamine and oleylamine.

5. A flaky porous silver powder, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 4.

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