A kind of high dispersibility silver powder and its preparation method and application

Abstract

The present invention provides a highly dispersible silver powder, a preparation method, and applications thereof. The method utilizes a simple liquid-phase reduction process to prepare the highly dispersible silver powder. Polyvinyl pyrrolidone, a readily available, water-soluble polymer, is used as the dispersant, eliminating the use of animal glues such as gelatin and bone glue, which are difficult to clean and would affect the conductivity of the silver powder. Furthermore, the amount of dispersant used is 13.3% to 15% of the mass of the reacted silver nitrate, far less than the commonly used amount of 20% to 40%. This significantly reduces the amount of dispersant used without affecting the dispersibility of the final silver powder, thereby significantly reducing the production cost of the highly dispersible silver powder.

Description

Technical Field

[0001] The present invention relates to the technical field of metal micro-nano powder materials, and in particular to a highly dispersible silver powder and a preparation method and application thereof. Background Art

[0002] With the development of the photovoltaic and emerging electronics industries, electronic conductive pastes are finding increasingly widespread application. As the primary conductive component, the properties of metal powders crucially impact the quality of electronic pastes. Due to its excellent conductivity and relatively low price, metallic silver has become the primary raw material for preparing paste powders. In industrial production, chemical reduction is the primary method for producing silver powder due to its mild reaction conditions, low production costs, and simple process.

[0003] Currently available technical solutions for silver powders used in photovoltaic cells claim that highly dispersible silver powders can reduce the contact resistance between electrodes and silicon wafers. However, poorly dispersible silver powders tend to agglomerate, creating large gaps between agglomerated silver powder particles. This hinders electron transport and increases contact resistance. Existing techniques typically increase the amount of dispersant used to disperse and adjust the silver powder particle size. However, this results in excessively high raw material costs, significantly increasing the production cost of highly dispersible silver powders and hindering the expansion of their production.

[0004] Therefore, there is an urgent need for a highly dispersible silver powder and its preparation method and application to meet client application needs. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the production cost of highly dispersed silver powder prepared in the existing silver powder preparation process is low due to the excessive amount of dispersant used.

[0006] To solve the above technical problems, the present invention first provides a method for preparing highly dispersible silver powder, comprising:

[0007] S10, mixing a silver nitrate solution, a reducing agent, a dispersant, a coating agent solution, and a solvent to obtain a reaction suspension;

[0008] S20, performing sedimentation treatment on the reaction suspension to obtain a precipitate, and then washing and drying the precipitate to obtain highly dispersible silver powder;

[0009] Wherein, in step S10: the dispersant is polyvinyl pyrrolidone, and the mass content of the dispersant is 13.3% to 15% of the mass content of silver nitrate in the silver nitrate solution.

[0010] Preferably, step S10 specifically includes:

[0011] S101, mixing a reducing agent with a portion of a solvent, stirring until dissolved, and adding an alkaline solution to obtain a first mixed solution;

[0012] S102, mixing the dispersant and another portion of the solvent and stirring until dissolved to obtain a second mixed solution;

[0013] S103, transferring the second mixed solution to a reactor for stirring, and adding the silver nitrate solution and the first mixed solution to the reactor at the same time and stirring at a uniform speed, then adding the coating agent solution, and continuing to stir until the reaction is completed to obtain a reaction suspension.

[0014] Preferably, in step S101: the reducing agent is at least one of ascorbic acid, formaldehyde, glucose, triethanolamine and hydrazine hydrate.

[0015] Preferably, in step S102: the specifications of the polyvinyl pyrrolidone used as the dispersant meet the following requirements: K value of 31.5-33, moisture <4%, pH value of 3-4, peroxide content ≤200ppm, and weight average molecular weight of 25000-40000.

[0016] Preferably, in step S103: the coating agent solution is formed by mixing coating agent powder and anhydrous ethanol; the coating agent powder is at least one of oleic acid, lauric acid, stearic acid and palmitic acid.

[0017] Preferably, the solvent is water; and the stirring rates in step S101, step S102, and step S103 are all 400-600 r / min.

[0018] Preferably, step S20 specifically includes:

[0019] S201, performing sedimentation treatment on the reaction suspension, removing the supernatant to obtain a precipitate;

[0020] S202, washing the precipitate with a detergent until the precipitate is washed to a conductivity of less than 20 μS / m, thereby obtaining wet silver powder;

[0021] S203, drying the wet silver powder to obtain highly dispersed silver powder.

[0022] Preferably, in step S203, the temperature of the drying process is 40°C to 80°C, and the drying time is 20h to 24h.

[0023] Correspondingly, the present invention also provides a highly dispersible silver powder, which is prepared by any of the above methods for preparing highly dispersible silver powder.

[0024] Correspondingly, the present invention further provides a use of the highly dispersible silver powder as described above in the preparation of conductive silver paste.

[0025] The present invention has the beneficial effects of providing a highly dispersible silver powder, a preparation method thereof, and its application, unlike the prior art. The method utilizes a simple liquid-phase reduction process to prepare the highly dispersible silver powder. Polyvinyl pyrrolidone, a readily available, water-soluble polymer, is used as the dispersant, eliminating the use of animal glues such as gelatin and bone glue, which are difficult to clean and would affect the conductivity of the silver powder. Furthermore, the amount of dispersant used is 13.3% to 15% of the mass of the reacted silver nitrate, far less than the commonly used amount of 20% to 40%. This significantly reduces the amount of dispersant used without affecting the dispersibility of the final silver powder, thereby significantly reducing the production cost of the highly dispersible silver powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a method for preparing highly dispersible silver powder provided in an embodiment of the present invention;

[0027] Figure 2 This is an electron microscope image of the highly dispersible silver powder provided in Example 1 of the present invention;

[0028] Figure 3 This is an electron microscope image of the highly dispersible silver powder provided in Example 2 of the present invention;

[0029] Figure 4 This is an electron microscope image of the highly dispersible silver powder provided in Example 3 of the present invention;

[0030] Figure 5 This is an electron microscope image of the highly dispersible silver powder provided in Comparative Example 1. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Currently available technical solutions for silver powders for photovoltaic cells primarily utilize an increased dispersant dosage to achieve dispersion and adjust the particle size of the silver powder. The inventors of this application discovered in actual production that further reducing the dispersant dosage, based on the existing dispersant to silver nitrate ratio, can also produce highly dispersible silver powder. Therefore, based on their own development experience, they have proposed a method and application for preparing highly dispersible silver powder using a low dispersant dosage, building on the technology behind spherical silver powders. This method focuses on reducing raw material costs without compromising product quality.

[0033] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0034] In a first aspect, the present invention first provides a method for preparing highly dispersible silver powder.

[0035] See also Figure 1 , Figure 1 A flow chart of a method for preparing highly dispersible silver powder provided in an embodiment of the present invention; wherein the above-mentioned preparation method specifically includes:

[0036] S10, mixing the silver nitrate solution, the reducing agent, the dispersant, the coating agent solution and the solvent to obtain a reaction suspension.

[0037] Specifically, step S10 includes:

[0038] S101, mixing a reducing agent with a portion of a solvent, stirring until dissolved, and adding an alkaline solution to obtain a first mixed solution;

[0039] S102, mixing the dispersant and another portion of the solvent and stirring until dissolved to obtain a second mixed solution;

[0040] S103, transferring the second mixed solution to a reactor for stirring, and adding the silver nitrate solution and the first mixed solution to the reactor at the same time and stirring at a uniform speed, then adding the coating agent solution, and continuing to stir until the reaction is completed to obtain a reaction suspension; wherein, after the reaction is completed, the pH value of the reaction suspension is about 7.

[0041] Specifically, in step S101: the reducing agent is at least one of ascorbic acid, formaldehyde, glucose, triethanolamine and hydrazine hydrate; wherein, the silver nitrate solution and the reducing agent undergo an oxidation-reduction reaction, so that the silver ions in the solution are reduced to silver powder; the amount of the reducing agent should exceed the theoretical value of the stoichiometric ratio by 5% to 10% to achieve the effect of completely reducing the silver ions in the solution.

[0042] Furthermore, the reason for adding an alkaline solution to the reducing agent is to increase the activity of the reducing agent to an appropriate level. If the pH is too high or too low, the reaction rate between the reducing agent and the silver nitrate may be too fast or too slow.

[0043] In one embodiment, the amount of reducing agent added is 54% of the mass of the reacted silver nitrate.

[0044] Furthermore, the role of dispersants is primarily reflected in preventing silver powder agglomeration, improving particle dispersibility, controlling particle morphology, and stabilizing the solution system. By selecting the right dispersant, the quality, uniformity, and processing performance of silver powder can be significantly improved, thereby optimizing its application in photovoltaics, electronics, and other fields.

[0045] In an embodiment of the present invention, the dispersant is polyvinylpyrrolidone (PVP), and the mass content of the dispersant is 13.3% to 15% of the mass content of silver nitrate in the silver nitrate solution; wherein, within this content range, PVP can effectively adsorb on the surface of the silver powder particles and play a dispersing role. When the PVP content is low, such as less than 8%, it may not provide enough molecules to wrap the silver powder particles, causing the silver powder to easily agglomerate during the formation process. When the PVP content is too high, exceeding 15%, although it can effectively disperse the silver powder, it may introduce too many organic impurities and increase costs.

[0046] Specifically, the specifications of polyvinyl pyrrolidone used as the dispersant meet the following requirements: K value of 31.5-33, moisture <4%, pH value of 3-4, peroxide content ≤200ppm, and weight average molecular weight of 25,000~40,000.

[0047] Furthermore, a K value of 31.5-33 corresponds to a moderate PVP molecular chain length. The K value primarily reflects the average molecular weight of PVP. A suitable K value indicates that the molecular chain length provides a good steric hindrance. When dispersing silver powder, the molecular chains can wrap around the surface of the silver powder particles, preventing the particles from approaching each other and agglomerating. If the K value is too small, the molecular chains are too short and cannot fully cover the silver powder particles, resulting in poor dispersion. If the K value is too large, the molecular chains are too long, which increases the viscosity of the solution and is not conducive to the dispersion of the silver powder.

[0048] Furthermore, the moisture content of PVP is less than 4% because excessive moisture can affect PVP's performance. High moisture content can alter the structure and state of PVP molecules, reducing their ability to adsorb silver powder particles. Furthermore, excessive moisture can cause PVP to hydrolyze, altering its chemical properties and thus affecting the dispersion of silver powder. For example, when the moisture content of PVP is too high, adsorption on the silver powder surface becomes unstable, resulting in poor silver powder dispersion.

[0049] Furthermore, PVP has an acidic pH of 3-4, which helps maintain its chemical stability. Within this pH range, the PVP molecular structure is relatively stable, allowing it to better exert its dispersing properties. A suitable pH also helps the surface charge of the silver powder particles better match the adsorption properties of PVP, enhancing adsorption and improving the dispersibility of the silver powder. If the pH is too high, PVP may undergo chemical reactions, destroying its structure and reducing its dispersibility.

[0050] Furthermore, the peroxide content of PVP should be ≤200 ppm. This is because peroxide is a strong oxidant. Excessive peroxide may trigger an oxidation reaction, oxidizing the silver powder surface, changing its surface properties, and affecting the silver powder's dispersibility and conductivity. Furthermore, peroxide can cause oxidative degradation of PVP molecules, reducing their molecular weight and breaking their molecular chains, thereby affecting their steric hindrance and adsorption properties, preventing them from effectively functioning as a dispersant.

[0051] Furthermore, the weight-average molecular weight of PVP is 25,000-40,000. This molecular weight range is related to the K value and directly affects the dispersion properties of PVP. Within this range, PVP molecules have an appropriate length and size, providing good steric hindrance and adsorption properties. If the molecular weight is too low, the molecular chain is too short and cannot effectively encapsulate the silver powder particles, resulting in poor dispersion. If the molecular weight is too high, the viscosity of the solution increases, which is also not conducive to dispersion.

[0052] Specifically, the coating solution is formed by mixing coating agent powder with anhydrous ethanol. The coating agent powder is at least one of oleic acid, lauric acid, stearic acid, and palmitic acid. The coating agent solution primarily forms a protective layer on the particle surface, preventing oxidation, controlling particle growth, preventing agglomeration, and improving dispersibility and sintering properties. A suitable coating agent solution not only improves the quality of silver powder but also enhances its performance during storage, transportation, and subsequent applications.

[0053] In one embodiment, the amount of the coating agent added is 1% of the mass of the reacted silver nitrate.

[0054] Specifically, the preparation method of the silver nitrate solution in step S103 is as follows: dissolve silver nitrate in a certain amount of deionized water to prepare a silver nitrate aqueous solution with a volume concentration of 266.7 g / L, heat it and keep it at 15° C.-40° C. to obtain the silver nitrate solution.

[0055] In the above embodiment, the solvent is water; the stirring rates in step S101, step S102 and step S103 are all 400-600 r / min; wherein, the stirring rate range of 400-600 r / min is optimized to ensure that the silver powder is evenly dispersed in the solution. During the reaction process, stirring can fully mix the reactants to avoid the occurrence of local concentrations that are too high or too low. At the same time, stirring can also promote the contact between the dispersant PVP and the silver powder particles, thereby improving the dispersion effect. If the stirring rate is too low, such as lower than 400 r / min, it may cause the silver powder particles to precipitate or agglomerate in the solution, affecting dispersibility; and if the stirring rate is too high, exceeding 600 r / min, it may generate excessive shear force, destroy the structure of the silver powder particles, and is not conducive to dispersion.

[0056] S20, performing sedimentation treatment on the reaction suspension to obtain a precipitate, and then performing washing and drying treatment on the precipitate to obtain highly dispersible silver powder.

[0057] Specifically, step S20 further includes:

[0058] S201, performing sedimentation treatment on the reaction suspension, removing the supernatant to obtain a precipitate;

[0059] S202, washing the precipitate with a detergent until the precipitate has a conductivity of less than 20 μS / m, thereby obtaining wet silver powder, wherein washing the precipitate to a conductivity of less than 20 μS / m indicates that the ionic impurity content in the precipitate is very low, thus meeting a high purity requirement;

[0060] S203, drying the wet silver powder to obtain highly dispersed silver powder.

[0061] Preferably, in step S203: the drying temperature is 40°C to 80°C, and the drying time is 20h to 24h;

[0062] Specifically, a lower temperature (around 40°C) can prevent undesirable silver powder agglomeration and oxidation during the drying process. If the temperature is too high, the silver powder particles may collide with each other due to excessive thermal motion, resulting in agglomeration and affecting the silver powder's dispersion. High temperatures can also cause oxidation reactions on the silver powder surface, forming silver oxide, which reduces its conductivity.

[0063] Specifically, a drying time of 20 to 24 hours can ensure that the moisture in the wet silver powder is fully removed. A sufficiently long drying time can allow the silver powder to reach an ideal dry state, giving it good fluidity and dispersibility. If the drying time is too short, moisture may remain in the silver powder, which will affect its performance and subsequent use. For example, during the subsequent electrode preparation process, silver powder containing moisture may cause bubbles or other defects in the electrode, thereby affecting the performance of the photovoltaic cell.

[0064] Correspondingly, the present invention also provides a highly dispersible silver powder, which is prepared by any of the above methods for preparing highly dispersible silver powder.

[0065] Correspondingly, the present invention further provides a use of the highly dispersible silver powder as described above in the preparation of conductive silver paste.

[0066] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0067] Example 1:

[0068] This embodiment 1 provides a highly dispersible silver powder and a preparation method thereof, the preparation method comprising the following steps:

[0069] Step 1, liquid preparation:

[0070] Solution A: Add 160g of silver nitrate to a beaker, add 600ml of deionized water, stir to dissolve, and heat to 25°C and keep warm to obtain Solution A.

[0071] Solution B: Add 86.4g of ascorbic acid to a beaker and add 600ml of deionized water. Stir and dissolve. Once completely dissolved, you will obtain Solution B.

[0072] Solution C: Add 17.92g of polyvinyl pyrrolidone (K30) to a beaker and add 900ml of deionized water, stirring to dissolve. Solution C is obtained after complete dissolution. The technical specifications of K30 are: K value should be 31.5-33, moisture <4%, pH value 3-4, peroxide content less than or equal to 200ppm, and weight average molecular weight 25,000-40,000.

[0073] Solution D: Add 0.5 g of oleic acid to a beaker and add 10 ml of anhydrous ethanol and stir to dissolve to obtain solution D.

[0074] Step 2: Preparation of silver powder:

[0075] (1) Transfer solution C to the reactor, start mechanical stirring, and control the stirring rate to 500 rpm;

[0076] (2) Adjust the pH value of solution B to 5.5 using a 10 mol / L sodium hydroxide solution, then transfer it to the reactor and mix it with solution C for 5 min;

[0077] (3) Add solution A and solution B to the reactor at a certain flow rate at the same time, and control the addition time to be between 1 and 3 minutes; after the addition is completed, stir for 5 minutes, and add solution D, continue stirring for 5 minutes, and the reaction is completed;

[0078] (4) The reaction suspension was settled, the supernatant was poured out, and the solid-liquid separation was performed. The silver powder was washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate was less than 20 μS / m. The silver powder was dried in a blast drying oven at 60°C for 22 hours to obtain highly dispersed silver powder. Figure 2 shown.

[0079] Example 2:

[0080] Step 1, liquid preparation:

[0081] Solution A: Add 160g of silver nitrate to a beaker, add 600ml of deionized water, stir to dissolve, and heat to 25°C and keep warm to obtain Solution A.

[0082] Solution B: Add 86.4g of ascorbic acid to a beaker and add 600ml of deionized water. Stir and dissolve. Once completely dissolved, you will obtain Solution B.

[0083] Solution C: Add 20.16g of polyvinyl pyrrolidone (K30) to a beaker and add 900ml of deionized water, stirring to dissolve. Solution C is obtained after complete dissolution. The technical specifications of K30 are: K value should be 31.5-33, moisture <4%, pH value 3-4, peroxide content less than or equal to 200ppm, and weight average molecular weight 25,000-40,000.

[0084] Solution D: Add 0.5 g of oleic acid to a beaker and add 10 ml of anhydrous ethanol and stir to dissolve to obtain solution D.

[0085] Step 2: Preparation of silver powder:

[0086] (1) Transfer solution C to the reactor, start mechanical stirring, and control the stirring rate to 500 rpm;

[0087] (2) Adjust the pH value of solution B to 5.5 using a 10 mol / L sodium hydroxide solution, then transfer it to the reactor and mix it with solution C for 5 min;

[0088] (3) Add solution A and solution B to the reactor at a certain flow rate at the same time, and control the addition time to be between 1 and 3 minutes; after the addition is completed, stir for 5 minutes, and add solution D, continue stirring for 5 minutes, and the reaction is completed;

[0089] (4) The reaction suspension was settled, the supernatant was poured out, and the solid-liquid separation was performed. The silver powder was washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate was less than 20 μS / m. The silver powder was dried in a blast drying oven at 60°C for 22 hours to obtain highly dispersed silver powder. Figure 3 shown.

[0090] Example 3:

[0091] Step 1, liquid preparation:

[0092] Solution A: Add 160g of silver nitrate to a beaker, add 600ml of deionized water, stir to dissolve, and heat to 25°C and keep warm to obtain Solution A.

[0093] Solution B: Add 86.4g of ascorbic acid to a beaker and add 600ml of deionized water. Stir and dissolve. Once completely dissolved, you will obtain Solution B.

[0094] Solution C: Add 21.28g of polyvinyl pyrrolidone (K30) to a beaker and add 900ml of deionized water, stirring to dissolve. Solution C is obtained after complete dissolution. The technical specifications of K30 are: K value should be 31.5-33, moisture <4%, pH value 3-4, peroxide content less than or equal to 200ppm, and weight average molecular weight 25,000-40,000.

[0095] Solution D: Add 0.5 g of oleic acid to a beaker and add 10 ml of anhydrous ethanol and stir to dissolve to obtain solution D.

[0096] Step 2: Preparation of silver powder:

[0097] (1) Transfer solution C to the reactor, start mechanical stirring, and control the stirring rate to 500 rpm;

[0098] (2) Adjust the pH value of solution B to 5.5 using a 10 mol / L sodium hydroxide solution, then transfer it to the reactor and mix it with solution C for 5 min;

[0099] (3) Add solution A and solution B to the reactor at a certain flow rate at the same time, and control the addition time to be between 1 and 3 minutes; after the addition is completed, stir for 5 minutes, and add solution D, continue stirring for 5 minutes, and the reaction is completed;

[0100] (4) The reaction suspension was settled, the supernatant was poured out, and the solid-liquid separation was performed. The silver powder was washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate was less than 20 μS / m. The silver powder was dried in a blast drying oven at 60°C for 22 hours to obtain highly dispersed silver powder. Figure 4 shown.

[0101] Comparative Example 1:

[0102] Step 1, liquid preparation:

[0103] Solution A: Add 160g of silver nitrate to a beaker, add 600ml of deionized water, stir to dissolve, and heat to 25°C and keep warm to obtain Solution A.

[0104] Solution B: Add 86.4g of ascorbic acid to a beaker and add 600ml of deionized water. Stir and dissolve. Once completely dissolved, you will obtain Solution B.

[0105] Solution C: Add 22.4g of polyvinyl pyrrolidone (K30) to a beaker and stir to dissolve in 900ml of deionized water. After complete dissolution, obtain Solution C. The technical specifications of K30 are: K value should be 31.5-33, moisture <4%, pH value 3-4, peroxide content less than or equal to 200ppm, and weight average molecular weight 25,000-40,000.

[0106] Solution D: Add 0.5 g of oleic acid to a beaker and add 10 ml of anhydrous ethanol and stir to dissolve to obtain solution D.

[0107] Step 2: Preparation of silver powder:

[0108] (1) Transfer solution C to the reactor, start mechanical stirring, and control the stirring rate to 500 rpm;

[0109] (2) Adjust the pH value of solution B to 5.5 using a 10 mol / L sodium hydroxide solution, then transfer it to the reactor and mix it with solution C for 5 min;

[0110] (3) Add solution A and solution B to the reactor at a certain flow rate at the same time, and control the addition time to be between 1 and 3 minutes; after the addition is completed, stir for 5 minutes, and add solution D, continue stirring for 5 minutes, and the reaction is completed;

[0111] (4) The reaction suspension was settled, the supernatant was poured out, and the solid-liquid separation was performed. The silver powder was washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate was less than 20 μS / m. The silver powder was dried in a blast drying oven at 60°C for 22 hours to obtain highly dispersed silver powder. Figure 4 shown.

[0112] Specifically, the performance of the silver powder prepared in Examples 1 to 3 and Comparative Example 1 was tested, and the test results are shown in Table 1:

[0113] Table 1 Performance indicators of Examples 1 to 3 and Comparative Example 1

[0114]

[0115] Specifically, in comparison between Comparative Example 1 and Examples 1 to 3, except for the amount of the dispersant polyvinyl pyrrolidone (K30) used, the preparation conditions remained the same, including the oxidant, reducing agent, reaction conditions, and additives.

[0116] As can be seen from Table 1, the amounts of the dispersant polyvinyl pyrrolidone (K30) used in Examples 1, 2, and 3 are 80%, 90%, and 95% of that in the comparative example, respectively. When the amount of the dispersant is less than 95%, the dispersibility is poor and the particle size is large. However, when the amount is 95%, the dispersion effect is good (such as in Example 3), which is basically consistent with that in Comparative Example 1 and can meet the use requirements. The amount of the dispersant PVP used is 13.3% of the mass of the silver nitrate.

[0117] It should be noted that the amount of PVP used is also related to the weight-average molecular weight of PVP. PVPs with different weight-average molecular weights have different dispersion effects, and the required amount will be different. Therefore, according to the steps of Comparative Example 1, except for the different weight-average molecular weights of the dispersant PVP used, other conditions are basically the same. The final PVP indicators and silver powder particle size data are shown in Table 2:

[0118] Table 2 Different performance indicators corresponding to different weight average molecular weights of PVP

[0119]

[0120] This application discloses a highly dispersible silver powder, its preparation method, and its application, belonging to the field of micro-nano powder preparation technology. The silver powder has a quasi-spherical individual particle morphology, good dispersibility, and uniform particle size. This silver powder is primarily used in solar photovoltaic cell slurries and exhibits excellent electrical properties and linearity. This preparation method features a short process flow, strong operability, easy process control, low raw material consumption, and the absence of hazardous chemicals, making it suitable for industrial production.

[0121] This invention uses silver nitrate as a silver source and develops a method and application for producing silver powder using a low dispersant dosage, thereby reducing raw material costs during the silver powder production process. By selecting a dispersant of specific technical specifications, PVP, due to its specific molecular weight and impurity content, significantly enhances the steric hindrance effect and improves the dispersion effect, achieving the goal of producing highly dispersible silver powder while reducing the amount of PVP used.

[0122] Compared with the prior art, the present invention has the following beneficial effects:

[0123] First, the present invention can prepare highly dispersed spherical and highly conductive silver powder, which can be directly used as the conductive phase of photovoltaic silver paste.

[0124] Second, the present invention adopts a simple liquid-phase reduction method to prepare highly dispersible silver powder. The dispersant used is polyvinylpyrrolidone (PVP), which is a simple and easily available water-soluble polymer. No animal glue such as gelatin and bone glue is used, which is difficult to clean and affects the conductivity of the silver powder.

[0125] Third, the present invention uses polyvinyl pyrrolidone (PVP) of specific specifications as a dispersant. The amount of the dispersant used is 13.3% to 15% of the mass of the reacted silver nitrate, which is much smaller than the commonly used amount of 20% to 40%. This can significantly reduce the amount of dispersant PVP used without affecting the dispersibility of the final silver powder.

[0126] Fourth, the cleaning process of the silver powder process of the present invention uses water and anhydrous ethanol. Washing in this way can significantly remove the water-soluble dispersant PVP and excess reducing agent on the surface of the silver powder.

[0127] Fifth, the silver powder preparation method of the present invention has high cost performance.

[0128] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0129] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing highly dispersible silver powder, characterized in that: The steps include: S10, mixing a silver nitrate solution, a reducing agent, a dispersant, a coating agent solution, and a solvent to obtain a reaction suspension; S20, performing sedimentation treatment on the reaction suspension to obtain a precipitate, and then washing and drying the precipitate to obtain highly dispersible silver powder; Wherein, in the step S10: the dispersant is polyvinyl pyrrolidone, and the specifications of polyvinyl pyrrolidone meet the following requirements: K value is 31.5-33, moisture <4%, pH value is 3-4, peroxide content is ≤200ppm, and weight average molecular weight is 25000-40000; the mass content of the dispersant is 13.3% to 15% of the mass content of silver nitrate in the silver nitrate solution; The step S10 specifically includes: S101, mixing the reducing agent with a portion of the solvent, stirring until dissolved, and adding an alkaline solution to obtain a first mixed solution; S102, mixing the dispersant and another portion of the solvent and stirring until dissolved to obtain a second mixed solution; S103, transferring the second mixed solution to a reactor for stirring, and simultaneously adding the silver nitrate solution and the first mixed solution to the reactor and stirring at a uniform speed, then adding the coating agent solution, and continuing stirring until the reaction is complete to obtain the reaction suspension; The solvent is water; and the stirring rates in step S101, step S102, and step S103 are all 400-600 r / min.

2. The method for preparing highly dispersible silver powder according to claim 1, wherein In the step S101: the reducing agent is at least one of ascorbic acid, formaldehyde, glucose, triethanolamine and hydrazine hydrate.

3. The method for preparing highly dispersible silver powder according to claim 1, wherein In the step S103, the coating agent solution is prepared by mixing coating agent powder with anhydrous ethanol; the coating agent powder is at least one of oleic acid, lauric acid, stearic acid and palmitic acid.

4. The method for preparing highly dispersible silver powder according to claim 1, wherein The S20 step specifically includes: S201, performing sedimentation treatment on the reaction suspension, and removing the supernatant to obtain the precipitate; S202, washing the precipitate with a cleaning agent until the precipitate is washed to a conductivity of less than 20 μS / m, thereby obtaining wet silver powder; S203, drying the wet silver powder to obtain the highly dispersible silver powder.

5. The method for preparing highly dispersible silver powder according to claim 4, wherein: In the step S203, the temperature of the drying process is 40°C to 80°C, and the drying time is 20h to 24h.

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

7. Use of the highly dispersible silver powder according to claim 6 in preparing conductive silver paste.

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