Spherical silver powder with high sintering activity as well as preparation method and application of spherical silver powder

Abstract

The invention discloses high-sintering-activity spherical silver powder and a preparation method and application thereof. The preparation method comprises the steps that under the condition of continuous stirring, a reducing agent, a silver-containing oxidizing agent and a dispersing agent are mixed, then a first auxiliary agent is added, a liquid-phase reduction reaction is conducted, and a silver powder initial product is obtained; and mixing the silver powder primary product, a modified dispersant and a second auxiliary agent, and modifying the silver powder primary product to prepare the high-sintering-activity spherical silver powder, the particle size distribution D50 of the high-sintering-activity spherical silver powder is 1.4-1.8 microns, the tap density is not smaller than 5.5 g / cm < 3 >, and the specific surface area is not smaller than 0.36 m < 2 > / g. The preparation method is simple in process, the high-sintering-activity spherical silver powder can be stably prepared, and the preparation method is widely applied to the fields of solar cells and electronic and electric appliances.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder material preparation, and specifically relates to a spherical silver powder with high sintering activity and a preparation method and application thereof. Background Art

[0002] Photovoltaic silver paste is the core auxiliary material for crystalline silicon solar photovoltaic power generation. The main component of silver paste is silver powder, and its performance mainly depends on the particle size distribution and morphology characteristics of the silver powder. With the continuous development of photovoltaic cell technology, silver paste adapted to different battery technologies has become the core issue of efficiency improvement. This puts more stringent requirements on the performance of silver powder, requiring silver powder to have higher sintering activity, narrower particle size distribution, and more controllable morphology.

[0003] At present, the conventional method for preparing spherical silver powder is to produce micron silver powder by inducing nanocrystal seeds. The silver powder prepared by this method has high crystallinity and smooth morphology, but its sintering activity is low. At the same time, the method of preparing silver powder by inducing nanocrystal seeds is highly dependent on nanocrystal seeds, and nanocrystal seeds will agglomerate and settle as the storage time increases, and have poor stability. When using, the method of use needs to be adjusted according to the situation of the seeds, and the nanocrystal seed preparation process is relatively long. The silver powder preparation process is limited by the properties of the nanocrystal seeds, which is not conducive to large-scale industrial applications. Summary of the invention

[0004] The main purpose of the present invention is to provide a spherical silver powder with high sintering activity and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: One aspect of the present invention provides a method for preparing spherical silver powder with high sintering activity, comprising: Under the condition of continuous stirring, the reducing agent, the silver-containing oxidizing agent and the dispersing agent are mixed, and then the first auxiliary agent is added to carry out a liquid phase reduction reaction to obtain a primary product of silver powder; The silver powder primary product, the modified dispersant and the second auxiliary agent are mixed to modify the silver powder primary product to obtain a spherical silver powder with high sintering activity; The particle size distribution D50 of the high sintering activity spherical silver powder is 1.4-1.8 μm, and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

[0006] Another aspect of the present invention provides a spherical silver powder with high sintering activity prepared by the above-mentioned preparation method, wherein the particle size distribution D50 of the spherical silver powder with high sintering activity is 1.4-1.8 μm and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

[0007] Another aspect of the present invention also provides the use of the above-mentioned high sintering activity spherical silver powder in the field of solar cells or electronic appliances.

[0008] Compared with the prior art, the technical solution of the present invention has at least the following advantages: 1) The silver powder prepared by the preparation method provided by the present invention is a silver powder grown by crystal coagulation, and interfaces of different crystal grains can be seen on its surface. The smaller the size of the coagulated crystal grains, the higher the activity. Moreover, the prepared silver powder has improved specific surface area and burning loss while maintaining the tap density and particle size distribution without significant changes, which is conducive to further improving the sintering activity of the silver powder; 2) The preparation method provided by the present invention eliminates the regulation of the reaction by the seed crystal, which on the one hand avoids the influence of the unstable performance of the seed crystal on the stability of the product, and on the other hand has fewer control links and a simple process. The preparation of spherical silver powder with high sintering activity can be achieved by simple raw materials and equipment, which is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0010] Figure 1 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 2 of the present invention; Figure 3 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 3 of the present invention; Figure 4 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 4 of the present invention; Figure 5 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 5 of the present invention; Figure 6 This is a scanning electron microscope image of the high sintering activity spherical silver powder prepared in Example 6 of the present invention; Figure 7 This is a scanning electron microscope image of the silver powder of Comparative Example 1 of the present invention; Figure 8 This is a scanning electron microscope image of the silver powder of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0011] The present invention will be more fully understood by reading the following specific embodiments. However, it should be understood that the specific embodiments disclosed below are only exemplary of the present invention, and the present invention can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be interpreted as limiting, but only as the basis for the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in any appropriate detailed embodiment.

[0012] As one aspect of the technical solution of the present invention, a method for preparing a spherical silver powder with high sintering activity comprises: Under the condition of continuous stirring, the reducing agent, the silver-containing oxidizing agent and the dispersing agent are mixed, and then the first auxiliary agent is added to carry out a liquid phase reduction reaction to obtain a primary product of silver powder; The silver powder primary product, the modified dispersant and the second auxiliary agent are mixed to modify the silver powder primary product to obtain a spherical silver powder with high sintering activity; The particle size distribution D50 of the high sintering activity spherical silver powder is 1.4-1.8 μm, and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

[0013] In some embodiments, the preparation method includes: under continuous stirring, sequentially adding a reducing agent solution and a silver-containing oxidant solution to a dispersant solution at a selected feed rate, and then adding a first auxiliary agent to perform a liquid phase reduction reaction to obtain the initial silver powder product.

[0014] In some preferred embodiments, the molar ratio of the reducing agent in the reducing agent solution to the silver element in the silver-containing oxidizing agent solution is 0.6-2.1:1.

[0015] In some preferred embodiments, the mass of the dispersant in the dispersant solution is 7.5-30% of the mass of the silver element in the silver-containing oxidant solution.

[0016] In some preferred embodiments, the stirring speed is 150-600 r / min.

[0017] In some preferred embodiments, the selected feed rate is 160-240 ml / min. By adopting the above scheme, changing the feed rate can change the particle size distribution. If the feed rate is less than 160 ml / min, the particle size will be larger, the reaction time will be relatively long, and abnormal grains will easily appear. Increasing the feed rate can narrow the distribution, but too fast a feed rate will cause particle agglomeration.

[0018] In some preferred embodiments, the temperature of the liquid phase reduction reaction is 10-70° C., and the reaction time is 3-30 min.

[0019] In some preferred embodiments, the time for the reducing agent solution and the silver-containing oxidizing agent solution to completely enter the first dispersant solution is 2-10 minutes.

[0020] In some preferred embodiments, the time difference between the reducing agent solution and the silver-containing oxidizing agent solution entering the first dispersant solution is within 3 seconds.

[0021] In some preferred embodiments, the preparation method comprises: after the reducing agent solution and the silver-containing oxidizing agent solution completely enter the dispersant solution, adding the first auxiliary agent within 0-30 minutes to carry out the liquid phase reduction reaction.

[0022] In some preferred embodiments, the mass concentration of the silver-containing oxidant in the silver-containing oxidant solution is 20-40wt%.

[0023] In some preferred embodiments, the silver-containing oxidizing agent includes, but is not limited to, silver nitrate.

[0024] In some preferred embodiments, the reducing agent solution comprises a reducing agent, a pH adjuster and water.

[0025] In some more preferred embodiments, the mass concentration of the reducing agent in the reducing agent solution is 14-30 wt %.

[0026] In some more preferred embodiments, the reducing agent includes but is not limited to any one or a combination of two or more of ascorbic acid, glucose, triethanolamine, hydrazine hydrate, hydroquinone, formaldehyde, and acetaldehyde.

[0027] In some more preferred embodiments, the pH adjuster includes but is not limited to any one of ammonia water, ammonium bicarbonate, sodium hydroxide, potassium hydroxide, or a combination of two or more thereof.

[0028] In some more preferred embodiments, the pH value of the reducing agent solution is 5-10.5. Applying pH adjustment to the reducing agent can ensure a continuous and rapid reaction.

[0029] In some preferred embodiments, the mass concentration of the dispersant in the dispersant solution is 1.12-5.0 wt %.

[0030] In some preferred embodiments, the dispersant includes but is not limited to any one of polyvinyl pyrrolidone, gum arabic, gelatin, or a combination of two or more thereof.

[0031] In some preferred embodiments, the mass ratio of the first auxiliary agent to the silver element in the silver-containing oxidant solution is 0.4-1.5:100.

[0032] In some preferred embodiments, the first auxiliary agent includes, but is not limited to, any one or a combination of two or more of lauric acid, stearic acid, ammonia water, hexadecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl hydroxy stearic acid, sodium dodecyl benzene sulfonate, and oleic acid. The first auxiliary agent plays the role of terminating the reaction, accelerating sedimentation, and surface modification in the reaction.

[0033] In some embodiments, the preparation method includes: mixing the silver powder primary product, the modified dispersant and the second auxiliary agent, performing stirring and dispersing treatment, modifying the silver powder primary product, and obtaining the high sintering activity spherical silver powder.

[0034] In some preferred embodiments, the mass ratio of the primary silver powder product, the modified dispersant and the second auxiliary agent is 100: (100-500): (0.5-2.0).

[0035] In some preferred embodiments, the modified dispersant includes but is not limited to any one of water and ethanol or a combination of both.

[0036] In some preferred embodiments, the second auxiliary agent includes, but is not limited to, any one or a combination of two or more of lauric acid, stearic acid, ammonia water, hexadecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl hydroxy stearic acid, sodium dodecyl benzene sulfonate, oleic acid, ethyl acetate, and methyl sugar. The second auxiliary agent mainly plays the role of surface modification and dispersion.

[0037] In some embodiments, the preparation method includes: washing the primary silver powder product until the conductivity is below 20 μS / cm, and then mixing with the modified dispersant and the second auxiliary agent to modify the primary silver powder product.

[0038] In some more specific embodiments, the method for preparing the high sintering activity spherical silver powder comprises the following steps: S1: preparing a solution: including preparing a reducing agent solution, a silver-containing oxidizing agent solution, a dispersant solution, a first auxiliary agent solution, and a second auxiliary agent solution; S2: Liquid phase reduction reaction: under high-speed stirring at 150-600 r / min, the reducing agent solution and the silver-containing oxidant solution are added to the dispersant solution in a certain order and flow rate, the stirring speed is adjusted during the addition process, the adjustment range is 150-600 r / min, and the temperature of the reaction system is controlled between 10-70°C. After the reducing agent solution and the silver-containing oxidant solution are completely added to the dispersant solution, the first auxiliary agent solution is quickly added to the reaction system within 0-30 minutes, and the stirring reaction is continued for 3-30 minutes after the addition is completed; S3: Silver powder modification: After the liquid phase reduction reaction in step S2 is completed, the reaction product is subjected to solid-liquid separation to obtain a primary silver powder product, which is transferred to a reactor or a cleaning bucket and cleaned until the conductivity is below 20 μS / cm; then it is transferred to a disperser, a modified dispersant is added, a second auxiliary agent solution is added, and after high-speed stirring and dispersion, it is dried at 60-100°C to obtain a spherical silver powder with high sintering activity; S4: Post-processing of silver powder: The silver powder obtained in step S3 is put into a pulverizer for crushing, and then put into an air mill for shaping and crushing.

[0039] As another aspect of the technical solution of the present invention, it relates to a high sintering activity spherical silver powder prepared by the above-mentioned preparation method, wherein the particle size distribution D50 of the high sintering activity spherical silver powder is 1.4-1.8 μm, and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

[0040] As another aspect of the technical solution of the present invention, it also involves the application of the above-mentioned high sintering activity spherical silver powder in solar cells or electronic appliances.

[0041] In some embodiments, the application includes: using the high sintering activity spherical silver powder to prepare silver paste for solar cells.

[0042] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The reagents and raw materials used in the following examples are commercially available, and the experimental methods without specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0043] Example 1 A method for preparing spherical silver powder with high sintering activity comprises the following steps: Liquid preparation: Dissolve 240 g of silver nitrate in 856 g of deionized water to obtain an oxidant solution with a mass fraction of 21.9 wt %; 153 g of ascorbic acid was dissolved in 801 g of deionized water and then 75 ml of 28% ammonia water was added thereto to prepare a reducing agent solution (pH=8); the mass concentration of the reducing agent in the reducing agent solution was 15.1 wt %, and the molar ratio of the reducing agent in the reducing agent solution to the silver element in the oxidant solution was 0.61:1; 45.6 g of polyvinyl pyrrolidone (PVP) was dissolved in 1020 g of deionized water to prepare a dispersant solution with a mass fraction of 4.28 wt %, wherein the mass of the dispersant in the dispersant solution was 30% of the mass of the silver element in the oxidant solution.

[0044] Lauric acid and alcohol are prepared into auxiliary agent A solution at a mass ratio of 1:10; Stearic acid and alcohol are prepared into additive B solution at a mass ratio of 1:20; reaction: Set the peristaltic pump feed rate of the oxidant solution and the reducing agent solution to 160 ml / min, fix the dispersant solution beaker to the center of the stirrer, fix the peristaltic pump feed pipes of the oxidant solution and the reducing agent solution, and start stirring the dispersant solution at a stirring speed of 300 r / min; Turn on the peristaltic pump for the reducing agent solution, add the reducing solution for 3 seconds, and then turn on the peristaltic pump for the oxidizing agent solution; When the oxidant solution material is completely introduced (approximately 5min20s), turn off the peristaltic pumps of the oxidant solution and the reducing agent solution, add the auxiliary agent A solution, stir for 5min and then stop; the mass ratio of lauric acid to the silver element in the oxidant solution is 0.4:100.

[0045] The reaction product is separated into solid and liquid to obtain the initial silver powder product, which is then transferred to a cleaning bucket and cleaned until the conductivity is below 20μS / cm; then transferred to a disperser, a modified dispersant (ethanol) and an auxiliary agent B solution are added, and the mass ratio of the initial silver powder product, ethanol and stearic acid is 100:100:0.5. After high-speed stirring and dispersion, it is dried at 100°C. The obtained silver powder is crushed in a pulverizer and then shaped and crushed in an air mill to obtain high sintering active silver powder. The scanning electron microscope image is shown in Figure 1 .

[0046] Example 2 A method for preparing spherical silver powder with high sintering activity comprises the following steps: Liquid preparation: Dissolve 360 ​​g of silver nitrate in 1014 g of deionized water to obtain an oxidant solution with a mass fraction of 26.2 wt %; 229.5 g of ascorbic acid was dissolved in 961 g of deionized water and 140 ml of 28% ammonia water was added thereto to prepare a reducing agent solution (pH = 9.2); the mass concentration of the reducing agent in the reducing agent solution was 19.3 wt %, and the molar ratio of the reducing agent in the reducing agent solution to the silver element in the oxidant solution was 0.62:1; 35 g of polyvinyl pyrrolidone was dissolved in 1014 g of deionized water to prepare a dispersant solution with a mass fraction of 3.33 wt %, wherein the mass of the dispersant in the dispersant solution was 15.3% of the mass of the silver element in the oxidant solution.

[0047] Lauric acid and alcohol are prepared into auxiliary agent A solution at a mass ratio of 1:10; Stearic acid and alcohol are prepared into additive B solution at a mass ratio of 1:20; reaction: Set the peristaltic pump feed rate of the oxidant solution and the reducing agent solution to 240 ml / min, fix the dispersant solution beaker to the center of the stirrer, fix the peristaltic pump feed pipes of the oxidant solution and the reducing agent solution, and start stirring the dispersant solution at a stirring speed of 300 r / min; Turn on the peristaltic pump for the reducing agent solution, add the reducing solution for 3 seconds, and then turn on the peristaltic pump for the oxidizing agent solution; When the oxidant solution material is completely introduced (approximately 5 minutes), turn off the peristaltic pumps of the oxidant solution and the reducing agent solution, add the auxiliary agent A solution, stir for 5 minutes and then stop; the mass ratio of lauric acid to the silver element in the oxidant solution is 1:100.

[0048] The reaction product is separated into solid and liquid to obtain the initial silver powder product, which is then transferred to a cleaning bucket and cleaned until the conductivity is below 20μS / cm; then transferred to a disperser, a modified dispersant (water) and an auxiliary agent B solution are added, and the mass ratio of the initial silver powder product, water and stearic acid is 100:200:1. After high-speed stirring and dispersion, it is dried at 100°C. The obtained silver powder is crushed in a pulverizer and then shaped and crushed in an air mill to obtain high sintering active silver powder. The scanning electron microscope image is shown in Figure 2 .

[0049] Example 3 A method for preparing spherical silver powder with high sintering activity comprises the following steps: Liquid preparation: Dissolve 480 g of silver nitrate in 720 g of deionized water to obtain an oxidant solution with a mass fraction of 40 wt %; 306 g of ascorbic acid was dissolved in 714 g of deionized water and then 180 ml of 28% ammonia water was added thereto to prepare a reducing agent solution (pH=10.2); the mass concentration of the reducing agent in the reducing agent solution was 30 wt %, and the molar ratio of the reducing agent in the reducing agent solution to the silver element in the oxidant solution was 0.62:1; 45.6 g of polyvinyl pyrrolidone was dissolved in 1014 g of deionized water to prepare a dispersant solution with a mass fraction of 4.3 wt %. The mass of the dispersant in the dispersant solution was 15.0% of the mass of the silver element in the oxidant solution.

[0050] Lauric acid and alcohol are prepared into auxiliary agent A solution at a mass ratio of 1:10; Stearic acid and alcohol are prepared into additive B solution at a mass ratio of 1:20; reaction: Set the peristaltic pump feed rate of the oxidant solution and the reducing agent solution to 200 ml / min, fix the dispersant solution beaker to the center of the stirrer, fix the peristaltic pump feed pipes of the oxidant solution and the reducing agent solution, and start stirring the dispersant solution at a stirring speed of 400 r / min; Turn on the peristaltic pump for the reducing agent solution, add the reducing solution 1 second later, and then turn on the peristaltic pump for the oxidizing agent solution; When the oxidant solution material is completely introduced (approximately 3 minutes), turn off the peristaltic pumps of the oxidant solution and the reducing agent solution, add the auxiliary agent A solution, stir for 5 minutes and then stop; the mass ratio of lauric acid to the silver element in the oxidant solution is 1.5:100.

[0051] The reaction product is separated into solid and liquid to obtain the initial silver powder product, which is then transferred to a cleaning bucket and cleaned until the conductivity is below 20μS / cm; then transferred to a disperser, a modified dispersant (ethanol) and an auxiliary agent B solution are added, and the mass ratio of the initial silver powder product, ethanol and stearic acid is 100:500:2. After high-speed stirring and dispersion, the product is dried at 100°C. The obtained silver powder is crushed in a pulverizer and then shaped and crushed in an air mill to obtain a high sintering active silver powder. The scanning electron microscope image is shown in Figure 3 .

[0052] Example 4 A method for preparing spherical silver powder with high sintering activity comprises the following steps: Liquid preparation: Dissolve 240 g of silver nitrate in 856 g of deionized water to obtain an oxidant solution with a mass fraction of 21.9 wt %; 153 g of ascorbic acid was dissolved in 801 g of deionized water and then 50 ml of 28% ammonia water was added thereto to prepare a reducing agent solution (pH=5.1); the mass concentration of the reducing agent in the reducing agent solution was 15.1 wt %, and the molar ratio of the reducing agent in the reducing agent solution to the silver element in the oxidant solution was 0.61:1; 45.6 g of polyvinyl pyrrolidone was dissolved in 1020 g of deionized water to prepare a dispersant solution with a mass fraction of 4.28 wt %. The mass of the dispersant in the dispersant solution was 30% of the mass of the silver element in the oxidant solution.

[0053] Lauric acid and alcohol are prepared into auxiliary agent A solution at a mass ratio of 1:10; Stearic acid and alcohol are prepared into additive B solution at a mass ratio of 1:20; reaction: Set the peristaltic pump feed rate of the oxidant solution and the reducing agent solution to 160 ml / min, fix the dispersant solution beaker to the center of the stirrer, fix the peristaltic pump feed pipes of the oxidant solution and the reducing agent solution, and start stirring the dispersant solution at a stirring speed of 300 r / min; Turn on the peristaltic pump for the reducing agent solution, add the reducing solution 1 second later, and then turn on the peristaltic pump for the oxidizing agent solution; When the oxidant solution material is completely introduced (approximately 5min20s), turn off the peristaltic pumps of the oxidant solution and the reducing agent solution, add the auxiliary agent A solution, stir for 5min and then stop; the mass ratio of lauric acid to the silver element in the oxidant solution is 0.4:100.

[0054] The reaction product is separated into solid and liquid to obtain the initial silver powder product, which is then transferred to a cleaning bucket and cleaned until the conductivity is below 20μS / cm; then transferred to a disperser, a modified dispersant (ethanol) and an auxiliary agent B solution are added, and the mass ratio of the initial silver powder product, ethanol and stearic acid is 100:100:0.5. After high-speed stirring and dispersion, it is dried at 100°C. The obtained silver powder is crushed in a pulverizer and then shaped and crushed in an air mill to obtain high sintering active silver powder. The scanning electron microscope image is shown in Figure 4 .

[0055] Example 5 Compared with Example 1, the difference is that the peristaltic pump for the reducing agent solution and the peristaltic pump for the oxidizing agent solution are turned on at the same time. Figure 5 .

[0056] Example 6 Compared with Example 1, the difference is that the peristaltic pump of the oxidant solution is turned on, and after adding the oxidizing solution for 3 seconds, the peristaltic pump of the reducing agent solution is turned on. Figure 6 .

[0057] Comparative Example 1 A domestic brand of commercial silver powder for electronic paste, the synthesis method is to produce micron silver powder by inducing nanocrystalline seeds. The silver powder prepared by this method has high crystallinity, smooth morphology and low sintering activity. Figure 7 .

[0058] Comparative Example 2 The commercial silver powder of a domestic brand of electronic paste has similar particle size and tap compaction, but has lower burnout and surface area, and poorer sphericity. See the SEM image for details. Figure 8 .

[0059] The parameters of the high sintering activity spherical silver powder prepared in the embodiment of the present invention and the comparative example product are compared, as shown in Table 1: Table 1 Parameters of the high sintering activity spherical silver powder prepared by the present invention and the comparative example product

[0060] It can be seen from the data in Table 1 that the silver powder prepared in Examples 1-6 of the present invention has improved specific surface area and burn-in loss while maintaining the tap density and particle size distribution without major changes, which is beneficial to improving the sintering activity of the silver powder; and the silver powder has a high burn-in loss, which can increase the coating amount to a certain extent, and has a certain benefit in improving the viscosity and wettability of the silver powder applied to the silver paste, and is more suitable for the use needs of the application end.

[0061] From the data in Table 1, it can be seen that the high activity of the silver powder of the present invention is specifically reflected in the lower sintering softening temperature and lower true density, specifically 10.1-10.2 g / cm 3 , that is, the particle density is less than the silver standard density of 10.49.

[0062] from Figures 1 to 8 It can be seen that the commercial silver powder of comparative example 1 has a smooth morphology, and the commercial silver powder of comparative example 2 has a poor sphericity. The silver powder prepared in Examples 1-6 of the present invention is a silver powder grown by crystal coagulation, and its external characteristics are rough morphology, and interfaces of different crystal grains can be seen on its surface. Generally, the smaller the size of the coagulated grains, the higher the activity. Therefore, the silver powder prepared in the present invention has better sintering activity.

[0063] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0064] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing spherical silver powder with high sintering activity, characterized in that: include: Under the condition of continuous stirring, the reducing agent, the silver-containing oxidizing agent and the dispersing agent are mixed, and then the first auxiliary agent is added to carry out a liquid phase reduction reaction to obtain a primary product of silver powder; The silver powder primary product, the modified dispersant and the second auxiliary agent are mixed to modify the silver powder primary product to obtain a spherical silver powder with high sintering activity; The particle size distribution D50 of the high sintering activity spherical silver powder is 1.4-1.8 μm, and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

2. The preparation method according to claim 1, characterized in that: include: Under the condition of continuous stirring, the reducing agent solution and the silver-containing oxidizing agent solution are sequentially added to the dispersant solution at a selected feeding rate, and then the first auxiliary agent is added to carry out a liquid phase reduction reaction to obtain the silver powder primary product; Preferably, the molar ratio of the reducing agent in the reducing agent solution to the silver element in the silver-containing oxidizing agent solution is 0.6-2.1:1; Preferably, the mass of the dispersant in the dispersant solution is 7.5-30% of the mass of the silver element in the silver-containing oxidant solution; Preferably, the stirring speed is 150-600r / min; Preferably, the selected feed rate is 160-240 ml / min; Preferably, the temperature of the liquid phase reduction reaction is 10-70°C and the time is 3-30min; Preferably, the time for the reducing agent solution and the silver-containing oxidizing agent solution to completely enter the first dispersant solution is 2-10 minutes; Preferably, the time difference between the reducing agent solution and the silver-containing oxidizing agent solution entering the first dispersant solution is within 3 seconds; Preferably, the preparation method comprises: after the reducing agent solution and the silver-containing oxidizing agent solution completely enter the dispersant solution, adding the first auxiliary agent within 0-30 minutes to carry out the liquid phase reduction reaction.

3. The preparation method according to claim 2, characterized in that: The mass concentration of the silver-containing oxidant in the silver-containing oxidant solution is 20-40 wt %; And / or, the silver-containing oxidizing agent comprises silver nitrate.

4. The preparation method according to claim 2, characterized in that: The reducing agent solution comprises a reducing agent, a pH adjusting agent and water; Preferably, the mass concentration of the reducing agent in the reducing agent solution is 14-30 wt %; Preferably, the reducing agent includes any one or a combination of two or more of ascorbic acid, glucose, triethanolamine, hydrazine hydrate, hydroquinone, formaldehyde, and acetaldehyde; Preferably, the pH regulator includes any one or a combination of two or more of ammonia water, ammonium bicarbonate, sodium hydroxide, and potassium hydroxide; Preferably, the pH value of the reducing agent solution is 5-10.

5.

5. The preparation method according to claim 2, characterized in that: The mass concentration of the dispersant in the dispersant solution is 1.12-5.00 wt %; And / or, the dispersant includes any one of polyvinyl pyrrolidone, gum arabic, gelatin, or a combination of two or more thereof.

6. The preparation method according to claim 2, characterized in that: The mass ratio of the first auxiliary agent to the silver element in the silver-containing oxidant solution is 0.4-1.5:100; And / or, the first auxiliary agent includes any one or a combination of two or more of lauric acid, stearic acid, ammonia water, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, dodecylhydroxystearic acid, sodium dodecylbenzenesulfonate, and oleic acid.

7. The preparation method according to claim 1, characterized in that: include: The silver powder primary product, the modified dispersant and the second auxiliary agent are mixed and stirred and dispersed to modify the silver powder primary product to obtain the high sintering activity spherical silver powder; Preferably, the mass ratio of the silver powder primary product, the modified dispersant and the second auxiliary agent is 100: (100-500): (0.5-2.0); Preferably, the modified dispersant includes any one of water and ethanol or a combination of the two; Preferably, the second auxiliary agent includes any one or a combination of two or more of lauric acid, stearic acid, ammonia water, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, dodecylhydroxystearic acid, sodium dodecylbenzenesulfonate, oleic acid, ethyl acetate, and methyl saccharate.

8. The preparation method according to claim 1, characterized in that: include: The silver powder primary product is washed until the conductivity is below 20 μS / cm, and then mixed with the modified dispersant and the second auxiliary agent to modify the silver powder primary product.

9. The high sintering active spherical silver powder prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The particle size distribution D50 of the high sintering activity spherical silver powder is 1.4-1.8 μm, and the tap density is not less than 5.5 g / cm 3 , the specific surface area is not less than 0.36m 2 / g.

10. Use of the high sintering activity spherical silver powder according to claim 9 in solar cells or electronic appliances; Preferably, the application includes: The high sintering activity spherical silver powder is used to prepare silver paste for solar cells.

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