Porous silver powder for TOPCon laser-assisted sintering, preparation of porous silver powder and conductive silver paste containing porous silver powder

Abstract

The invention discloses porous silver powder for TOPCon laser-assisted sintering, preparation and conductive silver paste containing the porous silver powder, and the silver powder is prepared through the following steps that a silver source-surfactant mixed solution and a first reducing agent solution are added into a dispersing agent solution at the same time, after a preset time is delayed, a second reducing agent-coating agent mixed solution continues to be added dropwise in a parallel flow mode, and the silver powder is obtained; stirring and reacting to obtain a mixed mother solution; and the mixed mother solution is filtered, washed and subjected to airflow crushing, and the porous silver powder for TOPCon laser-assisted sintering is obtained. According to the method, the specific surfactant is added into the silver nitrate solution to serve as a template, the pH value of the reducing agent is controlled, multi-stage adding is conducted, the concentration of the reducing agent in a reaction system is in an excessive state, the reaction rate can be accurately controlled to regulate and control formation of nanoscale holes in silver powder particles, and the prepared porous silver powder is low in true density and high in yield. And the requirement of the TOPCon laser-assisted sintering process on the microstructure of the silver powder is met.

Description

Technical Field

[0001] The present invention relates to the technical field of silver powder, and in particular to porous silver powder for TOPCon laser-assisted sintering, and preparation thereof and conductive silver paste containing the porous silver powder. Background Art

[0002] In TOPCon (Tunnel Oxide Passivated Contact) battery technology, the laser-assisted sintering process places higher demands on the performance of silver powder. Porous silver powder, due to its large specific surface area and unique pore structure, can better bond with electrode materials during the laser-assisted sintering process, improving the battery's conductivity and conversion efficiency.

[0003] At present, porous silver powder prepared by traditional methods has problems such as few and difficult-to-control pores, small specific surface area, and complex preparation process. As a result, it cannot meet the special requirements of laser-assisted sintering process in practical applications, limiting the further improvement of TOPCon battery performance.

[0004] Therefore, a solution is developed to prepare porous silver powder with multiple nano-scale or micro-nano-scale pore structures and a large specific surface area. Summary of the Invention

[0005] In view of this, the present application provides a porous silver powder for TOPCon laser-assisted sintering and a conductive silver paste containing the same, which is used to solve the problem of how to increase the specific surface area of ​​silver powder while reducing the true density.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for preparing porous silver powder for TOPCon laser-assisted sintering, comprising the following steps: Adding the silver source-surfactant mixture and the first reducing agent solution to the dispersant solution simultaneously, delaying for a preset time, and then adding the second reducing agent-coating agent mixture dropwise in parallel, and then stirring to react to obtain a mixed mother liquor; The mixed mother liquor is filtered, washed, and air flow crushed to obtain TOPCon porous silver powder for laser-assisted sintering.

[0007] Preferably, the preset time is 5-10s.

[0008] Preferably, the concentration of the second reducing agent is greater than or equal to the concentration of the first reducing agent; the addition rate of the second reducing agent is greater than or equal to the addition rate of the first reducing agent; and the reducing property of the second reducing agent is greater than or equal to the reducing property of the first reducing agent.

[0009] Preferably, the first reducing agent and the second reducing agent both include one or more of ascorbic acid, glucose, hydrazine hydrate, and formaldehyde; the sum of the masses of the first reducing agent and the second reducing agent is 0.5-2.2 times the mass of the silver source; and the pH value range of the first reducing agent and the second reducing agent is both 7-8.

[0010] Preferably, the surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, hexadecyltrimethylammonium bromide, polyacrylamide, and polyvinylpyrrolidone; the silver source includes silver nitrate; and the mass of the surfactant is 0.5-15% of the mass of the silver source.

[0011] Preferably, the coating agent includes one or more of lauric acid, stearic acid, ricinoleic acid, dodecylamine, hexadecylamine, and octadecylamine; and the mass of the coating agent is 0.001-0.005% of the mass of the silver source.

[0012] Preferably, the dispersant includes one or more of polyvinyl pyrrolidone, Tween-20, Tween-80, gum arabic, and gelatin; and the mass of the dispersant is 0.5-15% of the mass of the silver source.

[0013] Preferably, the specific steps of filtering, washing and air flow crushing the mixed mother liquor are: centrifuging the mixed mother liquor, washing with deionized water until the conductivity is ≤20μs / cm to obtain wet powder, drying the wet powder, and then crushing it by 0.6-1.1MPa pressure air flow to obtain porous silver powder for TOPCon laser assisted sintering.

[0014] In a second aspect, the present application provides a porous silver powder for TOPCon laser-assisted sintering.

[0015] In a third aspect, the present application provides a conductive silver paste comprising porous silver powder for TOPCon laser-assisted sintering.

[0016] The beneficial effects of this application are as follows: The present invention adds a specific surfactant as a template to the silver nitrate solution, controls the pH value of the reducing agent, and adds the reducing agent in multiple stages, so that the reducing agent concentration in the reaction system is in an excess state. This allows the reaction rate to be precisely controlled to regulate the formation of nanoscale pores inside the silver powder particles, resulting in a porous silver powder with a low true density, meeting the requirements of the TOPCon laser-assisted sintering process for the silver powder microstructure. The porous silver powder prepared by the present invention has a large specific surface area and a unique pore structure. During the TOPCon laser-assisted sintering process, it can better combine with the electrode material to form a denser and more conductive conductive network, thereby effectively improving the filling and opening voltage, and enhancing the overall performance of the battery. The preparation method of the present invention has relatively simple process steps, and the preparation of porous silver powder can be achieved by precise control of the raw material formula and reaction conditions. It is easy to industrialize production and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional electron microscope photograph of the silver powder in Example 1; Figure 2 This is an electron microscope photo of the silver powder in Example 1 Figure 3 This is an electron microscope photograph of the silver powder of Example 2; Figure 4 This is a cross-sectional electron microscope photograph of the silver powder in Comparative Example 1. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] The present application provides a method for preparing porous silver powder for TOPCon laser-assisted sintering, comprising the following steps: S1. In the dispersant solution, a silver source is added simultaneously - a surfactant mixture and a first reducing agent solution, and after a predetermined delay time, a second reducing agent - a coating agent mixture is added dropwise and then stirred to obtain a mixed mother liquor; S2. Filter, wash, and air flow-break the mixed mother liquor to obtain porous silver powder for TOPCon laser-assisted sintering.

[0020] The present application regulates the chemical activity of silver ions and controls the redox process by preferentially mixing a surfactant and a silver source so that the surfactant is electrostatically adsorbed on the surface of silver ions or coordinated with silver ions to form a complex. The staged addition of two reducing agent-containing solutions has the following effects: the first reducing agent is preferentially added to perform partial reduction and nucleation, and then the second reducing agent-coating agent mixture is added in parallel while the silver source-surfactant mixture and the first reducing agent solution are continued to be added. This ensures that the reducing agent is excessive in each reduction time period, so the reaction has a faster reduction rate, which is conducive to the formation of a pore structure and thus has a low true density. Furthermore, the addition of the coating agent when adding the second reducing agent in the present application helps to control the excessive growth of silver particles and prevent them from growing into larger particles or agglomerating. Ultimately, a dispersed silver powder with multiple nano-scale or micro-nano-scale pore structures and a large specific surface area is obtained.

[0021] In some embodiments, the preset time is 5-10 s; in some embodiments, the stirring reaction time is 5-15 min, the stirring speed is 200-600 r / min, and the reaction temperature is 10-40°C.

[0022] In this embodiment, the staged addition of the secondary reducing agent is performed by limiting the preset time period, which is beneficial to the formation of the pore structure.

[0023] In some embodiments, the concentration of the second reducing agent is greater than or equal to the concentration of the first reducing agent; the addition rate of the second reducing agent is greater than or equal to the addition rate of the first reducing agent; and the reducing property of the second reducing agent is greater than or equal to the reducing property of the first reducing agent.

[0024] In this embodiment, limiting the concentration, addition rate, and reducing strength of the first and second reducing agents is conducive to forming a porous structure. In some embodiments, the first reducing agent solution is the same as the second reducing agent solution and is added in the same manner.

[0025] In some embodiments, the first reducing agent and the second reducing agent both include one or more of ascorbic acid, glucose, hydrazine hydrate, and formaldehyde; the sum of the masses of the first reducing agent and the second reducing agent is 0.5-2.2 times the mass of the silver source; and the pH value range of the first reducing agent and the second reducing agent is both 7-8.

[0026] In some embodiments, the surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, hexadecyltrimethylammonium bromide, polyacrylamide, and polyvinylpyrrolidone; the silver source includes silver nitrate; and the mass of the surfactant is 0.5-15% of the mass of the silver source.

[0027] In this embodiment, the commonality of surfactants is that they all have a typical amphiphilic molecular structure, consisting of a hydrophilic group (such as a sulfonic acid group, a quaternary ammonium salt, an amide group, or a pyrrolidone group) and a hydrophobic alkyl chain (C 12 -C 16 ) composition, which can orientate at the interface by reducing the surface tension of the solution and inhibit particle agglomeration through electrostatic stabilization (such as the anionic characteristics of sodium dodecyl sulfate) or steric hindrance effect (such as the long chain entanglement of PVP).

[0028] In some embodiments, the coating agent includes one or more of lauric acid, stearic acid, ricinoleic acid, dodecylamine, hexadecylamine, and octadecylamine; and the mass of the coating agent is 0.001-0.005% of the mass of the silver source.

[0029] In some embodiments, the dispersant includes one or more of polyvinyl pyrrolidone, Tween-20, Tween-80, gum arabic, and gelatin; the mass of the dispersant is 0.5-15% of the mass of the silver source.

[0030] In this application, the pH value of the reducing agent solution, the type and amount of the surfactant, and the type and amount of the dispersant affect the silver powder particle size D50; while the concentration and amount of the reducing agent, and the type and amount of the surfactant affect the true density of the silver powder.

[0031] In some embodiments, the specific steps of filtering, washing, and air flow crushing the mixed mother liquor are as follows: centrifuging the mixed mother liquor, washing with deionized water until the conductivity is ≤20μs / cm to obtain a wet powder, drying the wet powder, and then crushing it with a 0.6-1.1MPa pressure air flow to obtain porous silver powder for TOPCon laser-assisted sintering.

[0032] The present application provides a porous silver powder for TOPCon laser-assisted sintering.

[0033] The silver powder D50 of this application is 0.8-3.0 μm, and the true density is less than 9.9 g / cm 3 The silver powder particles have multiple nano-sized holes inside, and their cross-section is circular or elliptical, with 1-2 submicron-sized large holes in the center and multiple nano-sized small holes spreading from the center to the surrounding areas.

[0034] The present application provides a conductive silver paste comprising porous silver powder for TOPCon laser-assisted sintering.

[0035] The conductive silver paste prepared in the present application has high filling and opening pressure after laser-assisted sintering and good conductive performance.

[0036] The present invention is further described below through specific examples.

[0037] Example 1 A method for preparing porous silver powder for TOPCon laser-assisted sintering comprises the following steps: S1. Dissolve 200g of silver nitrate in an appropriate amount of deionized water to prepare a silver nitrate solution, add 20g of sodium dodecylbenzenesulfonate thereto, and stir to mix evenly; dissolve 300g of ascorbic acid in an appropriate amount of deionized water to prepare a reducing agent solution; use a dilute sodium hydroxide solution to adjust its pH to 7, divide the reducing agent solution into two equal parts, add 0.6g of lauric acid to the second part, and stir until completely dissolved; place a dispersant solution containing 20g of polyvinyl pyrrolidone in a reactor, control the reaction temperature to 25°C, and the stirring speed to 400r / min. First, add the first part of ascorbic acid and the silver nitrate-sodium dodecylbenzenesulfonate mixture to the reactor at the same time. After 5s of starting to add the materials, add the second part of the ascorbic acid-lauric acid mixture dropwise to the reaction system at a uniform speed until all the materials have been added. Continue stirring the reaction for 10 minutes to obtain a mixed mother liquor; S2. The resulting mixed mother liquor is centrifuged and filtered, then washed with deionized water until the conductivity of the washing liquid reaches ≤20 μs / cm, yielding a wet powder. The wet powder is then placed on a plate and dried in a forced-air drying oven at 80°C for 12 hours. Finally, the powder is crushed with a 1.0 MPa pressure airflow to obtain porous silver powder for TOPCon laser-assisted sintering.

[0038] Example 2 A method for preparing porous silver powder for TOPCon laser-assisted sintering comprises the following steps: S1. 200g of silver nitrate was dissolved in an appropriate amount of deionized water to prepare a silver nitrate solution, 15g of cetyltrimethylammonium bromide was added thereto, and the mixture was stirred and mixed uniformly; 255g of ascorbic acid was dissolved in an appropriate amount of deionized water to prepare a reducing agent solution; the pH was adjusted to 8 using a dilute sodium hydroxide solution, the reducing agent solution was divided into two parts, 0.45g of dodecylamine was added to the second part, and the mixture was stirred until completely dissolved; a dispersant solution containing 5g of Tween-80 was placed in a reactor, the reaction temperature was controlled to 40°C, the stirring speed was 500r / min, the first ascorbic acid and silver nitrate-cetyltrimethylammonium bromide mixture were added to the reactor at the same time, and after 5s of feeding, the second ascorbic acid-dodecylamine mixture was added dropwise to the reaction system at a uniform rate until all the materials were added, and the reaction was stirred for 15 minutes to obtain a mixed mother liquor; S2. The resulting mixed mother liquor is centrifuged and filtered, then washed with deionized water until the conductivity of the washing liquid reaches ≤20 μs / cm to obtain a wet powder. The wet powder is then placed on a plate and dried in a forced air drying oven at 80°C for 12 hours. Finally, the powder is crushed using a 1.0 MPa pressure airflow to obtain porous silver powder for TOPCon laser-assisted sintering.

[0039] Example 3 A method for preparing porous silver powder for TOPCon laser-assisted sintering, the other contents of which are the same as those of Example 1, except that the pH values ​​of the first reducing agent and the second reducing agent are both 5.

[0040] Example 4 A method for preparing porous silver powder for TOPCon laser-assisted sintering, the other contents are the same as those in Example 1, except that the amount of surfactant used is 30 g.

[0041] Example 5 A method for preparing porous silver powder for TOPCon laser-assisted sintering, the other contents of which are the same as those of Example 1, except that the sum of the masses of the first reducing agent and the second reducing agent is three times the mass of the silver source.

[0042] Comparative Example 1 A method for preparing silver powder is the same as Example 1 in other aspects, except that no surfactant is used; the silver source, the first reducing agent solution, and the second reducing agent-coating agent mixture are added to the dispersant solution at one time.

[0043] Comparative Example 2 A method for preparing silver powder is the same as Example 1 except that no surfactant is used.

[0044] Comparative Example 3 A method for preparing silver powder is the same as Example 1 in other aspects, except that the silver source, the first reducing agent solution, and the second reducing agent-coating agent mixture are added to the dispersant solution at one time.

[0045] Testing and Evaluation The silver powder obtained in Examples 1, 2 and Comparative Example 1 was examined by electron microscopy. Figure 1 This is a cross-sectional electron microscope photo of the silver powder in Example 1. Figure 2 This is an electron microscope photo of the silver powder of Example 1. Figure 3 This is an electron microscope photo of the silver powder of Example 2. Figure 4 This is a cross-sectional electron microscope photograph of the silver powder in Comparative Example 1.

[0046] The particle size D50 of the silver powder obtained in different embodiments and comparative examples was tested by a Malvern laser particle size analyzer, the specific surface area of ​​the silver powder obtained in different embodiments and comparative examples was tested by a Bester BSD-BET400, and the true density of the silver powder obtained in different embodiments and comparative examples was tested by a Guoyi quantum true density meter. The results are shown in Table 1.

[0047] Table 1 Test results

[0048] The above results show that the silver powder obtained in the present application has a moderate particle size, a large specific surface area, and a low true density. The particles have multiple nanoscale pores inside. When made into a conductive silver paste, after laser-assisted sintering, the particles are well filled, have a high open-circuit voltage, and have excellent conductive properties. However, the silver powder particles of the comparative example have almost no or very few nanoscale pores inside. When made into a conductive silver paste, after laser-assisted sintering, the particles are poorly filled, have a low open-circuit voltage, and have significantly inferior conductive properties to the silver powder obtained in the example.

[0049] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing porous silver powder for TOPCon laser-assisted sintering, characterized in that: The following steps are involved: Adding the silver source-surfactant mixture and the first reducing agent solution to the dispersant solution simultaneously, delaying for a preset time, and then adding the second reducing agent-coating agent mixture dropwise in parallel, and then stirring to react to obtain a mixed mother liquor; The mixed mother liquor is filtered, washed, and air flow-broken to obtain the porous silver powder for TOPCon laser-assisted sintering.

2. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The preset time is 5-10s.

3. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The concentration of the second reducing agent is greater than or equal to the concentration of the first reducing agent; the addition rate of the second reducing agent is greater than or equal to the addition rate of the first reducing agent; and the reducing property of the second reducing agent is greater than or equal to the reducing property of the first reducing agent.

4. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The first reducing agent and the second reducing agent both include one or more of ascorbic acid, glucose, hydrazine hydrate, and formaldehyde; the sum of the masses of the first reducing agent and the second reducing agent is 0.5-2.2 times the mass of the silver source; and the pH value range of the first reducing agent and the second reducing agent is both 7-8.

5. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, hexadecyltrimethylammonium bromide, polyacrylamide, and polyvinylpyrrolidone; the silver source includes silver nitrate; and the mass of the surfactant is 0.5-15% of the mass of the silver source.

6. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The coating agent includes one or more of lauric acid, stearic acid, ricinoleic acid, dodecylamine, hexadecylamine, and octadecylamine; the mass of the coating agent is 0.001-0.005% of the mass of the silver source.

7. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The dispersant includes one or more of polyvinyl pyrrolidone, Tween-20, Tween-80, gum arabic, and gelatin; the mass of the dispersant is 0.5-15% of the mass of the silver source.

8. The method for preparing porous silver powder for TOPCon laser-assisted sintering according to claim 1, characterized in that: The specific steps of filtering, washing, and air flow crushing the mixed mother liquor are as follows: centrifugally filtering the mixed mother liquor, washing with deionized water until the conductivity is ≤20μs / cm to obtain wet powder, drying the wet powder, and then crushing it with a 0.6-1.1MPa pressure air flow to obtain porous silver powder for TOPCon laser-assisted sintering.

9. A porous silver powder for TOPCon laser-assisted sintering obtained by the preparation method according to any one of claims 1 to 8. 10 . A conductive silver paste comprising the porous silver powder for TOPCon laser-assisted sintering according to claim 9 .

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