Tin oxide-coated silver-coated copper powder, method for producing same, and use thereof

Abstract

The application relates to a tin oxide-coated silver-coated copper powder and a preparation method and application thereof. The preparation method of the tin oxide-coated silver-coated copper powder comprises the following steps: adding silver-coated copper powder into a solvent to form a silver-coated copper solution, wherein the solvent is selected from at least one or a combination of any number of isopropyl alcohol, acetone and DMF; adding a stannous salt or a stannous salt solution into the silver-coated copper solution to form a mixed solution, wherein the solvent of the stannous salt solution is selected from at least one or a combination of any number of isopropyl alcohol, acetone and DMF; and adding deionized water into the mixed solution to form the tin oxide-coated silver-coated copper powder. The method forms a surface coating layer through a solution hydrolysis method, the reaction is carried out in a solution, expensive equipment is not needed, the cost is low, the operation process is simple, and large-scale production can be realized; the reaction time and the concentration of stannous compounds are highly controllable, the thickness and compactness of the tin oxide coated on the silver-coated copper can be conveniently controlled, and the tin oxide-coated silver-coated copper powder has excellent conductivity and chemical stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials, in particular to a tin oxide coated silver-coated copper powder and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the rapid development of the industrial information industry has increased the demand for metal powders such as silver powder, copper powder, and nickel powder. Silver powder is widely used in conductive paste and conductive paint due to its high conductivity and plasticity. However, silver is in short supply on Earth, expensive, and prone to silver migration under high humidity and direct current conditions, leading to short circuits in electronic components and affecting their large-scale use. Therefore, researchers have successfully developed silver-coated copper powder materials to replace silver powder by coating silver on the surface of copper powder. Silver-coated copper powder has excellent conductivity, is less expensive than silver powder, and has better oxidation resistance and stability than copper powder. Currently, the main methods for preparing silver-coated copper powder include displacement, chemical reduction, and displacement combined with chemical deposition. However, the silver coating prepared by these methods is not dense, uniform, or oxidized, resulting in partial exposure of the silver-coated copper powder surface and affecting its performance.

[0003] Therefore, the present application provides a tin oxide coated silver-coated copper powder and a preparation method and application thereof to solve one of the above technical problems. SUMMARY

[0004] The various aspects and advantages of the present application will be described in the following description. To solve one of the above technical problems, the present application provides a low-cost, large-scale, simple tin oxide coated silver-coated copper powder and a preparation method and application thereof.

[0005] To achieve one of the above application purposes, the present application adopts the following technical solutions:

[0006] A preparation method of a tin oxide coated silver-coated copper powder, comprising the following steps:

[0007] The silver-coated copper powder is added to a solvent to form a silver-coated copper solution, and the solvent is selected from at least one or a combination of any number of isopropyl alcohol, acetone, and DMF;

[0008] Stannous salt or a stannous salt solution is added to the silver-coated copper solution to form a mixed solution, wherein the solvent of the stannous salt solution is selected from at least one or a combination of any number of isopropyl alcohol, acetone, and DMF;

[0009] Deionized water is added to the mixed solution to form a tin oxide coated silver-coated copper powder.

[0010] Further, the silver-coated copper powder is cleaned before forming the silver-coated copper solution, and then sequentially cleaned by a 5% sulfuric acid solution, water, and vacuum drying.

[0011] Further, the concentration of the formed silver-coated copper solution is 0.05 g / mL to 0.5 g / mL.

[0012] Further, the stannous salt is stannous octoate or stannous fluoride.

[0013] Further, the molar ratio of the stannous salt to silver in the silver-coated copper powder is 1:2 to 3:2.

[0014] Further, the deionized water is added under stirring, and the deionized water is added by using a syringe pump, a pipette, a dropper, or a syringe, and the reaction is continuously stirred at room temperature for 12 h to 24 h.

[0015] Further, the volume of the added deionized water accounts for 0.2% to 1% of the volume of the solvent of the mixed solution.

[0016] A tin oxide-coated silver-coated copper powder is prepared by the above-mentioned preparation method of the tin oxide-coated silver-coated copper powder.

[0017] Further, the change in the resistivity of the tin oxide-coated silver-coated copper powder before and after being placed in an environment with a temperature of 100°C to 150°C and a relative humidity of 95% or more for not less than 72 h is not more than 10%.

[0018] The above-mentioned tin oxide-coated silver-coated copper powder is applied in a photovoltaic conductive paste or a lithium battery conductive paste.

[0019] Compared with the prior art, the preparation method of the tin oxide-coated silver-coated copper powder has the following advantages: the surface coating layer is formed by a solution hydrolysis method, the reaction is performed in a solution, no expensive equipment is needed, the cost is low, the operation process is simple, and the tin oxide-coated silver-coated copper powder has excellent electrical conductivity and chemical stability. DETAILED DESCRIPTION

[0020] The embodiments of the present application will now be described in detail. It should be apparent that these are only examples to help illustrate the present application and are not intended to limit the scope of the application. Indeed, various modifications and changes can be made to the application by those skilled in the art which will be apparent from this disclosure without departing from the spirit and scope of the application. For example, features shown or described as part of one embodiment can be used with another embodiment to yield still a further embodiment. It is, therefore, desired that what is claimed be protected.

[0021] The inventors have found that there are few studies on coating metal oxides on the surface of silver-coated copper powder, and currently only zinc oxide, titanium dioxide is deposited on the surface of silver by atomic layer deposition, and metal nickel is deposited on the surface of silver by electrochemical deposition to improve the oxidation resistance and stability. However, atomic layer deposition has the disadvantages of expensive equipment and long deposition time; and electro-deposition has the disadvantages of uneven growth of nickel layer and uncontrollable thickness.

[0022] The present application aims to provide a low-cost, large-scale preparation method for simply coating silver-coated copper powder. Specifically, the preparation method of tin oxide coated silver-coated copper powder comprises the following steps:

[0023] S1 adding silver-coated copper powder into a solvent to form a silver-coated copper solution, wherein the solvent is selected from at least one or a combination of any of isopropyl alcohol, acetone and DMF;

[0024] S2 adding stannous salt or a stannous salt solution into the silver-coated copper solution to form a mixed solution, wherein the solvent of the stannous salt solution is selected from at least one or a combination of any of isopropyl alcohol, acetone and DMF;

[0025] S3 adding deionized water into the mixed solution to form tin oxide coated silver-coated copper powder.

[0026] The method forms a surface coating layer by a solution hydrolysis method, and the reaction is carried out in a solution, which does not require expensive equipment and has low cost; and the operation process is simple and can be mass-produced; the controllability of the hydrolysis speed, reaction time and the like of stannous salt is high, which facilitates the control of the thickness and compactness of the tin oxide coated on the silver-coated copper, so that the tin oxide coated silver-coated copper powder has excellent electrical conductivity and chemical stability.

[0027] The silver-coated copper powder obtained by the existing preparation method has a silver mass fraction of 10% to 30%, and the higher the mass fraction, the higher the silver coating. The silver-coated copper powder in this paper can be purchased on the market or synthesized by itself, and the silver mass fraction of the silver-coated copper powder is also 10% to 30%, preferably 20%, with high coverage and relatively low cost.

[0028] Further, before step S1, it also includes cleaning the silver-coated copper powder to remove impurities on the surface of the silver-coated copper powder. The silver in the silver-coated copper powder is not dense and uniform to completely cover the copper core, so there are a small amount of copper exposed points / areas on the surface, which is easy to be oxidized. Preferably, first, a 5% sulfuric acid solution is used for washing to remove oxides and other impurities formed by copper not covered by silver, and then water is used for cleaning to neutralize; and then vacuum drying is performed to avoid oxidation of copper during the drying process.

[0029] Specifically, silver-coated copper powder is added into a glass beaker, then sulfuric acid solution is added, and the mixture is stirred for 20-30 minutes under ultrasonic. After removing the impurities on the surface of the silver-coated copper powder, the supernatant is discarded. The above steps are repeated several times to obtain washed silver-coated copper powder. Finally, the silver-coated copper powder is dried in vacuum.

[0030] Of course, a cleaning solution compatible with the solvent in step S1 can also be used before and after the sulfuric acid cleaning. Preferably, the cleaning solution is consistent with the solvent to ensure the cleanliness of the subsequent silver-coated copper solution.

[0031] In step S1, isopropyl alcohol with less toxicity and slow evaporation is preferably used as the solvent, and the concentration of the silver-coated copper solution is 0.05-0.5 g / mL, preferably 0.1 g / mL. If the concentration is too high, a small amount of silver-coated copper particles will settle at the bottom of the reactor and cannot be coated. If the concentration is too low, the reaction yield will be low and the economic cost will be high.

[0032] In step S2, the stannous salt is a divalent tin compound, including but not limited to stannous octoate and stannous fluoride. After adding deionized water, the stannous salt is hydrolyzed to form tin oxide, which is finally deposited on the surface of the silver-coated copper powder to obtain silver-coated copper powder coated with tin oxide. The solvent of the stannous salt solution can be miscible with the solvent of the silver-coated copper solution, and does not need to be completely consistent.

[0033] Since the electronegativity of copper is 1.90, which is less than the electronegativity of silver (1.93), copper is more active than silver and more likely to lose electrons. Therefore, tin oxide will preferentially deposit on a small amount of exposed copper that is not covered by silver, and then deposit on the surface of silver, thereby obtaining silver-coated copper powder coated with tin oxide. The deposition of tin oxide will cover the exposed copper, i.e., the copper is completely coated with silver and tin oxide, so the chemical stability of the entire silver-coated copper powder coated with tin oxide is higher.

[0034] In the present application, deionized water is added to the mixed solution to easily control the degree of hydrolysis of the divalent tin compound. Specifically, the stannous salt or stannous salt solution is added and stirred for a predetermined time to make the solution uniform, i.e., the tin ions around the silver-coated copper powder are uniformly distributed. Then, deionized water is slowly added under stirring, which can be added by injection pump, pipette, dropper, syringe, etc. The reaction is continuously stirred at room temperature for 12-24 hours to control the degree of hydrolysis of the divalent tin compound and control the thickness of the tin oxide coating.

[0035] The molar ratio of the added stannous salt to silver in the silver-coated copper powder is 1:2-3:2, for example 2:2, to ensure that a dense tin oxide layer can be formed on the surface of the silver-coated copper powder without wasting tin material. The volume of the added deionized water accounts for 0.2%-1% of the volume of the solvent of the mixed solution to ensure sufficient hydrolysis of the stannous salt.

[0036] Furthermore, the preparation method of tin oxide-coated silver-coated copper powder also includes a post-processing step after step S3: centrifugation after the reaction is completed, washing three times with isopropanol, and vacuum drying at 60℃~70℃ to obtain tin oxide-coated silver-coated copper powder.

[0037] The tin oxide-coated silver-coated copper powder obtained by the above method of the present invention exhibits high stability. A damp heat test was conducted on the product: it was placed in an environment with a temperature of 100℃~150℃ and a relative humidity of over 95% for no less than 72 hours; the change in resistivity of the tin oxide-coated silver-coated copper powder before and after the damp heat test was no greater than 10%.

[0038] The method of the present invention will be described in detail below with two specific embodiments.

[0039] Example 1:

[0040] Cleaning the silver-coated copper powder: Add 10g of silver-coated copper powder to a glass beaker, then add 100mL of 5% sulfuric acid solution and stir for 20-30 minutes to remove a very small amount of copper oxide and other impurities on the surface, which is beneficial for the subsequent deposition of tin oxide on the surface of the silver-coated copper powder. Then discard the supernatant, wash with deionized water until neutral, and dry in a vacuum drying oven at 70℃ to obtain washed and vacuum-dried silver-coated copper powder.

[0041] Prepare the silver-coated copper solution: Add 10g of vacuum-dried silver-coated copper powder to a glass beaker, add 100mL of isopropanol, and stir well.

[0042] Deposition of tin oxide: Under stirring conditions, add 1.25 g / mL stannous octoate solution, with an amount of 0.02 mol of stannous octoate; then add 0.72 mL of deionized water to adjust the degree of hydrolysis of divalent tin compounds and control the thickness of the tin oxide coating layer. Stir the reaction at room temperature for 24 h.

[0043] Post-processing: After the reaction was completed, the mixture was centrifuged, washed three times with isopropanol, and dried under vacuum at 70°C to obtain tin oxide-coated silver-coated copper powder.

[0044] Damp heat test: After being placed at 150℃ and 100% relative humidity for 72 hours, the oxidation resistance and resistivity of silver-coated copper powder and tin oxide-coated silver-coated copper powder were tested.

[0045] Example 2:

[0046] Cleaning the silver-coated copper powder: Add 10g of silver-coated copper powder to a glass beaker, then add 100mL of isopropanol, and sonicate for 20min-30min to remove impurities and organic matter from the surface of the silver-coated copper powder. Discard the supernatant to obtain the silver-coated copper powder washed with isopropanol.

[0047] Prepare the silver-coated copper solution: Add 100 mL of isopropanol to the washed silver-coated copper powder and stir well.

[0048] Depositing tin oxide: Under stirring conditions, add tin oxide with a density of 4.5 g / cm³. 3 The solid tin fluoride was prepared in an amount of 0.01 mol; then 0.36 mL of deionized water was added to adjust the degree of hydrolysis of divalent tin oxide and control the thickness of the tin oxide coating. The reaction was stirred at room temperature for 12 h.

[0049] Post-processing: After the reaction was completed, the mixture was centrifuged, washed three times with isopropanol, and dried under vacuum at 70°C to obtain tin oxide-coated silver-coated copper powder.

[0050] Damp heat test: After being placed at 150℃ and 100% relative humidity for 72 hours, the oxidation resistance and resistivity of silver-coated copper powder and tin oxide-coated silver-coated copper powder were tested.

[0051] Comparative example: The cleaning steps and damp heat test were the same as in Example 1, but no tin oxide was deposited.

[0052] Table 1 Resistivity test results for each embodiment

[0053]

[0054] As can be seen from Table 1, the resistivity of the tin oxide-coated silver-coated copper powder in Examples 1 and 2 increased by no more than 10% after the damp heat test, specifically by 7.3% and 8.5% respectively. In contrast, the resistivity of the comparative silver-coated copper powder increased by 22.1%. This indicates that the tin oxide-coated silver-coated copper powder has higher oxidation resistance and corrosion resistance, thus exhibiting excellent conductivity and electrical stability.

[0055] The present invention also provides a tin oxide-coated silver-coated copper powder obtained by the above method, which can be used as a conductive material in photovoltaic conductive pastes and lithium battery conductive pastes.

[0056] In summary, compared with existing technologies, the preparation method of the present invention involves a reaction carried out in solution, eliminating the need for expensive equipment and resulting in low cost; the operation process is simple and can be mass-produced; the reaction time and solution concentration can be controlled to regulate the thickness and density of the tin oxide-coated silver-coated copper powder coating layer; thus, the tin oxide-coated silver-coated copper powder exhibits excellent conductivity and chemical stability.

[0057] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art without violating the principles.

[0058] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of preparing tin oxide-coated silver-coated copper powder, characterized by, The method comprises the following steps: adding silver-coated copper powder into a solvent to form a silver-coated copper solution, wherein the solvent is at least one selected from isopropyl alcohol, acetone and DMF; adding a stannous salt or a stannous salt solution into the silver-coated copper solution to form a mixed solution, wherein the solvent of the stannous salt solution is at least one selected from isopropyl alcohol, acetone and DMF; adding deionized water into the mixed solution to form the stannic oxide-coated silver-coated copper powder; the deionized water is added under stirring, and is added by using a syringe pump, a pipette, a dropper or a syringe; the reaction is continuously stirred at room temperature for 12-24 hours; the volume of the added deionized water accounts for 0.2%-1% of the volume of the solvent of the mixed solution; cleaning the silver-coated copper powder before forming the silver-coated copper solution, and then washing the silver-coated copper powder by using a 5% sulfuric acid solution, water and vacuum drying; the concentration of the formed silver-coated copper solution is 0.05 g / mL-0.5 g / mL, and the molar ratio of the stannous salt to silver in the silver-coated copper powder is 1:2-3:

2.

2. The method of making tin oxide-coated silver-coated copper powder according to claim 1, characterized in that, The stannous salt is stannous octoate or stannous fluoride.

3. A tin oxide-coated silver-coated copper powder, characterized in that, The stannic oxide-coated silver-coated copper powder is prepared by the preparation method of the stannic oxide-coated silver-coated copper powder in the above claim 1 or 2; the stannic oxide-coated silver-coated copper powder is subjected to a hydrothermal experiment: being placed in an environment with a temperature of 100-150 DEG C and a relative humidity of more than 95% for not less than 72 hours; the change of the resistivity of the stannic oxide-coated silver-coated copper powder before the hydrothermal experiment and the resistivity of the stannic oxide-coated silver-coated copper powder after the hydrothermal experiment is not more than 10%.

4. The stannic oxide-coated silver-coated copper powder in claim 3 is applied in a photovoltaic conductive paste or a lithium battery conductive paste.

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