Antioxidant copper powder for low-temperature slurry, low-temperature sintered copper slurry and preparation method of low-temperature sintered copper slurry

Abstract

The invention provides antioxidant copper powder for low-temperature slurry, low-temperature sintered copper slurry and a preparation method of the low-temperature sintered copper slurry, and belongs to the technical field of slurry for heterojunction batteries. The antioxidant copper powder comprises copper powder and a coating agent coating the surface of the copper powder; wherein the coating agent comprises acrylic acid, oleic acid and paraformaldehyde. The anti-oxidation copper powder is formed by coating the surface of the copper powder with the coating agent formed by the acrylic acid, the oleic acid and the paraformaldehyde, and the low-temperature sintering copper paste formed by matching the anti-oxidation copper powder with other components can realize low-temperature sintering in air, does not need a protective atmosphere and has good conductivity.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of slurry for heterojunction batteries, and specifically relates to an antioxidant copper powder for low-temperature slurry, a low-temperature sintered copper slurry, and a preparation method thereof. Background Art

[0002] Heterojunction with Intrinsic Thin-layer (HJT) solar cells are a type of solar cell technology that combines crystalline silicon with amorphous silicon thin films. They offer advantages such as high conversion efficiency, a low temperature coefficient, high bifacial power generation, and low degradation. Their core structure, consisting of an amorphous silicon passivation layer and a transparent conductive oxide (TCO) layer, significantly reduces carrier recombination and improves photoelectric conversion efficiency.

[0003] Low-temperature silver paste accounts for up to 25% of HJT cell manufacturing costs, with usage exceeding double that of PERC cells. It is also expensive (low-temperature silver paste costs 1.5 times more than high-temperature silver paste). Replacing silver paste with copper paste is considered a key cost-reduction strategy. Copper readily oxidizes in high-temperature air to form CuO or Cu2O, resulting in decreased conductivity (conductivity drops by more than 50%) and increased interfacial contact resistance. Traditional methods rely on inert gas shielding (such as nitrogen or argon), but this increases equipment complexity and production costs.

[0004] Current technologies often rely on complex protective atmospheres or costly additives, making it difficult to balance oxidation resistance, low-temperature, dense sintering, and cost-effectiveness. For example, Chinese patent CN118380181B, one of the existing technologies, uses nanographite slurry to coat copper powder. While this improves oxidation resistance, the insulating properties of graphite can weaken conductivity, and the process requires a protective atmosphere. Furthermore, Chinese patent application CN116936185A, another existing technology, coats glass powder using a sol-gel method, requiring multiple pretreatment steps, resulting in a complex and inefficient process.

[0005] Therefore, there is an urgent need to develop a copper paste formula that does not require a protective atmosphere and can be cured efficiently at low temperature to promote the large-scale commercial application of batteries. Summary of the Invention

[0006] The present disclosure aims to solve at least one of the technical problems existing in the prior art, and provides an antioxidant copper powder for low-temperature slurry, a low-temperature sintered copper slurry and a preparation method thereof.

[0007] In one aspect of the present disclosure, an antioxidant copper powder for low-temperature slurry is provided, the antioxidant copper powder comprising copper powder and a coating agent coated on the surface of the copper powder; wherein, The coating agent includes acrylic acid, oleic acid and paraformaldehyde.

[0008] Optionally, the copper powder includes: 25 to 45 parts by mass of large-particle spherical copper powder, wherein the large-particle spherical copper powder has a particle size of 1 to 3 μm; 25 to 45 parts by mass of small-particle spherical copper powder; the particle size of the small-particle spherical copper powder is 100 to 300 nm; 25 to 45 parts by mass of flaky copper powder, wherein the particle size of the flaky copper powder is 1 to 3 μm.

[0009] Optionally, the mass ratio of the acrylic acid, the oleic acid and the paraformaldehyde is 5:(2-4):(1-3).

[0010] Optionally, the content of the coating agent is 1-3% of the content of the copper powder.

[0011] Another aspect of the present disclosure provides a low-temperature sintered copper paste for a heterojunction battery, the low-temperature sintered copper paste comprising: 86-90 parts by mass of antioxidant copper powder, wherein the antioxidant copper powder is the antioxidant copper powder described above; 3.1 to 8.6 parts by mass of resin; 0.7~2.8 parts by mass of curing agent; 1.9 to 4.8 parts by mass of solvent; 0.05~0.5 parts by mass of leveling agent; 0.05~0.5 parts by mass of dispersant. Optionally, the resin includes: 2-6 parts by mass of bisphenol A epoxy resin; 0.1-0.6 parts by mass of benzonaphthazine; 0.5~1.0 parts by mass of epoxy diluent; 0.5~1.0 parts by mass of bisphenol F epoxy resin.

[0012] Optionally, the curing agent includes: 0.5-2 parts by mass of isocyanate; 0.2~0.8 parts by mass of imidazole or dicyandiamide.

[0013] Optionally, the solvent comprises: 1.5-3 parts by mass of DBAC diethylene glycol butyl ether acetate; 0.2~1 parts by mass of DBE mixed with dimethyl dibasic acid or dodecyl ester; 0.2~1.5 parts by mass of diethylene glycol dibutyl ether.

[0014] Optionally, the leveling agent is at least one of acrylate, silicone, polyether-modified siloxane and dibutyl phthalate.

[0015] Optionally, the dispersant is at least one of polyethylene glycol, sodium lauryl sulfate, sorbitan trioleate and lecithin.

[0016] Another aspect of the present disclosure provides a method for preparing the low-temperature sintered copper paste described above, the method comprising: Ultrasonic immersion of copper powder, washing and centrifugation to obtain wet copper powder, drying the wet copper powder, adding acrylic acid, oleic acid and paraformaldehyde to form a coating agent, mixing the coating agent with the dried copper powder, and ultrasonic treatment to obtain antioxidant copper powder; Mixing resin, curing agent, solvent, leveling agent and dispersant in proportion to obtain an organic vehicle; The organic carrier is mixed with the antioxidant copper powder, and subjected to a three-roll process to obtain a low-temperature sintered copper slurry.

[0017] This disclosure discloses an antioxidant copper powder for low-temperature slurries, a low-temperature sintered copper slurry, and a preparation method thereof. The antioxidant copper powder comprises copper powder and a coating agent coated on the surface of the copper powder; the coating agent comprises acrylic acid, oleic acid, and paraformaldehyde. The antioxidant copper powder is formed by coating the surface of the copper powder with a coating agent composed of acrylic acid, oleic acid, and paraformaldehyde. This coating agent, combined with other components, forms a copper slurry that can be cured and sintered in air at low temperatures without the need for a protective atmosphere and exhibits excellent electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flowchart of a method for preparing low-temperature sintered copper paste for heterojunction batteries according to a specific embodiment of the present disclosure. DETAILED DESCRIPTION

[0019] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present disclosure and are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present disclosure.

[0020] In one aspect of the present disclosure, an antioxidant copper powder for low-temperature slurry is provided. The antioxidant copper powder includes copper powder and a coating agent coated on the surface of the copper powder; wherein the coating agent includes acrylic acid, oleic acid and paraformaldehyde.

[0021] In this embodiment, the copper powder, one of the main components in the copper paste formula, is optimized and improved. For example, a coating agent formed by acrylic acid, oleic acid and paraformaldehyde is coated on the surface of the copper powder to make the copper powder have good oxidation resistance. When the antioxidant copper powder is used in a low-temperature copper paste, it can be cured and sintered at low temperature in the air without a protective atmosphere and has good conductive properties.

[0022] In some preferred embodiments, the copper powder includes: 25-45 parts by mass of large-particle spherical copper powder, wherein the large-particle spherical copper powder has a particle size of 1-3 μm; 25-45 parts by mass of small-particle spherical copper powder, wherein the small-particle spherical copper powder has a particle size of 100-300 nm; and 25-45 parts by mass of flake copper powder, wherein the flake copper powder has a particle size of 1-3 μm. Through the synergistic effect of the large-particle, small-particle, and flake copper powders, the small-particle copper powder effectively fills the gaps between the large-particle copper powders, helping to promote connections between the large-particle copper powders, increase packing density, and enhance conductive pathways. At the same time, the flake copper powders can form a continuous conductive path through stacked contact, thereby improving conductivity, reducing sintering shrinkage stress, and achieving low-temperature sintering.

[0023] In other preferred embodiments, the mass ratio of acrylic acid, oleic acid, and paraformaldehyde in the coating agent is 5:(2-4):(1-3). This coating agent effectively isolates oxygen, water vapor, and the like, inhibiting oxidation of the copper powder and improving its antioxidant properties. Furthermore, paraformaldehyde depolymerizes at temperatures above 220°C to formaldehyde, which undergoes a reduction reaction with CuO to form elemental Cu, helping to improve conductivity and ensure the effectiveness of the copper paste during application.

[0024] In other preferred embodiments, the content of the coating agent is 1-3% of the copper powder content, for example, preferably 1%, 2%, 3%, etc.

[0025] Another aspect of the present disclosure provides a low-temperature sintered copper paste for heterojunction batteries, comprising: 86 to 90 parts by mass of antioxidant copper powder, which is the antioxidant copper powder described above. For specific composition, please refer to the description above; 3.1 to 8.6 parts by mass of resin; 0.7 to 2.8 parts by mass of curing agent; 1.9 to 4.8 parts by mass of solvent; 0.05 to 0.5 parts by mass of leveling agent; and 0.05 to 0.5 parts by mass of dispersant. In some preferred embodiments, the resin comprises: 2-6 parts by weight of bisphenol A epoxy resin; 0.1-0.6 parts by weight of benzonaphthazine; 0.5-1.0 parts by weight of epoxy diluent; and 0.5-1.0 parts by weight of bisphenol F epoxy resin. The conjugated structure of benzonaphthazine ensures electron mobility, and after cross-linking with the bisphenol A resin, it provides a stable framework for the gate lines. The combination of epoxy diluent and bisphenol F epoxy resin further enhances the slurry's low-temperature moldability.

[0026] In other preferred embodiments, the curing agent includes: 0.5-2 parts by mass of isocyanate; 0.2-0.8 parts by mass of imidazole or dicyandiamide, providing low-temperature curing properties.

[0027] In other preferred embodiments, the solvent includes: 1.5-3 parts by weight of DBAC diethylene glycol butyl ether acetate; 0.2-1 parts by weight of DBE mixed dibasic acid dimethyl ester or dodecyl ester; and 0.2-1.5 parts by weight of diethylene glycol dibutyl ether. This controls the viscosity and thixotropy of the slurry to ensure fluidity during printing or coating.

[0028] In other preferred embodiments, the leveling agent is at least one of acrylate, silicone, polyether-modified siloxane and dibutyl phthalate to enhance wettability and grid line flatness.

[0029] In other preferred embodiments, the dispersant is at least one of polyethylene glycol, sodium lauryl sulfate, sorbitan trioleate and lecithin, which helps to improve the dispersibility of each component, especially the dispersibility of copper powder.

[0030] The present invention discloses a method of mixing antioxidant copper powder, resin, curing agent, dispersant and other components, especially the antioxidant copper powder is coated with acrylic acid + oleic acid + polyformaldehyde coating agent on the surface of the copper powder. The mixing of the above components can achieve the effect of low-temperature sintering of the slurry in an air atmosphere.

[0031] like Figure 1 As shown, another aspect of the present disclosure provides a method S100 for preparing the low-temperature sintered copper paste as described above, the method comprising the following steps S110-S130: S110, ultrasonically immersing the copper powder at 50° C. for 0.5 h, washing and centrifuging to obtain wet copper powder, drying the wet copper powder, forming a coating agent from acrylic acid, oleic acid and paraformaldehyde, mixing the coating agent with the dried copper powder, and ultrasonically treating to obtain antioxidant copper powder.

[0032] In step S110 , the solvent for ultrasonically immersing the copper powder may be acetic acid, sulfuric acid or nitric acid, which is not specifically limited.

[0033] In step S110, the process of washing and centrifuging the soaked copper powder includes: removing the upper solution by centrifugation, repeatedly washing with water, and removing the aqueous solution by centrifugation until the solution has no obvious blue color, and then washing with ethanol and removing the ethanol solution by centrifugation.

[0034] In step S110, the coating agent contains 1-3% of the copper powder, and the mass ratio of acrylic acid, oleic acid, and paraformaldehyde in the coating agent is 5:(2-4):(1-3).

[0035] In step S110, the copper powder is a combination of three copper powders with different particle sizes. For example, the copper powder includes 25 to 45 parts by mass of large-particle spherical copper powder, wherein the particle size of the large-particle spherical copper powder is 1 to 3 μm; 25 to 45 parts by mass of small-particle spherical copper powder, wherein the particle size of the small-particle spherical copper powder is 100 to 300 nm; and 25 to 45 parts by mass of flake copper powder, wherein the particle size of the flake copper powder is 1 to 3 μm.

[0036] S120, mixing the resin, curing agent, solvent, leveling agent, and dispersant in proportion to obtain an organic vehicle.

[0037] In step S120 , the content of the antioxidant copper powder is 86 to 90 parts by mass.

[0038] In step S120 , the content of the resin is 3.1-8.6 parts by mass, and the resin may include 2-6 parts by mass of bisphenol A epoxy resin; 0.1-0.6 parts by mass of benzonaphthazine; 0.5-1.0 parts by mass of epoxy diluent; and 0.5-1.0 parts by mass of bisphenol F epoxy resin.

[0039] In step S120 , the content of the curing agent is 0.7-2.8 parts by mass, and the curing agent may include: 0.5-2 parts by mass of isocyanate; 0.2-0.8 parts by mass of imidazole or dicyandiamide, providing low-temperature curing properties.

[0040] In step S120 , the content of the solvent is 1.9-4.8 parts by mass, and the solvent may include: 1.5-3 parts by mass of DBAC diethylene glycol butyl ether acetate; 0.2-1 parts by mass of DBE mixed dibasic acid dimethyl ester or dodecyl ester; and 0.2-1.5 parts by mass of diethylene glycol dibutyl ether.

[0041] In step S120 , the content of the leveling agent is 0.05 to 0.5 parts by mass, and the leveling agent can be at least one of acrylate, silicone, polyether-modified siloxane, and dibutyl phthalate.

[0042] In step S120 , the content of the dispersant is 0.05 to 0.5 parts by mass, and the dispersant is at least one of polyethylene glycol, sodium lauryl sulfate, sorbitan trioleate, and lecithin.

[0043] S130, mixing the organic carrier with the antioxidant copper powder, and subjecting the mixture to a three-roll process to obtain a low-temperature sintered copper slurry, wherein the fineness of the copper slurry is less than 10 μm.

[0044] The preparation method of this embodiment is simple and does not require a multi-step pretreatment process.

[0045] The following is a further description of the preparation method of low-temperature sintered copper paste for heterojunction batteries with reference to specific examples: Example 1 As shown in Table 1, the copper paste formula of this example is as follows: Antioxidant copper powder: 88 parts (the antioxidant copper powder comprises copper powder and a coating agent coated on the surface of the copper powder, wherein the copper powder comprises 29 parts by mass of large-particle spherical copper powder, wherein the large-particle spherical copper powder has a particle size of 1 to 3 μm; 29 parts by mass of small-particle spherical copper powder, wherein the particle size of the small-particle spherical copper powder is 100 to 300 nm; and 30 parts by mass of flaky copper powder, wherein the particle size of the flaky copper powder is 1 to 3 μm. The coating agent content is 2% of the copper powder, and the coating agent comprises acrylic acid: oleic acid: paraformaldehyde in a ratio of 5:3:2). For details, please refer to Table 1; Resin: 6.1 parts (4.5 parts of bisphenol A epoxy resin, 0.3 parts of benzonaphthazine, 0.6 parts of epoxy diluent, 0.7 parts of bisphenol F epoxy resin), please refer to Table 1 for details; Curing agent: 1.6 parts (1.3 parts isocyanate, 0.3 parts imidazole), please refer to Table 1 for details; Solvent: 3.9 parts (2.6 parts of diethylene glycol butyl ether acetate, 0.5 parts of mixed dibasic acid dimethyl ester or dodecyl alcohol, 0.8 parts of diethylene glycol dibutyl ether); Leveling agent: 0.2 parts of dibutyl phthalate; Dispersant: 0.2 parts of sodium lauryl sulfate.

[0046] Furthermore, the method for preparing the antioxidant copper powder comprises the following steps: At 50°C, the copper powder was first ultrasonically soaked in acetic acid for 0.5 h; the upper solution was removed by centrifugation, and the solution was repeatedly washed with water and centrifuged to remove the aqueous solution until the solution had no obvious blue color, and then washed with ethanol and centrifuged to remove the ethanol solution to obtain wet copper powder; the wet copper powder was dried and set aside; (4) the above coating agent was mixed with the copper powder in proportion (wherein acrylic acid + oleic acid + paraformaldehyde / copper powder = 2%), ultrasonicated, and then dried to obtain antioxidant copper powder. 。

[0047] Furthermore, the preparation method of the low-temperature sintered copper paste comprises the following steps: Resin, curing agent, solvent, leveling agent, and dispersant were mixed in appropriate proportions to form an organic vehicle. Antioxidant copper powder was then mixed with the organic vehicle and subjected to three-roll sintering to produce a low-temperature sintered copper paste with a fineness of less than 8.5 μm. Furthermore, the copper paste was screen-printed onto a heterojunction silicon wafer and cured by heating at 250°C in air or nitrogen atmosphere for 20 minutes. The electrical performance of the gate lines was then tested.

[0048] The results are shown in Table 2. When sintered under air and nitrogen conditions, the line resistivity of the corresponding gate lines is not much different, which shows that the copper paste of this embodiment can be sintered at low temperature in air.

[0049] Example 2 The copper paste formula and preparation method of this example are the same as those of Example 1, except that the ratio of the copper powder surface coating agent is changed to: acrylic acid: oleic acid: paraformaldehyde = 5:2:3.

[0050] The results are shown in Table 2. When sintered under air and nitrogen conditions, the line resistivity of the corresponding gate lines is not much different, which shows that the copper paste of this embodiment can be sintered at low temperature in air.

[0051] Example 3 The copper slurry formula and preparation method of this example are the same as those of Example 1, except that the ratio of the copper powder surface coating agent is changed to: acrylic acid: oleic acid: paraformaldehyde = 5:3:2.5.

[0052] The results are shown in Table 2. When sintered under air and nitrogen conditions, the line resistivity of the corresponding gate lines is not much different, which shows that the copper paste of this embodiment can be sintered at low temperature in air.

[0053] Example 4 The copper paste formula and preparation method of this example are the same as those of Example 1, except that the ratio of the copper powder surface coating agent and the resin are changed. For example, acrylic acid: oleic acid: paraformaldehyde = 5:2:3, and the resin includes 5.8 parts of bisphenol A epoxy resin and 0.3 parts of benzonaphthazine.

[0054] The results are shown in Table 2. When sintered under air and nitrogen conditions, the line resistivity of the corresponding gate lines is not much different, which shows that the copper paste of this embodiment can be sintered at low temperature in air.

[0055] Example 5 The copper paste formula and preparation method of this example are the same as those of Example 1, except that the ratio of the curing agent is changed to: the curing agent includes 1.3 parts of isocyanate and 0.3 parts of dicyandiamide.

[0056] The results are shown in Table 2. When sintered under air and nitrogen conditions, the line resistivity of the corresponding gate lines is not much different, which shows that the copper paste of this embodiment can be sintered at low temperature in air.

[0057] Comparative Example 1 The copper paste formula and preparation method of this example are the same as those of Example 1, except that the formula of the antioxidant copper powder coating agent is changed to acrylic acid.

[0058] The results are shown in Table 2. When only acrylic acid is used to coat copper powder, although nitrogen firing has little effect, the copper paste still cannot be air-fired and the electrical properties are poor.

[0059] Comparative Example 2 The copper slurry formula and preparation method of this example are the same as those of Example 1, except that copper powder is used and no coating agent is wrapped on the surface of the copper powder.

[0060] The results are shown in Table 2. When the copper powder is not coated, the electrical performance of nitrogen firing and air firing is poor, low-temperature air firing cannot be achieved, and the electrical performance is poor.

[0061] Table 1 Component formula of each embodiment and comparative example

[0062] Table 2 Wire resistivity results of various embodiments and comparative examples

[0063] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. An antioxidant copper powder for low-temperature slurry, characterized in that: The anti-oxidation copper powder comprises copper powder and a coating agent coated on the surface of the copper powder; wherein, The coating agent includes acrylic acid, oleic acid and paraformaldehyde.

2. The antioxidant copper powder according to claim 1, characterized in that The copper powder comprises: 25 to 45 parts by mass of large-particle spherical copper powder, wherein the large-particle spherical copper powder has a particle size of 1 to 3 μm; 25 to 45 parts by mass of small-particle spherical copper powder; the particle size of the small-particle spherical copper powder is 100 to 300 nm; 25 to 45 parts by mass of flaky copper powder, wherein the particle size of the flaky copper powder is 1 to 3 μm.

3. The antioxidant copper powder according to claim 1, characterized in that The mass ratio of the acrylic acid, the oleic acid and the paraformaldehyde is 5:(2-4):(1-3).

4. The antioxidant copper powder according to claim 1, characterized in that The content of the coating agent is 1-3% of the content of the copper powder.

5. A low-temperature sintered copper paste for heterojunction batteries, characterized in that: The low-temperature sintering copper paste comprises: 86-90 parts by mass of antioxidant copper powder, wherein the antioxidant copper powder is the antioxidant copper powder according to any one of claims 1-4; 3.1 to 8.6 parts by mass of resin; 0.7~2.8 parts by mass of curing agent; 1.9 to 4.8 parts by mass of solvent; 0.05~0.5 parts by mass of leveling agent; 0.05~0.5 parts by mass of dispersant.

6. The low-temperature sintered copper paste according to claim 5, characterized in that: The resin includes: 2-6 parts by mass of bisphenol A epoxy resin; 0.1-0.6 parts by mass of benzonaphthazine; 0.5~1.0 parts by mass of epoxy diluent; 0.5~1.0 parts by mass of bisphenol F epoxy resin.

7. The low-temperature sintered copper paste according to claim 5, characterized in that: The curing agent includes: 0.5-2 parts by mass of isocyanate; 0.2~0.8 parts by mass of imidazole or dicyandiamide.

8. The low-temperature sintered copper paste according to claim 5, characterized in that: The solvent includes: 1.5-3 parts by mass of DBAC diethylene glycol butyl ether acetate; 0.2~1 parts by mass of DBE mixed with dimethyl dibasic acid or dodecyl ester; 0.2~1.5 parts by mass of diethylene glycol dibutyl ether.

9. The low-temperature sintered copper paste according to claim 5, characterized in that: The leveling agent is at least one of acrylate, silicone, polyether-modified siloxane and dibutyl phthalate; and / or, The dispersant is at least one of polyethylene glycol, sodium lauryl sulfate, sorbitan trioleate and lecithin.

10. A method for preparing the low-temperature sintered copper paste according to any one of claims 5 to 9, characterized in that: The method comprises: Ultrasonic immersion of copper powder, washing and centrifugation to obtain wet copper powder, drying the wet copper powder, adding acrylic acid, oleic acid and paraformaldehyde to form a coating agent, mixing the coating agent with the dried copper powder, and ultrasonic treatment to obtain antioxidant copper powder; Mixing resin, curing agent, solvent, leveling agent and dispersant in proportion to obtain an organic vehicle; The organic carrier is mixed with the antioxidant copper powder, and subjected to a three-roll process to obtain a low-temperature sintered copper slurry.

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