Flaky copper powder, copper paste containing flaky copper powder, copper electrode, and solar cell

Abstract

The present application provides a flaky copper powder, wherein a ratio of a particle size D95 to a particle size D10 is 4.8-8.5. In the present application, it is found that the flaky copper powder having the ratio of the particle size D95 to the particle size D10 within this range can enable flaky copper powders having different particle sizes in a copper paste to work in conjunction with each other, such that particles of the copper powders are compactly packed. Therefore, the compactness of gate lines can be improved, voids within electrode gate lines can be reduced, electron transport paths can be increased, and conductivity can be enhanced. In addition, the peel strength of the gate lines can be increased, and the durability and service life of the gate lines can be enhanced.

Description

Flake copper powder, copper paste containing the flake copper powder, copper electrode and solar cell

[0001] This patent application claims priority to Chinese invention patent application No. 202510106515.8, filed on January 22, 2025, entitled "Flake Copper Powder, Copper Paste Containing the Flake Copper Powder, Copper Electrode and Solar Cell", and Chinese invention patent application No. 202610064751.2, filed on January 16, 2026, entitled "Flake Copper Powder, Copper Paste Containing the Flake Copper Powder, Copper Electrode and Solar Cell". Technical Field

[0002] This application relates to the field of batteries, and more specifically to a sheet-like copper powder for use in solar cell paste and its related applications. Background Technology

[0003] Energy, as an essential pillar of social development, has gradually become a hot social issue. Therefore, building a new clean energy structure system has become an important measure to solve the energy shortage problem. Solar energy can provide a huge energy supply needed for socio-economic development and is expected to become the cornerstone of building a new energy society.

[0004] However, the main obstacle to the widespread use of solar cells is their high cost, making cost reduction a crucial issue. Currently, the main materials for solar cell grids are silver or silver-plated copper. While silver-plated copper is cheaper than pure silver, the reduction is limited. Therefore, using base metals to replace silver is a feasible technical approach. Copper has conductivity similar to silver but is much cheaper, costing only one percent of silver. Developing a copper powder suitable for electronic pastes for use in solar cells is therefore essential. Summary of the Invention

[0005] As previously stated, this application aims to provide a sheet-like copper powder suitable for conductive pastes, which can provide a primary material for the manufacture of electrodes in solar cells that is inexpensive yet has conductivity close to that of silver.

[0006] In a first aspect of this application, a flake-shaped copper powder with a particle size D is provided. 95 With particle size D 10 The ratio is 4.8-8.5.

[0007] In a second aspect of this application, a mixed copper powder is provided, comprising the flake-shaped copper powder and the spherical copper powder of the first aspect.

[0008] In a third aspect of this application, a copper paste is provided, comprising copper powder and a dispersion medium, wherein the copper powder comprises the flake copper powder of the first aspect or the mixed copper powder of the second aspect.

[0009] In a fourth aspect of this application, a copper electrode is provided, which is prepared from the copper paste of the third aspect.

[0010] In a fifth aspect of this application, a solar cell is provided, which includes the copper electrode of the fourth aspect.

[0011] This application provides a sheet-like copper powder with a large particle size distribution width. Specifically, the particle size D of the sheet-like copper powder of this application... 95 With particle size D 10 The ratio is 4.8-8.5. The inventors discovered that the particle size D... 95 With particle size D 10 Flaky copper powder with a ratio within this range has a wide particle size distribution and contains a certain proportion of "large flakes." These "large flakes" easily overlap, which is beneficial for the conduction of larger currents in the final copper grid wire and helps reduce the resistance of the copper grid wire. Simultaneously, the flaky copper powder also contains a certain proportion of smaller "particles." During the pickling (removal of the primary oxide layer) and passivation processes of the flaky copper powder, the "small particles" themselves easily tumble, allowing for full contact with the solution and achieving better pickling and passivation effects. Furthermore, the "small particles" can also act as lubricating particles, which also facilitates the tumbling of the "large flakes" during stirring, thus ensuring that all particles in the entire flaky copper powder can achieve good pickling and passivation effects, ultimately improving the durability and lifespan of the copper grid wire. Secondly, the particle size D of the flaky copper powder... 95 With particle size D 10 Within this range, the ratio can also allow the flaky copper particles of different sizes in the slurry to cooperate with each other, making the copper powder particles compact. This can improve the compactness of the copper grid lines, reduce the gaps in the electrode grid lines, increase the electron transport path, and improve conductivity.

[0012] This application further provides a hybrid copper powder, which includes the sheet-like copper powder and spherical copper powder of this application. Utilizing spherical copper powder of a specific size can enhance its synergistic effect with the sheet-like copper powder of this application in terms of size and morphology, resulting in enhanced stacking order of the formed electrode grid lines, thereby increasing the peel strength and conductivity of the electrode grid lines and further reducing contact resistance. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0014] Figure 1 shows a scanning electron microscope (SEM) image of the sheet-like copper powder prepared according to one embodiment of the present application before passivation with oleic acid, and a schematic diagram of the ratio of the longest diameter a to the shortest diameter b.

[0015] Figure 2 shows a scanning electron microscope (SEM) image of oleic acid passivated sheet copper powder prepared according to one embodiment of this application.

[0016] Figure 3 shows a scanning electron microscope (SEM) image of oleylamine passivated sheet copper powder prepared according to one embodiment of this application. Detailed Implementation

[0017] The present application will be described in detail below. It should be understood that the following description is merely illustrative and is not intended to limit the scope of the application; the scope of protection of the present application is determined by the appended claims. Furthermore, those skilled in the art will understand that modifications can be made to the technical solutions of the present application without departing from its spirit and intent. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of this application pertains. Before a detailed description of this application, the following definitions are provided to better understand it.

[0019] In cases where numerical ranges are provided, such as concentration ranges, percentage ranges, or ratio ranges, it should be understood that, unless the context explicitly specifies otherwise, all intermediate values ​​between the upper and lower limits of the range, up to one-tenth of the lower limit unit, and any other values ​​or intermediate values ​​within the range are included in the subject matter. The upper and lower limits of these smaller ranges may be independently included in the smaller ranges, and such embodiments are also included in the subject matter, limited by any specific excluded limit values ​​within the range. Where the range includes one or two limit values, the range excluding any one or both of those included limit values ​​is also included in the subject matter.

[0020] In the context of this application, many embodiments use the expressions "comprising," "including," or "basically / mainly composed of...". The expressions "comprising," "including," or "basically / mainly composed of..." are generally understood as open-ended expressions, indicating that they include not only the elements, components, parts, or method steps specifically listed after the expression, but also other elements, components, parts, or method steps. However, in this document, the expressions "comprising," "including," or "basically / mainly composed of..." can also be understood as closed-ended expressions in certain situations, indicating that they only include the elements, components, parts, or method steps specifically listed after the expression, and exclude any other elements, components, parts, or method steps. In this case, the expression is equivalent to the expression "composed of...".

[0021] As mentioned above, this application aims to provide a conductive material that is more cost-effective in manufacturing electrodes for solar cells, while maintaining conductivity close to that of silver.

[0022] In this paper, the term "flaky copper powder" refers to a powder composed of a large number of copper particles, most of which are flaky and may contain no or a small number of spherical copper particles.

[0023] The term "sheet-like copper particle" refers to copper particles with a sheet-like two-dimensional planar structure, i.e., a small thickness and a large aspect ratio. Specifically, in this paper, a sheet-like two-dimensional planar structure can be a copper particle whose aspect ratio (i.e., shortest diameter / thickness) is greater than or equal to 2 when measured by scanning electron microscopy (SEM).

[0024] The term "spherical copper particle" refers to a copper particle whose aspect ratio (i.e., shortest diameter / thickness) is less than 2 when measured by a scanning electron microscope (SEM).

[0025] In a first aspect of this application, a flake-shaped copper powder with a particle size D is provided. 95 With particle size D 10 The ratio is 4.8-8.5. Specifically, the particle size D 95 With particle size D 10 The ratio can be 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4 or 8.5, or a range consisting of any two of these values.

[0026] In this application, the particle size D 95 With particle size D 10The ratio represents the width of the particle size distribution. The inventors discovered that particle size D... 95 With particle size D 10 Flaky copper powder with a ratio within this range has a wide particle size distribution and contains a certain proportion of "large flakes." These "large flakes" easily overlap, which is beneficial for the conduction of larger currents in the final copper grid wire and helps reduce the resistance of the copper grid wire. Simultaneously, the flaky copper powder also contains a certain proportion of smaller "particles." During the pickling (removal of the primary oxide layer) and passivation processes of the flaky copper powder, the "small particles" themselves easily tumble, allowing for sufficient contact with the solution and achieving better pickling and passivation effects. Furthermore, the "small particles" can also act as lubricating particles, facilitating the tumbling of the "large flakes" during stirring, thus ensuring that all particles in the entire flaky copper powder can achieve good pickling and passivation effects, ultimately improving the durability and lifespan of the copper grid wire. Secondly, the particle size D of the flaky copper powder... 95 With particle size D 10 Within this range, the ratio of different particle sizes in the slurry can also allow for better coordination between the flake-shaped copper particles, resulting in a compact packing of copper powder particles. This improves the density of the copper grid lines, reduces voids within the electrode grid lines, increases electron transport pathways, and enhances conductivity. Simultaneously, it increases the peel strength of the grid lines, enhancing their durability and lifespan. Such limited flake-shaped copper powder can serve as the primary source of conductive copper powder in the fabrication of electrode grid lines.

[0027] In one specific embodiment, the flake-shaped copper powder comprises flake-shaped copper particles and first spherical copper particles, wherein the particle size of the flake-shaped copper particles is larger than that of the first spherical copper particles. Preferably, by weight, the first spherical copper particles constitute 0-10% of the flake-shaped copper powder, including the endpoint value of 10% but excluding the endpoint value of 0%. If the flake-shaped copper powder contains a small amount of first spherical copper particles, and the particle size of the first spherical copper particles is smaller than that of the flake-shaped copper particles, the superior flowability of the first spherical copper particles in the pickling / passivation liquid can be further utilized to improve the passivation integrity and oxidation resistance of the flake-shaped copper powder, thereby enhancing the durability and lifespan of the copper grid lines.

[0028] Specifically, the flake-shaped copper powder may include first spherical copper particles in the range of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, or 10.0% by weight, or any two of these values.

[0029] As an example, the method for preparing flake-shaped copper powder in this application may include a ball milling step, i.e., the flake-shaped copper powder is obtained by ball milling small-sized spherical copper raw material powder into flakes. Specifically, spherical copper raw material powder and a certain proportion of grinding balls (e.g., steel balls, ceramic balls, agate balls, zirconia balls, etc.) are added to a ball milling jar. Grinding balls of one size or a mixture of grinding balls of various sizes can be used, specifically, for example, grinding balls of 5mm, 4mm, 3mm, 2mm, and 1mm. By setting the mass ratio of spherical copper raw material powder to grinding balls, the mass ratio of grinding balls of different sizes, the ball milling speed, and the ball milling time, the small-sized spherical copper raw material powder is wet-milled into flakes, adjusting the particle size D of the aforementioned flake-shaped copper powder. 95 With particle size D 10 The ratio of the two components is used. The resulting flake copper powder may contain a small amount (e.g., no more than 5%) of small, possibly unflattened, spherical copper raw material powder, which exists as spherical copper particles within the flake-shaped powder, thus achieving the presence of first spherical copper particles in the flake copper powder. Preferably, mixed grinding balls are used, for example, mixing 5mm, 3mm, and 1mm particles in a certain mass ratio. The mass ratio of the small-sized spherical copper raw material to the grinding balls can be 1:3 to 1:8.

[0030] It is understood that the preparation of the flake copper powder in this application is not limited to the above method, and other methods are also possible. For example, the flake copper powder can be prepared by adding mixed first spherical copper particles to pure flake powder (such as that prepared by chemical reduction). Another example is that a small amount of mixed first spherical copper particles are added after the original spherical copper raw material powder has been ball-milled.

[0031] The presence of a small amount of first spherical copper particles in the flake copper powder, with the particle size of the first spherical copper particles being smaller than that of the flake copper particles, is beneficial to the conductivity and durability of the flake copper powder and the copper electrode prepared therefrom. This is because the first spherical copper particles have good flowability, and a small proportion of them can further enhance the flowability of the copper powder in the pickling and passivation solutions. This allows the flake copper particles and the first spherical copper particles to fully contact the organic passivating agent in the pickling and passivation solutions, increasing the coverage area of ​​the organic passivating agent on the copper particles, improving the oxidation resistance of the flake copper powder, and thus improving the conductivity and durability of the copper electrode prepared therefrom.

[0032] In one specific implementation, the dimensions of the sheet-like copper particles can be 1μm-10μm in length, 1μm-7μm in width, and 10nm-500nm in thickness. Here, "length" refers to the longest diameter of the sheet-like copper particle (diameter a in Figure 1), "width" refers to the shortest diameter of the sheet-like copper particle (diameter b in Figure 1), and "thickness" refers to the thickness of the sheet-like copper particle in the direction perpendicular to the length and width planes. Specifically, the longest diameter of the sheet-like copper particles can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, or 10μm, or a range consisting of any two of these values. Specifically, the shortest diameter of the sheet-like copper particles can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, or 7μm, or a range consisting of any two of these values. Specifically, the thickness of the sheet-like copper particles can be 10nm, 30nm, 50nm, 70nm, 90nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 380nm, 400nm, 420nm, 450nm, 480nm, or 500nm, or a range consisting of any two of these values.

[0033] In this application, the ratio a / b of the longest diameter to the shortest diameter of the sheet-like copper particles can be 1-10, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, or a range consisting of any two of these values.

[0034] In another specific implementation, the median particle size of the first spherical copper particles is 50 nm to 200 nm. This median particle size range can be measured using a scanning electron microscope (SEM). One hundred first spherical copper particles are randomly selected from the SEM image, their particle sizes are measured, and the median value is calculated. Those skilled in the art will understand that the above method is merely exemplary, and they can appropriately reduce or increase the number of selected first spherical copper particles based on actual circumstances. Specifically, the median particle size of the first spherical copper particles can be 50 nm, 80 nm, 110 nm, 140 nm, 170 nm, or 200 nm, or a range consisting of any two of these values. First spherical copper particles with a median particle size within this range allow for better interaction between the first spherical copper particles and the flake-like copper particles of different diameters in the slurry, enhancing the organic passivation effect of the flake-like copper powder. Furthermore, it results in a compact packing of copper particles, increasing the density of the grid lines, reducing voids within the electrode grid lines, improving the conductivity and peel strength of the electrode grid lines, and enhancing the durability and lifespan of the grid lines.

[0035] In one specific implementation, the particle size D of the flake-shaped copper powder 10 The particle size can be 0.9-2μm, D. 50 The particle size is 3.0-4.5 μm, and the particle size D is... 95 The particle size is 7.3-10.0 μm. In this paper, the particle size D... 10 Particle size D 50 Particle size D 95 The particle size can be measured using a laser particle size analyzer. Specifically, the particle size D of the flake-shaped copper powder is... 10 The particle size D of the flake-like copper powder can be 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 μm, or a range consisting of any two of these values. 50 The particle size D of the flake-like copper powder can be 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5 μm, or a range consisting of any two of these values. 95 The particle size distribution can be 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10.0 μm, or a range consisting of any two of these values. The inventors have discovered that, during the formation of the gate lines, the above-mentioned particle size distribution facilitates orderly stacking during the formation of the electrode gate lines, thereby increasing the peel strength and conductivity of the gate lines.

[0036] In yet another specific implementation, the specific surface area of ​​the flake-shaped copper powder can be 0.1-0.9 m². 2 / g. Specifically, the specific surface area of ​​the flake-shaped copper powder can be 0.1m². 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g or 0.9m 2 / g, or a range consisting of any two of these values. If the specific surface area of ​​the flake-shaped copper powder is within the above range, the copper powder can be ensured to have good oxidation resistance. The larger the specific surface area, for example, above the upper limit, the higher the surface activity and the easier it is to be oxidized; the smaller the specific surface area, for example, below the lower limit, the larger the particle size of the copper powder, which will affect the low-temperature sintering properties of the conductive paste prepared from the copper powder, resulting in insufficient sintering at low temperatures or poor bonding between the copper powder and the substrate after sintering.

[0037] In this paper, the term "specific surface area" refers to the surface area per unit mass of a porous solid material, and the commonly used unit is square meters per gram (m²). 2 The specific surface area (g) can be measured using conventional methods, such as the determination of the specific surface area of ​​metal powders according to GB / T13390-2008.

[0038] In yet another specific implementation, the particle size D of the flake-shaped copper powder is... 50 The ratio of surface area to specific surface area can be 4.5 μm·g / m². 2 -8.0μm·g / m 2 Specifically, the particle size D of the flake-shaped copper powder 50 The ratio of surface area to total surface area can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9 or 8.0 μm·g / m². 2 , or a range consisting of any two of these values. In this paper, particle size D 50 The ratio of surface area to specific surface area represents, to some extent, the surface smoothness of flaky copper powder particles. The inventors discovered that particle size D... 50Flake copper powder with a surface area ratio within this range has a smooth surface, which further promotes the compactness of copper powder particle stacking, improves the compactness of grid lines, reduces voids in electrode grid lines, and thereby increases electron transport pathways and improves conductivity.

[0039] In another specific embodiment, the tap density of the flake-shaped copper powder is 4.4 g / mL–5.0 g / mL. Specifically, the tap density of the flake-shaped copper powder can be 4.4 g / mL, 4.5 g / mL, 4.6 g / mL, 4.7 g / mL, 4.8 g / mL, 4.9 g / mL, or 5 g / mL, or a range consisting of any two of these values. When the tap density of the flake-shaped copper powder is within this range, the copper electrode prepared from the flake-shaped copper powder has high density and low porosity, thereby exhibiting low resistivity.

[0040] In this article, the term "tap density" refers to the bulk density of powder after it has been tapped. It is the density of powder after it has been packed into a specific container and the container has been vibrated to break up the voids in the powder and bring it into a tightly packed state. By measuring the tap density, the flowability and porosity of the powder can be determined. The tap density can be calculated by measuring the volume after vibrating the BT-301 vibrator 1000 times.

[0041] In another specific embodiment, the flake-shaped copper particles in the flake-shaped copper powder include flake-shaped copper matrix particles and an organic passivating agent coated on the flake-shaped copper matrix particles. The first spherical copper particles include first spherical copper matrix particles and an organic passivating agent coated on the first spherical copper matrix particles. The copper powder is passivated by the organic passivating agent, which coats the surfaces of the flake-shaped copper matrix particles and the first spherical copper matrix particles, forming an anti-oxidation layer that isolates oxygen and moisture, thus solving the problem of easy oxidation of the copper powder.

[0042] In a further specific embodiment, the organic passivating agent is selected from one or more of organic amine compounds, organic acid compounds, organic acid salt compounds, imidazole compounds, thiazole compounds, and thiol compounds.

[0043] In a more specific embodiment, the organic amine compound may include, but is not limited to, linear or branched C6-C6 compounds. 22 Aliphatic amines, such as n-octylamine, n-hexylamine, dodecylamine, tetradecylamine, hexadecylamine, stearylamine, oleylamine, etc., can be used alone or in combination of two or more.

[0044] In a more specific embodiment, the organic acid compound can be a fatty acid compound, which may include, but is not limited to, linear or branched C6-C fatty acids.22 Saturated fatty acids or unsaturated fatty acids, these fatty acid compounds can be used alone or in combination of two or more.

[0045] In a more specific embodiment, the organic acid salt compound can be a fatty acid salt or a benzoate, such as sodium benzoate, sodium formate, nickel formate, sodium acetate, sodium citrate, copper citrate, sodium stearate, or calcium stearate. These organic acid salt compounds can be used alone or in combination of two or more.

[0046] In a more specific embodiment, the imidazole compound may include, but is not limited to, imidazole, benzimidazole, 2-thiobenzimidazole, alkyl imidazole (alkyl carbon atoms numbered 1-20), etc., and these imidazole compounds may be used alone or in combination of two or more.

[0047] In a more specific embodiment, the thiazole compound may include, but is not limited to, 2-thiobenzothiazole.

[0048] In a more specific embodiment, the thiol compounds may include, but are not limited to, ethanethiol, methanethiol, propanethiol, butanethiol, mercaptoethanol, etc., and these thiol compounds may be used alone or in combination of two or more.

[0049] The above are just examples. There are no special limitations on organic passivating agents, as long as they can effectively passivate copper powder to solve the problem of easy oxidation of copper powder.

[0050] In a second aspect of this application, a hybrid copper powder is provided, comprising the flake-shaped copper powder and the spherical copper powder of the first aspect, wherein the spherical copper powder includes second spherical copper particles. By adding the spherical copper powder, the synergistic effect between the spherical copper powder and the flake-shaped copper powder in terms of size and morphology can be enhanced, thereby increasing the orderliness of the stacking during the formation of electrode grid lines, increasing the peel strength and conductivity of the grid lines, and reducing the contact resistance.

[0051] In one specific embodiment, the mixed copper powder may comprise 40%-65% by weight of the spherical copper powder, relative to the total mass of the mixed copper powder. Specifically, the copper powder may comprise 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, or 65% by weight, or a range consisting of any two of these values.

[0052] In yet another specific implementation, the particle size D of the spherical copper powder is... 50The particle size is 200nm-1.2μm, and the particle size D is... 50 The particle size can be measured using a laser particle size analyzer. Specifically, the particle size D of the spherical copper powder is... 50 It can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1100nm, 1150nm or 1200nm, or a range consisting of any two of these values.

[0053] In yet another specific implementation, the specific surface area of ​​the spherical copper powder can be 0.5-3.0 m². 2 / g. Specifically, the specific surface area of ​​the spherical copper powder can be 0.5m². 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.3m 2 / g, 2.4m 2 / g, 2.5m 2 / g, 2.6m 2 / g, 2.7m 2 / g, 2.8m 2 / g, 2.9m 2 / g or 3.0m 2 / g, or a range consisting of any two of these values.

[0054] In yet another specific embodiment, the tap density of the spherical copper powder is 4.3-4.9 g / ml. Specifically, the tap density of the spherical copper powder can be 4.3 g / ml, 4.4 g / ml, 4.5 g / ml, 4.6 g / ml, 4.7 g / ml, 4.8 g / ml, or 4.9 g / ml, or a range consisting of any two of these values.

[0055] By selecting spherical copper powder with the above parameters, the synergistic effect between spherical copper powder and flake copper powder in terms of size and morphology can be further enhanced, thereby increasing the orderliness of the stacking when forming electrode grid lines and increasing the peel strength and conductivity of the grid lines.

[0056] In another specific embodiment, the second spherical copper particles in the mixed copper powder include second spherical copper matrix particles and an organic passivating agent coated on the outside of the second spherical copper matrix particles. The copper powder is passivated by the organic passivating agent, which coats the surface of the second spherical copper matrix particles, forming an antioxidant layer that isolates oxygen and moisture, thus solving the problem of easy oxidation of the copper powder.

[0057] In a further specific embodiment, the organic passivating agent is selected from one or more of organic amine compounds, organic acid compounds, organic acid salt compounds, imidazole compounds, thiazole compounds, and thiol compounds. In an even more specific embodiment, the organic amine compound may include, but is not limited to, linear or branched C6-C compounds. 22 Aliphatic amines, such as n-octylamine, n-hexylamine, dodecylamine, tetradecylamine, hexadecylamine, stearylamine, oleylamine, etc., can be used alone or in combination of two or more.

[0058] In a more specific embodiment, the organic acid compound can be a fatty acid compound, which may include, but is not limited to, linear or branched C6-C fatty acids. 22 Saturated fatty acids or unsaturated fatty acids, these fatty acid compounds can be used alone or in combination of two or more.

[0059] In a more specific embodiment, the organic acid salt compound can be a fatty acid salt or a benzoate, such as sodium benzoate, sodium formate, nickel formate, sodium acetate, sodium citrate, copper citrate, sodium stearate, or calcium stearate. These organic acid salt compounds can be used alone or in combination of two or more.

[0060] In a more specific embodiment, the imidazole compound may include, but is not limited to, imidazole, benzimidazole, 2-thiobenzimidazole, alkyl imidazole (alkyl carbon atoms numbered 1-20), etc., and these imidazole compounds may be used alone or in combination of two or more.

[0061] In a more specific embodiment, the thiazole compound may include, but is not limited to, 2-thiobenzothiazole.

[0062] In a more specific implementation, the thiol compounds may include, but are not limited to, ethanethiol, methanethiol, propanethiol, butanethiol, mercaptoethanol, etc., and these thiol compounds may be used alone or in combination of two or more.

[0063] The above are just examples. There are no special limitations on organic passivating agents, as long as they can effectively passivate copper powder to solve the problem of easy oxidation of copper powder.

[0064] As an example, the passivation treatment of the sheet-like copper matrix particles and / or spherical copper matrix particles of this application may include the following steps:

[0065] (1) Pretreatment of copper matrix particles:

[0066] Step a: Add the sheet-like copper matrix particles and / or spherical copper matrix particles to acid for pickling. The molar concentration of the acid is between 0.1 mol / L and 3 mol / L. The temperature during the pickling process is 20-60℃, and the pickling time is 30 min to 2 h.

[0067] Step b: Wash the acid-washed flake copper matrix particles and / or spherical copper matrix particles by centrifugation with water and ethanol until the pH reaches 7.

[0068] In the pretreatment step of the copper matrix particles, the acid may be one or more acids selected from hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, perchloric acid, sulfurous acid, phosphoric acid, hydrofluoric acid, acetic acid, carbonic acid, hydrosulfuric acid, and hypochlorous acid.

[0069] (2) Passivation treatment:

[0070] An organic passivating agent and an alcohol are mixed to prepare a passivation solution. Pretreated sheet-like copper matrix particles and / or spherical copper matrix particles are placed into the passivation solution, stirred at room temperature, and washed with ethanol until the conductivity is less than 30 μS / cm.

[0071] In the passivation treatment step, the alcohol includes, but is not limited to, one or more of ethanol, ethylene glycol, methanol, glycerol, tetramethylethylene glycol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, n-pentanol, sec-pentanol, 3-pentanol, tert-pentanol, and n-hexanol; the organic passivating agent can be the organic passivating agent listed above, but is not limited to it.

[0072] In a third aspect of this application, a copper paste is provided, comprising copper powder and a dispersion medium, wherein the copper powder comprises the flake copper powder of the first aspect or the mixed copper powder of the second aspect.

[0073] In one specific embodiment, the copper paste comprises 80%-95% copper powder and 5%-20% dispersion medium by mass. Specifically, relative to the total mass of the copper paste, the amount of copper powder can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%, or a range consisting of any two of these values. Specifically, relative to the total mass of the copper paste, the amount of dispersion medium can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or a range consisting of any two of these values.

[0074] In yet another specific embodiment, the dispersion medium includes a resin, a curing agent, a dispersant, a solvent, and optionally a curing accelerator.

[0075] In yet another specific implementation, the resin may be epoxy resin, phenolic resin, phenoxy resin, acrylic resin, aldehyde-ketone resin, polyurethane, polyester, etc., but is not limited thereto.

[0076] In a further specific embodiment, the epoxy resin may be a thermosetting resin, selected from one or more of bisphenol A type epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A type epoxy resin, polyurethane modified epoxy resin, dimer acid modified epoxy resin, siloxane modified epoxy resin, phenolic epoxy resin, polyol glycidyl ether type epoxy resin, and polyacid glycidyl ester type epoxy resin. Of course, other resins known in the art that can be used in this application may also be selected, and this application does not further limit them.

[0077] In another specific embodiment, the curing agent may be one or more selected from dicyandiamide curing agents, tertiary amine curing agents, isocyanates, imidazole curing agents, acid anhydride curing agents, and latent imidazole curing agents, such as triethanolamine, blocked isocyanates, 1-butyl-3-methylimidazolium dibutyl phosphate, and Busington (Lanxess) 7982. Isocyanates are selected from one or more selected from Trixene BI 7982 (a blocked isocyanate based on HDI), MF-K60X (a blocked polyisocyanate HDI curing agent), ketoxime-terminated isocyanates, hexamethylene diisocyanate-terminated with hexamethylene hexamethylene diisocyanate, and dodecyl mercaptan-terminated diphenyl diisocyanate. Of course, other curing agents known in the art that can be used in this application may also be selected, and this application does not further limit their use.

[0078] In another specific embodiment, the dispersant may be an ether, amine, carboxylic acid, or other dispersant with 16-20 carbon atoms and an amino group at the end or a polar group such as a hydroxyl group, for example, Tween, OP series, oleic acid, and Span. Of course, other dispersants known in the art that can be used in this application may also be selected, and this application does not further limit them.

[0079] In yet another specific embodiment, the solvent may be selected from esters, ethers, ketones, and alcohols, such as sec-amyl acetate, cyclohexanone, amyl propionate, isopropyl lactate, divalent esters (DBE), amyl acetate, diethylene glycol acetate, diethylene glycol butyl ether acetate, ethylene glycol carbonate, propylene glycol carbonate, tributyl borate, triphenyl phosphate, tricresyl phosphate, butyl acetate, diethyl carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, γ-butyrolactone, butyl carbitol acetate, and ethyl carbitol acetate. Diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol butyl ether, ethylene glycol diethyl ether, diethylene glycol butyl ether, ethylene glycol monoisopropyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol ether, ethylene glycol dimethyl ether, tripropylene glycol methyl ether, tripropylene glycol dimethyl ether, diethylene glycol monobutyl ether, 4-heptanone, sec-pentanol, ethylene glycol, propylene glycol, pentanol, hexanol, heptanol, octanol, methylpentanol, butyl carbitol, terpineol, dihydroterpineol.

[0080] In another specific embodiment, the copper paste may or may not contain a curing accelerator. The curing accelerator catalyzes the curing of the resin, lowers the curing temperature, and shortens the curing time. The curing accelerator is selected from one of quaternary ammonium salts, imidazole esters, imidazoleonium salts, or substituted ureas. Specifically, quaternary ammonium salts can be benzyltriethylammonium chloride, etc., and substituted ureas can be N-p-chlorophenyl-N,N'-dimethylurea, N-(3,4-dichlorophenyl)-N,N'-dimethylurea, N-(3-phenyl)-N,N'-dimethylurea, N-(4-phenyl)-N,N'-dimethylurea, 2-methylimidazolium, etc.; imidazoles and their esters or imidazolium salts can be imidazolium sulfonate / salt, imidazolium phosphate / salt, or imidazolium acetate / salt, such as imidazolium dibutyl phosphate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methane sulfonate, trimellitate 1-cyanoethyl-2-undecapidazolium, isocyanurate 2-methylimidazolium, tetraphenylboronic acid 2-ethyl-4-methylimidazolium, and tetraphenylboronic acid 2-ethyl-1,4-dimethylimidazolium.

[0081] In another specific embodiment, the copper paste may include: 80-95 parts by weight of copper powder, 1-15 parts by weight of resin, 0.5-5 parts by weight of curing agent, 0-10 parts by weight of dispersant, and 2-15 parts by weight of solvent. The copper powder includes flake copper powder or mixed copper powder as defined above. By combining the above components in a suitable mass ratio, copper particles of various sizes and / or shapes are densely packed, and the conductive channels between the conductive particles are more unobstructed, thereby improving the conductivity of the paste.

[0082] As an example, the method for preparing the copper paste of this application may include the following steps:

[0083] 1) Provide copper powder;

[0084] 2) The mixture of copper powder, resin, solvent, curing agent, dispersant and optional curing accelerator is mixed in a certain proportion and then ground by a three-roll mill.

[0085] In a fourth aspect of this application, a copper electrode is provided, which is prepared from the copper paste of the third aspect.

[0086] As an example, the method for preparing the copper electrode of this application may include the following steps: placing the aforementioned copper paste in a nitrogen atmosphere for heating and curing to obtain the electrode. The curing temperature can be 100-220℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, etc., and the curing time can be 10min-60min, for example, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0087] As an example, the method for preparing the copper electrode of this application may also include the following steps: applying a pre-prepared copper paste to a solar cell (e.g., HJT / HBC) by screen printing, with a grid line width of 40μm-120μm, and then heating and curing it in a nitrogen oven to form the electrode grid line.

[0088] In a fifth aspect of this application, a solar cell is provided, which includes the copper electrode described in the fourth aspect.

[0089] In yet another specific embodiment, the surface of the solar cell may have a textured surface, with the copper electrode located on top of the textured surface of the solar cell.

[0090] In one specific implementation, the solar cell may be selected from BC cells, HJT cells, or perovskite / crystalline silicon tandem cells.

[0091] In yet another specific implementation, the solar cell may be a crystalline silicon cell, and a conductive barrier layer exists between the copper electrode and the crystalline silicon cell.

[0092] Example

[0093] The following embodiments illustrate the preparation method and characterization of the related properties of the product of this application. Unless otherwise specified, all test methods used are conventional methods, and all test materials used in the following embodiments were purchased from conventional reagent stores. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0094] Example 1

[0095] First, the particle size D 50 Spherical copper raw material powder with a diameter of 2μm and zirconia grinding balls were added to a ball milling jar at a mass ratio of 1:5. 1% ethanol was added to wet the copper raw material powder. The mass ratio of grinding balls was 5mm:3mm:1mm = 1:2:8. The ball milling speed was set to 300r and the ball milling time was 4h. The spherical copper raw material powder was ball milled into flakes, and then cooled to obtain flake copper powder.

[0096] Then, 100g of flake copper powder is pickled and passivated, and the specific steps are as follows:

[0097] Step a: Place the flake copper powder in ethanol for ultrasonic cleaning;

[0098] Step b: The ultrasonically cleaned flaky copper powder is centrifuged and washed for the first time with water and ethanol;

[0099] Step c: The centrifuged and washed flaky copper powder is added to hydrochloric acid for acid washing; the molar concentration of the acid is 1 mol / L, the temperature during the acid washing process is 30℃, and the acid washing time is 1 h.

[0100] Step d: The acid-washed flake copper powder is centrifuged and washed a second time with water and ethanol until the pH reaches 7.

[0101] Step e: Prepare a passivation solution by mixing 40 mL of oleic acid, 100 mL of ethanol, and 100 mL of water. Place the acid-washed flake copper powder into the passivation solution and stir at 70 °C for 12 h. After the reaction is complete, perform solid-liquid separation on the flake copper powder suspension, wash it thoroughly with ethanol multiple times, and dry it in a displacement oven to obtain passivated flake copper powder.

[0102] Figure 1 shows a scanning electron microscope (SEM) image of the flake-shaped copper powder obtained in step d. Figure 2 shows a scanning electron microscope (SEM) image of the flake-shaped copper powder prepared in Example 1 after passivation with oleic acid. Through measurement and comparison, it was found that after passivation with oleic acid, the surface morphology of the flake-shaped copper particles became smoother, but the particle size of the copper powder remained essentially unchanged. Furthermore, as can be seen from Figures 1 and 2, the flake-shaped copper powder contains a small amount of first spherical copper particles. Measurements showed that the first spherical copper particles accounted for approximately 2%, with a median particle size of 50 nm-200 nm. The dimensions of the flake-shaped copper particles were 1 μm-10 μm in length, 1 μm-7 μm in width, and 100 nm-300 nm in thickness.

[0103] Example 2:

[0104] First, the same spherical copper raw material powder as in Example 1 and zirconia grinding balls were added to the ball milling jar at a mass ratio of 1:5. 1% ethanol was added to wet the spherical copper raw material powder. The grinding ball ratio was 5mm:3mm:1mm = 1:2:8. The ball milling speed was set to 300r and the ball milling time was 5h. The spherical copper raw material powder was ball milled into flakes, and then cooled to obtain flake copper powder.

[0105] Then, 100g of the ball-milled flake copper powder was acid-washed and passivated, with the following specific steps:

[0106] Step a: Place the flake copper powder in ethanol for ultrasonic cleaning;

[0107] Step b: The ultrasonically cleaned flaky copper powder is centrifuged and washed for the first time with water and ethanol;

[0108] Step c: The centrifuged and washed flaky copper powder is added to hydrochloric acid for acid washing; the molar concentration of the acid is 1 mol / L, the temperature during the acid washing process is 30℃, and the acid washing time is 1 h.

[0109] Step d: The acid-washed flake copper powder is centrifuged and washed a second time with water and ethanol until the pH reaches 7.

[0110] Step e: Prepare a passivation solution by mixing 40 mL of oleylamine, 100 mL of ethanol, and 100 mL of water. Place the acid-washed flake copper powder into the passivation solution and stir at 70 °C for 12 h. After the reaction is complete, perform solid-liquid separation on the flake copper powder suspension, wash it thoroughly with ethanol multiple times, and dry it in a displacement oven to obtain passivated flake copper powder.

[0111] Figure 3 shows a scanning electron microscope (SEM) image of the passivated oleylamine-coated flake copper powder prepared according to the embodiment of this application. As shown in Figure 3, the flake copper powder contains a small amount of first spherical copper particles that have not been ball-milled. After measurement, the first spherical copper particles account for about 1.5%, and the median particle size of the first spherical copper particles is 50 nm-150 nm. The size of the flake copper particles is 1 μm-10 μm in length, 1 μm-7 μm in width, and 100 nm-250 nm in thickness.

[0112] Comparative Example 1

[0113] The same spherical copper raw material powder as in Example 1 and zirconia grinding balls were added to the ball milling jar at a mass ratio of 1:5. 1% ethanol was added to wet the spherical copper raw material powder. The grinding ball ratio was 5mm:3mm:1mm = 1:3:8. The ball milling speed was set to 300r and the ball milling time was 1h. The spherical copper raw material powder was ball milled into flakes, and then cooled to obtain flake copper powder.

[0114] 100g of flaky copper powder obtained by ball milling was subjected to acid washing and passivation. The specific steps are as follows:

[0115] Step a: Place the flake copper powder in ethanol for ultrasonic cleaning;

[0116] Step b: The ultrasonically cleaned flaky copper powder is centrifuged and washed for the first time with water and ethanol;

[0117] Step c: The centrifuged and washed flaky copper powder is added to hydrochloric acid for acid washing; the molar concentration of the acid is 1 mol / L, the temperature during the acid washing process is 30℃, and the acid washing time is 1 h.

[0118] Step d: The acid-washed flake copper powder is centrifuged and washed a second time with water and ethanol until the pH reaches 7.

[0119] Step e: Prepare a passivation solution by mixing 40 mL of oleylamine, 100 mL of ethanol, and 100 mL of water. Place the acid-washed flake copper powder into the passivation solution and stir at 70 °C for 12 h. After the reaction is complete, perform solid-liquid separation on the flake copper powder suspension, wash it thoroughly with ethanol multiple times, and dry it in a displacement oven to obtain passivated flake copper powder.

[0120] The flake copper powder contains a portion of first spherical copper particles that have not been ball-milled. Measurements show that the first spherical copper particles account for approximately 7% of the total. The median particle size of the first spherical copper particles is 300 nm-500 nm. The flake copper particles have a particle size of 1 μm-10 μm, a width of 1 μm-7 μm, and a thickness of 200 nm-500 nm.

[0121] Comparative Example 2

[0122] The same spherical copper raw material powder as in Example 1 and zirconia grinding balls were added to the ball milling jar at a mass ratio of 1:5. 1% ethanol was added to wet the spherical copper raw material powder. The grinding ball ratio was 5mm:3mm:1mm = 1:2:7. The ball milling speed was set to 400r and the ball milling time was 2h. The spherical copper raw material powder was ball milled into flakes, and then cooled to obtain flake copper powder.

[0123] 100g of flaky copper powder obtained by ball milling was subjected to acid washing and passivation. The specific steps are as follows:

[0124] Step a: Place the flake copper powder in ethanol for ultrasonic cleaning;

[0125] Step b: The ultrasonically cleaned flaky copper powder is centrifuged and washed for the first time with water and ethanol;

[0126] Step c: The centrifuged and washed flaky copper powder is added to hydrochloric acid for acid washing; the molar concentration of the acid is 1 mol / L, the temperature during the acid washing process is 30℃, and the acid washing time is 1 h.

[0127] Step d: The acid-washed flake copper powder is centrifuged and washed a second time with water and ethanol until the pH reaches 7.

[0128] Step e: Prepare a passivation solution by mixing 40 mL of oleylamine, 100 mL of ethanol, and 100 mL of water. Place the acid-washed flake copper powder into the passivation solution and stir at 70 °C for 12 h. After the reaction is complete, perform solid-liquid separation on the flake copper powder suspension, wash it thoroughly with ethanol multiple times, and dry it in a displacement oven to obtain passivated flake copper powder.

[0129] The flake copper powder contains a portion of first spherical copper particles that have not been ball-milled. Measurements show that the first spherical copper particles account for approximately 6% of the total. The median particle size of the first spherical copper particles is 200 nm-500 nm. The size of the flake copper particles is 1 μm-10 μm in length, 1 μm-7 μm in width, and 200 nm-400 nm in thickness.

[0130] Example 3:

[0131] The particle size of the flaky copper powder obtained by ball milling was measured using a laser particle size analyzer.

[0132] The passivated sheet-like copper powders were subjected to the following tests:

[0133] Tap density: The passivated sheet copper powder was vibrated 1000 times using a BT-301 tap density meter, and its volume was measured and the tap density was calculated.

[0134] Specific surface area: Measured according to GB / T 13390-2008 Method for Determination of Specific Surface Area of ​​Metal Powders.

[0135] The relevant measurement results are shown in Table 1 below.

[0136] Table 1:

[0137] Example 4

[0138] The passivated flake copper powder was prepared into a slurry, and the specific steps are as follows:

[0139] 0.4g of bisphenol F epoxy resin, 0.15g of dicyandiamide curing agent, 0.2g of 2-propylimidazolium, 0.05g of oleic acid dispersant, and 0.3g of diethylene glycol butyl ether acetate solvent were stirred evenly in a petri dish to obtain a slurry mother liquor. 8g of passivated flake copper powder was added to the mother liquor, stirred, and then rolled and ground in a three-roll mill to obtain a homogeneous slurry. The slurry was then screen-printed onto a substrate and cured at 170℃ to obtain a grid line with a linewidth of 40μm and a length of 3cm. The electrical performance data of the slurry in its initial state (defined as the initial state) and after being placed at 85% humidity and 85℃ for 5 hours (defined as after DH5) were tested, and are shown in Table 2.

[0140] Resistivity (ρ) test method: The copper paste is screen printed by a screen printing plate and cured by heating in a nitrogen oven at 170℃ to form a copper film. The sheet resistance R (mΩ) is measured by a four-probe sheet resistance meter, and the film thickness t (μm) is measured by a micrometer. The resistivity ρ = R × t / 10.

[0141] Line resistance (Rx) test method: The obtained grid lines are tested using a low resistance tester.

[0142] Example 5

[0143] Preparation of passivated spherical copper powder

[0144] 100g of spherical copper powder was acid-washed and passivated. The specific steps are as follows:

[0145] Step a: Place the spherical copper powder in ethanol for ultrasonic cleaning;

[0146] Step b: The ultrasonically cleaned spherical copper powder is centrifuged and washed for the first time with water and ethanol;

[0147] Step c: The spherical copper powder after centrifugation and washing is added to hydrochloric acid for acid washing; the molar concentration of the acid is 1 mol / L, the temperature during the acid washing process is 30℃, and the acid washing time is 1 h.

[0148] Step d: The acid-washed spherical copper powder is then centrifuged and washed a second time with water and ethanol until the pH reaches 7.

[0149] Step e: Prepare a passivation solution by mixing 40 mL of oleic acid, 100 mL of ethanol, and 100 mL of water. Place the acid-washed spherical copper powder into the passivation solution and stir at 70 °C for 12 h. After the reaction is complete, perform solid-liquid separation on the spherical copper powder suspension, wash it thoroughly with ethanol multiple times, and dry it in a displacement gas oven to obtain passivated spherical copper powder.

[0150] After measurement, the D of the passivated spherical copper powder 50 It is 1.2μm.

[0151] The passivated flake copper powder from Example 1 and the passivated spherical copper powder were prepared into a slurry, and the specific steps are as follows:

[0152] 0.4g of bisphenol F epoxy resin, 0.15g of dicyandiamide curing agent, 0.2g of 2-propylimidazolium, 0.05g of oleic acid dispersant, and 0.3g of diethylene glycol butyl ether acetate solvent were stirred evenly in a petri dish to obtain a slurry mother liquor. 4g of passivated flake copper powder and 4g of passivated spherical copper powder were added to the mother liquor, stirred, and then rolled and ground in a three-roll mill to obtain a homogeneous slurry. The slurry was then screen-printed onto a substrate and cured at 170℃ to obtain a grid line with a linewidth of 40μm and a length of 3cm. Electrical performance was measured using the same test method as in Example 4.

[0153] Table 2: Electrical property data of the slurry

[0154] As can be seen from the results in Table 2, compared with Comparative Examples 1-2, Examples 1-2 showed better performance due to D. 95 / D 10 A ratio greater than 4.8 indicates lower resistivity and grid resistance, and better conductivity stability after light exposure and high temperature and humidity treatment, demonstrating that the grid lines prepared from the copper pastes of Examples 1-2 have higher durability and lifespan. A comparison between Example 5 and Example 1 shows that the addition of spherical copper powder further reduces the resistivity and grid resistance of the copper paste, and also provides better conductivity stability after light exposure and high temperature and humidity treatment.

[0155] It should be noted that the terminology used in this application's specification is for the purpose of describing specific embodiments only and is not intended to limit the application. The foregoing summary section and the following detailed description are for illustrative purposes only and are not intended to limit the application in any way. Without departing from the spirit and intent of this application, the scope of this application is defined by the appended claims.

Claims

1. A type of flake-shaped copper powder, wherein the particle size D 95 With particle size D 10 The ratio is 4.8-8.

5.

2. The flake-shaped copper powder according to claim 1, wherein, The flake copper powder includes flake copper particles and first spherical copper particles, wherein the particle size of the flake copper particles is larger than the particle size of the first spherical copper particles; preferably, the weight content of the first spherical copper particles in the flake copper powder is 0-10% by weight.

3. The flake-shaped copper powder according to claim 1 or 2, wherein, The particle size D of the flaky copper powder 10 The particle size is 0.9-2 μm, and the particle size D is... 50 The particle size is 3.0-4.5 μm, and the particle size D is... 95 The range is 7.3-10.0 μm.

4. The flake-shaped copper powder according to any one of claims 1-3, wherein, The specific surface area of ​​the flake-shaped copper powder is 0.1-0.9 m². 2 / g.

5. The flake-shaped copper powder according to any one of claims 1-4, wherein, The particle size D of the flaky copper powder 50 The ratio of specific surface area to total surface area is 4.5 μm·g / m². 2 -8.0μm·g / m 2 .

6. The flake-shaped copper powder according to any one of claims 1-5, wherein, The tap density of the flake copper powder is 4.4-5 g / mL.

7. The flake-shaped copper powder according to any one of claims 1-6, wherein, The dimensions of the sheet-like copper particles are 1μm-10μm in length, 1μm-7μm in width, and 10nm-500nm in thickness.

8. The flake-shaped copper powder according to claim 2, wherein, The median particle size of the first spherical copper particles is 50nm-200nm.

9. A mixed copper powder comprising flake copper powder and spherical copper powder according to any one of claims 1-8, preferably 40%-65% by weight of spherical copper powder, said spherical copper powder comprising second spherical copper particles.

10. The mixed copper powder according to claim 9, wherein the particle size D of the spherical copper powder is... 50 It ranges from 200nm to 1.2μm.

11. The flake copper powder according to any one of claims 1-8 or the mixed copper powder according to any one of claims 9-10, wherein, The flake-shaped copper particles comprise flake-shaped copper matrix particles and an organic passivating agent coated on the flake-shaped copper matrix particles. The first spherical copper particle comprises a first spherical copper matrix particle and an organic passivating agent coated on the first spherical copper matrix particle. The second spherical copper particle comprises a second spherical copper matrix particle and an organic passivating agent coated on the second spherical copper matrix particle. Preferably, the organic passivating agent is selected from one or more of organic amines, organic acids, organic acid salts, imidazoles, thiazoles, and thiols.

12. A copper paste comprising copper powder and a dispersion medium, wherein the copper powder comprises the flake copper powder according to any one of claims 1-8 and 11, or the mixed copper powder according to any one of claims 9-11; preferably, the copper paste comprises 80%-95% copper powder and 5%-20% dispersion medium by weight.

13. The copper paste according to claim 12, wherein, The dispersion medium includes a resin, a curing agent, a dispersant, a solvent, and optionally a curing accelerator.

14. A copper electrode prepared from the copper paste described in claim 12 or 13.

15. A solar cell comprising the copper electrode of claim 14.

16. The solar cell according to claim 15, wherein, The solar cell is selected from one of the following: BC cell, HJT cell, and perovskite / crystalline silicon tandem cell.

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