Laminated aluminum paste applied to BC cell grid and its preparation method, BC cell grid

Abstract

This disclosure discloses a multilayer aluminum paste for use on the grid of a BC battery and its preparation method, belonging to the field of battery paste technology. The multilayer aluminum paste comprises: 60-80 parts by weight of aluminum powder; 0.8-5 parts by weight of glass powder; 2-5 parts by weight of organic resin; 15-20 parts by weight of solvent; and 0-2 parts by weight of additives; wherein the glass powder comprises 50-70% low-melting-point glass powder and 30-50% of at least one high-melting-point glass powder. This disclosure reduces the silver-aluminum bonding resistance and controls surface recombination of the battery by designing glasses with different melting points and sintering them at approximately 600°C, ensuring reliability while guaranteeing photoelectric conversion efficiency.

Description

Technical Field

[0001] This disclosure belongs to the field of battery paste technology, specifically relating to a multilayer aluminum paste applied to the main grid of a BC battery and its preparation method, and the main grid of a BC battery. Background Technology

[0002] With increasing global focus on sustainable development and green energy, solar photovoltaic (PV) power generation, as a clean and environmentally friendly energy source, has gained popularity among more and more countries and households. Especially in China, with technological advancements and policy support, PV power generation has been widely adopted, with the aim of saving energy costs and reducing carbon emissions. Currently, mainstream solar cells on the market include Topcon, HJT, BC, and PERC cells. Among them, BC cells, with their theoretical efficiency of 28.7%, are very close to the limit of crystalline silicon cells, making them the ultimate choice for crystalline silicon cells and increasingly being established as the company's future technology roadmap.

[0003] Existing Topcon and BC cells primarily employ screen printing to imprint silver grid lines on the front and back of the cell, enabling efficient carrier transport and high-power applications for the cells and modules. However, due to limitations in global silver production capacity and the continuous increase in solar cell production, silver paste prices are rising, significantly hindering cost reduction in photovoltaics and the development of new energy cells. Base metals, such as copper and aluminum, are becoming an increasingly popular cost-reduction option for photovoltaic companies. Aluminum paste, as a metallization choice for the P-region in traditional and PERC cells, has proven its reliability and scalability in cell use, and its cost is the lowest among pastes, making it a crucial option for current cost reduction efforts.

[0004] To reduce battery costs without compromising electrical performance, aluminum grid lines are used to replace some silver grid lines. This involves replacing silver paste with aluminum paste in certain areas of the grid lines, thereby reducing silver consumption. However, after the aluminum and silver pastes overlap, a significant silver-aluminum alloy forms during sintering, resulting in a marked increase in the silver-aluminum overlap resistance, which is detrimental to carrier transport. Simultaneously, the aluminum paste exacerbates silver paste corrosion, increasing surface recombination and ultimately reducing electrical performance. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a multilayer aluminum paste applied to the main grid of a BC battery and its preparation method, as well as the main grid of a BC battery.

[0006] In one aspect, this disclosure provides a multilayer aluminum paste for use on the main grid of a BC battery, the multilayer aluminum paste comprising:

[0007] 60-80 parts by weight of aluminum powder;

[0008] 0.8-5 parts by weight of glass powder;

[0009] 2-5 parts by weight of organic resin;

[0010] 15-20 parts by weight of solvent;

[0011] 0-2 parts by weight of additives; wherein,

[0012] The glass powder comprises 50-70% low-melting-point glass powder and 30-50% at least one high-melting-point glass powder.

[0013] Optionally, the melting point of the low-melting-point glass powder is 560℃~600℃.

[0014] Optionally, the low-melting-point glass powder comprises:

[0015] 1-10 parts by weight of PbO;

[0016] 16-28 parts by weight of Bi2O3;

[0017] 8-22 parts by mass of B2O3;

[0018] 25-35 parts by weight of BaCO3;

[0019] 20-28 parts by weight of V2O5;

[0020] 0.5~3 parts by mass of Al2O3;

[0021] 0.5~5 parts by weight of SrCO3;

[0022] 1 to 8 parts by mass of SiO2.

[0023] Optionally, the high melting point glass powder has a melting point of 680℃~725℃.

[0024] Optionally, the high melting point glass powder comprises:

[0025] 10-28 parts by weight of Bi2O3;

[0026] 8-15 parts by weight of B2O3;

[0027] 25-35 parts by weight of BaCO3;

[0028] 5-28 parts by weight of V2O5;

[0029] 2-8 parts by weight of Al2O3;

[0030] 3-10 parts by mass of SiO2;

[0031] 0.5~5 parts by weight of SrCO3;

[0032] 0.5 to 2 parts by mass of ZrO2.

[0033] Optionally, the aluminum powder comprises 38-45% primary aluminum powder and 55-62% secondary aluminum powder.

[0034] Optionally, the main aluminum powder has a D50 of 8.1-9.5 μm, a D90 of 14-17 μm, and an oxygen content of 0.25-0.29%.

[0035] The secondary aluminum powder is selected from at least one of the following secondary aluminum powders:

[0036] The first batch of aluminum powder has a D50 of 7.5-7.9μm, a D90 of 12-14μm, and an oxygen content of 0.26-0.36%.

[0037] Secondary aluminum powder with D50 of 5.8-6.6μm, D90 of 10-14μm, and oxygen content of 0.32-0.40%;

[0038] The third type of aluminum powder has a D50 of 2.5-3.1μm, a D90 of 4.4-5.2μm, and an oxygen content of 0.8-0.95%.

[0039] The fourth type of aluminum powder has a D50 of 1.3-1.6μm, a D90 of 2.3-2.9μm, and an oxygen content of 0.8-0.9%.

[0040] The fifth type of aluminum powder has a D50 of 4.2-4.9μm, a D90 of 7.1-8.0μm, and an oxygen content of 0.34-0.42%.

[0041] Optionally, the organic resin includes acrylic resin, PVB resin, and ethyl cellulose;

[0042] The solvents include diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and divalent esters;

[0043] The additives include phosphate ester dispersants and organosilicon leveling agents.

[0044] In another aspect of this disclosure, a method for preparing the aforementioned multilayer aluminum paste is provided, the method comprising:

[0045] Disperse 60-80 parts by weight of aluminum powder, 0.8-5 parts by weight of glass powder, 2-5 parts by weight of organic resin, 15-20 parts by weight of solvent, and 0-2 parts by weight of additives into a dispersant for 10-30 minutes.

[0046] The dispersed slurry was ground and then dispersed on a three-roll mill, and the viscosity of the slurry was controlled at 12-20 Pa·s to obtain a laminated aluminum slurry.

[0047] In another aspect of this disclosure, a BC battery main grid is provided, the BC battery main grid comprising silver grid lines and aluminum grid lines overlaid on at least a portion of the silver grid lines, the aluminum grid lines being formed by sintering the laminated aluminum paste described above at 600°C.

[0048] This disclosure discloses a multilayer aluminum paste for use on the grid of a BC battery, its preparation method, and the BC battery grid. The multilayer aluminum paste comprises: 60-80 parts by weight of aluminum powder; 0.8-5 parts by weight of glass powder; 2-5 parts by weight of organic resin; 15-20 parts by weight of solvent; and 0-2 parts by weight of additives; wherein the glass powder comprises 50-70% low-melting-point glass powder and 30-50% of at least one high-melting-point glass powder. This disclosure prepares the paste by designing high and low melting point glass powders combined with highly active aluminum powder and conventional aluminum powder, and sintering it at a temperature of approximately 600°C. This ensures reliability while reducing the silver-aluminum bonding resistance and controlling surface recombination of the battery, thereby guaranteeing photoelectric conversion efficiency. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the method for preparing multilayer aluminum paste according to a specific embodiment of this disclosure. Detailed Implementation

[0050] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0051] In one aspect of this disclosure, a multilayer aluminum paste for use on the main grid of a BC battery is provided, the multilayer aluminum paste comprising: 60-80 parts by weight of aluminum powder; 0.8-5 parts by weight of glass powder; 2-5 parts by weight of organic resin; 15-20 parts by weight of solvent; and 0-2 parts by weight of additives; wherein the glass powder comprises 50-70% low-melting-point glass powder and 30-50% at least one high-melting-point glass powder.

[0052] This disclosure involves designing a combination of glass powders with different melting points (high and low) to form a laminated aluminum paste through the synergistic effect of the glass powders with other components. When this paste is overprinted onto a silver grid, it is sintered at a temperature of approximately 600°C. This approach reduces the silver-aluminum bonding resistance and controls surface recombination of the battery while ensuring reliability, thereby guaranteeing photoelectric conversion efficiency and reducing silver consumption.

[0053] It should be noted that in this embodiment, the content of low-melting-point glass powder is 50-70% of the total mass of glass powder. Too much low-melting-point glass powder will result in excessive corrosiveness, which will have the opposite effect, significantly increasing the amount of composite material and degrading the electrical properties. Furthermore, the melting point of the low-melting-point glass powder is 560℃~600℃, which is suitable for sintering at 580-630℃ to help the aluminum paste break through the alumina layer on the surface of the aluminum powder, thereby achieving the purpose of improving reliability and reducing the resistance of the aluminum grid lines.

[0054] In some preferred embodiments, as shown in Table 1, the low-melting-point glass powder comprises: 1-10 parts by mass of PbO; 16-28 parts by mass of Bi2O3; 8-22 parts by mass of B2O3; 25-35 parts by mass of BaCO3; 20-28 parts by mass of V2O5; 0.5-3 parts by mass of Al2O3; 0.5-5 parts by mass of SrCO3; and 1-8 parts by mass of SiO2.

[0055] As a further preferred embodiment, the low-melting-point glass powder comprises 3-8 parts by mass of PbO; 18-24 parts by mass of Bi₂O₃; 8-16 parts by mass of B₂O₃; 28-32 parts by mass of BaCO₃; 22-27 parts by mass of V₂O₅; 1-2 parts by mass of Al₂O₃; 0.5-3 parts by mass of SrCO₃; and 4-7 parts by mass of SiO₂. For example, the low-melting-point glass powder comprises 6 parts by mass of PbO; 18 parts by mass of Bi₂O₃; 12 parts by mass of B₂O₃; 30 parts by mass of BaCO₃; 25 parts by mass of V₂O₅; 2 parts by mass of Al₂O₃; 1 part by mass of SrCO₃; and 6 parts by mass of SiO₂.

[0056] It should be further noted that the content of high melting point glass powder in this embodiment is 30-50% of the mass of glass powder, and its melting point is 680℃~725℃. It is suitable for sintering at around 600℃ to help suppress excessive aluminum liquid outflow from aluminum powder particles in aluminum paste, and to prevent alloying reaction with silver paste, which would increase resistance. At the same time, it can reduce surface recombination of the battery and balance other properties.

[0057] In some preferred embodiments, as shown in Table 1, the high melting point glass powder comprises: 10-28 parts by mass of Bi2O3; 8-15 parts by mass of B2O3; 25-40 parts by mass of BaCO3; 5-30 parts by mass of V2O5; 2-8 parts by mass of Al2O3; 3-15 parts by mass of SiO2; 0.5-5 parts by mass of SrCO3; and 0.5-5 parts by mass of ZrO2.

[0058] It should be noted that at least one high melting point glass powder can be selected from the above-mentioned formulation components. One or more high melting point glass powders can be formed by adjusting the content of different components. For example, two high melting point glass powders, a first high melting point glass powder and a second high melting point glass powder, can be used in combination. The preferred components of the first high-melting-point glass powder are: 16-24 parts by mass of Bi₂O₃; 10-14 parts by mass of B₂O₃; 25-30 parts by mass of BaCO₃; 16-25 parts by mass of V₂O₅; 2-4 parts by mass of Al₂O₃; 8-12 parts by mass of SiO₂; 1-4 parts by mass of SrCO₃; and 3-5 parts by mass of ZrO₂. The preferred components of the second high-melting-point glass powder are: 10-15 parts by mass of Bi₂O₃; 8-12 parts by mass of B₂O₃; 30-40 parts by mass of BaCO₃; 25-30 parts by mass of V₂O₅; 4-8 parts by mass of Al₂O₃; 3-9 parts by mass of SiO₂; 1-3 parts by mass of SrCO₃; and 1-3 parts by mass of ZrO₂. For example, as shown in Table 1, the first high-melting-point glass powder comprises 20 parts by mass of Bi₂O₃; 12 parts by mass of B₂O₃; 27 parts by mass of BaCO₃; 22 parts by mass of V₂O₅; 2.5 parts by mass of Al₂O₃; 10 parts by mass of SiO₂; 2.5 parts by mass of SrCO₃; and 4 parts by mass of ZrO₂. The second high-melting-point glass powder comprises 12 parts by mass of Bi₂O₃; 9 parts by mass of B₂O₃; 35 parts by mass of BaCO₃; 28 parts by mass of V₂O₅; 6 parts by mass of Al₂O₃; 6 parts by mass of SiO₂; 2 parts by mass of SrCO₃; and 2 parts by mass of ZrO₂. Of course, in other embodiments, the composition of the first and second high-melting-point glass powders can be adjusted to other contents, and this is not specifically limited.

[0059] Table 1. Component Formulation of Glass Powder

[0060]

[0061] This embodiment, by using the low-melting-point glass powder and at least one high-melting-point glass powder in combination with highly active aluminum powder, can reduce the silver-aluminum bonding resistance and control surface recombination in the battery. During sintering, the low-melting-point glass powder helps break through the alumina layer on the aluminum powder surface, opening conductive pathways between aluminum powder particles and between aluminum powder and silver powder, reducing grid line resistance, fully wetting the surfaces of aluminum and silver powders, optimizing sintering performance, optimizing the silver-aluminum interface, ensuring adhesion of the aluminum paste to the silver grid lines, and improving reliability. The high-melting-point glass powder, not fully softened at 580-630℃, can disperse between aluminum powder particles, forming a physical "skeleton" or "barrier," inhibiting excessive flow of aluminum powder particles, reducing alloying reactions with the silver paste, inhibiting excessive erosion of the silver paste, reducing silver-aluminum bonding resistance and surface recombination, and maintaining stable electrical performance.

[0062] Furthermore, the aluminum powder comprises 38-45% primary aluminum powder and 55-62% secondary aluminum powder.

[0063] In some preferred embodiments, as shown in Table 2, the content of the main aluminum powder is 38-45% of the mass of aluminum powder, with a D50 of 8.1-9.5 μm, a D90 of 14-17 μm, and an oxygen content of 0.25-0.29%. The particle size of the main aluminum powder is suitable for providing excellent linearity.

[0064] In some other preferred embodiments, the content of secondary aluminum powder is 55-62% of the total mass of aluminum powder. The secondary aluminum powder can be selected from at least two of the following aluminum powders: for example, as shown in Table 2, a first secondary aluminum powder with a D50 of 7.5-7.9 μm, a D90 of 12-14 μm, and an oxygen content of 0.26-0.36%; a second secondary aluminum powder with a D50 of 5.8-6.6 μm, a D90 of 10-14 μm, and an oxygen content of 0.32-0.40%; and a third secondary aluminum powder with a D50 of... The primary aluminum powder has a particle size distribution of 2.5-3.1 μm, a D90 of 4.4-5.2 μm, and an oxygen content of 0.8-0.95%; the secondary aluminum powder has a D50 of 1.3-1.6 μm, a D90 of 2.3-2.9 μm, and an oxygen content of 0.8-0.9%; the fifth secondary aluminum powder has a D50 of 4.2-4.9 μm, a D90 of 7.1-8.0 μm, and an oxygen content of 0.34-0.42%. In other words, the aluminum powder in this embodiment includes a primary aluminum powder and at least one secondary aluminum powder with a different particle size range. By combining the primary aluminum powder with one or more of the aforementioned secondary aluminum powders, the grid line density is altered, thereby adjusting the line resistance.

[0065] Table 2 Relevant data for aluminum powder

[0066]

[0067] It should be noted that this embodiment does not specifically limit the type of primary aluminum powder and the secondary aluminum powder it is used with. The primary aluminum powder can be combined with one type of secondary aluminum powder, or with two or three other secondary aluminum powders. For example, the primary aluminum powder can be combined with the first or second secondary aluminum powder to form a combination of primary aluminum powder and one type of secondary aluminum powder. Of course, the primary aluminum powder can also be combined with the first and second secondary aluminum powders, the primary aluminum powder can be combined with the first and third secondary aluminum powders, the primary aluminum powder can be combined with the first and fourth secondary aluminum powders, or the primary aluminum powder can be combined with the first and fifth secondary aluminum powders to form a combination of primary aluminum powder and the first secondary aluminum powder and other secondary aluminum powders. Of course, the primary aluminum powder can also be combined with the second and third secondary aluminum powders, the primary aluminum powder can be combined with the second and fourth secondary aluminum powders, or the primary aluminum powder can be combined with the second and fifth secondary aluminum powders to form a combination of primary aluminum powder and the second secondary aluminum powder and other secondary aluminum powders. In addition to the various combinations listed above, the primary aluminum powder can also be combined with other secondary aluminum powders, which will not be listed here.

[0068] It should be further noted that when combining the main aluminum powder with any one of the secondary aluminum powders, the content of the main aluminum powder is preferably 38-45 parts by weight, and the content of the secondary aluminum powder is preferably 30-44 parts by weight. When combining the main aluminum powder with two of the secondary aluminum powders, the content of the main aluminum powder is preferably 38-45 parts by weight, and the content of the two secondary aluminum powders can be preferably 25-32 parts by weight and 5-12 parts by weight, respectively. It should be noted that the content of the first or second secondary aluminum powder is preferably 25-32 parts by weight, and the content of the third, fourth, or fifth secondary aluminum powder is preferably 5-12 parts by weight. Of course, in other embodiments, the secondary aluminum powder can also be selected in other different contents, which will not be listed here.

[0069] To improve grid line density and reduce line resistance, a preferred approach is to use the main aluminum powder in combination with large-particle-size secondary aluminum powder having a D50 of 5-8 μm, a D90 of 10-14 μm, and an oxygen content of 0.24-0.40%, such as the combination of the main aluminum powder in Table 1 with at least one of the first / second secondary aluminum powders. As a further preferred approach, the main aluminum powder is used in combination with large-particle-size secondary aluminum powder having a D50 of 5-8 μm, a D90 of 10-14 μm, and an oxygen content of 0.24-0.40%, and small-particle-size secondary aluminum powder having a D50 of 1.0-5.0 μm, a D90 of 2.0-8.0 μm, and an oxygen content of 0.30-1.0%, such as the combination of the main aluminum powder in Table 2 with at least one of the first / second / third / fourth secondary aluminum powders.

[0070] In this embodiment, aluminum powder serves as a conductive material, ensuring the printing of aluminum grid lines, providing conductivity, excellent bonding with silver grid lines, and by controlling the particle size of the aluminum powder, ensuring printability and conductivity. A suitable oxide layer can prevent excessive oxidation of the aluminum powder without affecting conductivity during sintering.

[0071] Furthermore, organic resins include acrylic resins, PVB resins, and ethyl cellulose.

[0072] As a further preferred option, the content ratio of acrylic resin, PVB resin and ethyl cellulose is (2~6):(2~1):(1~0.5), which is beneficial to provide plasticity of the paste, enhance the adhesion of aluminum and silver grid lines, optimize printing performance, and ensure the integrity of grid line shape.

[0073] Furthermore, the solvents include diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and divalent esters.

[0074] As a further preferred option, the content ratio of diethylene glycol butyl ether, diethylene glycol butyl ether acetate and divalent ester is (2~3):(0.5~1):(1~3), which is beneficial for adjusting the viscosity of the paste, controlling the rheological properties, and improving the printability of the paste.

[0075] Furthermore, the additives include phosphate dispersants and silicone leveling agents.

[0076] As a further preferred option, the content ratio of phosphate ester dispersant to silicone leveling agent is (5~10):(1~4). The dispersant prevents aluminum powder agglomeration, and the leveling agent improves the spreadability of the paste. The two work together to optimize printability and interfacial adhesion.

[0077] The multilayer aluminum paste of this embodiment can be sintered at a temperature of about 600°C, so that it is superimposed on the silver grid lines. While ensuring reliability, it reduces the silver-aluminum bonding resistance and controls the surface recombination of the battery, thus ensuring photoelectric conversion efficiency.

[0078] like Figure 1 As shown, in another aspect of this disclosure, a method S100 for preparing the aforementioned multilayer aluminum paste is provided, specifically including the following steps S110~S120:

[0079] S110. Disperse 60-80 parts by weight of aluminum powder, 0.8-5 parts by weight of glass powder, 2-5 parts by weight of organic resin, 15-20 parts by weight of solvent, and 0-2 parts by weight of additives into a dispersant for 10-30 minutes.

[0080] S120. The dispersed slurry is ground and then dispersed on a three-roll mill. The viscosity of the slurry is controlled at 12-20 Pa·s to obtain a layered slurry.

[0081] In step S110, the specific components of aluminum powder, glass powder, organic resin, solvent and additives can be referred to the above description.

[0082] In step S120, the dispersion speed is preferably 500-2000 rpm.

[0083] In another aspect of this disclosure, a BC battery main grid is provided, the BC battery main grid including silver grid lines and aluminum grid lines overlaid on at least a portion of the silver grid lines, the aluminum grid lines being formed by sintering the laminated aluminum paste described above at 600°C.

[0084] The multilayer aluminum paste of this embodiment can at least partially replace the silver grid lines of BC batteries, more preferably partially replace the silver grid lines of BC batteries, and even more preferably, the aluminum paste is overprinted on the silver grid lines in the thickness direction of the silicon wafer. For example, a small amount of silver seed layer is first printed on the silicon wafer to form silver grid lines, and then a portion of aluminum paste is overprinted on the silver grid lines to form aluminum grid lines. The aluminum grid lines overprinted on the silver grid lines replace part of the silver grid lines, which can reduce the use of main grid silver paste and reduce costs without affecting electrical performance. In other words, this disclosure aims to provide a multilayer aluminum paste for replacing the silver grid lines of BC batteries, without limiting the specific overprinting area, overprinting structure, overlapping method, overprinting pattern, overprinting direction, aluminum-silicon contact area, etc. of the silver grid lines and aluminum grid lines.

[0085] The following will further illustrate the application of laminated aluminum paste on the main grid of BC cells with specific embodiments:

[0086] Example 1

[0087] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3:

[0088] 78 parts by weight of aluminum powder, of which 40 parts by weight of main aluminum powder, 28 parts by weight of first auxiliary aluminum powder, and 10 parts by weight of fifth auxiliary aluminum powder. For specific parameters of the main aluminum powder, first auxiliary aluminum powder, and second auxiliary aluminum powder, please refer to Table 1.

[0089] Two parts by weight of glass powder, of which one part by weight is low-melting-point glass powder and one part by weight is high-melting-point glass powder. Please refer to Table 2 for the formulation of the low-melting-point glass powder and the high-melting-point glass powder.

[0090] Three parts by weight of organic resin, wherein the ratio of acrylic resin: PVB resin: ethyl cellulose is 4:2:1.

[0091] The solvent comprises 16 parts by mass, wherein the content of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and divalent ester is 2:1:2.

[0092] 1 part by weight of additive; wherein the content of phosphate ester dispersant and organosilicon leveling agent is 10:1.

[0093] The above components were placed in a dispersant and dispersed for 30 minutes; the dispersed slurry was then ground and further dispersed on a three-roll mill, and the viscosity of the slurry was controlled at 15 Pa·s to obtain a laminated aluminum slurry.

[0094] The aluminum paste was further overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.60 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.62Ω, and the PL composite resistance is 113fA / cm. 23M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0095] Example 2

[0096] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. It is basically the same as the formulation of Example 1, except that the glass powder includes 1 part by mass of low melting point glass powder and 1 part by mass of second high melting point glass powder.

[0097] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.78 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.56Ω, and the PL composite resistance is 98fA / cm. 2 3M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0098] Example 3

[0099] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. It is basically the same as the formulation of Example 1, except that the glass powder includes 0.7 parts by mass of low melting point glass powder and 1 part by mass of second high melting point glass powder, and the solvent is 15.7 parts by mass.

[0100] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.83 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.53Ω, and the PL composite resistance is 60fA / cm. 2 3M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0101] Example 4

[0102] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. It is basically the same as the formulation of Example 1, except that the glass powder includes 0.7 parts by mass of low melting point glass powder and 1 part by mass of second high melting point glass powder, the solvent is 15.7 parts by mass, and the aluminum powder includes 40 parts by mass of main aluminum powder, 28 parts by mass of second secondary aluminum powder and 10 parts by mass of third secondary aluminum powder.

[0103] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.76 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.63Ω, and the PL composite resistance is 51fA / cm. 2 3M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0104] Example 5

[0105] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. It is basically the same as the formulation of Example 1, except that the glass powder includes 0.7 parts by mass of low melting point glass powder and 1 part by mass of second high melting point glass powder, the solvent is 15.7 parts by mass, and the aluminum powder includes 40 parts by mass of main aluminum powder, 32 parts by mass of second secondary aluminum powder and 6 parts by mass of fourth secondary aluminum powder.

[0106] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.58 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.43Ω, and the PL composite resistance is 45fA / cm. 2 3M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0107] Comparative Example 1

[0108] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. The difference from Example 1 is that the glass powder includes 2 parts by mass of low melting point glass powder.

[0109] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 1.54 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 2.35Ω, and the PL composite resistance is 302fA / cm. 2 3M adhesion is excellent; after boiling in water for 20 minutes, 3M adhesion is excellent and there is no peeling.

[0110] Comparative Example 2

[0111] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. The difference from Example 1 is that the glass powder includes 2 parts by mass of a first high melting point glass powder.

[0112] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 2.17 × 10⁻⁶. -5 The silver-aluminum lap resistance at the main gate is 0.48Ω, and the PL composite resistance is 58fA / cm. 2 3M adhesion was good. After boiling in water for 20 minutes, 3M adhesion was still good, but some particles peeled off.

[0113] Comparative Example 3

[0114] The formulation of the laminated aluminum paste in this example is as follows, please refer to Table 3. The difference from Example 1 is that the glass powder includes 2 parts by mass of a second high melting point glass powder.

[0115] Furthermore, the multilayered aluminum paste was overprinted onto the silver grid lines and sintered at 600℃ to form aluminum grid lines. Testing showed that its resistivity was 2.78 × 10⁻⁶. -5The silver-aluminum lap resistance at the main gate is 0.4Ω, and the PL composite resistance is 40fA / cm. 2 The 3M adhesion was medium, but after boiling in water for 20 minutes, the 3M adhesion was poor, and some parts of the material peeled off.

[0116] Table 3 Aluminum paste formulations for each embodiment and comparative example

[0117]

[0118] Table 4 Results of each embodiment and comparative example

[0119]

[0120] In summary, comparing Comparative Example 1 with Examples 1-5, it is evident that in this system, without the addition of high-melting-point glass powder, the low-melting-point glass powder exhibits a stronger corrosive effect on the aluminum powder. The outflowing aluminum molten metal reacts with the silver grid lines to produce a strong alloying reaction, resulting in a high silver-aluminum interface resistance and high PL composite value at the main grid. Comparing Comparative Examples 2 and 3 with Examples 1-5, it is clear that when using a single high-melting-point glass powder, the melting amount is insufficient to break down the Al2O3 oxide layer on the aluminum powder surface. This leads to high contact resistance between aluminum particles, causing a surge in overall resistivity. It also hinders the bonding between the aluminum paste and the silver grid lines, resulting in insufficient interfacial bonding. After boiling in water, stress cracking and detachment easily occur, affecting the product's performance and lifespan. This indicates that the composite of glass powder helps reduce resistivity, contact resistance, and PL composite value. Furthermore, the aluminum and silver grid lines exhibit good bonding strength, with no detachment after boiling. This allows aluminum paste to replace some of the silver paste, reducing costs and improving the overall performance of the grid lines.

[0121] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A laminated aluminum paste applied to the main grid of a BC battery, characterized in that, The laminated aluminum paste includes: 60-80 parts by weight of aluminum powder; the aluminum powder includes 38-45 parts by weight of main aluminum powder and 55-62 parts by weight of secondary aluminum powder; The main aluminum powder has a D50 of 8.1-9.5 μm, a D90 of 14-17 μm, and an oxygen content of 0.25-0.29%. The secondary aluminum powder is selected from at least one of the following secondary aluminum powders: The first batch of aluminum powder has a D50 of 7.5-7.9μm, a D90 of 12-14μm, and an oxygen content of 0.26-0.36%. Secondary aluminum powder with D50 of 5.8-6.6μm, D90 of 10-14μm, and oxygen content of 0.32-0.40%; The third type of aluminum powder has a D50 of 2.5-3.1μm, a D90 of 4.4-5.2μm, and an oxygen content of 0.8-0.95%. The fourth type of aluminum powder has a D50 of 1.3-1.6μm, a D90 of 2.3-2.9μm, and an oxygen content of 0.8-0.9%. The fifth type of aluminum powder has a D50 of 4.2-4.9μm, a D90 of 7.1-8.0μm, and an oxygen content of 0.34-0.42%. 0.8-5 parts by weight of glass powder; wherein, The glass powder comprises 50-70% by mass of low-melting-point glass powder and 30-50% by mass of at least one high-melting-point glass powder; the melting point of the low-melting-point glass powder is 560℃~600℃; and the melting point of the high-melting-point glass powder is 680℃~725℃. 2-5 parts by weight of organic resin; 15-20 parts by weight of solvent; 0-2 parts by weight of additive.

2. The laminated aluminum paste according to claim 1, characterized in that, The low-melting-point glass powder comprises: 1-10 parts by weight of PbO; 16-28 parts by weight of Bi2O3; 8-22 parts by mass of B2O3; 25-35 parts by weight of BaCO3; 20-28 parts by weight of V2O5; 0.5~3 parts by mass of Al2O3; 0.5~5 parts by weight of SrCO3; 1 to 8 parts by mass of SiO2.

3. The laminated aluminum paste according to claim 1, characterized in that, The high melting point glass powder comprises: 10-28 parts by weight of Bi2O3; 8-15 parts by weight of B2O3; 25-40 parts by weight of BaCO3; 5-30 parts by weight of V2O5; 2-8 parts by weight of Al2O3; 3-15 parts by weight of SiO2; 0.5~5 parts by weight of SrCO3; 0.5 to 5 parts by weight of ZrO2.

4. The laminated aluminum paste according to any one of claims 1 to 3, characterized in that, The organic resin includes at least one of acrylic resin, PVB resin and ethyl cellulose; The solvent includes at least one of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and divalent esters; The additives include phosphate ester dispersants and silicone leveling agents.

5. A method for preparing the laminated aluminum paste as described in any one of claims 1 to 4, characterized in that, The method includes: Place 60-80 parts by weight of aluminum powder, 0.8-5 parts by weight of glass powder, 2-5 parts by weight of organic resin, 15-20 parts by weight of solvent, and 0-2 parts by weight of additive into a disperser and disperse for 10-30 minutes. The dispersed slurry was ground and then dispersed on a three-roll mill, and the viscosity of the slurry was controlled at 12-20 Pa·s to obtain a laminated aluminum slurry.

6. A BC battery main grid, characterized in that, The BC battery main grid includes silver grid lines and aluminum grid lines overlaid on at least a portion of the silver grid lines, wherein the aluminum grid lines are formed by sintering the laminated aluminum paste as described in any one of claims 1 to 4 at 600°C.

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