Laminated aluminum paste applied to BC battery main grid, preparation method of laminated aluminum paste and BC battery main grid

Abstract

The invention provides laminated aluminum paste applied to a BC battery main grid, a preparation method of the laminated aluminum paste and the BC battery main grid, and belongs to the technical field of battery paste. The laminated aluminum paste comprises the following components in parts by mass: 60-80 parts of aluminum powder; 0.8-5 parts by mass of glass powder; 2-5 parts by mass of an organic resin; 15-20 parts by mass of a solvent; 0-2 parts by mass of an additive; wherein the glass powder comprises 50-70% of low-melting-point glass powder and 30-50% of at least one kind of high-melting-point glass powder. Glass with high and low melting points is designed, sintering is carried out at the temperature of about 600 DEG C, on the premise that reliability is ensured, silver-aluminum lap joint resistance is reduced, cell surface recombination is controlled, and photoelectric conversion efficiency is ensured.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of battery slurry, and particularly relates to a laminated aluminum paste applied to a BC battery main grid and a preparation method thereof and a BC battery main grid. BACKGROUND

[0002] With the increasing global attention to sustainable development and green energy, solar photovoltaic power generation, as a clean and environmentally friendly form of energy, has been favored by more and more countries and families. In China, in particular, with technological progress and policy support, photovoltaic power generation has been widely used, with the expectation of saving energy costs and reducing carbon emissions through this approach. The current market mainstream cells include Topcon, HJT, BC, and PERC cells, among which the BC cell, with its theoretical efficiency of 28.7%, is close to the limit of crystalline silicon cells, becoming the ultimate choice for crystalline silicon cells and being established as the subsequent technology roadmap by more and more companies.

[0003] The metallization of existing Topcon cells and BC cells basically adopts the screen printing method to print silver grid lines on the front and back of the cell or the back of the cell, thereby achieving efficient transport of charge carriers and high power application of the cell and module. However, in the above prior art, due to the global silver production capacity limit and the continuous production increase of solar cells, the price of silver paste is becoming higher and higher, and the development of photovoltaic cost reduction and new energy cells is greatly restricted. The use of copper and aluminum as representative base metals has become a choice for many photovoltaic companies to reduce costs. As a choice for P-area metallization in traditional cells and PERC cells, aluminum paste has proven its reliability and scalability for use on cells, and its cost is the lowest among pastes, making it an important choice for current cost reduction.

[0004] To reduce the cost of the cell, while ensuring that the electrical performance is not affected, aluminum grid lines are used instead of part of the silver grid lines, i.e., aluminum paste is used instead of silver paste in part of the area of the grid lines, thereby reducing silver consumption. However, after the aluminum paste is overlapped with the silver paste, a relatively obvious silver-aluminum alloy occurs during the sintering process, which significantly increases the silver-aluminum overlap resistance, which is not conducive to the transport of charge carriers; at the same time, the aluminum paste increases the corrosion of the silver paste, increases the surface recombination of the cell, and reduces the electrical performance. SUMMARY

[0005] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a laminated aluminum paste applied to a BC battery main grid and a preparation method thereof and a BC battery main grid.

[0006] In one aspect of the present disclosure, a laminated aluminum paste applied to a BC battery main grid is provided, the laminated aluminum paste comprising: 60-80 parts by mass of aluminum powder; 0.8-5 parts by mass of glass powder; 2-5 parts by mass of an organic resin; 15-20 parts by mass of a solvent; 0-2 parts by mass of an additive; wherein, The glass powder includes 50-70% of a low-melting point glass powder and 30-50% of at least one high-melting point glass powder. Optionally, the low-melting point glass powder has a melting point of 560°C ~ 600°C.

[0007] Optionally, the low-melting point glass powder includes: 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; 1 ~ 8 parts by mass of SiO2.

[0008] Optionally, the high-melting point glass powder has a melting point of 680°C ~ 725°C.

[0009] Optionally, the high-melting point glass powder includes: 10 ~ 28 parts by mass of Bi2O3; 8 ~ 15 parts by mass of B2O3; 25 ~ 35 parts by mass of BaCO3; 5 ~ 28 parts by mass of V2O5; 2 ~ 8 parts by mass of Al2O3; 3 ~ 10 parts by mass of SiO2; 0.5 ~ 5 parts by mass of SrCO3; 0.5 ~ 2 parts by mass of ZrO2.

[0010] Optionally, the aluminum powder includes 38-45% of a main aluminum powder and 55-62% of a sub aluminum powder.

[0011] 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%; The sub aluminum powder is selected from at least one of the following sub aluminum powders: a first sub aluminum powder having 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 sub-aluminum powder having a D50 of 5.8-6.6 μm, a D90 of 10-14 μm, and an oxygen content of 0.32-0.40%; a third sub-aluminum powder having a D50 of 2.5-3.1 μm, a D90 of 4.4-5.2 μm, and an oxygen content of 0.8-0.95%; a fourth sub-aluminum powder having 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%; a fifth sub-aluminum powder having 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%.

[0012] Optionally, the organic resin comprises an acrylic resin, a PVB resin, and ethyl cellulose; The solvent comprises diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and a bivalent acid ester; The additive comprises a phosphate ester dispersant and an organic silicon leveling agent.

[0013] In another aspect of the present disclosure, a method for preparing the laminated aluminum paste described above is provided, and the method comprises: 60-80 parts by mass of aluminum powder, 0.8-5 parts by mass of glass powder, 2-5 parts by mass of organic resin, 15-20 parts by mass of solvent, and 0-2 parts by mass of additive are put into a dispersant for dispersion treatment for 10-30 min; The dispersed paste is ground and dispersed again on a three-roll mill, and the viscosity of the paste is controlled at 12-20 Pa·s to obtain the laminated aluminum paste.

[0014] In another aspect of the present disclosure, a BC battery main grid is provided, and the BC battery main grid comprises silver grid lines and aluminum grid lines superimposed on at least part of the silver grid lines, and the aluminum grid lines are formed by sintering the laminated aluminum paste described above at 600°C.

[0015] The present disclosure provides a laminated aluminum paste applied to a BC battery main grid, a preparation method of the laminated aluminum paste, and a BC battery main grid. The laminated aluminum paste comprises: 60-80 parts by mass of aluminum powder; 0.8-5 parts by mass of glass powder; 2-5 parts by mass of organic resin; 15-20 parts by mass of solvent; and 0-2 parts by mass of additive. The glass powder comprises 50-70% of low-melting-point glass powder and 30-50% of at least one high-melting-point glass powder. The present disclosure prepares a paste by designing high and low melting point glasses, high-activity aluminum powder, and conventional aluminum powder, and sintering at a temperature of about 600°C. Under the premise of ensuring reliability, the silver-aluminum lap joint resistance and the battery surface recombination are controlled to ensure the photoelectric conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1A flow chart of a preparation method of the laminated aluminum paste of the specific embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0017] In order to make the technical solutions of the present disclosure better understood by those skilled in the art, the present disclosure will be described in further detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are part of the embodiments of the present disclosure, but not all the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present disclosure.

[0018] In one aspect of the present disclosure, a laminated aluminum paste applied to a BC battery main grid is provided, which comprises: 60-80 parts by mass of aluminum powder; 0.8-5 parts by mass of glass powder; 2-5 parts by mass of organic resin; 15-20 parts by mass of solvent; and 0-2 parts by mass of additives; wherein the glass powder comprises 50-70% of low-melting-point glass powder and 30-50% of at least one high-melting-point glass powder. The present disclosure reduces the silver-aluminum lap joint resistance and controls the battery surface recombination by designing high and low melting point glass powders, forming a laminated aluminum paste through the synergistic effect of the glass powder and other components, and sintering the paste at a temperature of about 600°C when the paste is laminated on the silver grid, thereby ensuring reliability, ensuring photoelectric conversion efficiency, and reducing silver consumption.

[0019] It should be noted that the content of the low-melting-point glass powder in the present embodiment is 50-70% of the total mass of the glass powder. If the content of the low-melting-point glass powder is too high, the corrosion will be too strong and will have an adverse effect, the recombination will be significantly increased, and the electrical performance will be degraded. The melting point of the low-melting-point glass powder is 560°C-600°C, which is suitable for sintering at 580-630°C to help the aluminum paste break the aluminum oxide layer on the surface of the aluminum powder, thereby achieving the purposes of reliability and reducing the aluminum grid line resistance.

[0020] 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.

[0021] As a further preferred solution, the low-melting 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; 4-7 parts by mass of SiO2. For example, the low-melting 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; 6 parts by mass of SiO2.

[0022] Further, the high-melting glass powder of the present embodiment has a content of 30-50% by mass of the glass powder, and a melting point of 680-725°C, which is suitable for helping to inhibit the excessive outflow of aluminum liquid from the aluminum powder particles in the aluminum paste during sintering at about 600°C, to cause alloying reaction with the silver paste, to increase the resistance, to weaken the surface recombination of the battery, and to balance other properties.

[0023] In some preferred embodiments, as shown in Table 1, the high-melting 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; 0.5-5 parts by mass of ZrO2.

[0024] It should be noted that the at least one high-melting-point glass powder can be selected from the above-mentioned formula components, and one or more high-melting-point glass powders can be formed by adjusting the contents of different components, for example, two high-melting-point glass powders are used in combination, such as a first high-melting-point glass powder and a second high-melting-point glass powder. The first high-melting-point glass powder preferably contains 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 second high-melting-point glass powder preferably contains 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 contains 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 contains 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 components of the first high-melting-point glass powder and the second high-melting-point glass powder can also be adjusted to other contents, which are not specifically limited.

[0025] Table 1. Component formula of glass powder

[0026] The present embodiment can reduce the silver-aluminum joint resistance and control the surface recombination of the battery by using the low-melting-point glass powder and the at least one high-melting-point glass powder given above in combination with the high-activity aluminum powder. The low-melting-point glass powder can help break the aluminum oxide layer on the surface of the aluminum powder during sintering, open the conductive path between the aluminum powder-aluminum powder and the aluminum powder-silver powder, reduce the grid resistance, fully wet the surface of the aluminum powder and the silver powder, optimize the sintering performance, optimize the silver-aluminum interface, ensure the adhesion of the aluminum paste to the silver grid line, and improve the reliability. The high-melting-point glass powder is not completely softened at 580-630°C, can be dispersed between the aluminum powder particles, form a physical "skeleton" or "barrier", inhibit the excessive flow of the aluminum powder particles, reduce the alloying reaction with the silver paste, inhibit the excessive erosion of the silver paste, reduce the silver-aluminum joint resistance and the surface recombination, and maintain the stability of the electrical performance.

[0027] Further, the aluminum powder includes 38-45% of a main aluminum powder and 55-62% of a secondary aluminum powder.

[0028] In some preferred embodiments, the content of the main aluminum powder is 38-45% of the mass of the aluminum powder, the D50 is 8.1-9.5 μm, the D90 is 14-17 μm, and the oxygen content is 0.25-0.29%, as shown in Table 2. The particle size of the main aluminum powder is suitable for providing excellent line type.

[0029] In other preferred embodiments, the content of the secondary aluminum powder is 55-62% of the total mass of the aluminum powder. The secondary aluminum powder here can be selected from at least two of the following aluminum powders: for example, a first secondary aluminum powder having 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 having a D50 of 5.8-6.6 μm, a D90 of 10-14 μm, and an oxygen content of 0.32-0.40%; a third secondary aluminum powder having a D50 of 2.5-3.1 μm, a D90 of 4.4-5.2 μm, and an oxygen content of 0.8-0.95%; a fourth secondary aluminum powder having 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%; and a fifth secondary aluminum powder having 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%, as shown in Table 2. That is, the aluminum powder of the present embodiment includes a main aluminum powder and at least one secondary aluminum powder having a different particle size range, and by combining the main aluminum powder with one or more of the above-mentioned secondary aluminum powders, the effect of changing the grid line density and adjusting the line resistance is achieved.

[0030] Table 2 Related data of aluminum powder

[0031] It should be noted that the present embodiment does not specifically limit the type of secondary aluminum powder combined with the main aluminum powder, and the main aluminum powder can be combined with one type of secondary aluminum powder, or combined with two or three types of secondary aluminum powder, etc. For example, the main aluminum powder and the first secondary aluminum powder or the second secondary aluminum powder are combined to form a combination of the main aluminum powder and one type of secondary aluminum powder. Of course, the main aluminum powder can also be combined with the first secondary aluminum powder, the second secondary aluminum powder, the main aluminum powder and the first secondary aluminum powder, the third secondary aluminum powder, the main aluminum powder and the first secondary aluminum powder, the fourth secondary aluminum powder, the main aluminum powder and the first secondary aluminum powder, the fifth secondary aluminum powder, to form a combination of the main aluminum powder and the first secondary aluminum powder and other secondary aluminum powders. Of course, the main aluminum powder can also be combined with the second secondary aluminum powder, the third secondary aluminum powder, the main aluminum powder and the second secondary aluminum powder, the fourth secondary aluminum powder, the main aluminum powder and the second secondary aluminum powder, the fifth secondary aluminum powder, to form a combination of the main aluminum powder and the second secondary aluminum powder and other secondary aluminum powders. Of course, in addition to the above-mentioned various combinations, the main aluminum powder can also be combined with other secondary aluminum powders, which will not be listed one by one here.

[0032] Further, it is to be noted that, when the main aluminum powder is combined with any one of the secondary aluminum powders, the content of the main aluminum powder is preferably 38-45 parts by mass, and the content of the secondary aluminum powder is preferably 30-44 parts by mass. When the main aluminum powder is combined with two of the secondary aluminum powders, the content of the main aluminum powder is preferably 38-45 parts by mass, and the content of each of the two secondary aluminum powders can be preferably 25-32 parts by mass and 5-12 parts by mass, respectively. It is to be noted that the content of the first secondary aluminum powder or the second secondary aluminum powder can be preferably 25-32 parts by mass, and the content of the third secondary aluminum powder, the fourth secondary aluminum powder, or the fifth secondary aluminum powder can be preferably 5-12 parts by mass. Of course, in other embodiments, the secondary aluminum powder can also have other different contents, which are not listed here one by one.

[0033] In order to improve the density of the grid lines and reduce the line resistance, as a preferred solution, the main aluminum powder is combined with a 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 main aluminum powder combined with at least one of the first secondary aluminum powder / second secondary aluminum powder in Table 1. As a further preferred solution, the main aluminum powder is combined with a 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 a 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 main aluminum powder combined with at least one of the first secondary aluminum powder / second secondary aluminum powder and at least one of the third secondary aluminum powder / fourth secondary aluminum powder / fifth secondary aluminum powder in Table 2.

[0034] The aluminum powder of the present embodiment, as a conductive material, ensures the printing of the aluminum grid lines, provides excellent conductivity and lapping with the silver grid lines, and, by controlling the particle size of the aluminum powder, ensures the printability and conductivity, and a moderate oxidation layer can prevent the aluminum powder from being excessively oxidized, while not affecting the conductivity during sintering.

[0035] Further, the organic resin includes an acrylic resin, a PVB resin, and ethyl cellulose.

[0036] As a further preferred solution, the content ratio of the acrylic resin, the PVB resin, and the ethyl cellulose is (2-6):(2-1):(1-0.5), which is beneficial to provide the plasticity of the slurry, enhance the adhesion of the aluminum grid lines and the silver grid lines, optimize the printing performance, and ensure the integrity of the grid line shape.

[0037] Further, the solvent includes diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and divalent acid ester.

[0038] As a further preferred solution, the content ratio of diethylene glycol butyl ether, diethylene glycol butyl ether acetate and divalent acid ester is (2-3):(0.5-1):(1-3), which is conducive to adjusting the viscosity of the slurry, controlling the rheological properties, and improving the printing adaptability of the slurry.

[0039] Furthermore, the additive includes a phosphate dispersant and an organic silicon leveling agent.

[0040] As a further preferred solution, the content ratio of the phosphate dispersant and the organic silicon leveling agent is (5-10):(1-4), the dispersant prevents the agglomeration of aluminum powder, the leveling agent improves the spreading property of the slurry, and both of them synergistically optimize the printing adaptability and the interfacial adhesion.

[0041] The laminated aluminum slurry of the embodiment can be sintered at a temperature of about 600℃, and is laminated on the silver grid line, thereby reducing the silver-aluminum lap joint resistance and controlling the battery surface recombination under the premise of ensuring reliability, and ensuring the photoelectric conversion efficiency.

[0042] As shown in Figure 1 Another aspect of the present disclosure provides a method S100 for preparing the laminated aluminum slurry described above, which specifically includes the following steps S110-S120: S110, 60-80 parts by mass of aluminum powder, 0.8-5 parts by mass of glass powder, 2-5 parts by mass of organic resin, 15-20 parts by mass of solvent, and 0-2 parts by mass of additive are placed into a dispersant for dispersion treatment for 10-30 min.

[0043] S120, the dispersed slurry is ground and dispersed again on a three-roll mill, the viscosity of the slurry is controlled to be 12-20 Pa·s, and a laminated slurry is obtained.

[0044] In step S110, the specific components of the aluminum powder, the glass powder, the organic resin, the solvent, and the additive can be referred to the description above.

[0045] In step S120, the dispersion speed can be preferably 500-2000 rpm.

[0046] Another aspect of the present disclosure provides a BC battery main grid, which includes a silver grid line and an aluminum grid line laminated on at least part of the silver grid line, and the aluminum grid line is formed by sintering the laminated aluminum slurry described above at 600℃.

[0047] The laminated aluminum paste of the embodiment can realize at least partial replacement of the silver grid lines of the BC battery, and preferably partial replacement of the silver grid lines of the BC battery, and more preferably the aluminum paste is laminated on the silver grid lines in the thickness direction of the silicon wafer, for example, a small amount of silver seed layer is printed on the silicon wafer first to form the silver grid lines, and then part of the aluminum paste is laminated on the silver grid lines to form the aluminum grid lines, and the aluminum grid lines laminated on the silver grid lines replace part of the silver grid lines, which can reduce the use of the main grid silver paste and reduce the cost without affecting the electrical performance. That is, the present disclosure aims to provide a laminated aluminum paste for replacing the silver grid lines of the BC battery, without limiting the specific laminated area, laminated structure, lapping method, laminated pattern, laminated direction, aluminum-silicon contact area, and the like of the silver grid lines and the aluminum grid lines.

[0048] The laminated aluminum paste applied to the main grid of the BC battery will be further described below in conjunction with specific examples: Example 1 The formula of the laminated aluminum paste of the present example is as follows, please refer to Table 3: 78 parts by mass of aluminum powder, wherein the main aluminum powder is 40 parts by mass, the first auxiliary aluminum powder is 28 parts by mass, and the fifth auxiliary aluminum powder is 10 parts by mass. The specific parameters of the main aluminum powder and the first auxiliary aluminum powder, the second auxiliary aluminum powder are please refer to Table 1.

[0049] 2 parts by mass of glass powder, wherein the low-melting-point glass powder is 1 part by mass, and the first high-melting-point glass powder is 1 part by mass. The formula of the low-melting-point glass powder and the first high-melting-point glass powder is please refer to Table 2.

[0050] 3 parts by mass of organic resin, wherein the content of acrylic resin, PVB resin and ethyl cellulose is 4:2:1.

[0051] 16 parts by mass of solvent, wherein the content of diethylene glycol butyl ether, diethylene glycol butyl ether acetate and divalent acid ester is 2:1:2.

[0052] 1 part by mass of additive; wherein the content of phosphate ester dispersant and organic silicon leveling agent is 10:1.

[0053] The above components are placed in a dispersing agent for dispersion treatment for 30 min; the dispersed paste is ground and dispersed again on a three-roll grinding machine, and the viscosity of the paste is controlled at 15 Pa·s to obtain the laminated aluminum paste.

[0054] The laminated aluminum paste is further laminated on the silver grid lines, and the aluminum grid lines are formed after sintering at 600°C. The resistivity is 1.60×10 -5 , the silver-aluminum lapping resistance at the main grid is 0.62Ω, the PL composite is 113fA / cm 2 , the 3M adhesion is excellent, and after boiling for 20 min, the 3M adhesion is excellent and there is no falling off.

[0055] Example 2 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.

[0056] 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.

[0057] Example 3 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.

[0058] 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.

[0059] Example 4 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.

[0060] 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.

[0061] Example 5 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.

[0062] Further, the laminated aluminum paste is laminated on the silver gate line, and an aluminum gate line is formed by sintering at 600°C. The resistivity of the aluminum gate line is 1.58*10 -5 , the silver-aluminum overlap resistance at the main gate is 0.43Ω, the PL recombination is 45fA / cm 2 , the 3M adhesion is excellent, and the 3M adhesion is excellent after boiling for 20 minutes, without falling off.

[0063] Comparative Example 1 The formula of the laminated aluminum paste of the present 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.

[0064] Further, the laminated aluminum paste is laminated on the silver gate line, and an aluminum gate line is formed by sintering at 600°C. The resistivity of the aluminum gate line is 1.54*10 -5 , the silver-aluminum overlap resistance at the main gate is 2.35Ω, the PL recombination is 302fA / cm 2 , the 3M adhesion is excellent, and the 3M adhesion is excellent after boiling for 20 minutes, without falling off.

[0065] Comparative Example 2 The formula of the laminated aluminum paste of the present 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 first high-melting point glass powder.

[0066] Further, the laminated aluminum paste is laminated on the silver gate line, and an aluminum gate line is formed by sintering at 600°C. The resistivity of the aluminum gate line is 2.17*10 -5 , the silver-aluminum overlap resistance at the main gate is 0.48Ω, the PL recombination is 58fA / cm 2 , the 3M adhesion is good, and the 3M adhesion is good after boiling for 20 minutes, with individual falling off phenomenon.

[0067] Comparative Example 3 The formula of the laminated aluminum paste of the present 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 second high-melting point glass powder.

[0068] Further, the laminated aluminum paste is laminated on the silver gate line, and an aluminum gate line is formed by sintering at 600°C. The resistivity of the aluminum gate line is 2.78*10 -5 , the silver-aluminum overlap resistance at the main gate is 0.4Ω, the PL recombination is 40fA / cm 2 , the 3M adhesion is medium, and the 3M adhesion is poor after boiling for 20 minutes, with partial falling off phenomenon.

[0069] Table 3 Aluminum paste formula of each example and comparative example

[0070] Table 4 Results of each example and comparative example

[0071] In summary, the comparison between Comparative Example 1 and Examples 1-5 shows that, in the system, without adding high-melting-point glass powder, the low-melting-point glass powder has a strong corrosion effect on the aluminum powder, and the aluminum liquid flows out and reacts with the silver grid line to produce a strong alloying reaction, the silver-aluminum lap joint resistance at the main grid is high, and the PL composite is high. The comparison between Comparative Examples 2 and 3 and Examples 1-5 shows that, when only high-melting-point glass powder is used, the melting amount is insufficient, and the Al2O3 oxide layer on the surface of the aluminum powder cannot be broken, the contact resistance between aluminum particles is large, which leads to a sharp rise in overall resistivity, and also hinders the combination between the aluminum paste and the silver grid line, resulting in insufficient interface bonding force, and stress cracking and falling off after boiling, which affects the service performance and life of the product. This shows that the combination of glass powder helps to reduce the resistivity, contact resistance and PL composite value, and the aluminum grid line and the silver grid line have good bonding force, and there is no falling off phenomenon after boiling, which can realize the replacement of part of the silver paste with aluminum paste, reduce the cost, and improve the comprehensive performance of the grid line.

[0072] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the present 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; 0.8-5 parts by weight of glass powder; 2-5 parts by weight of organic resin; 15-20 parts by weight of solvent; 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.

2. The laminated aluminum paste according to claim 1, characterized in that, The melting point of the low-melting-point glass powder is 560℃~600℃.

3. The laminated aluminum paste according to claim 2, 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.

4. The laminated aluminum paste according to claim 1, characterized in that, The high melting point glass powder has a melting point of 680℃~725℃.

5. The laminated aluminum paste according to claim 4, 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.

6. The laminated aluminum paste according to any one of claims 1 to 5, characterized in that, The aluminum powder comprises 38-45 parts by weight of primary aluminum powder and 55-62 parts by weight of secondary aluminum powder.

7. The laminated aluminum paste according to claim 6, characterized in that, 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%.

8. The laminated aluminum paste according to any one of claims 1 to 5, 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.

9. A method for preparing the laminated aluminum paste as described in any one of claims 1 to 8, 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.

10. 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 8 at 600°C.

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