A BC battery silver-nickel conductive paste and its preparation method

Abstract

The present invention discloses a silver-nickel conductive paste for BC cells and its preparation method, belonging to the technical field of photovoltaic cells; by weight percentage, the raw material composition is: 39-69% of micron silver powder, 20-50% of modified nickel, 2-6% of glass powder, 0.1-10% of dispersant, 0-1% of silicone oil, and the balance is organic carrier; the modified nickel is elemental nickel powder subjected to modification treatment, and the modification treatment methods are surface organic modification and ball milling modification, or surface inorganic modification and ball milling modification. The present invention uses nickel powder to replace part of the silver powder, and the prepared conductive silver-nickel paste is used for BC cells, significantly reducing the cost, having high reliability, and the conversion efficiency is better than or equivalent to that of traditional all-silver electrode pastes.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic cells, and in particular to a silver-nickel conductive paste for a BC cell and a preparation method thereof. Background Art

[0002] Back contact (BC) cells refer to a type of solar cell in which both the emitter electrode and the base electrode are located on the back of the cell. With the advantages of relatively few process steps, high conversion efficiency, and beautiful appearance, it is a cell technology with great potential and a bright future. However, due to its relatively high manufacturing cost, especially the high cost of metallized conductive paste, the large-scale promotion of BC cells has a certain impact. Photovoltaic cell conductive silver paste, especially high-temperature sintering process cells, currently generally use silver paste to form conductive electrodes, which is costly. Some low-temperature cell technologies, such as HJT, use copper paste or silver-coated copper paste as conductive paste, but copper diffuses quickly in silicon, which can easily cause low cell efficiency and abnormality. Nickel diffuses slowly in silicon and is cheap. Using base metal nickel instead of silver powder can significantly reduce the cost of cell manufacturing, which is of great positive significance to the sustainable development of the photovoltaic industry and the entire green energy industry.

[0003] Patent publication number CN 118367063A, uses silver-coated nickel powder to partially replace silver powder for TOPCon battery electrode slurry. Although it reduces the cost to a certain extent, the cost of silver-coated nickel is still high. Patent publication number CN114334215A, an electrode slurry for ohmic contact of the P-type emitter region of a silicon solar cell, the base metal powder is mainly aluminum powder prepared by N2 protected atomization method, and some other base metal powders. Although the aluminum powder used in the invention helps to improve the contact ability, it also inevitably brings about the loss of Voc and the deterioration of acid resistance, and is limited to use in the P-type emitter region.

[0004] Nickel has a relatively higher resistance than silver, and oxidation during high temperature causes the resistance to increase further; it is difficult to disperse and affects printing. Summary of the invention

[0005] In order to reduce costs and minimize the problem of low battery conversion efficiency caused by high resistance due to oxidation of base metal nickel, the present invention provides a BC battery silver-nickel conductive paste and a preparation method thereof. The present invention uses nickel powder to replace part of the silver powder to prepare a conductive silver-nickel paste for BC batteries, which significantly reduces costs, has high reliability, and has a conversion efficiency that is better than or equivalent to that of traditional all-silver electrode paste.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention discloses a silver-nickel conductive paste for BC batteries, wherein the raw materials are composed of the following by weight percentage:

[0008] 39 - 69% of micron silver powder, 20 - 50% of nickel or modified nickel, 2 - 6% of glass powder, 0.1 - 10% of dispersant, 0 - 1% of silicone oil, and the balance is organic carrier.

[0009] In one embodiment of the present invention, the average particle size of the micron silver powder is 1 - 3 μm, and the tapped density is not less than 5.8 g / cm 3 。

[0010] In one embodiment of the present invention, the nickel is elemental nickel powder or nickel - based alloy powder; the modified nickel is elemental nickel powder or nickel - based alloy powder that has been modified, with an average particle size of 1 - 20 μm and a tapped density not less than 2 g / cm 3 。

[0011] In one embodiment of the present invention, the nickel - based alloy powder is one or more of nickel - chromium - boron - silicon, nickel - cobalt - chromium, nickel - chromium - aluminum - yttrium, nickel - titanium, nickel - iron, and nickel - chromium - iron alloy.

[0012] In one embodiment of the present invention, preferably, the average particle size of the modified nickel is 2 - 10 μm.

[0013] In one embodiment of the present invention, more preferably, the average particle size of the modified nickel is 2 - 8 μm.

[0014] In one embodiment of the present invention, the oxygen content of the modified nickel is not higher than 5000 ppm; preferably, not higher than 500 ppm.

[0015] In one embodiment of the present invention, the modification method of the modified nickel is surface organic modification, surface inorganic modification, surface organic modification and ball - milling modification, or surface inorganic modification and ball - milling modification.

[0016] The surface organic modifier is fatty acid and coupling agent; the fatty acid is one or more of oleic acid, stearic acid, and lauric acid; the coupling agent is one or more of silane coupling agent, titanate coupling agent, and aluminate coupling agent.

[0017] The surface inorganic modifier is one or more of nano - silver powder, nano - tin powder, nano - tungsten powder, nano - titanium powder, nano - aluminum powder, graphite powder, graphene powder, graphite fiber, and carbon nanotube.

[0018] In one embodiment of the present invention, the method of surface organic modification is:

[0019] The surface organic modifiers include coupling agents and fatty acids. By mass ratio, nickel powder or nickel-based alloy powder is mixed with absolute ethanol at a ratio of 1:2. The temperature is controlled at 20 - 25 °C in a water bath, and ultrasonic vibration at 25 - 35 kHz is applied for 30 min. Then it is transferred to a stirring kettle, the temperature is maintained at 20 - 25 °C, and stirred at 300 rpm. While stirring, 2 - 5% of a coupling agent (one of silane coupling agent, titanate coupling agent, or aluminate coupling agent) is dropped in, and the rotation speed remains unchanged while stirring for 15 min; then 2 - 5% of fatty acid (oleic acid, stearic acid, or lauric acid) is added while stirring, and stirred for 45 min. After stirring, the surface ethanol is poured out and dried in an oven at 50 °C for 3 h with heat preservation.

[0020] In an embodiment of the present invention, the method for surface inorganic modification is as follows:

[0021] Mix evenly according to the mass ratio of nickel powder or nickel-based alloy powder : surface inorganic modifier = 10 - 100 : 1, ball mill for 30 - 180 min, rotation speed 150 - 250 rpm, the weight ratio of nickel powder or nickel-based alloy powder to zirconium balls is 1 : 1 - 6. After ball milling, the modified material can be adsorbed and coated on the surface of nickel powder better, effectively playing a role in preventing nickel powder from oxidation.

[0022] In an embodiment of the present invention, the mass ratio of nickel powder or nickel-based alloy powder to surface inorganic modifier is 40 - 70 : 1.

[0023] In an embodiment of the present invention, the weight ratio of nickel powder or nickel-based alloy powder to zirconium balls is 1 : 3 - 5.

[0024] In an embodiment of the present invention, the diameter of zirconium balls is 1 - 10 mm. Preferably, the diameter of zirconium balls is 1 - 3 mm.

[0025] In an embodiment of the present invention, the method for ball milling modification is as follows:

[0026] The nickel powder or nickel-based alloy powder that has undergone surface organic or inorganic modification is mixed evenly with an antioxidant in a ball milling manner. After mixing evenly, ball mill for 30 - 180 min, 150 - 250 rpm, the weight ratio of the nickel powder or nickel-based alloy powder that has undergone surface organic or inorganic modification to zirconium balls is 1 : 1 - 6, and vibrate and filter through a 1500 - mesh sieve to obtain modified nickel.

[0027] In an embodiment of the present invention, by weight percentage, the nickel powder or nickel-based alloy powder that has undergone surface organic or inorganic modification is 90 - 99.9 wt%, and the antioxidant is 0.1 - 10%.

[0028] The antioxidant is one or more of benzotriazole, 1 - phenyl - 5 - mercapto - 1,2,3,4 - tetrazole, 8 - hydroxyquinoline, silicon powder, boron powder, chromium powder, and yttrium powder.

[0029] In one embodiment of the present invention, the weight ratio of nickel powder or nickel-based alloy powder surface-modified with organic or inorganic substances to zirconia beads is 1:3-5.

[0030] In one embodiment of the present invention, the diameter of the zirconia beads is 1-10 mm, preferably 1-3 mm.

[0031] In one embodiment of the present invention, the melting point of the glass powder is not higher than 800 °C, and the average particle size is 1-3 μm.

[0032] In the glass powder, by molar percentage, PbO is 30-40%, TeO2 is 20-50%, SiO2 is 0-10%, Li2O is 0-2%, other alkali metal oxides and alkaline earth metal oxides are 3-10%, and other metal and non-metal oxides are 10-40%.

[0033] In one embodiment of the present invention, in the glass powder, by molar percentage, PbO is 30%, TeO2 is 45%, SiO2 is 0.5%, Bi2O3 is 7.5%, WO3 is 5%, ZnO is 5%, Na2O is 5%, and Li2O is 2%.

[0034] In one embodiment of the present invention, the preparation method of the glass powder is as follows: by molar percentage, TeO2 is 45%, PbO is 30%, Bi2O3 is 7.5%, SiO2 is 0.5%, WO3 is 5%, ZnO is 5%, Na2O is 5%, and Li2O is 2%.

[0035] Weigh the above raw materials, mix them evenly, add them to an alumina crucible, place them in a muffle furnace, heat to 1000 °C, keep warm for 30-40 min, pour the melted glass into deionized water, quench, dry, and ball mill to obtain glass powder with D50 less than 2 μm and Dmax less than 7 μm.

[0036] In one embodiment of the present invention, Na2O and Li2O participate in the preparation of the glass powder in the forms of Na2CO3 and Li2CO3, respectively.

[0037] In one embodiment of the present invention, the dispersant is one or more of BYK-110, BYK-111, ED120, ED350, ED380, ED403, AD-374M, AKM-0531, TDO, TEGO Dispers 670, and TEGO Dispers 671.

[0038] In one embodiment of the present invention, the silicone oil is one or more of alkyl-modified silicone oil, phenyl-modified silicone oil, fluorine-modified silicone oil, amino-modified silicone oil, and polydimethylsiloxane.

[0039] In one embodiment of the present invention, the silicone oil is one or more of PMX-200, H201, and KF54, and the viscosity is 20-300 CS.

[0040] In one embodiment of the present invention, the organic carrier comprises 0.1-30% resin, 60-90% organic solvent, and 0.1-10% thixotropic agent;

[0041] The resin is at least three of acrylic resin, polyurethane resin, rosin resin, ethyl cellulose, styrene-acrylic resin, polyvinyl butyral, polyvinyl pyrrolidone, styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-butene-styrene block copolymer (SEBS), poly-α-methylstyrene, epoxy resin, and cellulose acetate butyrate;

[0042] The organic solvent is at least three of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol methyl ether acetate, terpineol, oleic acid, diethylene glycol butyl ether, diethylene glycol dibutyl ether, alcohol ester 12, alcohol ester 16, dimethyl adipate, dioctyl adipate, benzyl benzoate, and dimethyl phthalate;

[0043] The thixotropic agent is one or more of fumed silica, polyamide wax, and hydrogenated castor oil.

[0044] In one embodiment of the present invention, based on 100% of the organic carrier, the resin is a mixture of 5% CAB381-2, 8% G1652, 10% PVB-16HH, and 5% STD-4; the organic solvent is a mixture of 16% diethylene glycol butyl ether acetate, 20% alcohol ester 12, 16% alcohol ester 16, 10% benzyl benzoate, 5% dimethyl phthalate, and 5% polyamide wax.

[0045] In one embodiment of the present invention, the preparation method of the organic carrier is: weighing the resin, organic solvent, and thixotropic agent in proportion, mixing and heating to 80 °C, with a rotation speed not less than 1000 rpm, and keeping warm and stirring for 2-5 h to obtain the organic carrier.

[0046] The second object of the present invention is to provide a preparation method of the above-mentioned silver-nickel conductive paste for BC battery, comprising the following steps:

[0047] Mix 15-75% micron silver powder, 10-70% nickel or modified nickel, 2-6% glass powder, 0.1-10% dispersant, 0-1% silicone oil, and the balance is the organic carrier evenly, and then roll it with a three-roll mill to obtain the silver-nickel conductive paste for BC battery.

[0048] The beneficial technical effects of the present invention are as follows:

[0049] The nickel powder or nickel-based alloy powder used in the present invention has low cost, good stability, and will not have a significant impact on Voc. It can be used in both the P-type emitter and N-type emitter pastes of BC cells, and has obvious advantages.

[0050] Modifying the nickel surface has a good effect on the dispersion and stability of nickel in the paste, and can also improve the oxidation resistance of nickel under normal and high temperature conditions.

[0051] The ball milling method can further disperse the agglomerated nickel powder and mix the antioxidant evenly with the nickel powder. The extremely large nickel powder or nickel-based alloy powder particles are removed by screen filtration to avoid the influence of these large particles on the printing process. The evenly dispersed nickel powder or nickel-based alloy powder has a relatively small impact on the resistance. By mixing the antioxidant and nickel powder evenly by ball milling, the antioxidant is preferably adsorbed on the surface of the nickel powder or nickel-based alloy powder, and the role of the antioxidant can be effectively exerted to improve the oxidation resistance of the nickel powder or nickel-based alloy powder.

[0052] The present invention selects base metal nickel powder or nickel-based alloy powder to replace part of the silver powder to make silver-nickel paste for use in the P-type emitter and N-type emitter of BC cells. Compared with traditional silver paste or other silver-coated nickel paste or silver-coated copper paste, it has lower cost and higher efficiency. First, the nickel powder or nickel-based alloy powder with an average particle size of 1-20 μm, preferably 2-8 μm, is selected in the present invention. This kind of nickel powder or nickel-based alloy powder has good dispersion and low oxidation degree during the high-temperature process. Secondly, through the organic or inorganic modification of the surface of the nickel powder or nickel-based alloy powder, the first layer of antioxidant protection layer is formed. The modified nickel powder or nickel-based alloy powder and the antioxidant are mixed evenly by ball milling to form the second layer of antioxidant protection layer. Finally, silver powder with appropriate sintering activity, glass powder with good contact ability, organic carrier and other additives are selected to obtain silver-nickel paste with low cost and high efficiency. Specific embodiments

[0053] The present invention will be specifically described below in conjunction with embodiments.

[0054] The raw material information used in the following examples or comparative examples is:

[0055] The micron silver powder is the silver powder of Jianbang Colloid New Materials with the model of 152-16, and the average particle size is 1-3 μm.

[0056] Glass powder, by molar percentage, TeO2 45%, PbO 30%, Bi2O3 7.5%, SiO2 0.5%, WO3 5%, ZnO 5%, Na2CO3 5%, Li2CO3 2%. Weigh the above raw materials, mix them evenly, add them to an alumina crucible, place them in a muffle furnace, heat to 1000 °C, hold for 30 - 40 min. Pour the melted glass into deionized water, quench, dry, and ball mill to obtain a glass powder with D50 less than 2 μm and Dmax less than 7 μm; the Tg of the glass powder is less than 350 °C, and the melting point is not higher than 800 °C.

[0057] Nickel powder: The model of Ningbo Bohuasi Nanomaterials Co., Ltd. is brofos-Ni-W01, with an average particle size of 1 μm and an oxygen content of less than 500 ppm; the model of Ningbo Bohuasi Nanomaterials Co., Ltd. is brofos-Ni-W05, with an average particle size of 5 μm and an oxygen content of less than 500 ppm.

[0058] Organic carrier: By mass percentage, weigh 5% CAB381-2, 8% G1652, 10% PVB-16HH, and 5% STD-4 and mix them as the resin component; weigh 16% diethylene glycol butyl ether acetate, 20% alcohol ester twelve, 16% alcohol ester sixteen, 10% benzyl benzoate, 5% dimethyl phthalate, and 5% polyamide wax and mix them as the organic solvent component; after mixing the resin, organic solvent, and thixotropic agent, set the rotation speed at 2000 rpm, stir and disperse at room temperature for 2 hours, heat to 80 °C, rotate at 2000 pm, and stir for 2 hours to obtain the organic carrier.

[0059] Graphite powder: 4000 - 8000 mesh, preferably 5000 mesh.

[0060] Carbon nanotubes: The length is 1 - 2 μm, and the diameter is 50 - 120 nm.

[0061] Comparative Example 1

[0062] A preparation method of a BC battery conductive paste, comprising the following steps:

[0063] By mass percentage, weigh 9.8% organic carrier, 4.5% glass powder, 85% silver powder (152 - 16), 0.2% dispersant (TEGO Dispers 670), 0.5% silicone oil (H201-50CS); mix the above raw materials evenly, and then roll them through a three-roll mill to obtain the conductive paste.

[0064] Comparative Example 2

[0065] A preparation method of a BC battery conductive paste, comprising the following steps:

[0066] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152 - 16), 20% nickel powder (brofos - Ni - W01), 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201 - 50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three - roll mill to obtain the conductive paste.

[0067] Comparative Example 3

[0068] A preparation method of a conductive paste for BC cells includes the following steps:

[0069] Weigh 7.3% organic carrier, 3.0% glass powder, 89% silver powder (152 - 16), 0.20% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201 - 50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three - roll mill to obtain the conductive paste.

[0070] Comparative Example 4

[0071] A preparation method of a conductive paste for BC cells includes the following steps:

[0072] Weigh 7.3% organic carrier, 3.0% glass powder, 69% silver powder (152 - 16), 20% nickel powder (brofos - Ni - W01), 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201 - 50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three - roll mill to obtain the conductive paste.

[0073] Example 1

[0074] A preparation method of a silver - nickel conductive paste for BC cells includes the following steps:

[0075] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152 - 16), 20% nickel powder (brofos - Ni - W05), 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201 - 50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three - roll mill to obtain the silver - nickel conductive paste.

[0076] Example 2

[0077] A preparation method of a silver - nickel conductive paste for BC cells includes the following steps:

[0078] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152-16), 20% surface organically modified nickel powder A, 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201-50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three-roll mill to obtain a silver-nickel conductive paste.

[0079] The preparation method of surface organically modified nickel powder A is as follows: Weigh 400 g of nickel powder (brofos-Ni-W05) and 800 g of absolute ethanol, mix them, control the temperature at 25 °C in a water bath, apply ultrasonic vibration at 30 kHz for 30 min, then transfer it to a stirring kettle, keep the temperature at 25 °C and the rotation speed at 300 rpm, and drop 10 g of silane coupling agent (KH550) while stirring, keep the rotation speed unchanged, and stir for 15 min; then add 10 g of oleic acid while stirring and stir for 45 min. After the stirring is completed, pour out the surface ethanol, dry it in an oven at 50 °C, and keep it warm for 3 h to obtain surface organically modified nickel powder A with a particle size D50 of 2-8 μm.

[0080] Example 3

[0081] A preparation method of a silver-nickel conductive paste for BC cells includes the following steps:

[0082] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152-16), 20% surface inorganically modified nickel powder B, 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201-50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three-roll mill to obtain a silver-nickel conductive paste.

[0083] The preparation method of surface inorganically modified nickel powder B is as follows: Weigh 400 g of nickel powder (brofos-Ni-W05), 10 g of 5000-mesh graphite powder, and 1200 g of zirconia balls with a diameter of 2 mm, set the rotation speed at 200 rpm, and ball mill for 60 min to obtain surface inorganically modified nickel powder B with a particle size D50 of 2-8 μm.

[0084] Example 4

[0085] A preparation method of a silver-nickel conductive paste for BC cells includes the following steps:

[0086] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152-16), 20% modified nickel powder C, 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201-50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three-roll mill to obtain a silver-nickel conductive paste.

[0087] The preparation method of modified nickel powder C is as follows: Weigh 200 g of surface organically modified nickel powder A, 6 g of silicon powder with a particle size of 1 μm (Brofos-Si-W01), and 400 g of zirconia balls with a diameter of 2 mm. Set the rotation speed at 200 rpm and mill for 60 min to obtain modified nickel powder C with a D50 particle size of 2 - 8 μm.

[0088] Example 5

[0089] A preparation method of silver-nickel conductive paste for BC cells includes the following steps:

[0090] Weigh 9.8% organic carrier, 4.5% glass powder, 65% silver powder (152 - 16), 20% modified nickel powder D, 0.2% dispersant (TEGO Dispers 670), and 0.5% silicone oil (H201 - 50CS) by mass percentage; mix the above raw materials evenly, and then roll them through a three-roll mill to obtain silver-nickel conductive paste.

[0091] The preparation method of modified nickel powder D is as follows: Weigh 200 g of surface inorganically modified nickel powder B, 6 g of silicon powder with a particle size of 1 μm (Brofos-Si-W01), and 800 g of zirconia balls with a diameter of 2 mm. Set the rotation speed at 200 rpm and mill for 60 min to obtain modified nickel powder D with a D50 particle size of 2 - 8 μm.

[0092] Example 6

[0093] Same as Example 1, the only difference is that the dosage of silver powder is 69%, the dosage of organic carrier is 7.3%, and the dosage of glass powder is 3.0%.

[0094] Example 7

[0095] Same as Example 2, the only difference is that the dosage of silver powder is 69%, the dosage of organic carrier is 7.3%, and the dosage of glass powder is 3.0%.

[0096] Example 8

[0097] Same as Example 3, the only difference is that the dosage of silver powder is 69%, the dosage of organic carrier is 7.3%, and the dosage of glass powder is 3.0%.

[0098] Example 9

[0099] Same as Example 4, the only difference is that the dosage of silver powder is 69%, the dosage of organic carrier is 7.3%, and the dosage of glass powder is 3.0%.

[0100] Example 10

[0101] Same as Example 5, the only difference is that the dosage of silver powder is 69%, the dosage of organic carrier is 7.3%, and the dosage of glass powder is 3.0%.

[0102] Example 11

[0103] Same as Example 10, except that the amount of silver powder (152-16) is 54% and the amount of modified nickel powder D is 35%.

[0104] Example 12

[0105] Same as Example 10, except that the amount of silver powder (152-16) is 39% and the amount of modified nickel powder D is 50%.

[0106] Example 13

[0107] Same as Example 4, except that the nickel powder modifier is changed from silicon powder to graphite powder (5000 mesh).

[0108] Example 14

[0109] Same as Example 4, except that the nickel powder modifier is changed from silicon powder to carbon nanotubes.

[0110] Test Example

[0111] The compositions of the conductive pastes obtained in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1 below. The conductive pastes obtained in Examples 1-5, Examples 13-14, and Comparative Examples 1-2 were screen-printed onto the P region of the BC cell using a fine-grid screen printing plate (the line width of the screen printing plate was 12 μm) by screen printing to obtain P-region fine grid lines with a line height of about 6 μm and a line width of about 32 μm. After sintering at 750 °C, the conversion efficiency of the cell was measured using a solar halm I-V tester; the test results are shown in Table 2 below.

[0112] Table 1

[0113]

[0114] Table 2

[0115]

[0116] The compositions of the conductive pastes obtained in Examples 6-10 and Comparative Examples 3-4 are shown in Table 3 below. The conductive pastes obtained in Examples 6-12 and Comparative Examples 3-4 were screen-printed onto the N region of the BC cell using a fine-grid screen printing plate (the line width of the screen printing plate was 12 μm) by screen printing to obtain N-region fine grid lines with a line height of about 6 μm and a line width of about 32 μm. After sintering at 750 °C, the conversion efficiency of the cell was measured using a solar halm I-V tester; the test results are shown in Table 4 below.

[0117] Table 3

[0118]

[0119] Table 4

[0120]

[0121] As can be seen from Tables 2 and 4, in the present invention, nickel powder is used to replace part of silver powder. After the nickel powder is modified, the prepared conductive silver-nickel paste is used for BC cells, and its conversion efficiency is better than that of traditional all-silver electrode pastes or reaches a comparable level.

[0122] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing well-known common sense also fall within the protection scope defined by the claims of the present invention.

Claims

1. A silver-nickel conductive paste for BC cells, characterized in that, By weight percentage, the raw material composition is as follows: 39 - 69% of micron silver powder, 20 - 50% of modified nickel, 2 - 6% of glass powder, 0.1 - 10% of dispersant, 0 - 1% of silicone oil, and the balance is organic carrier; The average particle size of the micron silver powder is 1 - 3 μm, and the tapped density is not less than 5.8 g / cm 3 ; The modified nickel is elemental nickel powder that has undergone modification treatment, with an average particle size of 2 - 8 μm and a tapped density of not less than 2 g / cm 3 ; The modification treatment method of the modified nickel is surface organic modification and ball milling modification, or surface inorganic modification and ball milling modification; The surface organic modifiers include fatty acids and coupling agents; the fatty acids are one or more of oleic acid, stearic acid, and lauric acid; the coupling agents are one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents; The surface inorganic modifiers are graphite powder with a mesh size of 5000 meshes, and one or more of carbon nanotubes with a length of 1 - 2 μm and a diameter of 50 - 120 nm; The glass powder, by molar percentage, has the composition: 45% of TeO2, 30% of PbO, 7.5% of Bi2O3, 0.5% of SiO2, 5% of WO3, 5% of ZnO, 5% of Na2CO3, and 2% of Li2CO3.

2. The silver-nickel conductive paste for BC battery according to claim 1, wherein The method of ball milling modification is as follows: The nickel powder modified by surface organic or inorganic modification is mixed evenly with an antioxidant by ball milling. After mixing evenly, ball milling is carried out for 30 - 180 min at 150 - 250 rpm. The weight ratio of the nickel powder modified by surface organic or inorganic modification to the zirconia balls is 1:1 - 6, and vibration filtration is carried out through a 1500 - mesh sieve to obtain the modified nickel.

3. The silver-nickel conductive paste for BC battery according to claim 1, wherein The melting point of the glass powder is not higher than 800 °C, and the average particle size is 1 - 3 μm.

4. The silver-nickel conductive paste for BC battery according to claim 1, wherein, In the glass powder, by molar percentage, PbO is 30 - 40%, TeO2 is 20 - 50%, SiO2 is 0 - 10%, Li2O is 0 - 2%, other alkali metal oxides and alkaline earth metal oxides are 3 - 10%, and other metal and non - metal oxides are 10 - 40%.

5. The BC battery silver-nickel conductive paste according to claim 1, characterized in that, The dispersant is one or more of BYK - 110, BYK - 111, ED120, ED350, ED380, ED403, AD - 374M, AKM - 0531, TDO, TEGO Dispers 670, and TEGO Dispers 671.

6. The BC cell silver-nickel conductive paste according to claim 1, wherein, The silicone oil is one or more of alkyl - modified silicone oil, phenyl - modified silicone oil, fluorine - modified silicone oil, amino - modified silicone oil, and polydimethylsiloxane.

7. The silver-nickel conductive paste for BC battery according to claim 1, wherein The organic carrier contains 0.1 - 30% of resin, 60 - 90% of organic solvent, and 0.1 - 10% of thixotropic agent; The resin is at least three of acrylic resin, polyurethane resin, rosin resin, ethyl cellulose, styrene - acrylic resin, polyvinyl butyral, polyvinyl pyrrolidone, SEPS, SEBS, poly(α - methylstyrene), epoxy resin, and cellulose acetate butyrate; The organic solvents are at least three of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol methyl ether acetate, terpineol, oleic acid, diethylene glycol butyl ether, diethylene glycol dibutyl ether, alcohol ester 12, alcohol ester 16, dimethyl adipate, dioctyl adipate, benzyl benzoate, and dimethyl phthalate; The thixotropic agent is one or more of fumed silica, polyamide wax, and hydrogenated castor oil.

8. The preparation method of the BC battery silver-nickel conductive paste according to any one of claims 1-7, characterized in that, It includes the following steps: Mix 15 - 75% micron silver powder, 10 - 70% nickel or modified nickel, 2 - 6% glass powder, 0.1 - 10% dispersant, 0 - 1% silicone oil, with the balance being an organic carrier, and mix evenly. Then roll it with a three-roll mill to obtain the silver-nickel conductive paste for BC cells.

9. The P-region fine grid line made of the BC battery silver-nickel conductive paste according to any one of claims 1-7, characterized in that, The conductive paste uses a silk screen printing fine grid screen with a screen line width of 12 μm. Through the silk screen printing method, it is printed on the P region of the BC cell to obtain a P region fine grid line with a line height of 6 μm and a line width of 32 μm.

10. The N-region fine grid line made of the BC battery silver-nickel conductive paste according to any one of claims 1-7, characterized in that, The conductive paste uses a silk screen printing fine grid screen with a screen line width of 12 μm. Through the silk screen printing method, it is printed on the N region of the BC cell to obtain a P region fine grid line with a line height of 6 μm and a line width of 32 μm.

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