Battery piece welding method, photovoltaic module and photovoltaic power generation system

Abstract

The invention provides a battery piece welding method, a photovoltaic module and a photovoltaic power generation system, and relates to the technical field of battery piece welding. The welding method of the battery piece comprises the following steps: carrying out first coating on the surface of the battery piece by using a screen plate, and drying to obtain a coated battery piece; performing second coating on the bare copper strip to obtain a coated copper strip; and placing the coated copper strip on the coated battery piece for welding. According to the welding method of the battery piece, the bare copper strip replaces the metal coating to wrap the copper strip for welding, the cost of the welding material coating in the welding process can be reduced, and the welding quality is improved.

Description

Technical Field

[0001] This application relates to the field of solar cell welding technology, and more particularly to a solar cell welding method, a photovoltaic module, and a photovoltaic power generation system. Background Technology

[0002] In recent years, photovoltaic power generation has received widespread attention as a form of clean energy generation. With the development and breakthroughs in crystalline silicon solar cell and photovoltaic module technology, improving the photoelectric conversion efficiency of such solar cells and photovoltaic modules and reducing their manufacturing costs have become the main goals of the photovoltaic industry.

[0003] Currently, in traditional crystalline silicon solar cells, the positive and negative electrodes are located on opposite sides of the solar cell. The solder ribbon is an important raw material in photovoltaic modules, serving as an electrical connection and transmitting the current collected by the solar cell's main grid. The mainstream welding process in the industry is hot stringing, and the solder ribbon structure used in the welding process is copper strip coated with metals such as tin-lead or tin-lead-bismuth alloy, which is relatively expensive.

[0004] Therefore, how to achieve the welding of bare copper wire and further reduce the cost of solder strip is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a method for welding solar cells, a photovoltaic module, and a photovoltaic power generation system to solve the above-mentioned problems.

[0006] To achieve the above objectives, the first aspect of this application provides a method for welding solar cells, comprising:

[0007] A first coating is applied to the surface of the solar cell using a stencil, followed by drying to obtain the coated solar cell.

[0008] A second coating is applied to the bare copper strip to obtain a coated copper strip.

[0009] The coated copper strip is placed on the coated battery cell for welding.

[0010] Optionally, solder paste may be used for the first coating;

[0011] The raw materials of the solder paste include an alloy, which, by weight, comprises: 18%-65% tin, 20%-45% lead, 2%-15% silver, and 10%-37% bismuth.

[0012] Optionally, the solder paste may also include rosin and organic acids as raw materials;

[0013] The mass of the rosin is 1%-5% of the total mass of the solder paste;

[0014] The organic acid constitutes 2%-8% of the total mass of the solder paste.

[0015] Optionally, flux may be used for the second coating;

[0016] The flux comprises, by weight, 95%-99% solvent, 0.3%-0.5% film-forming agent, 1.5%-2.0% activator, and 0.2%-0.3% dispersant.

[0017] Optionally, the welding method of the battery cells satisfies at least one of the following conditions:

[0018] A. The solvent includes ethanol and / or isopropanol;

[0019] B. The film-forming agent includes rosin resin;

[0020] C. The activator includes organic acids;

[0021] D. The dispersant includes surfactants.

[0022] Optionally, the first coating includes:

[0023] The first coating and first drying are performed on the front or back of the battery cell to obtain a battery cell with single-sided coating;

[0024] The other side of the single-sided coated battery cell is then subjected to the first coating and the second drying process to obtain the coated battery cell shown.

[0025] Optionally, the welding method of the battery cells satisfies at least one of the following conditions:

[0026] A. The temperature of the first drying process is 170℃-300℃, and the time is 2s-30s;

[0027] B. The second drying temperature is 170℃-250℃, and the time is 3s-50s.

[0028] Optionally, the welding temperature is 110℃-280℃ and the welding time is 1.5s-3s.

[0029] A second aspect of this application provides a photovoltaic module comprising a plurality of solar cells welded together using the aforementioned solar cell welding method.

[0030] A third aspect of this application provides a photovoltaic power generation system, including the aforementioned photovoltaic module.

[0031] Compared with the prior art, the beneficial effects of this application include:

[0032] The battery cell welding method provided in this application involves, firstly, applying a first coating to the surface of the battery cell, which helps improve the welding pull-out force, increase process yield, and further enhance aging resistance under extreme outdoor conditions; secondly, applying a second coating to the bare copper strip removes oxides from the surface of the bare copper strip and forms a protective film on it, reducing the surface tension of the coated battery cell and making the adhesion between the coated battery cell and the coated copper strip stronger, thus allowing the bare copper strip to replace the metal coating for welding; this welding method can reduce the cost of welding material coatings during the welding process and improve welding quality.

[0033] The photovoltaic module provided in this application eliminates the use of coating on the solder ribbon during the welding process, thereby reducing the cost of the photovoltaic module. Furthermore, by applying solder paste to the cells, the mechanical properties of the solder joints are not reduced. Since the color of copper is different from that of conventional solder paste, the appearance of the module can be further improved.

[0034] The photovoltaic power generation system provided in this application has a lower cost and no further quality risks at the power generation system end. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0036] Figure 1 This is a schematic diagram of the TOPCon bifacial battery used in Example 1;

[0037] Figure 2 This is a schematic diagram of the stencil used in Example 1;

[0038] Figure 3 The flowchart illustrates the welding method for the battery cells provided in Example 1. Detailed Implementation

[0039] As used in this article:

[0040] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0041] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0042] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0043] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0044] "Parts by mass" is a basic unit of measurement used to express the total mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the masses of all components is not limited to 100 parts.

[0045] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0046] The first aspect of this application provides a method for welding battery cells, comprising:

[0047] A first coating is applied to the surface of the solar cell using a stencil, followed by drying to obtain the coated solar cell.

[0048] A second coating is applied to the bare copper strip to obtain a coated copper strip.

[0049] The coated copper strip is placed on the coated battery cell for welding.

[0050] In some embodiments, solder paste is used for the first coating;

[0051] The raw materials of the solder paste include an alloy, which, by weight, comprises: 18%-65% tin, 20%-45% lead, 2%-15% silver, and 10%-37% bismuth.

[0052] Optionally, based on the total mass of the alloy, tin can be any value between 18%, 20%, 30%, 40%, 50%, 60%, 65%, or 18%-65%; lead can be any value between 20%, 25%, 30%, 35%, 40%, 45%, or 20%-45%; silver can be any value between 2%, 5%, 10%, 15%, or 2%-15%; and bismuth can be any value between 10%, 20%, 30%, 37%, or 10%-37%.

[0053] It is important to note that different ratios of tin, lead, silver, and bismuth can produce alloys with different melting points, which helps to reduce the welding temperature. The higher the bismuth content, the lower the melting point of the corresponding alloy, and the lower the welding temperature required, which can improve the process yield and mitigate phenomena such as grid breakage caused during component welding.

[0054] In some embodiments, the solder paste may further include rosin and organic acids as raw materials;

[0055] The mass of the rosin is 1%-5% of the total mass of the solder paste;

[0056] Optionally, the rosin content may be 1%, 2%, 3%, 4%, 5%, or any value between 1% and 5% of the total solder paste content;

[0057] The organic acid constitutes 2%-8% of the total mass of the solder paste.

[0058] Optionally, the organic acid may be any value between 2%, 3%, 4%, 5%, 6%, 7%, 8% or 2%-8% of the total mass of the solder paste.

[0059] In some embodiments, flux is used for the second coating;

[0060] The flux comprises, by weight, 95%-99% solvent, 0.3%-0.5% film-forming agent, 1.5%-2.0% activator, and 0.2%-0.3% dispersant.

[0061] Optionally, the flux raw materials, based on a total mass of 100%, may include: solvents of any value between 95%, 96%, 97%, 98%, 99%, or 95%-99%; film-forming agents of any value between 0.3%, 0.4%, 0.5%, or 0.3%-0.5%; activators of any value between 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or 1.5%-2.0%; and dispersants of any value between 0.2%, 0.25%, 0.3%, or 0.2%-0.3%.

[0062] It is important to note that flux can remove oxides from the surface of the copper strip and form a protective film on the copper strip to prevent re-oxidation. It can also reduce the surface tension of the solder paste and improve the wettability of the solder paste on the surface of the battery cell.

[0063] In some embodiments, the welding method of the battery cells satisfies at least one of the following conditions:

[0064] A. The solvent includes ethanol and / or isopropanol;

[0065] It is important to note that the solvent acts as a carrier, dissolving other raw materials.

[0066] B. The film-forming agent includes rosin resin;

[0067] It should be noted that rosin resin can protect copper strips from oxidation and remove oxides from their surface.

[0068] C. The activator includes organic acids;

[0069] It should be noted that organic acids can remove oxides from their surface.

[0070] D. The dispersant includes a surfactant;

[0071] In some embodiments, the surfactant includes one or more of organic acids, organic amines, and organic halides.

[0072] It should be noted that surfactants increase solderability and improve the spread rate.

[0073] In some embodiments, the first coating includes:

[0074] The first coating and first drying are performed on the front or back of the battery cell to obtain a battery cell with single-sided coating;

[0075] The other side of the single-sided coated battery cell is then subjected to the first coating and the second drying process to obtain the coated battery cell shown.

[0076] In some embodiments, the welding method of the battery cells satisfies at least one of the following conditions:

[0077] A. The temperature of the first drying process is 170℃-300℃, and the time is 2s-30s;

[0078] Optionally, the temperature of the first drying can be any value between 170℃, 200℃, 250℃, 300℃ or 170℃-300℃, and the time can be any value between 2s, 10s, 20s, 30s or 2s-30s.

[0079] B. The second drying temperature is 170℃-250℃, and the time is 3s-50s.

[0080] Optionally, the temperature of the second drying can be any value between 170℃, 200℃, 250℃ or 170℃-250℃, and the time can be any value between 3s, 10s, 20s, 30s, 40s, 50s or 3s-50s.

[0081] It should be noted that the second drying temperature is lower than the first drying temperature. This is mainly because in some processes, the first drying is performed after the solder paste is applied to the front or back of the cell, and then the other side is coated. If the second drying temperature is higher, it will melt the solder paste obtained from the first drying.

[0082] In some embodiments, the welding temperature is 110℃-280℃ and the welding time is 1.5s-3s.

[0083] Optionally, the welding temperature can be any value between 110℃, 150℃, 200℃, 250℃, 280℃ or 110℃-280℃, and the time can be any value between 1.5s, 2s, 2.5s, 3s or 1.5s-3s.

[0084] It is important to note that when the soldering temperature is between 110℃ and 280℃ and the time is between 1.5s and 3s, the solder paste forms a metal layer. During this process, copper, tin, and silver undergo an intermetallic chemical reaction to generate Ag3Sn and Cu5Sn6. The optimal thickness of this metal layer is 1μm-3μm. The metal layer is relatively brittle. If the soldering time is too long or the soldering temperature is too high, the thickness of the metal layer will be too thick, which will affect the mechanical properties of the solder joint.

[0085] A second aspect of this application provides a photovoltaic module comprising a plurality of solar cells welded together using the aforementioned solar cell welding method.

[0086] A third aspect of this application provides a photovoltaic power generation system, including the aforementioned photovoltaic module.

[0087] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0088] Example 1

[0089] This embodiment provides a method for welding battery cells, including:

[0090] S1: Uses TOPCon bifacial solar cells, such as... Figure 1 As shown, solder paste is printed on the front side of the battery cell, using methods such as... Figure 2 The stencil shown evenly prints solder paste onto the PAD points of the battery cell. Figure 1 The black square area with intersecting black and thin lines is used to dry the printed battery cells. The drying temperature is 220℃ and the drying time is 6s. The temperature distribution uniformity of the drying equipment is ±10℃.

[0091] S2: Following the steps above, solder paste is printed and dried on the back of the battery cell to obtain the coated battery cell;

[0092] S3: Apply flux to bare copper wire to obtain coated copper strip;

[0093] S4: Place the coated copper strip on the front and back of the coated cell and heat it at 220°C for 2.5 seconds to complete the welding.

[0094] The welding process steps for this battery cell are as follows: Figure 3 As shown.

[0095] The raw materials for solder paste include alloys, rosin, and organic acids; the rosin accounts for 2% of the total mass of the solder paste; the organic acids account for 3% of the total mass of the solder paste, and the remainder is alloys.

[0096] The alloy, by total mass of 100%, comprises: 42% tin, 43% lead, 1% silver, and 14% bismuth.

[0097] The flux raw materials, based on a total mass of 100%, include: solvent (ethanol) 98%, film-forming agent (rosin resin) 0.4%, activator (organic acid) 1.7%, and dispersant (surfactant) 0.3%.

[0098] The organic acid is sulfonic acid, and the surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol polyoxyethylene ether.

[0099] Example 2

[0100] This embodiment provides a method for welding battery cells, including:

[0101] S1: Uses TOPCon bifacial solar cells, such as... Figure 1 As shown, solder paste is printed on the front side of the battery cell, using methods such as... Figure 2 The stencil shown evenly prints solder paste onto the PAD points of the battery cell. Figure 1 The white square area with intersecting fine white lines is used to dry the printed battery cells. The drying temperature is 160℃ and the drying time is 15s. The temperature distribution uniformity of the drying equipment is ±10℃.

[0102] S2: Following the steps above, solder paste is printed and dried on the back of the battery cell to obtain the coated battery cell;

[0103] S3: Apply flux to bare copper wire to obtain coated copper strip;

[0104] S4: Place the coated copper strip on the front and back of the coated cell and heat it at 220°C for 2.5 seconds to complete the welding.

[0105] The raw materials for solder paste include alloys, rosin, and organic acids; the rosin accounts for 2% of the total mass of the solder paste; the organic acids account for 3% of the total mass of the solder paste, and the remainder is alloys.

[0106] The alloy, by total mass of 100%, comprises: 42% tin, 43% lead, 1% silver, and 14% bismuth.

[0107] The flux raw materials, based on a total mass of 100%, include: solvent (ethanol) 98%, film-forming agent (rosin resin) 0.4%, activator (organic acid) 1.7%, and dispersant (surfactant) 0.3%.

[0108] The organic acid is sulfonic acid, and the surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol polyoxyethylene ether.

[0109] Example 3

[0110] This embodiment provides a method for welding battery cells, including:

[0111] S1: Uses TOPCon bifacial solar cells, such as... Figure 1 As shown, solder paste is printed on the front side of the battery cell, using methods such as... Figure 2 The stencil shown evenly prints solder paste onto the PAD points of the battery cell. Figure 1 The white square area with intersecting fine white lines is used to dry the printed battery cells. The drying temperature is 260℃ and the drying time is 4s. The temperature distribution uniformity of the drying equipment is ±10℃.

[0112] S2: Following the steps above, solder paste is printed and dried on the back of the battery cell to obtain the coated battery cell;

[0113] S3: Apply flux to bare copper wire to obtain coated copper strip;

[0114] S4: Place the coated copper strip on the front and back of the coated cell and heat it at 220°C for 2.5 seconds to complete the welding.

[0115] The raw materials for solder paste include alloys, rosin, and organic acids; the rosin accounts for 2% of the total mass of the solder paste; the organic acids account for 3% of the total mass of the solder paste, and the remainder is alloys.

[0116] The alloy, by total mass of 100%, comprises: 42% tin, 43% lead, 1% silver, and 14% bismuth.

[0117] The flux raw materials, based on a total mass of 100%, include: solvent (ethanol) 98%, film-forming agent (rosin resin) 0.4%, activator (organic acid) 1.7%, and dispersant (surfactant) 0.3%.

[0118] The organic acid is sulfonic acid, and the surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol polyoxyethylene ether.

[0119] Comparative Example 1

[0120] This comparative example provides a welding method for battery cells. The difference between this comparative example and Example 1 is that no flux is used in this comparative example, while the other conditions are the same as in Example 1.

[0121] Comparative Example 2

[0122] This comparative example provides a method for soldering battery cells. The difference from Example 1 is that the solder paste in this comparative example does not contain silver, while other conditions are the same as in Example 1.

[0123] Comparative Example 3

[0124] This comparative example provides a method for soldering battery cells. The difference from Example 1 is that the solder paste in this comparative example does not contain lead, while other conditions are the same as in Example 1.

[0125] Comparative Example 4

[0126] This comparative example provides a method for soldering a battery cell. The difference between this comparative example and Example 1 is that the solder paste used in this comparative example does not contain bismuth, while the other conditions are the same as in Example 1.

[0127] Comparative Example 5

[0128] This comparative example provides a method for welding a battery cell. This comparative example provides a conventional welding method in which a metal coating is applied to a copper strip, and then conventional solder paste is applied without flux. The flux used in the welding process is the same as in Example 1.

[0129] The electrode sheets prepared in the above embodiments and comparative examples were subjected to welding pull-out force tests. The test method was to use a horizontal tensile testing machine, lay the welded strip of the battery cell in the opposite direction to the welding point of the battery cell (with an included angle of 0°), fix the battery cell, clamp the welded strip with the equipment jaws, and move it in the opposite direction until all welding points on the welded strip were broken. The pull-out force values ​​of each point were recorded and the average value was taken. The specific test results are shown in Table 1.

[0130] Table 1 Weld Pull-out Force Test

[0131] sample Welding pull-out force Example 1 4.56 N / mm Example 2 4.70 N / mm Example 3 4.45 N / mm Comparative Example 1 3.35 N / mm Comparative Example 2 3.05 N / mm Comparative Example 3 1.83 N / mm Comparative Example 4 4.83 N / mm Comparative Example 5 3.95 N / mm

[0132] As shown in Table 1, the welding method for the battery cells provided in this application exhibits good welding results within a drying temperature range of 160-240℃. The absence of flux affects the welding pull-out force; adding a certain proportion of silver to the solder paste helps improve the pull-out force. Lead is indispensable in the solder paste, as it significantly affects the welding pull-out force. The pull-out force after welding in Comparative Example 4 is superior to that in the Example, mainly because the welding material lacks bismuth. Bismuth is inherently brittle, resulting in a lower pull-out force at the welding position compared to bismuth-free solder. However, the addition of bismuth in the Example can lower the melting point of the welding material (i.e., reduce the process temperature during manufacturing).

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0134] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for welding battery cells, characterized in that, include: A first coating is applied to the surface of the solar cell using a stencil, followed by drying to obtain the coated solar cell. A second coating is applied to the bare copper strip to obtain a coated copper strip. The coated copper strip is placed on the coated battery cell for welding.

2. The welding method for battery cells according to claim 1, characterized in that, The first coating is performed using solder paste; The raw materials of the solder paste include an alloy, which, by weight (100%), comprises: 18%-65% tin, 20%-45% lead, 2%-15% silver, and 10%-37% bismuth.

3. The welding method for battery cells according to claim 2, characterized in that, The solder paste also includes rosin and organic acids as raw materials; The rosin is 1%-5% of the total mass of the solder paste; The organic acid constitutes 2%-8% of the total mass of the solder paste.

4. The welding method for battery cells according to claim 1, characterized in that, The second coating is applied using flux; The flux comprises, by weight, 95%-99% solvent, 0.3%-0.5% film-forming agent, 1.5%-2.0% activator, and 0.2%-0.3% dispersant.

5. The welding method for battery cells according to claim 4, characterized in that, At least one of the following conditions must be met: A. The solvent includes ethanol and / or isopropanol; B. The film-forming agent includes rosin resin; C. The activator includes organic acids; D. The dispersant includes surfactants.

6. The welding method for battery cells according to claim 1, characterized in that, The first coating includes: The first coating and first drying are performed on the front or back of the battery cell to obtain a battery cell with single-sided coating; The other side of the single-sided coated battery cell is then subjected to the first coating and the second drying process to obtain the coated battery cell shown.

7. The welding method for battery cells according to claim 6, characterized in that, At least one of the following conditions must be met: A. The temperature of the first drying process is 170℃-300℃, and the time is 2s-30s; B. The second drying temperature is 170℃-250℃, and the time is 3s-50s.

8. The method for welding battery cells according to any one of claims 1-7, characterized in that, The welding temperature is 110℃-280℃, and the time is 1.5s-3s.

9. A photovoltaic module, characterized in that, It includes several battery cells welded together using the welding method described in any one of claims 1 to 8.

10. A photovoltaic power generation system, characterized in that, Includes the photovoltaic module as described in claim 9.

Images