Single-welded cell and preparation method thereof, cell string, and photovoltaic module

Abstract

The present application discloses a single-welded cell and its preparation method, a cell string, and a photovoltaic module, relating to the technical field of solar cells. The preparation method comprises: providing a cell, the cell comprising a substrate and a conductive layer bonded to at least one surface of the substrate; heating the cell to a temperature T1, maintaining the temperature for a period of time t, and then cooling the temperature to a temperature T2 to obtain an intermediate cell; and placing a soldering tape on the conductive layer of the intermediate cell to obtain a single-welded cell. The heating and cooling processes provide the cell with a buffer period to adapt to temperature T and room temperature. The combined effects of the heating, maintaining, and cooling processes facilitate the full volatilization of moisture from the cell, reduce the internal stress of the conductive layer, prevent oxidation of the conductive layer, enhance the strong bonding between the substrate and the conductive layer, and thereby enhance the welding tension of the conductive layer grid lines on the single-welded cell; and then performing single welding with the soldering tape to prepare for the series connection of the cell and enhance the conductivity of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a method for preparing a single-welded cell, a single-welded cell prepared by the preparation method, a cell string containing the single-welded cell, and a photovoltaic module containing the cell string. Background Art

[0002] Metallization is a key process in the manufacture of silicon solar cells. It is primarily used to create electrodes, establishing ohmic contact across the PN junction and enabling current output. Currently, screen printing is the most mature and common metallization process, but the high cost of the silver paste used has become a significant factor limiting its widespread adoption.

[0003] To further reduce the cost of solar cells and improve their efficiency, the use of electroplating to create metal electrodes for solar cells has been widely researched. Electroplating can reduce production costs by partially or completely replacing silver with cheaper metals such as nickel or copper. Furthermore, during the assembly process, solar cells typically require soldering ribbons to connect two or more cells and provide electrical conductivity. However, when electroplated cells are soldered at high temperatures, the copper-plated grid lines are easily oxidized, resulting in poor bonding strength and insufficient weld strength.

[0004] The welding tensile strength of electroplated solar cells needs to be further improved. Summary of the Invention

[0005] In view of this, the present application provides a single-welded cell and its preparation method, a cell string, and a photovoltaic module, aiming to improve the problem of low welding tension of existing electroplated cell sheets.

[0006] The embodiment of the present application is implemented as follows: a method for preparing a single-welded solar cell, comprising:

[0007] Providing a battery cell, the battery cell comprising a substrate and a conductive layer bonded to at least one surface of the substrate;

[0008] The battery cell is heated to a temperature T1, kept at this temperature for a period of time t, and then cooled to a temperature T2 to obtain an intermediate battery cell;

[0009] A welding strip is arranged on the conductive layer of the middle battery cell to obtain a single-welded battery cell.

[0010] Optionally, in some embodiments of the present application, the temperature T1 is 100-120° C.; and / or

[0011] The time t is 10 to 20 seconds; and / or

[0012] The temperature T2 is room temperature;

[0013] The heating rate is 1-3°C / s; and / or

[0014] The cooling rate is 1-3°C / s.

[0015] Optionally, in some embodiments of the present application, the conductive layer includes a nickel layer disposed on the substrate and a copper layer disposed on a surface of the nickel layer away from the substrate.

[0016] Optionally, in some embodiments of the present application, the thickness of the nickel layer is 0.5-1 μm; and / or

[0017] The thickness of the copper layer is 9-12 μm.

[0018] Optionally, in some embodiments of the present application, the method for preparing the battery cell includes:

[0019] providing a substrate;

[0020] placing the substrate in a nickel-based electroplating solution to perform a first electroplating to form a nickel layer on at least one surface of the substrate to obtain an intermediate;

[0021] The intermediate is placed in a copper-based electroplating solution and subjected to a second electroplating process to form a copper layer on the surface of the nickel layer of the intermediate away from the substrate, thereby obtaining a battery cell.

[0022] Optionally, in some embodiments of the present application, the thickness of the nickel layer is 0.5-1 μm; and / or

[0023] The thickness of the copper layer is 9-12 μm.

[0024] Optionally, in some embodiments of the present application, the method for preparing the battery cell includes: providing a substrate, placing it in a nickel-based electroplating solution, performing a first electroplating to obtain a nickel-containing substrate; placing the nickel-containing substrate in a copper-based electroplating solution, performing a second electroplating to obtain a battery cell.

[0025] Optionally, in some embodiments of the present application, the nickel-based electroplating solution includes a nickel salt main salt, a buffer and a wetting agent; and / or

[0026] The copper-based electroplating solution comprises a copper salt, a conductive agent and a brightener.

[0027] Optionally, in some embodiments of the present application, the main nickel salt comprises nickel sulfamate; and / or

[0028] The buffer comprises one or more of boric acid and aminosulfonic acid; and / or

[0029] The wetting agent includes one or more of sodium lauryl sulfate, sodium dihexyl sulfosuccinate, and sodium 2-ethylhexyl sulfate; and / or

[0030] The copper salt includes one or more of copper sulfate, copper pyrophosphate, and cuprous cyanide; and / or

[0031] The conductive agent includes sulfuric acid; and / or

[0032] The brightener includes copper chloride.

[0033] Optionally, in some embodiments of the present application, the mass concentration of the nickel salt main salt is 300-400 g / L; and / or

[0034] The mass concentration of the buffer is 30 to 50 g / L; and / or

[0035] The mass concentration of the wetting agent is 1 to 2 mg / L; and / or

[0036] The mass concentration of the copper salt is 200-250 g / L; and / or

[0037] The mass concentration of the conductive agent is 50 to 70 g / L; and / or

[0038] The mass concentration of the brightener is 50-100 mg / L.

[0039] Optionally, in some embodiments of the present application, the nickel-based electroplating solution further comprises an AMS-1003 additive; and / or

[0040] The copper-based electroplating solution also includes an AM-260C additive.

[0041] Optionally, in some embodiments of the present application, the mass concentration of the AMS-1003 additive is 6 to 12 mg / L; and / or

[0042] The mass concentration of the AM-260C additive is 5-10 mg / L.

[0043] Optionally, in some embodiments of the present application, the current density of the first electroplating is 4 to 8 A / dm 2 and / or

[0044] The first electroplating time is 30 to 60 seconds, and / or

[0045] The current density of the second electroplating is 4 to 8 A / dm 2 and / or

[0046] The second electroplating process lasts for 10 to 15 minutes.

[0047] Correspondingly, an embodiment of the present application further provides a single-welded battery cell, which is prepared by the above-mentioned preparation method.

[0048] Correspondingly, an embodiment of the present application further provides a battery string, which includes a plurality of single-welded battery cells manufactured by the above-mentioned preparation method, and the plurality of single-welded battery cells are connected in series through the welding ribbon.

[0049] Correspondingly, an embodiment of the present application further provides a photovoltaic assembly, which includes the above-mentioned battery string.

[0050] The preparation method of the single-welded battery cell described in the present application is that the battery cell undergoes the processes of heating, heat preservation and cooling. The heating process allows the battery cell to have a buffer period to adapt to the temperature T, and the cooling process allows the battery cell to have a buffer period to adapt to the room temperature. Under the combined action of heating, heat preservation and cooling treatment, it is beneficial to fully volatilize the moisture in the battery cell, effectively reduce the internal stress of the conductive layer, and avoid oxidation of the conductive layer, thereby increasing the strong bonding force between the substrate and the conductive layer, and thus increasing the welding tension of the conductive layer grid line on the single-welded battery cell; then, single welding is performed with a welding ribbon to prepare for the series connection of the battery cells and improve the conductivity of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 This is a flow chart of a method for preparing a single-welded battery cell provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0054] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as designations and do not impose numerical requirements or establish a sequential order.

[0055] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0056] In this application, "at least one" means one or more, and "plurality" means two or more. "One or several", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0057] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0058] The technical solution of this application is as follows:

[0059] like Figure 1 As shown, in a first aspect, an embodiment of the present application provides a method for preparing a single-welded solar cell, comprising:

[0060] Step S11: providing a battery cell, wherein the battery cell includes a substrate and a conductive layer bonded to at least one surface of the substrate;

[0061] Step S12: heating the battery cell to a temperature T1, keeping the temperature for a period of time t, and then cooling the temperature to a temperature T2 to obtain an intermediate battery cell;

[0062] Step S13: placing a soldering ribbon on the conductive layer of the middle cell to obtain a single-welded cell.

[0063] It can be understood that a single-welded cell is a cell with a welding strip set on a single cell substrate, and multiple single-welded cell cells can be welded together in series to form a cell string.

[0064] The preparation method of the single-welded battery cell described in the present application is that the battery cell undergoes the processes of heating, heat preservation and cooling. The heating process allows the battery cell to have a buffer period to adapt to the temperature T, and the cooling process allows the battery cell to have a buffer period to adapt to the room temperature. Under the combined action of heating, heat preservation and cooling treatment, it is beneficial to fully volatilize the moisture in the battery cell, effectively reduce the internal stress of the conductive layer, and avoid oxidation of the conductive layer, thereby increasing the strong bonding force between the substrate and the conductive layer, and thus increasing the welding tension of the conductive layer grid line on the single-welded battery cell; then, single welding is performed with a welding ribbon to prepare for the series connection of the battery cells and improve the conductivity of the battery.

[0065] In the step S11:

[0066] In some embodiments, the conductive layer includes a nickel layer disposed on the substrate and a copper layer disposed on a surface of the nickel layer away from the substrate.

[0067] In some embodiments, the method for preparing the battery cell includes:

[0068] Step S111, providing a substrate;

[0069] Step S112, placing the substrate in a nickel-based electroplating solution, performing a first electroplating, forming a nickel layer on at least one surface of the substrate, and obtaining an intermediate;

[0070] Step S113: placing the intermediate in a copper-based electroplating solution and performing a second electroplating to form a copper layer on the surface of the nickel layer of the intermediate away from the substrate, thereby obtaining a battery cell.

[0071] In the step S111:

[0072] In some embodiments, the substrate is a battery silicon wafer.

[0073] In some embodiments, the substrate is a substrate cleaned with a first detergent.

[0074] In some embodiments, the first detergent comprises hydrofluoric acid or sodium hydroxide.

[0075] In some embodiments, the volume fraction of the first detergent is 2% to 5%, for example, 2.2% to 4.8%, 2.5% to 4.5%, 2.8% to 4.2%, 3% to 4%, 3.2% to 3.5%, etc.

[0076] The volume fraction of the hydrofluoric acid is 3% to 5%.

[0077] The volume fraction of the sodium hydroxide is 2% to 4%.

[0078] In some embodiments, the cleaning time of the first detergent is 30 to 60 seconds, for example, 32 to 58 seconds, 35 to 55 seconds, 38 to 52 seconds, 40 to 50 seconds, 42 to 48 seconds, etc.

[0079] It can be understood that a silicon oxide layer will be produced during the laser grooving process of the substrate. The volume fraction of the first detergent and the cleaning time of the first detergent are conducive to cleaning and removing the silicon oxide layer, thereby facilitating nickel electroplating.

[0080] In step S112:

[0081] In some embodiments, the nickel-based electroplating solution includes a nickel salt, a buffer, and a wetting agent.

[0082] In some embodiments, the main nickel salt comprises an organic nickel salt.

[0083] The organic nickel salt includes nickel sulfamate.

[0084] In some embodiments, the nickel-based electroplating solution further includes a nickel salt auxiliary salt.

[0085] In some embodiments, the nickel salt auxiliary salt includes an inorganic nickel salt.

[0086] The inorganic nickel salt includes one or more of nickel chloride, nickel bromide and nickel sulfate.

[0087] In some embodiments, the mass concentration of the organic nickel salt is 300-400 g / L, for example, 310-390 g / L, 320-380 g / L, 330-370 g / L, 340-360 g / L, 345-350 g / L, etc. Within this mass concentration range, the electroplating efficiency is high and the nickel layer deposition speed is fast.

[0088] In some embodiments, the mass concentration of the inorganic nickel salt is 40-60 g / L, for example, 42-59 g / L, 44-58 g / L, 45-55 g / L, 46-52 g / L, 48-50 g / L, etc. Within this mass concentration range, the inorganic nickel salt can assist the organic nickel salt in efficiently electroplating the nickel layer.

[0089] In some embodiments, the buffer comprises one or more of boric acid and sulfamic acid.

[0090] In some embodiments, the mass concentration of the buffer is 30-50 g / L, for example, 32-49 g / L, 34-48 g / L, 35-45 g / L, 36-42 g / L, 38-40 g / L, etc. It can be understood that in the process of nickel electroplating, in addition to the reaction of nickel ions being discharged on the cathode and reduced to metallic nickel (Ni2+ +2e - =Ni), there is also a side reaction of hydrogen ion reduction to hydrogen gas: 2H + +2e - =H2↑, so the pH value in the cathode area of the electroplating tank will gradually rise due to the precipitation of hydrogen, thereby affecting the quality of the electroplated nickel layer. + It can replenish the H consumed by hydrogen evolution. + In order to maintain a certain acidity, prevent the rapid change of acidity and make the pH value relatively stable. Within the range of mass concentration, the buffering effect of the buffer is good and no waste is caused.

[0091] In some embodiments, the wetting agent includes one or more of sodium lauryl sulfate, sodium dihexyl sulfosuccinate, and sodium 2-ethylhexyl sulfate.

[0092] In some embodiments, the mass concentration of the wetting agent is 1-2 mg / L, for example, 1.1-1.9 mg / L, 1.2-1.8 mg / L, 1.3-1.7 mg / L, 1.4-1.6 mg / L, etc. Within the mass concentration range, the wetting agent can effectively reduce the surface tension of the nickel-based electroplating solution, so that H + The adhesion of small hydrogen bubbles formed by discharge decreases, making them difficult to retain and are removed in time, thereby reducing and eliminating gas pinholes and pitting, and improving the coating effect.

[0093] In some embodiments, the nickel-based electroplating solution further comprises an AMS-1003 additive, which is provided by Shenzhen Aomeis Technology Co., Ltd.

[0094] In some embodiments, the mass concentration of the AMS-1003 additive is 6 to 12 mg / L, for example, 6.5 to 11 mg / L, 7 to 10.5 mg / L, 8 to 10 mg / L, 8.5 to 9 mg / L, etc. Within this mass concentration range, the AMS-1003 additive facilitates the efficient preparation of a highly ductile coating, imparting low or controllable internal stress to the nickel coating, and helping to improve the bonding strength between the nickel layer and the solar cell silicon wafer substrate.

[0095] In some embodiments, the thickness of the nickel layer is 0.5-1 μm, for example, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, etc. Within the thickness range of the nickel layer, the nickel layer can fully play its role as a barrier layer, improve the conductivity of the battery grid line, and enhance the bonding strength between battery cells.

[0096] In some embodiments, the current density of the first electroplating is 4 to 8 A / dm 2 , for example, it can be 5A / dm2 , 6A / dm 2 , 7A / dm 2 wait.

[0097] In some embodiments, the electroplating time of the first electroplating is 30 to 60 seconds, for example, 32 to 58 seconds, 35 to 55 seconds, 38 to 52 seconds, 40 to 50 seconds, 42 to 48 seconds, etc.

[0098] Thus, within the range of the current density and the electroplating time, the performance of the electroplated nickel layer is good and the electroplating efficiency is high.

[0099] In some embodiments, after the first electroplating, an annealing process is further included.

[0100] In some embodiments, the annealing temperature is 300-600° C., for example, 320-580° C., 350-550° C., 380-520° C., 400-500° C., 420-480° C., etc.

[0101] In some embodiments, the annealing time is 60 to 90 seconds, for example, 62 to 88 seconds, 65 to 85 seconds, 68 to 82 seconds, 70 to 80 seconds, 72 to 78 seconds, etc.

[0102] In this way, within the annealing temperature and time range, it is beneficial for the nickel layer and the substrate to form a nickel-silicon alloy and be tightly bonded.

[0103] In some embodiments, after the first electroplating and before the annealing, the process further includes cleaning the first electroplating product.

[0104] In at least one embodiment, cleaning the first electroplated product includes washing the first electroplated product with deionized water 2 to 3 times, thereby removing residual electroplating solution and other impurities on the first electroplated product.

[0105] In some embodiments, after the annealing treatment, the annealing product is further cleaned with a second detergent.

[0106] In some embodiments, the second detergent comprises one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0107] In some embodiments, the volume fraction of the second detergent is 4% to 8%, for example, 5%, 6%, 7%, etc.

[0108] In some embodiments, the cleaning time of the second detergent is 60 to 90 seconds, for example, 62 to 88 seconds, 65 to 85 seconds, 68 to 82 seconds, 70 to 80 seconds, 72 to 78 seconds, etc.

[0109] It can be understood that since a nickel oxide layer is generated during the annealing process of the nickel layer, the nickel oxide layer can be effectively removed by cleaning with the second detergent, thereby facilitating the electroplating of the copper layer.

[0110] In step S112:

[0111] In some embodiments, the copper-based electroplating solution includes a copper salt, a conductive agent, and a brightener.

[0112] In some embodiments, the copper salt includes one or more of copper sulfate, copper pyrophosphate, and cuprous cyanide.

[0113] In some embodiments, the mass concentration of the copper salt is 200-250 g / L, for example, 205-245 g / L, 210-240 g / L, 215-235 g / L, 220-230 g / L, 222-228 g / L, etc. Within this mass concentration range, the solubility of the copper salt is moderate, and the efficiency of the electroplated copper layer is high.

[0114] In some embodiments, the conductive agent includes sulfuric acid.

[0115] In some embodiments, the mass concentration of the conductive agent is 50-70 g / L, for example, 52-69 g / L, 54-68 g / L, 55-65 g / L, 56-62 g / L, 58-60 g / L, etc. It is understood that the conductive agent can prevent the hydrolysis of copper from forming cuprous oxide or other basic salt precipitation; it can also reduce the effective concentration of copper ions, resulting in fine crystallization of the copper plating layer; the conductive agent can also reduce the resistance of the solution, increase the conductivity of the solution, reduce energy consumption, and promote the formation of the copper layer.

[0116] In some embodiments, the brightener includes copper chloride. Chloride ions in the copper chloride can expand the brightening range of the copper plating layer, while copper ions can assist the main salt in electroplating the copper layer.

[0117] In some embodiments, the mass concentration of the brightener is 50-100 mg / L, for example, 52-95 mg / L, 55-92 mg / L, 60-90 mg / L, 70-80 mg / L, etc. Within this mass concentration range, the brightener can expand the brightening range of the copper plating layer, thereby producing a smooth, bright, and dense copper plating layer.

[0118] In some embodiments, the copper-based electroplating solution further comprises an AM-260C additive, which is provided by Shenzhen Aomeis Technology Co., Ltd.

[0119] In some embodiments, the mass concentration of the AM-260C additive is 5 to 10 mg / L, for example, 6 mg / L, 7 mg / L, 8 mg / L, 9 mg / L, etc. Within this mass concentration range, the main component of the AM-260C additive does not contain sulfur, and an excellent copper layer with high ductility and low internal stress can be obtained.

[0120] In some embodiments, the copper layer has a thickness of 9 to 12 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, etc. Within the thickness range of the copper layer, the copper layer has good conductivity, thereby improving the efficiency of the battery cell.

[0121] In some embodiments, the current density of the second electroplating is 4 to 8 A / dm 2 , for example, it can be 5A / dm 2 , 6A / dm 2 , 7A / dm 2 wait.

[0122] In some embodiments, the second electroplating time is 10 to 15 minutes, for example, 11 minutes, 12 minutes, 13 minutes, 14 minutes, etc.

[0123] Thus, within the range of the current density and the electroplating time, the performance of the electroplated copper layer is good and the electroplating efficiency is high.

[0124] In some embodiments, after the second electroplating, the method further includes cleaning the second electroplating product.

[0125] In at least one embodiment, cleaning the second electroplated product includes washing the second electroplated product with deionized water 2 to 3 times, thereby removing residual electroplating solution and other impurities on the second electroplated product.

[0126] It can be understood that the nickel layer and the copper layer are prepared by electroplating, which can reduce production costs and improve the conductivity of the single-welded solar cell.

[0127] In the step S12:

[0128] In some embodiments, the battery cell is placed in a reaction container and passed through the reaction container. During the process of the battery cell passing through the reaction container, the temperature is raised to temperature T1, kept at this temperature for a period of time t, and then cooled to temperature T2 to obtain an intermediate battery cell.

[0129] In at least one embodiment, the reaction vessel comprises a tunnel furnace.

[0130] In some embodiments, the cell passes through the reaction vessel at a speed of 20 to 25 mm / s, for example, 21 mm / s, 22 mm / s, 23 mm / s, 24 mm / s, etc. Within this speed range, moisture in the cell can be fully evaporated, effectively releasing internal stress.

[0131] In some embodiments, the temperature T1 is 100-120° C., for example, 102-119° C., 103-118° C., 105-115° C., 108-114° C., 110-112° C., etc. Within this range, stress in the cell is released and the copper layer is not easily oxidized.

[0132] In some embodiments, the time t is 10-20 seconds, for example, 10.5-19 seconds, 11-18 seconds, 12-17 seconds, 13-16 seconds, 14-15 seconds, etc. Within the time range, the moisture in the cell can be fully volatilized and the internal stress can be effectively released.

[0133] In some embodiments, the temperature T2 is room temperature. The cooling is conducive to the release of internal stress, and avoids oxidation of the copper layer, thereby improving welding tension.

[0134] In some embodiments, the heating rate is 1-3° C. / s.

[0135] In some embodiments, the cooling rate is 1-3°C / s.

[0136] In the step S13:

[0137] It can be understood that the welding strip is arranged on the main grid of the middle battery cell.

[0138] In some embodiments, the solder ribbon comprises solder paste.

[0139] In some embodiments, after providing a solder strip on the conductive layer of the middle battery cell, vacuum drying is further included.

[0140] In some embodiments, the vacuum drying temperature is 160-180° C., for example, 162-178° C., 164-176° C., 165-175° C., 166-172° C., 168-170° C., etc. Within the vacuum drying temperature range, the solder strip is conducive to solidification.

[0141] In some embodiments, the vacuum drying time is 20-40 seconds, for example, 22-38° C., 24-36° C., 25-35° C., 26-32° C., 28-30° C., etc. Within the vacuum drying time range, the solder strip is conducive to full solidification.

[0142] In a second aspect, an embodiment of the present application further provides a single-welded battery cell, which is produced by the above-mentioned production method.

[0143] The single-welded cell described in the present application has undergone a process of heating, heat preservation and cooling, which can fully volatilize the moisture in the cell, effectively reduce the internal stress of the conductive layer, and avoid oxidation of the conductive layer, thereby increasing the strong bonding force between the substrate and the conductive layer, and thus increasing the welding tension of the conductive layer grid line on the single-welded cell; then single welding is performed with a welding ribbon to prepare for the series connection of the cell and improve the conductivity of the battery.

[0144] In a third aspect, an embodiment of the present application further provides a battery string, wherein the battery string comprises a plurality of the above-mentioned single-welded battery cells, and the plurality of the above-mentioned single-welded battery cells are connected in series via welding ribbons.

[0145] In a fourth aspect, an embodiment of the present application further provides a photovoltaic module, which includes the above-mentioned battery string.

[0146] The present application will be described in detail below through specific examples. The following examples are only some examples of the present application and are not limitations of the present application.

[0147] Example 1

[0148] This embodiment provides a single-welded solar cell, the preparation method of which is as follows:

[0149] Provide a 3% volume fraction hydrofluoric acid solution, place the laser grooved solar cell silicon wafer in the hydrofluoric acid solution for cleaning, remove the silicon oxide layer generated during the groove process, and then wash with water and dry;

[0150] The pickled solar cell silicon wafers were placed in a nickel-based electroplating solution for electroplating. The nickel-based electroplating solution was prepared by 300 g / L nickel sulfamate, 40 g / L nickel chloride, 30 g / L boric acid, 1 mg / L sodium dodecyl sulfate, 6 mg / L AMS-1003 additive provided by Shenzhen Aomeis Technology Co., Ltd., and deionized water. When electroplating nickel, the current density was 4 A / dm 2 The electroplating time is 30s. After the electroplating is completed, it is washed twice with deionized water and then blown dry;

[0151] The nickel-plated solar cell silicon wafer was annealed at 300°C for 60 seconds to form a nickel-silicon alloy.

[0152] Providing a 4% volume fraction sulfuric acid solution, placing the annealed solar cell silicon wafer in the sulfuric acid solution for cleaning to remove the nickel oxide layer generated during the annealing process, and then washing and drying;

[0153] The solar cell silicon wafer with the nickel oxide layer cleaned off was placed in a copper-based electroplating solution for electroplating. The copper-based electroplating solution was prepared by 200 g / L of copper sulfate pentahydrate, 50 g / L of sulfuric acid, 50 mg / L of copper chloride, 5 mg / L of AM-260C additive provided by Shenzhen Aomeis Technology Co., Ltd., and deionized water. When electroplating copper, the current density was 4 A / dm 2 The electroplating time is 10 min. After the electroplating is completed, the battery is washed twice with deionized water and dried to obtain a battery cell.

[0154] The battery cell is placed in an electric heating tunnel furnace and passed through at a constant speed of 20 mm / s. The tunnel furnace is heated to 100°C, kept warm for 20 seconds, and then cooled. A small amount of low-temperature solder paste is then placed on the main grid of the battery cell. The battery cell is placed in a vacuum drying oven and dried at 160°C for 20 seconds. After being taken out, a single-welded battery cell is obtained.

[0155] Example 2

[0156] This embodiment is substantially the same as embodiment 1, except that the concentration of the AMS-1003 additive in the nickel-based electroplating solution in this embodiment is 9 mg / L.

[0157] Example 3

[0158] This embodiment is substantially the same as embodiment 1, except that the concentration of the AMS-1003 additive in the nickel-based electroplating solution in this embodiment is 12 mg / L.

[0159] Example 4

[0160] This embodiment is substantially the same as embodiment 1, except that the concentration of the AM-260C additive in the copper-based electroplating solution in this embodiment is 7.5 mg / L.

[0161] Example 5

[0162] This embodiment is substantially the same as embodiment 1, except that the concentration of the AM-260C additive in the nickel-based electroplating solution in this embodiment is 12 mg / L.

[0163] Example 6

[0164] This embodiment is basically the same as embodiment 1, except that in this embodiment, the battery cells pass through the electric heating tunnel furnace at a constant speed of 22.5 mm / s.

[0165] Example 7

[0166] This embodiment is basically the same as embodiment 1, except that in this embodiment, the battery cells pass through the electric heating tunnel furnace at a constant speed of 25 mm / s.

[0167] Example 8

[0168] This embodiment is substantially the same as embodiment 1, except that in this embodiment, the tunnel furnace is heated to 110°C.

[0169] Example 9

[0170] This embodiment is substantially the same as embodiment 1, except that in this embodiment, the tunnel furnace is heated to 120°C.

[0171] Example 10

[0172] This embodiment is substantially the same as embodiment 1, except that the holding time at 100° C. is 15 seconds in this embodiment.

[0173] Example 11

[0174] This embodiment is basically the same as embodiment 1, except that the holding time at 100° C. in this embodiment is 20 seconds.

[0175] Example 12

[0176] This embodiment is basically the same as embodiment 1, except that the temperature in the vacuum drying oven in this embodiment is 170°C.

[0177] Example 13

[0178] This embodiment is basically the same as embodiment 1, except that the temperature in the vacuum drying oven in this embodiment is 180°C.

[0179] Example 14

[0180] This embodiment is basically the same as embodiment 1, except that the vacuum drying time in this embodiment is 30 seconds.

[0181] Example 15

[0182] This embodiment is basically the same as embodiment 1, except that the vacuum drying time in this embodiment is 40 seconds.

[0183] Comparative Example 1

[0184] This comparative example is basically the same as Example 1, except that in this comparative example, the battery cell is obtained, and after being affixed with solder paste, it is directly placed in an environment of 300° C. for sintering and welding.

[0185] Comparative Example 2

[0186] This comparative example is substantially the same as Example 1, except that the nickel-based electroplating solution in this comparative example does not contain the AMS-1003 additive.

[0187] Comparative Example 3

[0188] This comparative example is substantially the same as Example 1, except that the copper-based electroplating solution in this comparative example does not contain the AM-260C additive.

[0189] Comparative Example 4

[0190] This comparative example is basically the same as Example 1, except that the nickel-based electroplating solution in this comparative example does not contain the AMS-1003 additive, and the copper-based electroplating solution does not contain the AM-260C additive. After the obtained battery cell is affixed with solder paste, it is directly placed in an environment of 300°C for sintering and welding.

[0191] Referring to the above method, 8 single-welded battery cells were prepared for each embodiment and comparative example, and a tensile tester was used to perform welding tensile tests on the single-welded battery cells prepared in the above embodiments 1 to 15 and comparative examples 1 to 4. The welding tensile forces of the single-welded battery cells prepared in embodiments 1 to 15 and comparative examples 1 to 4 are shown in Table 1.

[0192] Table 1

[0193]

[0194]

[0195] As shown in Table 1, Example 1 and Comparative Example 1 show that by heating, keeping warm and cooling the cell, and controlling the keeping warm temperature at 100°C, the average tensile force of the single-welded cell in Example 1 is increased by 0.65N compared with the single-welded cell in Comparative Example 1. The single-welded cell in Comparative Example 1 is directly sintered at a high temperature of 300°C, which easily leads to oxidation of the grid line of the copper layer, thereby deteriorating its bonding strength. As shown in Example 1, Comparative Example 2 and Comparative Example 3, adding AMS-1003 additive to the nickel-based electroplating solution and adding AM-260C to the copper-based electroplating solution can effectively improve the welding tensile force of the single-welded cell. As shown in Example 1 and Comparative Example 4, the conventional nickel-based electroplating solution and the copper-based electroplating solution are used, and the electroplated copper layer is destroyed after high-temperature sintering, and the bonding strength between the nickel layer and the silicon substrate of the cell is weak, and the bonding strength between the copper layer and the welding strip is weak, and the welding tensile force of the single-welded cell is poor. The force is low and does not meet the use standard; it can be concluded from the average tensile force value that the welding tensile force of the single-welded battery cells of Examples 1 to 15 is much higher than that of Comparative Examples 1 to 4. This is because the nickel is electroplated with the AMS-1003 additive provided by Shenzhen Aomeis Technology Co., Ltd., which can reduce the internal stress of the nickel layer and help to improve the bonding strength between the nickel layer and the silicon substrate; the AM-260C additive provided by Shenzhen Aomeis Technology Co., Ltd. is used, the main component of which does not contain sulfur, and a copper layer with excellent ductility and low internal stress can be obtained, which helps to improve the bonding strength between the copper layer and the nickel layer; and the battery cell passes through a tunnel furnace at low temperature, and after heating, insulation and cooling stages, the moisture of the coating can be completely volatilized, the internal stress of the coating can be reduced, thereby achieving a strong bonding strength between the nickel-copper coating and the silicon substrate, and then the low-temperature solder paste is bonded through a vacuum drying oven to avoid copper oxidation and improve the welding tensile force of the nickel-copper coating grid line.

[0196] The above is a detailed introduction to the single-welded solar cell and its preparation method, battery string, and photovoltaic module provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a single-welded battery cell, characterized in that: include: Providing a battery cell, the battery cell comprising a substrate and a conductive layer bonded to at least one surface of the substrate; The conductive layer includes a nickel layer provided on the substrate and a copper layer provided on a surface of the nickel layer away from the substrate; the nickel layer is formed by a first electroplating process, and the copper layer is formed by a second electroplating process; The battery cell is heated to a temperature T1 of 100 to 120° C., kept at this temperature for a period of time t of 10 to 20 seconds, and then cooled to a temperature T2 of room temperature to obtain an intermediate battery cell; wherein the heating rate is 1 to 3° C. / s, and the cooling rate is 1 to 3° C. / s; A welding strip is arranged on the conductive layer of the middle battery cell to obtain a single-welded battery cell.

2. The preparation method according to claim 1, wherein The thickness of the nickel layer is 0.5 to 1 μm; and / or The thickness of the copper layer is 9-12 μm.

3. The preparation method according to claim 1, wherein The method for preparing the battery cell includes: providing a substrate; Placing the substrate in a nickel-based electroplating solution and performing the first electroplating to form a nickel layer on at least one surface of the substrate to obtain an intermediate; The intermediate is placed in a copper-based electroplating solution and the second electroplating is performed to form a copper layer on the surface of the nickel layer of the intermediate away from the substrate, thereby obtaining a battery cell.

4. The preparation method according to claim 3, wherein The nickel-based electroplating solution comprises a nickel salt main salt, a buffer and a wetting agent; and / or The copper-based electroplating solution comprises a copper salt, a conductive agent and a brightener.

5. The preparation method according to claim 4, wherein The nickel salt main salt comprises nickel sulfamate; and / or The buffer comprises one or more of boric acid and aminosulfonic acid; and / or The wetting agent includes one or more of sodium lauryl sulfate, sodium dihexyl sulfosuccinate, and sodium 2-ethylhexyl sulfate; and / or The copper salt includes one or more of copper sulfate, copper pyrophosphate, and cuprous cyanide; and / or The conductive agent includes sulfuric acid; and / or The brightener includes copper chloride.

6. The preparation method according to any one of claims 4 or 5, characterized in that The mass concentration of the nickel salt main salt is 300-400 g / L; and / or The mass concentration of the buffer is 30 to 50 g / L; and / or The mass concentration of the wetting agent is 1 to 2 mg / L; and / or The mass concentration of the copper salt is 200-250 g / L; and / or The mass concentration of the conductive agent is 50 to 70 g / L; and / or The mass concentration of the brightener is 50-100 mg / L.

7. The preparation method according to claim 3, wherein The current density of the first electroplating is 4 to 8 A / dm 2 and / or The first electroplating time is 30 to 60 seconds, and / or The current density of the second electroplating is 4 to 8 A / dm 2 and / or The second electroplating process lasts for 10 to 15 minutes.

8. A single-welded battery cell, characterized in that: The single-welded solar cell is prepared by the preparation method according to any one of claims 1 to 7.

9. A battery string, characterized in that: The battery string comprises a plurality of single-welded battery cells produced by the preparation method according to any one of claims 1 to 7, and the plurality of single-welded battery cells are connected in series via the welding ribbon.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises the cell string according to claim 9.

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