Back contact cells and methods of making the same

Abstract

This disclosure relates to a back-contact battery and its manufacturing method, belonging to the field of photovoltaic technology. The manufacturing method of the back-contact battery includes: providing a battery cell with welding points on its back side; providing a pre-fabricated welding strip, stretching the pre-fabricated welding strip at a first stretching ratio ≤3% to obtain a stretched welding strip; welding the welding surface of the stretched welding strip to the welding points; fixing the stretched welding strip to the back side of the battery cell; and ensuring that the warpage deformation of the battery cell after welding is ≤3.5mm. This disclosure reduces the length change of the stretched welding strip after welding compared to the pre-fabricated welding strip by controlling the stretching ratio to ≤3%, thereby reducing the difference in dimensional expansion and contraction between the stretched welding strip and the battery cell after welding, reducing the stress exerted by the stretched welding strip on the battery cell after welding, and reducing the warpage deformation of the battery cell after welding. This is beneficial for reducing the breakage rate of the battery cell after lamination.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic technology, and in particular to a back contact battery and a method for manufacturing the same. Background Technology

[0002] The positive and negative electrodes of the back-contact solar cell are both located on the back of the cell, and there are no grid lines blocking the front of the cell, which reduces the light loss from the front of the cell and maximizes the utilization of the incident light from the front of the cell, thereby improving the cell conversion efficiency.

[0003] However, during the stringing of back-contact solar cells, the solder ribbons are all welded to the back of the cell. Due to the different coefficients of thermal expansion between the solder ribbons and the cell, and improper control of the solder ribbon stretch ratio, the cell is subjected to uneven stress during the welding process. This stress accumulates inside the cell, eventually leading to cell warping. During lamination, this stress may cause the cell to shatter, forming fragments. The appearance of fragments not only affects the overall performance of the solar panel but may also increase the cost of repair and replacement. Summary of the Invention

[0004] Therefore, it is necessary to provide a back contact battery and its manufacturing method to address the problem of uneven stress causing battery cell warping in the welding of battery cells and solder strips in the prior art.

[0005] To achieve the above objectives, in a first aspect, this disclosure provides a method for manufacturing a back contact battery, comprising:

[0006] A battery cell is provided, wherein the back side of the battery cell has solder joints;

[0007] A prefabricated welding strip is provided, and the prefabricated welding strip is stretched to obtain a stretched welding strip, wherein the first stretching ratio is ≤3%;

[0008] The welding surface of the stretching welding strip is welded to the welding point, and the stretching welding strip is fixed to the back of the battery cell. The warpage deformation of the battery cell after welding is ≤3.5mm.

[0009] Optionally, the first stretching ratio is ≤1%.

[0010] Optionally, stretching the preformed weld strip to a first stretch ratio to obtain a stretched weld strip includes:

[0011] The precast welding strip is conveyed to the stretching mechanism, which fixes the precast welding strip and stretches both ends of the precast welding strip by a preset displacement to obtain the stretched welding strip;

[0012] The stretching mechanism conveys the stretched weld strip to the shaping tank for shaping.

[0013] Optionally, after stretching the pre-fabricated weld strip to obtain a stretched weld strip at a first stretching ratio, the method further includes: etching the welding surface of the stretched weld strip to form a plurality of grooves on the welding surface; and welding the stretched weld strip to the welding point, including:

[0014] Solder paste is applied to the solder joints, and the soldering surface of the stretched solder strip is positioned facing the back of the battery cell. The plurality of grooves on the soldering surface correspond to the plurality of solder joints, and the solder paste of the solder joints is filled into the grooves.

[0015] The reflow soldering solder paste bonds the stretched solder strip to the back of the battery cell.

[0016] Optionally, along the width direction of the battery cell, the size of the groove located at the edge of the battery cell is larger than the size of the groove located at the center of the battery cell.

[0017] Optionally, the back of the battery cell has a plurality of first welding points and a plurality of second welding points, wherein the plurality of first welding points are arranged along the width direction of the battery cell, and the plurality of second welding points are arranged along the width direction of the battery cell.

[0018] A first preformed welding strip is provided, and the first preformed welding strip is stretched at a first stretching ratio to obtain a first stretched welding strip, wherein the first stretching ratio is ≤3%;

[0019] A second preformed welding strip is provided, and the second preformed welding strip is stretched at a first stretching ratio to obtain a second stretched welding strip;

[0020] The welding surface of the first stretched welding strip is welded to a plurality of first welding points. One end of the first stretched welding strip is fixed to one side edge of the battery cell. The first stretched welding strip extends along the width direction of the battery cell to the other side edge of the battery cell and extends out of the battery cell.

[0021] The welding surface of the second stretching welding strip is welded to a plurality of second welding points. One end of the second stretching welding strip is fixed to the other edge of the battery cell. The second stretching welding strip extends along the width direction of the battery cell to one side edge of the battery cell and extends out of the battery cell.

[0022] The warpage deformation of the battery cell after welding with the first and second stretching strips is ≤3.5mm.

[0023] Secondly, this disclosure provides a back contact battery, comprising:

[0024] A battery cell, wherein the back side of the battery cell has welding points;

[0025] The stretched welding strip is obtained by stretching a pre-made welding strip at a first stretching ratio of ≤3%. The welding surface of the stretched welding strip is welded to the welding point. The stretched welding strip is fixed to the back of the battery cell. The stretched welding strip is laminated together with the battery cell. The warpage deformation of the battery cell is ≤3.5mm.

[0026] Optionally, the first stretching ratio is ≤1%.

[0027] Optionally, the welding surface of the stretched solder strip is provided with a plurality of grooves, the grooves are corresponding to a plurality of welding points, the grooves are filled with solder paste, and the stretched solder strip is welded to the back of the battery cell through the solder paste;

[0028] Wherein, along the width direction of the battery cell, the size of the groove located at the edge of the battery cell is larger than the size of the groove located at the center of the battery cell.

[0029] Optionally, the back side of the battery cell has a plurality of first welding points and a plurality of second welding points, wherein the plurality of first welding points are arranged along the width direction of the battery cell, and the plurality of second welding points are arranged along the width direction of the battery cell; the back contact battery includes:

[0030] The first stretched welding strip is obtained by stretching the first pre-made welding strip at the first stretching ratio. The welding surface of the first stretched welding strip is welded to multiple first welding points. One end of the first stretched welding strip is fixed to one side edge of the battery cell. The first stretched welding strip extends along the width direction of the battery cell to the other side edge of the battery cell and extends out of the battery cell.

[0031] The second stretched welding strip is obtained by stretching the second pre-made welding strip according to the first stretching ratio. The welding surface of the first stretched welding strip is welded to a plurality of second welding points. One end of the second stretched welding strip is fixed to the other edge of the battery cell. The second stretched welding strip extends along the width direction of the battery cell to one side edge of the battery cell and extends out of the battery cell.

[0032] The back contact battery and its manufacturing method disclosed herein reduce the length change of the stretched welding strip after welding compared to the stretched welding strip before welding by controlling the stretching ratio of the stretched pre-fabricated welding strip to ≤3%, thereby reducing the difference in dimensional expansion and contraction between the stretched welding strip after welding and the battery cell after welding, reducing the stress exerted on the battery cell by the stretched welding strip after welding, and reducing the warpage deformation of the battery cell after welding. This is beneficial for reducing the breakage rate of the battery cell after lamination. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments or conventional technologies of this disclosure, the accompanying drawings used in the description of the embodiments or conventional technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart of a method for manufacturing a back contact battery according to one embodiment;

[0035] Figure 2 A flowchart illustrating a method for manufacturing a back contact battery according to another embodiment;

[0036] Figure 3 This is a top view of a stretched weld strip provided in one embodiment;

[0037] Figure 4 A top view of the stretched weld strip provided in another embodiment;

[0038] Figure 5 This is a top view of the first and second stretched solder strips after they have been welded to the battery cell in one embodiment.

[0039] Figure 6 This is a side view of the first and second stretched solder strips after they have been welded to the battery cell in one embodiment.

[0040] Explanation of reference numerals in the attached figures:

[0041] 10. Battery cell; 30. Stretched welding strip; 130. First stretch welding strip; 230. Second stretch welding strip; 31. Groove; 311. First groove; 312. Second groove; 313. Third groove; 314. Fourth groove; 315. Fifth groove; 316. Sixth groove; 317. Seventh groove. Detailed Implementation

[0042] To facilitate understanding of this disclosure, a more complete description will now be given with reference to the accompanying drawings, in which preferred embodiments of the present disclosure are shown. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure.

[0044] The inventors of this disclosure have discovered that in the welding connection between solar cells and solder strips, the solder strips and solar cells have different coefficients of thermal expansion. During the high-temperature welding process, the solder strips elongate due to heat, while the solar cells, due to their smaller coefficient of thermal expansion, expand relatively less. After cooling, the solder strips shrink, while the solar cells almost return to their original size. This uneven expansion and contraction causes stress on the solar cells, resulting in warping. After warping, the internal stress of the solar cell further increases. During the lamination process, this stress may cause the solar cell to shatter, forming fragments. The appearance of fragments not only affects the overall performance of the solar panel but may also increase the cost of repair and replacement.

[0045] In view of this, the present disclosure provides a back contact battery and a method for manufacturing the same. By controlling the stretching ratio of the stretched pre-fabricated welding strip to form the stretched welding strip to be ≤3%, the length change of the stretched welding strip after welding and the stretched welding strip before welding are reduced, the difference in dimensional expansion and contraction between the stretched welding strip after welding and the battery cell after welding is reduced, the stress exerted on the battery cell by the stretched welding strip after welding is reduced, and the warpage deformation of the battery cell after welding is reduced. This is beneficial to reducing the breakage rate of the battery cell after lamination, and is beneficial to further increasing product yield and reducing production costs.

[0046] According to an exemplary embodiment, this disclosure provides a method for manufacturing a back contact battery, such as... Figure 1 As shown, the method for manufacturing a back contact battery provided in this embodiment includes the following steps:

[0047] Step S11: Provide a battery cell with solder joints on the back side;

[0048] Reference Figure 5 , Figure 6 As shown, the solar cell 10 is a back-contact solar cell 10, which has a front and a back side disposed opposite to each other. The positive and negative electrodes of the solar cell 10 are both disposed on the back side. The positive electrode of the solar cell 10 extends along the width direction of the solar cell 10, and the negative electrode also extends along the width direction of the solar cell 10. The front side of the solar cell 10 is the light-receiving surface. The back side of the solar cell 10 has multiple solder points (not shown in the figure). Multiple solder points are distributed on both the positive and negative electrodes of the solar cell 10. These solder points are used to connect the solder strip to the positive or negative electrode of the solar cell 10.

[0049] Along the width of the solar cell 10, multiple solder joints are evenly arranged at preset intervals, or the multiple solder joints may be spaced at different distances. Each solder joint is provided with a solder block or coated with solder paste for soldering the solder strip.

[0050] Step S12: Provide prefabricated welding strip, and stretch the prefabricated welding strip to obtain stretched welding strip at a first stretching ratio, wherein the first stretching ratio is ≤3%;

[0051] Pre-formed solder strips (not shown in the figure) are metal strips obtained by cutting and stamping metal sheets. Pre-formed solder strips can be copper solder strips, or aluminum solder strips, or tin solder strips, or solder strips comprising a copper substrate and a tin layer, or solder strips comprising an aluminum substrate and a tin layer.

[0052] Reference Figure 3 , Figure 4 As shown, the prefabricated welding strip is stretched at a first stretching ratio to make it straight, resulting in a stretched welding strip 30. This allows the stretched welding strip 30 to better fit the welding point on the positive or negative electrode of the battery cell 10, improving the welding effect and reducing contact resistance. The first stretching ratio is controlled to be ≤3% to minimize the length change of the stretched welding strip 30 relative to the prefabricated welding strip. This helps reduce the difference in dimensional expansion and contraction between the stretched welding strip 30 and the welded battery cell 10, thus reducing the warpage deformation of the welded battery cell 10. For example, the first stretching ratio can be 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.2%, 2%, 1.8%, 1.7%, 1.5%, 1.3%, 1.2%, 1.1%, or 1%.

[0053] It should be noted that "stretch ratio" refers to the ratio of the difference between the length of the stretched welding strip 30 and the length of the precast welding strip to the length of the precast welding strip.

[0054] Step S13: Weld the welding surface of the stretch welding strip to the welding point, fix the stretch welding strip to the back of the battery cell, and the warping deformation of the battery cell after welding is ≤3.5mm.

[0055] Reference Figure 5 , Figure 6 As shown, the battery cell 10 is fixed on the welding platform using a clamp or positioning device, the welding surface of the stretch welding strip 30 is aligned with the welding surface of the battery cell 10, and the stretch welding strip 30 is welded to the welding point on the positive electrode (or welding point on the negative electrode) of the battery cell 10 one by one to connect the stretch welding strip 30 to the positive electrode (or negative electrode) of the battery cell 10.

[0056] After the battery cell 10 is welded to the stretching ribbon 30, the battery cell 10 and the stretching ribbon 30 are cooled to room temperature. The warpage deformation of the welded battery cell 10 is then tested. The warpage deformation of the welded battery cell 10 is ≤3.5mm.

[0057] In some embodiments, the first stretching ratio is ≤1%. For example, the first stretching ratio can be 1%, 0.95%, 0.9%, 0.85%, 0.8%, etc. When the first stretching ratio is reduced to 1%, after the stretched welding strip 30 is welded to the battery cell 10, the warping deformation of the welded battery cell 10 is basically zero. That is, the welded battery cell 10 has basically no warping deformation, which can further reduce the breakage rate of the battery cell 10 after lamination.

[0058] In some embodiments, the first stretching ratio is 1%-3%. Stretching the prefabricated welding strip to obtain the stretched welding strip 30 with a stretching ratio of less than 1% may result in low flatness of the stretched welding strip 30, failing to meet welding requirements and causing welding strip waste. Therefore, this embodiment takes into account both production costs and the warpage deformation of the battery cell 10, setting the first stretching ratio to 1%-3%, which can both increase product yield and reduce welding strip loss.

[0059] In some embodiments, stretching a preformed solder strip to obtain a stretched solder strip 30 at a first stretching ratio includes:

[0060] Step S121: The precast welding strip is conveyed to the stretching mechanism. After the stretching mechanism fixes the precast welding strip, it stretches the two ends of the precast welding strip to a preset displacement, thereby obtaining the stretched welding strip 30.

[0061] The precast welding strip is conveyed to a stretching mechanism, which has clamps or clamping devices that hold both ends of the precast welding strip in place. The length of the precast welding strip is determined according to a first stretching ratio. The stretching displacement of the stretching mechanism is determined according to the stretching length, and the stretching mechanism stretches both ends of the precast welding strip to a preset displacement, resulting in a stretched welding strip 30.

[0062] Step S122: The stretching mechanism conveys the stretched weld strip 30 to the shaping groove for shaping.

[0063] After the stretching process is completed, the stretching mechanism will transfer the stretched welding strip 30 to the shaping groove. The size and shape of the shaping groove are designed and manufactured according to the size and shape of the stretched welding strip 30 required for production. The stretched welding strip 30 is shaped in the shaping groove to ensure that the stretched welding strip 30 can obtain an accurate shape and size in the shaping groove.

[0064] In some embodiments, after the stretched welding strip 30 is conveyed to the shaping tank, the stretched welding strip 30 in the shaping tank is subjected to shaping treatment, such as cold pressing, so that the stretched welding strip 30 is straighter, has a smoother and denser surface, and meets the requirements of subsequent production and use.

[0065] After the shaping process, the shape and size of the stretched welding strip 30 are further stabilized and optimized. At this point, it can be removed from the shaping groove for subsequent welding steps.

[0066] In some embodiments, refer to Figure 3 , Figure 4 As shown, after stretching the preformed welding strip to obtain the stretched welding strip 30 at the first stretching ratio, the process further includes: etching the welding surface of the stretched welding strip 30 to form a plurality of grooves 31 on the welding surface.

[0067] In this embodiment, the groove 31 is a blind hole provided on the welding surface. The groove 31 on the welding surface of the stretched solder ribbon 30 corresponds to the welding point on the back of the battery cell 10. The groove 31 is used to accommodate the solder block or solder paste of the welding point. The groove 31 can reduce the length change of the stretched solder ribbon 30 after welding compared with the stretched solder ribbon 30 before welding. At the same time, the groove 31 can buffer and absorb part of the stress exerted on the battery cell 10 by the stretched solder ribbon 30 after welding, which can reduce the warpage deformation of the battery cell 10 after welding and reduce the breakage rate of the battery cell 10 after lamination.

[0068] The groove 31 can be a circular groove, an elliptical groove, a square groove, a triangular groove, etc.

[0069] In this embodiment, the welding strip 30 is welded to the welding point, including the following steps:

[0070] Step S131: Apply solder paste to the solder joints, and set the soldering surface of the stretched solder ribbon 30 facing the back of the battery cell 10. The multiple grooves 31 of the soldering surface correspond to the multiple solder joints, and the solder paste of the solder joints fills the grooves 31. Apply solder paste to the solder joints of the battery cell 10, align one end of the stretched solder ribbon 30 with one side edge of the battery cell 10, extend the stretched solder ribbon 30 along the width direction of the battery cell 10, and extend the other end of the stretched solder ribbon 30 from the other side edge of the battery cell 10 to the outside of the battery cell 10. Attach the soldering surface of the stretched solder ribbon 30 to the back of the battery cell 10, and the multiple grooves 31 of the soldering surface correspond to the multiple solder joints. The solder paste of the solder joints fills the grooves 31.

[0071] Step S132: Reflow solder paste is used to solder the stretched solder strip 30 to the back of the cell 10.

[0072] Before reflow soldering begins, the solar cell 10, the stretched solder ribbon 30, and the solder paste are preheated at a temperature lower than the reflow soldering temperature. Preheating helps reduce thermal stress during the soldering process and improves soldering quality. Then, the module is placed in the reflow oven, where it undergoes rapid heating, holding, and cooling processes. During this process, the solder paste melts, flows, and solidifies, firmly soldering the stretched solder ribbon 30 to the back of the solar cell 10.

[0073] In some embodiments, refer to Figure 4As shown, along the width direction of the battery cell 10, the size of the groove 31 located at the edge of the battery cell 10 is larger than the size of the groove 31 located at the center of the battery cell 10.

[0074] After high-temperature welding, the uneven expansion and contraction of the stretched weld strip 30 and the battery cell 10 causes stress on the battery cell 10, resulting in warping. Testing revealed that along the width direction of the battery cell 10, the stress at the edge of the battery cell 10 is greater than the stress at the center. In this embodiment, by rationally designing the dimensions of the groove 31 at the edge and the groove 31 at the center of the battery cell 10, the groove 31 at the edge of the battery cell 10 absorbs more stress, thereby reducing the stress difference between the edge and center of the battery cell 10. This helps to further reduce the warping deformation of the battery cell 10.

[0075] The size ratio of the groove 31 located at the edge of the battery cell 10 to the groove 31 located at the center of the battery cell 10 is 1.4-2.1:1. For example, it can be 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1 or 2.1:1.

[0076] In one example, along the width direction of the solar cell 10, the solar cell 10 includes a first side and a second side disposed opposite to each other. From the first side to the second side, seven welding points are defined on the positive (or negative) electrode of the solar cell 10, and the seven welding points are evenly distributed.

[0077] Reference Figure 4 As shown, the welding surface of the stretched welding strip 30 has a first groove 311, a second groove 312, a third groove 313, a fourth groove 314, a fifth groove 315, a sixth groove 316, and a seventh groove 317 arranged sequentially from the first end face. The fourth groove 314 is the groove 31 located at the center of the battery cell 10. The first groove 311, the second groove 312, the third groove 313, the fifth groove 315, the sixth groove 316, and the seventh groove 317 are symmetrical about the fourth groove 314. The fourth groove 314 has the smallest size. From the fourth groove 314 towards the first groove 311, the size of each groove 31 gradually increases. From the fourth groove 314 towards the seventh groove 317, the size of each groove 31 gradually increases.

[0078] In one example, the area of ​​the fourth groove 314 is 1a, the area of ​​the first groove 311 and the seventh groove 317 is 1.8a, the area of ​​the second groove 312 and the sixth groove 316 is 1.5a, and the area of ​​the third groove 313 and the fifth groove 315 is 1.2a.

[0079] In some embodiments, refer to Figure 4As shown, along the width direction of the battery cell 10, from the edge of the battery cell 10 towards the center, the size between the grooves 31 of the stretching solder strip 30 gradually increases.

[0080] In one example, refer to Figure 4 As shown, from the first groove 311 to the fourth groove 314, the spacing between the grooves 31 increases. That is, the spacing between the first groove 311 and the second groove 312 is the smallest, the spacing between the second groove 312 and the third groove 313 is the next smallest, and the spacing between the third groove 313 and the fourth groove 314 is the smallest. The spacing between the grooves 31 from the seventh groove 317 to the fourth groove 314 follows the same principle.

[0081] In this way, by reasonably designing the spacing between the grooves 31, the grooves 31 located at the edge of the battery cell 10 can absorb more stress, thereby reducing the stress difference between the edge and the center of the battery cell 10. This is beneficial to further reduce the warping deformation of the battery cell 10.

[0082] In one example, refer to Figure 4 As shown, the groove 31 formed on the stretched welding strip 30 is an elliptical groove. The major axis of the ellipse is set along the length direction of the stretched welding strip 30 (the width direction of the battery cell 10). From the edge of the battery cell 10 to the center, the size between the grooves 31 of the stretched welding strip 30 gradually increases, and the size of the groove 31 gradually increases.

[0083] In some embodiments, refer to Figure 2 As shown, the method for manufacturing a back contact battery in this embodiment includes the following steps:

[0084] Step S21: Provide a battery cell 10. The back of the battery cell 10 has a plurality of first welding points and a plurality of second welding points. The plurality of first welding points are arranged along the width direction of the battery cell 10, and the plurality of second welding points are arranged along the width direction of the battery cell 10. Specifically, the plurality of first welding points are disposed on the positive electrode of the battery cell 10, and the plurality of second welding points are disposed on the negative electrode of the battery cell 10.

[0085] Step S22: Provide a first prefabricated weld strip, and stretch the first prefabricated weld strip at a first stretching ratio to obtain a first stretched weld strip 130, wherein the first stretching ratio is ≤3%;

[0086] Step S23: Provide a second preformed welding strip and stretch the second preformed welding strip at a first stretching ratio to obtain a second stretched welding strip 230; In this embodiment, the first stretched welding strip 130 and the second stretched welding strip 230 are obtained by stretching the preformed welding strip at the same stretching ratio, and the first stretched welding strip 130 has the same size, shape and material.

[0087] Step S24: Weld the welding surface of the first stretching welding strip 130 to a plurality of first welding points. One end of the first stretching welding strip 130 is fixed to one side edge of the battery cell 10. The first stretching welding strip 130 extends along the width direction of the battery cell 10 to the other side edge of the battery cell 10 and extends out of the battery cell 10. The first stretching welding strip 130 is welded to the positive electrode of the battery cell 10 to lead out the positive electrode of the battery cell 10.

[0088] Step S25: The welding surface of the second tensile welding strip 230 is welded to multiple second welding points. One end of the second tensile welding strip 230 is fixed to the other edge of the battery cell 10. The second tensile welding strip 230 extends along the width direction of the battery cell 10 towards one edge of the battery cell 10 and extends out of the battery cell 10. The warping deformation of the battery cell 10 after welding with the first tensile welding strip 130 and the second tensile welding strip 230 is ≤3.5mm. The second tensile welding strip 230 is welded to the negative electrode of the battery cell 10 to bring out the negative electrode of the battery cell 10.

[0089] In this embodiment, the first stretching weld strip 130 welded to the positive electrode of the battery cell 10 and the second stretching weld strip 230 connected to the negative electrode of the battery cell 10 both have a stretching ratio of ≤3%. The difference in dimensional expansion and contraction between the first stretching weld strip 130 and the second stretching weld strip 230 after welding and the battery cell 10 after welding can reduce the warpage of the battery cell 10 after welding, which is beneficial to reducing the breakage rate of the battery cell 10 after lamination, and further improving product yield and reducing production costs.

[0090] According to an exemplary embodiment, this embodiment provides a back contact battery, referring to... Figure 3 , Figure 4 , Figure 5 , Figure 6As shown, the back contact battery includes a battery cell 10 and a stretched welding ribbon 30. The battery cell 10 has a front and a back side arranged opposite to each other. The positive and negative electrodes of the battery cell 10 are both located on the back side. The positive electrode of the battery cell 10 extends along the width direction of the battery cell 10, and the negative electrode of the battery cell 10 extends along the width direction of the battery cell 10. The front side of the battery cell 10 is the light-receiving surface, and the back side of the battery cell 10 has welding points. Specifically, multiple welding points are distributed on both the positive and negative electrodes of the battery cell 10. The welding points are used to connect the welding ribbon to the positive electrode or the negative electrode of the battery. Along the width direction of the battery cell 10, the multiple welding points are evenly arranged at a preset interval, or the multiple welding points can be spaced at different distances. Each solder joint is provided with a solder block or coated with solder paste for soldering the solder strip; the stretched solder strip 30 is obtained by stretching the pre-made solder strip at a first stretching ratio. For example, the stretched solder strip 30 can be a solder strip composed of copper solder strip, aluminum solder strip, tin solder strip, copper substrate and tin layer, or the stretched solder strip 30 can be a solder strip including aluminum substrate and tin layer. The first stretching ratio is ≤3%. For example, the first stretching ratio can be 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.2%, 2%, 1.8%, 1.7%, 1.5%, 1.3%, 1.2%, 1.1% or 1%. The welding surface of the stretched solder strip 30 is welded to the solder joint. The stretched solder strip 30 is fixed to the back of the battery cell 10. The stretched solder strip 30 and the battery cell 10 are laminated together. The warpage deformation of the battery cell 10 is ≤3.5mm.

[0091] In some embodiments, the first stretching ratio is ≤1%. For example, the first stretching ratio can be 1%, 0.95%, 0.9%, 0.85%, 0.8%, etc. When the first stretching ratio is reduced to 1%, after the stretched welding strip 30 is welded to the battery cell 10, the warping deformation of the welded battery cell 10 is basically zero. That is, the welded battery cell 10 has basically no warping deformation, which can further reduce the breakage rate of the battery cell 10 after lamination.

[0092] In some embodiments, the first stretching ratio is 1%-3%. This can both increase product yield and reduce solder strip loss.

[0093] In some embodiments, refer to Figure 3 , Figure 4As shown, the welding surface of the stretch solder strip 30 is provided with multiple grooves 31, which can be circular, elliptical, square, triangular, etc. The grooves 31 are corresponding to multiple welding points, and the grooves 31 are filled with solder paste. The stretch solder strip 30 is soldered to the back of the battery cell 10 through the solder paste. The grooves 31 can reduce the length change of the stretched solder strip 30 after welding compared to before welding. Simultaneously, the grooves 31 can buffer and absorb some of the stress exerted on the battery cell 10 by the stretched solder strip 30 after welding, thereby reducing the warpage deformation of the battery cell 10 after welding and reducing the breakage rate of the battery cell 10 after lamination.

[0094] In some embodiments, refer to Figure 3 As shown, along the width direction of the solar cell 10, the size of the groove 31 located at the edge of the solar cell 10 is larger than the size of the groove 31 located at the center of the solar cell 10. In this way, the groove 31 at the edge of the solar cell 10 absorbs more stress, thereby reducing the stress difference between the edge and the center of the solar cell 10, which is beneficial to further reduce the warping deformation of the solar cell 10.

[0095] The size ratio of the groove 31 located at the edge of the battery cell 10 to the groove 31 located at the center of the battery cell 10 is 1.4-2.1:1. For example, it can be 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1 or 2.1:1.

[0096] In one example, refer to Figure 3 As shown, the welding surface of the stretched welding strip 30 has a first groove 311, a second groove 312, a third groove 313, a fourth groove 314, a fifth groove 315, a sixth groove 316, and a seventh groove 317 arranged sequentially from the first end face. The area of ​​the fourth groove 314 is 1a, the areas of the first groove 311 and the seventh groove 317 are 1.8a, the areas of the second groove 312 and the sixth groove 316 are 1.5a, and the areas of the third groove 313 and the fifth groove 315 are 1.2a.

[0097] In some embodiments, refer to Figure 3 As shown, along the width direction of the battery cell 10, from the edge of the battery cell 10 towards the center, the size between the grooves 31 of the stretching solder strip 30 gradually increases.

[0098] In one example, refer to Figure 3As shown, from the first groove 311 to the fourth groove 314, the spacing between the grooves 31 increases. That is, the spacing between the first groove 311 and the second groove 312 is the smallest, the spacing between the second groove 312 and the third groove 313 is the next smallest, and the spacing between the third groove 313 and the fourth groove 314 is the smallest. The spacing between the grooves 31 from the seventh groove 317 to the fourth groove 314 follows the same principle.

[0099] In this way, by reasonably designing the spacing between the grooves 31, the grooves 31 located at the edge of the battery cell 10 can absorb more stress, thereby reducing the stress difference between the edge and the center of the battery cell 10. This is beneficial to further reduce the warping deformation of the battery cell 10.

[0100] In one example, refer to Figure 3 As shown, the groove 31 formed on the stretched welding strip 30 is an elliptical groove. The major axis of the ellipse is set along the length direction of the stretched welding strip 30 (the width direction of the battery cell 10). From the edge of the battery cell 10 to the center, the size between the grooves 31 of the stretched welding strip 30 gradually increases, and the size of the groove 31 gradually increases.

[0101] In some embodiments, refer to Figure 5 , Figure 6 As shown, the back of the solar cell 10 has multiple first welding points and multiple second welding points. The multiple first welding points are arranged along the width direction of the solar cell 10, and the multiple second welding points are arranged along the width direction of the solar cell 10. Specifically, the multiple first welding points are disposed on the positive electrode of the solar cell 10, and the multiple second welding points are disposed on the negative electrode of the solar cell 10.

[0102] The back contact battery includes a first stretched welding strip 130 and a second stretched welding strip 230. The first stretched welding strip 130 is obtained by stretching a first pre-made welding strip at a first stretch ratio. The welding surface of the first stretched welding strip 130 is welded to a plurality of first welding points. One end of the first stretched welding strip 130 is fixed to one side edge of the battery cell 10. The first stretched welding strip 130 extends along the width direction of the battery cell 10 to the other side edge of the battery cell 10 and extends out of the battery cell 10. The first stretched welding strip 130 is welded to the positive electrode of the battery cell 10 to lead out the positive electrode of the battery cell 10.

[0103] The second stretched welding strip 230 is obtained by stretching the second pre-fabricated welding strip at a first stretching ratio. The welding surface of the first stretched welding strip 130 is welded to multiple second welding points. One end of the second stretched welding strip 230 is fixed to the other edge of the battery cell 10. The second stretched welding strip 230 extends along the width direction of the battery cell 10 towards one edge of the battery cell 10 and extends out of the battery cell 10. The second stretched welding strip 230 is welded to the negative electrode of the battery cell 10 to bring out the positive electrode of the battery cell 10.

[0104] According to an exemplary embodiment, this embodiment also provides a photovoltaic module, including a plurality of back contact cells as described above.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the scope of protection of this disclosure. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing a back-contact battery, characterized in that, include: A battery cell is provided, wherein the back side of the battery cell has solder joints; A prefabricated welding strip is provided, and the prefabricated welding strip is stretched to obtain a stretched welding strip, wherein the first stretching ratio is ≤3%; a plurality of grooves are formed on the welding surface of the stretched welding strip, wherein the grooves are blind holes, and the size of the grooves located at the edge of the battery cell is larger than the size of the grooves located at the center of the battery cell along the width direction of the battery cell. The welding surface of the stretching welding strip is welded to the welding point, and the stretching welding strip is fixed to the back of the battery cell. The warpage deformation of the battery cell after welding is ≤3.5mm.

2. The method for manufacturing a back contact battery according to claim 1, characterized in that, The first stretching ratio is ≤1%.

3. The method for manufacturing a back contact battery according to claim 1, characterized in that, The process of stretching the preformed weld strip to obtain a stretched weld strip by stretching it at a first stretching ratio includes: The precast welding strip is conveyed to the stretching mechanism, which fixes the precast welding strip and stretches both ends of the precast welding strip by a preset displacement to obtain the stretched welding strip; The stretching mechanism conveys the stretched weld strip to the shaping tank for shaping.

4. The method for manufacturing a back contact battery according to claim 3, characterized in that, After stretching the preformed weld strip to obtain a stretched weld strip at a first stretching ratio, the method further includes: etching the welding surface of the stretched weld strip to form a plurality of grooves on the welding surface; and welding the stretched weld strip to the welding point, including: Solder paste is applied to the solder joints, and the soldering surface of the stretched solder strip is positioned facing the back of the battery cell. The plurality of grooves on the soldering surface correspond to the plurality of solder joints, and the solder paste of the solder joints is filled into the grooves. The reflow soldering solder paste bonds the stretched solder strip to the back of the battery cell.

5. The method for manufacturing a back contact battery according to claim 1, characterized in that, The back of the battery cell has a plurality of first welding points and a plurality of second welding points, wherein the plurality of first welding points are arranged along the width direction of the battery cell and the plurality of second welding points are arranged along the width direction of the battery cell. A first preformed welding strip is provided, and the first preformed welding strip is stretched at a first stretching ratio to obtain a first stretched welding strip, wherein the first stretching ratio is ≤3%. A second preformed welding strip is provided, and the second preformed welding strip is stretched at a first stretching ratio to obtain a second stretched welding strip; The welding surface of the first stretched welding strip is welded to a plurality of first welding points. One end of the first stretched welding strip is fixed to one side edge of the battery cell. The first stretched welding strip extends along the width direction of the battery cell to the other side edge of the battery cell and extends out of the battery cell. The welding surface of the second stretching welding strip is welded to a plurality of second welding points. One end of the second stretching welding strip is fixed to the other edge of the battery cell. The second stretching welding strip extends along the width direction of the battery cell to one side edge of the battery cell and extends out of the battery cell. The warpage deformation of the battery cell after welding with the first and second stretching strips is ≤3.5mm.

6. A back-contact battery, characterized in that, include: A battery cell, wherein the back side of the battery cell has welding points; The stretched welding strip is obtained by stretching a pre-made welding strip at a first stretching ratio of ≤3%. The welding surface of the stretched welding strip is welded to the welding point. The stretched welding strip is fixed to the back of the battery cell. The stretched welding strip is laminated with the battery cell. The warpage deformation of the battery cell is ≤3.5mm. The welding surface of the stretched welding strip is provided with a plurality of grooves, the grooves being blind holes, and along the width direction of the battery cell, the size of the grooves located at the edge of the battery cell is larger than the size of the grooves located at the center of the battery cell.

7. The back contact battery according to claim 6, characterized in that, The first stretching ratio is ≤1%.

8. The back contact battery according to claim 6, characterized in that, The groove is provided corresponding to a plurality of the welding points, the groove is filled with solder paste, and the stretched solder strip is welded to the back of the battery cell through the solder paste.

9. The back contact battery according to claim 6, characterized in that, The back of the battery cell has multiple first welding points and multiple second welding points, the multiple first welding points being arranged along the width direction of the battery cell, and the multiple second welding points being arranged along the width direction of the battery cell; the back contact battery includes: The first stretched welding strip is obtained by stretching the first pre-made welding strip at the first stretching ratio. The welding surface of the first stretched welding strip is welded to multiple first welding points. One end of the first stretched welding strip is fixed to one side edge of the battery cell. The first stretched welding strip extends along the width direction of the battery cell to the other side edge of the battery cell and extends out of the battery cell. The second stretched welding strip is obtained by stretching the second pre-made welding strip according to the first stretching ratio. The welding surface of the first stretched welding strip is welded to a plurality of second welding points. One end of the second stretched welding strip is fixed to the other edge of the battery cell. The second stretched welding strip extends along the width direction of the battery cell to one side edge of the battery cell and extends out of the battery cell.

Images