Back contact battery and manufacturing method thereof

Abstract

The invention relates to a back contact battery and a manufacturing method thereof, and relates to the field of photovoltaic technology. The manufacturing method of the back contact battery comprises the following steps: providing a battery piece, wherein the back surface of the battery piece is provided with welding points; providing a prefabricated welding strip, and stretching the prefabricated welding strip according to a first stretching ratio which is less than or equal to 3% to obtain a stretched welding strip; the welding face of the stretching welding strip is connected with the welding points in a welding mode, the stretching welding strip is fixed to the back face of the battery piece, and the buckling deformation of the welded battery piece is smaller than or equal to 3.5 mm. The stretching proportion of the stretching welding strip formed by stretching the prefabricated welding strip is controlled to be smaller than or equal to 3%, so that the length variation of the stretching welding strip after welding and the stretching welding strip before welding is reduced, the size expansion difference value of the stretching welding strip after welding and the welded battery piece is reduced, the stress of the stretching welding strip after welding on the battery piece is reduced, and the welding quality of the battery piece is improved. And the warping deformation quantity of the welded battery piece is reduced, and the piece breaking rate of the laminated battery piece is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of photovoltaic technology, and in particular to a back contact cell and a manufacturing method thereof. Background Art

[0002] The positive and negative electrodes of the back-contact solar cell are both set on the back of the battery. There is no grid line blocking the front of the battery, which reduces the shading loss on the front of the battery, maximizes the use of incident light on the front of the battery, and improves the battery conversion rate.

[0003] However, when back-contact solar cells are serially soldered, the solder ribbons are all soldered to the back of the cells. Due to the different thermal expansion coefficients of the solder ribbons and the cells, as well as improper control of the solder ribbon stretch ratio, the cells are subjected to uneven stress during the welding process. This stress accumulates inside the cells, eventually causing the cells to warp. During the lamination process, this stress may cause the cells to break and form 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] Based on this, it is necessary to provide a back contact battery and a method for manufacturing the same to address the problem in the prior art that the battery cell is subjected to uneven stress when welded to the welding strip, resulting in warping of the battery cell.

[0005] In order to achieve the above objectives, in a first aspect, the present disclosure provides a method for manufacturing a back contact battery, comprising:

[0006] Providing a battery cell, wherein the back side of the battery cell has a welding point;

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

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

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

[0010] Optionally, stretching the prefabricated welding strip at a first stretching ratio to obtain a stretched welding strip comprises:

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

[0012] The stretching mechanism transfers the stretched welding strip to the shaping tank for shaping.

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

[0014] Applying solder paste on the soldering points, placing the soldering surface of the stretched solder strip toward the back of the battery cell, the plurality of grooves on the soldering surface corresponding to the plurality of soldering points, and filling the solder paste of the soldering points into the grooves;

[0015] The solder paste is reflowed to weld the stretched solder strip to the back side 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 greater than the size of the groove located at the center of the battery cell.

[0017] Optionally, the back side of the battery cell 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, and the plurality of second welding points are arranged along the width direction of the battery cell;

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

[0019] Providing a second prefabricated welding strip, and stretching the second prefabricated welding strip at a first stretching ratio to obtain a second stretched welding strip;

[0020] The welding surface of the first stretch welding strip is welded to the plurality of the first welding points, one end of the first stretch welding strip is fixed to one side edge of the battery cell, and the first stretch welding strip extends along the width direction of the battery cell toward the other side edge of the battery cell and extends out of the battery cell;

[0021] The welding surface of the second stretch welding strip is welded to the plurality of second welding points, one end of the second stretch welding strip is fixed to the other side edge of the battery cell, and the second stretch welding strip extends along the width direction of the battery cell toward one side edge of the battery cell and extends out of the battery cell;

[0022] The warping deformation of the battery cell after being welded with the first stretch welding ribbon and the second stretch welding ribbon is ≤3.5 mm.

[0023] In a second aspect, the present disclosure provides a back-contact battery, comprising:

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

[0025] A stretched welding strip is obtained by stretching a prefabricated welding strip at a first stretching ratio, wherein the first stretching ratio is ≤3%, the welding surface of the stretched welding strip is welded to the welding point, the stretched welding strip is fixed to the back side of the battery cell, the stretched welding strip is laminated together with the battery cell, and the warping deformation of the battery cell is ≤3.5mm.

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

[0027] Optionally, the welding surface of the stretched welding ribbon is provided with a plurality of grooves, the grooves are arranged corresponding to the plurality of welding points, the grooves are filled with solder paste, and the stretched welding ribbon is soldered to the back side 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 greater 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, 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 comprises:

[0030] a first stretched welding strip, wherein the first stretched welding strip is obtained by stretching the first prefabricated welding strip by the first stretching ratio, the welding surface of the first stretched welding strip is welded and connected to the plurality of the first welding points, one end of the first stretched welding strip is fixed to one side edge of the battery cell, and the first stretched welding strip extends along the width direction of the battery cell toward the other side edge of the battery cell and extends out of the battery cell;

[0031] A second stretched welding strip, wherein the second stretched welding strip is obtained by stretching a second prefabricated welding strip at the first stretching ratio, the welding surface of the first stretched welding strip is welded and connected to a plurality of the second welding points, one end of the second stretched welding strip is fixed to the other side edge of the battery cell, and the second stretched welding strip extends along the width direction of the battery cell toward one side edge of the battery cell and extends out of the battery cell.

[0032] The back-contact battery and the manufacturing method thereof disclosed in the present invention control the stretching ratio of the stretched solder strip formed by stretching the prefabricated solder strip to be ≤3%, so as to reduce the length change of the stretched solder strip after welding and the stretched solder strip before welding, reduce the difference in size expansion and contraction between the stretched solder strip after welding and the battery cell after welding, reduce the stress of the stretched solder strip after welding on the battery cell, reduce the warping deformation of the battery cell after welding, and help to reduce the breakage rate of the battery cell after lamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 is a flow chart of a method for manufacturing a back contact battery provided in one embodiment;

[0035] Figure 2 A flowchart of a method for manufacturing a back contact battery provided in another embodiment;

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

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

[0038] Figure 5 A top view of a first stretched welding ribbon, a second stretched welding ribbon and a battery cell after being welded in an embodiment;

[0039] Figure 6 It is a side view of a first stretched welding ribbon, a second stretched welding ribbon and a battery cell after being welded in one embodiment.

[0040] Description of reference numerals:

[0041] 10. Battery cell; 30. Stretched welding strip; 130. First stretched welding strip; 230. Second stretched 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 DESCRIPTION

[0042] In order to facilitate understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure.

[0044] The inventors of the present disclosure have discovered that the welding connection between the battery cell and the welding ribbon, the welding ribbon and the battery cell have different thermal expansion coefficients. During the high-temperature welding process, the welding ribbon is extended due to the heat, while the battery cell expands relatively less due to its smaller thermal expansion coefficient. After cooling, the welding ribbon shrinks, while the battery cell almost returns to its original size. This uneven expansion and contraction can cause stress on the battery cell, resulting in warping. After the battery cell warps, the stress inside it further increases. During the lamination process, this stress may cause the battery cell to break and form 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, which controls the stretching ratio of the stretched prefabricated welding strip to be ≤3% to reduce the length change of the stretched welding strip after welding and the stretched welding strip before welding, reduce the difference in size expansion and contraction between the stretched welding strip after welding and the battery cell after welding, reduce the stress of the stretched welding strip after welding on the battery cell, and reduce the warping deformation of the battery cell after welding, which is beneficial to reducing the breakage rate of the battery cell after lamination, and is beneficial to further increasing the output of the product and reducing the production cost.

[0046] According to an exemplary embodiment, the present 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: providing a battery cell, wherein the back of the battery cell has a welding point;

[0048] Reference Figure 5 , Figure 6 As shown, the battery cell 10 is a back contact battery cell 10, the battery cell 10 has a front side and a back side that are arranged opposite to each other, the positive electrode and the negative electrode of the battery cell 10 are arranged on the back side, the positive electrode of the battery cell 10 extends along the width direction of the battery cell 10, the negative electrode of the battery cell 10 extends along the width direction of the battery cell 10, and the front side of the battery cell 10 is a light receiving side. The back side of the battery cell 10 has a plurality of welding points (not shown in the figure), and the positive electrode of the battery cell 10 and the negative electrode of the battery cell 10 are both distributed with a plurality of welding points, and the welding points are used to connect the welding strip to the positive electrode of the battery cell 10 or to the negative electrode of the battery cell 10.

[0049] Along the width direction of the battery cell 10, the plurality of welding points are evenly arranged at preset intervals, or the plurality of welding points can be spaced at different distances. Each welding point is provided with a welding block or dotted with solder paste for welding the welding strip.

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

[0051] The prefabricated welding strip (not shown in the figure) is a metal strip obtained by cutting and stamping a metal sheet. The prefabricated welding strip may be a copper welding strip, or the prefabricated welding strip may be an aluminum welding strip, or the prefabricated welding strip may be a tin welding strip, or the prefabricated welding strip may be a welding strip including a copper substrate and a tin layer, or the prefabricated welding strip may be a welding strip including 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, and the prefabricated welding strip is stretched to make the welding strip straight, so as to obtain a stretched welding strip 30, so that the stretched welding strip 30 can be more closely fitted with the welding point on the positive or negative electrode of the battery cell 10, improve the welding effect, and reduce the contact resistance. The first stretching ratio is controlled to be less than 3%, so that the length change of the stretched welding strip 30 relative to the prefabricated welding strip is small, which is conducive to reducing the difference between the size expansion and contraction of the stretched welding strip 30 after welding and the battery cell 10 after welding, and reducing the warping deformation of the battery cell 10 after welding. 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 the “stretching ratio” refers to the ratio of the difference between the length of the stretched welding strip 30 and the length of the prefabricated welding strip to the length of the prefabricated welding strip.

[0054] Step S13: welding the welding surface of the stretched welding strip to the welding point, fixing the stretched welding strip on 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, a clamp or a positioning device is used to fix the battery cell 10 on the welding platform, the welding surface of the stretched welding strip 30 is aligned with the welding surface of the battery cell 10, and the stretched welding strip 30 is welded to the welding points on the positive electrode (or the welding points on the negative electrode) of the battery cell 10 one by one to connect the stretched welding strip 30 to the positive electrode (or the negative electrode) of the battery cell 10.

[0056] After the battery cell 10 and the stretching welding ribbon 30 are welded and connected, the battery cell 10 and the stretching welding ribbon 30 are cooled to room temperature, and the warping deformation amount of the welded battery cell 10 is detected. The warping deformation amount of the welded battery cell 10 is ≤3.5 mm.

[0057] In some embodiments, the first stretching ratio is ≤1%. For example, the first stretching ratio may be 1%, 0.95%, 0.9%, 0.85%, 0.8%, etc. When the first stretching ratio is reduced to 1%, after the stretched welding ribbon 30 is welded to the battery cell 10, the warping deformation of the battery cell 10 after welding is substantially zero, that is, the battery cell 10 after welding has substantially 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%. When the prefabricated solder strip is stretched at a stretching ratio of less than 1% to obtain the stretched solder strip 30, the stretched solder strip 30 may have a low straightness and fail to meet the welding requirements, resulting in a waste of solder strips. In view of this, this embodiment takes into account both the production cost and the warping deformation of the battery cell 10, and sets the first stretching ratio to 1%-3%, which can not only increase the product yield, but also reduce the loss of solder strips.

[0059] In some embodiments, stretching the prefabricated welding strip at a first stretching ratio to obtain the stretched welding strip 30 includes:

[0060] Step S121: the prefabricated welding strip is transferred to a stretching mechanism. The stretching mechanism fixes the prefabricated welding strip and then stretches the two ends of the prefabricated welding strip to a preset displacement to obtain a stretched welding strip 30 .

[0061] The prefabricated welding strip is conveyed to a stretching mechanism, which has a clamp or a clamping device, and the clamp or the clamping device of the stretching mechanism clamps the two ends of the prefabricated welding strip to fix the prefabricated welding strip. The length of the stretched prefabricated welding strip is determined according to the first stretching ratio. The stretching displacement of the stretching mechanism is determined according to the stretching length, and the stretching mechanism stretches the two ends of the prefabricated welding strip, and the prefabricated welding strip is stretched to a preset displacement to obtain a stretched welding strip 30.

[0062] Step S122: The stretching mechanism transfers the stretched welding ribbon 30 to the shaping tank for shaping.

[0063] After completing the stretching process, the stretching mechanism transfers the stretched weld strip 30 to the molding groove. The size and shape of the molding groove are designed and manufactured according to the size and shape of the stretched weld strip 30 required by production. The stretched weld strip 30 is molded in the molding groove to ensure that the stretched weld strip 30 can obtain accurate shape and size in the molding groove.

[0064] In some embodiments, after the stretched welding tape 30 is transferred to the shaping tank, the stretched welding tape 30 in the shaping tank is subjected to shaping treatment, such as cold pressing treatment, so as to make the stretched welding tape 30 straighter, smoother and denser on the surface, so as to meet 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 time, it can be taken out from the shaping groove for subsequent welding steps.

[0066] In some embodiments, reference Figure 3 , Figure 4 As shown, after the prefabricated welding strip is stretched at a first stretching ratio to obtain the stretched welding strip 30, the further step 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 arranged on the welding surface. The groove 31 on the welding surface of the stretched welding strip 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 at the welding point. The groove 31 can reduce the length change of the stretched welding strip 30 after welding and the stretched welding strip 30 before welding. At the same time, the groove 31 can buffer and absorb part of the stress of the stretched welding strip 30 after welding on the battery cell 10, which can reduce the warping deformation of the battery cell 10 after welding and reduce the breakage rate of the battery cell 10 after lamination.

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

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

[0070] Step S131: Apply solder paste to the welding points, set the welding surface of the stretched solder strip 30 toward the back side of the battery cell 10, the multiple grooves 31 on the welding surface correspond to the multiple welding points, and the solder paste at the welding points is filled into the grooves 31; apply solder paste to the welding points of the battery cell 10, align one end of the stretched solder strip 30 with one side edge of the battery cell 10, extend the stretched solder strip 30 along the width direction of the battery cell 10, and the other end of the stretched solder strip 30 extends from the other side edge of the battery cell 10 to the outside of the battery cell 10, adhere the welding surface of the stretched solder strip 30 to the back side of the battery cell 10, the multiple grooves 31 on the welding surface correspond to the multiple welding points, and the solder paste at the welding points is filled into the grooves 31.

[0071] Step S132 : reflow solder paste to weld the stretched solder ribbon 30 to the back side of the battery cell 10 .

[0072] Before starting the reflow soldering, the battery cell 10, the stretched solder strip 30 and the solder paste are preheated. The preheating temperature is lower than the flow soldering temperature. Preheating helps to reduce the thermal stress during the soldering process and improve the soldering quality. Then, the assembly is sent to the reflow soldering furnace. In the reflow soldering furnace, the assembly undergoes a process of rapid heating, heat preservation and cooling. During this process, the solder paste will undergo melting, flow and solidification to firmly solder the stretched solder strip 30 to the back of the battery cell 10.

[0073] In some embodiments, reference 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 greater 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 welding strip 30 and the battery cell 10 will cause the battery cell 10 to be subjected to stress, thereby causing warping. Through detection, it is found that along the width direction of the battery cell 10, the stress on the edge of the battery cell 10 is greater than the stress on the center of the battery cell 10. In this embodiment, by reasonably designing the size of the groove 31 at the edge of the battery cell 10 and the size of 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 the center of the battery cell 10, which is conducive to further reducing 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, the battery cell 10 includes a first side surface and a second side surface that are oppositely disposed along the width direction of the battery cell 10. From the first side surface to the second side surface, seven welding points are defined on the positive electrode (or negative electrode) of the battery cell 10, and the seven welding points are evenly spaced.

[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 in sequence from the first end face. The fourth groove 314 is a groove 31 located at the center of the battery cell 10, and the first groove 311, the second groove 312, the third groove 313 and the fifth groove 315, the sixth groove 316, and the seventh groove 317 are symmetrical with the fourth groove 314 as the center. The size of the fourth groove 314 is the smallest, and the size of each groove 31 gradually increases from the fourth groove 314 to the first groove 311, and the size of each groove 31 gradually increases from the fourth groove 314 to the seventh groove 317.

[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, reference Figure 4As shown, along the width direction of the battery cell 10 , from the edge to the center of the battery cell 10 , the size between the grooves 31 of the stretched solder strip 30 gradually increases.

[0080] In one example, refer to Figure 4 As shown, the spacing between the grooves 31 increases from the first groove 311 to the fourth groove 314, 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 second, 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 is the same.

[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 , which 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, and the major axis of the ellipse is arranged along the length direction of the stretched welding strip 30 (the width direction of the battery cell 10). From the edge to the center of the battery cell 10, the size between the grooves 31 of the stretched welding strip 30 gradually increases, and the size of the grooves 31 gradually increases.

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

[0084] Step S21: Provide a battery cell 10, the back side of the battery cell 10 having 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 arranged on the positive electrode of the battery cell 10, and the plurality of second welding points are arranged on the negative electrode of the battery cell 10.

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

[0086] Step S23: providing a second prefabricated welding strip, and stretching the second prefabricated 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 prefabricated welding strips at the same stretching ratio, and the first stretched welding strip 130 has the same size, shape and material.

[0087] Step S24: Welding the welding surface of the first stretched welding strip 130 to multiple first welding points, one end of the first stretched welding strip 130 is fixed to one side edge of the battery cell 10, and 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.

[0088] Step S25: The welding surface of the second stretching welding strip 230 is welded to a plurality of second welding points, one end of the second stretching welding strip 230 is fixed to the other side edge of the battery cell 10, and the second stretching welding strip 230 extends along the width direction of the battery cell 10 toward one side 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 stretching welding strip 130 and the second stretching welding strip 230 is ≤3.5mm. The second stretching welding strip 230 is welded to the negative electrode of the battery cell 10 to lead out the negative electrode of the battery cell 10.

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

[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 strip 30; the battery cell 10 has a front side and a back side that are relatively arranged, the positive electrode and the negative electrode of the battery cell 10 are both arranged 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 side, and the back side of the battery cell 10 has a welding point. Specifically, a plurality of welding points are distributed on the positive electrode of the battery cell 10 and the negative electrode of the battery cell 10, and the welding points are used to connect the welding strip to the positive electrode of the battery or to the negative electrode of the battery. Along the width direction of the battery cell 10, the plurality of welding points are evenly arranged at preset intervals, or the plurality of welding points can also be spaced at different distances. A welding block is provided on each welding point or solder paste is applied on each welding point for welding the welding strip; the stretched welding strip 30 is obtained by stretching the prefabricated welding strip at a first stretching ratio. By way of example, the stretched welding strip 30 may be a welding strip composed of a copper welding strip, an aluminum welding strip, a tin welding strip, a copper substrate and a tin layer, or the stretched welding strip 30 may be a welding strip including an aluminum substrate and a tin layer, and the first stretching ratio is ≤3%. By way of example, the first stretching ratio may 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 welding strip 30 is welded to the welding point, the stretched welding strip 30 is fixed on the back side of the battery cell 10, the stretched welding strip 30 is laminated with the battery cell 10, and the warping 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 may be 1%, 0.95%, 0.9%, 0.85%, 0.8%, etc. When the first stretching ratio is reduced to 1%, after the stretched welding ribbon 30 is welded to the battery cell 10, the warping deformation of the battery cell 10 after welding is substantially zero, that is, the battery cell 10 after welding has substantially 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%, so that the yield of the product can be increased and the loss of the welding ribbon can be reduced.

[0093] In some embodiments, reference Figure 3 , Figure 4As shown, the welding surface of the stretched solder strip 30 is provided with a plurality of grooves 31, wherein the grooves 31 may be circular grooves, elliptical grooves, square grooves, triangular grooves, etc. The grooves 31 are arranged corresponding to the plurality of welding points, and the grooves 31 are filled with solder paste, and the stretched 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 between the stretched solder strip 30 after welding and the stretched solder strip 30 before welding. At the same time, the grooves 31 can buffer and absorb part of the stress of the stretched solder strip 30 after welding acting on the battery cell 10, which can reduce the warping deformation of the battery cell 10 after welding and reduce the breakage rate of the battery cell 10 after lamination.

[0094] In some embodiments, reference Figure 3 As 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 greater than the size of the groove 31 located at the center of the battery cell 10. In this way, the groove 31 at the edge of the battery cell 10 absorbs more stress to reduce the stress difference between the edge and the center of the battery cell 10, which is conducive to further reducing the warping deformation of the battery 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, referring 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 in sequence from the first end face. 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.

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

[0098] In one example, refer to Figure 3As shown, the spacing between the grooves 31 increases from the first groove 311 to the fourth groove 314, 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 second, 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 is the same.

[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 , which 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, and the major axis of the ellipse is arranged along the length direction of the stretched welding strip 30 (the width direction of the battery cell 10). From the edge to the center of the battery cell 10, the size between the grooves 31 of the stretched welding strip 30 gradually increases, and the size of the grooves 31 gradually increases.

[0101] In some embodiments, reference Figure 5 , Figure 6 As shown, 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 arranged on the positive electrode of the battery cell 10, and the plurality of second welding points are arranged on the negative electrode of the battery 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 prefabricated welding strip at a first stretching ratio, the welding surface of the first stretched welding strip 130 is welded and connected with 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, and 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 and connected 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 prefabricated welding strip at the first stretching ratio, the welding surface of the first stretched welding strip 130 is welded and connected with a plurality of second welding points, one end of the second stretched welding strip 230 is fixed to the other side edge of the battery cell 10, and the second stretched welding strip 230 extends along the width direction of the battery cell 10 toward one side edge of the battery cell 10 and extends out of the battery cell 10. The second stretched welding strip 230 is welded and connected to the negative electrode of the battery cell 10 to lead 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-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described 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 above-described embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A method for manufacturing a back contact battery, characterized in that: include: Providing a battery cell, wherein the back side of the battery cell has a welding point; Providing a prefabricated welding strip, and stretching the prefabricated welding strip at a first stretching ratio to obtain a stretched welding strip, wherein the first stretching ratio is ≤3%; The welding surface of the stretched welding strip is welded to the welding point, and the stretched welding strip is fixed on the back side of the battery cell. The warping 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: Stretching the prefabricated welding strip at a first stretching ratio to obtain a stretched welding strip, comprising: The prefabricated welding strip is conveyed to a stretching mechanism, and the stretching mechanism fixes the prefabricated welding strip and then stretches the two ends of the prefabricated welding strip by a preset displacement to obtain the stretched welding strip; The stretching mechanism transfers the stretched welding strip to the shaping tank for shaping.

4. The method for manufacturing a back contact battery according to claim 3, characterized in that: After the prefabricated welding strip is stretched at a first stretching ratio to obtain a stretched welding strip, the method further includes: etching the welding surface of the stretched welding strip to form a plurality of grooves on the welding surface; welding the stretched welding strip to the welding point, including: Applying solder paste on the soldering points, placing the soldering surface of the stretched solder strip toward the back of the battery cell, the plurality of grooves on the soldering surface corresponding to the plurality of soldering points, and filling the solder paste of the soldering points into the grooves; The solder paste is reflowed to weld the stretched solder strip to the back side of the battery cell.

5. The method for manufacturing a back contact battery according to claim 4, characterized in that: Along the width direction of the battery cell, the size of the groove located at the edge of the battery cell is greater than the size of the groove located at the center of the battery cell.

6. The method for manufacturing a back contact battery according to claim 1, characterized in that: 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; Providing a first prefabricated welding strip, and stretching the first prefabricated welding strip at a first stretching ratio to obtain a first stretched welding strip, wherein the first stretching ratio is ≤3%; Providing a second prefabricated welding strip, and stretching the second prefabricated welding strip at a first stretching ratio to obtain a second stretched welding strip; The welding surface of the first stretch welding strip is welded to the plurality of the first welding points, one end of the first stretch welding strip is fixed to one side edge of the battery cell, and the first stretch welding strip extends along the width direction of the battery cell toward the other side edge of the battery cell and extends out of the battery cell; The welding surface of the second stretch welding strip is welded to the plurality of second welding points, one end of the second stretch welding strip is fixed to the other side edge of the battery cell, and the second stretch welding strip extends along the width direction of the battery cell toward one side edge of the battery cell and extends out of the battery cell; The warping deformation of the battery cell after being welded with the first stretch welding ribbon and the second stretch welding ribbon is ≤3.5 mm.

7. A back contact battery, characterized in that: include: A battery cell, wherein the back side of the battery cell has a welding point; A stretched welding strip is obtained by stretching a prefabricated welding strip at a first stretching ratio, wherein the first stretching ratio is ≤3%, the welding surface of the stretched welding strip is welded to the welding point, the stretched welding strip is fixed to the back side of the battery cell, the stretched welding strip is laminated together with the battery cell, and the warping deformation of the battery cell is ≤3.5mm.

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

9. The back contact cell according to claim 7, characterized in that: The welding surface of the stretched welding strip is provided with a plurality of grooves, the grooves are arranged corresponding to the plurality of welding points, the grooves are filled with solder paste, and the stretched welding strip is soldered to the back side of the battery cell through the solder paste; Wherein, along the width direction of the battery cell, the size of the groove located at the edge of the battery cell is greater than the size of the groove located at the center of the battery cell.

10. The back contact cell according to claim 7, characterized in that: The back side of the battery cell 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, and the plurality of second welding points are arranged along the width direction of the battery cell; the back contact battery comprises: a first stretched welding strip, wherein the first stretched welding strip is obtained by stretching the first prefabricated welding strip by the first stretching ratio, the welding surface of the first stretched welding strip is welded and connected to the plurality of the first welding points, one end of the first stretched welding strip is fixed to one side edge of the battery cell, and the first stretched welding strip extends along the width direction of the battery cell toward the other side edge of the battery cell and extends out of the battery cell; A second stretched welding strip, wherein the second stretched welding strip is obtained by stretching a second prefabricated welding strip at the first stretching ratio, the welding surface of the first stretched welding strip is welded and connected to a plurality of the second welding points, one end of the second stretched welding strip is fixed to the other side edge of the battery cell, and the second stretched welding strip extends along the width direction of the battery cell toward one side edge of the battery cell and extends out of the battery cell.

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