Solder strips, battery strings and their fabrication methods, photovoltaic modules

Abstract

This disclosure relates to a solder ribbon, a battery string, a method for manufacturing the same, and a photovoltaic module. The solder ribbon is used for battery strings with negative spacing and includes: a conductive body, the conductive body including a first connecting portion and second connecting portions disposed on both sides of the first connecting portion, the outer periphery of the first connecting portion being covered with a buffer layer, and the hardness of the first connecting portion being less than that of the second connecting portion; at least a portion of the first connecting portion is used for the overlapping area of ​​two adjacent battery cells in the battery string, and the two second connecting portions are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells. Therefore, the solder ribbon can reduce the risk of cell cracking and improve the reliability of the battery string during lamination by covering the first connecting portion and the outer periphery of the first connecting portion with a buffer layer, and by using at least a portion of the first connecting portion for the overlapping area of ​​two adjacent battery cells in the battery string.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic technology, specifically to a solder strip, a battery string and its preparation method, and a photovoltaic module. Background Technology

[0002] In related technologies, to increase the proportion of cell area in photovoltaic modules, adjacent cells are arranged with a negative spacing. However, this negative spacing arrangement results in solder ribbons in the overlapping area of ​​adjacent cells, which can easily cause microcracks in the overlapping area during lamination. Summary of the Invention

[0003] The purpose of this disclosure is to provide a solder ribbon, a cell string, a method for preparing the same, and a photovoltaic module. The solder ribbon can act as a buffer during the lamination of negative-pitch cell strings, reducing the risk of cell cracking, thereby at least partially solving the problems in the related technologies.

[0004] To achieve the above objectives, this disclosure provides a solder strip for a battery string with negative spacing, comprising: a conductive body, the conductive body including a first connecting portion and second connecting portions disposed on both sides of the first connecting portion, the outer periphery of the first connecting portion being covered with a buffer layer, and the hardness of the first connecting portion being less than that of the second connecting portion; at least a portion of the first connecting portion is used for the overlapping area of ​​two adjacent battery cells in the battery string, and the two second connecting portions are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells.

[0005] Optionally, the conductive body is copper-based, the first connection portion is formed after annealing a preset area of ​​the conductive body, and / or the buffer layer is one or more combinations of EVA, POE, and PVB.

[0006] Optionally, the Vickers hardness value of the first connecting part is HV1, where HV1 ≤ 80.

[0007] Optionally, the Vickers hardness value HV1 of the first connecting part is 60 ≤ HV1 ≤ 80; and the Vickers hardness value HV2 of the second connecting part is 80 < HV2 ≤ 140.

[0008] Optionally, the length of the first connecting portion is L1, where 2mm ≤ L1 ≤ 8mm; and / or The length of the second connecting part is L2, 52mm≤L2≤70mm.

[0009] Optionally, the thickness of the buffer layer is D1, where 0.2mm ≤ D1 ≤ 0.35mm.

[0010] A second aspect of this disclosure provides a battery string comprising a plurality of battery cells arranged with negative spacing and the aforementioned solder strip, wherein two adjacent battery cells are connected by the solder strip.

[0011] Optionally, the length of the overlapping area between two adjacent solar cells is L3, where 0.4mm ≤ L3 ≤ 2mm.

[0012] Optionally, the first connection portion in the solder strip is located in the middle of the overlapping area of ​​the two solar cells.

[0013] Optionally, the battery cell is a three-cell battery cell or a four-cell battery cell.

[0014] A third aspect of this disclosure provides a method for preparing a battery string, comprising: Provides multiple solar cells arranged with negative spacing; We provide solder strips. The welding strip includes a conductive body, which includes a first connecting part and a second connecting part disposed on both sides of the first connecting part. The outer periphery of the first connecting part is covered with a buffer layer. The first connecting part is located in the overlapping area of ​​two adjacent battery cells in the battery string, and the second connecting part is located in the non-overlapping area of ​​two adjacent battery cells in the battery string. The solder strips are welded to the battery cells to form a battery string.

[0015] Optionally, the step of providing solder strips may further include: annealing a preset area of ​​the conductive body, tinning the annealed preset area and covering it with a buffer layer.

[0016] Optionally, the annealing temperature of the preset region is 200℃-400℃, and the holding time is 5 seconds-15 seconds; and / or The buffer layer is one or a combination of at least two of the following: EVA, POE, and PVB. The buffer material is heated to 80℃-100℃, melted, and then uniformly coated onto a predetermined area of ​​the tin-plated conductive body and cured by water cooling.

[0017] This disclosure provides a photovoltaic module, including the aforementioned solder strip, the aforementioned cell string, or the aforementioned cell string prepared by the aforementioned preparation method.

[0018] Through the above technical solution, the solder strip in this disclosure is used for battery strings with negative spacing. The solder strip includes a conductive body, which includes a first connecting portion with an outer periphery covered by a buffer layer and second connecting portions disposed on both sides of the first connecting portion. At least a portion of the first connecting portion is used for the overlapping area of ​​two adjacent battery cells in the battery string, and the two second connecting portions are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells. Therefore, the solder strip can reduce the risk of cell cracking and improve the reliability of the battery string during lamination by using a buffer layer covering the first connecting portion and at least a portion of the first connecting portion for the overlapping area of ​​two adjacent battery cells in the battery string.

[0019] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the accompanying drawings...

[0021] Figure 1 This is a schematic diagram of the structure of the solder strip provided in an exemplary embodiment of this disclosure.

[0022] Figure 2 This is a schematic diagram of multiple solder strip combinations in production provided in an exemplary embodiment of this disclosure.

[0023] Figure 3 This is a schematic diagram of the structure in an exemplary embodiment of this disclosure, showing the connection between the solder strip and an adjacent battery cell.

[0024] Figure 4 This is a schematic diagram of the structure of the battery string provided in an exemplary embodiment of this disclosure.

[0025] Figure 5 This is a schematic flowchart of a battery string fabrication method provided in an exemplary embodiment of this disclosure.

[0026] Explanation of reference numerals in the attached figures 1-Soldering strip; 10-Conductive body; 11-First connecting part; 12-Second connecting part; 13-Buffer layer; 2-Battery string; 21-Battery cell. Detailed Implementation

[0027] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0028] In this disclosure, unless otherwise stated, directional terms such as "inner" and "outer" refer to the inner and outer contours of the corresponding components; "far" and "near" refer to the corresponding structure or component being away from or near another structure or component. Furthermore, the terms "first," "second," etc., used in this disclosure are for distinguishing one element from another and do not have sequential or importance implications. Additionally, in the following description, when referring to the accompanying drawings, unless otherwise explained, the same reference numerals in different drawings denote the same or similar elements. The above definitions are for explanation and illustration only and should not be construed as limiting this disclosure.

[0029] In related technologies, to increase the proportion of cell area in photovoltaic modules, adjacent cells are arranged with a negative spacing. However, this negative spacing arrangement results in solder ribbons in the overlapping area of ​​adjacent cells, which can easily cause microcracks in the overlapping area during lamination.

[0030] In order to solve the problems in related technologies, such as Figures 1-4 As shown, in a first aspect of this disclosure, a solder strip 1 is provided for a battery string 2 arranged with negative spacing. The solder strip 1 includes a conductive body 10, which includes a first connecting portion 11 and second connecting portions 12 disposed on both sides of the first connecting portion 11. A buffer layer 13 is covered around the outer periphery of the first connecting portion 11. The hardness of the first connecting portion 11 is less than that of the second connecting portion 12. At least a portion of the first connecting portion 11 is used for the overlapping area of ​​two adjacent battery cells 21 in the battery string 2, and the two second connecting portions 12 are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells 21.

[0031] Through the above technical solution, the solder strip 1 in this disclosure is used for battery strings 2 with negative spacing. The solder strip 1 includes a conductive body 10, which includes a first connecting portion 11 with an outer periphery covered by a buffer layer 13 and second connecting portions 12 disposed on both sides of the first connecting portion 11. The outer periphery of the first connecting portion 11 is covered by the buffer layer 13. At least a portion of the first connecting portion 11 is used in the overlapping area of ​​two adjacent battery cells 21 in the battery string 2, and the two second connecting portions 12 are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells 21. Thus, the solder strip 1 can cover the first connecting portion 11 and the outer periphery of the first connecting portion 11 with the buffer layer 13. At least a portion of the first connecting portion 11 is used in the overlapping area of ​​two adjacent battery cells 21 in the battery string 2. Therefore, during the lamination of the battery string 2, the buffer layer 13 provides basic buffering, and the first connecting portion 11 further disperses stress. The combination of the two can reduce the risk of cell cracking and improve the reliability of the battery string 2.

[0032] It should be noted that the conductive body 10 mentioned above is copper-based, that is, the main body of the conductive body 10 is made of copper, and the copper material is electrolytic copper of 99.9% or higher. The conductive body 10 needs to undergo external plating treatment, such as coating with lead-free tin-based plating, so as to form a solder ribbon 1 that can ensure conductivity and prevent copper oxidation through plating. In addition, the plating can also improve the welding compatibility between the solder ribbon 1 and the grid line of the battery cell 21.

[0033] In some possible implementations, the first connecting portion 11 is formed by partially annealing the conductive body 10 in a predetermined area. During the manufacturing process of the solder strip 1, for example, the conductive body 10 can be a copper rod, which is drawn into a copper wire and continuously drawn into a copper strip of a predetermined diameter through a multi-pass drawing die. It is then heated and annealed under nitrogen protection to eliminate work hardening and restore the ductility of the copper material. At this point, the conductive body 10 is entirely a second connecting portion 12 with higher hardness. Partial annealing is performed in a predetermined area of ​​the conductive body 10 to form the first connecting portion 11, which has a locally softer hardness. Subsequently, the first connecting portion 11 and the second connecting portion 12 are plated respectively. The buffer layer 13 is processed by heating and uniformly coating the soft material corresponding to the buffer layer 13 onto the first connecting part 11 to form the buffer layer 13 on the outer periphery of the first connecting part 11. For example, the soft material corresponding to the buffer layer 13 can be one or more combinations of EVA, POE and PVB. For example, in this embodiment, POE is preferred. The molten soft material is uniformly coated onto the outer periphery of the first connecting part 11 to form the buffer layer 13, thereby making a segmented solder strip 1, that is, the solder strip 1 includes the first connecting part 11, the buffer layer 13 covering the outer periphery of the first connecting part 11, and the second connecting parts 12 disposed on both sides of the first connecting part 11.

[0034] In actual production, such as Figure 3 As shown, a conductive body 10 with a rigid second connecting portion 12 can be manufactured first, and a first connecting portion 11 can be formed by local annealing in a preset area of ​​the conductive body 10. The first connecting portion 11 and the second connecting portion 12 are plated respectively, and a buffer layer 13 is uniformly coated on the outer periphery of the first connecting portion 11. Then, the conductive body 10 is cut to form a solder strip 1 for use between two battery cells 21.

[0035] In some possible implementations, the Vickers hardness value HV1 of the first connection portion 11 is ≤ 80. Since a solder strip 1 that is too hard can easily cause microcracks in the battery cells 21 during lamination when multiple battery cells 21 in the battery string 2 are connected in series via the solder strip 1, this can reduce the risk of microcracks in the battery cells 21. By limiting the Vickers hardness value HV1 of the first connection portion 11 to less than or equal to 80, the risk of microcracks in the battery cells 21 during lamination can be reduced. Furthermore, a buffer layer 13 can be wrapped around the outer periphery of the first connection portion 11 to further buffer the microcracks and reduce the risk of microcracks in the battery cells 21 during lamination.

[0036] Of course, it is understandable that the first connecting part 11 also needs to meet the requirements of welding process compatibility and structural strength. If the hardness of the first connecting part 11 is too low, the structural strength of the weld strip will be insufficient, making it prone to breakage and detachment. At the same time, it will not meet the requirements of welding process compatibility, and it will be prone to deformation during welding, leading to welding defects. In order to overcome the above defects, the Vickers hardness value HV1 of the first connecting part 11 in this disclosure is 60≤HV1≤80. By setting the Vickers hardness value HV1 of the first connecting part 11 between 60 and 80, where HV1 can be 60, 61, 62, 63, 64, 65, 70, 71, 72, 73, 74, 75, and 80, it can not only meet the requirements of welding process compatibility and structural strength, but also reduce the risk of microcracks during the lamination of the battery cells 21.

[0037] It is understood that the Vickers hardness value HV1 of the first connecting part 11 described above is illustrative. In other embodiments, the Vickers hardness value HV1 of the first connecting part 11 can also be any value between 60 and 80.

[0038] Furthermore, the second connecting portion 12 also needs to meet the requirements of welding process compatibility and structural strength, thus requiring a limitation on the hardness of the second connecting portion 12. For example, in this disclosure, the Vickers hardness value of the second connecting portion 12 is HV2, where HV2 > HV1, and 80 < HV2 ≤ 140. In this disclosure, the Vickers hardness value HV2 of the second connecting portion 12 can be 81, 85, 90, 91, 95, 100, 105, 110, 115, 120, 125, 130, 135, or 140. Therefore, by limiting the Vickers hardness value HV2 of the second connecting portion 12, the second connecting portion 12 can meet the requirements of welding process compatibility and structural strength, improving the reliability of the battery string 2 using the aforementioned welding strip.

[0039] The aforementioned solder strip 1 is applied to the battery string 2 with negative spacing arrangement. Negative spacing arrangement means that there is an overlapping area between adjacent battery cells 21 in the battery string 2. This reduces the gap between the battery cells 21, thereby increasing the light-receiving area of ​​the battery cells in the photovoltaic module and improving the power generation efficiency.

[0040] A second aspect of this disclosure provides a battery string 2, such as Figure 4 As shown, the battery string 2 includes multiple battery cells 21 arranged with negative spacing and the aforementioned solder strip 1, with adjacent battery cells 21 connected by the solder strip 1.

[0041] The aforementioned battery string 2 can be applied, for example, to HJT photovoltaic modules (heterojunction photovoltaic modules), TOPcon photovoltaic modules (tunneling oxide passivated contact photovoltaic modules), or IBC photovoltaic modules (interdigitated back contact photovoltaic modules). By employing a negative spacing arrangement, power generation efficiency can be improved. In this embodiment, the battery cell 21 can be a TOPcon cell. Two adjacent battery cells 21 are connected in series via a solder strip 1, wherein the two battery cells 21 are staggered vertically. The first connecting portion 11 in the solder strip 1 is located in the overlapping area of ​​the two battery cells 21. One of the two second connecting portions 12 is connected to the front positive main grid line of the preceding battery cell 21, and the other of the two second connecting portions 12 is connected to the back negative main grid line of the following battery cell 21. Thus, the two overlapping battery cells 21 can be connected in series via the solder strip 1. It is understood that the second connecting portion 12 here needs to be plated before connecting to the corresponding grid line.

[0042] In some possible implementations, the battery cells 21 in the battery string 2 can be arranged in a three-section or four-section configuration. Here, three-section and four-section refer to a single complete battery cell being laser-cut into three or four equal sections. Dividing the battery cells reduces the current per cell, decreases series resistance loss, and improves power generation efficiency. Furthermore, it reduces the risk of stress cracks and hot spots, resulting in higher reliability. The dimensions of the entire battery cell are defined as length H and width B, with H ranging from approximately 182mm to 215mm and B also ranging from approximately 182mm to 215mm. For example, when the overall battery cell size is 210mm × 210mm, in the three-section configuration, the length H of a single battery cell 21 can be 210mm and the width can be approximately 70mm; in the four-section configuration, the length H of a single battery cell 21 can be 210mm and the width can be approximately 52mm.

[0043] Of course, the arrangement of the battery cells 21 in three or four sections is illustrative. In other embodiments, the battery cells 21 can be arranged in other numbers of sections according to different operating conditions, such as a five-section arrangement.

[0044] It should be noted that when the solar cells 21 in the battery string 2 are arranged with negative spacing, a larger overlapping area is not necessarily better. The overlapping area needs to be controlled within a reasonable range to balance power generation efficiency, module reliability, and process feasibility. In related technologies, solar cells 21 are mostly arranged with positive spacing, resulting in physical gaps between adjacent solar cells. These physical gaps cannot absorb light to generate electricity, thus limiting the effective light-receiving area of ​​the photovoltaic module surface and reducing power generation efficiency. The negative spacing arrangement in the battery string 2 can solve the above-mentioned physical gaps and improve power generation efficiency. Of course, the range of the overlapping area also needs to avoid the risks of power generation efficiency cancellation, hot spot risk, and structural failure caused by excessive overlap. Therefore, in some possible implementations, the overlapping area of ​​the battery string 2 needs to be set within a preset range. For example, the length of the overlapping area between two adjacent solar cells 21 in the battery string 2 is L3, where 0.4mm ≤ L3 ≤ 2mm. That is, the length L3 of the overlapping area of ​​two adjacent battery cells 21 in the battery string 2 can be any value between 0.4mm and 2mm, and L3 can be 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1mm, 1.1mm, 1.2mm, 1.5mm, 1.8mm, or 2mm.

[0045] To accommodate the range of length L3 of the overlapping area between two adjacent battery cells 21 in the battery string 2, in some possible embodiments, the length of the first connecting portion 11 is L1, where 2mm ≤ L1 ≤ 8mm. Considering that the first connecting portion 11 needs to completely cover the length L3 of the overlapping area between two adjacent battery cells 21, the lower limit of the first connecting portion 11 is set to be greater than or equal to 2mm. Of course, an excessively long first connecting portion 11 would also affect the overall structural strength of the solder strip 1, so the upper limit of the first connecting portion 11 is set to be less than or equal to 8mm. That is, the length L1 of the first connecting portion 11 can be any value from 2mm to 8mm, for example, L1 can be 2mm, 2.1mm, 2.2mm, 2.5mm, 2.8mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 7mm, 8mm, etc. Of course, the above values ​​of L1 are only illustrative, and in other embodiments, the length L1 of the first connecting portion 11 can also be any other value from 2mm to 8mm.

[0046] In some possible implementations, to facilitate connection between the second connecting portion 12 and the corresponding battery cell 21, the length of the second connecting portion 12 is L2, where 52mm ≤ L2 ≤ 70mm. Figure 3As shown, the second connecting portion 12 is arranged along the direction extending from the short side of the battery cell 21. In this disclosure, the overall battery size is 210mm × 210mm, and it is divided into three or four sections. The width of a single battery cell 21 ranges from 52mm to 70mm. Therefore, the second connecting portion 12 can be set with reference to the width of a single battery cell 21. That is, the length of the second connecting portion 12 is L2, where 52mm ≤ L2 ≤ 70mm. Specifically, the length L2 of the second connecting portion 12 can be 52mm, 52.5mm, 53mm, 53.5mm, 54mm, 60mm, 65mm, 68mm, 70mm, etc. Of course, the values ​​of L2 mentioned above are only illustrative; in other embodiments, the length of the second connecting portion 12 can be any other value between 52mm and 70mm.

[0047] Of course, in some possible implementations, due to the negative spacing arrangement of the solar cells 21, the first connection portion 11 is located in the overlapping area of ​​the solar cells 21. In order to control the buffer layer 13 to both provide buffer insulation and meet the thickness restrictions of the photovoltaic module process, the thickness of the buffer layer 13 is D1, where 0.2mm ≤ D1 ≤ 0.35mm. For example, the thickness D1 of the buffer layer 13 can be 0.2mm, 0.22mm, 0.25mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm, etc. Of course, the above-mentioned values ​​of D1 are only illustrative. In other implementations, the thickness D1 of the buffer layer 13 can also be any other value from 0.2mm to 0.35mm.

[0048] In some possible implementations, the first connecting portion 11 in the solder ribbon 1 is located in the middle of the overlapping area of ​​the two solar cells 21. When the first connecting portion 11 and the buffer layer 13 on the solder ribbon 1 are arranged in the overlapping area of ​​the two solar cells 21, the presence of the solder ribbon 1 will change the stiffness distribution of the laminate. At this time, placing the first connecting portion 11 in the middle of the overlapping area of ​​the two solar cells 21 can eliminate stress eccentricity, make the pressure more uniform during the lamination process, and reduce the risk of microcracks. Of course, placing the first connecting portion 11 in the middle of the overlapping area of ​​the two solar cells 21 can also increase the redundancy of the solder ribbon 1 offset. The first connecting portion 11 in the middle of the overlapping area of ​​the two solar cells 21 can also form bidirectional symmetrical redundancy on both sides of the first connecting portion 11, so that the first connecting portion 11 and the outer buffer layer 13 can have sufficient area in the overlapping area of ​​the two solar cells 21, so as to have sufficient buffering during lamination and reduce the risk of microcracks.

[0049] like Figure 5 As shown, a third aspect of this disclosure provides a method for preparing a battery string, comprising: S10, providing multiple solar cells 21 arranged with negative spacing; S20. Provide solder ribbon 1, and weld solder ribbon 1 to battery cell 21 to form battery string 2. The welding strip 1 includes a conductive body 10, which includes a first connecting part 11 and a second connecting part 12 disposed on both sides of the first connecting part 11. A buffer layer 13 is wrapped around the outer periphery of the first connecting part 11. The first connecting part 11 is located in the overlapping area of ​​two adjacent battery cells 21 in the battery string 2, and the second connecting part 12 is located in the non-overlapping area of ​​two adjacent battery cells 21 in the battery string 2.

[0050] By using the above method, the first connecting part 11 and the buffer layer 13 are placed in the overlapping area of ​​the two battery cells 21, thereby reducing the risk of microcracks in the battery cells 21 during lamination and improving the reliability of the battery string.

[0051] It is understandable that in the above-mentioned dimensions of the entire battery, the length is H and the width is B, with H ranging from approximately 182mm to 215mm; when B ranges from approximately 182mm to 215mm, the battery cell 21 is a three- or four-part segment of the entire battery, that is, the entire battery cell 21 is divided into three or four equal parts. For example, when the dimensions of the entire battery are 210mm × 210mm, in the three-part segmentation method, the length H of a single battery cell 21 can be 210mm, the width can be approximately 70mm, the length of the overlapping area of ​​two adjacent battery cells 21 is L3, 0.4mm ≤ L3 ≤ 2mm, the thickness of the buffer layer 13 is D1, 0.2mm ≤ D1 ≤ 0.35mm, the length of the first connecting part 11 is L1, 2mm ≤ L1 ≤ 8mm, and the length of the second connecting part 12 is L2, 52mm ≤ L2 ≤ 70mm. The manufactured battery cells 21 are arranged in a preset negative spacing manner, and the first connecting part 11 of the manufactured solder strip 1 is placed in the overlapping area of ​​two adjacent battery cells 21. The second connecting part 12 is welded to the front electrode grid line and the back electrode grid line of the two battery cells 21 respectively, thereby completing the manufacturing of the battery string 2.

[0052] In some possible implementations, the step of providing solder strip 1 further includes: locally annealing a predetermined area of ​​the conductive body 10, tinning the annealed predetermined area, and then uniformly coating the corresponding buffer material onto the first connection portion 11 after heating to form a buffer layer 13. The locally annealed temperature is 200℃-400℃, and the holding time is 5 seconds-15 seconds. The buffer layer 13 can be one or a combination of at least two of EVA, POE, and PVB. The heating temperature of the buffer material is 80℃-100℃, and after melting, it is coated onto the predetermined area of ​​the tin-plated conductive body and water-cooled for curing. In the manufacturing process of the solder strip 1, for example, the conductive body 10 is constructed as a copper rod, the copper rod is drawn into copper wire, and then continuously drawn into a copper strip of a preset diameter through a multi-pass wire drawing die. It is then heated and annealed under nitrogen protection to eliminate work hardening and restore the ductility of the copper material. At this point, the conductive body 10 is entirely a second connecting part 12 with high hardness. Local annealing is then performed in a preset area of ​​the conductive body 10 to form a first connecting part 11 with locally softer hardness. Induction heating can be used at this time, with an annealing temperature of 200℃-400℃ and a holding time of 5-15 seconds. Afterwards, the first connecting part 11 and the second connecting part 12 are plated respectively. The tin plating layer corresponding to the first connecting part 11 has a tin content greater than 95% and is a lead-free plating layer, with nitrogen gas (at a flow rate of 5-20 m³ / h). 2 / h) To avoid oxidation and ensure weldability, after plating, the soft material corresponding to the buffer layer 13 is heated and uniformly coated onto the first connecting part 11 after plating to form the buffer layer 13 on the outer periphery of the first connecting part 11. For example, the soft material corresponding to the buffer layer 13 can be one or more combinations of EVA, POE and PVB. For example, in this embodiment, POE is preferred. The heating temperature of the buffer material is 80℃-100℃. The molten soft material is uniformly coated onto the outer periphery of the first connecting part 11 to form the buffer layer 13, thereby making a segmented solder strip 1, that is, the solder strip 1 includes the first connecting part 11, the buffer layer 13 covering the outer periphery of the first connecting part 11, and the second connecting part 12 disposed on both sides of the first connecting part 11.

[0053] This disclosure provides a photovoltaic module in a fourth aspect, comprising the aforementioned solder strip 1 or cell string 2, or cell string 2 manufactured using the aforementioned preparation method. It is understood that all the beneficial effects of the aforementioned photovoltaic module comprising the aforementioned solder strip 1 or cell string 2 are not elaborated here. Furthermore, the aforementioned photovoltaic module may include a front cover glass, a front encapsulating film, a cell string assembly, a back encapsulating film, and a backsheet. These components are sequentially layered and laminated to form a laminate. A junction box and an outer perimeter mounting frame are then attached to the laminate to form the photovoltaic module.

[0054] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0055] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0056] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A welding strip, characterized in that, A battery string for negative spacing arrangement includes: a conductive body, the conductive body including a first connecting portion and second connecting portions disposed on both sides of the first connecting portion, the outer periphery of the first connecting portion being covered with a buffer layer, and the hardness of the first connecting portion being less than that of the second connecting portion; at least a portion of the first connecting portion is used for the overlapping area of ​​two adjacent battery cells in the battery string, and the two second connecting portions are respectively used for electrical connection with the non-overlapping areas of two adjacent battery cells.

2. The welding strip according to claim 1, characterized in that, The conductive body is copper-based, the first connecting portion is formed after annealing a preset area of ​​the conductive body, and / or the buffer layer is one or more combinations of EVA, POE and PVB.

3. The welding strip according to claim 1, characterized in that, The Vickers hardness value of the first connecting part is HV1, and HV1 ≤ 80.

4. The welding strip according to claim 3, characterized in that, The Vickers hardness value of the first connecting part is HV1, 60≤HV1≤80; and / or The Vickers hardness value of the second connecting part is HV2, where 80 < HV2 ≤ 140.

5. The welding strip according to claim 1, characterized in that, The length of the first connecting part is L1, where 2mm ≤ L1 ≤ 8mm; and / or The length of the second connecting part is L2, 52mm≤L2≤70mm.

6. The welding strip according to claim 1, characterized in that, The thickness of the buffer layer is D1, where 0.2mm ≤ D1 ≤ 0.35mm.

7. A battery string, characterized in that, It includes a plurality of solar cells arranged with negative spacing and a solder strip as described in any one of claims 1-6, wherein two adjacent solar cells are connected by the solder strip.

8. The battery string according to claim 7, characterized in that, The length of the overlapping area between two adjacent battery cells is L3, where 0.4mm ≤ L3 ≤ 2mm.

9. The battery string according to claim 7, characterized in that, The first connection portion in the solder strip is located in the middle of the overlapping area of ​​the two battery cells.

10. The battery string according to claim 7, characterized in that, The battery cells are either three-cell or four-cell battery cells.

11. A method for preparing a battery string, characterized in that, include: Provides multiple solar cells arranged with negative spacing; We provide solder strips. The welding strip includes a conductive body, which includes a first connecting part and a second connecting part disposed on both sides of the first connecting part. The outer periphery of the first connecting part is covered with a buffer layer. The first connecting part is located in the overlapping area of ​​two adjacent battery cells in the battery string, and the second connecting part is located in the non-overlapping area of ​​two adjacent battery cells in the battery string. The solder strips are welded to the battery cells to form a battery string.

12. The method for preparing a battery string according to claim 11, characterized in that, The step of providing solder strips also includes: annealing a preset area of ​​the conductive body, tinning the preset area after annealing and covering it with a buffer layer.

13. The method for preparing a battery string according to claim 12, characterized in that, The annealing temperature of the preset region is 200℃-400℃, and the holding time is 5 seconds-15 seconds; and / or The buffer layer is one or a combination of at least two of the following buffer materials: EVA, POE, and PVB. The buffer material is heated to 80℃-100℃ to melt and then uniformly coated onto a predetermined area of ​​the tin-plated conductive body and cured by water cooling.

14. A photovoltaic module, characterized in that, This includes the solder strip as described in any one of claims 1-6, the battery string as described in any one of claims 7-10, or the battery string prepared by the preparation method described in any one of claims 11-13.

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