Back contact cell modules and photovoltaic systems

Abstract

This application relates to the technical field of solar cells, and provides a back-contact cell assembly and a photovoltaic system. The back-contact cell assembly includes a plurality of cell strings and busbars. The first solder ribbon includes a body segment, a bent segment, and an extension segment. The body segment is welded to the first cell through a solder joint. The extension segment extends between the second solder ribbon and the fourth solder ribbon adjacent to each other on the second cell and at least partially overlaps with the busbar to be welded to the busbar. The body segment and the extension segment are connected by the bent segment; in the thickness direction of the back-contact cell assembly, the extension segment and the second solder ribbon do not have an overlapping part. In the second direction, the distance D between the extension segment of at least one first solder ribbon and the adjacent second solder ribbon satisfies the following relational expression: 1 mm < D ≤ 0.63 * arctan(1.8 * L * D2 + H) * (D1 - W). In this way, the risk of hidden cracks during the lamination process can be reduced, and at the same time, the electrical loss of the assembly can be reduced, the bifaciality of the assembly can be improved, and the manufacturing process difficulty can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a back-contact cell assembly and a photovoltaic system. Background Art

[0002] Back-contact solar modules typically consist of an array of back-contact cells, including several strings of back-contact cells. In back-contact solar modules, edge busbars are typically located at the edges of the module, while center busbars are typically located in the center. Both require a certain amount of space within the module. This reduces the module's effective light-receiving area, impacting conversion efficiency and aesthetics.

[0003] In the related art, in order to solve the above problems, the bus bar can be set on the back of the battery cell in the battery string. For example, the bus bar can be set on the battery cell adjacent to the battery cell at the end of the battery string, and then the welding strips on the end battery cell are welded together with the bus bar to achieve the hiding of the bus bar and the bus output.

[0004] However, during the production process, the inventors of this application discovered that this technical solution had a high risk of hidden cracks and fragmentation, as well as a high fragmentation rate. After repeated research and demonstration, the inventors of this application discovered that this occurred because the solder ribbons on the end cells needed to extend onto the busbars. In the thickness direction, two solder ribbons and the busbars were stacked together. Due to the high stacking height, stress concentration was easily generated during the lamination process, leading to hidden cracks and fragmentation in the cells, a high risk of fragmentation, and a reduced yield rate. Summary of the Invention

[0005] The present application provides a back-contact cell assembly and a photovoltaic system.

[0006] The present application is implemented as follows: the back contact battery assembly of the embodiment of the present application includes:

[0007] a plurality of battery strings, the battery strings comprising a plurality of battery cells sequentially connected in series along a first direction, the plurality of battery cells comprising a first battery cell disposed at an end of the battery string and a second battery cell adjacent to the first battery cell, a plurality of first welding ribbons and a plurality of third welding ribbons alternately arranged along a second direction being provided on a back surface of the first battery cell, a plurality of second welding ribbons and a plurality of fourth welding ribbons alternately arranged along the second direction being provided on a back surface of the second battery cell, the second welding ribbons corresponding one-to-one to the first welding ribbons, the third welding ribbons corresponding one-to-one to and electrically connected to the fourth welding ribbons, and the second direction intersecting the first direction;

[0008] a bus bar disposed on the back side of the second battery cell, the bus bar being connected to the first welding ribbon and extending along the second direction;

[0009] The first welding strip includes a main body section, a bent section, and an extended section. The main body section is welded to the first battery cell via a plurality of welding points. The main body section extends along a first direction, and an extension line of the main body section in the first direction at least partially overlaps with the second welding strip. The extended section extends between the second welding strip and the fourth welding strip adjacent to each other on the second battery cell and at least partially overlaps with the bus bar to be welded to the bus bar. The main body section and the extended section are connected by the bent section. In the second direction, the bent section bends relative to the main body section toward the side where the extended section is located.

[0010] In the thickness direction of the back contact battery assembly, the extension section and the second welding ribbon have no overlapping portion, and in the second direction, a distance D between the extension section of at least one first welding ribbon and an adjacent second welding ribbon satisfies the following relationship:

[0011] 1mm <D≤0.63*arctan(1.8*L*D2+H)*(D1-W);

[0012] Among them, D1 is the distance between the second welding strip and the fourth welding strip adjacent to each other in the second direction, W is the width of the extension section, L is the distance between the bus bar in the first direction and the end of the second battery cell facing the first battery cell, H is the thickness of the first welding strip, D2 is the distance between the welding point closest to the second battery cell among the several welding points welded to the main body segment and the bending starting point of the bending section relative to the main body segment, and the units of D, D1, W, L, H and D2 are all millimeters.

[0013] In some embodiments, the bending section is arc-shaped.

[0014] In some embodiments, a bending angle of the bending segment relative to the main body segment is 10° to 70°.

[0015] In some embodiments, the extension section is arranged parallel to the second welding strip.

[0016] In some embodiments, on the first battery cell, the welding ribbons closest to the two edges of the first battery cell in the second direction are the first welding ribbons, and the bent sections of the first welding ribbons closest to the edges are bent toward the middle of the first battery cell; or

[0017] On the first battery cell, the welding strips closest to the two edges of the first battery cell in the second direction are the third welding strips. Among the plurality of first welding strips, the bent sections of the first welding strips closest to the edges are bent in a direction away from the middle of the first battery cell.

[0018] In some embodiments, the bent sections of all the first welding ribbons on the first battery cell are bent toward the same edge of the first battery cell in the second direction; or

[0019] The bent section of a portion of the first welding strip on the first battery cell is bent toward one edge of the first battery cell in the second direction, and the bent section of another portion of the first welding strip is bent toward the other edge of the first battery cell in the second direction.

[0020] In some embodiments, the second welding ribbon has a protruding portion located on a side of the bus bar facing the first battery cell and not overlapping with the bus bar.

[0021] In some embodiments, the length of the protrusion in the first direction is 0.5 mm to 6 mm.

[0022] In some embodiments, the first battery cell is provided with a plurality of glue spots for pre-fixing the first welding strip, and the bending starting point of the bending section relative to the main section is located on the side of the glue spot closest to the second battery cell facing the second battery cell.

[0023] In some embodiments, the number of the first welding ribbons and the number of the second welding ribbons are both multiple and one-to-one corresponding, the multiple first welding ribbons are arranged at intervals along the second direction, and the multiple second welding ribbons are also arranged at intervals along the second direction;

[0024] Among them, several first welding strips are arranged in pairs. In each pair of first welding strips, the bent section of one of the first welding strips is bent toward one edge of the first battery cell in the second direction, and the bent section of the other first welding strip is bent toward the other edge of the first battery cell in the second direction.

[0025] In some embodiments, the back-contact battery assembly further includes an insulating strip, wherein the insulating strip is located between the bus bar and the second battery cell, and the bus bar is insulated and isolated from the second welding ribbon and the fourth welding ribbon by the insulating strip.

[0026] In some embodiments, the insulating strip extends to a portion of the first battery cell on a side close to the second battery cell.

[0027] In some embodiments, a length of a portion of the extending segment overlapping the bus bar in the first direction is greater than or equal to half a length of the bus bar in the first direction.

[0028] In some embodiments, a length of a portion of the extending section overlapping the bus bar in the first direction is 6 mm to 12 mm.

[0029] In some embodiments, the extension section is located on a side of the bus bar facing away from the second battery cell, the second welding ribbon is located on a side of the bus bar facing the second battery cell, the bus bar is formed with a raised section at the second welding ribbon that is raised toward a side away from the second battery cell, and the bus bar is formed with a recessed section at the extension section that is recessed toward the second battery cell.

[0030] For at least a partial cross section of the busbar, an angle α between a line connecting the highest point of the raised section and the lowest point of the recessed section and a plane where the second battery cell is located satisfies the following formula: 0.075≤tanα≤3.

[0031] In some embodiments, the extension section is located on a side of the bus bar away from the second battery cell, the bus bar is formed with a convex section at the second welding ribbon that convexes toward a side away from the second battery cell, and the bus bar is formed with a concave section at the extension section that is concave toward the second battery cell;

[0032] For at least a partial cross-section of the back-contact battery assembly at the bus bar, a height difference between a highest point of the extension segment and a highest point of an adjacent protruding segment is smaller than a thickness of the first welding ribbon.

[0033] In some embodiments, the back-contact battery assembly includes at least one series-connected battery string group, wherein the series-connected battery string group includes two battery strings arranged along the second direction;

[0034] In the same series-connected battery string group, the same bus bar extends from the second battery cell in one battery string to the second battery cell in another battery string to connect the two battery strings in series in the series-connected battery string group.

[0035] In some embodiments, the back-contact battery assembly further includes an insulating strip, the insulating strip being located between the bus bar and the second battery cell, and the bus bar being insulated from the second welding ribbon and the fourth welding ribbon by the insulating strip;

[0036] The back-contact battery assembly includes a plurality of battery strings connected in series and arranged along the second direction. In the second direction, the insulating strip extends from the first battery string connected in series to the last battery string connected in series.

[0037] In some embodiments, the back-contact battery assembly includes at least one parallel battery string group, wherein the parallel battery string group includes at least two first battery strings and a second battery string arranged along the first direction;

[0038] In the parallel battery string group, the first battery cell includes a battery cell located in the first battery string closest to the second battery string, the second battery string includes a third battery cell, the third battery cell is the battery cell in the second battery string closest to the first battery string, the first welding ribbon connects the first battery cell and the third battery cell, and the first battery string and the second battery string are connected in parallel through the first welding ribbon.

[0039] The present application also provides a photovoltaic system, which includes the back-contact cell assembly described in any one of the above items.

[0040] In the back-contact cell assembly and photovoltaic system in the embodiments of the present application, on the one hand. The bus bar is arranged on the back of the second cell of the cell string, which can hide the bus bar, thereby increasing the unit light receiving area of ​​the back-contact cell assembly and improving the conversion efficiency of the assembly. At the same time, the overall aesthetics of the back-contact cell assembly is better. On the other hand, the extension section of the first welding strip is welded to the bus bar to achieve bus output. The extension section of the first welding strip does not overlap with the second welding strip in the thickness direction. During the lamination process, the extension section and the second welding strip are staggered with each other in the extension direction of the bus bar and will not be stacked. During the lamination process, the extension section can be pressed down close to the second cell, thereby reducing the overall stacking height of the entire assembly, effectively avoiding stress concentration during the lamination process, thereby reducing the risk of hidden cracks and splits in the cell, and improving the yield rate. At the same time, the spacing between the extended section of the first welding ribbon and the second welding ribbon in the second direction is adaptively designed based on several factors: the spacing between the second welding ribbon and the adjacent fourth welding ribbon in the second direction, the width of the extended section of the first welding ribbon, the location of the busbar on the second cell, the thickness of the first welding ribbon, and the starting point of the first welding ribbon's bend. Setting the spacing between the extended section and the second welding ribbon in the second direction to satisfy the above relationship effectively reduces the stacking height during the lamination process, effectively avoiding stress concentration during the lamination process. It also reduces the bending length of the bent section of the first welding ribbon, reducing electrical losses in the first welding ribbon during the busbar transmission process. Furthermore, reducing the bending length of the bent section of the first welding ribbon also reduces the first welding ribbon's obstruction of the cell on the back of the module, thereby improving the module's bifaciality. Furthermore, by comprehensively considering the above factors and setting the spacing between the extended section and the second welding ribbon in the second direction to satisfy the above relationship, it can effectively reduce the manufacturing process difficulty and improve manufacturing efficiency.

[0041] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a module schematic diagram of a photovoltaic system provided by an embodiment of the present application;

[0043] Figure 2 Schematic diagram of the structure of the back contact battery assembly provided in an embodiment of the present application;

[0044] Figure 3 1 is a schematic structural diagram of a series-connected battery string of a back-contact battery assembly provided in an embodiment of the present application;

[0045] Figure 4 yes Figure 3 Schematic diagram of the enlarged structure at IV in the middle;

[0046] Figure 5 yes Figure 4 Schematic diagram of the enlarged structure at V in the middle;

[0047] Figure 6 yes Figure 4 Schematic diagram of the enlarged structure at VI in the middle;

[0048] Figure 7 yes Figure 3 Another enlarged structural diagram of position IV in the middle;

[0049] Figure 8 yes Figure 7 Schematic diagram of the enlarged structure at position VIII;

[0050] Figure 9 1 is a schematic structural diagram of a parallel battery string group of a back-contact battery assembly provided in an embodiment of the present application;

[0051] Figure 10 yes Figure 9 Schematic diagram of the enlarged structure at X in the middle;

[0052] Figure 11 yes Figure 5 Schematic diagram of the cross section along line XI-XI;

[0053] Figure 12 Schematic diagram of the structure of the busbar of the back contact battery assembly provided in an embodiment of the present application;

[0054] Figure 13 yes Figure 8 Schematic diagram of the cross section along line XIII-XIII;

[0055] Figure 14 This is another structural schematic diagram of the bus bar of the back-contact battery assembly provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present application and are not intended to limit the present application.

[0057] In the description of this application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "longitudinal", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0060] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0061] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art will appreciate the application of other processes and / or the use scenarios of other materials.

[0062] See also Figure 1 The photovoltaic system 1000 in the embodiment of the present application may include at least one back-contact cell assembly 100 in the embodiment of the present application. In the photovoltaic system 1000, the back-contact cell assemblies 100 may be electrically connected in parallel or in series, and the specific configuration may be selected based on actual needs.

[0063] In the embodiments of the present application, the photovoltaic system 1000 can be applied to photovoltaic power stations, such as ground-mounted power stations, rooftop power stations, and water-based power stations. It can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system 1000 are not limited to these. In other words, the photovoltaic system 1000 can be applied to all fields that require solar energy generation.

[0064] Taking the photovoltaic power generation system network as an example, the photovoltaic system 1000 may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple battery components. For example, multiple battery components may form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box may converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains power network to realize solar power supply.

[0065] See also Figure 2-Figure 8 The back contact cell in the embodiment of the present application may include several cell strings 10 and bus bars 20 .

[0066] Each battery string 10 includes a plurality of battery cells 11 connected in series along a first direction. Within the battery string 10, the plurality of battery cells 11 include a first battery cell 111 located at the end of the battery string 10 and a second battery cell 112 adjacent to the first battery cell 111. Specifically, the ends of the battery string 10 refer to the two ends of the battery string 10 in the first direction. That is, at least one of the battery cells 11 located at the two ends of the battery string 10 is a first battery cell 111, and the battery cell 11 adjacent to the first battery cell 111 is a second battery cell 112. The first welding ribbon 12 is the end output terminal of the battery string 10 and is used to connect to the busbar 20.

[0067] A plurality of first welding ribbons 12 and a plurality of third welding ribbons 14 are provided on the back side of the first battery cell 111 . The plurality of third welding ribbons 14 and the plurality of first welding ribbons 12 are alternately arranged along a second direction, and the second direction intersects the first direction.

[0068] In the embodiment of the present application, the first direction is the direction in which the battery cells 11 in each battery string 10 are connected in series, and the second direction is preferably perpendicular to the first direction. Specifically, the first direction and the second direction may be the longitudinal direction and the transverse direction of the back-contact battery assembly 100, respectively. Of course, in some possible embodiments, the second direction may not be perpendicular to the first direction, and this is not a limitation herein.

[0069] The back side of the second cell 112 is provided with a plurality of second welding ribbons 13 and a plurality of fourth welding ribbons 15. The plurality of fourth welding ribbons 15 and the plurality of second welding ribbons 13 are also arranged alternately along the second direction. The second welding ribbons 13 correspond one-to-one with the first welding ribbons 12 and are insulated from each other. Specifically, the first welding ribbon 12 is insulated from the second welding ribbons 13 and the fourth welding ribbons 15. The third welding ribbons 14 and the fourth welding ribbons 15 correspond one-to-one and are electrically connected to connect the first cell 111 and the second cell 112 in series. The first welding ribbon 12 is the end output terminal of the cell string 10 and is used to connect to the busbar 20. The second welding ribbons 13, the third welding ribbons 14, and the fourth welding ribbons 15 all extend along the first direction.

[0070] It is readily understood that in some embodiments, the third and fourth welding ribbons 14, 15 may be a single continuous ribbon, i.e., the third and fourth welding ribbons 14, 15 may be integrally formed. Furthermore, in this application, the battery cells 11 in the battery string 10 are connected in series using conventional ribbon connection methods in the prior art and are not further described herein.

[0071] The bus bar 20 is provided on the back side of the second battery cell 112. The bus bar 20 is connected to the first welding ribbon 12 and is insulated from the second welding ribbon 13 and the fourth welding ribbon 15 to realize bus output of the battery string 10. The bus bar 20 extends along the second direction.

[0072] Please combine Figure 2 as well as Figure 4-Figure 6 The first welding ribbon 12 includes a main section 121, a bent section 123, and an extended section 122. The main section 121 extends along the first direction and is welded to the first battery cell 111 via a plurality of welding points 50. The main section 121 extends along the first direction, and the extension line of the main section 121 in the first direction at least partially overlaps with the second welding ribbon 13. In some examples, the main section 121 and the second welding ribbon 13 may be located on the same straight line in the first direction.

[0073] The extension section 122 extends between the second welding ribbon 13 and the fourth welding ribbon 15 adjacent to each other on the second battery cell 112, and the extension section 122 at least partially overlaps with the busbar 20 to be welded to the busbar 20. In other words, the portion of the extension section 122 extending onto the busbar 20 overlaps with the busbar 20 in the thickness direction. The extension section 122 is spaced apart from the main section 121 and the second welding ribbon 13 in the second direction. The main section 121 and the extension section 122 are connected by a bent section 123. In the second direction, the bent section 123 bends relative to the main section 121 toward the side where the extension section 122 is located.

[0074] Please combine Figure 2 as well as Figure 4-Figure 6 In the thickness direction of the back contact battery assembly 100, the extension section 122 and the second welding ribbon 13 do not have an overlapping portion. Figure 6 As shown, in the second direction, the distance D between at least one extension section 122 of the first welding ribbon 121 and the second welding ribbon 13 (the welding ribbon is the second welding ribbon 13 that at least partially overlaps the body section 121 connected to the extension section 122 in the first direction or the second welding ribbon 13 that is located on the same straight line as the body section 121 connected to the extension section 122) satisfies the following relationship:

[0075] 1mm <D≤0.63*arctan(1.8*L*D2+H)*(D1-W);

[0076] Among them, Figure 6 As shown, D1 is the distance between the second welding ribbon 13 and the fourth welding ribbon 15 adjacent to each other on the second battery cell 112 in the second direction, W is the width of the extension section 122 (i.e., the length in the second direction), L is the distance between the bus bar 20 and the end of the second battery cell 112 facing the first battery cell 111 in the first direction, H is the thickness of the first welding ribbon 12, D2 is the distance between the welding point 50 closest to the second battery cell 112 among the multiple welding points 50 welded to the main body section 121 and the bending starting point of the bending section 123 relative to the main body section 121 (i.e., the end point of the main body section 121 and the starting point of the bending section 123). The units of D, D1, W, L, H and D2 are all millimeters (mm), and D1 is greater than W.

[0077] For example, in some embodiments, D1 ranges from 6 mm to 18 mm, such as 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, or any value between 6 mm and 18 mm, without limitation. W ranges from 0.9 mm to 1.5 mm, such as 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, or any value between 0.9 mm and 1.5 mm, without limitation. L ranges from 0.5 mm to 6 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or any value between 0.5 mm and 6 mm, without limitation. The size range of D2 is 2mm-8mm, such as 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm or any value between 2mm and 8mm, and is not limited to this. The size range of H is 0.08mm-0.3mm, such as 0.08mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.4mm or any value between 0.08mm and 0.3mm, and is not limited to this. In this case, according to the above formula, it can be calculated that the size range of D is between 3.06mm and 16.81mm. For example, taking D1 as 11.8mm, W as 1.5mm, L as 1mm, D2 as 2mm, and H as 0.1mm as an example, substituting into the above formula, it can be obtained that the size of D is approximately 8.44mm.

[0078] It should be noted that the numerical ranges of the above parameters D1, W, L, D2 and H are only for exemplary reference. The specific numerical values ​​shall be based on the actual product requirements. D can be calculated based on the actual numerical value.

[0079] It should be noted that, in this application, "overlapping" refers to the stacking of two components in the thickness direction of the back-contact battery module 100. It is readily understood that during the manufacturing and assembly of the module, the placement of the solder ribbons may be subject to certain assembly errors. Therefore, "being located on the same straight line" means that the two components are substantially located on the same straight line parallel to the first direction in a first direction. The two components may be completely collinear, or the spacing between them may be within the range of assembly errors.

[0080] In addition, it should be noted that in this application, the distance between the extension section 122 and the second welding strip 13 in the second direction refers to: the length of the line connecting the two intersection points formed by a straight line parallel to the second direction on the extension section 122 and the second welding strip 13.

[0081] In addition, in the embodiment of the present application, the first welding ribbon 12 may be a uniform thickness welding ribbon, that is, the thickness of the first welding ribbon 12 at any position is substantially the same. In this case, W refers to the thickness of the first welding ribbon 12. Of course, in some embodiments, the first welding ribbon 12 may also be a non-uniform thickness welding ribbon. In this case, W can be understood as the average thickness of the first welding ribbon 12.

[0082] In the back-contact cell assembly 100 and photovoltaic system 1000 of the embodiments of the present application, on the one hand, the bus bar 20 is arranged on the back side of the second cell 112 of the cell string 10, which can hide the bus bar 20, thereby increasing the unit light receiving area of ​​the back-contact cell assembly 100 and improving the conversion efficiency of the assembly. At the same time, the overall aesthetics of the back-contact cell assembly 100 are improved. On the other hand, the extension section 122 of the first welding ribbon 12 is welded to the bus bar 20 to achieve bus output. The extension section 122 of the first welding ribbon 12 does not overlap with the second welding ribbon 13 in the thickness direction. During the lamination process, the extension section 122 and the second welding ribbon 13 are staggered in the extension direction of the bus bar 20 and do not overlap. During the lamination process, the extension section 122 can be pressed down close to the second cell 112, thereby reducing the overall stacking height of the entire assembly, effectively avoiding stress concentration during the lamination process, thereby reducing the risk of hidden cracks and splits in the cell 11, and improving the yield rate.

[0083] At the same time, after repeated research and demonstration, the inventors of this application discovered that by adaptively designing the distance D in the second direction between the extension 122 of the first welding ribbon 12 and the second welding ribbon 13, taking into account several factors: the distance D1 in the second direction between the second welding ribbon 13 and the adjacent fourth welding ribbon 15, the width W of the extension 122 of the first welding ribbon 12, the location of the bus bar 20 on the second solar cell 112, the thickness H of the first welding ribbon 12, and the starting point of the first welding ribbon 12's bend. Setting the distance D in the second direction between the extension 122 and the second welding ribbon 13 to satisfy the above relationship effectively reduces the stacking height during the lamination process, effectively avoiding stress concentration during the lamination process. This also reduces the bending length of the bending section 123 of the first welding ribbon 12, thereby reducing electrical losses in the first welding ribbon 12 during the busbar transmission process. Furthermore, reducing the bending length of the bending section 123 of the first welding ribbon 12 also reduces the first welding ribbon 12's obstruction of the solar cells on the back of the module, thereby improving the module's bifaciality. In addition, by comprehensively considering the above aspects, the distance D between the extension section 122 and the second welding strip 13 in the second direction is set to satisfy the above relationship, which can also effectively reduce the difficulty of process manufacturing and improve manufacturing efficiency.

[0084] Furthermore, this design can reduce the stacking height to reduce stress concentration while also reducing the amount of encapsulation film used, thereby lowering costs. Specifically, if the stacking height is high, a larger amount of film is required to fully encapsulate the stacking position during packaging. However, in this application, by adaptively designing the entire structure and the spacing between the extension section 122 and the second soldering ribbon 13, the stacking height can be reduced to effectively avoid stress concentration while reducing the amount of film used, thereby reducing costs.

[0085] Specifically, in the embodiment of the present application, the cell 11 can be a cell with a main grid back contact or a cell without a main grid back contact, and there is no specific limitation here. Figure 2-Figure 6 As shown, it is not difficult to understand that, in the embodiment of the present application, the bus bar 20 serves as the bus output end of the battery string 10 .

[0086] There are multiple first welding ribbons 12 and multiple second welding ribbons 13, with a one-to-one correspondence between the two. The main body 121 of the first welding ribbon 12 can be substantially aligned with the second welding ribbon 13. The first welding ribbon 12 serves as the output welding ribbon of the cell string 10, while the second, third, and fourth welding ribbons 13, 14, and 15 serve as the series welding ribbons of the cell string 10. The metal electrodes (busbars and / or grids) connected to the first welding ribbon 12 and the metal electrodes connected to the second welding ribbon 13 have opposite polarity. In other words, the polarity of the first and second welding ribbons 12 and 13 are opposite, while the polarity of the metal electrodes (busbars and / or grids) connected to the third welding ribbon 14 and the metal electrodes connected to the fourth welding ribbon 15 are opposite. On the first cell 111, the polarity of the metal electrodes connected to the first welding ribbon 12 and the third welding ribbon 14 are also opposite. On the second cell 112, the polarity of the metal electrodes connected to the second welding ribbon 13 and the fourth welding ribbon 15 are also opposite.

[0087] For example, taking a busbar-less back-contact cell as an example, if the first welding ribbon 12 is connected to the positive electrode fine grid on the first cell 111, the third welding ribbon 14 is connected to the negative electrode fine grid on the first cell 111, the second welding ribbon 13 is connected to the negative electrode fine grid on the second cell 112, and the fourth welding ribbon 15 is connected to the positive electrode fine grid on the second cell 112. Conversely, if the first welding ribbon 12 is connected to the negative electrode fine grid on the first cell 111, the third welding ribbon 14 is connected to the positive electrode fine grid on the first cell 111, the second welding ribbon 13 is connected to the positive electrode fine grid on the second cell 112, and the fourth welding ribbon 15 is connected to the negative electrode fine grid on the second cell 112.

[0088] Specifically, in some embodiments, the back contact battery assembly 100 may include two battery strings 10 arranged along a first direction and several battery strings 10 arranged along a second direction, thereby forming an array of 2*N battery strings 10. For example, Figure 2 As shown, Figure 2 The back contact battery assembly 100 is shown to include an array of 2*6 battery strings 10.

[0089] like Figure 2 As shown, the back contact battery assembly 100 may include twelve battery strings 10, which are arranged in six columns in the second direction, and each column includes two battery strings 10 arranged in the first direction. Figure 2 As shown, the back contact battery assembly 100 is divided into an upper half area and a lower half area (in Figure 2 The center line L in the figure is the limit).

[0090] like Figure 2As shown, the upper half of the back-contact battery assembly 100 has six battery strings 10 arranged along the second direction, and the lower half also has six battery strings 10 arranged along the second direction. In the back-contact battery assembly 100, the busbars 20 may include edge busbars located at the edges of the back-contact battery assembly 100 and middle busbars located in the middle of the back-contact battery assembly 100.

[0091] That is to say, in Figure 2 In the upper half, if the cell 11 closest to the upper edge of the battery string 10 is the first cell 111, the busbar 20 is an end busbar, which is used to connect two adjacent battery strings 10 in the upper half in series. In the upper half, if the cell 11 closest to the lower edge of the battery string 10 is the first cell 111, the busbar 20 is a middle busbar, which is used to connect the battery string 10 in parallel with the battery strings 10 in the lower half. In the upper half, if the cell 11 at both ends of the battery string 10 is the first cell 111, the busbar 20 closest to the upper edge is the end busbar, and the busbar 20 closest to the lower edge is the middle busbar.

[0092] Similarly, if Figure 2 As shown, in the lower half, if the cell 11 closest to the bottom edge of the battery string 10 is the first cell 111, then the busbar 20 is an end busbar, which is used to connect two adjacent battery strings 10 in the lower half in series. In the lower half, if the cell 11 closest to the top edge of the battery string 10 is the first cell 111, then the busbar 20 is an intermediate busbar, which is used to connect the battery string 10 in parallel with the battery strings 10 in the upper half. In the lower half, if the cell 11 at both ends of the battery string 10 is the first cell 111, then the busbar 20 closest to the bottom edge is the end busbar, and the busbar 20 closest to the top edge is the end busbar.

[0093] like Figure 2 As shown, it is not difficult to understand that in the back-contact battery assembly 100, if the battery cell 11 closest to the lower edge of the battery string 10 in the upper half is the first battery cell 111, then the bus bar 20 is the middle bus bar, and the battery cell 11 closest to the upper edge of the battery string 10 in the lower half is not the first battery cell 111. In this case, the battery cell 11 is the third battery cell 1211 described below.

[0094] See also Figure 2-Figure 4From another perspective, in an embodiment of the present application, the back-contact battery assembly 100 includes at least one series-connected battery string group 110, and the series-connected battery string group 110 includes two battery strings 10 arranged along the second direction. In the same series-connected battery string group 110, the same bus bar 20 extends from the second battery cell 112 in one battery string 10 to the second battery cell 112 in another battery string 10, so as to connect the two battery strings 10 in the series-connected battery string group 110 in series.

[0095] In this way, in the series battery string group 110 , two battery strings 10 can be connected in series through the same bus bar 20 , without the need to provide two different bus bars 20 to connect the battery strings 10 in the series battery string group 110 in series.

[0096] Specifically, in such an embodiment, the busbar 20 for connecting two battery strings 10 in series in the series battery string group 110 is the end busbar of the back contact battery assembly 100. There are as many end busbars as there are series battery strings 110 in the back contact battery assembly 100. For example, Figure 2 As shown, the upper half has 6 battery strings 10 and 3 series battery string groups 110, and the lower half also has 6 battery strings 10 and 3 series battery string groups 110. Therefore, the upper half has 3 end bus bars, and the lower half also has 3 end bus bars.

[0097] It is not difficult to understand that in the series-connected battery string group 110, the first battery cells 111 in the two battery strings 10 correspond to each other (i.e., are substantially aligned in the second direction). In order to achieve the series connection of the two battery strings 10, the polarities of the first welding strips 12 on the first battery cells 111 on the two battery strings 10 are opposite. That is, in the two battery strings 10 in the series-connected battery string group 110, the first welding strip 12 of the first battery cell 111 in one battery string 10 is electrically connected to the negative main grid and / or the negative fine grid on the corresponding first battery cell 111, and the first welding strip 12 on the other first battery cell 111 is electrically connected to the positive main grid and / or the positive fine grid on the corresponding first battery cell 111.

[0098] In some embodiments, in the second direction, the distance between the extension section 122 of the first welding ribbon 12 and the adjacent fourth welding ribbon 15 is greater than 1 mm. Thus, under the premise that the distance between the extension section 122 and the second welding ribbon 13 satisfies the above relationship, setting the distance between the extension section 122 of the first welding ribbon 12 and the adjacent fourth welding ribbon 15 to be greater than 1 mm can effectively prevent the extension section 122 from being too close to the second welding ribbon 13, resulting in the extension section 122 not being fully pressed down during the lamination process.

[0099] See also Figure 2-Figure 6In some embodiments, the back contact battery assembly 100 further includes an insulating strip 30 , which is located between the bus bar 20 and the second battery cell 112 , and the bus bar 20 is insulated from the second welding ribbon 13 and the fourth welding ribbon 15 by the insulating strip 30 .

[0100] In this way, by disposing the insulating strip 30 , the bus bar 20 can be insulated and isolated from the second welding ribbon 13 on the second battery cell 112 to avoid short circuit and leakage.

[0101] Specifically, in such an embodiment, the insulating strip 30 is disposed above the second welding ribbon 13 and the fourth welding ribbon 15. The insulating strip 30 may extend continuously along the second direction, and the bus bar 20 is disposed on the insulating strip 30 to achieve insulation from the second welding ribbon 13 and the fourth welding ribbon 15. In this way, by disposing the bus bar 20 and the insulating strip 30 on the second battery cell 112, the first welding ribbon 12 is welded to the bus bar 20 via the extension section 122, without the need to drill holes in the insulating strip 30. Only one entire insulating strip 30 is required, which reduces manufacturing difficulty.

[0102] The insulating strip 30 can be an insulating adhesive, or it can be a non-conductive tape or insulating film, such as a PET or PI tape with acrylic acid or silicone, or a PET or PI substrate with ethylene-vinyl acetate copolymer or hot melt adhesive coated on one or both sides. It can be understood that the insulating strip 30 can include materials such as ethylene-vinyl acetate copolymer, resin material, polyimide, polypropylene or polyethylene, and can also include an acrylic adhesive layer.

[0103] It should be noted that the thickness of the insulating strip 30 cannot be too thick or too thin. If the insulating strip 30 is too thin, it will be inconvenient to operate during pasting, it will be easily deformed when pulled, and there will be a risk of damage to the long-term insulation. If it is too thick, the height difference will increase, and the stress generated during the lamination process will be large, which will easily cause fragments and increase the risk of cold soldering. Based on this, in the embodiment of the present application, the thickness of the insulating strip 30 can be set between 0.05mm and 0.8mm. In this way, the insulating strip 30 will not be too thin or too thick. For example, the thickness of the insulating strip 30 can be 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm or 0.8mm.

[0104] The width of the insulating strip 30 (i.e., its length in the first direction) is greater than or equal to the width of the bus bar 20 (i.e., its length in the first direction). Thus, the insulating strip 30 can completely insulate the bus bar 20 from the second solder ribbon 13 and the fourth solder ribbon 15 on the second cell 112.

[0105] See also Figure 3 and Figure 4In some embodiments, the insulating strip 30 extends to a portion of the first battery cell 111 on a side close to the second battery cell 112 .

[0106] Thus, by setting the insulating strip 30 to be wider and extending it onto the first battery cell 111 , the bus bar 20 can be effectively prevented from being offset and contacting the third welding ribbon 14 on the first battery cell 111 , thereby causing a short circuit.

[0107] In some embodiments, the back-contact battery assembly 100 includes a plurality of series-connected battery strings 110 arranged along a second direction. In the second direction, the insulating strip 30 extends from the first series-connected battery string 110 to the last series-connected battery string 110 .

[0108] In this way, in the same row of series-connected battery strings 110, only one entire insulating strip 30 is required to insulate all the busbars 20, without the need to separately provide an insulating strip 30 for each busbar 20 in each series-connected battery string 110, thereby reducing the difficulty of manufacturing and laminating.

[0109] In an embodiment of the present application, a back-contact battery module 100 includes at least one parallel battery string group 120, which includes at least two first battery strings 1201 and second battery strings 1202 arranged along a first direction. Specifically, first battery string 1201 is located in the upper half of the module, and second battery string 1202 is located in the lower half of the module.

[0110] In the parallel battery string group 120, the first battery cell 111 includes the battery cell 11 located in the first battery string 1201 closest to the second battery string 1202 (that is, in the component, the battery cell 11 closest to the lower edge of the first battery string 1201 is the first battery cell 111), the second battery string 1202 includes the third battery cell 1211, and the third battery cell 1211 is the battery cell 11 in the second battery string 1202 closest to the first battery string 1201. The first welding ribbon 12 connects the first battery cell 111 and the third battery cell 1211, and the first battery string 1201 and the second battery string 1202 are connected in parallel through the first welding ribbon 12.

[0111] It is easy to understand that in this case, when the first cell 111 includes the cell 11 located closest to the second cell string 1202 in the first cell string 1201 , the bus bar 20 on the second cell 112 adjacent to the first cell 111 is the middle bus bar.

[0112] In this way, by setting the battery cell 11 of the first battery string 1201 closest to the second battery string 1202 in the parallel battery string group 120 to the first battery cell 111, the first welding strip 12 on the first battery cell 111 can be connected to the bus bar 20 while being connected to the battery cell 11 of the second battery string 1202 closest to the first battery string 1201 (i.e., the third battery cell 1211 mentioned above), thereby realizing parallel connection between the first battery string 1201 and the second battery string 1202.

[0113] Specifically, in such a case, the first welding ribbon 12 on the first battery cell 111 closest to the second battery string 1202 can extend to the third battery cell 1211 of the second battery string 1202, thereby connecting the first battery string 1201 and the second battery string 1202 in parallel to achieve parallel output of the two battery strings 10.

[0114] In addition, combined Figure 2 、 Figure 3 and Figure 9 It can be seen that it is not difficult to understand that in the back-contact battery assembly 100 of the embodiment of the present application, the battery cell 11 of the first battery string 1201 closest to the second battery string 1202 is the first battery cell 111, and the battery cell 11 of the first battery string 1201 located at the end away from the second battery string 1202 (that is, the battery cell 11 closest to the upper edge) is also the first battery cell 111, the battery cell 11 of the second battery string 1202 closest to the first battery string 1201 is the third battery cell 1211, and the battery cell 11 of the second battery string 1202 located at the end away from the first battery string 1201 (that is, the battery cell 11 closest to the lower edge) is also the first battery cell 111. That is to say, in such an embodiment, the battery cells 11 located at both ends of the first battery string 1201 are both first battery cells 111, the battery cell 11 at one end of the second battery string 1202 (the end close to the lower edge) is the first battery cell 111, and the battery cell 11 at the other end of the second battery string 1202 (i.e., the end close to the first battery string 1201) is the third battery cell 1211.

[0115] In such an embodiment, the first battery string 1201 has two first battery cells 111 and two second battery cells 112, and is correspondingly provided with two busbars 20, one of which is an end busbar and the other is a middle busbar. The second battery string 1202 has only one first battery cell 111 and one second battery cell 112, and is correspondingly provided with one busbar 20, which is an end busbar. It is not difficult to understand that in such a case, in the first battery string 1201, the polarity of the first welding ribbons 12 on the two first battery cells 111 is opposite, the first welding ribbon 12 of one first battery cell 111 is electrically connected to the negative electrode busbar and / or negative electrode fine grid on the corresponding first battery cell 111, and the first welding ribbon 12 on the other first battery cell 111 is electrically connected to the positive electrode busbar and / or positive electrode fine grid on the corresponding first battery cell 111. The polarity of the first soldering ribbon 12 on the first cell 111 in the second cell string 1202 is opposite to the polarity of the first soldering ribbon 12 on the first cell 111 in the first cell string 1201 that is closest to the second cell string 1202 .

[0116] In summary, in the embodiment of the present application, in the back-contact battery assembly 100 , the busbar 20 includes an end busbar and a middle busbar, and the specific type of the busbar 20 depends on the specific location where the busbar 20 is set.

[0117] In the embodiment of the present application, the first welding ribbon 12 is a bendable welding ribbon. By bending the first welding ribbon 12, the first welding ribbon 12 comprises a main section 121, a bend section 123, and an extension section 122, which are sequentially connected. The second welding ribbon 13 is a straight welding ribbon. The second welding ribbon 13 and the main section 121 of the first welding ribbon 12 can be located on the same straight line. The bending direction of the bend section 123 of the first welding ribbon 12 is determined by the relative position of the extension section 122 and the main section 121. Generally speaking, the bend section 123 bends relative to the main section 121 toward the side where the extension section 122 is located.

[0118] It is easy to understand that in the present application, the first welding ribbon 12 having the main body section 121, the bent section 123, and the extension section 122 can be formed by integrally stamping a single piece of welding ribbon, or can be formed by splicing multiple welding ribbons together. This is not limited in the present application. Preferably, the first welding ribbon 12 is formed by integrally stamping a single piece of welding ribbon, thereby eliminating redundant steps such as welding during the production of the first welding ribbon 12, reducing manpower consumption, and also avoiding phenomena such as cold welds and burrs generated during welding due to manual welding.

[0119] See also Figure 5 、 Figure 6 and Figure 8 In some embodiments, the bending section 123 is arc-shaped.

[0120] In this way, the main section 121 and the extension section 122 can be smoothly connected by the arc-shaped bend section 123. The smooth transition design can avoid the first welding ribbon 12 from forming a sharp angle at the bend position, which would cause stress concentration at this position and lead to fracture failure. It can also avoid the phenomenon of cold welding caused by sharp bends.

[0121] In some embodiments, the bending angle of the bending section 123 relative to the main body section 121 is between 10° and 70°. That is, the bending angle is greater than or equal to 10° and less than or equal to 70°. Preferably, the bending angle of the bending section 123 relative to the main body section 121 is greater than or equal to 30° and less than or equal to 60°. In such embodiments, the bending angle of the bending section 123 relative to the main body section 121 can be 30°, 40°, 50°, 60°, or any value between 30° and 60°, without limitation.

[0122] In this way, the bending angle of the bending section 123 relative to the main section 121 is set within this range, the metal material of the first welding strip 12 will not reduce its strength due to excessive deformation, and it can be more easily accurately processed by mechanical or automated equipment. The first welding strip 12 can be bent into the required curvature using less force, thereby improving production efficiency.

[0123] Specifically, in such an embodiment, the "bending angle of the bending section 123 relative to the main section 121" refers to the angle between the line connecting any point on the bending section 123 and the intersection of the bending section 123 and the main section 121 (that is, the bending starting point where the complete section 123 begins to bend relative to the main section 121) and the main section 121.

[0124] Of course, it is understandable that in some possible embodiments, while meeting production requirements, the bending section 123 and the main body section 121 may be bent at right angles instead of in an arc shape, and this is not specifically limited here.

[0125] See also Figure 3-10 In some embodiments, the extension section 122 is arranged in parallel with the second welding strip 13 , that is, the extension section 122 is arranged in parallel with the main section 121 and the second welding strip 13 .

[0126] In this way, the two are arranged in parallel. Even if the length of the extension section 122 is long, it can ensure that there is no overlapping part between the extension section 122 and the second welding strip 13 in the thickness direction, thereby reducing the stacking height at the position of the bus bar 20 and avoiding hidden cracks in the battery cell 11 caused by local stress concentration of the component.

[0127] See also Figure 4In some embodiments, on the first battery cell 111, in the second direction, the welding strips closest to the two edges of the first battery cell 111 may be the first welding strips 12, and the bending section 123 of the first welding strip 12 closest to the edge is bent toward the middle of the first battery cell 111 (that is, bent toward the middle position of the first battery cell 111 in the second direction).

[0128] In this way, when the two welding ribbons closest to the edges of the first battery cell 111 are both the first welding ribbons 12, the extension sections 122 are both located on the inner side of the first battery cell 111, and the bent sections 123 of the two first welding ribbons 12 located at the outermost edges are both bent toward the inner middle of the first battery cell 111. This can prevent the first welding ribbon 12 from bending toward the edge of the first battery cell 111, which would cause the extension section 122 to lose sufficient distance from the second welding ribbon 13. At the same time, it can also prevent the bent section 123 of the first welding ribbon 12 from bending toward the edge, which would cause the bent section 123 and the extension section 122 to be too close to the edge, making the first and second battery cells 111 and 112 more susceptible to hidden cracks. In other words, this arrangement can reduce the risk of hidden cracks.

[0129] Of course, in other cases, on the first battery cell 111, in the second direction, the welding strips closest to the two edges of the first battery cell 111 may also be the third welding strips 14. In such a case, among the several first welding strips 12, the bending section 123 of the first welding strip 12 closest to the edge may also be bent in a direction away from the middle of the first battery cell 111.

[0130] See also Figure 7 and Figure 8 In some embodiments, the bent sections 123 of all the first welding ribbons 12 on the first battery cell 111 are bent toward the same edge of the first battery cell 111 in the second direction.

[0131] In this way, the bending sections 123 of all the first welding strips 12 are bent in the same direction, and only one shape of first welding strip 12 is needed to achieve direct connection between the first welding strip 12 and the bus bar 20, without the need to separately manufacture two different types of first welding strips 12.

[0132] Of course, if Figure 4 As shown, in other embodiments, the bending sections 123 of part of the first welding ribbon 12 on the first battery cell 111 may be bent toward one edge of the first battery cell 111 in the second direction, while the bending sections 123 of another part of the first welding ribbon 12 may be bent toward the other edge of the first battery cell 111 in the second direction.

[0133] Also, see Figure 4In some embodiments, on the first battery cell 111, a plurality of first welding ribbons 12 are arranged in pairs. In each pair of first welding ribbons 12, the bent section 123 of one of the first welding ribbons 12 is bent toward one edge of the first battery cell 111 in the second direction, and the bent section 123 of the other first welding ribbon 12 is bent toward the other edge of the first battery cell 111 in the second direction.

[0134] That is, in each pair of first welding strips 12, the bending sections 123 of the two first welding strips 12 are bent toward the area between the two body sections 121. Specifically, there is a third welding strip 14 between each pair of first welding strips 12, and the two first welding strips 12 in each pair of first welding strips 12 are symmetrical about the third welding strip 14.

[0135] In this way, the first welding ribbons 12 are arranged in pairs, and the two bending sections 123 are bent toward the area between the two first welding ribbons 12, so that the force applied to the second battery cell 112 during the lamination process is more uniform, reducing the risk of hidden cracks and splits.

[0136] Specifically, if Figure 4 and Figure 7 As shown, in such an embodiment, a third welding ribbon 14 and a fourth welding ribbon 15 are provided between each pair of first welding ribbons 12. In each pair of first welding ribbons 12, the bending sections 123 of the two first welding ribbons 12 are bent toward the positions of the third welding ribbon 14 and the fourth welding ribbon 15 located between the two first welding ribbons 12, and the extension section 122 is located between the second welding ribbon 13 and the fourth welding ribbon 15. Each pair of first welding ribbons 12 is symmetrically arranged with respect to the third welding ribbon 14 and the fourth welding ribbon 15.

[0137] See also Figure 4 and Figure 5 In some embodiments, the second welding ribbon 13 further has a protruding portion 133 located on the side of the bus bar 20 facing the first battery cell 111 and not overlapping with the bus bar 20 .

[0138] In this way, the bus bar 20 is located on one side of the end of the second welding strip 13 and does not cover the end of the second welding strip 13, so that the distance between the bus bar 20 and the edge of the second battery cell 112 will not be too close, thereby increasing the risk of hidden cracks at the edge of the second battery cell 112.

[0139] In such an embodiment, the length of the protrusion 133 in the first direction is 0.5 mm to 6 mm.

[0140] In this way, it is possible to avoid the situation where the length of the protrusion 133 is too small, resulting in the distance between the bus bar 20 and the edge of the second battery cell 112 being too small, thereby increasing the risk of hidden cracks; it is also possible to avoid the situation where the length of the protrusion 133 is too large, resulting in the distance between the bus bar 20 and the edge of the second battery cell 112 being too large, resulting in the extension section 122 of the first welding strip 12 needing to be set too long, making the bus path too long, thereby causing excessive transmission loss.

[0141] Specifically, in such an embodiment, the length of the protrusion 133 in the first direction may be, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm or any value between 0.5mm and 6mm.

[0142] See also Figure 5 、 Figure 6 and Figure 8 In some embodiments, a plurality of glue spots 40 for pre-fixing the first welding ribbon 12 are provided on the first battery cell 111, and the bending starting point of the bending section 123 relative to the main body section 121 is located on the side of the glue spot 40 closest to the second battery cell 112 facing the second battery cell 112.

[0143] Thus, by designing the bending starting point of the bending section 123 after the location of the glue point at the outermost edge, it is possible to avoid bending too far forward and causing the extension section 122 to be too long, thereby eliminating the need for pre-fixing glue points at the location of the extension section 122. In other words, if the bending starting point is too far forward and the extension section 122 is too long, the first welding ribbon 12 cannot be pre-fixed more firmly without additional pre-fixing of the extension section 122.

[0144] In some embodiments, the spacing between the bus bar 20 in the first direction and the end of the second battery cell 112 facing the first battery cell 111 is 3 mm-15 mm, for example, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any value between 3 mm and 15 mm.

[0145] In this way, it is possible to avoid the risk of hidden cracks being increased due to the distance between the bus bar 20 and the edge of the second battery cell 112 being too small, and it is also possible to avoid the risk of hidden cracks being increased due to the distance between the bus bar 20 and the edge of the second battery cell 112 being too large, and the extension section 122 of the first welding strip 12 needing to be set too long, resulting in the bus path being too long and causing increased losses.

[0146] See also Figure 5 、 Figure 6 and Figure 10In some embodiments, the length of the portion where the extension section 122 overlaps the bus bar 20 in the first direction is greater than or equal to half the length of the bus bar 20 in the first direction.

[0147] In this way, it is possible to avoid the welding length between the extension section 122 and the bus bar 20 being too short, which would lead to unstable welding and reduce the risk of the first welding ribbon 12 falling off.

[0148] Specifically, in such an embodiment, the length of the portion where the extension section 122 overlaps the busbar 20 in the first direction may be 6 mm to 12 mm, for example, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm or any value between 6 mm and 12 mm.

[0149] In this way, the welding stability between the extension section 122 and the bus bar 20 can be ensured.

[0150] In a possible embodiment, the extension section 122 may be centrally disposed between the second welding ribbon 13 and the fourth welding ribbon 15 .

[0151] In this way, during the lamination process, the extension section 122 can be pressed as much as possible toward the second cell sheet 112, thereby reducing the stacking height of the entire assembly and the risk of hidden cracks caused by stress concentration. At the same time, the amount of adhesive film used can be reduced, thereby reducing costs.

[0152] See also Figure 11-14 In some embodiments, the extension section 122 is located on a side of the bus bar 20 facing away from the second battery cell 112 , and the second welding ribbon 13 is located on a side of the bus bar 20 facing the second battery cell 112 .

[0153] The bus bar 20 has a raised section 21 formed at the second welding strip 13, which is raised toward the side away from the second battery cell 112, and a recessed section 22 formed at the extension section 122, which is recessed toward the side of the second battery cell 112.

[0154] Among them, see Figure 12 and Figure 14 For at least a partial cross-section of the busbar 20 (i.e., at least a partial cross-section of the busbar 20 along the second direction), an angle α between a line connecting the highest point of the raised segment 21 and the lowest point of the adjacent recessed segment 22 and the plane where the second battery cell 112 is located satisfies the following formula: 0.075≤tanα≤3.

[0155] Specifically, the inventors of this application have discovered through research and verification that setting the angle α between the line connecting the highest point of the raised segment 21 and the lowest point of the recessed segment 22 and the plane on which the second cell 112 lies to satisfy 0.075 ≤ tanα ≤ 3 can prevent the busbar 20 from bending at an excessively large angle, which could cause one end of the second cell 112 to tilt relative to the other end during lamination, thereby increasing the unevenness of the second cell 112 and the risk of hidden cracks. It can also prevent the busbar 20 from bending at an excessively small angle, which could prevent the height of the cell from being effectively reduced during lamination and lead to stress concentration.

[0156] Furthermore, by setting the angle α between the line connecting the highest point of a raised segment 21 and the lowest point of a recessed segment 22 and the plane on which the second cell 112 lies to satisfy the above formula, it is also possible to reduce the lamination height to reduce stress concentration while also reducing the amount of encapsulation film used, thereby lowering costs. Specifically, if the lamination height is high, a larger amount of film is required during packaging to fully encapsulate the lamination locations. However, in this application, by designing the entire structure to reduce the lamination height, it is possible to reduce stress concentration during the lamination process while also reducing the amount of film used, thereby reducing costs.

[0157] See also Figure 11 and Figure 13 In some embodiments, for at least a partial cross-section of the back-contact battery assembly 100 at the bus bar 20 (i.e., the entire cross-section or partial cross-section of the back-contact battery assembly 100 along the second direction at the location of the bus bar 20), the height difference between the highest point of the raised segment 21 and the highest point of the adjacent extension segment 122 is less than the thickness of the first welding strip 12.

[0158] That is to say, in the present application, the highest point of the raised section 21 may be higher than the highest point of the adjacent extension section 122 and the height difference may be less than the thickness of the first welding strip 12, or the highest point of the raised section 21 may be flush with the highest point of the adjacent extension section 122, or the highest point of the raised section 21 may be lower than the highest point of the adjacent extension section 122 and the height difference between the two may be less than the thickness of the first welding strip 12. No specific restrictions are set here.

[0159] Thus, by setting the height difference between the highest point of the raised segment 21 and the highest point of the adjacent extended segment 122 to be less than the thickness of the first soldering ribbon 12, compared to conventional solutions where the first soldering ribbon 12 is directly stacked on the second soldering ribbon 13, the stacking height during the lamination process can be reduced, thereby reducing stress concentration and the risk of hidden cracks. Furthermore, the stacking height on the back side of the entire second cell 112 can be reduced, thereby reducing the amount of encapsulating film used and lowering costs.

[0160] In some embodiments, in the second direction, the extension section 122 is arranged closer to the second welding strip 13 than to the fourth welding strip 15, that is, the extension section 122 is arranged between the fourth welding strip 15 and the second welding strip 13 and closer to the second welding strip 13, and the highest point of the extension section 122 is higher than the highest point of the raised section 21.

[0161] In this way, the extension section 122 is not set in the middle of the fourth welding ribbon 15 and the second welding ribbon 13, which can reduce the bending angle of the bending section 123 of the first welding ribbon 12 and avoid excessive bending causing excessive stress and resulting in cold welding.

[0162] In other embodiments, the extension section 122 is centrally arranged between the second welding strip 13 and the fourth welding strip 15 of the second welding strip 13 adjacent to each other, and the highest point of the extension section 122 is lower than the highest point of the raised section 21, or the highest point of the extension section 122 is flush with the highest point of the raised section 21.

[0163] Thus, disposing the extension section 122 in the middle between the fourth welding ribbon 15 and the second welding ribbon 13 can further reduce the stacking height of the back side of the second battery cell 112 and further reduce the risk of hidden cracks caused by stress concentration.

[0164] In some embodiments, the thickness of the insulating strip 30 at the location of the extension section 122 is less than or equal to the thickness of the insulating strip 30 at other locations between the second welding ribbon 13 and the fourth welding ribbon 15 .

[0165] In this way, the highest point of the extension section 122 can be substantially flush with the highest point of the protruding section 21 or even lower than the highest point of the protruding section 21 .

[0166] Throughout this specification, reference to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0167] In addition, the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A back contact battery assembly, characterized in that: include: a plurality of battery strings, the battery strings comprising a plurality of battery cells sequentially connected in series along a first direction, the plurality of battery cells comprising a first battery cell disposed at an end of the battery string and a second battery cell adjacent to the first battery cell, a plurality of first welding ribbons and a plurality of third welding ribbons alternately arranged along a second direction being provided on a back surface of the first battery cell, a plurality of second welding ribbons and a plurality of fourth welding ribbons alternately arranged along the second direction being provided on a back surface of the second battery cell, the second welding ribbons corresponding one-to-one to the first welding ribbons, the third welding ribbons corresponding one-to-one to and electrically connected to the fourth welding ribbons, and the second direction intersecting the first direction; a bus bar disposed on the back side of the second battery cell, the bus bar being connected to the first welding ribbon and extending along the second direction; The first welding strip includes a main body section, a bent section, and an extended section. The main body section is welded to the first battery cell via a plurality of welding points. The main body section extends along a first direction, and an extension line of the main body section in the first direction at least partially overlaps with the second welding strip. The extended section extends between the second welding strip and the fourth welding strip adjacent to each other on the second battery cell and at least partially overlaps with the bus bar to be welded to the bus bar. The main body section and the extended section are connected by the bent section. In the second direction, the bent section bends relative to the main body section toward the side where the extended section is located. The extended section is located on a side of the bus bar facing away from the second battery cell, and the second welding strip and the fourth welding strip are located on a side of the bus bar facing the second battery cell. In the thickness direction of the back contact battery assembly, the extension section and the second welding ribbon have no overlapping portion, and in the second direction, a distance D between the extension section of at least one first welding ribbon and an adjacent second welding ribbon satisfies the following relationship: 1mm <D≤0.63*arctan(1.8*L*D2+H)*(D1-W); Among them, D1 is the distance between the second welding strip and the fourth welding strip adjacent to each other in the second direction, W is the width of the extension section, L is the distance between the bus bar in the first direction and the end of the second battery cell facing the first battery cell, H is the thickness of the first welding strip, D2 is the distance between the welding point closest to the second battery cell among the several welding points welded to the main body segment and the bending starting point of the bending section relative to the main body segment, and the units of D, D1, W, L, H and D2 are all millimeters.

2. The back contact battery assembly according to claim 1, characterized in that The bending section is arc-shaped.

3. The back contact battery assembly according to claim 1, characterized in that The bending angle of the bending section relative to the main body section is 10° to 70°.

4. The back contact battery assembly according to claim 1, wherein: The extension section is arranged parallel to the second welding strip.

5. The back contact battery assembly according to claim 1, wherein: On the first battery cell, the welding ribbons closest to the two edges of the first battery cell in the second direction are the first welding ribbons, and the bent sections of the first welding ribbons closest to the edges are bent toward the middle of the first battery cell; or On the first battery cell, the welding strips closest to the two edges of the first battery cell in the second direction are the third welding strips. Among the plurality of first welding strips, the bent sections of the first welding strips closest to the edges are bent in a direction away from the middle of the first battery cell.

6. The back contact battery assembly according to claim 1, characterized in that The bent sections of all the first welding strips on the first battery cell are bent toward the same edge of the first battery cell in the second direction; or The bent section of a portion of the first welding strip on the first battery cell is bent toward one edge of the first battery cell in the second direction, and the bent section of another portion of the first welding strip is bent toward the other edge of the first battery cell in the second direction.

7. The back contact battery assembly according to claim 1, characterized in that The second welding ribbon has a protruding portion located on a side of the bus bar facing the first battery cell and not overlapping with the bus bar.

8. The back contact battery assembly according to claim 7, characterized in that: The length of the protrusion in the first direction is 0.5 mm to 6 mm.

9. The back contact battery assembly according to claim 1, wherein: The first battery cell is provided with a plurality of glue spots for pre-fixing the first welding strip, and the bending starting point of the bending section relative to the main section is located on the side of the glue spot closest to the second battery cell facing the second battery cell.

10. The back contact battery assembly according to claim 1, wherein: The number of the first welding strips and the number of the second welding strips are both multiple and one-to-one corresponding, the multiple first welding strips are arranged at intervals along the second direction, and the multiple second welding strips are also arranged at intervals along the second direction; Among them, several first welding strips are arranged in pairs. In each pair of first welding strips, the bent section of one of the first welding strips is bent toward one edge of the first battery cell in the second direction, and the bent section of the other first welding strip is bent toward the other edge of the first battery cell in the second direction.

11. The back contact battery assembly according to claim 1, wherein: The back contact battery assembly further includes an insulating strip, which is located between the bus bar and the second battery cell. The bus bar is insulated and isolated from the second welding ribbon and the fourth welding ribbon by the insulating strip.

12. The back contact battery assembly according to claim 11, characterized in that: The insulating strip extends to a portion of the first battery cell on a side close to the second battery cell.

13. The back contact battery assembly according to claim 1, wherein: A length of a portion of the extending section overlapping the bus bar in the first direction is greater than or equal to half of a length of the bus bar in the first direction.

14. The back contact battery assembly according to claim 1, wherein: A length of a portion of the extending section overlapping the bus bar in the first direction is 6 mm to 12 mm.

15. The back contact battery assembly according to claim 1, wherein: The extension section is located on a side of the busbar facing away from the second battery cell, the second welding strip is located on a side of the busbar facing the second battery cell, the busbar is formed with a convex section at the second welding strip that convexes toward a side away from the second battery cell, and the busbar is formed with a concave section at the extension section that is concave toward the side of the second battery cell; For at least a partial cross section of the busbar, an angle α between a line connecting the highest point of the raised section and the lowest point of the recessed section and a plane where the second battery cell is located satisfies the following formula: 0.075≤tanα≤3.

16. The back contact battery assembly according to claim 15, characterized in that The extension section is located on a side of the busbar away from the second battery cell, the busbar is formed with a convex section at the second welding strip that convexes toward a side away from the second battery cell, and the busbar is formed with a concave section at the extension section that is concave toward the side of the second battery cell; For at least a partial cross-section of the back-contact battery assembly at the bus bar, a height difference between a highest point of the extension segment and a highest point of an adjacent protruding segment is smaller than a thickness of the first welding ribbon.

17. The back contact battery assembly according to claim 1, characterized in that The back contact battery assembly includes at least one series-connected battery string group, and the series-connected battery string group includes two battery strings arranged along the second direction; In the same series-connected battery string group, the same bus bar extends from the second battery cell in one battery string to the second battery cell in another battery string to connect the two battery strings in series in the series-connected battery string group.

18. The back contact battery assembly according to claim 17, characterized in that The back contact battery assembly further includes an insulating strip, the insulating strip being located between the bus bar and the second battery sheet, and the bus bar being insulated from the second welding ribbon and the fourth welding ribbon by the insulating strip; The back-contact battery assembly includes a plurality of battery strings connected in series and arranged along the second direction. In the second direction, the insulating strip extends from the first battery string connected in series to the last battery string connected in series.

19. The back contact battery assembly according to claim 1, wherein: The back contact battery assembly includes at least one parallel battery string group, and the parallel battery string group includes at least two first battery strings and a second battery string arranged along the first direction; In the parallel battery string group, the first battery cell includes a battery cell located in the first battery string closest to the second battery string, the second battery string includes a third battery cell, the third battery cell is the battery cell in the second battery string closest to the first battery string, the first welding ribbon connects the first battery cell and the third battery cell, and the first battery string and the second battery string are connected in parallel through the first welding ribbon.

20. A photovoltaic system, characterized in that: A back contact battery assembly comprising any one of claims 1-19.

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