Back contact battery assembly and photovoltaic system

Abstract

The invention provides a back contact battery assembly and a photovoltaic system, a back contact battery can comprise a plurality of battery strings and a bus bar, a first welding strip comprises a first body section connected with a first battery piece and a first extension section which extends to a second battery piece and is at least partially overlapped with the bus bar, the second welding strip comprises a second body section and a second extension section. And in the thickness direction of the back contact battery assembly, the first extension section and the second extension section do not have an overlapped part. The bus bar is provided with a protruding section protruding towards the side away from the second battery piece at the second extension section, and the bus bar is provided with a recessed section recessed towards the side of the second battery piece at the first extension section. For at least part of the cross section of the back contact battery assembly at the bus bar, the height difference between the highest point of the first extension section and the highest point of the adjacent convex section is smaller than the thickness of the first welding strip. In this way, the hidden crack risk in the laminating process 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, in such a technical solution, since the welding strips on the end battery cells need to extend to the busbar, there is a phenomenon that two welding strips and the busbar are stacked together in the thickness direction. Due to the high stacking height, stress concentration is likely to occur during the lamination process, resulting in hidden cracks and splits in the battery cells, a greater risk of fragmentation, and a reduced yield. 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, each 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 first welding ribbon being disposed on a back surface of the first battery cell, and a second welding ribbon being disposed on a back surface of the second battery cell;

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

[0009] The first welding ribbon includes a first body segment connected to the first battery cell and a first extension segment extending onto the second battery cell and at least partially overlapping the bus bar. The second welding ribbon includes a second body segment not overlapping the bus bar and a second extension segment overlapping the bus bar. The first body segment extends along the first direction, and an extension line of the first body segment in the first direction at least partially overlaps with the second body segment. In the thickness direction of the back-contact battery assembly, the first extension segment and the second extension segment do not have any overlapping portion.

[0010] The first 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 extension section that convexes toward a side away from the second battery cell, and the busbar is formed with a concave section at the first extension section that concave toward a side of the second battery cell;

[0011] Wherein, 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 first extension segment and a highest point of the adjacent raised segment is less than a thickness of the first welding strip.

[0012] In some embodiments, in the first welding strip, the first extension section and the first main body section are spaced apart from each other in the second direction, the first main body section and the first extension section are connected by a first connecting section, the second main body section and the second extension section are located on the same straight line in the first direction, and in the second direction, the first connecting section is bent relative to the first main body section toward the side where the first extension section is located.

[0013] In some embodiments, the first connecting segment is arc-shaped.

[0014] In some embodiments, a bending angle of the first connecting segment relative to the first main body segment is 10° to 90°.

[0015] In some embodiments, the first extension segment is arranged parallel to the second body segment and the second extension segment.

[0016] 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;

[0017] A plurality of third welding strips are further provided on the first battery cell, the third welding strips extending along the first direction, and the third welding strips and the first welding strips are alternately arranged along the second direction;

[0018] Wherein, on the first battery cell, in the second direction, the welding ribbons closest to the two edges of the first battery cell are the first welding ribbons, and the first connecting sections of the first welding ribbons closest to the edges are bent toward the center of the first battery cell; or

[0019] On the first battery cell, in the second direction, the welding strips closest to the two edges of the first battery cell are the third welding strips, and among the plurality of first welding strips, the first connecting sections of the first welding strips closest to the edges are bent in a direction away from the middle of the first battery cell.

[0020] 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;

[0021] wherein the first connecting 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

[0022] The first connecting section of a portion of the first welding ribbon on the first battery cell is bent toward one edge of the first battery cell in the second direction, and the first connecting section of another portion of the first welding ribbon is bent toward the other edge of the first battery cell in the second direction.

[0023] In some embodiments, the second welding strip further has a protruding section located on the side of the bus bar facing the first battery cell and not overlapping with the bus bar, and the second body section, the second extension section and the protruding section are located on the same straight line in the first direction.

[0024] In some embodiments, the length of the protruding segment in the first direction is 0.5 mm to 6 mm.

[0025] In some embodiments, the first battery cell is provided with a plurality of first welding points welded to the first body segment, and the bending point of the first connecting segment relative to the first body segment is located on the side of the first welding point closest to the second battery cell facing the second battery cell.

[0026] 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;

[0027] Among them, several first welding ribbons are arranged in pairs. In each pair of first welding ribbons, the first connecting section of one of the first welding ribbons is bent toward one edge of the first battery cell in the second direction, and the first connecting section of the other first welding ribbon is bent toward the other edge of the first battery cell in the second direction.

[0028] 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 sheet, and the bus bar is insulated and isolated from the second welding ribbon by the insulating strip.

[0029] In some embodiments, the insulating strip extends to a portion of the first battery cell on a side close to the second battery cell.

[0030] In some embodiments, a distance between the bus bar and an end of the second battery cell facing the first battery cell is 3 mm to 15 mm.

[0031] In some embodiments, a length of a portion of the first extending segment that overlaps the bus bar in the first direction is greater than or equal to half a length of the bus bar in the first direction.

[0032] In some embodiments, a length of a portion of the first extending segment overlapping the bus bar in the first direction is 6 mm to 12 mm.

[0033] 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, the multiple second welding ribbons are also arranged at intervals along the second direction, and the second battery cell is further provided with a plurality of fourth welding ribbons, the fourth welding ribbons extending along the first direction, and the plurality of the fourth welding ribbons and the plurality of the second welding ribbons are alternately arranged along the second direction;

[0034] Wherein, the first extension section is arranged between the second welding strip and the fourth welding strip adjacent to each other.

[0035] In some embodiments, the first extending section is centrally disposed between the second welding ribbon and the fourth welding ribbon adjacent to each other.

[0036] In some embodiments, in the second direction, the first extension segment is arranged closer to the second extension segment than to the fourth welding strip, and the highest point of the first extension segment is higher than the highest point of the raised segment.

[0037] In some embodiments, the first extension section is centrally arranged between the second extension section and the fourth welding strip of the second welding strip adjacent to each other, and the highest point of the first extension section is lower than the highest point of the raised section, or the highest point of the first extension section is flush with the highest point of the raised section.

[0038] 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;

[0039] The thickness of the insulating strip at the location of the first extension section is less than or equal to the thickness of the insulating strip at other locations between the second extension section and the fourth welding strip.

[0040] In some embodiments, for at least a partial cross-section of the busbar, an angle α between a line connecting the highest point of the raised segment and the lowest point of the adjacent recessed segment and the plane where the second battery cell is located satisfies the following formula: 0.075≤tanα≤3.

[0041] 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;

[0042] 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.

[0043] 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 sheet, and the bus bar is insulated and isolated from the second welding ribbon by the insulating strip;

[0044] The back-contact battery assembly includes a plurality of battery strings connected in series 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.

[0045] 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;

[0046] 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.

[0047] In some embodiments, in the second welding strip, the second extension section and the second body section are spaced apart from each other in the second direction, the second body section and the second extension section are connected by a second connecting section, the first body section and the first extension section are located on the same straight line in the first direction, and in the second direction, the second connecting section is bent relative to the second body section toward the side where the second extension section is located.

[0048] In some embodiments, the second connecting segment is arc-shaped.

[0049] In some embodiments, a bending angle of the second connecting segment relative to the second body segment is 10° to 90°.

[0050] In some embodiments, the second extension section is arranged parallel to the first welding strip.

[0051] In some embodiments, the number of the second welding ribbons and the number of the first welding ribbons are both multiple and one-to-one corresponding, the multiple second welding ribbons are arranged at intervals along the second direction, and the multiple first welding ribbons are also arranged at intervals along the second direction;

[0052] The second battery cell is further provided with a plurality of fourth welding strips, the fourth welding strips extending along the first direction, and the plurality of the fourth welding strips and the plurality of the second welding strips being alternately arranged along the second direction;

[0053] Wherein, on the second battery cell, in the second direction, the welding ribbons closest to the two edges of the second battery cell are the second welding ribbons, and the second connecting sections of the second welding ribbons closest to the edges are bent toward the middle of the second battery cell; or

[0054] On the second battery cell, in the second direction, the welding strips closest to the two edges of the second battery cell are the fourth welding strips, and among the plurality of second welding strips, the second connecting sections of the second welding strips closest to the edges are bent in a direction away from the middle of the second battery cell.

[0055] 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;

[0056] wherein the second connecting sections of all the second welding ribbons on the second battery cell are bent toward the same edge of the second battery cell in the second direction; or

[0057] The second connecting section of a portion of the second welding ribbon on the second battery cell is bent toward one edge of the second battery cell in the second direction, and the second connecting section of another portion of the second welding ribbon is bent toward the other edge of the second battery cell in the second direction.

[0058] In some embodiments, the second battery cell is provided with a plurality of second welding points welded to the second body segment, and the bending point of the second connecting segment relative to the second body segment is located on the side of the second welding point closest to the first battery cell facing the first battery cell.

[0059] 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;

[0060] Wherein, a plurality of the second welding strips are arranged in pairs, and in each pair of the second welding strips, the second connecting sections of the two second welding strips are bent in directions opposite to each other.

[0061] In some embodiments, 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 first extension segment and a highest point of an adjacent protruding segment is less than a thickness of the first welding ribbon.

[0062] The present application also provides a photovoltaic system, which includes the back-contact cell assembly described in any one of the above items.

[0063] In the back-contact cell assembly and photovoltaic system of the embodiments of the present application, on the one hand, the busbar is arranged on the back side of the second cell of the cell string, which can hide the busbar, 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 are improved. On the other hand, the first extension section of the first welding ribbon is welded to the busbar to achieve bus output. The first extension section of the first welding ribbon and the second extension section of the second welding ribbon do not overlap in the thickness direction. The first extension section of the first welding ribbon is located at the recessed section of the busbar. The height difference between the highest point of the raised section and the highest point of the adjacent first extension section is set to be less than the thickness of the first welding ribbon. Compared with the solution in which the first welding ribbon is directly stacked on the second welding ribbon in the traditional technical solution, the stacking height during the lamination process can be reduced, 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 stacking height of the entire back side of the second cell can be reduced, thereby reducing the amount of encapsulation film used and reducing costs.

[0064] 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

[0065] Figure 1 This is a module schematic diagram of a photovoltaic system provided by an embodiment of the present application;

[0066] Figure 2 Schematic diagram of the structure of the back contact battery assembly provided in an embodiment of the present application;

[0067] 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;

[0068] Figure 4 yes Figure 3 Schematic diagram of the enlarged structure at IV in the middle;

[0069] Figure 5 yes Figure 4 Schematic diagram of the enlarged structure at V in the middle;

[0070] Figure 6 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;

[0071] Figure 7 yes Figure 6 Schematic diagram of the enlarged structure at VII in the middle;

[0072] Figure 8 yes Figure 4 Another enlarged structural diagram of position IV in the middle;

[0073] Figure 9 yes Figure 8 A schematic diagram of the enlarged structure at line IX in the middle;

[0074] Figure 10 yes Figure 5 Schematic cross-section diagram along line XX;

[0075] Figure 11 Schematic diagram of the structure of the busbar of the back contact battery assembly provided in an embodiment of the present application;

[0076] Figure 12 yes Figure 9 Schematic diagram of the cross section along line XII-XII;

[0077] Figure 13 1 is another structural schematic diagram of a bus bar of a back-contact battery assembly provided in an embodiment of the present application;

[0078] Figure 14 yes Figure 3 Another enlarged structural diagram of position IV in the middle;

[0079] Figure 15 yes Figure 6 Another enlarged structural diagram at VII in the figure. DETAILED DESCRIPTION

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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, which 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.

[0089] 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 .

[0090] Each battery string 10 includes a plurality of battery cells 11 connected in series along a first direction. In 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. A first welding ribbon 12 is provided on the back of the first battery cell 111, and a second welding ribbon 13 is provided on the back of the second battery cell 112. 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. The first welding ribbon 12 is the end output end of the battery string 10, which is used to connect to the bus bar 20.

[0091] The bus bar 20 is disposed on the back of the second battery cell 112. The bus bar 20 is connected to the first welding ribbon 12 and insulated from the second welding ribbon 13 to realize bus output of the battery string 10. The bus bar 20 extends along a second direction that intersects the first direction.

[0092] 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.

[0093] Among them, such as Figure 4 、 Figure 5 as well as Figure 7 and Figure 8 As shown, the first welding ribbon 12 includes a first main section 121 and a first extension section 122. The first main section 121 is connected to the first battery cell 111, and the first extension section 122 extends onto the second battery cell 112 and at least partially overlaps with the busbar 20. In other words, the portion of the first extension section 122 extending onto the busbar 20 overlaps with the busbar 20 in the thickness direction, and the first extension section 122 is welded to the busbar 20.

[0094] The second welding ribbon 13 includes a second main section 131 and a second extension section 132. The second main section 131 does not overlap with the bus bar 20, while the second extension section 132 overlaps with the bus bar 20. In other words, the portion of the second welding ribbon 13 that overlaps with the bus bar 20 in the thickness direction is the second extension section 132.

[0095] The first body segment 121 extends along the first direction, and an extension line of the first body segment 121 in the first direction at least partially overlaps with the second body segment 131. In some examples, the first body segment 121 and the second body segment 131 may be located on the same straight line in the first direction.

[0096] like Figure 10 and Figure 12 As shown, the first extension section 122 is located on the side of the bus bar 20 facing away from the second battery cell 112 , and the second extension section 132 is located on the side of the bus bar 20 facing the second battery cell 112 .

[0097] The bus bar 20 has a raised section 21 formed at the second extension section 132 that is raised toward the side away from the second battery cell 112 , and a recessed section 22 formed at the first extension section 122 that is recessed toward the side of the second battery cell 112 .

[0098] See also Figure 10 and Figure 12 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 first extension segment 122 is less than the thickness of the first welding strip 12.

[0099] 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 first 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 first extension section 122, or the highest point of the raised section 21 may be lower than the highest point of the adjacent first 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.

[0100] In the back-contact cell assembly 100 and photovoltaic system 1000 in 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 assembly conversion efficiency. At the same time, the overall aesthetics of the back-contact cell assembly 100 is better. On the other hand, the first extension section 122 of the first welding ribbon 12 is welded to the busbar 20 to achieve busbar output. The first extension section 122 of the first welding ribbon 12 does not overlap with the second extension section 132 of the second welding ribbon 13 in the thickness direction. The first extension section 122 of the first welding ribbon 12 is located in the recessed section 22 of the busbar 20. The height difference between the highest point of the raised section 21 and the highest point of the adjacent first extension section 122 is set to be less than the thickness of the first welding ribbon 12. Compared with the conventional solution in which the first welding ribbon 12 is directly stacked on the second welding ribbon 13, this can reduce the stacking height during the lamination process, 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. At the same time, the stacking height of the entire back side of the second cell 112 can be reduced, thereby reducing the amount of encapsulating film used and reducing costs.

[0101] 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.

[0102] See also Figure 11 As shown in Figure 13, in some embodiments, 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), the angle α between the 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.

[0103] 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.

[0104] 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 aforementioned formula, the laminate stack height can be reduced to reduce stress concentration while also reducing the amount of encapsulation film used, thereby lowering costs. Specifically, if the stack height is high, a larger amount of film is required during packaging to fully encapsulate the stacked areas. However, in this application, by designing the entire structure to reduce the laminate stack height, stress concentration during the lamination process can be reduced while also reducing the amount of film used, thereby lowering costs.

[0105] 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 busbar 20 serves as the busbar output end of the battery string 10. The number of first welding ribbons 12 is multiple, and the number of second welding ribbons 13 is also multiple, and the two correspond one to one. The first welding ribbon 12 serves as the output welding ribbon of the battery string 10, and the second welding ribbon 13 serves as the series welding ribbon of the battery string 10. The polarity of the metal electrode (main grid and / or fine grid) connected to the first welding ribbon 12 is opposite to that of the metal electrode connected to the second welding ribbon 13. That is, from another perspective, the polarity of the first welding ribbon 12 and the second welding ribbon 13 are opposite.

[0106] like Figure 3-Figure 8 As shown, in the battery string 10, a plurality of third welding ribbons 14 are further provided on the first battery cell 111, and the plurality of third welding ribbons 14 and the plurality of first welding ribbons 12 are arranged alternately in sequence along the second direction. A plurality of fourth welding ribbons 15 are further provided on the second battery cell 112, and the plurality of fourth welding ribbons 15 and the plurality of second welding ribbons 13 are arranged alternately in sequence. The first welding ribbon 12 is insulated from the second welding ribbon 13 and the fourth welding ribbon 15, and the third welding ribbon 14 is connected to the fourth welding ribbon 15 to connect the first battery cell 111 and the second battery cell 112 in series.

[0107] That is, in this application, the second, third, and fourth ribbons 13, 14, and 15 are the series-connected ribbons of the cell string 10. The polarity of the metal electrode (busbar and / or fine grid) connected to the first ribbon 12 is opposite to that of the metal electrode connected to the second ribbon 13. In other words, from another perspective, the polarity of the first and second ribbons 12, 13 is opposite, and the polarity of the metal electrode (busbar and / or fine grid) connected to the third ribbon 14 is opposite to that of the metal electrode connected to the fourth ribbon 15. On the first cell 111, the polarity of the metal electrode connected to the first ribbon 12 is also opposite to that of the metal electrode connected to the third ribbon 14. On the second cell 112, the polarity of the metal electrode connected to the second ribbon 12 and the fifth ribbon 15 is also opposite.

[0108] 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.

[0109] 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. In this application, the back-contact 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.

[0110] 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.

[0111] 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 and a lower half in the first direction (with Figure 2 The center line L in the figure is the limit).

[0112] like Figure 2 As 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.

[0113] That is to say, in Figure 2In 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.

[0114] 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.

[0115] 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.

[0116] See also Figure 2-Figure 4 From 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.

[0117] 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.

[0118] 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.

[0119] 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 (that is, they are basically 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 of the battery strings 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.

[0120] See also Figure 2-Figure 8 In 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 .

[0121] 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.

[0122] 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.

[0123] The insulating strip 30 can be an insulating glue, 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 side or both sides. It can be understood that the insulating strip 30500 can include materials such as ethylene-vinyl acetate copolymer, resin material, polyimide or polypropylene or polyethylene, and can also include an acrylic adhesive layer.

[0124] 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, it will increase the height difference, 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 0.05 mm and 0.8 mm. 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 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm or 0.8 mm.

[0125] The width of the insulating strip 30 is greater than or equal to the width of the bus bar 20. In this way, the bus bar 20 can be completely insulated from the second welding ribbon 13 and the fourth welding ribbon 15 on the second battery cell 112.

[0126] See also Figure 3 and Figure 4 In 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 .

[0127] 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.

[0128] like Figure 2 As shown, in some embodiments, the back contact battery assembly 100 includes a plurality of series battery strings 110 arranged along a second direction, and in the second direction, the insulating strip 30 extends from the first series battery string 110 to the last series battery string 110 .

[0129] 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.

[0130] See also Figure 6As shown in Figure 7, in an embodiment of the present application, the back-contact battery module 100 includes at least one parallel battery string group 120, and the parallel battery string group 120 includes at least two first battery strings 1201 and second battery strings 1202 arranged along a first direction, the first battery string 1201 is located in the upper half of the module, and the second battery string 1202 is located in the lower half of the module.

[0131] 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, the second battery string 1202 includes the third battery cell 1211, 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.

[0132] 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.

[0133] 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 connecting 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.

[0134] 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.

[0135] In addition, combined Figure 3 and Figure 6 as well as Figure 7It 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 in 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 first edge) is also the first battery cell 111, and the battery cell 11 in the second battery string 1202 closest to the first battery string 1201 is the third battery cell 1211, and the battery cell 11 in 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 second 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 second 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.

[0136] 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. Illustratively, the polarity of the first soldering ribbon 12 on the first battery cell 111 in the second battery string 1202 is opposite to the polarity of the first soldering ribbon 12 on the first battery cell 111 closest to the second battery string 1202 in the first battery string 1201 .

[0137] 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.

[0138] See also Figure 4 、 Figure 5 as well as Figure 7-Figure 9In some embodiments, in the first welding strip 12, the first extension section 122 and the first main body section 121 are spaced apart from each other in the second direction, the first main body section 121 and the first extension section 122 are connected by the first connecting section 123, the second main body section 131 and the second extension section 132 are located on the same straight line in the first direction, and in the second direction, the first connecting section 123 is bent relative to the first main body section 121 toward the side where the first extension section 122 is located.

[0139] Thus, by spacing the first extension section 122 of the first welding ribbon 12 from the first main body section 121 and locating the second main body section 131 and the second extension section 132 on the same straight line in the first direction, the first extension section 122 and the second extension section 132 do not overlap in the thickness direction, thereby preventing excessive stacking height during the lamination process and causing hidden cracks. Furthermore, the bent first connecting section 123 allows for a transitional connection between the first main body section 121 and the second main body section 131, eliminating the need for additional connectors to connect the first main body section 121 and the first extension section 122.

[0140] Specifically, in this embodiment, the first welding ribbon 12 is a bent welding ribbon. By bending the first welding ribbon 12, the first welding ribbon 12 comprises a first main section 121, a first connecting section 123, and a first extension section 122 connected in sequence. The second welding ribbon 13 is a straight welding ribbon (i.e., the second main section 131 and the second extension section 132 are located on the same straight line in the first direction). The second welding ribbon 13 is located on the same straight line as the first main section 121 of the first welding ribbon 12. The bending direction of the first connecting section 123 of the first welding ribbon 12 is determined by the relative position of the first extension section 122 and the first main section 121. Generally speaking, the first connecting section 123 bends relative to the first main section 121 toward the side where the first extension section 122 is located.

[0141] It is readily understood that, in the present application, the first welding ribbon 12 having the first main body section 121, the first connecting section 123, and the first 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 a limitation of 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 labor costs, and also avoiding phenomena such as cold welds and burrs generated during the welding process due to manual welding.

[0142] Furthermore, in some embodiments, the first connecting segment 123 is arc-shaped.

[0143] In this way, the first main section 121 and the first extension section 122 can be smoothly connected by the arc-shaped first connecting section 123. The smooth transition design can prevent the first welding ribbon 12 from forming a sharp angle at the bend position, which could cause stress concentration at this position and lead to fracture failure. It can also avoid the phenomenon of cold welding caused by sharp bends.

[0144] In some embodiments, a bending angle of the first connecting segment 123 relative to the first body segment 121 is greater than or equal to 10° and less than or equal to 90°.

[0145] Preferably, the bending angle of the first connecting segment 123 relative to the first body segment 121 is greater than or equal to 30° and less than or equal to 60°. In such an embodiment, the bending angle of the connecting segment 203 relative to the first body segment 121 can be 30°, 40°, 50°, 60°, or any value between 30° and 60°, without limitation.

[0146] In this way, the bending angle of the first connecting section 123 relative to the first main body 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.

[0147] Specifically, in such an embodiment, the "bending angle of the first connecting segment 123 relative to the first main body segment 121" refers to the angle between the line between any point on the first connecting segment 123 and the intersection of the first connecting segment 123 and the first main body segment 121 (the intersection can also be regarded as the point where the first connecting segment 123 of the first welding strip 12 begins to bend relative to the first main body segment 121, that is, the bending starting point of the first connecting segment 123) and the first main body segment 121.

[0148] Of course, it is understandable that in some possible embodiments, while meeting production requirements, the first connecting section 123 and the first main section 121 may be bent at right angles instead of in an arc shape, and this is not specifically limited here.

[0149] See also Figure 3-Figure 9 In some embodiments, the first extension section 122 is arranged in parallel with the second welding strip 13 , that is, the first extension section 122 is arranged in parallel with the first body section 121 and the second welding strip 13 .

[0150] In this way, the two are arranged in parallel. Even if the length of the first extension section 122 is longer, it can ensure that there is no overlapping part between the first extension section 122 and the second extension section 132 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.

[0151] In some embodiments, as described above, the number of first welding ribbons 12 and second welding ribbons 13 are both multiple and one-to-one corresponding, multiple first welding ribbons 12 are arranged at intervals along the second direction, and multiple second welding ribbons 13 are also arranged at intervals along the second direction. A plurality of third welding ribbons 14 are also provided on the first battery cell 111, and the third welding ribbons 14 extend along the first direction. The plurality of third welding ribbons 14 and the plurality of first welding ribbons 12 are alternately arranged along the second direction.

[0152] In some embodiments, on the first battery cell 111 , in the second direction, the welding ribbons closest to the two edges of the first battery cell 111 are the first welding ribbons 12 , and the first connecting segments 123 of the first welding ribbons 12 closest to the edges are bent toward the center of the first battery cell 111 .

[0153] In this way, when the two welding ribbons closest to the edges of the first battery cell 111 are both first welding ribbons 12, the first extension sections 122 are both located on the inner side of the first battery cell 111, and the first connection sections 123 of the two first welding ribbons 12 located at the outermost edges are both bent toward the inner middle portion of the first battery cell 111. This can prevent the first welding ribbon 12 from bending toward the end of the first battery cell 11, which would cause the first extension section 122 to lose sufficient distance from the second extension section 132. At the same time, it can also prevent the first connection section 123 of the first welding ribbon 12 from bending toward the edge, causing the first connection section 123 and the first extension section 122 to be too close to the edge, which would make the first battery cell 111 and the second battery cell 112 more susceptible to hidden cracks. In other words, this arrangement can reduce the risk of hidden cracks.

[0154] 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 first connecting 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.

[0155] See also Figure 8 and Figure 9 In some embodiments, the first connection 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 11 in the second direction.

[0156] In this way, the first connecting 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.

[0157] Of course, if Figure 4 and Figure 7 As shown, in other embodiments, the first connecting segments 123 of part of the first welding ribbons 12 on the first battery cell 111 may be bent toward one of the edges of the first battery cell 11 in the second direction, while the first connecting segments 123 of another part of the first welding ribbons 12 may be bent toward the other edge of the first battery cell 11 in the second direction.

[0158] Also, see Figure 4 and Figure 7 In some embodiments, several first welding ribbons 12 are arranged in pairs on the first cell 111. In each pair of first welding ribbons 12, the first connecting segment 123 of one first welding ribbon 12 is bent toward one edge of the first cell 111 in the second direction, and the first connecting segment 123 of the other first welding ribbon 12 is bent toward the other edge of the first cell 111 in the second direction. That is, in each pair of first welding ribbons 12, the first connecting segments 123 of both first welding ribbons 12 are bent toward the area between the two first body segments 121. Specifically, a third welding ribbon 14 is provided between each pair of first welding ribbons 12, and the two first welding ribbons 12 in each pair of first welding ribbons 12 are symmetrical about the third welding ribbon 14.

[0159] In this way, the first welding ribbons 12 are arranged in pairs, and the two first connecting 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.

[0160] 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 first connecting sections 123 of the two first welding ribbons 12 are bent toward the position where the third welding ribbon 14 and the fourth welding ribbon 15 are located between the two first welding ribbons 12, and the first extending 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.

[0161] See also Figure 4 and Figure 5In some embodiments, the second welding strip 13 further has a protruding section 133 located on the side of the bus bar 20 facing the first battery cell 111 and not overlapping with the bus bar 20, and the second main section 131, the second extension section 132 and the protruding section 133 are located on the same straight line in the first direction.

[0162] 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.

[0163] Specifically, if Figure 4 and Figure 5 As shown, in such an embodiment, along the direction from the first battery cell 111 to the second battery cell 112 , the second welding ribbon 13 includes a protruding section 133 , a second extending section 132 and a second body section 131 that are sequentially connected.

[0164] In such an embodiment, the length of the protruding section 133 in the first direction is 0.5 mm to 6 mm.

[0165] In this way, it is possible to avoid the situation where the length of the protruding section 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 protruding section 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 first 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.

[0166] Specifically, in such an embodiment, the length of the protruding section 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.

[0167] See also Figure 5 and Figure 8 In some embodiments, the first battery cell 111 is provided with a plurality of first welding points 40 welded to the first body segment 121, and the bending point of the first connecting segment 123 relative to the first body segment 121 (i.e., the bending starting point of the first connecting segment 123) is located on the side of the first welding point 40 closest to the second battery cell 112 facing the second battery cell 112.

[0168] In this way, by designing the bending point of the first connecting section 123 to be behind the position of the first welding point 40 at the outermost edge, current can be better collected.

[0169] In some embodiments, the distance between the bus bar 20 and the end of the second battery cell 112 facing the first battery cell 111 is 3 mm to 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.

[0170] 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 first 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.

[0171] See also Figure 5 as well as Figure 7-Figure 8 In some embodiments, the length of the portion where the first 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.

[0172] In this way, it is possible to avoid the welding length between the first 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.

[0173] Specifically, in such an embodiment, the length of the portion where the first 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.

[0174] In this way, the welding stability between the first extension section 122 and the bus bar 20 can be ensured.

[0175] See also Figure 5 and Figure 8 In some embodiments, as described above, the second welding ribbon 13 is a straight welding ribbon, the first welding ribbon 12 is a bent welding ribbon, and the first extension section 122 is disposed between the second welding ribbon 13 and the fourth welding ribbon 15 adjacent to each other.

[0176] In a possible embodiment, the first extension section 122 may be centrally disposed between the second welding ribbon 13 and the fourth welding ribbon 15 .

[0177] In this way, during the lamination process, the first extension section 122 can be pressed as much as possible toward the second battery cell 112, thereby reducing the stacking height of the entire component 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.

[0178] In some embodiments, in the second direction, the first extension section 122 is arranged closer to the second extension section 132 than the fourth welding strip 15, that is, the first extension section 122 is arranged between the fourth welding strip 15 and the second extension section 132 and closer to the second extension section 132, and the highest point of the first extension section 122 is higher than the highest point of the raised section 21.

[0179] In this way, the first extension section 122 is not set in the middle of the fourth welding ribbon 15 and the second extension section 132, which can reduce the bending angle of the first connecting section 123 of the first welding ribbon 12 and avoid excessive bending causing excessive stress and resulting in cold welding.

[0180] In other embodiments, the first extension section 121 is centrally arranged between the second extension section 132 of the second welding strip 13 and the fourth welding strip 15 adjacent to each other, and the highest point of the first extension section 121 is lower than the highest point of the raised section 21, or the highest point of the first extension section 121 is flush with the highest point of the raised section 21.

[0181] Thus, disposing the first extension section 121 in the middle between the fourth welding ribbon 15 and the second extension section 132 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.

[0182] In some embodiments, the thickness of the insulating strip 30 at the location of the first extending section 121 is less than or equal to the thickness of the insulating strip 30 at other locations between the second extending section 132 and the fourth welding ribbon 15 .

[0183] In this way, the highest point of the first extension section 121 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 .

[0184] In the embodiment described above, the first welding ribbon 12 is a bent welding ribbon, and the second welding ribbon 13 is a straight welding ribbon. It should be noted that in the present application, the first welding ribbon 12 can also be a straight welding ribbon, and the second welding ribbon 13 can be a bent welding ribbon.

[0185] Specifically, see Figure 14 and Figure 15 In some embodiments, in the second welding strip 13, the second extension section 132 and the second main body section 131 are spaced apart from each other in the second direction, the second main body section 131 and the second extension section 132 are connected by a second connecting section 134, the second main body section 131 and the second extension section 132 are located on the same straight line in the first direction, and in the second direction, the second connecting section 134 is bent relative to the second main body section 131 toward the side where the second extension section 132 is located.

[0186] In this way, by spacing the second extension section 132 of the second welding ribbon 13 from the second main body section 131 and locating the second extension section 132 on the same straight line in the first direction, the second extension section 132 and the second extension section 132 do not overlap in the thickness direction, thereby preventing excessive stacking height during the lamination process and causing hidden cracks. Furthermore, the curved second connecting section 134 allows the second main body section 131 and the second main body section 131 to be transitionally connected, eliminating the need for additional connectors to connect the second main body section 131 and the second main body section 131. Furthermore, by configuring the first welding ribbon 12 as a straight ribbon and the second welding ribbon 13 as a curved ribbon, the first welding ribbon 12 does not need to be bent, thus avoiding the high internal stress generated by the first welding ribbon 12 being bent and welded to the busbar 20, which could lead to warping of the first welding ribbon 12. That is to say, setting the second welding strip 13 as a bent welding strip can reduce the laminate stacking height to reduce the risk of hidden cracks while allowing the first welding strip 12 to only be welded to the bus bar 20 without bending, thereby reducing the internal stress of the first welding strip 12 and reducing the risk of warping of the first welding strip 12.

[0187] Specifically, in this embodiment, the second welding ribbon 13 is a bent welding ribbon. By bending the second welding ribbon 13, the second welding ribbon 13 comprises a second main section 131, a second connecting section 134, and a second extension section 132, which are sequentially connected. The first welding ribbon 12 is a linear welding ribbon (i.e., the first welding ribbon 12 comprises only a first main section 121 and a first extension section 122, which are located on the same straight line in a first direction). The first welding ribbon 12 and the second main section 131 of the second welding ribbon 13 are located on the same straight line. The bending direction of the second connecting section 134 of the second welding ribbon 13 is determined by the relative position of the second extension section 132 and the second main section 131. Generally speaking, the second connecting section 134 bends relative to the second main section 131 toward the side where the second extension section 132 is located.

[0188] It is easy to understand that in the present application, the second welding ribbon 13 having the second main body section 131, the second connecting section 134, and the second extension section 132 can be formed by integrally stamping a single welding ribbon, or can be formed by splicing multiple welding ribbons together. This is not limited in the present application. Preferably, the second welding ribbon 13 is formed by integrally stamping a single welding ribbon, thereby eliminating redundant steps such as welding during the production of the second welding ribbon 13, reducing labor consumption, and also avoiding phenomena such as cold welds and burrs caused by manual welding during the welding process.

[0189] Furthermore, in some embodiments, the second connecting segment 134 is arc-shaped.

[0190] In this way, the second main section 131 and the second extension section 132 can be smoothly connected by the arc-shaped second connecting section 134. The smooth transition design can prevent the second welding ribbon 13 from forming a sharp angle at the bend position, which could cause stress concentration at this position and lead to fracture failure. It can also avoid the phenomenon of cold welding caused by sharp bends.

[0191] In some embodiments, the bending angle of the second connecting segment 134 relative to the second body segment 131 is greater than or equal to 10° and less than or equal to 90°. Preferably, the bending angle of the second connecting segment 134 relative to the second body segment 131 is greater than or equal to 30° and less than or equal to 60°. In such embodiments, the bending angle of the connecting segment 203 relative to the second body segment 131 can be 30°, 40°, 50°, 60°, or any value between 30° and 60°, without limitation.

[0192] In this way, the bending angle of the second connecting section 134 relative to the second main body section 131 is set within this range, the metal material of the second welding strip 13 will not reduce its strength due to excessive deformation, and it can be more easily accurately processed by mechanical or automated equipment. The second welding strip 13 can be bent into the required curvature using less force, thereby improving production efficiency.

[0193] Specifically, in such an embodiment, the "bending angle of the second connecting segment 134 relative to the second main body segment 131" refers to the angle between the line between any point on the second connecting segment 134 and the intersection of the second connecting segment 134 and the second main body segment 131 (the intersection can also be regarded as the point where the second connecting segment 134 of the second welding strip 13 begins to bend relative to the second main body segment 131, that is, the bending starting point of the second connecting segment 134) and the second main body segment 131.

[0194] Of course, it is understandable that in some possible embodiments, while meeting production requirements, the second connecting segment 134 and the second body segment 131 may be bent at right angles instead of in an arc shape, and this is not specifically limited here.

[0195] See also Figure 14 and Figure 15 In some embodiments, the second extension section 132 is arranged parallel to the first welding strip 12 , that is, the second extension section 132 is arranged parallel to the second body section 131 and the first welding strip 12 .

[0196] In this way, the two are arranged in parallel. Even if the lengths of the second extension sections 132 intersect, it can ensure that there is no overlapping part in the thickness direction of the second extension sections 132 and the second extension sections 132, 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.

[0197] See also Figure 14 and Figure 15 In some embodiments, as described above, the number of second welding ribbons 13 and the number of first welding ribbons 12 are both multiple and one-to-one corresponding, the multiple second welding ribbons 13 are arranged at intervals along the second direction, and the multiple first welding ribbons 12 are also arranged at intervals along the second direction. A plurality of fourth welding ribbons 15 are also provided on the first battery cell 111, and the fourth welding ribbons 15 extend along the first direction. The plurality of fourth welding ribbons 15 and the plurality of second welding ribbons 13 are alternately arranged along the second direction.

[0198] In some embodiments, on the second battery cell 112 , in the second direction, the welding ribbons closest to the two edges of the second battery cell 112 are the second welding ribbons 13 , and the second connecting segments 134 of the second welding ribbons 13 closest to the edges are bent toward the center of the second battery cell 112 .

[0199] In this way, when the two welding ribbons closest to the two edges of the second battery cell 112 are both second welding ribbons 13, the second extension sections 132 are both located on the inner side of the second battery cell 112, and the second connection sections 134 of the two second welding ribbons 13 located at the outermost edges are both bent toward the inner middle portion of the second battery cell 112. This can prevent the second welding ribbon 13 from bending toward the edge of the second battery cell 112, which could cause the second extension sections 132 to lose sufficient distance from each other. At the same time, it can also prevent the second connection sections 134 of the second welding ribbon 13 from bending toward the edge, which could cause the second connection sections 134 and the second extension sections 132 to be too close to the edge, making the second battery cell 112 more susceptible to hidden cracks. In other words, this arrangement can reduce the risk of hidden cracks.

[0200] Of course, in other cases, on the second battery cell 112, in the second direction, the welding strips closest to the two edges of the second battery cell 112 may also be the fourth welding strip 15. In such a case, among the several second welding strips 13, the second connecting section 134 of the second welding strip 13 closest to the edge may also be bent in the direction away from the middle of the second battery cell 112.

[0201] See also Figure 14 and Figure 15 In some embodiments, the second connection sections 134 of all the second welding ribbons 13 on the second battery cell 112 are bent toward the same edge of the second battery cell 112 in the second direction.

[0202] In this way, the second connecting sections 134 of all the second welding strips 13 are bent in the same direction, and only one shape of second welding strip 13 is needed to achieve direct connection between the second welding strip 13 and the bus bar 20, without the need to separately manufacture two different types of second welding strips 13.

[0203] Of course, in other embodiments, the second connecting segments 134 of some of the second welding strips 13 on the second battery cell 112 may be bent toward one of the edges of the first battery cell 11 in the second direction, while the second connecting segments 134 of another part of the second welding strips 13 may be bent toward the other edge of the first battery cell 11 in the second direction.

[0204] Furthermore, in some embodiments, multiple second welding ribbons 13 may be arranged in pairs on the second cell 112. In each pair of second welding ribbons 13, the second connecting segment 134 of one second welding ribbon 13 bends toward one edge of the second cell 112 in the second direction, while the second connecting segment 134 of the other second welding ribbon 13 bends toward the other edge of the second cell 112 in the second direction. That is, in each pair of second welding ribbons 13, the second connecting segments 134 of both second welding ribbons 13 bend toward the area between the two second body segments 131. Specifically, a fourth welding ribbon 15 is provided between each pair of second welding ribbons 13, and the two second welding ribbons 13 in each pair of second welding ribbons 13 are symmetrical about the fourth welding ribbon 15.

[0205] In this way, the second welding ribbons 13 are arranged in pairs, and the two second connecting sections 134 are bent toward the area between the two second welding ribbons 13, so that the force applied to the second battery cell 112 during the lamination process can be more uniform, reducing the risk of hidden cracks and splits.

[0206] Specifically, in such an embodiment, a fourth welding ribbon 15 is provided between each pair of second welding ribbons 13. In each pair of second welding ribbons 13, the second connecting sections 134 of the two second welding ribbons 13 are bent toward the position where the fourth welding ribbon 15 is located between the two second welding ribbons 13, and the second extending section 132 is located between the first welding ribbon 12 and the fourth welding ribbon 15. Each pair of second welding ribbons 13 is symmetrically arranged about the fourth welding ribbon 15.

[0207] In some embodiments, the second battery cell 112 is provided with a plurality of second welding points 50 welded to the second main body segment 131, and the bending point of the second connecting segment 134 relative to the second main body segment 131 (i.e., the bending starting point of the second connecting segment 134) is located on the side of the second welding point 50 closest to the first battery cell 111 facing the first battery cell 111.

[0208] In this way, by designing the bending point of the second connecting section 134 to be behind the location of the second welding point 50 at the outermost edge, current can be better collected.

[0209] In some embodiments, the second extension section 132 may be centrally disposed between the first welding ribbon 12 and the fourth welding ribbon 15 .

[0210] In this way, during the lamination process, the second extension section 132 can be pressed as much as possible toward the second battery cell 112, thereby reducing the stacking height of the entire component 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.

[0211] In some embodiments, the first extension section 121 is arranged between the second extension section 132 and the fourth welding strip 15. In the second direction, the first extension section 122 is arranged closer to the second extension section 132 than the fourth welding strip 15, that is, the first extension section 122 is arranged between the fourth welding strip 15 and the second extension section 132 and closer to the second extension section 132. The highest point of the first extension section 122 is higher than the highest point of the raised section 21.

[0212] In this way, the first extension section 122 is not set in the middle of the fourth welding strip 15 and the second extension section 132 and is closer to the second extension section 132. In this way, the offset distance of the second extension section 132 is smaller than that of the first extension section 122, which can reduce the bending angle of the second connecting section 134 of the second welding strip 13, avoiding excessive bending and causing excessive stress and resulting in cold welding.

[0213] In other embodiments, the first extension section 121 is centrally arranged between the second extension section 132 of the second welding strip 13 and the fourth welding strip 15 adjacent to each other, and the highest point of the first extension section 121 is lower than the highest point of the raised section 21, or the highest point of the first extension section 121 is flush with the highest point of the raised section 21.

[0214] Thus, disposing the first extension section 121 in the middle between the fourth welding ribbon 15 and the second extension section 132 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.

[0215] 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.

[0216] 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, each 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 first welding ribbon being disposed on a back surface of the first battery cell, and a second welding ribbon being disposed on a back surface of the second battery cell; a bus bar, the bus bar being disposed on the back side of the second battery cell, the bus bar being connected to the first welding ribbon and insulated from the second welding ribbon, the bus bar extending along a second direction, the second direction intersecting the first direction; The first welding ribbon includes a first body segment connected to the first battery cell and a first extension segment extending onto the second battery cell and at least partially overlapping the bus bar. The second welding ribbon includes a second body segment not overlapping the bus bar and a second extension segment overlapping the bus bar. The first body segment extends along the first direction, and an extension line of the first body segment in the first direction at least partially overlaps with the second body segment. In the thickness direction of the back-contact battery assembly, the first extension segment and the second extension segment do not have any overlapping portion. The first 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 extension section that convexes toward a side away from the second battery cell, and the busbar is formed with a concave section at the first extension section that concave toward a side of the second battery cell; Wherein, 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 first extension segment and a highest point of the adjacent raised segment is less than a thickness of the first welding strip.

2. The back contact battery assembly according to claim 1, characterized in that In the first welding strip, the first extension section and the first main body section are spaced apart from each other in the second direction, the first main body section and the first extension section are connected by a first connecting section, the second main body section and the second extension section are located on the same straight line in the first direction, and in the second direction, the first connecting section is bent relative to the first main body section toward the side where the first extension section is located.

3. The back contact battery assembly according to claim 2, characterized in that The first connecting section is arc-shaped.

4. The back contact battery assembly according to claim 2, characterized in that The bending angle of the first connecting section relative to the first main body section is 10° to 90°.

5. The back contact battery assembly according to claim 2, characterized in that The first extension section is arranged parallel to the second body section and the second extension section.

6. The back contact battery assembly according to claim 2, characterized in that 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; A plurality of third welding strips are further provided on the first battery cell, the third welding strips extending along the first direction, and the third welding strips and the first welding strips are alternately arranged along the second direction; Wherein, on the first battery cell, in the second direction, the welding ribbons closest to the two edges of the first battery cell are the first welding ribbons, and the first connecting sections of the first welding ribbons closest to the edges are bent toward the center of the first battery cell; or On the first battery cell, in the second direction, the welding strips closest to the two edges of the first battery cell are the third welding strips, and among the plurality of first welding strips, the first connecting sections of the first welding strips closest to the edges are bent in a direction away from the middle of the first battery cell.

7. The back contact battery assembly according to claim 2, characterized in that: 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; wherein the first connecting 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 first connecting section of a portion of the first welding ribbon on the first battery cell is bent toward one edge of the first battery cell in the second direction, and the first connecting section of another portion of the first welding ribbon is bent toward the other edge of the first battery cell in the second direction.

8. The back contact battery assembly according to claim 2, characterized in that: The second welding strip further has a protruding section located on a side of the bus bar facing the first battery cell and not overlapping the bus bar. The second body section, the second extension section, and the protruding section are located on the same straight line in the first direction.

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

10. The back contact battery assembly according to claim 2, characterized in that: The first battery cell is provided with a plurality of first welding points welded to the first body segment, and the bending point of the first connecting segment relative to the first body segment is located on the side of the first welding point closest to the second battery cell facing the second battery cell.

11. The back contact battery assembly according to claim 2, characterized in that: 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 ribbons are arranged in pairs. In each pair of first welding ribbons, the first connecting section of one of the first welding ribbons is bent toward one edge of the first battery cell in the second direction, and the first connecting section of the other first welding ribbon is bent toward the other edge of the first battery cell in the second direction.

12. 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 by the insulating strip.

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

14. The back contact battery assembly according to claim 1, wherein: A distance between the bus bar and an end of the second battery cell facing the first battery cell is 3 mm to 15 mm.

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

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

17. The back contact battery assembly according to claim 1, characterized in that 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. The second battery cell is further provided with a plurality of fourth welding ribbons, the fourth welding ribbons extending along the first direction, and the plurality of the fourth welding ribbons and the plurality of the second welding ribbons are alternately arranged along the second direction; Wherein, the first extension section is arranged between the second welding strip and the fourth welding strip adjacent to each other.

18. The back contact battery assembly according to claim 17, characterized in that In the second direction, the first extension segment is arranged closer to the second extension segment than to the fourth welding strip, and the highest point of the first extension segment is higher than the highest point of the raised segment.

19. The back contact battery assembly according to claim 17, wherein: The first extension section is centrally arranged between the second extension section and the fourth welding strip of the second welding strip adjacent to each other, and the highest point of the first extension section is lower than the highest point of the raised section, or the highest point of the first extension section is flush with the highest point of the raised section.

20. 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 thickness of the insulating strip at the location of the first extension section is less than or equal to the thickness of the insulating strip at other locations between the second extension section and the fourth welding strip.

21. The back contact battery assembly according to claim 1, wherein: 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.

22. The back contact battery assembly according to claim 21, 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 and isolated from the second welding ribbon by the insulating strip; The back-contact battery assembly includes a plurality of battery strings connected in series 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.

23. The back contact battery assembly according to claim 1, characterized in that 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.

24. The back contact battery assembly according to claim 1, wherein: In the second welding strip, the second extension section and the second main body section are spaced apart from each other in the second direction, the second main body section and the second extension section are connected by a second connecting section, the first main body section and the first extension section are located on the same straight line in the first direction, and in the second direction, the second connecting section is bent relative to the second main body section toward the side where the second extension section is located.

25. A photovoltaic system, characterized in that: A back contact battery assembly comprising any one of claims 1-24.

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