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 bus bar, the included angle alpha between the connecting line between the highest point of the convex section and the lowest point of the adjacent concave section and the plane where the second battery piece is located meets the following formula: 0.075 < = tan alpha < = 3. 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] The back contact cell module is usually composed of a back contact cell array, which includes a number of back contact cell strings. In the back contact cell module, the edge bus bar is usually set in the edge area of ​​the module, and the middle bus bar is usually set in the middle area of ​​the module. Both need to be placed in a certain space reserved on the module. This will reduce the effective light receiving area of ​​the module, affect the conversion efficiency of the module, and also affect the appearance of the module.

[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 strip on the end battery cell is welded to the bus bar to achieve the hiding of the bus bar and bus output.

[0004] However, in such a technical solution, since the welding strips on the end battery cells need to extend to the bus bar, there is a phenomenon that two welding strips and the bus bar 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 in this way. The back contact battery assembly of the embodiment of the present application includes:

[0007] A plurality of battery strings, the battery strings comprising a plurality of battery cells sequentially connected in series along a first direction, the plurality of battery cells comprising a first battery cell disposed at an end of the battery string and a second battery cell adjacent to the first battery cell, a first welding strip being disposed on the back of the first battery cell, and a second welding strip being disposed on the back of the second battery cell;

[0008] A bus bar, the bus bar is arranged on the back side of the second battery cell, the bus bar is connected to the first welding strip and is insulated from the second welding strip, the bus bar is extended along a second direction, and the second direction intersects the first direction;

[0009] The first welding strip includes a first body segment connected to the first battery cell and a first extension segment extending to the second battery cell and at least partially overlapping the bus bar, the second welding strip 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;

[0010] In the thickness direction of the back contact battery assembly, the first extension section and the second extension section have no overlapping part; the first extension section is located on the side of the bus bar away from the second battery sheet, and the second extension section is located on the side of the bus bar facing the second battery sheet, and the bus bar is formed with a convex section protruding toward the side away from the second battery sheet at the second extension section, and the bus bar is formed with a concave section concave toward the side of the second battery sheet at the first extension section;

[0011] 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 a plane where the second battery cell is located satisfies the following formula: 0.075≤tanα≤3.

[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 in parallel with the second body segment and the second extension segment.

[0016] In some embodiments, 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;

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

[0018] Wherein, on the first battery cell, in the second direction, the welding strips closest to the two edges of the first battery cell are the first welding strips, and the first connecting section of the first welding strip closest to the edge is bent toward a direction close to the middle 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 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;

[0021] wherein the first connection 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

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

[0027] Among them, several first welding strips are arranged in pairs, and in each pair of first welding strips, the first connecting section of one of the first welding strips is bent toward one edge of the first battery cell in the second direction, and the first connecting section of another first welding strip 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 extension segment overlapping the bus bar in the first direction is greater than or equal to half of a length of the bus bar in the first direction.

[0032] In some embodiments, a length of a portion of the first extension 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 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, the multiple second welding strips are also arranged at intervals along the second direction, and the second battery cell is further provided with a plurality of fourth welding strips, the fourth welding strips extend along the first direction, and the plurality of the fourth welding strips and the plurality of the second welding strips 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 extension section is centrally disposed between the second welding strip and the fourth welding strip adjacent to each other.

[0036] In some embodiments, the back contact battery assembly includes at least one battery string group connected in series, and the battery string group connected in series includes two battery strings arranged along the second direction;

[0037] 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 the series-connected battery string group in series.

[0038] In some embodiments, the back contact battery assembly further includes an insulating strip, 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 strip by the insulating strip;

[0039] 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.

[0040] In some embodiments, 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 second battery strings arranged along the first direction;

[0041] 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 via the first welding ribbon.

[0042] 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.

[0043] In some embodiments, the second connecting segment is arc-shaped.

[0044] In some embodiments, a bending angle of the second connecting segment relative to the second main body segment is 10° to 90°.

[0045] In some embodiments, the second extension section is disposed parallel to the first welding strip.

[0046] In some embodiments, the number of the second welding strips and the number of the first welding strips are both multiple and one-to-one corresponding, the multiple second welding strips are arranged at intervals along the second direction, and the multiple first welding strips are also arranged at intervals along the second direction;

[0047] A plurality of fourth welding strips are further provided on the second battery cell, the fourth welding strips extend along the first direction, and the plurality of the fourth welding strips and the plurality of the second welding strips are alternately arranged along the second direction;

[0048] Wherein, on the second battery cell, in the second direction, the welding strips closest to the two edges of the second battery cell are the second welding strips, and the second connecting section of the second welding strip closest to the edge is bent toward a direction close to the middle of the second battery cell; or

[0049] 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.

[0050] In some embodiments, 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;

[0051] wherein the second connection sections of all the second welding strips on the second battery cell are bent toward the same edge of the second battery cell in the second direction; or

[0052] The second connecting section of a portion of the second welding tape 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 tape is bent toward the other edge of the second battery cell in the second direction.

[0053] 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.

[0054] In some embodiments, 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;

[0055] 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.

[0056] 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 first protrusion segment is less than a thickness of the first welding strip.

[0057] The present application also provides a photovoltaic system, which includes the back contact cell assembly described in any one of the above items.

[0058] In the back contact battery assembly and photovoltaic system in the embodiment of the present application, the first extension section of the first welding strip is welded to the bus bar to realize bus output, the first extension section of the first welding strip and the second extension section of the second welding strip do not overlap in the thickness direction, the first extension section of the first welding strip is located at the recessed section of the bus bar, during the lamination process, the first extension section and the second extension section are staggered in the extension direction of the bus bar and will not be stacked, during the lamination process, the first extension section can be pressed down to approach the second battery cell, thereby reducing the overall stacking height of the entire assembly, effectively avoiding stress concentration during the lamination process, thereby reducing the risk of hidden cracks and splits of the battery cell, and improving the yield rate. At the same time, the angle α between the line between the highest point of the convex section and the lowest point of the concave section and the plane where the second battery cell is located is set to satisfy 0.075≤tanα≤3, which can avoid the bending angle of the bus bar being too large, resulting in one end of the second battery cell being tilted relative to the other end of the second battery cell during lamination, thereby increasing the unevenness of the second battery cell, resulting in an increased risk of hidden cracks. At the same time, it can also avoid that the bending angle of the busbar is too small, which makes it impossible to effectively reduce the height during the lamination process and causes stress concentration.

[0059] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a module schematic diagram of a photovoltaic system provided in an embodiment of the present application;

[0061] Figure 2 is a schematic structural diagram of a back-contact battery assembly provided in an embodiment of the present application;

[0062] Figure 3 is a schematic structural diagram of a series-connected battery string group of a back-contact battery assembly provided in an embodiment of the present application;

[0063] Figure 4 yes Figure 3 Schematic diagram of the enlarged structure at IV in the middle;

[0064] Figure 5 yes Figure 4 Schematic diagram of the enlarged structure at V in the middle;

[0065] Figure 6 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;

[0066] Figure 7 yes Figure 6 Schematic diagram of the enlarged structure at VII in the figure;

[0067] Figure 8 yes Figure 4Another enlarged structural diagram of position IV in the middle;

[0068] Fig. 9 yes Figure 8 A schematic diagram of the enlarged structure at line IX in the middle;

[0069] Fig.10 yes Figure 5 A schematic cross-sectional view of the middle section along line XX;

[0070] Fig.11 is a schematic structural diagram of a bus bar of a back contact battery assembly provided in an embodiment of the present application;

[0071] Fig.12 yes Figure 8 Schematic diagram of the section along line XII-XII;

[0072] Fig.13 is another structural schematic diagram of a bus bar of a back contact battery assembly provided in an embodiment of the present application;

[0073] Fig.14 yes Figure 3 Another enlarged structural diagram of position IV in the middle;

[0074] Fig.15 yes Figure 6 Another enlarged structural schematic diagram at VII in the figure. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with 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 should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0076] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "longitudinal", etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present 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, and therefore should not be understood as a limitation on the present application.

[0077] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0078] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0079] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0080] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the various specific processes and examples of materials provided by the present application, but those of ordinary skill in the art can be aware of the application of other processes and / or the use scenarios of other materials.

[0081] 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, each back-contact cell assembly 100 may be electrically connected in parallel or in series, which may be selected and set according to actual needs.

[0082] In the embodiments of the present application, the photovoltaic system 1000 can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system 1000 are not limited to this, that is, the photovoltaic system 1000 can be applied to all fields that require the use of solar energy for power generation.

[0083] 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 municipal power grid, and then connected to the municipal power network to realize solar power supply.

[0084] See also Figure 2-Figure 8 The back contact cell in the embodiment of the present application may include a plurality of cell strings 10 and bus bars 20 .

[0085] Each battery string 10 includes a plurality of battery cells 11 connected in series in a first direction. In the battery string 10, the plurality of battery cells 11 include a first battery cell 111 disposed at the end of the battery string 10 and a second battery cell 112 adjacent to the first battery cell 111. A first welding strip 12 is disposed on the back of the first battery cell 111, and a second welding strip 13 is disposed 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 at the two ends of the battery string 10 is a first battery cell 111. The first welding strip 12 is the end output end of the battery string 10, which is used to connect to the bus bar 20.

[0086] The bus bar 20 is disposed on the back of the second battery cell 112, and is connected to the first welding ribbon 12 and insulated from the second welding ribbon 13 to achieve bus output of the battery string 10. The bus bar 20 extends along the second direction, which intersects the first direction.

[0087] In the embodiment of the present application, the first direction is the connection direction of the battery cells 11 in each battery string 10, and the second direction may be preferably perpendicular to the first direction. Specifically, the first direction and the second direction may be respectively the longitudinal direction and the transverse direction of the back contact battery assembly 100. Of course, in some possible embodiments, the second direction may not be perpendicular to the first direction, which is not specifically limited here.

[0088] Among them, Figure 4 , Figure 5 as well as Figure 7 and Figure 8 As shown, the first welding ribbon 12 includes a first body section 121 and a first extension section 122, the first body section 121 is connected to the first battery cell 111, and the first extension section 122 extends to the second battery cell 112 and at least partially overlaps with the bus bar 20. That is, the portion of the first extension section 122 extending to the bus bar 20 overlaps with the bus bar 20 in the thickness direction, and the first extension section 122 is welded to the bus bar 20.

[0089] The second welding strip 13 includes a second body section 131 and a second extension section 132, wherein the second body section 131 does not overlap with the bus bar 20, and the second extension section 132 overlaps with the bus bar 20. In other words, the portion of the second welding strip 13 that overlaps with the bus bar 20 in the thickness direction is the second extension section 132.

[0090] 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.

[0091] like Fig.10 and Fig.12 As shown, the first extension section 122 is located on a side of the bus bar 20 away from the second battery cell 112 , and the second extension section 132 is located on a side of the bus bar 20 facing the second battery cell 112 .

[0092] The bus bar 20 has a convex section 21 convex toward the side away from the second battery cell 112 formed at the second extension section 132 , and a concave section 22 concave toward the side of the second battery cell 112 formed at the first extension section 122 ;

[0093] Among them, see Fig.11 As shown in Figure 13, 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.

[0094] It should be noted that, in the present application, "overlap" refers to the stacking of two components in the thickness direction of the back contact battery assembly 100. It is not difficult to understand that during the production and assembly process of the assembly, the placement of the solder strip may be subject to a certain assembly error. Therefore, "located on the same straight line" means that the two components are basically located on the same straight line parallel to the first direction in the first direction. The two components may be completely collinear, or the spacing between them may be within the range of the assembly error.

[0095] In the back-contact cell assembly 100 and the 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 strip 12 is welded to the bus bar 20 to achieve bus output. The first extension section 122 of the first welding strip 12 and the second extension section 132 of the second welding strip 13 do not overlap in the thickness direction. The first extension section 122 of the first welding strip 12 is located at the recessed section 22 of the bus bar 20. During the lamination process, the first extension section 122 and the second extension section 132 are staggered with each other in the extension direction of the bus bar 20 and will not be stacked. During the lamination process, the first extension section 122 can be pressed down close to the second battery cell 112, thereby reducing the overall stacking height of the entire component, effectively avoiding stress concentration during the lamination process, thereby reducing the risk of hidden cracks and splits of the battery cell 11 and improving the yield rate.

[0096] At the same time, the inventor of the present application has studied and verified that the angle α between the line connecting the highest point of the convex section 21 and the lowest point of the concave section 22 and the plane where the second battery cell 112 is located is set to satisfy 0.075≤tanα≤3, which can avoid the bending angle of the bus bar 20 being too large, causing one end of the second battery cell 112 to be lifted relative to the other end of the second battery cell 112 during lamination, thereby increasing the unevenness of the second battery cell 112 and increasing the risk of hidden cracks. At the same time, it can also avoid the bending angle of the bus bar 20 being too small, resulting in the inability to effectively reduce the height during the lamination process, resulting in stress concentration.

[0097] In addition, by setting the angle α between the line connecting the highest point of a convex section 21 and the lowest point of a concave section 22 and the plane where the second battery cell 112 is located to satisfy the above formula, the amount of packaging film can be reduced while reducing the lamination stacking height to reduce stress concentration, thereby reducing costs. Specifically, if the stacking height is high, during packaging, in order to completely encapsulate the stacking position, a large amount of film needs to be used. In the present application, by designing the entire structure and reducing the lamination stacking height, the stress concentration during the lamination process can be reduced while reducing the amount of film used, thereby reducing costs.

[0098] Specifically, in the embodiment of the present application, the cell 11 may be a cell with a main grid back contact or a cell without a main grid back contact, which is not specifically limited here. Figure 2-Figure 6As shown, it is not difficult to understand that in the embodiment of the present application, the bus bar 20 serves as the bus output end of the battery string 10, the number of the first welding strips 12 is multiple, and the number of the second welding strips 13 is also multiple, and the two correspond one to one. The first welding strip 12 serves as the output welding strip of the battery string 10, and the second welding strip 13 is the series welding strip of the battery string 10. The polarity of the metal electrode (main grid and / or fine grid) connected to the first welding strip 12 is opposite to that of the metal electrode connected to the second welding strip 13, that is, from another perspective, the polarity of the first welding strip 12 and the second welding strip 13 are opposite.

[0099] like Figure 3-Figure 8 As shown, in the battery string 10, a plurality of third welding strips 14 are further provided on the first battery cell 111, and the plurality of third welding strips 14 and the plurality of first welding strips 12 are arranged alternately in sequence along the second direction, and a plurality of fourth welding strips 15 are further provided on the second battery cell 112, and the plurality of fourth welding strips 15 and the plurality of second welding strips 13 are arranged alternately in sequence, the first welding strip 12 is insulated from the second welding strip 13 and the fourth welding strip 15, and the third welding strip 14 is connected to the fourth welding strip 15 to connect the first battery cell 111 and the second battery cell 112 in series.

[0100] That is to say, in the present application, the second welding strip 13, the third welding strip 14 and the fourth welding strip 15 are the series welding strips of the battery string 10, and the polarity of the metal electrode (main grid and / or fine grid) connected to the first welding strip 12 is opposite to that of the metal electrode connected to the second welding strip 13, that is, from another perspective, the polarity of the first welding strip 12 and the second welding strip 13 is opposite, and the polarity of the metal electrode (main grid and / or fine grid) connected to the third welding strip 14 is opposite to that of the metal electrode connected to the fourth welding strip 15. On the first battery cell 111, the polarity of the metal electrode connected to the first welding strip 12 and the polarity of the metal electrode connected to the third welding strip 14 are also opposite, and on the second battery cell 112, the polarity of the metal electrode connected to the second welding strip 12 and the fifth welding strip 15 are also opposite.

[0101] For example, taking a busbar-free 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. On the contrary, 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.

[0102] It is not difficult to understand that in some embodiments, the third welding ribbon 14 and the fourth welding ribbon 15 can be a whole continuous welding ribbon, that is, the third welding ribbon 14 and the fourth welding ribbon 15 can be integrally formed. In the present application, the back contact battery cells 11 in the battery string 10 are connected in series in a conventional welding ribbon connection manner in the prior art, which will not be described in detail here.

[0103] Specifically, in some embodiments, the back contact battery assembly 100 may include two battery strings 10 arranged along a first direction and a plurality of battery strings 10 arranged along a second direction, thereby forming an array of 2*N battery strings 10. Figure 2 As shown, Figure 2 What is shown is that the back contact battery assembly 100 includes a 2*6 array of battery strings 10.

[0104] like Figure 2 As shown, the back contact battery assembly 100 may include twelve battery strings 10, the twelve battery strings 10 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 is the limit).

[0105] like Figure 2 As shown, the upper half of the back contact battery assembly 100 has 6 battery strings 10 arranged along the second direction, and the lower half also has 6 battery strings 10 arranged along the second direction. In the back contact battery assembly 100, the bus bar 20 may include an edge bus bar located at the edge of the back contact battery assembly 100 and a middle bus bar located in the middle of the back contact battery assembly 100.

[0106] That is to say, in Figure 2 In the upper half, if the cell 11 closest to the upper edge of the cell string 10 is the first cell 111, the bus bar 20 is an end bus bar, which is used to connect two adjacent cell strings 10 in series in the upper half. In the upper half, if the cell 11 closest to the lower edge of the cell string 10 is the first cell 111, the bus bar 20 is an intermediate bus bar, which is used to connect the cell string 10 in parallel with the cell string 10 in the lower half. In the upper half, if the cell 11 at both ends of the cell string 10 is the first cell 111, the bus bar 20 closest to the upper edge is the end bus bar, and the bus bar 20 closest to the lower edge is the intermediate bus bar.

[0107] Similarly, if Figure 2As shown, in the lower half, if the battery cell 11 closest to the lower edge of the battery string 10 is the first battery cell 111, the bus bar 20 is an end bus bar, which is used to connect two adjacent battery strings 10 in series in the lower half. In the lower half, if the battery cell 11 closest to the upper edge of the battery string 10 is the first battery cell 111, the bus bar 20 is an intermediate bus bar, which is used to connect the battery string 10 in parallel with the battery string 10 in the upper half. In the lower half, if the battery cells 11 at both ends of the battery string 10 are the first battery cells 111, the bus bar 20 closest to the lower edge is the end bus bar, and the bus bar 20 closest to the upper edge is the end bus bar.

[0108] 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.

[0109] 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 to connect the two battery strings 10 in the series-connected battery string group 110 in series.

[0110] Thus, in the series battery string group 110 , two battery strings 10 can be connected in series through the same bus bar 20 , without providing two different bus bars 20 to connect the battery strings 10 in the series battery string group 110 .

[0111] Specifically, in such an embodiment, the bus bar 20 used for connecting two battery strings 10 in series in the series battery string group 110 is an end bus bar of the back contact battery assembly 100. There are as many end bus bars as there are series battery string groups 110 in the back contact battery assembly 100. For example, Figure 2 As shown, the upper half has 6 battery strings 10 and 3 battery string groups 110 connected in series, and the lower half also has 6 battery strings 10 and 3 battery string groups 110 connected in series. Therefore, the upper half has 3 end bus bars, and the lower half also has 3 end bus bars.

[0112] It is not difficult to understand that, in the series-connected battery string group 110, the first battery cells 111 in the two battery strings 10 correspond to each other (i.e., are basically aligned in the second direction). In order to realize 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.

[0113] 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 and isolated from the second welding ribbon 13 and the fourth welding ribbon 15 by the insulating strip 30 .

[0114] 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.

[0115] Specifically, in such an embodiment, the insulating strip 30 is disposed above the second welding strip 13 and the fourth welding strip 15, and the insulating strip 30 can be continuously extended along the second direction, and the bus bar 20 is disposed on the insulating strip 30 to achieve insulation from the second welding strip 13 and the fourth welding strip 15. In this way, by disposing the bus bar 20 and the insulating strip 30 on the second battery cell 112, the first welding strip 12 is welded to the bus bar 20 through the extension section 122, and there is no need to perform a hole processing on the insulating strip 30, and only one whole insulating strip 30 needs to be provided, which can reduce the manufacturing difficulty.

[0116] The insulating strip 30 can be an insulating adhesive, or it can be a non-conductive tape or insulating film, such as a PET or PI tape with acrylic acid or silicone, or a PET or PI substrate with ethylene-vinyl acetate copolymer or hot melt adhesive coated on one or both sides. It can be understood that the insulating strip 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.

[0117] It should be noted that the thickness of the insulating strip 30 cannot be made too thick or too thin. If the insulating strip 30 is too thin, it is not convenient to operate during pasting, it is easy to deform when pulled, and there is a risk of damage to long-term insulation. If it is too thick, the height difference will increase, and the stress generated during the lamination process is large, which is easy to 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.

[0118] 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 and isolated from the second welding strip 13 and the fourth welding strip 15 on the second battery cell 112.

[0119] 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 .

[0120] In this way, by setting the width of the insulating strip 30 to be relatively wide and extending it onto the first battery cell 111 , it is possible to effectively prevent the bus bar 20 from being offset and contacting the third welding strip 14 on the first battery cell 111 to cause a short circuit.

[0121] like Figure 2 As shown, in some embodiments, the back contact battery assembly 100 includes a plurality of series-connected battery strings 110 arranged along a second direction, and in the second direction, the insulating strip 30 extends from the first series-connected battery string 110 to the last series-connected battery string 110 .

[0122] In this way, in the same row of series-connected battery strings 110, only one entire insulating strip 30 is needed to insulate all the bus bars 20, without the need to separately provide an insulating strip 30 for each bus bar 20 in each series-connected battery string 110, thereby reducing the difficulty of manufacturing and coating.

[0123] See also Figure 6 As 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.

[0124] 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 strip 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 strip 12.

[0125] It is easy to understand that in this case, when 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 bus bar 20 on the second battery cell 112 adjacent to the first battery cell 111 is the middle bus bar.

[0126] In this way, by setting the battery cell 11 of the first battery string 1201 in the parallel battery string group 120 closest to the second battery string 1202 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 and at the same time connected to the battery cell 11 of the second battery string 1202 closest to the first battery string 1201 (i.e., the third battery cell 1211 mentioned above), thereby realizing the parallel connection between the first battery string 1201 and the second battery string 1202.

[0127] Specifically, in such a case, the first welding strip 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 to connect the first battery string 1201 and the second battery string 1202 in parallel to achieve parallel output of the two battery strings 10.

[0128] 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 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 cells 11 at one end of the second battery string 1202 (the end close to the second edge) are first battery cells 111, and the battery cells 11 at the other end of the second battery string 1202 (i.e., the end close to the first battery string 1201) are third battery cells 1211.

[0129] In such an embodiment, the first battery string 1201 has two first battery cells 111 and two second battery cells 112, which are correspondingly provided with two bus bars 20, one of which is an end bus bar and the other is a middle bus bar, and the second battery string 1202 has only one first battery cell 111 and one second battery cell 112, which are correspondingly provided with one bus bar 20, which is an end bus bar. It is not difficult to understand that in such a case, in the first battery string 1201, the polarities of the first welding strips 12 on the two first battery cells 111 are opposite, the first welding strip 12 of one first battery cell 111 is electrically connected to the negative electrode main grid and / or the negative electrode 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 electrode main grid and / or the positive electrode fine grid on the corresponding first battery cell 111. Exemplarily, the polarity of the first welding ribbon 12 on the first battery cell 111 in the second battery string 1202 is opposite to the polarity of the first welding ribbon 12 on the first battery cell 111 in the first battery string 1201 that is closest to the second battery string 1202 .

[0130] 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.

[0131] 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.

[0132] In this way, by spacing the first extension section 122 of the first welding strip 12 from the first body section 121, and the second body section 131 and the second extension section 132 are located on the same straight line in the first direction, the first extension section 122 and the second extension section 132 can be made to have no overlapping parts in the thickness direction, thereby avoiding the stacking height being too high during the lamination process and causing hidden cracks. In addition, the first body section 121 and the second body section 131 can be transitionally connected by the bent first connecting section 123, without the need to provide an additional additional connecting piece to connect the first body section 121 and the first extension section 122.

[0133] Specifically, in such an embodiment, the first welding strip 12 is a bent welding strip, and the first welding strip 12 can be bent to include a first body section 121, a first connecting section 123 and a first extension section 122 connected in sequence. The second welding strip 13 is a straight welding strip (that is, the second body section 131 and the second extension section 132 are located on the same straight line in the first direction), and the second welding strip 13 and the first body section 121 of the first welding strip 12 are located on the same straight line. The bending direction of the first connecting section 123 of the first welding strip 12 depends on the relative position of the first extension section 122 and the first body section 121. Generally speaking, the first connecting section 123 is bent relative to the first body section 121 toward the side where the first extension section 122 is located.

[0134] It is not difficult to understand that in the present application, the first welding strip 12 having the first main body section 121, the first connecting section 123 and the first extension section 122 can be a whole welding strip integrally stamped and formed, or can be formed by splicing multiple welding strips together. The present application does not limit this. Preferably, the morphological feature of the first welding strip 12 is that a whole welding strip is integrally stamped and formed, so that redundant processes such as welding are omitted when making the first welding strip 12, reducing the consumption of manpower, and also avoiding the phenomenon of cold welding caused by manual welding and burrs generated during welding.

[0135] Furthermore, in some embodiments, the first connecting segment 123 is arc-shaped.

[0136] In this way, the first body section 121 and the first extension section 122 can be connected by a smooth transition through the arc-shaped first connecting section 123. The smooth transition design can avoid the first welding strip 12 from forming a sharp angle at the bending position, thereby causing stress concentration at this position and causing fracture failure. At the same time, it can also avoid the phenomenon of cold welding caused by sharp bending.

[0137] 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°.

[0138] 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°, which is not specifically limited herein.

[0139] 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 precisely processed through mechanical or automated equipment. The first welding strip 12 can be bent to the required curvature using less force, thereby improving production efficiency.

[0140] 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.

[0141] Of course, it is understandable that in some possible embodiments, under the condition of meeting production requirements, the first connecting section 123 and the first main section 121 may be bent at right angles instead of arcs, and no specific limitation is made here.

[0142] See also Figure 3-Figure 9 In some embodiments, the first extension segment 122 is arranged in parallel with the second welding strip 13 , that is, the first extension segment 122 is arranged in parallel with the first body segment 121 and the second welding strip 13 .

[0143] 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.

[0144] In some embodiments, as described above, the number of first welding strips 12 and second welding strips 13 are both multiple and one-to-one corresponding, the multiple first welding strips 12 are arranged at intervals along the second direction, the multiple second welding strips 13 are also arranged at intervals along the second direction, and a plurality of third welding strips 14 are also provided on the first battery cell 111, the third welding strips 14 extend along the first direction, and the plurality of third welding strips 14 and the plurality of first welding strips 12 are alternately arranged along the second direction.

[0145] In some embodiments, on the first battery cell 111 , in the second direction, the welding strips closest to the two edges of the first battery cell 111 are the first welding strips 12 , and the first connecting segments 123 of the first welding strips 12 closest to the edges are bent toward the center of the first battery cell 111 .

[0146] In this way, when the welding strips at the two edges closest to the first battery cell 111 are both the first welding strips 12, the first extension sections 122 are both located inside the first battery cell 111, and the first connection sections 123 of the two first welding strips 12 located at the edge are both bent toward the middle of the inside of the first battery cell 111, which can prevent the first welding strip 12 from bending toward the end of the first battery cell 11, resulting in the first extension section 122 being unable to maintain a 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 strip 12 from bending toward the edge, resulting in the first connection section 123 and the first extension section 122 being too close to the edge, which makes it easier for the first battery cell 111 and the second battery cell 112 to have hidden cracks. In other words, such a setting can reduce the risk of hidden cracks.

[0147] 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 strip 14. In this 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 the direction away from the middle of the first battery cell 111.

[0148] See also Figure 8 and Fig. 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.

[0149] 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.

[0150] Of course, if Figure 4 and Figure 7 As shown, in other embodiments, part of the first connecting segments 123 of the first welding ribbons 12 on the first battery cell 111 may be bent toward one edge of the first battery cell 11 in the second direction, while another part of the first connecting segments 123 of the first welding ribbons 12 may be bent toward the other edge of the first battery cell 11 in the second direction.

[0151] Also, see Figure 4 and Figure 7 In some embodiments, on the first battery cell 111, a plurality of first welding strips 12 are arranged in pairs, and in each pair of first welding strips 12, the first connecting section 123 of one of the first welding strips 12 is bent toward one edge of the first battery cell 111 in the second direction, and the first connecting section 123 of another first welding strip 12 is bent toward the other edge of the first battery cell 11 in the second direction. That is, in each pair of first welding strips 12, the first connecting sections 123 of the two first welding strips 12 are bent toward the area between the two first body sections 121. Specifically, there is a third welding strip 14 between each pair of first welding strips 12, and the two first welding strips 12 in each pair of first welding strips 12 are symmetrical about the third welding strip 14.

[0152] In this way, the first welding strips 12 are arranged in pairs, and the two first connecting sections 123 are bent toward the area between the two first welding strips 12, so that the force on the second battery cell 112 during the lamination process can be more uniform, reducing the risk of hidden cracks and splits.

[0153] Specifically, if Figure 4 and Figure 7 As shown, in such an embodiment, a third welding strip 14 and a fourth welding strip 15 are provided between each pair of first welding strips 12. In each pair of first welding strips 12, the first connecting sections 123 of the two first welding strips 12 are bent toward the positions of the third welding strip 14 and the fourth welding strip 15 located between the two first welding strips 12, and the first extension section 122 is located between the second welding strip 13 and the fourth welding strip 15. Each pair of first welding strips 12 is symmetrically arranged about the third welding strip 14 and the fourth welding strip 15.

[0154] See also Figure 4 and Figure 5In some embodiments, the second welding strip 13 also 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.

[0155] 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.

[0156] Specifically, 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.

[0157] In such an embodiment, the length of the protruding section 133 in the first direction is 0.5 mm to 6 mm.

[0158] In this way, it is possible to avoid the situation where the length of the protruding section 133 is too small, resulting in the edge distance between the bus bar 20 and 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 edge distance between the bus bar 20 and 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] In some embodiments, the spacing 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.

[0163] In this way, it is possible to avoid the risk of hidden cracks increasing due to the edge distance between the bus bar 20 and the second battery cell 112 being too small, and it is also possible to avoid the risk of hidden cracks increasing due to the edge distance between the bus bar 20 and 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.

[0164] 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.

[0165] 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 may lead to unstable welding, and reduce the risk of the first welding ribbon 12 falling off.

[0166] Specifically, in such an embodiment, the length of the portion where the first extension segment 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 therebetween.

[0167] In this way, the welding stability between the first extension section 122 and the bus bar 20 can be ensured.

[0168] See also Figure 5 and Figure 8 In some embodiments, as described above, the second welding strip 13 is a straight welding strip, the first welding strip 12 is a bent welding strip, and the first extension section 122 is disposed between the second welding strip 13 and the fourth welding strip 15 adjacent to each other.

[0169] 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 .

[0170] Thus, 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 assembly and the risk of hidden cracks caused by stress concentration, while also reducing the amount of adhesive film used and reducing costs.

[0171] See also Fig.10 and Fig.12In 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.

[0172] 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; 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 limitation is made here.

[0173] In this way, the height difference between the highest point of the protruding section 21 and the highest point of the adjacent first extension section 122 is set to be smaller than the thickness of the first welding strip 12. Compared with the solution in which the first welding strip 12 is directly stacked on the second welding strip 13 in the conventional technical solution, the stacking height during the lamination process can be reduced, thereby reducing stress concentration and the risk of hidden cracks. At the same time, the stacking height of the back of the entire second battery cell 112 can be reduced, thereby reducing the amount of packaging film used and reducing costs.

[0174] In some embodiments, in the second direction, the first extension segment 122 is arranged closer to the second extension segment 132 than to the fourth welding strip 15, that is, the first extension segment 122 is arranged between the fourth welding strip 15 and the second extension segment 132 and closer to the second extension segment 132, and the highest point of the first extension segment 122 is higher than the highest point of the raised segment 21.

[0175] In this way, the first extension section 122 is not arranged in the middle of the fourth welding strip 15 and the second extension section 132, which can reduce the bending angle of the first connecting section 123 of the first welding strip 12 to avoid excessive stress caused by excessive bending and thus causing cold welding.

[0176] In other embodiments, the first extension section 121 is centrally disposed between the second extension section 132 and the fourth welding strip 15 of the second welding strip 13 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.

[0177] Thus, by disposing the first extension section 121 in the middle between the fourth welding strip 15 and the second extension section 132 , the stacking height of the back side of the second battery cell 112 can be further reduced, thereby further reducing the risk of hidden cracks caused by stress concentration.

[0178] In some embodiments, the thickness of the insulating strip 30 at the location of the first extension segment 121 is less than or equal to the thickness of the insulating strip 30 at other locations between the second extension segment 132 and the fourth welding strip 15 .

[0179] 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 .

[0180] In the above-described embodiment, the first welding strip 12 is a bent welding strip, and the second welding strip 13 is a straight welding strip. It should be noted that in the present application, the first welding strip 12 may be a straight welding strip, and the second welding strip 13 may be a bent welding strip.

[0181] Specifically, see Fig.14 and Fig.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.

[0182] In this way, by spacing the second extension section 132 of the second welding strip 13 from the second body section 131, and the second body section 131 and the second extension section 132 are located on the same straight line in the first direction, the second extension section 132 and the second extension section 132 can be made to have no overlapping parts in the thickness direction, thereby avoiding the stacking height being too high during the lamination process and causing hidden cracks. In addition, the second body section 131 and the second body section 131 can be transitionally connected by the bent second connecting section 134, without the need to set an additional additional connecting piece to connect the second body section 131 and the second body section 131. At the same time, the first welding strip 12 is set as a straight welding strip, and the second welding strip 13 is set as a bent welding strip. The first welding strip 12 does not need to be bent, which can avoid the first welding strip 12 having to be bent and welded to the bus bar 20 to generate a large internal stress, which makes the first welding strip 12 more likely to warp. That is to say, setting the second welding strip 13 as a bent welding strip can reduce the lamination stacking height to reduce the risk of hidden cracks while allowing the first welding strip 12 to only need to 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.

[0183] Specifically, in such an embodiment, the second welding strip 13 is a bent welding strip, and the second welding strip 13 can be bent to include a second body section 131, a second connecting section 134, and a second extension section 132 connected in sequence. The first welding strip 12 is a straight welding strip (that is, the first welding strip 12 only includes a first body section 121 and a first extension section 122 located on the same straight line in the first direction), and the first welding strip 12 and the second body section 131 of the second welding strip 13 are located on the same straight line. The bending direction of the second connecting section 134 of the second welding strip 13 depends on the relative position of the second extension section 132 and the second body section 131. Generally speaking, the second connecting section 134 is bent relative to the second body section 131 toward the side where the second extension section 132 is located.

[0184] It is not difficult to understand that in the present application, the second welding strip 13 having the second main body section 131, the second connecting section 134 and the second extension section 132 can be a whole welding strip integrally stamped and formed, or can be formed by splicing multiple welding strips together. The present application does not limit this. Preferably, the morphological feature of the second welding strip 13 is that a whole welding strip is integrally stamped and formed, so that redundant processes such as welding are omitted when making the second welding strip 13, reducing the consumption of manpower, and also avoiding the phenomenon of cold welding caused by manual welding and burrs generated during welding.

[0185] Furthermore, in some embodiments, the second connecting segment 134 is arc-shaped.

[0186] In this way, the second body section 131 and the second extension section 132 can be connected by a smooth transition through the arc-shaped second connecting section 134. The smooth transition design can avoid the second welding strip 13 from forming a sharp angle at the bending position, thereby causing stress concentration at the position and causing fracture failure. At the same time, it can also avoid the phenomenon of cold welding caused by sharp bending.

[0187] 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 an embodiment, 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°, and is not specifically limited here.

[0188] 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 precisely processed through mechanical or automated equipment. The second welding strip 13 can be bent to the required curvature with less force, thereby improving production efficiency.

[0189] 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.

[0190] Of course, it is understandable that in some possible embodiments, under the condition of meeting production requirements, the second connecting section 134 and the second main body section 131 may be bent at right angles instead of arcs, and no specific limitation is made here.

[0191] See also Fig.14 and Fig.15 In some embodiments, the second extension segment 132 is arranged in parallel with the first welding strip 12 , that is, the second extension segment 132 is arranged in parallel with the second body segment 131 and the first welding strip 12 .

[0192] In this way, the two are arranged in parallel. Even if the lengths of the second extension sections 132 are crossed, 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.

[0193] See also Fig.14 and Fig.15 In some embodiments, as described above, the number of the second welding ribbons 13 and the number of the 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.

[0194] In some embodiments, on the second battery cell 112 , in the second direction, the welding strips closest to the two edges of the second battery cell 112 are the second welding strips 13 , and the second connecting segments 134 of the second welding strips 13 closest to the edges are bent toward the middle of the second battery cell 112 .

[0195] In this way, when the welding strips at the two edges closest to the second battery cell 112 are both the second welding strips 13, the second extension sections 132 are both located inside the second battery cell 112, and the second connection sections 134 of the two second welding strips 13 located at the edge are both bent toward the middle of the inside of the second battery cell 112, which can avoid the second welding strip 13 bending toward the edge of the second battery cell 112, resulting in the second extension section 132 being unable to maintain a sufficient distance from the second extension section 132. At the same time, it can also avoid the second connection section 134 of the second welding strip 13 bending toward the edge, resulting in the second connection section 134 and the second extension section 132 being too close to the edge, which makes the second battery cell 112 more prone to hidden cracks, that is, such a setting can reduce the risk of hidden cracks.

[0196] 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.

[0197] See also Fig.14 and Fig.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.

[0198] 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.

[0199] 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.

[0200] In addition, in some embodiments, on the second battery cell 112, a plurality of second welding strips 13 may be arranged in pairs, and in each pair of second welding strips 13, the second connection segment 134 of one second welding strip 13 is bent toward one edge of the second battery cell 112 in the second direction, and the second connection segment 134 of another second welding strip 13 is bent toward the other edge of the second battery cell 112 in the second direction. That is, in each pair of second welding strips 13, the second connection segments 134 of the two second welding strips 13 are bent toward the area between the two second body segments 131. Specifically, there is a fourth welding strip 15 between each pair of second welding strips 13, and the two second welding strips 13 in each pair of second welding strips 13 are symmetrical about the fourth welding strip 15.

[0201] In this way, the second welding strips 13 are arranged in pairs, and the two second connecting sections 134 are bent toward the area between the two second welding strips 13, so that the force on the second battery cell 112 during the lamination process can be more uniform, reducing the risk of hidden cracks and splits.

[0202] Specifically, in such an embodiment, a fourth welding strip 15 is provided between each pair of second welding strips 13, and in each pair of second welding strips 13, the second connecting sections 134 of the two second welding strips 13 are bent toward the position where the fourth welding strip 15 is located between the two second welding strips 13, and the second extension section 132 is located between the first welding strip 12 and the fourth welding strip 15. Each pair of second welding strips 13 is symmetrically arranged about the fourth welding strip 15.

[0203] 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.

[0204] In this way, by designing the bending point of the second connecting section 134 to be behind the position of the second welding point 50 at the outermost edge, current can be better collected.

[0205] In some embodiments, the second extension section 132 may be centrally disposed between the first welding ribbon 12 and the fourth welding ribbon 15 .

[0206] Thus, 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 assembly and the risk of hidden cracks caused by stress concentration, while also reducing the amount of adhesive film used and reducing costs.

[0207] In some embodiments, the first extension section 121 is arranged between the second extension section 132 and the fourth welding strip 15, and in the second direction, the first extension section 122 is arranged closer to the second extension section 132 than to 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 is 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.

[0208] 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 to cause cold welding.

[0209] In other embodiments, the first extension section 121 is centrally disposed between the second extension section 132 and the fourth welding strip 15 of the second welding strip 13 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.

[0210] Thus, by disposing the first extension section 121 in the middle between the fourth welding strip 15 and the second extension section 132 , the stacking height of the back side of the second battery cell 112 can be further reduced, thereby further reducing the risk of hidden cracks caused by stress concentration.

[0211] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are 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. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0212] 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 substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A back contact battery assembly, characterized in that: include: A plurality of battery strings, the battery strings comprising a plurality of battery cells sequentially connected in series along a first direction, the plurality of battery cells comprising a first battery cell disposed at an end of the battery string and a second battery cell adjacent to the first battery cell, a first welding strip being disposed on the back of the first battery cell, and a second welding strip being disposed on the back of the second battery cell; A bus bar, the bus bar is arranged on the back side of the second battery cell, the bus bar is connected to the first welding strip and is insulated from the second welding strip, the bus bar is extended along a second direction, and the second direction intersects the first direction; The first welding strip includes a first body segment connected to the first battery cell and a first extension segment extending to the second battery cell and at least partially overlapping the bus bar, the second welding strip 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 section and the second extension section have no overlapping part; the first extension section is located on the side of the bus bar away from the second battery sheet, and the second extension section is located on the side of the bus bar facing the second battery sheet, and the bus bar is formed with a convex section protruding toward the side away from the second battery sheet at the second extension section, and the bus bar is formed with a concave section concave toward the side of the second battery sheet at the first extension section; 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 a plane where the second battery cell is located satisfies the following formula: 0.075≤tanα≤3.

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 in parallel with 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 extend along the first direction, and the plurality of third welding strips and the plurality of first welding strips are alternately arranged along the second direction; Wherein, on the first battery cell, in the second direction, the welding strips closest to the two edges of the first battery cell are the first welding strips, and the first connecting section of the first welding strip closest to the edge is bent toward a direction close to the middle 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 connection 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 strip 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 strip 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, and 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 a 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 strips are arranged in pairs, and in each pair of first welding strips, the first connecting section of one of the first welding strips is bent toward one edge of the first battery cell in the second direction, and the first connecting section of another first welding strip 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, characterized in that: 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 strip by the insulating strip.

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

14. The back contact battery assembly according to claim 1, characterized in that: The 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, characterized in that: A length of a portion of the first extension segment overlapping the bus bar in the first direction is greater than or equal to half of a length of the bus bar in the first direction.

16. The back contact battery assembly according to claim 1, characterized in that: A length of a portion where the first extension segment overlaps 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 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, the multiple second welding strips are also arranged at intervals along the second direction, and the second battery cell is further provided with a plurality of fourth welding strips, the fourth welding strips extend along the first direction, and the plurality of the fourth welding strips and the plurality of the second welding strips 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: The first extension section is centrally disposed between the second welding strip and the fourth welding strip adjacent to each other.

19. The back contact battery assembly according to claim 1, characterized in that: The back contact battery assembly includes at least one battery string group connected in series, and the battery string group connected in series 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 the series-connected battery string group in series.

20. The back contact battery assembly according to claim 19, characterized in that: The back contact battery assembly further comprises 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 strip 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.

21. 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 second battery strings 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 via the first welding ribbon.

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

23. A photovoltaic system, characterized in that: A back contact battery assembly comprising any one of claims 1-22.

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