Battery assembly and photovoltaic system

Abstract

The invention is applicable to the field of photovoltaic technology, and provides a battery assembly and a photovoltaic system, the battery assembly comprises a battery string, the battery string at least comprises a first battery piece and a second battery piece which are sequentially arranged along a first direction, and the first battery piece is arranged at the end part of the battery string; and the plurality of first welding strips are arranged on the back surface of the first battery piece at intervals along the second direction. The back surface of the battery piece is covered with the pre-fixing film, and all the welding strips on the back surface of the battery piece are fixed on the battery piece at the same time through the pre-fixing film layer; compared with the prior art in which the welding strip is pre-fixed in a pre-gluing mode, the pre-gluing mode needs to be accurately coated point by point, the process is time-consuming and depends on high-precision equipment, the pre-fixed film layer can cover the back face of the whole battery piece at a time, the production period is remarkably shortened, the welding strip is fixed by adopting the pre-fixed film layer, and the production efficiency is improved. Pseudo soldering can be effectively avoided, uniform pressure is applied to the solder strip by the pre-fixing film, and local stress concentration is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic technology, and in particular relates to a battery assembly and a photovoltaic system. Background Art

[0002] In the related art, in a back-contact solar cell, a solder paste pad is provided at the position on each fine grid for connecting with the solder strip. At the same time, in order to prevent the solder strip from being offset during lamination welding, a pre-adhesive is required to be provided near the solder paste pad to pre-fix the solder strip. In order to ensure accurate bonding, the pre-adhesive is usually required to be provided near the center of the solder strip, which is close to the solder paste pad. In such a case, since there is a height difference between the height of the pre-adhesive and the solder paste pad, if the height of the pre-adhesive is high, while ensuring stable bonding of the solder strip, due to the close distance between the pre-adhesive and the solder paste pad, the solder strip cannot contact the solder paste pad when pre-fixing the solder strip, thereby causing a cold solder joint in the subsequent welding process; and if the height of the solder paste pad is high, while ensuring that the solder strip is in contact with the solder paste pad, due to the close distance between the pre-adhesive and the solder paste pad, the adhesion between the solder strip and the pre-adhesive is reduced or even fails, thereby causing the offset of the solder strip. Summary of the invention

[0003] The present invention provides a battery assembly, aiming to solve the problem that the use of pre-adhesive to fix the welding strip easily leads to poor welding or deviation of the welding strip.

[0004] The present invention is implemented as follows: a battery assembly includes a battery string, the battery string includes at least a first battery cell and a second battery cell arranged in sequence along a first direction, the first battery cell is arranged at the end of the battery string; a plurality of first welding strips, the plurality of the first welding strips are arranged at intervals along a second direction on the back of the first battery cell; a plurality of second welding strips, the plurality of the second welding strips are arranged at intervals along the second direction on the back of the second battery cell; a pre-fixing film, the pre-fixing film is arranged at least on the back of the first battery cell and the back of the second battery cell, the pre-fixing film fixes the plurality of the first welding strips on the back of the first battery cell, the pre-fixing film fixes the plurality of the second welding strips on the back of the second battery cell, and the pre-fixing film forms a first exposed area; the first exposed area is formed on the back of the first battery cell or the back of the second battery cell; a bus bar, the bus bar is arranged in the first exposed area; an insulating strip, the insulating strip is arranged between the bus bar and the first battery cell or the second battery cell.

[0005] Optionally, the battery assembly further comprises an adhesive film, the adhesive film covers the pre-fixed film, and the fluidity of the pre-fixed film during the initial lamination process is lower than the fluidity of the adhesive film during the initial lamination process.

[0006] Optionally, the pre-fixed film includes at least one of PVB film, EVA film, EPE film, EP film and POE film, and the film includes at least one of POE film, EVA film, EPE film, EP film, PE film and PVB film.

[0007] Optionally, the pre-fixing film and the adhesive film are made of different materials.

[0008] Optionally, the first exposed area is formed on the back side of the first battery cell, and the insulating strip forms a second exposed area, the second exposed area exposes a portion of the first welding strip, the polarity of the remaining portion of the first welding strip and the portion of the first welding strip connected to the gate line are different, the insulating strip insulates the bus bar from the remaining portion of the first welding strip, and the bus bar is conductively connected to the portion of the first welding strip exposed corresponding to the second exposed area.

[0009] Optionally, the insulating strip is provided with a through hole forming the second exposed area.

[0010] Optionally, the insulating strip includes a plurality of insulating sublayers arranged at intervals, the plurality of insulating sublayers cover a portion of the first welding strip, and the interval areas between adjacent insulating sublayers form the second exposed area.

[0011] Optionally, the first exposed area is formed on the back side of the second battery cell, and the insulating strip is a complete strip structure, which insulates all the second welding strips and the bus bar, a portion of the first welding strip extends along the first direction and is electrically connected to the bus bar, and the remaining portion of the first welding strip is isolated from the bus bar, and the remaining portion of the first welding strip and the portion of the first welding strip have different polarities when connected to the grid line.

[0012] Optionally, in the first direction, the width of the insulating strip is greater than or equal to the width of the bus bar, and the width of the first exposed area is greater than or equal to the width of the insulating strip.

[0013] Optionally, the first welding strip includes a main section and a flat section, the flat section is arranged between the bus bar and the first battery sheet, and the thickness of the flat section is smaller than the thickness of the main section.

[0014] Optionally, along the first direction, the length of the flat segment is greater than the width of the bus bar.

[0015] Optionally, along the second direction, the width of the flat section is greater than the width of the main body section.

[0016] Optionally, the flat section and the main body section are integrally formed.

[0017] Optionally, the main body section and the flat section are overlapped and connected to each other.

[0018] Optionally, the cross-sectional area of ​​the main body segment is equal to the cross-sectional area of ​​the flat segment.

[0019] Optionally, the cross-sectional area of ​​the flat section is larger than the cross-sectional area of ​​the main body section.

[0020] Optionally, the main body segment is a round wire welding strip segment, and the flat segment is a flat welding strip segment.

[0021] The present invention uses a pre-fixed film to cover the back of the battery cell, and fixes all the soldering strips on the back of the battery cell to the battery cell at the same time through the pre-fixed film layer. Compared with the prior art that uses a pre-adhesive method to pre-fix the soldering strips, the pre-adhesive needs to be precisely applied point by point, and the process is time-consuming and relies on high-precision equipment. The pre-fixed film layer can cover the entire back of the battery cell at one time, significantly shortening the production cycle, and using the pre-fixed film layer to fix the soldering strip can effectively avoid cold soldering. The pre-fixed film applies uniform pressure to the soldering strip to avoid local stress concentration, and can also isolate environmental interference, such as external factors such as water vapor and oxygen, to prevent oxidation or corrosion of the soldering strip, thereby improving the long-term reliability of the battery assembly. In addition, by forming a first exposed area on the pre-fixed film, the bus bar can be hidden and set on the back of the battery cell, thereby improving the conversion efficiency of the solar cell assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the first battery assembly provided by the present invention;

[0023] Figure 2 It is a partial structural schematic diagram of the second battery assembly provided by the present invention;

[0024] Figure 3 It is a structural schematic diagram of the third battery assembly provided by the present invention;

[0025] Figure 4 It is a structural schematic diagram of the fourth battery assembly provided by the present invention;

[0026] Figure 5 It is a schematic structural diagram of the fifth battery assembly provided by the present invention.

[0027] Description of reference numerals:

[0028] 100, battery string; 101, first battery cell; 102, second battery cell; 103, first welding strip; 1031, main body section; 1032, flat section; 104, second welding strip; 200, pre-fixed film; 300, first exposed area; 400, bus bar; 500, insulation strip; 600, second exposed area. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention 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 invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] 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. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] In the description of the present invention, 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 the present invention can be understood according to specific circumstances.

[0033] In the present invention, 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.

[0034] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, 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 invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the examples of various specific processes and materials provided by the present invention, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0035] like Figure 1 As shown, in an embodiment of the present invention, a battery assembly includes a battery string 100, and the battery string 100 includes at least a first battery cell 101 and a second battery cell 102 arranged in sequence along a first direction, and the first battery cell 101 is arranged at the end of the battery string 100. It can be understood that in the battery string 100, the battery string 100 may include two battery cells connected in series, three battery cells connected in series, or other more battery cells. The number of battery cells that need to be connected in series can be determined according to actual usage, and the present invention does not limit this. In addition, the grid lines on the battery cells are not shown in the drawings, and the grid lines on the battery cells can be arranged according to actual conditions, for example, they can be battery cells with main grids or battery cells without main grids.

[0036] The first battery cell 101 is arranged at the end of the battery string 100. For the convenience of explanation, in this embodiment, the end where the first battery cell 101 is located is recorded as the tail end of the battery string 100, that is, in the first direction, the first battery cell 101 is the last battery cell of the battery string 100, and the second battery cell 102 is the second to last battery cell of the battery string 100. It is not difficult to understand that the end where the first battery cell 101 is located can also be recorded as the head end of the battery string 100, and the second battery cell 102 is the second positive battery cell of the battery string 100, which will not be repeated here. It should be noted that when the first battery cell 101 is arranged at the tail end of the battery string 100, at this time, the bus bar 400 can be used for the series connection between the adjacent battery strings 100 in the second direction; when the first battery cell 101 is arranged at the head end of the battery string 100, at this time, the bus bar 400 can be used for the parallel connection between the adjacent battery strings 100 in the first direction, and at this time, the bus bar 400 is equivalent to the middle bus bar 400 in the battery assembly.

[0037] In the embodiment of the present invention, the second direction intersects with the first direction. Specifically, the second direction may be perpendicular to the first direction. Exemplarily, the first direction may be the width direction of the battery cell, and the second direction may be the length direction of the battery cell.

[0038] In some embodiments, a plurality of first welding strips 103 are arranged at intervals along the second direction on the back side of the first battery cell 101; specifically, some of the plurality of first welding strips 103 are welding strips for connecting the positive electrode grid lines, and another portion of the first welding strips 103 are welding strips for connecting the negative electrode grid lines, or, some of the plurality of first welding strips 103 are welding strips for connecting the negative electrode grid lines, and another portion of the first welding strips 103 are welding strips for connecting the positive electrode grid lines; a plurality of second welding strips 104 are arranged at intervals along the second direction on the back side of the second battery cell 102; specifically, some of the plurality of second welding strips 104 are welding strips for connecting the positive electrode grid lines, and another portion of the second welding strips 104 are welding strips for connecting the negative electrode grid lines, or, some of the plurality of second welding strips 104 are welding strips for connecting the negative electrode grid lines, and another portion of the second welding strips 104 are welding strips for connecting the positive electrode grid lines.

[0039] It should be noted that the first battery cell and the second battery cell are connected in series through a part of the first welding strip and a part of the second welding strip in a one-to-one correspondence. Wherein, the polarity of the grid lines connected by the part of the first welding strip and the part of the second welding strip is opposite. For example, the part of the first welding strip 103 on the first battery cell 101 is a welding strip connected to the positive grid line, and the part of the second welding strip 104 on the second battery cell 102 is a welding strip connected to the negative grid line, or the part of the first welding strip 103 on the first battery cell 101 is a welding strip connected to the negative grid line, and the part of the second welding strip 104 on the second battery cell 102 is a welding strip connected to the positive grid line. In this way, the part of the first welding strip and the part of the second welding strip connect the first battery cell 101 and the second battery cell 102 to form a series connection.

[0040] In some embodiments, the pre-fixing film 200 is at least arranged on the back side of the first battery cell 101 and the back side of the second battery cell 102, that is, the pre-fixing film 200 can fix the solder strips on each battery cell separately. At this time, the pre-fixing film 200 is a sheet film layer structure corresponding to the size of a battery cell. The pre-fixing film 200 can also fix the solder strips on multiple battery cells at the same time. At this time, the pre-fixing film 200 is a continuous film layer structure, and the specific length can be cut as needed.

[0041] Generally speaking, a cell is a sheet structure, and the side that can absorb light energy and convert it into electrical energy is called the light-absorbing side or the front side, and the other side is called the back side. A solar cell with two polarity grid lines formed on the back side of the cell is a back contact cell. In the embodiment of the present invention, the pre-fixed film 200 fixes a plurality of first solder strips 103 on the back side of the first cell 101, and the pre-fixed film 200 fixes a plurality of second solder strips 104 on the back side of the second cell 102. Specifically, the pre-fixed film 200 is continuously produced by a roll-to-roll process. The pre-fixed film 200 is pre-processed in the form of a roll (the width is compatible with a 210mm cell), and is attached to the back side of the cell by an automatic film attaching machine. Then, the pre-fixed film 200 is adsorbed by an adsorption block, and the pre-fixed film 200 is placed on the cell and heated. During the heating process, pressure is applied to the pre-fixed film 200 by the adsorption block, so that the pre-fixed film 200 is slightly melted and then solidified to be bonded to the back side of the cell, thereby fixing the solder strips. Furthermore, when laying the pre-fixing film 200 , the temperature is maintained in the range of 50° C. to 150° C., so that the pre-fixing film 200 is slightly melted and then solidified to be bonded to the back side of the battery cell.

[0042] like Figure 1 and Figure 5As shown, in some embodiments, the pre-fixed film 200 is formed with a first exposed area 300; the first exposed area is formed on the back of the first battery cell or the back of the second battery cell, and the bus bar 400 is located in the first exposed area 300; the insulating strip 500 is arranged between the bus bar 400 and the first battery cell 101 or the second battery cell. By forming the first exposed area 300 on the pre-fixed film 200, the installation position of the bus bar 400 is reserved, so that the bus bar 400 can be hidden and arranged on the back of the battery cell, and the local height of the bus bar stacking position can be reduced, reducing the risk of hidden cracks in the battery cell. In addition, by setting the first exposed area on the pre-fixed film, all the welding strips on the battery cell are completely exposed, which facilitates the connection between the bus bar and a part of the welding strip, and then the insulating strip is set in the first exposed area, and the bus bar and the remaining welding strips are isolated by the insulating strip, which can reduce the risk of short circuit. Compared with opening holes corresponding to part of the welding strip in the pre-fixed film, since the pre-fixed film can be a flexible film layer structure, it is easy to deform when laid on the back of the battery cell, resulting in the hole opened on the pre-fixed film being misaligned with the preset position on the battery cell where the welding strip needs to be leaked, thereby causing a short circuit between the bus bar and the opposite-sex grid line. The first exposed area is formed on the back of the first battery cell, the bus bar 400 is arranged in the first exposed area 300, and the insulating strip 500 is used to isolate the bus bar 400 and part of the first welding strip 103, then the bus bar 400 and another part of the first welding strip 103 are electrically connected to realize the carrier convergence on the battery cell.

[0043] Further, in the back contact cell, the pre-fixed film 200 is laid on the back of the first cell, and the pre-fixed film 200 is formed with a first exposed area 300 to expose the entire first welding strip 103. At this time, an insulating strip 500 is required to isolate the bus bar 400 from a portion of the first welding strip 103, and then the bus bar 400 is electrically connected to another portion of the first welding strip 103. Alternatively, the pre-fixed film 200 is formed with a first exposed area 300 to expose another portion of the first welding strip 103, and then the pre-fixed film 200 isolates part of the first welding strip 103. At this time, the pre-fixed film 200 also has the function of the insulating strip 500. The first exposed area 300 partially exposes the welding strip, so that the bus bar 400 is directly in contact with the first welding strip 103 only in a specific electrode area, thereby realizing a precise current transmission path. This design avoids the short circuit problem caused by the accidental contact between the bus bar 400 and a portion of the first welding strip 103, so the insulating strip 500 can be omitted to simplify the battery assembly.

[0044] In some embodiments, the battery assembly further includes an adhesive film, which covers the pre-fixed film 200. The adhesive film is used for the final packaging of the battery assembly. Specifically, the adhesive film covers the upper and lower surfaces of the battery cell, and is laminated with the glass and the back plate to isolate the battery cell from mechanical damage (such as impact, vibration) and chemical erosion by the external environment. Furthermore, the fluidity of the pre-fixed film 200 during the initial lamination process is lower than the fluidity of the adhesive film during the initial lamination process. In this way, during the initial lamination process, the fluidity of the pre-fixed film 200 layer is low, which can effectively avoid the deviation of the solder strip during the production of the battery assembly, improve the positioning and alignment accuracy of the solder strip, and thus ensure the yield.

[0045] In some embodiments, the pre-fixed film 200 includes at least one of a PVB film, an EVA film, an EPE film, an EP film, and a POE film, and the adhesive film includes at least one of a POE film, an EVA film, an EPE film, an EP film, a PE film, and a PVB film. Specifically, it is only necessary to make the fluidity of the pre-fixed film 200 in the initial lamination process lower than the fluidity of the adhesive film in the initial lamination process, and there is no specific limitation here.

[0046] like Figure 2 As shown, in some embodiments, the first exposed area is formed on the back of the first cell, the insulating strip 500 forms a second exposed area 600, the second exposed area 600 exposes another part of the first welding strip 103, the polarity of the grid line connected to the part of the first welding strip 103 and the other part of the first welding strip 103 is different, the insulating strip 500 insulates the bus bar 400 from the part of the first welding strip 103, and the bus bar 400 is conductively connected to the other part of the first welding strip 103 corresponding to the second exposed area 600. In this way, with the perspective when the back of the cell is facing up as a reference, the bus bar 400 is located on the top layer of the first welding strip 103, or the first welding strip 103 is located on the side of the bus bar 400 facing the cell, so that even if the insulating strip 500 is provided, the first welding strip 103 can be completely attached to the electrode area of ​​the cell, that is, it can ensure that the first welding strip 103 is connected to enough fine grids, fully utilize each fine grid on the cell, better collect current, and improve the effect of collecting current. It can be understood that this structure of the battery assembly can effectively improve the current collection effect while hiding the bus bar 400.

[0047] Furthermore, the insulating strip 500 is provided with a through hole forming a second exposed area. That is, the through hole penetrating along the thickness direction of the insulating strip 500 forms the second exposed area. Since the insulating strip 500 has a through hole, the through hole can expose another part of the first welding strip 103, so that the bus bar 400 can be connected to another part of the first welding strip 103 at the through hole, and the insulating strip 500 can prevent the bus bar 400 from short-circuiting the battery cell. In addition, due to the presence of the through hole, the insulating strip 500 will not hinder the conductive connection between the bus bar 400 and another part of the first welding strip 103, and it is also convenient to completely attach the first welding strip 103 to the battery cell, so that the first welding strip 103 can be connected to more fine grids.

[0048] Exemplarily, the insulating strip 500 can be an insulating adhesive, or 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 coated with ethylene-vinyl acetate copolymer or hot melt adhesive on one or both sides. It can be understood that the insulating strip 500 can include materials such as ethylene-vinyl acetate copolymer, resin material, polyimide or polypropylene or polyethylene, and can also include an acrylic adhesive layer.

[0049] In some embodiments, the insulating strip 500 includes a plurality of insulating sublayers arranged at intervals, the plurality of insulating sublayers cover a portion of the first welding strip 103, and the interval area between adjacent insulating sublayers forms a second exposed area. In this way, the insulating sublayer only covers the first welding strip 103 of the portion that needs to be insulated, while the first welding strip 103 of the other portion welded to the bus bar 400 can be completely attached to the electrode area corresponding to the battery cell due to the presence of the second exposed area, so that the first welding strip 103 can be connected to more fine grids. It can be understood that the material of the above insulating sublayer can be the same as that of the insulating strip 500, which will not be repeated here.

[0050] In other embodiments, the first exposed area 300 is formed on the back of the second battery cell 102, the insulating strip 500 is a complete strip structure, the insulating strip 500 insulates all the second welding strips 104 and the bus bar, a portion of the first welding strip extends along the first direction and is electrically connected to the bus bar, the remaining portion of the first welding strip 103 is isolated from the bus bar, and the polarity of the grid line connected to the remaining portion of the first welding strip 103 and the portion of the first welding strip 103 is different. At this time, a portion of the first welding strip 103 includes a main section 1031 and a flat section 1032, the flat section of the first welding strip 103 is formed in the projection area of ​​the bus bar on the second battery cell, and the remaining first welding strip 103 may not be locally flattened, so that the bus bar 400 and the first welding strip have a reduced local height after being stacked, which helps to reduce the risk of hidden cracks in the battery cell during the lamination process. It can be understood that the bus bar 400 is also stacked with a second welding strip in the projection area of ​​the second battery cell 102, and the second welding strip 104 can also be set as a main section and a flat section. The flat section of the second welding strip is set between the bus bar and the second battery cell, further reducing the local stacking height of the battery assembly, thereby reducing the risk of hidden cracks in the battery assembly.

[0051] In some embodiments, in the first direction, the width of the insulating strip 500 is greater than or equal to the width of the bus bar 400, and the width of the first exposed area 300 is greater than or equal to the width of the insulating strip 500. By setting the width of the insulating strip 500 to be greater than or equal to the width of the bus bar 400, it can be ensured that the insulating strip 500 completely isolates the bus bar 400 from a portion of the welding strip. If the width of the insulating layer is too narrow, the bus bar 400 will be exposed, and there is a risk of short circuit caused by contact between the bus bar 400 and a portion of the welding strip. In addition, by setting the width of the first exposed area 300 to be greater than or equal to the width of the insulating strip 500, it can be ensured that the pre-fixed film 200 reserves enough space for placing the insulating strip 500. Further, when the width of the first exposed area 300 is set to be slightly greater than the width of the insulating strip 500, the alignment accuracy of installing the insulating strip 500 can be reduced, thereby ensuring the production yield of the battery assembly.

[0052] It can be understood that the area where the bus bar 400 is projected onto the first battery cell 101 is defined as the stacking area. When assembling the battery module, insulating strips 500 and bus bars 400 need to be set in the stacking area. This will cause local protrusions on the battery cell, which will make it easy for the battery cell to be hidden cracked due to stress concentration when the battery module is laminated. Especially when the bus bar 400 is set at the edge of the battery cell, the risk of hidden cracking increases, resulting in a decrease in the yield of the battery module.

[0053] like Figure 3 and Figure 4As shown, in some embodiments, the first welding ribbon 103 includes a main section 1031 and a flat section 1032, the flat section 1032 is arranged between the bus bar 400 and the first battery cell 101, and the thickness of the flat section 1032 is less than the thickness of the main section 1031. The first welding ribbon 103 adopts a two-stage differentiated thickness design, consisting of a main section 1031 and a flat section 1032. The main section 1031 is fixed to the surface of the first battery cell 101, and the flat section 1032 is arranged between the bus bar 400 and the first battery cell 101, and its thickness is thinner than the main section 1031. By arranging a thin flat section 1032 in the stacking area of ​​the bus bar 400 and the first battery cell 101, the stacking height at the location of the bus bar 400 is effectively reduced, thereby reducing the risk of hidden cracks in the battery cell during the lamination process of the battery assembly.

[0054] In some embodiments, along the first direction, the length of the flat section 1032 is greater than the width of the busbar 400. This can effectively reduce the local height of the stacking area where the busbar 400 is located, ensure that the stacking area has a lower thickness, and reduce the risk of hidden cracks during the lamination process of the battery assembly. In addition, the longer flat section 1032 provides a larger deformation space when the battery cell is heated or subjected to external forces, reducing stress concentration. For example, when temperature changes cause the battery cell to expand or contract, the longer flexible portion can absorb more strain and avoid cracking of the first welding ribbon 103 or the battery cell.

[0055] In some embodiments, along the second direction, the width of the flat section 1032 is greater than the width of the main section 1031. By widening the width of the flat section 1032 relative to the main section 1031, the contact area between the flat section 1032 and the battery cell can be increased, the lamination pressure can be dispersed, the risk of hidden cracks in the battery cell can be reduced, and the reliability of the battery assembly can be improved.

[0056] In some embodiments, the flat section 1032 and the main section 1031 are integrally formed. That is to say, by continuously processing a single material to form the two-section differentiated structure of the first welding strip 103, the interface defects (such as cold welds and pores) of the traditional segmented welding can be eliminated, so that the overall tensile strength of the first welding strip 103 is improved. And in the component lamination process, the continuous structure can evenly disperse the shear stress and avoid hidden cracks caused by local stress concentration. Exemplarily, the first welding strip 103 can be locally flattened to form the flat section 1032 by flattening, or the first welding strip 103 can be locally rolled to form the flat section 1032, or the first welding strip 103 can be locally processed by stamping to form the flat section 1032, and the present invention is not limited to this.

[0057] In other embodiments, the main section 1031 and the flat section 1032 are overlapped and connected to each other. The first welding strip 103 is overlapped and connected in sections, which can improve the flexibility of the arrangement of the first welding strip 103. When defects are found in EL detection, the overlapped section (rather than the entire welding strip) can be partially replaced, which shortens the component rework time and reduces the maintenance cost.

[0058] In some embodiments, the cross-sectional area of ​​the main section 1031 is equal to the cross-sectional area of ​​the flat section 1032. By controlling the cross-sectional size of the flat section 1032 to achieve resistance matching, under the premise of keeping the conductive cross-sectional area unchanged (compensating for the thickness reduction by increasing the width), the current transmission efficiency is maintained, and the resistance distribution of the welding ribbon is made more in line with the current density requirements, thereby reducing the risk of local hot spots.

[0059] In some embodiments, the cross-sectional area of ​​the flat segment is larger than the cross-sectional area of ​​the main segment. By designing the flat segment separately, its cross-sectional area can be increased while reducing the thickness of the flat segment, thereby further effectively reducing the resistance of the flat segment and improving the current transmission efficiency.

[0060] In some embodiments, the main body section 1031 is a round wire welding ribbon section, and the flat section 1032 is a flat welding ribbon section. It can be understood that since the second welding ribbon 104 does not need to be connected to the bus bar 400, the second welding ribbon 104 can be a complete round wire welding ribbon.

[0061] In some embodiments, a photovoltaic system includes a battery assembly as described above. In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water 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 are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple battery assemblies. For example, multiple battery assemblies can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.

[0062] 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 invention. 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.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery assembly, characterized in that: The invention comprises a battery string, wherein the battery string comprises at least a first battery cell and a second battery cell arranged in sequence along a first direction, wherein the first battery cell is arranged at an end of the battery string; a plurality of first welding strips, wherein the plurality of first welding strips are arranged at intervals along a second direction on the back side of the first battery cell; a plurality of second welding strips, wherein the plurality of second welding strips are arranged at intervals along the second direction on the back side of the second battery cell; a pre-fixing film, wherein the pre-fixing film is arranged at least on the back side of the first battery cell and the back side of the second battery cell, wherein the pre-fixing film fixes the plurality of first welding strips on the back side of the first battery cell, wherein the pre-fixing film fixes the plurality of second welding strips on the back side of the second battery cell, wherein the pre-fixing film is formed with a first exposed area, wherein the first exposed area is formed on the back side of the first battery cell or the back side of the second battery cell; a bus bar, wherein the bus bar is arranged in the first exposed area; and an insulating strip, wherein the insulating strip is arranged between the bus bar and the first battery cell or the second battery cell.

2. The battery assembly according to claim 1, characterized in that The battery assembly further includes an adhesive film, which covers the pre-fixed film, and the fluidity of the pre-fixed film during the initial lamination process is lower than the fluidity of the adhesive film during the initial lamination process.

3. The battery assembly according to claim 2, characterized in that: The pre-fixed film includes at least one of PVB film, EVA film, EPE film, EP film and POE film, and the film includes at least one of POE film, EVA film, EPE film, EP film, PE film and PVB film.

4. The battery assembly according to claim 3, characterized in that: The pre-fixing film and the adhesive film are made of different materials.

5. The battery assembly according to claim 1, characterized in that: The first exposed area is formed on the back side of the first battery cell, and the insulating strip forms a second exposed area. The second exposed area exposes a portion of the first welding strip, and the polarity of the remaining portion of the first welding strip and the portion of the first welding strip connected to the gate line is different. The insulating strip insulates the bus bar from the remaining portion of the first welding strip, and the bus bar is conductively connected to the portion of the first welding strip exposed corresponding to the second exposed area.

6. The battery assembly according to claim 5, characterized in that: The insulating strip is provided with a through hole forming the second exposed area.

7. The battery assembly according to claim 5, characterized in that: The insulating strip includes a plurality of insulating sublayers arranged at intervals, the plurality of insulating sublayers cover a portion of the first welding strip, and the interval area between adjacent insulating sublayers forms the second exposed area.

8. The battery assembly according to claim 1, wherein: The first exposed area is formed on the back side of the second battery cell, and the insulating strip is a complete strip structure. The insulating strip insulates all the second welding strips and the bus bar. A portion of the first welding strip extends along the first direction and is electrically connected to the bus bar, and the remaining portion of the first welding strip is isolated from the bus bar. The polarity of the grid line connected to the remaining portion of the first welding strip and the portion of the first welding strip is different.

9. The battery assembly according to claim 1, wherein: In the first direction, the width of the insulating strip is greater than or equal to the width of the bus bar, and the width of the first exposed area is greater than or equal to the width of the insulating strip.

10. The battery assembly according to claim 5, characterized in that: The first welding strip includes a main section and a flat section, the flat section is arranged between the bus bar and the first battery sheet, and the thickness of the flat section is smaller than the thickness of the main section.

11. The battery assembly according to claim 10, characterized in that Along the first direction, the length of the flat segment is greater than the width of the bus bar.

12. The battery assembly according to claim 10, characterized in that Along the second direction, the width of the flat section is greater than the width of the main body section.

13. The battery assembly according to claim 10, characterized in that: The flat section and the main body section are integrally formed.

14. The battery assembly according to claim 10, characterized in that: The main body section and the flat section are overlapped and connected to each other.

15. The battery assembly according to claim 10, characterized in that The cross-sectional area of ​​the main body section is equal to the cross-sectional area of ​​the flat section.

16. The battery assembly according to claim 10, characterized in that: The cross-sectional area of ​​the flat section is greater than the cross-sectional area of ​​the main body section.

17. The battery assembly according to claim 10, characterized in that: The main body section is a round wire welding strip section, and the flat section is a flat welding strip section.

18. A photovoltaic system, characterized in that: Comprising a battery assembly as described in any one of claims 1-17.

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