Battery structure and photovoltaic modules

Abstract

This utility model discloses a battery structure and photovoltaic module, including a battery substrate with interconnected grid grooves and solder joint grooves. Both the grid grooves and solder joint grooves are filled with conductive metal to form an embedded grid and solder joint base. Conductive solder joints are set on the solder joint base and protrude from the surface of the battery substrate. By slotting the battery substrate to form interconnected grid grooves and solder joint grooves, conductive solder joints connected to the grid grooves are fabricated. The conductive solder joints protrude from the surface of the battery substrate, enabling interconnection between different battery cells through the conductive solder joints and pre-formed circuit glass.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic technology, and in particular to a battery structure and a photovoltaic module. Background Technology

[0002] In photovoltaic cell technology, back contact (BC) technology improves conversion efficiency by removing the front grid lines of the cell and placing electrodes only on the back, thus reducing front shading. However, the encapsulation of back contact cell modules uses a solder ribbon welding process. When the back electrode of the cell is welded to the solder ribbon, the cell is heated as a whole. The localized high temperature at the solder ribbon connection point (e.g., 200~300℃) can cause thermal stress concentration in the cell, which can easily lead to warping after cooling, and in severe cases, even fragmentation. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a battery structure and photovoltaic module, which forms interconnected grid grooves and solder joint grooves by slotting the battery substrate, thereby processing conductive solder joints connected to the grid lines. This allows for interconnection between different battery cells through the conductive solder joints and pre-formed circuit glass.

[0004] On one hand, this utility model embodiment provides a battery structure, including:

[0005] The battery substrate has a connected grid groove and a solder joint groove, and both the grid groove and the solder joint groove are filled with conductive metal to form an embedded grid and solder joint base.

[0006] A conductive solder joint is provided on the basis of the solder joint, and the conductive solder joint protrudes from the surface of the battery substrate.

[0007] According to some embodiments of this utility model, the diameter of the conductive solder joint is 0.7~1.1mm and the height is 10~15μm.

[0008] According to some embodiments of the present invention, the surface roughness of the conductive solder joint is ≤0.5μm.

[0009] According to some embodiments of this utility model, the contact resistance between the conductive solder joint and the embedded grid line is ≤30mΩ.

[0010] On the other hand, this utility model embodiment provides a photovoltaic module, including multiple solar cells, wherein the solar cells adopt the above-described solar cell structure.

[0011] According to some embodiments of the present invention, the photovoltaic module further includes a back glass and a back film. The back film and the solar cell are stacked sequentially on the back glass. The back glass is provided with interconnecting strips and busbars. The interconnecting strips are provided with conductive pads. The positions of the conductive pads are adapted to the positions of the conductive solder joints. The back film is provided with openings adapted to the conductive pads.

[0012] According to some embodiments of the present invention, the gap between the back glass and the battery cell is filled with an elastic buffer pad or coated with a buffer adhesive.

[0013] According to some embodiments of the present invention, the thickness of the elastic buffer pad is 0.1~0.2mm, the hardness is 50~60 Shore A, and the elongation at break is ≥300%.

[0014] According to some embodiments of the present invention, the photovoltaic module further includes a front glass and a front encapsulating film, wherein the front glass and the front encapsulating film are sequentially stacked on the solar cell.

[0015] According to some embodiments of this utility model, the warpage of the photovoltaic module after pressing is ≤0.3%.

[0016] The embodiments of this utility model have at least the following beneficial effects:

[0017] The battery substrate has interconnected grid grooves and solder joint grooves, both filled with conductive metal to form the foundation for embedded grid lines and solder joints. Conductive solder joints are located on these foundations and protrude from the surface of the battery substrate. By creating grooves in the battery substrate to form interconnected grid grooves and solder joint grooves, conductive solder joints connected to the grid lines are fabricated. These conductive solder joints protrude from the surface of the battery substrate, enabling interconnection between different battery cells through the conductive solder joints and pre-formed glass circuitry.

[0018] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This is a plan view of the battery structure according to an embodiment of the present utility model;

[0021] Figure 2 for Figure 1 The center circle shows a magnified view of a portion at position A;

[0022] Figure 3 This is a longitudinal cross-sectional view of the battery structure according to an embodiment of the present invention.

[0023] Figure 4 This is one of the schematic diagrams of the stacked structure of the photovoltaic module according to an embodiment of the present utility model;

[0024] Figure 5 This is the second schematic diagram of the stacked structure of the photovoltaic module according to an embodiment of the present utility model.

[0025] Figure label:

[0026] 100 battery cell, 101 grid groove, 102 solder joint groove, 110 embedded grid line, 120 solder joint base, 130 conductive solder joint, 140 battery substrate, 200 back glass, 210 interconnecting strip, 211 conductive pad, 220 busbar, 300 back adhesive film, 301 window opening, 400 front glass, 500 front adhesive film. Detailed Implementation

[0027] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0028] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0029] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first," "second," etc., are used in the description, they are only for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0030] In the description of this utility model, unless otherwise explicitly defined, the terms "setting", "installation", "connection", etc. should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in combination with the specific content of the technical solution.

[0031] Please refer to Figure 1 , Figure 2 and Figure 3 This embodiment discloses a battery structure, including a battery substrate 140 and conductive solder joints 130. The battery substrate 140 is provided with a connected grid groove 101 and a solder joint groove 102. Both the grid groove 101 and the solder joint groove 102 are filled with conductive metal to form embedded grid lines 110 and solder joint bases 120. The conductive solder joints 130 are disposed on the solder joint bases 120 and protrude from the surface of the battery substrate 140. For example, the battery substrate 140 can be a silicon wafer. The conventional welding method is to use an infrared heating process to heat the entire battery structure, so that the solder strips on the battery structure are heated and connected to the main grid lines of the battery structure. This method is prone to uneven stress, resulting in warping of the battery structure after welding. In this embodiment, conductive solder joints 130 protruding from the surface of the battery substrate 140 are processed on the solder joint bases 120. This facilitates the local alloying welding of the conductive solder joints 130 with the conductive pads 211 described below, which helps to reduce thermal stress concentration.

[0032] In the above scheme, the battery substrate 140 is provided with a connected grid groove 101 and a solder joint groove 102. Both the grid groove 101 and the solder joint groove 102 are filled with conductive metal to form embedded grid lines 110 and solder joint bases 120. Conductive solder joints 130 are disposed on the solder joint bases 120 and protrude from the surface of the battery substrate 140. By slotting the battery substrate 140 to form the connected grid groove 101 and solder joint groove 102, conductive solder joints 130 connected to the grid lines are fabricated. The conductive solder joints 130 protrude from the surface of the battery substrate 140, enabling interconnection between different battery cells 100 through the conductive solder joints 130 and the pre-formed circuit glass.

[0033] The conductive solder joint 130 has a diameter of 0.7~1.1mm and a height of 10~15μm. Within this parameter range, the conductive solder joint 130 can form good contact with the conductive pad 211 described below, improving the reliability of the solder joint and preventing desoldering or cold solder joint problems caused by poor contact. Furthermore, the diameter of the conductive solder joint 130 is related to its conductivity; designing the diameter to be 0.7~1.1mm ensures sufficient current transmission area, avoiding excessively high current density due to insufficient contact area, thereby reducing heat generation and energy loss.

[0034] The surface roughness of the conductive solder joint 130 is ≤0.5μm. Surface roughness is an important parameter for measuring the microscopic geometric characteristics of a material surface; the smaller the surface roughness, the smoother the material surface. Lower surface roughness results in lower contact resistance between the conductive solder joint 130 and the conductive pad 211 (described below), which is beneficial for efficient battery transfer and reduces energy loss. Furthermore, the low-roughness surface helps improve the thermal conductivity of the conductive solder joint 130, allowing for more uniform heat distribution. When the conductive solder joint 130 and the conductive pad 211 are locally alloyed, the heat from the conductive pad 211 can be better conducted to the conductive solder joint 130, preventing localized overheating, reducing thermal stress concentration in the battery cell 100, and avoiding warping or fragmentation after cooling.

[0035] The contact resistance between the conductive solder joint 130 and the embedded grid line 110 is ≤30mΩ, which helps to reduce current transmission loss and improve the transmission efficiency of the battery.

[0036] This embodiment also provides a photovoltaic module, including multiple solar cells 100, which employ the aforementioned solar cell structure. A solar cell substrate 140 is provided with interconnected grid grooves 101 and solder joint grooves 102. Both the grid grooves 101 and solder joint grooves 102 are filled with conductive metal to form embedded grid lines 110 and solder joint bases 120. Conductive solder joints 130 are disposed on the solder joint bases 120 and protrude from the surface of the solar cell substrate 140. By slotting the solar cell substrate 140 to form interconnected grid grooves 101 and solder joint grooves 102, conductive solder joints 130 connected to the grid lines are fabricated. The conductive solder joints 130 protrude from the surface of the solar cell substrate 140, enabling interconnection between different solar cells 100 through the conductive solder joints 130 and pre-formed glass.

[0037] To facilitate understanding of the technical concept of the photovoltaic module in this embodiment, the following explanation will be provided in conjunction with the manufacturing method of the photovoltaic module.

[0038] The traditional manufacturing process of photovoltaic cells includes material preparation, cell welding, layout, stacking, and lamination. The cell welding process involves using welding ribbons to weld multiple cells 100 arranged on an assembly line, achieving series connection between them. Layout involves neatly stacking multiple sets of series-connected cells 100 onto the back glass 200 according to a preset arrangement. Stacking involves welding the busbar 220 to the welding ribbons of the multiple sets of cells 100 stacked on the back glass 200, achieving interconnection between them. Lamination refers to pressing the stacked back glass 200, back film 300, cells 100, front film 500, and front glass 400 together. During the cell welding process, when the back electrode of the cell 100 is welded to the welding ribbons, localized high temperatures (e.g., 200~300℃) can cause thermal stress concentration in the cell 100, leading to warping after cooling and, in severe cases, fragmentation. In addition, there is contact resistance at the welding interface between the welding ribbon and the electrode of the solar cell 100, which is usually ≥200mΩ, accounting for 300%~400% of the internal loss of the photovoltaic cell, resulting in low conversion efficiency of the photovoltaic cell. Furthermore, the tension of the welding ribbon during the welding process can easily cause microcracks in the solar cell 100, which will further increase the current transmission loss.

[0039] In the initial stage of production, the manufacturing method of this embodiment requires the preparation of materials, including a back glass 200, battery cells 100, and a back adhesive film 300. The battery cells 100 adopt the battery structure described above, and there are multiple battery cells 100. In conventional processes, the back glass 200 is a flat and smooth glass structure. However, in this embodiment, a pre-fabricated circuit is set on the back glass 200. The pre-fabricated circuit includes interconnecting strips 210 and busbars 220. The interconnecting strips 210 can replace traditional solder ribbons to achieve series connection between different battery cells 100. The battery cells 100 in this embodiment are XBC batteries, and the metal contacts (such as conductive solder joints 130) of the battery cells 100 are all located on the same side to facilitate connection with the interconnecting strips 210. XBC cell technology is a back-contact solar cell technology. The "X" indicates that it can be combined with various technologies, such as TOPCon (tunneling oxide passivation contact) and HJT (heterojunction technology). It can be combined with TOPCon technology to form TBC, or with HJT technology to form HBC. XBC cells place the PN junction and metal contacts on the back of the cell, with an anti-reflection passivation film covering the front. This avoids the metal electrodes blocking the front surface, maximizing the utilization of incident light, reducing optical losses, and increasing the effective power generation area, thereby achieving high conversion efficiency and making the cell module more aesthetically pleasing. The busbars 220 and interconnects 210 are pre-fabricated on the back glass 200 for pre-connection, thus eliminating the need for the traditional stacking welding process, i.e., there is no need to weld the busbars 220 to the solder strips.

[0040] The photovoltaic module also includes a back glass 200 and a back film 300. The back film 300 and the solar cell 100 are stacked sequentially on the back glass 200. The back glass 200 is provided with interconnecting strips 210 and busbars 220. The interconnecting strips 210 are provided with conductive pads 211. The position of the conductive pads 211 is adapted to the position of the conductive solder joints 130. The back film 300 is provided with openings 301 adapted to the conductive pads 211.

[0041] The back adhesive film 300 can be made of EVA film, EPE film, or POE film, etc. EVA film is a thermosetting and adhesive film. EVA is short for Polyethylene vinylacetate. EPE stands for Expandable Polyethylene, a non-crosslinked closed-cell material made of low-density polyethylene (LDPE) through a physical foaming process. POE stands for Polyolefin Elastomer, a synthetic biodegradable polymer material. The back adhesive film 300 needs to be pre-processed with openings 301 whose position and size are adapted to the conductive pads 211, so that the conductive pads 211 and conductive solder joints 130 can be connected to each other after lamination assembly.

[0042] After stacking and assembling the back glass 200, the back adhesive film 300, and the solar cell 100, the aforementioned semi-finished structure of the photovoltaic module can be obtained. The back adhesive film 300, after subsequent lamination, serves to bond the back glass 200 and the solar cell 100 together.

[0043] In some application examples, the stacking assembly process includes: placing the back glass 200 on a platform for fixation, stacking the back adhesive film 300 on the back glass 200, and then stacking the solar cell 100 on the back adhesive film 300 to complete the stacking assembly. It should be noted that the stacking assembly process is usually completed by automated equipment with high alignment accuracy, ensuring precise alignment of the back glass 200, the back adhesive film 300, and the solar cell 100. For example, the position of the window 301 on the back adhesive film 300 can be adapted to the position of the conductive pad 211 on the back glass 200, and the position of the conductive solder joint 130 on the solar cell 100 can be adapted to the position of the conductive pad 211 on the back glass 200.

[0044] After completing the stacked assembly, the conductive pads 211 of the back glass 200 and the conductive solder joints 130 of the battery cell 100 need to be welded. Since the back glass 200 and the battery cell 100 are stacked together, and the conductive pads 211 and conductive solder joints 130 are located on opposite inner sides of the back glass 200 and the battery cell 100, it is difficult to weld them using conventional welding methods. In this embodiment, the conductive pads 211 and conductive solder joints 130 are locally alloyed. After local alloying welding, the conductive pads 211 melt and are welded to the conductive solder joints 130, thus achieving welding between the two. Furthermore, the short duration of local alloying welding avoids thermal stress concentration and effectively prevents the battery cell 100 from warping or fragmenting after welding cooling. Local alloying welding can be achieved using pulsed thermocompression welding technology. Pulsed thermocompression welding involves applying a certain pulse voltage to the hot press head, heating the hot press head, and raising the temperature of the object connected to the hot press head, thereby achieving the purpose of fusion welding. Conventional cell welding uses infrared heating to heat the entire cell 100, which then heats the solder strips on the cell 100 to connect with the main grid lines of the cell 100. This process is prone to uneven stress, which can cause the cell 100 to warp after welding. In this embodiment, the working temperature is controlled at ~℃, which can reduce the heat of welding to a certain extent. Moreover, the heating time is 8~10 seconds. By shortening the heating time while ensuring that the melting depth of the solder joint is ≥70%, the heat stress concentration can be further reduced. Local heating is performed at the position where the back glass 200 and the conductive pad 211 are adapted, and the heat is radiated to the conductive solder joint 130 of the battery cell 100, so that the conductive pad 211 is in a hot melt state and connected to the conductive solder joint 130. There is no need to weld the battery cell 100, which can greatly reduce the stress problem of the battery cell 100. The pressure of the hot press head is 3~5N, and the applied pressure is small and evenly applied to the welding area. Since the solder strip is eliminated and the battery cell 100 is directly connected through the interconnecting strip 210, ultra-low stress is achieved, which can avoid local stress concentration and prevent the battery cell 100 from warping or breaking after cooling, thus ensuring the reliability of the battery cell 100.

[0045] After the back glass 200 and the solar cell 100 are welded together, the front glass 400, the front encapsulant film 500, and the aforementioned semi-finished structure can be stacked and assembled. Therefore, the photovoltaic module also includes the front glass 400 and the front encapsulant film 500, which are sequentially stacked on top of the solar cell 100. It should be considered that the front glass 400 and the front encapsulant film 500 can be prepared in advance during the material preparation stage. The material of the front glass 400 can be the same as that of the back glass 200, and the material of the front encapsulant film 500 can be the same as that of the back encapsulant film 300. It is worth mentioning that in traditional processes, the welding strips need to be welded using busbars 220 before the front encapsulant film 500 and the front glass 400 are stacked and assembled. Since the prefabricated circuit of the back glass 200 in this embodiment has already completed the interconnection of the busbars 220 and the interconnecting strips 210, and the conductive connection of the conductive pads 211 and the conductive solder joints 130 has been completed in the aforementioned steps, the basic circuit of the photovoltaic cell has been connected, and it can be directly laminated. Compared with the conventional process, the method of this embodiment can eliminate the welding process between the busbars 220 and the solder strips, which is beneficial to save materials and shorten production time, thereby reducing production costs and improving production efficiency. It is worth mentioning that no circuit structure is provided on the front glass 400 in this embodiment, therefore, the alignment accuracy requirements between the front glass 400 and the solar cell 100 and the back glass 200 can be reduced.

[0046] After the lamination assembly is completed, an elastic buffer pad or a buffer adhesive can be applied to the gap between the back glass 200 and the solar cell 100. Therefore, in some photovoltaic modules used in applications, the gap between the back glass 200 and the solar cell 100 is filled with an elastic buffer pad or coated with a buffer adhesive. Filling the gap between the solar cell 100 and the back glass 200 with an elastic buffer pad allows for the formation of a stress-relieving layer after lamination and curing, effectively preventing warping of the solar cell 100. The elastic buffer pad is made of silicone sheet with a thickness of 0.1~0.2mm, a hardness of 50~60 Shore A, and an elongation at break ≥300%, providing good cushioning between the solar cell 100 and the back glass 200. Alternatively, a buffer adhesive can be pre-applied to the gap between the edge of the solar cell 100 and the pre-fabricated circuitry of the back glass 200, filling the gap during lamination. After curing, a buffer layer with a hardness of 40~50 Shore A is formed, preventing mechanical stress concentration. The buffer adhesive can be made of silicone rubber with a viscosity of 500~800 cP (centipoise). By filling gaps and applying segmented pressure, the uniformity of lamination pressure distribution can be effectively improved, reducing the internal residual stress to below 5MPa, which is far lower than the ≥15MPa of traditional processes. This helps to improve the resistance to mechanical loads and thus avoid 100% warpage of the solar cells.

[0047] After the stacked assembly is completed, the semi-finished structure of the photovoltaic module in the stacked assembly state is sent to the lamination equipment for pressing, so that the back film 300 and the front film 500 undergo a chemical cross-linking reaction, thereby achieving bonding between the back glass 200 and the cell 100 through the back film 300, and bonding between the cell 100 and the front glass 400 through the front film 500. The warpage of the photovoltaic module after pressing is ≤0.3%, which can reduce the risk of fragmentation.

[0048] This embodiment utilizes a back glass 200 with pre-fabricated circuitry and battery cells with conductive solder joints 130 to interconnect multiple battery cells 100. This eliminates the need for solder strips and soldering processes, preventing the battery cells 100 from warping or breaking due to soldering, and simplifies the manufacturing process and improves processing efficiency.

[0049] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A battery structure, characterized in that, include: The battery substrate (140) is provided with a grid groove (101) and a solder joint groove (102) that are connected. The grid groove (101) and the solder joint groove (102) are filled with conductive metal to form an embedded grid line (110) and a solder joint base (120). A conductive solder joint (130) is disposed on the solder joint base (120) and the conductive solder joint (130) protrudes from the surface of the battery substrate (140).

2. The battery structure according to claim 1, characterized in that, The diameter of the conductive solder joint (130) is 0.7~1.1mm and the height is 10~15μm.

3. The battery structure according to claim 1 or 2, characterized in that, The surface roughness of the conductive solder joint (130) is ≤0.5μm.

4. The battery structure according to claim 3, characterized in that, The contact resistance between the conductive solder joint (130) and the embedded grid line (110) is ≤30mΩ.

5. A photovoltaic module, characterized in that, It includes multiple battery cells (100), said battery cells (100) employing the battery structure as described in any one of claims 1 to 4.

6. The photovoltaic module according to claim 5, characterized in that, The photovoltaic module also includes a back glass (200) and a back film (300). The back film (300) and the solar cell (100) are stacked on the back glass (200). The back glass (200) is provided with interconnecting strips (210) and busbars (220). The interconnecting strips (210) are provided with conductive pads (211). The position of the conductive pads (211) is adapted to the position of the conductive solder joints (130). The back film (300) is provided with openings (301) adapted to the conductive pads (211).

7. The photovoltaic module according to claim 6, characterized in that, The gap between the back glass (200) and the battery cell (100) is filled with an elastic cushioning pad or coated with a cushioning adhesive.

8. The photovoltaic module according to claim 7, characterized in that, The elastic buffer pad has a thickness of 0.1~0.2mm, a hardness of 50~60 Shore A, and an elongation at break of ≥300%.

9. The photovoltaic module according to claim 6, 7 or 8, characterized in that, The photovoltaic module further includes a front glass (400) and a front encapsulant film (500), which are stacked sequentially on the solar cell (100).

10. The photovoltaic module according to claim 9, characterized in that, The warpage of the photovoltaic module after pressing is ≤0.3%.

Images