Battery string and photovoltaic module

Abstract

The utility model discloses a battery string and a photovoltaic assembly, and relates to the field of photovoltaic technology. The battery string comprises a plurality of battery pieces, and transparent conductive films are arranged on the front surfaces and the back surfaces of the battery pieces; the first metal wire mesh is laid on the front surface of each battery piece and is electrically connected with the transparent conductive thin film on the front surface of the battery piece; the second metal wire mesh is laid on the back surface of each battery piece and is electrically connected with the back surface of the battery piece; and a plurality of bus bars. For every two adjacent battery pieces, the first metal wire mesh on one battery piece and the second metal wire mesh on the other adjacent battery piece are electrically connected with the same bus bar so as to connect a plurality of battery pieces in series. The metal wire mesh in the battery string is not easy to bend, small in stress and high in reliability.

Description

Technical Field

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

[0002] With the development of photovoltaic technology, in order to reduce costs and increase efficiency, gridless photovoltaic cells have emerged. Their core lies in eliminating the grid on the surface of the cell and collecting current through welding ribbons or metal mesh.

[0003] When current is collected in gridless solar cells using solder ribbons, the solder ribbons are alloyed with the fine grids. However, the large number of fine grids makes it impossible to reduce the cost of silver paste. Furthermore, the width of the fine grids is generally 20~28μm, which blocks sunlight and causes a loss in the efficiency of the solar cells. In addition, the solder ribbons are usually fixed by dispensing adhesive, which makes them prone to displacement during the welding process. The alloying of the solder ribbons with the fine grids results in a small contact area, lower reliability, and a higher risk of grid breakage.

[0004] Existing technology provides a photovoltaic module that uses a metal mesh for current harvesting. One end of the metal mesh is connected to the front of a cell in the photovoltaic module's cell string, and the other end is connected to the back of an adjacent cell in the cell string. Although this connection method can reduce the amount of silver paste used, it suffers from problems such as high stress on the metal mesh and low connection reliability. Utility Model Content

[0005] In view of this, the present invention provides a method for preparing a battery string, a photovoltaic module, and a battery string, which can collect and transmit current without setting grid lines and solder strips on the surface of the battery cells, while reducing the cost of metal paste.

[0006] To achieve the above objectives, according to one aspect of the present invention, a battery string is provided. The battery string of the present invention includes:

[0007] Several battery cells, each having a transparent conductive film on its front and back sides;

[0008] A first metal mesh laid on the front side of each of the aforementioned battery cells and electrically connected to the aforementioned transparent conductive film on the front side of the aforementioned battery cells;

[0009] A second metal wire mesh laid on the back of each of the aforementioned battery cells and electrically connected to the back of the aforementioned battery cells;

[0010] And several busbars;

[0011] For each pair of adjacent solar cells, the first metal mesh on one solar cell is electrically connected to the second metal mesh on the adjacent solar cell via the same busbar to connect several solar cells in series.

[0012] To achieve the above objectives, according to another aspect of the present invention, a photovoltaic module is provided. One such photovoltaic module includes a battery string as described above.

[0013] To achieve the above objectives, according to another aspect of the present invention, a method for preparing a battery string is provided. The method for preparing a battery string according to an embodiment of the present invention includes:

[0014] Step A1: Lay the battery cells on the second metal wire mesh so that the back of the battery cells is in contact with the second metal wire mesh;

[0015] Step A2: Lay a first metal wire mesh on the front side of the aforementioned battery cell;

[0016] Step A3: Press and cure the battery cells on which the first and second metal wire meshes are laid;

[0017] Step A4: Test and screen the cured solar cells;

[0018] Step A5: For adjacent screened battery cells, a busbar is used to electrically connect the first metal wire mesh of one of the screened battery cells to the second electrical connection portion, and to the fourth electrical connection portion of the second metal wire mesh of the other screened battery cell.

[0019] One embodiment of the above-mentioned utility model has the following advantages or beneficial effects: According to the battery string of the present utility model embodiment, by laying a first metal wire mesh on the front side of the battery cell with a transparent conductive film and laying a second metal wire mesh on the back side, the first metal wire mesh and the second metal wire mesh are electrically connected to the transparent conductive film, and the current can be collected and transmitted without setting grid lines and solder ribbons on the surface of the battery cell, thereby reducing the cost of metal paste.

[0020] By using a busbar to connect the first metal wire mesh of one battery cell to the second metal wire mesh of the other battery cell, the battery cells are connected in series to form a battery string. This avoids the problem of bending of the metal wire mesh in the middle of the two battery cells due to connecting two adjacent battery cells with the same metal wire mesh, thus solving the problem of excessive stress in this part reducing the reliability of the battery string and improving the structural stability of the battery string.

[0021] Furthermore, the first metal mesh includes a first metal wire parallel to a first direction and a second metal wire parallel to a second direction. The second metal mesh includes a third metal wire parallel to the first direction and a fourth metal wire parallel to the second direction. The first and second metal wires extend in two mutually perpendicular directions, as do the third and fourth metal wires. This mesh structure improves current collection and transmission capabilities. Neither a main grid nor a fine grid is needed on the surface of the solar cell, solving the problem of aligning the metal mesh with the fine grid during cell string fabrication. Moreover, the mesh structure of the first and second metal meshes allows the probe to connect with the metal meshes extending in different directions during IV testing of the solar cell, resolving the issue that solar cells without grid lines cannot pass IV testing for cell sorting.

[0022] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0023] The accompanying drawings are provided to better understand this utility model and do not constitute an undue limitation thereof. Wherein:

[0024] Figure 1 This is a schematic diagram of the longitudinal section structure of the battery string according to an embodiment of the present utility model;

[0025] Figure 2 This is a top view of the battery string according to an embodiment of the present utility model;

[0026] Figure 3 This is a schematic diagram of the structure of the first metal wire mesh placed on the front of the battery cell according to an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the second metal wire mesh placed on the back of the battery cell according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the longitudinal section structure of a battery cell with a first metal wire mesh and a second metal wire mesh laid according to an embodiment of the present utility model.

[0029] Figure 6 This is a structural diagram of the first metal wire mesh according to an embodiment of the present utility model;

[0030] Figure 7 This is an exploded view of a photovoltaic module according to an embodiment of the present utility model;

[0031] Figure 8 This is a schematic flowchart of a method for preparing a battery string according to an embodiment of the present invention;

[0032] Figure 9 This is a schematic flowchart of a method for preparing a battery string according to another embodiment of the present invention;

[0033] Figure 10 This is a schematic diagram of a battery string semi-finished product structure formed after the second metal wire mesh is laid on the laminated film layer according to an embodiment of the present utility model.

[0034] Figure 11 This is a schematic diagram of the battery string semi-finished product structure formed after step B5 according to an embodiment of the present utility model;

[0035] Figure 12 This is a schematic diagram of the semi-finished battery string structure after step B7, according to an embodiment of the present invention, which is pressed together by a press.

[0036] Figure 13 This is a schematic diagram of the structure of placing the battery string semi-finished product pressed by the press onto the roller 9 according to an embodiment of the present invention;

[0037] Figure 14 This is a schematic diagram of the structure of placing the battery string semi-finished product pressed by the press onto the conveyor belt according to an embodiment of the present invention.

[0038] Figure label:

[0039] 1-Battery string; 100-Battery cell; 200-First metal wire mesh; 210-First electrical connection part; 220-Second electrical connection part; 201-First metal wire; 202-Second metal wire; 300-Second metal wire mesh; 310-Third electrical connection part; 320-Fourth electrical connection part; 301-Third metal wire; 302-Fourth metal wire; 400-Busbar; 500-Conductive adhesive layer; 600-Carrier film; 2-Front adhesive film; 3-Back adhesive film; 4-Panel material; 5-Backsheet material; 6-Release film; 7-Pressure press; 8-Curing oven; 9-Roller; 10-Tray platform; 11-Transmission belt. Detailed Implementation

[0040] Existing gridless technologies mainly include two methods for current harvesting: using solder strips or metal mesh.

[0041] When using solder strips for current collection, the solder strips and the grid are alloyed. Due to the small diameter of the grid, the contact area between the solder strip and the grid is small, making the grid prone to breakage. To increase the reliability of solder strip welding, contact points (PADs) can be added at the contact point between the cell and the solder strip. However, the presence of the grid and PADs increases the cost of the metal paste.

[0042] When using a metal mesh for current collection, the metal mesh can be alloyed with a fine grid to fix it to the surface of the solar cell. During the mesh installation process, precise alignment between the metal mesh and the fine grid is required, demanding higher process precision, resulting in higher equipment costs and lower product yield. Furthermore, when the metal mesh is directly placed on the surface of the solar cell (without a fine grid), the mesh is only securely bonded to the cell surface, which is unreliable and cannot ensure proper contact between the mesh and the cell, affecting current transmission efficiency.

[0043] In gridless solar cells with fine grids, more fine grids are needed than in cells with main grids to enhance the reliability of the solder ribbons or metal mesh. However, a large number of fine grids prevents the reduction of the cost of the metal paste used to prepare the grid lines, and the presence of fine grids also requires higher process precision, leading to lower cell reliability. Removing the fine grids results in the following problems: 1. Reduced current collection capacity; 2. Direct exposure of the gridless cell surface, making it prone to scratches; 3. Inability to perform current-voltage (IV) characteristic curve testing, making it impossible to determine the cell's efficiency distribution and thus hindering cell sorting. It should be noted that during IV testing, the probes or wires of the IV testing device need to contact the main grid or fine grids of the cell. IV testing is impossible when there are no main grids or fine grids, and the solder ribbons or metal mesh extend in one direction.

[0044] Furthermore, for gridless solar cells without fine grids, a positioning layer for positioning the metal mesh needs to be printed on the cell first, and then the metal mesh is laid. Therefore, during the laying of the metal mesh, the metal mesh and the positioning layer need to be precisely aligned, which undoubtedly requires higher process precision, resulting in higher equipment costs and lower product yield.

[0045] To protect gridless solar cells and reduce scratches, a carrier film can be laid on the surface. This carrier film can also secure the solder ribbons or metal mesh. However, due to limitations such as process variations, the coating effect at the cell edges is often poor, resulting in scratches on the cell edges and inadequate securing of the solder ribbons or metal mesh, which can easily lead to misalignment. During electroluminescence (EL) testing, the exposed edges of the cells not covered by the carrier film are prone to blackening.

[0046] In addition, adjacent cells in a battery string are connected by solder ribbons or wire mesh laid on the surface of the cells. The solder ribbons or wire mesh extend from the front of one cell to the back of another, inevitably causing the solder ribbons or wire mesh between adjacent cells to bend. The bent part has greater stress, which reduces the reliability of the photovoltaic module.

[0047] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These embodiments should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0048] It should be noted that, where there is no conflict, the embodiments of this utility model and the technical features in the embodiments can be combined with each other.

[0049] It should be understood that in the various embodiments of this utility model, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this utility model.

[0050] It should be noted that, in this embodiment of the invention, the front side of the battery cell refers to the side facing sunlight or the side away from sunlight when the battery cell is working; correspondingly, the back side of the battery cell refers to the side away from the front side. For example, when the front side of the battery cell refers to the side facing sunlight when the battery cell is working, the back side of the battery cell refers to the side away from sunlight when the battery cell is working; conversely, when the back side of the battery cell refers to the side away from sunlight when the battery cell is working, the back side of the battery cell refers to the side facing sunlight when the battery cell is working.

[0051] Figure 1 This is a schematic diagram of the longitudinal section structure of the battery string according to an embodiment of the present invention. Figure 2 This is a top view of the battery string according to an embodiment of the present utility model; it should be noted that, Figure 1 and Figure 2 The battery string structure shown is merely an example of a structure containing two adjacent battery cells. In reality, the number of battery cells in the battery string can be set according to the actual situation, including but not limited to two.

[0052] like Figure 1 and Figure 2As shown, one aspect of this utility model embodiment provides a battery string 1, mainly comprising: a plurality of battery cells 100, wherein a transparent conductive oxide (TCO) film is disposed on both the front and back sides of each battery cell 100; a first metal mesh 200 disposed on the front side of each battery cell 100 and electrically connected to the transparent conductive oxide film on the front side of the battery cell 100; a second metal mesh 300 disposed on the back side of each battery cell 100 and electrically connected to the back side of the battery cell 100; and a plurality of busbars 400.

[0053] The transparent conductive film possesses both transparency and conductivity. When the TCO film is deposited on the surface of the solar cell 100, it can work in conjunction with the first metal mesh 200 and the second metal mesh 300 to enhance current collection capability. The first metal mesh 200 and the second metal mesh 300 are electrically connected to the transparent conductive film for current collection.

[0054] The first metal wire mesh 200 and the second metal wire mesh 300 can be made of tin-lead-bismuth alloy, but are not limited to this.

[0055] For each pair of adjacent battery cells 100, the first metal mesh 200 on one battery cell 100 is electrically connected to the same busbar 400 with the second metal mesh 300 on the adjacent battery cell 100, so as to connect a plurality of battery cells 100 in series.

[0056] In this embodiment of the invention, the surface of the battery cell 100 does not have main grids, fine grids, or PAD points. Instead, current is transmitted through a transparent conductive film laid on the surface of the battery cell 100 body, and the current is collected by a metal mesh, reducing the cost of metal pastes such as silver paste. The first metal mesh 200 and the second metal mesh 300 are used to collect the current transmitted by the transparent conductive film. Therefore, in this embodiment of the invention, the surface of the battery cell 100 does not need to have solder ribbons, nor does it need to align the first metal mesh 200 or the second metal mesh 300 with the grid lines, greatly simplifying the manufacturing process of the battery string 1.

[0057] In addition, by setting a busbar 400 between adjacent solar cells 100, this embodiment of the invention avoids the phenomenon of bending of part of the metal wire mesh located between adjacent solar cells 100 caused by using metal wire mesh to connect adjacent solar cells 100 in series, thus solving the problem of reduced reliability of photovoltaic modules due to excessive stress in the bent part.

[0058] In one alternative embodiment, such as Figure 3 As shown, the first metal mesh 200 includes: a first electrical connection portion 210 disposed on the transparent conductive film on the front side of the battery cell 100 and a second electrical connection portion 220 extending out of the battery cell 100.

[0059] The first electrical connection portion 210 is attached to the transparent conductive film on the front of the battery for current collection. The second electrical connection portion 220 is electrically connected to the busbar 400 and connected to the second metal mesh 300 of the adjacent battery cell 100 through the busbar 400.

[0060] Optionally, the width H1 of the second electrical connection portion 220 can be 3mm to 5mm. As an example, the width of the second electrical connection portion 220 can be 3mm, 4mm, 4.5mm, or 5mm, etc.

[0061] The busbar 400 can be configured in various ways, including tilted or vertical. As an example, when the second wire mesh 300 does not extend from the back of the other battery cell 100 to between two adjacent battery cells 100 (i.e., excluding the fourth electrical connection portion 320), in order to achieve electrical connection between the first wire mesh 200 and the second wire mesh 300 and to connect adjacent battery cells 100 in series via the busbar 400, the busbar 400 can be tilted below the second electrical connection portion 220, so that one end of the busbar 400 is electrically connected to the second electrical connection portion 220 and the other end is connected to the second wire mesh 300 of the adjacent battery cell 100.

[0062] In one alternative embodiment, such as Figure 4 As shown, the second metal mesh 300 includes a third electrical connection portion 310 corresponding to the transparent conductive film on the back side of the battery cell 100 and a fourth electrical connection portion 320 extending out of the battery cell 100.

[0063] The third electrical connection portion 310 is attached to the transparent conductive film on the back of the battery for current collection. The fourth electrical connection portion 320, extending from the battery cell 100, is electrically connected to the busbar 400 and connected to the first metal mesh 200 of the adjacent battery cell 100 through the busbar 400.

[0064] Optionally, the width H2 of the fourth electrical connection portion 320 can be 3mm to 5mm. As an example, the width of the fourth electrical connection portion 320 can be 3mm, 4mm, 4.5mm, or 5mm, etc.

[0065] The busbar 400 can be configured in various ways, including tilted or vertical. As an example, when the first wire mesh 200 does not extend from the back of another battery cell 100 to between two adjacent battery cells 100 (i.e., excluding the second electrical connection portion 220), in order to achieve electrical connection between the first wire mesh 200 and the second wire mesh 300 and to connect adjacent battery cells 100 in series via the busbar 400, the busbar 400 can be tilted above the fourth electrical connection portion 320, so that one end of the busbar 400 is electrically connected to the fourth electrical connection portion 320 and the other end is connected to the first wire mesh 200 of the adjacent battery cell 100.

[0066] Furthermore, such as Figure 1 and Figure 5 As shown, for the structure of the first metal mesh 200 including the second electrical connection portion 220 and the second metal mesh 300 including the fourth electrical connection portion 320, the second electrical connection portion 220 and the fourth electrical connection portion 320 corresponding to the same battery cell 100 extend in opposite directions; the busbar 400 is located between each two adjacent battery cells 100.

[0067] In this configuration, the first metal mesh 200 located on the front side of the battery cell 100 includes both a first electrical connection portion 210 and a second electrical connection portion 220, while the second metal mesh 300 located on the back side of the battery cell 100 includes both a third electrical connection portion 310 and a fourth electrical connection portion 320. On a plane parallel to the arrangement direction of the battery cells 100 (i.e., a plane parallel to the first metal mesh 200 and the second metal mesh 300), the projected portions of the second electrical connection portion 220 and the fourth electrical connection portion 320 overlap. The projection of the busbar 400 lies within this partially overlapping projection of the second electrical connection portion 220 and the fourth electrical connection portion 320, thus connecting the second electrical connection portion 220 and the fourth electrical connection portion 320.

[0068] In this case, such as Figure 1 As shown, the width of the busbar 400 is less than the distance between adjacent battery cells 100. Preferably, the width H3 of the busbar 400 can be 1mm to 1.5mm. As an example, the width of the busbar 400 can be 1mm, 1.1mm, 1.25mm, 1.4mm, or 1.5mm, etc.

[0069] In one alternative embodiment, such as Figure 5As shown, the aforementioned battery string 1 may further include a carrier film 600 disposed on the side of the first metal mesh 200 and / or the second metal mesh 300 away from the battery cell 100. To better fix the first metal mesh 200 and / or the second metal mesh 300, ensuring close contact between the first metal mesh 200 and / or the second metal mesh 300 and the battery cell 100, and to better achieve current transmission, the carrier film 600, by being disposed on the surface of the battery cell 100, can protect the surface of the battery cell 100, reduce the possibility of scratches on the battery cell 100 during manufacturing, and improve the yield of the battery cell 100.

[0070] As an example, the carrier film 600 may be disposed only on the side of the first wire mesh 200 away from the battery cell 100. In this case, the carrier film 600 is disposed only on the front side of the battery cell 100. As another example, the carrier film 600 may be disposed on the side of the second wire mesh 300 away from the battery cell 100. In this case, the carrier film 600 is disposed only on the back side of the battery cell 100. As yet another example, the carrier film 600 may be disposed on both the side of the first wire mesh 200 away from the battery cell 100 and the side of the second wire mesh 300 away from the battery cell 100. In this case, the carrier film 600 is disposed on both the front and back sides of each battery cell 100, and the carrier film 600 can protect both surfaces of the battery cell 100 simultaneously.

[0071] Optionally, the carrier membrane 600 can be made of thermoplastic or thermosetting materials. Specifically, the carrier membrane 600 can be made of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), or polyolefin (PO), but is not limited to these.

[0072] In one alternative embodiment, such as Figure 6 As shown, the first metal wire mesh 200 includes a plurality of first metal wires 201 parallel to a first direction and a plurality of second metal wires 202 parallel to a second direction, the first metal wires 201 and the second metal wires 202 intersecting to form a mesh structure; the second metal wire mesh 300 includes a plurality of third metal wires 301 parallel to the first direction and a plurality of fourth metal wires 302 parallel to the second direction, the third metal wires 301 and the fourth metal wires 302 intersecting to form a mesh structure; wherein, the first direction is perpendicular to the second direction.

[0073] The first direction can refer to the arrangement direction of the battery cells 100, that is, the extension direction of the main grid when the battery cells 100 are provided with a main grid; the second direction can refer to the direction perpendicular to the arrangement direction of the battery cells 100.

[0074] Furthermore, the first metal wire 201 and the third metal wire 301 can be arranged at equal intervals in the first direction, and the second metal wire 202 and the fourth metal wire 302 can be arranged at equal intervals in the second direction, so that the first metal wire 201 and the second metal wire 202 are evenly distributed in the first electrical connection portion 210, and the third metal wire 301 and the fourth metal wire 302 are evenly distributed in the fourth electrical connection portion 320, thereby better realizing current collection and transmission.

[0075] Furthermore, the second electrical connection portion 220 and the fourth electrical connection portion 320 can transmit current through the busbar 400. Therefore, the second electrical connection portion 220 may not have the second metal wire 202, and the fourth electrical connection portion 320 may not have the fourth metal wire 302. Optionally, the busbar 400 between adjacent battery cells 100 may be parallel to the second direction, so that when viewed from the front of the battery string 1, the busbar 400 is perpendicular to the first metal wire 201 and the third metal wire 301.

[0076] Optionally, the number of first metal wires 201 in each first metal wire mesh 200 can be 30 to 60, and the number of second metal wires 202 can be 70 to 130. As an example, the number of first metal wires 201 can be 30, 45, 50, or 60, etc., and the number of second metal wires 202 can be 70, 85, 100, 110, or 130, etc.

[0077] In each second wire mesh 300, the number of third wires 301 can be 30 to 60, and the number of fourth wires 302 can be 70 to 130. As an example, the number of third wires 301 can be 30, 45, 55, or 60, etc., and the number of fourth wires 302 can be 70, 87, 100, 112, or 130, etc.

[0078] The diameters of the first metal wire 201, the second metal wire 202, the third metal wire 301, and the fourth metal wire 302 can be 0.5 μm to 5 μm. For example, the diameters of the first metal wire 201, the second metal wire 202, the third metal wire 301, and the fourth metal wire 302 can be 0.5 μm, 1.0 μm, 2.5 μm, 3.5 μm, or 5 μm, etc.

[0079] It should be noted that the second metal wire mesh 300 has a basically the same structure as the first metal wire mesh 200, the only difference being that the fourth electrical connection portion 320 of the second metal wire mesh 300 extends in the opposite direction to the second electrical connection portion 220 of the first metal wire mesh 200.

[0080] In one alternative embodiment, such as Figure 3 and Figure 4 As shown, conductive adhesive layers 500 are spaced apart on the surfaces of the first metal wire 201, the second metal wire 202, the third metal wire 301, and the fourth metal wire 302. The conductive adhesive layers 500 are made of a material with both adhesive and conductive properties, and can fix the metal mesh to the surface of the battery cell 100 to facilitate electrical connection between the metal mesh and the TCO film on the surface of the battery cell 100.

[0081] Optionally, the conductive adhesive layer 500 can be prepared by using a conductive adhesive material or a conductive coating. The conductive adhesive material can be a conductive glue, and the conductive coating can be a polyamide-based wire coating, but is not limited to these.

[0082] Furthermore, a small amount of silver particles can be added to the wire coating to improve its conductivity. The volume percentage of silver particles in the wire coating is typically 8% to 12%. For example, the volume percentage of silver particles in the wire coating can be 8%, 9%, 10%, 11%, or 12%, etc.

[0083] By using materials with adhesive and conductive properties to prepare a conductive adhesive layer 500, on the one hand, the metal mesh can be firmly fixed to the surface of the battery cell 100 to prevent the metal mesh from moving; on the other hand, the conductive adhesive layer 500 can also enhance the electrical conductivity of the TCO film and the metal mesh, and improve the current transmission efficiency.

[0084] According to the battery string 1 of this utility model embodiment, by laying a first metal wire mesh 200 on the front side of the battery cell 100 with a transparent conductive film and laying a second metal wire mesh 300 on the back side, the first metal wire mesh 200 and the second metal wire mesh 300 are electrically connected to the transparent conductive film. There is no need to set grid lines and solder ribbons on the surface of the battery cell 100 to collect and transmit current, thereby reducing the cost of metal paste.

[0085] By using a busbar 400 to connect the first metal wire mesh 200 of one battery cell 100 and the second metal wire mesh 300 of the other battery cell 100, the battery cells 100 are connected in series to form a battery string 1. This avoids the bending of the metal wire mesh located in the middle of the two battery cells 100 caused by connecting two adjacent battery cells 100 with the same metal wire mesh, thus solving the problem of excessive stress in this part reducing the reliability of the battery string 1 and improving the structural stability of the battery string 1.

[0086] Furthermore, the first metal mesh 200 includes a first metal wire 201 parallel to a first direction and a second metal wire 202 parallel to a second direction, and the second metal mesh 300 includes a third metal wire 301 parallel to the first direction and a fourth metal wire 302 parallel to the second direction. This arrangement ensures that the first and second metal wires 201 and 202 extend in mutually perpendicular directions, and the third and fourth metal wires 301 and 302 also extend in mutually perpendicular directions. The first and second metal meshes 200 and 300 form a mesh structure, improving current collection and transmission capabilities. The surface of the battery cell 100 does not require either a main grid or a fine grid, solving the problem of aligning the metal mesh with the fine grid during the battery string 1 fabrication process. Moreover, the mesh structure of the first and second metal meshes 200 and 300 allows the probe to connect with the metal meshes extending in different directions during IV testing of the battery cell 100, solving the problem that battery cells 100 without grid lines cannot pass IV testing for battery sorting.

[0087] like Figure 7 As shown, one aspect of this utility model embodiment provides a photovoltaic module, including a battery string 1 according to this utility model embodiment.

[0088] In an optional embodiment, the photovoltaic module may further include a front encapsulating film 2 laid on the front side of the battery string 1, a rear encapsulating film 3 laid on the back side of the battery string 1, a panel material 4 located on the side of the front encapsulating film 2 away from the battery string 1, and a backsheet material 5 located on the side of the rear encapsulating film 3 away from the battery string 1.

[0089] Specifically, the photovoltaic module, facing away from sunlight when it is working, includes, in sequence: panel material 4, front encapsulating film 2, battery string 1, rear encapsulating film 3, and backsheet material 5.

[0090] According to the photovoltaic module of this utility model embodiment, by using a battery string 1 with a first metal wire mesh 200 and a second metal wire mesh 300 laid on it and electrically connected to a transparent conductive film, current can be collected and transmitted without setting grid lines and solder strips on the surface of the battery cell 100, thereby reducing the cost of metal paste for manufacturing photovoltaic modules.

[0091] In the battery string 1, a busbar 400 connects the first metal mesh 200 of one battery cell 100 and the second metal mesh 300 of the other battery cell 100. This avoids the bending of the metal mesh located between the two battery cells 100 due to connecting them with the same metal mesh, thus solving the problem of excessive stress in this area reducing the reliability of the photovoltaic module and improving the structural stability of the photovoltaic module. At the same time, it eliminates the need to align the first metal mesh 200 of one battery cell 100 and the second metal mesh 300 of the other battery cell 100, reducing the precision requirements during the fabrication of the battery string 1.

[0092] Furthermore, the first metal mesh 200 includes a first metal wire 201 parallel to a first direction and a second metal wire 202 parallel to a second direction, and the second metal mesh 300 includes a third metal wire 301 parallel to the first direction and a fourth metal wire 302 parallel to the second direction. This arrangement ensures that the first and second metal wires 201 and 202 extend in mutually perpendicular directions, and the third and fourth metal wires 301 and 302 also extend in mutually perpendicular directions. The first and second metal meshes 200 form a mesh structure, improving current collection and transmission capabilities. The surface of the solar cell 100 does not require either a main grid or a fine grid, solving the problem of aligning the metal mesh with the fine grid during the fabrication of the solar cell string 1. Moreover, the mesh structure of the first and second metal meshes 200 allows the probe to connect with the metal meshes extending in different directions during IV testing of the solar cell 100. This solves the problem that solar cells 100 without grid lines cannot pass IV testing for cell sorting, improving the yield rate of photovoltaic modules.

[0093] like Figure 8 As shown, another aspect of this utility model embodiment provides a method for preparing a battery string 1, comprising:

[0094] Step A1: Lay the battery cell 100 on the second metal wire mesh 300 so that the back of the battery cell 100 contacts the second metal wire mesh 300.

[0095] The battery cell 100 has a transparent conductive film on both the front and back sides, but no grid lines are provided.

[0096] Step A2: Lay a first metal wire mesh 200 on the front side of the aforementioned battery cell 100;

[0097] Step A3: Press and cure the battery cell 100 on which the first metal wire mesh 200 and the second metal wire mesh 300 are laid;

[0098] Step A4: Test and screen the cured solar cells;

[0099] Specifically, the cured solar cells undergo IV testing. Based on the obtained current-voltage characteristic curves, their performance is evaluated, and they are categorized into different grades according to performance parameters. Then, electroluminescent (EL) testing is performed on the solar cells of different grades. Solar cells that have passed the EL test are screened, and defective cells are discarded.

[0100] Step A5: For adjacent screened battery cells, a busbar 400 is electrically connected to the second electrical connection portion 220 of the first metal mesh 200 of one of the screened battery cells, and electrically connected to the fourth electrical connection portion 320 of the second metal mesh 300 of the other screened battery cell.

[0101] In an optional embodiment, prior to step A1, the method further includes:

[0102] Step A0: Lay the release film 6 and the carrier film 600 together to form a laminated film layer, and lay the second metal wire mesh 300 on the laminated film layer.

[0103] Step A2 further includes: laying the first metal wire mesh 200 on the laminated film layer.

[0104] For the battery string 1 including the carrier film 600, the carrier film 600 can be provided on both the front and back sides of each battery cell 100. To prevent the carrier film 600 from shrinking during subsequent fabrication and causing the edges of the battery cell 100 to be exposed, a release film 6 with a certain rigidity can be laminated on the side of the carrier film 600 away from the battery cell 100. The release film 6 can also assist in pressing, making the pressing effect of the carrier film 600, the metal mesh, and the battery cell 100 better.

[0105] The release film 6 can be made of polypropylene (PP) or polyethylene terephthalate (PET), but is not limited to these.

[0106] Specifically, step A0 may include: stacking the release film 6 and the carrier film 600 to form a laminated film layer. If the size of the laminated film layer is inconsistent with the size of the solar cell 100, the laminated film layer can be cut to make its size the same as that of the solar cell 100. Then, the second metal mesh 300 is laid on the cut laminated film layer. Then, step A1 is performed.

[0107] Step A2 may include: when laying the first metal wire mesh 200, the first metal wire mesh 200 may be laid on the laminated film layer first, flipped over, and then laid on the front side of the battery cell 100, so that the first metal wire mesh 200 is electrically connected to the transparent conductive film on the front side of the battery cell 100.

[0108] Furthermore, for a battery cell with stacked film layers, step A3 above also includes: after the pressing and curing is completed, removing the release film 6 disposed on the front and back sides of the battery cell.

[0109] Specifically, step A3 includes: placing the battery cell with the laminated film layer on the tray platform 10 to ensure uniform force on its back side and prevent cracking. A pressure mold 7 is placed on the front side of the battery cell with the laminated film layer, and the pressure mold 7 is used to press and fix the laminated film layer, the first metal mesh 200, the battery cell 100, the second metal mesh 300, and the laminated film layer. After pressing and fixing, the material with the pressed and fixed material is sent to the curing oven 8 for curing. After curing, the pressure mold 7 on the front side of the battery cell 100 is removed, and the release film 6 on the front side of the battery cell 100 is removed along with the pressure mold 7. The tray platform 10 on the back side of the battery cell 100 is removed, and the release film 6 on the back side of the battery cell 100 is removed along with the tray platform 10.

[0110] It should be noted that in step A0, the formed laminated film can be placed directly on the tray platform 10, and then the second metal wire mesh 300 can be laid on the laminated film, so that the laying of the battery cell 100, the laying of the first metal wire mesh 200 with the laminated film, and the placement of the press 7 are all carried out on the tray platform 10.

[0111] Optionally, during the curing process, the length of the curing oven 8 can be 3m to 5m; the curing temperature can vary with the melting point of the carrier film 600, generally ranging from 100℃ to 140℃; and the curing time can be approximately 20 seconds. As an example, the length of the curing oven 8 can be 3m, 3.5m, 4m, or 5m, etc.; and the curing temperature can be 100℃, 110℃, 120℃, 130℃, or 140℃, etc.

[0112] In an optional embodiment, the method further includes: printing conductive adhesive material at intervals onto each wire of the metal mesh to form a conductive adhesive layer 500.

[0113] In order to better fix the metal mesh to the surface of the battery cell 100, conductive adhesive material can be printed on each metal wire of the metal mesh at intervals in steps A0 and A2 to form a conductive adhesive layer 500.

[0114] Specifically, step A0 may further include: after the second metal mesh 300 is laid on the laminated film layer, conductive adhesive material can be printed at equal intervals on each metal wire (third metal wire 301 and fourth metal wire 302) of the second metal mesh 300 by screen printing, and conductive adhesive layers 500 are formed at intervals on the surface of each metal wire. When the battery cell 100 is laid on the second metal mesh 300, the second metal mesh 300 can be initially fixed to the back of the battery cell 100 by the adhesiveness of the conductive adhesive layer 500.

[0115] Step A2 may further include: after laying the first metal mesh 200 on the above-mentioned laminated film layer, before laying the first metal mesh 200 with the laminated film layer on the front side of the battery cell 100, conductive adhesive material can be printed at equal intervals on each metal wire (first metal wire 201 and second metal wire 202) of the first metal mesh 200 by screen printing, and conductive adhesive layer 500 is formed at intervals on the surface of each metal wire. When the first metal mesh 200 with the laminated film layer is laid on the front side of the battery cell 100, the first metal mesh 200 can be initially fixed to the back side of the battery cell 100 by the adhesiveness of the conductive adhesive layer 500.

[0116] Optionally, the printing width of the conductive adhesive material can be adjusted according to the wire diameter of the metal mesh. Each metal wire includes several segments of conductive adhesive layer 500, wherein the length of each segment of conductive adhesive layer 500 can be 2mm to 3mm. As an example, the length of each segment of conductive adhesive layer 500 can be 2mm, 2.5mm, or 3mm, etc.

[0117] Furthermore, when printing conductive adhesive materials, the printing position can be better determined by positioning the edges of the stacked film layers, which further reduces the precision requirements for the fabrication of the battery string 1.

[0118] After pressing and curing, the curing temperature enhances the adhesion of the conductive adhesive layer 500, firmly bonding the second metal mesh 300, the first metal mesh 200, and the battery cell 100. This improves the current collection capacity of the metal mesh, reduces contact resistance, and facilitates subsequent testing and screening of the battery cell 100.

[0119] In an optional embodiment, the above method further includes:

[0120] Conductive coating is sprayed intermittently onto each wire of the aforementioned metal mesh to form a conductive coating.

[0121] To better fix the metal mesh to the surface of the battery cell 100, conductive coating can be sprayed onto each metal wire of the metal mesh at intervals before step A0 to form a conductive adhesive layer 500.

[0122] Specifically, before step A0, the first metal wire 201 and the second metal wire 202 need to be crossed and fixed to form a first metal wire mesh 200, and the third metal wire 301 and the fourth metal wire 302 need to be crossed and fixed to form a second metal wire mesh 300. After the first metal wire mesh 200 and the second metal wire mesh 300 are prepared, a conductive coating is sprayed at equal intervals onto each metal wire of the first metal wire mesh 200 and the second metal wire mesh 300 using a spraying process to form a conductive adhesive layer 500. The first metal wire 201 and the second metal wire 202 are arranged vertically, as are the third metal wire 301 and the fourth metal wire 302.

[0123] After pressing and curing, the curing temperature enhances the adhesion of the conductive adhesive layer 500, firmly bonding the second metal mesh 300, the first metal mesh 200, and the battery cell 100. This improves the current collection capacity of the metal mesh, reduces contact resistance, and facilitates subsequent testing and screening of the battery cell 100.

[0124] Compared to printing conductive adhesive material onto the surface of a metal mesh, spraying conductive coating can simplify the preparation process of the battery string 1, and the spraying method can reduce the amount of material used, save costs, and form a more uniform conductive adhesive layer 500.

[0125] The preparation method of battery string 1 is further illustrated below through a specific embodiment:

[0126] like Figure 9 As shown, the method for preparing the battery string 1 in this embodiment of the present invention includes steps B1 to B10:

[0127] Step B1: A first metal wire mesh 200 is prepared by crossing a plurality of first metal wires 201 parallel to the first direction and a plurality of second metal wires 202 parallel to the second direction to form a mesh structure; a second metal wire mesh 300 is prepared by crossing a plurality of third metal wires 301 parallel to the first direction and a plurality of fourth metal wires 302 parallel to the second direction to form a mesh structure.

[0128] Step B2: Using a spraying process, conductive coating is sprayed at equal intervals onto each metal wire of the first metal wire mesh 200 and the second metal wire mesh 300, forming a conductive adhesive layer 500 on the surface of each metal wire of the first metal wire mesh 200 and the second metal wire mesh 300.

[0129] Step B3: Lay the release film 6 and the carrier film 600 together to form a laminated film layer, and cut the laminated film layer according to the size of the battery cell 100 so that its size is the same as that of the battery cell 100.

[0130] Step B4, as follows Figure 10As shown, the second wire mesh 300 is laid on the cut laminated film layer; the first wire mesh 200 is laid on the cut laminated film layer.

[0131] Step B5, as follows Figure 11 As shown, a second metal wire mesh 300 with a laminated film layer is placed on a tray platform 10, and a battery cell 100 is laid on the second metal wire mesh 300 with a laminated film layer so that the back of the battery cell 100 contacts the second metal wire mesh 300.

[0132] The battery cell 100 has a transparent conductive film on both the front and back sides, but no grid lines are provided.

[0133] Step B6: Lay a first metal wire mesh 200 with stacked film layers on the front side of the battery cell 100;

[0134] Step B7, as follows Figure 12 As shown, the press 7 is placed on the front side of the battery cell 100 with the laminated film layer, and the laminated film layer, the first metal mesh 200, the battery cell 100, the second metal mesh 300, and the laminated film layer are pressed and fixed by the press 7.

[0135] Step B8: After pressing and fixing, place the battery string semi-finished product pressed by the press 7 into the conveying device of the curing oven 8 and send it into the curing oven 8 for curing.

[0136] Specifically, the transmission device can be a roller 9 or a transmission belt 11. For example... Figure 13 As shown, when the conveying device is roller 9, the tray platform 10 containing the battery string semi-finished product pressed by the pressure mold 7 can be placed on roller 9. Through the rotation of roller 9, the battery string semi-finished product pressed by the pressure mold 7 is fed into curing oven 8; as shown... Figure 14 As shown, when the transmission device is the transmission belt 11, the battery string semi-finished product pressed by the press 7 can be directly placed on the transmission belt 11, so that the release film 6 on the back of the battery cell 100 directly contacts the transmission belt 11.

[0137] After curing, when the conveying device is a roller 9, the pressure 7 on the front of the battery cell 100 is removed, and the release film 6 on the front of the battery cell 100 is removed along with the pressure 7. The tray platform 10 on the back of the battery cell 100 is removed, and the release film 6 on the back of the battery cell 100 is removed along with the tray platform 10. When the conveying device is a conveyor belt 11, the pressure 7 on the front of the battery cell 100 is removed, and the release film 6 on the front of the battery cell 100 is removed along with the pressure 7. The battery cell 100 is then removed from the conveyor belt 11, and the release film 6 on the back of the battery cell 100 is adsorbed by the conveyor belt 11 and thus removed.

[0138] Step B9: Perform IV testing, sorting, EL testing and screening on the cured solar cells to remove defective solar cells;

[0139] Step B10: Arrange the screened battery cells along the first direction. For adjacent screened battery cells, use a busbar 400 to electrically connect the second electrical connection portion 220 of the first metal wire mesh 200 of one of the screened battery cells, and electrically connect the second metal wire mesh 300 of the other screened battery cell to obtain battery string 1.

[0140] According to the method for preparing the battery string 1 according to the present invention, by laying a first metal mesh 200 having a first metal wire 201 and a second metal wire 202 extending in different directions and a second metal mesh 300 having a third metal wire 301 and a fourth metal wire 302 extending in different directions on the battery cell 100, IV testing can be performed by the metal mesh even when no grid lines are provided on the surface of the battery cell 100, and there is no need to align the metal mesh with the grid lines when laying the metal mesh.

[0141] In addition, by covering the carrier film 600 with a rigid release film 6, the shrinkage of the carrier film 600 during the curing process can be prevented, thus avoiding the problem of battery edge exposure and reducing the possibility of battery scratches.

[0142] According to another aspect of the present invention, a method for preparing a photovoltaic module is provided, comprising: preparing a battery string 1; after preparing the battery string 1, sequentially stacking a panel material 4, a front adhesive film 2, a battery string 1, a back adhesive film 3 and a backsheet material 5, and performing lamination, framing, curing, cleaning, etc., to prepare the photovoltaic module of the present invention.

[0143] The battery string 1 is prepared using the method described in this embodiment of the invention, which will not be repeated here.

[0144] According to the photovoltaic module manufacturing method of this utility model embodiment, by laying a first metal mesh 200 having a first metal wire 201 and a second metal wire 202 extending in different directions and a second metal mesh 300 having a third metal wire 301 and a fourth metal wire 302 extending in different directions on the cell 100, IV testing can be performed through the metal mesh even when no grid lines are provided on the surface of the cell 100, and there is no need to align the metal mesh with the grid lines when laying the metal mesh.

[0145] In addition, by covering the carrier film 600 with a rigid release film 6, the shrinkage of the carrier film 600 during the curing process can be prevented, thus avoiding the problem of battery edge exposure and reducing the possibility of battery scratches.

[0146] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A battery string, characterized in that, include: A plurality of battery cells (100), wherein a transparent conductive film is provided on both the front and back sides of the battery cells (100); A first metal mesh (200) is laid on the front side of each of the battery cells (100) and electrically connected to the transparent conductive film on the front side of the battery cells (100). A second metal wire mesh (300) is laid on the back of each of the battery cells (100) and electrically connected to the back of the battery cells (100). and several busbars (400); for each two adjacent battery cells (100), a first metal mesh (200) on one battery cell (100) and a second metal mesh (300) on the other adjacent battery cell (100) are electrically connected to the same busbar (400) to connect several battery cells (100) in series.

2. The battery string according to claim 1, characterized in that, The first metal mesh (200) includes: a first electrical connection portion (210) disposed corresponding to the transparent conductive film on the front side of the battery cell (100) and a second electrical connection portion (220) extending out of the battery cell (100). The second electrical connection portion (220) is electrically connected to the busbar (400).

3. The battery string according to claim 1 or 2, characterized in that, The second metal mesh (300) includes a third electrical connection portion (310) disposed corresponding to the transparent conductive film on the back side of the battery cell (100) and a fourth electrical connection portion (320) extending out of the battery cell (100). The fourth electrical connection portion (320) of the battery cell (100) is electrically connected to the busbar (400).

4. The battery string according to claim 3, characterized in that, Regarding the structure where the first metal wire mesh (200) includes a second electrical connection portion (220) and the second metal wire mesh (300) includes the fourth electrical connection portion (320), The second electrical connection portion (220) and the fourth electrical connection portion (320) corresponding to the same battery cell (100) extend in opposite directions; The busbar (400) is located between each two adjacent battery cells (100).

5. The battery string according to claim 1, characterized in that, Also includes: A carrier film (600) is disposed on the side of the first metal wire mesh (200) and / or the second metal wire mesh (300) away from the battery cell (100).

6. The battery string according to claim 1, characterized in that, The first metal wire mesh (200) includes a plurality of first metal wires (201) parallel to a first direction and a plurality of second metal wires (202) parallel to a second direction, wherein the first metal wires (201) and the second metal wires (202) intersect to form a mesh structure; The second metal wire mesh (300) includes a plurality of third metal wires (301) parallel to the first direction and a plurality of fourth metal wires (302) parallel to the second direction, wherein the third metal wires (301) and the fourth metal wires (302) intersect to form a mesh structure; Wherein, the first direction is perpendicular to the second direction.

7. The battery string according to claim 6, characterized in that, Conductive adhesive layers (500) are provided at intervals on the surfaces of the first metal wire (201), the second metal wire (202), the third metal wire (301), and the fourth metal wire (302). And / or, The first direction is parallel to the arrangement direction of the battery cells (100); The number of the first metal wire (201) and the third metal wire (301) is 30 to 60. The number of the second metal wire (202) and the fourth metal wire (302) is 70 to 130. And / or, The diameters of the first metal wire (201), the second metal wire (202), the third metal wire (301), and the fourth metal wire (302) are 0.5μm to 5μm.

8. The battery string according to claim 1 or 2, characterized in that, When the first metal wire mesh (200) includes a second electrical connection portion (220), the width of the second electrical connection portion (220) is 3mm to 5mm; And / or, The width of the busbar (400) is 1mm to 1.5mm.

9. The battery string according to claim 3, characterized in that, The width of the fourth electrical connection portion (320) is 3mm to 5mm.

10. A photovoltaic module, characterized in that, Includes the battery string (1) as described in any one of claims 1-9.

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