Battery string and photovoltaic module

Abstract

The utility model relates to the field of photovoltaic technology, in particular to a battery string and a photovoltaic module, and the battery string comprises at least two battery pieces which are welded in sequence. A plurality of grid line units arranged on the battery piece, wherein each grid line unit comprises a grid line and a barrier layer arranged on the grid line; the plurality of metal connecting strips are connected between two adjacent battery pieces, and each metal connecting strip comprises a metal wire and a metal solder layer wrapping the metal wire; the metal connecting strips are respectively connected to the barrier layer of any grid line unit of the first battery piece and the barrier layer of the corresponding grid line unit of the second battery piece in two adjacent battery pieces through the metal solder layers; through the mode, the blocking layer stacked on the grid line can block heat transferred to the grid line in the series welding process of the battery piece, so that metal migration in the grid line is avoided, and the grid breaking phenomenon occurring in the series welding process of the battery piece is reduced; and meanwhile, the series welding temperature of the battery pieces can be improved, the series welding quality of the battery pieces can be improved, and the hot spot risk in the operation process of the photovoltaic module is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaics, and particularly to a battery string and a photovoltaic module. Background Art

[0002] At present, photovoltaic modules can convert the thermal radiation energy of the sun into electrical energy through the photovoltaic effect or the photochemical effect, and are applied to daily life and industrial production. The series soldering of solar cells is one of the important links in the production of photovoltaic modules. The solder ribbon is welded to the grid lines formed on the surface of the solar cells at a certain temperature by a series soldering machine to obtain a battery string. In the series soldering process of solar cells, due to the increase in temperature, the metal in the grid lines migrates to the tin-containing metal layer on the surface of the solder ribbon. For example, the "silver etching" phenomenon occurs when silver in the grid lines migrates to the tin-containing metal layer on the surface of the solder ribbon, resulting in broken grids. Especially when there are no PAD points on the surface of the solar cells and the grid lines are relatively thin, the broken grid phenomenon is more serious. In the background art, in order to reduce broken grids, the soldering temperature is reduced, but the broken grid phenomenon still cannot be avoided. Moreover, during long-term outdoor operation, the photovoltaic modules manufactured by low-temperature soldering have a high risk of hot spots. When the ambient temperature rises, the metal in the grid lines migrates to the tin-containing metal layer on the surface of the solder ribbon and the tin on the surface of the solder ribbon migrates to the grid lines, resulting in broken grids; when the ambient temperature continues to rise, the tin-containing metal layer on the surface of the solder ribbon may melt. Summary of the Utility Model

[0003] In view of the above problems, the embodiments of the present application provide a battery string and a photovoltaic module to solve the technical problems of broken grids caused by the metal migration in the grid lines and the risk of hot spots.

[0004] In a first aspect, the embodiments of the present application provide a battery string, including:

[0005] At least two sequentially welded solar cells;

[0006] A plurality of grid line units provided on the solar cells, the grid line units including grid lines provided on the solar cells and barrier layers provided on the grid lines; and

[0007] A plurality of metal connection bars connecting adjacent two of the solar cells, the metal connection bars including metal wires and metal solder layers covering the metal wires, and the metal connection bars are respectively connected to the barrier layers of one of the grid line units of the first solar cell and the barrier layers of one of the grid line units of the second solar cell among adjacent two solar cells through the metal solder layers.

[0008] Optionally, the melting point of the barrier layer is higher than the melting point of the metal solder layer.

[0009] Optionally, the projection of the metal solder layer on the cell along the thickness direction of the cell is located within the projection of the barrier layer on the cell along the thickness direction of the cell.

[0010] Optionally, the barrier layer includes a main body portion laminated on the grid line and two side portions extending from both ends in the width direction of the main body portion away from the main body portion respectively, and the main body portion and the two side portions are respectively in contact with the metal solder layer.

[0011] Optionally, the plurality of grid line units include a plurality of positive grid line units and a plurality of negative grid line units, and the metal connection strips are respectively connected to any one of the positive grid line units of the first cell and the corresponding negative grid line unit of the second cell among two adjacent cells.

[0012] Optionally, the plurality of positive grid line units are arranged on the first surface of the cell, the plurality of negative grid line units are arranged on the second surface of the cell, and the first surface and the second surface are oppositely arranged.

[0013] Optionally, the thickness of the barrier layer is 2 μm to 50 μm.

[0014] Optionally, the width of the barrier layer is 30 μm to 200 μm.

[0015] Optionally, the grid line is a main grid line or a sub-grid line.

[0016] In a second aspect, an embodiment of the present application provides a photovoltaic module, including the above-mentioned battery string.

[0017] The battery string and the photovoltaic module provided by the embodiments of the present application include at least two cells welded in sequence; a plurality of grid line units arranged on the cells, the grid line units including grid lines arranged on the cells and barrier layers arranged on the grid lines; and a plurality of metal connection strips connecting two adjacent cells, the metal connection strips including metal wires and metal solder layers coated on the metal wires, and the metal connection strips are respectively connected to the barrier layers of any one of the grid line units of the first cell and the corresponding grid line units of the second cell among two adjacent cells through the metal solder layers; in the above manner, the barrier layer laminated on the grid line can block the heat transferred to the grid line during the series welding process of the cells, thereby avoiding metal migration in the grid line and reducing the phenomenon of broken grid lines during the series welding process of the cells; at the same time, it is beneficial to increase the series welding temperature of the cells, improve the series welding quality of the cells, and reduce the hot spot risk during the operation of the photovoltaic module.

[0018] These aspects or other aspects of the present application will be more clearly understood in the following description of the embodiments. Description of the Drawings

[0019] Figure 1 It shows a schematic structural diagram of a battery string provided by an embodiment of the present application.

[0020] Figure 2 It is Figure 1 a schematic cross-sectional view along the A-A direction in

[0021] Figure 3 It is Figure 1 a schematic cross-sectional view along the B-B direction in

[0022] Figure 4 It shows a schematic fitting diagram of the cell and the metal connecting bar before welding in the battery string provided by an embodiment of the present application.

[0023] Figure 5 It shows a schematic fitting diagram of the barrier layer and the metal connecting bar in the battery string provided by an embodiment of the present application.

[0024] Figure 6 It shows a schematic fitting diagram of the barrier layer and the metal connecting bar in the battery string provided by an embodiment of the present application.

[0025] Figure 7 It shows a schematic structural diagram of a battery string provided by an embodiment of the present application.

[0026] Figure 8 It shows a schematic partial structural diagram of a photovoltaic module provided by an embodiment of the present application.

[0027] Figure 9 It shows a schematic structural diagram of a photovoltaic module provided by an embodiment of the present application.

[0028] The meanings of the reference numerals in the drawings are as follows:

[0029] 100 - battery string; 10 - cell; 11 - first surface; 12 - second surface; 20 - grid line unit; 21 - grid line; 22 - barrier layer; 20a - positive grid line unit; 20b - negative grid line unit; 30 - metal connecting bar; 31 - metal wire; 32 - metal welding layer; 301 - first section; 302 - second section; 303 - connecting section; 41 - first panel; 42 - second panel; 51 - first adhesive film; 52 - second adhesive film; 60 - battery pack; 70 - frame. Detailed Embodiments

[0030] The following details the embodiments of the present application. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application.

[0031] To enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope protected by this application.

[0032] In the embodiments of this application, it should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0033] Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0034] In the description of the embodiments of this application, words such as "example" or "for example" are used to indicate examples, explanations or descriptions. Any embodiment or design described as "for example" or "example" in the embodiments of this application is not construed as being more preferred or having more advantages than another embodiment or design. The use of words such as "example" or "for example" is intended to present relative concepts in a clear manner.

[0035] In addition, "a plurality of" in the embodiments of this application means two or more. In view of this, "a plurality of" in the embodiments of this application can also be understood as "at least two". "At least one" can be understood as one or more, for example, understood as one, two or more. For example, including at least one means including one, two or more, and does not limit which ones are included. For example, including at least one of A, B and C, then what can be included are A, B, C, A and B, A and C, B and C, or A and B and C.

[0036] It should be noted that in the embodiments of this application, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / ", unless otherwise specified, generally represents an "or" relationship between the front and back associated objects.

[0037] An embodiment of the present application provides a battery string 100. Please refer to Figures 1 to 3 As shown, the battery string 100 includes battery cells 10, grid line units 20, and metal connection bars 30.

[0038] Among them, at least two battery cells 10 are provided, and the at least two battery cells 10 are welded in sequence.

[0039] Among them, the grid line units 20 are arranged on the battery cells 10. Multiple grid line units 20 can be arranged on each battery cell 10. The grid line unit 20 includes grid lines 21 arranged on the battery cell 10 and a barrier layer 22 arranged on the grid lines 21.

[0040] Among them, the metal connection bar 30 includes a metal wire 31 and a metal solder layer 32 coated on the metal wire 31. Two adjacent battery cells 10 are electrically connected through multiple metal connection bars 30. The metal connection bar 30 connects one grid line unit 20 of the first battery cell 10 among two adjacent battery cells 10 to one grid line unit 20 of the second battery cell 10. The metal connection bar 30 is welded to the barrier layer 22 of the two grid line units 20 through the metal solder layer 32 respectively. Since the barrier layer 22 and the metal solder layer 32 are respectively conductive, the electrical connection of two adjacent battery cells 10 can be realized by welding the metal solder layer 32 to the barrier layer 22.

[0041] In this embodiment, the barrier layer laminated on the grid lines can block the heat transferred to the grid lines during the series soldering process of the battery cells, thereby avoiding the metal migration in the grid lines and reducing the phenomenon of broken grid lines during the series soldering process of the battery cells; at the same time, it is beneficial to increase the series soldering temperature of the battery cells, improve the series soldering quality of the battery cells, and reduce the hot spot risk during the operation of the photovoltaic module.

[0042] The setting method of the grid line unit in this embodiment can be applied to all battery string structures with grid lines. For example, it can be adapted to TOPCon (Tunnel Oxide Passivated Contact) batteries, HJT (Heterojunction with Intrinsic Thin-film) batteries, and IBC (Interdigitated Back Contact) batteries in the background technology.

[0043] As an implementation manner, the grid lines 21 can be main grid lines. The increase in the number of main grid lines can reduce the resistance of the battery string. The distance between adjacent main grid lines is shortened, the current conduction path is shortened, and the current conduction loss is reduced.

[0044] As an implementation manner, the battery string can be a battery string without a main grid, and the grid line 21 can be a sub-grid line. The adoption of the main-grid-free design can extend the battery life. Moreover, since the sub-grid line is generally a fine grid line, the setting of the barrier layer can reduce the welding difficulty of the sub-grid line and improve the welding quality of the battery string.

[0045] As an implementation manner, the battery cell 10 can be a whole battery cell.

[0046] As an implementation manner, the battery cell 10 can be a half battery cell. For example, the half battery cell can be prepared by cutting a single crystal silicon, which can reduce material waste and thus reduce the manufacturing cost.

[0047] As an implementation manner, the battery cell 10 can be a battery cell of any size. For example, the battery cell can also be prepared by cutting a single crystal silicon into any size, which can reduce material waste and thus reduce the manufacturing cost.

[0048] As an implementation manner, the barrier layer 22 can be a tin-containing metal layer, a silver-containing metal layer, a lead-containing metal layer or a copper-containing metal layer. Exemplarily, the barrier layer 22 can be one of the tin-based solder, lead-based solder and bismuth-based solder in the prior art. For example, the barrier layer 22 can be a tin-based solder and the barrier layer 22 further includes at least one element of lead (Pb), copper (Cu), and silver (Ag).

[0049] As an implementation manner, the metal wire 31 can be a copper wire, a silver wire, an aluminum wire or an alloy wire containing at least two of copper, silver and aluminum.

[0050] As an implementation manner, the diameter of the metal wire can be 0.15 - 0.40 mm.

[0051] As an implementation manner, the metal solder layer 32 is a tin alloy layer, a lead alloy layer or a bismuth alloy layer. Exemplarily, the metal solder layer 32 can be one of the tin-based solder, lead-based solder and bismuth-based solder in the prior art. For example, the metal solder layer 32 can be a tin-based solder and the metal solder layer 32 further includes at least one element of lead (Pb) and bismuth (Bi).

[0052] As an implementation manner, the thickness of the barrier layer 22 can be 2 μm - 50 μm.

[0053] As an implementation manner, the width of the barrier layer 22 can be 30 μm - 200 μm.

[0054] As an implementation, the melting point of the barrier layer 22 is higher than that of the metal solder layer 32. During the series welding process of the battery cells, the welding temperature can be greater than the melting point of the metal solder layer 32 and less than the melting point of the barrier layer 22. The metal solder layer 32 melts, while the barrier layer 22 does not melt, which can further improve the welding effect and enhance the stability during operation. During the series welding process of the battery cells, the elements at the contact interface between the barrier layer 22 and the metal solder layer 32 can migrate to each other, causing the metal components of the metal solder layer 32 to change, which is beneficial to increasing the melting point of the metal solder layer 32 and further improving the hot spot risk brought by the metal solder layer 32 during operation. Exemplarily, the barrier layer 22 is a high-temperature tin-based solder layer, and the metal solder layer 32 is a low-temperature tin-based solder layer. The barrier layer 22 and the metal solder layer 32 are respectively tin-containing alloy layers. The elements at the contact interface between the low-temperature tin-based solder layer and the high-temperature tin-based solder layer migrate to each other, causing the components of each solder layer to change, and the melting point temperature of the low-temperature tin-based solder layer increases.

[0055] In some implementations, the melting point of the barrier layer 22 can be 200 - 260 °C.

[0056] In some implementations, the melting point of the metal solder layer 32 can be 130 - 180 °C.

[0057] As an implementation, please refer to Figure 4 As shown, before welding, the cross-section of the metal connecting bar 30 is circular, and the thickness h of the metal solder layer 32 can be 0.01 - 0.05 mm. During the series welding process, the metal solder layer 32 melts and forms a shape such as Figure 3 shown.

[0058] As an implementation, please refer to Figure 5 As shown, the projection of the metal solder layer 32 on the battery cell 10 along the thickness direction S1 of the battery cell 10 is located within the projection of the barrier layer 22 on the battery cell 10 along the thickness direction S1 of the battery cell 10. In this implementation, the projected area of the barrier layer 22 is larger than that of the metal solder layer 32, which can further prevent the melted metal solder layer 32 from contacting the grid line 21 during the series welding process of the battery cells and improve the welding effect.

[0059] In some implementations, please refer to Figure 6 As shown, the barrier layer 22 includes a main body portion 211 laminated on the grid line 21 and two side portions 212. The two side portions 212 extend away from the main body portion 211 respectively from both ends in the width direction of the main body portion 211. The main body portion 211 and the two side portions 212 are respectively in contact with the metal solder layer 32. In this implementation, the cross-section of the barrier layer 22 is U-shaped, forming a receiving groove for receiving the metal solder layer 32, which can further prevent the melted metal solder layer 32 from contacting the grid line 21 during the series welding process of the battery cells and improve the welding effect.

[0060] Of course, the geometric shape of the barrier layer 22 in this embodiment may also be other shapes. For example, the geometric shape of the barrier layer 22 may be a cuboid, a prism, or a cylinder.

[0061] As an implementation, please refer to Figure 7 As shown, a plurality of grid line units 20 include a number of positive grid line units 20a and a number of negative grid line units 20b. The metal connection strips 30 are respectively connected to any positive grid line unit 20a of the first cell 10 and the corresponding negative grid line unit 20b of the second cell 10 among two adjacent cells 10. In this implementation, the metal connection strips connect the positive grid line units and the negative grid line units of two adjacent cells to connect the cells in series in sequence. The power of the cell string is determined by the number of series-connected cells and the power of a single cell.

[0062] In some implementations, please continue to refer to Figure 7 As shown, a number of positive grid line units 20a are provided on the first surface 11 of the cell 10, and a number of negative grid line units 20b are provided on the second surface 12 of the cell 10. The first surface 11 and the second surface 12 are disposed opposite to each other. In this implementation, the metal connection strip 30 includes a first section 301 welded to the barrier layer 22 of the first cell 10, a second section 302 welded to the barrier layer 22 of the second cell 10, and a connection section 303 for connecting the first section 301 and the second section 302. During string soldering, the metal connection strip 30 extends from the first surface 11 of the first cell 10 to the gap part between two adjacent cells 10, and after passing through this gap part, it extends to the second surface 12 of the second cell 10.

[0063] Exemplarily, the first surface 11 and the second surface 12 may be the front and back surfaces of the cell respectively, or the first surface 11 and the second surface 12 may also be the back and front surfaces of the cell respectively.

[0064] As an implementation, the cell string 100 can be prepared in the following manner:

[0065] S11, coat a layer of barrier layer 22 on the grid lines 21 on the surface of the cell 10 and dry it.

[0066] S12, weld the metal connection strip 30 to the barrier layer 22 at the welding temperature to obtain the cell string 100.

[0067] An embodiment of the present application provides a photovoltaic module, which includes the cell string 100 of any of the above embodiments or implementations.

[0068] In the photovoltaic module of this embodiment, when fabricating the battery string, a barrier layer 22 is laminated on the grid line 21 to form a grid line unit 20.

[0069] In this embodiment, the barrier layer laminated on the grid line can block the heat transferred to the grid line during the series soldering process of the battery chips, thereby avoiding metal migration in the grid line and reducing the phenomenon of broken grid lines during the series soldering process of the battery chips; at the same time, it is beneficial to increase the series soldering temperature of the battery chips, improve the series soldering quality of the battery chips, and reduce the hot spot risk during the operation of the photovoltaic module.

[0070] As an implementation manner, please refer to Figure 8 and Figure 9 As shown, the photovoltaic module includes a first panel 41, a first encapsulant film 51, a battery pack 60, a second encapsulant film 52, and a second panel 42 that are laminated in sequence.

[0071] Among them, the battery pack 60 includes a plurality of battery strings 100. The battery pack 60 can be formed by connecting a plurality of battery strings 100 in series and / or in parallel.

[0072] As an implementation manner, the first panel 41 and the second panel 42 can be photovoltaic glasses respectively.

[0073] As an implementation manner, the first encapsulant film 51 and the second encapsulant film 52 can be EVA (Ethylene Vinyl Acetate Copolymer), EPE (a co-extrusion of EVA and POE), or POE (Polyolefin Elastomer) respectively.

[0074] In some implementation manners, please refer to Figure 9 As shown, the photovoltaic module further includes a frame 70.

[0075] As an implementation manner, the photovoltaic module can be prepared in the following manner:

[0076] S21, after obtaining the battery string by series soldering, perform an EL (Electroluminescent) test on it to obtain the broken grid result;

[0077] S22, use the lamination method to sequentially lay a front panel (such as the first panel), a front encapsulant film (such as the first encapsulant film), several battery strings, a back encapsulant film (such as the second encapsulant film), and a back panel (such as the second panel) to obtain a photovoltaic encapsulation structure;

[0078] Among them, the front adhesive film and the back adhesive film can be EVA (Ethylene Vinyl Acetate Copolymer), EPE (a co-extrusion of EVA and POE), or POE (Polyolefin Elastomer) respectively; the front panel can be front photovoltaic glass; the back panel can be a backsheet or back photovoltaic glass.

[0079] S23, connecting and fixing the lead-out wires of the metal connection bars at both ends of the battery pack formed by at least one battery string to the bus bar;

[0080] S24, laminating, installing a frame, applying glue and curing the photovoltaic encapsulation structure in sequence to obtain a photovoltaic module, and testing for hidden cracks after lamination;

[0081] S25, performing a hot spot durability test on the photovoltaic module.

[0082] Table 1 shows the test results corresponding to photovoltaic modules with barrier layers of different thicknesses and widths

[0083]

[0084] Table 1 shows the test results of photovoltaic modules with barrier layers of different thicknesses and widths. As can be seen from Table 1, adding a barrier layer between the grid line and the metal welding layer of the metal connection bar can well solve the problems of broken grid and poor hot spot resistance performance caused by silver etching.

[0085] From the results of Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the thickness of the barrier layer has an important influence on the performance of the battery string and the photovoltaic module. If the height of the barrier layer is too small, it cannot play a good barrier role, and there will still be bad situations such as broken grids; while if the height of the barrier layer is too large, there will be a risk of battery hidden cracks during the lamination process.

[0086] Combining Example 1, Comparative Example 3 and Comparative Example 4, it can be seen that when the width of the barrier layer is too small, it cannot completely block the tin layer on the surface of the metal welding layer from flowing to the grid line; while when the width of the barrier layer is too large, although there are no bad situations such as broken grids and the hot spot resistance performance is good; but the too large barrier layer seriously blocks the surface of the battery chip, which is not conducive to improving the power of the photovoltaic module.

[0087] The above are only the implementation manners of the present application. It should be noted here that for those of ordinary skill in the art, without departing from the creative concept of the present application, improvements can still be made, but these all belong to the protection scope of the present application.

Claims

1. A battery string, characterized in that: include: At least two battery cells welded in sequence; A plurality of grid line units provided on the battery cell, wherein the grid line units include grid lines provided on the battery cell and a barrier layer provided on the grid lines; as well as A plurality of metal connecting bars connected to two adjacent battery cells, wherein the metal connecting bars include metal wires and a metal solder layer coated on the metal wires, and the metal connecting bars are respectively connected to the barrier layer of one of the gate line units of the first battery cell and the barrier layer of one of the gate line units of the second battery cell in the two adjacent battery cells through the metal solder layer.

2. The battery string according to claim 1, characterized in that: The melting point of the barrier layer is higher than the melting point of the metal solder layer.

3. The battery string according to claim 1, characterized in that: The projection of the metal solder layer on the battery cell along the thickness direction of the battery cell is located within the projection of the barrier layer on the battery cell along the thickness direction of the battery cell.

4. The battery string according to claim 3, characterized in that: The barrier layer includes a main body portion stacked on the gate line and two side portions extending from both ends of the main body portion in a width direction in a direction away from the main body portion, and the main body portion and the two side portions are in contact with the metal solder layer respectively.

5. The battery string according to claim 1, characterized in that: The plurality of grid line units include a plurality of positive grid line units and a plurality of negative grid line units, and the metal connecting strips are respectively connected to any positive grid line unit of the first battery cell and the corresponding negative grid line unit of the second battery cell of two adjacent battery cells.

6. The battery string according to claim 5, characterized in that: The plurality of positive electrode grid line units are arranged on the first surface of the battery cell, and the plurality of negative electrode grid line units are arranged on the second surface of the battery cell. The first surface and the second surface are arranged opposite to each other.

7. The battery string according to claim 1, characterized in that: The thickness of the barrier layer is 2 μm to 50 μm.

8. The battery string according to claim 1, characterized in that: The width of the barrier layer is 30 μm to 200 μm.

9. The battery string according to claim 1, characterized in that: The gate line is a main gate line or a secondary gate line.

10. A photovoltaic module, characterized in that: The invention comprises a battery string as claimed in any one of claims 1 to 9.

Images