Back-contact battery module and manufacturing method therefor

Abstract

The present application relates to the technical field of back-contact batteries, and in particular to a back-contact battery module and a manufacturing method therefor. The manufacturing method comprises: S1, alignment and interconnection: providing a back adhesive film on the upper surface of a backsheet base material, and then adhering welding strips to the upper surface of the back adhesive film by means of a double-sided tape to obtain a photovoltaic backsheet integrated with the welding strips; and placing a plurality of battery cells on said photovoltaic backsheet, and making main grids on the backs of the battery cells in contact with the welding strips and the double-sided tape in said photovoltaic backsheet; S2, busbar integration and stacking: placing, according to a preset mode, a busbar on the outer side of the end parts of the welding strips in said photovoltaic backsheet, and pre-fixing the busbar by means of the double-sided tape adhered to the welding strips; and then completing stacking; and S3, lamination. According to the present application, before the battery cells are stacked, a high-temperature process of high-temperature welding is not required, and the fronts of the battery cells will not come into contact and friction with a hard table top, so that the battery cells deform a little or will not deform, there is few battery scratches, and the advantage of a high module production yield is also achieved.

Description

Back contact battery module and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 202311213406.3 filed with the China Patent Office on September 20, 2023, entitled “A back contact battery module and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the technical field of back-contact batteries, and specifically relates to a back-contact battery module and a preparation method thereof. Background Art

[0004] Back-contact solar cells are designed with both the emitter and base contact electrodes on the back (non-light-receiving) side of the cell, leaving the light-receiving side unobstructed by any metal electrodes. Back-contact solar cell modules are encapsulated using back-contact solar cells. This eliminates the need for metal electrodes on the light-receiving side, resulting in not only high conversion efficiency but also a more aesthetically pleasing design. The production steps of the back contact battery module are generally shown in Figure 2, including: welding interconnection: providing back contact battery cells and welding ribbons, welding the welding ribbons to the main grid on the back of the battery cells, and connecting the battery cells in series. The welding temperature is generally greater than 160°C and the welding time is 1-10s; layout: arranging the backplane, rear film and battery string with the battery cells welded in series from bottom to top to complete the layout operation; convergence and lamination: welding the welding ribbons on the battery string to the bus bar in series and parallel to complete the convergence operation, and then laying the front film and front plate to complete the lamination operation; lamination: bonding the front and back panel glass, front and rear films, and battery strings together under vacuum, high temperature and pressure conditions to form a battery module; testing.

[0005] During the back-contact cell welding and interconnection process, the cells and solder ribbons need to be exposed to temperatures above 130°C to connect the ribbons to the cell. Since the back-contact cells are welded on one side, there is a lot of stress on the solder ribbons after welding, which causes the cell to deform significantly. As shown in Figure 1, a picture of the deformation of a 150μm thick back-contact solar cell after welding and interconnection shows that the maximum warpage in the middle reaches 10mm. The deformed cell is then flattened after layout / lamination.

[0006] The following problems exist with the deformation of the cell after welding: ① After welding, the cell goes through processes such as convergence and laying before lamination. This process requires forcibly flattening the deformed and bent cell. This poses a high risk of hidden cracks in the cell. It is also easy for the soldering ribbon to fall off the main grid, resulting in poor contact and a decrease in the yield of the back-contact battery module. ② The deformation of the cell after welding is directly related to the thickness of the silicon wafer. The thinner the silicon wafer, the greater the deformation of the cell after welding, and the greater the risk of hidden cracks. Therefore, the welding process seriously affects the space for thinning the silicon wafer thickness, thereby affecting the cost reduction space of the cell. ③ During the welding process, the light-receiving side of the cell faces downward, and the light-receiving side of the cell needs to be in direct contact with the welding platform. Because the light-receiving side of the cell is not protected by the grid line, it is prone to scratches and other adverse effects.

[0007] Summary of the Invention

[0008] The purpose of this application is to overcome the defect of the existing back-contact solar cells in the prior art that they have large deformation after welding and interconnection, and to provide a back-contact battery module and a preparation method thereof. When making the back-contact battery module of this application, the battery cells do not need to undergo a high-temperature welding process before stacking, and the front of the battery cells will not come into contact with or rub against the hard surface. Therefore, the battery cells have small deformation or even no deformation, and the battery is less scratched, and it has the advantages of a high module production yield.

[0009] To achieve the above objectives, in a first aspect, the present application provides a method for preparing a back-contact battery module, comprising the following steps:

[0010] S1, bit-to-bit interconnection:

[0011] A backing film is provided on the upper surface of a backsheet substrate, and then welding strips are adhered to the upper surface of the backing film via double-sided tape to obtain a photovoltaic backsheet with integrated welding strips, wherein the welding strips are respectively attached to the double-sided tapes and the width of the double-sided tapes is greater than the width of the welding strips, the bonding force between the double-sided tapes and the welding strips is not less than 0.2N, and the bonding force between the double-sided tapes and the backing film is not less than 0.5N, and the welding strips include a welding strip substrate and a first low-melting-point metal layer coated on the surface of the welding strip substrate, and the melting point of the first low-melting-point metal layer does not exceed 155°C;

[0012] Then, a plurality of solar cells are placed in series and / or parallel on the photovoltaic backsheet with integrated solder strips, with the main grid on the back of the solar cells contacting the solder strips and double-sided tape in the photovoltaic backsheet with integrated solder strips, and the solar cells are fixed to the photovoltaic backsheet with integrated solder strips by the double-sided tape;

[0013] S2, busbar and lamination: placing the busbar on the outside of the end of the solder strip in the photovoltaic backsheet with integrated solder strip according to a preset method, and pre-fixing the busbar with double-sided tape adhered to the solder strip; then, laying the front adhesive film and the front plate on the surface of the busbar in sequence to complete the lamination;

[0014] S3. Lamination: Lamination of the laminate obtained in S2 is performed under vacuum, pressure and heating.

[0015] In some preferred embodiments of the present application, the difference in width between the double-sided tape and the welding tape is 1-10 mm.

[0016] Preferably, the bonding force between the double-sided tape and the welding tape is greater than 0.6N, and the bonding force between the double-sided tape and the rear adhesive film is greater than 1N.

[0017] In some preferred embodiments of the present application, the welding strip is flat or circular.

[0018] In some preferred embodiments of the present application, the thickness of the first low-melting-point metal layer is 5-30 μm, and the thickness of the welding strip is 0.1-0.5 mm.

[0019] In some preferred embodiments of the present application, the thickness of the double-sided tape is 0.1-0.5 mm.

[0020] In some preferred embodiments of the present application, the thickness of the rear adhesive film is 0.3-1.0 mm.

[0021] In some preferred embodiments of the present application, the double-sided adhesive comprises a PET film, and a pressure-sensitive adhesive or a heat-sensitive adhesive coated on both sides of the PET film.

[0022] Preferably, the coating thickness of the pressure-sensitive adhesive or heat-sensitive adhesive is 30-150 μm.

[0023] In some preferred embodiments of the present application, the first low-melting-point metal layer is any one of tin alloy, indium alloy, and metallic indium.

[0024] In some preferred embodiments of the present application, the backplane substrate is glass, or the backplane substrate is a fluorine-containing photovoltaic material with low water vapor transmission rate, and the water vapor transmission rate of the fluorine-containing photovoltaic material is less than 0.5g / m 2 / sky.

[0025] Preferably, the fluorine-containing photovoltaic material is a composite material selected from any one or more of PET, PVDF, and PVF with a fluorine-coated surface.

[0026] In some preferred embodiments of the present application, the thickness of the battery cell is 70-200 μm, the width of the busbar is 2-8 mm, and the thickness of the busbar is 0.2-0.5 mm.

[0027] In some preferred embodiments of the present application, the busbar includes a busbar substrate and a second low-melting-point metal layer coated on a surface of the busbar substrate, wherein the melting point of the second low-melting-point metal layer does not exceed 155°C.

[0028] Preferably, the thickness of the second low-melting-point metal layer is 5-30 μm.

[0029] Preferably, the second low-melting-point metal layer is any one of tin alloy, indium alloy, and metallic indium.

[0030] In some preferred embodiments of the present application, in S3, the lamination conditions include: a temperature of 140-170° C., a vacuum degree of less than 1000 Pa, and a pressure of 1-1.5 standard atmospheres.

[0031] In a second aspect, the present application provides a back-contact battery module, which is prepared by the preparation method described in the first aspect. Beneficial effects:

[0032] The present application integrates a low-melting-point soldering ribbon and a back adhesive film with double-sided adhesive on a backplane substrate to obtain a photovoltaic backplane. When making the back-contact battery module of the present application, the battery cells do not need to undergo a high-temperature process of high-temperature welding before lamination, and the front of the battery cells will not be in contact with the hard table surface. Therefore, the battery cells have the advantages of small or even no deformation, few battery scratches, and high module production yield. At the same time, they can be compatible with thinner battery silicon wafers, which is beneficial to reducing the material cost of battery-end silicon wafers. Among them, the bonding force between the double-sided adhesive and the soldering ribbon is not less than 0.2N, and the bonding force between the double-sided adhesive and the back adhesive film is not less than 0.5N, which can prevent the soldering ribbon on the photovoltaic backplane from being displaced in the subsequent process, which is beneficial to improving the alignment accuracy between the battery cell and the photovoltaic backplane, thereby improving the production yield of the module. Under the same conditions, if the bonding force is insufficient, the soldering ribbon on the photovoltaic backplane will be greatly displaced, reducing the alignment accuracy between the battery cell and the photovoltaic backplane, thereby affecting the production yield of the module. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 is a photograph of the deformation of the battery cell after series welding in Comparative Example 1;

[0035] FIG2 is a process flow chart of manufacturing a back contact battery module in Comparative Example 1;

[0036] FIG3 is a process flow chart for manufacturing a back-contact battery module according to the present application;

[0037] FIG4 is a front view schematic diagram of a photovoltaic backsheet with integrated welding ribbon according to a specific embodiment of the present invention;

[0038] FIG5 is a schematic diagram of the cross-sectional structure of the photovoltaic backsheet with integrated welding strips of FIG4 of the present application;

[0039] FIG6 is a front view of the structure of the photovoltaic backsheet with integrated welding ribbons after placing solar cells;

[0040] FIG7 is a schematic front view of the structure of the battery cell of the present application;

[0041] FIG8 is a schematic diagram of the structure of the stacked layers of materials of the back contact battery module of the present application.

[0042] Description of Reference Numerals

[0043] 10. Photovoltaic backsheet, 101. Backsheet substrate, 102. Back film, 103. Double-sided tape, 104. Solder ribbon, 20. Solar cell, 201. Main grid, 30. Busbar, 40. Front film, 50. Front panel. DETAILED DESCRIPTION

[0044] In this application, unless otherwise specified, directional words such as "up, down, left, right" generally refer to the directions shown in the drawings and actual applications, and "inside and outside" refer to the inside and outside of the outline of the component.

[0045] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0046] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Among them, the terms "optional" and "optional" all mean that they may be included or not (or may be present or not).

[0047] In a first aspect, the present application provides a method for preparing a back-contact battery module, comprising the following steps:

[0048] S1, bit-to-bit interconnection:

[0049] A backing film is provided on the upper surface of a backsheet substrate, and then welding strips are adhered to the upper surface of the backing film via double-sided tape to obtain a photovoltaic backsheet with integrated welding strips, wherein the welding strips are respectively attached to the double-sided tapes and the width of the double-sided tapes is greater than the width of the welding strips, the bonding force between the double-sided tapes and the welding strips is not less than 0.2N, and the bonding force between the double-sided tapes and the backing film is not less than 0.5N, and the welding strips include a welding strip substrate and a first low-melting-point metal layer coated on the surface of the welding strip substrate, and the melting point of the first low-melting-point metal layer does not exceed 155°C;

[0050] Then, a plurality of solar cells are placed in series and / or parallel on the photovoltaic backsheet with integrated solder strips, with the main grid on the back of the solar cells contacting the solder strips and double-sided tape in the photovoltaic backsheet with integrated solder strips, and the solar cells are fixed to the photovoltaic backsheet with integrated solder strips by the double-sided tape;

[0051] S2, busbar and lamination: placing the busbar on the outside of the end of the solder strip in the photovoltaic backsheet with integrated solder strip according to a preset method, and pre-fixing the busbar with double-sided tape adhered to the solder strip; then, laying the front adhesive film and the front plate on the surface of the busbar in sequence to complete the lamination;

[0052] S3. Lamination: Lamination of the laminate obtained in S2 is performed under vacuum, pressure and heating.

[0053] It should be pointed out that the soldering tape of the present application is a low-temperature soldering tape, and the melting point of the first low-melting-point metal layer provided on the surface of the soldering tape does not exceed 155°C, so interconnection can be achieved at room temperature.

[0054] In this application, the soldering strips are all attached to the double-sided tape, which means that any soldering strip corresponds to a double-sided tape, and is adhered to the back adhesive film through the double-sided tape. One soldering strip can be fixed with one double-sided tape, or multiple soldering strips can be fixed with one double-sided tape, as long as the soldering strips can be adhered and fixed.

[0055] This application integrates the existing soldering ribbons, which were originally provided on the cell, into the photovoltaic backsheet, without improving the distribution of the soldering ribbons. Those skilled in the art can select the arrangement of the soldering ribbons based on actual needs to facilitate subsequent connection to the busbar structure of the cell. The arrangement of the soldering ribbons in the photovoltaic backsheet with integrated soldering ribbons corresponds to the arrangement of the busbars in the cell, allowing the soldering ribbons to be attached to the busbars and connect multiple cells in series and / or in parallel.

[0056] In some preferred embodiments of the present application, the difference in width between the double-sided tape and the welding tape is 1-10 mm, for example, it can be any value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm and any value between adjacent point values.

[0057] In the present application, the width range of the double-sided tape and the welding tape can be selected to be relatively wide, as long as the above-mentioned width difference is satisfied. The width of the welding tape can be, for example, 0.5-3 mm.

[0058] Preferably, the bonding force between the double-sided tape and the soldering tape is greater than 0.6 N, and the bonding force between the double-sided tape and the back film is greater than 1 N. This preferred solution is more conducive to improving the production yield of the manufactured battery module.

[0059] In this application, those skilled in the art can adjust the bonding force between the double-sided tape and the soldering tape, and the bonding force between the double-sided tape and the back film by adjusting the structure of the double-sided tape (such as the coating thickness of the pressure-sensitive adhesive or the heat-sensitive adhesive).

[0060] In some preferred embodiments of the present application, the welding ribbon is flat or round, more preferably flat. The flat shape is more conducive to improving the production yield of the battery module.

[0061] In some preferred embodiments of the present application, the thickness of the first low-melting-point metal layer is 5-30 μm.

[0062] Preferably, the thickness of the welding strip is 0.1-0.5 mm.

[0063] More preferably, the thickness of the flat welding strip is 0.1-0.2 mm, and the thickness of the round welding strip is 0.3-0.5 mm.

[0064] In the present application, the material of the solder strip substrate can be conventional solder strip metal materials, such as copper, aluminum, silver, etc.

[0065] In some preferred embodiments of the present application, the thickness of the double-sided tape is 0.1-0.5 mm.

[0066] In some preferred embodiments of the present application, the thickness of the rear adhesive film is 0.3-1.0 mm.

[0067] In the present application, the material of the rear film can be a conventional film material, for example, an EVA film and / or a POE film.

[0068] The double-sided adhesive tape of the present application satisfies the above-mentioned corresponding adhesive force. In some preferred embodiments of the present application, the double-sided adhesive tape comprises a PET film, and a pressure-sensitive adhesive or a heat-sensitive adhesive coated on both sides of the PET film.

[0069] Preferably, the coating thickness of the pressure-sensitive adhesive or heat-sensitive adhesive is 30-150 μm, preferably 50-150 μm.

[0070] In some preferred embodiments of the present application, the first low melting point metal layer is any one of tin alloy, indium alloy, and metallic indium. On this basis, those skilled in the art can further select corresponding alloys or metals that meet the corresponding low melting points.

[0071] In some preferred embodiments of the present application, the backplane substrate is glass, or the backplane substrate is a fluorine-containing photovoltaic material with low water vapor transmission rate, and the water vapor transmission rate of the fluorine-containing photovoltaic material is less than 0.5g / m 2 / sky.

[0072] Preferably, the fluorine-containing photovoltaic material is a composite material selected from any one or more of PET, PVDF, and PVF with a fluorine-coated surface.

[0073] The present application does not place any particular restriction on the thickness of the backplane substrate. Those skilled in the art may adopt the existing backplane substrate thickness range, which may all be configured in the present application.

[0074] In this application, those skilled in the art can arrange a plurality of battery cells in a desired series-parallel arrangement, and the arrangement can be carried out in accordance with the prior art. The corresponding positional relationships between the battery cells and the busbars, front film, and front plate are all carried out in accordance with the prior art. The busbars, front film, and front plate are all arranged in sequence on the light-receiving surface of the battery cells, and the busbars are located on the side of the ends of the battery cells.

[0075] In some preferred embodiments of the present application, the thickness of the cell is 70-200 μm. This application is compatible with thinner cells, which helps reduce the material cost of the silicon wafer at the cell end. In the production of modules with thinner cells, it has the advantages of small or no deformation, few cell scratches, and high module production yield.

[0076] The busbars in this application can be pre-set in the manner of the prior art. Generally, the busbars are located on the side of the cell, that is, on the outside of the ends of the welding ribbons, and are configured to achieve series and / or parallel welding of the busbars and the ends of the welding ribbons after subsequent lamination; wherein the busbars are perpendicular to the welding ribbons and are located on the side of the ends of the cell. In other words, the relative connection relationship or positional relationship between the busbars and the welding ribbons, and the busbars and the cell are the same as in the prior art, and this application does not make any improvements thereto. The improvement of this application is to first obtain a photovoltaic backplane with integrated welding ribbons, and then stack and laminate it with the busbars, etc.

[0077] Preferably, the width of the busbar is 2-8 mm, and the thickness of the busbar is 0.2-0.5 mm.

[0078] In some preferred embodiments of the present application, the busbar includes a busbar substrate and a second low-melting-point metal layer coated on a surface of the busbar substrate, wherein the melting point of the second low-melting-point metal layer does not exceed 155°C.

[0079] Preferably, the thickness of the second low-melting-point metal layer is 5-30 μm.

[0080] Preferably, the second low-melting-point metal layer is any one of tin alloy, indium alloy, and metallic indium.

[0081] The present application has no restrictions on the material and thickness of the front adhesive film and the front plate, and both can be made according to the existing technology.

[0082] In some preferred embodiments of the present application, in S3, the lamination conditions include: a temperature of 140-170° C., a vacuum degree of less than 1000 Pa, and a pressure of 1-1.5 standard atmospheres.

[0083] The preparation method described in the present application may also include other conventional steps, such as a testing step after lamination, which is a prior art and will not be described in detail here.

[0084] In a second aspect, the present application provides a back-contact battery module, which is prepared by the preparation method described in the first aspect.

[0085] The embodiments of the present application are described in detail below. These embodiments are exemplary and are only configured to explain the present application, but should not be construed as limiting the present application.

[0086] Example 1

[0087] A method for preparing a back-contact battery module, as shown in FIG3 , comprises the following steps:

[0088] S1, bit-to-bit interconnection:

[0089] A photovoltaic backsheet 10 with integrated soldering ribbons is provided. As shown in Figures 4 and 5 , the photovoltaic backsheet comprises a backsheet substrate 101, a backing film 102, a double-sided adhesive tape 103, and a soldering ribbon 104 located on the upper surface of the backsheet substrate 101. Two soldering ribbons 104 are adhered and secured together using a single strip of double-sided adhesive tape 103. The double-sided adhesive tape 103 is 7 mm wider than the soldering ribbons 104. The soldering ribbons 104 are flat.

[0090] The soldering ribbon 104 is a copper substrate coated on both sides with a tin-bismuth-silver alloy coating. The coating has a melting point of 140°C and a thickness of 20 μm. The total thickness of the soldering ribbon 104 is 0.18 mm, and the width of the soldering ribbon 104 is 1.2 mm. The double-sided adhesive tape 103 is a PET film tape coated on both sides with a pressure-sensitive adhesive. The pressure-sensitive adhesive coating thickness is 100 μm, and the thickness of the double-sided adhesive tape 103 is 0.2 mm. The bonding force between the soldering ribbon 104 and the double-sided adhesive tape 103 is 0.8 N, and the bonding force between the double-sided adhesive tape 103 and the back film 102 is 2 N. The backplane substrate 101 is glass and has a thickness of 2.3 mm. The back film 102 is an EVA film and has a thickness of 0.6 mm.

[0091] As shown in Figures 6 and 7, the aforementioned integrated solder ribbon photovoltaic backsheet 10 and solar cells 20 are provided. The spacing and connection pattern of the solder ribbons 104 on the photovoltaic backsheet 10 correspond to the arrangement of the busbars 201 of the solar cells 20. The thickness of the solar cells 20 is 150 μm. The solar cells 20 are placed on the photovoltaic backsheet 10 in a pre-set position. Double-sided tape 103 on the photovoltaic backsheet 10 serves to pre-secure the solar cells 20.

[0092] S2. Busbars and Lamination: As shown in FIG8 , busbars 30 are placed on the outside of the ends of the corresponding soldering ribbons 104 of the photovoltaic backsheet 10 in a pre-set series-parallel arrangement, so that the ends of the soldering ribbons 104 and the busbars 30 can be subsequently welded. The busbars 30 are located on the side of the solar cells 20 . The double-sided adhesive tape 103 on the photovoltaic backsheet 10 serves to pre-fix the busbars 30 . The front adhesive film 40 and the front plate 50 (made of glass) are then applied to complete the lamination operation. The base material of the busbars 30 is copper, and the surface of the base material is coated with a metal tin-bismuth-silver alloy layer. The melting point of the tin-bismuth-silver alloy layer does not exceed 155°C, and the thickness of the tin-bismuth-silver alloy layer is 10μm. The width of the busbars 30 is 5mm, and the thickness is 0.3mm.

[0093] S3, lamination: The photovoltaic backsheet 10, the cell 20, the busbar 30, the front adhesive film 40 and the front plate 50 are bonded together under vacuum, high temperature and pressure conditions to form a battery module. The lamination temperature in S3 is 155°C, the vacuum degree is 100 Pa, and the pressure corresponding to the pressurization is 1 standard atmosphere.

[0094] S4. Test.

[0095] Example 2

[0096] The process is carried out with reference to Example 1, except that the thickness of the battery cell 20 provided in S1 is 130 μm.

[0097] Example 3

[0098] The process is carried out with reference to Example 1, except that the thickness of the battery cell 20 provided in S1 is 110 μm.

[0099] Example 4

[0100] The process is carried out with reference to Example 1, except that the thickness of the battery cell 20 provided in S1 is 90 μm.

[0101] Example 5

[0102] The process is carried out with reference to Example 1, except that the welding strip 104 of the photovoltaic backsheet 10 is a circular welding strip with a diameter of 0.35 mm.

[0103] Example 6

[0104] The process is carried out with reference to Example 1, except that the width of the double-sided tape 103 is adjusted so that the width of the double-sided tape 103 is 3 mm wider than the width of the welding strip 104 .

[0105] Example 7

[0106] The process is carried out with reference to Example 1, except that the width of the double-sided tape 103 is adjusted so that the width of the double-sided tape 103 is 1 mm wider than the width of the welding strip 104 .

[0107] Example 8

[0108] Refer to Example 1, except that the bonding force between the soldering tape 104 and the double-sided tape 103 is 0.2N, and the bonding force between the double-sided tape 103 and the back film 102 is 0.5N. To meet this bonding force, the pressure-sensitive adhesive coating thickness needs to be adjusted to 30μm.

[0109] Comparative Example 1

[0110] The difference from Example 1 is that the battery module is prepared according to the conventional method shown in FIG2 :

[0111] Welding interconnection: Provide solar cells and high-temperature soldering ribbons, solder the high-temperature soldering ribbons to the main grid on the back of the solar cells, and connect several solar cells in series. The high-temperature soldering ribbons are made of a copper substrate with a tin-lead coating. The soldering temperature is 170°C and the soldering time is 2 seconds.

[0112] Layout: From bottom to top, set the back plate, back film and battery string with several battery cells welded in series, with the back of the battery cells facing down to complete the layout operation;

[0113] Convergence and lamination: The high-temperature solder ribbons on the battery strings are welded to the busbars in series and parallel connection to complete the convergence operation, and then the front film and front plate are laid to complete the lamination operation;

[0114] Lamination: The front and back sheets, front and back films, and battery strings are bonded together under vacuum, high temperature, and pressure (same conditions as in Example 1) to form a battery module. The materials and thicknesses of the battery cells, back sheet, back film, busbars, front film, and front sheet, as well as the arrangement of the corresponding solder strips, are the same as in Example 1.

[0115] Comparative Example 2

[0116] The process was carried out with reference to Comparative Example 1, except that the thickness of the cell was 130 μm.

[0117] Comparative Example 3

[0118] The process was carried out with reference to Comparative Example 1, except that the thickness of the cell was 110 μm.

[0119] Test Case

[0120] The battery modules obtained in the above examples and comparative examples were tested or inspected for various performance indicators, and the results are shown in Table 1.

[0121] Table 1

[0122] It can be seen from the above embodiments and comparative examples that, compared with the prior art of the comparative examples, in the solution of the battery module made of the photovoltaic backplane with integrated welding strips of the present application, the battery cells do not need to undergo high-temperature welding before lamination, and the front of the battery cells will not contact and rub against the hard table surface. Therefore, the battery cells have the advantages of small deformation or even no deformation, few scratches on the battery cells, and high module production yield. At the same time, it can be compatible with thinner battery cells, which is beneficial to reducing the material cost of the silicon wafers at the battery end.

[0123] Among them, it can be seen from Examples 1 and 5 that the battery module production yield rate is higher when using the preferred flat solder strip of this application. It can be seen from Examples 1 and 6-7 that the preferred double-sided tape width ratio of this application is more conducive to improving the production yield rate of the battery module. It can be seen from Examples 1 and 8 that the preferred double-sided tape bonding strength of this application is more conducive to improving the production yield rate of the battery module.

[0124] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, including combining the various technical features in any other appropriate manner. These simple modifications and combinations should also be regarded as the contents disclosed in the present application and fall within the scope of protection of the present application. Industrial Applicability

[0125] This solution ensures a minimum bond strength of 0.2N between the double-sided tape and the soldering ribbon, and a minimum bond strength of 0.5N between the double-sided tape and the backing film. This prevents displacement of the soldering ribbon on the photovoltaic backsheet during subsequent manufacturing processes, improving the alignment accuracy between the cells and the photovoltaic backsheet, and thus increasing the module production yield. The cells do not require high-temperature soldering prior to lamination, and the front of the cells are protected from contact and friction with hard surfaces. Consequently, cell deformation is minimal or non-existent, and scratches are minimized, resulting in a high module production yield and improved practicality.

Claims

1. A method for preparing a back contact battery module, characterized in that: The following steps are involved: S1, bit-to-bit interconnection: A rear adhesive film is arranged on the upper surface of the backplane substrate, and then a welding strip is adhered to the upper surface of the rear adhesive film by double-sided adhesive to obtain a photovoltaic backplane with integrated welding strips, wherein the welding strips are correspondingly attached to the double-sided adhesive and the width of the double-sided adhesive is greater than the width of the welding strip, the bonding force between the double-sided adhesive and the welding strip is not less than 0.2N, and the bonding force between the double-sided adhesive and the rear adhesive film is not less than 0.5N, and the welding strip includes a welding strip substrate and a first low-melting-point metal layer coated on the surface of the welding strip substrate, and the melting point of the first low-melting-point metal layer does not exceed 155°C; Then, a plurality of cells are placed in series and / or in parallel on the photovoltaic backplane with integrated solder strips, the main grid on the back of the cell contacts the solder strip and double-sided adhesive in the photovoltaic backplane with integrated solder strips, and the cell is fixed to the photovoltaic backplane with integrated solder strips by the double-sided adhesive; S2, busbar and lamination: placing the busbar on the outer side of the end of the solder strip in the photovoltaic backsheet with integrated solder strip according to a preset method, and pre-fixing the busbar by means of double-sided adhesive tape adhered to the solder strip; then, laying a front adhesive film and a front plate on the surface of the busbar in sequence to complete the lamination; S3. Lamination: Lamination of the laminate obtained in S2 is carried out under vacuum, pressure and heating.

2. The preparation method according to claim 1, characterized in that: The difference between the width of the double-sided adhesive tape and the welding strip is 1-10 mm, and / or the welding strip is flat or round.

3. The preparation method according to claim 1, characterized in that: The bonding force between the double-sided adhesive tape and the welding strip is greater than 0.6N, and the bonding force between the double-sided adhesive tape and the rear adhesive film is greater than 1N.

4. The preparation method according to claim 1, characterized in that: The thickness of the first low-melting-point metal layer is 5-30 μm, and the thickness of the welding strip is 0.1-0.5 mm; and / or, The first low melting point metal layer is any one of tin alloy, indium alloy and metal indium.

5. The preparation method according to claim 1, characterized in that: The thickness of the double-sided adhesive tape is 0.1-0.5 mm, and / or the thickness of the rear adhesive film is 0.3-1.0 mm.

6. The preparation method according to claim 1, characterized in that: The double-sided adhesive comprises a PET film, and a pressure-sensitive adhesive or a heat-sensitive adhesive coated on both sides of the PET film; the coating thickness of the pressure-sensitive adhesive or the heat-sensitive adhesive is 30-150 μm.

7. The preparation method according to claim 1, characterized in that: The backplane substrate is glass, or the backplane substrate is a fluorine-containing photovoltaic material with low water vapor transmission rate, and the water vapor transmission rate of the fluorine-containing photovoltaic material is less than 0.5g / m 2 / day, the fluorine-containing photovoltaic material is a composite material with a fluorine coating on the surface selected from any one or more of PET, PVDF and PVF; The busbar includes a bus substrate and a second low-melting-point metal layer coated on the surface of the bus substrate, the melting point of the second low-melting-point metal layer does not exceed 155°C, the thickness of the second low-melting-point metal layer is 5-30μm, and the second low-melting-point metal layer is any one of tin alloy, indium alloy, and metallic indium.

8. The preparation method according to claim 1, characterized in that: The thickness of the battery cell is 70-200 μm, the width of the bus bar is 2-8 mm, and the thickness of the bus bar is 0.2-0.5 mm.

9. The preparation method according to claim 1, characterized in that: In S3, the lamination conditions include: temperature of 140-170°C, vacuum degree less than 1000 Pa, and pressure of 1-1.5 standard atmospheres.

10. A back contact battery module, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 9.

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