Isolation rubber for BC battery piece and method for preventing lamination scratch of BC battery piece

Abstract

The invention provides isolation rubber for a BC battery piece and a method for preventing lamination scratching of the BC battery piece. The isolation rubber for the BC battery piece comprises the following components in percentage by weight: 35%-45% of film-forming resin, 20%-30% of a resin diluent, 4%-10% of a photoinitiator, 5%-10% of SiO2 (at) TiO2 core-shell nanospheres, 3%-10% of gamma-mercaptopropyltrimethoxysilane and 1%-5% of a liquid crystal type surfactant. After the isolation rubber for the BC battery piece is cured, the light transmittance can reach 94-96%, and the efficiency of the battery is not influenced; the peel strength after curing is high, and movement or falling cannot occur in the processes of subsequent assembly use, transportation and reliability verification; therefore, the solar cell can be effectively protected and prevented from being scratched while light absorption is guaranteed; compared with the prior art, the use of the isolation rubber can avoid the operation of taking and placing the isolation paper, the production process is simplified, and the production cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module manufacturing technology, and in particular to a separator for BC solar cells and a method for preventing scratches on stacked BC solar cells. Background Technology

[0002] BC cells, with their completely metal grid lines on the front and a single-sided cell short-circuit current density of 42.5mA / cm², feature a zero-shading optical design. They employ a composite passivation structure of tunneling oxide layer + polycrystalline silicon and can integrate TOPCon or HJT technology. Currently, their efficiency is close to 27.5%, approaching the theoretical limit of monocrystalline silicon, and they are increasingly becoming the mainstream of crystalline silicon cells.

[0003] However, BC batteries also have their drawbacks. Traditional batteries can distribute the stacking pressure (approximately 12 MPa) through the front grid lines, while BC batteries have no metal lines on the front, and the pressure acts directly on the passivation layer, resulting in a 3-5 times increase in the probability of microcracks (<10 μm). Furthermore, because there are no grid lines to protect the front, the composite passivation layer of aluminum oxide and silicon nitride has a hardness of only 3-4 GPa, which is lower than that of the silver grid lines in conventional batteries (6-8 GPa). During stacking, it is easy to be scratched by friction from the silver grid lines on the back (depth 50-200 nm), resulting in poor battery appearance and poor EL, which in turn affects the efficiency of BC batteries.

[0004] To address these issues, the current main approach involves placing a dedicated separator paper between every two cells during the cell testing and sorting process. This separator paper must be sulfur-free to prevent oxidation of the silver grid lines on the back side, and it must be smooth to prevent scratches on the front side. It also needs sufficient thickness and rigidity for automated handling. This results in a relatively high cost for the separator paper; the current unit price of dedicated sulfur-free separator paper is approximately 0.03 yuan per piece, increasing the cell cost by an additional 0.35%. Furthermore, the separator paper must be removed before module welding and during lamination, leaving the cell front side in direct contact with the PTFE fabric covering the module, inevitably causing some scratches and increasing the module degradation rate by 0.3‰.

[0005] Therefore, it is necessary to design a separator for BC solar cells and a method to prevent scratches from stacking BC solar cells in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a protective adhesive that provides full-process protection for the front of BC battery cells and prevents scratches.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a separator for BC battery cells, comprising the following components in the following weight ratios: 35%-45% film-forming resin, 20%-30% resin diluent, 4%-10% photoinitiator, 5%-10% SiO2@TiO2 core-shell nanospheres, 3%-10% γ-mercaptopropyltrimethoxysilane, and 1%-5% liquid crystal surfactant.

[0008] As a further improvement of the present invention, the film-forming resin is polyurethane acrylate, and the resin diluent is 3,3,5-trimethylcyclohexane acrylate.

[0009] As a further improvement of the present invention, the photoinitiator is a mixture of TPO and ITX, wherein the weight ratio of TPO in the mixture is 75%-85% and the weight ratio of ITX is 15%-25%.

[0010] As a further improved technical solution of the present invention, the D50 of SiO2@TiO2 core-shell nanospheres is 40-60nm.

[0011] As a further improvement of the present invention, the liquid crystal surfactant is ethoxylated cholesterol or alkyl polyglucoside.

[0012] As a further improvement of the present invention, the viscosity of the separator for the BC battery cell is 2000-3000 cps.

[0013] The present invention also aims to provide a method for preventing stacking scratches on BC battery cells, which, without affecting the efficiency of the battery cells, allows the separator to be firmly fixed to the front of the BC battery cells and has a certain mechanical strength to effectively protect the BC battery cells.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: a method for preventing stacked scratches on BC battery cells, comprising the following steps: S1. Print the BC battery cell described in any of the above items onto the front side of the BC battery using a separating adhesive, with a printing thickness of 5-15μm; S2. Use UV light to irradiate the front of the printed battery to cure the separator adhesive.

[0015] As a further improvement to the present invention, the printing method in step S1 is screen printing, with a printing speed of 50-600 mm / s, an ink return speed of 500-1300 mm / s, a screen mesh count of 200-350 mesh, a screen line diameter of 10-30 μm, and a total screen thickness of 20-60 μm. Specific line information can be set in the middle area of ​​the screen-printed pattern to facilitate subsequent traceability.

[0016] As a further improvement to the present invention, the printing method in step S1 is inkjet printing, with an inkjet speed of 200-1000 mm / s. The inkjet-printed release adhesive pattern can be the same as the conventional printed pattern. Depending on the nature of the inkjet printing equipment, a real-time updated QR code can also be set in the middle area of ​​the conventional printed pattern. Through the control system and subsequent process integration, the traceability process can be achieved through QR code recognition to accurately obtain information such as printing line number, time, and IV of the battery cell.

[0017] As a further improvement to the present invention, in step S2, UV light with a wavelength of 365nm is first used for curing for 3-8 seconds, followed by UV light with a wavelength of 405nm for 1-4 seconds, for a total curing time of 5-10 seconds; the light intensity of the UV light source is 50-150mW / cm². 2 The rated power of the UV light source is 50-500W.

[0018] As can be seen from the above technical solutions, the light transmittance of the BC solar cell separator of the present invention after curing can reach 94-96%, which will not affect the light transmission and absorption of the module and will not affect the cell efficiency. The peel strength after curing is 8.5N / cm-9.5N / cm, and it will not move or fall off during subsequent module use, transportation and reliability verification. Therefore, the use of the separator of the present invention can effectively protect the solar cell and prevent scratches while ensuring light absorption. Compared with the prior art, the use of the separator can eliminate the operation of taking and putting away the separator paper, simplify the production process and greatly reduce the production cost. Furthermore, since the separator is permanently present on the front side of the solar cell, it not only plays a role in isolation during the testing, sorting and packaging process of the cell, protecting the front side of the solar cell from hidden cracks and scratches, but also plays an effective protection role for the front side of the solar cell during subsequent module stringing and lamination processes. In addition, the separator is fixed on the solar cell by printing and light curing processes, which avoids stress damage to the solar cell caused by equipment pressure compared with hot pressing and other processes. Attached Figure Description

[0019] Figure 1 The images shown are printing patterns of the release adhesive in various embodiments and comparative examples of the present invention.

[0020] Figure 2 For other embodiments, the release adhesive can be printed with a pattern.

[0021] Figure 3 For other embodiments, the isolation adhesive can be printed with a pattern (the digital traceability pattern can be added by screen printing). Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] Preparation of the release liner: S1. Resin matrix premixing: Add film-forming resin (PUA) and resin diluent (TMCHA) to the main reactor and stir at 300-500 rpm for 10 min at 25°C; S2. Nanosphere pretreatment: SiO2@TiO2 nanospheres and γ-mercaptopropyltrimethoxysilane were dry-mixed in a ball mill for 5 min (2000 rpm). S3. Mix the resin matrix, pretreated nanospheres, photoinitiator (TPO (trimethylbenzoyl-diphenylphosphine oxide) + ITX (2-isopropylthioxanthone)) and liquid crystal surfactant, and stir at 500 rpm for 60 min under light-protected conditions to obtain the finished release adhesive. Applying the separator to BC solar cells: S4. Print the above-mentioned separating adhesive onto the front side of the BC battery. The printing speed is 300 mm / s, the ink return speed is 600 mm / s, the screen mesh count is 300 mesh, the screen line diameter is 20 μm, the total screen thickness is 30 μm, and the printing thickness is 10 μm. Please refer to the specific printing pattern. Figure 1 In other embodiments, S5. Use UV curing light to irradiate the front of the printed battery to cure the separator adhesive.

[0025] Examples 2-5

[0026] The preparation and curing steps of the release liner are largely the same, with the difference lying in some process parameters. Please refer to Table 1 for details.

[0027] Table 1. Detailed process parameters for Examples 1-5

[0028] Comparative Example 1

[0029] Preparation of the release liner: S1. Resin matrix premixing: Add film-forming resin (PUA) and resin diluent (TMCHA) to the main reactor and stir at 300-500 rpm for 10 min at 25°C; S2. Mix the resin matrix, photoinitiator (TPO+ITX), and liquid crystal surfactant, and stir at 500 rpm for 60 min under light-protected conditions to obtain the finished release adhesive. Applying the separator to BC solar cells: S4. Print the above-mentioned separating adhesive on the front side of the BC battery, with a printing thickness of 10μm; S5. Use UV curing light to irradiate the front of the printed battery to cure the separator adhesive.

[0030] Comparative Example 2

[0031] Preparation of the release liner: S1. Resin matrix premixing: Add film-forming resin (PUA) and resin diluent (TMCHA) to the main reactor and stir at 300-500 rpm for 10 min at 25°C; S2. Nanosphere pretreatment: SiO2@TiO2 nanospheres and γ-mercaptopropyltrimethoxysilane were dry-mixed in a ball mill for 5 min (2000 rpm). S3. Mix the resin matrix, pretreated nanospheres, photoinitiator (TPO+ITX), and liquid crystal surfactant, and stir at 500 rpm for 60 min under light-protected conditions to obtain the finished release adhesive. Applying the separator to BC solar cells: S4. Print the above-mentioned separating adhesive on the front side of the BC battery, with a printing thickness of 10μm; S5. Use UV curing light to irradiate the front of the printed battery to cure the separator adhesive.

[0032] Please refer to Table 2 for detailed process parameters of Comparative Examples 1-2: Table 2 Detailed process parameters for Comparative Examples 1-2

[0033] The cured release adhesive was subjected to DH1000 reliability testing, peel strength testing, and light transmittance testing. The specific test results are as follows: Table 3 Test results of the release liner in each embodiment and comparative example

[0034] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A separator for BC battery sheet, characterized by, The components include the following weight ratios: 35%-45% of a film-forming resin, 20%-30% of a resin diluent, 4%-10% of a photoinitiator, 5%-10% of SiO2@TiO2core-shell nanospheres, 3%-10% of γ-mercaptopropyl trimethoxysilane, and 1%-5% of a liquid crystal surfactant.

2. The separator for BC battery sheet according to claim 1, wherein: The film-forming resin is a polyurethane acrylate, and the resin diluent is 3,3,5-trimethylcyclohexane acrylate.

3. The separator for BC battery sheet according to claim 1, wherein: The photoinitiator is a mixture of TPO and ITX, the weight ratio of TPO in the mixture being 75%-85%, and the weight ratio of ITX being 15%-25%.

4. The separator for BC battery sheet according to claim 1, wherein: The D50 of the SiO2@TiO2core-shell nanospheres is 40-60 nm.

5. The separator for BC solar cells as described in claim 1, characterized in that: The liquid crystal surfactant is ethoxylated cholesterol or alkyl polyglucoside.

6. The separator for BC battery sheet according to claim 1, wherein: The viscosity of the BC battery sheet isolation glue is 2000-3000 cps.

7. A method of preventing laminated sheet scratches of a BC battery sheet, characterized by, The method comprises the following steps: S1, printing the BC battery sheet isolation glue according to any one of claims 1-6 on the front of the BC battery, the printing thickness being 5-15 μm; S2, irradiating the printed battery front with UV light to cure the isolation glue.

8. The method of claim 7, wherein the method further comprises: providing a BC battery cell with a plurality of electrode tabs; and providing a plurality of separators between the plurality of electrode tabs. In step S1, the printing method is screen printing, the printing speed is 50-600 mm / s, the ink return speed is 500-1300 mm / s, the screen mesh number used is 200-350 meshes, the screen line diameter is 10-30 μm, and the total thickness of the screen is 20-60 μm.

9. The method of claim 7, wherein the method further comprises: providing a BC battery cell with a plurality of electrode plates; and providing a plurality of separators between the plurality of electrode plates. In step S1, the printing method is inkjet printing, and the inkjet speed is 200-1000 mm / s.

10. The method of claim 7, wherein the method further comprises: providing a BC battery cell with a plurality of electrode plates; and providing a plurality of separators between the plurality of electrode plates. In step S2, first UV light with a wavelength of 365 nm is used for curing for 3-8 s, and then UV light with a wavelength of 405 nm is used for curing for 1-4 s, and the total curing time is 5-10 s; the light intensity of the UV light source is 50-150 mW / cm 2 ; the rated power of the UV light source is 50-500 W.

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