Back contact cell separator adhesive composition and back contact cell separator adhesive

Abstract

The application provides a back contact cell isolation glue composition and a back contact cell isolation glue. The back contact cell isolation glue composition comprises, in percentage by mass, 60-84% of a resin base material, 10-30% of an active diluent monomer, 0.5-2% of a filler and 2-8% of a photoinitiator; wherein the resin base material comprises silicone acrylate, acrylic monomer and polyurethane modified acrylate; the mass percentage content of amino groups in the polyurethane modified acrylate is 10-30%. The above technical scheme adjusts the proportion of the resin formula, ensures that the isolation glue keeps low yellowing and high light transmittance for a long time, and guarantees the power output and appearance stability of the photovoltaic module. The silicone acrylate makes the thermal decomposition temperature of the isolation glue reach 300-400 DEG C, meets the high-temperature edge passivation process, realizes continuous protection in the whole process of cell manufacturing, and solves the protection problem of the cell piece in the high-temperature process.

Description

Technical Field

[0001] This invention relates to the field of separator preparation technology, and more specifically, to a separator composition for back contact batteries and a separator for back contact batteries. Background Technology

[0002] Large-size half-cells can improve power through laser scribing, but the lattice defects exposed after scribing must be repaired in a high-temperature passivation process of 250℃~400℃, which places stringent temperature requirements on the auxiliary materials used in the process. Back-contact batteries achieve high conversion efficiency and aesthetics with their full back electrode and no grid lines on the front, but this also makes their front passivation layer extremely susceptible to scratches during manufacturing and transportation, affecting performance.

[0003] To address the aforementioned scratch problem, the traditional industry solution is to place a separator paper between the solar cells. However, this solution has fundamental drawbacks: 1) insufficient temperature resistance; 2) cost and efficiency issues; and 3) incomplete protection. Therefore, developing a chemical protective coating that can be used in high-temperature processes and provide end-to-end protection has become an urgent industry need.

[0004] To balance high-temperature passivation and comprehensive physical protection, traditional release paper needs to be replaced with a high-temperature heat-resistant release adhesive capable of withstanding 250℃~400℃ and providing reliable protection. However, while conventional acrylic resins possess superior properties such as high light transmittance and high hardness, they often exhibit poor heat resistance and low glass transition temperatures, softening, sticking together, or even decomposing and losing their protective function at temperatures of 200℃ and above. Epoxy resins, although possessing higher heat resistance, are prone to forming chromophores such as quinone structures under the influence of heat, oxygen, and ultraviolet light, leading to severe yellowing and significantly reducing the photocurrent output of the solar cells. Therefore, existing formulations need to be improved, and a high-temperature resistant, low-yellowing adhesive formulation capable of withstanding temperatures of 270℃ and above needs to be developed. Summary of the Invention

[0005] The main objective of this invention is to provide a separator composition and a separator for back contact batteries, so as to solve the problems of poor high-temperature stability and yellowing resistance of separators for back contact batteries in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a separator composition for a back contact battery is provided, comprising, by weight percentage, 60-84% of a resin substrate, 10-30% of an active diluent monomer, 0.5-2% of a filler, and 2-8% of a photoinitiator; wherein the resin substrate comprises an organosilicon acrylate, an acrylic monomer, and a polyurethane-modified acrylate; the structural formula of the organosilicon acrylate is as follows:

[0007]

[0008] Where n = 40~70, m = 40~80, and R1 is selected from C1~C 12 straight-chain alkylene, C3~C 12 R2 and R3 are each independently selected from any one of the branched alkylene groups of C1 to C4 and any one of the branched alkylene groups of C3 to C4; the mass percentage of amino groups in the polyurethane modified acrylate is 10 to 30%.

[0009] Furthermore, the mass ratio of the above-mentioned organosilicon acrylate, acrylic monomer and polyurethane modified acrylate is 20~50:10~40:10~35.

[0010] Furthermore, the above-mentioned back contact battery separator composition has at least one of the following technical features: (1) R1 is selected from C3~C 10 straight-chain alkylene, C3~C 10 (1) Any one of the branched alkylene groups; (2) R1 is selected from any one of the straight-chain alkylene groups of C4 to C8 and the branched alkylene groups of C4 to C5; (3) R1 is selected from any one of 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, and 1,8-octylene; (4) R2 and R3 are each independently selected from any one of methylene, ethylene, propylene, and 1,4-butylene.

[0011] Furthermore, the above-mentioned back contact battery separator composition has at least one of the following technical features: (1) the mass percentage of silicon atoms in the organosilicon acrylate is 30-40%; (2) the mass percentage of amino groups in the polyurethane modified acrylate is 10-20%.

[0012] Furthermore, the aforementioned polyurethane-modified acrylate is selected from any one or more of polyurethane acrylate (PU-A), polyurethane dihydroxy acrylate (Hydroxy-PU-A), polyurethane acrylate / butyl acrylate copolymer (PU-A / BA), polyurethane acrylate / silane copolymer (PU-A-Si), and polyurethane acrylate / epoxy copolymer (PU-A-Epoxy).

[0013] Furthermore, the aforementioned acrylic monomers are selected from any one or more of acrylic acid (AA), methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), isobutyl acrylate (IBA), isooctyl acrylate (2-EHA), methacrylic acid (MAA), methyl methacrylate (MMA), and ethyl methacrylate (EMA).

[0014] Furthermore, the aforementioned reactive diluent is a high-functionality reactive diluent monomer selected from any one or more of the following: difunctional tripropylene glycol diacrylate, difunctional 1,6-hexanediol diacrylate (HDDA), difunctional dipropylene glycol diacrylate (DPGDA), trifunctional trimethylolpropane triacrylate (TMPTA), trifunctional glyceryl triacrylate (OTA-480), dipentaerythritol pentaacrylate (DPHA), dipentaerythritol hexaacrylate (DPHA), and tripropylene glycol diacrylate derivatives.

[0015] Furthermore, the filler material is selected from any one or more of fumed silica, nano silica, and nano alumina.

[0016] Furthermore, the absorption wavelength of the above photoinitiator is 300~400 nm, and the photoinitiator is selected from any one or more of 2,4,6-trimethylphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and α-hydroxy ketone.

[0017] According to another aspect of the present invention, a separator for a back contact battery is provided, which is obtained by mixing a separator composition, wherein the separator composition is the aforementioned separator composition for a back contact battery, the thermal decomposition temperature of the separator for a back contact battery is 300~400°C, the initial cross-cut adhesion of the separator for a back contact battery is grade 0, the PCT48 cross-cut adhesion is grade 0~1, and the TC200 cross-cut adhesion is grade 0~1, the UV60 yellowing Δb of the separator for a back contact battery is +0.4~+1.5, and the separator for a back contact battery remains non-sticky for 2~3 hours under 5~9 kg pressure and 200~270°C, with a yellowing Δb of +2.3~+5.7.

[0018] By applying the technical solution of this invention, the separator composition for back contact batteries effectively solves the problem of insufficient material protection in the high-temperature passivation and full-process physical protection process of back contact batteries in the prior art through the rational selection of resin substrate, reactive diluent monomer, filler and photoinitiator. Specifically, the resin substrate includes organosilicon acrylate, acrylic monomer and polyurethane modified acrylate. Among them, the key of organosilicon acrylate is its unique molecular structure, which can endow the composition with excellent thermal stability and high temperature resistance, with a thermal decomposition temperature as high as 300~400℃, ensuring that the separator will not soften or decompose in the high-temperature passivation process, thereby achieving continuous protection of the battery cell. Specifically, controlling n=40~70 increases the molecular chain length, extends the polymer chain, strengthens the entanglement between chains, and makes the molecular network structure of the separator more compact, thereby significantly improving the toughness and interfacial bonding strength of the separator, ensuring that the separator can still provide reliable protection in harsh environments. Controlling the m=4~80 increases the content of organosilicon segments, thereby improving the thermal stability of the separator and ensuring its stability and strong adhesion to the battery cells in humid and hot environments, effectively preventing interfacial delamination. Acrylic monomers provide good film-forming properties and high transparency. Controlling the content of amino groups in polyurethane-modified acrylate effectively inhibits yellowing pathways, improves the optical stability, flexibility, and adhesion of the separator, and reduces its risk of brittleness at high temperatures. Furthermore, by selecting high-functionality reactive diluent monomers, more crosslinking points are formed during polymerization, increasing the crosslinking density of the separator and thus improving its heat resistance. This allows it to maintain structural stability and low yellowing characteristics even at high temperatures, ensuring that the appearance and power generation efficiency of photovoltaic modules are not affected. The addition of photoinitiators promotes rapid curing of the separator under ultraviolet light irradiation, forming a tight crosslinked structure, while ensuring rapid curing of the separator under high-temperature conditions, shortening the preparation cycle and reducing energy consumption. The use of fumed silica as a filler enhances the wear resistance and scratch resistance of the release liner, further improving its effectiveness in physical protection. At the same time, its fine particles help to disperse stress and avoid micro-cracks caused by excessive hardness under high temperature conditions. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0020] As analyzed in the background section of this application, traditional polyurethane acrylic resins, epoxy resins, epoxy-acrylic modified resins, and single organosilicon resins all experience chain segment breakage, oxidative degradation, or insufficient cross-linking at high temperatures, leading to softening, yellowing, and decreased light transmittance of the adhesive layer, thereby affecting the photoelectric conversion efficiency and lifespan of the battery. In other words, existing back contact battery separators suffer from poor high-temperature stability and yellowing resistance. To address these issues, this application provides a back contact battery separator composition and a back contact battery separator.

[0021] In a typical embodiment of this application, a separator composition for back contact batteries is provided. By weight percentage, the separator composition for back contact batteries comprises 60-84% resin substrate, 10-30% reactive diluent monomer, 0.5-2% filler, and 2-8% photoinitiator; wherein the resin substrate comprises silicone acrylate, acrylic monomer, and polyurethane-modified acrylate; the structural formula of the silicone acrylate is as follows:

[0022]

[0023] Where n = 40~70, m = 40~80, and R1 is selected from C1~C 12 straight-chain alkylene, C3~C 12 R2 and R3 are each independently selected from any one of the branched alkylene groups of C1 to C4 and any one of the branched alkylene groups of C3 to C4; the mass percentage of amino groups in the polyurethane modified acrylate is 10 to 30%.

[0024] The separator composition for back contact batteries effectively solves the problem of insufficient material protection in the high-temperature passivation and full-process physical protection process of existing back contact batteries by rationally selecting resin substrates, reactive diluent monomers, fillers, and photoinitiators. Specifically, the resin substrate includes organosilicon acrylates, acrylic monomers, and polyurethane-modified acrylates. The key to the organosilicon acrylate lies in its unique molecular structure, which endows the composition with excellent thermal stability and high-temperature resistance, with a thermal decomposition temperature as high as 300~400℃. This ensures that the separator will not soften or decompose during the high-temperature passivation process, thus achieving continuous protection for the battery cells. Specifically, controlling n=40~70 increases the molecular chain length, extends the polymer chains, strengthens the entanglement between chains, and makes the molecular network structure of the separator more compact, thereby significantly improving the toughness and interfacial adhesion strength of the separator, ensuring that the separator still provides reliable protection in harsh environments. Controlling the m=4~80 increases the content of organosilicon segments, thereby improving the thermal stability of the separator and ensuring its stability and strong adhesion to the battery cells in humid and hot environments, effectively preventing interfacial delamination. Acrylic monomers provide good film-forming properties and high transparency. Controlling the content of amino groups in polyurethane-modified acrylate effectively inhibits yellowing pathways, improves the optical stability, flexibility, and adhesion of the separator, and reduces its risk of brittleness at high temperatures. Furthermore, by selecting high-functionality reactive diluent monomers, more crosslinking points are formed during polymerization, increasing the crosslinking density of the separator and thus improving its heat resistance. This allows it to maintain structural stability and low yellowing characteristics even at high temperatures, ensuring that the appearance and power generation efficiency of photovoltaic modules are not affected. The addition of photoinitiators promotes rapid curing of the separator under ultraviolet light irradiation, forming a tight crosslinked structure, while ensuring rapid curing of the separator under high-temperature conditions, shortening the preparation cycle and reducing energy consumption. The use of fumed silica as a filler enhances the wear resistance and scratch resistance of the release liner, further improving its effectiveness in physical protection. At the same time, its fine particles help to disperse stress and avoid micro-cracks caused by excessive hardness under high temperature conditions.

[0025] Furthermore, by controlling the mass percentage of amino groups in polyurethane-modified acrylate to 10-30%, the tendency of the release liner to undergo thermo-oxidative yellowing and UV yellowing under thermo-oxidative and UV-induced environments is significantly reduced at the molecular level. This ensures that the release liner maintains excellent optical transparency even after long-term use, ultimately guaranteeing continuous and efficient power output of the photovoltaic module. In addition, this precise control of the content also balances the crosslinking density and toughness of the release liner, ensuring that the adhesive layer is not prone to brittleness under extreme temperatures, while maintaining good adhesion and resistance to damp heat.

[0026] In summary, the separator composition for back contact batteries provided by this invention, through adjusting the proportions and material selection of each component, not only meets the requirements of high-temperature passivation processes and effectively protects the battery cells from damage, but also maintains low yellowing and high light transmittance optical stability during long-term use. This ensures continuous and efficient power output of photovoltaic modules and overcomes the key technical obstacle of separators being unsuitable for high-temperature passivation processes. It makes it more widely applicable to passivation process windows including ALD and PECVD.

[0027] As some examples of this embodiment, the mass percentage of the resin substrate in the separator composition for back contact batteries can be 60%, 65%, 70%, 76%, 80%, 82%, or 84%; or, the mass percentage of the resin substrate can be controlled between any two of the above mass percentages. The mass percentage of the reactive diluent monomer in the separator composition for back contact batteries can be 10%, 15%, 20%, 25%, or 30%; or, the mass percentage of the reactive diluent monomer can be controlled between any two of the above mass percentages. The mass percentage of the filler in the separator composition for back contact batteries can be 0.5%, 1%, 1.5%, or 2%; or, the mass percentage of the filler can be controlled between any two of the above mass percentages. The mass percentage of the photoinitiator in the separator composition for back contact batteries can be 2%, 3%, 4%, 5%, 6%, 7%, or 8%; or, the mass percentage of the photoinitiator can be controlled between any two of the above mass percentages. The mass percentage of amino groups in the polyurethane-modified acrylate can be 10%, 15%, 20%, 25%, or 30%; or, the mass percentage of amino groups can be controlled between any two of the above mass percentages.

[0028] In one embodiment of this application, the mass ratio of the above-mentioned organosilicon acrylate, acrylic monomer and polyurethane modified acrylate is 20~50:10~40:10~35.

[0029] The optimal combination of silicone acrylates with acrylic monomers and polyurethane-modified acrylates in the above proportions helps to achieve the best synergistic effect. For example, the excellent film-forming properties of acrylates, the outstanding thermal stability of silicon-oxygen bonds (Si-O) in silicone, and the low yellowing properties of polyurethane-modified acrylates combine to effectively extend the molecular chain, enhance the entanglement between chain segments, and construct a dense and stable network structure. This significantly improves the toughness and interfacial adhesion of the release adhesive, ensuring that it can maintain reliable protective performance even in harsh environments.

[0030] As some examples of this embodiment, the mass ratio of silicone acrylate, acrylic monomer, and polyurethane-modified acrylate can be 20:40:35, 25:28:31, 40:15:29, 50:10:24, 40:15:27, 50:16:10, 25:28:31, 40:18:31, 40:15:27, or 25:28:31; or, the mass ratio of silicone acrylate, acrylic monomer, and polyurethane-modified acrylate can be controlled between any two of the above mass ratios.

[0031] In one embodiment of this application, the above-mentioned back contact battery separator composition has at least one of the following technical features: (1) R1 is selected from C3~C 10 straight-chain alkylene, C3~C 10 (1) Any one of the branched alkylene groups; (2) R1 is selected from any one of the straight-chain alkylene groups of C4 to C8 and the branched alkylene groups of C4 to C5; (3) R1 is selected from any one of 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, and 1,8-octylene; (4) R2 and R3 are each independently selected from any one of methylene, ethylene, propylene, and 1,4-butylene.

[0032] The selection of R1, R2 and R3 is beneficial to further improve the crosslinking density and network structure stability of the resin substrate, so that the release colloid can maintain good physical isolation performance during high-temperature passivation and effectively resist yellowing caused by thermo-oxidative aging and UV irradiation.

[0033] In one embodiment of this application, the above-mentioned back contact battery separator composition has at least one of the following technical features: (1) the mass percentage of silicon atoms in the organosilicon acrylate is 30-40%; (2) the mass percentage of amino groups in the polyurethane modified acrylate is 10-20%.

[0034] Setting the mass percentage of silicon atoms within the above range helps balance the thermal stability and optical transparency of the release ester, allowing it to maintain low yellowing and high light transmittance even after prolonged treatment in high-temperature environments above 270°C. This is achieved through precise control of the silicone segment content. A preferred mass percentage of 10-20% amino groups in the polyurethane-modified acrylate further helps reduce the tendency of the release ester to undergo thermo-oxidative yellowing and UV yellowing under thermo-oxidative and UV-induced conditions.

[0035] As some examples of this embodiment, the mass percentage of silicon atoms in the silicone acrylate can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%; or, the mass percentage of silicon atoms can be controlled between any two of the above-mentioned mass percentages. The mass percentage of amino groups in the polyurethane-modified acrylate can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%; or, the mass percentage of amino groups can be controlled between any two of the above-mentioned mass percentages.

[0036] To further optimize the crosslinking density and network structure of the release liner, thereby improving its high temperature resistance and low yellowing, in one embodiment of this application, the polyurethane modified acrylate is preferably selected from any one or more of polyurethane acrylate (PU-A), polyurethane dihydroxy acrylate (Hydroxy-PU-A), polyurethane acrylate / butyl acrylate copolymer (PU-A / BA), polyurethane acrylate / silane copolymer (PU-A-Si), and polyurethane acrylate / epoxy copolymer (PU-A-Epoxy).

[0037] In one embodiment of this application, the acrylic monomers are selected from any one or more of acrylic acid (AA), methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), isobutyl acrylate (IBA), isooctyl acrylate (2-EHA), methacrylic acid (MAA), methyl methacrylate (MMA), and ethyl methacrylate (EMA).

[0038] The selected acrylic monomers each possess different chain segment characteristics and reactivity. Through reasonable compounding, the hardness and light transmittance of the final separator can be controlled, ensuring that the cells are fully protected during high-temperature passivation and module encapsulation, while maintaining good visual effects and electrical performance.

[0039] In one embodiment of this application, the aforementioned reactive diluent is a high-functionality reactive diluent monomer selected from any one or more of the following: difunctional tripropylene glycol diacrylate, difunctional 1,6-hexanediol diacrylate (HDDA), difunctional dipropylene glycol diacrylate (DPGDA), trifunctional trimethylolpropane triacrylate (TMPTA), trifunctional glyceryl triacrylate (OTA-480), dipentaerythritol pentaacrylate (DPHA), dipentaerythritol hexaacrylate (DPHA), and tripropylene glycol diacrylate derivatives.

[0040] The addition of these high-functionality reactive diluents significantly increases the crosslinking density of the release liner by forming more crosslinking points. This high crosslinking density results in a denser cured liner structure, enhancing the release liner's mechanical strength and heat resistance, while reducing its yellowing tendency under heat, oxygen, and ultraviolet light conditions. This ensures the release liner's optical stability and long-lasting protective capabilities under complex processing conditions. Furthermore, the selection of high-functionality reactive diluents optimizes the rheological properties of the release liner, making it more suitable for precision coating processes such as inkjet printing, thereby improving production efficiency and product yield.

[0041] In one embodiment of this application, the filler is selected from any one or more of fumed silica, nano silica, and nano alumina.

[0042] The interaction between the filler and the resin substrate enhances the overall mechanical properties of the separator, reducing softening and thermal aging under high-temperature and humid conditions. This ensures the separator effectively maintains its physical isolation and chemical protection functions throughout the entire manufacturing process of photovoltaic back contact (BC) cells, especially during edge passivation. Specifically, fumed silica and nano-silica, due to their high surface area and unique structure, can form a nanoscale network, increasing the hardness and toughness of the separator layer. Meanwhile, nano-alumina, with its excellent thermal conductivity and high-temperature resistance, helps reduce thermal stress concentration within the separator layer during high-temperature passivation, preventing crack formation and further improving the separator's high-temperature and humid heat resistance.

[0043] In one embodiment of this application, the absorption wavelength of the photoinitiator is 300-400 nm, and the photoinitiator is selected from any one or more of 2,4,6-trimethylphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and α-hydroxy ketone.

[0044] The selected photoinitiator and its specific wavelength range promote the rapid curing of the release liner under light conditions, shortening the production cycle and improving production efficiency. Meanwhile, the specific wavelength selection of ultraviolet light helps reduce the yellowing tendency of the release liner during the curing process, because shorter wavelengths can more effectively excite the photoinitiator without overheating the release liner itself.

[0045] As some examples of this embodiment, the absorption wavelength of the photoinitiator can be 300nm, 320nm, 350nm, 365nm, 385nm, 395nm, or 400nm; or, the absorption wavelength of the photoinitiator can be controlled to be between any two of the above wavelengths.

[0046] In another typical embodiment of this application, a back contact battery separator is provided, which is obtained by mixing a separator composition. The separator composition is the aforementioned back contact battery separator composition. The thermal decomposition temperature of the back contact battery separator is 300~400℃. The initial cross-cut adhesion of the back contact battery separator is grade 0, the PCT48 cross-cut adhesion is grade 0~1, and the TC200 cross-cut adhesion is grade 0~1. The UV60 yellowing Δb of the back contact battery separator is +0.4~+1.5. The back contact battery separator remains non-sticky for 2~3 hours under 5~9kg pressure and 200~270℃, and the yellowing Δb is +2.3~+5.7.

[0047] The separator for back contact solar cells exhibits excellent thermal stability and low yellowing performance, meeting the requirements of high-temperature edge passivation processes. Its thermal decomposition temperature range is 300~400℃, ensuring structural integrity during high-temperature steps in photovoltaic cell manufacturing, preventing softening or decomposition and providing comprehensive protection for the cells. Simultaneously, the separator demonstrates excellent adhesion; even after PCT48 and TC200 tests, its cross-cut adhesion remains at level 0~1, indicating its strong adhesion to the cell surface under various environments, preventing external mechanical damage. Furthermore, UV60 testing shows that the yellowing value Δb remains between +0.4 and +1.5, proving its good optical transparency under ultraviolet irradiation and preventing yellowing from reducing the photoelectric conversion efficiency of the cells. More importantly, this separator can withstand pressures of 5-9 kg and temperatures of 200-270°C for 2-3 hours without sticking, and its yellowing value Δb is +2.3 to +5.7. This means that the separator can not only withstand high-temperature passivation processes but also avoid adhesion problems caused by overheating in actual operation, while maintaining a low level of yellowing, ensuring the photoelectric performance and appearance quality of the solar cells at high temperatures. All these characteristics work together to make the separator of this invention an ideal auxiliary material for the passivation process of back-contact batteries, effectively solving the problems of insufficient temperature resistance and yellowing in existing technologies, and ensuring high quality and high performance of solar cells throughout the entire manufacturing process.

[0048] As examples of this embodiment, the UV60 yellowing Δb of the separator for the back contact battery can be +0.4, +0.5, +0.6, +0.7, +0.8, +0.9, +1.0, +1.1, +1.2, +1.3, +1.4, +1.5, +1.6, +1.7, +1.8, or +1.9; or, the UV60 yellowing Δb of the separator can be controlled between any two of the above Δb values. The separator for the back contact battery remains non-adhesive for 2-3 hours under a pressure of 5-9 kg and a temperature of 200-270°C, and the yellowing Δb can be +2.3, +2.8, +3.1, +3.2, +3.3, +3.4, +4.1, +4.6, or +5.7; or, the yellowing Δb of the separator under a pressure of 5-9 kg and a temperature of 200-270°C can be controlled between any two of the above Δb values.

[0049] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0050] Example 1

[0051] Preparation steps:

[0052] 1. Raw material preparation (corresponding to the formula in Table 1, by mass percentage)

[0053] Organosilicon acrylate: 25wt%, where n=55, m=60, R1 is 1,6-hexylene, R2 is ethylene, and R3 is propylene;

[0054] Acrylic monomers (methyl acrylate): 28 wt%;

[0055] Polyurethane modified acrylate: 31 wt%;

[0056] Reactive diluent: Hydroxyethyl methacrylate (2wt%) / Trimethylolpropane triacrylate (8wt%)

[0057] Photoinitiator: TPO (2wt%) / 184 (3wt%);

[0058] Filler: Fumed silica: 1 wt%

[0059] 2. Preparation steps

[0060] Step 1: Under nitrogen atmosphere protection, a 500mL four-necked reactor equipped with a stirrer, thermometer, constant pressure dropping funnel and reflux condenser is preheated. In a nitrogen-protected high-speed dispersion vessel, 25wt% of silicone acrylate, 28wt% of methyl acrylate and 31wt% of polyurethane acrylate are added sequentially. The stirring speed is set to 1200rpm and stirred at room temperature for 15min to obtain a uniform resin substrate mixture.

[0061] Step 2: Add reactive diluent. Reduce the stirring speed to 800 rpm, add 2 wt% hydroxyethyl methacrylate and 8 wt% trimethylolpropane triacrylate to the resin matrix mixture, and continue stirring for 10 minutes to ensure complete dispersion of the reactive diluent.

[0062] Step 3: Introduce the packing material and maintain a rotation speed of 800 rpm. Add 1 wt% fumed silica and stir for 5 minutes. Then, turn on ultrasonic dispersion (power 300W) for 20 minutes to eliminate packing material agglomeration.

[0063] Step 4: Add photoinitiator TPO (2wt%) and 184 (3wt%) and degas. Adjust the stirring speed to 500 rpm, add 2% photoinitiator (TPO and 184 are mixed at a mass ratio of 2:3), stir for 5 min, and then turn on vacuum degassing (vacuum degree -0.09MPa) for 3 min to obtain the premixed solution of the release colloid.

[0064] Step 5: UV curing molding. The premixed liquid is uniformly coated on the surface of the battery cell substrate (wet film thickness 20±2μm), and cured by irradiation with a 395nm UV lamp. The irradiation energy is controlled at 10000mJ / cm², and the curing time is 2~3s to obtain the isolation adhesive product of Example 1.

[0065] The specific operations of Examples 1 to 8 and Comparative Examples 1 to 7 can be referred to Example 1. The specific types and proportions of components in Examples 1 to 8 and Comparative Examples 1 to 7 are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069]

[0070]

[0071] Performance testing:

[0072] Initial cross-cut adhesion test: GB / T 9286-1998 "Cross-cut test for paint and varnish films";

[0073] PCT48 Cross-cut Adhesion Test:

[0074] Sample preparation: The printed battery cells are encapsulated in a 300mm² package. Small parts are made on 300mm thick glass.

[0075] Test standards: IEC 62788-2; GB / T 41203-2021;

[0076] Test conditions: 120°C, RH 100%, 48 h;

[0077] Adhesion test: GB / T 9286-1998 "Paints and varnishes - Cross-cut test for films";

[0078] Adhesion by TC200 cross-cut method:

[0079] Sample preparation: Encapsulate the printed solar cells on a 300 mm 300 mm glass to make small pieces;

[0080] Test standards: IEC 61215-2:2021 MQT 21; GB / T 9535-2022 Thermal cycling;

[0081] Test conditions: ① The sample temperature cycles between -40°C ± 2 and 85 ± 2°C; ② The rate of change of the ambient temperature does not exceed 100°C / h, and it should be stable for at least 10 min at each extreme temperature, and one cycle does not exceed 6 h; ③ After the test is completed, there should be at least 1 h recovery time to test the performance; ④ The power is on throughout the test - 100% Impp current is applied during the temperature rise process from -40 to 80°C, and 1% Impp current is applied at other times; ⑤ A force of 5 N needs to be applied on the junction box;

[0082] Adhesion test: GB / T 9286-1998 "Paints and varnishes - Cross-cut test for films";

[0083] 270°C High-temperature tackiness test at 270°C for 3 h + 9 kg pressure:

[0084] 1) Tackiness test:

[0085] Sample preparation: Take a box of solar cells with cured glue on the surface and stack them normally;

[0086] Apply pressure: Press a 9 kg weight on the stacked solar cells (evenly covering the solar cells);

[0087] High-temperature treatment: Put the sample and the weight into an oven and keep it at 270°C for 3 h.

[0088] Cooling and observation: Take out after cooling below 80°C, remove the weight and separate the solar cells, and observe whether they are adhered;

[0089] Judgment: It is considered qualified if it can be easily separated and there is no glue cross-piece adhesion; otherwise, it is unqualified;

[0090] 2) High-temperature yellowing test:

[0091] Sample preparation: Prepare a 20-30 μm cured adhesive film, place it on a high-temperature cloth, and use a 300 mm thick cloth. 300mm glass stacking;

[0092] Apply pressure: Place a 9kg weight (evenly covering the glass) on the stacked solar cells.

[0093] High-temperature treatment: Same as above;

[0094] Yellowing test: Use a colorimeter to test the yellowing Δb value before and after high temperature;

[0095] UV60 yellowing:

[0096] Sample preparation method: Prepare a 20~30μm cured film and encapsulate it in two glass sandwich layers to make a small part;

[0097] UV60 testing standards: IEC 61215-2:2021 MQT 10; GB / T 19394-2003;

[0098] Test conditions: ① Temperature of small parts: 60±5℃; ② Total irradiance: 60KWh / m 2 The wavelength range of 280~400nm is used for at least 3%, and the irradiance in the 280~320nm range does not exceed 10%. The irradiance of light in the 280~400nm range does not exceed 250W / ㎡ (about 5 times that of natural light), and the uniformity is within ±15% on the test surface.

[0099] UV60 yellowing test: Use a colorimeter to test the yellowing Δb value before and after UV60.

[0100] The test results are listed in Table 2.

[0101] Table 2

[0102]

[0103] It should be noted that for 270℃ The adhesion under 3h+9kg pressure is described as follows: "slightly sticky", "non-sticky", and "sticky", indicating that the high temperature resistance of the release adhesive gradually deteriorates.

[0104] A comparison of Example 1 and Comparative Example 1 shows that this patent can improve the heat resistance of the material by adding organosilicon-modified acrylate. A comparison of Example 1 and Comparative Example 2 shows that this patent reduces yellowing by decreasing the amount of polyurethane acrylate and thus reducing the amount of yellowing nitrogen. A comparison of Example 1 and Comparative Example 3 shows that this patent can improve the heat resistance of the material through a high crosslinking density scheme. A comparison of Example 1 and Comparative Example 4 shows that increasing the molecular weight of the organosilicon acrylate can improve the toughness of the material and thus enhance adhesion. A comparison of Example 1 and Comparative Example 5 shows that a too small m value indicates too low an organosilicon segment content in the organosilicon acrylate, which is detrimental to improving the thermal stability of the release adhesive. A comparison of Example 1 and Comparative Example 6 shows that a high mass percentage of amino groups in the polyurethane acrylate is detrimental to improving the yellowing resistance of the release adhesive. A comparison of Example 1 and Comparative Example 7 shows that a low mass percentage of amino groups in the polyurethane acrylate is detrimental to improving the adhesion of the release adhesive.

[0105] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0106] The separator composition for back contact batteries effectively solves the problem of insufficient material protection in the high-temperature passivation and full-process physical protection process of existing back contact batteries by rationally selecting resin substrates, reactive diluent monomers, fillers, and photoinitiators. Specifically, the resin substrate includes organosilicon acrylates, acrylic monomers, and polyurethane-modified acrylates. The key to the organosilicon acrylate lies in its unique molecular structure, which endows the composition with excellent thermal stability and high-temperature resistance, with a thermal decomposition temperature as high as 300~400℃. This ensures that the separator will not soften or decompose during the high-temperature passivation process, thus achieving continuous protection for the battery cells. Specifically, controlling n=40~70 increases the molecular chain length, extends the polymer chains, strengthens the entanglement between chains, and makes the molecular network structure of the separator more compact, thereby significantly improving the toughness and interfacial adhesion strength of the separator, ensuring that the separator still provides reliable protection in harsh environments. Controlling the m=4~80 increases the content of organosilicon segments, thereby improving the thermal stability of the separator and ensuring its stability and strong adhesion to the battery cells in humid and hot environments, effectively preventing interfacial delamination. Acrylic monomers provide good film-forming properties and high transparency. Controlling the content of amino groups in polyurethane-modified acrylate effectively inhibits yellowing pathways, improves the optical stability, flexibility, and adhesion of the separator, and reduces its risk of brittleness at high temperatures. Furthermore, by selecting high-functionality reactive diluent monomers, more crosslinking points are formed during polymerization, increasing the crosslinking density of the separator and thus improving its heat resistance. This allows it to maintain structural stability and low yellowing characteristics even at high temperatures, ensuring that the appearance and power generation efficiency of photovoltaic modules are not affected. The addition of photoinitiators promotes rapid curing of the separator under ultraviolet light irradiation, forming a tight crosslinked structure, while ensuring rapid curing of the separator under high-temperature conditions, shortening the preparation cycle and reducing energy consumption. The use of fumed silica as a filler enhances the wear resistance and scratch resistance of the release liner, further improving its effectiveness in physical protection. At the same time, its fine particles help to disperse stress and avoid micro-cracks caused by excessive hardness under high temperature conditions.

[0107] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A separator composition for back contact batteries, characterized in that, The back contact battery separator composition comprises, by weight percentage: 60-84% resin substrate; 10-30% reactive diluent monomer; 0.5~2% filler; 2-8% photoinitiator; The resin substrate includes silicone acrylate, acrylic monomers, and polyurethane-modified acrylate; The structural formula of the organosilicon acrylate is as follows: Where n = 40~70, m = 40~80, and R1 is selected from C1~C 12 straight-chain alkylene, C3~C 12 R2 and R3 are each independently selected from any one of the branched alkylene groups of C1 to C4 and any one of the branched alkylene groups of C3 to C4; The mass percentage of amino groups in the polyurethane-modified acrylate is 10-30%.

2. The separator composition for back contact batteries according to claim 1, characterized in that, The mass ratio of the organosilicon acrylate, the acrylic monomer, and the polyurethane-modified acrylate is 20~50:10~40:10~35.

3. The separator composition for back contact batteries according to claim 1, characterized in that, The back contact battery separator composition has at least one of the following technical features: (1) R1 is selected from C3~C 10 straight-chain alkylene, C3~C 10 Any one of the branched alkylene groups; (2) R1 is selected from any one of C4~C8 straight-chain alkylene or C4~C5 branched alkylene; (3) The R1 is selected from any one of 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, and 1,8-octylene; (4) R2 and R3 are each independently selected from any one of methylene, ethylene, propylene, and 1,4-butylene.

4. The separator composition for back contact batteries according to any one of claims 1 to 3, characterized in that, The back contact battery separator composition has at least one of the following technical features: (1) The mass percentage of silicon atoms in the organosilicon acrylate is 30-40%; (2) The mass percentage of amino groups in the polyurethane modified acrylate is 10~20%.

5. The separator composition for back contact batteries according to claim 4, characterized in that, The polyurethane-modified acrylate is selected from any one or more of polyurethane acrylate, polyurethane dihydroxy acrylate, polyurethane acrylate / butyl acrylate copolymer, polyurethane acrylate / silane copolymer, and polyurethane acrylate / epoxy copolymer.

6. The separator composition for back contact batteries according to any one of claims 1 to 3, characterized in that, The acrylic monomers are selected from any one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isooctyl acrylate, methacrylic acid, methyl methacrylate, and ethyl methacrylate.

7. The separator composition for back contact batteries according to any one of claims 1 to 3, characterized in that, The reactive diluent is a high-functionality reactive diluent monomer selected from any one or more of the following: difunctional dipropylene glycol diacrylate, difunctional 1,6-hexanediol diacrylate, difunctional dipropylene glycol diacrylate, trifunctional trimethylolpropane triacrylate, trifunctional glyceryl triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and tripropylene glycol diacrylate derivatives.

8. The separator composition for back contact batteries according to any one of claims 1 to 3, characterized in that, The filler is selected from any one or more of fumed silica, nano silica, and nano alumina.

9. The separator composition for back contact batteries according to any one of claims 1 to 3, characterized in that, The photoinitiator has an absorption wavelength of 300-400 nm and is selected from any one or more of 2,4,6-trimethylphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and α-hydroxy ketone.

10. A separator for back contact batteries, obtained by mixing a separator composition, characterized in that, The separating adhesive composition is the separating adhesive composition for back contact batteries according to any one of claims 1 to 9, and the thermal decomposition temperature of the separating adhesive for back contact batteries is 300~400°C. The initial cross-cut adhesion of the back contact battery separator is grade 0, the PCT48 cross-cut adhesion is grade 0-1, and the TC200 cross-cut adhesion is grade 0-1. The UV60 yellowing Δb of the insulating adhesive used for the back contact battery is +0.4 to +1.

5. The back contact battery separator does not stick under pressure of 5-9 kg and temperature of 200-270 °C for 2-3 hours, and the yellowing Δb is +2.3 to +5.7.

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