An encapsulating film for BC battery modules and its preparation method

Abstract

This application relates to an encapsulating film for use in BC battery modules and its preparation method. The encapsulating film mainly consists of a surface layer and an inner layer of POE resin material, and an intermediate layer of nano-SiO2 modified POE resin material. Each layer contains organically modified montmorillonite (OMMT), aminosilane coupling agent KH-550, a composite stabilizer, a crosslinking agent DCP, and antioxidant 1010. The composite stabilizer includes UV-770, UV-P, and UV-327. The encapsulating film of this invention achieves high insulation, high adhesion, and low thermal deformation through a dedicated anti-ion migration system, a composite aging-resistant system, a three-layer functional partition structure, and a high-temperature stabilization formulation design, perfectly meeting the current requirements of high-voltage BC modules.

Description

Technical Field

[0001] This application relates to the field of BC battery manufacturing, and more specifically, to an encapsulating film for use in BC battery modules and a method for preparing the same. Background Technology

[0002] In existing technologies, potential-induced degradation (PID) is a core reliability bottleneck in the long-term operation of high-voltage BC solar modules. Under high-voltage conditions, sodium ions migrate from inside the module to the surface of the cells, leading to passivation layer failure and a significant decrease in photoelectric conversion efficiency. As the core insulating and protective material of the module, the encapsulating film's resistance to PID directly determines the module's long-term service life and operational stability.

[0003] Existing BC module encapsulation films mostly use ordinary POE or EVA as the substrate, which generally suffers from the following core technical defects and cannot meet the high reliability requirements of the high-end photovoltaic market: 1. Insufficient anti-PID performance: Most existing films do not contain dedicated anti-ion migration additives, or only contain a small amount of inorganic additives (such as magnesium oxide and aluminum oxide), which cannot effectively inhibit sodium ion migration. After 1000h PID testing at 1000V, 85℃ / 85%RH, the efficiency degradation rate is generally ≥8.5%, which does not meet the European market's ≤5.0% access standard.

[0004] 2. Poor aging resistance and short service life: Existing films mostly use a single type of UV stabilizer with low addition amount. After 3000h UV aging, the yellowing index is ≥3.0 and the elongation at break decreases by ≥30%. The film is prone to yellowing and cracking, and the actual service life of the module is ≤20 years, which cannot meet the warranty requirements of 25 years and above in overseas markets.

[0005] 3. Unreasonable structural design, unable to balance insulation and adhesion performance: Most existing adhesive films are single homogeneous structures, making it difficult to achieve high insulation and high adhesion strength at the same time. They generally have problems such as insulation strength ≤1500V, adhesion strength ≤0.6N / mm, and interlayer peeling rate ≥2.0%. Long-term operation is prone to interlayer peeling, affecting the reliability of the components.

[0006] 4. Insufficient high-temperature stability and poor mass production adaptability: The existing film has a cross-linking degree of ≥10% and a heat deformation of ≥0.15mm at a conventional lamination temperature of 150℃. This can easily lead to defects such as bubbles and delamination after module encapsulation, and it cannot adapt to the mass production process and insulation requirements of ≥1000V high-voltage BC modules.

[0007] 5. Lack of multi-performance synergy: Existing technologies cannot simultaneously solve the four core problems of "high resistance to PID, long life, high insulation and high adhesion". They often have the shortcoming of achieving single performance standards while other performances deteriorate. A systematic technical solution adapted to BC modules and high-end market standards has not been formed, and there is a significant technological gap.

[0008] The aforementioned defects mean that existing encapsulation films cannot meet the long-term use requirements of high-voltage BC modules in extreme environments, thus limiting the application of BC modules in high-end photovoltaic markets such as Europe and North America.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The primary objective of this application is to provide an encapsulating film for BC battery modules. Through a dedicated anti-ion migration system, a composite aging-resistant system, a three-layer functional partition structure, and a high-temperature stabilized formulation design, it achieves high insulation, high adhesion, and low thermal deformation, perfectly meeting the current application requirements of high-voltage BC modules.

[0011] The second objective of this application is to provide a method for preparing the encapsulating film, such that the prepared encapsulating film has the effects of high PID resistance, long life, high insulation, and high adhesion.

[0012] To achieve the above objectives, in a first aspect, the present invention provides an encapsulating film for BC battery modules, which is mainly composed of a surface layer and an inner layer of POE resin material, and an intermediate layer of nano-SiO2 modified POE resin material. Each layer contains organic modified montmorillonite OMMT, aminosilane coupling agent KH-550, composite stabilizer, crosslinking agent DCP, and antioxidant 1010, wherein the composite stabilizer includes UV-770, UV-P, and UV-327.

[0013] Because the encapsulating films used in existing BC battery modules have core problems such as weak anti-PID capability, poor aging resistance, inability to balance insulation and adhesion performance, insufficient high-temperature stability, and inability to synergistically improve multiple performance characteristics, this invention provides an encapsulating film that can solve the above-mentioned technical problems. Based on the systematic and innovative approach of "formula optimization - structural composite - standard adaptation", through a dedicated anti-ion migration system, composite aging resistance system, three-layer functional partition structure, and high-temperature stabilization formula design, the resulting encapsulating film achieves high anti-PID, long life, high insulation, and high adhesion.

[0014] The reason this invention employs a three-layer composite functional partitioned structure is primarily to balance the dual effects of high insulation and high adhesion of the adhesive film itself. In particular, the addition of nano-SiO2 to the middle layer significantly improves the insulation strength and dimensional stability of the adhesive film. Both the surface and inner layers are made of pure POE resin containing an anti-migration system, ensuring the adhesion performance between the adhesive film and the battery cell, glass / backsheet. Thus, after the three layers of resin materials are composited, the adhesive film exhibits an insulation strength ≥2500V, an adhesion strength ≥0.8N / mm, an interlayer peel rate ≤0.5%, and a thermal deformation ≤0.08mm at 150℃.

[0015] Compared to the single-layer adhesive film structure of existing technologies, which cannot simultaneously achieve both insulation and adhesion performance, this invention achieves high insulation, high adhesion, and low thermal deformation through a three-layer structure with functional partitions, perfectly meeting the requirements of high-voltage BC battery modules.

[0016] Preferably, as a further feasible option, the thickness of the outer and inner layers is 0.3-0.4 mm, and the thickness of the intermediate layer is 0.4-0.5 mm. Appropriate thickness control of each layer ensures a perfect fit between the film and the battery assembly.

[0017] Preferably, as a further feasible option, the POE resin is a high-purity POE resin with a melt index of 2.0-3.0 g / 10 min and a density of 0.87 g / cm³. This type of resin material has strong elasticity, high strength, and ultra-high elongation.

[0018] Preferably, as a further feasible option, the surface layer and the inner layer are composed of: 90-100 parts by mass of POE resin, 1-2 parts of OMMT, 0.5-1.5 parts of KH-550, 0.1-1 parts of UV-770, 0.1-1 parts of UV-P, 0.1-1 parts of UV-327, 0.2-0.4 parts of DCP, and 0.05-0.2 parts of antioxidant 1010.

[0019] In the specific formulation design of the film of the present invention, each layer is added with a composite anti-ion migration agent consisting of organically modified montmorillonite (OMMT) and aminosilane coupling agent (KH-550). OMMT is modified with hexadecyltrimethylammonium bromide, which expands the interlayer spacing to 20-30 nm and achieves physical barrier of sodium ions through the layered structure. KH-550 can improve the dispersibility of OMMT in the POE matrix and achieve chemical adsorption of sodium ions through amino groups. The two form a dual effect of "physical barrier + chemical adsorption".

[0020] Existing technologies mostly employ single inorganic anti-migration agents, resulting in poor dispersibility and limited effectiveness. The composite system of this invention can reduce sodium ion migration rate by more than 75%, exhibiting significantly superior anti-PID performance compared to existing technologies. With the above-described formulation design, the sodium ion migration rate of the film produced by this invention is ≤0.2 μm / h, and the efficiency decay rate after 1000 hours of PID testing is ≤3.5%.

[0021] Preferably, as a further feasible option, the intermediate layer is composed of: 90-100 parts of POE resin, 1-2 parts of nano-SiO2, 1-2 parts of OMMT, 0.5-1.5 parts of KH-550, 0.1-1 parts of UV-770, 0.1-1 parts of UV-P, 0.1-1 parts of UV-327, 0.2-0.4 parts of DCP, and 0.05-0.2 parts of antioxidant 1010.

[0022] In addition, the encapsulant film of this invention incorporates dicumyl peroxide (DCP) and 0.1-0.2% antioxidant 1010 in its formulation. The addition of DCP promotes the formation of a three-dimensional cross-linked network of POE molecular chains, enhancing the thermal stability and mechanical strength of the encapsulant film. Antioxidant 1010 inhibits oxidative degradation during high-temperature lamination, ensuring stable film performance. The encapsulant film with the optimized formulation exhibits a cross-linking degree ≥85% at a conventional lamination temperature of 150℃, free from encapsulation defects such as bubbles and delamination, and is fully compatible with the lamination process of existing BC module mass production lines.

[0023] Preferably, as a further feasible option, the composite stabilizers in each layer are formulated in the following mass proportions: 0.3-0.5 parts UV-770, 0.2-0.4 parts UV-P, and 0.1-0.3 parts UV-327.

[0024] Existing film formulations often employ a single type of stabilizer, failing to simultaneously address free radical capture and full-spectrum UV absorption. This invention, based on a synergistic anti-UV aging mechanism, combines polymer degradation mechanisms and UV absorption theory for multi-parameter synergistic optimization. A composite stabilizer is added to each layer of the film. Specifically, this composite stabilizer consists of a hindered amine light stabilizer (UV-770), a benzotriazole UV absorber (UV-P), and a UV absorber (UV-327), forming a ternary composite stabilizer. UV-770 captures free radicals from polymer degradation, while UV-P and UV-327 synergistically absorb UV light across the 280-400nm wavelength range. These three components construct a complete anti-aging system of "free radical capture + UV absorption." After adding the composite stabilizer with these specific components, the yellowing index after 3000 hours of UV aging is ≤1.5, and the elongation at break decreases by ≤15%, significantly improving the film's performance.

[0025] Secondly, the present invention also provides a method for preparing the above-mentioned encapsulating film, comprising the following steps: Each layer of components is co-extruded to prepare the film, with the extrusion temperature controlled at 160-170℃.

[0026] Preferably, as a further feasible option, the screw speed of the extrusion is controlled at 40-70 r / min and the die temperature is 160-180℃.

[0027] Preferably, as a further feasible option, the extrusion traction speed is 3-7 m / min.

[0028] Preferably, as a further feasible option, the temperature of the extruded cooling roller is 20-30°C.

[0029] The encapsulating film prepared by the above method has high resistance to PID, long life, high insulation and high adhesion. Specifically, controlling each parameter within an optimal range can significantly improve the performance of the film itself, and the prepared film can be perfectly adapted to existing BC battery modules.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly improved anti-PID performance: Sodium ion migration rate is reduced to 0.1-0.2μm / h, and efficiency decay rate is ≤4.0% after 1000h PID test, which is far better than the European market access requirement of ≤5.0%, and can be adapted to 1000-1500V high voltage BC modules.

[0031] (2) Significantly optimized aging resistance: After 3000h of UV aging, the yellowing index is ≤1.5, the elongation at break decreases by ≤15%, and the mechanical strength retention rate is ≥90% after 1000h of thermo-oxidative aging, which can support the service life of the components for 25-30 years and meet the long-term warranty requirements of overseas markets.

[0032] (3) Synergistic improvement of insulation and bonding performance: insulation strength ≥2500V, which is more than 60% higher than the existing technology; bonding strength ≥0.8N / mm, interlayer peeling rate ≤0.5%, and no defects such as interlayer peeling or cracking after 1000h of high temperature and high humidity aging.

[0033] (4) Excellent high temperature stability and strong mass production adaptability: the degree of crosslinking is ≥85% at 150℃ lamination temperature, the heat deformation is ≤0.08mm, the bubble rate of the module after lamination is ≤0.1%, which is fully compatible with the existing BC module mass production line and does not require production line modification.

[0034] (5) Wide range of application scenarios: It can be adapted to extreme environments such as large-scale ground photovoltaic, offshore photovoltaic, and desert photovoltaic, and is compatible with mainstream BC battery technologies such as IBC and HJT-BC. It meets the mainstream certification standards of the world and has outstanding market application value.

[0035] Other features and advantages of this application will be described in detail in the following detailed description section. Detailed Implementation

[0036] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] Example 1 The preparation method of the encapsulating film specifically for BC battery modules is as follows: Step 1: Raw material pretreatment High-purity POE resin (melt index 2.0 g / 10 min, density 0.87 g / cm³) was selected as the matrix; organically modified montmorillonite OMMT (hexadecyltrimethylammonium bromide modified, interlayer spacing 20-30 nm), aminosilane coupling agent KH-550, ternary composite stabilizers (UV-770, UV-P, UV-327), nano-SiO2 (particle size 20-30 nm, silane modified), crosslinking agent DCP, and antioxidant 1010 were used as additives. All raw materials were dried at 80℃ for 2 hours, and the moisture content after drying was ≤0.05%. They were then sealed and stored for later use.

[0038] Step 2: Ingredient formulation and three-layer co-extrusion preparation Prepare the ingredients according to the following mass ratio: Surface / inner layer formulation (parts by weight): POE resin 98.4 parts, OMMT 1.5 parts, KH-550 0.8 parts, UV-770 0.4 parts, UV-P 0.3 parts, UV-327 0.2 parts, DCP 0.3 parts, antioxidant 10100.1 parts; Intermediate layer formulation (mass fraction): POE resin 96.4 parts, nano SiO2 1.5 parts, OMMT 1.5 parts, KH-550 0.8 parts, UV-770 0.4 parts, UV-P 0.3 parts, UV-327 0.2 parts, DCP 0.3 parts, antioxidant 1010 0.1 parts.

[0039] The surface, intermediate, and inner layer materials were separately fed into a twin-screw extruder, and a three-layer co-extrusion process was used to prepare the film. The extrusion temperature was 160℃, the screw speed was 60 r / min, the die temperature was 165℃, the traction speed was 5 m / min, and the cooling roller temperature was 25℃. The total thickness of the film was 1.1 mm, with the surface and inner layers each being 0.35 mm and the intermediate layer being 0.4 mm. The thickness deviation was ≤ ±0.05 mm.

[0040] Step 3: Component Packaging and Performance Testing The battery module was encapsulated using the film of this embodiment. The encapsulation structure was: 3.2mm tempered glass + film of this embodiment + IBC battery cell + film of this embodiment + TPT backsheet. After the stacking was completed in a cleanroom, the module was laminated for 20 minutes at 150℃, 0.3MPa and vacuum degree ≤-0.095MPa to obtain the finished module.

[0041] Tested according to standards such as IEC61215 and IEC62804-1, the core performance is as follows: efficiency decay rate of 3.2% after 1000h PID test; yellowing index of 1.2 and elongation at break of 12% after 3000h UV aging; insulation strength of 2600V, adhesion strength to glass of 0.85N / mm, and interlayer peeling rate of 0.3%; crosslinking degree of 86% after lamination at 150℃, with no bubbles or delamination defects. All performance meets the design requirements and high-end market certification standards.

[0042] Example 2 The preparation method of the encapsulating film specifically for BC battery modules is as follows: Step 1: Raw material pretreatment High-purity POE resin (melt index 3.0 g / 10 min, density 0.87 g / cm³) was selected as the matrix; organically modified montmorillonite OMMT (hexadecyltrimethylammonium bromide modified, interlayer spacing 20-30 nm), aminosilane coupling agent KH-550, ternary composite stabilizers (UV-770, UV-P, UV-327), nano-SiO2 (particle size 20-30 nm, silane modified), crosslinking agent DCP, and antioxidant 1010 were used as additives. All raw materials were dried at 80℃ for 2 hours, and the moisture content after drying was ≤0.05%. They were then sealed and stored for later use.

[0043] Step 2: Ingredient formulation and three-layer co-extrusion preparation Prepare the ingredients according to the following mass ratio: Surface / inner layer formulation (parts by weight): POE resin 90 parts, OMMT 2 parts, KH-550 0.5 parts, UV-770 1 part, UV-P 0.1 parts, UV-327 1 part, DCP 0.2 parts, antioxidant 1010 0.05 parts; Intermediate layer formulation (mass fraction): 100 parts POE resin, 1 part nano SiO2, 1 part OMMT, 1.5 parts KH-550, 0.1 parts UV-770, 1 part UV-P, 0.1 parts UV-327, 0.4 parts DCP, and 0.2 parts antioxidant 1010.

[0044] The surface, intermediate, and inner layer materials were separately fed into a twin-screw extruder, and a three-layer co-extrusion process was used to prepare the film. The extrusion temperature was 170℃, the screw speed was 40 r / min, the die temperature was 180℃, the traction speed was 3 m / min, and the cooling roller temperature was 30℃. The total thickness of the film was 1.3 mm, with the surface and inner layers each being 0.3 mm and the intermediate layer being 0.5 mm. The thickness deviation was ≤ ±0.05 mm.

[0045] Step 3: Component Packaging and Performance Testing The battery module was encapsulated using the film of this embodiment. The encapsulation structure was: 3.2mm tempered glass + film of this embodiment + IBC battery cell + film of this embodiment + TPT backsheet. After the stacking was completed in a cleanroom, the module was laminated for 20 minutes at 150℃, 0.3MPa and vacuum degree ≤-0.095MPa to obtain the finished module.

[0046] Tested according to standards such as IEC61215 and IEC62804-1, the core performance is as follows: efficiency degradation rate of 3.5% after 1000h PID test; yellowing index of 1.3 and elongation at break of 14% after 3000h UV aging; insulation strength of 2700V, adhesion strength to glass of 0.87N / mm, and interlayer peeling rate of 0.4%; crosslinking degree of 87% after lamination at 150℃, with no bubbles or delamination defects. All performance meets the design requirements and high-end market certification standards.

[0047] Example 3 The preparation method of the encapsulating film specifically for BC battery modules is as follows: Step 1: Raw material pretreatment High-purity POE resin (melt index 2.5 g / 10 min, density 0.87 g / cm³) was selected as the matrix; organically modified montmorillonite OMMT (hexadecyltrimethylammonium bromide modified, interlayer spacing 20-30 nm), aminosilane coupling agent KH-550, ternary composite stabilizers (UV-770, UV-P, UV-327), nano-SiO2 (particle size 20-30 nm, silane modified), crosslinking agent DCP, and antioxidant 1010 were used as additives. All raw materials were dried at 80℃ for 2 hours, and the moisture content after drying was ≤0.05%. They were then sealed and stored for later use.

[0048] Step 2: Ingredient formulation and three-layer co-extrusion preparation Prepare the ingredients according to the following mass ratio: Surface / inner layer formulation (parts by weight): POE resin 100 parts, OMMT 1 part, KH-550 1.5 parts, UV-770 0.1 parts, UV-P 1 part, UV-327 0.1 parts, DCP 0.4 parts, antioxidant 1010 0.2 parts; Intermediate layer formulation (mass fraction): 90 parts POE resin, 2 parts nano SiO2, 2 parts OMMT, 0.5 parts KH-550, 1 part UV-770, 0.1 parts UV-P, 1 part UV-327, 0.2 parts DCP, and 0.05 parts antioxidant 1010.

[0049] The surface, intermediate, and inner layer materials were separately fed into a twin-screw extruder, and a three-layer co-extrusion process was used to prepare the film. The extrusion temperature was 165℃, the screw speed was 70 r / min, the die temperature was 160℃, the traction speed was 7 m / min, and the cooling roller temperature was 20℃. The total thickness of the film was 1.2 mm, with the surface and inner layers each being 0.4 mm and the intermediate layer being 0.4 mm. The thickness deviation was ≤ ±0.05 mm.

[0050] Step 3: Component Packaging and Performance Testing The battery module was encapsulated using the film of this embodiment. The encapsulation structure was: 3.2mm tempered glass + film of this embodiment + IBC battery cell + film of this embodiment + TPT backsheet. After the stacking was completed in a cleanroom, the module was laminated for 20 minutes at 150℃, 0.3MPa and vacuum degree ≤-0.095MPa to obtain the finished module.

[0051] Tested according to standards such as IEC61215 and IEC62804-1, the core performance is as follows: efficiency degradation rate of 3.6% after 1000h PID test; yellowing index of 1.4 and elongation at break of 13% after 3000h UV aging; insulation strength of 2600V, adhesion strength to glass of 0.83N / mm, and interlayer peeling rate of 0.45%; crosslinking degree of 86% after lamination at 150℃, with no bubbles or delamination defects. All performance meets the design requirements and high-end market certification standards.

[0052] Comparative Example 1 The existing methods for preparing encapsulating films are as follows: The same POE matrix as in Example 1 was used, with 0.5% magnesium oxide as the anti-ion migration agent, a single benzotriazole adjuvant as the stabilizer, and the film having a single homogeneous structure with a thickness of 1.1 mm. The rest of the preparation methods were the same as in Example 1.

[0053] The test results are as follows: after 1000h PID test, the efficiency decay rate is 8.5%; after 3000h UV aging, the yellowing index is 3.2 and the elongation at break decreases by 32%; the insulation strength is 1450V, the bonding strength is 0.55N / mm, and the interlayer peel rate is 2.2%, which is significantly worse than that of Example 1 of the present invention.

[0054] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0055] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An encapsulating film for use in BC battery modules, characterized in that, It mainly consists of the surface layer and inner layer of POE resin material, and the middle layer of nano-SiO2 modified POE resin material. Each layer contains organic modified montmorillonite OMMT, aminosilane coupling agent KH-550, composite stabilizer, crosslinking agent DCP, and antioxidant 1010, wherein the composite stabilizer includes UV-770, UV-P, and UV-327.

2. The encapsulating film according to claim 1, characterized in that, The outer and inner layers are composed of the following components by mass: 90-100 parts POE resin, 1-2 parts OMMT, 0.5-1.5 parts KH-550, 0.1-1 parts UV-770, 0.1-1 parts UV-P, 0.1-1 parts UV-327, 0.2-0.4 parts DCP, and 0.05-0.2 parts antioxidant 1010.

3. The encapsulating film according to claim 1, characterized in that, The intermediate layer is composed of: 90-100 parts POE resin, 1-2 parts nano SiO2, 1-2 parts OMMT, 0.5-1.5 parts KH-550, 0.1-1 parts UV-770, 0.1-1 parts UV-P, 0.1-1 parts UV-327, 0.2-0.4 parts DCP, and 0.05-0.2 parts antioxidant 1010.

4. The encapsulating film according to any one of claims 1-3, characterized in that, The composite stabilizers in each layer are formulated in the following proportions by weight: 0.3-0.5 parts of UV-770, 0.2-0.4 parts of UV-P, and 0.1-0.3 parts of UV-327.

5. The encapsulating film according to any one of claims 1-3, characterized in that, The thickness of the outer and inner layers is 0.3-0.4 mm, and the thickness of the intermediate layer is 0.4-0.5 mm.

6. The encapsulating film according to any one of claims 1-3, characterized in that, The POE resin is a high-purity POE resin with a melt index of 2.0-3.0 g / 10 min and a density of 0.87 g / cm³.

7. The method for preparing the encapsulating film according to any one of claims 1-6, characterized in that, Includes the following steps: Each layer of components is co-extruded to prepare the film, with the extrusion temperature controlled at 160-170℃.

8. The preparation method according to claim 7, characterized in that, The screw speed of the extrusion is controlled at 40-70 r / min, and the die temperature is 160-180℃.

9. The preparation method according to claim 7, characterized in that, The extrusion traction speed is 3-7 m / min.

10. The preparation method according to claim 7, characterized in that, The temperature of the extruded cooling roller is 20-30℃.