Insulating film, assembly, and system

Abstract

The present disclosure is applicable to the technical field of photovoltaics, and provides an insulating film, an assembly, and a system. The insulating film comprises: an insulating layer, the insulating layer having a first surface and a second surface disposed opposite to each other; a first adhesive layer disposed on the first surface; and a second adhesive layer disposed on the second surface, wherein a thickness of the first adhesive layer is less than a thickness of the second adhesive layer. The present application reduces the risk of micro-cracking of cells during a photovoltaic module lamination process.

Description

Insulating films, components and systems

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese patent application No. 2024233210391, entitled "Insulating Film, Battery Module and Photovoltaic System", filed on December 31, 2024, with the State Intellectual Property Office of China, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure pertains to the field of photovoltaic technology, and particularly relates to an insulating film, a battery module, and a photovoltaic system. Background Technology

[0004] Solar cells, also known as photovoltaic cells, are devices that directly convert light energy into direct current using the photovoltaic effect. The PN junction on the semiconductor in a solar cell can directly convert solar energy into electrical energy through the photovoltaic effect. The most common type is the crystalline silicon solar cell, which includes monocrystalline and polycrystalline silicon solar cells. Solar cells are typically in sheet form.

[0005] In related technologies, multiple solar cells are strung together to form a solar cell string. The solar cell strings are connected by busbars to form a solar cell module. The busbars are installed on the back of the solar cells. An insulating film is placed between the busbars and the solar cells so that the busbars can contact the same polarity solder strips on the solar cells while being insulated from the opposite polarity solder strips on the solar cells. The solder strips, insulating film and busbars are stacked. If the overlap area is too thick in some places, stress concentration will occur in the overlap area during the lamination of the photovoltaic module, which may lead to solar cell fragmentation or microcracks.

[0006] Application content

[0007] This disclosure provides an insulating film designed to address the issue of excessive thickness in the overlapping areas of the laminated solder strip, insulating film, and busbar, which leads to stress concentration in the overlapping areas during photovoltaic module lamination and consequently causes cell fragmentation or microcracks.

[0008] In a first aspect, this disclosure provides an insulating film, comprising: an insulating layer having a first surface and a second surface disposed opposite to each other in a thickness direction; a first adhesive layer disposed on the first surface; and a second adhesive layer disposed on the second surface, wherein the thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

[0009] This disclosure reduces the overall thickness of the insulating film, thereby reducing the thickness of local areas when the solder strip, insulating film, and busbar are stacked, and thus reducing the risk of microcracks in the solar cells during the lamination process of photovoltaic modules. Specifically, based on the actual usage requirements of the insulating film, without affecting the insulation effect of the insulating film and the bonding reliability between the insulating film and the solder strip and busbar, the thickness of the adhesive layers on both sides of the insulating layer is differentiated. That is, the thickness of the first adhesive layer is less than the thickness of the second adhesive layer. The first adhesive layer can be applied to substrates with low bonding strength requirements, while the second adhesive layer can be applied to substrates with high bonding strength requirements. The thickness of the insulating film is effectively reduced without sacrificing its performance.

[0010] In some embodiments, the ratio of the thickness of the second adhesive layer to the thickness of the first adhesive layer is greater than or equal to 1.5 and less than or equal to 10.

[0011] In some embodiments, the thickness of the insulating film is greater than or equal to 120 μm and less than or equal to 250 μm.

[0012] In some embodiments, the thickness of the first adhesive layer is 30–60 μm.

[0013] In some embodiments, the thickness of the second adhesive layer is 80–120 μm.

[0014] In some embodiments, the thickness of the insulating layer is 25–50 μm.

[0015] In some embodiments, the insulating film satisfies at least one of the following: the first adhesive layer comprises an EVA layer; the second adhesive layer comprises an EVA layer.

[0016] In some embodiments, the insulating layer comprises a PET layer.

[0017] Secondly, this disclosure provides a battery assembly, including: the aforementioned insulating film; a plurality of battery cells; a solder strip extending along a first direction to connect two adjacent battery cells; a busbar extending along a second direction and intersecting with the solder strip, the insulating film being disposed between the solder strip and the busbar, the insulating film and the busbar being arranged in the same direction.

[0018] In some embodiments, the first adhesive layer of the insulating film is connected to the busbar, and the second adhesive layer of the insulating film is connected to the solder strip and the battery cell.

[0019] In some embodiments, two adjacent battery cells are partially overlapped.

[0020] Thirdly, this disclosure provides a photovoltaic system including the aforementioned battery module. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of the insulating film provided in this application;

[0022] Figure 2 is a schematic diagram of the structure of the battery assembly provided in the current application.

[0023] Explanation of reference numerals in the attached drawings: 100, insulating film; 101, insulating layer; 102, first adhesive layer; 103, second adhesive layer; 104, first surface; 105, second surface; 200, battery cell; 300, solder strip; 400, busbar. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this disclosure and are not intended to limit this disclosure.

[0025] In the description of this disclosure, it should be understood that the terms “length”, “width”, “upper”, “lower”, “left”, “right”, “horizontal”, “top”, “bottom”, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" 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 mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0028] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0030] As shown in Figure 1, in this embodiment of the present disclosure, an insulating film 100 includes an insulating layer 101, a first adhesive layer 102, and a second adhesive layer 103. The insulating layer 101 has a first surface 104 and a second surface 105 disposed opposite each other in the thickness direction. The first adhesive layer 102 is disposed on the first surface 104, and the second adhesive layer 103 is disposed on the second surface 105. The thickness of the first adhesive layer 102 is less than the thickness of the second adhesive layer 103. The insulating layer 101 mainly serves an insulating function, preventing electrical conduction between the irregular solder ribbon 300 and the busbar 400. The first adhesive layer 102 and the second adhesive layer 103 mainly serve an adhesive function. The first adhesive layer 102 can be used to bond with the busbar 400, and the second adhesive layer 103 can be used to bond with the battery cell 200 and the solder ribbon 300, thereby achieving a fixed connection between the insulating film 100 and the battery cell 200 and the busbar 400.

[0031] It should be noted that the researchers discovered that the insulating film, placed between the solar cell and the busbar, serves two purposes: firstly, it acts as an adhesive, fixing the busbar to the solar cell; secondly, it seals the edges of the solder ribbon, preventing external factors such as moisture and oxygen from penetrating the solar cell and thus extending its lifespan. However, if the adhesive layer is too thin, it may not provide sufficient sealing, leading to a decrease in cell performance. Since the solder ribbon itself has a certain thickness, and it is placed on the solar cell, the adhesive layer needs to cover and wrap the solder ribbon during bonding to ensure sufficient contact between the other parts of the adhesive layer and the solar cell. In this disclosure, this requires a second adhesive layer with a significant thickness, exceeding the thickness of the solder ribbon. This is a problem easily overlooked by those skilled in the art, making it difficult to improve the structure of the insulating film. Based on this conclusion, the researchers made differentiated improvements to the adhesive layers on both sides of the insulation layer. The thickness of the second adhesive layer facing the battery cell was set to be larger, so that the welding ribbon could be wrapped and bonded to the battery cell after the second adhesive layer was hot-melted. The thickness of the first adhesive layer facing away from the battery cell was set to be smaller. The first adhesive layer only serves to bond and fix the busbar. Compared with the second adhesive layer, the first adhesive layer can be thinned, thereby thinning the insulation film as a whole and reducing the risk of microcracks in the battery cell.

[0032] Furthermore, if the adhesive layer is too thick, it may lead to uneven bonding or the formation of air bubbles, thus reducing the bonding strength. Conversely, if the adhesive layer is too thin, it may not provide sufficient bonding area and strength, resulting in decreased bonding performance. Therefore, in this embodiment, the thickness of the first adhesive layer 102 is 30–60 μm. In such an embodiment, the thickness of the first adhesive layer 102 can be any value between 30 μm, 40 μm, 50 μm, 60 μm, or 30 μm–60 μm, without any specific limitation. Preferably, the thickness of the first adhesive layer 102 is 40–50 μm. Within this range, a thinner first adhesive layer 102 can provide stronger adhesion and durability, ensuring the bonding strength between the insulating film and the substrate, and preventing the substrate from detaching. Exemplarily, the first adhesive layer 102 can be bonded to the busbar 400 to ensure that the busbar 400 is stably connected to the insulating film 100.

[0033] The thickness of the second adhesive layer 103 is 80–120 μm. In such embodiments, the thickness of the second adhesive layer 103 can be 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, or any value between 80 and 120 μm, and is not specifically limited herein. Preferably, the thickness of the second adhesive layer 103 is 100–120 μm. Within this range, the second adhesive layer 103 can provide strong adhesion and durability after hot melting. Furthermore, a thicker second adhesive layer 103 can completely enclose the solder ribbon 300 after lamination and hot melting, achieving complete contact between the second adhesive layer and the battery cell 200, strengthening the connection strength between the insulating film 100, the solder ribbon 300, and the battery cell 200, and the second adhesive layer 103 can act as a buffer during lamination, which helps reduce the risk of microcracks in the battery cell 200 lamination process. Furthermore, it should be noted that a second adhesive layer 103 with a thickness within a certain range can improve its adhesion to the substrate. However, when the thickness of the second adhesive layer 103 exceeds a certain range, the adhesion between the second adhesive layer 103 and the substrate tends to stabilize, and the cost increases. Moreover, an excessively thick second adhesive layer will overflow into the gap between the solder ribbon and the battery cell when it melts at high temperature, causing the solder ribbon to have a poor solder joint. The range selected in the embodiments of this disclosure is a preferred option.

[0034] In this embodiment, the thickness of the insulating film is greater than or equal to 120 μm and less than or equal to 250 μm. In such embodiments, the thickness of the insulating film can be any value between 120 μm, 130 μm, 180 μm, 200 μm, 250 μm, or 120-250 μm, and is not specifically limited herein. Preferably, the thickness of the insulating film is greater than or equal to 200 μm and less than or equal to 250 μm. Within this range, the risk of microcracks in the solar cell during the lamination process can be effectively reduced.

[0035] It should be noted that the thickness of the insulating film 100 should not be too thick or too thin. If the insulating film 100 is too thin, it will be inconvenient to apply, easily deformed when pulled, and may also be damaged during long-term insulation. If it is too thick, it will increase the height difference, generate greater stress during the lamination process, easily cause fragmentation, and increase the risk of poor soldering. By setting the thickness of the insulating layer 101, the first adhesive layer 102 and the second adhesive layer 103, the overall thickness of the insulating film 100 can be controlled within a suitable range to achieve good insulation of the insulating film 100.

[0036] This disclosure reduces the overall thickness of the insulating film 100, thereby reducing the thickness of local areas when the solder ribbon 300, insulating film 100, and busbar 400 are stacked, and thus reducing the risk of microcracks in the solar cell 200 during the lamination process of the photovoltaic module. Specifically, based on the actual usage requirements of the insulating film 100, without affecting the insulation effect of the insulating film 100 and the bonding reliability between the insulating film 100 and the solder ribbon 300 and busbar 400, the thickness of the adhesive layers on both sides of the insulating layer 101 is differentiated. That is, the thickness of the first adhesive layer 102 is less than the thickness of the second adhesive layer 103. The first adhesive layer 102 can be applied to substrates with low bonding strength requirements, while the second adhesive layer 103 can be applied to substrates with high bonding strength requirements. The thickness of the insulating film 100 is effectively reduced without sacrificing its performance.

[0037] In some embodiments, the ratio of the thickness of the second adhesive layer 103 to the thickness of the first adhesive layer 102 is greater than or equal to 1.5 and less than or equal to 10. In such embodiments, the ratio of the thickness of the second adhesive layer 103 to the thickness of the first adhesive layer 102 can be any value between 1.5, 2, 3, 4, 5, 7, 8, 9, 10, or 1.5-10, without specific limitation. Different substrates have different requirements for adhesive layer thickness. Within this ratio range, the thickness of the two adhesive layers can be adjusted according to the specific substrate to meet different application needs.

[0038] In some embodiments, the thickness of the insulating layer 101 is 25–50 μm. In such embodiments, the thickness of the insulating layer 101 can be any value between 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or 25–50 μm, without any specific limitation. Within this thickness range, the insulating layer 101 can effectively isolate the electrical conduction between the busbar 400 and the irregular solder ribbon 300, ensuring the normal operation and safety of the solar cell 200. Furthermore, a thicker insulating layer 101 can prevent burrs from the edges of the solder ribbon 300 from puncturing the cell, further reducing the risk of short circuits in the solar cell 200.

[0039] In some embodiments, the first adhesive layer 102 includes an EVA layer, and / or the second adhesive layer 103 includes an EVA layer. The EVA layer, or ethylene-vinyl acetate copolymer layer, has excellent adhesive properties. As an adhesive layer, the EVA layer can effectively bond different materials together to form a unified structure. The EVA layer also has high light transmittance, ensuring that light passes through smoothly without reducing transmittance due to the presence of the adhesive layer. In photovoltaic modules, the high light transmittance of the EVA layer ensures that the solar panel receives maximum light, thereby improving power generation efficiency. In other embodiments, the first adhesive layer 102 and the second adhesive layer 103 may also include a PU (polyurethane) layer, a PVB (polyvinyl butyral) layer, etc., and this disclosure does not limit this.

[0040] In some embodiments, the insulating layer 101 includes a PET layer. The PET layer (polyethylene terephthalate) has high insulation resistance and dielectric strength, effectively isolating current and preventing current leakage or short circuits. In other embodiments, the insulating layer 101 may also include a polymethyl methacrylate (PMMA) layer, a polyethylene naphthalate (PEN) layer, or a polycarbonate (PC) layer, etc., and this disclosure is not limiting in this regard.

[0041] As shown in Figure 2, a battery assembly includes the aforementioned insulating film 100, multiple battery cells 200, solder ribbons 300, and busbars 400. The solder ribbons 300 connect adjacent battery cells 200. The insulating film 100 is located on the side of the solder ribbons 300 facing away from the battery cells 200, and the busbars 400 are disposed on the side of the insulating film 100 facing away from the battery cells 200. Specifically, the multiple solder ribbons 300 extend along a first direction to connect adjacent battery cells 200 to form a battery string, and the busbars 400 extend along a second direction to connect adjacent battery strings. The busbars extend along the second direction and intersect with the solder ribbons. The insulating film 100 and the busbars 400 extend in the same direction, and the insulating film completely isolates the busbars and the irregularly shaped solder ribbons. Understandably, the width of the insulating film 100 is greater than the width of the busbar 400. If the width of the insulating film 100 is too narrow, the busbar 400 will be exposed, which may result in a short circuit due to the busbar 400 coming into contact with the dissimilar electrode area or the dissimilar solder strip 300.

[0042] In this embodiment of the present disclosure, the first adhesive layer 102 of the insulating film 100 is connected to the busbar 400, and the second adhesive layer 103 of the insulating film 100 is connected to the solder ribbon 300 and the battery cell 200. Since the insulating film 100 needs to be bonded to the battery cell 200 and the welding ribbon 300, a large bonding strength is required to ensure that the insulating film 100 is stably connected to the battery cell 200 and the welding ribbon 300. Therefore, the second adhesive layer 103 of the insulating film 100 is connected to the welding ribbon 300 and the battery cell 200. The thickness of the second adhesive layer 103 is greater than that of the first adhesive layer 102. After lamination and melting, the second adhesive layer 103 can achieve a tight bond between the insulating film 100, the battery cell 200 and the welding ribbon 300. On the basis of the tight bond between the insulating film 100, the battery cell 200 and the welding ribbon 300, the other side of the insulating film 100 only needs a lower bonding strength to achieve a fixed connection to the busbar 400. Therefore, the first adhesive layer 102 of the insulating film 100 can be connected to the busbar 400 to ensure that the busbar 400 will not shift. In this embodiment, even if the insulating film 100 is partially thinned, the overall reliability of the insulating film 100 can still be guaranteed.

[0043] Adjacent solar cells 200 are partially overlapped. Multiple solar cells 200 are partially overlapped to form a battery string. The contact areas between these overlaps are not electrically connected; that is, no conductive adhesive or other bonding agent is needed between the overlapping areas. The solar cells 200 are simply overlapped together. In the battery string, the overlapping areas of adjacent solar cells 200 are provided with solder ribbons 300 to securely connect adjacent solar cells 200. Thus, there are no gaps between the solar cells 200, allowing for better concealment of the solder ribbons 300. Furthermore, the overlapping arrangement of the solar cells 200 allows for a smaller battery string size, resulting in a smaller footprint. In other words, with a fixed battery string size, more solar cells 200 can be placed, increasing the power output of the battery string and reducing the cost per watt.

[0044] In shingled solar cell modules, the overlapping area of ​​the solar cells 200 is particularly vulnerable. Reducing the thickness of the insulating film 100 can significantly reduce the risk of microcracks in the solar cells 200 during the lamination process. This disclosure, without affecting the reliability of the insulating film 100, optimizes the thickness of each layer of the insulating film 100 by analyzing the bonding strength requirements between the insulating film 100 and other substrates, thereby improving the problem of microcracks in the lamination process of the solar cells 200 to a limited extent.

[0045] Understandably, the partial overlap of multiple battery cells 200 in a battery string refers to the overlapping of a portion of the area of ​​adjacent battery cells 200 in the battery string. For example, the overlap width can range from 0 mm to 0.5 mm, such as 0 mm, 0.1 mm, 0.2 mm, 0.4 mm, or 0.5 mm, and this disclosure does not impose any limitations.

[0046] A photovoltaic system includes the aforementioned battery modules. In this embodiment, the photovoltaic system can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants, and can also be applied to equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation system grid as an example, the photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple battery modules; for example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0047] In the description of this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. An insulating film, wherein, It includes: an insulating layer having a first surface and a second surface disposed opposite to each other in the thickness direction; a first adhesive layer disposed on the first surface; and a second adhesive layer disposed on the second surface, wherein the thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

2. The insulating film as described in claim 1, wherein, The ratio of the thickness of the second adhesive layer to the thickness of the first adhesive layer is greater than or equal to 1.5 and less than or equal to 10.

3. The insulating film as described in claim 1, wherein, The thickness of the insulating film is greater than or equal to 120 μm and less than or equal to 250 μm.

4. The insulating film as described in claim 1, wherein, The thickness of the first adhesive layer is 30–60 μm.

5. The insulating film as described in claim 1, wherein, The thickness of the second adhesive layer is 80–120 μm.

6. The insulating film as claimed in claim 1, wherein, The thickness of the insulating layer is 25–50 μm.

7. The insulating film as claimed in claim 1, wherein, The insulating film satisfies at least one of the following: the first adhesive layer includes an EVA layer; the second adhesive layer includes an EVA layer.

8. The insulating film as claimed in claim 1, wherein, The insulating layer includes a PET layer.

9. A battery assembly, wherein, include: The insulating film according to any one of claims 1-8; Multiple battery cells; A solder strip, which extends along a first direction to connect two adjacent battery cells; A busbar extends along a second direction and intersects with the solder strip. An insulating film is disposed between the solder strip and the busbar, and the insulating film and the busbar are arranged in the same direction.

10. The battery assembly of claim 9, wherein, The first adhesive layer of the insulating film is connected to the busbar, and the second adhesive layer of the insulating film is connected to the solder strip and the battery cell respectively.

11. The battery assembly of claim 9, wherein, The two adjacent battery cells are partially overlapped.

12. A photovoltaic system, wherein, Includes the battery assembly as described in any one of claims 9-11.

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