Battery assembly and photovoltaic system

Abstract

The invention is applicable to the field of photovoltaic technology, and provides a battery assembly and a photovoltaic system, the battery assembly comprises a front adhesive film, a rear adhesive film and a battery string; the battery string comprises a plurality of battery pieces which are arranged in an overlapped mode in the first direction, each battery piece comprises a first edge and a second edge which are opposite, and the backlight face of the first edge of one battery piece is in lap joint with the light facing face of the second edge of the adjacent battery piece. The rear adhesive film is arranged on the backlight surface of the battery piece, the front adhesive film is arranged on the light facing surface of the battery piece, and the first edge of the battery piece warps towards the front adhesive film. And the welding quality is improved, so that the overall performance of the battery assembly is improved, and meanwhile, the light receiving area is increased.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, and particularly relates to a battery module and a photovoltaic system. Background Technology

[0002] Current photovoltaic (PV) module encapsulation technologies face numerous challenges. Traditional cell string encapsulation often results in uneven backplane surfaces due to cell arrangement. This makes it difficult to lay the solder ribbon smoothly and evenly, frequently leading to bending and warping. Consequently, the solder ribbon cannot be accurately placed on the cell electrodes, resulting in poor contact between the ribbon and the cell, affecting welding quality and ultimately reducing the overall performance of the module. Furthermore, the cell layout is not conducive to maximizing the light-receiving area. Therefore, a new encapsulation structure and cell arrangement method are urgently needed to address these issues and improve module performance and power generation efficiency. Summary of the Invention

[0003] This invention provides a battery module and a photovoltaic system, which aims to solve the problems of limited light-receiving area and poor soldering of the solder strip.

[0004] The present invention is implemented as follows: a battery assembly includes: a front adhesive film, a rear adhesive film, and a battery string; The battery string includes a plurality of battery cells arranged in an overlapping manner along a first direction. Each battery cell includes a first edge and a second edge, and the back-light surface of the first edge of one battery cell overlaps with the light-facing surface of the second edge of the adjacent battery cell. The back adhesive film is disposed on the back surface of the battery cell, the front adhesive film is disposed on the light-facing surface of the battery cell, and the first edge of the battery cell is warped toward the front adhesive film.

[0005] Optionally, the warpage height of the first edge of the battery cell is less than or equal to half the thickness of the pre-coating film.

[0006] Optionally, the ratio of the thickness of the front adhesive film to the thickness of the rear adhesive film is 0.6 to 1.8.

[0007] Optionally, the ratio of the thickness of the front adhesive film to the thickness of the rear adhesive film is 0.75 to 1.2.

[0008] Optionally, the degree of crosslinking of the pre-adhesive film is greater than the degree of crosslinking of the post-adhesive film.

[0009] Optionally, the degree of crosslinking of the pre-adhesive film is 65% to 95%.

[0010] Optionally, the degree of crosslinking of the post-adhesive film is 70% to 98%.

[0011] Optionally, the stack width of the solar cells is greater than the thickness of the solar cells.

[0012] Optionally, the light-facing surface of the battery cell has a chamfer at the second edge, and the chamfer is inclined from the light-facing surface to the second edge to form an inclined surface. The backlight surface of the first edge of one battery cell overlaps with the light-facing surface of the second edge of the adjacent battery cell through the inclined surface.

[0013] Optionally, the battery cell is a back-contact battery cell.

[0014] The present invention also provides a photovoltaic system including the above-described battery module.

[0015] The beneficial effects achieved by this invention are as follows: because the battery string is disposed between the front and rear adhesive films, the battery string includes several overlapping battery cells, the rear adhesive film is disposed on the back surface of the battery cells, the front adhesive film is disposed on the light-facing surface of the battery cells, and the first edge of the battery cell is warped towards the front adhesive film, making the back surface of the battery string flat. This allows for smoother and more even laying of the solder ribbon, and the solder ribbon can be accurately placed on the electrodes of the battery cells, avoiding bending and warping of the solder ribbon, ensuring good contact between the solder ribbon and the battery cells, improving welding quality, thereby improving the overall performance of the battery module, and increasing the light-receiving area. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the battery assembly before lamination. Figure 2 This is a schematic diagram of the structure of a battery module during lamination provided by existing technology; Figure 3 This is a schematic diagram of the battery assembly lamination structure provided by the present invention; Figure 4 This is a schematic diagram of the structure of the battery cell provided by the present invention.

[0017] 100. Battery assembly; 110. Battery string; 111. Battery cell; 1111. First edge; 1112. Second edge; 1113. Chamfer; 120. Front adhesive film; 130. Rear adhesive film. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to 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 the invention, and should not be construed as limiting the invention. Furthermore, it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] In the description of this invention, 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. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] 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 invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In this invention, unless otherwise explicitly 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.

[0023] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. 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, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0024] In this invention, a battery string is disposed between a front adhesive film and a rear adhesive film. The battery string comprises several overlapping battery cells. The rear adhesive film is disposed on the back surface of the battery cells, and the front adhesive film is disposed on the light-facing surface of the battery cells. The first edge of the battery cell is curved towards the front adhesive film, making the back surface of the battery string flat. This allows for smoother and more even laying of the solder ribbon, ensuring that the solder ribbon can be accurately placed on the electrodes of the battery cells. This avoids bending and warping of the solder ribbon, guarantees good contact between the solder ribbon and the battery cells, improves welding quality, and thus improves the overall performance of the battery module. At the same time, it increases the light-receiving area.

[0025] Example 1 like Figures 1 to 4 As shown, this embodiment provides a battery assembly 100, including: a front adhesive film 120, a rear adhesive film 130, and a battery string 110; The battery string 110 includes a plurality of battery cells 111 arranged in an overlapping manner along a first direction. Each battery cell 111 includes a first edge 1111 and a second edge 1112 opposite to each other. The backlight surface of the first edge 1111 of one battery cell 111 overlaps with the light-facing surface of the second edge 1112 of the adjacent battery cell 111. The back film 130 is disposed on the back surface of the battery cell 111, and the front film 120 is disposed on the light-facing surface of the battery cell 111. The first edge 1111 of the battery cell 111 is warped towards the front film 120.

[0026] The battery string 110 includes a plurality of battery cells 111. Each battery cell 111 has a first edge 1111 and a second edge 1112 facing each other, as well as a light-facing surface and a back-facing surface arranged opposite each other. The plurality of battery cells 111 are arranged in an overlapping manner along a first direction. The back-facing surface of the first edge 1111 of one battery cell 111 overlaps with the light-facing surface of the second edge 1112 of the adjacent battery cell 111. The plurality of battery cells 111 are arranged in this manner extending along the first direction. Specifically, the battery cell 111 can be a back-contact battery, with the electrodes placed on the back side of the back-contact battery to eliminate the shading of the front grid lines and achieve higher photoelectric conversion efficiency.

[0027] It should be noted that during the manufacturing process of the battery module 100, the battery string 110 is positioned between the back film 130 and the front film 120, with the backlight side of the battery cell 111 facing the back film 130 and the light-facing side facing the front film 120. Traditional processes typically use the front film 120 as a support carrier, pre-crosslinking it before lamination. Pre-crosslinking involves using specific processes to create a certain degree of crosslinking between some molecules in the front film 120, resulting in a relatively stable morphology and lower flowability during lamination. The back film 130, however, is not pre-crosslinked or has a low degree of crosslinking, making it more prone to flow during lamination. Due to the lower flowability of the pre-crosslinked front film 120, it provides a relatively fixed support platform for the battery cell 111 during lamination. The solar cell 111 is subjected to a force in the direction of the forward adhesive film 120. The light-facing surface of the solar cell 111 is tightly bonded to the forward adhesive film 120. However, in the overlapping portion of the solar cells 111, the second edge 1112 of the solar cell 111 is blocked and deformed, warping in the direction of the rear adhesive film 130. In other words, the backlight surface of the solar cell 111 is uneven. Since the solder ribbon is set on the backlight surface of the solar cell 111, the unevenness of the backlight surface results in uneven laying of the solder ribbon.

[0028] In this application, the first edge 1111 of the solar cell 111 warps towards the adhesive film 120. Unlike conventional processes, the back adhesive film 130 is pre-crosslinked before lamination. The front adhesive film 120 is not pre-crosslinked or has a low degree of crosslinking, making it easier to flow during lamination. Due to the lower flowability of the back adhesive film 130 after pre-crosslinking, it transmits the lamination force to the solar cell 111 during lamination. The solar cell 111 is subjected to a force in the direction of the front adhesive film 120, and the light-facing surface of the solar cell 111 is tightly bonded to the front adhesive film 120. At the overlapping portion of the solar cells 111, the second edge 1112 of the solar cell 111 moves and adheres towards the front adhesive film 120, pushing the first edge 1111 of the adjacent solar cells 111 to warp towards the more fluid front adhesive film 120. This makes the back surface of the solar cell 111 flatter, and the solder ribbon is placed on the flat back surface of the solar cell 111, making the installation smoother and more even.

[0029] Specifically, battery cell A and battery cell B are arranged adjacently and overlappingly, with the light-facing surface of battery cell A in contact with the backlight surface of battery cell B, and the second edge 1112 of battery cell A pushing the first edge 1111 of battery cell B to warp in the direction of the forward adhesive film 120.

[0030] Understandably, the warped portion of the solar cell 111 also has various functional layers that generate charge carriers after illumination. The solar cell 111 is warped towards the light-facing side, which increases the light-receiving area compared to the solar cell 111 being warped towards the back-light side, thus further improving the power generation per watt of the module.

[0031] In this embodiment, the battery string 110 is disposed between the front adhesive film 120 and the rear adhesive film 130. The battery string 110 includes a plurality of battery cells 111 arranged in an overlapping manner. The rear adhesive film 130 is disposed on the back surface of the battery cells 111, and the front adhesive film 120 is disposed on the light-facing surface of the battery cells 111. The first edge 1111 of the battery cells 111 is warped towards the front adhesive film 120, making the back surface of the battery string 110 flat. This makes the subsequent solder ribbon laying smoother and allows the solder ribbon to be accurately placed on the electrodes of the battery cells 111, avoiding bending and warping of the solder ribbon. This ensures good contact between the solder ribbon and the battery cells 111, improves the welding quality, and thus improves the overall performance of the battery module 100. At the same time, it increases the light-receiving area.

[0032] In some embodiments, the light-facing surface of the battery cell 111 is provided with a chamfer 1113 at the second edge 1112. The chamfer 1113 is inclined from the light-facing surface to the second edge 1112 to form an inclined surface. The backlight surface of the first edge 1111 of one battery cell 111 overlaps with the light-facing surface of the second edge 1112 of the adjacent battery cell 111 through the inclined surface.

[0033] Specifically, when the second edge 1112 of the back surface of cell A is a right angle, when cell B warps, its back surface directly contacts the tip of the right angle. Under the same external force, the smaller the force-bearing area, the greater the pressure. The smaller the force-bearing area at the tip, the greater the pressure during lamination. This results in extremely high pressure acting on the back surface of cell B, which can easily damage the back surface of cell B.

[0034] A chamfer 1113 is provided at the second edge 1112 of the light-facing surface of the solar cell 111. That is, the contact between solar cell A and solar cell B changes from point contact to surface contact, which increases the force-bearing area. Under the condition that the lamination pressure remains unchanged, the pressure on the back surface of solar cell B is reduced, thus preventing the back surface of solar cell B from being damaged by solar cell A.

[0035] In some embodiments, the warpage height of the first edge 1111 of the battery cell 111 is less than or equal to half the thickness of the pre-adhesive film 120. For example, if the pre-adhesive film 120 is made of EVA material with a thickness of 400 μm, then the warpage height of the first edge 1111 is less than or equal to 200 μm. During lamination, the pre-adhesive film 120 can fully cover and wrap the warped edge of the battery cell 111. This avoids the pre-adhesive film 120 from being unable to completely fill due to excessive warpage height, thereby preventing defects such as bubbles and voids, ensuring the integrity and sealing of the battery assembly 100 encapsulation, improving the moisture-proof and waterproof performance of the battery assembly 100, and extending the service life of the battery assembly 100.

[0036] In some embodiments, the ratio of the thickness of the front adhesive film 120 to the thickness of the rear adhesive film 130 is 0.6 to 1.8.

[0037] The thickness of the front film 120 ranges from 350μm to 400μm, and the thickness of the rear film 130 ranges from 200μm to 600μm. The ratio of the thickness of the front film 120 to the thickness of the rear film 130 is 0.6 to 1.8. When the ratio is less than 1, the thickness of the front film 120 is less than the thickness of the rear film 130. When the ratio is equal to 1, the thicknesses of the front film 120 and the rear film 130 are the same. When the ratio is greater than 1, the thickness of the front film 120 is greater than the thickness of the rear film 130. The front film 120 mainly protects the light-facing side of the solar cell 111 and improves light transmittance, while the rear film 130 mainly provides insulation, moisture protection, and mechanical protection. When the thickness ratio of the two films is within the range of 0.6 to 1.8, sufficient protection can be provided for the backside of the solar cell 111 while ensuring the light transmittance of the light-facing side.

[0038] Furthermore, the ratio of the thickness of the front adhesive film 120 to the thickness of the rear adhesive film 130 is 0.75 to 1.2.

[0039] In some embodiments, the degree of crosslinking of the front film 120 is less than the degree of crosslinking of the rear film 130.

[0040] The front encapsulant film 120 has a low degree of cross-linking and a relatively loose molecular structure, which facilitates light penetration. When light shines on the surface of the battery module, the front encapsulant film 120 allows more light to pass through and reach the battery cell 111, thereby improving the light energy absorption efficiency of the battery cell 111 and thus enhancing the photoelectric conversion efficiency of the battery module. Simultaneously, the low degree of cross-linking of the front encapsulant film 120 gives it better flexibility and elasticity. When the battery module is subjected to external impact or vibration, the front encapsulant film 120 can act as a buffer, effectively absorbing and dispersing energy, protecting the first warped edge 1111 of the front encapsulant film 120. The back encapsulant film 130 has a high degree of cross-linking, forming a denser and more stable three-dimensional network structure with good mechanical strength and chemical stability. It can effectively protect the back surface of the battery cell 111, preventing the intrusion of moisture, oxygen, and other harmful substances, thus extending the lifespan of the battery module. At the same time, the highly cross-linked back encapsulant film 130 also provides sufficient support for the battery module, ensuring that the battery module maintains its structural integrity during long-term use.

[0041] The cross-linking degree of the front encapsulant film 120 is lower than that of the rear encapsulant film 130. The different cross-linking degrees of the front and rear encapsulant films 120 complement each other, enabling the battery module 100 to achieve a better balance in terms of optical performance, mechanical performance, and environmental adaptability. The low cross-linking degree of the front encapsulant film 120 ensures good light transmittance and buffering performance, while the high cross-linking degree of the rear encapsulant film 130 provides support and protection. Together, they improve the photoelectric conversion efficiency and long-term stability of the battery module 100, enhancing its competitiveness in the market.

[0042] Differences in the materials themselves, different process steps, and the types and amounts of crosslinking agents and additives can all lead to variations in the degree of crosslinking. One method for testing the degree of crosslinking is to take samples of the front encapsulant film 120 and the rear encapsulant film 130 from the battery assembly 100, place each sample in xylene organic solvent, and dissolve them at a preset temperature. After dissolution, filter, dry, and weigh the remaining residue. The percentage of the residue mass to the initial sample mass represents the degree of crosslinking. A larger mass of remaining residue indicates a greater degree of crosslinking.

[0043] Specifically, the cross-linking degree of the pre-coating film 120 is 65%–95%. That is, the mass of the residue after dissolving the pre-coating film 120 in xylene organic solvent accounts for 65%–95% of the sample mass. If the cross-linking degree of the pre-coating film 120 is less than 65%, it means that the formed three-dimensional network structure is not perfect, and the strength and toughness of the film are insufficient. During the encapsulation process of the battery module 100, it may not be able to effectively protect the battery cell 111 from external pressure and vibration, easily leading to problems such as microcracks in the battery cell 111. If the cross-linking degree of the pre-coating film 120 is greater than 95%, it will cause the pre-coating film 120 to form an overly dense network structure, resulting in a rigid film and a significant reduction in flexibility. When the battery module 100 is subjected to temperature changes or mechanical stress, the film cannot effectively buffer and deform, easily causing cracks.

[0044] The cross-linking degree of the back film 130 is 70%–98%. The adhesion between the back film 130 and the solar cells 111 and the backsheet material is affected by the degree of cross-linking. When the degree of cross-linking of the back film 130 is less than 70%, the adhesion between the back film 130 and other materials is not strong, and delamination is likely to occur during long-term use. This not only affects the mechanical stability of the battery module 100, but may also expose the solar cells 111 to the external environment, accelerating the damage of the battery module 100. Similar to the front film 120, if the degree of cross-linking of the back film 130 is too high (above 98%), it will lose its flexibility. When the battery module 100 is subjected to vibration or impact, it cannot play a buffering role and is prone to damage to the solar cells 111. Moreover, the rigid back film 130 is prone to breakage when bent or folded, affecting the installation and use of the battery module 100.

[0045] In some embodiments, the stack width of the solar cells 111 is greater than the thickness of the solar cells 111. That is, the width of the overlapping area of ​​two solar cells 111 is greater than the thickness of the solar cells 111. A stack width greater than the thickness of the solar cells 111 can provide a more robust mechanical connection. When the battery assembly 100 is subjected to external mechanical forces, a larger stack width can better disperse stress, prevent relative displacement or separation between the solar cells 111, and improve the mechanical stability and impact resistance of the battery assembly 100.

[0046] Example 2 This embodiment provides a photovoltaic system, including the aforementioned battery module 100.

[0047] Photovoltaic systems can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants. They 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's understandable that the application scenarios of photovoltaic systems are not limited to these; that is, photovoltaic systems can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation system grid as an example, a photovoltaic system can include photovoltaic arrays, combiner boxes, and inverters. The photovoltaic array can be an array combination of multiple battery modules 100. For example, multiple battery modules 100 can form multiple photovoltaic arrays. The photovoltaic arrays are connected to combiner boxes, which can collect the current generated by the photovoltaic arrays. The collected current flows through an 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.

[0048] The beneficial effects of the photovoltaic system in this embodiment are equivalent to the beneficial effects of the battery module 100 described above, and will not be repeated here.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery assembly, characterized in that, include: Front adhesive film, rear adhesive film, and battery string; The battery string includes a plurality of battery cells arranged in an overlapping manner along a first direction. Each battery cell includes a first edge and a second edge, and the back-light surface of the first edge of one battery cell overlaps with the light-facing surface of the second edge of the adjacent battery cell. The back adhesive film is disposed on the back surface of the battery cell, the front adhesive film is disposed on the light-facing surface of the battery cell, and the first edge of the battery cell is warped toward the front adhesive film.

2. The battery assembly as claimed in claim 1, characterized in that, The warpage height of the first edge of the battery cell is less than or equal to half the thickness of the pre-coating film.

3. The battery assembly as described in claim 1, characterized in that, The ratio of the thickness of the front adhesive film to the thickness of the rear adhesive film is 0.6 to 1.

8.

4. The battery assembly as described in claim 3, characterized in that, The ratio of the thickness of the front adhesive film to the thickness of the rear adhesive film is 0.75 to 1.

2.

5. The battery assembly as claimed in claim 1, characterized in that, The degree of crosslinking of the pre-film is less than that of the post-film.

6. The battery assembly as claimed in claim 5, characterized in that, The degree of cross-linking of the pre-adhesive film is 65% to 95%.

7. The battery assembly as claimed in claim 5, characterized in that, The degree of cross-linking of the post-adhesive film is 70% to 98%.

8. The battery assembly as claimed in claim 1, characterized in that, The stack width of the battery cells is greater than the thickness of the battery cells.

9. The battery assembly as claimed in claim 1, characterized in that, The light-facing surface of the battery cell has a chamfer at the second edge. The chamfer is inclined from the light-facing surface to the second edge to form an inclined surface. The backlight surface of the first edge of one battery cell overlaps with the light-facing surface of the second edge of the adjacent battery cell through the inclined surface.

10. The battery assembly as claimed in claim 1, characterized in that, The battery cell is a back-contact battery cell.

11. A photovoltaic system, characterized in that, Includes the battery assembly as described in any one of claims 1 to 10.

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