Liquid injection device

Abstract

The application relates to the technical field of battery processing, and discloses a liquid injection device, which comprises a receiving main body and a limiting main body. The receiving main body is provided with an open accommodating cavity for placing a battery shell, and at least part of the open edge of the accommodating cavity is provided with a guide portion for guiding the placement or removal of the battery shell. The limiting main body is provided with a protruding portion which is arranged in matching with the guide portion. During the liquid injection process, the limiting main body and the receiving main body are relatively fixed, and the gap between the guide portion and the battery shell is filled by the protruding portion, so that the expansion of the battery shell caused by the positive pressure during the liquid injection process is effectively prevented, the size precision and structural integrity of the battery shell are guaranteed, and the improvement of the battery performance and quality is facilitated.

Description

[0001] This case is a divisional application based on the utility model patent with an application date of 2024-07-12, application number "202421658989.0" and title "Liquid Injection Device". Technical Field

[0002] This application relates to the field of battery processing technology, and more particularly to a liquid injection device. Background Technology

[0003] Currently, in existing battery manufacturing processes, the electrolyte injection device is a key tool for injecting electrolyte into the battery. Traditional electrolyte injection fixtures typically employ a one-piece design, characterized by its simplicity and intuitive operation. However, this design has some limitations.

[0004] Specifically, traditional tooling features a guide ramp above the opening. While this design was intended to facilitate the placement of the battery casing, it also introduces the problem of insufficient support. Because a gap exists between the guide ramp and the battery casing, the casing is prone to expansion under positive pressure during electrolyte injection, especially after multiple injection cycles. This expansion not only leads to excessive cell thickness but also affects the production efficiency and product quality of subsequent processes. Utility Model Content

[0005] To address the aforementioned technical problems, the purpose of this application is to provide a liquid injection device that avoids the expansion phenomenon that easily occurs in the battery casing during the traditional battery liquid injection process, thereby improving the quality of battery production.

[0006] To achieve the above objectives, this application provides a liquid injection device, comprising: a receiving body and a limiting body, wherein the receiving body has an open receiving cavity for placing a battery casing, and at least a portion of the opening edge of the receiving cavity is provided with a guide portion for guiding the placement or removal of the battery casing;

[0007] The limiting body is provided with a protrusion, which is matched with the guide part; during the liquid injection process, the limiting body and the receiving body are relatively fixed, and the gap between the guide part and the battery housing is filled by the protrusion to prevent the battery housing from expanding.

[0008] In some embodiments, the limiting body is further provided with a connecting end face, the connecting end face and the protrusion are disposed adjacent to each other, and the vertical extension height of the protrusion exceeds the bottom of the connecting end face;

[0009] The top wall of the receiving body is adjacent to the guide portion. During liquid injection, the connecting end face abuts against the top wall of the receiving body, and the protrusion is embedded between the guide portion and the battery casing.

[0010] In some embodiments, a corresponding connection structure is provided between the connecting end face of the limiting body and the top wall of the receiving body to achieve relative fixation between the limiting body and the receiving body.

[0011] In some embodiments, the guide portion is circumferentially disposed along the opening edge of the receiving cavity to form an annular recessed structure;

[0012] The limiting body has a ring-shaped outline, and the protrusion is set along the ring-shaped outline of the limiting body.

[0013] In some embodiments, the limiting body includes two long-side limiting portions and two short-side limiting portions. The long-side limiting portions are respectively disposed corresponding to the two long sides of the battery casing, and the short-side limiting portions are respectively disposed corresponding to the two short sides of the battery casing, so as to jointly form the annular contour of the limiting body. Each of the long-side limiting portions has a long-side protrusion, and each of the short-side limiting portions has a short-side protrusion. The long-side protrusions and the short-side protrusions together form the protrusion portion.

[0014] In some embodiments, one of the long-side limiting portions and one of the short-side limiting portions are connected to jointly form an L-shaped limiting structure;

[0015] Alternatively, one of the long-side limiting portions and two of the short-side limiting portions are connected to jointly form a C-shaped limiting structure;

[0016] Alternatively, one of the short-side limiting portions and two of the long-side limiting portions are connected to jointly form a C-shaped limiting structure;

[0017] Alternatively, both of the long-side limiting parts and both of the short-side limiting parts may be independently configured.

[0018] In some embodiments, each of the long-side limiting portions is provided with a first limiting edge, and each of the short-side limiting portions is provided with a second limiting edge. Both the first limiting edge and the second limiting edge are inclined. During the injection process, the first limiting edge of the long-side limiting portion is in contact with the second limiting edge of the adjacent short-side limiting portion.

[0019] In some embodiments, each of the long-side limiting portions has a first connecting end face, and each of the short-side limiting portions has a second connecting end face. The first connecting end face and the second connecting end face together form the connecting end face, so that during liquid injection, the top wall of the receiving body is simultaneously connected and fixed to the two first connecting end faces and the two second connecting end faces.

[0020] In some embodiments, the limiting body also has an abutting end face, which is smoothly connected to the side wall of the protrusion on the side opposite to the connecting end face. When the protrusion is embedded in the guide portion, the abutting end face is flush with the inner wall of the accommodating cavity, so that the battery casing is in close contact with the abutting end face and the inner wall of the accommodating cavity during the liquid injection process.

[0021] In some embodiments, the guide portion is a chamfered structure and the protrusion is a triangular protrusion. During liquid injection, the triangular protrusion fits into the chamfered structure, so that the limiting body and the receiving body together form an integral structure adapted to the outer contour of the battery casing.

[0022] Compared with the prior art, the liquid injection device provided in this application has the following advantages:

[0023] 1. In this application, the protrusion on the limiting body fills the gap between the battery casing and the guide portion of the receiving body, effectively preventing the battery casing from expanding due to positive pressure during electrolyte injection, thereby maintaining the dimensional stability and structural integrity of the battery casing. This design not only enhances the stability of the battery casing during electrolyte injection and reduces the risk of electrolyte leakage, but also improves production efficiency and product quality, ensuring the continuity and reliability of the battery manufacturing process.

[0024] 2. In this application, the connecting end face on the limiting body and the top wall of the receiving body can achieve precise alignment during liquid injection, ensuring the stability and safety of the liquid injection device; on the other hand, the contact end face is smoothly connected to the side wall of the protrusion, ensuring that when the protrusion is embedded in the gap between the guide and the battery housing, the contact end face is flush with the inner wall of the accommodating cavity, so that the battery housing can fit tightly against the contact end face and the inner wall of the accommodating cavity during liquid injection, providing uniform and tight support, thereby effectively preventing any movement or expansion of the battery housing during liquid injection.

[0025] 3. In this application, by setting the guide part circumferentially along the opening edge of the accommodating cavity to form an annular recessed structure, and setting the protrusion part along the annular contour of the limiting body, a continuous support structure is formed. This not only enhances the stability and integrity of the battery casing during the liquid injection process, but also effectively avoids local stress concentration by uniformly distributing pressure through the annular contour, thereby reducing the risk of deformation of the battery casing. Attached Figure Description

[0026] The preferred embodiments will now be described in a clear and easy-to-understand manner, in conjunction with the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of this application.

[0027] Figure 1 This is a partial cross-sectional view of a battery casing placed inside a receiving body in one embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the structure of the receiving body in one embodiment of this application;

[0029] Figure 3 This is a schematic diagram of the structure of one embodiment of this application;

[0030] Figure 4 This is a cross-sectional view of one embodiment of this application;

[0031] Figure 5 yes Figure 4 A magnified view of a section at point A in the middle;

[0032] Figure 6 This is an exploded structural diagram of one embodiment of this application;

[0033] Figure 7 This is a schematic diagram of the structure of the long side limiting part in one embodiment of this application;

[0034] Figure 8 This is a schematic diagram of the structure of the short side limiting part in one embodiment of this application.

[0035] Reference numerals: Battery casing 1; Receiving body 2; Receiving cavity 200; Guide part 21; Limiting body 3; Protrusion 31; Contact end face 32; Connecting end face 33; Long side limiting part 34; Long side protrusion 341; First limiting edge 342; First connecting end face 343; Short side limiting part 35; Short side protrusion 351; Second limiting edge 352; Second connecting end face 353; Pin 4. Detailed Implementation

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the specific implementation methods of this application will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort.

[0037] To keep the drawings concise, each drawing only schematically shows the parts relevant to the application; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one."

[0038] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0039] In this document, 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 fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application.

[0041] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0042] In modern battery manufacturing, electrolyte filling is a crucial step in battery production, directly impacting battery performance and safety. Traditional electrolyte filling tooling designs typically employ a one-piece structure. While this design initially met basic production needs, its limitations have become increasingly apparent with advancements in battery technology and rising product quality requirements.

[0043] Specifically, while the chamfer (or similar structure) above the opening in traditional tooling facilitates the insertion of the battery casing, the lack of an effective support structure makes the casing prone to expansion during electrolyte injection, especially under positive pressure. This expansion not only leads to the battery casing exceeding size limits but can also affect the uniform injection of electrolyte, thus impacting battery performance and consistency. Furthermore, expansion during multiple electrolyte injection cycles can adversely affect subsequent processes such as encapsulation and welding, increasing production costs and reducing efficiency.

[0044] To resolve these issues, please refer to the attached instruction manual. Figure 3 and Figure 4 The liquid injection device provided in this application can effectively control the expansion of the battery casing 1 during the liquid injection process, thereby improving the stability of the liquid injection process and the quality of the battery product.

[0045] The liquid injection device provided in this application includes a receiving body 2 and a limiting body 3. Further details are provided with reference to the appendix. Figure 2 The receiving body 2 has an open receiving cavity 200, which can hold the battery casing 1 for subsequent liquid injection.

[0046] Reference manual attached Figure 1 and Figure 2 At least a portion of the opening edge of the accommodating cavity 200 is provided with a guide portion 21, which facilitates the insertion or removal of the battery casing 1. Wherein, for example... Figure 5 As shown, the limiting body 3 is provided with a protrusion 31, which is fitted together with the guide part 21. Specifically, during the liquid injection process, the limiting body 3 and the receiving body 2 are relatively fixed, and the gap between the guide part 21 and the battery housing 1 is filled by the protrusion 31. This tight fit effectively prevents the battery housing 1 from expanding due to positive pressure during the liquid injection process, thereby ensuring the dimensional accuracy and structural integrity of the battery housing 1.

[0047] This design not only enhances the stability of the battery casing 1 during the electrolyte injection process but also improves the quality and consistency of the battery product by reducing the expansion and deformation of the battery casing 1. Furthermore, the cooperation between the protrusion 31 and the guide 21 ensures that the battery casing 1 is precisely fixed in the receiving cavity 200, reducing uneven electrolyte injection caused by positional misalignment and further improving battery performance.

[0048] In this embodiment, the number of accommodating cavities 200 in the receiving body 2 is not specifically limited. Multiple independent accommodating cavities 200 can be designed in the receiving body 2, allowing multiple battery casings 1 to be injected with electrolyte simultaneously, thus improving production efficiency. Each accommodating cavity 200 is provided with a corresponding limiting body 3 to ensure that each battery casing 1 is properly positioned and supported during the electrolyte injection process. Furthermore, a shared limiting body 3 can also be designed, and through a corresponding mechanical layout, one limiting body 3 can provide support for multiple accommodating cavities 200 simultaneously, ensuring the stability of the battery casing 1 and the uniform injection of electrolyte during the electrolyte injection process; or a rotary electrolyte injection device can be used, allowing each accommodating cavity 200 to move sequentially to the injection position, positioned and supported by the same limiting body 3, which not only saves space but also improves the efficiency of equipment use.

[0049] In one embodiment, based on the above embodiments, such as Figure 5 As shown, the limiting body 3 is provided with a connecting end face 33, which is located adjacent to the protrusion 31, and the top wall of the receiving body 2 is adjacent to the guide part 21.

[0050] During liquid injection, the connecting end face 33 abuts against the top wall of the receiving body 2, forming a stable support platform, effectively preventing displacement or tilting of the battery casing 1 during the liquid injection process; simultaneously, the protrusion 31 is embedded between the guide portion 21 and the battery casing 1. As shown in the figure, the vertical extension height of the protrusion 31 exceeds the bottom surface of the connecting end face 33, ensuring that the protrusion 31 can penetrate deep into the gap between the guide portion 21 and the battery casing 1, forming a tight fit.

[0051] Furthermore, a corresponding connection structure is provided between the connecting end face 33 and the top wall of the receiving body 2 to achieve relative fixation between the limiting body 3 and the receiving body 2.

[0052] Understandably, the connection structure not only enhances the overall strength of the injection device, but also ensures precise alignment and stable cooperation between the receiving body 2 and the limiting body 3 during the injection process.

[0053] In other words, during the liquid injection operation, the connecting end face 33 of the limiting body 3 and the top wall of the receiving body 2 are seamlessly connected through the connecting structure, thereby providing a stable support platform for the battery housing 1. The precise embedding of the protrusion 31 further enhances the stability and ensures that the battery housing 1 will not be displaced or deformed due to pressure or improper operation during the liquid injection process.

[0054] In some embodiments, the connection structure described above may include multiple connectors. Both the connection end face 33 and the top wall of the receiving body 2 are provided with multiple corresponding mounting holes. The corresponding arrangement of these mounting holes provides a precise positioning basis for installing the connectors. The selected connector may be a pin 4. This design not only simplifies the assembly process but also improves the reliability and stability of the connection.

[0055] Using pin 4 as a connector allows the operator to quickly connect or separate the limiting body 3 from the receiving body 2. When pin 4 passes through the assembly hole, the limiting body 3 is firmly fixed to the receiving body 2, ensuring precise fit and stability during the liquid injection process. When equipment maintenance or battery housing 1 replacement is required, simply pulling out pin 4 easily separates the limiting body 3 and the receiving body 2, allowing for quick and easy operation.

[0056] In this embodiment, the advantage of this connection method lies in its ease of operation. It can be fixed simply by inserting the pin 4 into the assembly hole, and it is also easy to disassemble and maintain. On the other hand, by setting multiple assembly holes and corresponding pins 4 between the limiting body 3 and the receiving body 2, multi-point support can be achieved, thereby enhancing the stability of the overall structure.

[0057] In one embodiment, the guide portion 21 of the receiving body 2 is designed with a chamfered structure, while the corresponding protrusion 31 on the limiting body 3 is triangular in shape. During the electrolyte injection operation, the triangular protrusion fits into the chamfered structure, ensuring the precise positioning and stability of the battery casing 1 during the electrolyte injection process. This fit not only provides uniform support for the battery casing 1 but also effectively prevents deformation caused by uneven pressure or expansion, thereby ensuring that the electrolyte can be uniformly injected into the battery casing 1 and improving the overall quality of the battery product.

[0058] With this design, during liquid injection, the limiting body 3 and the receiving body 2 together form an integral structure. This structure is adapted to the outer contour of the battery casing 1, which can reduce the relative collision between the liquid injection device and the battery casing 1.

[0059] In addition, the compatibility with different battery housing models can be optimized by adjusting the shape or size of the triangular protrusions, or by changing the depth and angle of the chamfer structure.

[0060] Based on the above embodiments, the limiting body 3 is provided with an abutting end face 32, which is smoothly connected to the side wall of the protrusion 31 on the side opposite to the connecting end face 33. When the protrusion 31 is embedded in the guide portion 21 of the receiving body 2, the abutting end face 32 remains flush with the inner wall of the accommodating cavity 200, ensuring that the battery housing 1 can closely adhere to the abutting end face 32 and the inner wall of the accommodating cavity 200 during the liquid injection process, providing a continuous support surface and providing uniform contact and stable support for the battery housing 1.

[0061] Understandably, during the liquid injection process, the battery housing 1 is in close contact with the contact end face 32 and the inner wall of the accommodating cavity 200. This close contact not only improves the positioning accuracy of the battery housing 1, but also effectively prevents the battery housing 1 from expanding or deforming due to uneven pressure. On the other hand, the tight combination of the battery housing 1 with the contact end face 32 and the inner wall of the accommodating cavity 200 improves the sealing of the entire liquid injection environment, helps to maintain the pressure conditions required during the liquid injection process, and prevents the intrusion of air and other contaminants.

[0062] In another embodiment, based on the above embodiment, the guide portion 21 is arranged circumferentially along the opening edge of the accommodating cavity 200, thereby forming an annular recessed structure. This annular design not only provides uniform support for the stable placement of the battery housing 1, but also ensures a balanced pressure distribution in the circumferential direction of the battery housing 1 during the liquid injection process, thereby effectively preventing deformation of the battery housing 1 due to excessive local pressure.

[0063] Meanwhile, the limiting body 3 adopts a ring-shaped contour design, and the protrusion 31 is set along the ring-shaped contour of the limiting body 3. The cooperation between the protrusion 31 and the ring-shaped recessed structure realizes the precise positioning and stable support of the battery casing 1 during the liquid injection process.

[0064] Understandably, this design in this embodiment not only improves the stability of the battery casing 1 during the electrolyte injection process, but also promotes the uniform injection of electrolyte into the battery casing 1 through uniformly distributed pressure, avoiding uneven electrolyte distribution caused by uneven pressure, thereby improving battery performance and lifespan.

[0065] In addition, the protrusion 31 can be a continuous annular protrusion or a segmented protrusion, as long as it can correspond to the guide part 21 of the receiving body 2, so that the liquid injection device can provide customized support and positioning for battery housings 1 of different sizes while maintaining the overall structural stability.

[0066] In one embodiment, such as Figure 6 As shown, the limiting body 3 includes two oppositely arranged long-side limiting parts 34 and two oppositely arranged short-side limiting parts 35, which are respectively configured to correspond to the long and short sides of the battery housing 1. This design is based on the geometric characteristics of the cross-section of the battery housing 1. Whether it is rectangular or square, multiple such limiting parts corresponding to its sides can jointly form the annular contour of the limiting body 3, thereby precisely matching the edge of the battery housing 1 and achieving all-round stable support.

[0067] Furthermore, when the cross-section of the battery casing 1 is square, the long side limiting portion 34 and the short side limiting portion 35 can have the same size. This uniform size setting simplifies the production and maintenance process because the same parts can be used to fit all edges, reducing production costs and improving the versatility of the parts. In the case of a rectangular cross-section, by adjusting the size of the long side limiting portion 34 and the short side limiting portion 35, the specific length-to-width ratio of the battery casing 1 can be precisely fitted, further optimizing the liquid injection process.

[0068] Based on the above, such as Figure 7 and Figure 8 As shown, each long-side limiting part 34 and short-side limiting part 35 is equipped with a corresponding long-side protrusion 341 and short-side protrusion 351, which work together to form the protrusion 31 mentioned above. This ensures that the protrusion 31 can be tightly embedded between the guide part 21 of the receiving body 2 and the battery housing 1 in both long and short directions, thereby effectively filling the gap and improving the positioning accuracy and stability of the battery housing 1 during liquid injection.

[0069] It is understandable that the combined effect of the long-side protrusion 341 and the short-side protrusion 351 not only prevents the battery casing 1 from expanding and shifting during the liquid injection process, but also helps the battery casing 1 to more evenly bear the pressure generated during liquid injection by supporting the long and short sides of the battery casing 1. This even support helps to avoid excessive local stress and reduces the deformation or damage that may occur to the battery casing 1 during the liquid injection process.

[0070] Furthermore, various limiting structures are formed through different combinations of the long-side limiting part 34 and the short-side limiting part 35. The first form connects each long-side limiting part 34 to one short-side limiting part 35, forming an L-shaped structure. During injection, two L-shaped structures are used. In production, one long-side limiting part 34 and one short-side limiting part 35 are integrally molded or pre-fixed to improve subsequent operational efficiency. The second form connects one long-side limiting part 34 to two short-side limiting parts 35, forming a C-shaped structure centered on the long side. Conversely, one short-side limiting part 35 can also connect to two long-side limiting parts 34, forming a C-shaped structure centered on the short side. In this case, one C-shaped structure and one independent (long-side / short-side) limiting part are used. In the third form, all long-side limiting parts 34 and short-side limiting parts 35 are independently set, which is easier to understand; during operation, the four limiting parts are installed in their respective positions.

[0071] In one embodiment, each long-side limiting portion 34 is provided with a first limiting edge 342, while each short-side limiting portion 35 is provided with a second limiting edge 352. These edges are inclined to achieve a tighter and more stable fit. In the working state, the first limiting edge 342 of the long-side limiting portion 34 and the second limiting edge 352 of the adjacent short-side limiting portion 35 are in contact with each other, so that the multiple limiting portions form a continuous support surface.

[0072] Based on the above, this embodiment optimizes the stability of the injection device during injection by increasing the contact area and adjusting the contact angle, while effectively dispersing the local stress caused by the injection pressure. On the other hand, the inclined edge serves as a guide surface, assisting the long side limiting part 34 and the short side limiting part 35 to quickly align with the corresponding guide part 21, simplifying the assembly process and improving operating efficiency.

[0073] Furthermore, each long-side limiting part 34 has a first connecting end face 343, and each short-side limiting part 35 has a second connecting end face 353. In this embodiment, the connecting end face 33 is formed by all the first connecting end faces 343 and the second connecting end faces 353, ensuring that the top wall of the receiving body 2 can be simultaneously connected and fixed to both first connecting end faces 343 and both second connecting end faces 353, providing a balanced and comprehensive support structure for the battery housing 1. By evenly distributing the force on the battery housing 1 during the liquid injection process, the overall stability and support efficiency are significantly improved.

[0074] Meanwhile, the pin connection method in the above embodiment can also be applied to this embodiment. All the first connecting end faces 343 and the second connecting end faces 353 are opposite to the top wall of the receiving body 2 when liquid is injected. The pins 4 are used to achieve a stable connection and fixation. Moreover, the pins 4 can form multiple support points on each limiting part, thereby achieving the effect of multi-point support, improving the reliability and safety of the liquid injection device, and ensuring the fixing effect on the battery casing 1.

[0075] It should be noted that the above embodiments can be freely combined as needed. The above are merely preferred embodiments of this application. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A liquid injection device, characterized in that, include: The receiving body has an open receiving cavity for placing a battery casing, and at least a portion of the opening edge of the receiving cavity is provided with a guide portion for guiding the placement or removal of the battery casing; A limiting body is provided with a protrusion, which is matched with the guide portion; during the liquid injection process, the limiting body and the receiving body are relatively fixed, and the gap between the guide portion and the battery housing is filled by the protrusion to prevent the battery housing from expanding; Multiple assembly holes and corresponding pins are provided between the limiting body and the receiving body to achieve multi-point support; The limiting body includes two long-side limiting parts and two short-side limiting parts. The long-side limiting parts are respectively set for the two long sides of the battery casing, and the short-side limiting parts are respectively set for the two short sides of the battery casing. The two long-side limiting parts and the two short-side limiting parts are independently set.

2. The liquid injection device according to claim 1, characterized in that, in, Each of the long-side limiting portions has a long-side protrusion, and each of the short-side limiting portions has a short-side protrusion, the long-side protrusion and the short-side protrusion together forming the protrusion portion.

3. The liquid injection device according to claim 2, characterized in that, Each of the long-side limiting portions is provided with a first limiting edge, and each of the short-side limiting portions is provided with a second limiting edge. Both the first limiting edge and the second limiting edge are inclined. During the injection process, the first limiting edge of the long-side limiting portion is in contact with the second limiting edge of the adjacent short-side limiting portion.

4. The liquid injection device according to claim 3, characterized in that, The limiting body is also provided with a connecting end face, the connecting end face and the protrusion are arranged adjacent to each other, and the vertical extension height of the protrusion exceeds the bottom of the connecting end face; The top wall of the receiving body is adjacent to the guide portion. During liquid injection, the connecting end face abuts against the top wall of the receiving body, and the protrusion is embedded between the guide portion and the battery casing.

5. The liquid injection device according to claim 1, characterized in that, The guide portion is arranged circumferentially along the opening edge of the accommodating cavity to form an annular recessed structure; The limiting body has a ring-shaped outline, and the protrusion is set along the ring-shaped outline of the limiting body.

6. The liquid injection device according to claim 4, characterized in that, Each of the long-side limiting portions has a first connecting end face, and each of the short-side limiting portions has a second connecting end face. The first connecting end face and the second connecting end face together form the connecting end face, so that during liquid injection, the top wall of the receiving body is simultaneously connected and fixed to the two first connecting end faces and the two second connecting end faces.

7. The liquid injection device according to any one of claims 2-6, characterized in that, The limiting body also has an abutting end face, which is smoothly connected to the side wall of the protrusion on the side away from the connecting end face. When the protrusion is embedded in the guide portion, the abutting end face is flush with the inner wall of the accommodating cavity, so that the battery casing is in close contact with the abutting end face and the inner wall of the accommodating cavity during the liquid injection process.

8. The liquid injection device according to claim 7, characterized in that, The guide portion has a chamfered structure, and the protrusion is a triangular protrusion. During liquid injection, the triangular protrusion fits into the chamfered structure, so that the limiting body and the receiving body together form an integral structure that fits the outer contour of the battery casing.

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