Housing structure, electrochemical device, and electronic device

Abstract

The application discloses a shell structure, an electrochemical device and an electronic equipment, and relates to the technical field of electrochemical energy storage. The shell structure comprises a middle frame and two cover plates. The middle frame comprises a plurality of straight segments and a plurality of corner segments. The straight segments and the corner segments are alternately arranged along the circumference of the middle frame to form a ring structure. The two ends of the corner segment are connected to a straight segment. The cover plates are connected to the two sides of the middle frame along the thickness direction. The cover plates and the middle frame jointly define a receiving cavity for receiving an electric core. Each corner of each cover plate is provided with an arc segment. The projection of the arc segment along the thickness direction of the shell structure is located outside the projection of the corner segment at any corner position of the shell structure. The shell structure forms an overlapping compensation area by extending the corner position of the cover plate, ensures that the overlapping area of the middle frame and the cover plate is not affected, and thus improves the welding quality.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to shell structures, electrochemical devices and electronic equipment. Background Technology

[0002] Steel-cased batteries have certain advantages in terms of energy density, cycle life, and safety, and are therefore increasingly used. In existing technologies, a three-section structure is used to form the battery casing. This three-section structure includes a top cover, a bottom shell, and a middle frame. The top cover and bottom shell are welded to the two sides of the middle frame to form a closed containment space.

[0003] However, this three-section structure is prone to deformation due to the thinness of the middle frame. During the welding process, the four sides of the middle frame are positioned and abutted by positioning fixtures. If there is a certain deviation in the length and width dimensions of the middle frame, the positioning of the middle frame will cause deformation at the corners, resulting in a smaller overlap area between the middle frame and the top cover, or between the middle frame and the bottom shell, and insufficient welding area, which affects the welding strength and sealing performance. Utility Model Content

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a shell structure that, by extending the corners of the cover plate to form an overlap compensation area, ensures that the overlap area between the middle frame and the cover plate is not affected, thereby improving the welding quality.

[0005] This application also proposes an electrochemical device having the above-described shell structure.

[0006] This application also proposes an electronic device having the above-mentioned electrochemical device.

[0007] The housing structure according to the first aspect of this application includes: The middle frame includes multiple straight segments and multiple corner segments. The straight segments and corner segments are alternately arranged along the circumference of the middle frame to form a ring structure. The two ends of the corner segments are respectively connected to one of the straight segments. Two cover plates are respectively connected to both sides of the middle frame along its thickness direction. The cover plates and the middle frame together define a receiving cavity for accommodating the battery cell. Each corner of each cover plate is provided with an arc segment. Wherein, at any corner position of the shell structure, the projection of the arc segment along the thickness direction of the shell structure is outside the projection of the corner segment.

[0008] The shell structure according to the embodiments of this application has at least the following beneficial effects: The shell structure of this application extends the corner of the cover plate outward by a certain distance relative to the corner section of the middle frame, thereby forming an overlap compensation area. Even if the corner section of the middle frame deforms due to stress, the overlap area between the arc section on the cover plate and the corner section of the middle frame can remain stable, thereby ensuring that the welding strength and sealing performance are not affected, thus improving the welding quality and production yield.

[0009] According to some embodiments of this application, the chamfer of the corner segment is R1, and the chamfer of the arc segment is R2, wherein R2 < R1.

[0010] According to some embodiments of this application, the projection area of ​​the cover plate along the thickness direction of the housing structure covers the projection area of ​​the middle frame.

[0011] According to some embodiments of this application, the housing structure further includes a weld connecting the middle frame and the cover plate, the weld including a second weld portion extending to the middle frame and a first weld portion extending to the cover plate, the second weld portion and the first weld portion being integrally connected.

[0012] According to some embodiments of this application, the cover plate includes a first surface facing away from the middle frame, the first surface having a first weld mark formed thereon, the first welded portion being disposed corresponding to the first weld mark, and the dimension W1 of the first weld mark along the wall thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame having the following relationship: W2 < W1 < W3.

[0013] According to some embodiments of this application, the middle frame includes a second surface connected to the cover plate, the second surface having a second weld mark formed thereon, the second welded portion being disposed corresponding to the second weld mark, and the dimension W4 of the second weld mark along the wall thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame having the following relationship: W2 < W4 < W3.

[0014] According to some embodiments of this application, the distance L1 from the second weld mark to the inner wall of the middle frame has the following relationship with the wall thickness W3 of the middle frame: 0 < L1 < W3.

[0015] According to some embodiments of this application, the depth D1 of the second welded portion along the thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame have the following relationship: W2 < D1 < W3.

[0016] The electrochemical device according to a second aspect of this application includes the housing structure mentioned in any of the foregoing embodiments.

[0017] An electronic device according to a third aspect of this application includes the electrochemical device mentioned in any of the foregoing embodiments.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a top view of the shell structure according to an embodiment of this application; Figure 2 for Figure 1 Enlarged view of region B in the middle; Figure 3 for Figure 1 Schematic diagram of the cross section along the AA direction; Figure 4 for Figure 3 Enlarged view of region C in the middle; Figure 5 for Figure 4 Dimensioning diagram in the middle; Figure 6 To and Figure 2 Enlarged schematic diagram of the corresponding first embodiment; Figure 7 To and Figure 4 Enlarged cross-sectional view of the corresponding first embodiment; Figure 8 To and Figure 2 Enlarged schematic diagram of the corresponding second embodiment; Figure 9 To and Figure 4 Enlarged cross-sectional view of the corresponding second embodiment.

[0020] Figure label: Middle frame 100; Straight line segment 110; Corner segment 120; Second surface 130; Cover plate 200; curved segment 210; first surface 220; Weld 300; First welded section 310; Second welded section 320; 400 cells; Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0021] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0022] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the terms may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two numerical values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two numerical values ​​can be considered “generally” the same.

[0023] Furthermore, for ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0024] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0025] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0026] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0027] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0028] Throughout this specification, references to “implementation,” “partial implementation,” “one implementation,” “another approach,” “specific approach,” or “partial approach” mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0029] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0030] Steel-cased batteries have certain advantages in terms of energy density, cycle life, and safety, and are therefore increasingly used. In existing technologies, a three-section structure is used to form the battery casing. This three-section structure includes a top cover, a bottom shell, and a middle frame. The top cover and bottom shell are welded to the two sides of the middle frame to form a closed containment space.

[0031] However, this three-section structure is prone to deformation due to the thinness of the middle frame. During the welding process, the four sides of the middle frame are positioned and abutted by positioning fixtures. If there is a certain deviation in the length and width dimensions of the middle frame, the positioning of the middle frame will cause deformation at the corners, resulting in a smaller overlap area between the middle frame and the top cover, or between the middle frame and the bottom shell, and insufficient welding area, which affects the welding strength and sealing performance.

[0032] To address the aforementioned problems, this application proposes a shell structure, such as... Figure 3 As shown, the shell structure includes a middle frame 100 and two cover plates 200. It can be understood that the two cover plates 200 are the aforementioned top cover and bottom shell. The size and structure of the top cover and bottom shell can be the same or different.

[0033] like Figure 1 and Figure 3 As shown, the middle frame 100 is an annular frame structure with openings at both ends along its thickness direction. One cover plate 200 is placed over one end opening of the middle frame 100, and the other cover plate 200 is placed over the other end opening of the middle frame 100. Thus, the two cover plates 200 and the middle frame 100 together enclose a closed accommodating cavity, which is used to accommodate the battery cell 400.

[0034] It is understood that the middle frame 100 includes multiple straight segments 110 and multiple bent segments. The straight segments 110 and corner segments 120 are alternately connected along the circumference of the middle frame 100. The corner segments 120 are used to connect adjacent straight segments 110 so that the middle frame 100 as a whole forms a ring-shaped frame structure.

[0035] It is understood that the middle frame 100 can be a polygonal structure, such as a triangle, rectangle, or hexagon, and the shape of the cover plate 200 is adapted to the shape of the middle frame 100. Depending on the actual shape of the middle frame 100, the position and number of the straight segments 110 and corner segments 120 will also change accordingly. For example, Figure 1 As shown, the middle frame 100 has a rectangular frame structure, including two long side straight line segments 110, two short side straight line segments 110, and four corner segments 120 that connect adjacent straight line segments 110 respectively.

[0036] It should be noted that when connecting the middle frame 100 to the cover plate 200, each straight segment 110 of the middle frame 100 needs to be positioned separately to ensure the accuracy of the welding position between the four straight segments 110 of the middle frame 100 and the cover plate 200. This prevents the straight segments 110 from deforming due to temperature or internal stress during the welding process, which could lead to misalignment or weak welding. It is understandable that slight deviations in the length or width dimensions of the middle frame 100 may occur during manufacturing. Therefore, after the straight segments 110 are positioned and fixed, the corner segment 120 may undergo slight deformation due to stress concentration. For example, if the length of the middle frame 100 is smaller than expected, after the two straight segments 110 in the length direction of the middle frame 100 are positioned and clamped, the corner segment 120 will shrink inward due to shrinkage stress, resulting in a narrower overlap area between the corner segment 120 and the cover plate 200, thus affecting the reliability of the welding and the overall sealing performance of the structure.

[0037] Therefore, the cover plate 200 of this application is provided with an arc segment 210 at the position corresponding to the corner segment 120. Thus, an arc segment 210 is provided at each corner position of the cover plate 200. To avoid the problem of reduced overlap area between the corner segment 120 of the middle frame 100 and the cover plate 200 when the middle frame 100 deforms, the corner positions on the cover plate 200 extend outwards by a certain distance relative to the corner segment 120 of the middle frame 100. That is, at any corner position of the shell structure, the projection of the arc segment 210 along the thickness direction of the shell structure is outside the projection of the corner segment 120 (e.g., ...). Figure 2 As shown), to form an overlap compensation area. It should be explained that the middle frame 100 has a relatively inner side and an outer side. The inner side refers to the side of the middle frame 100 facing the receiving cavity, and the outer side refers to the side of the middle frame 100 away from the receiving cavity. Thus, in the projection view along the thickness direction of the shell structure, the arc segment 210 is located outside the corner segment 120.

[0038] Based on the above, the shell structure of this application extends the corner position of the cover plate 200 outward by a certain distance relative to the corner segment 120 of the middle frame 100, thereby forming an overlap compensation area. Even if the corner segment 120 of the middle frame 100 deforms due to stress, the overlap area between the arc segment 210 on the cover plate 200 and the corner segment 120 of the middle frame 100 can still remain stable, thereby ensuring that the welding strength and sealing performance are not affected, thereby improving the welding quality and production yield.

[0039] In some embodiments, the chamfer of the corner segment 120 is R1, and the chamfer of the arc segment 210 is R2, wherein R2 is smaller than R1, thereby making the arc segment 210 more outward in the projection direction compared to the corner segment 120. Furthermore, this type of cover plate 200 can be adapted to a variety of sizes of the mid-frame 100, for example, such as... Figure 2 and Figure 4 As shown, the length and width dimensions of the middle frame 100 are exactly equal to the length and width dimensions of the cover plate 200. At this time, the straight segment 110 of the middle frame 100 is flush with the straight edge of the cover plate 200. Alternatively, as... Figure 6 and Figure 7 As shown, the length and width dimensions of the middle frame 100 can be slightly smaller than those of the cover plate 200. In this case, the projected area of ​​the cover plate 200 along the thickness direction of the shell structure completely covers the projected area of ​​the middle frame 100. Alternatively, as... Figure 8 and Figure 9 As shown, the length and width of the middle frame 100 can also be slightly larger than the length and width of the cover plate 200. In this case, the corner segment 120 of the middle frame 100 can still maintain a sufficient overlap area with the corner of the cover plate 200. In addition, the straight segment 110 of the middle frame 100 and the straight edge of the cover plate 200 can also maintain good contact and welding effect.

[0040] The dimension of R1 is from 0.5mm to 5mm. For example, the dimension of R1 can be 0.5mm, 0.8mm, 1.0mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, etc., or within any two of the above values. The dimension of R2 is from 0.1mm to 4.95mm. For example, the dimension of R2 can be 0.1mm, 0.2mm, 0.5mm, 1.0mm, 1.5mm, 3mm, 4mm, 4.95mm, etc., or within any two of the above values. It should be noted that the chamfer dimensions of each arc segment 210 around the cover plate 200 can be the same or different according to specific design requirements. Furthermore, the chamfer dimensions of the corresponding arc segments 210 of the two cover plates 200 can be the same or different to adapt to the stress distribution characteristics of the middle frame 100 in different areas and further optimize the overlap compensation effect.

[0041] Furthermore, the difference between R1 and R2 is maintained between 0.05mm and 0.5mm. For example, the difference between R1 and R2 can be 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc., or fall within the range of any two of the above values. This ensures that the arc segment 210 is always located outside the corner segment 120 in the projection direction, while avoiding structural redundancy or assembly interference due to excessive extension. The reasonable control of this dimensional difference not only ensures the effectiveness of the overlap compensation area but also improves the alignment tolerance between the cover plate 200 and the middle frame 100 during the welding process.

[0042] In some embodiments, the cover plate 200 and the middle frame 100 are connected by welding, thereby forming a weld 300 on the cover plate 200 and the middle frame 100, such as... Figure 4 As shown, when welding is performed on the cover plate 200, a weld mark can be formed that penetrates the cover plate 200 and extends into the middle frame 100. The width of the weld mark gradually decreases along the direction from the cover plate 200 to the middle frame 100. For ease of description, the weld 300 is divided into a second weld portion 320 and a first weld portion 310. The second weld portion 320 is the part that extends into the middle frame 100, and the first weld portion 310 is the part that extends into the cover plate 200. It can be understood that the second weld portion 320 and the first weld portion 310 are fused together during welding, thereby forming a strong connection so that the cover plate 200 and the middle frame 100 can be tightly connected and maintain good structural strength and sealing performance.

[0043] Furthermore, such as Figure 4 and Figure 5 As shown, the cover plate 200 includes a first surface 220 facing away from the middle frame 100. During welding, a first weld mark is formed on the first surface 220. It can be understood that the first weld portion 310 is provided corresponding to the first weld mark. The dimension W1 of the first weld mark along the wall thickness direction of the middle frame 100, the thickness W2 of the cover plate 200, and the wall thickness W3 of the middle frame 100 have the following relationship: W2 < W1 < W3.

[0044] It should be explained that the dimension W1 of the first weld along the wall thickness direction of the middle frame 100, i.e., the surface weld width, can be controlled to ensure a balance between the fusion depth and width of the entire weld 300. The wall thickness of the middle frame 100 refers to the dimension of each plate constituting the middle frame 100 in the thickness direction, i.e., as shown in the diagram. Figure 5 As shown. The thickness of the middle frame 100 refers to the overall dimension of the middle frame 100 in the thickness direction of the shell structure, that is, the distance between the two cover plates 200.

[0045] In some embodiments, the middle frame 100 includes a second surface 130 connected to the cover plate 200. It is understood that the middle frame 100 includes two second surfaces 130 disposed opposite each other along its thickness direction; the second surfaces 130 are also the surfaces where the middle frame 100 and the cover plate 200 meet. During welding, the weld 300 extends from the first surface 220 to the second surface 130 of the middle frame 100, forming a second weld mark on the second surface 130, and continues to extend into the interior of the middle frame 100, thereby forming a complete welded connection structure. It is understood that the second weld portion 320 corresponds to the second weld mark.

[0046] The second weld mark, along the wall thickness direction of the middle frame 100, has the following relationship with the thickness of the cover plate 200, the wall thickness of the middle frame 100, and the wall thickness of the middle frame 100: W2 < W4 < W3. It should be explained that the dimension of the second weld along the wall thickness direction of the middle frame 100 is also the effective weld width. By controlling this welding dimension, the effective fusion area of ​​the weld 300 can be guaranteed, thus ensuring the welding quality.

[0047] In some embodiments, the distance L1 from the second weld mark to the inner wall of the middle frame 100 has the following relationship with the wall thickness W3 of the middle frame 100: 0 < L1 < W3, so that the weld 300 is located in the middle of the middle frame 100 along its thickness direction, and maintains a certain distance from the inner wall of the middle frame 100, so as to prevent the weld 300 from welding through the middle frame 100.

[0048] In some embodiments, the depth D1 of the second welded portion 320 along the thickness direction of the middle frame 100, the thickness W2 of the cover plate 200, and the wall thickness W3 of the middle frame 100 have the following relationship: W2 < D1 < W3. By controlling the depth D1 of the second welded part 320 along the thickness direction of the middle frame 100, the extension depth of the welded part inside the middle frame 100 can be effectively ensured to meet the strength requirements of the welded structure, while avoiding excessive welding that could lead to deformation or damage to the middle frame 100.

[0049] It should be noted that the depth and other dimensions of the aforementioned second welded portion 320 can be achieved by slicing the shell structure to form a shape such as... Figure 3 The cross-section shown (excluding the battery cell 400) is then ground to expose structures such as the weld 300 on the cross-section, and then the dimensions of the weld 300 are measured. Alternatively, the dimensions of the first weld, the second weld, etc., can also be measured directly after disassembling the cover plate 200 and the middle frame 100.

[0050] This application provides an electrochemical device, including any apparatus in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0051] In some embodiments, the electrochemical device includes a battery cell 400 and a housing structure, with the battery cell 400 placed inside the housing structure. The housing structure used in this electrochemical device is the housing structure described above in this application, and thus should include the technical effects of the above embodiments, which will not be repeated here.

[0052] This application provides an electronic device including the electrochemical device described above. The electronic device is not particularly limited and can be any electronic device known in the prior art. The application of the electrochemical device of this invention is not particularly limited and can be used in any electronic device known in the prior art. According to some embodiments of this invention, the electronic devices include, but are not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and android robots.

[0053] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A shell structure, characterized in that, include: The middle frame includes multiple straight segments and multiple corner segments. The straight segments and corner segments are alternately arranged along the circumference of the middle frame to form a ring structure. The two ends of the corner segments are respectively connected to one of the straight segments. Two cover plates are respectively connected to both sides of the middle frame along its thickness direction. The cover plates and the middle frame together define a receiving cavity for accommodating the battery cell. Each corner of each cover plate is provided with an arc segment. Wherein, at any corner position of the shell structure, the projection of the arc segment along the thickness direction of the shell structure is outside the projection of the corner segment.

2. The shell structure according to claim 1, characterized in that, The chamfer of the corner segment is R1, and the chamfer of the arc segment is R2, where R2 < R1.

3. The shell structure according to claim 1, characterized in that, The projection area of ​​the cover plate along the thickness direction of the shell structure covers the projection area of ​​the middle frame.

4. The shell structure according to claim 1, characterized in that, The housing structure also includes a weld connecting the middle frame and the cover plate. The weld includes a second weld portion extending to the middle frame and a first weld portion extending to the cover plate, wherein the second weld portion and the first weld portion are connected as a whole.

5. The shell structure according to claim 4, characterized in that, The cover plate includes a first surface facing away from the middle frame, the first surface having a first weld mark, the first welded portion being provided corresponding to the first weld mark, and the dimension W1 of the first weld mark along the wall thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame having the following relationship: W2 < W1 < W3.

6. The shell structure according to claim 4, characterized in that, The middle frame includes a second surface connected to the cover plate, the second surface having a second weld mark, and a second welded portion corresponding to the second weld mark. The dimension W4 of the second weld mark along the wall thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame have the following relationship: W2 < W4 < W3.

7. The shell structure according to claim 6, characterized in that, The distance L1 from the second weld mark to the inner wall of the middle frame has the following relationship with the wall thickness W3 of the middle frame: 0 < L1 < W3.

8. The shell structure according to claim 4, characterized in that, The depth D1 of the second welded portion along the thickness direction of the middle frame, the thickness W2 of the cover plate, and the wall thickness W3 of the middle frame have the following relationship: W2 < D1 < W3.

9. An electrochemical device, characterized in that, Includes the shell structure as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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