Battery cell

Abstract

The utility model relates to a battery cell which comprises a naked battery cell, a protective film; the surface of the naked battery core is coated with the folded battery core; a battery cell shell, wherein the naked battery cell and the protective film are accommodated in the battery cell shell; at least partial areas of the protective film are overlapped and form a supporting part, at least partial areas of the supporting part are positioned between the naked battery cell and the bottom surface of the battery cell shell so as to support the naked battery cell, partial areas of the protective film are overlapped, the overlapped areas form the supporting part, and the supporting part is positioned between the naked battery cell and the battery cell shell so as to support the naked battery cell. After the protective film wraps the naked battery cell and then is plugged into the battery cell shell, the supporting parts enable the two sides of the naked battery cell to form a distance with the internal fillet of the battery cell shell, so that interference between the straight edges of the two sides of the original naked battery cell and the fillet of the battery cell shell can be avoided, the risk of short circuit of the naked battery cell is avoided, and the service life of the naked battery cell is prolonged. Therefore, the production cost of the battery cell can be reduced, and the electrical property stability of the battery cell is ensured.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically a battery cell. Background Technology

[0002] In actual assembly, the bare cells of a stacked lithium-ion battery are assembled into a cubic battery casing. However, the bottom of the battery casing always has a rounded corner, meaning there is an arc between the bottom and side surfaces. The bare cells do not have rounded corners, so the edges of the bare cells will interfere with the rounded corners of the battery casing. Therefore, to avoid the influence of the rounded corners of the battery casing on the bare cells and to improve the safety performance of stacked lithium batteries, the bare cells need to avoid the rounded corner areas of the battery casing. Existing technology uses an insulating base plate at the bottom of the battery casing. A Mylar (polyester polymer) protective film is then heat-fused to the insulating base plate to wrap the bare cells, preventing the right angles on both sides of the bare cells from contacting the rounded corners of the battery aluminum casing, thereby reducing the risk of short circuits. However, the above method requires adding a process on the test line and introducing equipment stations on the mass production line. Furthermore, it is affected by yield rates, which will lead to increased costs. Utility Model Content

[0003] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a battery cell that can maintain a distance between the right angles on both sides of the bare battery cell and the rounded corners of the battery aluminum shell, so as to avoid interference between the right angles on both sides of the bare battery cell and the rounded corners of the battery aluminum shell.

[0004] To achieve the above and other related objectives, this utility model proposes a battery cell, comprising:

[0005] Bare battery cells;

[0006] A protective film; folded and applied to the surface of the bare battery cell;

[0007] A battery cell housing, wherein the bare battery cell and the protective film are housed within the battery cell housing;

[0008] The protective film is at least partially overlapped and forms a support portion, and the support portion is at least partially located between the bare cell and the bottom surface of the cell casing to support the bare cell.

[0009] In an optional embodiment of this utility model, at least two protective films are provided, and a portion of the space between the at least two protective films overlaps to form the support portion.

[0010] In an optional embodiment of this utility model, the protective film is provided with two pieces, one of which is folded to form a first covering surface and a second covering surface, and the other of which is folded to form a third covering surface and a fourth covering surface;

[0011] The first and third covering surfaces respectively cover the two opposite vertical surfaces of the bare cell, and the second and fourth covering surfaces overlap to form a support portion, which covers the bottom surface of the bare cell.

[0012] In an optional embodiment of this utility model, the first covering surface and the second covering surface are rectangular and their sides in the length direction are connected in sequence, and the third covering surface and the fourth covering surface are rectangular and their sides in the length direction are connected in sequence.

[0013] In an optional embodiment of this utility model, the protective film is generally a rectangular film.

[0014] In an optional embodiment of the present invention, the second covering surface is disposed on both sides of the first covering surface along its length, and the fourth covering surface is disposed on both sides of the third covering surface along its length.

[0015] In an optional embodiment of this utility model, the second covering surface and the fourth covering surface are thermally fused together as one unit.

[0016] In an optional embodiment of this utility model, the thickness of the second covering surface is greater than or equal to the thickness of the first covering surface, and the thickness of the fourth covering surface is greater than or equal to the thickness of the third covering surface.

[0017] In an optional embodiment of this utility model, the thickness of the first covering surface and the third covering surface is 0.1 to 0.3 mm.

[0018] In an optional embodiment of this utility model, the thickness of the second covering surface and the fourth covering surface is 0.1 to 0.5 mm.

[0019] By adopting the above technical solution, the technical effect of this utility model is as follows: This utility model improves the protective film used to cover bare battery cells. A portion of the upper area of ​​the protective film is overlapped, and this overlapped area constitutes a support portion. This support portion is located between the bare battery cell and the battery cell housing. After the protective film covers the bare battery cell and is inserted into the battery cell housing, the support portion creates a gap between the two sides of the bare battery cell and the rounded corners inside the battery cell housing. This avoids interference between the straight edges of the original bare battery cell and the rounded corners of the battery cell housing, avoiding the risk of short circuits in the bare battery cell. Therefore, it can reduce the production cost of the battery cell and ensure the electrical performance stability of the battery cell itself. Attached Figure Description

[0020] Figure 1 and Figure 2 These are schematic diagrams of two existing technologies for assembling a battery cell casing, a bare battery cell, and a protective film.

[0021] Figure 3 This is a front view of a bare battery cell in one embodiment of the present invention;

[0022] Figure 4 This is a three-dimensional structural diagram of a bare battery cell in one embodiment of the present invention;

[0023] Figure 5 This is a partial cross-sectional structural diagram of the assembly of the battery cell housing, bare battery cell and protective film in one embodiment of the present invention;

[0024] Figure 6 This is a planar schematic diagram of two protective films in one embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the end face where the two protective films are joined in one embodiment of the present invention;

[0026] Figure 8a , Figure 8b and Figure 8c These are schematic diagrams showing three states of the present invention where two protective films are wrapped around a bare battery cell in one embodiment.

[0027] Figure 9 This is a plan view of a single protective film in another embodiment of the present invention;

[0028] Figure 10 This is a schematic diagram of the end faces of two states of the single protective film being stacked in another embodiment of the present invention;

[0029] Figure 11a , Figure 11b and Figure 11c This is a schematic diagram showing three states of a single protective film covering a bare battery cell in another embodiment of the present invention.

[0030] Label Explanation:

[0031] Bare battery cell 10; protective film 20; first covering surface 21; second covering surface 22; third covering surface 23; fourth covering surface 24; battery cell casing 30; bottom surfaces on both sides S1, S3; vertical surfaces on both sides S2, S4; end surfaces S5, S6; rounded corners b; overlapping area E; two creases a1, a2; strip surface a3. Detailed Implementation

[0032] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0033] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0034] Throughout this description, numerous specific details, such as examples of components and / or methods, are provided to provide a complete understanding of embodiments of the present invention. However, those skilled in the art will recognize that embodiments of the present invention may be practiced without one or more of these specific details or by other devices, systems, components, methods, parts, materials, components, etc. In other instances, well-known structures, materials, or operations have not been specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.

[0035] Throughout this specification, references to "an embodiment," "an embodiment," or "a specific embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention, but not necessarily in all embodiments. Therefore, the various representations of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" in different places throughout the specification do not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic of any specific embodiment of the present invention can be combined with one or more other embodiments in any suitable manner. It should be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein may be based on the teachings herein and will be considered part of the spirit and scope of the present invention.

[0036] It should also be understood that one or more of the elements shown in the figures may be implemented in a more separate or more integrated manner, or may even be removed because they are inoperable in certain circumstances or provided because they may be useful for a particular application.

[0037] Furthermore, unless otherwise expressly stated, any arrows in the accompanying drawings should be considered illustrative only and not limiting. Additionally, unless otherwise stated, the term "or" as used herein is generally intended to mean "and / or". Where a term is anticipated to provide a separation or combination capability that is unclear, a combination of components or steps will also be considered as indicated.

[0038] As used herein and throughout the claims below, unless otherwise specified, “a” and “the” include the plural references. Similarly, as used herein and throughout the claims below, unless otherwise specified, “in” means “in” and “on”.

[0039] In actual production, please refer to the following: Figure 1 and Figure 2 The battery cell housing B and the bare battery cell A are respectively guided by equipment. The bare battery cell A is a rectangular plate structure formed by stacking multiple substrates. After the bare battery cell A is introduced into the production line, a protective film C is covered on the outer surface of the bare battery cell A. The protective film C is a polyester polymer plastic film (commonly known as: mylar). The two ends of the bare battery cell A covered with the protective film C still form right angles. After the protective film C is covered on the bare battery cell A, a hot melt equipment is required to weld the base D at the two ends of the bare battery cell A covered with the protective film C. Only after the base D is welded can the bare battery cell A be inserted into the battery cell housing B, and then the next step of production can be carried out. Therefore, the existing solution to the interference problem between the bare battery cell A and the inner rounded corner b of the battery cell housing B has the problem of high cost.

[0040] See Figure 6 , Figure 7 , Figure 9 and Figure 10 To address this, a battery cell is proposed, comprising a bare battery cell 10; a protective film 20; a folded film covering the surface of the bare battery cell 10; and a battery cell housing 30, in which the bare battery cell 10 and the protective film 20 are housed; the protective film 20 is at least partially overlapped and forms a support portion, the support portion being at least partially located between the bare battery cell 10 and the bottom surface of the battery cell housing 30 to support the bare battery cell 10.

[0041] In one embodiment, the overlapping area on the protective film 20 can be thicker than the thickness of other areas of the protective film 20. This overlapping area can form a support portion and is located at the bottom of the bare cell 10 and the cell housing 30. This allows the rounded corner b of the cell housing 30 to form a gap with the right angles on both sides of the cell housing 30 and maintain this gap. The bare cell 10 and the protective film 20 form a whole. When the bare cell 10 covered with the protective film 20 is introduced into the cell housing 30, the right angles on both sides of the bare cell 10 always form a gap with the rounded corners of the inner cavity of the cell housing 30. This can solve the short circuit problem caused by the interference between the right angles on both sides of the bare cell 10 and the rounded corner b of the inner cavity of the cell housing 30 in the existing method, and ensure the electrical performance stability of the cell.

[0042] In one embodiment of this utility model, see reference Figure 6 and Figure 7 The overlapping area can be formed by overlapping at least two protective films 20. The overlapping area between the two protective films 20 can form a support. When the bare cell 10 covered with two protective films 20 is placed into the cell housing 30, the support can make the right angles on both sides of the bare cell 10 form a gap with the rounded corners of the inner cavity of the cell housing 30.

[0043] In a specific embodiment of this utility model, see [reference needed]. Figure 3 and Figure 4 When two protective films 20 are used to cover the bare cell 10, the bare cell 10 has a strip-like structure, and the cell housing 30 is a rectangular cavity. For ease of understanding, the opening of the cell housing 30 is arranged vertically upwards. In this case, when the bare cell 10 is assembled with the cell housing 30, the cell housing 30 itself is also in a vertical position. (See reference...) Figure 4 Because the bare cell 10 has a vertically arranged strip-like structure, it comprises six surfaces, including two opposing vertical surfaces S2 and S4 (the large surfaces on both sides), two vertically arranged bottom surfaces S1 and S3 (the bottom surfaces on both sides are narrower, and their length is the same as the length of the opposing vertical surfaces S2 and S4), and two vertically arranged end surfaces S5 and S6 (the length of the end surfaces S5 and S6 is the same as the width of the vertical surfaces S2 and S4, and the width of the end surfaces S5 and S6 is the same as the width of the bottom surfaces S1 and S3). See reference. Figure 5 During assembly, the bottom surfaces S1 and S3 of the bare cell 10 on both sides are arranged to correspond with the rounded corners b of the cell housing 30, and the vertical surfaces S2 and S4 on both sides of the bare cell 10 correspond to the large surfaces of the cell housing 30 on both sides, so as to realize the installation of the bare cell 10 and the cell housing 30.

[0044] In one embodiment, see Figure 7 and Figures 8a to 8c When the two protective films 20 are folded and wrapped around the bare battery cell 10, there are two protective films. One of the two protective films is folded to form a first covering surface 21 and a second covering surface 22. The other of the two protective films is folded to form a third covering surface 23 and a fourth covering surface 24. The first covering surface 21 and the third covering surface 23 respectively cover the oppositely arranged vertical surfaces S2 and S4 of the bare battery cell 10. The second covering surface 22 and the fourth covering surface 24 are stacked to form a support part and cover the bottom surface S1 of the bare battery cell.

[0045] When the two protective films 20 are actually folded, they cover the vertical surfaces S2 and S4 on both sides of the bare cell 10 and the bottom surfaces S1 and S3 on both sides arranged vertically, which is actually four surfaces. The second covering surface 22 and the fourth covering surface 24 of the two protective films 20 overlap to form a support part that corresponds to the rounded corner b position of the cell housing 30. Therefore, the two sides of the bare cell 10 can always maintain a gap with the rounded corner b of the cell housing 30, thereby solving the problem of interference between the right angle and the rounded corner b on both sides of the bare cell 10.

[0046] In one embodiment, the thickness of the second covering surface 22 and the fourth covering surface 24 of the two protective films 20 can be set to be greater than the thickness of the first covering surface 21 and the third covering surface 23.

[0047] In one embodiment, after the bare battery cell 10 covered with the protective film 20 is installed in the battery cell housing 30, the support portion formed by the second covering surface 22 and the fourth covering surface 24 of the two protective films 20 overlapping together contacts the rounded corner b of the battery cell housing 30. The second covering surface 22 and the fourth covering surface 24 make gaps between the two sides of the bare battery cell 10 and the rounded corner b of the battery cell housing 30.

[0048] In practical applications, to facilitate the production of the protective film 20, the thickness of the second covering surface 22, the first covering surface 21, the third covering surface 23, and the fourth covering surface 24 of the two protective films 20 is uniform. This can reduce costs and maximize the internal space of the battery cell to maintain the battery cell's capacity.

[0049] In one specific embodiment, see Figure 6 Both protective films 20 are rectangular films. When the bare battery cell 10 is covered, the first covering surface 21, the second covering surface 22, the third covering surface 23 and the fourth covering surface 24 are all rectangular and their sides in the length direction are connected in sequence. The first covering surface 21 and the second covering surface 22 together form a rectangular film, and the third covering surface 23 and the fourth covering surface 24 together form a rectangular film. The second covering surface 22 is distributed on both sides of the first covering surface 21 in the length direction, and the fourth covering surface 24 is distributed on both sides of the third covering surface 23 in the length direction.

[0050] Specifically, see Figures 8a to 8c The diagram shows the process of coating the surface of the two protective films 20 with the bare battery cell 10:

[0051] See Figure 7 First, the second covering surface 22 and the fourth covering surface 24 of the two protective films 20 are bonded together. The second covering surface 22 and the fourth covering surface 24 of the two protective films 20 are then fixed together by heat fusion. Finally, the fixed protective film 20 is covered on the bare battery cell 10.

[0052] See Figure 8a When the protective film 20 covers the bare cell 10, the second covering surface 22 and the fourth covering surface 24 of the two protective films 20 are overlapped and covered on the narrower bottom surface S1 of the bare cell 10. When the protective film 20 covering the bottom surface S1 is installed on the cell housing 30, it forms a support part.

[0053] See Figure 8bThen, the protective film 20 is folded so that the two protective films 20 cover the vertical surfaces S2 and S4 on both sides of the bare cell 10. The protective films 20 covering the oppositely arranged vertical surfaces S2 and S4 form the first covering surface 21 and the third covering surface 23.

[0054] See Figure 8c Continue folding the protective film 20 so that the second covering surface 22 and the fourth covering surface 24 at one end of the two protective films 20 overlap each other and cover the narrower bottom surface S3. The second covering surface 22 and the fourth covering surface 24 of the protective film 20 covering the other bottom surface S3 of the bare cell 10 overlap to form a support part. The two overlapping second covering surfaces 22 and the fourth covering surface 24 can also be fixed into one piece by heat fusion.

[0055] In one embodiment, the thickness of the first covering surface 21 and the third covering surface 23 is 0.1 to 0.3 mm. The thickness of the first covering surface 21 and the third covering surface 23 is consistent with that of the existing protective film. The first covering surface 21 and the third covering surface 23 are located between the two vertical surfaces S2 and S4 of the bare cell 40 and the inner sidewall of the cell housing 30. The selection of their thickness can protect the bare cell 10 while maximizing the internal space of the cell housing 30, thereby increasing the amount of electrolyte injected and ensuring the cell's capacity.

[0056] In one embodiment, the thickness of the second covering surface 22 and the fourth covering surface 24 is 0.1-0.5 mm. The thicknesses of the second covering surface 22 and the first covering surface 21, and the third covering surface 23 and the fourth covering surface 24 of the two protective films 20 can actually be the same, which facilitates the production of the protective film 20. The thicknesses of the second covering surface 22 and the first covering surface 21, and the third covering surface 23 and the fourth covering surface 24 can also differ, and it is necessary to ensure that the thickness of the second covering surface 22 is as large as possible compared to the thickness of the first covering surface 21, and the thickness of the fourth covering surface 24... The thickness of the second covering surface 24 should be as large as possible compared to the thickness of the third covering surface 23. In practical applications, the compression of the second covering surface 22 and the fourth covering surface 24 should be taken into account to minimize or eliminate the use of internal space in the cell housing 30. This ensures that the second covering surface 22 and the fourth covering surface 24 of the protective film 20 can provide reliable support for the two bottom surfaces S1 and S3 of the bare cell 10, so that a safe gap can be maintained between the two bottom surfaces S1 and S3 of the bare cell 10 and the fillet b of the cell housing 30. This safe gap should be at least 0.2 mm.

[0057] In one embodiment, the protective film 20 is divided into regions of different thicknesses. In actual production, the thickness of the blown protective film 20 can be adjusted by controlling the parameters of the blow molding die so that regions of different thicknesses are formed on the protective film 20. Alternatively, the protective film 20 with uniform thickness can be stretched by a stretching device to form the final protective film 20 with the required structure.

[0058] See Figure 9 and Figure 10 In another embodiment of this utility model, the single protective film 20 can be folded to form an overlapping area. The single protective film 20 is rectangular in shape, and an overlapping area is provided in the middle of the protective film 20. The overlapping area is composed of multiple overlapping surfaces to form a support part. After the bare battery cell 10 covered with a protective film 20 is placed into the battery cell housing 30, the support part can make the right angles on both sides of the bare battery cell 10 form a gap with the rounded corners of the inner cavity of the battery cell housing 30.

[0059] Specifically, Figure 11a , Figure 11b and Figure 11c The diagram shows the process of coating the surface of the bare battery cell 10 with two protective films 20:

[0060] First, refer to Figure 10 The middle position of the protective film 20 can be folded in advance to form overlapping areas D. The overlapping areas E in the middle position of the protective film 20 can be folded as shown in the figure, along the two creases a1 and a2 in the middle position of the protective film 20. The area between the two creases a1 and a2 can form a strip surface a3. The strip surface a3 and the two surfaces of the protective film 20 overlap to form three overlapping areas E. The layers of the three overlapping areas E can be fixed together by heat fusion.

[0061] See Figure 11a When the protective film 20 covers the bare cell 10, the three overlapping areas E are covered on the narrower bottom surface S1 of the bare cell 10. When the protective film 20 covering the bottom surface S1 is installed on the cell housing 30, it forms a support part.

[0062] See Figure 11b Then, the protective film 20 is folded so that it covers the vertical surfaces S2 and S4 on both sides of the bare cell 10. The protective film 20 covering the vertical surfaces S2 and S4 on both sides of this side forms a large coverage area.

[0063] See Figure 11cContinue folding the protective film 20 so that the two ends of the protective film 20 overlap each other and cover the narrower bottom surface S3. The two ends of the protective film 20 covering the other bottom surface S3 of the bare cell 10 overlap to form a support part. After the two ends of the protective film 20 are overlapped, they can be fixed into one piece by heat fusion.

[0064] In one embodiment, the thickness of the protective film 20 can be kept uniform and can be controlled within 0.1 to 0.3 mm. While ensuring reliable coverage of the bare battery cell 10, the thickness of the protective film 20 is as thin as possible, which can effectively increase the internal space of the battery cell, maximize the effective volume inside the battery cell, and improve the electrical performance of the battery cell.

[0065] In summary, this invention improves the protective film 20 used to cover the bare battery cell 10. The protective film 20 has an overlapping area that forms a support portion. This support portion is located between the bare battery cell 10 and the battery cell housing 30. After the protective film 20 covers the bare battery cell 10 and is inserted into the battery cell housing 30, the support portion creates a gap between the two sides of the bare battery cell 10 and the rounded corners inside the battery cell housing 30. This avoids interference between the straight edges of the original bare battery cell 10 and the rounded corners of the battery cell housing 30, preventing the risk of short circuits in the bare battery cell 10. Therefore, it can reduce the production cost of the battery cell and ensure the stability of the battery cell's electrical performance.

[0066] The above description of the embodiments shown in this utility model (including the content set forth in the abstract of the specification) is not intended to be an exhaustive enumeration or to limit the utility model to the precise forms disclosed herein. Although specific embodiments and examples of the utility model have been described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the utility model, as will be recognized and understood by those skilled in the art. As indicated, these modifications can be made to the utility model in accordance with the above description of the embodiments described herein, and such modifications will be within the spirit and scope of the utility model.

[0067] This document has generally described the systems and methods in detail to aid in understanding the present invention. Furthermore, various specific details have been set forth to provide a general understanding of embodiments of the present invention. However, those skilled in the art will recognize that embodiments of the present invention can be practiced without one or more specific details, or using other devices, systems, accessories, methods, components, materials, parts, etc. In other instances, well-known structures, materials, and / or operations have not been specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.

[0068] Therefore, although the present invention has been described herein with reference to specific embodiments thereof, freedom of modification, various changes and substitutions are also within the scope of the above disclosure, and it should be understood that in some cases, certain features of the present invention may be adopted without departing from the scope and spirit of the invention and without corresponding use of other features. Thus, many modifications can be made to adapt a particular environment or material to the essential scope and spirit of the present invention. The present invention is not intended to be limited to the specific terms used in the following claims and / or the specific embodiments disclosed as the best mode of carrying out the present invention, but the present invention will include any and all embodiments and equivalents falling within the scope of the appended claims. Therefore, the scope of the present invention will be determined only by the appended claims.

Claims

1. An electric cell, characterized by, The application relates to a battery protection film. A bare battery core; A protection film; The protection film is folded to cover the surface of the bare battery core; A battery core shell, wherein the bare battery core and the protection film are accommodated in the battery core shell; The protection film is at least partially overlapped, so that the thickness of the overlapped area is greater than that of other areas of the protection film, and the overlapped area forms a support part, wherein the support part is at least partially located between the bare battery core and the bottom surface of the battery core shell to support the bare battery core.

2. The electric cell of claim 1, wherein: The protection film is provided with at least two pieces, and the support part is formed by the partial overlap between the at least two pieces of protection film.

3. The electric cell of claim 2, wherein, The protection film is provided with two pieces, one of which is folded to form a first covering surface and a second covering surface, and the other of which is folded to form a third covering surface and a fourth covering surface. The first covering surface and the third covering surface respectively cover two opposite vertical surfaces of the bare battery core, and the second covering surface and the fourth covering surface are overlapped to form a support part and cover the bottom surface of the bare battery core.

4. The electric cell of claim 3, wherein, The first covering surface and the second covering surface are rectangular and the lengthwise sides are sequentially connected, and the third covering surface and the fourth covering surface are rectangular and the lengthwise sides are sequentially connected.

5. The electric cell of claim 4, wherein, The protection film is a whole rectangular film piece.

6. The electric cell of claim 5, wherein, The second covering surface is arranged at the positions of the two lengthwise sides of the first covering surface, and the fourth covering surface is arranged at the positions of the two lengthwise sides of the third covering surface.

7. The electric cell of claim 3, wherein, The second covering surface and the fourth covering surface are integrally combined by hot melting.

8. The electric cell of claim 3, wherein, The thickness of the second covering surface is greater than or equal to that of the first covering surface, and the thickness of the fourth covering surface is greater than or equal to that of the third covering surface.

9. The electric cell of claim 8, wherein, The thickness of the first covering surface and the third covering surface is 0.1-0.3 mm.

10. The electric cell of claim 8, wherein, The thickness of the second covering surface and the fourth covering surface is 0.1-0.5 mm.

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