Battery module

Abstract

This invention provides a battery module comprising a flat battery cell and an outer casing made of packaging material for housing the battery cell. The outer casing is tightly sealed to the surface of the battery cell within the sealed battery module, minimizing wrinkles on the packaging material and preventing cracks or breakage of the outer casing under vibrations experienced when the battery module is mounted on a moving body. In the battery module, before sealing the outer casing, the surface of the outer casing facing the side of the flat structure of the battery cell extends substantially perpendicular to the surface direction of the flat structure of the battery cell, and the surface of the outer casing facing the planar portion of the flat structure of the battery cell extends substantially parallel to the surface direction of the flat structure of the battery cell. The periphery of the battery cell is surrounded by a frame member made of thermoplastic resin, and columnar protrusions with curved surfaces extending along the thickness direction of the battery cell and having convex end faces and side faces are formed at the corners of the frame member.

Description

Technical Field

[0001] This invention relates to a battery module, and more specifically, to a battery module in which the entire battery cell is covered by an outer casing to isolate the battery cell from the outside air. Background Technology

[0002] Modules of lithium-ion secondary batteries and other batteries have the following structure: the entire battery cell is covered by an outer casing formed of laminated packaging material to isolate the battery cell from the outside air. When such a battery module is mounted on a moving body such as a vehicle, the battery module is exposed to vibrations caused by the movement of the moving body, etc. Therefore, various structures have been proposed to prevent easy damage or breakage due to these vibrations. For example, in Patent Document 1, in a structure where the outer casing seals the outer periphery of a battery body that is a rectangular flat plate-shaped laminate, a structure is proposed in which a buffer member is inserted between the laminate at the corner of the rectangular flat plate-shaped laminate and the outer casing. In Patent Document 2, a structure is proposed where, in a structure where two outer casings are joined and housed within an electrode body that is quadrilateral in plan view, in order to suppress wrinkling at the corner of the joint of the outer casing and to suppress damage to the outer casing, a spacer with a protrusion extending toward the joint is arranged between the corner of the electrode body and the inner surface of the outer casing. Patent document 3 discloses the following structure: multiple units are stacked together in the stacking direction, a closure is disposed around the periphery of the multiple units, and the multiple units and the closure are housed in a sheet component.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-13637

[0004] Patent Document 2: Japanese Patent Application Publication No. 2023-100110

[0005] Patent Document 3: Japanese Patent Application Publication No. 2023-110291 Summary of the Invention

[0006] In cases where battery cells (typically multiple stacked cells) are housed and sealed within an outer casing to isolate them from external air, the edges of the packaging materials (except for a portion) are joined together while the battery cells are sandwiched between two sheet-like packaging materials that form the outer casing. Alternatively, the battery cells are placed inside a bag formed by the packaging materials, and the space containing the battery cells on the inside of the packaging materials is depressurized to expel air, ensuring a tight seal between the packaging materials and the outer surface of the battery cells, thus completely sealing the entire circumference of the packaging materials. The pressure is then restored to atmospheric pressure. In this process, the packaging materials need to be larger than the battery cells to accommodate them. If the remaining portion of the packaging materials is too large, wrinkles will form when depressurization is applied to seal the packaging materials against the outer surface of the battery cells. Furthermore, if these wrinkles are too large, the airtightness of the outer casing can be compromised by vibrations during the use of the battery module. Furthermore, as mentioned above, if the battery module is mounted on a moving body and subjected to vibration, the battery portion will shift relative to the outer casing, which may sometimes cause cracks or breaks in the packaging material, thereby compromising the airtightness of the outer casing. Such cracks or breaks in the packaging material are particularly prone to occur at the corners of rectangular, flat battery cells.

[0007] Therefore, through experiments, the inventors of this invention discovered the following structural conditions: in a structure described above, where the battery cell is housed within the outer casing, and pressure is applied to the outer casing to ensure a tight seal between the packaging material and the outer surface of the battery cell, a structure is created that minimizes wrinkles on the packaging material and prevents cracks or breakage from occurring on the packaging material under vibrations experienced by the battery module when mounted on a moving body. This insight can be utilized in this invention.

[0008] Thus, the objective of this invention is to house and seal the battery cell within an outer casing made of packaging material in order to isolate the battery cell from the outside air, so that the packaging material is as wrinkle-free as possible, and the outer casing is not prone to cracking or breaking under vibrations when the battery module is mounted on a moving body.

[0009] According to the present invention, the above-mentioned problem is achieved by a battery module comprising: a flat battery cell; and an outer casing made of packaging material for accommodating the battery cell, the outer casing being tightly fitted to and sealed to the surface of the battery cell.

[0010] Before the outer casing is sealed, the surface of the outer casing facing the side of the plate-shaped structure of the battery cell extends approximately perpendicular to the surface direction of the plate-shaped structure of the battery cell, and the surface of the outer casing facing the planar portion of the plate-shaped structure of the battery cell extends approximately parallel to the surface direction of the plate-shaped structure of the battery cell.

[0011] The periphery of the battery cell is surrounded by a frame component made of thermoplastic resin, and columnar protrusions with convex end faces and side faces are formed at the corners of the frame component.

[0012] In the above structure, the battery cell can be a non-aqueous secondary battery cell such as a lithium-ion secondary battery cell or other battery cells, or it can be a stack of multiple battery cells. Furthermore, in this specification, when referring to "battery cell," it refers not only to a single cell but also to a stack of multiple cells. Each battery cell typically has a stacked structure in which a positive electrode active material layer coated on the positive electrode current collector foil and a negative electrode active material layer coated on the negative electrode current collector foil are opposed to each other across a separator, and an electrolyte is injected between the current collector foils. In the battery cell as a whole, the area between the current collector foils at the periphery of the separator and the current collector foil is surrounded and sealed by a frame component made of thermoplastic resin. The flat structure of the battery cell can be rectangular in planar shape and has corners. Moreover, in the above-described battery cell, the packaging material is contained within an outer casing made of packaging material in a state of tight seal against the surface of the battery cell, thus sealing the outer casing. Here, the central region of the surface of the outer casing opposite the planar portion of the flat structure of the battery cell is a conductive plate. The conductive plate is bonded to the electrode foil of the planar portion of the flat structure of the battery cell in a conductive state, and the packaging material can be tightly sealed to the periphery of the conductive plate. That is, the packaging material covers the side portion (in the thickness direction) of the planar portion of the flat structure from the periphery of the planar portion of the battery cell, making it tightly sealed to the surface. The packaging material can be a sheet-like component commonly used in this field, typically a laminated packaging material in which a resin film is laminated on both sides of an aluminum sheet (or aluminum foil). The structure of housing and sealing a battery cell is generally achieved, in short, through the following process: The battery cell, which is surrounded by a frame component around the periphery of the current collector foil and separator, is clamped and pressed by two conductive plates and a sheet component with packaging material adhered to its periphery. The periphery of the packaging material on the side of the battery cell is heat-fused and sealed except for a portion. Then, the area clamped by the sheet component is depressurized to make the packaging material seal tightly to the side of the battery cell. Then, the periphery of the packaging material is heat-fused and sealed along its entire circumference. Finally, it is repressurized.

[0013] Furthermore, in the aforementioned battery module, under the present invention, firstly, the outer casing is configured such that, before it is sealed, the surface of the outer casing facing the side portion of the flat structure of the battery cell extends substantially perpendicularly to the surface direction of the flat structure of the battery cell, and the surface of the outer casing facing the planar portion of the flat structure of the battery cell extends substantially parallel to the surface direction of the flat structure of the battery cell. In this way, as explained in the experimental examples section below, when the packaging material of the outer casing is sealed to the battery cell, the size of the wrinkles in the packaging material can be minimized. Furthermore, under the present invention, columnar protrusions with curved surfaces extending along the thickness direction of the battery cell and having convex end faces and side faces are further formed at the corner portions of the frame member made of thermoplastic resin surrounding the periphery of the battery cell. In this way, as explained in the experimental examples section below, when the packaging material of the outer casing is sealed to the battery cell, or even when vibrations are applied as envisioned when the battery module is mounted on a moving body, cracks in the packaging material at the corners of the frame component can be prevented.

[0014] More specifically, regarding the protrusions formed at the corners of the frame components in the above structure, their sides are cylindrical or elliptical cylindrical, and their end faces are spherical or ellipsoidal. In a cross-section of the battery cell in a direction parallel to the surface direction, the outline of the protrusion can be a 3 / 4 arc or approximately a 3 / 4 arc of a circle or ellipse (e.g., 3 / 4 ± 10% arc). Thus, the corners of the frame components have no sharp parts, preventing cracks or breaks in the packaging material when it is tightly sealed to the frame components.

[0015] In the above structure, preferably, the two ends of the protrusion do not protrude further than the two sides of the battery cell in the thickness direction. Therefore, when multiple battery modules are stacked, no gaps are generated between the battery modules, and the state of the stacked battery modules is stabilized.

[0016] Furthermore, regarding the shape of the aforementioned protrusion, according to the experimental examples described later, it was found that when the length of the spherical or ellipsoidal portion of both ends of the protrusion in the thickness direction of the battery cell is more than 1 / 4 of the length between the two ends of the protrusion, it can effectively prevent the generation of cracks in the packaging material when subjected to vibrations conceived when the battery module is mounted on a moving body. In addition, according to the experimental examples described later, it was found that when the distance by which the protrusion extends from the frame member is 3mm to 12mm, it can effectively prevent the generation of cracks in the packaging material when subjected to vibrations conceived when the battery module is mounted on a moving body.

[0017] Invention Effects

[0018] Thus, according to the structure of the present invention, in a battery module comprising a flat battery cell and an outer casing made of packaging material accommodating the battery cell, and the outer casing being sealed to the surface of the battery cell, if the surface of the outer casing facing the side of the flat structure of the battery cell before sealing extends substantially perpendicularly to the surface direction of the flat structure of the battery cell, and the surface of the outer casing facing the planar portion of the flat structure of the battery cell extends substantially parallel to the surface direction of the flat structure of the battery cell, and columnar protrusions with curved surfaces extending along the thickness direction of the battery cell and having convex end faces and side faces are formed at the corners of the frame member made of thermoplastic resin surrounding the periphery of the battery cell, wrinkles can be minimized on the packaging material, and the outer casing will not easily crack or break under vibrations experienced when the battery module is mounted on a moving body. The structure of the present invention can be applied to battery modules with structures in which various battery cells are sealed by an outer casing.

[0019] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. Attached Figure Description

[0020] Figure 1 (A) Figure 1 (B) is a schematic cross-sectional view of a battery module applicable to this embodiment, which illustrates the process of accommodating and sealing the battery cells in the outer casing.

[0021] Figure 2 (A) is a schematic perspective view of a battery cell housed in an external casing to which this embodiment is applicable. Figure 2 (B) Figure 2 (C) is a schematic side view and top view of a battery cell in a battery module to which this embodiment is applicable, near a corner.

[0022] Figure 3 (A) is a schematic planar cross-sectional view near one corner of a battery cell housed within an outer casing when this embodiment is not applicable. Figure 3 (B) is a cross-sectional view of a battery cell housed in the outer casing near one corner, parallel to the schematic flat plate structure, in the case of this embodiment.

[0023] Figure 4 (A) Figure 4 (B) is a schematic side cross-sectional view near one corner of a battery cell housed in an outer casing when this embodiment is not applicable.

[0024] Symbol Explanation

[0025] 1-Battery cell, 2-Electrode foil, 3-Frame component, 5, 6-Packaging material, 7-Conductive plate, 10-Protrusion. Detailed Implementation

[0026] Hereinafter, several preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same symbols denote the same parts.

[0027] Battery module structure

[0028] like Figure 1 (A) Figure 1 As shown in (B), in the battery module to which this embodiment is applied, the battery cell 1 is sandwiched between outer bodies 5 and 6 formed of packaging material. With the outer bodies 5 and 6 in close contact with the surface of the battery cell 1, the periphery (X) of the outer bodies 5 and 6 is closed. Here, the battery cell 1 can be a non-aqueous secondary battery such as a lithium-ion secondary battery cell mentioned in the summary of the invention, or other battery cells. It is typically a stack of multiple battery cells, generally a roughly rectangular flat structure. Furthermore, in the battery cell 1, each cell typically has a stacked structure in which a positive electrode active material layer coated on the positive electrode current collector foil and a negative electrode active material layer coated on the negative electrode current collector foil are opposed to each other across a separator, and an electrolyte is injected between the current collector foils. With multiple such stacked structures overlapping, the area between the current collector foils at the periphery of the current collector foil and the separator is surrounded and closed by a frame member made of thermoplastic resin. Each unit has a thickness of 1 to 2 mm, and typically 30 units are stacked in a module.

[0029] The outer casings 5 ​​and 6, which house the battery cell 1, are sheet-like components as shown in the figure. They can be formed into a cup shape to simulate the shape of the battery cell 1. Furthermore, the area of ​​the outer casings 5 ​​and 6 that abuts against the central region of the planar portion of the battery cell 1 is typically composed of a conductive plate 7, and a flexible packaging material can be adhered to the periphery of this conductive plate. As mentioned, the packaging material can be a sheet-like component commonly used in this field, typically a laminated packaging material in which a resin film is laminated onto both sides of an aluminum sheet (or aluminum foil). The thickness of the packaging material is, for example, 200–900 μm.

[0030] As a method for accommodating the battery cell 1 within the outer casings 5 ​​and 6, typically, with the battery cell 1 configured in a cup-shaped configuration within the outer casings 5 ​​and 6, the outer casings 5 ​​and 6 are pressed together from both sides, and the peripheries of the outer casings 5 ​​and 6 are thermally fused together, except for a portion thereof. Furthermore, by depressurizing the space between the outer casings 5 ​​and 6, the packaging material portions of the outer casings 5 ​​and 6 are sealed to the planar portion and periphery to the sides of the battery cell 1. In this state, the entire periphery of the outer casings 5 ​​and 6 is thermally fused and sealed (and then, repressurization is performed).

[0031] As described above, regarding the housing and sealing of the battery cell 1 within the outer casings 5 ​​and 6, the longitudinal and transverse dimensions of the outer casings must be greater than those of the battery cell 1. If the remaining portion of the outer casing is too large, wrinkles will occur when the packaging material of the outer casings 5 ​​and 6 is sealed to the surface of the battery cell 1. If these wrinkles are large, vibrations during battery module use and relative displacement of the battery cell 1 within the outer casings 5 ​​and 6 will compromise airtightness and sealing. Regarding the generation of these wrinkles, as shown in the experimental examples described later, based on the experimental results conducted by the inventors of this embodiment, it was found that the generation of wrinkles depends on the angle of the portion of the cup-shaped outer casings 5 ​​and 6 that faces the side of the battery cell 1. More specifically, as... Figure 4 As shown in (A), it was found that if the angle φ formed by the portion opposite the side of battery cell 1 with respect to the surface direction of battery cell 1 is an acute angle, then when the packaging material is tightly sealed to the side surface of the battery cell, as... Figure 4 (B) In that case, the wrinkles w tend to grow larger. If the angle φ formed by the portion opposite the side of the battery cell 1 with respect to the surface direction of the battery cell 1 is approximately right angle (89° to 90°), the wrinkles w can be suppressed to a smaller extent. Therefore, in order to suppress the formation of wrinkles as much as possible, it is sufficient to set the angle φ formed by the portion of the cup-shaped shape of the outer body 5 and 6 opposite the side of the battery cell 1 with respect to the surface direction of the battery cell 1 to approximately right angle.

[0032] However, as mentioned above, it was found that when the angle φ formed by the portions of the outer casings 5 ​​and 6 opposite the side of the battery cell 1 with respect to the surface direction of the battery cell 1 is set to approximately right angle, the packaging material is pressed against the front end of the corner portion of the flat structure of the battery cell and becomes thin, or is prone to cracking or breaking (when the angle φ is acute, the packaging material is almost not prone to cracking or breaking).

[0033] Therefore, the inventors of this embodiment, through research on structures capable of suppressing cracks or breakage in packaging materials, discovered that... Figure 2 As schematically depicted in (A) to (C), if a columnar protrusion 10, extending along the thickness direction of the battery cell 1 and having convex end faces 12a, b and side faces 11, is formed at the corner of the frame member 3 of the battery cell 1, then cracks or breaks in the packaging material can be prevented when the packaging material is tightly sealed to the side surface of the battery cell. This is believed to be because, as... Figure 3 As schematically depicted in (A), when the corner of the frame member 3 of the battery cell remains sharp, and the packaging material 5 is sealed to the surface of the frame member 3, the front end of the packaging material 5 deforms into a bend at the corner, and the front end of the packaging material 5 attempts to penetrate the bend of the corner of the frame member 3, as shown in [the diagram]. Figure 3(B) In that case, when a convex curved protrusion 10 is formed at the corner of the frame member 3 of the battery cell, the packaging material 5 will bend gently when it is in close contact with the surface of the frame member 3, and will not form a part that is subjected to extreme pressure.

[0034] More specifically, regarding the structure forming the aforementioned protrusion, as shown in the figure, the protrusion 10 can be formed such that the side surface 11 is cylindrical or elliptical cylindrical, and the two end surfaces 12a and b are spherical or ellipsoidal. Figure 2 (C) In this manner, in a cross-section of the battery cell in a direction parallel to the surface direction, the outline of the protrusion is a 3 / 4 (or approximately 3 / 4) arc of a circle or ellipse. More specifically, the spherical or ellipsoidal portion of the two end faces 12a, 12b of the protrusion 10 has a length hs in the thickness direction of the battery cell that is at least 1 / 4 of the length h1 between the two ends of the protrusion 10. The protrusion distances a, b of the protrusion 10 in the surface direction of the battery cell protruding from the frame member are preferably 3mm to 12mm. This effectively prevents cracking of the packaging material during vibrations induced when the battery module is mounted on a moving body. Furthermore, the length h1 between the two ends of the protrusion 10 is preferably formed to be no more than the thickness hm of the frame member 3 of the battery cell 1. Therefore, when multiple battery modules are stacked, no gaps are formed between the battery modules, allowing for stable battery module placement. The protrusion can be integrally formed from the same material as the frame member. Specifically, the protrusion can be formed from high-density polyethylene, low-density polyethylene, etc.

[0035] Experimental Example

[0036] The effectiveness of this embodiment was confirmed by the following experimental examples. Furthermore, it should be understood that the following experimental examples are illustrative of the effectiveness of this embodiment and do not limit the scope of the invention.

[0037] (1) Verification of the dependence of the cup-shaped shape of the outer packaging body on the formation of wrinkles and the formation of cracks in the packaging material.

[0038] When housing and sealing the battery cell within the outer casing, an outer casing with an angle different from that formed by the side of the battery cell relative to the face of the battery cell was used to confirm the formation of wrinkles and the occurrence of cracks in the packaging material.

[0039] In the experiment, multiple single-cell units consisting of bipolar electrodes (LFP positive and graphite negative electrodes), separators, and sealing materials were stacked. Their peripheries were welded together with a polyethylene base to form a frame component, which served as the housing for the battery units. The outer packaging material used was an aluminum laminate packaging material with nylon film and polyethylene terephthalate film layered sequentially on the outside of the aluminum foil, and acid-modified polypropylene film and polypropylene film layered sequentially on the inside of the aluminum foil. The outer packaging used a cup-shaped portion that roughly simulated the shape of the battery units, with the portion opposite the planar portion of the battery units and the periphery extending parallel to the planar portion of the battery units and opposite the side portions of the battery units connecting them, at an angle relative to the surface direction of the battery units. Figure 3 (A) Angle φ) is adjusted in various ways by the outer casing. The battery cell is housed and sealed within the outer casing as follows: Figure 1 (A) Figure 1 (B) In this way, the battery cell is housed between two cup-shaped outer casings, and the pressure between the outer casings is reduced. In this state, the periphery of the outer casings is thermally welded to seal them.

[0040] In determining the presence of wrinkles in packaging materials, after sealing, the height of the wrinkles is measured. Wrinkles less than 0.4 mm are considered acceptable, while those exceeding 0.4 mm are considered unacceptable. Furthermore, in determining the presence of cracks in packaging materials, after forming the battery module, the packaging material is removed from the battery module. Light is shone from the back of the portion that contacts the corner of the battery cell to observe the light transmission. The material is then disassembled, and the thinnest section is cut using a slicer and observed under a microscope. A section where the aluminum layer becomes extremely thin or disappears is considered "cracked."

[0041] The results are shown in Table 1 below.

[0042] [Table 1]

[0043]

[0044] In the table above, No. represents the sample number, φ represents the angle of the portion of the outer casing opposite the side portion of the battery cell relative to the surface direction of the battery cell, P represents the presence or absence of the protrusion (N for no, Y for present), w_h represents the height of the wrinkle, Jw represents the sufficiency or inability to determine the presence or absence of the wrinkle (N for no, G for present), Cr represents the presence or absence of cracks (N for no cracks, Y for cracks), and Jt represents the sufficiency or inability to determine the presence or absence of the battery module (N for no, G for present). Regarding the protrusion, the length between the two ends is set to be the same as the thickness of the battery cell (h1=1.0hm), the length hs of the spherical portion of the two end faces in the thickness direction of the battery cell is set to 1 / 4 of the length between the two ends of the protrusion (hs=h1 / 4), and the protrusion distances a and b of the protrusion are set to 6mm.

[0045] Based on the above results, it was shown that when the portion of the outer casing of sample number 5 that faces the side portion of the battery cell has an angle of approximately 90° with respect to the surface direction of the battery cell and has a protrusion, the packaging material in the battery module will not wrinkle or crack.

[0046] (2) Verification of whether cracks are generated due to vibration when the moving body is mounted.

[0047] In the battery module, when the portion of the outer casing opposite the side portion of the battery cell has an angle φ of approximately 90° with respect to the surface direction of the battery cell and has protrusions of various shapes, vibrations were applied to the battery module when it was mounted on a moving body to verify whether the packaging material cracked. The structure of the battery cell is the same as (1) except for the shape of the protrusions, and the structure of the packaging material of the outer casing is also the same as (1).

[0048] The results are shown in Table 2 below.

[0049] [Table 2]

[0050]

[0051] In the above, No. is the sample number, h1 is the length between the two ends of the protrusion, hs is the length of the spherical portion of the two end faces of the protrusion, a and b are the distances the protrusion extends from the frame component, and Cr indicates whether there is a crack after vibration (yes if Y, no if N). Sample number 5 is the same as sample number 5 in Table 1.

[0052] Based on the above results, in samples 5, 6, 8, and 10-11, the generation of cracks after vibration was suppressed. Summarizing these conditions, it is shown that when the length hs of the spherical or ellipsoidal portion at both ends of the protrusion in the thickness direction of the battery cell is more than 1 / 4 of the length h1 between the two ends of the protrusion, and the protrusion distances a and b of the protrusion from the frame member in the direction of the battery cell surface are 3 mm to 12 mm, the generation of cracks after vibration can be suppressed.

[0053] Thus, according to this embodiment, in a battery module comprising a flat battery cell and an outer casing made of packaging material that houses the battery cell, and the outer casing being sealed to the surface of the battery cell, if the surface of the outer casing facing the side of the flat structure of the battery cell before sealing extends approximately perpendicularly to the surface direction of the flat structure of the battery cell, and the surface of the outer casing facing the planar portion of the flat structure of the battery cell extends approximately parallel to the surface direction of the flat structure of the battery cell, and columnar protrusions with curved surfaces extending along the thickness direction of the battery cell and having convex end faces and side faces are formed at the corners of the frame member made of thermoplastic resin surrounding the periphery of the battery cell, then wrinkles can be minimized on the packaging material, and the outer casing will not easily crack or break under vibrations when the battery module is mounted on a moving body.

[0054] The above description is made in connection with the embodiments of the present invention, but many modifications and changes can be easily made by those skilled in the art. The present invention is not limited to the embodiments illustrated above, and it can obviously be applied to various devices without departing from the concept of the present invention.

Claims

1. A battery module comprising: A flat-plate battery cell; and The outer casing is made of packaging material that houses the battery cells. The outer casing is tightly sealed to the surface of the battery cell, and the battery module is characterized in that... Before the outer casing is sealed, the surface of the outer casing facing the side of the plate-shaped structure of the battery cell extends approximately perpendicular to the surface direction of the plate-shaped structure of the battery cell, and the surface of the outer casing facing the planar portion of the plate-shaped structure of the battery cell extends approximately parallel to the surface direction of the plate-shaped structure of the battery cell. The periphery of the battery cell is surrounded by a frame component made of thermoplastic resin, and columnar protrusions with convex end faces and side faces are formed at the corners of the frame component.

2. The battery module according to claim 1, characterized in that, In the protrusion, the side surface is cylindrical or elliptical cylindrical, the two end surfaces are spherical or elliptical spherical, and in the cross-section of the battery cell in the direction parallel to the surface direction, the outline of the protrusion is a circle or an arc of 3 / 4 of an ellipse.

3. The battery module according to claim 1, characterized in that, The two ends of the protrusion do not protrude more than the two sides of the battery cell in the thickness direction.

4. The battery module according to claim 3, characterized in that, The length of the spherical or ellipsoidal portion of the two end faces of the protrusion in the thickness direction of the battery cell is more than 1 / 4 of the length between the two ends of the protrusion.

5. The battery module according to claim 1, characterized in that, The distance from which the protrusion extends from the frame component is 3mm to 12mm.

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