Secondary battery

Abstract

An embodiment of the present invention relates to a secondary battery, and a technical problem is to be solved by providing a secondary battery that increases the weldability of a can and can prevent the can from melting when an event occurs. To this end, the present invention provides the secondary battery comprising: an electrode assembly including a first electrode plate, a second electrode plate and a separator interposed between the first electrode plate and the second electrode plate; a can of which both ends are open and which accommodates the electrode assembly; a first side plate for sealing one open end of the can; and a second side plate for sealing the other open end of the can, wherein the can includes a first metal and a second metal formed on the outer surface of the first metal, the first metal being exposed and formed at both ends to which the first side plate and the second side plate are coupled.

Description

secondary battery

[0001] An embodiment of the present invention relates to a secondary battery.

[0002] Secondary batteries, unlike primary batteries that cannot be recharged, are batteries that can be charged and discharged. Low-capacity batteries are used in small portable electronic devices such as cell phones and camcorders, and large-capacity batteries are widely used as power sources for driving motors in hybrid vehicles and electric vehicles. These secondary batteries can be classified into cylindrical, prismatic, and pouch (or polymer) types depending on their external shape. Among these, prismatic batteries can be formed by including an electrode assembly formed by interposing a separator (113) between a positive electrode plate and a negative electrode plate, an electrolyte, etc., in a can, and a cap plate installed on the can.

[0003] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0004] An embodiment of the present invention provides a secondary battery that can prevent the can from melting when an event occurs while improving the weldability of the can.

[0005] A secondary battery according to an embodiment of the present invention comprises: an electrode assembly including a first electrode plate, a second electrode plate, and a separator interposed between the first electrode plate and the second electrode plate; a can configured to be open at both ends and to accommodate the electrode assembly; a first side plate for sealing the open end of the can; and a second side plate for sealing the open other end of the can, wherein the can includes a first metal and a second metal formed on an outer surface of the first metal, and the first metal can be formed to be exposed at both ends where the first side plate and the second side plate are joined.

[0006] And the thickness of the first metal constituting the can may be formed to be the same as the thickness of the second metal or thicker than the thickness of the second metal.

[0007] Additionally, the can includes a first metal forming an inner surface and a second metal forming an outer surface, wherein an edge of the first metal is formed to be thicker than the inner surface, and the second metal can be bonded to the inner side of the edge of the first metal.

[0008] Additionally, the outer surface of the edge of the first metal and the outer surface of the second metal on the inner side of the edge may form the same plane.

[0009] Additionally, the edge of the first metal may be provided with a step.

[0010] Additionally, either one of the first side terminal and the second side terminal may be coupled to the step.

[0011] Additionally, a chamfered area may be formed in the lower area where the first side plate or the second side plate is coupled to the step.

[0012] Additionally, the diameter of the first side plate or the second side plate can be reduced by the chamfered area of ​​the first side plate or the second side plate.

[0013] Additionally, the can may have a protrusion formed toward the inside to support the lower surface where the first side plate or the second side plate is coupled.

[0014] Additionally, a recessed groove may be formed on the outer surface of the can where the protrusion is formed.

[0015] Additionally, the protrusions may be provided in a plurality of pieces spaced apart from each other and positioned at the same distance from the step of the edge of the can.

[0016] Additionally, the can may be provided in the form of a pipe or a folded plate.

[0017] Additionally, the melting point of the second metal may be higher than the melting point of the first metal.

[0018] Additionally, the first metal has a step from the outer surface toward the inner surface, and the second metal can be inserted into and joined to the step of the first metal.

[0019] A secondary battery according to an embodiment of the present invention can prevent the can from melting even when an event occurs in the can while improving weldability between the can and the side plate by applying a different metal to the can.

[0020] In addition, the secondary battery according to an embodiment of the present invention has a protrusion that changes the shape of the can for fixing the side plate to the can, thereby facilitating the manufacture of the can and improving weldability between the can and the side plate.

[0021] Figure 1 is a perspective view of a secondary battery according to one embodiment of the present invention.

[0022] Figure 2 is a front view of a secondary battery according to one embodiment of the present invention.

[0023] Figure 3 is a plan view of a secondary battery according to one embodiment of the present invention.

[0024] Figure 4 is a bottom view of a secondary battery according to one embodiment of the present invention.

[0025] Figure 5 is a cross-sectional view of a secondary battery according to one embodiment of the present invention.

[0026] FIG. 6 is a cross-sectional view illustrating a case material of a secondary battery according to one embodiment of the present invention.

[0027] FIG. 7 is an enlarged view of a cross-section of a joint between a side plate and a can in a secondary battery according to one embodiment of the present invention.

[0028] FIG. 8 is a perspective view illustrating an electrode assembly in a secondary battery according to one embodiment of the present invention.

[0029] FIG. 9 is a perspective view illustrating a can separated from a secondary battery according to one embodiment of the present invention.

[0030] Figure 10 is a perspective view of a secondary battery according to another embodiment of the present invention.

[0031] FIG. 11A is a partial perspective view of a secondary battery according to another embodiment of the present invention.

[0032] FIG. 11b is a perspective view illustrating a can of a secondary battery according to another embodiment of the present invention.

[0033] FIG. 12 is an enlarged view of a cross-section of a joint between a side plate and a can in a secondary battery according to another embodiment of the present invention.

[0034] Figure 13 is a partial perspective view of a secondary battery according to another embodiment of the present invention.

[0035] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0036] The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The following embodiments may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art.

[0037] In addition, in the drawings below, the thickness and size of each layer are exaggerated for convenience and clarity of explanation, and the same reference numerals in the drawings indicate the same elements. As used herein, the term "and / or" may include any one and all combinations of one or more of the listed items. In addition, the meaning of "connected" in this specification means not only when member A and member B are directly connected, but also when member C is interposed between member A and member B, so that member A and member B are indirectly connected.

[0038] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. Furthermore, as used herein, the words "comprise" and "include" and / or "comprising" and "including" specify the presence of stated features, numbers, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, components, and / or groups thereof.

[0039] Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers, and / or portions, it is to be understood that these elements, components, regions, layers, and / or portions are not limited by these terms. These terms are only used to distinguish one element, component, region, layer, or portion from another element, layer, or portion. Thus, a first element, component, region, layer, or portion described below may also refer to a second element, component, region, layer, or portion without departing from the teachings of the present invention.

[0040] Spatial terms such as "beneath," "below," "lower," "above," and "upper" may be used to facilitate understanding of one element or feature depicted in the drawings relative to another element or feature. These spatial terms are provided to facilitate understanding of the present invention in various process states or usage states and are not intended to limit the present invention. For example, if an element or feature in a drawing is flipped, an element or feature described as "beneath" or "below" becomes "above" or "above." Therefore, "below" is a concept encompassing "upper" or "below."

[0041] FIG. 1 is a perspective view of a secondary battery according to an embodiment of the present invention. FIG. 2 is a front view of a secondary battery according to an embodiment of the present invention. FIG. 3 is a plan view of a secondary battery according to an embodiment of the present invention. FIG. 4 is a bottom view of a secondary battery according to an embodiment of the present invention. FIG. 5 is a cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0042] First, referring to FIGS. 1 to 5, a secondary battery (100) according to one embodiment of the present invention includes an electrode assembly, a can (120), a first side plate (130), a second side plate (140), a first side terminal (150), and a second side terminal (160). In the drawings, the electrode assembly is not shown because it is arranged inside the can (120).

[0043] The electrode assembly (110) includes a first electrode plate (111), a second electrode plate (112), and a separator (113).

[0044] The first electrode plate (111) may be either a negative electrode plate or a positive electrode plate. For example, when the first electrode plate (111) is a negative electrode plate, the first electrode plate (111) may include a negative electrode coating portion in which a negative electrode active material is coated on a negative electrode current collector plate made of a conductive metal plate, for example, a copper or nickel foil or mesh, and a negative electrode non-coated portion in which the negative electrode active material is not coated. The negative electrode active material may be made of, for example, a carbon-based material, Si, Sn, tin oxide, a tin alloy composite, a transition metal oxide, lithium metal nitrite, or a metal oxide.

[0045] The second electrode plate (112) may be the other of the negative electrode plate and the positive electrode plate. For example, when the second electrode plate (112) is a positive electrode plate, the second electrode plate (112) may include a positive electrode coated portion in which a positive electrode active material is coated on a positive electrode current collector plate made of a conductive metal thin plate, such as aluminum foil or mesh, and a positive electrode non-coated portion in which the positive electrode active material is not coated. The positive electrode active material may be made of a chalcogenide compound, such as a composite metal oxide such as LiCoO2, LiMn2O4, LiNiO2, or LiNiMnO2.

[0046] A separator (113) is interposed between the first electrode plate (111) and the second electrode plate (112) and serves to prevent electrical shorts between the first electrode plate (111) and the second electrode plate (112). The separator (113) may be made of, for example, polyethylene, polypropylene, a porous copolymer of polyethylene and polypropylene, etc.

[0047] The can (120) serves to accommodate the electrode assembly (111) together with the electrolyte. The can (120) has a structure in which a plate-shaped member is bent into a pipe shape and the facing corners (120a) are welded, thereby providing a space inside and opening both ends. In addition, a first side plate (130) and a second side plate (140) are respectively joined to the open ends, thereby sealing both ends of the can (120).

[0048] In addition, a safety vent (170) is provided on one side of the can (120). When gas is generated inside the can (120), the safety vent (170) is automatically cut by the resulting pressure to release the gas and pressure, thereby preventing the secondary battery (100) from exploding. To this end, the safety vent (170) may be formed with a notch (170a) that induces cutting. This safety vent (170) may be fixed by overlapping welding.

[0049] Meanwhile, the can (120) may be composed of dissimilar metals. For example, the can (120) may be composed of a first metal (121) having high thermal conductivity on the inner surface and a second metal (122) having a high melting temperature on the outer surface. For example, the first metal (121) may be composed of aluminum and the second metal (122) may be composed of stainless steel. These dissimilar metals may also be referred to as cladding. The can (120) may maintain high thermal conductivity on the inner surface while preventing melting on the outer surface through these dissimilar metals. Therefore, when an event occurs inside the can (120), the weldability with the first and second side plates (130, 140) can be improved through the first metal (121) on the inner surface, and the melting of the can (120) can be prevented through the second metal (122) having a high melting point on the outer surface. The structure and welding joint of these cans (120) will be described in detail later.

[0050] The first side plate (130) is formed in a square plate shape to correspond to the open end of the can (120). The first side plate (130) is welded to one end of the can (120) to seal the can (120).

[0051] The first side plate (130) may include a first cap plate (131), a first joining member (132), and a first seal gasket (133) that are coupled to an open end of the can (120). The first cap plate (131) may have a flat, square plate shape and may seal the left opening (121) of the can (120).

[0052] The first joining member (132) and the first seal gasket (133) may be interposed between the outer surface of the first cap plate (131) and the first side terminal (150). The first joining member (132) may be in close contact with the first cap plate (131) and may also be in close contact with the first seal gasket (133). The first joining member (132) and the first seal gasket (133) may be made of an insulating material and may insulate between the first cap plate (131) and the first side terminal (150).

[0053] The second side plate (140) is formed in a square plate shape to correspond to the other end located opposite the open end of the can (120). The second side plate (140) is also welded to the open other end of the can (120) to serve a sealing function. The second side plate (140) may include a second cap plate (141), a second joining member (142), and a second seal gasket (143) that are joined to the open other end of the can (120), and these configurations are similar to those of the first side plate (140).

[0054] The first side terminal (150) is electrically connected to the non-conductive portion (negative non-conductive portion) of the first electrode plate (111) of the electrode assembly and is exposed to the outside by penetrating the first side plate (130). Therefore, the first side terminal (150) functions as a negative terminal. The first side terminal (150) may include a first inner plate (151), a first terminal pillar (152), and a first outer plate (153).

[0055] The first side terminal (150) is formed of metal and can be electrically connected to the first electrode tab (114). In some examples, the first side terminal (150) can include a first inner plate (151), a first terminal pillar (152), and a first outer plate (153).

[0056] The first inner plate (151) may be positioned on the inner side of the first cap plate (131), and the first outer plate (153) may be positioned on the outer side of the first cap plate (131). Of course, a first connecting member (132) may be further interposed between the first outer plate (153) and the first cap plate (131). In addition, a first seal gasket (133) may be further interposed between the first terminal pillar (152) and the first cap plate (131) and between the first inner plate (151) and the first cap plate (131). Additionally, the first terminal pillar (152) can penetrate the first cap plate (131) and be coupled with the first outer plate (153) on the outer side of the first cap plate (131) and with the first inner plate (151) on the inner side of the first cap plate (131). The first inner plate (151) can be welded and coupled with the first electrode tab (114) on the inner side.

[0057] The first terminal pillar (152) can be inserted and joined by penetrating the first inner plate (151). For example, the first terminal pillar (152) can be inserted into the terminal hole of the first inner plate (151) and joined by riveting and / or welding on one side. The first terminal pillar (152) can be in the shape of a pillar and can protrude and extend outward from the first cap plate (131).

[0058] The first outer plate (153) may have a terminal hole penetrating between one side and the other side. A first terminal pillar (152) may pass through the terminal hole of the first outer plate (153) and be riveted and / or welded.

[0059] The second side terminal (160) is electrically connected to the non-conductive portion (positive non-conductive portion) of the second electrode plate (112) of the electrode assembly and is exposed to the outside by penetrating the second side plate (140). Therefore, the second side terminal (160) functions as a positive terminal. At this time, an insulating member (not shown) is also provided between the second side terminal (160) and the second side plate (140) to prevent an electrical short therebetween.

[0060] The second side terminal (160) may include a second inner plate (161), a second terminal pillar (162), and a second outer plate (163). The structure of the second side terminal (160) is similar to that of the first side terminal (150).

[0061] Hereinafter, the structure and bonding shape of the can (120) in the secondary battery (100) according to one embodiment of the present invention will be described in more detail.

[0062] Fig. 6 is a cross-sectional view illustrating a case base material in a secondary battery according to an embodiment of the present invention. Fig. 7 is an enlarged cross-sectional view of a joint section of a side plate and a can in a secondary battery according to an embodiment of the present invention. Fig. 8 is a perspective view illustrating an electrode assembly in a secondary battery according to an embodiment of the present invention. Fig. 9 is a perspective view illustrating a separated can in a secondary battery according to an embodiment of the present invention.

[0063] Referring to FIG. 6, before manufacturing the final can (120), the configuration of the first metal (121) and the second metal (122) constituting the base material (120') is such that the second metal (122) is bonded to the outer surface of the first metal (121), and among these, the second metal (122) may be surrounded by the edge (121a) of the first metal (121). That is, the edge (121a) of the first metal (121) may be formed to have a constant length (w), and the second metal (122) may be positioned in an area inside thereof. Accordingly, as shown in FIG. 6, the second metal (122) may be embedded in the interior of the first metal (121). However, even in this case, the second metal (122) can form the same plane as the edge (121a) of the first metal (121). Specifically, the edge (121a) can protrude to a second thickness (t2) with respect to the first thickness (t1) of the first metal (121), and the thickness of the second metal (122) can also be provided to have the second thickness (t2). Therefore, the base material (120') made of the first metal (121) and the second metal (122) can have a flat plate shape when viewed from the side.

[0064] In addition, the first thickness (t1) of the first metal (121) may be formed to be the same as the second thickness (t2) of the second metal (122) or thicker than the second thickness (t2). In this case, when a can (120) is formed in the future through the base material (120'), the thermal conductivity can be further increased through the first metal (121) forming the main structure of the can (120).

[0065] Meanwhile, referring to FIG. 7, a can (120) can be manufactured by forming a step portion (121b) through processing of a base material (120'). The first side plate (130) can be joined to the step portion (121b) of the can (120) in a state of being hung over it. Specifically, since the inner diameter of the first side plate (130) becomes smaller than the end portion where the first side plate (130) is joined through the step portion (121b), the first side plate (130) can hang over the step portion (121b). In this state, when welding is performed along the boundary surface of the first side plate (130) and the first metal (121) of the can (120), the first side plate (130) can be fixed to the can (120) and the first side plate (130) can seal the end portion of the can (120).

[0066] To this end, the thickness (t3) of the first side plate (130) may be formed to be greater than the depth at which the step portion (121b) is formed from the end of the first side plate (130), and a chamfered area (131a) may be formed at the inner end of the first side plate (130), so that the first side plate (130) may be firmly coupled to the inside of the can (120). In addition, even in this case, the length (w) of the first metal (121) may be formed to be longer than the thickness (t3) of the first side plate (130), so that pressure due to coupling may be prevented from being applied to the second metal (122) located within the first metal (121) when the first side plate (130) is coupled. Accordingly, the second metal (122) is maintained in a fixed position relative to the first metal (121), so that deformation of the can (120) may not occur.

[0067] As described above, the secondary battery (100) according to one embodiment of the present invention comprises a can (120) made of a first metal (121) and a second metal (122), and the second metal (122) is positioned on the outer surface of the first metal (121), thereby increasing weldability with the side plates (131, 132) through the first metal (121), and preventing melting even at high temperatures through the second metal (122), thereby increasing safety.

[0068] Hereinafter, the bonding relationship between the electrode assembly and the can in the secondary battery according to an embodiment of the present invention will be described in more detail.

[0069] Fig. 8 is a perspective view illustrating an electrode assembly in a secondary battery according to one embodiment of the present invention. Fig. 9 is a perspective view illustrating a can separated from a secondary battery according to one embodiment of the present invention.

[0070] First, referring to FIG. 8, the structure of the electrode assembly (110) may be configured to include a first electrode tab (114) formed on the uncoated portion (111a) of the first electrode plate, and a second electrode tab (115) formed on the uncoated portion (112a) of the second electrode plate. In this case, the first electrode tab (114) and the second electrode tab (115) are illustrated in the form of current collecting tabs formed by extending the uncoated portions (111a, 112a), but they may also be formed as separate tabs coupled to the uncoated portions (111a, 112a). The first electrode tab (114) and the second electrode tab (115) may be formed to protrude from both sides of the electrode assembly (110).

[0071] Next, with reference to FIG. 9 regarding the configuration and manufacturing method of the can (120), the can (120) may have the shape of a rectangular parallelepiped with both sides open, or in other words, the shape of a rectangular tube. The can (120) is formed by processing a plate-shaped base material (120') as described above in FIG. 6, and specifically, a rectangular tube shape as shown in FIG. 7 may be manufactured by folding the base material (120') multiple times. In this case, the can (120) formed by folding the base material (120') may have a boundary line (120b) where the folded ends come into contact, and the second metals (122) formed on the outer surface at the boundary line (120b) may be in contact with each other, and the first metals (121) located at the edges may be in contact with each other. In addition, welding may be performed along the boundary line (120a) to seal the side surface of the can (120).

[0072] Meanwhile, through the openings on both sides of the can (120), the electrode assembly (110) of FIG. 8 can be inserted, and then the first and second side plates (130, 140) can be joined to the can (120) to seal the can (120).

[0073] Below, the configuration of a secondary battery according to another embodiment of the present invention will be described.

[0074] Fig. 10 is a perspective view of a secondary battery according to another embodiment of the present invention. Fig. 11a is a partial perspective view of a secondary battery according to another embodiment of the present invention. Fig. 11b is a perspective view showing a detached can of a secondary battery according to another embodiment of the present invention. Fig. 12 is an enlarged view of a cross-section of a joint between a side plate and a can in a secondary battery according to another embodiment of the present invention.

[0075] Referring to FIGS. 10 to 12, a secondary battery (200) according to another embodiment of the present invention includes an electrode assembly, a can (220), a first side plate (130), a second side plate (140), a first side terminal (150), and a second side terminal. The same reference numerals are used for components identical or similar to those of the previous embodiment, and the following description will focus on differences from the previous embodiment.

[0076] The can (220) may have a dual structure of the first metal (121) and the second metal (122), similar to the previous embodiment. However, the can (220) may include a protrusion (221a) protruding inwardly on at least one side adjacent to the first and second side plates (130, 140). The protrusion (221a) may be formed from the outside toward the inside of the can (220) through plastic processing such as pressing. The protrusion (221a) may correspond to the step (121b) formed at the edge (121a) of the first metal (121) of the can (120) in the previous embodiment. That is, according to the present embodiment, instead of forming a separate step portion (121b) when processing the can (120), an external force such as a press may be applied from the outside of the can (220) to induce deformation, thereby forming a protrusion portion (221a). Accordingly, the can (220) forms a protrusion portion (221a) having a shape that protrudes inward in a simpler manner than the step portion (121b), thereby allowing the first and second side plates (130, 140) to be respectively seated thereon.

[0077] In addition, as illustrated in FIG. 12, for example, when welding is performed while the first side plate (130) is seated on the protrusion (221a), since there is no separate step portion in the can (220), the upper thickness can be secured to a desired degree, so that welding can be easily performed and the advantage of securing the desired welding strength can be achieved.

[0078] Below, the configuration of a secondary battery according to another embodiment of the present invention will be described.

[0079] Figure 13 is a partial perspective view of a secondary battery according to another embodiment of the present invention.

[0080] Referring to FIG. 13, a secondary battery (300) according to another embodiment of the present invention includes an electrode assembly, a can (320), a first side plate (130), a second side plate, a first side terminal (150), and a second side terminal. The same reference numerals are used for components that are the same or similar to those of the previous embodiment, and the following description will focus on differences from the previous embodiment.

[0081] The can (320) may have a dual structure of a first metal (121) and a second metal (122), similar to the previous embodiment. However, the can (320) may include a plurality of protrusions (321a) protruding inwardly on at least one side adjacent to the first and second side plates (130, 140).

[0082] The protrusion (321a) can be formed from the outside of the can (320) toward the inside through plastic processing such as pressing. The protrusion (321a) can correspond to the protrusion (221a) formed on the can (220) in the previous embodiment. However, the protrusion (321a) is provided in multiple numbers, and for this purpose, an external force such as pressing can be applied to multiple areas from the outside of the can (320). In addition, the can (320) can also form a protrusion (321a) in a shape that protrudes inwardly using a simple method, so that the first and second side plates (130, 140) can be respectively seated thereon.

[0083] The can (320) can have the advantage of being able to maintain the strength of the can (320) as much as possible while increasing the welding strength as described above by forming a protrusion (321a) through deformation only in the minimum area necessary for the settling of the first and second side plates (130, 140).

[0084] The above description is only one embodiment for implementing the secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present invention exists to the extent that various modifications can be implemented by anyone having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention.

Claims

1. An electrode assembly including a first electrode plate, a second electrode plate, and a separator interposed between the first electrode plate and the second electrode plate; A can configured to be open at both ends and to accommodate the electrode assembly; a first side plate for sealing the open end of the can; and A second side plate is included for sealing the open end of the can, A secondary battery formed by the can including a first metal and a second metal formed on an outer surface of the first metal, and wherein the first metal is exposed at both ends where the first side plate and the second side plate are joined.

2. In paragraph 1, A secondary battery in which the thickness of the first metal constituting the above can is formed to be equal to or thicker than the thickness of the second metal.

3. In paragraph 1, A secondary battery in which the can comprises a first metal forming an inner surface and a second metal forming an outer surface, wherein an edge of the first metal is formed thicker than the inner surface, and the second metal is bonded to the inner side of the edge of the first metal.

4. In paragraph 3, A secondary battery in which the outer surface of the edge of the first metal and the outer surface of the second metal on the inner side of the edge form the same plane.

5. In paragraph 3, A secondary battery having a step on the edge of the first metal.

6. In paragraph 5, A secondary battery in which one of the first side terminal and the second side terminal is coupled to the above step.

7. In paragraph 6, A secondary battery in which a chamfered area is formed in a lower area where the first side plate or the second side plate is coupled to the step.

8. In paragraph 7, A secondary battery in which the diameter of the first side plate or the second side plate is reduced by the chamfered area of ​​the first side plate or the second side plate.

9. A secondary battery having a protrusion formed toward the inside of the can to support the lower surface where the first side plate or the second side plate is combined.

10. In paragraph 9, A secondary battery in which a recessed groove is formed on the outer surface of the can in which the protrusion is formed.

11. In paragraph 9, A secondary battery having a plurality of protrusions spaced apart from each other and positioned at the same distance from the step of the edge of the can.

12. In paragraph 1, The above can is a secondary battery provided in the form of a pipe type or a folded plate.

13. In paragraph 1, A secondary battery in which the melting point of the second metal is higher than that of the first metal.

14. In paragraph 1, A secondary battery in which the first metal has a step from the outer surface toward the inner surface, and the second metal is inserted into the step of the first metal and combined.

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