Secondary battery and case for secondary battery

Abstract

The invention provides a secondary battery and a case for the secondary battery. The secondary battery includes: an electrode assembly; a lower case including a receiving portion having a receiving space for accommodating the electrode assembly, and a flange portion surrounding an open side surface of the receiving portion; and an upper cover connected to the flange portion of the lower case and sealing the open side surface of the receiving portion. The receiving portion of the lower case includes a bottom surface spaced apart from the flange portion, and a side wall portion connecting the flange portion and the bottom surface to each other. At least one edge of the side wall portion has a rounded shape including a curved surface having a first radius of curvature and a curved surface having a second radius of curvature, the curved surface having the second radius of curvature being joined to the curved surface having the first radius of curvature. The first radius of curvature is greater than the second radius of curvature.

Description

Technical Field

[0001] An aspect of the embodiments of this disclosure relates to a secondary battery and a housing for the secondary battery. Background Technology

[0002] Unlike primary batteries, which are not designed for (re)charging, secondary (or rechargeable) batteries are designed to discharge and be recharged. Low-capacity secondary batteries are used in portable small electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while high-capacity secondary batteries are widely used as power sources for motors in hybrid and electric vehicles, as well as for storing electricity (e.g., household and / or utility-scale power storage). Secondary batteries typically consist of an electrode assembly containing positive and negative electrodes, a housing, and electrode terminals connected to the electrode assembly.

[0003] Secondary batteries with high energy density (e.g., the amount of energy that can be stored per unit volume) can provide longer operating time or longer range for portable devices or electric vehicles, and the energy density of a secondary battery can be one of the key factors determining its performance. Therefore, various technologies for increasing energy density (e.g., by improving the structure of the casing in the secondary battery) may be needed.

[0004] The information disclosed in this background section is intended to enhance the understanding of the background of this disclosure, and therefore may contain information that does not constitute related (or prior art). Summary of the Invention

[0005] Embodiments of this disclosure may be directed to secondary batteries and housings for secondary batteries.

[0006] These and other aspects and features of this disclosure will be described in or will become apparent from the following description of embodiments of this disclosure.

[0007] According to one or more embodiments of this disclosure, a secondary battery includes: an electrode assembly including a first electrode, a second electrode, and a separator inserted between the first and second electrodes; a lower housing including a receiving portion having a receiving space for accommodating the electrode assembly, and a flange portion surrounding an open side surface of the receiving portion; and a top cover, coupled to the flange portion of the lower housing and sealing the open side surface of the receiving portion. The receiving portion of the lower housing includes a bottom surface spaced apart from the flange portion, and a sidewall portion connecting the flange portion and the bottom surface to each other. At least one edge of the sidewall portion has a rounded shape, the rounded shape including a surface having a first radius of curvature and a surface having a second radius of curvature, the surface having the second radius of curvature being coupled to the surface having the first radius of curvature. The first radius of curvature is greater than the second radius of curvature.

[0008] In one embodiment, at least one of the upper cover and the lower housing comprises stainless steel (SUS).

[0009] In one embodiment, the dimension of the first radius of curvature may increase as the thickness of the lower housing decreases.

[0010] In one embodiment, the thickness of the lower housing can be in the range of 0.02 mm to 0.1 mm.

[0011] In one embodiment, the thickness of the lower housing can be in the range of 0.02 mm to 0.04 mm, and the dimension of the first radius of curvature can be in the range of 3.0 mm to 6.0 mm.

[0012] In one embodiment, the size of the first radius of curvature can be in the range of 2.0 mm to 6.0 mm.

[0013] In one embodiment, the depth of the receiving part may be greater than 0 mm and equal to or less than 5.0 mm.

[0014] In one embodiment, the sidewall portion may include: a first side surface connected to a short side of the bottom surface; a second side surface facing the first side surface; a third side surface connected to a long side of the bottom surface; and a fourth side surface facing the third side surface.

[0015] In one embodiment, a first electrode terminal electrically connected to a first electrode and a second electrode terminal electrically connected to a second electrode may be located on at least a portion of a first side surface.

[0016] In one embodiment, each of the edges where the first and third side surfaces meet, the edges where the first and fourth side surfaces meet, the edges where the second and third side surfaces meet, and the edges where the second and fourth side surfaces meet can have a rounded shape in which a surface having a first radius of curvature and a surface having a second radius of curvature meet each other.

[0017] In one embodiment, a surface having a first radius of curvature may be connected to at least one of a first side surface and a second side surface, and a surface having a second radius of curvature may be connected to at least one of a third side surface and a fourth side surface.

[0018] In one embodiment, each of the edges where the bottom surface and the first side surface meet each other, and each of the edges where the bottom surface and the second side surface meet each other, may have a surface having a third radius of curvature. Each of the edges where the bottom surface and the third side surface meet each other, and each of the edges where the bottom surface and the fourth side surface meet each other, may have a surface having a fourth radius of curvature.

[0019] In one embodiment, the third radius of curvature may be the same as the fourth radius of curvature.

[0020] In one embodiment, the dimensions of the third radius of curvature and the fourth radius of curvature may increase as the thickness of the lower housing decreases.

[0021] In one embodiment, at least a portion of the upper cover can be laser welded to the flange of the lower housing.

[0022] In one embodiment, at least a portion of the upper cover and each of the flange of the lower housing may have a stacked structure comprising: a metal layer; an adhesive layer in contact with the metal layer; and a polymer layer in contact with the adhesive layer. At least a portion of the upper cover can be joined to the flange of the lower housing by thermally fusing the polymer layers in at least a portion of the upper cover and the lower housing flange to each other.

[0023] According to one or more embodiments of this disclosure, a housing for a secondary battery includes: a lower housing including a receiving portion having a receiving space for accommodating electrode assemblies, and a flange portion surrounding an open side surface of the receiving portion; and a top cover, coupled to the flange portion of the lower housing and sealing the open side surface of the receiving portion. The receiving portion of the lower housing includes a bottom surface spaced apart from the flange portion, and a sidewall portion connecting the flange portion and the bottom surface to each other. At least one edge of the sidewall portion has a rounded shape, the rounded shape including a surface having a first radius of curvature and a surface having a second radius of curvature, the surface having the second radius of curvature being coupled to the surface having the first radius of curvature. The first radius of curvature is greater than the second radius of curvature.

[0024] In one embodiment, the sidewall portion may include: a first side surface connected to a short side of the bottom surface; a second side surface facing the first side surface; a third side surface connected to a long side of the bottom surface; and a fourth side surface facing the third side surface.

[0025] In one embodiment, each of the edges where the first and third side surfaces meet, the edges where the first and fourth side surfaces meet, the edges where the second and third side surfaces meet, and the edges where the second and fourth side surfaces meet can have a rounded shape in which a surface having a first radius of curvature and a surface having a second radius of curvature meet each other.

[0026] In one embodiment, a surface having a first radius of curvature may be connected to at least one of a first side surface and a second side surface, and a surface having a second radius of curvature may be connected to at least one of a third side surface and a fourth side surface.

[0027] According to some embodiments of this disclosure, in the case of a secondary battery, each edge of the sidewall portion can be formed into a rounded shape in which surfaces having the same or substantially the same radius of curvature or having different radii of curvature are combined. Thus, by changing the size of one of the radii of curvature of the edges constituting the sidewall portion (e.g., changing only the size of one of the radii of curvature of the edges constituting the sidewall portion), without changing the size of the other radii of curvature, the size of the receiving space within the lower housing that can accommodate the electrode assembly can be increased, and the energy density of the secondary battery can be increased.

[0028] According to some embodiments of this disclosure, in the case of a secondary battery, each edge of the sidewall portion can be formed into a rounded shape in which curved surfaces having different radii of curvature from one another are joined together. Therefore, the structure of the housing can be strengthened, and cracks that may occur due to external impacts, etc., can be prevented or substantially prevented.

[0029] However, the aspects and features of this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the detailed description below that other aspects and features not mentioned will be apparent. Attached Figure Description

[0030] The following accompanying drawings illustrate embodiments of the present disclosure, and together with the detailed description of the present disclosure, aspects and features of the present disclosure are further described. Therefore, the present disclosure should not be construed as limited to the drawings.

[0031] Figure 1 This is an exploded perspective view illustrating an example of a secondary battery according to some embodiments of the present disclosure.

[0032] Figure 2 Examples of secondary batteries according to some embodiments of the present disclosure are shown.

[0033] Figure 3 This is an exploded perspective view showing the casing of a secondary battery according to some embodiments of the present disclosure.

[0034] Figure 4 This is a perspective view of the lower housing when viewed from below, according to some embodiments of the present disclosure.

[0035] Figure 5 It is along Figure 4 The cross-sectional view of the lower shell is shown by line AA.

[0036] Figure 6 The dimensions of the receiving space accommodating the electrode assembly vary depending on the radius of curvature.

[0037] Figure 7 The diagram shows the appearance of cracks as the radius of curvature decreases.

[0038] Figure 8 This is a table showing the appearance of cracks according to a change in the first radius of curvature, based on some embodiments of this disclosure.

[0039] Figure 9 This is an exploded perspective view showing a pouch-type secondary battery according to some embodiments of the present disclosure.

[0040] Figure 10 This is a cross-sectional view showing a pouch-type secondary battery according to some embodiments of the present disclosure. Detailed Implementation

[0041] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, and should be interpreted in a way consistent with the technical spirit of the present disclosure, based on the principle that the inventor can be his / her own lexicographer to appropriately define the concepts of the terms so as to best interpret his / her invention.

[0042] The embodiments described in this specification and the configurations shown in the accompanying drawings are merely some embodiments of this disclosure and do not represent all technical ideas, aspects, and features of this disclosure. Therefore, it should be understood that various equivalents and modifications may exist to replace or modify the embodiments described herein at the time of filing this application.

[0043] It should be understood that when a component or layer is described as being "on," "connected to," or "bonded to" another component or layer, it can be directly on, directly connected to, or directly bonded to the other component or layer, or one or more intermediate components or layers may be present. When a component or layer is described as being "directly on," "directly connected to," or "directly bonded to" another component or layer, no intermediate components or layers are present. For example, when a first component is described as being "bonded" or "connected" to a second component, the first component can be directly bonded to or connected to the second component, or the first component can be indirectly bonded to or connected to the second component via one or more intermediate components.

[0044] In the accompanying drawings, the dimensions of various elements, layers, etc., may be exaggerated for clarity. The same reference numerals denote the same elements. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Furthermore, when describing embodiments of this disclosure, the use of “may” refers to “one or more embodiments of this disclosure.” Expressions such as “at least one of…” and “any one of…” modify the entire column of elements, not individual elements within that column, when following a column of elements. When a column of elements A, B, and C is specified using phrases such as “at least one of A, B, and C,” “at least one of A, B, or C,” “at least one selected from the group consisting of A, B, and C,” or “at least one selected from A, B, and C,” the phrase may refer to any and all suitable combinations or subsets of A, B, and C, such as A, B, C, A and B, A and C, B and C, or A and B and C. As used herein, the terms “use,” “using…,” and “being used” may be considered synonymous with the terms “utilize,” “using…,” and “being exploited,” respectively. As used herein, the terms “substantially,” “about,” and similar terms are used as approximations rather than terms of degree, intended to describe the inherent biases of measurements or calculations that would be recognized by one of ordinary skill in the art.

[0045] It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, the first element, component, region, layer, or portion discussed below may be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0046] For ease of description, spatial relation terms such as “below,” “under,” “down,” “above,” and “above” are used herein to describe the relationship between one element or feature and another element or feature as shown in the figure. It will be understood that, in addition to the orientation depicted in the figure, spatial relation terms are also intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, the element described as “below” or “under” other elements or features will be oriented “above” or “above” other elements or features. Therefore, the term “below” can cover both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relation descriptors used herein should be interpreted accordingly.

[0047] The terminology used herein is for describing embodiments of the present disclosure and is not intended to limit the disclosure. As used herein, the singular form “a” is also intended to include the plural form unless the context clearly indicates otherwise. It will be further understood that the terms “comprising,” “including,” “including,” and / or “containing” as used in this specification indicate the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0048] Furthermore, any numerical range disclosed and / or described herein is intended to include all subranges containing the same numerical precision within said range. For example, the range “1.0 to 10.0” is intended to include all subranges between (and including) said minimum value 1.0 and said maximum value 10.0, i.e., all subranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limit described herein is intended to include all lower numerical limits contained therein, and any minimum numerical limit described in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to amend this specification (including the claims) to expressly describe any subranges contained within the range expressly described herein.

[0049] Referring to two compared elements, features, etc., as “identical” can mean that they are “substantially identical.” Therefore, the phrase “substantially identical” can include cases with deviations considered low in the art, such as 5% or less. Additionally, when a parameter is said to be uniform in a given region, it can mean that it is uniform in terms of the mean.

[0050] Throughout this specification, unless otherwise stated, each element may be singular or plural.

[0051] The phrase "any element arranged above (or below)" or "above (or below)" another element can mean that the arbitrary element can be positioned to contact the upper (or lower) surface of the element, and that the other element can be inserted between the element and the arbitrary element disposed on (or below) the element.

[0052] Additionally, it will be understood that when components are referred to as “linked,” “combined,” or “connected” to another component, these components can be directly “combined,” “linked,” or “connected” to each other, or additional components can be “inserted” between these components.

[0053] Throughout this specification, unless otherwise stated, when “A and / or B” is used, it means A, B, or A and B. That is, “and / or” includes any or all combinations of the listed items. When “C to D” is used, unless otherwise stated, it means C or greater and D or less.

[0054] In this specification, unless the context clearly indicates otherwise, singular expressions are intended to include plural expressions as well. Furthermore, unless the context clearly indicates otherwise, plural expressions are intended to include singular expressions as well. It will be further understood that, unless the context clearly indicates otherwise, the phrase "when a part includes a component" throughout this specification means not excluding other components, but rather that other components may be further included.

[0055] In this disclosure, for ease of illustration, the dimensions and relative dimensions of layers and regions shown in the accompanying drawings may be exaggerated. In other words, the dimensions illustrated in the drawings are provided for ease of illustration and are not limiting. Furthermore, throughout the specification and drawings, the same reference numerals denote the same or substantially the same elements.

[0056] Figure 1 This is an exploded perspective view showing an example of a secondary battery 100 according to some embodiments of the present disclosure. Figure 2 An example of a secondary battery 100 according to some embodiments of the present disclosure is shown.

[0057] Reference Figure 1 and Figure 2 According to some embodiments of the present disclosure, a secondary battery 100 may include an electrode assembly 110, a lower housing 120 for receiving the electrode assembly 110, and an upper cover 130 for sealing an open side surface of the lower housing 120. For example, the lower housing 120 may include a receiving portion 127 and a flange portion 128, wherein a receiving space for receiving the electrode assembly 110 is formed in the receiving portion 127, and the flange portion 128 surrounds an open side surface of the receiving portion 127. The upper cover 130 may engage with the flange portion 128 of the lower housing 120 to seal the open side surface of the receiving portion 127.

[0058] In some embodiments, the upper cover 130 and the lower housing 120 may form the overall appearance of the secondary battery 100 and may include conductive metals such as aluminum, aluminum alloys, and / or nickel-plated steel (e.g., may be formed of conductive metals such as aluminum, aluminum alloys, and / or nickel-plated steel). According to some embodiments, at least one of the upper cover 130 or the lower housing 120 may include metallic materials such as stainless steel (SUS) and / or aluminum (Al). However, this disclosure is not limited thereto, and the upper cover 130 and the lower housing 120 may include various suitable metallic materials that meet the strength and resistance to external impacts required by the secondary battery 100 (e.g., may be configured from various suitable metallic materials that meet the strength and resistance to external impacts required by the secondary battery 100).

[0059] Electrode assembly 110 can be housed within lower housing 120. Electrode assembly 110 can be formed by winding or stacking a first electrode plate, a diaphragm, and a second electrode plate, which are formed as plates or films. When electrode assembly 110 is a wound stack, the winding axis can be parallel to or substantially parallel to the longitudinal direction (e.g., the Y direction) of lower housing 120. In other embodiments, electrode assembly 110 can be stacked rather than wound, and the shape of electrode assembly 110 is not particularly limited in this disclosure. Furthermore, electrode assembly 110 can be a Z-stacked electrode assembly, wherein a positive electrode plate and a negative electrode plate are inserted into opposite sides (e.g., opposite sides) of a diaphragm bent into a Z-shape. Additionally, one or more electrode assemblies 110 can be stacked such that the long sides of electrode assemblies 110 are adjacent to each other and housed within lower housing 120, but the number of electrode assemblies 110 in the housing is not particularly limited in this disclosure. The first electrode plate of electrode assembly 110 can be used as a negative electrode, and the second electrode plate can be used as a positive electrode, and vice versa.

[0060] The first electrode plate can be formed by applying a first electrode active material (such as graphite or carbon) to a first electrode current collector formed of a metal foil (such as copper, copper alloy, nickel, or nickel alloy). The first electrode plate may include a first electrode tab (e.g., a first uncoated portion), which is a region where the first electrode active material is not applied. The first electrode tab 112 can serve as a current flow path between the first electrode plate and the first electrode terminal 122. In some embodiments, the first electrode tab 112 can be formed by pre-cutting it to protrude to one side of the electrode assembly during the manufacture of the first electrode plate, or the first electrode tab can protrude further (e.g., further than or beyond the diaphragm) to one side of the electrode assembly without being individually cut.

[0061] The second electrode plate can be formed by applying a second electrode active material (such as a transition metal oxide) to a second electrode current collector formed of a metal foil (such as aluminum or an aluminum alloy). The second electrode plate may include a second electrode tab (e.g., a second uncoated portion), which is a region where the second electrode active material is not applied. The second electrode tab 114 can serve as a current flow path between the second electrode plate and the second electrode terminal 124. In some embodiments, the second electrode tab 114 can be formed by pre-cutting it during the manufacture of the second electrode plate to protrude to the other side (e.g., the opposite side) of the electrode assembly, or the second electrode plate can protrude to the other side of the electrode assembly more than the diaphragm (e.g., further than or beyond the diaphragm) without being cut separately.

[0062] In some embodiments, the first electrode tab 112 may be connected to one side of the first electrode plate of the electrode assembly 110, and the second electrode tab 114 may be connected to one side of the second electrode plate of the electrode assembly 110. The first electrode tab 112 and the second electrode tab 114 may be connected to the first electrode plate and the second electrode plate respectively by soldering the tabs to the uncoated portions of the first electrode plate and the second electrode plate, or by stamping the uncoated portions of the first electrode plate and the second electrode plate. In a wound state, the first electrode tab 112 and the second electrode tab 114 may be positioned in the same direction and spaced apart from each other by a distance.

[0063] In some embodiments, the lower housing 120 may include a first electrode terminal 122 and a second electrode terminal 124. For example, the first electrode terminal 122 may be electrically connected to a first electrode tab 112 of the electrode assembly 110, and the second electrode terminal 124 may be electrically connected to a second electrode tab 114 of the electrode assembly 110. The positions of the first electrode terminal 122 and the second electrode terminal 124 according to embodiments of the present disclosure are not limited to... Figure 1 The positions shown can be modified as needed or desired. For example, with Figure 1 Depending on the location shown, the first electrode terminal 122 and the second electrode terminal 124 can be disposed in the long side surface of the lower housing 120, or they can be disposed in different surfaces of the lower housing 120.

[0064] In some embodiments, the lower housing 120 may include an electrolyte injection port 126. For example, the electrolyte injection port 126 may be a through hole formed in a surface of the lower housing 120. The electrolyte injection port 126 may serve as a channel for injecting electrolyte into the interior of the secondary battery 100 after the upper cover 130 and the lower housing 120 are engaged with each other to seal the housing. The electrolyte injection port 126 may be sealed with a sealing member after the electrolyte is injected into the interior of the secondary battery 100. The accompanying drawings show the electrolyte injection port 126 disposed between the first electrode terminal 122 and the second electrode terminal 124, but this disclosure is not limited thereto, and the position of the electrolyte injection port 126 may be modified in various ways as needed or desired. For example, the first electrode terminal 122 and the second electrode terminal 124 may be disposed sequentially, and the electrolyte injection port 126 may be disposed on one side of the first electrode terminal 122 or the second electrode terminal 124.

[0065] In some embodiments, the receiving portion 127 for accommodating the electrode assembly 110 may be formed in the central region of the lower housing 120 or substantially formed in the central region of the lower housing 120 by a pressing process or the like. A flange portion 128 surrounding an open side surface (e.g., around its periphery) of the receiving portion 127 in four directions may be formed in the upper edge portion of the receiving portion 127.

[0066] In some embodiments, the lower housing 120 and the upper cover 130 may be joined together to form the appearance of the secondary battery 100. The lower housing 120 and the upper cover 130 may be metal-jointed together, for example, by welding, brazing, soldering, and / or similar methods. For example, at least a portion of the upper cover 130 and the flange 128 of the lower housing 120 may be joined together by laser welding. In this example, the flange 128 of the lower housing 120 and the edge portion of the upper cover 130 may be joined together. Furthermore, after the lower housing 120 and the upper cover 130 are joined together, at least a portion of the flange 128 may be laser-cut to increase the energy density of the secondary battery 100.

[0067] Figure 3 This is an exploded perspective view showing the casing of a secondary battery 100 according to some embodiments of the present disclosure.

[0068] Reference Figure 3 The casing of the secondary battery 100 may include an upper cover 130 and a lower casing 120. For example... Figure 3 As shown, the upper cover 130 may have a plate shape. The upper cover 130 may be disposed on the upper side of the lower housing 120 and may cover one open side surface of the lower housing 120.

[0069] The lower housing 120 may include a receiving portion 127 and a flange portion 128. The receiving portion 127 has a receiving space formed for accommodating an electrode assembly. The flange portion 128 surrounds an open side surface of the receiving portion 127 (e.g., around its periphery). For example, the receiving portion 127 of the lower housing 120 may include a bottom surface 140 and a sidewall portion 150. The bottom surface 140 is spaced apart from the flange portion 128, and the sidewall portion 150 joins the flange portion 128 and the bottom surface 140 together. The sidewall portion 150 may include a first side surface 152 adjacent to a short side of the bottom surface 140, a second side surface 154 facing or opposite to the first side surface 152, a third side surface 156 adjacent to a long side of the bottom surface 140, and a fourth side surface 158 facing or opposite to the third side surface 156. Figure 3 As shown, a first electrode terminal electrically connected to a first electrode, a second electrode terminal electrically connected to a second electrode, and an electrolyte injection port serving as a channel for electrolyte injection can be disposed in at least a portion of the first side surface 152 of the lower housing 120. Therefore, the first side surface 152 can be defined as a surface in which the first electrode terminal, the second electrode terminal, and the electrolyte injection port are disposed, but this disclosure is not limited thereto.

[0070] The flange portion 128 of the lower housing 120 may be a region that contacts and engages with at least a portion of the upper cover 130. For example, at least a portion of the upper cover 130 and the flange portion 128 of the lower housing 120 may be joined to each other by welding, brazing, soldering, and / or similar methods. As an example, at least a portion of the upper cover 130 and the flange portion 128 of the lower housing 120 may be joined to each other by laser welding. However, this disclosure is not limited thereto, and various suitable methods for joining the upper cover 130 and the lower housing 120 to seal the housing may be used as methods for joining the housing of the secondary battery. Furthermore, after the upper cover 130 and the lower housing 120 are joined to each other, at least a portion of the flange portion 128 may be laser-cut to increase the energy density of the secondary battery 100.

[0071] Despite Figure 3The diagram shows a plate-shaped upper cover 130, but the shape of the upper cover 130 is not limited to this, and the shape of the upper cover 130 may be the same as or similar to the shape of the lower housing 120. For example, like the lower housing 120, the upper cover 130 may include a region in which an internal space is formed in the central region of the upper cover 130 by pressing the upper cover 130 by a pressing process. In addition, regions extending in four directions, such as the flange portion 128 of the lower housing 120, may be formed in the lower edge portion of the upper cover 130. For example, the flange portions formed in the upper cover 130 and the lower housing 120 respectively may face each other and may engage with each other, and the electrode assembly may be accommodated in a receiving space formed by engaging the upper cover 130 and the lower housing 120 with each other.

[0072] Figure 4 This is a perspective view of the lower housing 120 as viewed from below, according to some embodiments of the present disclosure. Figure 4 The perspective view of the lower housing 120 shown may be shown when it is on the lower side (e.g., Figure 3 When observing in the Z direction Figure 3 A view of the lower housing 120.

[0073] like Figure 4 As shown, the lower housing 120 according to some embodiments of the present disclosure may include a flange 128 surrounding an open side surface of the receiving portion (e.g., around its periphery), a bottom surface 140 spaced apart from the flange 128, and a sidewall portion joining the flange 128 and the bottom surface 140 to each other. For example, the sidewall portion may include a first side surface adjacent to a short side of the bottom surface 140, a second side surface 154 facing or opposite to the first side surface, a third side surface 156 adjacent to a long side of the bottom surface 140, and a fourth side surface facing or opposite to the third side surface 156.

[0074] In some embodiments, the edges of the sidewall portion joined to one side surface of the side surface adjacent to said side surface can be rounded. For example, the edges where the first side surface and the third side surface 156 join each other can be rounded. In this example, the edges where the first side surface and the third side surface 156 join each other can be formed into rounded shapes in which a surface having a first radius of curvature R1 and a surface having a second radius of curvature R2 join each other. Similarly, each of the edges where the first side surface and the fourth side surface join each other, the edges where the second side surface 154 and the third side surface 156 join each other, and the edges where the second side surface 154 and the fourth side surface join each other can be formed into rounded shapes in which a surface having a first radius of curvature R1 and a surface having a second radius of curvature R2 join each other.

[0075] In some embodiments, a surface having a first radius of curvature R1 may be adjacent to at least one of a first side surface or a second side surface 154, and a surface having a second radius of curvature R2 may be adjacent to at least one of a third side surface 156 or a fourth side surface. For example, the edges where the first side surface and the third side surface 156 meet may be formed into a rounded shape in which the surface having the first radius of curvature R1 and the surface having the second radius of curvature R2 meet. In this example, the first side surface and the surface having the first radius of curvature R1 may be adjacent to each other, and the third side surface 156 and the surface having the second radius of curvature R2 may be adjacent to each other. For example, the side surfaces and the surfaces may meet each other in the order of the first side surface, the surface having the first radius of curvature R1, the surface having the second radius of curvature R2, and the third side surface 156. Therefore, the surface having a first radius of curvature R1 can be defined as a portion of the short side surface of the side wall of the lower housing 120, and the surface having a second radius of curvature R2 can be defined as a portion of the long side surface of the side wall of the lower housing 120.

[0076] In some embodiments, the first radius of curvature R1 may be larger than the second radius of curvature R2. For example, if the second radius of curvature R2 is 2.0 mm (e.g., when the second radius of curvature R2 is 2.0 mm), the first radius of curvature R1 may be in the range of 3.0 mm to 6.0 mm, which is larger than the second radius of curvature R2. However, this disclosure is not limited thereto, and the dimensions of the first radius of curvature R1 and the second radius of curvature R2 may be modified to values ​​different from those described above.

[0077] In some embodiments, the edges where the bottom surface 140 and the sidewall portion meet can be rounded. For example, each of the edges where the bottom surface 140 meets the first side surface and the edges where the bottom surface 140 meets the second side surface 154 can be formed as a curved surface with a third radius of curvature R3. Each of the edges where the bottom surface 140 meets the third side surface 156 and the edges where the bottom surface 140 meets the fourth side surface can be formed as a curved surface with a fourth radius of curvature R4. Therefore, the edge where the bottom surface 140 meets the short side surface can be formed as a curved surface with a third radius of curvature R3, and the edge where the bottom surface 140 meets the long side surface can be formed as a curved surface with a fourth radius of curvature R4. For example, the dimension of the third radius of curvature R3 can be the same as or substantially the same as the dimension of the fourth radius of curvature R4, but this disclosure is not limited thereto.

[0078] In some embodiments, at least one of the dimensions of the first radius of curvature R1, the third radius of curvature R3, or the fourth radius of curvature R4 may increase as the thickness of the lower housing 120 decreases. (See below for reference.) Figure 7 To describe it in more detail, even when the surfaces have the same or substantially the same radius of curvature, as the thickness of the lower housing 120 decreases, the strength of each edge of the lower housing 120 can decrease, and therefore, the probability of cracks appearing in the corresponding edges in response to external impacts, etc., can increase. Therefore, when the thickness of the lower housing 120 decreases, the probability of cracks appearing in each edge of the lower housing 120 can be effectively reduced by controlling at least one of the dimensions of the first radius of curvature R1, the third radius of curvature R3, or the fourth radius of curvature R4. As an example, the thickness of the lower housing 120 can be in the range of 0.02 mm to 0.1 mm. The dimension of the first radius of curvature R1 can be in the range of 2.0 mm to 6.0 mm. In another example, the thickness of the lower housing 120 can be in the range of 0.02 mm to 0.04 mm, and the dimension of the first radius of curvature R1 can be in the range of 3.0 mm to 6.0 mm. When the thickness of the lower housing 120 is in the range of 0.02 mm to 0.04 mm and the size of the first radius of curvature R1 is equal to or greater than 3.0 mm, cracks that may occur in the lower housing 120 can be effectively prevented.

[0079] In some embodiments, the dimension of the first radius of curvature R1 can increase with the increase of the depth of the receiving portion of the lower housing 120. Even if the surfaces have the same radius of curvature as each other (e.g., when the surfaces have the same radius of curvature as each other), as the depth of the receiving portion increases, the strength of each edge of the sidewall portion of the lower housing 120 can decrease, thus increasing the likelihood that cracks may appear in the corresponding edges. The depth of the receiving portion and the dimension of the first radius of curvature R1 can be factors related to the likelihood of cracks appearing in the lower housing 120. Therefore, by controlling the dimension of the first radius of curvature R1, the likelihood of cracks appearing in each edge of the adjacent side surfaces of the sidewall portion of the lower housing 120 joining each other can be effectively reduced as the depth of the receiving portion increases. As an example, the depth of the receiving portion can be greater than 0 mm and equal to or less than 5.0 mm.

[0080] Figure 5 It is along Figure 4 The cross-sectional view of the lower housing 120 is shown by line AA.

[0081] Reference Figure 5 The lower housing 120 may include a bottom surface 140, a flange 128, and a side wall portion 150 that joins the flange 128 and the bottom surface 140 together. For example, the side wall portion 150 may include a first side surface 152 and a second side surface 154 corresponding to the short side surface, and a third side surface 156 and a fourth side surface 158 corresponding to the long side surface.

[0082] In some embodiments, the edges where adjacent side surfaces of the sidewall portion meet each other can be rounded. For example, the edges where the first side surface 152 and the third side surface 156 meet each other can be rounded. In this example, the edges where the first side surface 152 and the third side surface 156 meet each other can be formed into rounded shapes in which surfaces having a first radius of curvature R1 and surfaces having a second radius of curvature R2 meet each other. Similarly, each of the edges where the first side surface 152 and the fourth side surface 158 meet each other, the edges where the second side surface 154 and the third side surface 156 meet each other, and the edges where the second side surface 154 and the fourth side surface 158 meet each other can be formed into rounded shapes in which surfaces having a first radius of curvature R1 and surfaces having a second radius of curvature R2 meet each other.

[0083] In some embodiments, a surface having a first radius of curvature R1 may be adjacent to at least one of a first side surface 152 or a second side surface 154, and a surface having a second radius of curvature R2 may be adjacent to at least one of a third side surface 156 or a fourth side surface 158. For example, the edges where the first side surface 152 and the third side surface 156 meet may be formed into a rounded shape in which the surface having the first radius of curvature R1 and the surface having the second radius of curvature R2 meet each other. In this example, the first side surface 152 and the surface having the first radius of curvature R1 may be adjacent to each other, and the third side surface 156 and the surface having the second radius of curvature R2 may be adjacent to each other. For example, as Figure 5 As shown, the side surface and the curved surface can be combined with each other in the following order: first side surface 152, curved surface with a first radius of curvature R1, curved surface with a second radius of curvature R2, and third side surface 156. Therefore, the curved surface with the first radius of curvature R1 can be defined as the portion that combines with the short side surface of the side wall portion of the lower housing 120, and the curved surface with the second radius of curvature R2 can be defined as the portion that combines with the long side surface of the side wall portion of the lower housing 120.

[0084] In some embodiments, the size of the first radius of curvature R1 may increase as the thickness of the lower housing 120 decreases. In some embodiments, the size of the first radius of curvature R1 may be larger than the size of the second radius of curvature R2. In other embodiments, the size of the first radius of curvature R1 may increase as the depth of the receiving portion of the lower housing 120 increases. In this case, the size of the first radius of curvature R1 may also be larger than the size of the second radius of curvature R2.

[0085] When the thickness of the lower housing 120 is thinner or the depth of the receiving portion is deeper to improve the energy density of the secondary battery, even if the curved surfaces have the same radius of curvature, the possibility of cracks appearing at the edges where adjacent side surfaces of the sidewall portion of the lower housing 120 are joined together can be increased. When the thickness of the lower housing 120 is reduced or the depth of the receiving portion of the lower housing 120 is increased, the size of the first radius of curvature R1 or the second radius of curvature R2 can be increased, thereby preventing or substantially preventing cracks from appearing in the lower housing 120. However, increasing the size of the first radius of curvature R1 or the second radius of curvature R2 can lead to a reduction in the size of the receiving space inside the lower housing 120 that accommodates the electrode assembly, as will be discussed below. Figure 6 To describe in more detail. Therefore, in some embodiments of the secondary battery according to this disclosure, each edge of the sidewall portion can be formed as a rounded shape in which a surface having a first radius of curvature R1 and a surface having a second radius of curvature R2 combine with each other. Therefore, by changing the size of the first radius of curvature R1 (e.g., changing only the size of the first radius of curvature R1) without changing the size of the second radius of curvature R2, the reduction in the size of the receiving space accommodating the electrode assembly inside the lower housing 120 can be minimized or reduced, and simultaneously, cracks that may occur in the lower housing 120 can be prevented or substantially prevented. Therefore, some embodiments of this disclosure can increase the energy density of the secondary battery while simultaneously preventing or substantially preventing cracks that may occur in the lower housing 120.

[0086] Figure 6 The dimensions of the receiving space accommodating the electrode assembly vary depending on the radius of curvature.

[0087] Reference Figure 6 Examples of various lower housings 600 are shown as overlapping each other. For example, three lower housings 600 may have the same horizontal and vertical lengths, but may include edges with radii of curvature that are different from each other. Figure 6 The example of the lower housing 600 shown corresponds to a plan view of the lower housing 600 when viewed from above, and for ease of explanation, the flange portion of the lower housing 600 may be omitted.

[0088] In the lower housing 600_a according to the first example, each edge joining adjacent side surfaces of the sidewall portion can be formed as a curved surface with a radius of curvature Ra. In the lower housing 600_b according to the second example, each edge joining adjacent side surfaces of the sidewall portion can be formed as a curved surface with a radius of curvature Rb. In the lower housing 600_c according to the third example, each edge joining adjacent side surfaces of the sidewall portion can be formed as a curved surface with a radius of curvature Rc. In these examples, the dimension of the radius of curvature Ra can be larger than the dimension of the radius of curvature Rb, and the dimension of the radius of curvature Rb can be larger than the dimension of the radius of curvature Rc.

[0089] like Figure 6 As shown, as the radius of curvature increases, the size of the receiving space inside the lower housing 600 that houses the electrode assembly can be reduced. For example, the vertical length La of the receiving space of the lower housing 600_a with a radius of curvature Ra can be smaller than the vertical length Lb of the receiving space of the lower housing 600_b with a radius of curvature Rb. Similarly, the vertical length Lb of the receiving space of the lower housing 600_b with a radius of curvature Rb can be smaller than the vertical length Lc of the receiving space of the lower housing 600_c with a radius of curvature Rc. Therefore, reducing the radius of curvature is desirable in order to increase the receiving space inside the lower housing 600, or in other words, to improve the energy density of the secondary battery.

[0090] Figure 7 The diagram shows the appearance of cracks as the radius of curvature decreases. Figure 7 The lower housing 120 shown can be with Figure 4 The lower shell 120 is the same or substantially the same.

[0091] Reference Figure 7 Due to external impacts, cracks may appear at the edges where the sidewalls of the lower housing 120 and the bottom surface 140 meet. For example, cracks may appear at the edges where the second side surface 154 and the bottom surface 140 meet, the edges where the third side surface 156 and the bottom surface 140 meet, or the edges where the second side surface 154 and the third side surface 156 meet. More specifically, as... Figure 7As shown, cracks can appear at apexes where the edges where the second side surface 154 and the bottom surface 140 meet, the edges where the third side surface 156 and the bottom surface 140 meet, and the edges where the second side surface 154 and the third side surface 156 meet meet. Furthermore, cracks can appear at the edges where the bottom surface 140 and the sidewall portion of the lower housing 120 meet. For example, cracks can appear at the edges where the second side surface 154 and the bottom surface 140 meet, or at the edges where the third side surface 156 and the bottom surface 140 meet. For example, cracks can appear at the edges where the first side surface and the bottom surface 140 meet, or at the edges where the fourth side surface and the bottom surface 140 meet. The appearance of cracks can be due to a reduction in the radius of curvature of each edge while maintaining an equal thickness of the lower housing 120. For example, to improve the energy density of the secondary battery, a reduction in the radius of curvature of each edge of the lower housing 120 can lead to the appearance of cracks.

[0092] In the lower housing 120 according to some embodiments of the present disclosure, at least one edge of the sidewall portion can be formed into a rounded shape in which a curved surface having a first radius of curvature R1 and a curved surface having a second radius of curvature R2 are combined with each other, and the first radius of curvature R1 can be larger than the second radius of curvature R2. Furthermore, the dimension of the first radius of curvature R1 can decrease with the thickness of the lower housing 120 or increase with the depth of the receiving portion. Therefore, the dimension of the first radius of curvature R1 can be modified differently without significantly changing the dimension of the second radius of curvature R2. Thus, some embodiments of the present disclosure can increase the energy density of the secondary battery while simultaneously preventing or substantially preventing cracks that may occur in the lower housing 120.

[0093] Figure 8 It is a table indicating the appearance of cracks according to a change in a first radius of curvature, based on some embodiments of this disclosure.

[0094] refer to Figure 8 In the manufacture of a secondary battery casing, the receiving portion of the lower casing is formed by molding a flat plate made of stainless steel (SUS). Figure 1 When (127), the test results for the appearance of cracks in each edge of the lower shell, based on the thickness of the lower shell, are shown. For example... Figure 8 As shown, for example, fixed values ​​such as 4.5 mm and 2.4 mm are used as the depth and second radius of curvature of the receiving part, respectively (e.g., Figure 5 R2).

[0095] When forming the receiving portion of the lower housing by molding a flat plate made of stainless steel (SUS), if the thickness of the lower housing is in the range of 0.06 mm to 0.1 mm (e.g., when the thickness of the lower housing is in the range of 0.06 mm to 0.1 mm), even when the first radius of curvature (e.g., Figure 5 When the dimension of R1 is 2.4 mm (which is the same as the dimension of the second radius of curvature), no cracks will appear at the edge of the lower shell. The test results show that when the dimensions of the first radius of curvature and the second radius of curvature are about 2.4 mm, even when the thickness of the lower shell is formed to be as thin as about 0.06 mm, the possibility of cracks appearing at the edge of the lower shell is low.

[0096] When forming the receiving portion of the lower housing by molding a flat plate made of stainless steel (SUS), if the thickness of the lower housing is approximately 0.04 mm and the dimension of the first radius of curvature is 2.4 mm (which is the same as the dimension of the second radius of curvature) (e.g., when the thickness of the lower housing is approximately 0.04 mm and the dimension of the first radius of curvature is 2.4 mm (which is the same as the dimension of the second radius of curvature)), cracks may appear at the edges of the lower housing. Therefore, when the dimensions of the first and second radii of curvature are approximately 2.4 mm, if the thickness of the lower housing is thinned to be equal to or less than approximately 0.04 mm (e.g., when the thickness of the lower housing is thinned to be equal to or less than approximately 0.04 mm), the possibility of cracks appearing at the edges of the lower housing may increase. However, if the first radius of curvature is 3.4 mm or 4.4 mm (which is larger than the dimension of the second radius of curvature) (e.g., when the first radius of curvature is 3.4 mm or 4.4 mm (which is larger than the dimension of the second radius of curvature)), cracks may not appear at the edges of the lower housing. Therefore, by controlling the size of the first radius of curvature, cracks can be effectively prevented from appearing at the edge of the lower housing without significantly changing the size of the receiving space of the lower housing.

[0097] Similarly, when forming the receiving portion of the lower housing by molding a flat plate made of stainless steel (SUS), if the thickness of the lower housing is about 0.02 mm and the dimension of the first radius of curvature is in the range of about 2.4 mm to 4.4 mm (e.g., when the thickness of the lower housing is about 0.02 mm and the dimension of the first radius of curvature is in the range of about 2.4 mm to 4.4 mm), cracks may appear in the edges of the lower housing. However, if the first radius of curvature is 5.4 mm (e.g., when the first radius of curvature is 5.4 mm), cracks may not appear in the edges of the lower housing.

[0098] Furthermore, when forming the receiving part of the lower housing by molding a flat plate made of stainless steel (SUS), Figure 8The test results shown can also be applied to test results regarding the appearance of cracks at the edge of the lower housing based on the depth of the receiving portion. For example, when the thickness of the lower housing is approximately 0.1 mm and the dimensions of the first and second radii of curvature are each 2.4 mm, if the depth of the receiving portion is increased to greater than 4.5 mm (e.g., when the depth of the receiving portion increases to greater than 4.5 mm), cracks may appear at the edge of the lower housing at that specific depth of the receiving portion. Even in this example, the appearance of cracks at the edge of the lower housing can be improved by increasing the dimension of the first radius of curvature.

[0099] Figure 9 This is an exploded perspective view showing a pouch-type secondary battery according to some embodiments of the present disclosure. Figure 10 This is a cross-sectional view showing a pouch-type secondary battery according to some embodiments of the present disclosure.

[0100] Reference Figure 9 The secondary battery 900 may include an electrode assembly 910 and a housing 920 that accommodates the electrode assembly 910.

[0101] The electrode assembly 910 may include a negative electrode plate as a first electrode plate, a positive electrode plate as a second electrode plate, and a diaphragm inserted therebetween. The negative electrode plate may include a negative electrode tab 912a electrically connected to an uncoated portion of the negative electrode. The positive electrode plate may include a positive electrode tab 912b electrically connected to an uncoated portion of the positive electrode. The negative electrode tab 912a and positive electrode tab 912b may be soldered to negative electrode leads 916a and positive electrode leads 916b of external terminals for electrical connection to the outside. A tab membrane 914 for insulation from the bag may be attached to the negative electrode leads 916a and positive electrode leads 916b.

[0102] The housing 920 may include an upper cover 922 and a lower housing 924. For example, the upper cover 922 may have a plate shape. The lower housing 924 may include a receiving portion for receiving the electrode assembly 910, and a flange portion surrounding an open side surface of the receiving portion (e.g., around its periphery). With the electrode assembly 910 received in the receiving portion of the lower housing 924, the flange portion of the lower housing 924 and a portion of the upper cover 922 may contact each other, such that the upper cover 922 and the lower housing 924 can be sealed. For example, this portion of the upper cover 922 may correspond to the area facing the flange portion of the lower housing 924.

[0103] In some embodiments, at least a portion of the upper cover 922 and / or the lower cover 924 of the housing 920 may have a stacked structure comprising a metal layer 930, an adhesive layer 932 in contact with the metal layer 930, and a polymer layer 934 in contact with the adhesive layer 932. In this example, the metal layer 930 may comprise stainless steel (SUS).

[0104] In some embodiments, reference Figure 10 In the sealing area SP1, when the flange of the lower housing 924 and a portion of the upper cover 922 are in contact with each other for sealing, the polymer layer 934 of the upper cover 922 and the polymer layer 934 of the lower housing 924 can be bonded to each other. For example, at least a portion of the upper cover 922 and the flange of the lower housing 924 can be bonded to each other by thermal fusion of the polymer layers of the stacked structure, but this disclosure is not limited thereto.

[0105] In some embodiments, the edges where adjacent side surfaces of the sidewall portion of the lower housing 924 meet each other can be rounded. For example, each edge where adjacent side surfaces of the sidewall portion of the lower housing 924 meet each other can be formed as a rounded shape in which a surface having a first radius of curvature R1 and a surface having a second radius of curvature R2 meet each other. The surface having the first radius of curvature R1 can be joined to the short side surface of the sidewall portion of the lower housing 924, and the surface having the second radius of curvature R2 can be joined to the long side surface of the sidewall portion of the lower housing 924. The first radius of curvature R1 and the second radius of curvature R2 can be referenced above. Figures 4 to 8 The descriptions are identical or substantially the same; therefore, their redundant descriptions need not be repeated below. Furthermore, as... Figure 4 As shown, the edge where the bottom surface and sidewall of the lower housing 924 meet can be rounded. For example, the edge where the bottom surface and the short side surface meet can be formed with a third radius of curvature (e.g., Figure 4 The surface of the curve (R3) and the edge where the bottom surface and the long side surface meet each other can be formed to have a fourth radius of curvature (e.g., R3). Figure 4 The surface of radius R4 in the diagram. In this example, the dimension of the third radius of curvature may be the same as or substantially the same as the dimension of the fourth radius of curvature, but this disclosure is not limited thereto.

[0106] While some embodiments of this disclosure have been described above, this disclosure is not limited thereto. Those skilled in the art can make various modifications and variations to it within the spirit and scope of this disclosure as defined by the appended claims and their equivalents.

[0107] Explanation of some figure labels

[0108] 100: Secondary battery

[0109] 110: Electrode assembly

[0110] 112: First electrode connector

[0111] 114: Second electrode connector

[0112] 120: Lower housing

[0113] 122: First electrode terminal

[0114] 124: Second electrode terminal

[0115] 126: Electrolyte injection port

[0116] 127: Receiving Department

[0117] 128: Flange portion

[0118] 130: Top Cover

[0119] 140: Bottom surface

[0120] 150: Side wall portion

[0121] 152: First side surface

[0122] 154: Second side surface

[0123] 156: Third side surface

[0124] 158: Fourth side surface

Claims

1. A secondary battery, comprising: An electrode assembly includes a first electrode, a second electrode, and a diaphragm inserted between the first electrode and the second electrode; The lower housing includes a receiving portion having a receiving space for accommodating the electrode assembly, and a flange portion surrounding an open side surface of the receiving portion; as well as The upper cover is attached to the flange portion of the lower housing and seals the open side surface of the receiving portion. The receiving portion of the lower housing includes a bottom surface spaced apart from the flange portion and a side wall portion connecting the flange portion and the bottom surface to each other. Wherein, at least one edge of the sidewall portion has a rounded shape, the rounded shape comprising a surface having a first radius of curvature and a surface having a second radius of curvature, the surface having the second radius of curvature being coupled to the surface having the first radius of curvature, and The first radius of curvature is greater than the second radius of curvature.

2. The secondary battery according to claim 1, wherein at least one of the upper cover and the lower housing comprises stainless steel (SUS).

3. The secondary battery according to claim 1, wherein the dimension of the first radius of curvature increases as the thickness of the lower housing decreases.

4. The secondary battery according to claim 1, wherein the thickness of the lower casing is in the range of 0.02 mm to 0.1 mm.

5. The secondary battery according to claim 1, wherein the thickness of the lower casing is in the range of 0.02 mm to 0.04 mm, and the dimension of the first radius of curvature is in the range of 3.0 mm to 6.0 mm.

6. The secondary battery according to claim 1, wherein the first radius of curvature is in the range of 2.0 mm to 6.0 mm.

7. The secondary battery according to claim 1, wherein the depth of the receiving portion is greater than 0 mm and equal to or less than 5.0 mm.

8. The secondary battery according to claim 1, wherein, The sidewall portion includes: The first side surface is connected to a short side of the bottom surface; The second side surface faces the first side surface; The third side surface is connected to a long side of the bottom surface; and The fourth side surface faces the third side surface.

9. The secondary battery of claim 8, wherein a first electrode terminal electrically connected to the first electrode and a second electrode terminal electrically connected to the second electrode are located on at least a portion of the first side surface.

10. The secondary battery of claim 8, wherein each of the edges where the first side surface and the third side surface meet each other, the edges where the first side surface and the fourth side surface meet each other, the edges where the second side surface and the third side surface meet each other, and the edges where the second side surface and the fourth side surface meet each other has a rounded shape in which the surface having the first radius of curvature and the surface having the second radius of curvature meet each other.

11. The secondary battery of claim 10, wherein the curved surface having the first radius of curvature is connected to at least one of the first side surface and the second side surface, and The surface having the second radius of curvature is connected to at least one of the third side surface and the fourth side surface.

12. The secondary battery of claim 10, wherein each of the edges where the bottom surface and the first side surface meet each other, and the edges where the bottom surface and the second side surface meet each other, has a surface having a third radius of curvature. Each of the edges where the bottom surface and the third side surface meet each other, and the edges where the bottom surface and the fourth side surface meet each other, has a surface with a fourth radius of curvature.

13. The secondary battery according to claim 12, wherein the third radius of curvature is the same as the fourth radius of curvature.

14. The secondary battery according to claim 12, wherein the dimensions of the third radius of curvature and the fourth radius of curvature increase as the thickness of the lower housing decreases.

15. The secondary battery of claim 1, wherein at least a portion of the upper cover is laser welded to the flange of the lower housing.

16. The secondary battery of claim 1, wherein at least a portion of the upper cover and each of the flanges of the lower housing have a stacked structure, the stacked structure comprising: Metal layer; An adhesive layer in contact with the metal layer; as well as The polymer layer in contact with the adhesive layer, and The at least portion of the upper cover is joined to the flange of the lower housing by thermally fusing the polymer layer in at least a portion of the upper cover and the polymer layer in the flange of the lower housing with each other.

17. A casing for a secondary battery, comprising: The lower housing includes a receiving portion having a receiving space for accommodating an electrode assembly, and a flange portion surrounding an open side surface of the receiving portion; as well as The upper cover is attached to the flange portion of the lower housing and seals the open side surface of the receiving portion. The receiving portion of the lower housing includes a bottom surface spaced apart from the flange portion, and a side wall portion connecting the flange portion and the bottom surface to each other. Wherein, at least one edge of the sidewall portion has a rounded shape, the rounded shape comprising a surface having a first radius of curvature and a surface having a second radius of curvature, the surface having the second radius of curvature being coupled to the surface having the first radius of curvature, and The first radius of curvature is greater than the second radius of curvature.

18. The housing for a secondary battery according to claim 17, wherein the sidewall portion comprises: The first side surface is connected to a short side of the bottom surface; The second side surface faces the first side surface; The third side surface is connected to one long side of the bottom surface; as well as The fourth side surface faces the third side surface.

19. The housing for a secondary battery according to claim 18, wherein each of the edges where the first side surface and the third side surface meet each other, the edges where the first side surface and the fourth side surface meet each other, the edges where the second side surface and the third side surface meet each other, and the edges where the second side surface and the fourth side surface meet each other has a rounded shape in which the surface having the first radius of curvature and the surface having the second radius of curvature meet each other.

20. The housing for a secondary battery according to claim 19, wherein the curved surface having the first radius of curvature is connected to at least one of the first side surface and the second side surface, and The surface having the second radius of curvature is connected to at least one of the third side surface and the fourth side surface.

Images