Lithium secondary battery comprising battery case having one surface formed of laminate sheet and other surfaces formed of rigid material, and battery pack comprising same

Abstract

According to an embodiment of the present invention, provided is a lithium secondary battery comprising: an electrode assembly; and a battery case, wherein the battery case has a structure in which the electrode assembly is embedded ; in the battery case, among longitudinal surfaces perpendicular to a stacking direction of the electrode assembly one surface is formed of a laminate sheet which is deformable by pressure and the remaining surfaces are formed of a rigid material; and the lengths of at least one pair of opposite sides among four sides defining the one surface among the longitudinal surfaces are larger than the lengths of sides, corresponding to the pair of opposite sides, of the other surface among the longitudinal surfaces.

Description

A lithium secondary battery comprising a battery case having one side made of a laminate sheet and the other sides made of a rigid material, and a battery pack comprising the same.

[0001] Cross-citation with related application(s)

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0193384 filed on December 20, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of the specification. The present invention relates to a lithium secondary battery comprising a battery case having one side made of a laminate sheet and other sides made of a rigid material, and a battery pack comprising the same.

[0003] Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative or clean energy, and as part of this, the fields of power generation and energy storage utilizing electrochemistry are the most actively researched.

[0004] Currently, a representative example of an electrochemical device utilizing such electrochemical energy is the secondary battery, and its scope of application is steadily expanding.

[0005] Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has been rapidly increasing. Among these secondary batteries, a lot of research has been done on environmentally friendly lithium secondary batteries that exhibit high charge / discharge characteristics and lifespan characteristics, and they have also been commercialized and are widely used.

[0006] Generally, lithium secondary batteries have a structure in which an electrode assembly, consisting of a positive electrode, a negative electrode, and a porous separator, is impregnated with a non-aqueous electrolyte and housed in a battery case.

[0007] At this time, the above lithium secondary battery is generally classified according to the shape of the battery case into cylindrical or prismatic secondary batteries in which a stack / folding or wound electrode assembly is housed in a metal can as the battery case, and pouch-type batteries having a structure in which a stack or stack / folding electrode assembly is embedded in a pouch-type battery case made of an aluminum laminate sheet.

[0008] Here, prismatic batteries have an advantage over pouch-type batteries in terms of safety, and furthermore, prismatic batteries have the advantage of having a higher energy density than cylindrical batteries in terms of shape.

[0009] However, since the above-mentioned prismatic battery is manufactured using a rigid material such as metal in the form of a rectangular can, due to the rigidity and shape of the battery case, it exists only in the form of a positioning jig and cannot be pressed with the desired force.

[0010] On the other hand, pouch-type batteries are composed of laminate sheets with overall low rigidity, so they cannot sufficiently ensure safety.

[0011] Therefore, there is a need to develop technology for lithium secondary batteries that can apply desired pressure for control while ensuring the safety of each individual battery.

[0012] The objective of the present invention is to provide a lithium secondary battery that can control the pressure applied by a user to the lithium secondary battery while ensuring safety for individual lithium secondary batteries.

[0013] According to one embodiment of the present invention, a lithium secondary battery comprising an electrode assembly and a battery case, wherein the battery case has a structure for housing the electrode assembly,

[0014] In the battery case above, one of the rectangular surfaces perpendicular to the stacking direction of the electrode assembly is made of a laminate sheet capable of shape deformation by pressure, and the remaining surfaces are made of a rigid material.

[0015] A lithium secondary battery is provided in which the length of at least one pair of opposite sides among the lengths of the four sides forming one of the above-mentioned rectangular sides is longer than the length of the other side among the above-mentioned rectangular sides corresponding to the pair of sides.

[0016] At this time, the battery case comprises a main body having one side open and a storage portion for housing the electrode assembly, and a top cap coupled to the open side of the main body to seal the electrode assembly, and the laminate sheet may be formed on one of the longitudinal surfaces of the main body.

[0017] Alternatively, the battery case comprises a first case having a structure with one side open and a storage portion formed to accommodate the electrode assembly, and a second case coupled to the open portion of the first case to seal the electrode assembly.

[0018] The first case above may be made of the rigid material, and the second case may be made of a laminate sheet.

[0019] The battery case comprises a first case having a structure with one side open and a storage portion formed to accommodate the electrode assembly, and a second case coupled to the open portion of the first case to seal the electrode assembly.

[0020] The longitudinal surface of the storage portion of the first case may be made of a laminate sheet, and the other surface of the first case and the second case may be made of the rigid material. Here, the laminate sheet may include an outer coating layer, a metal layer, and an inner sealant layer, and the rigid material may be aluminum, aluminum alloy, stainless steel, nickel, nickel-plated iron, special reinforced plastic, or a combination thereof.

[0021] In the above lithium secondary battery, the laminate sheet may be indented into the inner side where the electrode assembly is embedded by applying pressure.

[0022] In this way, the length of at least one pair of sides facing each other among the lengths of the four sides forming one of the rectangular surfaces made of the laminate sheet may be 101% to 120% of the length of the other side among the rectangular surfaces corresponding to the pair of sides.

[0023] More specifically, the length of the four sides forming one of the above rectangular faces may be 101% to 120% of the length of the four sides forming the other side of the above rectangular faces corresponding thereto.

[0024] Meanwhile, in the portion corresponding to another surface among the above-mentioned rectangular surfaces, where the portion is located within one surface among the above-mentioned rectangular surfaces, a reinforcing material may be formed on one surface among the above-mentioned rectangular surfaces. Here, the reinforcing material may be a metal or a polymer.

[0025] According to another embodiment of the present invention, a battery pack in which two or more lithium secondary batteries are arranged,

[0026] The above two or more lithium secondary batteries are arranged such that one of the longitudinal surfaces of one lithium secondary battery faces the other of the longitudinal surfaces of another lithium secondary battery adjacent to the one lithium secondary battery.

[0027] A battery pack is provided in which, by applying pressure, another surface among the longitudinal surfaces of the adjacent lithium secondary battery indents one surface of the lithium secondary battery inward.

[0028] At this time, another surface among the longitudinal surfaces of the adjacent lithium secondary battery may indent one surface of the lithium secondary battery inwardly, thereby reinforcing the rigidity of one surface of the lithium secondary battery.

[0029] Meanwhile, a reinforcing material may be formed in the portion where the side forming the other side among the longitudinal surfaces of the adjacent lithium secondary battery is located within one surface among the longitudinal surfaces of the above-mentioned lithium secondary battery.

[0030] At this time, the reinforcing material may be a metal or a polymer.

[0031] FIG. 1 is a schematic cross-sectional view in the stacking direction of a lithium secondary battery according to one embodiment of the present invention.

[0032] FIG. 2 is a perspective view schematically illustrating one example of a lithium secondary battery according to one embodiment of the present invention.

[0033] FIG. 3 is a perspective view schematically illustrating another example of a lithium secondary battery according to one embodiment of the present invention.

[0034] FIG. 4 is a schematic cross-sectional view in the stacking direction to show the change pattern when a lithium secondary battery according to one embodiment of the present invention is pressurized.

[0035] FIG. 5 is a perspective view and a top view schematically illustrating various modified examples of a lithium secondary battery according to one embodiment of the present invention.

[0036] FIG. 6 is a schematic cross-sectional view in the stacking direction of a lithium secondary battery according to another embodiment of the present invention.

[0037] FIG. 7 is a schematic cross-sectional view in the stacking direction to show the change pattern when a battery pack according to one embodiment of the present invention is pressed.

[0038] FIG. 8 is a schematic cross-sectional view in the stacking direction to show the change pattern when a battery pack according to another embodiment of the present invention is pressed.

[0039] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0040] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0041] Furthermore, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and thus the present invention is not necessarily limited to what is illustrated. Thicknesses have been enlarged in the drawings to clearly represent various layers and regions. Additionally, for convenience of explanation, the thickness of some layers and regions has been exaggerated in the drawings.

[0042] Furthermore, throughout the specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0043] Additionally, throughout the specification, "plane" refers to the subject part as viewed from above, and "cross-section" refers to the cross-section of the subject part cut vertically as viewed from the side.

[0044] Furthermore, throughout the specification, “rectangular” refers to the portion having a larger area among the faces forming a three-dimensional object.

[0045] Terms such as “approximately,” “substantially,” etc., used throughout this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which precise or absolute values ​​are mentioned to aid in understanding this invention.

[0046] The terms “width,” “length,” “thickness,” and “breadth” used in this specification are based on their definitions in the specification.

[0047]

[0048] FIG. 1 is a schematic cross-sectional view in the stacking direction of a lithium secondary battery (100) according to one embodiment of the present invention.

[0049] Referring to FIG. 1, the lithium secondary battery (100) includes an electrode assembly (110) and a battery case (120), and has a structure in which the electrode assembly (110) and an electrolyte (not shown in the drawing) are embedded in the battery case (120).

[0050] At this time, the battery case (120) has one surface (122) of the rectangular surfaces perpendicular to the stacking direction of the electrode assembly (110) made of a laminate sheet that can be deformed by pressure, and the remaining surfaces (121) made of a rigid material.

[0051] In addition, among the lengths of the four sides forming one side (122) of the rectangular planes, the length (L) of at least one pair of opposite sides is longer than the length (l) of the other side among the rectangular planes corresponding to the pair of sides.

[0052] Referring to FIGS. 2 and FIGS. 3, examples of lithium secondary batteries having a cross-section similar to that of FIG. 1 are respectively illustrated.

[0053] Specifically, FIG. 2 schematically illustrates a perspective view of a prismatic secondary battery having the same structure as FIG. 1, and FIG. 3 schematically illustrates a perspective view of a pouch-type secondary battery having the same structure as FIG. 1.

[0054] First, referring to FIG. 2, the prismatic secondary battery (200) of FIG. 2 has a structure in which an electrode assembly (210) is embedded in a battery case (220), as described in FIG. 1. Here, the battery case (220) includes a main body (220a) having one side open and a storage portion for embedding the electrode assembly (210), and a top cap (220b) coupled to the open side of the main body (220a) to seal the electrode assembly (210).

[0055] Although not shown in the drawing, the top cap (220b) includes a cap terminal that is subsequently connected to the electrode terminal of the electrode assembly (210).

[0056] In this structure, the surface formed by the laminate sheet may be one surface (222) among the rectangular surfaces of the main body (220a), and thus, the structure has a structure in which the length of at least one pair of sides among the four sides forming one surface (222) is longer than the length of the side of the other side among the corresponding rectangular surfaces.

[0057] In addition, all of the surfaces (221), excluding one surface (222) among the above rectangular surfaces, may be made of a rigid material.

[0058] Referring to FIG. 3 as another example, the pouch-type secondary battery (300) of FIG. 3 also has a structure in which an electrode assembly (310) is embedded in a battery case (320) as described in FIG. 1, and an electrode terminal protruding from the electrode assembly (310) extends outside the battery case (320), and the electrode terminals are connected separately to an external terminal.

[0059] At this time, the battery case (320) has a structure comprising a first case (320a) having a structure with one side open and a storage portion formed to accommodate the electrode assembly (310), and a second case (320b) that is coupled to the open portion of the first case (320a) to seal the electrode assembly (310).

[0060] As described above, although there is a certain difference in the specific shape of the rectangular secondary battery (200) of FIG. 2 and the pouch-type secondary battery (300) of FIG. 3, the battery case (320) of FIG. 3 also has a structure in which, when the first case (320a) and the second case (320b) are combined, the second case (320b), which is one side (322) among the rectangular surfaces, is made of a laminate sheet, and the remaining surfaces (321) are made of a rigid material, and the length of at least one pair of sides among the four sides forming one side (322) among the rectangular surfaces is longer than the length of the side of the other side among the corresponding rectangular surfaces. At this time, as will be explained later, in order for one pouch-type secondary battery (300) to be stacked while indenting the laminate sheet of the second case (320b) of another pouch-type secondary battery (300), the length of the second case (320b) corresponding to the storage portion of the first case (320a) must be longer than the size of the storage portion of the first case (320a), even when based on the storage portion.

[0061] Meanwhile, although not illustrated in the drawing, the battery case comprises a first case having a structure with one side open and a storage portion formed to accommodate the electrode assembly, and a second case coupled to the open portion of the first case to seal the electrode assembly.

[0062] The scope of the present invention also includes cases where the rectangular surface of the storage portion of the first case is made of a laminate sheet, and the other surface of the first case and the second case are made of the rigid material.

[0063] That is, the present invention can be applied when multiple secondary batteries are stacked and the surfaces in contact with adjacent secondary batteries form a rectangular surface.

[0064] In addition, while FIGS. 2 and 3 show the position of the tab in the same direction as an example, it is known that it may be formed in both directions, and the position is not limited as long as it is in a form that enables the operation of the lithium secondary battery.

[0065] Here, the laminate sheet may be a material used in conventional pouch-type secondary batteries, and may include, for example, an outer coating layer, a metal layer, and an inner sealant layer.

[0066] The above-mentioned outer coating layer must not be affected by changes in the external environment and must not exhibit whitening as it is stretched during the molding process of the battery case; therefore, excellent tensile strength and weather resistance are required. For example, the polymer resin constituting the above-mentioned outer coating layer may be a polyester resin such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT); a polyolefin resin such as polyethylene (PE) or polypropylene (PP); a polystyrene resin such as polystyrene; a polyvinyl chloride resin; or a polyvinylidene chloride resin.

[0067] In addition to the function of preventing the ingress of foreign substances such as gas and moisture or the leakage of electrolyte, the metal layer may be made of aluminum (Al), aluminum alloy, or stainless steel to improve the strength of the battery case.

[0068] The metal layer above may be used alone or in combination of two or more materials, and in the case of using a combination of two or more materials, it may be applied in a form that forms a plurality of layered structures or in which different materials are applied partially.

[0069] Since stainless steel is a material with higher strength than aluminum, using stainless steel as the metal layer can improve the formability of the battery case. Therefore, compared to a battery case containing an aluminum layer, the occurrence of pinholes or cracks can be prevented when forming the groove for housing the electrode assembly, and the depth of the electrode assembly housing can also be formed relatively deeper.

[0070] In addition, when stainless steel is used as the metal layer of the battery case, a relatively thin metal layer can be formed compared to aluminum, which reduces the thickness of the battery case and thus enables the manufacture of a secondary battery with increased capacity relative to its volume.

[0071] The above internal resin layer has heat-fusibility (heat-sealability), and a material with low hygroscopicity to the electrolyte can be used to suppress the intrusion of the electrolyte, for example, non-oriented polypropylene (CPP) can be used.

[0072] Accordingly, the lithium secondary battery according to the present invention can be controlled by a user through the above-mentioned laminate sheet.

[0073] Specifically, to explain this, FIG. 4 shows a schematic cross-sectional view in the stacking direction to show the change pattern when the lithium secondary battery (100) of FIG. 1 is pressed.

[0074] Referring to FIG. 4, when pressure (P) is applied to one side (122') among the longitudinal sides of the lithium secondary battery (100'), the one side (122') is made of a laminate sheet and is therefore variable, so it can be indented inwardly into the battery case (120') in which the electrode assembly (110') is embedded. On the other hand, the other sides (121'), excluding the one side (122'), are made of a rigid material and protect the electrode assembly (110').

[0075] In order for one side (122') to be indented inward by the application of pressure (P) in this manner, specifically, the length of a pair of sides (L) on one side (122) among the rectangular sides has a structure that is longer than the length of a side (l) on the other side among the corresponding rectangular sides, specifically, the length of a pair of sides (L) on one side (122) among the rectangular sides may be 101% to 120% of the length of a side (l) on the other side among the corresponding rectangular sides, and more specifically, 102% to 105%.

[0076] If the lengths are similar outside the above range, it is difficult for one of the rectangular surfaces made of the laminate sheet of the lithium secondary battery to be indented inward, and it is undesirable for the other rectangular surface made of the rigid material of the other lithium secondary battery adjacent to the one lithium secondary battery to be inserted inward to complement the flexibility of the portion made of the laminate sheet of the one lithium secondary battery.

[0077] In contrast, if the difference exceeds the aforementioned range and is too large, it results in significant spatial loss, which is undesirable.

[0078] Meanwhile, FIG. 5 shows a perspective view and a top view schematically illustrating various modified examples of a lithium secondary battery according to one embodiment of the present invention.

[0079] Referring to FIG. 5, examples of structures in which one pair of sides forming one of the four sides of a rectangular surface made of a laminate sheet is longer than the other pair of sides forming the other of the corresponding rectangular surfaces are shown in (a) and (b).

[0080] In addition, an example of a structure in which the lengths of all four sides forming one of the above-mentioned rectangular faces are each longer than the lengths of the four sides forming the other of the above-mentioned rectangular faces that correspond thereto is illustrated in (c).

[0081] That is, when lithium secondary batteries are stacked, if the structure allows one of the rectangular surfaces formed by the laminate sheet to be indented inward, it is not limited to but is included in the scope of the present invention.

[0082] Even in a structure where the length of all four sides forming one side of the rectangular faces is longer than the length of the four sides forming the other side of the rectangular faces corresponding thereto, the length of the four sides forming one side of the rectangular faces may be 101% to 120% of the length of the four sides forming the other side of the rectangular faces corresponding thereto, and more specifically, 102% to 105%.

[0083] The above rigid material is a material such as a can used in conventional prismatic batteries, and may be, for example, aluminum, aluminum alloy, stainless steel, nickel, nickel-plated iron, special reinforced plastic, or a combination thereof, and specifically, may be aluminum, aluminum alloy, or stainless steel.

[0084] Therefore, the safety of the lithium secondary battery can be enhanced by the rigid material, and damage to the electrode assembly due to external impact can be effectively prevented. In addition, when a battery pack is manufactured by stacking lithium secondary batteries of this structure, the part where the laminate sheet of one lithium secondary battery comes into contact with the rigid material of another lithium secondary battery adjacent to the one lithium secondary battery becomes most vulnerable to impact when an event occurs, so there is an effect of ensuring a consistent direction of venting when venting occurs.

[0085] Meanwhile, according to another embodiment of the present invention, the safety of the lithium secondary battery may be further enhanced by reinforcing the vulnerable parts of such laminate sheets.

[0086] FIG. 6 schematically illustrates a cross-sectional view of a lithium secondary battery (400) according to another embodiment of the present invention to explain this.

[0087] Referring to FIG. 6, in a portion of a battery case (420) that houses an electrode assembly (410) in a lithium secondary battery (400) according to the present invention, a portion corresponding to another surface (421) among the rectangular surfaces is located within one surface (422) among the rectangular surfaces made of a laminate sheet, and a reinforcing material (430) may be formed on the one surface (422).

[0088] At this time, the reinforcing material is not limited but, for example, may be a metal or a polymer, and may be attached to the laminate sheet with an adhesive or adhesive.

[0089] Here, the metal may be aluminum, aluminum alloy, stainless steel, nickel, nickel-plated iron, as in examples of rigid materials, and specifically may be aluminum, aluminum alloy, or stainless steel, and the polymer may be a material such as a reinforced composite material such as polyolefin, polyethylene terephthalate, polypropylene, polycarbonate, polyamide, epoxy resin, polyurethane, acrylonitrile butadiene styrene (ABS), polyimide (PI), polyetheretherketone (PEEK), polyester resin, carbon fiber reinforced polymer (CFRP), and glass fiber reinforced polymer (GFRP).

[0090] By forming such a reinforcing material (430), the safety problem can be resolved when a laminate sheet, which is vulnerable to external impact and has lower safety compared to the rigid material during battery pack manufacturing, is pushed inward by the rigid material of an adjacent lithium secondary battery.

[0091] Meanwhile, another embodiment of the present invention provides a battery pack in which two or more of these lithium secondary batteries are arranged.

[0092] FIGS. 7 and 8 schematically illustrate cross-sectional views in the stacking direction of examples of these battery packs.

[0093] First, referring to FIG. 7, a battery pack (500) according to one embodiment of the present invention has a structure in which three lithium secondary batteries (510, 520, 530) are stacked.

[0094] In the drawing, a structure in which three lithium secondary batteries (510, 520, 530) are stacked is shown, but the number can be set as needed and is not limited.

[0095] At this time, when looking at the stacked structure of the lithium secondary batteries (510, 520, 530), one side (512) of the longitudinal surfaces of one lithium secondary battery (510) and the other side (521) of the longitudinal surfaces of another lithium secondary battery (520) adjacent to one lithium secondary battery (510) are arranged to face each other, and one side (522) of the longitudinal surfaces of the lithium secondary battery (520) and the other side (531) of the longitudinal surfaces of the lithium secondary battery (530) adjacent thereto are arranged to face each other.

[0096] And, after the lithium secondary batteries (510, 520, 530) are stacked, pressure (P) can be applied in the stacking direction. At this time, due to the pressure, one side (512) of the lithium secondary battery (510) made of a laminate sheet is pushed inward by the other side (521) made of a rigid material of the adjacent lithium secondary battery (520), and one side (522) of the lithium secondary battery (520) made of a laminate sheet is pushed inward by the other side (531) made of a rigid material of the adjacent lithium secondary battery (530).

[0097] At this time, the other side (521) of the lithium secondary battery (520) can act like the one side (511) of the lithium secondary battery (510) while indenting the one side (511) of the lithium secondary battery (510) inward, so the other side (521) of the lithium secondary battery (520), which is made of a rigid material, can protect the electrode assembly of the lithium secondary battery (510), thereby having both the safety of a conventional prismatic secondary battery and the ease of pressure control of a conventional pouch-type secondary battery.

[0098] In addition, since the rigidity of the contact area between the laminate sheet portion of the lithium secondary battery and the portion made of a rigid material of another lithium secondary battery adjacent to the one lithium secondary battery is the weakest, venting occurs in the said area when an event occurs, thereby providing the effect of ensuring a consistent direction of venting.

[0099] Meanwhile, referring to FIG. 8, a battery pack (600) according to one embodiment of the present invention has a structure in which three lithium secondary batteries (610, 620, 630) having a structure as shown in FIG. 6 are stacked.

[0100] At this time, when looking at the stacked structure of the lithium secondary batteries (610, 620, 630), one side (612) of the longitudinal surfaces of one lithium secondary battery (610) and the other side (621) of the longitudinal surfaces of another lithium secondary battery (620) adjacent to the one lithium secondary battery (610) are arranged to face each other.

[0101] And, after the lithium secondary batteries (610, 620, 630) are stacked, pressure (P) can be applied in the stacking direction. At this time, due to the pressure, one side (612) of the lithium secondary battery (610) made of a laminate sheet is indented inward by the other side (621) made of a rigid material of the adjacent lithium secondary battery (620).

[0102] At this time, the other side (621) of the lithium secondary battery (620) can act like the one side (611) of the lithium secondary battery (610) by indenting the one side (611) of the lithium secondary battery (610) inward, so the other side (621) of the lithium secondary battery (620), which is made of a rigid material, can protect the electrode assembly of the lithium secondary battery (610), thereby having both the safety of a conventional prismatic secondary battery and the ease of pressure control of a conventional pouch-type secondary battery.

[0103] Meanwhile, as a difference from FIG. 7, in order to increase the overall rigidity of the lithium secondary battery, a reinforcing material (613) may be formed on one side (611) of the rectangular surfaces of the lithium secondary batteries (610) in a portion corresponding to the other side (621) of the rectangular surfaces located within one side (611) of the rectangular surfaces.

[0104] From this, safety can be reinforced in the part where the safety of the laminate sheet becomes vulnerable in the part that contacts the side of the other side (621) among the longitudinal sides of the lithium secondary battery (620) by the reinforcing material (613).

[0105] Here, specific examples of reinforcing materials (613) are as described above.

[0106] Descriptions of structures or materials constituting other lithium secondary batteries and battery packs are not limited and can be applied as long as they are configurations conventionally known in the art.

[0107]

[0108] Although preferred embodiments of the present invention have been described in detail above with reference to the drawings, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

[0109] [Explanation of the symbol]

[0110] 100, 200, 300, 400, 510, 520, 530, 610, 620, 630: Lithium secondary battery,

[0111] 110, 210, 310, 110', 410: Electrode assembly,

[0112] 120, 220, 320, 120', 420: Battery case,

[0113] 500, 600: Battery pack.

[0114] A lithium secondary battery according to the present invention comprises, wherein one of the rectangular surfaces of a battery case is made of a laminate sheet capable of shape deformation by pressure, and the remaining surfaces are made of a rigid material, and the length of at least one pair of sides of the surface made of the laminate sheet is longer than the length of a corresponding side corresponding to the length of one pair of sides of the surface made of the rigid material. When these are stacked, the laminate sheet portion can be indented by an adjacent lithium secondary battery, thereby enabling pressure control by a user, while the individual lithium secondary battery as a whole can be protected by the rigid material, thus ensuring safety.

[0115] In addition, when an event occurs while the lithium secondary batteries are stacked, venting occurs at the contact point between the laminate sheet portion of one lithium secondary battery and another lithium secondary battery adjacent to the one lithium secondary battery, thereby ensuring a consistent direction of venting.

[0116] Furthermore, if a reinforcing material is formed on the laminate sheet portion facing the inner portion among the sides forming the battery case of another lithium secondary battery adjacent to the one lithium secondary battery, the effect of increasing safety is achieved.

Claims

1. A lithium secondary battery comprising an electrode assembly and a battery case, wherein The above battery case has a structure that houses the above electrode assembly, In the battery case above, one of the rectangular surfaces perpendicular to the stacking direction of the electrode assembly is made of a laminate sheet capable of shape deformation by pressure, and the remaining surfaces are made of a rigid material. A lithium secondary battery in which the length of at least one pair of opposite sides among the lengths of the four sides forming one of the above-mentioned rectangular sides is longer than the length of the other side among the above-mentioned rectangular sides corresponding to the pair of sides.

2. In Paragraph 1, The battery case comprises a main body having one side open and a storage portion for housing the electrode assembly, and a top cap coupled to the open side of the main body to seal the electrode assembly. The above laminated sheet is a lithium secondary battery formed on one of the longitudinal surfaces of the above main body.

3. In Paragraph 1, The battery case comprises a first case having a structure with one side open and a storage portion formed to accommodate the electrode assembly, and a second case coupled to the open portion of the first case to seal the electrode assembly. A lithium secondary battery in which the first case is made of the rigid material and the second case is made of a laminate sheet.

4. In Paragraph 1, The battery case comprises a first case having a structure with one side open and a storage portion formed to accommodate the electrode assembly, and a second case coupled to the open portion of the first case to seal the electrode assembly. A lithium secondary battery in which the longitudinal surface of the storage portion of the first case is made of a laminate sheet, and the other surface of the first case and the second case are made of the rigid material.

5. In Paragraph 1, The above laminate sheet is a lithium secondary battery comprising an outer coating layer, a metal layer, and an inner sealant layer.

6. In Paragraph 1, The above-mentioned rigid material is a lithium secondary battery made of aluminum, aluminum alloy, stainless steel, nickel, nickel-plated iron, special reinforced plastic, or a combination thereof.

7. In Paragraph 1, A lithium secondary battery in which the above laminate sheet is indented into the inner side where the electrode assembly is embedded by applying pressure.

8. In Paragraph 1, A lithium secondary battery in which the length of at least one pair of opposite sides among the lengths of the four sides forming one of the above-mentioned rectangular sides is 101% to 120% of the length of the other side among the above-mentioned rectangular sides corresponding to the pair of sides.

9. In Paragraph 8, A lithium secondary battery in which the length of the four sides forming one of the above-mentioned rectangular surfaces is 101% to 120% of the length of the four sides forming the other of the above-mentioned rectangular surfaces corresponding thereto.

10. In Paragraph 1, A lithium secondary battery in which a reinforcing material is formed on one of the rectangular surfaces in a portion corresponding to another surface among the above rectangular surfaces, wherein the portion corresponding to another surface among the above rectangular surfaces is located within one surface among the above rectangular surfaces.

11. In Paragraph 10, The above reinforcing material is a lithium secondary battery that is a metal or a polymer.

12. A battery pack having two or more lithium secondary batteries arranged according to paragraph 1, The above two or more lithium secondary batteries are arranged such that one of the longitudinal surfaces of one lithium secondary battery faces the other of the longitudinal surfaces of another lithium secondary battery adjacent to the one lithium secondary battery. A battery pack in which, by pressure, another surface among the longitudinal surfaces of the adjacent lithium secondary battery indents one surface of the lithium secondary battery.

13. In Paragraph 12, A battery pack in which another surface among the longitudinal surfaces of the adjacent lithium secondary battery indents one surface of the lithium secondary battery inwardly, thereby reinforcing the rigidity of one surface of the lithium secondary battery.

14. In Paragraph 12, A battery pack having a reinforcing material formed in a portion where a side forming another side among the longitudinal surfaces of the adjacent lithium secondary battery is located within one side among the longitudinal surfaces of the above-mentioned lithium secondary battery.

15. In Paragraph 14, The above reinforcing material is a metal or polymer battery pack.

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