Rechargeable battery

Abstract

An electrode assembly according to an embodiment comprises: a first electrode including a first electrode current collector and a first electrode active material layer; a second electrode including a second electrode current collector and a second electrode active material layer; and a separator arranged between the first electrode and the second electrode, the first electrode, the second electrode and the separator being wound, and comprises: a finishing member coupled to the end portion of the first electrode so as to fix the end portion of the first electrode to the outer side surface of the electrode assembly; and a stress mitigation member which is attached to the outer side surface of the electrode assembly while covering the end portion of the first electrode active material layer and the end portion of the second electrode active material layer, and which mitigates the stress generated with respect to the first electrode and the separator between the end portion of the first electrode active material layer and the end portion of the second electrode active material layer during charging and discharging.

Description

secondary battery

[0001] The present disclosure relates to a secondary battery.

[0002] Rechargeable batteries, unlike primary batteries, are batteries that undergo repeated charging and discharging. Small-capacity secondary batteries are used in small, portable electronic devices such as cell phones, laptops, and camcorders. Large-capacity, high-density secondary batteries are used as power sources for motor drives in hybrid and electric vehicles, or for energy storage.

[0003] Typically, secondary batteries are manufactured and used by placing the electrode assembly inside a container (e.g., a case such as a pouch or can) that can accommodate it, injecting electrolyte, and sealing the container.

[0004] The electrode assembly may be a rolled type formed by interposing a separator (or a membrane) between the positive and negative electrodes and then winding them in the form of a jelly-roll, or a laminated type formed by stacking a plurality of structures in which the positive and negative electrodes and the separator are interposed between them.

[0005] The positive and negative electrodes each include a current collector and an active material layer coated with an active material. The capacity of a secondary battery is proportional to the amount of active material, i.e., the thickness of the active material layer.

[0006] At this time, the current collector and separator of each electrode are not elements that primarily affect the capacity of the secondary battery, so it is important to manufacture them as thin as possible while maintaining the function of each component.

[0007] However, when a secondary battery is repeatedly charged and discharged, the repeated expansion and contraction of the electrode assembly can accelerate the thinning of the current collector and separator of each electrode. This can lead to damage to the current collector and separator, which can lead to stability issues and shortened secondary battery life.

[0008] Accordingly, various studies are being conducted on methods to manufacture the current collector and separator of each electrode thinly while preventing damage.

[0009] The above-described information disclosed in the background technology of this invention is only intended to enhance understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0010] An object of the present invention is to provide an electrode assembly having increased capacity, improved stability, and a shortened lifespan.

[0011] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0012] According to one embodiment of the present invention for solving the above technical problem, an electrode assembly comprises a first electrode including a first electrode current collector and a first electrode active material layer, a second electrode including a second electrode current collector and a second electrode active material layer, and a separator disposed between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the separator are wound and configured, and a closing member that is coupled to a terminal portion of the first electrode and fixes the terminal portion of the first electrode to an outer surface of the electrode assembly, and a stress relief member that is attached to the outer surface of the electrode assembly while covering the terminal portion of the first electrode active material layer and the terminal portion of the second electrode active material layer, and that relieves stress generated in the first electrode and the separator between the terminal portion of the first electrode active material layer and the terminal portion of the second electrode active material layer during charge and discharge.

[0013] The first electrode may be terminated longer than the second electrode.

[0014] The terminal portion of the first electrode active material layer may be arranged longer than the terminal portion of the second electrode active material layer.

[0015] When the length of the stress relief member is a, the width of the second electrode is b, and the width of the first electrode is c, c ≥ a > b.

[0016] The width of the stress relief member may be equal to or greater than the gap between the end portion of the first electrode active material layer and the end portion of the second electrode active material layer.

[0017] The width of the stress relief member may be less than half of the outer circumference of the electrode assembly.

[0018] The above stress relief member may include a material that reacts with the electrolyte.

[0019] The above stress relief member may be an OPS (oriented polystyrene) film.

[0020] The above-mentioned closing members are at least two in number and can be spaced apart at a certain interval in the width direction of the electrode assembly and connected to the terminal portion of the first electrode.

[0021] A secondary battery according to another embodiment of the present invention includes the electrode assembly mentioned above, a case accommodating the electrode assembly, an electrolyte injected into the case, and a cap assembly covering an opening of the case.

[0022] According to an embodiment of the present invention, a stress relief member is attached to an outer surface of an electrode assembly while covering an end portion of a negative electrode active material layer and an end portion of a positive electrode active material layer, thereby relieving stress generated in the negative electrode and the separator at a gap between the two end portions during charging and discharging.

[0023] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects that are not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0024] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0025] Figure 1 is an exploded perspective view of a secondary battery according to one embodiment of the present invention.

[0026] Figure 2 is a perspective view of the electrode assembly of the secondary battery of Figure 1.

[0027] Figure 3 is an enlarged plan view of III of Figure 2.

[0028] Figure 4 is a drawing showing a state in which the stress relief member in Figure 3 is at its minimum length.

[0029] FIG. 5 is a drawing corresponding to FIG. 3 of an electrode assembly according to a comparative example in which a stress relief member is not attached.

[0030] Figure 6a is a drawing for explaining the pressing phenomenon of the second electrode of the electrode assembly according to a comparative example.

[0031] FIG. 6b is a drawing for explaining that the pressing phenomenon of the second electrode of the electrode assembly according to one embodiment of the present invention is alleviated in contrast to FIG. 6a.

[0032] Figure 7a is a drawing for explaining the fracture of the first electrode and separator of the electrode assembly according to a comparative example.

[0033] FIG. 7b is a drawing for explaining the non-breakage of the first electrode and separator of the electrode assembly according to one embodiment of the present invention, in contrast to FIG. 7a.

[0034] Fig. 8 is a cross-sectional view according to VII-VII of Fig. 3.

[0035] Fig. 9 is a drawing showing a state in which the length of the stress relief member of Fig. 8 is at its maximum.

[0036] Figure 10 is a perspective view of an electrode assembly according to another embodiment of the present invention.

[0037] Figure 11 is a perspective view of an electrode assembly according to another embodiment of the present invention.

[0038] FIG. 12 is an exploded perspective view of a square secondary battery including the electrode assembly of FIG. 11.

[0039] Fig. 13 is an exploded perspective view of a pouch-type secondary battery including the electrode assembly of Fig. 11.

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0041] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0042] Additionally, to facilitate understanding of the invention, the attached drawings may not be drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0043] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0044] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0045] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0046] Any configuration being placed “on top (or bottom)” of a component or “on top (or bottom)” of a component may mean not only that any configuration is placed in contact with the top (or bottom) surface of said component, but also that other configurations may intervene between said component and any configuration placed on (or under) said component.

[0047] Additionally, when a component is described as being “on,” “connected to,” or “coupled to” another component, it should be understood that the components may be directly connected or coupled to one another, but that other components may also be “interposed” between the components, or that each component may be “connected,” “coupled,” or “connected” through other components.

[0048] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, the use of "may" when describing embodiments of the present disclosure refers to "one or more embodiments of the present disclosure." Expressions such as "one or more" and "one or more" preceding a list of elements modify the list as a whole and do not modify individual elements in the list.

[0049] When reference is made throughout the specification to “A and / or B,” this means A, B, or A and B, unless otherwise stated, and when reference is made to “C to D,” this means C or more and D or less, unless otherwise stated.

[0050] When 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 A, B, and C," or "at least one selected from A, B, and C," are used to specify a list of elements A, B, and C, the phrases can refer to any suitable combination.

[0051] The term "use" may be considered synonymous with the term "utilize." As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than degrees, and are intended to take into account inherent variations in measured or calculated values ​​that would be recognized by those skilled in the art.

[0052] Although terms such as first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could also be termed a second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0053] For ease of description, spatially relative terms such as "beneath," "below," "lower," "above," "upper," and the like may be used herein to describe the relationship of one element or feature to another element(s) or feature(s) as depicted in the drawings. It will be understood that spatially relative positions encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device in the drawings is turned over, an element described as "beneath" or "lower" another element would be understood to be "above" or "upper" the other element. Thus, the term "beneath" can encompass both the above and below orientations.

[0054] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure.

[0055] Fig. 1 is an exploded perspective view of a secondary battery (1000) according to one embodiment of the present invention. Referring to Fig. 1, the secondary battery (1000) according to one embodiment of the present invention includes a case (100), an electrode assembly (200), a lower insulating member (300a), an upper insulating member (300b), a cap assembly (400), and a gasket (500).

[0056] The case (100) may be cylindrical, square, or pouch-shaped, depending on the shape of the secondary battery (1000). In this embodiment, the case (100) is assumed to be cylindrical and described, and in another embodiment, the case is square (2100, see FIGS. 11 and 12) or pouch-shaped (3100, see FIG. 13) described.

[0057] The case (100) includes a circular bottom surface (not shown) and a cylindrical side wall (110) extending from the edge of the bottom surface. One end of the side wall (110) is closed by the bottom surface, and the other end of the side wall (110), i.e., the portion facing the bottom surface, has an opening (130) provided therein for inserting or receiving a lower insulating member (300a), an electrode assembly (200), an upper insulating member (300b), a cap assembly (400), and a gasket (500) into the case (100).

[0058] In addition, a beading portion (150) that is curved inward along the outer circumference of the side wall (110) adjacent to the opening (130) may be formed. The beading portion (150) can prevent the lower insulating member (300a), the electrode assembly (200), and the upper insulating member (300b) inserted into the case (100) from moving in a direction parallel to the longitudinal direction of the side wall (110) or perpendicular to the bottom surface (up and down direction based on FIG. 1) within the case (100).

[0059] A cap assembly (400) may be placed in the opening (130) of the case (100) to seal the opening (130). To this end, the case (100) may further include a crimping portion (not shown) provided at the end of the side wall (110).

[0060] The electrode assembly (200) includes a first electrode (210), a second electrode (230), and a separator (220). The electrode assembly (200) can be formed by winding the separator (220) while it is positioned between the first electrode (210), the separator (220), and the second electrode (230).

[0061] The first electrode (210) may be either an anode or a cathode, and the second electrode (230) may be the other of the anode or cathode. For example, if the first electrode (210) is a cathode, the second electrode (230) may be an anode.

[0062] However, this is not limited thereto, and when the first electrode (210) is an anode, the second electrode (230) may be a cathode. In this specification, the first electrode (210) is described as a cathode and the second electrode (230) is an anode. A detailed description of the electrode assembly (200) will be described later with reference to FIG. 2.

[0063] The electrode assembly (200) may further include a first electrode tab (217) and a second electrode tab (237). The first electrode tab (217) may be electrically connected to the first electrode (210), and the second electrode tab (237) may be electrically connected to the second electrode (230).

[0064] At this time, an insulating tape (not shown) may be placed at the connection boundary between the first electrode tab (217) and the first electrode (210) to prevent a short circuit between the two. An insulating tape (not shown) may also be placed at the connection boundary between the second electrode tab (237) and the second electrode (230) to prevent a short circuit between the two.

[0065] The first electrode tab (217) may protrude in a direction toward the bottom surface of the case (100) (downward direction based on FIG. 1). Accordingly, the first electrode tab (217) may be coupled to the bottom surface of the case (100). At this time, the coupling method may be by welding, but is not limited thereto, and may be any method capable of electrically connecting the first electrode (210) and the bottom surface of the case (100).

[0066] When the first electrode tab (217) is coupled to the bottom surface of the case (100), the case (100) may have a negative polarity in an embodiment of the present invention. Accordingly, the bottom surface of the case (100) may be used as a negative terminal of a secondary battery (1000) according to an embodiment of the present invention.

[0067] The second electrode tab (237) may protrude in the opposite direction to the first electrode tab (217). That is, it may protrude in the direction toward the opening (130) of the case (100) (upward in FIG. 1). The second electrode tab (237) may be electrically connected to the cap assembly (400).

[0068] The lower insulating member (300a) has a disc shape and can insulate between the electrode assembly (200) and the bottom surface of the case (100). The upper insulating member (300b) also has a disc shape and can insulate between the electrode assembly (200) and the beading portion (150) of the case (100).

[0069] The cap assembly (400) may include a cap up (410) and a safety vent (420). The cap up (410) is positioned to be exposed to the outside and may be utilized as a positive terminal of a secondary battery (1000).

[0070] The safety vent (420) can be deformed or ruptured when the pressure inside the case (100) rises above the reference pressure, releasing gas to the outside and blocking current flowing inside the secondary battery (1000).

[0071] The gasket (500) is arranged to surround the outer periphery of the cap assembly (400) and can be fixed by a beading portion (150) and a crimping portion (not shown) inside the case (100). Accordingly, the gasket (500) can insulate the cap assembly (400) and the case (100).

[0072] FIG. 2 is a perspective view of an electrode assembly (200) of the secondary battery (1000) of FIG. 1.

[0073] Referring to FIG. 2, as described above, the electrode assembly (200) is wound in the form of a cylindrical jelly roll, so that an empty space can be formed in the center (O) of the electrode assembly (200).

[0074] According to the stacking order, the first electrode (210) can be placed on the outermost side of the rolled electrode assembly (200), and can be alternately placed with the second electrode (230) with the separator (220) interposed in the direction toward the center (O) of the electrode assembly (200).

[0075] The first electrode (210) may include a first electrode current collector (211) and a first electrode active material layer (213) including a first electrode active material disposed on the first electrode current collector (211). The second electrode (230) may also include a second electrode current collector (231) and a second electrode active material layer (233) including a second electrode active material disposed on the second electrode current collector (231). A detailed description of the materials of the first electrode (210) and the second electrode (230) will be described later.

[0076] The secondary battery (1000) can produce energy by a chemical reaction between the first electrode active material layer (213) and the second electrode active material layer (233) formed in the electrode assembly (200). That is, the energy capacity of the secondary battery (1000) can be determined by the physical and chemical characteristics of the first electrode active material layer (213) and the second electrode active material layer (233).

[0077] Accordingly, the current collector (211, 231) and separator (220) of each electrode, which do not directly affect the energy capacity of the secondary battery (1000), can be formed thinner than the first electrode active material layer (213) and the second electrode active material layer (233).

[0078] The electrode assembly (200) may further include a closing member (240) and a stress relief member (250). The closing member (240) and the stress relief member (250) may have a single sheet shape, i.e., a rectangular band shape.

[0079] The closing member (240) can be attached to the outer surface of the electrode assembly (200). That is, the closing member (240) can be attached to the outer surface of the first electrode current collector (211) disposed at the outermost side of the rolled electrode assembly (200), and at the same time, can wrap the terminal portion of the first electrode (210).

[0080] In other words, the closing member (240) can be combined with the terminal portion of the first electrode (210) to fix the terminal portion of the first electrode (210) to the outer surface of the electrode assembly (200). As described below, the first electrode (210) can have a structure in which the first electrode current collector (211) is finished longer than the first electrode active material layer (213), so the closing member (240) can be combined with the terminal portion (211a) of the first electrode current collector (211) to fix the terminal portion (211a) of the first electrode current collector (211) to the outer surface of the electrode assembly (200).

[0081] The material of the finishing member (240) may be any one of OPS (oriented polystyrene), PET (polyethylene terephthalate), PI (polyimide), and PP (polypropylene), but is not limited thereto.

[0082] The stress relief member (250) may be attached to the outer surface of the electrode assembly (200). For example, the stress relief member (250) may be attached to the outer surface of the first electrode current collector (211) disposed at the outermost side of the electrode assembly (200).

[0083] The stress relief member (250) can be attached to the outer surface of the electrode assembly (200) while covering the terminal portion (213a, see FIG. 3) of the first electrode active material layer (213) and the terminal portion (233a, see FIG. 3) of the second electrode active material layer (233). Accordingly, the stress relief member (250) can relieve stress generated in the first electrode (210) and the separator (220) due to the difference in length between the terminal portion (213a) of the first electrode active material layer (213) and the terminal portion (233a) of the second electrode active material layer (233) during charging and discharging of the electrode assembly (200).

[0084] At this time, the stress relief member (250) may be a material whose properties change when reacting with an electrolyte. For example, the stress relief member (250) may be made of a material that is normally in a solid state but undergoes a phase change into a viscous liquid state when reacting with an organic solvent (e.g., an electrolyte, etc.). In one embodiment, the stress relief member (250) may be made of oriented polystyrene (OPS).

[0085] In this embodiment, the long side of each component is defined as the length, and the short side as the width. Accordingly, the length direction or width direction of each component on the same plane may be different from each other.

[0086] For example, the stress relief member (250) may have a vertical side (a side in the up-down direction based on FIG. 2) longer than a horizontal side (a side in the left-right direction based on FIG. 2). That is, the stress relief member (250) may have a vertical side that is the long side and a horizontal side that is the short side and a width.

[0087] On the other hand, in the case of the closing member (240), for example, the horizontal side (the side in the left-right direction based on FIG. 2) may be longer than the vertical side (the side in the up-down direction based on FIG. 2). Accordingly, in the closing member (240), the horizontal side may be the long side and the vertical side may be the width and the short side, respectively.

[0088] As a result, the width direction of the stress relief member (250) may be different from the width direction of the finishing member (240) and may be the same as the length direction of the finishing member (240). Also, in the same sense, the length direction of the stress relief member (250) may be the same as the width direction of the finishing member (240).

[0089] Fig. 3 is an enlarged plan view of III of Fig. 2. Fig. 4 is a drawing showing a state in which the stress relief member (250) of Fig. 3 is at its minimum length. Fig. 5 is a drawing showing a comparative example in which the stress relief member (250) of Fig. 3 is not attached.

[0090] Referring to FIGS. 3 to 5, the first electrode (210) is arranged at the outermost side of the electrode assembly (200), as described above. At this time, the first electrode current collector (211) of the first electrode (210) may be terminated longer than the first electrode active material layer (213). That is, the terminal portion (211a) of the first electrode current collector (211) may be arranged longer than the terminal portion (213a) of the first electrode active material layer (213).

[0091] The second electrode (230) is positioned inside the electrode assembly (200) relative to the first electrode (210) in a direction toward the center (O) of the electrode assembly (200) with the first electrode (210) and the separator (220) interposed therebetween. Here, the second electrode current collector (231) of the second electrode (230) may be finished substantially identically to the second electrode active material layer (233).

[0092] In other words, the terminal portion (231a) of the second electrode current collector (231) and the terminal portion (233a) of the second electrode active material layer (233) can be arranged without a difference in length. However, the structure of the second electrode (230) is not limited thereto, and the terminal portion (231a) of the second electrode current collector (231) can be arranged longer than the terminal portion (233a) of the second electrode active material layer (233).

[0093] Additionally, the first electrode (210) positioned at the outermost side of the electrode assembly (200) may be finished longer than the adjacent second electrode (230). Accordingly, a gap (D1) may be created between the end portion (213a) of the first electrode active material layer (213) and the end portion (233a) of the second electrode active material layer (233).

[0094] The electrode assembly (200) can repeat expansion and contraction during charging and discharging. Accordingly, an expansion force can occur inside the wound electrode assembly (200) when charging and discharging, moving from the center (O) of the electrode assembly (200) toward the outside.

[0095] When the above expansion force occurs, stress may be generated in the first electrode (210), the second electrode (230), and the separator (220) located between the terminal portion (213a) of the first electrode active material layer (213) and the terminal portion (233a) of the second electrode active material layer (233) due to the repulsive force of the case (100) pushing the electrode assembly (200).

[0096] For example, in the case of a second electrode (230) arranged one turn inside the second electrode (230) arranged at the outermost side of the electrode assembly (200) among the second electrodes (230), a pressing phenomenon may occur due to the repulsive force.

[0097] That is, a pressing phenomenon may occur at a portion (VI-1) that overlaps with the terminal portion (233a) of the second electrode active material layer (233) among the second electrodes (230), and a pressing phenomenon may also occur at a portion (VI-2) that overlaps with the terminal portion (213a) of the first electrode active material layer (213) among the second electrodes (230).

[0098] If a continuous pressing phenomenon occurs on the second electrode (230), ion movement between the second electrode (230) and the first electrode (210) may not be smooth, and thus the energy capacity of the electrode assembly (200) may decrease.

[0099] In addition, since the current collector (211, 231) and separator (220) of each electrode are becoming thinner, the first electrode current collector (211) and separator (220), which have become thinner due to the repulsive force as described above, may be subjected to an impact that cannot overcome the stress, and may even cause breakage and destruction.

[0100] That is, the separator (220) and the first electrode (210) may be broken at the portion (Ⅶ-1) that overlaps the terminal portion (233a) of the second electrode active material layer (233) of the separator (220).

[0101] Accordingly, if the separator (220) is broken (or damaged), the separation between the first electrode active material layer (213) and the second electrode active material layer (233) may not occur smoothly, resulting in a short circuit.

[0102] As a result, the gap (D1) between the terminals (213a, 233a) between each electrode active material layer may cause damage to the electrode assembly (200), thereby ultimately shortening the lifespan of the secondary battery (1000).

[0103] The stress relief member (250) may be attached to the outer surface of the electrode assembly (200) (or the outer surface of the first electrode current collector disposed at the outermost side) while covering the end portion (213a) of the first electrode active material layer (213) and the end portion (233a) of the second electrode active material layer (233). That is, the width of the stress relief member (250) may be equal to or greater than the spacing (D1) between the end portions of each electrode active material layer.

[0104] In the case where a stress relief member (250) exists corresponding to this gap (D1), even if an expansion force is generated from the inside to the outside of the electrode assembly (200) during charging and discharging of the electrode assembly (200), the first electrode current collector (211) may not directly contact the side wall (110) of the case (100).

[0105] In addition, when the stress relief member (250) undergoes a phase change into a viscous liquid state, the force applied by the first electrode current collector (211) to the side wall (110) of the case (100) can be absorbed and reduced by the stress relief member (250), so the repulsive force received by the first electrode (210), the second electrode (230), and the separator (220) from the side wall (110) can also be reduced.

[0106] That is, the stress relief member (250) can relieve stress generated in the first electrode (210), the second electrode (230), and the separator (220) located between the terminal portion (213a) of the first electrode active material layer (213) and the terminal portion (233a) of the second electrode active material layer (233).

[0107] As illustrated in Fig. 4, the stress relief member (250) may have the same width as the spacing (D1) between the terminal portions of each electrode active material layer. However, since the stress relief member (250) is attached to the outer surface of the rolled electrode assembly (200), it is necessary to consider tolerance during attachment by taking into account the positions of the terminal portions (213a) of the first electrode active material layer (213) and the terminal portions (233a) of the second electrode active material layer (233) arranged inside the electrode assembly (200).

[0108] Accordingly, the width of the stress relief member (250) may be greater than or equal to the tolerance added to the gap (D1) between the terminal portions (213a, 233a) between each electrode active material layer. In addition, considering that the length of the closing member (240) must be greater than half of the outer circumference of the electrode assembly (200) to be effective in the closing function, the width of the stress relief member (250) may be no greater than half of the outer circumference of the electrode assembly (200) so as not to overlap with the closing member (240).

[0109] Referring to FIG. 5, the electrode assembly (200') according to the comparative example has the same configuration and structure as the electrode assembly (200) according to one embodiment of the present invention, but does not include a stress relief member (250).

[0110] Accordingly, when an expansion force is generated from the inside to the outside of the electrode assembly (200) due to charging and discharging of the electrode assembly (200), the first electrode current collector (211) may come into direct contact with the side wall (110) of the case (100).

[0111] Accordingly, since the side wall (110) of the case (100) directly receives the repulsive force pushing the electrode assembly (200), the stress on the first electrode (210), the second electrode (230), and the separator (220) located between the end portion (213a) of the first electrode active material layer (213) and the end portion (233a) of the second electrode active material layer (233) can be stronger than in the embodiment of the present invention.

[0112] That is, unrelieved stress may cause a pressing phenomenon of the second electrode (230) and a fracture (or breakage) of the first electrode current collector (211) and / or separator (220), which may result in stability problems or shortened lifespan of the electrode assembly (200').

[0113] FIG. 6a is a drawing for explaining the pressing phenomenon of the second electrode (230) of the electrode assembly (200') according to a comparative example, and FIG. 6b is a drawing for explaining that the pressing phenomenon of the second electrode (230) of the electrode assembly (200) according to an embodiment of the present invention is alleviated in contrast to FIG. 6a.

[0114] Each drawing is a drawing showing the second electrodes (230', 230) after performing 1000 charge / discharge cycles on the electrode assembly (200') according to a comparative example and the electrode assembly (200) according to an embodiment of the present invention in a 45°C temperature atmosphere.

[0115] Referring to FIG. 6a, it can be confirmed that in the electrode assembly (200') according to the comparative example, a pressed area (A1') is generated in the width direction (upper and lower direction based on FIG. 6a) in a portion (VI-1', see FIG. 5) overlapping with the terminal portion (233a') of the second electrode active material layer (233') of the second electrode (230'), and a pressed area (A2') is generated in the width direction (upper and lower direction based on FIG. 6a) in a portion (VI-2', see FIG. 5) overlapping with the terminal portion (213a') of the first electrode active material layer (213') of the second electrode (230').

[0116] On the other hand, referring to FIG. 6b, it can be confirmed that in the electrode assembly (200) according to one embodiment of the present invention, no trace remains in the width direction of the second electrode (230) in the portion (A1, A2) corresponding to the pressed area (A1', A2') where the pressed phenomenon occurred in the second electrode (230') of the electrode assembly (200') according to the comparative example.

[0117] In other words, the electrode assembly (200) according to one embodiment of the present invention can reduce the repulsive force from the side wall (110) of the case (100) by the stress relief member (250) attached to the outer surface of the electrode assembly (200).

[0118] Accordingly, the stress relief member (250) can relieve the stress occurring in the second electrode (230) between the terminal portions (213a, 233a) of the active material layers (213, 233) of each electrode due to the repulsive force, thereby alleviating the pressing phenomenon occurring in the second electrode (230).

[0119] FIG. 7a is a drawing for explaining the fracture of the first electrode (210') and the separator (220') of the electrode assembly (200') according to a comparative example, and FIG. 7b is a drawing for explaining the non-fracture of the first electrode (210) and the separator (220) of the electrode assembly (200) according to an embodiment of the present invention in contrast to FIG. 7a.

[0120] FIG. 7a and FIG. 7b are also drawings showing the first electrode (210', 210) and the separator (220', 220) of the electrode assembly (200') according to the comparative example and the electrode assembly (200) according to one embodiment of the present invention after performing 1000 charge / discharge cycles at 45°C, similar to FIG. 6a and FIG. 6b.

[0121] Referring to FIG. 7a, it can be confirmed that in the electrode assembly (200') according to the comparative example, a fracture area (B1') is formed in the width direction (upper and lower direction based on FIG. 7a) in the portion (refer to FIG. 5 VII-1') overlapping with the terminal portion (233a') of the second electrode active material layer (233) of the first electrode current collector (211') of the first electrode (210').

[0122] On the other hand, referring to FIG. 7b, it can be confirmed that the electrode assembly (200) according to one embodiment of the present invention is not broken in the area (B1) corresponding to the broken area (B1') of the comparative example above.

[0123] Accordingly, the stress relief member (250) can relieve the stress generated in the first electrode (210) and the separator (220) between the terminal portions (213a, 233a) of the active material layers of each electrode due to the repulsive force, thereby preventing the fracture generated in the first electrode (210) and the separator (220).

[0124] As a result, when using a stress relief member (250), it is possible to prevent a pressing phenomenon in the second electrode (230) and a breakage in the first electrode (210) and the separator (220) that may occur due to the gap (D1) between the terminal portions (213a, 233a) of the active material layer of each electrode.

[0125] Through this, the structural and functional stability of the electrode assembly (200) can be improved, and its lifespan can also be extended.

[0126] Fig. 8 is a cross-sectional view according to VII-VII of Fig. 3, and Fig. 9 is a drawing showing a state in which the stress relief member (250) of Fig. 8 has a maximum length (L3) (L3'). Referring to Figs. 8 and 9, the stress relief member (250) can be attached to the outer surface of the first electrode current collector (211) of the first electrode (210) disposed at the outermost end of the electrode assembly (200).

[0127] At this time, considering that the second electrode (230) is a factor of fracture, the length (L3) of the stress relief member (250) may be greater than or equal to the width (L2) of the second electrode (230). That is, the stress relief member (250) may cover at least the entire width (L2) of the second electrode (230).

[0128] However, the width (L2) of the second electrode (230) is smaller than the width (L1) of the first electrode (210), and since the interfacing between the first electrode (210) and the second electrode (230) is flexible when the electrode assembly (200) is wound, tolerance management is necessary. Accordingly, the length (L3) of the stress relief member (250) may be greater than or equal to the value obtained by adding the upper and lower tolerance (O1) based on FIG. 7 to the width (L2) of the second electrode (230).

[0129] Meanwhile, the length (L3) of the stress relief member (250) may be smaller than or equal to the width (L1) of the first electrode (210). That is, the maximum length (L3') of the stress relief member (250) may be the width (L1) of the first electrode (210).

[0130] Fig. 10 is a perspective view of an electrode assembly (200'') according to another embodiment of the present invention. The configuration and structure of the electrode assembly (200'') are the same as those of the electrode assembly (200) according to one embodiment of the present invention, but there may be a plurality of closing members (240).

[0131] That is, at least two or more closing members (240) can be attached to the outer surface of the first electrode current collector (211) disposed at the outermost side of the rolled electrode assembly (200'') with a gap therebetween, and can simultaneously wrap the terminal portion (211a) of the first electrode (210). The closing members (240) can be combined with the terminal portion (211a) of the first electrode (210) to secure it to the outer surface of the electrode assembly (200'').

[0132] In the embodiment of FIG. 10, the two closing members (240) are spaced apart at a certain interval in the width direction (up-down direction based on FIG. 9) of the electrode assembly (200'') and are attached to the first electrode current collector (211) of the first electrode (210) while wrapping around the end portion (211a) of the first electrode (210).

[0133] Fig. 11 is a perspective view of an electrode assembly (600) according to another embodiment of the present invention. Since the electrode assembly (600) has some of the same structure and configuration as the electrode assembly (200) of Fig. 2, the present embodiment will focus on explaining the differences.

[0134] Referring to FIG. 11, the electrode assembly (600) includes a first electrode (210), a second electrode (230), and a separator (220) interposed between the first electrode (210) and the second electrode (230). The wound shape of the electrode assembly (600) may have a shape close to a rectangular parallelepiped.

[0135] In other words, the eccentricity of the planar shape of the electrode assembly (600) may not be 0. That is, the planar shape of the electrode assembly (600) may be elliptical and may have a major axis and a minor axis.

[0136] The electrode assembly (600) may further include a first electrode tab (217) and a second electrode tab (237), but the protrusion directions of the first electrode tab (217) and the second electrode tab (237) may be the same. For example, both the first electrode tab (217) and the second electrode tab (237) may protrude in the longitudinal direction of the electrode assembly (upward or upward direction with reference to FIG. 10).

[0137] Fig. 12 is an exploded perspective view of a square secondary battery (2000) including the electrode assembly (600) of Fig. 11. Referring to Fig. 12, the square secondary battery (2000) includes a case (2100), an electrode assembly (600) accommodated in the case (2100), and a cap assembly (2400) coupled to the upper portion of the case (2100).

[0138] The case (2100) includes a bottom surface (not shown) having a rectangular shape and a side wall (2110) extending vertically (up-down direction based on FIG. 12) from an edge of the bottom surface. An opening (2130) capable of accommodating an electrode assembly (600) and a cap assembly (2400) may be formed on the upper portion of the side wall (2110) of the case (2100). The case (2100) is formed of a metal material and may be used as a terminal of a square secondary battery (2000).

[0139] The cap assembly (2400) includes a cap plate (2410) formed to correspond to the opening (2130) of the case (2100). The cap plate (2410) may have a terminal hole (2411) in the center and an electrolyte injection hole (2413) on one side. The electrolyte injection hole (2413) may be sealed by being combined with a stopper (2403).

[0140] A first electrode terminal (2420) can be inserted into the terminal hole (2411). A gasket (2430) can be placed on the outer surface of the first electrode terminal (2420) to electrically insulate between the first electrode terminal (2420) and the cap plate (2410).

[0141] The lower portion of the first electrode terminal (2420) can be accommodated in an insulating plate (2440) and a terminal plate (2450) that include an opening capable of accommodating the first electrode terminal (2420). Accordingly, the first electrode terminal (2420) can be electrically connected to the terminal plate (2450).

[0142] The first electrode terminal (2420) can be electrically connected to the first electrode tab (217), and the second electrode tab (237) can be electrically connected to the cap plate (2410). The electrical connection method may be by welding, but is not limited thereto.

[0143] The cap assembly (2400) may further include an insulating case (2100). The insulating case (2100) may be formed to correspond to the opening (2130) of the case (2100) and may seal the opening (2130). In addition, the insulating case (2100) may include an electrolyte injection hole (2413) at a position corresponding to the electrolyte injection hole (2413) of the cap plate (2410). The electrode assembly (600) and the cap assembly (2400) may be electrically insulated through the insulating case (2100).

[0144] Fig. 13 is an exploded perspective view of a pouch-type secondary battery (3000) including the electrode assembly (600) of Fig. 11. Referring to Fig. 13, the pouch-type secondary battery (3000) includes a pouch-type case (3100) and an electrode assembly (600) accommodated in the pouch-type case (3100).

[0145] A pouch-type case (3100) may include a body (3110) including a space (3111) for accommodating an electrode assembly (600) and a cover (3120) capable of sealing the body (3110). When the electrode assembly (600) is accommodated in the space (3111) of the body (3110), the cover (3120) may be covered over the body (3110) and then sealed and bonded to manufacture a pouch-type secondary battery (3000).

[0146] The body (3110) and the cover (3120) may include a core (3121) made of a metal material, a heat-sealing layer (3123) formed on a first side of the core (3121), and an insulating film (3125) formed on a second side of the core (3121). The heat-sealing layer (3123) may function as an adhesive layer, and the insulating film (3125) may electrically insulate the electrode assembly (600) and the pouch-type case (3100).

[0147] Meanwhile, as described above, the first electrode (210) may be either an anode or a cathode, and the second electrode (230) may be either an anode or a cathode.

[0148] In this way, the closing member (240) and stress relief member (250) according to the present invention can also be applied to an electrode assembly for a square secondary battery or a pouch-type secondary battery.

[0149] In an embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) may be used as the positive electrode active material constituting the positive electrode active material layer of the positive electrode. For example, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0150] The above composite oxide may be a lithium transition metal composite oxide, and examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0151] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Nib Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0152] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0153] The cathode according to the embodiment includes a cathode current collector on which a cathode active material layer is disposed, and the cathode active material layer may further include a binder and / or a conductive material.

[0154] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0155] Aluminum (Al) may be used as the positive electrode collector, but is not limited thereto.

[0156] In an embodiment of the present invention, the negative electrode active material constituting the negative electrode active material layer of the negative electrode includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0157] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0158] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-based alloy, or a combination thereof.

[0159] The above silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles.

[0160] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0161] The negative electrode according to the embodiment includes a negative electrode current collector on which a negative electrode active material layer is disposed, and the negative electrode active material layer may further include a binder and / or a conductive material.

[0162] For example, the negative electrode active material layer may include 90 to 99 wt% of the negative electrode active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0163] The above binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof. When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0164] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0165] An electrolyte for a lithium secondary battery contains a non-aqueous organic solvent and a lithium salt.

[0166] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0167] The above non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof, and may be used alone or in combination of two or more thereof.

[0168] Additionally, when using a carbonate solvent, a mixture of cyclic carbonate and chain carbonate can be used.

[0169] Depending on the type of lithium secondary battery, a separator (or separator) may be present between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films comprising two or more of these.

[0170] The above separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof, positioned on one or both sides of the porous substrate.

[0171] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic polymer.

[0172] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0173] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0174] -Explanation of the symbol-

[0175] 200: Electrode assembly

[0176] 210: First electrode

[0177] 211: First electrode current collector

[0178] 211a: First electrode current collector terminal

[0179] 213: First electrode active material layer

[0180] 213a: End of first electrode active material layer

[0181] 230: Second electrode

[0182] 231: Second electrode current collector

[0183] 231a: Second electrode current collector terminal

[0184] 233: Second electrode active material layer

[0185] 233a: Second electrode active material layer terminal

[0186] 240: Absence of closure

[0187] 250: Stress relief absence

Claims

1. An electrode assembly comprising a first electrode including a first electrode current collector and a first electrode active material layer, a second electrode including a second electrode current collector and a second electrode active material layer, and a separator disposed between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the separator are wound and configured. A closing member that is coupled to the terminal end of the first electrode and fixes the terminal end of the first electrode to the outer surface of the electrode assembly; and A stress relief member that is attached to the outer surface of the electrode assembly while covering the terminal portion of the first electrode active material layer and the terminal portion of the second electrode active material layer, and that relieves the stress generated in the first electrode and the separator between the terminal portion of the first electrode active material layer and the terminal portion of the second electrode active material layer during charging and discharging. An electrode assembly comprising:

2. In paragraph 1, An electrode assembly wherein the first electrode is terminated longer than the second electrode.

3. In paragraph 2, An electrode assembly in which the terminal portion of the first electrode active material layer is arranged longer than the terminal portion of the second electrode active material layer.

4. In paragraph 1, An electrode assembly wherein the length of the stress relief member is a, the width of the second electrode is b, and the width of the first electrode is c, where c ≥ a > b.

5. In paragraph 1, An electrode assembly wherein the width of the stress relief member is equal to or greater than the gap between the end portion of the first electrode active material layer and the end portion of the second electrode active material layer.

6. In paragraph 5, An electrode assembly wherein the width of the stress relief member is less than half of the outer circumference of the electrode assembly.

7. In paragraph 1, The above stress relief member is an electrode assembly including a material that reacts with an electrolyte.

8. In paragraph 7, The above stress relief member is an electrode assembly which is an oriented polystyrene (OPS) film.

9. In paragraph 1, An electrode assembly in which the above-mentioned closing members are at least two in number and spaced apart at a certain interval in the width direction of the electrode assembly and are connected to the terminal portion of the first electrode.

10. An electrode assembly according to any one of claims 1 to 9; A case accommodating the electrode assembly; Electrolyte injected into the above case; and A cap assembly covering the opening of the above case; A secondary battery comprising:

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