Cylindrical secondary battery

Abstract

The present invention provides a cylindrical secondary battery having a structure in which a current collector of an electrode is disposed at the outermost part of a jelly-roll, and the electrode is in direct contact with the inner surface of a can to be electrically connected thereto. The first electrode is disposed on the outermost side of the electrode assembly in the winding direction, and a first current collector of the outermost first electrode is exposed to the outside in a radial direction. A swelling sheet impregnated with an electrolyte and expanded is interposed, radially inward of an outermost turn of the first electrode, in a region corresponding to a region in which the first current collector is exposed radially outward. The swelling sheets are respectively arranged on both axial sides outside a pressure relief section disposed in the central portion of the electrode assembly in the axial direction.

Description

Cylindrical secondary battery

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0160536 filed November 12, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0002] The present invention relates to a cylindrical secondary battery, and more specifically, to a cylindrical secondary battery having a structure in which an electrode current collector is disposed on the outermost edge of a jelly roll and the electrode is electrically connected by directly contacting the inner surface of a can.

[0003] Secondary batteries are classified according to the shape of the battery case into cylindrical batteries, in which the electrode assembly is housed in a cylindrical metal can; prismatic batteries, in which the electrode assembly is housed in a rectangular metal can; and pouch batteries, in which the electrode assembly is housed in a pouch-type case made of aluminum laminate sheets. Among these, cylindrical batteries have the advantage of relatively high capacity and structural stability.

[0004] The electrode assembly embedded in the battery case is a chargeable device composed of a stacked structure of a positive electrode, a separator, and a negative electrode, and is classified into jelly-roll type, stack type, and folding type. The jelly-roll type is a form in which a separator is interposed between a long sheet-type positive electrode and a negative electrode coated with an active material and wound, and has the advantages of easy manufacturing and high energy density per unit weight.

[0005] Recently, as the need for batteries capable of achieving high capacity and high output has increased, cylindrical batteries are undergoing optimization by modifying the thickness, size, and shape of current collectors and separators, or changing the structure of electrode tabs, in order to fit a large number of electrodes into a limited space.

[0006] As one such method, a technique was proposed in which the negative current collector is utilized as an outer tab; specifically, the negative current collector is positioned to wrap around the outermost edge of a jelly roll and brought into contact with the inner wall of a cylindrical can, thereby electrically connecting the negative current collector to the can. According to this method, the energy density of the battery cell can be increased and internal resistance can be lowered. Furthermore, since heat generated inside the battery cell can be rapidly transferred to the can, a heat dissipation effect can also be expected.

[0007] However, in practice, when the copper foil serving as the cathode current collector was exposed on the outer edge, there was a problem where incomplete contact occurred between the copper foil and the inner surface of the can's sidewall depending on the roundness of the jelly-roll.

[0008] Accordingly, swelling tape was interposed on the radial inner surface of the outermost copper foil to induce secure contact between the can and the copper foil. However, the swelling tape instead applied excessive pressure to the electrode assembly, causing a problem where the battery cell's lifespan was reduced.

[0009] The present invention has been devised to solve the aforementioned problems and aims to provide an electrode assembly having a structure that allows the current collector of the electrode assembly to maintain stable contact with the can despite the expansion and contraction of the electrode assembly during the charging and discharging process, and prevents excessive pressure from being generated on the electrode assembly, and a cylindrical secondary battery to which the same is applied.

[0010] The technical problems of the present invention are not limited to the purposes mentioned above, and other unmentioned purposes and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0011] The present invention can be applied to a battery cell comprising an electrode assembly and a can that accommodates the electrode assembly.

[0012] The above can is cylindrical.

[0013] The above electrode assembly is in the form of a jelly-roll in which the first electrode and the second electrode are wound with a separator in between.

[0014] The first electrode is disposed at the outermost part of the electrode assembly.

[0015] The first current collector of the outermost first electrode is exposed outward in the radial direction.

[0016] A swelling sheet that expands by being impregnated with an electrolyte is interposed on the inner side of the outermost turn of the first current collector in the radial direction.

[0017] The swelling sheet is placed in an area corresponding to the area where the first current collector is exposed radially outward.

[0018] According to the present invention, the swelling sheet is disposed on each of the axial sides outside the pressure relief section disposed in the central part of the electrode assembly in the axial direction.

[0019] Preferably, the pressure relief section may be set at the axial center of the electrode assembly at a height of at least 1 / 4 of the axial length of the electrode assembly.

[0020] More preferably, the pressure relief section may be set at the axial center of the electrode assembly at a height of at least 1 / 3 of the axial length of the electrode assembly.

[0021] The center of the pressure relief section with respect to the axial direction of the electrode assembly can substantially correspond to the center in the width direction of the first electrode.

[0022] The above swelling sheet may have a band shape that extends long in the circumferential direction.

[0023] In some examples, the swelling sheet may be continuously extended in the circumferential direction.

[0024] In some examples, the swelling sheet may be extended intermittently in the circumferential direction.

[0025] Preferably, the swelling sheet can be placed in a section of 180 degrees or more in the circumferential direction of the electrode assembly.

[0026] More preferably, the swelling sheet may be placed in a section of 270 degrees or more in the circumferential direction of the electrode assembly.

[0027] The swelling sheet above can be placed in a section of less than 360 degrees in the circumferential direction of the electrode assembly.

[0028] In some examples, the swelling sheet may have an adhesive surface on its radially outer surface.

[0029] In some examples, the swelling sheet may have an adhesive surface on its radially inner surface.

[0030] In some examples, the swelling sheet may include adhesive surfaces on both the radial inner surface and the outer surface.

[0031] In some examples, the outermost end of the winding direction of the swelling sheet may extend circumferentially from the outermost end of the winding direction of the first current collector to within 20 degrees of the center angle of the electrode assembly.

[0032] The radial outer surface of the first current collector may be exposed over the entire circumferential section of the electrode assembly.

[0033] At the outer end of the winding direction of the first electrode, a coated portion in which the first active material is coated only on the inner surface in the radiating direction of the first current collector is disposed in a manner of 0.8 turns or more and 1.2 turns or less, and further outward from the winding direction, an uncoated portion in which the first active material is not coated on both surfaces in the radiating direction of the first current collector may be disposed.

[0034] Preferably, the above-mentioned uncoated portion can be arranged in 0.5 turns or more.

[0035] More preferably, the uncoated portion may be arranged in 0.8 turns or more.

[0036] Preferably, the above-mentioned uncoated portion may be arranged in 2 turns or less.

[0037] More preferably, the above-mentioned uncoated portion may be arranged in 1.2 turns or less.

[0038] A separator may be disposed at the core-side end of the electrode assembly in the winding direction. In the winding direction, the first electrode may begin to be wound before the second electrode.

[0039] A first electrode tab may be attached to the core-side end of the first electrode in the winding direction. The first electrode tab may protrude axially from one side of the electrode assembly.

[0040] The first electrode above may be a negative electrode.

[0041] The above first current collector may include copper material.

[0042] The second electrode may have a second electrode tab protruding axially from the electrode assembly to the other side.

[0043] In some examples, the second electrode tab may be implemented by an uncoated region at the axial other end of the second electrode where the second active material is not coated on both surfaces of the second current collector.

[0044] In some examples, the second electrode tab may be implemented by a tab member bonded to the second current collector of the second electrode. The tab member may be bonded to a surface of the second current collector where the second active material is not coated.

[0045] According to the present invention, a first current collector disposed at the outermost end of an electrode assembly can maintain stable contact with the inner surface of the side wall of a can despite the expansion and contraction of the electrode assembly that occurs during the charging and discharging process.

[0046] According to the present invention, a swelling sheet is positioned in a section outside the pressure relief section, thereby preventing the swelling sheet from increasing the pressure in a region where a higher pressure occurs radially in the electrode assembly.

[0047] According to the present invention, the swelling sheet is extended more than 180 degrees in the circumferential direction, so that the effect of the swelling sheet on the cylindricality of the electrode assembly can be minimized and a sufficient contact area between the first electrode and the inner surface of the can can be secured.

[0048] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0049] FIG. 1 is an unfolded view of a first electrode, a first separator, a second electrode, and a second separator constituting an electrode assembly of a first embodiment.

[0050] Figure 2 is a diagram showing the process of winding around a core with a separator interposed between the first electrode and the second electrode of Figure 1.

[0051] FIGS. 3 and FIGS. 4 are, respectively, a side view and a top view of the first electrode, the first separator, the second electrode, and the second separator of FIG. 1 in a stacked unfolded state.

[0052] Figure 5 is a perspective view of an electrode assembly wound through the winding process of Figure 2.

[0053] Figure 6 is a planar cross-sectional view of the electrode assembly of Figure 5.

[0054] Figure 7 is a side cross-sectional view of the electrode assembly of Figure 5.

[0055] FIG. 8 is an unfolded view of the first electrode, the first separator, the second electrode, and the second separator constituting the electrode assembly of the second embodiment.

[0056] FIG. 9 is a cross-sectional view of a battery cell with an electrode assembly of the first or second embodiment applied.

[0057] FIG. 10 is an unfolded view of the first electrode, the first separator, the second electrode, and the second separator constituting the electrode assembly of the third embodiment.

[0058] FIG. 11 is a plan view of the first electrode, first separator, second electrode, and second separator of FIG. 10 in a stacked unfolded state.

[0059] FIG. 12 is a cross-sectional view of a battery cell with an electrode assembly of the third embodiment applied.

[0060] [Explanation of the symbol]

[0061] 10: Can (case) 11: Side wall 12: Bottom member 13: Cap assembly 14: First insulator 15: Second insulator 16: Gasket 20: Electrode assembly 21: First electrode 22: Second electrode 23: First current collector 24: Second current collector 25: First active material 26: Second active material 27: First electrode tab 28: Second electrode tab 29: Uncoated portion 30: Separator 31: First separator 32: Second separator 35: Pressure relief section 39: Winding core pin 40: Swelling sheet 41: First sheet 42: Second sheet 47: Current collector plate 50: Battery cell

[0062] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0063] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0064] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0065] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0066] In addition, where it is stated that one component is "connected," "combined," or "in contact" with another component, it should be understood that while the components may be directly connected or in contact with each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "in contact" through another component.

[0067] Singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as meaning that some of the components or steps may be omitted or additional components or steps may be included.

[0068] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less unless specifically stated otherwise.

[0069] In describing the embodiments, the term "axial direction" refers to the direction in which the axis forming the winding center of the jelly-roll type electrode assembly extends, the term "radial direction" refers to the direction toward or toward the said axis, and the term "circumferential direction" refers to the direction surrounding the said axis.

[0070] The winding direction of the electrode or separator of the electrode assembly corresponds to the longitudinal direction of the electrode or separator. In addition, the axial direction of the electrode assembly is parallel to the width direction of the electrode or separator. One side or the other side of the axial direction corresponds to the upper side or the lower side of the electrode assembly when the cylindrical electrode assembly is in an upright position. The longitudinal core-side end or the winding-direction core-side end refers to the center-side end of the electrode assembly along the longitudinal direction of the electrode or separator, and the longitudinal outer-side end or the winding-direction outer-side end refers to the outer-side end of the electrode assembly along the longitudinal direction of the electrode or separator. One side or the other side end of the electrode or separator in the width direction corresponds to one side or the other side end of the electrode assembly in the axial direction.

[0071] A battery cell (50) according to an embodiment of the present invention comprises an electrode assembly (20) and a can (10) that accommodates the electrode assembly (20).

[0072] Referring to FIGS. 1 to 7, the electrode assembly (20) is in the form of a wound jelly-roll in which a first electrode (21), a first separator (31), a second electrode (22), and a second separator (32) are stacked. Accordingly, a separator (30) is interposed between the first electrode (21) and the second electrode (22).

[0073] A separator (30) may be placed at the core-side end of the electrode assembly (20) in the winding direction. That is, the longitudinal core-side end of the first separator (31) and the second separator (32) begins to be wound while fixed to the winding pin (39), and then the first electrode (21) and the second electrode (22) begin to be wound. According to an embodiment, in the winding direction, the first electrode (21) may begin to be wound before the second electrode (22).

[0074] The above electrode assembly (20) may be in the form of a first electrode (21), a first separator (31), a second electrode (22), and a second separator (32) stacked in the stacking direction.

[0075] In an embodiment, the first electrode (21) may be a negative electrode and the second electrode (22) may be a positive electrode. However, the present invention is not limited thereto.

[0076] The first electrode (21) may be in the form in which a first active material (25) is coated on the surface of a first current collector (23). In an embodiment, the first current collector (23) may be a copper foil having a predetermined width and length. However, the present invention is not limited thereto.

[0077] The second electrode (22) may be in the form in which a second active material (26) is coated on the surface of a second current collector (24). In an embodiment, the second current collector (24) may be an aluminum foil having a predetermined width and length. However, the present invention is not limited thereto.

[0078] When considering a sheet-shaped electrode as a two-dimensional region, the two-dimensional region where an active material is coated on the surface of the current collector is referred to as the coated portion, and the region where an active material is not coated on the surface of the current collector is referred to as the uncoated portion. According to this, when considering a current collector that exists on both sides in the form of a sheet, if an active material is coated on either of the two sides of the current collector, that region can be referred to as the coated portion. On the other hand, if an active material is not coated on either side of the current collector, that region can be referred to as the uncoated portion.

[0079] Referring to FIGS. 3 and 4, in the winding direction of the electrode assembly (20), the core-side end of the separator (30) is positioned further towards the core than the core-side end of the first electrode (21), the core-side end of the separator (30) is positioned further towards the core than the core-side end of the second electrode (22), and the core-side end of the first electrode (21) is positioned further towards the core than the core-side end of the second electrode (22).

[0080] In the winding direction of the electrode assembly (20), the outer end of the first electrode (21) is positioned further outward than the outer end of the separator (30), the outer end of the first electrode (21) is positioned further outward than the outer end of the second electrode (22), and the outer end of the separator (30) is positioned further outward than the outer end of the second electrode (22).

[0081] In the winding direction of the electrode assembly (20), the core-side end of the coating portion of the first current collector (23) is positioned further towards the core than the core-side end of the coating portion of the second electrode (22), and the outer-side end of the coating portion of the first electrode (21) is positioned further towards the outer-side than the outer-side end of the coating portion of the second electrode (22).

[0082] In an embodiment, as shown in FIG. 3, when the electrode assembly (20) is stacked and unfolded, the core-side end of the region where the first active material (25) is coated on the first surface of the first current collector (23) facing the second electrode (22) with the first separator (31) in between is positioned further towards the core than the core-side end of the region where the second active material (26) is coated on the second surface of the second current collector (24) facing the first electrode (21) with the first separator (31) in between. And, the outer-side end of the region where the first active material (25) is coated on the first surface is positioned further towards the outer side than the outer-side end of the region where the second active material (26) is coated on the second surface.

[0083] In an embodiment, as shown in FIG. 4, when the electrode assembly (20) is stacked and unfolded, the width direction section of the coating portion of the second electrode (22) is included within the width direction section of the coating portion of the first electrode (21) in the width direction. That is, the coating portion of the second electrode (22) is positioned further inward in the width direction than the coating portion of the first electrode (21).

[0084] A first electrode tab (27) may be attached to the core-side end of the first electrode (21) in the winding direction. The first electrode tab (27) may protrude axially from one side of the electrode assembly (20). According to an embodiment, the first electrode tab (27) protrudes downward from the core side of the electrode assembly (20).

[0085] Referring to FIGS. 1, 3 and 4, the first electrode tab (27) may be placed in an area that does not overlap with the second electrode (22) in the stacking direction in the stacked unfolded state of the electrode assembly (20).

[0086] A first electrode (21) is disposed at the outermost part of the electrode assembly (20).

[0087] The first electrode (21) is placed on at least the outermost turn of the electrode assembly (20). When the longitudinal section in which the first electrode (21), the first separator (30), the second electrode (22), and the second separator (30) are all stacked is wound, the portion of the first electrode (21) that extends further outward from the separator (30) along the longitudinal direction can be wound further on the outermost edge of the electrode assembly (20).

[0088] A first current collector (23) of a first electrode (21) is disposed at the outermost portion of the electrode assembly (20). Accordingly, the radial outer surface of the first current collector (23) of the first electrode (21) at the outermost portion is exposed radially outward. Preferably, the radial outer surface of the first current collector (23) may be exposed over the entire circumferential portion of the electrode assembly (20).

[0089] Referring to FIG. 3, at the outer end of the first electrode (21) in the winding direction, an uncoated portion (29) in which the first active material (25) is not coated on both radial surfaces of the first current collector (23) may be disposed in a predetermined section (b). And, in the winding direction, a coated portion may be disposed on the inner side of the uncoated portion (29). Preferably, in a portion of the boundary part adjacent to the uncoated portion (29) in the winding direction from the coated portion, a first coated portion section (a) in which the first active material (25) is coated only on the radial inner surface of the first current collector (23) may be disposed. The first coated portion section (a) may be extended further outward than the separator (30) in the winding direction.

[0090] Accordingly, as illustrated in FIG. 6, the extended portions (E1~E3) of the first electrode (21) that extend further outward in the winding direction than the separator (30) may include at least a portion (E1~E2) of the first coated portion and the uncoated portion (29) portions (E2~E3). The extended portions (E1~E3) of the first electrode (21) may be wound in one or more turns and two or fewer turns at the outermost edge of the electrode assembly (20).

[0091] The first coating section (a) is positioned on the outer side of the outermost turn of the second electrode (22) with the second separator (32) in between, and may face an area where the second active material (26) is coated on the outer surface of the second current collector (24) in the radial direction. Accordingly, in an embodiment, the first coating section (a) may be wound in the electrode assembly (20) in 0.8 turns or more and 1.2 turns or less.

[0092] Preferably, the uncoated portion (29) can be wound on the electrode assembly (20) in 0.5 turns or more. More preferably, the uncoated portion (29) can be arranged in 0.8 turns or more. Accordingly, the uncoated portion (29) can sufficiently secure a winding direction section that faces the radial outer surface of the first current collector (23) of the first coated portion section (a) located further inside the winding direction, without a separator (30) in between.

[0093] Preferably, the uncoated portion (29) may be arranged in 2 turns or less. More preferably, the uncoated portion (29) may be arranged in 1.2 turns or less. Accordingly, there is no section where the uncoated portion (29) is meaninglessly wound at the outermost edge of the electrode assembly (20). Such a meaningless excess section may instead cause the current path to become longer.

[0094] A swelling sheet (40) is interposed on the inner side of the outermost turn of the first electrode (21) in the radial direction. The swelling sheet (40) may be a material that expands when impregnated with an electrolyte. The swelling sheet (40) may be made of one or more materials selected from the group consisting of polyurethane (PU), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyimide (PI). The swelling sheet (40) is not limited to these materials as long as it is a material that swells and has chemical resistance and voltage resistance. For example, the substrate of the swelling sheet (40) may be a polyolefin-based substrate, and may be, for example, polyethylene (PE) or polypropylene (PP).

[0095] The swelling sheet (40) may have an adhesive surface on its radially outer surface, an adhesive surface on its radially inner surface, or both an adhesive surface on its radially inner surface and an adhesive surface. The adhesive surface may be implemented by forming an adhesive layer on the substrate that includes one or more materials selected from the group consisting of polyacrylate (PA), rubber, and styrene.

[0096] The radial inner surface of the swelling sheet (40) contacts the radial outer surface of the first current collector (23), and the radial outer surface of the swelling sheet (40) can contact the radial inner surface of the first current collector (23). Accordingly, there is no problem with capacity reduction.

[0097] In addition, the swelling sheet (40) can also function as a finishing tape or fixing tape attached to the outer surface to prevent the outer end of the electrode assembly (20) from unraveling. That is, by applying the swelling sheet (40), the conventional finishing tape or fixing tape can be omitted.

[0098] According to the present invention, the swelling sheet (40) includes a first sheet (41) and a second sheet (42) respectively disposed on both axial sides outside the pressure relief section (35) disposed in the central part of the electrode assembly (20) in the axial direction.

[0099] The pressure relief section (35) may be set in a predetermined axial section including the axial center of the electrode assembly (20).

[0100] Preferably, the pressure relief section (35) may be set at the axial center of the electrode assembly (20) at a height of at least 1 / 4 of the axial length of the electrode assembly (20). More preferably, the pressure relief section (35) may be set at the axial center of the electrode assembly (20) at a height of at least 1 / 3 of the axial length of the electrode assembly (20).

[0101] Preferably, the center of the pressure relief section (35) in the axial direction of the electrode assembly (20) can substantially correspond to the center in the width direction of the coating portion of the first electrode (21).

[0102] When a first active material (25) of the silicon series with high electrical capacity is applied, the expansion / contraction rate of the first electrode (21) increases during the charging / discharging process of the battery cell (50), and accordingly, the pressure applied to the electrode assembly (20) in the radial direction within the internal space of the fixed can (10) increases, and especially in some sections of the axial central part.

[0103] According to the embodiment, the swelling sheet (40) is not placed in the pressure relief section (35) provided in a predetermined section of the axial center of the electrode assembly (20). That is, the pressure relief section (35) may have a clearance space equal to the thickness of the expanded swelling sheet (40). Accordingly, despite the expansion / contraction of the electrode assembly (20) due to charging / discharging, the first current collector (23) portion located on the radial outer side of the swelling sheet (40) can be maintained in a stable state of close contact with the inner surface of the can (10), while preventing excessive pressure from occurring in the axial center of the electrode assembly (20).

[0104] The swelling sheet (40) has a band shape that extends long in the circumferential direction. Accordingly, the limitation that the placement area is limited in the axial direction, which can be disadvantageous for securing the contact area between the first current collector (23) and the can (10), can be resolved.

[0105] In the first embodiment illustrated in FIGS. 1 to 4, the swelling sheet (40) is implemented in a form that is continuously extended along the circumferential direction.

[0106] However, the swelling sheet (40) may be extended intermittently, as in the second embodiment shown in FIG. 8. This further reduces the possibility that bubbles or gases generated during the impregnation process or activation process may be trapped and unable to escape by the swelling sheet (40) which is extended in the circumferential direction.

[0107] Preferably, the swelling sheet (40) is positioned in a section of 180 degrees or more in the circumferential direction of the electrode assembly (20), and more preferably, in a section of 270 degrees or more. Accordingly, the area of ​​the direct contact portion between the first current collector (23) and the inner surface of the can (10) can be sufficiently secured without compromising the cylindricality of the electrode assembly (20).

[0108] The swelling sheet (40) can be placed in a section of less than 360 degrees in the circumferential direction of the electrode assembly (20). Accordingly, the swelling sheet (40) overlaps in the radial direction, thereby eliminating factors that impair the cylindricality of the electrode assembly (20) and reduce energy density.

[0109] Referring to FIG. 6, the embodiment is implemented in such a way that the swelling sheet (40) is positioned in a range of 280 to 300 degrees (S1 to S2).

[0110] The outermost end of the winding direction of the swelling sheet (40) may extend circumferentially from the outermost end of the winding direction of the first current collector (23) to within 20 degrees of the center angle of the electrode assembly (20). For example, the angle between S2 and E3 in FIG. 6 may be within 20 degrees. It is preferable that the angle between S2 and E3 be smaller. However, if S2 and E3 coincide, the step difference at the outer circumferential end of the first electrode (21) may become somewhat larger. To resolve this step difference, it is desirable for the angle between S2 and E3 to exist.

[0111] Meanwhile, the second electrode (22) may have a second electrode tab (28) protruding axially from the electrode assembly (20).

[0112] Referring to FIGS. 1 to 9, in the first or second embodiment, the second electrode tab (28) is implemented by a tab member joined to the second current collector (24) of the second electrode (22). The tab member is joined to the surface of the second current collector (24) on which the second active material (26) is not coated, and extends further outward than the second electrode (22) in the axial direction.

[0113] The second electrode tab (28) may be positioned in the longitudinal center of the second electrode (22) in consideration of internal resistance. However, the number or position of the tab members is not limited to this.

[0114] Referring to FIG. 9, the electrode assembly (20) is housed inside the can (10) such that the first electrode tab (27) faces the bottom member (12) and the second electrode tab (28) faces the cap assembly (13). The can (10) may be made of an electrically conductive metal material and may have a hollow cylindrical shape.

[0115] The first electrode tab (27) is welded to the inner surface of the bottom member (12) of the can (10) through a welding process such as ultrasonic welding, resistance welding, or laser welding. If necessary, a first insulator (14) with electrical insulation properties may be interposed between the electrode assembly (20) and the bottom member (12).

[0116] The inner surface of the side wall (11) of the can (10) and the first current collector (23) exposed at the outermost edge of the electrode assembly (20) are in direct contact. When an electrolyte is injected into the interior of the can (10), the swelling sheet (40) expands and presses the first current collector (23) against the inner surface of the side wall (11).

[0117] An electrically insulating second insulator (15) is interposed on the upper part of the electrode assembly (20) to electrically insulate the can (10) and the electrode assembly (20). The cap assembly (13) welded to the second electrode tab (28) covers the opening of the can (10) and is pressed onto the upper part of the side wall (11) with a gasket (16) interposed therein to provide an insulating seal and secure fixation.

[0118] Meanwhile, referring to FIG. 10 and FIG. 11, the electrode assembly (20) of the third embodiment is implemented by an uncoated portion (29) in which the second active material (26) is not coated on both surfaces of the second current collector (24) at the axial other end of the second electrode (22).

[0119] As illustrated in FIG. 11, the uncoated portion (29) of the second electrode (22) is laminated so as to extend further axially outward than the separator (28) at the other axial end of the electrode assembly (20). The uncoated portion (29) itself functions as at least one electrode tab.

[0120] In the above uncoated portion (29), notches can be formed at predetermined intervals to form second electrode tabs (28) in the shape of flags.

[0121] In the third embodiment, the second electrode tabs (28) are implemented in the shape of an isosceles trapezoid. However, their shapes may be various shapes such as a semicircle, a semi-ellipse, a triangle, a rectangle, a parallelogram, etc.

[0122] In addition, in the third embodiment, the second electrode tabs (28) arranged along the length direction are implemented to have the same width. However, the width of the second electrode tabs may be gradually or stepwise widening from the core side to the outer circumference side.

[0123] In addition, in the third embodiment, as shown in FIGS. 10 and 11, the height of the second electrode tabs (28) is implemented to increase stepwise from the core side to the outer side. However, alternatively, the height of these second electrode tabs may be implemented to be constant or gradually decrease.

[0124] In addition, in the third embodiment, a structure is implemented in which the second electrode tab (28) is removed in a predetermined section of the core-side end and a predetermined section of the outer-side end of the uncoated part (29) in the winding direction. However, alternatively, the second electrode tab may not be removed from the core-side end of the uncoated part, the second electrode tab may not be removed from the outer-side end of the uncoated part, or the second electrode tab may not be removed from both sides.

[0125] In the jelly-roll type electrode assembly (20), the second electrode tab (28) can be folded and flattened in a radial direction as shown in FIG. 12. The second electrode tab (28) can be folded inward in the radial direction or folded outward. In a third embodiment, the second electrode tab (28) is implemented in a structure that is folded inward in the radial direction.

[0126] The second electrode tab (28) may be pre-folded one by one during the process of forming a jelly-roll type electrode assembly (20) by stacking and winding electrodes and a separator, and then finally folded again after being wound into a jelly-roll type. Alternatively, the second electrode tab (28) may be folded all at once after forming a jelly-roll type electrode assembly by stacking and winding electrodes and a separator.

[0127] The second electrode tabs (28) of the second electrode (22), which are bent radially and stacked in multiple axially, can provide a plane substantially perpendicular to the axial direction at the axial end of the electrode assembly (20).

[0128] A current collector plate (47) can be attached to a substantially flat surface provided by bending the second electrode tab (28).

[0129] The above current collector plate (47) may be manufactured by punching, trimming, piercing, or bending a metal sheet or a metal plate. In an embodiment, the above current collector plate (47) is implemented as an anode current collector plate including aluminum material. However, the present invention is not limited thereto.

[0130] Referring to FIG. 12, the inner surface of the side wall (11) of the can (10) and the first current collector (23) exposed at the outermost edge of the electrode assembly (20) are in direct contact. When an electrolyte is injected into the interior of the can (10), the swelling sheet (40) expands and presses the first current collector (23) against the inner surface of the side wall (11).

[0131] The cap assembly (13) welded to the current collector plate (47) covers the opening of the can (10) and is fixed to the upper part of the side wall (11) by being compressed with a gasket (16) interposed therein, thereby providing insulation sealing. Accordingly, the conductive route of the second electrode (22) and the cap assembly (13) is extended through the current collector plate (47), so that the internal resistance can be further reduced.

[0132] In addition to the various embodiments of the electrode assembly (20) and battery cell (50) described above, the present invention can be implemented in various forms.

[0133] The embodiments described above should be understood as exemplary in all respects and not limiting, and the scope of the invention will be defined by the claims set forth below rather than by the detailed description above. Furthermore, the meaning and scope of the claims set forth below, as well as all modifications and variations derived from equivalents thereof, should be interpreted as being included within the scope of the invention.

[0134] Although the present invention has been described above with reference to the illustrated drawings, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration according to the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. A battery cell having a jelly-roll type cylindrical electrode assembly embedded inside a cylindrical can, wherein a first electrode and a second electrode are wound with a separator in between. The first electrode is disposed at the outermost edge of the winding direction of the electrode assembly, and The first current collector of the outermost first electrode is exposed outward in the radial direction, and A swelling sheet that expands by being impregnated with an electrolyte is interposed in the radially inner side of the outermost turn of the first electrode, in an area corresponding to the region where the first current collector is exposed radially outward, and The above swelling sheet is a battery cell, each disposed on both axial sides outside the pressure relief section disposed in the central part of the electrode assembly in the axial direction.

2. A battery cell according to claim 1, wherein the pressure relief section is set at the axial center of the electrode assembly by a height of at least 1 / 4 of the axial length of the electrode assembly.

3. A battery cell according to claim 2, wherein the pressure relief section is set at the axial center of the electrode assembly by a height of at least 1 / 3 of the axial length of the electrode assembly.

4. A battery cell according to claim 1, wherein the swelling sheet has a band shape extending in the circumferential direction.

5. A battery cell according to claim 4, wherein the width of the band corresponding to the axial direction of the electrode assembly is less than 1 / 3 of the axial length of the electrode assembly.

6. The battery cell according to claim 1, wherein the swelling sheet surrounds a section of 180 degrees or more in the circumferential direction of the electrode assembly.

7. The battery cell according to claim 1, wherein the swelling sheet surrounds a section of less than 360 degrees in the circumferential direction of the electrode assembly.

8. The battery cell according to claim 1, wherein the swelling sheet comprises at least one surface of a radially outer surface or an inner surface having an adhesive surface.

9. A battery cell according to claim 1, wherein the outermost end of the swelling sheet in the winding direction extends circumferentially from the outermost end of the first current collector in the winding direction to within a center angle of 20 degrees of the electrode assembly.

10. The battery cell according to claim 1, wherein the swelling sheet is continuously extended in the circumferential direction.

11. The battery cell of claim 1, wherein the swelling sheet is intermittently extended in the circumferential direction.

12. A battery cell according to claim 1, wherein the radial outer surface of the first current collector is exposed over the entire circumferential section of the electrode assembly.

13. In claim 1, the outer end of the first electrode in the winding direction, A battery cell having a coating portion having a first active material coated only on the inner surface in the radial direction of a first current collector, arranged in a manner of 0.8 turns or more and 1.2 turns or less, and an uncoated portion having no coating of the first active material on both radial surfaces of the first current collector arranged further outward in the winding direction.

14. The battery cell of claim 13, wherein the uncoated portion is arranged in 0.8 turns or more.

15. The battery cell of claim 14, wherein the uncoated portion is arranged in 2 turns or less.

16. A battery cell according to claim 15, wherein the uncoated portion is arranged in 1.2 turns or less.

17. In claim 1, a separator is disposed at the core-side end of the electrode assembly in the winding direction, and A battery cell in which the first electrode begins to be wound before the second electrode in the above winding direction.

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