Electrode assembly comprising diagonally-formed electrode tab, and electrode assembly manufacturing method

Abstract

The present disclosure relates to an electrode assembly and an electrode assembly manufacturing method. The electrode assembly according to the present disclosure may comprise: a first electrode; a first electrode tab disposed on the first electrode; a separator; a second electrode; and a second electrode tab disposed on the second electrode, wherein an inner end of the first electrode tab is formed diagonally and can be disposed to be spaced apart from an inner end of the second electrode tab.

Description

Electrode assembly including diagonally formed electrode tabs and method for manufacturing the electrode assembly

[0001] The present disclosure relates to an electrode assembly and a method for manufacturing the electrode assembly.

[0002] Secondary batteries, unlike non-rechargeable primary batteries, are rechargeable and dischargeable. Low-capacity secondary batteries are used in small, portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while large-capacity secondary batteries are widely used as power sources for motor drives and power storage in hybrid and electric vehicles. These secondary batteries include an electrode assembly comprising a positive and negative electrode, a case housing the electrode assembly, and electrode terminals connected to the electrode assembly.

[0003] In secondary batteries, particularly lithium-ion batteries, the charging and discharging process occurs through the movement of lithium ions between the electrolyte and the electrodes. During this process, the electrodes containing the active material undergo physical volume changes as they absorb or release lithium ions. This shrinkage and expansion can cause problems that can significantly impact the battery's lifespan and performance.

[0004] For example, due to the step between the electrode and electrode tab of an electrode assembly inserted in a wound state into a secondary battery case, the electrode may be subjected to uneven mechanical stress when the electrode assembly shrinks and expands. In this case, cracks may occur in the electrode where the electrode tab is located. In the long term, these cracks may cause short circuits or delamination within the electrode assembly, leading to deterioration of battery performance, increased electrical resistance, or shortened lifespan, and further, may significantly reduce the safety and reliability of the battery.

[0005] In particular, in the case of conventional cylindrical cell-shaped secondary batteries, the positive and negative electrode tabs were arranged vertically in the same location in order to maximize the capacity relative to the battery size. However, when the electrode assembly expands, mechanical stress is generated around the electrode tabs, causing cracks in the electrode substrate and reducing the stability of the battery. In particular, in the case of cylindrical cell-shaped secondary batteries, since the jelly roll is wound, there is a problem in that a strong tension is generated in the wound direction where the expansion is large.

[0006] The problem to be solved by the present invention is to provide an electrode assembly and a battery including the same for solving the above technical problem.

[0007] 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.

[0008] An electrode assembly according to one embodiment of the present invention for solving a technical problem includes a first electrode, a first electrode tab disposed on the first electrode, a separator, a second electrode, and a second electrode tab disposed on the second electrode, wherein an inner end of the first electrode tab is formed diagonally and can be disposed spaced apart from an inner end of the second electrode tab.

[0009] According to one embodiment, the inner end of the second electrode tab can be formed into a diagonal shape corresponding to the shape of the inner end of the first electrode tab.

[0010] In one embodiment, the inner end of the first electrode tab and the inner end of the second electrode tab may be spaced apart from each other by 1 mm to 3 mm.

[0011] According to one embodiment, the vertical axis of the first electrode tab and the vertical axis of the second electrode tab may be parallel to each other.

[0012] According to one embodiment, the vertical axis of the first electrode tab and the vertical axis of the second electrode tab may be positioned on the same straight line.

[0013] According to one embodiment, the first electrode tab may be disposed on an inner surface of the first electrode facing the separator.

[0014] In one embodiment, the first electrode tab may be positioned on an outer surface of the first electrode that does not contact the separator.

[0015] According to one embodiment, the second electrode tab may be disposed on the inner surface of the second electrode facing the separator.

[0016] In one embodiment, the second electrode tab may be positioned on an outer surface of the second electrode that does not contact the separator.

[0017] According to one embodiment, the first electrode tab may be positioned on the uncoated portion of the first electrode, and the second electrode tab may be positioned on the uncoated portion of the second electrode.

[0018] According to one embodiment, at least a portion of the uncoated portion of the first electrode and the uncoated portion of the second electrode may be positioned on the same row transverse to the width direction of each of the first electrode and the second electrode.

[0019] According to one embodiment, the angle formed by the inner end of the first electrode tab with the longitudinal direction of the first electrode may be 15° to 75°.

[0020] According to one embodiment, the angle formed by the inner end of the first electrode tab with the longitudinal direction of the first electrode may be 30° to 60°.

[0021] According to one embodiment, the inner end of the first electrode tab includes a first vertex and a second vertex, and the first vertex can be rounded.

[0022] In one embodiment, the second vertex may be rounded.

[0023] According to one embodiment, the inner end of the second electrode tab includes a third vertex and a fourth vertex, and the third vertex can be rounded.

[0024] In one embodiment, the fourth vertex may be rounded.

[0025] A secondary battery according to another embodiment of the present invention for solving a technical problem includes an electrode assembly according to the present invention.

[0026] A method for manufacturing an electrode assembly according to another embodiment of the present invention for solving a technical problem may include a step of forming one end of a first electrode tab diagonally, a step of sequentially stacking a first electrode tab, a first electrode, a separator, a second electrode, and a second electrode tab by arranging the one end to be electrically connected to one side of the first electrode tab, and a step of winding the stacked first electrode tab, the first electrode, the separator, the second electrode, and the second electrode tab.

[0027] According to one embodiment, the method for manufacturing an electrode assembly may further include, prior to the laminating step, a step of forming one end of the second electrode tab into a diagonal shape corresponding to the shape of one end of the first electrode tab.

[0028] According to some embodiments of the present disclosure, by changing the shape of each electrode tab of a positive electrode and a negative electrode of an electrode assembly of a secondary battery while maintaining the distance between the electrode tabs, cracks that may occur within the electrode assembly can be suppressed without increasing battery resistance.

[0029] According to some embodiments of the present disclosure, by changing the shape of the terminal of each electrode tab of the positive and negative electrodes of the electrode assembly of the secondary battery to be inclined obliquely in the width direction or length direction of the electrode, the mechanical stress generated when the terminal of the electrode tab presses the electrode substrate can be reduced.

[0030] According to some embodiments of the present disclosure, by chamfering the apex portion of the shape of the terminal of each electrode tab of the positive and negative electrodes of the electrode assembly of the secondary battery, the mechanical stress generated when the terminal of the electrode tab presses the electrode substrate can be further reduced.

[0031] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0032] 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.

[0033] FIG. 1 is a drawing showing an electrode assembly according to one embodiment of the present disclosure.

[0034] FIG. 2 is a drawing showing an electrode assembly and electrode tab according to one embodiment of the present disclosure.

[0035] FIG. 3 is an exploded view of an electrode assembly according to one embodiment of the present disclosure.

[0036] FIG. 4 is a perspective view and a cross-sectional view of an electrode assembly according to one embodiment of the present disclosure.

[0037] FIG. 5 is a perspective view and a cross-sectional view of an electrode assembly according to another embodiment of the present disclosure.

[0038] FIGS. 6 to 8 are plan views showing the inner end of an electrode tab according to various embodiments of the present disclosure.

[0039] FIG. 9 is a drawing showing a first electrode tab and a second electrode tab according to various embodiments of the present disclosure.

[0040] FIG. 10 is a cross-sectional view of an electrode assembly according to various embodiments of the present disclosure.

[0041] Figure 11 is a flowchart illustrating an example of a method for manufacturing an electrode assembly according to the present disclosure.

[0042] Figure 12 is a drawing for explaining a problem occurring in a conventional electrode assembly.

[0043] FIG. 13 is a drawing showing a secondary battery according to one embodiment of the present disclosure.

[0044] 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.

[0045] 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.

[0046] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0047] 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 also mean uniformity on average.

[0048] 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.

[0049] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0050] Any configuration being arranged "on the top (or bottom)" of a component or "on the upper (or lower) side" of a component may mean not only that any configuration is arranged in contact with the upper surface (or lower surface) of the component, but also that another configuration may be interposed between the component and any configuration arranged on (or under) the component. In addition, in the drawings, the portion between the upper and lower portions of the components depicted or the remaining portion excluding the upper and lower portions may be referred to as a "side" or a "side surface." Additionally, the direction toward the internal space of the component may be referred to as "inner," and the direction protruding into the open external space may be referred to as "outer." Relative terms such as "upper," "top," etc. may be used to describe the relationship between the configurations depicted in the drawings, and the present disclosure is not limited by such terms.

[0051] 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.

[0052] 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.

[0053] 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." The use of phrases such as "one or more" before a list of elements modifies the list as a whole and does not modify individual elements in the list.

[0054] 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 through D,” this means C or more and D or less, unless otherwise stated.

[0055] 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.

[0056] 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.

[0057] FIG. 1 is a drawing showing an electrode assembly according to one embodiment of the present disclosure.

[0058] Referring to FIG. 1, an electrode assembly (100) according to one embodiment of the present invention for solving a technical problem may include a first electrode (110), a first electrode tab (120) disposed on the first electrode (110), a separator (130), a second electrode (140), and a second electrode tab (150) disposed on the second electrode (140).

[0059] The first electrode (110) of the battery may be a plate corresponding to the positive or negative electrode of the battery. In addition, the second electrode (140) of the battery may be an electrode corresponding to a pole opposite to the first electrode (110) of the battery. For example, if the first electrode (110) of the battery is the positive electrode, the second electrode (140) of the battery may be the negative electrode. In another example, conversely, if the first electrode (110) of the battery is the negative electrode, the second electrode (140) of the battery may be the positive electrode. Here, the negative electrode substrate may be made of copper (Cu), and the positive electrode substrate may be made of aluminum (Al), but the present invention is not limited thereto, and various substrates used in the art may be used.

[0060] Specifically, when the first electrode (110) is a cathode, the first electrode (110) is formed by applying a first electrode active material such as graphite or carbon to a first electrode substrate formed of a metal foil such as copper, a copper alloy, nickel, or a nickel alloy, and may include a first uncoated portion (112) which is a region where the first electrode active material is not applied. The first electrode tab (120) may be arranged on the first uncoated portion (112), and the first electrode tab (120) may serve as a path for current flow between the first electrode (110) and the cathode current collector.

[0061] Additionally, the first electrode tab (120) includes an inner end (122) and an outer end opposite the inner end (122), and the outer end may be formed to protrude further than one side of the first electrode (110) or one side of the separator (130).

[0062] When the second electrode (140) is an anode, the second electrode (140) is formed by applying a second electrode active material such as a transition metal oxide to a second electrode substrate formed of a metal foil such as aluminum or an aluminum alloy, and may include a second non-coated portion (142) which is an area where the second electrode active material is not applied. The second electrode tab (150) may be disposed on the second non-coated portion (142), and the second electrode tab (150) may serve as a passage for current flow between the second electrode (140) and the positive electrode current collector. In addition, the second electrode tab (150) may include an inner end arranged at a position facing the first electrode tab (120) and an outer end protruding to the outside of the second electrode (140) while the first electrode (110), the separator (130), and the second electrode (140) are interposed therebetween. The outer end of the second electrode tab (150) may be formed to protrude more than one side of the second electrode (140) or one side of the separator (130).

[0063] Referring to FIG. 1, the first uncoated portion (112) where the first electrode tab (120) is positioned is positioned at the middle of the length direction of the first electrode (110), and the second uncoated portion (142) where the second electrode tab (150) is positioned is positioned at the middle of the length direction of the second electrode (140), but is not limited thereto. In some examples, the first uncoated portion (112) and the first electrode tab (120) positioned on the first uncoated portion (112) may be positioned at one end of the length direction of the first electrode (110). Similarly, the second uncoated portion (142) and the second electrode tab (150) positioned on the second uncoated portion (142) may be positioned at one end of the length direction of the second electrode (140). At this time, it is preferable that the first uncoated portion (112) and the second uncoated portion (142) are positioned at the same location in the same direction on the first electrode (110) and the second electrode (140), respectively. This is described in detail in Fig. 4.

[0064] After stacking and winding of the plurality of electrodes, separators, and electrode tabs of the electrode assembly (100), the first electrode tab (120) may be positioned at the upper portion of the electrode assembly (100), and the second electrode tab (150) may be positioned at the lower portion of the electrode assembly (100), or may be positioned on one side in the same direction. Here, for convenience of explanation, 'upper portion' and 'lower portion' correspond to the upper portion and lower portion of the secondary battery illustrated in FIG. 13, for example, and their positions may change when the secondary battery is rotated left and right or up and down.

[0065] In one embodiment, the inner end (122) of the first electrode tab (120) may be formed diagonally. This is described in detail in FIG. 2. In addition, in one embodiment, the inner end (122) of the first electrode tab (120) may be positioned a specific distance apart from the inner end of the second electrode tab (150). This is described in detail in FIG. 4.

[0066] FIG. 2 is a drawing showing an electrode assembly and electrode tab according to one embodiment of the present disclosure.

[0067] Referring to FIG. 2, the inner end (122) of the first electrode tab (120) may be formed diagonally. Specifically, the angle at which the direction of the straight line tangent to the lower surface (126) of the inner end (122) intersects one side of the first uncoated portion (112) of the first electrode, or the angle at which the straight line tangent to the lower surface (126) of the inner end (122) intersects the longitudinal direction (200) of the first electrode, may correspond to a specific angle less than 90 degrees. Here, the lower surface (126) of the inner end (122) (or the cut surface of the inner end (122)) may be arranged perpendicular to the surface of the first uncoated portion (112) of the first electrode, but is not limited thereto. For example, the cut surface of the inner end (122) may be formed to be inclined with respect to the surface of the first uncoated portion (112) of the first electrode.

[0068] The longitudinal direction (200) of the first electrode may refer to the direction in which the electrode assembly is wound or the direction opposite to the direction in which the electrode assembly is wound, if the electrode assembly is of the winding type. Alternatively, the longitudinal direction (200) of the first electrode may refer to the direction perpendicular to the line segment that is bent for stacking, if the electrode assembly is of the stack type. Alternatively or additionally, the longitudinal direction (200) of the first electrode may refer to a longer direction in the first electrode (110) formed in a thin plate shape or film shape.

[0069] Angle of separation (°) Distance between tabs (mm) Probability of crack occurrence (%) Comparative example 0 1 9 4 Example 1 1 0 1 6 0 Example 2 1 5 1 4 4 Example 3 3 0 1 2 8 Example 4 4 ​​5 1 1 6 Example 5 6 0 1 2 8 Example 6 7 5 1 4 5 Example 7 8 0 1 8 9

[0070] Table 1 is data comparing the crack occurrence probability of examples and comparative examples in which the angle formed by the inner end (122) of the first electrode tab (120) with the longitudinal direction (200) of the first electrode is varied. Referring to Table 1, when the angle formed by the inner end (122) of the first electrode tab (120) with the longitudinal direction (200) of the first electrode is 15° to 75°, i.e., in examples 2 to 6, the probability of crack occurrence in the first uncoated portion (112) may be less than 50%.

[0071] In one embodiment, if the angle formed by the inner end (122) of the first electrode tab (120) with respect to the longitudinal direction (200) of the first electrode is an acute angle of 30° or less, the mechanical stress that the non-coated portion (112) receives from the lower surface (126) of the first electrode tab (120) due to shrinkage or expansion of the electrode assembly may not be effectively distributed, thereby reducing the crack inhibition effect according to the present invention. In another embodiment, if the angle formed by the inner end (122) of the first electrode tab (120) with respect to the longitudinal direction (200) of the first electrode is an acute angle of 60° or more, the inner end (122) of the first electrode tab (120) may become excessively sharp, thereby condensing the force with which the first electrode tab (120) presses the non-coated portion (112) to one point (for example, the vertex of the inner end (122)), thereby reducing the crack inhibition effect according to the present invention.

[0072] In Examples 3 to 5, the probability of a crack occurring in the first non-conductive portion (112) may be less than 30%. Therefore, according to one embodiment, it is preferable that the angle formed by the inner end (122) of the first electrode tab (120) and the longitudinal direction (200) of the first electrode (110) is 30° to 60°.

[0073] According to some embodiments of the present disclosure, by changing the shape of the terminal of each electrode tab of the positive and negative electrodes of the electrode assembly of the secondary battery to be inclined obliquely in the width direction or length direction of the electrode, the mechanical stress generated when the terminal of the electrode tab presses the electrode substrate can be reduced.

[0074] FIG. 3 is an exploded view of an electrode assembly according to one embodiment of the present disclosure.

[0075] Referring to FIG. 3, the first electrode tab (313) may be placed on the first uncoated portion (312) of the first electrode (311), and the second electrode tab (317) may be placed on the second uncoated portion (316) of the second electrode (315). The inner end of the first electrode tab (313) may be formed diagonally to form a specific angle (for example, less than 90 degrees) with respect to the longitudinal direction (i.e., the left-right direction in the drawing) of the first electrode (315). Although not shown, when laminated in an electrode assembly, a separator is placed between the first electrode (311) and the second electrode (315), so that the first electrode (311) and the second electrode (315) are electrically insulated from each other.

[0076] Meanwhile, the inner end of the second electrode tab (317) may be formed diagonally. That is, the second electrode tab (317) may be formed diagonally to form a specific angle with respect to the longitudinal direction (i.e., the left-right direction in the drawing) of the second electrode (315), similar to the inner end of the first electrode tab (313) described above. The shape of the second electrode tab (317) is described in detail in FIG. 4.

[0077] FIG. 4 is a perspective view (310) and a cross-sectional view (320) of an electrode assembly according to one embodiment of the present disclosure.

[0078] Referring to the perspective view (310) of FIG. 4, the inner end (327) of the second electrode tab (317) can be formed into a diagonal line corresponding to the shape of the inner end (323) of the first electrode tab (313). Specifically, the inner end (327) of the second electrode tab (317) can be formed such that the first diagonal line (324) drawn by the shape of the inner end (323) of the first electrode tab (313) and the second diagonal line (328) drawn by the shape of the inner end (327) of the second electrode tab are parallel to each other.

[0079] According to some embodiments of the present disclosure, the first diagonal line (324) and the second diagonal line (328) are parallel to each other, so that the phenomenon of external force being applied between the first electrode tab (313) and the non-conductive part or between the second electrode tab (317) and the non-conductive part can be minimized.

[0080] In one embodiment, the inner end (323) of the first electrode tab (313) may be spaced apart from the inner end (327) of the second electrode tab (317) by a specific distance. For example, the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317) may be spaced apart from each other by about 1 mm to 3 mm.

[0081] Table 2 shows the change in the probability of crack occurrence in the electrode according to the change in the distance between the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317). Referring to Table 2, as the distance between the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317) increases, the probability of crack occurrence in the electrode decreases. For example, as shown in Comparative Examples 1 to 3, the probability of crack occurrence decreased from 98% to 83% to 60% while the distance increased from about 1 mm to 3 mm. In addition, as shown in Examples 1 to 3, when the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317) are formed at a 45-degree angle, the probability of crack occurrence decreased from 16% to 10% to 0% while the distance between the inner ends increased from about 1 mm to 3 mm.

[0082] Angle of separation (°) Distance between tabs (mm) Probability of crack occurrence (%) Comparative example 10198 Comparative example 20283 Comparative example 30360 Example 145116 Example 245210 Example 34530

[0083] However, as the distance between the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317) increases, the area of ​​contact between the electrode tab and the non-conductive portion of the electrode decreases, which may result in an increase in current resistance in the battery assembly. Accordingly, a person skilled in the art can appropriately select and design the distance between the inner end (323) of the first electrode tab (313) and the inner end (327) of the second electrode tab (317) within the disclosed range, depending on the required output and purpose of the secondary battery.

[0084] Referring to the cross-sectional view (320) of FIG. 4, at least a portion of the uncoated portion (312) of the first electrode and the uncoated portion (316) of the second electrode may be positioned on the same row extending in the width direction of each of the first and second electrodes. That is, the uncoated portion (312) of the first electrode and the uncoated portion (316) of the second electrode may be positioned so that at least a portion overlaps in the perspective view (310).

[0085] The uncoated portion (312) of the first electrode has a thinner thickness than the other sections of the first electrode due to the absence of the first active material (332). Similarly, the uncoated portion (316) of the second electrode has a thinner thickness than the other sections of the second electrode due to the absence of the second active material (335). Therefore, the first electrode tab (313) and the second electrode tab (317) can be arranged in the region where the uncoated portion (312) of the first electrode exists when the first electrode and the second electrode are stacked. At the same time, the first electrode tab (313) and the second electrode tab (317) can be arranged in the region where the uncoated portion (316) of the second electrode exists when the first electrode and the second electrode are stacked. Specifically, the vertical axis (321) of the first electrode tab (313) may be positioned in an area where the uncoated portion (316) of the second electrode exists, and the vertical axis (325) of the second electrode tab (317) may be positioned in an area where the uncoated portion (312) of the first electrode exists. According to one embodiment, the vertical axis (321) of the first electrode tab (313) and the vertical axis (325) of the second electrode tab (317) may approximately overlap or be parallel to each other.

[0086] FIG. 5 is a perspective view (410) and a cross-sectional view (420) of an electrode assembly according to another embodiment of the present disclosure.

[0087] Referring to FIG. 5, in one embodiment, the vertical axis of the first electrode tab (413) and the vertical axis of the second electrode tab (417) may be positioned to overlap on the same straight line (412). In addition, similar to the embodiment illustrated in FIG. 4, the first diagonal line (424) drawn by the shape of the inner end of the first electrode tab (413) and the second diagonal line (428) drawn by the shape of the inner end of the second electrode tab (417) may be spaced apart from each other by a specific distance and may be parallel to each other. Through this, the phenomenon of the external force being biased between the first electrode tab (413) and the non-coated portion or between the second electrode tab (417) and the non-coated portion can be minimized.

[0088] FIGS. 6 to 8 are plan views showing the inner end of an electrode tab according to various embodiments of the present disclosure.

[0089] Referring to FIG. 6, in the first embodiment (501), the inner end (522) of the first electrode tab (520) disposed on the first uncoated portion (512) of the first electrode (510) may include a first vertex (523) and a second vertex (524). Specifically, the first vertex (523) may refer to a vertex including an acute angle, where the angle formed by the internal angles of the two sides touching at the vertex is less than 90 degrees. In addition, the second vertex (524) may refer to a vertex including an obtuse angle, where the angle formed by the internal angles of the two sides touching at the vertex is greater than 90 degrees. In FIG. 6, the first vertex (523) is illustrated as being located to the right of the second vertex (524), but this is not limited thereto, and various arrangements may be possible depending on the number and direction of the diagonal lines.

[0090] Referring to Fig. 7, in the second embodiment (502), the first vertex (563) can be rounded. The shape of the chamfered first vertex (563) is not limited thereto, and may include a polygonal, circular, or nearly circular curved surface. The method for chamfering the first vertex (563) may include any manufacturing method that a person skilled in the art can use to manufacture a curved surface of a plate-shaped or film-shaped material, such as a method of forming a first electrode tab (520) made of metal or a conductor using a high-speed press, a cutting method using a laser, or a grinding method.

[0091] Referring to Fig. 8, in the third embodiment (503), the second vertex (584) may be rounded. The shape and chamfering method of the second vertex (584) may be the same as or similar to those described above in Fig. 7. In addition, in the third embodiment (503), the first vertex (563) in the shape of the first electrode tab is also depicted as having a chamfered shape similar to the second vertex (584), but a shape in which only the second vertex (584) is chamfered while the first vertex (563) is not chamfered is also possible.

[0092] Table 3 shows the change in the probability of crack occurrence in the electrode depending on whether the inner end (522) of the first electrode tab (520) is chamfered. Referring to Table 3, regardless of the angle that the inner end (522) of the first electrode tab (520) forms with the longitudinal direction of the first electrode (510), if the inner end (522) of the first electrode tab (520) is chamfered, the probability of crack occurrence is further reduced.

[0093] Angle of distinction (°) Distance between tabs (mm) Presence of chamfering Probability of crack occurrence (%) Comparative example 101 None 98 Comparative example 202 Yes 83 Example 1451 No 16 Example 2452 Yes 10

[0094] A method of chamfering the inner end of an electrode tab in this manner can play a significant role in improving battery performance. According to some embodiments of the present disclosure, by chamfering the apex portion of the terminal shape of each of the positive and negative electrode tabs of an electrode assembly of a secondary battery, the mechanical stress generated when the terminal of the electrode tab presses against the electrode substrate can be further reduced.

[0095] FIG. 9 is a drawing showing a first electrode tab and a second electrode tab according to various embodiments of the present disclosure.

[0096] Referring to FIG. 9, the first example (601) illustrates a state in which both the inner end of the first electrode tab (610) and the inner end of the second electrode tab (620) are not chamfered. The second example (602) illustrates a state in which the inner end of the first electrode tab (610) is chamfered. The third example (603) illustrates a state in which the inner end of the second electrode tab (620) is chamfered. The fourth example (604) illustrates a state in which both the inner end of the first electrode tab (610) and the inner end of the second electrode tab (620) are rounded.

[0097] In the first example (601) to the fourth example (604), the inner end of the second electrode tab (620) includes a third vertex (623) and a fourth vertex (624). Here, the third vertex (623) may be rounded. Similarly, the fourth vertex (623) may be rounded. In the third example (603) and the fourth example (604), both the third vertex (623) and the fourth vertex (624) in the shape of the second electrode tab (620) are shown as being rounded, but a shape in which the third vertex (623) is not chamfered and only the fourth vertex (624) is chamfered is also possible. Conversely, a shape in which the fourth vertex (624) is not chamfered and only the third vertex (623) is chamfered is also possible.

[0098] According to the present invention, the electrode assembly of a secondary battery may include at least one of the first example (601) to the fourth example (604). Preferably, in order to minimize mechanical stress generated when the terminal of the electrode tab presses the electrode substrate, the electrode assembly may include a first electrode tab (610) and a second electrode tab (620) having a terminal shape according to the fourth example (604).

[0099] FIG. 10 is a cross-sectional view of an electrode assembly according to various embodiments of the present disclosure.

[0100] Specifically, referring to FIG. 10, the first example (701) to the fourth example (704) are cross-sectional views illustrating sections of an electrode assembly including a first electrode tab (720) and a second electrode tab (750) cut in the width direction of the electrode. For example, the fourth example (704) may be a cross-section cut along a straight line (412) in FIG. 5 where the vertical axis of the first electrode tab (414) and the vertical axis of the second electrode tab (417) are located. In the first example (701) to the fourth example (704), the first electrode tab (720) and the second electrode tab (750) may have at least one of the terminal shapes formed diagonally according to various embodiments described with reference to FIGS. 1 to 9.

[0101] According to the first example (701), the first electrode tab (720) may be placed on the outer surface (712) of the first electrode (710) that does not contact the separator (730). At the same time, the second electrode tab (750) may be placed on the outer surface (742) of the second electrode (740) that does not contact the separator (730).

[0102] According to the second example (702), the first electrode tab (720) may be placed on the outer surface (712) of the first electrode (710) that does not contact the separator (730). At the same time, the second electrode tab (750) may be placed on the inner surface (744) of the second electrode (740) facing the separator (730).

[0103] According to the third example (703), the first electrode tab (720) may be placed on the inner surface (714) of the first electrode (710) facing the separator (730). At the same time, the second electrode tab (750) may be placed on the outer surface (742) of the second electrode (740) that does not contact the separator (730).

[0104] According to the fourth example (704), the first electrode tab (720) may be placed on the inner surface (714) of the first electrode (710) facing the separator (730). At the same time, the second electrode tab (750) may be placed on the inner surface (744) of the second electrode (740) facing the separator (730).

[0105] Figure 11 is a flowchart illustrating an example of a method for manufacturing an electrode assembly according to the present disclosure.

[0106] A method for manufacturing an electrode assembly (800) according to one embodiment of the present invention may be initiated by forming one end of a first electrode tab in a diagonal direction (S810). Additionally, one end of the first electrode tab may be positioned toward the inside of the electrode assembly to form an inner end of the first electrode tab. According to one embodiment, the inner end of the first electrode tab includes a first vertex and a second vertex, and the first vertex or the second vertex may be rounded.

[0107] Thereafter, the first electrode tab, the first electrode, the separator, the second electrode, and the second electrode tab may be sequentially stacked by arranging one end portion to be electrically connected to one side of the first electrode tab (S820). Specifically, the first electrode tab may be arranged on the uncoated portion of the first electrode, and the second electrode tab may be arranged on the uncoated portion of the second electrode. At least a portion of the uncoated portion of the first electrode and the uncoated portion of the second electrode may be arranged to be positioned on the same row crossing the width direction of each of the first electrode and the second electrode.

[0108] In one embodiment, the inner end of the first electrode tab may be formed diagonally and may be positioned spaced apart from the inner end of the second electrode tab. Specifically, the inner end of the first electrode tab and the inner end of the second electrode tab may be spaced apart by 1 mm to 3 mm. The angle formed by the inner end of the first electrode tab with respect to the longitudinal direction of the first electrode may be 15° to 75°, preferably 30° to 60°. In addition, according to one embodiment, before the laminating step, the method may further include a step of forming one end of the second electrode tab into a diagonal shape corresponding to the shape of one end of the first electrode tab.

[0109] In one embodiment, the vertical axis of the first electrode tab and the vertical axis of the second electrode tab may be parallel to each other. Additionally, the vertical axis of the first electrode tab and the vertical axis of the second electrode tab may be positioned on the same straight line.

[0110] In one embodiment, the first electrode tab may be disposed on an outer surface of the first electrode that does not contact the separator or on an inner surface of the first electrode that faces the separator. In another embodiment, the second electrode tab may be disposed on an inner surface of the second electrode that faces the separator or on an outer surface of the second electrode that does not contact the separator.

[0111] After that, the laminated first electrode tab, the first electrode, the separator, the second electrode, and the second electrode tab can be wound (S830).

[0112] Figure 12 is a drawing for explaining a problem occurring in a conventional electrode assembly.

[0113] Referring to the perspective view (901) in Fig. 12, in a conventional cylindrical cell secondary battery, in order to maximize the capacity relative to the battery size in an electrode assembly in which a positive electrode, a separator, and a negative electrode are laminated and wound, a non-active material-free region is placed in the same area on each electrode plate. Through this, the positive electrode tab (910) and the negative electrode tab (920) are placed vertically in the same location.

[0114] Referring to Fig. 12, the first cross-sectional view (902) illustrates the appearance of a conventional secondary battery before a crack occurs, and the second cross-sectional view (903) illustrates the appearance of a conventional secondary battery after a crack occurs. In a conventional secondary battery, particularly a lithium ion battery, during the charging and discharging process, lithium ions move between the electrolyte and the electrode, and the electrode including the active material undergoes a physical volume change.

[0115] In particular, in the case of a circular cell secondary battery, since the electrode assembly has a coiled structure, a problem occurs in which cracks (930) occur in the electrode substrate due to uneven mechanical stress around the step between the electrode and the electrode tab in the coiled direction where significant expansion occurs.

[0116] To solve the problem of cracks (930) occurring in the electrode substrate, methods such as improving the strength of the substrate of each electrode and increasing the distance between the electrode tabs on the positive and negative electrodes can be utilized. However, as the distance between the electrode tabs increases, the area of ​​contact between the electrode tabs and the non-conductive portion of the electrode decreases, which may have the effect of increasing the current resistance in the battery assembly.

[0117] Therefore, in order to solve the problems of the prior art described above, according to some embodiments of the present disclosure, by changing the terminal shape of each electrode tab of the positive and negative electrodes of the electrode assembly of a secondary battery to a substantially diagonal shape or chamfering while maintaining the distance between the electrode tabs, cracks that may occur within the electrode assembly can be suppressed without increasing battery resistance.

[0118] FIG. 13 is a drawing showing a secondary battery (1000) according to one embodiment of the present disclosure.

[0119] A secondary battery according to one embodiment of the present invention for solving a technical problem includes an electrode assembly according to the present invention.

[0120] Referring to FIG. 13, a secondary battery (1000) according to one embodiment includes an electrode tab having a diagonally formed terminal shape of the present invention. For the purpose of explaining the invention, the secondary battery (1000) is illustrated in FIG. 13 as a cylindrical battery, but the scope of the present disclosure is not limited thereto. The secondary battery (1000) of the present invention is not limited to a cylindrical battery, and includes batteries of any shape, such as a square battery, a pouch battery, and a coin battery. Here, the battery may be a type of secondary battery.

[0121] A secondary battery (1000) may include an electrode assembly (40) with a separator (30) interposed between a positive electrode (10) and a negative electrode (20), a case (50) in which the electrode assembly (40) is built, and a sealing member (60) that seals the case (50). The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown).

[0122] In one embodiment, the positive electrode (10) and the negative electrode (20) may include a coated portion, which is a region where an active material is applied to a current collector (or substrate) formed of a thin metal foil, and a non-coated portion, which is a region where the active material is not coated. The positive electrode (10) and the negative electrode (20) may be wound with a separator (30) as an insulator interposed therebetween. However, the present invention is not limited thereto, and the electrode assembly (40) may also have a structure in which a positive electrode (10) and a negative electrode (20) formed of a plurality of sheets are alternately laminated with a separator (30) interposed therebetween.

[0123] The electrode assembly (40) may be formed by winding or stacking a stack of a positive electrode (10), a separator (30), and a negative electrode (20) formed in a thin plate shape or film shape. When the electrode assembly (40) is a rolled stack, the winding axis may be parallel to the longitudinal direction (y) of the case (50). In addition, the electrode assembly (40) may be a stack type rather than a rolled type, and the shape of the electrode assembly (40) is not limited in the present invention. In addition, the electrode assembly (40) may be a Z-stack electrode assembly in which the positive electrode (10) and the negative electrode (20) are inserted on both sides of a separator folded into a Z-stack. In addition, the electrode assembly (40) may be housed inside the case (50) by stacking one or more electrode assemblies (40) so that their long sides are adjacent to each other, and the number of electrode assemblies (40) is not limited in the present invention.

[0124] The case (50) may be composed of materials commonly used in the art to protect internal components of the battery from external impact or fire. For example, it may be composed of a metal case including aluminum, an aluminum alloy, nickel-plated steel, or stainless steel, a plastic case including GFRP, or a combination thereof, depending on the selection of a person skilled in the art in light of the intended use and function of the battery. In addition, the case (50) may form the overall appearance of the battery (1000) by providing a space in which the electrode assembly (40) is accommodated. For example, if the battery (1000) is a cylindrical battery, the case (50) may have a cylindrical shape, and the positive electrode (10), the negative electrode (20), and the separator (30) may be wound into a cylindrical shape. In some examples, the electrode assembly (40) may be accommodated in the case (50) together with an electrolyte.

[0125] The electrode tabs (1010) having terminal shapes formed diagonally can be arranged to overlap at least partially at substantially the same positions in the longitudinal direction (i.e., the winding direction of the electrode assembly (40)) of each of the positive electrode (10) and the negative electrode (20). Through such a configuration, cracks that may occur within the electrode assembly can be suppressed without increasing battery resistance. In addition, by changing the shape of the terminals of the electrode tabs of each of the positive electrode (10) and the negative electrode (20) of the electrode assembly (40) of the battery (1000) to be obliquely inclined in the width direction or the longitudinal direction of each electrode, the mechanical stress generated when the terminals of the electrode tabs press against the electrode substrate can be reduced. Although only one pair of electrode tabs is illustrated in FIG. 13, one or more electrode tabs may be installed in other positions as needed, and there is no particular limitation on the number of electrode tabs.

[0126] In some examples, the electrode assembly (40) may be housed in a case (50) together with an electrolyte. In addition, the electrode assembly (40) is positioned by welding and connecting the current collector (1) to the electrode tabs (1010) of the positive electrode (10) and negative electrode (20) exposed on both sides.

[0127] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various modifications and variations can be made by those skilled in the art within the scope of the technical idea of ​​the present invention and the equivalent scope of the claims to be described below. Those skilled in the art can make various substitutions, variations, and changes without departing from the technical idea of ​​the present invention, and therefore the present invention is not limited by the above-described embodiments and the attached drawings.

Claims

1. First electrode; A first electrode tab disposed on the first electrode; membrane; a second electrode; and including a second electrode tab disposed on the second electrode, An electrode assembly in which the inner end of the first electrode tab is formed diagonally and is positioned spaced apart from the inner end of the second electrode tab.

2. In paragraph 1, An electrode assembly, wherein the inner end of the second electrode tab is formed in a diagonal shape corresponding to the shape of the inner end of the first electrode tab.

3. In paragraph 1, An electrode assembly, wherein the inner end of the first electrode tab and the inner end of the second electrode tab are spaced apart from each other by 1 mm to 3 mm.

4. In paragraph 1, An electrode assembly wherein the vertical axis of the first electrode tab and the vertical axis of the second electrode tab are parallel to each other.

5. In paragraph 1, An electrode assembly in which the vertical axis of the first electrode tab and the vertical axis of the second electrode tab are positioned on the same straight line.

6. In paragraph 1, An electrode assembly, wherein the first electrode tab is disposed on the inner surface of the first electrode facing the separator.

7. In paragraph 1, An electrode assembly, wherein the first electrode tab is disposed on the outer surface of the first electrode that does not contact the separator.

8. In paragraph 1, An electrode assembly, wherein the second electrode tab is disposed on the inner surface of the second electrode facing the separator.

9. In paragraph 1, An electrode assembly, wherein the second electrode tab is positioned on the outer surface of the second electrode that does not contact the separator.

10. In paragraph 1, The first electrode tab is placed on the uncoated portion of the first electrode, An electrode assembly wherein the second electrode tab is positioned on the uncoated portion of the second electrode.

11. In paragraph 10, An electrode assembly, wherein at least a portion of the uncoated portion of the first electrode and the uncoated portion of the second electrode are positioned on the same row extending in the width direction of each of the first electrode and the second electrode.

12. In paragraph 1, An electrode assembly, wherein the angle formed by the inner end of the first electrode tab with the longitudinal direction of the first electrode is 15° to 75°.

13. In paragraph 1, An electrode assembly, wherein the angle formed by the inner end of the first electrode tab with the longitudinal direction of the first electrode is 30° to 60°.

14. In paragraph 1, An electrode assembly, wherein the inner end of the first electrode tab includes a first vertex and a second vertex, and the first vertex is rounded.

15. In paragraph 14, The electrode assembly, wherein the second vertex is rounded.

16. In paragraph 1, An electrode assembly, wherein the inner end of the second electrode tab includes a third vertex and a fourth vertex, and the third vertex is rounded.

17. In paragraph 16, The above fourth vertex is a rounded, chamfered electrode assembly.

18. A secondary battery comprising the electrode assembly of paragraph 1.

19. Step of forming one end of the first electrode tab into a diagonal line; A step of sequentially stacking the first electrode tab, the first electrode, the separator, the second electrode, and the second electrode tab by arranging the one end portion so as to be electrically connected to one side of the first electrode tab; and A method for manufacturing an electrode assembly, comprising a step of winding the laminated first electrode tab, the first electrode, the separator, the second electrode, and the second electrode tab.

20. In paragraph 19, Before the above laminating step, A method for manufacturing an electrode assembly, further comprising the step of forming one end of the second electrode tab into a diagonal shape corresponding to the shape of one end of the first electrode tab.

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