Electrode assembly and battery cell containing the same

Abstract

To provide an electrode assembly that can prevent the occurrence of overhang. [Solution] An electrode assembly in which electrodes and separation membrane sheets are alternately stacked, wherein the electrodes include a first electrode and a second electrode, the separation membrane sheet has a zigzag shape, the length of the second electrode is shorter than that of the first electrode, the side of the first electrode opposite to the side surrounded by the separation membrane sheet protrudes more than the side of the second electrode surrounded by the separation membrane sheet, the separation distance between the separation membrane sheet and the side of the second electrode is the same as or shorter than the length to which the first electrode protrudes more than the second electrode on the side of the second electrode surrounded by the separation membrane sheet, electrode taps extending from a plurality of first and second electrodes are joined, and the electrode assembly includes electrode leads extending to both ends or one end in a direction perpendicular to the direction in which the separation membrane sheet of the electrode assembly is folded, and fixing tape is attached to the outer surface of the electrode assembly.

Description

Technical Field

[0001] Cross-reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0046806 filed on Apr. 15, 2022, and all the contents disclosed in the document of the Korean Patent Application are incorporated herein by reference in their entirety.

[0002] The present invention relates to an electrode assembly and a battery cell including the same, and more specifically, to an electrode assembly in which electrodes and a separator sheet are alternately laminated in a Z-folding type and a battery cell including the same, and to an electrode assembly and a battery cell including the same that can prevent the occurrence of an overhang in which the positive electrode is displaced from the negative electrode and the alignment is disturbed.

Background Art

[0003] Generally, types of secondary batteries include nickel cadmium batteries, nickel metal hydride batteries, lithium ion batteries, and lithium ion polymer batteries. These secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs (registered trademarks), Portable Game Devices, Power Tools, and E-bikes, but also in large products that require high power such as electric vehicles and hybrid vehicles, power storage devices for storing surplus generated power and new renewable energy, and backup power storage devices.

[0004] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and a predetermined-shaped electrode assembly is formed by laminating them on both sides of a separator. Then, the electrode assembly is housed in a battery case, an electrolyte is injected, and then sealed.

[0005] Electrode assemblies are classified into various types. For example, there is the simple stack type, which simply involves stacking positive electrodes, separator membranes, negative electrodes, etc. in a crisscross pattern without manufacturing unit cells; the lamination and stack type (L&S), which first manufactures unit cells using positive electrodes, separator membranes, negative electrodes, etc., and then stacks these unit cells; the stack and folding type (S&F), which involves attaching multiple unit cells spaced apart to one side of a separator membrane sheet that is longer on one side, and repeatedly folding the separator membrane sheet from one end in the same direction; and the Z-folding type, which involves alternately attaching multiple electrodes or unit cells to one side and the other side of a separator membrane sheet that is longer on one side, and then repeatedly folding the separator membrane sheet from one end in a specific direction, and then in the opposite direction. Among these, the Z-folding type is frequently used recently because of its high degree of alignment and electrolyte impregnation.

[0006] However, conventionally, when electrodes and separator membrane sheets were stacked in this Z-folding type, the portion of the separator membrane sheet surrounding the electrodes significantly exceeded the negative and positive electrodes, and as the positive electrode's area became smaller than the negative electrode's, there was a high possibility of overhang occurring, where the positive electrode shifted from the negative electrode and the alignment became disordered. When this overhang phenomenon occurs, not only does the performance of the electrode assembly and the battery cell containing it deteriorate, but the possibility of defects such as short circuits can also become very high.

[0007] Therefore, it is necessary to develop an electrode assembly and a battery cell containing it that have a structure capable of preventing overhang, where the positive electrode is misaligned from the negative electrode and the alignment is disrupted. [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that the present invention aims to solve is to provide an electrode assembly in which electrodes and separation membrane sheets are alternately stacked in a Z-folding manner, and a battery cell including the same, which can prevent the occurrence of overhangs where the positive electrode is misaligned from the negative electrode and the alignment is disrupted.

[0009] The problems that this invention aims to solve are not limited to those described above, and any problems not mentioned will be clearly understood by a person with ordinary skill in the art to which this invention pertains from this specification and the accompanying drawings. [Means for solving the problem]

[0010] An electrode assembly according to one embodiment of the present invention is an electrode assembly in which electrodes and a separation membrane sheet are alternately stacked, wherein the electrodes include a first electrode and a second electrode, the separation membrane sheet has a zigzag shape formed by folding at least twice, the length of the second electrode is shorter than the length of the first electrode, the sides of the first electrode surrounded by the separation membrane sheet and the sides of the second electrode surrounded by the separation membrane sheet are separated from the separation membrane sheet, the sides of the first electrode opposite to the sides of the first electrode surrounded by the separation membrane sheet protrude from the sides of the second electrode surrounded by the separation membrane sheet compared to the second electrode, and the separation distance between the separation membrane sheet and the sides of the second electrode is the same as or shorter than the length by which the first electrode protrudes from the sides of the second electrode surrounded by the separation membrane sheet compared to the second electrode.

[0011] The separation distance between the separation membrane sheet and the side surface of the first electrode may be the same as, or shorter than, the length by which the first electrode protrudes from the side surface of the second electrode that is surrounded by the separation membrane sheet, compared to the second electrode.

[0012] The separation distance between the separation membrane sheet and the side surface of the first electrode may be the same as, or shorter than, the separation distance between the separation membrane sheet and the side surface of the second electrode.

[0013] Of the two sides of the first electrode, the side surrounded by the separation membrane sheet may protrude from the side opposite to the side surrounded by the separation membrane sheet of the second electrode compared to the second electrode.

[0014] Of the two sides of the first electrode, the side opposite to the side enclosed by the separation membrane sheet may be located on the same vertical line as the outer surface of the electrode assembly.

[0015] The side of the first electrode opposite to the side surrounded by the separation membrane sheet and the side of the second electrode surrounded by the separation membrane sheet may be positioned adjacent to each other.

[0016] The separation membrane sheet may be interposed between the upper surface of the first electrode and the lower surface of the second electrode, and between the upper surface of the second electrode and the lower surface of the first electrode.

[0017] If one of the two sides of the second electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, the side of the first electrode opposite to the side surrounded by the separation membrane sheet may be maintained so as to protrude from the side of the second electrode that is surrounded by the separation membrane sheet compared to the second electrode.

[0018] If one of the two sides of the first electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, the other side of the first electrode opposite to the side surrounded by the separation membrane sheet may be maintained to protrude from the side of the second electrode that is surrounded by the separation membrane sheet compared to the second electrode.

[0019] If one of the two sides of the first electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, the other side of the first electrode opposite to the side surrounded by the separation membrane sheet may be located on the same vertical line as the second electrode, with reference to the side surrounded by the separation membrane sheet.

[0020] One end of the separation membrane sheet in the electrode assembly according to another embodiment of the present invention may extend along the outer surface of the electrode assembly.

[0021] One end of the separation membrane sheet may surround the entire outer surface of the electrode assembly.

[0022] Another embodiment of the present invention includes an electrode assembly as described above. [Effects of the Invention]

[0023] In an embodiment, the present invention is characterized in which electrodes and separation membrane sheets are alternately stacked in a Z-folding configuration, and the separation distance between the separation membrane sheet and the side surface of the positive electrode is formed to be the same as, or shorter than, the length by which the negative electrode protrudes from the side surface of the positive electrode surrounded by the separation membrane sheet compared to the positive electrode, thereby preventing the occurrence of overhangs that cause the positive electrode to shift away from the negative electrode and disrupt alignment.

[0024] Furthermore, in the present invention, electrodes and separation membrane sheets are alternately stacked in a Z-folding type, and the separation distance between the separation membrane sheet and the side surface of the negative electrode is formed to be the same as, or shorter than, the length by which the negative electrode protrudes from the side surface of the positive electrode surrounded by the separation membrane sheet compared to the positive electrode, thereby preventing the occurrence of overhangs that cause the positive electrode to shift away from the negative electrode and disrupt alignment.

[0025] The effects of the present invention are not limited to those described above, and any effects not mentioned can be clearly understood by a person with ordinary skill in the art to which the present invention pertains from this specification and the accompanying drawings. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a diagram showing a final electrode assembly according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of the electrode assembly cut along the A-A' axis of Figure 1. [Figure 3] Figure 3 is a diagram showing a part of the cross-section of the electrode assembly of Figure 2. [Figure 4] Figure 4 is a diagram showing a part of the cross-section of the electrode assembly of Figure 2. [Figure 5] Figure 5 is a diagram showing the slip of the second electrode of Figure 4. [Figure 6] Figure 6 is an enlarged view of part A of Figure 5. [Figure 7] Figure 7 is a diagram showing a part of the cross-section of the electrode assembly of Figure 2. [Figure 8] Figure 8 is a diagram showing the slip of the first electrode of Figure 7. [Figure 9] Figure 9 is an enlarged view of part B of Figure 8. [Figure 10] Figure 10 is a cross-sectional view of an electrode assembly according to another embodiment of the present invention. [Figure 11] Figure 11 is a diagram showing a part of the cross-section of the electrode assembly according to the comparative example.

Mode for Carrying Out the Invention

[0027] Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be embodied in various different forms and is not limited to the embodiments described herein.

[0028] In order to clearly explain the present invention, parts that are not relevant to the explanation will be omitted, and the same reference numerals will be assigned to the same or similar components throughout the specification.

[0029] Furthermore, the dimensions and thicknesses of each component shown in the drawings are arbitrary for the sake of explanation, and the present invention is not necessarily limited to those shown. The thicknesses are shown enlarged in the drawings to clearly represent various layers and regions. In addition, the thicknesses of some layers and regions are exaggerated in the drawings for the sake of explanation.

[0030] Furthermore, when a specification as a whole states that a certain part "includes" a certain component, this does not mean that other components are excluded, unless otherwise specifically stated, and it means that other components may be included as well.

[0031] Furthermore, throughout the specification, "on a plane" means when the subject is viewed from above, and "on a cross-section" means when the subject is viewed from the side of a cross-section obtained by cutting the subject perpendicularly.

[0032] The following describes an electrode assembly according to an embodiment of the present invention. However, although the description here is based on a partial cross-section of the electrode assembly, it is not necessarily limited to this, and the same or similar content can be described for other cross-sections as well.

[0033] Figure 1 shows a final electrode assembly according to one embodiment of the present invention. Figure 2 is a cross-sectional view of the electrode assembly cut along the A-A' axis in Figure 1.

[0034] Referring to Figures 1 and 2, the final electrode assembly 100 in this embodiment can also mean a structure in which the fixing tape 300 is attached to the outer surface of the electrode assembly 200. This allows the final electrode assembly 100 to maintain the stacked alignment between the first electrode 210, the second electrode 220, and the separation membrane sheet 250 contained in the electrode assembly 200. In particular, as will be described later, the fixing tape 300 can maintain the stacked alignment between the electrodes (first electrode 210, second electrode 220) and the separation membrane sheet 250 such that the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 is located on the same vertical line as the outer surface of the electrode assembly 200. However, it is not limited to this, and the fixing tape 300 can be omitted from the final electrode assembly 100 or replaced with other components, while still maintaining the stacked alignment between the first electrode 210, the second electrode 220, and the separation membrane sheet 250.

[0035] Furthermore, the final electrode assembly 100 may include electrode leads 400 to which electrode taps extending from a plurality of first electrodes 210 and a plurality of second electrodes 220 included in the electrode assembly 200 are joined. For example, as shown in Figure 1, the electrode leads 400 may extend to both ends of the electrode assembly 200, and the electrode leads 400 may be classified as positive leads or negative leads depending on the polarity of the first electrodes 210 and the second electrodes 220. However, the position of the electrode leads 400 is not limited to this, and unlike in Figure 1, they may both extend to one end of the electrode assembly 200.

[0036] Furthermore, the final electrode assembly 100 may include lead films 500 located above and below the electrode leads 400. Here, when the final electrode assembly 100 is mounted in a battery case (not shown), the lead films 500 may be sealed together with the outer periphery of the battery case (not shown) by a sealing portion (not shown).

[0037] Referring to Figures 1 and 2, the electrode assembly 200 according to one embodiment of the present invention may be an electrode assembly in which electrodes (first electrode 210, second electrode 220) and separation membrane sheets 250 are alternately stacked.

[0038] The electrodes (first electrode 210, second electrode 220) may include a first electrode 210 and a second electrode 220. Here, the first electrode 210 and the second electrode 220 may include electrode active materials having opposite polarities. In other words, the first electrode 210 and the second electrode 220 may be electrodes with opposite polarities. For example, if the first electrode 210 is the negative electrode, the second electrode 220 may be the positive electrode.

[0039] Furthermore, the length of the second electrode 220 may be shorter than the length of the first electrode 210. In other words, the length of the first electrode 210 may be longer than the length of the second electrode 220. That is, the first electrode 210 and the second electrode 220 may have different lengths, and there may be a difference in length between the first electrode 210 and the second electrode 220.

[0040] The separation membrane sheet 250 may have a zigzag shape formed by folding at least twice. More specifically, as shown in Figure 2, the separation membrane sheet 250 may be folded in a direction that covers the first electrode 210 when the first electrode 210 is stacked on it. Alternatively, the separation membrane sheet 250 covering the first electrode 210 may be folded in a direction that covers the second electrode 220 when the second electrode 220 is stacked on it. Subsequently, the separation membrane sheet 250 covering the second electrode 220 may be folded in a direction that covers the first electrode 210 when the first electrode 210 is stacked on it. In other words, the electrode assembly 200 may be formed by repeatedly stacking the first electrode 210 or the second electrode 220 and folding the separation membrane sheet 250.

[0041] Therefore, the separation membrane sheet 250 may be interposed between the upper surface of the first electrode 210 and the lower surface of the second electrode 220, and between the upper surface of the second electrode 220 and the lower surface of the first electrode 210.

[0042] Furthermore, as described above, the folding of the separation membrane may result in a structure in which the side opposite to the side surrounded by the separation membrane sheet 250 of the first electrode 210 and the side of the second electrode 220 that is surrounded by the separation membrane sheet 250 are adjacent to each other. At the same time, the side of the first electrode 210 that is surrounded by the separation membrane sheet 250 and the side of the second electrode 220 that is opposite to the side surrounded by the separation membrane sheet 250 are adjacent to each other. Thus, a Z-folding type electrode assembly can be formed.

[0043] Furthermore, the sides of the second electrode 220 that are surrounded by the separation membrane sheet 250 may be separated from the separation membrane sheet 250, and the sides of the first electrode 210 that are surrounded by the separation membrane sheet may be separated from the separation membrane sheet 250. In other words, the sides of the first electrode 210 that are surrounded by the separation membrane sheet 250, and the sides of the second electrode 220 that are surrounded by the separation membrane sheet 250 may each be separated from the separation membrane sheet 250. Here, the meaning of the sides of the first electrode 210 or the second electrode 220 being separated from the separation membrane sheet 250 can also mean that the separation membrane sheet 250 extends away from the sides of the first electrode 210 or the second electrode 220, or that the separation membrane sheet 250 separates from the sides of the first electrode 210 or the second electrode 220 and forms a space that surrounds the first electrode 210 or the second electrode 220.

[0044] In this case, the sides of the first electrode 210 and the second electrode 220 surrounded by the separation membrane sheet 250 are separated from the separation membrane sheet 250, thereby preventing damage to the electrodes (first electrode 210 and second electrode 220) by the separation membrane sheet 250. If there is no separation between the separation membrane sheet 250 and the electrodes (first electrode 210 and second electrode 220), damage may occur to the electrodes (first electrode 210 and second electrode 220) due to tension caused by a change in the direction of the separation membrane sheet 250 during the assembly process between the separation membrane sheet 250 and the electrodes (first electrode 210 and second electrode 220), such as cracking or breaking. Therefore, by separating the sides of the first electrode 210 and the second electrode 220, which are surrounded by the separation membrane sheet 250, from the separation membrane sheet 250, damage to the electrodes (first electrode 210 and second electrode 220) by the separation membrane sheet 250 can be prevented, and the stability of the electrode assembly can be improved.

[0045] Furthermore, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may protrude from the side of the second electrode 220 that is enclosed by the separation membrane sheet 250 compared to the second electrode 220. At the same time, the side of the first electrode 210 that is enclosed by the separation membrane sheet 250 may protrude from the side of the second electrode 220 that is enclosed by the separation membrane sheet 250 compared to the second electrode 220. In other words, the first electrode 210 may be formed such that at least one side protrudes from the second electrode 220, and specifically, both sides may protrude. Therefore, it can also be said that, with respect to both sides, the second electrode 220 is located inside the first electrode 210.

[0046] On the other hand, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may be located on the same vertical line as the outer surface of the electrode assembly 200. In other words, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may protrude toward the outer surface of the electrode assembly 200 or may not be recessed. This prevents the separation membrane sheet 250 located above the first electrode 210 and the separation membrane sheet 250 located below the first electrode 210 from being folded during the manufacturing process in this embodiment.

[0047] In the following section, an electrode assembly according to one embodiment of the present invention will be described in more detail with reference to Figures 3 to 9.

[0048] Figures 3 and 4 show a portion of the cross-section of the electrode assembly in Figure 2. Figure 5 shows the slip of the second electrode in Figure 4. Figure 6 is an enlarged view of portion A in Figure 5. Figure 7 shows a portion of the cross-section of the electrode assembly in Figure 2. Figure 8 shows the slip of the first electrode in Figure 7. Figure 9 is an enlarged view of portion B in Figure 8. Figure 11 shows a portion of the cross-section of an electrode assembly related to a comparative example.

[0049] Referring to Figures 3 and 4, the side surfaces of the first electrode 210 and the second electrode 220, which are surrounded by the separation membrane sheet 250, are separated from the separation membrane sheet 250. In this case, the separation distance G2 between the separation membrane sheet 250 and the side surfaces of the second electrode 220 may be the same as, or shorter than, the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surfaces of the second electrode 220 that are surrounded by the separation membrane sheet 250.

[0050] Referring to Figure 11, in the case of the conventional electrode assembly 20, the portion of the separation membrane sheet 25 surrounding the electrodes 21 and 22 is formed to extend significantly beyond the first electrode 21 and the second electrode 22, which increased the likelihood of overhang, where the second electrode 22 shifts from the first electrode 21 and its alignment becomes disordered. In particular, if the separation distance gg1 between the separation membrane sheet 25 and the first electrode 21, and the separation distance gg2 between the separation membrane sheet 25 and the second electrode 22 are formed to be even longer than the length difference gg3 between the first electrode 21 and the second electrode 22, and slip occurs between the first electrode 21 and the second electrode 22, the likelihood of overhang is very high.

[0051] When the overhang phenomenon occurs, not only does the performance of the electrode assembly and the battery cell containing it deteriorate, but the possibility of defects such as short circuits becomes very high, leading to problems in ensuring the stability of the electrode assembly and battery cell. Therefore, it was necessary to develop an electrode assembly structure that can prevent the occurrence of overhang, where the second electrode is misaligned from the first electrode.

[0052] As a result, referring to Figures 5 and 6, the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220 in the electrode assembly 200 according to this embodiment is formed to be the same as, or shorter than, the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 that is surrounded by the separation membrane sheet 250. In this case, the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220 may be the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220 that is surrounded by the separation membrane sheet 250. Also, the side surface of the first electrode 210 opposite to the side surface surrounded by the separation membrane sheet 250 may be located on the same vertical line as the outer surface of the electrode assembly 200. In other words, the side surface of the first electrode 210 opposite to the side surface surrounded by the separation membrane sheet 250 may protrude toward the outer surface of the electrode assembly 200 or may not be recessed.

[0053] In this case, even if the second electrode 220 slips, the side of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 can be maintained to protrude more than the side of the second electrode 220 that is surrounded by the separation membrane sheet 250.

[0054] In particular, referring to Figure 6, even when one of the two sides of the second electrode 220 is surrounded by the separation membrane sheet 250 and is in contact with the separation membrane sheet 250, the side of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 can still maintain a shape that protrudes further outward from the second electrode 220 towards the electrode assembly 200. Therefore, even if the second electrode 220 slips, an overhang phenomenon in which the second electrode 220 shifts away from the first electrode 210 and disrupts its alignment may not occur.

[0055] Furthermore, if one of the two sides of the second electrode 220 is surrounded by the separation membrane sheet 250 and is in contact with the separation membrane sheet 250, the side of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 may be located on the same vertical line as the second electrode 220, with reference to the side surrounded by the separation membrane sheet 250. This can be assumed to be the case when the thickness of the separation membrane sheet 250 is so thin that it can be ignored, and therefore, even if the second electrode 220 slips, an overhang phenomenon in which the second electrode 220 shifts away from the first electrode 210 and disrupts the alignment may not occur.

[0056] If the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220 is formed to be longer than the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 surrounded by the separation membrane sheet 250, that is, if the separation membrane sheet 250 is formed to extend beyond the thickness of the separation membrane sheet 250 toward the side surface of the first electrode 210 opposite to the side surface surrounded by the separation membrane sheet 250, the second electrode 220 may slide and shift away from the first electrode 210, disrupting the alignment and potentially causing an overhang phenomenon.

[0057] Therefore, the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220 in the electrode assembly according to this embodiment is the same as, or shorter than, the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 surrounded by the separation membrane sheet 250, and the side surface of the first electrode 210 opposite to the side surface surrounded by the separation membrane sheet 250 is located on the same vertical line as the outer surface of the electrode assembly 200. This prevents the overhang phenomenon caused by the slip phenomenon of the second electrode 220, minimizes the deterioration of the electrode assembly's performance and the occurrence of short circuits, and further improves stability.

[0058] On the other hand, referring to Figures 3 and 7, the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 of the electrode assembly 200 according to this embodiment may be the same as, or shorter than, the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 that is surrounded by the separation membrane sheet 250. In this case, the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 may be the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 that is surrounded by the separation membrane sheet 250.

[0059] Furthermore, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may be located on the same vertical line as the outer surface of the electrode assembly 200. In other words, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may protrude toward the outer surface of the electrode assembly 200 or may not be recessed. In other words, the side of the first electrode 210 opposite to the side enclosed by the separation membrane sheet 250 may be located on the same vertical line as the side of the second electrode 220 other than the separation membrane sheet 250.

[0060] In this case, even if the first electrode 210 slips, the side of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 can be maintained to protrude more than the side of the second electrode 220 that is surrounded by the separation membrane sheet 250.

[0061] In particular, referring to Figures 8 and 9, even when one of the two sides of the first electrode 210 is surrounded by the separation membrane sheet 250 and is in contact with the separation membrane sheet 250, the side of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 can still maintain a shape that protrudes further outward from the second electrode 220 towards the electrode assembly 200. Therefore, even if the first electrode 210 slips, it is possible to prevent the overhang phenomenon in which the second electrode 220 shifts away from the first electrode 210 and disrupts its alignment.

[0062] Furthermore, when the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 is the same as the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 surrounded by the separation membrane sheet 250, even when the side surface of the first electrode 210 surrounded by the separation membrane sheet 250 is in contact with the separation membrane sheet 250, the side surface of the first electrode 210 opposite to the side surface surrounded by the separation membrane sheet 250 is located on the same vertical line as the second electrode 220 with respect to the side surface surrounded by the separation membrane sheet 250 of the second electrode 220. Therefore, the first electrode 210 may not protrude further than the second electrode 220 in the direction of the outer surface of the electrode assembly 200. Consequently, even if the first electrode 210 slips, it is possible to prevent the overhang phenomenon in which the second electrode 220 shifts away from the first electrode 210 and disrupts the alignment.

[0063] If the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 is formed to be longer than the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 that is surrounded by the separation membrane sheet 250, then the first electrode 210 may slide and the second electrode 220 may shift away from the first electrode 210, disrupting the alignment and causing an overhang phenomenon. In other words, as shown in Figure 9, the first electrode 210 may slide and be positioned further inward from the second electrode 220 towards the electrode assembly 200, causing an overhang phenomenon in which the second electrode 220 protrudes from the first electrode 210.

[0064] Therefore, the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 in the electrode assembly according to this embodiment is the same as, or shorter than, the length G3 by which the first electrode 210 protrudes compared to the second electrode 220 on the side surface of the second electrode 220 surrounded by the separation membrane sheet 250. This prevents the overhang phenomenon caused by the slip phenomenon of the first electrode 210, thereby minimizing the performance degradation and short-circuit occurrence of the electrode assembly and further improving stability.

[0065] On the other hand, referring to Figure 3, the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 of the electrode assembly 200 according to this embodiment may be the same as or shorter than the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220. In this case, if the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 is even shorter than the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220, the tolerance between the second electrode 220 and the outer surface of the electrode assembly 200 caused by the first electrode 210 and the second electrode 220 having different lengths can be further reduced. In addition, the possibility of overhang occurring due to slippage of the first electrode 210 can be further reduced.

[0066] Furthermore, even if the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 of the electrode assembly 200 according to this embodiment is the same as the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220, the first electrode 210 still protrudes by a length corresponding to the thickness of the separation membrane sheet 250. Therefore, even if a slip phenomenon occurs in the first electrode 210, the side surface of the first electrode 210 opposite to the side surrounded by the separation membrane sheet 250 can still maintain a shape that protrudes outward from the second electrode 220 towards the outer surface of the electrode assembly 200. Thus, the occurrence of an overhang phenomenon can be prevented.

[0067] Therefore, the separation distance G1 between the separation membrane sheet 250 and the side surface of the first electrode 210 of the electrode assembly 200 according to this embodiment can be made the same as or shorter than the separation distance G2 between the separation membrane sheet 250 and the side surface of the second electrode 220, thereby further reducing the possibility of overhang occurring.

[0068] Figure 10 is a cross-sectional view of an electrode assembly according to another embodiment of the present invention.

[0069] Referring to Figure 10, the electrode assembly 201 according to another embodiment of the present invention can be described in much the same way as the electrode assembly 200 described above, and below we will only describe the parts that differ from the electrode assembly 200.

[0070] Referring to Figure 10, one end of the separation membrane sheet 250 of the electrode assembly 201 in this embodiment may extend along the outer surface of the electrode assembly 201. More specifically, one end of the separation membrane sheet 250 may surround the entire outer surface of the electrode assembly 201. In other words, one end of the separation membrane sheet 250 may surround both sides and the top and bottom surfaces of the electrode assembly 201.

[0071] As an example, as shown in Figure 10, the end of the separation membrane sheet 250 surrounding the outer surface of the electrode assembly 201 may be the end of the separation membrane sheet 250 adjacent to the bottom surface. As another example, unlike in Figure 10, the end of the separation membrane sheet 250 surrounding the outer surface of the electrode assembly 201 may be the end of the separation membrane sheet 250 adjacent to the upper end of the electrode assembly 201.

[0072] As a result, in this embodiment, the electrode assembly 201 can prevent the first electrode 210 from protruding to the outside by having the separation membrane sheet 250 surround the outer surface of the electrode assembly 201. Furthermore, this embodiment can reduce costs and improve economic efficiency because no additional components are required.

[0073] A battery cell according to yet another embodiment of the present invention includes the electrode assemblies described above. The battery cell may also include a battery case (not shown) that houses the electrode assemblies 200 and 201 together with the electrolyte. In this case, the electrode assemblies 200 and 201 may be manufactured as the final electrode assembly 100 described above and housed in the battery case (not shown).

[0074] Here, the battery case (not shown) may be a laminate sheet including a resin layer and a metal layer. More specifically, the battery case (not shown) may be made of a laminate sheet and consist of an outer resin layer forming the outermost corner, a barrier metal layer to prevent penetration of materials, and an inner resin layer for sealing.

[0075] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, using the basic concepts of the present invention as defined in the following claims, also fall within the scope of the present invention. [Explanation of symbols]

[0076] 100: Final electrode assembly 200: Electrode assembly 210: 1st electrode 220: 2nd electrode 250: Separation membrane sheet 300: Fixing tape 400: Electrode Lead 500: Lead film

Claims

1. An electrode assembly in which electrodes and separation membrane sheets are alternately stacked, The electrode includes a first electrode and a second electrode, The separation membrane sheet has a zigzag shape formed by folding at least twice, The length of the second electrode is shorter than the length of the first electrode. The sides of the first electrode surrounded by the separation membrane sheet, and the sides of the second electrode surrounded by the separation membrane sheet, are each separated from the separation membrane sheet. Of the two sides of the first electrode, the side opposite to the side surrounded by the separation membrane sheet protrudes from the side of the second electrode that is surrounded by the separation membrane sheet, compared to the second electrode. An electrode assembly in which the separation distance between the separation membrane sheet and the side surface of the second electrode is the same as, or shorter than, the length by which the first electrode protrudes compared to the second electrode on the side surface of the second electrode that is surrounded by the separation membrane sheet.

2. The electrode assembly according to claim 1, wherein the separation distance between the separation membrane sheet and the side surface of the first electrode is the same as, or shorter than, the length to which the first electrode protrudes compared to the second electrode on the side surface of the second electrode that is surrounded by the separation membrane sheet.

3. The electrode assembly according to claim 2, wherein the separation distance between the separation membrane sheet and the side surface of the first electrode is the same as or shorter than the separation distance between the separation membrane sheet and the side surface of the second electrode.

4. The electrode assembly according to claim 1, wherein the side of the first electrode surrounded by the separation membrane sheet protrudes from the side of the second electrode opposite to the side of the second electrode surrounded by the separation membrane sheet.

5. The electrode assembly according to claim 1, wherein the side opposite to the side enclosed by the separation membrane sheet among the two sides of the first electrode is located on the same vertical line as the outer surface of the electrode assembly.

6. The electrode assembly according to claim 1, wherein the side opposite to the side surrounded by the separation membrane sheet among the two sides of the first electrode and the side surrounded by the separation membrane sheet among the two sides of the second electrode are located adjacent to each other.

7. The electrode assembly according to claim 1, wherein the separation membrane sheet is interposed between the upper surface of the first electrode and the lower surface of the second electrode, and between the upper surface of the second electrode and the lower surface of the first electrode.

8. When one of the two sides of the second electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, The electrode assembly according to claim 1, wherein the side of the first electrode opposite to the side surrounded by the separation membrane sheet is maintained to protrude from the side of the second electrode that is surrounded by the separation membrane sheet, compared to the second electrode.

9. When one of the two sides of the first electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, The electrode assembly according to claim 1, wherein the side of the first electrode opposite to the side surrounded by the separation membrane sheet is maintained to protrude from the side of the second electrode that is surrounded by the separation membrane sheet compared to the second electrode.

10. When one of the two sides of the first electrode is surrounded by the separation membrane sheet and is in contact with the separation membrane sheet, The electrode assembly according to claim 1, wherein the side of the first electrode opposite to the side enclosed by the separation membrane sheet is located on the same vertical line as the second electrode, with reference to the side of the second electrode enclosed by the separation membrane sheet.

11. The electrode assembly according to claim 1, wherein one end of the separation membrane sheet extends along the outer surface of the electrode assembly.

12. The electrode assembly according to claim 11, wherein one end of the separation membrane sheet surrounds the entire outer surface of the electrode assembly.

13. A battery cell comprising an electrode assembly according to any one of claims 1 to 12.

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