Electrode assembly with insulating tape attached and lithium secondary battery containing the same

Abstract

The present invention comprises an electrode laminate in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator membrane in between; a positive electrode lead coupled to a bundle of positive electrode tabs in which positive electrode tabs protruding from the outer periphery of each of the plurality of positive electrodes are superimposed; a negative electrode lead coupled to a bundle of negative electrode tabs in which negative electrode tabs protruding from the outer periphery of each of the plurality of negative electrodes are superimposed; a first insulating tape attached to at least a portion of the upper surface of the electrode laminate, the upper surface of the positive electrode coupling portion in which the bundle of positive electrode tabs and the positive electrode lead are coupled, and the upper surface of the negative electrode coupling portion in which the bundle of negative electrode tabs and the negative electrode lead are coupled; and at least a portion of the lower surface of the electrode laminate. The present invention relates to an electrode assembly to which insulating tape is attached and a lithium secondary battery including the same, wherein the positive electrode tab bundle and the positive electrode lead are joined together, the lower surface of the positive electrode coupling portion to which the positive electrode tab bundle and the positive electrode lead are joined together, and the lower surface of the negative electrode coupling portion to which the negative electrode tab bundle and the negative electrode lead are joined together, the positive electrode tab bundle and the negative electrode tab bundle are formed on the same outer periphery and are positioned apart from each other, and at least one of the first insulating tape and the second insulating tape has a cut portion formed in which at least a part between the positive electrode portion attached to the positive electrode coupling portion and the negative electrode portion attached to the negative electrode coupling portion is removed.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0038034 filed on March 19, 2024 and Korean Patent Application No. 10-2024-0067483 filed on May 24, 2024, and all the contents disclosed in the Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly with an insulating tape attached thereto and a lithium secondary battery including the same. Specifically, the present invention relates to an electrode assembly with an insulating tape attached thereto and a lithium secondary battery including the same, which is deformed so as to prevent the insulating tape attached to the upper and lower portions of the tab lead connection part in a pouch-type battery cell from fusing and affecting gas discharge.

Background Art

[0003] In the case of a laminated electrode assembly including a positive electrode, a negative electrode, and a separator positioned on at least one outer surface of the positive electrode and the negative electrode, and the positive electrode and the negative electrode being alternately laminated, at least one positive electrode tab and at least one negative electrode tab protrude from at least one outer peripheral side of all the positive electrodes and all the negative electrodes.

[0004] In the case of a pouch-type battery cell in which the laminated electrode assembly is accommodated in a pouch-type battery case, the positive electrode tabs protruding from all the positive electrodes are joined so as to overlap to form a positive electrode tab bundle, and the negative electrode tabs protruding from all the negative electrodes are joined so as to overlap to form a negative electrode tab bundle.

[0005] The positive electrode tab bundle is joined to a positive electrode lead, the negative electrode tab bundle is joined to a negative electrode lead, and the positive electrode lead and the negative electrode lead protrude outside the pouch-type battery case and function as electrode terminals.

[0006] Each of the positive electrode tab bundle and the negative electrode tab bundle, while connected to the positive electrode lead and the negative electrode lead, is bent into a V-shape inside the pouch-type battery case. This bent portion is called the V-forming portion.

[0007] If the pointed portion of the V-forming section comes into contact with the conductive metal layer of the pouch-type battery case, there is a risk of an internal short circuit occurring.

[0008] Therefore, in order to prevent contact between the V-forming portion and the conductive metal layer of the pouch-type battery case, insulating tape is attached to the outer surface of the V-forming portion.

[0009] In this regard, Figure 1 is a plan view of a conventional electrode assembly, and Figure 2 is a vertical cross-sectional view of the electrode assembly of Figure 1 and a pouch-type battery cell containing it.

[0010] Referring to Figures 1 and 2, the electrode assembly 100 is formed by stacking electrodes such that a separation membrane 112 is interposed between the positive electrode 111 and the negative electrode (not shown) to form the electrode stack 110. The negative electrode is located on the opposite side of the positive electrode 111 with respect to the separation membrane 112, and has a smaller area than the separation membrane 112, so the negative electrode is omitted in Figure 1.

[0011] Multiple positive electrode tabs 121 protruding from the positive electrode 111 form a positive electrode tab bundle, and the end of the positive electrode tab bundle is connected to the positive electrode lead 131. Multiple negative electrode tabs 122 protruding from the negative electrode form a negative electrode tab bundle, and the end of the negative electrode tab bundle is connected to the negative electrode lead 132. A pair of lead films 140 are attached to the upper and lower surfaces of each of the positive electrode lead 131 and the negative electrode lead 132.

[0012] A first insulating tape 151 is attached to the upper surface of the upper end in the longitudinal direction y of the electrode stack 110, the upper surface of the positive electrode tab 121, and the upper surface of the negative electrode tab 122. A second insulating tape 152 is attached to the lower surface of the upper end in the longitudinal direction y of the electrode stack 110, the lower surface of the positive electrode tab 121, and the lower surface of the negative electrode tab 122.

[0013] Figure 1 shows the electrode assembly divided into sections L1, L2, L3, L4, and L5 along the width direction x. Figure 2(a) is a vertical cross-sectional view of the electrode assembly cut parallel to the longitudinal direction y in each of sections L1, L2, L3, L4, and L5. Figure 2(b) shows the electrode assembly of Figure 2(a) with the electrode tab bundle bent to form a V-forming section 133, and housed in the pouch-type battery case 201 in the bent state.

[0014] Since the vertical cross-sectional views of L1 and L5 are identical, Figures 2(a) and 2(b) show the vertical cross-sectional view of L1. Similarly, since the vertical cross-sectional views of L2 and L4 are identical except for the difference in electrode polarity, Figures 2(a) and 2(b) show the vertical cross-sectional view of L2.

[0015] The first insulating tape 151 is attached so as to cover the top of L3, and the second insulating tape 152 is attached so as to cover the bottom of L3.

[0016] The first insulating tape 151 and the second insulating tape 152 are unoriented polypropylene (cast polypropylene, hereinafter referred to as CPP) tapes, and the melting point of CPP is 160°C.

[0017] Referring to Figure 2, at L3 in (a), the first insulating tape 151 and the second insulating tape 152 are not attached to each other, but at L3 in (b), the first insulating tape 151 and the second insulating tape 152 move closer to each other while forming a V-forming portion 133. Here, the first insulating tape 151 and the second insulating tape 152 may be attached to each other.

[0018] Figure 3 is a vertical cross-sectional view showing the state in which the pouch-type battery case expands when the internal pressure of the pouch-type battery cell in Figure 2 increases. For ease of explanation, Figure 3 shows a configuration in which the electrode tabs, electrode leads, and lead films are omitted, and is a vertical cross-sectional view of L3 in Figure 2.

[0019] Referring to Figure 3, (a) shows the state in which the pouch-type battery case 201 has expanded due to gas generated during the charging and discharging process of the lithium secondary battery, and the thick arrow indicates the direction of gas expansion. (b) shows the state in which the temperature of the lithium secondary battery has risen above the temperature at which the internal adhesive layer of the pouch-type battery case 201 melts, and venting has begun, which is approximately 130°C or higher. The thick arrow indicates the flow of gas, and the internal gas of the pouch-type battery case is discharged to the outside through the venting section. (c) shows the state in which the temperature of the lithium secondary battery has risen above 160°C, and the first insulating tape 151 and the second insulating tape 152 have melted, forming a fused section 156. The fused first insulating tape 151 and the second insulating tape 152 block the venting section of the pouch-type battery case 201 from which gas was discharged in (b), so gas is not discharged and gradually accumulates inside the pouch-type battery case 201. The thick arrow indicates the flow of gas.

[0020] In such situations, the pouch-type battery case 201, unable to withstand the internal pressure, may explode, which has been pointed out as a problem that threatens the safety of lithium-ion battery users.

[0021] Therefore, even if insulating tape is applied to prevent damage to the pouch-type battery case from the V-forming portion of the electrode tab bundle, there is a need for technology that allows gas to be smoothly discharged when the internal pressure of the battery cell increases, thereby improving safety. [Overview of the project] [Problems that the invention aims to solve]

[0022] The present invention aims to solve the aforementioned problems and to provide an electrode assembly and a lithium secondary battery containing the same, on which insulating tape is attached, so as to prevent damage to the pouch-type battery case and internal short circuit caused by the V-forming portion of the electrode tab bundle, the passage for gas to be discharged is secured, thereby preventing thermal runaway and explosion of the battery cells. [Means for solving the problem]

[0023] An electrode assembly according to the present invention for achieving such an object includes an electrode laminate in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with a separator interposed therebetween, a positive electrode lead coupled to a positive electrode tab bundle in which positive electrode tabs protruding from outer peripheral edges of each of the plurality of positive electrodes are superimposed, a negative electrode lead coupled to a negative electrode tab bundle in which negative electrode tabs protruding from outer peripheral edges of each of the plurality of negative electrodes are superimposed, a first insulating tape attached to at least a part of the upper surface of the electrode laminate, the upper surface of a positive electrode coupling portion to which the positive electrode tab bundle and the positive electrode lead are coupled, and the upper surface of a negative electrode coupling portion to which the negative electrode tab bundle and the negative electrode lead are coupled, a second insulating tape attached to at least a part of the lower surface of the electrode laminate, the lower surface of a positive electrode coupling portion to which the positive electrode tab bundle and the positive electrode lead are coupled, and the lower surface of a negative electrode coupling portion to which the negative electrode tab bundle and the negative electrode lead are coupled. The positive electrode tab bundle and the negative electrode tab bundle are formed on the same outer peripheral edge and are positioned so as to be separated from each other. At least one of the first insulating tape and the second insulating tape has a cut-out portion in which at least a part between a positive electrode portion attached to the positive electrode coupling portion and a negative electrode portion attached to the negative electrode coupling portion is removed.

[0024] The cut-out portion can include a first cut-out portion formed in the first insulating tape and a second cut-out portion formed in the second insulating tape.

[0025] The cut-out portion can be configured in one form selected from the group consisting of a rectangle, a square, a triangle, a trapezoid, a semi-circle, and a semi-ellipse on a plane.

[0026] The width of the positive electrode portion of the first insulating tape and the second insulating tape may be larger than the width of the positive electrode tab, and the width of the negative electrode portion of the first insulating tape and the second insulating tape may be larger than the width of the negative electrode tab.

[0027] The first insulating tape and the second insulating tape include a first region attached to the outer surface of the electrode laminate, and a second region which is the remaining portion excluding the first region and includes the positive electrode portion and the negative electrode portion. The first region may include an extension portion extending beyond both ends of the second region with reference to the width direction of the electrode laminate.

[0028] The shortest distance from the first end of the first region in the longitudinal direction of the electrode laminate to the cut portion may be the same as the distance from the first end of the extension portion in the longitudinal direction to the second end on the opposite side of the first end.

[0029] The extension portion of the first insulating tape extends downward along the side surface in the thickness direction of the electrode laminate, the extension portion of the second insulating tape extends upward along the side surface in the thickness direction of the electrode laminate, and the extension portion of the first insulating tape and the extension portion of the second insulating tape may not overlap on the side surface of the electrode laminate.

[0030] The extension portion of the first insulating tape extends downward along the side surface in the thickness direction of the electrode laminate, the extension portion of the second insulating tape extends upward along the side surface in the thickness direction of the electrode laminate, and the extension portion of the first insulating tape and the extension portion of the second insulating tape may overlap on the side surface of the electrode laminate.

[0031] The extension portion of the first insulating tape extends to the lower surface of the electrode laminate through the side surface in the thickness direction of the electrode laminate, the extension portion of the second insulating tape extends to the upper surface of the electrode laminate through the side surface in the thickness direction of the electrode laminate, and the extension portion of the first insulating tape and the extension portion of the second insulating tape may overlap on the side surface, the upper surface and the lower surface of the electrode laminate.

[0032] The first insulating tape and the second insulating tape include a first layer attached to the electrode laminate, the positive electrode connection portion and the negative electrode connection portion, and a second layer located on the first layer. The first layer is an adhesive layer containing an adhesive substance, and the second layer may be an insulating layer.

[0033] Furthermore, the electrode assembly according to the present invention may include an electrode laminate in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator membrane in between; a positive electrode lead coupled to a bundle of positive electrode tabs in which positive electrode tabs protruding from the outer periphery of each of the plurality of positive electrodes are superimposed; a negative electrode lead coupled to a bundle of negative electrode tabs in which negative electrode tabs protruding from the outer periphery of each of the plurality of negative electrodes are superimposed; a first insulating tape attached to at least a portion of the upper surface of the electrode laminate, the upper surface of the positive electrode coupling portion where the bundle of positive electrode tabs and the positive electrode lead are coupled, the upper surface of the negative electrode coupling portion where the bundle of negative electrode tabs and the negative electrode lead are coupled, and the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion; and a second insulating tape attached to at least a portion of the lower surface of the electrode laminate, the lower surface of the positive electrode coupling portion where the bundle of positive electrode tabs and the positive electrode lead are coupled, the lower surface of the negative electrode coupling portion where the bundle of negative electrode tabs and the negative electrode lead are coupled, and the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion.

[0034] The first insulating tape and the second insulating tape can overlap each other on the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion.

[0035] The present invention provides a lithium secondary battery including the electrode assembly, specifically the lithium secondary battery comprising the electrode assembly and a battery case housing the electrode assembly, wherein the battery case comprises a first case and a second case made of laminate sheets including a metal layer and a resin layer, at least one of the first case and the second case has an electrode assembly housing portion, the first case and the second case are sealed by heat-sealing their outer peripheries together, and the positive electrode tab bundle and negative electrode tab bundle of the electrode assembly can be bent in the space between the electrode stack and the battery case to form a V-forming portion.

[0036] Of the first and second insulating tapes, the one with the relatively thicker thickness can be attached to the outside of the V-forming portion.

[0037] Furthermore, the present invention provides a battery pack that includes the lithium secondary battery as a unit cell.

[0038] Furthermore, the present invention can also be provided in forms that combine various means for solving the above-mentioned problems. [Effects of the Invention]

[0039] This invention makes it possible to maintain an open state of the venting portion during venting of a lithium secondary battery by removing the portion from which unnecessary fusion occurs in the insulating tape attached to the outer surface of the V-forming portion of the electrode tab bundle.

[0040] This allows for the smooth release of internal gases, preventing the temperature of the lithium-ion battery from rising above a certain level.

[0041] Therefore, since thermal runaway and explosion of lithium secondary batteries can be prevented, secondary disasters such as loss of life can be prevented in advance.

[0042] Furthermore, since the positive electrode, separator membrane, and negative electrode constituting the electrode assembly are configured to be in close contact with each other, resistance can be reduced. [Brief explanation of the drawing]

[0043] [Figure 1] This is a plan view of a conventional electrode assembly. [Figure 2] Figure 1 is a vertical cross-sectional view of the electrode assembly and the pouch-type battery cell containing it. [Figure 3] Figure 2 is a vertical cross-sectional view showing the state in which the pouch-type battery case expands when the internal pressure of the pouch-type battery cell increases. [Figure 4] This is a plan view of an electrode assembly according to the first embodiment of the present invention. [Figure 5] Figure 4 is a perspective view of the electrode assembly. [Figure 6] Figure 4 is a vertical cross-sectional view of the electrode assembly and the pouch-type battery cell containing it. [Figure 7]This is a plan view showing various forms of cutouts for the electrode assembly according to the present invention. [Figure 8] This is a perspective view of an electrode assembly according to a second embodiment of the present invention. [Figure 9] This is a perspective view of an electrode assembly according to a third embodiment of the present invention. [Figure 10] This is a perspective view of an electrode assembly according to a fourth embodiment of the present invention. [Figure 11] This is a perspective view of an electrode assembly according to a fifth embodiment of the present invention. [Figure 12] This graph shows the temperature change over time for the comparative example. [Figure 13] This is a photograph showing the results of the comparative example. [Figure 14] This graph shows the temperature change over time in the example. [Figure 15] This is a photograph showing the results of the example. [Modes for carrying out the invention]

[0044] Hereinafter, with reference to the attached drawings, embodiments that allow a person with ordinary skill in the art to which the present invention belongs to to be easily carried out will be described in detail. In describing the operating principles of embodiments of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0045] Throughout the drawings, the same reference numerals shall be used for parts that have similar functions and operations. In the specification, when it is said that one part is connected to another part, this includes not only direct connection but also indirect connection through other elements in between. Furthermore, when it is said that a component is included, unless otherwise stated, it does not mean that other components are excluded, but rather that other components may be included.

[0046] Descriptions that limit or specify the constituent elements are applicable to all inventions and are not limited to a particular invention, unless otherwise specified.

[0047] Throughout the description of this invention and the claims, singular nouns include plural nouns unless otherwise specified.

[0048] Throughout the description and claims of this invention, "or" includes "and" unless otherwise specified. Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0049] The present invention will be described in detail with reference to the accompanying drawings, along with specific embodiments.

[0050] Figure 4 is a plan view of an electrode assembly according to the first embodiment of the present invention, Figure 5 is a perspective view of the electrode assembly of Figure 4, and Figure 6 is a vertical cross-sectional view of the electrode assembly of Figure 4 and a pouch-type battery cell containing it.

[0051] Referring to Figures 4 to 6, the electrode assembly 100 according to the present invention comprises an electrode stack 110 in which a plurality of positive electrodes 111 and a plurality of negative electrodes (not shown) are alternately stacked with a separation membrane 112 in between, a positive electrode lead 131 coupled to a bundle of positive electrode tabs 121 that protrude from the outer periphery of each of the plurality of positive electrodes 111, a negative electrode lead 132 coupled to a bundle of negative electrode tabs 122 that protrude from the outer periphery of each of the plurality of negative electrodes, and the electrode stack 11 The electrode laminate includes a first insulating tape 151 attached to at least a portion of the upper surface of 0, the upper surface of the positive electrode coupling portion 123 where the positive electrode tab bundle and the positive electrode lead 131 are joined, and the upper surface of the negative electrode coupling portion 124 where the negative electrode tab bundle and the negative electrode lead 132 are joined, and a second insulating tape 152 attached to at least a portion of the lower surface of the electrode laminate 110, the lower surface of the positive electrode coupling portion 123 where the positive electrode tab bundle and the positive electrode lead 131 are joined, and the lower surface of the negative electrode coupling portion 124 where the negative electrode tab bundle and the negative electrode lead 132 are joined.

[0052] The first insulating tape 151 and the second insulating tape 152 are attached to the upper end of the electrode laminate 110 in the longitudinal direction y, and extend further in the direction of the positive electrode lead 131 and the negative electrode lead 132, passing through the positive electrode tab bundle and the negative electrode tab bundle to the positive electrode coupling portion 123 and the negative electrode coupling portion 124. However, if the first insulating tape 151 and the second insulating tape 152 are located on the upper side of the electrode laminate 110 in the longitudinal direction y, they can also extend downward in the longitudinal direction y, contrary to what is shown in the drawing.

[0053] A pair of lead films 140 may be further attached to the upper and lower surfaces of the positive lead 131 and the negative lead 132, respectively. The lead films 140 are attached to improve the adhesion between the pouch-type battery case and the positive lead 131 and the negative lead 132, and are positioned to overlap with the outer peripheral sealing portion of the pouch-type battery case after the electrode assembly 100 is housed in the pouch-type battery case. In other words, the outer peripheral of the pouch-type battery case is sealed with the lead films 140 positioned to overlap with the outer peripheral sealing portion of the pouch-type battery case.

[0054] The positive electrode tab bundle and the negative electrode tab bundle are formed on the same outer periphery of the electrode stack 110 and are positioned apart from each other.

[0055] At least one of the first insulating tape 151 and the second insulating tape 152 has a cut portion 160 formed between the positive electrode portion 153 attached to the positive electrode coupling portion and the negative electrode portion 154 attached to the negative electrode coupling portion, with at least a portion of it removed.

[0056] When comparing the first insulating tape 151 and the second insulating tape 152 according to the present invention with the first insulating tape 151 and the second insulating tape 152 shown in Figure 1, the difference is that at least a portion of the part covering the upper and lower parts of the L3 region in Figure 4 has been removed.

[0057] The present invention includes not only cases in which the cut portion 160 is formed on at least one of the first insulating tape 151 and the second insulating tape 152, but also cases in which the cut portion 160 is formed on both the first insulating tape 151 and the second insulating tape 152.

[0058] The electrode assembly according to the present invention is in a form in which the fused portion that blocked the venting portion while the first insulating tape and the second insulating tape were melted and thermally fused together as in the conventional method has been removed, and since it includes a cut portion 160, the internal gas of the lithium secondary battery can be smoothly discharged.

[0059] The first insulating tape 151 and the second insulating tape 152 are attached to the outer surfaces of the positive electrode tab bundle and the negative electrode tab bundle and serve to prevent internal short circuits from occurring in the lithium secondary battery. Therefore, it is preferable that the width of the positive electrode portion 153 of the first insulating tape 151 and the second insulating tape 152 is equal to or greater than the width G1 of the positive electrode tab 121, and the width of the negative electrode portion 154 is equal to or greater than the width G2 of the negative electrode tab 122.

[0060] Specifically, as shown in Figure 4, with the first insulating tape 151 and the second insulating tape 152 attached to the electrode laminate 110, the positive electrode tab bundle, the positive electrode connector, the negative electrode tab bundle, and the negative electrode connector, the minimum dimensions of the first insulating tape 151 and the second insulating tape 152 can be determined as follows.

[0061] The maximum dimension A in the width direction x of the first insulating tape 151 and the maximum dimension B in the width direction x of the second insulating tape 152 may vary depending on the width of the electrode laminate 110.

[0062] Since the size of the positive electrode 111 constituting the electrode stack 110 is minimal and the size of the separation film 112 is maximum, the lengths C1 and C2 between the outer periphery of the positive electrode and the first and second insulating tapes are 0 mm or more, and more specifically, 1.5 mm or more.

[0063] The length D1 between the first insulating tape 151 and the lead film 140 and the length D2 between the second insulating tape 152 and the lead film 140 may be 0.08 ± 0.75 mm.

[0064] In the longitudinal direction y, the minimum length E1 between the end of the positive electrode tab 121 and the respective ends of the first and second insulating tapes, and the minimum length E2 between the end of the negative electrode tab 122 and the respective ends of the first and second insulating tapes, are 0.1 mm.

[0065] When the width of the positive electrode portion 153 of the first and second insulating tapes is greater than the width G1 of the positive electrode tab 121, and the width of the negative electrode portion 154 is greater than the width G2 of the negative electrode tab 122, the minimum length F1 of the first and second insulating tapes extending further in the width direction x from the positive electrode tab 121 and the minimum length F2 of the first and second insulating tapes extending further in the width direction x from the negative electrode tab 122 are 0.1 mm.

[0066] Furthermore, since the thicknesses of the first insulating tape 151 and the second insulating tape 152 are configured to be different from each other, as shown in Figure 6, when the bent V-forming portion of the electrode tab bundle is bent so that it bulges downwards, the thickness of the second insulating tape 152 attached to the outside of the bulging portion may be thicker than the thickness of the first insulating tape 151. This is because there is a higher risk of the second insulating tape 152 being damaged by the sharp portion due to the bending, so the thickness is supplemented to prevent the risk of internal short circuits.

[0067] For example, the thickness of the relatively thinner of the first and second insulating tapes is 10 μm to 50 μm, and the thickness of the relatively thicker one is 30 μm to 70 μm, with the one attached to the bulging outer surface of the V-forming portion of the electrode tab bundle being configured to be relatively thick, and can be selected within the above range.

[0068] The first insulating tape 151 and the second insulating tape 152 are attached to the outer surface of the electrode laminate 110, and the remaining portion excluding the first region 150a includes a second region 150b which includes a positive electrode portion 153 and a negative electrode portion 154.

[0069] The first region 150a includes extensions 155 that extend beyond both ends of the second region 150b with respect to the width direction x of the electrode stack 110.

[0070] The first insulating tape 151 and the second insulating tape 152 attached to the first region 150a can play a role in compressing the electrode laminate 110, and by including the extension portion 155, the pressing force on the electrode laminate 110 can be increased. In particular, when a sliding portion occurs in which the outer periphery of the electrode mixture layer gradually becomes lower and slopes, a state of non-adhesion occurs between the electrode and the separation film, increasing resistance and potentially causing lithium deposition. In such cases, increasing the size of the extension portion 155 in the longitudinal direction y and the width direction x can increase the force pressing on the electrode laminate 110.

[0071] Figure 4 shows the electrode assembly divided into sections L1, L2, L3, L4, and L5 along the width direction x. Figure 6(a) is a vertical cross-sectional view of the electrode assembly cut parallel to the longitudinal direction y at each of L1, L2, L3, L4, and L5. Figure 6(b) shows the electrode assembly from Figure 6(a) with the electrode tab bundle bent to form the V-forming section 133, housed in the pouch-type battery case 201.

[0072] The lithium secondary battery shown in Figure 6(b) is a pouch-type battery cell and includes a pouch-type battery case 201 that houses an electrode assembly inside. The battery case 201 is made of a laminate sheet containing a metal layer and a resin layer.

[0073] The battery case 201 includes a first case 201a and a second case 201b, which may be in a form that is separate from each other, or in a form that is connected to each other and folded at one outer perimeter.

[0074] In Figure 6(b), a concave electrode assembly housing section 200 is formed in the second case 201b to accommodate the electrode assembly. Alternatively, the electrode assembly housing section may be formed in the first case 201a, and the V-forming section 133 may have an upward-bulging shape.

[0075] The first case 201a and the second case 201b are sealed by heat-sealing their outer periphery to each other, and the V-forming portion 133, formed by bending the positive electrode tab bundle and negative electrode tab bundle of the electrode assembly, is located in the space between the electrode stack 110 and the battery case 201.

[0076] Since the vertical cross-sectional views of L1 and L5 are identical, Figures 6(a) and 6(b) show the vertical cross-sectional view of L1. Similarly, since the vertical cross-sectional views of L2 and L4 are identical except for the difference in electrode polarity, Figures 6(a) and 6(b) show the vertical cross-sectional view of L2.

[0077] The first insulating tape 151 and the second insulating tape 152 are in a state where the portions attached to the upper and lower parts of L3 have been removed. In L3 in Figures 6(a) and 6(b), the first insulating tape 151 and the second insulating tape 152 are separated and in the same state as L1 and L5. That is, the first insulating tape 151 and the second insulating tape 152 do not adhere to each other at the cut portion 160.

[0078] The first insulating tape 151 and the second insulating tape 152 may be unoriented polypropylene (cast polypropylene, hereinafter referred to as CPP) tapes. The melting point of CPP is 160°C. Alternatively, the first insulating tape 151 and the second insulating tape 152 may be in a form in which an acrylic adhesive is applied to one surface of the polypropylene layer.

[0079] In one specific example, the first insulating tape 151 and the second insulating tape 152 include first layers 151a and 152a that are attached to the electrode laminate 110, the positive electrode coupling portion 123, and the negative electrode coupling portion 124, and second layers 151b and 152b located on the first layers 151a and 152a, wherein the first layers 151a and 152a are adhesive layers containing an adhesive substance, and the second layers 151b and 152b may be insulating layers.

[0080] The adhesive layer ensures that the first insulating tape and the second insulating tape are stably attached to the electrode laminate 110, the positive electrode coupling portion 123, and the negative electrode coupling portion 124, and the insulating layer prevents contact between the positive electrode and the negative electrode.

[0081] The adhesive material contained in the adhesive layer may include, for example, epoxy adhesives, acrylic adhesives, or cyanoacrylate adhesives, and the insulating material constituting the insulating layer may include, for example, one or more selected from the group consisting of silicon, mica, rubber, ceramics, and insulating polymers including polyvinyl alcohol, polyimide, polymethyl methacrylate, and polystyrene.

[0082] Figure 7 is a plan view showing various forms of cutouts of the electrode assembly according to the present invention.

[0083] In the electrode assembly shown in Figure 4, the cut-out portion 160 is rectangular or square on a plane.

[0084] Referring to Figure 7, (a) the cut portion 160 is triangular in the plane, (b) the cut portion 160 is trapezoidal, and (c) the cut portion 160 is semi-elliptical.

[0085] However, the form of the cut portion is not limited to the form shown in the drawings of this specification, as long as at least one of the first insulating tape and the second insulating tape is cut off at least a portion of L3.

[0086] Thus, even if the shape of the cut portion 160 is diverse, the shortest distance H from the first end 155a in the longitudinal direction of the first region 150a to the cut portion 160 is the same as the distance from the first end 155a in the longitudinal direction of the extension portion 155 to the second end 155b on the opposite side of the first end 155a.

[0087] Figure 8 is a perspective view of an electrode assembly according to a second embodiment of the present invention. Referring to Figure 8, the extension portion 155 of the first insulating tape 151 attached to the electrode laminate 110 extends downward along the side surface 170 in the thickness direction z of the electrode laminate 110, and the extension portion 155 of the second insulating tape 152 extends upward along the side surface 170 in the thickness direction z of the electrode laminate 110. The extension portion 155 of the first insulating tape 151 and the extension portion 155 of the second insulating tape 152 do not overlap on the side surface 170 of the electrode laminate 110.

[0088] Figure 9 is a perspective view of an electrode assembly according to a third embodiment of the present invention. Referring to Figure 9, the extension portion 155 of the first insulating tape 151 attached to the electrode laminate 110 extends downward along the side surface 170 in the thickness direction z of the electrode laminate 110, the extension portion 155 of the second insulating tape 152 extends upward along the side surface 170 in the thickness direction z of the electrode laminate 110, and the extension portions 155 of the first insulating tape 151 and the second insulating tape 152 overlap on the side surface 170 of the electrode laminate 110.

[0089] Figure 10 is a perspective view of an electrode assembly according to a fourth embodiment of the present invention. Referring to Figure 10, the extension 155 of the first insulating tape 151 extends to the lower surface of the electrode stack 110 via the side surface 170 in the thickness direction z of the electrode stack 110, and the extension 155 of the second insulating tape 152 extends to the upper surface 180 of the electrode stack 110 via the side surface 170 in the thickness direction z of the electrode stack 110, and the extension 155 of the first insulating tape 151 and the extension 155 of the second insulating tape 152 overlap the side surface 170, the upper surface 180, and the lower surface of the electrode stack 110.

[0090] At this point, the first insulating tape 151 and the second insulating tape 152 press against the electrode laminate 110. If a sliding portion is formed in the positive electrode mixture layer and the negative electrode mixture layer where the outer peripheral side with the electrode tab is located is thinner, the adhesive force between the electrode and the separation film can be increased in the sliding portion.

[0091] Figure 11 is a perspective view of an electrode assembly according to a fifth embodiment of the present invention. Referring to Figure 11, the electrode assembly 100 according to the present invention comprises an electrode stack 110 in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator membrane in between; a positive electrode lead 131 coupled to a bundle of positive electrode tabs in which positive electrode tabs protruding from the outer periphery of each of the plurality of positive electrodes are superimposed; a negative electrode lead 132 coupled to a bundle of negative electrode tabs in which negative electrode tabs protruding from the outer periphery of each of the plurality of negative electrodes are superimposed; and at least a portion of the upper surface 180 of the electrode stack 110, the upper surface of the positive electrode coupling portion 123 in which the bundle of positive electrode tabs and the positive electrode lead 131 are coupled, The electrode laminate 110 includes a first insulating tape 151 attached to the upper surface of the negative electrode coupling portion 124 where the negative electrode tab bundle and the negative electrode lead 132 are coupled, and to the side surface 171 of the electrode laminate 110 between the positive electrode coupling portion 123 and the negative electrode coupling portion 124, and a second insulating tape 152 attached to at least a portion of the lower surface of the electrode laminate 110, the lower surface of the positive electrode coupling portion 123 where the positive electrode tab bundle and the positive electrode lead 131 are coupled, the lower surface of the negative electrode coupling portion 124 where the negative electrode tab bundle and the negative electrode lead 132 are coupled, and to the side surface 171 of the electrode laminate 110 between the positive electrode coupling portion 123 and the negative electrode coupling portion 124.

[0092] The first insulating tape 151 and the second insulating tape 152 may overlap each other on the side surface 171 of the electrode laminate 110 between the positive electrode coupling portion 123 and the negative electrode coupling portion 124. Alternatively, unlike in Figure 11, the first insulating tape 151 and the second insulating tape 152 may be attached in a manner that they do not overlap each other on the side surface 171 of the electrode laminate 110 between the positive electrode coupling portion 123 and the negative electrode coupling portion 124.

[0093] Here, the first insulating tape 151 and the second insulating tape 152 press against the outer periphery of the electrode laminate 110 on the side where the electrode tab protrudes, surrounding it. In this case, if a sliding portion is formed in the positive electrode mixture layer and the negative electrode mixture layer where the thickness of the outer periphery side of the electrode tab is reduced, the adhesive force between the electrode and the separation film can be increased in the sliding portion.

[0094] The following description will refer to embodiments of the present invention, but this is for the purpose of making the invention easier to understand and does not limit the scope of the invention thereto.

[0095] <Comparative Example> An electrode stack was prepared in which multiple positive electrodes and multiple negative electrodes were alternately stacked with a separator membrane in between. After welding the positive electrode tabs of the electrode stack to form a bundle of positive electrode tabs, positive electrode leads were attached. After welding the negative electrode tabs of the electrode stack to form a bundle of negative electrode tabs, negative electrode leads were attached.

[0096] An electrode assembly was manufactured by attaching the first insulating tape and the second insulating tape, as shown in Figure 1, to the electrode laminate, positive electrode tab bundle, positive electrode connector, negative electrode tab bundle, and negative electrode connector.

[0097] After housing the electrode assembly in a pouch-type battery case, the electrolyte was injected and sealed to assemble the pouch-type battery cell.

[0098] Twelve pouch-type battery cells manufactured using the method described above were prepared.

[0099] In the aforementioned pouch-type battery cell, a temperature sensor was attached to the center of the broad outer surface of the electrode stack.

[0100] After setting the temperature of the heating experiment chamber to 130°C, the 12 pouch-type battery cells were placed in the heating experiment chamber, and the temperature change of the temperature sensor was measured for 30 minutes.

[0101] Figure 12 is a graph showing the temperature change over time for the comparative example.

[0102] Referring to Figure 12, it was measured that the temperature of the heating experiment chamber and the battery cells rose from approximately 120°C to 130°C over time, and after about 30 minutes, the temperature of the five pouch-type battery cells and the heating experiment chamber rose rapidly to 200°C.

[0103] Figure 13 is a photograph showing the results of the comparative example.

[0104] Figure 13 is a photograph of the electrode assembly housing and sealing section of the pouch-type battery case after disassembling the pouch-type battery cell and removing the electrode stack.

[0105] Referring to Figure 13, it can be seen that the first insulating tape 151 and the second insulating tape 152 are strongly fused together between the positive electrode tab 121 and the negative electrode tab 122, forming a fused portion 156. In this way, the fusion of the first insulating tape and the second insulating tape seals the venting portion of the pouch-type battery cell, which can be expected to cause thermal runaway, as shown in Figure 12.

[0106] <Examples> Except for using the first and second insulating tapes in the form shown in Figure 4 as the electrode assemblies, 20 pouch-type battery cells were manufactured in the same manner as in the comparative example, and a heating experiment was conducted under the same conditions as in the comparative example.

[0107] Figure 14 is a graph showing the temperature change over time in the example.

[0108] Referring to Figure 14, the temperature of the heating experiment chamber rises to 130°C over time and is maintained at a constant temperature.

[0109] Although the temperature of the battery cells rose to a higher temperature than the heating experiment chamber, the maximum temperature of the 20 pouch-type battery cells was approximately 150°C, and all 20 pouch-type battery cells remained at the same temperature as the heating experiment chamber after reaching their maximum temperature.

[0110] Figure 15 is a photograph showing the results of the example.

[0111] Figure 15 was taken under the same conditions as Figure 13.

[0112] Referring to Figure 15, since the first insulating tape 151 and the second insulating tape 152 have cut portions 160 formed thereon, there is no configuration in which the first insulating tape 151 and the second insulating tape 152 are located between the positive electrode tab 121 and the negative electrode tab 122.

[0113] When the temperature reaches 130°C, the melting point of the adhesive layer in the pouch-type battery case, venting of the pouch-type battery cell begins, and since no fused joint is formed, the venting area does not become blocked. Therefore, it can be expected that the gas was discharged smoothly. Furthermore, the thermal runaway phenomenon seen in the comparative example did not occur.

[0114] A person with ordinary skill in the field to which this invention belongs will be able to make various applications and modifications within the scope of this invention based on the above content. [Explanation of symbols]

[0115] 100 electrode assembly 110 Electrode Stack 111 Positive electrode 112 Separation membrane 121 Positive Tab 122 Negative Electrode Tab 123 Positive electrode coupling section 124 Negative electrode coupling section 131 Positive lead 132 Negative lead 133 V-forming section 140 Lead Film 150a 1st area 150b 2nd area 151 First insulating tape 151a, 152a 1st layer 151b, 152b 2nd layer 152 Second insulating tape 156 Fusion part 153 Positive electrode section 154 Negative electrode section 155 Extension 155a 1st end 155b 2nd end 160 Cutout 170, 171 Side view 180 Top 200 Electrode assembly housing section 201 Pouch-type battery case 201a Case 1 201b Case 2

Claims

1. An electrode laminate in which multiple positive electrodes and multiple negative electrodes are alternately stacked with a separation membrane in between, A positive electrode lead is coupled to a bundle of positive electrode tabs, each of which has positive electrode tabs protruding from the outer periphery of the aforementioned plurality of positive electrodes, and A negative electrode lead is connected to a bundle of negative electrode tabs, each of which has negative electrode tabs protruding from the outer periphery of the aforementioned multiple negative electrodes, and A first insulating tape is attached to at least a portion of the upper surface of the electrode laminate, to the upper surface of the positive electrode coupling portion where the positive electrode tab bundle and the positive electrode lead are coupled, and to the upper surface of the negative electrode coupling portion where the negative electrode tab bundle and the negative electrode lead are coupled. A second insulating tape is attached to at least a portion of the lower surface of the electrode laminate, to the lower surface of the positive electrode coupling portion where the positive electrode tab bundle and the positive electrode lead are coupled, and to the lower surface of the negative electrode coupling portion where the negative electrode tab bundle and the negative electrode lead are coupled. Includes, The positive electrode tab bundle and the negative electrode tab bundle are formed on the same outer periphery and are positioned apart from each other. An electrode assembly in which at least one of the first insulating tape and the second insulating tape has a cut portion formed thereon, where at least a portion between the positive electrode portion attached to the positive electrode coupling portion and the negative electrode portion attached to the negative electrode coupling portion is removed.

2. The electrode assembly according to claim 1, wherein the cut portion includes a first cut portion formed on the first insulating tape and a second cut portion formed on the second insulating tape.

3. The electrode assembly according to claim 2, wherein the cut portion is configured on a plane in one shape selected from the group consisting of rectangles, squares, triangles, trapezoids, semicircles, and semi-ellipses.

4. The width of the positive electrode portion of the first insulating tape and the second insulating tape is greater than the width of the positive electrode tab. The electrode assembly according to claim 1, wherein the width of the negative electrode portion of the first insulating tape and the second insulating tape is greater than the width of the negative electrode tab.

5. The first insulating tape and the second insulating tape each include a first region attached to the outer surface of the electrode laminate and a second region which is the remaining portion excluding the first region and includes the positive electrode portion and the negative electrode portion. The electrode assembly according to claim 4, wherein the first region includes extensions that extend beyond both ends of the second region with respect to the width direction of the electrode stack.

6. The electrode assembly according to claim 5, wherein the shortest distance from the first end of the first region in the longitudinal direction of the electrode stack to the cut portion is the same as the distance from the first end of the extension portion in the longitudinal direction to the second end opposite to the first end.

7. The extension of the first insulating tape extends downward along the side surface in the thickness direction of the electrode laminate, The extension of the second insulating tape extends upward along the side surface in the thickness direction of the electrode laminate, The electrode assembly according to claim 5, wherein the extension portion of the first insulating tape and the extension portion of the second insulating tape do not overlap on the side surface of the electrode laminate.

8. The extension of the first insulating tape extends downward along the side surface in the thickness direction of the electrode laminate, The extension of the second insulating tape extends upward along the side surface in the thickness direction of the electrode laminate, The electrode assembly according to claim 5, wherein the extension portion of the first insulating tape and the extension portion of the second insulating tape overlap on the side surface of the electrode laminate.

9. The extension of the first insulating tape extends to the lower surface of the electrode stack, passing through the side surface in the thickness direction of the electrode stack. The extension of the second insulating tape extends to the upper surface of the electrode stack, passing through the side surface in the thickness direction of the electrode stack. The electrode assembly according to claim 5, wherein the extension portion of the first insulating tape and the extension portion of the second insulating tape overlap the side surface of the electrode stack, the upper surface of the electrode stack, and the lower surface of the electrode stack.

10. The first insulating tape and the second insulating tape each include a first layer attached to the electrode laminate, the positive electrode coupling portion, and the negative electrode coupling portion, and a second layer located on the first layer. The electrode assembly according to claim 1, wherein the first layer is an adhesive layer containing an adhesive substance, and the second layer is an insulating layer.

11. An electrode laminate in which multiple positive electrodes and multiple negative electrodes are alternately stacked with a separation membrane in between, A positive electrode lead is coupled to a bundle of positive electrode tabs, each of which has positive electrode tabs protruding from the outer periphery of the aforementioned plurality of positive electrodes, and A negative electrode lead is connected to a bundle of negative electrode tabs, each of which has negative electrode tabs protruding from the outer periphery of the aforementioned multiple negative electrodes, and A first insulating tape is attached to at least a portion of the upper surface of the electrode laminate, the upper surface of the positive electrode coupling portion where the positive electrode tab bundle and the positive electrode lead are coupled, the upper surface of the negative electrode coupling portion where the negative electrode tab bundle and the negative electrode lead are coupled, and the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion. A second insulating tape is attached to at least a portion of the lower surface of the electrode laminate, the lower surface of the positive electrode coupling portion where the positive electrode tab bundle and the positive electrode lead are coupled, the lower surface of the negative electrode coupling portion where the negative electrode tab bundle and the negative electrode lead are coupled, and the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion. An electrode assembly, including the electrode assembly.

12. The electrode assembly according to claim 11, wherein the first insulating tape and the second insulating tape overlap each other on the side surface of the electrode laminate between the positive electrode coupling portion and the negative electrode coupling portion.

13. An electrode assembly according to any one of claims 1 to 12, The battery case includes the electrode assembly housed inside, The battery case includes a first case and a second case made of laminate sheets containing a metal layer and a resin layer. At least one of the first case and the second case has an electrode assembly housing section, The first case and the second case are sealed by heat-sealing their outer peripheries together. A lithium secondary battery in which the positive electrode tab bundle and the negative electrode tab bundle of the electrode assembly are bent in the space between the electrode stack and the battery case to form a V-formed portion.

14. The lithium secondary battery according to claim 13, wherein the one with the relatively thicker thickness among the first insulating tape and the second insulating tape is attached to the outside of the V-forming portion.

15. A battery pack comprising a lithium secondary battery as described in claim 13 as a unit cell.

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