KR20230021335A - Electrode assembly and secondary battery including the same - Google Patents

Abstract

The electrode assembly according to an embodiment of the present invention comprises: a first electrode sheet; a second electrode sheet; and a separator interposed between the first electrode sheet and the second electrode sheet, wherein the first electrode sheet, the second electrode sheet, and the separator are wound to form a jelly roll structure. The first electrode sheet includes a first electrode current collector and a first active material unit formed by applying an electrode active material to the surface of the first electrode current collector, and a first electrode tab is bonded to a portion of the first electrode sheet where the first electrode current collector is exposed. A protective tape is attached to cover the first electrode tab, and the protective tape includes a first layer and a second layer located outside the first layer. The first layer includes a recessed unit, and the first electrode tab is located in the recessed unit. Accordingly, the present invention can improve the safety of secondary batteries by minimizing adverse structural effects.

Description

Electrode assembly and secondary battery including the same {ELECTRODE ASSEMBLY AND SECONDARY BATTERY INCLUDING THE SAME}

The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly, to a jelly roll type electrode assembly and a secondary battery including the same.

In recent years, as the demand for portable electronic products such as laptop computers, video cameras, and mobile phones has rapidly increased, and development of electric vehicles, batteries for energy storage, robots, and satellites has been in full swing, secondary batteries used as driving power sources A lot of research is being done about it.

Secondary batteries include, for example, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, lithium secondary batteries, and the like. Among these, lithium secondary batteries are widely used in the field of advanced electronic devices because of the advantages of free charging and discharging due to almost no memory effect compared to nickel-based secondary batteries, very low self-discharge rate, high operating voltage and high energy density per unit weight. there is.

Depending on the shape of the battery case, the secondary battery is a cylindrical battery in which the electrode assembly is embedded in a cylindrical metal can, a prismatic battery in which the electrode assembly is embedded in a prismatic metal can, and an electrode assembly in a pouch-type case of an aluminum laminate sheet. It is classified as a pouch-type battery with Among them, the cylindrical battery has the advantage of having a relatively large capacity and structural stability.

The electrode assembly built into the battery case is a power generating device capable of charging and discharging composed of a laminated structure of an anode, a separator, and a cathode, and is classified into a jelly roll type, a stack type, and a stack/folding type. The jelly roll type is a form in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material, and the stack type is a form in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked with a separator interposed. /Folding type is a complex structure of jelly roll type and stack type. Among them, the jelly roll-type electrode assembly has the advantage of being easy to manufacture and having a high energy density per weight.

An electrode tab is attached to each of the positive electrode and the negative electrode. Specifically, a positive electrode tab made of aluminum may be attached to the positive electrode, and a negative electrode tab made of a material containing at least one of nickel and copper may be attached to the negative electrode.

However, the attached positive electrode tab and negative electrode tab create a difference in thickness between the positive and negative electrodes, respectively, and a stepped structure occurs in the jelly roll-type electrode assembly. When an impact test is performed on a secondary battery in which such an electrode assembly is housed, a stronger impact is induced in a specific area due to the stepped structure formed by the positive electrode tab and the negative electrode tab, which impairs the safety of the secondary battery. become a factor This is a problem that may appear even when the secondary battery is exposed to an external shock as well as an impact test.

During charging and discharging of the electrode assembly, the electrode assembly repeats expansion and contraction. The stepped structure formed by the positive and negative tabs causes local deformation or shape distortion in the volume change of the electrode assembly during charging and discharging. It can also cause distortion.

Accordingly, there is a high need for a technology capable of solving the above problems caused by the stepped structure formed by the electrode tab.

An object to be solved by the present invention is to provide an electrode assembly with improved safety and a secondary battery including the same by mitigating a stepped structure caused by an electrode tab in a jelly roll form.

However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and can be variously extended within the scope of the technical idea included in the present invention.

An electrode assembly according to an embodiment of the present invention includes a first electrode sheet; a second electrode sheet; and a separator interposed between the first electrode sheet and the second electrode sheet, and the first electrode sheet, the second electrode sheet, and the separator are wound to form a jelly roll structure. The first electrode sheet includes a first electrode current collector and a first active material portion formed by coating an electrode active material on a surface of the first electrode current collector, and a portion of the first electrode sheet where the first electrode current collector is exposed. The first electrode tab is bonded to. A protective tape is attached to cover the first electrode tab, and the protective tape includes a first layer and a second layer positioned outside the first layer. The first layer includes a recessed portion, and the first electrode tab is positioned in the recessed portion.

The first layer may include a polyurethane (PU) material, and the second layer may include a polyimide (PI) material.

The first layer may include an outer circumferential portion adjacent to the indented portion, and the indented portion may have a thickness smaller than that of the outer circumferential portion.

A thickness of the outer circumferential portion may be 1.2 times or more and 7.5 times or less of the thickness of the indented portion.

The recessed portion may be positioned to correspond to the first electrode tab.

The recess portion may be formed on a surface of the first layer facing the first electrode tab, and the first electrode tab may be inserted into the recess portion.

The protection tape may further include a third layer disposed between the first layer and the second layer, and the third layer may include an adhesive material.

The protection tape may further include a fourth layer disposed between the first layer and the first electrode sheet, and the fourth layer may include an adhesive material.

The first electrode sheet may be a cathode sheet, and the second electrode sheet may be a cathode sheet.

The first electrode sheet may be a rectangular sheet, and a portion of the first electrode sheet where the first electrode current collector is exposed may be an area spaced apart from both ends of the first electrode sheet.

According to embodiments of the present invention, a step structure caused by the electrode tab may be minimized by attaching a protection tape having a recessed portion on the electrode tab. Accordingly, the safety of the secondary battery can be improved by minimizing structural adverse effects such as stress concentration due to the stepped structure, local deformation or distortion of the shape of the electrode assembly.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view showing an electrode assembly included in the secondary battery of FIG. 1 before being wound.
FIG. 3 is an enlarged plan view of part A of FIG. 2 .
FIG. 4 is a front view viewed from the direction B of FIG. 3 .
FIG. 5 is a front view showing a state in which the first layer of the protective tape in FIG. 4 is expanded by absorbing the electrolyte.
6 is a front view for explaining a state in which a protective tape is attached according to a comparative example of the present invention.
7 is a front view for explaining a protection tape according to another embodiment of the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to the shown bar. In the drawings, the thickness is shown enlarged to clearly express the various layers and regions. And in the drawings, for convenience of explanation, the thicknesses of some layers and regions are exaggerated.

In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in the middle. . Conversely, when a part is said to be "directly on" another part, it means that there is no other part in between. In addition, to be "on" or "on" a reference part means to be located above or below the reference part, and to necessarily be located "on" or "on" in the opposite direction of gravity does not mean no.

In addition, throughout the specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

In addition, throughout the specification, when it is referred to as "planar image", it means when the target part is viewed from above, and when it is referred to as "cross-sectional image", it means when a cross section of the target part cut vertically is viewed from the side.

1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention.

Referring to FIG. 1 , a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200 . Specifically, the secondary battery 100 may include an electrode assembly 200, a battery can 300 having an open top accommodating the electrode assembly 200, and a cap assembly 700 coupled to the battery can 300. there is. More specifically, after accommodating the electrode assembly 200 in the battery can 300 and injecting the electrolyte solution into the battery can 300, the cap assembly 700 is coupled to the top of the battery can 300, and the secondary battery ( 100) can be prepared.

The battery can 300 is a structure for accommodating the electrode assembly 200 impregnated with electrolyte, and may include a metal material such as aluminum and may be a cylindrical can.

The cap assembly 700 may include a top cap 710 and a safety vent 720 . The top cap 710 is positioned on the safety vent 720 and may be electrically connected to the safety vent 720 by forming a structure in close contact with each other. The upper cap 710 protrudes upward in the center and is electrically connected to the first electrode sheet 210 of the electrode assembly 200 through a first electrode tab 210t to be described later, for connection with an external circuit. It can function as an electrode terminal.

Meanwhile, a gasket 800 for sealing may be positioned between the battery can 300 and the cap assembly 700 . Specifically, a crimping bond may be formed by placing a gasket 800 between the battery can 300 and the cap assembly 700 and bending an end of the battery can 300 . Through this, the cap assembly 700 may be mounted and the secondary battery 100 may be sealed.

The electrode assembly 200 according to an embodiment of the present invention included in the secondary battery 100 is a jelly roll type electrode assembly. Hereinafter, with reference to FIG. 2 , the electrode assembly 200 according to an embodiment of the present invention will be described in detail.

FIG. 2 is an exploded perspective view showing an electrode assembly included in the secondary battery of FIG. 1 before being wound.

Referring to FIGS. 1 and 2 together, the electrode assembly 200 according to an embodiment of the present invention includes a first electrode sheet 210, a second electrode sheet 220, and a first electrode sheet 210. A separator 230 interposed between the two electrode sheets 220 is included. In addition, the first electrode sheet 210, the second electrode sheet 220, and the separator 230 are wound to form a jelly roll structure. In addition, the separator 230 is additionally disposed under the first electrode sheet 210 to prevent the first electrode sheet 210 and the second electrode sheet 220 from contacting each other when rolled in a jelly roll form. desirable. The first electrode sheet 210, the second electrode sheet 220, and the separator 230 may have a rectangular long sheet shape.

The first electrode sheet 210 includes a first electrode current collector 211 and a first active material portion 212 formed by coating an electrode active material on a surface of the first electrode current collector 211 . In addition, the first electrode tab 210t is bonded to a portion of the first electrode sheet 210 where the first electrode current collector 211 is exposed. More specifically, the electrode active material is not applied to a portion of the first electrode current collector 211 and the first electrode current collector 211 is exposed. In this way, the portion where the first electrode current collector 211 is exposed may be referred to as a first uncoated portion 211uc. The first electrode tab 210t may be bonded to the first uncoated portion 211uc by welding or the like. A protective tape 400 is attached to cover the first electrode tab 210t. The protective tape 400 will be described later along with FIGS. 3 to 5 .

The second electrode sheet 220 includes a second electrode current collector 221 and a second active material portion 222 formed by coating an electrode active material on the surface of the second electrode current collector 221 . In addition, the second electrode tab 220t is bonded to a portion of the second electrode sheet 220 where the second electrode current collector 221 is exposed. More specifically, the electrode active material is not applied to a portion of the second electrode current collector 221 and the second electrode current collector 221 is exposed. In this way, the portion where the second electrode current collector 221 is exposed may be referred to as a second uncoated portion 221uc. The second electrode tab 220t may be bonded to the second uncoated portion 221uc by welding or the like.

In this case, the first electrode sheet 210 may be a cathode sheet, and the second electrode sheet 220 may be a cathode sheet. Specifically, the first active material portion 212 may include a positive electrode active material, and the first electrode tab 210t bonded to the first uncoated portion 211uc may be a positive electrode tab. As described above, the first electrode tab 210t is connected to the cap assembly 700, and the top cap 710 may function as a positive electrode terminal among electrode terminals for connection to an external circuit. Next, the second active material portion 222 may include a negative electrode active material, and the second electrode tab 220t bonded to the second uncoated portion 221uc may be a negative electrode tab. The second electrode tab 220t may protrude toward the bottom of the battery can 300 and be bonded to the bottom of the battery can 300 . Thus, the battery can 300 may function as a negative electrode terminal among electrode terminals for connection with an external circuit.

Meanwhile, in the electrode assembly 200 according to the present embodiment, a protective tape 400 may be additionally attached to cover the second electrode tab 220t as well as the first electrode tab 210t. However, hereinafter, the protection tape 400 attached to the first electrode tab 210t will be described as a standard. This is to avoid repetition of description, and the protection tape 400 attached to the second electrode tab 220t may have the same or similar structure as the protection tape 400 attached to the first electrode tab 210t. .

Hereinafter, the protective tape according to the present embodiment will be described in detail with reference to FIGS. 3 and 4 .

FIG. 3 is an enlarged plan view of part A of FIG. 2 . FIG. 4 is a front view viewed from the direction B of FIG. 3 .

2 to 4 , the first electrode tab 210t is attached to the first uncoated portion 211uc, and the protective tape 400 is attached to cover the first electrode tab 210t. The protective tape 400 includes a first layer 410 and a second layer 420 positioned outside the first layer 410 . Here, the outer side of the first layer 410 means a side opposite to the side where the first electrode tab 210t is located based on the first layer 410 . That is, the first layer 410 may be positioned relatively close to the first electrode tab 210t, and the second layer 420 may face the separator 230 .

The first layer 410 includes a recessed portion 410D having a recessed shape, and the first electrode tab 210t is positioned in the recessed portion 410D. Specifically, the first layer 410 may further include an outer peripheral portion 410U adjacent to the indented portion 410D, and the indented portion 410D may have a thinner thickness than the outer peripheral portion 410U. In the present invention, the indented portion 410D may refer to an area of the first layer 410 facing the first electrode tab 210t that is relatively thinner than an adjacent area, that is, the outer circumferential portion 410U.

This indentation 410D may be positioned to correspond to the first electrode tab 210t. That is, as shown in FIGS. 3 and 4 , a region of the first layer 410 of the protective tape 400 that does not correspond to the first electrode tab 210t may be configured as the outer peripheral portion 410U. A recessed portion 410D may be formed on a surface of the first layer 410 facing the first electrode tab 210t, and the first electrode tab 210t may be inserted into the recessed portion 410D.

The first layer 410 may include a polyurethane (PU) material, and the second layer 420 may include a polyimide (PI) material. Since the second layer 420 made of polyimide has excellent thermal stability and electrical insulation, it protects the first electrode tab 210t even in a high-temperature environment such as a thermal runaway phenomenon, and the first electrode tab 210t is protected. By blocking the electrical connection between 210t and other parts, it is possible to prevent a short from occurring. The first layer 410 made of a porous polyurethane material has excellent elasticity, so that an impact applied to the first electrode tab 210t and its neighboring area can be alleviated when an external impact occurs.

Referring again to FIG. 4 , as described above, the electrode active material is coated on the surface of the first electrode current collector 211 to form the first active material portion 212 . In particular, the electrode active material may be coated on both sides of the first electrode current collector 211 . In addition, the first electrode tab 210t is bonded to a portion where the first electrode current collector 211 is exposed, that is, to the first uncoated portion 211uc.

In this case, the thickness of the first electrode current collector 211 may be 10 μm or more and 20 μm or less, and the thickness of one first active material part 212 may be 50 μm or more and 60 μm or less. In this case, the thickness of the first electrode tab 210t may be 90 μm or more and 160 μm or less. That is, the thickness of the first electrode tab 210t may be greater than the thickness of one first active material portion 212 , and a stepped structure may occur due to the first electrode tab 210t in the jelly roll structure. Since it is desirable for the first electrode tab 210t to have a certain thickness in order to lower resistance, the thickness of the first electrode tab 210t cannot be made thin in order to eliminate the stepped structure.

In this case, in the first layer 410 according to the present embodiment, the thickness t2 of the outer peripheral portion 410U may be 1.2 times or more and 7.5 times or less than the thickness t1 of the indented portion 410D. If the thickness t2 of the outer circumferential portion 410U is less than 1.2 times the thickness t1 of the indented portion 410D, the depth formed by the indented portion 410D is insufficient, resulting in a stepped structure of the first electrode tab 210t. can be difficult to alleviate. On the other hand, when the thickness t2 of the outer peripheral portion 410U exceeds 7.5 times the thickness t1 of the recessed portion 410D, the thickness of the outer peripheral portion 410U is unnecessarily thick or the thickness of the recessed portion 410D is too thick. can be thin If the thickness of the outer circumferential portion 410U is thicker than necessary, the entire thickness of the protection tape 400 becomes thick, which means that the protection tape 400 rather causes local deformation or shape distortion of the electrode assembly 200. (distortion). If the thickness of the recessed portion 410D is too thin, it is difficult to effectively alleviate the impact applied to the first electrode tab 210t.

For example, the thickness t1 of the indented portion 410D may be 20 μm or more and 50 μm or less, and the thickness t2 of the outer peripheral portion 410U may be 60 μm or more and 150 μm or less.

As the protective tape 400 including the first layer 410 having a thickness change is attached to the first electrode tab 210t as described above, the stepped structure caused by the first electrode tab 210t can be alleviated and minimized. there is. Therefore, when the first electrode sheet 210, the second electrode sheet 220, and the separator 230 are wound to form a jelly roll structure, stress concentration due to the stepped structure and local deformation of the electrode assembly 200 ( The safety of the secondary battery 100 may be improved by minimizing adverse structural effects such as deformation or distortion.

Meanwhile, the protective tape 400 according to the present embodiment may further include a third layer 430 positioned between the first layer 410 and the second layer 420 . This third layer 430 may include an adhesive material. For example, the adhesive material may be a silicone adhesive. The second layer 420 including polyimide may be adhered to the first layer 410 by the third layer 430 having adhesiveness.

The thickness of each of the second layer 420 and the third layer 430 is not particularly limited, but in one example, the thickness of the second layer 420 may be 10 μm or more and 100 μm or less, and the thickness of the third layer 430 may be 10 μm or more and 50 μm or less. A polyimide tape may be formed by integrating the second layer 420 including polyimide and the third layer 430 including silicone adhesive.

FIG. 5 is a front view showing a state in which the first layer of the protective tape in FIG. 4 is expanded by absorbing the electrolyte.

Referring to FIGS. 4 and 5 together with FIG. 1 , when the electrode assembly 200 is accommodated in the battery can 300 together with the electrolyte, the first layer 410 including a polyurethane material partially absorbs the electrolyte and can be inflated. The expanded first layer 410 may fill an empty space between the protection tape 400 , the first electrode tab 210t and the first electrode current collector 211 . Accordingly, in the wound electrode assembly 200, empty space is minimized. In addition, since the first layer 410 having good elasticity surrounds the first electrode tab 210t, the impact applied to the first electrode tab 210t can be alleviated, and the electrode in the impact test breakage can be minimized.

Meanwhile, referring to FIG. 2 again, as described above, the first electrode sheet 210, the second electrode sheet 220, and the separator 230 may have a long rectangular sheet shape. At this time, the portion of the first electrode sheet 210 where the first electrode current collector 211 is exposed, that is, the first uncoated portion 211uc, is spaced apart from both end sides 210S of the first electrode sheet 210. area may be The both short sides 210S correspond to a portion where winding starts and a portion where winding is finished, respectively.

In other words, the first electrode tab 210t may be a middle tab model located in the center of the first electrode sheet 210 . In the case of the middle tap model, a stepped structure caused by the first electrode tab 210t is formed between the winding center and the outer circumferential surface of the electrode assembly 200 based on the rolled electrode assembly 200 . When the stepped structure is formed in the middle portion as described above, local deformation or shape distortion of the electrode assembly may be further intensified. At this time, according to the present embodiment, the protection tape 400 in which the indentation 410D is formed covers the first electrode tab 210t of the middle-tap model, minimizing the stepped structure, thereby preventing deformation of the electrode assembly or The distortion of the shape can be reduced.

Meanwhile, in FIG. 2 , the second electrode tab 220t is shown attached to be adjacent to one side of the second electrode sheet 220, but in another embodiment, the second electrode tab 220t also has a second electrode tab 220t. It may be a shape located in the center of the seat 220, that is, a middle tap model.

6 is a front view for explaining a state in which a protective tape is attached according to a comparative example of the present invention.

Referring to FIG. 6 , a protective tape 40 may be attached to cover the first electrode tab 210t. The protective tape 40 may include a base layer 42 and an adhesive layer 43 . The base layer 42 may include polyimide, and the adhesive layer 43 may include an adhesive material such as silicone adhesive. An attachment position of the protective tape 40 may be similar to that of the protective tape 400 according to the present embodiment described above. At this time, the protective tape 40 of the present invention may have a certain thickness (t'). Although the protection tape 40 can prevent a short from occurring in the first electrode tab 210t, it is difficult to alleviate the stepped structure formed by the first electrode tab 210t. Since it does not contain a porous elastic material such as polyurethane and has a constant thickness (t') without change, even if the protective tape 40 is attached, the step ST still exists. In contrast, in the protective tape 400 according to the present embodiment, a protective tape 400 including a first layer 410 of polyurethane material and a second layer 420 of polyimide material is applied, and the first The problem caused by the stepped structure of the first electrode tab 210t as described above is solved by forming the recessed portion 410D in the region corresponding to the electrode tab 210t.

In the protective tape 400 according to the present embodiment, there is no particular limitation on the method of forming the indentation portion 410D in the first layer 410, but a polyurethane material may be molded to realize the shape of the indentation portion 410D, or A method of applying physical compression for a predetermined period of time may be used.

7 is a front view for explaining a protection tape according to another embodiment of the present invention.

Referring to FIG. 7 , a protective tape 400' according to another embodiment of the present invention is attached to the first electrode sheet to cover the first electrode tab 210t. As described above, the first electrode sheet includes the first electrode current collector 211 and the first active material part 212 . The protective tape 400' may include a first layer 410, a second layer 420, and a third layer 430. The description of each layer is omitted because it is redundant with the previous description.

The protective tape 400' according to the present embodiment may further include a fourth layer 440 positioned between the first layer 410 and the first electrode sheet, and the fourth layer 440 is an adhesive material. can include For example, the adhesive material may be a silicone adhesive. Since the adhesive strength of the first layer 410 including polyurethane is relatively weak, it may not be easy to fix it to the first electrode sheet. Accordingly, the adhesive strength of the protective tape 400' may be supplemented by providing a fourth layer 440 having adhesiveness to the first layer 410.

Meanwhile, the thickness of the fourth layer 440 is not particularly limited, but may be, for example, 10 μm or more and 50 μm or less.

In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are only for convenience of description and may vary depending on the location of the target object or the location of the observer. .

A plurality of secondary batteries according to the present embodiment described above may be gathered to form a battery module. The battery module may be mounted together with various control and protection systems such as a battery management system (BMS), a battery disconnect unit (BDU), and a cooling system to form a battery pack.

The secondary battery, the battery module, or the battery pack may be applied to various devices. Specifically, it can be applied to means of transportation such as electric bicycles, electric vehicles, hybrids, or energy storage systems (ESS), but is not limited thereto and can be applied to various devices that can use secondary batteries.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also made according to the present invention. falls within the scope of the rights of

100: secondary battery
200: electrode assembly
210: first electrode sheet
211: first electrode current collector
212: first active material part
210t: first electrode tab
220: second electrode sheet
230: separator
400: protective tape
410: first layer
410D: indentation
420: second layer
430: third layer

Claims (11)

a first electrode sheet;
a second electrode sheet; and
A separator interposed between the first electrode sheet and the second electrode sheet,
The first electrode sheet, the second electrode sheet, and the separator are wound to form a jelly roll structure,
The first electrode sheet includes a first electrode current collector and a first active material portion formed by coating an electrode active material on a surface of the first electrode current collector,
A first electrode tab is bonded to a portion of the first electrode sheet where the first electrode current collector is exposed;
A protective tape is attached to cover the first electrode tab,
The protective tape includes a first layer and a second layer positioned outside the first layer,
The electrode assembly of claim 1 , wherein the first layer includes a recessed portion, and the first electrode tab is positioned in the recessed portion. In paragraph 1,
The first layer includes a polyurethane (PU) material,
The second layer is an electrode assembly comprising a polyimide (PI) material. In paragraph 1,
The first layer includes an outer circumferential portion adjacent to the indented portion,
The electrode assembly wherein the indentation portion is thinner than the outer circumferential portion. In paragraph 3,
The thickness of the outer circumferential portion is 1.2 times or more and 7.5 times or less of the thickness of the indented portion. In paragraph 3,
The electrode assembly of claim 1 , wherein the indentation portion is positioned to correspond to the first electrode tab. In paragraph 1,
The recess portion is formed on a surface of the first layer facing the first electrode tab,
An electrode assembly having a form in which the first electrode tab is inserted into the recessed portion. In paragraph 1,
The protective tape further comprises a third layer positioned between the first layer and the second layer,
The third layer is an electrode assembly comprising an adhesive material. In paragraph 1,
The protective tape further includes a fourth layer positioned between the first layer and the first electrode sheet,
The fourth layer is an electrode assembly comprising an adhesive material. In paragraph 1,
The first electrode sheet is a cathode sheet,
The electrode assembly wherein the second electrode sheet is a negative electrode sheet. In paragraph 1,
The first electrode sheet is a rectangular sheet,
The portion of the first electrode sheet where the first electrode current collector is exposed is an area spaced apart from both short sides of the first electrode sheet. A secondary battery comprising the electrode assembly according to claim 1.

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