Electrode assembly and secondary battery including the same

Abstract

The present invention relates to an electrode assembly and a secondary battery including the same. The electrode assembly according to one embodiment of the present invention is formed by winding a positive electrode, a separator, and a negative electrode, and may include a protective member disposed to face an end of at least one of the positive electrode and the negative electrode, and filled with a flame retardant.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0125849, filed September 30, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a device including the same, and more particularly to an electrode assembly that can improve safety, and a secondary battery including the same. [Background technology]

[0003] In recent years, demand for portable electronic products such as laptops, video cameras, and mobile phones has increased dramatically. As development of electric vehicles, energy storage batteries, robots, satellites, and other products gains momentum, much research is being conducted on secondary batteries, which are used as power sources for these products.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly attached to the inside of the battery case is a power generating element that can be charged and discharged, and is made up of a laminated structure of electrodes and separators.

[0005] When a secondary battery including such an electrode assembly is repeatedly charged and discharged, the electrode assembly may swell, causing deformation of the wound center of the electrode assembly. If the wound center of the electrode assembly is deformed and unable to maintain its circular shape, an internal short circuit or disconnection may occur during the charge and discharge cycle, significantly reducing safety. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode assembly and a secondary battery including the same that can improve safety.

[0007] The technical problems of the present invention are not limited to those mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] According to an embodiment of the present invention, an electrode assembly is formed by winding a positive electrode, a separator, and a negative electrode, and may include a protective member disposed to face an end of at least one of the positive electrode and the negative electrode, and filled with a flame retardant.

[0009] According to an embodiment, the protective member may face one of the positive and negative electrodes, which has a shorter length.

[0010] According to one embodiment, the protective member can be disposed on the separator so as to face the starting end of the positive electrode from which winding begins.

[0011] According to an embodiment, the negative electrode may include an extension region extending from the positive electrode in a direction opposite to a winding direction of the electrode assembly, and the protective member may overlap the extension region of the negative electrode.

[0012] According to one embodiment, the protective member may include a first insulating layer disposed on the separator and having a plurality of pores formed therein into which the flame retardant is filled, a second insulating layer disposed on the first insulating layer and facing the winding center of the electrode assembly, and an adhesive layer disposed between the first insulating layer and the second insulating layer.

[0013] According to one embodiment, the second insulating layer may be thinner than the first insulating layer and may have a thickness equal to or greater than that of the adhesive layer.

[0014] According to one embodiment, the first insulating layer may have a thickness of 50 to 70% of the total thickness of the protective member, the second insulating layer may have a thickness of 20 to 30% of the total thickness of the protective member, and the adhesive layer may have a thickness of 10 to 20% of the total thickness of the protective member.

[0015] According to an embodiment, the second insulating layer may have a melting temperature lower than that of the first insulating layer.

[0016] According to one embodiment, the first insulating layer may include at least one of polyimide (PI) and polyethylene terephthalate (PET), and the second insulating layer may include one of polyethylene (PE), polypropylene (PP), and polyurethane (PU).

[0017] According to one embodiment, the first insulating layer includes a first insulating region and a second insulating region disposed on both sides of the first insulating region, and the plurality of pores may be formed in the first insulating region excluding the second insulating region.

[0018] According to one embodiment, the flame retardant may be a fluorine-containing flame retardant liquid.

[0019] According to one embodiment, the positive electrode includes a positive electrode current collector, a first active material layer disposed on an upper portion of the positive electrode current collector, and a second active material layer disposed on a lower portion of the positive electrode current collector, and the protective member may be in contact with a starting end of at least one of the positive electrode current collector, the first active material layer, and the second active material layer.

[0020] According to an embodiment, the electrode assembly may further include a negative electrode tab electrically connected to the negative electrode, and the protective member may have a width equal to or less than a distance between a leading end of the positive electrode and the negative electrode tab.

[0021] According to an embodiment, the thickness of the protective member may be the same as the thickness of the positive electrode.

[0022] According to an embodiment, the electrode assembly may further include a fire extinguishing agent filled inside the protective member.

[0023] A secondary battery according to an embodiment of the present invention may include the above-described electrode assembly. [Effects of the Invention]

[0024] According to an embodiment of the present invention, the electrode assembly may include a protective member facing the winding start end where winding of the positive electrode begins. This protective member prevents cracks in the negative electrode that contact the winding start end of the positive electrode, and prevents breakage and short circuits, thereby improving the safety of the secondary battery.

[0025] Furthermore, according to an embodiment of the present invention, the protective member can easily maintain the circular shape of the wound center of the electrode assembly, thereby preventing an internal short circuit from occurring during charge / discharge cycles of a secondary battery including the electrode assembly, thereby ensuring safety.

[0026] Furthermore, according to an embodiment of the present invention, the protective member may be filled with a filler containing a flame retardant, which can prevent a temperature rise in the secondary battery from leading to a fire or explosion.

[0027] In addition, various other effects may be provided that can be directly or indirectly grasped from this document. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a perspective view showing a secondary battery including an electrode assembly according to a first embodiment of the present invention; [Figure 2] 2 is an exploded perspective view showing the electrode assembly shown in FIG. 1 in an unfolded state before being wound up. FIG. [Figure 3] 2 is a cross-sectional view showing the electrode assembly shown in FIG. 1 in an unfolded state before being wound up. [Figure 4] 1A and 1B are a plan view and a cross-sectional view showing a protective member according to the present invention. [Figure 5] 3 is an enlarged cross-sectional view showing the periphery of the center of the winding after the electrode assembly shown in FIG. 2 has been wound. [Figure 6] FIG. 10 is a cross-sectional view showing an electrode assembly according to a second embodiment of the present invention in an unfolded state before being wound up. DETAILED DESCRIPTION OF THE INVENTION

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand the preferred embodiments of the present invention. However, the present invention may be realized in various different forms and is not limited to the following embodiments.

[0030] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the explanation or related known technologies that may obscure the gist of the present invention will be omitted, and in this specification, when adding reference symbols to components in each drawing, the same or similar reference symbols will be used throughout the specification to refer to the same or similar components.

[0031] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary and dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0032] Secondary battery including electrode assembly according to the first embodiment FIG. 1 is a perspective view showing a secondary battery including an electrode assembly according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view showing the electrode assembly shown in FIG. 1 in an unfolded state before being wound up.

[0033] Referring to FIGS. 1 and 2, a secondary battery 10 according to the present invention may include an electrode assembly 100 and a battery case 180.

[0034] The electrode assembly 100 may be housed in the battery case 180. The battery case 180 may include a battery can 182 and a cap assembly 181.

[0035] The battery can 182 may include a receiving portion 183 capable of receiving the electrode assembly 100. An electrolyte may be poured into the receiving portion 183 so that the electrode assembly 100 is completely immersed in the battery can 182. The top of the battery can 182 may be open so that it can be used as an inlet passage for the electrode assembly 100. The battery can 182 may include metal. For example, the battery can 182 may include stainless steel.

[0036] The battery can 182 may be formed in a shape corresponding to the shape of the electrode assembly 100 to accommodate the electrode assembly 100. For example, the battery can 182 may be formed in a cylindrical shape to accommodate the electrode assembly 100 formed in a jelly roll shape.

[0037] The cap assembly 181 may be mounted on the battery can 182 to cover the open top of the battery can 182 and may be coupled to the battery can 182. The cap assembly 181 may be formed by sequentially stacking a safety vent, a current interruption device, a positive temperature coefficient (PTC) device, and a top cap. The top cap is mounted on and coupled to the top of the cap assembly 181 to transmit current generated in the secondary battery to the outside.

[0038] One of the battery can 182 and the cap assembly 181 may be electrically connected to the positive electrode tab 171 of the electrode assembly 100, and the other of the battery can 182 and the cap 181 may be electrically connected to the negative electrode tab 172. For example, the cap assembly 181 may be electrically connected to the positive electrode tab 171 by a welding process, and the bottom surface of the battery can 182 may be electrically connected to the negative electrode tab 172 by a welding process. As another example, one of the battery can 182 and the cap assembly 181 may be electrically connected to the positive electrode tab 171 and the negative electrode tab 172.

[0039] The electrode assembly 100 may be a power generating element capable of charging and discharging. The electrode assembly 100 has a structure in which electrodes 130 and separators 160 are assembled and stacked alternately. The electrode assembly 100 may be formed in a form in which the electrodes 130 and separators 160 are assembled alternately and wound up. The electrode assembly 100 may have a structure in which its diameter expands radially in proportion to the number of winding rotations. In this case, the electrode assembly 100 may be wound into a cylindrical shape wound around a winding center (or central axis) C. For example, the electrode 130 may include a positive electrode 110 and a negative electrode 120, and the separator 160 may include a first separator 140 and a second separator 150. The electrode assembly 100 may be in the form of a jelly roll in which a positive electrode 110, a first separator 140, a negative electrode 120, and a second separator 150 are stacked in order and wound into a cylindrical shape.

[0040] The positive electrode 110 may include a positive electrode current collector 113, a first positive electrode active material layer 111 formed on an outer surface 123b (e.g., a surface facing the unwrapping portion O) of the positive electrode current collector 113, and a second positive electrode active material layer 112 formed on an inner surface (e.g., a surface facing the winding center C) of the positive electrode current collector 113. The positive electrode current collector 113 may be formed to extend from at least one of the first positive electrode active material layer 111 and the second positive electrode active material layer 112 toward the unwrapping portion O. A region where at least one of the first positive electrode active material layer 111 and the second positive electrode active material layer 112 is not formed and where the positive electrode current collector 113 is formed may be a positive electrode uncoated portion 115. At least one positive electrode tab 171 may be fused to the positive electrode current collector 113 in the positive electrode uncoated portion 115 by a method such as welding.

[0041] The positive electrode current collector 113 may be made of, for example, an aluminum foil. At least one of the first positive electrode active material layer 111 and the second positive electrode active material layer 112 may be made of, for example, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound or mixture containing one or more of these.

[0042] The negative electrode 120 may include a negative electrode current collector 123, a first negative electrode active material layer 121 formed on an outer surface (e.g., a surface facing the unwinding portion O) of the negative electrode current collector 123, and a second negative electrode active material layer 122 formed on an inner surface (e.g., a surface facing the winding center portion C) of the negative electrode current collector 123. The negative electrode 120 may be divided into a negative electrode coated portion (or coated portion) and a negative electrode uncoated portion (or uncoated portion) 125 depending on the positions where the first negative electrode active material layer 121 and the second negative electrode active material layer 122 are formed. The negative electrode coated portion may be a region where the first negative electrode active material layer 121 and the second negative electrode active material layer 122 are formed. The negative electrode uncoated portion 125 may be a region where at least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 is not formed. At least one negative electrode tab 172 may be fused onto the negative electrode current collector 123 of the negative electrode uncoated portion 125 by a method such as welding.

[0043] The negative electrode current collector 123 may be made of, for example, a foil containing copper (Cu) and / or nickel (Ni). At least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 may be made of artificial graphite, lithium metal, a lithium alloy, carbon, petroleum coke, activated carbon, graphite, a silicon compound, a tin compound, a titanium compound, or an alloy thereof. At least one of the first negative electrode active material layer 121 and the second negative electrode active material layer 122 may contain, for example, non-graphite-based SiO (silica) or SiC (silicon carbide).

[0044] The separator 160 is disposed between the positive electrode 110 and the negative electrode 120 to separate and electrically insulate the positive electrode 110 and the negative electrode 120. The separator 160 may include a first separator 140 and a second separator 150. The first separator 140 may be stacked on the outside of either the positive electrode 110 or the negative electrode 120. The second separator 150 may be stacked on the outside of the other of the positive electrode 110 and the negative electrode 120. For example, when the first separator 140 is stacked on the outside of the positive electrode 110, the first separator 140 may be disposed between the first positive electrode active material layer 111 and the second negative electrode active material layer 122. When the second separator 150 is stacked on the outside of the negative electrode 120, the second separator 150 may be disposed between the second positive electrode active material layer 112 and the first negative electrode active material layer 121. Meanwhile, when a laminate in which the positive electrode 110, the first separator 140, the negative electrode 120, and the second separator 150 are stacked in order is wound up, a jelly roll-type electrode assembly 100 in which the second separator 150 is formed on the outermost surface can be formed.

[0045] At least one of the first separator 140 and the second separator 150 can be, for example, a multilayer film made of polyethylene, polypropylene, or a combination thereof, or a polymer film for a solid polymer electrolyte or a gel polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride-hexafluoropropylene copolymer.

[0046] The electrode assembly 100 according to the present invention may include a protective member 200 disposed to face an end of at least one of the positive electrode 110 and the negative electrode 120. The protective member 200 may be disposed to face a starting end of the shorter electrode among the positive electrode 110 and the negative electrode 120. The protective member 200 may be located closer to the winding center C than the unwinding portion O. The protective member 200 may be formed to extend along the width direction of one of the first separator 140 and the second separator 150. The protective member 200 may be formed adjacent to at least one of the positive electrode tab 171 and the negative electrode tab 172.

[0047] Fig. 3 is a cross-sectional view showing the electrode assembly shown in Fig. 2 in an unfolded state before being wound up. In Fig. 3, the positive electrode 110, the first separator 140, the negative electrode 120, and the second separator 150 are shown as being spaced apart, but after being wound up, the positive electrode 110, the first separator 140, the negative electrode 120, and the second separator 150 may be in close contact with each other.

[0048] 3, the negative electrode 120 may be formed to wrap around the positive electrode 110 during winding, and therefore may be longer than the positive electrode 110. The negative electrode 120 may include an extension region 126 that extends beyond the positive electrode 110 in the opposite direction to the winding direction (WD) of the electrode assembly. The winding direction (WD) may refer to the direction in which the negative electrode 120 and the positive electrode 110 are wound. In FIG. 3, the winding direction (WD) may be clockwise.

[0049] The protective member 200 can be arranged to overlap the extension region 126 of the negative electrode 120 and face the winding start end AE of the positive electrode 110. The protective member 200 can be arranged on the first separator 140 and can contact the winding start end AE of the positive electrode 110. The protective member 200 can contact the winding start end AE of at least one of the first positive electrode active material layer 111, the second positive electrode active material layer 112, and the positive electrode current collector 113.

[0050] The protective member 200 may be disposed on one surface of the first separator 140 facing the winding center C. The protective member 200 may have a thickness T corresponding to that of the positive electrode 110. The thickness T of the protective member 200 may be the same as that of the positive electrode 110. For example, the thickness of the protective member 200 may be formed to be 90 μm to 150 μm, and the present invention does not limit the thickness of the protective member 200. Because the thickness of the positive electrode 110 may vary from product to product depending on the product characteristics of the electrode assembly, the thickness of the protective member 200 may be formed to be the same as that of the positive electrode depending on the product characteristics.

[0051] The protective member 200 may be formed to be wound from the winding start end AE of the positive electrode 110 toward the winding center C. The protective member 200 may extend from the winding start end AE of the positive electrode 110 toward the winding center C. For example, the protective member 200 may be disposed between the winding start end AE of the positive electrode 110 and the winding start end CE of the negative electrode 120. For another example, the protective member 200 may be disposed between the winding start end AE of the positive electrode 110 and the negative electrode tab 172. The width W of the protective member 200 may be equal to or less than the distance D from the winding start end AE of the positive electrode to the negative electrode tab 172. For example, the width W of the protective member 200 may be 10 mm to 21 mm. Meanwhile, a protective tab 173 may be attached to at least one of the negative electrode tab 172 and the positive electrode tab (e.g., the positive electrode tab 171 in FIG. 1). The protective tab 173 reduces the step formed by the positive electrode tab 171 and the negative electrode tab 172, and can prevent damage to the first separator 140 and the second separator 150 that face the positive electrode tab 171 and the negative electrode tab 172.

[0052] The protective member 200 can cover the step at the winding start end AE of the positive electrode 110. The protective member 200 can remove the step at the winding start end AE corresponding to the maximum thickness of the positive electrode 110. The protective member 200 prevents the negative electrode 120, which contracts and expands as the secondary battery is charged and discharged, from folding at the winding start end AE of the positive electrode 110. The winding start end AE of the positive electrode 110 can be prevented from coming into contact with the negative electrode. This can prevent cracks from occurring in the first separator 140 due to the winding start end AE of the positive electrode 110, thereby preventing an electrical short circuit from occurring between the negative electrode 120 and the positive electrode 110.

[0053] In addition, the protective member 200 allows the winding center C of the electrode assembly to easily maintain its circular shape, thereby preventing the occurrence of an internal short circuit during the charge / discharge cycle of a secondary battery including the electrode assembly and ensuring safety.

[0054] 4 is a plan view and a cross-sectional view showing a protective member according to the present invention, and FIG. 5 is an enlarged cross-sectional view showing the area around the winding center C after the electrode assembly shown in FIG. 2 has been wound.

[0055] 4 and 5, the protective member 200 may be formed in the form of an insulating tape. The protective member 200 may include a first insulating layer 301, an adhesive layer 201, and a second insulating layer 302, which are laminated in this order on one surface of the first separator 140.

[0056] The adhesive layer 201 is disposed between the first insulating layer 301 and the second insulating layer 302 and can bond the first insulating layer 301 and the second insulating layer 302. In addition, the protective member 200 can be attached onto the first separator 140 via the second adhesive layer 202. The second adhesive layer 202 can be disposed between the first insulating layer 301 and the first separator 140.

[0057] The first insulating layer 301 may include a first insulating region 310 and a second insulating region 320 .

[0058] The first insulating region 310 may include a first surface 311, a second surface 312, and a third surface 313. The first surface 311 may be formed to face the winding center C (or the second insulating layer 302). The second surface 312 may be formed to face the opposite direction of the first surface 311 (or the second adhesive layer 202 or the first separator 140). A plurality of third surfaces 313 may be disposed between the first surface 311 and the second surface 312. The plurality of third surfaces 313 may be formed to intersect with the first surface 311 and the second surface 312.

[0059] The first insulating region 310 may include a plurality of pores 330. The plurality of pores 330 may be filled with a first filling member 340. For example, the first filling member 340 may be a flame-retardant liquid (or flame retardant) containing fluorine (F). The liquid first filling member 340 may flow out of the protective member 200 in an abnormal operating state of the secondary battery (e.g., the secondary battery 10 of FIG. 1), such as an overcurrent state or a high temperature state. The first filling member 340 may flow out to the winding center C in an abnormal operating state of the secondary battery 10, thereby cooling the electrode assembly. The first filling member 340 may prevent a temperature rise in the secondary battery from leading to fire or explosion.

[0060] The second insulating region 320 may be formed to surround a portion of the first insulating region 310. As an example, the second insulating region 320 may be formed to surround a plurality of third surfaces 313 of the first insulating region 310 excluding the first surface 311 and the second surface 312. As another example, the second insulating region 320 may be formed to surround the second surface 312 of the first insulating region 310 excluding the first surface 311 and the plurality of third surfaces 313. The second insulating region 320 may serve to confine the first filling member 340 within the first insulating region 310 to prevent the liquid first filling member 340 from flowing out during normal operation of the secondary battery.

[0061] The first insulating region 310 and the second insulating region 320 may be formed of different materials or may be formed integrally with each other using the same material. At least one of the first insulating region 310 and the second insulating region 320 may be formed of a plastic material that exhibits electrical insulation. The first insulating region 310 and the second insulating region 320 may be formed of a material that has a higher melting point than the second insulating layer 302 and is less likely to melt at high temperatures. For example, the first insulating layer 301 including the first insulating region 310 and the second insulating region 320 may include at least one of polyimide (PI) and polyethylene terephthalate (PET).

[0062] The second insulating layer 302 may be disposed on the adhesive layer 201 so as to face the winding center C. The second insulating layer 302 may be disposed closer to the winding center C than at least one of the adhesive layer 201 and the first insulating layer 301.

[0063] The second insulating layer 302 and the adhesive layer 201 may be formed to melt easily at high temperatures. For example, the second insulating layer 302 and the adhesive layer 201 may be formed to melt when the internal temperature of the secondary battery reaches 100 degrees Celsius or higher. As the second insulating layer 302 and the adhesive layer 201 melt at high temperatures, the flame retardant in the first insulating layer 301 may flow out to the outside of the protective member 200. The second insulating layer 302 may be formed of a material having a lower melting point than the first insulating layer 301. For example, the second insulating layer 302 may include any one of polyethylene (PE), polypropylene (PP), and polyurethane (PU).

[0064] The first insulating layer 301 included in the protective member 200 may be formed thicker than the adhesive layer 201 and the second insulating layer 302. The second insulating layer 302 may be formed to have the same thickness as or thicker than the adhesive layer 201. The thickness T301 of the first insulating layer 301 may account for 50 to 70% of the total thickness of the protective member 200. The thickness T302 of the second insulating layer 302 may account for 20 to 30% of the total thickness of the protective member 200. The thickness T201 of the adhesive layer 201 may account for 10 to 20% of the total thickness of the protective member 200. Because the first insulating layer 301 is formed thicker than the adhesive layer 201 and the second insulating layer 302, the first filling member 340 filling the first insulating layer 301 may account for a higher proportion of the protective member 200. As a result, the protective member including the first filling member 340 can prevent a rise in temperature of the secondary battery from leading to fire or explosion.

[0065] Electrode assembly according to a second embodiment FIG. 6 is a cross-sectional view showing an electrode assembly according to a second embodiment of the present invention in an unfolded state before being wound up.

[0066] The electrode assembly according to the second embodiment of the present invention has the same components as the electrode assembly according to the first embodiment of the present invention shown in Figures 1 to 5, except that the first filling member 340 and the second filling member 600 are filled into the plurality of pores 330. Therefore, the detailed description of the same components is given in reference to Figures 1 to 5.

[0067] Referring to FIG. 6 , the protective member 200 may include a plurality of pores 330. Some of the pores 330 may be filled with a first filler member 340. The remaining pores 330 may be filled with a second filler member 600. The first filler member 340 and the second filler member 600 may be formed of different materials. The first filler member 340 may include a fire-retardant liquid. For example, the second filler member 600 may include a fire-extinguishing agent 610. For another example, the second filler member 600 may be formed in a form in which a shell 620 surrounds a core containing the fire-extinguishing agent 610. When the secondary battery ignites, the shell 620 melts, allowing the fire-extinguishing agent 610 contained in the core to be discharged toward the winding center C. The fire-extinguishing agent 610 contained in the second filler member 600 may not chemically react with the fire-retardant contained in the first filler member 340.

[0068] When the secondary battery catches fire, the fire extinguishing agent 610 is discharged toward the winding center C, thereby quickly extinguishing the fire and preventing the fire from spreading to adjacent electrode assemblies 100.

[0069] The secondary battery including the electrode assembly described above can be applied to various devices, including, but not limited to, transportation means such as electric bicycles, electric vehicles, and hybrid vehicles, and can be applied to various devices that can use a battery module.

[0070] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the technical spirit of the present invention and the scope of equivalents of the appended claims by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0071] 100 electrode assembly 110 Positive electrode 120 negative electrode 140 First separator 150 Second separator 171 Positive electrode tab 172 Negative electrode tab 200 Protective material 340 First filling member 600 Second filling member

Claims

1. An electrode assembly formed by winding a positive electrode, a separator, and a negative electrode, The electrode assembly further includes a protective member disposed to face an end of at least one of the positive electrode and the negative electrode, the protective member being filled with a flame retardant.

2. The electrode assembly according to claim 1 , wherein the protective member faces one of the positive electrode and the negative electrode, which has a shorter length.

3. The electrode assembly according to claim 1 , wherein the protective member is disposed on the separator so as to face a starting end of the positive electrode from which winding begins.

4. The negative electrode is an extension region extending from the positive electrode in a direction opposite to the winding direction of the electrode assembly; The electrode assembly according to claim 1 , wherein the protective member overlaps the extension region of the negative electrode.

5. The protective member is a first insulating layer disposed on the separator, the first insulating layer having a plurality of pores formed therein and filled with the flame retardant; a second insulating layer disposed on the first insulating layer and facing the winding center of the electrode assembly; The electrode assembly of claim 1 , further comprising: an adhesive layer disposed between the first insulating layer and the second insulating layer.

6. The electrode assembly of claim 5 , wherein the second insulating layer is thinner than the first insulating layer and has a thickness equal to or greater than that of the adhesive layer.

7. the first insulating layer has a thickness of 50 to 70% of the total thickness of the protective member; the second insulating layer has a thickness of 20 to 30% of the total thickness of the protective member; 6. The electrode assembly according to claim 5, wherein the adhesive layer has a thickness of 10 to 20% of the total thickness of the protective member.

8. The electrode assembly of claim 5 , wherein the second insulating layer has a melting temperature lower than that of the first insulating layer.

9. the first insulating layer includes at least one of polyimide (PI) and polyethylene terephthalate (PET); The electrode assembly of claim 5 , wherein the second insulating layer includes any one of polyethylene (PE), polypropylene (PP), and polyurethane (PU).

10. The first insulating layer is a first insulating region; second insulating regions disposed on both sides of the first insulating region; The electrode assembly of claim 5 , wherein the plurality of pores are formed in the first insulating region excluding the second insulating region.

11. 2. The electrode assembly according to claim 1, wherein the flame retardant is a fluorine-containing flame retardant liquid.

12. The positive electrode is a positive electrode current collector; a first active material layer disposed on the positive electrode current collector; a second active material layer disposed below the positive electrode current collector, The electrode assembly of claim 1 , wherein the protective member contacts a leading end of at least one of the positive electrode current collector, the first active material layer, and the second active material layer.

13. a negative electrode tab electrically connected to the negative electrode, The electrode assembly according to claim 1 , wherein the protective member has a width equal to or smaller than the distance between the leading end of the positive electrode and the negative electrode tab.

14. The electrode assembly according to claim 1 , wherein the thickness of the protective member is the same as the thickness of the positive electrode.

15. The electrode assembly according to claim 1 , further comprising a fire extinguishing agent filled inside the protective member.

16. A secondary battery comprising the electrode assembly according to claim 1 .

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