Electrode assembly for secondary battery and cylindrical secondary battery including the same

Abstract

The present invention relates to an electrode assembly for a secondary battery and a cylindrical secondary battery comprising the same, the electrode assembly having a wound electrode laminate comprising: a positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector; a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector; and a separator interposed between the positive electrode and the negative electrode, in which an end portion facing the winding center portion among opposite end portions of the negative electrode in the longitudinal direction is a negative electrode uncoated portion in which the negative electrode active material layer is not formed, and an end portion facing the winding center portion among opposite end portions in the longitudinal direction of the positive electrode has a membrane member containing a ceramic.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2022-0141905 filed on October 28, 2022 and Korean Patent Application No. 10-2023-0141161 filed on October 20, 2023, and the disclosures of the above two Korean patent applications are incorporated herein.

[0002] The present invention relates to an electrode assembly for a secondary battery and a cylindrical type secondary battery including the electrode assembly for a secondary battery, which can prevent an internal short circuit caused by damage to a separator. Background Art

[0003] According to the shape of the battery case, secondary batteries can be classified into: cylindrical batteries and prismatic batteries, each of which has an electrode assembly embedded in a cylindrical metal can or a prismatic metal can; and pouch-type batteries, which have an electrode assembly embedded in a pouch-type case made of a laminate sheet of aluminum.

[0004] In addition, the electrode assembly embedded in the battery case is a rechargeable and dischargeable power generation device having a structure in which a positive electrode / separator / negative electrode is stacked, and can be classified into: an electrode assembly having a winding type structure in which a long sheet-type positive electrode and a long sheet-type negative electrode are wound with a separator interposed therebetween, each of the long sheet-type positive electrode and the long sheet-type negative electrode being coated with an active material; an electrode assembly having a stacking type structure in which a plurality of positive electrodes and negative electrodes are stacked in sequence with a separator interposed therebetween, each of the plurality of positive electrodes and negative electrodes having a predetermined size; and a stacked and folded type electrode assembly having a structure in which a double cell or a full cell is wound, in which the positive electrode and the negative electrode in a predetermined unit are stacked with a separator interposed therebetween.

[0005] Among these electrode assemblies, a wound electrode assembly has advantages such as easy manufacturing and high energy density per unit weight, and thus is widely manufactured. The wound electrode assembly can be manufactured by assembling a stack of a long sheet-type positive electrode, a long sheet-type negative electrode, and a separator interposed between the long sheet-type positive electrode and the long sheet-type negative electrode, and winding the stack in the longitudinal direction of the sheet in a state in which a core is in contact with one end of the stack of electrodes.

[0006] Specifically, Figure 6 As illustrated in FIG. 1 , in a state where separators 1a and 1b are first input in the core and fixed to overlap each other, the negative electrode 2 is input while the core is rotated, and then the positive electrode 3 is input at predetermined time intervals. When the core is rotated at a predetermined rotation in a state where even the positive electrode 3 is input, as shown in FIG. Figure 7As shown in FIG. 1 , a wound type shape is realized. That is, separators 1a and 1b, negative electrode 2, and positive electrode 3 are arranged outward from the center of the wound type shape. Figure 7 The diagram shows the space existing inside when the negative electrode, separator and positive electrode rotate, but the spacing is only intentionally shown for identification. In fact, while rotating, the negative electrode, separator and positive electrode are in close contact with each other to be wound into a cylindrical shape with a close arrangement.

[0007] At the same time, during the charge-discharge period of the battery, the electrode may be deformed when it expands and contracts repeatedly. In particular, since the wound electrode assembly has a dense shape, the internal temperature may rise when such deformation occurs. As described above, when the electrode is deformed or the internal temperature rises excessively, the separator in the electrode assembly may be damaged, and therefore there is a risk of a short circuit between the positive electrode and the negative electrode. This may further increase the internal temperature of the electrode assembly, thereby causing serious safety problems, such as fire or explosion. Therefore, solutions for solving these safety problems are needed. Summary of the invention

[0008] Technical issues

[0009] An object of the present invention is to provide an electrode assembly for a secondary battery and a cylindrical type secondary battery, in which a film member including ceramics is introduced to solve the above safety issues.

[0010] Technical Solution

[0011] The present invention provides an electrode assembly for a secondary battery, the electrode assembly having a shape in which an electrode stack is wound, the electrode stack comprising: a positive electrode including a positive electrode collector and a positive electrode active material layer disposed on at least one surface of the positive electrode collector;

[0012] a negative electrode including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; and

[0013] a separator, the separator being interposed between the positive electrode and the negative electrode,

[0014] wherein one of the two ends in the longitudinal direction of the negative electrode facing the winding center is a negative electrode uncoated portion on which the negative electrode active material layer is not provided, and

[0015] An end portion facing the winding center among both end portions in the longitudinal direction of the positive electrode is provided with a film member containing ceramic.

[0016] The present invention also provides a cylindrical secondary battery, the cylindrical secondary battery comprising: an electrode assembly for a secondary battery;

[0017] a battery can in which the electrode assembly is accommodated; and

[0018] A cap assembly seals the open end of the battery can.

[0019] Beneficial Effects

[0020] When a cylindrical secondary battery is manufactured by including the electrode assembly for a secondary battery according to the present invention, deformation of the electrode during charge-discharge and damage to the separator caused thereby can be prevented. Ultimately, the risk of internal short circuit can be reduced to improve the safety of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a view illustrating an electrode stack according to an embodiment of the present invention.

[0022] Figure 2 Illustrated are views for comparing the state of a winding center between a case where a film member containing ceramics is not introduced in a wound type electrode assembly (left) and a case where a film member containing ceramics is introduced (right).

[0023] Figure 3 2 is a view illustrating a membrane member including ceramics according to an embodiment of the present invention.

[0024] Figure 4 It is a graphic Figure 3 0047] Figure 2 shows several suitable shapes for a cross-section of the portion AA' of the ceramic-containing membrane member illustrated in FIG.

[0025] Figure 5 is a view illustrating results obtained by measuring changes in voltage over time in secondary batteries manufactured according to Examples and Comparative Examples.

[0026] Figure 6 is a view illustrating a process of inputting a separator, a negative electrode, and a positive electrode into a core when a wound type electrode assembly is manufactured by a method according to the related art.

[0027] Figure 7 It is shown in Figure 6 A view of the process of achieving a wound shape when the core is rotated in a state of FIG.

[0028] Figure 8 is a vertical cross-sectional perspective view illustrating a cylindrical type secondary battery according to an embodiment of the present invention.

[0029] Fig. 9 is a view illustrating the structure of a cap assembly according to an embodiment of the present invention.

[0030] [Description of Reference Signs]

[0031] 1, 1a, 1b: Separator

[0032] 2: Negative electrode

[0033] 21: Uncoated part of negative electrode

[0034] 21a: Uncoated area of ​​negative electrode

[0035] 2a: Negative electrode current collector

[0036] 2b: Negative electrode active material layer

[0037] 3: Positive electrode

[0038] 3a: Positive electrode current collector

[0039] 3b: Positive electrode active material layer

[0040] 31: Membrane components containing ceramics

[0041] 31a: Region where a membrane member including ceramic is provided

[0042] 50: Polymer membrane

[0043] 51: Ceramics

[0044] 10: Top cover

[0045] 20: Safety exhaust parts

[0046] 30: CID filter

[0047] T: Notch

[0048] 40: Electrode tab

[0049] 32: Padding

[0050] 60: Curling part

[0051] 70: Crimping part

[0052] 100: Cylindrical secondary battery

[0053] 120: Electrode assembly

[0054] 130: Battery Can

[0055] 140: Cover assembly

[0056] 150: Center pin DETAILED DESCRIPTION

[0057] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention belongs can easily implement the present invention. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein.

[0058] Parts not related to the description of the present invention will be omitted in the drawings.

[0059] Furthermore, the terms or words used in the present specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts consistent with the scope of the present invention based on the principle that the inventor can appropriately define the concepts of the terms to best describe and interpret his or her invention.

[0060] As described above, due to repeated expansion and contraction during the charge-discharge period of the secondary battery, the electrode may be deformed and the separator may be damaged, resulting in a short circuit between the positive electrode and the negative electrode. In a cylindrical secondary battery, these problems may occur more frequently when the pressure is concentrated on the winding center. In particular, in the case where the positive electrode is a free edge positive electrode that does not include an uncoated portion, these problems may be further aggravated due to a large thickness difference.

[0061] Therefore, the inventors introduced a film member containing ceramic into the end portion facing the winding center of both ends in the longitudinal direction of the positive electrode to promote the effect of preventing deformation of the electrode and reducing the thickness difference. Therefore, it has been found that the problem of damage to the separator and internal short circuit generated at the winding center of the electrode assembly can be solved.

[0062] Hereinafter, each of the elements of the present invention will be described in more detail.

[0063] [Electrode assembly]

[0064] The electrode assembly for a secondary battery according to the present invention has a shape in which an electrode stack is wound, and the electrode stack includes: a positive electrode including a positive electrode collector and a positive electrode active material layer provided on at least one surface of the positive electrode collector; a negative electrode including a negative electrode collector and a negative electrode active material layer provided on at least one surface of the negative electrode collector; and a separator, which is interposed between the positive electrode and the negative electrode. The end facing the winding center of the two ends in the longitudinal direction of the negative electrode is a negative electrode uncoated portion, on which the negative electrode active material layer is not provided. The end facing the winding center of the two ends in the longitudinal direction of the positive electrode is provided with a film member containing ceramic.

[0065] like Figure 1 As shown in the figure, the electrode stack can have a structure in which a separator 1b, a positive electrode 3 having a positive electrode active material layer 3a arranged on each of the two surfaces of a positive electrode collector 3b, a separator 1a, and a negative electrode 2 having a negative electrode active material layer 2a arranged on each of the two surfaces of a negative electrode collector 2b are stacked in sequence.

[0066] The membrane member containing ceramics may be disposed on an area matching or larger than the area of ​​the negative electrode uncoated portion, wherein the separator is located between the membrane member containing ceramics and the negative electrode uncoated portion. That is, the area 31a where the membrane member containing ceramics is disposed may match or be larger than the area 21a of the negative electrode uncoated portion, wherein the separator 1a is located between the area 31a and the area 21a. Figure 1 It can be confirmed that the ceramic-containing film member 31 attached to the end of the positive electrode 3 is set wider (longer in the drawing) so as to cover the entire area 21a of the uncoated portion of the negative electrode, which is set on the end of the negative electrode 2 which becomes the winding center C.

[0067] In addition, a film member including ceramics may be provided on each of both surfaces of the positive electrode.

[0068] In the embodiment of the present invention, the film member containing ceramics may be a film of a polymer having a melting point of 130° C. or more to which ceramics are added, and as a preferred example, may be a member containing ceramics 51 in a strip shape at fixed intervals in a polymer film 50, such as Figure 3 shown. Figure 4 It is a graphic Figure 3 Schematic diagram of the cross section of the portion AA' in FIG. The cross section may have a shape in which a polymer film and a ceramic are alternately attached as in (a), a shape in which a portion of the polymer film is replaced by a ceramic 51 as in (b), or a shape in which a ceramic 51 is attached or coated on a single surface or each of the two surfaces of the polymer film 50 as in (c) and (d).

[0069] Due to the high strength characteristics of ceramics, the film into which the ceramics are introduced as above can have high physical rigidity and fixing force compared to the film of the polymer according to the related art. Therefore, the length change of the electrode according to charge-discharge can be more effectively suppressed, and thus the separator can be prevented from being damaged due to the deformation of the electrode. Specifically, the film member containing ceramics can have a tensile strength of 200N / cm to 400N / cm, preferably a tensile strength of 250N / cm to 350N / cm, or more preferably a tensile strength of 280N / cm to 320N / cm.

[0070] In an embodiment of the present invention, the film member containing ceramics is a member in which ceramics in the shape of stripes at fixed intervals are contained in a film of a polymer, and one stripe of the ceramics may have a width of 1 mm to 3 mm ( Figure 4 w in ), and the distance between the stripes ( Figure 4 The y) in the figure can be 7 mm to 10 mm.

[0071] In the surface contacting the separator of the two surfaces of the film member containing ceramic, the surface area where the ceramic is exposed may be 5% or more of the entire surface area of ​​the film member containing ceramic, and preferably 10% or less in view of flexibility during winding. The thickness of the film member containing ceramic may be 20 μm or more, but 170 μm or less, preferably 150 μm or less, or more preferably 50 μm or less. When the thickness of the film member containing ceramic is within the above range, the energy density may not be reduced, and the effect of the present invention may also be achieved.

[0072] In addition, the polymer may include one or more selected from polyimide, polypropylene, polyethylene terephthalate, polystyrene, polycarbonate and polysulfone, or preferably one or more selected from polyimide, polypropylene and polyethylene terephthalate. In view of chemical resistance, the polymer may most preferably be polypropylene. Specifically, the film member containing ceramics may be a member in which ceramics are introduced into a polymer band in a stripe shape as described above.

[0073] In addition, the ceramic may include one or more selected from glass fiber, tungsten carbide (WC), Al2O3, Cr2O3, SiO2, MnO, ZnO, SnO, PbO, TiO2, B4C, TiC, SiC, AlN, Si3N4, MgB2, TiB2, TiAl, NiTi, and Al2Si2O5(OH)4. In view of electrical stability and strength, the ceramic may preferably include one or more selected from glass fiber, Al2O3, and SiC, and most preferably glass fiber.

[0074] The positive electrode, the negative electrode, and the separator may not be limited as long as they are generally used in secondary batteries. As a preferred example, the following description may be referred to.

[0075] The positive electrode 3 may be a sheet-type positive electrode, and includes a positive electrode current collector 3b made of a thin metal film having excellent conductivity, such as aluminum foil, and a positive electrode active material layer 3a, each of the two surfaces of the positive electrode current collector 3b is coated with the positive electrode active material layer 3a. The negative electrode 2 may be a sheet-type negative electrode, and includes a negative electrode current collector 2b made of a thin metal film having excellent conductivity, such as copper (Cu) foil or nickel (Ni) foil, and a negative electrode active material layer 2a, each of the two surfaces of the negative electrode current collector 2b is coated with the negative electrode active material layer 2a.

[0076] The positive electrode active material layer may include a lithium metal oxide containing lithium and a transition metal such as cobalt, manganese and / or nickel as a positive electrode active material, and may also include a conductive material and / or a binder when necessary. Various materials commonly used in the manufacture of secondary batteries may be used for the positive electrode active material, the conductive material and the binder, but are not limited thereto.

[0077] In the end facing the winding center of the two ends in the longitudinal direction of the positive electrode, the end of the positive electrode active material layer may match the end of the positive electrode current collector. That is, the positive electrode uncoated portion may not be provided on the end facing the winding center of the two ends in the longitudinal direction, and more specifically, the positive electrode may be a free edge positive electrode in which each of the two ends in the longitudinal direction does not include the positive electrode uncoated portion. Here, the positive electrode uncoated portion refers to an area of ​​the positive electrode where the positive electrode active material layer is not provided.

[0078] When the positive electrode includes a positive electrode uncoated portion, the active material slurry scattered when forming the positive electrode active material layer may be attached to the uncoated portion, and the positive electrode active material layer may be arranged in an island shape. This may cause an internal short circuit when the electrode stack expands and contracts during charge-discharge of the battery.

[0079] In order to prevent the internal short circuit, a free edge positive electrode may be introduced. However, as described above, when an electrode stack including a free edge positive electrode is wound, damage to the separator and an internal short circuit problem occurring at the winding center may more easily occur due to a thickness difference.

[0080] Therefore, in the free edge positive electrode, the need for introducing the ceramic-containing film member according to the present invention may increase, and the effect produced by applying the ceramic-containing film member may be further maximized.

[0081] The negative electrode active material layer may include: a negative electrode active material including a carbonaceous material such as natural graphite and artificial graphite, a metal or an alloy including a metal, an oxide of a metal, a composite of a metal and carbon, etc., and may also include a conductive material and / or a binder when necessary. Various materials commonly used in the manufacture of secondary batteries may be used for the negative electrode active material, the conductive material, and the binder, but are not limited thereto.

[0082] As separators 1a and 1b included in the electrode stack, a polyolefin-based porous polymer film as a typical porous polymer film used as a separator according to the related art can be used alone or in a stack, and the polyolefin-based porous polymer film is such as an ethylene homopolymer, a propylene homopolymer, a copolymer of ethylene and butene, a copolymer of ethylene and hexene, and a copolymer of ethylene and methacrylate. In addition, a polyolefin-based porous polymer film coated with inorganic particles (e.g., Al2O3) or a typical porous non-woven fabric, such as a non-woven fabric made of glass fibers, polyethylene terephthalate fibers, etc. each having a high melting point, can be used. However, the present invention is not limited thereto.

[0083] like Figure 1 As illustrated in , the electrode assembly according to the embodiment of the present invention may be provided by winding the electrode stack in the direction R, and the portion C may be the winding center after the winding. The electrode assembly wound as above may be, for example, a wound type member.

[0084] Figure 2 The winding center of the electrode assembly is illustrated. In the left figure, according to the related art, a film member including ceramic is not provided on the end of the positive electrode 3. In this case, when the negative electrode uncoated portion 21 is deformed due to stress applied to the electrode during charge-discharge, the separator 1a may be damaged, resulting in a risk of short circuit between the positive electrode 3 and the negative electrode uncoated portion 21.

[0085] As shown in the right figure, when the film member 31 containing ceramic is attached to the end of the positive electrode 3, there is an effect that the positive electrode 3 is fixed. Therefore, the stress applied to the electrode during charge-discharge can be endured, and deformation of the negative electrode uncoated portion 21 can be prevented.

[0086] The membrane member including ceramic may be a member into which ceramic is introduced in a stripe shape parallel to the winding direction of the electrode stack. Figure 3 , the membrane member including ceramics can be arranged so that the portion C is located at the center of the winding and the portion E is located at the distal end of the winding. This situation is advantageous in having a force for bearing the stress applied in the winding direction.

[0087] [Cylindrical secondary battery]

[0088] The cylindrical secondary battery according to the present invention includes an electrode assembly, a battery can in which the electrode assembly is housed, and a cap assembly that seals an open end of the battery can. Specifically, the cylindrical secondary battery may be as follows: Figure 8The cylindrical secondary battery 100 in the embodiment of the present invention can be manufactured by accommodating a wound electrode assembly 120 in a battery can 130, injecting an electrolyte into the battery can 130, and then mounting a cap assembly 140 on an open top surface of the battery can 130 to seal the open top surface. Here, the cap assembly 140 is electrically connected to the electrode assembly through an electrode tab (e.g., a positive electrode tab) extending from the electrode assembly 120.

[0089] As described above, the electrode assembly 120 has a structure in which the positive electrode 3 and the negative electrode 2 are wound into a circular shape with the separator 1 interposed therebetween, and the center pin 150 having a circular shape is inserted into the core (the center of the wound form) of the electrode assembly 120. Generally, the center pin 150 is made of a metal material so as to impart a predetermined strength, and has a hollow circular structure in which a sheet material is circularly bent. The center pin 150 is used to fix and support the electrode assembly, and serves as a channel for exhausting gas generated due to internal reactions during charge / discharge and operation.

[0090] Referring to the typical structure of the cover assembly 140 Fig. 9 , the top cover 10 provides a positive terminal having a protruding shape and is perforated with a vent (not shown), and a safety vent 20 is provided in the lower portion of the top cover. A portion of the top surface of the CID filter 30 is connected to the safety vent 20, and a portion of its bottom surface is connected to the electrode of the electrode assembly 120. When gas is generated from the electrode assembly 120 due to, for example, overcharging or high temperature, thereby increasing the internal pressure, the safety vent 20 protrudes upward while its shape is inverted, so that the gas is discharged. Here, when the CID filter 30 also moves upward, the area of ​​the notch portion T can be destroyed to interrupt the flow of current. Therefore, the battery can be prevented from further overcharging and explosion.

[0091] In addition, the cover assembly may include a gasket 32 ​​that provides airtightness and insulation performance between the top cover 10 and the battery can 130. The top cover 10 may be pressed on the curling portion 60 provided in the battery can 130 and fixed by the crimping portion 70. The top cover 10 is a component made of a conductive metal material and covers the upper opening portion of the battery can 130. The top cover 10 is electrically connected to the positive electrode of the electrode assembly 120 and is electrically insulated from the battery can 130 by the gasket 32. Therefore, the top cover 10 can be used as a positive terminal of a cylindrical secondary battery. The top cover 10 may include a protrusion protruding upward from the central portion of the top cover 10, and the protrusion is allowed to contact with an external power source so that current is applied from the external power source.

[0092] The electrolyte may not be limited as long as lithium ions generated by electrochemical reactions in the electrodes at the time of charge-discharge can move in the electrolyte. For example, the electrolyte may be a non-aqueous organic solvent in which a lithium salt is dissolved.

[0093] The lithium salt may be unrestricted as long as it is a compound that can provide lithium ions for lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO2, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. can be used as lithium salts. The lithium salt may have a concentration that varies appropriately within a generally available range, but may be used in a concentration range of 0.1M to 5.0M, preferably in a concentration range of 0.1M to 3.0M.

[0094] The non-aqueous organic solvent is not particularly limited as long as it can be used as a medium in which ions involved in the electrochemical reaction of the battery can move. For example, a cyclic carbonate-based solvent such as ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, a chain carbonate-based organic solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), or a mixed organic solvent thereof can be used.

[0095] The cylindrical secondary battery can be applied to various devices. For example, the cylindrical secondary battery can be applied to the field of electric vehicles such as electric bicycles, electric vehicles, or hybrid electric vehicles (HEV).

[0096] Therefore, according to another embodiment of the present invention, a battery module including a cylindrical type secondary battery as a unit battery and a battery pack including the battery module are provided.

[0097] The battery module or battery pack can be used as a power source for one or more medium-sized to large-sized devices of the following equipment: power tools, electric transportation tools including electric vehicles (EV), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEV), or systems for storing energy.

[0098] Hereinafter, the present invention will be described in more detail using specific embodiments.

[0099] Embodiments of the present invention

[0100] <Example: Production of cylindrical secondary battery>

[0101] Example 1

[0102] The composition is Li[Ni 0.60 Co 0.20 Mn 0.20 ]O2 lithium nickel cobalt manganese-based oxide, carbon black conductive material and PVDF binder are mixed in N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare a positive electrode slurry. The positive electrode slurry is applied on one surface of an aluminum current collector and dried, and then a roll pressing process is performed to manufacture a positive electrode.

[0103] Graphite, SBR-CMC binder and carbon black conductive material were added to water as a solvent at a weight ratio of 95:3.5:1.5 to prepare negative electrode slurry. The negative electrode slurry was applied on a thin copper foil as a negative electrode collector and dried, and then a roll pressing process was performed to manufacture a negative electrode.

[0104] Afterwards, in Figure 1 In the structure in, a ceramic ribbon (3MScotch Filament Tape 8915) in which glass fibers are contained in a polypropylene fabric is attached to the end portion of the positive electrode that becomes the winding center. Here, the area to which the ceramic ribbon 31 is attached is set to cover the entire area corresponding to the negative electrode uncoated portion 21 set at the winding center.

[0105] Then, the polyethylene separator 1b, the positive electrode 3 attached with the ceramic ribbon 31, the polyethylene separator 1a and the negative electrode 2 are stacked in sequence and then wound together in the direction R to manufacture an electrode assembly having a wound shape, each of the polyethylene separator 1b, the positive electrode 3, the polyethylene separator 1a and the negative electrode 2 having a sheet shape.

[0106] The manufactured electrode assembly is disposed inside the battery box. Then, the electrolyte is injected into the box, and the upper portion of the box is sealed using a cap assembly to manufacture a cylindrical secondary battery. The electrolyte is prepared by dissolving LiPF6 with a concentration of 1M in a mixed organic solvent in which ethylene carbonate and ethyl methyl carbonate are mixed in a volume ratio of 3:7.

[0107] Comparative Example 1

[0108] A cylindrical type secondary battery was manufactured through the same procedure as Example 1, except that the ceramic ribbon in Example 1 was not attached to the end of the positive electrode.

[0109] <Experimental Example: Performance Evaluation of Cylindrical Secondary Batteries>

[0110] The cylindrical type secondary batteries manufactured according to the example and the comparative example were subjected to constant current charging at a current of 0.3 C at 25° C. until each of the cylindrical type secondary batteries reached 4.2V. Figure 5Results obtained by measuring the voltage change over time of a battery for full charge during a rest period of about 50 hours are shown.

[0111] pass Figure 5 From the results in FIG. 1 , it can be confirmed that the case where the ceramic ribbon is attached to the end of the positive electrode according to the embodiment of the present invention exhibits a high voltage holding ratio compared to the case where the ceramic ribbon is not attached to the end of the positive electrode. In summary, Comparative Example 1 exhibits separator damage, while Example 1 having a membrane member containing ceramics is expected to have prevented such damage.

Claims

1. An electrode assembly for a secondary battery, the electrode assembly having a shape in which an electrode stack is wound, the electrode stack comprising: a positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector; a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; and a separator, the separator being interposed between the positive electrode and the negative electrode, wherein one of the two ends of the negative electrode in the longitudinal direction facing the winding center is a negative electrode uncoated portion on which the negative electrode active material layer is not provided, and An end portion facing the winding center among both end portions in the longitudinal direction of the positive electrode is provided with a film member containing ceramic.

2. The electrode assembly according to claim 1, wherein: The ceramic-containing membrane member is disposed on an area matching or larger than an area of ​​the negative electrode uncoated portion, wherein the separator is located between the ceramic-containing membrane member and the negative electrode uncoated portion.

3. The electrode assembly according to claim 1, wherein: The film member including ceramic is provided on each of both surfaces of the positive electrode.

4. The electrode assembly according to claim 1, wherein: In the end facing the winding center among both end portions in the longitudinal direction of the positive electrode, the end portion of the positive electrode active material layer matches with the end portion of the positive electrode current collector.

5. The electrode assembly according to claim 1, wherein: The membrane member including ceramic has a tensile strength of 200 N / cm to 400 N / cm.

6. The electrode assembly according to claim 1, wherein: The ceramic-containing film member is a film of a polymer having a melting point of 130° C. or higher to which ceramic is added.

7. The electrode assembly according to claim 6, wherein: Of the two surfaces of the ceramic-containing membrane member, a surface area in which the ceramic is exposed, which is in contact with the separator, is 5% or more of the entire surface area of ​​the ceramic-containing membrane member.

8. The electrode assembly according to claim 6, wherein: The polymer includes one or more selected from the group consisting of polyimide, polypropylene, polyethylene terephthalate, polystyrene, polycarbonate, and polysulfone.

9. The electrode assembly according to claim 6, wherein: The ceramic includes one or more selected from glass fiber, tungsten carbide, Al2O3, Cr2O3, SiO2, MnO, ZnO, SnO, PbO, TiO2, B4C, TiC, SiC, AlN, Si3N4, MgB2, TiB2, TiAl, NiTi and Al2Si2O5(OH)4.

10. The electrode assembly according to claim 1, wherein: Ceramic is introduced into the ceramic-containing membrane member in a stripe shape parallel to the winding direction of the electrode stack.

11. A cylindrical secondary battery, comprising: The electrode assembly for a secondary battery according to claim 1; a battery can in which the electrode assembly is accommodated; as well as A cap assembly is configured to seal the open end of the battery can.

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