Electrode for electrochemical element and electrochemical element including the same

Abstract

To provide an electrode for an electrochemical element, which improves safety, and the electrochemical element having the same.SOLUTION: An electrode for an electrochemical element according to the present invention includes a conductive polymer layer which is positioned on at least one surface of an electrode current collector, and an electrode active material layer which is positioned on the top surface of the conductive polymer layer and which contains an electrode active material and a binder polymer. The conductive polymer layer contains a polythiophene-based polymer represented by chemical formula 1 in the description of the invention.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims priority based on Patent Application No. 2021-0120653 filed on September 9, 2021, and Patent Application No. 2022-0110984 filed on September 1, 2022, with the Korean Intellectual Property Office, and all contents disclosed in the specifications of those applications are incorporated herein by reference.

[0002] The present invention relates to an electrode for an electrochemical device and an electrochemical device including the same, and more particularly to an electrode for an electrochemical device with improved safety and an electrochemical device including the same. [Background technology]

[0003] Recently, interest in energy storage technology has been increasing. As the range of applications expands to include energy storage in mobile phones, camcorders, laptops, and even electric vehicles, research and development efforts into electrochemical devices are becoming more and more focused.

[0004] Such electrochemical elements are broadly divided into a positive electrode, a negative electrode, a separator, and an electrolyte. However, such electrochemical elements can ignite or explode due to overcharging, exposure to high temperatures, external impact, etc. If the electrochemical element is overcharged or exposed to high temperatures, the internal temperature of the battery rises and the separator contracts, or if the internal structure of the electrochemical element is destroyed by external impact, a short circuit occurs between the positive and negative electrodes, resulting in thermal runaway.

[0005] When a short circuit occurs, the movement of lithium ions and other electrons is concentrated at the point where the positive and negative electrodes come into direct contact, accelerating heat generation inside the battery, which is known to increase the risk of volume expansion and fire due to gas generation.

[0006] Therefore, there is a great need for a technology that can reduce the risk of battery fire due to a short circuit phenomenon. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide an electrode for an electrochemical device with improved safety, and an electrochemical device including the electrode. [Means for solving the problem]

[0008] In order to solve the above problems, according to one aspect of the present invention, there is provided an electrode for an electrochemical device according to the following embodiment.

[0009] The electrode for an electrochemical element according to the first embodiment is Electrode current collector; a conductive polymer layer disposed on at least one surface of the electrode current collector; and an electrode active material layer located on the conductive polymer layer and including an electrode active material and a binder polymer; The conductive polymer layer includes a poly(thiophene)-based polymer represented by the following Chemical Formula 1:

[0010] [Chemical formula 1] [ka]

[0011] In the above chemical formula 1, wherein R1, R2, R3, and R4 each independently represent hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and at least one of the total number of carbon atoms of R1 and R2 and the total number of carbon atoms of R3 and R4 is 3 or more; The m and n are each independently an integer of 0 to 20,000, and m+n>0.

[0012] The second embodiment is the same as the first embodiment, The adhesive strength between the conductive polymer layer and the electrode current collector may be 200 gf / 20 mm or more.

[0013] The third embodiment is the same as the first or second embodiment. The interface resistance between the conductive polymer layer and the electrode active material layer is 3.0 ohm cm 2 It may be the following:

[0014] The fourth embodiment is any one of the first to third embodiments, At least one of the total number of carbon atoms in R1 and R2 and the total number of carbon atoms in R3 and R4 may be 5 or more.

[0015] The fifth embodiment is any one of the first to fourth embodiments, The m or n may be 0.

[0016] The sixth embodiment is any one of the first to fifth embodiments, The conductive polymer layer may have a thickness of 0.1 μm to 8 μm.

[0017] The seventh embodiment is any one of the first to sixth embodiments, The conductive polymer layer may further include a polyaniline-based polymer; a polypyrrole-based polymer; a polyphenylene-based polymer; a polyacetylene-based polymer; a derivative thereof; or two or more of these.

[0018] The eighth embodiment is any one of the first to seventh embodiments, The electrode for an electrochemical device may be a positive electrode.

[0019] In order to solve the above problems, according to one aspect of the present invention, an electrochemical device according to the following embodiment is provided: The electrochemical device according to the ninth embodiment comprises: The battery includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The positive electrode or negative electrode may include an electrode for an electrochemical device according to any one of the first to eighth embodiments. [Effects of the Invention]

[0020] In an electrode for an electrochemical device according to an embodiment of the present invention, a conductive polymer layer is disposed between an electrode current collector and an electrode active material layer, so that the conductive polymer layer does not interfere with the conductive path between the electrode current collector and the electrode active material layer during normal operation of the battery, and can prevent direct contact between the electrode current collectors when a short circuit occurs.

[0021] In the electrode for an electrochemical device according to one embodiment of the present invention, the conductive polymer layer located between the electrode current collector and the electrode active material layer serves as a resistance layer, thereby increasing short-circuit resistance and blocking the flow of a sudden short-circuit current, thereby ensuring safety.

[0022] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited only to the matters depicted in such drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram schematically illustrating an electrode for an electrochemical device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts that correspond to the technical ideas of the present invention, based on the principle that the inventor can appropriately define the concepts of terms in order to best describe his / her invention.

[0025] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

[0026] The electrode for an electrochemical device according to one embodiment of the present invention comprises: Electrode current collector; a conductive polymer layer disposed on at least one surface of the electrode current collector; and an electrode active material layer located on the conductive polymer layer and including an electrode active material and a binder polymer; The conductive polymer layer includes a poly(thiophene)-based polymer represented by the following Chemical Formula 1:

[0027] [Chemical formula 1] [ka]

[0028] In the above Chemical Formula 1, R1, R2, R3, and R4 are each independently hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and at least one of the total number of carbon atoms of R1 and R2 and the total number of carbon atoms of R3 and R4 is 3 or more, and m and n are each independently an integer of 0 to 20,000, and m+n>0.

[0029] In Formula 1, when m and n are each an integer of 1 or greater, the monomer represented by the repeating unit m and the monomer represented by the repeating unit n have different structures.

[0030] In one embodiment of the present invention, when m and n in Formula 1 are each an integer of 1 or greater, the polythiophene-based polymer represented by Formula 1 may be, but is not limited to, an alternating polymer, a random copolymer, or a block polymer of a monomer represented by repeating unit m and a monomer represented by repeating unit n.

[0031] FIG. 1 is a diagram schematically illustrating an electrode for an electrochemical device according to one embodiment of the present invention.

[0032] Referring to FIG. 1, an electrode 1 for an electrochemical device according to one embodiment of the present invention includes an electrode current collector 10.

[0033] The electrode current collector 10 may be made of any material that is conductive and does not cause chemical changes in the electrochemical device. For example, in one embodiment of the present invention, the electrode current collector 10 may be made of copper; stainless steel; aluminum; nickel; titanium; calcined carbon; copper, aluminum, or stainless steel surface-treated with carbon, nickel, titanium, silver, chromium, or the like; or an aluminum-cadmium alloy. The current collector may also have fine irregularities on its surface to enhance the adhesive strength of the active material, and may be in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0034] In one embodiment of the present invention, when the electrode 1 for an electrochemical device is a positive electrode, the electrode current collector 10 can be made of stainless steel; aluminum; nickel; titanium; calcined carbon; or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, chromium, or the like.

[0035] In another embodiment of the present invention, when the electrode 1 for an electrochemical device is a negative electrode, the electrode current collector 10 can be made of copper; stainless steel; nickel; titanium; calcined carbon; copper or stainless steel surface-treated with carbon, nickel, titanium, silver, chromium, or the like; an aluminum-cadmium alloy, or the like.

[0036] In one embodiment of the present invention, the thickness of the electrode current collector 10 may be 3 to 500 μm, for example, 10 μm to 50 μm or 10 μm to 20 μm, but is not particularly limited thereto.

[0037] Referring to FIG. 1, an electrode 1 for an electrochemical device according to an embodiment of the present invention includes a conductive polymer layer 20 on at least one surface of the electrode current collector 10 .

[0038] If the electrochemical device is overcharged or exposed to high temperatures, causing the internal temperature of the electrochemical device to rise, the separator may shrink, causing a short circuit between the positive and negative electrodes. Alternatively, an external impact may destroy the internal structure of the electrochemical device, causing a short circuit between the positive and negative electrodes.

[0039] Such short circuits include soft short circuits caused by contact between the positive and negative active materials, and hard short circuits caused by direct contact between the positive and negative current collectors, or between the positive and negative active materials, or between the negative and positive active materials. In the case of hard short circuits, the short circuit resistance is low, which generates more heat and poses a serious threat to the safety of the battery.

[0040] The conductive polymer layer 20 is formed on at least one surface of the electrode current collector 10 and serves as a protective film for the electrode current collector 10 in the event of a short circuit. The conductive polymer layer 20 is formed on at least one surface of the electrode current collector 10 to prevent the electrode current collector 10 from coming into direct contact with the opposing electrode current collector or the opposing electrode active material, thereby preventing a hard short circuit from occurring.

[0041] In order for the conductive polymer layer 20 to function as a protective film for the electrode current collector 10, the conductive polymer layer 20 must be strongly bonded to the electrode current collector 10 so that the conductive polymer layer 20 does not peel off from the electrode current collector 10 even when a short circuit occurs. If the conductive polymer layer 20 easily peels off from the electrode current collector 10, it will not be able to function as a protective film for the electrode current collector 10 when a short circuit occurs.

[0042] In one embodiment of the present invention, the adhesive strength between the conductive polymer layer 20 and the electrode current collector 10 may be 200 gf / 20 mm or more, specifically 210 gf / 20 mm or more. The upper limit of the adhesive strength between the conductive polymer layer and the electrode current collector is not particularly limited, but may be, for example, 400 gf / 20 mm or less, or 350 gf / 20 mm or less. When the adhesive strength between the conductive polymer layer 20 and the electrode current collector 10 satisfies the above range, in the event of a short circuit, the conductive polymer layer 20 is likely to be strongly bonded to the electrode current collector 10 without detaching from the electrode current collector 10, and the conductive polymer layer 20 is likely to function as a protective film for the electrode current collector 10.

[0043] The adhesive strength between the conductive polymer layer 20 and the electrode current collector 10 can be confirmed by attaching and fixing the electrode current collector 10 on which the conductive polymer layer 20 is formed to a glass plate using double-sided tape, and then peeling the electrode current collector 10 at an angle of 90° at a rate of 20 mm / min at 25°C, and measuring the strength.

[0044] In addition, the conductive polymer layer 20 is positioned between the electrode current collector 10 and the electrode active material layer described below, and increases the interfacial resistance between the electrode current collector 10 and the electrode active material layer compared to when the electrode current collector 10 and the electrode active material layer are in direct contact with each other, thereby preventing the electrochemical device from catching fire due to such interfacial resistance even if a short circuit occurs.

[0045] In one embodiment of the present invention, the interface resistance between the conductive polymer layer 20 and the electrode active material layer may be increased by 0.1 to 1000%, or 1 to 500%, compared to the interface resistance when the conventional electrode current collector and the electrode active material layer are in direct contact with each other.

[0046] In one embodiment of the present invention, the interface resistance between the conductive polymer layer 20 and the electrode active material layer is 3.0 ohm cm. 2 or less, or 2.5 ohm cm 2 or less, or 0.01 ohm cm 2 ~2.5ohm·cm 2 When the interfacial resistance between the conductive polymer layer 20 and the electrode active material layer satisfies the above range, it is possible to easily prevent the electrochemical device from catching fire when a short circuit occurs while maintaining cycle characteristics. For example, it is possible to easily prevent the electrochemical device from catching fire when a short circuit occurs while preventing the cycle efficiency from falling below 80%.

[0047] The interface resistance between the conductive polymer layer 20 and the electrode active material layer can be measured using a multi-probe tester.

[0048] In addition, the conductive polymer layer 20 includes a polymer that interacts with the salt present in the electrolyte to become conductive, thereby connecting a conductive network between the electrode current collector 10 and the electrode active material layer (described later). As a result, when the battery operates normally, the performance of the electrode can be maintained even if the conductive polymer layer 20 is present between the electrode current collector 10 and the electrode active material layer.

[0049] In one embodiment of the present invention, in Chemical Formula 1, which represents the polythiophene-based polymer contained in the conductive polymer layer, at least one of the total number of carbon atoms of R1 and R2 and the total number of carbon atoms of R3 and R4 may be 5 or more, for example, 6 to 20, 7 to 20, 8 to 20, 8 to 15, or 8 to 10. When at least one of the total number of carbon atoms of R1 and R2 and the total number of carbon atoms of R3 and R4 is within the above range, it may be advantageous in that excellent adhesion between the conductive polymer layer and the electrode current collector is maintained while the life of the battery using the conductive polymer layer may be further improved, but the present invention is not limited thereto.

[0050] In one embodiment of the present invention, in Formula 1, which represents the polythiophene-based polymer contained in the conductive polymer layer, m or n may be 0. When m or n is 0, excellent adhesion between the conductive polymer layer and the electrode current collector can be maintained, and advantageous effects can be obtained in terms of further improving the lifespan of a battery using the conductive polymer layer, but the present invention is not limited thereto.

[0051] In one embodiment of the present invention, the weight-average molecular weight (Mw) of the conductive polymer may be, for example, 10,000 g / mol to 100,000 g / mol. Specifically, the weight-average molecular weight (Mw) of the conductive polymer may be 10,000 g / mol to 80,000 g / mol or 30,000 g / mol to 60,000 g / mol. When the weight-average molecular weight of the conductive polymer is within the above range, advantageous effects can be obtained in terms of adhesion strength and interfacial resistance between the conductive polymer layer and the electrode active material layer, but the present invention is not limited thereto.

[0052] In this specification, the weight-average molecular weight of the conductive polymer may be a value measured using gel permeation chromatography. Specifically, the weight-average molecular weight may be a value measured using PL GPC220 (Agilent Technologies) under the following conditions:

[0053] -Column: PL Olexis (Polymer Laboratories) -Solvent: TCB (Trichlorobenzene) -Flow rate: 1.0ml / min -Sample concentration: 1.0mg / ml -Injection volume: 200μl -Column temperature: 160℃ -Detector: Agilent High Temperature RI detector -Standard: Polystyrene (corrected by a cubic function)

[0054] In one embodiment of the present invention, the thickness of the conductive polymer layer may be, for example, 0.1 μm to 15 μm, specifically 0.1 μm to 10 μm, 0.1 μm to 8 μm, 0.5 μm to 10 μm, 0.5 μm to 8 μm, 0.5 μm to 5 μm, 1 μm to 5 μm, or 1 μm to 3 μm. When the thickness of the conductive polymer layer is within the above range, it can be advantageously effective in improving the interfacial resistance between the conductive polymer layer and the electrode current collector, thereby improving the lifespan characteristics of the battery, but the present invention is not limited thereto.

[0055] In this specification, the "thickness" of the conductive polymer layer may refer to a value measured by a known method for measuring thickness, including, but not limited to, a thickness measurement method using a thickness meter (Mitutoyo, VL-50S-B).

[0056] In one embodiment of the present invention, the conductive polymer layer 20 may further include, in addition to the polythiophene-based polymer, a polyaniline-based polymer; a polypyrrole-based polymer; a polyphenylene-based polymer; a polyacetylene-based polymer; derivatives thereof; or two or more of these.

[0057] The polyaniline-based polymer is not particularly limited as long as it contains aniline repeating units, and may include, for example, a homopolymer composed of only aniline repeating units, or a copolymer of aniline monomers with other monomers.

[0058] The polypyrrole-based polymer is not particularly limited as long as it contains a pyrrole repeating unit, and may include, for example, a homopolymer composed of only pyrrole repeating units, or a copolymer of a pyrrole monomer and another monomer.

[0059] The polypyrrole-based polymer may include the structure of Formula 2 or 3 below: [Chemical formula 2] [ka]

[0060] In the above chemical formula 2, R1 and R2 each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, The m is 1 to 20,000.

[0061] [Chemical formula 3] [ka]

[0062] In the above chemical formula 3, The X is [ka] and wherein Q is oxygen or sulfur; wherein R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms; The p is a natural number equal to or greater than 1, The n is 1 to 20,000.

[0063] Throughout this specification, "substituted" can refer to substitution with alkyl groups such as methyl, ethyl, isopropyl, and butyl; alkoxy groups such as methoxy and ethoxy; allene groups; alcohol groups; carboxylic acid groups, and the like.

[0064] The polyphenylene polymer is not particularly limited as long as it contains a phenylene repeat unit, and may include, for example, a homopolymer composed of only phenylene repeat units, or a copolymer of a phenylene monomer and another monomer.

[0065] The polyphenylene-based polymer may include one or more of the following structures: [ka]

[0066] R1, R2, R3, and R4 each independently represent one of hydrogen or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms; The above n is 1 to 20,000.

[0067] The polyacetylene polymer is a repeating unit in which one carbon atom and one hydrogen atom have a polyene structure, for example, (CH) x There are no significant limitations as long as the repeating unit has a polyene structure, and the polymer may include, for example, a homopolymer composed only of repeating units having a polyene structure, or a copolymer of a polyene monomer and another monomer.

[0068] The polyacetylene-based polymer may have the structure of Formula 4: [Chemical formula 4] [ka]

[0069] In the above chemical formula 4, n is 1 to 20,000.

[0070] In one embodiment of the present invention, the conductive polymer layer 20 may be formed by coating a conductive polymer solution on the electrode current collector 10 and then drying it.

[0071] 1, an electrode 1 for an electrochemical device according to an embodiment of the present invention includes an electrode active material layer 30 on the conductive polymer layer 20. The electrode active material layer 30 includes an electrode active material and a binder polymer.

[0072] In one embodiment of the present invention, the electrode active material layer may further include a conductive material in addition to the electrode active material and the binder polymer.

[0073] In one embodiment of the present invention, when the electrode 1 for an electrochemical device is a positive electrode, the electrode active material (i.e., positive electrode active material) may include, but is not limited to, lithium transition metal oxide; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; an oxide in which a portion of lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more of these. Specifically, the positive electrode active material may include, for example, layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3) 2-x M xLithium manganese composite oxides represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 - 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); Lithium metal phosphate LiMPO4 (where M = Fe, CO, Ni, or Mn); Lithium nickel - manganese - cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-x O2 (x = 0 - 0.03, a = 0.3 - 0.95, b = 0.01 - 0.35, c = 0.01 - 0.5, a + b + c = 1); Oxides in which part of the lithium nickel - manganese - cobalt oxide is substituted with aluminum Li a [Ni b Co c Mn d Al e 1-f M1 f O2 (M1 is one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S; 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.99, 0 < c < 0.5, 0 < d < 0.5, 0.01 ≤ e ≤ 0.1, 0 ≤ f ≤ 0.1); Oxides in which part of the lithium nickel - manganese - cobalt oxide is substituted with other transition metals Li 1+x (Ni a Co b Mn c M d ) 1-x O2 (x = 0 - 0.03, a = 0.3 - 0.95, b = 0.01 - 0.35, c = 0.01 - 0.5, d = 0.001 - 0.03, a + b + c + d = 1, M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg and Mo), disulfide compounds; Examples include Fe2(MoO4)3, but are not limited thereto.

[0074] In another embodiment of the present invention, when the electrode 1 for an electrochemical device is a negative electrode, the electrode active material (i.e., negative electrode active material) may typically include a carbon material that absorbs and releases lithium ions, lithium metal, a silicon-based material, or tin. Examples of the carbon material include natural graphite, artificial graphite, low-crystalline carbon, and high-crystalline carbon. Examples of low-crystalline carbon include soft carbon and hard carbon, while examples of high-crystalline carbon include natural graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-calcined carbon such as petroleum or coal tar pitch-derived cokes. Examples of the silicon-based material include silicon dioxide.

[0075] The binder polymer may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, acrylonitrile-butadiene rubber, styrene-butadiene rubber, acrylic rubber, or two or more thereof.

[0076] The conductive material is not particularly limited as long as it is conductive without inducing a chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives; and conductive materials such as graphene.

[0077] In one embodiment of the present invention, the weight ratio of the electrode active material to the binder polymer may be 90:10 to 98:2, 95:5 to 98:2, or 97:3 to 98:2.

[0078] In another embodiment of the present invention, when the electrode active material layer further includes a conductive material, the weight ratio of the electrode active material, the conductive material, and the binder polymer may be 90:5:5 to 98:1:1, or 95:2:3 to 98:1:1, or 97:1:2 to 98:1:1.

[0079] The electrode active material layer 30 may be prepared by coating a slurry for forming the electrode active material layer, which is a mixture of an electrode active material, a binder polymer, and optionally a conductive material, with a dispersion medium, on the upper surface of the conductive polymer layer 20, drying the slurry, and then rolling the coated slurry.

[0080] In an electrode for an electrochemical device according to an embodiment of the present invention, a conductive polymer layer is present on at least one surface of an electrode current collector, and in the event of a short circuit, direct short circuit between electrode current collectors can be prevented.

[0081] The potential of the positive electrode for an electrochemical device is similar to the potential at which the conductive polymer layer 20 interacts with the salt present in the electrolyte, so it is advantageous to apply the conductive polymer layer 20 to the positive electrode. When the electrode for an electrochemical device is the positive electrode, it is possible to protect the positive electrode from a hard short circuit, which is more advantageous in ensuring the safety of the electrochemical device.

[0082] In particular, the electrode for an electrochemical device according to one embodiment of the present invention has a conductive polymer layer on at least one surface of the electrode current collector, which can surround the electrode current collector, compared to when the electrode active material layer includes a conductive polymer together with the electrode active material layer, and is therefore more effective in improving the safety of the electrode when a short circuit occurs.

[0083] The electrode for an electrochemical device according to an embodiment of the present invention can be fabricated into an electrochemical device together with a separator.

[0084] The electrochemical device according to an embodiment of the present invention may have improved safety by including an electrode for an electrochemical device according to an embodiment of the present invention.

[0085] The electrochemical device includes all devices that perform electrochemical reactions, and specific examples thereof include all types of primary and secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors.

[0086] In one embodiment of the present invention, the electrochemical device may be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0087] The separator is not particularly limited and may be composed of only a porous polymer substrate, or may comprise a porous polymer substrate and an organic-inorganic composite porous layer formed on at least one surface of the porous polymer substrate and including a plurality of inorganic particles and a binder polymer. The separator is interposed between the positive electrode and the negative electrode to provide insulation between the positive electrode and the negative electrode.

[0088] The porous polymer substrate may be any porous polymer substrate commonly used in the art, including, but not limited to, a polyolefin-based porous polymer membrane or nonwoven fabric.

[0089] The polyolefin-based porous polymer membrane may be a polyolefin-based polymer such as polyethylene (e.g., high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene), polypropylene, polybutylene, or polypentene, or a membrane formed from two or more of these.

[0090] In addition to polyolefin-based nonwoven fabrics, examples of the nonwoven fabric include polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, and nonwoven fabrics made from two or more of these. The nonwoven fabric may have a spunbonded or meltblown structure made of long fibers.

[0091] The thickness of the porous polymer substrate is not particularly limited, but may be 3 μm to 50 μm, or 3 μm to 15 μm. The size and porosity of the pores present in the porous polymer substrate are also not particularly limited, but may be 0.01 μm to 50 μm and 10% to 95%, respectively.

[0092] In one embodiment of the present invention, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are those that can be used in the range of the operating voltage of the applied battery (e.g., Li / Li + There are no particular limitations on the inorganic particles as long as they do not undergo oxidation and / or reduction reactions at a voltage of 0 to 5 V relative to the reference voltage. The inorganic particles may include high-dielectric-constant inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion transfer ability, or two or more of these. Inorganic particles having a dielectric constant of 5 or more include BaTiO3, BaSO4, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT, where 0 <x<1、0<y<1である)、Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, Y2O3, SiO2, Al2O3, γ-AlOOH, Al(OH)3, SiC, TiO2, or a mixture of two or more of these can be used, but are not limited to these.

[0093] In one embodiment of the present invention, the size of the inorganic particles is not limited, but may have an average particle size in the range of 0.01 to 10 μm or 0.05 to 1.0 μm to form an organic-inorganic composite porous layer of uniform thickness and to achieve an appropriate porosity. The average particle size of the inorganic particles refers to the particle size at 50% of the smallest particle size (D50), calculated based on the particle size distribution of classified particles measured using a conventional particle size distribution analyzer. This particle size distribution can be measured using laser diffraction analysis.

[0094] In one embodiment of the present invention, the binder polymer contained in the separator is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate. The polymer may include, but is not limited to, cellulose acetate, cyanoethyl propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more thereof.

[0095] In one embodiment of the present invention, the ratio of inorganic particles to binder polymer contained in the separator may be 20:80 to 99.9:0.1, 50:50 to 99.5:0.5, or 70:30 to 80:20. When the ratio of inorganic particles to binder polymer is within the above range, sufficient adhesive strength between the inorganic particles can be ensured while sufficient void space can be formed between the inorganic particles.

[0096] In one embodiment of the present invention, the organic-inorganic composite porous layer may have a structure in which the inorganic particles are filled and contacted with each other and bound by the binder polymer, thereby forming interstitial volumes between the inorganic particles, and the interstitial volumes between the inorganic particles may become empty spaces to form pores.

[0097] In one embodiment of the present invention, the electrochemical device includes an electrolyte solution, which may include an organic solvent and a lithium salt. The electrolyte solution may be an organic solid electrolyte or an inorganic solid electrolyte.

[0098] Examples of the organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0099] The lithium salt is a substance that is easily soluble in the organic solvent, such as LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylates, lithium 4-phenylborate, imides, etc. can be used.

[0100] In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., the electrolyte solution may contain, for example, pyridine, triethyl phosphate, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, a halogen-containing solvent such as carbon tetrachloride or trifluoroethylene may be further added to impart non-flammability, and carbon dioxide may be further added to improve high-temperature storage properties.

[0101] Examples of the organic solid electrolyte that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociative groups.

[0102] Examples of the inorganic solid electrolyte that can be used include nitrides, halides, and sulfates of Li, such as LiN, LiI, LiNI, LiN-LiI-LiOH, LiSiO, LiSiO-LiI-LiOH, LiSiS, LiSiO, LiSiO-LiI-LiOH, and LiPO-LiS-SiS.

[0103] The electrolyte injection can be performed at an appropriate stage in the manufacturing process of the electrochemical device depending on the manufacturing process and required properties of the final product, i.e., before assembling the electrochemical device or at the final stage of assembling the electrochemical device.

[0104] In addition to the general winding process, the separator can be applied to an electrochemical device by laminating or folding the separator and electrodes.

[0105] The separator may be interposed between the positive and negative electrodes of an electrochemical device, or may be interposed between adjacent cells or electrodes when a plurality of cells or electrodes are assembled to form an electrode assembly. The electrode assembly may have various structures such as a simple stack type, a jelly-roll type, a stack-folding type, and a lamination-stack type.

[0106] The shape of the electrochemical device is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0107] The present invention will be described in detail below with reference to examples to aid in understanding the present invention. However, the examples according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art. [Example]

[0108] Example 1 Conductive polymer synthesis and conductive polymer solution preparation The conductive polymer was synthesized according to the following reaction scheme 1.

[0109] [Reaction Scheme 1] [ka]

[0110] Specifically, 1 g (5.093 mmol, 1 eq) of 3-octylthiophene (compound 1) was added as a monomer to a solution of 2.48 g (15.3 mmol, 3 eq) of iron(III) chloride dissolved in 70 ml of chloroform and stirred at room temperature for 24 hours. The mixed solution was placed in a permeation membrane with a molecular weight cut-off (MWCO) of 5000 and then immersed in 200 ml of acetonitrile to selectively remove unreacted iron(III) chloride and remaining reactants. The residue deposited inside the permeation membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer with a weight-average molecular weight of 50,000 g / mol and a structure similar to compound 2 as a conductive polymer.

[0111] The conductive polymer was dissolved in chloroform to prepare a 1 wt % conductive polymer solution, which was then filtered using a poly(tetrafluoroethylene) (PTFE) filter having 1 μm pores.

[0112] electrode manufacturing The conductive polymer solution was coated on one side of an aluminum current collector and electrode tab with a thickness of 20 μm and dried to form a conductive polymer layer with a thickness of 1 μm on one side of the electrode current collector. The total thickness of the current collector coated with the conductive polymer was 21 μm.

[0113] LiCoO, carbon black, and poly(vinylidene fluoride) were added to an N-methyl-2-pyrrolidone (NMP) solution in a weight ratio of 97.5:1:1.5 and mixed to prepare a slurry for forming an electrode active material layer. The solid content of the slurry for forming an electrode active material layer was 60 wt%.

[0114] The electrode active material layer forming slurry was coated on the electrode current collector on which the conductive polymer layer was formed, dried, and then roll pressed to prepare an electrode having a total thickness of 50 μm.

[0115] Example 2 An electrode was manufactured in the same manner as in Example 1, except that the conductive polymer solution was coated on one surface of the current collector so that the thickness of the conductive polymer layer formed on the surface was 10 μm.

[0116] Example 3 An electrode was manufactured in the same manner as in Example 1, except that the conductive polymer synthesized according to the following [Reaction Scheme 2] was used.

[0117] [Reaction Scheme 2] [ka]

[0118] Specifically, 6.09 g (37.6 mmol) of iron(III) chloride was dissolved in 200 ml of methylene chloride, to which 1.23 g (6.26 mmol) of 3-octylthiophene and 1.41 g (6.26 mmol) of 3-decylthiophene were added and stirred at room temperature for 24 hours. The mixed solution was placed in a 5000 MWCO (molecular weight of cut-off) permeation membrane and immersed in 150 ml of acetonitrile to selectively remove unreacted iron(III) chloride and remaining reactants. The residue deposited inside the permeation membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer with a weight-average molecular weight (Mw) of 33,000 g / mol, which has the same structure as compound 4, as a conductive polymer.

[0119] Comparative Example 1 An electrode was prepared in the same manner as in Example 1, except that one surface of the electrode current collector was not coated with a conductive polymer.

[0120] Comparative Example 2 LiCoO, carbon black, poly(vinylidene fluoride), and the conductive polymer obtained in Example 1 were added to an N-methyl-2-pyrrolidone (NMP) solution in a weight ratio of 95.5:1:1.5:2 and mixed to prepare a slurry for forming an electrode active material layer. The solid content of the slurry for forming an electrode active material layer was 60 wt%.

[0121] The slurry for forming an electrode active material layer was coated on an aluminum current collector having a thickness of 20 μm, dried, and then roll-pressed to prepare an electrode having a total thickness of 50 μm.

[0122] Comparative Example 3 An electrode was fabricated in the same manner as in Example 1, except that poly(iso-thianaphthene) was used as the conductive polymer.

[0123] Comparative Example 4 An electrode was manufactured in the same manner as in Example 1, except that the conductive polymer synthesized according to the following [Reaction Scheme 3] was used.

[0124] [Reaction Scheme 3] [ka]

[0125] Specifically, 2.5g (22.3mmol) of 3-ethylthiophene was added to a solution of 10.84g (66.85mmol) of iron(III) chloride dissolved in 200ml of methylene chloride and stirred at room temperature for 24 hours. The mixed solution was placed in a permeation membrane with a molecular weight of cut-off (MWCO) of 5000 and then immersed in 150ml of acetonitrile to selectively remove unreacted iron(III) chloride and remaining reactants. The residue deposited inside the permeation membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer with a weight-average molecular weight (Mw) of 25,000g / mol as a conductive polymer.

[0126] Evaluation example The adhesive strength between the conductive polymer layer and the electrode current collector, the interfacial resistance between the conductive polymer layer and the electrode active material layer, the cycle efficiency, and the safety of the electrodes produced in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated and are shown in Table 1 below.

[0127] (1) Measurement of adhesion between the conductive polymer layer and the electrode current collector The electrode current collector on which the conductive polymer layer was formed was attached and fixed to a glass plate using double-sided tape, and the electrode current collector was peeled off at an angle of 90° at a rate of 20 mm / min at 25°C, and the strength measured when this was done was taken as the adhesive strength between the conductive polymer layer and the electrode current collector.

[0128] (2) Measurement of the interfacial resistance between the conductive polymer layer and the electrode active material layer The interfacial resistance between the conductive polymer layer and the electrode active material layer in the electrodes prepared in Examples 1 to 3 and Comparative Examples 3 and 4 was measured using a multi-probe tester.

[0129] In addition, the interfacial resistance between the electrode current collector and the electrode active material layer of the electrodes prepared in Comparative Examples 1 and 2 was measured using a multi-probe tester.

[0130] (3) Cycle efficiency evaluation Artificial graphite, carbon black, and styrene-butadiene rubber were mixed in a weight ratio of 95:3.5:1.5 to prepare a slurry for forming an anode active material layer. The slurry was then coated on one side of an 8 μm-thick copper thin film, dried, and rolled using a roll press to prepare an anode.

[0131] The electrodes (positive electrodes) and negative electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were pressed at 80° C. between a polyethylene raw film having a thickness of 10 μm.

[0132] An electrochemical device was fabricated by injecting an electrolyte (EC:PC:EP:PP=2:1:2.5:4.5, LiPF61.4M) (ionic conductivity≧6.5 mS / cm) into the fabricated electrode assembly.

[0133] The electrochemical device was subjected to constant current / constant voltage (CC / CV) charging at a 0.7 C rate to 4.48 V, followed by a 0.025 C cut-off charge, and constant current (CC) discharging at a 0.2 C rate to 3.0 V to evaluate the cycle efficiency.

[0134] (4) Safety evaluation Ten electrochemical devices were prepared and placed on a flat plate. An iron rod with a diameter of 15.8 mm was placed on the plate, and a 9.1 kg weight was dropped from a height of 61 cm onto the iron rod. This was used for an impact test, and the electrochemical devices were then checked for ignition.

[0135] [Table 1]

[0136] As can be seen from Table 1 above, in Examples 1 to 3, it was confirmed that excellent safety was achieved by providing the conductive polymer layer.

[0137] In particular, in Examples 1 and 3, the interface resistance between the conductive polymer layer and the electrode active material layer was 3.0 ohm cm 2 It was confirmed that the cycle efficiency was even better than that of Example 2 because of the following.

[0138] In addition, in the case of Example 1, it was confirmed that the adhesive strength between the conductive polymer layer and the electrode current collector was better, and thus the safety was further improved compared to Example 3.

[0139] On the other hand, in the case of Comparative Examples 1 and 2, the conductive polymer layer was not provided, and therefore sufficient safety could not be ensured.

[0140] In particular, in the case of Comparative Examples 3 and 4, although a conductive polymer layer was provided, it was confirmed that sufficient adhesive strength was not secured between the conductive polymer layer and the current collector due to the different types of conductive polymer used. [Explanation of symbols]

[0141] 1: Electrode for electrochemical elements 10: Electrode current collector 20: Conductive polymer layer 30: Electrode active material layer

Claims

1. Electrode current collector; a conductive polymer layer disposed on at least one surface of the electrode current collector; and an electrode active material layer located on the conductive polymer layer and including an electrode active material and a binder polymer; The conductive polymer layer comprises a polythiophene-based polymer represented by the following formula 1: [Chemical formula 1] 【Chemistry 1】 In the above chemical formula 1, The R １ , R ２ , R ３ and R ４ are each independently hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and R １ and R ２ The total number of carbon atoms in R ３ and R ４ at least one of the total carbon numbers is 3 or more, wherein m and n are each independently an integer of 0 to 20,000, and m+n>0; The weight average molecular weight (Mw) of the conductive polymer is 30,000 g / mol to 60,000 g / mol.

2. 2. The electrode for an electrochemical device according to claim 1, wherein the adhesive strength between the conductive polymer layer and the electrode current collector is 200 gf / 20 mm or more.

3. The interface resistance between the conductive polymer layer and the electrode active material layer is 3.0 ohm cm ２ 2. The electrode for an electrochemical element according to claim 1, wherein:

4. The R １ and R ２ The total number of carbon atoms in R ３ and R ４ 2. The electrode for an electrochemical element according to claim 1, wherein at least one of the total carbon numbers of the above is 5 or more.

5. 2. The electrode for an electrochemical element according to claim 1, wherein m or n is 0.

6. 2. The electrode for an electrochemical device according to claim 1, wherein the conductive polymer layer has a thickness of 0.1 μm to 8 μm.

7. 2. The electrode for an electrochemical device according to claim 1, wherein the conductive polymer layer further comprises a polyaniline-based polymer; a polypyrrole-based polymer; a polyphenylene-based polymer; a polyacetylene-based polymer; a derivative thereof; or two or more of these.

8. 2. The electrode for an electrochemical device according to claim 1, wherein the electrode for an electrochemical device is a positive electrode.

9. The battery includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, An electrochemical element, wherein the positive electrode or negative electrode comprises the electrode for an electrochemical element according to any one of claims 1 to 8.

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