Electrode for electrochemical element and electrochemical element including the same

Abstract

The present invention includes a conductive polymer layer disposed on at least one surface of an electrode current collector; and an electrode active material layer disposed on an upper surface of the conductive polymer layer and including an electrode active material and a binder polymer, the conductive polymer layer including a poly(thiophene)-based polymer represented by Chemical Formula 1 in the description of the invention.

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, to the Korean Intellectual Property Office, and all contents disclosed in the specification of said 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 having 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 is expanding to include energy for mobile phones, camcorders, and notebook computers, as well as electric vehicles, research and development efforts into electrochemical devices are becoming more and more concrete.

[0004] Such electrochemical elements are largely divided into a positive electrode, a negative electrode, a separator, and an electrolyte. However, such electrochemical elements can catch fire or explode due to overcharging, exposure to high temperatures, external impact, etc. If the electrochemical element is overcharged or exposed to high temperatures, which causes the internal temperature of the battery to rise and the separator to shrink, or if the internal structure of the electrochemical element is destroyed by external impact, a short circuit occurs where the positive and negative electrodes come into contact, 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 are in 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 having 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 electrochemical devices 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 disposed on an upper surface of 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, 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; R 1 and R 2 The total number of carbon atoms in 3 and R 4 At least one of the total carbon numbers is 3 or more, The above m and n each independently represent 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, R 1 and R 2 The total number of carbon atoms in 3 and R 4 At least one of the total carbon numbers 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 poly(aniline)-based polymer; a poly(pyrrole)-based polymer; a poly(phenylene)-based polymer; a poly(acetylene)-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 the negative electrode may include an electrode for an electrochemical device according to any one of the first to eighth embodiments. Effect 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 collector and an electrode active material layer, so that the conductive path between the electrode collector and the electrode active material layer is not interrupted during normal operation of the battery, and direct contact between the electrode collectors can be prevented when a short circuit occurs.

[0021] In the electrode for electrochemical devices 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 the 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-mentioned content of the invention, serve to further understand the technical concept of the present invention. Therefore, the present invention should not be interpreted as being limited only to the matters depicted in such drawings. [Brief description of the drawings]

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

[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 words used in the present specification and claims should not be interpreted in a limited manner based on their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that corresponds to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term in order to best describe his / her invention.

[0025] Therefore, it should be understood that the embodiment described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of ​​the present invention, and therefore 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 disposed on an upper surface of 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 Formula 1:

[0027] [Chemical formula 1] [ka]

[0028] In the above formula 1, 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; R 1 and R 2 The total number of carbon atoms in 3 and R 4At least one of the total carbon numbers is 3 or more, and the m and n are each independently an integer of 0 to 20,000, and m+n>0.

[0029] In the above Chemical Formula 1, when m and n are each an integer of 1 or more, 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 more, the polythiophene-based polymer represented by Formula 1 may be an alternating polymer, a random copolymer, or a block polymer of a monomer represented by a repeating unit m and a monomer represented by a repeating unit n, but is not limited thereto.

[0031] FIG. 1 is a diagram illustrating a schematic diagram of 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 an embodiment of the present invention includes an electrode current collector 10.

[0033] The electrode current collector 10 may be any material that does not induce chemical changes in the electrochemical device and has electrical conductivity. 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 that has been 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 increase the adhesive strength of the active material, and may be in various forms such as a film, sheet, foil, net, porous body, 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 element is a negative electrode, the electrode current collector 10 can be made of copper; stainless steel; nickel; titanium; calcined carbon; copper or stainless steel whose surface is 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 electrode current collector 10 may have a thickness of 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 and cause a short circuit between the positive and negative electrodes, or the internal structure of the electrochemical device may be destroyed by external impact, causing a short circuit between the positive and negative electrodes.

[0039] There are two types of short circuit: soft short circuit caused by contact between the positive and negative active materials, and hard short circuit caused by direct contact between the positive and negative current collectors, or the positive and negative active materials, or the negative and positive active materials. In the case of a hard short circuit, the short circuit resistance is low and the associated heat generation is increased, posing 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, and can prevent the electrode current collector 10 from directly contacting the opposing electrode current collector or the opposing electrode active material, thereby preventing the occurrence of a hard short circuit.

[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 even if a short circuit occurs, the conductive polymer layer 20 must not peel off from the electrode current collector 10. 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, when a short circuit occurs, the conductive polymer layer 20 is easily strongly bonded to the electrode current collector 10 without being detached from the electrode current collector 10, and the conductive polymer layer 20 is easily able to serve as a protective film for the electrode current collector 10.

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

[0044] In addition, the conductive polymer layer 20 is located between the electrode collector 10 and an electrode active material layer described below, and increases the interfacial resistance between the electrode collector 10 and the electrode active material layer compared to when the electrode collector 10 and the electrode active material layer are in direct contact with each other. This makes it possible to prevent 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 interfacial 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 interfacial resistance in a conventional case where the electrode 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 Less than or equal to 2.5ohm cm 2 Less than or equal to 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-mentioned range, it is easy to prevent the electrochemical device from catching fire when a short circuit occurs while ensuring cycle characteristics. For example, it is easy to 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, and connects a conductive network between the electrode collector 10 and an electrode active material layer (described later). As a result, when the battery is operating normally, the performance of the electrode can be maintained even if the conductive polymer layer 20 is present between the electrode collector 10 and the electrode active material layer.

[0049] In one embodiment of the present invention, in Formula 1, which shows the polythiophene-based polymer contained in the conductive polymer layer, 1 and R 2 The total number of carbon atoms in 3 and R 4 At least one of the total carbon numbers of R may be 5 or more, for example, 6 to 20, 7 to 20, 8 to 20, 8 to 15, or 8 to 10. 1 and R 2 The total number of carbon atoms in 3 and R 4 When at least one of the total carbon numbers is within the above range, the adhesive strength between the conductive polymer layer and the electrode current collector using the same can be maintained excellent, and the life of the battery using the same can be further improved, which is an advantageous effect, but the present invention is not limited thereto.

[0050] In one embodiment of the present invention, in Formula 1 showing the polythiophene-based polymer contained in the conductive polymer layer, m or n may be 0. When m or n is 0, it may be advantageous in that the adhesive strength between the conductive polymer layer and the electrode current collector using the conductive polymer layer can be maintained excellent and the life of the battery using the conductive polymer layer can be further improved, 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 may be obtained in terms of adhesion and interfacial resistance between the conductive polymer layer and the electrode active material layer, but the present invention is not limited thereto.

[0052] In the present specification, the weight average molecular weight of the conductive polymer may be a value measured by gel permeation chromatography. Specifically, the weight average molecular weight may be a value measured by 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°C -Detector: Agilent High Temperature RI detector -Standard: Polystyrene (corrected by a cubic function)

[0054] In one embodiment of the present invention, the conductive polymer layer may have a thickness of, 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 conductive polymer layer has a thickness in the above range, it is possible to improve the interfacial resistance between the conductive polymer layer and the electrode current collector, thereby exhibiting an advantageous effect in terms of improving the life characteristics of the battery, but the present invention is not limited thereto.

[0055] In the present specification, the "thickness" of the conductive polymer layer may refer to a value measured by a known method for measuring thickness. The method for measuring thickness is not limited thereto, and may be, for example, a value measured 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 poly(aniline)-based polymer; a poly(pyrrole)-based polymer; a poly(phenylene)-based polymer; a poly(acetylene)-based polymer; derivatives thereof; or two or more of these.

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

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

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

[0060] In the above chemical formula 2, R 1 , and R 2 each independently represents 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 Q is oxygen or sulfur; R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, The p is a natural number of 1 or more, The n is 1 to 20,000.

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

[0064] The polyphenylene-based polymer is not particularly limited as long as it contains a phenylene repeat unit, for example, it may include a homopolymer composed of only phenylene repeat units, or it may include 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] Above R 1 , R 2 , R 3 , and R 4 each independently represents any 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) xThere are no significant limitations as long as the repeating unit has a polyene structure. For example, the polymer may include 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 following 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 an 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 part of lithium nickel-manganese-cobalt oxide is replaced with another transition metal; or two or more of these. Specifically, the positive electrode active material may be, for example, lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ) and compounds substituted with one or more transition metals;1+x Mn 2-x O 4 (where x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 Lithium manganese oxides such as lithium copper oxide (Li 2 CuO 2 );LiV 3 O 8 , LiV 3 O 4 , V 2 O 5 , Cu 2 V 2 O 7 Vanadium oxides such as LiNi 1-x M x O 2 (wherein M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); 2-x M x O 2 (wherein M=Co, Ni, Fe, Cr, Zn or Ta, and x=0.01 to 0.1) or Li 2 Mn 3 MO 8 Lithium manganese composite oxide represented by the formula (where M=Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO 4 (where M=Fe, CO, Ni, or Mn); lithium nickel-manganese-cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-x O 2 (x=0~0.03, a=0.3~0.95, b=0.01~0.35, c=0.01~0.5, a+b+c=1); Lithium nickel-manganese-cobalt oxide in which a part of the oxide is replaced by aluminum a [Ni b Co c Mn d Al e ] 1-f M1 fO 2 (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, where 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); an oxide 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 O 2 (x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, d = 0.001 to 0.03, a + b + c + d = 1, and M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg, and Mo), a disulfide compound; Fe 2 (MoO 4 ) 3 and the like can be mentioned, but it is not limited to only these.

[0074] In another embodiment of the present invention, when the electrode 1 for the electrochemical element is a negative electrode, the electrode active material (i.e., the negative electrode active material) can usually contain a carbon material in which lithium ions are occluded and released, lithium metal, a silicon - based material, tin, or the like. The carbon material can include natural graphite, artificial graphite, low - crystalline carbon, and high - crystalline carbon. Soft carbon and hard carbon are typical of low - crystalline carbon, and natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch - based carbon fiber, meso - carbon microbeads, mesophase pitches, and high - temperature calcined carbon such as petroleum or coal tar pitch derived cokes are typical of high - crystalline carbon. The silicon - based material can include silicon dioxide and the like.

[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 of these.

[0076] The conductive material is not particularly limited as long as it is conductive without inducing a chemical change in the battery. The conductive material may include, for example, graphite such as natural graphite or 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 and 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 an electrode active material layer, which is a mixture of an electrode active material, a binder polymer, and, if necessary, a conductive material, with a dispersion medium, on the upper surface of the conductive polymer layer 20, drying the slurry, and then rolling the slurry.

[0080] In the 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 collector, and therefore, when a short circuit occurs, a direct short circuit between electrode collectors can be prevented.

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

[0082] In particular, in the electrode for electrochemical devices according to an embodiment of the present invention, a conductive polymer layer is present on at least one surface of the electrode current collector, so that the electrode current collector is surrounded by the conductive polymer layer, compared to a case in which the electrode active material layer includes a conductive polymer together with the electrode active material layer, which is 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 further improve its 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 kinds of primary and secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitor devices.

[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 include 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 number of inorganic particles and a binder polymer. The separator is interposed between the positive electrode and the negative electrode to serve as an insulator between the positive electrode and the negative electrode.

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

[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, polypentene, or a membrane formed from two or more of these.

[0090] Examples of the nonwoven fabric include, in addition to polyolefin-based nonwoven fabrics, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, and nonwoven fabrics formed from two or more of these. The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a meltblown nonwoven fabric 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 within the operating voltage range (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. The inorganic particles having a dielectric constant of 5 or more may be BaTiO 3 , BaSO 4 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT, where 0 <x<1、0<y<1である)、Pb(Mg 1 / 3 Nb 2 / 3 )O 3 -PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CEO 2 , MgO, Mg(OH) 2 , NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , SiO 2 , Al 2 O 3 , γ-AlOOH, Al(OH) 3 , SiC, TiO 2 or a mixture of two or more of these may be used, but is not limited thereto.

[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, in order to form an organic-inorganic composite porous layer with a uniform thickness and to have a suitable porosity. Here, the average particle size of the inorganic particles means a particle size (D50) of 50% of the integrated value from the small particle size side calculated based on the particle size distribution of the particles after classification using a general particle size distribution meter. Such particle size distribution can be measured by 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, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, The polymerizable material may include, but is not limited to, cellulose acetate, cellulose ester, cellulose acylate, cellulose acetate copolymer, cellulose acetate ester ...

[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 force between inorganic particles can be secured while sufficient empty space can be secured between 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 an embodiment of the present invention, the electrochemical device includes an electrolyte solution, and the electrolyte solution 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, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, and ethyl propionate.

[0099] The lithium salt is a substance that is easily dissolved in the organic solvent, and examples of the lithium salt include LiCl, LiBr, LiI, and LiClO. 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , C.H. 3 SO 3 Li, C.F. 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lithium lower aliphatic carboxylates, lithium 4-phenylborate, imides, and the like can be used.

[0100] In addition, for the purpose of improving the charge / discharge characteristics, flame retardancy, etc., the electrolyte 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 ethylene trifluoride may be further added to impart non-flammability, and carbon dioxide may be further added to improve high-temperature storage characteristics.

[0101] As the organic solid electrolyte, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, and the like can be used.

[0102] The inorganic solid electrolyte may be, for example, Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4 -LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 2 S-SiS 2 Nitrides, halides, sulfates, etc. of Li such as Li may be used.

[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 order to apply the separator to an electrochemical device, in addition to a typical winding process, a lamination or stack process of the separator and an electrode and a folding process can be used.

[0105] The separator may be interposed between a positive electrode and a negative electrode of an electrochemical device, or 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, a coin shape, or the like.

[0107] The present invention will be described in detail below with reference to examples for better understanding. 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 having ordinary skill in the art. EXAMPLES

[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, 1g (5.093mmol, 1eq) of 3-octylthiophene (compound 1) was added as a monomer to a solution of 2.48g (15.3mmol, 3eq) of iron(III) chloride dissolved in 70ml of chloroform, and the solution was 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 200ml of acetonitrile solvent to selectively remove unreacted iron(III) chloride and remaining reactants. The residue precipitated 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 50,000g / mol, which has 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 an electrode tap having a thickness of 20 μm and dried to form a conductive polymer layer having 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 2 The 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 then 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 slurry for forming an electrode active material layer was coated on the electrode current collector on which the conductive polymer layer was formed, dried, and then roll pressed to manufacture 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 so that the conductive polymer layer formed on one surface of the current collector had a thickness of 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, 1.23g (6.26mmol) of 3-octylthiophene and 1.41g (6.26mmol) of 3-decylthiophene were added to a solution of 6.09g (37.6mmol) of iron chloride (III) dissolved in 200ml of methylene chloride, and the solution was 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 solvent to selectively remove unreacted iron chloride (III) and remaining reactants. The residue precipitated 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 33,000g / mol, which has a structure similar to 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 2 The 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 then 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 prepared 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 solvent to selectively remove unreacted iron(III) chloride and remaining reactants. The residue precipitated 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 conductive polymer layer and 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 part was peeled off at an angle of 90° at a speed of 20 mm / min at 25°C, and the strength measured 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 in 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 a negative electrode active material layer, which was then coated on one side of a copper thin film having a thickness of 8 μm, dried, and rolled using a roll press to prepare a negative electrode.

[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 roll having a thickness of 10 μm at a temperature of 80° C. to prepare electrode assemblies.

[0132] The electrode assembly was then placed in an electrolyte (EC:PC:EP:PP=2:1:2.5:4.5, LiPF 6 1.4 M) (ionic conductivity ≧6.5 mS / cm) was injected to prepare an electrochemical element.

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

[0134] (4) Safety assessment Ten of each of the 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 then a 9.1 kg weight was dropped from a height of 61 cm onto the iron rod to perform an impact test. Then, the electrochemical devices were checked for ignition.

[0135] [Table 1]

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

[0137] In particular, in the case of 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] Also, in the case of Example 1, it was confirmed that the adhesive strength between the conductive polymer layer and the electrode current collector was more excellent, 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 adhesion 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 disposed on an upper surface of 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 formula 1: An electrode for an electrochemical element, characterized in that the adhesive strength between the conductive polymer layer and the electrode current collector is 200 gf / 20 mm or more. [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; R １ and R ２ and the total number of carbon atoms in R ３ and R ４ At least one of the total carbon numbers is 3 or more, The above m and n each independently represent an integer of 0 to 20,000, and m+n>0.

2. 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:

3. The R １ and R ２ and 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.

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

5. 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.

6. 2. The electrode for an electrochemical device according to claim 1, wherein the conductive polymer layer further comprises a poly(aniline)-based polymer; a poly(pyrrole)-based polymer; a poly(phenylene)-based polymer; a poly(acetylene)-based polymer; a derivative thereof; or two or more of these.

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

8. 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 the negative electrode comprises the electrode for an electrochemical element according to any one of claims 1 to 7.

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