KR20230037451A - An electrode for electrochemical device and an electrochemical device comprising the same - Google Patents

Abstract

The present invention comprises: a conductive polymer layer located on at least one surface of an electrode current collector; and an electrode active material layer located 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 chemical formula 1 in the description of the invention.

Description

Electrode for electrochemical device and electrochemical device having the same

The present invention relates to an electrode for an electrochemical device and an electrochemical device having the same. More specifically, it relates to an electrode for an electrochemical device having improved safety and an electrochemical device having the same.

Recently, interest in energy storage technology is increasing. Efforts in the research and development of electrochemical devices are becoming more and more specific as the fields of application are expanded to mobile phones, camcorders, notebook PCs, and even the energy of electric vehicles.

These electrochemical devices can be largely classified into an anode, a cathode, a separator, and an electrolyte solution. However, such an electrochemical device may ignite or explode due to overcharging, high temperature exposure, external impact, and the like. If the electrochemical device 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 device is destroyed by external shock, a short-circuit phenomenon occurs where the anode and cathode meet, resulting in heat runaway will occur.

When a short circuit occurs, the movement of electrons, including lithium ions, is concentrated through the direct contact between the positive electrode and the negative electrode, thereby promoting internal heat generation of the battery. Due to this, it is known that the risk of volume expansion and ignition due to gas generation increases.

Therefore, there is a very high need for a technology capable of reducing the risk of ignition of a battery due to a short circuit.

Therefore, the problem to be solved by the present invention is to provide an electrode for an electrochemical device having improved safety and an electrochemical device having the same.

In order to solve the above problems, according to an aspect of the present invention, an electrode for an electrochemical device of the following embodiments is provided.

The electrode for an electrochemical device according to the first embodiment,

electrode current collector;

a conductive polymer layer located on at least one surface of the electrode current collector; and

Located on the upper surface of the conductive polymer layer, and comprising an electrode active material layer containing an electrode active material and a binder polymer.

The conductive polymer layer includes a poly(thiophene)-based polymer represented by Formula 1 below.

The second embodiment, in the first embodiment,

Adhesion between the conductive polymer layer and the electrode current collector may be 200 gf/20 mm or more.

In the third embodiment, in the first embodiment or the second embodiment,

An interface resistance between the conductive polymer layer and the electrode active material layer may be 3.0 ohm·cm ² or less.

In the fourth embodiment, in any one of the first to third embodiments,

At least one of the sum of carbon atoms of R ₁ and R ₂ and the sum of carbon atoms of R ₃ and R ₄ may be 5 or more.

In the fifth embodiment, in any one of the first to fourth embodiments,

The m or n may be 0.

In the sixth embodiment, in any one of the first to fifth embodiments

The conductive polymer layer may have a thickness of 0.1 μm to 8 μm.

In the seventh embodiment, in any one of the first to sixth embodiments

The conductive polymer layer may be a polyaniline (poly(aniline))-based polymer; polypyrrole (poly(pyrrole))-based polymer; poly(phenylene)-based polymer; poly(acetylene)-based polymer; derivatives thereof; Or it may further include two or more of these.

In the eighth embodiment, in any one of the first to seventh embodiments,

The electrode for the electrochemical device may be an anode.

In order to solve the above problems, according to an aspect of the present invention, an electrochemical device of the following embodiment is provided.

The electrochemical device according to the eighth embodiment,

Including 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 the electrode for an electrochemical device according to any one of the first to eighth embodiments.

In the electrode for an electrochemical device according to an embodiment of the present invention, a conductive polymer layer is positioned between an electrode current collector and an electrode active material layer so that the conductive path between the electrode current collector and the electrode active material layer is not disturbed during normal operation of the battery. However, when a short circuit occurs, direct contact between electrode current collectors can be prevented.

In the electrode for an electrochemical device according to an embodiment of the present invention, as the conductive polymer layer positioned between the electrode current collector and the electrode active material layer serves as a resistance layer, the short-circuit resistance is increased to prevent the rapid flow of short-circuit current, resulting in safety. can be obtained.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a diagram schematically showing an electrode for an electrochemical device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the usual or dictionary meaning, and the inventor appropriately uses the concept of the term in order to explain his/her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, since the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, various alternatives may be used at the time of this application. It should be understood that there may be equivalents and variations.

An electrode for an electrochemical device according to an embodiment of the present invention,

electrode current collector;

a conductive polymer layer located on at least one surface of the electrode current collector; and

Located on the upper surface of the conductive polymer layer, comprising an electrode active material layer containing an electrode active material and a binder polymer,

The conductive polymer layer is characterized by comprising a poly(thiophene)-based polymer represented by Formula 1 below.

[Formula 1]

In 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, and the sum of carbon atoms of R ₁ and R ₂ and R ₃ and At least one of the sum of carbon atoms in R ₄ is 3 or more, m and n are each independently an integer of 0 to 20,000, and m+n > 0.

In 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 represent different structures from each other.

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 is a monomer represented by repeating unit m and a monomer represented by repeating unit n. It may be an alternating polymer, random polymer or block polymer of, but is not limited thereto.

1 is a diagram schematically showing an electrode for an electrochemical device according to an embodiment of the present invention.

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 .

The electrode current collector 10 may be used without particular limitation as long as it has conductivity without causing chemical change in the electrochemical device. For example, in one embodiment of the present invention, copper as the electrode current collector 10; stainless steel; aluminum; nickel; titanium; calcined carbon; Surface treatment of copper, aluminum, or stainless steel with carbon, nickel, titanium, silver, chromium, or the like, an aluminum-cadmium alloy, or the like may be used. The current collector may also form fine irregularities on its surface to increase the adhesive strength of the active material, and various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics are possible.

In one embodiment of the present invention, when the electrode 1 for the electrochemical device is an anode, the electrode current collector 10 is made of stainless steel; aluminum; nickel; titanium; calcined carbon; Alternatively, aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, chromium, etc. may be used.

In another embodiment of the present invention, when the electrode 1 for the electrochemical device is a negative electrode, the electrode current collector 10 is copper; stainless steel; nickel; titanium; calcined carbon; Surface treatment of copper or stainless steel with carbon, nickel, titanium, silver, chromium, etc., aluminum-cadmium alloy, etc. may be used.

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.

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 .

When the electrochemical device is overcharged or exposed to a high temperature and the internal temperature of the electrochemical device rises, the separator shrinks and a short circuit between the anode and the cathode may occur. Alternatively, the internal structure of the electrochemical device may be destroyed by an external impact, causing a short circuit between the positive electrode and the negative electrode.

Such a short circuit is a soft short circuit caused by contact between the positive electrode active material and the negative electrode active material and a hard short circuit caused by direct contact between the positive current collector and the negative electrode current collector, the positive current collector and the negative electrode current collector, or the negative electrode current collector and the positive electrode active material. there is a paragraph In the case of a hard short circuit, short circuit resistance is low, resulting in more heat generation, which poses a serious threat to the safety of the battery.

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 when a short circuit occurs. 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 directly contacting the opposing electrode current collector or the opposing electrode active material. Accordingly, it is possible to prevent a hard short circuit from occurring.

In order for the conductive polymer layer 20 to serve as a protective film for the electrode current collector 10, the conductive polymer layer 20 is strongly bonded to the electrode current collector 10 and the conductive polymer layer 20 remains intact even when a short circuit occurs. It should not be peeled off from the electrode current collector 10 . If the conductive polymer layer 20 is easily peeled off from the electrode current collector 10, it cannot serve as a protective film for the electrode current collector 10 when a short circuit occurs.

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 force 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 force between the conductive polymer layer 20 and the electrode current collector 10 satisfies the above range, the conductive polymer layer 20 does not detach from the electrode current collector 10 when a short circuit occurs and the electrode current collector Since it is easy to strongly bond with (10), the conductive polymer layer 20 can easily serve as a protective film for the electrode current collector 10.

The adhesive strength between the conductive polymer layer 20 and the electrode current collector 10 is determined 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 the electrode current collector 10 It can be found by measuring the strength when the part is peeled at an angle of 90° at a rate of 20 mm/min at 25°C.

In addition, the conductive polymer layer 20 is located between the electrode current collector 10 and the electrode active material layer to be described later, so that the electrode current collector 10 and the electrode active material layer are in direct contact with each other, rather than in direct contact. By increasing the interfacial resistance between the electrode active material layers, even if a short circuit occurs, ignition of the electrochemical device due to the interfacial resistance can be prevented.

In one embodiment of the present invention, the interface resistance between the conductive polymer layer 20 and the electrode active material layer is 0.1 to 1000%, or 1 to 500%, compared to the case where the electrode current collector and the electrode active material layer are in direct contact. may have increased

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 to 2.5 It may be ohm·cm ² . When the interfacial resistance between the conductive polymer layer 20 and the electrode active material layer satisfies the aforementioned range, it is possible to secure cycle characteristics and easily prevent ignition of an electrochemical device when a short circuit occurs. For example, it may be easy to prevent ignition of an electrochemical device when a short circuit occurs while preventing cycle efficiency from being less than 80%.

The interface resistance between the conductive polymer layer 20 and the electrode active material layer can be measured with a multi probe tester.

In addition, the conductive polymer layer 20 includes a polymer exhibiting conductivity by interacting with a salt in the electrolyte solution, so that a conductive network between the electrode current collector 10 and the electrode active material layer described later can be connected. Accordingly, 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.

In one embodiment of the present invention, in Formula 1 representing the polythiophene-based polymer included in the conductive polymer layer, at least one of the sum of carbon atoms of R ₁ and R ₂ and the sum of carbon atoms of R ₃ and R ₄ 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 sum of carbon atoms of R ₁ and R ₂ and the sum of carbon atoms of R ₃ and R ₄ is within the above range, the adhesive force between the conductive polymer layer using the same and the electrode current collector is excellently maintained, and the life of the battery using the same There may be advantageous effects in terms of further improving, but the present invention is not limited thereto.

In one embodiment of the present invention, in Formula 1 representing the polythiophene-based polymer included in the conductive polymer layer, m or n may be 0. When m or n is 0, there may be an advantageous effect in terms of further improving the lifespan of a battery using the same while maintaining excellent adhesion between the conductive polymer layer and the electrode current collector using the same, but the present invention is limited thereto. It is not.

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.

In the present 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 under the following conditions using PL GPC220 (Agilent Technologies Co.).

- Column: PL Olexis (Polymer Laboratories)

- Solvent: TCB (Trichlorobenzene)

- Flow rate: 1.0 ml/min

- Sample concentration: 1.0 mg/ml

- Injection amount: 200 μl

- Column temperature: 160 ℃

- Detector: Agilent High Temperature RI detector

- Standard: Polystyrene (correction with cubic function)

In one embodiment of the present invention, the thickness of the conductive polymer layer is, 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 to 8 μm, or 0.5 μm. 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, an advantageous effect may be exhibited in terms of improving the interface resistance between the conductive polymer layer and the electrode current collector and thus improving the lifespan characteristics of the battery, but the present invention is not limited thereto. no.

In the present specification, the “thickness” of the conductive polymer layer may represent a value measured by a known method for measuring thickness. The method for measuring the thickness may be, but is not limited to, a value measured using, for example, a thickness meter (Mitutoyo, VL-50S-B).

In one embodiment of the present invention, the conductive polymer layer 20 is a poly(aniline)-based polymer in addition to the polythiophene-based polymer as a conductive polymer; polypyrrole (poly(pyrrole))-based polymer; poly(phenylene)-based polymer; poly(acetylene)-based polymer; derivatives thereof; Or two or more of these may be further included.

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 may include a copolymer of aniline monomers and other monomers.

The polypyrrole-based polymer is not particularly limited as long as it includes a pyrrole repeating unit. For example, it may include a homopolymer composed of only pyrrole repeating units, or may include a copolymer of a pyrrole monomer and other monomers.

The polypyrrole-based polymer may include a structure represented by Chemical Formula 2 or 3 below:

[Formula 2]

In Formula 2,

Wherein R ₁ and R ₂ are each independently hydrogen or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms,

The m is 1 to 20,000.

[Formula 3]

In Formula 3,

이고,The X is

ego,

Wherein Q is oxygen or sulfur,

Wherein R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,

Wherein p is a natural number of 1 or more,

The n is 1 to 20,000.

Throughout this specification, “substitution” refers to an alkyl group such as a methyl group, an ethyl group, an isopropyl group, or a butyl group; Alkoxy groups, such as a methoxy group and an ethoxy group; Arengi; alcohol group; It may refer to a case where it is substituted with a carboxylic acid group or the like.

The polyphenylene-based polymer is not particularly limited as long as it includes a phenylene repeating unit. For example, it may include a homopolymer composed of only phenylene repeating units, or may include a copolymer of a phenylene monomer and another monomer.

The polyphenylene-based polymer may include any one or more of the following structures:

,

,

,

,

.

,

,

,

,

.

Wherein R ₁ , R ₂ , R ₃ , and R ₄ are each independently hydrogen or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms,

The n is 1 to 20,000.

The polyacetylene-based polymer is not particularly limited as long as it includes a repeating unit having a polyene structure, for example, a repeating unit having a (CH) _x structure, in which one carbon atom and one hydrogen atom each have a polyene structure. For example, it may include a homopolymer composed only of repeating units having a polyene structure, or may include a copolymer of a polyene monomer and another monomer.

The polyacetylene-based polymer may have a structure represented by Formula 4 below:

[Formula 4]

In Formula 4, n is 1 to 20,000.

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.

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

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.

In one embodiment of the present invention, when the electrode 1 for the electrochemical device is a positive electrode, the electrode active material (ie, positive electrode active material) is, for example, 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 substituted with another transition metal; Or it may include two or more of these, but is not limited thereto. Specifically, the cathode active material may include, for example, layered compounds such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), or compounds substituted with one or more transition metals; lithium manganese oxides such as Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1 or Li ₂ Mn ₃ MO ₈ where M = Fe, Co, Ni, Cu or Zn) lithium manganese composite oxide; lithium metal phosphate LiMPO ₄ where M is 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 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, a +b+c=1); Lithium nickel-manganese-cobalt oxide partially substituted with aluminum Li _a [Ni _b Co _c Mn _d Al _e ] _1-f M1 _f O ₂ (M1 is Zr, B, W, Mg, Ce, Hf, Ta , La, Ti, Sr, Ba, F, P, and at least one selected from the group consisting of 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 lithium nickel-manganese-cobalt oxide is partially substituted with other transition metals Li _1+x (Ni _a Co _b Mn _c M _d ) _1-x O ₂ (x = 0 ~ 0.03, a = 0.3 ~ 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, M is any selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg and Mo one), disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. are mentioned, but it is not limited only to these.

In another embodiment of the present invention, when the electrode 1 for the electrochemical device is a negative electrode, the electrode active material (ie, negative electrode active material) is a carbon material capable of occluding and releasing lithium ions, lithium metal, silicon It may contain sub-total materials or tin. The carbon material may include natural graphite, artificial graphite, low crystalline carbon, and high crystalline carbon. Soft carbon and hard carbon are typical examples of low crystalline carbon, and examples of high crystalline carbon include natural graphite, kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fibers. High-temperature calcined carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes are representative examples. The silicon-based material may include silicon dioxide and the like.

The binder polymer is 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.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. The conductive material may be, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, farnes 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; A conductive material such as graphene may be included.

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.

In another embodiment of the present invention, when a conductive material is further included in the electrode active material layer, the weight ratio of the electrode active material, the conductive material, and the binder polymer is 90:5:5 to 98:1:1, or 95:2:3 to 98:1:1, or 97:1:2 to 98:1:1.

The electrode active material layer 30 may be prepared by coating a slurry for forming an electrode active material layer in which an electrode active material, a binder polymer, and, if necessary, a conductive material is mixed with a dispersion medium, on the upper surface of the conductive polymer layer 20, drying, and then rolling. there is.

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 current collector, so that when a short circuit occurs, a direct short circuit between electrode current collectors can be prevented.

Since the potential of the anode for an electrochemical device and the potential at which the conductive polymer layer 20 interacts with the salt in the electrolyte are similar, it may be advantageous to apply the conductive polymer layer 20 to the anode. When the electrode for the electrochemical device is an anode, it can protect the anode from a hard short path, which can be more advantageous in securing the safety of the electrochemical device.

In particular, the electrode for an electrochemical device according to an embodiment of the present invention has a conductive polymer layer on at least one surface of the electrode current collector, compared to the case where the electrode active material layer and the conductive polymer are included together with the electrode active material layer. Since the entire conductive polymer layer can be wrapped, it can be more effective in improving the safety of the electrode when a short circuit occurs.

An electrode for an electrochemical device according to an embodiment of the present invention may be manufactured as an electrochemical device together with a separator.

Safety of the electrochemical device according to an embodiment of the present invention may be further improved by having an electrode of the electrochemical device according to an embodiment of the present invention.

The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples include all types of primary and secondary cells, fuel cells, solar cells, and capacitors such as supercapacitor devices.

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.

The separator is not particularly limited, and is composed of only a porous polymer substrate, or a porous polymer substrate; and an organic-inorganic composite porous layer formed on at least one surface of the porous polymer substrate and containing a plurality of inorganic particles and a binder polymer. The separator is interposed between the positive electrode and the negative electrode and serves to insulate between the positive electrode and the negative electrode.

Any porous polymer substrate commonly used in the art may be used as the porous polymer substrate. For example, a polyolefin-based porous polymer membrane or non-woven fabric may be used as the porous polymer substrate, but is not particularly limited thereto.

The polyolefin-based porous polymer membrane is polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polyolefin-based polymers such as polypropylene, polybutylene, and polypentene, or a membrane formed of two or more of these can be heard

In addition to the polyolefin nonwoven fabric, the nonwoven fabric includes, for example, polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, and polycarbonate. ), polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, or two or more of these and nonwoven fabrics formed by The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a melt blown nonwoven fabric composed of long fibers.

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 pore size and porosity 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.

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 not particularly limited as long as oxidation and/or reduction reactions do not occur in the operating voltage range of the applied battery (eg, 0 to 5V based on Li/Li ⁺ ). 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 them. Inorganic particles with a dielectric constant of 5 or more are 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), 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.

In one embodiment of the present invention, the size of the inorganic particles is not limited, but has an average particle diameter 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 an appropriate porosity. can At this time, the average particle diameter of the inorganic particles means the particle size (D50) of 50% of the integrated value from the small particle diameter side calculated based on the particle size distribution of the particles after classification by a general particle size distribution analyzer and the measurement result. do. This particle size distribution can be measured by laser diffraction analysis.

In one embodiment of the present invention, the binder polymer included in the separator is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-hexafluoropropylene, Trichlorethylene (polyvinylidene fluoride-co-trichloroethylene), polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, Polyvinylpyrrolidone, polyvinylacetate, ethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate butyrate), cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, It may include pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or two or more of these, Not limited to this.

In one embodiment of the present invention, the content ratio of the inorganic particles and the binder polymer included 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 content ratio of the inorganic particles to the binder polymer is within the above-described range, it is possible to sufficiently secure an empty space formed between the inorganic particles while securing sufficient adhesion between the inorganic particles.

In one embodiment of the present invention, the organic-inorganic composite porous layer is bound to each other by the binder polymer in a state in which the inorganic particles are filled and in contact with each other, thereby forming interstitial volumes between the inorganic particles is formed, and the interstitial volume between the inorganic particles becomes an empty space and may have a structure in which pores are formed.

In one 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. In addition, an organic solid electrolyte or an inorganic solid electrolyte may be used as the electrolyte solution.

Examples of the organic solvent include N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane , tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid Triester, trimethoxy methane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-ibidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate An aprotic organic solvent such as may be used.

The lithium salt is a material that is easily soluble in the organic solvent, and is, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carbonate, lithium 4-phenyl borate, imide, and the like can be used. there is.

In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc. in the electrolyte solution, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. there is. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included to impart incombustibility, and carbon dioxide gas may be further included to improve high-temperature storage properties.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, A polymer containing an ionic dissociation group or the like can be used.

Examples of the inorganic solid electrolyte include 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 , Nitride, halide, sulfate, and the like of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , etc. may be used.

The injection of the electrolyte solution may be performed at an appropriate stage during the manufacturing process of the electrochemical device according to the manufacturing process and required physical properties of the final product. That is, it may be applied before assembling the electrochemical device or at the final stage of assembling the electrochemical device.

As a process of applying the separator to an electrochemical device, lamination, stack, and folding processes of the separator and the electrode may be performed in addition to winding, which is a general process.

The separator may be interposed between an anode and a cathode of an electrochemical device, and may be interposed between adjacent cells or electrodes when configuring an electrode assembly by assembling a plurality of cells or electrodes. 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.

The appearance of the electrochemical device is not particularly limited, but may be a cylindrical shape using a can, an angular shape, a pouch shape, or a coin shape.

Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the following examples. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

Synthesis of conductive polymer and preparation of conductive polymer solution

A conductive polymer was synthesized according to the following [Scheme 1].

[Scheme 1]

Specifically, 1 g (5.093 mmol, 1 eq) of 3-Octylthiophene (Compound 1) as a monomer was added to a solution in which 2.48 g (15.3 mmol, 3 eq) of iron (III) chloride was dissolved in 70 mL of chloroform, and the mixture was incubated at room temperature for 24 hours. Stir for an hour. After putting the mixed solution in an osmosis membrane having a molecular weight of cut off (MWCO) of 5000, it was immersed in 200 mL of acetonitrile solvent to selectively remove unreacted iron (III) chloride and remaining reactants. The residue precipitated inside the osmosis membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer having the same structure as Compound 2 as a conductive polymer and having a weight average molecular weight of 50,000 g/mol.

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

electrode manufacturing

The conductive polymer solution was coated on one surface of the main body of an aluminum current collector and an electrode tab having a thickness of 20 μm and dried to form a conductive polymer layer having a thickness of 1 μm on one surface of the electrode current collector. The total thickness of the current collector coated with the conductive polymer was 21 μm.

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

After coating and drying the slurry for forming the electrode active material layer on the electrode current collector on which the conductive polymer layer was formed, a roll press was performed to prepare an electrode having a total thickness of 50 μm.

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 thickness of the conductive polymer layer formed on one surface of the current collector was 10 μm.

Example 3

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

[Scheme 2]

Specifically, 1.23 g (6.26 mmol) of 3-octylthiophene and 1.41 g (6.26 mmol) of 3-decylthiophene were added to a solution in which 6.09 g (37.6 mmol) of iron (III) chloride was dissolved in 200 ml of methylene chloride, and the mixture was stirred at room temperature for 24 hours. Stir for an hour. After putting the mixed solution in an osmosis membrane having a molecular weight of cut-off (MWCO) of 5000, it was immersed in 150 ml of acetonitrile solvent to selectively remove unreacted iron (III) chloride and remaining reactants. The residue precipitated inside the osmosis membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer having the same structure as Compound 4 as a conductive polymer and having a weight average molecular weight (Mw) of 33,000 g/mol.

Comparative Example 1

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

Comparative Example 2

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

After coating and drying the slurry for forming the electrode active material layer on an aluminum current collector having a thickness of 20 μm, a roll press was performed to prepare an electrode having a total thickness of 50 μm.

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.

Comparative Example 4

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

[Scheme 3]

Specifically, 2.5 g (22.3 mmol) of 3-ethylthiophene was added to a solution of 10.84 g (66.85 mmol) of iron (III) chloride dissolved in 200 ml of methylene chloride, followed by stirring at room temperature for 24 hours. After putting the mixed solution in an osmosis membrane having a molecular weight of cut-off (MWCO) of 5000, it was immersed in 150 ml of acetonitrile solvent to selectively remove unreacted iron (III) chloride and remaining reactants. The residue precipitated inside the osmosis membrane was washed with methanol and dried at room temperature to obtain a polythiophene-based polymer having a weight average molecular weight (Mw) of 25,000 g/mol as a conductive polymer.

evaluation example

The adhesion between the conductive polymer layer and the electrode current collector, the interface resistance between the conductive polymer layer and the electrode active material layer, the cycle efficiency, and the safety of the electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated and are shown in Table 1 below. was

(1) Measurement of adhesive strength 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 strength when the electrode current collector was peeled at an angle of 90° at a rate of 20 mm/min at 25 ° C was measured from that of the conductive polymer layer. It was taken as the adhesive force between electrode current collectors.

(2) Measurement of interfacial resistance between the conductive polymer layer and the electrode active material layer

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 to 4 was measured using a multi probe tester.

In addition, the interface 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.

(3) Evaluation of cycle efficiency

A slurry for forming an anode active material layer was prepared by mixing artificial graphite, carbon black, and styrene butadiene rubber in a weight ratio of 95:3.5:1.5, coated on one side of an 8 μm thick copper film, dried, and then used with a roll press. and rolled to prepare a negative electrode.

Electrode assemblies were prepared by interposing a polyethylene fabric having a thickness of 10 μm between the electrodes (anode) and the cathode prepared in Examples 1 to 3 and Comparative Examples 1 to 4 and pressing at 80° C.

An electrochemical device was prepared by injecting an electrolyte solution (EC:PC:EP:PP=2:1:2.5:4.5, LiPF ₆ 1.4M) (ionic conductivity ≥ 6.5 mS/cm) into the prepared electrode assembly.

The electrochemical device prepared above is subjected to constant current/constant voltage (CC/CV) charging and 0.025C cut off charging to 4.48 V at a rate of 0.7C, and constant current (CC) discharging to 3.0V at a rate of 0.2C to evaluate cycle efficiency. did

(4) Safety evaluation

After preparing 10 electrochemical devices prepared above, placing them on a flat plate, placing an iron bar with a diameter of 15.8 mm, and then performing an impact test by freely dropping a weight of 9.1 kg from a height of 61 cm above it, It was confirmed whether the electrochemical element was ignited.

Thickness of conductive polymer layer (㎛) Adhesion between the conductive polymer layer and the electrode current collector
(gf/20mm) Interfacial resistance between the conductive polymer layer (or current collector) and the electrode active material layer
(ohm cm ² ) cycle efficiency
(300 cycles) Safety test (Impact test)
Pass/Total Example 1 One 246 0.62 92.2% 9/10 Example 2 10 237 4.32 75.1% 9/10 Example 3 One 212 0.49 90.1% 8/10 Comparative Example 1 0 - 0.21 92.5% 0/10 Comparative Example 2 0 - 0.33 91.9% 5/10 Comparative Example 3 One 84 0.57 92.4% 3/10 Comparative Example 4 One 28 0.33 90.3% 2/10

As can be seen in Table 1, in the case of Examples 1 to 3, it was confirmed that they had excellent safety as they were provided with a conductive polymer layer.

In particular, in the case of Examples 1 and 3, since the interface resistance between the conductive polymer layer and the electrode active material layer was 3.0 ohm·cm ² or less, it was confirmed that the cycle efficiency was more excellent than that of Example 2.

In addition, in the case of Example 1, it was confirmed that the safety was further improved compared to Example 3 as the adhesion between the conductive polymer layer and the electrode current collector was better.

On the other hand, in the case of Comparative Examples 1 and 2, since the conductive polymer layer was not provided, sufficient safety could not be secured.

In particular, in Comparative Example 3 and Comparative Example 4, despite having a conductive polymer layer, it was confirmed that sufficient adhesion between the conductive polymer layer and the current collector was not secured due to the different types of conductive polymers used.

1: electrode for electrochemical device
10: electrode current collector
20: conductive polymer layer
30: electrode active material layer

Claims (9)

electrode current collector;
a conductive polymer layer located on at least one surface of the electrode current collector; and
Located on the upper surface of the conductive polymer layer, comprising an electrode active material layer containing an electrode active material and a binder polymer,
The conductive polymer layer is an electrode for an electrochemical device, characterized in that it comprises a poly (thiophene)-based polymer represented by the following formula (1):
[Formula 1]

In Formula 1,
Wherein 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 the sum of carbon atoms of R ₁ and R ₂ and the carbon atoms of R ₃ and R ₄ at least one of the sums is 3 or greater;
The m and n are each independently an integer of 0 to 20,000, and m+n > 0. The method of claim 1,
An electrode for an electrochemical device, characterized in that the adhesive strength between the conductive polymer layer and the electrode current collector is 200 gf / 20 mm or more. The method of claim 1,
An electrode for an electrochemical device, characterized in that the interface resistance between the conductive polymer layer and the electrode active material layer is 3.0 ohm·cm ² or less. The method of claim 1,
The electrode for an electrochemical device, characterized in that at least one of the sum of carbon atoms of R ₁ and R ₂ and the sum of carbon atoms of R ₃ and R ₄ is 5 or more. The method of claim 1,
An electrode for an electrochemical device, characterized in that the m or n is 0. The method of claim 1,
An electrode for an electrochemical device, characterized in that the thickness of the conductive polymer layer is 0.1 ㎛ to 8 ㎛. The method of claim 1,
The conductive polymer layer may be a polyaniline (poly(aniline))-based polymer; polypyrrole (poly(pyrrole))-based polymer; poly(phenylene)-based polymer; poly(acetylene)-based polymer; derivatives thereof; Or an electrode for an electrochemical device, characterized in that it further comprises two or more of these. The method of claim 1,
An electrode for an electrochemical device, characterized in that the electrode for the electrochemical device is an anode. Including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
An electrochemical device wherein the anode or cathode comprises the electrode for an electrochemical device according to any one of claims 1 to 8.

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