Co-composite

Abstract

This specification discloses a copolymer and its uses. The copolymer can exhibit a tailored positive temperature coefficient (PTC) effect and oxidation potential. Such a conductive copolymer exhibits excellent electrical properties, such as low resistance, under normal conditions, and can form electrode current collectors, electrodes, and secondary batteries containing the same that do not affect, but rather improve, the performance and operation of secondary batteries and ensure stability under abnormal conditions. This specification further discloses uses of the copolymer.

Description

[Technical Field]

[0001] Cross-reference to related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0134842, dated October 19, 2022, the entire contents of which are incorporated herein by reference.

[0002] Technical Field This specification discloses copolymers and their uses. [Background technology]

[0003] Energy storage technology is finding applications in a wide range of devices, including mobile phones, tablets, laptops, and even electric vehicles.

[0004] As the data processing speeds of mobile devices such as mobile phones and tablets increase and their usage times become longer, development of secondary batteries with high energy density, working potential, long cycle life, and low self-discharge rate is progressing.

[0005] In addition, as major developed countries curb the production of internal combustion engine vehicles in order to eliminate global warming and air pollution, major automakers are also developing various electric vehicles, and the importance of secondary batteries, which have high energy density, high discharge voltage and output stability as a driving source for these vehicles, is becoming increasingly important.

[0006] However, in accordance with this trend, the frequency of fires or explosions caused by overcharging, exposure to high temperatures, external impacts, etc., in devices and automobiles that use secondary batteries as their energy source is also increasing.

[0007] The main cause of such accidents is known to be a short circuit, which occurs when the positive and negative electrodes in the electrode assembly come into direct contact due to an external stimulus.When a secondary battery is overcharged or exposed to high temperatures or external stimuli, the short circuit can occur due to the contraction of the separator caused by an increase in the internal temperature of the secondary battery, or the destruction of the internal structure of the secondary battery due to an external impact.

[0008] When a short circuit occurs, the movement of lithium ions and electrons can be concentrated at the point where the positive and negative electrodes come into direct contact, which can accelerate internal heat generation, generating gases inside the battery and causing it to expand in volume, increasing the risk of fire. Summary of the Invention [Problem to be solved by the invention]

[0009] This specification discloses copolymers and uses thereof. It is an object of this specification to disclose conductive copolymers that exhibit a tailored PTC (positive temperature coefficient) effect and oxidation potential. Such conductive copolymers exhibit excellent electrical properties, such as low resistance, under normal conditions, and can be used to form electrode current collectors, electrodes, and secondary batteries containing the same that do not affect, but rather improve, the performance and operation of secondary batteries and ensure stability under abnormal conditions. It is a further object of this specification to disclose uses of the copolymers. [Means for solving the problem]

[0010] As used herein, the term "room temperature" means a natural temperature that is neither heated nor cooled. For example, room temperature may be any temperature within the range of 10°C to 30°C, or a temperature of about 23°C, about 25°C, or about 27°C.

[0011] In the present specification, when the measurement temperature affects a physical property, the physical property is measured at room temperature unless otherwise specified.

[0012] Unless otherwise specified herein, the unit of temperature herein is Celsius (°C).

[0013] In this specification, the term "normal pressure" means natural pressure that is neither pressurized nor reduced, and generally means a pressure of about 730 mmHg to 790 mmHg.

[0014] When a physical property referred to in this specification is affected by the measurement pressure, the physical property is measured at normal pressure unless otherwise specified.

[0015] When the humidity at which a physical property is measured affects the physical property referred to in this specification, the physical property is measured at standard humidity unless otherwise specified.

[0016] Humidity under standard conditions means a relative humidity within a range of 40% to 60%, for example, a relative humidity of about 55% or 60%.

[0017] In this specification, the term "normal state" refers to a normal operating state of a secondary battery (for example, a normal charging or discharging state of a secondary battery) or a storage state.

[0018] As used herein, the term "abnormal condition" refers to a dangerous condition in which an abnormal charge flow, abnormal heat generation, or explosion occurs due to an external impact and / or short circuit phenomenon, or in which the likelihood of such an abnormal condition occurring is increased.

[0019] This specification discloses copolymers.

[0020] The copolymer can exhibit precisely controlled PTC (positive temperature coefficient) effect and oxidation potential according to the purpose.

[0021] The positive temperature coefficient (PTC) effect is an effect in which resistance increases with temperature. Therefore, if the PTC effect of the conductive copolymer is designed to be suppressed or not exhibited under normal temperature conditions, abnormal charge flow can be suppressed and the stability of the secondary battery can be ensured.

[0022] In addition, by adjusting the oxidation potential of the conductive copolymer, a secondary battery using the copolymer can be stably operated during repeated charge and discharge in a normal state and during high-speed charge and discharge.

[0023] The copolymer contains at least two different monomer units. In this specification, the term "monomer unit" means a structure in which a monomer is polymerized and contained in the copolymer, unless otherwise specified.

[0024] The copolymer may be a polythiophene or a thiophene polymer. As used herein, the term "polythiophene" or "thiophene polymer" refers to a polymer containing a certain level of thiophene units. As used herein, the term "thiophene unit" refers to a monomer unit formed by polymerization of a thiophene-based monomer, and the thiophene-based monomer refers to a monomer containing a thiophene skeleton.

[0025] The lower limit of the proportion of thiophene units in the polythiophene or thiophene polymer may be about 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, or 75 mol%, based on the total number of moles of all monomer units in the polythiophene or thiophene polymer, and the upper limit may be about 99 mol%, 97 mol%, 95 mol%, 93 mol%, 91 mol%, 89 mol%, 87 mol%, 85 mol%, 83 mol%, 81 mol%, 79 mol%, 77 mol%, 75 mol%, 73 mol%, 71 mol%, 69 mol%, 67 mol%, 65 mol%, 63 mol%, 61 mol%, 59 mol%, 57 mol%, 55 mol%, 53 mol%, or 51 mol%. The proportion of thiophene units in the polythiophene or thiophene polymer may be within a range equal to or greater than any one of the above-mentioned lower limits, or may be within a range equal to or less than any one of the above-mentioned upper limits but equal to or greater than any one of the above-mentioned lower limits.

[0026] The thiophene unit may be a thiophene unit having a hydrocarbon functional group. As used herein, the term "hydrocarbon functional group" refers to a monovalent hydrocarbon group (i.e., a monovalent functional group consisting of carbon and hydrogen) or a monovalent functional group containing the monovalent hydrocarbon group. Therefore, the hydrocarbon functional group may contain atoms other than carbon and hydrogen.

[0027] The lower limit of the number of carbon atoms in the hydrocarbon functional group or monovalent hydrocarbon group may be about 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, and the upper limit may be about 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, or 3. The number of carbon atoms in the hydrocarbon functional group or monovalent hydrocarbon group may be equal to or greater than any of the above-mentioned lower limits, or equal to or less than any of the above-mentioned upper limits, or equal to or less than any of the above-mentioned upper limits but equal to or greater than any of the above-mentioned lower limits.

[0028] The carbon number may be the total number of carbon atoms present in the hydrocarbon functional group or monovalent hydrocarbon group, or the number of carbon atoms in the linear hydrocarbon chain contained in the hydrocarbon functional group or monovalent hydrocarbon group. That is, the hydrocarbon functional group or monovalent hydrocarbon group may have a linear or branched chain structure, and even in the case of a branched chain structure, the number of carbon atoms constituting the longest linear chain in the branched chain structure may be within the above range. For example, if the branched chain structure is a 2-ethylhexyl group, the number of carbon atoms constituting the longest linear chain is 6, which is contained in the hexyl chain.

[0029] Examples of the monovalent hydrocarbon group include an alkyl group, an alkynyl group, or an alkenyl group, and examples of the hydrocarbon functional group may be, but are not limited to, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylcarbonyl group, or an alkylcarbonyloxy group, etc. In suitable examples, the hydrocarbon functional group may be an alkyl group and / or an alkoxy group.

[0030] The number of carbon atoms present in the alkyl group, alkenyl group, alkynyl group, alkoxy group, alkyl group of the alkylcarbonyl group, and alkyl group of the alkylcarbonyloxy group may be within the range of the number of carbon atoms present in the hydrocarbon functional group or monovalent hydrocarbon group.

[0031] For example, the alkyl group, alkenyl group, alkynyl group, alkoxy group, alkyl group of an alkylcarbonyl group, and alkyl group of an alkylcarbonyloxy group may have a linear or branched chain structure, and in the case of a branched chain, the number of carbon atoms constituting the longest linear chain in the branched chain structure may be within the range of the number of carbon atoms present in the hydrocarbon functional group or monovalent hydrocarbon group.

[0032] The hydrocarbon functional group, alkyl group, alkenyl group, alkynyl group, alkoxy group, alkylcarbonyl group or alkylcarbonyloxy group, may be optionally substituted with one or more substituents.

[0033] In the conductive copolymer, the lower limit of the mole ratio of the thiophene units having a hydrocarbon functional group may be approximately 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, or 70 mol%, and the upper limit may be approximately 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, 50 mol%, or 45 mol%. The mole ratio is based on the total moles of all monomer units contained in the copolymer. The mole ratio may be less than or equal to any of the upper limits, greater than or equal to any of the lower limits, or less than or equal to any of the upper limits but greater than or equal to any of the lower limits.

[0034] Under such a ratio, the conductive copolymer or the polymer layer exhibits an appropriate PTC (Positive Temperature Coefficient) effect, and its surface properties are controlled, thereby ensuring excellent adhesion to the electrode or electrode current collector, and exhibiting an appropriate level of oxidation potential.

[0035] The hydrocarbon functional group is a functional group that can impart appropriate fluidity to the conductive polymer itself or during the polymerization process of the conductive polymer. Such functional groups impart appropriate fluidity to the monomer mixture and diffuse within the monomer mixture, allowing for efficient polymerization. Furthermore, conductive polymers having such functional groups can ensure stable and uniform formation of a polymer layer between the current collector body and the active material layer through appropriate fluidity.

[0036] The hydrocarbon functional groups are appropriately oriented during the drying or annealing process (heat treatment process) used in the formation of the polymer layer, and can impart suitable PTC effect and oxidation potential characteristics to the copolymer.

[0037] When a certain amount of thermal energy is applied, the hydrocarbon functional group vibrates due to the heat. This vibration (thermal vibration) promotes the dedoping of anions bound to the copolymer, thereby inducing an increase in resistance. The temperature at which the thermal vibration occurs can be controlled by the length and / or amount of the hydrocarbon functional group. For example, at the same temperature, the thermal vibration of a relatively long chain is greater than that of a relatively short chain, and therefore, the long chain can induce a resistance increase effect at a relatively low temperature. Therefore, the desired PTC effect can be achieved by controlling the length and / or proportion of the hydrocarbon functional group.

[0038] The thiophene units contained in the copolymer may be a first thiophene unit having a long-chain hydrocarbon functional group and a second thiophene unit having a short-chain hydrocarbon functional group.

[0039] In this specification, the term "long-chain hydrocarbon functional group" refers to a hydrocarbon functional group that belongs to the above-mentioned category of hydrocarbon functional groups and has a carbon number equal to or greater than a certain level as described above.

[0040] As used herein, the term "short-chain hydrocarbon functional group" refers to a hydrocarbon functional group that belongs to the above-mentioned category of hydrocarbon functional groups and has a carbon number not exceeding a certain level as described above.

[0041] The lower limit of the number of carbon atoms in the long-chain hydrocarbon group may be about 10, 11, or 12, and the upper limit may be about 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10. The number of carbon atoms in the long-chain hydrocarbon group may be equal to or greater than any of the above-mentioned lower limits, or may be equal to or less than any of the above-mentioned upper limits but equal to or greater than any of the above-mentioned lower limits.

[0042] The lower limit of the number of carbon atoms in the short-chain hydrocarbon group may be about 3, 4, 5, 6, 7, or 8, and the upper limit may be about 9, 8, 7, or 6. The number of carbon atoms in the short-chain hydrocarbon group may be less than or equal to any of the above-mentioned upper limits, or may be less than or equal to any of the above-mentioned upper limits but greater than or equal to any of the above-mentioned lower limits.

[0043] With respect to the long-chain and short-chain hydrocarbon functional groups, other matters, such as the meaning of the carbon number and the specific type of functional group, except for the aforementioned number of carbon atoms, are as described above for the hydrocarbon functional group.

[0044] Therefore, for example, the carbon number may be the total number of carbon atoms present in the long-chain and short-chain hydrocarbon functional groups, or the number of carbon atoms in the linear hydrocarbon chain contained in the functional group. For example, the monovalent hydrocarbon group present in the long-chain and short-chain hydrocarbon functional groups may have a linear or branched structure, and even in the case of a branched structure, the number of carbon atoms constituting the longest linear chain in the branched structure may be within the above range. For example, when the branched chain structure is a 2-ethylhexyl group, the number of carbon atoms constituting the longest linear chain is 6.

[0045] Examples of the long-chain and short-chain hydrocarbon functional groups include at least one selected from the group consisting of alkyl groups, alkenyl groups, alkynyl groups, alkoxy groups, alkylcarbonyl groups, and alkylcarbonyloxy groups. In suitable examples, the long-chain and short-chain hydrocarbon functional groups may be alkyl groups and / or alkoxy groups.

[0046] The number of carbon atoms present in the alkyl group, alkenyl group, alkynyl group, alkoxy group, alkyl group of the alkylcarbonyl group, and alkyl group of the alkylcarbonyloxy group may be within the range of the number of carbon atoms present in the long-chain or short-chain hydrocarbon functional group.

[0047] The hydrocarbon functional group, alkyl group, alkenyl group, alkynyl group, alkoxy group, alkylcarbonyl group or alkylcarbonyloxy group, may be optionally substituted with one or more substituents.

[0048] In the conductive copolymer, the lower limit of the total mole ratio of the first and second thiophene units may be approximately 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, or 70 mol%, and the upper limit may be approximately 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, 50 mol%, or 45 mol%. The percentage is based on the total mole ratio of all monomer units contained in the copolymer. The percentage may be less than or equal to any of the above-mentioned upper limits, greater than or equal to any of the above-mentioned lower limits, or less than or equal to any of the above-mentioned upper limits but greater than or equal to any of the above-mentioned lower limits.

[0049] The ratio (M2 / M1) of the number of moles of thiophene units having a short-chain hydrocarbon functional group (M2) to the number of moles of thiophene units having a long-chain hydrocarbon functional group (M1) in the conductive copolymer may have a lower limit of about 0.01, 0.05, 0.1, or 0.5, and the upper limit may be about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.8, 0.7, 0.6, or 0.55. The ratio may be less than or equal to any of the upper limits, greater than or equal to any of the lower limits, or less than or equal to any of the upper limits but greater than or equal to any of the lower limits.

[0050] This ratio allows the conductive copolymer or the polymer layer to exhibit a suitable PTC (Positive Temperature Coefficient) effect and adjusts its surface properties, thereby ensuring excellent adhesion to the electrode or electrode current collector.

[0051] The copolymer may further include, as the thiophene units, a thiophene unit having a polar functional group in addition to the thiophene unit having a hydrocarbon functional group.

[0052] As used herein, the term "polar functional group" refers to a functional group containing one or more polar atoms, such as oxygen and / or nitrogen. Examples of such polar functional groups include, but are not limited to, a carboxyl group, a hydroxyl group, an amino group, a cyano group, a nitro group, an ether group, or a functional group represented by the following formula 4:

[0053] [ka]

[0054] In Chemical Formula 4, L3 is a single bond, an alkylene group, or an alkylidene group, L4 is an alkylene group or an alkylidene group, R8 is hydrogen or an alkyl group, and n is any number.

[0055] In Chemical Formula 4, when L3 is a single bond, it means that L3 is absent and the oxygen atom between L4 and L3 is connected to the backbone of the monomer or polymer.

[0056] As used herein, the term "alkylene group" refers to a divalent functional group formed by removing hydrogen atoms from two different carbon atoms of an alkane, and the term alkylidene group refers to a divalent functional group formed by removing two hydrogen atoms from one carbon atom of an alkane.

[0057] In this specification, unless otherwise specified, the term "alkylene group" may refer to an alkylene group having 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or 2 to 4 carbon atoms. The alkylene group may be linear, branched, or cyclic, and may be optionally substituted with one or more substituents.

[0058] In this specification, unless otherwise specified, the term "alkylidene group" may be an alkylidene group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkylidene group may be linear, branched, or cyclic, and may be optionally substituted with one or more substituents.

[0059] In Chemical Formula 4, the alkyl group of R8 may be, for example, an alkyl group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, or may be a methyl group or an ethyl group. The alkyl group may be linear, branched, or cyclic, and may suitably be linear or branched.

[0060] In Chemical Formula 4, the lower limit of n may be about 1, 2, 3, or 4, and the upper limit may be about 10, 9, 8, 7, 6, 5, 4, or 3. The n may be less than or equal to any of the above upper limits, or greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits.

[0061] By applying the polar functional group, a polymer layer including a conductive polymer can be bonded to other layers with appropriate bonding strength, and the conductive polymer layer can be uniformly formed to efficiently achieve the desired protective function.

[0062] When the thiophene units having a polar functional group are present in the conductive copolymer, the thiophene units having a polar functional group may be present such that the total number of moles of the thiophene units having a hydrocarbon functional group falls within a predetermined range per mole of the thiophene units having a polar functional group.

[0063] For example, the lower limit of the total number of moles of the thiophene units having the hydrocarbon functional group per mole of the thiophene units having the polar functional group may be about 1 mole, 2 moles, 3 moles, 4 moles, 5 moles, 6 moles, 7 moles, 8 moles, 8.5 moles, or 9 moles, and the upper limit thereof may be about 500 moles, 450 moles, 400 moles, 350 moles, 300 moles, 250 moles, 200 moles, 150 moles, 100 moles, 95 moles, 90 moles, 85 moles, 80 moles, 75 moles, 70 moles, 65 moles, 60 moles, 55 moles, 50 moles, 45 moles, 40 moles, 35 moles, 30 moles, 25 moles, 20 moles, 15 moles, 10 moles, 9.5 moles, or 9 moles. The ratio may be within a range equal to or less than any of the aforementioned upper limits, or equal to or greater than any of the aforementioned lower limits, or may be within a range equal to or less than any of the aforementioned upper limits but equal to or greater than any of the aforementioned lower limits.

[0064] Such a thiophene unit may be, for example, a unit of the following formula 1:

[0065] [ka]

[0066] In Chemical Formula 1, R1 and R2 may each independently be hydrogen, the polar functional group, or the hydrocarbon functional group.

[0067] In another example, R1 and R2 in Chemical Formula 1 may be linked together to form a divalent functional group of Chemical Formula 2 below.

[0068] [ka]

[0069] In Chemical Formula 2, L1 and L2 are each independently a single bond, an alkylene group, or an alkylidene group, and R3 and R4 are each independently hydrogen, the polar functional group, or the hydrocarbon functional group.

[0070] For example, when the unit of Formula 1 is a thiophene unit having the aforementioned hydrocarbon functional group, at least one of R1 and R2 may be the hydrocarbon functional group (when R1 and R2 are not linked), or at least one of R3 and R4 may be the hydrocarbon functional group (when R1 and R2 are linked).

[0071] For example, when the unit of Formula 1 is a thiophene unit having the polar functional group described above, at least one of R1 and R2 may be the polar functional group (when R1 and R2 are not linked), or at least one of R3 and R4 may be the polar functional group (when R1 and R2 are linked).

[0072] For example, when the unit of Formula 1 is a thiophene unit having the long-chain hydrocarbon functional group, at least one of R1 and R2 may be the long-chain hydrocarbon functional group (when R1 and R2 are not linked), or at least one of R3 and R4 may be the long-chain hydrocarbon functional group (when R1 and R2 are linked).

[0073] For example, when the unit of Chemical Formula 1 is a thiophene unit having the short-chain hydrocarbon functional group described above, at least one of R1 and R2 may be the short-chain hydrocarbon functional group described above (when R1 and R2 are not linked), or at least one of R3 and R4 may be the short-chain hydrocarbon functional group described above (when R1 and R2 are linked).

[0074] The hydrocarbon functional group, polar functional group, long-chain hydrocarbon functional group, and short-chain hydrocarbon functional group have been specifically described above.

[0075] The alkylene group and alkylidene group in the above Chemical Formula 2 are described in detail in the above Chemical Formula 4.

[0076] The copolymer may contain additional monomer units in addition to the thiophene units, for example, to adjust the oxidation potential of the copolymer.

[0077] Such monomers include, for example, pyrrole or monomers containing a pyrrole skeleton, which can reduce the high oxidation potential of the thiophene unit.

[0078] For example, the copolymer may include units of the following formula 3 together with the thiophene units:

[0079] [ka]

[0080] In the formula, R5, R6, and R7 are each independently hydrogen, a polar functional group, or a hydrocarbon functional group, the specific details of which are the same as those described for the thiophene unit.

[0081] A copolymer containing these units can exhibit a PTC effect and an appropriate oxidation potential, thereby enabling stable operation of a secondary battery when applied to an electrode without increasing resistance under normal conditions.

[0082] The ratio of the unit of Formula 3 in the copolymer is not particularly limited and may be adjusted depending on the desired PTC effect and / or oxidation potential.

[0083] In one example, the lower limit of the proportion of units of Formula 3 in the copolymer may be about 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, or 50 mol%, and the upper limit may be about 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, 50 mol%, 45 mol%, 40 mol%, 35 mol%, 30 mol%, 25 mol%, or 20 mol%. The proportion is based on the total number of moles of all monomer units contained in the copolymer. The proportion may be less than or equal to any of the above upper limits, greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits.

[0084] The lower limit of the ratio of the total number of moles of the thiophene units and the units of Formula 3 in the copolymer may be about 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%, and the upper limit may be about 100 mol% or 95 mol%. The ratio is based on the total number of moles of all monomer units contained in the copolymer. The ratio may be less than or equal to any of the above upper limits, greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits.

[0085] The copolymer may further contain other monomer units within a range that does not impair the desired effects, such as the PTC effect and / or the oxidation potential.

[0086] The copolymer may have a weight average molecular weight (Mw) within a predetermined range. The lower limit of the weight average molecular weight of the copolymer may be about 10,000 g / mol, 20,000 g / mol, 30,000 g / mol, 40,000 g / mol, 50,000 g / mol, 60,000 g / mol, 70,000 g / mol, 80,000 g / mol, 90,000 g / mol, or 100,000 g / mol, and the upper limit may be about 2,000,000 g / mol, 1,500,000 g / mol, 1,000,000 g / mol, 900,000 g / mol, or 100,000 g / mol. 000g / mol, 800,000g / mol, 700,000g / mol, 600,000g / mol, 500,000g / mol, 400,000g / mol, 300,000g / mol, 295,000g / mol, 290 ,000g / mol, 285,000g / mol, 280,000g / mol, 275,000g / mol, 270,000g / mol, 265,000g / mol, 260,000g / mol, 255,000g / mol, 25 0,000g / mol, 245,000g / mol, 240,000g / mol, 235,000g / mol, 230,000g / mol, 225,000g / mol, 220,000g / mol, 215,000g / mol, 2 10,000g / mol, 205,000g / mol, 200,000g / mol, 195,000g / mol, 190,000g / mol, 185,000g / mol, 180,000g / mol, 175,000g / mol, It may be about 170,000 g / mol, 165,000 g / mol, 160,000 g / mol, 155,000 g / mol, 150,000 g / mol, 145,000 g / mol, 140,000 g / mol, 135,000 g / mol, 130,000 g / mol, 125,000 g / mol, 120,000 g / mol, 115,000 g / mol, 110,000 g / mol, 105,000 g / mol or 100,000 g / mol.The weight average molecular weight may be within a range equal to or less than any of the above upper limits, or equal to or greater than any of the above lower limits, or may be within a range equal to or less than any of the above upper limits but equal to or greater than any of the above lower limits.

[0087] The molecular weight distribution of the copolymer, i.e., the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), may be within a predetermined range. The lower limit of the molecular weight distribution may be about 2, 2.5, 3, 3.5, or 4, and the upper limit may be about 8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, or 4. The molecular weight distribution may be less than or equal to any of the above upper limits, greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits.

[0088] The weight average molecular weight and molecular weight distribution are measured by the method described in "2. GPC (Gel Precipitation Chromatograph)" in the Examples section of this specification.

[0089] The copolymers can exhibit a controlled oxidation potential. For example, the lower limit of the oxidation potential of the copolymer may be about 0 V, 0.1 V, 0.2 V, 0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9 V, 3 V, 3.1 V, 3.2 V, 3.3 V, 3.4 V, 3.5 V, 3.6 V, 3.7 V, 3.8 V, or 3.9 V, and the upper limit may be about 6.0 V, 5.5 V, 5 V, 4.5 V, 4.0 V, or 3.9 V. The oxidation potential may be within a range equal to or less than any of the upper limits mentioned above, or may be within a range equal to or less than any of the upper limits mentioned above but equal to or greater than any of the lower limits mentioned above. The oxidation potential of the copolymer is expressed as the oxidation potential relative to lithium, and is calculated based on the ratio of lithium and lithium ions (Li / Li + The oxidation potential is measured using the oxidation potential of the copolymer as a standard. The method for measuring the oxidation potential is described in "4. Method for measuring the oxidation potential of the copolymer" in the Examples section of this specification.

[0090] In one example, the upper limit of the DC resistance of the copolymer at 25°C is 10 4Ω·cm, 9500Ω·cm, 9000Ω·cm, 8500Ω·cm, 8000Ω·cm, 7500Ω·cm, 7000Ω·cm, 6500Ω·cm, 6000Ω·cm, 5500Ω·cm, 5000 Ω cm, 4500 Ω cm, 4000 Ω cm, 3500 Ω cm, 3000 Ω cm, 2500 Ω cm, 2000 Ω cm, 1500 Ω cm, 1000 Ω cm, 950 Ω cm, 900 Ω cm The DC resistance may be about 10 Ω·cm, 850 Ω·cm, 800 Ω·cm, 750 Ω·cm, 700 Ω·cm, 650 Ω·cm, 600 Ω·cm, 550 Ω·cm, 500 Ω·cm, 450 Ω·cm, or 400 Ω·cm, and the lower limit may be about 10 Ω·cm, 50 Ω·cm, 100 Ω·cm, 150 Ω·cm, 200 Ω·cm, 250 Ω·cm, 300 Ω·cm, 350 Ω·cm, or 400 Ω·cm. The DC resistance may be less than or equal to any of the upper limits, or may be less than or equal to any of the upper limits but greater than or equal to any of the lower limits. The DC resistance was measured using the method described in "6. DC Resistance Measurement Method" in the Examples section of this specification.

[0091] The upper limit of AC impedance resistance of the copolymer is 10 3 Ω, 950Ω, 900Ω, 850Ω, 800Ω, 750Ω, 700Ω, 650Ω, 600Ω, 550Ω, 500Ω, 450Ω, 400Ω, 350Ω, 300Ω, 250Ω, 200Ω, 150Ω, 100Ω, 95Ω, 90Ω, 85Ω, 80Ω, 75Ω, 70Ω, 65Ω, 60Ω, 55Ω, or 50Ω, and the lower limit may be about 10Ω, 15Ω, 20Ω, 25Ω, 30Ω, 35Ω, 40Ω, 45Ω, or 50Ω. The AC impedance resistance may be within a range equal to or less than any of the upper limits recited above, or within a range equal to or less than any of the upper limits recited above but equal to or greater than any of the lower limits recited above. The AC impedance resistance was measured by the method described in "7. Interface resistance (AC impedance resistance)" in the Examples of this specification.

[0092] Since the copolymer exhibits the DC resistance and / or AC impedance resistance, a secondary battery or an electrode assembly using the copolymer may be stably operated or stored under normal conditions.

[0093] The copolymers are capable of exhibiting a purpose-designed PTC effect.

[0094] For example, the copolymer may exhibit a property in which ΔR1 in the following formula 1 falls within a predetermined range.

[0095] [Formula 1] △R1=Max{(R n+5 / R n ) / 5}

[0096] In Equation 1, R n is the DC resistance at any temperature n°C between 25°C and 135°C, and R n+5 is the DC resistance at a temperature 5°C higher than the temperature n°C ((n+5)°C), and Max{(R n+5 / R n ) / 5} was confirmed within the temperature range of 25℃ to 135℃ (R n+5 / R n ) / 5 is the maximum value.

[0097] In Equation 1, ΔR1 is measured for a coin cell to which the copolymer is applied, and the specific method is described in "8. Measurement of Maximum Resistance Change Rate (DC Resistance)" in the Examples. In the method for determining ΔR1, the initial temperature is 25°C and the final temperature is 135°C. The temperature is increased by 5°C from the initial temperature of 25°C, and the DC resistance is measured at each temperature to determine the R n+5 and R n For example, if n is 90, R 95 / R 90is the ratio of the DC resistance at 95°C to the DC resistance at 90°C. For example, if ΔR1 is 100 Ω·cm / °C or more at any temperature within the temperature range of 25°C to 135°C, this means that the resistance of the copolymer increases relatively rapidly at any temperature within the temperature range.

[0098] The lower limit of ΔR1 may be about 100, 150, or 200, and the upper limit may be about 1,000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, or 200. The unit of ΔR1 is Ω·cm / °C. ΔR1 may be greater than or exceed any of the lower limits, or may be less than or equal to any of the upper limits but greater than or exceed any of the lower limits. Due to these characteristics, an electrode using the copolymer can ensure the stability of secondary batteries and the like under abnormal conditions.

[0099] The temperature at which ΔR1 is confirmed, i.e., R n The lower limit of the temperature in may be about 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C, and the upper limit may be about 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, 130°C, 110°C, 100°C, or 95°C. The temperature may be less than or equal to any of the upper limits mentioned above, or greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. The temperature is adjusted to a temperature at which an abnormal state occurs or there is a risk of an abnormal state occurring. When a copolymer exhibiting these properties is used, an electrode, an electrode assembly, or a secondary battery can maintain stable performance even when stored at a relatively high temperature under normal conditions and when charged and discharged at a high temperature, and can also ensure stability under abnormal conditions.

[0100] The copolymer may exhibit a characteristic in which ΔR2 in the following formula 2 is within a predetermined range.

[0101] [Formula 2] △R2=Max{(R z+5 / R z ) / 5}

[0102] In Equation 2, R z is the AC impedance resistance at any temperature n°C within the range of 25°C to 135°C, and R z+5 is the AC impedance resistance at a temperature ((n+5)°C) 5°C higher than the temperature n°C, and Max{(R z+5 / R z ) / 5} was confirmed within the temperature range of 25℃ to 135℃ (R z+5 / R z ) / 5 is the maximum value.

[0103] In Equation 2, ΔR2 is measured for a coin cell to which the copolymer is applied, and the specific method is described in "9. Measurement of maximum resistance change rate (AC impedance)" in the Examples. In the method for determining ΔR2, the initial temperature is 25°C and the final temperature is 135°C. The temperature is increased by 5°C from the initial temperature of 25°C, and AC impedance resistance is measured at each temperature to determine the R z+5 and R z For example, if n is 90, R 95 / R 90 is the ratio of the AC impedance resistance at 95°C to the AC impedance resistance at 90°C. For example, if ΔR2 is 10 Ω / °C or more at any temperature within the temperature range of 25°C to 135°C, this means that the resistance of the copolymer increases relatively rapidly at any temperature within the temperature range.

[0104] The lower limit of ΔR2 may be about 10, 12, 14, 16, 18, 20, 22, or 24, and the upper limit may be about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 24. The unit of ΔR2 is Ω / °C. ΔR2 may be less than or equal to any of the upper limits mentioned above, or greater than or equal to any of the lower limits mentioned above, or may be less than or equal to any of the upper limits but greater than or equal to any of the lower limits mentioned above. Due to these characteristics, an electrode using the copolymer can ensure the stability of a secondary battery under abnormal conditions.

[0105] The temperature at which ΔR2 in the above range is confirmed, i.e., R z The lower limit of the temperature in may be about 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C, and the upper limit may be about 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, 130°C, 120°C, 110°C, 100°C, or 95°C. The temperature may be less than or equal to any of the upper limits mentioned above, or greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. The temperature is adjusted to a temperature at which an abnormal state occurs or there is a risk of an abnormal state occurring. When a copolymer exhibiting these properties is used, an electrode, an electrode assembly, or a secondary battery can maintain stable performance even when stored at a relatively high temperature under normal conditions and when charged and discharged at a high temperature, and can also ensure stability under abnormal conditions.

[0106] The present specification discloses a current collector for an electrode or an electrode to which the copolymer is applied.

[0107] The electrode current collector may include a current collector body and a polymer layer formed on the body, and the polymer layer may include the copolymer described above.

[0108] The electrode current collector may be used to form an electrode. For example, an electrode formed using the electrode current collector may include the electrode current collector and an active material layer formed on a polymer layer of the current collector. Figure 1 shows an electrode in which an active material layer 300 is formed on the polymer layer 200 of the electrode current collector including the current collector body 100 and the polymer layer 200.

[0109] As shown in the drawings, in the current collector for an electrode or electrode, the current collector body 100 and the polymer layer 200, and the polymer layer 200 and the active material layer 300 may be in contact with each other, or other elements may be present between them. In addition, while the drawings show a case in which the active material layer 300 is present on only one side of the current collector body 100, the active material layer 300 may be present on both sides of the current collector body 100. In this case, two layers of polymer layer 200 may be present between the current collector body 100 and each of the active material layers 300 present on both sides of the current collector body 100, or one layer of polymer layer 200 may be present between the current collector body 100 and one of the active material layers 300 present on both sides.

[0110] The electrode formed from the electrode current collector may be an anode or a cathode applied to a secondary battery.

[0111] The polymer layer in the electrode current collector and electrode contains the copolymer described above, which allows stable operation or maintenance under normal conditions and ensures stability under abnormal conditions.

[0112] In the electrode, in order to more effectively achieve the above object, the relationship between the active material layer formed on the polymer layer or the electrode active material contained therein and the oxidation potential of the polymer layer or the copolymer contained therein may be adjusted.

[0113] For example, in the electrode, the oxidation potential of the active material layer or the electrode active material may be adjusted to be higher than the oxidation potential of the polymer layer or the copolymer.

[0114] For example, in the electrode, RV in the following formula 3 may be in a predetermined range.

[0115] [Formula 3] RV=100×Va / Vp

[0116] In Equation 3, Va is the oxidation potential of the electrode active material or active material layer, and Vp is the oxidation potential of the copolymer or polymer layer.

[0117] The oxidation potentials Va and Vp are the oxidation potentials of lithium and lithium ions (Li / Li + The method for measuring the oxidation potential Vp is described in "4. Method for measuring the oxidation potential of copolymers" in the Examples section of this specification, and the method for measuring the oxidation potential Va is described in "5. Method for measuring the oxidation potential of electrode active materials" in the Examples section of this specification.

[0118] The lower limit of RV in Equation 3 may be about 100.5, 101, 101.5, 102, 102.5, 103, 103.5, 104, or 104.5, and the upper limit may be about 200, 150, 145, 140, 135, 130, 125, 120, 115, 110, 109, 108, 107, 106, or 105. The RV may be greater than or equal to any of the lower limits, or less than or equal to any of the upper limits but greater than or equal to any of the lower limits.

[0119] The oxidation potential Va of the active material layer or the electrode active material is not particularly limited as long as it is within the range of RV in Formula 3. For example, the lower limit of the oxidation potential Va may be about 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9 V, 3 V, 3.1 V, 3.2 V, 3.3 V, 3.4 V, 3.5 V, 3.6 V, 3.7 V, 3.8 V, 3.9 V, or 4.0 V, and the upper limit may be about 5 V, 4.9 V, 4.8 V, 4.7 V, 4.6 V, 4.5 V, 4.4 V, 4.3 V, 4.2 V, or 4.1 V. The oxidation potential may be within a range equal to or less than any of the above upper limits, or equal to or greater than any of the above lower limits, or may be within a range equal to or less than any of the above upper limits but equal to or greater than any of the above lower limits.

[0120] The current collector for an electrode or the current collector body applied to an electrode is not particularly limited, and may be one that is normally used as a current collector body for a positive electrode or a negative electrode.

[0121] The type, size, and shape of the current collector body are not particularly limited as long as they are conductive and do not induce chemical changes in the device to which they are applied, such as a secondary battery. Examples of materials that can be used for the current collector body include copper, aluminum, stainless steel, nickel, titanium, and calcined carbon, as well as materials in which the surface of copper, aluminum, or stainless steel is surface-treated with carbon, nickel, titanium, or silver. The current collector body may be in the form of a film, sheet, foil, net, porous material, foam, nonwoven fabric, or the like, containing the above material. In some cases, the surface of the current collector body may be subjected to a known surface treatment to improve adhesion to other layers, such as a polymer layer or an active material layer.

[0122] Such a current collector body may generally have a thickness in the range of 3 μm to 500 μm, but is not limited to this.

[0123] As the active material layer, a layer that is usually applied may be used.

[0124] The active material layer typically contains an electrode active material. The specific type of the electrode active material is not particularly limited, and materials that typically form a positive electrode or a negative electrode may be used.

[0125] For example, when the active material layer is a positive electrode active material layer, the electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals, a lithium iron oxide such as LiFe3O4, or a compound having the chemical formula Li 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, or LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, V2O5, or Cu2V2O7, chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≦c2≦0.3). 2-c3 M c3 The oxide may be, but is not limited to, a lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn), a lithium nickel cobalt manganese (NCM) composite oxide, a lithium nickel cobalt manganese aluminum (NCMA) composite oxide, or LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion.

[0126] When the active material layer is a negative electrode active material layer, as the electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon, metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy, and SiO a (0 < a < 2), metal oxides capable of doping and undoping lithium such as SnO2, vanadium oxides, and lithium vanadium oxides, or composites containing the above metallic compounds and carbonaceous materials such as Si-C composites or Sn-C composites, etc. Among these, any one or a mixture of two or more thereof may be used.

[0127] As the negative electrode active material, a lithium thin film may be used, and as the carbon material, low-crystalline carbon and highly crystalline carbon may be used. Representative low-crystalline carbons are soft carbon and hard carbon, and representative highly crystalline carbons are amorphous, plate-like, scaly, spherical or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum and coal tar pitch coke.

[0128] The electrode active material may be contained in the active material layer within a range of about 40% to 99.5% by weight based on the total weight of the active material layer, but the ratio may be changed depending on the use and design of the electrode, etc.

[0129] The active material layer may further include a binder. The binder serves to improve adhesion between active materials and between the active material layer and the current collector body. Examples of the binder are not particularly limited and include, for example, poly(vinylidene fluoride) (PVDF), poly(vinyl alcohol) (PVA), styrene butadiene rubber (SBR), poly(ethylene oxide) (PEO), carboxyl methyl cellulose (CMC), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. One or more selected from the group consisting of sucrose, pullulan, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, and polyarylate may be used.

[0130] In one example, the binder may be contained in the active material layer in an amount ranging from 0.1 to 10 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0131] The active material layer may further contain a conductive material, if necessary. Any known conductive material may be used as the conductive material, as long as it does not induce chemical changes in the secondary battery and is conductive. For example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, gas black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes (CNTs); fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and / or conductive materials such as polyphenylene derivatives.

[0132] In one example, the conductive material may be contained in the active material layer in an amount of 0.1 to 20 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0133] The active material layer may further contain any necessary known components in addition to the components described above.

[0134] The polymer layer present on the current collector body may include the copolymer. The polymer layer may be composed solely of the copolymer, or may further contain any other necessary additives. The use of the copolymer may effectively form a desired electrode. In one example, the lower limit of the copolymer content in the polymer layer may be approximately 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt%, and the upper limit may be approximately 100 wt%, 95 wt%, 90 wt%, or 85 wt%, based on the total weight of the polymer layer. The percentages are based on the total weight of the polymer layer. The range of the ratio may be within a range equal to or less than any of the upper limits mentioned above, or within a range equal to or greater than any of the lower limits mentioned above, or within a range equal to or less than any of the upper limits mentioned above but equal to or greater than any of the lower limits mentioned above.

[0135] The thickness of the polymer layer may be appropriately controlled depending on the purpose. For example, the lower limit of the thickness may be approximately 10 nm, 50 nm, 100 nm, 150 nm, or 200 nm, and the upper limit may be approximately 2 μm, 1.5 μm, 1 μm, 950 nm, 900 nm, 850 nm, 800 nm, 750 nm, 700 nm, 650 nm, 600 nm, 550 nm, 500 nm, 450 nm, 400 nm, 350 nm, or 300 nm. The thickness may be less than or equal to any of the upper limits, greater than or equal to any of the lower limits, or less than or equal to any of the upper limits but greater than or equal to any of the lower limits. The thickness may be measured by the method described in "3. Thickness Measurement" in the Examples section of this specification.

[0136] The present specification further discloses a method for producing the electrode current collector or electrode.

[0137] A method for manufacturing a current collector for an electrode of the present application may include a step of forming the polymer layer on the current collector body, and a method for manufacturing the electrode may include a step of forming the active material layer on the polymer layer.

[0138] The method for forming the polymer layer on the current collector body is not particularly limited. For example, the polymer layer may be formed by preparing a coating solution by diluting the conductive polymer and, if necessary, other additives in an appropriate solvent, coating the coating solution on the current collector, and then drying the coating solution.

[0139] In another example, the polymer layer may be formed by directly polymerizing the monomer that forms the conductive polymer on the current collector body.

[0140] The preparation and coating method of the coating composition for forming the polymer layer are not particularly limited, and known coating methods may be used. Furthermore, the method for polymerizing the conductive polymer is also not particularly limited, and known methods may be used. For example, methods using oxidative polymerization reactions and radical reactions are typically known for preparing polythiophene, and these methods may also be used in the process of forming the conductive polymer in the present application.

[0141] The prepared coating composition may be used to form a polymer layer on a current collector body. This process may typically include coating the coating composition on the current collector body and heat-treating the coated coating composition. In this process, the properties of the polymer layer may be controlled by the conditions of the heat treatment.

[0142] For example, the temperature T of the heat treatment and / or the time H of the heat treatment may be adjusted.

[0143] For example, the lower limit of the temperature T may be about 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, and the upper limit may be about 300°C, 295°C, 290°C, 285°C, 280°C, 275°C, 270°C, The temperature may be about 265°C, 260°C, 255°C, 250°C, 245°C, 240°C, 235°C, 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, 200°C, 195°C, 190°C, 185°C, 180°C, 175°C, 170°C, 165°C, 160°C, 155°C, 150°C, 145°C, 140°C, 135°C, or 130°C. The temperature may be less than or equal to any of the upper limits mentioned above, greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. Within this range, the alignment state of the hydrocarbon groups of the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0144] To achieve this, the product (T×H) of the heat treatment temperature T and the time H may be adjusted. For example, the lower limit of the product (T×H) of the heat treatment temperature T and the time H may be 0.01°C·hour, 0.05°C·hour, 0.1°C·hour, 0.2°C·hour, 0.3°C·hour, 0.5°C·hour, 1°C·hour, 5°C·hour, 10°C·hour, 15°C·hour, 20°C·hour, 25°C·hour, 30°C·hour, 35°C·hour, 40°C·hour, 45°C·hour, 50°C·hour, 75°C·hour, 100°C·hour, 110°C·hour, 120°C·hour, or 130°C·hour. The upper limit is 100000°C·hour, 95000°C·hour, 90000°C·hour, 85000°C·hour, 80000°C·hour, 75000°C·hour, 70000°C·hour, 65000°C·hour, 60000°C·hour, 55000°C·hour, 50000°C·hour, 45000°C·hour, 40000°C·hour, 35000°C·hour, 30000°C·hour, 25000°C·hour, 20000°C·hour, 15000°C·hour, 10000℃・hour, 9500℃・hour, 9000℃・hour, 8500℃・hour, 8000℃・hour, 7500℃・hour, 7000℃・hour, 6500℃・hour, 6000℃・hour, 5500℃・hour, 5000℃・h our, 4500℃・hour, 4000℃・hour, 3500℃・hour, 3000℃・hour, 2500℃・hour, 2000℃・hour, 1500℃・hour, 1400℃・hour, 1300℃・hour, 1200℃・hour, 1100 ℃・hour, 1000℃・hour, 900℃・hour, 800℃・hour, 700℃・hour, 600℃・hour, 500℃・hour, 400℃・hour, 300℃・hour, 200℃・hour, 100℃・hour, 90℃・hour, 8 It may be about 0°C·hour, 70°C·hour, 60°C·hour, 50°C·hour, 45°C·hour, 40°C·hour, 35°C·hour, 30°C·hour, 25°C·hour, 20°C·hour, 15°C·hour or 10°C·hour.The product (T×H) may be within a range of less than or equal to any of the upper limits mentioned above, or greater than or equal to any of the lower limits mentioned above, or may be within a range of less than or equal to any of the upper limits but greater than or equal to any of the lower limits mentioned above. Within such a range, the alignment state of the hydrocarbon groups in the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0145] To more effectively ensure the desired properties, the heat treatment may be carried out in two stages.

[0146] For example, the heat treatment may include a step of first heat treating the coating composition at a first temperature T1 for a first time H1 and a step of second heat treating the coating composition at a second temperature T2 for a second time H2, in which the temperatures T1 and T2 are different from each other and / or the times H1 and H2 are different from each other.

[0147] For example, the lower limit of the temperature T1 may be about 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, and the upper limit may be about 300°C, 295°C, 290°C, 285°C, 280°C, 275°C, The temperature may be about 270°C, 265°C, 260°C, 255°C, 250°C, 245°C, 240°C, 235°C, 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, 200°C, 195°C, 190°C, 185°C, 180°C, 175°C, 170°C, 165°C, 160°C, 155°C, 150°C, 145°C, or 140°C. The temperature may be less than or equal to any of the upper limits mentioned above, greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. Within this range, the alignment state of the hydrocarbon groups of the conductive copolymer can be appropriately adjusted, thereby ensuring desired properties.

[0148] For example, the lower limit of the product (T1 × H1) of the temperature T1 and the time H1 of the primary heat treatment may be about 0.01°C·hour, 0.05°C·hour, 0.1°C·hour, 0.2°C·hour, 0.3°C·hour, 1°C·hour, 2°C·hour, 3°C·hour, 4°C·hour, 5°C·hour, 6°C·hour, 7°C·hour, 8°C·hour, or 9°C·hour, and the upper limit may be about 1000°C·hour, 900°C·hour, 800°C·hour, or 1000°C·hour. The product (T1 × H1) may be about 1 / hour, 700°C·hour, 600°C·hour, 500°C·hour, 400°C·hour, 300°C·hour, 200°C·hour, 100°C·hour, 90°C·hour, 80°C·hour, 70°C·hour, 60°C·hour, 50°C·hour, 45°C·hour, 40°C·hour, 35°C·hour, 30°C·hour, 25°C·hour, 20°C·hour, 15°C·hour, or 10°C·hour. The product (T1 × H1) may be less than or equal to any of the upper limits mentioned above, greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. Within this range, the alignment state of the hydrocarbon groups of the conductive copolymer can be appropriately adjusted, thereby ensuring desired properties.

[0149] For example, the lower limit of the heat treatment temperature T2 of the second heat treatment may be about 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, or 130°C, and the upper limit may be about 300°C, 295°C, 290°C, 285°C, 280°C, 275°C, 275°C, 28 ... The temperature may be about 0°C, 265°C, 260°C, 255°C, 250°C, 245°C, 240°C, 235°C, 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, 200°C, 195°C, 185°C, 180°C, 175°C, 170°C, 165°C, 160°C, 155°C, 150°C, 145°C, 140°C, 135°C, or 130°C. The temperature may be less than or equal to any of the upper limits mentioned above, greater than or equal to any of the lower limits mentioned above, or less than or equal to any of the upper limits mentioned above but greater than or equal to any of the lower limits mentioned above. Within this range, the alignment state of the hydrocarbon groups of the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0150] The product of the second heat treatment temperature T2 and the time H2 (T2×H2) may be adjusted. For example, the lower limit of the product of the heat treatment temperature T and time H (T2 × H2) may be about 10°C·hour, 15°C·hour, 20°C·hour, 25°C·hour, 30°C·hour, 35°C·hour, 40°C·hour, 45°C·hour, 50°C·hour, 75°C·hour, 100°C·hour, 110°C·hour, 120°C·hour, or 130°C·hour, and the upper limit may be about 1000°C·hour, 900°C·hour, 800°C·hour, 700°C·hour, 600°C·hour, 500°C·hour, 400°C·hour, 300°C·hour, 200°C·hour, 180°C·hour, 160°C·hour, 150°C·hour, 145°C·hour, 140°C·hour, 135°C·hour, or 130°C·hour. The product (T2 × H2) may be within a range of less than or equal to any of the upper limits mentioned above, or greater than or equal to any of the lower limits mentioned above, or may be within a range of less than or equal to any of the upper limits but greater than or equal to any of the lower limits mentioned above. Within such a range, the alignment state of the hydrocarbon groups in the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0151] In this case, the lower limit of the ratio T1 / T2 of the temperature T1 of the first heat treatment to the temperature T2 of the second heat treatment may be about 0.1, 0.3, 0.5, 0.7, 0.9, 0.95, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, or 1.07, and the upper limit may be about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, or 1.1. The ratio T1 / T2 may be less than or equal to any of the above upper limits, greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits. Within this range, the alignment state of the hydrocarbon groups of the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0152] In this case, the lower limit of the ratio H2 / H1 of the time H1 of the first heat treatment to the time H2 of the second heat treatment may be about 0.5, 1, 3, 5, 7, 9, 10, 11, 12, 13, 14, 14.5, or 15, and the upper limit may be about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15.5, or 15. The ratio H2 / H1 may be less than or equal to any of the above upper limits, greater than or equal to any of the above lower limits, or less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits. Within this range, the alignment of hydrocarbon groups in the conductive copolymer can be appropriately controlled, thereby ensuring desired properties.

[0153] In the manufacturing process, a post-process such as an appropriate drying process may be further carried out after the coating and / or polymerization process.

[0154] There is no particular limitation on the method for forming the active material layer on the polymer layer. Typically, the active material layer is formed by coating a slurry containing the electrode active material, a binder, and a conductive material on a current collector (on the polymer layer), drying the coating, and then rolling the coating. Such a known method may also be applied to the present application.

[0155] The present specification further discloses an electrode assembly or an electrochemical device, such as a secondary battery, that includes the electrode. [Effects of the Invention]

[0156] This specification discloses a copolymer and its uses. The copolymer can exhibit a tailored positive temperature coefficient (PTC) effect and oxidation potential. Such a conductive copolymer exhibits excellent electrical properties, such as low resistance, under normal conditions, and can form electrode current collectors, electrodes, and secondary batteries containing the same that do not affect, but rather improve, the performance and operation of secondary batteries and ensure stability under abnormal conditions. This specification further discloses uses of the copolymer. [Brief explanation of the drawings]

[0157] FIG. 1 is a cross-sectional view of an exemplary electrode of the present application. FIG. 2 shows the results of NMR analysis of the monomer produced in the production example. DETAILED DESCRIPTION OF THE INVENTION

[0158] The copolymers disclosed herein will be described in more detail with reference to the following examples and comparative examples, but the scope of the copolymers is not limited to the following examples.

[0159] 1.NMR analysis method 11H-NMR analysis was performed at room temperature (about 25 °C) using an NMR spectrometer including a Bruker UltraShield spectrometer (300 MHz) with a triple resonance 5 mm probe. The sample was diluted in an NMR measurement solvent (CDCl3) at a concentration of about 10 mg / ml and used, and the chemical shift was expressed in ppm.

[0160] 2. GPC (Gel Permeation Chromatograph) The molecular weight characteristics were measured using GPC (Gel permeation chromatography). The sample was placed in a 5 mL vial and diluted with chloroform to a concentration of about 1 mg / mL. Then, the calibration standard sample and the sample to be analyzed were filtered through a syringe filter (pore size: 0.45 μm) and then measured. The analysis program used Empower3 from Waters. The elution time of the sample was compared with the calibration curve to determine the weight average molecular weight (Mw) and the number average molecular weight (Mn) respectively, and the molecular weight distribution (PDI) was calculated by the ratio (Mw / Mn). The measurement conditions of GPC are as follows.

[0161] <GPC measurement conditions> Equipment: 2414 from Waters Columns: Three Styragel columns from Waters were used Solvent: THF (Tetrahydrofuran) Column temperature: 35 °C Sample concentration: 1 mg / mL, 1 μL injection Standard sample: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940, 485)

[0162] 3. Measurement of thickness The thickness of the polymer layer was measured by cross-sectioning the electrode using an ion milling device (Hitachi, IM5000) and then capturing images with a scanning electron microscope (SEM) (JEOL, JSM-7200F). The conditions for cross-section formation by ion milling were set as follows: the device was in cross-section milling mode, the speed (reciprocation / min) was 3, the acceleration voltage was 6.0 kV, the discharge voltage was 15 kV, the current was 150 μA, and the time was 4 hours.

[0163] 4.Method for measuring the oxidation potential of copolymers The oxidation potential of the copolymer was measured by the following method. A layer (hereinafter referred to as the polymer layer) with a thickness of approximately 10 μm was formed on an aluminum foil (Al Foil) with a thickness of approximately 15 μm using the copolymer to be measured for its oxidation potential. The polymer layer was formed by coating a coating solution prepared by dispersing the copolymer in a solvent (Chloroform) at a concentration of approximately 2.0 wt% onto the aluminum foil using a bar coating method, and then by holding the solution at 140°C for approximately 4 minutes and then at 130°C for approximately 60 minutes.

[0164] A separator and a lithium film were then laminated on the polymer layer to produce a laminate of aluminum foil / polymer layer / separator / lithium film, and the laminate was punched into a circle with a diameter of approximately 1.4 cm. A coin cell was fabricated using the punched-out circle and electrolyte (a Wellcose CR2032 coin cell kit was used).

[0165] The separator used was a WL20C model manufactured by Double U Scope Korea, the lithium film used was a film with a thickness of approximately 100 μm, and the electrolyte used was a 1M LIPF6 solution (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethylmethyl carbonate) manufactured by Enchem.

[0166] The oxidation potential of the coin cell was measured using an electrochemical potentiostat (Princeton Applied Research, PARASTAT-MC) at 25° C. Cyclic voltammetry (CV) was measured at a scan rate of 0.17 mV / sec to 0.5 mV / sec in the range of 1.5 V to 5.5 V.

[0167] The oxidation potential is the ratio of lithium to lithium ions (Li / Li + ) was measured as a standard.

[0168] 5.Method for measuring the oxidation potential of electrode active materials The oxidation potential of the electrode active material was measured by the following method.

[0169] An electrode active material layer was formed on an aluminum foil (Al Foil) with a thickness of approximately 15 μm. The active material layer was formed using a slurry. The slurry was prepared by blending an electrode active material, a conductive material (ECP (Ketjen Black) 0.5%, SFG (Trimrex graphite) 0.4%, DB (Denka Black) 0.4%), PVDF (poly(vinylidene fluoride)), and NMP (N-Methyl-2-pyrrolidone) in a weight ratio of 100:16:6:100 (electrode active material: conductive material: PVDF: NMP). The slurry was applied to the aluminum foil with a doctor blade, dried at room temperature (approximately 25°C), and then placed in a drying oven at 130°C for approximately 30 minutes. The mixture was then rolled to form an active material layer with a thickness of approximately 50 to 70 μm.

[0170] The electrode active material used was the electrode active material whose oxidation potential was to be measured. A separator and a lithium film were laminated on the active material to produce a laminate consisting of aluminum foil / active material layer / separator / lithium film. The laminate was then punched into a circle with a diameter of approximately 1.4 cm. A coin cell was fabricated using the punched-out circle and electrolyte (a Wellcose CR2032 coin cell kit was used).

[0171] The separator used was a WL20C model manufactured by Double U Scope Korea, the lithium film used was a film with a thickness of approximately 100 μm, and the electrolyte used was a 1M LIPF6 solution (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethylmethyl carbonate) manufactured by Enchem.

[0172] The oxidation potential of the coin cell was measured using an electrochemical measuring instrument (potentiostat) (manufacturer: Princeton Applied Research, product name: PARASTAT-MC) at 25° C. The oxidation potential was measured by measuring cyclic voltammetry (CV) at a scan rate of 0.17 mV / sec to 0.5 mV / sec in the range of 1.5 V to 5.5 V.

[0173] 6.DC resistance measurement method The DC resistance was evaluated using the same coin cell as used in "4. Method for Measuring the Oxidation Potential of the Copolymer" above. A voltage of 4.3 eV was applied to the coin cell at room temperature (25°C) for 10 minutes, and the DC resistance was measured using a Fluke digital multitester (FLUKE-87-5).

[0174] 7.Interface resistance (AC impedance resistance) The interfacial resistance was evaluated by EIS (Electrochemical Impedance Spectroscopy) using the same coin cell as used in "4. Method for Measuring the Oxidation Potential of the Copolymer" above. A voltage of 4.3 V was applied to the coin cell at room temperature (25°C) for 10 minutes, and the interfacial resistance in the high frequency region was measured using a Nyquist plot obtained by EIS measurement at frequencies from 50,000 Hz to 0.1 Hz. The EIS measurement equipment used was an electrochemical analyzer (Pontentiostat) (Princeton Applied Research, PARASTAT-MC).

[0175] 8. Measurement of maximum resistance change rate (DC resistance) The maximum resistance change rate ΔR1 is determined by the following formula 1.

[0176] [Formula 1] △R1=Max{(R n+5 / R n ) / 5}

[0177] The ΔR1 is measured by the following method.

[0178] The coin cell for measuring DC resistance (the coin cell used in "6. DC Resistance Measurement Method" above) was placed in the center of a convection oven (JOTECH, OF3-05W), and the oven temperature was set to increase at a rate of 5°C per minute from an initial temperature of 25°C to a final temperature of 135°C. The coin cell was connected to a resistance measurement multimeter (Fluke digital multitester (FLUKE-87-5)) outside the oven to enable resistance measurement. Next, the DC resistance was measured at each temperature as the temperature was increased as set. That is, the DC resistance is measured at 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, and 130°C. Each temperature is held for 1 minute according to the settings, and the DC resistance is measured after 1 minute has elapsed at that temperature. The DC resistance at each temperature is calculated using the R n The DC resistance at a temperature 5°C higher than the temperature in question is R n+5 Of the measured DC resistances, the DC resistances at 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ and 125℃ are R n 21 values ​​of (R n+5 / R n ) / 5, and then the maximum value is used as Max{(R n+5 / R n ) / 5}(=△R1), and the maximum value of (R n+5 / R n The temperature n°C at ) / 5 is the On-Set temperature.

[0179] 9. Measurement of maximum resistance change rate (AC impedance) The maximum resistance change rate ΔR2 is determined by the following formula 2.

[0180] [Formula 2] △R2=Max{(R z+5 / R z ) / 5}

[0181] △R2 is measured using the following method.

[0182] The coin cell for measuring AC impedance resistance (the coin cell used in "7. Interface Resistance (AC Impedance Resistance)" above) was placed in the center of a convection oven (JOTECH, OF3-05W), and the oven temperature was set to increase from an initial temperature of 25°C to a final temperature of 135°C at a rate of 5°C per minute. The coin cell was connected to a resistance meter (the meter used in "6. Interface Resistance (AC Impedance Resistance)" above) outside the oven to enable resistance measurement. Next, the temperature was increased as set, and the AC impedance resistance was measured at each temperature. That is, the AC impedance resistance is measured at each of the following temperatures: 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, and 130°C. Each temperature is held for one minute according to the settings, and the AC impedance resistance is measured after one minute has elapsed at that temperature.

[0183] The AC impedance resistance at each temperature is R z The AC impedance resistance at a temperature 5°C higher than the target temperature is R z+5 Of the measured AC impedance resistances, the AC impedance resistances at 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ and 125℃ are R z The temperature range of 25℃ to 130℃ is 21 values ​​(R z+5 / R z ) / 5, and then the maximum value is used as Max{(R z+5 / Rz ) / 5}(=△R2), and the maximum value of (R z+5 / R z The temperature z°C at ) / 5 is the On-Set temperature.

[0184] The AC impedance resistance was determined as the resistance obtained in a semicircle in the high frequency region of a Nyquist plot obtained by applying a voltage of 4.3 V for 10 minutes and using an EIS measurement method at 50,000 Hz to 0.1 Hz.

[0185] Production Example 1. Synthesis of Monomer (A) Monomer (A) of the following chemical formula A was synthesized by the following method.

[0186] [ka]

[0187] 1.372 g (12.02 mmol, 1 eq) of 3-methoxythiophene and 3 g (16.83 mmol, 1.4 eq) of triethylene glycol monomethyl ether were dissolved in 100 ml of toluene and mixed with 230 mg of p-toluenesulfonic acid (p-TsOH). The mixture was refluxed at 120 °C for transetherification, and the resulting methanol was removed using a 4A molecular sieve filter packed in a soxhlet extractor. After refluxing for 24 hours, the reaction mixture was quenched with water, extracted with ethyl acetate, washed with brine, and dried over magnesium sulfate (MgSO). The solvent was removed using a rotary evaporator, and the residue was purified by column chromatography eluting with methylene chloride / hexane (2:1) to obtain the target compound (Monomer (A)). Figure 2 shows the NMR analysis results for the monomer.

[0188] Production Example 2: Synthesis of conductive copolymer (A) To a solution prepared by dissolving 3.20 g (19.71 mmol, 3 eq) of iron (III) chloride in 150 ml of methylene chloride, 0.7 g (2.96 mmol, 0.6 eq) of 3-dodecylthiophene, 0.3 g (1.48 mmol, 0.3 eq) of 3-hexylthiophene, 0.12 g (0.49 mmol, 0.1 eq) of Monomer (A) of Production Example 1, and 0.37 g (1.64 mmol, 0.3 eq) of pyrrole were added, and the mixture was polymerized at 25°C for 24 hours to synthesize a conductive copolymer (A). In the conductive copolymer (A), the molar ratio of the 3-dodecylthiophene unit (I), the 3-hexylthiophene unit (II), the monomer (A) unit (III) of Production Example 1, and the pyrrole unit (IV) was 2.96:1.48:0.49:1.23 (I:II:III:IV).

[0189] The polymerization solution was poured into a permeation membrane with a molecular weight cut-off (MWCO) of 5000, which was then immersed in 200 ml of acetonitrile to remove unreacted iron chloride and monomer. The residue deposited inside the permeation membrane was washed with methanol and dried at 60°C for 12 hours to obtain conductive copolymer (A). The weight-average molecular weight (Mw) and water-average molecular weight (Mn) of conductive copolymer (A) were approximately 99,000 g / mol and 28,000 g / mol, respectively, and the oxidation potential was approximately 3.95 V.

[0190] Production Example 3: Synthesis of conductive copolymer (B) 0.41 g (1.97 mmol, 0.6 eq) of 3-dodecylthiophene, 0.24 g (0.98 mmol, 0.3 eq) of 3-hexylthiophene, 0.1 g (0.33 mmol, 0.1 eq) of Monomer (A) of Production Example 1, and 0.74 g (3.28 mmol, 0.3 eq) of pyrrole were added to a solution prepared by dissolving 3.20 g (19.71 mmol, 3 eq) of iron (III) chloride in 150 ml of methylene chloride, and the mixture was polymerized at 25°C for 24 hours to synthesize a conductive copolymer (B). In the conductive copolymer (B), the molar ratio of the 3-dodecylthiophene unit (I), the 3-hexylthiophene unit (II), the unit (III) of the monomer (A) of Production Example 1, and the pyrrole unit (IV) was 1.97:0.98:0.33:3.28 (I:II:III:IV).

[0191] The polymerization solution was poured into a permeation membrane with a molecular weight cut-off (MWCO) of 5000, which was then immersed in 200 ml of acetonitrile to remove unreacted iron chloride and monomer. The residue deposited inside the permeation membrane was washed with methanol and dried at 60°C for 12 hours to obtain conductive copolymer (B). The weight-average molecular weight (Mw) and water-average molecular weight (Mn) of conductive copolymer (B) were approximately 102,000 g / mol and 25,000 g / mol, respectively, and the oxidation potential was approximately 3.90 V.

[0192] Production Example 4: Synthesis of conductive copolymer (C) 3.20 g (19.71 mmol, 3 eq) of iron(III) chloride was dissolved in 150 ml of methylene chloride, and 1 g (3.94 mmol, 0.6 eq) of 3-dodecylthiophene, 0.33 g (1.97 mmol, 0.3 eq) of 3-hexylthiophene, and 0.16 g (0.66 mmol, 0.1 eq) of Monomer (A) of Preparation Example 1 were added to the solution and polymerized at 30°C for 24 hours to produce a conductive copolymer (C). In the conductive copolymer (C), the molar ratio of the 3-dodecylthiophene unit (I), the 3-hexylthiophene unit (II), and the unit (III) of the monomer (A) of Production Example 1 is about 3.94:1.97:0.66 (I:II:III).

[0193] The polymerization solution was poured into a membrane with a molecular weight cut-off (MWCO) of 5000, which was then immersed in 200 ml of acetonitrile to remove unreacted iron(III) chloride, monomers, and low-molecular-weight oligomers. The residue precipitated inside the membrane was washed with methanol and dried at 60°C for 12 hours to obtain conductive copolymer (C).

[0194] The weight average molecular weight (Mw) and water average molecular weight (Mn) of the conductive copolymer (C) were 118,000 g / mol and 24,500 g / mol, respectively, and the oxidation potential was about 4.04V.

[0195] Example 1 An aluminum foil with a thickness of approximately 15 μm was used as the current collector layer. A coating solution was prepared by dispersing copolymer (A) from Preparation Example 2 in a solvent (chloroform) at a concentration of approximately 2.0 wt %. The coating solution was coated onto the current collector layer using a bar coating method. The current collector layer with the coating layer formed thereon was then placed in a drying oven at 140°C for approximately 4 minutes, and then again at approximately 130°C for 1 hour to form a layer (polymer layer) with a thickness of approximately 200 nm.

[0196] Next, an active material layer was formed on the polymer layer. The active material layer was formed using a slurry. The slurry was prepared by blending an electrode active material, a conductive material (ECP (Ketjen Black) 0.5%, SFG (Trimrex graphite) 0.4%, DB (Denka Black) 0.4%), PVDF (poly(vinylidene fluoride)), and NMP (N-Methyl-2-pyrrolidone) in a solids ratio of 100:16:6:100 (electrode active material: conductive material: PVDF: NMP). The slurry was applied to the polymer layer using a doctor blade, dried at room temperature, and then placed in a drying oven at 130°C for approximately 30 minutes. The layer was then rolled to a thickness of approximately 60 μm.

[0197] The electrode active material is an NCM-based positive electrode active material (Li[NiO .8 Co 0.1 Mn 0.1 ]O2) was used, and the oxidation potential of the active material was about 4.08V.

[0198] Example 2. An electrode was prepared in the same manner as in Example 1, except that the copolymer (B) of Preparation Example 3 was used instead of the copolymer (A) of Preparation Example 2.

[0199] Comparative Example 1 An electrode was prepared in the same manner as in Example 1, except that the copolymer (C) of Preparation Example 4 was used instead of the copolymer (A) of Preparation Example 2.

[0200] Test example 1. Charge / discharge test Charge-discharge tests were conducted by fabricating coin cells. The coin cells were fabricated using a CR2032 standard coin cell kit (Wellcourse CR2032 coin cell kit). When fabricating the coin cells, the electrode fabricated in the example or comparative example was used as the positive electrode, and a lithium film (thickness: approximately 100 μm) was used as the negative electrode. The electrolyte was a 1M LiPF6 solution (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethylmethyl carbonate) manufactured by Enchem, and the separator was a PE (poly(ethylene)) separator (WU Scope Korea, WL20C model).

[0201] A charge-discharge test was conducted using the coin cell at room temperature (approximately 25°C). The coin cell was charged and discharged at a rate of 0.1C using a CC (Constant Current) / CV (Constant Voltage) method with a charge cut-off voltage of 4.5V and a charge cut-off current of 1mA, and the initial capacity was measured. The results are summarized in the 0.1C / 0.1C initial capacity column in Table 1 below. In this column, Ch means charge and Dch means discharge.

[0202] Next, the coin cell was charged at a rate of 0.5C using the CC (Constant Current) / CV (Constant Voltage) method with a charge cut-off voltage of 4.5V and a charge cut-off current of 1mA, and the capacity change was measured while discharging at 0.1C, 0.5C, 1C, and 2C.

[0203] The results are summarized in the 0.5C Ch (0.5C charging) section of Table 1 below. In this section, 0.1C Dch, 0.5C Dch, 1C Dch, and 2C Dch are the capacities measured while discharging the coin cell charged at 0.5C at 0.1C, 0.5C, 1C, and 2C conditions.

[0204] [Table 1]

[0205] In Table 1, Ref. is an electrode manufactured in the same manner as Example 1, except that the active material layer was formed directly on the current collector without forming a polymer layer as in Example 1. Looking at the results in Table 1, it can be seen that the initial capacities of Examples 1 and 2 and Comparative Example 1 were all at the same level as Ref. However, in the case of Comparative Example 1, it can be seen that the faster the discharge rate in the charge-discharge test, the greater the decrease in capacity.

[0206] On the other hand, in Examples 1 and 2, no decrease in capacity was observed even when the discharge rate increased, and rather a high capacity was confirmed relative to Ref.

[0207] Therefore, it can be confirmed that the electrodes of Examples 1 and 2 can be stably driven in a normal state.

[0208] Test example 2. PTC effect test The results of evaluation of the DC resistance, interface resistance, etc. for Example 1 are shown in Table 2 below.

[0209] [Table 2]

[0210] From Table 2, it can be seen that both the Examples and Comparative Examples exhibited appropriate PTC effects. However, in the case of Comparative Example 1, as in the results of Test Example 1, an undesirable increase in the resistance of the SFL occurred during discharge, making stable operation under normal conditions difficult. [Explanation of symbols]

[0211] 100 Current collector body 200 polymer layer 300 active material layer

Claims

1. A copolymer comprising a thiophene unit and a unit of the following formula 3: 【Chemical 1】 In Chemical Formula 3, R ５ , R ６ and R ７ are each independently hydrogen, a polar functional group, or a hydrocarbon functional group.

2. The copolymer according to claim 1, wherein the polar functional group is a carboxyl group, a hydroxyl group, an amino group, a cyano group, a nitro group, an ether group, or a functional group of the following chemical formula 4, and the hydrocarbon functional group is an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylcarbonyl group, or an alkylcarbonyloxy group: 【Chemistry 2】 In Chemical Formula 4, L ３ is a single bond, an alkylene group, or an alkylidene group, and L ４ is an alkylene group or an alkylidene group, and R ８ is hydrogen or an alkyl group, and n is a number in the range of 1-10.

3. 2. The copolymer according to claim 1, having an oxidation potential of 4.00 V or less with respect to lithium.

4. The copolymer according to claim 1 , wherein the thiophene units include thiophene units having a hydrocarbon functional group.

5. The copolymer according to claim 1 , comprising, as the thiophene units, a first thiophene unit having a hydrocarbon functional group with 10 or more carbon atoms and a second thiophene unit having a hydrocarbon functional group with 9 or less carbon atoms.

6. 6. The copolymer of claim 5, wherein the hydrocarbon functional group of the first or second thiophene unit is a linear or branched alkyl, alkenyl, or alkynyl group.

7. The copolymer according to claim 5 , wherein the ratio of the total number of moles of the first and second thiophene units is 30 mol % or more.

8. 6. The copolymer according to claim 5, wherein a ratio M2 / M1 of the number of moles M2 of the second thiophene units to the number of moles M1 of the first thiophene units is in the range of 0.01 to 100.

9. The copolymer according to claim 4 , further comprising, as the thiophene units, thiophene units having a polar functional group.

10. 10. The copolymer of claim 9, comprising 1 mole to 500 moles of thiophene units having a hydrocarbon functional group per mole of thiophene units having a polar functional group.

11. The copolymer according to claim 1, comprising the unit of Chemical Formula 3 in a ratio of 1 to 90 mol %.

12. 2. The copolymer of claim 1, having a DC resistivity of 10,000 Ω·cm or less.

13. 10. The copolymer of claim 1, having an AC impedance resistance of 1,000 ohms or less.

14. ΔR1 in the following formula 1 is 100 Ω·cm / °C or more, and the temperature R at which ΔR1 of 100 Ω·cm / °C or more is confirmed ｎ The copolymer according to claim 1, wherein the temperature is 80°C or higher. [Formula 1] △R1=Max{(R ｎ＋５ / R ｎ ) / 5} In Formula 1, R ｎ is the DC resistance at any temperature n°C in the range of 25°C to 135°C, and R ｎ＋５ is the DC resistance at a temperature ((n+5) ° C) 5 ° C higher than the temperature n ° C, and Max{(R ｎ＋５／ R ｎ ) / 5} was confirmed within the temperature range of 25°C to 135°C (R ｎ＋５ / R ｎ ) / 5 values.

15. The copolymer according to claim 1, wherein ΔR2 in the following formula 2 is 10Ω / °C or more, and the temperature at which ΔR2 of 10Ω / °C or more is confirmed is 80°C or more: [Formula 2] △R2=Max{(R ｚ＋５ / R ｚ ) / 5} In Formula 2, R ｚ is the AC impedance resistance at any temperature n°C in the range of 25°C to 135°C, and R ｚ＋５ is the AC impedance resistance at a temperature ((n+5) ° C) 5 ° C higher than the temperature n ° C, and Max{(R ｚ＋５ / R ｚ ) / 5} was confirmed within the temperature range of 25°C to 135°C (R ｚ＋５ / R ｚ ) / 5 values.

16. A current collector body; A current collector for an electrode, comprising: a polymer layer formed on the current collector body and comprising the copolymer according to any one of claims 1 to 15.

17. A current collector body; an active material layer formed on the current collector body and containing an electrode active material; An electrode having a polymer layer formed between the current collector body and the active material layer, the polymer layer containing the copolymer according to any one of claims 1 to 15.

18. 18. The electrode according to claim 17, wherein RV of the following formula 3 is greater than 100: [Formula 3] RV=100×Va / Vp In Equation 3, Va is the oxidation potential of the electrode active material, and Vp is the oxidation potential of the copolymer or polymer layer.

19. An electrode assembly comprising the electrode of claim 17.

20. A secondary battery comprising the electrode of claim 17.

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