electrode

Abstract

This specification discloses an electrode and its uses. The electrode includes a polymer layer that exhibits a purposefully controlled PTC (positive temperature coefficient) effect and oxidation potential. Under normal conditions, such an electrode exhibits excellent electrical properties, such as low resistance, and does not affect or even improves the performance and operation of a secondary battery, while ensuring stability under abnormal conditions. This specification also discloses uses of the electrode.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0135150, dated October 19, 2022, the entire contents of which are incorporated herein by reference.

[0002] This specification discloses an electrode and its 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 speed of mobile devices such as mobile phones and tablets increases 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 to combat global warming and air pollution, major automakers are also developing a variety of electric vehicles, and the importance of secondary batteries, which have high energy density, high discharge voltage, and output stability as the 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., is also increasing in devices and automobiles that use secondary batteries as their energy source.

[0007] The main cause of such accidents is known to be a short circuit, which occurs when the positive and negative electrodes inside the electrode assembly come into direct contact due to an external stimulus.When a secondary battery is overcharged, exposed to high temperatures, or exposed to 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 are in 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 an electrode and its uses. It is an object of this specification to disclose an electrode including a polymer layer that exhibits a tailored PTC (positive temperature coefficient) effect and oxidation potential. Under normal conditions, such an electrode exhibits excellent electrical properties, such as low resistance, and does not affect or even improves the performance and operation of a secondary battery, while ensuring stability under abnormal conditions. It is also an object of this specification to disclose uses of the electrode. [Means for solving the problem]

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

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

[0012] Unless otherwise specified, temperatures are given in degrees Celsius (°C) herein.

[0013] As used herein, the term "normal pressure" refers to natural pressure without pressure or decompression, and typically refers to a pressure of about 730 mmHg to 790 mmHg. When the measurement pressure affects a physical property mentioned in this specification, the physical property is measured at normal pressure unless otherwise specified.

[0014] When the humidity at which a physical property is measured affects the results of the physical property referred to in this specification, the physical property is measured at standard humidity unless otherwise specified.

[0015] Humidity under standard conditions means any relative humidity within a range of 40% to 60%, for example, a relative humidity of about 55% or 60%.

[0016] As used herein, 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.

[0017] 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, or in which the likelihood of such an abnormal condition occurring is increased.

[0018] The present specification discloses an electrode.

[0019] The electrode may include a current collector, an active material layer formed on the current collector, and a polymer layer formed between the current collector and the active material layer. FIG. 1 is a cross-sectional view of an exemplary electrode sequentially including the current collector 100, polymer layer 200, and active material layer 300. As shown in the drawing, the current collector 100, polymer layer 200, and active material layer 300 may be in contact with each other. If necessary, other elements may be present between the current collector 100 and the polymer layer 200 and / or between the polymer layer 200 and the active material layer 300. Although the drawing illustrates a case in which the active material layer 300 is present on only one side of the current collector 100, the active material layer 300 may be present on both sides of the current collector 100. In this case, two polymer layers 200 may be present between the current collector 100 and each of the active material layers 300 present on both sides of the current collector 100, or one layer may be present between the current collector 100 and either of the active material layers 300 present on both sides.

[0020] The electrode may be, for example, an anode or a cathode applied to a secondary battery.

[0021] The polymer layer included in the electrode is a layer containing a polymer, which may be a conductive polymer as described below.

[0022] The polymer layer of the electrode is configured to exhibit a controlled PTC (Positive Temperature Coefficient) effect. As is well known, the PTC effect is an effect in which resistance increases with temperature. The polymer layer is configured to exhibit the PTC effect at the abnormal temperature. Therefore, the electrode exhibits stable performance under normal conditions due to the excellent electrical properties of the polymer layer, and maintains stability under abnormal conditions through the increase in resistance of the polymer layer.

[0023] In the electrode, the polymer layer can exhibit an oxidation potential adjusted in relation to the active material layer.

[0024] For example, the polymer layer or the conductive polymer contained therein in the electrode may have a low oxidation potential relative to the electrode active material or active material layer, allowing a secondary battery incorporating the electrode to maintain stable performance even when repeatedly charged and discharged or when high-speed charging and / or high-speed discharging is performed.

[0025] The oxidation potential of the conductive polymer or polymer layer is the oxidation potential relative to lithium, and is the oxidation potential relative to lithium and lithium ions (Li / Li + The oxidation potential is the standard, and can be measured by the method described in "4. Method for measuring oxidation potential (conductive polymer / polymer layer)" in the Examples section of this specification.

[0026] The oxidation potential of the electrode active material or active material layer is the oxidation potential relative to lithium, and is the oxidation potential relative to lithium and lithium ions (Li / Li +The oxidation potential is the standard, and can be measured by the method described in "5. Method for measuring oxidation potential (electrode active material)" in the Examples section of this specification.

[0027] For example, the electrode may be designed so that RV in the following equation 1 is within a predetermined range.

[0028] [Formula 1] RV=100×Va / Vs

[0029] In Equation 1, Va is the oxidation potential of the electrode active material or active material layer, and Vs is the oxidation potential of the conductive polymer or polymer layer.

[0030] The lower limit of RV in Formula 1 can be on the order of 100, 100.5, 101, 101.5, 102, or 102.5, and the upper limit can be on the order of 200, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 125, 120, 115, 110, 109, 108, 107, 106, 105, 104, or 103. The RV can have a range that is equal to or greater than any of the aforementioned lower limits; or a range that is equal to or less than any of the aforementioned upper limits, but equal to or greater than any of the aforementioned lower limits.

[0031] In Equation 1, the oxidation potential Va is determined depending on the type of electrode active material and is not particularly limited. 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, 4.9 V, 5.0 V, 5.1 V, 5.2 V, 5.3 V, 5.4 V, 5.5 V, 5.6 V, 5.7 V, 5.8 V, 5.9 V, or 4.0 V. The oxidation potential Va may be about 7 V, 4.6 V, 4.5 V, 4.4 V, 4.3 V, 4.2 V, 4.1 V, 4.0 V, 3.9 V, 3.8 V, 3.7 V, 3.6 V, 3.5 V, 3.4 V, 3.3 V, 3.2 V, 3.1 V, 3.0 V, 2.9 V, 2.8 V, 2.7 V, 2.6 V, 2.5 V, 2.4 V, 2.3 V, 2.2 V, 2.1 V, or 2.0 V. The oxidation potential Va may be within a range that is equal to or greater than any of the lower limits mentioned above; or within a range that is equal to or less than any of the upper limits mentioned above; or within a range that is equal to or less than any of the upper limits mentioned above, but is equal to or greater than any of the lower limits mentioned above.

[0032] Vs in the formula 1 is not particularly limited as long as it is controlled to satisfy the range of RV according to the oxidation potential of the applied electrode active material or active material layer. For example, the lower limit of the oxidation potential Vs can be 0V, 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, 1.6V, 1.7V, 1.8V, 1.9V, 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, 3V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, The upper limit may be about 5V, 4.9V, 4.8V, 4.7V, 4.6V, 4.5V, 4.4V, 4.3V, 4.2V, 4.1V, 4.0V, 3.9V, 3.8V, 3.7V, 3.6V, 3.5V, 3.4V, 3.3V, 3.2V, 3.1V, 3.0V, 2.9V, 2.8V, 2.7V, 2.6V, 2.5V, 2.4V, 2.3V, 2.2V, 2.1V, or 2.0V. The oxidation potential Vs may be in a range that is greater than or equal to any of the aforementioned lower limits; or less than or equal to any of the aforementioned upper limits; or less than or equal to any of the aforementioned upper limits but greater than or equal to any of the aforementioned lower limits.

[0033] The upper limit of the DC resistance of the polymer layer in the electrode at 25°C is 10,000 Ω·cm, 9,500 Ω·cm, 9,000 Ω·cm, 8,500 Ω·cm, 8,000 Ω·cm, 7,500 Ω·cm, 7,000 Ω·cm, 6,500 Ω·cm, 6,000 Ω·cm, 5,500 Ω·cm, 5,000 Ω·cm, 4,500 Ω·cm, 4,000 Ω·cm, 3,500 Ω·cm, 3,000 Ω·cm, 2,500 Ω·cm, 2,000 Ω·cm, 1,500 Ω·cm, 1,000 Ω·cm, 950 Ω·cm m, 900 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, 400 Ω·cm, or 350 Ω·cm, with a lower limit of 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, 400 Ω·cm, 450 Ω·cm, 500 Ω·cm, 550 Ω·cm, or 600 Ω·cm. The DC resistivity may range up to or below any of the aforementioned upper limits; or may range up to or below any of the aforementioned upper limits but up to or above any of the aforementioned lower limits. The DC resistance was measured by the method described in "6. Method for measuring DC resistance" in the Examples of this specification.

[0034] The upper limit of the AC impedance resistance of the polymer layer in the electrode may be about 1,000Ω, 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, 50Ω, 55Ω, 60Ω, 65Ω, 70Ω, 75Ω, 80Ω, or 85Ω. The AC impedance resistance 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 and greater than or exceeding any of the lower limits mentioned above. The AC impedance resistance is measured by the method described in "7. Interface Resistance (AC Impedance Resistance)" in the Examples section of this specification.

[0035] Since the polymer layer exhibits the DC resistance and / or AC impedance resistance, the electrode or a secondary battery or electrode assembly to which the electrode is applied can be stably operated or stored in a normal state.

[0036] The polymer layer is capable of exhibiting a purposefully designed PTC effect.

[0037] For example, the polymer layer may exhibit a characteristic such that ΔR1 in the following formula 2 falls within a predetermined range.

[0038] [Formula 2] △R1=Max{(R n+5 / R n ) / 5}

[0039] 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.

[0040] ΔR1 in Equation 2 is measured for a coin cell to which the polymer layer 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, then R 95 / R 90 is 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 greater at any temperature within the temperature range of 25°C to 135°C, this means that the resistance of the polymer layer increases relatively rapidly at any temperature within the temperature range.

[0041] The lower limit of ΔR1 may be about 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 100, 150, 200, 250, 300, 350, or 400, and the upper limit may be about 1,000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, or 150. The unit of ΔR1 is Ω·cm / °C. ΔR1 may be within a range equal to or greater than any of the lower limits listed above; or within a range equal to or less than any of the upper limits listed above, but equal to or greater than any of the lower limits listed above. These characteristics enable the electrode to ensure the stability of secondary batteries and the like under abnormal conditions.

[0042] The temperature at which ΔR1 is confirmed, i.e., R nThe lower limit of the temperature may be about 70°C, 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 90°C. The temperature may be within a range equal to or less than any of the upper limits mentioned above; or equal to or greater than any of the lower limits mentioned above; or equal to or less than any of the upper limits but equal to or greater than any of the lower limits mentioned above. The temperature is adjusted to a temperature at which an abnormal condition occurs or there is a risk of an abnormal condition occurring. When a polymer layer exhibiting the above properties is applied, 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 ensure stability under abnormal conditions.

[0043] The polymer may exhibit a property in which ΔR2 in the following formula 3 is within a predetermined range.

[0044] [Formula 3] △R2=Max{(R z+5 / R z ) / 5}

[0045] R in Equation 2 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 5°C higher than the temperature n°C ((n+5)°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.

[0046] ΔR2 in Equation 3 is measured for a coin cell to which the polymer layer 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, then 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, it means that the resistance of the polymer layer increases relatively rapidly at any temperature within the temperature range.

[0047] The lower limit of ΔR2 may be about 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 33, 34, 36, 38, 40, 42, or 44, and the upper limit may be about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 18, or 16. The unit of ΔR2 is Ω / °C. ΔR2 may be less than or equal to any of the upper limits, greater than or equal to any of the lower limits, or may be in a range between less than or equal to any of the upper limits and greater than or equal to any of the lower limits. Due to these characteristics, an electrode having the polymer layer applied thereto can ensure the stability of a secondary battery under abnormal conditions.

[0048] The temperature at which ΔR2 in the above range is confirmed, i.e., R zThe lower limit of the temperature 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 90°C. The temperature may be within a range that is 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 between a range that is less than or equal to any of the upper limits mentioned above and greater than or equal to any of the lower limits mentioned above. The temperature is adjusted to a temperature at which an abnormal condition occurs or there is a risk of an abnormal condition occurring. When a polymer layer exhibiting the above properties is applied, 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 ensure stability under abnormal conditions.

[0049] The conductive polymer forming the polymer layer can be controlled so that the polymer layer exhibits the controlled oxidation potential and PTC effect as described above.

[0050] The conductive polymer contained in the polymer layer may be 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. The thiophene unit refers to a monomer unit formed by polymerizing a thiophene-based monomer, and the thiophene-based monomer refers to a monomer containing a thiophene skeleton.

[0051] The term "monomer unit" refers to a structure in which a monomer is polymerized and contained within a polymer.

[0052] The lower limit of the ratio of the thiophene unit in the polythiophene or thiophene polymer is 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%, 75 mol%, 80 mol%, 85 mol%, 90 mol% or more based on the total number of moles of all monomer units in the polythiophene or thiophene polymer. %, or 95 mol%, with the upper limit being 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 ratio of the thiophene units may be within a range that is equal to or greater than any of the lower limits listed above; or may be within a range that is equal to or less than any of the upper limits listed above, but is equal to or greater than any of the lower limits listed above.

[0053] The thiophene unit contained in the polythiophene may be a thiophene unit having a hydrocarbon functional group.

[0054] 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. Examples of the monovalent hydrocarbon group include an alkyl group, an alkynyl group, or an alkenyl group, and examples of the monovalent functional group containing the monovalent hydrocarbon group include an alkoxy group, an alkylcarbonyl group, or an alkylcarbonyloxy group, but the types of hydrocarbon functional groups are not limited to these.

[0055] The lower limit of the number of carbon atoms in the hydrocarbon functional 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 may be greater than or equal to any of the lower limits; or less than or equal to any of the upper limits; or less than or equal to any of the upper limits but greater than or equal to any of the lower limits.

[0056] The carbon number may be the total number of carbon atoms in the hydrocarbon functional group or the monovalent hydrocarbon group contained therein, or the carbon number of the longest linear hydrocarbon chain contained in the hydrocarbon functional group or the monovalent hydrocarbon group contained therein. That is, the hydrocarbon functional group or monovalent hydrocarbon group may have a linear or branched structure, and even if it has 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, if the branched structure is a 2-ethylhexyl group, the number of carbon atoms constituting the longest chain may be 6.

[0057] The hydrocarbon functional groups, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, and alkylcarbonyloxy, may be optionally substituted with one or more substituents.

[0058] In the conductive polymer, the lower limit of the mole ratio of the thiophene units having a hydrocarbon functional group 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%, 75 mol%, 80 mol%, or 85 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%, or 45 mol%, which is based on the total moles of all monomer units contained in the polymer. The ratio may be in a range that is less than or equal to any of the aforementioned upper limits; or greater than or equal to any of the aforementioned lower limits; or less than or equal to any of the aforementioned upper limits but greater than or equal to any of the aforementioned lower limits.

[0059] When the conductive polymer contains the thiophene unit, the polymer or the polymer layer containing the same exhibits an appropriate PTC (Positive Temperature Coefficient) effect, and its surface properties are controlled to ensure excellent adhesion to an electrode or current collector, and the conductive polymer can exhibit an appropriate level of oxidation potential.

[0060] The hydrocarbon functional group is a functional group that can impart appropriate mobility to the conductive polymer itself or to the polymerization process of the conductive polymer. Such functional groups impart appropriate mobility to the monomer mixture and diffuse within the monomer mixture, enabling efficient polymerization. Furthermore, conductive polymers having such functional groups can ensure stable and uniform formation of a polymer layer between the current collector and the active material layer through appropriate mobility.

[0061] The hydrocarbon functional groups may be properly oriented during the drying or annealing process (heat treatment process) applied during the formation of the polymer layer to impart PTC effect and oxidation potential characteristics suited to the polymer.

[0062] 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 polymer, 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 ratio of the hydrocarbon functional group.

[0063] The thiophene units having the hydrocarbon functional groups may include a first thiophene unit having a long-chain hydrocarbon functional group and a second thiophene unit having a short-chain hydrocarbon functional group in the polymer.

[0064] The term "long-chain hydrocarbon functional group" refers to a hydrocarbon functional group as described above, except that the number of carbon atoms is adjusted to a certain level or more.

[0065] The term "short chain hydrocarbon functional group" refers to a hydrocarbon functional group as described above, except that the number of carbon atoms is controlled to be below a certain level.

[0066] The lower limit of the number of carbon atoms in the long-chain hydrocarbon functional 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 functional group may be within a range that is equal to or greater than any of the above-mentioned lower limits; or within a range that is equal to or less than any of the above-mentioned upper limits, but is equal to or greater than any of the above-mentioned lower limits.

[0067] The lower limit of the number of carbon atoms in the short-chain hydrocarbon functional 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 functional group may be within a range equal to or less than any of the above upper 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.

[0068] The specific details of the long-chain and short-chain hydrocarbon functional groups are the same as those described above for the hydrocarbon functional groups, except for the carbon number.

[0069] In the conductive polymer, the lower limit of the ratio of the total number of moles of the first and second thiophene units 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%, 75 mol%, 80 mol%, or 85 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%, or 45 mol%, where the ratio is based on the total number of moles of all monomer units contained in the polymer. The ratio may be in a range that is less than or equal to any of the aforementioned upper limits; or greater than or equal to any of the aforementioned lower limits; or less than or equal to any of the aforementioned upper limits but greater than or equal to any of the aforementioned lower limits.

[0070] The ratio (M2 / M1) of the moles of the second thiophene units (M2) to the moles of the first thiophene units (M1) in the conductive polymer may have a lower limit of about 0.01, 0.05, 0.1, 0.5, 1, 1.5, or 2, and an upper limit of 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 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.

[0071] Under such a ratio, the conductive polymer or the polymer layer exhibits an appropriate PTC (Positive Temperature Coefficient) effect, and its surface properties are controlled to ensure excellent adhesion to the electrode or current collector.

[0072] The polymer 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.

[0073] 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 carboxy group, a hydroxy group, an amino group, a cyano group, a nitro group, an ether group, or a functional group of the following formula 1:

[0074] [ka]

[0075] In Chemical Formula 1, 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 an arbitrary number.

[0076] In Chemical Formula 1, L3 being a single bond means that L3 is absent and the oxygen atom between L4 and L3 is directly linked to the backbone of the monomer or polymer.

[0077] 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.

[0078] As used herein, the term "alkylene group" refers 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, unless otherwise specified. The alkylene group may be linear, branched, or cyclic, and may be optionally substituted with one or more substituents.

[0079] As used herein, unless otherwise specified, the term "alkylidene group" may refer to 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.

[0080] The alkyl group of R8 in Chemical Formula 1 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 be suitably linear or branched.

[0081] In Chemical Formula 1, 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. n may be in a range that is less than or equal to any of the upper limits mentioned above; or in a range that is greater than or equal to any of the lower limits mentioned above; or in a range that is 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.

[0082] 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 intended protective function.

[0083] When the thiophene unit having a polar functional group is present in the conductive polymer, the thiophene unit having a polar functional group can be present such that the total number of moles of the thiophene unit having the hydrocarbon functional group falls within a predetermined range per mole of the thiophene unit having the polar functional group.

[0084] For example, the ratio of the total number of moles (M) of thiophene units having a hydrocarbon functional group to the number of moles (M) of thiophene units having a polar functional group (i.e., M / M) can be about 1, 2, 3, 4, 5, 6, 8, or 8.5 moles, and the upper limit can be about 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9.5, or 9 moles. The ratio can be in a range that is less than or equal to any of the upper limits mentioned above; or in a range that is greater than or equal to any of the lower limits mentioned above; or in a range that is 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.

[0085] The thiophene unit may be, for example, a unit of Formula 2 below:

[0086] [ka]

[0087] In Formula 2, R1 and R2 may each independently be hydrogen, the polar functional group, or the hydrocarbon functional group.

[0088] In another example, R1 and R2 in Chemical Formula 1 may be linked together to form a divalent functional group of Chemical Formula 3 below.

[0089] [ka]

[0090] In Chemical Formula 3, L1 and L2 are each independently a single bond, an alkylene group, or an alkylidene group, and R3 and R4 are each independently a hydrogen atom, the polar functional group, or the hydrocarbon functional group.

[0091] For example, when the unit of Formula 2 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 not linked).

[0092] For example, when the unit of Formula 2 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 not linked).

[0093] For example, when the unit of Formula 2 is the first thiophene unit described above, at least one of R1 and R2 may be the long-chain hydrocarbon functional group described above (when R1 and R2 are not linked), or at least one of R3 and R4 may be the long-chain hydrocarbon functional group described above (when R1 and R2 are not linked).

[0094] For example, when the unit of Formula 2 is the second thiophene unit described above, one or more of R1 and R2 may be the short-chain hydrocarbon functional group described above (when R1 and R2 are not linked), or one or more of R3 and R4 may be the short-chain hydrocarbon functional group described above (when R1 and R2 are not linked).

[0095] The hydrocarbon functional group, polar functional group, long-chain hydrocarbon functional group, and short-chain hydrocarbon functional group have been described above in detail.

[0096] In addition, the alkylene group and alkylidene group in the formula (3) are the same as those described in the formula (1).

[0097] The polymer may include additional monomer units in addition to the thiophene units. For example, additional monomers may be included to adjust the oxidation potential of the polymer. For example, units exhibiting a lower or higher oxidation potential relative to the thiophene units may be included in the conductive polymer as needed.

[0098] The polymer may have a weight average molecular weight (Mw) within a predetermined range. The lower limit of the weight average molecular weight of the polymer is 10,000 g / mol, 11,000 g / mol, 12,000 g / mol, 13,000 g / mol, 14,000 g / mol, 15,000 g / mol, 16,000 g / mol, 17,000 g / mol, 18,000 g / mol, 19,000 g / mol, 20,000 g / mol, 21,000 g / mol, 22,000 g / mol, 23,000 g / mol, 24,000 g / mol, 25,000 g / mol, 26,000 g / mol, or 27,000 g / mol. , 28,000 g / mol, 29,000 g / mol, 30,000 g / mol, 31,000 g / mol, 32,000 g / mol, 33,000 g / mol, 34,000 g / mol, 35,000 g / mol, 36,000 g / mol, 37,000 g / mol, 38,000 g / mol, 39,000 g / mol, or 40,000 g / mol, with upper limits of 2,000,000 g / mol, 1,500,000 g / mol, 1,000,000 g / mol, 900,000 g / mol, 800,000 g / mol, and 1000,000 g / mol. 00g / 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, 250,000g / mol, 245,000g / mol, 240,000g / mol, 235, 000g / mol, 230,000g / mol, 225,000g / mol, 220,000g / mol, 215,000g / mol, 210,000g / mol, 205,000g / mol, 200,000g / mol, 195,000g / mol, 190, 000g / mol, 185,000g / mol, 180,000g / mol, 175,000g / mol, 170,000g / mol, 165,000g / mol, 160,000g / mol, 155,000g / mol, 150,000g / mol, 145,The weight average molecular weight may be about 100,000 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 in a range that is 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.

[0099] The molecular weight distribution of the polymer, 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, 4, or 3.5. The molecular weight distribution may be within a range that is less than or equal to any of the above upper limits; or within a range that is greater than or equal to any of the above lower limits; or within a range that is less than or equal to any of the above upper limits but greater than or equal to any of the above lower limits.

[0100] The weight average molecular weight and molecular weight distribution are measured by the method described in "2. GPC (Gel Permeation Chromatograph)" in the Examples section of this specification.

[0101] The polymer layer may include the polymer. The polymer layer may be composed of only the polymer, or may further include other necessary additives in addition to the polymer. The use of the polymer may effectively form a desired electrode. For example, the lower limit of the polymer 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 ratio is based on the total weight of the polymer layer. The ratio may range between less than or equal to any of the upper limits listed above; between greater than or equal to any of the lower limits listed above; or between less than or equal to any of the upper limits and greater than or equal to any of the lower limits listed above.

[0102] The thickness of the polymer layer can be appropriately controlled depending on the purpose. For example, the lower limit of the thickness can be about 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, and the upper limit can be about 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 can be within a range that is equal to or less than any of the upper limits mentioned above; or equal to or greater than any of the lower limits mentioned above; or 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 thickness can be measured by the method described in "3. Thickness Measurement" in the Examples section of this specification.

[0103] The current collector included in the electrode is not particularly limited, and may be a current collector commonly used for a positive electrode or a negative electrode.

[0104] The current collector may be any material that does not undergo chemical changes in an application device such as a secondary battery and has conductivity, without any particular limitations on its type, size, or shape. Examples of materials that can be used for the current collector 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 may be in the form of a film, sheet, foil, net, porous material, foam, or nonwoven fabric containing the above material. In some cases, the surface of the current collector may be subjected to a known surface treatment to improve adhesion to other layers, such as a polymer layer or an active material layer.

[0105] Such a current collector can generally have a thickness in the range of 3 μm to 500 μm, but is not limited to this.

[0106] The active material layer may also be a layer that is commonly used.

[0107] The active material layer typically includes 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 can be used.

[0108] 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) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 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 LiNi1-c2 M c2 O2 (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); nickel-site type lithium nickel oxide represented by the chemical formula LiMn 2-c3 M c3 O2 (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 lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); lithium nickel cobalt manganese (NCM) composite oxide, lithium nickel cobalt manganese aluminum (NCMA) composite oxide, and LiMn2O4 in which a part of Li in the chemical formula is substituted with an alkaline earth metal ion, etc. can be used, but are not limited thereto.

[0109] 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 can 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, or Al alloy; metal oxides such as SiO a (0 < a < 2), SnO2, vanadium oxide, metal oxides capable of doping and undoping lithium such as lithium vanadium oxide; or composites containing the metallic compound and the carbonaceous material such as Si-C composite or Sn-C composite, etc. can be mentioned, and one or a mixture of two or more of these can be used.

[0110] The negative electrode active material may be a lithium thin film, and the carbon material may be low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, scaly, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, carbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0111] The electrode active material may be contained in the active material layer in a range of about 80 wt % to 99.5 wt % or 88 wt % to 99 wt % based on the total weight of the active material layer, but the ratio may be changed depending on the application or design of the electrode.

[0112] 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. Examples of the binder are not particularly limited and include, for example, PVDF (Poly(vinylidene fluoride)), PVA (Poly(vinyl alcohol)), SBR (Styrene butadiene rubber), PEO (Poly(ethylene oxide)), CMC (Carboxyl methyl cellulose), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. At least one selected from the group consisting of sucrose, pullulan, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate, and polyarylate may be used.

[0113] The binder may be included in the active material layer in an amount of, for example, 0.1 to 10 parts by weight or 0.5 to 5 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0114] The active material layer may further include a conductive material, if necessary. Any known conductive material may be used as long as it does not induce chemical changes in the secondary battery and is conductive. Examples of such conductive materials include graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fiber and metal fiber; conductive tubes, such as carbon nanotubes (CNTs); metal powders, such as fluorocarbon, aluminum, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide, and / or polyphenylene derivatives.

[0115] The conductive material may be contained in the active material layer in an amount of, for example, 0.1 to 20 parts by weight or 0.3 to 10 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0116] The active material layer may optionally contain necessary known components in addition to the components described above.

[0117] The present specification also discloses a method for manufacturing the electrode.

[0118] The manufacturing method may include forming the polymer layer on the current collector, and may include forming the active material layer on the polymer layer.

[0119] There is no particular limitation on the method for forming the polymer layer on the current collector. 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.

[0120] In another example, the polymer layer may be formed by directly polymerizing a monomer that forms the conductive polymer on the current collector.

[0121] The preparation and coating method of the coating composition for forming the polymer layer are not particularly limited, and known coating methods can be used. Furthermore, the method for polymerizing the conductive polymer is also not particularly limited, and known methods can be used. For example, methods using oxidative polymerization or radical reaction are typically known for preparing polythiophene, and these methods can also be used in the process of forming the conductive polymer in the present invention.

[0122] The prepared coating composition can be used to form a polymer layer on a current collector. This process typically includes coating the coating composition on a current collector and heat-treating the coated coating composition. During this process, the properties of the polymer layer can be controlled by the conditions of the heat treatment.

[0123] For example, the temperature T of the heat treatment and / or the time H of the heat treatment may be adjusted.

[0124] 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, 265°C, 260°C, 255°C, 250°C, The temperature may be about 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., 130° C., 125° C., 120° C., 115° C., 110° C., 105° C., 100° C., 95° C., or 90° C. The temperature may be in a range that is less than or equal to any of the upper limits recited above; or in a range that is greater than or equal to any of the lower limits recited above; or in a range that is less than or equal to any of the upper limits recited above, but greater than or equal to any of the lower limits recited above. Within this range, the alignment state of the hydrocarbon groups of the conductive polymer is appropriately adjusted, and the desired properties can be secured accordingly.

[0125] To achieve the objective, the product (T×H) of the heat treatment temperature T and the time H can be adjusted.For example, the lower limit of the product (T×H) of the heat treatment temperature T and the time H may be on the order of 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, and the upper limit thereof may be on the order of 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 °C·hour, 9500 °C·hour, 9000 °C·hour, 8500 °C·hour, 8000 °C·hour, 7500 °C·hour, 7000 °C·hour, 6500 °C·hour, 6000 °C·hour, 5500 °C·hour, 5000 °C·hour, 4500 °C·hour, 4000 °C·hour, 3500 °C·hour, 3000 °C·hour, 2500 °C·hour, 2000 °C·hour, 1500 °C·hour, 1400 °C·hour, 1300 °C·hour, 1200 °C·hour, 1100 °C·hour, 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, 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, 10 °C·hour, 5 °C·hour, 4 °C·hour, 3 °C·hour, 2 °C·hour, 1 °C·hour or 0.5 °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 may be within a range of 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 mentioned above but greater than or equal to any of the lower limits mentioned above. Within such a range, the alignment state of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring the desired properties.

[0126] To more effectively secure the desired properties, the heat treatment can be carried out in two stages.

[0127] 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, wherein the temperatures T1 and T2 are different from each other and / or the times H1 and H2 are different from each other.

[0128] 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 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. Within this range, the alignment state of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring the desired properties.

[0129] For example, the lower limit of the product of the temperature T1 and the time H1 of the primary heat treatment (T1 x H1) may be about 0.01°C / hour, 0.05°C / hour, 0.1°C / hour, 0.2°C / hour, or 0.3°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. The product (T1 × H1) may be about 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, 10°C / hour, 5°C / hour, 4°C / hour, 3°C / hour, 2°C / hour, 1°C / hour, or 0.5°C / hour. The product (T1 × H1) 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. Within these ranges, the alignment of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring the desired properties.

[0130] 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, or 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, 140°C, 135°C, or 130°C. The temperature may be within a range equal to or less than any of the upper limits mentioned above; or 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. Within this range, the alignment state of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring the desired properties.

[0131] The product of the second heat treatment temperature T2 and the time H2 (T2×H2) can 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 equal to or less than any of the upper limits mentioned above; or equal to or greater than any of the lower limits mentioned above; or 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. Within such a range, the alignment state of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring the desired properties.

[0132] 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 within a range equal to or less than any of the above upper limits; or within a range equal to or greater than any of the above lower limits; or 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. Within this range, the alignment state of the hydrocarbon groups of the conductive polymer is appropriately adjusted, and the desired properties can be secured accordingly.

[0133] In this case, the lower limit of the ratio H2 / H1 of the time H1 for the first heat treatment to the time H2 for 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 within a range equal to or less than any of the above upper limits; or within a range equal to or greater than any of the above lower limits; or 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. Within this range, the alignment state of the hydrocarbon groups of the conductive polymer can be appropriately controlled, thereby ensuring desired properties.

[0134] In the manufacturing process, a post-process such as an appropriate drying process may be additionally performed following the coating and / or polymerization process.

[0135] 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, binder, and conductive material on a current collector (polymer layer), drying the coating, and then rolling the coating. Such a known method can be equally applied to the present invention.

[0136] This specification also provides an electrode assembly or electrochemical device, e.g., a secondary battery, including the electrodes. The electrode assembly and electrochemical device are not particularly limited in terms of their other components, as long as they include the electrodes described above. For example, the electrode assembly may include a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, as is well known. In this case, either one or both of the positive electrode and the negative electrode may be the electrodes described above. The electrochemical device, e.g., a secondary battery, may also include an electrolyte between the electrodes or the electrode assembly. [Effects of the Invention]

[0137] This specification discloses an electrode and its uses. The electrode includes a polymer layer that exhibits a purposefully controlled PTC (positive temperature coefficient) effect and oxidation potential. Under normal conditions, such an electrode exhibits excellent electrical properties, such as low resistance, and does not affect or even improves the performance and operation of a secondary battery, while ensuring stability under abnormal conditions. This specification also discloses uses of the electrode. [Brief explanation of the drawings]

[0138] [Figure 1] 1 is a cross-sectional view of an exemplary electrode. [Figure 2] 1 shows the results of NMR analysis of the monomer produced in the production example. [Figure 3] 1 shows the performance evaluation results for the electrode of Example 1. [Figure 4] 1 shows the performance evaluation results for the electrode of Example 1. [Figure 5] 1 shows the performance evaluation results for the electrode of Comparative Example 1. [Figure 6]These are the performance evaluation results for the electrode of Comparative Example 1.

Embodiments for Carrying Out the Invention

[0139] Hereinafter, electrodes and the like disclosed in this specification will be specifically described through Examples and Comparative Examples. However, the scope of the electrodes and the like is not limited by the following Examples.

[0140] 1. NMR Analysis Method 1 1H-NMR analysis was performed at room temperature using an NMR spectrometer including a Bruker UltraShield spectrometer (300 MHz) with a triple resonance 5 mm probe. The sample was diluted to a concentration of about 10 mg / ml in the NMR measurement solvent (CDCl3), and the chemical shift was expressed in ppm.

[0141] 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 Empower 3 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 using the ratio (Mw / Mn). The GPC measurement conditions are as follows.

[0142] <GPC Measurement Conditions> Equipment: 2414 from Waters Columns: Three Styragel columns from Waters were used. Solvent: THF (Tetrahydrofuran) Column temperature: 35℃ Sample concentration: 1 mg / mL, 1 μL injection Standard sample: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940, 485)

[0143] 3. Thickness measurement The thickness of the polymer layer was measured by cross-sectioning the electrode using an ion milling device (Hitachi, IM5000) and then taking 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.

[0144] 4. Oxidation potential measurement method (conductive polymer / polymer layer) The oxidation potential was measured as follows: A layer (hereinafter referred to as a polymer layer) of approximately 10 μm thick was formed on an aluminum foil of approximately 15 μm thick using a conductive polymer for measuring the oxidation potential. The polymer layer was formed using the same method as in Example 1 below.

[0145] 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 circular laminate and electrolyte (Welcos CR2032 coin cell kit).

[0146] The separator was a WL20C model manufactured by Double Scope Korea, the lithium film was a film with a thickness of about 100 μm, and the electrolyte was a 1M LiPF solution manufactured by Enchem (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethylmethyl carbonate).

[0147] The oxidation potential of the coin cell was measured at 25°C using an electrochemical measuring instrument (potentiostat) (Princeton Applied Research, PARASTAT-MC). The oxidation potential was measured by measuring CV (Cyclic Voltammetry) 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. The oxidation potential is the oxidation potential relative to lithium, and is the ratio of lithium to lithium ions (Li / Li + ) was measured as a standard.

[0148] 5. Oxidation potential measurement method (electrode active material) The oxidation potential of the electrode active material was measured by manufacturing a coin cell using an electrode prepared using the electrode active material.

[0149] A slurry was prepared by blending the electrode active material to be measured, 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 75:1:1:23 (electrode active material: conductive material: PVDF: NMP). The slurry was applied to a current collector using 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 resulting mixture was then rolled to form an electrode active material layer approximately 53 μm thick, thereby producing an electrode.

[0150] The electrode active material used was the electrode active material to be measured.

[0151] The rolling was performed so that the porosity of the active material layer was about 25%. The porosity of the active material layer was calculated by comparing the ratio of the difference between the actual density and the density after rolling, and this method of calculating the porosity is well known.

[0152] The current collector was an aluminum foil having a thickness of about 15 μm.

[0153] A separator and a lithium film were then laminated on the electrode active material layer of the electrode to prepare a laminate of electrode / separator / lithium film, which was then punched into a circle with a diameter of approximately 1.4 cm. A coin cell was fabricated using the punched circular laminate and electrolyte (Welcos CR2032 coin cell kit).

[0154] The separator was a WL20C model manufactured by Double Scope Korea, the lithium fill was a film with a thickness of approximately 100 μm, and the electrolyte was a 1M LiPF solution manufactured by Enchem (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethylmethyl carbonate).

[0155] 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.

[0156] The oxidation potential is the oxidation potential of lithium and lithium ions (Li / Li + ) was measured as a standard.

[0157] 6. DC Resistance Measurement Method DC resistance was evaluated using the same coin cell as used in "4. Oxidation Potential Measurement Method (Conductive Polymer / Polymer Layer)" above. However, the thickness of the polymer layer in the coin cell was approximately 200 nm. 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 multi-tester (FLUKE-87-5).

[0158] 7.Interface resistance (AC impedance resistance) The interfacial resistance was evaluated through EIS (Electrochemical Impedance Spectroscopy) using the same coin cell as used in "4. Oxidation Potential Measurement Method (Conductive Polymer / Polymer Layer)" above. However, the polymer layer thickness in the coin cell was approximately 200 nm. 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 potentiostat (Princeton Applied Research, PARASTAT-MC).

[0159] 8. Maximum resistance change rate measurement (DC resistance) The maximum resistance change rate ΔR1 is determined by the following formula 1.

[0160] <Expression 1> △R1=Max{(R n+5 / R n ) / 5}

[0161] The ΔR1 is measured in the following manner.

[0162] 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 (JEOTECH, OF3-05W), and the oven temperature was set to increase by 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. Subsequently, the DC resistance was measured at each temperature as the temperature 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 maintained for one minute according to the settings, and the DC resistance is measured after one 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 target temperature is R n+5 Among 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 (R n+5 / R n ) / 5, the temperature n°C is set to the On-Set temperature.

[0163] 9. Maximum resistance change rate measurement (AC impedance) The maximum resistance change rate ΔR2 is determined by the following formula 2.

[0164] <Expression 2> △R2=Max{(R z+5 / R z ) / 5}

[0165] The ΔR2 is measured in the following manner.

[0166] The coin cell for measuring AC impedance resistance (the coin cell used in "7. Interface Resistance (AC Impedance Resistance)" above) is placed in the center of a convection oven (JEOTECH, OF3-05W), and the oven temperature is set to increase by 5°C per minute from an initial temperature of 25°C to a final temperature of 135°C. The coin cell is connected to a resistance meter (the same meter used in "7. Interface Resistance (AC Impedance Resistance)" above) outside the oven to enable resistance measurement. The temperature is then increased as set, and the AC impedance resistance is 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 maintained for one minute according to the settings, and the AC impedance resistance is measured after one minute has elapsed at that temperature.

[0167] 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 The AC impedance resistance measured at 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ and 125℃ is R z 21 values ​​of (R z+5 / R z ) / 5, and then the maximum value is used as Max{(R z+5 / R z) / 5}(=△R2), and the maximum value (R z+5 / R z ) / 5 is set to the On-Set temperature.

[0168] The AC impedance resistance was measured by applying a voltage of 4.3 V for 10 minutes and measuring the resistance in a semicircle in the high frequency region of a Nyquist plot obtained by EIS measurement at 50,000 Hz to 0.1 Hz.

[0169] Preparation Example 1. Synthesis of Monomer (A) The monomer of the following formula A was synthesized in the following manner.

[0170] [ka]

[0171] 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, and the methanol produced during the transetherification was removed using a 4A-type molecular sieve filter loaded 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)). The NMR analysis results for the target compound (monomer (A)) are shown in Figure 2.

[0172] Production Example 2: Synthesis of conductive polymer (polythiophene (A)) 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 and polymerized at 30°C for 24 hours to prepare polythiophene (A). In the conductive polymer (A), the molar ratio of 3-dodecylthiophene units (I), 3-hexylthiophene units (II), and units (III) of the monomer (A) of Preparation Example 1 is about 3.94:1.97:0.66 (I:II:III).

[0173] The polymerization solution was poured into a membrane with a molecular weight cut-off (MWCO) of 5000 and 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 polythiophene (A).

[0174] The polythiophene (A) had a weight average molecular weight (Mw) of 118,000 g / mol and a number average molecular weight (Mn) of 24,500 g / mol, respectively, and an oxidation potential of about 3.7 V.

[0175] Example 1 An aluminum foil with a thickness of approximately 15 μm was used as the current collector. Polythiophene (A) from Preparation Example 2 was dispersed in a solvent (chloroform) at a concentration of approximately 2.0 wt % to prepare a coating solution. The coating solution was coated onto the current collector using a bar coating method. The current collector with the coating layer formed thereon was then placed in a drying oven at 140°C for approximately 4 minutes, and then again at 130°C for 1 hour to form a layer (polymer layer) with a thickness of approximately 200 nm.

[0176] An active material layer was then formed on the conductive polymer layer. The active material layer was formed using a slurry. The slurry was prepared by blending a positive electrode active material, conductive materials (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 75:1:1:23 (electrode active material: conductive material: PVDF: NMP). The slurry was applied to the conductive 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 mixture was then rolled to form an active material layer with a thickness of approximately 53 μm (based on an electrode active material weight of 0.03 g and a porosity of 18%).

[0177] The electrode active material used was LCO (LiCoO2), and the oxidation potential of the electrode active material measured by the method described in "5. Oxidation Potential Measurement Method (Electrode Active Material)" was about 3.8V.

[0178] Comparative Example 1 When forming the active material layer on the conductive polymer layer, NCM (Li[N 0.8 Co 0.1 Mn 0.1 An electrode was fabricated in the same manner as in Example 1, except that ]O2) was used. The oxidation potential of the electrode active material (NCM) was measured using the method described in "5. Oxidation Potential Measurement Method (Electrode Active Material)" above, and was found to be about 3.7 V.

[0179] Test example 1. Charge / discharge test The charge-discharge test was carried out by fabricating coin cells. The coin cells were fabricated using a CR2032 coin cell kit (Welcos CR2032 coin cell kit). 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 Co., Ltd., and the separator was a PE (poly(ethylene)) separator (Double Scope Korea, WL20C model).

[0180] A charge-discharge test was conducted using the coin cell. The test was performed in a constant current-constant voltage (CC-CV) mode for 6 cycles in the following order: 0.1C charge / 0.1C discharge (1 cycle), 0.2C charge / 0.2C discharge (2 cycles), 0.5C charge / 0.1C discharge (3 cycles), 0.5C charge / 0.5C discharge (4 cycles), 0.5C charge / 1C discharge (5 cycles), and 0.5C charge / 2C discharge (6 cycles).

[0181] 3 and 4 show charge-discharge curves obtained by carrying out a charge-discharge test on the electrode of Example 1, and FIGS. 5 and 6 show charge-discharge curves obtained by carrying out a charge-discharge test on the electrode of Comparative Example 1.

[0182] In FIGS. 3 and 4, LCO(Ref) denotes a charge / discharge curve in a charge / discharge test performed on an electrode prepared in the same manner as in Example 1 but without forming a conductive polymer layer, and LCO(SFL) denotes a charge / discharge curve in a charge / discharge test performed on an electrode including a current collector layer, a conductive polymer layer, and an active material layer prepared in Example 1.

[0183] In FIGS. 5 and 6, NCM(Ref) denotes a charge / discharge curve in a charge / discharge test performed on an electrode prepared in the same manner as in Comparative Example 1 but without forming a conductive polymer layer, and NCM(SFL) denotes a charge / discharge curve in a charge / discharge test performed on an electrode including a current collector layer, a conductive polymer layer, and an active material layer prepared in Comparative Example 1.

[0184] From the comparison of the figures, it can be seen that in Example 1, where the oxidation potential of the conductive polymer in the conductive polymer layer (polymer layer) is lower than that of the electrode active material, the efficiency did not decrease after charging and discharging, but in Comparative Example 1, the efficiency of the coin cell decreased after charging and discharging.

[0185] Test example 2. PTC effect test The DC resistance, interface resistance, ΔR1, onset temperature relative to ΔR1, ΔR2, and onset temperature relative to ΔR2 of the electrode of Example 1 were evaluated. The results are shown in Table 1 below.

[0186] In Table 1 below, Ref. indicates the results obtained by manufacturing coin cells for evaluating the DC resistance, interface resistance, ΔR1, onset temperature for ΔR1, ΔR2, and onset temperature for ΔR2, with only the polymer layer formation conditions changed and the other conditions being the same as in Example 1.

[0187] That is, in Table 1 below, the results of Example 1 are for a coin cell including a polymer layer formed by coating a current collector (Al foil) with a coating solution prepared by dispersing polythiophene (A) of Preparation Example 2 in a solvent (Chloroform) at a concentration of about 2.0 wt % using a bar coating method, and then storing the current collector with the coating layer in a drying oven at 140°C for about 4 minutes and then at 130°C for about 1 hour. Reference is for a coin cell including a polymer layer formed by coating the same coating solution on the same current collector (Al foil) using a bar coating method, and then storing the current collector with the coating layer in a drying oven at 90°C for about 20 minutes.

[0188] [Table 1]

[0189] From Table 1, it can be seen that a PTC (Positive Temperature Coefficient) effect designed to suit the purpose can be obtained by applying a specific conductive polymer, and that even if the same conductive polymer is used, the PTC effect can be additionally controlled depending on the formation method.

Claims

1. current collector; an active material layer formed on the current collector and containing an electrode active material; and a polymer layer containing a conductive polymer between the current collector and the active material layer; An electrode, wherein the oxidation potential of the conductive polymer or polymer layer is lower than the oxidation potential of the electrode active material or active material layer.

2. 2. The electrode according to claim 1, wherein RV of the following formula 1 is greater than 100: [Formula 1] RV=100×Va / Vs In Equation 1, Va is the oxidation potential of the electrode active material or active material layer, and Vs is the oxidation potential of the conductive polymer or polymer layer.

3. 3. The electrode according to claim 2, wherein the oxidation potential Va is in the range of 2V to 5V.

4. 3. The electrode according to claim 2, wherein the oxidation potential Vs is in the range of 0V to 5V.

5. 10. The electrode of claim 1, wherein the polymer layer has a DC resistivity of 10,000 ohm-cm or less at 25°C.

6. 10. The electrode of claim 1, wherein the polymer layer has an AC impedance resistance of 1,000 ohms or less.

7. The electrode according to claim 1, wherein ΔR1 in the following formula 2 is 100 Ω cm / °C or more: [Formula 2] △R1=Max{(R ｎ＋５ / R ｎ ) / 5} In Equation 2, R ｎ is the DC resistance of the polymer layer at any temperature n°C in the range of 25°C to 135°C, and R ｎ＋５ is the DC resistance of the polymer layer 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°C to 135°C (R ｎ＋５ / R ｎ ) / 5 values.

8. 8. The electrode according to claim 7, wherein the temperature at which ΔR1 of 100 Ω·cm / ° C. or more is confirmed is 80° C. or higher.

9. The electrode according to claim 1, wherein ΔR2 in the following formula 3 is 10Ω / °C or more: [Formula 3] △R2=Max{(R ｚ＋５ / R ｚ ) / 5} In Equation 2, R ｚ is the AC impedance resistance of the polymer layer at any temperature n°C within the range of 25°C to 135°C, and R ｚ＋５ is the AC impedance resistance of the polymer layer at a temperature 5°C higher than the temperature n°C ((n+5)°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.

10. 10. The electrode according to claim 9, wherein the temperature at which ΔR2 of 10 Ω / °C or more is confirmed is 80°C or higher.

11. 10. The electrode of claim 1, wherein the conductive polymer is a polythiophene comprising thiophene units with hydrocarbon functional groups.

12. The electrode according to claim 11 , wherein the polythiophene comprises, as 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.

13. 12. The electrode of claim 11, wherein the polythiophene comprises at least 30 mole percent of thiophene units having hydrocarbon functional groups.

14. 13. The electrode according to claim 12, wherein the ratio M2 / M1 of the number of moles of the second thiophene units M2 to the number of moles of the first thiophene units M1 is in the range of 0.01 to 100.

15. 12. The electrode of claim 11, wherein the polythiophene additionally comprises a thiophene unit having a polar functional group.

16. 16. The electrode of claim 15, wherein the polythiophene comprises 1 mole to 500 moles of thiophene units having a hydrocarbon functional group per mole of thiophene units having a polar functional group.

17. a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode; An electrode assembly, wherein the positive electrode or the negative electrode is the electrode according to any one of claims 1 to 16.

18. A secondary battery comprising the electrode assembly according to claim 17.

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