Current collector

Abstract

The invention discloses a current collector. The current collector includes a polymer layer that exhibits a so-called PTC (Positive Temperature Coefficient) effect. The polymer layer exhibits a PTC effect that is very precise in response to temperature and external voltage. The polymer layer may rapidly switch, if necessary, between a state exhibiting excellent electrical properties such as low resistance and a state exhibiting insulator properties due to increased resistance. According to the present invention, the current collector is applied to various electronic / electrical devices such that, in a normal state, it does not affect the driving of the device by means of excellent electrical properties, and, in an abnormal state, it is possible to secure stability by means of a rapid resistance increase.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0131049 and No. 10-2023-0131050, dated September 27, 2023, the disclosures of which are incorporated herein by reference in their entirety.

[0002] This specification discloses a current collector and its applications. Background Technology

[0003] Conductive polymers are materials used in a variety of fields.

[0004] Conductive polymers change their conductivity depending on their doping and dedoping states. This property can be applied, for example, to ensure the stability of electronic / electrical devices such as secondary batteries.

[0005] For example, in addition to the traditionally used portable electronic devices, the application of secondary batteries such as lithium-ion batteries has been expanded to various fields including electric vehicles (EVs) or renewable energy storage systems. Therefore, many efforts have been made to improve storage capacity and output.

[0006] However, with improvements in the capacity and output of electronic / electrical devices such as secondary batteries, concerns about stability and potentially hazardous performance have also increased. For example, although electric vehicles are about 60 times less fire-resistant than vehicles with internal combustion engines, they pose serious risks of TR (thermal runaway) and TP (thermal propagation), which can lead to uncontrolled temperature rises and hazardous chemical leaks.

[0007] To prevent these risks, commercial electric vehicles are equipped with various external safety mechanisms (pressure relief valves, battery-to-battery fire extinguishers, or high-temperature insulation materials, etc.), but these safety mechanisms still cannot effectively respond to TR and TP, or show a very slow response speed. Summary of the Invention

[0008] Technical issues

[0009] This specification discloses a current collector. The current collector comprises a polymer layer exhibiting a so-called PTC (positive temperature coefficient) effect. This specification discloses that the PTC effect of the polymer layer can be controlled very precisely in response to temperature and external voltage. This specification discloses that the polymer layer can rapidly exhibit a state exhibiting excellent electrical properties, such as low resistance, and a state exhibiting insulating properties due to increased resistance, when necessary.

[0010] Therefore, current collectors including the polymer layer are applied to various electronic / electrical devices, such that under normal conditions, their excellent electrical properties do not affect the operation of the device, etc., while under abnormal conditions, stability is ensured through a rapid increase in resistance. For example, current collectors are applied to secondary batteries to switch to insulators under abnormal conditions, thereby suppressing the flow of extra current, thus ensuring excellent stability against risks caused by TR and TP, etc.

[0011] This specification also discloses electrode assemblies and secondary batteries, including the current collector.

[0012] Technical solution

[0013] Unless otherwise stated, the physical properties mentioned in this specification that are affected by temperature are those measured at room temperature.

[0014] The term room temperature refers to the natural temperature without artificial heating or cooling, which can be any temperature in the range of approximately 10°C to 30°C, such as approximately 23°C or approximately 25°C.

[0015] Unless otherwise defined, the temperature unit mentioned in this specification is Celsius (°C).

[0016] Unless otherwise stated, the physical properties mentioned in this specification that are affected by the measurement pressure are those measured at normal pressure.

[0017] The term atmospheric pressure is the natural pressure without artificial pressurization or depressurization, and pressures in the range of about 700 mmHg to 800 mmHg are generally referred to as atmospheric pressure.

[0018] Unless otherwise stated, the physical properties mentioned in this specification that are affected by the measured humidity are those measured under standard humidity conditions. Standard humidity conditions are any relative humidity in the range of 40% to 60%, which means, for example, relative humidity of around 40%, 45%, 50%, 55%, or 60%.

[0019] In this specification, the term normal state refers to the normal operating state of an electrical / electronic device such as a secondary battery (e.g., the normal charging or discharging state of a secondary battery) and / or its storage state.

[0020] In this specification, the term "abnormal state" refers to a state in which abnormal heating, ignition, and / or explosion occurs in an electrical / electronic device such as a secondary battery, or the risk of abnormal heating, ignition, and / or explosion increases. For example, in a secondary battery, an abnormal state may be a state in which abnormal heating, ignition, or explosion occurs due to a short circuit, or a dangerous state in which the possibility of heating, ignition, or explosion increases.

[0021] This specification discloses a current collector. The current collector may be an electrode current collector, such as an electrode current collector used in a secondary battery.

[0022] The current collector may include a current collector body and a polymer layer formed on the current collector body. 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 the polymer layer of the current collector. Figure 1 This is an exemplary cross-sectional view of an electrode current collector including a current collector body (100) and a polymer layer (200). Figure 2 This is an exemplary cross-sectional view of an electrode in which an active material layer (300) is formed on a polymer layer (200) of a current collector.

[0023] As shown in the figures, in the current collector or electrode, the current collector body (100) and the polymer layer (200), as well as the polymer layer (200) and the active material layer (300), can also be in contact with each other. In some cases, other elements may also be present between the current collector body (100) and the polymer layer (200) or between the polymer layer (200) and the active material layer (300). Furthermore, although these figures show the case where the active material layer (300) exists only on one side of the current collector body (100), the active material layer (300) may also exist on both sides of the current collector body (100). In this case, the polymer layer (200) may exist as two layers between each of the active material layers (300) existing on both sides of the current collector body (100) and the current collector body (100), or it may exist as one layer between any one of the active material layers (300) existing on both sides and the current collector body (100).

[0024] The polymer layer can be designed to exhibit a so-called PTC (positive temperature coefficient) effect. This polymer layer exhibits changes in conductivity depending on variations in temperature and / or applied voltage. Therefore, the polymer layer can variably control charge migration through the electrodes according to temperature.

[0025] By applying such a polymer layer, an electrode with the current collector is applied to a secondary battery, which can exhibit excellent electrical properties, including low resistance under normal conditions, and stability can be ensured by increasing resistance under abnormal conditions.

[0026] In order to apply the polymer layer to the electrode to exhibit this effect, the tendency of the PTC effect exhibited by the polymer layer must be controlled.

[0027] The polymer layer can suppress abnormal charge flow, such as under abnormal conditions, by increasing resistance, thus preventing temperature increases and reducing the rate of temperature increase. Furthermore, the polymer layer can suppress or block abnormal voltage drops by inhibiting abnormal charge migration under abnormal conditions. Therefore, electrodes and secondary cells with excellent performance and stability can be obtained by using current collectors with applied polymer layers.

[0028] For example, the polymer layer can suppress abnormal overcurrents by increasing resistance under abnormal conditions, thereby preventing so-called thermal runaway (TR (thermal runaway) or TP (thermal propagation) phenomena), and can prevent volume expansion due to the generation of internal gas, thereby reducing the risk of overheating and explosion.

[0029] The polymer layer can control the temperature at which the PTC effect occurs, thereby maintaining a stable oxidation potential and electrical properties under normal conditions.

[0030] For example, the polymer layer or the current collector or electrode comprising it may have a ΔT within a certain range of Equation 1 below.

[0031] [Equation 1]

[0032] ΔT=(T2-T1) / T2×100

[0033] In Equation 1, T1 is the highest temperature in the nail penetration test of a fully charged single cell including a polymer layer or current collector, and T2 is the highest temperature in the nail penetration test of a reference single cell.

[0034] A fully charged single cell is a single cell manufactured by applying a polymer layer or current collector to the positive electrode, and is a single cell in a fully charged state. The method for manufacturing such a single cell is described in "5. Needle Penetration Test" of this specification.

[0035] The reference cell is the same as a fully charged cell except for the absence of the polymer layer, and is also a cell in a fully charged state. The method for manufacturing such a reference cell is also described in "5. Needle Penetration Test" of this specification.

[0036] The needle penetration test is a test used to check temperature and voltage while passing a needle through a single cell. The method for performing this test is described in "5. Needle Penetration Test" of this manual.

[0037] A needle is a needle with a temperature measuring device (e.g., a thermocouple) inserted therein, and the highest temperature is measured by the temperature measuring device.

[0038] The lower limit of ΔT can be approximately 15%, 20%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, or 38%, while the upper limit can be approximately 99%, 90%, 80%, 70%, 60%, 55%, 50%, 45%, or 40%. ΔT can be greater than or equal to, or greater than, any of the lower limits listed above; or greater than, or equal to, or greater than, any of the lower limits listed above while being less than, or equal to, or less than any of the upper limits listed above. This means that the higher the value of ΔT, the more effective the polymer layer is in suppressing temperature rise under abnormal conditions.

[0039] There are no specific restrictions on the lower limit T1 in Equation 1, but it can be around 10℃, 20℃, 30℃, 40℃, 45℃, or 50℃, and its upper limit can be around 90℃, 88℃, 86℃, 84℃, 82℃, 80℃, 78℃, 70℃, 68℃, 66℃, 64℃, 62℃, 60℃, or 58℃. T1 can be less than or equal to, or less than, any of the upper limits selected above; or it can be greater than or equal to, or greater than, any of the lower limits selected above, while being less than or equal to, or less than any of the upper limits selected above. This means that the lower the T1 value, the more effective the polymer layer is in suppressing temperature rise under abnormal conditions.

[0040] The polymer layer, or the current collector or electrode using it, can have a certain level of S below Equation 2 below.

[0041] [Equation 2]

[0042] S=(T1-T0) / S1

[0043] In Equation 2, T1 is the same as T1 in Equation 1.

[0044] In Equation 2, T0 is the temperature (measured by a temperature measuring device in the inserted needle) at the time point (reference time point) when the minimum voltage of the single cell is confirmed in the nail penetration test described in Equation 1. This reference time point can represent the time point at which a short circuit occurs in the single cell. When monitoring the voltage of the single cell in the nail penetration test, a voltage drop phenomenon occurs, where the voltage decreases due to abnormal charge migration, and the time point at which the minimum voltage is confirmed due to this voltage drop phenomenon becomes the reference time point.

[0045] In Equation 2, S1 is the time required from the reference time point (the time point at which temperature T0 is confirmed) to the time point at which temperature T1 is confirmed, in seconds.

[0046] The method for checking S in Equation 2 is also described in the "5. Needle Puncture Test" section of the Detailed Implementation section of this specification.

[0047] The lower limit of S can be approximately 1, 5, 10, 15, 20, 25, 30, 35, or 40, and its upper limit can be approximately 70, 65, 60, 55, 50, or 45. S can be less than or equal to, or less than, any of the upper limits selected above; or greater than or equal to, or greater than, any of the lower limits selected above, while being less than or equal to, or less than, any of the upper limits selected above. This means that the lower the value of S, the more effective the polymer layer is in suppressing temperature rise under abnormal conditions, and this suppression effect occurs rapidly.

[0048] The lower limit S1 in Equation 2 can be approximately 0.5 seconds, 0.55 seconds, 0.6 seconds, 0.65 seconds, 0.7 seconds, 0.75 seconds, or 0.8 seconds, and its upper limit can be approximately 100 seconds, 90 seconds, 80 seconds, 70 seconds, 60 seconds, 50 seconds, 40 seconds, 30 seconds, 20 seconds, 10 seconds, 9 seconds, 8 seconds, 7 seconds, 6 seconds, 5 seconds, 4 seconds, 3 seconds, 2 seconds, 1 second, or 0.8 seconds. S1 can be greater than or equal to or greater than any of the lower limits listed above; or greater than or equal to or greater than any of the lower limits listed above while being less than or equal to or less than any of the upper limits listed above. This means that the higher the value of S1, the more effective the polymer layer is in suppressing temperature rise under abnormal conditions.

[0049] The reference time point is the point in the nail penetration test where the needle penetrates the fully charged single cell. The minimum voltage of the single cell is then confirmed, and this minimum voltage is the first voltage change observed within the single cell. In other words, the minimum voltage is the minimum voltage at which a voltage drop is first observed during the nail penetration test. If the voltage drop no longer occurs at the first voltage drop, or if a voltage drop occurs and then the voltage increases, the voltage immediately preceding the increase is the minimum voltage. In some cases, the voltage increases after the first voltage drop and then decreases again, resulting in a lower voltage observed compared to the first confirmed minimum voltage. However, even in such cases, the minimum voltage at the reference time point is still the minimum voltage at the first confirmed voltage drop.

[0050] A reference time point can represent the point in time when a short circuit occurs in a single cell. For example, when a needle pierces a single cell, a short circuit may occur once or multiple times. If a short circuit occurs once or multiple times, the voltage of a fully charged single cell may drop the most during the first short circuit. Additionally, a short circuit can be used to reduce the voltage to a minimum.

[0051] For example, if a short circuit occurs two or more times, the voltage may drop rapidly during the first short circuit, and then decrease or increase by a small amount, as many times as the number of short circuits. The voltage drop is greatest during the first short circuit, so the voltage drop caused by the first short circuit can be considered the minimum voltage. Furthermore, for example, when a short circuit occurs two or more times, the degree of voltage drop caused by the first short circuit may have the greatest impact on T1.

[0052] The point at which the minimum voltage is confirmed when the voltage first drops can be considered the point at which T0 is confirmed.

[0053] The T1 in Equation 2 is the same as the T1 in Equation 1, and the T0 in Equation 2 corresponds to the temperature at the reference time point, so that it can be considered the same as the temperature confirmed by the thermocouple at the time point when the short circuit occurs. When the short circuit occurs, T0 increases, thereby reaching the highest temperature corresponding to T1 as described above.

[0054] For example, regarding Equation 2, if the temperature change required to reach the maximum temperature is the same, then the longer the time required to confirm reaching the maximum temperature, the greater the stability that can be ensured under abnormal conditions. Furthermore, for example, if the time required to confirm reaching the maximum temperature is the same, then a lower maximum temperature can be supported, thus a smaller temperature change, and greater stability that can be ensured under abnormal conditions.

[0055] The polymer layer, or the current collector or electrode using it, can have a ΔV below a certain level as shown in Equation 3 below.

[0056] [Equation 3]

[0057] ΔV = (V1 - V2) / V1× 100

[0058] In Equation 3, V1 is the voltage confirmed for a single cell in a fully charged state prior to the nail penetration test.

[0059] In Equation 3, V2 is the minimum voltage determined by penetrating a single cell in a fully charged state with a needle. V2 can be the voltage at a reference time point.

[0060] The method for confirming ΔV is described in "5. Needle Puncture Test" of the Detailed Implementation section of this specification.

[0061] If a polymer layer is used or a current collector with a polymer layer is applied, the abnormal flow of charge in abnormal states, such as short circuits, can be blocked or suppressed, thus suppressing voltage drop.

[0062] The lower limit of ΔV can be, for example, approximately 5%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%, and its upper limit can be approximately 87%, 85%, 80%, 75%, 70%, 65%, 60%, or 55%. ΔV can be less than or equal to, or less than, any of the upper limits listed above; or it can be greater than or equal to, or greater than, any of the lower limits listed above, while being less than or equal to, or less than, any of the upper limits listed above. This means that the higher the value of S1, the more effective the polymer layer is in suppressing temperature rise under abnormal conditions.

[0063] To meet these requirements, specific conductive polymers can be introduced into the polymer layer.

[0064] If desired, the polymer layer can further contain a conductive material. By controlling the content, dispersion state, and / or density of this conductive material, the desired effect can be ensured more effectively.

[0065] The thickness of the polymer layer can be appropriately selected according to the purpose. For example, the lower limit of the polymer layer thickness can be approximately 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600 nm, and the upper limit can be approximately 2,000, 1,500, 1,000, 900, 800, 700, 600, 500, 400, or 350 nm. The unit of thickness is nm. The thickness can be greater than or equal to or greater than any of the lower limits listed above; or greater than or equal to or greater than any of the lower limits listed above while being less than or equal to or less than any of the upper limits listed above.

[0066] The thicker the polymer layer is within this range, the more effectively the desired effect can be achieved. Therefore, in suitable embodiments, the lower limit of the polymer layer thickness can be close to the values ​​of the embodiments in this specification (especially Embodiments 2 and 4).

[0067] As the current collector, any current collector commonly used in the positive or negative electrode can be used without any special restrictions.

[0068] There are no particular limitations on the type, size, and shape of the current collector if it is conductive without causing chemical changes in the device to which it is applied, such as a secondary battery. Examples of materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, or calcined carbon, or materials that can be surface-treated from copper, aluminum, or stainless steel with carbon, nickel, titanium, or silver. The current collector can be in the form of a film, sheet, foil, mesh, porous body, foam, or nonwoven fabric containing the above materials. In some cases, known surface treatments can be applied to the surface of the current collector to improve adhesion to other layers, such as polymer layers or active material layers.

[0069] Such current collectors can typically have a thickness ranging from 3 μm to 500 μm, but are not limited to this.

[0070] The polymer layer exists on one or both sides of the current collector body.

[0071] The term "polymer layer" refers to a layer containing a polymer. For example, the lower limit of the polymer content in a polymer layer can be approximately 30% by weight, 35% by weight, 40% by weight, 45% by weight, 50% by weight, 55% by weight, 60% by weight, 65% by weight, 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, or 95% by weight, and the upper limit can be approximately 100% by weight, 95% by weight, 90% by weight, 85% by weight, 80% by weight, 75% by weight, 70% by weight, 65% by weight, 60% by weight, 55% by weight, or 50% by weight. This content is the polymer content based on the total weight of the polymer layer. This content can be greater than or equal to or greater than any of the lower limits listed above; or less than or equal to or less than any of the upper limits listed above while being greater than or equal to or greater than any of the lower limits listed above.

[0072] The polymer layer may not be the so-called active material layer of the electrode. Therefore, the content of the electrode active material in the polymer layer can be controlled. For example, the upper limit of the content of the electrode active material in the polymer layer can be approximately 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.1 wt%, 0.05 wt%, 0.01 wt%, 0.005 wt%, or 0.001 wt%, and the lower limit can be 0 wt%. This content is the content of electrode active material based on the total weight of the polymer layer. This content can be less than or equal to or less than any of the upper limits listed above; or less than or equal to or less than any of the upper limits listed above while being greater than or equal to or greater than any of the lower limits listed above. Specific types of electrode active materials are described below.

[0073] The polymer contained in the polymer layer can be a conductive polymer. It is well known that conductive polymers exhibit conductivity through conjugated systems of polymer chains and / or doping. In one instance, a conductive polymer can be one whose conductivity is altered through doping and dedoping.

[0074] Conductive polymers can have a weight-average molecular weight within a predetermined range. For example, the lower limit of the weight-average molecular weight of conductive polymers can be 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, 105,000, 110,000, 115,000, 120,000, 125,000, 130,000, 14 ...160,000, 170,000, 180,000, 190,000, 125, The values ​​can be around 0, 135,000, 140,000, 145,000, or 150,000, with upper limits of around 1,000,000, 950,000, 900,000, 850,000, 800,000, 750,000, 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, 350,000, 300,000, 250,000, 200,000, 150,000, or 110,000. The weight-average molecular weight can be greater than or equal to or greater than any of the lower limits selected above; or less than or equal to or less than any of the upper limits selected above; or greater than or equal to or greater than any of the lower limits selected above while being less than or equal to or less than any of the upper limits selected above. The unit of weight-average molecular weight is g / mol, which is measured by the method described in "2. GPC (Gel Permeation Chromatography)" of the Detailed Description section of this specification.

[0075] The molecular weight distribution of the conductive polymer, i.e., the ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn), can be within a predetermined range. The lower limit of this molecular weight distribution can be approximately 2, 2.5, 3, 3.5, 4, or 4.5, and the upper limit can be approximately 8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, 4, or 3.5. This molecular weight distribution can be greater than or equal to any of the lower limits selected above; or less than or equal to any of the upper limits selected above; or greater than or equal to any of the lower limits selected above while being less than or equal to any of the upper limits selected above.

[0076] When a conductive polymer possesses the aforementioned molecular weight characteristics, the desired PTC effect can be effectively controlled. As described below, the PTC effect of a conductive polymer can be expressed as adjusting the dedoping efficiency by modulating the vibrations of functional groups (e.g., long-chain hydrocarbon functional groups described below) contained in the conductive polymer at elevated temperatures. As described below, the type of vibration of these functional groups varies depending on the number of carbon atoms in the functional group, and also varies depending on the size and size distribution of the polymer containing the functional group. Weight-average molecular weight and molecular weight distribution reflect size and size distribution, etc.

[0077] The lower and upper limits of the weight-average molecular weights mentioned above are closer to the weight-average molecular weights of the polymers used in the examples of this specification (approximately 118,000 g / mol), which can more effectively achieve the desired effect.

[0078] The lower and upper limits of the molecular weight distribution described above are closer to the molecular weight distribution of the polymer used in the examples of this specification (approximately 4.8), which can more effectively achieve the desired effect.

[0079] The conductive polymer can be polythiophene.

[0080] The term polythiophene refers to a polymer containing a certain level or higher of thiophene units.

[0081] In this specification, the term "unit" of polymer refers to the state in which a monomer is polymerized and contained in a polymer, and thiophene unit refers to the state in which thiophene monomer is polymerized and contained in a polymer.

[0082] Thiophene monomers are monomers of the thiophene series, and can be monomers containing a thiophene skeleton.

[0083] Based on the total number of moles of all units contained in polythiophene, the lower limit of the molar ratio of thiophene units in polythiophene can be approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%, and the upper limit can be approximately 100 mol%, 95 mol%, or 90 mol%. This ratio of thiophene units can be greater than or equal to or greater than any of the lower limits listed above; or it can be greater than or equal to or greater than any of the lower limits listed above while being less than or equal to or less than any of the upper limits listed above.

[0084] The conductive polymer may contain units with long-chain hydrocarbon functional groups (hereinafter referred to as Unit A). The conductive polymer may be polythiophene. In this case, the monomer with long-chain hydrocarbon functional groups may be a thiophene monomer.

[0085] In this specification, the term long-chain hydrocarbon functional group refers to a monovalent hydrocarbon group having a certain number of carbon atoms or a monovalent functional group containing said monovalent hydrocarbon group.

[0086] For example, the lower limit of the number of carbons present in the functional group of long-chain hydrocarbons (i.e., the number of carbons in the monovalent hydrocarbon group) can be approximately 4, 5, 6, 7, 8, 9, 10, 11, or 12, and its upper limit can be approximately 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4. This number of carbons can be greater than or equal to or greater than any lower limit selected from the lower limits listed above; or it can be less than or equal to or less than any upper limit selected from the upper limits listed above while being greater than or equal to or greater than any lower limit selected from the lower limits listed above.

[0087] The carbon number can be the total number of carbons present in the functional group of a long-chain hydrocarbon, or the number of carbons in the hydrocarbon chain with a straight-chain structure contained within the functional group. That is, the monovalent hydrocarbon group present in the functional group of a long-chain hydrocarbon can have a straight-chain structure or a branched structure, wherein even in the case of a branched structure, the number of carbons constituting the longest straight chain in the relevant branched structure can be within the aforementioned range. For example, if the branched structure is 2-ethylhexyl, then the number of carbons constituting the longest straight chain is 6.

[0088] Examples of long-chain hydrocarbon functional groups may be selected from one or more of alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, and alkylcarbonyloxy groups. In suitable examples, the long-chain hydrocarbon functional group may be alkyl and / or alkoxy.

[0089] The number of carbon atoms present in alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy groups can be within the range of the number of carbon atoms present in long-chain hydrocarbon functional groups (i.e., the number of carbon atoms in monovalent hydrocarbon groups).

[0090] For example, alkyl, alkenyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy can be straight-chain or branched structures, and in the case of branched structures, the number of carbons forming the longest straight chain in the relevant branched structure can be within that range.

[0091] Alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, or alkyl carbonyloxy groups, which are long-chain hydrocarbon functional groups, may optionally be substituted by one or more substituents.

[0092] This long-chain hydrocarbon functional group is a functional group that can impart appropriate mobility to the monomer or the conductive polymer itself during the polymerization process of the conductive polymer. Monomers containing this long-chain hydrocarbon functional group impart appropriate mobility to the monomer mixture and diffuse within the monomer mixture so that polymerization can occur with excellent efficiency. Furthermore, conductive polymers with long-chain hydrocarbon functional groups enable the stable and uniform formation of a polymer layer between the current collector and the active material layer through appropriate mobility.

[0093] During the drying or annealing process applied during polymer layer formation, long-chain hydrocarbon functional groups are appropriately oriented, thereby ensuring the desired PTC effect. Long-chain hydrocarbon functional groups exhibit enhanced vibrational energy at elevated temperatures, which can modulate the dedoping efficiency of anions bound to the polymer. This dedoping causes an increase in electrical resistance. The dedoping efficiency can be controlled by the length and / or amount of long-chain hydrocarbon functional groups. For example, at the same temperature, the vibrational energy of relatively long chains is greater than that of relatively short chains; therefore, the desired PTC effect can be set by controlling the type, length, and / or ratio of long-chain hydrocarbon functional groups.

[0094] For example, to achieve this effect appropriately, the molar number (M) of the monomeric unit (unit A) with long-chain hydrocarbon functional groups can be adjusted. A The ratio of the number of moles (M) of all monomer units in the conductive polymer to the total number of moles (100×M) A / M). For example, the lower limit of this molar ratio can be approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, or 95 mol%, and its upper limit can be approximately 99 mol%, 98 mol%, 96 mol%, 95 mol%, 94 mol%, 92 mol%, or 90 mol%. This ratio can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or it can be less than or equal to, or less than, any upper limit selected from the upper limits listed above, while being greater than or equal to, or greater than, any lower limit selected from the lower limits listed above. Ratio (100 × M) A The closer the lower and upper limits of ( / M) are to the values ​​presented in the embodiments of this specification (approximately 90 mol%), the more effectively the desired effect can be achieved.

[0095] Conductive polymers may contain first and second hydrocarbon functional groups with different carbon numbers as long-chain hydrocarbon functional groups.

[0096] Therefore, conductive polymers can contain units having a first hydrocarbon functional group and units having a second hydrocarbon functional group.

[0097] The first hydrocarbon functional group is a functional group with a relatively large number of carbons in a long-chain hydrocarbon functional group. For example, the lower limit of the number of carbons in the first hydrocarbon functional group can be around 10, 11, or 12, and the upper limit can be around 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10. The number of carbons in the first hydrocarbon functional group can be greater than or equal to or greater than any lower limit selected from the lower limits listed above; or less than or equal to or less than any upper limit selected from the upper limits listed above while being greater than or equal to or greater than any lower limit selected from the lower limits listed above. The closer the lower limit of the number of carbons in the first hydrocarbon functional group is to the value (12) presented in the examples of this specification, the more effectively the intended effect can be achieved.

[0098] This first hydrocarbon functional group exhibits enhanced vibrational energy at elevated temperatures, thereby allowing control over the dedoping efficiency of the conductive polymer. The dedoping initiation temperature (starting point) of the conductive polymer can be controlled by the content of the first hydrocarbon functional group or the combination of the second hydrocarbon functional groups described below.

[0099] The second hydrocarbon functional group is a functional group with a relatively small number of carbons in a long-chain hydrocarbon functional group. The lower limit of the number of carbons in the second hydrocarbon functional group can be around 3, 4, 5, 6, 7, or 8, and the upper limit can be around 9, 8, 7, or 6. The number of carbons in the second hydrocarbon functional group can be less than or equal to or less than any of the upper limits selected above; or it can be less than or equal to or less than any of the upper limits selected above, while being greater than or equal to or greater than any of the lower limits selected above. The closer the lower limit and upper limit of the number of carbons in the second hydrocarbon functional group are to the values ​​(6) presented in the examples of this specification, the more effectively the desired effect can be achieved.

[0100] This second hydrocarbon functional group dilutes the vibrational energy effect exhibited by the first hydrocarbon functional group at a predetermined temperature. Therefore, the first hydrocarbon functional group has the effect of lowering the onset point of the PTC effect, while the second hydrocarbon functional group has the effect of diluting this first hydrocarbon functional group.

[0101] The number of carbon atoms in each of the first and second hydrocarbon functional groups can be the number of carbon atoms in the linear hydrocarbon chain present in the hydrocarbon functional group. For example, the first and second hydrocarbon functional groups can each independently be one or more selected from alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, and alkylcarbonyloxy, and in suitable examples, can be alkyl and / or alkoxy, wherein the number of carbon atoms can be the number of carbon atoms in the alkyl group of the alkyl group, alkenyl, alkynyl, alkoxy, alkylcarbonyl group, and alkyl group of the alkyl group of the alkylcarbonyloxy group.

[0102] Alkyl, alkenyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy can have straight-chain or branched structures, wherein in the case of a straight chain, the total number of carbons can be within the range described above, and in the case of a branched chain, the number of carbons constituting the longest straight chain in the relevant branched structure can be within the range described above.

[0103] As mentioned above, the carbon number of the functional group of long-chain hydrocarbons is related to the vibrational properties caused by applied heat energy. If the carbon number changes, the vibrational properties also change, and the vibrational properties are also related to the PTC properties of the conductive polymer. In the conductive polymer of this application, the first hydrocarbon functional group mainly plays a role in regulating the temperature at which the PTC effect is expressed, i.e., the temperature at which the resistance increases, while the second hydrocarbon functional group plays a role in suppressing the increase in resistance at relatively low temperatures.

[0104] The ratio of the total molar number of units having the first hydrocarbon functional group and units having the second hydrocarbon functional group to the molar number of all units present in the conductive polymer can be adjusted to the ratio of unit A as described above (100×M). A The range of / M) is the same.

[0105] The lower limit of the ratio M2 / M1, which is the molar number of units with a second hydrocarbon functional group M2 to the molar number of units with a first hydrocarbon functional group M1 in the conductive polymer, can be approximately 0.01, 0.05, 0.1, 0.3, 0.4, 0.45, 0.5, 1, 1.5 or 2, and the upper limit can be approximately 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 0.5. The ratio can also be less than or equal to or less than any of the upper limits selected above; or greater than or equal to or greater than any of the lower limits selected above; or less than or equal to or less than any of the upper limits selected above, while being greater than or equal to or greater than any of the lower limits selected above. The closer the lower and upper limits of the ratio M2 / M1 are to the values ​​presented in the embodiments of this specification (approximately 0.5), the more effectively the intended effect can be achieved.

[0106] At this ratio, the conductive polymer or polymer layer can exhibit a suitable PTC (positive temperature coefficient) effect. That is, at the above ratio, the polymer layer, the current collector using the polymer layer, or their use can exhibit the effect of suppressing the decrease in the maximum temperature and / or voltage during abnormal state expression.

[0107] The conductive polymer may contain a polar functional group or a unit having said polar functional group (hereinafter referred to as unit B) together with a long-chain hydrocarbon functional group or unit A. The monomer having the polar functional group forming the unit may be a thiophene monomer.

[0108] By applying polar functional groups, a polymer layer containing a conductive polymer can bond with another layer to achieve appropriate bonding strength, and the desired function can be effectively achieved by uniformly forming a conductive copolymer layer. Furthermore, the polar functional groups can additionally influence the onset temperature of the PTC, which is regulated by the first and second hydrocarbon functional groups.

[0109] The term polar functional group is a functional group containing one or two or more polar atoms, such as oxygen and / or nitrogen. Examples of such functional groups include, but are not limited to, carboxyl, hydroxyl, amino, cyano, nitro, ether, or functional groups of Formula 3 below. In one instance, a functional group of Formula 5 below may be used as a polar functional group.

[0110] [Formula 5]

[0111] In Formula 5, L5 is a single bond, alkylene group, or alkylidene group; L6 is an alkylene group or alkylidene group; R9 is hydrogen or alkyl group; and n is any number.

[0112] In Equation 5, the case where L5 is a single bond means that L5 is absent and the oxygen atom between L5 and L6 is directly connected to the second monomer.

[0113] In one example, R9 alkyl in Formula 5 may be 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 methyl or ethyl. The alkyl group may be straight-chain, branched, or cyclic, and may suitably be straight-chain or branched. The alkyl group may optionally be substituted with one or more substituents.

[0114] The term alkylene refers to a divalent functional group formed by removing hydrogen atoms from two different carbon atoms in an alkane, while the term alkylidene refers to a divalent functional group formed by removing two hydrogen atoms from one carbon atom in an alkane.

[0115] In one example, the alkylene groups L5 and L6 in Formula 5 may each be 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, or may be ethylene or propylene. The alkylene group may be straight-chain, branched, or cyclic, and may suitably be straight-chain or branched. The alkylene group may optionally be substituted with one or more substituents.

[0116] In one example, the alkylidene groups L5 and L6 in Formula 5 may each 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, or may be methylene, ethoxy, or propionyl. The alkylidene group may be straight-chain, branched, or cyclic, and may suitably be straight-chain or branched. The alkylidene group may optionally be substituted with one or more substituents.

[0117] In Equation 5, the lower limit of n can be 1, 2, 3, or 4, and its upper limit can be approximately 10, 9, 8, 7, 6, 5, 4, or 3. n can be less than or equal to or less than any of the upper limits selected above, while being greater than or equal to or greater than any of the lower limits selected above.

[0118] The molar number of polar functional groups and long-chain hydrocarbon functional groups in conductive polymers can be controlled to ensure appropriate effects.

[0119] For example, the number M moles of long-chain hydrocarbon functional groups or units having said functional groups in a conductive polymer. A The number M of moles of polar functional groups or units having said functional groups P The ratio M A / M P The lower limit can be approximately 0.5, 1, 5, 10, 15, 16, 17, 18, or 19, while the upper limit can be approximately 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, or 10. This ratio M A / M P The ratio M can be less than or equal to or less than any upper limit selected from the upper limits listed above; greater than or equal to or greater than any lower limit selected from the lower limits listed above; or less than or equal to or less than any upper limit selected from the upper limits listed above while being greater than or equal to or greater than any lower limit selected from the lower limits listed above. A / M P The closer the lower and upper limits are to the values ​​presented in the embodiments of this specification (approximately 9), the more effectively the desired effect can be achieved.

[0120] The lower limit of the ratio of the total moles of units A and B of the conductive polymer to the total moles of all monomer units can be approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, or 95 mol%, and the upper limit can be approximately 100 mol%, 95 mol%, or 90 mol%. This ratio can be greater than or equal to or greater than any of the lower limits listed above; or it can be less than or equal to or less than any of the upper limits listed above while being greater than or equal to or greater than any of the lower limits listed above.

[0121] If the monomers forming the units in the conductive polymer have long-chain hydrocarbon functional groups and / or polar functional groups as described above, there are no particular restrictions on their specific structure.

[0122] For example, conductive polymers may contain units of Formula I as thiophene units.

[0123] [Formula I]

[0124] In Formula I, R1 and R2 can each be hydrogen, a polar functional group, or a long-chain hydrocarbon functional group, independently.

[0125] In another instance, R1 and R2 of Equation I can also be connected to each other to form a divalent functional group of Equation II below.

[0126] [Formula II]

[0127] In Formula II, L1 and L2 can each be a single bond, an alkylene group, or an alkylidene group, and R3 and R4 can each be a hydrogen group, a polar functional group, or a long-chain hydrocarbon functional group.

[0128] When R1 and R2 in Formula I above are each independently hydrogen, a polar functional group or a long-chain hydrocarbon functional group, at least one of R1 and R2 can be a polar functional group or a long-chain hydrocarbon functional group.

[0129] In the case where R1 and R2 in Formula I form a divalent functional group in Formula II, at least one of R3 and R4 can be a polar functional group or a long-chain hydrocarbon functional group.

[0130] In Formula II, the meanings and specific examples of single bonds, alkylene groups, and alkylidenes are the same as in Formula 5.

[0131] The technical significance and specific examples of long-chain hydrocarbon functional groups and polar functional groups in Formulas I and II are as described above.

[0132] Based on the total unit of the conductive polymer, the lower limit of the ratio of the molar numbers of the units in Formula I above can be approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, or 95 mol%, and the upper limit can be approximately 100 mol%, 95 mol%, or 90 mol%. This ratio can be greater than or equal to or greater than any lower limit selected from the lower limits listed above; or less than or equal to or less than any upper limit selected from the upper limits listed above; or greater than or equal to or greater than any lower limit selected from the lower limits listed above while being less than or equal to or less than any upper limit selected from the upper limits listed above.

[0133] In one example, the conductive polymer may contain a unit represented by Formula 1 below. The unit represented by Formula 1 below may be a unit containing the first hydrocarbon functional group as described above.

[0134] [Formula 1]

[0135] In Equation 1, R5 and R6 can each be either hydrogen or a first hydrocarbon functional group. In this case, at least one of R5 and R6 can be a first hydrocarbon functional group.

[0136] In another instance, R5 and R6 can be connected to each other to form a divalent functional group as shown in Equation 2 below.

[0137] [Equation 2]

[0138] In Formula 2, L3 and L4 are each independently a single bond, alkylene group, or alkylidene group, and R7 and R8 are each independently a hydrogen group or a first hydrocarbon functional group, but at least one of R7 and R8 can be a first hydrocarbon functional group.

[0139] The specific details of the first hydrocarbon functional group are as described above. Furthermore, the details of the single bond, alkylene group, or alkylidene group are as described in Formula 5 above.

[0140] The conductive polymer may contain units represented by Formula 3 below. These units may be units having a second hydrocarbon functional group.

[0141] [Formula 3]

[0142] In Equation 3, R 10 and R 11 Each can be an independent hydrogen or second hydrocarbon functional group; in this case, R 10 and R 11At least one of them can be a second hydrocarbon functional group.

[0143] In another instance, R 10 and R 11 They can connect to each other to form a divalent functional group as shown in Equation 4 below.

[0144] [Formula 4]

[0145] In Formula 4, L7 and L8 are each independently a single bond, an alkylene group, or an alkylidene group, and R 12 and R 13 Each is independently a hydrogen or second hydrocarbon functional group, but R 12 and R 13 At least one of them is a second hydrocarbon functional group.

[0146] The specific details of the second hydrocarbon functional group are as described above. Furthermore, the specific details of the single bond, alkylene group, and alkylidene group are as described in Formula 5 above.

[0147] Conductive polymers may contain units represented by Equation 6 below. The unit in Equation 6 above is an example of a unit containing polar functional groups.

[0148] [Formula 6]

[0149] In Equation 6, R 14 and R 15 Each can be an independent hydrogen or polar functional group, and in this case, the above R 14 and R 15 At least one of them is a polar functional group.

[0150] In another example, R in Equation 6 above 14 and R 15 They can connect with each other to form a divalent functional group as shown in Equation 7 below.

[0151] [Formula 7]

[0152] In Equation 7, L9 and L 10 Each is independently a single bond, alkylene group, or alkylidene group, R 16 and R 17 Each is independently either hydrogen or a polar functional group, but R 16 and R 17 At least one of them is a polar functional group.

[0153] The specific details of the polar functional groups are as described above. The specific details of the single bonds, alkylene groups, or alkylidenes are as described in Formula 5 above.

[0154] When the conductive polymer contains units of Formulas 1 and 3 above, the total number of moles M of the units of Formulas 1 and 3 above is... 13 The ratio of 100 × M to the total number of moles M of all units contained in the conductive polymer 13 / M can be compared to the above ratio 100×M A Adjust within the same range as / M.

[0155] The ratio M3 / M1 of the number of moles of the unit in Equation 1 to the number of moles of the unit in Equation 3 can be adjusted within the same range as the ratio M2 / M1 of the number of moles mentioned above. Here, the number of moles M1 can be the number of moles of the unit in Equation 1, and the number of moles M2 can be the number of moles of the unit in Equation 3.

[0156] When the conductive polymer contains units of Formula 6 above, the molar number M of units of Formula 1 and / or Formula 3 above... P With the number of moles M of the unit A The ratio M A / M P The unit can be in the above molar ratio M A / M P Adjust within the same range. Here, the number of moles in unit 6 of Equation 6 can be M. P Number of moles M A It can be the number of moles of Unit 1, the number of moles of Unit 3, or the total number of moles of Units 1 and 3.

[0157] If the conductive polymer contains units in the aforementioned ratio, it may further contain other units. The polymer layer contains the conductive polymer, and therefore can exhibit the aforementioned properties.

[0158] For example, the lower limit of the conductive polymer content in the polymer layer can be approximately 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, and the upper limit can be approximately 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, or 50%. This content is the conductive polymer content based on the total weight of the polymer layer. This content can be greater than or equal to or greater than any of the lower limits listed above; or less than or equal to or less than any of the upper limits listed above while being greater than or equal to or greater than any of the lower limits listed above. The closer the lower and upper limits of the conductive polymer content are to the ranges disclosed in the examples of this specification (about 50% to 90% by weight) or the ranges presented in Examples 1 to 4 (about 50% to 75% by weight), the more effectively the desired effect can be expressed.

[0159] The polymer layer may further contain conductive materials. In addition, it may optionally contain other necessary additives.

[0160] As the conductive material contained in the polymer layer, a material with appropriate electrical conductivity can be used. For example, one or more of the following can be used as the conductive material: carbon particles, carbon fibers, graphene, graphite, carbon black, and carbon nanotubes.

[0161] As a conductive material, appropriate types can be selected and used from the foregoing, wherein the shape of the material can be granular (spherical, irregular or other shapes), plate-shaped or fiber-shaped, etc., but is not limited to these.

[0162] The dimensions of conductive materials can also be adjusted appropriately as needed. For example, the lower limit of the conductive material's dimensions can be approximately 10, 30, 50, 55, 60, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1,000, 5,000, or 10,000, while the upper limit can be approximately 100,000, 90,000, 80,000, or 10,000. The dimensions are approximately 00, 70,000, 60,000, 50,000, 40,000, 30,000, 20,000, 10,000, 5,000, 1,000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 200, 150, 100, 90, 70, or 65. The unit of measurement is nm. The dimension can be greater than or equal to or greater than any of the lower limits selected above; or less than or equal to or less than any of the upper limits selected above; or greater than or equal to or greater than any of the lower limits selected above while being less than or equal to or less than any of the upper limits selected above. The closer the upper and lower limits of the dimensions are to the dimensions of the conductive material used in the embodiments of this specification (approximately 60 nm), the more effectively the expected effect can be expressed.

[0163] When the conductive material is in granular shape, the size can be the average particle size (the so-called D50 particle size). When the conductive material is in plate shape, the size can be the thickness, long side, or cross-section. And when the conductive material is in fiber shape, the size can be the diameter or length of the cross-section.

[0164] When the conductive material is fibrous, the lower limit of the aspect ratio (length / cross-sectional diameter) can be 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, or 65, etc., and the upper limit can be 200, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 125, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, or 70, etc. This aspect ratio can be greater than or equal to or greater than any of the lower limits selected above; or less than or equal to or less than any of the upper limits selected above; or greater than or equal to or greater than any of the lower limits selected above while being less than or equal to or less than any of the upper limits selected above.

[0165] Considering factors such as dispersibility, conductive materials can also undergo surface treatment.

[0166] In this case, a surface treatment agent with suitable compatibility with the conductive polymer can be used as the surface treatment agent. For example, conductive materials can be surface-treated with polyphenolic compounds. Polyphenolic compounds are compounds containing a structure comprising two or more substituted hydroxyl groups linked to benzene. Such compounds can be exemplified by so-called catechol compounds (i.e., catechols or compounds containing related structures), and examples include, but are not limited to, dopamine, polydopamine, 3,4-dihydroxyphenylalanine, norepinephrine, tannic acid, humic acid, and / or lignin.

[0167] There are no restrictions on the methods for surface-treating conductive materials with surface treatment agents. For example, methods such as mixing conductive materials and surface treatment agents in a suitable solvent or synthesizing or polymerizing surface treatment agents on the surface of conductive materials can be used.

[0168] The weight ratio of the conductive material can be adjusted according to the purpose within the polymer layer. For example, relative to 100 parts by weight of conductive polymer in the polymer layer, the lower limit of the weight ratio (parts by weight) of the conductive material can be approximately 5, 10, 15, 20, 25, 30, 40, 50, 60, 65, 70, 80, 90, 95, or 100 parts by weight, while the upper limit can be approximately 195, 190, 180, 170, 160, 150, 145, 140, 135, 130, 125, 120, 100, 80, 60, or 50 parts by weight. The content can be greater than or equal to or greater than any of the lower limits selected above; or less than or equal to or less than any of the upper limits selected above; or greater than or equal to or greater than any of the lower limits selected above while being less than or equal to or less than any of the upper limits selected above. The closer the upper and lower limits of the weight ratio of the conductive material are to the ratios used in the embodiments of this specification, the more effectively the desired characteristics can be expressed.

[0169] In another example, the conductive material can be present in the polymer layer such that D in Equation 4 below is within a predetermined range.

[0170] [Equation 4]

[0171] D=W / T

[0172] In Equation 4, W is the content of conductive material in the polymer layer, and T is the thickness of the polymer layer.

[0173] The content of conductive material, expressed as a percentage by weight, is the weight ratio of conductive material contained in the polymer layer based on the total weight of the polymer layer, and the thickness of the polymer layer is expressed in μm.

[0174] In Equation 4 above, D can represent the distribution density of the conductive material within the polymer layer.

[0175] The lower limit of D in Equation 4 above can be, for example, approximately 40, 60, 80, 100, 150, 200, 250, or 300, and its upper limit can be, for example, approximately 600, 550, 500, 450, 400, 350, 300, 250, 200, 180, 150, 100, 80, or 60. The unit of D is weight% / μm, where weight% is weight%. D can be greater than or equal to or greater than any of the lower limits listed above, while being less than or equal to or less than any of the upper limits listed above. The closer the lower and upper limits of D are to the ranges of Examples 1 to 4 disclosed in this specification, the more effectively the desired effect can be ensured.

[0176] In another example, the lower limit of D in Equation 4 above can be, for example, around 0, 5, 10, or 15, and its upper limit can be, for example, around 30, 25, or 20. The unit of D is weight% / μm, where weight% is weight%. D can be greater than or equal to or greater than any of the lower limits listed above, while being less than or equal to or less than any of the upper limits listed above. The closer the lower and upper limits of D are to the range of Embodiment 5 disclosed in this specification, the more effectively the desired effect can be ensured.

[0177] Therefore, the conductive material contained therein interacts appropriately with the conductive polymer, thereby enabling the effective formation of the desired polymer layer.

[0178] This specification discloses a method for manufacturing an electrode current collector or a method for forming a polymer layer. As described above, the PTC effect of the polymer layer can be adjusted according to the functional groups and conductive materials contained in the conductive polymer, wherein the method includes a process for controlling the appropriate orientation or arrangement of the functional groups and the distribution of the conductive material.

[0179] The method may include the step of forming a polymer layer using a solution containing a conductive polymer, and, if desired, a conductive material.

[0180] In addition, the method may include, for example, the steps of forming a polymer layer precursor and heat-treating the polymer layer precursor.

[0181] The precursor may contain a conductive polymer, and may additionally contain a conductive material if desired.

[0182] As the conductive polymer and / or conductive material used to form the precursor, the conductive polymer and conductive material described above can be used. The conductive polymer, etc., can be prepared by known methods, or commercially available products can be used. For example, as methods for preparing polythiophene, methods using oxidative polymerization reactions, methods using free radical reactions, etc., are known, and these methods can also be applied to the process of forming conductive polymers. Furthermore, commercially available products can also be used as conductive materials, and their surface treatment can be performed in known ways.

[0183] The precursor is a layer containing a conductive polymer and / or a conductive material, which refers to a layer that has been converted into a polymer layer.

[0184] Such precursors can be formed in known ways, for example, by coating a polymer solution in which a conductive polymer or the like is dispersed in a suitable solvent.

[0185] As a solvent, a suitable solvent capable of dispersing conductive polymers and conductive materials can be selected. For example, ether solvents such as diethyl ether, tetrahydrofuran, dioxane, trioxane, dimethoxyethane, or toluene can be used; aromatic hydrocarbon solvents such as ethylbenzene; or alicyclic hydrocarbon solvents such as cyclohexane; or tertiary amine solvents such as tetramethylethylenediamine (TMEDA) or hexamethylphosphoric triamine (HMPA), etc., or mixed solvents containing two or more of the foregoing can be used, but are not limited thereto.

[0186] In this step, the lower limit of the solid content concentration of the polymer solution, i.e., the concentration of the conductive polymer and / or conductive material present in the solution, can be approximately 0.5, 1, 1.5, 2, 2.5, 3, or 3.5, and the upper limit can be approximately 20, 18, 16, 14, 12, 10, 9, 8, 7, 6, 5, 4, or 3. The unit of concentration is weight %. This concentration can be less than or equal to, or less than, any of the upper limits selected above, while being greater than or equal to, or greater than any of the lower limits selected above. This concentration can be changed as needed.

[0187] The polymer solution is used to form the precursor of the polymer layer. This process can typically be carried out by coating the polymer solution onto a suitable process substrate. In this case, there are no particular limitations on the coating method.

[0188] The method further includes a step of heat-treating the precursor of the polymer layer. By adjusting the conditions in this method, the orientation state of the functional groups in the conductive polymer and / or the dispersion state of the conductive material can be adjusted or stabilized, thereby forming a polymer layer that satisfies the desired PTC effect and other properties.

[0189] Polymer solutions can be used to form a polymer layer on a current collector substrate. The method typically includes the steps of coating the current collector substrate with a polymer solution and then subjecting the coated solution to heat treatment, such as drying or annealing. In this method, the orientation state of the functional groups and the dispersion state of the conductive material can be controlled by the heat treatment conditions.

[0190] The heat treatment process can be performed in two steps. For example, the heat treatment process may include a first step of performing a heat treatment on the precursor at temperature T1; and a second step of performing a secondary heat treatment on the precursor at temperature T2 after the first step.

[0191] For example, the temperature T1 of a heat treatment can be adjusted within a predetermined range. For instance, the lower limit of temperature T1 can be approximately 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 its upper limit can be approximately 300°C, 290°C, 280°C, 270°C, 260°C, 250°C, 240°C, 230°C, 220°C, 210°C, 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, or 140°C. This temperature T1 can be greater than or equal to, or greater than, any of the lower limits selected above, while being less than or equal to, or less than, any of the upper limits selected above.

[0192] In the heat treatment process, the temperature T1 of the primary heat treatment and the temperature T2 of the secondary heat treatment can be adjusted. For example, the lower limit of the ratio T1 / T2 can be approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or 1.05, and the upper limit can be approximately 5, 4.5, 4, 3.5, 3, 2.5, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, or 1.1. This ratio T1 / T2 can be greater than or equal to or greater than any of the lower limits listed above, while being less than or equal to or less than any of the upper limits listed above.

[0193] In one example, during the heat treatment step, the temperature T1 of the first heat treatment can be adjusted to be higher than the temperature T2 of the second heat treatment.

[0194] The ratio Q2 / Q1, which represents the heat treatment time Q1 in the primary heat treatment and Q2 in the secondary heat treatment, can be adjusted. For example, the lower limit of this ratio Q2 / Q1 can be approximately 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, and the upper limit can be approximately 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18, 17, 16, or 15. This ratio Q2 / Q1 can be greater than or equal to or greater than any of the lower limits listed above, while being less than or equal to or less than any of the upper limits listed above.

[0195] The lower limit of the secondary heat treatment time Q2 can be approximately 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 51 minutes, 52 minutes, 53 minutes, 54 minutes, 55 minutes, 56 minutes, 57 minutes, 58 minutes, 59 minutes, or 60 minutes, and its upper limit can be approximately 300 minutes, 280 minutes, 260 minutes, 240 minutes, 220 minutes, 200 minutes, 180 minutes, 160 minutes, 140 minutes, 120 minutes, 100 minutes, 80 minutes, or 60 minutes. This secondary heat treatment time Q2 can be greater than or equal to, or greater than, any of the lower limits selected above, while being less than or equal to, or less than, any of the upper limits selected above.

[0196] Polymer layers can be formed using this method.

[0197] This heat treatment process adjusts or stabilizes the orientation state of the conductive polymer (e.g., the orientation state of long-chain hydrocarbon functional groups and / or polar functional groups) and / or the dispersion state of the conductive material, thereby forming a polymer layer that satisfies the expected PTC effect and other properties.

[0198] This method produces the desired polymer layer and a current collector containing that polymer layer. If desired, the method may include appropriate post-processing steps.

[0199] This specification also discloses an electrode including the current collector.

[0200] The electrode may include a current collector and an active material layer formed on a polymer layer of the current collector.

[0201] The layers used in conventional applications can also be used as active material layers.

[0202] Typically, the active material layer contains the electrode active material. There are no particular restrictions on the specific type of electrode active material; materials that form either the positive or negative electrode can generally be used.

[0203] For example, when the active material layer is a positive electrode active material layer, the electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted by one or more transition metals; lithium iron oxide such as LiFe3O4; lithium manganese oxide such as the formula Li 1+c1 Mn 2-c1 O4 (0 ≤ c1 ≤ 0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, V2O5 or Cu2V2O7; Ni-site lithium nickel oxide represented by the formula LiNi 1-c2 M c2 O2 (where M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B and Ga, and 0.01 ≤ c2 ≤ 0.3); lithium manganese composite oxide represented by the formula LiMn 2-c3 M c3 O2 (where M is at least one selected from Co, Ni, Fe, Cr, Zn and Ta, and 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (here, M is at least one selected from 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 formula is substituted by an alkaline earth metal ion, etc., but not limited thereto.

[0204] When the active material layer is a negative electrode active material layer, as the electrode active material, for example, a compound capable of reversibly inserting and extracting lithium can be used. Specific examples may include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon; metal 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 capable of doping and dedoping lithium such as SiO a (0 < a < 2), SnO2, vanadium oxide and lithium vanadium oxide; or a composite material containing a metal compound and a carbonaceous material such as Si-C composite material or Sn-C composite material, etc., and any one of the foregoing or a mixture of two or more thereof can be used.

[0205] A thin film of metallic lithium can also be used as the negative electrode active material, and as the carbon material, low-crystalline carbon and high-crystalline carbon, etc. can also be used. As the low-crystalline carbon, soft carbon and hard carbon are representative, and as the high-crystalline carbon, high-temperature calcined carbon such as amorphous, plate-like, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbead, mesophase pitch, and coke derived from petroleum and coal tar pitch are representative.

[0206] The content of electrode active material in the active material layer can be in the range of about 80% to 99.5% by weight or in the range of 88% to 99% by weight relative to the total weight of the active material layer, but this ratio can be changed depending on the application or design of the electrode.

[0207] The active material layer may further include an adhesive. The adhesive is used to improve the adhesion between the active materials and the adhesive strength between the active material layer and the current collector body. There are no particular limitations on examples of the adhesive, and one or more of the following can be selected and used: PVDF (polyvinylidene fluoride), PVA (polyvinyl alcohol), SBR (styrene-butadiene rubber), PEO (polyethylene oxide), CMC (carboxymethyl cellulose), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), and polyarylates.

[0208] In one example, the amount of binder in the active material layer may be in the range of 0.1 parts by weight to 10 parts by weight, or 0.5 parts by weight to 5 parts by weight, relative to 100 parts by weight of electrode active material, but is not limited thereto.

[0209] As needed, the active material layer may further comprise a conductive material. Any known material can be used without particular limitation, provided the conductive material is conductive without causing chemical changes in the secondary battery. For example, graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers, such as carbon fibers or metal fibers; conductive tubes, such as carbon nanotubes (CNTs); metal powders, such as fluorocarbons, aluminum or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives, etc.

[0210] In one example, the content of conductive material in the active material layer may be from 0.1 parts by weight to 20 parts by weight, or from 0.3 parts by weight to 10 parts by weight, relative to 100 parts by weight of electrode active material, but is not limited thereto.

[0211] In addition to the components mentioned above, the active material layer may optionally contain any necessary known components.

[0212] If a current collector is used, the electrode can be manufactured according to conventional electrode forming methods.

[0213] This specification also relates to an electrode assembly or electrochemical element that includes the electrode, such as a secondary battery.

[0214] Electrochemical elements may include electrodes that serve as positive and / or negative electrodes. If electrodes are used as positive and / or negative electrodes, there are no particular limitations on other configurations or manufacturing methods of the electrochemical element, and known methods can be applied.

[0215] Beneficial effects

[0216] This specification discloses a current collector. The current collector includes a polymer layer exhibiting a so-called PTC (Positive Temperature Coefficient) effect. The polymer layer exhibits a PTC effect that responds very precisely to temperature and external voltage. The polymer layer can rapidly switch between a state exhibiting excellent electrical properties, such as low resistance, and a state exhibiting insulating properties due to increased resistance, when necessary. Applying the current collector to various electronic / electrical devices ensures that, under normal conditions, its excellent electrical properties do not affect the device's operation, etc., while under abnormal conditions, stability is ensured through a rapid increase in resistance. For example, applying the current collector to a secondary battery to switch to an insulator under abnormal conditions, thereby suppressing the flow of extra current, can ensure excellent stability against risks caused by factors such as TR and TP.

[0217] This specification also discloses an electrode assembly including the current collector and a secondary battery, etc. Attached Figure Description

[0218] Figure 1 This is a cross-sectional view of an exemplary current collector.

[0219] Figure 2 This is a cross-sectional view of an exemplary electrode.

[0220] Figure 3 The results are NMR analysis of the monomer from Preparation Example 1.

[0221] Figure 4 It is a diagram showing the shape of the positive electrode.

[0222] Figure 5 This is a diagram showing the shape of the negative electrode.

[0223] Figure 6 This is a side view of an exemplary electrode assembly.

[0224] Figure 7 This is a front view of an exemplary electrode assembly.

[0225] Figure 8 This is a cross-sectional view of an exemplary needle.

[0226] Figure 9 This is a side view of an exemplary needle.

[0227] Figure 10 It is a figure showing an exemplary acupuncture test procedure. Detailed implementation

[0228] Hereinafter, conductive polymers and the like will be specifically described through examples and comparative examples, but the scope of conductive polymers and the like is not limited by the following examples.

[0229] 1. NMR analysis

[0230] It is carried out at room temperature (about 25 °C) using an NMR device with a 5 mm triple resonance probe and including a Bruker UltraShield spectrometer (300 MHz). 1 1H-NMR analysis. The sample is diluted in a solvent (CDCl3) for NMR measurement to a concentration of about 10 mg / ml and used, and the chemical shift is expressed in ppm.

[0231] 2. GPC (Gel Permeation Chromatography)

[0232] The molecular weight characteristics are measured using GPC (Gel Permeation Chromatography). The sample is placed in a 5 mL vial and diluted with chloroform to a concentration of about 1 mg / mL. The standard sample for calibration and the analysis sample are filtered through a syringe filter (pore size: 0.45 μm) and then measured. As the analysis program, Empower 3 from Waters is used, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are obtained respectively by comparing the elution time of the sample with the calibration curve, and the molecular weight distribution (PDI) is calculated by the ratio (Mw / Mn).

[0233] The measurement conditions of GPC are as follows.

[0234] <GPC measurement conditions>

[0235] Device: 2414 from Waters

[0236] Column: Use 3 Styragels from Waters

[0237] Solvent: THF (tetrahydrofuran)

[0238] Column temperature: 35 °C

[0239] Sample concentration: 1 mg / mL, inject 1 μL

[0240] Standard sample: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940, 485)

[0241] 3. Thickness measurement

[0242] The thickness of the polymer layer was measured using a KEYENCE VK-X series confocal laser microscope. A sample was prepared by cutting an aluminum foil with the polymer layer formed on it to a width and length of 3 cm, and removing approximately half of the polymer layer from the sample with acetone to expose the underlying aluminum foil. The aluminum foil side of the sample without the polymer layer was pressed onto a plate, and measurement began. An area with a width and length of 100 μm was observed under the microscope, but the polymer layer of the sample and the exposed aluminum foil were each positioned within approximately half of the observation area, and a 3D scan was performed. The average height P was measured by optionally specifying 10 points in the polymer layer within the observation area, and the average height A was obtained by optionally measuring the height at 10 points on the aluminum foil. The value obtained by subtracting the average value A from the average value P was then used as the thickness of the polymer layer.

[0243] 4. Average particle size

[0244] The average particle size (D50 diameter) of conductive particles, electrode active materials, and particulate binders was measured according to ISO-13320 standard using a MASTERSIZER 3000 instrument from Marvern. Toluene was used as the measurement solvent. If the sample (conductive particles) is dispersed in the solvent and a laser is irradiated, the laser light is scattered by the sample dispersed in the solvent. Since the intensity and directionality of the scattered laser light vary according to the particle size, the average particle size can be obtained by analyzing it using Mie theory. Based on the above analysis, the measurement results are converted into the particle size of spheres with the same volume as the dispersed sample to obtain a cumulative plot of the volume-based particle size distribution, and the particle size at 50% cumulatively in this plot (the median particle size) is designated as the average particle size (D50 diameter).

[0245] 5. Needle prick test

[0246] A single cell for nail penetration testing is manufactured in the following manner.

[0247] The positive electrode was manufactured by forming a positive electrode active material layer on the surface of the polymer layer of each electrode current collector obtained in the examples or comparative examples (in the case of Comparative Example 1, the positive electrode active material layer was formed on aluminum foil). A slurry was applied to the polymer layer using a doctor blade and dried at 130°C for 30 minutes (slurry loading: approximately 24.4 mg / cm³). 2 Then, it is rolled to a porosity of about 18%, forming a positive electrode active material layer with a thickness of about 61 μm.

[0248] A slurry was prepared by mixing lithium cobalt oxide (LiCoO2), conductive materials (ECP (Kejtien Black) 0.5%, SFG (Trimrex graphite) 0.4%, DB (Denka Black) 0.4%), PVDF (polyvinylidene fluoride), and NMP (N-methyl-2-pyrrolidone) in a weight ratio of 90.5:1:1:7.5 (LiCoO2: conductive materials: PVDF: NMP).

[0249] The positive electrode is formed to have the following characteristics: Figure 4 The shape shown.

[0250] exist Figure 4 In the figure, the length L1 is approximately 42 mm, the width W1 is approximately 30 mm, the length L2 is approximately 7 mm, and the width W2 is approximately 6 mm. The polymer layer and the positive electrode active material layer are formed only in the region defined by the length L1 and the width W1, and the positive electrode active material layer and the polymer layer are not formed on the tab portion having the length L2 and the width W2.

[0251] The negative electrode is manufactured in the following manner.

[0252] A copper foil with a thickness of 8 μm was used as the current collector. A negative electrode active material layer was formed on the copper foil using a slurry. The slurry was prepared by mixing water, SBR (styrene-butadiene rubber) (particulate binder, average particle size (D50 particle size): approximately 150 nm), thickener (CMC, carboxymethyl cellulose), and electrode active materials (1) (artificial graphite (GT), average particle size (D50 particle size): 20 μm) and (2) (natural graphite (PAS), average particle size (D50 particle size): 15 μm) in a weight ratio of 48.5:1:0.5:45:5 (water:SBR:CMC:active material (1):active material (2)). The slurry was coated by a gap coating method and dried at approximately 75 °C for approximately 10 minutes. After drying, the loading of the slurry was approximately 13.88 mg / cm³. 2 The porosity is approximately 26% by rolling it into an active material layer.

[0253] This negative electrode is formed to have Figure 5 The shape.

[0254] exist Figure 5 In the diagram, length L3 is the same as the length L1 of the positive electrode, width W3 is the same as the width W1 of the positive electrode, length L4 is the same as the length L2 of the tab portion of the positive electrode, and width W4 is the same as the width W2 of the tab portion of the positive electrode. The active material layer is formed only in the region defined by length L3 and width W3, and the active material layer is not formed on the tab portion having length L4 and width W4.

[0255] A single cell was manufactured using a positive and a negative electrode. The single cell was manufactured using a W-SCOPE KOREA WL20C model separator and an Enchem electrolyte (1M LiPF6 solution (solvent: EC / DMC / EMC = 3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethyl methyl carbonate)).

[0256] like Figure 6 As shown, electrode assemblies are manufactured by laminating a positive electrode, a negative electrode, and a separator. (As in...) Figure 6 In the side view of the electrode assembly, the laminate is manufactured by sequentially laminating aluminum foil (C1), a polymer layer (C2), a positive electrode active material layer (C3), a separator (S), a negative electrode active material layer (A2), and a negative electrode current collector (copper foil) (A1), and as shown in Figure 7 In the middle, when viewed from the front, the tabs of the positive and negative electrodes are positioned at the ends that are spaced apart from each other in the same direction.

[0257] Subsequently, the electrode assembly was inserted into an envelope-style pouch (manufacturer: DNP, product name: D-EL408PH(3)) with a thickness of approximately 152 μm, and the electrolyte was injected into the pouch. The pouch was then sealed to manufacture a single cell. The sealing process was performed so that the tab portions of the positive and negative electrodes were exposed to the outside.

[0258] A single cell manufactured in the same manner using the current collector of Comparative Example 1 was used as a reference single cell.

[0259] As the needle used for needle prick testing, needle (N) (Korea Vaccine, KOVAX-NEEDLE 18G) is used. This needle (N) has a circular cross-sectional shape with a diameter (D1) of approximately 1.2 mm and a hole with a diameter (D2) of approximately 0.9 mm formed at the center of the circle. (The text abruptly ends here.) Figure 8 and Figure 9 As shown, the needle is manufactured by inserting a type K thermocouple (T) (OMEGA, TT-K-30-SLE) into the hole. Figure 8 This is a cross-sectional view of the needle (N) into which the thermocouple (T) is inserted. Figure 9 This is a side view of the needle (N) into which the thermocouple (T) is inserted.

[0260] Using a single battery and a needle, the following test was conducted.

[0261] The needle is mounted on the syringe pump assembly (KDS scientific., LEGATO 200) and moved at a constant speed to prepare it for penetration of the single cell. The single cell is held in place by a clamp, and the needle is used to penetrate the held single cell.

[0262] like Figure 10As shown, after setting the single cell to a fully charged state (SOC 100%), the pouch (P) on the positive current collector (C1, aluminum foil) side is removed from the pouch (P) to expose the positive current collector (C1), and a needle (N) is advanced toward the exposed positive current collector (C1), thereby penetrating the single cell. Penetration is then achieved by advancing the needle (N) at a speed of 0.02 mm / s, aiming to penetrate the center (weighted center) of the electrode assembly. Furthermore, penetration continues until the needle (N) penetrates the negative current collector (A1, copper foil) and reaches the pouch (P). Figure 10 In this context, ST is a surface temperature sensor mounted on the positive current collector (C1).

[0263] If the needle (N) is allowed to penetrate from the positive current collector (C1) to the negative current collector (A1) in this manner, a short circuit occurs, and a voltage drop is observed. The time point at which the voltage first reaches its minimum due to the voltage drop is set to 0 seconds. From the time point when the voltage reaches its minimum (0 seconds), the temperature rise is measured over time with the thermocouple inserted into the needle to determine the time point at which the highest temperature is confirmed, and also to determine the highest temperature and voltage at that time point.

[0264] like Figure 10 As shown, the voltage is determined by connecting a voltmeter (V) to the tabs of the positive and negative terminals.

[0265] The reference single cell was also subjected to a nail penetration test in the same manner.

[0266] Preparation Example 1. Synthesis of Monomer (A)

[0267] The monomer of formula A is synthesized in the following manner.

[0268] [Formula A]

[0269] 3 g (26.28 mmol, 1 equivalent) of 3-methoxythiophene and 7.03 g (39.42 mmol, 1.5 equivalent) of triethylene glycol monomethyl ether were dissolved together with 500 mg of p-toluenesulfonic acid (p-TsOH) (2.63 mmol, 0.1 equivalent) in 150 mL of toluene. The mixture was refluxed at 120 °C under a nitrogen atmosphere while reacting (ester exchange), thereby removing methanol produced by the reaction through a Soxhlet extractor filled with a type 4A molecular sieve. After refluxing the reaction mixture for 24 hours, it was cooled to room temperature, quenched with water, extracted with ethyl acetate, washed with brine, and dried with magnesium sulfate (MgSO4). The solvent was removed by rotary evaporation, and the residue was purified by column chromatography, eluting with dichloromethane / hexane (2:1) to obtain the target compound (monomer (A)). The NMR analysis results of monomer (A) are as follows. Figure 3 As shown.

[0270] Preparation Example 2. Synthesis of Polythiophene (B)

[0271] 3.20 g (19.71 mmol, 3 equivalents) of ferric chloride (III) was dissolved in 150 mL of dichloromethane solution. 1 g (3.94 mmol, 0.6 equivalents) of 3-dodecylthiophene, 0.33 g (1.97 mmol, 0.3 equivalents) of 3-hexylthiophene, and 0.16 g (0.66 mmol, 0.1 equivalents) of monomer (A) from Preparation Example 1 were introduced, and polymerization was carried out at 30 °C for 24 hours to prepare polythiophene (A). The polymerization solution was placed in a permeation membrane with a MWCO (molecular weight cutoff) of 5000, and then immersed in 200 mL of acetonitrile solvent to remove unreacted ferric chloride, monomer, and low molecular weight oligomers. The residue precipitated in the permeation membrane was washed with methanol, and dried at 60 °C for 12 hours to prepare polythiophene (A). The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polythiophene (A) are 118,000 g / mol and 24,500 g / mol, respectively.

[0272] Preparation Example 3. Polydopamine-coated conductive particles

[0273] Carbon black particles (IMERYS, C-NERGY) TM SUPER C65 is used as conductive particles. The average particle size (D50 particle size) of the conductive particles is approximately 60 nm.

[0274] DHC (dopamine hydrochloride) (CAS No. 62-31-7) was added to a buffer solution and stirred at room temperature (approximately 25°C). A 0.1M pH 8.5 Tris buffer product from BIOSESANG was used as the buffer solution. The final concentration of DHC in the solution was approximately 2 mg / mL. Conductive particles were dispersed at a concentration of approximately 4 mg / mL (sonicated for 1 hour) in the mixture of buffer solution and DHC, and stirred for an additional approximately 18 hours to form a polydopamine coating on the conductive particles. After vacuum filtration using a paper filter, the resulting particles were vacuum dried to obtain polydopamine-coated conductive particles.

[0275] Example 1.

[0276] A polymer solution was prepared by dispersing a mixture of polythiophene (B) from Preparation Example 2 and conductive particles (P) from Preparation Example 3 at a weight ratio of 3:1 (B:P) in toluene at a concentration of approximately 4% by weight. The polymer solution was prepared by dispersing the polythiophene (B) and conductive particles (P) in toluene at approximately 30°C for approximately 4 hours using an ultrasonic disperser. The polymer solution was coated onto the current collector substrate using the Meyer rod coating method, dried in a drying oven at approximately 140°C for approximately 4 minutes (first heat treatment), and then further heat-treated at 130°C for approximately 60 minutes (second heat treatment) to form a polymer layer with a thickness of approximately 300 nm, thereby manufacturing the electrode current collector. An Al foil with a thickness of approximately 15 μm was used as the current collector substrate.

[0277] Example 2.

[0278] Except that the thickness of the polymer layer is set to about 600 nm, the electrode current collector is manufactured by forming the polymer layer in the same manner as in Example 1.

[0279] Example 3.

[0280] Except for the polymer solution prepared by dispersing a mixture of polythiophene (B) of Preparation Example 2 and conductive particles (P) of Preparation Example 3 in toluene at a weight ratio of 1:1 (B:P) in toluene at a concentration of about 4% by weight, the electrode current collector was manufactured in the same manner as in Example 1.

[0281] Example 4.

[0282] Except that the thickness of the polymer layer is set to about 600 nm, the electrode current collector is manufactured by forming the polymer layer in the same manner as in Example 3.

[0283] Example 5.

[0284] The electrode current collector was manufactured in the same manner as in Example 2, except that a polymer solution was prepared by dispersing a mixture of polythiophene (B) of Preparation Example 2 and conductive particles (P) of Preparation Example 3 in a weight ratio of 9:1 (B:P) in toluene at a concentration of about 4% by weight.

[0285] Example 6.

[0286] A polymer solution was prepared by dispersing polythiophene (B) from Preparation Example 2 in toluene at a concentration of approximately 4% by weight. The polymer solution was prepared by dispersing polythiophene (B) in toluene at approximately 30°C for approximately 4 hours using an ultrasonic disperser. The polymer solution was coated onto the current collector substrate using the Meyer rod coating method, dried in a drying oven at approximately 140°C for approximately 4 minutes (first heat treatment), and then further heat-treated at 130°C for approximately 60 minutes (second heat treatment) to form a polymer layer with a thickness of approximately 300 nm, thereby fabricating the electrode current collector. An Al foil with a thickness of approximately 15 μm was used as the current collector substrate.

[0287] Example 7.

[0288] Except for the polymer solution prepared by dispersing a mixture of polythiophene (B) of Preparation Example 2 and conductive particles (P) of Preparation Example 3 in toluene at a weight ratio of 9:1 (B:P) in toluene at a concentration of about 4% by weight, the electrode current collector was manufactured in the same manner as in Example 1.

[0289] Comparative Example 1

[0290] In the absence of a polymer layer, an Al foil with a thickness of approximately 15 μm is used as the electrode current collector.

[0291] Compare Example 2.

[0292] The electrode current collector was manufactured in the same manner as in Example 1, except that a polymer solution was prepared by dispersing a mixture of polythiophene (B) of Preparation Example 2 and conductive particles (P) of Preparation Example 3 in a weight ratio of 1:2 (B:P) in toluene at a concentration of about 4% by weight.

[0293] Comparative Example 3.

[0294] Except that the thickness of the polymer layer is set to about 600 nm, the electrode current collector is manufactured by forming the polymer layer in the same manner as in Comparative Example 2.

[0295] The results of the needle penetration tests performed on the electrode current collectors of the embodiments and comparative examples are described in Tables 1 and 2 below.

[0296] In Tables 1 and 2 below, T2 is the highest temperature confirmed by a thermocouple by performing a nail penetration test on a reference single cell (a single cell manufactured using the current collector of Comparative Example 1), and T1 is the highest temperature confirmed by a thermocouple by performing a nail penetration test on each of the Examples and Comparative Examples. The units for temperatures T1 and T2 are °C. In Table 1 below, ΔT is the value obtained by substituting temperatures T1 and T2 into the equation (T2-T1) / T2×100, and its unit is %.

[0297] In Tables 1 and 2, T0 is the temperature determined by the needle thermocouple at time 0 seconds during the needle penetration test (the time when the voltage becomes minimum due to the short circuit in the needle penetration test = the time when the voltage becomes minimum due to the voltage drop in the needle penetration test), and its unit is °C.

[0298] S1 in Tables 1 and 2 is the time required from the 0-second mark in the needle prick test to the time point at which the highest temperature T1 is confirmed, and its unit is seconds.

[0299] In Tables 1 and 2, V1 is the voltage of a single cell in a fully charged state before the needle penetration test, and V2 is the minimum voltage confirmed by needle penetration tests on the electrode current collectors of each of the examples and comparative examples, and the unit is volts (V). ΔV in Tables 1 and 2 is the value obtained by substituting voltages V1 and V2 into the equation (V1-V2) / V1×100, and the unit is %. S in Tables 1 and 2 is the value obtained by substituting temperatures T1 and T0 and time S1 into the equation (T1-T2) / S1, and the unit is °C / second.

[0300] [Table 1]

[0301] [Table 2]

[0302] As can be seen from Tables 1 and 2, when the electrode current collector disclosed in this specification is used, even if a short circuit occurs, the temperature rise is effectively suppressed by blocking abnormal charge migration.

[0303] On the other hand, in Comparative Example 1, where a current collector without any polymer layer was applied, it was observed that a severe voltage drop occurred, and the temperature rose rapidly due to the abnormally rapid migration of charge when a short circuit occurred.

Claims

1. A current collector, comprising: The main body of the current collector; and A polymer layer formed on the current collector body The polymer layer comprises a conductive polymer, and The ΔT in Equation 1 below is greater than 15%: [Equation 1] ΔT=(T2-T1) / T2×100 Wherein, T1 is the highest temperature in the nail penetration test of a fully charged single cell including the current collector, and T2 is the highest temperature in the nail penetration test of a reference single cell.

2. The current collector according to claim 1, wherein, In Equation 1, T1 is below 90℃.

3. The current collector according to claim 1, wherein, For equation 2 below, S is below 70: [Equation 2] S=(T1-T0) / S1 Wherein, T1 is the same as T1 in Equation 1, T0 is the temperature at the point in time when the minimum voltage is confirmed in the nail penetration test of a fully charged single cell including the current collector, and S1 is the time required from the point in time when the temperature T0 is confirmed to the point in time when the temperature T1 is confirmed.

4. The current collector according to claim 3, wherein, The S1 of Equation 2 is more than 0.5 seconds.

5. The current collector according to claim 1, wherein, The ΔV in Equation 3 below is below 80%: [Equation 3] ΔV = (V1 - V2) / V1× 100 Wherein, V2 is the minimum voltage in the nail penetration test of a fully charged single cell including the current collector, and V1 is the voltage of a fully charged single cell before the nail penetration test.

6. The current collector according to claim 1, wherein, The conductive polymer comprises units having long-chain hydrocarbon functional groups.

7. The current collector according to claim 6, wherein, The conductive polymer comprises units having a first hydrocarbon functional group having more than 10 carbon atoms and units having a second hydrocarbon functional group having fewer than 9 carbon atoms.

8. The current collector according to claim 7, wherein, The sum of the molar numbers of units having a first hydrocarbon functional group and units having a second hydrocarbon functional group is at least 70 mol% relative to the total molar number of all units contained in the conductive polymer.

9. The current collector according to claim 8, wherein, The ratio M2 / M1 of the number of moles of units with a second hydrocarbon functional group M2 to the number of moles of units with a first hydrocarbon functional group M1 is from 0.01 to 100.

10. The current collector according to claim 6, wherein, The conductive polymer further comprises units having polar functional groups.

11. The current collector according to claim 10, wherein the polar functional group is a carboxyl, hydroxyl, amino, cyano, nitro, ether, or a functional group of formula 5 below: [Formula 5] in, L5 is a single bond, alkylene group, or alkylidene group; L6 is an alkylene group or alkylidene group; R9 is hydrogen or alkyl group; and n is a number in the range of 1 to 10.

12. The current collector according to claim 1, wherein, The polymer layer further comprises a conductive material.

13. The current collector according to claim 12, wherein, The conductive material is surface-treated with polyphenolic compounds.

14. The current collector according to claim 12, wherein, The amount of the conductive polymer in the polymer layer is in the range of 30% to 95% by weight, and the content of the conductive material is from 5 parts by weight to 195 parts by weight relative to 100 parts by weight of the conductive polymer.

15. The current collector according to claim 12, wherein, In Equation 4 below, D is in the range of 40 wt% / μm to 400 wt% / μm: [Equation 4] D=W / T Where W is the amount of conductive material in the polymer layer, and T is the thickness of the polymer layer.

16. The current collector according to claim 1, wherein, The polymer layer has a thickness in the range of 100 nm to 2,000 nm.

17. An electrode comprising: The current collector as described in claim 1; and An electrode active material layer is formed on the polymer layer of the current collector.

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

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

20. A secondary battery comprising the electrode assembly of claim 18.

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