Electrode assembly

Abstract

The present specification discloses an electrode assembly and a secondary battery. The electrode assembly can exhibit low resistance and excellent electrical characteristics in a normal state, and ensure stability by rapidly transitioning to an insulator in an abnormal state. The present specification also discloses a secondary battery including the electrode assembly.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0012285 dated January 26, 2024 and Korean Patent Application No. 10-2024-0030200 dated February 29, 2024, all disclosures of which are incorporated herein by reference.

[0002] This specification discloses an electrode assembly and a secondary battery including the electrode assembly. Background Technology

[0003] Secondary batteries (such as lithium-ion batteries) have a wide range of applications, including portable electronic devices, electric vehicles (EVs), and renewable energy storage systems.

[0004] For example, secondary batteries used as a power source for transportation vehicles such as electric vehicles require greater capacity and power.

[0005] The increase in the capacity and power of secondary batteries leads to problems with battery stability. For example, with the increase in capacity and power, the risk of phenomena such as thermal runaway, which can lead to uncontrolled temperature rise and hazardous chemical leaks, also increases.

[0006] Commercially available secondary batteries are equipped with external safety devices (such as pressure relief valves, battery compartment fire extinguishers, or high-temperature insulation materials), but these safety devices are not effective in dealing with dangerous situations such as thermal runaway, or exhibit slow response times. Summary of the Invention

[0007] Technical issues

[0008] This specification discloses an electrode assembly and a secondary battery. The present specification aims to disclose an electrode assembly comprising an electrode that exhibits low resistance and excellent electrical properties under normal conditions and ensures stability by rapidly transforming into an insulator under abnormal conditions. The stability of the electrode assembly can be further improved when the electrode is combined with a separator known as an SRS (Safety Reinforced Separator). This specification also discloses a secondary battery including the electrode assembly.

[0009] Technical solution

[0010] In this specification, the term room temperature refers to the natural temperature without artificial heating or cooling. Room temperature can be any temperature in the range of 10°C to 30°C, or around 23°C or around 25°C.

[0011] Unless otherwise stated, the physical properties mentioned in this specification that are affected by the test temperature are those measured at room temperature.

[0012] In this manual, unless otherwise stated, the temperature unit is Celsius (°C).

[0013] In this specification, the term atmospheric pressure refers to natural pressure without artificial pressurization or depressurization, which typically refers to pressure in the range of approximately 730 mmHg to 790 mmHg.

[0014] Unless otherwise stated, the physical properties mentioned in this specification that are affected by the test pressure are those measured at atmospheric pressure.

[0015] Unless otherwise stated, the physical properties mentioned in this specification that are affected by the measured humidity are physical properties measured at room temperature and normal pressure without artificial adjustment.

[0016] In this specification, the term "normal state" refers to the normal operating or storage state of a secondary battery. For example, the normal charging, discharging, or storage state of a secondary battery is a normal state.

[0017] In this specification, the term "abnormal state" refers to a state in which an abnormal temperature rise, heat generation, or explosion occurs, or a state in which the risk of such a state occurring increases.

[0018] This specification discloses an electrode assembly.

[0019] The electrode assembly includes a positive electrode (cathode), a negative electrode (anode), and a separator. The separator may be present between the positive and negative electrodes. In the electrode assembly, the positive electrode, separator, and negative electrode may be stacked in this order to form a laminate.

[0020] Figure 1 This is an example of a laminate, in which the positive electrode (C), the separator (S), and the negative electrode (A) are stacked in sequence.

[0021] The diaphragm applied to the electrode assembly can be a diaphragm known as a so-called SRS (Safety Reinforced Diaphragm).

[0022] SRS is a type of separator that includes an inorganic particulate layer on the surface of a separator substrate (porous polymer membrane). Compared to conventional separators, this separator exhibits stability and maintains its performance even at higher temperatures. Significantly improved stability can be ensured by combining this separator with electrodes having a polymer layer, which will be described below.

[0023] This type of SRS is well known.

[0024] For example, such as Figure 2 As shown, the SRS may include a porous polymer membrane (100) and an inorganic particulate layer (200). Figure 2In one form, the inorganic particle layer (200) is formed on one surface of the polymer film (100), but the inorganic particle layer (200) can also be formed on both surfaces of the polymer film (100).

[0025] As a porous polymer membrane, polymer membranes commonly used in SRS can be used. For example, materials that promote lithium-ion movement and have excellent wettability in the electrolyte can be used.

[0026] In one instance, a polyolefin polymer membrane can be used as a porous polymer membrane.

[0027] Polyolefin polymer membranes that can be used as porous polymer membranes in SRS are known in industry. For example, porous polymer membranes can be applied to them, said porous polymer membranes being produced from one or more combinations of the following: polyethylene, such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene and ultra-high molecular weight polyethylene; polypropylene; polybutene; polypentene, polyhexene, polyoctene; and copolymers containing two or more monomer units selected from ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene.

[0028] Porous polymer membranes typically have a thickness of about 1 μm to 100 μm, or about 5 μm to 50 μm. In such porous polymer membranes, pores with a size of about 0.001 μm to 50 μm are typically formed, and the porosity is typically adjusted to be in the range of 10% to 95%.

[0029] SRS comprises an inorganic particulate layer formed on one or both surfaces of a porous polymer membrane. The term inorganic particulate layer is a layer containing inorganic particles.

[0030] As inorganic particles, they can be used in the operating voltage range of electrochemical devices such as secondary batteries (e.g., based on Li / Li). + Particles that do not undergo oxidation and reduction reactions within a voltage range of 0V to 5V can be used, and inorganic particles with ion transport capabilities can also be used. For example, if inorganic particles with high dielectric constants are used, they help to increase the degree of dissociation of electrolyte salts such as lithium salts in the electrolyte, thereby increasing the ionic conductivity of the electrolyte.

[0031] For example, inorganic particles with a dielectric constant of 5 or higher and / or inorganic particles with lithium-ion transport capability can be used as inorganic particles.

[0032] As examples of such inorganic particles, one or more inorganic particles selected from the following can be used: BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Tiy O3 (PLZT), Pb(Mg3Nb2 / 3)O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC; and / or one or more inorganic particles selected from the following: (LiAlTiP) x O y (0 < x < 4, 0 < y < 13) series glasses such as Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3) and / or 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5, Li x La y TiO3 (0 < x < 2, 0 < y < 3), and / or Li x Ge y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5) such as Li3. 25 Ge0. 25 P0. 75 S4; and / or SiS2 series glasses (Li x Si y S z (, 0 < x < 3, 0 < y < 2, 0 < z < 4) such as Li3PO4 - Li2S - SiS2, and / or P2S5 series glasses (Li x P y S z (, 0 < x < 3, 0 < y < 3, 0 < z < 7) such as LiI - Li2S - P2S5.

[0033] Such inorganic particles generally have a size in the range of 0.001 μm to 10 μm.

[0034] In SRS, the inorganic particulate layer can comprise a polymer binder as well as inorganic particles. Commonly used polymer binders include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, and / or polyimide, and mixtures of one, two, or more of these binders can be used.

[0035] Typically, the content of inorganic particles in the inorganic particle layer can be 10% to 95% by weight, 30% to 95% by weight, 50% to 95% by weight, or 70% to 90% by weight. When a binder is included, the binder can be included in a proportion of about 5% to 100% by weight or about 10% to 50% by weight relative to 100 parts by weight of inorganic particles.

[0036] In addition to the binder, the inorganic particulate layer may further contain known essential components, such as organic particles, to enhance the bonding strength with the binder polymer and improve air permeability, heat shrinkage and peel strength.

[0037] The inorganic particulate layer can typically have a thickness of 0.1 μm to 50 μm, or 1 μm to 10 μm. Methods for preparing such SRS are known, and the inorganic particulate layer can be formed using these known methods.

[0038] SRS membranes can be used as the separators for the electrode assemblies disclosed in this specification, but the types of separators that can be used are not necessarily limited to this. In addition to SRS separators, other known separators can also be used as the separators.

[0039] The electrode assembly includes a positive electrode, a negative electrode, and a separator.

[0040] The positive and negative electrodes each include a current collector and an active material layer formed on one or both surfaces of the current collector.

[0041] Either or both of the positive and negative electrodes may include, for example, a polymer layer. Figure 3 This is an example of an electrode structure that includes a polymer layer. When a polymer layer is included, the polymer layer (1002) may be present between the current collector (1001) and the active material layer (1003) of the positive and / or negative electrode.

[0042] For example, when the positive electrode includes a polymer layer, the positive electrode may include a current collector, a polymer layer formed on the current collector, and an active material layer formed on the polymer layer.

[0043] In the electrode, the current collector and the polymer layer, as well as the polymer layer and the active material layer, can be in contact with each other. In some cases, other elements may also be present between the current collector and the polymer layer, or between the polymer layer and the active material layer. Although Figure 3 The illustration shows the case where the active material layer (1003) exists only on one surface of the current collector (1001), but the active material layer (1003) can also exist on both surfaces of the current collector (1001). In this case, the polymer layer (1002) can also exist as two layers between each active material layer (1003) present on both surfaces of the current collector (1001) and the current collector (1001), and can also exist as one layer between any one of the active material layers (1003) present on the two surfaces and the current collector (1001).

[0044] The polymer layer exhibits a so-called PTC (positive temperature coefficient) effect. Therefore, the charge transport through the electrodes can be variably controlled according to the temperature of the polymer layer.

[0045] By applying this polymer layer, the electrode can exhibit low resistance and excellent electrical performance under normal conditions, and stability can be ensured by increasing resistance under abnormal conditions.

[0046] To ensure the polymer layer exhibits the aforementioned effects, the tendency of the PTC effect exhibited by the polymer layer must be controlled. The PTC effect is an effect where resistance increases proportionally with temperature. The temperature at which the resistance increases due to the PTC effect, and the resistance of the polymer layer before the increase, affect the performance of the secondary battery. If the PTC effect is excessively pronounced under normal conditions, the performance of the secondary battery will not be able to reach its full potential until stability is ensured.

[0047] The polymer layer disclosed in this specification has a PTC effect, which does not affect the performance of the secondary battery under normal conditions and is controlled to ensure stability under abnormal conditions.

[0048] The aforementioned effect can be ensured by applying conductive polymers with long-chain hydrocarbon functional groups and / or polar functional groups. If desired, a suitable PTC effect can also be ensured by controlling the drying or annealing temperature during the polymer layer formation process. Furthermore, the oxidation potential of the polymer layer can be tuned by combining this conductive polymer with a conductive material.

[0049] 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, 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. The content is the polymer content based on the total weight of the polymer layer, expressed as a percentage by weight (wt%). This polymer can be a conductive polymer and / or an adhesion improver, as described below. The content can be greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above; or it can be less than or equal to, or less than, any upper limit chosen from the upper limits listed above, while being greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above.

[0050] The polymer layer does not necessarily have to be a so-called electrode active material layer. Therefore, the content of electrode active material in the polymer layer can be controlled. For example, the upper limit of the content of electrode active material in the polymer layer can be approximately 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, 0.1, 0.05, 0.01, 0.005, or 0.001, and its lower limit can be 0. The content is the content of electrode active material based on the total weight of the polymer layer, expressed as a percentage by weight. The content can be less than or equal to, or less than, any upper limit chosen from the upper limits listed above; or, while being less than or equal to, or less than, any upper limit chosen from the upper limits listed above, greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above. Specific types of electrode active materials will be described below.

[0051] In this specification, the term conductive polymer has a known meaning. For example, the term conductive polymer refers to a polymer that exhibits conductivity, as is known, through a conjugated system of polymer chains and / or doping, etc.

[0052] In this specification, the term non-conductive polymer refers to a polymer rather than a conductive polymer.

[0053] 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. The content is the conductive polymer content based on the total weight of the polymer layer, expressed as a percentage by weight. The conductive polymer content can be greater than or equal to, or greater than, any lower limit chosen from the list of lower limits above; or it can be less than or equal to, or less than, any upper limit chosen from the list of upper limits above, while being greater than or equal to, or greater than, any lower limit chosen from the list of lower limits above.

[0054] The polymer layer can be tuned to exhibit excellent electroreactivity. For example, a polymer layer can be formed such that Q in Equation 1 below falls within a predetermined range.

[0055] [Equation 1]

[0056] Q=R 3V / R 3.5V

[0057] In Equation 1, R 3V R is the AC impedance resistance under the conditions of 25℃ and 3V external voltage. 3.5V The AC impedance resistance is the resistance at the point in time 1 second after the external voltage is converted from 25℃ and 3V to 3.5V. AC impedance resistance R 3V and R 3.5V The resistance was confirmed in a coin cell with the polymer layer applied, and the method of measurement followed the manner described in the "AC Impedance Resistance Measurement at 13.3V and 3.5V" section of the Examples section of this specification.

[0058] The lower limit of the Q value can be 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 115, 120, 125, 130, 135, or 140. The upper limit can be approximately 400, 350, 300, 250, 200, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 130, 120, 110, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 85, 80, 70, 60, 50, 30, 20, or 10. The Q value can be greater than or equal to, or greater than, any lower limit chosen from the list above; or greater than or equal to, or greater than, any lower limit chosen from the list above, while being less than or equal to, or less than, any upper limit chosen from the list above.

[0059] The fact that the Q value in Equation 1 is above a certain value means that if the external voltage condition changes from 3V to 3.5V, a rapid decrease in resistance occurs in a short time, which indicates the excellent electroreactivity of the polymer layer or the conductive polymer contained therein.

[0060] The AC impedance R in Equation 1 3.5V It can be within a certain range. For example, the AC impedance resistance R 3.5V The upper limit can be approximately 5000, 4500, 4000, 3500, 3000, 2500, 2000, 1500, 1000, 900, 800, 700, 600, 500, 400, 350, 300, or 250, while the lower limit can be approximately 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, or 5000. AC impedance resistor R 3.5V The unit is Ω, and the range can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0061] The polymer layer exhibits a precisely designed PTC (positive temperature coefficient) effect. Therefore, when the polymer layer is applied to the electrode, the electrode can maintain excellent electrical performance at normal temperatures and then exhibit an increased resistance effect under abnormal conditions.

[0062] For example, the polymer layer can be designed such that P in Equation 2 below falls within a predetermined range.

[0063] [Equation 2]

[0064] P=R 130 / R 25

[0065] In Equation 2, R 130 It is the AC impedance resistance at 130℃, R 25 This is the AC impedance resistance at 25℃. AC impedance resistance R 130 and R 25 The resistance was confirmed in a button cell with the polymer layer applied, and the method of measurement followed the method described in "14. AC impedance resistance measurement at room temperature (25°C) and 130°C" of the Examples section of this specification.

[0066] The lower limit of P in Equation 2 can be around 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1,000, 1,100, 1,200, 1,300, 1,400, or 1,450. The upper limit is not particularly restricted, but can be around 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,000, 3,000, 2,000, 1,500, 1,400, 1,300, 1,200, 1,100, 1,000, 950, 900, or 850. P can be greater than or equal to any lower limit chosen from the lower limits listed above; or it can be greater than or equal to any lower limit chosen from the lower limits listed above, while being less than or equal to any upper limit chosen from the upper limits listed above.

[0067] The polymer layer exhibits a large resistance difference between room temperature (approximately 25°C) and high temperature (130°C) due to the PTC effect.

[0068] The polymer layer, the current collector containing the polymer layer, or the electrode containing the polymer layer can exhibit low resistance at room temperature (approximately 25°C) while also exhibiting the stated P value.

[0069] For example, the resistance R of the AC impedance in Equation 2 above. 25 The upper limit can be 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 28, 26, 24, or 22, etc., and the lower limit can be, for example, 10, 15, 20, 25, 30, 35, or 40, etc. The resistance R of the AC impedance... 25 The unit is Ω, and the range can be less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above, while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0070] The conductive polymer included in the polymer layer may have a weight-average molecular weight within a predetermined range. The lower limit of the weight-average molecular weight of the conductive polymer may 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, or 130,000. 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 unit of weight-average molecular weight is g / mol, and its range can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0071] The molecular weight distribution of the conductive polymer, i.e., the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), can be within a predetermined range. The lower limit of this molecular weight distribution can be approximately 2, 2.5, 3, 3.5, or 4, and the upper limit can be approximately 8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, 4, or 3.5. The molecular weight distribution can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0072] Weight-average molecular weight and molecular weight distribution can be evaluated in accordance with the method described in "2. GPC (Gel Permeation Chromatography)" of the Examples section of this specification.

[0073] The conductive polymer can be polythiophene.

[0074] The term polythiophene refers to a polymer containing a certain level or higher of thiophene units.

[0075] The term thiophene unit refers to a monomer unit in which the monomer is a thiophene monomer.

[0076] The term thiophene monomer refers to monomers in the thiophene series, specifically monomers containing a thiophene skeleton.

[0077] The term monomer unit refers to any monomer polymerized into a form contained in a polymer.

[0078] For example, the lower limit of the molar proportion of thiophene units in the polythiophene relative to the total number of moles of all monomer units 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 relative to the total number of moles of all monomer units in the polythiophene can be approximately 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. The proportion of thiophene units can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0079] Conductive polymers may contain long-chain hydrocarbon functional groups or monomer units with long-chain hydrocarbon functional groups (hereinafter referred to as Unit A). Monomers with long-chain hydrocarbon functional groups may be thiophene monomers.

[0080] The term long-chain hydrocarbon functional group refers to a monovalent hydrocarbon group with a certain number of carbon atoms or above, or a monovalent functional group containing a monovalent hydrocarbon group with a certain number of carbon atoms or above.

[0081] For example, the lower limit of the number of carbons present in the functional groups of long-chain hydrocarbons (i.e., the number of carbons in monovalent hydrocarbon groups) can be approximately 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, and the 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. The number of carbons can be greater than or equal to, or greater than, any of the lower limits mentioned above; or it can be less than or equal to, or less than, any of the upper limits mentioned above, while being greater than or equal to, or greater than, any of the lower limits mentioned above.

[0082] The carbon number can be the total number of carbons present in the functional groups of a long-chain hydrocarbon, or the number of carbons in the straight-chain hydrocarbon chain contained within the functional group. That is, the monovalent hydrocarbon groups present in the functional groups of a long-chain hydrocarbon can have straight-chain or branched structures, and even in the case of branched structures, 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.

[0083] 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.

[0084] The number of carbon atoms present in alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, and alkyl carbonyl 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).

[0085] For example, alkyl, alkenyl, alkynyl, alkyloxy, alkylcarbonyl, and alkylcarbonyloxy can be straight-chain or branched structures. In the case of branched structures, the number of carbons in the longest straight chain constituting the relevant branched structure can be within the range described above.

[0086] Alkyl, alkenyl, alkoxy, alkyl carbonyl, or alkyl carbonyloxy groups, which are long-chain hydrocarbon functional groups, may also be optionally substituted by one or more substituents.

[0087] This long-chain hydrocarbon functional group is one that imparts suitable flowability to the monomer or the conductive polymer itself during the polymerization process. Monomers containing this long-chain hydrocarbon functional group impart suitable flowability to the monomer mixture and also diffuse within the monomer mixture, thereby enabling polymerization to occur with excellent efficiency. Furthermore, the suitable flowability between the current collector and the active material layer allows the polymer layer to form stably and uniformly.

[0088] Long-chain hydrocarbon functional groups are appropriately oriented during the drying or annealing process in the formation of polymer layers, thereby making the PTC effect suitable for the polymer adjustable. If a certain amount of heat energy is applied to the long-chain hydrocarbon functional groups, they vibrate due to the heat, and this vibration (thermal vibration) promotes the dedoping of anions bound to the polymer, thus causing an increase in electrical resistance. The temperature at which thermal vibration occurs can be controlled by the length and / or amount of the long-chain hydrocarbon functional groups. For example, at the same temperature, the thermal vibration of relatively long chains is greater than that of relatively short chains, thus allowing long chains to induce an enhanced electrical resistance effect at relatively low temperatures. Therefore, the desired PTC effect can be set by controlling the length and / or proportion of long-chain hydrocarbon functional groups.

[0089] For example, to properly achieve the aforementioned effect, the molar ratio of the monomer unit (unit A) with long-chain hydrocarbon functional groups to the total number of monomer units in the conductive polymer can be adjusted. For instance, 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 the upper limit can be approximately 99 mol%, 98 mol%, 96 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, or 60 mol%. The ratio can be greater than or equal to any of the lower limits mentioned above; or it can be less than or equal to any of the upper limits mentioned above while being greater than or equal to any of the lower limits mentioned above.

[0090] Conductive polymers may contain hydrocarbon functional groups with more than 10 carbon atoms (hereinafter referred to as first hydrocarbon functional groups) and hydrocarbon functional groups with fewer than 9 carbon atoms (hereinafter referred to as second hydrocarbon functional groups).

[0091] For example, the lower limit for the number of carbon atoms 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 carbon atoms in the first hydrocarbon functional group can be greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above; or it can be less than or equal to, or less than, any upper limit chosen from the upper limits listed above, while being greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above.

[0092] The lower limit for the number of carbon atoms in the second hydrocarbon functional group can be approximately 3, 4, 5, 6, 7, or 8, and the upper limit can be approximately 9, 8, 7, or 6. The number of carbon atoms in the second hydrocarbon functional group can be less than or equal to, or less than, any upper limit chosen from the list of upper limits above; or it can be less than or equal to, or less than, any upper limit chosen from the list of upper limits above, while being greater than or equal to, or greater than, any lower limit chosen from the list of lower limits above.

[0093] The number of carbon atoms in each of the first and second hydrocarbon functional groups can be the number of carbon atoms in a straight-chain hydrocarbon chain present in the hydrocarbon functional group. For example, the first and second hydrocarbon functional groups can each independently be at least one 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 alkylcarbonyloxy group.

[0094] Alkyl, alkenyl, alkoxy, alkyl carbonyl, and alkyl carbonyl groups 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.

[0095] As mentioned above, the carbon number of the long-chain hydrocarbon functional group is related to the vibrational properties caused by applied heat energy. If the carbon number changes, these vibrational properties also change, and these 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.

[0096] In a conductive polymer, the ratio of the total number of monomer units having a first hydrocarbon functional group to the total number of monomer units having a second hydrocarbon functional group relative to the total number of monomer units in the conductive polymer can be adjusted within the ratio range of unit A as described above.

[0097] The lower limit of the ratio M2 / M1 of the number of moles of the second hydrocarbon functional group to the number of moles of the first hydrocarbon functional group in the conductive polymer, or the ratio M2 / M1 of the number of moles of monomer units with the second hydrocarbon functional group to the number of moles of monomer units with the first hydrocarbon functional group, can be approximately 0.01, 0.05, 0.1, 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 or 0.7. The ratio may be less than or equal to or less than any upper limit chosen from the upper limits listed above; or may be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or may have a range that is less than or equal to or less than any upper limit chosen from the upper limits listed above, while being greater than or equal to or greater than any lower limit chosen from the lower limits listed above.

[0098] At the stated ratio, the conductive polymer or polymer layer can exhibit an appropriate PTC (positive temperature coefficient) effect, exhibiting stable electrical properties at normal temperatures, and as the surface properties of the polymer layer are tuned, it can ensure excellent adhesion in electrodes or current collectors.

[0099] The conductive polymer may contain polar functional groups or monomeric units having said polar functional groups (hereinafter referred to as unit B), as well as long-chain hydrocarbon functional groups or unit A. The monomer having polar functional groups may be a thiophene monomer.

[0100] 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 1 below. In one instance, a functional group of Formula 1 below may be used as a polar functional group.

[0101] [Formula 1]

[0102] In Formula 1, L1 is a single bond, alkylene group, or alkylidene group; L2 is an alkylene group or alkylidene group; R1 is hydrogen or alkyl group; and n is any number.

[0103] In Equation 1, L1 being a single bond means that L1 does not exist and the oxygen atom between L1 and L2 is directly attached to the monomer.

[0104] In one example, R1 alkyl in Formula 1 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 be straight-chain or branched, as appropriate. The alkyl group may optionally be substituted with one or more substituents.

[0105] The term alkylene refers to a divalent functional group formed by removing one hydrogen atom from each of 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.

[0106] In one example, the alkylene groups L1 and L2 in Formula 1 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 each be ethylene or propylene. The alkylene group may be straight-chain, branched, or cyclic, and may be straight-chain or branched, as appropriate. The alkylene group may optionally be substituted with one or more substituents.

[0107] In one example, the alkylidene groups L1 and L2 in Formula 1 can 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 can be methylene, ethoxy, or propionyl. The alkylidene group can be straight-chain, branched, or cyclic, and can be straight-chain or branched, as appropriate. The alkylidene group can optionally be substituted by one or more substituents.

[0108] In Equation 1, 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 mentioned above, while being greater than or equal to or greater than any of the lower limits mentioned above.

[0109] By applying the aforementioned polar functional groups, polymer layers can be bonded to other layers with appropriate bonding strength, and this conductive polymer layer can be uniformly formed to effectively achieve the desired protective function. Furthermore, the polar functional groups can also suppress the PTC effect at relatively low temperatures.

[0110] The molar number of polar functional groups and long-chain hydrocarbon functional groups in conductive polymers can be controlled to ensure appropriate effects.

[0111] For example, the molar number M of functional groups in long-chain hydrocarbons L The number of moles of polar functional groups M P The ratio of M L / M Por the number of moles M of monomeric units having the long-chain hydrocarbon functional groups. L The molar number M of the monomer unit having the said polar functional group P The ratio of M L / M P The lower limit can be approximately 1, 5, 10, 15, 16, 17, 18, or 19, and 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. The ratio M... L / M P It can be less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above while being greater than or equal to or greater than any lower limit chosen from the lower limits listed above.

[0112] The lower limit of the ratio of the total moles of unit A and unit B in 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%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, or 50 mol%. This ratio can be greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above; or it can be less than or equal to, or less than, any upper limit chosen from the upper limits listed above, while being greater than or equal to, or greater than, any lower limit chosen from the lower limits listed above.

[0113] If the monomer contained in the conductive polymer is a thiophene monomer having long-chain hydrocarbon functional groups and / or polar functional groups as described above, there are no particular restrictions on its specific structure.

[0114] For example, conductive polymers may contain units of Formula 2 below as thiophene units.

[0115] [Equation 2]

[0116] In Equation 2, R2 and R3 can each be independently hydrogen, a polar functional group, or a long-chain hydrocarbon functional group. In another example, R2 and R3 in Equation 2 can also be connected to each other to form a divalent functional group in Equation 3.

[0117] [Formula 3]

[0118] In Formula 3, L3 and L4 can each be a single bond, an alkylene group, or an alkylidene group, and R4 and R5 can each be a hydrogen group, a polar functional group, or a long-chain hydrocarbon functional group.

[0119] In Equation 2, when R2 and R3 are each independently hydrogen, a polar functional group or a long-chain hydrocarbon functional group, at least one of R2 and R3 can be a polar functional group or a long-chain hydrocarbon functional group.

[0120] In Equation 2, when R2 and R3 form a divalent functional group of Equation 3, at least one of R4 and R5 can be a polar functional group or a long-chain hydrocarbon functional group.

[0121] In Formula 3, the meanings and specific examples of single bonds, alkylene groups, and alkylidenes are the same as in Formula 1.

[0122] The technical significance and specific examples of the long-chain hydrocarbon functional groups and polar functional groups in Formulas 2 and 3 are as described above.

[0123] The lower limit of the molar ratio of all monomer units based on the conductive polymer in Formula 2 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%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, or 50 mol%. The ratio can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0124] In one instance, the conductive polymer may comprise a monomer unit represented by Formula 4 below. The monomer unit of Formula 4 may be an example of a monomer unit having a first hydrocarbon functional group.

[0125] [Formula 4]

[0126] In Equation 4, R6 and R7 can each be independently a hydrogen or a first hydrocarbon functional group. In this case, one or more of R6 and R7 mentioned above can be a first hydrocarbon functional group.

[0127] In another instance, R6 and R7 can be connected to each other to form a divalent functional group as shown in Equation 5 below.

[0128] [Formula 5]

[0129] In Formula 5, L5 and L6 are each independently a single bond, alkylene group, or alkylidene group, and R8 and R9 are each independently a hydrogen group or a first hydrocarbon functional group, but at least one of R8 and R9 can be a first hydrocarbon functional group.

[0130] The specific details of the first hydrocarbon functional group are as described above, and the specific details of the single bond, alkylene group, or alkylidene group are as described in Formula 1 above.

[0131] Conductive polymers may also contain monomer units represented by Formula 6 below.

[0132] The monomer unit in Equation 6 above can be an example of a monomer unit having a second hydrocarbon functional group.

[0133] [Formula 6]

[0134] In Equation 3, R 10 and R 11 Each can be an independent hydrogen or second hydrocarbon functional group; in this case, the above R... 10 and R 11 One or more of them can be second hydrocarbon functional groups.

[0135] In another instance, the aforementioned R 10 and R 11 They can connect with each other to form a divalent functional group as shown in Equation 7 below.

[0136] [Formula 7]

[0137] In Formula 7, 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.

[0138] The specific details of the second hydrocarbon functional group are as described above, and the specific details of the single bond, alkylene group, and alkylidene group are as described in Formula 1.

[0139] Conductive polymers may also contain monomer units represented by Formula 8 below. The monomer unit in Formula 8 may be an instance of a monomer unit having polar functional groups.

[0140] [Formula 8]

[0141] In Equation 8, R 14 and R 15 Each can be an independent hydrogen or polar functional group. The above R... 14 and R 15 One or more of them are polar functional groups.

[0142] In another example, R in Equation 8 above 14 and R 15 They can connect with each other to form a divalent functional group as shown in Equation 9 below.

[0143] [Formula 9]

[0144] In Equation 9, 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.

[0145] The specific details of the polar functional groups are as described above, and the specific details of the single bonds, alkylene groups, and alkylidenes are as described in Formula 1.

[0146] When the conductive polymer contains both the monomer unit of Formula 4 and the monomer unit of Formula 6, the ratio of the sum of the molar numbers of the monomer units of Formula 4 and Formula 6 to the total molar number M of the monomer units contained in the conductive polymer can be adjusted within the same range as the molar ratio of the unit A.

[0147] The ratio of the number of moles of the monomer unit in Equation 4 to the number of moles of the monomer unit in Equation 6 can be adjusted within the same range as the ratio M1 / M2. In this case, the number of moles M1 can be the number of moles of the monomer unit in Equation 4, and the number of moles M2 can be the number of moles of the monomer unit in Equation 6.

[0148] When the conductive polymer contains monomer units of Formula 8 above, the units can be in the form of M as described above. L / M P The quantities within the molar ratio range are included. In this case, the number of moles of the monomer unit in Equation 8 above becomes the number of moles M. P In addition, the number of moles M L It can be the number of moles of the single unit in Formula 4 above, the number of moles of the single unit in Formula 6 above, or the sum of the total number of moles of the single unit in Formula 4 above and the single unit in Formula 6 above.

[0149] When the monomer units of Formulas 4, 6, and 8 are present in the conductive polymer, the lower limit of the ratio of the total molar number of monomer units of Formulas 4, 6, and 8 to the total molar number of all monomer units in the conductive polymer 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%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, 60 mol%, 55 mol%, or 50 mol%. The ratio can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0150] If the aforementioned units are included in the above ratios, the conductive polymer may further include other monomer units. The polymer layer contains the conductive polymer and therefore can exhibit the aforementioned properties.

[0151] If the above-mentioned units are included in the above-mentioned ratio, the conductive polymer may further include other monomer units.

[0152] Along with the conductive polymer, the polymer layer may further comprise an adhesion improver. The term adhesion improver refers to a compound that enables the polymer layer to exhibit excellent adhesion to the current collector in an electrode to which the polymer layer is applied.

[0153] Here, the term "excellent adhesion" refers to adhesion that reaches a certain level or higher, as evaluated in accordance with the method described in "7. Adhesion Evaluation" of the Embodiments section of this specification. For example, the lower limit of the adhesion can be approximately 20, 25, 30, 35, or 40, and the upper limit can be approximately 100, 90, 80, 70, 60, 50, 40, 35, 30, or 25. The unit of adhesion is gf / 20mm. The adhesion can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0154] As the adhesion improver, a non-conductive polymer can be used, for example, a material that can be used as a binder during the preparation process of positive or negative electrode active materials.

[0155] For example, rubber-based polymers such as SBR (styrene-butadiene rubber), SBL (styrene-butadiene latex), NBR (nitrile-butadiene rubber), HNBR (hydrogenated nitrile-butadiene rubber), or natural rubber can be used; fluoropolymers such as PVDF (polyvinylidene fluoride), polyvinylidene fluoride-co-hexafluoropropylene, or polyvinylidene fluoride-co-trichloroethylene; cellulose-based polymers such as cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, or CMC (carboxymethyl cellulose); acrylic polymers such as PMMA (polymethyl methacrylate) and / or polyvinyl alcohol, etc. Examples of polyvinyl alcohol may include polyvinyl alcohol, polyvinyl acetate, or ethylene-vinyl acetate copolymers (polyvinyl-co-vinyl acetate), etc.

[0156] When using adhesion improvers, their proportion in the polymer layer can be adjusted according to the purpose. For example, in the polymer layer, the lower limit of the weight ratio of the adhesion improver relative to 100 parts by weight of conductive polymer can be approximately 0.01 parts by weight, 0.05 parts by weight, 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, or 20 parts by weight, and the upper limit can be approximately 40 parts by weight, 35 parts by weight, 30 parts by weight, 25 parts by weight, 20 parts by weight, 15 parts by weight, 10 parts by weight, or 5 parts by weight. The content can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0157] The polymer layer may further contain conductive materials.

[0158] As a conductive material, any material with suitable conductivity can be used. For example, one or more of the following can be used as a conductive material: carbon particles, carbon fibers, graphene, graphite, carbon black, carbon nanotubes, and metal particles.

[0159] As a conductive material, an appropriate type can be selected and used from the above types, and the material can be in the form of particles (spherical, irregular or other shapes), plates or fibers, etc., but is not limited to these.

[0160] The dimensions of conductive materials can also be adjusted appropriately as needed. For example, the lower limit of the dimensions of conductive materials can be around 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 5000nm, or 10000nm, while the upper limit can be 100000nm, 90000nm, 80000nm, 70000nm, etc. The dimensions are approximately 60,000nm, 50,000nm, 40,000nm, 30,000nm, 20,000nm, 10,000nm, 5,000nm, 1,000nm, 950nm, 900nm, 850nm, 800nm, 750nm, 700nm, 650nm, 600nm, 550nm, 500nm, 450nm, 400nm, 350nm, 300nm, 250nm, 200nm, 200nm or 150nm, 100nm, 90nm, 80nm, 70nm or 65nm. The dimensions can be greater than or equal to any lower limit chosen from the lower limits listed above, or less than or less than any upper limit chosen from the upper limits listed above, or can have a range greater than or equal to any lower limit chosen from the lower limits listed above while being less than or less than any upper limit chosen from the upper limits listed above. When the conductive material is in the form of particles, the size can be the average diameter (so-called D50 particle diameter); when it is in the form of a plate, it can be the thickness, long side, or cross-section; when it is in the form of fibers, it can be the diameter or length of the cross-section.

[0161] When the conductive material is in the form of fibers, the lower limit of the aspect ratio (length / diameter of cross section) can be around 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or 65, and the upper limit can be around 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. The aspect ratio can be less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above while being greater than or equal to or greater than any lower limit chosen from the lower limits listed above.

[0162] If necessary, surface treatments such as those for dispersibility can be considered for conductive materials.

[0163] In this case, a surface treatment agent with suitable compatibility with the conductive polymer can be used as the surface treatment agent. For example, the conductive material can be surface-treated with a polyphenolic compound as the surface treatment agent. In this case, it can include a surface layer containing a polyphenolic compound as the conductive material. The polyphenolic compound refers to a compound having two or more hydroxyl groups substituted on a benzene ring and said hydroxyl groups being attached to said benzene ring. Such compounds can be exemplified by so-called catechol compounds (i.e., catechol 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.

[0164] 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.

[0165] When using conductive materials, the ratio of conductive materials within the polymer layer can be adjusted according to the purpose (e.g., the desired oxidation potential). For example, the lower limit of the weight ratio of conductive material in the polymer layer relative to 100 parts by weight of conductive polymer can be 1 part by weight. Other possible ratios include approximately 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 54 parts by weight, 56 parts by weight, 58 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight, or 100 parts by weight, and the upper limit can be, for example, 1,000 parts by weight, 950 parts by weight, 900 parts by weight, 850 parts by weight, 800 parts by weight, 750 parts by weight, 70 parts by weight, etc. 0 parts by weight, 650 parts by weight, 600 parts by weight, 550 parts by weight, 500 parts by weight, 450 parts by weight, 400 parts by weight, 350 parts by weight, 300 parts by weight, 250 parts by weight, 200 parts by weight, 150 parts by weight, 145 parts by weight, 140 parts by weight, 135 parts by weight, 130 parts by weight, 125 parts by weight, 120 parts by weight, 115 parts by weight, 110 parts by weight, 105 parts by weight, 100 parts by weight, 95 parts by weight, 90 parts by weight, 85 parts by weight, 80 parts by weight, 75 parts by weight, 70 parts by weight, 65 parts by weight, 60 parts by weight, 55 parts by weight, or approximately 50 parts by weight. The content can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or less than or equal to or less than any upper limit chosen from the upper limits listed above; or greater than or equal to or greater than any lower limit chosen from the lower limits listed above while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0166] At this ratio, the conductive material and the conductive polymer interact appropriately, thereby enabling the effective formation of a polymer layer with the desired shape.

[0167] For example, conductive materials can exhibit the effect of modulating the oxidation potential of polymer layers and improving the electroreactivity of related polymer layers.

[0168] If the polymer layer contains conductive polymers and conductive materials, the polymer layer may also contain any additional components.

[0169] The thickness of the polymer layer can be appropriately controlled according to the purpose. For example, the lower limit of the thickness of the polymer layer can be approximately 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, or 1000nm, and its upper limit can be approximately 2μm, 1.5μm, 1μm, 950nm, 900nm, 850nm, 800nm, 750nm, 700nm, 650nm, 600nm, 550nm, 500nm, 450nm, 400nm, 350nm, or 300nm. The thickness can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0170] The polymer layer can be manufactured in the manner described below.

[0171] For example, a method of manufacturing a polymer layer may include, for instance, a first step of forming a precursor comprising a conductive polymer and a conductive material, and a step of heat-treating the precursor.

[0172] As the conductive polymer and 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 processes for forming conductive polymers. Furthermore, commercially available products can also be used as conductive materials, and their surface treatment can be performed in known ways.

[0173] The precursor is, for example, a layer comprising the conductive polymer and conductive particles, which ultimately refers to the layer that becomes the polymer layer.

[0174] This precursor can be formed in known ways, for example, it can be formed by coating a polymer solution in which a conductive polymer or the like is dispersed in a suitable solvent.

[0175] 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 triamide (HMPA), etc., or mixed solvents containing two or more of the foregoing can be used, but are not limited thereto.

[0176] The polymer solution is used to form the precursor. The 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.

[0177] The manufacturing method further includes a step of heat-treating the precursor of the polymer layer. By adjusting the conditions in the process, 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 can be adjusted or stabilized, thereby forming a polymer layer that satisfies the desired PTC effect, oxidation potential characteristics, and other properties.

[0178] The heat treatment process can be performed in two steps. For example, the heat treatment process may include: a second step, in which the precursor of the first step is subjected to a heat treatment at a temperature range T1; and a third step, in which the precursor is subjected to a second heat treatment at a temperature range T2 after the second step.

[0179] To achieve the orientation or alignment of the conductive polymer and the dispersion state of the conductive material, the conditions of the second and third steps can be adjusted.

[0180] For example, the temperature range T1 of a single heat treatment can be adjusted within a predetermined range. For example, the lower limit of the temperature range T1 can be approximately 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ or 140℃, and its upper limit can be approximately 300℃, 290℃, 280℃, 270℃, 260℃, 250℃, 240℃, 230℃, 220℃, 210℃, 200℃, 190℃, 180℃, 170℃, 160℃, 150℃ or 140℃. The temperature range T1 can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above; or it can be greater than or equal to or greater than any lower limit chosen from the lower limits listed above, while being less than or equal to or less than any upper limit chosen from the upper limits listed above.

[0181] In the heat treatment step, the temperature range T1 for the primary heat treatment and the temperature range T2 for the secondary heat treatment can be adjusted. For example, the lower limit of the ratio (T1 / T2) of temperature ranges T1 and T2 can be approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or 1.2, 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. The ratio can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0182] In one example, the temperature range T1 of the first heat treatment step can be adjusted to be higher than the temperature range T2 of the second heat treatment step.

[0183] The ratio of heat treatment time M1 in the primary heat treatment to heat treatment time M2 in the secondary heat treatment can be further adjusted. For example, the lower limit of the ratio M2 / M1 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 50, 70, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, or 26. The value is approximately 0 or 270, with an upper limit of approximately 1,000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 290, 280, 270, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, or 20. The ratio M2 / M1 can be greater than or equal to any lower limit chosen from the list above; or less than or equal to any upper limit chosen from the list above; or greater than or equal to any lower limit chosen from the list above while being less than or equal to any upper limit chosen from the list above.

[0184] The lower limit of the secondary heat treatment time M2 can be approximately 0.1 hours, 0.2 hours, 0.3 hours, 0.4 hours, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours, while the upper limit can be approximately 50 hours, 48 ​​hours, 46 hours, 44 hours, 42 hours, 40 hours, 38 hours, 36 hours, 34 hours, 32 hours, 30 hours, 28 hours, 26 hours, 24 hours, 22 hours, 20 hours, 18 hours, 15 hours, 10 hours, 9 hours, 8 hours, 7 hours, 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, 1.5 hours, or 1 hour. The secondary heat treatment time M2 can be greater than or equal to any lower limit chosen from the lower limits listed above; or less than or equal to any upper limit chosen from the upper limits listed above; or greater than or equal to any lower limit chosen from the lower limits listed above while being less than or equal to any upper limit chosen from the upper limits listed above.

[0185] The polymer layer can be formed using the above process.

[0186] 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 desired PTC effect, oxidation potential characteristics, and other properties.

[0187] As current collectors for both positive and negative electrodes, any current collectors commonly used as positive or negative electrodes can be used without any particular restrictions.

[0188] There are no particular limitations on the type, size, and shape of the current collector if it is conductive and does not cause 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 can be exemplified by materials in which the surfaces of copper, aluminum, or stainless steel are surface-treated with materials such as 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-mentioned materials. In some cases, known surface treatments can also be applied to the surface of the current collector to improve adhesion to other layers such as polymer layers or active material layers.

[0189] Current collectors typically have a thickness ranging from 3 μm to 500 μm, but are not limited to this.

[0190] As the active material layer for forming an electrode, a commonly applied layer can also be used. Generally, the active material layer contains an electrode active material. There is no particular limitation on the specific type of the electrode active material, and generally, materials for forming a positive electrode or a negative electrode can be used.

[0191] For example, when the active material layer is a positive electrode active material layer, the electrode active material can include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds 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 satisfies 0.01 ≤ c2 ≤ 0.3); lithium manganese composite oxide represented by the formula LiMn 2-c3 MO8 (where M is at least one selected from Co, Ni, Fe, Cr, Zn and Ta, and satisfies 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.

[0192] 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 can 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.

[0193] Lithium metal films can also be used as negative electrode active materials, and as carbon materials, both low-crystallinity carbon and high-crystallinity carbon can be used. Soft carbon and hard carbon are representative examples of low-crystallinity carbon, while high-crystallinity carbon includes high-temperature calcined carbons such as amorphous, plate-like, scaly, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and coke derived from petroleum and coal tar pitch.

[0194] The content of electrode active material in the active material layer may 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 the ratio may vary depending on the application or design of the electrode.

[0195] The active material layer may further include an adhesive. The adhesive is used to improve the adhesion between the active materials and the adhesion between the active material layer and the current collector. There are no particular limitations on examples of adhesives, 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.

[0196] In one example, the binder content 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.

[0197] 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.

[0198] 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.

[0199] In addition to the components mentioned above, the active material layer may optionally contain any necessary known components.

[0200] There are no particular limitations on the method for forming an active material layer on a polymer layer to manufacture an electrode. Typically, the active material layer is formed by coating a slurry containing electrode active materials, binders, and conductive materials onto a current collector (on the polymer layer), drying it, and then rolling it. This known method can also be applied in the same manner to this application.

[0201] An electrode assembly can be formed using the positive and negative electrodes formed in the manner described above, as well as the diaphragm described above.

[0202] This specification also discloses an electrochemical element, such as a secondary battery, including the electrode assembly described herein. If the electrode assembly is used, there are no particular limitations on other components or manufacturing methods for the electrochemical element, and known methods can be applied.

[0203] Beneficial effects

[0204] This specification discloses an electrode assembly and a secondary battery. The electrode assembly exhibits low resistance and excellent electrical characteristics under normal conditions, and ensures stability under abnormal conditions by rapidly transforming into an insulator. This specification also discloses a secondary battery including the electrode assembly. Attached Figure Description

[0205] Figure 1 This is a side view of an exemplary electrode assembly.

[0206] Figure 2 This is a side view of an exemplary diaphragm.

[0207] Figure 3 This is a side view of an exemplary electrode.

[0208] Figure 4 These are the NMR analysis results of the compounds prepared in the preparation examples. Detailed Implementation

[0209] In the following description, electrode assemblies and the like are described in detail by way of examples and comparative examples, but the scope of electrode assemblies and the like is not limited to the examples below.

[0210] 1. NMR analysis

[0211] NMR spectrometers with 5 mm triple resonance probes (including Bruker UltraShield spectrometers (300 MHz)) were used at room temperature (25 °C). 11H-NMR analysis. The sample was diluted to a concentration of about 10 mg / ml in a solvent (CDCl3) for NMR measurement and used, and the chemical shift was expressed in ppm.

[0212] 2. GPC (Gel Permeation Chromatograph)

[0213] The molecular weight characteristics were measured using GPC (Gel Permeation Chromatograph). The sample was placed in a 5 mL vial and diluted to a concentration of about 1 mg / mL with chloroform. The standard sample for calibration and the analytical sample were filtered through a syringe filter (pore size: 0.45 μm) and then measured. As an analytical procedure, Empower 3 from Waters was used, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were obtained respectively by comparing the elution time of the sample with the calibration curve. The molecular weight distribution (PDI) is the value Mw / Mn obtained by dividing the weight-average molecular weight Mw by the number-average molecular weight Mn. The GPC measurement conditions are as follows.

[0214] <GPC measurement conditions>

[0215] Instrument: 2414 from Waters

[0216] Column: Three polystyrene-type cross-linked copolymers from Waters were used

[0217] Solvent: THF (tetrahydrofuran)

[0218] Column temperature: 35 °C

[0219] Sample concentration: 1 mg / mL, 1 μL injection

[0220] Standard sample: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940, 485)

[0221] 3. Thickness measurement

[0222] The cross-section of the target with the thickness to be measured was exposed using an ion milling device (Hitachi, IM5000), and then a scanning electron microscope (SEM) (JEOL, JSM-7200F) image of the cross-section was captured, and the thickness was obtained from the image. The cross-section was exposed in cross-section grinding mode using an ion milling device (Hitachi, IM5000) under the conditions of: speed (reciprocating times / minute) of 3, acceleration voltage of 6 kV, discharge voltage of 15 kV, current of 150 μA, and the time was set to 4 hours. The SEM (scanning electron microscope) (JEOL, JSM-7200F) image was magnified within the range of 500 times to 20,000 times and captured under the voltage condition of 5 kV.

[0223] AC impedance measurement at 4.3V and 3.5V

[0224] Sample manufacturing

[0225] A polymer layer was formed on a 15 μm thick aluminum foil (Al foil). The method of forming the polymer layer and the thickness were the same as those described in the various examples or comparative examples. A separator and a lithium film were laminated on the polymer layer to prepare an aluminum foil / polymer layer / separator / lithium film laminate, and the laminate was punched into a circle with a diameter of about 1.4 cm. A coin cell was manufactured using the circularly punched laminate and an electrolyte (using Wellcos' CR2032 coin cell kit), and the impedance was measured using the coin cell. In the manufacture of the coin cell, LG Energy Solution's SRS (Safety Enhanced Separator) was used as the separator. SRS is a separator in which an inorganic particulate layer containing PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) and Al2O3 is formed on a polymer membrane (polyethylene separator) (porosity of about 45%), and the weight ratio of PVDF-HFP to Al2O3 (PVDF-HFP:Al2O3) is about 1:4. As the lithium film, a lithium film with a thickness of about 300 μm is used, and Enchem's product (1M LiPF6 solution (solvent: EC / DMC / EMC=3 / 4 / 3 (mass ratio), EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethyl methyl carbonate)) is used.

[0226] External voltage 3V condition

[0227] For button cells, AC impedance resistance was determined using EIS (electrochemical impedance spectroscopy). A 3V voltage was applied to the button cell for 10 minutes at room temperature (25°C), and Nyquist plots were obtained in the range of 50,000 Hz to 0.1 Hz using EIS. The resistance (Ro) was then measured. 3V The values ​​were obtained in the high-frequency region of the Nyquist plot. A potentiostat (Princeton Applied Research, PARASTAT-MC) was used as the EIS measurement device.

[0228] External voltage 3.5V condition

[0229] For the measured resistance R 3V A button cell battery was used to convert the applied external voltage to 3.5V, and the AC impedance resistance R was measured in the same manner after 1 second. 3.5V .

[0230] 5. Measurement of AC impedance resistance at room temperature (25℃) and 130℃

[0231] The AC impedance was measured using the same coin cell used in the "AC Impedance Measurement at 4.3V and 3.5V". For the coin cell, the AC impedance was measured using EIS (electrochemical impedance spectroscopy). Specifically, Nyquist plots were obtained in the range of 50,000 Hz to 0.1 Hz using the EIS method, and the interfacial resistance was measured from the high-frequency region of the obtained Nyquist plots. A potentiostat (manufacturer: Princeton Applied Research, product name: PARASTAT-MC) was used as the EIS measurement device.

[0232] A 4.5V voltage was applied to the button cell at room temperature (25°C) for 10 minutes to maintain the doping state of the conductive polymer. Then, with the external voltage set to 0V (open circuit voltage), the AC impedance resistance R was measured after approximately 1 minute. 25 The measured values ​​were evaluated as the AC impedance resistance (R0) of the polymer layer at room temperature (25°C). 25 ).

[0233] Additionally, the button cell was placed in the center of a convection oven (Jeotech, OF3-05W), and the oven was set to a final temperature of 130°C. The button cell was connected to an external potentiostat (Princeton Applied Research, PARASTAT-MC) for EIS resistance measurement. The external voltage was maintained at 0V (open circuit voltage). The AC impedance resistance R of the polymer layer at 130°C was evaluated under these conditions. 130 .

[0234] 6. Average particle size

[0235] The average particle size (D50 diameter) of conductive particles (samples) was determined using a Marvern MasterSizer 3000 apparatus according to ISO-13320. Toluene was used as the solvent for the determination. If the sample is dispersed in a solvent and irradiated with a laser, the laser light is scattered by the sample dispersed in the solvent. Since the intensity and directionality of the scattered laser light vary with particle size, the average particle size can be obtained by analyzing them using Mie theory. The determination results were then converted into the particle size of spheres with the same volume as the dispersed sample, resulting in a volume-based cumulative curve of the particle size distribution. The particle size at which the cumulative amount reaches 50% (the median particle size) in this curve was designated as the average particle size (D50 diameter).

[0236] 7. Adhesion Evaluation

[0237] A 3-Ah pouch cell was assembled using electrodes from the examples or comparative examples as positive electrodes. In manufacturing the 3-Ah pouch cell, the same separator and electrolyte used in the above-described "AC impedance resistance measurement at 4.3V and 3.5V" were used as the separator and electrolyte, and a conventional graphite negative electrode was used. Three charge-discharge cycles were performed on the manufactured 3-Ah pouch cell. The charge and discharge were performed in a constant current-constant voltage (CC-CV) manner, and each charge-discharge cycle at 0.1C was repeated three times.

[0238] During charging, the final charging voltage is set to 4.5V, and during discharging, the final discharging voltage is set to 3V.

[0239] Subsequently, the 3-Ah pouch cell was disassembled to separate the electrodes. The surface of the current collector, without any polymer layer, was attached to a glass slide using double-sided tape, and this attachment was performed by reciprocating a roller on the electrodes ten times at approximately 2 kg. Adhesion was then evaluated using a TA analyzer, while the polymer layer and active material layer were peeled from the current collector at a peel angle of 90 degrees and a peel speed of 5 mm / s.

[0240] 8. Battery life evaluation

[0241] Battery life was evaluated using a 3-Ah pouch cell used in the adhesion evaluation. For the 3-Ah pouch cell, 100 charge-discharge cycles were performed, and battery life was evaluated by the discharge capacity at the 100th cycle. This process was conducted at room temperature (approximately 25°C). During this process, charging was performed in a constant current (CC) / constant voltage (CV) manner by setting the final charging voltage to 4.5V and the final charging current to 1mA at 0.7C, and discharging was performed in a constant current (CC) manner by setting the final discharge voltage to 3.0V at 1C.

[0242] Preparation Example 1. Polydopamine-coated conductive particles

[0243] 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.

[0244] DHC (dopamine hydrochloride) (CAS No. 62-31-7) was added to a buffer solution and stirred at room temperature (approximately 25°C). Here, a 0.1 M pH 8.5 Tris buffer product from BIOSESANG was used as the buffer solution. The final molar 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.

[0245] Preparation Example 2. Synthesis of Monomer (A)

[0246] The monomer of formula A is synthesized in the following manner.

[0247] [Formula A]

[0248] 1.372 g (12.02 mmol, 1 equivalent) of 3-methoxythiophene and 3 g (16.83 mmol, 1.4 equivalent) of triethylene glycol monomethyl ether were dissolved together with 230 mg of p-toluenesulfonic acid (p-TsOH) in 100 mL of toluene and mixed. The mixture was refluxed at 120 °C while reacting, thereby removing methanol produced in the reaction (transetherification) through a 4 Å molecular sieve packed in an extractor (Soxhlet extractor). The reactants were refluxed for 24 h, then quenched with water, extracted with ethyl acetate, washed with brine, and dried over magnesium sulfate (MgSO4). The solvent was removed by rotary evaporator, 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 the target compound (monomer (A)) are as follows: Figure 2 As shown.

[0249] Preparation Example 3. Synthesis of Polythiophene (B)

[0250] Conductive polymers were prepared by polymerizing 3-dodecylthiophene (3-DT), 3-hexylthiophene (3-HT), and monomer (A) of formula A from Preparation Example 2. 3.20 g (19.71 mmol, 3 equivalents) of ferric chloride (III) was dissolved in 150 mL of dichloromethane. 0.787 g (3.12 mmol, 0.475 equivalents) of 3-dodecylthiophene, 0.525 g (3.12 mmol, 0.475 equivalents) of 3-hexylthiophene, and 0.083 g (0.3285 mmol, 0.05 equivalents) of monomer (A) from Preparation Example 2 were added, and polymerization was carried out at 25 °C for 24 hours to prepare polythiophene (B). The polymerization solution was placed in a permeation membrane with a MWCO (molecular weight cutoff) of 5,000, and then immersed in 200 mL of acetonitrile solvent to remove unreacted ferric chloride (III), monomer, and low molecular weight oligomers. The residue precipitated within the permeate membrane was washed with methanol and dried at 60°C for 12 hours to prepare polythiophene (B). The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polythiophene (B) were 136,000 g / mol and 40,000 g / mol, respectively.

[0251] Example 1.

[0252] Formation of polymer layer

[0253] A polymer solution was prepared by mixing polythiophene (B) from Preparation Example 3, SBR (styrene-butadiene rubber) as an adhesion improver (A), and polydopamine-coated conductive material particles (P) from Preparation Example 1 in a weight ratio of 60:3:40 (B:A:P), and dispersing the mixture in toluene at a concentration of approximately 4% by weight. As the SBR, an SBR with a weight-average molecular weight of approximately 20,000 g / mol and a molecular weight distribution of approximately 10 was used, dissolved in a mixed solvent of toluene and THF (tetrahydrofuran). After preparing the polymer solution, the mixture was dispersed using an ultrasonic disperser at a temperature of approximately 30°C for approximately 4 hours. The prepared polymer solution was coated onto a current collector using a bar coating method (Mayer bar) and dried in a drying oven at approximately 140°C for approximately 4 minutes (one heat treatment). Subsequently, the current collector coated with the polymer solution was placed in an oven and heat-treated at 110°C for approximately 18 hours (secondary heat treatment) to form a layer (polymer layer) with a thickness of approximately 400 nm. An Al foil with a thickness of approximately 15 μm was used as the current collector.

[0254] Manufacturing of electrodes and electrode assemblies

[0255] An active material layer is formed on the polymer layer to fabricate the electrode. Using a doctor blade, a slurry containing lithium cobalt oxide (LiCoO2), conductive material (0.5% ECP (Ketjen Black), 0.4% SFG (Trimrex graphite), 0.4% DB (Denka Black)), PVDF (polyvinylidene fluoride), and NMP (N-methyl-2-pyrrolidone) in a weight ratio of 77.5:1:1:20.5 (LiCoO2:conductive material:PVDF:NMP) is coated onto the polymer layer and dried at 130°C for 30 minutes to form the active material layer (slurry loading: approximately 16 mg / cm³). 2 The active material layer is rolled to a porosity of approximately 18% to form an active material layer with a thickness of approximately 58 μm, thereby manufacturing an electrode.

[0256] An electrode is used as the positive electrode and is stacked with a separator and a negative electrode to fabricate an electrode assembly. The electrode assembly is fabricated by sequentially stacking a positive electrode, a separator, and a negative electrode, wherein the separator (SRS) and the negative electrode (lithium film) used in the above-mentioned "AC impedance resistance measurement at 4.3V and 3.5V" are used as the separator and the negative electrode.

[0257] Example 2.

[0258] Except that when preparing the polymer solution, the polythiophene (B) of Preparation Example 3, the SBR (A) used in Example 1, and the polydopamine-coated conductive particles (P) of Preparation Example 1 were mixed in a weight ratio of 60:6:40 (B:A:P), a polymer layer was formed in the same manner as in Example 1, and the polymer layer was used to manufacture electrodes and electrode assemblies.

[0259] Example 3.

[0260] Except that when preparing the polymer solution, the polythiophene (B) of Preparation Example 3, the SBR (A) used in Example 1, and the polydopamine-coated conductive particles (P) of Preparation Example 1 were mixed in a weight ratio of 60:12:40 (B:A:P), a polymer layer was formed in the same manner as in Example 1, and the polymer layer was used to manufacture electrodes and electrode assemblies.

[0261] Example 4.

[0262] The electrode assembly was manufactured in the same manner as in Example 1, except that HNBR (hydrogenated nitrile butadiene rubber) was used instead of SBR.

[0263] Example 5.

[0264] The electrode assembly was manufactured in the same manner as in Example 1, except that PMMA (polymethyl methacrylate) was used instead of SBR.

[0265] Comparative Example 1.

[0266] Except that when preparing the polymer solution, the polythiophene (B) of Preparation Example 3 and the polydopamine-coated conductive particles (P) of Preparation Example 1 were mixed at a weight ratio of 60:40 (B:P), the polymer layer was formed in the same manner as in Example 1, and the polymer layer was used to manufacture electrodes and electrode assemblies.

[0267] Table 1 summarizes the adhesion evaluated in accordance with the method described in section 7. Adhesion Evaluation and the discharge capacity evaluated in accordance with the method described in section 8. Battery Life Evaluation.

[0268] [Table 1]

[0269] Table 2 summarizes the R values ​​measured according to the methods described in "AC Impedance Resistance Measurement at 4.3V and 3.5V" and "5. AC Impedance Resistance Measurement at Room Temperature (25°C) and 130°C". 3V R 3.5V R 25 and R 130 The results. In Table 2, Q is obtained by using R. 3V Divide by R 3.5V The value obtained (R) 3V / R 3.5V P is achieved by passing R 130 Divide by R 25 The value obtained (R) 130 / R 25 In Table 2, R 3V R 3.5V R 25 and R 130 The unit is Ω.

[0270] [Table 2]

[0271] As can be seen in Table 2, in the examples, the impedance reduction ratio (Q) confirmed when the external voltage increased from 3V to 3.5V was significantly higher than that in the comparative examples, demonstrating excellent electroreactivity. The fact that the AC impedance resistance was low at room temperature (25°C) means that charge flow can be stably achieved through the polymer layer under normal conditions. Furthermore, the fact that the AC impedance resistance value was measured at high temperature (130°C) suggests excellent PTC characteristics.

Claims

1. An electrode assembly, comprising: positive electrode; negative electrode; and The membrane between the positive electrode and the negative electrode. Wherein, at least one of the positive electrode and the negative electrode includes a polymer layer. The polymer layer comprises a conductive polymer and an adhesion improver.

2. The electrode assembly according to claim 1, wherein, The conductive polymer contains long-chain hydrocarbon functional groups.

3. The electrode assembly according to claim 1, wherein, The conductive polymer comprises a first hydrocarbon functional group having more than 10 carbon atoms and a second hydrocarbon functional group having fewer than 9 carbon atoms.

4. The electrode assembly according to claim 3, wherein, The ratio of the total molar number of monomer units having the first hydrocarbon functional group to the total molar number of monomer units having the second hydrocarbon functional group in the conductive polymer is 80 mol% or more.

5. The electrode assembly according to claim 4, wherein, The ratio M2 / M1 of the number of moles of the second hydrocarbon functional group or monomeric unit having the functional group to the number of moles of the first hydrocarbon functional group or monomeric unit having the functional group is in the range of 0.01 to 100.

6. The electrode assembly according to claim 2, wherein, The conductive polymer further comprises polar functional groups.

7. The electrode assembly according to claim 6, wherein, The polar functional group is a carboxyl, hydroxyl, amino, cyano, nitro, ether, or a functional group of Formula 1 below: [Formula 1] Where L1 is a single bond, alkylene group, or alkylidene group, L2 is an alkylene group or alkylidene group, R1 is hydrogen or alkyl group, and n is a number in the range of 1 to 10.

8. The electrode assembly according to claim 6, wherein, The ratio of the number of moles of monomer units having the long-chain hydrocarbon functional group to the number of moles of monomer units having the polar functional group in the conductive polymer is in the range of 1 to 500.

9. The electrode assembly according to claim 1, wherein, The adhesion improver is a non-conductive polymer.

10. The electrode assembly according to claim 1, wherein, The adhesion improver is selected from one or more of rubber polymers, fluoropolymers, cellulose polymers, acrylic polymers, and polyvinyl alcohol.

11. The electrode assembly according to claim 1, wherein, The polymer layer comprises 30% by weight or more of the conductive polymer, and 0.01 parts by weight or more of the adhesion improver relative to 100 parts by weight of the conductive polymer.

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

13. The electrode assembly according to claim 12, wherein, The conductive material is carbon particles, carbon fiber, graphene, graphite, carbon black, carbon nanotubes, or metal particles.

14. The electrode assembly according to claim 1, wherein, The diaphragm comprises a porous polymer membrane and an inorganic particulate layer.

15. A secondary battery comprising an electrode assembly according to any one of claims 1 to 14.

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