Electrode assembly

Abstract

This specification discloses an electrode assembly and a secondary battery. The electrode assembly is formed by combining the following components: electrodes that exhibit low resistance and excellent electrical characteristics under normal conditions and ensure stability by rapidly transforming into an insulator under abnormal conditions; and a separator known as an SRS (Safety Reinforced Separator). This 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 filed on January 26, 2024, and Korean Patent Application Nos. 10-2024-0030198, 10-2024-0030197 and 10-2024-0030195 filed on February 29, 2024, all disclosures of which are incorporated herein by reference.

[0002] This specification discloses electrode assemblies and secondary batteries including them. 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 tools such as electric vehicles need to have greater capacity and power.

[0005] Increased capacity and power in secondary batteries lead to stability issues. For example, with increased capacity and power, the risk of phenomena known as thermal runaway, such as uncontrolled temperature rise and hazardous chemical leaks, also increases.

[0006] Therefore, 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 speeds. Summary of the Invention

[0007] Technical issues

[0008] This specification discloses an electrode assembly. The present specification is intended to disclose an electrode assembly formed by combining: an electrode capable of exhibiting low resistance and excellent electrical properties under normal conditions of a secondary battery, and ensuring stability by rapidly transforming into an insulator under abnormal conditions; and a separator referred to as a so-called SRS (Safety Reinforced Separator).

[0009] This specification also discloses a secondary battery including the electrode assembly described above.

[0010] Technical solution

[0011] In this specification, the term room temperature means the natural temperature without artificial heating or cooling. Room temperature can be any temperature in the range of 10°C to 30°C, or approximately 23°C or approximately 25°C.

[0012] Unless otherwise stated, the physical properties mentioned herein that are affected by the measurement temperature are those measured at room temperature.

[0013] In this instruction manual, unless otherwise specified, the unit of temperature is degrees Celsius (°C).

[0014] In this specification, the term atmospheric pressure means natural pressure without artificial pressurization and depressurization, which can generally refer to pressure in the range of approximately 730 mmHg to 790 mmHg.

[0015] Unless otherwise stated, the physical properties mentioned herein that are affected by the measurement pressure are those measured at atmospheric pressure.

[0016] Unless otherwise stated, the physical properties mentioned herein that are affected by the measured humidity are those measured at room temperature and normal pressure under unadjusted humidity conditions.

[0017] 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 considered a normal state.

[0018] The term "abnormal state" refers to a dangerous state that has occurred or may occur in secondary batteries or similar devices, such as abnormal temperature rise, overheating, or explosion.

[0019] This specification discloses an electrode assembly.

[0020] 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 laminated in this order to form a laminate.

[0021] Figure 1 This is an example of a laminate in which the positive electrode (C), the separator (S), and the negative electrode (A) are laminated sequentially.

[0022] The diaphragm used in electrode assemblies can be a diaphragm known as a so-called SRS (Safety Reinforced Diaphragm).

[0023] SRS is a type of separator that includes a layer of inorganic particles on the surface of a separator substrate (porous polymer membrane). The SRS exhibits stability and maintains its performance even at higher temperatures compared to conventional separators. By combining such a separator with the polymer layer described below, significantly improved stability can be ensured.

[0024] Such SRS is common knowledge.

[0025] For example, such as Figure 2As shown, the SRS may include a porous polymer membrane (100) and an inorganic particulate layer (200). Figure 2 In 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).

[0026] 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.

[0027] In one instance, a polyolefin polymer membrane can be used as a porous polymer membrane.

[0028] Polyolefin polymer membranes that can be used as porous polymer membranes in SRS are known in the industry. For example, porous polymer membranes can be applied to them, said porous polymer membranes being made from one or more combinations of copolymers containing two or more monomer units selected from 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.

[0029] Porous polymer membranes typically have a thickness of about 1 μm to 100 μm or about 5 μm to 50 μm. Furthermore, pores with a size of about 0.001 μm to 50 μm are typically formed in such porous polymer membranes, and the porosity is typically adjusted to be in the range of 10% to 95%.

[0030] SRS comprises an inorganic particulate layer formed on one or both surfaces of a porous polymer membrane. The term inorganic particulate layer refers to a layer containing inorganic particles.

[0031] 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). + For electrolytes that do not undergo oxidation and reduction reactions within a voltage range of 0V to 5V, inorganic particles with ion transport capabilities can also be used. For example, if inorganic particles with high dielectric constants are applied, 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.

[0032] For example, inorganic particles with a dielectric constant of 5 or greater and / or inorganic particles with lithium-ion transport capability can be used as inorganic particles.

[0033] Examples of such inorganic particles include those selected from BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb. 1-x La x Zr 1-y Ti y O3 (PLZT), PB(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC; and / or selected from (LiAlTiP) x O y (0 < x < 4, 0 < y < 13) series of 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 Li 3.25 Ge 0.25 P 0.75 S4 and / or SiS2 series of 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 of glasses (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7) such as LiI - Li2S - P2S5; one or more types of inorganic particles.

[0034] Such inorganic particles typically have a size in the range of 0.001 μm to 10 μm.

[0035] In SRS, the inorganic particle layer can comprise both a polymeric binder and inorganic particles. Commonly used polymeric 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 pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, and / or polyimide, and mixtures of one, two, or more of these binders can be used.

[0036] The inorganic particle content in the inorganic particle layer can be from 10% to 95% by weight, 30% to 95% by weight, 50% to 95% by weight, or 70% to 90% by weight, and when a binder is included, the binder can be included at a ratio of about 5 to 100 parts by weight or about 10 to 50 parts by weight relative to 100 parts by weight of inorganic particles.

[0037] In addition to the adhesive, the inorganic particulate layer may further contain known essential components, such as organic particles, to enhance adhesion to the adhesive polymer and improve breathability, heat shrinkage and peel strength.

[0038] The inorganic particle layer can typically have a thickness of 0.1 μm to 50 μm, or about 1 μm to 10 μm. Methods for manufacturing such SRS are known, and the inorganic particle layer can be formed using such known methods.

[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 electrode 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) of the positive and / or negative electrode and the active material layer (1003).

[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 exist 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 of the active material layers (1003) present on both surfaces of the current collector (1001) and the current collector (1001), and can also exist as one layer between either 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 such a 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] The term polymer layer refers to a layer containing a polymer. For example, the lower limit of the polymer content contained 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 polymer content based on the total weight of the polymer layer, expressed as a percentage by weight. The content can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or greater than or equal to, or greater than, any lower limit selected from the lower limits listed above and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0047] The polymer layer may not 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 electrode active material content 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 electrode active material content 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 selected from the upper limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above, and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above. Specific types of electrode active materials will be described below.

[0048] As is known, conductive polymers contained in polymer layers are polymers that exhibit conductivity through conjugated systems of polymer chains and / or doping, etc.

[0049] For example, the lower limit of the conductive polymer content in the polymer layer can be approximately 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95, and the upper limit can be approximately 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50. The content is the conductive polymer content based on the total weight of the polymer layer, expressed as a percentage by weight. The content can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or greater than or equal to, or greater than, any lower limit selected from the lower limits listed above while simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0050] The polymer layer exhibits a so-called PTC (positive temperature coefficient) effect. Therefore, the polymer layer can variably control the charge transport through the electrodes according to the temperature.

[0051] By applying such a polymer layer, the electrode assembly can be applied to secondary batteries, etc., to exhibit excellent electrical characteristics, including low resistance, under normal conditions, and to ensure stability under abnormal conditions by increasing resistance.

[0052] To ensure the polymer layer exhibits the aforementioned effect, the tendency of the PTC effect must be controlled. The PTC effect is an effect in which the resistance increases proportionally with temperature. To ensure stable operation of the electrode with the polymer layer exhibiting the PTC effect and to guarantee stability under abnormal conditions, it is necessary to adjust the oxidation potential of the polymer layer, the electrical characteristics before the resistance increases due to the PTC effect, and the timing of the resistance increase due to the PTC effect.

[0053] For example, when the oxidation potential of the polymer layer is higher than that of the electrode active material, a potential drop will occur under normal conditions during repeated charging and discharging, as well as high-speed charging and discharging. Furthermore, if the resistance of the polymer layer is too high under normal conditions, charge movement is restricted, thus adversely affecting the operation of the secondary battery. Additionally, if the temperature exhibiting the PTC effect is within the normal temperature range, the performance of the secondary battery cannot be adequately expressed.

[0054] The polymer layer exhibits a PTC effect and controls the controlled onset time of the PTC effect, maintaining stable oxidation potential and electrical properties before the PTC effect manifests. To exhibit this PTC effect, a specific conductive polymer can be introduced into the polymer layer. For example, as described below, by applying a conductive polymer with relatively long hydrocarbon chains (long-chain hydrocarbon functional groups) and controlling the drying or annealing temperature during polymer layer formation, a suitable PTC effect (e.g., inducing an increase in the resistance of the polymer layer at a desired temperature (the temperature at which the battery is in an abnormal state) can be ensured.

[0055] By introducing conductive materials into the polymer layer and uniformly dispersing the conductive materials, it is also possible to appropriately maintain the oxidation potential or electrical properties.

[0056] For example, a polymer layer, a current collector or electrode applied to the polymer layer can be provided such that Q in Equation 1 below falls within a predetermined range.

[0057] [Equation 1]

[0058] Q = R 3v / R 3.5v

[0059] In equation 1, R 3V R is the AC impedance resistance under the conditions of 25℃ and 3V voltage. 3.5V The AC impedance resistance is measured at 1 second after the voltage has been converted from 25°C and 3V to 3.5V. AC impedance resistance R 3V and R 3.5V The resistance is confirmed in a coin cell where a current collector on which a polymer layer is formed or an electrode made using the current collector is applied, and the measurement method follows the manner described in the "AC Impedance Resistance Measurement at 4.3V and 3.5V" section of the Embodiments section of this specification.

[0060] The lower limit of Q can be approximately 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, or 100, and its upper limit can be approximately 300, 200, 190, 180, 170, 160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, or 20. Q can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or less than, equal to, or less than, any upper limit selected from the upper limits listed above, and simultaneously greater than or equal to, or greater than, any lower limit selected from the lower limits listed above. The fact that a rapid decrease in resistance occurs within a short time after the voltage condition changes from 3V to 3.5V demonstrates the excellent electroreactivity of the polymer layer.

[0061] The AC impedance R in Equation 1 3V The upper limit can be approximately 50,000, 45,000, 40,000, or 35,000, and its lower limit can be approximately 10,000, 20,000, 30,000, or 35,000. The above R... 3V The unit is Ω, and its range can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0062] The AC impedance R in Equation 1 3.5V The upper limit can be approximately 2,500, 2,000, 1,500, 1,000, 800, 600, or 400, and its lower limit can be approximately 100, 200, 300, 500, 700, 900, 1,100, 1,300, or 1,500. 3.5V The unit is Ω, and its range can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0063] Polymer layers can contain conductive materials to ensure excellent electroreactivity. While excellent electroreactivity can be maintained by applying conductive materials, these materials can also increase the surface roughness of the polymer layer. If the surface roughness of the polymer layer is too high, it may become difficult to uniformly form the active material layer applied on top of the corresponding layer, and this may degrade the rolling efficiency used for electrode fabrication. The polymer layers disclosed herein maintain a stable surface roughness even when the polymer layer contains conductive materials.

[0064] The thickness of the polymer layer can be appropriately selected according to the intended purpose. For example, the lower limit of the thickness of the polymer layer can be approximately 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm, and its upper limit can be approximately 1,000 nm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, or 400 nm. The thickness can be greater than or equal to, or greater than, any lower limit selected above; or less than, or equal to, or less than, any upper limit selected above; or less than, or equal to, or less than, any upper limit selected above and simultaneously greater than or equal to, or greater than, any lower limit selected above.

[0065] For example, the ratio of the arithmetic mean roughness Ra of the polymer layer to its thickness can be within a predetermined range. The upper limit of this ratio can be approximately 50%, 45%, 40%, 38%, 36%, 34%, 32%, 30%, 28%, 26%, or 25%, and the lower limit is not particularly limited, but can be approximately 0.001%, 0.01%, 0.1%, 1%, 5%, 10%, 15%, or 20%. This ratio can be less than, equal to, or less than any of the upper limits listed above; or less than, equal to, or less than any of the upper limits listed above and simultaneously greater than, equal to, or greater than any of the lower limits listed above. Here, the ratio of the arithmetic mean roughness Ra of the polymer layer to its thickness (T) is calculated using the equation 100 × Ra / T. Furthermore, the applied thickness T of the polymer layer is the average thickness of the polymer layer. The thickness of the polymer layer used for the calculation is measured in the manner described in "3. Thickness Measurement" of the Embodiments section of this specification, and the arithmetic mean roughness is measured in the manner described in "7. Arithmetic Mean Roughness Ra" of the Embodiments section of this specification.

[0066] For example, the upper limit of the arithmetic mean roughness Ra of the polymer layer can be approximately 500 nm, 400 nm, 350 nm, 300 nm, 250 nm, 230 nm, 200 nm, 190 nm, 180 nm, 170 nm, 160 nm, 150 nm, 140 nm, 130 nm, 120 nm, 110 nm, or 100 nm, and its lower limit can be approximately 1 nm, 5 nm, 10 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 130 nm, 140 nm, or 150 nm. The arithmetic mean roughness Ra can be less than, equal to, or less than any upper limit selected from the upper limits listed above; or less than, equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than, equal to, or greater than any lower limit selected from the lower limits listed above. The arithmetic mean roughness Ra is measured in the manner described in “7. Arithmetic mean roughness Ra” of the Embodiments section of this specification.

[0067] When conductive materials are incorporated into a polymer layer, their dispersion can be stably maintained. Therefore, the polymer layer can maintain a uniform surface with low roughness while ensuring the advantages of using conductive materials, such as excellent electroreactivity. This low surface roughness helps ensure scratch resistance and allows for the stable formation of additional layers, such as active material layers, on the polymer layer, and enables stable subsequent processes, such as rolling processes.

[0068] The polymer layer or the current collector or electrode comprising it can exhibit a precisely designed PTC effect, thereby maintaining excellent electrical performance at normal temperatures and subsequently exhibiting a resistance-enhancing effect under abnormal conditions.

[0069] For example, a polymer layer or current collector or electrode including it can be designed such that P in Equation 2 below falls within a predetermined range.

[0070] [Equation 2]

[0071] P = R 130 / R 25

[0072] 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 25The resistance is confirmed in a coin cell using a current collector having a polymer layer formed thereon or using an electrode having a current collector having a polymer layer formed thereon, and the measurement method follows the manner described in section "5. AC Impedance Measurement at Room Temperature (25°C) and 130°C" of the Examples section of this specification.

[0073] The lower limit of P in Equation 2 can be approximately 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, or 950, and its upper limit is not particularly restricted, but can be approximately 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, 850, 800, 750, 700, 650, 600, 550, or 500. P can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0074] The polymer layer, the current collector therein, or the electrode therein exhibits a large resistance difference at room temperature (approximately 25°C) and at high temperature (130°C) due to the PTC effect.

[0075] The polymer layer, the current collector therein, or the electrode therein can exhibit low resistance at room temperature (approximately 25°C) while exhibiting the P value.

[0076] For example, the AC impedance R in Equation 2 above 25 The upper limit can be approximately 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 45, or 40, and its lower limit is not particularly restricted, but can be, for example, approximately 10, 15, 20, 25, 30, 35, 40, or 45. AC impedance resistance R 25 The unit is Ω, and the range can be less than, equal to, or less than any upper limit selected from the upper limits listed above; or less than, equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than, equal to, or greater than any lower limit selected from the lower limits listed above. This characteristic enables the electronic device to operate or store data stably under normal conditions.

[0077] The AC impedance R in Equation 2 130 The lower limit can be around 10,000, 10,200, 10,400, 10,600, 10,800, 11,000, 13,000, 15,000, 17,000, 19,000, 21,000, 23,000, 25,000, 27,000, 29,000, or 31,000, and its upper limit is not particularly limited, but can be around 60,000, 50,000, 40,000, 35,000, 34,000, or 32,000. AC impedance resistor R 130 The unit is Ω, and the range can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0078] The electrode assembly, including the polymer layer and the diaphragm, exhibits excellent stability even when subjected to external impacts.

[0079] For example, the electrode assembly may exhibit a certain level or a lower level of maximum temperature during an impact test.

[0080] The maximum temperature is the highest temperature confirmed during the impact test conducted according to Test Example 4 of this specification. The upper limit of this maximum temperature may be approximately 200°C, 150°C, or 100°C, and its lower limit may be approximately 20°C, 40°C, 60°C, or 80°C. The maximum temperature may be less than or equal to, or less than, any upper limit selected from the upper limits listed above; or may be less than or equal to, or less than, any upper limit selected from the upper limits listed above, and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0081] Furthermore, the electrode assembly can exhibit a certain or lower heating rate during the impact test. The upper limit of the heating rate can be approximately 40, 35, 30, 25, 20, 15, 10, 5, 1, or 0.5, and its lower limit can be approximately 0.01, 0.05, 0.1, 0.15, or 0.2. The heating rate can be less than or equal to, or less than, any upper limit selected from the above-listed upper limits; or less than or equal to, or less than, any upper limit selected from the above-listed upper limits and simultaneously greater than or equal to, or greater than any lower limit selected from the above-listed lower limits. The unit of heating rate is 40°C / second.

[0082] The maximum temperature and heating rate can be determined according to the contents of Test Example 4 in this specification.

[0083] As a current collector for the positive or negative electrode, those commonly used for the positive or negative electrode can be used without any special restrictions.

[0084] There are no particular restrictions on the type, size, and shape of the current collector if it is conductive and will not cause chemical changes in the application device, such as a secondary battery. Examples of materials that can be used as current collectors include materials in which the surface of copper, aluminum, or stainless steel is surface-treated with materials such as carbon, nickel, titanium, or silver. Current collectors can be in the form of films, sheets, foils, meshes, porous bodies, foams, or nonwoven fabrics, incorporating the aforementioned materials. In some cases, the surface of the current collector may be subjected to known surface treatments to improve adhesion to other layers, such as polymer layers or active material layers.

[0085] Such current collectors can typically have a thickness ranging from 3 μm to 500 μm, but are not limited to this.

[0086] The polymer layer exists on one or both surfaces of the current collector. As is known, conductive polymers are polymers that exhibit conductivity through conjugated systems of polymer chains and / or doping, etc.

[0087] The conductive polymer may have a weight-average molecular weight within a predetermined range. For example, 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, 130,000, 135,000, 140 The values ​​can be around 1,000, 145,000, or 150,000, with an upper limit of approximately 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, 110,000, 100,000, 80,000, 60,000, or 55,000. The unit of weight-average molecular weight is g / mol, and the range can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above. By using conductive polymers having the above weight-average molecular weight, polymer layers and electrodes with desired properties can be effectively formed.

[0088] 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 the molecular weight distribution can be approximately 2, 2.5, 3, 3.5, or 4, and its 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, or greater than any lower limit selected from the above-listed lower limits; or less than, or equal to, or less than any upper limit selected from the above-listed upper limits; or less than, or equal to, or less than any upper limit selected from the above-listed upper limits. By using a conductive polymer with the above molecular weight distribution, polymer layers, electrode current collectors, and electrodes with desired properties can be effectively formed.

[0089] The weight-average molecular weight and molecular weight distribution can be evaluated in the manner described in “2. GPC (Gel Permeation Chromatography)” of the Examples section of this specification.

[0090] The conductive polymer may be polythiophene.

[0091] The term polythiophene refers to a polymer containing thiophene monomer units at a certain level or higher. The lower limit of the ratio of thiophene monomer units in polythiophene, based on the total number of monomer units in the polymer, 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 monomer units in polythiophene can be approximately 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. The ratio of thiophene monomer units can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or less than, or equal to, or less than, any upper limit selected from the upper limits listed above, and simultaneously greater than or equal to, or greater than, any lower limit selected from the lower limits listed above.

[0092] In this specification, a monomer unit refers to a form in which any monomer is polymerized to be contained in a polymer; and the thiophene monomer is a monomer of the thiophene series, which refers to a monomer containing a thiophene skeleton.

[0093] The conductive polymer may contain long-chain hydrocarbon functional groups or monomer units having long-chain hydrocarbon functional groups (hereinafter referred to as Unit A). The conductive polymer may be polythiophene. In this case, the monomer having long-chain hydrocarbon functional groups may be a thiophene monomer.

[0094] The term long-chain hydrocarbon functional group refers to a monovalent hydrocarbon group with a certain number of carbon atoms or a monovalent functional group containing a certain number of carbon atoms.

[0095] For example, the lower limit for 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 its upper limit can be approximately 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4. The number of carbons can be greater than or equal to, or greater than any of the lower limits mentioned above; or greater than or equal to, or greater than any of the lower limits mentioned above and simultaneously less than or equal to, or less than any of the upper limits mentioned above.

[0096] The carbon number can be the total number of carbons present in the functional group of the long-chain hydrocarbon, or the number of carbons in the straight-chain hydrocarbon chain contained in the functional group. That is, the monovalent hydrocarbon group present in the functional group of the long-chain hydrocarbon can have a straight-chain or branched structure, and even in the case of a branched structure, the number of carbons in the longest straight chain constituting the relevant branched structure can be within the aforementioned range. For example, if the branched structure is 2-ethylhexyl, the number of carbons constituting the longest straight chain is 6.

[0097] 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.

[0098] The number of carbon atoms present in alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy groups can be within the range of the number of carbon atoms present in the long-chain hydrocarbon functional group (i.e., the number of carbon atoms in the monovalent hydrocarbon group).

[0099] For example, alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy can be straight-chain or branched structures. In the case of branching, the number of carbons in the longest straight chain constituting the relevant branched structure can be within the range described.

[0100] 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.

[0101] Such long-chain hydrocarbon functional groups are functional groups that can impart appropriate mobility to the monomers or the conductive polymer itself during the polymerization process of conductive polymers. Monomers containing such long-chain hydrocarbon functional groups impart appropriate mobility to monomer mixtures and also diffuse within the monomer mixtures, thereby enabling polymerization with excellent efficiency. Furthermore, conductive polymers having said long-chain hydrocarbon functional groups can achieve stable and uniform formation of polymer layers through appropriate mobility between the current collector and the active material layer.

[0102] Long-chain hydrocarbon functional groups are appropriately oriented during the drying or annealing process in the formation of polymer layers, thereby enabling the tuning of the PTC effect suitable for the polymer. 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 the 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 ratio of the long-chain hydrocarbon functional groups.

[0103] For example, to properly achieve the 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 example, the lower limit of the molar ratio relative to the total number of monomer units in polythiophene can be approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%, and the upper limit can be approximately 98 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. The ratio can be greater than or equal to, or greater than any of the lower limits mentioned above; or greater than, or greater than any of the lower limits mentioned above, and simultaneously less than, or equal to, or less than any of the upper limits mentioned above.

[0104] The conductive polymer may contain a hydrocarbon functional group having 10 or more carbon atoms (hereinafter referred to as the first hydrocarbon functional group) and a hydrocarbon functional group having 9 or fewer carbon atoms (hereinafter referred to as the second hydrocarbon functional group).

[0105] The lower limit of the number of carbon atoms in the first hydrocarbon functional group can be approximately 10, 11, or 12, and the upper limit can be approximately 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 selected from the lower limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above, and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0106] 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 selected from the upper limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above, while simultaneously being less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0107] 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 alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, and alkylcarbonyloxy.

[0108] Alkyl, alkenyl, alkynyl, alkoxy, alkyl carbonyl, and alkyl carbonyloxy can have straight-chain or branched structures, wherein in the case of a straight chain, the total number of carbons can be within the range described above, and in the case of a branched chain, the number of carbons in the longest straight chain constituting the relevant branched structure can be within the range described above.

[0109] The carbon number of long-chain hydrocarbon functional groups 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.

[0110] In the conductive polymer, the ratio of the total number of monomer units having a first hydrocarbon functional group and monomer units having a second hydrocarbon functional group to the total number of monomer units in the conductive polymer can be adjusted within the range of the ratio of unit A as described above.

[0111] The ratio (M2 / M1) of the number of moles of the second hydrocarbon functional group (M2) to the number of moles of the first hydrocarbon functional group (M1) in the conductive polymer; or the ratio (M2 / M1) of the number of moles of monomer units with the second hydrocarbon functional group (M2) to the number of moles of monomer units with the first hydrocarbon functional group (M1) can have a lower limit of approximately 0.01, 0.05, 0.1, 0.5, 1, 1.5 or 2, and an upper limit of 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 selected from the upper limits listed above, or may be greater than or equal to, or greater than any lower limit selected from the lower limits listed above, or may have a range that is greater than or equal to, or greater than any lower limit selected from the lower limits listed above and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0112] At such a 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 the electrode or electrode current collector.

[0113] The conductive polymer may contain polar functional groups or monomer units with polar functional groups (hereinafter referred to as unit B), as well as long-chain hydrocarbon functional groups or unit A. The monomer with polar functional groups may be a thiophene monomer.

[0114] In this specification, the term polar functional group is a functional group containing one or more polar atoms (e.g., 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.

[0115] [Formula 1]

[0116] 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.

[0117] In Equation 1, L1 being a single bond means that L1 does not exist and the oxygen atom between L1 and L2 is directly connected to the monomer.

[0118] In one example, the alkyl group of R1 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.

[0119] In this specification, the term alkylene refers to a divalent functional group formed by removing one hydrogen atom from each of the two different carbon atoms of an alkane, and the term alkylidene refers to a divalent functional group formed by removing two hydrogen atoms from one carbon atom of an alkane.

[0120] In one example, the alkylene groups L2 and L1 in Formula 1 may each be alkylene groups 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 groups may be straight-chain, branched, or cyclic, and may be straight-chain or branched, as appropriate. The alkylene groups may optionally be substituted with one or more substituents.

[0121] In one example, the alkylidene groups of L2 and L1 in Formula 1 may each be alkylidene groups 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 each be methylene, ethoxy, or propylidene. The alkylidene group may be straight-chain, branched, or cyclic, and may be straight-chain or branched, as appropriate. The alkylidene group may optionally be substituted with one or more substituents.

[0122] 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 greater than or equal to, or greater than any of the aforementioned lower limits, and simultaneously less than or equal to, or less than any of the aforementioned upper limits.

[0123] By applying the aforementioned polar functional groups, polymer layers can be bonded to other layers with appropriate bonding strength, and such conductive polymer layers 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.

[0124] The molar number of polar functional groups and long-chain hydrocarbon functional groups in conductive polymers can be controlled to ensure appropriate effects.

[0125] For example, the number of moles of long-chain hydrocarbon functional groups (M) in conductive polymers L ) and the number of moles of polar functional groups (M) P The ratio of (M) L / M P The lower limit of M can be approximately 1, 5, 10, 15, 16, 17, 18, or 19, and its 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, or 20. The ratio M... L / M P It can be less than or equal to, or less than any upper limit selected from the upper limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0126] Unit A (M) in conductive polymer A ) and the number of moles of unit B (M) B The ratio of (M) A / M B The lower limit of M 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, or 20. The ratio M... A / M BIt can be less than or equal to, or less than any upper limit selected from the upper limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0127] The ratio of the total number of moles of units A and B relative to the total number of moles of all monomer units of the conductive polymer can have a lower limit of approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%, and an upper limit of approximately 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. This ratio can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or greater than or equal to, or greater than any lower limit selected from the lower limits listed above, and simultaneously less than or equal to, or less than any upper limit selected from the upper limits listed above.

[0128] 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.

[0129] For example, conductive polymers may contain units of Formula 2 below as thiophene units.

[0130] [Equation 2]

[0131] 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.

[0132] [Formula 3]

[0133] 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.

[0134] 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.

[0135] 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.

[0136] In Formula 3, the meanings and specific examples of single bonds, alkylene groups, and alkylidenes are the same as in Formula 1.

[0137] 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.

[0138] Relative to the molar number of all monomer units of polythiophene, the lower limit of the molar ratio of all monomer units of 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%, or 90 mol%, and its upper limit can be approximately 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. The ratio can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or less than, or equal to, or less than, any upper limit selected from the upper limits listed above; or less than, or equal to, or less than, any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than, any lower limit selected from the lower limits listed above.

[0139] In one example, the conductive polymer may contain a monomer unit represented by Formula 4. The monomer unit of Formula 4 may be an example of a monomer unit having a first hydrocarbon functional group.

[0140] [Formula 4]

[0141] 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.

[0142] In another instance, R6 and R7 can be connected to each other to form a divalent functional group as shown in Equation 5.

[0143] [Formula 5]

[0144] 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.

[0145] 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.

[0146] The conductive polymer may also contain monomer units represented by Formula 6 below.

[0147] The monomer unit in Equation 6 above can be an example of a monomer unit having a second hydrocarbon functional group.

[0148] [Formula 6]

[0149] In Equation 6, R 10 and R 11 Each can be an independent hydrogen or second hydrocarbon functional group, and in this case, the above R 10 and R 11 One or more of them can be second hydrocarbon functional groups.

[0150] In another instance, the aforementioned R 10 and R 11 They can connect with each other to form divalent functional groups as shown in Equation 7.

[0151] [Formula 7]

[0152] 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.

[0153] 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.

[0154] The conductive polymer may also contain monomer units represented by Formula 8. The monomer unit of Formula 8 may be an example of a monomer unit having polar functional groups.

[0155] [Formula 8]

[0156] 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.

[0157] 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.

[0158] [Formula 9]

[0159] In Equation 9, L9 and L 10 Each is independently a single bond, alkylene group, or alkylidene group, and 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.

[0160] 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.

[0161] When the conductive polymer contains both the monomer unit of Formula 4 and the monomer unit of Formula 6, the ratio of the total number of moles of the monomer unit of Formula 4 and the monomer unit of Formula 6 to the total number of moles 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.

[0162] Furthermore, in this case, the ratio of the number of moles of the monomer unit of Formula 4 to the number of moles of the monomer unit of Formula 6 can be adjusted within the same range as the mole ratio M1 / M2. In this case, the number of moles M1 can be the number of moles of the monomer unit of Formula 4, and the number of moles M2 can be the number of moles of the monomer unit of Formula 6.

[0163] When the conductive polymer contains monomer units of Formula 8 above, it can be used at the above molar ratio M A / M B The range includes the unit. In this case, the number of moles of the single-unit in Equation 8 above becomes the number of moles M. B In addition, the number of moles M A 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 total number of moles of the single unit in Formula 4 above and the single unit in Formula 6 above.

[0164] 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 number of monomer units of Formulas 4, 6, and 8 to the total number of monomer units in the conductive polymer relative to the total number of moles of all monomer units in the polythiophene is approximately 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%, and the upper limit is approximately 100 mol%, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 75 mol%, 70 mol%, 65 mol%, or 60 mol%. This ratio can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above; or less than, or equal to, or less than, any upper limit selected from the upper limits listed above; or less than, or equal to, or less than, any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than, any lower limit selected from the lower limits listed above.

[0165] If the conductive polymer contains the aforementioned units at the above-described ratio, it may further contain other monomer units. The polymer layer contains the conductive polymer, and therefore can exhibit the aforementioned properties.

[0166] The polymer layer may contain only conductive polymer, or may further contain conductive polymer and other necessary additives. In one example, based on the total weight of the polymer layer, the lower limit of the conductive polymer content in the polymer layer may be approximately 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95, and the upper limit may also be approximately 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50. The content is expressed in weight percent. The range of the content may be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0167] For example, the polymer layer may further comprise a conductive material and the conductive polymer. As the conductive material, any material having suitable conductivity can be used, and for example, one or more selected from carbon particles, carbon fibers, graphene, graphite, carbon black, carbon nanotubes, and metal particles can be used.

[0168] As a conductive material, an appropriate type can be selected and used from the above types. The shape of the material can be granular (spherical, irregular, or other shapes), plate-shaped, or fiber-shaped, but is not limited to these.

[0169] The size of the conductive material can also be adjusted as needed. For example, the lower limit of the size of the conductive material can be approximately 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 5000 nm, or 10000 nm, and its upper limit can be approximately 100000 nm, 90000 nm, 80000 nm, 70000 nm, 60000 nm, 50000 nm, 40000 nm, 30000 nm, 20000 nm, 10000 nm, 5000 nm, 1000 nm, 950 nm, 900 nm, 850 nm, 800 nm, 750 nm, 700 nm, etc. The dimensions are approximately 150 nm, 650 nm, 600 nm, 550 nm, 500 nm, 450 nm, 400 nm, 350 nm, 300 nm, 250 nm, 200 nm, 200 nm, or 150 nm. The dimensions may be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0170] When the conductive material is in granular form, the size can be the average particle size (so-called D50 particle size); when it is in plate form, the size can be the thickness, long side, or cross-section; and when it is in fiber form, the size can be the diameter or length of the cross-section.

[0171] When the conductive material is in the form of fibers, the lower limit of the aspect ratio (length / diameter of cross section) can be approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or 65, and its upper limit can be approximately 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 greater than or equal to, or greater than any of the lower limits selected above; or less than, or equal to, or less than any of the upper limits selected above; or less than, or equal to, or less than any of the upper limits selected above and simultaneously greater than, or equal to, or greater than any of the lower limits selected above.

[0172] If necessary, the conductive material can be surface-treated, taking into account factors such as dispersibility.

[0173] In this case, it may include a conductive core and a surface layer present on the surface of the core. In this case, one or more conductive materials selected from carbon particles, carbon fibers, graphene, graphite, carbon black, carbon nanotubes, and metal particles serve as the conductive core.

[0174] Surface treatment agents with suitable compatibility with the conductive polymer can be used as surface treatment agents. For example, conductive materials can be surface-treated with polyphenolic compounds as surface treatment agents. In this case, the surface layer can contain polyphenolic compounds. The polyphenolic compounds refer to compounds containing a structure in which two or more hydroxyl groups are substituted on a benzene ring and said hydroxyl groups are attached to said benzene ring. Such compounds can be exemplified by so-called catechol compounds (i.e., catechols or compounds containing related structures), examples of which include, but are not limited to, dopamine, polydopamine, 3,4-dihydroxyphenylalanine, norepinephrine, tannic acid, humic acid, and / or lignin.

[0175] There are no limitations on the methods of surface treatment of conductive materials with surface treatment agents. For example, methods such as mixing conductive materials and surface treatment agents in a suitable solvent can be used, or methods of synthesizing or polymerizing surface treatment agents on the surface of conductive materials can be used.

[0176] When using conductive materials, the ratio of conductive material within the polymer layer can be adjusted according to the intended use. For example, the lower limit of the weight ratio (parts by weight) of conductive material in the polymer layer relative to 100 parts by weight of the conductive polymer can be 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 25 parts by weight, or 30 parts by weight. Approximately 40, 50, 60, or 65 parts by weight, with upper limits of approximately 1,000, 800, 600, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, or 15 parts by weight. The content may be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0177] At this ratio, the conductive material and the conductive polymer interact appropriately, thereby enabling the efficient formation of a polymer layer with the desired shape.

[0178] The polymer layer can be manufactured in the following ways. For example, a method of manufacturing a polymer layer may include the step of forming a polymer layer using a polymer solution comprising a conductive polymer and, where necessary, a conductive material. Furthermore, the method may include, for example, a first step of forming a polymer layer precursor comprising a conductive polymer and a conductive material, and a step of heat-treating the polymer layer precursor.

[0179] As the conductive polymer and conductive material used to form the precursor of the polymer layer, the conductive polymer and conductive material described above can be used. The conductive polymer, etc., can be manufactured by known methods, or commercially available products can be used. For example, methods using oxidative polymerization reactions, methods using free radical reactions, etc., are known as methods for manufacturing polythiophene, and such methods can also be applied to the process of forming the conductive polymer in this application. Furthermore, commercially available products can also be used as conductive materials, and their surface treatment can also be performed in known manners.

[0180] The polymer layer precursor is, for example, a layer containing the conductive polymer and conductive particles, which ultimately means a layer that is converted into the polymer layer.

[0181] Such precursors can be formed in known ways, and for example, by coating a polymer solution in which a conductive polymer or the like is dispersed in a suitable solvent.

[0182] Here, as a solvent, an appropriate solvent capable of dispersing the conductive polymer and the conductive material can be selected. For example, ether solvents such as diethyl ether, tetrahydrofuran, dioxane, trioxane, dimethoxyethane, or toluene can be used; aromatic hydrocarbon solvents such as ethylbenzene, or alicyclic hydrocarbon solvents such as cyclohexane; or tertiary amine solvents such as tetramethylethylenediamine (TMEDA) or hexamethylphosphoric triamine (HMPA), etc., or a mixed solvent containing two or more of the aforementioned solvents can be used, but not limited to these.

[0183] In this step, the lower limit of the concentration of the conductive polymer present in the polymer solution can be approximately 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, or 3 wt%, and the upper limit can be approximately 20 wt%, 18 wt%, 16 wt%, 14 wt%, 12 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, or 3 wt%. The ratio can be greater than or equal to, or greater than, any lower limit selected from the lower limits listed above, or less than, or equal to, or less than, any upper limit selected from the upper limits listed above, or greater than, or equal to, or greater than, any lower limit selected from the lower limits listed above and simultaneously less than, or equal to, or less than any upper limit selected from the upper limits listed above. Such concentrations can be changed as needed.

[0184] The polymer solution is used to form a polymer layer precursor. This process can typically be carried out by coating the polymer solution onto a suitable substrate. In this case, there are no particular limitations on the coating method.

[0185] The manufacturing method further includes a step of heat-treating the precursor of the polymer layer. By adjusting the conditions in this 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.

[0186] A polymer layer is formed on the current collector using the polymer solution. This process typically involves coating the current collector with the polymer solution and then heat-treating the coated solution (e.g., drying or annealing). The crystallinity of the conductive polymer can also be controlled by the heat treatment conditions during this process.

[0187] The heat treatment step can be performed in two steps. For example, the heat treatment step 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.

[0188] To achieve the desired 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.

[0189] 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°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, and its upper limit can be approximately 300°C, 290°C, 280°C, 270°C, 260°C, 250°C, 240°C, 230°C, 220°C, 210°C, 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, or 140°C. The temperature range T1 can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0190] 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, or 1, and its upper limit can be approximately 10, 8, 6, 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, or greater than, any lower limit selected from the lower limits listed above; or less than or equal to, or less than, any upper limit selected from the upper limits listed above; or less than or equal to, or less than, any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than, any lower limit selected from the lower limits listed above.

[0191] 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.

[0192] The ratio of heat treatment time Q1 in the primary heat treatment to heat treatment time Q2 in the secondary heat treatment can be further adjusted. For example, the lower limit of the ratio Q2 / Q1 can be approximately 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 50, 100, 150, 200, or 250, and its upper limit can be approximately 1,000, 800, 600, 400, 300, 280, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18, 17, 16, or 15. The ratio Q2 / Q1 can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above; or less than, or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0193] The lower limit of the secondary heat treatment time Q2 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, and its 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 Q2 can be greater than or equal to, or greater than any lower limit selected from the lower limits listed above; or less than or equal to, or less than any upper limit selected from the upper limits listed above; or less than or equal to, or less than any upper limit selected from the upper limits listed above and simultaneously greater than or equal to, or greater than any lower limit selected from the lower limits listed above.

[0194] The polymer layer can be formed using the above process.

[0195] By adjusting or stabilizing 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 through this heat treatment process, a polymer layer that satisfies the expected PTC effect, oxidation potential characteristics and other properties can be formed.

[0196] For example, the desired polymer layer can be formed on the current collector using the process described above, and then an active material layer can be formed on the polymer layer using common methods, thereby obtaining the electrode (positive or negative electrode).

[0197] As the active material layer used to form the electrode, a commonly used layer can also be used.

[0198] Typically, the active material layer contains the electrode active material. There are no particular restrictions on the specific type of electrode active material; materials that form either the positive or negative electrode can generally be used.

[0199] For example, when the active material layer is a positive electrode active material layer, the electrode active material may include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium manganese oxide such as Li 1+c1 Mn 2-c1O4 (0≤c1≤0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5 or Cu2V2O7; formula LiNi 1-c2 M c2 Lithium nickel oxide with nickel sites represented by 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); LiMn 2-c3 M c3 Lithium manganese composite oxides represented by O2 (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 oxides, lithium nickel cobalt manganese aluminum (NCMA) composite oxides, and LiMn2O4 in which a portion of the Li in the formula is replaced by alkaline earth metal ions, etc., but not limited thereto.

[0200] When the active material layer is a negative electrode active material layer, compounds capable of reversibly inserting and de-intercalating lithium can be used as electrode active materials. Specific examples may include: carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and metal oxides capable of doping and de-doping lithium, such as SiO₂. a (0 < a < 2), SnO2, vanadium oxide and lithium vanadium oxide; or composite materials containing metal compounds and carbonaceous materials, such as Si-C composite materials or Sn-C composite materials, and any one or a mixture of two or more of the foregoing may be used.

[0201] Lithium metal films can also be used as anode active materials, and as carbon materials, 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.

[0202] The electrode active material may be contained in the active material layer at approximately 80% to 99.5% by weight or 88% to 99% by weight relative to the total weight of the active material layer, but this ratio may vary depending on the application or design of the electrode.

[0203] The active material layer may further comprise 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. Examples of the adhesive are not particularly limited, and may include, for example, one or more of 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 pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer (polyethylene-co-vinyl acetate), and polyarylates.

[0204] In one example, the binder may be included in the active material layer in amounts of 0.1 to 10 parts by weight or 0.5 to 5 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0205] The active material layer may further include conductive materials as needed. There are no particular limitations on the conductive material; any known material can be used, provided it is conductive and does not cause 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.

[0206] In one example, the conductive material may be included in the active material layer in amounts of 0.1 to 20 parts by weight or 0.3 to 10 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto.

[0207] In addition to the components described above, the active material layer may optionally further contain any necessary known components.

[0208] There are no particular limitations on the method of 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 an electrode active material, a binder, and a conductive material onto a current collector (on the polymer layer), drying it, and then rolling it. Such known methods can be applied here in the same manner.

[0209] Such an electrode may sequentially comprise: a current collector; a conductive polymer layer; and an active material layer.

[0210] As described above, the conductive polymer layer can have a uniform and stable thickness due to its excellent coating properties.

[0211] Therefore, even before rolling, the active material layer in the electrode does not include bulges at the end. For example, the active material layer in the electrode contains sliding regions. When forming the active material layer using electrode slurry, the sliding regions are due to the viscosity characteristics of the slurry, the region where the thickness of the active material layer increases along the coating direction at and near the beginning of the coating, and the region where the thickness of the active material layer decreases along the coating direction at and near the end of the coating.

[0212] This sliding region is a common phenomenon that occurs during the electrode manufacturing process. For example, as... Figure 4 As exemplarily shown, to prepare an electrode, a conductive polymer layer (200) is formed on a current collector (100), and an active material layer (300) is formed thereon by coating an electrode slurry. In this case, it is assumed that the coating direction is... Figure 4 From left to right, a sliding region (S) appears in which the thickness of the active material layer (300) increases from the start of the coating process to a certain area. After a certain period, a region with stable thickness (N) appears. Then, a sliding region (S) with decreasing thickness appears again in a certain region (3002).

[0213] However, problems arise during subsequent electrode fabrication when bulges appear in the sliding region (S). These bulges are located at the beginning and end of the sliding region (S). Figure 4 In the case of: the area between 3001 and 3002, excluding the area (in Figure 4 In the case of 3001, 3002), this means that it is formed as a portion longer than the beginning and end portions (in... Figure 4 In the case of 3001 and 3002, the thicker part is...

[0214] If such bulges exist, problems will occur during the subsequent rolling process of the active material layer.

[0215] Because the conductive polymer layer forms with a stable and uniform thickness, the maximum thickness is determined at the end point of the sliding region within the thickness distribution of the sliding region. In this case, the end point of the sliding region refers to the beginning and end portions of the sliding region (S). Figure 4 In the case of: 3001, 3002) thicker points.

[0216] Even when the active material layer is an unrolled active material layer, i.e., the active material layer before rolling, it does not include any bulges at the end. If rolling is performed, even if some bulges exist, it is possible to eliminate any bulges, but damage to the current collector may occur during this process, or uneven rolling may occur. The active material layer of the electrode does not have bulges in the unrolled state, so the rolling process can also be performed effectively. Such an active material layer can be included in the electrode assembly after the rolling process.

[0217] The conductive polymer layer of the electrode can be an untreated conductive polymer layer. That is, even when an active material layer is formed on the conductive polymer layer without surface treatment such as corona treatment or plasma treatment, a sliding region without any protrusions can be formed.

[0218] 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.

[0219] This specification also discloses an electrochemical element, such as a secondary battery, incorporating the electrode assembly described above. If the electrode assembly is used, the electrochemical element is not particularly limited in terms of other components or manufacturing methods, and known methods can be applied.

[0220] Beneficial effects

[0221] This specification discloses an electrode assembly and a secondary battery. The electrode assembly is formed by combining the following components: electrodes that exhibit low resistance and excellent electrical characteristics under normal conditions and ensure stability by rapidly transforming into an insulator under abnormal conditions; and a separator known as an SRS (Safety Reinforced Separator). This specification also discloses a secondary battery comprising the electrode assembly. Attached Figure Description

[0222] Figure 1 This is a side view of an exemplary electrode assembly.

[0223] Figure 2 This is a side view of an exemplary diaphragm.

[0224] Figure 3 This is a side view of an exemplary electrode.

[0225] Figure 4 This is a cross-sectional view of the electrode used to illustrate the sliding region.

[0226] Figure 5 These are the NMR analysis results of the compounds prepared in the preparation examples.

[0227] Figure 6 This is an SEM image of the electrode in the embodiment.

[0228] Figure 7 This is a thickness distribution diagram of the sliding region in the active material layer of the electrode.

[0229] Figure 8 The results are from the analysis of the button half-cell in Experiment Example 1.

[0230] Figure 9 This is the charge / discharge curve of the cycle test in Example 1.

[0231] Figure 10 This is the energy density retention rate (140 cycles) result of Experiment Example 1.

[0232] Figure 11 The results are from the rate test of the 3-Ah pouch cell in Example 1.

[0233] Figure 12 The results are from the cycle test of the 3-Ah pouch cell in Example 1.

[0234] Figure 13 This is a diagram used to illustrate the method of conducting impact tests.

[0235] Figure 14 It is a view showing the highest temperature and heating rate during the impact test. Detailed Implementation

[0236] The electrode assembly is described in detail below with reference to embodiments and comparative examples, but the scope of the electrode assembly, etc., is not limited to the following embodiments.

[0237] 1. NMR analysis method

[0238] 1 H-NMR analysis was performed at room temperature (25 °C) using an NMR spectrometer with a 5 mm triple resonance probe (including a Bruker UltraShield spectrometer (300 MHz)). Samples were diluted to approximately 10 mg / ml in the solvent (CDCl3) used for NMR measurements, and chemical shifts are expressed in ppm.

[0239] 2. GPC (Gel Permeation Chromatography)

[0240] The molecular weight characteristics were measured using GPC (gel permeation chromatography). The sample was placed in a 5 mL vial and diluted with chloroform to a concentration of about 1 mg / mL. The standard sample for calibration and the analytical sample were filtered through a syringe filter (pore size: 0.45 μm) and then measured. As the analytical program, Empower 3 from Waters was used, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were obtained by comparing the elution time of the sample with the calibration curve, respectively. 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.

[0241] <GPC measurement conditions>

[0242] Instrument: 2414 from Waters

[0243] Column: Use 3 Styragels from Waters

[0244] Solvent: THF (tetrahydrofuran)

[0245] Column temperature: 35 °C

[0246] Sample concentration: 1 mg / mL, 1 μL injection

[0247] Standard sample: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940, 485)

[0248] 3. Thickness measurement

[0249] The thickness of the polymer layer was measured using a KEYENCE VK-X series confocal laser microscope. The aluminum foil on which the polymer layer was formed was cut so that the width and length were each 3 cm, thus preparing a specimen, and about half of the polymer layer was removed from the specimen with acetone to expose the underlying aluminum foil. The side of the specimen with the aluminum foil where the polymer layer was not formed was pressed against a flat plate and measurement was started. A region with a width and length of 100 μm each was observed under the microscope, but the polymer layer and the exposed aluminum foil of the specimen were each adjusted to be approximately half within the observation region, and 3D scanning was performed. Ten points were arbitrarily designated on the polymer layer within the observation region to measure the average value P of the height, and the height was measured at ten points on the aluminum foil arbitrarily to obtain the average value A. Subsequently, the value obtained by subtracting the average value A from the average value P was used as the thickness of the polymer layer.

[0250] 4. AC impedance resistance measurement at 3V and 3.5V

[0251] Sample manufacturing

[0252] 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 each example and comparative example. Subsequently, a separator and a lithium film were laminated onto the polymer layer to manufacture a laminate in which the aluminum foil / polymer layer / separator / lithium film were laminated, and the laminate was punched into a circle with a diameter of approximately 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 of the coin cell was measured. As the separator, LG Energy Solution's SRS (Safety Enhanced Separator) was used. The SRS is a separator in which an inorganic particulate layer comprising PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) and Al2O3 is formed on a polymer membrane (polyethylene separator) (porosity approximately 45%), and the weight ratio of PVDF-HFP to Al2O3 (PVDF-HFP:Al2O3) is approximately 1:4. As the lithium membrane, a lithium membrane with a thickness of about 300 μm is used. As the electrolyte, 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.

[0253] External voltage 3V condition

[0254] For button cells, AC impedance resistance was measured using EIS (electrochemical impedance spectroscopy). A 3V voltage was applied to the button cell for 10 minutes at room temperature (25°C), and the interfacial resistance R was measured. 3V The resistance value was obtained in the high-frequency region of the Nyquist plot in the range of 50,000 Hz to 0.1 Hz using EIS measurement methods. A potentiostat (Princeton Applied Research, PARASTAT-MC) was used as the EIS measurement device.

[0255] External voltage 3.5V condition

[0256] The applied force will be applied to the measured resistance R. 3V The external voltage of the button cell battery was converted to 3.5V, and the AC impedance resistance R was measured in the same manner after 1 second. 3.5V .

[0257] 5. AC impedance resistance measurement at room temperature (25℃) and 130℃

[0258] The AC impedance resistance was measured using the same coin cell as used in “AC Impedance Resistance Measurement at 4.3V and 3.5V”. For the coin cell, the AC impedance resistance was measured using EIS (electrochemical impedance spectroscopy). Specifically, the interfacial resistance was measured in the high-frequency region of the Nyquist plot obtained by EIS measurement in the range of 50,000Hz to 0.1Hz. A potentiostat (manufacturer: Princeton Applied Research, product name: PARASTAT-MC) was used as the EIS measurement device.

[0259] A 4.5V voltage was applied to the button cell for 10 minutes at room temperature (25°C) to maintain the doping state of the conductive polymer. Then, the AC impedance resistance R was measured after approximately 1 minute with the external voltage set to 0V (open circuit voltage). 25 The measured value was evaluated as the AC impedance resistance R of the polymer layer at room temperature (25°C). 25 .

[0260] The button cell was placed individually 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) to allow for EIS resistance measurements. 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 .

[0261] 6. Average particle size

[0262] The average particle size (D50 diameter) of conductive particles was measured using a Marvern MASTERSIZER 3000 apparatus according to ISO-13320 standard. Toluene was used as the solvent during the measurement. If the sample (conductive particles) is dispersed in the 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 according to particle size, the average particle size can be obtained by analyzing them using Mie theory. Through this analysis, the measurement results are converted into the particle size of spheres with the same volume as the dispersed sample, thereby obtaining a volume-based cumulative curve of the particle size distribution. The particle size at the 50% cumulative point in this curve (the median particle size) is designated as the average particle size (D50 diameter).

[0263] 7. Arithmetic mean roughness Ra

[0264] The arithmetic mean roughness Ra was measured using a KEYENCE VK-X series confocal laser microscope. Samples were prepared by cutting polymer-coated aluminum foil to a width and length of 3 cm. The unpolymer-coated surface of the aluminum foil sample was pressed against a plate and 3D scanned.

[0265] A 3D scan is performed on an area of ​​100 μm width and 100 μm length of the polymer layer. After arbitrarily specifying an area of ​​50 μm width and 50 μm length within the 3D scanned area, the arithmetic mean roughness Ra is measured using the 3D scan image.

[0266] 8. Scratch resistance

[0267] The surface of the polymer layer was rubbed 10 times with a 100 g load and a speed of 27 rpm using a clean cloth (Hansong Wiper MIRACLEAN322 Polyester). If a scratch was observed with the naked eye, the rating was X; if no scratch was observed with the naked eye, the rating was O.

[0268] Preparation Example 1. Polydopamine-coated conductive particles

[0269] 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.

[0270] DHC (dopamine hydrochloride) (CAS No. 62-31-7) was added to a buffer solution and stirred at room temperature (approximately 25°C). Here, BIOSESANG's 0.1M pH 8.5 Tris buffer product 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 approximately 18 hours to form a polydopamine coating on the conductive particles. After filtration under reduced pressure using a paper filter, the resulting particles were vacuum-dried to obtain polydopamine-coated conductive particles.

[0271] Preparation Example 2. Synthesis of Monomer (A)

[0272] The monomer of formula A is synthesized in the following manner.

[0273] [Formula A]

[0274] 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 Soxhlet extractor filled with a type 4A molecular sieve. 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 elution 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 5 As shown.

[0275] Preparation Example 3. Synthesis of Polythiophene (A)

[0276] Conductive polymers were prepared by polymerizing 3-dodecylthiophene (3-DT), 3-hexylthiophene (3-octylthiophene) (3-HT), and monomer (A) of formula A from Preparation Example 2. 0.787 g (3.12 mmol, 0.475 equivalent) of 3-dodecylthiophene, 0.525 g (3.12 mmol, 0.475 equivalent) of 3-hexylthiophene, and 0.083 g (0.3285 mmol, 0.05 equivalent) of monomer (A) from Preparation Example 2 were introduced into a solution in which 3.20 g (19.71 mmol, 3 equivalents) of ferric chloride (III) was dissolved in 150 mL of dichloromethane, and polymerization was carried out at 25°C for 24 hours to produce polythiophene (A). The polymerization solution was placed in a permeation membrane with a molecular weight cutoff (MWCO) of 5,000, and then immersed in 200 ml of acetonitrile solvent to remove unreacted ferric chloride (III), monomers, and low molecular weight oligomers. The residue precipitated inside the permeation membrane was washed with methanol and dried at 60 °C for 12 hours to produce polythiophene (A). The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polythiophene (A) were 150,000 g / mol and 50,000 g / mol, respectively.

[0277] Preparation Example 4. Synthesis of Polythiophene (B)

[0278] Conductive polymers were prepared by polymerizing 3-dodecylthiophene (3-DT), 3-octylthiophene (3-OT), and monomer (A) of formula A from Preparation Example 2. 0.79 g (3.135 mmol, 0.475 equivalent) of 3-dodecylthiophene, 0.62 g (3.315 mmol, 0.475 equivalent) of 3-octylthiophene, and 0.081 g (0.33 mmol, 0.05 equivalent) of monomer (A) from Preparation Example 2 were introduced into a solution in which 3.20 g (19.71 mmol, 3 equivalents) of ferric chloride (III) was dissolved in 150 mL of dichloromethane, and polymerization was carried out at 25 °C for 24 hours to produce polythiophene (B). The polymerization solution was placed in a permeation membrane with a MWCO (molecular weight cutoff) of 5000, and then immersed in 200 mL of acetonitrile solvent to remove unreacted ferric chloride (III), monomer, and low molecular weight oligomers. The residue precipitated inside the permeate membrane was washed with methanol and dried at 60°C for 12 hours to produce polythiophene (B). The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polythiophene (B) were 51,200 g / mol and 13,400 g / mol, respectively.

[0279] Example 1

[0280] Forming polymer layer

[0281] A polymer solution was prepared by mixing polythiophene (A) from Preparation Example 3 and conductive material particles coated with polydopamine (P) from Preparation Example 1 at a weight ratio of 8:2 (A:P) and dispersing the mixture in toluene at a concentration of approximately 4% by weight. During the preparation of the polymer solution, the mixture was dispersed using an ultrasonic disperser at a temperature of approximately 30°C for approximately 4 hours. The polymer solution was coated onto a current collector using a Mayer rod and dried in a drying oven at approximately 140°C for approximately 4 minutes (first heat treatment). Subsequently, the current collector coated with the polymer solution was placed in an oven and dried at 110°C for approximately 18 hours (second 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.

[0282] Manufacturing electrodes and electrode assemblies

[0283] An active material layer is formed on the polymer layer to fabricate the electrode. A slurry containing lithium cobalt oxide (LiCoO2), carbon-based conductive materials (ECP (Kejtien Black) 0.5%, SFG (Trimrex graphite) 0.4%, DB (Denka Black) 0.4%), PVDF (polyvinylidene fluoride), and NMP (N-methyl-2-pyrrolidone) in a weight ratio of 77.5:1:1:20.5 (LiCoO2:conductive material:PVDF:NMP) is applied to the polymer layer using a doctor blade and dried at 130°C for 30 minutes to form the active material layer (slurry loading: approximately 16 mg / cm³). 2 The electrode is manufactured by rolling the active material layer of the electrode to a porosity of approximately 18% to form an active material layer with a thickness of approximately 58 μm. Figure 6 This is a SEM image of the electrode. This electrode serves as the positive electrode and is laminated together with a separator and a negative electrode to fabricate an electrode assembly. The electrode assembly is fabricated by sequentially laminating the positive electrode, separator, and negative electrode, wherein the separator (SRS) used in the above “AC Impedance Resistance Measurement at 4.3V and 3.5V” serves as the separator, and the graphite negative electrode serves as the negative electrode.

[0284] Example 2

[0285] The polymer layer was formed in the same manner as in Example 1, except that when preparing the polymer solution, the polythiophene (A) of Preparation Example 3 and the conductive material particles (P) coated with polydopamine of Preparation Example 1 were mixed in a weight ratio of 6:4 (A:P) and used to manufacture electrodes and electrode assemblies.

[0286] Example 3

[0287] The polymer layer was formed in the same manner as in Example 1, except that polythiophene (B) from Preparation Example 4 was used instead of polythiophene (A) from Preparation Example 3 when preparing the polymer solution, and the electrode and electrode assembly were manufactured using it. In this case, the temperature was set to 130°C and the time was set to 60 minutes during the secondary heat treatment.

[0288] Example 4

[0289] The polymer layer was formed in the same manner as in Example 2, except that the polythiophene (B) of Preparation Example 4 was used instead of the polythiophene (A) of Preparation Example 3 when preparing the polymer solution, and the electrode and electrode assembly were manufactured using it.

[0290] Example 5

[0291] The polymer layer was formed in the same manner as in Example 1, except that uncoated polydopamine carbon black particles (C-NERGY™ SUPER C65) were used instead of the polydopamine-coated conductive material particles (P) of Example 1 when preparing the polymer solution, and the electrodes and electrode assemblies were manufactured using them.

[0292] Example 6

[0293] The polymer layer was formed in the same manner as in Example 2, except that uncoated polydopamine carbon black particles (C-NERGY™ SUPER C65) were used instead of the polydopamine-coated conductive material particles (P) of Preparation Example 1 when preparing the polymer solution, and the electrodes and electrode assemblies were manufactured using them.

[0294] Comparative Example 1

[0295] Forming polymer layer

[0296] A polymer solution was prepared by dispersing the polythiophene (A) of Preparation Example 3 in toluene at a concentration of approximately 4% by weight. During the preparation of the polymer solution, the polythiophene was dispersed using an ultrasonic disperser at a temperature of approximately 30°C for approximately 4 hours. The polymer solution was coated onto a current collector using a Mayer rod and dried in a drying oven at approximately 140°C for approximately 4 minutes (first heat treatment). Subsequently, the current collector coated with the polymer solution was placed in an oven and heat-treated at 130°C for approximately 60 minutes (second heat treatment) to form a polymer layer (thickness the same as in Example 1). An Al foil with a thickness of approximately 15 μm was used as the current collector.

[0297] Manufacturing electrodes and electrode assemblies

[0298] An active material layer is formed on the polymer layer to fabricate the electrode. A slurry containing lithium cobalt oxide (LiCoO2), carbon-based conductive materials (ECP (Kejtien Black) 0.5%, SFG (Trimrex graphite) 0.4%, DB (Denka Black) 0.4%), PVDF (polyvinylidene fluoride), and NMP (N-methyl-2-pyrrolidone) in a weight ratio of 77.5:1:1:20.5 (LiCoO2:conductive material:PVDF:NMP) is applied to the polymer layer using a doctor blade 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 of the electrode is rolled to a porosity of approximately 18% to form an active material layer with a thickness of approximately 58 μm, thereby manufacturing the electrode. The electrode assembly is then manufactured using this electrode as the positive electrode in the same manner as in Example 1.

[0299] Tables 1 and 2 summarize the R values ​​measured in the above methods for the embodiments and comparative examples. 3V R 3.5V R 25 R 130 The results of the arithmetic mean surface roughness Ra and scratch resistance evaluation are shown in Tables 1 and 2 below. 3V R 3.5V R 25 and R 130 The unit is Ω, and the unit of arithmetic mean roughness Ra is nm.

[0300] In Tables 1 and 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 ).

[0301] Reference Example 1 in Table 2 is a case in which the polymer layer is formed and the electrode and electrode assembly are manufactured in the same manner as in Example 1, but the weight ratio (A:P) of polythiophene (A) in Preparation Example 3 to conductive material particles (P) coated with polydopamine in Preparation Example 1 is 9:1.

[0302] [Table 1]

[0303] [Table 2]

[0304] From the results in Tables 1 and 2, in the case of the embodiment, the impedance reduction rate (Q) confirmed when the external voltage is increased from 3V to 3.5V is significantly higher than that in the comparative example, which supports excellent electroreactivity. When conductive particles with a specific material surface treatment are used as the conductive material, it is evident that even with an increase in the conductive material content, low surface roughness is maintained, and scratch resistance is consistently ensured. In the case of the embodiment, high-temperature impedance (R0) can be confirmed. 130 ) for room temperature impedance (R 25 The ratio of PTC is also very high, thus it can stably show the PTC effect.

[0305] Experimental Example 1

[0306] The cross-section of the electrode before rolling was imaged using a confocal laser microscope (with...). Figure 4The cross-sectional diagram of the electrode is used to obtain the thickness distribution of the active material layer (300) from the beginning (edge ​​portion) (3001) of the sliding region (S) to the end (3002) of the sliding region (S), and the results are summarized in Figure 7 middle.

[0307] exist Figure 7 In the graph, the x-axis represents the starting point of the sliding region (S). Figure 2 Within the range from point 3001 (set to 0) to the end point (3002) of the sliding region (S), the distance (in μm) of any point within this range from the starting point is represented by the y-axis, which indicates the active material layer at each point. Figure 4 The thickness (in μm) of 300.

[0308] exist Figure 7 In the text, the lines marked with ● represent Example 1. The marked line is from Example 2. The marked lines are for Comparative Example 1, the lines marked with ◆ are for Reference Example 2, and the lines marked with ■ are for Reference Example 3.

[0309] Reference Example 2 above describes a case in which the electrode and electrode assembly are manufactured in the same manner as Comparative Example 1, but the polymer layer is subjected to corona treatment (discharge current: approximately 200 mA) before the active material layer is formed. Reference Example 3 describes a case in which the electrode is manufactured in the same manner as Example 1, but the electrode active material layer is formed directly thereon without forming a polymer layer.

[0310] pass Figure 7 It can be confirmed that in the case where the active material layer is formed directly on the current collector surface without forming any polymer layer for obtaining PTC (positive temperature coefficient) (Ref. Example 3), no bulges appear. However, in the case where a polymer layer is formed (Comparative Example 1), bulges form at the midpoint of the sliding region (approximately 200 μm to 1,200 μm in the figure). During subsequent rolling processes, such bulges damage the electrode and cause problems such as reduced electrode performance or difficulty in electrode application. However, when the surface properties of the conductive polymer layer are adjusted by corona treatment (Ref. Example 2), no bulges appear.

[0311] In the cases of Examples 1 and 2, it can be confirmed that even when a polymer layer for the PTC effect is formed and the conductive polymer layer is not subjected to separate corona treatment, no raised portions are observed by introducing specific conductive particles to ensure coating performance and adjust surface properties.

[0312] Table 3 below summarizes the results of the above figures into numerical values.

[0313] In Table 3, the distance (μm) is Figure 7 The x-axis coordinates are given, and the thickness (μm) at the corresponding x-axis coordinates is summarized and described.

[0314] [Table 3]

[0315] Experimental Example 2

[0316] The evaluation was conducted using the electrodes of the embodiments and a reference electrode (the electrode of Reference Example 3 in Test Example 1). The thickness of the active material layer in the reference electrode was adjusted to ensure that the electrodes of the embodiments and the reference electrode had the same thickness. The rate performance of the electrodes of the embodiments was compared with that of the reference electrode. The rate performance was confirmed by a constant current cycling test, in which the C-rate increased from 0.1C to 2C.

[0317] Figures 8 to 12 The results of the experiments are shown. In each figure, SC20 represents the results of Example 1, SC40 or SFL represents the results of Example 2, and Ref represents the results of the reference electrode.

[0318] Figure 8 This is the result of a button cell, where the circle symbol represents capacity and the square symbol represents coulombic efficiency.

[0319] Figure 9 These are the charge / discharge curves from the cyclic test.

[0320] Figure 10 The results show the energy density retention rate (140 cycles).

[0321] Figure 11 These are the results of a rate test on a 3-Ah soft-pack battery.

[0322] Figure 12 The results of the cycle test of the 3-Ah pouch cell are shown.

[0323] As can be confirmed from the accompanying drawings, the electrode of the embodiment exhibits a capacity of 179.5 mAhg. -1 The initial discharge capacity and capacity loss were less than 1.2%. In the case of the electrode in the examples, the capacity difference remained below 2.2% even at 2C, thus confirming that there is almost no capacity reduction caused by the polymer layer under typical battery operating conditions. In the electrodes of the examples, after 140 cycles, the energy density retention rates of the electrodes of Examples 1 and 2 were 92% and 95%, respectively, which are negligible compared to the reference electrode. Figure 8 and Figure 10 ).

[0324] Each 3-Ah pouch cell was assembled using the electrode of Example 2 as the positive electrode and a 3-Ah pouch cell using the reference electrode as the positive electrode.

[0325] The following methods are used to manufacture each positive electrode.

[0326] <Electrodes of the Example>

[0327] In the same manner as in Example 2, polymer layers were formed on each of the two surfaces of the same current collector used in Example 2, and positive electrode active material layers were formed on the respective polymer layers in the same manner as in Example 2, thereby manufacturing the electrode of the embodiment. The positive electrode active material layer was formed to have a loading density of approximately 24.29 mg / cm and a porosity of approximately 3.99 g / cc.

[0328] <Reference Electrode>

[0329] The positive electrode serving as the reference electrode is manufactured in the same manner as the electrode in the embodiment, but by forming positive electrode active material layers on the two surfaces of the current collector instead of forming polymer layers.

[0330] The negative electrode is manufactured using the following method when producing a 3-Ah pouch cell.

[0331] <Negative electrode>

[0332] The negative electrode was fabricated by forming a negative electrode active material layer on both sides of a Cu foil (copper foil) (thickness: approximately 8 μm). The negative electrode active material layer was formed to have a loading density of approximately 13.88 mg / cm and a porosity of approximately 1.75 g / cc. A slurry was prepared by mixing water (I), SBR (styrene-butadiene rubber) (average particle size (D50 particle size): 150 nm) (II), thickener (CMC, carboxymethyl cellulose) (III), electrode active material (1) (IV) (artificial graphite (GT), average particle size (D50 particle size): 20 μm) and electrode active material (2) (V) (natural graphite (PAS), average particle size (D50 particle size): 15 μm) in a weight ratio of 48.5:1:0.5:45:5 (I:II:III:IV:V). The slurry is applied to the surface of the Cu foil to a thickness of about 280 μm by a gap coating method, dried at about 75°C for about 10 minutes, and then rolled to form an active material layer.

[0333] A stacked battery was fabricated by laminating 14 negative electrodes and 13 positive electrodes. The electrode or reference electrode of the embodiment was used as the positive electrode. A separator was located between the negative and positive electrodes. The SRS separator used in the embodiment was used as the separator. A 3-Ah pouch cell was prepared using the stacked battery and electrolyte. The electrolyte was GTHR KOREA electrolyte (1M LiPF6 solution, solvent = EC:DMC:DEC (3:3:4, volume ratio), (EC: ethylene carbonate, DMC: dimethyl carbonate, EMC: ethyl methyl carbonate)) (3 μL mAh). -1 As the outer casing, an envelope-type pouch (DNP, D-EL408PH(3)) is used. The pouch battery is manufactured with horizontal and vertical dimensions of 50 mm and 90 mm, respectively.

[0334] During cycling from 0.1C to 2.5C, the capacity difference between the reference electrode and the electrode of the example remained less than 1.5%. In the case of the electrode of the example, the capacity retention was 97% in the recovery cycle after 300 cycles, which is consistent with the reference electrode. These results confirm that even with the introduction of the polymer layer, the gravimetric / volume energy density and power density in the actual battery remain unchanged.

[0335] Experimental Example 3

[0336] A nail penetration test was conducted, in which a nail was inserted into the battery to measure temperature fluctuations. An SUS nail (diameter: approximately 2.5 mm, tip angle: 60 degrees) was passed through the center of a 3-Ah pouch cell manufactured in Test Example 2 to determine if the 3-Ah pouch cell ignited. Penetration was achieved by moving the nail at a speed of approximately 50 mm / s. In the case of the 3-Ah pouch cell with the reference electrode introduced, more than six out of ten 3-Ah pouch cells used in the test were confirmed to have ignited; however, in the case of the 3-Ah pouch cell with the electrode of the application example, only one out of ten 3-Ah pouch cells used in the test was confirmed to have ignited.

[0337] Test Example 4

[0338] To investigate how to improve battery stability under mechanical abuse conditions using the 3-Ah pouch battery manufactured in Example 2, impact tests were conducted.

[0339] The impact test was conducted at 100% SOC (state of charge).

[0340] by Figure 13 Impact tests were conducted as shown.

[0341] In other words, the temperature measuring device (T) (temperature controller (TC)) is attached to the surface of the 3-Ah pouch battery (1000) using insulating tape, and the rod (2000) is positioned at the vertical center. The rod (2000) is an SUS rod with a circular cross-section of approximately 20 mm in diameter and a length of approximately 100 mm. A cylinder (3000) is positioned on the rod (2000). The cross-section of the cylinder (3000) is a diameter (D) out It is a circular shape of approximately 900 mm, with a diameter (D) formed at the center of the corresponding circle. in The hole is about 800 mm in diameter. Then, an impact test is performed by letting a SUS spherical impact ball (4000) with a diameter of about 750 mm (weight: about 9.1 kg) pass through the hole in the center of the cylinder (3000) from a height of about 610 mm toward the 3-Ah pouch cell (1000).

[0342] Nineteen 3-Ah pouch cells with a reference electrode and nineteen with the electrode of the embodiment were manufactured for testing. With the reference electrode, 12 of the 19 3-Ah pouch cells exploded, while with the electrode of the embodiment, 17 of the 19 3-Ah pouch cells remained intact. The unexploded 3-Ah pouch cells were disassembled, and the condition of each component was inspected. In the unexploded cells with the reference electrode, the positive (cathode) and negative (anode) electrodes of the cells with the reference electrode were significantly burned, and the separator (SRS) was severely deformed. Conversely, in the unexploded cells with the electrode of the embodiment, all components remained intact even after an external impact.

[0343] Figure 14 The display shows the temperature change (in situ) measured using a TC (temperature controller) (T) attached to the outer surface of the pouch cell. In the event of a fire, the temperature rises rapidly (ignition) to as high as 59°C / second due to the cascaded exothermic reaction between the battery components.

[0344] Even without an explosion, the pouch cell with the reference electrode (w / o SRL) experienced localized heating, attributed to structural deformation from the strong current flow caused by the impact. The temperature rise in the pouch cell with the reference electrode introduced and not exploded was 1.7 times faster than that in the pouch cell with the electrode of the embodiment introduced.

Claims

1. An electrode assembly, comprising: positive electrode; negative electrode; and The membrane between the positive electrode and the negative electrode. The membrane comprises a porous polymer membrane and an inorganic particulate layer. The positive electrode includes a current collector and a polymer layer on the current collector. The polymer layer comprises a conductive polymer and a conductive material, and The positive electrode has a Q value in the range of 10 or higher according to Equation 1 below: [Equation 1] Q = R 3v / R 3.5v Among them, R 3V The AC impedance resistor R at the positive terminal is described under conditions of 25℃ and 3V. 3.5V The AC impedance resistor at the positive terminal is located 1 second after the conditions of 25°C and 3V are changed to 25°C and 3.5V.

2. The electrode assembly according to claim 1, wherein, According to Equation 2 below, the value of P is 60 or higher: [Equation 2] P = R 130 / R 25 Among them, R 25 R is the AC impedance resistance of the polymer layer at 25°C. 130 It is the AC impedance resistance of the polymer layer at 130°C.

3. The electrode assembly according to claim 1, wherein, The ratio of the arithmetic mean roughness Ra of the polymer layer to the thickness of the polymer layer is 50% or less.

4. The electrode assembly according to claim 1, wherein, The polymer layer has an arithmetic mean roughness Ra of 230 nm or less.

5. The electrode assembly according to claim 1, wherein, The maximum temperature in the impact test is 200°C or lower, and the heating rate is 40°C / second or lower.

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

7. The electrode assembly according to claim 6, wherein, The conductive polymer contains a first hydrocarbon functional group having more than 10 carbon atoms and a second hydrocarbon functional group having fewer than 9 carbon atoms, which are long-chain hydrocarbon functional groups.

8. The electrode assembly according to claim 7, wherein, The ratio of the total molar number of monomer units having a first hydrocarbon functional group to the total molar number of monomer units having a second hydrocarbon functional group in the conductive polymer is 80 mol% or higher.

9. The electrode assembly according to claim 8, wherein, The ratio M2 / M1 of the number of moles of the second hydrocarbon functional group or the monomer unit having said functional group to the number of moles of the first hydrocarbon functional group or the monomer unit having said functional group is in the range of 0.01 to 100.

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

11. The electrode assembly of claim 10, wherein, The polar functional group is a carboxyl, hydroxyl, amino, cyano, nitro, ether, or a functional group of Formula 1 below: [Formula 1] Wherein, 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.

12. The electrode assembly according to claim 10, wherein, The ratio of the number of moles of monomer units with long-chain hydrocarbon functional groups to the number of moles of monomer units with polar functional groups in the conductive polymer is in the range of 1 to 500.

13. The electrode assembly according to claim 1, 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 conductive material includes a conductive core and a surface layer present on the surface of the core, and the surface layer contains polyphenolic compounds.

15. The electrode assembly according to claim 1, wherein, The positive electrode further includes an active material layer formed on the polymer layer.

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

Images