Electrode for secondary battery and secondary battery comprising same

Abstract

The present disclosure relates to an electrode for a secondary battery and a secondary battery comprising same. The electrode for a secondary battery according to one embodiment comprises: a coated portion where an electrode active material layer is positioned on a current collector and an uncoated portion where the electrode active material layer is not positioned on the current collector; and an insulating coating layer disposed on at least a portion of the uncoated portion and including an electrode insulating polymer, wherein the thermal expansion coefficient of the electrode insulating polymer may be 66 μm / m°C to 127 μm / m°C.

Description

Electrode for secondary battery and secondary battery including same

[0001] The present disclosure relates to an electrode for a secondary battery and a secondary battery including the same.

[0002] The recent increase in the use of portable electronic devices such as cell phones and laptop computers, coupled with ongoing research and development into electric and hybrid electric vehicles that can replace fossil fuel-powered vehicles like gasoline and diesel, has led to a growing demand for smaller, lighter, and longer-lasting secondary batteries. In particular, research into high-energy-density secondary batteries is actively underway to achieve miniaturization and weight reduction.

[0003] Achieving high energy densities requires the use of high-density electrodes. However, manufacturing high-density electrodes requires a high-pressure rolling process, which can result in various quality defects, such as ripples, wrinkles, fractures, and delamination. These types of quality defects are primarily due to differences in the properties of the materials used in the electrode, such as the current collector and active material, particularly their thermal properties.

[0004] Meanwhile, in the event of direct contact between the positive and negative current collectors of a secondary battery, a short circuit can occur. Such a short circuit can lead to a high risk of fire, posing a potentially fatal hazard. To prevent this, efforts are being made to apply an insulating coating to the electrode uncoated portion of the current collector, where the active material is not coated.

[0005] However, if the thermal properties of the insulating coating are not taken into consideration, the quality defects described above may occur more seriously at each boundary of the current collector, active material layer, and coating layer.

[0006] Therefore, there is a need to develop an electrode for secondary batteries that can achieve safety and high energy density while simultaneously improving various defects that may occur during the secondary battery manufacturing process.

[0007] According to one aspect of the present disclosure, it is possible to provide an electrode for a secondary battery that exhibits high energy density and can improve various defects that may occur in the electrode manufacturing process.

[0008] According to another aspect of the present disclosure, a secondary battery with improved safety can be provided.

[0009] The secondary battery electrode of the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-powered solar and wind power generation. Furthermore, the secondary battery electrode of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, and other vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0010] An electrode for a secondary battery according to the present disclosure includes a holding portion having an electrode active material layer positioned on a current collector and a non-conducting portion having no electrode active material layer positioned on the current collector; and an insulating coating layer positioned on at least a portion of the non-conducting portion and including an electrode insulating polymer; wherein the electrode insulating polymer has a thermal expansion coefficient of 66 μm / m°C to 127 μm / m°C.

[0011] The coefficient of thermal expansion of the electrode insulating polymer according to one embodiment may be 72 μm / m℃ to 80 μm / m℃.

[0012] According to one embodiment, the electrode insulating polymer may include at least one selected from the group consisting of polyamide-based polymers, polyamideimide-based polymers, fluoroethylene-based polymers, butadiene-based rubbers, and copolymers thereof.

[0013] According to one embodiment, the electrode insulating polymer includes a polyamide-based polymer and a fluoroethylene-based polymer, and may include the polyamide-based polymer and the fluoroethylene-based polymer in a weight ratio of 1:8.5 to 1:9.5.

[0014] An electrode insulating polymer according to one embodiment may include a copolymer comprising a first repeating unit of an amide-imide system; and at least one second repeating unit selected from the group consisting of a butadiene system, a nitrile system, and a styrene system.

[0015] According to one embodiment, the first repeating unit may comprise an aromatic ring.

[0016] According to one embodiment, the second repeating unit may comprise a benzene ring.

[0017] The second repeating unit according to one embodiment may be at least one selected from the group consisting of butadiene-based, acrylonitrile-butadiene-based, and hydrogenated acrylonitrile-butadiene-based.

[0018] According to one embodiment, the molar ratio of the first repeating unit and the second repeating unit may be 60 to 80:40 to 20.

[0019] According to one embodiment, the copolymer may be at least one selected from the group consisting of random copolymers, alternating copolymers, block copolymers, and graft copolymers.

[0020] According to one embodiment, the insulating coating layer may be positioned on at least a portion of the retaining portion and at least a portion of the non-retaining portion.

[0021] In one embodiment, the insulating coating layer positioned on at least a portion of the non-conductive portion and the insulating coating layer positioned on at least a portion of the retaining portion may be continuous.

[0022] According to one embodiment, the electrode is an anode, and the current collector may include at least one metal selected from the group consisting of stainless steel, nickel, titanium, aluminum, and alloys thereof.

[0023] According to one embodiment, the elongation of the non-woven portion where the insulating coating layer is located may be 25% to 43%.

[0024] A secondary battery according to the present disclosure includes an electrode according to one embodiment.

[0025] According to one embodiment of the present disclosure, the processability of a high-energy density electrode for a secondary battery can be improved, thereby improving the defect rate of the electrode for a secondary battery.

[0026] According to another embodiment of the present disclosure, the energy efficiency and safety of a secondary battery can be improved.

[0027] The embodiments described herein may be modified in many different forms, and thus the technology according to one implementation is not limited to the embodiments described below. Furthermore, throughout the specification, the terms "comprises," "includes," "contains," or "has" a component do not exclude other components unless specifically stated to the contrary, but rather imply that other components may be included, and do not exclude additional elements, materials, or processes that are not listed.

[0028] The numerical ranges used herein include the lower and upper limits and all values ​​within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of the upper and lower limits of numerical ranges defined in different shapes. For example, if the content of a composition is defined as 10% to 80% or 20% to 50%, the numerical ranges of 10% to 50% or 50% to 80% should also be interpreted as being described herein. Unless otherwise specified herein, values ​​outside the numerical range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0029] Unless otherwise specifically defined herein, “about” may be considered a value within 30%, 25%, 20%, 15%, 10% or 5% of the stated value.

[0030] The term "secondary battery" used herein may refer to a lithium secondary battery that generates electrical energy by oxidation and reduction reactions when lithium ions are inserted and removed from the positive and negative electrodes.

[0031] Below, the present disclosure will be described in detail. However, this is merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0032] Electrode insulating polymer

[0033] An electrode insulating polymer according to one embodiment of the present disclosure may refer to an electrode insulating polymer applied to at least a portion of an electrode non-conductive portion so that a short circuit does not occur even when both electrodes of a secondary battery come into contact. The electrode insulating polymer according to one embodiment may have a lower limit of a thermal expansion coefficient of 66 μm / m℃ or more, 70 μm / m℃ or more, 72 μm / m℃ or more, or 74 μm / m℃ or more, and an upper limit of 127 μm / m℃ or less, 120 μm / m℃ or less, 110 μm / m℃ or less, 100 μm / m℃ or less, 90 μm / m℃ or less, 80 μm / m℃ or less, or 78 μm / m℃ or less, and specifically, may be 66 μm / m℃ to 127 μm / m℃ or 72 μm / m℃ to 80 μm / m℃.

[0034] According to one embodiment, the electrode insulating polymer may include at least one selected from polyamide-based polymers, polyamideimide-based polymers, fluoroethylene-based polymers, butadiene-based rubbers, and copolymers thereof.

[0035] In one embodiment, the polyamide polymer refers to a polymer that includes a repeating unit containing an amide group, and may be polyamide or polycaprolactam.

[0036] According to one embodiment, the polyamideimide polymer refers to a polymer including repeating units including an amide group and an imide group, and may be a bis-(4-aminophenyl)-methane-trimellitic anhydride copolymer, a 4,4'-diaminodiphenyl sulfone-trimellitic anhydride copolymer, a bisphenol A-diamine-trimellitic anhydride copolymer, or a p-phenylenediamine-trimellitic anhydride copolymer.

[0037] In one embodiment, the fluoroethylene polymer may be polyvinylidene fluoride, polytetrafluoroethylene, or

[0038] According to one embodiment, the butadiene-based rubber may be butadiene rubber (BR), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (H-NBR), or styrene butadiene rubber (SBR).

[0039] According to one embodiment, the electrode insulating polymer may include at least two or more selected from a polyamide-based polymer, a polyamideimide-based polymer, a fluoroethylene-based polymer, or a butadiene-based rubber (specifically, a mixture of two or more polymers); or a copolymer of a polyamide-based polymer, a polyamideimide-based polymer, a fluoroethylene-based polymer, or a butadiene-based rubber.

[0040] According to one embodiment, the electrode insulating polymer may include a polyamide-based polymer and a fluoroethylene-based polymer, and specifically, the weight ratio of the polyamide-based polymer and the fluoroethylene-based polymer may be 1:8.5 to 1:9.5, more specifically, 1:8.8 to 1:9.2, and even more specifically, 1:8.8 to 1:9.0. If the content of the polyamide-based polymer is too low beyond the above weight ratio, there is a disadvantage in that excessive swelling occurs during electrolyte impregnation in the assembly process, making it difficult to secure adhesion to the substrate, and if the content of the polyamide-based polymer is too high, it is difficult to effectively distribute stress applied during the rolling process, etc., which may lead to deterioration of runnability such as fracture.

[0041] Additionally, the electrode insulating polymer according to one embodiment may be a copolymer including a first repeating unit of amide-imide type; and at least one second repeating unit selected from the group consisting of butadiene type, nitrile type, and styrene type.

[0042] The term "repeating unit" as used herein means that the monomers for forming a polymer are linked to each other through addition polymerization or condensation polymerization, and the structure of the monomers appears repeatedly within the polymer. For example, polybutadiene, which is a butadiene rubber, is a polymer having repeating units derived from butadiene, and this means that the structure of the butadiene monomers appears repeatedly within the polybutadiene polymer as the butadiene monomers are linked to each other through addition polymerization.

[0043] According to one embodiment, the first repeating unit may comprise an aromatic ring, and specifically, may comprise at least one selected from the group consisting of a substituted or unsubstituted C6 to C20 aromatic ring, a substituted or unsubstituted C6 to C10 aromatic ring, a substituted or unsubstituted C6 to C20 heteroaromatic ring, and a substituted or unsubstituted C6 to C10 heteroaromatic ring, and specifically, may comprise substituted or unsubstituted benzene, or substituted or unsubstituted naphthalene.

[0044] For example, the first repeating unit, the amide-imide repeating unit, can be prepared from monomer components including a diamine-based compound and a carboxylic acid-based compound, or a diamine-based compound and an isocyanate-based compound. Specifically, the first repeating unit may be prepared by subjecting a diamine-based compound and a carboxylic acid-based compound, or a diamine-based compound and an isocyanate-based compound to a condensation polymerization reaction, such that a linked repeating unit structure of an amide structure and an imide structure repeatedly appears within the electrode insulating polymer. The specific structure of the amide-imide repeating unit may vary depending on the reacting monomer.

[0045] In one embodiment, the second repeating unit may be at least one selected from the group consisting of butadiene-based, acrylonitrile-butadiene-based, and hydrogenated acrylonitrile-butadiene-based.

[0046] For example, the second repeating unit, the hydrogenated acrylonitrile-butadiene repeating unit, can be prepared from monomer components including an acrylonitrile compound and a butadiene compound. Specifically, the second repeating unit may be prepared by performing an addition polymerization reaction of an acrylonitrile compound and a butadiene compound such that a linked repeating unit structure of a hydrogenated acrylonitrile structure and a butadiene structure repeatedly appears within the electrode insulating polymer. The specific structure of the hydrogenated acrylonitrile-butadiene repeating unit may vary depending on the reacting monomer.

[0047] In one embodiment, the molar ratio of the first repeating unit and the second repeating unit may be 60 to 80:40 to 20, and more specifically, 70 to 75:30 to 25. When the copolymer has such a molar ratio of repeating units, the thermal expansion coefficient of the electrode insulating polymer may satisfy the numerical range described above.

[0048] According to one embodiment, the copolymer may be at least one selected from the group consisting of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer, and more specifically, may be a graft copolymer.

[0049] In the field of conventional secondary batteries, polyamide-imide can be applied to the non-coated portion of the positive or negative electrode and utilized as an electrode insulating polymer to prevent short circuits when the positive or negative electrodes contact each other. However, conventional electrode insulating polymers containing only polyamide-imide have concerns about quality defects, such as curling in the non-coated portion due to relaxation of residual stress during the drying process in the secondary battery electrode manufacturing process. In addition, there is a problem that fracture easily occurs at the boundary between the holding portion and the non-coated portion of the current collector during the rolling and winding process of the electrode. In addition, there is a possibility of fatal process defects, such as peeling of the insulating coating layer during electrolyte impregnation. These problems can be more serious in high-density electrodes for high energy density, and the density of the electrode can be limited due to the above-mentioned process problems.

[0050] On the other hand, the electrode insulating polymer according to the present disclosure includes at least one selected from the group consisting of polyamide-based polymers, polyamideimide-based polymers, fluoroethylene-based polymers, butadiene-based rubbers, and copolymers thereof, and has the advantage of being able to improve process-related problems by satisfying a thermal expansion coefficient within a specific range.

[0051] <Electrode for secondary batteries>

[0052] According to one embodiment of the present disclosure, an electrode for a secondary battery may include a holding portion having an electrode active material layer positioned on a current collector and a non-coated portion on the current collector where the electrode active material layer is not positioned, and an insulating coating layer positioned on at least a portion of the non-coated portion and including an electrode insulating polymer. The electrode for a secondary battery according to one embodiment may refer to a positive electrode. The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the current collector, and the current collector may include a holding portion having a positive electrode active material layer positioned on at least one surface, a non-coated portion of the current collector where the positive electrode active material layer is not positioned, and an insulating coating layer on at least a portion of the non-coated portion where the electrode insulating polymer as described above is applied.

[0053] In one embodiment, the positive electrode current collector may comprise at least one metal selected from the group consisting of stainless steel, nickel, titanium, aluminum, or alloys thereof. Specifically, the metal may be aluminum, and the metal may be untreated aluminum or aluminum surface-treated with carbon, nickel, titanium, or silver. The positive electrode current collector may have, but is not limited to, a thickness of, for example, 10 to 50 μm.

[0054] Meanwhile, as described above, the thermal expansion coefficient of the electrode insulating polymer according to one embodiment of the present disclosure may be 66 μm / m℃ or more, 70 μm / m℃ or more, 72 μm / m℃ or more, or 74 μm / m℃ or more as a lower limit, and 127 μm / m℃ or less, 120 μm / m℃ or less, 110 μm / m℃ or less, 100 μm / m℃ or less, 90 μm / m℃ or less, 80 μm / m℃ or less, or 78 μm / m℃ or less as an upper limit, and specifically, may be 66 μm / m℃ to 127 μm / m℃ or 72 μm / m℃ to 80 μm / m℃. By having a coefficient of thermal expansion in this numerical range, it is understood that the process defects or safety defects mainly caused by the difference in elongation and stress relaxation behavior between the current collector, the holding portion, and the non-conducting portion can be improved compared to the case where a conventional electrode insulating polymer is introduced when introducing the electrode insulating coating to the current collector.

[0055] In one embodiment, the maintenance portion may mean an area in which an electrode active material layer is positioned on at least one surface of the current collector, among the entire area of ​​the current collector.

[0056] In one embodiment, an insulating coating layer may be positioned on at least a portion of the retaining portion and at least a portion of the non-retaining portion. Additionally, the insulating coating layer positioned on at least a portion of the non-retaining portion and the insulating coating layer positioned on at least a portion of the retaining portion may be continuous.

[0057] The above positive electrode active material layer may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0058] According to exemplary embodiments, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0059] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061] Li x Ni a M b O 2+z

[0062] In Chemical Formula 1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, -0.5≤z≤0.1 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0063] The chemical structure represented by Chemical Formula 1 represents the bonding relationship included in the layered structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can serve as the main active element of the positive electrode active material together with Ni. Chemical Formula 1 is provided to express the bonding relationship of the above main active elements and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0064] In one embodiment, in addition to the main active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated into the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 1.

[0065] The auxiliary element may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may also act as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn, for example, Al.

[0066] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1-1.

[0067] [Chemical Formula 1-1]

[0068] Li x Ni a M1 b1 M2 b2 O 2+z

[0069] In Chemical Formula 1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 1-1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, -0.5≤z≤0.1 may be satisfied.

[0070] The above-described positive electrode active material may further include a coating element or doping element. For example, elements substantially identical to or similar to the above-described auxiliary elements may be used as the coating element or doping element. For example, the above-described elements may be used singly or in combination of two or more.

[0071] The above coating element or doping element may be present on the surface of the lithium-nickel metal oxide particle, or may penetrate through the surface of the lithium-nickel metal composite oxide particle and be included in the bonding structure represented by the above chemical formula 1 or chemical formula 1-1.

[0072] The above positive electrode active material may include a nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0073] Ni can be provided as a transition metal associated with the output and capacity of a lithium secondary battery. Therefore, by employing a high-content (High-Ni) composition as described above in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0074] However, as the Ni content increases, the long-term storage stability and lifespan stability of the cathode or secondary battery may relatively deteriorate, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, the inclusion of Co can maintain electrical conductivity, while improving lifespan stability and capacity retention characteristics through Mn.

[0075] The content of Ni (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0076] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0077] In some embodiments, the positive electrode active material may include, for example, a Mn-rich active material, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide) active material, or a Co-less active material having a chemical structure or crystal structure represented by Chemical Formula 2.

[0078] [Chemical Formula 2]

[0079] p[Li2MnO3]·(1-p)[Li q JO2]

[0080] In chemical formula 2, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg 및 B 중 적어도 하나의 원소를 포함할 수 있다.

[0081] In one embodiment, the anode may further comprise a binder and a conductive material.

[0082] The above binder may include polyvinylidenefluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, butadiene rubber, etc. In one embodiment, a PVDF series binder may be used as the positive electrode binder.

[0083] The conductive material may be added to enhance the conductivity and / or mobility of lithium ions or electrons of the positive electrode active material layer. For example, the conductive material may include, but is not limited to, carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0084] In one embodiment, the non-conductive region may refer to a region in which no electrode active material layer is positioned on any surface of the current collector within the entire area of ​​the current collector. Alternatively, it may refer to a region in the entire area of ​​the current collector excluding the maintenance region.

[0085] In one embodiment, the elongation of the non-coated portion where the insulating coating layer is located may be 25% to 43%, and more specifically, 30% to 38%.

[0086] In some embodiments, the electrode insulating polymer included in the insulating coating layer may be an electrode insulating polymer having a coefficient of thermal expansion according to one embodiment of the present disclosure described above, and the current collector may include aluminum.

[0087] The above elongation may refer to the maximum elongation measured by separately collecting the non-coated portion where the insulating coating layer is located in the electrode for a secondary battery according to one embodiment of the present disclosure and subjecting the collected non-coated portion to a tensile test using, for example, a universal testing machine.

[0088] In some embodiments, when an electrode insulating polymer having a thermal expansion coefficient as described above is applied to the non-conductive portion, the non-conductive portion can exhibit an elongation in the range as described above.

[0089] It is understood that since the above-mentioned non-conductive portion has an elongation within the above-mentioned numerical range, the process defects or safety defects mainly caused by the difference in elongation and stress relaxation behavior between the current collector, the holding portion, and the non-conductive portion can be improved compared to the case where an insulating coating layer is formed by introducing a conventional electrode insulating polymer to the non-conductive portion.

[0090] The electrode for a secondary battery according to one embodiment may be a positive electrode as described above, but is not necessarily limited thereto, and in an exemplary embodiment, the electrode for a secondary battery may mean a negative electrode, or may mean both a positive electrode and a negative electrode.

[0091] When the electrode for a secondary battery according to one embodiment refers to a negative electrode, the negative electrode may include a negative current collector and a negative active material layer disposed on at least one surface of the current collector, and may include a holding portion on which an electrode active material layer is positioned on the current collector and a non-conductive portion on which an electrode active material layer is not positioned on the current collector, and may include an insulating coating layer on which an electrode insulating polymer as described above is applied and positioned on at least a portion of the non-conductive portion.

[0092] Secondary battery

[0093] One embodiment of the present disclosure may provide a secondary battery comprising an electrode, a separator interposed between the electrodes, and an electrolyte and other additives. The secondary battery may include the secondary battery electrode according to the above-described embodiment of the present disclosure as at least one of a positive electrode and a negative electrode.

[0094] The above secondary battery can be manufactured in a shape selected from, for example, a pouch shape, a square shape, a cylindrical shape, a coin shape, etc.

[0095] A secondary battery according to an embodiment of the present disclosure can be applied to various fields such as laptop computers, mobile phones, electric vehicles, and hybrid electric vehicles.

[0096] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and technical idea of ​​the present disclosure, and it is also natural that such changes and modifications fall within the scope of the appended claims.

[0097] Experimental example

[0098] (Example 1)

[0099] On an aluminum foil current collector, a slurry for forming a positive electrode active material layer having a composition shown in Table 1 below was slot-die coated to form a non-coated region of about 15 mm on both sides in the width direction of the current collector, thereby forming a positive electrode active material layer. Here, the width direction means a direction perpendicular to the direction of running of the current collector, and may also mean a direction perpendicular to the boundary line of the non-coated region and the support region.

[0100] An insulating coating layer-forming composition was applied across the non-coated portion of the positive electrode active material layer and a portion of the positive electrode active material layer in contact with the non-coated portion to form an insulating coating layer with a width of about 5 mm. The insulating coating layer-forming composition includes a graft copolymer of polyamideimide (PAI) and hydrogenated acrylonitrile butadiene rubber (HNBR) as an electrode insulating polymer (PAI: HNBR repeat unit molar ratio = 75:25, copolymerization temperature 130°C), and specifically, the polyamideimide (PAI) was a bis-(4-aminophenyl)-methane-trimellitic anhydride copolymer. Thereafter, the composition was dried at 120°C to manufacture a positive electrode having a positive electrode active material layer and an insulating coating layer formed on a current collector.

[0101] Slurry content for forming a cathode active material layer: cathode active material Li[Ni 0.6 Co 0.2 Mn 0.2 ]O296 wt%ChallengerCarbon Black2 wt%BinderPVDF2 wt%Slurry Loading18 mg / cm2

[0102] (Example 2) An anode was manufactured in the same manner as in Example 1, except that polyvinylidenefluoride (PVDF) polymer and polyamide (PA) polymer were mixed in a weight ratio of 9:1 as the electrode insulating polymer.

[0103] (Example 3)

[0104] An anode was manufactured in the same manner as in Example 1, except that the copolymer was polymerized at a high temperature higher than 130°C.

[0105] (Comparative Example 1)

[0106] An anode was manufactured in the same manner as in Example 1, except that PVDF polymer was used as the electrode insulating polymer.

[0107] (Comparative Example 2)

[0108] An anode was manufactured in the same manner as in Example 1, except that polyamideimide (PAI) polymer was used as the electrode insulating polymer.

[0109] (Comparative Example 3)

[0110] An anode was manufactured in the same manner as in Example 1, except that polyacrylonitrile (PAN) polymer was used as the electrode insulating polymer.

[0111] <Evaluation example>

[0112] Evaluation Example 1: Evaluation of the thermal expansion coefficient and collector elongation of electrode insulating polymer

[0113] The coefficient of thermal expansion of each polymer used as the electrode insulating polymer in Examples 1 to 3 and Comparative Examples 1 to 3, and the elongation of the current collector of the portion where each polymer was applied and an insulating coating layer was formed, were evaluated, and the results are shown in Table 2 below. The coefficient of thermal expansion was measured by heating each polymer at a temperature range of 25°C to 200°C at a rate of 5°C / min using a thermal mechanical analysis device (TMA Q400, TA Instruments) and measuring the strain, and calculating the coefficient of thermal expansion through the change in slope of the dimension change-temperature curve obtained therefrom. The elongation was measured by collecting only the portion where the insulating polymer was applied on each current collector and an insulating coating layer was formed, and then a universal testing machine (UTM 3400, Instron) was used to conduct a tensile test at a gauge length of 50 mm and a tensile speed of 20 mm / min to measure the maximum elongation.

[0114] Thermal expansion coefficient (μm / m℃) Elongation (%) Example 177.0635 Example 2126.0218 Example 374.6633 Comparative Example 1127.810 Comparative Example 23118 Comparative Example 36520

[0115] Evaluation Example 2: Fairness Evaluation of Electrode for Secondary Battery The positive electrodes on which the positive electrode active material layer and the insulating coating layer prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were formed were rolled using a roll press to produce a positive electrode of 800 m. At this time, the running speed of the roll press was 20 m / min.

[0116] During the rolling process for the anode, the number of times the electrode broke was checked to evaluate the rolling fairness, which is shown in Table 3 below. Excluding cases where breakage occurred due to reasons unrelated to the polymer, such as operator error, during the rolling process for the anode prepared by Examples 1 to 3 and Comparative Examples 1 to 3, cases where the number of breakages was 8 or more were evaluated as X, cases where the number of breakages was 5 or more but less than 8 were evaluated as △, and cases where the number of breakages was less than 5 were evaluated as O.

[0117] Meanwhile, the positive electrodes prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were notched to a predetermined size, and then the occurrence of wrinkles and tears was checked to evaluate the notching process, which is shown in Table 3 below. A state in which there were no special issues, similar to the shape of a typical secondary battery electrode in which no electrode insulating polymer was applied on the non-coated portion, was evaluated as O, and in comparison, a case in which wrinkles occurred was evaluated as △, and a case in which tears occurred was evaluated as X.

[0118] In addition, the positive electrodes manufactured by Examples 1 to 3 and Comparative Examples 1 to 3 were notched to a predetermined size, vacuum-dried at 120°C and 5 Torr for 12 hours, and the degree of camber at the electrode non-coated end from the ground was evaluated, which is shown in Table 3 below. The degree of camber was measured using a ruler, and the average value of the values ​​measured at the upper, middle, and lower portions based on the electrode longitudinal direction was calculated as the curl average value to measure the measurement. Here, the longitudinal direction means the direction parallel to the running direction of the positive electrode during slurry coating and rolling, and may also mean the direction parallel to the boundary line between the non-coated portion and the retained portion.

[0119] In addition, the electrolyte resistance of the positive electrodes prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 was evaluated by checking the swelling ratio and surface peeling after immersing them in the electrolyte for 24 hours, and the results are shown in Table 3 below. The presence of surface peeling was evaluated based on whether surface peeling occurred in the insulating coating layer during electrolyte impregnation, and the swelling ratio was evaluated by measuring the thickness of the insulating coating layer before and after electrolyte impregnation and calculating it using the following relationship.

[0120] [Relationship]

[0121] Swelling (%) = ((thickness of insulating coating layer after electrolyte impregnation) - (thickness of insulating coating layer before electrolyte impregnation)) / (thickness of insulating coating layer before electrolyte impregnation)

[0122] Classification Curl average value (mm) Rolling processability Notching processability Surface peeling Swelling degree (%) Example 14OO Normal 7 Example 29OO Normal 8 Example 33.5OO Normal 6.6 Comparative example 115XX Peeling occurred 19 Comparative example 210△△ Normal 5 Comparative example 314X△ Normal 6

[0123] Referring to Table 3 above, it was confirmed that Examples 1 to 3, in which an electrode insulating polymer having a thermal expansion coefficient range according to an embodiment of the present disclosure was applied, had a number of fractures less than 5 times during an 800 m run, whereas Comparative Examples 1 and 3, in which an electrode insulating polymer other than the above was applied, had a number of fractures of 8 or more times, or Comparative Example 2 had a number of fractures of 5 or more and less than 8 times. Accordingly, it was confirmed that Examples 1 to 3 having a thermal expansion coefficient range according to an embodiment of the present disclosure had improved rolling processability compared to Comparative Examples 1 to 3.

[0124] Although not intended to be bound by a specific theory, it is understood that in the case of Examples 1 to 3, by using an electrode insulating polymer having a thermal expansion coefficient range according to an embodiment of the present disclosure, the difference in elongation between the aluminum current collector and the holding portion and the non-conducting portion, which are commonly used, can be alleviated despite including an insulating coating layer, and thus, fracture hardly occurs during the driving process.

[0125] Meanwhile, as shown in Table 3 above, in Examples 1 to 3 in which an electrode insulating polymer having a thermal expansion coefficient range according to an embodiment of the present disclosure was applied, no particular special issues were observed during the notching process, but in Comparative Examples 1 to 3 in which an electrode insulating polymer other than the above was applied, tearing occurred during the notching process, and in Comparative Example 3, tearing did not occur, but wrinkles were observed. Thus, it was confirmed that the notching processability of Examples 1 to 3 was improved compared to the Comparative Example. It is understood that this difference is also due to the presence or absence or the size of the difference in elongation described above.

[0126] In addition, as shown in Table 3 above, in Examples 1 to 3 in which an electrode insulating polymer having a thermal expansion coefficient range according to one embodiment of the present disclosure was applied, curling hardly occurred even after vacuum drying, but in Comparative Examples 1 to 3 in which an electrode insulating polymer other than the above was applied, curling occurred to a large extent.

[0127] This is understood to be due to the improvement in the relaxation of the difference in elongation and / or the stress relaxation behavior as described above in Examples 1 to 3. On the other hand, it is understood that Comparative Examples 1 to 3, unlike Example 1, have inappropriate thermal properties of the electrode insulating polymer, which leads to an increase in subsequent curl occurrence due to relaxation of residual stress, particularly during the drying process.

[0128] In addition, as shown in Table 3 above, Examples 1 to 3, in which an electrode insulating polymer having a thermal expansion coefficient range according to one embodiment of the present disclosure was applied, had a swelling degree of only about 7% after electrolyte impregnation, and no surface peeling due to electrolyte impregnation was observed, whereas Comparative Example 1, which did not have this effect, showed a high swelling degree of about 19%, confirming that surface peeling occurred. Accordingly, in the case of Example 1, even when an electrode insulating polymer was applied to the electrode non-coated portion as described above, it was confirmed that the fairness of the manufacturing process could be greatly improved, while at the same time having an equivalent or higher electrolyte resistance compared to a conventional electrode insulating polymer.

[0129] The above swelling degree refers to the degree to which the structure of the insulating coating layer applied to the non-conductive portion becomes loose in an electrolyte-impregnated environment, and a higher swelling degree may indicate that the frequency of penetration of electrolyte molecules into the coating layer is more frequent. Therefore, without being bound by a specific theory, a higher swelling degree may increase the possibility of peeling of the coating layer in an electrolyte-impregnated environment, and such peeling within the battery cell may seriously reduce battery capacity and also present serious safety issues. As can be seen above, in the case of Example 1, it can be confirmed that the electrolyte resistance is excellent, so that concerns about unnecessary capacity reduction or safety degradation can be prevented.

[0130] As a result, it can be confirmed that the application of an insulating coating layer of an electrode insulating polymer according to one embodiment of the present disclosure can fundamentally improve safety (short-circuit prevention, etc.) and at the same time improve fairness degradation or other defects caused by its application.

[0131]

[0132] The above description is merely an example of applying the principles of the present disclosure, and other configurations may be further included without departing from the scope of the present disclosure.

Claims

1. It includes a holding portion having an electrode active material layer positioned on a current collector and a non-holding portion having no electrode active material layer positioned on a current collector; An insulating coating layer positioned on at least a portion of the above-mentioned portion and including an electrode insulating polymer; An electrode for a secondary battery, wherein the thermal expansion coefficient of the electrode insulating polymer is 66 μm / m℃ to 127 μm / m℃.

2. In paragraph 1, An electrode for a secondary battery, wherein the thermal expansion coefficient of the electrode insulating polymer is 72 μm / m℃ to 80 μm / m℃.

3. In paragraph 1, The electrode insulating polymer is a secondary battery electrode comprising at least one selected from polyamide-based polymers, polyamideimide-based polymers, fluoroethylene-based polymers, butadiene-based rubbers, and copolymers thereof.

4. In paragraph 3, An electrode for a secondary battery, wherein the electrode insulating polymer comprises a polyamide-based polymer and a fluoroethylene-based polymer, and the polyamide-based polymer and the fluoroethylene-based polymer are contained in a weight ratio of 1:8.5 to 1:9.

5.

5. In paragraph 1, The above electrode insulating polymer Amide-imide first repeating unit; and An electrode for a secondary battery, comprising a copolymer comprising at least one second repeating unit selected from the group consisting of butadiene-based, nitrile-based, and styrene-based polymers.

6. In paragraph 5, An electrode for a secondary battery, wherein the first repeating unit comprises an aromatic ring.

7. In paragraph 5, An electrode for a secondary battery, wherein the first repeating unit comprises a benzene ring.

8. In paragraph 5, An electrode for a secondary battery, wherein the second repeating unit is at least one selected from the group consisting of butadiene-based, acrylonitrile-butadiene-based, and hydrogenated acrylonitrile-butadiene-based.

9. In paragraph 5, An electrode for a secondary battery, wherein the molar ratio of the first repeating unit and the second repeating unit is 60 to 80: 40 to 20.

10. In paragraph 5, An electrode for a secondary battery, wherein the copolymer is at least one selected from the group consisting of random copolymers, alternating copolymers, block copolymers, and graft copolymers.

11. In paragraph 1, An electrode for a secondary battery, wherein the insulating coating layer is positioned on at least a part of the maintenance portion and at least a part of the non-conductive portion.

12. In paragraph 11, An electrode for a continuous secondary battery, wherein an insulating coating layer positioned on at least a part of the above-mentioned portion and an insulating coating layer positioned on at least a part of the above-mentioned portion are provided.

13. In paragraph 1, The above electrode is the anode, An electrode for a secondary battery, wherein the above-mentioned collector comprises at least one metal selected from the group consisting of stainless steel, nickel, titanium, aluminum, and alloys thereof.

14. In paragraph 1, An electrode for a secondary battery having an elongation of the non-conductive portion where the insulating coating layer is located of 25% to 43%.

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