Positive electrode slurry composition and positive electrode manufactured using same

Abstract

The present invention provides a positive electrode slurry composition comprising: a positive electrode active material; a conductive material; and a binder, wherein the binder comprises an aramid-based polyamide polymer including a repeating unit of chemical formula 1 below and a hydrogenated nitrile butadiene rubber (H-NBR), and a mole fraction of the repeating unit of chemical formula 1 is 95-100 mol% based on the total number of moles of the repeating units of the aramid-based polyamide polymer. [Chemical Formula 1] -[NH-A1-NHCO-A2-CO]- In chemical formula 1, A1 and A2 are each independently a divalent organic group containing an aromatic ring.

Description

Anode slurry composition and anode manufactured using the same

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0128578 filed on September 23, 2024, and all contents disclosed in said Korean Patent Application are incorporated herein as part of this specification.

[0002] The present invention relates to an anode slurry composition comprising an aramid-based polyamide polymer as a binder and an anode manufactured using the same.

[0003]

[0004] As industries utilizing secondary batteries, such as mobile phones, laptop computers, and electric vehicles, grow rapidly, active research and development efforts are underway to improve their performance. Among these, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0005] Here, the electrode for a lithium-ion secondary battery typically comprises a current collector and an electrode composite layer formed as a functional layer on the current collector. The electrode composite layer is formed by applying a slurry-like composition, for example, comprising an electrode active material and a binder composition including a polymer that acts as a binder, onto a current collector and drying it.

[0006] Conventionally, polyvinylidene fluoride (PVdF) binder, which has excellent electrochemical performance and thermal stability, was used as an anode binder. However, there was a problem because the anode slurry composition containing polyvinylidene fluoride showed a phenomenon where viscosity increased or gelled over time.

[0007]

[0008] The present invention provides an anode slurry composition with minimal change over time to solve such problems.

[0009] In addition, the present invention provides a highly flexible anode with excellent electrochemical performance and thermal stability.

[0010]

[0011] The present invention provides an anode slurry composition comprising an aramid-based polyamide polymer and hydrogenated nitrile butadiene rubber (H-NBR) as binders. That is, the present invention provides an anode slurry composition comprising an anode active material; a conductive material; and a binder, wherein the binder comprises an aramid-based polyamide polymer comprising repeating units of the following chemical formula 1 and hydrogenated nitrile butadiene rubber (H-NBR), and the mole fraction of the repeating units of the chemical formula 1 is 95 to 100 mol% relative to the total number of moles of repeating units of the aramid-based polyamide polymer.

[0012] [Chemical Formula 1]

[0013] -[NH-A1-NHCO-A2-CO]-

[0014] In the above chemical formula 1, A1 and A2 are each independently divalent organic groups containing an aromatic ring.

[0015]

[0016] In addition, the present invention provides an anode comprising an anode current collector; an anode active material; a conductive material; and an anode active material layer comprising a binder, wherein the binder comprises a repeating unit of Formula 1 and hydrogenated nitrile butadiene rubber (H-NBR), and the mole fraction of the repeating unit of Formula 1 is 95 to 100 mol% relative to the total number of repeating units of an aramid-based polyamide polymer.

[0017]

[0018] The aramid-based polyamide polymer binder included in the anode slurry composition of the present invention does not undergo reactions such as dehydrofluorination with lithium byproducts, and therefore does not form an active material / binder / conductive material composite. For this reason, the anode slurry composition of the present invention has the effect of suppressing changes over time and gelation. For this reason, using the anode slurry composition of the present invention has the advantage of improving processability by facilitating stirring and transport of the slurry.

[0019] In addition, the anode produced from the anode slurry composition of the present invention has a uniformly coated anode active material layer, so the entire electrode has uniform physical properties, and thus has the effect of improving overall characteristics.

[0020] The anode slurry composition of the present invention includes hydrogenated nitrile butadiene rubber as a binder along with a polymer containing repeating units including aromatic rings in its structure at a level of 95 to 100 mol%, thereby maintaining the viscosity of the anode slurry composition at a level that is neither too low nor too high. That is, the anode slurry composition of the present invention can provide an anode slurry composition in which the slurry viscosity is not high even when the solid content is high. Accordingly, the amount of solvent that must be evaporated during the formation of the anode active material layer is reduced, thereby decreasing the use of thermal energy and increasing the process efficiency of the drying process. In addition, since the drying time during the formation of the anode active material layer is short, there is an effect of reducing thermal wrinkles or cracks in the manufactured anode.

[0021]

[0022] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0023] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0024] In addition, in the description of "a to b carbon atoms" within this specification, "a" and "b" refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "alkylene group having 1 to 5 carbon atoms" refers to an alkylene group containing 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, or -CH(CH3)CH2CH2-, etc.

[0025] In addition, all alkyl groups in this specification may be substituted or unsubstituted. Unless otherwise defined, "substituted" means that at least one hydrogen bonded to a carbon is substituted with an element other than hydrogen, for example, a halogen atom, a nitro group, a nitrile group, etc.

[0026]

[0027] In this specification, "weight-average molecular weight" can be measured using a gel permeation chromatography (GPC) device. Specifically, in this invention, the measurement is performed using an Agilent 1200 series under GPC conditions, and the column used may be an Agilent PL mixed B column, and the solvent may be tetrahydrofuran (THF) or dimethylformamide (DMF). Meanwhile, unless otherwise specifically defined in this specification, molecular weight may refer to weight-average molecular weight.

[0028]

[0029] In addition, "viscosity" in this specification may be measured using a commercially available viscometer. Specifically, in this invention, "viscosity" was measured using an Anton Paar Rheometer MCR 302, and the viscosity was measured at a temperature of 25 degrees and a shear rate of 2.5 (1 / s).

[0030]

[0031] Polyvinylidene fluoride (PVDF), which is widely used as a conventional anode binder, exhibits increasing viscosity over time, hindering the workability of the electrode manufacturing process and resulting in insufficient mechanical properties of the manufactured electrodes. Furthermore, there were issues regarding environmental pollution caused by environmental persistence and toxicity. Consequently, the use of hydrogenated nitrile butadiene rubber (H-NBR) as a substitute for polyvinylidene fluoride (PVDF) was considered, but even in this case, limitations existed in terms of electrode adhesion and chemical resistance. Therefore, a combination of polyvinylidene fluoride (PVDF) and hydrogenated nitrile butadiene rubber (H-NBR) was considered as an anode binder, but the balance between slurry stability and electrode properties remained insufficient. Meanwhile, when aramid-based polyamide polymers were applied alone, heat resistance and mechanical strength were improved, but problems existed in terms of slurry viscosity and suitability for electrode manufacturing.

[0032] Accordingly, the inventors of the present invention completed the present invention by researching to solve the above problems and confirming that when an aramid-based polyamide polymer and hydrogenated nitrile butadiene rubber (H-NBR) are combined and used as an anode binder, the slitting viscosity is stabilized, the mechanical properties and heat resistance of the electrode are simultaneously secured, and the electrode manufacturing processability is also improved.

[0033]

[0034] The present invention will be described in more detail below.

[0035]

[0036] Anode slurry composition

[0037] The present invention provides an anode slurry composition comprising an anode active material, an anode conductive material, and an anode binder. The anode binder included in the anode slurry of the present invention is characterized by comprising an aramid-based polyamide polymer comprising repeating units of the following chemical formula 1 and hydrogenated nitrile butadiene rubber (H-NBR).

[0038] The anode binder included in the anode slurry of the present invention may include an aramid-based polyamide polymer comprising repeating units of the following chemical formula 1.

[0039] [Chemical Formula 1]

[0040] -[NH-A1-NHCO-A2-CO]-

[0041] In the above chemical formula 1, A1 and A2 may each independently be a divalent organic group containing an aromatic ring. The aromatic ring refers to an arylene group having 6 to 12 carbon atoms. Additionally, A1 and A2 may each independently include -SO2-, -CO-, -COO-, -COOH, etc. within their structure.

[0042] In the above chemical formula 1, A1 and A2 may each be a divalent organic group independently selected from any one of chemical formulas 1-1 to 1-5.

[0043] [Chemical Formula 1-1]

[0044]

[0045] [Chemical Formula 1-2]

[0046]

[0047] [Chemical Formula 1-3]

[0048]

[0049] [Chemical Formula 1-4]

[0050]

[0051] [Chemical Formula 1-5]

[0052]

[0053]

[0054] In the above chemical formulas 1-1 to 1-5, * is a binding site.

[0055] In the above chemical formula 1, A1 may be a divalent organic group selected from either chemical formula 1-1 or chemical formula 1-2.

[0056] In the above chemical formula 1, A2 may be a divalent organic group selected from any one of chemical formulas 1-3 to 1-5.

[0057]

[0058] The aramid-based polyamide polymer included in the anode slurry composition of the present invention may include the repeating unit of Formula 1 in a mole fraction of 95 mol% to 100 mol% relative to the total number of repeating units of the aramid-based polyamide polymer, preferably 96 mol% to 99 mol%, and more preferably 97 mol% to 98 mol%.

[0059]

[0060] The above aramid-based polyamide polymer may additionally include repeating units of the following chemical formula 2.

[0061] [Chemical Formula 2]

[0062] -[NH-B1-NHCO-B2-CO]-

[0063] In the above chemical formula 2, B1 and B2 may each independently be a divalent aliphatic organic group. Specifically, B1 and B2 may each independently be an alkylene group having 2 to 50 carbon atoms. B1 and B2 may each independently be -(CH2)n-, where the range of n may be 2 ≤ n ≤ 50, 2 ≤ n ≤ 20, or 2 ≤ n ≤ 10.

[0064]

[0065] The aramid-based polyamide polymer included in the anode slurry composition of the present invention may include the repeating unit of Formula 2 in a mole fraction of 0.1 mol% to 5.0 mol% relative to the total number of repeating units of the aramid-based polyamide polymer, preferably in a mole fraction of 1 mol% to 4 mol%, and more preferably in a mole fraction of 2 mol% to 3 mol%.

[0066]

[0067] The aramid-based polyamide polymer included in the anode slurry composition of the present invention may have a weight-average molecular weight of 200,000 g / mol to 600,000 g / mol, preferably 250,000 g / mol to 550,000 g / mol, and more preferably 300,000 g / mol to 500,000 g / mol. When the molecular weight satisfies the above range, phase separation of the slurry composition does not occur, the anode active material is sufficiently dispersed, and uniform stirring is possible. In addition, when manufacturing an anode active material layer using the anode slurry composition, there is an effect of excellent adhesion to the electrode current collector.

[0068]

[0069] The aramid-based polyamide polymer included in the anode slurry composition of the present invention may include one or more functional groups selected from the group consisting of carbonyl groups, carboxyl groups, and ester groups.

[0070] In addition, the above functional group may be included in an amount of 0.01 to 0.3 mol% relative to the total molar amount of the aramid-based polyamide polymer.

[0071]

[0072] The hydrogenated nitrile butadiene rubber (H-NBR) included in the anode slurry composition of the present invention may have a weight-average molecular weight of 200,000 g / mol to 600,000 g / mol, preferably 250,000 g / mol to 550,000 g / mol, and more preferably 300,000 g / mol to 500,000 g / mol. When the molecular weight satisfies the above range, phase separation of the slurry composition does not occur, the anode active material is sufficiently dispersed, and uniform stirring is possible. In addition, when manufacturing an anode active material layer using the anode slurry composition, there is an effect of excellent adhesion to the electrode current collector.

[0073]

[0074] Among the repeating units constituting the hydrogenated nitrile butadiene rubber (H-NBR) included in the anode slurry composition of the present invention, repeating units derived from acrylonitrile (AN) may be included in a molar fraction of 30 mol% to 40 mol%, preferably 31 mol% to 38 mol%, and more preferably 32 mol% to 36 mol%. If the molar ratio of acrylonitrile is higher than the above range, swelling caused by electrolyte impregnation becomes too large, resulting in a problem where the mechanical properties of the anode deteriorate. If the molar ratio of acrylonitrile is lower than the above range, solubility in the solvent decreases, resulting in a problem where the binder is not uniformly dispersed in the solvent.

[0075]

[0076] The weight ratio of the aramid-based polyamide polymer and hydrogenated nitrile butadiene rubber (H-NBR) included in the anode slurry composition of the present invention may be 0.5:1 to 10:1, preferably 1:1 to 7:1, and more preferably 2:1 to 5:1. When the binder content ratio satisfies the above range, the phase stability of the anode slurry is excellent, and the adhesion to the anode current collector can be sufficiently high when manufacturing the anode active material layer with the anode slurry composition. In addition, sufficient flexibility can be ensured for the anode manufactured therefrom.

[0077]

[0078] The anode slurry composition of the present invention is characterized by not including a fluorine-based binder such as polyvinylidene fluoride (PVdF). Because of this, the anode slurry composition of the present invention has the advantage of being environmentally friendly, and can have a viscosity suitable for manufacturing an anode that exhibits improved phase stability and excellent performance.

[0079] The viscosity of the anode slurry composition of the present invention at 25°C may be 6,000 cP to 50,000 cP, preferably 6,000 cP to 30,000 cP, and more preferably 10,000 cP to 20,000 cP.

[0080]

[0081] The solid content of the entire anode slurry composition of the present invention may be 55% by weight or more and 80% by weight or less, 60% by weight or more and 79% by weight or less, or 65% by weight or more and 75% by weight or less. Since the viscosity of the anode slurry composition of the present invention is maintained at a low level despite having a high solid content, the motor of the stirrer or the transfer pump is not subjected to a heavy load during the preparation of the slurry composition, thereby improving the processability of the anode manufacturing process. In addition, when manufacturing an anode using the anode slurry composition of the present invention, the anode active material layer is uniformly coated.

[0082]

[0083] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide comprising lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2Examples include )O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are each atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc., and any one or more of these compounds may be included.

[0084] Among these, the lithium metal oxides mentioned above include LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxide (e.g., Li(Ni)) in that they can improve the capacity characteristics and stability of the battery. 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be O2, etc., and any one or more of these may be used.

[0085]

[0086] Among these, the positive active material included in the positive slurry composition of the present invention may be a lithium transition metal oxide having a composition represented by the following chemical formula 3. As the nickel content increases, lithium by-products such as LiOH and Li2CO3 are leached from the positive active material, causing the positive slurry composition to change over time easily. However, the positive slurry composition of the present invention can suppress such changes over time by controlling the mole fraction of aromatic repeating units in the aramid-based polyamide polymer binder and including hydrogenated nitrile butadiene rubber (H-NBR) together with the aramid-based polyamide polymer.

[0087] [Chemical Formula 3]

[0088] Li a Ni 1-x-y Co x M 1 y M 2 z O2

[0089] In the above chemical formula 3, M 1 It may be one or more selected from Mn and Al, and preferably may be Mn or a combination of Mn and Al.

[0090] In the above chemical formula 3, M 2 may be any one or more elements selected from the group consisting of Zr, Ti, Mg, Ta, Nb, W, Mo and Cr.

[0091] The above a represents the molar ratio of lithium in the lithium transition metal oxide, and may be 1.0≤a≤1.3, 1.0≤a≤1.2, or 1.0≤a≤1.1.

[0092] The above 1-xy represents the molar ratio of nickel among metal elements excluding lithium in the lithium transition metal oxide, and may be 0.80≤1-xy<1.0, 0.80≤1-xy≤0.98, 0.80≤1-xy≤0.95, 0.83≤1-xy≤0.95, or 0.90≤1-xy≤0.95. When the nickel content satisfies the above range, high capacity characteristics can be achieved.

[0093] The above x represents the molar ratio of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, where 0 <x<0.4, 0<x≤0.2, 또는 0.01≤x≤0.10일 수 있다.

[0094] The above y is M among the metal elements excluding lithium in the lithium transition metal oxide. 1 Representing the molar ratio of, 0 <y<0.4, 0<y≤0.2, 또는 0.01≤y≤0.10일 수 있다.

[0095] The above z is M among the metal elements excluding lithium in the lithium transition metal oxide. 2 It represents the molar ratio of 0≤z≤0.1 or 0≤z≤0.05.

[0096]

[0097] The positive active material included in the positive active material layer of the present invention may be included in an amount of 95% to 100% by weight, preferably 98% to 100% by weight, and more preferably 99% to 100% by weight, based on the weight of the total positive active material included in the positive active material layer.

[0098]

[0099] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1 to 15 weight% based on the total weight of the anode slurry composition.

[0100]

[0101] The binder of the present invention may additionally include conventional binders. Examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above additional binder may be included in an amount of 0.1 to 5 weight percent based on the total weight of the anode slurry composition.

[0102]

[0103] The anode slurry composition of the present invention can be prepared by dissolving or dispersing an anode active material, a conductive material, and a binder, etc., in a solvent.

[0104] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used.

[0105]

[0106] The amount of the above solvent used may be 20% by weight or more and 45% by weight or less, 21% by weight or more and 40% by weight or less, or 25% by weight or more and 35% by weight or less, based on the total weight of the anode slurry composition.

[0107]

[0108] anode

[0109] The anode of the present invention comprises an anode current collector; an anode active material; a conductive material; and an anode active material layer comprising a binder. Since the anode active material, conductive material, and binder have been described above, a detailed description thereof is omitted, and only the remaining components are described in detail below.

[0110] The anode of the present invention can be manufactured by applying the anode slurry composition described above, followed by drying and rolling. Alternatively, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0111]

[0112] The positive current collector of the present invention may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the positive current collector may typically have a thickness of 3 to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0113]

[0114] The aramid-based polyamide polymer may be included in an amount of 0.1 wt% or more and 5 wt% or less, 0.5 wt% or more and 3.5 wt% or less, 0.8 wt% or more and 3.0 wt% or less, or 1.0 wt% or more and 2.0 wt% or less with respect to the entire anode active material layer.

[0115]

[0116] electrochemical device

[0117] Next, an electrochemical device according to the present invention will be described. The electrochemical device according to the present invention comprises the positive electrode of the present invention described above. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0118] Specifically, the above lithium secondary battery comprises a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is identical to the one described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0119] Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0120]

[0121] In the lithium secondary battery of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0122] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0123]

[0124] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0125] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon may be used as the carbon material. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0126] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0127]

[0128] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0129] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used.

[0130]

[0131] The above-mentioned negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, or by casting the composition for forming a negative electrode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0132]

[0133] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0134]

[0135] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0136]

[0137] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0138] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0139]

[0140] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0141]

[0142] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0143]

[0144] As described above, since the lithium secondary battery including the positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0145] Accordingly, according to another embodiment of the present invention, a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same are provided.

[0146] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0147] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0148] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0149] Examples of the above-mentioned medium-to-large devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, but are not limited to these.

[0150]

[0151] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0152]

[0153] Examples

[0154] Example 1

[0155] An aramid-based polyamide polymer was prepared containing 78 mol% of the repeating unit of Chemical Formula 1A, 20 mol% of the repeating unit of Chemical Formula 1B, and 2 mol% of the repeating unit of Chemical Formula 2A among the total repeating units.

[0156] [Chemical Formula 1A]

[0157]

[0158] [Chemical Formula 1B]

[0159]

[0160] [Chemical Formula 2A]

[0161] -[NH-(CH2)6-NHCO-(CH2)6-CO]-

[0162] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08 O2), a conductive material (carbon black), the aramid-based polyamide polymer of Preparation Example 1, and styrene butadiene rubber were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96.0 : 2.0 : 1.6 : 0.4, and stirred with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours to prepare an anode slurry composition.

[0163] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0164]

[0165] Example 2

[0166] An aramid-based polyamide polymer was prepared containing 78 mol% of the repeating unit of Chemical Formula 1A, 20 mol% of the repeating unit of Chemical Formula 1B, and 2 mol% of the repeating unit of Chemical Formula 2A among the total repeating units.

[0167] [Chemical Formula 1A]

[0168]

[0169] [Chemical Formula 1B]

[0170]

[0171] [Chemical Formula 2A]

[0172] -[NH-(CH2)6-NHCO-(CH2)6-CO]-

[0173] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08O2), a conductive material (carbon black), the aramid-based polyamide polymer, and hydrogenated nitrile butadiene rubber were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96.0 : 2.0 : 1.4 : 0.6, and stirred with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours to prepare an anode slurry composition.

[0174] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0175]

[0176] Example 3

[0177] An aramid-based polyamide polymer was prepared containing 78 mol% of the repeating unit of Chemical Formula 1A, 20 mol% of the repeating unit of Chemical Formula 1B, and 2 mol% of the repeating unit of Chemical Formula 2A among the total repeating units.

[0178] [Chemical Formula 1A]

[0179]

[0180] [Chemical Formula 1B]

[0181]

[0182] [Chemical Formula 2A]

[0183] -[NH-(CH2)6-NHCO-(CH2)6-CO]-

[0184] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08 O2), a conductive material (carbon black), the aramid-based polyamide polymer, and hydrogenated nitrile butadiene rubber were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96.0 : 2.0 : 0.6 : 1.4, and stirred with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours to prepare an anode slurry composition.

[0185] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0186]

[0187] Comparative Example 1

[0188] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08 O2), a conductive material (carbon black), and a binder (polyvinylidene fluoride, PVdF) were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96:2:2, and an anode slurry composition was prepared by stirring with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours.

[0189] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0190]

[0191] Comparative Example 2

[0192] An aramid-based polyamide polymer was prepared containing 80 mol% of the repeating unit of Chemical Formula 1A and 20 mol% of the repeating unit of Chemical Formula 1B among the total repeating units.

[0193] [Chemical Formula 1A]

[0194]

[0195]

[0196] [Chemical Formula 1B]

[0197]

[0198] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08 O2), a conductive material (carbon black), and the aramid-based polyamide polymer were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96.0 : 2.0 : 2.0, and stirred with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours to prepare an anode slurry composition.

[0199] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0200]

[0201] Comparative Example 3

[0202] Cathode active material (LiNi 0.84 Co 0.08 Mn 0.08 O2), a conductive material (carbon black), and hydrogenated nitrile butadiene rubber were mixed in N-methyl-2-pyrrolidone in a weight ratio of 96.0 : 2.0 : 2.0, and stirred with a high-speed stirrer (Homodisper) at 1500 rpm for 2 hours to prepare an anode slurry composition.

[0203] At this time, the solid content of the anode slurry composition was 70% by weight based on the total weight of the anode slurry composition.

[0204]

[0205] Experimental Example 1 - Viscosity Evaluation

[0206] The anode slurry compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured using an Anton Paar Rheometer MCR 302, and the viscosity at 25°C was measured at a shear rate of 2.5 (1 / s). In addition, each was stored at 25°C, and the viscosity at 25°C was measured after 3 days and after 7 days. The measured viscosity results are shown in Table 1 below.

[0207] Viscosity after 0 days (cP) Viscosity after 3 days (cP) Viscosity after 7 days (cP) Example 1 12,500 12,700 13,000 Example 2 13,100 12,900 13,500 Example 3 11,000 12,200 12,500 Comparative Example 1 12,100 37,500 Unmeasurable Comparative Example 2 7,800 8,200 8,100 Comparative Example 3 5,300 5,500 5,200

[0208] In the case of Examples 1 to 3, it was confirmed that a stable phase was maintained even after 7 days of storage compared to Comparative Example 1, which used a conventional polyvinylidene fluoride (PVdF) binder. In addition, in the case of Examples 1 to 3, it was confirmed that a stable phase was maintained and had an appropriate level of viscosity compared to Comparative Example 2, which contained only an aramid-based polyamide polymer, and Comparative Example 3, which contained only hydrogenated nitrile butadiene rubber.

[0209] Experimental Example 2 - Measurement of Adsorption Amount

[0210] 5 g each of the anode slurry compositions prepared in Examples 1 to 3 and Comparative Example 1 were taken, and they were centrifuged at 20,000 rpm for 30 minutes using a centrifuge (Supra R30, Hanil Scientific Inc.) to separate them into a solid component and a supernatant.

[0211] The viscosity of the supernatant was measured using a Brookfield viscometer (DV-II + PRO Viscometer, Brookfield) at a temperature of 25°C, a humidity of 50 RH%, and a frequency of 30 Hz. The concentration of the supernatant was then determined by comparing this with previously obtained viscosity data based on the content (mg / g) of polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP). From this, the residual amount of binder in the supernatant was calculated, and after subtracting this from the amount of binder added, the content (mg / g) of the adsorbed binder based on 1 g of cathode active material was determined.

[0212] The results are shown in Table 2 below.

[0213] Content of adsorbed binder (mg / g) Example 10.3 Example 20.3 Example 30.2 Comparative Example 110.2

[0214] In the case of Examples 1 to 3, the content of the adsorbed binder per 1 g of cathode active material was measured to be much lower compared to Comparative Example 1, which used a conventional polyvinylidene fluoride (PVdF) binder, so it is expected that there will be less change over time during long-term storage. Experimental Example 3 - Evaluation of Cathode Flexibility

[0215] The anode slurry compositions prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were each applied to one surface of an aluminum current collector (thickness 12 μm), dried at 130°C to form an anode active material layer on the aluminum current collector, and then rolled to produce an anode.

[0216] Each anode was cut to a width of 20 mm and a length of 150 mm, and the cut samples were placed on the center of a three-point bending jig of a measuring device (UTM, Zwick). Under temperature conditions of 25°C, the force (N) was measured when the center of the electrode bent 2 cm downward relative to the electrode ends in the vertical direction (180° direction) at a speed of 10 mm / min. The magnitude of the measured force was divided by the deformation length of 2 cm to determine the yield strength (N / m), which is the Young's modulus. The measurement results are shown in Table 3 below.

[0217] Yield Strength (N / m) Example 160 Example 245 Example 340 Comparative Example 1150 Comparative Example 2210

[0218] It was confirmed that the anode prepared from the anode slurry compositions of Examples 1 to 3 had lower tensile strength at break compared to the anode prepared from the anode slurry composition of Comparative Example 1, which used a conventional polyvinylidene fluoride (PVdF) binder, and thus had higher flexibility. In addition, it was confirmed that the anode prepared from Examples 1 to 3 had lower tensile strength at break compared to the anode prepared from the anode slurry composition of Comparative Example 2, which contained only an aramid-based polyamide polymer, and thus had higher flexibility.

Claims

1. A positive electrode slurry composition comprising a positive electrode active material; a conductive material; and a binder, wherein The above binder comprises an aramid-based polyamide polymer containing repeating units of the following chemical formula 1 and hydrogenated nitrile butadiene rubber (H-NBR), and An anode slurry composition in which the molar fraction of the repeating unit of the above chemical formula 1 is 95 to 100 mol% relative to the total molar number of repeating units of the aramid-based polyamide polymer. [Chemical Formula 1] -[NH-A1-NHCO-A2-CO]- In the above chemical formula 1, A1 and A2 are each independently divalent organic groups containing an aromatic ring.

2. In Paragraph 1, A1 and A2 are each independently selected from any one of the following chemical formulas 1-1 to 1-5, an anode slurry composition. [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] In the above chemical formulas 1-1 to 1-5, * is the binding site.

3. In Paragraph 1, The anode slurry composition wherein the above aramid-based polyamide polymer further comprises a repeating unit of the following chemical formula 2. [Chemical Formula 2] -[NH-B1-NHCO-B2-CO]- In the above chemical formula 2, B1 and B2 are each independently divalent aliphatic organic groups.

4. In Paragraph 3, An anode slurry composition in which the molar fraction of the repeating unit of Chemical Formula 2 above is 0.1 to 5.0 mol% relative to the total molar number of repeating units of the aramid-based polyamide polymer.

5. In Paragraph 3, The above B1 and B2 are each independently an anode slurry composition having 2 to 50 carbon atoms.

6. In Paragraph 1, The above aramid-based polyamide polymer is an anode slurry composition having a weight-average molecular weight of 200,000 g / mol to 600,000 g / mol.

7. In Paragraph 1, The above aramid-based polyamide polymer is an anode slurry composition comprising one or more functional groups selected from the group consisting of carbonyl groups, carboxyl groups, and ester groups.

8. In Paragraph 7, An anode slurry composition in which the above functional group is included in an amount of 0.01 to 0.3 mol% with respect to the total components forming the aramid-based polyamide polymer.

9. In Paragraph 1, The above hydrogenated nitrile butadiene rubber (H-NBR) is an anode slurry composition having a weight-average molecular weight of 200,000 to 600,000 g / mol.

10. In Paragraph 1, An anode slurry composition in which the molar ratio of repeating units derived from acrylonitrile (AN) among the repeating units constituting the hydrogenated nitrile butadiene rubber (H-NBR) is 30 to 40 mol%.

11. In Paragraph 1, An anode slurry composition in which the weight ratio of the aramid-based polyamide polymer and hydrogenated nitrile butadiene rubber (H-NBR) is 0.5:1 to 10:

1.

12. In Paragraph 1, An anode slurry composition having a solid content of 55 to 80 weight% relative to the total anode slurry composition.

13. A positive electrode comprising a positive current collector; a positive active material; a conductive material; and a positive active material layer comprising a binder, wherein The above binder comprises an aramid-based polyamide polymer containing repeating units of the following chemical formula 1 and hydrogenated nitrile butadiene rubber (H-NBR), and An anode in which the molar fraction of the repeating unit of Chemical Formula 1 is 95 to 100 mol% relative to the total molar number of repeating units of the aramid-based polyamide polymer. [Chemical Formula 1] -[NH-A1-NHCO-A2-CO]- In the above chemical formula 1, A1 and A2 are each independently divalent organic groups containing an aromatic ring.

14. In Paragraph 13, The aramid-based polyamide polymer is included in an amount of 0.1 to 5 weight percent relative to the entire anode active material layer.

15. In Paragraph 13, The above-mentioned positive active material is a positive electrode comprising a lithium transition metal oxide represented by the following chemical formula 3. [Chemical Formula 3] Li a Ni 1-x-y Co x M 1 y M 2 z O2 In the above chemical formula 3, M 1 is Al, Mn, or a combination thereof,, M 2 is one or more elements selected from the group consisting of Zr, Ti, Mg, Ta, Nb, W, Mo, and Cr, and 1.0≤a≤1.3, 0 <x<0.1, 0<y<0.1, 0≤z≤0.1, 0.8≤1-x-y<1.0이다.

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