Positive electrode slurry composition for secondary battery, and positive electrode for secondary battery and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode slurry composition, and a positive electrode and a lithium secondary battery comprising same. The positive electrode slurry composition comprises: a lithium transition metal oxide containing nickel; and a polyamide-based binder, wherein the polyamide-based binder includes a polyamide-based polymer including an aliphatic structure and an aromatic structure in a main chain and including at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in a side chain, the polyamide-based polymer includes 90-99 mol% of the aromatic structure on the basis of the total number of moles of repeating units in the polymer, and the polyamide-based polymer includes 0.005-1 mol% of the functional group on the basis of the total number of moles of the polymer.

Description

Cathode slurry composition for secondary batteries, anode for secondary batteries and lithium secondary batteries comprising the same

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0080648, filed June 20, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a positive electrode slurry composition for a secondary battery, a positive electrode for a secondary battery comprising the positive electrode slurry composition, and a lithium secondary battery.

[0003] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, are being commercialized and widely used.

[0004] The electrode of a lithium secondary battery is manufactured by mixing a positive electrode active material or negative electrode active material with a binder resin component, dispersing the mixture in a solvent to create a slurry, applying this to the surface of the electrode current collector, drying it, and forming a composite layer.

[0005] As positive electrode active materials, lithium-containing cobalt oxides such as LiCoO2 with a layered structure, lithium-containing nickel oxides such as LiNiO2 with a layered structure, and lithium-containing manganese oxides such as LiMn2O4 with a spinel crystal structure are used.

[0006] Among these, LiCoO2 is widely used due to its excellent physical properties such as excellent cycle characteristics, but its safety is low, and it is expensive due to the limited resources of cobalt as a raw material, which limits its use in large quantities as a power source in fields such as electric vehicles. In addition, LiNiO2 is relatively cheap and shows battery characteristics with high discharge capacity, but there is a problem that the crystal structure undergoes a rapid phase transition due to the volume change accompanying the charge / discharge cycle, and the stability is rapidly reduced when exposed to air and moisture. On the other hand, lithium manganese oxides such as LiMnO2 and LiMn2O4 have the advantage of using manganese, which is abundant and environmentally friendly, as a raw material, but they have the disadvantages of small capacity and poor high-temperature characteristics and cycle characteristics.

[0007] To address these issues, research and experiments are being conducted to utilize lithium transition metal oxides mixed with nickel, cobalt, and manganese as cathode active materials. Cathode active materials manufactured by mixing nickel, cobalt, and manganese exhibit improved physical properties compared to batteries manufactured using each transition metal separately.

[0008] However, in the case of the lithium transition metal oxide mixed with the nickel-cobalt-manganese, there is a problem that stability is reduced when exposed to moisture in the air due to nickel. Specifically, moisture in the air and nickel in the nickel-cobalt-manganese react to generate hydroxyl groups. In addition, the generated hydroxyl groups react with the binder typically included in the positive electrode slurry composition to cause gelation. When the binder gels, the viscosity of the positive electrode slurry composition also increases rapidly, which reduces the uniformity of the positive electrode active material layer, resulting in a decrease in the adhesive strength of the electrode and the inside of the electrode, and causing problems such as non-development of the capacity of the cell and a decrease in the output.

[0009] Polyvinylidene fluoride (PVdF) has long been used as a binder for cathode slurry compositions due to its high electrochemical and thermal stability, as well as excellent oxidation and chemical resistance. However, PVdF exhibits the aforementioned binder gelation and increased viscosity of the cathode slurry composition, which require resolution. Furthermore, it cannot be ruled out that PVdF may become subject to future regulations for social and environmental reasons.

[0010] Therefore, when using a lithium transition metal oxide containing a nickel-cobalt-manganese ternary transition metal, improved resistance to moisture is required, and for this purpose, development of a cathode slurry composition containing a binder that is not affected by the reaction between nickel and moisture is required.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent Publication No. 2016-0039835

[0014] In order to solve the above problems, the first technical task of the present invention is to provide a positive electrode slurry composition that can prevent deterioration of the electrochemical performance of a battery by suppressing gelation of a binder due to moisture in the air.

[0015] A second technical task of the present invention is to provide a positive electrode for a lithium secondary battery comprising the positive electrode slurry composition.

[0016] The third technical task of the present invention is to provide a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0017] [1] The present invention provides a positive electrode slurry composition comprising: a lithium transition metal oxide including nickel; and a polyamide-based binder, wherein the polyamide-based binder includes a polyamide-based polymer having an aliphatic structure and an aromatic structure in a main chain and at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in a side chain, wherein the polyamide-based polymer includes 90 mol% to 99 mol% of the aromatic structure based on the total mole number of repeating units of the polymer, and wherein the polyamide-based polymer includes the functional group in an amount of 0.005 mol% to 1 mol% based on the total mole number of the polymer.

[0018] [2] The present invention provides a positive electrode slurry composition in the above [1], wherein the polyamide-based polymer contains 1 mol% to 10 mol% of the aliphatic structure relative to the total mole number of repeating units of the polymer.

[0019] [3] The present invention provides a positive electrode slurry composition, wherein in at least one of the above [1] or [2], the aromatic structure includes a repeating unit represented by the following chemical formula 1:

[0020] [Chemical Formula 1] -[NH-A1-NHCO-A2-CO]-

[0021] In the above chemical formula 1, A1 and A2 are each independently a divalent organic group containing an aromatic ring.

[0022] [4] The present invention provides a positive electrode slurry composition in the above [3], wherein A1 and A2 are each independently selected from the following chemical formulas 1-1 to 1-5:

[0023] [Chemical Formula 1-1]

[0024]

[0025] [Chemical Formula 1-2]

[0026]

[0027] [Chemical Formula 1-3]

[0028]

[0029] [Chemical Formula 1-4]

[0030]

[0031] [Chemical Formula 1-5]

[0032]

[0033] In the above chemical formulas 1-1 to 1-5, * represents a binding site.

[0034] [5] The present invention provides a positive electrode slurry composition, wherein in at least one of the above [1] to [4], the aliphatic structure includes a repeating unit represented by the following chemical formula 2:

[0035] [Chemical Formula 2] -[NH-B1-NHCO-B2-CO]-

[0036] In the above chemical formula 2, B1 and B2 are each independently a divalent aliphatic organic group.

[0037] [6] The present invention provides a positive electrode slurry composition in the above [5], wherein B1 and B2 are each independently an alkylene group having 2 to 50 carbon atoms.

[0038] [7] The present invention provides a positive electrode slurry composition in which the polyamide-based polymer has a weight average molecular weight of 100,000 g / mol to 1,000,000 g / mol in any one or more of the above [1] to [6].

[0039] [8] The present invention provides a positive electrode slurry composition in which the polyamide-based binder has an adsorption amount of the positive electrode active material of 6.5 mg / g or less in any one or more of the above [1] to [7].

[0040] [9] The present invention provides a positive electrode slurry composition according to any one or more of the above [1] to [8], wherein the positive electrode slurry does not contain polyvinylidene fluoride (PVdF).

[0041]

[0010] The present invention provides a positive electrode slurry composition according to any one or more of the above [1] to [9], wherein the positive electrode slurry composition further includes a conductive material.

[0042]

[0011] The present invention provides a positive electrode slurry composition, wherein, in the above

[0010] , the positive electrode slurry composition comprises 85 wt% to 99.6 wt% of the lithium transition metal oxide, 0.1 wt% to 10 wt% of the conductive material, and 0.1 wt% to 10 wt% of the polyamide-based binder, based on the total weight of the total solid content.

[0043]

[0012] The present invention provides a positive electrode slurry composition, wherein in any one or more of the above [1] to

[0011] , the lithium transition metal oxide has a content of Ni among transition metals of 50 mol% or more.

[0044]

[0013] The present invention provides a positive electrode slurry composition, wherein in any one or more of the above [1] to

[0012] , the lithium transition metal oxide is represented by the following chemical formula 3:

[0045] [Chemical Formula 3] Li 1+x (Ni a Co b Mn c ) 1-x O2

[0046] In the above chemical formula 3, -0.3≤x≤0.3, 0.5≤a<1, 0 <b≤0.3, 0<c≤0.3, 및 a+b+c=1임.

[0047]

[0014] The present invention provides a positive electrode slurry composition, wherein in any one or more of the above [1] to

[0013] , the positive electrode slurry composition has a solid content of 50 wt% to 80 wt% based on the total weight of the positive electrode slurry composition.

[0048]

[0015] The present invention provides a positive electrode slurry composition, wherein in any one or more of the above [1] to

[0014] , the positive electrode slurry composition has a difference of 20% or less between the initial viscosity and the viscosity after being left in an environment with a relative humidity of 30% or higher for 7 days.

[0049]

[0016] The present invention provides a positive electrode for a lithium secondary battery, comprising a positive electrode current collector, and a positive electrode slurry composition according to any one or more of [1] to

[0015] applied to at least one surface of the positive electrode current collector.

[0050]

[0017] The present invention provides a lithium secondary battery including a positive electrode for a lithium secondary battery according to the above

[0016] .

[0051] The positive electrode active material composition according to the present invention comprises a polyamide-based binder having an aliphatic structure and an aromatic structure in the main chain and at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in the side chain, thereby preventing gelation of the polyamide-based binder even when a lithium transition metal oxide containing nickel is included. Accordingly, when an electrode is manufactured using a positive electrode slurry containing the polyamide-based binder, the deterioration of electrode uniformity is suppressed, thereby maintaining adhesive strength and exhibiting more stable electrochemical performance, and thus the positive electrode slurry can be usefully used in the manufacture of a lithium secondary battery.

[0052] Figure 1 is a graph showing the change in viscosity over time in a 100% humidity environment of a positive electrode slurry composition manufactured according to Example 1 and Comparative Example 1 of the present invention.

[0053] Hereinafter, the present invention will be described in more detail.

[0054] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0055]

[0056] Positive slurry composition

[0057] According to one embodiment of the present invention, a cathode slurry composition comprises: a lithium transition metal oxide containing nickel; and

[0058] Contains a polyamide binder,

[0059] The polyamide-based binder includes a polyamide-based polymer having an aliphatic structure and an aromatic structure in a main chain and at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in a side chain, wherein the polyamide-based polymer includes 90 mol% to 99 mol% of the aromatic structure based on the total mole number of repeating units of the polymer, and the polyamide-based polymer includes the functional group in an amount of 0.005 mol% to 1 mol% based on the total mole number of the polymer.

[0060]

[0061] Since the positive electrode slurry composition includes a polyamide-based binder including a polyamide-based polymer having an aliphatic structure and an aromatic structure in the main chain and at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in the side chain, gelation of the binder, which occurs when polyvinylidene fluoride (PVDF) is used in the related art, can be prevented. That is, even when nickel included in a lithium transition metal oxide including nickel reacts with moisture in the air to form a hydroxyl group and thereby increases the pH of the positive electrode slurry composition, the aliphatic structure included in the polyamide-based binder does not interact with the hydroxyl group, so that gelation of the positive electrode slurry composition including the polyamide-based binder does not occur. In addition, since gelation of the positive electrode slurry composition including the polyamide-based binder does not occur, the uniformity of the electrode is improved when manufacturing the electrode using this, so that the electrochemical performance of the secondary battery can be improved.

[0062] The polyamide-based polymer may have the aliphatic structure and the aromatic structure linked by an amide bond, and the substitution position of the functional group may be, for example, at least one of the aliphatic structure and the aromatic structure of the main chain, or a terminal of the polyamide-based binder, and the functional group may be included in a side chain. The polyamide-based polymer is different from a polyamide binder mixture simply mixing an aliphatic polyamide and an aromatic polyamide in that the aliphatic structure and the aromatic structure are linked by an amide bond. In the case of a polyamide binder mixture simply mixing an aliphatic polyamide and an aromatic polyamide, when applied to a positive electrode slurry composition, the binder may partially aggregate due to the binding properties of the binder, and when applied to a positive electrode current collector, the uniformity of the electrode may deteriorate due to the aggregation of the binder.

[0063] The polyamide polymer may contain the aromatic structure in an amount of 90 mol% to 99 mol% based on the total moles of the aliphatic structure and the aromatic structure, specifically, the total number of repeating units of the polymer. In addition, the polyamide polymer may contain the aromatic structure in an amount of 92 mol% to 98 mol%, more specifically, 93 mol% to 97 mol%.

[0064] When the polyamide polymer contains an aromatic structure within the above range, the binder may have an increased modulus, which may help increase the cycle performance of a lithium secondary battery containing the binder. When the content of the aromatic structure is less than the above range, it is difficult to expect the effect of increasing the modulus of the binder, and when the content of the aromatic structure is greater than the above range, the slurry viscosity of the binder may excessively increase.

[0065] The polyamide polymer may contain 1 mol% to 10 mol% of the aliphatic structure relative to the total mole number of repeating units of the polymer, specifically 2 mol% to 8 mol%, and more specifically 3 mol% to 7 mol%. When the content of the aliphatic structure contained in the polyamide polymer satisfies the above range, the viscosity of the slurry becomes an appropriate level, phase separation does not occur, and the effect of improving the brittleness of the manufactured positive electrode can be exhibited.

[0066] The above polyamide-based polymer includes the aliphatic structure and the aromatic structure in the main chain, and the content of the aliphatic structure and the content of the aromatic structure may be the mole fraction of the structure forming the main chain of the polyamide-based polymer.

[0067] The polyamide polymer may contain the functional group in an amount of 0.005 mol% to 1 mol% based on the total mole number of the polymer, specifically 0.01 mol% to 0.5 mol%, and more specifically 0.01 mol% to 0.3 mol%.

[0068] When the polyamide-based polymer contains only an aliphatic structure and an aromatic structure, the electrode adhesion is low, so it is necessary to additionally introduce a functional group into the side chain, and when the functional group is included in the above range, the polyamide-based binder including the polyamide-based polymer can exhibit an appropriate electrode adhesion. When the content of the functional group is less than the above range, it is difficult to describe an appropriate level of electrode adhesion, and when the content of the functional group is more than the above range, the electrolyte affinity increases, so that the binder easily swells in the battery, which may reduce the physical bonding force. In addition, as a result, the positive electrode active material may be isolated, the capacity may decrease, the resistance may increase, and the output and rate characteristics may deteriorate.

[0069] The polyamide-based polymer included in the polyamide-based binder according to the present invention may have a weight average molecular weight of 100,000 g / mol to 1,000,000 g / mol, specifically 200,000 g / mol to 800,000 g / mol, more specifically 400,000 g / mol to 800,000 g / mol. When the weight average molecular weight of the polyamide-based polymer is low, the viscosity of the positive electrode slurry composition may be low, causing phase separation, making it difficult to sufficiently disperse the positive electrode active material, and reducing the adhesion effect between the electrode layer and the current collector. In addition, when the weight average molecular weight of the polyamide-based polymer is large, the resistance of the electrode layer in the positive electrode slurry composition may be increased, thereby deteriorating the output characteristics. In addition, the phase stability of the slurry may be shifted to a high-elasticity region, thereby reducing the uniformity of electrode quality. Here, the weight average molecular weight refers to a conversion value for standard polystyrene measured using gel permeation chromatography (GPC). For example, after preparing a sample of a certain concentration, the GPC measuring device is stabilized. Once the device is stabilized, the standard sample and sample are injected into the device to obtain a chromatogram, and the molecular weight is calculated according to the analysis method.

[0070] <Measurement conditions>

[0071] Measuring instrument: Agilent GPC (Agulent 1200 series, USA)

[0072] Column: PL Mixed B 2 connections

[0073] Column temperature: 40℃

[0074] Eluent: Tetrohydrofuran

[0075] Flow rate: 1.0 mL / min

[0076] Concentration: ~ 1 mg / mL (100 μL injection)

[0077]

[0078] The polyamide-based binder may have an adsorption amount of 6.5 mg / g or less for the positive electrode active material, specifically 0.1 mg / g to 5.0 mg / g, and more specifically 0.1 mg / g to 3.0 mg / g. When the adsorption amount of the binder for the positive electrode active material increases, the change in viscosity of the positive electrode slurry composition over time may increase. Since the polyamide-based binder of the present invention satisfies the adsorption amount of the positive electrode active material in the above range, the change in viscosity of the positive electrode slurry composition containing the same over time can be minimized.

[0079] The adsorption amount of the polyamide-based binder for the positive electrode active material can be obtained by a method of (1) preparing a preliminary slurry by adding the positive electrode active material and the polyamide-based binder to a dispersion medium, (2) taking a portion of the preliminary slurry and centrifuging it to separate it into a solid content and a supernatant, and (3) measuring the binder concentration in the supernatant to calculate the adsorption amount of the binder adsorbed to the positive electrode active material.

[0080]

[0081] The method for producing the above polyamide-based binder is not particularly limited as long as it is a method used for producing a conventional polyamide-based polymer, and may be produced, for example, through polymerization of a diamine compound and a polyfunctional carboxylic acid compound or a polyfunctional acyl halide compound. The polyamide-based binder may be produced, for example, by a method of inducing a polycondensation reaction by adding an aliphatic diamine compound to a molten aromatic polyfunctional carboxylic acid compound and / or an aromatic polyfunctional acyl halide compound, or by a method of inducing a polycondensation reaction by adding an aliphatic polyfunctional carboxylic acid compound and / or an aliphatic polyfunctional acyl halide compound to a molten aromatic diamine compound, but is not limited thereto.

[0082]

[0083] The above aromatic polyfunctional carboxylic acid compound may be an aromatic polyfunctional carboxylic acid compound containing 8 to 20 carbon atoms substituted or unsubstituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group. The above aromatic polyfunctional carboxylic acid compound may include at least one selected from the group consisting of terephthalic acid, isophthalic acid, 2-methylterephthalic acid, 2,5-dichloroterephthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 2,2'-biphenyl dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, 1,4-phenylenedioxyphenylene acid, 1,3-phenylenedioxy-diacetic acid, 4',4'-oxybisbenzoic acid, diphenylsulfone-4,4'-dicarboxylic acid, and 2,2'-biphenyl dicarboxylic acid, which is substituted or unsubstituted with at least one selected from the group consisting of a carbonyl group, a carboxy group, and an ester group.

[0084] The aliphatic dicarboxylic acid may be an aliphatic dicarboxylic acid containing 4 to 14 carbon atoms, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group. The aliphatic dicarboxylic acid may be, for example, at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, and 2-methylsuccinic acid, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group.

[0085]

[0086] In addition, the aromatic polyfunctional acyl halide compound may be an aromatic polyfunctional acyl halide compound having 8 to 20 carbon atoms, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group. The aromatic polyfunctional acyl halide compound may include, for example, at least one selected from the group consisting of trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, biphenyl dicarboxylic acid chloride, and naphthalene dicarboxylic acid dichloride, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group.

[0087]

[0088] The above aromatic diamine compound may be an aromatic diamine compound having 8 to 20 carbon atoms, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group. The above aromatic diamine compound may include at least one selected from the group consisting of 1,4-phenylenediamine, 1,3-phenylenediamine, 2,5-diaminotoluene, diphenyldiamine, 4-methoxyphenylenediamine, methylenedianiline, piperazine, triaminobenzene, m-xylenediamine, p-xylenediamine, and bis-4-aminophenylpropane, which is unsubstituted or substituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group.

[0089] The above aliphatic diamine compound may be an aliphatic diamine containing 2 to 14 carbon atoms, which is substituted or unsubstituted with at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group. The above aliphatic diamine compound is, for example, 1,2-ethanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexamethylene diamine, 1,8-octane diamine, 1,9-nonameethylene diamine, 1,10-decamethylene diamine, 1,11-hendecane diamine, 1,12-dodecane diamine, 2-methyl-1,5-pentamethylene diamine, 3-methyl-1,5-pentamethylene diamine, 2,4-dimethyl-1,6-hexamethylene diamine, 2,2,4-trimethyl-1,6-hexamethylene diamine, 2,4,4-trimethyl-1,6-hexamethylene diamine, It may include at least one selected from the group consisting of 2-methyl-1,8-octane diamine, 5-methyl-1,9-nonameethylene diamine, cyclohexane diamine, methyl cyclohexane diamine, and 4,4'-diaminodicyclohexyl methane.

[0090]

[0091] In one embodiment of the present invention, the aromatic structure may include a repeating unit represented by the following chemical formula 1.

[0092] [Chemical Formula 1]

[0093] -[NH-A1-NHCO-A2-CO]-

[0094] In the above chemical formula 1, A1 and A2 are each independently a divalent organic group containing an aromatic ring.

[0095]

[0096] In one embodiment of the present invention, A1 and A2 may each independently be one selected from the following chemical formulas 1-1 to 1-5.

[0097] [Chemical Formula 1-1]

[0098]

[0099] [Chemical Formula 1-2]

[0100]

[0101] [Chemical Formula 1-3]

[0102]

[0103] [Chemical Formula 1-4]

[0104]

[0105] [Chemical Formula 1-5]

[0106]

[0107] In the above chemical formulas 1-1 to 1-5, * represents a binding site.

[0108] In the above chemical formula 1, A1 may be a divalent organic group selected from chemical formula 1-1 or chemical formula 1-2.

[0109] 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.

[0110]

[0111] In one embodiment of the present invention, the aliphatic structure may include a repeating unit represented by the following chemical formula 2.

[0112] [Chemical Formula 2]

[0113] -[NH-B1-NHCO-B2-CO]-

[0114] In the above chemical formula 2, B1 and B2 are each independently a divalent aliphatic organic group.

[0115] In one embodiment of the present invention, 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-, wherein the range of n may be 2 ≤ n ≤ 50, 2 ≤ n ≤ 20, or 2 ≤ n ≤ 10.

[0116]

[0117] In addition, the lithium transition metal oxide containing nickel included in the positive electrode slurry composition according to the present invention may be selected from the group consisting of lithium-nickel oxides, lithium-nickel-manganese oxides, lithium-nickel-cobalt oxides, and lithium-nickel-manganese-cobalt oxides, and specifically Li 1+x (Ni a Co b Mn c ) 1-x O2(0<a<1, 0 <b<1, 0<c<1, -0.3≤x≤0.3, 및 a+b+c=1), Li(Ni d Co e Mn f )O4(0<d<2, 0<e<2, 0<f<2, d+e+f=2), Li g NiO2(0.5 <g<1.3), LiNi 1-h M h O2 (M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, 0≤h<1), LiMn 2-y Ni y O4(0<y<2), LiMn 2-z Co z It may include at least one selected from O4(0<Z<2).

[0118] Preferably, the lithium transition metal oxide is represented by the following chemical formula 3, and may include a lithium transition metal oxide having a Ni content of 50% or more, 60% or more, preferably 75% or more.

[0119] [Chemical Formula 3]

[0120] Li 1+x (Ni a Cob Mn c ) 1-x O2

[0121] In the above chemical formula 3,

[0122] -0.3≤x≤0.3, 0.5≤a<1, 0 <b≤0.3, 0<c≤0.3, 및 a+b+c=1임.

[0123] Also, in the above chemical formula 3, -0.3≤x≤0.3, 0.7≤a<1, 0 <b≤0.2, 0<c≤0.2, 및 a+b+c=1일 수 있고, 구체적으로 -0.3≤x≤0.3, 0.8≤a<1, 0<b<0.2, 0<c<0.2, 및 a+b+c=1일 수 있으며, 더욱 구체적으로 -0.3≤x≤0.3, 0.9≤a<1, 0<b<0.1, 0<c<0.1, 및 a+b+c=1일 수 있다.

[0124]

[0125] As described above, when a lithium transition metal oxide having a nickel content of 50% or more is used as a lithium transition metal oxide, high-capacity characteristics are exhibited, but as the nickel content of the lithium transition metal oxide increases, the generation of hydroxyl groups due to the reaction between nickel and moisture in the air may also increase. Accordingly, the higher the nickel content included in the lithium transition metal oxide, the more accelerated the gelation of the composition for forming a positive electrode including the same may be. When the polyamide-based binder is applied as a binder to the lithium transition metal oxide having a high nickel content, the aliphatic structure included in the polyamide-based binder does not interact with the hydroxyl groups generated due to the reaction between nickel included in the lithium transition metal oxide and moisture in the air, so that gelation can be suppressed despite the increased generation of hydroxyl groups.

[0126] Therefore, the positive electrode slurry composition of the present invention may include a lithium transition metal oxide having a high nickel content together with the polyamide-based binder.

[0127]

[0128] The above positive electrode slurry composition can be prepared by a conventional method known in the art. For example, it can be prepared by mixing and stirring a lithium transition metal oxide containing nickel as a positive electrode active material, a polyamide-based binder according to the present invention, a solvent, and optionally a conductive agent and / or dispersant.

[0129]

[0130] For example, the positive electrode slurry composition may include 85 wt% to 99.6 wt% of a lithium transition metal oxide, 0.1 wt% to 10 wt% of a conductive material, and 0.1 wt% to 10 wt% of a polyamide-based binder based on the total weight of the total solid content, specifically 90.0 wt% to 98.7 wt% of a lithium transition metal oxide, 0.3 wt% to 5.0 wt% of a conductive material, and 1.0 wt% to 5.0 wt% of a polyamide-based binder, and more specifically 93.0 wt% to 98.7 wt% of a lithium transition metal oxide, 0.3 wt% to 4.0 wt% of a conductive material, and 1.0 wt% to 4.0 wt% of a polyamide-based binder. When the content of the polyamide-based binder included in the positive electrode slurry composition increases, the adhesive strength increases, but as the content increases, the viscosity of the slurry may increase. Therefore, when the positive electrode slurry composition satisfies the above ranges of the lithium transition metal oxide, the conductive agent, and the polyamide-based binder, the viscosity and electrode coating properties and adhesive strength of the positive electrode slurry can be appropriately exhibited, and when it satisfies the above specific ranges, the viscosity and electrode coating properties and adhesive strength of the positive electrode slurry can be even more appropriately exhibited, and when it satisfies the above more specific ranges, the viscosity and electrode coating properties and adhesive strength of the positive electrode slurry can be even more appropriately exhibited.

[0131] The solvent included in the above positive electrode slurry composition includes organic solvents such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide, etc., or water, and these solvents may be used alone or in combination of at least one or more. The amount of solvent used is sufficient to dissolve and disperse the positive electrode active material, polyamide-based binder, and conductive material, taking into account the coating thickness and manufacturing yield of the slurry.

[0132]

[0133] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and includes, for example, conductive materials in the form of dots, lines, or plates. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0134]

[0135] The above dispersant may be an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone, which may be selectively used as needed.

[0136]

[0137] The positive electrode slurry composition according to the present invention may have a solid content of 50 wt% to 80 wt%, preferably 60 wt% to 70 wt%, and more preferably 65 wt% to 70 wt%, based on the total weight of the positive electrode slurry composition. For example, when the positive electrode slurry composition includes a solid content of 50 wt% to 80 wt% based on the total weight of the positive electrode slurry composition, when the solid content of the positive electrode slurry composition is less than 50 wt% based on the total weight of the positive electrode slurry composition, it is impossible to manufacture a thick electrode having a predetermined thickness or more, and when it is desired to manufacture a thick electrode, the number of current collectors must be increased, which may increase the cost during cell manufacturing. Conversely, if the solid content of the positive electrode slurry composition exceeds 80 wt% based on the total weight of the positive electrode slurry composition, it is difficult to uniformly coat the slurry composition on the current collector, so separate equipment must be used to disperse the slurry composition on the current collector, or the slurry composition must be coated on another support and then transferred to the current collector, which also raises concerns about increased costs.

[0138]

[0139] The positive electrode slurry composition according to the present invention may be manufactured in the atmosphere, and when the lithium transition metal oxide containing nickel included in the positive electrode slurry composition reacts with moisture included in the atmosphere to form a hydroxyl group, even if the pH increases, gelation of the positive electrode slurry composition may be suppressed by including the polyamide-based binder as described above, and accordingly, the viscosity of the positive electrode slurry composition may not increase.

[0140]

[0141] Specifically, the positive electrode slurry composition prepared by mixing the lithium transition metal oxide, the polyamide-based binder, and the conductive material may have a difference in initial viscosity and viscosity after being left in a harsh environment of 30% or more, 50% or more, specifically 80% to 100% relative humidity for 7 days, within 20%, and specifically the difference in viscosity may be within 15%, and more specifically within 10%. At this time, the viscosity is measured at 25°C and 12 rpm using a Brookfield B-type viscometer.

[0142] That is, even when the positive electrode slurry composition according to the present invention is prepared and left for 7 days or more in a harsh environment with a relative humidity of 80% or more, specifically, a relative humidity of 80% to 100%, the viscosity hardly increases compared to immediately after the positive electrode slurry composition is prepared, so that when preparing the positive electrode using this, the positive electrode layer can be maintained in a more uniform state, thereby preventing problems such as a decrease in positive electrode capacity and a decrease in output.

[0143] The environment with a relative humidity of 80% or higher refers to an environment with a relative humidity of 80% or higher, regardless of a specific temperature, as long as the temperature is typically acceptable during the manufacturing process of the positive electrode slurry composition. For example, the relative humidity may be a relative humidity measured at a typical manufacturing temperature of the positive electrode slurry composition, and the temperature may be room temperature, specifically 25°C.

[0144]

[0145] Cathode for secondary batteries

[0146] Meanwhile, the present invention provides a positive electrode for a lithium secondary battery, comprising a positive electrode current collector and the positive electrode slurry composition applied to at least one surface of the positive electrode current collector.

[0147] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, conductive polymer, carbon-coated paper (carbon paper), calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, conductive polymer, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, a wire, a pin, etc.

[0148] The above-described positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material slurry composition is used. Specifically, the positive electrode can be manufactured by applying (coating) the above-described positive electrode slurry composition onto a positive electrode current collector, followed by drying and rolling. For example, the drying of the electrode can be performed at a temperature range of 60°C to 130°C.

[0149] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling the resulting film from the support, and laminating the resulting film onto a positive electrode current collector.

[0150]

[0151] lithium secondary battery

[0152] In addition, the present invention can manufacture an electrochemical device including the positive electrode. The electrochemical device may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0153] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0154]

[0155] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0156] The negative electrode 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., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0157] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0158] As the 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 alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, 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.

[0159] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0160]

[0161] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0162]

[0163] The negative electrode active material layer may be manufactured by, for example, applying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, a binder, and a conductive material in a solvent on a negative electrode current collector and drying the composition, or by casting the composition for forming a negative electrode active material layer on a separate support and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0164]

[0165] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0166]

[0167] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0168] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0169] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0170] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the above lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2 can be used. It is recommended that the concentration of the lithium salt be within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0171] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0172]

[0173] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0174] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0175] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0176] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0177] 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0178]

[0179] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0180]

[0181] <Example>

[0182] Example 1: Preparation of anode slurry composition

[0183] A polyamide polymer was prepared which contained 74.4 mol% of the repeating unit of the following chemical formula 1A among the total repeating units, 18.6 mol% of the repeating unit of the following chemical formula 1B, 7 mol% of the repeating unit of the following chemical formula 2A, and 0.2 mol% of the functional group content of the side chain.

[0184] [Chemical Formula 1A]

[0185]

[0186] [Chemical Formula 1B]

[0187]

[0188] [Chemical Formula 2A]

[0189] -[NH-(CH2)6-NHCO-(CH2)6-CO]-

[0190]

[0191] Li(Ni) 0.94 Co 0.03 Mn 0.03 )O2, the polyamide-based binder, and CNT as a conductive material were added to NMP as a solvent at a weight ratio of 96:3:1, and stirred at 1,500 rpm for 2 hours using a homo disper mixer at room temperature to prepare a positive electrode slurry composition. The solid content of the positive electrode slurry composition was 70 wt%.

[0192]

[0193] Example 2: Preparation of anode slurry composition

[0194] Li(Ni) 0.94 Co 0.03 Mn 0.03)O2, a polyamide-based binder, and CNT as a conductive agent were added in a weight ratio of 90:5:5, and a positive electrode slurry composition was prepared in the same manner as in Example 1. The solid content of the positive electrode slurry composition was 70 wt%.

[0195]

[0196] Example 3: Preparation of anode slurry composition

[0197] A positive electrode slurry composition was prepared in the same manner as in Example 1, except that a polyamide polymer containing 77.6 mol% of the repeating unit of Chemical Formula 1A, 19.4 mol% of the repeating unit of Chemical Formula 1B, 3 mol% of the repeating unit of Chemical Formula 2A, and having a side chain functional group content of 0.2 mol% was prepared and used as a polyamide-based binder. The solid content of the positive electrode slurry composition was 70 wt%.

[0198]

[0199] Comparative Example 1: Preparation of anode slurry composition

[0200] A positive electrode slurry composition was prepared in the same manner as in Example 1, except that PVDF was used as a binder. The solids content of the positive electrode slurry composition was 70 wt%.

[0201]

[0202] Comparative Example 2: Preparation of anode slurry composition

[0203] A positive electrode slurry composition was prepared in the same manner as in Example 1, except that a polyamide polymer containing 68 mol% of the repeating unit of Chemical Formula 1A, 17 mol% of the repeating unit of Chemical Formula 1B, 15 mol% of the repeating unit of Chemical Formula 2A, and having a side chain functional group content of 0.2 mol% was prepared and used as a polyamide-based binder. The solid content of the positive electrode slurry composition was 70 wt%.

[0204]

[0205] Comparative Example 3: Preparation of anode slurry composition

[0206] A positive electrode slurry composition was prepared in the same manner as in Example 1, except that a polyamide polymer containing 80 mol% of the repeating unit of Chemical Formula 1A, 20 mol% of the repeating unit of Chemical Formula 1B, and having a side chain functional group content of 0.2 mol% was prepared and used as a polyamide-based binder. The solid content of the positive electrode slurry composition was 70 wt%.

[0207]

[0208] Comparative Example 4: Preparation of anode slurry composition

[0209] A polyamide polymer containing 74.4 mol% of the repeating unit of Chemical Formula 1A, 18.6 mol% of the repeating unit of Chemical Formula 1B, 7 mol% of the repeating unit of Chemical Formula 2A, and 0 mol% of the functional group content of the side chain was prepared. A positive electrode slurry composition was prepared in the same manner as in Example 1, except that this was used as a polyamide-based binder. The solid content of the positive electrode slurry composition was 70 wt%.

[0210]

[0211] Comparative Example 5: Preparation of anode slurry composition

[0212] A polyamide polymer containing 74.4 mol% of the repeating unit of Chemical Formula 1A, 18.6 mol% of the repeating unit of Chemical Formula 1B, 7 mol% of the repeating unit of Chemical Formula 2A, and 2 mol% of the functional group content of the side chain was prepared. A positive electrode slurry composition was prepared in the same manner as in Example 1, except that this was used as a polyamide-based binder. The solid content of the positive electrode slurry composition was 70 wt%.

[0213]

[0214] Experimental example

[0215] (1) Measurement of binder adsorption amount for positive electrode active material

[0216] Each of the polyamide-based binders manufactured in Examples 1 and 2 and Comparative Examples 2 to 5 and PVdF was prepared in an amount of 2 g. Each of the binders was prepared by mixing 2 g of PVdF and Li(Ni 0.95 Co 0.03 Mn 0.02 )O2100 g and 40 g of solvent (NMP) were each added and mixed and dispersed using a homo disper mixer at room temperature to prepare each slurry.

[0217] Each slurry was taken in an amount of 5 g and centrifuged at 20,000 rpm for 30 minutes using a centrifuge (Supra R30, Hanil Scientific Inc.) to separate each slurry into a solid and a supernatant.

[0218] Each supernatant obtained as described above was taken and dried in a 120°C oven for 24 hours to obtain a polymer film. The weight of the polymer film was measured to calculate the solid content.

[0219] [Formula 1]

[0220] Solid content (weight %) = polymer film (g) / supernatant added (g) × 100

[0221] The residual amount of binder in the supernatant was calculated using the content of the above solid content, and then subtracted from the amount of binder introduced to obtain the content (mg / g) of adsorbed binder based on 1 g of positive electrode active material.

[0222]

[0223] (2) Viscosity measurement of the positive electrode slurry composition

[0224] The positive electrode slurry compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were measured using a Rheometer MCR 302 from Anton Paar, and the viscosity at 25°C was measured at a shear rate of 2.5 (1 / s). In addition, each of these was stored at 25°C, and the viscosity at 25°C was measured two days later. The measured viscosity results are shown in Table 1 below.

[0225] In addition, the change in viscosity over time of the positive electrode slurry compositions manufactured in Example 1 and Comparative Example 1 is shown in Figure 1.

[0226] Additionally, the viscosity of the positive electrode slurry compositions prepared in Examples 1 and 2 and Comparative Example 1 was additionally measured after 7 days, and the viscosity change rate after 7 days was calculated. The results are shown in Table 2 below.

[0227]

[0228] (3) Adhesion measurement and coating evaluation

[0229] The positive electrode slurry prepared in Examples 1 to 3 and the positive electrode slurry prepared in Comparative Examples 1 to 5 were applied to a positive electrode current collector (Al thin film) having a thickness of 15 μm (25 mg / cm 2 ), drying and roll pressing were performed, and the positive electrode was manufactured.

[0230] The manufactured anodes were each cut to a size of 150 mm in length and 20 mm in width, and the electrode surfaces were attached to a 75 mm in length and 25 mm in width slide glass using double-sided tape in the longitudinal direction. That is, the slide glass was attached to an area corresponding to half of the longitudinal direction of the anode. Then, a roller with a load of 2 kg was rubbed 10 times to ensure that the double-sided tape was evenly attached, thereby preparing an evaluation sample. The slide glass part of the evaluation sample was fixed to the sample stage of a universal testing machine (UTM) (LF Plus, LLOYD), and the half of the anode without the slide glass was connected to the load cell of the UTM equipment. The load cell was moved up to 50 mm at a speed of 100 mm / min, and the load applied to the load cell was measured. At this time, the minimum value of the load measured in the section of 20 mm to 40 mm during the moving section was measured as the electrode adhesive force (gf / 20mm) of each sample. After evaluating each pole a total of 5 times, the average values ​​are shown in Table 1 below.

[0231] In addition, the coating properties of the positive electrode slurry were evaluated when applying the positive electrode slurry to the positive electrode current collector during the positive electrode manufacturing process. If the positive electrode slurry coating was performed smoothly, it was evaluated as good. If the positive electrode slurry coating was possible but unevenness occurred in the positive electrode active material layer, it was evaluated as uneven. If the positive electrode slurry coating was difficult, it was evaluated as unacceptable.

[0232]

[0233] Aromatic and aliphatic mole ratio of the positive electrode slurry binder Functional group content (mol%) Binder content in the positive electrode slurry (wt%) Binder adsorption amount (mg / g) Binder molecular weight (g / mol) Initial slurry viscosity (cP) Slurry viscosity after 2 days (cP) Electrode coating Adhesion (gf / 20mm) Example 193:70.230.8700,0006,0006,100 Good 32 Example 293:70.250.8700,00012,00015,000 Good 64 Example 397:30.230.7700,0007,5007,700 Good 25 Comparative Example 1--39.06,1007,500 Good 28 Comparative Example 285:50.230.1700,0003,000Phase separation is not possible, cannot be measured, comparison example 3100:00.231.2700,0009,00012,000Unevenness is not possible, comparison example 493:7030.3700,0006,0005,900Good12Comparison example 593:7231.5700,00012,00024,500Unevenness16

[0234] Aromatic and aliphatic mole ratio of binder Functional group content Binder content in cathode slurry (wt%) Initial slurry viscosity (cP) Slurry viscosity after 2 days (cP) Viscosity change after 7 days (%) Example 1 93:70.2 3 6,000 6,100 7 Example 2 93:70.2 5 12,000 15,000-5 Comparative Example 1 PVdF 3 6,100 7,500 1,700 (after 4 days)

[0235] The positive electrode slurry compositions of Examples 1 to 3 showed a small increase in slurry viscosity over time, good electrode coating properties, and excellent adhesive strength.

[0236] On the other hand, the viscosity of the positive electrode slurry composition of Comparative Example 1 increased significantly after a certain period of time.

[0237] The positive electrode slurry of Comparative Example 2 had a relatively low content of aromatic structures of the polyamide polymer contained in the polyamide binder. The positive electrode slurry of Comparative Example 2 experienced phase separation after 2 days, and electrode coating was impossible due to the phase separation.

[0238] The positive electrode slurry of Comparative Example 3 did not contain an aliphatic structure in the polyamide polymer contained in the polyamide binder, and thus, unevenness occurred during electrode coating, resulting in low coatability, and thus, it was not possible to form a positive electrode active material layer to a degree appropriate for measuring electrode adhesion.

[0239] The positive electrode slurry of Comparative Example 4 did not contain a functional group included in the side chain, and thus exhibited low adhesive strength due to the lack of a functional group.

[0240] The positive electrode slurry of Comparative Example 5 had a large content of functional groups included in the side chain, and due to the large content of functional groups, the viscosity increased significantly over time. In addition, unevenness occurred during electrode coating, resulting in low coatability. Accordingly, the degree of increase in adhesive strength was insufficient compared to the content of functional groups.

[0241]

[0242] Meanwhile, when the amount of binder adsorbed to the positive electrode active material was measured, the polyamide-based binder included in the positive electrode slurries of Examples 1 to 3 showed values ​​of 0.7 mg / g and 0.8 mg / g, respectively, but the binder used in Comparative Example 1, PVdF, was 9.0 mg / g. It can be predicted that as the amount of binder adsorbed to the positive electrode active material increases, the change in viscosity of the positive electrode active material slurry over time will be greater, and this result is consistent with the viscosity increase rate of 1,700% after 4 days in Comparative Example 1.

[0243] In the case of Example 1, when measuring the change in viscosity over 7 days, there was an increase in the viscosity of the positive electrode slurry composition within about 7%, and in the case of Example 2, the viscosity of the slurry increased after 2 days, but decreased after 7 days, so there was no clear trend of viscosity increase over time.

[0244] On the other hand, in the case of Comparative Example 1, the viscosity increase of the positive electrode slurry composition was approximately 23% after 2 days, but the viscosity increase of the positive electrode slurry composition reached 1,700% after 4 days, confirming that the viscosity increased significantly over time. When the viscosity increased in this way, transport or uniform coating of the positive electrode slurry was impossible, and therefore, measurement of viscosity changes was stopped thereafter.

Claims

Lithium transition metal oxide containing nickel; and Contains a polyamide binder, The above polyamide-based binder includes a polyamide-based polymer having an aliphatic structure and an aromatic structure in the main chain and at least one selected from the group consisting of a carbonyl group, a carboxyl group, and an ester group as a functional group in the side chain. The polyamide polymer contains 90 to 99 mol% of the aromatic structure relative to the total mole number of repeating units of the polymer, A positive electrode slurry composition, wherein the polyamide-based polymer contains the functional group in an amount of 0.005 mol% to 1 mol% based on the total mole number of the polymer. In the first paragraph, A positive electrode slurry composition, wherein the polyamide polymer comprises 1 mol% to 10 mol% of the aliphatic structure relative to the total mole number of repeating units of the polymer. In the first paragraph, The above aromatic structure is a positive electrode slurry composition comprising a repeating unit represented by the following chemical formula 1: [Chemical Formula 1] -[NH-A1-NHCO-A2-CO]- In the above chemical formula 1, A1 and A2 are each independently a divalent organic group containing an aromatic ring. In the third paragraph, The above A1 and A2 are each independently one of the following chemical formulas 1-1 to 1-5: a cathode 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, * represents a binding site. In the first paragraph, The aliphatic structure is a positive electrode slurry composition comprising a repeating unit represented by 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 a divalent aliphatic organic group. In paragraph 5, The positive electrode slurry composition wherein the above B1 and B2 are each independently an alkylene group having 2 to 50 carbon atoms. In the first paragraph, The above polyamide-based polymer is a positive electrode slurry composition having a weight average molecular weight of 100,000 g / mol to 1,000,000 g / mol. In the first paragraph, The above polyamide-based binder is a positive electrode slurry composition having an adsorption amount for a lithium transition metal oxide containing nickel of 6.5 mg / g or less. In the first paragraph, The above positive electrode slurry is a positive electrode slurry composition that does not contain polyvinylidene fluoride (PVdF). In the first paragraph, The above positive electrode slurry composition further comprises a conductive material. In paragraph 10, A positive electrode slurry composition comprising, based on the total weight of the total solid content, 85 to 99.6 wt% of the lithium transition metal oxide, 0.1 to 10 wt% of the conductive material, and 0.1 to 10 wt% of the polyamide-based binder. In the first paragraph, The above lithium transition metal oxide is a positive electrode slurry composition in which the content of Ni among transition metals is 50 mol% or more. In the first paragraph, The above lithium transition metal oxide is represented by the following chemical formula 3, a positive electrode slurry composition: [Chemical Formula 3] Li 1+x (Ni a Co b Mr c ) 1-x O2 In the above chemical formula 3, -0.3≤x≤0.3, 0.5≤a<1, 0 <b≤0.3, 0<c≤0.3, 및 a+b+c=1임. In the first paragraph, The above positive electrode slurry composition is a positive electrode slurry composition having a solid content of 50 wt% to 80 wt% based on the total weight of the positive electrode slurry composition. In the first paragraph, The above positive electrode slurry composition is a positive electrode slurry composition in which the difference between the initial viscosity and the viscosity after being left in an environment with a relative humidity of 30% or higher for 7 days is within 20%. anode current collector, and A positive electrode for a lithium secondary battery comprising a positive electrode slurry composition according to any one of claims 1 to 15, applied to at least one surface of the positive electrode current collector. A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to Article 16.

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