Powdery rubber containing lithium stearate, and their use as an electrode binder

Abstract

The present invention relates to a powdered rubber containing a lithium salt as an anti-dusting agent and their use as binders in battery applications.

Description

Technical Field

[0001] The present invention generally relates to a binder for an electrode composition for a cathode of a lithium ion battery cell, a cathode slurry composition comprising the electrode composition, a cathode, a process for making the cathode, and a lithium ion battery having one or more cells incorporating the cathode. More particularly, the present invention relates to powdered rubbers containing lithium salts as anti-dusting agents and their use as binders in battery applications.

Background Art

[0002] A lithium ion battery consists of at least two conductive Coulomb electrodes of opposite polarities, namely a negative electrode or anode (generally made of graphite) and a positive electrode or cathode, with a separator disposed between the electrodes, the separator being an electrical insulator impregnated with a non-protic electrolyte based on Li + ion cations and retaining ionic conductivity. The electrolytes used in these lithium ion batteries typically are lithium salts such as LiPF 6 、LiAsF 6 、LiCF 3 SO 3 、or LiCO 4It consists of, and they are dissolved in a mixture of non-aqueous solvents such as: acetonitrile, tetrahydrofuran, or more often, carbonates such as ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, vinylene carbonate or propylene carbonate. Thanks to the active material of the cathode of the lithium-ion battery, lithium ions can enter and exit this cathode in a reversible discharge / uptake, and the higher the mass fraction of this active material in that cathode, the greater its capacity. Furthermore, the cathode must contain a conductive compound such as carbon black to impart sufficient mechanical cohesion, and a polymer binder required for good adhesion to its current collector foil as well. Therefore, the binder must maintain electrochemical stability and high flexibility while interacting with both the active material and the conductor. Therefore, the lithium-ion battery is based on the reversible exchange of lithium ions between the anode and the cathode during charging and discharging of the battery, and due to the physical properties of lithium, it has an extremely low weight, and such a battery has a high energy density.

[0003] The cathode of a lithium-ion battery is often manufactured using a process that successively includes the following steps: dissolving and / or dispersing a polymer binder, an active material, a conductive material and optionally a dispersant in a solvent, applying the cathode slurry composition thus obtained onto a current collector, and finally, evaporating this solvent.

[0004] The polymer binder is dispersed in the cathode slurry composition to improve the adhesion between the cathode active materials and the adhesion between the cathode active material and the current collector. At the same time, the polymer binder also helps in the dispersion of the conductive material. The electrolyte retention ability of the polymer binder improves the battery characteristics.

[0005] During the charge-discharge process, lithium ions are carried in and released from the active material. Due to the movement of such lithium ions, expansion and dilation of the cathode and anode materials may occur. Therefore, it is highly desirable to use an elastomeric material as a binder for a lithium ion battery to facilitate the movement of the active material during use and prevent delamination or cracking between layers from the current collector. Unfortunately, a highly crystalline binder may be too hard to move, so a rubber-type binder would be preferred.

[0006] The polymer binder is an important element of the electrode. By using it, it helps to disperse the active material and the conductive material in the cathode slurry composition, stabilizes those materials in the slurry during cathode preparation, and enables a smooth cathode with a well-defined pore structure. During use, the cohesiveness of the cathode and its adhesion to the current collector are extremely important and are strongly influenced by the type of binder used and the respective functional parts of the polymer. The adhesion-cohesion is a key property of the polymer binder, which determines the ultimate performance of the lithium ion battery, especially over a long period. A good polymer binder ensures a stable bond to the metal current collector along with a uniform dispersion of both the active material and the conductive material.

[0007] Many types of polymer binders are available, yet, a gradual shift is occurring from conventional electrodes that use PVDF (polyvinylidene fluoride), or fluorinated polymers based on mixtures of PVDF and various other polymer binders such as carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR) or polyacrylic acid (PAA), which are readily available in powder form and are easily compatible with cathodes used at high operating voltages. PVDF has been the most widely used polymer binder in lithium-ion batteries because it exhibits electrochemical stability, binding strength, and low thermal decomposability. Due to its high crystallinity level, PVDF imparts high resistance in typical electrolytes used in lithium-ion batteries. However, when flexible electrodes are required, or when the expansion / contraction process of the cathode active material occurs repeatedly during cycling, or even when higher adhesion is needed to reduce the total amount of binder in the cathode, the low flexibility of PVDF can cause the adhesion between the cathode active material and the conductive material to break, failing to meet the requirements at the cathode. Other fluorine-free polymer binders such as HNBR are still not available in various powder forms to enable easier battery processing.

[0008] Furthermore, there has been increased concern, particularly related to the risk of spontaneous ignition and the extreme heat generated by such ignition, as batteries sometimes catch fire. The fire itself and the heat it generates are a serious threat in many situations, but the risk of gases and smoke released from malfunctioning lithium-ion batteries can be an even greater threat in some environments, especially in confined environments equipped with battery energy storage systems, particularly where people are present, such as in aircraft, submarines, mines, spacecraft, or in the home. At high temperatures, components of the battery, such as the polyvinylidene fluoride (PVDF) binder in the electrodes, can generate toxic gases such as hydrogen fluoride (HF).

[0009] Furthermore, many studies have focused on optimizing cathode active materials for the purpose of improving the electrochemical performance of lithium-ion batteries. In contrast, in the past, the improvement of electrochemically inactive components of the cathode, such as polymer binders, has received relatively little attention. However, in recent years, in order to achieve long battery life, there has been a trend to develop new electrode compositions based on typical cathode active materials to replace polymer binders containing fluor, such as PVDF, with polymer binders having good adhesion and cohesion, and even high retention capacity.

[0010] (Patent Document 1) relates to a powdery mixture containing at least one nitrile rubber and at least one separating agent characterized by a specific average particle diameter. The mixture has a particularly low release level and is extremely suitable for manufacturing substances and components for indoor use. The powdery mixture with a low release level is obtained by using a specific molecular weight regulator. In that invention, various anti-dusting agents are described, but nevertheless, the use of any lithium-containing salts and the use of those powdered rubbers in various battery applications are not described.

[0011] (Patent Document 2) relates to a powdery mixture based on a specific pre-crosslinked nitrile rubber and at least one release agent, a method for producing a vulcanizable mixture, a vulcanizate from those powdery mixtures, and the use of the resulting vulcanizate, particularly in tire treads. By using a specific trifunctional acrylate crosslinking agent in the polymerization of nitrile rubber, it is possible to prepare powdered rubber from them using a standard anti-dusting agent as silica or a Ca salt. When those powdered nitrile rubbers are used as additives in tire treads, the wet grip performance of the tire can be improved. In that invention, various anti-dusting agents are described, but the use of any lithium-containing salts and the use of those powdered rubbers in various battery applications are not described.

[0012] (Patent Document 3) relates to an epoxy group-containing and fluorine-free copolymer, an electrode composition for a cathode of a cell of a lithium-ion battery including a cathode slurry composition containing the electrode composition, a cathode, a process for producing this cathode, and a lithium-ion battery having one or more cells incorporating this cathode. The epoxy group-containing and fluorine-free copolymer is either an NBR or an EVM polymer. There is no description of the conversion method to the powder of these rubbers or the use of powdered rubber in battery applications.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0014] However, a polymer binder in powder form that is suitable for the preparation of batteries and applicable to Li-containing cathode active materials in terms of showing improvement compared to a standard PVDF binder for the cathode of a cell of a lithium-ion battery has not yet been found.

[0015] Therefore, one object of the present invention is to provide an electrode composition for a cathode for a lithium-ion battery that overcomes some or all of the aforementioned drawbacks.

[0016] One object of the present invention is to provide an electrode composition that can be used to obtain a cathode having improved performance compared to a cathode containing a standard PVDF binder.

Means for Solving the Problem

[0017] Surprisingly, it has been found that lithium stearate as an anti-dusting agent for elastomers gives a free-flowing powdered rubber, which further exhibits good processability for electrodes and rapid solubility in typical battery solvents. Furthermore, the anti-dusting agent used in this way can function as a sacrificial anode to provide improved battery performance.

[0018] Through the screening and evaluation of various anti-dusting agents and their use in the preparation of powdered polymer binders, surprisingly, it has been found that lithium salts are novel anti-dusting agents for battery preparations. By using these lithium salts as novel anti-dusting agents, it is possible to obtain free-flowing polymer powders, and in battery application tests, higher adhesion was retained in the cathode sheet with various polymer powders compared to the standard PVDF binder. Furthermore, the discharging specific capacity attenuation was improved compared to polymer powders not of the present invention and even non-powdered rubber samples. It is considered that the added lithium salt can function as a sacrificial anode in the battery to improve the holding capacity.

[0019] The object of the present invention has been achieved by providing a powdery mixture of elastomers comprising the following: (1) (a) An ethylene-vinyl acetate copolymer (EVA) comprising the following repeating units: - Ethylene monomer, and - Vinyl acetate monomer (in an amount of at least 70% by weight based on the total weight of the ethylene-vinyl acetate copolymer); Or (b) A nitrile rubber copolymer (NBR) (which may optionally be carboxylated (XNBR)) containing the following repeating units: - An α,β-unsaturated nitrile monomer selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and mixtures thereof (preferably, in each case, in an amount of at least 15% by weight based on the total weight of the nitrile rubber copolymer) and - A conjugated diene monomer (which may optionally be fully hydrogenated or partially hydrogenated (HNBR) and is selected from the group consisting of 1,2-butadiene, 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene, and mixtures thereof); And (2) An antidusting agent containing lithium stearate.

[0020] In the context of the present invention, the terms "pulverulent" and "powderous", preferably "free-flowing powderous", can be used as synonyms.

[0021] In the context of the present invention, the terms "antidusting agent" and "separating agent" can be used as synonyms and refer to a powdery mixture for avoiding the aggregation of individual elastomer particles.

[0022] Preferably, the powdery mixture preferably has a particle size distribution D90 of at least 100 μm, more preferably 200 μm to 750 μm, determined using a laser diffuser and the Fraunhofer approximation.

[0023] The powdery mixture is preferably fluorine-free.

[0024] The nitrile rubber copolymer (b) is preferably carboxylated nitrile rubber (XNBR).

[0025] The ethylene-vinyl acetate copolymer (a) or its nitrile rubber copolymer (b) preferably has a Mooney viscosity (ML(1+4)100°C) of 25 Mooney units (MU) or more, more preferably 28 Mooney units (MU) to 120 Mooney units (MU), as measured at 100°C by means of a shear disc viscometer in accordance with DIN 53523 / 3 or ASTM D 1646.

[0026] Lithium stearate is preferably present in an amount of at least 3% by weight, more preferably 3% by weight to 60% by weight, even more preferably 5% by weight to 40% by weight, and still more preferably 5% by weight to 20% by weight, based on the total weight of the powder mixture in each case.

[0027] Lithium stearate preferably functions as an anti-dusting agent.

[0028] The powder mixture preferably does not contain an anti-dusting agent other than lithium stearate.

[0029] However, in another preferred embodiment, the powder mixture contains at least one anti-dusting agent in addition to lithium stearate.

[0030] Those skilled in the art can obtain suitable copolymers and lithium stearate. For example, suitable copolymers are supplied under the following trade names: Levapren® 900, Therban® XT, Therban® AT LT2004VP, Therban® LT1707VP, Therban® 3407, Nanoprene® M20VP, Therban® 4307, Perbunan® 3945, Nanoprene® M20VP, and Krynac® X146. Similarly, methods for manufacturing and measuring suitable copolymers are available to those skilled in the art (see, for example, European Patent No. 3 283 538, European Patent No. 3 902 855, and European Patent No. 3 900 086).

[0031] The term "copolymer" encompasses polymers having two or more monomer units. In one embodiment of the present invention, each copolymer is derived, for example, solely from monomers of the above types. The term "copolymer" similarly encompasses, for example, further terpolymers or quaterpolymers derived from monomers of the above types and at least one additional monomer unit.

[0032] Preferably, those monomers are statistically distributed over the polymer chains of the copolymers used in the present invention.

[0033] Preferably, the fully hydrogenated nitrile rubber copolymer (b) contains less than 1% of the remaining double bonds of the fully unsaturated copolymer (b). Preferably, the partially hydrogenated nitrile rubber copolymer (b) contains 1% or more of the remaining double bonds of the fully unsaturated copolymer (b).

[0034] In a second aspect, the present invention relates to a cathode slurry composition comprising a powdery mixture according to the present invention, at least one cathode active material, at least one conductive material, and at least one solvent.

[0035] In a third aspect, the present invention relates to a cathode including a current collector and a cathode active material layer, where the cathode active material layer contains the powdery mixture and the conductive material in the present invention.

[0036] In a fourth aspect, the present invention relates to a lithium-ion battery including an anode, a cathode according to the present invention, a separator, and at least one cell including an electrolyte based on a lithium salt and an organic solvent.

[0037] The peel strength of the cathode sheet of the lithium-ion battery is preferably at least 340 N / m when measured according to the experimental section of the present application.

[0038] In a fifth aspect, the present invention relates to the use of the powdery mixture in the present invention as a binder in an electrode composition for a cathode of a cell of a battery.

Mode for Carrying Out the Invention

[0039] Additional monomer units Copolymers (a), (b), and (c) may contain at least one additional monomer unit in addition to the above monomer units. Examples of additional monomer units are defined below.

[0040] Preferred examples of the additional epoxy group-containing monomer are selected from the group consisting of: 2-ethylglycidyl acrylate, 2-ethylglycidyl methacrylate, 2-(n-propyl)glycidyl acrylate, 2-(n-propyl)glycidyl methacrylate, 2-(n-butyl)glycidyl acrylate, 2-(n-butyl)glycidyl methacrylate, glycidyl methyl acrylate, glycidyl methyl methacrylate, glycidyl acrylate, glycidyl methacrylate, (3’,4’-epoxyheptyl)-2-ethyl acrylate, (3’,4’-epoxyheptyl)-2-ethyl methacrylate, 6’,7’-epoxyheptyl acrylate, 6’,7’-epoxyheptyl methacrylate, allyl glycidyl ether, allyl 3,4-epoxyheptyl ether, 6,7-epoxyheptyl allyl ether, vinyl glycidyl ether, vinyl 3,4-epoxyheptyl ether, 3,4-epoxyheptyl vinyl ether, 6,7-epoxyheptyl vinyl ether, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, and 3-vinylcyclohexene oxide.

[0041] Most preferably, the epoxy group-containing monomer is (alkyl)glycidyl acrylate, preferably glycidyl acrylate and / or glycidyl methacrylate.

[0042] Furthermore, examples of the copolymer used in the present invention further include repeating units of one or more additional copolymerizable monomers known in the art, such as: α,β-unsaturated (preferably monounsaturated) monocarboxylic acids, their esters and amides, α,β-unsaturated (preferably monounsaturated) dicarboxylic acids, their monoesters or diesters, and further anhydrides or amides of each of the above α,β-unsaturated dicarboxylic acids, vinyl esters, vinyl ketones, vinyl aromatic compounds, α-monoolefins, vinyl monomers having a hydroxyl group, and carbon monoxide.

[0043] As the α,β-unsaturated monocarboxylic acid, it is preferable to use acrylic acid and methacrylic acid.

[0044] It is also possible to use esters of α,β-unsaturated monocarboxylic acids, preferably their alkyl esters and alkoxyalkyl esters. Alkyl esters of α,β-unsaturated monocarboxylic acids, especially C 1 ~C 18 -alkyl esters are preferred. Particularly preferred are the following: alkyl esters of acrylic acid or methacrylic acid, especially C 1 ~C 18 -alkyl esters, especially methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. Further preferred examples include: alkoxyalkyl esters of α,β-unsaturated monocarboxylic acids, particularly preferably alkoxyalkyl esters of acrylic acid or methacrylic acid, especially C 2 ~C 14- Alkoxyalkyl esters, and very particularly preferably methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and methoxyethoxyethyl (meth)acrylate; butoxydiethylene glycol methacrylate, polyethylene glycol acrylate, and polyethylene glycol methacrylate. It is also possible to use a mixture of an alkyl ester such as those listed above and an alkoxyalkyl ester in the form such as those listed above. It is also possible to use hydroxyalkyl acrylates and hydroxyalkyl methacrylates in which the number of carbon atoms of the hydroxyalkyl group therein is 1 to 12, preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 3-hydroxypropyl acrylate. Furthermore, it is also possible to use esters of α,β-unsaturated carboxylic acids containing an amino group, for example, dimethylaminomethyl acrylate and diethylaminoethyl acrylate, N-(2-hydroxyethyl)acrylamide, N-(2-hydroxymethyl)acrylamide, urethane methacrylate, and diethylaminoethyl acrylate.

[0045] As further copolymerizable monomers, it is also possible to use α,β-unsaturated dicarboxylic acids, preferably maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and mesaconic acid.

[0046] Anhydrides of α,β-unsaturated dicarboxylic acids, preferably maleic anhydride, itaconic anhydride, citraconic anhydride, and mesaconic anhydride can also be used.

[0047] Monoesters or diesters of α,β-unsaturated dicarboxylic acids can also be used. These monoesters or diesters of α,β-unsaturated dicarboxylic acids may be, for example, the following: alkyl, preferably C 1 ~C 10- mono - or diesters of alkyl, especially ethyl, n - propyl, isopropyl, n - butyl, tert - butyl, n - pentyl, or n - hexyl, alkoxyalkyl, preferably C 2 ~C 12 - alkoxyalkyl, particularly preferably C 3 ~C 8 - mono - or diesters of alkoxyalkyl, hydroxyalkyl, preferably C 1 ~C 12 - hydroxyalkyl, particularly preferably C 3 ~C 8 - mono - or diesters of hydroxyalkyl, cycloalkyl, preferably C 5 ~C 12 - cycloalkyl, particularly preferably C 6 ~C 12 - mono - or diesters of cycloalkyl, alkylcycloalkyl, preferably C 6 ~C 12 - alkylcycloalkyl, particularly preferably C 7 ~C 10 - mono - or diesters of alkylcycloalkyl, aryl, preferably C 6 ~C 14 - mono - or diesters of aryl (the diesters may be mixed esters in each case).

[0048] As the α,β - unsaturated dicarboxylic acid diesters, similar diesters based on the above - mentioned mono - ester groups can be used, and their ester groups may be chemically different ester groups.

[0049] As the vinyl esters, for example, vinyl propionate and vinyl butyrate can be used.

[0050] As the vinyl ketones, for example, methyl vinyl ketone and ethyl vinyl ketone can be used.

[0051] As the vinyl aromatic compound, for example, styrene, α-methylstyrene and vinyltoluene can be used.

[0052] As the α-monoolefin, for example, C 2 ~C 12 -olefins such as propylene, 1-butene, 4-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene can be used.

[0053] Possible further copolymerizable monomers further include free radical polymerizable compounds containing at least two ethylenic double bonds per molecule. Therefore, such monomers provide a certain degree of pre-crosslinking to the copolymers (a), (b) or (c). Examples of compounds having a plurality of unsaturations include the following: acrylates, methacrylates, or itaconates of polyols, for example, ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,2-propanediol diacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol diacrylate, trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerol diacrylate and triacrylate, pentaerythritol di-, tri- and tetra-acrylate, or di-, tri- and tetra-methacrylate, dipentaerythritol tetra-, penta- and hexa-acrylate or tetra-, penta- and hexa-methacrylate or tetra-, penta- and hexa-itaconate, sorbitol tetraacrylate, sorbitol hexamethacrylate, 1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, 2,2-bis(4-hydroxyphenyl)propane, polyethylene glycol, or diacrylates or dimethacrylates of oligoesters or oligourethanes having terminal hydroxyl groups. It is also possible to use the following as monomers having a plurality of unsaturations: acrylamides, for example, methylenebisacrylamide, hexamethylene-1,6-bisacrylamide, diethylenetriamine trismethacrylamide, bis(methacrylamide-propoxy)ethane, or 2-acrylamidoethyl acrylate. Examples of vinyl and allyl compounds having a plurality of unsaturations include the following: divinylbenzene, ethylene glycol divinyl ether, diallyl phthalate, allyl methacrylate, diallyl maleate, triallyl isocyanurate, or triallyl phosphate.

[0054] Acetatoacetoxyethyl methacrylate is yet another example of a preferred additional monomer.

[0055] The total ratio of the additional copolymerizable monomers to be incorporated is less than 35% by weight, preferably less than 25% by weight, particularly preferably less than 20% by weight, and especially preferably less than 15% by weight, based on the copolymer (a), (b) or (c). The total content of the monomers and the additional monomers used in some cases as described above is 100% by weight in total, based on the copolymer (a), (b) or (c).

[0056] Cathode active material The cathode active material in the present invention is preferably selected from the group of lithium-containing metal oxides such as the following (including layered lithium-containing metal oxides in some cases); LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , or LiNiMnCoO 2 , lithium manganese oxide such as, for example, LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , etc., lithium nickel manganese cobalt oxide such as, for example, Li w Ni x Mn y Co z O 2 , etc., lithium nickel cobalt aluminum oxide such as, for example, LiNiCoAlO 2 , etc., or even further, modified lithium nickel manganese cobalt such as, for example, Li 1+a Ni x Mn z Co y M w O 2[wherein, M may be at least one selected from the group consisting of aluminum (Al), copper (Cu), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), zirconium (Zr), zinc (Zn), tantalum (Ta), niobium (Nb), magnesium (Mg), boron (B), tungsten (W), and molybdenum (Mo), and a, x, y, z, and w each represent an atomic fraction of an independent element, where -0.5 ≦ a ≦ 0.5, 0 < x ≦ 1, 0 < y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1, and 0 < x + y + z ≦ 1], lithium titanate, for example, Li 4 Ti 5 O 12 and the like, lithium copper oxide, for example, Li 2 CuO 2 , vanadium oxide, for example, LiV 3 O 8 , LiFe 3 O 4 , or phosphate, for example, LiCoPO 4 or LiFePO 4 (which transfers electrons in the cathode).

[0057] In one preferred embodiment, the at least one cathode active material comprises a compound of Formula 1 below or lithium iron phosphate (LFP): Li 1+a Ni x Co y Mn z M w O 2 [Formula 1] [wherein, M may be at least one selected from the group consisting of aluminum (Al), copper (Cu), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), zirconium (Zr), zinc (Zn), tantalum (Ta), niobium (Nb), magnesium (Mg), boron (B), tungsten (W), and molybdenum (Mo), and a, x, y, z, and w each represent an atomic fraction of an independent element, where -0.5 ≦ a ≦ 0.5, 0 < x ≦ 1, 0 < y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1, and 0 < x + y + z ≦ 1).

[0058] In another preferred embodiment, the cathode active material may contain a nickel-rich lithium composite metal oxide such that in Formula 1, -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, 0 ≦ w ≦ 1, and y + z ≦ x.

[0059] In another preferred embodiment, the cathode active material contains LiNi 0.3 Mn 0.3 Co 0.3 O 2 、LiNi 0.6 Mn 0.2 Co 0.2 O 2 、LiNi 0.5 Mn 0.3 CO 0.2 O 2 、LiNi 0.7 Mn 0.15 CO 0.15 O 2 、or LiNi 0.8 Mn 0.1 Co 0.1 O 2 may be included, and any one of them or a mixture of two or more of them may be used.

[0060] Particularly preferred cathode active materials in the invention are lithium-nickel-cobalt-manganese-oxide (NMC), lithium iron phosphate (LFP), or lithium-nickel-cobalt-aluminum-oxide (NCA). Particularly preferred is lithium-nickel-cobalt-manganese-oxide (NMC).

[0061] Conductive material The cathode slurry composition contains at least one conductive material (hereinafter referred to as "conductive material"). Preferred conductive materials are selected from the group consisting of: carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black, natural and artificial graphite, expanded graphite, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powders, and carbon nanotubes, graphene, graphene oxide, and mixtures thereof. By including the conductive material, the electrical connection of the cathode active material can be improved, and the discharge rate characteristics can be improved.

[0062] In one preferred embodiment, the conductive material is present in the cathode slurry composition in an amount of 0.5 to 50% by weight based on the total solid weight of the cathode slurry composition.

[0063] Solvent The cathode slurry composition contains at least one solvent. The solvent is not particularly limited as long as the binder in the present invention can be (partially) dispersed or homogeneously dissolved, and water or an organic solvent can be used. Examples of the organic solvent include: cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as chlorobenzene, toluene, xylene, and cyclobenzene; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, cyclohexanone, methyl cyclohexane, and ethyl cyclohexane; chlorine-based aliphatic hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride; esters such as ethyl acetate, butyl acetate, γ-butyrolactone, and ε-caprolactone; acyl nitriles such as acetonitrile or propionitrile; ethers such as tetrahydrofuran or ethylene glycol diethyl ether; alcohols such as tert-butanol, glycerol, methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol, or ethylene glycol monomethyl ether; sulfones such as diethyl sulfone, ethyl methyl sulfone, or tetramethylene sulfone; nitriles such as malononitrile or succinonitrile; amides such as N-methylpyrrolidone (NMP), N-formylmorpholine, and N,N-dimethylformamide. Preferred solvents are methyl ethyl ketone, toluene, and N-methylpyrrolidone. Particularly preferred is N-methylpyrrolidone.

[0064] Method for producing a cathode slurry composition There is no particular limitation on the method for producing the cathode slurry composition used in the present invention, and it is produced by mixing the binder in the present invention with a cathode active material, a conductive material, and optionally further additives. By way of example and not limitation, as another method, the binder in the present invention is first mixed with a cathode active material, a conductive material, and optionally further additives, and then a solvent is added.

[0065] As long as the binder solution, the cathode active material, and the conductive material can be uniformly mixed, there are no particular restrictions on the mixing device, and methods of using mixing devices such as stirring type, shaking type, and rotating type can be mentioned. Furthermore, methods of using dispersion kneaders such as homogenizers, ball mills, sand mills, roll mills, planetary kneaders such as planetary mixers, or extruders can be mentioned.

[0066] Cathode (positive electrode) The cathode of the secondary battery of the present invention includes a current collector and a cathode active material layer. The cathode active material layer includes the electrode composition of the present invention and a conductive material, and may also include other components that are added as necessary in some cases. The cathode active material layer is formed on the current collector.

[0067] Current collector There is no particular limitation on the current collector as long as it is a substance having conductivity and electrochemical durability. From the viewpoint of heat resistance, it is preferable that the current collector is selected from the group consisting of the following: iron, copper, aluminum, nickel, sintered carbon, stainless steel, carbon-treated stainless steel, titanium, tantalum, gold, platinum, titanium or silver on its surface; an aluminum-cadmium alloy on its surface, a non-conductive polymer treated with a conductive substance; a conductive polymer, or a metal paste containing metal powders of Ni, Al, Au, Ag, Pd, Cr, Ta, Cu or Ba. Among these, aluminum is particularly preferable as the current collector of the cathode. The current collector may be formed in various shapes such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. There is no particular limitation on the shape of the current collector, and a sheet-shaped current collector having a thickness of about 0.001 to 0.5 mm is preferable, and more preferably a thickness of 3 to 500 μm. It is preferable that the current collector is previously subjected to a roughening treatment before use to enhance the adhesion strength with the cathode active material layer. Examples of the roughening treatment method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing of the cathode, a coated polishing cathode with abrasive grains fixed thereon, a grinding wheel, an emery buff, or a wire brush equipped with steel wire can be used. Further, an intermediate layer or a primer layer may be formed on the surface of the current collector to increase the adhesion strength and conductivity between the cathode active material layer and the current collector.

[0068] Process for manufacturing a cathode The present invention further relates to a process for manufacturing a cathode, for example, as defined above, which is characterized by including the following steps: (1) Dissolving the binder in the present invention in a solvent to form a binder solution; and (2) Mixing the binder solution from step (1) with the cathode active material, the conductive substance, and optionally further additives to form a cathode slurry composition; (3) Coating the cathode slurry composition from step (2) onto a current collector to form a cathode sheet; and (4) Drying the cathode sheet of step (3).

[0069] In an alternative embodiment, in steps (1) and (2), the binder, cathode active material, conductive material, and optionally further additives in the present invention are first mixed, and then a solvent is added. In one preferred embodiment, according to step (1), the binder in the present invention is first dissolved in a solvent.

[0070] Without limitation, in one preferred embodiment of the present invention, step (1) may be carried out by dissolving the binder in the present invention in a shaker at room temperature overnight. In one preferred embodiment of the present invention, the binder solution formed in step (1) has a concentration of 0.1 to 30% by weight, preferably 0.25 to 20% by weight, more preferably 0.5 to 15% by weight based on the total weight of the binder solution.

[0071] Without limitation, in one preferred embodiment of the present invention, step (2) may be carried out in a ball mill (including dry ball milling method, wet ball milling method, planetary ball milling method), or in a tumble mixer.

[0072] Without limitation, in one preferred embodiment of the present invention, step (3) may be carried out using a bar coater or a doctor blade, more preferably using a bar coater having a slit gap of 50 to 750 μm.

[0073] In one preferred embodiment of the present invention, step (4) may be carried out in an oven at a temperature of more preferably 50°C to 200°C, even more preferably 50°C to 150°C.

[0074] Although not necessarily limiting, in one preferred embodiment, after the drying step (4), the cathode sheet is calendered to adjust the areal density.

[0075] The cathode is punched out from the calendered cathode sheet.

[0076] Lithium ion battery The present invention further relates to a lithium ion battery including one or more cells containing the cathode of the present invention. The lithium ion battery according to the present invention includes at least one cell including an anode, a cathode as defined above, a separator, and an electrolytic solution based on a lithium salt and an organic solvent.

[0077] Electrolytic solution As the electrolytic solution for a lithium ion battery, an organic electrolytic solution can be used, in which a supporting electrolyte is dissolved in an organic solvent.

[0078] As the supporting electrolyte, a lithium salt is preferably used. Although there is no particular limitation on the lithium salt, for example, the following can be used: LiNO 3 , LiCl, LiBr, LiI, LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl4, LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi, (CF 3 SO 2 ) 2 , (C 2 F 5 SO 2 )NLi, lithium chloroborate, lithium tetraphenylborate, etc. Among these, LiPF 6 , LiClO 4 , CF3 SO 3 Li is preferred because they are easily soluble in organic solvents and exhibit a high degree of dissociation. Two or more of them can also be used simultaneously. When the supporting electrolyte has a higher degree of dissociation, the lithium ion conductivity becomes higher, and thus it is possible to control the lithium ion conductivity depending on the type of the supporting electrolyte.

[0079] Regarding the organic solvent used in the electrolyte for a lithium ion battery, there is no particular limitation as long as the supporting electrolyte can be dissolved therein. For example, the following can be used: carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), or methyl ethyl carbonate (MEC); esters such as γ-butyrolactone or methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. A mixed solvent thereof can also be used in the same manner. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. The lower the viscosity of the solvent used, the higher the lithium ion conductivity, so the lithium ion conductivity can be adjusted depending on the type of the solvent.

[0080] It is also possible to add a further additive to the electrolyte. A carbonate such as vinylene carbonate (VC) is preferred as the additive.

[0081] For the purpose of improving charge / discharge characteristics and flame retardancy, at least one additive selected from the group consisting of the following may be added to the electrolyte: pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, diglyme, benzene derivative, sulfur, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, or 2-methoxyethanol.

[0082] The concentration of the supporting electrolyte in the electrolyte for a lithium-ion battery is typically 0.01 to 30% by weight, preferably 0.05 to 20% by weight, and particularly preferably 0.1 to 15% by weight based on the total weight of the electrolyte. When the concentration of the supporting electrolyte is too high or too low, the ionic conductivity tends to decrease.

[0083] Separator As separators for lithium-ion batteries, known separators such as the following can be used; microporous films or non-woven fabrics containing aromatic polyamide resins or polyolefin-based polymers such as polyethylene or polypropylene. For example, the following can be mentioned; resins such as polyolefin type polymers (polyethylene, polypropylene, polybutene, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methacrylate copolymer, and polyvinyl chloride) and microporous films formed from their mixtures or copolymers; microporous films made of polyethylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimide amide, polyaramid, polycycloolefin, nylon or polytetrafluoroethylene; woven fabrics or non-woven fabrics woven from those polyolefin type fibers, and aggregates of insulating material particles. Similarly, it is also good if the separator is made of a porous substrate made of a mixture of inorganic particles and a polymer, or the separator has a porous coating layer formed on at least one surface of the porous polymer substrate and may contain inorganic particles and a binder polymer. Among these, microporous films formed from polyolefin type polymers are preferred because the thickness of the separator can be made thin as a whole, and by increasing the ratio of the active material in the battery, the capacity per unit volume can be increased.

[0084] The thickness of the separator is typically 0.01 to 300 μm, preferably 1 to 100 μm, more preferably 1 to 40 μm. Within this range, the resistance of the separator in the battery becomes lower, and the processability during battery formation becomes excellent.

[0085] In some cases, a gel polymer electrolyte may be applied on the separator to improve the stability of the cell. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

[0086] Anode (negative electrode) In addition to the anode active material, a binder and a conductive agent are selectively included in the anode active material layer. The anode active material layer may be prepared by coating a composition for forming an anode (selectively including a binder and a conductive agent in addition to the anode active material) on the anode current collector and drying the coated anode current collector, or by casting a composition for forming an anode on an independent support and then laminating a film separated from the support on the anode current collector. Examples of the current collector include those described for the cathode of a lithium-ion battery, and there is no particular limitation as long as the material has conductivity and electrochemical durability, but copper is preferred as the anode of a lithium-ion battery.

[0087] Anode active material Examples of the anode active material for the anode of a lithium-ion battery include the following: carbon materials such as amorphous carbon, natural graphite, artificial graphite, natural graphite, mesocarbon microbeads, and pitch-based carbon fibers; conductive polymers such as polyacene or polyaniline. As the anode active material, metals such as silicon, tin, zinc, manganese, iron, and nickel, their alloys, and oxides and sulfates of the above-mentioned metals or alloys can be used. In addition, the following can also be used in the same way: metals such as Si, Na, Al, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe, alloys of these metals; metal oxides such as LiCoO 2 , LiNiO 2 , LiMn2O 4 , MnO 2 , FeO 2 , V 2 O5 , TiO 2 , Li x Ni 0.5 Mn 1.5 O 4 , Li x Mn 0.5 Ni 0.5 O 2 , metal hydroxides, metal sulfides such as, LiVS 2 , LiTiS 2 , VS 2 or TiS 2 , metal phosphates such as, LiCoPO 4 , Li 3 V 2 PO 4 , LiTi 2 (PO 4 ) 3 , LiFePO 4 , thiophosphates such as, LiTi 2 (PS 4 ) 3 , composites of the above metals and carbon materials, and mixtures thereof; lithium, lithium alloys such as, LiC 6 , Li 13 Sn 5 , Li 9 Al 4 , Li 22 Si 5 or lithium-transition metal nitrides. As the anode active material, those obtained by attaching a conductive substance on the surface by a mechanical surface modification method can also be used in the same manner.

[0088] The content ratio of the anode active material in the anode active material layer is preferably 85 to 99.9% by weight, more preferably 90 to 99.75% by weight, based on the total weight of the anode active material layer. When using a metal such as Si, Na, Al, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe as the anode active material, the content can be up to 100%. By setting the content ratio of the anode active material within the above range, it can exhibit high capacity while showing flexibility and binding performance.

[0089] Among the anodes for lithium-ion batteries, in addition to the above-mentioned components, a solvent used in the above-mentioned cathode or an electrolyte additive having a function of suppressing the decomposition of the electrolyte may further be included. As long as they do not affect the battery reaction, there are no special restrictions on them.

[0090] Anode Binder As the binder for the anode of a lithium-ion battery, known substances can be used without special restrictions. Examples of such binders for lithium-ion batteries include the following: polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, lignin, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyvinyl alcohol, polyamideimide, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber derivatives or polyacrylonitrile derivatives; soft polymers such as acrylic soft polymers. They can be used alone or in combination of two or more of them.

[0091] The negative electrode for a lithium-ion battery can be manufactured in the same manner as in the case of the above-mentioned positive electrode.

[0092] Process for Manufacturing a Lithium-Ion Battery As a specific manufacturing method of a lithium-ion battery, the above-described cathode and anode are laminated via a separator, and then it is wound or bent according to the shape of the battery to fit into the battery case. Subsequently, the battery case is filled with an electrolyte and the case is sealed. Further, if necessary, by incorporating a foamed metal such as nickel sponge, an overcurrent protection element such as a fuse and a PTC element, and a lead plate, etc., it is also possible to prevent an increase in pressure and overcharge-overdischarge inside the battery. Examples of the shape of the battery include a coin shape, a button shape, a sheet shape, a cylindrical shape, a rectangular shape, and a flat shape.

[0093] The present invention will be described by the following non-limiting examples.

Example

[0094] The following raw materials were used:

[0095]

Table 1

[0096]

Table 2

[0097]

Table 3

[0098] Test method Acrylonitrile content The nitrogen content for measuring the acrylonitrile content in nitrile rubber (1) was measured by the Kjeldahl method according to DIN 53 625.

[0099] Mooney viscosity The value of the Mooney viscosity (ML1+4@100 °C) is measured at 100 °C in each case by means of a shear disc viscometer in accordance with DIN 53523 / 3 or ASTM D 1646. The MSR (Mooney stress relaxation) is measured at 100 °C in each case by means of a shear disc viscometer in accordance with ISO 289-4:2003(E).

[0100] Measurement of particle size: The particle size of the powdered sample was measured using a laser diffuser. The Fraunhofer approximation was applied to the sample, and the particle size distribution of the article was calculated and determined using a refractive index and an absorption rate of "1". As an output of the analysis, D90 was obtained from the volume histogram. D90 represents the diameter at which 90% of the distribution has a smaller particle size and 10% has a larger particle size.

[0101] Blocking tendency The blocking tendency of the powder was visually evaluated and evaluated using the following criteria: 1 = The sample does not block and has free flowability 2 = The sample blocks slightly and breaks apart when a little pressure is applied 3 = The sample shows slight blocking and adheres to each other, but can be broken apart with a gentle force 4 = The sample has a hard block and can only be separated when force is applied, and the fragments remain adhered to each other 5 = The sample cannot be separated into powdery particles

[0102] Solubility The samples were dissolved according to the following procedure and their solubility was evaluated using the following criteria. 1 wt% of the sample was placed in a predetermined solvent and shaken at room temperature at 150 rpm using an IKA shaker KS4000i control. After a predetermined time, the samples were visually evaluated. A = The sample does not dissolve B = The sample is starting to dissolve, but the particles are swelling and most of the sample remains undissolved. C = The sample is starting to dissolve, but undissolved particles remain. D = Most of the sample dissolves, but a small amount remains or there is partial cloudiness. E = The sample dissolves completely with no residue observed.

[0103] NMR The microstructure and comonomer content of each polymer were measured by means of 1H NMR (instrument: Bruker DPX 400, with XWIN - NMR 3.1 software, measurement frequency 400 MHz, solvent CDCl 3 3).

[0104] Evaluation method for peel strength The evaluation of peel strength was carried out according to ASTM D903. The cathode sheet was cut into test pieces with a width of 25 mm and a length of 175 mm. A 3M vinyl insulating tape was attached onto the surface of the coated cathode active material of the cathode sheet. The peel test was carried out for the test pieces using an Instron tensile testing machine, peeling at a speed of 100 mm / min in a 180 - degree direction. During the test, the peel force was recorded. The peel strength was calculated according to the following formula:

Equation

[0105] The average peel strength was calculated based on the data at displacements between 50 and 200 mm, and the average of three measurements was adopted as the peel strength value.

[0106] Evaluation method for discharge specific capacity The secondary battery manufactured in this way was charged at a rate of 0.2C at 23°C until the battery voltage reached 4.2V. Then, 20 minutes later, constant current discharge at a rate of 0.2C was carried out at 23°C until the battery voltage reached 2.75V. Then, charging and discharging of the coin cell secondary battery were performed in a constant current mode (CC mode, rate of 0.2C). Between each cycle, the cell was left as it was for 5 minutes. The discharge specific capacity of the secondary battery was calculated as the average value between 2 and 5 cycles.

[0107] Evaluation method for retention capacity For the coin cell secondary battery, charging and discharging were carried out for 30 cycles in a constant current mode (CC mode, rate of 0.2C). The retention capacity was determined as the ratio (unit: percent) of the discharge specific capacity after 30 cycles to the discharge specific capacity after 2 cycles.

[0108] Preparation of fully hydrogenated methacrylic acid acetoacetoxyalkyl containing acrylonitrile butadiene terpolymer C The following substances were used as received: Monomer units: acrylonitrile and acetoacetoxyethyl methacrylate (manufactured by Sigma-Aldrich), 1,3-butadiene (manufactured by INEOS). Fe(II)SO 4 Solution: In the premix solution, 0.986 g of Fe(II)SO was dissolved in 400 g of water. 4 ·7H 2 O and 2.0 g of Rongalit® C were included. EDTA: manufactured by Sigma-Aldrich, used as a complexing agent. Fatty acid: CAS 67701-08-8, used as an emulsifier for polymerization. Rosin acid: Na salt of disproportionated rosin acid, CAS 61790-51-0. t-DDM: molecular weight regulator, manufactured by Arlanxeo Deutschland GmbH. Trigonox® NT50, p-menthanehydroxide, manufactured by Akzo-Degussa. Initiator for emulsion polymerization. Diethylhydroxylamine: Polymerization terminator, CAS 3710-84-7. Antioxidants: Irganox® 1520 = 2-methyl-4,6-bis(octylsulfanylmethyl)phenol (BASF AG, Germany), Irganox® 1076 = n-octadecyl-β-(4-hydroxy-3,5-di-tert-butyl-phenyl)-propionate (BASF AG, Germany), and an equal mixture of Wingstay® L = poly(dicyclopentadiene-co-p-cresol) (Omnova, Italy). Monochlorobenzene anhydride (MCB), manufactured by VWR. Wilkinson catalyst (manufactured by Materia Inc.) and triphenylphosphine (manufactured by VWR) as hydrogenation catalysts.

[0109] The acetoxyalkyl group-containing fully hydrogenated acrylonitrile-butadiene terpolymer C (used as a base polymer for preparing powdered rubber in the following series of examples) was produced according to the following, but all raw materials are expressed in parts by weight based on 100 parts by weight of the monomer mixture in Table 1.

[0110] The acrylonitrile-butadiene terpolymer C was produced by a batch method in a 5 L autoclave equipped with a stirring system. In the autoclave batch, 1.25 kg of the monomer mixture and a total of 2.1 kg of water were used, and EDTA was used in an equimolar amount based on Fe(II). First, 1.9 kg of water was charged into the autoclave together with the emulsifier and purged with a nitrogen stream. Then, the destabilized monomer and t-DDM (tert-dodecyl mercaptan) as a molecular weight regulator were added, and the reactor was closed. After raising the temperature of the reactor contents to a predetermined temperature, Fe(II)SO 4Polymerization was initiated by adding a premix solution and para-menthane hydroperoxide (Trigonox® NT50). The progress of the polymerization was monitored by gravimetric analysis of the conversion rate. When the conversion rate described in Table 1 was reached, the polymerization was terminated by adding an aqueous solution of diethylhydroxylamine. Unconverted monomers and other volatile components were removed by means of steam distillation.

[0111] A 50% dispersion of the antioxidant was mixed with a dispersion of its acrylonitrile-butadiene terpolymer and adjusted to a solids content of 17.5% by weight. Thereafter, the dispersion thus obtained, containing an acryloyloxyalkyl group-containing acrylonitrile-butadiene terpolymer and an antioxidant, was gradually added to an aqueous solution of calcium chloride having a concentration of 0.34% by weight at 60 °C and a constant pH of 6 with vigorous stirring. The core coagulated terpolymer thus stabilized was washed with water at pH 6 and a temperature of 60 °C and dried in a vacuum oven for 16 hours.

[0112] According to Table 1, the hydrogenated acryloyloxyalkyl group-containing acrylonitrile-butadiene terpolymer C obtained after hydrogenation using a standard Ru-based hydrogenation catalyst in chlorobenzene had the performance described in Table 2. Spectra of the acryloyloxyalkyl group-containing acrylonitrile-butadiene rubber terpolymer before, during, and after the hydrogenation reaction were recorded with a Perkin Elmer spectrum 100FT-IR spectrometer. A solution of the acrylonitrile-butadiene rubber terpolymer in chlorobenzene was cast onto a KBr disk, dried, and a film for testing was formed. The conversion rate of the hydrogenation was determined by FT-IR analysis according to the ASTM D5670-95 method.

[0113]

Table 4

[0114]

Table 5

[0115] Preparation of powdered rubber In a beaker, the rubber was intimately mixed with a predetermined amount of a separating agent in each case and gradually added to a ZM 200 ultra-centrifugal mill (Retsch (registered trademark)). An annular sieve with an average mesh size of 0.25 mm was attached to the mill and it was operated at a speed of 10,000 rpm. During milling, the mill was cooled using liquid nitrogen. After milling, the powder was withdrawn from the milling chamber by means of a cyclone and collected. All the obtained powder was dried at 55 °C for 24 hours. The powder thus obtained was evaluated.

[0116] The powdered mixture according to the invention using lithium stearate as a separating agent preferably has an average particle diameter D(90) in the range of 0.05 mm to 3 mm, more preferably in the range of 0.08 mm to 2 mm, particularly in the range of 0.10 mm to 1.75 mm, and particularly preferably in the range of 0.10 mm to 1.5 mm.

[0117] The results of the powders of the polymers of the present invention and the comparative examples prepared are shown in Tables 3 to 6.

[0118] [Table 6]

[0119] [Table 7]

[0120] [Table 8]

[0121] [Table 9]

[0122]

Table 10

[0123]

Table 11

[0124] When lithium stearate is used as an anti-dusting agent, it can be seen that a free-flowing powder can be easily obtained. This applies to several types of elastomers. Compared with other free-flowing powders, Sample 16 (Levapren® 900, using silica as an anti-dusting agent) requires a larger amount of anti-dusting agent compared to Sample 1 (Levapren® 900, using lithium stearate), and furthermore, a powder having a larger particle size than the powder of the present invention was obtained. The same also applies when using Therban® XT as the base polymer, and even with a smaller amount of anti-dusting agent, a powder with a smaller particle size can be obtained.

[0125] Various powdery samples of the present invention and their respective base polymers were dissolved in NMP, and after 90 minutes, their solubility was evaluated. It can be seen that all the powdery samples of the present invention dissolve faster than the base polymer, bringing about an improvement in the productivity of the battery cell.

[0126]

Table 12

[0127]

Table 13

[0128] General method for manufacturing coin cells Step (1) - Dissolution: Dissolve a quantified amount of polymer in a solvent (NMP) overnight at room temperature in a shaker to form a binder solution (5 wt%).

[0129] Step (2) - Preparation of the cathode slurry composition: In a planetary ball mill, mix the binder solution from Step 1 with the active material (NMC111) and the conductive material (conductive carbon black, Super P) (grinding conditions: 28 Hz, 6 minutes, room temperature) to obtain a cathode slurry composition.

[0130]

Table 14

[0131] Weight ratio: NMC / polymer / NMP / Super P = 80 / 10 / 190 / 10 (polymer concentration in NMP = 5 wt%)

[0132] Step (3) - Fabrication of the cathode disk: Apply the cathode slurry composition onto a current collector (aluminum foil) using a bar coater at a coating speed of 2.8 mm / sec to form a cathode sheet. Adjust the coater slit gap of the coating machine to 150 μm to obtain a predetermined coating thickness.

[0133] Step (4) - Drying: Dry the cathode sheet in an oven at 80 °C for 120 minutes to remove NMP and moisture. After drying, calender the cathode sheet to adjust the areal density (weight: 12 - 19 mg / disk; disk area: 201 mm 2 ; density: 60 - 95 g / m 2 ). Punch out a cathode disk (φ = 16 mm) from the calendered cathode sheet using a machine Model: PX-CP-S2 manufactured by ShenZhen PengXiang YunDa Machinery Technology Co. The punched edge was sharp without any burrs.

[0134] Step (5) - Assembly of Lithium-Ion Secondary Battery: The assembly and pressing of the lithium-ion secondary battery are carried out in a glove box. The assembly includes the following: coin cell casing top (2032 type; negative electrode side), nickel sponge, lithium disk (as anode), porous separator (Celgard 2340), cathode disk, and casing bottom (positive electrode side). All components were assembled layer by layer. During the assembly step, an electrolyte solution was dropped to completely fill the free volume of the coin cell. Finally, the coin cell case was press-molded by a press in the glove box. An open-circuit voltage test was carried out to check whether there was any short circuit.

[0135]

Table 15

[0136] Example 4 of the present invention shows a higher peel strength compared to Comparative Example 3 using PVDF as the cathode binder. By using a powdery polymer as the cathode binder, a higher peel strength of the electrode sheet can be obtained compared to Comparative Examples 1 and 2.

[0137]

Table 16

[0138] The results in Tables 10 - 11 show that by using a free-flowing powdery rubber containing lithium stearate, which can be used as a binder for the battery, a higher holding capacity can be obtained compared to the base polymer or polymer powders using different types of anti-dusting agents. Compared to the base polymer, they can dissolve faster, which is advantageous in the manufacture of battery cells.

[0139] The detailed description of the various aspects and embodiments as disclosed in this specification shows specific ways of making and using the present invention, and it should be understood that, referring to the claims and the detailed description section, it does not limit the scope of the present invention. It will also be understood that the features from the various aspects and embodiments of the present invention can be combined with the features from other aspects and embodiments of the present invention.

Claims

1. A powdered mixture of elastomers, （１） (a) Ethylene-vinyl acetate copolymers containing the following repeating units: - Ethylene monomer, and - Vinyl acetate monomer (at least 70% by weight based on the total weight of the ethylene-vinyl acetate copolymer); or (b) Nitrile rubber copolymers containing the following repeating units (which may be carboxylated in some cases): - α,β-unsaturated nitrile monomers selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and mixtures thereof (in each case, in an amount of at least 15% by weight based on the total weight of the nitrile rubber copolymer) and - Conjugated diene monomers (which may be fully hydrogenated or partially hydrogenated in some cases, selected from the group consisting of 1,2-butadiene, 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene, and mixtures thereof); and (2) Antidusting agents containing lithium stearate; A powdery mixture containing [the specified ingredient].

2. The powdery mixture according to claim 1, having a particle size distribution D90 of at least 100 μm as measured using a laser diffuser.

3. The powdered mixture according to claim 1, wherein the nitrile rubber copolymer (b) is, in some cases, a fully hydrogenated or partially hydrogenated carboxylated nitrile rubber (XNBR).

4. The powdery mixture according to claim 1, wherein the ethylene-vinyl acetate copolymer (a) and / or the nitrile rubber copolymer (b) have a Mooney viscosity of 25 Mooney units (MU) or more (ML(1+4)100°C) as measured at 100°C by means of a shear disk viscometer in accordance with DIN 53523 / 3 or ASTM D 1646.

5. The powder mixture according to claim 1, further comprising an epoxy-containing fluorine-free copolymer comprising repeating units derived from one or more epoxy-containing monomers of general formula (I). 【Chemistry 1】 [In the formula, m is either 0 or 1. X is O, O(CR ２ ), (CR ｐ ), (CR ２ ), C(=O)O, C(=O)O(CR ｐ ), C(=O)NR, (CR ２ ), (CR ｐ ), N(R), N(R)(CR ２ ), (CR ｐ ), N(R), N(R)(CR ２ ), (CR ｐ ), P(R), P(R)(CR ２ ), (CR ｐ ), P(=O)(R), P(=O)(R)(CR ２ ), (CR ｐ ), S, S(CR ２ ), (CR ｐ ), S(=O), S(=O)(CR ２ ), (CR ｐ ), S(=O) ２ )(CR ２ ), (CR ｐ ), or S(=O) ２ ), where R in these groups may have the same definition as R １ to R ６ . Y represents a repeating unit derived from one or more mono- or poly-unsaturated monomers, including conjugated or unconjugated dienes, alkynes, and vinyl compounds, or a structural element derived from polymers, including polyethers, more particularly polyalkylene glycol ethers and polyalkylene oxides, polysiloxanes, polyols, polycarbonates, polyurethanes, polyisocyanates, polysaccharides, polyesters, and polyamides. n and p are either the same or different, and each is in the range of 0 to 10000. R, R １ , R ２ , R ３ , R ４ , R ５ , and R ６ [These are the same or different H, linear or branched saturated or mono- or polyunsaturated alkyl groups, saturated or mono- or polyunsaturated carbocyrill or heterocyclyl groups, aryl, heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, amino, amide, carbamoyl, alkylthio, arylthio, sulfanyl, thiocarboxyl, sulfinyl, sulfon, sulfino, sulfino, sulfeno, sulfonic acid, sulfamoyl, hydroxyimino, alkoxycarbonyl, F, Cl, Br, I, hydroxyl, phosphonato, phosphinato, silyl, silyloxy, nitrile, borate, selenate, carbonyl, carboxyl, oxycarbonyl, oxysulfonyl, oxo, thioxo, epoxy, cyanate, thiocyanate, isocyanate, thioisocyanate, or isocyanide]

6. Cathode slurry composition, - The powdered mixture according to claim 1, - At least one type of cathode active material, - At least one conductive material, and - At least one solvent, A cathode slurry composition containing the following:

7. The cathode slurry composition according to claim 6, wherein the at least one cathode active material comprises a compound of the following formula I or lithium iron phosphate (LFP). Li １＋ａ Ni ｘ Co ｙ Mn ｚ M ｗ O ２ [Formula 1] [In the formula, M may be at least one selected from the group consisting of aluminum (Al), copper (Cu), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), zirconium (Zr), zinc (Zn), tantalum (Ta), niobium (Nb), magnesium (Mg), boron (B), tungsten (W), and molybdenum (Mo), and a, x, y, z, and w each represent the atomic fraction of an independent element, where -0.5 ≤ a ≤ 0.5, 0 < x ≤ 1, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ w ≤ 1, and 0 < x + y + z ≤ 1]

8. The cathode slurry composition according to claim 6, wherein the at least one conductive material is selected from the group consisting of carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, natural and artificial graphite, foamed graphite, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, and carbon nanotubes, graphene, graphene oxide, and mixtures thereof.

9. The cathode slurry composition according to claim 6, wherein the at least one conductive substance is present in an amount of 0.5 to 50% by weight, based on the total solid content weight of the cathode slurry composition.

10. The cathode slurry composition according to claim 6, wherein the at least one solvent comprises a cyclic aliphatic hydrocarbon, an aromatic hydrocarbon, a ketone, a chlorinated aliphatic hydrocarbon, an ester, an asylonitrile, an ether, an alcohol, a nitrile, or an amide, preferably methyl ethyl ketone, toluene, and / or N-methylpyrrolidone.

11. A cathode comprising a current collector and a cathode active material layer, wherein the cathode active material layer comprises the powdered mixture described in claim 1 and the conductive material.

12. The cathode according to claim 11, wherein the current collector is selected from the group consisting of iron, copper, aluminum, nickel, sintered carbon, stainless steel, carbon-treated stainless steel, titanium, tantalum, gold, platinum, titanium, or silver on its surface; an aluminum-cadmium alloy, a non-conductive polymer treated with a conductive material; a conductive polymer, or a metal paste containing metal powder of Ni, Al, Au, Ag, Pd, Cr, Ta, Cu, or Ba on its surface.

13. A lithium-ion battery comprising at least one cell containing an anode, a cathode as described in claim 11, a separator, and an electrolyte based on a lithium salt and an organic solvent.

14. Use of the powdered mixture according to claim 1, for use as a binder in an electrode composition for the cathode of a battery cell.

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