Additives for viscosity stabilization of lithium-ion battery electrode slurry

Abstract

Disclosed is an electrode slurry composition with stable viscosity comprising a binder containing a fluorinated polymer, a hydroperoxide, an electrode active material, a conductive additive, and a solvent. Also disclosed is an electrode prepared from the slurry of the present invention.

Description

[Technical Field]

[0001] The present invention relates to a slurry used in lithium-ion battery electrodes, and in particular, the slurry contains a hydroperoxide that provides viscosity stabilization for the slurry. [Background technology]

[0002] In the manufacture of lithium-ion battery electrodes, a metal substrate is coated using a slurry containing electrode active material, conductive agent, and binder, such as poly(vinylidene fluoride) ("PVDF"), in a solvent, and the electrode is formed after high-temperature drying. The viscosity of the slurry can increase over time, and sometimes it has been observed to gel, making it difficult to handle in the coating process. Both increased viscosity and gelation are undesirable for battery manufacturing because they negatively impact the electrode casting process and the final quality.

[0003] In the manufacturing process of lithium-ion batteries, electrodes, particularly cathodes, are made through a solvent-based slurry by mixing active material, conductive carbon, and a binder with the help of an organic solvent, usually N-methyl-2-pyrrolidone (NMP). Two requirements for the electrode slurry are that it has a suitable slurry viscosity for the electrode casting process, and that its viscosity must be stable for a certain period, usually at least 48 hours.

[0004] One problem with slurry viscosity is that even with the same formulation, the initial viscosity can vary from batch to batch. This can lead to variability in electrode quality or necessitate adjustments to process parameters during the electrode casting process. Another problem that can occur with slurry processing is that the slurry may become more viscous or gel over time. Both of these pose problems for battery manufacturing. If the slurry viscosity is too high, it can cause problems with the slurry's pumping / transfer, lead to inconsistent quality, and result in defects in the electrode casting process. Slurry gelling usually necessitates stopping the manufacturing process to remove the gel, clean the equipment, and discard the batch of electrode material.

[0005] In the lithium-ion battery manufacturing process, the slurry is typically pumped into a storage tank before being used in the electrode casting line. During slurry transfer (pumping) and electrode coating processes, there is an optimal range of slurry viscosity defined by the equipment. Therefore, it is highly desirable that the slurry maintain a consistent fresh slurry viscosity profile from batch to batch and remain stable during storage (at least 48 hours).

[0006] WO2021250355A1 mentions peroxides as radical generators, but does not mention whether such radical generators can help stabilize dispersions or slurries.

[0007] Therefore, there is still a need to develop stable slurry compositions for Li-ion batteries that maintain slurry stability, especially when the active material has a high nickel content or is based on lithium metal phosphate.

[0008] This invention discloses a family of compounds that can help stabilize the slurry viscosity over time, leading to improved process productivity, reduced waste, and ultimately improved electrode quality. We have found that hydroperoxide compounds can increase the slurry stability viscosity of electrode or separator slurries.

[0009] This invention addresses the problem of slurry viscosity by using hydroperoxide as a stabilizer in the slurry formulation / mixing process. The addition of hydroperoxide to the slurry stabilizes the viscosity of the slurry, resulting in a smaller change in viscosity over time. SUMMARY OF THE INVENTION

[0010] The present invention provides an electrode slurry composition comprising a binder containing a polymer P1 comprising repeating units derived from a fluorinated monomer, a hydroperoxide, an electrode active material, a conductive additive, and a solvent. The present invention provides a slurry with stable viscosity. Surprisingly, the applicant has found that an electrode slurry composition containing hydroperoxide in an amount of at least 0.01% by weight based on the weight of the solvent in the electrode slurry composition provides improved slurry viscosity stability. The present invention also provides an electrode made from the slurry of the present invention.

[0011] Aspects of the Present Invention A first aspect of the present invention - an electrode slurry composition, comprising: a) a binder containing a polymer P1 comprising repeating units derived from a fluorinated monomer, b) a hydroperoxide, c) an electrode active material, d) a conductive additive, and e) a solvent An electrode slurry composition comprising the above.

[0012] Aspect 2: The viscosity of the electrode slurry is stable for at least 48 hours after standing, and as a measure, the ratio of the viscosity at 48 hours to the viscosity within 20 minutes after slurry preparation is less than 150% for the electrode slurry composition of Aspect 1.

[0013] Aspect 3: The electrode slurry composition according to Aspect 1 or 2, wherein the amount of the hydroperoxide is 0.01 to 5% by weight based on the weight of the solvent.

[0014] Aspect 4: The electrode slurry composition according to any one or more of Aspects 1 to 3, wherein the hydroperoxide is selected from the group consisting of tert-butyl hydroperoxide (TBHP), 5-hydroperoxy-1-methyl-2-pyrrolidinone (NMP-5-OOH), and combinations thereof.

[0015] Aspect 5: The electrode slurry composition according to any one or more of Aspects 1 to 4, wherein the amount of the binder is 0.1 to 10% by weight, preferably 0.3 to 6% by weight, based on the total weight of the binder, the electrode active material, and the conductive additive.

[0016] Aspect 6: The electrode slurry composition according to any one or more of Aspects 1 to 5, wherein the polymer P1 of the binder is selected from the group consisting of PVDF homopolymer or PVDF copolymer.

[0017] Aspect 7: The electrode slurry composition according to any one or more of Aspects 1 to 6, wherein the binder contains a PVDF copolymer.

[0018] Aspect 8: The electrode slurry composition according to Aspect 7, wherein the PVDF copolymer contains at least one comonomer selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene, or a mixture thereof.

[0019] Aspect 9: The electrode slurry composition of Aspect 7, wherein the PVDF copolymer contains at least one comonomer unit having at least one of the following functionalities: carboxylic acid, carboxylic anhydride, carboxylic acid ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid.

[0020] Aspect 10: The electrode slurry composition according to any one or more of Aspects 1 to 9, wherein the conductive additive contains one or more materials selected from the group consisting of carbon black, carbon nanotubes, carbon fibers, metal powders, and combinations thereof.

[0021] Aspect 11: The aforementioned electrode active material is selected from the group consisting of lithium salts of transition metal oxides, sulfides, phosphates, and hydroxides. Preferably, the aforementioned active material has a composition represented by LiMPO4 (where M represents Fe, Mn, Co, or Ni), a lithium metal phosphate, LiCoO2, LiNi x Co 1-x O2, LiMn2O2, LiNiO2, LiNi x Co y Mn z O m 、LiNi x Co y Al z O m and LiNi x Mn y Al z O m selected from the group consisting of, where x + y + z = 1, and m is an integer representing the number of oxygen atoms in the oxide to provide a balanced molecule. In particular, the aforementioned active material is selected from the group consisting of LiFePO4 and LiNi x Co y Mn z O m selected from the group consisting of, where x is 0.6 or more, y is 0.2 or less, z is 0.2 or more, x + y + z = 1, and m is an integer representing the number of oxygen atoms in the oxide to provide a balanced molecule. The electrode slurry composition according to any one or more of Aspects 1 to 10.

[0022] Embodiment 12: An electrode slurry composition comprising one or more of Embodiments 1 to 11, wherein the electrode active material contains a lithium metal oxide.

[0023] Embodiment 13: An electrode slurry composition comprising one or more of Embodiments 1 to 12, wherein the solvent comprises at least one of NMP, DMAc, DMF, DMSO, TEP, or HMPA.

[0024] Embodiment 14: A method for manufacturing an electrode, comprising the steps of applying one or more electrode slurry compositions from Embodiments 1 to 13 to a current conductor substrate, and then drying the slurry.

[0025] Embodiment 15: An electrode manufactured by the method of Embodiment 14.

[0026] Embodiment 16: An electrode, f) A binder containing polymer P1 which contains repeating units derived from fluorinated monomers, g) Hydroperoxide, h) Electrode active material, and i) Conductive additives Electrodes, including

[0027] Embodiment 17: The electrode according to Embodiment 16, wherein the amount of binder is 0.1 to 10% by weight, preferably 0.3 to 6% by weight, relative to the total weight of the binder, electrode active material, and conductive additive.

[0028] Embodiment 18: The electrode according to Embodiment 16 or 17, wherein the binder polymer P1 is selected from the group consisting of PVDF homopolymers or PVDF copolymers.

[0029] Embodiment 19: One or more electrodes from any of Embodiments 16 to 18, wherein the binder comprises a PVDF copolymer.

[0030] Embodiment 20: The electrode of Embodiment 19, wherein the PVDF copolymer comprises at least one comonomer selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene, or mixtures thereof.

[0031] Embodiment 21: The electrode of Embodiment 19, wherein the PVDF copolymer comprises at least one comonomer unit having at least one of the following functionalities: carboxylic acid, carboxylic acid anhydride, carboxylic acid ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid.

[0032] Embodiment 22: One or more electrodes from Embodiments 16 to 21, wherein the electrode active material contains a lithium metal oxide.

[0033] Embodiment 23: A battery comprising one or more electrodes as specified in Embodiments 15 to 22. [Modes for carrying out the invention]

[0034] The present invention will be described in more detail and in a non-limiting manner in the following description. According to various embodiments, the aforementioned electrode slurry compositions include the following features, in combination as appropriate. The indicated contents are expressed by weight unless otherwise specified. All indicated ranges include limit values ​​unless otherwise specified.

[0035] Electrode slurry composition

[0036] The electrode slurry composition according to this embodiment comprises a binder composition, a hydroperoxide, a conductive additive, an electrode active material, and a solvent. The electrode can be prepared by forming an electrode slurry composition layer by coating this electrode mixture onto a current collector.

[0037] The present invention relates to an electrode slurry composition, a) Binder composition - containing polymer P1 which includes repeating units derived from fluorinated monomers, b) Hydroperoxide, c) electrode active material, d) Conductive additives, and e) Solvent The present invention provides an electrode slurry composition containing [a specific compound / component].

[0038] Surprisingly, the electrode slurry composition of the present invention was found to exhibit improved viscosity stability, as measured by a Brookfield viscosity change of less than 100% over 48 hours.

[0039] Furthermore, the present invention also provides electrodes comprising a binder composition, a hydroperoxide, a conductive additive, and an electrode active material.

[0040] Binder-Polymer P1

[0041] The binder contains a fluorinated polymer. The fluorinated polymer may be a homopolymer or a copolymer containing at least 50% by weight of fluorinated monomer units.

[0042] The fluorinated monomer units can be selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene (HFP), trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, (perfluorobutyl)ethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene (CTFE), chlorotrifluoropropene, and mixtures thereof.

[0043] Examples of trifluoropropenes include 3,3,3-trifluoropropene. Examples of tetrafluoropropenes include 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene. Examples of pentafluoropropenes include 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Examples of perfluoroalkyl vinyl ethers include those with the general formula Rf-O-CF=CF2, where Rf is a perfluorinated alkyl group, preferably a C1-C4 perfluorinated alkyl group (preferred examples are perfluoropropyl vinyl ether and perfluoromethyl vinyl ether). Chlorofluoroethylene can refer to either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene, with the 1-chloro-1-fluoroethylene isomer being preferred. Chlorotrifluoropropene may be 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0044] Furthermore, polymer P1 may include non-halogenated monomer units, such as ethylene, acrylic acid, or methacrylic acid, and fluorinated monomers, particularly other monomers known in the art that copolymerize with vinylidene fluoride.

[0045] Preferably, the fluorinated polymer P1 contains repeating units derived from vinylidene fluoride (PVDF polymer). Polymer P1 can be a polyvinylidene fluoride homopolymer or a polyvinylidene fluoride copolymer containing at least one comonomer copolymerizable with vinylidene fluoride. Polymer P1 may also be a blend of PVDF polymers. The copolymer may contain one unit from the fluorinated monomers listed above. One preferred copolymer contains VDF and HFP monomer units.

[0046] Polymer P1 may contain at least 60% by weight of vinylidene fluoride units, preferably at least 70% by weight of vinylidene fluoride, more preferably at least 80% by weight of vinylidene fluoride, and particularly at least 90% by weight of vinylidene fluoride units.

[0047] The aforementioned polymer P1 may include monomer units having at least one of the following functional groups: carboxylic acids, carboxylic acid anhydrides, carboxylic acid esters, epoxy groups (such as glycidyl), amines, amides, hydroxyl, carbonyl, mercapto, sulfides, oxazolines, phenols, esters, ethers, siloxanes, sulfonic acids, sulfinic acids, sulfuric acids, phosphoric acids, or phosphonic acids. The functional groups are introduced by grafting a monomer having at least one of the aforementioned functional groups and ethylene functionality (carbon-carbon double bond) copolymerizable with fluoromonomers, or by a chemical reaction that allows copolymerization between the monomer and the fluoromonomer, which is well known to those skilled in the art. Such monomer units having functional groups can be found in US8337725, US5415958, JP20100292594, EP247029B1, US9343744B2, FR3079834, and US20210171693, all of which are incorporated herein by reference.

[0048] Polymer P1 may contain repeating units having carboxylic acid functionality. Monomers having carboxylic acid functionality can be of the (meth)acrylic acid type, such as acrylic acid, methacrylic acid, or (2-carboxyethyl)acrylate. Monomer units having carboxylic acid functionality may further contain heteroatoms selected from oxygen, sulfur, nitrogen, and phosphorus. Furthermore, polymer P1 may contain repeating units having non-carboxylic acid functionality, such as hydroxyl or other as described above. Monomers having hydroxyl functionality can be of the (meth)acrylic acid type, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxyethylhexyl (meth)acrylate. Polymer P1 may also be a PVDF polymer having (meth)acrylic acid type comonomer units. Polymer P1 may also be a PVDF polymer having (meth)acrylic acid type comonomer units and further containing the additional fluorinated monomers described above, such as HFP or CTFE or perfluoroalkyl fluorinated vinyl ether.

[0049] Functionality can also be introduced into polymer P1 by a chain transfer agent used during the copolymerization process. This type of chain transfer agent is a polymer having the functional groups described above. An example of this type of chain transfer agent is an acrylic acid polymer. According to a preferred embodiment, the chain transfer agent is an acrylic acid polymer with a molar mass of 100,000 g / mol or less, preferably 10,000 g / mol or less.

[0050] If polymer P1 contains monomer units having functional groups, the content of these monomer units in polymer P1 is at least 0.01 mol%, preferably at least 0.1 mol%, and 15 mol% or less, preferably 10 mol% or less. As is known in the art, the mol% can be determined using 19F NMR.

[0051] Polymer P1 preferably has a high molecular weight. The term "high molecular weight" as used herein refers to the molecular weight measured according to the ASTM D-3835 method at 232°C and 100 sec. -1 This is understood to mean polymer P1 whose melt viscosity, as measured, exceeds 100 Pa.s, preferably 500 Pa.s, and more preferably 1000 Pa.s.

[0052] The polymer P1 used in the present invention can be obtained by known polymerization methods, such as emulsion polymerization, solution polymerization, or suspension polymerization. Preferably, polymer P1 is prepared by an emulsion polymerization process in the absence of a fluorinated surfactant.

[0053] Hydroperoxide

[0054] The electrode slurry composition of the present invention contains a hydroperoxide. The hydroperoxide of the present invention contains at least one -OOH group. For the purposes of the present invention, peroxy acids are included in the term hydroperoxide. Hydroperoxides are generally, Formula A: ROOH Defined by, Here, R is an organic group with a formula weight of 500 g / mol or less. Preferably, R is C1-C 18 Alkyl, or C4-C 18 Branched alkyl, C4~C 18 Acyl, or C3~C 18 It is a cycloalkyl group and may optionally contain one or more heteroatoms selected from oxygen, sulfur, nitrogen, and phosphorus atoms.

[0055] Examples of hydroperoxides, though not limited to them, include tert-butyl hydroperoxide (TBHP), cumene hydroperoxide, linalool hydroperoxide, hydroxymethyl hydroperoxide, performic acid, methyl hydroperoxide, hydroperoxymethyl formate, peracetic acid, cyclohexyl hydroperoxide, ethylbenzene hydroperoxide (EBHP), and 5-hydroperoxy-1-methyl-2-pyrrolidinone. Further examples can be found in *Organic Peroxides*, Vol. 1; Swern., D. ed.; John Wiley & Sons, 1970, Chapters 1 and 6.

[0056] Method for introducing hydroperoxide into electrode slurry composition

[0057] One way to use hydroperoxides in electrode slurry formulation processes is to dissolve them in the processing solvent. They can be added during the fluoropolymer / solvent dissolution step and / or slurry mixing step, when diluting a concentrated slurry by adding small amounts of solvent multiple times to achieve the target viscosity.

[0058] Alternatively, hydroperoxides can be added as-is (liquid or solid, in their original form) during the slurry formulation process. Alternatively, hydroperoxides can be generated in situ by contacting a hydroperoxide precursor with oxygen. For example, NMP exposed to an oxygen source for a certain period of time will produce a hydroproxy of N-methyl-2-pyrrolidone.

[0059] The concentration of hydroperoxide in the solvent can be in the range of 0.01 to 5% by weight, preferably 0.05 to 4% by weight, relative to the weight of the solvent in the slurry.

[0060] electrode active material

[0061] The electrode active material is not particularly limited, and for example, known electrode active materials for negative electrodes (negative electrode active material) or electrode active materials for positive electrodes (positive electrode active material) can be used.

[0062] Examples of negative electrode active materials include carbon materials (graphite, graphene, hard carbon, soft carbon, etc.), silicon materials (Si, SiO, etc.), metal / alloy materials (Li, Tin, Al, etc.), and metal oxides (lithium titanate (LTO), etc.), as well as mixtures thereof. Among these, carbon materials are preferred. When such carbon materials are used, even higher energy densities can be achieved in the battery.

[0063] As the positive electrode active material, a lithium-based positive electrode active material containing at least lithium is preferred. Examples of lithium-based positive electrode active materials are not limited to, but include composite metal chalcogen compounds represented by the general formula LiMY2 (where M is a transition metal, for example, at least one type such as Co, Ni, Fe, Mn, Cr, or V), such as LiCoO2 or LiNi x Co 1-x Examples include composite metal oxides having a spinel structure, such as O2 (0 ≤ x ≤ 1), such as LiMn2O4, and olivine-type lithium compounds, such as LiFePO4.

[0064] The active material is preferably selected from the group consisting of transition metal oxides, sulfides, phosphates, and lithium hydroxide salts. Preferably, the active material is a lithium metal phosphate, LiCoO2, or LiNi having a composition represented by LiMPO4 (where M represents Fe, Mn, Co, or Ni). x Co 1-x O2, LiMn2O2, LiNiO2, LiNi x Co y Mn z O m Li Limited x Co y Al z O m and LiNi x Mn y Al z O mSelected from the group consisting of, where x+y+z=1 and m is an integer representing the number of oxygen atoms in the oxide to provide an electron-balanced molecule.

[0065] More preferably, the active material is LiFePO4 and LiNi x Co y Mn z O m Selected from the group consisting of, where x is greater than or equal to 0.6, y is less than or equal to 0.2, z is greater than or equal to 0.2, x + y + z = 1, and m is an integer representing the number of oxygen atoms in the oxide to provide an electron-balanced molecule.

[0066] conductive additives

[0067] The conductive additive is not particularly limited and may include, for example, known conductive additives such as carbon black, such as acetylene black or Ketjen black; carbon fibers, such as carbon nanotubes, carbon nanofibers, or vapor-grown carbon fibers; metal powders, such as stainless steel powder and aluminum powder; or mixtures thereof.

[0068] solvent

[0069] The electrode slurry composition contains an organic solvent. The solvent is used to dissolve a binder containing polymer P1. The resulting binder solution is used to mix / disperse electrode active material and conductive additives to form a slurry for the electrode coating process.

[0070] The organic solvent is preferably selected from the group consisting of n-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), triethyl phosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate (EA), butyl acetate (BA), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), gamma butyrolactone, N-butylpyrrolidone, and combinations thereof. Generally, the weight percentage of the solvent in the electrode slurry is in the range of about 15 to 65% of the total weight of the slurry.

[0071] Other components of the electrode mixture

[0072] The electrode mixture of this embodiment may contain other components in addition to the components described above. Examples of such other components include pigment dispersants such as polyvinylpyrrolidone.

[0073] composition

[0074] The content of the binder, electrode active material, and conductive additive in the electrode slurry composition (excluding the solvent) is preferably as follows (all figures are based on 100 parts by mass of the dry electrode composition - the dry electrode composition is the total mass of the binder + electrode active material + conductive additive).

[0075] The binder is preferably included in an amount of 0.1 to 10 parts by mass, more preferably 0.3 to 6 parts by mass.

[0076] The content of the conductive additive is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass.

[0077] The electrode active material is preferably included in an amount of 80 to 99.8 parts by mass, more preferably 89.0 to 99.7 parts by mass.

[0078] Method for manufacturing electrode mixtures

[0079] The method for producing an electrode mixture according to this embodiment may include mixing a binder, a hydroperoxide, an electrode active material, and a conductive additive to form a uniform slurry, and the order of mixing is not particularly limited. For example, the electrode active material and / or the conductive additive and / or the hydroperoxide can be combined with the binder, and then a solvent can be added to form an electrode slurry composition. When the components are mixed in the presence of an organic solvent, the binder is preferably in powder form.

[0080] Alternatively, the binder can be dissolved in the solvent first, and then the other components can be added to the dissolved binder. Furthermore, the electrode active material and / or conductive additive can be dispersed in the solvent, then the binder can be added and stirred, and any remaining components can be added and mixed to obtain the electrode mixture. Hydroperoxides can be added in any combination with the other components, regardless of the order in which the components are added.

[0081] electrode

[0082] The electrode according to this embodiment has a structure in which a layer formed from an electrode slurry composition ("electrode mixture layer") is provided on a current collector. The electrode mixture layer can be formed on at least one surface of the current collector, preferably on both surfaces of the current collector. In another aspect of the present invention, a positive electrode is provided. The aforementioned positive electrode comprises a current collector and an electrode mixture layer according to the present invention. The aforementioned positive electrode is formed by depositing an electrode slurry composition on at least one surface on the aforementioned current collector, wherein after the aforementioned electrode slurry composition is placed on at least one surface on the aforementioned current collector, the electrode is dried to remove the organic solvent in the slurry forming the electrode.

[0083] Current collector

[0084] The current collector is the base material for the electrodes and the terminal from which electricity is extracted. The material of the current collector is not particularly limited, and known materials such as aluminum or copper can be used.

[0085] The thickness of the current collector is not particularly limited, but is preferably 5 to 100 μm, and more preferably 5 to 20 μm.

[0086] electrode mixture layer

[0087] The electrode mixture layer is a layer obtained by coating the current collector with the above electrode mixture and drying it.

[0088] The method for coating the electrode mixture is not particularly limited. Examples include, but are not limited to, coating using a bar coater, die coater, or comma coater.

[0089] The thickness of the electrode mixture layer is not particularly limited, but is typically 20 to 250 μm, preferably 20 to 150 μm. Furthermore, the coating amount of the electrode mixture layer is not particularly limited, but is typically 20 to 700 g / m². 2 The amount is preferably 30-500 g / m². 2 That is the case.

[0090] The drying temperature and drying time for forming the electrode mixture layer are typically 50–150°C for 1–300 minutes. The drying pressure is not particularly limited, but drying is usually carried out under atmospheric pressure or reduced pressure.

[0091] Furthermore, pressing can be performed. When pressing, the pressure is typically 1 to 200 MPa·G.

[0092] Nonaqueous electrolyte secondary battery

[0093] The non-aqueous electrolyte secondary battery according to this embodiment has electrodes according to this embodiment. The non-aqueous electrolyte secondary battery according to this embodiment may also include polymer batteries containing gel electrolytes, etc. Other components in the non-aqueous electrolyte secondary battery (e.g., separators) are not particularly limited, and any components used can be used.

[0094] The present invention also provides a lithium-ion secondary battery. The aforementioned lithium-ion secondary battery comprises a negative electrode, a positive electrode according to the present invention, and a separator between the aforementioned negative electrode and the aforementioned positive electrode.

[0095] In another aspect of the present invention, an electrochemical device is provided. The aforementioned electrochemical device comprises a negative electrode, a positive electrode according to the present invention, and an electrolyte containing lithium. [Examples]

[0096] The following non-limiting examples illustrate the scope of the present invention.

[0097] Cathode formulation and manufacturing

[0098] An exemplary cathode slurry preparation procedure for laboratory scale is described here. The procedure is for laboratory scale, and the target formulation is NMC622 / SuperP / binder = 97 / 1.5 / 1.5 on a dry basis.

[0099] Typical slurry mixing procedure

[0100] First, the PVDF (binder) powder is dissolved in NMP (Biograde from Alfa Aesar) at a concentration of 8.0% by weight and mixed in a roll mixer for at least 48 hours ("binder solution").

[0101] 0.33 g of the conductive additive, SuperP-Li from Timcal, is added to 2.64 g of 8.0% binder solution and mixed for 120 seconds at 2000 rpm using a centrifugal planetary mixer Thinky AR-310. Then 0.66 g of 8.0% binder is added to the mixture and mixed for 120 seconds at 200 rpm. Then 0.825 g of binder solution is added to the mixture and mixed for 120 seconds at 2000 rpm three times. After the conductive additive is dispersed in the binder solution, 21.34 g of the active material Celcore® NMC622 (Umicore) is added to the mixture and mixed for 60 seconds three times at 2000 rpm, with 1 minute of air cooling in between. At this stage, the slurry is a thick paste with a solid content of 85.3% by weight. Next, a small amount of NMP (0.46g) is added to the paste and mixed at 60 seconds / 2000 rpm to gradually reduce the solidity and viscosity of the slurry. This dilution process is repeated multiple times until the slurry viscosity reaches a level suitable for coating, typically 10,000-150,000 cP at a shear rate of 1 / s. Typically, the final solidity level of the NMC622 / SuperP / PVDF binder = 97 / 1.5 / 1.5 formulation is 81-76% by weight.

[0102] Slurry viscosity measurement

[0103] Slurry viscosity was measured using a Brookfield rotational viscometer with a CP-52 type spindle at 25°C and a shear rate of 1 second. -1 The viscosity can be measured using the following method. The viscosity of the fresh slurry was measured within 20 minutes of preparation. The slurry was then kept in a lidded container in a drying room for 48 hours for standing. After 48 hours of standing, the slurry viscosity was measured again. The ratio of the viscosity at 48 hours to that of the fresh slurry was calculated to evaluate the stability of the slurry. If the ratio is greater than 150%, the slurry is considered to have too high a viscosity or not to be sufficiently stable. In some cases, after the 48-hour test, the viscosity of the slurry becomes very high, it stops flowing, and exhibits gel-like behavior. In this case, the viscometer could not obtain a good measurement because it was outside the instrument's range. The result indicates gelation, or a ratio of >200%.

[0104] Examples 1-5: An aqueous solution of 70 wt% t-butyl hydroperoxide (TBHP) was added to fresh NMP to produce the target wt% TBHP in NMP shown in the table. This modified NMP was used to dissolve PVDF in the slurry mixing procedure (described above), to prepare the binder solution, and to adjust the viscosity by adding it during the slurry mixing process. The PVDF binder tested was 8% Kynar® HSV1810 prepared with fresh NMP and modified NMP. The entire mixing process for preparing the slurry samples was carried out in a drying room. From slurry viscosity tests after 2 hours and 48 hours, the comparative sample with fresh NMP completely gelled after 48 hours of standing, while the examples prepared with varying amounts of TBHP additive did not gel and remained flowable. The improved stability of slurry viscosity (anti-gelling) is demonstrated by the fact that the comparative slurry gelled or became too viscous to begin flowing, while the slurry of the present invention did not form a gel and remained fluid.

[0105] [Table 1]

[0106] Examples 6-10: Comparative additives:

[0107] Other forms of peroxides, such as hydrogen peroxide (H2O2) and di-tert-butyl peroxide (DTBP), were tested for their effect on the viscosity stability of the slurry as 1% by weight additives in NMP, as shown in Table 2, Examples 6 and 7. The experimental procedure was the same as in Example 1, except that the additive was H2O2 or DTBP. The slurry viscosity showed a similar increase as the fresh NMP control without additives. Neither H2O2 nor DTBP showed a stabilizing effect on the slurry.

[0108] NMP-5-OOH is a hydroperoxide from the decomposition of NMP exposed to air. Other possible decomposition compounds in NMP are N-methylsuccinimide (NMS), 2-pyrrolidione, and gamma-butyrolactone (GBL). Experiments were conducted to individually increase the levels of N-methylsuccinimide (NMS), 2-pyrrolidione, and gamma-butyrolactone (GBL) to 2500 ppm in fresh NMP. Their effect on slurry stability was then tested, as shown in Table 2 as Examples 8-10. The tests followed the same procedure as in Example 1, except that the additives were GBL, 2-pyrrolidione, and NMS, respectively. The comparative slurry samples were not viscous and gelled after standing for 48 hours.

[0109] [Table 2]

[0110] Examples 6-10 demonstrate that other types of peroxides and radical generators do not provide stability.

[0111] No improvement in slurry viscosity stability or slurry anti-gelling properties was observed with the comparative additive.

Claims

1. a) A binder containing polymer P1 which contains repeating units derived from fluorinated monomers, b) Hydroperoxide, c) electrode active material; d) Conductive additives, and e) Solvent An electrode slurry composition containing [a specific substance].

2. The electrode slurry composition according to claim 1, wherein the viscosity of the electrode slurry is stable for at least 48 hours after standing, and as a measure, the ratio of the viscosity at 48 hours to the viscosity within 20 minutes after slurry preparation is less than 150%.

3. The electrode slurry composition according to claim 1, wherein the amount of the hydroperoxide is 0.01 to 5% by weight relative to the weight of the solvent.

4. The electrode slurry composition according to claim 1, wherein the hydroperoxide is selected from the group consisting of tert-butyl hydroperoxide (TBHP), 5-hydroperoxy-1-methyl-2-pyrrolidinone (NMP-5-OOH), and combinations thereof.

5. The electrode slurry composition according to any one or more of claims 1 to 4, wherein the amount of the binder is 0.1 to 10% by weight, preferably 0.3 to 6% by weight, relative to the total weight of the binder, the electrode active material, and the conductive additive.

6. The electrode slurry composition according to any one or more of claims 1 to 4, wherein the polymer P1 of the binder is selected from the group consisting of PVDF homopolymers or PVDF copolymers.

7. The electrode slurry composition according to any one or more of claims 1 to 4, wherein the binder comprises a PVDF copolymer.

8. The electrode slurry composition according to claim 7, wherein the PVDF copolymer comprises at least one comonomer selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene, or mixtures thereof.

9. The electrode slurry composition according to claim 7, wherein the PVDF copolymer comprises at least one comonomer unit having at least one of the functionalities of carboxylic acid, carboxylic acid anhydride, carboxylic acid ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid.

10. The electrode slurry composition according to any one or more of claims 1 to 9, wherein the conductive additive comprises one or more materials selected from the group consisting of carbon black, carbon nanotubes, carbon fibers, metal powders, and combinations thereof.

11. The electrode active material is selected from the group consisting of lithium salts of transition metal oxides, sulfides, phosphates, and hydroxides, and preferably the active material is LiMPO 4 (where M represents Fe, Mn, Co, or Ni), a lithium metal phosphate having a composition represented by, LiCoO 2 , LiNi x Co 1-x O 2 , LiMnO 2 O 2 , LiNiO 2 , LiNi x Co y Mn z O m , LiNi x Co y Al z O m and LiNi x Mn y Al z O m selected from the group consisting of, where x + y + z = 1, and m is an integer representing the number of oxygen atoms in the oxide for providing a molecule with a balanced electron, particularly the active material is LiFePO 4 and LiNi x Co y Mn z O m selected from the group consisting of, where x is 0.6 or more, y is 0.2 or less, z is 0.2 or more, x + y + z = 1, and m is an integer representing the number of oxygen atoms in the oxide for providing a molecule with a balanced electron, the electrode slurry composition according to any one or more of claims 1 to 10.

12. The electrode slurry composition according to any one or more of claims 1 to 11, wherein the electrode active material comprises a lithium metal oxide.

13. The electrode slurry composition according to any one or more of claims 1 to 12, wherein the solvent comprises at least one of NMP, DMAc, DMF, DMSO, TEP, or HMPA.

14. A method for manufacturing an electrode, comprising the steps of applying an electrode slurry composition according to any one or more of claims 1 to 13 to a current conductor substrate, and then drying the slurry.

15. An electrode manufactured by the method of claim 14.

16. a) A binder containing polymer P1 which contains repeating units derived from fluorinated monomers, b) Hydroperoxide, c) Electrode active material, and d) Conductive additives Electrodes, including

17. The electrode according to claim 16, wherein the amount of the binder is 0.1 to 10% by weight, preferably 0.3 to 6% by weight, relative to the total weight of the binder, the electrode active material, and the conductive additive.

18. The electrode according to claim 16 or 17, wherein the polymer P1 of the binder is selected from the group consisting of PVDF homopolymers or PVDF copolymers.

19. The electrode according to claim 16 or 17, wherein the binder comprises a PVDF copolymer.

20. The electrode according to claim 18, wherein the PVDF copolymer comprises at least one comonomer selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroalkyl vinyl ether, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropene, or mixtures thereof.

21. The electrode according to any one or more of claims 16 to 20, wherein the PVDF copolymer comprises at least one comonomer unit having at least one of the functionalities of a carboxylic acid, carboxylic acid anhydride, carboxylic acid ester, epoxy group, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenol, ester, ether, siloxane, sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid.

22. The electrode according to any one or more of claims 16 to 21, wherein the electrode active material comprises a lithium metal oxide.

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