Battery electrodes and methods for manufacturing them

Abstract

This invention relates to a binder for the positive electrode of a secondary battery, a method for manufacturing the electrode, and its use in a secondary battery. The invention also relates to a secondary battery manufactured by incorporating the electrode.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to European Patent Application Publication No. 23160872.0, filed on 9 March 2023, and all contents of this application are incorporated herein by reference for any purpose.

[0002] The present invention relates to a binder for the positive electrode of a secondary battery, a method for manufacturing the electrode, and its use in a secondary battery.

[0003] The present invention also relates to a secondary battery manufactured by incorporating the aforementioned electrodes. [Background technology]

[0004] Electrochemical devices such as rechargeable batteries typically include a positive electrode, a negative electrode, and an electrolyte.

[0005] Lithium battery electrodes are typically manufactured by mixing a binder with powdered electrode active material.

[0006] Fluororesins, such as vinylidene fluoride polymers, are used as binders for forming positive electrodes. In particular, polyvinylidene fluoride (PVDF) provides good electrochemical stability and high adhesion to electrode materials. Therefore, PVDF is a preferred binder material for electrode slurries.

[0007] U.S. Patent No. 2018 / 0355206 discloses the use of a copolymer of methyl methacrylate and methacrylic acid as a mixture with PVDF for the preparation of a LiNMC electrode slurry with excellent adhesion to current collectors. The mixture has a viscosity that allows the active material to spread easily on a metal current collector, thereby facilitating the manufacture of electrodes for lithium-ion batteries.

[0008] U.S. Patent Application Publication No. 2015 / 0280238 discloses a stable electrode binder dispersion for use in the manufacture of LFP cathodes for lithium-ion batteries, the dispersion comprising PVDF dispersed in an organic diluent and a (meth)acrylic polymer dispersant.

[0009] The solutions currently available in this field rely on the use of PVDF homopolymer-based binders, but this has the problem of poor adhesion to current collectors.

[0010] Modified polar PVDF polymers, such as those containing repeating units derived from hydrophilic (meth)acrylic monomers (e.g., acrylic acid), are well known in the art. Such copolymers have been developed to add suitable adhesion to metals, such as aluminum or copper, to the mechanical properties and chemical inertness of PVDF.

[0011] However, when used to prepare slurries for forming positive electrodes using specific active materials, modified polar PVDF polymers are preferable. In particular, in lithium-ion batteries, when LiFePO4 (LFP) active materials are used, the slurry often undergoes a rapid increase in viscosity, leading to gel formation and a significant drawback that prevents it from being used as a binder for the LPF cathode.

[0012] The time dependence of the rheological properties of composite electrode slurries is also observed in sodium-ion secondary batteries. In fact, the gelation of the slurry is initiated by NaOH present on the material when exposed to air, which can result in dehydration and fluorination accompanied by PVDF crosslinking. This gelation generates a non-uniform coating.

[0013] In particular, the need for higher-performance polymers that guarantee superior mechanical properties and better adhesion to current collectors remains felt in both research and industry.

[0014] Therefore, one approach is to find a polymer blend that avoids the drawbacks of modified polar PVDF polymers in contact with specific active materials such as PVDF homopolymers and LFPs, while simultaneously ensuring the feasibility of wet-cast electrodes and high adhesion of the final product. [Overview of the project]

[0015] Therefore, the object of the present invention is a) At least one positive electrode active material (AM), b) A type of binder (B), i) at least one vinylidene fluoride (VDF) copolymer [polymer (F)], (ia) Repeating unit derived from VDF, (ib) Optionally, an amount of 0.05 to 10 mol% of the total moles of repeating units of polymer (F), with respect to formula (I): [ka] (In the formula, - R1, R2 and R3 are equal to or different from each other, independently selected from hydrogen atoms and C1-C3 hydrocarbon groups, and - R X C1-C12 contains at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, phosphate, and ether groups. 20 (This is the hydrocarbon portion.) Repeating units derived from at least one hydrophilic vinyl monomer (MA) At least one vinylidene fluoride (VDF) copolymer [polymer (F)] containing, ii) At least one polymer [polymer (A)] obtained from polymerization of at least one monomer (I) and at least one monomer (II), wherein the monomer is - Monomer (I): Ethylene-unsaturated linear or branched aliphatic, cyclic or aromatic polycarboxylic acid or anhydride, - Monomer(II): Ethylene-unsaturated linear or branched aliphatic, cyclic, or aromatic hydrocarbons At least one polymer [polymer (A)] corresponding to One type of binder (B) containing, c) at least one solvent (S), d) Optionally, at least one conductivity-imparting additive and This is a positive electrode forming composition (C) containing the following.

[0016] In a second example, the present invention relates to the use of the electrode-forming composition (C) of the present invention in a method for producing a positive electrode [electrode (E)] for an electrochemical device, wherein the method is (i) To provide a metal substrate having at least one surface, (ii) To provide the electrode-forming composition (C) defined above, (iii) Applying composition (C) to at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate in which at least one surface is coated with composition (C), (iv) Dry the assembly provided in step (iii). Including, regarding use.

[0017] In a third example, the present invention relates to a positive electrode (E) that can be obtained by the method of the present invention.

[0018] In the fourth example, the present invention relates to an electrochemical device comprising the positive electrode (E) of the present invention. [Modes for carrying out the invention]

[0019] In relation to the present invention, the use of parentheses "(...)" before and after a symbol or number that identifies a formula or part of a formula is solely intended to better distinguish the symbol or number from the rest of the sentence, and therefore, such parentheses may be omitted.

[0020] The terms "acrylic" and "acrylate" are used interchangeably (so long as the intended meaning does not change by doing so) and include acrylic acid and its derivatives. The term "(meth)acrylic" or "(meth)acrylate" is intended to cover both the acrylic / acrylate and methacrylic / methacrylate forms of the material shown, for example, a (meth)acrylate monomer.

[0021] The positive electrode active material (AM) is preferably a compound capable of inserting lithium ions or sodium ions.

[0022] Conventional active materials (AM) in the positive electrode of a sodium ion battery are generally selected from Na-based layered transition metal oxides, Prussian blue analogs, and polyanion-type materials.

[0023] In some embodiments, the active material is a Na-based layered transition metal oxide classified as O3 type, P2 type, and P3 type according to the stacking order of oxygen layers. The P2-type structure generally corresponds to the general formula NaxMO2 (where M represents a transition metal ion such as Co, Mn, etc., and x is 2 / 3).

[0024] In some embodiments, the active material is Na 0.81 Fe[Fe(CN)6] 0.79□0.21 , NaFe2(CN)6, Na1 .63 Fe 1.89 (CN)6, Na 1.72 MnFe(CN)6, Na 1.76 Ni 0.12 Mn 0.88 [Fe(CN)6] 0.98 , Na2Ni x Co 1-x Fe(CN)6 (0 ≦ x ≦ 1, for example, Na2CoFe(CN)6, etc.), where 0 ≦ x ≦ 2 and 0 ≦ y < 1, A is an alkali metal ion, P is an N-coordinated transition metal ion, R is a C-coordinated transition metal ion, and □ is a [R(CN)6] vacancy, of the general formula A x P[R(CN)6] 1-y□y .mH2O Prussian blue analog (PBA).

[0025] In some other embodiments, the active material is a series of tetrahedral anionic units (XO4) n -and their derivatives (X m O 3m+1 ) n- Having the general formula Na x M y (XO4) n These are polyanionic materials of the form (wherein X = S, P, Si, As, Mo, and W, and M is a transition metal). In particular, NaFePO4, Na 0.7 Phosphates such as FePO4 or NaMnPO4, NaMPO4, general formula Na x Sodium superionic conductors of the NASICON type structure M2(XO4)3 (wherein 1≦x≦4, M=V, Fe, Ni, Mn, Ti, Cr, Zr..., X=P, S, Si, Se, Mo...), and single transition metal types such as Na3V2(PO4)3(NVP), Na3Cr2(PO4)3, Na3Fe2(PO4)3, binary transition metal types such as Na2VTi(PO4)3, Na3FeV(PO4)3, Na4MnV(PO4)3, Na3MnZr(PO4)3, Na3MnTi(PO4)3, Na4Fe3(PO4)2(P2O7)(NFPP), pyrophosphates Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na 4-x Fe 2+x / 2 (P2O7)2 (wherein 2 / 3 ≤ x ≤ 7 / 8), for example, Na 3.12 Fe 2.44 (P2O7)2 or Na 3.32 Fe 2.34 (P2O7)2, Na2(VO)P2O7, Na7V3(P2O7)4, Fluorophosphate NaVPO4F, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VO 1-x PO4)2F 1+2x(where 0 ≤ x ≤ 1), for example, Na3(VOPO4)2F or Na3V2(PO4)2F3 (NVPF), fluorosulfate, for example NaMSO4F (where M = Fe, Co, Ni), mixed phosphate / pyrophosphate of the general formula Na4M3(PO4)2(P2O7) (where M represents a transition metal), for example Na4Mn3(PO4)2(P2O7), Na4Co3(PO4)2(P2O7), Na4Ni3(PO4)2(P2O7), Na4Fe3(PO4)2(P2O7) (NFPP), Na7V4(P2O7)4(PO4), sulfate, for example Na2Fe2(SO4)3, Na 2+2x Fe 2-x (SO4)3, Na 2+2x Co 2-x (SO4)3, Na 2+2x Mn 2-x (SO4)3 (where 0 ≤ x ≤ 1), silicates of the general formula Na2MSiO4 (where M = Mn, Fe, Co and Ni) can be mentioned.

[0026] In some preferred embodiments, the active material is preferably a fluorophosphate selected from the list consisting of NaVPO4F, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VO 1-x PO4)2F 1+2x (where 0 ≤ x ≤ 1), for example, Na3(VOPO4)2F or Na3V2(PO4)2F3 (NVPF).

[0027] Conventional active materials (AM) for the positive electrode of lithium-ion batteries can include composite metal chalcogenides of the formula LiMQ2 (where M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V, and Q is a chalcogen such as O or S). Among these, it is preferable to use lithium-based composite metal oxides of the formula LiMO2 (where M is the same as defined above). Preferred examples of these include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (where 0 < x < 1) and spinel-structured LiMn2O4.

[0028] As an alternative form, furthermore, the electrode active material is of the formula M1M2(JO4) f E 1-f (where M1 is lithium which can be partially replaced by another alkali metal occupying less than 20% of the M1 metal, M2 is a transition metal of +2 oxidation level selected from Fe, Mn, Ni or a mixture thereof which can be partially replaced by one or more further metals occupying less than 35% (including 0) of the M2 metal at an oxidation level of +1 to +5, JO4 is any oxyanion, J is any of P, S, V, Si, Nb, Mo or a combination thereof, E is a fluoride, hydroxide or chloride anion, and f is usually the molar fraction of the JO4 oxyanion included in 0.75 to 1) and may contain a lithiated or partially lithiated transition metal oxyanion-based electrode active material.)

[0029] M1M2(JO4) as defined above f E 1-f The electrode active material is preferably phosphate-based and may have an ordered or modified olivine structure.

[0030] More preferably, the electrode active material has the formula Li 3-x M’ y M’’ 2-y (JO4)3 (where 0≦x≦3, 0≦y≦2, M’ and M’’ are the same or different metals, at least one of which is a transition metal, JO4 is preferably PO4 which can be partially substituted by another oxyanion, and J is any of S, V, Si, Nb, Mo or a combination thereof). Even more preferably, the electrode active material (AM) has the formula Li x A y D z PO4 (where A is selected from the group consisting of Mn, Fe, Co, Ni and Cu, D is selected from the group consisting of Mg, Ca, Sr, Ba, and x, y and z are numbers satisfying the following relationships: 0<x<2, 0<y<1.5, 0≦z<1.5) and is a phosphate-based electrode active material.

[0031] Component A is preferably Fe, Mn, and Ni, and particularly preferably Fe.

[0032] Component D is preferably Mg or Ca.

[0033] Examples of compounds having an olivine structure include lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), and lithium manganese phosphate.

[0034] Furthermore, as the positive electrode active material (AM), it is also possible to use a material whose surface is partially or entirely coated with carbon to enhance conductivity.

[0035] The amount of coated carbon is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less, based on 100 parts by weight of positive electrode active material.

[0036] Compounds having an olivine structure are present in composition (C) in an amount of 70% by mass or more relative to 100% by mass of the total cathode active material (AM).

[0037] More preferably, this is 90% by mass or more, and most preferably, the positive electrode active material (AM) consists only of compounds having an olivine structure.

[0038] Most preferably, the positive electrode active material (AM) consists solely of lithium iron phosphate (LFP).

[0039] In the positive electrode composition of the present invention, the active material (AM) has an average particle size of 3 μm or less.

[0040] The average particle size (D50) of the compound having an olivine structure is more preferably in the range of 0.01 to 1.8 μm.

[0041] The average particle size of the positive electrode active material can be measured by a particle size analyzer for dynamic light scattering.

[0042] As the average particle size decreases, the surface area increases, requiring a smaller amount of binder to bond the particles, thus necessitating the binder's flexibility.

[0043] By using a positive electrode active material containing a compound having an olivine structure with an average particle size of 3 μm or less, the electrical properties, such as output characteristics, when the positive electrode composition for a secondary battery is used as the positive electrode of the battery are improved.

[0044] Composition (C) of the present invention is i) at least one vinylidene fluoride (VDF) copolymer [polymer (F)] as defined above, ii) At least one polymer (A) as defined above and Includes binder (B).

[0045] Polymer (F) consists of repeating units derived from vinylidene fluoride (VDF) and an amount of 0.05 to 10 mol% of the total moles of repeating units of polymer (F), as shown in formula (I): [ka] (In the formula, - R1, R2 and R3 are equal to or different from each other, independently selected from hydrogen atoms and C1-C3 hydrocarbon groups, and - R X C1-C12 contains at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, phosphate, and ether groups. 20 (This is the hydrocarbon portion.) It comprises repeating units derived from at least one hydrophilic vinyl monomer (MA).

[0046] As used herein, the term “hydrophilic vinyl monomer” may include repeating units derived from one or more of the hydrophilic (meth)acrylic monomers (MA) described above. For the remainder of this specification, the expression “hydrophilic vinyl monomer (MA)” is intended to be both plural and singular, i.e., they refer to both one or more hydrophilic vinyl monomers (MA).

[0047] More preferably, the hydrophilic vinyl monomer (MA) is preferably of formula (II): [ka] (In the formula, R1 and R2 each have the meaning defined above, R3 is hydrogen, and R OH R1 is a C1-C5 hydrocarbon moiety containing hydrogen or at least one hydroxyl group and / or at least one carboxyl group, more preferably R1, R2, and R3 are each hydrogen, and R OH (This has the same meaning as described in detail above.) It satisfies the condition.

[0048] Non-limiting examples of hydrophilic vinyl monomers (MA) include, in particular, acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxyethylhexyl (meth)acrylate.

[0049] The monomer (MA) is more preferably, - Formula: [ka] Hydroxyethyl acrylate (HEA), - Formula: [ka] Any of the following 2-hydroxypropyl acrylates (HPA), - Formula: [ka] Acrylic acid (AA), and - those mixtures It is selected from among them.

[0050] Most preferably, the monomer (MA) is AA and / or HEA.

[0051] Polymer (F) may further contain other parts such as defects, end groups, etc., which do not affect or impair its physicochemical properties.

[0052] The polymer (F) is semicrystalline. The term semicrystalline is intended to mean polymer (F) having a detectable melting point. Semicrystalline polymers (F) are generally understood to have a heat of fusion measured according to ASTM D3418, advantageously at least 0.4 J / g, preferably at least 0.5 J / g, and more preferably at least 1 J / g.

[0053] The polymer (F) is preferably a linear copolymer, that is, it is composed of a polymer made up of a substantially linear arrangement of repeating units derived from VDF monomer and (MA) monomer, and thus polymer (F) is distinguishable from grafted and / or comb-type polymers.

[0054] The polymer (F) contains at least 0.05 mol%, more preferably at least 0.1 mol%, and even more preferably at least 0.2 mol%, of repeating units derived from the hydrophilic (meth)acrylic monomer (MA).

[0055] The polymer (F) preferably contains repeating units derived from the hydrophilic vinyl monomer (MA) in an amount of up to 2 mol%, more preferably up to 1.8 mol%, and even more preferably up to 1.5 mol%.

[0056] In a preferred embodiment of the present invention, the polymer (F) contains repeating units derived from the hydrophilic vinyl monomer (MA) of formula (I) in an amount of 0.2 to 1 mol% relative to the total moles of repeating units of the polymer (F).

[0057] The polymer (F) advantageously has an intrinsic viscosity measured in dimethylformamide at 25°C, which is greater than 0.15 l / g and at most 0.60 l / g, preferably in the range of 0.20 to 0.50 l / g, and more preferably in the range of 0.25 to 0.40 l / g.

[0058] The polymer (F) may further contain repeating units derived from one or more fluorinated comonomers (CF) different from VDF.

[0059] In this specification, the term "fluorinated comonomer (CF)" is intended to mean an ethylenically unsaturated comonomer containing at least one fluorine atom.

[0060] Non-limiting examples of suitable fluorinated comonomers (CFs) include, in particular: (a) C2-C8 fluoro and / or perfluoroolefins such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene and hexafluoroisobutylene, (b) C2-C8 hydrogen-containing monofluoroolefins such as vinyl fluoride, 1,2-difluoroethylene and trifluoroethylene, (c)Formula CH2=CH-R f0 (In the formula, R f0 (These are perfluoroalkylethylenes, which are C1-C6 perfluoroalkyl groups.) (d) Chloro-, and / or bromo-, and / or iodo-C2~C6 fluoroolefins such as chlorotrifluoroethylene (CTFE).

[0061] In one embodiment of the present invention, the polymer (F) contains 0.1 mol% to 10.0 mol%, preferably 0.3 mol% to 5.0 mol%, and more preferably 0.5 mol% to 3.0 mol%, of repeating units derived from the fluorinated comonomer (CF).

[0062] Polymer (F) is more preferably, - At least 70 mol%, preferably at least 75 mol%, more preferably at least 85 mol%, of vinylidene fluoride (VDF), - 0.2 mol% to 1 mol% of hydrophilic (meth)acrylic monomer (MA) of formula (I), - Optionally, repeating units derived from at least one fluorinated comonomer (CF) in an amount of 0.5 to 3.0 mol% Includes repeating units derived from

[0063] Polymer (F) can be obtained by polymerizing a VDF monomer, at least one monomer (MA), and optionally at least one comonomer (CF) in a suspension in an organic medium, for example, according to the procedure described in International Publication No. 2008 / 129041, or by carrying out in an aqueous emulsion, typically as described in the Art (see, for example, U.S. Patent No. 4016,345, U.S. Patent No. 4,725,644, and U.S. Patent No. 6,479,591).

[0064] The procedure for preparing polymer (F) in suspension comprises polymerizing vinylidene fluoride (VDF) monomer, monomer (MA), and optionally comonomer (CF) in an aqueous medium in a reaction vessel in the presence of a radical initiator, wherein the method is - Continuously supplying an aqueous solution containing monomers (MA), - Maintaining the pressure inside the reaction vessel above the critical pressure of vinylidene fluoride Includes.

[0065] Throughout the suspension polymerization process, the pressure is maintained above the critical pressure of vinylidene fluoride. Generally, the pressure is maintained at a value greater than 50 bar, preferably greater than 75 bar, and more preferably greater than 100 bar.

[0066] The expression “continuous supply,” “continuous addition,” or “continuous supply” means that a slow, gradually increasing amount of aqueous solution of hydrophilic vinyl monomer (MA) is added until polymerization is complete.

[0067] The polymer (F) thus obtained has high uniformity in the distribution of monomers (MA) in the polymer backbone, which advantageously maximizes the influence of the modified monomers (MA) on both the adhesive and / or hydrophilic behavior of the resulting copolymer.

[0068] In addition, the applicant has surprisingly found that the presence of monomers (MA) uniformly distributed in polymer (F) has the effect of improving the thermal stability of VDF copolymers, which is unsatisfactorily low in the absence of monomers, and in particular lower than the thermal stability of VDF homopolymers.

[0069] Polymer (A) is a copolymer derived from the polymerization of at least one monomer (I) and at least one monomer (II), - Monomer (I) is an ethylenically unsaturated linear or branched aliphatic, cyclic or aromatic polycarboxylic acid or anhydride. - Monomer(II) is an ethylenically unsaturated linear or branched aliphatic, cyclic, or aromatic hydrocarbon monomer.

[0070] As used herein, “copolymer” is intended to represent a polymer having two or more different monomer units. A copolymer may be a terpolymer having three or more different monomer units, or it may have four or more different monomer units. A copolymer may be a random copolymer, a gradient copolymer, or a block copolymer formed by a controlled polymerization process. Preferably, the copolymer is formed by a free radical polymerization process or an anionic polymerization process, which may be any polymerization method known in the art, such as solution polymerization or suspension polymerization, and may be carried out by bulk polymerization or semi-bulk polymerization.

[0071] The monomer (I) is preferably of the following formula: (R 1 )(R 2 )C=C(R 3 )-COOR X (In the formula, R 1 , R 2 and R 3 The groups are either identical or different, and optionally contain a hydrogen atom and a -COOH group (C1-C1). 10 Selected from the group consisting of hydrocarbon groups and -COOH groups, R 1 , R 2 and R 3 At least one of them is not a hydrogen atom, R X C1-C containing a hydrogen atom or at least one carboxyl functional group 20 Selected from the hydrocarbon portion, R 1 and R 2 Any of the -COOH groups can be optionally, at least partially, COOR X (It can combine with the base to form an anhydrous substance.) It is a monomer.

[0072] According to a preferred embodiment of the present invention, monomer (I) is of the following formula: (R 4 )HC=C(R 5 )COOR X (In the formula, R4 is selected from the group consisting of a hydrogen atom, a -COOH group or -(CH2) n -COOH group (where n is 1 to 4) or a C1-C4 alkyl group, R 5 is selected from the group consisting of a hydrogen atom, -(CH2) m -COOH group (where m is 1 to 4) or a C1-C4 alkyl group, R 4 and R 5 at least one of which is not a hydrogen atom, R X is as defined above) is a polycarboxylic acid or carboxylic anhydride corresponding to)

[0073] Preferably, R 4 is selected from the group consisting of a hydrogen atom, a -COOH group or a (CH2)-COOH group, a methyl group, R 5 is selected from the group consisting of a hydrogen atom, -CH2COOH or a methyl group, R 4 and R 5 at least one of which is not a hydrogen atom.

[0074] According to a more specific embodiment, the monomer (I) is selected from the group consisting of citraconic acid, maleic acid, fumaric acid or itaconic acid, citraconic acid ester, maleic acid ester, fumaric acid ester or itaconic acid ester or citraconic anhydride, maleic anhydride, fumaric anhydride or itaconic anhydride, (meth)acryloyloxyalkyl succinic acid, such as (meth)acryloyloxyethyl succinic acid and (meth)acryloyloxypropyl succinic acid.

[0075] More preferably, the monomer (I) is maleic anhydride.

[0076] The monomer (II) is preferably the following formula: (R 6 )(R 7 )C=CH2 (where R 6 and R 7The groups are the same or different, and consist of hydrogen atoms or linear or branched aliphatic or cyclic saturated or ethylenically unsaturated C1-C1 atoms. 10 (Selected from a group consisting of elements) It is a monomer.

[0077] More specifically, the aforementioned R 6 and R 7 The groups are identical or different, consisting of a hydrogen atom or saturated linear or branched aliphatic or cyclic C1-C atoms. 10 Selected from a group consisting of elements.

[0078] Preferably, the monomer (II) is selected from the group consisting of ethylene, propylene, 1-butene, isobutylene, n-1-pentene, 2-methyl-1-butene, n-1-hexene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene (or 2,4,4-trimethyl-1-pentene), and 2-methyl-3,3-dimethyl-1-pentene.

[0079] In one embodiment of this application, polymer (A) is preferably a copolymer of maleic anhydride and diisobutylene.

[0080] In one embodiment, polymer (A) is more specifically a copolymer of monomer (I) in 40 mol% to 60 mol% and monomer (II) in 60 mol% to 40 mol%.

[0081] In a preferred embodiment of the present invention, polymer (A) is a copolymer of maleic anhydride and diisobutylene, comprising about 40 mol% to 60 mol%, preferably about 50 mol%, of maleic anhydride monomer units and 60 mol% to 40 mol%, preferably about 50 mol%, of diisobutylene monomer units.

[0082] The molecular weight Mw of the copolymer used as polymer (A) is typically 10,000 Da to 500,000 Da, preferably 15,000 Da to 75,000 Da.

[0083] Polymer (A) is prepared by polymerizing a mixture of monomer (I) and monomer (II) optionally in the presence of other α,β-ethylenically unsaturated monomers such as acrylonitrile, N-vinylimidazole, N-vinylpyrrolidone, vinylphosphonic acid.

[0084] Polymer (A) can be at least partially further neutralized to obtain at least a part of the anhydride or carboxylic acid moiety in the form of a salt.

[0085] Thus, in one embodiment of the present invention, a binder (B) containing at least partially chlorinated polymer (A) is provided.

[0086] Thus, the preparation of polymer (A) may further include the step of neutralizing at least a part of the anhydride group or carboxyl group with a salt [salt (SA)] containing a monovalent or divalent cation in a suitable solvent.

[0087] Salt (SA) can be any salt capable of neutralizing an anhydride group or carboxylic acid group, which is preferably selected from salts capable of supplying an alkali metal cation, an alkaline earth metal cation, a tertiary or quaternary ammonium cation, more preferably Na + , K + , Li + and / or a quaternary ammonium cation.

[0088] The selection of the solvent (S) is not particularly limited as long as it is suitable for solubilizing the polymer (F) and the dispersed / dissolved polymer (A).

[0089] The solvent (S) is typically - alcohols such as methyl alcohol, ethyl alcohol and diacetone alcohol, - ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone and isophorone, - Linear or cyclic esters such as isopropyl acetate, n-butyl acetate, methyl acetate, dimethyl phthalate, and γ-butyrolactone, - Linear or cyclic amides such as N,N-diethylacetamide, N,N-dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone, and - Dimethyl sulfoxide It is selected from the group consisting of the following.

[0090] The electrode-forming composition of the present invention may further comprise one or more optionally conductive additives to improve the conductivity of electrodes produced from the composition of the present invention. Conductive additives for batteries are known in the art.

[0091] Examples of such materials include carbonaceous materials such as carbon black, graphite powder, carbon nanotubes, graphene, or fibers, or fine powders or fibers of metals such as nickel or aluminum. The optional conductive agent is preferably carbon black or carbon nanotubes.

[0092] The amount of the optional conductive agent is preferably 0 to 30% by weight relative to the total solid content in the electrode-forming composition. In particular, for the positive electrode-forming composition, the optional conductive agent is typically 0% to 10% by weight, more preferably 0% to 5% by weight, of the total solid content in composition (C).

[0093] Composition (C) may further comprise at least one wetting agent and / or at least one surfactant, and one or more additional additives.

[0094] Composition (C) may further comprise at least one non-electroactive inorganic filler material.

[0095] The term "non-electroactive inorganic filler material" is intended in this specification to mean a non-conductive inorganic filler material suitable for the manufacture of electrical insulating separators for electrochemical cells.

[0096] The non-electroactive inorganic filler material in the separator according to the present invention typically has an electrical resistivity (p) of at least 0.1 × 10¹⁰ ohms / cm, preferably at least 0.1 × 10¹² ohms / cm, as measured at 20°C according to ASTM D 257.

[0097] Suitable non-electroactive inorganic fillers include, but are not limited to, natural and synthetic silica, zeolites, alumina, titania, metal carbonates, zirconia, silicon phosphate, and silicates.

[0098] A binder (B) for use in composition (C) according to the present invention can be prepared by any method known in the art.

[0099] The appropriate method is, - Dissolving polymer (F) in solvent (S), - Add the polymer (A) in powder form or, alternatively, in a dispersed / dissolved state in the solvent (S). - Mix to obtain binder mixture (B) Includes.

[0100] The weight ratio of polymer (F) to polymer (A) in the binder (B) is preferably in the range of 95:5 to 70:30. In a preferred embodiment of the present invention, the weight ratio of polymer (F) to polymer (A) in the binder (B) is 90:10.

[0101] The electrode-forming composition (C) can be obtained by adding and dispersing powdered electrode material and optional additives, such as conductivity-imparting additives and / or viscosity modifiers, to the binder mixture (B) thus obtained, thereby obtaining a uniform slurry.

[0102] The solution of polymer (F) in solvent (S) contains particularly 5-20% by weight, preferably about 7-10% by weight of polymer (F).

[0103] When polymer (A) is added as a dispersion or solution in solvent (S), the amount of polymer (A) in solvent (S) is, in particular, in the range of 0.1 to 15% by weight per 100 parts by weight of such solvent.

[0104] To prepare the binder mixture (B), it is preferable to first dissolve the polymer (F) in the solvent at a temperature of 20-50°C, and then disperse or dissolve the polymer (A) in the solvent (S).

[0105] Alternatively, the binder solution (B) can be prepared by first dissolving the polymer (F) in the solvent (S), and then adding the solid polymer (A) to the prepared mixture.

[0106] The total solids content (TSC) of composition (C) of the present invention is typically 15 to 70% by weight, preferably 40 to 60% by weight, relative to the total weight of composition (C). The total solids content of composition (C) is understood to be the accumulation of all its non-volatile components, particularly polymer (F), polymer (A), electrode active material, and any additional solid non-volatile additives.

[0107] When preparing composition (C) by combining a solution of polymer (F) with polymer (A), an electrode active material, an optional conductive material, and other additives, a sufficient amount of solvent is used to form a stable solution of polymer (F). The amount of solvent used may range from the minimum amount required to form a stable solution of polymer (F) to the amount required to achieve the desired total solid content in the electrode mixture after the addition of polymer (A), the electrode active material, the optional conductive material, and other solid additives.

[0108] The presence of polymer (A) in composition (C) makes it possible to obtain a uniform slurry composition without any signs of gelation in all preparation steps. Therefore, it is possible to use a polymer (F) having polar groups in an electrode-forming composition containing an olivine-type active material electrode, and to utilize the properties of such a polymer in the electrode, such as excellent adhesion to the current collector, improved flexibility, and excellent mechanical properties.

[0109] In addition, polymer (A) functions as a dispersant in the binder composition and has the same TSC, but reduces the viscosity of the slurry compared to a composition containing only polymer (F), an active material, and a conductivity-imparting additive.

[0110] Another advantage of composition (C) of the present invention is that it provides an electrode containing a binder with a relatively low weight content and can allow for an increase in the content of the active material in the positive electrode to maximize the capacity of the battery.

[0111] The electrode-forming composition (C) of the present invention may be used in a method for producing a positive electrode [electrode (E)], the method being (i) To provide a metal substrate having at least one surface, (ii) To provide the electrode-forming composition [composition (C)] defined above, (iii) Applying composition (C) to at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate in which at least one surface is coated with composition (C), (iv) Dry the assembly provided in step (iii). Includes.

[0112] The metal substrate is typically a foil, mesh, or net made from metals such as aluminum, nickel, titanium, and their alloys.

[0113] In step (iii) of the method of the present invention, the electrode-forming composition (C) is typically applied to at least one surface of a metal substrate by any preferred procedure such as casting, printing, and roll coating.

[0114] Optionally, step (iii) can be repeated typically one or more times by applying the electrode-forming composition (C) provided in step (ii) onto the assembly provided in step (iv).

[0115] In step (iv) of the method of the present invention, drying may be carried out under either atmospheric pressure or vacuum. Alternatively, drying may be carried out in a modified atmosphere, such as an inert gas, typically with particularly removed moisture (water vapor content less than 0.001% v / v).

[0116] The drying temperature is selected to achieve the removal of the aqueous medium from the electrode (E) of the present invention by evaporation.

[0117] By further performing a compression process, such as a calendering process, on the dried assembly obtained in step (iv), the target porosity and density of the electrode (E) of the present invention can be achieved.

[0118] Preferably, the dried assembly obtained in step (iv) is hot-pressed, and the temperature during the compression step is between 25°C and 130°C, preferably about 60°C.

[0119] The preferred target density of electrode (E) is 2–3 g / cc, preferably at least 2.1 g / cc. The density of electrode (E) is calculated as the sum of the products of the densities of the electrode components multiplied by their mass ratios in the electrode formulation.

[0120] In a further embodiment, the present invention relates to a positive electrode (E) that can be obtained by the method of the present invention.

[0121] Therefore, the present invention is - A metal substrate having at least one surface, - At least one layer directly bonded to at least one surface of the metal substrate and A positive electrode (E) comprising, the at least one layer being a) At least one positive electrode active material (AM), b) Binder composition [Binder (B')], b') At least one [polymer (F)] as defined above, b'') At least one [polymer (A)] as defined above A binder composition containing [binder (B')], c) Optionally, at least one conductivity-imparting additive This relates to a positive electrode (E) comprising a composition [composition (C')] containing the above.

[0122] The composition (C') directly bonded to at least one surface of the metal substrate corresponds to the electrode-forming composition (C) of the present invention, in which the solvent is at least partially removed during the electrode manufacturing process, for example in step (iv) (drying) and / or a further compression step.

[0123] Accordingly, all preferred embodiments described with respect to the electrode-forming composition (C) of the present invention are also applicable to the composition (C') directly bonded to at least one surface of the metal substrate in the electrode of the present invention, except for the aqueous medium which is removed during the manufacturing process.

[0124] The preferred positive electrode (E) is: - A metal substrate having at least one surface, - At least one layer directly bonded to at least one surface of the metal substrate and It includes, and at least one layer, j) A positive electrode active material (AM) in an amount of 90-98% by weight, jj) A binder (B') in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, jjj) 0.5~5% by weight of a conductivity-imparting additive and It consists of the above, and the weight percentages mentioned above are relative to the total weight of j) + jj) + jjj).

[0125] Preferably, the positive electrode (E) contains at least 95% by weight of active material (AM) and 8-20 mg / cm³ of active material. 2 Preferably about 15 mg / cm³ 2 This includes the electrode load.

[0126] The positive electrode (E) of the present invention is particularly suitable for use in electrochemical devices.

[0127] The term "electrochemical device" is intended herein to mean an electrochemical cell / assembly comprising a positive electrode, a negative electrode, and a liquid electrolyte, wherein a single-layer or multi-layer separator is in contact with at least one surface of one of the electrodes. Non-limiting examples of suitable electrochemical devices include, in particular, secondary batteries, especially alkaline or alkaline earth secondary batteries such as lithium-ion batteries, lead-acid batteries, and capacitors, in particular lithium-ion capacitors and electric double-layer capacitors (supercapacitors). Non-limiting examples of electrochemical cells include, in particular, batteries, preferably secondary batteries, and electric double-layer capacitors.

[0128] For the purposes of this invention, "secondary battery" is intended to refer to a rechargeable battery. Non-limiting examples of secondary batteries include, in particular, alkaline or alkaline earth secondary batteries.

[0129] The secondary battery of the present invention is more preferably a lithium-ion secondary battery.

[0130] The electrochemical device according to the present invention can be fabricated by standard methods known to those skilled in the art.

[0131] If any disclosure of a patent, patent application, or publication incorporated herein by reference conflicts with any description in this application to such an extent that it obscures certain terms, the description herein shall prevail.

[0132] The present invention will be described here in relation to the following embodiments, but the purpose is merely illustrative and not intended to limit the scope of the invention. [Examples]

[0133] raw materials Polymer (F-1): VDF-AA (1.0 mol%) polymer with an intrinsic viscosity of 0.30 l / g in DMF at 25°C.

[0134] Polymer (A-1): Maleic anhydride / diisobutylene copolymer neutralized with NaOH, available from Solvay as Geropon® T36.

[0135] Nano-LFP:LFP P2 / C-life C04, density: 3.34g / cm 3 Effective relative capacity: 153mAh / g, commercially available from Johnson Matthey.

[0136] Carbon nanotubes: Orgacyl NMP0402. Thin, multi-walled carbon nanotubes (MWCNTs) at a concentration of 4% in N-methyl-2-pyrrolidone (NMP) solvent.

[0137] Determination of molecular weight The mass distribution of the polymer was measured by SEC MALS analysis (SEC: size exclusion chromatography - MALLS: multi-angle laser light scattering) to obtain real values ​​expressed in g / mol.

[0138] SEC MALLS analysis using two detectors: - Differential Refractometer (RI) - Concentration Detector - MALLS detector (multi-angle laser light scattering) - Mass detector, - UV detector This was done using [a specific method / tool].

[0139] For each slice of the chromatogram (of polymer chemical species), the software calculates the following: - Polymer concentration, RI signal = constant * dn / dc * concentration, - Slice mass Mi, - From specific Mi data, the software calculates the mass distribution: Mw, Mn, and polyvariance index Ip = Mw / Mn.

[0140] Calculating the molar mass requires an increment in the polymer's refractive index, dn / dc. This is constant, depending, among other things, on the properties of the mobile phase, the temperature under experimental conditions, and the wavelength of the laser.

[0141] The value "dn / dc" is calculated by software according to the mass recovery rate of the elution fraction. For the polymer of the present invention, dn / dc is 0.085 mL / g obtained from a mass recovery rate of 95–100 wt%. Molar mass was calculated based on the actual Mi point without any adjustment of the log(M) curve.

[0142] The detailed analysis conditions are as follows: - Analytical equipment: SEC system with MALLS detector (Mini Dawn TREOS); Agilent differential refractometer (RI) and Agilent UV detector (254nm) - Pump: Agilent 1100 - Mobile phase: THF containing 0.01 M tetrabutylammonium tetrafluoroborate and 100 μL of trifluoroacetic acid per 1 kg of eluent. - Column (manufacturer, model number): Agilent Polypore (2*30cm) + guard column - Temperature: 35℃ - Flow rate: 1.0mL / min - Injection volume and sample concentration: 100 μL, 3 mg / mL in mobile phase -1 .

[0143] Example 1: An 8 wt% NMP solution of polymer (F-1) was prepared.

[0144] Powdered polymer (A-1) was mixed with a solution of polymer (F-1) in NMP in a 9:1 ratio (29.77 g of polymer (F-1) solution and 0.87 g of polymer (A-1)).

[0145] HSV900: A PVDF homopolymer commercially available from Arkema.

[0146] Nano-LFP (72.4 g), carbon nanotubes (13.8 g of a 4.1 wt% NMP solution), and an additional 23.8 g of NMP were simultaneously added to polymer (A-1) by planetary mixing and subsequent dispersed phase into a solution containing polymer (F-1) to obtain composition 1, which is a cathode slurry with a total solids content (TSC) of 54% (LFP 95.75%, carbon nanotubes 0.75%, and binder 3.5%).

[0147] A uniform slurry was obtained, and no signs of gelation were observed in any of the preparation steps. The results of the visual evaluation of slurry quality are summarized in Table 1.

[0148] Comparative Example 1: An 8 wt% NMP solution of HSV900 was prepared.

[0149] Nano-LFP (72.4 g), carbon nanotubes (13.8 g of a 4.1 wt% NMP solution), and 20.71 g of additional NMP were added to 33.08 g of a solution containing HSV900 by planetary mixing and subsequent dispersed phase to obtain composition (C-1), which is a cathode slurry with a total solids content (TSC) of 54% and a binder content of 3.5%.

[0150] The results of the visual evaluation of slurry quality are summarized in Table 1.

[0151] [Table 1]

[0152] Example 2: Evaluation of gelation of electrode-forming composition The change in viscosity over time of composition 1 and composition C-1, which were prepared as defined above, was evaluated as follows.

[0153] The viscosity of the composition at different maturation times up to 72 hours was evaluated at different shear rates (0.1 to 100 rad / s) by comparing values ​​at the same shear rate using Anton Paar's MCR52 plate-to-plate apparatus.

[0154] Composition 1 exhibits excellent slurry stability over time, comparable to that of Composition C-1, from time 0 to time 72 hours.

[0155] Example 3: Electrode fabrication The positive electrode is formed by applying the above electrode-forming composition to a 15 μm thick aluminum foil, with a concentration of 15 mg / cm². 2 The dry cathode-supported mass was obtained by obtaining a block of the material. The solvent was completely evaporated by drying in an oven at a temperature of 90°C to prepare a strip-shaped cathode.

[0156] The positive electrodes obtained in this manner (electrodes (E1) and (EC-1), respectively) were visually evaluated. The results are reported in Table 3.

[0157] [Table 2]

[0158] Positive electrode adhesion evaluation The positive electrodes (E1) and (EC-1) were cut into strips (10 cm long, 2.5 cm wide) and attached to a 2 mm thick rigid aluminum foil using 2.5 x 8 cm double-sided adhesive tape. The coated side of the electrodes was facing the aluminum plate. Because a portion of the electrodes was held so as not to adhere to the tape, one end of each stripe could be pulled away from the foil without contacting the double-sided adhesive tape.

[0159] Each test specimen was peeled from the foil at a 180° angle using a dynamometer that allowed for the measurement of the force required to peel the sample from the double-sided adhesive tape. The peeling rate was 300 mm / min at T=25°C. The results are summarized in Table 4.

[0160] [Table 3]

Claims

1. a) At least one positive electrode active material (AM), b) A type of binder (B), i) At least one vinylidene fluoride (VDF) copolymer [polymer (F)], (ia) Repeating units derived from VDF, (ib) Optionally, an amount of 0.05 to 10 mol% of the total moles of repeating units of polymer (F), containing formula (I): 【Chemistry 1】 (In the formula, - R １ , R ２ and R ３ They are equal to or different from each other, and independently, hydrogen atoms and C １ ~C ３ Selected from hydrocarbon groups, and - R Ｘ C comprises at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, phosphate, and ether groups. １ ~C ２０ (This is the hydrocarbon portion.) Repeating units derived from at least one hydrophilic vinyl monomer (MA) At least one vinylidene fluoride (VDF) copolymer [polymer (F)] containing, ii) At least one polymer [polymer (A)] obtained from polymerization of at least one monomer (I) and at least one monomer (II), wherein the monomer is - Monomer (I): Ethylene-unsaturated linear or branched aliphatic, cyclic or aromatic polycarboxylic acid or anhydride, - Monomer (II): Ethylene-unsaturated linear or branched aliphatic, cyclic, or aromatic hydrocarbons At least one polymer [polymer (A)] corresponding to [polymer (A)] One type of binder (B) containing, c) At least one solvent (S), d) Optionally, at least one conductivity-imparting additive and A positive electrode forming composition (C) comprising the above.

2. The composition (C) according to claim 1, wherein the hydrophilic vinyl monomer (MA) is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxyethylhexyl (meth)acrylate.

3. The composition according to claim 1 or 2, wherein the active material (AM) is selected from lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), and lithium manganese phosphate.

4. The monomer (I) is given by the following formula: (R １ )(R ２ )C=C(R ３ )-COOR Ｘ (In the formula, R １ , R ２ and R ３ The groups are identical or different, and optionally contain a hydrogen atom and a -COOH group. １ ~C １０ Selected from the group consisting of hydrocarbon groups and -COOH groups, R １ , R ２ and R ３ At least one of them is not a hydrogen atom, R Ｘ C contains a hydrogen atom or at least one carboxyl functional group. １ ~C ２０ Selected from the hydrocarbon portion, R １ and R ２ Any of the aforementioned -COOH groups may optionally be at least partially COOR Ｘ (It can combine with the base to form an anhydrous substance.) A composition (C) according to any one of claims 1 to 3, wherein the monomer is [the monomer].

5. The composition (C) according to claim 4, wherein monomer (I) is selected from the group consisting of citraconic acid, maleic acid, fumaric acid or itaconic acid, citraconic acid ester, maleic acid ester, fumaric acid ester or itaconic acid ester, or citraconic acid anhydride, maleic acid anhydride, fumaric acid anhydride or itaconic acid anhydride, (meth)acryloyloxyalkyl succinic acid, for example, (meth)acryloyloxyethyl succinic acid and (meth)acryloyloxypropyl succinic acid.

6. The monomer (II) is given by the following formula: (R ６ )(R ７ )C=CH ２ (In the formula, R ６ and R ７ The groups are the same or different, and consist of a hydrogen atom or a linear or branched aliphatic or cyclic saturated or ethylenically unsaturated C １ ~C １０ (Selected from a group consisting of elements) A composition (C) according to any one of claims 1 to 5, wherein the monomer is [the monomer].

7. The composition (C) according to claim 6, wherein monomer (II) is selected from ethylene, propylene, 1-butene, isobutylene, n-1-pentene, 2-methyl-1-butene, n-1-hexene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene (or 2,4,4-trimethyl-1-pentene), and 2-methyl-3,3-dimethyl-1-pentene, and preferably monomer (II) is diisobutylene.

8. The composition (C) according to any one of claims 1 to 7, wherein polymer (A) is a copolymer of maleic anhydride and diisobutylene monomer units.

9. The composition according to claim 8, wherein polymer (A) is at least partially chlorinated.

10. The composition (C) according to any one of claims 1 to 9, wherein the weight ratio of polymer (F) to polymer (A) in the binder (B) is in the range of 95:5 to 70:30, preferably 90:

10.

11. A method for manufacturing a positive electrode [electrode (E)], (i) To provide a metal substrate having at least one surface, (ii) To provide an electrode-forming composition [composition (C)] according to any one of claims 1 to 10, (iii) Applying the composition (C) provided in step (iii) onto the at least one surface of the metal substrate provided in step (i), thereby providing an assembly comprising the metal substrate in which the at least one surface is coated with the composition (C). (iv) Dry the assembly provided in step (iii). A method that includes this.

12. A positive electrode (E) that can be obtained by the method described in claim 11.

13. - A metal substrate having at least one surface, - At least one layer directly bonded to at least one surface of the metal substrate and A positive electrode (E) comprising, the at least one layer is a) At least one positive electrode active material (AM), b) Binder composition [Binder (B')], b') At least one vinylidene fluoride (VDF) copolymer [polymer (F)], (i) Repeating units derived from VDF, (ii) Formula (I) in an amount of 0.05 to 10 mol% relative to the total moles of repeating units of polymer (F): 【Chemistry 2】 (In the formula, - R １ , R ２ and R ３ They are equal to or different from each other, and independently, hydrogen atoms and C １ ~C ３ Selected from hydrocarbon groups, and - R Ｘ C comprises at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, phosphate, and ether groups. １ ~C ２０ (This is the hydrocarbon portion.) Repeating units derived from at least one hydrophilic (meth)acrylic monomer (MA) At least one vinylidene fluoride (VDF) copolymer [polymer (F)] containing, b'') At least one polymer (A) obtained from the polymerization of at least one monomer (I) and at least one monomer (II), wherein the monomers are - Monomer (I): Ethylene-unsaturated linear or branched aliphatic, cyclic or aromatic polycarboxylic acid or anhydride, - Monomer (II): Ethylene-unsaturated linear or branched aliphatic, cyclic, or aromatic hydrocarbon monomers A corresponding at least one polymer (A) A binder composition containing [binder (B')], c) Optionally, at least one conductivity-imparting additive and A positive electrode (E) comprising a composition [composition (C')] containing the above.

14. An electrochemical device comprising a positive electrode (E) as described in claim 12 or 13.

15. The electrochemical device according to claim 14, which is a lithium-ion secondary battery.

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