Positive electrode binder for lithium-ion batteries

Abstract

The present invention relates to a binder for the positive electrode of a lithium-ion battery, a method for preparing the electrode, and its use in a lithium-ion battery. The present invention also relates to a lithium-ion battery manufactured by incorporating the electrode.

Description

Technical Field

[0001] The present invention relates to a binder for a Li-ion battery cathode, a method for preparing the electrode, and its use in a Li-ion battery.

[0002] The present invention also relates to a Li-ion battery manufactured by incorporating the electrode.

Background Art

[0003] Electrochemical devices such as secondary batteries typically include a positive electrode, a negative electrode, and an electrolyte.

[0004] Electrodes for lithium batteries are usually manufactured by mixing a binder with a powdery electrode active material.

[0005] Fluorine resins such as vinylidene fluoride-based polymers are used as binders for forming positive electrodes. In particular, polyvinylidene fluoride (PVDF) provides good electrochemical stability and high adhesiveness to electrode materials. Therefore, PVDF is a preferred binder material for electrode slurries.

[0006] U.S. Patent Application Publication No. 2018 / 0355206 discloses the use of a copolymer of methyl methacrylate and methacrylic acid in a mixture with PVDF for the preparation of a LiNMC electrode slurry having good adhesion to a current collector, the mixture having a viscosity that allows the active material to be easily spread on a metal current collector and thus facilitating the manufacture of an electrode for a lithium-ion battery.

[0007] U.S. Patent Application Publication No. 2015 / 0280238 discloses a stable electrode binder dispersion for use in the preparation of an LFP cathode for a lithium-ion battery, the dispersion comprising PVDF dispersed in an organic diluent and a (meth)acrylic polymer dispersant.

[0008] The solutions currently available in this field rely on the use of PVDF homopolymer binders, but these face the challenge of insufficient adhesion to current collectors.

[0009] Modified 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 with the aim of adding suitable adhesion to metals, such as aluminum or copper, to the mechanical properties and chemical inertness of PVDF.

[0010] However, there are modified PVDF polymers that are used in the preparation of slurries for forming positive electrodes using specific active materials. In particular, in lithium-ion batteries, when LiFePO4 (LFP) active material is used, a significant drawback is that the slurry often undergoes a rapid increase in viscosity, leading to gel formation and thus hindering its use as a binder for LFP cathodes.

[0011] The time dependence of the rheological properties of composite electrode slurries has also been observed in sodium-ion secondary batteries. In fact, when the slurry is exposed to air, gelation is initiated by NaOH present on the material, which can result in dehydration and fluorination accompanied by PVDF crosslinking. This gelation leads to the formation of a non-uniform coating.

[0012] The need for higher-performance polymers, particularly those that guarantee better mechanical performance and greater adhesion to current collectors, remains evident both in research and industry.

[0013] One approach is to find a polymer blend that avoids the drawbacks of modified PVDF polymers in contact with certain active materials such as PVDF homopolymers and LFPs, while simultaneously ensuring the feasibility of electrodes by wet casting and high adhesion of the final product.

[0014] In addition, the industry recognizes the need for polymers with improved resistance, particularly in terms of swelling resistance, when in contact with battery electrolytes, especially when using carbonate-based electrolytes.

[0015] The present invention provides a positive electrode forming composition that can prevent gelation while simultaneously enabling the manufacture of electrodes with improved adhesion, reduced polymer swelling upon contact with the electrolyte, lower resistivity, electrochemical stability, and longer battery life. [Overview of the Initiative]

[0016] Therefore, the object of the present invention is a positive electrode forming composition (C), - At least one positive electrode active material (AM), - At least one type of binder (B), a) at least one vinylidene fluoride (VDF) polymer [polymer (F)], (i) Repeating units derived from VDF, (ii) Optionally, an amount of 0.05 to 10 mol% of the total moles of repeating units of polymer (F), containing formula (I): [ka] (In the formula, - R1, R2, and R3, which are equal to or different from each other, are 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 monomer (MA) At least one vinylidene fluoride (VDF) polymer [polymer(F)] containing, b) At least one branched (meth)acrylic polymer [polymer (A)] derived from the polymerization of at least one (meth)acryloyl monomer [monomer (MAM)] and at least one molecule [monomer (BM)] containing at least two vinyl groups, wherein monomer (BM) is a divinylaryl monomer, e.g., divinylbenzene; (meth)acrylate diesters, e.g., alkylenedi(meth)acrylate, e.g., ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, oligoalkylene glyco A selection from the group consisting of di(meth)acrylates, such as tetraethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, poly(propylene glycol) di(meth)acrylate, etc., divinyl(meth)acrylamide, such as methylenebisacrylamide, divinyl ether, such as poly(ethylene glycol) divinyl ether, and tetra- or tri-(meth)acrylate esters, such as pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, or glucose di-~penta(meth)acrylate, Polymer (A) is a branched (meth)acrylic polymer [polymer (A)] containing less than 1 mol% of monomer (BM). A binder (B) containing at least one type of binder (B), - At least one solvent (S), - Optionally, at least one conductivity-imparting additive and This is a positive electrode forming composition (C) containing the following.

[0017] In a second example, the present invention relates to the use of the electrode-forming composition (C) of the present invention in a process for manufacturing a positive electrode [electrode (E)] for an electrochemical device, wherein the process is: (i) A step of providing a metal substrate having at least one surface, (ii) A step of providing an electrode-forming composition (C) as defined above, (iii) Applying composition (C) to at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate coated with composition (C) on at least one surface, (iv) A step of drying the assembly provided in step (iii). Including, regarding use.

[0018] In a third example, the present invention relates to a positive electrode (E) that can be obtained by the process of the present invention.

[0019] 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]

[0020] 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 for the purpose of better identifying that symbol or number from the rest of the text, and therefore such parentheses may be omitted.

[0021] The terms “acrylic” and “acrylate” are used interchangeably (as long as doing so does not alter the intended meaning) and include acrylic acid and its derivatives. The terms “(meth)acrylic” or “(meth)acrylate” are intended to encompass both the acrylic / acrylate and methacrylic / methacrylate forms of the material being shown, e.g., (meth)acrylate monomers.

[0022] The electrode active material (AM) of the positive electrode is preferably a compound into which lithium ions or sodium ions can be inserted.

[0023] Conventional active materials (AMs) for the positive electrode of sodium-ion batteries are generally selected from Na-based layered transition metal oxides, Prussian blue analogs, and polyanionic materials.

[0024] 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 the oxygen layer. The P2-type structure generally corresponds to the general formula NaxMO2 (where M represents transition metal ions such as Co and Mn, and x is 2 / 3).

[0025] In some embodiments, the active material is Na 0.81 Fe[Fe(CN)6] 0.79 , NaFe2(CN)6, Na 1.63 Fe 1.89 (CN)6, Na 1.72 MnFe(CN)6, Na 1.76 Ni 0.12 Mn 0.88 [Fe(CN)6] [[ID=]21] 0.98 , 0≦x≦1 of Na2Ni x Co 1-x Fe(CN)6, such as Na2CoFe(CN)6), etc., the general formula A x P[R(CN)6] 1-y . mH2O (where A is an alkali metal ion, P is an N-coordinated transition metal ion, R is a C-coordinated transition metal ion, y is a [R(CN)6] vacancy, 0≦x≦2 and 0≦y<1) is a Prussian blue analog (PBA).

[0026] In some other embodiments, the active material is a series of tetrahedral anion units (XO4) n- and its derivatives (X m O 3m+1 ) n- having a general formula Na x M y (XO4) n (where X = S, P, Si, As, Mo, and W, and M is a transition metal) is a polyanion-type material. Among them, phosphates such as NaFePO4, Na 0.7 FePO4 or NaMnPO4, NaMPO4 of the general formula Na xSodium superionic conductors of the NASICON type M2(XO4)3 (wherein 1≦x≦4, M=V, Fe, Ni, Mn, Ti, Cr, Zr, X=P, S, Si, Se, Mo) include single transition metal types such as -Na3V2(PO4)3(NVP), Na3Cr2(PO4)3, Na3Fe2(PO4)3, and binary transition metal pyrophosphates such as Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na2Fe3(PO4)2(P2O7)(NFPP), with a 2 / 3≦x≦7 / 8 Na 4-x Fe 2+x / 2 (P2O7)2, 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, fluorophosphates NaVPO4F, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VO) where 0≦x≦1 1-x PO4)2F 1+2x Fluorosulfates such as Na3(VOPO4)2F or Na3V2(PO4)2F3(NVPF), NaMSO4F where M=Fe, Co, or Ni, mixed phosphates / pyrophosphates of the general formula Na4M3(PO4)2(P2O7) (where M represents a transition metal), such as Na4Mn3(PO4)2(P2O7), Na4Co3(PO4)2(P2O7), Na4Ni3(PO4)2(P2O7), Na4Fe3(PO4)2(P2O7)(NFPP), Na7V4(P2O7)4(PO4), 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 Examples include sulfates such as (SO4)3 (where 0 ≤ x ≤ 1) and silicates with the general formula Na2MSiO4 (where M = Mn, Fe, Co, and Ni).

[0027] 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 , for example Na3(VOPO4)2F or Na3V2(PO4)2F3 (NVPF).

[0028] Conventional active materials (AMs) 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 thereof can include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1) and spinel-structured LiMn2O4.

[0029] As an alternative, further, the electrode active material can include a lithiated or partially lithiated transition metal oxyanion-based electrode active material of the formula M1M2(JO4) f E 1-f (where M1 is lithium that can be partially replaced by another alkali metal representing 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 that can be partially replaced by one or more additional metals representing 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 mole fraction of the JO4 oxyanion included in the range of 0.75 to 1).

[0030] M1M2(JO4) f E 1-fThe electrode active material is preferably phosphate-based and may have an ordered or modified olivine structure.

[0031] More preferably, the electrode active material is of 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, and at least one of them is a transition metal, JO4 is preferably PO4 which can be partially substituted by another oxyanion, and J is any one of S, V, Si, Nb, Mo or a combination thereof). Even more preferably, the electrode active material (AM) is of 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) is a phosphate-based electrode active material.

[0032] The A component is preferably Fe, Mn and Ni, particularly preferably Fe.

[0033] The D component is preferably Mg or Ca.

[0034] Examples of compounds having an olivine structure include lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP) and lithium manganese phosphate.

[0035] Furthermore, as the positive electrode active material (AM), it is possible to use a material whose surface is partially or entirely coated with carbon to supplement conductivity.

[0036] The amount of the coated carbon is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less based on 100 parts by weight of the positive electrode active material.

[0037] 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).

[0038] More preferably, it is 90% by mass or more, and most preferably, the positive electrode active material (AM) consists only of compounds having an olivine structure.

[0039] Most preferably, the positive electrode active material (AM) consists solely of lithium iron phosphate (LFP).

[0040] In the positive electrode composition of the present invention, the active material (AM) has an average particle size of 3 μm or less.

[0041] 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.

[0042] The average particle size of the positive electrode active material can be measured by a particle size analyzer for dynamic light scattering.

[0043] As the average particle size decreases, the surface area increases, requiring a smaller amount of binder to bond the particles, which in turn necessitates the binder's flexibility.

[0044] 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 positive electrode composition for secondary batteries exhibits superior electrical properties, such as output characteristics, when used as the positive electrode of the battery.

[0045] Composition (C) of the present invention is a) at least one vinylidene fluoride (VDF) copolymer [polymer (F)], b) at least one branched (meth)acrylic polymer [polymer (A)], c) at least one solvent (S), d) Optionally, at least one conductive additive and It further includes a binder (B) containing the following.

[0046] Polymer (F) consists of repeating units derived from vinylidene fluoride (VDF) and optionally, 0.05 to 10 mol% of the total moles of repeating units of polymer (F), of formula (I): [ka] (In the formula, - R1, R2, and R3, which are equal to or different from each other, are 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 includes repeating units derived from at least one monomer (MA).

[0047] More preferably, the monomer (MA) is preferably of formula (II): [ka] (In the formula, R1 and R2 each have the meanings 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, while R OH (This has the same meaning as described in detail above.) Follow the rules.

[0048] Non-limiting examples of monomers (MA) include, among others, 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 ethyl acrylate (HPA), - Formula: [ka] Acrylic acid (AA), and - those mixtures It is selected from among them.

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

[0051] Polymer (F) may still contain other parts such as defects and end groups that 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 D 3418, 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, i.e., it is composed of a polymer made 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 monomer (MA).

[0055] The polymer (F) preferably contains repeating units derived from the 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 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) has an intrinsic viscosity, as measured in dimethylformamide at 25°C, which is advantageously 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] Some 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) Chlorotrifluoroethylene (CTFE) and other chloro- and / or bromo- and / or iodo-C2-C6 fluoroolefins These are some examples.

[0061] In one embodiment of the present invention, the polymer (F) contains 0.1 to 10.0 mol%, preferably 0.3 to 5.0 mol%, and more preferably 0.5 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%, vinylidene fluoride (VDF), - 0.2 mol% to 1 mol% of 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 polymerization of a VDF monomer, at least one monomer (MA), and optionally at least one comonomer (CF) in either a suspension in an organic medium or an aqueous emulsion typically carried out as described in the Art (see, for example, U.S. Patent No. 4,016,345, U.S. Patent No. 4,725,644, and U.S. Patent No. 6,479,591), following the procedure described in International Publication No. 2008 / 129041.

[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 the presence of a radical initiator in a reaction vessel, wherein the process 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 expressions "continuous supply," "continuous addition," or "continuous supply" mean that a slow, gradually increasing amount of aqueous solution of 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 otherwise are unsatisfactorily low, particularly lower than that of VDF homopolymers.

[0069] A branched (meth)acrylic polymer (A), distinct from polymer (F), is a polymer comprising repeating units derived from at least one (meth)acryloyl monomer [monomer (MAM)] and at least one branched monomer [monomer (MAM)] which is a molecule containing at least two vinyl groups.

[0070] Polymer (A) is a copolymer. As used herein, “copolymer” is intended to mean 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 emulsion polymerization, solution polymerization, or suspension polymerization, and may be carried out in bulk or semi-bulk.

[0071] The term (meth)acryloyl monomer (MAM) refers to a monomer that has a (meth)acryloyl group in its molecule.

[0072] Suitable (meth)acryloyl monomers (MAMs) are hydrophobic (meth)acryloyl monomers that can be selected from, for example, (meth)acrylamidoic acid esters of the formula CH2=C(R)-C(=O)-NH-Rh or (meth)acrylic acid esters of the formula CH2=C(R)-C(=O)-O-Rh (wherein R means hydrogen or an alkyl group having 1 to 3 carbon atoms, and Rh means a linear or branched alkyl residue having 1 to 30 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 5 carbon atoms).

[0073] Non-limiting examples of such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, octyl (meth)acrylate), isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloalkyl (meth)acrylate, and phenyl (meth)acrylate.

[0074] Polymer (A) may also include repeating units derived from other alpha,beta-ethylenically unsaturated monomers having functional groups such as carboxyl groups or substituted alkyl esters.

[0075] Suitable alpha,beta-ethylenically unsaturated monomers having functional groups can be selected from hydrophilic (meth)acryloyl monomers such as monoethylenically unsaturated monocarboxylic acids and their derivatives. These include, in particular, acrylic acid, methacrylic acid (MAA), hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate, crotonic acid, 2-carboxyethyl acrylate oligomers, such as Sipomer® B-CEA.

[0076] Within the framework of this invention, the expression "methyl methacrylate polymer" is used to refer to a polymer made of repeating units in which more than 50 mol% of the repeating units are derived from methyl methacrylate (MMA).

[0077] A preferred (meth)acrylic polymer (A) for use in composition (C) of the present invention is a methyl methacrylate polymer.

[0078] In a preferred embodiment of the present invention, polymer (A) is a methyl methacrylate polymer containing at least 50 mol% of methyl methacrylate monomer units, preferably at least 70 mol% of methyl methacrylate monomer units.

[0079] According to the preferred embodiment described above, polymer (A) may contain 1 to 45, preferably 3 to 30, more preferably 5 to 20 mol%, of at least one comonomer copolymerizable with methyl methacrylate, such as a monomer (MAM) as defined above or another alpha,beta-ethylenically unsaturated monomer having a functional group such as a carboxyl group or a substituted alkyl ester.

[0080] Polymer (A) contains at least one branched monomer (BM).

[0081] According to the present invention, a branched monomer is a monomer that can react at at least two different positions during polymerization, resulting in branched chain growth.

[0082] During the preparation of polymer (A), the (meth)acryloyl monomer (MAM) can grow in two directions through polymerization reactions with another (meth)acryloyl monomer or branched monomer.

[0083] According to the present invention, a branched monomer (BM) is a molecule containing at least two vinyl groups. A branched monomer (BM) may also contain three or more vinyl groups. These vinyl groups are suitable for polymerization in addition polymerization reactions. Many such molecules are readily available or can be prepared by reacting any bifunctional or polyfunctional molecule with a suitably reactive vinyl-based reagent. Examples include di- or multi-vinyl esters, di- or multi-vinyl amides, di- or multi-vinylaryl compounds (including those having heterocyclic aryl groups), and di- or multi-vinyl alkyl / aryl ethers.

[0084] The branched monomer (BM) is selected from the group consisting of divinylaryl monomers such as divinylbenzene, (meth)acrylate diesters such as alkylenedi(meth)acrylate, for example ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, for example tetraethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, poly(propylene glycol di(meth)acrylate, etc., oligoalkylene glycol di(meth)acrylates, divinyl(meth)acrylamides such as methylenebisacrylamide, divinyl ethers such as poly(ethylene glycol)divinyl ether, and tetra- or tri-(meth)acrylate esters or glucose di-~penta(meth)acrylates such as pentaerythritol tetra(meth)acrylate and trimethylolpropane tri(meth)acrylate.

[0085] Preferred branched monomers are divinylbenzene, α,ω-alkylenedi(meth)acrylate, or divinyl(meth)acrylamide, most preferably α,ω-alkylenedi(meth)acrylate such as ethylene glycol di(meth)acrylate and 1,4-butylene glycol di(meth)acrylate, or divinyl(meth)acrylamide such as methylenebisacrylamide.

[0086] More preferably, the branched monomer (BM) is divinylbenzene (DVB).

[0087] Polymer (A) contains at least one branched monomer (BM) in less than 1 mol%, preferably at least one branched monomer (BM) in 0.2 to less than 1 mol%.

[0088] The applicant has surprisingly found that the presence of at least one branched monomer (BM) in polymer (A) in an amount of less than 1 mol% makes it possible to obtain a solution of polymer (A) in solvent (S). At higher amounts of monomer (BM) in polymer (A), the solubility of polymer (A) in solvent (S) may become an issue.

[0089] The branched (meth)acrylic polymer (A) is prepared by polymerizing a mixture of at least one hydrophilic (meth)acryloyl monomer (MAM) and at least one monomer (BM) in the presence of other alpha,beta-ethylenically unsaturated monomers having functional groups such as carboxyl groups or substituted alkyl esters, which are optionally available.

[0090] If the branched (meth)acrylic polymer (A) contains a hydrophilic (meth)acryloyl monomer such as a monoethylenically unsaturated monocarboxylic acid, the polymer (A) may at least partially form further salts to obtain at least a portion of the acidic portion in the form of salts.

[0091] In one embodiment of the present invention, a branched (meth)acrylic polymer (A) is provided which at least partially forms a salt.

[0092] Therefore, the preparation of the branched (meth)acrylic polymer (A) may further include a step of neutralizing at least some of the acidic groups with a monovalent cation-containing salt [salt (SA)] in a suitable solvent.

[0093] The salt (SA) can be any salt that can neutralize the acid group, and it is preferably an alkali metal cation, a tertiary or quaternary ammonium cation, more preferably Na + , K + Li + Selected from salts that can provide and / or quaternary ammonium cations.

[0094] The polymer (A) for use in composition (C) of the present invention preferably has a number-average molecular weight (Mn) of at least 1 kDa, for example, 1 to 150 kDa. More preferably, the polymer (A) has a number-average molecular weight (Mn) of 15 to 100 kDa.

[0095] The polymer (A) used in composition (C) of the present invention preferably has a weight-average molecular weight (Mw) of about 1 kDa to 150 kDa, preferably 5 kDa to 100 kDa.

[0096] In one embodiment of the present invention, polymer (A) is a methyl methacrylate polymer (methyl methacrylate homopolymer) containing 100 mol% methyl methacrylate monomer units.

[0097] According to another preferred embodiment, polymer (A) is a methyl methacrylate copolymer comprising at least 70 mol% methyl methacrylate monomer units, up to 20 mol% methacrylic acid monomer units, and less than 1 mol% branched monomer (BM).

[0098] The choice of solvent (S) is not particularly limited, provided that it is suitable for solubilizing polymers (F) and (A).

[0099] 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.

[0100] The electrode-forming composition of the present invention may further comprise one or more optionally selected conductivity-imparting additives to improve the conductivity of electrodes manufactured from the composition of the present invention. Conductivity-imparting additives for batteries are known in the art.

[0101] Examples of such materials include carbonaceous materials such as carbon black, graphite powder, carbon nanotubes, graphene, or fibers, or metal powders or fibers such as nickel or aluminum. The optional conductive agent is preferably carbon black or carbon nanotubes.

[0102] 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).

[0103] Composition (C) may further comprise at least one wetting agent and / or at least one surfactant, and one or more additional additives.

[0104] Composition (C) may further comprise at least one non-electroactive inorganic filler material.

[0105] The term "non-electroactive inorganic filler" is intended in this specification to mean a non-conductive inorganic filler suitable for the manufacture of electrical insulating separators for electrochemical cells.

[0106] 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.

[0107] 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.

[0108] A binder (B) for use in composition (C) according to the present invention can be prepared by any method known in the art. A preferred method is: - Dissolving the polymer (F) in the solvent (S), - Dissolve polymer (A) in solvent (S), preferably the same solvent used to dissolve polymer (F), - Mixing the two solutions to obtain binder solution (B) and Includes.

[0109] The weight ratio of polymer (F) to polymer (A) in binder (B) is conveniently 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 binder (B) is 90:10.

[0110] The electrode-forming composition (C) can be obtained by adding powdered electrode material and optional additives, such as conductivity-imparting additives and / or viscosity modifiers, to the binder solution (B) thus obtained, dispersing them, and obtaining a uniform slurry.

[0111] The solution of polymer (F) in solvent (S) contains, in particular, 5 to 20% by weight, preferably about 7 to 10% by weight of polymer (F).

[0112] A solution of polymer (A) in solvent (S) contains, in particular, 5 to 10% by weight of polymer (A) per 100 parts by weight of such solvent.

[0113] To obtain a binder solution (B) containing polymer (F) and polymer (A) as detailed above, it is preferable to dissolve polymer (F) separately in a solvent (S) and polymer (A) at a concentration of 5 to 10% by weight per 100 parts by weight of such solvent.

[0114] To prepare the binder solution (B), it is preferable to dissolve polymer (F) and polymer (A) in solvent (S) at a temperature of 20 to 50°C.

[0115] Alternatively, the binder solution (B) can be prepared by first dissolving the polymer (F) in a solvent (S), followed by the addition of the solid polymer (A) to the prepared mixture.

[0116] 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, including, among other things, polymer (F), polymer (A), electrode active material, and any additional solid non-volatile additives.

[0117] When solutions of polymer (F) and polymer (A) are prepared separately and then combined with an electrode active material, an optional conductive material, and other additives to prepare composition (C), a sufficient amount of solvent is used to produce a stable solution. The amount of solvent used may range from the minimum amount required to produce a stable solution to the amount required to achieve the desired total solid content in the electrode mixture after the electrode active material, optional conductive material, and other solid additives have been added.

[0118] The mixing of the two solutions is carried out by any method known in the art, such as planetary mixing followed by a dispersion step.

[0119] The presence of polymer (A) in composition (C) makes it possible to obtain a homogeneous slurry composition without any trace 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 electrode active material, and to utilize the properties of such polymer in the electrode, such as greater adhesion to the current collector, improved flexibility, and good mechanical performance.

[0120] 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 compositions containing only polymer (F), active material, and conductivity-imparting additives.

[0121] Another advantage of composition (C) of the present invention is that it is possible to provide an electrode containing a binder with a relatively low weight content and to increase the content of the active material in the positive electrode in order to maximize the capacity of the battery.

[0122] The electrode-forming composition (C) of the present invention may be used in a process for manufacturing a positive electrode [electrode (E)], the process being: (i) A step of providing a metal substrate having at least one surface, (ii) A step of providing an electrode-forming composition [composition (C)] as defined above, (iii) Applying composition (C) to at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate coated with composition (C) on at least one surface, (iv) A step of drying the assembly provided in step (iii). Includes.

[0123] The metal substrate is typically a foil, mesh, or net made from metal such as aluminum, nickel, titanium, or their alloys.

[0124] In step (iii) of the process 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.

[0125] Optionally, step (iii) may 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).

[0126] In step (iv) of the process 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, for example, typically under an inert gas from which moisture has been removed (water vapor content of less than 0.001 v / v%).

[0127] The drying temperature is selected to achieve the removal of the aqueous medium from the electrode (E) of the present invention by evaporation.

[0128] The dried assembly obtained in step (iv) can be subjected to a compression step such as a calendering process to achieve the target porosity and density of the electrode (E) of the present invention.

[0129] Preferably, the dried assembly obtained in step (iv) is hot-pressed, and the temperature during the compression step is in the range of 25°C to 130°C, preferably about 60°C.

[0130] 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.

[0131] In a further embodiment, the present invention relates to an electrode [electrode (E)] that can be obtained by the process of the present invention.

[0132] 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 An electrode (E) comprising, where at least one layer is 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 Binder composition containing [Binder (B')], c) Optionally, at least one conductivity-imparting additive Composition containing [Composition (C')] This relates to an electrode (E) consisting of the following.

[0133] 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. Therefore, 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 that is removed during the manufacturing process.

[0134] 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) having an olivine structure 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 weight percentages, and the above weight percentages are relative to the total weight of j) + jj) + jjj).

[0135] Preferably, the positive electrode (E) comprises at least 95% by weight of active material (AM) and consists of an electrode loading of 8 to 20 mg / cm², preferably about 15 mg / cm².

[0136] Advantageously, the electrode (E) according to the present invention has excellent resistance to electrolyte swelling.

[0137] The electrode (E) of the present invention is particularly suitable for use in electrochemical devices, especially secondary batteries, exhibiting reduced polymer swelling, lower resistivity, and longer battery life when in contact with an electrolyte.

[0138] The secondary battery of the present invention is preferably an alkaline secondary battery or an alkaline earth secondary battery.

[0139] The secondary battery of the present invention is more preferably a lithium-ion secondary battery.

[0140] The electrochemical device according to the present invention can be prepared by standard methods known to those skilled in the art.

[0141] The present invention will be described here in relation to the following embodiments, and its purpose is merely illustrative and not intended to limit the scope of the invention. [Examples]

[0142] 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.

[0143] MMA: Methyl methacrylate, commercially available from Sigma Aldrich.

[0144] MAA: Methacrylic acid, commercially available from Sigma-Aldrich.

[0145] DVB: Divinylbenzene, commercially available from Sigma-Aldrich.

[0146] AMBN: 2,2'-azobis(2-methylbutyronitrile), commercially available from Sigma-Aldrich.

[0147] Nano-LFP:LFP DY-3, density: 3.53g / cm 3 Effective relative capacity: 153mAh / g, commercially available from Shenzhen Dynanonic Co., Ltd.

[0148] Carbon nanotubes: Orgacyl NMP0402. 4% thin multiwalled carbon nanotubes (MWCNTs) in N-methyl-2-pyrrolidone (NMP) solvent.

[0149] Preparation 1: Polymer (A-1): Poly(MMA-MAA-DVB) in MNP 79.8 / 20 / 0.2 mol% A 2 L jacketed reactor equipped with a multi-stage Lightning A320 impeller, counter-impellers, a condenser connected to a mini-chiller, and a low-temperature bath contained 24.864 g, 0.246 mol, MMA (5.358 g, 0.061 mol), DVB (0.100 g, 0.616 mmol, 80% purity), AMBN (2.821 g, 0.014 mol), and 414.583 g of NMP at room temperature. The mixture was purged with nitrogen for 20 minutes at room temperature with stirring, and after releasing the nitrogen stream into the air, the temperature of the low-temperature bath was programmed to 75°C over a 1-hour temperature gradient. In parallel, solutions of monomers MMA (140.89 g, 1.393 mol), MAA (30.36 g, 0.349 mol), and DVB (0.568 g, 3.492 mmol, 80% purity) were prepared. As soon as the reactor reached a temperature of 75°C, the pre-prepared monomer solution was introduced over 1 hour. After the addition was complete, the reaction was aged at 75°C for a further 6 hours. Finally, the reactants were diluted with NMP to 25.40% by weight, cooled to room temperature, and discharged from the reactor. The conversion rates of monomers MMA, MAA, and DVB were: 1¹H NMR (performed in CDCl3) revealed that the results were almost quantitative (over 99%).

[0150] Preparation 2: Polymer (A-2): Poly(MMA-MAA-DVB) in MNP 79.5 / 20 / 0.5 mol% A 2 L jacketed reactor equipped with a multi-stage Lightning A320 impeller, counter-impeller, a condenser connected to a mini-chiller, and a low-temperature bath was introduced at room temperature with MMA (27.747 g, 0.245 mol), MAA (5.353 g, 0.062 mol), DVB (0.250 g, 1.539 mmol, 80% purity), AMBN (2.818 g, 0.014 mol), and 599.089 g of NMP. The mixture was purged with nitrogen for 20 minutes at room temperature with stirring, and after releasing the nitrogen stream into the air, the temperature of the low-temperature bath was programmed to 75°C over a 1-hour temperature gradient. In parallel, solutions of monomers MMA (140.235 g, 1.387 mol), MAA (30.33 g, 0.349 mol), and DVB (1.419 g, 8.721 mmol, 80% purity) were prepared. As soon as the reactor reached a temperature of 75°C, the pre-prepared monomer solution was introduced over 1 hour. After the addition was complete, the reaction was aged at 75°C for a further 6 hours. Finally, the reactants were diluted with NMP to 10.7% by weight, cooled to room temperature, and discharged from the reactor. The conversion rates of monomers MMA, MAA, and DVB were: 1 ¹H NMR (performed in CDCl3) revealed that the results were almost quantitative (over 99%).

[0151] Preparation 3: Polymer (A-3): Poly(MMA-MAA-DVB) 79.65 / 20 / 0.35 mol% in NMP A 2 L jacketed reactor equipped with a multi-stage Lightning A320 impeller, counter-impellers, a condenser connected to a mini-chiller, and a low-temperature bath was introduced at room temperature with MMA (14.734 g, 0.147 mol), MAA (3.181 g, 0.037 mol), DVB (0.105 g, 0.647 mmol, 80% purity), AMBN (1.658 g, 8.623 mmol), and 658.175 g of NMP. The mixture was purged with nitrogen for 20 minutes at room temperature and with stirring, and after releasing the nitrogen stream into the air, the temperature of the low-temperature bath was programmed to 75°C over a 1-hour temperature gradient. In parallel, solutions of monomers MMA (83.495 g, 0.834 mol), MAA (18.028 g, 0.209 mol), and DVB (0.596 g, 3.665 mmol, 80% purity) were prepared. As soon as the reactor reached a temperature of 75°C, the pre-prepared monomer solutions were added over 1 hour. After the addition was complete, the reaction was aged at 75°C for a further 6 hours. Finally, the reactants were cooled to room temperature and discharged from the reactor. The conversion rates of monomers MMA, MAA, and DVB were: 1 ¹H NMR (performed in CDCl3) revealed that the results were nearly quantitative (over 99%). A solid content equivalent to 14.54% by weight was measured.

[0152] Preparation 4: Polymer (A-4): Poly(MMA-MAA-DVB) in MNP 79.5 / 20 / 0.5 mol% A 2 L jacketed reactor equipped with a multi-stage Lightning A320 impeller, counter-impellers, a condenser connected to a mini-chiller, and a low-temperature bath was introduced at room temperature into a reactor containing MMA (14.700 g, 0.147 mol), MAA (3.180 g, 0.037 mol), DVB (0.150 g, 0.923 mmol, 80% purity), AMBN (1.657 g, 8.618 mmol), and 658.141 g of NMP. The mixture was purged with nitrogen for 20 minutes at room temperature and with stirring, and after releasing the nitrogen stream into the air, the temperature of the low-temperature bath was programmed to 75°C over a 1-hour temperature gradient. In parallel, solutions of monomers MMA (83.299 g, 0.832 mol), MAA (18.019 g, 0.209 mol), and DVB (0.852 g, 5.233 mmol, 80% purity) were prepared. As soon as the reactor reached a temperature of 75°C, the pre-prepared monomer solutions were added over 1 hour. After the addition was complete, the reaction was aged at 75°C for a further 6 hours. Finally, the reactants were cooled to room temperature and discharged from the reactor. The conversion rates of monomers MMA, MAA, and DVB were: 1 ¹H NMR (performed in CDCl3) revealed that the results were nearly quantitative (over 99%). A solid content equivalent to 14.58% by weight was measured.

[0153] Preparation 5: Polymer (A-5): Poly(MMA-MAA-DVB) in MNP 79.25 / 20 / 0.75 mol% A 2 L jacketed reactor equipped with a multi-stage Lightning A320 impeller, counter-impellers, a condenser connected to a mini-chiller, and a low-temperature bath was introduced at room temperature with MMA (14.642 g, 0.146 mol), MAA (3.177 g, 0.037 mol), DVB (0.225 g, 1.384 mmol, 80% purity), AMBN (1.656 g, 8.612 mmol), and 658.083 g of NMP. The mixture was purged with nitrogen for 20 minutes at room temperature and with stirring, and after releasing the nitrogen stream into the air, the temperature of the low-temperature bath was programmed to 75°C over a 1-hour temperature gradient. In parallel, solutions of monomers MMA (82.974 g, 0.829 mol), MAA (18.005 g, 0.209 mol), and DVB (1.276 g, 7.843 mmol, 80% purity) were prepared. As soon as the reactor reached a temperature of 75°C, the pre-prepared monomer solutions were added over 1 hour. After the addition was complete, the reaction was aged at 75°C for a further 6 hours. Finally, the reactants were cooled to room temperature and discharged from the reactor. The conversion rates of monomers MMA, MAA, and DVB were: 1 ¹H NMR (performed in CDCl3) revealed that the results were nearly quantitative (over 99%). A solid content equivalent to 14.00 wt% was measured.

[0154] Preparation 6: PMMA polymer: MMA homopolymer in DMF solution 15.15 g (0.15 mol) of MMA, 1.37 g (7.12 mmol) of AMBN, and 123.63 g of DMF were introduced into a 500 mL three-necked round-bottom flask equipped with a reflux condenser and mechanical stirring at room temperature. The mixture was purged with nitrogen for 15 minutes at room temperature and then immersed in an oil bath preheated to 80°C. After stabilizing the temperature at 75°C in mass, 85.86 g (0.86 mol) of MMA was added to the reaction mixture over 1 hour using a syringe pump. After the addition was complete, the reaction was allowed to continue stirring for a further 6 hours. After this final maturation step, the mixture was cooled to ambient temperature. Finally, the product was diluted to a solution with a solid content of 34.61%.

[0155] 1Samples were taken for 1H NMR analysis, and the conversion rate of MMA monomers was measured (in CDCl3). 1 H RMN):>99%.

[0156] Example 1: An 8 wt% solution of polymer (F-1) in NMP was prepared.

[0157] Starting with the solution of polymer (A-1) in NMP obtained in Preparation 1 above, an 8 wt% solution of polymer (A-1) in NMP was prepared.

[0158] A solution of polymer (F-1) in NMP and an MP solution of polymer (A-1) in NMP were mixed in a ratio of 9:1 (30.87 g of polymer (F-1) solution and 3.43 g of polymer (A-1) solution).

[0159] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt% solution in NMP), and an additional 15.94 g of NMP were added to a solution containing polymer (F-1) and polymer (A-1) by planetary mixing followed by a dispersion step to obtain composition 1, a cathode slurry, having a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, and 3.5% binder).

[0160] A uniform slurry was obtained, and there was no evidence of gelation at any of the preparation steps. The results of the visual evaluation of slurry quality are summarized in Table 1.

[0161] Comparative Example 1: An 8 wt% solution of HSV900 in NMP was prepared.

[0162] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt% solution in NMP), and an additional 15.94 g of NMP were added to 34.3 g of a solution containing HSV900 by planetary mixing followed by a dispersion step to obtain a composition (C-1) cathode slurry having a total solids content (TSC) of 56% and a binder content of 3.5%.

[0163] Comparative Example 2: An 8 wt% solution of polymer (F-1) in NMP was prepared.

[0164] Starting from the solution of PMMA polymer in NMP obtained in Preparation 6 above, an 8 wt% solution of PMMA polymer in NMP was prepared.

[0165] A solution of polymer (F-1) in NMP and a solution of PMMA polymer in NMP were mixed in a 9:1 ratio (30.87 g of polymer (F-1) solution and 3.43 g of PMMA polymer solution).

[0166] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt% solution in NMP), and an additional 15.94 g of NMP were added to a solution containing polymer (F-1) and PMMMA polymer by planetary mixing followed by a dispersion step to obtain composition (C-2) and cathode slurry having a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, and 3.5% binder).

[0167] The results of the visual evaluation of slurry quality are summarized in Table 1.

[0168] [Table 1]

[0169] Example 4: Evaluation of gelation of electrode-forming composition The viscosity (t0 viscosity) of compositions 1, C-1, and C-2 was measured immediately after preparation, and a viscosity of -50% was detected for the composition obtained in Example 1 compared to those from Comparative Examples 1 and 2 (these last two compositions showed equivalent values).

[0170] The results are reported in Table 2.

[0171] [Table 2]

[0172] Over time, without emphasizing the gelation problem, we qualitatively monitored viscosity changes that made casting feasible for the slurry after several hours / day.

[0173] Example 5: Electrode preparation The positive electrode concentration is 15 mg / cm³. 2 The electrode-forming composition described above was applied to 15 μm thick aluminum foil to obtain a mass of dry cathode loading. The solvent was completely evaporated by drying in an oven at a temperature of 90°C to produce a strip-shaped cathode.

[0174] The resulting positive electrodes (electrodes (E1), (EC-1), and (EC-2)) were visually evaluated. The results are reported in Table 3.

[0175] [Table 3]

[0176] Positive electrode adhesion evaluation The positive electrodes (E1), (EC-1), and (EC-2) were cut into strips (10 cm long and 2.5 cm wide), and attached to a 2 mm thick rigid aluminum foil using 2.5 x 8 cm double-sided adhesive tape, with the coated side of the electrodes facing the aluminum plate. A portion of the electrodes was kept from adhering to the tape, so that one end of each stripe did not come into contact with the double-sided adhesive tape, allowing for its removal from the foil.

[0177] Each sample was separated 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 speed was 300 mm / min at T=25°C. The results are summarized in Table 4.

[0178] [Table 4]

[0179] The electrodes of the present invention have been demonstrated to have improved adhesion to metal foils compared to standard electrodes of the prior art, including those made of PVDF.

Claims

1. A positive electrode forming composition (C), - At least one type of positive electrode active material (AM), - At least one type of binder (B), a) At least one vinylidene fluoride (VDF) polymer [polymer (F)], (i) Repeating units derived from VDF, (ii) 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 values ​​that are equal to or different from each other １ , R ２ and R ３ is a hydrogen atom and C １ ~C ３ Independently 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 monomer (MA) At least one vinylidene fluoride (VDF) polymer [polymer (F)] containing, b) At least one branched (meth)acrylic polymer [polymer (A)] derived from the polymerization of at least one (meth)acryloyl monomer [monomer (MAM)] and at least one molecule [monomer (BM)] containing at least two vinyl groups, wherein monomer (BM) is a divinylaryl monomer, e.g., divinylbenzene; (meth)acrylate diesters, e.g., alkylenedi(meth)acrylate, e.g., ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, oligoalkylene glyco Selected from the group consisting of di(meth)acrylates, such as tetraethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, poly(propylene glycol) di(meth)acrylate, etc., divinyl(meth)acrylamide, such as methylenebisacrylamide, divinyl ether, such as poly(ethylene glycol) divinyl ether, and tetra- or tri-(meth)acrylate esters, such as pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, or glucose di- to penta(meth)acrylate, Polymer (A) is a branched (meth)acrylic polymer [polymer (A)] containing less than 1 mol% monomer (BM). A binder (B) containing at least one type of binder (B), - At least one solvent (S), - 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 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 active material (AM) is given by the following formula: Li ｘ A ｙ D ｚ PO ４ (In the formula, 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, and Ba; and x, y, and z are numbers that satisfy the following relationships: 0 < x < 2, 0 < y < 1.5, 0 ≤ z < 1.5) A composition (C) according to claim 1 or 2, having the following characteristics.

4. The composition according to any one of claims 1 to 3, wherein the active material (AM) is selected from lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), and lithium manganese phosphate.

5. Polymer (A) is of the formula CH ２ =C(R)-C(=O)-NH-Rh (meth)acrylamide ester or formula CH ２ A composition (C) according to any one of claims 1 to 4, comprising a repeating unit derived from at least one (meth)acryloyl monomer (MAM) selected from the group consisting of =C(R)-C(=O)-O-Rh (meth)acrylic acid esters (wherein R means hydrogen or an alkyl group having 1 to 3 carbon atoms, and Rh means a linear or branched alkyl residue having 1 to 30 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 5 carbon atoms).

6. The above at least one (meth)acryloyl monomer (MAM) is methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, oc The composition according to claim 5, selected from the group consisting of cycloalkyl (meth)acrylates such as tyl (meth)acrylate, iso-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, cyclohexyl (meth)acrylate, and phenyl (meth)acrylate.

7. The composition (C) according to any one of claims 1 to 6, wherein polymer (A) further comprises repeating units of at least one hydrophilic (meth)acryloyl monomer selected from the group consisting of acrylic acid, methacrylic acid (MAA), hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate, crotonic acid, 2-carboxyethyl acrylate oligomer, and, for example, Sipomer® B-CEA.

8. The composition (C) according to any one of claims 1 to 7, wherein polymer (A) is a methyl methacrylate polymer containing at least 70 mol% methyl methacrylate monomer units, up to 20 mol% methacrylic acid monomer units, and less than 1 mol% monomer (BM).

9. The composition (C) according to any one of claims 1 to 8, wherein polymer (A) forms at least partially a salt.

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 process for manufacturing a positive electrode [electrode (E)], (i) A step of providing a metal substrate having at least one surface, (ii) A step of providing an electrode-forming composition [composition (C)] according to any one of claims 1 to 10, (iii) A step of 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 coated with the composition (C) on the at least one surface, (iv) A step of drying the assembly provided in step (iii). A process that includes this.

12. A positive electrode (E) that can be obtained by the process 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 j) 90-98% by weight of positive electrode active material (AM), jj) 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 values ​​that are equal to or different from each other １ , R ２ and R ３ is a hydrogen atom and C １ ~C ３ Independently selected from hydrocarbon groups, and - R Ｘ C comprises at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, and ether groups. １ ~C ２０ (This is the hydrocarbon portion.) Repeating units derived from at least one monomer (MA) A vinylidene fluoride (VDF) copolymer [polymer (F)] containing at least one such copolymer, b'') At least one branched (meth)acrylic polymer [polymer (A)], Optionally, at least one conductivity-imparting additive and A binder (B') containing the above, in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, jjj) 0.5 to 5% by weight of a conductivity-imparting additive and The positive electrode (E) consists of the above weight percentages relative to the total weight of j) + jj) + jjj).

14. An electrochemical device comprising the electrode (E) described in claim 13.

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