Cathode binder for lithium-ion batteries

Abstract

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

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to European Patent Application No. 22305526.0, filed April 16, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a binder for a positive electrode of a Li-ion battery, a method for making said electrode and its use in a Li-ion battery.

[0003] The present invention also relates to a Li-ion battery manufactured by incorporating said electrode. [Background technology]

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

[0005] The most important component of a lithium-ion secondary battery is the positive electrode (cathode) material, the performance of which affects the overall performance of the lithium-ion secondary battery. Various attempts have been made to obtain a cathode material that has low manufacturing cost and high energy capacity while maintaining high temperature stability.

[0006] Conventional positive electrode active materials are generally of the LiMO2 type, LiMPO4 type, Li2MPO3F type, Li2MSiO4 type (wherein M is Co, Ni, Mn, Fe, or a combination thereof), LiMn2O4 type, or S8 type.

[0007] Among these materials, lithium iron phosphate (LiFePO4 or LFP) with an olivine structure has a high theoretical capacity (170 mAhg -1 ) is attracting attention as a positive electrode material for lithium-ion batteries due to its high safety and economic advantages.

[0008] Lithium battery electrodes are typically manufactured by mixing a binder with powdered electrode active material.

[0009] Fluororesins, such as vinylidene fluoride-based polymers, have been used as binders to form positive electrodes. In particular, polyvinylidene fluoride (PVDF) provides good electrochemical stability and high adhesion to electrode materials and current collectors. Therefore, PVDF is a preferred binder material for electrode slurries.

[0010] US 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 with good adhesion to the current collector, the mixture having a viscosity that allows the active material to be easily spread onto the metal current collector, facilitating the manufacture of electrodes for lithium-ion batteries.

[0011] US 2015 / 0280238 discloses a stable electrode binder dispersion for use in fabricating LFP cathodes for lithium ion batteries, the dispersion comprising PVDF dispersed in an organic diluent and a (meth)acrylic polymer dispersant.

[0012] Modified polar PVDF polymers, such as those containing repeat 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 to the mechanical properties and chemical inertness of PVDF suitable adhesion to metals, e.g., aluminum or copper.

[0013] However, modified polar PVDF polymers have a significant drawback in that when used to prepare a slurry to form a positive electrode with LiFePO4 active material, the viscosity of the slurry increases rapidly and often forms a gel, thereby preventing its use as a binder in LPF cathodes.

[0014] The present invention provides a positive electrode-forming composition containing an LFP active material that can prevent gelation while at the same time enabling the fabrication of electrodes with improved adhesion and electrochemical stability. Summary of the Invention

[0015] The object of the present invention is therefore to provide a positive electrode forming composition (C) comprising at least one positive electrode active material (AM) having an olivine structure and one binder (B), the binder (B) being a) at least one vinylidene fluoride (VDF) copolymer [polymer (F)], (i) a repeating unit derived from VDF, (ii) a compound of formula (I): in an amount of 0.05 to 10 mol % based on the total moles of repeating units of the polymer (F): [ka] (In the formula, R1, R2 and R3 are equal to or different from each other and are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group; and - R X is a C1-C aryl group containing at least one functional group selected from hydroxyl, carboxyl, epoxide, ester and ether groups; 20 (It is a hydrocarbon part.) Repeating units derived from at least one hydrophilic (meth)acrylic monomer (MA) At least one vinylidene fluoride (VDF) copolymer [polymer (F)] comprising b) at least one (meth)acrylic polymer [polymer (A)]; c) at least one solvent (S); d) optionally, at least one conductive additive; The positive electrode forming composition (C) comprises, or preferably consists of,

[0016] In a second embodiment, the present invention relates to the use of an electrode-forming composition (C) of the present invention in a process for producing a positive electrode [electrode (E)] for an electrochemical device, said process comprising: (i) providing a metal substrate having at least one surface; (ii) providing an electrode-forming composition (C) as defined above; (iii) applying composition (C) onto at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate having at least one surface coated with said composition (C); (iv) drying the assembly provided in step (iii). Including, regarding use.

[0017] In a third embodiment, the invention relates to a positive electrode (E) obtainable by the process of the invention.

[0018] In a fourth embodiment, the present invention relates to an electrochemical device comprising a positive electrode (E) of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In the context of the present invention, the use of parentheses "(...)" around a symbol or number identifying a formula or part of a formula has the sole intention of better identifying the symbol or number with respect to the remainder of the sentence, and therefore said parentheses may also be omitted.

[0020] The terms "acrylic" and "acrylate" are used interchangeably (unless doing so changes the intended meaning) and include acrylic acid and its derivatives. The terms "(meth)acrylic" or "(meth)acrylate" are intended to cover both the acrylic / acrylate and methacrylic / methacrylate forms of a given material, for example, (meth)acrylate monomers.

[0021] The active material having an olivine structure (AM) has the following formula: Li x A y D z PO4 (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 satisfy the following relationships: 0 < x < 2, 0 < y < 1.5, 0 ≦ z < 1.5.) It is a compound having

[0022] The A component is preferably Fe, Mn, and Ni, and particularly preferably Fe.

[0023] The D component is preferably Mg or Ca.

[0024] Examples of the compound having an olivine structure include lithium iron phosphate (LFP) and lithium manganese phosphate.

[0025] 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 in order to supplement conductivity.

[0026] The amount of the coated carbon is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less based on 100 parts by weight of the positive electrode active material.

[0027] The compound having an olivine structure is present in the composition (C) in an amount of 70% by mass or more with respect to 100% by mass of the entire positive electrode active material (AM).

[0028] More preferably, this is 90% by mass or more, and most preferably, the positive electrode active material (AM) is composed only of the compound having an olivine structure.

[0029] Most preferably, the positive electrode active material (AM) consists only of lithium iron phosphate (LFP).

[0030] In the positive electrode composition of the present invention, the active material (AM) has an average particle diameter of 1 μm or less.

[0031] The average particle size of the compound having an olivine structure is more preferably 0.01 to 0.8 μm.

[0032] The average particle size of the positive electrode active material can be measured by a particle size distribution meter for dynamic light scattering.

[0033] As the average particle size decreases, the surface area increases and the binder must be held together with less binder, necessitating binder flexibility.

[0034] By using a positive electrode active material containing a compound having an olivine structure with an average particle size of 1 μm or less, the electrical characteristics such as output characteristics can be excellent when the positive electrode composition for a secondary battery is used as the positive electrode of the battery.

[0035] The composition (C) of the present invention is a) at least one vinylidene fluoride (VDF) copolymer [polymer (F)]; b) at least one (meth)acrylic polymer [polymer (A)]; c) at least one solvent (S); d) optionally, at least one conductivity-imparting additive; It further comprises a binder (B) comprising, preferably consisting of,

[0036] The polymer (F) contains a repeating unit derived from vinylidene fluoride (VDF) and a repeating unit of the formula (I): [ka] (In the formula, R1, R2 and R3 are equal to or different from each other and are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group; and - R X is a C1-C aryl group containing at least one functional group selected from hydroxyl, carboxyl, epoxide, ester and ether groups; 20 (It is a hydrocarbon part.) and a repeating unit derived from at least one hydrophilic (meth)acrylic monomer (MA).

[0037] As used herein, the term "hydrophilic (meth)acrylic monomer" may include repeat units derived from one or more of the hydrophilic (meth)acrylic monomers (MA) described above. In the remainder of the specification, the expressions "hydrophilic (meth)acrylic monomers (MA)" are intended to refer to both the plural and the singular, i.e., they refer to both one or more of the hydrophilic (meth)acrylic monomers (MA).

[0038] More preferably, the hydrophilic (meth)acrylic monomer (MA) is preferably of formula (II): [ka] wherein R1 and R2 each have the meaning defined above, R3 is hydrogen, and R OH is hydrogen or a C1-C5 hydrocarbon moiety containing at least one hydroxyl group and / or at least one carboxyl group, more preferably, each of R1, R2, and R3 is hydrogen, and R OH have the same meaning as detailed above) Meet the following.

[0039] Non-limiting examples of hydrophilic (meth)acrylic monomers (MA) are, among others, acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate.

[0040] The monomer (MA) is more preferably - Formula: [ka] Hydroxyethyl acrylate (HEA) - expression [ka] 2-Hydroxypropyl acrylate (HPA) - Formula: [ka] of acrylic acid (AA), and - A mixture of these is selected from among:

[0041] Most preferably, the monomer (MA) is AA and / or HEA.

[0042] The polymer (F) may further comprise other moieties such as defects, end groups, etc., which do not affect or impair its physicochemical properties.

[0043] The polymer (F) is semi-crystalline. The term semi-crystalline is intended to mean a polymer (F) that has a detectable melting point. A semi-crystalline polymer (F) is generally understood to advantageously have a heat of fusion, measured according to ASTM D3418, of at least 0.4 J / g, preferably at least 0.5 J / g, more preferably at least 1 J / g.

[0044] The polymer (F) is preferably a linear copolymer, i.e. it is composed of a macromolecule made of a substantially linear sequence of repeat units derived from VDF and (MA) monomers, thus making the polymer (F) distinguishable from grafted and / or comb polymers.

[0045] Polymer (F) comprises at least 0.05 mol %, more preferably at least 0.1 mol %, even more preferably at least 0.2 mol % of repeat units derived from said hydrophilic (meth)acrylic monomer (MA).

[0046] Polymer (F) preferably comprises at most 2 mol %, more preferably at most 1.8 mol %, even more preferably at most 1.5 mol % of repeat units derived from said hydrophilic (meth)acrylic monomers (MA).

[0047] In a preferred embodiment of the present invention, the repeating units derived from the hydrophilic (meth)acrylic monomer (MA) of formula (I) in the polymer (F) are contained in an amount of 0.2 to 1 mol % based on the total moles of the repeating units in the polymer (F).

[0048] The polymer (F) advantageously has an intrinsic viscosity, measured in dimethylformamide at 25° C., greater than 0.15 l / g and at most 0.60 l / g, preferably comprised in the range from 0.20 to 0.50 l / g and more preferably in the range from 0.25 to 0.40 l / g.

[0049] The polymer (F) may further comprise repeat units derived from one or more fluorinated comonomers (CF) different from VDF.

[0050] The term "fluorinated comonomer (CF)" is intended herein to mean an ethylenically unsaturated comonomer that contains at least one fluorine atom.

[0051] Non-limiting examples of suitable fluorinated comonomers (CF) 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 is a C1-C6 perfluoroalkyl group), (d) Chloro-, and / or bromo-, and / or iodo-C2 to C6 fluoroolefins, such as chlorotrifluoroethylene (CTFE).

[0052] In one embodiment of the present invention, polymer (F) contains 0.1 mol % to 10.0 mol %, preferably 0.3 mol % to 5.0 mol %, more preferably 0.5 mol % to 3.0 mol % of repeat units derived from said fluorinated comonomer (CF).

[0053] In one preferred embodiment of the present invention, the polymer (F) is 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 a hydrophilic (meth)acrylic monomer (MA) of formula (I), - optionally, 0.5 to 3.0 mol % of repeat units derived from at least one fluorinated comonomer (CF) It contains repeating units derived from:

[0054] The polymer (F) can be obtained by polymerizing VDF monomer, at least one monomer (MA) and optionally at least one comonomer (CF) in suspension in an organic medium, for example according to the procedures described in WO 2008 / 129041, or in aqueous emulsion, typically as described in the art (see for example US Pat. Nos. 4,016,345, 4,725,644 and 6,479,591).

[0055] The procedure for preparing the 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, the process being: - continuously supplying an aqueous solution comprising monomer (MA); - maintaining a pressure in the reaction vessel above the critical pressure of vinylidene fluoride; Includes.

[0056] During the entire suspension polymerization, 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 even more preferably greater than 100 bar.

[0057] The expressions "continuous feed", or "continuous addition", or "continuously fed" mean that slow, small, incremental additions of an aqueous solution of hydrophilic (meth)acrylic monomer (MA) are made until polymerization is complete.

[0058] The polymer (F) thus obtained has a high uniformity of distribution of the monomer (MA) in the polymer backbone, which advantageously maximizes the influence of the modifying monomer (MA) on both the adhesive and / or hydrophilic behavior of the resulting copolymer.

[0059] In addition, the Applicant has surprisingly found that the presence of monomer (MA) homogeneously distributed in polymer (F) has the effect of improving the thermal stability of the VDF copolymer which, in its absence, is unsatisfactorily low, in particular lower than that of the VDF homopolymer.

[0060] The at least one (meth)acrylic polymer (A) different from the polymer (F) is a polymer comprising repeat units derived from at least one (meth)acryloyl monomer (MAM).

[0061] The polymer (A) may be a homopolymer or a copolymer. As used herein, "copolymer" is intended to refer to a polymer having two or more different monomer units. The copolymer may be a terpolymer having three or more different monomer units, or may have four or more different monomer units. The 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 or anionic polymerization process, which may be formed by any polymerization method known in the art, including, but not limited to, emulsion polymerization, solution polymerization, suspension polymerization, and may be carried out in bulk or semi-bulk polymerization.

[0062] The term (meth)acryloyl monomer (MAM) refers to a monomer that has a (meth)acryloyl group in the molecule.

[0063] Suitable (meth)acryloyl monomers (MAM) are hydrophobic (meth)acryloyl monomers which may be selected, for example, from (meth)acrylamido acid esters of formula CH2=C(R)-C(=O)-NH-Rh or (meth)acrylic acid esters of formula CH2=C(R)-C(=O)-O-Rh, where R represents hydrogen or an alkyl group having 1 to 3 carbon atoms and Rh represents a linear or branched alkyl residue having 1 to 30 carbon atoms, preferably 1 to 15 carbons, more preferably 1 to 5 carbons.

[0064] Non-limiting examples of such monomers are 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, cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, phenyl (meth)acrylate.

[0065] Polymer (A) may also contain repeat units derived from at least one hydrophilic (meth)acryloyl monomer, such as monoethylenically unsaturated monocarboxylic acids and derivatives, including 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.

[0066] The expression "methyl methacrylate polymer" is used within the framework of the present invention to denote a polymer made of repeat units of which more than 50 mol % are derived from methyl methacrylate (MMA).

[0067] Preferred (meth)acrylic polymers (A) for use in the composition (C) of the present invention are methyl methacrylate polymers.

[0068] In a preferred embodiment of the invention, polymer (A) is a methyl methacrylate polymer containing at least 50 mole % methyl methacrylate monomer units, preferably at least 70% by weight, more preferably at least 80 mole % methyl methacrylate monomer units.

[0069] According to said preferred embodiment, when the polymer (A) is a copolymer, it may contain from 1 to 50% by weight, preferably from 3 to 30% by weight, more preferably from 5 to 20% by weight of at least one comonomer copolymerizable with methyl methacrylate, such as (but not limited to) the monomers (MAM) defined above or other ethylenically unsaturated monomers.

[0070] The (meth)acrylic polymer (A) is prepared by polymerizing a mixture of α,β-ethylenically unsaturated (meth)acryloyl monomers (MAM), optionally in the presence of other α,β-ethylenically unsaturated monomers bearing functional groups such as carboxyl groups and substituted alkyl esters.

[0071] According to an embodiment of the present invention, the polymer (A) has the following formula (III): [ka] (In the formula, R 1 is H or an alkyl group, the alkyl group being preferably a methyl group; R 2 is H or an alkyl group, R 3 and R 4 are the same or different and may be selected from a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms; A is, - a single covalent bond, and - Spacer is a bond selected from the group consisting of X, Y and Z are each independently selected from carbon atoms or nitrogen atoms; a, b and c are each independently selected from integers 1 to 2; Each dashed dotted line represents an optional double bond. The monomer may further comprise a repeating unit derived from one or more ethylenically unsaturated monomers having an unsaturated heterocyclic group having at least one nitrogen atom [monomer (M1)],

[0072] The "unsaturated heterocyclic group having at least one nitrogen atom" in the monomer (M1) of formula (II) is preferably a 5- to 6-membered aromatic cyclic group having at least one N in the ring, for example, [ka] (wherein * represents the attachment point of bond A) Includes.

[0073] Bond A and Residue R 2 may be attached to the heterocyclic group at any position, either at a carbon atom or at a nitrogen atom.

[0074] The monomer (M1) is, for example, - Formula (IIIa): [ka] Vinylimidazole (VIm) - Formula (IIIb) [ka] 2-Methyl-1-vinylimidazole - Formula (IIIc) [ka] 1-vinyl-1,2,4-triazole - Formula (IIId) [ka] 2-Vinylpyrazine - Formula (IIIe) [ka] 4-Vinylpyridine - Formula (IIIf) [ka] of 2-vinylpyridine - Formula (IIIg) [ka] Hydroxyl-(meth)acrylate imidazole derivatives of It could be.

[0075] When any of X, Y and Z in formula (III) is carbon, it may typically be the carbon of a carbonyl group.

[0076] Thus, the monomer (M1) can be, for example, Formula (IIIh) [ka] N-vinylpyrrolidone - Formula (IIIi) [ka] Compound It could be.

[0077] The divalent spacer group A in formula (III) is typically a group -CO-NH-(CH2) n -, -CO-O-(CH2) n or -CO-O-(CH2) n -O-CO-, for example, formula (III-X): [ka] (In the formula, R 6 , R 8 and R 9 is as defined above) and a compound of formula (III-Y): [ka] (In the formula, R 2 is as defined above, and A 1 and A 2 are two groups that react together to form a covalent bond) Any covalent linking group may be envisaged, such as that obtained by reaction with a compound of the formula:

[0078] For example, A 2 is -(CH2) m -NH2 group, where m is 1 to 4, preferably 2 or 3. In that case, A 1 can be, for example, a carboxylic acid, an acid chloride, an acid anhydride, or an epoxy.

[0079] According to another variant, A 2 is -(CH2) m In the formula, m is 1 to 4, preferably 2 or 3. In that case, A 1 can be, for example, a carboxylic acid, an acid chloride, an anhydride or an ester.

[0080] When the (meth)acrylic polymer (A) comprises a hydrophilic (meth)acryloyl monomer, such as a monoethylenically unsaturated monocarboxylic acid, said polymer (A) may be at least partially further salified to obtain at least a portion of the acidic sites in the salt form.

[0081] Thus, in one embodiment of the present invention, there is provided an at least partially salified (meth)acrylic polymer (A).

[0082] Therefore, the preparation of the (meth)acrylic polymer (A) may further comprise a step of neutralizing at least a portion of the acid groups with a salt comprising a monovalent cation [salt (SA)] in a suitable solvent.

[0083] The salt (SA) may be any salt capable of neutralizing the acid group, which is preferably a salt capable of providing an alkali metal cation, a tertiary or quaternary ammonium cation, more preferably Na + , K + , Li + and / or quaternary ammonium cations.

[0084] The polymer (A) for use in the composition (C) of the present invention preferably has a number average molecular weight (Mn) of at least 1 kDa, for example from 1 to 150 kDa, more preferably from 15 to 100 kDa.

[0085] The polymer (A) for use in the 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.

[0086] In one embodiment of the present invention, polymer (A) is a methyl methacrylate polymer containing 100 mol % methyl methacrylate monomer units (methyl methacrylate homopolymer).

[0087] According to another preferred embodiment, the polymer (A) is a methyl methacrylate copolymer comprising at least 80 mol % of methyl methacrylate monomer units and at most 20 mol % of methacrylic acid monomer units.

[0088] The choice of solvent (S) is not particularly limited, provided that it is suitable for solubilizing the polymer (F) and the 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 acetoacetate, dimethyl phthalate and gamma-butyrolactone, - linear or cyclic amides such as N,N-diethylacetamide, N,N-dimethylacetamide, dimethylformamide and N-methyl-2-pyrrolidone, and - Dimethyl sulfoxide is selected from the group consisting of:

[0090] The electrode-forming compositions of the present invention may further comprise one or more optional conductivity-imparting additives to improve the electrical conductivity of electrodes made from the compositions of the present invention. Conductivity-imparting additives for batteries are known in the art.

[0091] Examples of these may include carbonaceous materials such as carbon black, graphite fine powders, 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 based on 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 amount of solid content in the composition (C).

[0093] Composition (C) may further comprise at least one wetting agent and / or at least one surfactant, as well as 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 herein to mean a non-conductive inorganic filler material that is suitable for the manufacture of electrically 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) measured at 20° C. according to ASTM D 257 of at least 0.1×10 10 ohm cm, preferably at least 0.1×10 12 ohm cm.

[0097] Non-limiting examples of suitable non-electroactive inorganic filler materials include natural and synthetic silicas, zeolites, aluminas, titania, metal carbonates, zirconia, silicon phosphates and silicates, among others.

[0098] The binder (B) for use in the composition (C) according to the invention may be prepared by any method known in the art. Suitable methods include: - dissolving the polymer (F) in a solvent (S); - dissolving the polymer (A) in a solvent (S), preferably the same solvent as that used to dissolve the polymer (F), and - Mix the two solutions to obtain the binder solution (B) Includes.

[0099] The weight ratio of polymer (F) to polymer (A) in binder (B) is advantageously in the range of 95:5 to 70:30. In a preferred embodiment of the invention, the weight ratio of polymer (F) to polymer (A) in binder (B) is 90:10.

[0100] The electrode-forming composition (C) can be obtained by adding and dispersing a powdered electrode material and optional additives, such as a conductivity-imparting additive and / or a viscosity modifier, into the binder solution (B) thus obtained to obtain a uniform slurry.

[0101] 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).

[0102] The solution of polymer (A) in solvent (S) contains in particular an amount of polymer (A) ranging from 5 to 10% by weight relative to 100 parts by weight of such solvent.

[0103] To obtain the binder solution (B) containing the polymer (F) and the polymer (A) described above, it is preferable to separately dissolve the polymer (F) in the solvent (S) and the polymer (A) in an amount of 5 to 10% by weight per 100 parts by weight of such a solvent.

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

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

[0107] When solutions of polymer (F) and polymer (A) are prepared separately and then mixed with the electrode active material, optional conductive material, and other additives to prepare composition (C), a sufficient amount of solvent is used to form a stable solution. The amount of solvent used can range from the minimum amount required to form a stable solution to the amount required to achieve the desired total solids content in the electrode mixture after the electrode active material, optional conductive material, and other solid additives have been added.

[0108] Mixing of the two solutions is accomplished by any method known in the art, such as planetary mixing followed by a dispersed phase.

[0109] The presence of polymer (A) in composition (C) makes it possible to obtain a homogeneous slurry composition without any evidence of gelation in all preparation steps. It is therefore possible to use polymer (F) having polar groups in electrode-forming compositions including olivine-type active material electrodes and to take advantage of the properties of such polymers in the electrodes, such as excellent adhesion to current collectors, improved flexibility and excellent mechanical properties.

[0110] In addition, polymer (A) functions as a dispersant in the binder composition, reducing the viscosity of the slurry compared to a composition having the same TSC but containing only polymer (F), an active material and a conductivity-imparting additive.

[0111] Another advantage of the composition (C) of the present invention is that it provides an electrode with a relatively low weight content of binder and can allow for an increased content of active material in the positive electrode to maximize the capacity of the battery.

[0112] The electrode-forming composition (C) of the present invention may be used in a process for producing a positive electrode [electrode (E)], the process comprising: (i) providing a metal substrate having at least one surface; (ii) providing an electrode-forming composition [composition (C)] as defined above; (iii) applying composition (C) onto at least one surface of a metal substrate, thereby providing an assembly comprising a metal substrate having at least one surface coated with said composition (C); (iv) drying the assembly provided in step (iii). Includes.

[0113] The metal substrate is typically a foil, mesh or netting made from metals such as aluminum, nickel, titanium and their alloys.

[0114] In step (iii) of the process of the present invention, the electrode-forming composition (C) is typically applied onto at least one surface of the metal substrate by any suitable procedure, such as casting, printing, and roll coating.

[0115] 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).

[0116] In step (iv) of the process of the invention, drying can be carried out either under atmospheric pressure or under vacuum. Alternatively, drying can be carried out under a modified atmosphere, such as an inert gas, typically specifically devoid of moisture (water vapor content less than 0.001% v / v).

[0117] The drying temperature is selected to achieve evaporative removal of the aqueous medium from the electrode (E) of the invention.

[0118] The dried assembly obtained in step (iv) may be subjected to a further compression step, such as a calendaring process, to achieve the target porosity and density of the electrode (E) of the present invention.

[0119] Preferably, the dried assembly obtained in step (iv) is hot pressed, the temperature during the pressing step being comprised between 25°C and 130°C, preferably about 60°C.

[0120] The preferred target density of the electrode (E) is comprised between 2 and 3 g / cc, preferably at least 2.1 g / cc. The density of the electrode (E) is calculated as the sum of the products of the densities of the electrode's constituents multiplied by their mass ratio in the electrode formulation.

[0121] In a further aspect, the present invention relates to an electrode [electrode (E)] obtainable by the process of the present invention.

[0122] Thus, the present invention provides - a metal substrate having at least one surface; at least one layer directly adhered onto at least one surface of said metal substrate; A positive electrode (E) comprising: a) at least one positive electrode active material (AM) having an olivine structure; b) a binder composition [binder (B')], b') at least one [polymer (F)] as defined above, b'') at least one [polymer (A)] defined in A binder composition [binder (B')] comprising c) optionally, at least one conductivity-imparting additive; The present invention relates to an electrode (E) comprising a composition [composition (C')] comprising:

[0123] The composition (C') directly adhered onto at least one surface of the metal substrate corresponds to the inventive electrode-forming composition (C) from which the solvent has been at least partially removed during the manufacturing process of the electrode, for example in step (iv) (drying) and / or in a further pressing step. Thus, all of the preferred embodiments described with respect to the inventive electrode-forming composition (C) are also applicable to the composition (C') directly adhered onto at least one surface of the metal substrate in the inventive electrode, except for the aqueous medium removed during the manufacturing process.

[0124] A preferred positive electrode (E) is - a metal substrate having at least one surface; at least one layer adhered directly onto at least one surface of said metal substrate, j) a positive electrode active material (AM) having an olivine structure in an amount of 90 to 98% by weight; jj) a binder (B') in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, jjj) a conductive additive in an amount of 0.5 to 5% by weight; At least one layer consisting of and the above weight percentages are based on 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 to 20 mg / cm 2, preferably about 15 mg / cm 2 and the electrode carrying amount.

[0126] The Applicant has surprisingly found that a copolymer obtained by radical polymerization of at least one phosphorus-containing unsaturated monomer with acrylic acid and / or methacrylic acid [polymer (P)] can advantageously be used as a primer providing excellent adhesion between the electroactive material of the cathode and the current collector.

[0127] The Applicant has surprisingly found that such good adhesion can be achieved by using small amounts of said polymer (P) so as not to adversely affect the electrochemical performance of the final electrode.

[0128] Thus, in another embodiment, the present invention comprises: - a metal substrate having at least one surface; - a first layer adhered to said at least one surface of said metal substrate, said first layer comprising at least one polymer (P) obtained by radical polymerization of at least one phosphorus-containing unsaturated monomer with acrylic acid and / or methacrylic acid; - a second layer adhered to said first layer, said second layer comprising at least a composition as defined above [composition (C')]; The present invention relates to an electrode [electrode (E1)] comprising:

[0129] The metal substrate having at least one surface is preferably a surface-modified metal substrate having at least one surface that is at least partially chemically modified.

[0130] Preferably, the polymer (P) is - Formula (a) or (b) below: (a) [ka] (wherein n is 1 or 2), (b) H2C=CH-P(=O)-(OH)2 and acrylic acid and / or methacrylic acid.

[0131] Preferably, the polymer (P) has a molecular weight of at least 7,500 Da, more preferably from 10 kDa to 1500 kDa, even more preferably from 10 kDa to 150 kDa, especially from 10 kDa to 100 kDa.

[0132] According to a preferred embodiment, said polymer (P) is obtained by radical copolymerization of a phosphorus-containing unsaturated monomer of formula (b) above and of acrylic acid.

[0133] According to this embodiment, the phosphorus-containing unsaturated monomer of formula (b) to acrylic acid is in a molar ratio of 40:60 to 20:80, preferably 35:65 to 25:75, even more preferably 30:70.

[0134] Preferably, according to this first embodiment, the polymer (P) has a molecular weight between 25 kDa and 85 kDa.

[0135] According to another preferred embodiment, said polymer (P) is obtained by radical copolymerization of 2-hydroxyethyl methacrylate phosphate according to formula (a) above, where n is 1 and 2, with a mixture of acrylic acid and methacrylic acid.

[0136] More preferably, said polymer (P) is obtained by radical copolymerization of a mixture having the following molar ratios, based on the total amount of acrylic acid, methacrylic acid and 2-hydroxyethyl methacrylate phosphate of formula (a): - acrylic acid: 65 to 90%, preferably 80 to 90%, more preferably 83 to 85%, - methacrylic acid: 5 to 30%, preferably 5 to 15%, more preferably 11 to 13%, - 2-hydroxyethyl methacrylate phosphate: 2-12%, preferably 2-10%, more preferably 2-6%, even more preferably about 4%.

[0137] Preferably, according to this embodiment, the polymer (P) has a molecular weight of between 15 kDa and 35 kDa.

[0138] The average molecular weight (typically the weight average molecular weight) is measured by size exclusion chromatography (SEC).

[0139] Advantageously, said first layer comprising polymer (P) has a thickness of less than 1 μm.

[0140] The electrode (E1) is (1) providing a metal substrate having at least one surface; Optionally, surface treating the at least one surface of the metal substrate to provide a surface-modified metal substrate having at least one surface that is at least partially chemically modified (1b); (2) contacting said at least one surface of said metal substrate with at least one polymer (P) to provide a first layer; Step (3) of contacting the layer obtained in step (2) with an electrode-forming composition [composition (C)] as defined above. It can be produced by a method comprising:

[0141] The electrodes (E) and electrodes (E1) of the present invention are particularly suitable for use in electrochemical devices, in particular secondary batteries.

[0142] The secondary battery of the present invention is preferably an alkaline secondary battery or an alkaline earth secondary battery.

[0143] The secondary battery of the present invention is more preferably a lithium ion secondary battery.

[0144] Electrochemical devices according to the present invention can be prepared by standard methods known to those skilled in the art.

[0145] To the extent that the disclosures of any patents, patent applications, and publications incorporated herein by reference conflict with the statements of this application to the extent that any term may be unclear, the statements of this application shall control.

[0146] The invention will now be described with reference to the following examples, the purposes of which are merely illustrative and are not intended to limit the scope of the invention. EXAMPLES

[0147] raw materials Polymer (F-1): A VDF-AA (1.0 mol %) polymer having an intrinsic viscosity of 0.30 l / g in DMF at 25°C. HSV900: A PVDF homopolymer commercially available from Arkema. Nano-LFP:LFP P2 / C-life C04, density: 3.34g / cm 3 , Effective specific capacity: 153mAh / g, commercially available from Johnson Matthey. Carbon Nanotubes: Orgacyl NMP0402. 4% thin multi-walled carbon nanotubes (MWCNTs) in N-methyl-2-pyrrolidone (NMP) solvent. AMBN: 2,2'-azobis(2-methylbutyronitrile) Vim: vinylimidazole

[0148] Molecular weight determination The mass distribution of the polymers was determined by SEC MALS analysis (SEC: size exclusion chromatography - MALS: multi-angle laser light scattering) to give real values ​​expressed in g / mol.

[0149] SEC MALLS analysis with two detectors: - Differential Refractometer RI-Concentration Detector - MALLS detector (multi-angle laser light scattering) - Mass detection - Ultraviolet detector UV The experiment was carried out using

[0150] For each slice of the chromatogram (for the polymer species), the software: - Concentration of polymer, RI signal = constant * dn / dc * concentration - mass of slice Mi Calculate. - From the given Mi data, the software calculates the mass distribution: Mw, Mn and the polydispersity index Ip=Mw / Mn Calculate.

[0151] The calculation of the molar mass requires the increment of the refractive index of the polymer, dn / dc, which is a constant depending, among other things, on the nature of the mobile phase, the temperature of the experimental conditions and the wavelength of the laser.

[0152] The value "dn / dc" is calculated by the software according to the mass recovery of the eluted fractions: dn / dc for the polymer of the present invention is 0.085 mL / g, obtained from a mass recovery of 95-100 wt%. The molar mass was calculated based on the actual Mi point, without any adjustment of the log(M) curve.

[0153] Detailed analysis conditions are as follows: Preparations 1 and 2: - Analytical equipment: SEC system (Mini Dawn TREOS) with MALLS detector, Agilent differential refractometer (RI) and Agilent UV detector (254 nm) - Pump: Agilent 1100 - Mobile phase: THF containing 0.01 M tetrabutylammonium tetrafluoroborate and 100 μL trifluoroacetic acid per 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 .

[0154] Preparations 3 and 4: Size exclusion chromatography (SEC) samples were diluted with mobile phase (THF+0.01 M tetrabutylammonium tetrafluoroborate) and filtered (0.45 μm Millipore) before analysis.

[0155] Samples were analyzed by SEC equipped with a multi-angle laser light scattering (MALLS) detector according to the following conditions: Eluent: THF + 0.01M tetrabutylammonium tetrafluoroborate Flow rate: 1mL / min Column: Agilent PL Gel 2*mixed B+1*100Å+guard column Detection: RI (Agilent detector) + MALLS (TRISTAR) Sample concentration: 0.4 wt% in mobile phase Injection volume: 100μL

[0156] Preparation 1: Polymer (A-1): MMA homopolymer solution in DMF solution A 500 mL three-neck round bottom flask equipped with a reflux condenser and mechanical stirring device was charged with 15.15 g (0.15 mol) MMA, 1.37 g (7.12 mmol) AMBN, and 123.63 g DMF 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 the temperature of the reaction mass was stabilized at 75° C., 85.86 g (0.86 mol) MMA was added to the reaction mixture over 1 hour using a syringe pump. After the addition was complete, the reaction was left stirring for an additional 6 hours. After this final digestion step, the mixture was cooled to ambient temperature. Finally, dilution was performed to bring the product to a solution with 34.61% solids.

[0157] 1 A sample was taken for H NMR analysis to determine the conversion of MMA monomer (in CDCl3 1 HRMN):>99%

[0158] Samples were also taken for molecular weight determination. Samples were diluted with mobile phase (THF + 0.01 M tetrabutylammonium tetrafluoroborate + 100 μL trifluoroacetic acid per kg eluent) and filtered (0.45 μm Millipore) before analysis.

[0159] result: M n,SEC-MALLS =21,000 g mol -1 M n,SEC-MALLS =43,000 g mol -1 D=2.0

[0160] Preparation 2: Polymer (A-2): Poly(MMA-co-MAA) copolymer solution in DMF A 500 mL three-necked round bottom flask equipped with a reflux condenser and mechanical stirring device was charged with 12.47 g (0.12 mol) MMA, 2.68 g (0.03 mol) MAA, 1.37 g (7.34 mmol) AMBN, and 123.58 g DMF at room temperature. The mixture was purged with nitrogen for 20 minutes at room temperature and then immersed in an oil bath preheated to 80° C. After the temperature of the reaction mass was stabilized at 75° C., a mixture of 70.7 g (0.71 mol) MMA and 15.19 g (0.18 mol) MAA was added to the reaction mixture over 1 hour using a syringe pump. After the addition was complete, the reaction was left stirring for an additional 6 hours. After this final aging step, the mixture was cooled to ambient temperature. Finally, dilution was performed to bring the product to a solution of 29.93% solids.

[0161] 1 A sample was taken for 1 H NMR analysis to determine the conversion of MMA and MAA monomers. MMA monomer conversion (in CDCl3 1 HRMN):>99% MAA monomer conversion (in CDCl3 1 HRMN):>99%

[0162] Preparation 3: Polymer (A-3): Poly(MMA-co-VIm) 80:20 copolymer solution in MNPs A 1 L jacketed reactor equipped with a multi-stage lightnin A320 stirring blade, counter-blade, a condenser connected to a mini-chiller, and a low-temperature bath was charged at room temperature with MMA (24.537 g, 0.243 mol), VIm (5.766 g, 0.061 mol), AMBN (2.777 g, 0.014 mol) and 421.379 g of NMP. The mixture was purged with nitrogen for 20 min at room temperature, and after releasing the nitrogen stream into the air while stirring, the temperature of the low-temperature bath was programmed to 75 ° C with a 1-h temperature gradient. In parallel, a solution of the monomers MMA (139.040 g, 1.375 mol) and NVI (32.677 g, 0.344 mol) was prepared. After the temperature in the reactor reached 75 ° C, the previously prepared monomer solution was introduced over 1 h. After the addition was complete, the reaction was aged at 75 ° C for another 6 h. The reaction was then cooled to room temperature and discharged from the reactor.

[0163] The monomer conversion was determined by 1H NMR. The copolymers were analyzed for number-average and weight-average molar mass (M n and M w ) could not be determined.

[0164] result: MMA monomer conversion (in CDCl3 1 H RMN)>99% VIm monomer conversion (in CDCl3) 1 H RMN)>99% Solid content: 30.38% by weight

[0165] Preparation 4: Polymer (A-4): Poly(MMA-co-VIm) 95:5 copolymer solution in NMP A 1 L jacketed reactor equipped with a multi-stage lightnin A320 stirring blade, counter-blade, a condenser connected to a mini-chiller, and a low-temperature bath was charged at room temperature with MMA (28.874 g, 0.286 mol), VIm (1.429 g, 0.015 mol), AMBN (2.751 g, 0.014 mol) and 421.063 g of NMP. The mixture was purged with nitrogen for 20 min at room temperature, and after releasing the nitrogen stream into the air while stirring, the temperature of the low-temperature bath was programmed to 75 ° C with a 1-h temperature gradient. In parallel, a solution of the monomers MMA (163.622 g, 1.618 mol) and NVI (8.096 g, 0.085 mol) was prepared. After the temperature in the reactor reached 75 ° C, the previously prepared monomer solution was introduced over 1 h. After the addition was complete, the reaction was aged at 75 ° C for another 6 h. The reaction was then cooled to room temperature and discharged from the reactor.

[0166] The monomer conversion was determined by 1H NMR. The number-average and weight-average molar masses (M n and M w ) was determined by size exclusion chromatography.

[0167] Results and Methods: MMA monomer conversion (in CDCl3 1 HRMN)>99% VIm monomer conversion (in CDCl3) 1 HRMN)>99% M n,SEC-MALLS =35,000 g mol -1 M n,SEC-MALLS =51,000 g mol -1 D=1.5 Solid content: 31.54% by weight

[0168] Example 1: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0169] Starting from the DMF solution of polymer (A-1) obtained in Preparation 1 above, an 8 wt% NMP solution of polymer (A-1) was prepared. Polymer (A-1) in powder form was precipitated from the DMF solution in distilled water, and the precipitate obtained was dried overnight in a vacuum oven at 90°C. The powder of polymer (A-1) thus obtained was dissolved in NMP at 8 wt%.

[0170] The NMP solution of polymer (F-1) and the NMP solution of polymer (A-1) were mixed in a ratio of 9:1 (30.87 g of the solution of polymer (F-1) and 3.43 g of the solution of polymer (A-1).

[0171] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of 4 wt % NMP solution) and 15.94 g additional NMP were added to the solution containing polymer (F-1) and polymer (A-1) by planetary mixing followed by a dispersed phase to obtain a cathode slurry composition 1 with a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, 3.5% binder).

[0172] A homogeneous slurry was obtained and no evidence of gelation was observed during all preparation steps. The results of visual assessment of the slurry quality are summarized in Table 1.

[0173] Example 2: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0174] Starting from the DMF solution of polymer (A-2) obtained in Preparation 2 above, an 8 wt% NMP solution of polymer (A-2) was prepared. The powder form of polymer (A-2) was precipitated in distilled water, and the precipitate obtained was dried overnight in a vacuum oven at 90°C. The powder of polymer (A-2) thus obtained was dissolved in NMP at 8 wt%.

[0175] The NMP solution of polymer (F-1) and the NMP solution of polymer (A-2) were mixed in a ratio of 9:1 (30.87 g of the solution of polymer (F-1) and 3.43 g of the solution of polymer (A-2).

[0176] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt % solution in NMP) and 15.94 g of additional NMP were added to the solution containing polymer (F-1) and polymer (A-2) by planetary mixing followed by a dispersed phase to obtain Composition 2, a cathode slurry with a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, 3.5% binder).

[0177] A homogeneous slurry was obtained and no evidence of gelation was observed during all preparation steps. The results of visual assessment of the slurry quality are summarized in Table 1.

[0178] Example 3: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0179] Starting from the DMF solution of polymer (A-2) obtained in preparation 2 above, an 8 wt% NMP solution of polymer (A-2) was prepared. The polymer (A-2) in powder form was precipitated from the DMF solution in distilled water, and the precipitate obtained was dried overnight in a vacuum oven at 90°C. The powder of polymer (A-2) thus obtained was dissolved in NMP at 8 wt%.

[0180] The NMP solution of polymer (F-1) and the NMP solution of polymer (A-2) were mixed in a ratio of 9:1 (13.3 g of the solution of polymer (F-1) and 1.47 g of the solution of polymer (A-2).

[0181] Nano-LFP (76.64 g), carbon nanotubes (14.7 g of a 4 wt % solution in NMP) and 33.97 g of additional NMP were added to the solution containing polymer (F-1) and polymer (A-2) by planetary mixing followed by a dispersed phase to obtain composition 3, a cathode slurry with a total solids content (TSC) of 56% (97.5% LFP, 1% carbon nanotubes, 1.5% binder).

[0182] A homogeneous slurry was obtained and no evidence of gelling was observed during all preparation steps.

[0183] Example 4: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0184] Starting from the NMP solution of polymer (A-3) obtained in Preparation 3 above, an 8 wt % NMP solution of polymer (A-3) was prepared.

[0185] The NMP solution of polymer (F-1) and the NMP solution of polymer (A-3) were mixed in a ratio of 9:1 (30.87 g of the solution of polymer (F-1) and 3.43 g of the solution of polymer (A-3).

[0186] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt % solution in NMP) and 15.94 g of additional NMP were added to the solution containing polymer (F-1) and polymer (A-3) by planetary mixing followed by a dispersed phase to obtain composition 4, a cathode slurry with a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, 3.5% binder).

[0187] A homogeneous slurry was obtained and no evidence of gelation was observed during all preparation steps. The results of visual assessment of the slurry quality are summarized in Table 1.

[0188] Example 5: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0189] Starting from the DMF solution of polymer (A-4) obtained in Preparation 4 above, an 8 wt % NMP solution of polymer (A-4) was prepared.

[0190] The NMP solution of polymer (F-1) and the NMP solution of polymer (A-4) were mixed in a ratio of 9:1 (30.87 g of the solution of polymer (F-1) and 3.43 g of the solution of polymer (A-4).

[0191] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of a 4 wt % solution in NMP) and 15.94 g of additional NMP were added to the solution containing polymer (F-1) and polymer (A-4) by planetary mixing followed by a dispersed phase to obtain composition 5, a cathode slurry with a total solids content (TSC) of 56% (95.75% LFP, 0.75% carbon nanotubes, 3.5% binder).

[0192] A homogeneous slurry was obtained and no evidence of gelation was observed during all preparation steps. The results of visual assessment of the slurry quality are summarized in Table 1.

[0193] Comparative Example 1: An 8 wt % solution of HSV900 in NMP was prepared.

[0194] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of 4 wt % NMP solution) and 15.94 g additional NMP were added to 34.3 g of the solution containing HSV900 by planetary mixing followed by dispersion phase to obtain composition (C-1), a cathode slurry with a total solids content (TSC) of 56% and a binder content of 3.5%.

[0195] The results of the visual assessment of slurry quality are summarized in Table 1.

[0196] Comparative Example 2: An 8 wt % NMP solution of polymer (F-1) was prepared.

[0197] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of 4 wt % NMP solution) and 15.94 g additional NMP were added to 34.3 g of the solution containing polymer (F-1) by planetary mixing followed by dispersion phase to obtain composition (C-2), a cathode slurry with a total solids content (TSC) of 56% and a binder content of 3.5%.

[0198] The results of the visual assessment of slurry quality are summarized in Table 1.

[0199] Comparative Example 3: Starting from the DMF solution of polymer (A-1) obtained in Preparation 1 above, an 8 wt % NMP solution of polymer (A-1) was prepared. Polymer (A-1) in powder form was precipitated from the DMF solution in distilled water, and the precipitate obtained was dried overnight at 90° C. in a vacuum oven.

[0200] The powder of polymer (A-1) thus obtained was dissolved in NMP at 8% by weight.

[0201] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of 4 wt % NMP solution) and 15.94 g additional NMP were added to 34.3 g of the solution containing polymer (A-1) by planetary mixing followed by dispersion phase to obtain composition (C-3), a cathode slurry with a total solids content (TSC) of 56% and a binder content of 3.5%.

[0202] The results of the visual assessment of slurry quality are summarized in Table 1.

[0203] Comparative Example 4: Starting from the DMF solution of polymer (A-2) obtained in preparation 2 above, an 8 wt% NMP solution of polymer (A-2) was prepared. The polymer (A-2) in powder form was precipitated from the DMF solution in distilled water, and the precipitate obtained was dried overnight in a vacuum oven at 90°C. The powder of polymer (A-2) thus obtained was dissolved in NMP at 8 wt%.

[0204] Nano-LFP (75.07 g), carbon nanotubes (14.7 g of 4 wt % NMP solution) and 15.94 g additional NMP were added to 34.3 g of the solution containing polymer (A-2) by planetary mixing followed by dispersion phase to obtain composition (C-4), a cathode slurry with a total solids content (TSC) of 56% and a binder content of 3.5%.

[0205] The results of the visual assessment of slurry quality are summarized in Table 1.

[0206] [Table 1]

[0207] Example 6: Evaluation of gelation of electrode-forming composition The change in viscosity over time of compositions 2 and (C-1) prepared as defined above was evaluated as follows: The viscosity of the compositions at different aging times up to 72 hours was evaluated at different shear rates (0.1 to 100 rad / s) using an Anton Paar apparatus in MCR52 plate-to-plate configuration, by comparing the values ​​at the same shear rate.

[0208] The results are reported in Table 2.

[0209] [Table 2]

[0210] In view of the above, it has been found that the positive electrode forming composition (C) according to the present invention is characterized by improved resistance to gelation due to the presence of the binder (B) comprising the polymer (A).

[0211] Example 7: Preparation of electrodes The positive electrode was prepared by applying the above-mentioned electrode-forming compositions 1 to 5 and compositions (C-1) to (C-4) to an aluminum foil having a thickness of 15 μm, and applying the composition at a concentration of 15 mg / cm 2 The solvent was completely evaporated by drying in an oven at a temperature of 90° C. to prepare a strip-shaped cathode.

[0212] The positive electrodes thus obtained (electrodes (E1), (E2), (E4), (E5), (EC-1), (EC-2), (EC-3) and (EC-4), respectively) were visually evaluated. The results are reported in Table 3.

[0213] [Table 3]

[0214] Example 8: Preparation of electrodes using primers The Al current collector was etched using a 5 wt % HNO3 solution at 40 °C for 4 min.

[0215] This was then dip-coated with a solution of polymer (P)-1, a random copolymer obtained by copolymerization of a mixture of acrylic acid and vinyl phosphoric acid in a molar ratio of 70:30. Polymer (P)-1 had a weight average molecular weight (Mw) in the range of about 30-80 kDa, as measured by GPC using the following conditions: SEC was equipped with a multi-angle laser light scattering (MALLS) Mini Dawn TREOS detector and an Agilent concentration detector (RI detector). The SEC-MALLS system was operated with three Varian Aquagel OH mixed H, 8 μm, 3*30 cm columns, with a flow rate of 1 mL / min and the following mobile phase: 100% water, 100 mM NaCl, 25 mM NaH2PO4, 25 mM Na2HPO4 buffer solution (pH=7). The polymer samples were diluted in mobile phase for at least 4 hours to 0.5 wt% actives, then filtered through a Millipore filter 0.45 μm and 100 microliters were injected into the mobile phase flow. The absolute molar mass was obtained using the dn / dC of poly(acrylic acid) equal to 0.1875 mL / g. As detector, RI (Agilent concentration detector) + MALLS (multi-angle laser light scattering) Mini Dawn TREOS was used.

[0216] The immersion was carried out at 45°C for 2 minutes, followed by rinsing and drying at room temperature up to 100°C for 5 minutes.

[0217] An appropriate amount of composition 2 was cast onto the treated Al current collector, and then dried to obtain a positive electrode (E6).

[0218] Positive electrode adhesion evaluation The positive electrodes (E2), (E3) and (EC-1) were cut into stripes (10 cm long, 2.5 cm wide) and attached to 2 mm thick rigid aluminum foil using double-sided adhesive tape with dimensions 2.5 x 8 cm. The coated side of the electrodes was held facing the aluminum plate so that the part of the electrode did not adhere to the tape, so that one end of each stripe was not in contact with the double-sided adhesive tape and could be pulled from the foil.

[0219] Each specimen was peeled from the foil at an angle of 180° by a dynamometer that allows the measurement of the force required to peel the sample from the double-sided adhesive tape. The peel speed is 300 mm / min at T=25° C. The results are summarized in Table 4.

[0220] [Table 4]

[0221] Positive electrode adhesion evaluation Positive electrodes (E2), (E4), (E5) and (E6) were cut into strips (10 cm long, 2.5 cm wide) and attached to 2 mm thick rigid aluminum foil using double-sided adhesive tape with dimensions 2.5 x 8 cm. The coated side of the electrodes faced the aluminum plate. Part of the electrodes was held from adhering to the tape so that one end of each stripe was not in contact with the double-sided adhesive tape and could be pulled from the foil.

[0222] Each specimen was peeled from the foil at an angle of 180° by a dynamometer that allows the measurement of the force required to peel the sample from the double-sided adhesive tape. The peel speed is 300 mm / min at T=25° C. The results are summarized in Table 5.

[0223] [Table 5]

[0224] Electrodes of the present invention have demonstrated improved adhesion to metal foils compared to standard prior art electrodes comprising PVDF.

Claims

1. A positive electrode forming composition (C) comprising at least one positive electrode active material (AM) having an olivine structure and at least one binder (B), wherein the binder (B) is a) 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 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, and ether groups. １ ~C ２０ (It is a hydrocarbon part.) Repeating units derived from at least one hydrophilic (meth)acrylic monomer (MA) A vinylidene fluoride (VDF) copolymer [polymer (F)] containing at least one such copolymer, b) at least one (meth)acrylic polymer [polymer (A)], c) At least one solvent [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 (meth)acrylic 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) The composition (C) according to claim 1, having the following characteristics.

4. The composition according to claim 1, wherein the active material (AM) is lithium iron phosphate (LFP).

5. Polymer (A) is of the formula CH ２ =C(R)-C(=O)-NH-Rh (meth)acrylamide ester or formula CH ２ The composition (C) according to claim 1, 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 aforementioned 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, octyl The composition (C) according to claim 5, selected from the group consisting of (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, cycloalkyl(meth)acrylate, for example, cyclohexyl(meth)acrylate and phenyl(meth)acrylate.

7. Polymer (A) is a repeating unit derived from 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, Sipomer® B-CEA, and other 2-carboxyethyl acrylate oligomers, or the following formula (III): 【Chemistry 2】 (In the formula, R １ is H or an alkyl group, and the alkyl group is preferably a methyl group. R ２ is H or an alkyl group, R ３ and R ４ These may be the same or different from each other, and may be selected from linear or branched alkyl groups having hydrogen atoms or 1 to 6 carbon atoms. A is, - A single covalent bond, and - Spacer A combination selected from the group consisting of, X, Y, and Z are independently selected from carbon atoms or nitrogen atoms. a, b, and c are independently selected from integers 1 to 2. Each dashed line represents an optional double bond. The composition (C) according to claim 1, further comprising repeating units derived from one or more ethylenically unsaturated monomers [monomer (M1)] having an unsaturated heterocyclic group having at least one nitrogen atom.

8. The monomer (M1) is - Formula (IIIa): 【Transformation 3】 vinylimidazole (VIm) - Formula (IIIb) 【Chemistry 4】 2-methyl-1-vinylimidazole - Formula (IIIc) 【Transformation 5】 1-vinyl-1,2,4-triazole - Equation (IIId) 【Transformation 6】 2-vinylpyrazine - Equation (IIIe) 【Transformation 7】 4-vinylpyridine - Formula (IIIf) 【Transformation 8】 2-vinylpyridine - Equation (IIIg) 【Chemistry 9】 Hydroxyl-(meth)acrylate imidazole derivatives A composition (C) according to claim 7, selected from the group consisting of the following.

9. The composition (C) according to claim 1, wherein polymer (A) is a methyl methacrylate polymer containing at least 50% by weight of methyl methacrylate monomer units, preferably at least 70% by weight, and more preferably at least 80% by weight of methyl methacrylate monomer units.

10. The composition (C) according to claim 9, wherein polymer (A) is a methyl methacrylate polymer containing 100% by weight of methyl methacrylate monomer units.

11. The composition (C) according to claim 9, which is a methyl methacrylate polymer comprising at least 80% by weight of methyl methacrylate monomer units and up to 20% by weight of methacrylic acid monomer units.

12. The composition (C) according to claim 1, wherein polymer (A) is at least partially chlorinated.

13. The composition (C) according to claim 1, 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.

14. A process 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 13, (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 process that includes this.

15. A positive electrode (E) that can be obtained by the process described in claim 14.

16. - 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) A positive electrode active material (AM) having an olivine structure in an amount of 90-98% by weight, jj) Binder (B') in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, 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 10】 (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, and ether groups. １ ~C ２０ (It is a hydrocarbon part.) Repeating units derived from at least one hydrophilic (meth)acrylic monomer (MA) A vinylidene fluoride (VDF) copolymer [polymer (F)] containing at least one such copolymer, b'') at least one (meth)acrylic polymer [polymer (A)], Optionally, at least one conductivity-imparting additive and Binder (B') containing, 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).

17. An electrochemical device comprising the electrode (E) described in claim 16.

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