Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
  • C08F14/18—Monomers containing fluorine
  • C08F14/22—Vinylidene fluoride
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
  • C08F214/18—Monomers containing fluorine
  • C08F214/22—Vinylidene fluoride
  • C08F214/225—Vinylidene fluoride with non-fluorinated comonomers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
  • C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
  • C09D127/12—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C09D127/16—Homopolymers or copolymers of vinylidene fluoride
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J127/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers
  • C09J127/02—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
  • C09J127/12—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C09J127/16—Homopolymers or copolymers of vinylidene fluoride
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/043—Processes of manufacture in general involving compressing or compaction
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention pertains to vinylidene fluoride copolymers comprising recurring units derived from hydrophilic monomers and to their use as binder for electrodes in Li-ion batteries.
• Fluoropolymers are known in the art to be suitable as binders for the manufacture of electrodes for use in electrochemical devices such as secondary batteries.
• WO 2008/129041 discloses linear semi-crystalline vinylidene fluoride (VDF) copolymers comprising from 0.05% to 10% by moles of recurring units derived from (meth)acrylic monomers and uses thereof as binder in electrodes for lithium-ion batteries.
• VDF linear semi-crystalline vinylidene fluoride
• This invention provides a solution to this problem by combining easiness in the electrode fabrication process by dealing with electrode-forming formulation having low viscosity at low shear rates, whit the provision of electrodes having a very high adhesion towards the current collector.
• VDF vinylidene fluoride
• HA hydroxyl group-containing vinyl monomer
• RO is a divalent radical containing at least one oxygen atom
• R a is a C1-C5 linear or branched hydrocarbon groupand
• Rb is hydrogen or a Ci- C5 linear or branched hydrocarbon groupand x is an integer selected from 1 and zero, wherein said end groups are present in an amount of at least 1/10000 VDF units, preferably higher than 1.5/10000 VDF units, more preferably higher than 2/10000 VDF units.
• a second object of the present invention pertains to an electrode-forming composition (C) comprising: a) at least one electrode active material (AM); b) at least one binder (B), wherein binder (B) comprises at least one polymer (F) as above defined; and c) at least one solvent (S).
• AM electrode active material
• B binder
• S solvent
• the present invention pertains to the use of the electrode-forming composition (C) in a process for the manufacture of an electrode [electrode (E)j, said process comprising:
• composition (B) providing an electrode-forming composition [composition (C)] as above defined;
• step (C) applying the composition (C) provided in step (B) onto the at least one surface of the metal substrate provided in step (A), thereby providing an assembly comprising a metal substrate coated with said composition (C) onto the at least one surface;
• step (D) drying the assembly provided in step (C);
• step (E) submitting the dried assembly obtained in step (D) to a compression step to obtain the electrode (E) of the invention.
• the present invention pertains to the electrode [electrode (E)] obtainable by the process of the invention.
• the present invention pertains to an electrochemical device comprising at least one electrode (E) of the present invention.
• Suitable hydroxyl group-containing vinyl monomers are compounds of formula (I): wherein:
• Ri , R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a halogen atom, and a C1-C3 hydrocarbon group and ROH is a C2-C10 hydrocarbon chain moiety comprising at least one hydroxyl group and possibly containing in the chain one or more oxygen atoms, carbonyl groups or carboxy groups.
• monomers (HA) are compounds of formula (la): wherein:
• Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group and R’OH is a C1-C5 hydrocarbon moiety comprising at least one hydroxyl group.
• Non-limitative examples of monomers (HA) of formula (la) include, notably:
• the at least one monomer (HA) is hydroxyethyl(meth)acrylate (HEA) or 2-hydroxypropyl acrylate (HPA).
• Suitable carboxyl group-containing vinyl monomers are compounds of formula (II): wherein:
• Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group and RH is a C2-C10 hydrocarbon moiety comprising at least one carboxyl group and comprising no hydroxyl groups.
• monomers (CA) are compounds of formula (lla):
• Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group and R’H is a hydrogen or a C1-C5 hydrocarbon moiety comprising at least one carboxyl group and comprising no hydroxyl groups.
• R’H may further contain in the chain one or more oxygen atoms, carbonyl groups or ester groups.
• Non-limitative examples of monomers (CA) of formula (lla) include, notably:
• the at least one monomer (CA) is acrylic acid (AA).
• the molar ratio between recurring units (ii) and recurring units (iii) in polymer (F) is preferably comprised in the range from 20:1 to 1 :20, preferably from 10:1 to 1 :10, more preferably from 1 :5 to 5:1.
• polymer (F) It is essential that in polymer (F) a fraction of at least 40% of monomer (HA) and a fraction of at least 40% of monomer (CA) are randomly distributed into said polymer (F).
• fraction of randomly distributed monomer (HA) is intended to denote the percent ratio between the average number of (HA) monomer sequences (%), said sequences being comprised between two recurring units derived from VDF monomer, and the total average number of (MA) monomer recurring units (%), according to the following formula: average number of (HA) sequences ⁇ %)
• fraction of randomly distributed monomer (CA) is intended to denote the percent ratio between the average number of (CA) monomer sequences (%), said sequences being comprised between two recurring units derived from VDF monomer, and the total average number of (CA) monomer recurring units (%), according to the following formula: average number of (CA) sequences (%)
• Determination of total average number of (HA) monomer recurring units and of (CA) monomer recurring units in polymer (F) can be performed by any suitable method, NMR being preferred.
• the fraction of randomly distributed units (HA) and (CA) is preferably of at least 50%, more preferably of at least 60%, most preferably of at least 70 %.
• Polymer (F) comprises preferably at least 0.01 %, more preferably at least 0.02 % moles of recurring units derived from said monomer (HA).
• Polymer (F) comprises preferably at most 5.0 %, more preferably at most 3.0 % moles, even more preferably at most 2.0 % moles of recurring units derived from monomer (HA).
• Polymer (F) comprises preferably at least 0.01 %, more preferably at least 0.02 % moles of recurring units derived from said monomer (CA).
• Polymer (F) comprises preferably at most 5.0 %, more preferably at most 3.0 % moles, even more preferably at most 2.0 % moles of recurring units derived from monomer (CA).
• the polymer (F) can be an elastomer or a semi-crystalline polymer, preferably being a semi-crystalline polymer.
• the term “semi-crystalline” means a fluoropolymer that has, besides the glass transition temperature Tg, at least one crystalline melting point on DSC analysis.
• a semi-crystalline fluoropolymer is hereby intended to denote a fluoropolymer having a heat of fusion of from 10 to 90 J/g, preferably of from 30 to 80 J/g, more preferably of from 35 to 75 J/g, as measured according to ASTM D3418-08.
• the term “elastomer” is intended to designate a true elastomer or a polymer resin serving as a base constituent for obtaining a true elastomer.
• True elastomers are defined by the ASTM, Special Technical Bulletin, No. 184 standard as materials capable of being stretched, at room temperature, to twice their intrinsic length and which, once they have been released after holding them under tension for 5 minutes, return to within 10 % of their initial length in the same time.
• the intrinsic viscosity of polymer (F), measured in dimethylformamide at 25 ° C, is between 0.05 l/g and 0.70 l/g more preferably between 0.20 l/g and 0.50 l/g.
• the polymer (F) of the present invention usually has a melting temperature (Tm) comprised in the range from 130 to 200°C.
• the polymer (F) of the present invention possesses a quasi-linear structure, with a very low amount of branching, which results in the insoluble fraction due to long branched chains being substantially decreased.
• the polymer (F) of the present invention has in fact preferably a low fraction of insoluble components in standard polar aprotic solvents for PVDF, such as NMP. More preferably, solutions of polymer (F) in said standard polar aprotic solvents remain homogeneous and stable for several weeks, with substantially no insoluble residue.
• the melting temperature may be determined from a DSC curve obtained by differential scanning calorimetry (hereinafter, also referred to as DSC).
• the melting temperature (Tm) is determined on the basis of the peak having the largest peak area.
• the polymer (F) may further comprise recurring units derived from one or more fluorinated comonomers (CF) different from VDF.
• fluorinated comonomer CF
• fluorinated comonomer CF
• Non-limitative examples of suitable fluorinated comonomers include, notably, the followings:
• C2-C8 fluoro- and/or perfluoroolefins such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene and hexafluoroisobutylene;
• chloro- and/or bromo- and/or iodo-C2-C6 fluoroolefins such as chlorotrifluoroethylene (CTFE).
• the fluorinated comonomer (CF) is preferably HFP.
• polymer (F) is semi-crystalline and comprises from 0.1 to 15.0% by moles, preferably from 0.3 to 5.0% by moles, more preferably from 0.5 to 3.0% by moles of recurring units derived from said fluorinated comonomer (CF).
• the polymer (F) more preferably comprises recurring units derived from:
• VDF vinylidene fluoride
• HA hydroxyl group-containing vinyl monomer
• CA carboxyl group-containing vinyl monomer
• CF fluorinated comonomer
• the polymer (F) of the present invention comprises end groups of formula (I):
• - RO is a divalent radical containing at least one oxygen atom
• R a is a C1-C5 linear or branched hydrocarbon group
• Rb is hydrogen or a C1-C5 linear or branched hydrocarbon group
• end groups are present in an amount of at least 1/10000 VDF units, preferably higher than 2/10000 VDF units.
• Non limitative examples of divalent radical RO include, notably: ether (-0-), ester (-O-CO-), ketone (-CO-), epoxide, and per-carbonate (-O-CO-O-) groups.
• RO is a divalent radical containing at least two oxygen atoms. More preferably, RO is a per-carbonate group.
• R a and Rb are both C2-C3 linear or branched hydrocarbon groups, more preferably C3 linear or branched hydrocarbon groups.
• x is zero.
• the polymer (F) of the present invention may be obtained by polymerization of a VDF monomer, at least one monomer (HA), at least one monomer (CA) and optionally at least one comonomer (CF), either in suspension in organic medium, according to the procedures described, for example, in WO 2008129041 , or in aqueous emulsion, typically carried out as described in the art (see e.g. US 4,016,345, US 4,725,644 and US 6,479,591).
• the preferred process for preparing the polymer (F) comprises polymerizing the vinylidene fluoride (VDF) monomer, monomer (HA) and monomer (CA), and optionally comonomer (CF), in an aqueous medium in the presence of a radical initiator, said process comprising
• Suitable initiator known for the polymerization of fluorinated monomers are organic peroxides, such as those selected from the group consisting of: dialkyl peroxides, diacyl-peroxides, peroxyesters, and peroxydicarbonates.
• Exemplary dialkyl peroxides is di-t-butyl peroxide, of peroxyesters are t- butyl peroxypivalate and t-amyl peroxypivalate, and of peroxydicarbonate, are di(ethyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, diisopropyl peroxydicarbonate, di(sec-butyl) peroxydicarbonate, di(2- ethylhexyl) peroxydicarbonate and di(4-tert-butylcyclohexyl) peroxydicarbonate.
• the initiator used for preparing polymer (F) of the present invention is an organic peroxide, more preferably is selected from di(ethyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, di(iso-propyl) peroxydicarbonate and di(4-tert-butylcyclohexyl) peroxydicarbonate.
• the quantity of an initiator required for a polymerization is related to its activity and the temperature used for the polymerization.
• the total amount of initiator used is generally between 100 to 30000 ppm by weight on the total monomer weight used.
• the initiator may be added in pure form, in solution, in suspension, or in emulsion, depending upon the initiator chosen.
• a chain transfer agent, CTA can be added to the polymerization.
• Suitable CTA for this polymerization are known in the art and are typically short hydrocarbon chains like ethane and propane, esters such as ethyl acetate or diethyl maliate, diethylcarbonate and others.
• esters such as ethyl acetate or diethyl maliate, diethylcarbonate and others.
• organic peroxide is used as the initiator, it could act also as effective CTA during the course of free radical polymerization.
• the additional CTA however, may be added all at once at the beginning of the reaction, or it may be added in portions, or continuously throughout the course of the reaction. The amount of CTA and its mode of addition depend on the desired properties.
• pressure is maintained above critical pressure of vinylidene fluoride.
• the pressure is maintained at a value of more than 50 bars, preferably of more than 75 bars, even more preferably of more than 100 bars.
• continuous feeding means that slow, small, incremental additions the aqueous solution of monomer (HA) and monomer (CA) take place until polymerization has concluded.
• the aqueous solution of monomer (HA) and monomer (CA) continuously fed during polymerization amounts for at least 50 % wt of the total amount of monomer (HA) and monomer (CA) supplied during the reaction (i.e. initial charge plus continuous feed).
• % wt the total amount of monomer (HA) and monomer (CA) supplied during the reaction
• at least 60 % wt, more preferably at least 70 % wt, most preferably at least 80 % wt of the total amount of monomer (HA) and monomer (CA) is continuously fed during polymerization.
• An incremental addition of VDF monomer can be effected during polymerization, even if this requirement is not mandatory.
• the process of the invention is carried out at a temperature of at least 35° C, preferably of at least 40° C, more preferably of at least 45°
• polymer (F) is typically provided in form of powder.
• polymer (F) is typically provided in the form of an aqueous dispersion (D), which may be used as directly obtained by the emulsion polymerization or after a concentration step.
• D aqueous dispersion
• Polymer (F) obtained by emulsion polymerization can be isolated from the aqueous dispersion (D) by concentration and/or coagulation of the dispersion and obtained in powder form by subsequent drying.
• Polymer (F) in the form of powder may be optionally further extruded to provide polymer (F) in the form of pellets.
• the polymer (F) as above detailed may be used as binder for electrodes in Li-ion batteries.
• a second object of the present invention pertains to an electrode-forming composition (C) comprising: a) at least one electrode active material (AM); b) at least one binder (B), wherein binder (B) comprises at least one polymer (F) as above defined; c) at least one solvent (S); and d) optionally, at least one conductive agent.
• the term “electro-active material (AM)” is intended to denote a compound which is able to incorporate or insert into its structure and substantially release therefrom alkaline or alkaline-earth metal ions during the charging phase and the discharging phase of an electrochemical device.
• the compound (AM) is preferably able to incorporate or insert and release lithium ions.
• composition (C) The nature of the compound (AM) in composition (C) depends on whether said composition is used in the manufacture of a positive electrode [electrode (Ep)] or a negative electrode [electrode (En)].
• the compound (AM) may comprise a composite metal chalcogenide of formula L1MQ2, wherein M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V or a metal such as Al and a mixture of thereof and Q is a chalcogen such as O or S.
• M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V or a metal such as Al and a mixture of thereof and Q is a chalcogen such as O or S.
• M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V or a metal such as Al and a mixture of thereof and Q is a chalcogen such as O or S.
• M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V or a metal such as Al and a mixture of thereof
• Q is a chalcogen such as O or S.
• UMO2 lithium-based composite metal
• the compound (AM) may comprise a lithiated or partially lithiated transition metal oxyanion-based electro-active material of formula MiM2(JC )fEi-f, wherein Mi is lithium, which may be partially substituted by another alkali metal representing less than 20% of the Mi metals, M2 is a transition metal at the oxidation level of +2 selected from Fe, Mn, Ni or mixtures thereof, which may be partially substituted by one or more additional metals at oxidation levels between +1 and +5 and representing less than 35% of the M2 metals, including 0, JCU is any oxyanion wherein J is either P, S, V
• E is a fluoride, hydroxide or chloride anion
• f is the molar fraction of the JCU oxyanion, generally comprised between 0.75 and 1.
• the MiM2(JCU)fEi-f electro-active material as defined above is preferably phosphate-based and may have an ordered or modified olivine structure.
• the compound (AM) in the case of forming a positive electrode (Ep) has formula Lb-xM’ y M’ ’ 2- y (JCU)3 wherein 0 ⁇ x ⁇ 3, 0 ⁇ y ⁇ 2, M’ and M’ ’ are the same or different metals, at least one of which being a transition metal, JCU is preferably PCU which may be partially substituted with another oxyanion, wherein J is either S, V, Si, Nb, Mo or a combination thereof.
• the compound (AM) is a phosphate-based electro-active material of formula Li(FexMni-x)PCU wherein 0 ⁇ x ⁇ 1, wherein x is preferably 1 (that is to say, lithium iron phosphate of formula LiFePCU).
• the compound (AM) may preferably comprise a carbon-based material and/or a silicon-based material.
• the carbon-based material may be, for example, graphite, such as natural or artificial graphite, graphene, or carbon black.
• the carbon-based material is preferably graphite.
• the silicon-based compound may be one or more selected from the group consisting of chlorosilane, alkoxysilane, aminosilane, fluoroalkylsilane, silicon, silicon chloride, silicon carbide and silicon oxide. More particularly, the silicon-based compound may be silicon oxide or silicon carbide.
• the at least one silicon-based compound is comprised in the compound (AM) in an amount ranging from 1 to 30 % by weight, preferably from 5 to 20 % by weight with respect to the total weight of the compound (AM).
• the solvent (S) may preferably be an organic polar one, examples of which may include: N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N- dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate. These solvents may be used singly or in mixture of two or more species.
• An optional conductive agent may be added in order to improve the conductivity of a resulting electrode (AM).
• Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder carbon nanotubes (CNT), graphene, or fiber, or fine powder or fibers of metals such as nickel or aluminum.
• the optional conductive agent is preferably carbon black. Carbon black is available, for example, under the brand names, Super P ® or Ketjenblack ® .
• the conductive agent is different from the carbon-based material described above.
• an electrode-forming composition (C) for use in the preparation of a positive electrode (Ep) comprising: a) at least one electrode active material (AM); b) at least one binder (B), wherein binder (B) comprises at least one polymer (F) as above defined; c) at least one solvent (S); and d) at least one conductive agent, preferably selected from carbon black or graphite fine powder carbon nanotubes.
• the polymer (F) of the present invention possesses a quasi-linear structure, and very low amount of insoluble fraction when dissolved in standard polar aprotic solvents such as NMP.
• polymer (F) provides solutions in organic solvents, which are not detrimentally affected by the presence of insoluble residues, which are generally referred as “gels” , and are hence more adapted for use in formulating electrodes-forming compositions.
• the present invention pertains to the use of the electrode-forming composition (C) for the manufacture of an electrode [electrode (E)], said process comprising:
• composition (B) providing an electrode-forming composition [composition (C)] as above defined;
• step (C) applying the composition (C) provided in step (B) onto the at least one surface of the metal substrate provided in step (A), thereby providing an assembly comprising a metal substrate coated with said composition (C) onto the at least one surface;
• step (D) drying the assembly provided in step (C);
• step (E) submitting the dried assembly obtained in step (iv) to a compression step to obtain the electrode (E) of the invention.
• the present invention pertains to the electrode [electrode (E)] obtainable by the process of the invention.
• the Applicant has surprisingly found that the electrode (E) of the present invention shows outstanding adhesion of the binder to current collector. [00101]
• the electrode (E) of the invention is thus particularly suitable for use in electrochemical devices, in particular in secondary batteries.
• secondary battery is intended to denote a rechargeable battery.
• the secondary battery of the invention is preferably an alkaline or an alkaline-earth metal secondary battery.
• the secondary battery of the invention is more preferably a Lithium-ion secondary battery.
• the present invention pertains to an electrochemical device comprising at least one electrode (E) of the present invention.
• the electrochemical device according to the present invention being preferably a secondary battery, comprises:
• the positive electrode and the negative electrode is the electrode (E) of the present invention.
• an electrochemical device is a secondary battery comprising:
• the negative electrode is the electrode (E) according to the present invention.
• An electrochemical device according to the present invention can be prepared by standard methods known to a person skilled in the art.
• Intrinsic viscosity ( h ) [dl/g] was measured using the following equation on the basis of dropping time, at 25° C, of a solution obtained by dissolving the polymer (F) in N,N-dimethylformamide at a concentration of about 0.2 g/dl using a Ubbelhode viscosimeter: where c is polymer concentration [g/dl], h r is the relative viscosity, i.e. the ratio between the dropping time of sample solution and the dropping time of solvent, h sp is the specific viscosity, i.e. h r -1 , and G is an experimental factor, which for polymer (F) corresponds to 3.
• VDF is the intensity, normalized to one hydrogen, of the integrals of normal and reverse VDF recurring units.
• Example 1 Preparation of Polymer F-1 [00120]
• a 4L reactor equipped with an impeller running at a speed of 650 rpm were introduced in sequence: 2,014 g of demineralized water and 0.4 g of PEO (Alkox® -E45 from Alkorox) per kg of total VDF monomers and 0.5 g of hydroxypropyl methylcellulose (Methocel®-K100 from Dow) per kg of total VDF monomers and 59.91 g of a solution of trisodium phosphate.
• the oxygen present in the reactor was removed with a sequence of vacuum and purge of nitrogen at a fixed temperature of 14°C. This sequence was repeated 3 times.
• the pressure was kept constantly equal to 120 bars during the whole polymerization run by feeding an aqueous solution comprising 9.40 g of AA per liter of solution and 4.70 g of HEA per liter of solution. After 365 minutes the polymerization was stopped by degassing the suspension until reaching atmospheric pressure. A total of 721 g of the AA and HEA solution was charged to the reactor.
• the polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C for twelve hours. 919 g of dry powder were collected.
• a polymer comprising VDF-AA (0.45% by moles)-HEA (0.15% by moles), having an intrinsic viscosity of 0.28 l/g in DMF at 25°C and a T2f of 165.5°C was obtained
• the polymer contained 3.0 /10000 VDF units of the end-group CH3CH2- OCOO-.
• the polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C for twelve hours. 872 g of dry powder were collected.
• the polymer contained 2.8/10000 VDF units of the end-group CH3CH2- OCOO-.
• the pressure was kept constantly equal to 120 bars during the whole polymerization run by feeding an aqueous solution comprising 13.38 g of AA per liter of solution and 1.61 g of HPA per liter of solution. After 369 minutes the polymerization was stopped by degassing the suspension until reaching atmospheric pressure. A total of 700 g of the AA and HPA solution was charged to the reactor.
• the polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C for twelve hours. 864 g of dry powder were collected.
• the polymer contained 3.6 /10000 VDF units of the end-group CH3CH2- OCOO-.
• Example 4 comparative Preparation of Polymer A
• a 4L reactor equipped with an impeller running at a speed of 650 rpm were introduced in sequence: 1.928 g of demineralized water and 0.4 g of PEO (Alkox® -E45 from Alkorox) per kg of total VDF monomers and 0.5 g of hydroxypropyl methylcellulose (Methocel®-K100 from Dow) per kg of total VDF monomers.
• the oxygen present in the reactor was removed with a sequence of vacuum and purge of nitrogen at a fixed temperature of 11 °C. This sequence was repeated 3 times.
• the pressure was kept constantly equal to 120 bars during the whole polymerization run by feeding an aqueous solution comprising 11.91 g of AA per liter of solution and 1.49 g of hydroxypropyl acrylate (HPA) per liter of solution. After 480 minutes the polymerization was stopped by degassing the suspension until reaching atmospheric pressure. A total of 787 g of the AA and HPA solution was charged to the reactor.
• HPA hydroxypropyl acrylate
• the polymer was then collected by filtration and suspended against clean water in a stirred tank. After the washing treatment, the polymer was dried in an oven at 65°C for twelve hours. 896 g of dry powder were collected.
• the polymer contained: 2.2 /10000 VDF units of -C(CH 3 )3, 6.4 /10000 VDF units of -CF2H and 2.7/10000 VDF units of -CF2CH3 end-groups.
• the positive electrodes having final composition of 96.5% by weight of NMC, 1.5% by weight of polymer, 2% by weight of conductive additive were prepared as follows.
• a first dispersion was prepared by pre-mixing for 10 minutes in a centrifugal mixer 34.7 g of a 6% by weight solution of a polymer in NMP, 133.8 g of NMC, 2.8 g of SC-65 and 8.8 g of NMP.
• the mixture was then mixed using a high speed disk impeller at 2000 rpm for 50 minutes. Additional 7.2 g of NMP were subsequently added to the dispersion, which was further mixed with a butterfly type impeller for 20 minutes at lOOOrpm. Positive electrodes were obtained by casting the as obtained compositions on 15 pm thick Al foil with doctor blade and drying the as coated layers in a vacuum oven at temperature of 90°C for about 50 minutes. The thickness of the dried coating layers was about 110 pm.
• the slurry viscosity was measured with an AntonPaar Rheolab QC using a Concentric cylinder setup (Measuring Cup: C-CC27/QC-LTD Bob: CC27/P6) with peltier temperature control at 25°C. Steady state viscosities were measured from shear rate of 0.1 to 200 1/s.
• Example 5 Adhesion and slurry viscosity

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