Classifications

• • 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
  • H01M4/0435—Rolling or calendering
• • 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
  • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• • 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
• • 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
• • 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
• • 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
• • 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
  • H01M4/624—Electric conductive fillers
• • 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
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • 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 generally relates to the field of electrical energy storage in Li-ion type lithium storage batteries. More specifically, the invention relates to a binder for a dry coated electrode for a Li-ion battery. Another subject of the invention is a process for the preparation of an electrode using said binder. The invention also relates to lithium-ion batteries manufactured by incorporating said electrode.
• An elementary cell of a Li-ion storage battery or a lithium battery comprises an anode (at the discharge), and a cathode (also at the discharge) generally composed of a lithium insertion compound of the type metal oxide, such as LiMn2O4, LiCoO2 or LiNiO2, between which an electrolyte is inserted which conducts lithium ions.
• a lithium insertion compound of the type metal oxide such as LiMn2O4, LiCoO2 or LiNiO2
• Rechargeable or secondary cells are more advantageous than primary (non-rechargeable) cells since the associated chemical reactions that take place at the positive and negative electrodes of the battery are reversible. Secondary cell electrodes can be regenerated multiple times by applying an electrical charge. Many advanced electrode systems have been developed to store an electrical charge. At the same time, much effort has been devoted to the development of electrolytes capable of improving the electrochemical capabilities of cells.
• the electrodes generally comprise at least one current collector on which is deposited, in the form of a film, a composite material consisting of a material called active material because it has electrochemical activity compared to lithium. , a polymer that acts as a binder, plus one or more electronically conductive additives that are typically carbon black or acetylene black, and possibly a surfactant.
• Binders are classified as inactive components since they do not directly contribute to the capacity of the cell. However, their key role in electrode processing and considerable influence on electrochemical performance electrodes have been widely described.
• the main relevant physical and chemical properties of binders are thermal stability, chemical and electrochemical stability, tensile strength (strong adhesion and cohesion), and flexibility.
• the main objective of using a binder is to form stable networks of the solid components of the electrodes, i.e. active materials and conductive agents (cohesion). Additionally, the binder must ensure close contact of the composite electrode to the current collector (adhesion).
• the current manufacturing process for Lithium-ion battery electrodes uses a solvent.
• This process consists of preparing an ink by mixing an active material, a conductive filler and a polymer binder in a solvent. This ink is then deposited on a current collector and the solvent is evaporated. A large part of the energy consumed by this process comes from the solvent evaporation step.
• a strong trend in the field of Lithium-ion batteries is to reduce manufacturing costs, which involves limiting the costs linked to energy consumption for manufacturing.
• binder offering good electrochemical resistance, providing good adhesion to a metallic current collector via a solvent-free manufacturing process. It is also essential that said binder has a high affinity with the other ingredients of the solvent-free formulation so that during pressing this binder provides intimate cohesion.
• the present invention relates to a binder for a dry coated electrode of a secondary battery comprising a fluoropolymer A and an acrylic polymer B, characterized in that said binder is in the form of a powder.
• the binder according to the present invention comprising two types of polymers, i.e. a fluoropolymer and an acrylic-based polymer, makes it possible to improve adhesion to the current collector.
• the use of the binder in powder form allows implementation without solvent from the mixing phase of the constituents to the deposition phases on the current collector and consolidation.
• the use of a binder in powder form for the manufacture of the electrode makes it possible to avoid having to resort to grinding or dispersion steps after mixing with the active materials and the conductive agents.
• said binder has a particle size distribution with a D90 less than or equal to 750 pm.
• said acrylic polymer B has a pH of between 1.5 and 4.0 measured in water at room temperature.
• said acrylic polymer B comprises at least 20% by weight of monomeric units containing a -CO 2 H functional group based on the total weight of said acrylic polymer B.
• the fluoropolymer A is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1 ,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof.
• said fluoropolymer A comprises monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl , amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolics, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic.
• the acrylic polymer B has a glass transition temperature less than or equal to 230°C.
• the acrylic polymer B has a number molar mass greater than or equal to 3000 g.mol-1.
• the acrylic polymer B comprises monomeric units carrying a carboxylic acid or carboxylic acid anhydride functional group and monomeric units carrying a carboxylic acid ester functional group.
• the mass ratio of acrylic polymer B relative to the fluoropolymer A is 1 to 70%.
• the present invention provides a process for preparing the binder, according to the present invention, characterized in that it comprises a step of:
• the present invention provides a dry coated electrode comprising the binder according to the present invention, a dry active material and optionally a conductive agent.
• the electrode has the following mass composition: a. 50% to 99.9% active material, preferably 50% to 99%, b. 25% to 0% conductive agent, preferably 25% to 0.5%, c. 25% to 0.05% binder according to the present invention, preferably 25% to 0.5%, d. 0% to 5% of at least one additive chosen from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for a conductive additive, and an auxiliary flow agent; the sum of all these percentages being 100%.
• said conductive agents being composed of one or more materials from carbon blacks, such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor phase growth carbon fiber; metal powders such as SUS powder, and aluminum powder.
• carbon blacks such as acetylene black, Ketjen black
• carbon fibers such as carbon nanotube, carbon nanofiber, vapor phase growth carbon fiber
• metal powders such as SUS powder, and aluminum powder.
• said active material is chosen from the group consisting of: a lithium alloy, a metal oxide, a carbon material such as graphite or hard carbon, silicon, an alloy silicon and Li4TiO12.
• the present invention provides a process for the preparation of the dry coated electrode according to the present invention, comprising a thermomechanical treatment step carried out at a temperature Tl between Tf - 50°C ⁇ Tl ⁇ Tg + 50 °C when Tg > Tf or at a temperature Tl between Tg - 50°C ⁇ Tl ⁇ Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluoropolymer A and Tg being the glass transition temperature of the acrylic polymer B.
• the present invention provides a Li-ion battery comprising a positive electrode, a negative electrode and a separator, at least one electrode being a dry coated electrode according to the present invention.
• a binder for a secondary battery dry coated electrode comprising a mixture of at least two polymers.
• said binder comprises a fluoropolymer A and an acrylic polymer B.
• said binder is in the form of a powder.
• said powder has a particle size distribution with a D90 less than or equal to 750 pm, advantageously less than or equal to 700 pm, preferably less than or equal to 650 pm, more preferably less than or equal to 600 pm, in particular less than or equal to 550 pm, more particularly less than or equal to 500 pm.
• said powder has a particle size distribution with a D90 less than or equal to 450 pm, preferably less than or equal to 400 pm, more preferably less than or equal to 350 pm, in particular less than or equal to 300 pm, more particularly less than or equal to 250 pm, preferably less than or equal to 200 pm, advantageously preferred less than or equal to 150 pm, preferably preferably less than or equal to 100 pm, particularly preferably less than or equal to 50 p.m.
• the D90 is the particle size at the 90th percentile (by volume) of the cumulative particle size distribution. This parameter is determined by laser particle size analysis. A Malvern INSITEC System particle size analyzer is used for the measurement. This is carried out dry by laser diffraction on a powder with a focal length of 100 mm. This applies to all D90s described in this description.
• the mass ratio of acrylic polymer B relative to the fluoropolymer A is from 1 to 70%, advantageously from 2 to 60%, preferably from 3 to 50%, more preferably from 4 to 40%, in particular from 5 to 30%.
• said fluoropolymer A contains in its chain at least one monomer chosen from compounds containing a vinyl group capable of opening to polymerize and which contains, directly attached to this vinyl group, at least one atom fluorine, a fluoroalkyl group or a fluoroalkoxy group.
• Chlorofluoroethylene can refer to either 1-chloro-l-fluoroethylene or l-chloro-2-fluoroethylene.
• the 1-chloro-1-fluoroethylene isomer is preferred.
• the chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.
• said fluoropolymer A comprises at least monomeric units derived from vinylidene fluoride.
• Fluorinated polymer A may be a homopolymer or a copolymer.
• the copolymer may also comprise non-fluorinated monomers.
• the fluoropolymer A is a homopolymer of vinylidene fluoride.
• the fluoropolymer A is a polymer comprising units derived from vinylidene fluoride, and is preferably chosen from polyvinylidene fluoride homopolymer and copolymers comprising units of vinylidene fluoride and units derived from at least one other comonomer copolymerizable with vinylidene fluoride.
• the fluoropolymer A is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene or a mixture of these.
• the mass content of the vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.
• the fluoropolymer A is functionalized in whole or in part, which allows it to improve adhesion to metal.
• said fluoropolymer A may comprise monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl , carbonyl, mercapto, sulfide, oxazoline, phenolics, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic; preferably at least one carboxylic acid or hydroxyl function.
• the function is introduced by a chemical reaction which can be grafting, or a copolymerization of the fluorinated monomer with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with the fluorinated monomer, according to techniques well known by the professional.
• the functional group carries a carboxylic acid function which is a (meth)acrylic acid type group chosen from acrylic acid, methacrylic acid, methyl acrylic acid, hydroxyethyl(meth )acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.
• a (meth)acrylic acid type group chosen from acrylic acid, methacrylic acid, methyl acrylic acid, hydroxyethyl(meth )acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.
• the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus.
• the functionality is introduced via the transfer agent used during the synthesis process.
• the transfer agent is a polymer with a molar mass less than or equal to 20,000 g/mol and carrying functional groups chosen from the groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolics, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic.
• An example of such a transfer agent are acrylic acid oligomers.
• the transfer agent is an acrylic acid oligomer with a molar mass less than or equal to 20,000 g/mol. The molar mass of the transfer agent is determined according to a method as described below for acrylic polymer B.
• the functional group content of the PVDF is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.
• PVDF preferably has a high molecular weight.
• high molecular weight as used here, is meant a PVDF having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to the ASTM D-3835 method measured at 232°C and 100 sec-1.
• PVDF homopolymers and the VDF copolymers used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.
• they are prepared by an emulsion polymerization process in the absence of fluorinated surfactant.
• Polymerization of PVDF results in a latex generally having a solids content of 10 to 60% by weight, preferably 10 to 50%, and having a weight average particle size of less than 1 micrometer, preferably less than 1000 nm , preferably less than 800 nm, and more preferably less than 600 nm.
• the weight average size of the particles is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm.
• the polymer particles can form agglomerates whose weight average size is 1 to 30 micrometers, and preferably 2 to 10 micrometers. Agglomerates may break into discrete particles during formulation and application to a substrate.
• the homopolymer PVDF and VDF copolymers are composed of bio-based VDF.
• biosourced means “from biomass”. This makes it possible to improve the ecological footprint of the polymer.
• the biosourced VDF can be characterized by a renewable carbon content, that is to say carbon of natural origin and coming from a biomaterial or biomass, of at least 1 atomic % as determined by the carbon content. 14C according to standard NF EN 16640.
• renewable carbon indicates that the carbon is of natural origin and comes from a biomaterial (or biomass), as indicated below.
• the bio-carbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50% , preferably greater than or equal to 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100% .
• Acrylic polymer B As mentioned above, said binder also comprises an acrylic polymer B.
• said acrylic polymer B has a pH of between 1.5 and 4.0, advantageously between 1.6 and 3.9, preferably between 1.7 and 3.8, more preferably between 1.8 and 3, 7, in particular between 1.9 and 3.6, more particularly between 2.0 and 3.5, measured in water at room temperature.
• said acrylic polymer B comprises at least 20% by weight of monomeric units containing a -CO2H functional group based on the total weight of said acrylic polymer B.
• said acrylic polymer B has a glass transition temperature less than or equal to 230°C.
• said acrylic polymer B has a glass transition temperature less than or equal to 220°C, preferably less than 200°C, more preferably less than 180°C, in particular less than 160°C, more particularly less than or equal to 150°C.
• the acrylic polymer B has a number molar mass greater than or equal to 3000 g.mol-1, advantageously greater than or equal to 10000 g.mol-1, preferably greater than or equal to 50000 g.mol -1, more preferably greater than or equal to 100,000 g.mol-1, in particular greater than or equal to 150,000 g.mol-1.
• the molecular or molar mass is determined by Size Exclusion Chromatography (SEC). A test portion of the polymer solution corresponding to 90 mg of dry matter is introduced into a 10 mL bottle. The mobile phase, supplemented with 0.04% dimethylformamide (DMF), is added to a total mass of 10 g.
• SEC Size Exclusion Chromatography
• the composition of this mobile phase is as follows: NaHCOs: 0.05 mol/L, NaNOs: 0.1 mol/L, triethanolamine: 0.02 mol/L, NaNs 0.03% by weight.
• the CES chain is composed of a Waters 510 type isocratic pump, the flow rate of which is set at 0.8 mL/min, a Waters 717+ sample changer, an oven containing a Guard type precolumn Column Ultrahydrogel Waters 6 cm long and 40 mm internal diameter, followed by a linear column of Ultrahydrogel Waters type 30 cm long and 7.8 mm internal diameter. Detection is carried out using a differential refractometer of the RI Waters 410 type.
• the oven is brought to a temperature of 60°C and the refractometer is brought to a temperature of 45°C.
• the CES device is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standards Service with peak molecular weight between 1000 g/mol and 1.10 6 g/mol and polymolecularity index between 1, 4 and 1.7.
• the calibration curve is linear and takes into account the correction obtained using the flow marker: dimethylformamide (DMF).
• the acrylic polymer B comprises monomeric units carrying a carboxylic acid or carboxylic acid anhydride functional group and optionally monomeric units carrying a carboxylic acid ester functional group.
• the use of an acrylic polymer B with this type of functional group according to the present invention makes it possible to improve adhesion to the current collector.
• carboxylic acid functions and carboxylic acid esters makes it possible both to improve adhesion to the current collector but also to obtain deformable polymer particles compatible with the fluoropolymer A.
• Said heterocycle may be saturated or unsaturated or aromatic.
• Said heterocycle can be monocyclic or bicyclic.
• Said heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, deltalactam, succinimide, 2- ring. imidazolidinone, 4-imidazolidinone.
• Said heterocycle may be substituted by one or more C1-C5 alkyl groups.
• the Ci-Ci 8 alkyl is optionally substituted by said heterocycle.
• the latter can be linked to the alkyl chain by the nitrogen atom or any other atoms forming the heterocycle.
• the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.
• R 7 is selected from the group consisting of -NHC(CH 3 )2CH2C(O)CH 3 or -OR' with R' selected from the group consisting of Ci-Ci 8 alkyl optionally substituted by one or more group(s) - OH a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain.
• the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.
• alkyl includes linear and branched alkyls.
• the substituent R' is selected from the group consisting of methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxybutyl, hydroxypropyl, ethyl substituted with a ureido group, hydroxyethyl.
• said acrylic polymer B comprises monomeric units M2 derived from methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylate t-butyl, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, acrylate lauryl, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, methyl acrylic acid, methyl methacrylate or ureido methacrylate.
• acrylate here includes acrylates and methacrylates.
• the monomeric units M3 may come from a monomer selected from the group consisting of fumaric acid, crotonic acid, itaconic acid, vinyl acetate, vinyl neodecanoate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetone acrylamide, 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylate, dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate , n-octyl methacrylate, t-
• itaconic acid fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, acrylamido-2-methylpropane sulfonic acid, 2-hydroxyethyl acrylate are preferred.
• These compounds can be used alone or in a mixture of two or more.
• said acrylic polymer B comprises at least 30% by weight, advantageously at least 40% by weight, preferably at least 50% by weight of monomeric units Ml based on the weight of said acrylic polymer B.
• said acrylic polymer B comprises at least 90% by weight, advantageously at least 95% by weight, preferably at least 99% by weight, in particular 100% by weight of monomeric units Ml based on the weight of said acrylic polymer B .
• said acrylic polymer B comprises at least 1%, advantageously at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, in particular at least 30% by weight. weight, more particularly at least 40% by weight of monomeric units M2 based on the weight of said acrylic polymer B.
• the acrylic polymer B may not contain monomeric units M2.
• the acrylic polymer B comprises less than 30% by weight, advantageously less than 20% by weight, preferably less than 10% by weight, in particular less than 5% by weight, more particularly less than 1 % by weight of M3 monomeric units based on the weight of said acrylic polymer B.
• the acrylic polymer B may not contain M3 monomeric units.
• the acrylic polymer B used in the invention can be obtained by polymerization of the monomers according to known polymerization methods such as emulsion or suspension polymerization.
• the present invention provides a process for preparing said binder according to the present invention.
• said method comprises a step of:
• the drying step can be carried out by atomization or co-atomization, preferably at a temperature of 100°C to 220°C.
• the powder can also be obtained by grinding techniques, such as cryo-grinding, where the mixture is brought to a temperature below ambient temperature, using liquid nitrogen for example, before grinding.
• the particle size can be adjusted and optimized by selection or screening processes and/or by grinding.
• said binder has a pH of between 1.5 and 4.0, advantageously between 1.6 and 3.9, preferably between 1.7 and 3.8, more preferably between 1.8 and 3.7, in particular between 1.9 and 3.6, more particularly between 2.0 and 3.5, measured in water at room temperature.
• the present invention provides a dry coated electrode.
• the dry coated electrode comprises said binder according to the present invention, a conductive agent and a dry active material.
• the dry-coated electrode has the following mass composition: a. 50% to 99.9% active material, preferably 50% to 99%, b. 25% to 0% conductive agent, preferably 25% to 0.5%, c. 25% to 0.05% of said binder, preferably 25% to 0.5%, d. 0% to 5% of at least one additive chosen from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for a conductive additive, and an auxiliary flow agent; the sum of all these percentages being 100%.
• the conductive agents in the dry coated electrode are composed of one or more materials that can improve conductivity.
• Some examples include carbon blacks such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor phase growth carbon fiber; metal powders such as SUS powder, and aluminum powder.
• Active materials are materials that are capable of storing and releasing lithium ions.
• said electrode is a negative electrode.
• said active material is chosen from the group consisting of a lithium alloy, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy and Li4TiO12.
• the shape of the negative electrode active material is not particularly limited but is preferably particulate.
• said electrode is a positive electrode.
• the coating material is not particularly limited as long as it has lithium ion conductivity and contains a material capable of being maintained as a coating layer on the surface of the active material.
• Examples of the coating material include LiNbO3, Li4Ti5O12, and LÎ3PO4.
• the shape of the positive electrode active material is not particularly limited but is preferably particulate.
• a method of preparing the dry coated electrode comprises a thermomechanical treatment step carried out at a temperature Tl between Tf - 50°C ⁇ Tl ⁇ Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C ⁇ Tl ⁇ Tf + 50 °C when Tf > Tg with Tf being the melting temperature of fluoropolymer A and Tg being the glass transition temperature of acrylic polymer B.
• Said process for preparing the dry coated electrode comprises the following steps:
• thermomechanical treatment carried out at a temperature Tl between Tf - 50°C ⁇ Tl ⁇ Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C ⁇ Tl ⁇ Tf + 50°C when Tf > Tg with Tf being the melting temperature of fluoropolymer A and Tg being the glass transition temperature of acrylic polymer B.
• a “solvent-free” process is a process that does not require a residual solvent evaporation step after the deposition step.
• thermomechanical treatment refers to the application Tl between Tf - 50°C ⁇ Tl ⁇ Tg + 50°C when Tg > Tf or at a temperature Tl between Tg - 50°C ⁇ Tl ⁇ Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluoropolymer A and Tg being the glass transition temperature of acrylic polymer B, with mechanical pressure.
• thermomechanical treatment can be carried out for example by a calendering machine comprising rollers which can be heated or a plate press which can also be heated.
• the electrode is manufactured by a solvent-free spraying process, by deposition of the formulation on the metal substrate, by a pneumatic spraying process, by electrostatic spraying, by dipping in a bed of fluidized powder, by sprinkling, by electrostatic screen printing, by deposition with rotating brushes, by deposition with rotating addition rollers, by calendering.
• the consolidation of the electrode after a deposition process on the metal substrate by spraying without solvent is carried out by a calendering process.
• This process consists of applying pressure to the electrode using two rollers which may be heated.
• the electrode is manufactured by a two-step solvent-free process.
• a first step consists of the manufacture of a self-supporting film from the premixed formulation with a thermomechanical process such as extrusion, calendering or thermo-compression.
• the self-supporting film is laminated onto the metal substrate by a process combining temperature and pressure such as calendering or thermo-compression.
• the electrode is manufactured by a solvent-free process using a calendering process which makes it possible to carry out the filming step and transfer the coating to the current collector. in a single step, that is to say without going through a step of manufacturing a self-supported film.
• the calender used has several rollers (at least three).
• the powder obtained after the step mixing is introduced between the first two rollers, most often heated and having differential rotation speeds to shear the powder.
• the coating formed and stuck on the fastest roller is then laminated directly onto the current collector with a third roller.
• the electrode thus obtained can subsequently be passed through a calender to adjust its porosity or thickness if necessary.
• the mass ratio of the conductive agents relative to the active material is preferably 0 to 10%, more preferably 0 to 7%.
• the mass ratio of binder to active material is preferably 0.1 to 10%, more preferably 0.5 to 7%.
• the electrode components are all mixed at once using conventional methods, leading to an electrode formulation.
• the electrode components are sequentially mixed according to conventional methods, resulting in an electrode formulation.
• said electrode formulation is applied to a substrate by electrostatic screen printing.
• substrates are current collectors such as metal foil and metal mesh, polymer films, or a solid electrolyte layer of a solid state battery.
• the preferred thickness of an electrode is 0.1 pm to 1000 pm, preferably 0.1 pm to 300 pm.
• a Li-ion battery comprises a positive electrode, a negative electrode and a separator, at least one electrode being a dry coated electrode according to the present invention.
• the device is calibrated with buffer solutions of pH 10, 7 and 4. To calibrate, the electrode is dipped in the solution pH 10 buffers and press Cal, once the pH has stabilized repeat the operation with the pH 7 then 4 buffer. Rinse with distilled water and dry the electrode between each buffer. The electrode is prepared beforehand before measurement by soaking in a 0.1M HCl solution for one to two hours then rinsed with deionized water. To measure the pH, the electrode is dipped in the product in the state to be tested and stirred for a few seconds. The measurement is allowed to stabilize for 15 minutes and the value displayed by the pH meter is read. The measurement is made at room temperature.
• the glass transition temperatures shown here are calculated using the Fox equation.
• the Fox equation is an equation used to predict the glass transition temperature of random copolymers:
• Tg, copo is the glass transition temperature of the copolymer
• Tg,i are those of the homopolymers i corresponding to each comonomer, coi are the mass fractions of the monomers i composing this copolymer. Mass fractions are expressed without units. Glass transition temperatures are expressed in degrees Kelvin. The temperature is then converted to degrees Celsius.
• a solution was prepared consisting of 0.1g of sodium metabisulfite, 10g of deionized water.
• the reactor was heated to 76°C.
• the contents of the second container and the third container were introduced into it, then the contents of the first container were introduced still with stirring using of a peristaltic pump in the reactor in 120 minutes at 76°C.
• the dispersion was heated to 78°C for 60 min.
• a dispersion containing 28% dry matter was obtained.
• the particles have a median diameter measured by DOF of 100nm.
• the pH of the aqueous dispersion is 3.1.
• Polymer B-2 was prepared according to the process described in patent WO2011/1611511A1. It consists of 57.7% ethyl acrylate, 40.9% methacrylic acid, 0.3% diallyl phthalate and 1.1% AMPS. The dispersion obtained contained 25.8% dry matter. The particles have a median diameter measured by DDL of 187 nm. The pH of the aqueous dispersion is 3.0.
• Polymer B-3 is produced according to the process described in patent W02011/161508A1.
• the dispersion obtained contained 19.8% dry matter.
• the particles have a median diameter measured by DDL of 191 nm.
• the pH of the aqueous dispersion is 2.1.
• a solution is prepared consisting of 0.1g of sodium metabisulfite, 10g of deionized water.
• the reactor was heated to 76°C.
• the contents of the second container and the third container are introduced into it, then the contents of the first container are introduced with stirring using a peristaltic pump into the reactor over 120 minutes at 76°C.
• the pump was flushed with deionized water.
• the temperature is maintained at 78°C for 60 min.
• the polymer is then cooled.
• a dispersion containing 30% dry matter was obtained.
• the particles have a median diameter measured by DDL of 95nm.
• the pH of the aqueous dispersion is 2.8.
• PVDF is a copolymer of vinylidene fluoride and hexafluoropropylene characterized by a melting temperature of 148°C measured by DSC (differential scanning calorimetry).
• aqueous formulations are produced according to the following process:
• the polymer A is weighed into a container and, with stirring using a mechanical stirrer, the acrylic polymer B is introduced in lOmn.
• the stirring time after introduction of the acrylic polymer is lOmn.
• a stable aqueous dispersion with a pH of 2.7, a dry extract of 23% and a measured particle diameter of 270 nm is obtained.
• a stable aqueous dispersion of pH 2.5, dry extract 24% and measured particle diameter of 174 nm is obtained.
• Example 6 We weigh 195.5g of polymer A and add 60.3g of polymer B-6. An aqueous dispersion of pH 2, dry extract 26.1% and measured particle diameter of 155 nm is obtained.
• aqueous formulation containing a dry ratio of 70% by weight of PVDF and 30% of acrylic polymer is placed in a crystallizer and dried for 24 hours in an oven at 110°C.
• homogeneous powders are obtained which are ground using an electric knife grinder of the coffee grinder type firstly, then cryo-crushed using a ball mill secondly.
• the powders obtained are particularly homogeneous and can be very easily compressed in order to obtain polymeric layers on metal surfaces, using for example presses or calendering machines.
• This original process therefore makes it possible to carry out dry coating on aluminum type supports, which makes it possible to produce cathodes without the presence of toxic solvents such as NMP or even to avoid aqueous processes which require particularly expensive drying and complex formulations requiring difficult mastery of rheology.
• the same type of solvent-free process can be used for anode manufacturing.
• Graphite lithium-ion battery anodes were produced using a solvent-free process.
• the graphite used is Actilion GHDR 15-4 graphite sold by the company IMERYS.
• the anodes consist of 95% by weight of graphite and 5% by weight of polymer binder according to the invention.
• Each electrode is prepared according to the following protocol.
• the graphite and the polymer binder powder are weighed and introduced into a 250ml metal pot.
• the graphite/binder formulation is mixed for 1 minute and a half using a Minimix type vibrating mixer sold by the company MERRIS. Once mixed, the formulation in powder form is deposited by sprinkling onto a copper current collector 18 pm thick.
• the quantity deposited is between 15 and 20 mg/cm 2 on a surface of 10x5 cm 2 .
• the electrode is consolidated using a table calender (model CA3/200-SP marketed by SUMET GmbH).
• the temperature and speed of the rollers are respectively set at 110°C and 0.1 m/min. Compression force is controlled so as to apply a force per unit length of 44 N/mm.
• a sheet of temperature-resistant silicone paper is introduced between the covering and the upper roller.
• Adhesion is judged to be zero if the coating spontaneously delaminates at the end of the consolidation stage.
• Table 1 Results of the evaluation of adhesion on copper All coatings of the electrodes with a binder of the invention exhibit adhesion with a cohesive break in the coating. The level of adhesion obtained is sufficient to allow manipulation of the electrode. On the contrary, the coating with a pure PVDF binder does not show any adhesion, the coating spontaneously detaches from the copper after the calendering step.

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• 2022
  • 2022-12-16 FR FR2213518A patent/FR3143870B1/fr active Active
• 2023
  • 2023-12-15 CN CN202380085497.9A patent/CN120303785A/zh active Pending
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