WO2024078923A1 - Électrode de batterie et son procédé de fabrication - Google Patents

Électrode de batterie et son procédé de fabrication Download PDF

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Publication number
WO2024078923A1
WO2024078923A1 PCT/EP2023/077355 EP2023077355W WO2024078923A1 WO 2024078923 A1 WO2024078923 A1 WO 2024078923A1 EP 2023077355 W EP2023077355 W EP 2023077355W WO 2024078923 A1 WO2024078923 A1 WO 2024078923A1
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Prior art keywords
electrode
composition
binder
polymer
ptfe
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PCT/EP2023/077355
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English (en)
Inventor
Fulvia RONCATI
Romain DEBORTOLI
Guillaume DOLPHIJN
Stefano Mauri
Maurizio Biso
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Solvay Specialty Polymers Italy S.P.A.
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Publication of WO2024078923A1 publication Critical patent/WO2024078923A1/fr

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    • 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
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • 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
    • H01M4/043—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
    • H01M4/13—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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
    • 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 relates to electrode compositions comprising certain polytetrafluoroethylene polymers, to a method for their preparation and to their use for the manufacture of electrochemical cell components.
  • the electrodes of a lithium secondary battery are mainly manufactured by a wet process that comprises preparing a slurry in which an electrode active material, additives and a binder are dispersed in a solvent or an aqueous medium, and processing the slurry in a way that forms an electrode film.
  • Dry electrode processes have been developed to reduce the timeconsuming and costly drying procedures required by the aforementioned wet processes.
  • Typical dry processes use the fibrillation properties of certain polymers to provide a matrix for embedded conductive material.
  • Some of the polymers in the family of fluoropolymers, such as polytetrafluoroethylene (PTFE), are particularly inert and stable in the common electrolyte solvents used in secondary batteries, even those using organic solvent at high working or storage temperatures.
  • PTFE polytetrafluoroethylene
  • the stability of an electrode made using PTFE can be higher than those made with other binders.
  • dry electrode preparation processes can include combining a PTFE binder with active electrode material in powder form, and calendering to form an electrode film.
  • PTFE has good adhesiveness to the electrode active material, it has difficulty in adhesiveness to the current collector.
  • the Applicant has now found that the adhesiveness to the current collector of a dry electrode film made of PTFE is dependent on the particle size of the polymer.
  • an electrode film formed using PTFE of a certain particle size as described herein exhibits improved performance relative to one formed using typical PTFE in dry electrode film forming processes.
  • Manufacturing such films requires specific polymerization process of the PTFE to create particles of a certain size, which can undergo f ibri II ization to create a matrix suitable for providing structure to the electrode film.
  • An object of the present invention is thus to provide an electrode which can secure sufficient adhesive strength and that can be prepared by an efficient process.
  • composition (C) for use in the preparation of electrodes for electrochemical devices, characterized by comprising: a) at least one electrode active material (AM); b) a binder [binder (B)] comprising, preferably consisting of, a polytetrafluoroethylene (PTFE) in the form of powder having a particle size, measured with the method ASTM D4895-89, comprised in the range from 100 to 300 pm [polymer (A)], said polymer (A) being obtained by coagulating a PTFE latex at a temperature lower than 30°C and under a stirring speed of more than 450 rpm; and c) optionally, at least one conductive agent; said composition (C) being obtained by dry mixing with high shear forces involving at least a partial fibril lization of the particles of polymer (A) the at least one electrode active material (AM), the binder (B) as above defined, and optionally the at least one conductive agent,
  • an electrode [electrode (E)] for electrochemical cell comprising the following steps: i) providing a composition (C) as above defined; ii) feeding the composition (C) to a compactor to form a self-supporting dry film; and iii) applying the dry film obtained in step iii) to an electrically conductive substrate to form the electrode.
  • the present invention provides an electrode (E) for a secondary battery obtainable by the process as above defined.
  • the present invention relates to an electrochemical device, such as a secondary battery or a capacitor, comprising at least one electrode (E) as defined above.
  • weight percent indicates the content of a specific component in a mixture, calculated as the ratio between the weight of the component and the total weight of the mixture.
  • weight percent (wt %) indicates the ratio between the weight of the recurring units of such monomer over the total weight of the polymer/copolymer.
  • weight percent (wt %) indicates the ratio between the weight of all non-volatile ingredients in the liquid.
  • adhereres and “adhesion” indicate that two layers are permanently attached to each other via their surfaces of contact.
  • electrochemical device By the term “electrochemical device”, it is hereby intended to denote an electrochemical cell/assembly comprising a positive electrode, a negative electrode and a liquid electrolyte, wherein a monolayer or multilayer separator is in contact to at least one surface of one of the said electrodes.
  • suitable electrochemical devices include, notably, secondary batteries, especially, alkaline or an alkaline- earth secondary batteries such as lithium ion batteries, lead-acid batteries, and capacitors, especially lithium ion-based capacitors and electric double layer capacitors (supercapacitors).
  • electrochemical cells include, notably, batteries, preferably secondary batteries, and electric double layer capacitors.
  • secondary battery it is intended to denote a rechargeable battery.
  • Non-limitative examples of secondary batteries include, notably, alkaline or alkaline-earth secondary batteries.
  • PTFE indicates a polymer obtained from the polymerization of tetrafluoroethylene (TFE).
  • the PTFE polymer may also comprise minor amounts of one or more co-monomers such as, but not limited to, hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), perfluoro-(2,2- dimethyl-l,3-dioxole), and the like, provided, however that the latter do not significantly adversely affect the unique properties of the tetrafluoroethylene homopolymer, such as thermal and chemical stability.
  • co-monomers such as, but not limited to, hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), perfluoro-(2,2- dimethyl-l,3-dioxole), and the like, provided, however that the latter do not significantly adversely affect the unique properties of the tetrafluoroethylene homopolymer, such as thermal and chemical stability.
  • the amount of such co-monomer does not exceed about 3 % by moles, and more preferably less than about 1 % by moles; particularly preferred is a co-monomer content of less than 0.5 % by moles.
  • the overall co-monomer content is greater than 0.5 % by moles, it is preferred that the amount of the perfluoro(alkyl vinylether) co-monomer is less than about 0.5 % by moles.
  • Most preferred are PTFE homopolymers.
  • the PTFE suitable for use as polymer (A) of the present invention is in the form of powder, having a particle size comprised in the range from 100 to 300 pm, obtained by coagulating PTFE lattices with the addition of an electrolyte.
  • the lattices may be obtained according to, for example, US 6790932.
  • Preferred examples of electrolytes are:
  • the PTFE lattices are generally obtained by dispersion or emulsion polymerization.
  • the powder of PTFE may be obtained from PTFE lattices in the form of gels by means of coagulation with the electrolytes mentioned above.
  • the gels may be obtained according to patents US 6790932 and US 6780966.
  • the coagulation is carried out into a coagulator endowed of a stirrer, by adding the electrolyte to the PTFE latex optionally diluted to a PTFE concentration in the range from 10 to 20%, preferably from 12 to 17%.
  • the stirring speed in the coagulator to obtain the coagulation of polymer (A) is set to more than 450 revolutions per minute (rpm), preferably between 450 and 100 rpm, more preferably between 500 and 800 rpm.
  • Said stirring speed corresponds to that applied for obtaining the coagulation of polymer (A) from a PTFE latex obtained as above defined, in a coagulator of 49 L endowed of a stirrer; in particular, with the stirrer having 6 blades of 5.8 cm and the central tree of 3 cm diameter.
  • the coagulation of polymer (A) is carried out at a temperature lower than 30°C, preferably at a temperature comprised between 10 and 25°C.
  • the polymer is washed at room temperature with demineralized water. After coagulation and washing, the PTFE powder obtained therein is then dried.
  • the Applicant has found that the selection of a stirring speed of more than 450 rpm and a temperature lower than 30°C for the coagulation of the PTFE latex allows the obtainment of a polymer (A) in the form of powder having a particle size of between 100 and 300 microns, preferably from 120 to 280 microns, which is particularly suitable for use as electrode binder.
  • the particle size of PTFE in the form of powder can be suitably measured with the method of ASTM D4895-89.
  • binder (B) may further include additives such as polymers and polymer-like substances.
  • the binder (B) may further include at least one fluororesins as binder additive.
  • binder (B) may be obtained by mixing the polymer (A) both in the powder form in the latex form before coagulation, with the additional polymer in the form of latex, followed by co-coagulation and isolation.
  • the amount of binder (B) which may be used in the electrode-forming composition (C) is subject to various factors.
  • One such factor is the surface area and amount of the active material, and the surface area and amount of any electroconductivity-imparting additive which are added to the electrode-forming composition. These factors are believed to be important because the binder particles provide bridges between the conductor particles and conductive material particles, keeping them in contact.
  • Suitable amounts of binder (B) in composition (C) of the present invention range from 0.1 to 10% by weight, preferably 2 to 10% by weight, with respect to the total weight of the composition (C).
  • the electrode forming composition [composition (C)] of the present invention includes one or more electrode active material (AM).
  • AM electrode active material
  • the term “electrode active material” is intended to denote a compound that 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 cell.
  • the electrode active material is preferably able to incorporate or insert and release lithium ions.
  • the nature of the electrode active material in the electrode forming composition (C) of the invention depends on whether said composition is used in the manufacture of a negative electrode (anode) or a positive electrode (cathode).
  • the electrode active material may comprise a composite metal chalcogenide of formula LiMCte, wherein M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V and Q is a chalcogen such as 0 or S.
  • M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V
  • Q is a chalcogen such as 0 or S.
  • Preferred examples thereof may include:
  • LiNi x Mn y Co z O 2 NMC
  • LiNi x Mn y Co z O 2 NMC
  • NMC LiNio.333Mno.333Coo.3330 2
  • NMC622 LiNio.6Mno.2Coo.2O2
  • NMC811 LiNio.8Mno.1Coo.1O2
  • NCA Lithium nickel cobalt aluminum oxides
  • the electrode active material may comprise a lithiated or partially lithiated transition metal oxyanion-based electroactive material of formula MiM 2 (JO4)fEi-f, wherein Mi is lithium, which may be partially substituted by another alkali metal representing less than 20% of the Mi metals, M 2 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 M 2 metals, including 0, JO4 is any oxyanion wherein J is either P, S, V, Si, Nb, Mo or a combination thereof, E is a fluoride, hydroxide or chloride anion, f is the molar fraction of the JO4 oxyanion, generally comprised between 0.75 and 1.
  • MiM 2 (JO4)fEi-f formula MiM 2 (JO4)fEi-f
  • the MiM 2 (JO4)fEi-f electro-active material as defined above is preferably phosphate-based and may have an ordered or modified olivine structure.
  • the electrode active material in the case of forming a positive electrode has formula Li3-xM’ y M” 2 -y(JO4)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, JO4 is preferably PO4 which may be partially substituted with another oxyanion, wherein J is either S, V, Si, Nb, Mo or a combination thereof.
  • the electrode active material is a phosphate-based electro-active material of formula Li(Fe x Mm-x)PO4 wherein 0 ⁇ x ⁇ 1 , wherein x is preferably 1 (that is to say, lithium iron phosphate of formula LiFePCM).
  • the electrode active material may preferably comprise one or more carbon-based materials and/or one or more silicon-based materials.
  • the carbon-based materials may be selected from graphite, such as natural or artificial graphite, graphene, or carbon black. These materials may be used alone or as a mixture of two or more thereof.
  • 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.
  • the silicon-based compound may be silicon oxide or silicon carbide.
  • the silicon-based compounds are comprised in an amount ranging from 1 to 60 % by weight, preferably from 5 to 30 % by weight with respect to the total weight of the electro active compounds.
  • One or more optional electroconductivity-imparting additives may be added in order to improve the conductivity of a resulting electrode made from the composition of the present invention.
  • Conducting agents for batteries are known in the art.
  • Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder, carbon nanotubes, 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.
  • the amount of optional conductive agent is preferably from 0 to 30 wt. % of the total solids in the electrode forming composition.
  • the optional conductive agent is typically from 0 wt. % to 10 wt. %, more preferably from 0 wt. % to 5 wt. % of the total amount of the solids within the composition.
  • the optional conductive agent is typically from 0 wt. % to 5 wt. %, more preferably from 0 wt.
  • compositions comprising silicon based electro active compounds it has been found to be beneficial to introduce a larger amount of optional conductive agent, typically from 0.5 to 30 wt. % of the total amount of the solids within the composition.
  • the electrode-forming composition (C) may be prepared by thoroughly mixing with high shear forces the at least one electrode active material (AM), the binder (B) and optionally, the at least one conductive agent.
  • Dry mixing the at least one electrode active material (AM), the binder (B) as above defined, and optionally, the at least one conductive agent with high shear forces is performed by dry-blending these ingredients without the addition of any solvents, liquids, processing aids, or the like to the particle mixture. Dry-mixing may be carried out, for example, in a pestle with a mortar, in a mill, in a mixer or blender (such as a V-blender equipped with a high intensity mixing bar, or other alternative equipment as described further below), until a uniform dry mixture is formed.
  • blending time can vary based on batch size, materials, particle size, densities, as well as other properties, and yet remain within the scope hereof.
  • Dry mixing is conveniently carried out at a temperature of about 20°C to about 75°C.
  • Mixing with high shear forces involves at least a partial fibri II ization of the particles of polymer (A) to produce fibrils that eventually form a matrix or lattice for supporting the resulting composition of matter.
  • Composition (C) is thus suitably an at least partially fibrillized dry mixture.
  • the electrode-forming composition (C) of the invention can be used in a process for the manufacture of an electrode [electrode (E)], said process comprising: i) providing a composition (C) as above defined; ii) feeding the composition (C) to a compactor to form a self-supporting dry film; and iii) applying the dry film obtained in step iii) to an electrically conductive substrate to form the electrode.
  • step i) a composition (C) is prepared as above described.
  • step ii) of the process of the invention the at least partially fibrillized dry composition (C) is subjected to mechanical compaction step to provide a fibrillized self-supporting dry film.
  • the compacting of the at least partially fibrillized dry composition (C) can take place as a mechanical compaction, for example by means of a roller compactor or a tablet press, but it can also take place as rolling, build-up or by any other technique suitable for this purpose.
  • Step ii) may suitably be carried out in a calendar with rolls having a slight speed difference in order to cause shearing forces in the calendering gap.
  • High shear forces in step ii) can also be provided by subjecting the mixture to an extruder.
  • Step ii) may be carried out at a temperature of about 20 to about 200°C.
  • the compaction step is conveniently carried out at a temperature not exceeding 200 °C, preferably at a temperature lower than 180 °C.
  • the dry composition (C) may be subjected many times to the mechanical compaction, reducing the gap stepwise to apply progressive shearing forces onto the film. Rotational speed and gap of the rolls may be changed in the different passages through the calender, in order to produce a conductive film of desired thickness and density.
  • the mechanical compaction step may be associated to a thermal consolidation step.
  • the combination of an applied pressure and a heat treatment makes thermal consolidation possible at lower temperatures than if it were done alone.
  • the mechanical compaction step is carried out by compression, suitably by compressing the composition (C) between two metal foils.
  • the mechanical compaction step is done by application of a compression pressure between 5 and 50 MPa, and preferably between 10 and 30 MPa.
  • the fibrillized self-supporting dry film obtained at the end of step ii) is suitably a fibrillized self-supporting dry film.
  • the thickness of the self-supporting film obtained in step ii) is suitably in the range from 60 to 300 pm, preferably from 100 to 250 pm.
  • PTFE having particle size in the range from 100 to 300 pm is beneficial for the use in a dry electrode process based on polymer fibrillation properties.
  • the particles of PTFE having said size allow a uniform and homogeneous distribution of the fibrils during the dry mixing and compaction to provide a dry film.
  • the specific particle size of PTFE influences not only the homogeneity of the materials but also boost the adhesion properties of the electrode to current collector.
  • the dry film obtained in step ii) can be applied onto the electrically conductive substrate without the need for any primer or adhesive layer.
  • step iii) the dry film obtained in step ii) is applied onto an electrically conductive substrate to form the electrode.
  • the sheet of substrate material may comprise a metal foil, an aluminum or copper foil in particular.
  • the metal foil is preferably an etched metal foil, which can be obtained according to any procedure known to the skilled persons.
  • Step iii) is carried out in a pressure-controlled calender, where the self- supporting dry film obtained in step ii) is co-laminated onto a metal foil, preferably an etched metal foil.
  • the pressure applied in the calendar is suitably in the range of from 0.01 to 40 MPa.
  • Step iii) is carried out at a temperature in the range of from about 20 °C to about 300°C
  • the electrode (E) obtained according to the process of the present invention has a porosity of about 15 to 40%.
  • the present invention provides a positive electrode having an approximate porosity of 30 %, which fits with the use of current generation cathodes.
  • the electrode (E) of the invention is particularly suitable for use in electrochemical devices, in particular in secondary batteries.
  • the present invention provides an electrochemical device being a secondary battery comprising:
  • the positive electrode and the negative electrode is the electrode (E) according to the present invention.
  • the electrochemical device is a secondary battery comprising:
  • the positive electrode is the electrode (E) according to the present invention.
  • the secondary battery of the invention is preferably an alkaline or an alkaline-earth secondary battery.
  • the secondary battery of the invention is more preferably a lithium-ion secondary battery.
  • An electrochemical device according to the present invention can be prepared by standard methods known to a person skilled in the art.
  • Latex 1 Latex of Algoflon® DF 681 F with PTFE concentration of 22-35%.
  • Latex 2 Latex of Algoflon® DF 120 F with PTFE concentration of 22-35%.
  • NMC 111 available from MTI Corporation
  • Latex 1 was diluted at 14% (+/-1 %) PTFE concentration, with demineralized water.
  • the coagulation has been observed after 15-20 minutes of stirring.
  • the agitation was kept after coagulation, for 10 (+/-2) minutes still.
  • the liquid part (water and acid) was drained from the bottom part of the coagulator, then the powder was washed two times into the coagulator by adding, 28-32 liters of demineralized water for each washing, and keeping the system under agitation at 700 rpm for 15 minutes.
  • the powder was dried in a static oven at 140°C (+/- 5°C), for 32 hours. Dampness was measured after the drying and resulted ⁇ 0.1 %w. In case of higher dampness, additional 16 hours of drying would have been applied.
  • the resulting polymer (1 ) has a mean particle size of the dried powder of 225 pm, measured with the method ASTM D4895-89.
  • Latex 1 was diluted at 14% (+/-1 %) PTFE concentration, with demineralized water.
  • the coagulation has been observed after 15-20 minutes of stirring.
  • the agitation was kept after coagulation, for 10 (+/-2) minutes still.
  • the resulting polymer (2) has a mean particle size of the dried powder of 153 pm, measured with the method ASTM D4895-89.
  • Latex 2 was diluted at 14% (+/-1%) PTFE concentration, with demineralized water.
  • the coagulation has been observed after 15-20 minutes of stirring.
  • the agitation was kept after coagulation, for 10 (+/-2) minutes still.
  • the liquid part (water and acid) was drained from the bottom part of the coagulator, then the powder was washed two times into the coagulator by adding, 28-32 liters of demineralized water for each washing, and keeping the system under agitation at 700 rpm for 15 minutes.
  • the powder was dried in a static oven at 140°C (+/- 5°C), for 32 hours. Dampness was measured after the drying and resulted ⁇ 0.1 %w. In case of higher dampness, additional 16 hours of drying would have been applied.
  • the resulting polymer (3) has a mean particle size of the dried powder of 253 pm, measured with the method ASTM D4895-89.
  • Cathodes comprising polymer (1 ) to (3), Polymer (C-1 ) and polymer (C-2) were produced by a two-step process.
  • the second step was a hot-rolling step in a 2-roll calender (Collin W100 T) preheated at 90°C.
  • the calender rolls were set to have a slight speed difference in order to cause shearing forces in the calendaring gap, with a 1.2 to 1 ratio. Ratios up to 1.5:1 provide good results as well.
  • the main roll was driven at a rotational speed of 2 rpm and the second roll at a speed of 2.4 rpm.
  • the material was introduced and processed 5 times into the calender, reducing the gap stepwise from 2000 pm to 250 pm to apply progressive shearing forces onto the membrane thus avoiding excessive increment in terms of compaction forces. At each step, the gap became about 75% of the previous gap.
  • the membrane was folded in 4 and rotated 90° before being inserted and processed again into the calender according to the same methodology, now starting from 1000 pm and going down to 250 pm in around 6-7 reduction passages. As a result, a self-standing membrane of around 250 pm was obtained, which corresponds to the thinnest gap of the equipment.
  • the thickness of the cathodes produced by said process was further reduced using another calendering machine (MSK-HRP-01 ).
  • This second calendering machine having 2 rolls rotating at the same speed but allowing a gap between the rolls as low as 50 pm.
  • electrodes with the targeted thickness of 90 pm were obtained.
  • the porosity of the electrode was calculated as the complementary to unity of the ratio between the measured density and the theoretical density of the electrode, wherein:
  • the measured density is given by the mass divided by the volume of a circular portion of electrode having diameter equal to 18 mm and a measured thickness;
  • the theoretical density of the electrode is calculated as the sum of the product of the densities of the components of the electrode multiplied by their volume ratio in the electrode formulation.
  • Electrode 3a and electrode 1a were evaluated in half cell using Li as counter electrode and 1 M LiPFe in EC/DMC (1/1 vol ratio) as electrolyte.
  • the cathode presented an aerial capacity of 3.5-3.8 mAh/cm 2
  • Both cathodes showed a first columbic efficiency of 90% using a current intensity equivalent to C/20 and a potential window from 3 to 4.2V vs Li/Li+.
  • both electrodes were cycled in half cells at different current intensity (from C/20 to 1 C) between 3 and 4.2V vs Li/Li+ and showed identical performances.
  • Electrode 3a and electrode 1a were evaluated as follows: [00123] Specimen of 18 mm diameter of either electrode 3a or electrode 1a was placed on a flat glass surface and placed in a goniometer (Dataphysics TBU 90E) equipped with a 500 pl syringe filled with EC/DMC (1/1 vol.) and 0.7 mm PTFE needle (Sysmex NE43). A drop of electrolyte was deposited on each electrode at a rate of 0.5 pl/s and a temperature of 20 ⁇ 1 °C. The contact angle was measured 2 seconds after the drop gets in contact with the electrode using an Ellipse fitting model. The operation was repeated 10 times on each electrode.
  • the contact angle on the electrode 3a and electrode 1a was, respectively, 48° and 44°.
  • the wettability of the electrode increases with reducing PTFE particle size.
  • the data show that the electrode forming compositions of the present invention, comprising PTFE with particle size from 100 to 300 pm, have improved adhesion to current collectors, while at the same time they keep good ionic and electric conductivity properties and mechanical properties very similar to those of the prior art having higher PTFE particle size, so that they can be suitably used in the preparation of electrodes.
  • the data in Table 1 show that the PTFE polymers with particle size from 100 to 300 pm, obtained by coagulation at a temperature lower than 30°C and a stirring speed of at least 450 rpm, allow to obtain electrodes with greater adhesion when prepared at the same conditions of electrode thickness and pressure of co-lamination. This is evident from the comparison of electrode 1a with electrode 4a, or from the comparison of electrode 3a with electrode 5a, for example.

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Abstract

La présente invention concerne des compositions d'électrode comprenant certains polymères de polytétrafluoroéthylène, un procédé pour leur préparation et leur utilisation pour la fabrication de composants de cellules électrochimiques.
PCT/EP2023/077355 2022-10-10 2023-10-03 Électrode de batterie et son procédé de fabrication WO2024078923A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6780966B2 (en) 2001-07-26 2004-08-24 Ausimont S.P.A. Coagulation process of PTFE fine powders
US6790932B2 (en) 2001-07-26 2004-09-14 Ausimont S.P.A. Process for obtaining non thermoprocessable fine powders of homopolymer or modified PTFE
KR20190051354A (ko) * 2017-11-06 2019-05-15 주식회사 엘지화학 양극의 제조 방법
US20210249657A1 (en) * 2018-05-02 2021-08-12 Maxwell Technologies, Inc. Compositions and methods for silicon containing dry anode films

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6780966B2 (en) 2001-07-26 2004-08-24 Ausimont S.P.A. Coagulation process of PTFE fine powders
US6790932B2 (en) 2001-07-26 2004-09-14 Ausimont S.P.A. Process for obtaining non thermoprocessable fine powders of homopolymer or modified PTFE
KR20190051354A (ko) * 2017-11-06 2019-05-15 주식회사 엘지화학 양극의 제조 방법
US20210249657A1 (en) * 2018-05-02 2021-08-12 Maxwell Technologies, Inc. Compositions and methods for silicon containing dry anode films

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