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
• • 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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • 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
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0411—Methods of deposition of the material by extrusion
• • 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
  • 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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • 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
  • H01M4/625—Carbon or graphite
• • 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 generally to the field of electrical energy storage in rechargeable secondary batteries of Li-ion type. More specifically, the invention relates to an electrode formulation for a Li-ion battery. The invention also relates to a process for preparing electrodes using said formulation, by compounding / low residence time extrusion. Finally, the invention relates to an electrode obtained by this process as well as to secondary Li-ion batteries comprising at least one such electrode.
• a Li-ion battery includes at least one negative electrode or anode coupled to a copper current collector, a positive electrode or cathode coupled to an aluminum current collector, a separator, and an electrolyte.
• the electrolyte consists of a lithium salt, usually lithium hexafluorophosphate, mixed with a solvent which is a mixture of organic carbonates, chosen to optimize the transport and dissociation of ions.
• a high dielectric constant favors the dissociation of ions, and therefore, the number of ions available in a given volume, while a low viscosity favors ionic diffusion which plays an essential role, among other parameters, in the rates of charge and discharge of the electrochemical system.
• the electrodes generally comprise at least one current collector on which is deposited a composite material which consists of: a so-called active material because it has electrochemical activity with respect to lithium, a polymer which plays the role binder, plus one or more electronically conductive additives which are generally carbon black or acetylene black, and optionally a surfactant.
• lithium is inserted into the active material of the negative electrode and its concentration is kept constant in the solvent by the deintercalation of an equivalent amount of the active material from the positive electrode.
• the insertion in the negative electrode results in a reduction of lithium and it is therefore necessary to provide, via a circuit outside, the electrons to this electrode, coming from the positive electrode. At the discharge, the reverse reactions take place.
• CNTs carbon nanotubes
• document WO 2011/117530 a masterbatch in agglomerated solid form comprising from 15 to 40% by weight of CNT, at least one solvent and from 1 to 40% by weight of at least one polymeric binder.
• document EP 2 081 244 describes a liquid dispersion based on CNTs, a solvent and a binder, which is intended to be sprayed onto a layer of active electrode material.
• document US 2011/171364 describes a paste based on CNT agglomerates mixed with a dispersant such as poly (vinyl pyrrolidone) or PVP, with an aqueous or organic solvent, and optionally with a binder.
• the method of manufacturing this paste comprises a step of grinding (or sonication) of tangled clusters of CNTs, having an average diameter of about 100 mm. This step makes it possible to obtain CNT agglomerates having a size less than 10 mm in at least one dimension, that is to say a degree of dispersion, on the Hegman scale, greater than 7. Grinding can be carried out before or after mixing the CNTs with the dispersant, the solvent, and the optional binder.
• the solution proposed in this document has the drawback of using a manufacturing process comprising a grinding step, preferably by spraying, which is liable to present risks of environmental pollution, or even health risks.
• the paste obtained has a viscosity of at least 5,000 cPs, which can cause dispersion difficulties in some cases.
• Document US 2011/0171371 describes the preparation of a Li-ion battery electrode, comprising a composition based on carbon nanotubes.
• a Li-ion battery electrode comprising a composition based on carbon nanotubes.
• the size of the CNT agglomerates is reduced, in particular using a jet mill.
• the aim of the invention is therefore to remedy at least one of the drawbacks of the prior art, namely to provide a complete electrode formulation which is introduced directly into the metering units of an extruder.
• the invention also aims to provide a method for manufacturing a Li-ion battery electrode which comprises a single step of extrusion from a complete formulation of the electrode, with a very low residence time.
• the invention also relates to electrodes prepared by means of this process. Finally, the invention aims to provide rechargeable Li-ion secondary batteries comprising at least one such electrode.
• the invention relates firstly to a method for continuously manufacturing a Li-ion battery electrode, said method comprising the following steps:
• said electrode formulation comprises 65 to 95% of solid mixture and 5 to 35% of solvent, and preferably from 70 to 90% of solid mixture for 10 to 30% of solvent.
• said solid mixture comprises:
• the solvent is water.
• said solvent is an organic solvent chosen from: N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), ketones, acetates, furans, alkylcarbonates, alcohols and their mixtures.
• NMP N-methyl pyrrolidone
• DMSO dimethyl sulfoxide
• DMF dimethylformamide
• ketones ketones
• acetates furans
• alkylcarbonates alcohols and their mixtures.
• said active electrode material is in particular a metal oxide containing lithium.
• said fluoropolymer binder is in particular chosen from homopolymers of polyvinylidene fluoride (PVDF) and copolymers or terpolymers based on vinylidene fluoride, polytetrafluoroethylene (PTFE), and mixtures thereof.
• PVDF polyvinylidene fluoride
• PTFE polytetrafluoroethylene
• the carbon nanotubes can be of the single-walled, double-walled or multi-walled type, and are preferably multi-walled carbon nanotubes obtained by a chemical vapor deposition process.
• said carbonaceous conductive filler distinct from the carbon nanotubes is chosen from carbon nanofibers, carbon black and graphene.
• the polymeric dispersant which is distinct from said binder, is chosen from poly (vinyl pyrrolidone), poly (phenyl acetylene), pommelaphenylene vinylidene), polypyrrole, poly (para-phenylene benzobisoxazole, poly (vinyl alcohol), and mixtures thereof.
• said metal support for the electrodes is generally made of aluminum for the cathode and of copper for the anode.
• the method according to the invention makes it possible to obtain an electrode from a paste applied to said metal support.
• the invention also relates to a Li-ion battery electrode obtained by the method described above.
• said electrode is a cathode.
• said electrode is an anode.
• Another object of the invention is a Li-ion secondary battery comprising a negative electrode, a positive electrode and an electrolyte, in which at least one of the electrodes is obtained by the method described above.
• Another object of the invention is a complete electrode formulation comprising from 65 to 95% of solid mixture and from 5 to 35% of solvent, and preferably from 70 to 90% of solid mixture for 10 to 30% of solvent. .
• said solid mixture comprises:
• the present invention overcomes the drawbacks of the prior art. More particularly, it provides a complete electrode formulation intended to be introduced directly into the dosers of an extruder. The invention also provides a simplified Li-ion battery electrode manufacturing process;
• the process comprises a single extrusion step from said complete electrode formulation, with a very low residence time, less than 5 minutes. This has a major impact on the quality of the formulation and on the performance of the electrode, as well as on the production cost which decreases significantly. Indeed, an extrusion unit implementing the method according to the invention can replace up to 8 mixing units intended to supply 8 extrusion lines in current electrode manufacturing processes.
• FIG. 1 is a graph illustrating a Ragone diagram showing the variation in the discharge capacity of an electrode formulation, measured in mAh / g, as a function of the discharge rate (C-rate).
• the invention relates to a method for continuously manufacturing a Li-ion battery electrode, said method comprising the following steps:
• this process uses a complete electrode formulation obtained by compounding a solid mixture comprising all the ingredients of the electrode, and a solvent.
• said method comprises the following characters, if necessary combined.
• the contents indicated are expressed by weight, unless indicated otherwise.
• said electrode formulation of 70 to 90% solid mixture for 10 to 30% solvent.
• said solid mixture comprises:
• the solvent used in the electrode formulation is water or an organic solvent. According to one embodiment, the solvent is water.
• said solvent is an organic solvent chosen from: N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), ketones, acetates, furans, alkylcarbonates, alcohols and their mixtures.
• NMP N-methyl pyrrolidone
• DMSO dimethyl sulfoxide
• DMF dimethylformamide
• ketones acetates, furans, alkylcarbonates, alcohols and their mixtures.
• the active electrode material is chosen from the group consisting of:
• transition metal oxides with a spinel structure of LiM2O4 type where M represents a metal atom containing at least one of the metal atoms selected from the group formed by Mn, Fe, Co and Ni, said oxides preferably containing at least one Mn and / or Ni atom;
• - M represents a metal atom containing at least one of the metal atoms selected from the group formed by Mn, Fe and Co, and
• - X represents one of the atoms selected from the group formed by P, Si, Ge, S and As.
• the active electrode materials i) to iii) are more suitable for the preparation of cathodes, while the active materials of the electrodes iv) and ix) are more suitable for the preparation of anodes.
• the polymeric binder is chosen from the group consisting of fluoropolymers defined in particular as follows:
• CFX 1 CX 2 X 3 (I) where Xi, X2 and X3 independently denote a hydrogen or halogen atom (in particular fluorine or chlorine), such as poly (vinylidene fluoride) (PVDF), preferably in a form, poly (trifluoroethylene) (PVF3), polytetrafluoroethylene (PTFE), copolymers of vinylidene fluoride with either hexafluoropropylene (HFP), or trifluoroethylene (VF3), or tetrafluoroethylene (TFE), either chlorotrifluoroethylene (CTFE), fluoroethylene / propylene (FEP) copolymers, ethylene copolymers with either fluoroethylene / propylene (FEP), or tetrafluoroethylene (TFE), or chlorotrifluoroethylene (CTFE);
• PVDF poly (vinylidene fluoride)
• PVDF poly (trifluoroethylene)
• PPVE perfluoropropyl vinyl ether
• PEVE perfluoroethyl vinyl ether
• PMVE perfluoromethyl vinyl ether
• PVDF includes homopolymers of vinylidene fluoride (VDF) or copolymers of VDF and at least one other comonomer in which the VDF is at least 50 mol%.
• the copolymer is a terpolymer.
• said binder is a fluoropolymer carrying function (s) capable of developing adhesion to a metal substrate and good cohesion of the material making up the electrode.
• It may be a VDF-based polymer (containing at least 50 mol% of VDF) further comprising units bearing at least one of the following functions: carboxylic acid, carboxylic acid anhydride, esters of carboxylic acid, epoxy groups (such as glycidyl), amide groups, alcohol groups, carbonyl groups, mercapto groups, sulfide, oxazoline groups and phenolic groups.
• the function is introduced into the fluoropolymer by a chemical reaction which can be grafting or a copolymerization of the fluoropolymer with a compound bearing at least one of said functional groups, according to techniques well known to those skilled in the art.
• the carboxylic acid function is a hydrophilic group of (meth) acrylic acid type chosen from acrylic acid, methacrylic acid, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxyethylhexyl (meth) acrylate .
• the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus.
• the content of functional groups ensuring the adhesion of the binder to a metal is at least 0.05 mol%, preferably at least 0.15 mol%.
• the carbon nanotubes used in the formulation according to the invention can be of the single-wall, double-wall or multiple-wall type.
• Double-walled nanotubes can in particular be prepared as described by FLAHAUT et al. in Chem. Corn. (2003), 1442.
• Nanotubes with multiple walls can for their part be prepared as described in document WO 03/02456.
• the nanotubes usually have an average diameter ranging from 0.1 to 100 nm, preferably from 0.4 to 50 nm and, better, from 1 to 30 nm, or even from 10 to 15 nm, and advantageously a length of 0.1 to 10 mm.
• Their length / diameter ratio is preferably greater than 10 and most often greater than 100.
• Their specific surface area is for example between 100 and 300 m 2 / g, advantageously between 200 and 300 m 2 / g, and their apparent density can in particular be between 0.05 and 0.5 g / cm3 and more preferably between 0.1 and 0.2 g / cm3.
• the multi-walled nanotubes can for example comprise from 5 to 15 sheets (or walls) and more preferably from 7 to 10 sheets. These nanotubes may or may not be treated.
• crude carbon nanotubes is in particular commercially available from the company ARKEMA under the trade name Graphistrength® C100.
• nanotubes can be purified and / or treated (for example oxidized) and / or functionalized, before their use in the process according to the invention.
• the purification of the nanotubes can be carried out by washing with a solution of sulfuric acid, so as to rid them of any residual mineral and metallic impurities, such as iron, from their preparation process.
• the weight ratio of nanotubes to sulfuric acid can in particular be between 1: 2 and 1: 3.
• the purification operation can also be carried out at a temperature ranging from 90 to 120 ° C, for example for a period of 5 to 10 hours. This operation can advantageously be followed by steps of rinsing with water and drying the purified nanotubes.
• the nanotubes can alternatively be purified by heat treatment at high temperature, typically greater than 1000 ° C.
• the oxidation of the nanotubes is advantageously carried out by bringing them into contact with a sodium hypochlorite solution containing from 0.5 to 15% by weight of NaOCI and preferably from 1 to 10% by weight of NaOCI, for example in a weight ratio of nanotubes to sodium hypochlorite ranging from 1: 0.1 to 1: 1.
• the oxidation is advantageously carried out at a temperature below 60 ° C. and preferably at room temperature, for a period ranging from a few minutes to 24 hours. This oxidation operation can advantageously be followed by stages of filtration and / or centrifugation, washing and drying of the oxidized nanotubes.
• the functionalization of the nanotubes can be carried out by grafting reactive units such as vinyl monomers on the surface of the nanotubes.
• the material constituting the nanotubes is used as a radical polymerization initiator after having been subjected to a heat treatment at more than 900 ° C, in an anhydrous and oxygen-free medium, which is intended to remove oxygen groups from its surface. It is thus possible to polymerize methyl methacrylate or hydroxyethyl methacrylate on the surface of carbon nanotubes with a view to facilitating in particular their dispersion in the fluorinated binder.
• Crude nanotubes can be used in the present invention, that is to say nanotubes which are not oxidized, purified or functionalized and have not undergone any other chemical and / or thermal treatment.
• purified nanotubes in particular by heat treatment at high temperature.
• carbon nanotubes are used in the present invention in the form of solid aggregates of size between 1 mm to 5 mm, preferably between 200 mm and 3 mm.
• These fillers comprise at least one filler chosen from carbon nanofibers, graphenes and carbon black.
• Carbon black is used in powder form or in compacted form.
• Carbon nanofibers are, like carbon nanotubes, nanofilaments produced by chemical vapor deposition (or CVD) from a carbon source which is decomposed on a catalyst comprising a transition metal (Fe, Ni, Co, Cu), in the presence of hydrogen, at temperatures of 500 to 1200 ° C.
• a catalyst comprising a transition metal (Fe, Ni, Co, Cu)
• these two carbonaceous charges are differentiated by their structure (I. MARTI N-GULLON et al. Carbon 44 (2006) 1572-1580).
• carbon nanotubes consist of one or more graphene sheets wound concentrically around the axis of the fiber to form a cylinder having a diameter of 10 to 100 nm.
• carbon nanofibers are composed of more or less organized graphitic zones (or turbostratic stacks) whose planes are inclined at variable angles with respect to the axis of the fiber.
• These stacks can take the form of platelets, fishbones or cups stacked to form structures having a diameter generally ranging from 100 nm to 500 nm or even more.
• carbon black is a colloidal carbonaceous material manufactured industrially by incomplete combustion of heavy petroleum products, which is in the form of carbon spheres and aggregates of these spheres and whose dimensions are generally between 10 and 1000 nm. .
• carbon nanofibers having a diameter of 100 to 200 nm for example of about 150 nm (such as those sold under the reference VGCF ® from SHOWA DENKO), and advantageously a length of 100 to 200 mm.
• graphene denotes a flat, isolated and individualized sheet of graphite, but also, by extension, an assembly comprising between one and a few tens of sheets and having a planar or more or less corrugated structure.
• This definition therefore encompasses FLGs (Few Layer Graphene or weakly stacked graphene), NGP (Nanosized Graphene Plates or graphene plates of nanometric dimension), CNS (Carbon NanoSheets or graphene nano-sheets), GNR (Graphene NanoRibbons or nano-ribbons of graphene).
• FLGs Few Layer Graphene or weakly stacked graphene
• NGP Nanosized Graphene Plates or graphene plates of nanometric dimension
• CNS Carbon NanoSheets or graphene nano-sheets
• GNR Graphene NanoRibbons or nano-ribbons of graphene.
• carbon nanotubes and nanofibers which consist respectively of the winding of one or
• the graphene used according to the invention is not subjected to an additional stage of chemical oxidation or functionalization.
• the graphene used according to the invention is advantageously obtained by chemical vapor deposition or CVD, preferably according to a process using a pulverulent catalyst based on a mixed oxide. It is typically in the form of particles with a thickness of less than 50 nm, preferably less than 15 nm, more preferably less than 5 nm and lateral dimensions less than one micron, preferably 10 nm. at less than 1000 nm, more preferably from 50 to 600 nm, or even from 100 to 400 nm. Each of these particles generally contains from 1 to 50 sheets, preferably from 1 to 20 sheets and more preferably from 1 to 10 sheets, or even from 1 to 5 sheets which are capable of being separated from each other in the form of independent sheets, for example during ultrasonic treatment. Dispersing
• the polymeric dispersant is distinct from said fluorinated binder. It is advantageously chosen from poly (vinyl pyrrolidone), poly (phenyl acetylene), poly (meta-phenylene vinylidene), polypyrrole, poly (para-phenylene benzobisoxazole, poly (vinyl alcohol), and mixtures thereof. .
• the electrode manufacturing process according to the invention uses as a compounding device a micro-extruder marketed by the company DSM at the laboratory level.
• BUSS co-mixers or twin-screw extruders are used.
• the micro-extruder comprises: feed means, in particular at least one hopper for powdery materials and / or at least one injection pump for liquid materials; high shear mixing means, for example a co-rotating or counter-rotating twin-screw extruder; an exit head which shapes the exiting material; and means of cooling, in air or using a water circuit, the material.
• the solvent and the components of the solid mixture are introduced into the extruder, namely: the active electrode material, the fluorinated polymeric binder, the carbon nanotubes, the other carbon-based conductive fillers. , and the polymeric dispersant, which have been premixed beforehand.
• the solid mixture is introduced gradually, monitoring the rise in torque.
• the temperature in the extruder is maintained between 50 and 200 ° C, depending on the configuration of the extruder
• the CNTs and / or the carbon-based conductive filler distinct from the carbon nanotubes are mixed with solvent, in the pre-metering unit of the extrusion line.
• CNTs have the capacity to adsorb liquids without losing the solid form.
• 100 g of CNTs Graphistrength ® C100 can absorb 800 g of NMP solvent without losing the fluidity of the powder.
• carbon black has a high solvent adsorption capacity.
• the mixtures of CNTs and / or other conductive fillers with the solvent, carried out in the pre-doser of the extrusion line can be made with the gravimetric doser directly in the main hopper of the extruder at the same time as the other constituents of solid mixture. This avoids the injection of liquid into the compounding zone and considerably improves the mixing quality.
• This pre-dispersion step is particularly suitable for high grammages of electrodes (greater than or equal to 25 mg / cm 2 ).
• all or part of the solvent present in the electrode formulation comes from a latex comprising the particles of fluoropolymer binder and said solvent.
• the extrusion of said formulation is carried out in a single step the duration of which is less than 5 minutes, preferably between 30 seconds and 3 minutes, to obtain an electrode material in the form of a paste with a Brookfield viscosity between 1500 and 20,000 cP .
• the extrusion line can be equipped with a vacuum pump after the compounding zone to remove some of the solvent.
• the purpose of this is to recover the electrode material in the form of powder which can be used for the deposition of the coating by the dry process ("dry process”) or by the powder route, followed by calendering.
• Said material suitable for the dry process "dry process” may contain small amounts of organic solvent or water, because this does not change the physical state of the formulation, the material remains handleable in the solid state.
• the electrode material obtained after extrusion can be stored and conditioned for up to 7 days with stirring in liquid state, or up to 6 months in solid state, before being used in the manufacture. of the electrode.
• the electrode material thus obtained is applied to a metal collector to obtain a Li-ion battery electrode, for example by means of a scraper blade device for coating.
• Metal electrode supports are usually aluminum for the cathode and copper for the anode.
• the electrode material is then dried, and is then subjected to calendering.
• the calendering is carried out in several stages, of which at least one stage is carried out hot (between 70 and 160 ° C depending on the amount of solvent residual), during which the powder is transformed into a film having a thickness of 50 to 150 mm and a porosity of 10 to 40 mg / cm 2 .
• Another object of the invention is the electrode obtained by the method described above.
• said electrode is a cathode.
• said electrode is an anode.
• Another object of the invention is a Li-ion secondary battery comprising a negative electrode, a positive electrode and an electrolyte, in which at least one of the electrodes is obtained by the method described above.
• the quality of the complete electrode formulation and its rapid transformation by the process according to the invention have a beneficial impact on the performance of the electrode.
• Another object of the invention is the complete electrode formulation described above, comprising from 65 to 95% of solid mixture and from 5 to 35% of solvent, and preferably from 70 to 90% of solid mixture per 10 at 30% solvent.
• This formulation is particularly suitable for use in the dry process according to the invention.
• Example 1 according to the invention
• a complete cathode formulation is prepared in which the solid mixture having the following mass composition is prepared by dry premixing beforehand:
• a micro-extruder marketed by the company DSM is used. NMP is introduced and then said solid mixture. The amount of NMP added to said solid mixture is adjusted so as to obtain viscosities of between 6000 and 8000 cP.
• the product (cathode material) is recovered in the form of a paste, the NMP content of which and the North Gauge fineness of 0 to 100 miti) are tested; the dry mass is 78%;
• the paste thus obtained is used to coat an aluminum foil by means of a device with a scraper blade for coating; the electrode is then dried in a ventilated oven at 130 ° C for 30 minutes;
• the thickness of the coating is adjusted as a function of the desired surface load, at 18 mg / cm 2 ;
• the cathodes thus prepared are used to prepare a button cell with a Li anode, a Celgard PP2500 separator and an electrolyte formulation (1
• Example 2 The same electrode formulation as in Example 1 was prepared using a conventional mixer.
• the temperature setpoints and the flow rate within the co-mixer were as follows: Zone 1: 80 ° C, Zone 2: 80 ° C, Screw: 60 ° C, flow rate: 15 kg / h.
• the granules of the masterbatch were cut dry.
• the granules were packaged in an airtight container to prevent loss of NMP during storage.
• the composition of the final masterbatch was as follows: 30% by weight of carbon nanotubes, 3.5% by weight of PVDF resin and 66.5% by weight of NMP.
• Step a 20 g of masterbatch granules were wetted with 160 g of NMP solvent. After 2 h of static impregnation at room temperature, the pellets of the masterbatch were dispersed in the solvent using a Silverson L4RT ® type mixer at 6,000 rev / min for 15 minutes. Significant heating during the dispersion operation was observed: the mixture containing the CNTs reached a temperature of 67 ° C. The solution obtained was referred to as “Premix NTC”.
• Step b) 14.3 g of Kynar ® HSV 900 and 5.72 g of PVP was dissolved in 276g of NMP solvent using a mixer type agitator disc for 4 hours.
• Step c) 279 g of powder of NMC 622 (LiNi 0.6 Mn 0.2 Co 0.2 O 2 ) sold by the company UMICORE were dispersed in Kynar's solution; during this step, the powder was added gradually with stirring (600 rpm). The suspension obtained was referred to as "Premix NMC".
• Step d) In order to obtain a good dispersion of the CNTs around the active material NMC, the 2 Premix CNTs and NMC obtained respectively during steps a) and c) were mixed for 10 minutes using a flocculator stirrer at 600rpm and then using a Silverson ® L4RT mixer for 15 minutes at 3000rpm.
• the composition of the ink in dry matter was as follows: 2% CNT; 5% of Kynar ® HSV 900 and 93% of NMC 622 with a dry matter content of 40% in the solvent NMP.
• Step e) The pasty formulation thus obtained is used to coat an aluminum foil by means of a device with a scraper blade for coating; the electrode is then dried in a ventilated oven at 130 ° C for 30 minutes.
• Step f) The calendering process is then carried out at 70 ° C and the density of the electrode is checked so as to obtain a porosity of 40%.
• the cathode formulation contains:
• NMC 622 LiNio, 6Mno, 2Coo, 202
• Step b) The mixture from step a) was introduced into a 10 liter drum containing 9390 g of NMC622, 150 g of PVDF and 60 g of PVP. The keg was placed on the rotating rollers for 15 min.
• the mixture from step b) was introduced into the gravimetric feeder, including the main feeder of Clextral's BC21 extruder.
• the extruder is equipped with a feed hopper.
• the screw profile has two mixing zones and one then atmospheric degassing upstream of the 2nd mixing zone.
• the mixture was fed at the rate of 10 kg / hr into the feed hopper.
• the screw speed is 300 rpm.
• the material was recovered directly from the screws (without die) as a homogeneous powder with the "wet" appearance in a drum.
• the set temperature of all zones of the extruder is 60 ° C.
• the mass% of NMP in the extruded formulation is 8.5%.
• Step d) The extruded formulation was applied to a 25mm aluminum (Al) sheet, by means of a scraper blade device for coating, the support-scraper space being 400 mm. Then, the Al support with the powder coating was placed in a fan oven at 160 ° C for 3 min to consolidate the particles before calendering.
• the Al-supported coating is then calendered at 160 ° C in 3 steps, reducing the gap between the calender rolls: 1st pass at 300mm, 2nd at 250mm and 3rd at 150mm. Then, the coating was dried at 130 ° C for 30 min to remove residual NMP. The gap for the final calendering was adjusted to respect the final porosity of 40% as in Examples 1 and 2.

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• 2019
  • 2019-03-29 FR FR1903315A patent/FR3094371B1/fr active Active
• 2020
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