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
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  • 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
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  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
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  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
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  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
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  • 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
  • H01M10/058—Construction or 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
  • H01M4/04—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
  • H01M4/0409—Methods of deposition of the material by a doctor blade method, slip-casting or roller coating
• • 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
  • H01M4/0414—Methods of deposition of the material by screen printing
• • 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
  • H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
• • 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
  • H01M4/0421—Methods of deposition of the material involving vapour deposition
• • 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
  • H01M4/0438—Processes of manufacture in general by electrochemical processing
  • H01M4/045—Electrochemical coating; Electrochemical impregnation
  • H01M4/0457—Electrochemical coating; Electrochemical impregnation from dispersions or suspensions; Electrophoresis
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, 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
  • 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
• • 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
• • 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
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the invention relates to the field of electrochemistry, and more particularly to electrochemical systems. It relates more precisely to the porous electrode / separator assemblies which can be used in lithium ion microbatteries.
• the invention applies to negative electrodes and positive electrodes. These porous electrode / separator assemblies can be impregnated with a solid electrolyte without a liquid phase or a liquid electrolyte.
• the invention also relates to a method for preparing such a porous electrode / separator assembly which uses nanoparticles of an electrode material and nanoparticles of an inorganic material which will constitute the separator, and the porous electrode / sets. separator thus obtained.
• the invention also relates to a method of manufacturing a lithium ion microbattery comprising at least one of these assemblies, and the devices thus obtained.
• Lithium ion batteries have the best energy density among the various storage technologies available. There are different architectures and chemical compositions of electrodes and separators to make these batteries. The manufacturing processes for lithium ion batteries are presented in numerous articles and patents; an inventory is given in the book “Advances in Lithium-Ion Batteries” (ed. W. van Schalkwijk and B. Scrosati), published in 2002 (Kluever internationale / Plénum Publishers).
• microbatteries ie rechargeable batteries of very small size, capable of being integrated on electronic cards; these electronic circuits can be used in many fields, for example in cards to secure transactions, in electronic labels, in implantable medical devices, in various micromechanical systems.
• the electrodes of lithium ion batteries can be manufactured using coating techniques, in particular by roller coating (in English "roll coating”), doctor blade coating (in English “doctor blade ”), tape casting, coating through a slot-shaped die. With these methods, an ink consisting of particles of active materials in the form of powder is deposited on the surface of a substrate; the particles constituting this powder have an average particle size which is typically between 5 ⁇ m and 15 ⁇ m in diameter.
• the power and energy of the battery can be modulated by adapting the thickness and porosity of the layers, and the size of the active particles that constitute them.
• the inks (or pastes) deposited to form the electrodes contain particles of active materials, but also (organic) binders, carbon powder to ensure electrical contact between the particles, and solvents which are evaporated during the step of drying the electrodes.
• a calendering step is carried out on the electrodes. After this compression step, the active particles of the electrodes occupy about 50% to 70% of the volume of the deposit, which means that there is generally 30% to 50% of porosity between the particles.
• dense layers devoid of porosity; thus the volume energy density of the electrode is maximum.
• dense layers can be produced using vacuum deposition techniques, for example by physical vapor deposition (abbreviated PVD, “Physical Vapor Deposition”).
• PVD physical vapor deposition
• conductive filler electronic conductive charges
• the thickness of these electrodes can be greatly increased compared to what is possible with the techniques of vacuum deposition, which lead to compact but more resistive layers. This increase in the thickness of the electrodes increases the energy density of the battery cells thus obtained.
• Fully ceramic mesoporous electrode layers for lithium ion batteries can be deposited by electrophoresis; this is known from WO 2019/215407 (1-TEN). They can be impregnated with a liquid electrolyte, but their electrical resistivity remains quite high.
• Liquid electrolytes used to impregnate porous electrodes consist of aprotic solvents in which lithium salts have been dissolved. They are very flammable and can give rise to violent combustions of the battery cells, especially when the active cathode materials are stressed in voltage ranges outside their stability voltage range, or when hot spots appear locally in the battery. cell.
• ionic liquids which are extremely stable in temperature.
• ionic liquids do not wet the surfaces of organic materials, and the presence of PVDF and other organic binders in the electrodes of conventional lithium ion batteries prevents wetting of the electrodes by this type of electrolyte; the performance of the electrodes is affected. Ceramic separators have been developed to solve this problem at the level of the electrolytic junction between electrodes, but the fact remains that the presence of organic binders in the electrodes continues to pose problems for the use of electrolytes based. ionic liquids.
• a second axis one can seek to homogenize the sizes of particles, in order to avoid local imbalances of states of charge which can lead during intensive discharges to locally stress active materials outside their range. conventional operating voltage ranges. This optimization would then be done to the detriment of the energy density of the cell.
• conductive charges usually carbon black
• NMP N-methyl-2-pyrrolidone
• the drying of the NMP contained in the electrodes is of real economic importance.
• the high boiling point of NMP coupled with its very low vapor pressure makes it difficult to dry in an industrial environment. Solvent vapors must be collected and reprocessed.
• the drying temperature of the NMP must not be too high, which tends to increase the drying time and its cost once again; this is described in the publication “Technical and economy analysis of solvent-based lithium-ion electrode drying with water and NMP” by D.L. Wood & al., published in the journal Drying Technology, vol. 36, n ° 2 (2018).
• inks in particular water and ethanol.
• their surface tension is greater than that of NMP, and they therefore wet the surface of metallic current collectors less well.
• particles tend to agglomerate in water, especially carbon black nanoparticles. These agglomerations lead to a heterogeneous distribution of the components entering into the composition of the electrode (binders, carbon black, etc.).
• traces of water can remain adsorbed on the surface of the particles of active materials, even after drying.
• separator when it is desired to manufacture a battery cell, it is known to position a separator between the electrodes.
• the electrodes and the separator of each elementary cell are typically impregnated with a liquid electrolyte.
• the separators used in lithium ion batteries are most often polymeric membranes whose pores are impregnated with a liquid electrolyte containing lithium salts such as LiPF 6 .
• LiPF 6 lithium salts
• the fact that these separators are in polymeric form poses problems of wettability of ionic liquids. Surface treatments can be carried out on these separators, or mineral fillers can be integrated within these separators in order to increase their mechanical strength and their wetting property with respect to ionic liquids.
• these separators typically have thicknesses of the order of 25 micrometers. They must withstand energization during the manufacturing stages of the battery cells. For this, they generally consist of several layers of polymers. These are essentially layers of polyethylene (PE) and polypropylene (PP) which respectively provide safety functions, in particular closing the porosity in the event of local overheating, and mechanical.
• PE polyethylene
• PP polypropylene
• separators have a microporosity which can be impregnated with an electrolyte and thus ensure the migration of ions.
• lithium dendrites are liable to form in the thickness of the separator, which creates the risk of thermal runaway.
• Conductive carbon black nanoparticles can also detach from the electrodes, enter the separator and thus create a risk of an internal short circuit. These risks can be exacerbated by the presence of faults in the separator.
• the great thickness of the separators reduces the energy and power density of the battery containing them. The thicker the separator, the greater the ionic resistance between the negative electrode and the positive electrode.
• the volume occupied by the separator does not store energy; the smaller the thickness of the separator, the better the specific energy density of the elementary cell of the battery.
• the solid electrolyte is in the form of a polymer
• the absence of liquid electrolytes dissolved in the polymer (solvated or in the form of an ionic liquid at room temperature) makes it possible to limit or even prevent the appearance of dendrites.
• the risk of developing lithium dendrites is primarily present when the operating potential of the negative electrode is low.
• the negative electrodes based on titanates, operating at potentials of the order of 1.5 V do not present a risk of lithium dendrites forming during the recharging of the battery. These negative electrodes are also particularly well suited for applications requiring rapid recharging.
• these solid, ceramic, mesoporous electrolyte layers are sintered in the presence of air.
• the heat treatment used makes it possible to calcine the organic residues (solvents and / or stabilizers and / or binders used in the suspensions of nanoparticles) that they contain while preventing these organic residues from turning into a thin layer of carbon which would harm the water. electrical insulation, in particular by short-circuiting the electrodes of opposite polarities.
• the inorganic separator obtained can easily be impregnated with a liquid electrolyte (solvated and / or an ionic liquid at room temperature). It is particularly well suited to ceramic electrodes which can withstand heat treatments.
• the problem that the present invention seeks to solve is to provide a porous electrode / separator assembly for a lithium ion battery provided with an electrode having a very high energy density coupled with a very high power density and a separator. having a stable mechanical structure as well as good thermal stability, which is able to operate reliably and which exhibits excellent cycling life as well as increased safety.
• Another problem that the present invention seeks to solve is to provide a method of manufacturing such a porous electrode / separator assembly which is simple, safe, rapid, easy to implement, easy to industrialize and inexpensive.
• Another aim of the invention is to provide a method of manufacturing a battery comprising a porous electrode / separator assembly according to the invention.
• Another object of the invention is to provide a rigid structure battery having a long life, having a high power density, having increased reliability and capable of mechanically withstanding shocks and vibrations.
• the present invention applies to assemblies consisting of a porous electrode and a porous separator.
• Said separator can serve as a host structure to accommodate an ion-conducting electrolyte; said ion-conducting electrolyte can also invade said porous electrode.
• electrolytes based on organic solvents are replaced by mixtures of organic solvents and ionic liquids or by ionic liquids, which are extremely stable in temperature.
• ionic liquids do not wet on the surfaces of organic materials and the presence of PVDF and other organic binders in the electrodes of conventional batteries prevents wetting of the electrodes by this type of electrolyte, and the performance of the electrodes is affected. affected. Ceramic separators have been developed to solve this problem at the level of the electrolytic junction between electrodes, but the fact remains that the presence of organic binders in the electrodes continues to pose problems for the use of electrolytes based. ionic liquids.
• conductive additives in English "conductive fillers”; only carbon black is used in practice
• the problem is solved by an assembly consisting of a porous electrode and a separator for a lithium ion microbattery which is totally porous, preferably mesoporous, devoid of organic binders, and the porosity of which is between 25 and 50%, and the size of the channels and pores is homogeneous, within the whole, in order to ensure perfect dynamic balancing of the cell.
• the porosities, expressed in relative pore volume, of the electrodes and of the separator may be the same or may be different; we prefer them to be different. This can be achieved by thermal consolidation in two stages, one for the electrode, which is deposited before the separator, the other for the electrode-separator assembly.
• the porosity of the electrode is advantageously between 25% and 35% to optimize the energy density, that of the separator between 40% and 60% (and preferably between 45% and 55%) to optimize ionic conduction.
• the porosity of the electrode is about 30% and that of the separator is about 50%. Below a value of 25%, impregnation becomes difficult and remains incomplete because the porosities can be at least partially closed.
• the porous structure preferably mesoporous, entirely solid, without organic components, of the porous electrode, respectively of the separator, is obtained by the deposition, on a substrate, of agglomerates and / or aggregates of nanoparticles of active electrode materials. P, respectively of inorganic material E to form the separator.
• the sizes of the primary particles constituting these agglomerates and / or aggregates are of the order of one nanometer or ten nanometers, and said agglomerates and / or aggregates contain at least four primary particles.
• Said substrate may be, in a first embodiment, a substrate capable of acting as an electric current collector, or be, in a second embodiment, an intermediate, temporary substrate which will be explained in more detail below.
• agglomerates of a few tens or even hundreds of nanometers in diameter rather than primary, non-agglomerated particles each with a size of the order of one nanometer or ten nanometers makes it possible to increase the deposit thicknesses.
• the agglomerates should be less than 300 nm in size.
• the sintering of Agglomerates larger than 500 nm would not make it possible to obtain a continuous mesoporous film.
• two different porosity sizes are observed in the deposit, namely a porosity between agglomerates and a porosity inside the agglomerates.
• h max 0.41 [(GM0 rcp R 3 ) / 2 Y ] where h max denotes the critical thickness, G the shear modulus of the nanoparticles, M the number of coordination, 0 rc the volume fraction of nanoparticles, R the radius of the particles and g the interfacial tension between the solvent and the air.
• agglomerates mesoporous, made up of primary nanoparticles at least ten times smaller than the size of the agglomerate, considerably increases the cracking limit thickness of the layers.
• a lower surface tension solvent such as isopropyl alcohol (abbreviated IPA)
• IPA isopropyl alcohol
• binders and dispersants can be removed by heat treatment in air, such as by debinding, during a sintering treatment or during a heat treatment carried out prior to the sintering treatment.
• a porous layer preferably mesoporous, or a plate, without carbon black or organic compounds, is obtained, in which all the nanoparticles are welded together (by the necking phenomenon, known elsewhere).
• the method of manufacturing a mesoporous deposit, as described above, was used to make the porous electrode as well as the separator of the assembly consisting of a porous electrode and a separator according to the invention.
• the porous, preferably mesoporous, layer thus obtained is entirely solid and ceramic. There is no longer any risk of loss of electrical contact between the particles of active materials during cycling, which is likely to improve the cycling performance of the battery. Furthermore, after sintering, the electrode adheres perfectly to the metal substrate on which it has been deposited or transferred (in the case of an initial deposit on an intermediate substrate).
• the heat treatments carried out at high temperature to sinter the nanoparticles together allow the electrode to dry perfectly and remove all traces of water or solvents or other organic additives (stabilizers, binders) adsorbed on the surface of the particles. of active material.
• the high temperature heat treatment (sintering) can be preceded by a lower temperature heat treatment (debinding) to dry the placed or deposited electrode and to remove traces of water or solvents or other organic additives ( stabilizers, binders) adsorbed on the surface of the particles of active material; this debinding can be carried out in an oxidizing atmosphere.
• the porosity of the final electrode can be adjusted within a range of 50% to 25% porosity.
• the power density of the electrodes thus obtained remains extremely high due to the mesoporosity.
• the dynamic balancing of the cell remains perfect, which helps to maximize the power densities and lifespans of the battery cell.
• the electrode of the assembly according to the invention has a high specific surface area, which reduces the ionic resistance of the electrode.
• this electrode for this electrode to deliver maximum power, it must still have very good electronic conductivity to avoid ohmic losses in the battery. This improvement in the electronic conductivity of the cell will be all the more critical the greater the thickness of the electrode. Furthermore, this electronic conductivity must be perfectly homogeneous throughout the electrode in order to avoid the local formation of hot spots.
• a coating of an electronically conductive material is deposited on and inside the pores of the porous layer obtained from the active material.
• This electronically conductive material can be deposited by the atomic layer deposition technique (abbreviated ALD, Atomic Layer Deposition) or from a liquid precursor.
• Said electronically conductive material may be carbon. This deposit of an electronically conductive material is carried out only on the electrode and not on the separator.
• the mesoporous layer can be immersed in a rich solution of a carbon precursor (eg, sucrose solution). Then the electrode is dried and subjected to heat treatment under nitrogen at a temperature sufficient to pyrolize the carbon precursor. This forms a very thin coating of carbon over the entire internal surface of the electrode, which is perfectly distributed. This coating gives the electrode good electronic conduction, regardless of its thickness. It should be noted that this treatment is possible after sintering because the electrode is entirely solid, without organic residues, and withstands the thermal cycles imposed by the various thermal treatments.
• a carbon precursor eg, sucrose solution
• the separator of the assembly according to the invention is then obtained in accordance with the method for manufacturing a mesoporous deposit, as described above on the porous electrode of the assembly.
• the separator thus obtained is entirely solid, ceramic and has good mechanical strength. Moreover, after sintering, the deposit of the inorganic layer adheres perfectly to the porous electrode so as to form the assembly according to the invention.
• the heat treatments carried out at high temperature to sinter the nanoparticles together allow the separator to dry perfectly and remove all traces of water adsorbed on the surface of the particles of inorganic material E which constitutes the separator. Depending on the sintering time and temperature, the porosity of the separator can be adjusted.
• the assembly consisting of a porous electrode and a separator according to the invention can advantageously be assembled to an electrode or to another assembly according to the invention, so as to obtain a functional battery.
• a first object of the invention is a method of manufacturing an assembly consisting of a porous electrode and a porous separator, in particular for electrochemical devices, said electrode comprising a porous layer deposited on a substrate, said layer being free of binder, having a porosity of between 20% and 60% by volume, preferably between 25% and 50%, and pores with an average diameter of less than 50 nm, said separator comprising a porous inorganic layer deposited on said electrode, said inorganic layer porous being free of binder, having a porosity of between 25% and 60% by volume, preferably between 30% and 50%, and pores with an average diameter of less than 50 nm, said manufacturing process being characterized in that:
• step (b) depositing on at least one face of said substrate a layer from said first colloidal suspension or paste supplied in step (a), by a technique preferably selected from the group formed by: electrophoresis, a method printing, including inkjet printing or flexographic printing, and a coating process, including scrap coating, roller coating, curtain coating, dip coating and coating by extrusion through a slot-shaped die;
• a technique preferably selected from the group formed by: electrophoresis, a method printing, including inkjet printing or flexographic printing, and a coating process, including scrap coating, roller coating, curtain coating, dip coating and coating by extrusion through a slot-shaped die;
• step (c) said layer obtained in step (b) is dried, where appropriate before or after having separated said layer from its intermediate substrate, then, optionally, said dried layer is heat treated, preferably under an oxidizing atmosphere, and it is consolidated, by pressing and / or heating, to obtain a porous layer, preferably inorganic and mesoporous;
• step (e) depositing on said porous electrode obtained in step (d), a porous inorganic layer from said second colloidal suspension supplied in step (a), by a technique preferably selected from the group formed by: electrophoresis, a printing process, including inkjet printing or flexographic printing, or a coating process, including scrap coating, roller coating, curtain coating , dip coating and extrusion coating through a slot-shaped die;
• step (f) said porous inorganic layer of the structure obtained in step (e) is dried, preferably under an air flow, and a heat treatment is carried out in air at a temperature below 500 ° C, preferably at approximately 400 ° C in order to obtain said assembly consisting of a porous electrode and a porous separator, knowing that said substrate may be a substrate capable of acting as an electric current collector, or an intermediate substrate.
• said assembly consisting of a porous electrode and a separator is impregnated with an electrolyte, preferably a phase carrying lithium ions, selected from the group formed through : o an electrolyte composed of at least one aprotic solvent and at least one lithium salt; o an electrolyte composed of at least one ionic liquid or ionic polyliquid and at least one lithium salt; o a mixture of aprotic solvents and ionic liquids or ionic polyliquids and lithium salts; o a polymer made ionic conductive by adding at least one lithium salt; and o a polymer rendered ionic conductive by the addition of a liquid electrolyte, either in the polymer phase or in the mesoporous structure.
• an electrolyte preferably a phase carrying lithium ions, selected from the group formed through : o an electrolyte composed of at least one aprotic solvent and at least one lithium salt; o an electrolyte composed of at least one ionic
• the electrode obtained can be coated with an ionic conductive layer in order to improve the life of the batteries and their performance.
• the ionic conductive layer can be Lii , 3 Alo , 3Tii , 7 (R0 4 ) 3 , nafion, U3BO3 , PEO, or a mixture of PEO and a phase carrying lithium ions, such as lithium salts.
• step (b) the deposition can be done on one or on both sides of the substrate.
• said layer is separated in step (c) from said intermediate substrate, to form, after consolidation, a porous plate.
• This separation step can be carried out before or after the drying of the layer obtained in step b).
• an electrically conductive sheet is supplied, covered on at least one face, respectively on its two faces, with a thin layer of conductive glue or a thin layer of nanoparticles of at least one active electrode material P, then at least one porous plate is glued on one side, preferably on each side, of the electrically conductive sheet, so as to obtain a porous, preferably mesoporous, layer on a substrate capable of acting as a current collector.
• said colloidal suspension or paste supplied in step (a) comprises organic additives, such as ligands, stabilizers, binders or residual organic solvents
• said dried layer is heat treated, preferably under an oxidizing atmosphere.
• This heat treatment, allowing debinding can be carried out at the same time as the consolidation (sintering) when it is carried out under an oxidizing atmosphere or before the step of consolidating the dried layer in step c).
• said substrate is a substrate capable of acting as an electric current collector. Said substrate on which said layer is deposited performs the function of current collector in the electrode.
• a metal substrate is chosen, which can in particular be made of tungsten, molybdenum, chromium, titanium, tantalum, stainless steel, or an alloy of two or more of these materials. Such metal substrates are quite expensive and can greatly increase the cost of the battery. This metal substrate can also be coated with a conductive or semiconductor oxide before depositing the layer of material P, which makes it possible in particular to protect less noble substrates such as copper and nickel.
• the thickness of the layer after step (c) is advantageously between approximately 1 ⁇ m and approximately 300 ⁇ m, preferably between 1 ⁇ m and 150 ⁇ m, more preferably between 10 ⁇ m and 50 ⁇ m, or even between 10 ⁇ m and 30 ⁇ m .
• the thickness of the layer after step (c) is limited in order to avoid any cracking problem.
• said substrate is an intermediate, temporary substrate, such as a flexible substrate, which may be a polymer film.
• the deposition step is advantageously carried out on one face of said intermediate substrate in order to facilitate the subsequent separation of the layer from its substrate.
• the layer can be separated from its substrate after drying, preferably before heating it, but at the latest at the end of step (c).
• the thickness of the layer after step (c) is advantageously less than or equal to 5 mm, advantageously between about 1 ⁇ m and about 500 ⁇ m.
• the thickness of the layer after step (c) is advantageously less than 300 ⁇ m, preferably between about 5 ⁇ m and about 300 ⁇ m, preferably between 5 ⁇ m and 150 ⁇ m.
• said porous layer obtained at the end of step (c) has a specific surface area of between approximately 10 m 2 / g and approximately 500 m 2 / g. Its thickness is advantageously between 1 and 500 ⁇ m, preferably between approximately 4 ⁇ m and approximately 400 ⁇ m.
• the deposit obtained at the end of step (e) advantageously has a thickness of between approximately 3 ⁇ m and approximately 20 ⁇ m, and preferably between approximately 5 ⁇ m and approximately 10 ⁇ m.
• said porous inorganic layer obtained at the end of step (f) has a specific surface area of between approximately 10 m 2 / g and approximately 500 m 2 / g. Its thickness is advantageously between 3 ⁇ m and 20 ⁇ m, and preferably between 5 ⁇ m and 10 ⁇ m.
• the size distribution of the primary particles of the active material P and / or of the inorganic material E is preferably narrow.
• said agglomerates preferably comprise at least three primary particles.
• the size distribution of said agglomerates is preferably polydisperse.
• the size distribution of the agglomerates is bimodal, that is, it has two size distribution peaks, these two sizes being called D1 and D2 where D1> D2; the D2 / D1 ratio may for example be between 3 and 7 and preferably between 4 and 6; this prevents the formation of large cavities and ensures good compactness of the mesoporous layer.
• the suspension of nanoparticles can be produced in water or in ethanol, or in a mixture of water and ethanol, or alternatively in a mixture of ethanol and isopropyl alcohol (with less than 3% of Isopropylic alcohol). It does not contain carbon black.
• the suspension is advantageously characterized by a solids content of at least 15% and preferably at least 50%.
• the deposition of said coating of electronically conductive material can be carried out by the ALD atomic layer deposition technique, or by immersion of the layer in a liquid phase comprising a precursor of said electronically conductive material, followed by the transformation of said precursor into electronically conductive material.
• Said precursor is advantageously a compound rich in carbon, such as a carbohydrate carbohydrate, in particular a polysaccharide (for example sucrose, lactose, glucose), and said transformation into electronically conductive material is in this case carried out by pyrolysis, preferably under an inert atmosphere (eg nitrogen).
• Said electronically conductive material may be carbon. It can be deposited in particular by ALD or by immersion in a liquid phase comprising a carbon precursor.
• the process for manufacturing the porous battery electrode uses an intermediate polymer substrate (such as PET) and results in a so-called “green strip”. This raw strip is then separated from its substrate; it then forms plates or sheets (hereinafter the term “plate” is used, regardless of its thickness).
• Said porous plate obtained in step (c) has a thickness advantageously less than or equal to 5 mm, preferably between approximately 1 ⁇ m and approximately 500 ⁇ m.
• the thickness of the layer after step (c) is advantageously less than 300 ⁇ m, preferably between approximately 5 ⁇ m and approximately 300 ⁇ m, preferably between 5 ⁇ m and 150 ⁇ m.
• a coating of an electronically conductive material is then deposited on and inside the pores of the porous layer or of the porous plate, preferably mesoporous, as has just been described.
• an electrically conductive sheet is also supplied, covered on both sides with a thin intermediate layer of nanoparticles preferably identical to those constituting the electrode plate or covered on both sides with a thin layer of nanoparticles.
• conductive glue preferably have a thickness of less than 1 ⁇ m.
• This sheet can be a metal strip or a graphite sheet.
• This electrically conductive sheet is then interposed between two plates of porous electrodes obtained previously, respectively between two porous plates obtained after step c).
• the assembly is then heat-pressed so that said intermediate thin layer of nanoparticles is transformed by sintering and consolidates the electrode / substrate / electrode assembly, respectively the porous plate / substrate / porous plate assembly to obtain a sub-assembly rigid and one-piece.
• the bond between the electrode layer, respectively the porous plate, and the intermediate layer is established by atom diffusion; this phenomenon is known by the English term "diffusion bonding".
• This assembly is done with two electrode plates, respectively two porous plates, of the same polarity (typically between two anodes or between two cathodes), and the metal sheet between these two electrode plates, respectively two porous plates, of the same polarity establishes a parallel connection between them.
• One of the advantages of the second embodiment is that it allows the use of inexpensive substrates such as aluminum foil, copper foil or graphite foil. Indeed, these strips would not withstand the heat treatments for consolidating the deposited layers; sticking them to the electrode plates after their heat treatment also helps prevent oxidation.
• the coating of an electronically conductive material can then advantageously be deposited on and inside the pores of the porous plates. , preferably mesoporous, of the porous plate / substrate / porous plate assembly, as has been described above, in particular when the porous plates used are thick.
• the deposition of said coating of electronically conductive material can be carried out by the ALD atomic layer deposition technique, or by immersion of the porous layer in a liquid phase comprising a precursor of said electronically conductive material, followed by the transformation of said precursor into electronically conductive material .
• This assembly by "diffusion bonding" can be carried out separately as has just been described, and the electrode / substrate / electrode sub-assemblies thus obtained can be used to manufacture a battery.
• This diffusion bonding assembly can also be achieved by stacking and heat-pressing the entire battery structure; in this case, a multilayer stack is assembled comprising a first porous anode layer, its metallic substrate, a second porous anode layer, a solid electrolyte layer, a first cathode layer, its metallic substrate, a second layer of cathode, a new layer of solid electrolyte, and so on.
• This electrode / substrate / electrode sub-assembly can be obtained by bonding the electrode plates to an electrically conductive sheet capable of subsequently acting as an electric current collector, or by depositing and then sintering layers on a substrate capable of acting as electric current collector, in particular a metal substrate.
• the electrolyte film is then deposited on the latter.
• the necessary cutouts are then made to produce a battery with several elementary cells, then the sub-assemblies are stacked (typically in "head to tail” mode) and the thermocompression is carried out to weld the electrodes together at the level of the solid electrolyte.
• the cutouts necessary to produce a battery with several elementary cells can be made before the deposition on each electrode / substrate / electrode sub-assembly of an electrolyte film (separator), then the sub-assemblies are stacked (typically in “head to tail” mode) and thermocompression is carried out to weld the electrodes together at the level of the electrolyte film (separator).
• thermocompression welding takes place at a relatively low temperature, which is possible thanks to the very small size of the nanoparticles. As a result, oxidation of the metal layers of the substrate is not observed.
• a conductive adhesive loaded with graphite
• a sol-gel type deposit loaded with conductive particles, or even metal strips, preferably low melting point (eg aluminum); during the thermomechanical treatment (heat pressing) the metal strip can deform by creep and come to make this weld between the plates.
• a porous layer according to the invention made with one of these materials, can perform the function of a positive electrode in a battery, and in particular in a lithium ion battery.
• M is at least one of the elements chosen from the group consisting of Fe, Ga, Mo, Al, B, and where 0 ⁇ x £ 0.20 and -0.3 £ d £ 0.3; Ga 0.10 Ti 0.80 Nb 2.10 O 7 ;
• M is an element whose degree of oxidation is + III, more particularly M is at least one of the elements chosen from the group consisting of Fe, Ga, Mo, Al, B, and where 0 ⁇ x £ 0.40 and -0.3 £ d £ 0.3; Tii- x M 1 x Nb 2 -yM 2 y0 7-z M 3 z or Li w Tii- x M 1 x Nb 2 -yM 2 y0 7-z M 3 z in which o M 1 and M 2 are each at minus one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr , Si, Sr, K, Cs and Sn, o M 1 and M 2 may be identical or different from each other, o M 3 is at least one halogen, o and in which 0 £ w £ 5 and0 £ x £
• ⁇ M 1 and M 2 are at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca , Ba, Pb, Al, Zr, Si, Sr, K, Cs and Sn;
• ⁇ M 1 and M 2 are each at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr, Si, Sr, K, Cs, Ce and Sn,
• ⁇ M 1 and M 2 can be identical or different from each other
• a porous layer according to the invention can perform the function of a negative electrode in a battery, and in particular in a lithium ion battery.
• a negative electrode material is advantageously used which has a lithium insertion potential greater than 1 V; this allows very fast recharging of the battery.
• the negative electrode can be made of titanate and / or mixed titanium oxides.
• the electrodes of the assembly according to the invention are impregnated with an ionic liquid containing a lithium salt.
• the substrate capable of acting as an electric current collector is preferably a noble metal.
• Such a battery has the advantage of being able to operate at high temperature.
• the inorganic material E advantageously comprises an electronically insulating material, preferably chosen from: o I ⁇ I2O3, S1O2, Zr0 2 , and / or o a material selected from the group formed by lithiated phosphates, preferably chosen from: lithiated phosphates of the type NaSICON, U3PO4; UPO3; Li 3 Alo, 4Sci, 6 (P0 4 ) 3 called "LASP"; Lii + x Zr 2 -xCa x (PO4) 3 with £ 0 x £ 0.25; Ui + 2X Zr 2-x Ca x (P0 4 ) 3 with 0 £ x £ 0.25 such as Lii, 2 Zri, gCao, i (P0 4 ) 3 or Lii, 4Zri, 8Cao, 2 (P04 ) 3; uZG2 (R0 4 ) 3; Lii + 3x Zr2 (Pi- xSi x 0 4
• a porous layer according to the invention made with one of these materials, can perform the function of a separator in a battery, and in particular in a lithium ion battery.
• Another object of the present invention is an assembly consisting of a porous electrode and a porous separator obtainable by the method of manufacturing an assembly consisting of a porous electrode and a porous separator according to l 'invention.
• This porous assembly is advantageously free of binder. Its porosity is preferably between 20% and 60% by volume, and the average diameter of its pores is less than 50 nm. It can be intended to act as a positive electrode / separator assembly or as a negative electrode / separator assembly in an electrochemical device.
• An electrode of the assembly according to the invention enables a lithium ion battery which has both high energy density and high power density.
• This performance is the result of a limited porosity (which increases the energy density), of a very high specific surface (which is favored by the very small size of the primary particles of the electrode, and which leads to the (increase in the exchange surface, which decreases the ionic resistance), the absence of organic binder (the binder can locally mask the access of lithium to the surface of active materials).
• a coating of an electronically conductive material is deposited on and inside the pores of the porous layer of active material constituting the electrode. This coating decreases the series resistance of the battery.
• Yet another object of the invention is the use of a method of manufacturing an assembly consisting of a porous electrode and a separator according to the invention for the manufacture of an assembly consisting of a porous electrode. and a separator in lithium ion batteries.
• Yet another object of the invention is a method of manufacturing a battery designed to have a capacity not exceeding 1 mAh, implementing the method of manufacturing an assembly consisting of a porous electrode and a separator. according to the invention, or using an assembly consisting of a porous electrode and a separator according to the invention.
• Said battery is advantageously a lithium ion battery.
• this method of manufacturing an assembly consisting of a porous electrode and a separator can be implemented to manufacture an assembly in which the porous electrode is a positive electrode or a negative electrode.
• This method of manufacturing a battery may include a step in which said assembly consisting of a porous electrode and a separator is impregnated with an electrolyte, preferably a phase carrying lithium ions, selected from the group formed by : o an electrolyte composed of at least one aprotic solvent and at least one lithium salt; o an electrolyte composed of at least one ionic liquid or ionic polyliquid and at least one lithium salt; o a mixture of at least one aprotic solvent and at least one ionic liquid or ionic polyliquid and at least one lithium salt; o a polymer made ionic conductive by adding at least one lithium salt; and o a polymer rendered ionic conductive by the addition of a liquid electrolyte, either in the polymer phase or in the mesoporous structure.
• Said polymers are preferably selected from the group formed by poly (ethylene oxide), poly (propylene oxide), polydimethylsiloxane, polyacrylonitrile, poly (methyl methacrylate), poly (vinyl chloride), poly (vinylidene fluoride) ), PVDF-hexafluoropropylene.
• Said ionic liquids can be salts molten at room temperature (these products are known under the designation RTIL, Room Temperature Ionie Liquid), or ionic liquids which are solid at room temperature. These ionic liquids which are solid at room temperature must be heated to liquefy them to impregnate the electrodes; they solidify in the porous layer.
• RTIL Room Temperature Ionie Liquid
• a final object of the invention is a lithium ion battery capable of being obtained by the method of manufacturing a battery according to the invention.
• the battery according to the invention can in particular be designed and dimensioned so as to have a capacity less than or equal to approximately 1 mAh (commonly called a “microbattery”).
• microbatteries are designed to be compatible with microelectronics manufacturing processes. detailed description
• the size of a particle is defined by its largest dimension.
• nanoparticle is understood to mean any particle or object of nanometric size having at least one of its dimensions less than or equal to 100 nm.
• ionic liquid is meant any liquid salt, capable of transporting electricity, which differs from all molten salts by a melting point of less than 100 ° C. Some of these salts remain liquid at room temperature and do not solidify, even at very low temperatures. Such salts are called “ionic liquids at room temperature”.
• mesoporous materials is understood to mean any solid which has within its structure so-called “mesopore” pores having a size intermediate between that of the micropores (width less than 2 nm) and that of the macropores (width greater than 50 nm), namely a size between 2 nm and 50 nm.
• This terminology corresponds to that adopted by IUPAC (International Union for Pure and Applied Chemistry), which is a reference for those skilled in the art.
• nanopore is therefore not used here, even if the mesopores as defined above have nanometric dimensions within the meaning of the definition of nanoparticles, knowing the pores of size smaller than that of the mesopores are called by the those skilled in the art of "micropores”.
• the term “mesoporous layer” is understood to mean a layer which has mesopores. As will be explained below, in these layers the mesopores contribute significantly to the total pore volume; this fact is reflected by the expression “mesoporous layer of mesoporous porosity greater than X% by volume” used in the description below, and applicable to the porous electrode and to the separator used in the assembly according to the invention. .
• aggregate means, as defined by IUPAC, a loosely bound assembly of primary particles.
• these primary particles are nanoparticles having a diameter which can be determined by transmission electron microscopy.
• An aggregate of aggregated primary nanoparticles can normally be destroyed (ie reduced to primary nanoparticles) in suspension in a liquid phase under the effect of ultrasound, according to a technique known to those skilled in the art.
• agglomerate means, as defined by IUPAC, a tightly bonded assembly of primary particles or aggregates.
• microbattery is used herein for a battery with a capacity not exceeding 1 mAh.
• microbatteries are designed to be compatible with microelectronics manufacturing processes.
• the process for preparing the porous electrodes and the separator according to the invention starts from a suspension of nanoparticles. It is preferable not to prepare these suspensions of nanoparticles from dry nanopowders. They can be prepared by grinding powders or nanopowders in the liquid phase, and / or using ultrasound treatment to deagglomerate the nanoparticles.
• the nanoparticles are prepared in suspension directly by precipitation.
• the synthesis of nanoparticles by precipitation makes it possible to obtain primary nanoparticles of very homogeneous size with a unimodal size distribution i.e. very tight and monodisperse, of good crystallinity and purity.
• the use of these nanoparticles of very homogeneous size and narrow distribution makes it possible to obtain, after deposition, a porous structure of controlled and open porosity.
• the porous structure obtained after depositing these nanoparticles has little, preferably no closed pores.
• the nanoparticles are prepared directly at their primary size by hydrothermal or solvothermal synthesis; this technique makes it possible to obtain nanoparticles with a very narrow size distribution, called “monodisperse nanoparticles”.
• the size of these non-aggregated or non-agglomerated nanopowders / nanoparticles is called the primary size. It is typically between 2 nm and 150 nm. It is advantageously between 10 nm and 50 nm, preferably between 10 nm and 30 nm; this promotes, during subsequent process steps, the formation of an interconnected mesoporous network, thanks to the “necking” phenomenon.
• the electronic and ionic conduction of the porous electrode according to the invention takes place by virtue of the “necking” phenomenon forming the interconnected mesoporous network.
• the suspension of monodisperse nanoparticles is produced in the presence of ligands or organic stabilizers so as to avoid aggregation, or even agglomeration, of the nanoparticles.
• Binders can also be added to the suspension of nanoparticles to facilitate the production of deposits or bare bands, in particular thick deposits without cracks.
• This suspension of monodisperse nanoparticles can be purified to remove any potentially troublesome ions. Depending on the degree of purification it can then be specially treated to form aggregates or agglomerates of a controlled size. More precisely, the formation of aggregates or agglomerates can result from the destabilization of the suspension caused in particular by ions, by the increase in the dry extract of the suspension, by changing the solvent of the suspension, by the addition of destabilizing agent. If the suspension has been completely purified it is stable, and ions are added to destabilize it, typically in the form of a salt; these ions are preferably lithium ions (preferably added in the form of LiOH).
• One of the essential aspects for the manufacture of electrodes and of the separator of the assembly according to the invention consists in having good control of the size of the primary particles of the electrode materials P and / or of inorganic materials E and their degree of aggregation or agglomeration.
• the stabilization of the suspension of nanoparticles occurs after the formation of agglomerates, the latter will remain in the form of agglomerates; the suspension obtained can be used to make mesoporous deposits.
• a mesoporous layer having a mean diameter of the mesopores between 2 nm and 50 nm.
• the porous electrode layer can be deposited by the dip coating process, by the inkjet printing process, by spray coating. roller, by curtain coating or by scraping, and this from a fairly concentrated suspension comprising aggregates or agglomerates of nanoparticles of the active material P, respectively of the inorganic material E.
• a less concentrated suspension is used containing agglomerates of nanoparticles of the active material P, respectively of the inorganic material E to produce the porous electrode layer, respectively to produce the inorganic layer corresponding to the separator of the assembly according to l 'invention.
• Electrophoretic deposition is a technique which allows uniform deposition over large areas with high deposition rates. Coating techniques, in particular by dipping, roller, curtain or scraping, simplify the management of baths compared to electrophoretic deposition techniques. Inkjet printing deposition allows for localized deposits.
• Porous thick layer layers or thick layer separators can be made in a single step by roller coating, by curtain coating, by coating through a slot (called “slot die coating” in English), or by scraping (ie with a doctor blade). It is noted that the colloidal suspensions in water and / or ethanol and / or IPA and their mixtures are more fluid than those obtained in NMP. It is thus possible to increase the dry extract of the suspension in agglomerates of nanoparticles. These agglomerates preferably have sizes less than or equal to 200 nm and are of polydisperse sizes, or even with two populations of different sizes.
• a layer of a suspension of nanoparticles is deposited on a substrate, by any suitable technique, and in particular by a method selected from the group formed by: electrophoresis, a printing process and preferably inkjet printing or flexographic printing, a coating process and preferably with a doctor blade, roller, curtain, dipping, or through a shaped die slot.
• the suspension is typically in the form of an ink, that is, a fairly fluid liquid, but can also have a pasty consistency.
• the deposition technique and the conduct of the deposition process must be compatible with the viscosity of the suspension, and vice versa.
• the deposited layer will then be dried.
• the layer is then consolidated to obtain the desired ceramic mesoporous structure.
• This consolidation will be described below. It can be carried out by heat treatment, by heat treatment preceded by mechanical treatment, and possibly by thermomechanical treatment, typically thermocompression. During this thermomechanical or thermal treatment, the electrode layer will be free of any constituent and organic residue (such as the liquid phase of the suspension of nanoparticles and any surfactant products): it becomes an inorganic layer (ceramic).
• the consolidation of a plate is preferably carried out after its separation from its intermediate substrate, because the latter could be degraded during this treatment.
• the layers of electrodes are each deposited on a substrate capable of acting as an electric current collector.
• Layers comprising the suspension of nanoparticles or agglomerates of nanoparticles can be deposited on both sides by the deposition techniques indicated above.
• the substrate serving as a current collector in batteries employing porous electrodes according to the invention can be metallic, for example a metal strip (i.e. a laminated metal sheet).
• the substrate is preferably chosen from strips of tungsten, molybdenum, chromium, titanium, tantalum, stainless steel, or an alloy of two or more of these materials. Less noble substrates such as copper or nickel may receive a conductive and protective coating against oxidation.
• the metal foil can be coated with a layer of noble metal, in particular chosen from gold, platinum, palladium, titanium or alloys predominantly containing at least one or more of these metals, or with a layer of material.
• noble metal in particular chosen from gold, platinum, palladium, titanium or alloys predominantly containing at least one or more of these metals, or with a layer of material.
• ITO type conductor which has the advantage of also acting as a diffusion barrier).
• this substrate capable of acting as an electric current collector must withstand the conditions of heat treatment of the deposited layer, and the operating conditions within the battery cell.
• copper and nickel are suitable in contact with the anode material; they may oxidize at the cathode.
• the electrophoresis process (especially in water) can be used.
• the substrate is subjected to an electrochemical polarization which leads either to its oxidation or to its dissolution in the suspension of nanoparticles.
• only substrates which do not exhibit anodization and / or corrosion phenomena can be used. This is particularly the case with stainless steel and noble metals.
• the nanopowders and / or agglomerates are crystallized, obtained by hydro-solvothermal synthesis with the right phase and crystalline structure, then it is possible to use consolidation heat treatments under a controlled atmosphere, which will allow the use of less noble substrates. such as nickel, copper, aluminum, and because of the very small size of the primary particles obtained by hydrothermal synthesis, it will also be possible to reduce the temperature and / or the duration of the consolidation heat treatment to values close to 350 - 500 ° C, which also allows a wider choice of substrates.
• these less noble substrates must resist the heat treatment making it possible to remove the organic additives possibly contained in the suspension of nanoparticles used such as ligands, stabilizers, binders or residual organic solvents (debinding), this heat treatment being advantageously carried out under oxidizing atmosphere.
• These substrates capable of acting as an electric current collector can optionally be covered with a thin film of conductive oxide.
• This oxide may have the same composition as the electrode.
• These thin films can be produced by sol-gel. This oxide-based interface helps limit corrosion of the substrate and provides a better bonding base for the electrode with the substrate.
• the liquid electrolytes which come to impregnate the porous electrode are in direct contact with the substrate capable of acting as a current collector.
• substrates capable of acting as a current collector ie metal substrates and polarized at very anodic potentials for the cathode and very cathodic for the anode, these electrolytes are liable to induce a dissolution of the current collector.
• parasitic reactions can degrade the life of the battery and accelerate its self-discharge.
• substrates capable of acting as a current collector such as aluminum current collectors are used at the cathode in all lithium ion batteries.
• Aluminum has the particularity of anodizing at very anodic potentials, and the oxide layer thus formed on its surface protects it from dissolution.
• aluminum has a melting temperature close to 600 ° C. and cannot be used for the manufacture of batteries according to the invention, if the electrodes consolidation treatments risk melting the current collector.
• a titanium strip is advantageously used as a current collector at the cathode.
• the titanium strip will, like aluminum, anodize and its oxide layer will prevent possible side reactions of dissolution of the titanium in contact with the liquid electrolyte.
• fully solid electrodes according to the invention can be made directly on this type of strip.
• Stainless steel can also be used as a current collector, especially when it contains titanium or aluminum as an alloying element, or when it has a thin layer of protective oxide on the surface.
• substrates serving as current collector can be used such as less noble metal strips covered with a protective coating, allowing to avoid the possible dissolution of these strips induced by the presence of electrolytes in contact with them.
• These less noble metal strips can be copper, nickel or metal alloy strips such as stainless steel strips, Fe-Ni alloy, Be-Ni-Cr alloy, alloy Ni-Cr or Ni-Ti alloy.
• the coating that can be used to protect the substrates serving as current collectors can be of different types. He can be :
• a dense, defect-free metallic thin layer such as a metallic thin layer of gold, titanium, platinum, palladium, tungsten or molybdenum.
• metallic thin layer can be used to protect current collectors because they have good conduction properties and can withstand heat treatments during the subsequent electrode fabrication process.
• This layer can in particular be produced by electrochemistry, PVD, CVD, evaporation, ALD;
• a thin layer of carbon such as diamond carbon, graphic, deposited by ALD, PVD, CVD or by inking of a sol-gel solution making it possible to obtain after heat treatment an inorganic phase doped with carbon to make it conductive
• a layer of conductive or semiconductor oxides such as an ITO (indium-tin oxide) layer deposited only on the cathode substrate because the oxides are reduced at low potentials;
• a layer of conductive nitrides such as a layer of TiN only deposited on the cathode substrate because the nitrides insert lithium at low potentials.
• the coating that can be used to protect the substrates serving as current collectors must be electronically conductive so as not to interfere with the operation of the electrode subsequently deposited on this coating, by making it too resistive.
• the maximum dissolution currents measured on the substrates which can act as a current collector, at the operating potentials of the electrodes, expressed in pA / cm 2 must be 1000 times lower than the surface capacities of the electrodes expressed in pAh / cm 2 .
• the shrinkage generated by the consolidation can lead either to the cracking of the layers, or to a shear stress at the interface between the substrate (which is of fixed dimension) and the ceramic electrode.
• this shear stress exceeds a threshold, the layer detaches from its substrate.
• the thickness of the electrodes by a succession of deposition - sintering operations.
• This first variant of the first embodiment of the deposition of the layers gives a good result, but is not very productive.
• layers of greater thickness are deposited on both sides of a perforated substrate.
• the perforations must be of sufficient diameter so that the two layers of the front and back are in contact at the perforations.
• the nanoparticles and / or agglomerates of nanoparticles of electrode material in contact through the perforations in the substrate weld together, forming an attachment point (weld point between the deposits on the two faces). This limits the loss of adhesion of the layers to the substrate during the consolidation steps.
• binders and dispersants can be added by heat treatment, preferably in an oxidizing atmosphere, such as by debinding, during a sintering treatment or during a heat treatment carried out prior to the sintering treatment.
• the electrode layers are not deposited on a substrate capable of acting as an electric current collector, but on an intermediate, temporary substrate.
• a substrate capable of acting as an electric current collector
• These thick layers are deposited for example by a coating process, preferably with a doctor blade (a technique known in English under the term “doctor blade” or “tape casting") or through a slot-shaped die (in English " slot-die ”).
• Said intermediate substrate may be a polymeric sheet, for example poly (ethylene terephthalate), abbreviated PET.
• these layers do not crack, in particular when drying takes place after the separation of the layer obtained in step (b) from its intermediate substrate.
• a stack of three layers is then made, namely two plates of electrodes of the same polarity separated by an electrically conductive foil capable of acting as an electric current collector, such as a metal foil or a graphite foil.
• This stack is then assembled by a thermomechanical treatment, comprising pressing and a heat treatment, preferably carried out simultaneously.
• the interface may be coated with a layer allowing electronically conductive bonding.
• This layer can be a sol-gel layer (preferably of the type allowing the chemical composition of the electrodes to be obtained after heat treatment) possibly loaded with particles of an electronically conductive material, which will make a ceramic weld between the mesoporous electrode and the sheet.
• metallic This layer can also consist of a thin layer of non-sintered electrode nanoparticles, or of a thin layer of a conductive adhesive (loaded with graphite particles for example), or even a metallic layer of a metal to low melting point.
• said electrically conductive sheet is metallic, it is preferably a laminated sheet, i.e. obtained by lamination. Rolling can optionally be followed by a final annealing, which can be soft annealing (full or partial) or recrystallization, depending on metallurgical terminology. It is also possible to use an electrochemically deposited sheet, for example an electrodeposited copper sheet or an electrodeposited nickel sheet.
• a ceramic electrode without organic binder, mesoporous, located on either side of a metal substrate serving as an electronic current collector.
• the electrodes according to the invention can be manufactured from suspensions of nanoparticles, using known coating techniques. These techniques which can be used are the same printing and coating techniques as those presented above in the subchapter entitled "Preparation of suspensions of nanoparticles".
• the dry extract of the suspension is advantageous for the dry extract of the suspension to be greater than 20%, and preferably greater than 40%; this decreases the risk of cracking on drying.
• Electrophoresis can also be used.
• the method according to the invention advantageously uses the electrophoresis of suspensions of nanoparticles as a technique for depositing porous, preferably mesoporous, electrode layers.
• the method of depositing electrode layers from a suspension of nanoparticles is known as such (see for example EP 2 774 194 B1).
• the substrate can be metallic, for example a metallic foil.
• the substrate serving as a current collector in batteries employing porous electrodes according to the invention is preferably chosen from strips of titanium, copper, stainless steel or molybdenum.
• a sheet of stainless steel with a thickness of 5 ⁇ m can be used.
• the metal foil may be coated with a layer of noble metal, in particular chosen from gold, platinum, palladium, titanium or alloys predominantly containing at least one or more of these metals, or with a layer of material.
• ITO type conductor which has the advantage of also acting as a diffusion barrier).
• a layer, preferably a thin layer, of an electrode material is deposited on the metal layer; this deposit must be very thin (typically a few tens of nanometers, and more generally between 10 nm and 100 nm). It can be carried out by a sol-gel process.
• LiMn 2 0 4 can be used for a porous LiMn 2 0 4 cathode.
• a counter electrode is placed in the suspension and a voltage is applied between the conductive substrate and said counter electrode.
• the electrophoretic deposition of the aggregates or agglomerates of nanoparticles is carried out by galvanostatic electrodeposition in pulsed mode; high frequency current pulses are applied, this avoids the formation of bubbles on the surface of the deposited layers and the variations of the electric field in the suspension during the deposition.
• the thickness of the layer thus deposited by electrophoresis, preferably by galvanostatic electrodeposition in pulsed mode is advantageously less than 10 ⁇ m, preferably less than 8 ⁇ m, and is even more preferably between 1 ⁇ m and 6 ⁇ m.
• aggregates or agglomerates of nanoparticles can be deposited by the dip coating process (called “dip-coating” in English), regardless of the chemical nature of the nanoparticles used. This deposition process is preferred when the nanoparticles used have little or no electric charge.
• the step of deposition by dip-coating of aggregates or agglomerates of nanoparticles followed by the step of drying the layer obtained are repeated as much as necessary.
• at least one organic additive such as ligands, stabilizers, thickeners, binders or residual organic solvents .
• the dip-coating deposition process is a simple, safe process, easy to implement, to industrialize and to obtain a homogeneous final layer and compact.
• Consolidation treatment of deposited layers Consolidation treatment is applied to the electrode layer.
• the deposited layers must be dried; drying must not induce the formation of cracks. For this reason, it is preferred to carry it out under controlled humidity and temperature conditions or to use, to produce the porous layer, colloidal suspensions and / or pastes comprising, in addition to aggregates or agglomerates of nanoparticles.
• monodisperse primers at least one P electrode active material according to the invention, organic additives such as ligands, stabilizers, thickeners, binders or residual organic solvents.
• the dried layers can be consolidated by a pressing and / or heating step (heat treatment).
• this treatment leads to a partial coalescence of the primary nanoparticles in the aggregates, or the agglomerates, and between neighboring aggregates or agglomerates; this phenomenon is called “necking” or “neck formation”. It is characterized by the partial coalescence of two particles in contact, which remain separate but connected by a neck (constricted). Lithium ions and electrons are mobile within these necks and can diffuse from particle to particle without encountering grain boundaries. The nanoparticles weld together to ensure the conduction of electrons from one particle to another.
• a three-dimensional network of interconnected particles with high ionic mobility and electronic conduction is formed; this network comprises pores, preferably mesopores where the notion of particle disappears after heat treatment.
• the temperature necessary to obtain "necking" depends on the material; taking into account the diffusive nature of the phenomenon which leads to necking, the duration of the treatment depends on the temperature. This process can be called sintering; depending on its duration and temperature, a more or less pronounced coalescence (necking) is obtained, which has repercussions on the porosity. It is thus possible to go down to 30% (or even 25%) of porosity while maintaining a perfectly homogeneous channel size.
• the heat treatment can also be used to eliminate the organic additives possibly contained in the suspension of nanoparticles used, such as ligands, stabilizers, binders or residual organic solvents.
• an additional heat treatment under an oxidizing atmosphere, can be carried out to remove these organic additives possibly contained in the suspension of nanoparticles used. This additional heat treatment is advantageously carried out before the consolidation treatment of step c) making it possible to obtain a porous, preferably mesoporous, layer.
• a coating of an electronically conductive material is deposited on and inside the pores of said porous layer so as to obtain the porous electrode. of the assembly according to the invention.
• the method according to the invention which necessarily involves a step of depositing agglomerated nanoparticles of electrode material (active material), causes the nanoparticles to “weld” naturally to each other to generate , after consolidation such as annealing, a porous, rigid, three-dimensional structure, without organic binder; this porous layer, preferably mesoporous, is perfectly suited to the application of a surface treatment, by gas or liquid, which goes into the depth of the open porous structure of the layer.
• this deposit is carried out by a technique allowing an encapsulating coating (also called “conformal deposit”), ie a deposit which faithfully reproduces the atomic topography of the substrate on which it is applied, and which goes deep into the porosity network. open the layer.
• Said electronically conductive material may be carbon.
• ALD Atomic Layer Deposition
• CSD Chemical Solution Deposition
• the techniques of ALD (Atomic Layer Deposition) or CSD (Chemical Solution Deposition), known as such, may be suitable. They can be implemented on the porous layers after manufacture, before the deposition of the separator particles and before the assembly of the cell.
• the ALD deposition technique is carried out layer by layer, by a cyclic process, and makes it possible to produce an encapsulating coating which faithfully reproduces the topography of the substrate; the coating lines the entire surface of the electrodes.
• This coating coating typically has a thickness of between 1 nm and 5 nm.
• the deposition by ALD is carried out at a temperature typically between 100 ° C and 300 ° C. It is important that the diapers are free of organic matter: they must not contain an organic binder, any residues of stabilizing ligands used to stabilize the suspension must have been removed by purification of the suspension and / or during the heat treatment of the layer after drying. Indeed, at the temperature of the ALD deposit, the organic materials forming the organic binder (for example the polymers contained in the electrodes produced by ink tape casting) risk decomposing and will pollute the ALD reactor. Furthermore, the presence of residual polymers in contact with the particles of electrode active material can prevent the ALD coating from coating all of the surfaces of the particles, which affects its effectiveness.
• the CSD deposition technique also makes it possible to produce an encapsulating coating with a precursor of the electronically conductive material which faithfully reproduces the topography of the substrate; it covers the entire surface of the electrodes.
• This coating coating typically has a thickness of less than 5 nm, preferably between 1 nm and 5 nm. It must then be transformed into an electronically conductive material. In the case of a carbon precursor, this will be done by pyrolysis, preferably under inert gas (as is nitrogen).
• the diameter D50 of the primary particles of electrode material is at least 10 nm in order to prevent the conductive layer from blocking the open porosity of layer.
• porous electrode preferably mesoporous, comprising a coating of an electronically conductive material is deposited, preferably after drying, a layer of at least one inorganic material E, from suspensions of nanoparticles of inorganic material E, to using known coating techniques as indicated in paragraph 4 above.
• the process for depositing porous inorganic layers from a suspension of nanoparticles is known as such (see for example WO 2019/215411 A1).
• the material used for the manufacture of porous layers which can serve as a separator according to the invention is chosen from inorganic materials with a low melting point, electronic insulating material and stable in contact with the electrodes during the hot pressing steps. .
• Materials comprising lithium are to be preferred because they make it possible to avoid or even eliminate these phenomena of lithium depletion.
• the material used for the manufacture of porous inorganic layers according to the invention can be an ionically conductive material such as a solid electrolyte comprising lithium in order to avoid the formation of lithium depletion zones at the electrode / electrolytic separator interfaces.
• the inorganic material E advantageously comprises an electronically insulating material, preferably chosen from the materials selected from the group formed by lithiated phosphates, preferably chosen from: lithiated phosphates of NaSICON type, U3PO4; UPO3; Li 3 Alo, 4Sci, 6 (P0 4 ) 3 called "LASP"; Lii + x Zr 2 -xCa x (PO4) 3 with £ 0 x £ 0.25; Lii + 2x Zr 2 - x Ca x (PC> 4) 3 with 0 £ x £ 0.25 such as Lii, 2 Zri, 9 Ca 0, i (PO4) 3 Or Lii, 4 Zri, 8 Cao, 2 (PO4) 3; LiZr
• This inorganic layer is a porous ceramic film, preferably mesoporous, which performs the function of electrolytic separation.
• the ceramic nanoparticles used to manufacture the separator of the assembly according to the invention must be electrochemically stable in contact with the electrodes and be electronically insulating, and preferably conductive of lithium ions.
• the fact of depositing this inorganic layer makes it possible to reduce the thickness of the electrolytic film. This layer exhibits excellent mechanical properties. This reduction in thickness makes it possible to increase the volume energy density of the batteries.
• the completely ceramic and / or glass-ceramic character of this porous inorganic layer guarantees excellent mechanical strength, perfect wetting by liquid electrolytes, even by ionic liquids at room temperature, and also ensures the operation of battery cells in very wide temperature ranges (no risk of melting and / or breakage of the separator).
• porous inorganic layer ie of such a separator
• the performance of the porous electrodes according to the invention comes in part from the fact that they are covered on the surface by a coating of an electronically conductive material, such as carbon.
• an electronically conductive material such as carbon.
• the deposits of agglomerates of inorganic nanoparticles E serving to ensure the electrolytic separation function are, after deposit, rich in organic matter. These organic materials are found in the solvent adsorbed on the surface of the nanoparticles as well as in the organic stabilizers used in the formulation of the suspension of inorganic nanoparticles E.
• This heat treatment is carried out in air, at a moderate temperature, in order to allow the elimination of the organics contained in the electrolytic separator deposit in the form of CO 2 while retaining the coating of electronically conductive material, such as the carbon coating present. on the surface of porous electrodes.
• a heat treatment at less than 500 ° C and preferably at a temperature between approximately 250 ° C and approximately 450 ° C, and optimally) approximately 400 ° C, is carried out.
• the assembly is impregnated with a polymer containing lithium salts, and which is therefore an ionic conductor, the ion species transported being lithium ions.
• the assembly is impregnated with a liquid electrolyte; it may be, for example, an ionic liquid or an aprotic solvent in which one or more lithium salts have been dissolved. It is also possible to use an ionic polyliquide (in English “poly (ionic liquid)”, abbreviated PIL).
• the assembly according to the invention does not contain organic compounds, and this absence of organic compounds coupled with a mesoporous structure promotes wetting by an electrolyte which conducts lithium ions.
• This electrolyte can then equally be selected from the group formed by: an electrolyte composed of at least one aprotic solvent and of at least one lithium salt, an electrolyte composed of at least one ionic liquid or ionic polyliquid and at least one ionic liquid.
• At least one lithium salt at least one lithium salt, a mixture of aprotic solvents and ionic liquids or ionic polyliquids and lithium salts, an ionically conductive polymer containing at least one lithium salt, or a polymer made ionic conductive by the addition of minus a lithium salt.
• Said polymer is advantageously selected from the group formed by poly (ethylene oxide) (commonly abbreviated PEO), poly (propylene oxide), polydimethylsiloxane (commonly abbreviated PDMS), polyacrylonitrile (commonly abbreviated PAN), poly (methyl methacrylate) ) (commonly abbreviated PMMA), poly (vinyl chloride) (commonly abbreviated PVC), poly (vinylidene fluoride) (commonly abbreviated PVDF), PVDF-hexafluoropropylene.
• PEO poly (ethylene oxide)
• PEO poly (propylene oxide)
• PAN polyacrylonitrile
• PMMA poly (methyl methacrylate)
• PVC poly (vinyl chloride)
• PVDF poly (vinylidene fluoride)
• Said polymer whether or not containing lithium salts, is typically solid at room temperature and can be melted and this molten phase can then be impregnated into the mesoporosity of the assembly. Once cooled, an assembly comprising an electrode and a solid electrolyte is obtained.
• This assembly comprising an electrode and a solid electrolyte can be used in several ways to produce elementary battery cells.
• the assembly comprising a porous electrode and a solid electrolyte to produce elementary battery cells
• the assembly according to the invention can be impregnated with a molten phase comprising an ionic conductive polymer, and optionally salts. lithium. Once cooled, an assembly comprising a porous electrode for an electrode and a solid electrolyte is obtained.
• This assembly comprising an electrode and a solid electrolyte can be used in several ways to produce elementary battery cells, and, ultimately, batteries.
• This assembly comprising an electrode and a solid electrolyte may be backed up: to another assembly comprising an electrode and a solid electrolyte, or to a dense electrode, or to a porous electrode previously impregnated with a polymer, or to a dense electrode previously covered with a layer of electrolyte, or to a porous electrode previously covered with a porous electrolyte, the whole of which is impregnated with a polymer.
• the stacks obtained are then hot thermocompressed so as to assemble the elementary cells of the batteries.
• the impregnated ionic conductive polymer will soften and allow the solder to be made between the assembly comprising an electrode and a solid electrolyte and the subsystem to which it is backed.
• a thin layer of core-shell particles the core of which is made with from the same material inorganic E as that used to make the separator of the assembly according to the invention, and the shell is made from the same ionic conductive polymer used during the impregnation of the assembly according to the invention.
• the assembly consisting of a porous positive electrode and a separator according to the invention and impregnated with an ionic conductive polymer, is particularly well suited to the production of battery cells of very high energy density using negative lithium electrodes.
• metallic Indeed, to use negative electrodes made of metallic lithium it is imperative that the cell is entirely solid, devoid of liquid electrolyte and / or pockets of liquid electrolyte trapped in polymers or other phases. These liquid phases are privileged areas for precipitation of metallic lithium.
• the assembly of the stack obtained must be carried out by hot thermopressing. In the event that there are no organic materials to make the connection between the different sub-assemblies, the pressing temperatures must be relatively high and preferably greater than 400 ° C. Also, these treatments should be carried out under an inert atmosphere or under vacuum to avoid damaging the coating of electronically conductive material present on the porous electrode of the assembly according to the invention.
• the assembly obtained can be impregnated subsequently with an electrolyte, whether solid or liquid. Impregnation with a solid electrolyte, such as an ionic conductive polymer comprising lithium salts without a liquid phase, makes it possible to produce batteries operating with negative electrodes with low insertion potential without forming lithium dendrites.
• Example 1 Production of a porous positive electrode based on LiM ⁇ CL:
• a suspension of LiMn 2 0 4 nanoparticles was prepared by hydrothermal synthesis according to the process described in the article by Liddle et al. titled “A new one pot hydrothermal synthesis and electrochemical characterization of Lii + x Mn 2-y 04 spinel structured compounds", Energy & Environmental Science (2010) vol.3, page 1339-1346: 14.85 g of LiOH.h O were dissolved in 500 ml of water. To this solution was added 43.1 g of KMnCL and this liquid phase was poured into an autoclave.
• PVP polyvinylpyrrolidone
• the deposit obtained was then consolidated at 600 ° C. for 1 h in air in order to weld the nanoparticles together, to improve adhesion to the substrate and to perfect the recrystallization of LiMn 2 0 4 .
• the porous film obtained has an open porosity of about 45% by volume with pores of a size between 10 nm and 20 nm.
• porous film was then impregnated with an aqueous solution of sucrose at approximately 20 g / l, then was annealed at 400 ° C under N2 in order to obtain a carbon nanocoating over the entire accessible surface of the porous film. .
• Example 2 Manufacture of a porous electrode and integrated electrolytic separator assembly using the electrode according to Example 1 A cathode was produced according to Example 1. This electrode was covered with a porous layer from a suspension of U 3 PO 4 nanoparticles as indicated below.
• solution B 4.0584 g of H 3 PO 4 were diluted in 105.6 ml of water, then 45.6 ml of ethanol were added to this solution in order to obtain a second solution called hereinafter solution B.
• Solution B was then added, with vigorous stirring, to solution A.
• the reaction medium was homogenized for 5 minutes then was kept for 10 minutes with magnetic stirring. It was allowed to settle for 1 to 2 hours. The supernatant was discarded and then the remaining suspension was centrifuged for 10 minutes at 6000 rpm. Then 300 ml of water were added to resuspend the precipitate (use of a sonotrode, magnetic stirring). With vigorous stirring, 125 ml of a sodium tripolyphosphate solution at 10Og / l were added to the colloidal suspension thus obtained. The suspension has thus become more stable. The suspension was then sonicated using a sonotrode. The suspension was then centrifuged for 15 minutes at 8000 rpm. The pellet was then redispersed in 150 ml of water. The suspension obtained was then centrifuged again for 15 minutes at 8000 rpm and the pellets obtained redispersed in 300 ml of ethanol in order to obtain a suspension suitable for carrying out an electrophoretic deposit.
• Agglomerates of about 100 nm consisting of primary particles of U 3 PO 4 of 15 nm were thus obtained in suspension in ethanol, with Bis (Monoacylglycero) Phosphate (abbreviated BMP) as stabilizer.
• BMP Bis (Monoacylglycero) Phosphate
• the layer was then dried in air at 120 ° C followed by a calcination treatment at approximately 350 ° C to 400 ° C for 60 minutes was carried out on this previously dried layer in order to remove all traces of organic residues from the separator while retaining the carbon nanocoating of the porous electrode.

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