Classifications

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  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
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  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/30—Electrodes characterised by their material
  • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
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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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  • H01M4/1315—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx containing halogen atoms, e.g. LiCoOxFy
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  • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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  • H01M4/13915—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx containing halogen atoms, e.g. LiCoOxFy
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  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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  • H01M4/581—Chalcogenides or intercalation compounds thereof
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• • 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
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  • 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
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  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the invention relates to the field of electrochemistry, and more particularly thin-film electrochemical devices. It relates more specifically to electrodes which can be used in electrochemical devices such as capacitors, lithium ion batteries, mini-batteries or lithium ion batteries having a capacity greater than 1 mA h.
• the invention applies to negative electrodes and to positive electrodes. It relates to porous electrodes which can be impregnated with a solid electrolyte without liquid phase or with a liquid electrolyte.
• the invention also relates to a method for preparing such a porous electrode which implements nanoparticles of an electrode material, and the electrodes thus obtained.
• the invention also relates to a method of manufacturing a lithium ion battery comprising at least one of these electrodes, and the batteries thus obtained.
• STATE OF THE ART Lithium ion batteries have the best energy density among the various electrochemical storage technologies offered on the market. There are different architectures and chemical compositions of electrodes making it possible to produce these batteries. The methods of manufacturing lithium ion batteries are presented in numerous articles and patents; an inventory is given in the work “Advances in Lithium-Ion Batteries” (ed. W. van Schalkwijk and B.
• the electrodes of lithium ion batteries can be manufactured using coating techniques, in particular by coating. These processes make it possible to deposit on the surface of a substrate, an ink consisting of particles of active materials in the form of powder; the particles constituting this powder have an average particle size which is typically between 5 ⁇ m and 15 ⁇ m in diameter.
• deposition techniques make it possible to produce layers with a thickness of between around 50 ⁇ m and around 400 ⁇ m.
• the power and energy of the battery can be modulated by adapting the thickness and the porosity of the layers, the size of the active particles which constitute them and by the presence of various constituents within the layer such as binders or even electronic conductive materials.
• To produce microbatteries it is desired to have a lower thickness of each constituent layer of the microbattery.
• the ratio between the energy density and the power density of the electrodes can be adjusted according to the size of the particles of active materials, and indirectly to the porosity of the layers of electrodes and their thickness.
• the article by J. Newman (“Optimization of Porosity and Thickness of a Battery Electrode by Means of A Reaction-Zone Model”, J. Electrochem. Soc., 142 (1), p. 97-101 (1995)) demonstrates the respective effects of the thicknesses of the electrodes and their porosity on their discharge regime (power) and energy density.
• Mesoporous electrode layers without binder 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.
• the electronic conductor particles should be available at any point on the surface of the electrode active material particle to allow simultaneous insertion/disinsertion over the entire surface of the electrode active particles, thereby maximizing current density and minimizing local stress and heating due to inhomogeneous electrical transport.
• a mesoporous electrode comprising a mesoporous layer of at least one active electrode material having on and inside the pores of this mesoporous layer, a carbonaceous coating; this is known from WO 2021/220174 (1-TEN).
• WO 2021/220174 1-TEN
• the presence of this carbonaceous electronic conductive coating on the electrode makes it possible to reduce its electrical resistivity but does not make it possible to significantly increase its voltage and temperature resistance and its electrochemical stability.
• the production of a carbonaceous electronic conductive coating on the electrode is expensive and difficult to implement.
• the electrodes must meet increasingly stringent specifications. They must have high chemical and electrochemical stability, solidity and resistance to corrosion so as to give the batteries comprising them high cycling performance, storage stability, temperature stability and long-term reliability.
• the present invention seeks to remedy at least in part the drawbacks of the prior art mentioned above.
• the problem that the present invention seeks to solve is to provide a process for manufacturing porous electrodes having an electronic conductivity high, homogeneous and controlled pore density which is simple, safe, fast, easy to implement, inexpensive.
• the present invention also aims to provide safe porous electrodes having a high electronic conductivity, a stable mechanical structure, good thermal stability, especially at high temperature, a long life, and this regardless of the thickness of the electrode,
• Another object of the invention is to provide electrodes for batteries capable of operating at high temperature without reliability problems and without risk of fire.
• Another object of the invention is to provide porous electrodes which, in addition to the preceding characteristics, can easily be wetted and impregnated by an ionic liquid.
• Another object of the invention is to provide a method of manufacturing an electrochemical device such as a battery, a capacitor, a supercapacitor comprising a porous electrode according to the invention.
• Another object of the invention is to provide a method of manufacturing a battery having a capacity not exceeding 1 mA h, called here “microbattery”, comprising a porous electrode according to the invention.
• Yet another object of the invention is to provide electrochemical devices such as batteries, in particular lithium ion batteries and microbatteries, capacitors, supercapacitors capable of storing high energy densities, of restoring this energy with very high power densities (in particular in capacitors or supercapacitors), of withstanding high temperatures which has an excellent cycle life as well as increased safety.
• batteries in particular lithium ion batteries and microbatteries, capacitors, supercapacitors capable of storing high energy densities, of restoring this energy with very high power densities (in particular in capacitors or supercapacitors), of withstanding high temperatures which has an excellent cycle life as well as increased safety.
• an electrode for a lithium ion battery which is totally ceramic, mesoporous devoid of organic binders, the porosity of which is between 25% and 50%, the size of the channels and pores of which is homogeneous in order to ensure perfect dynamic balancing of the cell.
• the electrode according to the invention comprises a porous layer, preferably mesoporous, of at least one active material electrode whose porosity is between 25% and 50%, whose size of the channels and pores is homogeneous in order to ensure perfect dynamic balancing of the cell, and having on and inside the pores of the porous layer, a coating of an electronically conductive oxide material.
• This porous layer preferably mesoporous, entirely solid, without organic components, is obtained by the deposition, on a substrate, of agglomerates and/or aggregates of nanoparticles of active electrode materials.
• the sizes of the primary particles constituting these agglomerates and/or aggregates are of the order of a nanometer or ten nanometers, and the 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 particles, not agglomerated, each with a size of the order of a nanometer or ten nanometers makes it possible to increase the thicknesses of the deposit.
• the agglomerates must have a size of less than 300 nm.
• 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.
• agglomerates mesoporous, consisting of primary nanoparticles at least ten times smaller than the size of the agglomerate, makes it possible to considerably increase the limiting thickness of cracking of the layers.
• a lower surface tension solvent such as isopropyl alcohol (abbreviated IPA)
• IPA isopropyl alcohol
• binders, dispersants These additives and organic solvents can be removed by a heat treatment in air, such as by debinding, during a sintering treatment or during a heat treatment carried out prior to the sintering treatment.
• the agglomerates must remain small in order to be able to form during the heat treatment of the layer a continuous mesoporous film. If the agglomerates are too large, this hinders their sintering and the formation of two distinct porosities is observed in the layer: a porosity between agglomerates and a porosity inside the agglomerates.
• a porous layer preferably mesoporous, or a plate is obtained, without carbon black or organic binders, in which all the nanoparticles are welded together (by the phenomenon of necking, known elsewhere) to form a continuous mesoporous network characterized by unimodal porosity.
• the porous layer, preferably mesoporous, 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.
• the porous layer preferably mesoporous, is perfectly adherent to the metal substrate on which it was deposited or transferred (in the case of an initial deposit carried out on an intermediate substrate).
• the heat treatments carried out at high temperature to sinter the nanoparticles together make it possible to dry the electrode perfectly and to eliminate all traces of water or solvents or other organic additives (stabilizers, binders) adsorbed on the surface of the particles of active material.
• High temperature heat treatment may be preceded by 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 between 25% and 50% 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 contributes to maximizing the power densities and lifetimes of the battery cell.
• the electrode according to the invention has a high specific surface, which reduces the ionic resistance of the electrode.
• this electrode 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 as the thickness of the electrode increases.
• this electronic conductivity must be perfectly homogeneous throughout the electrode in order to avoid locally having more electrically resistive zones which could lead to the formation of a hot spot during the battery's power operation.
• a coating of an electronically conductive oxide material is produced on and inside the pores of the porous layer.
• This electronically conductive oxide material can be deposited from a precursor of said electronically conductive oxide material, in particular from a liquid precursor of said electronically conductive oxide material.
• the method according to the invention which necessarily involves a step of deposition of agglomerated nanoparticles of electrode material (active material), causes the nanoparticles to "weld” together naturally to generate, after consolidation such as annealing, a porous, rigid, three-dimensional structure, without organic binder; this porous layer, preferably mesoporous, is perfectly well suited to the application of a surface treatment, by gaseous or liquid means, which goes into the depth of the open porous structure of the layer.
• a first object of the invention is a process for manufacturing a porous electrode, in particular for electrochemical devices, such as a battery, in particular a lithium ion microbattery or a lithium ion battery having a capacity greater than 1 mA h, said electrode comprising a porous layer of at least one P electrode active material deposited on a substrate, and a layer of an electronically conductive oxide material present on and inside the pores of said porous layer, said electrode 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 manufacturing method being characterized in that:
• a substrate and a colloidal suspension or a paste comprising aggregates or agglomerates of monodisperse primary nanoparticles, of at least one electrode active material P, with an average primary diameter D 5 o of between 2 nm and 150 nm, preferably between 2 nm and 100 nm, and more preferably between 2 nm and 60 nm, are supplied, said aggregates or agglomerates having an average diameter D50 between 50 nm and 300 nm, and preferably between 100 nm to 200 nm, knowing that said substrate may be a substrate capable of acting as an electric current collector, or be an intermediate substrate,
• a layer is deposited on at least one face of said substrate from said colloidal suspension or paste provided in step (a), by a process selected from the group formed by: electrophoresis, extrusion, a printing process, preferably ink-jet printing or flexographic printing, a coating process, preferably by doctor blade, roller, curtain, dip-shrink, or through a slot-shaped die,
• step (c) said layer obtained in step (b) is dried, if necessary, before or after having separated said layer from its intermediate substrate, then, optionally, said dried layer is heat-treated, preferably under an oxidizing atmosphere; then said layer is consolidated, by heat and/or mechanical treatment, preferably by sintering, to obtain a porous layer, preferably mesoporous,
• an ionic conductive and electronic insulating layer is formed on and inside the pores of said porous layer coated with a layer of an electronically conductive oxide material obtained in step (d).
• step (b) the deposition can take place on one or both sides of the substrate.
• said layer is separated in step (c) from said intermediate substrate, to form, in particular 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 provided, covered on at least one side, respectively on both sides, with a thin layer of conductive adhesive or with a thin layer of nanoparticles of at least one P electrode active material, then at least one porous plate is glued on one side, preferably on each of the sides, of the electrically conductive sheet, so as to obtain a porous plate or layer, of mesoporous preference on a substrate capable of acting as a current collector.
• the terms "porous layer” and "porous plate” are interchangeable.
• step (d) during a step (d1), a layer of a precursor of an electronically conductive oxide material is deposited on and inside the pores of said porous layer, and during a step (d2), the transformation of the precursor of an electronically conductive oxide material, deposited during step (d1) on said porous layer, into an electronically conductive material is carried out, so that said porous layer has on and inside the pores, a layer of said oxide material.
• electronic conductor during a step (d1), a layer of a precursor of an electronically conductive oxide material is deposited on and inside the pores of said porous layer, and during a step (d2), the transformation of the precursor of an electronically conductive oxide material, deposited during step (d1) on said porous layer, into an electronically conductive material is carried out, so that said porous layer has on and inside the pores, a layer of said oxide material. electronic conductor.
• step (d1) is carried out by immersing the porous layer in a liquid phase comprising a precursor of said electronically conductive oxide material, and said transformation of the precursor of an electronically conductive oxide material into electronically conductive material, during step (d2), is carried out by heat treatment such as calcination, preferably carried out in air or in an oxidizing atmosphere.
• said precursor of the electronically conductive oxide material is chosen from organic salts containing one or more metallic elements capable, after heat treatment such as calcination, of forming an electronically conductive oxide, and said transformation into electronically conductive material is a heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere.
• organic salts are preferably chosen from:
• the metallic element capable, after heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere, of forming an electronically conductive oxide, and/or preferably, the metallic element is chosen from tin, zinc, indium, gallium, or a mixture of two or three or four of these elements.
• said porous layer obtained at the end of step (c) has a specific surface of between 10 m 2 /g and 500 m 2 /g and/or a thickness of between 4 ⁇ m and 400 ⁇ m.
• said colloidal suspension or paste supplied in step (a) comprises organic additives, such as residual organic ligands, stabilizers, binders or solvents
• said layer dried in step c) or said porous plate is heat treated, preferably under an oxidizing atmosphere.
• said aforementioned P electrode active material is used to manufacture a cathode.
• 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 ⁇ 0.20 and -0.3 ⁇ 5 ⁇ 0.3; Ga0.10 Ti 0.80 Nb 2.10 O 7 ; Fe 0.10 Ti 0.80 Nb 2.10 O 7 ; o MxTi 2 -2xNbio + x0 2 9 ⁇ 5 o in which 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 ⁇ 5 ⁇ 0.3; o Tii.
• o M 1 and M 2 are each at least one element chosen 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 possibly being identical or different from each other, o M 3 is at least one halogen, o and in which 0 ⁇ w ⁇ 5 and 0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 2 and z ⁇ 0.3; o TiNb 2 C>7-zM 3 z or Li w TiNb 2 O 2 -zM 3 z in which M 3 is at least one halogen, preferably chosen from F, Cl, Br, I or a
• the oxides SnC>2, SnO, Ii 2 SnO 3 , SnSiCh, Li x SiO y with x> 0 and 2>y>0, Li4Ti50i2, TiNb2O?, CO3O4, SnBo.ePo, 402.9 and TiO2, o the composite oxides TiNb2O? comprising between 0% and 10% by mass of carbon, preferably the carbon being chosen from graphene and carbon nanotubes.
• said aforementioned P-electrode active material is used to manufacture an anode.
• Another object of the invention is a porous electrode, in particular for electrochemical devices, comprising a porous layer of at least one active P electrode material deposited on a substrate, and a layer of an electronically conductive oxide material arranged on and inside the pores of said porous layer, in that it is free of binder, that it has a porosity of between 20% and 60% by volume, preferably between 25% and 50%, and pores of average diameter less than 50 nm.
• Another object of the invention is a porous electrode capable of being obtained by the process according to the invention, characterized in that the porous electrode comprises a porous layer of at least one active electrode material P deposited on a substrate, and a layer of an electronically conductive oxide material placed on and inside the pores of said porous layer, in that it is free of binder, that it has 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.
• Another object of the invention is a method of manufacturing an electrochemical device, such as a battery, a capacitor, a supercapacitor, a cell photoelectrochemical, or an electronic device, such as a photovoltaic cell, implementing the process for manufacturing a porous electrode according to the invention or implementing a porous electrode according to the invention.
• an electrochemical device such as a battery, a capacitor, a supercapacitor, a cell photoelectrochemical, or an electronic device, such as a photovoltaic cell
• Another object of the invention is a process for manufacturing an electrochemical or electronic device, such as a battery, a capacitor, a supercapacitor, a photoelectrochemical cell, a photovoltaic cell, and in particular a process for manufacturing a lithium ion battery, such as a microbattery or a lithium ion battery having a capacity greater than 1 mA h, implementing the process for manufacturing a porous electrode according to the invention or implementing a porous electrode according to the invention.
• an electrochemical or electronic device such as a battery, a capacitor, a supercapacitor, a photoelectrochemical cell, a photovoltaic cell
• a lithium ion battery such as a microbattery or a lithium ion battery having a capacity greater than 1 mA h
• the battery according to the invention can be designed and dimensioned so as to have a capacity less than or equal to 1 mA h and up to about 1 mA h (commonly called “microbattery”), or it can be designed and dimensioned so as to have a greater capacity, greater than 1 mA h or even significantly greater than this value.
• microbatteries but also certain batteries with a larger capacity, are designed as surface-mounted components (a technology commonly abbreviated as "SMT", Surface-Mount Technology), so as to be compatible with microelectronics manufacturing processes, in particular with robotic processes for filling electronic boards known under the term "pick and place”.
• said porous electrode 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 and at least one lithium salt; o a mixture of at least one aprotic solvent and at least one ionic liquid and at least one lithium salt; o a polymer made ionically conductive by the addition of at least one lithium salt; and o a polymer made ionically 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 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 and at least one lithium salt; o a mixture of at least one
• Another object of the invention is a battery, preferably a lithium ion battery, capable of being obtained by the process according to the invention.
• the battery according to the invention can be a micro-battery, the capacity of which is less than approximately 1 mA h, a mini-battery, the capacity of which is greater than 1 mA h and up to approximately 1 mA h, or a battery whose capacity is greater than 1 mA h.
• the method according to the invention lends itself particularly well to the production of layers with a thickness greater than 1 ⁇ m or even greater than 5 ⁇ m, while ensuring a low series resistance of the battery.
• Another object of the invention is an electrochemical or electronic device, such as a battery, a capacitor, a supercapacitor, a photovoltaic cell, comprising a porous electrode according to the invention or capable of being obtained by the method according to the invention.
• the present invention relates to a porous electrode whose accessible surface, i.e. the external surface of the electrode as well as the interior of the accessible pores of the electrode, is coated with an electronically conductive oxide material.
• electronically conductive oxide includes electronic conductive oxides and electronic semiconductor oxides.
• the size of a particle is defined by its largest dimension.
• nanoparticle is meant any particle or object of nanometric size having at least one of its dimensions less than or equal to 100 nm.
• ionic liquid any liquid salt, capable of transporting electricity, differing from all molten salts by a melting temperature below 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 we mean any solid which has within its structure pores called “mesopores” having an intermediate size between that of micropores (width less than 2 nm) and that of 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.
• the term “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 that the pores of a size smaller than that of the mesopores are called by those skilled in the art “micropores”.
• porous layer means a layer which has pores.
• mesoporous layer means a layer which has mesopores. In these layers, pores and mesopores contribute significantly to the total pore volume; this state of affairs is translated by the expression “Porous/mesoporous layer with a porosity greater than X% by volume” used in the present description.
• aggregate means, according to IUPAC definitions, a loosely bound assembly of primary particles.
• these primary particles are nanoparticles with a diameter that can be determined by transmission electron microscopy.
• An aggregate of aggregated primary nanoparticles can normally be destroyed (i.e. 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, according to IUPAC definitions, a strongly bound assembly of primary particles or aggregates.
• the porous electrodes according to the invention are produced from a colloidal suspension of clusters and/or agglomerates of nanoparticles or a paste.
• the nanoparticles are prepared directly at their primary size by precipitation, Pechini synthesis, 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 favors during the subsequent process steps the formation of an interconnected mesoporous network with electronic and ionic conduction, thanks to the “necking” phenomenon.
• Binders can also be added to the suspension of nanoparticles (clusters and/or agglomerates of nanoparticles, knowing that these clusters are also in the form of nanoparticles) to facilitate the production of deposits or raw bands, in particular thick deposits without cracks. It is a colloidal suspension or a paste comprising aggregates or agglomerates of nanoparticles which is then used for the manufacture of a dried porous layer of an active P-electrode material.
• the process for manufacturing an electrode according to the invention comprises the application of such a colloidal suspension or a paste comprising aggregates or agglomerates of monodisperse primary nanoparticles of at least one active material of electrode P, on a substrate to form a layer, then the drying of said layer in order to obtain a porous layer.
• This sequence comprising the application of this colloidal suspension or paste on a substrate to form a layer and its drying can be repeated several times in order to increase the thickness of the porous layer.
• the final thickness of this porous layer is advantageously less than or equal to 5 mm, preferably between around 1 ⁇ m and around 500 ⁇ m.
• the thickness of this porous layer is advantageously less than 300 ⁇ m, preferably between about 5 ⁇ m and about 300 ⁇ m, preferably between 5 ⁇ m and 150 ⁇ m.
• the colloidal suspension or paste is deposited on a substrate, by any appropriate technique, and in particular by electrophoresis, by extrusion, by the ink-jet printing process hereinafter "ink-jet", by spraying, by flexographic printing, by a coating process, preferably with a doctor blade (technique known in English under the term “doctor blade” or “tape casting"), by roller coating (in English "roll coating"), by curtain coating (in English "curtain coating”) , by extrusion through a die in the form of a slot (in English “slot-die”), or by soaking-withdrawal (in English “dip-coating”).
• the colloidal suspension or paste (ink) has a viscosity adapted to the coating techniques usually used for the manufacture of electrodes, and thus can be deposited on a substrate, it is advantageous to use a colloidal suspension or paste having a dry extract of less than 30% by mass.
• a mesoporous layer is obtained during the subsequent process steps having an average diameter of the mesopores of between 2 nm and 50 nm.
• the porous layer of at least one active material of electrode P can be deposited by the ink-jet printing process (called “ink-jet” in English) or by a coating process, and in particular by the coating process by dipping (called “dip-coating” in English), by roller coating (called “roll coating” in English), by curtain coating (called “curtain coating” in English), by coating through a slot-shaped die (called “slot-die” in English), or by scraping (called “doctor blade” in English), and this from a fairly concentrated suspension comprising aggregates or agglomerates of nanoparticles of the active material P.
• porous electrode layer by electrophoresis, but a less concentrated suspension containing agglomerates of nanoparticles of the active material P is then advantageously used.
• the processes for depositing aggregates or agglomerates of nanoparticles by electrophoresis, by extrusion, by the dip coating process, by ink jet, by roller coating, by curtain coating, by coating through a die in the form of a slot or by scraping are simple, safe, easy to implement, easy to industrialize processes and which make it possible to obtain a homogeneous final porous layer.
• Electrophoretic deposition allows layers to be deposited uniformly over large areas with high deposition rates. Coating techniques, in particular those mentioned above, make it possible to simplify the management of baths compared to electrophoretic deposition techniques because the suspension does not become depleted in particles during deposition. Deposition by inkjet printing makes it possible to make localized deposits.
• Porous layers in thick layer can be produced in a single step by roller coating, by curtain coating, by coating through a slot (called “slot die coating” in English), or by scraping (i.e. with a doctor blade).
• the technique for depositing the colloidal suspension or paste (ink), and the conduct of the deposition process must be compatible with the viscosity of the colloidal suspension or paste (ink) used, and vice versa.
• the substrate is advantageously an intermediate substrate or a substrate that can serve as a current collector.
• said substrate is a substrate capable of acting as an electric current collector.
• the substrate can advantageously be a metal substrate or an electronically conductive carbon substrate, in particular based on graphite, graphene and/or carbon nanotubes.
• Said substrate on which the colloidal suspension or paste (ink) is deposited acts as a current collector for the electrode.
• the colloidal suspension or paste (ink) can be deposited on one or both sides of the substrate, in particular by the deposition techniques indicated above.
• the current collector within electrochemical devices employing electrodes according to the invention can be a stable substrate within the operating potential range of the electrochemical device.
• the current collector must be a stable substrate in a potential range, preferably between 2.5 V and 5 V for the cathode and between 0 V and 2.5 V for the anode, relative to the lithium potential.
• a metal substrate is chosen, for example a metal strip (ie a laminated metal sheet).
• the substrate may in particular be made of tungsten, molybdenum, chromium, titanium, tantalum, zirconium, niobium, 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.
• Tungsten, molybdenum, chromium, titanium, tantalum, zirconium, niobium, stainless steel and their alloys are particularly resistant to high temperature heat treatments; they are thus particularly well suited as sintered electrode substrate.
• this substrate capable of acting as an electric current collector, with a conductive or semi-conductive oxide before the deposition of the colloidal suspension or paste (ink), which makes it possible in particular to protect less noble substrates such as copper, nickel, aluminum and carbon, in particular in the form of graphite.
• These less noble substrates can thus be used as electrode substrate.
• It can be a conductive carbon sheet (typically graphite), a metallic sheet, or a metallized non-metallic sheet (i.e. coated with a layer of metal).
• the substrate is preferably chosen from copper, nickel, molybdenum, tungsten, tantalum, chromium, niobium, zirconium, titanium foils, and alloy foils comprising at least one of these elements. You can also use stainless steel. These substrates have the advantage of being stable over a wide potential range and resistant to heat treatment.
• Copper, nickel, molybdenum and their alloys are preferably used as anode substrate.
• Carbon-based substrates in particular in the form of graphite, based on nickel-chromium alloys, stainless steels, chromium, titanium, aluminum, tungsten, molybdenum, tantalum, zirconium, niobium or alloys containing at least one of these elements are preferably used as cathode electrical current collector substrate.
• These anodic and/or cathodic substrates may or may not be coated with a conductive and electrochemically inert layer. Such layers can be produced by deposition of nitrides, carbides, graphites, gold, palladium and/or platinum.
• the colloidal suspension or paste (ink) can be deposited on one or both sides of the substrate capable of acting as a current collector.
• the layer deposited on this substrate is then dried so as to obtain a porous layer of an active material of P electrode.
• This porous layer of an active P-electrode material thus dried is then consolidated.
• This consolidation can be carried out by pressing and/or heat treatment, ie by heat treatment (heating), by heat treatment preceded by mechanical treatment, and optionally by thermomechanical treatment, typically thermocompression.
• this treatment leads to a partial coalescence of the primary nanoparticles in the aggregates, or the agglomerates, and between adjacent aggregates or agglomerates; this phenomenon is called “necking” or “neck formation”.
• the temperature needed to obtain “necking” depends on the material; taking into account the diffusive character 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 affects the porosity. It is thus possible to obtain an electrode with a desired porous or mesoporous ceramic structure of controlled porosity while maintaining a perfectly homogeneous channel size. During this thermomechanical or thermal treatment, the electrode layer will be freed of any constituent and organic residue (such as the liquid phase of the suspension of nanoparticles, binders and any surfactants): it becomes an inorganic layer (ceramic).
• a coating of an electronically conductive oxide material is produced on and inside the pores of said porous layer, i.e. on the accessible surface of said porous layer, as will be explained later in paragraph 3.3.
• the colloidal suspension or paste (ink) is not deposited on a substrate capable of acting as an electric current collector, but on an intermediate substrate, which is typically used temporarily.
• the colloidal suspension or paste (ink) is deposited on one face of the intermediate substrate, so as to be able subsequently to easily separate the layer obtained from this intermediate substrate.
• a suspension of nanoparticles and/or agglomerates of nanoparticles of P electrode active material preferably from a concentrated suspension containing nanoparticles of P electrode active material (i.e. less fluid, preferably pasty), fairly thick layers (called “green sheet” in English).
• These thick layers can be deposited by any appropriate means, in particular by the inkjet printing process, by spraying, by flexographic printing, by a coating process, preferably with a doctor blade, by roller coating, by curtain coating, by extrusion through a slot-shaped die, or by dipping.
• the processes for depositing nanoparticles, by the dipping coating process, by the inkjet printing process, by roller coating, by curtain coating, by extrusion through a slot-shaped die, by spraying, by flexographic printing or by coating by scraping are simple, safe, easy to implement and industrialize processes that make it possible to obtain a homogeneous deposit.
• Inkjet printing makes it possible to deposit the colloidal suspension or paste (ink) in a localized manner, in the same way as deposits by scraping under a mask. Thick layers can be obtained in a single step by roller, curtain, slot-die, dipping or doctor coating techniques.
• Said intermediate substrate may be a flexible substrate, which may be a polymer sheet, for example poly(ethylene terephthalate), abbreviated PET.
• 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 before or after drying, preferably after drying and before any heat treatment.
• the thickness of the layer after drying is advantageously less than or equal to 5 mm, advantageously between around 1 ⁇ m and around 500 ⁇ m.
• the thickness of the layer after drying, ie of the unsintered electrode is advantageously less than 300 ⁇ m, preferably between about 5 ⁇ m and about 300 ⁇ m, preferentially between 5 ⁇ m and 150 ⁇ m.
• the method for manufacturing an electrode for an electrochemical device uses an intermediate polymer substrate (such as PET) and results in a strip called “raw strip”.
• This raw strip is then separated from its substrate; it then forms self-supporting plates or sheets (the term “plate” is used hereafter, whatever its thickness).
• These self-supporting porous plates or sheets are then dried. After drying, these self-supporting porous plates or sheets can then be heat treated, preferably under an oxidizing atmosphere, if necessary, in order to remove organic constituents. These self-supporting porous plates or sheets are then consolidated, as explained above in paragraph 3.1.
• These plates thus sintered have a thickness advantageously less than or equal to 5 mm, preferably between about 1 ⁇ m and about 500 ⁇ m.
• the thickness of the porous plate after sintering is advantageously less than 300 ⁇ m, preferably between around 5 ⁇ m and around 300 ⁇ m, preferably between 5 ⁇ m and 150 ⁇ m.
• an electrically conductive sheet is also provided, covered on at least one of its faces, preferably on both faces, with a thin intermediate layer of nanoparticles of the active electrode material P, preferably identical to those constituting the plate, or covered on at least one of its faces, preferably on both faces with a thin layer of conductive adhesive (filled with graphite) or a sol-gel deposit loaded with conductive particles.
• Said thin layers preferably have a thickness of less than 1 ⁇ m.
• This electrically conductive sheet can be a metal strip or a sheet of graphite.
• said electrically conductive sheet is metallic, it is preferably a rolled sheet, i.e. obtained by rolling. Rolling may optionally be followed by a final anneal, which may be a softening (total or partial) or recrystallization annealing, depending on the terminology of metallurgy. It is also possible to use a sheet deposited by electrochemical means, for example an electrodeposited copper sheet or an electrodeposited nickel sheet.
• This electrically conductive sheet is then placed on a plate or interposed between two plates obtained previously after drying and possibly heat treatment (ie sintering).
• the assembly is then heat-pressed so that said thin intermediate layer of nanoparticles is transformed by sintering and consolidates the plate/substrate or plate/substrate/plate assembly to obtain a rigid and one-piece subassembly.
• sintering the bond between the plate and the layer intermediary is established by diffusion of atoms; this phenomenon is known by the English term “diffusion bonding”.
• This assembly is done with two plates, preferably made from the same nanoparticles of the electrode active material P, and the metal sheet placed between these two plates.
• One of the advantages of the second embodiment is that it makes it possible to use inexpensive substrates such as aluminum strips, copper or graphite strips. Indeed, these strips do not withstand the heat treatments for consolidating the deposited layers; gluing them to the plates after their heat treatment also prevents their oxidation.
• This assembly by "diffusion bonding" can be carried out separately as has just been described, and the plate/substrate or plate/substrate/plate subassemblies thus obtained, once coated with a layer of an electronically conductive oxide material, can be used in the manufacture of an electrochemical device such as a battery.
• an electronic conductive oxide coating is produced on and inside the pores of these porous layers, porous plates or self-supporting porous sheets (hereinafter referred to interchangeably as porous layers or porous plates), i.e. on the accessible surface of these porous layers or porous plates, so that they can be used as porous electrodes, in particular in electrochemical devices such as in batteries, microbatteries. te ri es or capacitors.
• the layer of electronically conductive oxide material can be obtained in different ways, in particular by the technique of depositing atomic layers ALD (Atomic Layer Deposition) or by immersion in a liquid phase comprising a precursor of the electronically conductive oxide material followed by the transformation of said precursor from an electronically conductive material into an electronically conductive material, in particular by heat treatment.
• ALD Atomic Layer Deposition
• the techniques for producing the coating of an electronically conductive oxide material indicated here only the free surfaces of the pores are covered, in particular the accessible surfaces of the porous layer or plate and those of the substrate.
• the “welding” zone between the porous layer and the substrate is not covered by the electronically conductive oxide material.
• the techniques indicated here make it possible to obtain a constant thickness of said layer of an electronically conductive oxide material within the porous, preferably mesoporous, layer or plate. Its thickness is typically between 0.5 nm and 10 nm, preferably less than 2 nm.
• ALD deposition techniques are particularly well suited to cover, layer by layer, by a cyclic process, rigid surfaces having a high roughness in a completely sealed and compliant manner. They make it possible to produce conformal layers (totally covering) of very thin thickness, free of defects, such as holes (layers called “pinhole free”, free of holes).
• ALD atomic layer deposition
• the deposition by ALD being typically carried out at a temperature comprised between 100° C. and 300° C., the residual organic matter, such as organic binders, would risk, in this temperature range, decomposing and polluting the deposition reactor by ALD.
• the growth of the layer deposited by ALD is influenced by the nature of the substrate. A layer deposited by ALD on a substrate presenting different zones of different chemical natures will have an inhomogeneous growth, which can lead to a loss of integrity.
• a layer of an electronically conductive material can be formed, very advantageously, by immersion in a liquid phase comprising a precursor of said electronically conductive material followed by the transformation of said precursor from an electronically conductive material into an electronically conductive material by heat treatment.
• This method is simple, fast, easy to implement and is less expensive than the ALD atomic layer deposition technique.
• said precursor of the electronic conductive material is chosen from organic salts containing one or more metallic elements capable, after heat treatment such as calcination, of preferably carried out in air or under an oxidizing atmosphere, to form an electronically conductive oxide.
• These metallic elements, preferably these metallic cations can advantageously be chosen from tin, zinc, indium, gallium, or a mixture of two or three or four of these elements.
• the organic salts are preferably chosen from an alcoholate of at least one metallic element capable, after heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere, of forming an electronically conductive oxide, an oxalate of at least one metallic element capable, after heat treatment such as calcination, preferably carried out under air or under an oxidizing atmosphere, of forming an electronic conductive oxide and an acetate of at least one metallic element capable, after heat treatment such as calcination, of preferably carried out in air or under an oxidizing atmosphere, to form an electronically conductive oxide.
• said electronically conductive material may be an electronically conductive oxide material, preferably chosen from:
• doped oxides based on zinc oxide the doping being preferably with gallium (Ga) and/or aluminum (Al) and/or boron (B) and/or beryllium (Be), and/or chromium (Cr) and/or cerium (Ce) and/or titanium (Ti) and/or indium (In) and/or cobalt (Co) and/or nickel (Ni) and/or copper (Cu) ) and/or manganese (Mn) and/or germanium (Ge),
• doped oxides based on indium oxide the doping being preferably with tin (Sn), and/or gallium (Ga) and/or chromium (Cr) and/or cerium (Ce) and/or titanium (Ti) and/or indium (In) and/or cobalt (Co) and/or nickel (Ni) and/or copper (Cu) and/or manganese (Mn) and/or germanium (Ge),
• the doping being preferably with arsenic (As) and/or with fluorine (F) and/or with nitrogen (N) and/or with niobium (Nb) and/or with phosphorus (P) and/or with antimony (Sb) and/or with aluminum (Al) and/or with titanium (Ti), and/or with gallium (Ga) and/or with chromium (Cr) and/or with cerium (Ce) and/or indium (In) and/or cobalt (Co) and/or nickel (Ni) and/or copper (Cu) and/or manganese (Mn) and/or germanium (Ge).
• an electronically conductive material preferably an electronically conductive oxide material
• the porous layer can be immersed in a rich solution of the precursor of the desired electronically conductive material.
• the electrode is dried and subjected to a heat treatment, preferably in air or in an oxidizing atmosphere, at a temperature sufficient to transform the precursor of the electronic conductive material of interest into an electronic conductive material.
• a coating of electronically conductive material is formed, preferably a coating of an electronically conductive oxide material, more preferably SnC>2, ZnO, I ⁇ Ch, Ga2O3, or indium-tin oxide, over the entire internal surface of the electrode, perfectly distributed.
• the presence of this layer of electronically conductive oxide on and inside the pores of the porous layer or plate, in particular because the electronically conductive coating is in the form of oxide makes it possible to improve the final properties of the electrode, in particular to improve the voltage resistance of the electrode, its temperature resistance, to improve the electrochemical stability of the electrode, in particular when it is in contact with a liquid electrolyte, to reduce the polarization resistance of the electrode, and this even when the electrode is thick.
• an electronically conductive coating in the form of an oxide, in particular of the I n 2 C>3, SnC>2, ZnO, Ga2O3 type or a mixture of one or more of these oxides, on and inside the pores of the porous layer of an active electrode material, when the electrode is thick, and/or when the active materials of the porous layer are too resistive.
• the electrode according to the invention is porous, preferably mesoporous, and its specific surface is large.
• the increase in the specific surface of the electrode multiplies the exchange surfaces, and consequently, the power of the battery, but it also accelerates the parasitic reactions.
• the presence of these electronically conductive coatings in the form of oxide on and inside the pores of the porous layer will make it possible to block these parasitic reactions.
• the electronic conductive coating in the form of oxide on and inside the pores of a porous layer is easier and less expensive to achieve than a carbonaceous coating.
• the transformation of the precursor of the electronically conductive material into an electronically conductive coating does not need to be carried out under an inert atmosphere, unlike the carbonaceous coating.
• This coating of an encapsulating electronic conductive oxide material typically has a thickness of less than 10 nm, preferably less than 5 nm and more preferably less than 2 nm.
• This coating gives the electrode good electronic conduction, regardless of its thickness.
• the fact of using an electronically conductive coating in the form of an oxide instead of a carbonaceous coating gives, in particular, better performance to the final electrode. It is noted that the formation of this coating of an electronically conductive oxide material is possible after sintering because the electrode is entirely solid, without organic residues, and resists the thermal cycles imposed by the various heat treatments.
• an electronically conductive oxide material a layer which is electronically insulating and which has good ionic conductivity; its thickness is typically of the order of 0.5 nm to 20 nm, preferably less than 5 nm, and even more preferably less than 2 nm.
• Said ionic conductive and electronic insulating layer can be of inorganic or organic nature. More particularly, among the inorganic layers one can use for example an oxide, a phosphate or a borate conducting lithium ions, and among the organic layers one can use polymers (for example PEO containing optionally lithium salts, or a sulfonated tetrafluoroethylene copolymer such as NationalTM, CAS No. 31175-20-9).
• This ionic conductive and electronic insulating layer makes it possible to limit the dissolution of ions from the electrode and their migration towards the electrolyte, knowing that in LiM ⁇ C electrodes manganese risks dissolving in certain liquid electrolytes, in particular at high temperature.
• the layer of electronically conductive oxide material is covered with an ionic conductive layer, it is the latter which will mainly perform the protective functions, as described above (in particular preventing the dissolution of the electrode).
• a porous electrode according to the invention is obtained, arranged on a metallic substrate serving as an electronic current collector or located on either side of a metallic substrate serving as an electronic current collector.
• the electrode/substrate/electrode subassemblies thus obtained, by the first or the second embodiment, can be used in the manufacture of an electrochemical device such as a battery, and in particular a microbattery.
• An assembly by diffusion bonding can also be achieved by stacking and thermopressing the entire structure of the electrochemical device (such as a battery and in particular a microbattery); in this case, a multilayer stack is assembled comprising a first anode according to the invention, its metallic substrate, a second anode according to the invention, a layer of solid electrolyte, a first cathode according to the invention, its metallic substrate, a second cathode according to the invention, a new layer of solid electrolyte, and so on.
• This electrode/substrate/electrode subassembly can be used to manufacture electrochemical devices such as batteries (and in particular microbatteries). Whatever the embodiment of the electrode/substrate/electrode subassembly, the electrolyte film is then deposited on the latter. We then make the cutouts necessary to make a battery with several elementary cells, then we stack the subassemblies (typically in “head to tail” mode) and thermocompression is carried out to weld the anodes and cathodes together at the level of the solid electrolyte.
• the cutouts needed to make a battery with several elementary cells can be made, before depositing a film of electrolyte, on each anode/substrate/anode and cathode/substrate/cathode subassembly. Then the anode/substrate/anode subassemblies and/or the cathode/substrate/cathode subassemblies are coated with an electrolyte film, then the subassemblies are stacked (typically in “head to tail” mode) and thermocompression is carried out to weld the anodes and the cathodes together at the level of the electrolyte film.
• thermocompression is done at a relatively low temperature, which is possible thanks to the very small size of the nanoparticles. As a result, no oxidation of the metal layers of the substrate is observed.
• Example 1 Production of a Mesoporous Cathode Based on LiM 2 C According to the Invention A suspension of LiMn 2 O 4 nanoparticles was prepared by hydrothermal synthesis according to the method described in the article by Liddle et al. entitled “A new one pot hydrothermal synthesis and electrochemical characterization of Lii +x Mn2- y O4 spinel structured compounds”, Energy & Environmental Science (2010) vol.3, page 1339-1346:
• the aggregates obtained consisted of aggregated primary particles with a size of 10 to 20 nm.
• the aggregates obtained had a spherical shape and an average diameter of about 150 nm; they were characterized by X-ray diffraction and electron microscopy.
• PVP polyvinylpyrrolidone
• This layer was consolidated at 600°C for 1 hour in air in order to bond the primary nanoparticles together, to improve adhesion to the substrate and to perfect the recrystallization of LiMn2O4.
• the porous layer thus obtained has an open porosity of about 45% by volume with pores of a size between 10 nm and 20 nm.
• a thin layer of ZnO was then produced on and inside the pores of the mesoporous cathode based on LiM ⁇ C, in a P300B type ALD reactor (supplier: Picosun), under an argon pressure of 2 mbar at 180°C.
• Argon (Ar) was used here both as carrier gas and for purging. Before each deposition, a drying time of 3 hours was applied.
• the precursors used were water and diethylzinc.
• a deposition cycle consisted of the following steps: Injection of diethylzinc, purge of the chamber with Ar, injection of water, purge of the chamber with Ar.
• This cycle is repeated to reach a coating thickness of 1.5 nm.
• the product was dried under vacuum at 120° C. for 12 hours to remove the residues of reagents on the surface and thus obtain a mesoporous cathode based on LiMn2C>4 having on all of its accessible surface a coating of 1.5 nm of ZnO.
• a suspension of Li4TisOi2 nanoparticles was prepared by glycothermal synthesis: 190 ml of 1,4-butanediol were poured into a beaker, and 4.25 g of lithium acetate was added with stirring. The solution was kept under stirring until the acetate was completely dissolved. 16.9 g of titanium butoxide were taken under an inert atmosphere and introduced into the acetate solution. The solution was then stirred for a few minutes before being transferred to an autoclave previously filled with an additional 60 ml of butanediol. The autoclave was then closed and purged with nitrogen for at least 10 minutes. The autoclave was then heated to 300°C at a rate of 3°C/min and maintained at this temperature for 2 hours, with stirring. At the end, it was left to cool, still stirring.
• a white precipitate suspended in the solvent was obtained.
• This precipitate was subjected to a succession of centrifugation-redispersion steps in ethanol to obtain a pure colloidal suspension, with low ionic conductivity. It contained aggregates of approximately 150 nm made up of primary particles of 10 nm.
• the zeta potential was of the order of -45 mV.
• the product was characterized by X-ray diffraction and electron microscopy.
• a thin layer of SnO2 was then produced on and inside the pores of the mesoporous anode based on Li4Ti50i2.
• PVP polyvinyl pyrrolidone
• SnC2C>4 tin oxalate were added to this aqueous solution of PVP.
• the Li4TisOi2-based mesoporous anode was then immersed in this solution so that the tin oxalate could deposit on and inside the pores of the Li4TisOi2-based mesoporous anode.
• the electrode was dried and then subjected to a heat treatment, preferably under nitrogen, at 600°C for 5 hours so as to form a homogeneous coating of SnC>2 2 nm thick, over the entire accessible surface of the electrode, i.e. on and inside the pores of the anode and this, in a perfectly distributed manner.
• the reaction medium was homogenized for 5 minutes then was maintained for 10 minutes with magnetic stirring. It was left to settle for 1 to 2 hours. The supernatant was discarded then the remaining suspension was centrifuged for 10 minutes at 6000 rpm. Then 300 ml of water was added to resuspend the precipitate (use of a sonotrode, magnetic stirring). With vigorous stirring, 125 ml of a 100 g/l sodium tripolyphosphate solution were added to the colloidal suspension thus obtained. The suspension thus became 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. Then the suspension obtained was again centrifuged 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 electrophoretic deposition.
• Thin porous layers of U3PO4 were then deposited by electrophoresis on the surface of the anode and cathode previously prepared by applying an electric field of 20V/cm to the suspension of U3PO4 nanoparticles previously obtained, for 90 seconds to obtain a layer with a thickness of about 1.5 ⁇ m. This layer was air-dried at 120°C to remove all traces of organic residue, and then it was calcined at 350°C for one hour in air. vs. Realization of an electrochemical cell
• the stack was placed under a pressure of 1.5 MPa then dried under vacuum for 30 minutes at 10 -3 bars.
• the press platens were then heated to 450°C with a rate of 4°C/second.
• the stack was then thermo-compressed under a pressure of 45 MPa for 1 minute, then the system was cooled to ambient temperature.
• This assembly was then impregnated in an electrolytic solution comprising PYR14TFSI and LiTFSI at 0.7 M.
• the ionic liquid instantly enters the porosities by capillarity.
• the system was kept immersed for 1 minute, then the surface of the cell stack was dried with an N2 slide.

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