FR3131449A1 - METHOD FOR MANUFACTURING A POROUS ELECTRODE, AND MICROBATTERY CONTAINING SUCH ELECTRODE - Google Patents

Abstract

The present invention relates to a porous electrode usable in batteries, such as a lithium ion microbattery. This porous electrode comprises a porous layer of at least one P electrode active material deposited on a substrate, and a coating of electronically conductive oxide material present on and inside the pores of said porous layer of at least one material P-electrode active.

Description

METHOD FOR MANUFACTURING A POROUS ELECTRODE, AND MICROBATTERY CONTAINING SUCH AN ELECTRODE Technical field of the invention

The invention relates to the field of electrochemistry, and more particularly to thin film batteries. It concerns more precisely the electrodes which can be used in lithium ion microbatteries. The invention applies to negative electrodes and positive electrodes. It relates to porous electrodes which can be impregnated with a solid electrolyte without a liquid phase or with a liquid electrolyte.

The invention also relates to a method for preparing such a porous electrode which uses nanoparticles of an electrode material, and the electrodes thus obtained. The invention also relates to a method for manufacturing a lithium ion microbattery comprising at least one of these electrodes, and the microbatteries thus obtained.

State of the art

Lithium ion batteries have the best energy density among the different electrochemical storage technologies available on the market. There are different architectures and chemical compositions of electrodes allowing these batteries to be produced. The manufacturing processes for lithium ion batteries are presented in numerous articles and patents; an overview is given in the work “Advances in Lithium-Ion Batteries” (ed. W. van Schalkwijk and B. Scrosati), published in 2002 (Kluever Academic / Plenum Publishers).

There is a growing need for very small rechargeable batteries, capable of being integrated into 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.

According to the state of the art, 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 µm and 15 µm in diameter.

These deposition techniques, in particular by coating, make it possible to produce layers with a thickness of between approximately 50 µm and approximately 400 µm. The power and energy of the battery can be modulated by adapting the thickness and 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, we want to have a lower thickness of each layer constituting the microbattery.

In addition to the issues related to the formulation of inks to obtain a high-performance electrode at low manufacturing costs, it must be kept in mind that the ratio between the energy density and the power density of the electrodes can be adjusted depending on the particle size of active materials, and indirectly the porosity of the electrode layers 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.

Binder-free mesoporous electrode layers for lithium ion batteries can be deposited by electrophoresis; this is known from WO 2019/215 407 (I-TEN). They can be impregnated with a liquid electrolyte, but their electrical resistivity remains quite high.

To increase the low electronic conductivity of the electrodes, especially when these electrodes are very thick or made from active electrode materials with low electronic conductivity, a certain quantity of electronic conductive material, such as carbon black, is generally added to the electrodes. particles of active electrode material. Ideally, electronic conductor particles should be available at any point on the surface of the electrode active material particle to enable simultaneous insertion/deinsertion across the entire surface of the electrode active particles, thereby maximizing current density and minimizing local stress and heating due to inhomogeneous electrical transport.

In practice, it is very difficult to control the arrangement of the carbon black within the electrodes. Furthermore, with the increasing use of increasingly smaller particles of active material, these problems are even more significant. A non-uniform distribution of carbon black in the electrode induces a much higher polarization of the electrode, which leads to an increase in the series resistance of the battery comprising such an electrode. These local state of charge imbalances will be all the more pronounced as the current density increases. These imbalances therefore lead to a loss of cycling performance, a safety risk and a limitation of the power of the battery cell. The same applies when the electrodes have an inhomogeneous porosity, namely distributed in size; this inhomogeneity contributes to making wetting of the electrode pores more difficult.

In this context and in order to reduce the electrical resistivity of mesoporous electrodes, the applicant has developed 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 carbon coating; this is known from WO 2021/220 174 (I-TEN). The presence of this carbon electronic conductive coating on the electrode makes it possible to reduce its electrical resistivity but does not significantly increase its voltage, temperature and electrochemical stability. In addition, producing a carbon electronic conductive coating on the electrode is expensive and difficult to implement.

As there is a growing need for very small rechargeable batteries, the electrodes must meet increasingly stringent specifications. They must have high chemical and electrochemical stability, strength and corrosion resistance 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 disadvantages of the prior art mentioned above.

More precisely, the problem that the present invention seeks to solve is to provide a process for manufacturing porous electrodes having a high, homogeneous electronic conductivity and a controlled pore density which is simple, safe, rapid, easy to implement, inexpensive. expensive.

The present invention also aims to provide safe porous electrodes having high electronic conductivity, a stable mechanical structure, good thermal stability, especially at high temperatures, a long lifespan, whatever the thickness of the electrode. .

Another aim of the invention is to propose electrodes for batteries capable of operating at high temperatures without reliability problems and without risk of fire.

Another aim of the invention is to provide porous electrodes which, in addition to the preceding characteristics, can easily be wetted and impregnated with an ionic liquid.

Another aim 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 aim of the invention is to propose microbatteries, in particular lithium ion microbatteries, capable of storing high energy densities, of restoring this energy with very high power densities (in particular in capacitors or supercapacitors ), to withstand high temperatures which has an excellent cycling lifespan as well as increased safety.

Objects of the invention

In order to increase the performance of electrodes usable in conventional lithium ion batteries, in particular by reducing their electrical resistivity while significantly increasing their voltage and temperature resistance and their electrochemical stability, the inventors sought to find an alternative to the conductive coating. carbon electronics presented in the application of WO 2021/220 174 (I-TEN).

According to the invention, the problem is solved by an electrode for a lithium ion battery which is completely ceramic, mesoporous without organic binders, whose porosity is between 25% and 50%, whose channel and pore size 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 electrode material whose porosity is between 25% and 50%, the size of the channels and pores of which is homogeneous in order to ensuring perfect dynamic balancing of the cell, and presenting 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 can 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.

The fact of using 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 a nanometer or tens of nanometers, makes it possible to increase the deposit thicknesses. The agglomerates must have a size less than 300 nm. Sintering agglomerates larger than 500 nm would not make it possible to obtain a continuous mesoporous film. In this case, two different porosity sizes are observed in the deposit, namely porosity between agglomerates and porosity within the agglomerates.

Indeed, we observe that during the drying of nanoparticle deposits on a substrate capable of acting as an electric current collector, cracks appear in the layer. We see that the appearance of these cracks essentially depends on the size of the particles, the compactness of the deposit and its thickness. This cracking limit thickness is defined by the following relationship:

h _max = 0.41 [(GM∅ _rcp R ³ )/2γ]

where h _max designates the critical thickness, G the shear modulus of the nanoparticles, M the coordination number, ∅ _rcp the volume fraction of nanoparticles, R the radius of the particles and γ the interfacial tension between the solvent and the air.

It follows that the use of mesoporous agglomerates, made up of primary nanoparticles at least ten times smaller than the size of the agglomerate, makes it possible to considerably increase the limit thickness for cracking of the layers. Similarly, it is possible to add a few percent of a lower surface tension solvent (such as isopropyl alcohol (abbreviated IPA)) to water or ethanol to improve wettability and the adhesion of the deposit, and to reduce the risk of cracking. In order to increase deposit thicknesses while limiting or even eliminating the appearance of cracks, it is possible to add binders and dispersants. These additives and organic solvents can be eliminated 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.

Furthermore, for the same size of primary particles when these particles are produced by hydrothermal synthesis, it is possible during their synthesis by precipitation to modify the size of the agglomerates by modulating the quantity of binders (for example poly vinyl pyrrolidone, abbreviated PVP) in the synthesis reactor. Thus, it is possible to produce an ink containing agglomerates that are very dispersed in size or having two complementary size populations, so as to maximize the compactness of the agglomerate deposit. Unlike the sintering of non-agglomerated nanoparticles, the sintering conditions between agglomerates of different sizes will not be modified. These are the primary nanoparticles, which constitute the agglomerates which will weld together. These primary nanoparticles have identical sizes regardless of the size of the agglomerate. The size distribution of the agglomerates will improve the compactness of the deposits and increase the contact points between nanoparticles, but will not modify the consolidation temperature.

However, the agglomerates must remain small to be able to form a continuous mesoporous film during the heat treatment of the layer. If the agglomerates are too large, this hinders their sintering and we observe the formation of two distinct porosities in the layer: a porosity between agglomerates and a porosity inside the agglomerates.

After sintering, we obtain a porous layer, preferably mesoporous, or a plate, without carbon black or organic binders, in which all the nanoparticles are welded together (by the necking phenomenon, known elsewhere) to form a network continuous mesoporous 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. Furthermore, after sintering, the porous layer, preferably mesoporous, is perfectly adherent to the metal substrate on which it has been deposited or transferred (in the case of an initial deposit made on an intermediate substrate).

The heat treatments carried out at high temperature to sinter the nanoparticles together allow the electrode to be perfectly dried 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. The high temperature heat treatment (sintering) may be preceded by a lower temperature heat treatment (debinding) to dry the installed or deposited electrode and to remove traces of water or solvents or other organic additives ( stabilizers, binders) adsorbed on the surface of the active material particles; this debinding can be carried out in an oxidizing atmosphere.

Depending on the sintering times and temperature, it is possible to adjust the porosity of the final electrode. Depending on the energy density requirements, the latter can be adjusted in a range between 25% and 50% porosity.

In all cases, the power density of the electrodes thus obtained remains extremely high due to mesoporosity. Furthermore, independently of the size of the mesopores in the active material (knowing that after sintering the notion of nanoparticle no longer applies to the material which then has a three-dimensional structure with a network of channels and mesopores), the balancing Cell dynamics remain perfect, which helps maximize power densities and battery cell lifespans.

The electrode according to the invention has a high specific surface area, which reduces the ionic resistance of the electrode. However, for this electrode to deliver maximum power, it must 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 becomes greater. Furthermore, 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 operation at power of the battery.

According to an essential characteristic of the present invention, 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.

Indeed, as explained above, the process according to the invention, which necessarily involves a step of depositing agglomerated nanoparticles of electrode material (active material), causes the nanoparticles to naturally "weld" together 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 enters into the depth of the open porous structure of the layer.

A first object of the invention is a method of manufacturing a porous electrode, in particular for a battery, said electrode comprising a porous layer of at least one active electrode material P deposited on a substrate, and a layer of a 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 process being characterized in that:

(a) a substrate and a colloidal suspension or a paste are provided comprising aggregates or agglomerates of monodisperse primary nanoparticles, of at least one active electrode material P, of average primary diameter D ₅₀ of between 2 nm and 150 nm , preferably between 2 nm and 100 nm, and more preferably between 2 nm and 60 nm, said aggregates or agglomerates having an average diameter D ₅₀ of 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,

(b) a layer is deposited on at least one face of said substrate from said colloidal suspension or paste supplied in step (a), by a process selected from the group formed by: electrophoresis, extrusion, a printing process, preferably inkjet printing or flexographic printing, a coating process, preferably by squeegee, roller, curtain, by dip-shrinkage, or through a die slot shape,

(c) said layer obtained in step (b) is dried, where appropriate, before or after separating said layer from its intermediate substrate, then, optionally, said dried layer is thermally treated, preferably under an oxidizing atmosphere; then said layer is consolidated, by thermal and/or mechanical treatment, preferably by sintering, to obtain a porous layer, preferably mesoporous,

(d) a layer of an electronically conductive oxide material is formed on and inside the pores of said porous layer so as to form a porous layer coated with a layer of an electronically conductive oxide material,

(e) optionally, 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).

In step (b) the deposition can be done on one or both sides of the substrate.

Advantageously, when said substrate is an intermediate 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 drying the layer obtained in step b).

Advantageously, when said substrate is an intermediate substrate, after step c) and before step d), an electrically conductive sheet is supplied, covered on at least one side, respectively on its two sides, 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 face, preferably on each of the faces, of the electrically conductive sheet, so as to obtain a porous plate or layer, preferably mesoporous on a substrate capable of acting as a current collector. In the present application, the terms “porous layer” and “porous plate” are interchangeable.

Advantageously, in step (d), a layer of a precursor of an electronically conductive oxide material is deposited in a step (d1), on and inside the pores of said porous layer, and when in a step (d2), the precursor of an electronically conductive oxide material, deposited during step (d1) on said porous layer, is transformed into an electronically conductive material, so that said porous layer presents on and inside the pores, a layer of said electronically conductive oxide material.

Advantageously, step (d1) is carried out by immersion of 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 an electronically conductive material, during step (d2) is carried out by heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere.

Advantageously, 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 an electronically conductive material is a heat treatment. such as calcination, preferably carried out in air or under an oxidizing atmosphere.

These organic salts are preferably chosen from:

- an alkoxide 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 in air or under an oxidizing atmosphere, of forming an electronically conductive oxide, and

- an acetate 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,

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.

Advantageously, said porous layer obtained at the end of step (c) has a specific surface area of between 10 m ² /g and 500 m ² /g and/or a thickness of between 4 µm and 400 µm.

Advantageously, when said colloidal suspension or paste supplied in step (a) comprises organic additives, such as ligands, stabilizers, binders or residual organic solvents, said layer dried with heat is treated thermally, preferably under an oxidizing atmosphere. step c) or said porous plate.

Advantageously, said active electrode material P is selected from the group formed by:

• LiMn oxides₂O₄, Li_1+xMn_2-xO₄with 0 < x < 0.15, LiCoO₂, LiNiO₂, LiMn_1.5Neither_0.5O₄, LiMn_1.5Neither_0.5-xX_xO₄where X is selected from Al, Fe, Cr, Co, Rh, Nd, other rare earths such as Sc, Y, Lu, La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and where 0 < x < 0.1, LiMn_2-xM_xO₄with M = Er, Dy, Gd, Tb, Yb, Al, Y, Ni, Co, Ti, Sn, As, Mg or a mixture of these compounds and where 0 < x < 0.4, LiFeO₂, LiMn_1/3Neither_1/3Co_1/3O_2,LiNi_0.8Co_0.15Al_0.05O_2, LiAl_xMn_2-xO₄with 0 ≤ x < 0.15, LiNi_1/xCo_1/yMn_1/zO₂with x+y+z =10;
• Li _x M _y O ₂ where 0.6≤y≤0.85; 0≤x+y≤2; and M is chosen from Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, and Sb or a mixture of these elements; Li _1.20 Nb _0.20 Mn _0.60 O ₂ ;
• Li _1+x Nb _y Me _z A _p O ₂ where Me is at least one transition metal chosen from: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs and Mt, and where 0.6<x<1;0<y<0.5;0.25≤z<1; with A ≠ Me and A ≠ Nb, and 0≤p≤0.2;
• Li _x Nb _y-a N _a M _zb P _b O _2-c F _c where 1.2<x≤1.75;0≤y<0.55;0.1<z<1;0≤a<0.5;0≤b<1;0≤c<0.8; and where M, N, and P are each at least one of the elements chosen from the group consisting of Ti, Ta, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru , Rh, and Sb;
• Li _1.25 Nb _0.25 Mn _0.50 O ₂ ; Li _1.3 Nb _0.3 Mn _0.40 O ₂ ; Li _1.3 Nb _0.3 Fe _0.40 O ₂ ; Li _1.3 Nb _0.43 Ni _0.27 O ₂ ; Li _1.3 Nb _0.43 Co _0.27 O ₂ ; Li _1.4 Nb _0.2 Mn _0.53 O ₂ ;
• Li _x Ni _0.2 Mn _0.6 O _y where 0.00≤x≤1.52; 1.07≤y<2.4; Li _1.2 Ni _0.2 Mn _0.6 O ₂ ;
• LiNi _x Co _y Mn _1−x−y O ₂ where 0 ≤ x and y ≤ 0.5; LiNi _x Ce _z Co _y Mn _1−x−y O ₂ where 0 ≤ x and y ≤ 0.5 and 0 ≤ z;
• phosphates LiFePO ₄ , LiMnPO ₄ , LiCoPO 4, LiNiPO ₄ , Li _{3 V 2 (} PO ₄ ) _3, Li ₂ MPO ₄ F with M = Fe, Co, Ni or a mixture of these different elements, LiMPO ₄ F with M = V, Fe, T or a mixture of these different elements; phosphates of formula LiMM'PO ₄ , with M and M' (M ≠ M') selected from Fe, Mn, Ni, Co, V such as LiFe _x Co _1-x PO ₄ and where 0 < x <1;
• Fe _0.9 Co _0.1 OF; LiMSO ₄ F with M = Fe, Co, Ni, Mn, Zn, Mg;
• all lithiated forms of the following chalcogenides: V ₂ O ₅ , V ₃ O ₈ , TiS ₂ , titanium oxysulphides (TiO _y S _z with z=2-y and 0.3≤y≤1), tungsten oxysulphides (WO _y S _z with 0.6<y<3 and 0.1<z<2), CuS, CuS ₂ , preferably Li _x V ₂ O ₅ with 0 < x ≤ 2, Li _x V ₃ O ₈ with 0 < x ≤ 1.7, Li _x TiS ₂ with 0 < x ≤ 1, titanium and lithium oxysulphides Li _x TiO _y S _z with z=2-y, 0.3≤y≤1 and 0 < x ≤ 1, Li _x WO _y S _z with z=2-y, 0.3≤y≤1 and 0 < x ≤ 1, Li _x CuS with 0 < x ≤ 1, Li _x CuS ₂ with 0 < x ≤ 1.

Advantageously, said aforementioned active electrode material P is used to manufacture a cathode.

Advantageously, said active electrode material P is selected from the group formed by:

• Li ₄ Ti ₅ O ₁₂ , Li ₄ Ti _5-x M _x O ₁₂ with M = V, Zr, Hf, Nb, Ta and 0 ≤ x ≤ 0.25;
• niobium oxides and mixed oxides of niobium with titanium, germanium, cerium or tungsten, and preferably in the group formed by:
• Nb ₂ O _{5± δ} , Nb ₁₈ W ₁₆ O _{93± δ} , Nb ₁₆ W ₅ O _{55± δ} with 0 ≤ x < 1 and 0 ≤ δ ≤ 2, LiNbO ₃ ,
• TiNb₂O_{7± δ}, Li_wTiNb₂O₇with w≥0, Ti_1-xM¹ _xNo._2-yM² _yO_{7± δ}or Li_wTi_1-xM¹ _xNo._2-yM² _yO_{7± δ}in which M¹and M²are 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, M¹and M²which may be the same or different from each other, and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and 0 ≤ δ ≤ 0.3;
  • La _x Ti _1-2x Nb _2+x O ₇ where 0<x<0.5;
  • M_xTi_1-2xNo._2+xO_7±δ
    • in which M is an element whose oxidation state 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≤ δ ≤0.3; Ga_0.10Ti_0.80No._2.10O₇; Fe_0.10Ti_0.80No._2.10O₇;
  • M_xTi_2-2xNo._10+xO_29±δ
    • in which M is an element whose oxidation state 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≤ δ ≤0.3;
• Ti _1-x M ¹ _x Nb _2-y M ² _y O _7-z M ³ _z or Li _w Ti _1-x M ¹ _x Nb _2-y M ² _y O _7-z M ³ _z in which
• 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,
• M ¹ and M ² may be identical or different from each other,
• M ³ is at least one halogen,
• and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
• TiNb₂O_7-zM³ _zor Li_wTiNb₂O_7-zM³ _zin which M³is at least one halogen, preferably chosen from F, Cl, Br, I or a mixture thereof, and 0 < z ≤ 0.3;
  • Ti_1-xGe_xNo._2-yM¹ _yO_7±z, Li_wTi_1-xGe_xNo._2-yM¹ _yO_7±z,Ti_1-xThis_xNo._2-yM¹ _yO_7±z, Li_wTi_1-xThis_xNo._2-yM¹ _yO_7±zwherein
    • M ¹ is 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;
    • 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
  • Ti _1-x Ge _x Nb _2-y M ¹ _y O _7-z M ² _z , Li _w Ti _1-x Ge _x Nb _2-y M ¹ _y O _7-z M ² _z , Ti _1-x Ce _x Nb _2-y M ¹ _y O _7-z M ² _z , Li _w Ti _1-x Ce _x Nb _2-y M ¹ _y O _7-z M ² _{z ,} in which
    • 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, Ce and Sn,
    • M ¹ and M ² may be identical or different from each other,
    • and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
• TiO ₂ ; TiO _x N _y with x<2 and 0<y<0.2;
• LiSiTON, oxynitrides based on tin and silicon, and more particularly the SiSn _0.87 O _1.20 N _1.72 formulation and their lithiated forms;
• nitrides and oxynitrides of the MO _x N _y type where M is at least one element chosen from Ge, Si, Sn, Zn or a mixture of one or more of these elements, and where x>=0 and y>=0, 3;
• Li _3-X M _x N with M is at least one element chosen from Cu, Ni, Co or a mixture of one or more of these elements;
• Li _3-X M _x N with M being cobalt (Co) and 0 ≤ x ≤ 0.5; Li _3-X M _x N with M being nickel (Ni) and 0 ≤ x ≤ 0.6; Li _3-X M _x N with M being copper (Cu) and 0 ≤ x ≤ 0.3.

Advantageously, said aforementioned active electrode material P is used to manufacture an anode.

Another object of the invention is a porous electrode capable of being obtained by the method 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 a battery having a capacity not exceeding 1 mA h, preferably a lithium ion battery having a capacity not exceeding 1 mA h, implementing the method of manufacturing a porous electrode according to the invention or using a porous electrode according to the invention.

Generally speaking, the battery according to the invention can be a lithium ion microbattery. In particular, it can be designed and dimensioned so as to have a capacity less than or equal to 1mA h and up to approximately 1 mA h (commonly called “microbattery”). Typically, microbatteries are designed to be compatible with microelectronics manufacturing processes.

Advantageously, said porous electrode is impregnated with an electrolyte, preferably a phase carrying lithium ions selected from the group formed by:

• an electrolyte composed of at least one aprotic solvent and at least one lithium salt;
• an electrolyte composed of at least one ionic liquid and at least lithium salt;
• a mixture of at least one aprotic solvent and at least one ionic liquid and at least one lithium salt;
• a polymer made ionic conductive by the addition of at least one lithium salt; And
• a polymer made ionic conductive by the addition of a liquid electrolyte, either in the polymer phase or in the mesoporous structure.

Another object of the invention is a lithium ion battery having a capacity not exceeding 1 mA h capable of being obtained by the method according to the invention.

Detailed description of the invention

1. Definitions

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. The term “electronic conductive oxide” includes electronic conductive oxides and electronic semiconductor oxides.

For the purposes of this document, the size of a particle is defined by its largest dimension. By “nanoparticle” we mean any particle or object of nanometric size having at least one of its dimensions less than or equal to 100 nm.

By “ionic liquid” we mean any liquid salt, capable of transporting electricity, differing from all molten salts by a melting temperature lower 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 “room temperature ionic liquids”.

By “mesoporous” materials we mean any solid which has within its structure so-called “mesopores” pores 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 the reference for those skilled in the art. We therefore do not use the term "nanopore" here, even if the mesopores as defined above have nanometric dimensions in the sense of the definition of nanoparticles, knowing the pores of size smaller than that of the mesopores are called by the skilled in the art of “micropores”.

A presentation of the concepts of porosity (and the terminology which has just been explained above) is given in the article “Texture of powdery or porous materials” by F. Rouquerol et al., published in the collection “Techniques de the Engineer”, treatise Analysis and Characterization, booklet P 1050; This article also describes porosity characterization techniques, including the BET method.

For the purposes of the present invention, the term “porous layer” means a layer which has pores. By “mesoporous layer” is meant 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 porosity greater than X% by volume” used in the present description.

The term “aggregate” means, according to IUPAC definitions, a loosely bound assembly of primary particles. In this case, 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 (i.e. reduced to primary nanoparticles) suspended in a liquid phase under the effect of ultrasound, according to a technique known to those skilled in the art.

The term “agglomerate” means, according to IUPAC definitions, a strongly bonded assembly of primary particles or aggregates.

2. Preparation of nanoparticle suspensions

The porous electrodes according to the invention are produced from a colloidal suspension of clusters and/or agglomerates of nanoparticles or a paste.

In an even more preferred embodiment of the invention 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; during subsequent process steps, this promotes 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 raw deposits or strips, in particular thick deposits without cracks.

It is a colloidal suspension or paste comprising aggregates or agglomerates of nanoparticles which is then used for the manufacture of a dried porous layer of an active electrode material P.

3. Manufacturing a porous layer

The method of 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 electrode material P, on a substrate to form a layer, then drying said layer 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 approximately 1 µm and approximately 500 µm. The thickness of this porous layer is advantageously less than 300 µm, preferably between approximately 5 µm and approximately 300 µm, preferably between 5 µm and 150 µm. Generally speaking, 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 by doctor blade (technique known in English under the term "doctor blade" or "tape casting"), by roll coating (in English "roll coating" ), by curtain coating, by extrusion through a slot-die, or by dip-coating.

So that 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 weight.

According to the findings of the applicant, with an average diameter of the aggregates or agglomerates of nanoparticles between 80 nm and 300 nm (preferably between 100 nm to 200 nm) we obtain, during the subsequent process steps, a mesoporous layer having a average diameter of the mesopores between 2 nm and 50 nm.

According to the invention, the porous layer of at least one active electrode material 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 dipping coating process (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.

The porous electrode layer can also be deposited by electrophoresis, but then a less concentrated suspension containing agglomerates of nanoparticles of the active material P is advantageously used.

Processes for deposition of aggregates or agglomerates of nanoparticles electrophoretically, by extrusion, by the dip coating process, by ink jet, by roller coating, by curtain coating, by cross-coating slot-shaped die or by scraping are simple, safe processes, easy to implement, to industrialize and to obtain a homogeneous final porous layer. Electrophoretic deposition allows layers to be deposited uniformly over large areas with high deposition rates. Coating techniques, particularly those mentioned above, make it possible to simplify bath management compared to electrophoretic deposition techniques because the suspension does not become depleted in particles during deposition. Deposition by inkjet printing allows localized deposits to be made.

Porous layers in thick layers 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 deposition of 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 which can serve as a current collector.

3.1. Substrate capable of acting as a current collector

In a first embodiment, 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 provides the electrode with the function of current collector. The colloidal suspension or paste (ink) can be deposited on one or both sides of the substrate, in particular not using the deposition techniques indicated previously.

The current collector within the batteries employing electrodes according to the invention can be a stable substrate in the operating potential range of the electrochemical device. Within batteries using electrodes according to the invention, 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, compared to the potential of lithium. Advantageously, a metal substrate is chosen, for example a metal strip (i.e. 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 significantly 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 therefore particularly well suited as a sintered electrode substrate.

This substrate capable of acting as an electric current collector can also be coated with a conductive or semiconductor oxide before 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, particularly in the form of graphite. These less noble substrates can thus be used as electrode substrates. It may 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 strips of copper, nickel, molybdenum, tungsten, tantalum, chromium, niobium, zirconium, titanium, and alloy strips 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 thermal treatments.

Copper, nickel, molybdenum and their alloys are preferentially used as an anodic substrate. Carbon-based substrates, particularly 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 an electric current collector substrate for cathodes. 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 faces 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 electrode material P.

This porous layer of an active electrode material P thus dried is then consolidated. This consolidation can be carried out by pressing and/or heat treatment, i.e. by a heat treatment (heating), by a heat treatment preceded by a mechanical treatment, and possibly by a thermomechanical treatment, typically thermocompression. In a very advantageous embodiment of the invention this treatment leads to a partial coalescence of the primary nanoparticles in the aggregates, or 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 separated but connected by a (restricted) neck. Lithium ions and electrons are mobile within these necks and can diffuse from one particle to another without encountering grain boundaries. The nanoparticles are welded together to ensure the conduction of electrons from one particle to another. Thus, a continuous, rigid mesoporous film is formed from the primary nanoparticles, without organic binder, forming a three-dimensional network with high ionic mobility and electronic conduction; this network comprises interconnected pores, preferably mesopores. This porous layer, preferably mesoporous thus obtained, is perfectly suited to the application of a surface treatment, by gas or liquid, which enters into the depth of the open porous structure of the layer.

The temperature necessary to obtain “necking” depends on the material; given 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 its temperature, a more or less pronounced coalescence (necking) is obtained, which has repercussions on the porosity. It is thus possible to obtain an electrode with a desired porous or mesoporous ceramic structure with controlled porosity while maintaining a perfectly homogeneous channel size. During this thermomechanical or thermal treatment, the electrode layer will be freed of any organic constituent and residue (such as the liquid phase of the nanoparticle suspension, binders and possible surfactant products): it becomes an inorganic layer (ceramic ).

According to an essential characteristic of the present invention, 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.

3.2. Intermediate substrate

According to a second embodiment, 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.

In this embodiment, the colloidal suspension or paste (ink) is deposited on one face of the intermediate substrate, so as to subsequently be able to easily separate the layer obtained from this intermediate substrate.

In particular, it is possible to deposit, from a suspension of nanoparticles and/or agglomerates of nanoparticles of active electrode material P, preferably from a concentrated suspension containing nanoparticles of active electrode material P ( 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 by doctor blade, by roller coating, by curtain coating, by extrusion through a slot-shaped die, or by dipping.

The methods of deposition of nanoparticles, by the dip 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 processes, easy to implement, to industrialize and 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 achieved in a single step using roller, curtain, slot-die, dip or scrape coating techniques.

Said intermediate substrate may be a flexible substrate, which may be a polymer sheet, for example poly(ethylene terephthalate), abbreviated PET. In this second embodiment, 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. In this second embodiment, 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 approximately 1 µm and approximately 500 µm. The thickness of the layer after drying, i.e. of the non-sintered electrode, is advantageously less than 300 µm, preferably between approximately 5 µm and approximately 300 µm, preferably between 5 µm and 150 µm.

In said second embodiment, the method of manufacturing an electrode for an electrochemical device such as a battery uses an intermediate polymer substrate (such as PET) and leads to a strip called a “raw strip”. This raw strip is then separated from its substrate; it then forms self-supporting plates or sheets (hereinafter the term “plate” is used, 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 eliminate 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 approximately 1 µm and approximately 500 µm. The thickness of the porous plate after sintering is advantageously less than 300 µm, preferably between approximately 5 µm and approximately 300 µm, preferably between 5 µm and 150 µm.

According to the second embodiment and in order to obtain a porous electrode placed on a substrate capable of acting as a current collector, an electrically conductive sheet is also provided, covered on at least one of its faces, preferably on both of its faces. , 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 of its faces with a thin layer of conductive glue (loaded with graphite) or a sol-gel type deposit loaded with conductive particles. Said thin layers preferably have a thickness of less than 1 μm. This electrically conductive sheet can be a metal strip or a graphite sheet.

When said electrically conductive sheet is metallic, it is preferably a laminated sheet, i.e. obtained by rolling. Rolling can optionally be followed by a final anneal, which can be a softening anneal (total or partial) or recrystallization, according to metallurgical terminology. It is also possible to use an electrochemically deposited foil, for example an electroplated copper foil or an electroplated nickel foil.

This electrically conductive sheet is then placed on a plate or inserted between two plates previously obtained after drying and possibly heat treatment (i.e. 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. During this sintering the connection between the plate and the intermediate layer 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 active electrode material P, and the metal foil placed between these two plates.

One of the advantages of the second embodiment is that it allows the use of inexpensive substrates such as aluminum strips, copper strips or graphite strips. In fact, these strips do not resist thermal treatments to consolidate the deposited layers; sticking them on the plates after their heat treatment also helps prevent 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.

3.3. Production of a coating or layer of an electronically conductive oxide material on and inside the porous layer or porous plate

According to an essential characteristic of the present invention, after drying and consolidation, an electronically conductive oxide coating is produced on and inside the pores of these porous layers, porous plates or self-supporting porous sheets (hereinafter called indifferently 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 batteries, microbatteries.

The fact of using an electronically conductive coating in the form of an oxide instead of a carbon coating gives, among other things, better performance to the final electrode. Indeed, the presence of this electronically conductive oxide layer on and inside the pores of the porous layer or plate, particularly due to the fact that the electronically conductive coating is in oxide form, 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, even when the electrode is thick. It is essentially the synergistic combination of a porous layer or plate produced from an active electrode material, and an electronically conductive coating in the form of an oxide placed on and inside the pores of said layer. or porous plate which makes it possible to improve the final properties of the electrode, in particular to obtain thick electrodes without increasing the internal resistance of the electrode.

Very advantageously, the layer of electronically conductive oxide material can be obtained in different ways, in particular by the technique of deposition of atomic layers ALD (Atomic Layer Deposition) or by immersion in a liquid phase comprising a precursor of the electronically conductive oxide material followed by of the transformation of said precursor of an electronic conductive material into an electronic conductive material, in particular by heat treatment. More generally, with 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 “weld” 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 covering, layer by layer, by a cyclic process, rigid surfaces with high roughness in a completely waterproof and compliant manner. They make it possible to produce conformal layers (totally covering) of very thin thickness, free of defects, such as holes (so-called “pinhole free” layers). However, before carrying out any deposition using the atomic layer deposition (ALD) technique, it is necessary to first eliminate, on the surface of the porous layer, all traces of organic compounds. As deposition by ALD is typically carried out at a temperature between 100 °C and 300 °C, the residual organic matter, such as organic binders, could, in this temperature range, decompose and pollute the deposition reactor by ALD. Furthermore, 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 nature will have inhomogeneous growth, which may cause a loss of integrity.

A layer of an electronic conductive material can be formed, very advantageously, by immersion in a liquid phase comprising a precursor of said electronic conductive material followed by the transformation of said precursor of an electronic conductive material into an electronic conductive material by heat treatment. This process is simple, fast, easy to implement and is less expensive than the ALD atomic layer deposition technique. Advantageously, 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, preferably carried out in air or under an oxidizing atmosphere, of forming an electronic 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 alkoxide 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 in air or under an oxidizing atmosphere, of forming an electronically conductive oxide and an acetate of at least one metallic element capable, after heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere, to form an electronically conductive oxide.

Advantageously, said electronic conductive material can be an electronic conductive oxide material, preferably chosen from:

- tin oxide (SnO ₂₎ , zinc oxide (ZnO), indium oxide (In₂O₃), gallium oxide (Ga₂O₃), a mixture of two of these oxides such as indium-tin oxide corresponding to a mixture of indium oxide (In₂O₃) and tin oxide (SnO ₂₎ , a mixture of three of these oxides or a mixture of four of these oxides,

- doped oxides based on zinc oxide, the doping preferably being 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 preferably being 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),

- doped tin oxides, the doping preferably being with arsenic (As) and/or fluorine (F) and/or nitrogen (N) and/or niobium (Nb) and/or phosphorus (P) and/or antimony (Sb) and/or aluminum (Al) and/or titanium (Ti), and/or gallium (Ga) and/or chromium (Cr) and /or 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).

To obtain a layer of an electronic conductive material, preferably an electronic conductive oxide material, from an alkoxide, an oxalate or an acetate, the porous layer can be immersed in a rich solution of the precursor of the desired electronic conductive material. Then the electrode is dried and subjected to a heat treatment, preferably in air or under 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 the electronically conductive material is thus formed, preferably a coating of an electronically conductive oxide material, more preferably SnO ₂ , ZnO, In ₂ O ₃ , Ga ₂ O ₃ , or indium-tin oxide. , over the entire internal surface of the electrode, perfectly distributed.

The presence of an electronically conductive coating in the form of an oxide instead of a carbon coating on and inside the pores of the porous layer gives the electrode better electrochemical performance at high temperatures, and makes it possible to significantly increase the stability of the electrode. The fact of using an electronically conductive coating in the form of an oxide instead of a carbon coating gives, among other things, better performance to the final electrode. Indeed, the presence of this electronically conductive oxide layer on and inside the pores of the porous layer or plate, particularly due to the fact that the electronically conductive coating is in oxide form, 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, even when the electrode is thick. It is particularly advantageous to use an electronic conductive coating in the form of an oxide, in particular of the type In ₂ O ₃ , SnO ₂ , ZnO, Ga ₂ O ₃ 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 the active materials of the porous layer are too resistive.

The electrode according to the invention is porous, preferably mesoporous and its specific surface area 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 parasitic reactions. The presence of these electronic 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.

Furthermore, due to the very large specific surface area, the effect of these electronic conductive coatings in the form of oxide on the electronic conductivity of the electrode will be much more pronounced than in the case of a conventional electrode, where the surface specific is less, even if the conductive coatings deposited have a low thickness. These electronically conductive oxide coatings, deposited on and inside the pores of the porous layer, give the electrode excellent electronic conductivity, particularly when the porous layer is produced from active electrode material with low electronic conductivity. This layer of electronically conductive oxide material makes it possible to improve the electrical conductivity of the electrode while limiting the dissolution of the electrode and also makes it possible to increase the power of the battery; This is all the more true as the coating layer of electronically conductive oxide material has a low thickness.

It is essentially the synergistic combination of a porous layer or plate produced from an active electrode material, and an electronically conductive coating in the form of an oxide placed on and inside the pores of said layer. or porous plate which makes it possible to improve the final properties of the electrode, in particular to obtain thick electrodes without increasing the internal resistance of the electrode.

Furthermore, the electronically conductive coating in the form of an oxide on and inside the pores of a porous layer is easier and less expensive to produce than a carbon coating. Indeed, in the case of coatings made of electronically conductive material in oxide form, 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 a coating electronically 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, whatever its thickness. The fact of using an electronic conductive coating in the form of an oxide instead of a carbon coating gives, in particular, better performance to the final electrode. We note 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 different heat treatments.

Optionally, it is possible to deposit above this layer of 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 may be of inorganic or organic nature. More particularly, among the inorganic layers, it is possible to use for example an oxide, a phosphate or a borate that conducts lithium ions, and among the organic layers, polymers can be used (for example PEO possibly containing lithium salts, or a sulfonated tetrafluoroethylene copolymer such as Nafion™, 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 LiMn ₂ O ₄ electrodes the manganese risks dissolving in certain liquid electrolytes, in particular at high temperature.

When the layer of electronically conductive oxide material is covered with an ionic conductive layer, it is the latter which will mainly provide the protective functions, as described above (in particular preventing the dissolution of the electrode).

To summarize, with these coatings deposited on and inside the pores of the porous electrode layer, we seek to obtain two effects: increasing electronic conductivity and protection against dissolution in the electrolyte at high temperature. . Either these two effects are obtained with only the layer of electronically conductive oxide material, or a single coating is not enough to obtain both effects in which case two layers can be deposited, for example, a first layer of an electronically conductive oxide material according to the invention to obtain electronic conduction and a second layer, ionic conductive and electronic insulating; to obtain additional protection at high temperatures.

According to the first and second embodiment, a porous electrode according to the invention is obtained, placed on a metal substrate serving as an electronic current collector or located on either side of a metal substrate serving as an electronic current collector . The electrode/substrate/electrode subassemblies thus obtained, by the first or second embodiment, can be used in the manufacture of a battery, in particular a microbattery. An assembly by diffusion bonding can also be carried out by stacking and heat-pressing the entire structure of a battery, in particular a microbattery; in this case we assemble a multilayer stack 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 batteries, 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 necessary cuts to make a battery with several elementary cells, then we stack the subassemblies (typically in “head to tail” mode) and we carry out thermocompression to weld the anodes and cathodes together at the level of the electrolyte. solid.

Alternatively, the cuts necessary to produce a battery with several elementary cells can be made, before depositing an electrolyte film, 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 we carries out thermocompression to weld anodes and cathodes together at the level of the electrolyte film.

In the two variants which have just been presented, welding by thermocompression is carried out 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 LiMn ₂ O ₄ according to the invention

A suspension of LiMn ₂ O ₄ nanoparticles was prepared by hydrothermal synthesis according to the process described in the article by Liddle et al. entitled “A new one pot hydrothermal synthesis and electrochemical characterization of Li _1+x Mn _2-y O ₄ spinel structured compounds” , Energy & Environmental Science (2010) vol.3, page 1339-1346:

14.85 g of LiOH,H ₂ O were dissolved in 500 ml of water. 43.1 g of KMnO ₄ were added to this solution and this liquid phase was poured into an autoclave. With stirring, 28 ml of isobutyraldehyde and water were added until a total volume of 3.54 l was reached. The autoclave was then heated to 180°C and maintained at this temperature for 6 hours. After slow cooling, a black precipitate suspended in the solvent was obtained. This precipitate was subjected to a succession of centrifugation - redispersion steps in water, until an aggregated suspension was obtained with a conductivity of approximately 300 µS/cm and a zeta potential of -30mV. 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 approximately 150 nm; they were characterized by X-ray diffraction and electron microscopy.

Approximately 10 to 15% by mass of polyvinylpyrrolidone (PVP) at 360,000 g/mol was then added to the aqueous aggregate suspension. The water was evaporated until the aggregate suspension had a solids content of 10%. The ink thus obtained was applied to a stainless steel strip (316L) with a thickness of 5 µm. The layer obtained was dried in an oven controlled by temperature and humidity in order to avoid the formation of cracks during drying. The ink deposition and drying were repeated to obtain a layer approximately 10 µm thick.

This layer was consolidated at 600 °C for 1 h in air in order to weld the primary nanoparticles together, to improve adhesion to the substrate and to complete the recrystallization of the LiMn ₂ O ₄ . The porous layer thus obtained has an open porosity of approximately 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 LiMn ₂ O ₄ , in an ALD reactor of type P300B (supplier: Picosun), under an argon pressure of 2 mbars at 180°C. Argon (Ar) was used here both as a carrier gas and for purging. Before each deposit, 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, purging of the chamber with Ar, injection of water, purging of the chamber with Ar.

This cycle is repeated to achieve a coating thickness of 1.5 nm. After these different cycles, the product was dried under vacuum at 120°C for 12 hours to eliminate surface reagent residues and thus obtain a mesoporous cathode based on LiMn ₂ O ₄ having a coating on its entire accessible surface. of 1.5 nm of ZnO.

Example 2: Production of a mesoporous anode based on Li ₄ Ti ₅ O ₁₂

A suspension of Li ₄ Ti ₅ O ₁₂ 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 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, we let it cool, still stirring.

A white precipitate was obtained suspended in the solvent. This precipitate was subjected to a succession of centrifugation - redispersion steps in ethanol to obtain a pure colloidal suspension, with low ionic conductivity. It comprised aggregates of approximately 150 nm made up of primary particles of 10 nm. The zeta potential was around -45 mV. The product was characterized by X-ray diffraction and electron microscopy.

These aggregates were deposited by electrophoresis on stainless steel strips with a thickness of 5 μm, in an aqueous medium, by applying pulsed currents of 0.6 A peak and 0.2 A on average; the applied voltage was of the order of 3 to 5 V for 500 s. A deposit of approximately 4 µm thickness was thus obtained. It was consolidated by RTA annealing at 40% power for 1 s under nitrogen in order to weld the nanoparticles together, to improve adhesion to the substrate and to complete the recrystallization of Li ₄ Ti ₅ O ₁₂ .

A thin layer of SnO ₂ was then produced on and inside the pores of the mesoporous anode based on Li ₄ Ti ₅ O ₁₂ .

1g of polyvinyl pyrrolidone (abbreviated PVP) with a molecular mass by weight of 55,000 g/mol were added to 50 mL of distilled water at 40°C, then 3 g of tin oxalate SnC ₂ O ₄ were added to this aqueous solution of PVP. The mesoporous anode based on Li ₄ Ti ₅ O ₁₂ was then immersed in this solution so that the tin oxalate could be deposited on and inside the pores of the mesoporous anode based on Li ₄ Ti ₅ O ₁₂ . Then the electrode was dried then subjected to a heat treatment, preferably under nitrogen, at 600°C for 5 hours so as to form a homogeneous coating of SnO ₂ 2 nm thick, over the entire accessible surface of the electrode. electrode, ie on and inside the pores of the anode and this, in a perfectly distributed manner.

Example 3: Manufacturing of a battery using a porous cathode according to the invention and a porous anode according to the invention

has. Production of a suspension of Li ₃ PO ₄ nanoparticles

Two solutions were prepared. 11.44 g of CH ₃ COOLi, 2H ₂ O were dissolved in 112 ml of water, then 56 ml of water were added with vigorous stirring to the medium in order to obtain solution A. 4.0584g 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 hereinafter called solution B.

Solution B was then added, with vigorous stirring, to solution A. The solution obtained, perfectly clear after the disappearance of the bubbles formed during mixing, was added to 1.2 liters of acetone under the action of a homogenizer. Ultraturrax™ type in order to homogenize the medium. A white precipitation was immediately observed suspended in the liquid phase.

The reaction medium was homogenized for 5 minutes and then maintained for 10 minutes under magnetic stirring. We left it 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 were 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.

Agglomerates of approximately 100 nm made up of primary particles of Li ₃ PO ₄ of 10 nm were thus obtained suspended in ethanol.

b. Production on the anode and cathode layers previously developed of a porous inorganic layer from the suspension of Li ₃ PO ₄ nanoparticles previously described in part a)

Thin porous layers of Li ₃ PO ₄ were then deposited by electrophoresis on the surface of the anode and cathode previously produced by applying an electric field of 20V/cm to the suspension of Li ₃ PO ₄ nanoparticles previously obtained, for 90 seconds to obtain a layer with a thickness of approximately 1.5 µm. 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. Creation of an electrochemical cell

After having deposited 1.5 µm of porous Li ₃ PO ₄ on each of the electrodes previously developed (see examples 1 & 2), the two subsystems were stacked so that the Li ₃ PO ₄ films were in contact. This stack was then hot pressed under vacuum.

To do this, the stack was placed under a pressure of 1.5 MPa then dried under vacuum for 30 minutes at 10 ^-3 bar. The press plates were then heated to 450°C with a speed of 4°C/seconds. At 450°C, the stack was then thermo-compressed under a pressure of 45 MPa for 1 minute, then the system was cooled to room temperature.

Once the assembly has been carried out, a rigid, multilayer system consisting of one or more assembled battery cells has been obtained.

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 capillary action. The system was kept immersed for 1 minute, then the surface of the cell stack was dried with an N ₂ blade.

Claims (15)

Method of manufacturing a porous electrode, in particular for batteries, said electrode comprising a porous layer of at least one active electrode material P deposited on a substrate, and a layer of an electronically conductive oxide material present on and at the 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 process being characterized in that:
(a) a substrate and a colloidal suspension or a paste are provided comprising aggregates or agglomerates of monodisperse primary nanoparticles, of at least one active electrode material P, of average primary diameter D ₅₀ of between 2 nm and 150 nm , preferably between 2 nm and 100 nm, and more preferably between 2 nm and 60 nm, said aggregates or agglomerates having an average diameter D ₅₀ of 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,
(b) a layer is deposited on at least one face of said substrate from said colloidal suspension or paste supplied in step (a), by a process selected from the group formed by: electrophoresis, extrusion, a printing process, preferably inkjet printing or flexographic printing, a coating process, preferably by squeegee, roller, curtain, by dip-shrinkage, or through a die slot shape,
(c) said layer obtained in step (b) is dried, where appropriate, before or after separating said layer from its intermediate substrate, then, optionally, said dried layer is thermally treated, preferably under an oxidizing atmosphere; then said layer is consolidated, by thermal and/or mechanical treatment, preferably by sintering, to obtain a porous layer, preferably mesoporous,
(d) a layer of an electronically conductive oxide material is formed on and inside the pores of said porous layer so as to form a porous layer coated with a layer of an electronically conductive oxide material,
(e) optionally, 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). Method of manufacturing a porous electrode according to claim 1, characterized in that in step (d), during a step (d1), on and inside the pores of said porous layer, a layer of a precursor of an electronically conductive oxide material, and during a step (d2), the transformation of the precursor of an electronically conductive oxide material is carried out, deposited during step (d1) on said porous layer , made of electronically conductive material, so that said porous layer presents on and inside the pores, a layer of said electronically conductive oxide material. Method of manufacturing a porous electrode according to claim 2, characterized in that step (d1) is carried out by immersion of the porous layer in a liquid phase comprising a precursor of said electronically conductive oxide material, and in that 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 under an oxidizing atmosphere. Method of manufacturing a porous electrode according to claim 3, characterized in that 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 a electronic conductive oxide, and in that said transformation into electronic conductive material is a heat treatment such as calcination, preferably carried out in air or under an oxidizing atmosphere, these organic salts being, preferably, chosen from
- an alkoxide 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 in air or under an oxidizing atmosphere, of forming an electronically conductive oxide, and
- an acetate 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,
and/or in that, preferably, the metallic element is chosen from tin, zinc, indium, gallium, or a mixture of two or three or four of these elements. Method of manufacturing a porous electrode according to any one of claims 1 to 4, characterized in that said electronically conductive oxide material is chosen from:
- tin oxide (SnO ₂₎ , zinc oxide (ZnO), indium oxide (In₂O₃), gallium oxide (Ga₂O₃), a mixture of two of these oxides such as indium-tin oxide corresponding to a mixture of indium oxide (In₂O₃) and tin oxide (SnO ₂₎ , a mixture of three of these oxides or a mixture of four of these oxides,
- doped oxides based on zinc oxide, the doping preferably being 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 preferably being 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),
- doped tin oxides, the doping preferably being with arsenic (As) and/or fluorine (F) and/or nitrogen (N) and/or niobium (Nb) and/or phosphorus (P) and/or antimony (Sb) and/or aluminum (Al) and/or titanium (Ti), and/or gallium (Ga) and/or chromium (Cr) and /or 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). Process for manufacturing a porous electrode according to any one of claims 1 to 5, characterized in that said porous layer obtained at the end of step (c) has a specific surface area of between 10 m ² /g and 500 m ² /g and/or a thickness between 4 µm and 400 µm. Method of manufacturing a porous electrode according to any one of claims 1 to 6, characterized in that when said substrate is an intermediate substrate, said layer is separated in step (c) before or after drying from said intermediate substrate , to form a porous plate. Process for manufacturing a porous electrode, characterized in that when said colloidal suspension or paste supplied in step (a) comprises organic additives, such as ligands, stabilizers, binders or residual organic solvents, heat treatment is carried out, preferably under an oxidizing atmosphere, said dried layer obtained in step c) of the process for manufacturing a porous electrode according to any one of claims 1 to 6, or said porous plate formed according to the process for manufacturing a porous electrode according to claim 7. Method of manufacturing a porous electrode according to any one of claims 1 to 8, in which said active electrode material P is selected from the group formed by:

• LiMn oxides₂O₄, Li_1+xMn_2-xO₄with 0 < x < 0.15, LiCoO₂, LiNiO₂, LiMn_1.5Neither_0.5O₄, LiMn_1.5Neither_0.5-xX_xO₄where X is selected from Al, Fe, Cr, Co, Rh, Nd, other rare earths such as Sc, Y, Lu, La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and where 0 < x < 0.1, LiMn_2-xM_xO₄with M = Er, Dy, Gd, Tb, Yb, Al, Y, Ni, Co, Ti, Sn, As, Mg or a mixture of these compounds and where 0 < x < 0.4, LiFeO₂, LiMn_1/3Neither_1/3Co_1/3O_2,LiNi_0.8Co_0.15Al_0.05O_2, LiAl_xMn_2-xO₄with 0 ≤ x < 0.15, LiNi_1/xCo_1/yMn_1/zO₂with x+y+z =10;
• Li _x M _y O ₂ where 0.6≤y≤0.85; 0≤x+y≤2; and M is chosen from Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, and Sb or a mixture of these elements; Li _1.20 Nb _0.20 Mn _0.60 O ₂ ;
• Li _1+x Nb _y Me _z A _p O ₂ where Me is at least one transition metal chosen from: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs and Mt, and where 0.6<x<1;0<y<0.5;0.25≤z<1; with A ≠ Me and A ≠ Nb, and 0≤p≤0.2;
• Li _x Nb _y-a N _a M _zb P _b O _2-c F _c where 1.2<x≤1.75;0≤y<0.55;0.1<z<1;0≤a<0.5;0≤b<1;0≤c<0.8; and where M, N, and P are each at least one of the elements chosen from the group consisting of Ti, Ta, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru , Rh, and Sb;
• Li _1.25 Nb _0.25 Mn _0.50 O ₂ ; Li _1.3 Nb _0.3 Mn _0.40 O ₂ ; Li _1.3 Nb _0.3 Fe _0.40 O ₂ ; Li _1.3 Nb _0.43 Ni _0.27 O ₂ ; Li _1.3 Nb _0.43 Co _0.27 O ₂ ; Li _1.4 Nb _0.2 Mn _0.53 O ₂ ;
• Li _x Ni _0.2 Mn _0.6 O _y where 0.00≤x≤1.52; 1.07≤y<2.4; Li _1.2 Ni _0.2 Mn _0.6 O ₂ ;
• LiNi _x Co _y Mn _1−x−y O ₂ where 0 ≤ x and y ≤ 0.5; LiNi _x Ce _z Co _y Mn _1−x−y O ₂ where 0 ≤ x and y ≤ 0.5 and 0 ≤ z;
• phosphates LiFePO ₄ , LiMnPO ₄ , LiCoPO 4, LiNiPO ₄ , Li _{3 V 2 (} PO ₄ ) _3, Li ₂ MPO ₄ F with M = Fe, Co, Ni or a mixture of these different elements, LiMPO ₄ F with M = V, Fe, T or a mixture of these different elements; phosphates of formula LiMM'PO ₄ , with M and M' (M ≠ M') selected from Fe, Mn, Ni, Co, V such as LiFe _x Co _1-x PO ₄ and where 0 < x <1;
• Fe _0.9 Co _0.1 OF; LiMSO ₄ F with M = Fe, Co, Ni, Mn, Zn, Mg;
• all lithiated forms of the following chalcogenides: V ₂ O ₅ , V ₃ O ₈ , TiS ₂ , titanium oxysulphides (TiO _y S _z with z=2-y and 0.3≤y≤1), tungsten oxysulphides (WO _y S _z with 0.6<y<3 and 0.1<z<2), CuS, CuS ₂ , preferably Li _x V ₂ O ₅ with 0 < x ≤ 2, Li _x V ₃ O ₈ with 0 < x ≤ 1.7, Li _x TiS ₂ with 0 < x ≤ 1, titanium and lithium oxysulphides Li _x TiO _y S _z with z=2-y, 0.3≤y≤1 and 0 < x ≤ 1, Li _x WO _y S _z with z=2-y, 0.3≤y≤1 and 0 < x ≤ 1, Li _x CuS with 0 < x ≤ 1, Li _x CuS ₂ with 0 < x ≤ 1.

Method of manufacturing a porous electrode according to any one of claims 1 to 8, in which said active electrode material P is selected from the group formed by:

• Li ₄ Ti ₅ O ₁₂ , Li ₄ Ti _5-x M _x O ₁₂ with M = V, Zr, Hf, Nb, Ta and 0 ≤ x ≤ 0.25;
• niobium oxides and mixed oxides of niobium with titanium, germanium, cerium or tungsten, and preferably in the group formed by:
• Nb ₂ O _{5± δ} , Nb ₁₈ W ₁₆ O _{93± δ} , Nb ₁₆ W ₅ O _{55± δ} with 0 ≤ x < 1 and 0 ≤ δ ≤ 2, LiNbO ₃ ,
• TiNb₂O_{7± δ}, Li_wTiNb₂O₇with w≥0, Ti_1-xM¹ _xNo._2-yM² _yO_{7± δ}or Li_wTi_1-xM¹ _xNo._2-yM² _yO_{7± δ}in which M¹and M²are 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, M¹and M²which may be the same or different from each other, and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and 0 ≤ δ ≤ 0.3;
  • La _x Ti _1-2x Nb _2+x O ₇ where 0<x<0.5;
  • M_xTi_1-2xNo._2+xO_7±δ
    • in which M is an element whose oxidation state 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≤ δ ≤0.3; Ga_0.10Ti_0.80No._2.10O₇; Fe_0.10Ti_0.80No._2.10O₇;
  • M_xTi_2-2xNo._10+xO_29±δ
    • in which M is an element whose oxidation state 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≤ δ ≤0.3;
• Ti _1-x M ¹ _x Nb _2-y M ² _y O _7-z M ³ _z or Li _w Ti _1-x M ¹ _x Nb _2-y M ² _y O _7-z M ³ _z in which
• 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,
• M ¹ and M ² may be identical or different from each other,
• M ³ is at least one halogen,
• and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
• TiNb₂O_7-zM³ _zor Li_wTiNb₂O_7-zM³ _zin which M³is at least one halogen, preferably chosen from F, Cl, Br, I or a mixture thereof, and 0 < z ≤ 0.3;
  • Ti_1-xGe_xNo._2-yM¹ _yO_7±z, Li_wTi_1-xGe_xNo._2-yM¹ _yO_7±z,Ti_1-xThis_xNo._2-yM¹ _yO_7±z, Li_wTi_1-xThis_xNo._2-yM¹ _yO_7±zwherein
    • M ¹ is 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;
    • 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
  • Ti _1-x Ge _x Nb _2-y M ¹ _y O _7-z M ² _z , Li _w Ti _1-x Ge _x Nb _2-y M ¹ _y O _7-z M ² _z , Ti _1-x Ce _x Nb _2-y M ¹ _y O _7-z M ² _z , Li _w Ti _1-x Ce _x Nb _2-y M ¹ _y O _7-z M ² _{z ,} in which
    • 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, Ce and Sn,
    • M ¹ and M ² may be identical or different from each other,
    • and in which 0 ≤ w ≤ 5 and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and z ≤ 0.3;
• TiO ₂ ; TiO _x N _y with x<2 and 0<y<0.2;
• LiSiTON, oxynitrides based on tin and silicon, and more particularly the SiSn _0.87 O _1.20 N _1.72 formulation and their lithiated forms;
• nitrides and oxynitrides of the MO _x N _y type where M is at least one element chosen from Ge, Si, Sn, Zn or a mixture of one or more of these elements, and where x>=0 and y>=0, 3;
• Li _3-X M _x N with M is at least one element chosen from Cu, Ni, Co or a mixture of one or more of these elements;

Li_3-XM_xN with M being cobalt (Co) and 0 ≤ x ≤ 0.5; Li_3-XM_xN with M being nickel (Ni) and 0 ≤ x ≤ 0.6; Li_3-XM_xN with M being copper (Cu) and 0 ≤ x ≤ 0.3. Porous electrode capable of being obtained by the method according to any one of claims 1 to 10 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. Method for manufacturing a battery having a capacity not exceeding 1 mA h, preferably a lithium ion battery having a capacity not exceeding 1 mA h, implementing the method for manufacturing a porous electrode according to one of claims 1 to 10, or using a porous electrode according to claim 11. Method of manufacturing a battery according to claim 12, in which the method of manufacturing a porous electrode according to claim 9 is implemented to manufacture a cathode or the method according to claim 10 is implemented to manufacture an anode . Method of manufacturing a battery according to any one of claims 12 to 13, in which said porous electrode is impregnated with an electrolyte, preferably a phase carrying lithium ions selected from the group formed by:

• an electrolyte composed of at least one aprotic solvent and at least one lithium salt;
• an electrolyte composed of at least one ionic liquid and at least lithium salt;
• a mixture of at least one aprotic solvent and at least one ionic liquid and at least one lithium salt;
• a polymer made ionic conductor by the addition of at least one lithium salt; And
• a polymer made ionic conductive by the addition of a liquid electrolyte, either in the polymer phase or in the mesoporous structure.

Lithium ion battery having a capacity not exceeding 1 mA h capable of being obtained by the method according to any one of claims 12 to 14.