METHOD FOR MANUFACTURING AN ASSEMBLY COMPRISING A SEPARATOR AND POROUS ELECTRODE, AN ASSEMBLY COMPRISING A SEPARATOR AND POROUS ELECTRODE, AND MICROBATTERY CONTAINING SUCH AN ASSEMBLY

Abstract

A method for manufacturing a lithium-ion microbattery having a capacity not exceeding 1 mAh, implementing a method for manufacturing an assembly comprising a porous electrode and a porous separator comprising a porous layer deposited on a substrate having a porosity comprised between 20% and 60% by volume, and pores with an average diameter of less than 50 nm. The separator comprises a porous inorganic layer deposited on the electrode, the porous inorganic layer having a porosity comprised between 20% and 60% by volume, and pores with an average diameter of less than 50 nm.

Claims

1-17. (canceled)

18. A method for manufacturing a lithium-ion battery that includes an assembly having a porous electrode and a porous separator, the porous electrode having a porous layer free of binder deposited on a substrate and having a porosity of between 25% and 50% by volume and pores with an average diameter of less than 50 nm, the porous separator including a porous inorganic layer free of binder deposited on the porous electrode, the porous inorganic layer having a porosity of between 25% and 50% by volume and pores with an average diameter of less than 50 nm, the method comprising: (a) providing a substrate, a first colloidal suspension or a paste comprising aggregates or agglomerates of monodisperse primary nanoparticles of at least one active electrode material, having an average primary diameter of between 2 nm and 60 nm, said aggregates or agglomerates having an average diameter of between 100 nm and 200 nm, and a second colloidal suspension comprising aggregates or agglomerates of nanoparticles of at least one inorganic material, having an average primary diameter of between 2 nm and 60 nm, said aggregates or agglomerates having an average diameter of between 100 nm and 200 nm, wherein the substrate is a substrate acting as an electric current collector or an intermediate substrate; (b) depositing a layer from said first colloidal suspension or paste on at least one face of said substrate using one of: electrophoresis, ink-jet printing, flexographic printing, doctor blade coating, roll coating, curtain coating, dip-coating, and extrusion slot-die coating; (c) drying the deposited layer before or after separating said deposited layer from the intermediate substrate, then heat treating the dried layer under an oxidising atmosphere, then consolidating the heat treated layer by pressing and/or heating to obtain a mesoporous, inorganic layer; (d) depositing a coating of an electronically conductive material on and inside the pores of said mesoporous, inorganic layer to form said porous electrode; (e) depositing a porous inorganic layer from the second colloidal suspension on said porous electrode by one of: electrophoresis, ink-jet printing, flexographic printing, roll coating, curtain coating, doctor blade coating, extrusion slot-die coating, and dip-coating; and (f) drying the deposited porous inorganic layer under an air flow, and then heat treating the dried porous inorganic layer at a temperature below 400° C. to obtain said assembly.

19. The method of claim 18, wherein said mesoporous, inorganic layer has a specific surface of between 10 m.sup.2/g and 500 m.sup.2/g.

20. The method of claim 18, wherein said mesoporous, inorganic layer has a thickness of between 4 μm and 400 μm.

21. The method of claim 18, wherein when said substrate comprises an intermediate substrate, said layer is separated before or after drying from said intermediate substrate to form a porous plate.

22. The method of claim 21, wherein when said colloidal suspension or paste comprises organic additives: the dried deposited layer is heat treated under an oxidising atmosphere, or said porous plate is heat treated under an oxidising atmosphere.

23. The method of claim 18, wherein said deposited porous inorganic layer has a thickness of between 5 μm and 10 μm.

24. The method of claim 18, wherein said electronically conductive material is carbon.

25. The method of claim 18, wherein depositing said coating of electronically conductive material is carried out by atomic layer deposition or immersion in a liquid phase including a precursor of said electronically conductive material, and then transforming said precursor into an electronically conductive material.

26. The method of claim 25, wherein: said precursor comprises a polysaccharide, and transforming said precursor into the electronically conductive material is conducted by pyrolysis under an inert atmosphere.

27. The method of claim 18, wherein said at least one active electrode material is selected from the group consisting of: oxides LiMn.sub.2O.sub.4, Li.sub.1+xMn.sub.2−xO.sub.4 with 0<x<0.15, LiCoO.sub.2, LiNiO.sub.2, LiMn.sub.1.5Ni.sub.0.5O.sub.4, LiMn.sub.1.5Ni.sub.0.5−xX.sub.xO.sub.4 where 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.sub.2−xM.sub.xO.sub.4 with M=Er, Dy, Gd, Tb, Yb, Al, Y, Ni, Co, Ti, Sn, As, Mg or a mixture thereof and where 0<x<0.4, LiFeO.sub.2, LiMn.sub.1/3Ni.sub.1/3Co.sub.1/3O.sub.2, LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2, LiAl.sub.xMn.sub.2−xO.sub.4 with 0≤x<0.15, LiNi.sub.1/xCo.sub.1/yMn.sub.1/zO.sub.2 with x+y+z=10; Li.sub.xM.sub.yO.sub.2 where 0.6≤y≤0.85; 0≤x+y≤2; and M is selected from Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, and Sb or a mixture thereof; Li.sub.1.20Nb.sub.0.20Mn.sub.0.60O.sub.2; Li.sub.1+xNb.sub.yMe.sub.zA.sub.pO.sub.2 where Me is at least one transition metal selected 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.sub.xNb.sub.y−aN.sub.aM.sub.z−bP.sub.bO.sub.2−cF.sub.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 selected from the group consisting of Ti, Ta, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh, and Sb; Li.sub.1.25Nb.sub.0.25Mn.sub.0.50O.sub.2; Li.sub.1.3Nb.sub.0.3Mn.sub.0.40O.sub.2; Li.sub.1.3Nb.sub.0.3Fe.sub.0.40O.sub.2; Li.sub.1.3Nb.sub.0.43Ni.sub.0.27O.sub.2; Li.sub.1.3Nb.sub.0.43Co.sub.0.27O.sub.2; Li.sub.1.4Nb.sub.0.2Mn.sub.0.53O.sub.2; Li.sub.xNi.sub.0.2Mn.sub.0.6O.sub.y where 0.00≤x≤1.52; 1.07≤y<2.4; Li.sub.1.2Ni.sub.0.2Mn.sub.0.6O.sub.2; LiNi.sub.xCo.sub.yMn.sub.1−x−yO.sub.2 where 0≤x and y≤0.5; LiNi.sub.xCe.sub.zCo.sub.yMn.sub.1−x−yO.sub.2 where 0≤x and y≤0.5 and 0≤z; phosphates LiFePO.sub.4, LiMnPO.sub.4, LiCoPO.sub.4, LiNiPO.sub.4, Li.sub.3V.sub.2(PO.sub.4).sub.3; Li.sub.2MPO.sub.4F with M=Fe, Co, Ni or a mixture thereof, LiMPO.sub.4F with M=V, Fe, T or a mixture thereof; the phosphates of formula LiMMPO.sub.4, with M and M′ (M≠M′) selected from Fe, Mn, Ni, Co, V such as the LiFe.sub.xCo.sub.1−xPO.sub.4 and where 0<x<1; oxyfluorides of a type Fe.sub.0.9Co.sub.0.10OF; LiMSO.sub.4F with M=Fe, Co, Ni, Mn, Zn, Mg; and all lithiated forms of chalcogenides that include: V.sub.2O.sub.5, V.sub.3O.sub.8, TiS.sub.2, titanium oxysulfides (TiO.sub.yS.sub.z with z32 2−y and 0.3≤y≤1), tungsten oxysulfides (WO.sub.yS.sub.z with 0.6<y<3 and 0.1<z<2), CuS, CuS.sub.2, Li.sub.xV.sub.2O.sub.5 with 0<x≤2, Li.sub.xV.sub.3O.sub.8 with 0<x≤1.7,Li.sub.xTiS.sub.2 with 0<x≤1, titanium and lithium oxysulfides with Li.sub.xTiO.sub.yS.sub.z with z=2−y, 0.3≤y≤1 and 0<x≤1, Li.sub.xWO.sub.yS.sub.z with z=2−y, 0.3≤y≤1 and 0<x≤1, Li.sub.xCuS with 0<x≤1, Li.sub.xCuS.sub.2 with 0<x≤1.

28. The method of claim 18, wherein said at least one active electrode material is selected from the group consisting of: Li.sub.4Ti.sub.5O.sub.12, Li.sub.4Ti.sub.5−xM.sub.xO.sub.12 where M=V, Zr, Hf, Nb, Ta and 0≤x≤0.25; niobium oxides and mixed niobium oxides with titanium, germanium, cerium or tungsten, and one selected from the group consisting of: Nb.sub.2O.sub.5±δ, Nb.sub.18W.sub.16O.sub.93±δ, Nb.sub.16W.sub.5O.sub.55±δwith 0≤x<1 and 0≤δ≤2, LiNbO.sub.3, TiNb.sub.2O.sub.7±δ, Li.sub.wTiNb.sub.2O.sub.7 where w≥0, Ti.sub.1−xM.sup.1.sub.xNb.sub.2−yM.sup.2.sub.yO.sub.7±δor Li.sub.wTi.sub.1−xM.sup.1.sub.xNb.sub.2−yM.sup.2.sub.yO.sub.7±δwhere M.sup.1 and M.sup.2 are each at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr, Si, Sr, K, Cs and Sn, M.sup.1 and M.sup.2 are identical or different from each other, and where 0≤w≤5 and 0≤x≤1 and 0≤y≤2 and 0≤δ≤0.3; La.sub.xTi.sub.1−2xNb.sub.2+xO.sub.7 where 0<x<0.5; M.sub.xTi.sub.1−2xNb.sub.2+xO.sub.7±δ, where M is at least one element selected from the group consisting of Fe, Ga, Mo, Al, B, where 0<x≤0.20 and −0.3≤δ≤0.3; Ga.sub.0.10Ti.sub.0.80Nb.sub.2.10O.sub.7; Fe.sub.0.10Ti.sub.0.80Nb.sub.2.10O.sub.7; M.sub.xTi.sub.2−2xNb.sub.10+xO.sub.29±δ, where M is at least one element selected from the group consisting of Fe, Ga, Mo, Al, B, where 0<x≤0.40 and −0.3≤δ≤0.3; Ti.sub.1−xM.sup.1.sub.xNb.sub.2−yM.sup.2.sub.yO.sub.7−zM.sup.3.sub.z or Li.sub.wTi.sub.1−xM.sup.1.sub.xNb.sub.2−yM.sup.2.sub.yO.sub.7−zM.sup.3.sub.z where M.sup.1 and M.sup.2 are each at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr, Si, Sr, K, Cs and Sn, M.sup.1 and M.sup.2 are identical or different from each other, M.sup.3 is at least one halogen, and where 0≤w≤5 and 0≤x≤1 and 0≤y≤2 and z≤0.3; TiNb.sub.2O.sub.7−zM.sup.3.sub.z or Li.sub.wTiNb.sub.2O.sub.7−zM.sup.3.sub.z wherein M.sup.3 is at least one halogen, selected from F, Cl, Br, I or a mixture thereof, and 0<z≤0.3; Ti.sub.1−xGe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7±z, Li.sub.wTi.sub.1−xGe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7±z, Ti.sub.1−xCe.sub.xNb.sub.1−yM.sup.1.sub.yO.sub.7±z, Li.sub.wTi.sub.1−xCe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7±z, where M.sup.1 and M.sup.2 are at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr, Si, Sr, K, Cs and Sn, where 0≤w≤5 and 0≤x≤1 and 0≤y≤2 and z≤0.3; Ti.sub.1−xGe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7−zM.sup.2.sub.z, Li.sub.wTi.sub.1−xGe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7−zM.sup.2.sub.z, Ti.sub.1−xCe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7−zM.sup.2.sub.z, Li.sub.wTi.sub.1−xCe.sub.xNb.sub.2−yM.sup.1.sub.yO.sub.7−zM.sup.2.sub.x, where M.sup.1 and M.sup.2 are each at least one element selected from the group consisting of Nb, V, Ta, Fe, Co, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Ca, Ba, Pb, Al, Zr, Si, Sr, K, Cs, Ce and Sn, M.sup.1 and M.sup.2 are identical or different from each other, and where 0≤w≤5 and 0≤x≤1 and 0≤y≤2 and z≤0.3; TiO.sub.2; and LiSiTON.

29. The method of claim 18, wherein said inorganic material comprises an electronically insulating material selected from: Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, and/or a material selected from lithiated phosphates that includes: lithiated phosphates of an NaSICON type, Li.sub.3PO.sub.4; LiPO.sub.3; Li.sub.3Al.sub.0.4Sc.sub.1.6(PO.sub.4).sub.3 called “LASP”; Li.sub.1+xZr.sub.2−xCa.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25; Li.sub.1+2xZr.sub.2−xCa.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25 including Li.sub.1.2Zr.sub.1.9Ca.sub.0.1(PO.sub.4).sub.3 or Li.sub.1.4Zr.sub.1.8Ca.sub.0.2(PO.sub.4).sub.3, LiZr.sub.2(PO.sub.4).sub.3, Li.sub.1+3xZr.sub.2(P.sub.1−xSi.sub.xO.sub.4).sub.3 with 1.8<x<2.3; Li.sub.1+6xZr.sub.2(P.sub.1−xB.sub.xO.sub.4).sub.3 with 0≤x≤0.25; Li.sub.3(Sc.sub.2−xM.sub.x)(PO.sub.4).sub.3 with M=Al or Y and 0≤x≤1; Li.sub.1+xM.sub.x(Sc).sub.2−x(PO.sub.4).sub.3 with M=Al, Y, Ga or a mixture thereof and 0≤x≤0.8; Li.sub.1+xM.sub.x(Ga.sub.1−ySc.sub.y).sub.2−x(PO.sub.4).sub.3 with 0≤x≤0.8; 0≤y≤1 and M=Al and/or Y; Li.sub.1+xM.sub.x(Ga).sub.2−x(PO.sub.4).sub.3 with M=Al and/or Y and 0≤x≤0.8; Li.sub.1+xAl.sub.xTi.sub.2−x(PO.sub.4).sub.3 with 0≤x≤1 called “LATP”; or Li.sub.1+xAl.sub.xGe.sub.2−x(PO.sub.4).sub.3 with 0≤x≤1 called “LAGP”; or Li.sub.1+x+zM.sub.x(Ge.sub.1−yTi.sub.y).sub.2−xSi.sub.zP.sub.3−zO.sub.12 with 0≤x≤0.8 and 0≤y≤1.0 and 0≤z≤0.6 and M=Al, Ga or Y or a mixture of two or three thereof; Li.sub.3+y(Sc.sub.2−xM.sub.x)Q.sub.yP.sub.3−yO.sub.12 with M=Al and/or Y and Q=Si and/or Se, 0≤x≤0.8 0≤y≤1; or Li.sub.1+x+yM.sub.xSc.sub.2−xQ.sub.yP.sub.3−yO.sub.12 with M=Al, Y, Ga or a mixture thereof and Q=Si and/or Se, 0≤x≤0.8 and 0≤y≤1; or Li.sub.1+x+y+zM.sub.x(Ga.sub.1−ySc.sub.y).sub.2−xQ.sub.zP.sub.3−zO.sub.12 with 0≤x≤0.8, 0≤y≤1, 0≤z≤0.6 with M=Al and/or Y and Q=Si and/or Se; or Li.sub.1+xZr.sub.2−xB.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25; or Li.sub.1+xM.sup.3.sub.xM.sub.2−xP.sub.3O.sub.12 with 0≤x≤1 and M.sup.3=Cr, V, Ca, B, Mg, Bi and/or Mo, M=Sc, Sn, Zr, Hf, Se or Si, or a mixture thereof.

30. The method of claim 18, wherein said assembly is impregnated with an electrolyte that includes phase carrying lithium ions selected from: an electrolyte composed of at least one aprotic solvent and at least one lithium salt; an electrolyte composed of at least one ionic liquid or polyionic liquid and at least one lithium salt; a mixture of at least one aprotic solvent and at least one ionic liquid or polyionic liquid and at least one lithium salt; a polymer made ionically conductive by adding at least one lithium salt; and a polymer made ionically conductive by adding a liquid electrolyte, either in a polymer phase or a mesoporous structure, said polymer being selected from: poly(ethylene oxide), poly(propylene oxide), polydimethylsiloxane, polyacrylonitrile, poly(methyl methacrylate), poly(vinyl chloride), poly(vinylidene fluoride), and PVDF-hexafluoropropylene.

31. The method of claim 18, wherein said porous electrode is a positive porous electrode.

32. The method of claim 18, wherein said porous electrode is a negative porous electrode.

33. The method of claim 18, wherein said assembly is impregnated with an electrolyte that includes phase carrying lithium ions selected from: 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 one lithium salt; a mixture of at least one aprotic solvent, at least one ionic liquid, and at least one lithium salt; a polymer made ionically conductive by adding at least one lithium salt; and a polymer made ionically conductive by adding a liquid electrolyte or ionic polyliquid, either in a polymer phase or a mesoporous structure, said polymer being selected from: poly(ethylene oxide), poly(propylene oxide), polydimethylsiloxane, polyacrylonitrile, poly(methyl methacrylate), poly(vinyl chloride), poly(vinylidene fluoride), PVDF-hexafluoropropylene.

34. A lithium-ion battery, obtained by the method of claim 19, wherein the lithium-ion battery has a capacity not exceeding 1 mAh.

Description

DESCRIPTION

1. Definitions

[0150] As part of this document, the size of a particle is defined by its largest dimension. “Nanoparticle” means any particle or object of nanometric size having at least one of its dimensions less than or equal to 100 nm.

[0151] “Ionic liquid” means any liquid salt, capable of transporting electricity, being different from all the melted salts by a melting temperature below 100° C. Some of these salts remain liquid at room temperature and do not solidify, even at very low temperature. Such salts are called “ionic liquids at room temperature.”

[0152] “Mesoporous” materials mean any solid that has within its structure pores called “mesopores” having an intermediate size between that of the micropores (width less than 2 nm) and that of the macropores (width greater than 50 nm), namely a size comprised between 2 nm and 50 nm. This terminology corresponds to that adopted by IUPAC (International Union for Pure and Applied Chemistry), which serves as a reference for the person skilled in the art. The term “nanopore” is therefore not used here, even if the mesopores as defined above have nanoscale dimensions within the meaning of the definition of the nanoparticles, knowing that the pores with a size smaller than that of the mesopores are called by the person skilled in the art “micropores.”

[0153] A presentation of the concepts of porosity (and the terminology that has just been exposed above) is given in the article “Texture des matériaux pulvérulents ou poreux” by F. Rouquercol and al., published in the collection “Techniques de I'Ingénieur,” treaty of Analysis and Characterisation, fascicle P 1050; this article also describes the techniques for characterising porosity, in particular the BET method.

[0154] Within the meaning of the present invention, “mesoporous layer” means a layer which has mesopores. As will be explained below, in these layers the mesopores contribute significantly to the total porous volume; this fact is translated by the term “mesoporous layer of mesoporous porosity greater than X% by volume” used in the description below, and applicable to the porous electrode and to the separator used in the assembly according to the invention.

[0155] The term “aggregate” means, according to the definitions of IUPAC a weakly bound assembly of primary particles. In this case, these primary particles are nanoparticles having a diameter that can be determined by transmission electron microscopy. An aggregate of aggregated primary nanoparticles can normally be destroyed (that is to say reduced to primary nanoparticles) to make the primary nanoparticles suspended in a liquid phase under the effect of ultrasound, according to a technique known to the person skilled in the art.

[0156] The term “agglomerate” means, according to the definitions of IUPAC, a strongly bound assembly of primary particles or aggregates.

[0157] The term “microbattery” is used here for a battery of a capacity not exceeding 1 mAh. Typically, microbatteries are designed to be compatible with microelectronics manufacturing methods.

2. Preparation of Suspensions of Nanoparticles

[0158] The method for preparing the porous electrodes and the separator according to the invention starts from a suspension of nanoparticles. It is preferable not to prepare these suspensions of nanoparticles from dry nanopowders. They can be prepared by grinding powders or nanopowders in the liquid phase, and/or using ultrasonic treatment to deagglomerate nanoparticles.

[0159] In another embodiment of the invention the nanoparticles are prepared in suspension directly by precipitation. The synthesis of nanoparticles by precipitation allows to obtain primary nanoparticles of very homogeneous size with a unimodal size distribution that is to say a very tight and monodisperse distribution, of good crystallinity and purity. The use of these very homogeneous nanoparticles and narrow distribution allows to obtain a porous structure of controlled and open porosity after deposition. The porous structure obtained after deposition of these nanoparticles has little, preferably no closed pores.

[0160] In an even more preferred embodiment of the invention the nanoparticles are prepared directly at their primary size by hydrothermal or solvothermal synthesis; this technique allows 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 primary size. It is typically comprised between 2 nm and 150 nm. It is advantageously comprised between 10 nm and 50 nm, preferably between 10 nm and 30 nm; this promotes in subsequent method steps the formation of an interconnected mesoporous network, thanks to the phenomenon of “necking”. The electronic and ionic conduction of the porous electrode according to the invention takes place thanks to the phenomenon of “necking” forming the interconnected mesoporous network.

[0161] In an advantageous embodiment, the suspension of monodisperse nanoparticles is carried out in the presence of ligands or organic stabilisers so as to avoid aggregation, or even the agglomeration of nanoparticles. Binders may also be added in the suspension of nanoparticles to facilitate the production of depositions or raw tapes, in particular thick depositions without cracks. Indeed, in the context of the present invention, it proves to be preferable to start from a suspension of non-agglomerated primary particles, within which the agglomeration is then induced or caused, rather than allowing the agglomeration of the primary particles to occur spontaneously at the stage of preparation of the suspension.

[0162] This suspension of monodisperse nanoparticles can be purified to remove any potentially interfering ions. Depending on the degree of purification it can then be specially treated to form aggregates or agglomerates of a controlled size. More specifically, the formation of aggregates or agglomerates can result from the destabilisation of the suspension caused in particular by ions, by the increase in the dry extract of the suspension, by changing the solvent of the suspension, by adding a destabilising agent. If the suspension has been completely purified it is stable, and ions are added to destabilise it, typically in the form of a salt; these ions are preferably lithium ions (preferably added in the form of LiOH).

[0163] If the suspension has not been completely purified the formation of aggregates or agglomerates can be done alone in a spontaneous way or by ageing. This way of proceeding is simpler because it involves fewer purification steps, but it is more difficult to control the size of aggregates or agglomerates. One of the essential aspects for the manufacture of electrodes and a separator of the assembly according to the invention consists in properly controlling the size of the primary particles of electrode materials P and/or of inorganic materials E and their degree of aggregation or agglomeration.

[0164] If the stabilisation of the suspension of nanoparticles occurs after the formation of agglomerates, they will remain in the form of agglomerates; the suspension obtained can be used to make mesoporous depositions.

[0165] It is this suspension of aggregates or agglomerates of nanoparticles which is then used to deposit by electrophoresis, by the ink-jet printing method, by flexographic printing, by doctor blade coating, by roll coating, by curtain coating, by extrusion slot-die coating, or by dip-coating, or else by tape casting the porous, preferably mesoporous, electrode layers, and the inorganic layers, that is to say the separator of the assembly according to the invention.

[0166] According to the observations of the applicant, with an average diameter of the aggregates or agglomerates of nanoparticles comprised between 80 nm and 300 nm (preferably between 100 nm to 200 nm), a mesoporous layer having an average diameter of mesopores comprised between 2 nm and 50 nm is obtained during the subsequent steps of the method.

[0167] The porous electrode layer, respectively the inorganic layer corresponding to the separator of the assembly according to the invention, can be deposited by the dip-coating method, by the ink-jet printing method, by roll coating, by curtain coating or by doctor blade coating, from a fairly concentrated suspension comprising aggregates or agglomerates of nanoparticles of the active material P, respectively of the inorganic material E.

[0168] For electrophoresis, use is made of a less concentrated suspension containing agglomerates of nanoparticles of the active material P, respectively of the inorganic material E to produce the porous electrode layer, respectively to produce the inorganic layer corresponding to the separator of the assembly according to the invention.

[0169] The methods for depositing aggregates or agglomerates of nanoparticles by electrophoresis, by the dip-coating method, by ink-jet, by roll coating, by curtain coating or by doctor blade coating are methods which are simple, safe that easy to implement and to industrialise and which allow to obtain a final homogeneous porous layer. Electrophoretic deposition is a technique which enables uniform deposition over large areas with high deposition rates. The coating techniques, in particular dip-coating, roll coating, curtain coating or doctor blade coating, allow to simplify the management of the baths compared to the electrophoretic deposition techniques. Ink-jet printing deposition allows for localised depositions.

[0170] Porous layers made of a thick layer or separators made of a thick layer can be made in one step by roll coating, curtain coating, slot die coating, or by doctor blade coating (that is to say using a doctor blade).

[0171] It is noted that colloidal suspensions in water and/or ethanol and/or IPA and mixtures thereof are more fluid than those obtained in the NMP. It is thus possible to increase the dry extract of the suspensionof nanoparticle agglomerates. These agglomerates preferably have sizes of less than or equal to 200 nm and have polydisperse sizes, even with two populations with different sizes.

[0172] Compared to the prior art, the formulation of inks and pastes for the production of the electrodes is simplified. There is no more risk of carbon black agglomerates in the suspension when increasing dry extract.

[0173] The production of an assembly consisting of a porous electrode and a separator according to the invention will be presented below.

3. Deposition of Layers and their Consolidation

[0174] In general, a layer of a suspension of nanoparticles is deposited on a substrate, by any appropriate technique, and in particular by a method selected from the group formed of: electrophoresis, a printing method and preferably ink-jet printing or flexographic printing, a coating method and preferably doctor blade coating, roll coating, curtain coating, dip-coating, or slot-die coating. The suspension is typically in the form of an ink, that is to say a fairly fluid liquid, but can also have a pasty consistency. The deposition technique and the implementation of the deposition method must be compatible with the viscosity of the suspension, and vice versa.

[0175] The deposited layer will then be dried. The layer is then consolidated to obtain the desired mesoporous ceramic structure. This consolidation will be described below. It can be performed by heat treatment, by a heat treatment preceded by a mechanical treatment, and optionally by a thermomechanical treatment, typically a thermocompression. During this thermomechanical or heat treatment the electrode layer will be freed of any organic constituent and organic residue (such as the liquid phase of the suspension of the nanoparticles and any surfactant products): it becomes an inorganic (ceramic) layer. The consolidation of a plate is preferably carried out after its separation from its intermediate substrate, since the latter would risk being degraded during this treatment.

[0176] The deposition of the layers, their drying and their consolidation are likely to raise some problems which will be discussed now. These problems are partly linked to the fact that during the consolidation of the layers a shrinkage occurs which generates internal stresses.

3.1 Substrate Capable of Acting as a Current Collector

[0177] According to a first embodiment, the layers of electrodes are each deposited on a substrate capable of acting as an electric current collector. Layers including the suspension of nanoparticles or agglomerates of nanoparticles can be deposited on both faces, by the deposition techniques indicated above. The substrate serving as a current collector within batteries using porous electrodes according to the invention can be metallic, for example a metal strip (that is to say a rolled metal sheet). The substrate is preferably selected from strips of tungsten, molybdenum, chromium, titanium, tantalum, stainless steel, or an alloy of two or more of these materials. Less noble substrates such as copper or nickel may receive a conductive and protective coating against oxidation.

[0178] The metal sheet can be coated with a noble metal layer, in particular selected from gold, platinum, palladium, titanium or alloys containing mainly at least one or more of these metals, or a layer of ITO type conductive material (which has the advantage of acting as a diffusion barrier).

[0179] In general, this substrate capable of acting as an electric current collector must withstand the conditions of heat treatment of the deposited layer, and the operating conditions within the battery cell. As such, copper and nickel are suitable in contact with the anode material; they may oxidise the cathode.

[0180] Regarding the deposition of the layers, the electrophoresis method (especially in water) can be used. In this particular case, the substrate is subjected to an electrochemical polarisation which leads either to its oxidation or to its dissolution in the suspension of nanoparticles. In this case, only substrates which do not have anodisation and/or corrosion phenomena can be used. This is in particular the case with stainless steel and noble metals.

[0181] When the deposition of nanoparticles and/or agglomerates is carried out by one of the other techniques mentioned below (such as coating, printing) then it is possible to broaden the choice of substrates. This choice will then be made rather depending on the stability of the metal at the operating potential of the electrodes which are associated therewith and upon contact with the electrolytes. However, depending on the synthetic route used to produce the nanoparticles, more or less aggressive heat treatments must be carried out for the consolidation and possible recrystallisation of the nanopowders: this aspect will be further explored in section 5 below.

[0182] In all cases, a consolidation heat treatment is necessary to obtain these mesoporous electrodes. It is essential that the substrate capable of acting as an electric current collector can withstand these heat treatments without being oxidised. Several strategies can be used.

[0183] When the nanopowders deposited on the substrate by inking are amorphous and/or with numerous point defects, it is necessary to carry out a heat treatment which, in addition to consolidation, will also allow to recrystallise the material in the correct crystalline phase with the correct stoichiometry. For this purpose, it is generally necessary to carry out heat treatments at temperatures between 500 and 700° C. The substrate will then have to withstand this type of heat treatment, and it is necessary to use materials that withstand these high temperature treatments. Strips of stainless steel, titanium, molybdenum, tungsten, tantalum, chromium, as well as their alloys can for example be used.

[0184] When the nanopowders and/or agglomerates are crystallised, obtained by hydro-solvothermal synthesis with the correct phase and crystalline structure, then it is possible to use consolidation heat treatments under a controlled atmosphere, which will allow to use less noble substrates such as nickel, copper, aluminium, and due to the very small size of the primary particles obtained by hydrothermal synthesis, it will also be possible to reduce the temperature and/or the duration of the consolidation heat treatment to values close to 350-500° C., which also allows a wider choice of substrates. However, these less noble substrates must withstand the heat treatment allowing to remove the organic additives possibly contained in the suspension of nanoparticles used such as ligands, stabilisers, binders or residual organic solvents (debinding), this heat treatment being advantageously carried out under an oxidising atmosphere.

[0185] It is also possible that pseudo-hydrothermal syntheses result in amorphous nanoparticles which will need to be recrystallised later.

[0186] These substrates capable of acting as an electric current collector can optionally be covered with a thin film of conductive oxide. This oxide may have the same composition as the electrode. These thin films can be produced by sol-gel. This oxide-based interface allows to limit the corrosion of the substrate and ensures a better attachment base for the electrode with the substrate.

[0187] With regard to the operating conditions within the battery cell, it should be noted first of all that in the batteries using porous electrodes according to the invention, the liquid electrolytes which impregnate the porous electrode are in direct contact with the substrate capable of acting as a current collector. However, when these electrolytes are in contact with substrates capable of acting as a current collector, that is to say substrates which are metallic and polarised at potentials which are very anodic for the cathode and very cathodic for the anode, these electrolytes are capable of inducing a dissolution of the current collector. These parasitic reactions can degrade the battery life and accelerate its self-discharge. To avoid this, substrates capable of acting as a current collector such as aluminium current collectors are used at the cathode in all lithium-ion batteries. Aluminium has this peculiarity of being anodised at very anodic potentials, and the oxide layer thus formed at its surface protects it from the dissolution. However, aluminium has a melting temperature close to 600° C. and cannot be used for the manufacture of batteries according to the invention, if the electrode consolidation treatments may melt the current collector.

[0188] Thus, to avoid parasitic reactions that can degrade the life of the battery and accelerate its self-discharge, a titanium strip is advantageously used as a current collector at the cathode. When operating the battery, the titanium strip, such as aluminium, will be anodised and its oxide layer will prevent any parasitic reactions of titanium dissolution in contact with the liquid electrolyte. In addition, as titanium has a much higher melting point than aluminium, fully solid electrodes according to the invention can be made directly on this type of strip.

[0189] The use of these massive materials, in particular titanium strips, also allows to protect the cutting edges of the battery electrodes from corrosion phenomena. The use of copper strips advantageously allows to protect the cutting edges of the battery anodes from corrosion phenomena.

[0190] Stainless steel can also be used as a current collector, in particular when containing titanium or aluminium as an alloy element, or when it has a thin layer of protective oxide.

[0191] Other substrates serving as a current collector can be used such as less noble metal strips covered with a protective coating, allowing to avoid the possible dissolution of these strips induced by the presence of electrolytes at their contact.

[0192] These less noble metal strips can be Copper, Nickel or metal alloy strips such as stainless steel strips, Fe-Ni alloy, Be-Ni-Cr alloy, Ni-Cr alloy or Ni-Ti alloy strips.

[0193] The coating that can be used to protect the substrates serving as current collectors may be of different natures. It may be: [0194] a thin layer obtained by the sol-gel method of the same material as that of the electrode. The absence of porosity in this film allows to prevent contacts between the electrolyte and the metal current collector; [0195] a thin layer obtained by vacuum deposition, in particular by Physical Vapour Deposition (abbreviated PVD) or by Chemical Vapour Deposition (abbreviated CVD), of the same material as that of the electrode; [0196] a thin metal layer, which is dense, flawless, such as a thin metal layer of gold, titanium, platinum, palladium, tungsten or molybdenum. These metals can be used to protect current collectors as they have good conduction properties and can withstand heat treatments during the subsequent electrode manufacturing method. This layer can in particular be produced by electrochemistry, PVD, CVD, evaporation, ALD; [0197] a thin carbon layer such as diamond, graphite carbon, deposited by ALD, PVD, CVD or inking of a sol-gel solution allowing to obtain after heat treatment a carbon-doped inorganic phase to make it conductive, [0198] a layer of conductive or semiconductor oxides, such as an ITO (indium-tin oxide) layer only deposited on the cathode substrate because the oxides are reduced at low potentials; [0199] a layer of conductive nitrides such as a TiN layer only deposited on the cathode substrate because nitrides insert lithium at low potentials.

[0200] The coating that can be used to protect the substrates serving as current collectors must be electronically conductive so as not to interfere with the operation of the electrode subsequently deposited on this coating, by making it too resistive.

[0201] In general, in order not to impact too heavily the operation of the battery cells, the maximum dissolution currents measured on the substrates which can act as a current collector, at the operating potentials of the electrodes, expressed in μA/cm.sup.2, must be 1000 times lower than the surface capacities of the electrodes expressed in μAh/cm.sup.2.

[0202] When seeking to increase the thickness of the electrodes, it is observed that the shrinkage generated by consolidation can lead either to a cracking of the layers or to a shear stress at the interface between the substrate (which has a fixed dimension) and the ceramic electrode. When this shear stress exceeds a threshold, the layer detaches from its substrate.

[0203] To avoid this phenomenon, it is preferable to increase the thickness of the electrodes by a succession of deposition—sintering operations. This first variant of the first embodiment of the deposition of the layers gives a good result, but is not very productive. Alternatively, in a second variant, layers of greater thickness are deposited on both faces of a perforated substrate. The perforations must be of sufficient diameter so that the two layers of the front and back are in contact at the perforations. Thus, during consolidation, the nanoparticles and/or agglomerates of nanoparticles of electrode material in contact through the perforations in the substrate are welded together, forming an attachment point (welding point between the depositions of the two faces). This limits the loss of adhesion of the layers to the substrate during the consolidation steps.

[0204] To avoid this phenomenon, that is to say in order to increase the deposition thicknesses while limiting or eliminating the appearance of cracks, it is possible to add binders, dispersants. These additives and organic solvents can be eliminated by heat treatment, preferably under oxidising atmosphere, such as by debinding, during a sintering treatment or during a heat treatment carried out prior to the sintering treatment.

3.2 Intermediate Substrate

[0205] According to a second embodiment, the electrode layers are not deposited on a substrate capable of acting as an electric current collector, but on an intermediate, temporary substrate. In particular, it is possible to deposit, from suspensions that are more concentrated in nanoparticles and/or agglomerates of nanoparticles (that is to say less fluid, preferably pasty), fairly thick layers (called “green sheet”). These thick layers are deposited for example by a coating method, preferably by a doctor blade coating (a technique known under the term “tape casting”) or a slot-die coating. Said intermediate substrate may be a polymeric sheet, for example poly(ethylene terephthalate), abbreviated PET. During drying, these layers do not crack, in particular when drying occurs after the separation of the layer obtained in step (b) from its intermediate substrate. For consolidation by heat treatment (and preferably already for drying) they can be detached from their substrate; plates are thus obtained after cutting electrodes called “raw” electrodes which after calcination heat treatment and partial sintering will give mesoporous and self-supporting ceramic plates.

[0206] A stack of three layers is then made, namely two plates of electrodes of the same polarity separated by an electrically conductive sheet capable of acting as an electric current collector, such as a metal sheet or a graphite sheet. This stack is then assembled by a thermomechanical treatment, comprising a pressing and a heat treatment, preferably carried out simultaneously. Alternatively, to facilitate gluing between the ceramic plates and the metal sheet, the interface may be coated with a layer allowing an electronically conductive gluing. This layer can be a sol-gel layer (preferably of the type allowing the chemical composition of the electrodes to be obtained after heat treatment) possibly loaded with particles of an electronically conductive material, which will make a ceramic weld between the mesoporous electrode and the metal sheet. This layer can also consist of a thin layer of non-sintered electrode nanoparticles, or of a thin layer of a conductive glue (loaded with graphite particles for example), or else a metallic layer of a metal having a low melting point.

[0207] When said electrically conductive sheet is metallic, it is preferably a rolled sheet, that is to say obtained by rolling. The rolling may optionally be followed by a final annealing, which can be a (total or partial) softening or recrystallisation annealing, depending on the terminology of metallurgy. It is also possible to use an electrochemically deposited sheet, for example an electrodeposited copper sheet or an electrodeposited nickel sheet.

[0208] In any case, a ceramic electrode is obtained, without organic binder, which is mesoporous, located on either side of a metal substrate serving as an electronic current collector.

4. Deposition of the Layers of Active Material P

[0209] In general, and as has already been mentioned, the electrodes according to the invention can be manufactured from suspensions of nanoparticles, using known coating techniques. These techniques that can be used are the same printing and coating techniques as those presented above in the subchapter entitled “Preparation of suspensions of nanoparticles”.

[0210] For all these techniques, it is advantageous for the dry extract of the suspension to be greater than 20%, and preferably greater than 40%; this decreases the risk of cracking when drying.

[0211] Electrophoresis can also be used.

[0212] In a first embodiment, the method according to the invention advantageously uses the electrophoresis of suspensions of nanoparticles as a technique for depositing porous, preferably mesoporous, electrode layers. The method for depositing layers of electrodes from a suspension of nanoparticles is known as such (see for example EP 2 774 194 B1). The substrate can be metallic, for example a metallic sheet. The substrate serving as a current collector within the batteries using porous electrodes according to the invention is preferably selected from strips of titanium, copper, stainless steel or molybdenum.

[0213] For example, a sheet of stainless steel with a thickness of 5 μm can be used. The metal sheet may be coated with a layer of noble metal, in particular selected from gold, platinum, palladium, titanium or alloys predominantly containing at least one or more of these metals, or with a layer of ITO type conductive material (which has the advantage of also acting as a diffusion barrier).

[0214] In a particular embodiment, a layer, preferably a thin layer, of an electrode material is deposited on the metal layer; this deposition must be very thin (typically a few tens of nanometres, and more generally comprised between 10 nm and 100 nm). It can be carried out by a sol-gel method. For example, LiMn2O4 can be used for a porous LiMn2O4 cathode.

[0215] For electrophoresis to take place, a counter electrode is placed in the suspension and a voltage is applied between the conductive substrate and said counter electrode.

[0216] In an advantageous embodiment, the electrophoretic deposition of the aggregates or agglomerates of nanoparticles is carried out by galvanostatic electrodeposition in pulsed mode; high frequency current pulses are applied, this avoids the formation of bubbles on the surface of the deposited layers and the variations of the electric field in the suspension during the deposition. The thickness of the layer thus deposited by electrophoresis, preferably by galvanostatic electrodeposition in pulsed mode is advantageously less than 10 μm, preferably less than 8 μm, and is even more preferably between 1 μm and 6 μm.

[0217] In another embodiment, aggregates or agglomerates of nanoparticles can be deposited by the dip-coating method, regardless of the chemical nature of the nanoparticles used. This deposition method is preferred when the nanoparticles used have little or no electric charge. In order to obtain a layer of the desired thickness, the step of depositing the aggregates or agglomerates of nanoparticles by dip-coating followed by the step of drying the resulting layer are repeated as necessary. In order to increase the thickness of the layers free of cracks, it is advantageous to use in the colloidal suspension or the deposited paste, at least one organic additive such as ligands, stabilisers, thickeners, binders or residual organic solvents.

[0218] Although this succession of dip-coating/drying steps is time consuming, the dip-coating deposition method is a method which is simple, safe, easy to implement, to industrialise and allowing to obtain a homogeneous and compact final layer.

5. Consolidation Treatment of the Deposited Layers

[0219] The consolidation treatment is applied to the electrode layer. The deposited layers must be dried; drying must not induce the formation of cracks. For this reason, it is preferred to carry it out under controlled humidity and temperature conditions or to use, to produce the porous layer, colloidal suspensions and/or pastes comprising, in addition to aggregates or agglomerates of monodisperse primary nanoparticles, at least one electrode active material P according to the invention, organic additives such as ligands, stabilisers, thickeners, binders or residual organic solvents.

[0220] The dried layers can be consolidated by a pressing and/or heating step (heat treatment). 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 neighbouring aggregates or agglomerates; this phenomenon is called “necking” or “neck formation”. It is characterised by the partial coalescence of two particles in contact, which remain separate but connected by a (constricted) neck. Lithium ions and electrons are movable within these necks and can diffuse from particle to particle without encountering grain boundaries. The nanoparticles weld together to ensure the conduction of electrons from one particle to another. Thus, a three-dimensional network of interconnected particles with high ionic mobility and electronic conduction is formed; this network includes pores, preferably mesopores where the notion of particle disappears after heat treatment.

[0221] The temperature necessary to obtain “necking” depends on the material; taking into account the diffusive nature of the phenomenon which leads to necking, the duration of the treatment depends on the temperature. This method can be called sintering; depending on its duration and temperature, a more or less pronounced coalescence (necking) is obtained, which has repercussions on the porosity. It is thus possible to go down to 30% (or even 25%) of porosity while maintaining a perfectly homogeneous channel size.

[0222] The heat treatment can also be used to eliminate the organic additives possibly contained in the suspension of nanoparticles used, such as ligands, stabilisers, binders or residual organic solvents. According to another variant, an additional heat treatment, under an oxidising atmosphere, can be carried out to remove these organic additives possibly contained in the suspension of nanoparticles used. This additional heat treatment is advantageously carried out before the consolidation treatment of step c) allowing to obtain a porous, preferably mesoporous, layer.

6. Deposition of the Coating of Electronically Conductive Material

[0223] According to an essential feature of the present invention, a coating of an electronically conductive material is deposited on and inside the pores of said porous layer so as to obtain the porous electrode of the assembly according to the invention.

[0224] Indeed, as explained above, the method according to the invention, which necessarily involves a step of depositing agglomerated nanoparticles of electrode material (active material), causes the nanoparticles to “weld” naturally to each other to generate, after consolidation such as annealing, a porous, rigid, three-dimensional structure, without organic binder; this porous, preferably mesoporous, layer, is perfectly adapted to the application of a surface treatment, by gas or liquid, which goes deep into the open porous structure of the layer.

[0225] Very advantageously, this deposition is carried out by a technique allowing an encapsulating coating (also called “conformal deposition”), that is to say a deposition which faithfully reproduces the atomic topography of the substrate on which it is applied, and which goes deep into the open porosity network of the layer. Said electronically conductive material may be carbon.

[0226] The techniques of ALD (Atomic Layer Deposition) or CSD (Chemical Solution Deposition), known as such, may be suitable. They can be implemented on the porous layers after manufacture, before the deposition of the separator particles and before the assembly of the cell. The ALD deposition technique is carried out layer by layer, by a cyclic method, and allows to produce an encapsulating coating which faithfully reproduces the topography of the substrate; the coating lines the entire surface of the electrodes. This encapsulating coating typically has a thickness comprised between 1 nm and 5 nm.

[0227] The deposition by ALD is carried out at a temperature typically comprised between 100° C. and 300° C. It is important that the layers are free from organic materials: they must not include any organic binder, any residues of stabilising ligands used to stabilise the suspension must have been removed by purification of the suspension and/or during the heat treatment of the layer after drying. Indeed, at the temperature of the ALD deposition, the organic materials forming the organic binder (for example the polymers contained in the electrodes produced by ink tape casting) risk decomposing and will pollute the ALD reactor. Moreover, the presence of residual polymers in contact with the electrode active material particles can prevent the ALD coating from encapsulating all the particle surfaces, which impairs its effectiveness.

[0228] The CSD deposition technique also allows to produce an encapsulating coating with a precursor of the electronically conductive material which faithfully reproduces the topography of the substrate; it lines the entire surface of the electrodes. This encapsulating coating typically has a thickness of less than 5 nm, preferably comprised between 1 nm and 5 nm. It must then be transformed into an electronically conductive material. In the case of a carbon precursor, this will be done by pyrolysis, preferably under inert gas (such as nitrogen).

[0229] In this variant of depositing a nanolayer of electronically conductive material, it is preferable that the diameter D.sub.50 of the primary particles of electrode material is at least 10 nm in order to prevent the conductive layer from blocking the open porosity of the layer.

7. Production of the Separator (Layer of Inorganic Material E) on the porous Electrode

[0230] A layer of at least one inorganic material E, from suspensions of nanoparticles of inorganic material E, is deposited on the porous, preferably mesoporous, electrode comprising a coating of an electronically conductive material, preferably after drying, using known coating techniques as indicated in paragraph 4 above. The method for depositing porous inorganic layers from a suspension of nanoparticles is known as such (see for example WO 2019/215411 A1).

[0231] In one embodiment, the material used for the manufacture of porous layers which can serve as a separator according to the invention is selected from inorganic materials with a low melting point, electronic insulators and which are stable in contact with the electrodes during the heat pressing steps. The more refractory the materials, the more it will be necessary to heat at the electrode/electrolytic separator interfaces, at high temperatures thus risking modifying the interfaces with the electrode materials, in particular by interdiffusion, which generates parasitic reactions and creates depletion layers whose electrochemical properties differ from those found in the same material at a greater depth from the interface. Materials comprising lithium are preferred because they prevent or even eliminate these lithium depletion phenomena.

[0232] The material used for the manufacture of porous inorganic layers according to the invention can be an ionic conductive material such as a solid electrolyte comprising lithium in order to avoid the formation of lithium depletion areas at the electrode/electrolytic separator interfaces. The inorganic material E advantageously comprises an electronically insulating material, preferably chosen from the materials selected from the group formed of lithiated phosphates, preferably selected from: lithiated phosphates of the NaSICON type, Li.sub.3PO.sub.4; LiPO.sub.3; Li.sub.3Al.sub.0.4Sc.sub.1.6(PO.sub.4).sub.3 called “LASP”; Li.sub.1+xZr.sub.2−xCa.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25; Li.sub.1+2xZr.sub.2−xCa.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25 such as Li.sub.1.2Zr.sub.1.9Ca.sub.0.1(PO.sub.4).sub.3 or Li.sub.1.4Zr.sub.1.8Ca.sub.0.2(PO.sub.4).sub.3, LiZr.sub.2(PO.sub.4).sub.3, Li.sub.1+3xZr.sub.2(P.sub.1−xSi.sub.xO.sub.4).sub.3 with 1.8<x<2.3; Li.sub.1+6xZr.sub.2(P.sub.1−xB.sub.xO.sub.4).sub.3 with 0≤x≤0.25; Li.sub.3(Sc.sub.2−xM.sub.x)(PO.sub.4).sub.3 with M=A1 or Y and 0≤x≤1; Li.sub.1+xM.sub.x(Sc).sub.2−x(PO.sub.4).sub.3 with M=Al, Y, Ga or a mixture of these three elements and 0≤x≤ 0.8; Li.sub.1+xM.sub.x(Ga.sub.1−ySc.sub.y).sub.2−x(PO.sub.4).sub.3 with 0≤x≤0.8; 0≤y≤1 and M=Al and/or Y; Li.sub.1+xM.sub.x(Ga).sub.2−x(PO.sub.4).sub.3 with M=Al and/or Y and 0≤x≤0.8; Li.sub.1+xAl.sub.xTi.sub.2−x(PO.sub.4).sub.3 with 0≤x≤1 called “LATP”; or Li.sub.1+xAl.sub.xGe.sub.2−x(PO.sub.4).sub.3 with 0≤x≤1 called “LAGP”; or Li.sub.1+x+zM.sub.x(Ge.sub.1−yTi.sub.y).sub.2−xSi.sub.zP.sub.3−zO.sub.12 with 0≤x≤0.8 and 0≤y≤1.0 and 0≤z≤0.6 and M=Al, Ga or Y or a mixture of two or three of these elements; Li.sub.3+y(Sc.sub.2−xM.sub.x)Q.sub.yP.sub.3−yO.sub.12 with M=Al and/or Y and Q=Si and/or Se, 0≤x≤0.8 and 0≤y≤1; or Li.sub.1+x+yM.sub.xSC.sub.2−xQ.sub.yP.sub.3−yO.sub.12 with M=Al, Y, Ga or a mixture of these three elements and Q=Si and/or Se, 0≤x≤0.8 and 0≤y≤1; or Li.sub.1+x+y+zM.sub.x(Ga.sub.1−ySc.sub.y).sub.2−xQ.sub.zP.sub.3−zO.sub.12 with 0≤x≤0.8, 0≤y≤1, 0≤z≤0.6 with M=Al and/or Y and Q=Si and/or Se; or Li.sub.1+xZr.sub.2−xB.sub.x(PO.sub.4).sub.3 with 0≤x≤0.25; or Li.sub.1+xM.sup.3.sub.xM.sub.2−xP.sub.3O.sub.12 with 0≤x≤1 and M.sup.3=Cr, V, Ca, B, Mg, Bi and/or Mo, M=Sc, Sn, Zr, Hf, Se or Si, or a mixture of these elements. Li.sub.3PO.sub.4 is particularly preferred.

[0233] This inorganic layer is a porous, preferably mesoporous, ceramic film which performs the function of electrolytic separation. The ceramic nanoparticles used to manufacture the separator of the assembly according to the invention must be electrochemically stable in contact with the electrodes and be electronically insulating, and preferably conductive of lithium ions. Depositing this inorganic layer (mesoporous ceramic film) allows to reduce the thickness of the electrolytic film. This layer has excellent mechanical properties. This reduction in thickness increases the volume energy density of the batteries.

[0234] The completely ceramic and/or glass-ceramic nature of this porous inorganic layer, free from organic elements, allows to guarantee an excellent mechanical strength, perfect wetting by liquid electrolytes, even by ionic liquids at room temperature, and also ensures the operation of battery cells in very wide temperature ranges (no risk of melting and/or breakage of the separator).

[0235] The production of such a porous inorganic layer, that is to say such a separator, on the porous electrodes remains very difficult to achieve. Indeed, the performance of the porous electrodes according to the invention comes in part from the fact that they are covered on the surface by a coating of an electronically conductive material, such as carbon. However, the depositions of agglomerates of inorganic nanoparticles E serving to ensure the electrolytic separation function are, after deposition, rich in organic materials. These organic materials being in the solvent adsorbed on the surface of the nanoparticles as well as in the organic stabilisers used in the formulation of the suspension of inorganic nanoparticles E. Thus, before impregnating the assembly consisting of a porous electrode and a separator according to the invention, these organic residues should be removed from the separator. For this purpose, it is necessary to carry out calcination treatments. These calcination treatments are carried out by annealing under air in order to transform these organics into CO.sub.2 and eliminate them. However, to guarantee the performance of the porous electrode associated with this ceramic separator, it is essential that the coating of electronically conductive material, such as the carbon coating present on the surface of the porous electrodes, is not removed by the calcination treatment of the organics. For this purpose, the applicant has identified treatment conditions which allow to remove the organics while maintaining the coating of electronically conductive material, such as the carbon coating on the porous electrode, without there being any carbon deposition in the separator which could harm the electrical insulation of the cell, in particular its self-discharge.

[0236] This heat treatment is carried out under air, at a moderate temperature, in order to allow the removal of the organics contained in the electrolytic separator deposition in the form of CO.sub.2 while maintaining the coating of electronically conductive material, such as the carbon coating present at the surface of the porous electrodes. For this purpose, a heat treatment at less than 500° C. and preferably at a temperature comprised between approximately 250° C. and approximately 450° C., and optimally) approximately 400° C., is carried out.

[0237] After heat treatment, an assembly consisting of a porous electrode and a separator according to the invention is obtained.

8. Impregnation of the Assembly with an Electrolyte in Order to Obtain a Functional Member of a Battery

[0238] According to a first embodiment of the invention, the assembly is impregnated with a polymer containing lithium salts, and which is therefore an ionic conductor, the ion species transported being lithium ions.

[0239] According to a second embodiment of the invention, the assembly is impregnated with a liquid electrolyte; it may be, for example, an ionic liquid or an aprotic solvent wherein one or more lithium salts have been dissolved. It is also possible to use a poly(ionic liquid) (abbreviated PIL).

[0240] More specifically, the assembly according to the invention (before its impregnation) does not contain organic compounds, and this absence of organic compounds coupled with a mesoporous structure promotes wetting by an electrolyte which conducts lithium ions. This electrolyte can then be selected without distinction from the group formed of: an electrolyte composed of at least one aprotic solvent and of at least one lithium salt, an electrolyte composed of at least one ionic liquid or poly(ionic liquid) and at least one lithium salt, a mixture of aprotic solvents and ionic liquids or poly(ionic liquids) and lithium salts, an ionically conductive polymer containing at least one lithium salt, or else a polymer made ionically conductive by adding at least one lithium salt. Said polymer is advantageously selected from the group formed of poly(ethylene oxide) (commonly abbreviated PEO), poly(propylene oxide), polydimethylsiloxane (commonly abbreviated PDMS), polyacrylonitrile (commonly abbreviated PAN), poly(methyl methacrylate) (commonly abbreviated PMMA), poly(vinyl chloride) (commonly abbreviated PVC), poly(vinylidene fluoride) (commonly abbreviated PVDF), PVDF-hexafluoropropylene.

[0241] Said polymer, whether or not containing lithium salts, is typically solid at room temperature and can be melted and this molten phase can then be impregnated into the mesoporosity of the assembly. Once cooled, an assembly comprising an electrode and a solid electrolyte is obtained.

[0242] This assembly comprising an electrode and a solid electrolyte can be used in several ways to produce elementary battery cells.

9. Use of the Assembly Comprising a Porous Electrode and a Solid Electrolyte to Produce Elementary Battery Cells

[0243] As indicated above, the assembly according to the invention can be impregnated with a molten phase comprising an ionically conductive polymer, and optionally lithium salts. Once cooled, an assembly comprising a porous electrode for an electrode and a solid electrolyte is obtained. This assembly comprising an electrode and a solid electrolyte can be used in several ways to produce elementary battery cells, and, ultimately, batteries.

[0244] This assembly comprising an electrode and a solid electrolyte can be attached: [0245] to another assembly comprising an electrode and a solid electrolyte, or [0246] to a dense electrode, or [0247] to a porous electrode previously impregnated with a polymer, or [0248] to a dense electrode previously covered with a layer of electrolyte, or [0249] a porous electrode previously covered with a porous electrolyte, whose assembly is impregnated with a polymer.

[0250] The stacks obtained are then thermocompressed so as to assemble the elementary cells of the batteries. During thermocompression, the impregnated ionic conductive polymer will soften and allow the welding to be made between the assembly comprising an electrode and a solid electrolyte and the subsystem to which it is attached.

[0251] To make the welding reliable, during thermocompression, between the assembly comprising an electrode and a solid electrolyte and the subsystem to which it is attached, it is also possible to deposit on the assembly comprising an electrode and a solid electrolyte, and/or on the subsystem to which it will be attached, a thin layer of the same ionically conductive polymer used to impregnate the assembly according to the invention. This allows the operating temperature range of the final battery to be increased.

[0252] For the same purpose, it is also possible to deposit on the assembly comprising an electrode and a solid electrolyte, and/or on the subsystem to which it will be attached, a thin layer of core-shell particles, the core of which is made from the same inorganic material E as that used to make the separator of the assembly according to the invention, and the shell is made from the same ionic conductive polymer used during the impregnation of the assembly according to the invention. This allows to increase the mechanical properties of the separator as well as its adhesion to the subsystem to which it is attached.

[0253] The assembly consisting of a porous positive electrode and a separator according to the invention and impregnated with an ionic conductive polymer, is particularly well adapted to the production of very high energy density battery cells using negative metallic lithium electrodes. Indeed, to use negative electrodes made of metallic lithium it is imperative that the cell is fully solid, devoid of liquid electrolyte and/or pockets of liquid electrolyte trapped in polymers or other phases. These liquid phases are privileged areas for precipitation of metallic lithium.

[0254] In another embodiment, it is also possible to attach and then assemble the assembly consisting of a porous electrode and a separator according to the invention and impregnated with an ionic conductive polymer comprising or not lithium salts: [0255] with a porous electrode of opposite sign, or [0256] with a porous electrode of opposite sign covered with a porous separator, or [0257] with an assembly consisting of a porous electrode and a separator according to the invention.

[0258] The assembly of the resulting stack must be carried out by thermopressing. In the event that there is no organic material to make the connection between the different subassemblies, the pressing temperatures should be relatively high and preferably greater than 400° C. Also, these treatments should be carried out under an inert atmosphere or under vacuum to avoid altering the coating of electronically conductive material present on the porous electrode of the assembly according to the invention. The resulting assembly can be impregnated subsequently with an electrolyte, whether solid or liquid. Impregnation with a solid electrolyte, such as an ionic conductive polymer comprising lithium salts without liquid phase, allows to produce batteries operating with negative electrodes with low insertion potential without forming lithium dendrites.

EXAMPLES

Example 1: Production of a Porous Positive Electrode Based on LiMn.SUB.2.O.SUB.4

[0259] A suspension of LiMn.sub.2O.sub.4 nanoparticles was prepared by hydrothermal synthesis according to the method described in the article by Liddle and al. titled “A new one pot hydrothermal synthesis and electrochemical characterisation of Li.sub.1−xMn.sub.2−yO.sub.4 spinel structured compounds”, Energy & Environmental Science (2010) vol.3, page 1339-1346: 14.85 g of LiOH, H.sub.2O were dissolved in 500 ml of water. 43.1g of KMnO.sub.4 was added to this solution and this liquid phase was poured into an autoclave. With stirring, 28 ml of isobutyraldehyde, 25 g/I of 40 000 g/mol polyvinylpyrrolidone (PVP), and water were added until a total volume of 3.54 I was reached. The autoclave was then heated to 180° C. and maintained at that temperature for 6 hours. After cooling slowly, a black precipitate suspended in the solvent was obtained. This precipitate was subjected to a succession of steps of centrifugation—redispersion in water, until an aggregated suspension is obtained. The obtained aggregates consisted of aggregated primary particles 10 to 20 nm in size. The aggregates obtained had a spherical shape and an average diameter of about 150 nm. The amount of PVP added to the reaction medium allowed to adjust the size and shape of the agglomerates obtained.

[0260] About 10 to 15 wt % of 360 000 g/mol polyvinylpyrrolidone (PVP) was then added to the aqueous suspension of aggregates. The water was then evaporated until the aqueous suspension of aggregates had a dry extract of 10%. The ink thus obtained was then applied to a stainless steel strip (316 L) with a thickness of 5 μm. The deposition obtained was then dried in a temperature and humidity controlled oven in order to prevent the formation of cracks during drying. This resulted in a deposition approximately 10 μm thick.

[0261] The deposition obtained was then consolidated at 600° C. for 1 hour under air in order to weld the nanoparticles together, to improve adhesion to the substrate and to complete the recrystallisation of LiMn.sub.2O.sub.4. The porous film obtained has an open porosity of approximately 45% by volume with pores having a size comprised between 10 nm to 20 nm.

[0262] The porous film was then impregnated with an aqueous solution of sucrose at approximately 20 g/l, then was annealed at 400° C. under N.sub.2 in order to obtain a carbon nanocoating over the entire accessible surface of the porous film.

Example 2: Manufacture of a Porous Electrode and Integrated Electrolytic Separator Assembly Using the Electrode According to Example 1

[0263] A cathode was produced according to Example 1. This electrode was covered with a porous layer from a suspension of Li.sub.3PO.sub.4 nanoparticles as indicated below.

Making a Suspension Of Li.SUB.3.PO.SUB.4 .Nanoparticles

[0264] Two solutions were prepared: 11.44 g of CH.sub.3COOLi, 2H.sub.2O were dissolved in 112 ml of water, then 56 ml of water were added with vigorous stirring to the medium in order to obtain a solution A. 4.0584 g of H.sub.3PO.sub.4 were diluted in 105.6 ml of water, then 45.6 ml of ethanol were added to this solution in order to obtain a second solution called hereinafter solution B. Solution B was then added, with vigorous stirring, to solution A.

[0265] The solution obtained, which was perfectly clear after the bubbles formed during mixing had disappeared, was added to 1.2 litres of acetone under the action of an Ultraturrax TM type homogeniser in order to homogenise the medium. A white precipitation suspended in the liquid phase was immediately observed.

[0266] The reaction medium was homogenised for 5 minutes then was maintained for 10 minutes with magnetic stirring. It was left to settle for 1 to 2 hours. The supernatant was removed 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 has thus become more stable. The suspension was then sonicated using a sonotrode. The suspension was then centrifuged for 15 minutes at 8000 rpm. The pellet was then redispersed in 150 ml of water. The suspension obtained was then centrifuged again for 15 minutes at 8000 rpm and the pellets obtained redispersed in 300 ml of ethanol in order to obtain a suspension suitable for carrying out an electrophoretic deposition.

[0267] Agglomerates of about 100 nm consisting of primary Li.sub.3PO.sub.4 particles of 15 nm were thus obtained in suspension in ethanol, with Bis(Monoacylglycero)Phosphate (abbreviated BMP) as stabiliser.

Producing on the Previously Developed Cathode a Porous Layer from the Suspension of Li.SUB.3.PO.SUB.4 .Nanoparticles Previously Described

[0268] A thin porous layer of Li.sub.3PO.sub.4 was then deposited by dip-coating in the suspension of Li.sub.3PO.sub.4 nanoparticles previously obtained, containing 20 g/L of agglomerated nanoparticles, with a deposition speed of approximately 10 mm/s. This produces a layer approximately 3 μm to 4 μm thick on the electrode. The layer was then dried in air at 120° C. then a calcination treatment at approximately 350° C. to 400° C. for 60 minutes was carried out on this previously dried layer in order to remove all traces of organic residues from the separator while retaining the carbon nanocoating of the porous electrode.