SOLID ELECTROLYTE ELECTROCHEMICAL ELEMENT

Abstract

SOLID ELECTROCHEMICAL ELEMENT The present invention relates to a solid electrochemical element with a bimodal particle size distribution comprising particles of a size whose particle size is distributed according to two distinct distributions. Figure for the abstract: none

Description

Title of the invention: SOLID ELECTROLYTE ELECTROCHEMICAL ELEMENT

[0001] The present invention relates to the field of batteries, and in particular solid electrolyte batteries.

[0002] Unlike flammable liquid organic electrolytes, solid electrolytes represent promising candidates for the development of safer lithium metal and Li-ion batteries.

[0003] However, they present drawbacks which impose technological challenges to consider their use:

[0004] In particular, it is necessary to control the interfaces between the electrolyte and the electrodes to ensure good diffusion of the Li+ ions, and improve the electrochemical performances.

[0005] It is also important to inhibit the accumulation of heterogeneous lithium to prevent the formation of dendrites and avoid short circuits and capacity losses.

[0006] Finally, solid electrolyte elements are particularly sensitive to mechanical pressure in order to maintain an electronic percolating network within the electrodes and an ionic percolating network within the battery as a whole. The exercise of optimal pressure is thus necessary to avoid loss of contact in the different layers (electrodes, separating electrolyte layer, current collectors) or at their interfaces.

[0007] EP 3 093 913 describes an electrochemical element with solid electrolyte, comprising two layers of solid electrolyte, each consisting of different ingredients.

[0008] However, this configuration does not have the effect of improving the mechanical resistance to pressure and of inhibiting the formation of dendrites.

[0009] The aim of the invention is then to propose a solid electrolyte element making it possible to avoid the aforementioned drawbacks.

[0010] To this end, the invention proposes a layer of solid electrolyte with bimodal particle size distribution.

[0011] According to a first subject, the invention relates to an electrochemical element with solid electrolyte, said element comprising a positive electrode and a negative electrode, said electrodes being separated from each other by a layer C of solid electrolyte of thickness e, characterized in that said electrolyte layer comprises at least one population of solid electrolyte particles PI of chemical formula SI and a population of solid electrolyte particles P2 of chemical formula S2, the chemical formulas SI and S2 being identical or different, and such that particles PI and P2 have respectively a median diameter (Dv50)i and (Dv50)2, and such that (Dv50)i <(Dv50)2.

[0012] As used herein, the term "median diameter Dv50" means that 50% of the volume of the particles consists of particles having an equivalent diameter less than said value considered, and 50% of the volume of the particles consists of particles having an equivalent diameter greater than said value. The term equivalent diameter of a particle refers to the diameter of a sphere having the same volume as this particle. The measurement of the size of the particles can be carried out by the technique of laser diffraction granulometry.

[0013] The electrochemical element

[0014] The term "electrochemical element" means an elementary electrochemical cell comprising an assembly of positive and negative electrodes, electrolyte, and possibly separators, container and terminals, making it possible to store the electrical energy supplied by a chemical reaction and to restore it in the form of current. The electrolyte can be solid or liquid, preferably solid.

[0015] In all-solid-state electrochemical elements, the electrolytic compound(s) included in the electrolytic layer may also be included in part within the electrodes.

[0016] The solid electrolyte

[0017] The invention therefore provides a bimodal solid electrolyte element, the term bimodal referring here to the granulometry, i.e. the distribution of the size of the particles constituting the solid electrolyte layer C (SEL for "Solid electrolyte layer"), designated here "bimodal layer C".

[0018] According to the invention, said layer C of bimodal solid electrolyte comprises particles distributed mainly according to two distinct average sizes, represented respectively by distinct median diameters (Dv50)i and (Dv50)2, such that (Dv50)i <(Dv50)2.

[0019] The bimodal particle size distribution according to the invention has the effect of reducing the porosity and therefore increasing the compactness of the electrolyte layer. In fact, a reduction in porosity is expected to a porosity of approximately 8%.

[0020] In addition to the reduction in porosity, the advantages of a bimodal particle size distribution electrolyte layer are also related to the reduction in the amount of grain boundaries.

[0021] The term “grain boundary” means the junction (i.e.) the point of contact between two particles.

[0022] These two factors ensure ease of manufacturing during calendering as well as better diffusion of Li+ ions.

[0023] In fact, grain boundaries can be likened in operation to obstacles to the passage of Li+ ions: Reducing the number of grain boundaries therefore makes it possible to reduce ionic resistance.

[0024] The bimodal particle size distribution according to the invention therefore makes it possible to improve the diffusion of Li+ ions within the electrolyte layer C.

[0025] It is understood that the bimodal distribution is not necessarily linked to the chemical nature of the constituent(s) of the solid electrolytes constituting the solid electrolyte layer.

[0026] Solid electrolyte particles having the desired particle size may be commercially available or obtained by sieving or mechanical grinding.

[0027] According to an alternative, said bimodal layer C may actually comprise two solid electrolytes of distinct chemical nature, i.e. of different respective chemical formulas SI and S2, SI being made up of a population of particles PI and S2 being made up of a population of particles P2, and PI and P2 having respectively a median diameter (Dv50)i and (Dv50)2, and such that (Dv50)i <(Dv50)2.

[0028] According to another alternative, said bimodal layer C can be composed of a single solid electrolyte which comprises two populations PI and P2 of particles, each having the same chemical nature and therefore corresponding to the same chemical formula (S1=S2), it being understood that the populations PI and P2 have a median diameter (Dv50)i and (Dv50)2, respectively, and such that (Dv50)i <(Dv50)2.

[0029] According to either of the alternatives, the median diameter of PI is generally between Ipm and 8pm, i.e. Ipm <(Dv50)i <8pm, preferably 5pm <(Dv50)i <8pm and / or the median diameter of P2 is generally between 10pm and 20pm, i.e. 10pm <(Dv50)2 <20pm, preferably 10pm <(Dv50)2 <15pm. Preferably, the ratio (Dv50)2 / (Dv50)i is between 1.5 and 5, preferably between 2 and 2.5.

[0030] Typically, the bimodal layer C comprises an average number of particles PI and an average number of particles P2 that are substantially equal. Thus, within said layer the number (nl)i of particles PI and the number (n2)i of particles P2 are such that (nl)i / (n2)i=l±10%, in particular (nl)i / (n2)i=l±5%, particularly (ni)i / (n2)i = 1+1%.

[0031] Preferably, the population of solid electrolyte particles PI of formula SI and a population of solid electrolyte particles P2 of formula S2 are such that (nl)i / (n2)i=l and (Dv50)2 / (Dv50)i=2.5 approximately.

[0032] The solid electrolyte layer has a thickness e, such that e is generally less than 300 pm, in particular 200 pm, typically between 5 pm and 300 pm.

[0033] According to one embodiment, said element comprises as electrolyte only said layer C of solid electrolyte. Thus, in such an element, the electrolyte consists of the bimodal layer C ("monolayer") in which the distribution of the particles PI and P2 is homogeneous in its thickness e.

[0034] According to another embodiment, said element comprises, in addition to the layer C of bimodal solid electrolyte, one or two additional, optional layers mainly consisting of PI particles.

[0035] According to an advantageous alternative, said element comprises, in addition to layer C, one or two additional layers chosen from: - an additional layer Cl located between the positive electrode and the bimodal layer C, and / or - an additional layer C2 located between the negative electrode and the bimodal layer C.

[0036] Thus, according to one or other of the alternatives, each of the additional layers C1 and C2 comprises mainly P1 particles and possibly P2 particles. Thus:

[0037] within Cl the number (ni)i of particles PI and the number (n2)i of particles P2 are such that (nl)i>100x(n2)i, preferably (nl)i>1000x(n2)i, and

[0038] within C2 the number (ni)2 of PI particles and the number (n2)2 of P2 particles are such that (nl)2>100x(n2)2.

[0039] Typically, Cl and / or C2 comprises less than 10%, in particular less than 5%, particularly less than 1% of P2 particles, particularly no P2 particles.

[0040] When present, each of the layers C1 and / or C2 has a thickness typically less than the total thickness of the electrolyte layer:

[0041] Cl and / or C2 has a thickness eb respectively e2, such that 0 <ei<e et / ou 0<e2 <e.

[0042] Typically, 0pm <ei<300pm et 0pm<e2<300pm.

[0043] Advantageously, the additional, optional layer(s) C1 and / or C2 essentially involve small particles, thus ensuring the continuity of said layer C1 and / or C2, while ensuring good interaction with the bimodal layer C.

[0044] Said layers C1 and C2 also make it possible to establish a granulometry gradient from the electrode considered, towards the bimodal layer C, thus making it possible to avoid the propagation of dendrites and to improve the mechanical strength of the system.

[0045] According to one embodiment, the solid electrolytes of chemical formula S1 and S2 may be chemically identical (S1=S2) or different (S1^S2).

[0046] According to a preferred embodiment, the solid electrolytes of chemical formula S1 and S2 are chemically identical (S1=S2).

[0047] Each of the solid electrolytes of chemical formula S1 and S2 can be independently selected from inorganic electrolytes of sulfide, oxide, oxysulfide and halide type.

[0048] Typically, the bimodal layer C has a porosity of between approximately 8% and 30%, preferably less than or equal to 20%, in particular less than or equal to 15%, in particular less than or equal to 10%.

[0049] The chemical nature of the solid electrolyte is not particularly limited according to the invention. Compounds usually used as solid electrolyte can be used here.

[0050] Thus, as solid electrolyte, mention may in particular be made of sulfur compounds alone or in a mixture with other constituents. Mention may thus be made of oxide type electrolytes, partially or completely crystallized sulfides as well as amorphous sulfides.

[0051] Examples of these materials can be selected from sulfides of composition A Li2S - B P2S5 (with 0 <A<l ,0<B<l et A+B = 1) et leurs dérivés (par exemple avec dopage Lil, LiBr, LiCI,...) ; les sulfures de structure argyrodite ; ou ayant une structure cristallographique similaire au composé LGPS (Lii0GeP2Si2), et ses dérivés.

[0052] Illustrative examples of sulfide electrolytes are described in particular by Park, K. h. et al (2018). Design Strategies, Practical Considerations, and New Solution Processes of Sulfide Solid Electrolytes for Al-Solid-State Batteries. Advanced Energy Materials, 1800035.

[0053] Examples of sulfide electrolytes include: Li3PS4 - The phases [(Li2S)y(P2S5)i_ y]( i_z)(LiX)z (with X chosen from halogens; 0 <y<l; 0<z<l), — (Li3PS4)os(LiI)o,2 - Argyrodites such as Li6PS5X, with X = Cl, Br, I, or Li7P3Sn, - Sulphide electrolytes having a crystallographic structure equivalent to that of the compound Lii0GeP2Si2 - The phases [(Li2S)y(Li2O)t(P2S5)i_y_t]i_z) (LiX)zwith X chosen from the halides; 0 <y<l; 0<z<l; 0<t<l.

[0054] The solid electrolyte particles possibly present in the negative electrode and / or in the positive electrode may also be chosen from these solid electrolytes, it being understood that the solid electrolyte possibly present in the electrode negative and / or in the positive electrode on the one hand and in the layer C and Cl and / or C2 on the other hand may be identical or different.

[0055] Typically, solid electrolyte particles may be present within the positive electrode. Typically, said predominantly present particles are those of the smallest size. Thus, according to one embodiment, the positive electrode may comprise PI particles.

[0056] The positive electrode

[0057] The term positive electrode designates the electrode where the electrons enter, and where the cations (Li+) arrive in discharge.

[0058] The positive electrode generally consists of a conductive support used as a current collector which is coated with a layer of positive electrode material containing the positive electrode active material, to which an electronically conductive carbon additive and solid electrolyte particles may be added in the case of an all-solid electrochemical element.

[0059] Typically the positive electrode may also comprise a binder.

[0060] The positive electrode active materials are not particularly limited by the present invention. Thus, as positive electrode active materials, mention may in particular be made of: - a lithiated oxide of at least one transition metal chosen from: i. a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; ii. a lithium oxide of nickel, cobalt and aluminum of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; iii. a compound of formula Lii+xMi x02 yFy with a cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ; iv. a lithium oxide of nickel and manganese (NMX) of formula Lia(Nii_x y zMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x ; 0 <y<0,02 ; 0<z ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La and mixtures thereof; and v. a lithium oxide of nickel and manganese of formula Liw(NixMnyCozMt)O2 where 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ;

[0061] or - a lithium phosphate of at least one transition metal chosen from:

[0062] a) a lithium iron phosphate of formula LixFei yMyPO4 (LFP), where 0.8 <x<l,2 ; 0 <y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0063] b) a lithium manganese phosphate of formula LixMni yMyPO4 (LMP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0064] c) a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; et

[0065] d) a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule Lii+xVi yMyPO4Fz (LVMPF) où0<x<0,15, 0<y<0,5, 0,8<z<l,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, et Zr ;

[0066] or - a mixture of compounds a) to d) and i) to v).

[0067] According to one embodiment, the positive electrode comprises as active material a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; l’électrode négative comprend à titre de matière active du lithium métal ; et les électrolytes solides de formule chimique SI et S2, identiques ou différentes comprennent des électrolytes sulfure.

[0068] According to another embodiment, the positive electrode comprises as active material a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; l’électrode négative comprend à active material title of silicon; and solid electrolytes of chemical formula S1 and S2, identical or different, include sulfide electrolytes.

[0069] Carbon Additive

[0070] The carbon electronic material or conductive material is generally chosen from graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes, carbon fibers, such as vapour-deposited carbon fibers (VGCF) or a mixture thereof.

[0071] The negative electrode

[0072] The term "negative electrode" refers to the electrode functioning as an anode when the battery is discharging, the anode being defined as the electrode where an electrochemical oxidation reaction (emission of electrons) takes place. The term negative electrode also refers to the electrode from which the electrons leave, and from which the cations (Li+) are released during discharge.

[0073] In the context of the present invention, the negative electrode may be of any known type, such as lithium metal and its alloys and silicon, but may also be chosen from electrodes based on graphite and / or carbon, titanium oxide, and mixtures thereof. The negative electrode typically consists of a conductive support used as a current collector on which is deposited the layer of negative electrode material comprising the negative electrode active material to which solid electrolyte particles and an electronically conductive material may be added. A binder may also be incorporated into the mixture. It is understood that in anode-free systems called "anode free", a negative electrode is also present (generally initially limited to the current collector alone).

[0074] Thus, by way of illustration, the negative electrode may comprise as active material:

[0075] - Metallic lithium or a metallic lithium alloy

[0076] - Graphite;

[0077] - Silicon or alloy, carbon and silicon based compounds, and compounds SiOx with x<=2;

[0078] - Anode-free type;

[0079] - A titanium and niobium oxide TNG having the formula: LixTi,vMvNbh ZM'ZO «x+4a+5b) / 2) c dXc where: 0 <x<5; 0<y<l; 0<z<2; l<a<5; l<b<25; 0.25<a / b<2; 0<c< 2 and 0<d<2; a-y> 0; bz>0; • M and M' each represent at least one element chosen from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm; • X represents at least one element chosen from the group consisting of S, F, Cl and Br; • The index d represents an oxygen vacancy less than or equal to 0.5; or

[0080] - A lithiated titanium oxide or a titanium oxide capable of being lithiated. LTO is chosen among the following oxides:

[0081] I) Lix-aMaTiy_bM'bO4_c_dXcwhere 0 <x<3; l<y<2.5; 0<a<l; 0<b<l; 0<c<2 and

[0082] -2.5 <d<2.5; • M represents at least one element selected from the group consisting of Na, K, Mg, Ca, B, Mn, Fe, Co, Cr, Ni, Al, Cu, Ag, Pr, Y and La; • M' represents at least one element selected from the group consisting of B, Mo, Mn, Ce, Sn, Zr, Si, W, V, Ta, Sb, Nb, Ru, Ag, Fe, Co, Ni, Zn, Al, Cr, La, Pr, Bi, Sc, Eu, Sm, Gd, Ti, Ce, Y and Eu; • X represents at least one element selected from the group consisting of S, F, Cl and Br; • The index d represents an oxygen vacancy, less than or equal to 0.5

[0083] II) HxTiyO4 in which 0 <x<l; 0<y<2,

[0084] III) un mélange des composés I) à II)

[0085] Ou leurs mélanges.

[0086] Binder

[0087] The term "binder" means any material that provides the electrode with mechanical cohesion between its various components and its adhesion to the current collector. In addition, the binder may also be used within the bimodal solid electrolyte layer C and the optional additional layers C1 and C2.

[0088] Mention may thus be made, as binders, of: polyvinylidene fluoride (PVDF) and its copolymers, polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl) or (butyl) methacrylate, polyvinyl chloride (PVC), polyvinyl formaldehyde, polyester, polyether block amides, polymers of acrylic acid, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomer and cellulose compounds. The elastomer(s) which may be used as binder may be chosen from styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR) and a mixture of several of these elastomers.

[0089] The current collector

[0090] The nature of the current collectors suitable for the invention is not limited. Current collectors conventionally used for positive and negative electrodes for solid lithium electrochemical cells can thus be envisaged. For example, the current collectors can be made of copper or a copper-based alloy, aluminum or an aluminum-based alloy, stainless steel.

[0091] Before the current collector is coated with the active material composition layer, it may be coated, on one or both of its faces, with a coating intended to improve the electronic conductivity between the active material composition layer and the foil. The coating material may be selected from the group consisting of amorphous carbon, graphite, carbon fibers, carbon nanotubes and mixtures thereof.

[0092] According to another object, the invention also relates to the method for preparing an element according to the invention, said method comprising the deposition of said layer C on the positive electrode or on the negative electrode, and the assembly with, respectively, the negative electrode or the positive electrode, said positive and / or negative electrodes being optionally coated beforehand with a layer Cl or C2 respectively, Cl and C2 being defined as discussed above.

[0093] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0094] [Fig-1] [Fig.l] represents a reference electrochemical element, that is to say comprising particles of a single size.

[0095] [Fig.2] [Fig.2] represents an electrochemical element according to the invention comprising a layer of solid electrolyte with bimodal particle size distribution, comprising a mixture of small and large particles.

[0096] [Fig.3] [Fig.3] represents an electrochemical element according to the invention according to a advantageous embodiment in which an additional Cl layer is present between the bimodal electrolyte layer and the negative electrode.

[0097] [Fig.4] Figure 4A schematically represents the arrangement of the PI particles and P2 in a bimodal electrolyte layer C according to one embodiment of the invention. Figure 4B schematically represents the arrangement of the particles in a reference solid electrolyte, i.e. comprising particles of a single size.

[0098] In all of Figures 1 to 3, an electrochemical element comprises the current collectors 5 and 5' of the negative electrode and the positive electrode, respectively. The negative electrode consists of a layer of active material 6, such as lithium metal for example. The positive electrode consists of particles of active material 2, binder 3 and carbon additive 4.

[0099] These two electrodes are separated by a layer of solid electrolyte.

[0100] In a reference electrochemical element ([Fig.l]), only one particle size 1 of solid electrolyte is present.

[0101] In an electrochemical element according to the invention (Figures 2 and 3), the solid electrolyte layer comprises small particles 1 and large particles 1' of solid electrolyte.

[0102] [Fig.3] differs from [Fig.2] in that the electrochemical element further comprises an additional layer C2 located between the bimodal electrolyte layer and the negative electrode 6, said layer C2 comprising exclusively small particles 1. EXAMPLES:

[0103] 1. Preparation of the positive electrode

[0104] The positive electrode consists of a conductive support used as a current collector which is coated with a layer containing the active materials, a binder, an electronically conductive material and a solid electrolyte material Li6PS5Cl having a Dv50 equal to 5pm.

[0105] Polyvinylidene fluoride (PVDF) is used here as a binder.

[0106] The electronically conductive material is carbon black.

[0107] The active material is a mixture of active materials comprising 70% LiMno.7Feo.3 PO4 and 30% LiNi0.sMn0.1Co0.1O2.

[0108] The quantity of solvent is adapted so that the mixture has a viscosity allowing a homogeneous deposition of the ink on the aluminum current collector. 1. Grinding of part of the solid electrolyte#

[0109] The grinding of 5g of Li6PS5Cl powder having a Dv50 = 12 pm is carried out using a ball mill. Typically, the grinding is carried out by a mill marketed by Fritsch (Fritsch Pulverisette 7 premium), with 25g of balls with a diameter of 10 mm, in 80 ml bowls, during cycles alternating 10 min of grinding, separated by a pause time of 10 min for a total duration of 3 h, at a rotation speed of 400 rpm

[0110] Typically, the Dv50 particle size of the mixture after grinding is 5 μm. 1. Realization of the accumulator #

[0111] All powder handling is carried out in a glove box under an Argon atmosphere.

[0112] The powdery electrolytic layer Li6PS5Cl comprising 50% of previously prepared ground particles Dv50 = 5 pm and 50% of unground particles Dv50 = 12 pm is cold compressed (250 MPa) in a pelletizing mold 7 mm in diameter to form a pellet about 300 pm thick. It forms the separating electrolytic layer for electronically insulating the two electrodes.

[0113] A positive electrode disc, prepared under the conditions described above, is added to one side of the electrolytic layer in the pelletizing mold, the assembly being compressed again (250 MPa) to form a dense and solid assembly. On the other side of the electrolytic layer, a 6mm diameter lithium metal pellet is added and compressed again to approximately 50MPa.

[0114] The assembly is then placed in a sealed electrochemical cell allowing electrical connection with the 2 electrodes, while maintaining a mechanical pressure of approximately 50MPa. 1. Comparison of porosity#

[0115] In the case of an electrolyte comprising particles with a bimodal particle size distribution according to the invention, the arrangement of the particles is illustrated in Figure 4A:

[0116] Porosity is calculated by taking the ratio of the surface area of ​​the void present in a reference square (pm2) and the surface area of ​​the reference square (pm2), the reference square being a 2D projection of a volume of particle mixture.

[0117] Grain boundaries are represented by crosses in Figure 4A.

[0118] The porosity of a solid electrolyte consisting of such particles was estimated as follows:

[0119] [Tables 1] Diameter of large particles P2 ( pm) Diameter of small particles PI ( pm) Area of ​​the reference square (pm2) Area of ​​large particles P2 (pm2) in the reference square Area of ​​small particles PI (pm2) in the reference square Empty area (pm2) in the reference square Porosity (%) Number of grain boundaries per reference square 12 5 288 226.2 38.8 23.0 8.0 16

[0120] The porosity is therefore of the order of 8%.

[0121] For comparison, in the case of an electrolyte comprising PI particles of the same size, the arrangement of the particles within the same volume is shown schematically in Figure 4B:

[0122] Porosity is calculated by taking the ratio of the surface area of ​​the void present in the reference square (pm2) and the surface area of ​​the reference square (pm2), the reference square being a 2D projection of a volume of particle mixture.

[0123] The porosity was also calculated:

[0124] [Tables2] Diameter Diameter Surface area d Surface area d Surface area vi Porosity Number of large small u square references large small of (pm2) (%) e joints of of parts particular particles particles in the grain by P2 (the PI (p (pm2) es P2 (pm PI (pm2) rreferred square reference pm) m) 2) in the ntial ntial reference square in the reference square - 5,288 - 38.8 23.0 9.04 43

[0125] The bimodal solid electrolyte layer according to the invention therefore allows:

[0126] # To decrease the porosity to about 8%; and

[0127] # To reduce the quantity of grain boundaries.

[0128] The porosity of a solid electrolyte consisting of particles with a bimodal particle size distribution for other examples, according to a similar procedure, was estimated as follows:

[0129] [Tables3] Diameter of large particles P2 (pm) Diameter of small particles PI (pm) Ratio of number of small particles PI / number of large particles P2 Area of ​​the reference square (pm2) Area of ​​large particles P2 (pm2) in the reference square Area of ​​small particles PI (pm2) in the reference square Void area (pm2) in the reference square Porosity (%) Number of grain boundaries per reference square 12 2.5 4 288 226.2 38.8 23.0 8.0 28 17 7 1 578 454.0 77.9 46.2 8.0 16

[0130] The porosity is therefore of the order of 8%

[0131] For comparison, in the case of an electrolyte comprising PI particles of the same size, the porosity was also calculated:

[0132] [Tables4] Diameter of large particles P2 (pm) Diameter of small particles PI (pm) Ratio of number of small particles PI / number of large particles P2 Area of ​​the reference square (pm2) Area of ​​large particles P2 (pm2) in the reference square Area of ​​small particles PI (pm2) in the reference square Void area (pm2) in the reference square Porosity (%) Number of grain boundaries per reference square - 2.5 - 288 - 252.2 35.8 12.43 >150 - 7 - 578 - 525.7 52.3 9.04 43

[0133] The bimodal solid electrolyte layer according to the invention therefore makes it possible to: - Reduce the porosity to approximately 8%; and - Reduce the quantity of grain boundaries.

Claims

Claims

1. Electrochemical element with solid electrolyte, said element comprising a positive electrode and a negative electrode, said electrodes being separated from each other by a layer C of solid electrolyte of thickness e, characterized in that said electrolyte layer comprises at least one population of solid electrolyte particles PI of chemical formula SI and a population of solid electrolyte particles P2 of chemical formula S2, the chemical formulas SI and S2 being identical or different, and such that the particles PI and P2 respectively have a median diameter (Dv50)i and (Dv50)2, and such that (Dv50)i <(Dv50)2.

2. An element according to claim 1 such that lpm<(Dv50)i<8pm and 10pm<(Dv50)2<20pm.

3. An element according to any preceding claim such that the chemical formulas of the solid electrolytes S1 and S2 are identical.

4. An element according to any preceding claim such that the positive electrode comprises PI particles.

5. Element according to any one of the preceding claims such that within said layer C the number (nl)i of particles PI and the number (n2)i of particles P2 are such that (nl)i / (n2)i=l±10%.

6. An element according to any one of the preceding claims such that said element further comprises one or more optional additional layers C1 and / or C2 of solid electrolyte.

7. Element according to claim 6 such that said layer comprises an additional layer Cl of thickness eb Cl being located between the positive electrode and the layer C, such that 0 <ei<e, ladite couche Cl comprenant des particules PI et éventuellement des particules P2, et telle que au sein de Cl le nombre (nl)i de particules PI et le nombre (n2)i de particules P2 sont tels que (nl)i> 100x(n2)i.

8. Element according to claim 6 or 7 such that said layer comprises an additional layer C2 of thickness e2, C2 being located between the layer C and the negative electrode, such that 0 <e2<e, ladite couche C2 comprenant des particules PI et éventuellement des particules P2, et telle que au sein de C2 le nombre (nl)2 de particules PI et le nombre (n2)2 de particules P2 sont tels que (nl)2> 100x(n2)2.

9.

10.

11.

12. Element according to any one of the preceding claims such that 5pm <e<300pm. Element according to one of claims 7 or 8 such that 0pm <ei <300pm et 0pm<e2<300pm. Element according to any one of the preceding claims such that the solid electrolytes of chemical formula S1 and S2, identical or different, are chosen from sulfide, oxide, oxysulfide and halide electrolytes. Element according to any one of the preceding claims such that the positive electrode comprises as active material - a lithiated oxide of at least one transition metal chosen from: i. a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; ii. a lithium oxide of nickel, cobalt and aluminum of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; iii. a compound of formula Lii+xMi_xO2.yFy with a cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ; iv. a lithium oxide of nickel and manganese (NMX) of formula Lia(Nii.xyzMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x ; 0<y<0,02 ; 0<z ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci ; et v. a lithium oxide of nickel and manganese of formula Liw (NixMnyCozMt)O2 where 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ;

13. 0 <z<0,02 ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; Or - a lithium phosphate of at least one transition metal chosen from: a) a lithium iron phosphate of formula LixFei yMyPO4 (LFP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; b) a lithium manganese phosphate of formula LixMni yMyPO4 (LMP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; c) a lithium manganese and iron phosphate of formula: LixMn iy zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; et d) a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule Lii+xVi yM yPO4Fz (LVMPF) où0<x<0,15, 0<y<0,5, 0,8<z<l,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, et Zr ; Or - a mixture of compounds a) to d) and i) to v). Element according to any one of the preceding claims such that the negative electrode comprises as active material: - Metallic lithium or a metallic lithium alloy - Graphite; - Silicon or alloy, carbon and silicon-based compounds, and SiOx compounds with x<=2; - A titanium and niobium oxide TNG having the formula: Lix Tia_yMyNbb_zM'zO((x+4a+5b) / 2)-c dXc where: 0 <x<5; 0<y<l; 0<z<2; l<a<5; l<b<25; 0.25<a / b<2; 0<c< 2 and 0<d<2; a-y> 0; bz>0; • M and M' each represent at least one element selected from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm; • X represents at least one element selected from the group consisting of S, F, Cl and Br; • The index d represents an oxygen vacancy less than or equal to 0.5; or - A lithiated titanium oxide or a titanium oxide capable of being lithiated. LTO is selected from the following oxides: I) Lix-aMaTiy_bM'bO4.c.dXcoù 0 <x<3; l<y<2.5; 0<a<l; 0<b<l; 0<c<2 et -2.5<d<2.5; •       m représente au moins un élément choisi dans le groupe constitué de na, k, mg, ca, b, mn, fe, co, cr, ni, al, cu, ag, pr, y and la;       m’ mo, ce, sn, zr, si, w, v, ta, sb, nb, ru, zn, la, bi, sc, eu, sm, gd, ti, eu;       x s, f, cl br;       l’indice d une lacune en oxygène, inférieur ou égal à 0,5 ii) hxtiyo4 lequel 0<x<l; 0<y<2, iii) mélange des composés i) ii), ou leurs mélanges.

14. Element according to any one of the preceding claims such that the positive electrode comprises as active material a lithium manganese and iron phosphate of formula: LixMni y zFeyM ZPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 0<y<0,50 et 0<z<0,2 m est choisi dans le groupe constitué de al, b, mg, k, si, ca, ti, v, cr, co, cu, ni, zn, y, zr, nb, w, pb, mo, s des mélanges ceux-ci l’électrode négative comprend à titre matière active du lithium métal les électrolytes solides dechemical formula SI and S2, identical or different, include sulfide electrolytes.

15. Element according to any one of claims 1 to 13 such that the positive electrode comprises as active material a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 0<y<0,50 et 0<z<0,2 m est choisi dans le groupe constitué de al, b, mg, k, si, ca, ti, v, cr, co, cu, ni, zn, y, zr, nb, w, pb, mo, s des mélanges ceux-ci l’électrode négative comprend à titre matière active du silicium les électrolytes solides formule chimique s1 s2, identiques ou différentes comprennent sulfure.

16. A method of preparing an element according to any one of the preceding claims comprising deposition of said layer C on the positive electrode or on the negative electrode, and assembly with, respectively, the negative electrode or the positive electrode, respectively, said positive and / or negative electrodes being optionally coated beforehand with a layer Cl or C2 respectively, Cl and C2 being defined according to any one of claims 6 to 8.

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