Active material for lithium-ion electrochemical element

Abstract

A negative electrode for a lithium-ion electrochemical cell, the electrode comprising:- a current collector,- an active material composition deposited on at least one of the faces of the current collector and comprising an active material which is a compound of formula M15 - xM'xM''1 - yM'''yO40-aXb in which:M represents one or more elements selected from Nb, Ta and V,M' represents one or more elements selected from Ti, Zr, Mo, Cr, As and Sb, M'' represents one or more elements selected from Mo and W,M'''represents one or more elements selected from Cr, V and Te,X represents a halogen,0≤x≤7.5 ;0≤y<1 ;0≤a≤5 ;0≤b≤1,the compound satisfying the relation (15-x)*5 + nx + (1-y)*6 + my =(40-a)*2 + b; n and m indicating the average oxidation states of M' and M''' respectively. Abstract figure: Figure 1

Description

Title of the invention: Active material for lithium-ion electrochemical element Technical field

[0001] The technical field of the invention is that of active materials for lithium-ion electrochemical elements, in particular active materials for a negative electrode of a lithium-ion electrochemical element. Background

[0002] Lithium-ion electrochemical elements are known from the state of the art. They are commonly used in many fields such as automobiles, telephony, electronic devices or aeronautics. Their operating principle is based on the reversible exchange of the lithium ion between a positive electrode (cathode), most often a lithium transition metal oxide or a lithium transition metal phosphate and a negative electrode (anode), for example made of graphite. The negative electrode and the positive electrode are separated by a separator. The assembly formed by the negative electrode, the positive electrode and the separator forms an electrochemical bundle. This is for example impregnated with a liquid organic electrolyte often composed of a mixture of alkyl carbonates in which a lithium salt is dissolved, for example lithium hexafluorophosphate LiPF6.

[0003] A graphite-based negative electrode has a potential close to 0 V compared to the Lr7Li pair. Its mass capacity is approximately 350 mAh / g. [Fig.l] shows the variation of the potential of a graphite-based electrode compared to the Lr7Li pair during a charge / discharge cycle. The fact that the potential of the graphite electrode is close to 0 V, however, leads to a risk of formation of metallic lithium on the negative electrode when the electrochemical element approaches the end of charging or when charging is too rapid. The agglomeration of metallic lithium leads to the formation of dendrites which can end up piercing the separator and causing an internal short circuit in the electrochemical element. The risk of an internal short circuit occurring has led to the search for other negative active materials that are safer to use.

[0004] Active materials with a potential further from the potential of the Li+ / Li couple than graphite have been discovered. Examples include titanium-based lithium oxides, such as Li4Ti50i2. This compound has an average potential close to 1.5 V vs. Lr7Li. [Fig.l] shows the variation of the potential of an electrode based on Li4Ti50i2 with respect to the Li+ / Li couple during a charge / discharge cycle. Electro-elements Chemicals comprising a negative electrode based on Li4Ti50i2 can be charged under high current with zero risk of dendrite formation. The disadvantage associated with the use of Li4Ti50i2, however, is its low mass capacity, which is only about 170 mAh / g, which is half the mass capacity of graphite, as shown in [Fig.l].

[0005] Active materials having a potential of approximately 1.5 V relative to the Li + / Li couple and a mass capacity greater than that of Li4Ti5Oi2 have been discovered. Mention may be made of lithiated oxides of titanium and niobium, such as the compound of formula TiNb2O7, described for example in patent FR-B-3102890.

[0006] We are looking for new active materials having a potential sufficiently far from the potential of the Lr7Li couple, i.e. close to 1.5 V vs. Lr7Li, and a mass capacity greater than that of Li4Ti50i2. Summary

[0007] To this end, the invention proposes an electrode comprising: - a current collector, - an active material composition deposited on at least one of the faces of the current collector and comprising an active material which is a compound of formula Mi5_xM'xM”i_yM”'y04o aXb in which: M represents one or more elements chosen from Nb, Ta and V, M' represents one or more elements selected from Ti, Zr, Mo, Cr, As and Sb, M' ' represents one or more elements selected from Mo and W, M'” represents one or more elements selected from Cr, V and Te, X represents a halogen, 0 <x<7,5 ; 0 <y<l; 0 <a<5; 0 <b<l, the compound satisfying the relation (15-x)*5 + nx + (ly)*6 + my =(40-a)*2 + b; n and m indicating respectively the average oxidation states of M' and M'” .

[0008] The invention is based on the discovery that compounds of formula Mi5.xM'xM”iy M”'y04o aXb can be used as an active material of a negative electrode for a lithium-ion electrochemical element. This active material combines safety of use and high mass capacity.

[0009] According to one embodiment, x=0.

[0010] According to one embodiment, M is Nb.

[0011] According to one embodiment, y=0.

[0012] According to one embodiment, M'' is Mo.

[0013] According to one embodiment, a=0 and b=1.

[0014] According to one embodiment, the compound has the formula Nbi5Mo04oF.

[0015] According to one embodiment, the compound has a crystalline structure in in which M and M' occupy octahedral sites whose vertices are surrounding oxygen atoms or X atoms and M” and M'” occupy tetrahedral sites whose vertices are surrounding oxygen atoms.

[0016] According to one embodiment, the octahedra form planes parallel to each other which are connected by the tetrahedra.

[0017] The invention also relates to an electrochemical element comprising: - at least one positive electrode, - at least one negative electrode which is the electrode as described above.

[0018] According to one embodiment, the positive electrode comprises one or more positive active materials 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: 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 ; d) 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 ; e) 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 ; f) 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 ; (g) 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 et des mélanges de ceux-ci ; h) 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. (i) a lithium oxide of nickel and manganese of formula LixMn2_y_zM'yM"zO4_ô where M' and M" are selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 ; 0<z<0,2 ; 0<ô<l. Brief description of the figures

[0019] [Fig. 1] represents the variation of the potential of different active materials with respect to the Lr7Li couple during a charge and discharge cycle.

[0020] [Fig.2] represents the alternation of the octahedral blocks NbO6 and NbO4F2 within the crystal structure of the compound of formula Nbi5MoO40F.

[0021] [Fig.3] represents the position of molybdenum and oxygen atoms in a MoO4 tetrahedron, the position of niobium and oxygen atoms in a NbO 6 octahedron and the position of niobium, oxygen and fluorine atoms in a NbO4F2 octahedron.

[0022] [Fig.4] represents the variation of the voltage of the compound of formula Nbi5MoO40F during the first two cycles. Charging and discharging are carried out at room temperature, at the regimes of C / 10 and D / 10 respectively. The legend is given from the point of view of the use of Nbi5MoO40F as a negative material. Thus the charge corresponds to the intercalation of lithium within the structure of Nbi5MoO40F and the discharge corresponds to the deintercalation of lithium within the structure of Nbi5MoO 4oF.

[0023] [Fig.5] represents the variation of the voltage of an electrochemical element comprising a negative electrode based on Nbi5MoO40F during a cycling of 50 cycles. The charge and discharge are carried out at room temperature, at the regimes of C / 5 and D / 5 respectively. Detailed description of the embodiments Negative electrode:

[0024] The general formula of the compounds is Mi5.xM'xM' ' i yM” 'yO40 aXb in which: M represents one or more elements chosen from Nb, Ta and V, M' represents one or more elements chosen from Ti, Zr, Mo, Cr, As and Sb, M' ' represents one or more elements chosen from Mo and W, M'” represents one or more elements chosen from Cr, V and Te, X represents a halogen, 0 <x<7,5 ; 0 <y<l; 0 <a<5 ; 0 <b<l, the compound satisfying the relation (15-x)*5 + nx + (ly)*6 + my =(40-a)*2 + b; n and m indicating respectively the average oxidation states of M' and M”', the average oxidation state of M' (respectively M'”) being the average of the oxidation states of the elements constituting M' (respectively M'”).

[0025] The elements Nb, Ta and V in M ​​are in the oxidation state +V.

[0026] The elements Mo and W in M” are in the oxidation state +VI.

[0027] The optional substituent elements M' and M”' may be incorporated into the compound which is the subject of the invention using precursors containing these elements. The precursors and their quantities are chosen by a person skilled in the art so as to respect the relationship described above. The oxidation degrees n and m depend on the precursors chosen and are known to a person skilled in the art. - Ti and Zr in M' can be in oxidation state +IV. - Sb and As in M' can be in the oxidation state +V. - Mo and Cr in M' can be in the oxidation state +VI. - V in M'” can be in the oxidation state +V. - Cr and Te in M' ' ' can be in the oxidation state +VI.

[0028] The compound Mi5M”04o-aXb can have a crystalline form which is the monoclinic form of space group C2. MO6 and MO4X2 octahedra are grouped in planes of 3 x 5 octahedra sharing vertices in the (ab) plane of the unit cell. The MO4X2 octahedron occupies the center of the group of 3 x 5 octahedra. The planes alternate along the b axis at values ​​y = 0 and y = U2 and are connected to each other between the two values ​​of y by M”O4 tetrahedra.

[0029] In a preferred embodiment, X is fluorine, x=0, y=0, a=0 and b=1.

[0030] A preferred example of the compound is Nbi5Mo04oF. It is obtained by heating at a temperature between 900 and 1000°C of a mixture of the compounds Nb2O5, MoO3 and NbO2F in stoichiometric proportions. The reaction is:

[0031] 7Nb2O5 + MoO3 + NbO2F -> MoNb15O40F

[0032] The synthesis and characterization of this compound are described in the article entitled "Crystal structure of MoNbi5O40F" by J. Galy and S. Andersson published in Acta. Cryst. (1968), B24, 1027.

[0033] [Fig.2] partially represents the crystal structure of the compound Nbi5MoO40F. It shows two types of blocks: a first block of 15 octahedra forming a plane in position z=0 or z=l and a second block of 15 octahedra forming a plane in position z=l / 2 also formed of 15 octahedra. The octahedron located at the center of each block of 15 octahedra is an NbO4F2 octahedron. Each block has been individualized to facilitate understanding of the crystal structure.

[0034] [Fig.3] shows the position of molybdenum and oxygen atoms in a MoO4 tetrahedron, the position of niobium and oxygen atoms in a NbO 6 octahedron and the position of niobium, oxygen and fluorine atoms in a NbO4F2 octahedron. A block consisting of 3 x 5 octahedra has been individualized to facilitate the understanding of the crystal structure.

[0035] Mi5_xM'xM” i yM' ”yO40 aXb may be the only active material of the negative electrode.

[0036] It can also be associated with one or more negative active materials having a potential of approximately 1.5 V vs. Li+ / Li. Examples include lithiated titanium oxides such as compounds of formula: i) Lix.aMaTiy.bM'b04_c.dXc in which 0 <x<3 ; l<y<2,5 ; 0<a<l ; 0<b<l ; 0<c<2 et -2,5<d<2,5 ; L’indice d représente une lacune en oxygène. L’indice d peut être inférieur ou égal à 0,5, 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, Ce, Y and Eu; X represents at least one element selected from the group consisting of S, F, Cl and Br. This family includes compounds with the formula Li4Ti50i2, Li2TiO3>Li2Ti3O7 LiTi2O4 and Li2 Na2Ti60i4. Preferably 0.5 <x<3 ; Preferably a<0.5; Preferably b<0.25; Preferably c<0.5. ii) HxTiyO4 in which 0 <x<l ; 0<y<2. Cette famille inclut H2Ti60i3, H2Tii2O25 et TiO2 ; et iii) a mixture of compounds i) and ii).

[0037] Mention may also be made of titanium and niobium oxides, such as the compounds of formula: iv) LixTia_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 et 0 <d<2 ; a-y> 0 ; bz>0 ; The d index represents an oxygen vacancy. The d index can be less than or equal to 0.5. 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; This family includes compounds of formula TiNb2O7, Ti2Nb2O9 and Ti2NbmO2l).

[0038] Titanium and niobium oxide can be partially substituted by vanadium and have the formula LixTii_yMyNb2_(zi+Z2)VziM'Z2O7_c_dXc where 0 <x<5 ; 0<y<l ; 0<zl<0,5 ; 0<z2<0,5 ; 0<c<2 ; 0<d<2 ; M represents one or more elements selected from the group consisting of Mg, Ca, B, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm; M' represents one or more elements selected from the group consisting of Mg, Ca, B, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm; X represents one or more elements selected from the group consisting of S, F, Cl and Br. This family includes compounds with the formula TiNbi>98Vo,o207 and TiNb1.95V0.05O7.

[0039] To obtain the negative active material composition, an ink is prepared by dispersing in a solvent or in a mixture of solvents, one or more negative active materials, one of them being Mi5_xM'xM”i_yM”'y04o-aXb, and optionally one or more binders and one or more electronically conductive compounds. The solvent(s) may be organic or aqueous. Preferably, it is N-methylpyrrolidone. The binder may be selected from poly(vinylidene fluoride) (PVDF) and its copolymers, polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl or butyl methacrylate), poly(vinyl chloride) (PVC), poly(vinyl formal), polyester, block polyether-amides, polymers of acrylic acid, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers, and cellulosic compounds such as carboxymethylcellulose (CMC).The elastomers that can be used as binders can be chosen from styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR). Preferably, said at least one binder is a binder dispersible in an aqueous medium, such as polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR) and polyvinyl alcohol (PVA).

[0040] The electronically conductive material is generally chosen from graphite, carbon black, acetylene black, soot, graphene, carbon fibers, carbon nanotubes or a mixture thereof.

[0041] By varying the amount of solvent incorporated in the mixture, the viscosity of the ink can be varied before it is deposited on one side of a current collector. The negative current collector is a solid or perforated metal strip which may be made of copper or a copper-based alloy, or made of aluminum or an aluminum-based alloy. Preferably, it is aluminum or an alloy with aluminum base, because it is lighter than copper. Its thickness can range from 3 to 25 μm, preferably from 5 to 8 μm. The ink-coated current collector is dried and then rolled to adjust its thickness. After evaporation of the solvent(s), a layer of a composition of one or more active ingredients is obtained, the proportions of the various constituents of which are typically: - from 85 to 98% or from 90 to 98% by mass of one or more negative active ingredients, - from 1 to 10% or from 1 to 5% by mass of one or more binders, - from 0 to 5% by mass or from 1 to 5% of one or more electronically conductive materials. Positive electrode:

[0042] The positive electrode comprises a current collector, at least one of the faces of which is coated with a layer of a composition of positive active materials, which comprises one or more active materials and optionally one or more binders and one or more electronically conductive materials.

[0043] The positive current collector is a solid or perforated metal strip which may be made of aluminum or an aluminum alloy or steel or stainless steel. Its thickness may be in the range of 6 to 30 μm or 5 to 20 μm or 10 to 15 μm, preferably 10 to 15 μm.

[0044] The positive active material may be any positive active material known in lithium-ion electrochemical cell technology. It may be selected from the following different types or be a mixture thereof: 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 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 des mélanges de ceux-ci 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 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 d) 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 ceux-ci e) 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 and mixtures thereof; f) a compound of formula Lii+xMi_xO2_yFy with a cubic crystal structure where 0 <x<0,5 et 0<y<l 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 sm des mélanges ceux-ci ; g) a lithium nickel and manganese oxide (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 des mélanges de ceux-ci h) 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 ceux-ci. (i) a lithium oxide of nickel and manganese of formula LixMn2.y.zM'yM"zO4.ô where M' and M" are selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 0<z<0,2 0<ô<l.

[0045] Preferably, it is a compound of type c), i.e. a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4(LMFP). Typical formulas of lithium manganese and iron phosphate are LiMno8Feoj2P04, LiMno.7Fco.iPO4.LiMn 2 / 3Fei / 3PO4 and LiMn0j5Feoj5P04.

[0046] An ink is prepared by dispersing one or more positive active materials in a solvent or in a mixture of several solvents. Optionally, a binder and an electronically conductive material are added to the dispersion. By varying the amount of solvent incorporated in the mixture, the viscosity of the ink can be varied before it is deposited on one face of the current collector. The ink-coated current collector is dried and then rolled so that its thickness is adjusted. After evaporation of the solvent(s), a layer of a composition of one or more active materials is obtained, the proportions of the various constituents of which are typically: - from 80 to 98% or from 90 to 95% by mass of one or more positive active ingredients, - from 1 to 10% or from 2 to 5% by mass of one or more binders, - from 0.1 to 10% or from 2 to 5% by mass of one or more electronically conductive materials.

[0047] The binder(s) may be chosen from the same list as that described in relation to the negative electrode, without necessarily being the same as those of the negative electrode. Similarly, the electronically conductive material(s) may be chosen from the same list as that described in relation to the negative electrode, without necessarily being necessarily the same as those of the negative electrode. Electrolyte:

[0048] The electrolyte can be in solid, liquid or gel form.

[0049] a) Solid electrolyte: It may be a lithium ion-conducting compound, chosen for example from lithium ion-conducting oxides and lithium ion-conducting sulfides. The electrolyte may also be a lithium ion-conducting polymer, such as polyethylene oxide (PEO), polyphenylene sulfide (PPS) and polycarbonate.

[0050] b) Liquid electrolyte: It consists of one or more organic solvents in which one or more lithium salts are dissolved. Organic solvents: The organic solvent(s) may be chosen from linear alkyl carbonates, cyclic alkyl carbonates, linear ethers and cyclic ethers. The linear alkyl carbonate may be selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propyl methyl carbonate (PMC). Dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are particularly preferred. The linear carbonate may represent 50 to 100% or 60 to 90%, or 70 to 80% by volume of the total volume of the linear or cyclic alkyl carbonate(s). The at least one linear alkyl carbonate may be used in combination with one or more cyclic alkyl carbonates. Examples of cyclic alkyl carbonates are ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC). Ethylene carbonate (EC), propylene carbonate (PC) and a mixture thereof are particularly preferred. The cyclic carbonate may represent from 1 to 50% or from 10 to 40%, or from 20 to 30% by volume of the total volume of the linear or cyclic alkyl carbonate(s).

[0051] Lithium salt: The nature of the lithium salt is not particularly limited. Examples include lithium hexafluorophosphate LiPF6, lithium hexafluoroarsenate LiAsF6, lithium hexafluoroantimonate LiSbF6 and lithium tetrafluoroborate LiBF4, lithium perchlorate LiC104, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium tris(fluoromethanesulfonyl)methylide LiC(CF3SO2)3 (LiTFSM), lithium bis(pentafluoroethylsulfonyl)imide LiN(C2F5SO2)2 (LiBETI), lithium 4,5-dicyano-2-(trifluoromethyl) imidazolide (LiTDI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LIDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP), lithium difluorophosphate LiPO2F2 and mixtures thereof. Preferably, it is LiPF6. The concentration of said at least one lithium salt may range from 0.75 to 1.5 mol.L *. Preferably, it ranges from 1 to 1.5 mol.L *. More preferably, it is approximately equal to 1 mol.L *.

[0052] cl Gelled electrolyte: it is obtained by impregnating a polymer with a liquid mixture comprising at least one lithium salt and at least one organic solvent. The lithium salt and the organic solvent may be chosen from the examples of lithium salts and organic solvents described above in relation to the liquid electrolyte. Separator:

[0053] A separator is generally interposed between a negative electrode and a positive electrode to avoid possible short circuits. It prevents electrical contact between a negative electrode and a positive electrode but nevertheless allows the transport of ions between these two electrodes. The material of the separator can be chosen from the following materials: a polyolefin, for example polypropylene and polyethylene, a polyester, glass fibers bonded together by a polymer, polyimide, polyamide, polyaramid, polyamideimide and cellulose. The polyester can be chosen from polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Advantageously, the polyester or polypropylene or polyethylene contains or is coated with a material chosen from the group consisting of a metal oxide, a carbide, a nitride, a boride, a silicide and a sulfide. This material can be SiO2 or Al2O3.The separator may be coated with an organic coating, for example comprising an acrylate or PVDF or P(VdF-HFP). A preferred separator is made of polyethylene or is made of the combination of three layers which are polypropylene PP / polyethylene PE / poly-propylene PP.

[0054] The electrochemical element is manufactured in a conventional manner. It can be prismatic, cylindrical, pocket or button format. Example

[0055] The electrochemical characterization of Nbi5Mo04oF was carried out in an electrochemical half-element, i.e. with a counter-electrode which is metallic lithium. The electrochemical half-element underwent two charge / discharge cycles (“formation”) at room temperature in the C / 10 and D / 10 regime. It then underwent a cycling of 50 cycles at room temperature in the C / 5 and D / 5 regime.

[0056] [Fig.l] shows that Nbi5Mo04oF has an average potential of about 1.7 V vs. Li+ / Li, which is far enough away from the potential of Li+ / Li to reduce the risk of formation of dendrites.

[0057] [Fig.4] shows a first charge mass capacity of approximately 250 mAh / g.

[0058] [Fig.5] shows a reversible capacity of approximately 200 mAh / g at the start of cycling, therefore higher than that of Li4Ti5Oi2 (170 mAh / g).

[0059] Nbi5Mo04oF therefore meets the criteria of safety of use, high capacity and suitability for cycling.

Claims

Claims

1. Electrode comprising: - a current collector, - an active material composition deposited on at least one of the faces of the current collector and comprising an active material which is a compound of formula Mi5_xM'xM”i_yM'”y04o-aXb in which: M represents one or more elements chosen from Nb, Ta and V, M' represents one or more elements chosen from Ti, Zr, Mo, Cr, As and Sb, M” represents one or more elements chosen from Mo and W, M”' represents one or more elements chosen from Cr, V and Te, X represents a halogen, 0 <x<7,5 ; 0<y<l; 0<a<5; 0<b<l, le composé satisfaisant la relation (15-x)*5 + nx + (l-y)*6 + my =(40-a)*2 + b; n et m indiquant respectivement les degrés d’oxydation moyens de M’ et de M”’.

2.

3.

4.

5. Electrode according to claim 1, wherein x=0. Electrode according to claim 1 or 2, wherein M is Nb. Electrode according to one of the preceding claims, wherein y=0 Electrode according to one of the preceding claims, wherein M” is Mo.

6. Electrode according to one of the preceding claims, in which a=0 and b=1.

7. Electrode according to one of the preceding claims, in which the compound has the formula NbisMoO^F.

8. An electrode according to any preceding claim, wherein the compound has a crystal structure in which M and M' occupy octahedral sites whose vertices are surrounding oxygen atoms or X atoms and M” and M'” occupy tetrahedral sites whose vertices are surrounding oxygen atoms.

9. An electrode according to claim 8, wherein the octahedra form parallel planes between them which are connected by the tetrahedra.

10. Electrochemical element comprising: - at least one positive electrode, - at least one negative electrode which is the electrode according to one of the preceding claims.

11. An electrochemical element according to claim 10, wherein the positive electrode comprises one or more positive active materials chosen from: a) a lithium iron phosphate of formula LixFei yMyP04 (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 yMyP04 (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: LixMni y zFey MzPO4(LMFP) where 0.8 <x<1,2 ; 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 ; d) 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 ; e) 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 ; f) 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 ; g) 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 and mixtures thereof; h) a lithium oxide of nickel and manganese of formula Liw(NixMnyCoz Mt)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. (i) a lithium oxide of nickel and manganese of formula LixMn2_y_zM'yM"zO4_ô where M' and M" are selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 ; 0<z<0,2 ; 0<ô<l.

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