Active material for lithium-ion electrochemical element

Abstract

A negative electrode for a lithium-ion electrochemical element, the electrode comprising: - a current collector, - a composition of active material 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 wherein: 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 equation (15-x)*5 + nx + (1-y)*6 + my =(40-a)*2 + b; n and m respectively indicating the average degrees of oxidation of M' and M'''.

Description

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 cells, in particular active materials for a negative electrode of a lithium-ion electrochemical cell. Background

[0002] Lithium-ion electrochemical cells 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 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 Li couple + / Li. Its mass capacity is about 350 mAh / g. Figure 1 shows the variation of the potential of a graphite-based electrode with respect to the Li couple + / Li during a charge / discharge cycle. However, the fact that the potential of the graphite electrode is close to 0 V leads to a risk of metallic lithium formation 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 eventually pierce the separator and cause 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 couple + / Li than graphite have been discovered. Examples include titanium-based lithium oxides, such as Li4Ti5O 12 . This compound has an average potential close to 1.5 V vs. Li + / Li. Figure 1 shows the variation of the potential of a Li4Ti5O12-based electrode with respect to the Li couple + / Li during a charge / discharge cycle. Electrochemical cells comprising a negative electrode based on Li4Ti5O 12 can be charged under high current with zero risk of dendrite formation. The disadvantage associated with the use of Li4Ti5O12, however, is its low specific capacity, which is only about 170 mAh / g, which is half the specific capacity of graphite, as shown in Figure 1.

[0005] Active materials with a potential of approximately 1.5 V relative to the Li couple + / Li and a mass capacity greater than that of Li4Ti5O12 have been discovered. Examples include lithium 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 with a potential sufficiently far from the potential of the Li couple + / Li, i.e. close to 1.5 V vs. Li + / Li, and a mass capacity greater than that of Li4Ti5O 12 . Summary

[0007] To this end, the invention provides 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 M15-xM'xM''1-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<1; 0≤a≤5; 0≤b≤1, the compound satisfying the relationship (15-x)*5 + nx + (1-y)*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 M15-xM'xM''1-yM'''yO40-aXb can be used as an active material for a negative electrode for a lithium-ion electrochemical cell. 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 Nb15MoO40F.

[0015] According to one embodiment, 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.

[0016] According to one embodiment, the octahedra form parallel planes between them 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 selected from: a) a lithium iron phosphate of formula LixFe1-yMyPO4 (LFP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; b) a lithium manganese phosphate of formula Li x Mn 1-y M y PO4(LMP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; c) a lithium manganese iron phosphate of formula: Li x Mn 1-y-z Fe y M zPO4(LMFP) where 0.8≤x≤1.2; 0.5≤1-yz<1; 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) un oxyde lithié de nickel, manganèse et cobalt de formule Liw(NixMnyCozMt)O2 (NMC) où 0,9≤w≤1,1 ; 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) un oxyde lithié de nickel, cobalt et aluminium de formule Liw(NixCoyAlzMt)O2 (NCA) où 0,9≤w≤1,1 ; 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) un composé de formule Li 1+x M 1-x O 2-y F yof cubic crystal structure where 0≤x≤0.5 and 0≤y≤1 and M represents an element selected from the group consisting of 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 and mixtures thereof; g) a lithium nickel manganese oxide (NMX) of formula Li a (Neither 1-x-y-z Mn x Co y M z )O2with 0.9≤a≤1.1; 0.60≤1-xyz<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) un oxyde lithié de nickel et de manganèse de formule Li w (Neither x Mn y Co z M t)O2where 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) un oxyde lithié de nickel et de manganèse de formule Li x Mn 2-y-z M' y M'' z O 4-δ 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≤δ≤1. Brief description of the figures

[0019] [Fig.1] represents the variation of the potential of different active materials with respect to the Li couple + / Li 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 Nb15MoO40F.

[0021] [Fig.3] represents the position of molybdenum and oxygen atoms in a MoO4 tetrahedron, the position of niobium and oxygen atoms in a NbO6 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 Nb15MoO40F during the first two cycles. Charging and discharging are carried out at room temperature, at the C / 10 and D / 10 regimes respectively. The legend is given from the point of view of the use of Nb15MoO40F as a negative material. Thus the charge corresponds to the intercalation of lithium within the structure of Nb 15 MoO 40 F and the discharge corresponds to the deintercalation of lithium within the Nb structure 15 MoO 40 F.

[0023] [Fig.5] represents the variation of the voltage of an electrochemical element comprising a negative electrode based on Nb15MoO40F during a cycling of 50 cycles. Charging and discharging 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 M 15-x M' x M'' 1-y M''' y O 40-a X bin 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 electroneutrality relation: (15-x)*5 + nx + (1-y)*6 + my =(40-a)*2 + b; n and m respectively indicating 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 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 states 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 at oxidation state +IV. - Sb and As in M' can be at oxidation state +V. - Mo and Cr in M' can be at oxidation state +VI. - V in M''' can be at oxidation state +V. - Cr and Te in M''' can be at oxidation state +VI.

[0028] The compound M15M''O40-aXb can exhibit a crystal 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 = ½ 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] Preferred examples of compounds according to the invention are Nb 15 MoO 40 F; Nb15CrO40F; Nb15MoO40Cl; Nb12.5V2.5MoO40F and Nb10V5MoO40F.

[0031] A particularly preferred example of a compound is Nb15MoO40F. It is obtained by heating a mixture of the compounds Nb2O5, MoO3 and NbO2F in stoichiometric proportions to a temperature between 900 and 1000°C. The reaction is: 7Nb2O5 + MoO3 + NbO2F --> MoNb15O40F

[0032] The synthesis and characterization of this compound are described in the article entitled “Crystal structure of MoNb 15 O 40 F » by J. Galy and S. Andersson published in Acta. Cryst. (1968), B24, 1027.

[0033] Figure 2 partially represents the crystal structure of the compound Nb15MoO40F. It shows two types of blocks: a first block of 15 octahedra forming a plane in position z=0 or z=1 and a second block of 15 octahedra forming a plane in position z=1 / 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 the understanding of the crystal structure.

[0034] Figure 3 shows the position of molybdenum and oxygen atoms in a MoO4 tetrahedron, the position of niobium and oxygen atoms in a NbO6 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 understanding of the crystal structure.

[0035] M 15-x M' x M'' 1-y M''' y O 40-a X bmay be the only active material of the negative electrode.

[0036] It can also be associated with one or more negative active materials presenting a potential of approximately 1.5 V vs. Li + / Li. Examples include lithiated titanium oxides such as compounds of formula: i) Lix-aMaTiy-bM'bO4-c-dXc in which 0 <x≤3 ; 1≤y≤2,5 ; 0≤a≤1 ; 0≤b≤1 ; 0≤c≤2 et -2.5≤d≤2.5; The index d represents an oxygen vacancy. The index d may be less than or equal to 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 of formula Li4Ti5O 12 , Li2TiO3, Li2Ti3O 7, LiTi2O4 and Li2Na2Ti6O14. Preferably 0.5≤x≤3; Preferably a≤0.5; Preferably b≤0.25; Preferably c≤0.5. ii) H x You y O4 in which 0≤x≤1; 0≤y≤2. This family includes H2Ti6O 13 , H2Ti 12 O 25 and TiO2; and iii) a mixture of compounds i) and ii).

[0037] Titanium and niobium oxides may also be mentioned, such as compounds of formula: iv) LixTia-yMyNbb-zM'zO((x+4a+5b) / 2)-c-dXc where 0≤x≤5; 0≤y≤1; 0≤z≤2; 1≤a≤5; 1≤b≤25; 0.25≤a / b≤2; 0≤c≤2 and 0≤d≤2; ay>0; bz>0; The subscript d represents an oxygen vacancy. The subscript d may 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 Ti2Nb 10 O 29 .

[0038] Titanium and niobium oxide can be partially substituted by vanadium and have the formula LixTi1-yMyNb2-(z1+z2)Vz1M'z2O7-c-dXc where 0≤x≤5 ; 0≤y<1 ; 0 <z1<0,5 ; 0≤z2<0,5 ; 0≤c≤2 ; 0≤d≤2 ; M représente un ou plusieurs éléments choisi(s) dans le groupe consistant en 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 et Sm ; M’ représente un ou plusieurs éléments choisi(s) dans le groupe consistant en 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 of formula TiNb 1,98 V 0,02 O7 and TiNb 1,95 V 0,05 O7.

[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 M15-xM'xM''1-yM'''yO40-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 polyetheramides, polymers of acrylic acid, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers, and cellulose 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 selected from graphite, carbon black, acetylene black, soot, graphene, carbon fibers, carbon nanotubes, or a mixture thereof.

[0041] By varying the amount of solvent incorporated into 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 that can be made of copper or a copper-based alloy, or made of aluminum or an aluminum-based alloy. Preferably, it is aluminum or an aluminum-based alloy, as 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 materials 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 materials, - 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 Li x Fe 1-y M y PO4(LFP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; b) a lithium manganese phosphate of formula Li x Mn 1-y M yPO4(LMP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; c) a lithium manganese iron phosphate of formula: Li x Mn 1-y-z Fe y M z PO4(LMFP) where 0.8≤x≤1.2; 0.5≤1-yz<1; 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) un oxyde lithié de nickel, manganèse et cobalt de formule Liw(NixMnyCozMt)O2 (NMC) où 0,9≤w≤1,1 ; 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) un oxyde lithié de nickel, cobalt et aluminium de formule Li w (Neither x Co y Al z M t)O2(NCA) where 0.9≤w≤1.1; 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) un composé de formule Li 1+x M 1-x O 2-y F y of cubic crystal structure where 0≤x≤0.5 and 0≤y≤1 and M represents an element selected from the group consisting of 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 and mixtures thereof; g) a lithium nickel manganese oxide (NMX) of formula Li a (Neither 1-x-y-z Mn x Co y M z )O2with 0.9≤a≤1.1; 0.60≤1-xyz<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) un oxyde lithié de nickel et de manganèse de formule Liw (Neither x Mn y Co z M t )O2where 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) un oxyde lithié de nickel et de manganèse de formule LixMn2-y-zM'yM''zO4-δ où M' et M" sont choisis dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb et Mo; M' et M" étant différents l’un de l’autre, et 1≤x≤1,4 ; 0≤y≤0,6 ; 0≤z≤0,2 ; 0≤δ≤1.

[0045] Preferably, it is a compound of type c), i.e. a lithium manganese iron phosphate of formula: LixMn1-y-zFeyMzPO4 (LMFP). Typical formulas of lithium manganese iron phosphate are LiMn 0,8 Fe 0,2 PO4, LiMn 0,7 Fe 0,3 PO4, LiMn 2 / 3 Fe 1 / 3 PO4 and LiMn 0,5 Fe 0,5 PO4.

[0046] An ink is prepared by dispersing one or more positive active materials in a solvent or 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 side of the current collector. 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 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 materials, - 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 selected 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 selected from the same list as that described in relation to the negative electrode, without necessarily being 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 chosen from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC) and methyl propyl carbonate (PMC). Dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) are particularly preferred. The linear carbonate may represent from 50 to 100% or from 60 to 90%, or from 70 to 80% by volume of the total volume of the linear or cyclic alkyl carbonate(s). Said 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). 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 LiClO4, 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 can range from 0.75 to 1.5 mol.L -1. Preferably, it ranges from 1 to 1.5 mol.L -1 . Preferably, it is approximately equal to 1 mol.L -1 .

[0051] c) 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:

[0052] A separator is generally inserted between a negative electrode and a positive electrode to prevent 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 / polypropylene PP.

[0053] The electrochemical element is manufactured in a conventional manner. It can be prismatic, cylindrical, pocket or button. Example

[0054] Electrochemical characterization of Nb 15 MoO 40 F was carried out in electrochemical half-cell, i.e. with a counter-electrode which is metallic lithium. The electrochemical half-cell 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.

[0055] Figure 1 shows that Nb15MoO40F has an average potential of about 1.7 V vs. Li + / Li, which is far enough away from Li's potential + / Li to reduce the risk of dendrite formation.

[0056] Figure 4 shows a first charge mass capacity of approximately 250 mAh / g.

[0057] Figure 5 shows a reversible capacity of approximately 200 mAh / g at the start of cycling, therefore higher than that of Li4Ti5O12 (170 mAh / g).

[0058] Nb 15 MoO 40 F 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 M 15-x M' x M'' 1-y M''' y O 40-a X bwherein: 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 relationship (15-x)*5 + nx + (1-y)*6 + my =(40-a)*2 + b; n and m respectively indicating the average oxidation states of M' and M'''.

2. An electrode according to claim 1, wherein x=0.

3. An electrode according to claim 1 or 2, wherein M is Nb.

4. Electrode according to one of the preceding claims, in which y=0

5. Electrode according to one of the preceding claims, in which 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 Nb. 15 MoO 40F.

8. An electrode according to one of the preceding claims, 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 mutually parallel planes which are connected by the tetrahedra.

10. An 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 Li x Fe 1-y M y PO 4(LFP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; b) a lithium manganese phosphate of formula LixMn1-yMyPO4 (LMP), where 0.8≤x≤1.2; 0≤y≤0.6 and M is selected from the group consisting of Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S and mixtures thereof; c) a lithium manganese and iron phosphate of formula: LixMn1-y-zFeyMzPO4 (LMFP) where 0.8≤x≤1.2; 0.5≤1-yz<1; 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) un oxyde lithié de nickel, manganèse et cobalt de formule Liw(NixMnyCozMt)O2 (NMC) où 0,9≤w≤1,1 ; 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≤1.1; 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) un composé de formule Li1+xM1-xO2-yFy de structure cristalline cubique où 0≤x≤0,5 et 0≤y≤1 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) un oxyde lithié de nickel et de manganèse (NMX) de formule Li; a (Neither 1-x-y-z Mn x Co y M z )O 2with 0.9≤a≤1.1; 0.60≤1-xyz<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) un oxyde lithié de nickel et de manganèse de formule Liw(NixMnyCozMt)O2 où 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) un oxyde lithié de nickel et de manganèse de formule Li x Mn 2-y-z M' y M'' z O 4-δ 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≤δ≤1.

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