ELECTROCHEMICAL ELEMENT WITH ADDITIVES IN THE ELECTROLYTE AND LITHIUM PHOSPHATE-BASED ELECTRODE

Abstract

ELECTROCHEMICAL ELEMENT WITH ADDITIVES IN THE ELECTROLYTE AND ELECTRODE BASED ON LITHIUM PHOSPHATE Electrochemical element comprising: - at least one positive electrode comprising, as positive active material, at least one lithium phosphate compound of formula LixMn1-y-zFeyMzPO4 with 0.8≤x≤1.2; 0≤1-yz<1; 0

Description

Title of the invention: ELECTROCHEMICAL ELEMENT WITH ADDITIVES IN THE ELECTROLYTE AND BASED ELECTRODE OF LITHIUM PHOSPHATE

[0001] The present invention relates to the field of energy storage and lithium batteries in particular. More specifically, the present application relates to electrochemical elements comprising a positive active material of the lithium phosphate type and usable over a wide temperature range, typically ranging from -15°C to 85°C.

[0002] The invention is particularly useful in the field of rechargeable electrochemical elements of the lithium-ion (Li-ion) type.

[0003] Rechargeable electrochemical elements of the lithium-ion type are known from the state of the art. Due to their high mass and volume energy density, they constitute a promising source of electrical energy. They comprise at least one positive electrode and at least one negative electrode, separated by a layer of electrolyte.

[0004] The electrodes consist of a metal current collector on which is coated a composition of active material and additives such as binder(s), dispersant(s), conductive element(s), etc.

[0005] The electrodes are prepared from an ink comprising the composition, generally formulated in an organic solvent medium, coated on a current collector, the solvent of which is evaporated, before calendering so as to adjust the thickness of the ink layer on the collector.

[0006] Lithium manganese and iron phosphates of formula LixMni y zFeyMzPO4 (LMFP) with 0.8 <x<l,2 ; 0<l-y-z<l; 0<y<l ; 0< z< 0,6 sont connus pour leur utilisation comme matière active cathodique d’éléments lithium-ion. Ces phosphates contiennent du manganèse, du fer et un ou plusieurs éléments substituants symbolisés par le symbole M. Ces composés sont connus pour offrir une sécurité d’utilisation supérieure en raison du fait que les phosphates lithiés de métaux de transition sont stables à température élevée.

[0007] The mixture of a lithium phosphate with a lithium nickel oxide has been proposed. The nickel of the lithium oxide can be associated with manganese, cobalt, and possibly one or more chemical elements (NMC type oxide), or can be associated with cobalt, aluminum and possibly one or more chemical elements (NCA type oxide). The mixture of a lithium phosphate and a lithium nickel oxide allows a good compromise between energy and safety.

[0008] Thus, positive electrodes based on active material consisting of lithium manganese and iron phosphate compounds (LMFP), alone or mixed with lithium nickel oxides of the NMC and / or NCA type have been described.

[0009] These positive electrodes are conventionally used at operating temperatures close to room temperature, typically 25°C, where they are perfectly functional. However, attempts are being made to improve their use at low and / or high temperatures. Indeed, at low temperatures (i.e. at negative operating temperatures typically down to -15°C), attempts are being made to improve their dischargeability and their ability to be used for applications requiring high power. Furthermore, at high temperatures typically up to 85°C, attempts are being made to improve their lifetime and capacity retention.

[0010] It is also known to integrate one or more additives into the electrolyte composition, in order to improve certain properties of the final element. For example, the addition of tris(trimethylsilyl)phosphite (TMSP) and / or hexatricarbonitrile (HTCN) is known in particular from CN 113140797 A1 and US 2022 / 0181690 A1. In particular, tris(trimethylsilyl)phosphite (TMSP) is known for its ability to trap water molecules (in English "Water scavenger"). Hexatricarbonitrile (HTCN) is known for stabilizing the interface between the positive electrode and the electrolyte by absorbing itself on the surface of the transition metals of the cathode materials.

[0011] However, none of these documents specifically addresses electrochemical elements based on a positive active material of the lithium phosphate type. In particular, none of these documents seeks to broaden the temperature ranges of use of electrochemical elements based on a positive active material of the lithium phosphate type.

[0012] It therefore remains to provide electrochemical elements, based on a positive active material of the lithium phosphate type, usable over wide temperature ranges. In particular, there remains the need for electrochemical elements comprising a positive electrode whose active material is of the lithium phosphate type and which can be used both at low temperatures, typically down to -15°C, and at high temperatures, typically up to 85°C.

[0013] An aim of the invention is then to propose electrochemical elements, based on a positive active material of the lithium phosphate type, whose operating temperature range is significantly widened.

[0014] The broadening of the range of operating temperatures of an electrochemical element involves in particular an improvement in its dischargeability at low temperature, typically down to -15°C, and / or an extension of its service life, in particular at operating temperatures up to 85°C.

[0015] An aim of the invention is then to propose electrochemical elements, based on of a positive active material of the lithium phosphate type, having improved dischargeability at low temperature, typically at temperatures ranging from -15°C to 25°C.

[0016] Another object of the invention is to provide electrochemical elements, based on a positive active material of the lithium phosphate type, having an extended lifetime both at room temperature and at high temperature, typically at temperatures ranging from 25°C to 85°C.

[0017] A particular aim of the invention is to propose electrochemical elements, based on a positive active material of the lithium phosphate type, having both i) improved dischargeability at low temperature and ii) an extended lifetime at room temperature and at high temperature. Summary of the invention

[0018] The invention firstly relates to an electrochemical element comprising:

[0019] - at least one positive electrode comprising, as positive active material, at minus a lithium phosphate compound of formula LixMni y zFeyMzPO4 with 0.8 <x<l,2 ; 0<l-y-z<l; 0<y<l ; 0<z<0,6 ; et M choisi dans le groupe constitué de : B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, S, K, Pb et leurs mélanges ;

[0020] - at least one negative electrode;

[0021] - at least one electrolyte comprising at least one additive chosen from: tris(trimethylsilyl)phosphite (TMSP), hexatricarbonitrile (HTCN) and any mixtures thereof.

[0022] Preferably, 1 > 1-yz > 0.5; 0 < y < 0.5; 0 < z < 0.2.

[0023] According to one embodiment, the positive electrode comprises one or more additional lithiated compounds chosen from:

[0024] i) lithium nickel, manganese and cobalt (NMC) oxide type compounds of formula Liw(NixMnyCozMt)O2 with 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; et M 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 leurs mélanges,

[0025] ii) lithium nickel, cobalt and aluminum (NCA) oxide type compounds of formula Liw(NixCoyAlzMt)O2 with 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; et M choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr, La et leurs mélanges,

[0026] iii) compounds of formula Lii+xMi.xO2.yFy of cubic structure where M represents at least one element chosen 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, Sm and mixtures thereof; where 0 < x < 0.5 and 0 < y < 1;

[0027] iv) lithium nickel manganese oxide (NMX) compounds of formula

[0028] 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 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 leurs mélanges ;

[0029] v) lithium oxide compounds of nickel and manganese of formula Liw(NixMnyCozMt )O2 with 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t et M 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, Ta, Ga, Nd, Pr, La et leurs mélanges ;

[0030] vi) mixtures thereof.

[0031] Preferably, the tris(trimethylsilyl)phosphite (TMSP) content is from 0% to 2% by mass, relative to the total mass of the electrolyte, preferably from 0.5% to 1.5% by mass, more preferably from 0.7% to 1.2% by mass.

[0032] Preferably, the hexatricarbonitrile (HTCN) content is from 0% to 5% by mass, relative to the total mass of the electrolyte, preferably from 0.5% to 2% by mass, more preferably from 0.7% to 1.2% by mass.

[0033] Advantageously, the electrolyte further comprises at least one lithium salt chosen from lithium hexafluorophosphate LiPF6, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI) and mixtures thereof.

[0034] According to one embodiment, said at least one lithium salt is lithium hexafluorophosphate LiPF6, optionally mixed with lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI).

[0035] According to an alternative embodiment, said at least one lithium salt is lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), and said additive is hexatricarbonitrile (HTCN), alone or in a mixture with tris(trimethylsilyl)phosphite (TMSP).

[0036] Advantageously, the electrolyte comprises both tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN).

[0037] More advantageously, tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN) are present in a mass ratio ranging from 10:1 to 1:10, preferably from 5:1 to 1:5, more preferably in a mass ratio of 1:1.

[0038] Preferably, the electrolyte comprises at least one organic solvent comprising: - at least one cyclic carbonate, preferably chosen from ethylene carbonate (EC), propylene carbonate (PC) and any of their mixtures, and - at least one linear carbonate, preferably chosen from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and any of their mixtures.

[0039] Preferably, the electrolyte further comprises at least one additive chosen from the group consisting of: vinylene carbonate (VC), ethylene sulfate (ESA), fluoroethylene carbonate (FEC), lithium difluorophosphate LiPO2F2 and any mixtures thereof.

[0040] According to a preferred embodiment, the electrolyte comprises: from 0% to 5% by mass of vinylene carbonate (VC), from 0% to 3% by mass of ethylene sulfate (ESA), from 0% to 5% by mass of fluoroethylene carbonate (FEC), from 0% to 2% by mass of lithium difluorophosphate LiPO2F2,

[0041] relative to the total mass of the electrolyte.

[0042] The invention also relates to an electrochemical module comprising a stack of at least two electrochemical elements as defined above and described in detail below, each electrochemical element being electrically connected with one or more other electrochemical element(s).

[0043] The invention further relates to the use of an electrochemical element or an electrochemical module as defined above and described in detail below, in storage, charging or discharging at a temperature ranging from -15°C to 85°C.

[0044] The incorporation of tris(trimethylsilyl)phosphite (TMSP) into the electrolyte composition makes it possible to significantly reduce the charge transfer impedances at the electrode / electrolyte interfaces, thus improving the dischargeability of the element at low operating temperatures, typically down to a temperature of -15°C.

[0045] The incorporation into the electrolyte composition of hexatricarbonitrile (HTCN) makes it possible to improve the capacity retention of the systems at room temperature and at elevated temperature, typically up to a temperature equal to 85°C, this improvement in capacity retention resulting in an extended service life.

[0046] The incorporation into the electrolyte composition of tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN) makes it possible both to improve the dischargeability of the cell at low temperature and to extend the life of the cells when used at room temperature or at elevated temperatures, typically up to 85°C.

[0047] The incorporation of tris(trimethylsilyl)phosphite (TMSP) and / or hexatricarbonitrile (HTCN) is furthermore advantageous in that it is not associated with any degradation of the cycling performance at room temperature of the electrochemical element. Detailed description

[0048] The invention firstly relates to an electrochemical element comprising:

[0049] - at least one positive electrode comprising, as positive active material, at minus a lithium phosphate compound of formula LixMni y zFeyMzPO4 with 0.8 < x < 1.2; 0 <l-y-z<l ; 0 < y <1 ; 0 < z < 0,6 ; et M choisi dans le groupe constitué de : B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, S, K, Pb et leurs mélanges ;

[0050] - at least one negative electrode;

[0051] - at least one electrolyte comprising at least one additive chosen from: tris(trimethylsilyl)phosphite (TMSP), hexatricarbonitrile (HTCN) and any mixture thereof. The electrodes

[0052] The electrodes, in particular positive ones, are typically made up of a metal current collector on which is coated a composition of active material(s) and additive(s) such as binder(s), dispersant(s), conductive element(s), etc.

[0053] The active material composition is coated on the current collector.

[0054] The coated current collector can therefore be covered on one or each of its faces with said composition of active materials.

[0055] The term “composition of active materials” means the composition comprising all of the compounds, including the electrochemically active materials, which cover the current collector on at least one of its faces. Generally, this composition comprises, in addition to the electrochemically active materials, electronically conductive materials, and possible additives, such as binders, etc.

[0056] The current collector

[0057] The current collector of the positive and / or negative electrodes is generally in the form of a solid or perforated metal strip. The strip can be made from different materials. Examples include copper or copper alloys, aluminum or aluminum alloys, nickel or nickel alloys, steel, and stainless steel.

[0058] The current collector of the positive electrode is generally a foil made of aluminum or an alloy comprising mainly aluminum. The current collector of the negative electrode is generally a foil made of copper or an alloy comprising mainly copper. The thickness of the foil of the positive electrode may be different from that of the foil of the negative electrode. The foil of the positive or negative electrode typically has a thickness of 6 μm to 30 μm.

[0059] According to one embodiment, the aluminum collector of the positive electrode is covered with a conductive coating, such as for example carbon black, graphite and their mixtures.

[0060] Positive active ingredient

[0061] The positive electrode comprises, as positive active material, at least one lithium phosphate compound of formula LixMni y zFeyMzPO4 with 0.8 <x<l,2 ; 0<l-y-z<l ; 0<y<l ; 0<z<0,6 ; et M choisi dans le groupe constitué de : B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, S, K, Pb et leurs mélanges.

[0062] According to one embodiment, said at least one lithium phosphate compound is lithium iron phosphate LiFePO4 (LFP).

[0063] According to a preferred embodiment, said at least one lithium phosphate compound is chosen from lithium manganese phosphate compounds in which l>lyz> 0.5; 0 <y< 0,5 ; 0<z<0,2.

[0064] More preferably, said at least one lithium phosphate compound is chosen from lithium manganese and iron phosphate (LMFP) compounds corresponding to the formula LixMni y zFeyMzPO4 in which:

[0065] M is selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, S, K, Pb and mixtures thereof,

[0066] 0.8 <x<l,2;

[0067] 0.5 <l-y-z<l;

[0068] 0.05< y <0.5;

[0069] 0< z <0.2.

[0070] Advantageously, 0.7 <l-y-z<0,9.

[0071] Even more advantageously, 0.7 <l-y-z<0,85.

[0072] As active material of LMFP type, mention may be made, for example, of compounds of formula LiMno8Feoj2P04, LiMno 6Feoj4P04, LiMno 7Feo 3P04, LiMn2 / 3Fei / 3PO4 and LiMn0>5 Fe0j5PO4.

[0073] The lithium phosphate compound(s), in particular the lithium manganese and iron phosphate compound(s) (LMFP), may be coated with a layer of carbon and / or carbon nanotubes, in particular in order to increase their electronic conductivity and / or their ionic diffusivity.

[0074] According to one embodiment, the entirety of the positive active material consists of lithium phosphate type compounds.

[0075] According to another embodiment, the positive electrode comprises, in addition to the lithium phosphate compound(s), at least one additional lithium compound chosen from the following groups: a. lithium nickel oxide type compounds, b. compounds of formula Lii+xMi_xO2 yFy of cubic structure where M represents at least one 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, Sm and mixtures thereof; where 0 < x < 0.5 and 0 < y < 1; c. mixtures of compounds a) and b).

[0076] The compounds of the lithium nickel oxide type are preferentially chosen from nickel-rich lithium nickel oxides, preferably comprising more than 60% (based on the atomic ratio) of nickel.

[0077] Thus, they are chosen from:

[0078] i) lithium nickel, manganese and cobalt (NMC) oxide type compounds of formula Liw(NixMnyCozMt)O2 with 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; et M 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 leurs mélanges,

[0079] ii) lithium nickel, cobalt and aluminum (NCA) oxide type compounds of formula Liw(NixCoyAlzMt)O2 with 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; et M choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr, La et leurs mélanges,

[0080] iii) lithium nickel manganese oxide (NMX) compounds of formula

[0081] 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 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 leurs mélanges ;

[0082] iv) lithium oxide compounds of nickel and manganese of formula Liw(NixMnyCozM t)O2 with 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t et M 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, Ta, Ga, Nd, Pr, La et leurs mélanges ;

[0083] v) mixtures thereof.

[0084] Nickel-rich NMC type compounds have the formula:

[0085] Liw(NixMnyCozMt)O2

[0086] In which

[0087] 0.9 <w<l,l ;

[0088] 0.60 <x ;

[0089] 0 <y ;

[0090] 0 <z ;

[0091] 0 <t ;

[0092] M being at least one element chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ta, Ga, Nd, Pr, La and mixtures thereof.

[0093] M may be chosen in particular from the group consisting of Al, B, Mg and their mixtures. Preferably, M is Al and t<0.05. The majority transition element is preferably nickel, preferably x>0.6. A high amount of nickel in the lithium nickel oxide is preferable because it provides high energy to the lithium nickel oxide.

[0094] As a lithium oxide type compound of nickel, manganese and cobalt (NMC), rich in nickel, the following compounds may be mentioned in particular:

[0095] LiNio.6Mno.2Co0.202 (NMC 622),

[0096] LiNio.8Mno.1Coo.jO2 (NMC 811).

[0097] Nickel-rich lithium nickel, cobalt, and aluminum (NCA) oxide compounds have the formula:

[0098] Liw(NixCoyAlzMt)O2

[0099] in which

[0100] 0.9 <w<l,l ;

[0101] 0.8 <x ;

[0102] 0 <y ;

[0103] 0 <z ;

[0104] 0 <t ;

[0105] M being at least one element chosen from the group consisting of B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr, La and mixtures thereof.

[0106] Preferably M can be chosen from the group consisting of B, Mg and their mixtures. Examples include: LiNiO.sCoO I^AIqi^Oo.

[0107] Preferably, the lithium phosphate type compound(s), in particular the lithium manganese and iron phosphate type compound(s) (LMFP), represent(s) at least 30% by mass of the positive active material of the electrode, more preferably at least 50% by mass, even more preferably at least 70% by mass, advantageously at least 80% by mass, relative to the total mass of the positive active material.

[0108] More preferably, the positive active material comprises, preferably consists of:

[0109] - from 30% to 100% by mass of lithium phosphate type compound(s), in particular lithium manganese iron phosphate (LMFP) compound(s), and

[0110] - from 0% to 70% by mass of additional active compound, preferably chosen from NMC compounds, NCA compounds, NMX compounds and their mixtures, more preferably chosen from NMC compounds.

[0111] Advantageously, the positive active material comprises, preferably consists of:

[0112] - from 70% to 100% by mass of lithium phosphate type compound(s), in particular lithium manganese iron phosphate (LMFP) compound(s), and

[0113] - from 0% to 30% by mass of additional active compound, preferably chosen from NMC compounds, NCA compounds, NMX compounds and their mixtures, more preferably chosen from NMC compounds.

[0114] Negative active ingredient

[0115] In the context of the present invention, the negative electrode may be of any known type. The anode typically consists of a conductive support used as a current collector on which the anodic active material and a carbon electronic material are deposited. A binder may also be incorporated into the mixture.

[0116] It is understood that in “anode free” systems, a negative electrode is also present (generally initially limited to the current collector only).

[0117] The anodic active material is not particularly limited. It can be selected from the following groups and mixtures thereof:

[0118] - Metallic lithium or a metallic lithium alloy

[0119] -Graphite

[0120] - Silicon

[0121] - Anode-free type

[0122] - a titanium and niobium oxide TNO having the formula:

[0123] LixT ia_yMyNbb_zM ' zO((X+4a+5b) / 2)_c_dXc

[0124] where:

[0125] 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; ay > 0; bz > 0;

[0126] 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;

[0127] X represents at least one element selected from the group consisting of S, F, Cl and Br.

[0128] The index d represents an oxygen vacancy. The index d can be less than or equal to 0.5.

[0129] Said at least one titanium and niobium oxide may be chosen from TiNb2O7, Ti2 Nb2O7jTi2Nb2O9 and Ti2Nbi0O29.

[0130] - a lithiated titanium oxide or a titanium oxide capable of being lithiated. The oxide of lithium titanium is chosen from the following oxides:

[0131] i) LixaMaTiy_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 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 la

[0132] 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;

[0133] X represents at least one element selected from the group consisting of S, F, Cl and Br;

[0134] The index d represents an oxygen vacancy. The index d can be less than or equal to 0.5.

[0135] ii) HxTiyO4 in which 0 <x<l ; 0<y<2, et

[0136] iii) a mixture of compounds i) to ii).

[0137] Examples of lithiated titanium oxides belonging to group i) are spinel Li4 Ti50i2, Li2TiO3 laramsdellite Li2Ti3O7,LiTi2O4, LixTi2O4, with 0 <x<2 et li2na2ti60i4.

[0138] A preferred LTO compound has the formula Lq aMaTi5 bM'bO4, for example Li4Ti50i2 which is also written Li4 / 3Ti5 / 3O4.

[0139] According to a preferred embodiment, the anodic active material is graphite.

[0140] Binder

[0141] The positive and / or negative active materials of the electrochemical element are generally mixed with one or more binders, the function of which is to bind the particles of active material together as well as to bind them to the current collector on which they are deposited.

[0142] The binder may be selected from carboxymethylcellulose (CMC), styrene butadiene copolymer (SBR), polytetrafluoroethylene (PTFE), polyamideimide (PAI), polyimide (PI), styrene butradiene rubber (SBR), polyvinyl alcohol, polyvinylidene fluoride (PVDF) and a mixture thereof. These binders may typically be used in the cathode and / or in the anode.

[0143] Optional additive(s)

[0144] The active ingredient composition may further comprise one or more ingredients selected from electronically conductive materials, dispersants, and / or pH buffers.

[0145] The electronically conductive material may generally be selected from graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes or a mixture thereof.

[0146] The composition of active ingredients may also comprise one or more dispersants. Polyvinylpyrrolidone (PVP) may thus be mentioned as a dispersant suitable for the invention.

[0147] Manufacture of electrodes

[0148] Generally, an electrode can be manufactured by preparing an ink comprising one or more active materials mixed with a solvent or a mixture of several solvents, with one or more binders, and optionally with one or more electronically conductive materials,

[0149] This ink can then be coated on at least one of the faces of a current collector.

[0150] The ink can then be dried.

[0151] The thickness of the composition thus coated can then be adjusted in a calendering step, by passing the electrode between two rollers exerting pressure on the surface of the electrode.

[0152] After evaporation of the solvent(s), an ink composition is obtained which can be:

[0153] - from 80 to 98% or from 90 to 95% by mass of active materials,

[0154] - from 1 to 10% or from 2 to 5% by mass of binder(s),

[0155] - from 0 to 10% or from 2 to 5% by mass of electronically conductive material. Electrolyte

[0156] The electrolyte is typically in liquid form.

[0157] It typically comprises at least one organic solvent in which a or more alkali metal salt(s) and at least one additive selected from tris(trimethylsilyl)phosphite (TMSP), hexatricarbonitrile (HTCN) and mixtures thereof. The electrolyte may further comprise optional additives.

[0158] According to an alternative embodiment, the electrolyte is in the form of a gel obtained by impregnating a polymer with a liquid mixture comprising at least one lithium salt and an organic solvent.

[0159] Solvent

[0160] Preferably, the electrolyte comprises at least one organic solvent, more preferably chosen from the group consisting of cyclic or linear carbonates, cyclic or linear esters, cyclic or linear ethers and a mixture thereof.

[0161] Examples of cyclic carbonates are ethylene carbonate (EC) and propylene carbonate (PC). Ethylene carbonate (EC), propylene carbonate (PC) and a mixture thereof are particularly preferred. The electrolyte composition may be free of cyclic carbonates other than EC and PC.

[0162] Examples of linear carbonates are dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and a mixture thereof are particularly preferred. The electrolyte composition may be free of linear carbonates other than DMC and EMC.

[0163] The cyclic or linear carbonate(s) as well as the cyclic or linear ester(s) may be substituted by one or more halogen atoms, such as fluorine.

[0164] Examples of linear esters are ethyl acetate, methyl acetate, propyl acetate, ethyl butyrate, methyl butyrate, propyl butyrate, ethyl propionate, methyl propionate and propyl propionate.

[0165] Examples of cyclic esters are gamma-butyrolactone and gamma-va-lerolactone.

[0166] Examples of linear ethers are dimethoxyethane and propyl ethyl ether.

[0167] An example of a cyclic ether is tetrahydrofuran.

[0168] Advantageously, the solvent is in the form of a mixture comprising:

[0169] - at least one cyclic carbonate, and

[0170] - at least one linear carbonate.

[0171] Preferably, the electrolyte does not comprise solvent compounds other than cyclic or linear carbonates.

[0172] In the case where the solvent compounds are a mixture of cyclic and linear carbonates, the cyclic carbonate(s) may represent up to 50% by volume of the volume of the carbonates and the linear carbonate(s) may represent at least 50% by volume of the volume of the carbonates. Preferably, the carbonate(s) cyclic carbonates represent 10% to 40% by volume of the carbonate volume and the linear carbonate(s) represent 90% to 60% of the carbonate volume. A preferred mixture of organic solvents is the mixture of EC, PC, EMC and DMC. EC may represent 5% to 15% by volume of the organic solvent mixture volume. PC may represent 15% to 25% by volume of the organic solvent mixture volume. EMC may represent 20% to 30% by volume of the organic solvent mixture volume. DMC may represent 40% to 50% by volume of the organic solvent mixture volume.

[0173] Alkali metal salt

[0174] Preferably, the electrolyte comprises at least one alkali metal salt, more preferably at least one lithium salt.

[0175] Preferably, the lithium salt is selected from the group consisting of: lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, lithium hexafluoroantimonate LiSbF6, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2(LiTFSI), lithium trifluoromethanesulfonemethide LiC(CF3SO2)3(LiTFSM), lithium bisperfluoroethylsulfonylimide LiN(C2F5SO2)2(LiBETI), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), lithium bis(oxalatoborate) (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3(LiFAP) and any mixtures thereof.

[0176] Even more preferably, said at least one lithium salt is chosen from the group consisting of: lithium hexafluorophosphate LiPF6, lithium hexafluoroarsenate LiAsF6, lithium hexafluoroantimonate LiSbF6, lithium tetrafluoroborate LiBF4, lithium bis(fluorosulfonyl)imide LiFSI and any of their mixtures.

[0177] Advantageously, said at least one lithium salt is chosen from lithium hexafluorophosphate LiPF6, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI) and any of their mixtures.

[0178] According to one embodiment, the electrolyte composition does not contain any lithium salts other than the lithium salts described above. Preferably, according to this embodiment, the only lithium salts in the electrolyte composition are LiPF6 and / or LiFSI.

[0179] According to another embodiment, lithium hexafluorophosphate LiPF6 and / or lithium bis(fluorosulfonyl)imide LiFSI represent at least 50% by mass of the lithium salts, relative to the total mass of the lithium salts present in the electrolyte, preferably at least 70% by mass, more preferably at least 80% by mass.

[0180] Lithium difluorophosphate LiPO2F2 dissociates very weakly in an organic medium and its presence contributes negligibly to the increase in the quantity of lithium ions in the electrolyte. It will be considered in the following as an additive and not as a salt of the electrolyte.

[0181] Preferably, the total lithium ion concentration in the electrolyte composition is from 0.1 mol.L 1 to 3 mol.L *, preferably from 0.5 mol.L 1 to 1.5 mol.L *, more preferably approximately equal to 1 mol.L '.

[0182] According to one embodiment, said at least one alkali metal salt, in particular said at least one lithium salt, is lithium hexafluorophosphate (LiPF6), taken alone or in a mixture with lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI).

[0183] According to another embodiment, lithium bis(fluorosulfonyl)imide Li(FSO2)2 N (LiFSI) is the only lithium salt, in particular the only alkali metal salt, in the electrolyte composition.

[0184] Preferably, according to this other embodiment, the electrolyte comprises, as an additive, hexatricarbonitrile (HTCN), alone or in a mixture with tris(trimethylsilyl)phosphite (TMSP).

[0185] Additives according to the invention

[0186] The electrolyte comprises at least one additive chosen from: tris(trimethylsilyl)phosphite (TMSP), hexatricarbonitrile (HTCN) and any of their mixtures.

[0187] Preferably, the electrolyte has a tris(trimethylsilyl)phosphite (TMSP) content of 0% to 2% by mass, relative to the total mass of the electrolyte, more preferably from 0.5% to 1.5% by mass, more preferably from 0.7% to 1.2% by mass.

[0188] Preferably, the electrolyte has a hexatricarbonitrile (HTCN) content of 0% to 5% by mass, relative to the total mass of the electrolyte, more preferably from 0.5% to 2% by mass, more preferably from 0.7% to 1.2% by mass.

[0189] According to a first embodiment, said additive is tris(trimethylsilyl)phosphite (TMSP).

[0190] Preferably, according to this embodiment, the only additive (excluding optional additives described below) present in the composition is tris(trimethylsilyl)phosphite (TMSP). In particular, according to this embodiment, the electrolyte does not comprise hexatricarbonitrile (HTCN).

[0191] According to a second embodiment, said additive is hexatricarbonitrile (HTCN).

[0192] Preferably, according to this second embodiment, the only additive (apart from optional additives described below) present in the composition is hexatricarbonitrile (HTCN). In particular, according to this second embodiment, the electrolyte does not comprise tris(trimethylsilyl)phosphite (TMSP).

[0193] According to a third embodiment, the electrolyte comprises both tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN).

[0194] Preferably, according to this third embodiment, tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN) are present in a mass ratio ranging from 10:1 to 1:10, preferably from 5:1 to 1:5, more preferably in a mass ratio of 1:1.

[0195] Additional additives (optional)

[0196] The electrolyte may further comprise one or more optional additional additive(s).

[0197] Preferably, the electrolyte comprises at least one additive selected from the group consisting of: vinylene carbonate (VC), ethylene sulfate (ESA), fluoroethylene carbonate (FEC), lithium difluorophosphate LiPO2F2, and any of their mixtures.

[0198] Preferably, the electrolyte has a vinylene carbonate (VC) content ranging from 0% to 5% by mass, relative to the total mass of the electrolyte, more preferably from 0.1% to 4% by mass, even more preferably from 1% to 3% by mass.

[0199] Preferably, the electrolyte has an ethylene sulfate (ESA) content ranging from 0% to 3% by mass, relative to the total mass of the electrolyte, more preferably from 0.1% to 4% by mass, even more preferably from 1% to 3% by mass.

[0200] Preferably, the electrolyte has a fluoroethylene carbonate (FEC) content ranging from 0% to 3% by mass, relative to the total mass of the electrolyte, more preferably from 0.1% to 4% by mass, even more preferably from 1% to 3% by mass.

[0201] Preferably, the electrolyte has a lithium difluorophosphate LiPO2F2 content ranging from 0% to 2% by mass, relative to the total mass of the electrolyte, more preferably from 0.1% to 1.5% by mass, even more preferably from 0.5% to 1% by mass. Electrochemical element

[0202] According to one embodiment, the electrochemical element is of the lithium-ion type.

[0203] The lithium-ion element can be manufactured in a conventional manner. At least one cathode, at least one separator and at least one anode are superimposed. The assembly can be rolled up to form a cylindrical electrochemical bundle, then inserted into a container. The invention is not limited to the manufacture of elements of cylindrical format. The format of the element can also be prismatic or of the pouch type. (pouch). The electrodes can also be stacked to form a planar electrochemical bundle. A connecting piece is attached to an edge of the cathode not covered with active material. It is connected to a current output terminal.

[0204] The anode may be electrically connected to the cell container. Conversely, the cathode may be connected to the cell container and the anode to a current output terminal. After being inserted into the cell container, the electrochemical bundle is impregnated with electrolyte. The cell is then sealed. The cell may also be conventionally equipped with a safety valve causing the cell container to open in the event that the internal pressure of the cell exceeds a predetermined value.

[0205] The separator may consist of a layer of polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyester such as polyethylene terephthalate (PET), poly(butylene) terephthalate (PBT), cellulose, polyimide, glass fibers or a mixture of layers of different natures. The polymers mentioned may be coated with a ceramic layer and / or polyvinylidene difluoride (PVdF) or poly(vinylidene fluoride-hexafluoropropylene (PVdF-HFP) or acrylates. Applications

[0206] The invention also relates to an electrochemical module comprising the stack of at least two electrochemical elements according to the invention, each element being electrically connected with one or more other element(s), in particular via their current collectors.

[0207] The invention also relates to a battery comprising one or more modules according to the invention.

[0208] For the purposes of the invention, the term “battery” means the assembly of several modules.

[0209] Said assemblies may be in series and / or parallel.

[0210] The invention also relates to the use of an electrochemical element as defined above or of an electrochemical module as described below, in storage, charging or discharging at a temperature ranging from -15°C to 85°C. FIGURES

[0211] [Fig. 1] [Fig. 1] is a graph representing the variation of the discharged capacity of the electrochemical elements EA to Ee prepared in the examples, for a discharge regime at D / 2 and at a temperature of -15°C.

[0212] [Fig.2] [Fig.2] represents the capacity retention of electrochemical elements E f, Eg and Eh prepared in the examples during cycling at a C / 2 regime and a temperature of 60°C. EXAMPLES 1. Preparation of electrochemical elements

[0213] The lithium-ion electrochemical elements EA to EK were manufactured. They all comprise a negative electrode whose active material is graphite and a positive electrode whose active material is composed of a mixture of 70% by mass of an LMFP compound and 30% by mass of LiNi8 / ioMni / ioCoi / io02 (NMC). The separator is a PP / PE / PP tri-layer separator (PP: polypropylene; PE: polyethylene). Each of the containers was filled with one of the electrolytes A to H whose compositions are given in Table 1 below.

[0214] For convenience, the electrochemical cells are designated Ex, with X designating the electrolyte used to fill the separator of the electrochemical cell Ex. Thus, by way of example, the container of the electrochemical cell EA was filled with the electrolyte composition A.

[0215] [Tables 1] Ref. electrolyte Composition of the electrolyte Solvent (% by volume1) Lithium salt TMSP (% by mass2) HTCN (% by mass2) Other additive(s) (% by mass2) A* EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (1.0 mol.L1) - - VC (3%) B EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (1.0 mol.L 1 ) 1 % - VC (3%) LiPO2F2 (1%) C EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (1.0 mol.L1 ) 1 % FEC (3%) ESA(1%) LiPO2F2 (1%) D EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (1.0 mol.L 1) 1% 1% VC (3%) LiPO2F2 (1%) E EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (0.3 mol.L *) + LiFSI (0.7 mol.L 1) 1% 1% VC (3%) LiPO2F2 (1%) F EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiPF6 (1.0 mol.L 1 ) - 1 % - G* EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiFSI (1.0 mol.L1 ) - - - H EC / PC / DMC / EM C (10% / 20% / 45% / 2 5%) LiFSI (1.0 mol.L 1) - 1% -

[0216] 1 percentage by volume, relative to the total volume of solvent

[0217] 2 mass content, relative to the total mass of the electrolyte composition

[0218] The electrochemical elements EB to EF and EH are according to the invention.

[0219] The electrochemical elements EA and EG are comparative in that the electrolyte does not includes neither tris(trimethylsilyl)phosphite (TMSP) nor hexatricarbonitrile (HTCN). 2. Cycling resistance (at low temperature)

[0220] After undergoing an electrical formation step at C / 10 - D / 10, the lithium-ion electrochemical elements EA to Ee were subjected to cycling involving significant temperature variations. The different characteristics of the cycling are indicated in Table 2 below.

[0221] [Tables2] Step Protocol Temperature 1 Charge C / 5 (up to a voltage of 4.2 V) 25°C 2 Discharge D / 2 (up to a voltage of 2.7 V) -15°C

[0222] [Fig. 1] represents the variation of the discharged capacity of the elements EA to Ee at a discharge rate D / 2 and at a temperature of -15°C. It is observed that under these cycling conditions, the capacity discharged by the elements EB, Ec, ED and Ee according to the invention is greater than that of the comparative element EA. This illustrates the benefit in dischargeability at low temperature (step 4 of Table 2) of the electrochemical elements of the invention. 3. Capacity retention (at high temperature)

[0223] After undergoing an electrical formation step at C / 10 - D / 10, the electrochemical elements Ee, Eg and Eh were subjected to cycling with the characteristics indicated in Table 3 below:

[0224] [Tables3] Step Protocol Temperature 1 50 cycles at C / 2-D / 2 60°C

[0225] [Fig.2] represents the capacity retention of the electrochemical elements Ee, EG and Eh during cycling at a C / 2 regime and a temperature of 60°C.

[0226] It is observed that, under these cycling conditions, the capacity retention of the electrochemical elements EF and EH is greater than that of the reference element EG. The electrochemical elements EF and EH according to the invention thus have an improved lifetime compared to the reference electrochemical element EG.

Claims

Claims

1. Electrochemical element comprising: - at least one positive electrode comprising, as positive active material, at least one lithium phosphate compound of formula LixMni.y.zFey MZPO4 with 0.8 <x<l,2 ; 0<l-y-z<l; 0<y<l ; 0<z<0,6 ; et M choisi dans le groupe constitué de : B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, S, K, Pb et leurs mélanges ; - au moins une électrode négative ; - au moins un électrolyte comprenant au moins un additif choisi parmi : le tris(triméthylsilyl)phosphite (TMSP), rhexatricarbonitrile (HTCN) et l’un quelconque de leurs mélanges.

2. An electrochemical element according to claim 1, wherein 1 > 1-yz > 0.5; 0 < y < 0.5; 0 < z < 0.

2.

3. An electrochemical element according to claim 1 or claim 2, wherein the positive electrode comprises one or more additional lithium compounds selected from: i) lithium nickel, manganese and cobalt (NMC) oxide type compounds of formula Liw(NixMnyCozMt)O2with 0.9 <w<l,l ; 0<x 0<y 0<z 0<t et m 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 leurs mélanges, ii) les composés type oxyde lithié nickel, cobalt aluminium (nca) formule liw(nixcoyalzmt)o2 avec 0,9<w<l,l mn, iii) composé lii+xmi.xo2.yfy structure cubique où représente au moins un élément na, k, sc, co, ni, ru, ag, sn, sb, bi, la, eu, sm mélanges 0 < x < 0,5 < y < 1 iv) nickel manganèse (nmx) lia(nii.x.y.zmnxcoymz)o2 0,9<a<l,l 0,60<l-x-y-z<0,80 0<y<0,02 consistant en ;v) lithium oxide compounds of nickel and manganese of formula Liw (NixMnyCozMt)O2 with 1.1 <w<1,6 ; 0<x 0,50<y<0,80 0<z<0,02 0<t et m 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, ta, ga, nd, pr, la leurs mélanges vi) les de ceux-ci.

4. An electrochemical element according to any one of the preceding claims, wherein the tris(trimethylsilyl)phosphite (TMSP) content is 0% to 2% by mass, relative to the total mass of the electrolyte, preferably 0.5% to 1.5% by mass, more preferably 0.7% to 1.2% by mass.

5. An electrochemical element according to any one of the preceding claims, wherein the hexatricarbonitrile (HTCN) content is 0% to 5% by mass, relative to the total mass of the electrolyte, preferably 0.5% to 2% by mass, more preferably 0.7% to 1.2% by mass.

6. An electrochemical element according to any one of claims 1 to 3, wherein the electrolyte further comprises at least one lithium salt selected from lithium hexafluorophosphate LiPF6, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI) and mixtures thereof.

7. Electrochemical element according to the preceding claim, in which said at least one lithium salt is lithium hexafluorophosphate LiPF6, optionally mixed with lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI).

8. An electrochemical element according to claim 6, wherein the lithium salt is lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), and wherein said additive is hexatricarbonitrile (HTCN), alone or in admixture with tris(trimethylsilyl)phosphite (TMSP).

9. An electrochemical element according to any preceding claim, wherein the electrolyte comprises both tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN).

10. An electrochemical element according to claim 9, wherein tris(trimethylsilyl)phosphite (TMSP) and hexatricarbonitrile (HTCN) are present in a mass ratio ranging from 10:1 to 1:10, preferably from 5:1 to 1:5, more preferably in a mass ratio of 1:

1.

11. An electrochemical element according to any one of the preceding claims. preceding, wherein the electrolyte comprises at least one organic solvent, said solvent comprising: - at least one cyclic carbonate, preferably chosen from ethylene carbonate (EC), propylene carbonate (PC) and any of their mixtures, and - at least one linear carbonate, preferably chosen from dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC) and any of their mixtures.

12. An electrochemical element according to any preceding claim, wherein the electrolyte further comprises at least one additive selected from the group consisting of: vinylene carbonate (VC), ethylene sulfate (ESA), fluoroethylene carbonate (FEC), lithium difluorophosphate LiPO2F2 and any mixture thereof.

13. Electrochemical element according to claim 12, comprising: - from 0% to 5% by mass of vinylene carbonate (VC), - from 0% to 3% by mass of ethylene sulfate (ESA), - from 0% to 5% by mass of fluoroethylene carbonate (FEC), - from 0% to 2% by mass of lithium difluorophosphate LiPO2F 2, relative to the total mass of the electrolyte.

14. Electrochemical module comprising a stack of at least two electrochemical elements according to any one of the preceding claims, each electrochemical element being electrically connected with one or more other electrochemical element(s).

15. Use of an electrochemical element according to any one of claims 1 to 13 or of an electrochemical module according to claim 14, in storage, charging or discharging at a temperature ranging from -15°C to 85°C.

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