High power and chargeability lithium-ion electrochemical element

Abstract

High Power and Chargeability Lithium-ion Electrochemical Element The present invention relates to an electrochemical element comprising: - a negative electrode comprising a negative active layer comprising, as active material, at least one silicon-carbon composite, the negative active layer having a porosity ranging from 35% to 50%, - a positive electrode comprising a positive active layer comprising, as active material: a) at least one lithium phosphate compound of manganese and iron of formula (I): LixMn1-y-zFeyMzPO4 (I), in which: M is selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, S, W, K, Pb, V, Mo, Hf, Bi, Se and any mixture thereof, 0.8 ≤ x ≤ 1.2; 0.5 ≤ 1-yz < 1; 0 < y ≤ 0.5; 0 ≤ z ≤ 0.2;b) at least one lamellar oxide compound of formula (II): Liw(NixMnyCozM't)O2(II), in which: M' is chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La and any mixture thereof; 0.9 ≤ w ≤ 1.4; 0 < x; 0 ≤ y; 0 ≤ z; 0 ≤ t. Figure for the abstract: None;

Description

Title of the invention: High power and chargeability lithium-ion electrochemical element

[0001] The present invention relates to the field of energy storage, and lithium batteries in particular. More specifically, the present application relates to an electrochemical element comprising a specific combination of negative and positive active materials, enabling improved electrochemical performance while maintaining a high level of safety.

[0002] The invention is particularly useful in the field of rechargeable lithium-ion (Li-ion) type electrochemical elements, in particular those used in electric or hybrid vehicles.

[0003] The operation of lithium-ion batteries is based on the reversible exchange of lithium ions between a positive electrode and a negative electrode, separated by an electrolyte, with lithium being stored at the negative electrode during charging operation.

[0004] Rechargeable lithium-ion batteries offer excellent energy and volume densities compared to other electrochemical energy storage technologies and now occupy a dominant position, particularly in the electric propulsion market, which includes but is not limited to electric and hybrid vehicles as well as electric aeronautics.

[0005] Although based on the same technology, these two applications do not have exactly the same specifications. In the field of electric vehicles, one of the major issues is chargeability, in order to ensure users can fully recharge as quickly as possible, whereas aeronautics primarily requires high power. The electric vehicle sector also tends to favor a high energy density by volume, while aeronautics seeks to optimize energy density by mass. However, these two consumer applications share the common goal of a high level of safety.

[0006] However, it is desirable to develop Li-ion type electrochemical cells that allow for the development of Li-ion batteries usable in both types of applications; that is, electrochemical cells exhibiting both high volumetric and mass energy density, high power, and high chargeability, while ensuring a high level of safety. These objectives are a priori incompatible since a high energy density implies a loss of power, and an increase in power implies a degradation of safety.

[0007] The aim of the invention is therefore to provide a Li-ion type electrochemical element exhibiting high volumetric and / or mass energy density, and / or high power and / or chargeability, while ensuring a high level of safety during charge and discharge cycles. The aim of the invention is, in particular, to provide a Li-ion type electrochemical element exhibiting high volumetric and mass energy density, and high power and chargeability, while ensuring a high level of safety and a long lifespan.

[0008] A particular object of the invention is to provide a Li-ion electrochemical cell having a volumetric energy density of at least 500 Wh / L and / or a mass energy density of at least 250 Wh / kg. This same electrochemical cell must be capable of operating in continuous discharge at a rate of at least 5D and / or in continuous charge at a rate of at least 2C while ensuring a high level of safety and a long service life. The rate, denoted nD for discharge or nC for charge, corresponds to the current that must be applied to discharge or charge the nominal capacity of the cell in 1 / n hours. The reference nominal capacity is measured between the fully charged and discharged states over a period of 5 hours.

[0009] To this end, the invention relates to an electrochemical element comprising:

[0010] - a negative electrode comprising a negative active layer comprising, as of active material, at least a silicon-carbon composite, the negative active layer having a porosity ranging from 35% to 50%,

[0011] - a positive electrode comprising a positive active layer comprising, as a active ingredient:

[0012] a) at least one lithium phosphate compound of manganese and iron of formula (I): Lix Mni y zFeyMzPO4 (I), wherein:

[0013] M is chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, S, W, K, Pb, V, Mo, Hf, Bi, Se and any of their mixtures,

[0014] 0.8 < x < 1.2;

[0015] 0.5 < 1-yz < 1;

[0016] 0 < y < 0.5;

[0017] 0 < z < 0.2;

[0018] b) at least one lamellar oxide-type compound of formula (II): Liw(NixMnyCozM' t)O2(II), wherein:

[0019] M' is chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La and any of their mixtures;

[0020] 0.9 < w < 1.4;

[0021] 0 < x ;

[0022] 0 < y ;

[0023] 0 < z ;

[0024] 0 < t.

[0025] The inventors discovered that the combination of the active materials of formula (I) and (II) of the positive active layer, and the active materials of the negative active layer, combined with a specific porosity of the negative active layer, makes it possible to obtain an electrochemical element exhibiting:

[0026] - a high volumetric energy density (typically at least 500 Wh / L),

[0027] - a high specific energy density (typically at least 250 Wh / kg),

[0028] - continuous discharge operation at a minimum 5D regime,

[0029] - a high chargeability (typically at a rate of at least 2C (continuous)),

[0030] - combined with a high level of security.

[0031] In particular, the presence of the compound of formula (I) in the positive active layer makes it possible to maintain the high safety of the electrochemical element despite the increased energy supplied by the Si-C composite to the negative electrode. The porosity of the negative active layer also plays a role in improving the power of the electrochemical element and its lifespan. Negative electrode

[0032] The negative electrode generally comprises a current collector covered by a negative active layer.

[0033] The term "current collector" means an element such as a pad, plate, sheet, or other, with a 2D or 3D structure, made of a conductive material, and ensuring the conduction of the flow of electrons between the electrodes and the terminals of the battery. The current collector is generally in the form of a solid or perforated metal strip. The strip can be made from various materials. Examples include copper or copper alloys, aluminum or aluminum alloys, nickel or nickel alloys, steel, and stainless steel. The current collector may also consist of a layer of plastic material covered with a metallic layer as defined in the preceding sentence.

[0034] The current collector of the negative electrode is generally a copper strip or a strip of an alloy consisting mainly of copper. The strip of the negative electrode typically has a thickness of 4 µm to 18 µm, preferably 4 µm to 10 µm.

[0035] According to one embodiment, the copper collector of the negative electrode is coated with a conductive coating, such as carbon black, graphite, carbon nanotubes, and mixtures thereof. Thus, the strips can optionally be coated on one or two of their faces with a layer of carbon not exceeding a few micrometers in thickness.

[0036] The term "negative active layer" refers to all the materials that coat the current collector of the negative electrode on at least one of its faces. Generally, this layer includes, in addition to electrochemically active materials, electronically conductive materials, binders, and any additives.

[0037] The expression "electrochemically active material" or "active material" refers to materials which are the site of the electrochemical reaction.

[0038] The negative electrode of the electrochemical element according to the invention comprises a negative active layer comprising at least one silicon-carbon composite, also called Si-C.

[0039] Preferably, the silicon-carbon composite content is between 10% and 98% by mass expressed in relation to the total mass of the active material of the negative active layer, preferably between 10% and 80%, preferably between 20% and 60%, preferably between 30% and 50%, preferably between 40% and 50%.

[0040] The silicon-carbon composite particles preferably have a Silicon content of between 30% and 70% by mass, preferably between 40% and 65% by mass, preferably between 40% and 60% by mass, relative to the mass of the silicon-carbon composite particles.

[0041] The negative active layer of the negative electrode has a porosity ranging from 35% to 50%.

[0042] Preferably, the porosity of the negative active layer ranges from 35% to 45%.

[0043] The porosity of the negative active layer is defined as the percentage of the pore volume relative to the geometric volume of the electrode, excluding the current collector. The pore volume includes the volume of the void space between the compound particles in the negative active layer deposited on the current collector and the volume of the pores within the compound particles in the negative active layer deposited on the current collector. The pores within the particles include both accessible and inaccessible pores. The porosity of the negative active layer can be obtained by the following method:

[0044] The theoretical density dreue is calculated from the density of each compound in the negative active layer deposited on the current collector. The apparent density dapsente is calculated by knowing the mass and volume of the negative active layer deposited on the current collector. The relationship that links the porosity with the actual density and with the apparent density is:

[0045] Porosity = l-(apparentd / actuald).

[0046] Such porosity makes it possible to improve both the lifespan of the electrochemical element and its power.

[0047] According to one embodiment, the active material of the negative active layer may also comprise graphite particles. Preferably, according to this embodiment of in realization, the content of graphite particles in the active material of the negative active layer is between 2% and 90% by mass expressed in relation to the mass of the active material of the negative active layer, preferably between 20% and 90%, preferably between 40% and 80%, preferably between 50% and 70%, preferably between 50% and 60%.

[0048] According to one embodiment, the active material of the negative active layer consists of graphite particles and the Si-C composite.

[0049] Typically, the active material of the negative active layer comprises (or even consists of):

[0050] - from 10% to 98%, preferably from 10% to 80%, particularly from 20% to 60%, plus particularly 30% to 50% Si-C composite; and

[0051] - from 2% to 90%, preferably from 20% to 90%, particularly from 40% to 80%, plus particularly 50% to 70% graphite;

[0052] the percentages being understood as being in mass, expressed in relation to the total mass of silicon-carbon composite and graphite particles (or in relation to the total mass of the active material of the negative active layer).

[0053] By way of particular example, the active material of the negative active layer comprises, or even consists of, 45% by mass of Si-C composite and 55% by mass of graphite, expressed in relation to the mass of the active material of the negative active layer.

[0054] The term “binder” means a compound that strengthens the cohesion between the particles of active materials and improves the viscosity and / or adhesion of the negative active layer with the current collector.

[0055] The binder can be selected from butadiene-styrene copolymer (SBR), polyethylene oxide (PEO), polyamideimide (PAI), polyimide (PI), polyvinyl alcohol, functionalized or non-functionalized polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl)- or (butyl) methacrylate, polyvinyl chloride (PVC), poly(vinyl formaldehyde), polyesters, sequenced polyetheramides, acrylic acid polymers, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers such as poly(styrene / butadiene) (SBR) and hydrogenated butadiene-acetonitrile copolymers (HNBR), cellulosic compounds such as carboxymethylcellulose (CMC) and any of their mixtures.

[0056] Preferably, the binder can be chosen from carboxymethylcellulose (CMC), styrene-butadiene (SBR), lithium polyacrylic acid (LiPAA) and non-lithiumized polyacrylic acid (PAA, PAAH or PAAN).

[0057] These binders can typically be used for the positive electrode and / or the negative electrode.

[0058] The term “conductive material” typically refers to an electronic conductor, such as a carbonaceous material, for example graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes (CNTs), or a mixture thereof. In one embodiment, the conductive material is selected from carbon black and carbon nanotubes.

[0059] These electronically conductive materials can typically be used for the positive electrode and / or the negative electrode.

[0060] Possible additives may include dispersants and / or pH buffers. Polyvinylpyrrolidone (PVP) is one example of a dispersant.

[0061] These additives can typically be used for the positive electrode and / or the negative electrode.

[0062] The negative electrode is typically obtained by applying a composition comprising the compounds of the negative active layer to the current collector. This application can be carried out by any technique known to those skilled in the art. Positive electrode

[0063] The positive electrode generally comprises a current collector covered by a positive active layer.

[0064] The current collector of the positive electrode is generally in the form of a solid or perforated metal strip. The strip can be made from various materials. Examples include copper or copper alloys, aluminum or aluminum alloys, nickel or nickel alloys, steel, and stainless steel. The current collector can also consist of a layer of plastic material covered with a metallic layer as defined in the preceding sentence.

[0065] The current collector of the positive electrode is generally an aluminum strip or an alloy consisting mainly of aluminum. The positive electrode strip typically has a thickness of 6 µm to 30 µm.

[0066] According to one embodiment, the aluminum collector of the positive electrode is coated with a conductive coating, such as carbon black, graphite, carbon nanotubes, and mixtures thereof. Thus, the strips can optionally be coated on one or two of their faces with a layer of carbon not exceeding a few micrometers in thickness.

[0067] The thickness of the positive electrode strip may be different from that of the negative electrode strip.

[0068] The term “active positive layer” means all the materials that cover the current collector of the positive electrode on at least one of its faces. Generally this layer includes, in addition to electrochemically active materials, electronically conductive materials, binders, and possible additives.

[0069] As an active material, the positive electrode comprises at least one compound of formula (I) and at least one compound of formula (II).

[0070] Thus, according to the invention, the positive active layer comprises:

[0071] a) at least one lithium manganese iron phosphate compound (LMFP) of formula (I): LixMni y zFeyMzPO4 (I), wherein:

[0072] M is chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, S, W, K, Pb, V, Mo, Hf, Bi, Se and any of their mixtures,

[0073] 0.8 < x < 1.2;

[0074] 0.5 < 1-yz < 1;

[0075] 0 < y < 0.5; and

[0076] 0 < z < 0.2;

[0077] b) at least one lamellar oxide-type compound of formula (II): Liw(NixMnyCozM' t)O2(II), wherein:

[0078] M' is chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La and any of their mixtures;

[0079] 0.9 < w < 1.4;

[0080] 0 < x ;

[0081] 0 <y;

[0082] 0 < z ; and

[0083] 0 < t.

[0084] Preferably, in the compound of formula (I):

[0085] - 0.05 < y < 0.5, preferably 0.1 < y < 0.5, and / or

[0086] - 0.5 < 1-yz < 0.95, advantageously, 0.5 < 1-yz < 0.9, and / or

[0087] -x=l, and / or

[0088] - z = 0.

[0089] Preferably, the compound of formula (I) has a Mn / Fe molar ratio ranging from 50 / 50 to 80 / 20.

[0090] Typically, the compound of formula (I) can be chosen from LiMnoj8Feoj2P04, LiMnoj7Feoj3P04, LiMn2 / 3Fei / 3PO4 and LiMn0j5Feoj5P04.

[0091] Advantageously, the lithium manganese iron phosphate (LMFP) type compound(s) of formula (I) are coated with a layer of carbon and / or carbon nanotubes, in particular to increase their conductivity and / or ionic diffusivity.

[0092] Preferably, the compound of formula (II) is such that 0.5 < x < 1.1 and / or 0 < y < 1.1 and / or 0 < z < 1.1 and / or 0 < t < 1.1.

[0093] Preferably, the compound of formula (II) may be chosen from the list below:

[0094] i) a lithium nickel, manganese, and cobalt oxide (NMC) of formula (lia) Liw (NixMnyCozMt)O2 where 0.9 < w < 1.1 ; 0 <x<l,l ; 0<y<l, 1 ; 0<z<l,l ; 0<t<l,l; M étant au moins un élément choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ta, Ga, Nd, Pr et La, et plus particulièrement 0,5 < x ;

[0095] ii) a lithium nickel, cobalt, and aluminium (NCA) oxide of formula (Ilb) Liw(Ni xCoyAlzMt)O2 where 0.9 < w < 1.1 ; 0 <x<l,l ; 0<y< 1,1 ; 0<z<l,l ; 0<t< 1,1; M étant au moins un élément 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 et La ; plus particulièrement 0,80 < x ; et

[0096] iii) a lithium oxide of nickel, manganese, cobalt and aluminium (NMCA) of formula (Ile)Liw(NixCoyAlzMntMs)O2 where 0.9 < w < 1.1 ; 0 <x<l,l ; 0<y< 1,1 ; 0<z<l,l; 0<t< 1,1, 0 < s <1,1, M étant au moins un élément 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 et La, plus particulièrement 0,83 < x.

[0097] iv) a lithium nickel manganese oxide (NMX) compound of formula

[0098] Lia(Nii_x_y_zMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x<l,l ; 0 <y<0,02 ; 0<z<l,l ; 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 ;

[0099] v) les mélanges de ceux-ci.

[0100] Preferably, in the compound of formula (lia), 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.

[0101] As examples of lithium nickel, manganese and cobalt oxide compounds of formula (lia) (NMC), the following compounds may be cited in particular:

[0102] LiNio.6Mno.2Co0.202 (NMC 622),

[0103] LiNio.8MnojCoo.jO2 (NMC 811).

[0104] As an example of a lithium nickel, cobalt and aluminium oxide compound of formula (Ilb) (NCA), the following compound may be mentioned in particular:

[0105] LiNio.8oCoo.i5Alo.o502

[0106] Preferably, the content of compound of formula (I) is between 10% and 99% by mass expressed in relation to the total mass of the active material of the positive active layer, preferably between 20% and 85%, preferably between 30% and 80%, preferably between 40% and 70%.

[0107] Preferably, the content of compound of formula (I) is between 10% and 99% by mass expressed relative to the total mass of compound of formula (I) and in composed of formula (II), preferably between 20% and 85%, preferably between 30% and 80%.

[0108] According to one embodiment, the active material of the positive active layer consists of one or more compounds of formula (I) and one or more compounds of formula (II).

[0109] According to one embodiment, the active material of the positive active layer of the positive electrode comprises, or even consists of:

[0110] - between 10% and 99% by mass, preferably between 20% and 85% by mass, of preference between 30% and 80% of compound(s) of formula (I); and

[0111] - between 1% and 90% by mass, preferably between 15% and 80% by mass, preferably between 20% and 70% by mass of compound(s) of formula (II);

[0112] the percentages being expressed in relation to the total mass of compound(s) of formula (I) and of compound(s) of formula (II) (or in relation to the total mass of the active material of the positive active layer).

[0113] Preferably, the positive electrode has a porosity of less than 50%, more preferably less than or equal to 45%, even more preferably ranging from 32% to 45%.

[0114] The binders, electronically conductive materials and possible additives can be chosen from the same lists as for the negative electrode.

[0115] The positive electrode is typically obtained by applying a composition comprising the compounds of the positive active layer to the current collector. This application can be carried out by any technique known to those skilled in the art.

[0116] Preferably, the electrochemical element according to the invention further comprises a separator and an electrolyte.

[0117] Separator

[0118] The electrochemical element may include a separator, typically between the positive and negative electrodes. The separator is designed to prevent short circuits while remaining permeable to lithium ions. It may, in particular, be made of a nonwoven fabric or a polymer film. 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 materials. The aforementioned polymers may be coated with a ceramic layer and / or polyvinylidene difluoride (PVdF) or poly(vinylidene-hexafluoropropylene fluoride (PVdF-HFP) or acrylates.

[0119] Electrolyte

[0120] The electrolyte may be liquid and comprise a lithium salt dissolved in an organic solvent. This lithium salt may be selected from lithium perchlorate. LiC104, lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium hexafluoroarsenate LiAsF6, lithium hexafluoroantimonate LiSbF6, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium trifluoromethanesulfonemethide LiC(CF3SO2)3 (LiTFSM), lithium bisperfluoroethylsulfonimide LiN(C2F5SO2)2 (LiBETI), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), lithium bis(oxalatoborate) (LiBOB), lithium difluoro(oxalato)borate (LIDFOB), the lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP) and mixtures thereof.

[0121] The solvent may be selected from saturated cyclic carbonates, unsaturated cyclic carbonates, non-cyclic carbonates, alkyl esters, ethers, nitrile-type solvents, tetrahydrothiophene dioxide (sulfolane), and ethylene sulfate (ESA). Saturated cyclic carbonates include ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), butylene carbonate (BC), and mixtures thereof. Unsaturated cyclic carbonates include vinylene carbonate (VC). Non-cyclic carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and mixtures thereof. Alkyl esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and mixtures thereof.Ethers include dimethyl ether (DME), diethyl ether (DEE) and mixtures thereof.

[0122] The concentration of said at least one lithium salt may be in the range of 0.75 mol / L to 1.5 mol / L. It is preferably in the range of 1 mol / L to 1.5 mol / L. It is even better in the range of 1 to 1.2 mol / L.

[0123] The electrolyte can also be 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. Electrochemical element

[0124] According to one embodiment, the electrochemical element is of the lithium-ion type.

[0125] A lithium-ion element can be manufactured conventionally. At least one positive electrode, at least one separator, and at least one negative electrode are superimposed, and then the resulting superposition is impregnated with an electrolyte composition.

[0126] More specifically, at least one positive electrode, at least one separator, and at least one negative electrode are superimposed. The assembly can be wound to form a cylindrical electrochemical bundle and then inserted into a container. The invention is not limited to the manufacture of cylindrical elements. The element can also be prismatic or pouch-shaped. The electrodes can also be stacked to form a planar electrochemical beam. A connecting piece is attached to an edge of the positive electrode not covered with active material. It is connected to a current output terminal.

[0127] The negative electrode can be electrically connected to the electrochemical element container. Conversely, the positive electrode can be connected to the electrochemical element container and the negative electrode to a current output terminal. After being inserted into the electrochemical element container, the electrochemical bundle is impregnated with electrolyte. The electrochemical element is then hermetically sealed. The electrochemical element can also be conventionally equipped with a safety valve that opens the electrochemical element container if the internal pressure of the element exceeds a predetermined value.

[0128] According to another object, the present invention also relates to an electrochemical module comprising the stacking of at least two electrochemical elements according to the invention, each electrochemical element being electrically connected with one or more other element(s).

[0129] The term “module” therefore refers here to the assembly of several electrochemical elements, said assemblies being able to be in series and / or parallel.

[0130] Another object of the invention is yet another battery comprising one or more modules according to the invention.

[0131] The term “battery” or accumulator means the assembly of several modules according to the invention. Uses

[0132] The electrochemical element according to the invention is particularly intended to be used within an electrical power storage system on board a vehicle such as an aircraft, a rail transport vehicle, a road transport vehicle or a maritime or river transport vehicle, in particular in an electric or hybrid aircraft or road transport vehicle.

[0133] The invention therefore relates in particular to the use of an electrochemical element according to the invention, to improve the chargeability of a battery comprising such an electrochemical element at a charging regime up to at least 2C.

[0134] The invention also relates to the use of an electrochemical element according to the invention, to improve the chargeability of an electric or hybrid vehicle battery comprising such an electrochemical element at a charging regime up to at least 2C.

[0135] The invention also relates to the use of an electrochemical element according to the invention, to improve the power of a battery comprising such an electrochemical element by allowing continuous discharge operation under a regime of at least 5D.

[0136] The invention also relates to the use of an electrochemical element according to the invention, to improve the power of an electric or hybrid aircraft battery comprising such an electrochemical element by allowing continuous discharge operation under a regime of at least 5D.

[0137] The invention also relates to the use of an electrochemical element according to the invention, to improve the electric propulsion of a means of transport, for example an electric or hybrid road vehicle or an electric aircraft.

[0138] The invention will become clearer upon reading the following examples, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0139] [Fig-1] [Fig. 1] is a graph representing the evolution of the voltage as a function of the capacitance in the complete cell of the electrochemical elements of Example 1.

[0140] [Fig.2] [Fig.2] is a graph representing the evolution of the percentage of charge depending on the charging regime for the electrochemical elements in example 1.

[0141] [Fig.3] [Fig.3] is a graph representing the evolution of the percentage of discharge as a function of the discharge regime for the electrochemical elements of example 1.

[0142] [Fig.4] [Fig.4] is a graph comparing the evolution of the discharged capacity during a C / 3 / D / 3 cycling between 2.5V and 4.2V of electrochemical elements analogous to electrochemical element A of example 1 but whose negative electrode porosity is 32% or 45% (example 2).

[0143] EXAMPLES

[0144] Example 1: Effect of the presence of Si-C composite in the negative active layer

[0145] Two electrochemical elements A (according to the invention) and B (comparative) were prepared as follows:

[0146] Electrochemical elements A and B can be manufactured according to the following method: They all comprise a positive electrode whose active material layer composition is composed of a mixture of 60% NMC and 40% LMFP in both cases and a negative electrode whose active material layer composition is for electrochemical element A a mixture of 45% Si-C and 55% graphite and for electrochemical element B only graphite, in both cases the active materials are accompanied by a mixture of binder and percolating carbons.

[0147] The electrolyte comprises a mixture of cyclic carbonates and linear carbonates with lithium salts and additives. The separator interposed between the positive and negative electrodes is of the polyolefin type.

[0148] The positive electrode can be prepared and coated on an aluminum collector by any technique known to those skilled in the art. It is then calendered before being mounted with the separator and the negative electrode.

[0149] The negative electrode can be prepared according to the mixtures described and coated onto a copper collector by any technique known to those skilled in the art; it is then calendered before being mounted with the separator and the positive electrode.

[0150] The electrodes assembled with the separator are then mounted in a pouch format and then filled with the electrolyte.

[0151] These two electrochemical elements A and B are then evaluated according to criteria of chargeability, dischargeability, capacity, volumetric and mass energy and safety, the results are presented in Table 1.

[0152] The cell capacity is measured after a charge at C / 5 up to 4.2V with a holding potential ('floating') until the residual value of the measured current is less than C / 100, during a discharge at D / 5 up to 2.5V. The voltage profile is shown in [Fig. 1].

[0153] Chargeability is tested by charging the electrochemical elements at increasing rates from C / 10 to 2C without holding the potential ('floating') at the end of the charge up to 4.2V and with discharges at C / 10 between each charge. The charged capacitance is compared to that obtained for a C / 5 rate. The results are presented in [Fig. 2].

[0154] Dischargeability is tested by charging the electrochemical elements at increasing rates from D / 10 to 5D up to 2.5V and with C / 10 charges up to 4.2V, maintaining the potential until the measured residual current is less than C / 100 between each discharge. The discharged capacitance is compared to that obtained for a D / 5 rate. The results are shown in [Fig. 3].

[0155] Fig. 1 illustrates the gain in capacity obtained by going from the electrochemical element B to the object of the invention (electrochemical element A).

[0156] Fig. 2 illustrates the improvement in chargeability for continuous 2C charging with a 14% gain in charged capacity.

[0157] Fig. 3 illustrates the improvement in dischargeability for continuous discharge at D / 5 with a 40% gain in discharged capacity.

[0158] The results obtained during these various tests are used to calculate the volumetric and mass energy by taking the capacitance restored during a discharge at D / 5 multiplied by the average voltage of the electrochemical element and divided by either the volume of the electrochemical element or its mass to arrive at the values ​​mentioned in table 1.

[0159] The overload and overheating results mentioned in this table are obtained by subjecting electrochemical elements A and B to overheating tests (cell charged to 100% state of charge (4.2V) heated at a rate of 5°C / min until an event occurs), and overload tests (from the discharged state, one electrochemical element is charged at a rate of 2C without voltage limit until an event occurs). The temperatures mentioned are the average over two electrochemical elements and refer to the temperature at which thermal runaway begins.

[0160] [Tables 1] A (according to the invention) B (comparative) Capacity (Ah) 12 9.7 Cell format Pouch (same size and weight) Wh / L (at the battery) 690 580 Wh / Kg (at the battery) 280 260 Overcharge Thermal runaway start temperature: 124°C 123°C Overheat Thermal runaway start temperature: 190°C 196°C

[0161] These results show that, for a similar weight and format, the addition of Si-C composite in the negative active layer makes it possible to improve the power of the electrochemical element and the energy density, without degrading the safety that usually accompanies an increase in power.

[0162] Example 2: Influence of the porosity of the negative active layer

[0163] Two electrochemical elements C (according to the invention) and D (comparative) having different negative porosities were prepared according to the protocol described in Example 1. They share the composition of the electrochemical element A of Example 1 and the only differentiating factor is the porosity of the negative electrode, equal to 45% (electrochemical element C) or 32% (electrochemical element D).

[0164] The porosity is modulated during the calendering step in which the negative electrode is compressed by rollers of significant mass and defined distance.

[0165] The lifetime of these electrochemical elements C and D was evaluated according to the following protocol: following a first cycle carried out at C / 10-D / 10 and a second at C / 5-D / 5, the electrochemical elements C and D were cycled at a C / 3 - D / 3 regime for 250 cycles. The capacitance is normalized with respect to the second cycle at C / 5 - D / 5. on the graph in [Fig.4] and shows a higher value after 250 cycles for the electrochemical element C whose negative electrode has a porosity of 45%.

[0166] The results obtained are shown in [Fig.4].

Claims

Demands

1. Electrochemical element comprising: - a negative electrode comprising a negative active layer comprising, as active material, at least one silicon-carbon composite, the negative active layer having a porosity of 35% to 50%, - a positive electrode comprising a positive active layer comprising, as active material: a) at least one lithium phosphate compound of manganese and iron of formula (I): LixMni y zFeyMzPO4 (I), in which: M is selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Y, Zr, Nb, S, W, K, Pb, V, Mo, Hf, Bi, Se and any mixture thereof, 0.8 < x < 1.2; 0.5 < 1-yz < 1; 0 < y < 0.5; 0 < z < 0.2; b) at least one lamellar oxide type compound of formula (II): Liw(NixMnyCozM't)O2(II), in which: M' is chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La and any mixture thereof;0.9 < w < 1.4 ; 0 <x; 0<y ; 0 < z ; 0<t.;

2. Electrochemical element according to claim 1, wherein the silicon-carbon composite content in the active material of the negative active layer is between 10% and 98% by mass expressed relative to the mass of the active material of the negative active layer, preferably between 10% and 80%, preferably between 20% and 60%, preferably between 30% and 50%, preferably between 40% and 50%.

3. Electrochemical element according to claim 1 or 2, wherein the porosity of the negative active layer ranges from 35% to 45%

4. Electrochemical element according to any one of the preceding claims, wherein the active material of the negative active layer further comprises graphite particles.

5. Electrochemical element according to claim 4, wherein the graphite particle content in the active material of the negative active layer is between 2% and 90% by mass expressed relative to the mass of the active material of the negative active layer, preferably between 20% and 90%, preferably between 40% and 80%, preferably between 50% and 70%, preferably between 50% and 60%.

6. Electrochemical element according to any one of the preceding claims, wherein the active material of the negative active layer comprises 45% by mass of Si-C composite and 55% by mass of graphite, expressed relative to the mass of the active material of the negative active layer.

7. Electrochemical element according to any one of the preceding claims, wherein the compound of formula (I) has a Mn / Fe molar ratio ranging from 50 / 50 to 80 / 20.

8. Electrochemical element according to any one of the preceding claims, wherein the compound of formula (II) is such that 0.5 < x < 1.1 and / or 0 < y < 1.1 and / or 0 < z < 1.1 and / or 0 < t < 1.

1.

9. Electrochemical element according to any one of the preceding claims, wherein the active material of the positive active layer consists of one or more compounds of formula (I) and one or more compounds of formula (II), and consists of: - between 10% and 99% by mass, preferably between 20% and 85% by mass, preferably between 30% and 80% of compound(s) of formula (I); and - between 1% and 90% by mass, preferably between 15% and 80% by mass, preferably between 20% and 70% by mass of compound(s) of formula (II); the percentages being expressed with respect to the total mass of compound(s) of formula (I) and compound(s) of formula (II).

10. Use of an electrochemical element according to any one of claims 1 to 9, to improve the chargeability of a battery comprising such an electrochemical element at a charging regime up to at least 2C.

11. Use of an electrochemical element according to any one of claims 1 to 9, to improve the chargeability of a electric or hybrid vehicle battery comprising such an electrochemical element at a charging regime up to at least 2C.

12. Use of an electrochemical element according to any one of claims 1 to 9, to improve the power of a battery comprising such an electrochemical element by enabling continuous discharge operation under a regime of at least 5D.

13. Use of an electrochemical element according to any one of claims 1 to 9, to improve the power of an electric or hybrid aircraft battery comprising such an electrochemical element by enabling continuous discharge operation under a regime of at least 5D.

14. Use of an electrochemical element according to any one of claims 1 to 9, to improve the electric propulsion of a means of transport, for example an electric or hybrid road vehicle or an electric aircraft.

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