NEW ACTIVE INGREDIENT COMPOSITIONS

Abstract

ELASTIC ELECTRODE ACTIVE MIXTURES The present invention relates to an elastic electrode active material composition capable of accommodating volumetric expansions during cycling. Figure for the abstract: 1

Description

TITLE#:

[0001] Compositions of active materials for elastic electrodes

[0002] The present invention relates to the field of energy storage and lithium batteries in particular. More specifically, this application relates to active material compositions for electrodes, particularly for positive electrodes, as well as cathodes and the electrochemical elements containing them.

[0003] The invention is particularly useful in the field of rechargeable lithium-ion (Li-ion) type electrochemical elements.

[0004] Rechargeable lithium-ion type electrochemical elements are known in the prior art. Due to their high mass and volume energy densities, they constitute a promising source of electrical energy. They comprise at least one positive electrode and at least one negative electrode, and an electrolyte.

[0005] The electrodes, particularly the positive electrodes, consist of a metal current collector coated with a composition of active materials comprising the active material and additives such as binder(s), dispersant(s), conductive element(s), etc. The matrix consisting of binder(s) and carbon-based conductive element(s) is generally referred to as the "carbon binder domain" (or CBD). These electrodes are typically prepared by coating a current collector with an ink comprising the aforementioned ingredients, generally formulated in a solvent medium, followed by solvent evaporation, before calendering to adjust the thickness of the ink layer on the collector.

[0006] During its use, the active material undergoes significant volumetric variations, linked in particular to the repeated intercalation and deintercalation of lithium at each discharge / charge cycle. These repeated variations affect the electronic percolation network and can cause the loss of contact points and network interruption.

[0007] This results in an increase in internal resistance and, ultimately, wear and tear on the battery.

[0008] Also, it is important to improve the elasticity of the composition of active materials to accommodate these volume expansions.

[0009] CN108390016 describes a porous electrode comprising a material composition active comprising further a high elasticity binder, a conductive agent and an additive.

[0010] However, the described electrodes require the application of an adhesive to the current collector, which becomes conductive after drying. Furthermore, they contain a low concentration of conductive agent within the CBD matrix, relative to the weight of said matrix, resulting in moderate electronic conductivity.

[0011] Finally, we are constantly seeking to improve the elasticity criteria compatible with sustained electronic percolation during cycling.

[0012] It therefore remains to provide alternative active ingredient compositions free from these drawbacks.

[0013] It has now been identified that elasticity can be improved depending on the nature of the composition, in particular the carbon black content and the nature of the binder and / or carbon black, in order to increase the absorption of mechanical stresses.

[0014] One object of the invention is therefore to provide an elastic composition of active electrode materials capable of accommodating volumetric expansions during cycling. One of the aims is thus to prevent the degradation of the electrode percolation network.

[0015] Another objective is also to provide a composition of active materials that limits the increase in internal resistance during operation.

[0016] To this end, the invention relates to an active electrode material composition comprising

[0017] at least one electrochemically active material, and

[0018] a matrix which includes

[0019] at least one polymeric binder of molar mass M chosen from among low molar mass polymeric binders such as M<500 kg / mol, high molar mass polymeric binders such as M>500 kg / mol and mixtures thereof, and

[0020] at least one specific surface area carbon black (SSA) selected from low specific surface area carbon blacks such as SSA < 200 m² / g, high specific surface area carbon blacks such as SSA > 200 m² / g, and mixtures thereof,

[0021] said composition being characterized in that: - The mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s))] is such that l / 3 <r< 1 / 2 ; - Etant entendu que - si la composition comprend à titre de seul(s) noir(s) de carbone un ou des noir(s) de carbone ayant une haute surface spécifique tel que SSA > 200 m2 / g, then said composition comprises at least one high molar mass polymeric binder M such that M>500 kg / mol.

[0022] Advantageously, the composition according to the invention provides sufficient elasticity to compensate for volumetric variations and thus maintain efficient electronic percolation during cycling. It therefore limits the increase in internal resistance and capacitance loss by ensuring a robust percolation network that adapts to volumetric variations.

[0023] The elasticity of a matrix illustrates its ability to accommodate volumetric variations during cycling. It can be determined by the elastic return, which characterizes the matrix's ability to recover its original geometric characteristics following deformation.

[0024] Elastic recovery can be measured using a texture analyzer by applying several cycles of compression (40 N) and decompression (return to ON) to a specimen of the matrix, the retraction distance of which is measured. This retraction distance is called “Elastic Recovery” and is expressed as a percentage of the initial elongation.

[0025] Typically, the matrix of the composition according to the invention has an elastic return > 5%, in particular greater than 6%.

[0026] According to other advantageous aspects of the invention, the composition according to the invention comprises one or more of the following features, taken individually or in all technically possible combinations:

[0027] The term "composition of active materials" means the composition comprising all the ingredients which coats the current collector of an electrode on at least one of its faces.

[0028] It is obtained from an ink prepared with said ingredients, generally in a solvent medium such as N-Methyl-2-pyrrolidone (NMP) for example, intended to be coated on the collector, then subjected to drying and calendering in order to lead to said composition.

[0029] Generally this composition of active materials of the positive and / or negative electrode includes in addition to the electrochemically active materials, electronic conductive materials, binders, and possible additives etc.

[0030] According to one embodiment, the composition according to the invention is suitable for a positive electrode, in particular for electrochemical elements of the Li-ion type.

[0031] The expression "electrochemically active material" or "active material" typically refers to the materials that are the site of the electrochemical reaction. It is not particularly limited according to the invention. However, the invention is particularly advantageous in the case of active materials with high volume expansion, such as lithium nickel oxides at the positive electrode, or silicon and its derivatives such as silicon oxides, carbon-encapsulated silicon, etc., at the negative electrode.

[0032] One can thus cite compounds of the type of lithia nickel oxide, chosen in particular from lithia nickel oxides rich in nickel, preferably comprising more than 60% (relative to the atomic ratio) of nickel.

[0033] Thus, they can be advantageously chosen from among the lithium oxides of nickel, manganese and cobalt (NMC) corresponding to the formula:

[0034] Liw(NixMnyCozMt)O2

[0035] In which

[0036] 0.9 <w<l,l ;

[0037] 0.40 <x<l,l ;

[0038] 0 <y<l,l ;

[0039] 0 <z<l,l ;

[0040] 0 <t<l,l ;

[0041] 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 and La and their mixtures;

[0042] In formula (I), in particular:

[0043] 0.9 <w<l,l ;

[0044] 0.60 <x<l,l ;

[0045] 0 <y<l,l ;

[0046] 0 <z<l,l ;

[0047] 0 <t<l,l ;

[0048] M can in particular be chosen from the group consisting of Al, B, Mg and their mixtures. Preferably, M is Al and t<0.05. The major 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.

[0049] As examples of nickel-rich lithium oxide compounds of nickel, manganese and cobalt (NMC), the following compounds may be cited in particular:

[0050] LiNio.6Mn0.2Coo.202 (NMC 622),

[0051] LiNio.8Mn0.iCoo.i02 (NMC 811).

[0052] As an active material suitable for the positive electrode, we can also mention

[0053] • the lithia oxides of at least one transition metal, such as: i. a lithium oxide of nickel, cobalt and aluminium of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x<l,l ; 0<y< 1,1 ; 0<z<l,l ; 0<t< 1,1 ; 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 ; ii. a compound of formula Lii+xMi xO2 yFy with cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ; iii. a lithium nickel manganese oxide (NMX) of formula Lia(Nii_x_y_zMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x ; 0<y<0,02 ; 0<z ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci ; et iv. a lithium oxide of nickel and manganese of formula Liw(NixMnyCozMt)O2 where 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ;

[0054] or • Lithified phosphates of at least one transition metal such as:

[0055] a) a lithified iron phosphate of formula LixFei yMyPO4 (LFP), where 0.8 <x<l,2 ; 0 <y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0056] b) a lithium manganese phosphate of formula LixMni yMyPO4 (LMP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0057] c) a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ; et

[0058] d) a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule Lii+xVi yMyPO4Fz (LVMPF) où0<x<0,15, 0<y<0,5, 0,8<z<l,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, et Zr ;

[0059] or • a mixture of compounds a) to d) and i) to iv).

[0060] As an active material suitable for the negative electrode, we can also mention:

[0061] - Graphite;

[0062] - Silicon or alloy, carbon-silicon-based compounds, and compounds SiOx with x<=2 ;

[0063] - A titanium niobium oxide (TNG) having the formula: LixTia yMyNbb ZM'ZO "(x+4a+5b) / 2) c dXc where: 0 <x<5; 0<y<l; 0<z<2; l<a<5; l<b<25; 0.25<a / b<2; 0<c< 2 and 0<d<2; a-y> 0; bz>0; • M and M' each represent at least one element chosen from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm; • X represents at least one element chosen from the group consisting of S, F, Cl and Br; • The subscript d represents an oxygen vacancy of 0.5 or less; or

[0064] - Lithified titanium oxide or a titanium oxide capable of being lithified. LTO is chosen among the following oxides:

[0065] I) Lix-aMaTiy_bM'bO4_c_dXcwhere 0 <x<3; l<y<2.5; 0<a<l; 0<b<l; 0<c<2 et

[0066] -2.5<d<2.5; • M represents at least one element chosen 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 chosen from the group consisting of B, Mo, Mn, Ce, Sn, Zr, Si, W, V, Ta, Sb, Nb, Ru, Ag, Fe, Co, Ni, Zn, Al, Cr, La, Pr, Bi, Sc, Eu, Sm, Gd, Ti, Ce, Y and Eu; • X represents at least one element chosen from the group consisting of S, F, Cl and Br; • The index d represents an oxygen vacancy, less than or equal to 0.5

[0067] II) HxTiyO4 in which 0 <x<l; 0<y<2,

[0068] III) un mélange des composés I) à II),

[0069] Ou leurs mélanges.

[0070] 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 composition of active materials to the current collector.

[0071] According to the invention, the binder(s) is / are chosen from among polymeric binders (i.e.) derived from polymers having a molar mass M.

[0072] As used here, the binders can be:

[0073] of low molar mass (i.e.) such that M<500 kg / mol, or

[0074] of high molar mass (i.e.) such that M>500 kg / mol.

[0075] According to one embodiment, said polymeric binder(s) may be selected from butadiene-styrene copolymers (SBR), polyamideimide (PAI), polyimide (PI), polyvinyl alcohol, polyvinylidene fluoride (PVDF), 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 polymers, acrylamide polymers, itaconic acid polymers, sulfonic acid polymers, elastomers, cellulosic compounds such as carboxymethylcellulose (CMC), as well as these functionalized polymers, and rubber. butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile rubber (HNBR) and any mixture thereof.

[0076] In particular, polyvinylidene fluorides (PVDF), functionalized PVDFs, PVDF copolymers such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and their mixtures can be cited as binder(s).

[0077] One can thus cite in particular the PVDF.

[0078] Such low or high molecular weight polymeric binders are generally available commercially.

[0079] The carbon black(s) referred to herein act as percolating electronic conducting agent(s) in the composition of active materials.

[0080] Carbon black is a partially crystalline carbonaceous product resulting from the partial decomposition of hydrocarbons which has a structure in the form of primary particles, connected in aggregates and possibly agglomerated.

[0081] Thus, carbon black can be obtained from: - acetylene black, for example by thermal decomposition at 1200°C; - furnace black, for example by gaseous phase recovery with a water curtain in a furnace, - soot, - lamp black, - black thermal with natural gas, or - black in the tunnel from the walls of the furnace.

[0082] In particular, graphite, graphene, fullerene, carbon fibers, carbon nanotubes and activated carbon do not fall within the definition of the term "carbon black".

[0083] Carbon black typically has a divided appearance. It can be characterized by the specific surface area (SSA) of the primary particle aggregates.

[0084] The primary particle size of carbon black can typically be between 20 nm and 100 nm.

[0085] Thus, according to the invention, we distinguish between carbon blacks with low specific surface area such as SSA<200 m2 / g, and carbon blacks with high specific surface area such as SSA>200 m2 / g.

[0086] The specific surface area can be measured by the BET method (Brunauer, Emmett, and Teller Theory), based on the assumption that the adsorbed gas molecules are located in monomolecular layers on the surface of the material (gas physisorption). The amount of gas adsorbed at a given pressure is measured (adsorption isotherm curve) and used to calculate the specific surface area using the BET equation.

[0087] The procedure for measuring specific surface area using the BET method is indicated in ASTM D6556-21.

[0088] According to one embodiment, the composition according to the invention may comprise one or more carbon blacks, distinct, for example, by their origin, size and / or specific surface area (SSA).

[0089] Thus, the composition according to the invention may comprise a mixture of low specific surface area carbon black(s) and high specific surface area carbon black(s). It may also comprise several high specific surface area carbon blacks, or several low specific surface area carbon blacks.

[0090] According to the invention, if the composition comprises as the sole carbon black(s) one or more carbon black(s) having a high specific surface area such as SSA >200 m2 / g, then said composition comprises at least one polymeric binder of high molar mass M such that M>500 kg / mol.

[0091] As used herein, the expression "as the sole carbon black(s)" refers to a composition comprising one or more carbon blacks, it being understood that this or these carbon black(s) have a high specific surface area such as SSA >200 m2 / g.

[0092] This expression therefore refers to a composition which would not include carbon black having a low specific surface area such as SSA <200 m2 / g.

[0093] In other words, this expression excludes the presence of carbon black(s) having a low specific surface area, the carbon black(s) present within said composition having exclusively a high specific surface area.

[0094] Said composition may further include one or more additives such as dispersants.

[0095] Polyvinylpyrrolidone (PVP) can thus be cited as a suitable dispersant for the invention.

[0096] The mixture of polymeric binder(s) and carbon black(s) is herein referred to as the "matrix", which can typically be described as the CBD matrix or "binding black domain".

[0097] The matrix is ​​characterized in particular by the ratio r, defined as the mass ratio of the carbon black(s) to the mass of the mixture consisting of the carbon black(s) and the polymeric binder(s).

[0098] According to the invention, r is such that l / 3 <r< 1 / 2, de préférence 0,4<r<0,5.

[0099] According to the invention, within the matrix, several combinations of carbon black(s) and polymeric binder(s) are conceivable, depending on their specific surface area and molar mass, respectively.

[0100] Thus, according to one embodiment, the invention relates to a composition whose matrix comprises at least one electrochemically active material, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g, and one or more polymeric binder(s) with a low molar mass such as M <500 kg / mol.

[0101] According to another embodiment, the invention relates to a composition whose matrix comprises at least one electrochemically active material, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g, one or more polymeric binders with a high molar mass such as M>500 kg / mol and one or more polymeric binders with a low molar mass such as M<500 kg / mol.

[0102] According to another embodiment, the invention also relates to a composition whose matrix comprises at least one electrochemically active material, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g and one or more carbon blacks with a high specific surface area such as SSA>200 m2 / g, and one or more polymeric binder(s) with a low molar mass such as M<500 kg / mol.

[0103] According to another embodiment, the invention further relates to a composition whose matrix comprises at least one electrochemically active material, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g and one or more carbon blacks with a high specific surface area such as SSA>200 m2 / g, one or more polymeric binder(s) with a low molar mass such as M<500 kg / mol and one or more polymeric binder(s) with a high molar mass such as M>500 kg / mol.

[0104] These particular embodiments can also be cited: - a composition whose matrix comprises at least one active substance, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g, and one or more polymeric binder(s) with a high molar mass such as M>500 kg / mol; - a composition whose matrix comprises at least one active substance, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g and one or more carbon blacks with a high specific surface area such as SSA>200 m2 / g, and one or more polymeric binders with a high molar mass such as M>500 kg / mol; and - a composition whose matrix comprises at least one active substance, one or more carbon blacks with a high specific surface area such as SSA>200 m2 / g, one or more polymeric binders with a low molar mass such as M<500 kg / mol and one or more polymeric binders with a high molar mass such as M>500 kg / mol.

[0105] According to one embodiment, the composition of active materials comprises:

[0106] - from 90 to 97% of electrochemically active material(s);

[0107] - from 0.1.5 to 5% of carbon black(s);

[0108] - from 1.5 to 5% of polymeric binder(s);

[0109] - from 0 to 1% of one or more dispersants; and

[0110] the percentages being by weight, relative to the total weight of dry matter. [YES] The electrode

[0112] The electrode is typically made up of a current collector covered on at least one of its faces by the composition of active materials according to the invention.

[0113] Typically, the electrode acts as a positive electrode.

[0114] A metal strip can act as a current collector.

[0115] Said metal strip may be made of aluminium or an alloy comprising mainly aluminium, possibly covered with a conductive material, such as carbon.

[0116] Advantageously, the metal strip is made of aluminum.

[0117] Electrode preparation

[0118] Generally, an electrode can be manufactured by preparing an ink comprising the ingredients of the composition mixed with a solvent, which is then coated onto the current collector. The ink can be dried in an oven, a furnace, and / or by infrared to evaporate the solvent.

[0119] The thickness of the ink 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.

[0120] After evaporation of the solvent(s), a composition of active materials is obtained.

[0121] The ink therefore ultimately gives rise to the composition of active materials.

[0122] According to another object, the present invention also relates to a method for preparing an electrode comprising:

[0123] - The preparation of an ink comprising the addition and mixing in a solvent of ingredients of the composition according to the invention;

[0124] - the application of said ink to the coating of said metal strip;

[0125] - drying; and

[0126] - calendering.

[0127] The electrochemical element

[0128] The invention also relates to an electrochemical element comprising at least one positive electrode (cathode) as defined above, a negative electrode (anode), a separator and at least one electrolyte.

[0129] According to one embodiment, said electrode is a positive electrode (cathode) within said element.

[0130] According to one embodiment, the electrochemical element is of the lithium-ion type.

[0131] The lithium-ion element can be manufactured conventionally. At least one cathode, at least one separator, and at least one anode are superimposed. The assembly can be wound to form a cylindrical electrochemical bundle. The invention is not limited to the manufacture of cylindrical elements. The element format It can also be prismatic or pouch-type. The electrodes can also be stacked to form a planar electrochemical beam. A connecting piece is attached to an edge of the cathode not covered with active material. It is connected to a current output terminal.

[0132] The anode can be electrically connected to the element container. Conversely, the cathode can be connected to the element container and the anode to a current output terminal. After being inserted into the element container, the electrochemical bundle is impregnated with electrolyte. The element is then hermetically sealed. The element can also be conventionally equipped with a safety valve that opens the element container if the internal pressure of the element exceeds a predetermined value.

[0133] The electrolyte may be liquid and comprise a lithium salt dissolved in an organic solvent. This lithium salt can be chosen from lithium perchlorate LiClO4, 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), the lithium difluoro(oxalato)borate (LIDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP), lithium difluorophosphate LiPO2F2 and mixtures thereof.

[0134] The electrolyte solvent can be chosen from saturated cyclic carbonates, unsaturated cyclic carbonates, linear carbonates, alkyl esters, ethers, cyclic esters, such as lactones.

[0135] As an alternative, the electrolyte can be solid. In this embodiment, the composition is particularly advantageous in that its elasticity allows it to accommodate deformations, which are particularly constrained in this type of element with a solid electrolyte.

[0136] Said solid electrolyte may be a lithium-ion conducting compound, selected 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.

[0137] 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.

[0138] 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 aforementioned polymers may be coated with a ceramic layer and / or polyvinylidene difluoride (PVdF) or poly(vinylidene-hexafluoropropylene fluoride (PVdF-HFP) or acrylates. Figures

[0139] [Fig. 1] [Fig. 1] illustrates the effect of the binder and carbon black on the elasticity of the carbon black matrix and polymeric binder(s). Specifically, [Fig. 1] schematically represents the elastic recovery (in %) for matrices comprising different (50 / 50) mixtures:

[0140] A: low molecular weight (350kg / mol) PVDF type polymeric binder

[0141] B: High molar mass (1000 kg / mol) PVDF type polymeric binder

[0142] C: High molar mass functionalized PVDF-type polymer binder (1100 kg / mol)

[0143] D: Low molar mass PVDF / HFP type copolymer (250 kg / mol)

[0144] With

[0145] 1: low specific surface area carbon black SSA (50 m2 / g), or

[0146] 2: SSA high specific surface area carbon black (800 m2 / g).

[0147] [Fig.2] Fig.2 illustrates the effect on the elasticity of the carbon black matrix(s) and polymeric binder(s) of the various carbon blacks mentioned above (J, 2 and 50 / 50 mixture of 1 and 2) in a mixture (50 / 50) with the low molar mass PVDF type polymeric binder (A).

[0148] [Fig.3] Fig.3 illustrates the effect on the elasticity of the carbon black matrix and polymeric binder(s) of the various aforementioned polymeric binders (A, C and 50 / 50 mixture of A and C) in a mixture (50 / 50) with carbon black (1).

[0149] [Fig.4] Fig.4 illustrates the effect on the elasticity of the carbon black matrix and polymeric binder(s) of the mass ratio r of carbon black / (carbon black + polymeric binder), illustrated in the case of the mixture (carbon black 1 and binder A).

[0150] [Fig.5] The [Fig.5] illustrates the evolution of the internal resistance in a cycling test of an electrochemical element whose composition for positive electrode includes carbon black 1 or 2 with the polymeric binder Aet NMC811 as the active material.

[0151] The invention will become clearer upon reading the following examples given solely by way of illustration, not limitation of the invention. EXAMPLES

[0152] Mechanical characterization of the matrix (carbon black(s) + polymeric binder(s))

[0153] In the examples below, the carbon black(s) + polymeric binder(s) matrix is ​​prepared by homogeneously mixing a paste comprising carbon black(s) in a solvent. • polymeric binder(s)

[0154] then evaporation of the solvent.

[0155] It was thus used:

[0156] A: low molecular weight (350kg / mol) PVDF type polymeric binder

[0157] B: High molar mass (1000 kg / mol) PVDF type polymeric binder

[0158] C: High molar mass functionalized PVDF-type polymer binder (1100 kg / mol)

[0159] D: Low molar mass PVDF / HFP type copolymer (250 kg / mol)

[0160] With

[0161] 1: low specific surface area carbon black SSA (50 m2 / g), or

[0162] 2: SSA high specific surface area carbon black (800 m2 / g).

[0163] Such binders are commercially available from suppliers such as Solvay, Arkema, Kureha, for example.

[0164] Carbon blacks are commercially available from Orion, Imerys, Ketjenblack, for example.

[0165] The quantities of carbon black(s) and polymeric binder(s) in the matrix vary depending on the different mixtures tested. Typically, for a 2% / 2% mixture of carbon black and PVDF, 80g of solvent (NMP) is mixed with 2% PVDF and 2% carbon black (mass %) so as to maintain 8% dry extract in the mixture.

[0166] A layer is deposited by coating, which is then scraped off in fragments after the solvent has evaporated. These fragments are then agglomerated to an isoporosity of 60% using a press to obtain a tablet with a homogeneous distribution and regular geometry (cylindrical with a diameter of 12.5 mm). The surface of the tablets can be polished to ensure homogeneous contact with the characterization device.

[0167] The elastic recovery of the matrix (carbon black(s) + polymeric binder(s)) is evaluated using a texture analyzer by applying several cycles of compression (40 N) and decompression (return to ON). The value is retained at the second cycle to eliminate any potential sample defects (inter-fragment porosity) as the difference as a percentage of the initial height and the recovered height for a pressure of ON during decompression.

[0168] The results obtained on the elastic recovery of the different mixtures tested are illustrated in Figures 1-4:

[0169] Fig. 1 represents the elastic recovery of the matrix (carbon black(s) + polymeric binder(s)) for the 50 / 50 mixtures (mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s)] of 0.5) A+L A+2, B+l, B+2. Ç+l, Ç+2, D+1 and D+2.

[0170] It is observed that the elastic recovery is satisfactory in the case of the series with carbon black 1, regardless of the type of binder used. However, in the case of the series with carbon black 2, only high molar mass binders (B and C) allow for satisfactory elasticity. Such a value is considered satisfactory when >5% and more preferably >6%.

[0171] Figure [Fig. 2] represents the elastic recovery of the matrix (carbon black(s) + binder(s) polymeric(s)) for 50 / 50 mixtures (mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s)] of 0.5) A+L A+2 and A+Q+2).

[0172] It is observed that the combination of carbon blacks 1 and 2 allows for the recovery of satisfactory elasticity, where carbon black 2 alone did not allow for such a value to be achieved.

[0173] Figure [Fig. 3] represents the elastic recovery of the matrix (carbon black(s) + binder(s) polymeric(s)) for 50 / 50 mixtures (mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s)] of 0.5) A+L Ç+l and (A+Ç)+L

[0174] It is observed that the association of binders A and Ç allows for greater elasticity (synergistic effect) than binder A or binder Ç separately.

[0175] Figure 4 illustrates the effect on the elasticity of the matrix (carbon black(s) + binder(s) polymeric(s) of the mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s)] , illustrated in the case of the A+L mixture

[0176] It is observed that for values ​​of r < 0.5, the elasticity of the CBD matrix is ​​satisfactory. Values ​​of r < 1 / 3 exhibit unsatisfactory electronic conductivity. It is also observed that this leads to an increase in the internal resistance of the electrochemical element. Electrical Characterization

[0177] Preparation of electrochemical elements

[0178] In the examples below, the positive electrode comprises a current-collecting support which is an aluminum strip. A homogeneously mixed layer consisting of a paste, after solvent evaporation, is deposited onto this support by coating: • 95% by mass of a lithium oxide-type active ingredient composition NMC811 (LiNi0.8Mn0.iCoo.i02). • 2.5% by mass of carbon black, serving as an electronic conductive agent; being either of low specific surface area (1) or of high specific surface area (2) • 2.5% by mass of polyvinylidene fluoride (PVDF) used as a binder.

[0179] We have thus used:

[0180] A: low molecular weight (350kg / mol) PVDF type polymeric binder

[0181] With

[0182] 1: low specific surface area carbon black SSA (50 m2 / g), or

[0183] 2: SSA high specific surface area carbon black (800 m2 / g).

[0184] Such binders are commercially available from suppliers such as Solvay, Arkema, Kureha, etc.

[0185] Carbon blacks are commercially available, notably from Orion, Imerys, Ketjenblack...

[0186] The electrode thus produced is then calendered.

[0187] For electrochemical characterization purposes, the positive electrode is assembled in "half-battery" format electrochemical generators opposite a negative electrode comprising metallic lithium as the active material.

[0188] The separator used comprises polypropylene and polyethylene.

[0189] The electrolyte is a lithium salt dissolved in an alkyl carbonate-based solvent.

[0190] They differ in the composition (nature) of the electronic conductive agent used in the positive electrode as described in the invention. These different electrodes are nevertheless calendered in the same way. The quantity of conductive agent, the quantity and nature of the binder in the positive electrode remain unchanged. The negative electrodes, the separators, and the electrolyte are identical.

[0191] These electrochemical generators underwent a lifetime cycling test at room temperature between 3.8V and 4.3V. The discharge current is C / 5, where C is the generator's nominal capacity. Charging is carried out at a current of C / 5 up to a voltage of 4.3V without a float charge.

[0192] Every 50 cycles, a cycle under the same charging and discharging conditions is carried out between 2.7V and 4.3V. During the discharge phase, a current draw of 2C is applied for 10 seconds at 50% of the discharged capacitance in order to evaluate the internal resistance of the electrochemical element (Ri).

[0193] The results are illustrated in [Fig. 5]. A relatively stable internal resistance is observed over 1000 cycles for the series with carbon black 1 (a series exhibiting high measured elasticity), whereas the series with carbon black 2 shows a double increase in internal resistance. This series exhibits moderate elasticity deemed unsatisfactory ([Fig.2]).

Claims

Demands

1. Electrode active material composition comprising at least one electrochemically active material, a matrix comprising at least one polymeric binder of molar mass M selected from low molar mass polymeric binders such as M < 500 kg / mol, high molar mass polymeric binders such as M > 500 kg / mol and mixtures thereof, and at least one carbon black of specific surface area SSA selected from low specific surface area carbon blacks such as SSA < 200 m² / g, high specific surface area carbon blacks such as SSA > 200 m² / g, and mixtures thereof, said composition being characterized in that: - The mass ratio r [carbon black(s) / (carbon black(s) + polymeric binder(s))] is such that 1 / 3 <r< 1 / 2 ;- It being understood that - if the composition comprises as the sole carbon black(s) one or more carbon black(s) having a high specific surface area such as SSA >200 m2 / g, then said composition comprises at least one polymeric binder of high molar mass M such that M>500 kg / mol.;

2. Composition according to claim 1 wherein it comprises at least one electrochemically active material, one or more carbon blacks with a low specific surface area such as SSA<200 m2 / g, and one or more polymeric binder(s) with a low molar mass such as M <500 kg / mol.

3. Composition according to claim 1 wherein it comprises at least one electrochemically active material, one or more low specific surface area carbon blacks such as SSA<200 m2 / g, one or more high molar mass polymeric binder(s) such as M>500 kg / mol and one or more low molar mass polymeric binder(s) such as M<500 kg / mol.

4. Composition according to claim 1 wherein it comprises at least one electrochemically active material, carbon black(s) with a low specific surface area such as SSA<200 m2 / g and carbon black(s) with a high specific surface area such as SSA>200 m2 / g, and one or more low molar mass polymeric binder(s) such that M<500 kg / mol.

5. Composition according to claim 1 wherein it comprises at least one electrochemically active material, carbon black(s) with a low specific surface area such as SSA<200 m2 / g and carbon black(s) with a high specific surface area such as SSA>200 m2 / g, one or more polymeric binder(s) with a low molar mass such as M<500 kg / mol and one or more polymeric binder(s) with a high molar mass such as M>500 kg / mol.

6. Composition according to any one of the preceding claims, wherein the polymeric binder(s) are selected from polyvinylidene fluorides (PVDF), functionalized PVDFs, functionalized or non-functionalized PVDF copolymers such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and mixtures thereof.

7. Composition according to any one of the preceding claims further comprising one or more additives selected from the dispersants.

8. Composition according to any one of the preceding claims comprising: - 90 to 97% of electrochemically active material(s); - 1.5 to 5% of carbon black(s); - 1.5 to 5% of polymeric binder(s); - 0 to 1% of one or more dispersants; and the percentages being by weight relative to the total weight of dry matter.

9. Composition according to any one of the preceding claims such that said matrix has elastic return > 5%.

10. Electrode comprising a metal strip covered on at least one of its faces by a composition according to any one of the preceding claims.

11. Electrochemical element comprising at least one positive electrode according to claim 10, one negative electrode, a separator and at least one electrolyte.

12. A method for preparing an electrode according to claim 10 comprising: - The preparation of an ink comprising the addition and mixing in a solvent of the ingredients of the composition according to any one of claims 1 to 9; - the application of said ink to the coating of said metal strip; - drying; and - calendering.

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