Active materials based on lithium manganese and iron phosphate and lithium-ion electrochemical element electrode comprising said active materials

Abstract

An electrode comprising one or more active materials, one of the active materials being a lithium manganese and iron phosphate of formula LixMn1-y-zFeyMzPO4 (LMFP) where 0.8≤x≤1.2; 0.5≤1-yz<1; 0

Description

Title of the invention: Active materials based on lithium manganese and iron phosphate and lithium-ion electrochemical element electrode comprising said active materials Technical field of the invention

[0001] The technical field of the present invention is that of active materials based on lithium manganese and iron phosphate (LMFP) intended to be used in the cathode, i.e. the positive electrode, of a lithium-ion type electrochemical element, also called a lithium-ion element. Context of the invention

[0002] Lithium manganese and iron phosphates, abbreviated LMFP hereafter, are known as the active material in the positive electrode of lithium-ion electrochemical elements. These phosphates exhibit satisfactory thermal stability but insufficient volumetric capacitance. This is partly due to the difficulty in obtaining a low-porosity electrode. Available LMFP particles have a flaky or granular shape with irregular contours. This particular shape makes it difficult to obtain a low-porosity positive electrode, and therefore one with high volumetric capacitance. Typically, an LMFP-based positive electrode has a porosity ranging from 40 to 50%. Approximately half of the electrode volume is therefore empty space. The aim was thus to increase the volumetric capacitance of an electrode containing an LMFP-based active material.

[0003] Document CN 113072049 (A) describes, for example, a process for preparing spherical LMFP nanoparticles. The value of the internal porosity of the particles produced is not mentioned. No density value for the particles produced is given.

[0004] Document CN 1821065 (A) describes a process for preparing spherical LiFePO4 (LFP) lithium iron phosphate particles. The density values ​​obtained range from 2.0 to 2.3 g / cm³. However, the theoretical density of LiFePO4 is 3.6 g / cm³. Consequently, the porosity of the LiFePO4 powder produced under the process conditions described in this document is approximately 40%, which remains high.

[0005] CN 1632970 (A) describes a process for preparing spherical LFP or LMFP particles. Examples 4 to 7 of this document describe the preparation of a powder of LMFP particles with a size ranging from 8 to 10 pm and a density of 2.08–2.20 g / cm³. However, the average theoretical density of LMFP is 3.3 g / cm³. Consequently, the porosity of the LMFP powder produced under the conditions of this process is approximately 36%, which remains high.

[0006] We seek to obtain a powder porosity less than or equal to 30%, which guarantees obtaining an electrode porosity of 30% by applying reasonable pressure forces. Summary of the invention

[0007] The object of the present invention is an electrode comprising one or more active materials, one of them being 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<0,5 ; 0 <z<0,2 ; M being one or more elements chosen from the group consisting of Al, B, Mg, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W and Mo, the electrode being characterized in that: - Lithified manganese and iron phosphate is in the form of particles, at least 90% by number of the particles having a sphericity factor greater than or equal to 0.90 and less than 1, the sphericity factor of a particle being defined as the ratio between the surface area of ​​a sphere having the same volume as the particle and the surface area of ​​that particle, and in that - the internal porosity of the manganese and iron phosphate lithium particles is less than or equal to 5%, the internal porosity being defined by the ratio Vvoid / VLMFpOÙ Vvide represents the volume of void space inside the lithium manganese and iron phosphate particles, VLMFP represents the geometric volume of lithium manganese and iron phosphate particles.

[0008] The invention is based on the discovery that using LMFP particles having, on the one hand, a nearly spherical shape and, on the other hand, an internal porosity of less than or equal to 5%, makes it possible to reduce the porosity of the electrode. Low electrode porosity values ​​in the range of 20 to 30% are achievable.

[0009] According to one embodiment, the sphericity factor is greater than or equal to 0.95.

[0010] According to one embodiment, the sphericity factor is greater than or equal to 0.98.

[0011] According to one embodiment, the internal porosity of the lithium phosphate particles of Manganese and iron levels range from 2 to 3%.

[0012] According to one embodiment, at least 95% by number of the lithium manganese and iron phosphate particles have a sphericity factor greater than or equal to 0.9 and less than 1.

[0013] According to one embodiment, the lithium manganese and iron phosphate particles are in the form of primary particles having a volume median diameter Dv50 ranging from 500 nm to 20 pm or from 5 to 15 pm or from 1.5 to 4 pm.

[0014] According to one embodiment, the lithium phosphate particles of manganese and iron are in the form of secondary particles having a median volume diameter Dv50 ranging from 1 pm to 50 pm, a secondary particle being made up of the agglomeration of primary particles having a median volume diameter Dv50 located in the range from 50 nm to 20 pm.

[0015] According to one embodiment, the lithium phosphate particles of manganese and iron have a bimodal distribution, the first population being characterized by a first median diameter Dyso1, the second population being characterized by a second median diameter DV5o2, the ratio between Dyso1 and Dv5o2 ranging from 3 to 10.

[0016] According to one embodiment, in the lithium phosphate of manganese and iron, 0.70 <l-y-z<l.

[0017] According to one embodiment, the electrode further comprises one or more active materials selected from: - a lithium iron phosphate of formula iii) LixFei yMyPO4 (LFP) where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Cu, Zn, Y, Zr, Nb et Mo ; - a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule v) Lii+xVi yMyPO4Fz (LVMPF) où 0<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 ; - a lithium oxide of nickel, manganese and cobalt of formula a) Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci, - a lithium oxide of nickel, cobalt and aluminium of formula b) Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci, - a lithium oxide of nickel and manganese of formula c) Liw(NixMnyCozMt)O2(NMX) where 0.9 <w<l,l ; 0,60<x<0,80 ; 0<y ; 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, - un oxyde lithié de nickel et de manganèse de formule d) Liw(NixMnyCozMt)O2où 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.

[0018] According to one embodiment, said one or more active substances is an oxide nickel lithium selected from: - a lithium oxide of nickel, manganese and cobalt of formula a) Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci, - un oxyde lithié de nickel, de cobalt et d’aluminium de formule b) Liw(NixCoyAlzMt)O2(NCA) où 0,9<w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant 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 des mélanges de ceux-ci, et - a lithium oxide of nickel and manganese of formula c) Liw(NixMnyCozMt)O2(NMX) where 0.9 <w<l,l ; 0,60<x<0,80 ; 0<y ; 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, - un oxyde lithié de nickel et de manganèse de formule d) 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.

[0019] According to one embodiment, the lithium manganese and iron phosphate represents from 40 to 99% by mass of the total mass of lithium manganese and iron phosphate and lithium nickel oxide(s) and said one or more lithium nickel oxides represent from 1 to 60% by mass of the total mass of lithium manganese and iron phosphate and lithium nickel oxide(s).

[0020] According to one embodiment, the lithium manganese and iron phosphate represents from 70 to 99% by mass of the total mass of lithium manganese and iron phosphate and lithium nickel oxide(s) and said one or more lithium nickel oxides represent from 1 to 30% by mass of the total mass of lithium manganese and iron phosphate and lithium nickel oxide(s).

[0021] The invention also relates to a lithium-ion electrochemical element comprising at least one positive electrode, which is the electrode as described above, and at least one negative electrode. Brief description of the figures

[0022] Embodiments of the invention are described below in more detail with reference to the figures below.

[0023] [Fig. 1] is a scanning electron micrograph of a powder of the active material of Example A. This powder consists of non-porous, non-spherical LMFP primary nanoparticles with dimensions of approximately 100 nm. The outline of a primary nanoparticle has been drawn to distinguish it and highlight its features. the size.

[0024] [Fig.2] is a scanning electron microscopy photograph of a powder of the active material of example B. This powder consists of porous spherical agglomerates resulting from the agglomeration of the primary nanoparticles of example A. The outline of an agglomerate has been drawn in order to individualize it and highlight its diameter.

[0025] [Fig.3] represents the variation in the porosity of powder particles of the materials Examples A to D are active, depending on the pressure applied to these powders. The porosity on the ordinate is the sum of the porosity between the particles and the internal porosity of the particles. Description of embodiments of the invention: Active material(s) of the positive electrode

[0026] A positive electrode according to the invention comprises one or more active materials, one of which is made up of LMFP particles characterized on the one hand by a nearly spherical shape and on the other hand by an internal porosity less than or equal to 5%. By nearly spherical, we mean a sphericity factor greater than or equal to 0.9, preferably greater than or equal to 0.95, and more preferably greater than or equal to 0.97.

[0027] Preferably, at least 90% or at least 95% of the LMFP particles meet the sphericity criterion.

[0028] The evaluation of the degree of sphericity of LMFP particles can be carried out by scanning electron microscopy (SEM). On an SEM image of particles, the smallest and largest dimensions are measured for each particle, and a statistical average of the ratio of the two is calculated.

[0029] The fact that LMFP particles only have a shape close to a sphere does not allow for low electrode porosity values. It is necessary that the LMFP particles also have an internal porosity of less than or equal to 5%.

[0030] LMFP particles having a nearly spherical shape and an internal porosity of 5% or less can be obtained by preparing an unlithied spherical Fe and Mn phosphate precursor by sol-gel or hydrothermal means, preferably using an acidic complexing agent rather than a basic one or no complexing agent at all. Sintering is then carried out by heat treatment, preferably at a temperature below 500°C, on this spherical precursor. Further sintering steps are performed during heat treatments, preferably at a temperature of 600°C or higher, applied after lithiation of the precursor and during the application of any carbon coating by pyrolysis of a carbon precursor.

[0031] Characterization of the porosity of LMFP particles: Mercury porosimetry on powder allows visualization of the progressive absorption of mercury in the sample in two stages: - a first stage at low pressure (<150 bar) due to the absorption of mercury in the interparticle spaces, - a second stage at high pressure (>150 bar) corresponding to the absorption of mercury in the open intraparticle porosity. The volume of mercury absorbed in this stage represents the internal open porosity of the LFMP. The closed internal porosity of the particles is inaccessible to mercury and is evaluated by helium pycnometry. The difference in density between the theoretical density and the density measured by helium pycnometry is due to the closed internal porosity of the particles. The term "internal porosity of LFMP particles" here refers to the sum of the closed internal porosity and the open internal porosity of the LFMP particles.

[0032] Lithium manganese and iron phosphate has the formula LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l ; 0<y<0,5 ; 0<z<0,2 ; M étant un ou plusieurs éléments choisis dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W et Mo.

[0033] The stoichiometric index 1-yz of manganese can be at least 0.6, or at least 0.7, or at least 0.8. It can range from 0.7 to 0.9 or from 0.75 to 0.80. Preferably, 0.70 <l-y-z<l.

[0034] The stoichiometric index y of iron can be at most 0.4 or at most 0.3 or at most 0.2.

[0035] Examples of LMFP are LiMno>8Feoj2PC)4, LiMnojsFeo^PCL, LiMnoj7Feoj3P04, LiMn2 / 3Fei / 3PO4 and LiMnojFeojPCL.

[0036] LMFP can be coated with a layer of carbon. In particular, it can be coated with graphite or amorphous carbon or carbon nanotubes.

[0037] Several LMFP type compounds of different formulas can be used in mixture.

[0038] The invention can be implemented using: - either disjoint LMFP particles, also called primary particles, with a median diameter DV5o ranging from 500 nm to 20 pm or from 1 to 20 pm or from 5 to 15 pm or from 1.5 to 4 pm; - either agglomerates of primary LMFP particles, also called secondary particles, these agglomerates resulting from the agglomeration of primary particles characterized by a median diameter DVso ranging from 50 nm to 20 pm or from 5 pm to 15 pm or 1.5 pm to 4 pm. The median diameter of secondary particles can range from 1 to 50 pm.

[0039] The expression "median volume diameter Dv50" means that, in a given population of particles, 50% of the particle volume consists of particles having a Equivalent diameter less than the Dv50 value and 50% of the particle volume consist of particles with an equivalent diameter equal to or greater than the Dv50 value. The term "equivalent diameter" of a particle refers to the diameter of a sphere having the same volume as that particle. Dv50 can be measured by laser granulometry.

[0040] The particle size distribution of LMFP can be unimodal or bimodal. A unimodal distribution allows for powder porosity values ​​ranging from 25 to 30%. Preferably, the distribution is bimodal. The first population is characterized by a first median diameter Dyso1, the second population by a second median diameter Dv5o2, and the ratio between Dyso1 and Dv5o2 preferably ranges from 3 to 10. Such a particle size distribution reduces the void volume between the LMFP particles and thus decreases the electrode porosity. A bimodal distribution allows for powder porosity values ​​ranging from 20 to 30%. In one embodiment, the mass percentage of particles characterized by a second median diameter Dv5o2 smaller than the first median diameter Dvso1 ranges from 10 to 20% relative to the total mass of all LMFP particles.

[0041] LMFP can be mixed with one or more lithium phosphates containing cobalt or nickel or iron of respective formulas: i) LixCoi yMyPO4 (LCP) and 0.8 <x<l,2 ; 0<y<0,6 où M est choisi dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb et Mo ; ii) LixNii yMyPO4 (LNP) and 0.8 <x<l,2 ; 0<y<0,6 où M est choisi dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Y, Zr, Nb et Mo ; iii) LixFei yMyPO4 (LFP) and 0.8 <x<l,2 ; 0<y<0,6 où M est choisi dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Cu, Zn, Y, Zr, Nb et Mo. Preferably, it should be LFP.

[0042] LMFP can be mixed with a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule v) 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.

[0043] LMFP can be mixed with one or more layered lithia-coated oxides of transition metals selected from: a) Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci, b) Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci, et c) Liw(NixMnyCozMt)O2(NMX) where 0.9 <w<l,l ; 0,60<x<0,80 ; 0<y ; 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. NMX peut être monocristallin ou polycristallin. d) 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.

[0044] Preferably, LMFP is mixed with one or more NMC-type compounds.

[0045] Preferably, the mass percentage of LMFP represents at least 50% or at less than 70% or at least 90% of the mass of all the active materials of the positive electrode. In this embodiment in which LMFP is the major component, the preferred lamellar lithium oxide is of the NMC type. Positive electrode

[0046] The positive electrode of the element comprises a current collector, at least one face of which is coated with a layer of a positive active material composition. "Active material composition" means a composition comprising: - one or more active substances as described above, one of which consists of LMFP particles of almost spherical shape and with an internal porosity of less than or equal to 5%, and - possibly one or more binders and one or more electronically conductive materials.

[0047] The overall porosity of the electrode is the sum of the open internal porosity, the closed internal porosity of the active material particles (including the LMFP particles), and the porosity between the active material particles, the binder particles, and any incorporated electronically conductive additive particles. The technique for measuring the open internal porosity and the closed internal porosity of the LMFP particles is described above.

[0048] The positive current collector is a solid or perforated metal strip which may be made of aluminum or an aluminum alloy or steel or stainless steel. Its thickness may be in the range of 6 to 30 µm or 5 to 20 µm or 10 to 15 µm, preferably 10 to 15 µm.

[0049] Before the current collector is coated with the active material composition layer, it may be coated, on one or both of its faces, with a coating designed to improve the electronic conductivity between the active material composition layer and the foil and / or to improve the adhesion of the active material composition layer to the foil. The coating material may be chosen from the group consisting of amorphous carbon, graphite, fibers of Carbon, carbon nanotubes, and mixtures thereof. It is preferably made of amorphous carbon. The coating material can be obtained by coating the foil with a dispersion of the material and then evaporating the solvent from the dispersion, or it can be obtained by sputtering. Only certain parts of the foil may be coated with the coating material. The coated parts may be separated from each other by predetermined or periodic intervals ("intermittent coating"). The intermittent coating is preferably present on both sides of the foil. It facilitates electrode processing. Alternatively, one or both sides of the foil may have undergone a surface treatment designed to increase the adhesion of the active material composition layer to the foil. This may be a surface treatment creating asperities or microroughness, such as chemical etching or laser treatment.

[0050] The binder generally used in the composition of active materials strengthens the cohesion between the active material particles and improves the adhesion of the active material composition layer to the current collector. The binder may contain one or more of the following compounds: poly(vinylidene fluoride) (PVDF) and its copolymers, polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl or butyl methacrylate), poly(vinyl chloride) (PVC), poly(vinyl formalin), polyester, sequenced polyetheramides, acrylic acid polymers, methacrylic acid polymers, acrylamide polymers, itaconic acid polymers, sulfonic acid polymers, elastomers, and cellulosic compounds such as carboxymethylcellulose (CMC). The elastomers that can be used as a binder can be chosen from styrene-butadiene (SBR), butadiene-acrylonitrile (NBR), hydrogenated butadiene-acrylonitrile (HNBR).The binder can represent 1% to 10%, 1% to 5%, or 2% to 5% of the mass of the dry composition of active ingredients.

[0051] The electronically conductive material is generally selected from graphite, carbon black, acetylene black, soot, graphene, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof. It may represent from 0.1 to 10% or from 0.1 to 5% of the mass of the dry composition of active materials. Preparation of the positive electrode:

[0052] An ink is prepared by dispersing the active material(s) in a solvent or a mixture of several solvents. Optionally, a binder and an electronically conductive material are added to the dispersion. By varying the amount of solvent incorporated into the mixture, the viscosity of the ink can be varied before it is deposited on a face of the current collector. The ink-coated current collector is dried and then laminated to adjust its thickness. After evaporation of the solvent(s), a layer of a material composition is obtained. active ingredients whose proportions of the various constituents are typically: - 80 to 98% or 90 to 95% by mass of positive active ingredients, - 1 to 10% or 2 to 5% by mass of binder(s), - 0.1 to 10% or 2 to 5% by mass of electronically conductive material. Negative electrode:

[0053] At least one negative electrode comprises a current collector, at least one of whose two faces is coated with a layer of a negative active material composition. The negative active material composition comprises at least one negative active material and optionally a binder and an electronically conductive material. The negative current collector is a solid or perforated metal strip that may be made of copper or a copper-based alloy. Its thickness may range from 3 to 10 µm, preferably from 5 to 8 µm.

[0054] Before the current collector is coated with the active material composition layer, it may be coated, on one or both of its faces, with a coating designed to improve the electronic conductivity between the active material composition layer and the foil and / or to improve the adhesion of the active material composition layer to the foil. The coating material and the coating deposition process may be the same as those described for the current collector of the positive electrode.

[0055] The negative active material may be selected from carbon, graphite, coke, carbon black, vitreous carbon, silicon, silicon dioxide, a silicon-carbon composite, silicon carbide, titanium dioxide, lithium titanium dioxide, titanium niobium oxide, and a mixture thereof. Titanium dioxide may be selected from H₂Ti₆O₃, H₂Ti₂O₅, and TiO₂. Lithium titanium dioxide may be selected from Li₄Ti₅O₂, Li₂TiO₃, Li₂Ti₃O₇, LiTi₂O₄, and Li₂Na₂Ti₆O₄. Titanium niobium oxide may be selected from TiNb₂O₇, Ti₂Nb₂O₇, and Ti₂Nb₂O₇. Negative electrode preparation procedure:

[0056] The negative electrode is prepared in a conventional manner. An ink is prepared by dispersing one or more negative active substances, optionally with a binder, in a solvent or a mixture of solvents. The binder may be such as those described in relation to the positive electrode.

[0057] The ink-coated current collector is dried and then laminated to adjust its thickness. This produces a negative electrode. The typical proportions of the components of the negative active material composition layer, after evaporation of the solvent contained in the ink, are: - 85 to 98% or 90 to 98% by mass of negative active ingredients, - 1 to 10% or 1 to 5% by mass of binder(s), - 0 to 5% by mass or 1 to 5% of an electronically conductive material. Electrolyte:

[0058] The electrolyte may be liquid or solid. The liquid electrolyte is obtained by dissolving one or more lithium salts in one or more organic solvents. The solvent may be chosen from saturated cyclic carbonates, unsaturated cyclic carbonates, non-cyclic carbonates, alkyl esters, ethers, nitrile-type solvents, and tetrahydrothiophene dioxide (sulfolane).

[0059] Saturated cyclic carbonates include ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), butylene carbonate (BC), and mixtures thereof.

[0060] Unsaturated cyclic carbonates include vinylene carbonate (VC).

[0061] Non-cyclic carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and mixtures thereof.

[0062] Alkyl esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and mixtures thereof.

[0063] Ethers include dimethyl ether (DME), diethyl ether (DEE) and mixtures thereof.

[0064] The lithium salt can be selected from lithium perchlorate LiC104, lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium hexafluoroarsenate LiAsF6, lithium hexafluorantimonate LiSbF6, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imidide Li(FSO2)2N (LiFSI), lithium bis(trifluoromethanesulfonyl)imidide LiN(CF3SO2)2 (LiTFSI), lithium tris(fluoromethanesulfonyl)methylide LiC(CF3SO2)3 (LiTFSM), lithium bis(pentafluoroethylsulfonyl)imidide LiN(C2F(SO2)2) (LiBeTI), lithium-4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), the lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LIDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP), lithium difluorophosphate LiPO2F2, and mixtures thereof.

[0065] The concentration of said at least one lithium salt may be in the range of 0.75 to 1.5 mol / L. It is preferably in the range of 1 to 1.5 mol / L. It is even better in the range of 1 to 1.2 mol / L. Separator:

[0066] A separator is interposed between a positive electrode and a negative electrode. The separator material can be chosen from the following materials: a polyolefin, for example polypropylene PP, polyethylene PE, a polyester, glass fibers bonded by a polymer, polyimide, polyamide, polyaramid, polyamide-imide, and cellulose. The polyester may be selected from poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). Advantageously, the polyester, polypropylene, or polyethylene contains or is coated with a ceramic material selected from the group consisting of metal oxides, oxyhydroxides, carbides, nitrides, borides, silicon dioxides, and sulfides. This ceramic material may be SiO₂ or Al₂O₃. The separator may be a ceramic-coated polyolefin layer, preferably a ceramic-coated polyethylene layer on both sides. Preparation of the electrochemical beam:

[0067] An electrochemical beam is formed by inserting a separator between at least one positive electrode and at least one negative electrode. The electrochemical beam is inserted into the element container. The element container may be parallelepiped-shaped or cylindrical. In the latter case, the electrochemical beam is spiraled to form a cylindrical arrangement of the electrodes.

[0068] The electrochemical element can also be in pouch format. Filling and closing the container:

[0069] In the case of a parallelepiped or cylindrical container, a lid is assembled onto the container of the element, for example by laser welding. The container of the element is filled with electrolyte. For this purpose, the lid may include a filling hole through which the electrolyte is introduced. Once the electrolyte has been introduced, this filling hole is closed by a stainless steel ball by electrically welding the ball to the hole. EXAMPLES

[0070] The porosities of powders of different active ingredients were compared. Table 1 below indicates the active ingredients used. [Tables 1] Active ingredient A* Non-porous, non-spherical LMFP primary particles of approximately 100 nm B* Porous, spherical LMFP secondary particles with a diameter of approximately 10 pm. C Non-porous spherical LMFP particles with a unimodal size distribution D Non-porous spherical LMFP particles with a bimodal size distribution characterized by a Dvso' / Dvso2 ratio of 7 * Electrode not invented

[0071] Figures 1 and 2 are SEM photographs of the powders of active substances A and B. A primary particle is shown in [Fig. 1]. An agglomerate is shown in [Fig. 2].

[0072] The powders of active materials A and B were subjected to increasing compressive force. Figure 3 shows the variation in porosity of a powder of active material A and that of a powder of active material B as a function of the applied pressure. It can be seen that even at a high pressure of 1000 bar, the porosity of a powder of active material A or B outside the scope of the invention remains greater than 40%. Regarding the powder of active material A, its high porosity is due to the non-spherical nature of the particles. Regarding the powder of active material B, its high porosity is due to the porous nature of the particles. The theoretical porosity of a powder of active material C according to the invention, comprising particles with a unimodal size distribution, is 26%. That of a powder of active material D according to the invention, comprising particles with a bimodal size distribution, is 20%.The lower porosity value of active ingredient powder D compared to active ingredient powder C is explained by the bimodal particle distribution. Active ingredients C and D therefore increase the volumetric capacitance of the positive electrode by approximately 40 to 50% compared to active ingredients A and B.

Claims

Demands

1. Electrode comprising one or more active substances, one of the active substances being a lithium manganese iron phosphate of formula LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l ; 0<y<0,5 ; 0<z<0,2 ; M étant un ou plusieurs éléments choisis dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W et Mo, l’électrode étant caractérisée en ce que : - Lithified manganese and iron phosphate is in the form of particles, at least 90% by number of the particles having a sphericity factor greater than or equal to 0.90 and less than 1, the sphericity factor of a particle being defined as the ratio between the surface area of ​​a sphere having the same volume as the particle and the surface area of ​​that particle, and in that - the internal porosity of the lithium manganese and iron phosphate particles is less than or equal to 5%, the internal porosity being defined by the ratio Vvoid / VLMFP where Vvide represents the volume of void space inside the lithium manganese and iron phosphate particles, VLMFP represents the geometric volume of lithium manganese and iron phosphate particles, which electrode further comprises one or more active substances selected from: - a lithium iron phosphate of formula iii) LixFei yMyPO4 (LFP) where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Co, Cu, Zn, Y, Zr, Nb et Mo ; - a lithium vanadium fluorophosphate of formula iv) Lii+XVPO4F (LVPF) where 0 <x<0,15, ou à un de ses dérivés de formule v) Lii+xVFyMy PO4Fz (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 ; - a lithium oxide of nickel, manganese and cobalt of formula a) Liw (NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci, - a lithium oxide of nickel, cobalt and aluminium of formula b) Liw (NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant 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, - a lithium oxide of nickel and manganese of formula c) Liw(NixMnyCozMt)O2(NMX) where 0.9 <w<l,l ; 0,60<x<0,80 ; 0<y ; 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, - un oxyde lithié de nickel et de manganèse de formule d) Liw(NixMnyCo zMt)O2où 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.

2. Electrode according to claim 1, wherein the sphericity factor is greater than or equal to 0.

95.

3. Electrode according to claim 2, wherein the sphericity factor is greater than or equal to 0.

98.

4. Electrode according to any one of claims 1 to 3, wherein the internal porosity of the manganese and iron lithium phosphate particles ranges from 2 to 3%.

5. Electrode according to any one of the preceding claims, wherein at least 95% by number of the lithium manganese and iron phosphate particles have a sphericity factor greater than or equal to 0.9 and less than 1.

6. Electrode according to any one of the preceding claims, wherein the lithium manganese and iron phosphate particles are in the form of primary particles having a volume median diameter Dv50 ranging from 500 nm to 20 pm or from 5 to 15 pm or from 1.5 to 4 pm.

7. Electrode according to any one of claims 1 to 5, wherein the lithium manganese and iron phosphate particles are in the form of secondary particles having a median volume diameter Dv50 ranging from 1 pm to 50 pm, a secondary particle being made up of the agglomeration of primary particles having a median volume diameter Dv50 in the range of 50 nm to 20 pm.

8. Electrode according to any one of the preceding claims, wherein the lithium manganese and iron phosphate particles exhibit a bimodal distribution, the first population being characterized by a first median diameter Dvso1, the second population being characterized by a second median diameter DV5o2, the ratio between Dyso1 and DV5o2 ranging from 3 to 10.

9. Electrode according to any one of the preceding claims, wherein in the lithium phosphate of manganese and iron, 0.70 <l-y-z<l.

10. Electrode according to claim 1, wherein said one or more active materials are one or more lithiaated nickel oxides selected from: - a lithiaated nickel, manganese, and cobalt oxide of formula a) Liw (NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci, - un oxyde lithié de nickel, de cobalt et d’aluminium de formule b) Liw(NixCoyAlzMt)O2(NCA) où 0,9<w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant 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 des mélanges de ceux-ci, et - un oxyde lithié de nickel et de manganèse de formule c) Liw(NixMnyCozMt)O2(NMX) où 0,9<w<l,l ; 0,60<x<0,80 ; 0<y ; 0<z<0,02 ; 0<t ;M being 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 mixtures thereof, and - a lithium oxide of nickel and manganese of formula d) Liw(NixMnyCo zMt)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.;

11. Electrode according to claim 10, wherein: - the lithium manganese iron phosphate represents from 40 to 99% by mass of the total mass of lithium manganese iron phosphate and lithium nickel oxide(s); - said one or more lithium nickel oxides represent from 1 to 60% by mass of the total mass of lithium manganese iron phosphate and lithium nickel oxide(s).

12. Electrode according to claim 11, wherein: - the lithium manganese and iron phosphate represents from 70 to 99% by mass of the total mass of lithium manganese and iron phosphate and lithium nickel oxide(s); - said one or more lithia nickel oxides represent from 1 to 30% by mass of the total mass of lithia manganese and iron phosphate and lithia nickel oxide(s).

13. Lithium-ion electrochemical element comprising: - at least one positive electrode which is the electrode according to any one of claims 1 to 12, - at least one negative electrode.

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