Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/134—Electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers

Definitions

• TITLE Negative electrodes based on silicon and fluorine additive
• the present invention relates to the field of energy storage, and more precisely to lithium accumulators.
• lithium-ion accumulators The operation of lithium-ion accumulators is based on the reversible exchange of the lithium ion between a positive electrode and a negative electrode, separated by an electrolyte, the lithium being stored at the negative electrode, during charging operation.
• Rechargeable lithium-ion accumulators offer excellent energy and volume densities compared to other electrochemical energy storage technologies and today occupy a dominant place in the market for portable electronics, electric and hybrid vehicles or even stationary energy storage systems.
• electrochemically active negative electrode materials may include silicon, which has ten times the capacitance of graphite.
• the intercalation/deintercalation of lithium within silicon is accompanied by a strong volume expansion, of the order of 300%.
• This expansion will be the cause of the degradation of the Li-ion cell: i) degradation of the integrity of the electrode which leads to a reduction in the use of the electrode, ii) fracture of the interface electrode-electrolyte (or SEI for “Solid Electrolyte Interphase”) which leads to the continuous formation of degradation product and the consumption of the electrolyte, and iii) application of mechanical stresses on the entire battery and degradation of the others components.
• EP 3 618 150 relates to a negative electrode based on particles whose core consists of SiO x , coated with a layer comprising carbon or a polymer, and a fluorinated material.
• the preparation of this type of particle is often complex and leads to a material whose cost makes deployment on a large scale complex.
• EP 3 471 177 describes a negative electrode comprising composite particles comprising a carbon material, silicon and LiF, the carbon phase of which comprises mixed Si-LiF particles dispersed uniformly or not in said carbon phase.
• This approach therefore requires careful control of each step: 1) coating (e.g. Si by LiF), 2) dispersion (e.g. Si-LiF particles in the carbon phase) and 3) coating the phase carbon containing Si-LiF particles.
• electrodes for lithium batteries are generally manufactured from a composition containing at least one electrochemically active material, at least one binder and optionally at least one electronically conductive additive, coated on a current collector.
• the invention therefore aims in particular to provide an improved electrode composition for a negative electrode for Li-ion batteries.
• the invention thus aims at a negative electrode composition
• a negative electrode composition comprising:
• particles comprising silicon particles comprising silicon
• At least one binder At least one binder
• composition further comprises at least one fluorinated additive distributed uniformly between the particles of active material, binder and possible conductive material within said composition.
• the invention relates to a negative electrode composition
• a negative electrode composition comprising:
• composition further comprises at least one fluorinated additive distributed uniformly between the particles of active material, binder and possible conductive material within said composition.
• negative electrode designates, when the accumulator is discharging, the electrode functioning as an anode, the anode being defined as the electrode where an electrochemical oxidation reaction (emission of electrons) takes place. .
• the term negative electrode also designates the electrode from which the electrons leave, and from which the cations (Li+) are released in discharge.
• the distribution of the additive is uniform within the composition.
• a distribution is devoid of agglomerate, the term “agglomerate” designating the assembly of several primary particles of additive and measuring several times the size of these, typically with a diameter greater than 10 pm.
• the active material designates the electrochemically active (or electroactive) material that is lithiophilic, that is to say capable of storing lithium, for example by intercalation of lithium and/or formation of lithium alloy.
• the active material is based on silicon. It therefore comprises particles of material comprising silicon. According to one embodiment, said particles are chosen from silicon-carbon composite particles (Si-C) and silicon oxide particles SiO x where 0 ⁇ x ⁇ 2.
• the active material may also comprise graphite particles.
• binder we mean here the agents making it possible to give the composition and/or the electrode the cohesion of the different components and its mechanical strength and its adhesion to the current collector.
• binders polymers such as polyethylene oxide (PEO), polyvinylidene fluoride (PVdF) and its copolymers such as polyvinylidene fluoride and hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl)- or (butyl) methacrylate, polyvinyl chloride (PVC), poly(vinyl formai), polyester, block polyetheramides, acrylic acid polymers, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers such as poly(styrene/butadiene) (SBR) and hydrogenated butadiene-acetonitrile cop
• SBR poly(
• the binder can be chosen from carboxymethylcellulose (CMC), styrene-butadiene (SBR), lithiated polyacrylic acid (LiPAA) and unlithiated polyacrylic acid (PAA, PAAH or PAAN).
• CMC carboxymethylcellulose
• SBR styrene-butadiene
• LiPAA lithiated polyacrylic acid
• PAA PAAH or PAAN
• conductive material typically refers to an electronic conductor, such as a carbon material, such as graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes (CNT) or a mixture of these.
• the conductive material is chosen from carbon black and carbon nanotubes.
• the fluorinated additive can be chosen from LiF or MgF 2 .
• the electrode composition advantageously comprises Si-C particles, and the MgF 2 additive.
• the composition comprises SiOx particles. where x is as defined previously, and LiF.
• the composition comprises from 0.05% to 5% (by weight) of the fluorinated additive, in particular from 0.1 to 3% (by weight), said percentage being related to the total weight of the constituents of the composition.
• composition may further comprise other constituents such as one or more solvents and/or additives aimed at improving the electrochemical properties of the electrode.
• the electrode composition according to the invention comprises the aforementioned ingredients, in liquid suspension, typically called “ink”.
• Said electrode composition is then a mixture of particles of active material, binder, additive, and possible conductor as defined above, in suspension, organic or aqueous.
• the nature of the organic or aqueous solvent generally depends on the nature of the binder used.
• the suspension is aqueous, in particular when the binder is chosen from carboxymethylcellulose (CMC), styrene-butadiene (SBR), lithiated polyacrylic acid (LiPAA) and unlithiated polyacrylic acid (PAA, PAAH or PAAN ).
• CMC carboxymethylcellulose
• SBR styrene-butadiene
• LiPAA lithiated polyacrylic acid
• PAA unlithiated polyacrylic acid
• PAAN unlithiated polyacrylic acid
• the formulation is an organic suspension, in N-methyl-2-pyrrolidone when PVdF is used as a binder.
• said composition can also be devoid of solvent.
• the present invention also targets a negative electrode comprising a current collector on which is coated on at least one of its faces a coating comprising the composition according to the invention.
• said coating essentially corresponds to the composition after drying of the ink (ie) after evaporation of the solvent. It therefore includes the same constituents as ink, with the exception of the solvent generally evaporated during drying.
• composition used here therefore includes the suspension (ie) the ink as well as the coating obtained after drying of the ink.
• coating thickness depends on 1) the material used and 2) the application.
• the thickness of the coating per side after evaporation of the solvent is typically between 5 and 200 pm.
• current collector is meant an element such as pad, plate, sheet or other, of 2D or 3D structure, made of conductive material, connected to the positive or negative electrode, and ensuring the conduction of the flow of electrons between the electrodes and battery terminals.
• the current collector is preferably a two-dimensional conductive support such as a solid or perforated strip, based on metal, for example copper, nickel, steel, stainless steel or aluminum.
• Said collector at the negative electrode is generally in the form of a copper strip.
• the current collector/coating assembly constituting the electrode is typically obtained by applying an electrode composition according to the invention to said current collector.
• the present invention also aims at a process for preparing the electrode according to the invention, said process comprising
• the method also comprises the step of prior preparation of an electrode composition according to the invention in aqueous or organic suspension, by mixing its constituents in aqueous or organic suspension, in particular with stirring.
• This step can typically be carried out over a sufficiently long time (generally one to several hours) with a high shear rate mixer or a planetary mixer, for example until no evolution of the ink is observed, typically the absence of agglomeration to the naked eye.
• This step generally results in a uniform distribution without agglomeration.
• the deposition step is typically carried out by coating the electrode composition on all or part of at least one of the faces of the collector. This can be carried out manually or automatically by film application process or by spraying.
• the drying step aims to eliminate the solvent contained in the electrode composition, and is typically carried out by heating, generally until its complete evaporation at a suitable temperature, typically between 50°C and 200°C , under vacuum or not and in a heated enclosure or using any other relevant technique such as, for example, infrared radiation.
• a suitable temperature typically between 50°C and 200°C
• any other relevant technique such as, for example, infrared radiation.
• the presence of the fluorinated additive according to the invention does not substantially modify the usual process for preparing said electrode composition.
• the fluorinated additive is dissolved or dispersed in the suspension.
• the coating is in the form of a film adhering to the current collector.
• the electrode thus obtained can then be calendered in order to reduce its porosity, that is to say by reducing the space between the different constituents of the electrode.
• the invention also relates to an electrochemical element comprising the negative electrode according to the invention.
• electrochemical element we mean an elementary electrochemical cell, making it possible to store the electrical energy provided by a chemical reaction and to release it in the form of current.
• the electrochemical element according to the invention is typically a Li-ion element.
• the invention also targets an electrochemical element of the Li-ion type comprising:
• the positive electrode can be of any known type suitable for Li-ion elements.
• positive electrode designates the electrode where the electrons enter, and where the cations (Li + ) arrive in discharge.
• the positive electrode generally consists of a conductive support used as a current collector which is coated on at least one of its faces with the positive electrode formulation, which typically contains at least one positive electrode active material, a material electronic conductor and a possible binder.
• the active material of the positive electrode is not particularly limited. It can be chosen from the following groups:
• LiMO 2 of so-called “lamellar” or “lamellar oxide” structure where M is at least one element chosen from Ni, Co and Mn and where 0 ⁇ x ⁇ 1;
• the active material of the positive electrode comprises, as active material, a lamellar oxide, such as LiNii. yz Mn y Co z O 2 with 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1 and y+z ⁇ 1.
• a lamellar oxide such as LiNii. yz Mn y Co z O 2 with 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1 and y+z ⁇ 1.
• the positive electrode electronic conductor material is generally chosen from graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes or a mixture thereof.
• the electrolyte may be liquid and comprise a lithium salt dissolved in an organic solvent.
• This lithium salt can be chosen from lithium perchlorate UCIO 4 , lithium hexafluorophosphate LiPF 6 , lithium tetrafluoroborate LiBF 4 , lithium hexafluoroarsenate LiAsF 6 , lithium hexafluoroantimonate LiSbF 6 , lithium trifluoromethanesulfonate ÜCF3SO3, lithium bis(fluorosulfonyl)imide Li(FSO 2 ) 2 N (LiFSI), lithium trifluoromethanesulfonimide LiN(CFsSO 2 ) 2 (LiTFSI), lithium trifluoromethanesulfonemethide LiC(CF 3 SO 2 )3 (LiTFSM) , THE lithium bisperfluoroethylsulfonimide LiN(C2F 5 SO2)2 (LiBETI), lithium 4,5-di
• the electrolyte solvent may be chosen from saturated cyclic carbonates, unsaturated cyclic carbonates, linear carbonates, alkyl esters, ethers or cyclic esters, such as lactones and mixtures thereof.
• 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.
• the separator is to avoid short circuits, while being permeable to lithium ions. It may in particular consist of a non-woven 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 natures.
• the polymers mentioned can be coated with a ceramic layer and/or polyvinylidene difluoride (PVdF) or poly(vinylidene fluoride-hexafluoropropylene (PVdF-HFP) or acrylates.
• PVdF polyvinylidene difluoride
• PVdF-HFP poly(vinylidene fluoride-hexafluoropropylene
• the lithium-ion cell is manufactured in a conventional manner. At least one cathode, at least one separator and at least one anode are superposed. The assembly can be rolled up to form a cylindrical electrochemical beam. The electrodes can also be stacked to form a planar electrochemical beam. A connection piece is fixed on an edge of the cathode not covered with active material. It is connected to a current output terminal. The anode may 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 beam is impregnated with electrolyte. The element is then closed tightly. The element may also be conventionally equipped with a safety valve causing the container of the element to open in the event that the internal pressure of the element exceeds a predetermined value.
• the present invention also relates to an electrochemical module comprising the stack of at least two elements according to the invention, each element being electrically connected with one or more other element(s).
• module therefore designates here the assembly of several electrochemical elements, said assemblies being able to be in series and/or parallel.
• Another object of the invention is yet a battery comprising one or more modules according to the invention.
• battery or accumulator is meant the assembly of several modules according to the invention.
• Figure 1 illustrates the normalized evolution of the capacity recorded at C/5 - D/5 (charge in 5h - discharge in 5h), at room temperature, where curve 1 corresponds to an electrode based on SiO x +graphite ( LiPAA binder) with the LiF additive and curve 2 corresponds to an electrode based on SiOx + graphite (LiPAA binder) without additive.
• the arrow represents a 5-fold increase in the number of cycles before reaching 80% retention of the reference capacity.
• Figure 2 illustrates the normalized evolution of the capacitance at C/5 - D/5, at room temperature, with a curve 1 corresponding to an electrode based on SiO x +graphite//Li° with the additive LiF, and curve 2 corresponding to an electrode based on SiO x +graphite//Li° without additive.
• the arrow represents a 15% increase in the number of cycles for the electrode with LiF additive compared to the electrode without additive.
• Figure 3 illustrates the normalized evolution of the capacitance at C/5 - D/5, ambient temperature, where curve 1 corresponds to an electrode based on Si-C+graphite//Li° with the additive MgF 2 , and curve 2 corresponds to an electrode based on Si-C+g raphite//Li° without additive.
• the arrow represents a 28% increase in the number of cycles for the electrode with MgF 2 additive compared to the electrode without additive.
• Figure 4 illustrates the normalized evolution of the capacitance at C/3 - D/3, room temperature, where curve 1 corresponds to an NMC811 cell //Si-C + graphite composite with MgF 2 in the electrode and the curve 2 corresponds to an NMC811 //Si-C + graphite composite cell without MgF 2 in the electrode.
• Figure 5 illustrates the normalized evolution of the internal resistance, where curve 1 corresponds to an NMC81 1 //composite Si-C + graphite cell with MgF 2 in the electrode and curve 2 corresponds to an NMC811 //composite cell Si-C + graphite without MgF 2 in the electrode.
• Figure 6 represents the structure of the electrode composition according to one embodiment of the invention, where the composition comprises Si-C particles (1) and graphite particles (4) as active materials, MgF 2 (2) as an additive to the electrode, the binder (3).
• the composition does not contain any conductive material; it is understood, however, that when a conductive material is present, the particles of conductive material do not affect the uniform distribution of the additive within the structure of said composition.
• Ink formulations according to the invention were prepared according to the milk steps with the active materials SiOx or Si-C.
• the percentages indicated represent the percentages by weight of the ingredients added at the step considered, by weight relative to the total weight of the ingredients of the suspension.
• x is equal to approximately 1.
• agitation implies “until complete dissolution or homogeneous distribution to the naked eye”.
• the suspensions of the inks thus prepared in steps 1 a-1 f are then coated on a copper strip, and the whole is subjected to 80°C for a period typically between a few minutes and an hour, until the evaporation of the ink 'water.
• the evaporation of water can be identified by weighing, when the mass no longer varies over time when the drying time is increased.
• the calendering of the electrode thus prepared is carried out by passing the electrode between two rollers in order to reduce the porosity of the electrode to the desired value.
• the electrode after drying can be characterized by scanning electron microscopy (SEM) in order to reveal the distribution of the additive within the electrode so that it is uniform and without agglomerates, the additive being located between the particles of active materials without however completely covering them.
• SEM scanning electron microscopy
• the previously prepared electrode is cut to the correct diameter in order to be inserted into the button cell battery holder
• LiPF 6 lithium salt
• the button cell battery is sealed, it is connected to a potentiostat type cycling system making it possible to generate a current of a few pA to a few mA which will depend on the capacity (mAh) of the battery tested and the desired current regime (C /X),
• the start of the cycling begins with a temperature training cycle ( 1st point of the curves), then aging (for the study of the lifespan) is carried out at ambient T°C. “Control cycles”, carried out at slower cycling speeds, can be inserted during aging.

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• Electric Double-Layer Capacitors Or The Like (AREA)

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• 2022
  • 2022-12-16 FR FR2213660A patent/FR3143868B1/fr active Active
• 2023
  • 2023-12-15 WO PCT/EP2023/086087 patent/WO2024126799A1/fr not_active Ceased
  • 2023-12-15 EP EP23833694.5A patent/EP4635007A1/de active Pending

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