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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0421—Methods of deposition of the material involving vapour deposition
• • 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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/40—Alloys based on alkali metals
  • H01M4/405—Alloys based on lithium
• • 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
  • H01M4/623—Binders being polymers fluorinated 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
  • H01M4/625—Carbon or graphite
• • 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
  • H01M4/626—Metals
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/70—Carriers or collectors characterised by shape or form
  • H01M4/75—Wires, rods or strips
• • 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
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • 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
  • H01M2004/027—Negative 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
  • H01M4/13—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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to the field of energy storage, and more specifically to accumulators, in particular of the lithium type.
• Rechargeable lithium-ion batteries indeed offer excellent energy and volume densities and today occupy a prominent place in the market for portable electronics, electric and hybrid vehicles and stationary energy storage systems.
• Solid electrolytes also offer a significant improvement in terms of safety as they present a much lower risk of flammability than liquid electrolytes.
• lithium batteries The operation of lithium batteries is based on the reversible exchange of lithium ion between a positive electrode and a negative electrode, separated by an electrolyte, the lithium being deposited at the negative electrode during operation under charge.
• Capacitor electrodes comprising aluminum current collectors on which carbon nanotubes (CNTs) are deposited have been described by Arcila-Velez et al Nano Energy 2014, 8, 9-16.
• KR101746927 describes an electrode comprising a protective layer containing a lithium salt, in order to prevent corrosion of lithium by the liquid electrolyte.
• the protective layer can also include CNTs.
• CNTs due to its very high nucleation energy, lithium dendrites will form on the carbon surface. This structure therefore does not allow homogeneous deposition of lithium.
• US 2019/088981 describes a cell for a battery, such that the negative electrode comprises conductive elements: here again, the deposition of lithium or of lithiated alloy will greatly increase the thickness of the electrode, which leads to weakening the structure during charge and discharge cycles.
• US2017 / 133662 describes a lithium battery comprising a composite type anode in which the lithium metal is inserted within the porous matrix.
• lithium is present here initially and this type of solution does not allow lithium to be kept in the porosity of the carbon during cycling, which causes a significant variation in the thickness of the negative electrode. It was actually observed that after several cycles, lithium no longer fits into the porous carbon structure but between the porous carbon layer and the current collector (YG Lee et al, Nat Energy (2020). https://doi.org /10.1038/s41560-020-0575-z). This phenomenon is explained by the migration of particles of the material forming alloys with lithium towards the surface of the current collector under the layer of carbon particles. This solution does not allow lithium to be stored in the porosity of the carbon and therefore will generate significant variations in thickness of the negative electrode causing a degradation of the service life and moreover, it requires '' apply high mechanical pressures to the accumulator during operation.
• the invention therefore aims in particular to provide a nanoporous negative electrode comprising conductor pillars arranged on the current collector, said electrode being characterized in that the surface of said pillars is at least partially covered with a layer of a material consisting of '' at least one element forming alloys with lithium
• the pillars are such that they consist of electronically conductive particles which are in direct contact with the current collector.
• the electrode structure according to the invention thus allows the deposit of lithium in a homogeneous manner within the nanoporous structure while greatly limiting the volume variations of the electrode.
• nanoporous means a pore size of less than 300 nm.
• the pore size corresponds to the structure of the material having an organized network of channels of very small variable pore size (typically less than 300 nanometers), which gives them a particularly large active area per unit electrode area.
• negative electrode designates when the accumulator is discharging, the electrode operating as an anode and when the accumulator is charging, the electrode operating as a cathode, the anode being defined as the electrode where a reaction takes place. electrochemical reaction of oxidation (emission of electrons), while the cathode is the seat of the reduction.
• the term "conductor pillars” particularly refers to pillars as described by Wei et al (Microelectronic Engineering, Vol. 158, 2016, 22-25).
• this term illustrates the arrangement of several elements made of a conductive material, such that said elements are generally parallel to each other, and such that they are arranged on a surface at an angle varying between approximately 70 and 90 ° with the surface, for example at a right angle.
• the pillars form the porous structure and serve as a support for the alloy forming compound.
• said pillars are arranged in a comb shape, such that the spaces located between said pillars form channels of length which may vary from 1 ⁇ m to 1 mm, typically from a few micrometers to several hundred micrometers.
• Said pillars can have sizes and spacings of a few nanometers to several hundred nanometers, preferably from 10 to 10Onm.
• the conductor pillars are chosen from copper pillars, carbon nanotubes or microporous carbons.
• the carbon nanotubes are vertically aligned carbon nanotubes (VACNT).
• VACNT vertically aligned carbon nanotubes
• the electrode according to the invention does not contain lithium metal before it is put into operation.
• the lithiophilic element is chosen from silver, zinc and magnesium.
• the alloys formed by these elements with lithium include Li x Zn y , Li x Mg y and Li x Ag y type alloys, with variable x / y atomic ratios.
• a second nanometric conductive layer of lithium is deposited on at least part of the surface of the first layer.
• nanoscale layer refers to the thickness of the second layer, which can vary from a few nanometers to less than 10Onm, typically about less than 50nm.
• the second layer comprises a polymer, ceramic or gel.
• the second layer conducts lithium, in that it allows the transit of Li + ions from the electrolyte layer to the first layer. It can also allow homogenization of the lithium deposit by allowing the formation of local batteries: in fact during charging, a potential difference is created in the thickness of the electrode; this difference in potentials can then allow an electrochemical rebalancing on the thickness of the electrode by oxidation of lithium in the areas of the most positive potentials and a reduction of Li + in the areas of the most negative potentials.
• the porosity of the electrode is between 45 and 98% to make it possible, on the one hand, to accommodate the lithium metal in the porosity and at the same time to maintain mechanical strength of the electrode.
• the negative electrode according to the invention further comprises a third layer comprising an electrolyte.
• the surface density of CNT is between 10 9 and 2.10 11 CNT / cm 2 .
• the porosity of the electrode is such that:
• said electrode has a thickness in the charged state (Ec) and a thickness in the discharged state (Ed), and such that:
• area capacitance refers to the amount of electricity that the electrode can deliver per unit area.
• the present invention also relates to a method for preparing a negative electrode according to the invention, said method comprising the step of successively depositing the first layer then the second layer, each of the deposition steps being carried out. by physical or chemical vapor route (PVD or CVD, respectively), or liquid.
• PVD physical or chemical vapor route
• CVD chemical vapor route
• CVD chemical vapor deposition
• PVD atomic layer deposition
• ALD atomic layer deposition
• the present invention also relates to an electrochemical element comprising a negative electrode according to the invention, characterized in that it is a battery of the all-solid or hybrid type (containing at least one inorganic electrolyte and one electrolyte organic polymer), for example a Li free type battery.
• the present invention also relates to an electrochemical element comprising a negative electrode according to the invention, characterized in that it is a battery of the "lithium free” type.
• lithium free defines the fact that the battery does not contain lithium metal during assembly of the accumulator, but that lithium is deposited in metallic form and then consumed in a controlled and reversible manner in situ during battery operation. Typically, lithium is deposited within the negative electrode during charging and consumed during discharge.
• electrochemical element an elementary electrochemical cell made up of the positive electrode / electrolyte / negative electrode assembly, allowing the electrical energy supplied by a chemical reaction to be stored and returned in the form of current.
• 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 still a battery comprising one or more modules according to the invention.
• battery or accumulator is understood to mean the assembly of several modules according to the invention.
• the batteries according to the invention are accumulators whose capacity is greater than 100 mAh, typically 1 to 100Ah.
• FIG 1 shows a schematic representation of the structure of an electrode according to the invention.
• the current collector (1) such as a metal strip has a flat surface, on which stand pillars of conductive material (2), such as copper pillars or carbon nanotubes.
• These pillars (2) are covered with at least one layer:
• a first layer (3) made of a material capable of forming alloys with lithium
• the Li + ions arrive from the solid electrolyte layer separating the 2 positive and negative electrodes, and react at the ends of the pillar.
• the pillar is made of carbon
• the latter forms a lithiated compound of varying formula (for example, in the case of graphite, its composition is CL10 .17 )
• the potential of the negative electrode reaches potentials below 0V
• a deposit of lithium should form; nevertheless the formation of lithium metal requires a nucleation energy which can be relatively high on the carbon corresponding to an overvoltage.
• a supersaturation of carbon with lithium can thus take place and the lithium will thus diffuse in the pillar; adding a material forming alloys with lithium to the surface of the CNT will reduce the lithium metal formation overvoltage.
• the lithium in the structure of the supersaturated lithiated carbon will thus be able to transform into lithium metal on the layer deposited on the surface of the CNT. It should be noted in passing that the material forming alloys will have already lithiated before the precipitation of lithium metal because its formation potential is greater than that of lithium metal. In parallel with this process, the lithium ions can also pass through said possible second layer to be deposited, in the form of Li metal under this layer.
• FIG 2 is a schematic representation of the structure of an electrode according to Figure 1 above, in the charged state, where Li (5) is present around the pillars.
• the deposition of VACNT can be carried out as described in the article by Arcila-Velez et al., Nano Energy, Volume 8, 2014, 9-16: the VACNT tubes are made in a quartz tube with a diameter of 5cm; the 2 ends of the tube are partially closed with stainless steel. The tube is placed in an oven with 2 hot zones, the first zone serving as preheating and in the second the reaction takes place.
• a pump makes it possible to inject the precursor (solution of ferrocene in xylene, containing for example 0.5 at% iron) in the center of the preheating zone.
• Acetone-cleaned copper sheets, a few cm wide and long, are placed in the center of the reaction zone in the furnace.
• the system is brought to 600 ° C. under a flow of argon and hydrogen (17% by volume of H2).
• the precursor is injected at 600 ° C with a low flow rate, for example from 0.1 to 1 5ml / h, in a flow of C2H2 with a flow rate of 30cm 3 / min.
• the duration of treatment varies from 5 to 50 min depending on the length of the CNTs desired.
• Deposits of the first and second layer can be carried out according to the following 5 methodologies:
• the preparation of the electrolyte layer and of the positive electrode is carried out under an argon atmosphere ( ⁇ 1 ppm H2O). 0
• the electrolyte membrane is obtained in several stages.
• a first step of mixing sulfide electrolyte of U6PS5CI argyrodite type with 2% by mass of a copolymer binder based on polyvinylidene fluoride is carried out in a planetary mill. This mixing is carried out at a speed of 1000 rpm for 10 min with several solvents: xylene and isobutyl isobutyrate previously dried using molecular sieves (pore size of 3 ⁇ ).
• the ink thus obtained is coated on a PET film allowing the membrane to be peeled off after drying. The thickness of this membrane is 50 ⁇ m.
• the positive electrode is made from an NMC type material of composition LiNiO.6OMnO.2OCoO.2OO 2 covered with a 10 nm layer of LiNbOs, mixed with solid electrolyte U 6 PS 5 CI, carbon fibers (VGCF) and copolymer binder based on polyvinylidene fluoride in mass proportions NMC: Li 6 PS 5 CI: VGCF: binder 70: 30: 3: 3. These materials are dispersed in a mixture of xylene and isobutyl isobutyrate solvents. A homogeneous ink is obtained after passing through the planetary mixer. This ink is then coated on an aluminum current collector previously covered with a thin layer of carbon. The weight of the electrode is varied between 15 and 95 mg / cm 2 .
• a 12mm diameter disc is cut from the electrolytic membrane along with a 10mm diameter positive electrode disc. These two discs are pressed against each other in a mold under a pressure of 5.61.
• a 10 mm diameter disc is cut from the negative electrode corresponding to the example and placed on the other side of the electrolytic membrane. This stack is then compressed at a pressure of 1 t / cm 2 and can be subjected to a heat treatment of between 80 and 130 ° C. for 12 h.
• the stack is then placed in a Swagelok-type cell compressed at a pressure of between 1 and 5 MPa.
• the charge and the discharge are carried out at a rate of C / 20.
• CNT powder 40 nm in diameter and between 20 and 50 ⁇ m in length is dispersed in an organic solvent (for example NMP) in the presence of 2% PVDF.
• the mixture is deposited on a copper collector then dried at 120 ° C. and compressed; the layer thickness is 25pm.
• a silver deposit is then made by PECVD on the layer thus obtained followed by a deposit of LiPON by ALD.
• the negative electrode is then obtained by cutting a 10mm diameter disc of coated collector.
• the electrochemical cells are then prepared in an identical manner to Examples 1 to 6.
• the examples described in Tables 2 and 3 show that the variations in thickness are significantly smaller than Comparative Examples 1 and 4 described in Tables 4 and 5; in fact the negative electrodes of comparative examples 4 and 5 correspond to an increase in thickness corresponding to more than 60% of the initial thickness.
• Comparative Examples 2, 3 and 5 show too high inter CNT distances which give rise to problems with the mechanical strength of the CNTs under pressure associated with a heterogeneous lithium deposit resulting in a shorter lifetime.
• Example 1 interCNT distance of the order of 300nm;
• Example 2 low thickness of the surface layers;
• Example 6 very high surface capacity.
• Example 5 Poor penetration of lithium into the porosity and low developed surface area of carbon leading to the formation of dendrite.

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