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
  • H01M4/64—Carriers or collectors
• • 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
  • H01M4/66—Selection of materials
  • H01M4/664—Ceramic materials
• • 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
  • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
  • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
• • 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
  • 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
  • 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
  • H01M2004/028—Positive electrodes
• • 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 even stationary energy storage systems.
• the positive electrode is generally protected by an insulating film.
• US 2008/0299461 relates to the prevention of short circuits caused by contact between the positive and negative electrodes, and describes the application of a ceramic insulating layer on the positive electrode. Nevertheless, the ceramic composition is produced by mixing the ceramic powder with a polymer binder, in a solvent medium (N-methyl-2-pyrrolidone, NMP). NMP is a toxic solvent, classified as CMR. In addition, an ink drying step is necessary. This step, carried out in an oven, consumes a lot of energy and requires significant facilities in a Li-ion cell manufacturing plant.
• NMP N-methyl-2-pyrrolidone
• Dry electrode coating productions are described, for example in US 2015/0061176. However, it is a cathode film comprising the active material, and not a coating of a cathode insulating film containing a ceramic.
• the present invention relates to a process for preparing an insulating film by a dry process for the edge of the positive electrode current collector of a Li-ion cell, said process comprising the steps:
• insulator is understood here to define the character of electrical insulation (ie) the ability to inhibit the flow of electric current.
• the method according to the invention makes it possible to provide an insulating film making it possible to limit short-circuits at the level of the banks of current collectors of the positive electrodes of a Li-ion cell.
• bank in English “tab" used here defines the portion of the current collector not coated by the active material of the electrode. It is therefore a generally “bare” section of the current collector, typically consisting of a sheet of metal, such as an aluminum strip, for example in the case of a current collector edge of positive electrode. In the context of the invention, a generally “bare” surface of the bank is covered with the insulating film.
• Said edge comprises an upper face and a lower face.
• the film is applied to the surface of the edge intended to face the negative electrode when mounting a Li-ion electrochemical cell.
• the insulating film is applied to the portion of one and/or the other of the faces intended to be in contact with the current collector of the negative electrode or the edge thereof, in the configuration of the electrochemical cell under consideration.
• the film is applied to a portion of the lower face and a portion of the upper face.
• the insulating film is applied to a portion located at the end of the edge connected to the collector, it being understood that at least one portion located at the end of the edge intended to be in contact with the connector is devoid of said film.
• Said collector is generally in the form of a strip of conductive material, such as a metal.
• the cathode current collector may consist of an aluminum strip, optionally coated, for example coated with carbon.
• said insulating film consists of a mixture of ceramic powder and polymer binder.
• the ceramic powder represents between 50 and 99%, in particular between 30 and 99% by weight of the mixture of the ceramic and the polymer binder, and the polymer binder represents between 1 and 50%, in particular between 1 and 30% by weight of said mixture.
• the quantity of binder can be measured by thermogravimetric analysis for example.
• the ceramic coating layer is obtained by the dry process, i.e. without the use of solvent.
• the method according to the invention therefore makes it possible to avoid the drying step generally required in the methods of the prior art.
• the method comprises in one step the mixing of ceramic powders and polymer binder.
• this mixing step can be carried out by jet milling or by a shearing process, for example in an internal mixer or an extruder.
• the shaping is advantageously carried out in a mixer with external rollers or in a single or twin-screw extruder.
• the shaping step makes it possible to obtain a homogeneous film.
• the temperature T1 is generally higher than the melting or softening temperature of said polymer binder.
• the thickness of the film to be obtained can be adjusted according to the desired use.
• the mixing step and the shaping step can be carried out simultaneously or separately.
• the adhesion of the film obtained on the edge of the current collector can be achieved by colamination on said edge of the current collector.
• the colamination can be carried out by means of a hot press, roller mixer, or a calender, for example with hot rollers, and/or rolling mill.
• the ceramic powder is chosen from among boehmite, alumina, magnesia, ATH (AIOH 3 ) powders, and phosphorus fillers.
• the ceramic powder can be Boehmite with the formula AIO(OH).
• polymer binder designates one or more polymers in a mixture, more particularly a mixture of polymers.
• Said polymers can be chosen from nitrile rubbers of the NBR (nitrile butadiene rubber) type or of the HNBR (hydrogenated nitrile butadiene rubber) type, rubbers of the EPDM (ethylene-propylene-diene monomer) type, rubbers of the EVA (ethylene-propylene) type. vinyl acetate), elastomers, thermoplastics, polyamides, PVDF and PTFE in particular, alone or in mixtures including their mixtures with co-binders.
• the method according to the invention may also comprise the addition of one or more additives chosen from crosslinking agents, lubricants, plasticizers, antioxidants during the mixing step.
• the present invention also relates to an insulating film on the edge of a positive electrode current collector for a Li-ion cell comprising a mixture of ceramic and polymer binder, devoid of solvent or traces of solvent, and having a porosity less than 10%, in particular less than 5%.
• the present invention therefore also relates to an insulating film on the edge of a positive electrode current collector for a Li-ion cell capable of being obtained by the method according to the invention.
• said insulating film has a thickness of between 10 and 100 micrometers ( ⁇ m).
• the porosity of the film is linked to the nature of the process used: thus, the low porosity of less than 10%, in particular less than 5%, is characteristic of a process for obtaining by dry process . Indeed, a film obtained by a wet process has a porosity greater than 40%, or even around 50 to 60%.
• the porosity (in %) can be estimated according to the formula:
• Porosity (in %) (1 -(Etheoretical/Ereal))*100 where Etheoretical represents the theoretical thickness of the film (for a porosity of 0%), which can be calculated according to the composition of the coating and the grammage (in g/cm 2 ); and Ereaiie represents the actual thickness.
• porosity can also be measured by Hg or He porosimetry.
• the low porosity of the film according to the invention is also associated with a strong insulating character:
• the film according to the invention has a higher insulating character than that of a film obtained by a wet process.
• the present invention relates to a positive electrode whose edge is at least partially covered with an insulating film according to the invention.
• FIG. 5 An embodiment of a positive electrode A is illustrated in Figure 5 where the insulating film 4 according to the invention partially covers the bank of the current collector 2 of the positive electrode.
• the opposite end of the current collector, intended to be in contact with the connector, is devoid of film 4.
• the invention also relates to a Li-ion type electrochemical element comprising a positive electrode according to the invention as presented above.
• electrochemical element is understood to mean an elementary electrochemical cell consisting of the positive electrode/electrolyte/negative electrode assembly, allowing to store the electrical energy provided by a chemical reaction and to restore it in the form of current.
• Such an electrochemical element is notably represented schematically in FIG.
• the electrochemical cell 1 is connected to the external connectors by bank 2 of the positive electrode current collector and by bank 3 of the negative electrode current collector.
• the bank 2 is partially covered by the ceramic insulating film 4.
• the film 4 is present on the portion of the bank located at the end connected to the cathode collector, while the opposite end, intended to be in contact with the connector, is devoid of movie.
• the electrochemical elements according to the invention are preferably accumulators whose capacity is greater than 100 mAh, typically 1 to 100 Ah.
• a positive electrode A and a negative electrode B are separated by a separator C. There is an offset A between the end of the negative electrode B beyond the end of the positive electrode A.
• the edges of the current collectors 2 of the positive electrodes are bent according to a deformation represented by the dotted arrow, to be brought together at the level of the connector. Due to this curvature, the bank 2 can be in contact with the separator C and/or the negative electrode B.
• the insulating film 4 covering the bank 2 on the face facing the negative electrode thus makes it possible to avoid short circuits.
• the present invention also relates to an electrochemical module comprising the stack of one or more elements as defined above.
• each element is electrically connected with one or more other element(s).
• module therefore designates here the assembly of several electrochemical elements, said assemblies possibly being in series and/or parallel.
• One element is illustrated in Figure 6: in this photograph, positive A, negative B electrodes and C separators constitute the central part.
• the edges of the current collectors 2 covered with the film 4 are curved to be brought together and ensure the connection with the connector:
• the positive edges are welded together on the cover of the prismatic cup.
• the negative edges, located behind the assembly, are not visible in this photograph.
• the invention also relates to a battery comprising one or more modules according to the invention.
• battery is meant the assembly of several modules according to the invention.
• FIG. 1 schematically represents a Li-ion electrochemical cell with ceramic insulating film on the positive side.
• FIG. 2 represents the steps of the process for preparing an electrode comprising the film according to the invention: 2A: mixing in an internal mixer; 2B: extrusion in a single screw; 2C: colamination on a strip coated with carbon.
• FIG. 3 is a photograph of a dielectric test carried out on an insulating film.
• the black dot on the film (identified by the dotted circle) is the mark of the dielectric breakdown that took place on this film.
• FIG. 4 shows a close-up of the respective arrangement of the positive electrode bank according to the invention within an electrochemical element.
• FIG. 5 shows the structure of a positive electrode incorporating the edge covered with an insulating film according to the invention.
• FIG. 6 shows a photograph of a sectional section of the internal structure of an electrochemical element incorporating the banks of positive electrodes covered with an insulating film according to the invention.
• the temperatures and mixing speeds were adapted according to the binder.
• the polymer is first added to the internal mixer at its softening temperature or its melting temperature. This is mixed alone for 5 minutes until a fluid is obtained.
• the ceramic fillers (here of the boehmite type) are added gradually to avoid too sudden an increase in the temperature of the mixture and in the machine torque.
• the paste is recovered and introduced into a single-screw extruder having at its outlet a fixed flat die with a thickness of 50 ⁇ m.
• the temperature of the extruder is adapted according to the type of binder and modeled on the temperatures of the internal mixer.
• a continuous strip of ceramic film is then recovered and then adhered to an Al current collector having a carbon-type bonding primer on its surface. This last step is obtained using a heated rolling mill (roller temperature set at 125°C) in which the insulating film placed on the current collector is co-rolled. The pressure applied during co-rolling then allows adhesion.
• the materials obtained are then characterized in a breakdown test.
• a direct current voltage is applied between the upper part of the film and the current collector.
• the breakdown voltage is identified with the dielectric breakdown of the insulating film. The higher the breakdown voltage, the better the insulation of the film. For information, these tests are carried out at room temperature.
• the breakdown voltage is higher (over 1 kV) than that of a film prepared by the wet process (approximately 600V) at iso-thickness.
• differences are also observed when the nature of the binder of the dry films is changed: 1.1 kV for EVA, 1.5 kV for HNBR and 3.5 kV for EPDM.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Electric Double-Layer Capacitors Or The Like (AREA)
• Cell Separators (AREA)
• Secondary Cells (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Family Cites Families (4)

• 2021
  • 2021-10-14 FR FR2110909A patent/FR3128317B1/fr active Active
• 2022
  • 2022-10-12 US US18/699,823 patent/US20240413348A1/en active Pending
  • 2022-10-12 EP EP22802581.3A patent/EP4416775A1/de active Pending
  • 2022-10-12 CA CA3233860A patent/CA3233860A1/fr active Pending
  • 2022-10-12 WO PCT/EP2022/078417 patent/WO2023062089A1/fr not_active Ceased

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