WO2025024409A1 - Bilayer polymer composite coating for lithium metal anode - Google Patents

Bilayer polymer composite coating for lithium metal anode Download PDF

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Publication number
WO2025024409A1
WO2025024409A1 PCT/US2024/039090 US2024039090W WO2025024409A1 WO 2025024409 A1 WO2025024409 A1 WO 2025024409A1 US 2024039090 W US2024039090 W US 2024039090W WO 2025024409 A1 WO2025024409 A1 WO 2025024409A1
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Prior art keywords
electric conductor
mixed ionic
polymer composite
electrochemical cell
electronic insulator
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PCT/US2024/039090
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French (fr)
Inventor
Sipei Li
Jeffrey Layton SWOYER
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Ionic Materials, Inc.
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Application filed by Ionic Materials, Inc. filed Critical Ionic Materials, Inc.
Publication of WO2025024409A1 publication Critical patent/WO2025024409A1/en

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    • 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
    • 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
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/497—Ionic conductivity
    • 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

  • Lithium metal anodes can be unstable in fuel cells.
  • fuel cells with nickel- cobalt-manganese (NCM) cathodes and lithium anodes have low coulombic efficiency and short cycling life.
  • NCM nickel- cobalt-manganese
  • different types of coatings have been applied to the surface of the lithium metal, including polymeric coatings, inorganic coatings, and polymer/inorganic composites in an attempt to promote stability of the lithium anode.
  • this approach has not adequately addressed the issue.
  • the present disclosure relates to a bilayer polymer composite for an electrochemical cell.
  • the bilayer polymer composite may be directly coated onto the surface of an anode (such as lithium foil) to improve the stability of the lithium plating and stripping.
  • anode such as lithium foil
  • lithium metal batteries that include the disclosed bilayer coating have exhibited improved cycle life and high-rate capabilities.
  • Embodiments of the subject disclosure include a bilayer design that may be applied between the existing separator and the lithium metal or current collector (in the case of an anode- free cell), and then paired with an existing cathode.
  • the separator can either be filled with liquid electrolytes or ionically conductive solid-state electrolytes.
  • the first layer positioned close to the anode side is an “MIEC” layer (i.e., a mixed ionic-electronic mixed conductor layer).
  • MIEC a mixed ionic-electronic mixed conductor layer
  • the layer that is closer to the separator side is an electronic insulator, but is ionically conductive (i.e., an electronic insulator layer or “El” layer).
  • an electrochemical cell having a separator, an anode, and a bilayer polymer composite positioned between the separator and the anode.
  • the bilayer polymer composite includes a mixed ionic-electric conductor and an electronic insulator.
  • the electronic insulator is in contact with the separator
  • the mixed ionic-electric conductor is in contact with the anode and the electronic insulator.
  • the anode of the electrochemical cell may include lithium metal or copper.
  • the bilayer polymer composite consists of the mixed ionic-electric conductor and the electronic insulator.
  • the mixed ionic-electric conductor may have a porous structure, and the electronic insulator may be partially or fully infiltrated into pores of the mixed ionic-electric conductor.
  • the electronic insulator includes a polyaziridine polymer and an ether-based electrolyte.
  • the mixed ionic-electric conductor may include conductive particles and a polymeric binder.
  • the polymeric binder may have a molecular weight higher than 2,000 g/mol.
  • the conductive particles may include silver nanoparticles and a conductive carbon.
  • the mixed ionic-electric conductor may include between 10-30 wt% silver nanoparticles and between 45-80 wt% conductive carbon. In select embodiments, the mixed ionic-electric conductor includes between 10-30 wt% of the polymeric binder.
  • methods of forming a bilayer polymer composite on an electrode include applying a mixed ionic-electric conductor mixture to the electrode, drying the mixed ionic-electric conductor mixture to form a porous mixed ionic-electric conductor on the electrode, and applying an electronic insulator mixture to the porous mixed ionic-electric conductor to form the bilayer polymer composite.
  • the electrode may be an anode, which, for example, may be implemented with a lithium foil.
  • the mixed ionic-electric conductor mixture may be applied directly onto the lithium foil.
  • the mixed ionic-electric conductor mixture may be applied as a paste, a slurry, or a liquid.
  • the electronic insulator mixture may also be applied to the porous mixed ionicelectric conductor in the form of a liquid, a slurry, or a paste.
  • the electronic insulator infiltrates pores of the porous mixed ionic-electric conductor.
  • numerous other variations are possible and contemplated herein.
  • FIG. 1 illustrates a sample bilayer polymer composite, configured in accordance with some embodiments of the present disclosure
  • FIG. 2 illustrates a sample method of forming a bilayer polymer composite, in accordance with some embodiments of the present disclosure
  • FIGS. 3A-3B show measured Coulombic efficiency data for various electrochemical cells.
  • the cell tested in FIG. 3A includes a bilayer polymer composite configured in accordance with the present disclosure, and the cell tested in FIG. 3B is a comparative cell without a bilayer polymer composite;
  • FIGS. 4A-4B show measured voltage profiles for the cells tested in FIGS. 3 A and 3B.
  • FIG. 4A shows the voltage profile of the cell tested in FIG. 3A
  • FIG. 4B shows the voltage profile of the cell tested in FIG. 3B;
  • FIG. 5 shows the improved cycle life for full lithium-ion cells with Lithium Metal Anode vs Lithium Mixed Metal Oxide Cathodes (NMC) with the incorporation of improved generations of the bilayer polymer composite films.
  • the “Control” represents cell testing without any bilayer polymer composite film applied.
  • FIG. 1 illustrates a sample bilayer polymer composite 100 for an electrochemical cell.
  • the bilayer polymer composite 100 is configured to be positioned between a separator 10 and an electrode 40 of an electrochemical cell.
  • the bilayer polymer composite 100 includes an electronic insulator 20 and a mixed ionic-electric conductor 30.
  • the electronic insulator 20 at times referred to herein as “El”
  • the mixed ionic-electric conductor 30 at times referred to herein as “MIEC” are distinct components.
  • the chemical composition of the electronic insulator 20 is distinct from the chemical composition of the mixed ionic-electric conductor 30 in some embodiments.
  • features of the electronic insulator 20 and the mixed ionic-electric conductor 30 are intermixed.
  • the electronic insulator 20 may be partially or fully infiltrated into pores of the mixed ionic-electric conductor 30.
  • the bilayer polymer composite 100 can provide numerous advantages for an electrochemical cell, specifically a cell having a lithium anode.
  • the electronic insulator 20 may promote adhesion between the mixed ionic-electric conductor 30 and the separator 10.
  • the electronic insulator 20 may also have lower electronic conductivity to make the interphase of the separator 10 and the mixed ionic-electric conductor 30 lithium-repellant.
  • the electronic insulator 20 may have one or more of the following properties: strong adhesiveness, high elasticity, toughness, ionic conductivity, denseness, low thickness, and/or electronic insulation.
  • the mixed ionic-electric conductor 30 may advantageously prevent side reactions between the electrolyte and the electrode material (i.e., lithium). Additionally, in select embodiments, the mixed ionic-electric conductor 30 may also provide sites for lithium plating within its pores. The mixed ionic-electric conductor 30 may also relieve stress attack from dendrites and/or guide lithium growth between the mixed ionic-electric conductor 30 and electronic insulator 20 interphase.
  • the mixed ionic-electric conductor 30 may have one or more of the following properties: high porosity, high lithium wettability, high ionic conductivity, and/or high electronic conductivity.
  • the bilayer polymer composite 100 may be formed using any suitable formation or assembly process. In some implementations, the bilayer polymer composite 100 is formed using a sequential coating process. However, in other implementations, the bilayer polymer composite 100 may be created by forming each layer independently and then joining the layers together (for example, using an adhesive or a heating process).
  • FIG. 2 illustrates a sample process 200 that may be used to form a bilayer polymer composite 100 directly on an electrode 40. As shown in FIG. 2, process 200 includes applying a mixed ionic-electric conductor mixture to an electrode (step 210).
  • the mixed ionic-electric conductor mixture may include any compounds discussed herein with respect to the mixed ionic-electric conductor 30 as well as one or more solvents, and/or any desired additives.
  • the electrode may be an anode or a cathode, as desired.
  • the electrode may be in the form of a solid material.
  • the mixed ionic-electric conductor mixture is applied to a lithium metal anode.
  • the mixed ionic-electric conductor mixture may be applied as a paste, slurry, or a liquid.
  • the mixed ionic-electric conductor mixture may then be dried (while on the electrode). Drying the mixed ionic-electric conductor mixture involves removing any solvent or other liquid from the mixed ionic-electric conductor mixture to form a porous mixed ionic-electric conductor layer (step 220).
  • Method 200 continues with forming an electronic insulator layer on the porous mixed ionic-electric conductor layer (step 230).
  • the electronic insulator layer may be formed by applying an electronic insulator mixture to the porous mixed ionic-electric conductor layer.
  • the electronic insulator mixture may be in the form of a liquid, slurry, or a paste.
  • the electronic insulator mixture may contain any compounds discussed herein with respect to the electronic insulator 20 as well as one or more solvents, and/or other additives.
  • the electronic insulator mixture may then be dried to remove any solvent present while on the mixed ionic-electric conductor layer.
  • the resulting bilayer polymer composite may be formed such that portions of the electronic insulator layer infiltrate pores of the mixed ionic-electric conductor layer.
  • the polymeric binder comprises poly (3, 4-ethylenedi oxythiophene) (PEDOT) / poly(ethylene oxide) (PEO) (“PEDOT/PEO”) blends, polyaniline / poly (ethylene oxide) (“PANi/PEO”) blends, or any type of blends of electronically conductive polymer and ionically conductive polymer.
  • the mixed ionic-electric conductor 30 may be inorganic, such as TiN with or without polymer, Lanthanum Strontium cobaltite, Ceria dopped with Gadolinium (GDC), etc. Numerous configurations and variations are possible and contemplated herein.
  • the electronic insulator 20 may contain a polyaziridine polymer and/or an ether-based electrolyte.
  • the electronic insulator 20 comprises, consists of, or consists essentially of crosslinked polyaziridine gelated within an ether-based electrolyte.
  • the electronic insulator 20 may be a distinct layer or may be partially or fully infiltrated into pores of the mixed ionic-electric conductor 30.
  • bilayer polymer composite 100 includes additional layers are also contemplated herein.
  • one or more additional layers may be positioned either: between the mixed ionic-electric conductor 30 and the electrode 40; between the mixed ionic-electric conductor 30 and the electronic insulator 20; and/or between the electronic insulator 20 and the separator 10.
  • a Li/Cu half-cell was tested with and without the disclosed bilayer polymer composite.
  • the bilayer tested had an MIEC layer formed of 20wt% silver nanoparticles, 60wt% conductive carbon black, and 20wt% of a polymer binder containing poly(vinylidene fluoridehexafluoropropylene) (referred to herein as “PVDF-HFP”).
  • PVDF-HFP poly(vinylidene fluoridehexafluoropropylene)
  • the El layer was a crosslinked polyaziridine gelated within an ether-based electrolyte.
  • the current density of the cell was 1.5 mA/cm 2 and the plating capacity was 1.5 mAh/cm 2 .
  • Testing data for the Coulombic efficiency of the cells are shown in FIGS. 3A and 3B.
  • FIG. 3A shows testing data for the cell with the bilayer polymer composite and
  • FIG. 3B shows comparative testing data for the cell without the bilayer.
  • FIGS. 4A and 4B show voltage profiles of the Li/Cu cell with and without a bilayer polymer composite.
  • FIG. 4A shows testing data for the cell with the bilayer polymer composite coating and
  • FIG. 4B shows comparative testing data for the cell without the bilayer polymer composite coating.
  • FIG. 5 improved cycle life testing is shown for full lithium-ion cells with Lithium Metal Anode vs Lithium Mixed Metal Oxide Cathodes (NMC).
  • the “Control” represents baseline cell testing without any bilayer polymer composite film applied.
  • the cycle life to 70% of the starting capacity was improved from 210 cycles (Control) up to 375 cycles with the Gen. 5 formulation.

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Abstract

A bilayer polymer composite for an electrochemical cell is described herein. The bilayer polymer composite includes a mixed ionic-electric conductor and an electronic insulator. The bilayer polymer composite is arranged to be positioned between the anode and separator of the cell. In select embodiments, the bilayer polymer composite may be formed through a coating process directly on the anode.

Description

BILAYER POLYMER COMPOSITE COATING FOR LITHIUM METAL ANODE
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to and the benefit of U.S. Provisional Patent Application Serial Number 63/528,538, filed July 24, 2023, titled “Bilayer Polymer Composite Coating for Lithium Metal Anode,” the entire contents of which are incorporated by reference herein.
BACKGROUND
Lithium metal anodes can be unstable in fuel cells. In particular, fuel cells with nickel- cobalt-manganese (NCM) cathodes and lithium anodes have low coulombic efficiency and short cycling life. Previously, different types of coatings have been applied to the surface of the lithium metal, including polymeric coatings, inorganic coatings, and polymer/inorganic composites in an attempt to promote stability of the lithium anode. However, this approach has not adequately addressed the issue.
SUMMARY
The present disclosure relates to a bilayer polymer composite for an electrochemical cell. The bilayer polymer composite may be directly coated onto the surface of an anode (such as lithium foil) to improve the stability of the lithium plating and stripping. As discussed in detail herein, lithium metal batteries that include the disclosed bilayer coating have exhibited improved cycle life and high-rate capabilities. Embodiments of the subject disclosure include a bilayer design that may be applied between the existing separator and the lithium metal or current collector (in the case of an anode- free cell), and then paired with an existing cathode. The separator can either be filled with liquid electrolytes or ionically conductive solid-state electrolytes. In the disclosed bilayer, the first layer positioned close to the anode side is an “MIEC” layer (i.e., a mixed ionic-electronic mixed conductor layer). In the bilayer, the layer that is closer to the separator side is an electronic insulator, but is ionically conductive (i.e., an electronic insulator layer or “El” layer).
In accordance with some aspects of the present disclosure, an electrochemical cell is disclosed having a separator, an anode, and a bilayer polymer composite positioned between the separator and the anode. The bilayer polymer composite includes a mixed ionic-electric conductor and an electronic insulator. In these and other implementations, the electronic insulator is in contact with the separator, and the mixed ionic-electric conductor is in contact with the anode and the electronic insulator. The anode of the electrochemical cell may include lithium metal or copper. In some embodiments, the bilayer polymer composite consists of the mixed ionic-electric conductor and the electronic insulator. The mixed ionic-electric conductor may have a porous structure, and the electronic insulator may be partially or fully infiltrated into pores of the mixed ionic-electric conductor. In these and other implementations, the electronic insulator includes a polyaziridine polymer and an ether-based electrolyte. The mixed ionic-electric conductor may include conductive particles and a polymeric binder. The polymeric binder may have a molecular weight higher than 2,000 g/mol. In some embodiments, the conductive particles may include silver nanoparticles and a conductive carbon. In these and other embodiments, the mixed ionic-electric conductor may include between 10-30 wt% silver nanoparticles and between 45-80 wt% conductive carbon. In select embodiments, the mixed ionic-electric conductor includes between 10-30 wt% of the polymeric binder.
In another aspect of the present disclosure, methods of forming a bilayer polymer composite on an electrode are described. The methods include applying a mixed ionic-electric conductor mixture to the electrode, drying the mixed ionic-electric conductor mixture to form a porous mixed ionic-electric conductor on the electrode, and applying an electronic insulator mixture to the porous mixed ionic-electric conductor to form the bilayer polymer composite. The electrode may be an anode, which, for example, may be implemented with a lithium foil. In some such embodiments, the mixed ionic-electric conductor mixture may be applied directly onto the lithium foil. The mixed ionic-electric conductor mixture may be applied as a paste, a slurry, or a liquid. Similarly, the electronic insulator mixture may also be applied to the porous mixed ionicelectric conductor in the form of a liquid, a slurry, or a paste. In these and other embodiments, at least some of the electronic insulator infiltrates pores of the porous mixed ionic-electric conductor. In addition to these embodiments, numerous other variations are possible and contemplated herein.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a sample bilayer polymer composite, configured in accordance with some embodiments of the present disclosure;
FIG. 2 illustrates a sample method of forming a bilayer polymer composite, in accordance with some embodiments of the present disclosure;
FIGS. 3A-3B show measured Coulombic efficiency data for various electrochemical cells. The cell tested in FIG. 3A includes a bilayer polymer composite configured in accordance with the present disclosure, and the cell tested in FIG. 3B is a comparative cell without a bilayer polymer composite;
FIGS. 4A-4B show measured voltage profiles for the cells tested in FIGS. 3 A and 3B. FIG. 4A shows the voltage profile of the cell tested in FIG. 3A and FIG. 4B shows the voltage profile of the cell tested in FIG. 3B; and
FIG. 5 shows the improved cycle life for full lithium-ion cells with Lithium Metal Anode vs Lithium Mixed Metal Oxide Cathodes (NMC) with the incorporation of improved generations of the bilayer polymer composite films. The “Control” represents cell testing without any bilayer polymer composite film applied.
DETAILED DESCRIPTION
A bilayer polymer composite is described herein. As described in additional detail below, the bilayer polymer composite may provide numerous advantages over previous electrochemical cells having a lithium anode. FIG. 1 illustrates a sample bilayer polymer composite 100 for an electrochemical cell. The bilayer polymer composite 100 is configured to be positioned between a separator 10 and an electrode 40 of an electrochemical cell. The bilayer polymer composite 100 includes an electronic insulator 20 and a mixed ionic-electric conductor 30. In some implementations, the electronic insulator 20 (at times referred to herein as “El”) and the mixed ionic-electric conductor 30 (at times referred to herein as “MIEC”) are distinct components. In other words, the chemical composition of the electronic insulator 20 is distinct from the chemical composition of the mixed ionic-electric conductor 30 in some embodiments. However, in other implementations, features of the electronic insulator 20 and the mixed ionic-electric conductor 30 are intermixed. For example, in embodiments in which the mixed ionic-electric conductor 30 is a porous structure, the electronic insulator 20 may be partially or fully infiltrated into pores of the mixed ionic-electric conductor 30.
The bilayer polymer composite 100 can provide numerous advantages for an electrochemical cell, specifically a cell having a lithium anode. For example, the electronic insulator 20 may promote adhesion between the mixed ionic-electric conductor 30 and the separator 10. In these and other embodiments, the electronic insulator 20 may also have lower electronic conductivity to make the interphase of the separator 10 and the mixed ionic-electric conductor 30 lithium-repellant. In some embodiments, the electronic insulator 20 may have one or more of the following properties: strong adhesiveness, high elasticity, toughness, ionic conductivity, denseness, low thickness, and/or electronic insulation.
The mixed ionic-electric conductor 30 may advantageously prevent side reactions between the electrolyte and the electrode material (i.e., lithium). Additionally, in select embodiments, the mixed ionic-electric conductor 30 may also provide sites for lithium plating within its pores. The mixed ionic-electric conductor 30 may also relieve stress attack from dendrites and/or guide lithium growth between the mixed ionic-electric conductor 30 and electronic insulator 20 interphase. The mixed ionic-electric conductor 30 may have one or more of the following properties: high porosity, high lithium wettability, high ionic conductivity, and/or high electronic conductivity.
The bilayer polymer composite 100 may be formed using any suitable formation or assembly process. In some implementations, the bilayer polymer composite 100 is formed using a sequential coating process. However, in other implementations, the bilayer polymer composite 100 may be created by forming each layer independently and then joining the layers together (for example, using an adhesive or a heating process). FIG. 2 illustrates a sample process 200 that may be used to form a bilayer polymer composite 100 directly on an electrode 40. As shown in FIG. 2, process 200 includes applying a mixed ionic-electric conductor mixture to an electrode (step 210). The mixed ionic-electric conductor mixture may include any compounds discussed herein with respect to the mixed ionic-electric conductor 30 as well as one or more solvents, and/or any desired additives. The electrode may be an anode or a cathode, as desired. The electrode may be in the form of a solid material. In select embodiments, the mixed ionic-electric conductor mixture is applied to a lithium metal anode. The mixed ionic-electric conductor mixture may be applied as a paste, slurry, or a liquid. The mixed ionic-electric conductor mixture may then be dried (while on the electrode). Drying the mixed ionic-electric conductor mixture involves removing any solvent or other liquid from the mixed ionic-electric conductor mixture to form a porous mixed ionic-electric conductor layer (step 220).
Method 200 continues with forming an electronic insulator layer on the porous mixed ionic-electric conductor layer (step 230). The electronic insulator layer may be formed by applying an electronic insulator mixture to the porous mixed ionic-electric conductor layer. The electronic insulator mixture may be in the form of a liquid, slurry, or a paste. The electronic insulator mixture may contain any compounds discussed herein with respect to the electronic insulator 20 as well as one or more solvents, and/or other additives. The electronic insulator mixture may then be dried to remove any solvent present while on the mixed ionic-electric conductor layer. The resulting bilayer polymer composite may be formed such that portions of the electronic insulator layer infiltrate pores of the mixed ionic-electric conductor layer.
The mixed ionic-electric conductor 30 may be include conductive particles and a polymeric binder. For example, in some embodiments, the mixed ionic-electric conductor 30 comprises, consists of, or consists essentially of: silver nanoparticles, a conductive carbon, and a polymeric binder. Various amounts and particle sizes of silver may be included in the mixed ionic-electric conductor 30. The conductive carbon may be carbon black, carbon nanotubes, graphene, amorphous carbon, or another form of conductive carbon. In select embodiments, the mixed ionicelectric conductor includes between 5-50 wt%, 10-30 wt%, 15-25 wt%, or approximately 20 wt% silver nanoparticles. In these and other embodiments, the mixed ionic-electric conductor includes between 45-80 wt%, 50-70 wt%, or approximately 60 wt% conductive carbon.
The mixed ionic-electric conductor 30 may contain between 10-30 wt%, 15-25 wt%, or approximately 20% of the polymeric binder. The polymeric binder in the mixed ionic-electric conductor 30 may be a single polymer or a mixture or two or more polymers. The mixed ionicelectric conductor 30 may include at least one polymeric binder with a molecular weight (MW) higher than 2,000 g/mol. In these and other embodiments, the mixed ionic-electric conductor 30 comprises one or more polymer inorganic hybrids and/or supramolecular networks. In some embodiments, the polymeric binder comprises poly (3, 4-ethylenedi oxythiophene) (PEDOT) / poly(ethylene oxide) (PEO) (“PEDOT/PEO”) blends, polyaniline / poly (ethylene oxide) (“PANi/PEO”) blends, or any type of blends of electronically conductive polymer and ionically conductive polymer. In these and other embodiments, the mixed ionic-electric conductor 30 may be inorganic, such as TiN with or without polymer, Lanthanum Strontium cobaltite, Ceria dopped with Gadolinium (GDC), etc. Numerous configurations and variations are possible and contemplated herein.
The electronic insulator 20 may contain a polyaziridine polymer and/or an ether-based electrolyte. In some embodiments, the electronic insulator 20 comprises, consists of, or consists essentially of crosslinked polyaziridine gelated within an ether-based electrolyte. The electronic insulator 20 may be a distinct layer or may be partially or fully infiltrated into pores of the mixed ionic-electric conductor 30.
Separator 10 may be any known type of separator 10 for an electrochemical cell. For example, the separator 10 may be formed of a polyolefin material. In these and other embodiments, the separator 10 may include one or more ceramic materials. Numerous types of separators 10 may be used with the disclosed bilayer polymer composite 100. The separator 10 may either be filled with liquid electrolytes or ionically conductive solid-state electrolytes, as desired.
The bilayer polymer composite 100 may be used in connection with any known type of electrode 40. Electrode 40 may be an anode or cathode, as desired. For example, the electrode 40 may be implemented with a lithium metal or a copper metal. The electrode 40 may be porous or non-porous. In some embodiments, the electrode 40 is a lithium metal, such as a lithium foil.
Various alternative embodiments aside from the embodiment illustrated in FIG. 1 are also contemplated herein. For example, embodiments in which the bilayer polymer composite 100 includes additional layers are also within the scope of the present disclosure. If present, one or more additional layers may be positioned either: between the mixed ionic-electric conductor 30 and the electrode 40; between the mixed ionic-electric conductor 30 and the electronic insulator 20; and/or between the electronic insulator 20 and the separator 10.
Experimental Testing
A Li/Cu half-cell was tested with and without the disclosed bilayer polymer composite. The bilayer tested had an MIEC layer formed of 20wt% silver nanoparticles, 60wt% conductive carbon black, and 20wt% of a polymer binder containing poly(vinylidene fluoridehexafluoropropylene) (referred to herein as “PVDF-HFP”).
The El layer was a crosslinked polyaziridine gelated within an ether-based electrolyte. The current density of the cell was 1.5 mA/cm2 and the plating capacity was 1.5 mAh/cm2. Testing data for the Coulombic efficiency of the cells are shown in FIGS. 3A and 3B. FIG. 3A shows testing data for the cell with the bilayer polymer composite and FIG. 3B shows comparative testing data for the cell without the bilayer.
FIGS. 4A and 4B show voltage profiles of the Li/Cu cell with and without a bilayer polymer composite. FIG. 4A shows testing data for the cell with the bilayer polymer composite coating and FIG. 4B shows comparative testing data for the cell without the bilayer polymer composite coating.
In FIG. 5, improved cycle life testing is shown for full lithium-ion cells with Lithium Metal Anode vs Lithium Mixed Metal Oxide Cathodes (NMC). The “Control” represents baseline cell testing without any bilayer polymer composite film applied. Through optimization work of the applied bilayer polymer composite formulation, the cycle life to 70% of the starting capacity was improved from 210 cycles (Control) up to 375 cycles with the Gen. 5 formulation.
As shown in FIGS. 3A-3B, FIGS. 4A-4B and FIG. 5, the protected lithium showed longer cycling life with more stable Coulombic efficiency. The disclosed bilayer protective coating significantly improved the cycling life and efficiency of lithium metal anode, and enabled plating between the protective coating and lithium metal or copper, rather than between the protective coating and the separator. Although the present inventive subject matter has been described with reference to particular embodiments, this description is not meant to be construed in a limiting sense. For example, various modifications of the disclosed embodiments as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon consideration of the present disclosure. It is therefore contemplated that the appended claims will cover any such modifications or embodiments that fall within the scope of the invention as described herein.

Claims

CLAIMS What is claimed is:
1. An electrochemical cell comprising: a separator; an anode; and a bilayer polymer composite positioned between the separator and the anode, wherein the bilayer polymer composite comprises a mixed ionic-electric conductor and an electronic insulator.
2. The electrochemical cell of claim 1, wherein the electronic insulator is in contact with the separator, and the mixed ionic-electric conductor is in contact with the anode and the electronic insulator.
3. The electrochemical cell of claim 1, wherein the anode comprises lithium metal or copper.
4. The electrochemical cell of claim 1, wherein the bilayer polymer composite consists of the mixed ionic-electric conductor and the electronic insulator.
5. The electrochemical cell of claim 1, wherein the mixed ionic-electric conductor has a porous structure, and the electronic insulator is partially or fully infiltrated into pores of the mixed ionic-electric conductor.
6. The electrochemical cell of claim 5, wherein the electronic insulator comprises a polyaziridine polymer and an ether-based electrolyte.
7. The electrochemical cell of claim 1, wherein the mixed ionic-electric conductor comprises conductive particles and a polymeric binder.
8. The electrochemical cell of claim 7, wherein the conductive particles comprise silver nanoparticles and a conductive carbon.
9. The electrochemical cell of claim 8, wherein the mixed ionic-electric conductor comprises between 10-30 wt% silver nanoparticles and between 45-80 wt% conductive carbon.
10. The electrochemical cell of claim 7, wherein the polymeric binder has a molecular weight higher than 2,000 g/mol.
11. The electrochemical cell of claim 7, wherein the mixed ionic-electric conductor comprises between 10-30 wt% of the polymeric binder.
12. A method of forming a bilayer polymer composite on an electrode, the method comprising: applying a mixed ionic-electric conductor mixture to the electrode; drying the mixed ionic-electric conductor mixture to form a porous mixed ionic-electric conductor on the electrode; and applying an electronic insulator mixture to the porous mixed ionic-electric conductor to form the bilayer polymer composite.
13. The method of claim 12, wherein the electrode is an anode.
14. The method of claim 12, wherein the electrode is a lithium foil and the mixed ionic- electric conductor mixture is applied directly onto the lithium foil.
15. The method of claim 14, wherein the mixed ionic-electric conductor mixture is applied as a paste, a slurry, or a liquid.
16. The method of claim 12, wherein the electronic insulator mixture is applied to the porous mixed ionic-electric conductor in the form of a liquid, a slurry, or a paste.
17. The method of claim 16, wherein at least some of the electronic insulator infiltrates pores of the porous mixed ionic-electric conductor.
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* Cited by examiner, † Cited by third party
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US11539045B2 (en) * 2017-11-13 2022-12-27 Lg Energy Solution, Ltd. Negative electrode for lithium secondary battery and lithium secondary battery comprising same

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