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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • 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
• • 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
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0568—Liquid materials characterised by the solutes
• • 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
  • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
• • 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
• • 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
  • 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
• • 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
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/582—Halogenides
• • 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

• Patent Application No. 62/676,693 entitled“Composite Electrode Materials for Fluoride-Ion Electrochemical Cells,” filed May 25, 2018. This application also claims priority to U.S. Patent Application No. 62/676,693. Each of the preceding applications is incorporated herein by reference in its entirety.
• the present disclosure relates to electro chemically active materials, and more particularly to fluoride ion battery systems that include electrode materials with tailored structures and compositions to improve batter performance. More specifically, this disclosure relates to core-shell nanoparticles, methods for making the same, and use of the same in electrochemical cells.
• Metal nanoparticles are highly desirable for use in a number of applications including as catalysts, and as electrode materials for batteries.
• the use of metal nanoparticles may be limited by the system operating conditions or other factors.
• fluoride shuttle batteries are of growing interest as an alternative to lithium-ion batteries.
• the materials available for use in fluoride shuttle battery systems are limited, due in part to operating conditions that are detrimental to many materials that could otherwise be included in the fluoride shuttle battery electrodes.
• Fluoride-ion batteries are electrochemical cells that operate via fluoride-mediated electrode reactions (i.e. accommodation or release of fluoride ions at the electrode upon charge or discharge, often through a conversion- type reaction).
• Such electrochemical cells can offer greater energy density, lower cost and/or improved safety characteristics compared to lithium and lithium-ion batteries.
• Fluoride-ion systems have been demonstrated in the solid state, for example, in US 7,722,993 to Potanin, which describes an embodiment of a secondary electrochemical cell where fluoride ions are reversibly exchanged between anode and cathode during charge-discharge cycles, with these electrodes in contact with a solid-state fluoride-conducting electrolyte.
• Potanin describes solid state electrolytes containing fluorides of La, Ce or the compound fluorides based on them, together with an alloying additives, such as fluoride/fluorides of alkaline-earth metals (CaF2, SrF2, BaF2) and/or fluorides of alkaline metals (LiF, KF, NaF) and/or alkaline metal chlorides (LiCl, KC1, NaCl), as well as a wide range of other compound fluorides.
• an alloying additives such as fluoride/fluorides of alkaline-earth metals (CaF2, SrF2, BaF2) and/or fluorides of alkaline metals (LiF, KF, NaF) and/or alkaline metal chlorides (LiCl, KC1, NaCl), as well as a wide range of other compound fluorides.
• CaF2, SrF2, BaF2 alkaline-earth metals
• LiF, KF, NaF alka
• the present disclosure is directed to an electro chemically active structure, comprising: a core comprising an active material, and a fluoride-containing shell at least partially surrounding the active material, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is barium.
• the present disclosure is directed to a method of making coated metal nanoparticles, the method comprising: a) providing a water/metal nanoparticle mixture; b) exposing the water/metal nanoparticle mixture to an inert atmosphere; and c) forming a fluoride-containing shell around a metal nanoparticle core, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is barium.
• the present disclosure is directed to an electrode comprising: a core comprising copper nanoparticles, and a fluoride containing shell at least partially surrounding the copper nanoparticles, wherein the fluoride-containing shell comprises barium and lanthanum in a ratio of x to l-x, such that a sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1.
• the present disclosure is directed to an electro chemically active structure, comprising: a core comprising an active material, and a fluoride-containing shell at least partially surrounding the active material, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is a divalent or tetravalent metal cation.
• FIG. 1A shows a cross section of a core-shell nanoparticle including a core comprising a metal nanoparticle, and a shell comprising a metal halide or a metal oxyhalide in an aspect of the present disclosure.
• FIG. IB outlines a general route to "yolk-shell" composites using a sacrificial inorganic "middle” layer.
• FIG. 1C describes a route to "yolk-shell" composites using a sacrificial polymer "middle” layer.
• FIG. ID delineates an alternative route a route to "yolk-shell" composites in the absence of a sacrificial "middle” layer.
• FIG. IE depicts a variation on “sacrificial” syntheses of "yolk-shell” composites, whereby nanoparticles of the active material are grown on the surface of a "sacrificial" material
• FIG. IF outlines the growth of active material in the internal structure or pores of a pre- formed "sacrificial" material
• FIG. 1G outlines the growth of active material in the internal structure or pores of a pre- formed "sacrificial" material where the shell constituents are chosen to be electrochemically-inactive at the electrochemical reaction potentials of interest.
• FIG. 2 is a schematic illustration of a fluoride ion electrochemical cell in an aspect of the present disclosure.
• FIG. 3 shows an XRD spectrum of isolated copper nanoparticles of Comparative Example 1, with no shell, immediately after synthesis and isolation (“as-made”).
• FIG. 4 shows stacked XRD spectra of isolated copper nanoparticles of Comparative Example 1, with no shell, as-made and after exposure to air for 4 days and 9 days.
• FIG. 5 shows an XRD spectrum of Cu-LaFs core-shell nanoparticles of Experimental Example 1 as synthesized in an aspect of the present disclosure.
• FIG. 6 shows stacked XRD spectra of Cu-LaFs core-shell nanoparticles of Experimental Example 1 after exposure to air for 9, 16, and 23 days.
• FIGS. 7 A and 7B are transmission electron microscopy (TEM) images of Cu-LaFs core- shell nanoparticles of Experimental Example 1, as-made.
• FIG. 8A shows a high-resolution TEM image of Cu-LaFs core-shell nanoparticles of Experimental Example 1, indicating the Cu (core) and LaF 3 (shell) areas.
• FIGS. 8B and 8C show zoomed-out images of the same nanoparticles.
• FIG. 9 is a schematic of illustration of a fluoride ion electrochemical cell including the Cu-LaFs core-shell nanoparticle of Experimental Example 1 as an active material in the negative electrode (anode) in an aspect of the present disclosure.
• FIG. 10A is a plot of voltage as a function of specific capacity for electrochemical tests of a half cell battery including the Cu-LaFs core-shell nanoparticle of Experimental Example 1 as an active material in an electrode in an aspect of the present disclosure.
• FIG. 10B is an X-ray diffraction spectrum of the electrode of the half cell battery test of FIG. 10A, measured under initial conditions, after discharge, and after charge.
• FIG. 11 shows an XRD spectrum of nanoparticles of Comparative Example 2 as synthesized.
• FIG. 12 shows stacked XRD spectra of nanoparticles of Comparative Example 2 after exposure to air for 8, 15, and 22 days.
• FIG. 13 is a TEM image of the nanoparticles of Comparative Example 2 showing inhomogeneous, partial coverage of copper nanoparticles with LaF 3 , as well as LaF 3 that is not associated with copper nanoparticles.
• FIG. 14 shows LaF 3 /Cu and Cu thin-film configurations and cyclic voltammetry data.
• FIG. 15A shows a cyclic voltammogram for a LaF 3 /Cu double-layered thin film.
• FIGS. 15A shows a cyclic voltammogram for a LaF 3 /Cu double-layered thin film.
• 15B and 15C show x-ray photoelectron spectroscopy (XPS) data for C, La, O, F, and Cu at various length of etching times at the voltages 1 and 2 indicated in FIG. 15A.
• XPS x-ray photoelectron spectroscopy
• FIG. 16 shows schematic representations of Cu@LaF 3 and Cu@Ba x Lai -x F 3-x nanoparticles according to some aspects of the present disclosure.
• FIG. 17A shows an example of a scanning electron microscopy (SEM) image of Cu@Lao.97Ba 0.03 F2.97 according to some aspects of the present disclosure.
• FIGS. 17B-C shows examples of transmission electron microscopy (TEM) images of Cu@Lao.97Ba 0.03 F2.97 according to some aspects of the present disclosure.
• FIG. 17D shows an example of an energy dispersive x-ray (EDX) image of Cu@Lao .97 Ba 0.03 F 2.97 according to some aspects of the present disclosure.
• FIGS. 17E-H show the component Cu, F, La, and Ba image maps, respectively.
• FIGS. 18A-D show x-ray photoelectron spectroscopy (XPS) spectra for Cu@Lao.97Ba 0.03 F2.97 according to some aspects of the present disclosure.
• FIG. 19 shows XRD spectra for Cu@LaF 3 and Cu@La 0.97 Ba 0.05 F 2.97 according to some aspects of the present disclosure.
• FIG. 20A shows the voltage profile of the first charge-discharge cycle of a Cu@LaF 3 electrode or a Cu@Ba x Lai -x F 3-x electrode, compared to the Ag/Ag + reference electrode, according to some aspects of the present disclosure .
• FIG. 20B shows a comparison of the capacity achieved for Cu@LaF 3 and for Cu@Lao.97Ba 0.03 F2.97 according to some aspects of the present disclosure.
• FIG. 20C shows XRD spectra of Cu@La 0.97 Ba 0.05 F 2.97 in initial condition and after a first charge and a subsequent first discharge, according to some aspects of the present disclosure.
• FIG. 20D shows XRD spectra of Cu@LaF 3 in initial condition and after a first charge and a subsequent first discharge, according to some aspects of the present disclosure.
• the present disclosure is related to electrochemically active materials, and fluoride-ion battery systems that include electrode materials with tailored structures and compositions to improve battery performance.
• the present disclosure is related to core-shell nanoparticles, devices incorporating the core-shell nanoparticles, as well as methods of making and using the core-shell nanoparticles and devices including the core-shell nanoparticles.
• Primary and secondary electrochemical cells such as batteries, utilizing fluoride ion charge carriers, active electrode materials, and suitable liquid electrolytes can provide an alternative to conventional state of the art lithium batteries and lithium ion batteries.
• fluoride-ion battery (FIB) systems can operate usefully at room temperature while utilizing fluoride anions carried in a liquid electrolyte as at least some of the charge carriers in an electrochemical cell.
• the FIB system has an anode and cathode physically separated from each other, but in common contact with a fluoride ion conducting electrolyte.
• the anode is typically a low potential element or compound, and can be a metal, metal fluoride, or intercalating composition.
• the cathode can be element or composition, and can be a metal, metal fluoride, or intercalating composition that has a higher potential than the anode.
• Fluoride ions (F ) in the fluoride conducting electrolyte go from the cathode to the anode during discharge and from the anode to the cathode during the charge of the battery:
• FIB cell reaction based on fluoride anion transfer between Ca and Cu both metals capable of forming metal fluorides, might be:
• the metal or metal fluoride active materials are nano-sized (i.e. at least one of the particle size dimensions is less than 1 pm).
• particles with such small dimensions have high surface energies and are often reactive with the electrolyte components (e.g. F ) to give undesirable side-reactions including "self-discharge” (i.e. a chemical reaction such as M + nF MF n that does not general electrical current).
• self-discharge i.e. a chemical reaction such as M + nF MF n that does not general electrical current.
• the encapsulating material can also protect the active materials from such side-reactions, enabling long-term cycling stability of these electrode materials.
• compositions and processes that protect the electrode active material from side reactions with the electrolyte, allow ion conduction through an encapsulant, and have sufficient void space within the encapsulant and/or encapsulant expansion/contraction properties to accommodate the volume changes of the active material during charge and discharge without permitting direct contact between the active material and the electrolyte.
• sufficient void space may be no void space.
• the term“about” is defined to being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the term“about” is defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.
• the core-shell nanoparticles include a core that comprises a metal or metal alloy (“Me”), and a shell that comprises a metal halide or a metal oxyhalide.
• the metal of the core may be the same as the metal of the metal halide shell.
• the metal of the core and the metal of the metal halide or metal oxyhalide shell are different metals.
• the metal halide shell may itself comprise two metals.
• the core-shell nanoparticles of the present disclosure may be incorporated into a variety of methods and applications including, but not limited to, electrodes for use in electrochemical cells, including fluoride shuttle batteries as shown in FIG. 2.
• the metals or metal alloys used to form the core include, but are not limited to, iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles, and alkaline earth metal nanoparticles.
• the metal nanoparticles are selected from the group consisting of cobalt nanoparticles and copper nanoparticles.
• the metal nanoparticles are copper nanoparticles.
• the metals used to form the core may be synthesized by mixing a metal precursor solution with a reducing agent to form metal nanoparticles.
• the metal nanoparticles used to form the core may be synthesized in the presence of a stabilizer that prevents or otherwise inhibits oxidation of the metal nanoparticles during synthesis, and is readily removable from the metal nanoparticles prior to formation of the metal halide or metal oxyhalide shell thereon.
• a stabilizer that prevents or otherwise inhibits oxidation of the metal nanoparticles during synthesis, and is readily removable from the metal nanoparticles prior to formation of the metal halide or metal oxyhalide shell thereon.
• bulky polymers such as polyvinylpyrrolidone (molecular weight of 55,000 g/mol) used during metal nanoparticle synthesis inhibit oxidation of metal nanoparticles.
• stabilizers are not readily removable from the metal nanoparticles following synthesis.
• residual stabilizer can form an additional layer between the core formed by the metal nanoparticles and the metal halide or oxyhalide shell that detracts from the performance of the core-shell nanoparticle in the desired system. For example, it is desirable to maintain the conductivity of core-shell nanoparticles used as electrode material in an F-Shuttle battery.
• core-shell materials including an additional layer of residual stabilizer between the core and the shell will likely result in an increased space between electrode materials; the additional layer of residual stabilizer and/or the resulting increased space may decrease the conductivity of the core-shell material.
• the additional layer of stabilizer may impede contact between the core and the shell to conduct fluoride ion, while the absence of the stabilizer may increase the likelihood of conducting fluoride ion from the core to the shell.
• a stabilizer may be used in the synthesis of the metal nanoparticles used to form the core that is readily removable therefrom to minimize the amount of stabilizer on the surface of the core prior to formation of the metal halide or metal oxyhalide shell directly thereon.
• the one or more stabilizers that may be used in the synthesis of the metal nanoparticles includes a molecular weight (either individually or a weight average) of less than 1000 g/mol, optionally less than 500 g/mol, optionally less than 375 g/mol, and optionally less than 350 g/mol.
• Illustrative examples include hexadecyltrimethylammonium bromide (CTAB) with a molecular weight of 364 g/mol, citric acid with a molecular weight of 192 g/mol, and mixtures thereof.
• CTAB hexadecyltrimethylammonium bromide
• the shell of the core-shell nanoparticles may be formed by mixing isolated metal nanoparticles used to form the core with, for example, a metal salt solution and a halide salt solution that react to form the metal halide shell on the core.
• the shell is deposited directly on the metal core and may entirely surround the core as shown in FIG. 1 A.
• the metal salt used to form the shell is selected from the group consisting of alkali metal salts, alkaline earth metal salts, and transition metal salts.
• the metal salt used to form the shell is a transition metal salt.
• the metal salt used to form the shell is selected from the group consisting of lanthanum salts, cerium salts, and magnesium salts.
• the metal salt used to form the shell is selected from the group consisting of lanthanum salts and cerium salts.
• the metal salt is a lanthanum salt.
• the lanthanum salt is lanthanum nitrate.
• the halide salt is sodium fluoride.
• the shell comprises a metal fluoride or metal oxyfluoride containing material (i.e. CeF 3 , CeOF, LaOF, LaF 3 ).
• the metal salt solution comprises two metal salts. In some such embodiments, one of the two metal salts is a barium salt. In some embodiments, the metal salt solution comprises a barium salt and a lanthanum salt. In some embodiments, the metal salt solution comprises barium nitrate and lanthanum nitrate. In some embodiments, the metal salt solution comprises barium nitrate and lanthanum nitrate in a ratio of about 1 : 10.
• the core (or electrode active material) may be separated from the shell (or encapsulant) by a void space.
• Compositions and processes according to such embodiments may protect the electrode active material from side reactions with the electrolyte, allow ion conduction through an encapsulant, and have sufficient void space within the encapsulant and/or encapsulant expansion/contraction properties to accommodate the volume changes of the active material during charge and discharge, without permitting direct contact between the active material and the electrolyte.
• core and electrode active material are used interchangeably herein.
• shell and encapsulant are used interchangeably herein.
• the present disclosure is directed to an electrode comprising the core-shell nanoparticles disclosed herein. All aspects and embodiments described with respect to the core-shell nanoparticles and methods of making thereof apply with equal force to the electrode.
• the electrode is part of an F-shuttle battery system.
• the present disclosure is directed to an electro chemically active structure, comprising: a core comprising an active material, and a fluoride-containing shell at least partially surrounding the active material, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is barium. All aspects described with respect to the aforementioned embodiments apply to the present embodiment with equal force, and vice versa.
• the active material comprises metal nanoparticles selected from iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles, and alkaline earth metal nanoparticles.
• the active material comprises copper nanoparticles.
• the fluoride-containing shell is directly attached to the core.
• the fluoride-containing shell is spaced from the core so as to define a void space therebetween.
• the second metal is lanthanum.
• the barium and the lanthanum are present in a ratio of x to l-x, such that a sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1.
• x is about 0.03 to about 0.15.
• x is about 0.03.
• the present disclosure is directed to a method of making coated metal nanoparticles, the method comprising: a) providing a water/metal nanoparticle mixture; b) exposing the water/metal nanoparticle mixture to an inert atmosphere; and c) forming a fluoride-containing shell around a metal nanoparticle core, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is barium. All aspects described with respect to the aforementioned embodiments apply to the present embodiment with equal force, and vice versa.
• the metal nanoparticles comprise iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles, or alkaline earth metal nanoparticles.
• the metal nanoparticles comprise copper nanoparticles.
• the fluoride-containing shell is directly attached to the core.
• the fluoride-containing shell is spaced from the core so as to define a void space therebetween.
• the second metal is lanthanum.
• the barium and the lanthanum are present in a ratio of x to l-x, such that a sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1.
• x is about 0.03 to about 0.15.
• the forming the fluoride-containing shell comprises adding a first metal salt, a second metal salt, and a fluoride-containing salt to the water/metal nanoparticle mixture to create a fluoride-containing shell around the metal nanoparticle core, wherein the first metal is a barium salt.
• the second metal is a lanthanum salt.
• the first metal salt is barium nitrate and the second metal salt is lanthanum nitrate.
• the barium nitrate and the lanthanum nitrate are used in a molar ratio of about 1:10.
• the present disclosure is directed to an electrode comprising: a core comprising copper nanoparticles, and a fluoride containing shell at least partially surrounding the copper nanoparticles, wherein the fluoride-containing shell comprises barium and lanthanum in a ratio of x to l-x, such that a sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1. All aspects described with respect to the aforementioned embodiments apply to the present embodiment with equal force, and vice versa.
• x is about 0.03 to about 0.15.
• the present disclosure is directed to a fluoride shuttle battery comprising the electrode and a liquid electrolyte.
• the present disclosure is directed to an electrochemically active structure, comprising: a core comprising an active material, and a fluoride-containing shell at least partially surrounding the active material, wherein the fluoride-containing shell comprises a first metal and a second metal, and the first metal is a divalent or tetravalent metal cation. All aspects and embodiments described with respect to the aforementioned embodiments apply to the present embodiment with equal force, and vice versa.
• the fluoride-containing shell may be doped with barium (i.e., to make a barium- doped shell) or with any possible divalent or tetravalent metal cation (i.e., to make a divalent metal cation-doped shell or a tetravalent metal cation-doped shell); in other words, the doping is not limited to doping with barium.
• An“inert atmosphere” refers to a gaseous mixture that contains little or no oxygen and comprises inert or non-reactive gases or gases that have a high threshold before they react.
• An inert atmosphere may be, but is not limited to, molecular nitrogen or an inert gas, such as argon, or mixtures thereof.
• A“reducing agent” is a substance that causes the reduction of another substance, while it itself is oxidized. Reduction refers to a gain of electron(s) by a chemical species, and oxidation refers to a loss of electron(s) by a chemical species.
• A“metal salt” is an ionic complex wherein the cation(s) is(are) a positively charged metal ion(s) and the anion(s) is(are) a negatively charged ion(s).“Cation” refers to a positively charged ion, and“anion” refers to a negatively charged ion.
• the anion may be any negatively charged chemical species.
• Metals in metal salts according to the present disclosure may include but are not limited to alkali metal salts, alkaline earth metal salts, transition metal salts, aluminum salts, or post-transition metal salts, and hydrates thereof.
• Alkali metal salts are metal salts in which the metal ions are alkali metal ions, or metals in Group I of the periodic table of the elements, such as lithium, sodium, potassium, rubidium, cesium, or francium.
• Alkaline earth metal salts are metal salts in which the metal ions are alkaline earth metal ions, or metals in Group II of the periodic table of the elements, such as beryllium, magnesium, calcium, strontium, barium, or radium.
• Transition metal salts are metal salts in which the metal ions are transition metal ions, or metals in the d-block of the periodic table of the elements, including the lanthanide and actinide series.
• Transition metal salts include, but are not limited to, salts of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, i
• “Post-transition metal salts” are metal salts in which the metal ions are post-transition metal ions, such as gallium, indium, tin, thallium, lead, bismuth, or polonium.
• A“halide salt” is an ionic complex in which the anion(s) is(are) halide ion(s), including but not limited to fluoride ion(s), chloride ion(s), bromide ion(s), and iodide ion(s).
• a “fluoride salt” is an ionic complex in which the anion(s) is(are) fluoride ion(s). According to the present disclosure, the cation of the halide salt or the fluoride salt may be any positively charged chemical species.
• A“metal fluoride” is an ionic complex in which the cation is one or more metal ion(s) and the anion(s) is(are) fluoride ion(s). According to some aspects of the present disclosure, the metal salt(s) and the fluoride salt react to create a metal fluoride shell around the metal nanoparticle core.
• a“metal halide” is an ionic complex in which the cation is one or more metal ion(s) and the anion(s) is(are) halide ion(s).
• A“fluoride-containing” salt is an ionic complex in which the anion(s) contain fluoride ion but are not limited to being solely fluoride. Instead,“fluoride-containing” salts include ionic complexes where the anion(s) contain fluoride itself in complex with other ions or atoms.“Fluoride-containing” salts suitable for use in aspects of the present disclosure include those known to persons of ordinary skill in the art, including, but not limited to, fluoride salts, non-metal fluoroanions such as tetrafluoroborate salts and hexafhiorophosphate salts, and oxyfluoride salts.
• the fluoride-containing salts may include quaternary ammonium fluorides and fluorinated organic compounds. According to some aspects of the present disclosure, the metal salt and the fluoride-containing salt react to create a fluoride-containing shell around the metal nanoparticle core.
• Electrode refers to an electrical conductor where ions and electrons are exchanged with an electrolyte and an outer circuit.
• “Positive electrode” and“cathode” are used synonymously in the present description and refer to the electrode having the higher electrode potential in an electrochemical cell (i.e. higher than the negative electrode).
• “Negative electrode” and“anode” are used synonymously in the present description and refer to the electrode having the lower electrode potential in an electrochemical cell (i.e. lower than the positive electrode).
• Cathodic reduction refers to a gain of electron(s) of a chemical species
• anodic oxidation refers to the loss of electron(s) of a chemical species.
• Positive and negative electrodes of the present invention may be provided in a range of useful configurations and form factors as known in the art of electrochemistry and battery science, including thin electrode designs, such as thin film electrode configurations. Electrodes are manufactured as known in the art, including as disclosed in, for example, U.S. Pat. No. 4,052,539, and Oxtoby et al., Principles of Modem Chemistry (1999), pp. 401-443.
• Electrochemical cell refers to devices and/or device components that convert chemical energy into electrical energy or vice versa. Electrochemical cells have two or more electrodes (e.g., positive and negative electrodes) and an electrolyte, wherein electrode reactions occurring at the electrode surfaces result in charge transfer processes. Electrochemical cells include, but are not limited to, primary batteries, secondary batteries, and electrolysis systems. General cell and/or battery construction is known in the art (see, e.g., Oxtoby et al., Principles of Modern Chemistry (1999), pp. 401-443).
• Electrode refers to an ionic conductor which can be in the solid state, the liquid state (most common), or more rarely a gas (e.g., plasma).
• a core-shell nanoparticle that comprises a metal core that is surrounded by a metal halide or a metal oxyhalide shell.
• the core-shell nanoparticle may be included in an electrode of a rechargeable battery, such as an F-shuttle battery.
• a halide shell is provided that is tailored to protect the metal core nanoparticle from the environment of the electrode while maintaining the desired performance of the metal nanoparticle.
• the core may comprise copper metal and the shell may comprise LaF 3 .
• the core may comprise copper metal, and the shell may comprise Ba x Lai- x F3- x .
• a method of making the core-shell nanoparticle may comprise providing a first mixture comprising a metal nanoparticle and a reducing agent, and mixing the first mixture with a solution comprising one or more metal salts and a halide salt to form a metal halide or oxyhalide shell on the metal nanoparticles.
• the solution comprises a metal salt and a halide salt.
• the solution comprises two metal salts and a halide salt.
• one of the two metal salts is a barium salt.
• the two metal salts comprise a barium salt and a lanthanum salt.
• metal nanoparticles for use as the metal core may be synthesized by reacting a metal salt solution with a reducing agent in the presence of one or more stabilizers.
• the metal salt solution comprises a copper (II) nitrate hemipentahydrate (Cu(N0 3 ) 2‘ 2.5H 2 0) as the metal salt.
• the metal salt is mixed with CTAB and water, and the pH of the mixture may be adjusted to a pH of about 10 - 11, with for example, ammonium or sodium hydroxide.
• the reducing agent Prior to addition of the reducing agent to the metal salt solution, the reducing agent may be mixed with one or more stabilizers and water, and mixed for a period of time, such as twenty minutes, prior to combining with the metal salt solution.
• the reducing agent is selected from the group consisting of hydrazine, sodium borohydride, sodium cyanoborohydride, sodium dithionate, sodium dithionite, iron (II) sulfate, tin (II) chloride, potassium iodide, oxalic acid, formic acid, ascorbic acid, thiosulfate salts, dithionate salts, phosphorous acid, phosphite salts, and hypophosphite salts.
• the reducing agent is hydrazine.
• the metal salt solution and the reducing agent are combined to form the metal nanoparticles.
• Synthesis of the metal nanoparticles is performed in an atmosphere free of oxygen.
• atmospheres free of oxygen include, but are not limited to, nitrogen, argon, helium, hydrogen, and mixtures thereof.
• the metal nanoparticles are isolated from the synthesis solution. It is to be understood that the method of isolating the metal nanoparticles is not limited, and may include one or more techniques such as filtering, decanting, and centrifuging.
• the metal nanoparticles may be washed one or more times with a solvent, such as ethanol, to remove any residual stabilizer or other organic material from the surface thereof.
• the isolated metal nanoparticles may be redispersed in an aqueous solution containing additional reducing agent under an atmosphere that is free of oxygen.
• the mixture containing the isolated metal nanoparticles and reducing agent is then mixed under an atmosphere free of oxygen with a metal salt solution and a halide salt solution used to form the metal halide shell on the metal nanoparticle core.
• the metal salt solution and the fluoride salt solution used to form the shell may be added sequentially to the nanoparticle mixture, or the metal salt solution and the fluoride salt solution used to form the shell may be added simultaneously to the nanoparticle mixture.
• the metal salt solution comprises a single metal salt. In other aspects, the metal salt solution comprises two metal salts.
• the metal salt solution comprises a barium salt. In some such aspects, the metal salt solution comprises a barium salt and a lanthanum salt. In some such aspects, the metal salt solution comprises barium nitrate and lanthanum nitrate. In some such aspects, the metal salt solution comprises barium nitrate and lanthanum nitrate in a ratio of about 1:10.
• Useful protective encapsulating coatings include fluoride-ion conducting phases that are chemically and electrochemically stable in the presence of a liquid FIB electrolyte. Such phases permit the exchange of F- between the electrolyte and the active material. Suitable phases are known in the art and are described, for example, in "The CRC Handbook of Solid State Electrochemistry", Chapter 6 (CRC, 1997, P. J. Gellings and H. J. M. Bouwmeester, Eds.), Sorokin and Sobolev, Crystallography Reports 2007, 52, 5, 842-863, Sobolev et. ah, Crystallography Reports 2005,50, 3, 478-485, and Tmovcova et.
• crystalline phases such as LaF 3 , CaF 2 , SnF 2 , PbF 2 , PbSnF 4 , analogous doped and/or solid solution phases (e.g. Lao . 9Bao . 1Fx9, Cao . sYo .2 F 2.2 , Cao . 5Bao . 5Fx and Pbo . 75Bio . xFxx), glassy phases such as 35InF 3‘ 30SnF 2 -35PbF 2 , and mixed fluoride/other anion phases such as LaOF.
• crystalline phases such as LaF 3 , CaF 2 , SnF 2 , PbF 2 , PbSnF 4
• analogous doped and/or solid solution phases e.g. Lao . 9Bao . 1Fx9, Cao . sYo .2 F 2.2 , Cao . 5Bao . 5Fx and Pbo . 75Bio
• any material or phase that permits the exchange of F- between the electrolyte and the active material, with bulk ionic conductivity above 10-10 S/cm at 298K is within the scope of the invention.
• These phases are chosen with constituents selected to be electrochemically stable at the potentials required for reaction of the species contained within the coatings by considering the standard redox potentials of the shell constituents and the inner species available in standard texts. See the example of FIG. 1G for a more detailed discussion of the selection of coating constituents in this regard.
• Alternative protective coatings include polymers that are conducting for fluoride ions, for example boronate-functionalized polymers, alkylammonium-functionalized polymers, or those featuring suitable functional groups such as those described in Gorski et. al., Anal. Chim. Acta 2009, 633, 181-187 and Gorski, et ah, Anal. Chim.
• the thickness of the protective coating is chosen so that exchange of F- between the electrolyte and the active material occurs on a timescale such that charge/discharge of the electrochemical cell can be achieved at suitable rates of operation around 298K (e.g C-rate, corresponding to full charge or discharge of the energy stored in the electrochemical cell in one hour), and will depend on the ionic conductivity of the coating material or phase.
• a coating of LaF 3 or Ba x Lai- x F3- x is most usefully between 1-200 nm thick, such as between about 5 nm and about 20 nm thick, or any integer or subrange in between. More generally, the coating thickness can be from about 1 nm to about 1 pm.
• the coating can be made by any suitable method of synthesis. These may include solution chemistry techniques such as the formation of the coating by precipitation of a solid from a solution containing the fluoride or its constituent precursors, sol-gel or other soft chemistry or "chimiezing" methods, hydrothermal synthesis, vacuum methods such as chemical vapor deposition, physical vapor deposition, sputtering, laser ablation and molecular beam epitaxy, electrochemical deposition, or fluorination of a material after deposition by reaction with a fluorine source.
• solution chemistry techniques such as the formation of the coating by precipitation of a solid from a solution containing the fluoride or its constituent precursors, sol-gel or other soft chemistry or “chimieless" methods, hydrothermal synthesis, vacuum methods such as chemical vapor deposition, physical vapor deposition, sputtering, laser ablation and molecular beam epitaxy, electrochemical deposition, or fluorination of a material after deposition by reaction with a fluorine source.
• one preferred method for the preparation of a LaF 3 coating is a sol-gel synthesis similar to those described in Riidiger and Kemnitz, Dalton Trans., 2008, 1117-1127 and Fujihara et ah, J. Ceram. Soc. Japan, 1998, 106, 124-126, using soluble lanthanum and fluorine sources in a suitable solvent (for example, La(CH 3 COO) 3 and CF 3 COOH in water).
• a suitable solvent for example, La(CH 3 COO) 3 and CF 3 COOH in water.
• the coating as prepared may, optionally, be subjected to elevated temperature either in air or inert gas such as Ar for an annealing step, as desired.
• a LaF 3 coating prepared by the sol-gel method may be heated to 500 °C in air to anneal the coating and assist with removal of impurities such as solvent.
• fluoride-conducting coating phases may be synthesized as desired by adjusting the precursor materials, their stoichiometric ratios, and the post initial reaction annealing step.
• This sol-gel synthesis of the LaF 3 coating may also modified to prepare a coating of Ba x La l-x F 3-x , by methods known to those of ordinary skill in the art.
• the LaF 3 coating can be obtained from precipitation, by slowly adding NH 4 F into La(N0 3 ) 3 aqueous solution with nanoparticles of the core material suspended therein. Since LaF 3 is extremely insoluble in water, its crystallization will start on the surface of the suspended nanoparticles.
• the precipitation synthesis of the LaF 3 coating may also be modified to prepare a coating of Ba x Lai- x F3- x , by methods known to those of ordinary skill in the art.
• a sol-gel approach can be used to make a La 2 C> 3 coating, followed by post-fluorination using F 2 or HF to convert a substantial portion of this oxide to LaOF and/or LaF3.
• This sol-gel approach may also be used to prepare a coating of Ba x Lai- x F3- x, by methods known to those of ordinary skill in the art.
• Fluoride-conducting encapsulants and/or coating phases and materials may be prepared on a three-dimensional structure (e.g. a metal or metal fluoride nanoparticle, or aggregate of nanoparticles), a two-dimensional structure (e.g. a metal or metal fluoride thin film), or a one-dimensional structure (e.g. a fiber or tube of metal or metal fluoride) as required.
• fluoride-conducting phases maybe prepared on the external and/or internal surfaces of complex micro- or mesoporous structures such as a zeolite or highly ordered templated material. This can include, but is not limited to mesoporous silicas such as MCM-41 or SBA-15, or metal-organic frameworks or similar coordination polymers (ii) Active materials encapsulated within a fluoride-ion conductive coating
• Useful structures and compositions include those in which a metal or metal fluoride is encapsulated within a fluoride-ion conductive coating (as described in (i) above) such that there exists sufficient void space within the encapsulation for the volume change between metal and metal fluoride phases (or, between a lower-valent metal fluoride species MFm and a higher-valent metal fluoride species MFn where n>m for the same metal M) to be accommodated upon conversion without rupture of the coating phase or material.
• a fluoride-ion conductive coating as described in (i) above
• Such structures and compositions are sized to fit within an fluoride conducting encapsulant, in certain cases with at least enough void space available for up to 100% of the encapsulated metal atoms to be converted to the appropriate metal fluoride phase (e.g. for the process Fe FeF3 at least 211% void space is required compared to the starting volume of Fe, from Table 1).
• the degree of conversion may be controlled electrochemically (e.g. by controlling the voltage limits and/or charge/discharge capacity) so that the encapsulant does not rupture during cycling in the cases whereby there is not enough void space for 100% conversion to be achieved.
• compositions are also contemplated where the fluoride conducting encapsulant is conformal or has a void space insufficient to fully accommodate conversion from the metal to metal fluoride, but has suitable flexibility to stretch or contract without rupture or cracking of the encapsulant.
• Such compositions may be two-dimensional (e.g. film-void-coating), or three-dimensional (e.g. nanoparticle- void-coating, or a more complex arrangement such as metal-impregnated zeolite-void- coating) as desired.
• multiple, concentrically arranged encapsulants are contemplated.
• the respective concentrically arranged encapsulants can be separated by voids, and may be constructed of the same or different materials.
• the active material and the outermost encapsulant may be separated by a polymer or other flexible material that is able to permit the passage of fluoride ions and is dimensionally able accommodate the volume changes upon cycling with rupturing the outermost encapsulant.
• an active material completely surrounded and positioned within an encapsulant, but with at least some remaining void space and/or compressible non-active material (such as a polymer) can be referred to as a "yolk-shell" nanocomposite structure.
• Such fully encapsulated structures can be based on various compositional arrangements of active material and fluoride-conducting encapsulant. However, other arrangements that include an active material only partially surrounded by a fluoride-conducting protective coating are also contemplated.
• Such structures may include two or three dimensional non-fluoride conducting support structures (e.g.
• Such support structures can include void space or dimensionally flexible polymer or other material to accommodate the volume changes upon cycling without rupturing the support structure or the encapsulant.
• Cu metal or CuF 2 will be used as examples of the active material "yolk” and LaF 3 will be used as an example of an encapsulant or "shell” material; as before, these are not limiting of the invention as any material that can accommodate or release fluoride ions upon electrochemical reaction can be envisaged to constitute the "yolk” and any phase or material that permits the exchange of F- between the electrolyte and the active material can be envisaged to constitute the encapsulant or shell.
• the active material is less than 1 micron in diameter, and most usefully, the active material "yolk” is between 1 and 500 nm in diameter and the encapsulant is from 2 to 100 nm thick.
• FIG. 1B outlines a general route using a sacrificial inorganic "middle" layer such as Si0 2 .
• Cu nanoparticles can be prepared by reduction of a solution of Cu 2+ ions using hydrazine or similar reducing agent in the presence of stabilizing and/or coordinating species such as sodium citrate and/or surfactant (e.g. cetyltrimethylammonium bromide).
• stabilizing and/or coordinating species such as sodium citrate and/or surfactant (e.g. cetyltrimethylammonium bromide).
• a surface-modifying ligand such as aminopropyltrimethoxysilane, APTS, (or other suitable bifunctional species such that one part of the molecule coordinates to the Cu surface, and the other part is presents a reactive silicon moiety to the external environment) followed by addition of hydrolyzable silica source such as tetraethylorthosilicate (TEOS) or sodium silicate solution (water glass) under appropriate conditions (e.g. Stober synthesis or sol-gel reaction) results in conformal coating of the Cu nanoparticles with Si0 2 .
• TEOS tetraethylorthosilicate
• sodium silicate solution water glass
• the Si0 2 -coated Cu nanoparticles are then coated with an outer layer of LaF 3 by sol-gel reaction (optionally in the presence of surfactant such as Lutensol AO), whereby the thickness of this coating can be modified by the amount of LaF 3 precursors used and the reaction conditions.
• This step can be done after separation and/or purification of the intermediate Cu@Si0 2 material, or can be performed in the same reaction mixture after formation of the Si0 2 layer.
• the resulting Cu@Si0 2 @LaF 3 composite may, optionally, undergo an annealing step, and/or the Si0 2 layer is then removed by exposure of the composite to a Si0 2 etchant material such as NaOH or HF under appropriate conditions to afford the Cu@LaF 3 "yolk- shell" composition.
• a Si0 2 etchant material such as NaOH or HF under appropriate conditions to afford the Cu@LaF 3 "yolk- shell" composition.
• This material may subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H 2 to purify the Cu surface.
• FIG. 1C describes a similar route using a sacrificial polymer "middle" layer.
• Cu nanoparticles are coordinated by a polymer shell, by formation of Cu nanoparticles in the presence of a polymer or copolymer that features amino-, hydroxyl-, carboxylate or other ionizable functional groups (such as poly(acrylic acid), poly(ethyleneimine), poly(vinyl alcohol), poly(styrene sulfonate), a protein, a polysaccharide, or gelatin), or by growth of a polymer from the surface of suitably- modified Cu nanoparticles (e.g.
• a polymer or copolymer that features amino-, hydroxyl-, carboxylate or other ionizable functional groups (such as poly(acrylic acid), poly(ethyleneimine), poly(vinyl alcohol), poly(styrene sulfonate), a protein, a polysaccharide, or gelatin), or by growth of a
• the thickness of the polymer layer (and, hence the resulting void space) can be controlled by the polymer concentration and/or molecular weight.
• a shell of LaF 3 is grown around the outside of this Cu@polymer nanocomposite by sol-gel reaction to afford a Cu@polymer@LaF3 nanocomposite.
• the polymer layer is then removed by decomposition at elevated temperature (in air or under inert gas such as Ar) or dissolution in suitable solvent (e.g.
• toluene, dichloromethane or acetone to give the desired Cu@LaF 3 "yolk-shell" composition.
• This material may subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H 2 to purify the Cu surface.
• a polymer core-shell architecture such as the hollow latex-type particles described in McDonald and Devon, Adv. Colloid. Interf.
• Sci., 2002, 99, 181-213 may be employed as a template in which Cu nanoparticles are entrapped (either by exposure of Cu nanoparticles to pre-formed hollow latex particles or by coordination of Cu ions in solution to the ionizable pre-polymer or copolymer, followed by reduction of the Cu ions to give Cu nanoparticles and then generation of the hollow structure through e.g. solvent removal), followed by growth of LaF 3 shell, removal of polymer and annealing, as necessary, to generate a Cu@LaF 3 "yolk-shell" composition.
• FIG. 1D delineates an alternative route in the absence of a sacrificial "middle" layer.
• a suitable surface-modifying ligand e.g. 1 l-aminoundecanoic acid, AUDA
• an outer layer of LaF 3 is grown by sol-gel reaction to give a Cu@LaF 3 "core-shell" composite, which may then, optionally, subsequently undergo an annealing step.
• Partial etching of the Cu “core” using an appropriate etchant for example, KCN, HCI/H2O2 or FeCh; suitable etchants for a wide variety of metals and compounds are given in "The CRC Handbook of Metal Etchants" (CRC, 1990, P. Walker and W. H. Tarn eds.), and may be chosen so as to not affect the "shell” material) enabled through control over the reaction conditions (e.g. etchant concentration, temperature, reaction time) generates void space in the Cu@LaF 3 particle, affording a "yolk-shell" Cu@LaF 3 composition.
• This material may subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H 2 to purify the Cu surface.
• FIG. 1E depicts a variation on the "sacrificial" syntheses described above, whereby nanoparticles of the active material are grown on the surface of a "sacrificial" material (here, it is the innermost material that is removed).
• a “sacrificial” material here, it is the innermost material that is removed.
• one or more Cu nanoparticles are grown on the surface of amino-functionalized poly(styrene) or Si0 2 particles.
• the resulting composite material is treated with a suitable Cu surface-modifying ligand (e.g. AUDA), after which an outer layer of LaF 3 is grown by sol-gel reaction.
• a suitable Cu surface-modifying ligand e.g. AUDA
• the innermost material is removed by thermal decomposition, etching or dissolution, resulting in a "yolk-shell" Cu@LaF 3 composition featuring one or more Cu nanoparticles.
• This material may subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H 2 to purify the Cu surface(s) and, optionally, to aggregate the Cu nanoparticles.
• a reducing agent such as H 2
• FIG. 1F outlines an alternative strategy, in which active material is grown in the internal structure or pores of a pre-formed "sacrificial" material.
• Cu nanoparticles may be grown inside hollow Si0 2 nanospheres (see e.g. Hah et ah, Chem. Commun., 2004, 1012-1013 for a possible synthetic approach).
• These Cu@Si0 2 "core shell” nanocomposites are then coated with an outer layer of LaF 3 by sol-gel reaction (optionally in the presence of surfactant such as Lutensol AO), whereby the thickness of this coating can be modified by the amount of LaF 3 precursors used and the reaction conditions.
• the resulting Cu@Si0 2 @LaF 3 composite may, optionally, undergo an annealing step, and/or the Si0 2 layer is then removed by exposure of the composite to a Si0 2 etchant material such as NaOH or HF under appropriate conditions to afford the Cu@LaF 3 "yolk-shell" composition.
• a Si0 2 etchant material such as NaOH or HF under appropriate conditions to afford the Cu@LaF 3 "yolk-shell" composition.
• This material may subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H 2 to purify the Cu surface.
• micro- or mesoporous materials such as zeolites may be used as the "template" for Cu nanoparticle formation, followed by subsequent Cu@LaF 3 "yolk-shell" generation in analogous fashion.
• FIG. 1G also depicts an analogous alternative strategy whereby a highly- electropositive metal or its metal fluoride, such as CaF 2 , is grown within the interior space of a hollow material such as a poly(styrene)-poly(acrylic acid) latex copolymer in a suitable solvent. These polymer-encapsulated CaF 2 nanocrystals are then coated with an outer layer of fluoride-ion conducting material of suitable electrochemical stability so as not to be itself reduced at the conversion potential of CaF 2 to Ca ( ⁇ 0.2 Y vs. Li+/Li).
• a highly- electropositive metal or its metal fluoride such as CaF 2
• the resulting CaF 2 @polymer@Ca x Ba y F 2 composite may, optionally, undergo an annealing step, and/or the polymer layer is then removed by exposure of the composite to high temperature or a suitable solvent etchant material that removes the polymer to the CaF 2 @Ca x Ba y F 2 "yolk-shell" composition.
• electrolytes suitable for FIB battery systems can include a fluoride salt and a solvent in which the fluoride salt is at least partially present in a dissolved state.
• the fluoride salt can be a metal fluoride or a non-metal fluoride.
• the solvent can be an organic liquid or an ionic liquid, or a mixture of the two.
• electrolytes suitable for FIB battery systems can include a composite electrolyte containing fluoride salt, a polymer and optionally an organic liquid, an ionic liquid, or a mixture of the two.
• Electrolytes can include, but are not limited to combinations of fluoride salts and solvents disclosed in US patent 9,166,249, titled “Fluoride Ion Battery Compositions”, the disclosure of which is herein incorporated by reference.
• liquid electrolyte salts suitable for FIB systems may contain complex cations in combination with the fluoride anion.
• the cation may feature organic groups, such as alkylammmonium, alkylphosphonium or alkylsulfonium species, or may consist of metal-organic or metal-coordination complex motifs, such as metallocenium species.
• Useful solvents for such liquid electrolyte salts may include non-aqueous solvents (denoted here as“organic”) that are capable of dissolving the aforementioned fluoride salts to molar concentrations of 0.01 M and above, preferred concentrations being between 0.1 and 3 M.
• solvents examples include acetone, acetonitrile, benzonitrile, 4-fluorobenzonitrile, pentafluorobenzonitrile, triethylamine (TEA), diisopropylethylamine, 1 ,2-dimethoxyethane, ethylene carbonate, propylene carbonate (PC), g-butyrolactone, dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate, propyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, nitromethane, benzene, toluene, chloroform, dichloromethane, l,2-dichloroethane, dimethylsulfoxide, sulfolane, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), carbon disulfide, ethyl acetate, methyl butyrate, n-propy
• room temperature ionic liquid materials or ionic liquids that remain liquid at temperatures below 200 degrees Celsius (such as those described in "Electrochemical Aspects of Ionic Liquids", E. Ohno ed., Wiley Interscience, New York, 2005), are preferred.
• ionic liquids that remain liquid at temperatures below 100 degrees Celsius
• ionic liquids that remain liquid at temperatures below 100 degrees Celsius
• ionic liquids that remain liquid at temperatures below 100 degrees Celsius
• MPPFFSI l-propylpiperidinium bis(trifluoromethanes
• the electrolytes suitable for FIB battery systems can include the compositions disclosed above with the addition of a fluoride-ion complexing species such as an anion receptor, a cation complexing species such as a crown ether, or a combination of both.
• Suitable anion receptors include species capable of binding fluoride anion such as boron, aluminum, ammonium, H-bond donor or similar groups, including aza ethers and alkyl and aryl boron and boronate complexes such as those described in McBreen et al, J. Power Sources, 2000, 89, 163 and West et ah, J. Electrochem.
• fluoride ion batteries are suitable for a wide range of primary or rechargeable applications, including but not limited to vehicle traction batteries (electric vehicles (EV), hybrid vehicles (HEY), and plug-in hybrid (PHEV)) or vehicle starter or ignition batteries.
• FIB systems can be useful stationary batteries for emergency power, local energy storage, starter or ignition, remote relay stations, communication base stations, uninterruptible power supplies (UPS), spinning reserve, peak shaving, or load leveling, or other electric grid electric storage or optimization applications.
• UPS uninterruptible power supplies
• Small format or miniature battery applications including watch batteries, implanted medical device batteries, or sensing and monitoring system batteries (including gas or electric metering) are contemplated, as are other portable applications such as flashlights, toys, power tools, portable radio and television, mobile phones, camcorders, lap-top, tablet or hand-held computers, portable instruments, cordless devices, wireless peripherals, or emergency beacons.
• military or extreme environment applications including use in satellites, munitions, robots, unmanned aerial vehicles, or for military emergency power or communications are also possible.
• FIG. 3 shows an X-ray diffraction (XRD) spectrum of the copper nanoparticles as-made. Three peaks are visible, all corresponding to Cu (°2Q): 43.0, 50.5, and 74.0. However, upon exposure to air, Cu is oxidized to Cu 2 0, which begins forming at least as early as 4 days and is the main product after 9 days. This is illustrated in FIG. 4, which shows appearance of new peaks at 29.5, 42.3, 61.3, and 73.5 °20, corresponding to Cu 2 0.
• XRD X-ray diffraction
• FIG. 5 shows stacked XRD spectra of the core-shell nanoparticles upon exposure to air for 9, 16, and 23 days. In contrast to Comparative Example 1, no spectral changes were observed.
• FIGS. 7 A and 7B show TEM images of the core-shell nanoparticles as synthesized. As shown, the copper nanoparticle cores are covered with the LaF 3 shell.
• FIGS. 8A-8C show high-resolution TEM images of the core-shell nanoparticles as synthesized.
• the central black areas correspond to the copper core, and the peripheral black and white areas correspond to the LaFs shell.
• the figures show homogeneous coverage of the copper core directly coated with the LaFs shell.
• the core-shell nanoparticle synthesized in Experimental Example 1 provides a shell capable of protecting the underlying metal core.
• Such a core-shell nanoparticle is useful for applications where the operating conditions would dissolve, oxidize, or otherwise contaminate the metal core.
• Illustrative examples include use of the core-shell nanoparticles as battery electrode materials.
• the core-shell nanoparticle of Experimental Example 1 may be included as an active material in a negative electrode (anode) of an F-shuttle battery.
• the LaF 3 shell protects the copper core allowing it to operate as an active material without being dissolved.
• FIG. 10A and 10B the core-shell nanoparticles of Experimental Example 1 were tested as the active material in an anode.
• the anode included the core-shell nanoparticles, a conductive agent (super P carbon), and PVdF binder in a ratio of 8: 1 : 1.
• the XRD spectrum of the nanoparticles as synthesized in Comparative Example 2 is shown in FIG. 11.
• the XRD spectrum shows 5 peaks (°2Q): 24.5 (LaF 3 ), 27.6 (LaF 3 ), 43.6 (Cu), 50.5 (Cu), 74.1 (Cu). Therefore, the Cu remains during the course of the reaction of LaCb and NaF.
• FIG. 12 shows stacked XRD spectra of the nanoparticles synthesized in Comparative Example 2 upon exposure to air for 8, 15, and 22 days. Additional peaks are observed starting at 8 days (°2Q): 35.4, 36.4, 38.8, 42.5, 44.8, 48.7, 52.3, 61.5, 73.5. At least the peaks at 36.4, 42.5, 61.5, and 73.5 °2Q are consistent with Cu 2 0 formation. The peaks at 43.6, 50.5, and 74.1 °20, which are consistent with Cu, have also diminished in intensity. As shown in FIG.
• the TEM image shows inhomogeneous, partial coverage of Cu nanoparticles with LaF 3 , as well as LaF 3 that is not associated with Cu nanoparticles. Accordingly, shells made with LaCl 3* 7H 2 0 do not result in a desirable core-shell composition as it would leave the Cu core exposed to the environment of an electrochemical cell that might dissolve the Cu core. In addition, the LaF 3 that is not associated with Cu nanoparticles would decrease the overall efficiency of any system incorporating the mixture.
• the core and shell materials may also be studied in a thin film electrode configuration. Briefly, copper was sputtered to a thickness of about 80 nm onto a glassy carbon substrate of 1 mm thickness. After formation of a Cu film, LaF 3 was sputtered onto the Cu layer toa thickness of less than 5 nm, to form a double-layered thin film; for comparison purposes, a single layered Cu thin film without the LaF 3 coating was also prepared.
• the thin films were studied in a three electrode cell configuration, with a Ag- wire soaked in 1 -methyl- l-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPPyTFSI) and 0.01 M AgOTf as the reference electrode and a Pt-wire as a counter electrode, and using 0.1M tetramethylammonium fluoride (TMAF) in MPPyTFSI as the electrolyte. Cyclic voltammetry was measured in the range from -2.4V to -0.7V vs. Ag/Ag+. Evaluation was conducted in a moisture- and oxygen-free glove box.
• MPPyTFSI 1 -methyl- l-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide
• TMAF 0.1M tetramethylammonium fluoride
• the Cu-LaF 3 double layered thin film electrode was also studied by XPS, initially and after fluorination at the voltages indicated in FIG. 15A.
• the initial time point (1 in FIG. 15A) was studied as deposited.
• the potential was then swept from OCY (about - 1.5V vs Ag/Ag+) to -0.8Y and maintained for 1 hour. After fluorination reaction, a sample of the electrode was taken for XPS depth profiling analysis.
• Core-shell nanoparticles with shells of the formula Cu@Ba x Lai -x F 3-x are shown schematically in FIG. 16; Cu@LaF 3 is included for comparison.
• the copper nanoparticle core may be up to about 50 nm in diameter and the LaF 3 or Ba x Lai- x F3- x coating may be about 5 nm thick.
• the CuF 2 layer that forms on the Cu core during battery charging can grow to a thickness of about 3 nm in Cu@LaF 3 nanoparticles. However, by doping in Ba into the LaF 3 shell, the CuF 2 layer can grow to a greater thickness.
• FIGS. 17A-H SEM, TEM, and EDX images of exemplary Cu@Ba x Lai -x F 3-x nanoparticles are included in FIGS. 17A-H.
• XPS can be used to determine the composition of each element.
• FIGS. 18A-D shows representative XPS spectral data for a core@shell nanoparticle comprising Cu (64.83%), La (14.68%), Ba (0.28%), F (20.21%), where the shell itself comprises La (41.75%), Ba (0.79%), F (57.46%), confirming that the nanoparticles are Cu@La 0. 97Ba 0. o 3 F 2. 97.
• XRD spectra of Cu@LaF 3 and Cu@La 0. 97Ba 0. o 3 F 2 .97 are shown in FIG. 19.
• FIGS. 20A-20B demonstrate the capacity improvement achieved upon Ba-doping according to some aspects of the present disclosure.
• Fig. 20A shows the voltage profile of the first charge-discharge cycle of a Cu@LaF 3 electrode or a Cu@Ba x Lai -x F 3-x electrode, compared to the Ag/Ag + reference electrode.
• the capacity delivery of the Ba- doped electrode reaches 95.2 mAh/g compared to only 50.2 mAh/g for Cu@LaF 3 (Fig. 20B).
• Ba-doping of the LaF 3 shell nearly doubles the capacity.
• the ionic conductivity of the LaF 3 shell is improved about 100 times; see, e.g., M. Anji Reddy and M.
• Fluoride ion can more readily travel thorugh the shell to react with Cu to form CuF 2 , and the amount of CuF 2 formation directly determines the capacity of the battery. The more CuF 2 that is formed, the higher the capacity of the battery. Therefore, the utilization of Cu can be nearly doubled by Ba-doping of the LaF 3 shell.
• FIG. 20C and 20D show XRD spectra of Cu@La 0. 97Ba 0. o 3 F 2 .97 and Cu@LaF 3 in initial condition, i.e., in an electrode before a first use, and then after a first charge and a subsequent first discharge, respectively.
• CuF 2 can be formed after I st charge and then reduced to Cu after I st discharge.
• Figs. 20C and 20D indicate that Cu can be cycled in liquid electrolytes with the two types of shells.
• Cu is a good cathode material for a fluoride shuttle battery because Cu is a cheap, light metal and has high capacity (theoretical capacity of 843.5 mAh/g).
• the major challenge to its use is that Cu can not be charged to form CuF 2 in a liquid electrolyte/cell due to Cu dissolution.
• the LaF 3 shell effectively provents Cu from dissolution during charge/discharge. As a result, Cu can be charged to CuF 2 during charge, and CuF 2 can be reduced to Cu during discharge. But its capacity is low due to low ionic conductivity of LaF 3 .
• the ionic conductivity of the shell can be improved 100 times, i.e., the shell has low resistance.
• F ion is earsier to go through the shell so that more Cu can be fluorinated to CuF 2 during charge.
• Capacity is increased by double compared to the undoped LaF 3 shell.
• CUF 2 can be detected after charge.
• CuF 2 is reduced to Cu after discharge. It can be confirmed that Cu is rechargeable in liquid cell and that Cu ulitization can be improved with Ba-doped shell.
• the word“example” is used herein to mean“serving as an example, instance, or illustration.” Any aspect described herein as“example” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term“some” refers to one or more. Combinations such as“at least one of
• A, B, or C “at least one of A, B, and C,” and“A, B, C, or any combination thereof’ include any combination of A, B, and/or C, and may include multiples of A, multiples of
• combinations such as“at least one of A, B, or C,”“at least one of A, B, and C,” and“A, B, C, or any combination thereof’ may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C.
• Nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

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