Barium-doped electrochemically active structure, method for producing the same, electrode and battery

Abstract

Electrochemically active structure comprising: a core comprising metal nanoparticles, and a fluoride-containing shell which at least partially surrounds the metal nanoparticles, wherein the fluoride-containing shell comprises a first and a second metal, and the first metal is barium.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 16 / 013,739, entitled "Barium-Doped Composite Electrode Materials for Fluoride Electrochemical Cells," filed June 20, 2018, which is a continuation-in-part of U.S. Patent Application No. 15 / 844,079, entitled "Composite Electrode Materials for Fluoride-Ion Electrochemical Cells," filed December 15, 2017, and which claims priority to U.S. Patent Application No. 62 / 434,611, entitled "Composite Electrode Materials for Fluoride-Ion Electrochemical Cells," filed December 15, 2016, and U.S. Patent Application No. 62 / 453,295, entitled "Core Shell," filed February 1, 2017. US Patent Application No. 16 / 013,739 also claims priority to US Patent Application No. 62 / 676,693, entitled "Composite Electrode Materials for Fluoride-Ion Electrochemical Cells," filed on May 25, 2018.This application also claims priority to U.S. Patent Application No. 62 / 676,693. TECHNICAL FIELD

[0002] The present disclosure relates to electrochemically active materials, and more particularly, to fluoride-ion battery systems including electrode materials with structures and compositions adapted to improve battery performance. More specifically, this disclosure relates to core-shell nanoparticles, methods for preparing the same, and the use of the same in electrochemical cells. BACKGROUND

[0003] Metal nanoparticles are highly desirable for use in a number of applications, including as catalysts and as electrode materials for batteries. However, the use of metal nanoparticles may be limited by system operating conditions or other factors. For example, there is growing interest in fluoride shuttle batteries as an alternative to lithium-ion batteries. However, materials available for use in fluoride shuttle battery systems are limited, partly due to operating conditions that are detrimental to many materials that might otherwise be incorporated into the fluoride shuttle battery electrodes.

[0004] Fluoride-ion batteries are electrochemical cells that operate via fluoride-mediated electrode reactions (i.e., uptake or release of fluoride ions at the electrode upon charge or discharge, often through a reaction-by-transformation process). Such electrochemical cells may offer higher energy densities, lower costs, and / or improved safety characteristics compared to lithium and lithium-ion batteries. Solid-state fluoride-ion systems have been demonstrated, for example, in US Pat. No. 7,722,993 B2 to Potanin, which describes an embodiment of a secondary electrochemical cell in which fluoride ions are reversibly exchanged between the anode and cathode during charge-discharge cycles, with these electrodes in contact with a fluoride-conducting solid-state electrolyte.Potanin describes solid-state electrolytes containing fluorides of La, Ce, or mixed fluorides based on these together with alloying additives, such as one or more alkaline earth metal fluorides (CaF2, SrF2, BaF2) and / or alkali metal fluorides (LiF, KF, NaF) and / or alkali metal chlorides (LiCl, KCl, NaCl), as well as a wide range of other fluoride compounds. However, such electrochemical cells only operate effectively above room temperature (e.g., 150°C) due to the limited conductivity of the solid-state electrolytes.

[0005] Attempts have also been made to provide fluoride ion-based electrochemical systems in which liquid electrolytes can be used. For example, US 2011 / 0143219 A1 by Weiss et al. and US 9,166,249 B2 by Darolles et al. disclose fluoride ion battery configurations chosen to include a solvent-based fluoride salt that is at least partially dissolved in the electrolyte. However, for many applications, the chemical reactivity of the electrode materials with the liquid electrolyte is critical, and these liquid electrolyte systems do not provide sufficiently reliable high-discharge and / or high-capacity operation.

[0006] Fluoride-containing cathode materials are already disclosed in WO 2006 / 109930 A1, wherein the active cathode material used for lithium secondary batteries has a surface coated with a fluorine compound. Further work in the field of the present disclosure is also described in EP 3 555 940 B1. This document teaches, for example, a specific fluoride-ion battery system comprising core-shell nanoparticles containing a core comprising an active material and a fluoride-containing shell at least partially surrounding the active material. Furthermore, JP 2018-63905 A teaches solid-state electrolyte secondary batteries with a good capacity retention rate whose defluorination potential is higher than the reduction potential of the solid electrolyte.These secondary batteries include, for example, a positive electrode active material layer and a solid electrolyte layer, wherein at least one of the positive electrode active material layer and the solid electrolyte layer includes a solid electrolyte including Pb (lead), Sn (tin), and F (fluorine). SUMMARY

[0007] The following is a simplified summary of one or more aspects of the present disclosure and is intended to provide a basic understanding of such aspects. This summary is not a comprehensive overview of all aspects considered and is not intended to identify key or critical elements of all aspects, nor to define the scope of any or all aspects. Its purpose is to introduce some concepts of one or more aspects in a simplified form as a prelude to a later, more detailed description.

[0008] In some embodiments, the present disclosure is directed to an electrochemically active structure comprising: a core comprising metal nanoparticles, 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.

[0009] In some embodiments, the present disclosure is directed to a method for preparing 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 material is barium.

[0010] In some embodiments, 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 1-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.

[0011] These and other aspects of the invention will be more fully understood upon review of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A shows, in one aspect of the present disclosure, a cross-section of a core-shell nanoparticle including a core comprising metal nanoparticles and a shell comprising a metal halide or a metal oxyhalide. Fig. Figure 1B shows a general route to yolk-shell composites using an inorganic sacrificial middle layer. Fig. Figure 1C shows a route to yolk-shell composites using a sacrificial polymer middle layer. Fig. 1D represents an alternative route to yolk-shell composite materials in the absence of a middle sacrificial layer. Fig. Figure 1E represents a variation of sacrificial syntheses of yolkshell composites, in which nanoparticles of the active material are assembled on the surface of a sacrificial material. Fig. Figure 1F outlines the growth of active material in the internal structure or pores of a preformed sacrificial material. Fig. Figure 1G outlines the growth of active material in the internal structure or pores of a preformed sacrificial material, where the shell components are chosen to be electrochemically inactive at the relevant electrochemical reaction potential. Fig. 2 is a schematic representation of a fluoride ion electrochemical cell according to one aspect of the present disclosure. Fig. Figure 3 shows an XRD spectrum of isolated copper nanoparticles from Comparative Example 1 without shell directly after synthesis and isolation (“freshly prepared”). Fig. Figure 4 shows superimposed XRD spectra of isolated copper nanoparticles from Comparative Example 1 without shell, freshly prepared and after air contact for 4 days and 9 days. Fig. Figure 5 shows an XRD spectrum of Cu-LaF3 core-shell nanoparticles from Embodiment 1 as synthesized in one aspect of the present disclosure. Fig. Figure 6 shows superimposed XRD spectra of Cu-LaF3 core-shell nanoparticles from Example 1 after air contact for 9, 16 and 23 days. Fig. 7A and Fig. Figure 7B are transmission electron microscopy (TEM) images of Cu-LaF3 core-shell nanoparticles from Embodiment 1, freshly prepared. Fig. Figure 8A shows a high-resolution TEM image of Cu-LaF3 core-shell nanoparticles according to embodiment 1, in which the Cu (core) and LaF3 (shell) regions are identified. Fig. 8B and Fig. 8C show reduced images of the same nanoparticles. Fig. 9 is a schematic representation of a fluoride ion electrochemical cell including the Cu-LaF3 core-shell nanoparticles of Embodiment 1 as an active material in the negative electrode (anode) according to one aspect of the present disclosure. Fig. 10A is a plot of voltage versus specific capacity for electrochemical testing of a half-cell battery incorporating the Cu-LaF3 core-shell nanoparticles of Embodiment 1 as an active material in an electrode according to one aspect of the present disclosure. Fig. Figure 10B is an X-ray diffraction spectrum of the electrode of the half-cell battery test of Fig. 10A, measured under initial 15 conditions, after discharge and after charge: Fig. Figure 11 shows an XRD spectrum of nanoparticles from Comparative Example 2 as prepared. Fig. Figure 12 shows superimposed XRD spectra of nanoparticles from Comparative Example 2 after storage in air for 8, 15, and 22 days. Fig. Figure 13 is a TEM image of the nanoparticles from Comparative Example 2, showing inhomogeneous partial encapsulation of the copper nanoparticles with LaF3, as well as LaF3 not associated with copper particles. Fig. Figure 14 shows LaF3 / Cu and Cu thin film configurations and cyclic voltammetry data. Fig. Figure 15A shows a cyclic voltammogram for a LaF3 / Cu bilayer thin film. Fig. 15B and Fig. 15C show X-ray photoelectron spectroscopy (XPS) data for C, La, O, F and Cu at different etching times at voltages 1 and 2 as in Fig. 15A is specified. Fig. 16 shows schematic representations of Cu@LaF3 and Cu@Ba x La 1-x F 3-x nanoparticles according to some aspects of the present disclosure. Fig. Figure 17A shows an example of a scanning electron microscope (SEM) image of Cu@La 0,97 Ba 0,03 F 2,97 according to some aspects of the present disclosure. Fig. 17B-C show examples of transmission electron microscopy (TEM) images of Cu@La 0,97 Ba 0,03 F 2,97according to some aspects 15 of the present disclosure. Fig. Figure 17D shows an example of an energy dispersive X-ray spectroscopy (EDX) image of Cu@La 0,97 Ba 0,03 F 2,97 according to some aspects of the present disclosure. Fig. 17E-H show the respective image maps of the components Cu, F, La and Ba. Fig. 18A-D show X-ray photoelectron spectroscopy (XPS) spectra for Cu@La 0,97 Ba 0,03 F 2,97 according to some aspects of the present disclosure. Fig. 19 shows XRD spectra for Cu@LaF3 and Cu@La 0,97 Ba 0,03 F 2,97 according to some aspects of the present disclosure. Fig. Figure 20A shows the voltage profile of the first charge-discharge cycle of a Cu@LaF3 electrode or a Cu@BaxLa 1-x F3-x electrode, compared to the Ag / Ag + -Reference electrode, according to some aspects of the present disclosure. Fig. Figure 20B shows a comparison of the capacity obtained for Cu@LaF3 and for Cu@La 0,97 Ba 0,03 F 2,97 according to some aspects of the present disclosure. Fig. 20C shows XRD spectra of Cu@La 0,97 Ba 0,03 F 2,97 in the initial state and after a first charge and a subsequent first discharge, according to some aspects of the present disclosure. Fig. Figure 20D shows XRD spectra of Cu@LaF3 in the initial state and after a first charge and a subsequent first discharge, according to some aspects of the present disclosure DETAILED DESCRIPTION

[0012] Together with the accompanying drawings, the following detailed description is intended to serve as a description of various embodiments, and is not merely representative of the particular embodiments in which the concepts described herein may be embodied. The detailed description includes specific details to provide a thorough understanding of the various concepts. However, those skilled in the art will recognize that these concepts may be embodied without these specific details. In some instances, well-known components are shown in block diagram form to avoid obscuring such concepts.

[0013] Generally, the present disclosure relates to electrochemically active materials and fluoride-ion battery systems, including electrode materials with tailored structures, and compositions that improve battery performance. In some aspects, the present disclosure relates to core-shell nanoparticles, devices containing the core-shell nanoparticles, and methods for making and using the core-shell nanoparticles and devices containing the core-shell nanoparticles.

[0014] Primary and secondary electrochemical cells such as batteries that utilize fluoride ion charge carriers, active electrode materials, and suitable liquid electrolytes can offer an alternative to conventional modern lithium batteries and lithium-ion batteries. Such fluoride ion battery (FIB) systems can be usefully operated at room temperature, using fluoride anions supported in a liquid electrolyte as at least some of the charge carriers in an electrochemical cell. The FIB system comprises an anode and a cathode in physically separate form, 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 an intercalating compound.Similarly, the cathode can be an element or compound and can be a metal, metal fluoride, or an intercalating compound that has a higher potential than the anode. Fluoride ions (F - ) migrate in the fluoride-conducting electrolyte from the cathode to the anode during discharge and from the anode to the cathode during charging of the battery: Discharge: Anode: MF x + nF - → MF x+n + no - (Fluoride ion uptake, oxidation) Cathode: MF y + no - → MF y-n + nF - (Fluoride ion release, reduction)

[0015] During charging, the reverse reactions take place.

[0016] For example, a FIB cell reaction based on fluoride ion transfer between Ca and Cu, both of which are suitable metals for the formation of metal fluorides, can proceed as follows: Discharge: Ca + CuF2 → CaF2 + Cu Charge: CaF2 + Cu → Ca + CuF2

[0017] There are two major challenges to enable reliable long-term cycling of FIB electrodes. First, reversibility of the above electrochemical reactions is observed when the active metal or metal fluoride materials are nanosized (i.e., at least one of the particle size dimensions is less than 1 µm). However, particles with such small dimensions have high surface energies and can often react with the electrolyte components (e.g., F-) to produce undesirable side reactions, including “self-discharge” (i.e., a chemical reaction such as M + nF - → MF n(which does not generate an electric current). Formation of a coating, shell, layer, or similar is required to encapsulate the active material particles while still allowing the passage of F- ions where desired (i.e., during electrochemical charging or discharging). The encapsulating material can also protect the active materials from such side reactions, thereby achieving long-term cycling stability of these electrode materials.

[0018] Second, such electrochemical reactions can be conversion processes, in which the structure of the metal or metal fluoride is disrupted during the electrochemical process and reformed as metal fluoride or metal, respectively. Such a conversion process leads to a significant volume change between charged and uncharged states of the active material, as shown by the examples in Table 1 below: Table 1: Volume change during metal-to-metal fluoride conversion Metal Metallfluorid Volumenänderung während Umwandlung M + nF - → MF n Fe FeF3 311% Pb PbF2 73% Bi BiF3 134% Co CoF3 351% Cu CuF2 238% Sn SnF2 113% La LaF3 46% Ca CaF2 -5% Mg MgF2 42% Li LiF -24%

[0019] Such significant volume changes limit the usability of conformal protective coatings enclosing a FIB electrode material particle, since due to the volume change, a given charge state is not necessarily the same shape as the particle in another charge state. Compositions and methods are needed that protect the electrode active material from side reactions with the electrolyte, allow ionic conduction through a casing, and have sufficient free space within the casing and / or casing expansion / contraction properties that accommodate the volume changes of the active material during charge and discharge without allowing direct contact between the active material and the electrolyte. In some embodiments, sufficient free space may mean no free space. Such compositions and their preparation are presented below.

[0020] As used herein, the term "about" is defined as close to, as understood by one of ordinary skill in the art. In one non-limiting embodiment, the term "about" is defined as within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0021] In some, such as Fig. 1A, the core-shell nanoparticles include a core comprising a metal or metal alloy ("Me") and a shell comprising a metal halide or a metal oxyhalide. The metal of the core may be the same as the metal of the metal halide shell. In some embodiments, the metal of the core and the metal of the metal halide or metal oxyhalide shell are different metals. In some embodiments, the metal halide shell itself may comprise two metals. The core-shell nanoparticles of the present disclosure can 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 in Fig. 2 shown.

[0022] 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. In a preferred embodiment, the metal nanoparticles are selected from the group consisting of cobalt nanoparticles and copper nanoparticles. In another preferred embodiment, the metal nanoparticles are copper nanoparticles. The metals used to form the core can be prepared by mixing a metal precursor solution with a reducing agent to form metal nanoparticles.

[0023] In some embodiments, the metal nanoparticles used to form the core can be prepared in the presence of a stabilizer that prevents or otherwise inhibits the oxidation of the metal nanoparticles during synthesis and can be easily removed from the metal nanoparticles prior to the formation of the metal halide or metal oxyhalide shell thereon. For example, bulky polymers such as polyvinylpyrrolidone (molecular weight of 55,000 g / mol), which are used during the synthesis of the metal nanoparticles, inhibit the oxidation of metal nanoparticles. However, such stabilizers are not easily removed from the metal nanoparticles after synthesis.Without being limited to any particular theory, residual stabilizers may form an additional layer between the core formed from the metal nanoparticles and the metal halide or oxyhalide shell, thereby impairing the performance of the core-shell nanoparticles 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. However, core-shell materials that include an additional layer of residual stabilizer between the core and the shell are likely to result in increased spacing between electrode materials; the additional layer of residual stabilizer and / or the resulting increased spacing may decrease the conductivity of the core-shell material.Without wishing to be bound by any particular theory, the additional stabilizer layer may impair fluoride ion-conducting contact between the core and the shell, while the absence of stabilizer increases the probability of conduction of fluoride ions from the core to the shell.

[0024] For this reason, in the synthesis of metal nanoparticles, a stabilizer that can be easily removed from the core can be used 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. In one non-limiting example, the one or more stabilizers that can be used in the synthesis of the metal nanoparticles have a molecular weight (either individually or as 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.

[0025] In some embodiments, the shell of the core-shell nanoparticles can be formed by mixing isolated metal nanoparticles used to form the core with, for example, a metal salt solution and a halogen salt solution, which react to form the metal halide shell on the core. The shell is deposited directly on the metal core and can surround the core as in Fig. 1A shown. In some embodiments, 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. In certain embodiments, the metal salt used to form the shell is a transition metal salt. In certain embodiments, the metal salt used to form the shell is selected from the group consisting of lanthanum salts, cerium salts, and magnesium salts. In certain embodiments, the metal salt used to form the shell is selected from the group consisting of lanthanum salts and cerium salts. In certain embodiments, the metal salt is a lanthanum salt. In a preferred embodiment, the lanthanum salt is lanthanum nitrate. In some embodiments, the halide salt is sodium fluoride. In a non-limiting example, the shell comprises a metal fluoride or metal oxyfluoride-containing material (i.e.CeF3, CeOF, LaOF, LaF3).

[0026] In some embodiments, 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 approximately 1:10.

[0027] In other embodiments, the core (or active electrode material) may be separated from the shell (or cladding material) by an empty space. Compositions and methods according to such embodiments may protect the active electrode material from side reactions with the electrolyte, allow ionic conduction through a cladding material, and have sufficient empty space within the cladding material and / or cladding material expansion / contraction properties to accommodate volume changes of the active material during charge and discharge without allowing direct contact between the active material and the electrolyte.

[0028] The terms core and electrode active material are used interchangeably herein. Likewise, the terms shell and encapsulation material are used interchangeably herein.

[0029] In other embodiments, 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 the same apply equally to the electrode. In one non-limiting example, the electrode is part of an F-shuttle battery system.

[0030] In some embodiments, the present disclosure is directed to an active electrochemical 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 equally to the present embodiment, and vice versa.

[0031] In some aspects, the active material comprises metal nanoparticles selected from iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles, and alkaline earth metal nanoparticles.

[0032] In some aspects, the active material comprises copper nanoparticles.

[0033] In some aspects, the fluoride-containing shell is directly bonded to the core.

[0034] In some aspects, the fluoride-containing shell is spaced from the core, defining an empty space between them.

[0035] In some aspects, the second metal is lanthanum.

[0036] In some aspects, the barium and lanthanum are present in a ratio of x to 1-x, so that the sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1.

[0037] In some aspects, x is about 0.03 to about 0.15.

[0038] In some aspects, x is approximately 0.03.

[0039] In some embodiments, the present disclosure is directed to a method for producing 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 equally to the present embodiment, and vice versa.

[0040] In some embodiments, the metal nanoparticles comprise iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles, or alkaline earth metal nanoparticles.

[0041] In some aspects, the metal nanoparticles comprise copper nanoparticles.

[0042] In some aspects, the fluoride-containing shell is directly bonded to the core.

[0043] In some aspects, the fluoride-containing shell is located at a distance from the core to define an empty space between them.

[0044] In some aspects, the second metal is lanthanum.

[0045] In some aspects, the barium and lanthanum are present in a ratio of x to 1-x, so that the sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1.

[0046] In some aspects, x is about 0.03 to about 0.15.

[0047] In some aspects, 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 form a fluoride-containing shell around the metal nanoparticle core, wherein the first metal is a barium salt.

[0048] In some aspects, the second metal salt is a lanthanum salt.

[0049] In some aspects, the first metal salt is barium nitrate and the second metal salt is lanthanum nitrate.

[0050] In some aspects, barium nitrate and lanthanum nitrate are used in a molar ratio of approximately 1:10.

[0051] In some embodiments, 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 1-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 equally to the present embodiment, and vice versa.

[0052] In some aspects, x is about 0.03 to about 0.15.

[0053] In some aspects, the present disclosure is directed to a fluoride shuttle battery comprising the electrode and a liquid electrolyte.

[0054] Disclosed is an electrochemically active structure comprising: a core comprising an active material and a fluoride-containing shell at least partially surrounding the more 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 regard to the aforementioned embodiments apply equally to the present embodiment. The fluoride-containing shell may be doped with barium (i.e., to create a barium-doped shell) or with any possible divalent or tetravalent metal cation (i.e., to create a divalent metal cation-doped shell or a tetravalent metal cation-doped shell); this disclosed shell is not limited to doping with barium.

[0055] An "inert atmosphere" refers to a gaseous mixture containing little or no oxygen and comprising inert or non-reactive gases, or gases that have a high threshold before reacting. An inert atmosphere may include, but is not limited to, molecular nitrogen or an inert gas such as argon, or mixtures thereof.

[0056] A "reducing agent" is a substance that causes the reduction of another substance while itself being oxidized. Reduction refers to a gain of electron(s) by a chemical species, and oxidation refers to the loss of electron(s) by a chemical species.

[0057] A "metal salt" is an ionic complex in which the cation(s) is (are) one or more positively charged metal ions or the anion(s) is (are) one or more negatively charged ions. "Cation" refers to a positively charged ion and "anion" refers to a negatively charged ion. In a "metal salt" according to the present disclosure, the anion can be any negatively charged chemical species. Metals in metal salts according to the present disclosure can 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.

[0058] "Alkali metal salts" are metal salts in which the metal ions are alkali metal ions or metals of Group I of the periodic table of elements, such as lithium, sodium, potassium, rubidium, cesium, or francium.

[0059] "Alkali earth metal salts" are metal salts in which the metal ions are alkaline earth metal ions or metals of Group II of the Periodic Table of Elements, such as beryllium, magnesium, calcium, strontium, barium or radium.

[0060] "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 elements, including the lanthanides and actinides. 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, iridium, platinum, gold, mercury, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.

[0061] “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.

[0062] A "halide salt" is an ionic complex in which the anion(s) is (are) one or more halide ions, 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) one or more fluoride ions. According to the present disclosure, the cation of the halide salt or fluoride salt can be any positively charged chemical species.

[0063] A "metal fluoride" is an ionic complex in which the cation is one or more metal ions 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 form a metal fluoride shell around the metal nanoparticle core. Similarly, a "metal halide" is an ionic complex in which the cation is one or more metal ions and the anion(s) is / are one or more halide ions.

[0064] A "fluoride-containing" salt is an ionic complex in which the anion(s) contain fluoride ion(s), but they are not necessarily only fluorides. Rather, "fluoride-containing" salts include ionic complexes in which the anion(s) contain the fluoride complexed with other ions or atoms. "Fluoride-containing" salts suitable for use in aspects of the present disclosure include those known to those of ordinary skill in the art, including but not limited to fluoride salts, non-metallic fluorine anions such as tetrafluoroborate salts and hexafluorophosphate salts, and oxyfluoride salts. In some aspects of the present disclosure, the fluoride-containing salt 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 form a fluoride-containing shell around the metal nanoparticle core.

[0065] The term "electrode" refers to an electrical conductor in which ions and electrons are exchanged with an electrolyte and an external circuit. "Positive electrode" and "cathode" are used synonymously in this description and refer to the electrode which has the higher electrode potential in an electrochemical cell (i.e. higher than the negative electrode). "Negative electrode" and "anode" are used synonymously in this description and refer to the electrode which has the lower electrode potential in an electrochemical cell (i.e. lower than the positive electrode). Cathodic reduction refers to the 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 can be provided in a variety of suitable configurations and form factors as are known in the art of electrochemistry and battery science, including thin electrode designs, such as thin-film electrode configurations. Electrodes are fabricated as known in the art, including, for example, as disclosed in U.S. Patent No. 6,052,539 or by Oxtoby et al., Principles of Modern Chemistry (1999), pages 401-443.

[0066] The term "electrochemical cell" refers to devices 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, with electrode reactions taking place at the electrode surface leading to 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 well known (see, for example, Oxtoby et al., Principles of Modern Chemistry (1999), pp. 401-443).

[0067] "Electrolyte" refers to an ionic conductor that exists in the solid state, in the liquid state (mostly) or, more rarely, as a gas (e.g., plasma). I. Core-shell nanoparticles comprising a metal core and a metal halide or metal oxyhalide shell

[0068] In one embodiment, a core-shell nanoparticle is provided comprising a metal core surrounded by a metal halide or metal oxyhalide shell.

[0069] In one illustrative example, the core-shell nanoparticle may be included in an electrode of a rechargeable battery, such as an F-shuttle battery. For example, it is difficult to use metal nanoparticles in the electrode of an F-shuttle battery because the metal is exposed to conditions that lead to undesirable oxidation or dissolution of the metal. Therefore, a halide shell is provided that is adapted to protect the metal core nanoparticle from the electrode environment while maintaining the desired performance of the metal nanoparticle. In one non-limiting example, the core may comprise copper metal and the shell LaF3. In another non-limiting example, the core may comprise copper metal and the shell may Ba x La 1-x F 3-x include.

[0070] A method for preparing 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. In one non-limiting example, the solution comprises a metal salt and a halide salt. In another non-limiting example, the solution comprises two metal salts and a halide salt. In some such examples, one of the two metal salts is a barium salt. In another such example, the two metal salts comprise a barium salt and a lanthanum salt. I(a) Synthesis and isolation of the metal core

[0071] Metal nanoparticles for use as the metal core are generally prepared by reacting a metal salt solution with a reducing agent in the presence of one or more stabilizers. In one illustrative example, the metal salt solution comprises copper(II) nitrate hemipentahydrate (Cu(NO3)2·2.5H2O) as the metal salt. The metal salt is mixed with CTAB and water, and the pH of the mixture can be adjusted to approximately 10–11, for example, with ammonium or sodium hydroxide.

[0072] Before adding the reducing agent to the metal salt solution, the reducing agent may be mixed with one or more stabilizers and water and allowed to mix for a period of, for example, 20 minutes before 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, ferrous sulfate, stannous chloride, potassium iodide, oxalic acid, formic acid, ascorbic acid, thiosulfate salts, dithionate salts, phosphoric acid, phosphite salts, and hydrophosphite salts. In a preferred embodiment, the reducing agent is hydrazine.

[0073] The metal salt solution and the reducing agent are combined to form the metal nanoparticles. The synthesis of the metal nanoparticles is carried out in an oxygen-free atmosphere. Illustrative examples of oxygen-free atmospheres include, but are not limited to, nitrogen, argon, helium, hydrogen, and mixtures thereof. After synthesis, the metal nanoparticles are isolated from the synthesis solution. It is understood that the method for isolating the metal nanoparticles is not limited and may include one or more techniques such as filtration, decantation, and centrifugation. The metal nanoparticles may be washed one or more times with a solvent, such as ethanol, to remove any remaining stabilizer or other organic material from their surface. I(b) Generation of the shell

[0074] The isolated metal nanoparticles can generally be redispersed in an aqueous solution containing additional reducing agent under an oxygen-free atmosphere. The mixture containing the isolated metal nanoparticles and reducing agent is then mixed under an oxygen-free atmosphere with a metal salt solution and a halide salt solution used to form the metal halide shells on the metal nanoparticle core. The metal salt and fluoride salt solutions used to form the shell can be added sequentially to the nanoparticle mixture, or the metal salt and fluoride salt solutions used to form the shell can be added simultaneously to the nanoparticle mixture. In some aspects, the metal salt solution comprises a single metal salt. In other aspects, the metal salt solution comprises two metal salts. In some such aspects, 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 approximately 1:10. II Yolk-shell nanoparticles(i) Protective, fluoride ion-conducting coatings

[0075] Suitable protective overcoatings include fluoride ion-conducting phases that are chemically and electrochemically stable in the presence of a liquid FIB electrolyte. Such phases allow the exchange of F- between the electrolyte and the active material. Suitable phases are well known and described, for example, in "The CRC Handbook of Solid State Electrochemistry," Chapter 6 (CRC, 1997, PJ Gellings and HJM Bouwmeester, Eds.), Sorokin and Sobolev, Crystallography Reports 2007, 52, 5, 842-863, Sobolev et al., Crystallography Reports 2005, 50, 3, 478-485, and Trnovcova et al., Russian Journal of Electrochemistry, 2009, 45, 6, 630-639. These include, for example, crystalline phases such as LaF3, CaF2, SnF2, PbF2, PbSnF4, analogous doped and / or solid solution phases (for example La 0,9 Ba 0,1 F 2,9 , Ca 0,8 Y 0,2 F 2,2 , Ca 0,5 Ba 0,5 F2 and Pb 0,75 Bi 0,25 F2,25 ), glassy phases such as 35InF3·30SnF2·35PbF2, and mixed phases of fluoride / other ions such as LaOF. For the purposes of this disclosure, any material or phase that allows the exchange of F- between the electrolyte and the active material, with an ionic conductivity above 10 -10 S / cm at 298 K are included within the scope of the present invention. These phases are selected with components that are chosen to be electrochemically stable at the potentials required for the reaction of the species contained in the coatings, taking into account the standard redox potential of the shell components and the internal species available from standard literature. See, for example, Fig. 1G for a more detailed discussion of the selection of coating components in this regard.

[0076] Alternative protective coatings include polymers that are conductive to fluoride ions, for example, boronate-functionalized polymers, alkylammonium-functionalized polymers, or those containing suitable functional groups, as described, for example, in Gorski et al., Anal. Chim. Acta 2009, 633, 181-187 and Gorski et al., Anal. Chim. Acta 2010, 665, 39-46.

[0077] The thickness of the protective coating is selected so that exchange of F- between the electrolyte and the active material takes place within a time horizon that allows charging / discharging of the electrochemical cells at suitable operating rates at approximately 298 K (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. For example, a coating of LaF3 or Ba x La1-x F 3-x Preferably, the thickness is between 1 and 200 nm, such as between approximately 5 nm and approximately 20 mm thick, or any integer or subrange therebetween. More generally, the coating thickness can be from approximately 1 nm to approximately 1 µm.

[0078] The coating can be prepared by any suitable synthesis method. These may include solution chemical 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 "chimie douce" methods, hydrothermal synthesis, vacuum processes such as chemical vapor deposition, physical vapor deposition, sputtering, laser ablation and molecular beam epitaxy, electrochemical deposition, or fluoridation of a material after deposition by reaction with a fluorine source. For example, a preferred method for preparing a LaF3 coating is sol-gel synthesis, which is similar to those described by Rüdiger and Kemnitz, Dalton Trans., 2008, 1117-1127 and Fujihara et al., J. Ceram. Soc.Japan, 1998, 106, 124-126, using soluble lanthanum and fluorine sources in a suitable solvent (e.g., La(CH3COO)3 and CF3COOH in water). The thus-prepared coating can optionally be subjected to an elevated temperature either in air or an inert gas such as argon for an annealing step. For example, a LaF3 coating prepared by the sol-gel method can be heated to 500°C in air to anneal the coating and assist in the removal of impurities such as solvent. In such a manner, fluoride-containing coating phases can be synthesized as desired by adjusting the precursor materials, their stoichiometric ratios, and the annealing step following the initial reaction. This sol-gel synthesis of the LaF3 coating can also be modified to produce a coating of Ba. x La 1-x F 3-xaccording to methods known to the person skilled in the art.

[0079] According to another example, the LaF3 coating can be obtained by precipitation, by slowly adding NH4F to an aqueous La(NO3)3 solution containing suspended nanoparticles of the core material. Since LaF3 is extremely insoluble in water, its crystallization will begin on the surface of the suspended nanoparticles. The precipitation synthesis of the LaF3 coating can be modified to form a coating of Ba x La 1-x F 3-x can be produced according to methods known to the person skilled in the art.

[0080] Alternatively, a sol-gel approach can be used to prepare a La2O3 coating, followed by post-fluoridation using F2 or HF to convert a substantial portion of the oxide to LaOF and / or LaF3. This sol-gel approach can also be used to prepare a coating of Ba xLa 1-x F 3-x according to methods known to the person skilled in the art.

[0081] Fluoride-conducting encapsulants and / or coating phases and materials can be fabricated 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 metal or metal fluoride fiber or tube) as required. Similarly, fluoride-conducting phases can be fabricated on external and / or internal surfaces of complex micro- or mesoporous structures such as a zeolite or highly ordered templated material. This may 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 coated with a fluoride ion-conductive coating

[0082] Suitable structures and compositions include those in which a metal or metal fluoride is encased in a fluoride ion-conductive coating (as described in (i) above) such that sufficient void space exists within the coating to accommodate a volume change between metal and metal fluoride phases (or between a lower valence metal fluoride species MFm and a higher valence metal fluoride species MFn, where n > m for the same metal M) upon conversion without fracture of the coating phase or material. Such structures and compositions are sized to fit within a fluoride-conductive coating, with at least enough void space available in certain cases to allow up to 100% of the encased metal atoms to be converted into 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, as shown in Table 1). In other cases, the degree of conversion can be electrochemically controlled (e.g., by regulating the voltage limits and / or charge / discharge capacity) so that the cladding does not break during cycling in cases where not enough void space can be achieved for 100% conversion. Structures and compositions are also additionally considered in which the fluoride-conducting cladding is conformal and / or has insufficient void space to fully accommodate the conversion of the metal to metal fluoride, but has sufficient flexibility to expand or contract without cracking or breaking the cladding. Such compositions can be two-dimensional (e.g., film-void coating), or three-dimensional (e.g.,Nanoparticle void coating or more complex arrangements such as metal-impregnated zeolite void coating).

[0083] In still further embodiments, multiple concentrically arranged claddings are contemplated. The respective concentrically arranged claddings may be separated by voids and may be made of the same or different materials. In still further embodiments of concentrically arranged claddings, the active material and the outermost cladding (which is in contact with the electrolyte) may be separated by a polymer or other flexible material that can allow the passage of fluoride ions and is dimensionally suitable to accommodate the volume changes due to cycling and rupture of the outermost cladding.

[0084] As will become clear, an active material that is completely surrounded by and positioned within a shell, 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 encased structures can be based on various compositional arrangements of active material and fluoride-conducting shell material. However, other arrangements enclosing an active material only partially surrounded by a fluoride-conducting protective shell are also contemplated.Such structures may include two- or three-dimensional non-fluoride-based conductive support structures (e.g., films, open-sided cells, tubes, and the like) containing an active material with one or more sides coated with a fluoride-conductive material to enable ion transport. Such support structures may include voids or dimensionally flexible polymers or other materials to accommodate volume changes during cycling without fracture of the support structure or enclosure.

[0085] General preparative strategies for yolk-shell nanocomposite structures are described in Lou et al., Adv. Mater., 2008, 20, 3987-4019. The metal yolk material discussed is usually Au, which is considered unsuitable as an active material for FIB electrochemical cells. Similarly, the shell material described is often SiO2, which is not considered a suitable fluoride ion-conducting material. Therefore, suitable preparative strategies for yolk-shell nanocomposites usable in FIB electrochemical cells are presented below. These are intended as examples and do not limit the present invention.In certain examples, Cu metal or CuF2 is used as an example of the active yolk material, and LaF3 is used as an example of a cladding or shell material. As before, these do not limit the invention, since any material capable of accepting or releasing fluoride ions during electrochemical reaction can be used to form the yolk, and any phase or material that allows the exchange of F- between the electrode and the active material can be envisaged for forming the shell. In certain embodiments, the active material has a diameter of less than 1 µm, and most conveniently, the active yolk material has a diameter of between 1 and 500 nm, and the shell is between 2 and 100 nm thick.

[0086] Fig. Figure 1B illustrates a general approach using an inorganic “middle” sacrificial layer, such as SiO2. Copper nanoparticles can be prepared, for example, by reducing a solution of Cu 2+-ions using hydrazine or a similar reducing agent in the presence of a stabilizer and / or coordinating species such as sodium citrate and / or a surfactant (e.g., cetyltrimethylammonium bromide). Exposure of copper nanoparticles to a surface-modifying ligand such as aminopropyltrimethoxysilane, APTS, (or another suitable bifunctional species such that one part of the molecule coordinates to the Cu surface and the other part represents a reactive silicon moiety towards the external environment), followed by addition of a hydrolyzable silicon dioxide source such as tetraethylortosilicate (TEOS) or sodium silicate solution (water glass) under suitable conditions (e.g., Stöber synthesis or sol-gel reaction), leads to the conformal coating of copper nanoparticles with SiO2.The thickness of the SiO2 layer (and thus the resulting void space) can be controlled by changing the amount of SiO2 precursor used and the reaction conditions. The SiO2-coated Cu nanoparticles are then coated with an outer layer of LaF3 by sol-gel reaction (optionally in the presence of a surfactant such as Lutensol AO). The thickness of this shell can be varied by the amount of LaF3 precursor used and the reaction conditions. This step can be performed after the separation and / or purification of the Cu@SiO2 intermediate or can be carried out in the same reaction mixture after formation of the SiO2 layer. The resulting Cu@SiO2@LaF3 composite can optionally undergo an annealing step and / or the SiO2 layer can then be removed by exposing the composite to a SiO2 etching material such as NaOH or HF under suitable conditions to achieve the Cu@LaF3 yolk-shell composition.This material can then undergo a final annealing step, optionally in the presence of a reducing agent such as H2, to clean the Cu surface.

[0087] Fig. Figure 1C describes a similar approach using a sacrificial "middle" polymer layer. For example, copper nanoparticles are coordinated with a polymer shell by forming copper nanoparticles in the presence of a polymer or copolymer containing amino, hydroxyl, carboxylate, or other ionizable functional groups (such as polyacrylic acid, polyethyleneimine, polyvinyl alcohol, polystyrenesulfonate, a protein, a polysaccharide, or gelatin), or by growing a polymer from the surface of appropriately modified copper nanoparticles (e.g., polystyrenesulfonate) grown by atom-transfer radical polymerization from an 11-aminoundecyl-2-bromoisobutyrate-functionalized surface. The thickness of the polymer layer (and therefore the resulting void space) can be controlled by the polymer concentration and / or the polymer molecular weight.A LaF3 shell is built up around the exterior of this Cu@polymer nanocomposite by sol-gel reaction to form a Cu@polymer@LaF3 nanocomposite. The polymer layer is then removed by decomposition at elevated temperature (in air or under inert gas such as argon) or dissolution in a suitable solvent (e.g., toluene, dichloromethane, or acetone) to generate the desired Cu@LaF3 yolk-shell composition. This material can subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H2, to clean the Cu surface. Alternatively, a polymer core-shell structure, such as the hollow latex-type particles described in McDonald and Devon, Adv. Colloid. Interf. Sci., 2002, 99, 181-213, can be used as a template in which copper nanoparticles are encapsulated (either by exposing copper nanoparticles to preformed hollow latex particles or by coordination of copper ions in solution to the ionizable prepolymer or copolymer, followed by reduction of the copper ions to form copper nanoparticles and then formation of the hollow structure by, e.g., removal of solvent), followed by LaF3 shell growth, removal of polymer and annealing, if necessary, to form a Cu@LaF3 yolk-shell composition.

[0088] Fig. Figure 1D describes an alternative route in the absence of a sacrificial "intermediate" layer. For example, copper nanoparticles are treated with a suitable surface-modifying ligand (e.g., 11-aminoundecanoic acid, AUDA) before an outer layer of LaF3 is generated by sol-gel reaction to form a Cu@LaF3 "core-shell" composite, which can then optionally undergo a subsequent annealing step. Partial etching of the Cu "core" using a suitable etchant (e.g., KCN, HCl / H2O2, or FeCl3; suitable etchants for a wide range of metals and compounds are described in "The CRC Handbook of Metal Etchants" (CRC, 1990, P. Walker and WH Tarn eds.) and can be chosen so as not to affect the "shell" material), enabled by controlling the reaction conditions (e.g., etchant concentration, temperature, reaction time), leads to the formation of void space within the Cu@LaF3 particle, yielding a "yolk-shell" Cu@LaF3 composition. This material can subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H2, to clean the Cu surface.

[0089] Fig. Figure 1E illustrates a variation of the sacrificial syntheses described above, in which nanoparticles of the active material are assembled on the surface of a sacrificial material (here, it is the innermost material that is removed). For example, one or more copper nanoparticles are assembled on the surface of an amino-functionalized polystyrene or SiO2 particle. The resulting composite material is treated with a suitable Cu surface-modifying ligand (e.g., AUDA), after which an outer layer of LaF3 is assembled by sol-gel reaction. The innermost material is removed by thermal decomposition, etching, or dissolution, yielding a yolk-shell Cu@LaF3 composition containing one or more Cu nanoparticles.This material can then undergo a final annealing step, optionally in the presence of a reducing agent such as H2, to clean the Cu surface(s) and, optionally, to aggregate the Cu nanoparticles.

[0090] Fig. 1F represents another alternative strategy, in which active material is constructed within the internal structures or pores of a preformed sacrificial material. For example, Cu nanoparticles can be generated within hollow SiO2 nanospheres (see, for example, Hah et al., Chem. Commun., 2004, 1012-1013 for a possible synthetic approach). These Cu@SiO2 core-shell nanocomposites are then coated with an outer layer of LaF3 by sol-gel reaction (optionally in the presence of a surfactant such as Lutensol AO). The thickness of this coating can be modified by the amount of LaF3 precursor used and the reaction conditions.The resulting Cu@SiO2@LaF3 composite can optionally undergo an annealing step and / or the SiO2 layer is then removed by exposing the composite to a SiO2 etching material such as NaOH or HF under suitable conditions to form the Cu@LaF3 yolk-shell composition. This material can subsequently undergo a final annealing step, optionally in the presence of a reducing agent such as H2, to clean the Cu surface. In related syntheses, micro- or mesoporous materials such as zeolites can be used as a template for Cu nanoparticle formation, followed by subsequent Cu@LaF3 yolk-shell formation in an analogous manner.

[0091] Fig. Figure 1G also shows an analogous alternative strategy, in which a strongly electropositive metal or its metal fluorides, such as CaF2, is grown within the interior of a hollow material such as a polystyrene-polyacrylic acid latex copolymer in a suitable solvent. These polymer-encapsulated CaF2 nanocrystals are then coated with an outer layer of a fluoride ion-conducting material with suitable electrochemical stability so that they are not themselves reduced at the conversion potential of CaF2 to Ca (~0.2 V vs. Li+ / Li). Examples of suitable protecting materials include solid solutions such as Ca x Ba y F2 (x + y = 1), where the Ca 2+ and Ba 2+-ions in the protective shell are not significantly reduced during the conversion reaction of CaF2 particles within the shell. In contrast, a shell containing a less electropositive metal element (e.g., LaF3) would be reduced even in the presence of the inner CaF2 particles. The resulting CaF2@polymer@Ca x Ba y F2 composite can optionally undergo an annealing step and / or the polymer layer is then removed by subjecting the composite to high temperatures or a suitable solvent etching material, which degrades the polymer to form the CaF 2@ Ca x Ba y F2 “yolk-shell” composition removed.

[0092] Use of the described encapsulated active materials and / or yolk-shell nanocomposite electrodes together with electrolytes, binders, additives, separators, battery casings or packaging, current collectors, electrical contacts, electrical charge and discharge controllers, and other battery design elements known to those skilled in the art allows the fabrication of useful lithium-free electrochemical cells operable at temperatures ranging between -40 degrees Celsius and 200 degrees Celsius. Such electrochemical cells can exhibit substantially irreversible electrochemical reactions during discharge, making them suitable for forming galvanic cells or primary batteries. Alternatively, secondary (rechargeable) batteries can be formed with certain structures and compositions that exhibit an electrochemical reaction that is at least partially reversible upon application of an electrical charge.

[0093] In certain embodiments, electrolytes suitable for FIB battery systems may include a fluoride salt and a solvent in which the fluoride salt is at least partially dissolved. The fluoride salt may be a metal fluoride or a non-metal fluoride. The solvent may be an organic liquid or an ionic liquid, or a mixture of the two. In other embodiments, electrolytes suitable for FIB battery systems may include a composite electrolyte comprising a fluoride salt, a polymer, and optionally an organic liquid, an ionic liquid, or a mixture of the two. Electrolytes may include, but are not limited to, combinations of fluoride salts and solvents, as described in U.S. Patent 9,166,249, entitled "Fluoride Ion Battery Compositions."

[0094] For example, liquid electrolyte salts suitable for FIB systems may contain complex cations in combination with fluoride anions. The cation may comprise organic groups such as alkylammonium, alkylphosphonium, or alkylsulfonium species, or it may consist of organometallic or metal coordination complex motifs such as metallocene species. Suitable solvents for such liquid electrolyte salts may include non-aqueous solvents (hereinafter referred to as "organic") capable of dissolving the aforementioned fluoride salts up to molar concentrations of 0.01 M and above, with preferred concentrations between 0.1 and 3 M. Examples of such solvents include acetone, acetonitrile, benzonitrile, 4-fluorobenzonitrile, pentafluorobenzonitrile, triethylamine (TEA), diisopropylethylamine, 1,2-dimethoxyethane, ethylene carbonate, propylene carbonate (PC), γ-butyrolactone, dimethyl carbonate, diethyl carbonate (DEC),Methyl ethyl carbonate, propyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, nitromethane, benzene, toluene, chloroform, dichloromethane, 1,2-dichloroethane, dimethyl sulfoxide, sulfolane, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), carbon disulfide, ethyl acetate, methyl butyrate, n-propyl acetate, methyl propionate, methyl formate, 4-methyl-1,3-dioxolane, pyridine, methyl isobutyl ketone, methyl ethyl ketone, hexamethylphosphoramide, hexamethylphosphotriamide, 1-methyl2-pyrrolidinone, 2-methoxyethyl acetate, trimethyl borate, triethyl borate and substituted derivatives thereof, as well as sulfones such as ethyl methyl sulfone, trimethyl sulfone, 1-methyltrimethylsulfone, ethyl sec-butylsulfone, Ethylisopropylsulfone (EIPS), 3,3,3-trifluoropropylmethylsulfone, 2,2,2-trifluoroethylsulfone, bis(2,2,2-trifluoroethyl)ether (BTFE), glymes (e.g. diglyme, tetraglyme), 1,2-Dimethoxyethane (DME) and mixtures thereof. In certain embodiments, ionic materials that are liquid at room temperature 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, Network York, 2005) are preferred. These may include ionic liquids that remain liquid at temperatures below 100 degrees Celsius, such as 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (MPPTFSI), butyltrimethylammonium bis(trifluoromethanesulfonyl)imide (BTMATFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMPTFSI), and their fluoroalkyl phosphate (FAP) anion derivatives (for example, MPPFAP), where FAP is a hydrophobic anion such as tris(pentafluoroethyl)trifluorophosphate), all of which, alone or in combination, are considered suitable solvents.

[0095] In certain further embodiments, electrolytes suitable for FIB battery systems may include the compositions disclosed above and additionally 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 anions such as boron, aluminum, ammonium, H-bond donors, or similar groups, including azaethers and alkyl and aryl boron and borate complexes such as those described in McBreen et al., J. Power Sources, 2000, 89, 163 and West et al., J. Electrochem. Soc., 154, A929 (2007), and boroxine species as described in Nair et al., J. Phys. Chem. A, 113, 5918 (2009).In particular, tris(hexafluoroisopropyl)borate, tris(pentafluorophenyl)borane and all possible regioisomers of difluorophenylboroxine (DFB), trifluorophenylboroxine, bis(trifluoromethyl)phenylboroxine, trifluoromethylphenylboroxine and fluoro(trifluoromethyl)phenylboroxine can be used.

[0096] Fluoride-ion batteries are recognized as suitable for a variety of primary or rechargeable applications, including but not limited to vehicle propulsion batteries (electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs)) or vehicle starting or ignition batteries. FIB systems can be useful stationary batteries for backup power, local energy storage, starter or ignition, remote relay stations, communications base stations, uninterruptible power supplies (UPSs), rotating reserves, peak-sharing or leveling, or other electrical grid or electrical storage or optimization applications.Small or miniature battery applications, including watch batteries, batteries for implanted medical devices, or sensor and monitor system batteries (including for gas or electricity payments), are also contemplated, as are other portable applications such as flashlights, toys, power tools, portable radio and television, mobile phones, camcorders, laptops, tablets or handheld computers, portable instruments, cordless devices, wireless peripherals, or emergency beacons. Military or extreme environmental applications, including use in satellites, munitions, robots, unmanned aerial vehicles, or for military emergency power or communications, are also possible. III (c) Comparative Example 1 and Experimental Example 1

[0097] In Comparative Example 1, uncoated copper nanoparticles were prepared and analyzed. First, 2 mmol of Cu(NO3)2 2.5 H2O and 1.87 mmol of CTAB were dissolved in 75 mL of water at room temperature, and 0.5 mL of NH4OH (28–30 wt% NH3 in water, 14.8 M) was added to adjust the pH to approximately 10–11. A solution containing hydrazine (3 mL, 50–60%, reagent grade), CTAB (1.87 mmol), and citric acid (0.38 mmol) in water (75 mL) was prepared under argon and mixed for approximately 20 minutes before the copper nitrate solution was added. The reaction mixture was stirred for 1.5 hours to maximize copper nanoparticle growth. The resulting copper nanoparticles (~50 nm) were isolated and washed. In particular, the reaction synthesis mixture was centrifuged, decanted, mixed with ethanol and sonicated. Fig. Figure 3 shows an X-ray diffraction (XRD) spectrum of the thus prepared copper nanoparticles. Three peaks are visible, all belonging to Cu (°20): 43.0, 50.5, and 74.0. However, upon exposure to air, the copper is oxidized to Cu2O, which begins to form at least after 4 days and is the main product after 9 days. This is illustrated in Fig. 4, which shows the appearance of new peaks at 29.5, 42.3, 61.3 and 73.5 °20, corresponding to Cu2O.

[0098] In Experimental Example 1, core-shell nanoparticles according to the present disclosure were prepared, comprising a core comprising a copper nanoparticle and coated with a shell comprising lanthanum fluoride (Cu / LaF3). The ~50 nm copper nanoparticles were prepared using the same method as in Comparative Example 1, but redispersed in water with 3 mL of hydrazine (3 mL 50-60%, reagent grade) under an argon atmosphere, followed by isolation and washing of the copper nanoparticles. To the mixture of water, copper nanoparticles, and hydrazine, a solution of La(NO3)3·6H2O (1 mmol in 15 mL H2O) and a solution of NaF (1 mmol in 15 mL H2O) were added. The reaction mixture was stirred for 10 minutes and then centrifuged.

[0099] The precipitate was isolated by centrifuge and analyzed by XRD. The XRD spectrum of the prepared core-shell nanoparticles is shown in Fig. 5. The XRD spectrum shows 5 peaks (°20): 25.0 (LaF3), 28.0 (LaF3), 43.5 (Cu), 50.4 (Cu), 74.0 (Cu). Fig. Figure 6 shows stacked XRD spectra of the core-shell nanoparticles after exposure to air for 9, 16, and 23 days. In contrast to Comparative Example 1, no changes in the spectrum are observed. Fig. 7A and Fig. Figure 7B shows TEM images of the prepared core-shell nanoparticles. As shown, the copper nanoparticle cores are coated with the LaF3 shell. The shell has a thickness of approximately 0.30 nanometers. Fig. Figures 8A to 8C show high-resolution TEM images of the prepared core-shell nanoparticles. The central black areas correspond to the copper core, and the peripheral black and white areas correspond to the LaF3 shell. The figures show homogeneous encapsulation of the copper cores, which are directly coated with the LaF3 shell.

[0100] Accordingly, the core-shell nanoparticles synthesized in Experimental Example 1 provide a shell capable of protecting the underlying metal core. Such a core-shell nanoparticle is useful for applications where operating conditions would dissolve, oxidize, or otherwise contaminate the metal core. Illustrative examples include the use of the core-shell nanoparticles as battery electrode materials.

[0101] In a non-limiting example, which is shown in Fig. As shown in Figure 9, the core-shell nanoparticles of Experimental Example 1 can be incorporated as the active material into a negative electrode (anode) of an F-shuttle battery. The LaF3 shell protects the copper core, allowing it to act as the active material without being dissolved. As shown in Fig. 10A and Fig. As shown in Figure 10B, the core-shell nanoparticles of Experimental Example 1 were investigated as active materials in an anode. The anode included the core-shell nanoparticles, a conductive agent (super P carbon), and a PVdF binder in a ratio of 8:1:1. Comparison example 2

[0102] An attempt was made to prepare a core-shell nanoparticle with a core comprising a copper nanoparticle directly coated with a shell comprising lanthanum fluoride (Cu / LaF3). Comparative Example 2 was carried out identically to Experimental Example 1, except that 1 mmol of LaCl was used. 3· 7H2O was used instead of La(NO3)3·6H2O.

[0103] The XRD spectrum of the nanoparticles synthesized in Comparative Example 2 is shown in Fig. 11. The XRD spectrum shows five peaks (20°C): 24.5 (LaF3), 27.6 (LaF3), 43.6 (Cu), 50.5 (Cu), and 74.1 (Cu). Therefore, Cu is retained during the reaction of LaCl3 and NaF.

[0104] However, oxidation of the copper after exposure of the core-shell nanoparticles of Comparative Example 2 shows that the shell was not correctly formed. Fig. Figure 12 shows stacked XRD spectra of the nanoparticles synthesized in Comparative Example 2 after exposure to air for 8, 15, and 22 days. Additional peaks are observed starting on day 8 (°20): 35.4, 36.4, 38.8, 42.5, 44.8, 48.7, 52.3, 61.5, and 73.5. At least the peaks at 36.4, 42.5, 61.5, and 73.5 °20 are consistent with Cu2O formation. The peaks at 43.6, 50.5, and 74.1 °20, consistent with copper formation, have also decreased in intensity. As in Fig. As shown in Figure 13, the TEM image shows inhomogeneous, partial coverage of the Cu nanoparticles with LaF3, as well as LaF3 not associated with the copper nanoparticles. Consequently, shells prepared with LaF3 · 7H2O do not result in a desirable core-shell composition, as they leave the copper cores exposed to the environment in an electrochemical cell, which could dissolve the copper cores. Additionally, the LaF3 not associated with the copper nanoparticles would reduce the overall efficiency of any system incorporating this mixture. Study with layered thin-film electrodes

[0105] The core and shell materials can also be investigated in a thin-film electrode configuration. Copper was briefly sputtered to a thickness of approximately 80 nm onto a 1 mm thick glassy carbon substrate. After forming a copper film, LaF3 was sputtered onto the copper layer to a thickness of less than 5 nm to form a double-layer thin film; for comparison purposes, a single-layer copper thin film without LaF3 coating was also prepared. The thin films were investigated in a three-electrode cell configuration using a silver wire soaked in 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPPyTFSI) and 0.01 M AgOTf as the reference electrode and a platinum wire as the counter electrode, and using 0.1 M tetramethylammonium fluoride (TMAF) in MPPyTFSI as the electrolyte. Cyclic voltammetry was performed in the range of -2.4 V to -0.7 V vs. Ag / Ag +measured. Evaluation was carried out in a humidity- and oxygen-free glove box.

[0106] The obtained cyclic voltammograms are shown in Fig. 14. For the double-layer thin film, the measured anodic peak was symmetric to the cathodic peak, with no copper ions detected in the electrolyte by ICP-MS. These results indicate reversible transport of fluoride ions from the LaF3 layer into the copper layer. In comparison, the cyclic voltammogram obtained for single-layer copper thin films is asymmetric. The anodic current is larger than the cathodic current, indicating copper dissolution during the anodic reaction. ICPMS data confirm this, showing 5 ppm of Cu in the electrolyte.

[0107] The double-layered Cu-LaF3 thin-film electrode was also investigated by XPS, at the initial and after fluorination at the voltages determined in Fig. 15A. The initial time (1 in Fig. 15A) was investigated as deposited. The potential was then determined from the open circuit voltage (OCV, approximately -1.5V vs. Ag / Ag + ) was changed to -0.8V and held for 1 hour. After the fluorination reaction, a sample of the electrode was taken for XPS depth profiling analysis.

[0108] In the initial XPS spectrum ( Fig. 15B), the surface contains more La and F than Cu. After fluorination, fluoride ions can be detected to a greater extent at greater depths than in the initial XPS spectrum. In the initial spectrum, fluoride amounts decreased more sharply with increasing depth. Taken together, the XPS data indicate that fluoride ions can penetrate the copper layer. Therefore, fluoride ions can diffuse into the copper cores after reduction. Example 3

[0109] Core-shell nanoparticles with shells of the formula Cu@Ba x La 1-x F 3-x are shown schematically in Fig. 16; Cu@LaF3 is included for comparison purposes. Initially, the copper nanoparticle core can be up to approximately 50 nm in diameter and the LaF3 or Ba x La 1-x The F3-x shell can be approximately 5 nm thick. The CuF2 layer, which forms on the copper core during battery charging, can grow to a thickness of approximately 3 nm in Cu@LaF3 nanoparticles. However, the CuF2 layer can grow to a greater thickness by doping Ba into the LaF3 shell.

[0110] The ionic conductivity of LaF3 is quite low, especially at room temperature, and is only approximately 10 -8,5 S / Cm, which limits F anion transfer. However, the inclusion of Ba doping in the LaF3 shell (i.e., generation of Cu@Ba x La 1-x F 3-x) the conductivity of the shell. The conductivity of LaF3 has been reported to be increased 100-fold by Ba doping; see, for example, M. Anji Reddy and M. Fichtner, Batteries based on fluoride shuttle, J. Mater. Chem. 2011, 21, 17059-17062. The high ionic conductivity promotes CuF2 generation during charging, leading to an improvement in capacity.

[0111] SEM, TEM and EDX images of exemplary Cu@Ba x La 1-x F3-x nanoparticles are in Fig. 17A-H included. XPS can be used to determine the composition of each of the elements. Fig. Figures 18A-D show representative XPS spectral data for a core@shell nanoparticle comprising Cu (64.83%), La (14.68%), Ba (0.28%), F (20.21%), with the shell itself comprising La (41.75%), Ba (0.79%), F (57.46%), confirming that the nanoparticles Cu@La 0,97 Ba 0,03 F 2,97 XRD spectra of Cu@LaF3 and Cu@La 0,97 Ba 0,03F 2,97 are in Fig. 19 shown.

[0112] Fig. 20A-20B demonstrate the capacity improvement achieved by Ba doping according to some aspects of the present disclosure. Fig. Figure 20A shows the voltage profile of the first charge / discharge cycle of a Cu@LaF3 electrode or a Cu@Ba x La 1-x F3-x electrode compared to the Ag / Ag + -reference electrode. The capacity provision of the Ba-doped electrode reaches 95.2 mAh / g compared to only 50.2 mAh / g for Cu@LaF3 ( Fig. 20B). Therefore, Ba doping results in approximately a doubling of the capacity of the LaF3 shell. With the help of Ba doping, the ionic conductivity of the LaF3 shell is increased approximately 100-fold; see, for example, M. Anji Reddy and M. Fichtner, Batteries based on fluoride shuttle, J. Mater. Chem. 2011, 21, 17059-17062. Fluoride ions can more easily migrate through the shell to react with copper to form CuF2, and the amount of CuF2 formation directly determines the battery capacity. The more CuF2 is formed, the higher the battery capacity. Therefore, the utilization of Cu can be approximately doubled by Ba doping of the LaF3 shell.

[0113] Additionally show Fig. 20C and Fig. 20D XRD spectra of Cu@La 0,97 Ba 0,03 F 2,97and Cu@LaF3 in the initial state, i.e., in an electrode before first use, and then after a first charge and a subsequent first discharge. CuF2 can be formed after the first charge and then reduced to copper after the first discharge. Fig. 20C and Fig. 20D suggest that copper can be cycled in liquid electrolytes with both types of shells.

[0114] Copper is a good cathode material for a fluoride shuttle battery because it is an inexpensive, lightweight metal and has a high capacity (theoretical capacity of 843.5 mAh / g). The main challenge with its use is that copper cannot be charged to CuF2 in a liquid electrolyte cell due to Cu dissolution. In Cu@LaF3, the LaF3 shell effectively prevents Cu dissolution during charge / discharge. Therefore, Cu can be charged to CuF2 during charge, and CuF2 can be discharged to Cu during discharge. However, its capacity is low due to the low ionic conductivity of LaF3. With a Ba-doped shell (for example, La 0,97 Ba 0,03 F 2,97) can improve the ionic conductivity of the shell by 100 times, meaning the shell has low resistance. F ions can migrate more easily through the shell, allowing more Cu to be fluorinated to CuF2 during charging. The capacity is doubled compared to the undoped LaF3 shell. With a Ba-doped shell, CuF2 can be detected after charging. CuF2 is reduced to Cu after discharging. It can be confirmed that Cu is rechargeable in liquid cells and that Cu utilization can be improved by Ba-doped shells.

[0115] While the aspects described herein are described in connection with the above examples, various alternatives, modifications, variations, improvements, and / or substantial equivalents that are either already known or that are or may be unforeseen may become apparent to those having at least ordinary skill in the art. Accordingly, the exemplary aspects, as set forth above, are intended to be illustrative only, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.

[0116] Therefore, the claims are not intended to be limited to the aspects shown herein, but are to be given the full scope consistent with the language of the claims, and reference to an element in the singular is not intended to mean "one and only one" unless specifically stated, but rather is intended to mean "one or more".

[0117] Furthermore, the word "example" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as an "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 B, or multiples of C.In particular, 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 mean only A, only B, only C, A and B, A and C, B and C or A and B and C, where any such combination may contain one or more elements of A, B or C.

Claims

[1] Electrochemically active structure comprising: a core comprising metal nanoparticles, and a fluoride-containing shell which at least partially surrounds the metal nanoparticles, wherein the fluoride-containing shell comprises a first and a second metal, and the first metal is barium. [2] The electrochemical structure according to claim 1, wherein the metal nanoparticles are selected from iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles and alkaline earth metal nanoparticles. [3] The electrochemically active structure according to claim 1, wherein the metal nanoparticles comprise copper nanoparticles. [4] An electrochemically active structure according to claim 1, wherein the fluoride-containing shell is directly attached to the core. [5] An electrochemically active structure according to claim 1, wherein the fluoride-containing shell is spaced from the core so as to define a void space therebetween. [6] An electrochemically active structure according to claim 1, wherein the second metal is lanthanum. [7] An electrochemically active structure according to claim 6, wherein the barium and the lanthanum are present in a ratio of x to 1-x such that the sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1. [8] An electrochemically active structure according to claim 7, wherein x is 0.03 to 0.

15. [9] An electrochemically active structure according to claim 8, wherein x is 0.

03. [10] A process for producing coated metal nanoparticles, the process 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. [11] The method of claim 10, wherein the metal nanoparticles comprise iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, copper nanoparticles, lead nanoparticles or alkaline earth metal nanoparticles. [12] The method of claim 10, wherein the metal nanoparticles comprise copper nanoparticles. [13] A method according to claim 10, wherein the fluoride-containing shell is directly attached to the core. [14] A method according to claim 10, wherein the fluoride-containing shell is spaced from the core so as to define a void space therebetween. [15] The process of claim 10, wherein the second metal is lanthanum. [16] A process according to claim 15, wherein the barium and the lanthanum are present in a ratio of x to 1-x and the sum of the moles of barium and the moles of lanthanum in an empirical formula of the fluoride-containing shell is 1. [17] The process of claim 16, wherein x is 0.03 to 0.

15. [18] The method of claim 10, wherein 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 form a fluoride-containing shell around the metal nanoparticle core, wherein the first metal salt is barium salt. [19] The process of claim 18, wherein the second metal salt is a lanthanum salt. [20] The method of claim 19, wherein the first metal salt is barium nitrate and the second metal salt is lanthanum nitrate. [21] A process according to claim 20, wherein the barium nitrate and the lanthanum nitrate are used in a molar ratio of 1:

10. [22] Electrode comprising: a core comprising copper nanoparticles, and a fluoride-containing shell that at least partially surrounds the copper nanoparticles, wherein the fluoride-containing shell comprises barium and lanthanum in a ratio of x to 1 -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. [23] An electrode according to claim 22, wherein x is 0.03 to 0.

15. [24] A fluoride-containing shuttle battery comprising the electrode of claim 22 and a liquid electrolyte.

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