CN104934631B - Metal nanoparticle via novel agent synthesis and the application in electrochemical appliance - Google Patents

Abstract

Application the present invention provides the metal nanoparticle synthesized via novel agent and in electrochemical appliance.Specifically, the nano particle for providing the method for synthesis metal nanoparticle and so preparing.This method includes the novel agent complex compound addition surfactant between zero-valent metal and hydride.The nano particle prepared by this method is included in the zeroth order tin nanoparticles for making oxide-free useful in battery terminal.

Description

Metal nanoparticles synthesized via novel reagents and their application in electrochemical devices

Cross References to Related Applications

This application is a continuation-in-part of Application No. 14/046,120 filed October 4, 2013, which is hereby incorporated by reference in its entirety.

technical field

The present invention relates generally to methods of synthesizing nanoparticles containing two or more zero-valent metals, and also generally to electrodes comprising such nanoparticles and electrochemical cells comprising such electrodes.

Background technique

Metallic nanoparticles, ie, particles of elemental metals in pure or alloyed form with dimensions smaller than 100 nm, possess unique physical, chemical, electrical, magnetic, optical, and other properties compared to their bulk metal counterparts. They are therefore used and developed in fields such as, inter alia, chemistry, medicine, energy and advanced electronics.

Synthetic approaches to metallic nanoparticles are often characterized as "top-down" or "bottom-up" and involve various chemical, physical and even biological pathways. Top-down techniques involve the physical breakdown of macroscale or bulk metals into nanoscale particles using various physical forces. The bottom-up approach involves the formation of nanoparticles from isolated atoms, molecules or clusters.

Physical force methods for top-down metal nanoparticle synthesis include milling of macroscale metal particles, laser ablation of macroscale metals, and spark erosion of macroscale metals. Bottom-up synthetic chemical routes typically involve reduction of metal salts to zero-valent metals combined with growth around nucleating seed particles or self-nucleation and growth into metal nanoparticles.

While each of these approaches may be effective in certain situations, each also has disadvantages or inapplicability to situations. Direct milling methods can be limited in available particle sizes (preparing particles smaller than -20 nm is often difficult) and can result in a loss of stoichiometric control of the alloy. Other physical methods can be expensive or unnamenable for industrial scale.

In cases where the metal cation is resistant to reduction, chemical reduction techniques may not be effective. For example, it is well known that Mn(II) is not affected by chemical reduction. Conventional chemical reaction routes may also not be suitable for preparing nanoparticles for applications that are highly sensitive to oxidation. For example, tin nanoparticles of a size less than 20 nm can be difficult to obtain by reduction routes and even when so obtained they tend to contain a large proportion of SnO ₂ .

Tin is a promising material for battery electrodes. For example, as an anode in Li-ion batteries, tin can store about three times the charge density of commonly used graphite anodes. It has recently been shown that tin-based materials hold promise for use as Mg ion insertion anodes for high energy density Mg ion batteries. In particular, anode materials fabricated from ~100 nm tin powder achieve high capacity and low insertion/extraction voltage.

Upon magnesization of bismuth, which can occur during operation of Mg-ion batteries with _bismuth -based anodes, the superionic conducting material _Mg3Bi2 is believed to form. In contrast, magnesiumized tin does not form a superionic conducting material and as mentioned it is susceptible to poor rate capability. As anode active materials that incorporate the beneficial properties of both tin and bismuth, such as tin-bismuth core-shell nanoparticles, may have the ability to improve the performance of electrochemical cells in general and Mg-ion electrochemical cells in particular.

Contents of the invention

Methods for the synthesis of metal nanoparticles via novel reagents are provided. Electrodes comprising core-shell metal nanoparticles synthesized by the disclosed methods are also provided. Electrochemical cells employing such electrodes are additionally provided.

In one aspect, methods of synthesizing metal nanoparticles are disclosed. The method comprises the step of adding a surfactant to a nuclear agent complex described by formula I to prepare nuclear nanoparticles,

in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero. The method further comprises the step of adding a surfactant to the shell reagent complex described by formula II, in the presence of the core nanoparticles,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero.

In another aspect, electrodes comprising core-shell metal nanoparticles are disclosed. The core-shell metal nanoparticles making up the electrode are synthesized by a method comprising adding a surfactant to a core reagent complex described by formula I to prepare the core nanoparticles,

in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero. The method further comprises the step of adding a surfactant to the shell reagent complex described by formula II, in the presence of the core particle nanometer,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero.

In another aspect, an electrochemical cell is disclosed. The electrochemical cell has electrodes comprising core-shell metal nanoparticles. The core-shell metal nanoparticles making up the electrode are synthesized by a method comprising adding a surfactant to a core reagent complex described by formula I to prepare the core nanoparticles,

in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero. The method further comprises the step of adding a surfactant to the shell reagent complex described by formula II, in the presence of the core nanoparticles,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero.

Description of drawings

Various aspects and advantages of the present invention will become apparent and more readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which:

Figure 1 is the X-ray diffraction spectrum of tin nanoparticles synthesized by the method reported herein; and

Fig. 2A is the X-ray photoelectron spectrum of Sn ⁰ powder;

Figure 2B is the X-ray photoelectron spectrum of the Sn·(LiBH ₄ ) ₂ complex prepared by the method reported herein; and

Figure 2C is the X-ray energy spectrum of the Sn ⁰ powder of Figure 2A and the overlap of the X-ray photoelectron energy spectrum of the Sn·(LiBH ₄ ) ₂ complex prepared by the method of Figure 2B;

Figure 3 is a first cycle magnesification curve for a Mg-ion electrochemical cell with an anode comprising Sn-Bi core-shell nanoparticles synthesized by the method reported herein; and

Figure 4 is the first cycle magnesization curve of a Mg-ion electrochemical cell with an anode comprising Bi-Sn core-shell nanoparticles synthesized by the method reported herein.

Detailed ways

Methods of synthesizing metal nanoparticles, the nanoparticles so synthesized, and electrochemical devices comprising the nanoparticles are described. As explained in the description below, the method involves the reaction between surfactants and novel reagent complexes comprising zero-valent metals and hydrides. A "zero-valent metal" may alternatively be described as an elemental metal or a metal in the zero oxidation state. The novel reagent complexes may alternatively be described as complexes.

As used herein, "metal" may mean alkaline earth metals, alkali metals, transition metals, or post-transition metals. The phrase "transition metal" may mean any D-block metal of Groups 3-12. The phrase "post-transition metal" may mean any metal of Groups 13 to 16, including aluminum, gallium, indium, tin, thallium, lead, or bismuth. In some variations, the metal will be a transition or post-transition metal. In some instances, the metal will be tin.

As used herein, a "hydride" may be a solid metal hydride (such as NaH or MgH ₂ ), a metalloid hydride (such as BH ₃ ), a complex metal hydride (such as LiAlH ₄ ), or also known as a hydride salt Metalloid hydride salts (eg LiBH ₄ ). The term "metalloid" may mean any metalloid among boron, silicon, germanium, arsenic, antimony, tellurium, or polonium. In some examples, the hydride will be LiBH ₄ . Any member of the group consisting of complex metal hydrides and metalloid hydride salts may be referred to as a "complex hydride". It should be understood that the term hydride as used herein may also include the corresponding deuteride or tritium.

The method of synthesizing metal nanoparticles comprises the step of adding a surfactant to a nuclear reagent complex described by formula I to prepare nuclear nanoparticles:

in is a zero-valent metal, where X is a hydride molecule, and where y is an integer or fractional value greater than zero. In some cases, y will be an integer or fractional value equal to or less than four.

The method of synthesizing metal nanoparticles comprises a further step of adding a surfactant to a shell reagent complex described by formula II, in the presence of core nanoparticles,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero. In many cases, y can be a value greater than zero and less than or equal to four. The value represented by y may be an integer value or a fractional value, such as 2.5. The surfactants used in the above two steps may be the same or different.

In some variations of this method, and Will be selected from tin (ten) and bismuth. In some such variants, will be tin and will be bismuth. Among other such variants, will be bismuth and Will be tin.

Without being bound by any particular theory, it is believed that the metal nanoparticles prepared by the above method involving two steps are core-shell metal nanoparticles. As used herein, the phrase "core-shell" means a property in which enrichment at the center of mass of a nanoparticle associated zero-valent metals, while enrichment at the surface is associated with Related zero-valent metals. In some contexts, the phrase "core-shell" may mean a structure in which the Discontinuous cores of associated zero-valent metals are partially or completely surface-coated with Discontinuous layers of associated zero-valent metals. Accordingly, metal nanoparticles synthesized by the disclosed methods will sometimes be referred to herein as "core-shell metal nanoparticles."

Optionally, the second step above can be repeated in order to synthesize nanoparticles with multiple shells. In cases where sequential application of the shell reagent complex and surfactant is employed, the subsequent application should utilize a different method than the immediately preceding application of the shell reagent complex. shell reagent complexes.

As used herein, the term "reagent complex" may mean a core reagent complex, a shell reagent complex, or both. The reagent complex may be a complex of a single molecular entity, such as a single metal atom in the zero oxidation state complexed with one or more hydride molecules. Alternatively, the reagent complex may exist as a molecular cluster, such as a cluster of metal atoms in the zero oxidation state interspersed with hydride molecules, or a cluster of metal atoms in the zero oxidation state coated with hydride molecules or hydride Salt is spread throughout the cluster.

In some aspects of the methods of synthesizing metal nanoparticles, the reagent complex can be contacted in suspension with a solvent or solvent system. In some variations, suitable solvents or solvent systems will include those in which the suspension of the reagent complex is stable in an inert environment for an interval of at least one day. In some variations, suitable solvents or solvent systems will include those in which the suspension of the reagent complex is stable in an inert environment for an interval of at least one hour. In some variations, suitable solvents or solvent systems will include those in which the suspension of the reagent complex is stable in an inert environment for an interval of at least five minutes.

As used herein, the phrase "inert environment" may include an atmospheric environment that is anhydrous. As used herein, the phrase "inert environment" may include an oxygen-free atmospheric environment. As used herein, the phrase "inert environment" may include an atmospheric environment devoid of both water and oxygen. The phrase "inert environment" as used herein may include an enclosure in an ambient atmosphere comprising an inert gas, such as argon, or an enclosure in a space under vacuum.

The term "stable" as used in the phrase "wherein the reagent complex is stable for an interval" may mean that the reagent complex does not significantly dissociate or undergo covalent transitions.

The solvent or solvent system employed in certain of the various aspects disclosed herein can be a material that is non-reactive towards the hydride incorporated into the reagent complex. As used above in the phrase "a material that is non-reactive to a hydride," the term "non-reactive" may mean that the material, i.e., the solvent or solvent system, does not directly participate in or cause the reaction of the hydrogen compound of the reagent complex. Covalently react to a thermodynamically significant degree. According to such criteria, suitable solvents or solvent systems may vary depending on the hydride used. In some variations, this may include solvents or solvent systems that are aprotic, non-oxidizing, or both.

Non-limiting examples of suitable solvents or solvent system components may include acetone, acetonitrile, benzene, 1-butanol, 2-butanol, 2-butanone, t-butanol, carbon tetrachloride, chlorobenzene, chloroform, Cyclohexane, 1,2-dichloroethane, diethyl ether, diethylene glycol, diglyme (diethylene glycol, dimethyl ether), 1,2-dimethoxy-ethane (ethylene glycol Dimethyl ether, DME), dimethyl ether, dimethylformamide (DMF), dimethylsulfoxide (DMSO), dioxane, ethanol, ethyl acetate, ethylene glycol, glycerol, heptane, Hexamethylphosphoramide (HMPA), hexamethylphosphorous triamide (HMPT), hexane, methanol, methyl tert-butyl ether (MTBE), dichloromethane, N-methyl-2-pyrrolidone ( pyrrol idinone) (NMP), nitromethane, pentane, petroleum ether (petroleum), 1-propanol, 2-propanol, pyridine, tetrahydrofuran (THF), toluene, triethylamine, o-xylene, m-di toluene or p-xylene.

As non-limiting examples, halogenated alkyl solvents may be acceptable in some cases, alkyl sulfoxides may be acceptable in some cases, and ethereal solvents may be acceptable in other cases. THF may be a suitable solvent or solvent system component in some variations.

In some aspects of the method of synthesizing metal nanoparticles, the surfactant can be suspended or dissolved in a solvent or solvent system. In the different variants in which the reagent complex is contacted in suspension with a solvent or solvent system and the surfactant is suspended or dissolved in the solvent or solvent system, the reagent complex can be mixed with a solvent or solvent system in which it is dissolved or suspended. The solvent or solvent system of the surfactant is contacted in suspension with the same or different composition of the solvent or solvent system.

In some aspects of the methods of synthesizing metal nanoparticles, the reagent complex can be combined with a surfactant in the absence of a solvent. In some such cases, a solvent or solvent system may be added after such combining. In other aspects, a surfactant that is not suspended or dissolved in the solvent or solvent system can be added to the reagent complex in suspension contact with the solvent or solvent system. In yet another aspect, a surfactant suspended or dissolved in a solvent or solvent system can be added to the reagent complex which is not in suspension contact with the solvent or solvent system.

As used herein, the phrase "surfactant" may mean a surfactant used in one or both steps of the disclosed method for the synthesis of core-shell nanoparticles. The surfactant can be any surfactant known in the art. Useful surfactants may include nonionic, cationic, anionic, amphoteric, zwitterionic, and polymeric surfactants and combinations thereof. Such surfactants typically have a lipophilic moiety that is hydrocarbon-based, organosilane-based, or fluorocarbon-based. Without being meant to be limiting, examples of types of surfactants that may be suitable include alkyl sulfates and sulfonates, petroleum and lignosulfonates, phosphates, sulfosuccinates, carboxylic acids Salts/esters, alcohols, ethoxylated alcohols and alkylphenols, fatty acid esters, ethoxylated acids, alkanolamides, ethoxylated amines, amine oxides, alkylamines, nitriles, quaternary ammonium salts , carboxybetaine, sultaine or polymeric surfactant.

In some cases, the surfactant employed in the method of synthesizing the metal nanoparticles will be a surfactant capable of oxidizing, protonating, or otherwise covalently modifying the hydride incorporated into the reagent complex. In some variations the surfactant may be a carboxylate, nitrile, or amine. In some examples the surfactant can be octylamine.

In some variations the method of synthesizing metal nanoparticles can be performed in an anhydrous environment, in an oxygen-free environment, or in an anhydrous and oxygen-free environment. For example, the method of synthesizing metal nanoparticles can be performed under argon or under vacuum. Although the zero-valent metal ^M0 may contain some impurities such as metal oxides, the method of synthesizing metal nanoparticles can in some cases produce pure metal nanoparticles free of oxide species. Such a situation is shown in Fig. 1 (X-ray diffraction spectrum of zero-valent tin nanoparticles prepared by this method). It should be noted that the diffraction spectrum of Figure 1 indicates pure zero-valent tin without oxides and measures an average largest particle size of 11 nm.

Reagent complexes can be prepared by any suitable method. A non-limiting example of a suitable method of preparing the reagent complex includes the step of ball milling the hydride with a formulation composed of a zero-valent metal. The method for preparing the reagent complex using this step is referred to herein as the "exemplary method". In many cases, formulations comprised of zero-valent metals employed in this exemplary method will have a high surface area to mass ratio. In some cases, formulations comprised of zero-valent metals will be metal powders. It is contemplated that formulations comprised of zero-valent metals may be highly porous metals, metals with a honeycomb structure, or some other formulation with a high surface area to mass ratio.

In some cases, zero-valent metal-containing formulations can include zero-valent transition metals. Suitable transition metals include, but are not limited to, cadmium, cobalt, copper, chromium, iron, manganese, gold, silver, platinum, titanium, nickel, niobium, molybdenum, rhodium, palladium, scandium, vanadium, and zinc. In some cases, a zero-valent metal-containing formulation may include a zero-valent post-transition metal. Suitable post-transition metals include aluminum, gallium, indium, tin, thallium, lead or bismuth.

It should be understood that a zero-valent metal that is a transition metal, post-transition metal, alkali metal or alkaline earth metal will be in the zero oxidation state. As used herein, by "zero valence" and "zero oxidation state" is meant that the material may exhibit an apparent, but not necessarily complete, zero oxidation state. For example, formulations containing zero-valent metals may include some surface impurities such as oxides.

It is contemplated that the phrase "high surface area to mass ratio" may include a wide range of surface area to mass ratios and that generally the surface area to mass ratio of formulations comprised of zero-valent metals employed will be determined by the exemplary method. Time constraints are required. In many cases, a higher surface area to mass ratio formulation composed of zero-valent metal will result in more rapid completion of the exemplary method. For example, where the formulation comprised of zero-valent metals is a metal powder, a smaller particle size of the metal powder may tend to result in more rapid completion of the exemplary method and thus reagent complex preparation.

Non-limiting examples of hydrides suitable for use in this exemplary method include sodium borohydride, lithium aluminum hydride, diisobutylaluminum hydride (DIBAL), lithium triethylborohydride (superhydride), sodium hydride, and potassium hydride , calcium hydride, lithium hydride or borane.

In some variations of this exemplary method, a hydride may be mixed with a formulation composed of a zero-valent metal in a 1:1 stoichiometric ratio of hydride molecules to metal atoms. In other variations, the stoichiometric ratio may be 2:1, 3:1, 4:1 or higher. In some variations, the stoichiometric ratio of hydride molecules to metal atoms in the formulation composed of zero-valent metal may also include fractional amounts, eg, 2.5:1. It will be appreciated that in cases where reagent complexes are prepared using this exemplary method, the stoichiometry of the mixture in this exemplary method will tend to dominate the stoichiometry of the complex according to Formula I as indicated by the value of y.

It is contemplated that the ball mill used in this exemplary method may be of any type. For example, the ball mill used may be a barrel ball mill, a jet mill, a sand mill, a horizontal rotary ball mill, a vibration ball mill or a planetary ball mill. In some examples, the ball mill employed in this exemplary method will be a planetary ball mill.

It is contemplated that the milling media used in this exemplary method may be of any composition. For example, the ball milling media employed may consist of metals such as stainless steel, brass, or hardened lead, or they may consist of ceramics such as alumina or silica. In some variations, the milling media in this exemplary method will be stainless steel. It should be understood that the milling media can be of various shapes, for example they can be cylindrical or spherical. In some variations, the milling media will be spherical.

Optionally, various analytical techniques can be employed to monitor the exemplary method and determine its successful completion. Some such techniques are discussed below, such as X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), but any analytical means known in the art to be useful can optionally be employed.

XPS scans in the tin region for elemental tin powder and for reagent complex Sn·(LiBH ₄ ) ₂ are shown in FIGS. 2A and 2B , respectively. In Figures 2A and 2B, the thick solid line shows the original XPS data and the thin solid line shows the adjusted data. Dashed and/or dotted lines show individual deconvoluted peaks of the spectra. The center point of the eV of the deconvoluted peak maximum is indicated by the arrow.

Figure 2C shows the overlay of the adjusted spectrum of uncomplexed tin (dashed line) from Figure 2A with the adjusted spectrum of the Sn·( _LiBH4 ) ₂ complex from Figure 2B (solid line). As can be seen from Figure 2C, complex formation between zero-valent tin and lithium borohydride leads to the appearance of new peaks and an overall shift in the spectrum towards the lower electron energies of the electrons observed for the zero-valent metal. In some cases where reagent complexes were prepared by this exemplary method, the X-ray photoelectron spectra of the zero-valent metals incorporated into the reagent complexes would overall be in the direction of Lower energy offset. In some cases, reagent complexes in which ^M0 is tin and X is lithium borohydride can be identified by the presence of an X-ray photoelectron spectrum peak centered at about 484 eV.

In some variations, the exemplary methods can be performed in an anhydrous environment, an oxygen-free environment, or an anhydrous and oxygen-free environment. For example, this exemplary method can be performed under argon or under vacuum. This optional feature may be included, for example, when the hydride used in the exemplary method is a hydride sensitive to molecular oxygen, water, or both.

Battery electrodes comprising core-shell metal nanoparticles synthesized by the methods described above are disclosed. As mentioned, Mg-ion batteries employing tin-based anodes have shown promise as high energy density alternatives to conventional Li-ion batteries (N. Singh et al., Chem. Commun., 2013, 49, 149-151; by reference in its The full text is included in this article). In particular, tin anodes based on ~100 nm Sn ⁰ powders show impressive capacities and insertion/extraction voltages in such systems. The drastic reduction of the tin nanostructure of such anodes can improve the rate capability and cyclability of such systems, but oxide-free tin nanoparticles are required. Tin nanoparticles such as the 11 nm oxide-free tin nanoparticles disclosed herein and represented in Figure 1 may be useful anode materials in such battery systems. Furthermore, by forming a bismuth shell around the tin core, defects caused by poor ion diffusion rates in tin can be reduced by exploiting the superconducting properties of magnesized bismuth.

The electrode may include an active material comprising core-shell nanoparticles synthesized by the method for synthesizing core-shell nanoparticles disclosed above. The method comprises the step of adding a surfactant to the reagent complex according to formula I:

in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero. In some cases, y can be a value greater than zero and less than or equal to four. The value represented by y may be an integer value or a fractional value, such as 2.5. The product of this step may be referred to as "core nanoparticles".

The synthesis of the core-shell metal nanoparticles constituting the electrode may include the additional step of adding a surfactant to the shell reagent complex described by formula II, in the presence of the core nanoparticles,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero. In many cases, y can be a value greater than zero and less than or equal to four. The value represented by y may be an integer value or a fractional value, such as 2.5. The surfactants used in the above two steps may be the same or different. In some cases, and Can be Sn and Bi, respectively. In other cases, and Can be Bi and Sn, respectively.

The electrode may be fabricated by any suitable technique, such as pressing powder film, and may include an inactive material such as carbon black and a binder. In some cases, the electrode can comprise metal nanoparticles having an average largest dimension of less than 50 nm. In some cases, the electrode can comprise metal nanoparticles having an average largest dimension of less than 20 nm. In some cases, the electrode can comprise metal nanoparticles having an average largest dimension of about 10 nm. In some cases, the electrode can comprise metal nanoparticles having an average largest dimension of less than 10 nm.

The electrode may comprise nanoparticles of transition metals or post-transition metals. In some variations, the electrode may include tin nanoparticles. In some particular variations, the electrode may comprise tin nanoparticles having an average largest dimension of about 10 nm.

Furthermore, electrochemical cells having electrodes of the type disclosed above are also disclosed. As mentioned, the core-shell nanoparticles constituting the electrode were synthesized by a method comprising the step of adding a surfactant to the reagent complex according to formula I:

in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero. In many cases, y can be a value greater than zero and less than or equal to four. The value represented by y may be an integer value or a fractional value, such as 2.5. The product of this step may be referred to as "core nanoparticles".

The synthesis of the core-shell metal nanoparticles constituting the electrodes included in the electrochemical cell may include the additional step of adding a surfactant in the presence of the core nanoparticles to the shell reagent complex, which is given by the formula II description,

in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero. In many cases, y can be a value greater than zero and less than or equal to four. The value represented by y may be an integer value or a fractional value, such as 2.5. The surfactants used in the above two steps may be the same or different. In some cases, and Can be Sn and Bi, respectively. In other cases, and Can be Bi and Sn, respectively.

The electrodes of the electrochemical cells mentioned above may be anodes or cathodes, but in some special cases may be anodes. In some such special cases, the electrode can be an insertion anode. The electrochemical cell may employ any electrochemical reaction and may be of a type suitable for storage batteries, such as lithium cells as found in lithium-ion batteries, or of a type suitable for fuel cells, such as hydrogen fuel cells.

In some cases, the electrochemical cell may be a magnesium electrochemical cell or a Mg-ion electrochemical cell with a general half-cell reaction of the type described by Reaction Section I:

In some specific cases, the electrochemical cell may be a Mg-ion electrochemical cell with an intercalated anode comprising nanoparticles synthesized according to the present disclosure and comprising a working half-cell reaction according to Reaction II:

where ^M represents the zero-valent metal incorporated into the shell of the core-shell metal nanoparticles according to the present disclosure, where x is the stoichiometric amount, which can be an integer value greater than zero, and where ω is the stoichiometric amount, which Can be an integer value greater than zero. In some such special cases, x can be any of one, two, and three, and ω can be any of one, two, and three.

In still some more specific cases, the electrochemical cell may be a Mg-ion electrochemical cell having an intercalation type containing tin-bismuth core-shell nanoparticles or bismuth-tin core-shell nanoparticles synthesized according to the present disclosure. an anode, and comprising a working half-cell reaction according to at least one of Reaction III and Reaction IV:

Various aspects of the disclosure are further illustrated with respect to the following examples. It should be understood that these examples are provided to illustrate particular embodiments of the disclosure, and that these examples should not be construed to limit the scope of the disclosure in any particular respect or to limit the scope of the disclosure to any particular aspect.

Embodiment 1. Synthesis of tin core nanoparticles

0.503g of tin metal powder and 0.187g of lithium borohydride were combined in a planetary ball mill. The combination was ball milled in a planetary ball mill (using a Fritsch pulervisette 7 planetary ball mill) at 400 rpm in a 250 mL stainless steel airtight ball milling jar for 4 hours to prepare the Sn·(LiBH ₄ ) ₂ reagent complex with 1 ³ / ₄ ", 3 ^1/2 ", and 5 ^1/4 _" 316 stainless steel ball _bearings . The resulting ball-milled complex was suspended in THF. The suspension was titrated with a solution of 0.443 g octylamine in 10 mL THF. The ensuing reaction proceeded to completion at ambient temperature in about 3 hours, resulting in zero-valent tin nanoparticles with an average grain size of about 11 nm, as shown in the X-ray diffraction spectrum of FIG. 1 . The spectrum of Figure 1 indicates pure tin metal without oxide species. The entire synthetic procedure was performed under inert conditions in a glove box to avoid oxidation.

The synthesis of embodiment 2.Sn-Bi core-shell nanoparticles

Bismuth powder and lithium borohydride were combined in a planetary ball mill and ball milled at 400 rpm for 4 hours to prepare Bi·(LiBH ₄ ) ₂ reagent complex. The Bi·(LiBH ₄ ) ₂ reagent complex was co-suspended with the tin nanoparticles of Example 1 in THF and titrated with a 2:1 molar excess of octylamine:Bi·(LiBH ₄ ) ₂ reagent complex to prepare Sn -Bi core-shell nanoparticles. The entire synthetic procedure was performed under inert conditions in a glove box to avoid oxidation.

Example 3. Synthesis of Bi-Sn core-shell nanoparticles

The Bi·(LiBH ₄ ) ₂ reagent complex of Example 2 was suspended in THF and titrated with a 2:1 molar excess of octylamine:Bi·(LiBH ₄ ) ₂ reagent complex to prepare Bi-core nanoparticles. The Sn (LiBH ₄ ) reagent complex of Example 1 was co-suspended with _Bi core nanoparticles in THF and titrated with _a 2:1 molar excess of octylamine:Sn (LiBH ₄ ) reagent complex to prepare Bi-Sn core-shell nanoparticles. The entire synthetic procedure was performed under inert conditions in a glove box to avoid oxidation.

Example 4. Electrode fabrication

Electrodes were formed from Sn—Bi nanoparticles of the type synthesized in Example 2 by a pressed powder film method. Briefly, Sn-Bi nanoparticles (also referred to herein as "active material"), carbon black and polyvinylidene fluoride (also referred to herein as "binder") according to Example 2 were mixed with 70% active material , 20% carbon black and 10% binder (all percentages (w/w)) pressed together. This method prepares Sn-Bi electrodes.

Similarly, electrodes were formed from Bi-Sn nanoparticles of the type synthesized in Example 3 by the pressed powder film method. Briefly, Bi-Sn nanoparticles (also referred to herein as "active material"), carbon black and polyvinylidene fluoride (also referred to herein as "binder") according to Example 3 were mixed with 70% active material , 20% carbon black and 10% binder (all percentages (w/w)) pressed together. This method prepares Bi-Sn electrodes. All electrode fabrication procedures were performed under inert conditions in a glove box to avoid material oxidation.

Example 5. Electrochemical Cell Construction and Testing

Two electrochemical cells were constructed, one using the Sn-Bi electrode of Example 4 and the other using the Bi-Sn electrode of Example 4 as its electrodes. Each electrochemical cell uses a Tomcell structure. Briefly, the electrode of Example 4 (Sn—Bi or Bi—Sn) was opposed to a Mg foil electrode with a glass fiber separator. The electrolyte solution was 3:1 LiBH ₄ :Mg(BH ₄ ) ₂ in 1,2-dimethoxyethane.

One cycle of anodic magnesization was tested at 50°C and at a C rate of C/200. The first cycle magnesiumization curve of the Sn-Bi electrode is shown in FIG. 3 , while the first cycle magnesiumization curve of the Bi-Sn electrode is shown in FIG. 4 . It should be noted that for the bismuth or tin anode active materials, the voltage did not appreciably plateau at the theoretical voltage of the cell, suggesting some degree of alloying at the core-shell interface for each of the two anode types.

The foregoing description relates to what is presently considered to be the most practical implementation. It should be understood, however, that the present disclosure is not limited to these embodiments, but on the contrary, it is intended to cover various changes and equivalent arrangements included within the spirit and scope of the appended claims, which should be given the broadest interpretation , thereby including all such variations and equivalent constructions permitted by law.

Claims (4)

1. A method for synthesizing metal nanoparticles, the method comprising: A surfactant is added to a nuclear reagent complex, which is described by formula I, to prepare core nanoparticles, in is a zero-valent metal, where X is a hydride molecule, and where y is a value greater than zero; and Surfactant is added to the shell reagent complex described by formula II in the presence of core nanoparticles: in is the atomic number different from where X' is a hydride molecule, which may be the same as or different from X, and where y is a value greater than zero. 2. The method of claim 1, wherein and Each is selected from the group comprising zero-valent transition metals and zero-valent post-transition metals. 3. The method of claim 2, wherein and Each is selected from the group consisting of tin and bismuth. 4. The method of claim 3, wherein for tin and for bismuth.