JP6240115B2 - Method for synthesizing metal nanoparticles, electrode comprising core-shell nanoparticles and electrochemical cell having said electrode - Google Patents

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of patent application No. 14 / 046,120 filed on Oct. 4, 2013, which is hereby incorporated by reference in its entirety. Is done.

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

Background Metal nanoparticles are elemental metal particles in a pure or alloy form with a size of less than 100 nm, which are unique physical, chemical, electrical, magnetic, optical compared to the corresponding bulk metal. , And other properties. For this reason, it is used or under development, especially in fields such as chemistry, medicine, energy, and advanced electronics.

  Methods for synthesizing metallic nanoparticles are typically characterized as being “top-down” or “bottom-up” and include various chemical, physical and even biological approaches. Top-down techniques involve physically breaking macroscale or bulk metals into nanoscale particles using various physical forces. Bottom-up methods involve forming nanoparticles from free atoms, molecules, or clusters.

  Methods using physical forces for top-down metal nanoparticle synthesis include milling of macroscale metal particles, laser ablation of macroscale metal, and electrical discharge machining of macroscale metal. The chemical approach of bottom-up synthesis generally involves the reduction of a metal salt to a zero valent metal combined with growth around nucleated seed particles, or self-nucleation and growth into metal nanoparticles.

  While each of these methods can be effective in certain circumstances, it has drawbacks or situational incompatibility. The direct milling method is limited in the size of the particles that can be obtained (it is often difficult to produce particles smaller than about 20 nm) and can lose control of the stoichiometric ratio of the alloy. Other physical methods may be expensive or may not fit on an industrial scale.

Chemical reduction techniques can fail in situations where the metal cation is resistant to reduction. For example, it is well known that Mn (II) is not affected by chemical reduction. Traditional chemical reduction approaches may also be inappropriate for the production of nanoparticles for applications that are very sensitive to oxidation. For example Suzunano particles, to obtain a reduction approach in a size of less than 20nm is difficult, it may tend comprising SnO ₂ be obtained even in a large proportion.

  Tin is a promising material for battery electrodes. For example, as the anode of a Li-ion battery, tin can accumulate about three times the charge density of commonly used graphite anodes. Recently, tin-based materials have shown great promise for use as Mg ion insertion type anodes for high energy density Mg ion batteries. In particular, anode materials made from about 100 nm tin powder achieve high capacity and low insertion / extraction voltage.

When bismuth magnesiumation occurs, this may occur during operation of a Mg ion battery with a bismuth-based anode, but it is believed that the superionic conductive material Mg ₃ Bi ₂ is formed. On the other hand, the magnesium-tin does not form a superionic conductive material and tends to have a low possible output rate as described above. 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 in particular Mg ion electrochemical cells.

SUMMARY A method for synthesizing metal nanoparticles via a novel reagent is provided. An electrode comprising core-shell metal nanoparticles synthesized by the disclosed method is also provided. Further provided is an electrochemical cell using such an electrode.

  In one aspect, a method for synthesizing metal nanoparticles is disclosed. The method comprises the step of adding a surfactant to the core reagent complex to produce core nanoparticles, wherein the core reagent complex is of formula I

Where M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is a value greater than zero. The method also includes adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, wherein the shell reagent complex has the formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X and includes a step where y is greater than zero.

  In another aspect, an electrode comprising core-shell metal nanoparticles is disclosed. The core-shell metal nanoparticles included in this electrode are the addition of a surfactant to the core reagent complex to produce core nanoparticles, wherein the core reagent complex has the formula I

Where M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is synthesized by a method involving a value greater than zero. The method also includes adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, wherein the shell reagent complex has the formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X and includes a step where y is greater than zero.

  In another aspect, an electrochemical cell is disclosed. The electrochemical cell has an electrode comprising core-shell metal nanoparticles. The core-shell metal nanoparticles included in the electrode are formed by adding a surfactant to the core reagent complex to form core nanoparticles, wherein the core reagent complex has the formula I

Where M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is synthesized by a method involving a value greater than zero. The method also includes adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, wherein the shell reagent complex has the formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X, and includes methods where y is greater than zero.

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings, in which:

It is an X-ray-diffraction spectrum of the tin nanoparticle synthesize | combined by the method described here. Sn is an X-ray photoelectron spectrum of ⁰ powder. Here Sn · (LiBH ₄₎ prepared by the process described is an X-ray photoelectron spectrum of the ₂ complex. 2A is an overlay of the X-ray spectrum of the Sn ⁰ powder of FIG. 2A and the X-ray photoelectron spectrum of the Sn. (LiBH ₄ ) ₂ complex prepared by the process of FIG. 2B of FIG. 2 is a first cycle magnesiumation curve for an Mg ion electrochemical cell having an anode comprising Sn—Bi core-shell nanoparticles synthesized by the method described herein. 2 is a first cycle magnesiumation curve for an Mg ion electrochemical cell having an anode comprising Bi—Sn core-shell nanoparticles synthesized by the method described herein.

DETAILED DESCRIPTION A method for synthesizing metal nanoparticles, the nanoparticles thus synthesized, and an electrochemical device comprising the nanoparticles are described. As explained below, this method involves a reaction between a surfactant and a novel reagent complex comprising a zerovalent metal and a hydride. A “zero valent metal” may alternatively be expressed as an elemental metal or a metal with a zero oxidation state. New reagent complexes can alternatively be expressed as complexes.

  As used herein, “metal” may refer to an alkaline earth metal, alkali metal, transition metal, or post-transition metal. The phrase “transition metal” can refer to any D-block metal of Groups 3-12. The phrase “post-transition metal” may refer to any group 13-16 metal including aluminum, gallium, indium, tin, thallium, lead, or bismuth. In some variations, the metal is a transition metal or post-transition metal, and in some examples, the metal is tin.

As used herein, “hydride” is also referred to as solid metal hydride (eg, NaH or MgH ₂ ), metalloid hydride (eg, BH ₃ ), complex metal hydride (eg, LiAlH ₄ ), or salt hydride. It may be a salt metalloid hydride (eg LiBH ₄ ). The term “metalloid” may refer to either boron, silicon, germanium, arsenic, antimony, tellurium, or polonium. In some examples, the hydride is LiBH ₄ . Any member of the group consisting of complex metal hydrides and salt metalloid hydrides may be referred to as “complex hydrides”. It should be understood that the term hydride as used herein can also encompass the corresponding deuteride or tritide.

  The method of synthesizing metal nanoparticles includes adding a surfactant to the core reagent complex to produce core nanoparticles, wherein the core reagent complex has the formula I

Where M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is an integer greater or less than zero. In some cases, y is an integer of 4 or less or a decimal value.

  The method of synthesizing the metal nanoparticles includes another step of adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, the shell reagent complex having the formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X, and y is a value greater than zero. In many cases, y can be a value greater than 0 and less than or equal to 4. The value represented by y can be an integer value or a decimal value such as 2.5. The surfactants used in the above two steps may be the same or different.

In some variations of the method, M _core ⁰ and M _shell ⁰ are selected from the group consisting of tin and bismuth. In some such variations, M _core ⁰ is tin and M _shell ⁰ is bismuth. In other such variations, M _core ⁰ is bismuth and M _shell ⁰ is tin.

Without being bound by any particular theory, it is believed that the metal nanoparticles produced by the above method having two steps are core-shell metal nanoparticles. As used herein, the phrase “core-shell” refers to the property that the zero valent metal associated with M _core ⁰ is concentrated at the center of mass of the nanoparticle while the zero valent metal associated with M _shell ⁰ is enriched at the surface. . In some cases, the phrase “core-shell” means that an individual core of zero valent metal associated with M _core ⁰ is partially or fully surface coated with an individual layer of zero valent metal associated with M _shell ^0. May refer to the structure. Thus, metal nanoparticles synthesized by the disclosed method may be referred to herein as “core-shell metal nanoparticles”.

Optionally, the second step described above can be repeated to synthesize nanoparticles with multiple shell layers. If the shell reagent complex and surfactant are used in succession, the next use should utilize a shell reagent complex having a different M _shell ⁰ compared to the shell reagent complex used immediately before.

As used herein, the term “reagent complex” may refer to a core reagent complex, a shell reagent complex, or both. A reagent complex can be a complex of individual molecular entities, such as a single metal atom with zero oxidation state complexed with one or more hydride molecules . Alternatively, the reagent complexes, clusters of zero oxidation state of the metal atom hydride molecules are scattered or a zero oxidation state of the metal atom clusters, with a hydride molecules or hydrogenated salts are scattered throughout the cluster, It can exist as a molecular cluster such as a surface coated cluster.

  In some embodiments of the method of synthesizing metal nanoparticles, the reagent complex can be in suspension contact with a solvent or solvent system. In some variations, suitable solvents or solvent systems include those in which the suspension of reagent complexes is stable for at least one day in an inert environment. In some variations, suitable solvents or solvent systems include those in which the suspension of reagent complexes is stable for at least 1 hour in an inert environment. In some variations, suitable solvents or solvent systems include those in which the suspension of reagent complexes is stable for at least 5 minutes in an inert environment.

  As used herein, the phrase “inert environment” may include an anhydrous atmospheric environment. As used herein, the phrase “inert environment” may include an anoxic atmospheric environment. As used herein, the phrase “inert environment” may include an anhydrous and anoxic atmospheric environment. As used herein, the phrase “inert environment” may include containment in an atmosphere containing an inert gas such as argon, or containment in a space under vacuum.

  The term “stable” as used in the phrase “reagent complex is stable for a period of time” can mean that the reagent complex does not appreciably separate or covalently convert.

  The solvent or solvent system used in the various particular embodiments disclosed herein can be a material that is unreactive with the hydride contained in the reagent complex. The term “no reaction” as used in the above phrase “material non-reactive with hydride” refers to the covalent reaction of the hydride of the reagent complex to the extent that the material, ie the solvent or solvent system, is thermodynamically significant. It can mean joining directly or not causing this. According to such criteria, the appropriate solvent or solvent system may vary depending on the hydride being used. In some variations, this may include a solvent or solvent system that is aprotic, non-oxidizing, or both.

  Examples of suitable solvents or solvent system components include acetone, acetonitrile, benzene, 1-butanol, 2-butanol, 2-butanone, t-butyl alcohol, carbon tetrachloride, chlorobenzene, chloroform, cyclohexane, 1,2-dichloroethane. , Diethyl ether, diethylene glycol, diglyme (diethylene glycol, dimethyl ether), 1,2-dimethoxy-ethane (glyme, DME), dimethyl ether, dimethyl-formamide (DMF), dimethyl sulfoxide (DMSO), dioxane, ethanol, ethyl acetate, ethylene glycol , Glycerin, heptane, hexamethylphosphoric acid amide (HMPA), hexamethylphosphoric acid triamide (HMPT), hexane, methanol, methyl t-butyl ether ( TBE), methylene chloride, N-methyl-2-pyrrolidinone (NMP), nitromethane, pentane, petroleum ether (ligroin), 1-propanol, 2-propanol, pyridine, tetrahydrofuran (THF), toluene, triethylamine, o-xylene, There can be, but is not limited to, m-xylene or p-xylene.

  In some examples, an alkyl halide solvent may be tolerated, in some examples an alkyl sulfoxide, and in other examples an ethereal solvent may be tolerated, but not limited thereto. In some variations, THF may be a suitable solvent or solvent system component.

  In some embodiments of the method of synthesizing metal nanoparticles, the surfactant can be suspended or dissolved in a solvent or solvent system. In a different variation in which the reagent complex is in suspension contact with a solvent or solvent system and the surfactant is suspended or dissolved in the solvent or solvent system, the reagent complex is a solvent or solvent system in which the surfactant is dissolved or suspended. In suspension contact with a solvent or solvent system of the same or different composition.

  In some embodiments of the method 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 can be added after such coupling. In other embodiments, a surfactant that is not suspended or dissolved in a solvent or solvent system can be added to the reagent complex that is 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 a reagent complex that is not in suspending contact with the solvent or solvent system.

  As used herein, the phrase “surfactant” may refer to a surfactant used in either or both of the steps disclosed for the method of synthesizing core-shell nanoparticles. The surfactant may be any known in the art. Available surfactants can include nonionic, cationic, anionic, amphoteric, zwitterionic, and polymeric surfactants, and combinations thereof. Such surfactants typically have a hydrocarbon-based, organosilane-based, or fluorocarbon-based lipophilic moiety. Examples of types of surfactants that may be suitable include sulfuric acid and alkyl sulfonates, petroleum and lignin sulfonates, phosphate esters, sulfosuccinate esters, carboxylic acid esters, alcohols, ethoxylated alcohols and alkylphenols, fatty acid esters, Examples include, but are not limited to, ethoxylated acids, alkanolamides, ethoxylated amines, amine oxides, alkylamines, nitriles, quaternary ammonium salts, carboxybetaines, sulfobetaines, or polymeric surfactants.

  In some examples, the surfactant used in the method of synthesizing the metal nanoparticles is one that can oxidize, protonate, or covalently modify the hydride contained in the reagent complex. In some variations, the surfactant can be a carboxylate, a nitrile, or an amine. In some examples, the surfactant can be octylamine.

In some variations, the method of synthesizing the metal nanoparticles can be performed in an anhydrous environment, an anoxic environment, or an anhydrous and anoxic environment. For example, the method of synthesizing metal nanoparticles can be performed under argon gas or under vacuum. Although the zero-valent metal M ⁰ may contain some impurities such as metal oxides, the method of synthesizing metal nanoparticles can in some instances produce pure metal nanoparticles that do not contain oxide species. . Such an example is shown in the X-ray diffraction spectrum of the zerovalent tin nanoparticles produced by the method of FIG. It should be understood that the diffraction spectrum of FIG. 1 shows pure zero-valent tin with no oxide, and measures an average maximum particle size of 11 nm.

  The reagent complex can be generated by any suitable process. An example of a suitable process for preparing a reagent complex includes, but is not limited to, ball milling a hydride with a preparation comprising a zerovalent metal. The process using this step of reagent complex formation will be referred to herein as the “exemplary process”. In many instances, preparations composed of zero valent metals used in the example process have a high surface area to mass ratio. In some examples, the preparation consisting of a zero valent metal is a metal powder. It is contemplated that the preparation consisting of a zero valent metal can be a highly porous metal, a honeycomb metal, or other preparation with a high surface to mass ratio.

  In some examples, a preparation containing a zero valent metal can include a zero valent transition metal. 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 examples, a preparation containing a zero valent metal may include a zero valent post transition metal. Suitable post transition metals can include aluminum, gallium, indium, tin, thallium, lead, or bismuth.

  It should be understood that a zero valent metal is zero in the oxidation state, whether it is a transition metal, post-transition metal, alkali metal, or alkaline earth metal. As used herein, “zero valence” and “zero in oxidation state” are intended to mean that the material may exhibit a substantial but not necessarily complete zero oxidation state. For example, a preparation containing a zero valent metal may include some surface impurities such as oxides.

  The phrase “high surface area to mass ratio” encompasses a wide range of surface area to mass ratios, usually where the surface area to mass ratio of the preparation of the zero-valent metal used is required by the time constraints of the example process It is thought that. In many instances, the higher the surface area to mass ratio of a zero-valent metal preparation, the faster the example process will complete. If the preparation of zero-valent metal is, for example, a metal powder, the smaller the particle size of the metal powder, the more likely the completion of the example process and the associated reagent complex formation will be faster.

  Examples of hydrides suitable for use in the example process include sodium borohydride, lithium aluminum hydride, diisobutylaluminum hydride (DIBAL), lithium triethylborohydride (super hydride), sodium hydride and hydrogen. Examples include but are not limited to potassium hydride, calcium hydride, lithium hydride, or boron.

In some variations of the example process, the hydride can be mixed with a preparation of zero valent metal at a 1: 1 hydride molecule to metal atom stoichiometry. In other variations, the stoichiometric ratio can be 2: 1, 3: 1, 4: 1, or higher. In some variations, the stoichiometric ratio of hydride molecules to metal atoms in a preparation consisting of a zerovalent metal may also include a small quantity, such as 2.5: 1. When using an example process for the formation of a reagent complex, the stoichiometry of the mixture in the example process tends to control the stoichiometry as indicated by the y value of the complex according to Formula I. I want you to understand.

  It is contemplated that the ball mill used in the example process may be of any type. For example, the ball mill used can be a drum ball mill, a jet mill, a bead miss, a horizontal rotary ball mill, a vibrating ball mill, or a planetary ball mill. In some examples, the ball mill used in the example process is a planetary ball mill.

  It is contemplated that the ball mill grinding media used in the example process can be of any composition. For example, the ball mill grinding media used may be made of a metal such as stainless steel, brass or hardened lead, or may be made of a ceramic such as alumina or silica. In some variations, the ball mill grinding media in the example process is stainless steel. It should be understood that the ball mill grinding media can be of various shapes, such as cylindrical or spherical. In some variations, the ball mill grinding media is spherical.

  Optionally, various analytical techniques can be used to monitor the example process and determine that it has been successfully completed. Several such techniques, such as X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) are described below, but any analytical approach known to be useful in the art is optionally used. be able to.

XPS scans in the tin region for elemental tin powder and reagent complex Sn. (LiBH ₄ ) ₂ are shown in FIGS. 2A and 2B, respectively. 2A and 2B, a thick solid line indicates raw XPS data, and a thin solid line indicates adjusted data. Dashed lines and / or dotted lines indicate individual deconvoluted peaks of the spectrum. The center point of the deconvoluted peak maximum electron volt is indicated by an arrow.

FIG. 2C shows an overlay of the adjusted spectrum (dotted line) of tin not forming the complex from FIG. 2A with the adjusted spectrum (solid line) of the Sn. (LiBH ₄ ) ₂ complex from FIG. 2B. As can be seen in FIG. 2C, as a result of complex formation between zero-valent tin and lithium borohydride, a new peak appears and the spectrum is entirely transferred to the lower electron energy of the confirmation electrons of the zero-valent metal. doing. In some examples where the reagent complex is prepared by an example process, the X-ray photoelectron spectrum of the zero valent metal contained in the reagent complex is entirely lower toward the lower energy than the spectrum of the non-complexed zero valent metal. Move on. In some examples, reagent complexes in which M ⁰ is tin and X is lithium borohydride can be distinguished by the presence of an X-ray photoelectron spectroscopy peak centered at about 484 eV.

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

Disclosed is a battery electrode comprising core-shell metal nanoparticles synthesized by the method described above. As noted above, Mg ion batteries using 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; hereby incorporated by reference in its entirety). In particular, Suzuanodo based on Sn ⁰ powder of approximately 100nm shows a remarkable capacity and insertion / extraction voltage in such a system. A dramatic reduction in the tin nanostructure of the anode can improve the potential output rate and cycleability of the system, but requires oxygen-free tin nanoparticles. Nanoparticles such as the 11 nm oxygen-free tin nanoparticles disclosed herein and shown in FIG. 1 can be useful anode materials in such battery systems. In addition, by forming a bismuth shell around the tin core, defects caused by the low ion diffusion rate of tin can be mitigated by utilizing the superconducting properties of magnesium bismuth.

  The electrode may comprise an active material comprising core-shell nanoparticles synthesized by the method of synthesizing core-shell nanoparticles disclosed above. The method includes the step of adding a surfactant to the reagent complex according to Formula I;

Here, M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is a value greater than zero. In many cases, y can be a value greater than 0 and less than or equal to 4. The value represented by y can be an integer value or a decimal value such as 2.5. The product of this step can be called “core nanoparticles”.

  The synthesis of the core-shell metal nanoparticles that the electrode comprises includes the additional step of adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, wherein the shell reagent complex has the formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X, and y is a value greater than zero. In many cases, y can be a value greater than 0 and less than or equal to 4. The value represented by y can be an integer value or a decimal value such as 2.5. The surfactants used in the above two steps may be the same or different. In some examples, M _core ⁰ and M _shell ⁰ can be Sn and Bi, respectively. In another example, M _core ⁰ and M _shell ⁰ can be Bi and Sn, respectively.

  The electrode can be made by any suitable technique, such as a compacted membrane method, and can include non-active materials such as carbon black and binders. In some examples, the electrode can include metal nanoparticles with an average maximum dimension of less than 50 nm. In some examples, the electrode can include metal nanoparticles having an average maximum dimension of less than 20 nm. In some examples, the electrode can include metal nanoparticles with an average maximum dimension of about 10 nm. In some examples, the electrode can include metal nanoparticles with an average maximum dimension of less than 10 nm.

  The electrodes can include transition metal or post-transition metal nanoparticles. In some variations, the electrode may include tin nanoparticles. In some particular variations, the electrode may include tin nanoparticles with an average maximum dimension of about 10 nm.

  Also disclosed is an electrochemical cell having an electrode of the type disclosed above. As described above, the core-shell nanoparticles that the electrode comprises are synthesized by a method comprising the step of adding a surfactant to the reagent according to Formula I;

Here, M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is a value greater than zero. In many cases, y can be a value greater than 0 and less than or equal to 4. The value represented by y can be an integer value or a decimal value such as 2.5. The product of this step can be called “core nanoparticles”.

  The synthesis of the core-shell nanoparticles contained by the electrodes contained within the electrochemical cell includes the additional step of adding a surfactant to the shell reagent complex in the presence of the core nanoparticles, where the shell reagent complex is of formula II

Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may have the same or different identity compared to X, and y is a value greater than zero. In many cases, y can be a value greater than 0 and less than or equal to 4. The value represented by y can be an integer value or a decimal value such as 2.5. The surfactants used in the above two steps may be the same or different. In some examples, M _core ⁰ and M _shell ⁰ can be Sn and Bi, respectively. In another example, M _core ⁰ and M _shell ⁰ can be Bi and Sn, respectively.

  The electrode of the electrochemical cell described above may be an anode or a cathode, but in some particular cases may be an anode. In these particular cases, the electrode may be an insertion type anode. The electrochemical cell can be used in any electrochemical reaction, and is suitable for use in a battery such as a lithium cell that can be used in a lithium ion battery, or suitable for use as a fuel cell such as a hydrogen fuel cell. Can be.

  In some examples, the electrochemical cell is a reaction I

May be a magnesium electrochemical cell or Mg ion electrochemical cell having a common half-cell reaction of the type partially represented by

  In some specific examples, the electrochemical cell has an insertion-type anode comprising nanoparticles synthesized according to the present disclosure, and reaction II

Can be an Mg ion electrochemical cell with an effective half-cell reaction according to where M ⁰ represents a zero valent metal incorporated into the shell layer of the core-shell metal nanoparticles according to the present disclosure, and χ is 0 A stoichiometric amount that can be a larger integer value, and ω is a stoichiometric amount that can be an integer value greater than zero. In such a specific example, χ can be any of 1, 2, and 3, and ω can be any of 1, 2, and 3.

  In some other specific examples, the electrochemical cell has an insertion type anode comprising tin-bismuth core-shell nanoparticles or bismuth-tin core-shell nanoparticles synthesized according to the present disclosure, and the reaction III and reaction IV

Mg ion electrochemical cell comprising an effective half-cell reaction by at least one of the following.
Various aspects of the disclosure are further described with reference to the following examples. These examples are provided to illustrate specific embodiments of the present disclosure and should not be construed as limiting the scope of the present disclosure in any particular manner or to any particular aspect. I want you to understand.

Example 1 Synthesis of Tin Core Nanoparticles 0.53 g of tin metal powder and 0.187 g of lithium borohydride are mixed in a planetary ball mill. The mixture is placed on a planetary ball mill for 4 hours in a 250 mL stainless steel airtight ball mill jar equipped with 1-3 / 4 inch, 3-1 / 2 inch, and 5-1 / 4 inch 316 stainless steel ball bearings. Ball milling is performed at 400 rpm (using a Fritsch pullervette 7 ball mill) to produce a Sn. (LiBH ₄ ) ₂ reagent complex. The resulting ball milled complex is suspended in THF. The suspension is titrated with 10 mL of 0.443 g octylamine in THF. The subsequent reaction proceeds at ambient temperature and is completed in about 3 hours, resulting in zero-valent tin nanoparticles having an average particle size of about 11 nm, as shown in the X-ray diffraction spectrum of FIG. The spectrum in FIG. 1 indicates pure tin metal without oxygen species. The entire synthesis procedure is performed in a glove box under inert conditions to avoid oxidation.

Example 2 Synthesis of Sn-Bi core-shell nanoparticles Bismuth powder and lithium borohydride are mixed and ball milled at 400 rpm in a planetary ball mill for 4 hours to produce a Bi. (LiBH ₄ ) ₂ reagent complex. The Bi. (LiBH ₄ ) ₂ reagent complex is 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 form Sn. -Bi core-shell nanoparticles are produced. The entire synthesis procedure is performed in a glove box under inert conditions 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 a 2: 1 molar excess of octylamine: Bi · (LiBH ₄ ) _2. Titration with reagent complex produces Bi core nanoparticles. The Sn · (LiBH ₄ ) ₂ reagent complex of Example 1 was suspended with Bi core nanoparticles in THF and titrated with a 2: 1 molar excess of octylamine: Sn · (LiBH ₄ ) ₂ reagent complex to give Bi. -Sn core-shell nanoparticles are produced. The entire synthesis procedure is performed in a glove box under inert conditions to avoid oxidation.

Example 4 Electrode Production Electrodes are formed from Sn-Bi nanoparticles of the type synthesized in Example 2 by the compaction membrane method. Briefly, Sn-Bi nanoparticles according to Example 2 (also referred to herein as “active substance”), carbon black, and polyvinylidene fluoride (also referred to herein as “binder”) are 70% active substance, Carbon black 20% and binder 10%, all in percentage (w / w), were compressed together. An Sn-Bi electrode was produced by this method.

  Similarly, electrodes are formed from the Bi-Sn nanoparticles of the type synthesized in Example 3 by the compacted film method. Briefly, Bi-Sn nanoparticles according to Example 3 (also referred to herein as "active substance"), carbon black, and polyvinylidene fluoride (also referred to herein as "binder") are 70% active substance, Carbon black 20% and binder 10%, all in percentage (w / w), were compressed together. Bi-Sn electrodes were produced by this method. All electrode manufacturing procedures are performed in a glove box under inert conditions to avoid oxidation of the material.

Example 5 Electrochemical Cell Assembly and Testing Two electrochemical cells were assembled, 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 used a Tomcell structure. Briefly, the electrode of Example 4 (either Sn-Bi or Bi-Sn) was placed on the opposite side of the Mg foil electrode with a glass fiber separator in between. The electrolyte solution was 3: 1 LiBH ₄ : Mg (BH ₄ ) ₂ in 1,2-dimethoxyethane.

  One cycle of anodic magnesium was tested at 50 ° C. and C / 200 C rate. The first cycle magnesiumation curve for the Sn-Bi electrode is shown in FIG. 3, and the first cycle magnesiumation curve for the Bi-Sn electrode is shown in FIG. It should be noted that the voltage does not substantially level at the theoretical cell voltage for either the bismuth or tin anode active material, and some alloy at the core-shell interface for each of the two anode types. Synthesis is suggested.

  The above description relates to what is presently considered to be the most specific embodiment. However, the present disclosure is not limited to these embodiments and, conversely, is intended to include various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which fall within this scope. It is to be understood that the broadest interpretation permitted under law is provided to encompass all such modifications and equivalent structures.

Claims (4)

A method of synthesizing metal nanoparticles,
Adding a surfactant to the core reagent complex to form core nanoparticles, wherein the core reagent complex has the formula I
Where M _core ⁰ is a zero-valent metal, X is a hydride molecule , and y is greater than 0;
Adding a surfactant to the shell reagent complex in the presence of core nanoparticles, said shell reagent complex having the formula II
Where M _shell ⁰ is a zero-valent metal with a different atomic number than M _core ⁰ ,
X ′ is a hydride molecule that may be the same as or different from X, and y is a value greater than 0. The method of claim 1, wherein M _core ⁰ and M _shell ⁰ are each selected from the group comprising a zero-valent transition metal and a zero-valent post-transition metal. The method of claim 2, wherein M _core ⁰ and M _shell ⁰ are each selected from the group comprising tin and bismuth. _4. The method of claim 3, wherein M _core ⁰ is tin and M _shell ⁰ is bismuth.