WO2023007751A1

WO2023007751A1 - Si-containing metal hydrides with expanded superlattice structure for use in proton-conducting rechargeable electrochemical cells

Info

Publication number: WO2023007751A1
Application number: PCT/JP2021/028513
Authority: WO
Inventors: Kwohsiung YOUNG; Ryohei Yoshida
Original assignee: Kawasaki Motors, Ltd.
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2023-02-02

Abstract

Provided are metal hydride materials for use as an electrochemically active material in the anode of a proton-conducting rechargeable battery that includes a hydride of with one or more lattice constants of 7.45 angstroms to 7.55 angstroms when said proton-conducting rechargeable battery is discharged optionally wherein Si is present in the metal hydride at 20 atomic percent or greater. These materials show excellent solid hydride formation leading to improved discharge capacity of proton-conducting rechargeable batteries employing the materials.

Description

Si-containing metal hydrides with Expanded superlattice structure for use in proton-conducting rechargeable electrochemical cells

This disclosure relates to batteries, more specifically rechargeable batteries that cycle protons between the anode and the cathode in the generation of an electrical current that may be used to power one or more devices.

In the field of rechargeable batteries, cycling of the very low molecular weight hydrogen atom represents an attractive alternative to the low equivalent weight alkali metals, such as lithium. Unlike, lithium ion cells, hydrogen ion cycling does not lead to similar internal shorting due to dendrite formation that is common on a lithium anode. Moreover, the dramatic volumetric expansion and contraction observed in a Si anode material when cycling Li is not observed in cells that cycle the much smaller hydrogen ion.

Research has revealed that some metal hydride alloys are capable of absorbing and desorbing hydrogen. When paired with an appropriate cathode material, these hydrogen storage materials possess excellent characteristics that allow them to be employed in proton conducting fuel cells and metal hydride batteries. Early transition metals have a strong tendency for hydride formation that decreases as one moves to the right on the periodic table. Thus, typical proton conducting batteries prefer the use of these strong hydride forming transition metals as a key component in the alloy for use in anode. Other metals contribute as modifiers to improve the electrochemical performance of the metal hydride alloy.

Silicon is a theoretically attractive anode material in proton conducting batteries due to an ability to provide high gravimetric energy of hydrogen storage. The lack of known solid hydrides as well as the relatively low tendency to hydride formation, however, has led away from the use of Si in such systems. As such, there is a need for improved proton conducting electrochemical cells that employ hydrogen storage materials and processes of their manufacture or activation. As will be explained herein below, the present disclosure addresses these needs by providing metal hydrides and proton conducing electrochemical cells with silicon containing anodes that exhibit excellent capacity so they may be effectively used in numerous electrochemical devices. These and other advantages of the disclosure will be apparent from the drawings, discussion, and description that follow.

Summary

The following summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the various aspects of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole. The inventions as described herein are presented in the claims that follow.

The known hydrides of Si are all understood as gas or liquid at room temperature making them unsuitable for use in a battery system. For example, SiH₄ and Si₂H₆ are both gas at room temperature. Si₄H₁₀, Si₅H₁₂, and Si₆H₁₄ are all liquid at room temperature. Moreover, the alkaline aqueous electrolyte typically used in hydroxide ion-conducting batteries is corrosive to silicon based materials making efforts at producing proton conducing rechargeable batteries employing Si as an anode active material difficult. Thus, Si has not been considered a suitable material for proton-conducting batteries that require the electrode active material to be solid at operating temperatures.

Despite these issues, proton conducting batteries have numerous advantages including relatively low cost and improved safety profiles relative to lithium ion batteries. Among the challenges of proton conducing batteries has been improving capacity. Thus, addressing the needs of providing high capacity proton conducting battery systems is desirable. Provided herein are metal hydride materials and proton conducing batteries that employ these metal hydride materials as electrochemically active materials in the anode and for the first time demonstrate high discharge capacities.

As such, provided are metal hydride materials for use as an electrochemically active material in the anode of a proton-conducting rechargeable battery and batteries that include this material, that include: a hydride of Si or a hydride of a Si alloy with one or more superlattice phases, optionally two or more superlattice phases, with one or more lattice constants that is, for the first time, observed in the absence of a carbon binder. The one or more lattice constants is optionally in excess of 7.45 angstroms. This increased lattice constant provides for improved battery capacity. In some aspects, the Si is present in said metal hydride host material at 60 atomic percent or greater relative to all metals in the metal hydride. In some aspects, the Si or Si alloy forms hydrides that are solid at room temperature.

The metal hydride materials before hydrogenation as provided herein have a microstructure. The microstructure is optionally amorphous, nanocrystalline, polycrystalline, a mixture of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous. In some particular aspects, the metal hydride host materials include a polycrystalline microstructure.

In the metal hydride materials as provided herein or batteries employing such materials, the metal hydride may include in some aspects Si_xM_1-x wherein x comprises one or more non-Si group 14 elements, and wherein 0 < x ≦ 1. Optionally, the metal hydride includes Si and 1-3 non-Si group 14 elements, optionally 2 non-Si group 14 elements, optionally 1 non-Si group 14 element. A group 14 element in an anode electrochemically active material is optionally Si. Optionally, Si is the sole non-oxygen and non-hydrogen element in the metal hydride material. In some aspects, the anode active material contains no metals or metalloids other than Si alone or in conjunction with one or more group 14 elements. Optionally, the anode electrochemically active material includes Si and one or more non-Si group 14 elements, optionally C, Ge or combinations thereof. The non-Si group 14 elements are optionally present at 50 atomic percent or less relative to the total group 14 elements in the anode electrochemically active material. In addition, in some aspects and anode electrochemically active material further includes one or more non-group 14 element containing hydrogen storage materials, optionally at 50 weight percent or less.

The metal hydride materials as provided herein are optionally formed into an anode, wherein the anode optionally includes a binder that does not include carbon. Optionally, an anode excludes a TAB-2 binder.

Batteries employing an anode including as an anode electrochemically active material of any of the preceding paragraphs may have a discharge capacity above 800 mAh/g of anode electrochemically active material above 1 Volt vs. Ni(OH)₂ positive electrode, optionally above 1000 mAh/g above 1 Volt, optionally above 1500 mAh/g above 1 Volt. In some aspects, a battery has a maximum discharge capacity of the rechargeable battery is above 3500 mAh/g of anode electrochemically active material.

The battery of any one or more of the preceding paragraphs optionally include a nonaqueous electrolyte that includes one or more aprotic compounds and acid(s) as proton source. The aprotic compounds may optionally include 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium acetate (EMIM), 1,3-dimethylimdiazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris-(hydroxyethyl)methylammonium, or 1,2,4-trimethylpyrazolium. The electrolyte may further include a proton conducting additive, a salt additive, or both. The proton conductive additive optionally includes acetic acid. The salt additive optionally includes potassium. The electrolyte in any of the forgoing paragraphs of this section optionally include less than 10 ppm water.

In any of the aspects of any of the preceding paragraphs of this section optionally include a cathode with a cathode electrochemically active material that may include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, a hydride thereof, an oxide thereof, a hydroxide thereof, an oxyhydroxide thereof, or any combination of the foregoing. In some aspects, the cathode electrochemically active material includes Ni at greater than or equal to 10 atomic percent relative to all metals in the cathode electrochemically active material, optionally at equal to or greater than 80 atomic percent, optionally 90 atomic percent. Optionally, the cathode electrochemically active material includes a hydroxide of Ni, Co, Mn, Zn, Al, or combinations thereof.

The cathode, anode, and electrolyte of any of the foregoing paragraphs are optionally presented in a housing. The anode and cathode are optionally separated by a separator. The anode includes an anode current collector, and the cathode includes a cathode current collector, whereby the anode current collector and the cathode current collector are electrically associated by one or more electron conducting conduits.

The proton conducting batteries are capable of achieving excellent discharge capacity and dramatically pushing the technologies closer to theoretical maximums.

FIG. 1 illustrates an x-ray diffraction (XRD) patterns of a polycrystalline silicon sample in as purchased form and as a charged and discharged anode using the polycrystalline Si according to some aspects as provided herein illustrating the presence of two independent diffraction peaks indicative two superlattice phases of Si in solid form in the anode electrochemically active material; FIG. 2 illustrates an XRD patterns of a nanocrystalline/amorphous silicon sample in as purchased form and as a charged and discharged anode using the crystalline Si according to some aspects as provided herein illustrating the presence of two independent diffraction peaks indicative two superlattice phases of Si in solid form in the anode electrochemically active material; FIG. 3 illustrates a test cell as used to characterize anode electrochemically active materials and electrolytes as provided herein; FIG. 4 illustrates the discharge voltage profile at cycle 2 for superlattice containing sample 1 (polycrystalline Si); and FIG. 5 illustrates the discharge voltage profile at cycle 2 for superlattice containing sample 2 (nanocrystalline and amorphous Si).

DETAILED DESCRIPTION OF VARIOUS ASPECTS

Provided are Si containing metal hydrides suitable for use in proton-conducting rechargeable batteries that demonstrate for the first time superlattice phases with one or more lattice constants in excess of 7.45 angstroms observable in the absence of a carbon containing binder and leading to excellent electrochemical discharge capacity. Metal hydride materials are suitable for use as an anode electrochemically active material, optionally in in powder form associated by a binder, optionally where the binder excludes carbon, or is predominantly non-carbon. As used herein, the metal hydride material may be termed anode electrochemically active material, but are not limited to use in anodes unless otherwise so described. The metal hydride materials include Si or a Si alloy as a hydriding element to produce improved discharge capacities. The metal hydride materials include a hydride of Si or Si alloy with one or more superlattice phases with a lattice constant in excess of 7.45 angstroms. As such, proton-conducting batteries also as provided herein for the first time employ solid hydrides of Si or Si alloys capable of efficiently and effectively reversibly storing protons for use in driving electrical currents.

The metal hydride materials as provided herein are one or more hydrides of Si or Si alloys wherein the hydrides are optionally formed in an anode employing the material during charge. This hydride is formed reversibly such that during discharge the hydride becomes the elemental portion of the anode electrochemically active material generating both a proton and an electron. The half reaction that takes place at the anode can be described as per the following:

where M as provided herein is or includes Si and optionally one or more non-Si group 14 elements.

The corresponding cathode reaction half reaction is typically:

wherein M_c is any suitable metal(s) for use in a cathode electrochemically active material, optionally Ni.

As used herein, the term “battery” or “cell” may be used interchangeably. Optionally, a battery is a collection of two or more cells, wherein each cell may function as a proton conducting battery.

As used herein, an “anode” includes an electrochemically active material that acts as an electron acceptor during charge.

As used herein, a “cathode” includes an electrochemically active material that acts as an electron donor during charge.

As used herein, an “electrochemically active” material is one that includes one or more elements that are able to reversibly absorb a proton (e.g. hydrogen ion).

When atomic percentages (at%) are presented and not otherwise defined, the atomic percentages are presented on the basis of the amount of all elements in the described material other than hydrogen and oxygen.

A “metal” as used in the term “metal hydride” includes elements traditionally considered metals or metalloids such as Si, Ge, and B, and optionally carbon.

A “superlattice” as used herein is understood as a periodic structure of layers of differing physical or chemical characteristics. Different hydrides of the same host metal(s) may have different superlattice structures with different hydrogen content.

Provided herein are metal hydride materials and proton conducting electrochemical cells that include a cathode, an anode employing one or more of the metal hydride materials, and an electrolyte, optionally a non-aqueous electrolyte. The cells employ an anode with an anode electrochemically active material that includes a metal hydride material as provided herein. The metal hydrides as provided herein includes a hydride of Si of Si alloy, optionally where the Si is present at 20 atomic percent or greater of the total metal in the metal hydride material. The hydride of Si or Si alloy is characterized by a superlattice phase with one or more lattice constants of 7.45 angstroms to 7.55 angstroms.

Pure Si materials are known to have a lattice constant of about 5.43 angstroms. Hydrogenation of Si, as well as other metals, results in an expansion of the crystal lattice of the material. For expansion of Si, the expansion direction may be, but need not necessarily be in the c direction. For example, the silicon hydride SiH may have a lattice constant of 7.45 angstroms to 7.55 angstroms and/or SiH₂ of 7.75 angstroms to 7.88 angstroms, which is a significant expansion relative to crystalline Si. These expanded lattice constants are indicative of the formation of interstitial Si hydrides in a material. As such, the Si hydrides as provided herein include material with an observable (by XRD) lattice constant in excess of 7.45 angstroms to 7.55 angstroms, optionally wherein the lattice constant is observable in the absence of a carbon containing binder. As such, for the first time expanded lattice constants indicative of Si or Si alloy hydrides are not due to contributions of a binder in which the samples are analyzed. Optionally, metal hydride material or anode employing a metal hydride material as provided herein excludes an observable peak as measured by XRD of less than 7.45 angstroms.

In some aspects, a metal hydride material is characterized by the presence of a lattice constant of 7.45 angstroms to 7.55 angstroms, which is indicative of the presence of solid SiH in the material. Optionally, one or more lattice constants of about 7.45 angstroms is present in the material. Optionally, on or more lattice constants of about 7.5 angstroms is present in the material. Optionally, on or more lattice constants of about 7.55 angstroms is present in the material. In some aspects, a metal hydride material includes a superlattice constant of about 7.45, about 7.5, and about 7.55 angstroms. These metal hydride materials are solid at the operating temperature of a metal hydride cell and the lattice constants may be measured by XRD and following discharge.

Optionally, a metal hydride material is characterized by the presence of a lattice constants indicative of SiH₂ in the material. Optionally, a superlattice is present with a lattice constant of 7.75 angstroms to 7.88 angstroms, which is indicative of SiH₂ in the material. In some aspects, a lattice constant present is about 7.78 angstroms, optionally about 7.85, optionally both 7.78 and 7.85 angstroms. Optionally, a metal hydride material includes a lattice constant of about 7.5 angstroms and a lattice constant of about 7.8 angstroms. These metal hydride materials are solid at the operating temperature of a metal hydride cell and the lattice constants may be measured by XRD and following discharge.

In some aspects, a metal hydride material is characterized by the presence of a lattice constant of 7.45 angstroms to 7.55 angstroms, which is indicative of the presence of solid SiH in the material, and a lattice constant of 7.75 angstroms to 7.88 angstroms, which is indicative of SiH₂ in the material. Optionally, one or more lattice constants of about 7.45 angstroms is present in the material. Optionally, on or more lattice constants of about 7.5 angstroms is present in the material. Optionally, on or more lattice constants of about 7.55 angstroms is present in the material, optionally about 7.78 angstroms, optionally about 7.85 angstroms, or any combination thereof. Optionally, a metal hydride material includes a lattice constant of about 7.5 angstroms, a lattice constant of about 7.8 angstroms, or both. In some aspects, a metal hydride material includes a superlattice constant of about 7.45, about 7.5, and about 7.55 angstroms. These metal hydride materials are solid at the operating temperature of a metal hydride cell and the lattice constants may be measured by XRD and following discharge.

The metal hydride materials as provided herein may be used as an anode electrochemically active material that optionally includes Si at 20 atomic percent or greater. The anode electrochemically active material is suitable to reversibly absorb hydrogen for use in a proton-conducting electrochemical cell (battery). As such, an anode electrochemically active material optionally includes Si alone or in combination with one or more other metals and/or one or more non-Si group 14 elements. Group 14 elements include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). In some aspects, a group 14 element excludes Pb. Optionally, a group 14 element is C, Si, Ge, or any combination thereof. In some aspects, an anode electrochemically active material includes Si as the sole group 14 element. Optionally, an anode electrochemically active material includes C. Optionally, an anode electrochemically active material includes Ge.

In some aspects, an anode electrochemically active material includes two or more group 14 elements. Optionally, an anode electrochemically active material includes two group 14 elements. Optionally, an anode electrochemically active material includes three group 14 elements. In some aspects, an anode electrochemically active material includes Si and C. Optionally, an anode electrochemically active material includes Si and Ge. Optionally, an anode electrochemically active material includes Si, C, and Ge.

An anode electrochemically active material according to some aspects includes Si and one or more non-Si group 14 elements, optionally C and/or Ge. The non-Si group 14 elements are optionally present at 50 atomic percent or less relative to all group 14 elements in the anode electrochemically active material. Optionally, the non-Si group 14 elements are optionally present at 45 atomic percent or less, optionally 40 atomic percent or less, optionally 35 atomic percent or less, optionally 30 atomic percent or less, optionally 29 atomic percent or less, optionally 28 atomic percent or less, optionally 27 atomic percent or less, optionally 26 atomic percent or less, optionally 25 atomic percent or less, optionally 24 atomic percent or less, optionally 23 atomic percent or less, optionally 22 atomic percent or less, optionally 21 atomic percent or less, optionally 20 atomic percent or less, optionally 15 atomic percent or less, optionally 10 atomic percent or less, optionally 5 atomic percent or less, optionally 4 atomic percent or less, optionally 3 atomic percent or less, optionally 2 atomic percent or less, or optionally 1 atomic percent or less.

In some aspects, an anode electrochemically active material includes Si and Ge, wherein the Ge is present at 50 atomic percent or less relative to all group 14 elements in the anode electrochemically active material. Optionally, the Ge is present at 45 atomic percent or less, optionally 40 atomic percent or less, optionally 35 atomic percent or less, optionally 30 atomic percent or less, optionally 29 atomic percent or less, optionally 28 atomic percent or less, optionally 27 atomic percent or less, optionally 26 atomic percent or less, optionally 25 atomic percent or less, optionally 24 atomic percent or less, optionally 23 atomic percent or less, optionally 22 atomic percent or less, optionally 21 atomic percent or less, optionally 20 atomic percent or less, optionally 15 atomic percent or less, optionally 10 atomic percent or less, optionally 5 atomic percent or less, optionally 4 atomic percent or less, optionally 3 atomic percent or less, optionally 2 atomic percent or less, or optionally 1 atomic percent or less.

In other aspects, an anode electrochemically active material includes Si and C, wherein the C is present at 50 atomic percent or less relative to all group 14 elements in the anode electrochemically active material. Optionally, the C is present at 45 atomic percent or less, optionally 40 atomic percent or less, optionally 35 atomic percent or less, optionally 30 atomic percent or less, optionally 29 atomic percent or less, optionally 28 atomic percent or less, optionally 27 atomic percent or less, optionally 26 atomic percent or less, optionally 25 atomic percent or less, optionally 24 atomic percent or less, optionally 23 atomic percent or less, optionally 22 atomic percent or less, optionally 21 atomic percent or less, optionally 20 atomic percent or less, optionally 15 atomic percent or less, optionally 10 atomic percent or less, optionally 5 atomic percent or less, optionally 4 atomic percent or less, optionally 3 atomic percent or less, optionally 2 atomic percent or less, or optionally 1 atomic percent or less.

An anode electrochemically active material optionally includes Si_xM_1-x wherein M comprises one or more non-Si group 14 elements, and wherein 0 < x ≦ 1, optionally 0 < x < 1. M is optionally C, Ge, a transition metal or other hydride forming element, or any combination thereof. Optionally, M is C. Optionally, M is Ge. Optionally, x is 0.2 or greater, optionally x is 0.25 or greater, optionally x is 0.3 or greater, optionally x is 0.35 or greater, optionally x is 0.4 or greater, optionally x is 0.45 or greater, optionally x is 0.5 or greater, optionally x is 0.55 or greater, optionally x is 0.6 or greater, optionally x is 0.65 or greater, optionally x is 0.7 or greater, optionally x is 0.71 or greater, optionally x is 0.72 or greater, optionally x is 0.73 or greater, optionally x is 0.74 or greater, optionally x is 0.75 or greater, optionally x is 0.76 or greater, optionally x is 0.77 or greater, optionally x is 0.78 or greater, optionally x is 0.79 or greater, optionally x is 0.8 or greater, optionally x is 0.85 or greater, optionally x is 9 or greater, optionally x is 0.95 or greater, optionally x is 0.96 or greater, optionally x is 0.97 or greater, optionally x is 0.98 or greater, or optionally x is 0.99 or greater.

It is appreciated that an anode electrochemically active material may include one or more other non-group 14 elements. Illustrative examples of non-group 14 elements include, but are not limited to lithium, boron, sodium, magnesium, and aluminum. Optionally, when a non-group 14 element(s) is present, the element is at 50 atomic percent or less, optionally 20 at% or less, optionally 10 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less.

An anode electrochemically active material optionally includes one or more non-group 14 element containing hydrogen storage materials. If a non-group 14 element containing hydrogen storage material is present in an anode electrochemically active material, the non-group 14 element containing hydrogen storage material is optionally present at 50 weight percent or less. Optionally the non-group 14 element containing hydrogen storage material is present at 40 weight percent or less, optionally 30 weight percent or less, optionally 20 weight percent or less, optionally 10 weight percent or less, optionally 5 weight percent or less, optionally 3 weight percent or less, optionally 20 weight percent or less, optionally 1 weight percent or less, optionally 0.1 weight percent or less, optionally 0.01 weight percent or less.

Illustrative examples of a non-group 14 element containing hydrogen storage materials that may be included in an anode electrochemically active material include any material known in the art as capable of electrochemically and reversibly storing hydrogen. Illustrative examples of such materials are the AB_x class of hydrogen storage materials where A is a hydride forming element, B is a non-hydride forming element and x is from 1-5. Illustrative examples include the AB, AB₂, AB₃, A₂B₇, A₅B₁₉, and AB₅ type materials as they are known in the art. A hydride forming metal component (A) optionally includes but is not limited to titanium, zirconium, vanadium, hafnium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, or combinations thereof or other metal(s) such as a mischmetal. A B (non-hydride forming) component optionally includes a metal selected from the group of aluminum, chromium, manganese, iron, nickel, cobalt, copper, and tin, or combinations thereof. In some aspects, AB_x type materials that may be further included in an anode electrochemically active material are disclosed, for example, in U.S. Patent 5,536,591 and U.S. Patent 6,210,498. Optionally, non-group 14 element containing hydrogen storage materials are as described in Young, et al., International Journal of Hydrogen Energy, 2014; 39(36):21489-21499 or Young, et al., Int. J. Hydrogen Energy, 2012; 37:9882. Optionally, non-group 14 element containing hydrogen storage materials are as described in U.S. Patent Application Publication No: 2016/0118654. In some aspects, a non-group 14 containing hydrogen storage material includes hydroxides, oxides, or oxyhydroxides of Ni, Co, Al, Mn, or combinations thereof, optionally as described in U.S. Patent No. 9,502,715. Optionally, a non-group 14 containing hydrogen storage material includes a transition metal such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, Sn, Cd, or combinations thereof, optionally as disclosed in U.S. Patent No: 9,859,531.

The Si component of the anode electrochemically active material is characterized by a microstructure. The microstructure of Si in an anode electrochemically active material before hydrogenation is optionally polycrystalline, nanocrystalline, a mixture of nanocrystalline and amorphous, amorphous, or a combination of polycrystalline, nanocrystalline and amorphous. Optionally, a microstructure is not solely amorphous. Optionally, a microstructure is not solely nanocrystalline.

Optionally, a microstructure of the Si material in the anode electrochemically active material before hydrogenation is or includes polycrystalline. Polycrystalline silicon is formed of multiple small silicon crystals or crystallites. The multiple crystallites are typically randomly arranged. Illustratively, polycrystalline Si may be obtained from any recognized commercial supplier, illustratively Wacker Chemi or Hemlock Semiconductor, among others.

Optionally, a microstructure of the Si in the anode electrochemically active material before hydrogenation is a combination of nanocrystalline and amorphous. Nanocrystalline silicon is a form of silicon with a polycrystalline structure that typically includes an amorphous phase, but the nanocrystalline silicon differs from amorphous Si in that the nanocrystalline silicon also includes grains of crystalline silicon within the amorphous phase. Typical sources of amorphous/nanocrystalline silicon include Strem (USA) and Cenate (Norway).

In some aspects, a microstructure of the Si before hydrogenation in the anode electrochemically active material is a combination of polycrystalline, nanocrystalline and amorphous. When polycrystalline Si is present in a mixture of other microstructure silicon(s), the percentage (mass) of polycrystalline phase is 20 percent or less. Optionally, the percentage of polycrystalline Si is 15 percent or less, optionally 10 percent or less, optionally 5 percent or less.

The anode electrochemically active material is optionally presented in a powder form, meaning that the anode electrochemically active material is a solid at 25 degrees Celsius (°C) and free of any substrate. Despite prior belief to the contrary, it was found that solid Si or Si alloys may form hydrides in the solid state and be useful for hydrogen storage or battery applications. The powder is held together by an anode binder that associates the powder particles in a layer that is coated on a current collector in the formation of an anode.

A binder suitable for use in forming an anode (anode binder) is optionally a binder that is not predominantly carbon. Optionally, an anode binder excludes carbon. Optionally, an anode binder is used alone in the absence of any carbon containing binder materials as is known in the art. The ratio of anode electrochemically active material to anode binder is optionally from 4:1 to 1:4. Optionally, the ratio of anode electrochemically active material to anode binder is 1:3 to 1:2. An illustrative example of an anode binder is copper. Cu particles that may be used as an anode binder may be obtained from commercial sources, optionally Kojundo Chemical Laboratory, Japan. Optionally, Cu is the only material used as an anode binder.

An anode binder optionally excludes styrene-butadiene (SB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS) and styrene-ethylene-butadiene-styrene block copolymer (SEBS), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), teflonized acetylene black (TAB-2), styrene-butadiene binder materials, carboxymethyl cellulose (CMC), or any other material that is capable of forming a hydride other than Si or Si alloy of the anode electrochemically active material. Optionally, an anode binder excludes teflonized acetylene black.

In some aspects, an anode binder includes carbon. Illustratively, an anode binder optionally may be styrene-butadiene (SB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS) and styrene-ethylene-butadiene-styrene block copolymer (SEBS), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), teflonized acetylene black (TAB-2), styrene-butadiene binder materials, carboxymethyl cellulose (CMC), or any other material that is capable of forming a hydride other than Si or Si alloy of the anode electrochemically active material. Optionally, an anode binder excludes teflonized acetylene black.

An electrochemical cell with an anode including an anode electrochemically active material as provided herein also includes a cathode that includes a cathode electrochemically active material. A cathode electrochemically active material has the capability to absorb and desorb a hydrogen ion in the cycling of a proton conducting battery so that the cathode active material functions in pair with the anode electrochemically active material to cycle hydrogen and produce an electrical current. Illustrative materials suitable for use in a cathode electrochemically active material include metal hydroxides. Illustrative examples of metal hydroxides that may be used in a cathode electrochemically active material include those described in U.S. Patent Nos: 5,348,822; 5,637,423; 5,366,831; 5,451,475; 5,455,125; 5,466,543; 5,498,403; 5,489,314; 5,506,070; 5,571,636; 6,177,213; and 6,228,535.

In some aspects, a cathode electrochemically active material includes a hydroxide of Ni alone or in combination with one or more additional metals. Optionally, an electrochemically active material includes Ni and 1, 2, 3, 4, 5, 6, 7, 8, 9, or more additional metals. Optionally, a cathode electrochemically active material include Ni as the sole metal.

Optionally, a cathode electrochemically active material includes one or more metals selected from the group of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, a hydride thereof, an oxide thereof, a hydroxide thereof, an oxyhydroxide thereof, or any combination of the foregoing. Optionally, a cathode electrochemically active material includes one or more of Ni, Co, Mn, Zn, Al, Zr, Mo, Mn, a rare earth, or combinations thereof. In some aspects, a cathode electrochemically active material includes Ni, Co, Al, or combinations thereof.

A cathode electrochemically active material may include Ni. Ni is optionally present at an atomic percentage relative to the total metals in the cathode electrochemically active material of 10 atomic percent (at%) or greater. Optionally, Ni is present at 15 at% or greater, optionally 20 at% or greater, optionally 25 at% or greater, optionally 30 at% or greater, optionally 35 at% or greater, optionally 40 at% or greater, optionally 45 at% or greater, optionally 50 at% or greater, optionally 55 at% or greater, optionally 60 at% or greater, optionally 65 at% or greater, optionally 70 at% or greater, optionally 75 at% or greater, optionally 80 at% or greater, optionally 85 at% or greater, optionally 90 at% or greater, optionally 91 at% or greater, optionally 92 at% or greater, optionally 93 at% or greater, optionally 94 at% or greater, optionally 95 at% or greater, optionally 96 at% or greater, optionally 97 at% or greater, optionally 98 at% or greater, optionally 99 at% or greater. Optionally the sole metal in the cathode electrochemically active material is Ni.

A cathode electrochemically active material is optionally in a powder or particulate form. The particles may be held together by a cathode binder to form a layer on a current collector in the formation of the cathode. A binder suitable for use in forming a cathode (cathode binder) is optionally any binder known in the art suitable for such purposes and for the conduction of a proton.

Illustratively, a binder for use in the formation of a cathode (cathode binder) includes but is not limited to polymeric binder materials. Optionally, a cathode binder material is an elastomeric material, optionally styrene-butadiene (SB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS) and styrene-ethylene-butadiene-styrene block copolymer (SEBS). Illustrative specific examples of a cathode binder include, but are not limited to polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyvinyl alcohol (PVA), carbon nanotubes, teflonized acetylene black (TAB-2), styrene-butadiene binder materials, or/and carboxymethyl cellulose (CMC). Illustrative examples may be found in U.S. Patent No: 10,522,827. The ratio of cathode electrochemically active material to cathode binder is optionally from 4:1 to 1:4. Optionally, the ratio of cathode electrochemically active material to cathode binder is 1:3 to 1:2.

A cathode, anode or both may further include one or more additives intermixed with the electrochemically active materials. An additive is optionally a conductive material. A conductive material is optimally a conductive carbon. Illustrative examples of a conductive carbon include graphite. Other examples are materials that contain graphitic carbons, such as graphitized cokes. Still other examples of possible carbon materials include non-graphitic carbons that may be amorphous, non-crystalline, and disordered, such as petroleum cokes and carbon black. A conductive material is optionally present in an anode or a cathode at a weight percent (wt%) of 0.1 wt% to 20 wt%, or any value or range therebetween.

An anode or a cathode may be formed by any method known in the art. For example, an anode electrochemically active material or a cathode electrochemically active material may be combined with a binder, and optionally conductive material, in an appropriate solvent to form a slurry. The slurry may be coated onto a current collector and dried to evaporate some or all of the solvent to thereby form an electrochemically active layer on the surface of the current collector.

A current collector may be in the form of a mesh, foil, or other suitable form. Optionally, a current collector may be formed of aluminum, such as an aluminum alloy, nickel or nickel alloy, steel such as stainless steel, copper or copper alloys, or other such material. A current collector is optionally in the form of a sheet, and may be in the form of a foil, solid substrate, porous substrate, grid, foam or foam coated with one or more metals, or other form known in the art. In some aspects a current collector is in the form of a foil. Optionally, a grid may include expanded metal grids and perforated foil grids. A current collector is optionally formed of any suitable electronically conductive and optionally impermeable or substantially impermeable material, including, but not limited to copper, stainless steel, titanium, or carbon papers/films, a non-perforated metal foil, aluminum foil, cladding material including nickel and aluminum, cladding material including copper and aluminum, nickel plated steel, nickel plated copper, nickel plated aluminum, gold, silver, any other suitable electronically conductive and impermeable material or any suitable combination thereof. Optionally, a current collector may be formed of one or more suitable metals or combination of metals (e.g., alloys, solid solutions, plated metals). Optionally, a current collector for an anode includes or is exclusively steel such as stainless steel.

A proton conducing electrochemical cell may include a separator interposed between an anode and a cathode. A separator may be permeable to a hydrogen ion so as to not appreciably or unacceptably restrict ion transfer between the anode and the cathode. Illustrative examples of a separator include but are not limited to materials such as nylons, polyesters, polyvinyl chloride, glass fibers, and cotton, among others. Illustratively, a separator may be polyethylene or polypropylene.

The proton conducting batteries as provided herein include a non-aqueous proton conducting electrolyte. The electrolyte is disposed between the anode electrochemically active material and the cathode electrochemically active material and allows the flow or other transfer of protons between the anode and the cathode. A non-aqueous electrolyte optionally includes less than 10 wt% water, optionally less than 5 wt% water, optionally less than 1 wt% water. In some aspects, a nonaqueous electrolyte includes less than 100 ppm water, less than 50 ppm water, optionally less than 10 ppm water.

The nonaqueous electrolyte optionally includes one or more aprotic compounds alone or in combination with one or more proton sources such as an organic acid. An aprotic compound is any compound suitable for use in an electrolyte and that is not otherwise detrimentally reactive with any other component of an electrochemical cell. Illustrative examples of an aprotic acid include ammonium or phosphonium compounds, optionally where the ammonium or phosphonium includes one or more linear, branched or cyclic substituted or non-substituted alkyl groups connected to a nitrogen or phosphorous.

A nonaqueous electrolyte optionally includes an ammonium or phosphonium compound with 1, 2, or more linear, branched or cyclic substituted or non-substituted alkyl groups bound to a positively charged nitrogen or phosphorus atom. Optionally, the compounds include one such alkyl, optionally two such alkyls that may be the same or different. Optionally, the ammonium or phosphonium compound alkyl is or includes 1-6 carbon atoms, optionally 1-4 carbon atoms and may be branched, linear or cyclic. In some aspects, the nitrogen or phosphorous is a member of a 5 or 6 membered ring structure that may have one or more pendant groups extending from the central ring. Optionally, ammonium ion is an imidazolium ion. Optionally, a phosphonium ion is a pyrrolidinium ion.

In some aspects, an ammonium or phosphonium includes 1 or 2 linear or cyclic, substituted or unsubstituted alkyls of 1-6 carbon atoms. Optionally, the alkyl includes 2, 3, 4, 5, or 6 carbons. In some aspects, the aprotic compound includes 1 or 2 alkyls of 1-6 carbons. A substitution in an alkyl is optionally a nitrogen, oxygen, sulfur, or other such element. Optionally, an ammonium or phosphonium includes a ring structure with 5-6 members where the ring is substituted with an N, an O, or P.

Illustrative examples of an aprotic compound for use as an electrolyte include, but are not limited to 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium (EMIM), 1,3-dimethylimdiazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris-(hydroxyethyl)methylammonium, 1,2,4-trimethylpyrazolium, or combinations thereof.

The aprotic compound optionally includes one or more anions in conjunction with the aprotic compound. Illustrative examples of an anion include but are not limited to methides, nitrate, carboxylates, imides, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates. Further illustrative examples may be found in U.S. Patent Nos: 6,254,797 and 9,006,457. In specific exemplary aspects, an anion includes carboxylates such as an acetate, phosphates such as a hydrogen, alkyl, or fluorophospate, phophinates such as alkyl phosphinates, among others. Illustrative examples of such aprotic compounds include but are not limited to acetates, sulfonates, or borates of 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium (EMIM), 1,3-dimethylimdiazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris-(hydroxyethyl)methylammonium, 1,2,4-trimethylpyrazolium, or combinations thereof. Specific examples include diethylmethylammonium trifluoromethanesulfonate (DEMA TfO), 1-ethyl-3-methylimidazolium acetate (EMIM Ac) or 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI).

In addition to the aprotic compound, an electrolyte is optionally further supplemented with an organic acid that serves as a proton donor. The presence of the organic acid improves the overall proton conductivity of the electrolyte and thereby improves the function of the proton conducting battery employing the electrolyte. Optionally, an organic acid is a carboxylate. Illustrative examples of a carboxylate include those with 0-10 or more carbons attached to a terminal carboxylic acid. Specific illustrative examples include an acetic acid such as acetic acid or haloacetic acid (e.g. with 1-3 fluorine or chlorine atoms). Optionally an organic acid is acetic acid.

The organic acid is optionally present in the electrolyte at 1-5 moles/kg (m). Optionally, the organic acid is present at 3-4 m. Optionally, the organic acid is present at a molar concentration that is 3-3.5 m.

A nonaqueous electrolyte as used in any of the aspects as provided above or otherwise herein optionally includes one or more additives suitable to produce a maximum capacity of a proton conducting electrochemical cell housing the electrolyte to a discharge capacity of greater than 1000 mAh/g per weight of anode electrochemically active material. It was found that the addition of one or more suitable additives, such as a suitable salt, dramatically improves the formation of a proton conducting electrochemical cell as provided herein, and thereby improves the discharge capacity achievable by the cell. In the otherwise identical cell, it was found that the addition of one or more such additives could boost the maximum capacity, often by as much as 3-7 fold. Without being limited to one particular theory, it is believed that during formation, the availability of free hydrogen within the electrolyte varies to such an extent that cell formation is inhibited. The addition of a suitable salt stabilizes the free hydrogen concentration to thereby boost the resulting capacity achievable by the cell.

A salt additive suitable to produce a maximum capacity of a proton conducting electrochemical cell housing the electrolyte to a discharge capacity of greater than 1000 mAh/g per weight of anode electrochemically active material optionally includes those with a pKa in water of 1-14, optionally 3-13, optionally 7-13, optionally 3-8.

Illustrative examples of a salt additive suitable to produce a maximum capacity of a proton conducting electrochemical cell housing the electrolyte to a discharge capacity of greater than 1000 mAh/g per weight of anode electrochemically active material optionally includes salts of potassium or sodium. Suitable salts include phosphates, carbonates, or sulfates of potassium or sodium. Specific illustrative examples of potassium salts include, but are not limited to potassium phosphate such as mono- or dipotassium phosphate, potassium carbonate, potassium sulfate, among others. Illustrative examples of sodium salts include, but are not limited to sodium mono-, di-, tetra-phosphate, sodium bicarbonate, and sodium hydrogen sulfate.

The salt additive suitable to produce a maximum capacity of a proton conducting electrochemical cell housing the electrolyte to a discharge capacity of greater than 1000 mAh/g per weight of anode electrochemically active material may be present in an electrolyte at 0.01 to 1 m, optionally 0.01 to 0.2 m, optionally 0.5 to 1 m.

The anode, cathode, separator, and nonaqueous electrolyte may be housed in a cell case (e.g. housing). The housing may be in the form of a metal or polymeric can, or can be a laminate film, such as a heat-sealable aluminum foil, such as an aluminum coated polypropylene film. As such, an electrochemical cell as provided herein may be in any known cell form, illustratively, a button cell, pouch cell, cylindrical cell, or other suitable configuration. In some aspects, a housing in is in the form of a flexible film, optionally a polypropylene film. Such housings are commonly used to form a pouch cell. The proton conducting battery may have any suitable configuration or shape, and may be cylindrical or prismatic.

The current collector or substrates may include one or more tabs to allow the transfer of electrons from the current collector to a region exterior of the cell and to connect the current collector(s) to a circuit so that the electrons produced during discharge of the cell may be used to power one or more devices. A tab may be formed of any suitable conductive material (e.g. Ni, Al, or other metal) and may be welded onto the current collector. Optionally, each electrode has a single tab.

The resulting proton conducting batteries as provided herein in any aspect described optionally has a discharge capacity of the rechargeable battery above 800 mAh/g of the anode electrochemically active material above 1 Volt vs. Ni(OH)₂ cathode. Optionally, the discharge capacity is measured following cell formation, optionally at

cycle

1, 2, 3, 4, or 5. The battery optionally has a discharge capacity at or in excess of 900 mAh/g as measured per above, optionally 1000 mAh/g, optionally 1100 mAh/g, optionally 1200 mAh/g, optionally 1300 mAh/g, optionally 1400 mAh/g, optionally 1500 mAh/g, optionally 1600 mAh/g, optionally 1700 mAh/g, optionally 1800 mAh/g, optionally 1900 mAh/g, optionally 2000 mAh/g.

In some aspects, a proton conducting battery as provided herein has a maximum capacity of or in excess of 1000 mAh/g where grams is the weight of the anode electrochemically active material and as measured against a Ni(OH)₂ cathode. Optionally, the maximum capacity, is or is in excess of 1100 mAh/g, optionally 1200 mAh/g, optionally 1300 mAh/g, optionally 1400 mAh/g, optionally 1500 mAh/g, optionally 1600 mAh/g, optionally 1700 mAh/g, optionally 1800 mAh/g, optionally 1900 mAh/g, optionally 2000 mAh/g, optionally 2500 mAh/g, optionally 3000 mAh/g, optionally 3500 mAh/g, optionally 4000 mAh/g, optionally 4500 mAh/g, optionally 5000 mAh/g, optionally 5500 mAh/g, optionally 6000 mAh/g, optionally 6500 mAh/g.

In particular aspects, an electrochemical cell as provided herein includes a cathode comprising a cathode electrochemically active material capable of storing and releasing hydrogen, an anode comprising an anode electrochemically active material of the Si or Si alloy as provided herein including the one or more lattice constants of 7.45 angstroms to 7.55 angstroms when said proton-conducting rechargeable battery is discharged, the anode electrochemically active material in powder form and optionally associated by a binder, optionally a binder that excludes carbon or any other element capable of forming hydrides, wherein a microstructure of the anode electrochemically active material is polycrystalline, a mixture of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous. An electrochemical cell may also optionally include or exclude a non-aqueous electrolyte that includes an ammonium aprotic compound and a carboxylic acid additive, and optionally includes one or more salt additives of potassium or sodium.

In other aspects, an electrochemical cell as provided herein includes a cathode comprising a cathode electrochemically active material comprising Ni, an anode comprising an anode electrochemically active material of a hydride of Si or Si alloy with one or more lattice constants of 7.45 angstroms to 7.55 angstroms and of 7.75 angstroms to 7.88 angstroms when said proton-conducting rechargeable battery is discharged, the anode electrochemically active material in the powder form and associated by a binder, wherein a microstructure of the anode electrochemically active material is polycrystalline, a mixture of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous. The electrochemical cell optionally, but not necessarily, include a non-aqueous electrolyte that includes an ammonium aprotic compound and a carboxylic acid additive, optionally where the anode electrochemically active material includes one or more salt additives of potassium or sodium.

EXPERIMENTAL

Example 1:
A series of silicon containing compositions were obtained from commercial sources. Polycrystalline silicon (sample 1) was obtained from Paraclete (USA). Amorphous/nanocrystalline silicon (sample 2) was obtained from Cenate (Norway). To confirm the microstructure of the silicon, each sample was subjected to analysis by XRD utilizing a Bruker D2 PHASER x-ray diffractometer with Cu-K_α as radiation source.

Anodes were constructed from each of the sample silicon containing materials. The Silicon materials were in powder form and combined with a Cu binder (1 micrometer particle average diameter; Kojundo Chemical Laboratory, Japan) in the dry form at a weight ratio of 1:3. The materials were pressed into a Ni mesh substrate as a current collector (density: 500 g/m², Sumitomo). Ni(OH)₂ cathodes were made by standard methods using commercially sourced and sintered Ni(OH)₂ (Shangdong Xinxu (PRC)) on a stainless steel current collector. The electrolyte was EMIM/AC (1-ethyl-3-methylimidazolium acetate) with 3.3 M acetic acid and 0.1 M K₂HPO₄.

To test the electrochemical properties, the anodes were tested by forming an electrochemical cell within an all-teflon Swagelock tee. The cell used for electrochemical analyses is illustrated in FIG. 3 and includes a central gland 1 capped with ferrules 2 at both ends secured by collars 3. The sample 4 is sandwiched between two current collector rods 5 made from Ni-plated steel (NS) or stainless steel (SS). The top channel is covered with a parafilm 6 as a pressure vent device. The sample is a sandwich of an anode, cathode, and separated by a standard separator. The cell is flooded with an electrolyte including EMIM/AC with 3.33 m acetic acid that included one or more salt additives.

The sample Si anodes were charged at a charge rate of 700 mA/g for 20 hours, and the charged material subjected to analyses by XRD as per the raw Si materials. The anodes were discharged at a discharge rate of 70 mA/g to a discharge cut-off of 0 V and the discharged electrode material also analyzed by XRD. FIG. 1 illustrates XRD spectra of the pristine (before cycling), charged and discharged materials for sample 1. The pristine sample showed the characteristic polycrystalline Si peak only, which is expected of this material. Following charge, however, the XRD spectrum showed a clear peak at 11.8° clearly corresponding to an interlayer distance (e.g superlattice phase) of 7.5 Å (marked as B) and corresponding to the presence of solid SiH. Following discharge, the material showed in addition to the B peak, a second peak (marked as A) locating at 11.3° corresponding to an interlayer distance of 7.8 Å demonstrating the presence of solid SiH₂. These spectra demonstrate that the polycrystalline Si was converted to solid Si hydride material with a strong superlattice structure during discharge that evolved (at least partially) into an amorphous structure during charge.

Similar results are observed for sample 2. As revealed in FIG. 2, XRD from the pristine electrode showed the expected broad nanocrystalline Si peak with no other observed structures. Following charge, the XRD spectrum from was absent any peak at all suggesting an amorphous structure. Following discharge, the XRD spectrum produced two peaks (A (interlayer distance of 7.8 Å) and B (interlayer distance of 7.5 Å)) indicating that the amorphous/nanocrystalline Si in the charged state was converted to a strong superlattice structure during discharge. These data reveal a conversion from a strong superlattice structure in the discharged state to an amorphous/nanocrystalline state following charge.

Overall, these data demonstrate the presence of large superlattice structures formed with extensive lattice constants indicating the presence of solid Si hydride formation in the anode electrochemically active material, without a contribution to the lattice constant from any carbon or other material capable of forming hydrides.

Cells with the Si electrochemically active material in the anodes formed as per above were cycled with a charge rate of 700 mA/g, charge time: 20 hours and a discharge rate of 70 mA/g to a discharge cut-off of 1.0 V, 0.5 V or 0 V. The charge and discharge profiles following cell formation at cycle 2 for polycrystalline Si (sample 1) (FIG. 4) and cycle 2 for a mix of nanocrystalline and amorphous silicon (sample 2) (FIG. 5) demonstrate high capacity in excess of 1800 mA/g (of Si) for all samples tested. There was little observed difference between the profiles of

samples

1 and 2. Discharge capacities at the first five cycles for both samples are illustrated in Table 1.

The foregoing description of particular aspect(s) is merely exemplary in nature and is in no way intended to limit the scope of the invention as claimed below, its application, or uses, which may, of course, vary. The disclosure is provided with relation to the non-limiting definitions and terminology included herein. These definitions and terminology are not designed to function as a limitation on the scope or practice of the invention but are presented for illustrative and descriptive purposes only. While the processes or compositions are described as an order of individual steps or using specific materials, it is appreciated that steps or materials may be interchangeable such that the description of the invention may include multiple parts or steps arranged in many ways as is readily appreciated by one of skill in the art.

It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, “a first element,” “component,” “region,” “layer,” or “section” discussed below could be termed a second (or other) element, component, region, layer, or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. The term “or a combination thereof” means a combination including at least one of the foregoing elements.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Patents, publications, and applications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. These patents, publications, and applications are incorporated herein by reference to the same extent as if each individual patent, publication, or application was specifically and individually incorporated herein by reference.

In view of the foregoing, it is to be understood that other modifications and variations of the present invention may be implemented. The foregoing drawings, discussion, and description are illustrative of some specific embodiments of the invention but are not meant to be limitations upon the practice thereof. It is the following claims, including all equivalents, which define the scope of the invention.

Claims

A metal hydride material for use as an electrochemically active material in an anode of a proton-conducting rechargeable battery comprising:
a hydride of Si or Si alloy with one or more superlattice phases with one or more lattice constants of 7.45 angstroms to 7.55 angstroms when said proton-conducting rechargeable battery is discharged.
The material of claim 1 wherein said one or more lattice constants is about 7.5 angstroms when said proton-conducting rechargeable battery is discharged.
The material of claim 1 wherein said hydride of Si is solid at room temperature.
The material of claim 1 wherein said metal hydride material comprises equal to or greater than 60 atomic percent Si relative to all metal in said material.
The material of any one of claims 1-4 wherein said metal hydride material before hydrogenation has a microstructure that is amorphous, polycrystalline, a mixture of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous.
The material of claim 5 wherein said metal hydride material before hydrogenation comprising a polycrystalline microstructure.
The material of claim 5 comprising two or more superlattice phases.
The material of any one of claims 1-4 wherein said metal hydride material comprises Si_xM_1-x wherein M comprises one or more transition metals or a non-Si group 14 element, or both, and wherein 0 < x ≦ 1.
The material of any one of claims 1-4 wherein the metal hydride material comprises two or more group 14 elements.
The material of any one of claims 1-4 wherein the metal hydride material consists of Si as the sole non-oxygen or non-hydrogen element.
The material of any one of claims 1-4 wherein the metal hydride material comprises Si and one or more non-Si group 14 elements.
The material of claim 11 wherein the one or more non-Si group 14 elements is Ge, C, or a combination thereof.
The material of any one of claims 1-4 wherein the hydride of Si or Si alloy further comprises one or more superlattice phases with one or more lattice constants of 7.75 angstroms to 7.88 angstroms when said proton-conducting rechargeable battery is discharged.
A proton-conducting rechargeable battery comprising:
a cathode comprising a cathode electrochemically active material capable of storing and releasing hydrogen;
an anode comprising the metal hydride material of any one of claims 1-4, and
a non-aqueous electrolyte between the anode and the cathode.
The battery of claim 14 wherein said metal hydride material before charge/discharge has a microstructure that is amorphous, polycrystalline, a mixture of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous.
The battery of claim 15 wherein the alloy before charge/discharge comprises a polycrystalline microstructure.
The battery of claim 15 wherein the alloy before charge/discharge excludes amorphous Si.
The battery of any one of claims 14-17 wherein said metal hydride material comprises Si_xM_1-x wherein M comprises one or more non-Si group 14 elements, a transition metal, or combinations thereof, and wherein 0 < x ≦ 1.
The battery of any one of claims 14-17 wherein the metal hydride material comprises two or more group 14 elements.
The battery of any one of claims 14-17 wherein the metal hydride material consists of Si as the sole non-hydrogen or oxygen element in said metal hydride material.
The battery of any one of claims 14-17 wherein the metal hydride material comprises Si and one or more non-Si group 14 elements.
The battery of claim 21 wherein the one or more non-Si group 14 elements is Ge, C, or a combination thereof.
The battery of any one of claims 14-17 wherein the metal hydride comprises one or more non-Si group 14 elements, wherein an amount of non-Si group 14 elements is 50 atomic percent or less relative to the total group 14 elements in the metal hydride material, optionally wherein the amount of non-Si group 14 elements is less than 40 atomic percent.
The battery of any one of claims 14-17 wherein the hydride of Si or Si alloy further comprises one or more superlattice phases with one or more lattice constants of 7.75 angstroms to 7.88 angstroms when said proton-conducting rechargeable battery is discharged.
The battery of any one of claims 14-17 having a discharge capacity greater than 800 mAh/g per weight of anode electrochemically active material above 1 Volt, optionally greater than 1000 mAh/g above 1 Volt, optionally greater than 1500 mAh/g above 1 Volt.
The battery of any one of claims 14-17 having a maximum discharge capacity is above 3500 mAh/g per weight of anode electrochemically active material.
The battery of any one of claims 14-17 wherein the electrolyte comprises one or more aprotic compounds.
The battery of claim 27 wherein the aprotic compounds comprise 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium acetate (EMIM), 1,3-dimethylimdiazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris-(hydroxyethyl)methylammonium, or 1,2,4-trimethylpyrazolium.
The battery of claim 27 wherein the electrolyte further comprises an additive, the additive comprising potassium, sodium, calcium, magnesium, or combinations thereof.
The battery of claim 29 wherein the additive is a phosphate, carbonate, or sulfate of potassium.
The battery of any one of claims 14-17 wherein the electrolyte comprises less than 5 weight percent of water.
The battery of any one of claims 14-17 wherein the cathode electrochemically active material comprises Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, a hydride thereof, an oxide thereof, a hydroxide thereof, or an combination of the foregoing.
The battery of claim 32 wherein the cathode electrochemically active material comprises Ni at greater than or equal to 10 atomic percent relative to all metals in the cathode electrochemically active material.
The battery of claim 33 wherein Ni is present at equal to or greater than 80 atomic percent, optionally 90 atomic percent.
The battery of claim 32 wherein the cathode electrochemically active material comprises a hydroxide of Ni, Co, Mn, Zn, Al, or combinations thereof.
The battery of claim 32 wherein the cathode electrochemically active material comprises Mn, Ni, or a combination thereof.