Bulk Si negative electrode used in a proton-conducting secondary battery

Abstract

A proton-conducting secondary battery exhibiting excellent capacity is provided. The secondary battery includes a positive electrode including a positive electrode electrochemically active material capable of absorbing and releasing hydrogen, for example, including Ni, and a negative electrode including one or more Group 14 elements, the negative electrode electrochemically active material being in powder form and bound by a binder, the microstructure of the negative electrode electrochemically active material being polycrystalline, a combination of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous. The battery includes a non-aqueous electrolyte and is characterized by exhibiting a discharge capacity of greater than 800 mAh / g in the negative electrode electrochemically active material at a voltage greater than 1 volt.

Description

Technical Field

[0001] The present disclosure relates to a battery, and more specifically, to a secondary battery that circulates protons between a negative electrode and a positive electrode in the generation of an electric current used to supply power to one or more devices.

Background Art

[0002] Alkali metals with a small equivalent weight such as lithium are particularly useful as battery constituent materials. By using lithium, the energy per unit weight can be increased compared to nickel and cadmium that have been conventionally used. However, in the development of rechargeable lithium metal batteries, an effective battery cycle is an important development issue. When charging and discharging are repeated, "dendrites" of lithium are gradually generated on the surface of the lithium metal electrode, and these grow to the extent of finally contacting the positive electrode, causing an internal short circuit of the battery, and there is a possibility that the battery becomes unusable after a relatively small number of cycles. On the other hand, silicon is generally used as a negative electrode material for lithium-ion batteries because of its extremely high theoretical specific capacity (4000 mAh / g), but when circulated with lithium, it causes a remarkable volume lattice expansion of as much as 400%. Due to this volume expansion, the cycle life is further shortened, and the material cannot be effectively used in many systems.

[0003] Therefore, a technology that circulates hydrogen atoms with an extremely low molecular weight is considered promising as a secondary battery technology. Some materials such as metal hydride alloys and nickel hydroxide are known to be able to occlude and release hydrogen. By combining with an appropriate negative electrode material, these hydrogen storage materials can be used in fuel cells and metal hydride batteries.

[0004] Silicon is also a useful anode material in proton-conducting batteries because it theoretically provides high gravimetric energy in hydrogen storage. However, the alkaline aqueous electrolytes commonly used in these systems are corrosive to silicon-based materials, so efforts are required to realize a proton-conducting secondary battery using Si as the anode active material. In recent years, attempts have been made to use new electrolyte materials to enable the use of silicon-based anode active materials in batteries. However, silicon (Si) has been considered to be usable only for applications in thin films because when the film thickness is increased to, for example, about 250 nanometers, the fracture stress reaches a critical value, resulting in a reduction in capacity and insufficient cycle life.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Thus, improvements to proton-conducting electrochemical cells of the type using hydrogen storage materials and to the processes for their manufacture and activation have been sought. As will be described below in this specification, the present disclosure provides a proton-conducting electrochemical cell comprising a non-aqueous electrolyte and a silicon-based anode, thereby realizing a cell with excellent capacity, making it usefully applicable in numerous electrochemical devices, and addressing the above needs. These and other advantages of the present disclosure will become apparent from the following drawings, discussion, and description.

Means for Solving the Problems

[0006] The following summary is provided to facilitate easy understanding of some of the novel features specific to the present disclosure and is not intended to be a complete description. A complete understanding of the various aspects of the present disclosure can be obtained by considering the entire specification, claims, drawings, and abstract together. The invention described in this specification is set forth in the following claims.

[0007] Proton-conducting batteries have numerous advantages, such as being relatively low-cost and having improved high-stability characteristics compared to lithium-ion batteries. Among multiple issues, proton-conducting batteries have particularly improved their capacity. Therefore, it has been desired to address the need for providing a high-capacity proton-conducting battery system. This specification provides a proton-conducting battery using Si as the negative electrode, and demonstrates that it has achieved a high discharge capacity of 800 mAh / gram as the negative electrode active material at a voltage higher than 1V, ahead of others.

[0008] Thus, the proton-conducting secondary battery includes a positive electrode containing a positive electrode electrochemically active material capable of storing and releasing hydrogen, a negative electrode containing a negative electrode electrochemically active material of one or more Group 14 elements, the negative electrode electrochemically active material being in powder form and bonded by a binder, and the microstructure of the negative electrode electrochemically active material being polycrystalline, a combination of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline, and amorphous, a non-aqueous electrolyte interposed between the negative electrode and the positive electrode, and the discharge capacity of the secondary battery exceeds 800 mAh / g in the negative electrode electrochemically active material when the voltage is higher than 1 volt with respect to the Ni(OH)2 positive electrode.

[0009] In the above battery, the negative electrode active material may contain, in some aspects, 1 to 3 different Group 14 elements, for example, 2 Group 14 elements, for example, 1 Group 14 element. The Group 14 element in the negative electrode electrochemically active material is, for example, Si. In some aspects, this negative electrode active material does not contain metals or metalloids other than one or more Group 14 elements. For example, the negative electrode electrochemically active material includes Si and one or more non-Si Group 14 elements, such as C, Ge, or a combination thereof. The non-Si Group 14 element is present, for example, at 50 atomic percent or less with respect to all Group 14 elements in the negative electrode electrochemically active material. Also, in some aspects, the negative electrode electrochemically active material further includes, for example, at 50 weight percent or less, one or more non-Group 14 element-containing hydrogen storage materials.

[0010] One or both of the batteries in the previous two paragraphs have a discharge capacity exceeding 1000 mAh / g in the negative electrode electrochemical active material when the voltage is higher than 1 V, for example, a discharge capacity exceeding 1500 mAh / g when the voltage is higher than 1 V. In some aspects, the battery has the maximum discharge capacity of a secondary battery, and the discharge capacity exceeds 3500 mAh / g in the negative electrode electrochemical active material.

[0011] Any one or more of the batteries in the previous paragraph includes, for example, a non-aqueous electrolyte containing one or more aprotic compounds and an acid as a proton source. The aprotic compound may include, for example, 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium acetate (EMIM), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris(hydroxyethyl)methylammonium, or 1,2,4-trimethylpyrazolium. The electrolyte may further include a proton-conductive additive, a salt additive, or both. The salt additive includes, for example, acetic acid. The salt additive includes, for example, potassium. The electrolyte in any of the previous paragraphs of this section contains, for example, less than 10 ppm of water.

[0012] In any aspect of the previous paragraphs of this section, the positive electrode includes a positive electrode electrochemical active material that may include, for example, 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, their hydrides, their oxides, their hydroxides, their oxyhydroxides, or any combination of the foregoing. In some aspects, the positive electrode electrochemical active material contains Ni at 10 atomic percent or more, for example 80 atomic percent or more, for example 90 atomic percent or more, based on all the metals in the positive electrode electrochemical active material. For example, the positive electrode electrochemical active material includes hydroxides of Ni, Co, Mn, Zn, Al, or combinations thereof.

[0013] The positive electrode, negative electrode, and electrolytic solution shown in any of the foregoing paragraphs may be disposed, for example, within a housing. The negative electrode and the positive electrode may be separated by a separator, for example. The negative electrode includes a negative electrode current collector, and the positive electrode includes a positive electrode current collector. Thereby, the negative electrode current collector and the positive electrode current collector are electrically coupled by one or more electron conductive conductors.

Advantages of the Invention

[0014] According to this proton conductive battery, excellent capacity can be realized, the capacity can be brought close to the theoretical maximum, and the technology can be advanced by leaps and bounds.

Brief Description of the Drawings

[0015]

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BRIEF DESCRIPTION OF THE INVENTION

[0016] Provided is a proton-conducting secondary battery that has been demonstrated to have excellent capacity. The proton-conducting battery provided herein does not require a thin-film anode, eliminating concerns such as film delamination and its associated capacity loss as in the case of conventional Si-containing anode electroactive materials. The battery uses an anode containing an anode electroactive material in the form of powder agglomerated by a binder. This powdered anode uses solid Si as a hydrogenating element ahead of others in the proton-conducting battery, thereby achieving a large capacity. By using one or more Group 14 elements with a microstructure that is polycrystalline, amorphous, a combination of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline, and amorphous, the battery produces an excellent discharge capacity of over 800 mAh / g for the anode electroactive material at a voltage higher than 1 volt compared to the Ni(OH)2 cathode.

[0017] The "proton-conducting secondary battery" as used herein differs in many respects from conventional batteries that use metal hydrides, such as not using an aqueous electrolyte. This new type of proton-conducting secondary battery operates, like conventional batteries, by circulating hydrogen between the anode and the cathode. Thereby, during charging, hydrides of one or more elements are formed at the anode. This hydride is a reversible product and, during discharge, generates both protons and electrons as part of the anode electroactive material. The half-reaction occurring at the anode is explained by the following half-reaction formula.

[0018]

Chemical formula

[0019] The half-reaction formula in the corresponding cathode reaction usually is as follows.

[0020] [Chemical] In the formula, M c is any suitable type of metal used as the positive electrode electrochemically active material, and may be, for example, Ni.

[0021] The terms "battery" or "cell" used in this specification may be used interchangeably. For example, a battery may be a collection of two or more cells, and each cell may function as a proton-conducting battery.

[0022] As used herein, the "negative electrode" contains an electrochemically active material that acts as an electron acceptor during charging.

[0023] As used herein, the "positive electrode" contains an electrochemically active material that acts as an electron donor during charging.

[0024] A substance having "electrochemically active" as used herein contains one or more elements capable of reversibly occluding hydrogen ions.

[0025] When atomic percentages (at%) are indicated and there is no other definition, the atomic percentages are indicated based on the amounts of all elements in the described materials other than hydrogen and oxygen.

[0026] Thus, a proton-conducting electrochemical cell including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided herein. The cell uses a negative electrode containing a negative electrode electrochemically active material including one or more Group 14 elements. Different from the uses of conventional thin films formed by Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD), the negative electrode electrochemically active material provided herein has a microstructure that is polycrystalline, or composed of a combination of nanocrystals and amorphous, or composed of a combination of polycrystals, nanocrystals and amorphous.

[0027] The negative electrode electrochemical active material contains, for example, one or more Group 14 elements. The Group 14 elements include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). In some aspects, the Group 14 elements do not include Pb. For example, the Group 14 elements may be C, Si, Ge, or any combination thereof. In some aspects, the negative electrode electrochemical active material may contain Si. For example, the negative electrode electrochemical active material may contain C. For example, the negative electrode electrochemical active material may contain Ge.

[0028] In some aspects, the negative electrode electrochemical active material may have two or more Group 14 elements. For example, the negative electrode electrochemical active material may contain two Group 14 elements. For example, the negative electrode electrochemical active material may include three Group 14 elements. In some aspects, the negative electrode electrochemical active material may contain Si and C. For example, the negative electrode electrochemical active material may contain Si and Ge. For example, the negative electrode electrochemical active material may contain C and Ge. For example, the negative electrode electrochemical active material may contain Si, C, and Ge.

[0029] The negative electrode electrochemical active material according to some aspects contains Si and one or more Group 14 non-Si elements, and may contain, for example, C and / or Ge. The Group 14 non-Si element may be present, for example, at 50 atomic percent or less with respect to all Group 14 elements in the negative electrode electrochemical active material. The Group 14 non-Si element may be present, for example, at 45 atomic percent or less, for example, 40 atomic percent or less, for example, 35 atomic percent or less, for example, 30 atomic percent or less, for example, 29 atomic percent or less, for example, 28 atomic percent or less, for example, 27 atomic percent or less, for example, 26 atomic percent or less, for example, 25 atomic percent or less, for example, 24 atomic percent or less, for example, 23 atomic percent or less, for example, 22 atomic percent or less, for example, 21 atomic percent or less, for example, 20 atomic percent or less, for example, 15 atomic percent or less, for example, 10 atomic percent or less, for example, 5 atomic percent or less, for example, 4 atomic percent or less, for example, 3 atomic percent or less, for example, 2 atomic percent or less, or for example, 1 atomic percent or less.

[0030] In some aspects, the negative electrode electrochemical active material contains Si and Ge, and Ge may be present at 50 atomic percent or less with respect to all Group 14 elements in the negative electrode electrochemical active material. Ge may be present, for example, at 45 atomic percent or less, for example, 40 atomic percent or less, for example, 35 atomic percent or less, for example, 30 atomic percent or less, for example, 29 atomic percent or less, for example, 28 atomic percent or less, for example, 27 atomic percent or less, for example, 26 atomic percent or less, for example, 25 atomic percent or less, for example, 24 atomic percent or less, for example, 23 atomic percent or less, for example, 22 atomic percent or less, for example, 21 atomic percent or less, for example, 20 atomic percent or less, for example, 15 atomic percent or less, for example, 10 atomic percent or less, for example, 5 atomic percent or less, for example, 4 atomic percent or less, for example, 3 atomic percent or less, for example, 2 atomic percent or less, or for example, 1 atomic percent or less.

[0031] In other aspects, the negative electrode electrochemical active material contains Si and C, and C may be present at 50 atomic percent or less relative to all Group 14 elements in the negative electrode electrochemical active material. C may be, for example, 45 atomic percent or less, for example 40 atomic percent or less, for example 35 atomic percent or less, for example 30 atomic percent or less, for example 29 atomic percent or less, for example 28 atomic percent or less, for example 27 atomic percent or less, for example 26 atomic percent or less, for example 25 atomic percent or less, for example 24 atomic percent or less, for example 23 atomic percent or less, for example 22 atomic percent or less, for example 21 atomic percent or less, for example 20 atomic percent or less, for example 15 atomic percent or less, for example 10 atomic percent or less, for example 5 atomic percent or less, for example 4 atomic percent or less, for example 3 atomic percent or less, for example 2 atomic percent or less, or for example 1 atomic percent or less.

[0032] The negative electrode electrochemical active material is, for example, Si x M 1-x and contains M, where M consists of one or more non-Si Group 14 elements, and it may be that 0 < x < 1. As described above, M may be, for example, C, Ge, or any combination thereof. For example, M may be C. For example, M may be Ge. For example, x may be 0.5 or more, for example x may be 0.55 or more, for example x may be 0.6 or more, for example x may be 0.65 or more, for example x may be 0.7 or more, for example x may be 0.71 or more, for example x may be 0.72 or more, for example x may be 0.73 or more, for example x may be 0.74 or more, for example x may be 0.75 or more, for example x may be 0.76 or more, for example x may be 0.77 or more, for example x may be 0.78 or more, for example x may be 0.79 or more, for example x may be 0.8 or more, for example x may be 0.85 or more, for example x may be 0.9 or more, for example x may be 0.95 or more, for example x may be 0.96 or more, for example x may be 0.97 or more, for example x may be 0.98 or more, or for example x may be 0.99 or more.

[0033] The negative electrode electrochemically active material is understood to be able to contain one or more other non-Group 14 elements. Specific examples of non-Group 14 elements include, but are not limited to, lithium, boron, sodium, magnesium, and aluminum. For example, when a non-Group 14 element is present, the element is present in a proportion of 50 atomic percent (hereinafter sometimes referred to as “at%”) or less, for example 20 at% or less, for example 10 at% or less, for example 5 at% or less, for example 4 at% or less, for example 3 at% or less, for example 2 at% or less, for example 1 at% or less.

[0034] The Si component of the negative electrode electrochemically active material is characterized by having a microstructure. The microstructure of Si in the negative electrode electrochemically active material may be, for example, polycrystalline, a combination of nanocrystalline and amorphous, amorphous, or a combination of polycrystalline, nanocrystalline, and amorphous. For example, the microstructure may not be amorphous alone.

[0035] For example, the microstructure of the Si material in the negative electrode electrochemically active material may include polycrystals or be polycrystals itself. The polycrystalline silicon may be formed of a number of small silicon crystals or crystallites. The number of crystallites may typically be randomly arranged. As an example, the polycrystalline Si may be obtained from any recognized commercial supplier, for example, among many suppliers, Wacker Chemi, or Hemlock Semiconductor, etc.

[0036] For example, the microstructure of Si in the negative electrode electrochemically active material may be a combination of nanocrystalline and amorphous. This nanocrystalline silicon is typically in the form of silicon with a quasi-crystalline structure containing an amorphous phase, but is different from amorphous Si in that it also contains particles of crystalline silicon in the amorphous phase. Typical suppliers of nanocrystalline silicon include Strem (USA) and Cenate (Norway), etc.

[0037] In some aspects, the microstructure of Si in the negative electrode electrochemical active material may be a combination of polycrystalline, nanocrystalline, and amorphous. When polycrystalline Si is present in silicon combined with other microstructures, the proportion (mass) of the polycrystalline phase may be 20 percent or less. For example, the proportion of polycrystalline Si may be 15 percent or less, for example 10 percent or less, for example 5 percent or less.

[0038] The negative electrode electrochemical active material may contain, for example, one or more Group 14 element-free hydrogen storage materials. When the Group 14 element-free hydrogen storage material is present in the negative electrode electrochemical active material, the Group 14 element-free hydrogen storage material may be present, for example, in a proportion of 50 weight percent or less. For example, the Group 14 element-free hydrogen storage material may be 40 weight percent or less, for example 30 weight percent or less, for example 20 weight percent or less, for example 10 weight percent or less, for example 5 weight percent or less, for example 3 weight percent or less, for example 2 weight percent or less, for example 1 weight percent or less, for example 0.1 weight percent or less, for example 0.01 weight percent or less.

[0039] Specific examples of the Group 14 element-free hydrogen storage material that may be included in the negative electrode electrochemical active material include any material known in the art that can electrochemically and reversibly store hydrogen. Specific examples of such materials are AB xIt is a type of hydrogen storage material, where A is a hydride-forming element, B is a non-hydride-forming element, and x ranges from 1 to 5. Specific examples include AB2, AB5, and A2B7-type (series) materials known in the art. The component (A) of the hydride-forming metal includes, for example, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, or a combination thereof or other metal(s) such as mischmetal, but is not limited thereto. The B (non-hydride-forming) component includes a metal selected from the group consisting of, for example, aluminum, nickel, cobalt, copper, and manganese, or a combination thereof. In some aspects, the AB x type (series) materials are disclosed, for example, in U.S. Patent No. 5,536,591 and U.S. Patent No. 6,210,498. For example, the group 14 element-free 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. For example, the group 14 element-free hydrogen storage materials are as disclosed in U.S. Patent Application Publication No. 2016 / 0118654. In some aspects, the group 14 element-free hydrogen storage materials include hydroxides, oxides, or oxyhydroxides of Ni, Co, Al, Mn, or a combination thereof, as disclosed, for example, in U.S. Patent No. 9,502,715. For example, the group 14 element-free hydrogen storage materials include transition metals such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, Cd, or a combination thereof, as disclosed, for example, in U.S. Patent No. 9,859,531.

[0040] The negative electrode electrochemical active material exists in powder form, which means that the negative electrode electrochemical active material is in a solid state at 25 degrees Celsius (°C) and without a substrate. Despite the contrary being believed until now, it has been found that group 14 elements in a solid state can be used to form solid state hydrides and can be useful for hydrogen storage or battery applications. This powder is held by a binder, which binds these powder particles to a layer formed on a current collector during the formation of the negative electrode.

[0041] The electrochemical cell provided herein also includes a positive electrode that houses a positive electrode electrochemical active material. The positive electrode electrochemical active material has the property of occluding and releasing hydrogen ions in the circulation in a proton-conducting battery so that the positive electrode active material functions as a pair with the negative electrode electrochemical active material to circulate hydrogen and generate an electric current. Exemplary materials suitable for use in the positive electrode electrochemical active material include metal hydroxides. Specific examples of metal hydroxides that can be used in the positive electrode electrochemical 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.

[0042] In some aspects, the positive electrode electrochemical active material includes nickel hydroxide alone or in combination with one or more additional metals. For example, the electrochemical active material includes nickel and 1, 2, 3, 4, 5, 6, 7, 8, 9, or more types of additional metals. For example, the positive electrode electrochemical active material may include nickel as the only metal.

[0043] For example, the positive electrode electrochemical active material contains one or more metals selected from the group consisting 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, their hydrides, their oxides, their hydroxides, their oxyhydroxides, and any combination of the foregoing. For example, the positive electrode electrochemical active material contains one or more of Ni, Co, Mn, Zn, Al, Zr, Mo, Mn, rare earths, and combinations thereof. In some aspects, the positive electrode electrochemical active material contains Ni, Co, Al, or a combination thereof.

[0044] The positive electrode electrochemical active material may contain Ni. For example, Ni is present at an atomic percentage of 10 atomic percent (at%) or more with respect to all metals in the positive electrode electrochemical active material. For example, Ni may be 15 at% or more, for example 20 at% or more, for example 25 at% or more, for example 30 at% or more, for example 35 at% or more, for example 40 at% or more, for example 45 at% or more, for example 50 at% or more, for example 55 at% or more, for example 60 at% or more, for example 65 at% or more, for example 70 at% or more, for example 75 at% or more, for example 80 at% or more, for example 85 at% or more, for example 90 at% or more, for example 91 at% or more, for example 92 at% or more, for example 93 at% or more, for example 94 at% or more, for example 95 at% or more, for example 96 at% or more, for example 97 at% or more, for example 98 at% or more, for example 99 at% or more. For example, the only metal in the positive electrode electrochemical active material may be Ni.

[0045] One or both of the negative electrode electrochemical active material and the positive electrode electrochemical active material may be in a powder or granular form, for example. The particles may be held by a binder so as to form a layer on the current collector during the formation of the negative electrode or the positive electrode. As the binder, any binder known in the art can be used as long as it is suitable for use in the formation of the negative electrode, the positive electrode, or both, and is suitable for proton conduction.

[0046] Examples of binders used in the formation of the negative electrode include, but are not limited to, polymer binder materials. Examples of binder materials include elastomer materials, such as styrene-butadiene (SB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-ethylene-butadiene-styrene block copolymer (SEBS). More specific examples of binders include, but are not limited to, polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), Teflon (registered trademark) -treated acetylene black (TAB-2), styrene-butadiene binder materials, or carboxymethyl cellulose (CMC). Specific examples can be verified in U.S. Patent No. 10,522,827. The ratio of the electrochemically active material to the binder is, for example, from 4:1 to 1:4. For example, the ratio of the electrochemically active material to the binder is from 1:3 to 1:2.

[0047] One or both of the positive electrode and the negative electrode may further contain one or more additives contained in the electrochemically active material. The additive is, for example, a conductive material. The conductive material is preferably conductive carbon. Specific examples of conductive carbon include graphite. As another example, materials containing graphite-like carbon such as graphitized coke are mentioned. Still other examples of carbon materials that can be considered include amorphous and non-crystalline disordered non-graphitized carbon, such as petroleum coke and carbon black. The conductive material is present in the negative electrode or the positive electrode, for example, in a weight percentage (wt%) ratio of 0.1 wt% to 20 wt%, or at any ratio represented by a value or within a range thereof.

[0048] The negative electrode and the positive electrode may be formed by any method known in the art. For example, the negative electrode electrochemically active material or the positive electrode electrochemically active material is mixed with a binder and optionally a conductive material in a suitable solvent to form a slurry, the slurry is coated on a current collector, and dried to evaporate part or all of the solvent, thereby forming a layer of the electrochemically active material on the surface of the current collector.

[0049] The current collector may be in the form of a mesh, foil, or other suitable form. For example, the current collector may be formed of aluminum such as an aluminum alloy, nickel or a nickel alloy, steel such as stainless steel, copper or a copper alloy, or other materials of such types. The current collector may be, for example, in the form of a sheet, a foil, a solid substrate, a porous substrate, a grid, a foam, or a foam coated with one or more metals, or other forms known in the art. In some aspects, the current collector is in the form of a foil. For example, the grid may include an expanded metal grid and a perforated foil grid. The current collector may be a material having any suitable electronic conductivity and selective impermeability or substantial impermeability, examples of which include copper, stainless steel, titanium, or carbon paper / film, non-perforated metal foil, aluminum foil, clad materials including nickel and aluminum, clad materials including copper and aluminum, nickel-plated steel, nickel-plated copper, nickel-plated aluminum, gold, silver, any suitable material having electronic conductivity and impermeability, or any suitable combination thereof. For example, the current collector may be formed of one or more suitable metals, or may be formed by combining metals (e.g., alloys, solid solutions, plated metals). For example, the current collector for the negative electrode may contain steel such as stainless steel, or may be stainless steel itself exclusively.

[0050] The proton-conducting electrochemical cell may include a separator interposed between the negative electrode and the positive electrode. As the separator, a material having permeability to hydrogen ions can be used so as not to limit the ion movement between the negative electrode and the positive electrode to an unacceptable or unacceptable extent. Specific examples of the separator include, but are not limited to, materials such as nylon, polyester, polyvinyl chloride, glass fiber, and cotton. As an example, the separator may be polyethylene or polypropylene.

[0051] The proton-conducting battery provided in this specification includes a non-aqueous proton-conducting electrolyte. The electrolyte is located between the negative electrode electrochemically active material and the positive electrode electrochemically active material, enabling the flow and other movements of protons between the negative electrode and the positive electrode. The non-aqueous electrolyte can include, for example, less than 10 wt% of water, for example, less than 5 wt% of water, for example, 1 wt% of water. In some aspects, the non-aqueous electrolyte may include less than 100 ppm of water, less than 50 ppm of water, for example, less than 10 ppm of water.

[0052] The non-aqueous electrolyte may, for example, include one or more aprotic compounds alone or in combination with one or more proton sources such as organic acids. The aprotic compound may be any compound suitable for use in the electrolyte as long as it does not cause a harmful reaction with other components in the electrochemical cell. Specific examples of aprotic acids include ammonium or phosphonium compounds. For example, this ammonium or phosphonium may include one or more linear, branched, or cyclic substituted or unsubstituted alkyl groups bonded to nitrogen or phosphorus.

[0053] The non-aqueous electrolyte may be, for example, an ammonium or phosphonium compound containing one or more linear, branched, or cyclic substituted or unsubstituted alkyl groups bonded to a positively charged nitrogen or phosphorus atom. For example, the compound may contain one such alkyl, or for example, two such alkyls which may be the same or different. For example, the alkyl of the ammonium or phosphonium compound has or includes 1 to 6 carbon atoms, for example, has or includes 1 to 4 carbon atoms, and may be branched, linear, or cyclic. In some aspects, nitrogen or phosphorus may be a constituent element of a 5- or 6-membered ring structure that may have one or more pendant groups extending from the central ring. For example, the ammonium ion may be an imidazolium ion. For example, the phosphonium ion may be a pyrrolidinium ion.

[0054] In some embodiments, the ammonium or phosphonium includes one or two linear or cyclic, substituted or unsubstituted alkyls having 1 to 6 carbon atoms. For example, the alkyl contains 2, 3, 4, 5, or 6 carbons. In some embodiments, the aprotic compound includes one or two alkyls having 1 to 6 carbons. The substitution element of the alkyl is, for example, nitrogen, oxygen, sulfur, or other elements of such types. For example, the ammonium or phosphonium includes a 5- or 6-membered ring structure in which the ring is substituted with N, O, or P.

[0055] Specific examples of the aprotic compound used as the electrolyte include, but are not limited to, 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium (EMIM), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris(hydroxyethyl)methylammonium, 1,2,4-trimethylpyrazolium, or combinations thereof.

[0056] The aprotic compound includes, for example, one or more anions in combination with the aprotic compound. Specific examples of the anion include, but are not limited to, methide, nitrate, carboxylate, imide, halide, borate, phosphate, phosphinate, phosphonate, sulfonate, sulfate, carbonate, and aluminate. More specific examples can be found in U.S. Patent Nos. 6,254,797 and 9,006,457. In a specific exemplary aspect, the anion includes carboxylates such as acetate, hydrogen, alkyl, or phosphates such as fluorophosphate, phosphinates such as alkyl phosphinate, and the like. Specific examples of such aprotic compounds include 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium (EMIM), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris(hydroxyethyl)methylammonium, 1,2,4-trimethylpyrazolium, or acetates, sulfonates, or borates of combinations thereof, but are not limited thereto. Specific examples include diethylmethylammonium trifluoromethanesulfonate (DEMA TfO), 1-ethyl-3-methylimidazolium acetate (EMIM Ac), or 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI).

[0057] In addition to the aprotic compound, an organic acid that acts as a proton donor, for example, may be further added to the electrolyte. The presence of the organic acid improves the overall proton conductivity of the electrolyte, thereby improving the function of the proton-conducting battery using the electrolyte. For example, the organic acid may be a carboxylate. Specific examples of the carboxylate include those having 0 to 10 or more carbons added to the terminal carboxylic acid. More specific examples include acetic acid such as acetic acid or haloacetic acid (for example, having 1 to 3 fluorine or chlorine atoms). For example, the organic acid may be acetic acid.

[0058] The organic acid is present in the electrolytic solution, for example, at a concentration of 1 to 5 mol / kg (hereinafter, this unit may be referred to as "m"). For example, the organic acid may be present at a concentration of 3 to 4 m. For example, the organic acid may be present at a concentration of 3 to 3.5 m.

[0059] The non-aqueous electrolytic solution used in any of the above or aspects provided in this specification contains, for example, one or more additives suitable for giving the proton-conducting electrochemical cell containing the electrolytic solution a maximum capacity with respect to a discharge capacity exceeding 1000 mAh / g per unit weight of the negative electrode electrochemical active material. By adding one or more suitable additives such as appropriate salts, the formation of the proton-conducting electrochemical cell provided in this specification is remarkably improved, and as a result, it has been found that the discharge capacity achievable by the battery is improved. In other identical cells, it has been found that by adding one or more such additives, the maximum capacity can often be increased by 3 to 7 times. Without being limited to one specific theory, the availability of free hydrogen in the electrolytic solution changes during formation to the extent that cell formation is suppressed. The addition of an appropriate salt stabilizes the free hydrogen concentration and increases the resulting capacity achievable by the cell.

[0060] In order to give the proton-conducting electrochemical cell containing the electrolytic solution a maximum capacity while the negative electrode electrochemical active material has a discharge capacity exceeding 1000 mAh / g per unit weight, it is suitable to use, for example, salts as additives having a pKa in water of 1 to 14, for example, 3 to 13, for example, 7 to 13, for example, 3 to 8.

[0061] While the negative electrode electrochemical active material has a discharge capacity exceeding 1000 mAh / g per unit weight, specific examples of salt additives for providing the proton-conducting electrochemical cell containing an electrolytic solution with a maximum capacity include salts of potassium or sodium. Suitable salts include potassium or sodium phosphates, carbonates, or sulfates. More specific examples of potassium salts include, but are not limited to, potassium phosphates such as monopotassium phosphate or dipotassium phosphate, potassium carbonate, potassium sulfate, etc. Specific examples of sodium salts include, but are not limited to, sodium mono-, di-, tetra-phosphates, sodium bicarbonate, and sodium hydrogen sulfate.

[0062] While the negative electrode electrochemical active material has a discharge capacity exceeding 1000 mAh / g per unit weight, in order to provide the proton-conducting electrochemical cell containing an electrolytic solution with a maximum capacity, the salt additive may be present in the electrolytic solution at a concentration of 0.01 to 1 m, for example 0.01 to 0.2 m, for example 0.5 to 1 m.

[0063] The negative electrode, positive electrode, separator, and non-aqueous electrolytic solution may be housed in a cell case (for example, an exterior body). The exterior body may be a metal or polymer can, or a laminated film such as a heat-sealable aluminum foil like a polypropylene film coated with aluminum. Thus, the electrochemical cell provided herein may be in any known cell form, for example, a button cell, a pouch cell, a cylindrical cell, or other suitable structures. In some aspects, the exterior body is in the form of a flexible film, for example, a polypropylene film. Such an exterior body is generally used to form a pouch cell. The proton-conducting cell may have any suitable structure or shape and may be cylindrical or prismatic.

[0064] The current collector or substrate may include one or more tabs, which allows electrons to move from the current collector to the external region of the cell, enabling the current collector to be connected to a circuit and the electrons generated during discharge of the cell to be utilized to supply power to one or more devices. The tabs can be formed of any suitable conductive material (e.g., Ni, Al, or other metals) and may be welded to the current collector. For example, each electrode may have a single tab.

[0065] The proton-conducting battery provided herein has a secondary battery discharge capacity exceeding 800 mAh / g in the negative electrode electrochemical active material when, for example, a voltage exceeding 1 volt is applied to the Ni(OH)2 positive electrode in any of the described aspects. For example, the discharge capacity after cell formation is measured with, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 cycles. The discharge capacity of the battery is measured for each of the above conditions and is, for example, 900 mAh / g, for example, 1000 mAh / g, for example, 1100 mAh / g, for example, 1200 mAh / g, for example, 1300 mAh / g, for example, 1400 mAh / g, for example, 1500 mAh / g, for example, 1600 mAh / g, for example, 1700 mAh / g, for example, 1800 mAh / g, for example, 1900 mAh / g, for example, 2000 mAh / g, or exceeds this.

[0066] In some aspects, the proton-conducting battery provided herein has a maximum capacity of 1000 mAh / g or more, where the gram is the weight of the negative electrode electrochemical active material and is measured with respect to the Ni(OH)2 positive electrode. For example, the maximum capacity is 1100 mAh / g, such as 1200 mAh / g, such as 1300 mAh / g, such as 1400 mAh / g, such as 1500 mAh / g, such as 1600 mAh / g, such as 1700 mAh / g, such as 1800 mAh / g, such as 1900 mAh / g, such as 2000 mAh / g, such as 2500 mAh / g, such as 3000 mAh / g, such as 3500 mAh / g, such as 4000 mAh / g, such as 4500 mAh / g, such as 5000 mAh / g, such as 5500 mAh / g, such as 6000 mAh / g, such as 6500 mAh / g or more.

[0067] In certain aspects, the electrochemical cell provided herein includes a positive electrode including a positive electrode electrochemical active material capable of storing and releasing hydrogen, and a negative electrode including a negative electrode electrochemical active material of one or more Group 14 elements, the negative electrode electrochemical active material being in powder form and bound by a binder, and the microstructure of the negative electrode electrochemical active material being polycrystalline, a combination of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline, and amorphous, and a non-aqueous electrolyte including an ammonium aprotic compound and a carboxylic acid additive, where, for example, the negative electrode electrochemical active material includes Si and, for example, contains one or more salt additives of potassium or sodium.

[0068] In other aspects, the electrochemical cell provided by this specification includes a positive electrode including a positive electrode electrochemical active material containing Ni, and a negative electrode, where the negative electrode includes a negative electrode electrochemical active material of Si and one or more Group 14 elements other than Si, and the negative electrode electrochemical active material is in the form of powder and is bonded by a binder, and the microstructure of the negative electrode electrochemical active material is polycrystalline, or a combination of nanocrystals and amorphous, or a combination of polycrystals, nanocrystals and amorphous, a negative electrode, an ammonium aprotic compound and a carboxylic acid additive, for example, here the negative electrode electrochemical active material contains Si, for example, a non-aqueous electrolyte containing one or more salt additives of potassium or sodium.

[0069] In some aspects, the electrochemical cell provided by this specification includes a positive electrode including a positive electrode electrochemical active material mainly composed of Ni, and a negative electrode, where the negative electrode includes a negative electrode electrochemical active material of one or more Group 14 elements, and the negative electrode electrochemical active material is in the form of powder and is bonded by a binder, and the microstructure of the negative electrode electrochemical active material is amorphous, or polycrystalline, or a combination of nanocrystals and amorphous, or a combination of polycrystals, nanocrystals and amorphous, a negative electrode, an ammonium aprotic compound and an acetic acid additive, for example, here the negative electrode electrochemical active material is mainly composed of Si in atomic percentage, for example, a non-aqueous electrolyte containing one or more potassium-based salt additives provided by this specification. [Examples]

[0070] Example 1 A series of silicon-containing compositions were obtained from commercial sources. Polycrystalline silicon was obtained from Alfa Aesar (USA), Fijifilm (Japan), Hongwu (China), Silican (Taiwan), and Paraclete (USA). Amorphous / nanocrystalline silicon was obtained from Cenate (Norway) and Strem (USA). To confirm the microstructure of each silicon used, for each sample, Cu-K was used as the radiation source. αAnalysis was performed using a Philips X’Pert Pro X-ray diffractometer. Sample 1 contained polycrystalline Si. The diffraction pattern is shown in Figure 1. The diffraction shows sharp peaks around approximately 48° and 56°, which are typical features of polycrystalline silicon. The material does not seem to contain amorphous or nanocrystalline silicon. The analysis results of Sample 2 are shown in Figure 2, which contains a combination of polycrystalline silicon with nanocrystalline and amorphous silicon. The nanocrystals appear as broad peaks around 29°, and the amorphous phase is shown as a broad peak around 52°. The presence of some polycrystalline Si in the sample is also evident from the small sharp peaks around 48° and 56°. Sample 3, as shown in Figure 3, shows a combination of nanocrystalline Si and amorphous Si in the absence of polycrystalline Si.

[0071] The negative electrode was composed of each sample silicon-containing material as the raw material. The silicon material was in the form of dry powder and was mixed with the dry TAB-2 binder at a weight ratio of 1:3. The material was pressed onto a Ni mesh substrate, which is a current collector. The Ni(OH)2 positive electrode was fabricated by a standard method using commercially supplied and sintered Ni(OH)2. To test the electrochemical properties, the negative electrode was tested by forming an electrochemical cell inside a Teflon® Swagelok tee. The cell used for the electrochemical analysis is shown in Figure 4. The cell includes a central ground 1 covered at both ends with ferrules 2 fixed by color 3. Sample 4 is sandwiched between two current collector rods 5 formed from Ni-plated steel (NS) or stainless steel (SS). The upper channel is covered with parafilm 6, which is a pressure vent device. The sample was formed by laminating the negative electrode and the positive electrode through a standard separator. The cell was filled with an electrolyte containing EMIM / AC with a concentration of 3.33 m acetic acid containing one or more salt additives.

[0072] This cell was cycled at a charge rate of 700 mA / g, a charge time of 20 hours, a discharge rate of 70 mA / g, and a discharge cut-off of 1 V or 0 V. Discharging after cell formation was carried out up to cycle 28 for samples 1 and 2 (Figure 5) and up to cycle 31 for sample 3 (Figure 6), and a large capacity exceeding 3800 mA / g (Si) was demonstrated for all samples tested. The maximum discharge capacity exceeded 5500 mAh / g for both the polycrystalline Si anode and the combination of nanocrystalline Si and amorphous Si. The results and test conditions for all three samples are shown in Table 1.

Table 1

[0073] Example 2 It has been found that adding a specific salt to the electrolyte of a proton-conducting battery using an Si-containing anode stabilizes and improves cell formation, thereby improving the electrochemical characteristics of the cell. Tests are conducted on the cell of Example 1 with or without the addition of one or more salt additives to the electrolyte. These investigations were carried out using potassium salts simply because potassium salts are more readily soluble, but similar functions are expected to be shown for sodium salt additives.

[0074] Further tests were conducted on the EMIM / Ac electrolyte containing acetic acid at a concentration of 3.33 m, either as is or with the addition of K2HPO4, KH2PO4, KHCO3, KHSO4, or K2C2O4 at concentrations of 0.1 or 0.05 m. Investigations of the electrolyte were carried out in a cell containing the polycrystalline Si anode of sample 1 of Example 1. The cell was charged under conditions of 700 mA / g for 20 hours and then discharged at 70 mA / g until a cut-off voltage of 0 V was reached, and the capacity up to 31 cycles was investigated. The results are shown in Table 2.

Table 2

[0075] While excellent maximum capacity was achieved when no salt additive was used, it was demonstrated that the maximum capacity of the cell exceeded threefold by adding a potassium salt additive. The capacity of the cell using the K2HPO4 additive showed a remarkable maximum capacity exceeding 6800 mAh / g in the Si negative electrode material.

[0076] The foregoing description of specific aspects is essentially illustrative only and is not intended to limit the scope, application, or inherently possible variations of the invention claimed below. This disclosure is provided in connection with the non-limiting definitions and terms included herein. These definitions and terms are not intended to function to limit the scope or practice of the invention and are presented for illustrative and descriptive purposes only. While a process or composition is described as an order of individual steps or using specific materials, it is understood that the steps or materials are replaceable such that the description of the invention may include numerous elements or steps encompassed in many ways readily understandable by those skilled in the art.

[0077] 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, intervening elements are absent.

[0078] The terms “first,” “second,” “third,” etc. may be used herein to describe various elements, components, regions, layers, and / or sections, but it is understood that these elements, components, regions, layers, and / or sections are not limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another. Thus, the “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.

[0079] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, including "at least one", unless the context clearly dictates 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. Further, the terms "consisting of" and / or "consisted of" or "including" and / or "included" when used in this specification, while indicating the presence of the stated features, regions, integers, steps, operations, elements, and / or components, are not to be construed as excluding the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof. The term "or combinations thereof" means a combination including at least one of the above elements.

[0080] 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. Further, terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning that does not conflict with their meaning in the context of the relevant art and this disclosure, and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0081] The patents, publications, and applications referred to in this specification are indicative of the level of those of ordinary skill in the art to which the present invention pertains. These patents, publications, and applications are incorporated herein by reference to the extent that each patent, publication, or application is specifically and individually incorporated herein by reference.

[0082] It is understood that other modifications and variations of the present invention can be made in view of the above. The above drawings, considerations, and descriptions are illustrative of some specific embodiments of the invention and are not meant to limit its implementation. The following claims include all equivalents that define the scope of the invention. Note that the present disclosure includes the following content as embodiments. [Aspect 1] A proton-conducting secondary battery, a positive electrode including a positive electrode electrochemically active material capable of storing and releasing hydrogen, a negative electrode, the negative electrode including a negative electrode electrochemically active material containing one or more Group 14 elements, the negative electrode electrochemically active material being in powder form and bound by a binder, and the microstructure of the negative electrode electrochemically active material being polycrystalline, a combination of nanocrystals and amorphous, or a combination of polycrystals, nanocrystals and amorphous, a non-aqueous electrolyte interposed between the negative electrode and the positive electrode, wherein the discharge capacity of the secondary battery exceeds 800 mAh / g in the negative electrode electrochemically active material at a voltage higher than 1 Volt, a proton-conducting secondary battery. [Aspect 2] The battery according to Aspect 1, wherein the negative electrode electrochemically active material contains two or more Group 14 elements. [Aspect 3] The battery according to Aspect 1, wherein the negative electrode electrochemically active material contains Si. [Aspect 4] The battery according to any one of Aspects 1 to 3, wherein the negative electrode electrochemically active material contains Si and one or more non-Si Group 14 elements. [Aspect 5] The battery according to Aspect 4, wherein the one or more non-Si Group 14 elements are C, Ge, or a combination thereof. [Aspect 6] The battery according to Aspect 4, wherein the amount of the non-Si Group 14 element is 50 atomic percent or less with respect to all Group 14 elements in the negative electrode electrochemically active material. [Aspect 7] The discharge capacity of the secondary battery is 2 more than 1000 mAh / g in the negative electrode electrochemically active material at a voltage higher than 1 Volt with respect to the positive electrode, (especially more than 1500 mAh / g at a voltage higher than 1 Volt, for example), the battery according to any one of Aspects 1 to 3. [Aspect 8] The battery according to any one of Aspects 1 to 3, wherein the maximum discharge capacity of the secondary battery exceeds 3500 mAh / g in the negative electrode electrochemically active material. [Aspect 9] The battery according to any one of Aspects 1 to 3, wherein the electrolyte contains one or more aprotic compounds and an acid as a proton source. [Aspect 10] The aprotic compound-containing battery according to Aspect 9, wherein the aprotic compound includes 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium acetate (EMIM), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris(hydroxyethyl)methylammonium, or 1,2,4-trimethylpyrazolium. [Aspect 11] The battery according to Aspect 9, wherein the electrolyte further includes an additive, and the additive includes potassium, acetic acid, or a combination thereof. [Aspect 12] The battery according to Aspect 11, wherein the additive is a salt additive including a phosphate, carbonate, or sulfate of potassium. [Aspect 13] The battery according to any one of Aspects 1 to 3, wherein the negative electrode electrochemically active material further includes one or more Group 14 element-free hydrogen storage materials, and the non-Si hydrogen storage material is present in a proportion of 50 wt% or less. [Aspect 14] The battery according to any one of Aspects 1 to 3, wherein the positive electrode electrochemically active material includes 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. [Aspect 15] The battery according to Aspect 14, wherein the positive electrode electrochemically active material includes Ni. [Aspect 16] The battery according to Aspect 14, wherein the positive electrode electrochemically active material includes Ni in a proportion of 10 atomic percent or more based on all the metals in the positive electrode electrochemically active material. [Aspect 17] The battery according to Aspect 14, wherein Ni is present in a proportion of 80 atomic percent or more (particularly, for example, 90 atomic percent or more) in the metal component of the positive electrode electrochemically active material. [Aspect 18] The battery according to Aspect 14, wherein the positive electrode electrochemically active material includes a hydroxide of Ni, Co, Mn, Zn, Al, or a combination thereof.

Claims

1. A proton-conducting secondary battery comprising: a positive electrode containing a positive electrode electrochemically active material capable of occluding and releasing hydrogen; a negative electrode containing a negative electrode electrochemically active material containing one or more Group 14 elements, the negative electrode electrochemically active material being in powder form and bound by a binder, and the microstructure of the negative electrode electrochemically active material being polycrystalline, a combination of nanocrystalline and amorphous, or a combination of polycrystalline, nanocrystalline and amorphous; a non-aqueous electrolyte interposed between the negative electrode and the positive electrode; the negative electrode electrochemically active material contains Si; the electrolyte contains an additive; the additive is a salt additive containing a phosphate, carbonate or sulfate of potassium, or a phosphate, carbonate or sulfate of sodium; the discharge capacity of the secondary battery exceeds 800 mAh / g in the negative electrode electrochemically active material at a voltage higher than 1 V. A proton-conducting secondary battery.

2. The battery according to claim 1, wherein the negative electrode electrochemically active material contains two or more Group 14 elements.

3. The battery according to claim 1 or 2, wherein the negative electrode electrochemically active material contains one or more non-Si Group 14 elements.

4. The battery according to claim 3, wherein the one or more non-Si Group 14 elements are C, Ge, or a combination thereof.

5. The battery according to claim 3, wherein the amount of the non-Si Group 14 element is 50 atomic percent or less based on all Group 14 elements in the negative electrode electrochemically active material.

6. The discharge capacity of the secondary battery exceeds 1000 mAh / g in the negative electrode electrochemically active material at a voltage higher than 1 V with respect to the positive electrode. The battery according to claim 1 or 2. ２ ​

7. The battery according to claim 1 or 2, wherein the maximum discharge capacity of the secondary battery exceeds 3500 mAh / g in the negative electrode electrochemically active material.

8. The battery according to claim 1 or 2, wherein the electrolytic solution contains one or more aprotic compounds and an acid as a proton source.

9. The battery according to claim 8, wherein the aprotic compound contains 1-butyl-3-methylimidazolium (BMIM), 1-ethyl-3-methylimidazolium acetate (EMIM), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, tris(hydroxyethyl)methylammonium, or 1,2,4-trimethylpyrazolium.

10. The battery according to claim 8, wherein the additive contains potassium, acetic acid, or a combination thereof.

11. The battery according to claim 1 or 2, wherein the negative electrode electrochemically active material further contains one or more Group 14 element-free hydrogen storage materials, and the Group 14 element-free hydrogen storage materials are present in a proportion of 50 weight percent or less.

12. The battery according to claim 1 or 2, wherein the positive electrode electrochemically active material contains 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, their hydrides, their oxides, their hydroxides, oxyhydroxides, or any combination of the foregoing.

13. The battery according to claim 12, wherein the positive electrode electrochemically active material contains Ni.

14. The battery according to claim 12, wherein the positive electrode electrochemically active material contains Ni in a proportion of 10 atomic percent or more based on all the metals in the positive electrode electrochemically active material.

15. The battery according to claim 12, wherein Ni is present in the metal component of the positive electrode electrochemically active material at a ratio of 80 atomic percent or more.

16. The battery according to claim 12, wherein the positive electrode electrochemically active material contains a hydroxide of Ni, Co, Mn, Zn, Al, or a combination thereof.

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